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Laboratory assessment of the potential of Nigerian-grown Gmelina Arborea Roxb. for newsprint manufacture 1977

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LABORATORY ASSESSMENT OF THE POTENTIAL OF NIGERIAN-GROWN GMELINA ARBOREA ROXB. FOR NEWSPRINT MANUFACTURE by CHRIS I.S. ILOABACHIE B.Sc. (Hons), U n i v e r s i t y o f Ibadan, 1974 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF FORESTRY i n THE FACULTY OF GRADUATE STUDIES i n THE FACULTY OF FORESTRY (4 u n i t s ) We a c c e p t t h i s t h e s i s as c o n f o r m i n g t o t h e r e q u i r e d s t a n d a r d THE UNIVERSITY OF BRITISH COLUMBIA A u g u s t , 1977 © C . I . S . I l o a b a c h i e In presenting th i s thes is in pa r t i a l fu l f i lment of the requirements for an advanced degree at the Univers i ty of B r i t i s h Columbia, I agree that the L ibrary sha l l make it f ree ly ava i l ab le for reference and study. I fur ther agree that permission for extensive copying of th i s thesis for scho lar ly purposes may be granted by the Head of my Department or by his representat ives. It is understood that copying or publ ication of th i s thes is fo r f inanc ia l gain sha l l not be allowed without my written permission. Department of The Univers i ty of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 ABSTRACT E x t e n s i o n o f p u l p and paper raw m a t e r i a l base by i n c r e a s e d u t i l i z a t i o n o f hardwood s p e c i e s i s one r e a s o n a b l e approach t o the s o l u t i o n o f t h e w o r l d f i b e r s h o r t a g e problem. T h i s i s p a r t i c u l a r l y so i f m e c h a n i c a l p u l p w i t h adequate m e c h a n i c a l and o p t i c a l p r o p e r t i e s can be produced from f a s t - g r o w i n g hardwoods which have n o t been used t o any g r e a t e x t e n t i n the p a s t as a raw m a t e r i a l . L a b o r a t o r y s t u d i e s r e p o r t e d i n t h i s t h e s i s were c a r r i e d o u t t o a s s e s s the response o f Gmelina a r b o r e a Roxb., a hardwood grown e x t e n s i v e l y i n N i g e r i a , t o m e c h a n i c a l p u l p - i n g . I n t h i s work, b o t h open d i s c h a r g e and s i m u l a t e d thermo- m e c h a n i c a l r e f i n e r groundwood p u l p s were produced. I n the l a t t e r c a s e , the e f f e c t o f c h e m i c a l p r e t r e a t m e n t w i t h b o t h sodium s u l f i t e and sodium h y d r o x i d e was a l s o e v a l u a t e d . I t was found t h a t w h i l e open d i s c h a r g e and s t a n d a r d thermo- m e c h a n i c a l t r e a t m e n t s r e s u l t e d i n m e c h a n i c a l p u l p w i t h i n f e r i o r p r o p e r t i e s , t h e t r e a t m e n t o f c h i p s o f Gmelina a r b o r e a Roxb. w i t h a 1% sodium h y d r o x i d e s o l u t i o n a t 250 DF (121°C) f o r 10 minutes p r i o r t o open d i s c h a r g e r e f i n i n g r e s u l t e d i n a m e c h a n i c a l p u l p h a v i n g m e c h a n i c a l and o p t i c a l p r o p e r t i e s comparable t o and, i n c e r t a i n a s p e c t s , b e t t e r t h a n those o f sto n e groundwood used i n N o r t h American n e w s p r i n t . i The b e h a v i o u r o f t h i s c h e m i c a l l y p r e t r e a t e d r e f i n e r p u l p from Gmelina i n a d m i x t u r e w i t h softwood k r a f t was a l s o i n v e s t i g a t e d . I t was found t h a t t h e p r o p e r t i e s o f n e w s p r i n t f u r n i s h handsheets c o n t a i n i n g m i x t u r e s o f Gmelina m e c h a n i c a l p u l p and West Coa s t s e m i - b l e a c h e d k r a f t (SBK) compared f a v o u r - a b l y w i t h those o f handsheets produced from t y p i c a l West Coast n e w s p r i n t f u r n i s h e s , t h u s i n d i c a t i n g t h e p o s s i b i l i t y o f u s i n g c h e m i c a l l y p r e t r e a t e d Gmelina thermomechanical p u l p (TMP) w i t h reduced amounts d f so f t w o o d SBK. To c o v e r t h e s i t u a t i o n f o r a f u l l y i n t e g r a t e d m i l l , a b r i e f s t u d y was i n c l u d e d t o a s s e s s t h e response o f Gmelina t o k r a f t c o o k i n g , and t o e v a l u a t e t h e b e h a v i o u r o f t h i s p u l p i n a d m i x t u r e w i t h Gmelina m e c h a n i c a l p u l p . As e x p e c t e d , t h e k r a f t p u l p from Gmelina was s i g n i f i c a n t l y weaker, mechani- c a l l y , t h a n N o r t h American k r a f t p u l p s and i t s d e f i c i e n c i e s were c l e a r l y e v i d e n t i n the p r o p e r t i e s o f mixed f u r n i s h h andsheets. I t was c o n c l u d e d , from t h i s p a r t o f t h e s t u d y , t h a t n e w s p r i n t c o n t a i n i n g b o t h i t s c h e m i c a l and i t s mechani- c a l p u l p components from Gmelina would r e q u i r e e x c e s s i v e l y l a r g e p r o p o r t i o n s o f Gmelina c h e m i c a l p u l p and s t i l l e x e r t a l i m i t i n g i n f l u e n c e on paper machine speed and subsequent p r i n t i n g o p e r a t i o n s because o f i t s s t r e n g t h d e f i c i e n c i e s . TABLE OF CONTENTS Page ABSTRACT i TABLE OF CONTENTS i i i LIST OF TABLES v i LIST OF FIGURES v i i ACKNOWLEDGEMENTS i x Chapter I . INTRODUCTION . 1 I I . LITERATURE SURVEY 4 G e n e r a l I n t r o d u c t i o n 4 S i l v i c u l t u r e , P l a n t a t i o n E s t a b l i s h m e n t and Growth 4 Wood and F i b e r P r o p e r t i e s 6 P r e v i o u s P u l p i n g S t u d i e s 8 M e c h a n i c a l P u l p i n g 13 1. Stone Groundwood (SGW) P r o c e s s . . . 14 2. C h i p R e f i n e r M e c h a n i c a l P u l p i n g . . . 16 a) C h i p R e f i n e r M e c h a n i c a l P u l p (RMP) 16 b.) Thermomechanical P r o c e s s (TMP). . 16 c) S i g n i f i c a n c e o f Ch i p R e f i n e r M e c h a n i c a l P u l p i n g 18 C h i p p i n g . 21 Chi p P r e t r e a t m e n t s 21 1. P r e t r e a t m e n t by Steaming 21 2. C h e m i c a l P r e t r e a t m e n t 25 S i g n i f i c a n c e o f F i b e r L e n g t h and F i b e r F r a c t i o n s 27 P u l p B l e n d i n g 29 i i i i v C h a p ter Page I I I EXPERIMENTAL WORK . . 32 I n t r o d u c t i o n 32 Source o f M a t e r i a l s and M a t e r i a l s S t o r a g e . . 33 C h i p p i n g and C h i p H a n d l i n g 33 M e c h a n i c a l P u l p i n g 34 P u l p E v a l u a t i o n 35 1. L a t e n c y Removal 35 2. D e b r i s C o n t e n t 36 3. F r e e n e s s 36 4. Y i e l d 37 5. F i b e r L e n g t h C l a s s i f i c a t i o n s . . . . 38 S u l f a t e P u l p i n g 39 1. Kappa Number o f S u l f a t e P u l p s . . . . 40 2. S e m i - B l e a c h i n g o f S u l f a t e P u l p . . . 40 a) C h l o r i n a t i o n Stage 41 b) E x t r a c t i o n Stage 42 c) H y p o c h l o r i t e Stage 4 3 Handsheet Making and E v a l u a t i o n 4 3 IV RESULTS AND DISCUSSION 45 M e c h a n i c a l P u l p s from Gmelina 45 Y i e l d 45 S p e c i f i c Energy Consumption 46 D e b r i s Content 49 M e c h a n i c a l P r o p e r t i e s 49 O p t i c a l P r o p e r t i e s 50 Comparison of West Coa s t Groundwood and C a u s t i c T r e a t e d Gmelina P u l p s . . . . 51 C h e m i c a l P u l p from Gmelina 52 The P o t e n t i a l o f Gmelina M e c h a n i c a l P u l p s f o r N e w s p r i n t 53 V SUMMARY 55 V Chapter Page VI CONCLUSIONS AND RECOMMENDATIONS 5 7 C o n c l u s i o n s 57 Recommendations 5 7 BIBLIOGRAPHY 59 TABLES 6 7 FIGURES 80 APPENDIX 97 LIST OF TABLES T a b l e Page 1. Import o f paper and p a p e r b o a r d , F e d e r a l R e p u b l i c o f N i g e r i a 67 2. F i b e r c h a r a c t e r i s t i c s o f Gmelina A r b o r e a . . . 68 3. E f f e c t o f c h i p s p e c i f i c a t i o n s i n p u l p i n g p r o c e s s e s 69 4. E f f e c t o f c h e m i c a l p r e t r e a t m e n t on the c h a r a c t e r i s t i c s o f open d i s c h a r g e and p r e s s u r e r e f i n e r p u l p s made from s o f t w o o d s . . 70 5. Dependence o f p h y s i c a l p r o p e r t i e s o f m e c h a n i c a l p u l p on L- and S - f a c t o r s 71 6. R e s u l t s o f e v a l u a t i o n o f t h e p r o p e r t i e s o f the Gmelina m e c h a n i c a l p u l p s 72 7. R e s u l t s o f Bauer-McNett c l a s s i f i c a t i o n o f t h e Gmelina m e c h a n i c a l p u l p s . . . . 73 8. L- and S - f a c t o r s o f t h e Gmelina m e c h a n i c a l p u l p s 74 9. V a l u e s o f Gmelina m e c h a n i c a l p u l p s p r o p e r t i e s e x t r a p o l a t e d a t 90 ml C s f 75 10. R e s u l t s o f e v a l u a t i o n o f Gmelina ( c a u s t i c t r e a t e d ) p u l p and West Coa s t s t o n e 76 groundwood 11. R e s u l t s o f e v a l u a t i o n West Coast and Gmelina s e m i - b l e a c h e d k r a f t (SBK) p u l p s 77 12. R e s u l t s o f e v a l u a t i o n o f s i m u l a t e d n e w s p r i n t handsheets 78 13. Wet s t r e n g t h t e s t r e s u l t s o f t h e s i m u l a t e d n e w s p r i n t mixes 79 v i LIST OF FIGURES F i g u r e Page 1. P a r t c r o s s - s e c t i o n stem o f Gmelina a r b o r e a Roxb. (2.4X) "". . . 80 2. Use o f r e s i d u e m a t e r i a l s f o r p u l p i n g i n B r i t i s h Columbia and Canada 81 3. D i a g r a m a t i c r e p r e s e n t a t i o n o f a t y p i c a l c h i p . . 82 4. P h o t o m i c r o g r a p h u n t r e a t e d m e c h a n i c a l p u l p sample (A) (40X) . 8 3 5. P h o t o m i c r o g r a p h steam p r e t r e a t e d p u l p sample (B) (40X) 84 6. P h o t o m i c r o g r a p h c a u s t i c p r e t r e a t e d p u l p sample (C) (40X) . . 8 5 7. P h o t o m i c r o g r a p h sodium s u l f i t e p r e t r e a t e d p u l p sample (D) (40X) 86 8. C e l l u l o s e o x i d a t i o n 87 9. P h o t o m i c r o g r a p h West Coast s e m i - b l e a c h e d k r a f t p u l p (26X) 88 10. P h o t o m i c r o g r a p h Gmelina s e m i - b l e a c h e d k r a f t p u l p (26X) 88 11. P h o t o m i c r o g r a p h c r o s s - s e c t i o n West C o a s t s e m i - b l e a c h e d k r a f t p u l p f i b e r s (160X phase c o n t r a s t ) 89 12. P h o t o m i c r o g r a p h c r o s s - s e c t i o n Gmelina semi- b l e a c h e d k r a f t p u l p f i b e r s (160X phase c o n t r a s t ) 89 v i i v i i i F i g u r e Page 13. Graph o f d e n s i t y on s e m i - b l e a c h e d k r a f t c o n t e n t o f s i m u l a t e d n e w s p r i n t handsheets . . 90 14. Graph o f t e a r i n d e x on s e m i - b l e a c h e d k r a f t c o n t e n t o f s i m u l a t e d n e w s p r i n t handsheets . . 90 15. Graph o f b u r s t i n d e x on s e m i - b l e a c h e d k r a f t c o n t e n t o f s i m u l a t e d n e w s p r i n t handsheets . . 91 16. Graph o f b r e a k i n g l e n g t h on s e m i - b l e a c h e d k r a f t c o n t e n t o f s i m u l a t e d n e w s p r i n t handsheets . . 91 17. Graph o f s t r e t c h on s e m i - b l e a c h e d k r a f t c o n t e n t o f s i m u l a t e d n e w s p r i n t handsheets . . 92 18. Graph o f b r i g h t n e s s on s e m i - b l e a c h e d k r a f t c o n t e n t o f s i m u l a t e d n e w s p r i n t handsheets . . 9 3 19. Graph o f o p a c i t y on s e m i - b l e a c h e d k r a f t c o n t e n t o f s i m u l a t e d n e w s p r i n t handsheets . . 9 3 20. Graph o f s c a t t e r i n g c o e f f i c i e n t on s emi- b l e a c h e d k r a f t c o n t e n t o f s i m u l a t e d n e w s p r i n t handsheets 94 21. Graph o f a b s o r p t i o n c o e f f i c i e n t on semi- b l e a c h e d k r a f t c o n t e n t o f s i m u l a t e d n e w s p r i n t handsheets 94 22. Graph of wet s t r e n g t h c h a r a c t e r i s t i c s ( s t r e s s ) on s e m i - b l e a c h e d k r a f t c o n t e n t o f s i m u l a t e d n e w s p r i n t handsheets 95 23. Graph o f wet s t r e n g t h c h a r a c t e r i s t i c s ( s t r a i n ) on s e m i - b l e a c h e d k r a f t c o n t e n t o f s i m u l a t e d n e w s p r i n t handsheets 96 ACKNOWLEDGEMENTS I w i s h t o e x p r e s s my s i n c e r e g r a t i t u d e t o the f o l l o w i n g i n d i v i d u a l s and group o f p e o p l e : L. Roche, Dept. of F o r . and Wood S c i e n c e , UCNW, Bangor; J.S. Redhead, FAO; J.B. H a l l , Dept. o f F o r . Res. Mgt., U l , Ibadan and Dr s . R.W. Wellwood and D. H a l e y , F a c u l t y o f F o r e s t r y , UBC; C. Kowalsky, C h a r n e l l and A s s o c i a t e s L t d . , Vancouver and E.R. S i e d l a k , SNC Ru s t L t d . , M o n t r e a l , f o r m a t e r i a l s procurement: J . B a g l e y , WFPL, f o r h i s a s s i s t a n c e d u r i n g m a t e r i a l s p r e p a r a t i o n : S. B e r g h o l d , P u l p i n g S e c t i o n , BCIT, f o r g r a n t i n g me p e r m i s s i o n t o use t h e i r e x p e r i m e n t a l c h i p p e r : L. V a l g , F a c u l t y of F o r e s t r y , UBC, f o r a r r a n g i n g my c o n n e c t i o n w i t h MBR L t d . where I c a r r i e d o u t ray r e s e a r c h p r o j e c t : the e n t i r e management and s t a f f o f MBR L t d . , Vancouver, f o r t h e i r c o o p e r a t i o n , s u p p o r t and f r i e n d s h i p : J.W. W i l s o n , F a c u l t y o f F o r e s t r y , UBC, f o r the i n t e r e s t he showed i n my work and the r e l e v a n t l i t e r a t u r e he s u p p l i e d me: L. P a s z n e r , F a c u l t y o f F o r e s t r y , UBC, f o r d i r e c t i n g the w r i t e - u p , s u p p l y i n g me w i t h p e r t i n e n t l i t e r a t u r e , m a t e r i a l s and g i v i n g me o t h e r i n v a l u a b l e a s s i s t a n c e : i n d e f a t i g a b l e M. J a c k s o n , Head, M e c h a n i c a l P u l p i n g S e c t i o n , MBR L t d . , Vancouver, and my r e s e a r c h s u p e r v i s o r , f o r baby s i t t i n g my t h e s i s p r o j e c t , from i t s e x p e r i m e n t a l , through the d r a f t i n g s t a g e s t o c o m p l e t i o n , d e s p i t e h i s i n n u m e r a b l e o f f i c i a l commitments. F i n a l l y , t o those who I d i d n o t mention b u t who, o t h e r w i s e , d e s e r v e t o be remembered, I a l s o send my s i n c e r e g r a t i t u d e . i x CHAPTER I INTRODUCTION Hardwood p u l p s have g e n e r a l l y , i n t h e p a s t , been used i n t h e manufacture o f t i s s u e and f i n e p a p e r s , o r as f i l l e r p u l p s . I n r e c e n t t i m e s , however, th e d e c r e a s i n g a v a i l a b i l i t y o f t h e p r e f e r r e d softwood s p e c i e s , t h e i n c r e a s - i n g c o n c e r n r e g a r d i n g the w o r l d f u t u r e demand f o r f i b e r s , and t h e f o r e i g n exchange c o n s e r v a t i o n p o l i c i e s o f some p u l p - p r o d u c i n g c o u n t r i e s n o t endowed w i t h t h e f a v o r e d softwood s p e c i e s , have l e d t o an e v e r - i n c r e a s i n g i n c e n t i v e t o make use o f hardwood p u l p s f o r paper p r o d u c t s . The p u l p and paper i n d u s t r y can no l o n g e r a f f o r d t h e l u x u r y o f r e g a r d i n g h a r d - wood p u l p s j u s t as secondary m a t e r i a l . . As r e p o r t e d by A l a d e ( 3 ) , t h e consumption o f paper and p a p e r b o a r d i n N i g e r i a was about 111,583,723 kg (123,000 s h o r t t o n s ) i n 1975 and i s e x p e c t e d t o r e a c h 199,580,643 kg (2 20,000 tons) by the y e a r 19 80. The government's s p e n d i n g on t h e s e i t e m s , r e p o r t e d by FAO ( 8 ) , f o r t h e y e a r s 1963, 1964 and 1965 i s shown i n T a b l e I . A l t h o u g h more r e c e n t s u p p o r t i n g f i g u r e s are not a v a i l a b l e t o t h e w r i t e r , i t i s e s s e n t i a l t o p o i n t out t h a t t h e consumption o f p aper and p a p e r b o a r d i n N i g e r i a has r i s e n r e m a r k a b l y d u r i n g t h e p a s t decade. T h i s t r e n d c o n t i n u e s , , l a r g e l y as a r e s u l t o f t h e r e c e n t l y i n t r o d u c e d u n i v e r s a l f r e e p r i m a r y e d u c a t i o n i n the c o u n t r y , and t h e g e n e r a l advancement i n l i t e r a c y and s t a n d a r d o f l i v i n g . 1 2. Work by v a r i o u s r e s e a r c h e r s (4, 17, 18, 20, 26, 30, 27, 38, 51, 58, 59, 63, 65, 66, 68, 69, 70, 72, 74, 78) has i d e n t i f i e d t h e p o t e n t i a l of hardwood p u l p s f o r use i n f i b e r p r o d u c t s . C o n s e q u e n t l y , a t the p r e s e n t t i m e , hardwood p u l p s are b e i n g used more and more t o supplement the softwood raw m a t e r i a l r e s o u r c e . Even i n N o r t h A m e r i c a , s m a l l p e r c e n t a g e s o f hardwoods a r e b e i n g c o n t e m p l a t e d f o r use i n n e w s p r i n t manufacture ( 4 6 ) . The p r e s e n t s t u d y was c a r r i e d o u t w i t h t h e l i m i t e d o b j e c t i v e o f i n v e s t i g a t i n g the p r o p e r t i e s o f Gmelina a r b o r e a Roxb., a hardwood s p e c i e s grown e x t e n s i v e l y i n N i g e r i a , and c o n s i d e r i n g f u t u r e p o t e n t i a l o f t h i s m a t e r i a l f o r use i n the manufacture o f n e w s p r i n t . S i n c e t h e main component o f news- p r i n t i s some form o f m e c h a n i c a l p u l p , t h e major p a r t o f t h e s t u d y was concerned w i t h a s s e s s i n g the p o t e n t i a l o f Gmelina f o r t h i s t y pe o f p u l p . L a b o r a t o r y work has been c a r r i e d out t o determine the p r o p e r t i e s o f open d i s c h a r g e r e f i n e r p u l p from Gmelina and t h e s e have been compared t o t h o s e o f mech- a n i c a l p u l p s used f o r t h e manufacture o f n e w s p r i n t i n N o r t h A m e r i c a . I n v i e w o f t h e poor m e c h a n i c a l p r o p e r t i e s o f t h i s t y p e o f p u l p , t h r e e p o s s i b l e approaches t o u p g r a d i n g t h e s t r e n g t h p r o p e r t i e s have been e v a l u a t e d . These have i n c l u d e d p r e s t e a m i n g o f t h e c h i p s p r i o r t o r e f i n i n g w i t h o u t c h e m i c a l t r e a t m e n t as w e l l as p r e s t e a m i n g w i t h two d i f f e r e n t t y p e s o f c h e m i c a l p r e t r e a t m e n t s . I n o r d e r t o complete t h e p i c t u r e , a 3. b r i e f e v a l u a t i o n was a l s o c a r r i e d o u t t o a s s e s s t h e p o t e n t i a l o f the s p e c i e s as a raw m a t e r i a l f o r k r a f t p u l p . CHAPTER I I LITERATURE SURVEY G e n e r a l I n t r o d u c t i o n G melina, a member o f t h e Angiospermous f a m i l y , Verbenaceae, i s i n d i g e n o u s t o T r o p i c a l A s i a and A u s t r a l i a ( 4 8 ) . I t i s known by t h e f o l l o w i n g v e r n a c u l a r names - Gumhar, Sewan, Gomari, S h i v a n , S h i v a n i , Gumadi, Yemani, and i n e x o t i c p l a n t a t i o n s as Yemane o r Gmelina (57). Gmelina has been i n t r o d u c e d t o A f r i c a and C e n t r a l and South America (6) and, i n t h e s e p l a c e s , has been p u t t o a wide range o f u s e s : i n c o n s t r u c t i o n work, g e n e r a l c a r p e n t r y , p a c k a g i n g and i n the cheaper grades o f f u r n i t u r e . I t p e e l s w e l l and has been found t o be s u i t a b l e f o r use as c o r e s t o c k i n plywood manufacture (6, 1 6 ) , f o r match boxes and s p l i n t s ( 6 ) , and f o r c o n s t r u c t i o n plywood (16). C h i t t e n d e n e t a l . (26) c o n s i d e r e d Gmelina t o be an e x t r e m e l y p r o m i s i n g s p e c i e s f o r p u l p p r o d u c t i o n i n N i g e r i a and o t h e r t r o p i c a l c o u n t r i e s where s u i t a b l e g r owing c o n d i t i o n s f o r t h e s p e c i e s e x i s t . S i l v i c u l t u r e , P l a n t a t i o n E s t a b l i s h m e n t and Growth The s i l v i c u l t u r e o f Gmelina has been d i s c u s s e d i n a number o f d i f f e r e n t p u b l i c a t i o n s (10, 12, 5 7 ) . Gmelina i s e a s i l y e s t a b l i s h e d i n p l a n t a t i o n s because o f i t s a d a p t a b i l i t y t o a wide range o f s o i l and c l i m a t i c c o n d i t i o n s . I t f r u i t s r e g u l a r l y and p l e n t i f u l l y and the seeds have a h i g h g e r m i n a t i v e 4 5. power, which has been shown by Lamb (5 7) t o dec r e a s e w i t h the l e n g t h o f s t o r a g e p e r i o d . The c o s t o f e s t a b l i s h m e n t i n p l a n t - a t i o n s i s r e l a t i v e l y low and, as e s t i m a t e d by FAO ( 8 ) , amounted t o $82 t o $99 US d o l l a r s p e r a c r e i n N i g e r i a , i n 1968. The r a t e o f growth i s i n i t i a l l y f a s t , b u t d e c r e a s e s a f t e r t he f i r s t 7 y e a r s (57, 69). Palmer (69) e s t i m a t e d t h a t , g i v e n good gr o w i n g c o n d i t i o n s and a r o t a t i o n o f 7 t o 8 y e a r s , t h e p l a n t a t i o n a r e a r e q u i r e d t o s u s t a i n a 300 t/day (100,000 t/a) k r a f t p u l p m i l l would be 15,000 ha. A l t h o u g h a s p e c i e s r a t e o f growth i s a f u n c t i o n o f a m u l t i - p l i c i t y o f f a c t o r s , Gmelina i s g e n e r a l l y a b l e t o produce pulpwood i n 6 t o 10 y e a r s (8, 6 9 ) . A c c o r d i n g t o Obiaga and Wayman (65), under f a v o u r a b l e c o n d i t i o n s , Gmelina c o u l d produce a crop o f t i m b e r s i z e s u i t a b l e f o r pulpwood i n 3 t o 4 y e a r s a f t e r p l a n t i n g . They based t h i s d e d u c t i o n on the N i g e r i a n e x p e r i e n c e w i t h t h e s p e c i e s . As r e p o r t e d by Palmer (69) , the growth o f Gmelina i n N i g e r i a i s 84 m 3/ha (1,200 f t 3 / a c ) on poor sandy s o i l s a f t e r 12 y e a r s growth, 210 m 3/ha (3,000 f t 3 / a c ) on good c l a y or l a t e r i t e s o i l s a f t e r 12 y e a r s growth, and 252 m 3/ha (3,600 f t 3 / a c ) on the most f a v o r a b l e savanna s i t e s a f t e r 10 y e a r s growth. A maximum v a l u e o f 252 m 3/ha has been r e c o r d e d f o r the R a i n F o r e s t Zone a f t e r 8 .years growth. C h i t t e n d e n e t a l . (2 6) p o i n t e d o u t t h a t t h e s e v a l u e s c o r r e s p o n d t o a mean a n n u a l 6. in c r e m e n t o f 7 t o 31.5 m 3/ha/a, f o r h i g h f o r e s t a r e a s . Yeom and Sandrasegaran (92) summarized t h e Malayan e x p e r i e n c e w i t h Gmelina by i n d i c a t i n g t h a t t h e mean y i e l d from a p l o t p l a n t e d a t a s p a c i n g o f 10 x 10 f t (approx. 3 x 3 meters) i s o f t h e o r d e r o f 259 m 3/ha (3,700 f t 3 / a c ) between the ages o f 7 t o 9 y e a r s . These f i g u r e s , however, r e p r e s e n t i d e a l growth c o n d i - t i o n s , and i t has been p o i n t e d o u t (12) t h a t u n l e s s c a r e f u l a t t e n t i o n i s p a i d t o c l e a n c u l t i v a t i o n o f young s t a n d s , t h e growth and y i e l d o f t h e s p e c i e s a r e bound t o be poor. The p r i n c i p a l enemies o f Gmelina i n c l u d e p a r a s i t e s , i n s e c t p e s t s , f u n g a l d i s e a s e s and f r o s t , f i r e and h u r r i c a n e damage. Under any one o r more o f t h e s e c o n d i t i o n s , b o t h the growth and y i e l d of t h e s p e c i e s w i l l s u f f e r . Gmelina c o p p i c e s w e l l and i t s growth a f t e r the f i r s t c l e a r - f e l l i n g and subsequent second, t h i r d and even f o u r t h r o t a t i o n on the o r i g i n a l stump has shown no r e d u c t i o n i n y i e l d . As i n d i c a t e d by FAO ( 8 ) , a Gmelina p l a n t a t i o n may r e q u i r e r e p l a n t i n g o n l y once e v e r y 50 y e a r s . Wood and F i b e r P r o p e r t i e s Gmelina wood i s y e l l o w i s h - g r a y o r p i n k i s h - w h i t e , c h a n g i n g t o b r o w n i s h - y e l l o w w i t h age. As shown c l e a r l y i n F i g u r e 1, i t / i s d i f f u s e - p o r e d , f i r m and o f u n i f o r m d e n s i t y d e s p i t e t h e s p e c i e s f a s t growth r a t e . As r e p o r t e d (7, 93) i t has a d e n s i t y o f 497 kg/m 3 (31 l b / f t 3 ) a t 12% m o i s t u r e c o n t e n t , and 625 kg/m 3 (39 l b / f t 3 ) a t 50% m o i s t u r e c o n t e n t . 7. Palmer (69) r e p o r t e d a d e n s i t y range o f 380 t o 420 kg/m 3 (24 t o 26 l b / f t 3 ) . As p o i n t e d o u t by Lamb (5 7 ) , and o t h e r s ( 6 ) , t h e d e n s i t y o f Gmelina wood i s comparable t o t h a t o f B a l t i c redwood (P i n u s s i l v e s t r i s ) . The g r o s s wood and f i b e r m o r p h o l o g i c a l c h a r a c t e r - i s t i c s o f Gmelina have been d i s c u s s e d by v a r i o u s r e s e a r c h e r s (2, 7, 10, 30, 44, 67, 69, 70, 8 4 ) . I n T a b l e I I , d a t a on Gmelina f i b e r • c h a r a c t e r i s t i c s a r e g i v e n . C h i t t e n d e n e t a l . (26), p o i n t e d o u t t h a t t h e f i b e r c h a r a c t e r i s t i c s o f Gmelina a r e comparable t o th o s e o f o t h e r hardwoods, p a r t i c u l a r l y w i t h aspen ( P o p u l u s . t r e m u l o i d e s ) , b i r c h ( B e t u l a a l b a ) and v a r i o u s s p e c i e s o f E u c a l y p t u s . As i s common w i t h hardwoods, Gmelina has o n l y one k i n d o f f i b e r i n the growth zone. Softwoods g e n e r a l l y c o n t a i n two t y p e s - t h e f l e x i b l e e a r l y w o o d (EW) t r a c h e i d s , w i t h t h i n c e l l w a l l s , and the s t i f f e r l a t e w o o d (LW) t r a c h e i d s , w i t h t h i c k e r f i b e r w a l l s . The r e l a t i v e amounts o f t h e s e two t y p e s o f f i b e r components s t r o n g l y a f f e c t the y i e l d and q u a l i t y o f p u l p s . Thus a h i g h e r p r o p o r t i o n o f LW t r a c h e i d s r e l a t i v e t o the EW t r a c h e i d s p o r t i o n r e s u l t s i n a h i g h e r y i e l d o f p u l p p e r u n i t volume o f wood. F u r t h e r m o r e , t h e p r o p o r t i o n s o f LW and EW a f f e c t p u l p q u a l i t y t h r o u g h t h e d i f f e r e n c e i n t h e i r c e l l - w a l l t h i c k n e s s . A h i g h p r o p o r t i o n o f EW t r a c h e i d s r e s u l t s i n a b e t t e r f i b e r c o n f o r m a b i l i t y d u r i n g s h e e t f o r m a t i o n . F i b e r c o n f o r m a b i l i t y r e s u l t s i n l a r g e r f i b e r t o f i b e r c o n t a c t a r e a s , 8. t h u s e nhancing i n t e r f i b e r . b o n d i n g . C o n s e q u e n t l y , i t has a p o s i t i v e e f f e c t on t h e c h a r a c t e r i s t i c s o f a p u l p . On the o t h e r hand, p u l p s w i t h h i g h e r LW t r a c h e i d p r o p o r t i o n s are u s u a l l y h a r d and y i e l d b u l k y papers because LW f i b e r s do not conform r e a d i l y . N e v e r t h e l e s s , the f i b e r c h a r a c t e r i s t i c s o f Gmelina, as g i v e n i n T a b l e I I , enhance f i b e r c o n f o r m a b i l i t y and t h u s a l s o l e a d t o the f o r m a t i o n o f s h e e t s o f good d e n s i t y . P r e v i o u s P u l p i n g S t u d i e s A l i m i t e d number o f p u l p i n g s t u d i e s have been c a r r i e d o u t on Gmelina and a l m o s t a l l have been concerned w i t h the p o t e n t i a l o f t h e s p e c i e s f o r use i n t h e manufacture o f chemi- c a l o r s e m i c h e m i c a l p u l p s . A d e t a i l e d r e v i e w o f t h e s e s t u d i e s w i l l , t h e r e f o r e , n o t be a t t e m p t e d , but r a t h e r t h e i r main f i n d i n g s w i l l be summarized. I n 1961, Guha and Saxena (37) c a r r i e d o u t s u l f a t e p u l p i n g s t u d i e s of Gmelina. T h e i r s t u d i e s showed Gmelina s u l f a t e p u l p t o be s u i t a b l e f o r the manufacture o f w r i t i n g and wrapping p a p e r s . They a l s o c a r r i e d o u t a c h e m i c a l a n a l y s i s o f Gmelina wood and showed i t t o have a h i g h c e l l u - l o s e c o n t e n t , comparing f a v o r a b l y w i t h o t h e r m a t e r i a l s gener- a l l y used f o r papermaking. C h i t t e n d e n e t a l . (26) r e p o r t e d t h e r e s u l t s o f s u l f a t e and n e u t r a l s u l f i t e s e m i c h e m i c a l (NSSC) p u l p i n g t r i a l s o f Gmelina and showed t h a t t h e unbleached s u l f a t e p u l p c o u l d be used i n t h e p r o d u c t i o n o f l o w e r grades o f wrapping p a p e r s . 9. They a l s o showed t h e b l e a c h e d p r o d u c t s t o be s u i t a b l e f o r a wide range o f w r i t i n g and p r i n t i n g p a p e r s , w h i l e t h e NSSC p u l p would be s u i t a b l e , i n t h e unblea c h e d c o n d i t i o n , f o r t h e manufacture o f p a p e r b o a r d f o r c a r t o n s and b o a r d manufacture. They c o n s i d e r e d t h a t a r a t h e r h i g h e r q u a l i t y s e m i c h e m i c a l p u l p s h o u l d f i n d a p p l i c a t i o n f o r t h e manufacture o f l o w e r and i n t e r m e d i a t e grades o f book and magazine p a p e r s . Peh (72) o b t a i n e d good y i e l d s o f unbleached and b l e a c h e d s u l f a t e p u l p s o f Gmelina. H i s s t u d y showed t h a t t h e p h y s i c a l s t r e n g t h p r o p e r t i e s o f b l e a c h e d and u n b l e a c h e d s u l f a t e p u l p s from Gmelina were b e t t e r t h a n t h o s e o f t h e A u s t r a l i a n c ommercial E u c a l y p t s u l f a t e p u l p . He c a r r i e d o u t h i s s t u d y on Gmelina grown i n Malaya. Obiaga and Wayman (65), s t u d i e d the k i n e t i c s o f d e l i g n i f i c a t i o n o f Gmelina from N i g e r i a i n k r a f t and p o l y - s u l f i d e p u l p i n g . They demonstrated t h a t o v e r a Kappa number range o f 25 t o 34, p o l y s u l f i d e d i g e s t i o n s o f Gmelina r e s u l t e d i n p u l p y i e l d s o f 55 t o 64%. They found t h e s e v a l u e s t o be about 1 0 % . h i g h e r t h a n t h e y i e l d s o f k r a f t p u l p s i n t h e same Kappa number range. B a l l o n e t a l . (17) i n d i c a t e d t h a t u n b l e a c h e d y i e l d s o f the o r d e r o f 57 t o 5 8% c o u l d be a c h i e v e d from Gmelina by the s u l f a t e p u l p i n g p r o c e s s . T h e i r r e s u l t s d i f f e r m arkedly from t h o s e r e p o r t e d i n most l i t e r a t u r e and t h a t o b t a i n e d i n the p r e s e n t s t u d y , about 50%, but i s s i m i l a r t o t h a t r e p o r t e d by Palmer ( 6 9 ) , f o r P h i l i p p i n e t r i a l s d i g e s t e d f o r a s h o r t 10. time a t maximum t e m p e r a t u r e . B a l l o n e t a l . d i d not mention d e t a i l s o f t h e c o o k i n g c o n d i t i o n , b u t i t does appear t h a t t h e c h i p s were n o t f u l l y cooked. I f , i n d e e d , t h e c h i p s were undercooked, t h e n the low b l e a c h i n g c h e m i c a l r e q u i r e m e n t t h e y r e p o r t e d appears t o be i n c o n s i s t e n t . N e v e r t h e l e s s , t h e i r work showed t h a t the b l e a c h e d k r a f t p u l p o f Gmelina may s e r v e i n the p r o d u c t i o n o f good q u a l i t y bond and w r i t i n g p a p e r s . They c i t e d an u n p u b l i s h e d work by E s t u d i l l o and a s s o c i a t e s , on P h i l i p p i n e - g r o w n m a t e r i a l , w h i c h showed t h a t i n the s u l - f a t e p u l p i n g o f Gmelina, p u l p y i e l d i n c r e a s e d from 52.7 t o 60.4% w i t h an i n c r e a s e i n s u l f i d i t y up t o 45%. T h i s seems c o n s i s t e n t w i t h t h e work o f Obiaga and Wayman (65) , a l t h o u g h the c o n d i t i o n s o f t h e cook were not i n d i c a t e d . The p u l p s a l s o showed a p p r o x i m a t e l y t h e same degree o f b l e a c h a b i l i t y w i t h a l m o s t i d e n t i c a l permanganate numbers a t 11 ± 0.5. E s t u d i l l o e t a l . (30) s t u d i e d t h e e f f e c t s o f s u l - f i d i t y and l e n g t h o f c o o k i n g time on p u l p y i e l d , b l e a c h a - b i l i t y and m e c h a n i c a l p r o p e r t i e s o f Gmelina grown i n t h e P h i l l i p i n e s . They e s t a b l i s h e d the optimum p u l p i n g c o n d i t i o n s t o be a t 25.5% s u l f i d i t y and an a c t i v e a l k a l i o f 15.6%, u s i n g a l i q u o r t o wood r a t i o o f 4:1 and a 30 t o 90 minute c o o k i n g s c h e d u l e a t a maximum temp e r a t u r e o f 338°F (170°C). Palmer (69) r e p o r t e d p u l p i n g t r i a l s o f Gmelina o b t a i n e d from seven d i f f e r e n t c o u n t r i e s . The f o l l o w i n g were the major f i n d i n g s d e s c r i b e d i n h i s r e p o r t : 1. P u l p i n g t r i a l s by the s u l f a t e p r o c e s s showed t h a t d i g e s - t i o n w i t h about 15% a c t i v e a l k a l i a t 338°F (170°C) r e s u l t e d i n an un b l e a c h e d p u l p o f 50% y i e l d . The p u l p had good s t r e n g t h c h a r a c t e r i s t i c s and c o u l d be b l e a c h e d t o a h i g h degree o f b r i g h t n e s s a d o p t i n g f o u r d i f f e r e n t b l e a c h i n g sequences: CEHH, HEH, CEH and CEHD. The p u l p was found t o be comparable o r s u p e r i o r t o hardwood p u l p s such as t h o s e o f E u c a l y p t u s , b i r c h and p o p l a r , and t o be u s e f u l f o r w r i t i n g , p r i n t i n g , bond, o n i o n s k i n and wr a p p i n g p a p e r s . 2. I n t r i a l s by t h e NSSC p r o c e s s , between 66 and 76% o f unbleached p u l p was o b t a i n e d w i t h s a t i s f a c t o r y s t r e n g t h s f o r t h i s t y p e o f p u l p . The p u l p c o u l d be f u l l y b l e a c h e d o n l y by u s i n g a h i g h a p p l i c a t i o n o f c h l o r i n e , and t h e s t r e n g t h and b r i g h t n e s s c h a r a c t e r i s t i c s o f t h e f u l l y b l e a c h e d NSSC p u l p were comparable t o t h o s e o f b l e a c h e d s u l f a t e p u l p . W i t h lower a p p l i c a t i o n l e v e l s o f c h l o r i n e , a u s e f u l s e m i - b l e a c h e d p u l p was o b t a i n e d . 3. I n g e n e r a l , o v e r a wide range o f d r a i n a g e c h a r a c t e r i s t i c s (600 t o 200 Canadian s t a n d a r d f r e e n e s s ( C s f ) ) , a l l p r o p e r t i e s t h a t depend m a i n l y on t h e bonding o f f i b e r s ( t e n s i l e , b u r s t i n g and f o l d i n g s t r e n g t h s ) i n c r e a s e w i t h b e a t i n g , b u t t h e t e a r i n g s t r e n g t h remains f a i r l y c o n s t a n t . The Malayan t r i a l d i f f e r e d and showed a marked i n c r e a s e i n t e a r i n g s t r e n g t h w i t h i n c r e a s e d b e a t i n g . T h i s i n c r e a s e i n t e a r i n g s t r e n g t h w i t h i n c r e a s e d b e a t i n g r e p o r t e d f o r t h e Malayan t r i a l , however, appears u n r e a l i s t i c . 12. 4. I n s u l f i t e d i g e s t i o n s , r a t h e r s e v e r e c o n d i t i o n s were r e q u i r e d f o r p u l p i n g and the p u l p was i n f e r i o r t o s u l f a t e p u l p s i n s t r e n g t h c h a r a c t e r i s t i c s and, i n t h e case o f b l e a c h e d p u l p , i n b r i g h t n e s s . 5. C o l d soda s e m i c h e m i c a l p u l p s were o b t a i n e d i n y i e l d s o f about 80%. The p u l p s were b u l k i e r and weaker t h a n s u l f a t e p u l p s and a l s o more d i f f i c u l t t o b l e a c h t o a lo w e r b r i g h t - ness . Palmer and Gibbs ( 7 0 ) , i n 1974, found t h a t Gmelina s u l f a t e p u l p s c o u l d be b l e a c h e d t o a good b r i g h t n e s s f o l l o w - i n g a s i m p l e f o u r - s t a g e b l e a c h i n g sequence and demonstrated t h a t the b l e a c h e d s u l f a t e p u l p gave denser s h e e t s t h a n t h o s e o f hardwoods from Southern U n i t e d S t a t e s o f America and E u c a l y p t s from A u s t r a l i a . They a l s o showed t h e y i e l d o f Gmelina s u l f a t e p u l p s t o be comparable t o t h o s e o f hardwoods from t h e S o u t h e r n U n i t e d S t a t e s o f A m e r i c a , p u l p e d under s i m i l a r c o n d i t i o n s . A r e c e n t FAO s t u d y (10) showed t h a t i n t h e s u l f a t e p u l p i n g o f Gmelina, the consumption o f a c t i v e a l k a l i depended t o some e x t e n t on s p e c i e s p r ovenances, whereas NSSC p u l p i n g was not a f f e c t e d by s p e c i e s provenance o r p l a c e o f o r i g i n . Sosanwo (8 3) c a r r i e d o u t k r a f t and s u l f a t e - o x y g e n (two-stage) d i g e s t i o n s o f Gmelina c h i p s . He found t h a t u nbleached Gmelina k r a f t p u l p compared f a v o r a b l y i n p h y s i c a l p r o p e r t i e s t o unbleac h e d b i r c h k r a f t p u l p and t h a t t h e b l e a c h i n g o f t h e s u l f a t e p u l p was not a s s o c i a t e d w i t h a l o s s o f p u l p p h y s i c a l s t r e n g t h , t h u s c o n f i r m i n g an e a r l i e r o b s e r - v a t i o n by C h i t t e n d e n e t a l . (26). He a l s o showed Gmelina k r a f t and s u l f a t e - o x y g e n p u l p s t o have comparable p r o p e r t i e s . The s i n g l e m e c h a n i c a l p u l p i n g s t u d y on Gmelina r e p o r t e d i n the l i t e r a t u r e was t h a t c a r r i e d o u t by O r g i l l ( 68). I n t h i s s t u d y i t was shown t h a t i m p r e g n a t i n g Gmelina c h i p s w i t h a m i x t u r e o f sodium h y d r o x i d e (NaOH) and sodium s u l f i t e (Na2S03) p r i o r t o thermomechanical p u l p i n g (TMP) reduced power consumption, l o w e r e d s h i v e c o n t e n t and improved t h e s t r e n g t h p r o p e r t i e s o f t h e p u l p . The s t u d y a l s o suggested t h a t Gmelina thermomechanical p u l p would f i n d use i n t h e manufacture o f d i a p e r s and o t h e r d i s p o s a b l e p r o d u c t s where the main r e q u i r e m e n t o f t h e p u l p i s i t s a b i l i t y t o absorb l i q u i d under p r e s s u r e . O r g i l l d i d n o t c o n s i d e r the p o t e n t i a l o f t h e s p e c i e s f o r use i n n e w s p r i n t manufacture. M e c h a n i c a l P u l p i n g The term, m e c h a n i c a l p u l p , i s a g e n e r i c one and r e f e r s t o t h o s e p u l p s produced by the d i r e c t a t t r i t i o n o f wood by m e c h a n i c a l means. Thus c o n v e n t i o n a l s t o n e groundwood (SGW) p u l p , chemigroundwood p u l p and c h i p r e f i n e r m e c h a n i c a l p u l p s a l l f a l l i n t h i s c a t e g o r y . M e c h a n i c a l p u l p i n g p r o c e s s e s a r e c h a r a c t e r i z e d by e x t r e m e l y h i g h y i e l d (above 9 0%, based on wood) (89) , s i n c e t h e l i g n i n b i n d e r , w h i c h i s removed i n the case o f c h e m i c a l p u l p i n g , remains as an i n t e g r a l p a r t o f 14. the f i b e r i n m e c h a n i c a l p u l p s . M e c h a n i c a l p u l p i s t h e main component o f the n e w s p r i n t f u r n i s h and u n t i l f a i r l y r e c e n t l y , n e w s p r i n t was produced from a m i x t u r e o f 2 0 t o 30 p e r c e n t c h e m i c a l p u l p and 80 t o 70 p e r c e n t m e c h a n i c a l p u l p . The advent o f h i g h e r s t r e n g t h m e c h a n i c a l o r pseudomechanical p u l p s i n t h e l a s t few y e a r s has o f f e r e d some p o t e n t i a l f o r r e d u c i n g t h e c h e m i c a l p u l p c o n t e n t o f n e w s p r i n t f u r n i s h and i n one o r two c a s e s , i t has been p o s s i b l e t o e l i m i n a t e , c o m p l e t e l y , the c h e m i c a l p u l p component from n e w s p r i n t f u r n i s h . The b a s i c p r i n c i p l e s i n v o l v e d i n the manufacture o f t h e s e m e c h a n i c a l p u l p s a r e s i m p l e and, e s s e n t i a l l y , i n v o l v e the d i r e c t a t t r i t i o n o f wood i n a g r i n d i n g p r o c e s s (SGW), o r i n a r e f i n i n g p r o c e s s (RMP o r TMP), w i t h o r w i t h o u t t h e a d d i - t i o n o f r e l a t i v e l y s m a l l amounts o f c h e m i c a l s . These v a r i o u s p r o c e s s e s f o r the p r o d u c t i o n o f m e c h a n i c a l p u l p a r e b r i e f l y o u t l i n e d below. 1. Stone Groundwood (SGW) P r o c e s s The SGW p r o c e s s i n v o l v e s the a t t r i t i o n o f l o g s o f wood by p r e s s i n g them a g a i n s t t h e a b r a s i v e s u r f a c e o f a r o t a t i n g g r i n d s t o n e i n the p r e s e n c e o f w a t e r . By t h i s means, the wood i s r e d u c e d t o p u l p . The w a t e r c o o l s and l u b r i c a t e s t h e g r i n d i n g s u r f a c e and a l s o conveys t h e p u l p i n t o t h e p i t . The SGW p r o c e s s i s one o f random a t t r i t i o n and, as a r e s u l t , i s d i f f i c u l t t o b r i n g under t e c h n i c a l c o n t r o l . C o n s e q u e n t l y , groundwood p u l p s a r e s u b j e c t t o a wide range o f v a r i a t i o n i n 15. physical properties, one of the main contributing factors being the gradual wearing and consequent change i n shape of the stone surface c h a r a c t e r i s t i c s . Furthermore, a large number of grinders are required to supply the mechanical pulp requirements of modern newsprint machines. Thus the proper- t i e s of the pulp fed to the machine depend on the properties of the pulp produced at each i n d i v i d u a l grindstone. The SGW process causes extensive f i b e r damage and, as a consequence, the r e s u l t i n g pulps have r e l a t i v e l y poor strengths. Nevertheless, i t s high y i e l d of pulp of good bulk, high opacity and good p r i n t i n g properties, makes i t highly desirable for newsprint. The chemigroundwood process e s s e n t i a l l y involves a treatment of the wood raw material, i n grinder lengths, with chemicals p r i o r to grinding. To ensure adequate liquor pene- tration., the chemical treatment i s usually c a r r i e d out i n large cooking vessels at elevated temperature and pressure. A complete l i q u o r penetration, however, does not seem to be tenable with material i n grinder lengths, but i n general, the extent of penetration r e f l e c t s species anatomical differences. Nevertheless, the process e n t a i l s a sizeable c a p i t a l invest- ment and t h i s i s probably one of the main reasons for i t s lim i t e d acceptance. 16. 2. Ch i p R e f i n e r M e c h a n i c a l P u l p i n g a) C h i p R e f i n e r M e c h a n i c a l P u l p (RMP) Compared t o t h e SGW p r o c e s s , c h i p r e f i n e r m e c h a n i c a l p u l p i n g promotes t h e p r e s e r v a t i o n o f f i b e r l e n g t h , one o f t h e two f a c t o r s c o n s i d e r e d t o be e s s e n t i a l f o r t h e development o f a s t r o n g p u l p . I t has, however, been p o i n t e d o u t by P e t e r s o n and N e l s o n (74), and J a c k s o n (46 ) , t h a t the RMP p r o c e s s does no t do much t o enhance the bonding c h a r a c t e r i s t i c s o f a p u l p . C o n s e q u e n t l y , t h o s e p h y s i c a l p r o p e r t i e s o f paper w h i c h depend s o l e l y on t h e bonding p o t e n t i a l o f the f i b e r s and t h u s on t h e hydrodynamic s u r f a c e a r e a o f t h e p u l p as i t emerges from t h e m e c h a n i c a l p u l p i n g p r o c e s s , a r e n o t l i k e l y t o be s i g n i f i c a n t l y improved beyond t h e l e v e l o b t a i n e d w i t h SGW p u l p s . A more d e t a i l e d i n f o r m a t i o n on c h i p r e f i n e r mechani- c a l p u l p i s beyond the scope o f t h i s t h e s i s , b u t has been p u b l i s h e d e l s e w h e r e by Keays and Leask (50). b) Thermomechanical P r o c e s s (TMP) A l t h o u g h TMP has been known f o r a l o n g t i m e , i t s a p p l i c a t i o n had been l i m i t e d t o the manufacture o f b o a r d , f l o o r i n g and r o o f i n g f e l t s . I t i s o n l y d u r i n g t h e l a s t f i v e y e a r s t h a t TMP has been employed e x t e n s i v e l y i n t h e manufac- t u r e o f n e w s p r i n t grades (19). The l a s t two I n t e r n a t i o n a l M e c h a n i c a l P u l p i n g C o n f e r e n c e s (IMPC) (49) h i g h l i g h t e d the importance o f TMP t o t h e p u l p and paper i n d u s t r y . TMP has brought about a s i g n i f i c a n t improvement i n t h e p r o p e r t i e s o f 17. r e f i n e r m e c h a n i c a l p u l p s . A l t h o u g h , i n p r i n c i p l e , t h e TMP p r o c e s s i s s i m i l a r t o open d i s c h a r g e r e f i n i n g , i t d i f f e r s from i t i n two impor- t a n t a s p e c t s . I n c o n t r a s t t o c o n v e n t i o n a l c h i p r e f i n i n g , t h e c h i p s f o r TMP a r e p r e h e a t e d i n h i g h t e m p e r a t u r e steam i n t h e range 250 t o 260°F (121 t o 130°C) (19, 46, 47) f o r a p e r i o d o f 2 t o 3 m i n u t e s . F u r t h e r m o r e , t h e f i r s t r e f i n i n g s t a g e of the o p e r a t i o n i s a l s o c a r r i e d o u t a t e l e v a t e d p r e s s u r e o f about 30 p s i g t h u s e n s u r i n g h i g h t e m p e r a t u r e i n t h e r e f i n i n g zone, and t h e e l i m i n a t i o n o f problems a s s o c i a t e d w i t h steam g e n e r a t i o n i n the r e f i n e r . R e f i n i n g g e n e r a l l y p roceeds i n two s t a g e s , the p r e s s u r e i n t h e p r i m a r y s t a g e b e i n g above a t m o s p h e r i c i n o r d e r t o m a i n t a i n t h e p u l p t e m p e r a t u r e i n the range 240 t o 250°F (115 t o 121°C). The second s t a g e o f t h e p r o c e s s i s c a r r i e d out a t a t m o s p h e r i c p r e s s u r e as i n the case o f RMP. As r e p o r t e d ( 5 ) , t h r e e - s t a g e r e f i n i n g i s c a r r i e d o u t u s i n g one o f the two C-E Bauer TMP systems a t B l a n d i n , and a l s o a t t h e Bowater C a r o l i n a m i l l i n Catawba. The TMP p r o c e s s p r e s e r v e s f i b e r l e n g t h and a l s o enhances the development o f good bonding p o t e n t i a l . S i n c e most o f t h e c o n v e n t i o n a l p h y s i c a l p r o p e r t i e s o f m e c h a n i c a l p u l p s can be a s c r i b e d t o t h o s e p a r a m e t e r s , the p h y s i c a l p r o - p e r t i e s o f thermomechanical p u l p s a re g e n e r a l l y b e t t e r t h a n t h o s e o f open d i s c h a r g e r e f i n e r p u l p s and s i g n i f i c a n t l y s u p e r i o r t o t h o s e e x h i b i t e d by sto n e groundwood p u l p s . 18. c) S i g n i f i c a n c e o f C h i p R e f i n e r M e c h a n i c a l P u l p i n g Both t h e RMP and TMP p r o c e s s e s p e r m i t t h e manufacture o f good q u a l i t y p u l p from c h i p p e d f o r e s t and s a w m i l l r e s i d u e m a t e r i a l s and t h e r e b y b r i n g about a c o n s i d e r a b l e e x t e n s i o n i n f o r e s t r e s o u r c e u t i l i z a t i o n . T h i s i s p a r t i c u l a r l y s i g n i f i c a n t i n a r e a s where t h e r e i s s e r i o u s c o m p e t i t i o n f o r pulpwood, o r i n t h e P a c i f i c N o r t h w e s t c o a s t o f N o r t h A m e r i c a , where l o g g i n g and s a w m i l l o p e r a t i o n s g e n e r a t e l a r g e volumes of r e s i d u e mat- e r i a l s . The use o f r e s i d u e m a t e r i a l s f o r p u l p i n g has become phenomenal i n r e c e n t t i m e s and t h e t r e n d i s s t e a d i l y r i s i n g . F i g u r e 2 shows the t r e n d i n t h e use o f r e s i d u e m a t e r i a l f o r p u l p i n g i n B r i t i s h Columbia and Canada i n g e n e r a l (24). A p a r t from t h e e x t e n s i o n o f the raw m a t e r i a l base, r e f i n e r m e c h a n i c a l p u l p i n g p r o c e s s e s o f f e r t h e o p p o r t u n i t y f o r i n c o r p o r a t i n g a more e f f e c t i v e c h e m i c a l t r e a t m e n t t h a n i s p o s s i b l e w i t h t h e chemigroundwood p r o c e s s . As d i s c u s s e d by Keays and Leask ( 5 0 ) , a number o f c h e m i c a l s , i n c l u d i n g sodium h y d r o x i d e (NaOH), sodium b i s u l f i t e (NaHSOs) and sodium s u l f i t e (N«2S0 3) have been used on hardwoods w i t h b e n e f i c i a l e f f e c t s . Sodium b o r o h y d r i d e (NaHB4) may a l s o be used (36, 61, 7 5 ) , b u t i s e x t r e m e l y e x p e n s i v e . R e f i n e r m e c h a n i c a l p u l p s have g e n e r a l l y improved s t r e n g t h p r o p e r t i e s over s t o n e groundwood and t h e i r use p e r - m i t s a r e d u c t i o n i n t h e e x p e n s i v e c h e m i c a l p u l p component i n paper p r o d u c t s . As quoted by Keays and Leask ( 5 0 ) , s u c c e s s f u l 19. t r i a l s have been made on t h e p r o d u c t i o n o f n e w s p r i n t from 100% open d i s c h a r g e r e f i n e r groundwood. The n e w s p r i n t p r o - duced was, however, b u l k y and c o n s e q u e n t l y l a c k i n g i n b o n d i n g p o t e n t i a l and, t h e r e f o r e , not i d e a l l y a d a p t a b l e t o c u r r e n t l y used p r i n t i n g methods. Keays (49) c i t e d t h e p r o d u c t i o n o f TMP i n the H a l l s t a m i l l i n Sweden where i t was found t h a t when TMP r e p l a c e d 75% o f the s t o n e groundwood i n the manufac- t u r e o f 48.8 g/m2 (30 lb/3,000 f t 2 ) b a s i s w e i g h t n e w s p r i n t a t 840 meters (2,756 f t ) p e r minute machine speed, t h e c h e m i c a l p u l p component c o u l d be reduced from 22 t o 12%. The use o f 100% TMP has been s p e c u l a t e d upon (20, 60) and s e v e r a l m i l l s i n N o r t h A m e r i c a and S c a n d i n a v i a have run 10 0% TMP n e w s p r i n t f o r s h o r t p e r i o d s o f time (46). T h i s s i n g l e f u r n i s h not o n l y r e duces p r o d u c t i o n c o s t s , b u t a l s o d e c r e a s e s e n v i r o n m e n t a l problems a s s o c i a t e d w i t h t h e manufacture o f c h e m i c a l p u l p . O ther s i g n i f i c a n t c o n s i d e r a t i o n s i n f a v o r o f r e f i n e r m e c h a n i c a l p u l p i n g p r o c e s s e s i n c l u d e , among o t h e r s , t h e i r r e l a t i v e l y low l a b o r c o n t e n t and ease o f c o n t r o l . B e t t e r c o n t r o l r e s u l t s i n the p r o d u c t i o n o f p u l p s w i t h l e s s v a r i a - t i o n , w h i c h , i n t u r n , r e l a t e s t o more s t a b l e paper machine o p e r a t i o n . F u r t h e r c o n s i d e r a t i o n o f the s i g n i f i c a n c e o f the r e f i n e r m e c h a n i c a l p u l p i n g p r o c e s s e s i s beyond the scope o f the p r e s e n t s t u d y . C h i p p i n g F o r g r e a t e r o p e r a t i o n a l e f f i c i e n c y d u r i n g p u l p i n g , 20. i t i s e s s e n t i a l t o reduce pulpwood t o c h i p s , p r i o r t o f i b e r - i z i n g . An o v e r a l l summary o f the e f f e c t o f c h i p s p e c i f i c a - t i o n s i n p u l p p r o c e s s i n g i s g i v e n i n T a b l e I I I , w h i l e i n F i g u r e 3, a d i a g r a m a t i c r e p r e s e n t a t i o n o f a t y p i c a l c h i p i s shown. L i q u o r p e n e t r a t i o n , i n the case o f c h e m i c a l p u l p i n g , and w a t e r p e n e t r a t i o n , i n the case o f m e c h a n i c a l p u l p i n g , a r e r e l a t e d t o the t o t a l s u r f a c e a r e a o f t h e s t a r t i n g m a t e r i a l , and i s g e n e r a l l y b e t t e r t h e t h i n n e r t h e c h i p . The i n c i d e n c e o f d e b r i s o r r e j e c t m a t e r i a l s i n c r e a s e s w i t h c h i p t h i c k n e s s , t h e s i t u a t i o n b e i n g more c r i t i c a l i n the case o f hardwoods th a n f o r so f t w o o d s , because o f p e n e t r a t i o n problems. Chip l e n g t h i s i m p o r t a n t from t h e p a c k i n g d e n s i t y p o i n t o f v i e w d u r i n g t h e c h a r g i n g o f the d i g e s t e r , w h i l e c o r r u g a t i o n s and c r a c k s r e l a t e t o e f f e c t i v e c h i p t h i c k n e s s and a l s o enhance l i q u o r and water p e n e t r a t i o n . A l t h o u g h c o n v e n t i o n a l c h i p p e r s p r o d u c e c h i p s o f f a i r l y u n i f o r m s i z e , r a n g i n g from 1.6 t o 1.9 cm (0.6 t o 0.8 i n ) l o n g and 0.3 cm (0.1 i n ) t h i c k ( 6 1 ) , c h i p s may g e n e r a l l y be c l a s s i - f i e d , a c c o r d i n g t o s i z e , as o v e r - l a r g e , o v e r - t h i c k , a c c e p t s , p i n c h i p s , and f i n e s i n a s c r e e n i n g o p e r a t i o n . O v e r - l a r g e c h i p s a re g e n e r a l l y r e - c h i p p e d and o v e r - t h i c k c h i p s p a s s e d t h r o u g h c o m p r e s s i o n r o l l s t o cause them t o c r a c k , w h i l e p i n c h i p s and f i n e s a r e used as f u e l . I n p r e s e n t t i m e s , however, most m i l l s o b t a i n p a r t o r a l l o f t h e i r c h i p s u p p l y from o u t - s i d e s o u r c e s and c h i p q u a l i t y i s not n e c e s s a r i l y under t h e i r 21. c o n t r o l . C h i p P r e t r e a t m e n t s The p r i m a r y o b j e c t i v e o f p r e t r e a t m e n t o f c h i p s p r i o r t o r e f i n i n g o r m e c h a n i c a l f i b e r i z i n g i s t o a c h i e v e a s o f t e n - i n g o f the l i g n i n o r i n t e r f i b e r b onding m a t e r i a l , t h e r e b y f a c i l i t a t i n g f i b e r s e p a r a t i o n and t h e subsequent development o f p u l p . T h i s may g e n e r a l l y be a c h i e v e d t h r o u g h steam o r c h e m i c a l p r e t r e a t m e n t , o r a c o m b i n a t i o n o f b o t h . I t has been shown by Rydholm (79) t h a t adequate c h i p p r e t r e a t m e n t has b e n e f i c i a l e f f e c t s on f i b e r l e n g t h p r e s e r v a t i o n , as w e l l as on t h e energy r e q u i r e m e n t f o r f i b e r i z i n g the m a t e r i a l . Chem- i c a l p r e t r e a t m e n t s a l s o a f f e c t t h e c h a r a c t e r i s t i c s o f t h e r e s u l t i n g p u l p s i n t h e p o s i t i v e d i r e c t i o n . 1. P r e t r e a t m e n t by Steaming The t e m p e r a t u r e dependence o f m e c h a n i c a l p r o p e r t i e s o f wood has been d i s c u s s e d a t l e n g t h by Rydholm ( 7 9 ) . I n t h i s book, i t was p o i n t e d o ut t h a t w e t t e r wood shows a l e s s marked tem p e r a t u r e dependence w h i l e t h e r e v e r s e c o n d i t i o n e x i s t s f o r t h e s w e l l i n g and r e s i d u a l e l a s t i c i t y p r o p e r t i e s o f wood. The e x p l a n a t i o n f o r the wood m e c h a n i c a l s t r e n g t h - t e m p - e r a t u r e r e l a t i o n may be based on the s o f t e n i n g range o f l i g n i n w h i c h , as quoted by Rydholm (79) and A t a c k ( 1 5 ) , o c c u r s i n t h e range 329 t o 347°F (165 t o 175°C). I t i s n e c e s s a r y t o p o i n t out a t t h i s j u n c t u r e t h a t the p r e s e n c e o f w a t e r may n e c e s s a r - i l y a l s o depress o r broaden t h e s o f t e n i n g i n t e r v a l o f l i g n i n . The s o f t e n i n g e f f e c t o f water on wood a t room temp- e r a t u r e i s w e l l known and i l l u s t r a t e d by t h e d i f f e r e n c e i n m e c h a n i c a l s t r e n g t h t e s t v a l u e s on s m a l l c l e a r specimens o f wood. As i n d i c a t e d by I l o a b a c h i e (45) w o r k i n g on T e r m i n a l i a i v o r e n s i s ( I d i g b o ) , w i t h the e x c e p t i o n o f impact b e n d i n g r e - s i s t a n c e , a l l o t h e r s t r e n g t h p r o p e r t i e s o f wood d e c r e a s e w i t h an i n c r e a s e i n m o i s t u r e c o n t e n t i n the z e r o t o f i b e r s a t u r a - t i o n p o i n t ( f s p ) range. T h i s i s p o s s i b l y due t o t h e s p l i t t i n g of hydrogen bonds w i t h i n t h e wood and t h e subsequent s w e l l i n g o f t h e c a r b o h y d r a t e p o r t i o n s o f t h e wood. C h e m i c a l l y , water does n o t seem t o have a s i g n i f i c a n t e f f e c t on wood a t normal room t e m p e r a t u r e . A t p r e s t e a m i n g t e m p e r a t u r e s , however, t h e r e may o c c u r s p l i t t i n g o f a c e t y l groups o f h e m i - c e l l u l o s e s a t t h e g l y c o s i d i c bonds of carbohy- d a t e s ; the much-debated l i g n i n - c a r b o h y d r a t e bonds w h i c h are p r o b a b l y a l s o g l y c o s i d i c o r e t h e r bonds (61); and the i n t r a - l i g n i n bonds w h i c h are m a i n l y b e n z y l - a l k y l e t h e r bonds (54, 79)^. The i n c i d e n c e o f t h e s e r e s u l t s i n a d e c r e a s e i n pH and c o n s e q u e n t l y a r a p i d removal o f some c a r b o h y d r a t e m a t e r i a l and l i g n i n by m i l d a c i d h y d r o l y s i s (42, 54, 61, 79). As p o i n t e d o u t by Rydholm (79) , a c i d h y d r o l y s i s i s pH-dependent and i t s r a t e may be a p p r e c i a b l e even a t tempera- t u r e s below 212°F (100°C), i f pH i s s i g n i f i c a n t l y low. T h i s was c o n f i r m e d by K r a t z l and P a s z n e r ( 5 4 ) , who showed t h a t a c o n t i n u o u s d e g r a d a t i o n o f the l i g n i n macromolecule o c c u r s a t 212°F (100°C). They based t h e i r f i n d i n g s on t h e f a c t t h a t monomeric b u i l d i n g u n i t s such as c o n i f e r y l a l d e h y d e , v a n i l l i n , g u a i a c o l , t h e 3-ether and o t h e r minor p r o d u c t s were i s o l a t e d from wood a t a t e m p e r a t u r e o f 212°F (100°C). C e l l u l o s e t e n d s t o r e s i s t a c i d h y d r o l y s i s b e t t e r t h a n the h e m i c e l l u l o s e s ( 6 1 ) . T h i s i s due p r i m a r i l y t o the s u p e r - m o l e c u l a r s t r u c t u r e o f c e l l u l o s e because o f wh i c h c e l l u l o s e i s n o t r e a d i l y a c c e s s i b l e even t o p o l a r s o l v e n t s d e s p i t e i t s p o l a r i t y . However, t h e s w e l l i n g o f t h e car b o h y - d r a t e f r a c t i o n o f wood f o l l o w i n g t h e f o r m a t i o n o f a d d i t i o n compounds o f c e l l u l o s e t e n d t o "open up" t h e s t r u c t u r e , t h e r e - by e n hancing i t s a v a i l a b i l i t y t o p o l a r r e a g e n t s . A c i d h y d r o - l y s i s , n e v e r t h e l e s s , causes a d e g r a d a d a t i o n o f t h e wood sub- s t a n c e and t h u s a d v e r s e l y a f f e c t s the y i e l d o f p u l p . The a p p l i c a t i o n o f sodium b o r o h y d r i d e (NaHBi,) f o r t h e purpose o f c o n t r o l l i n g t h e r m a l d e g r a d a t i o n d u r i n g the t r e a t m e n t o f wood c h i p s has been d i s c u s s e d by P i e t r o ( 7 5 ) . The same r e s u l t may a l s o be a c h i e v e d i f c h i p s a r e impregnated w i t h a weak a l k a l i n e s o l u t i o n p r i o r t o p r e s t e a m i n g . I t has a l s o been shown by Hoglund and B o d i n (42) t h a t a p p l i c a t i o n o f sodium s u l f i t e (Na2S0 3) a t c o n c e n t r a t i o n s up to 18% based on bone d r y wood w e i g h t p r e v e n t s d i s s o l u t i o n o f woody m a t e r i a l . I n the p r o c e s s , t h e N a 2 S 0 3 a c t s as a b u f f e r i n g agent a g a i n s t a u t o c a t a l y t i c a c t i o n o f o r g a n i c a c i d s r e s u l t i n g from the s p l i t t i n g o f a c e t y l s and u r o n i c a c i d s from wood. 24. The u l t i m a t e e f f e c t o f p r e s t e a m i n g p r e t r e a t m e n t i s to reduce f i b e r c l e a v a g e and t h u s p r e s e r v e f i b e r l e n g t h , and t o cause r u p t u r e , p r e f e r e n t i a l l y on t h e o u t e r p a r t s o f t h e f i b e r w a l l . A compromise tem p e r a t u r e i s , however, n e c e s s a r y as too h i g h a s o f t e n i n g t e m p e r a t u r e may cause f i b e r s e p a r a t i o n t o t a k e p l a c e i n the l i g n i n - r i c h m i d d l e l a m e l l a (ML) t h e r e b y r e d u c i n g the bonding p o t e n t i a l o f the f i b e r s . On the o t h e r hand, l o w e r s o f t e n i n g t e m p e r a t u r e s may cause t h e f i b e r s t o s e p a r a t e a t the S i l a y e r (15, 34, 41, 60) t h e r e b y compro- m i s i n g t h e p r e s e r v a t i o n o f f i b e r l e n g t h , w h i l e , as p o i n t e d o u t by Hoglund e t a l . ( 4 1 ) , e n h a n c i n g f i b e r . b o n d i n g p o t e n t i a l . A p r e s t e a m i n g t e m p e r a t u r e o f 250 t o 260°F (121 t o 127°C) i s g e n e r a l l y c o n s i d e r e d adequate f o r optimum s t r e n g t h d e v e l o p - ment. As demonstrated by G i e r t z . ( 3 5 ) , when s o f t e n e d a t t h e h i g h temperature p r e v a i l i n g i n the r e f i n i n g p r o c e s s , the p r i m a r y w a l l i s r o l l e d back a l o n g t h e f i b e r as a s l e e v e and s i m u l t a n e o u s l y the h e l i x o f t h e Si l a y e r c r a c k s and f i b r i l s and l a m e l l a e a re p e e l e d o f f . T h i s o c c u r r e n c e r e s u l t s i n i n c r e a s e d f i b e r f l e x i b i l i t y , w h i c h has been shown by Fo r g a c s (31) t o be an i m p o r t a n t f e a t u r e f o r s t r o n g m e c h a n i c a l p u l p s . T h i s i s so because t h e r e s u l t i n g r i b b o n s and f i b r i l s have a h i g h bonding p o t e n t i a l . P r e s t e a m i n g p r e t r e a t m e n t g e n e r a l l y a l s o r e s u l t s i n a d a r k e n i n g o f t h e p u l p . However, as i n d i c a t e d by Keays and Leask (50), and B y s t e d t and Vardheim (23), t h i s b r i g h t e n i n g l o s s may be c o n t r o l l e d by s u i t a b l y b a l a n c i n g time and p r e s s - ure d u r i n g t h e p r e s t e a m i n g o p e r a t i o n , o r , as quoted by A t a c k (15) and Leask (60), by q u i c k l y r e d u c i n g t h e t e m p e r a t u r e o f t h e p u l p as i t emerges from t h e r e f i n e r . A l t e r n a t i v e l y , i n c o r p o r a t i n g a m i l d t r e a t m e n t w i t h a b r i g h t e n i n g agent a t some s t a g e o f t h e r e f i n i n g p r o c e s s w i l l a l s o a c h i e v e a s i m i - l a r r e s u l t . 2. C h e m i c a l P r e t r e a t m e n t V a r i o u s c h e m i c a l s are known t o a c h i e v e t h e d e s i r e d s o f t e n i n g o f the i n t e r - f i b e r b o n d i n g m a t e r i a l and t h e r e b y b r i n g about a more e f f i c i e n t f i b e r s e p a r a t i o n w i t h a minimum r e q u i r e m e n t o f energy. C h e m i c a l s are a b l e t o a c h i e v e s o f t - e n i n g o f i n t e r - f i b e r m a t e r i a l e i t h e r by d i r e c t l y c a u s i n g i t t o s o l u b i l i z e o r by t h e i r d i f f e r e n t i a l s w e l l i n g a c t i o n on t h e wood s u b s t a n c e . The p u l p s from c h e m i c a l l y p r e t r e a t e d softwood c h i p s have been shown by Hoglund and B o d i n (42) t o have comparable m e c h a n i c a l s t r e n g t h p r o p e r t i e s t o those o f c h e m i c a l p u l p s . The b e s t r e s u l t s i n terms o f p h y s i c a l s t r e n g t h p r o - p e r t i e s seem t o be t h o s e o b t a i n e d by t r e a t m e n t s w i t h a l k a l i n e h y d r o x i d e s (41, 49, 86) and t h e improvement i n s t r e n g t h has been shown by Beecher e t a l . (20) t o i n c r e a s e w i t h a l k a l i c o n c e n t r a t i o n . T h i s i s m a i n l y because a l k a l i h y d r o x i d e s a c t as s w e l l i n g agents f o r most forms o f c e l l u l o s e , and as s o l - v e n t s f o r m o d i f i e d and degraded forms o f c e l l u l o s e , hemi- c e l l u l o s e s and l i g n i n s . Treatment w i t h an aqueous s o l u t i o n o f sodium h y d r o - x i d e (NaOH) has been shown by K r u g e r e t a l . (55) and Rydholm (79) t o have a c o o k i n g a c t i o n on wood and t h u s r e s u l t s i n a y i e l d o f between 85 t o 94% on wood. Y i e l d l o s s f o l l o w i n g c a u s t i c p r e t r e a t m e n t may a l s o be e x p l a i n e d by the f a c t t h a t a l k a l i n e h y d r o l y s i s o f m o n o x i d i z e d c e l l u l o s e may r e s u l t i n the s p l i t t i n g o f f of one g l u c o s e u n i t a t a time i n the form o f s a c c h a r i n i c a c i d ( p e e l i n g ) , o r i n a random h y d r o l y t i c c l e a v a g e o f t h e a c e t y l l i n k a g e i n c e l l u l o s e ( 6 1 ) . The former c o n d i t i o n i s f a v o r e d a t t e m p e r a t u r e s o v e r 15 8°F (70°C), w h i l e th e l a t t e r i s f a v o r e d a t t e m p e r a t u r e s above 302°F (150°C), such as i s e n c o u n t e r e d i n the s u l f a t e p u l p i n g p r o c e s s . Y i e l d l o s s due t o d e g r a d a t i o n o f c a r b o h y d r a t e and l i g n i n f r a c t i o n s by a c i d h y d r o l y s i s a t e l e v a t e d t e m p e r a t u r e s has been d i s c u s s e d e a r l i e r under the e f f e c t o f p r e s t e a m i n g p r e t r e a t m e n t . C a u s t i c p r e t r e a t m e n t i s g e n e r a l l y accompanied by a r a p i d s w e l l i n g o f t h e wood. The s w e l l i n g i s , however, l i m i t e d t o t h e c a r b o h y d r a t e f r a c t i o n as l i g n i n tends t o r e s t r i c t i t . T h i s s w e l l i n g d i f f e r e n t i a l r e s u l t s i n the b u i l d - u p o f c o n s i d - e r a b l e s t r e s s e s w i t h i n the f i b e r s t r u c t u r e , and f o l l o w i n g the k n e a d i n g a c t i o n o f the r e f i n i n g p r o c e s s , t h e more l i g n i f i e d o u t e r p o r t i o n s of the f i b e r , a l r e a d y under t e n s i o n , p e e l o f f . T h i s amounts t o i n c r e a s e d f i b e r f l e x i b i l i t y and a l s o exposes the more h y d r o p h y l i c c a r b o h y d r a t e p a r t s which have been shown by F o r g a c s ( 3 1 ) , G i e r t z (35) and Rydholm (79) t o have good bond i n g p o t e n t i a l . I n a s i m i l a r manner, as noted f o r t h e p r e s t e a m i n g t r e a t m e n t , a l k a l i p r e t r e a t m e n t u s u a l l y a l s o r e s u l t s i n p u l p d i s c o l o r a t i o n r a n g i n g from p a l e y e l l o w t o dark brown. The r e s u l t i n g p u l p s c o n s e q u e n t l y need t o be b r i g h t e n e d . A s a t i s - f a c t o r y b r i g h t n e s s may be a c h i e v e d w i t h a s i n g l e s t a g e a p p l i - c a t i o n o f sodium p e r o x i d e (Na202)/ c a l c i u m h y p o c h l o r i t e ( C a ( O C l ) 2 ) , o r sodium h y p o c h l o r i t e (NaOCl); o r by i n c o r p o r a t - i n g a b r i g h t e n i n g agent a t some st a g e i n the r e f i n i n g p r o c e s s . T h i s adds t o t h e c o s t o f p r o d u c t i o n , b u t the g a i n s i n p u l p q u a l i t y and the e x p e c t e d s a v i n g s i n energy r e q u i r e m e n t t e n d t o j u s t i f y the added c o s t . The e f f e c t o f c h e m i c a l p r e t r e a t m e n t on the c h a r a c t e r i s t i c s o f open d i s c h a r g e and p r e s s u r e r e f i n e r p u l p s a r e shown i n Table IV. From t h i s t a b l e , i t i s e v i d e n t t h a t c h e m i c a l t r e a t m e n t , i n the case o f open d i s c h a r g e r e f i n - i n g , r e s u l t e d i n h i g h e r d e n s i t y , s t r e n g t h and b r i g h t n e s s v a l - ues, b u t d e c r e a s e d o p a c i t y . I n the case o f p r e s s u r i z e d r e f i n - i n g , the r e s u l t s a r e more d i f f i c u l t t o i n t e r p r e t s i n c e the p u l p s a r e a t d i f f e r e n t f r e e n e s s l e v e l s . I t seems, however, t h a t a l t h o u g h sodium s u l f a t e would have a modest e f f e c t on s t r e n g t h c h a r a c t e r i s t i c s , i t has a n e g a t i v e e f f e c t on b r i g h t - ness . S i g n i f i c a n c e o f F i b e r Length and F i b e r F r a c t i o n s The importance o f f i b e r l e n g t h as a fundamental f a c t o r c o n t r o l l i n g t h e p h y s i c a l p r o p e r t i e s o f a p u l p has l o n g been r e c o g n i z e d . More r e c e n t , the s i g n i f i c a n c e o f some o t h e r f i b e r c h a r a c t e r i s t i c s has been c l a r i f i e d . The r a t i o between c e l l 28. lumen w i d t h and c e l l w a l l t h i c k n e s s , and p a r t i c u l a r l y the r a t i o o f f i b e r l e n g t h t o f i b e r w i d t h ( a s p e c t r a t i o ) have been shown by Dinwoodie (28) t o a f f e c t p u l p and paper p r o p e r t i e s t o a g r e a t e r e x t e n t t h a n f i b e r l e n g t h a l o n e . I n v e s t i g a t i o n s by the Regie I n d u s t r i e l l e de l a C e l l u l o s e C o l o n i a l s (RICC), on West A f r i c a n T r o p i c a l Woods, c i t e d by P e t e r i (73), showed t h a t no r e l a t i o n e x i s t e d between the l e n g t h s o f f i b e r s and the t e n - s i l e and b u r s t i n g s t r e n g t h s , b u t t h a t r e l a t i o n s h i p s e x i s t e d between these p r o p e r t i e s and the c o e f f i c i e n t s o f f l e x i b i l i t y o f t h e f i b e r s . As p o i n t e d o u t by P a n s h i n and de Zeeuw (7 1 ) , and as q u o t e d by F o rgacs (31), f i b e r l e n g t h i s i m p o r t a n t i n s o f a r as a minimum f i b e r l e n g t h i s r e q u i r e d t o p r o v i d e s u f f i c i e n t b o nding s u r f a c e f o r e f f e c t i v e s t r e s s d i s t r i b u t i o n over the e n t i r e a r e a o f the s h e e t . The same a u t h o r s a l s o p o i n t e d o u t t h a t paper c o n s i s t i n g o f s h o r t f i b e r s w i l l o f f e r l e s s r e s i s - t a nce t o p u l l - o u t because s h o r t f i b e r s have more f r e e f i b e r ends per u n i t volume o f p u l p . I n a r e v i e w o f the e f f e c t o f f i b e r l e n g t h on s t r e n g t h p r o p e r t i e s , F o r g a c s (31) showed t h a t the e f f e c t o f f i b e r l e n g t h on p r o p e r t i e s o t h e r than t e a r was secondary and f u r t h e r i n d i c a t e d t h a t the wet web s t r e n g t h and the t e a r i n g s t r e n g t h , b u r s t s t r e n g t h , b r e a k i n g l e n g t h , b u l k and a i r r e s i s t a n c e o f l a b o r a t o r y handsheets made from a wide range of m e c h a n i c a l p u l p s are a l m o s t w h o l l y dependent on s t r u c t u r a l c o m p o s i t i o n , and c o u l d be p r e d i c t e d w i t h c o n s i d e r a b l e a c c u r a c y from th e L- and S - f a c t o r . T h i s was i l l u s t r a t e d by J a c k s o n (46), i n Table V. A l t h o u g h a number o f t e c h n i q u e s can be used t o i d e n t i f y a l e n g t h and shape f a c t o r , the F o r g a c s ' Length p r L - f a c t o r was d e f i n e d (31) as t h a t f r a c t i o n o f p u l p r e t a i n e d on the 48 mesh screen' d u r i n g a Bauer McNett f r a c t i o n a t i o n , w h i l e the F o r g a c s 1 Shape or S - f a c t o r was d e f i n e d as the hydrodynamic s p e c i f i c s u r f a c e of the 48/100 mesh f r a c t i o n . From T a b l e V, r e f e r r e d t o above, i t i s c l e a r t h a t S - f a c t o r p l a y s a more s i g n i f i c a n t r o l e i n d e t e r m i n i n g the p r o p e r t i e s o f SGW p u l p t h a n i n t h e case o f TMP where b o t h L- and S - f a c t o r seem t o have e q u a l i m p o r t a n c e . The t a b l e a l s o shows t h a t those p r o p e r t i e s w hich depend on f i b e r bonding p o t e n t i a l , f o r example, b u l k , b u r s t i n g s t r e n g t h , and b r e a k i n g l e n g t h , p r i m a r i l y depend on S - f a c t o r , whereas t e a r depends p r i m a r i l y on L - f a c t o r . I n g e n e r a l , however, a number o f f a c t o r s combine t o determine the f i n a l c h a r a c t e r i s t i c s o f a p u l p . These, as c i t e d by S c h u t t (81) i n c l u d e f i b e r d i m e n s i o n s , f i b e r s t r e n g t h , f i b e r c o n f o r m a b i l i t y , s u r f a c e a r e a , s w o l l e n s p e c i f i c volume, bonding a r e a , b o n d i n g s t r e n g t h p e r u n i t o f bonded a r e a , d i s t r i b u t i o n o f bonds (shee t f o r m a t i o n ) , and s t r e s s d i s t r i b u - t i o n . P u l p B l e n d i n g C l a s s i c a l c h e m i c a l p u l p i n g p r o c e s s e s g i v e a r e l a - t i v e l y low y i e l d o f p u l p ; c o n s e q u e n t l y , the p u l p s are expen- s i v e and, t h e r e f o r e , h i g h - g r a d e f o r some c a t e g o r i e s o f use. 30. F u r t h e r m o r e , the m e c h a n i c a l p r o p e r t i e s o f c h e m i c a l p u l p s may g e n e r a l l y exceed t h o s e r e q u i r e d i n some paper p r o d u c t s . Mech- a n i c a l p u l p i n g p r o c e s s e s have a v e r y s i g n i f i c a n t y i e l d advan- tage o v e r t h e c h e m i c a l p u l p i n g p r o c e s s e s , b u t t h e r e s u l t i n g p u l p s a r e r e l a t i v e l y weak f o r most a p p l i c a t i o n s . T h i s i s p a r t i c u l a r l y t r u e i n the case o f s t o n e groundwood p u l p . Mech- a n i c a l p u l p s , however, i n f l u e n c e paper s u r f a c e and p r i n t i n g p r o p e r t i e s i n t h e p o s i t i v e d i r e c t i o n (46, 91). The b l e n d i n g o f p u l p s , t h e r e f o r e , i s i m p o r t a n t , n o t o n l y i n making a v a i l - a b l e a m a t e r i a l o f a s u i t a b l e q u a l i t y f o r a g i v e n paper p r o - d u c t , but a l s o from the c o s t - s a v i n g p o i n t o f view. The b l e n d i n g o f Gmelina s u l f a t e p u l p w i t h l o n g - f i b e r s u l f a t e p u l p s t o enhance t h e m e c h a n i c a l s t r e n g t h p r o p e r t i e s o f t h e former had been c o n t e m p l a t e d by C h i t t e n d e n e t a l . ( 2 6 ) . P r i n t i n g p apers are e x p e c t e d t o e x h i b i t a s u i t a b l e c o m b i n a t i o n o f p r i n t a b i l i t y , p h y s i c a l and m e c h a n i c a l s t r e n g t h p r o p e r t i e s . The b l e n d i n g o f c h e m i c a l and m e c h a n i c a l p u l p s f o r the p r o d u c t i o n o f n e w s p r i n t , t h e r e f o r e , demands c a r e f u l c o n s i d e r a t i o n and compromise. T h i s i s because, as i l l u s t r a t e d by Wahren (91) , t h e r e i s a c l o s e r e l a t i o n s h i p between mechani- c a l and o p t i c a l p r o p e r t i e s . P u l p b l e n d i n g may be a c h i e v e d i n a v a r i e t y o f ways, depending upon what c o n d i t i o n s a p p l y . Where t h e aim i s t o improve th e m e c h a n i c a l s t r e n g t h o f s h o r t - f i b e r p u l p s w i t h those o f l o n g - f i b e r p u l p s , the wood raw m a t e r i a l f o r the 31. d i f f e r e n t t y p e s may be b l e n d e d p r i o r t o p u l p i n g (32, 39, 76) o r d u r i n g t h e b e a t i n g o p e r a t i o n . I n some c a s e s , t h e p u l p s may be beaten s e p a r a t e l y and t h e n b l e n d e d ( 3 9 ) . The major component o f t h e n e w s p r i n t f u r n i s h i s m e c h a n i c a l p u l p , w h i c h may be up.to 75 t o 80%, the r e m a i n i n g 25 t o 20% b e i n g chemi- c a l p u l p . The p r o p o r t i o n s may, however, be v a r i e d depending on the p r o p e r t i e s o f the p u l p s t o be b l e n d e d , and/or a n t i c i - p a t e d p r o d u c t q u a l i t y . F o r example, Paper I n d u s t r i e s C o r p o r - a t i o n o f t h e P h i l i p p i n e s produces n e w s p r i n t from 100% hardwood p u l p s u s i n g 60% r e f i n e r m e c h a n i c a l p u l p and 40% s e m i - b l e a c h e d k r a f t p u l p ( 2 5 ) . The a p p l i c a t i o n o f l i n e a r programming meth- ods f o r a g r e a t e r e f f i c i e n c y o f b l e n d i n g o p e r a t i o n s was d i s - c u ssed by F o s t e r ( 3 2 ) . CHAPTER I I I EXPERIMENTAL WORK I n t r o d u c t i o n The e n t i r e range o f m e c h a n i c a l p u l p s o b t a i n a b l e by r e f i n i n g were produced from Gmelina a r b o r e a Roxb., by simu- l a t i o n o f b o t h open d i s c h a r g e and p r e s s u r i z e d r e f i n i n g on l a b o r a t o r y equipment. I n t h e case o f s i m u l a t e d p r e s s u r i z e d r e f i n i n g , t h r e e c o n d i t i o n s were used. The f i r s t one simu- l a t e d c o n v e n t i o n a l TMP, and t h e o t h e r two s i m u l a t e d chemi- c a l l y p r e t r e a t e d TMP u s i n g NaOH i n one case and N a 2 S 0 3 i n the o t h e r . The p h y s i c a l p r o p e r t i e s o f a l l p u l p s were e v a l u a t e d and TAPPI s t a n d a r d handsheets were produced f o r t h e e v a l u a - t i o n o f m e c h a n i c a l and o p t i c a l p r o p e r t i e s . S i n c e t h e s p e c i f i c energy consumption i n r e f i n i n g and the d r a i n a g e c h a r a c t e r - i s t i c s o f the p u l p s were known, t h i s p e r m i t t e d i n t e r p o l a t i o n o f the p h y s i c a l p r o p e r t y d a t a t o a g i v e n l e v e l o f e i t h e r energy i n p u t o r d r a i n a g e c h a r a c t e r i s t i c . F o r compa r i s o n , s i m i l a r d a t a were a l s o o b t a i n e d on SGW p u l p s p r o d u c e d on t h e West Coast o f Canada for;.use i n n e w s p r i n t . As n e w s p r i n t i n N o r t h A m e r i c a g e n e r a l l y c o n s i s t s o f 25% c h e m i c a l p u l p ( k r a f t o r s u l f i t e ) and 75% SGW, handsheets were a l s o produced from m i x t u r e s o f Gmelina m e c h a n i c a l p u l p and k r a f t p u l p i n the r a t i o s 75:25, 80:20 and 85:15. The p r o p e r t i e s o f the s i m u l a t e d n e w s p r i n t handsheets were then 32 compared t o t h o s e o f handsheets produced from West Coast SBK and SGW. However, s i n c e t h i s s i t u a t i o n i m p l i e s t h a t a m i l l p r o d u c i n g such n e w s p r i n t would o p e r a t e w i t h market SBK (which i s e x p e n s i v e and would, t h e r e f o r e , a f f e c t m i l l p r o f i t a b i l i t y a d v e r s e l y ) , t h e a l t e r n a t i v e would be t o con- s i d e r an i n t e g r a t e d m i l l w i t h i t s own s o u r c e o f c h e m i c a l p u l p . To c o v e r t h i s p o s s i b i l i t y , a t h i r d s e t o f s i m u l a t e d n e w s p r i n t s h e e t s were made u s i n g Gmelina f o r b o t h t h e c h e m i c a l p u l p and t h e m e c h a n i c a l p u l p . Source o f M a t e r i a l s and M a t e r i a l s S t o r a g e The Gmelina wood used f o r t h e p r e s e n t s t u d y was grown i n t h e former Mid-Western p a r t o f N i g e r i a , c u r r e n t l y known as B e n d e l S t a t e o f N i g e r i a . I t was t h e r e m a i n i n g p o r - t i o n o f a sample used i n an e a r l i e r s t u d y i n E a s t e r n Canada. Logs o f Gmelina measuring about 2.4 meters (8 f e e t ) l o n g and 15 t o 25 cm (6 to 10 i n c h e s ) d i a m e t e r a r r i v e d unbarked i n Vancouver i n good c o n d i t i o n , e x h i b i t i n g an average m o i s t u r e c o n t e n t o f 95%. The l o g s were s t o r e d a t the Western F o r e s t P r o d u c t s L a b o r a t o r y (WFPL) and t h e i r m o i s t u r e c o n t e n t was m a i n t a i n e d by s p r i n k l e r i r r i g a t i o n u n t i l t h e y were r e q u i r e d f o r c h i p p i n g . C h i p p i n g and Chip H a n d l i n g P r i o r t o c h i p p i n g , t h e l o g s were debarked m a n u a l l y and c u t i n t o 0.6 t o 0.9 meter (2 t o 3 f o o t ) s e c t i o n s , as governed by such f e a t u r e s as prominent k n o t s o r c r o o k e d n e s s . Each s e c t i o n was then s p l i t a x i a l l y i n t o f o u r p i e c e s w i t h an axe and a c l u b t o p r o v i d e m a t e r i a l h a v i n g s u i t a b l e d i m e n s i o n s f o r the p r e p a r a t i o n o f c h i p s . C h i p p i n g was c a r r i e d o u t a t the B r i t i s h Columbia I n s t i t u t e o f Technology (BCIT), u s i n g an e x p e r i m e n t a l , 30 i n d i a m e t e r , t w o - k n i f e , CAE c h i p p e r , s e t t o produce 5/8 i n l o n g c h i p s . The c h i p s were s c r e e n e d u s i n g a c h i p s c r e e n w i t h a v e r t i c a l g y r a t o r y m o t i o n . F i n e s and o v e r s i z e c h i p s were d i s - c a r d e d a n d.accepts s t o r e d i n p o l y t h e n e bags a t 42°F (6°C) and 76% r e l a t i v e h u m i d i t y . M e c h a n i c a l P u l p i n g Hardwoods i n g e n e r a l have s h o r t e r f i b e r l e n g t h s t h a n softwoods and c o n s e q u e n t l y have been used t o a much l e s s e r e x t e n t i n SGW p u l p manufacture. Open d i s c h a r g e r e f i n i n g may be a r e a s o n a b l e a l t e r n a t i v e f o r m e c h a n i c a l p u l p i n g o f Gmelina but t h e poor b o n d i n g p o t e n t i a l o f such p u l p s would l i m i t t he e x t e n t t o which t h e p u l p p o t e n t i a l s t r e n g t h might be r e a l i z e d The b e s t approach, t h e r e f o r e , appears t o be TMP, p o s s i b l y i n c o n j u n c t i o n w i t h c h e m i c a l p r e t r e a t m e n t . A l t h o u g h a s u i t a b l e p i l o t p l a n t f o r TMP was not a v a i l a b l e f o r t h e p r e s e n t s t u d y , a r e a s o n a b l e a p p r o x i m a t i o n o f TMP was at t e m p t e d by p r e s t e a m i n g the c h i p s i n an e x p e r i - m e n t a l d i g e s t e r and th e n r a p i d l y t r a n s f e r r i n g them t o a 12- i n c h S p r o u t Waldron l a b o r a t o r y open d i s c h a r g e r e f i n e r , w h i c h had p r e v i o u s l y been h e a t e d t o the b o i l i n g p o i n t o f w a t e r . 35. The e x p e r i m e n t a l work was c a r r i e d o u t t o c o v e r t h e e n t i r e range o f p u l p s c a p a b l e o f b e i n g produced by r e f i n i n g . Thus, b o t h open d i s c h a r g e and p r e s s u r i z e d r e f i n i n g were s i m u l a t e d . I n t h e l a t t e r c a s e , the e f f e c t o f c h e m i c a l p r e t r e a t m e n t was a l s o e v a l u a t e d . The v a r i o u s t r e a t m e n t s c a r r i e d o u t are o u t l i n e d i n Ta b l e VI... I n each c a s e , t h e e q u i v a l e n t wet w e i g h t o f 908 g (2 l b ) bone d r y w e i g h t o f c h i p s was t r e a t e d p r i o r t o f i b e r - i z i n g . As many r e f i n e r p a s s e s as were n e c e s s a r y t o o b t a i n p u l p s h a v i n g s i m i l a r d r a i n a g e c h a r a c t e r i s t i c s t o t h o s e o f SGW p u l p s used i n the manufacture o f n e w s p r i n t , 100 ± 2 0 ml (Csf) (46) were made i n each c a s e . As r e f i n i n g proceeded, r e f i n e r p a sses t o be s t u d i e d i n d e t a i l were i d e n t i f i e d and s u f f i c i e n t amounts o f p u l p s r e p r e s e n t i n g them were withdrawn f o r s t u d y . P u l p E v a l u a t i o n 1. L a t e n c y Removal L a t e n c y r e f e r s t o t h e p r e s e n c e o f l a t e n t s t r e n g t h i n r e f i n e r p u l p s and a r i s e s as a r e s u l t o f a c o m b i n a t i o n o f h i g h l y k i n k e d and c u r l e d f i b e r e x i t i n g from a hot r e f i n e r and e x p e r i e n c i n g temperature shock (46) . The shock r e l a t e s t o the temp e r a t u r e d i f f e r e n c e between t h e r e f i n i n g zone and the r e f i n e d s t o c k c h e s t . The k i n k e d f i b e r s t e n d t o s e t i n t h e i r c u r l e d c o n d i t i o n and a r e un a b l e t o a c h i e v e the same degree o f o p t i c a l c o n t a c t o r bonding as t h e y would i f t h e y were s t r a i g h t e n e d o u t . L a t e n c y may a l s o r e s u l t i f t h e p u l p i s d r i e d t o any degree, as shown by Sk e e t and A l l a n ( 8 2 ) . P u l p s e x h i b i t i n g l a t e n c y o n l y e x h i b i t p a r t of t h e i r f u l l p o t e n t i a l s t r e n g t h and, t h e r e f o r e , r e q u i r e r e v i v a l by a d i s p e r s i o n o p e r a t i o n a t h i g h t e m p e r a t u r e . As demonstrated by Skeet and A l l a n ( 8 2 ) , a 15 min (1,800 r ev) d i s i n t e g r a t i o n a t 85°F (29°C) i n a s t a n d a r d d i s i n t e g r a t o r i s s u f f i c i e n t t o s t r a i g h t e n t h e k i n k e d f i b e r s and t h u s p e r m i t a p u l p t o e x h i b i t i t s f u l l p o t e n t i a l s t r e n g t h . The l a t e n c y removal o p e r a t i o n d e s c r i b e d above was c a r r i e d o u t on the Gmelina m e c h a n i c a l p u l p s a t a temp e r a t u r e o f 85°F (29°C) u s i n g a s t a n d a r d d i s i n t e g r a t o r . The o p e r a t i o n l a s t e d 15 min. 2. D e b r i s Content F o l l o w i n g h o t d i s i n t e g r a t i o n , t h e p u l p s were s c r e e n e d on a 150-mesh f l a t s c r e e n f o r measurement o f d e b r i s o r r e j e c t c o n t e n t . T h i s p r o p e r t y i s g e n e r a l l y e x p r e s s e d as a p e r c e n t a g e and p r o v i d e s an i n d i c a t i o n o f how w e l l p r e t r e a t m e n t and r e f i n - i n g o p e r a t i o n s have s e p a r a t e d t h e i n d i v i d u a l f i b e r s i n t h e wood. The d e b r i s c o n t e n t s o f t h e d i f f e r e n t p u l p samples a r e g i v e n i n Ta b l e V I . 3. F r e e n e s s F r e e n e s s , though d i f f i c u l t t o d e f i n e , i s a s t a n d a r d p u l p t e s t t h a t p r o v i d e s an i n d i c a t i o n o f t h e d r a i n a g e c h a r - a c t e r i s t i c s o f a s u s p e n s i o n o f f i b e r s . As p o i n t e d o u t ( 6 1 ) , and as quoted by Kwei and Garceau (5 6 ) , i t i s m a i n l y a meas- ure of the f i n e s w h i c h p a s s e d t h r o u g h t h e 200-mesh s c r e e n . The v a l u e o b t a i n e d from the f r e e n e s s t e s t i s , t o a f i r s t a p p r o x i m a t i o n , i n v e r s e l y p r o p o r t i o n a l t o the bonding p o t e n - t i a l o f a p u l p . F r e e n e s s t e s t i n g was c a r r i e d o u t i n accordance w i t h T227os-58 o f TAPPI S t a n d a r d s (88), u s i n g a f r e e n e s s t e s t e r . The r e s u l t o f the t e s t i s termed Canadian s t a n d a r d f r e e n e s s ( C s f ) , and i s g e n e r a l l y r e p o r t e d i n m i l l i l i t e r s ( m l ) . The d r a i n a g e c h a r a c t e r i s t i c s o f t h e p u l p s produced d u r i n g t h i s i n v e s t i g a t i o n were measured by f r e e n e s s t e s t s and t h e s e d a t a are g i v e n i n T a b l e V I . 4. Y i e l d W i t h t h e s t e a d y d e c r e a s e i n the a v a i l a b i l i t y o f pulpwood, y i e l d o f p u l p from t h e c u r r e n t l y used p u l p i n g p r o - c e s s e s i s becoming more and more a c r i t i c a l c o n s i d e r a t i o n . Y i e l d s from t h e d i f f e r e n t p r e t r e a t m e n t s , u s i n g t h e same d r y w e i g h t o f c h i p s as was r e f i n e d d u r i n g the manufacture o f m e c h a n i c a l p u l p s , were d e t e r m i n e d f o r c h i p s t r e a t e d i n the way g i v e n i n T a b l e V I . A known w e i g h t of c h i p s from each t r e a t m e n t was p u l p e d s e p a r a t e l y i n a b l e n d e r and the r e s u l t - i n g p u l p washed and made i n t o a pad. The pads were d r i e d o v e r n i g h t a t 221°F (105°C). Y i e l d was c a l c u l a t e d based on bone dry w e i g h t o f c h i p s p u l p e d . The r e s u l t s o f y i e l d d e t e r m i n a t i o n a r e a l s o g i v e n i n Table V I . 38. 5. F i b e r L e n g t h C l a s s i f i c a t i o n The i m p o r t a n c e o f f i b e r l e n g t h and f i b e r l e n g t h f r a c t i o n s i n t h e d e t e r m i n a t i o n o f p u l p c h a r a c t e r i s t i c s has been d i s c u s s e d i n an e a r l i e r s e c t i o n . F i b e r c l a s s i f i c a t i o n was c a r r i e d o u t i n accordance w i t h T233os-75 o f TAPPI S t a n - dards (88), u s i n g a Bauer-McNett C l a s s i f i e r . S c r e e n s i z e s were R14, 14/28, 28/48, 48/100 and 100/200. Average f i b e r l e n g t h measurements, f o r the s c r e e n f r a c t i o n s , were c a r r i e d o u t by means o f a p r o j e c t i o n m i c r o s c o p e , and t h e i r m o i s t u r e - f r e e w e i g h t s were d e t e r m i n e d . Weighted f i b e r l e n g t h ( L ) , was c a l c u l a t e d from t h e r e l a t i o n ( 8 8 ) : _ W i & i + W2&2 + W3&3 + wi+A i> + W5&5 ^ • Where 11, Z2, £ 3 , £ it and £ 5 are t h e average l e n g t h s i n mm o f f i b e r s i n t h e r e s p e c t i v e f r a c t i o n s , W i , W 2 , w 3 and wi* a r e t h e m o i s t u r e - f r e e w e i g h t s o f pads from each f r a c t i o n , and w 5 i s o b t a i n e d , by d i f f e r e n c e , from t h e r e l a t i o n : .W = o r i g i n a l m o i s t u r e - f r e e w e i g h t o f p u l p sample c l a s s i f i e d . The r e s u l t s o f the Bauer McNett c l a s s i f i c a t i o n o f t h e d i f f e r - e n t t y p e s o f p u l p a r e g i v e n i n Ta b l e V I I , w h i l e i n F i g u r e s 4 th r o u g h 7 ph o t o m i c r o g r a p h s o f the p u l p s a re shown. As n o t e d above, F o r g a c s has i n d i c a t e d t h a t most o f the p h y s i c a l p r o p e r t i e s o f m e c h a n i c a l p u l p s can be r e l a t e d t o the s o - c a l l e d L-and S - f a c t o r s ( 3 1 ) . The d e t e r m i n a t i o n o f L - f a c t o r i s based on t h e Bauer-McNett l o n g f i b e r , R48, f r a c - t i o n , w h i l e S - f a c t o r i s quoted as the f r e e n e s s o f t h e Bauer- McNett P48/100 f r a c t i o n . The v a l u e s o f L~and S - f a c t o r s d e t e r m i n e d . f o r t h e p u l p s produced d u r i n g t h e s e i n v e s t i g a t i o n s a r e g i v e n i n Ta b l e V I I I . S u l f a t e P u l p i n g S u l f a t e o r k r a f t p u l p i n g i n v o l v e s the d i g e s t i o n o f wood under a l k a l i n e c o n d i t i o n s . The response o f Gmelina t o s u l f a t e p u l p i n g was e v a l u a t e d i n the l a b o r a t o r y by d i g e s t i n g the e q u i v a l e n t o f 4.0 kg (8.8 l b ) bone d r y w e i g h t o f c h i p s under t h e f o l l o w i n g c o n d i t i o n s : L i q u o r t o wood r a t i o 4:1 A c t i v e a l k a l i i n w h i t e l i q u o r 14.7% A c t i v e a l k a l i on wood 15.5% S u l f i d i t y 24.6% Maximum te m p e r a t u r e 338°F (170°C) Time t o maximum temp e r a t u r e 90 min Time a t maximum te m p e r a t u r e 120 min These c o n d i t i o n s are comparable t o t h o s e i d e n t i f i e d by Palmer (69) and E s t u d i l l o e t a l . (30) as b e i n g s u i t a b l e f o r p r o d u c i n g good q u a l i t y s u l f a t e p u l p f rom Gmelina. A t the t e r m i n a t i o n o f t h e cook, t h e d i g e s t e r was blown, and t h e p u l p washed and s c r e e n e d on a 150-mesh f l a t s c r e e n . D u r i n g s c r e e n i n g , some foaming was o b s e r v e d . C h i t t e n d e n e t a l . ( 2 6 ) , e a r l i e r made a s i m i l a r o b s e r v a t i o n 40. and a t t r i b u t e d i t t o t h e h i g h r e s i n c o n t e n t o f t h e s p e c i e s . The y i e l d o f p u l p was 50.05%, and t h e d e b r i s o r r e - j e c t c o n t e n t was as h i g h as 2.65%. The r e j e c t s c o n s i s t e d m a i n l y o f i n c o m p l e t e l y p u l p e d k n o t s . 1. Kappa Number o f S u l f a t e Pulp, The Kappa number i s an i n d e x o f t h e r e s i d u a l l i g n i n i n a c h e m i c a l p u l p . I t i s , t h e r e f o r e , a measure o f the degree o f d e l i g n i f i c a t i o n a c h i e v e d i n a cook, and t h u s r e p r e s e n t s a c o n v e n i e n t base f o r t h e comparison o f such p u l p c h a r a c t e r i z a - t i o n parameters as y i e l d , s c r e e n i n g s , b r i g h t n e s s and o t h e r p h y s i c a l p r o p e r t i e s . The d e t e r m i n a t i o n o f b l e a c h i n g c h e m i c a l s r e q u i r e m e n t , p a r t i c u l a r l y f o r t h e i n i t i a l c h l o r i n a t i o n s t a g e , i s a l s o based on Kappa number. As d e f i n e d i n TAPPI S t a n d a r d s (88 ) , t h e Kappa number i s t h e number o f m i l l i l i t e r s o f O.IN p o t a s s i u m permanganate (KMnOit) s o l u t i o n consumed p e r gram o f m o i s t u r e - f r e e p u l p under c o n d i t i o n s s p e c i f i e d i n the s t a n d a r d . The d e t e r m i n a t i o n was c a r r i e d o u t i n accordance w i t h T236m-6 (88), and a v a l u e o f 16 was o b t a i n e d f o r the Gmelina k r a f t p u l p . As i n d i c a t e d by Rydholm (79)., f o r a hardwood s u l f a t e p u l p , t h i s v a l u e c o r r e - sponds t o 2.08 p e r c e n t r e s i d u a l l i g n i n . 2. S e m i - b l e a c h i n g o f S u l f a t e P u l p The s u l f a t e p u l p was s e m i - b l e a c h e d i n a t h r e e - s t a g e , CEH ( C h l o r i n a t i o n , E x t r a c t i o n and H y p o c h l o r i t e ) b l e a c h i n g 41. sequence. A b r i g h t n e s s o f 77 t o 80 E l r e p h o r e f l e c t a n c e , as d e t e r m i n e d a t 45 7 nm w a v e l e n g t h on t h e g l a z e d s i d e o f hand- s h e e t , was a c h i e v e d . a) C h l o r i n a t i o n Stage The c h o i c e o f c h l o r i n e f o r use i n t h i s s t a g e was based on t h e f a c t t h a t c h l o r i n e and o t h e r h a l o g e n s are c a p a b l e o f r e n d e r i n g l i g n i n s o l u b l e t h r o u g h a r o m a t i c s u b s t i t u t i o n i n aqueous a l k a l i ( p a r t i a l l y i n water) by r e a c t i o n a t room temp- e r a t u r e . C h l o r i n e - w a t e r a t a c o n c e n t r a t i o n o f 3.5 8% on the d r y w e i g h t o f p u l p was added, w i t h s t i r r i n g , t o t h e p u l p sample. C h l o r i n e c o n c e n t r a t i o n on p u l p i s g e n e r a l l y d e t e r - mined by c o n s i d e r a t i o n o f Kappa, Roe C h l o r i n e o r Permangan- a t e numbers o r any o t h e r e q u i v a l e n t p a r a m e t e r s . As c i t e d by Rydholm (79), Roe C h l o r i n e number r o u g h l y d e s c r i b e s t h e c h l o r i n e demand e x p r e s s e d as.a p e r c e n t a g e o f t h e p u l p . Roe C h l o r i n e number may, however, be i n f l u e n c e d by the p r e s e n c e o f r e s i n and, on a c c o u n t o f t h i s , Kappa number i s g e n e r a l l y p r e f e r r e d . C h l o r i n a t i o n l a s t e d 50 min d u r i n g w h i c h t i m e the temperature was m a i n t a i n e d a t 70°F (21°C). The y i e l d o f the p u l p a f t e r c h l o r i n a t i o n and washing was 96.5%, and t h e r e s i - d u a l l i q u o r had a pH o f 2. The low pH i s due t o t h e forma- t i o n o f h y p o c h l o r o u s a c i d (HOC1) d u r i n g t h e l i g n i n s u b s t i t u - t i o n and e x c i t a t i o n r e a c t i o n s (61, 77). The same works showed t h a t HOC1 i s a s t r o n g o x i d i z i n g agent f o r c e l l u l o s e and may cause i t s o r g a n i c o x i d a t i o n , t h e r e b y p r e d i s p o s i n g i t t o a l k a l i n e d e g r a d a t i o n , a l t h o u g h a l k a l i n e h y d r o l y s i s does n o t r e a d i l y o c c u r under normal c o n d i t i o n s o f b l e a c h i n g , b u t would under more severe c o n d i t i o n s such as may e x i s t d u r i n g c h e m i c a l p u l p i n g p r o c e s s e s . I t i s i m p o r t a n t t o p o i n t o ut t h a t c h l o r i n e i s non- s p e c i f i c under the p r e v a i l i n g c h l o r i n a t i o n c o n d i t i o n s and i t s a t t a c k on c e l l u l o s e , w h i l e u n l i k e l y , cannot be e x c l u d e d . When o x i d i z e d c e l l u l o s e i s a t t a c k e d by c h l o r i n e , c a r b o n y l and c a r - b o x y l groups a r e formed, as shown i n F i g u r e 8. The p r e s e n c e o f t h e s e groups i n g l y c o s i d e u n i t s has been shown by Rydholm (79) and o t h e r s ( 7 7 ) , and a r e b e l i e v e d t o have an i m p o r t a n t e f f e c t on f u r t h e r r e a c t i v i t y o f g l y c o s i d i c l i n k a g e s . I n g e n e r a l , r e a c t i v i t y i n c r e a s e s w i t h . t h e i n t r o d u c t i o n o f -OH, -CO, and -COOH groups i n t o t h e a n h y d r o g l u c o s e u n i t . T h i s c o n d i t i o n p redominates at.pH 2 (77) l e a d i n g t o o x i d a t i v e random d e p o l y m e r i z a t i o n o f i n d i v i d u a l c e l l u l o s e c h a i n s . Together w i t h l o s s o f f i n e s d u r i n g p u l p washing a f t e r c h l o r - i n a t i o n , t h i s a c c o u n t s f o r t h e l o s s o f y i e l d a f t e r t h e c h l o r - i n a t i o n s t a g e . b) E x t r a c t i o n Stage E x t r a c t i o n was c a r r i e d o u t u s i n g sodium h y d r o x i d e (NaOH) s o l u t i o n a t a c o n c e n t r a t i o n o f 2.14% on p u l p . S t i r r i n g was c o n t i n u e d t h r o u g h o u t t h e e x t r a c t i o n p e r i o d o f 2 0 min, d u r i n g which t i m e t h e temperature was m a i n t a i n e d c o n s t a n t a t 149°F (65°C). The y i e l d was 97.2%. The a l k a l i charge f o r e x t r a c t i o n g e n e r a l l y depends on t h e e f f i c i e n c y of t h e p r e c e d i n g wash i n removing HC1 and c h l o r o l i g n i n . I n commercial o p e r a t i o n , Rydholm (79) c o n s i d - e r e d a c o n c e n t r a t i o n o f 20 t o 25 kg (9 t o 11 l b ) o f NaOH p e r ton o f p u l p t o be a normal charge f o r b o t h s u l f a t e and s u l - f i t e p u l p s . c) H y p o c h l o r i t e Stage C a l c i u m h y p o c h l o r i t e ( C a ( O C l ) 2 ) was used a t a concen- t r a t i o n o f 0.25% on p u l p . The st a g e l a s t e d 9 0 min d u r i n g w h i c h p e r i o d t h e te m p e r a t u r e was m a i n t a i n e d a t 95°F (35°C). The p u l p was s t i r r e d t h r o u g h o u t t h e e n t i r e p e r i o d and t h e r e s u l t i n g y i e l d was 99.3%. Handsheet Making and E v a l u a t i o n The g e n e r a l p r i n c i p l e s c o n c e r n i n g , and t h e v a r i a b l e s a f f e c t i n g the p r e p a r a t i o n o f l a b o r a t o r y handsheets have been e x h a u s t i v e l y d i s c u s s e d by S c h u t t (80, 81). Handsheets were p r e p a r e d d u r i n g t h e i n v e s t i g a t i o n i n accordance w i t h T205os-71 (88) , u s i n g a S t a n d a r d B r i t i s h Hand- sheet machine. I n t h e case o f . t h e m e c h a n i c a l p u l p s , t h e hand- s h e e t s were produced a f t e r t h e p u l p s had been hot d i s i n t e - g r a t e d . The handsheets were produced a t a w e i g h t o f 1.20 g ± 5% ( m o i s t u r e - f r e e b a s i s ) , c o r r e s p o n d i n g t o a b a s i s w e i g h t o f 60 g/m2. Sheet c o n d i t i o n i n g was c a r r i e d o u t a t 50.0 ± 2.0% RH and 73.4 ± 1 .8°F (23.0 ± 1.0°C). A l l w e i g h i n g and t e s t i n g , e x c e p t wet web s t r e n g t h t e s t i n g , was c a r r i e d out i n the c o n d i - t i o n i n g room. TAPPI s t a n d a r d p r o c e d u r e s were adopted a l l t h r o u g h . I n t h e case o f each p r o p e r t y , t e n o b s e r v a t i o n s were made. The c a l c u l a t i o n s were based on the f o r m u l a s g i v e n i n t h e Appendix. The r e s u l t s o f t h e s e t e s t s a r e g i v e n i n T a b l e s V I , IX, X, X I , X I I and X I I I . CHAPTER IV RESULTS AND DISCUSSION M e c h a n i c a l P u l p s from Gmelina Data g e n e r a t e d from t h e t e s t i n g o f l a b o r a t o r y hand- s h e e t s , made from t h e Gmelina m e c h a n i c a l p u l p s produced a re g i v e n i n Table V I , f o r t h e m e c h a n i c a l s t r e n g t h and o p t i c a l p r o p e r t i e s . The v a l u e s o b t a i n e d f o r t h e v a r i o u s p h y s i c a l p r o p e r t i e s were p l o t t e d a g a i n s t t h e i r r e s p e c t i v e d r a i n a g e c h a r a c t e r i s t i c s . Because a m e a n i n g f u l comparison o f the p h y s i c a l p r o p e r t i e s o f t h e v a r i o u s t r e a t m e n t s can o n l y be made under c o n d i t i o n s o f e q u i v a l e n t d r a i n a g e o r e q u i v a l e n t energy a p p l i c a t i o n , t h e v a l u e s a t a g i v e n l e v e l o f d r a i n a g e (90 ml Cs f ) were d e t e r m i n e d by i n t e r p o l a t i o n from the e x p e r i m e n t a l data,.and a re g i v e n i n Table IX. A f r e e n e s s o f 90 ml C s f r e p r e s e n t s a - r e a s o n a b l e d r a i n a g e l e v e l f o r N o r t h American m e c h a n i c a l p u l p s i n t e n d e d f o r use i n n e w s p r i n t manufacture. V a r i o u s a s p e c t s o f t h e m e c h a n i c a l p u l p s p r e p a r e d are d i s c u s s e d below. Y i e l d Compared t o t h e y i e l d v a l u e s o f c h e m i c a l p u l p s , w h i c h a r e g e n e r a l l y i n t h e range 4 0 t o 5 0%, m e c h a n i c a l p u l p s e x h i b i t y i e l d s i n ex c e s s o f 90%, v a r i a t i o n s about t h i s l e v e l b e i n g g e n e r a l l y r e l a t e d t o wood c o m p o s i t i o n , p r e s e n c e o f e x t r a c t i v e s and p r e t r e a t m e n t . The l a r g e d i f f e r e n c e i n y i e l d between c h e m i c a l and m e c h a n i c a l p u l p s i s due t o t h e f a c t t h a t w h i l e c h e m i c a l p u l p s a r e produced by p r o c e s s e s i n v o l v i n g de- g r a d a t i o n and s o l u b i l i z a t i o n o f l i g n i n , i n m e c h a n i c a l p u l p s , l i g n i n remains an i n t e g r a l p a r t o f t h e f i b e r c h e m i c a l s t r u c - t u r e . I n T a b l e V I , t h e y i e l d s f o l l o w i n g the d i f f e r e n t c h i p t r e a t m e n t s a re g i v e n . A y i e l d o f 9 6 . 8 % was o b t a i n e d f o r t h e u n t r e a t e d sample, A, and 9 5 . 7 % f o r the presteamed sample, B. The 1 % d i f f e r e n c e i n y i e l d f o r t h e s e two cases may be due t o t h e f a c t t h a t , w h i l e i n b o t h c a s e s some water s o l u b l e s and f i n e s were l o s t , i n B an a d d i t i o n a l ' l o s s o f wood su b s t a n c e was, p o s s i b l y , s u s t a i n e d t h r o u g h a c i d h y d r o l y s i s a t t h e p r e - steaming t e m p e r a t u r e s . The low y i e l d o f 8 9 . 6 % r e c o r d e d f o r the c a u s t i c - t r e a t e d sample, C, was due t o t h e c o o k i n g a c t i o n o f c a u s t i c on wood, and i s p a r t l y r e s p o n s i b l e f o r t h e r e l a - t i v e l y h i g h s t r e n g t h v a l u e s o b t a i n e d f o r t h e c a u s t i c - t r e a t e d sample. Y i e l d was r e l a t i v e l y h i g h e r f o r t h e s u l f i t e t r e a t e d c h i p s , D, 9 5 . 3 % , not o n l y because i n comparison t o c a u s t i c , sodium s u l f i t e has o n l y a m i l d c o o k i n g a c t i o n on wood, b u t . a l s o because a t c o n c e n t r a t i o n s o f Na2SC>3 up t o 1 8 % , i t a c t s as a b u f f e r i n t h e s o l u t i o n , p r e v e n t i n g t h e d i s s o l u t i o n o f wood su b s t a n c e ( 4 2 ) . S p e c i f i c Energy Consumption The manufacture o f m e c h a n i c a l p u l p by d i f f e r e n t p r o - c e s s e s i n v o l v e s e x p e n d i t u r e s o f l a r g e amounts o f energy. I n Table VI the amounts o f energy expended i n t h e manufacture o f m e c h a n i c a l p u l p s o f Gmelina a r e g i v e n , w h i l e i n T a b l e I X , s p e c i f i c energy consumption t o a t t a i n 90 ml C s f i s g i v e n . I t i s e v i d e n t from t h i s t a b l e t h a t more energy was r e q u i r e d i n th e case o f the c h e m i c a l l y p r e t r e a t e d c h i p s , 120 HPD/T f o r c a u s t i c and 113 HPD/T f o r s u l f i t e , t o o b t a i n p u l p s o f 90 ml C s f , t h a n i n the c a s e s o f u n t r e a t e d open d i s c h a r g e r e f i n e r groundwood and steam p r e t r e a t e d r e f i n e r groundwood p u l p s , w h i c h r e q u i r e d 81 HPD/T and 9 3 HPD/T, r e s p e c t i v e l y . S t a t i s t i c a l a n a l y s i s o f t h e r e s u l t s g i v e n i n T a b l e VI showed t h a t t h e c a u s t i c p r e t r e a t m e n t r e s u l t e d i n t h e b e s t m e c h a n i c a l s t r e n g t h p r o p e r t i e s . T h i s c o n f i r m s t h e r e l a t i o n - s h i p o b s e r v e d by Jensen (4 7 ) , and i m p l i e s t h a t t h e same r e l a - t i o n between s p e c i f i c energy consumption and m e c h a n i c a l p u l p s a l s o e x i s t s f o r m e c h a n i c a l p u l p s made from Gmelina wood. Jensen's o b s e r v a t i o n , however, does n o t seem t o h o l d f o r the o t h e r t r e a t m e n t s t r i e d . F o r example, t h e second h i g h e s t s p e c i f i c energy consumption was n o t e d f o r t h e s u l f i t e p r e - t r e a t e d sample, D, and y e t i t s m e c h a n i c a l p r o p e r t i e s , c o m p i l e d i n T a b l e V I , a r e not s i g n i f i c a n t l y d i f f e r e n t from t h o s e o f t h e u n t r e a t e d sample, A, whi c h consumed 40% l e s s energy, and the presteamed sample, B, w h i c h consumed 20% l e s s energy. S p e c i f i c energy consumption d u r i n g r e f i n i n g , i n g e n e r a l , depends on a number o f f a c t o r s . These i n c l u d e among o t h e r s , wood s p e c i e s c h a r a c t e r i s t i c s , t y p e o f p r e t r e a t m e n t , r e f i n e r geometry and f e e d f a c t o r s ( 50). The i n d i v i d u a l e f f e c t s o f t h e s e f a c t o r s on energy consumption have n o t been 48. c l e a r l y defined and, consequently, the actual relationship between energy consumption and the drainage c h a r a c t e r i s t i c s of pulp i s not clear. Data r e l a t i n g these factors should, therefore, be regarded only from the comparative standpoint and not as absolute values. Energy consumption i s generally higher i n laboratory r e f i n i n g than for commercial r e f i n i n g to the same drainage. This i s p a r t l y because, while i t takes only two r e f i n e r passes to reduce chips to the desired drainage l e v e l i n commercial operations, i t takes frequently up to s i x or more r e f i n e r passes to at t a i n the same drainage using a laboratory r e f i n e r . The reason for t h i s may be pa r t l y due to the differences i n consistency during r e f i n i n g , and p a r t l y to a higher e f f i c i e n c y factor with the commercial operation. Consistencies i n the range of 20 to 30% r e s u l t i n a s i g n i f i c a n t reduction i n power consumption (50, 79), while as shown (11), at lower consis- tencies i t i s more d i f f i c u l t to put load into the r e f i n i n g and the available power i s not f u l l y u t i l i z e d . In the present study, a l l r e f i n i n g was ca r r i e d out at consistencies between 9 and 13%, t h i s being the l i m i t of c a p a b i l i t y of the small laboratory r e f i n e r . This implies that more energy than nece- ssary may have been expended to prepare the Gmelina mechani- c a l pulps, and that less may be required under commercial conditions. D e b r i s Content The d e b r i s c o n t e n t o f p u l p s i s g e n e r a l l y e x p r e s s e d as t h a t p r o p o r t i o n o f t h e m a t e r i a l w h i c h i s r e t a i n e d on a s t a n d a r d s c r e e n p l a t e h a v i n g a s l o t w i d t h o f 150 , under s t a n d a r d s c r e e n i n g c o n d i t i o n s . I t g e n e r a l l y c o n s i s t s o f i n c o m p l e t e l y s e p a r a t e d f i b e r s and f i b e r b u n d l e s , and i t s p a r t i c l e s a r e t h u s g r e a t e r t h a n one f i b e r d i a m e t e r i n w i d t h . C o n s e q u e n t l y , d e b r i s has a d e t r i m e n t a l e f f e c t on t h e p h y s i c a l p r o p e r t i e s o f n e w s p r i n t . I t i s l a r g e l y because o f i t s p r e s - ence i n m e c h a n i c a l p u l p s t h a t a s e p a r a t e d e b r i s h a n d l i n g system i s n e c e s s a r y as an i n t e g r a l p a r t o f m e c h a n i c a l p u l p i n g p r o c e s s f l o w s h e e t . From T a b l e V I , the e f f e c t o f the v a r i o u s t y p e s o f p r e t r e a t m e n t s employed on d e b r i s c o n t e n t may be i d e n t i f i e d . I t i s c l e a r from t h i s t a b l e t h a t t h e p r e s t e a m i n g p r e t r e a t m e n t caused a s i g n i f i c a n t r e d u c t i o n i n d e b r i s c o n t e n t o v e r conven- t i o n a l open d i s c h a r g e r e f i n i n g . The t a b l e a l s o i n d i c a t e s t h a t c h e m i c a l t r e a t m e n t caused a f u r t h e r d e c r e a s e i n d e b r i s c o n t e n t , i n d i c a t i n g a more complete d e f i b e r i z a t i o n d u r i n g t h e r e f i n i n g . M e c h a n i c a l P r o p e r t i e s From d a t a i n T a b l e IX, i t i s e v i d e n t t h a t a l l t h r e e p r e t r e a t e d p u l p s e x h i b i t somewhat b e t t e r m e c h a n i c a l p r o p e r t i e s t h a n t h o s e o f the n o n - t r e a t e d sample. The t a b l e a l s o i n d i - c a t e s , t h a t the c h e m i c a l l y t r e a t e d p u l p s e x h i b i t b e t t e r c h a r - a c t e r i s t i c s than t h o s e a c h i e v e d by p r e s t e a m i n g a l o n e . I t i s 50 . assumed t h a t t h e improved p r o p e r t i e s depend upon b o t h f i b e r l e n g t h p r e s e r v a t i o n and improved bonding c h a r a c t e r i s t i c s o f the p u l p f i b e r s . T h i s assumption i s c o n f i r m e d by F i g u r e s 4 t h r o u g h 7. The improved t e a r s t r e n g t h of a l l samples o v e r the u n t r e a t e d sample i s d i r e c t l y r e l a t e d t o t h e p r e s e r v a t i o n o f f i b e r l e n g t h , w h i l e the improved b u r s t s t r e n g t h i s e n t i r e l y r e l a t e d t o improved b o n d i n g . The improved b r e a k i n g l e n g t h o f the two c h e m i c a l l y t r e a t e d p u l p s i s the r e s u l t o f b o t h improved f i b e r l e n g t h and improved b o n d i n g p o t e n t i a l . T h i s r e a s o n i n g i s i n l i n e w i t h the i n t e r p r e t a t i o n o f F o r g a c s 1 L- and S - F a c t o r s ( 3 1 ) . I t i s c l e a r from the d a t a i n T a b l e IX t h a t t h e caus- t i c - t r e a t e d sample shows the g r e a t e s t g a i n i n s t r e n g t h p r o - p e r t i e s . I f m a x i m i z i n g the m e c h a n i c a l s t r e n g t h were the o n l y c o n s i d e r a t i o n , i t i s e v i d e n t t h a t t h i s t y p e o f a l k l i n e p r e - t r e a t m e n t would be t h e most advantageous t o use. O p t i c a l P r o p e r t i e s Compared t o t h e n o n - p r e t r e a t e d p u l p , b o t h the p r e - steamed and c a u s t i c p r e t r e a t e d p u l p s e x h i b i t h i g h e r a b s o r p t i o n c o e f f i c i e n t s and, c o n s e q u e n t l y , d e c r e a s e d b r i g h t n e s s (Table I X ) . The s u l f i t e p r e t r e a t e d p u l p , on the o t h e r hand, e x h i b i t s a d e c r e a s e d a b s o r p t i o n c o e f f i c i e n t , compared t o t h e c o n t r o l , and c o n s e q u e n t l y , improved b r i g h t n e s s . W h i l e the presteamed p u l p e x h i b i t s a s i m i l a r s c a t t e r i n g c o e f f i c i e n t , b o t h c h e m i c a l l y - t r e a t e d p u l p s e x h i b i t d e c r e a s e d s c a t t e r i n g c o e f f i - c i e n t s , t h u s c l e a r l y i d e n t i f y i n g t h a t t h e s e p u l p s have im- p r o v e d b o n d i n g c h a r a c t e r i s t i c s o v e r t h e u n t r e a t e d p u l p . T h i s f a c t i s a l s o r e f l e c t e d i n t h e sheet d e n s i t y w h i c h was h i g h e r f o r t h e s e p u l p s than f o r t h e s t a n d a r d open d i s c h a r g e p u l p . Thus, i n terms o f b r i g h t n e s s , s u l f i t e p r e t r e a t m e n t , had t h e most b e n e f i c i a l e f f e c t , w h i l e t h e c a u s t i c t r e a t m e n t had a s t r o n g l y d e t r i m e n t a l e f f e c t . However, i n v i e w o f the s t r o n g e f f e c t o f c a u s t i c t r e a t m e n t on p u l p s t r e n g t h p r o p e r - t i e s , i t would seem a p p r o p r i a t e t o use t h i s t y p e o f t r e a t - ment t o maximize t h e m e c h a n i c a l p r o p e r t i e s and overcome th e l o w e r b r i g h t n e s s by hydrogen p e r o x i d e t r e a t m e n t o f t h e p u l p . A l t e r n a t i v e l y , a combined t r e a t m e n t w i t h c a u s t i c and sodium s u l f i t e would a i d s t r e n g t h improvement w i t h o u t s e v e r e degrada- t i o n , of b r i g h t n e s s . Such o p t i m i z a t i o n o f c h e m i c a l p r e t r e a t - ment and subsequent b r i g h t e n i n g was beyond th e scope o f t h i s p a r t i c u l a r s t u d y . Comparison o f West Coast Groundwood and C a u s t i c Treated. Gmelina P u l p I n T a b l e X, the c h a r a c t e r i s t i c s of t h e Gmelina c a u s - t i c t r e a t e d p u l p a t 90 ml C s f are compared t o t h o s e o f West Coast s t o n e groundwood a t 84 ml C s f . From th e d a t a i n t h i s t a b l e , i t i s e v i d e n t t h a t , i n terms o f s t r e n g t h p r o p e r t i e s , m e c h a n i c a l p u l p s produced by the c a u s t i c p r e t r e a t m e n t o f Gmelina compare f a v o r a b l y w i t h West Coast stone groundwood. 52. From t h i s t a b l e , i t i s e v i d e n t t h a t t h e Gmelina c a u s t i c p r e - t r e a t e d p u l p e x h i b i t e d h i g h e r t e a r , b u r s t , b r e a k i n g l e n g t h and o p a c i t y , b u t l o w e r d e n s i t y and s t r e t c h t h a n West Coast SGW. B r i g h t n e s s , however, r e p r e s e n t s a problem, b u t , as o u t l i n e d e a r l i e r , t h i s c o u l d be overcome by m o d i f y i n g t h e form o f p r e t r e a t m e n t t o a c o m b i n a t i o n o f c a u s t i c and sodium s u l - f i t e , o r by u s i n g p e r o x i d e b r i g h t e n i n g p r i o r t o papermaking. C h e m i c a l P u l p from Gmelina The p h y s i c a l and m e c h a n i c a l p r o p e r t i e s o f the semi- b l e a c h e d k r a f t (SBK) p u l p produced from Gmelina a r e g i v e n i n T a b l e X I . From t h i s t a b l e , i t i s c l e a r t h a t t h e p h y s i c a l s t r e n g t h p r o p e r t i e s o f SBK from Gmelina a r e s i g n i f i c a n t l y l o w e r t h a n t h o s e o f West Coast SBK g e n e r a l l y produced from softwoods, among whi c h a r e Douglas f i r and Western hemlock. D i f f e r e n c e s i n the m e c h a n i c a l p r o p e r t i e s o f t h e s e SBK p u l p s a r e l a r g e l y due t o t h e d i f f e r e n c e s i n t h e i r f i b e r c h a r a c t e r - i s t i c s , p a r t i c u l a r l y the low f i b e r l e n g t h o f t h e Gmelina SBK compared t o the West Coast SBK. These may be o b s e r v e d i n F i g u r e s 9 t h r o u g h 12. The b r i g h t n e s s o f Gmelina k r a f t , as i n d i c a t e d i n T a b l e X I , i s s u p e r i o r t o t h a t o f t h e West Coast c o u n t e r p a r t . B r i g h t n e s s would t h u s be a s t r o n g p o s i t i v e f e a t u r e o f Gmelina, p a r t i c u l a r l y i f i t were t o be used i n f i n e paper f u r n i s h e s . The P o t e n t i a l o f Gmelina M e c h a n i c a l P u l p s f o r N e w s p r i n t The Gmelina m e c h a n i c a l p u l p used f o r t h e n e w s p r i n t t r i a l s was t h a t produced by t h e c a u s t i c p r e t r e a t m e n t as i t gave the b e s t m e c h a n i c a l p r o p e r t i e s compared t o t h e o t h e r p r e t r e a t m e n t s i n v e s t i g a t e d . An o v e r a l l summary o f t h e d r y s t r e n g t h d a t a r e l a t i n g t o the s t u d y o f t h e s e s i m u l a t e d news- p r i n t mixes i s g i v e n i n T a b l e X I I and the wet s t r e n g t h d a t a a r e p r o v i d e d i n T a b l e X I I I . F i g u r e s 13 t h r o u g h 2 3 a r e t h e p l o t s o f n e w s p r i n t handsheet p r o p e r t i e s o v e r t h e c h e m i c a l p u l p c o n t e n t . From t h e s e t a b l e s and f i g u r e s t h e e f f e c t o f c h e m i c a l p u l p c o n t e n t on t h e mixed f u r n i s h s h e e t p r o p e r t i e s can be i d e n t i f i e d . The r e l a t i o n s h i p between c h e m i c a l p u l p c o n t e n t and n e w s p r i n t handsheet p r o p e r t i e s i s e s s e n t i a l l y l i n e a r i n t h e c h e m i c a l p u l p range o f i n t e r e s t , t h e b r i g h t n e s s and s t r e n g t h c h a r a c t e r i s t i c s i n c r e a s i n g , as e x p e c t e d , w i t h i n - c r e a s i n g c h e m i c a l p u l p c o n t e n t w h i l e t h e o p a c i t y t o g e t h e r w i t h s c a t t e r i n g and a b s o r p t i o n c o e f f i c i e n t s e x h i b i t a r e d u c t i o n . I n g e n e r a l , t h e d a t a i n d i c a t e t h a t the s t r e n g t h p r o p e r t i e s o f Gmelina m e c h a n i c a l p u l p m i x t u r e s compare f a v o r a b l y w i t h t h o s e o f t y p i c a l West Coa s t n e w s p r i n t m i x t u r e s , whereas m i x t u r e s c o n t a i n i n g b o t h m e c h a n i c a l and c h e m i c a l p u l p from Gmelina a r e l a c k i n g i n c e r t a i n a s p e c t s . The low b r i g h t n e s s o f m i x t u r e s c o n t a i n i n g Gmelina r e f i n e r m e c h a n i c a l p u l p i s a d e f i c i e n c y w h i c h would have t o be overcome. A l t h o u g h t h e i d e n t i f i c a t i o n o f the manner i n w h i c h t h i s s h o u l d be a c h i e v e d i s beyond t h e scope o f t h i s t h e s i s , i t i s e v i d e n t t h a t t h i s d e f i c i e n c y can be overcome by approaches w h i c h have been suggested e l s e w h e r e i n t h e t h e s i s . CHAPTER V SUMMARY M e c h a n i c a l p u l p s c o v e r i n g a br o a d spectrum o f p u l p s c a p a b l e o f b e i n g produced by r e f i n i n g were made i n t h e l a b o r - a t o r y from Gmelina a r b o r e a Roxb., a hardwood. I n t h e case o f p r e s s u r i z e d r e f i n i n g , the e f f e c t o f p r e t r e a t m e n t by steaming and c h e m i c a l i m p r e g n a t i o n were i n v e s t i g a t e d . I n g e n e r a l , t h o s e p u l p s produced by s i m u l a t e d p r e s s - u r i z e d r e f i n i n g e x h i b i t e d b e t t e r m e c h a n i c a l p r o p e r t i e s t h a n t h e open d i s c h a r g e r e f i n e d p u l p . C h i p p r e t r e a t m e n t s u s i n g , i n one c a s e , sodium s u l f i t e (20% on wood) and, i n t h e o t h e r c a s e , sodium h y d r o x i d e (10% on wood) r e s u l t e d i n f u r t h e r improvements i n p u l p c h a r a c t e r i s t i c s . I n terms o f t h e p h y s i - c a l s t r e n g t h p r o p e r t i e s t h e c a u s t i c t r e a t e d p u l p compared f a v o r a b l y w i t h t y p i c a l s t o n e groundwood p u l p manufactured on t h e West Coa s t o f N o r t h A m e r i c a f o r use i n n e w s p r i n t . The c a u s t i c t r e a t e d p u l p , however, e x h i b i t e d h i g h a d s o r p t i o n c o e f f i c i e n t and c o n s e q u e n t l y low b r i g h t n e s s . W h i l e t h i s r e p r e s e n t s a p o t e n t i a l p r o blem i n t h e commercial use o f t h i s t y p e o f p u l p i n n e w s p r i n t , t h e d e f i c i e n c y i s surmountable e i t h e r by e m p l o y i n g hydrogen p e r o x i d e b r i g h t e n i n g t r e a t m e n t i n c o n j u n c t i o n w i t h the r e f i n i n g o p e r a t i o n , o r by u s i n g a c o m b i n a t i o n o f c a u s t i c and sodium s u l f i t e p r e t r e a t m e n t . To e v a l u a t e t h e s u i t a b i l i t y o f t h e Gmelina r e f i n e r groundwood f o r use as the major component o f the n e w s p r i n t f u r n i s h , i t s b e h a v i o r i n a d m i x t u r e w i t h West Coast semi- b l e a c h e d k r a f t was i n v e s t i g a t e d . A t a g i v e n l e v e l o f chemi- c a l p u l p e q u i v a l e n t t o t h a t used i n s t a n d a r d n e w s p r i n t , t h e p r o p e r t i e s o f the mixed f u r n i s h Gmelina handsheets were found t o be comparable t o t h o s e o f West Coast n e w s p r i n t m i x t u r e s . O p t i m i z a t i o n o f the p r e t r e a t m e n t and r e f i n i n g p r o c e s s may r e s u l t i n Gmelina p u l p s s u i t a b l e f o r t h e p r o d u c t i o n o f news- p r i n t a t l o w e r c h e m i c a l p u l p l e v e l s . The above s i t u a t i o n c l e a r l y r e p r e s e n t s t h e case o f a n o n - i n t e g r a t e d m i l l u s i n g market k r a f t as t h e c h e m i c a l p u l p component. To c o v e r t h e case f o r the i n t e g r a t e d m i l l , a b r i e f s t u d y was a l s o c a r r i e d o u t t o a s s e s s t h e response o f Gmelina t o k r a f t p u l p i n g and t o e v a l u a t e t h e b e h a v i o r o f t h i s p u l p i n a d m i x t u r e w i t h Gmelina m e c h a n i c a l p u l p . As e x p e c t e d , i n view o f the s h o r t e r mean f i b e r l e n g t h o f Gmelina compared t o s o f t - woods i n g e n e r a l , Gmelina k r a f t was s i g n i f i c a n t l y weaker, m e c h a n i c a l l y , t h a n t y p i c a l N o r t h American k r a f t p u l p s . I t s s t r e n g t h d e f i c i e n c i e s were c l e a r l y r e f l e c t e d i n the m e c h a n i c a l p r o p e r t i e s o f mixed f u r n i s h handsheets a t normal m i x t u r e r a t i o s . CHAPTER VI CONCLUSIONS AND RECOMMENDATIONS Conclusions 1. A wide variety of r e f i n e r mechanical pulps can be pro- duced from Gmelina arborea Roxb. 2. Caustic pretreated Gmelina r e f i n e r mechanical pulp has comparable mechanical properties to West Coast stone groundwood used i n newsprint furnishes, and i s , there- fore, also suitable for use i n newsprint manufacture. 3. The use of caustic pretreated Gmelina r e f i n e r groundwood i n admixture with softwood semi-bleached k r a f t i n normal newsprint r a t i o s (3:1) resulted i n mixed furnish hand- sheets with properties comparable to handsheets from North American newsprint furnishes. 4. Newsprint furnish handsheets produced from mixtures of Gmelina r e f i n e r pulp and Gmelina semi-bleached k r a f t exhibit mechanical properties which are i n f e r i o r to those of s i m i l a r handsheets from. North American newsprint mix- tures. Recommendations 1. The strong p o t e n t i a l i n d i c a t i n g the s u i t a b i l i t y of chemi- c a l l y pretreated mechanical pulp from Gmelina arborea Roxb. for newsprint manufacture should be exploited. 2. The extent of Gmelina arborea Roxb. plantation resources in Nigeria, coupled with the rapidly increasing demand 57 58. f o r paper and p a p e r b o a r d , c a l l f o r development programs wh i c h c a t e r t o t h e n a t i o n ' s demand f o r f i b e r and f i b e r p r o d u c t s . I n d i g e n o u s hardwood s p e c i e s s h o u l d be e v a l u a t e d f o r t h e i r p o t e n t i a l f o r use as supplementary m a t e r i a l s f o r p u l p and paper, and a d d i t i o n a l p l a n t a t i o n s s h o u l d be e s t a b l i s h e d t o guarantee r e g u l a r and a d e q u a t e . s u p p l y o f pulpwood t o the m i l l s . F u r t h e r work s h o u l d be conducted t o o p t i m i z e t h e c h e m i c a l p r e t r e a t m e n t f o r thermomechanical p u l p from Gmelina a r b o r e a Roxb. w i t h r e g a r d t o m e c h a n i c a l p r o p e r t i e s , and p a r t i c u l a r a t t e n t i o n s h o u l d be d i r e c t e d towards b r i g h t e n - i n g t e c h n o l o g y . BIBLIOGRAPHY * 1. Abayomi, J.O. 1974. A stu d y o f t h e growth o f f i v e permanent p l o t s o f Gmelina a r b o r e a i n the d e r i v e d Savanna zone. Paper 5 t h An n u a l Conference o f t h e F o r e s t r y A s s o c i a t i o n o f N i g e r i a . 24 pp. 2. A d e m i l u y i , E.O. and Okeke, R.E. 1973. S p e c i f i c g r a v i t y and f i b e r c h a r a c t e r i s t i c s o f Gmelina a r b o r e a i n some N i g e r i a n p l a n t a t i o n s . Paper 4 t h Annual Conference o f t h e F o r e s t r y A s s o c i a t i o n o f N i g e r i a . 10 pp. 3. A l a d e , G.A. 1973. 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K r a t z l , K. and P a s z n e r , L. 1970. The aqueous h y d r o l y - s i s , e t h a n o l y s i s and o x i d a t i o n o f g - a r y l e t h e r bonded l i g n i n b u i l d i n g u n i t s and t h e i r s u l f o n i c a c i d s . C e l l u l o s e Chem. T e c h n o l . 5, 293-303. 55. K r u g e r , E., R u f f i n i , G., G r a n d i n i , G. and G h i s l a n d i . 1973. Method o f p r o d u c i n g h i g h y i e l d p u l p a t h i g h b r i g h t n e s s f o r papermaking. Canadian P a t e n t No. 934,107. 56. Kwei, N.L. and Garceau, J . J . 1975. Optimum c o m b i n a t i o n s o f groundwood f r a c t i o n s f o r maximum sh e e t s t r e n g t h . TAPPI/CPPA I n t e r n . Mech. P u l p i n g Conf., San F r a n - c i s c o : 23-9. ( P r e p r i n t ) . 57. Lamb, A.F.A. 1968. F a s t growing t i m b e r t r e e s o f t h e l o w l a n d t r o p i c s , No. 1 Gmelina a r b o r e a . Common- w e a l t h F o r e s t r y I n s t i t u t e , O x f o r d . 30 pp. 58. L a p s i n k a , I . 1972. Worldwide u t i l i z i a t i o n o f hardwoods i n t h e p u l p i n d u s t r y . P r z e g l a d P a p i e r 28 ( 4 ) : i 1 2 3 - 7 . 59. Leask, R.A. 1968. Chemimechanical p u l p s from hardwoods. T a p p i 51 ( 1 2 ) : 117-20A. 60. Leask, R.A. 1975. Review o f thermomechanical p u l p i n g . P u l p Paper Mag. Can. 76 (10: 52-60. * Not c i t e d i n t e x t . 64. 61. Macdonald, R.G. and F r a n k l i n , J.N. Ed. (1970 r e v . e d . ) . P u l p and Paper M a n u f a c t u r e . Second Ed. V o l . I . The P u l p i n g o f Wood. McGraw H i l l , New Y o r k . 769 pp. *62. M e r e t , R.G. 1976. M a c M i l l a n B l o e d e l R e s e a r c h L t d . , Vancouver, B.C. 63. N a m i k i , N. 1973. M a n u f a c t u r e o f n e w s p r i n t w i t h i n t e n s e u t i l i z a t i o n o f hardwood and o t h e r wood r e s o u r c e s . T a p p i 56 ( 1 0 ) : 92-5. *64. Nokoe, T.S. 19 74. S p e c i f i c g r a v i t y v a r i a t i o n i n Gmelina a r b o r e a L i n n , grown f o r pulpwood i n some p a r t s o f N i g e r i a , West A f r i c a . FRST 545 Seminar, U n i v e r s i t y o f B r i t i s h Columbia. 17 pp. 65. Obiaga, R.I. and Wayman, M. 1969. K r a f t and p o l y s u l - f i d e d e l i g n i f i c a t i o n o f a t r o p i c a l hardwood, Gmelina a r b o r e a . P u l p Paper Mag. Can. 70 (T270-8). 66. O h n i s h i , K., Awaya, S. and Egawa, K. 1968. Hardwood r e f i n e r groundwood as n e w s p r i n t f u r n i s h component. P u l p Paper Mag. Can. 69 ( 1 9 ) : 79-83. 67. Okereke, 0.0. 19 62. S t u d i e s on t h e f i b e r d i m e n s i o n s o f some N i g e r i a n t i m b e r s and o t h e r raw m a t e r i a l s . P a r t I . F e d e r a l I n s t i t u t e o f I n d u s t r i a l R e s e a r c h , R e p o r t No. 16. 9 pp. 68. O r g i l l , B. 1975. E f f e c t o f c h e m i c a l p r e i m p r e g n a t i o n on thermomechanical p u l p i n g o f hardwoods. TAPPI/CPPA I n t e r n . Mech. P u l p i n g Conf., San F r a n c i s c o : p 127-9. ( P r e p r i n t ) . 69. P a l m e r , E.R. 1973. Gmelina a r b o r e a as a p o t e n t i a l s o u r c e o f hardwood p u l p . R e p r i n t T r o p i c a l S c i e n c e , 15 ( 3 ) . 17 pp. 70. Palmer, E.R. and G i b b s , J.A. 1974. P u l p i n g c h a r a c t e r - i s t i c s o f Gmelina a r b o r e a and B u r s e r a simaruba from B e l i z e . T r o p i c a l P r o d u c t s I n s t i t u t e , London. 27 pp. 71. P a n s h i n , A . J . and de Zeeuw, C. 1970. Textbook o f Wood Technology. T h i r d ed. V o l . I . M c G r a w - H i l l , New Y o r k . 705 pp. 72. Peh, T.B. 1964. P u l p i n g s t u d i e s on Malayan e x o t i c s p e c i e s . 1. Gmelina a r b o r e a Roxb. Res. Pamphlet No. 44. F o r e s t Res. I n s t . , F o r e s t Dept., Malaya. 22 pp. * Not c i t e d i n t e x t . 65. 73. P e t e r i , R. 1952. P u l p i n g s t u d i e s w i t h A f r i c a n t r o p i c a l woods. T a p p i 35 ( 4 ) : 157-60. 74. P e t e r s o n , H.E. and N e l s o n , D.G. 1972. P r o d u c t i o n o f r e f i n e r m e c h a n i c a l p u l p from aspen f o r p u b l i c a t i o n p r i n t i n g p a p e r s . T a p p i 55 ( 3 ) : 396-401. 75. P i e t r o , G. 1975. System t o a v o i d t h e r m a l d e g r a d a t i o n o f c h e m i c a l compounds d u r i n g the t r e a t m e n t o f wood c h i p s . Canadian P a t e n t No. 977,905. 6 pp. 76. P r e j e t , J . 19 74. New Bauer p r o c e s s f o r m a n u f a c t u r i n g m e c h a n i c a l p u l p . ATIP Rev. 28 ( 2 ) : 105-21. 77. Rapson, W.H. Ed. 1963. The b l e a c h i n g o f p u l p . TAPPI Monograph S e r i e s No. 27. TAPPI, A t l a n t a , G e o r g i a , USA. 416 pp. 78. R i c h e s , A.W. and M i t c h e l l , G.W. 1977. E x p e r i e n c e w i t h cottonwood (Populus t r i c h o c a r p a ) i n thermomechanical p u l p f u r n i s h . Paper, J o i n t M e e t i n g o f t h e P a c i f i c C oast S e c t i o n and West S e c t i o n o f CPPA T e c h n i c a l S e c t i o n , V i c t o r i a . 79. Rydholm, S.A. 1965. P u l p i n g p r o c e s s e s . I n t e r s c i e n c e . John W i l e y and Sons I n c . New York - London - Sydney. 80. S c h u t t , C. 1964. Forming t e s t s h e e t s i n t h e l a b o r a t o r y . I . A Review o f L i t e r a t u r e . P a p e r i j a Puu No. 4a, p 167-92. 81. S c h u t t , C. 1964. Forming t e s t s h e e t s i n the l a b o r a t o r y . I I . A Review o f L i t e r a t u r e . P a p e r i j a Puu 6 ( 4 ) : 315-22. 82. S k e e t , C.W. and A l l a n , R.S. 1968. S t a n d a r d i z a t i o n o f hot d i s i n t e g r a t i o n method f o r m e c h a n i c a l p u l p e v a l u a t i o n . P u l p P aper Mag. Can. 69 ( 4 ) : 71-3. 83. Sosanwo, 0. 1976. S t u d i e s on Gmelina a r b o r e a . P a r t IV. S u l f a t e - o x y g e n c o o k i n g o f N i g e r i a n Gmelina a r b o r e a wood. P a p e r i j a Puu No. 6-7, p. 419-26. 84. Sosanwo, 0. and L i n d b e r g , J . J . 1975. S t u d i e s on Gmelina a r b o r e a . P a r t I I . F i b e r dimensions and some a n a t o m i c a l a s p e c t s o f N i g e r i a n Gmelina a r b o r e a wood. P a p e r i j a Puu No. 7, p. 482-85. *85. Sosanwo, 0. and L i n d b e r g , J . J . 1976. S t u d i e s on Gmelina a r b o r e a . P a r t I I I . S t r u c t u r a l a n a l y s i s o f m i l l e d wood l i g n i n from t h e N i g e r i a n Gmelina a r b o r e a wood. P a p e r i j a Puu, S p e c i a l Number 4a, p. 201-6. 86. Stamm, A . J . 1964. Wood and C e l l u l o s e S c i e n c e . Ronald P r e s s , New York. 549 pp. *87. S t y a n , G.E. 1975. C h e m i c a l f a c t o r s a f f e c t i n g groundwood b r i g h t n e s s . P u l p Paper Mag. Can. 76 (12): 88-90. 88. TAPPI S t a n d a r d s and P r o v i s i o n a l Methods. 1977. A t l a n t a , G e o r g i a , USA. 89. TAPPI. 1976. I n t r o d u c t i o n t o p u l p i n g t e c h n o l o g y . T a p p i Home Study Course. No. 2 (audio tape and s t u d y g u i d e ) . *90. Valkama, E. and K o s t i a i n e n , A. 1973. L a t e s t e x p e r i e n c e s o f r e f i n e r m e c h a n i c a l p u l p manufacture i n F i n l a n d . P a p e r i j a Puu 55 ( 5 ) : 373-5, 379-80, 382-4. 91. Wahren, D. ( C o m p i l e r ) , J a c k s o n , M. (MB L t d . , Vancouver, B.C.) ( T r a n s l a t o r f rom o r i g i n a l S w e d i s h ) . 1973. P r i n t i n g paper i n f o r m a t i o n t e x t i s s u e d by Holmens Bruk AB, N o r k o p i n g , Sweden. 20 pp. 92. Yeom, F.B.C. and S a n d r a s e g a r a n , K. 1966. Growth and y i e l d o f Yemane (Gmelina a r b o r e a Roxb.). Malayan F o r e s t e r 29 ( 3 ) : 140-51. 93. de Zeeuw, C. and Gray, R.L. 1972. S p e c i f i c g r a v i t y v a r i a t i o n i n Gmelina a r b o r e a Roxb. IAWA B u l l e t i n No. 3, 3-11. 20 pp. * Not c i t e d i n t e x t . TABLE I IMPORT OF PAPER AND PAPERBOARD FEDERAL REPUBLIC OF NIGERIA P r o d u c t Type 1963 1964 1965 Kg $ Kg $. Kg $ N e w s p r i n t P r i n t i n g & W r i t i n g K r a f t Paper & B o a r d C i g a r e t t e Paper Machine-Made Paper and B o a r d F i b e r b o a r d & O t h e r B u i l d i n g B o a r d Hand-Made P a p e r Paper & P a p e r b o a r d 4,808,079 8,119,303 3,011,853 199,581 1,279,130 2,404,040 18,144 20,865,249 926,271 2,388,002 935,542 195,644 628,712 486,312 11,497 824,975 4,236,553 6,196,072 1,469,639 263,084 1,741,795 1,778,082 907 6,985,322 979,073 2,439,049 566,658 212,394 725,690 367,609 804 2,010,476 4,717,361 9,253,284 5,170,953 326,587 2,340,537 2,159,100 136,078 6,622,449 1,076,121 3,588,362 1,507,951 207,766 922,771 498,050 36,520 883,420 S u b t o t a l 21,926,655 6,396,955 22,671,454 7,301,753 30,817,066 8,722,641 P a c k i n g C o n t a i n e r s F i l l i n g C o n t a i n e r s E n v e l o p e s , W r i t i n g B l o c k s , e t c . E x e r c i s e Books, S t a t i o n e r y , e t c . A r t i c l e s o f P u l p , Paper & B o a r d 10,886,217 444,521 961,616 4,030,720 220,548 659,851 997,105 2,491,196 11,430,528 562,455 1,288,202 4,451,821 253,392 886,071 1,046,172 3,116,403 6,059,994 417,305 1,170,268 3,633,504 200,794 781,301 1,024,607 3,517,517 S u b t o t a l 8,402,220 9,753,859 9,157,722 GRAND TOTAL 14,799,175 17,055,612 17,882,363 S o u r c e : FAO Rome No. TA252 9 ( 8 ) . TABLE II FIBER CHARACTERISTICS OF GMELINA ARBOREA S t a t i s t i c Observation Fibe r length (ym) 1 1010 Fiber width (ym)1 28 Fiber wall thickness (ym) 1 3 Lumen width (ym)1 22 Length-width r a t i o 36 Runkel r a t i o 2 0.27 F l e x i b i l i t y r a t i o 3 .... 0.79 1. 2. 3. 4. Source: FAO Rome Fo: MISC/75/31 (10). 00 1000 microns (ym) = 1 mm. Runkel r a t i o = 2W L where W = c e l l - w a l l thickness L = Lumen diameter. F l e x i b i l i t y r a t i o = C o e f f i c i e n t of f l e x i b i l i t y k expressed in percent. „ J-J- • . . c el • i_ • n • x. Width of Lumen n n r, C o e f f i c i e n t of f l e x i b i l i t y = ~ • -,., * c • . — x 100 1 Width of f i b e r TABLE I I I EFFECT OF CHIP SPECIFICATION IN PULPING PROCESS C h i p P a r a m e t e r K r a f t S u l f i t e NSSC R e f i n e r - M e c h a n i c a l L e n g t h P r e f e r r e d Range, mm Width T h i c k n e s s P r e f e r r e d Range, mm C h i p D e n s i t y Bark C o n t e n t P r e f e r r e d Range, mm Hard I m p u r i t i e s (sand, m e t a l ) C h i p Damage M o i s t u r e C o n t e n t Not t o o c r i t i c a l 15-25 Not c r i t i c a l V e r y c r i t i c a l 1.5-4 ( s o l i d wood) C r i t i c a l 25-35 Not c r i t i c a l Not c r i t i c a l C r i t i c a l f o r p r o d u c t i o n economy C r i t i c a l f o r h i g h y i e l d Not c r i t i c a l Not c r i t i c a l C o n s t a n c y c r i t i c a l I V e r y c r i t i c a l 1 Not known Not c r i t i c a l Not known Not known Not known Not known 1% C r i t i c a l f o r d i s s o l v i n g p u l p V e r y c r i t i c a l Not c r i t i c a l C onstancy c r i t i c a l C r i t i c a l f o r | C r i t i c a l p r o d u c t i o n economy Ve r y c r i t i c a l f o r p l a t e l i f e Not c r i t i c a l Not c r i t i c a l Not known V e r y c r i t i c a l TABLE IV EFFECT OF CHEMICAL PRETREATMENT ON THE CHARACTERISTICS OF OPEN DISCHARGE AND PRESSURE REFINER PULPS MADE FROM SOFTWOODS R e f i n e d by Open D i s c h a r g e P r e s s u r e Ref, 280°F P r e t r e a t m e n t None 2% N a 2 S 0 3 10 min, 250°F pH 6.5 None 2% N a 2 S 0 3 10 min, 250°F pH 6.5 C s f , ml 121 134 81 116 D e n s i t y , g/cc 0.36 0. 37 0. 39 0.42 Tear F a c t o r 78 92 86 82 B u r s t F a c t o r 13 19.5 24 20 B r e a k i n g L e n g t h , m 3180 4090 4730 3770 O p a c i t y 97.1 9 2.6 97.2 96.1 B r i g h t n e s s - E l r e p h o 45 57.5 51. 3 54.8 1% Z n S 2 0 4 58.6 64.1 59.5 58.7 1 h r . R e v e r s i o n , 105°C 55.4 59. 8 56. 3 .54.6 S o u r c e : P e r s o n a l communication (33). TABLE V DEPENDENCE OF PHYSICAL PROPERTIES OF MECHANICAL PULP ON L AND S FACTORS Model: Y± = a L + b S + c Physical Property, Y^ Linear Regression Equation : Stone Groundwood Thermomechanical Pulp Freeness, ml Bulk, cm3/g Burst Index, kPa.m2/g Breaking Length, m Tear Index, mN.m2/g Wet Web Strength, g/cm -170.4S + 1.20L + 278 -0.419S + 0.0067L + 3.03 0.68S + 0.014L - 0.35 2173.7S + 20.9L - 897 0.063L + 0.943S + 1.03 40. 8S + 32.8 9.2L - 104S - 116 0.043L - 0.65S - 2.23 0.96S - 0.019L + 0.24 1270S - 53L + 2874 0.14L + 1.93S - 3.6 28S - 0.40L + 45 Source: Personal Communication (46) . TABLE VI RESULTS OF EVALUATION OF THE PROPERTIES OF THE GMELINA MECHANICAL PULPS Presteamed, Presteamed, Presteamed, 10 min, 265 F, 10 min, 265 F, 10 min, 265°F, P r e t r e a t m e n t 24 p s i g 24 p s i g , 24 p s i g , 1% NaOH 2% N a 2 S 0 3 10% on Wood 20% on Wood, Sample I d e n t . None pH 6.5 A3 A4 A5 B3 B4 B5 C4 C5 C6 D4 D5 D6 Y i e l d , % 96.8 95.7. 89.6 95.3 S p e c i f i c E nergy, HPD/T 64.2 80.1 87.2 71.5 92.0 98.1 98.6 109.2 116.0 94.0 106.2 116.5 D e b r i s , % 1.6 0.4 0.2 0.9 0.4 0.3 0.1 0.1 0.0 0.2 0.2 0.1 C s f , ml 205 94 46 373 89 47 235 153 120 187 116 76 B a s i s Weight, g/m2 62.0 62.6 61.4 60.5 62.4 61.0 60.8 62. 5 61.5 57.6 61.1 62.1 D e n s i t y , g/cm 3 0.25 0.28 0.29 0.24 0.29 0.31 0. 33 0.35 0. 35 0.27 0.29 0.31 Tear Index, mN.m2/g 1.0 1.4 1.5 1.3 1.8 2.1 4.0 3.7 3.7 1.7 1.7 1.6 B u r s t Index, kPa.m 2/g 0.2 0.3 0.4 0.2 0.3 0.4 0.8 1.0 1.0 0.3 0.4 0.5 B r e a k i n g L e n g t h , km 0.7 1.1 1.4 0.6 1.0 1.1 2.3 2.6 2.7 0.9 1.2 1.4 S t r e t c h , % 0.5 0.6 0.6 0.5 0.6 0.5 0.6 0.7 0.7 0.5 0.5 0.6 TEA Index, mJ/g 20.9 35. 7 50.4 12. 8 28.2 28.3 32. 7 45. 3 45.7 24. 3 31.6 39.9 B r i g h t n e s s , ( E l r e p h o ) , % 52.5 53.9 54.5 48 .4 49.8 50.5 39.6 40 .4 40.7 56.2 56.8 56.5 O p a c i t y , % 97.6 98.5 99.2 95.7 99.6 99.7 97.6 99. 3 99.0 94.8 97.2 96.9 S c a t t e r i n g C o e f f . , cm 2/g 771 900 1066 576 1056 1089 590 773 776 664 787 763 A b s o r p t i o n C o e f f . , cm 2/g 73.2 78.5 92.1 67.8 131.2 130. 3 98.2 126. 8 127.2 47.3 58. 7 55. 0 TABLE V I I RESULTS OF BAUER McNETT CLASSIFICATION OF THE GMELINA MECHANICAL PULPS Sample I d e n t i f i c a t i o n P a r a meter S c r e e n R14 14/28 28/48 48/100 100/200 P200 A5 Weight, g L e n g t h , mm Weighted F i b e r L e n g t h (WL) 0.0066 0.943 0.0062238 0.1301 1.347 0.1752447 1.2585 0.920 1.15782 2.6572 0.748 1.9875856 2.2257 0.456 1.0159192 3.7219 0.1. 0.37219 B 4 (Presteamed) Weight, g L e n g t h , mm Weighted F i b e r L e n g t h (WL) 0.0084 0.943 0.0079212 0. 1276 1. 347 0.1718772 1.3347 0.920 1.227924 2.9225 0.748 2.18603 2.6075 0.456 1.18902 2.9993 0.1 0.29993 ( C a u s t i c P r e t r e a t m e n t ) Weight, g L e n g t h , mm Weighted F i b e r Length.(WL) 0.0001 0.943 0.0000943 0. 0214 1. 347 0.028858 3.3414 0.920 3.074088 2.1641 0.748 1.6187468 2.0164 0.456 0.9194784 2.4566 0.1 0.24566 D5 ( S u l f i t e P r e t r e a t m e n t ) W e i g h t , g L e n g t h , mm W e i g h t e d F i b e r L e n g t h (WL) 0.0108 0.943 0.0101844 0.1789 1.347 0.2409783 3.53172 0.920 3.249164 2.0802 0.748 1.5559896 1,7203 0.456 0.7844568 2.4781 0.1 0.24781 TABLE V I I I L- AND S-FACTORS OF THE GMELINA MECHANICAL PULPS Sample I d e n t i f i c a t i o n L - F a c t o r S - F a c t o r ml A4 (No P r e t r e a t m e n t ) 13.95 705 B4 (Presteamed) 14. 71 737 Cq ( C a u s t i c P r e t r e a t m e n t ) 33.63 650 D5 ( S u l f i t e P r e t r e a t m e n t ) 37.21 724 TABLE IX VALUES OF GMELINA MECHANICAL PULP PROPERTIES EXTRAPOLATED AT 90 ml C s f Sample I d e n t i f i c a t i o n P r e t r e a t m e n t A None B Presteamed C C a u s t i c D S u l f i t e C s f , ml 90 90 90 90 S p e c i f i c E n ergy, HPD/T 81 93 1 2 0 1 1 3 D e n s i t y , g/cm 3 0.28 0.30 0.36 0.30 Tear Index, mN.m2/g 1.4 1.9 3.6 1.6 B u r s t I ndex, kPa.m 2/g 0.33 0.35 1.1 0.47 B r e a k i n g L e n g t h , km 1.2 1.0 2.8 1.3 . S t r e t c h , % 0.6 0.6 0.8 0.6 TEA Index, mJ/g 40 28 52 '3« 7 B r i g h t n e s s ( E l r e p h o ) , % 54 50 41 57 O p a c i t y , % 9 8 . 5 99.4 9 9 . 9 9 7 . 3 S c a t t e r i n g C o e f f i c i e n t , cm 2/g 960 1 0 3 8 854 7 9 5 A b s o r p t i o n C o e f f i c i e n t , cm 2/g 80 127 142 58 TABLE X RESULTS OF EVALUATION OF GMELINA (CAUSTIC TREATED) PULP AND WEST COAST STONE GROUNDWOOD Sample I d e n t i f i c a t i o n Gmelina ( C a u s t i c T r e a t e d ) West Coast SGW C s f , ml 90 84 B a s i s Weight, g/m2 61.6 61.2 D e n s i t y , g/cm 3 0.36 0. 37 Tear I n d e x , mN.m2/g 3.6 3.4 B u r s t I n d e x , kPa.m 2/g 1.1 0.8 B r e a k i n g L e n g t h , km 2.8 2.5 S t r e t c h , % 0.8 1.4 B r i g h t n e s s ( E l r e p h o ) , % 41 52.2 O p a c i t y , % 99.9 97.8 S c a t t e r i n g C o e f f i c i e n t , cm 2/g 854 781 A b s o r p t i o n C o e f f i c i e n t , cm 2/g 142 76.9 TABLE XI RESULTS OF EVALUATION OF WEST COAST AND GMELINA SEMI-BLEACHED KRAFT (SBK) PULPS Sample I d e n t i f i c a t i o n Gmelina SBK West Co a s t SBK C s f , ml B a s i s Weight, g/m2 D e n s i t y , g/cm 3 Tear Index, mN.m2/g B u r s t I n d e x , kPa.m 2/g • B r e a k i n g L e n g t h , km S t r e t c h , % TEA In d e x , mJ/g B r i g h t n e s s ( E l r e p h o ) , % O p a c i t y , % S c a t t e r i n g C o e f f i c i e n t , cm 2/g A b s o r p t i o n C o e f f i c i e n t , cm 2/g 520 684 59.0 63.2 0. 66 0.58 10.6 23.5 2.7 4 . 6 . 4.2 5.7 1.9 2.1 590.8 835.1 72.5 62.8 81.0 72. 9 390 260 6.2 4.2 TABLE X I I RESULTS OF EVALUATION OF SIMULATED NEWSPRINT HANDSHEETS Sample I d e n t i f i c a t i o n WC/SBK and Gmelina Mech. WC/SBK and WC/SGW G/SBK and Gmelina Mech. P r o p o r t i o n s (Mech/SBK) 85/15 80/20 75/25 80/20 75/25 70/30 75/25 70/30 60/40 C s f , ml 195 236 254 169 209 237 180 194 233 B a s i s Weight, g/m2 62.1 61.4 58. 7 60.9 61.4 61.8 62.4 63.8 64 . 9 D e n s i t y , g/cm 3 0. 37 0.38 0. 39 0.40 0.41 0.42 0.39 0.42 0.42 Tear Index, mN.m2/g 7.8 9.3 10.0 7.8 9.1 9.8 4.7 5.1 6.0 B u r s t Index, kPa.m 2/g 1.2 1.3 1.4 1.5 1.7 1.9 1.4 1.4 1.5 B r e a k i n g L e n g t h , km 2.8 3.2 3.2 3.2 3.4 3.7 3.1 3.0 3.4 S t r e t c h , % 0.7 0.9 0.9 1.9 2.0 2.1 0.9 0.9 1.0 B r i g h t n e s s ( E l r e p h o ) , % 41.7 42.1 42. 3 52.4 53.2 54.3 43.5 43.5 45.2 O p a c i t y , % 96.7 96.0 93.5 96.0 95.6 93.9 96.8 96.8 96.7 S c a t t e r i n g C o e f f i c i e n t , cm 2/g 545 530 454 633 608 583 550 540 550 A b s o r p t i o n C o e f f i c i e n t , cm 2/g 81. 0 77.5 68.2 59.6 52.9 45.6 76. 7 75. 4 69.6 WC/SBK West C o a s t S e m i - B l e a c h e d K r a f t WC/SGW West C o a s t Stone Groundwood G/SBK Gmelina S e m i - B l e a c h e d K r a f t TABLE X I I I WET STRENGTH TEST RESULTS OF THE SIMULATED NEWSPRINT MIXES Sample I d e n t i f i c a t i o n WC/SBK and G/SBK and Gme! _ina Mech. Gmelina Mech. L e v e l P r o p e r t y 85/15 80/20 75/25 75/25 70/30 60/40 S t r e s s , g/cm w i d t h 55.5 55.1 57.5 4 7. 6 51.6 54. 7 Low P r e s s i n g S t r a i n , % 4.3 6.0 6.0 5.8 6.0 6.3 S o l i d s , % 28.6 24.1 28.4 28. 8 28.1 28.8 S t r e s s , g/cm w i d t h 90.2 89.8 85.8 79.9 81.9 83.9 H i g h P r e s s i n g S t r a i n , % 5.3 5.0 5.1 4.4 5.1 5.2 S o l i d s , % 38.7 38.9 38.9 38. 7 38.6 38.9 WC/SBK West C o a s t S e m i - B l e a c h e d K r a f t G/SBK Gmelina S e m i - B l e a c h e d K r a f t FIGURE 1. Part Cross-Section Stem of Gmelina arborea Roxb. (2.4X) CO o 81. 0 .01 1950 1954 1966 FIGURE 2. Use o f Residue M a t e r i a l s f o r P u l p i n g i n B r i t i s h Columbia and Canada : Source: S t a t i s t i c s Canada (24). FIGURE 3. D i a g r a m a t i c R e p r e s e n t a t i o n o f a T y p i c a l C h i p oo   FIGURE 6. P h o t o m i c r o g r a p h C a u s t i c P r e t r e a t e d P u l p Sample (C) (40X)  87. RUPTURE) I CHOH I COOK FIGURE 8. C e l l u l o s e O x i d a t i o n S o u r c e : The P u l p i n g o f Wood (61) 88. FIGURE 9. P h o t o m i c r o g r a p h West Coast Semi-Bleached K r a f t P u l p (26X) FIGURE 10. Ph o t o m i c r o g r a p h Gmelina Semi-Bleached K r a f t P u l p (26 X) 8 9 . FIGURE 11. P h o t o m i c r o g r a p h C r o s s - S e c t i o n West Coast Semi-Bleached K r a f t P u l p (160X Phase C o n t r a s t ) FIGURE 12. P h o t o m i c r o g r a p h C r o s s - S e c t i o n Gmelina Semi-Bleached K r a f t P u l p (160X Phase C o n t r a s t ) 90. • 5 i g u \ Cn >i -P •H CO g O . 3-1 0 t O Gmelina Mech. + WC/SBK A WC/SGW and WC/SBK * Gmelina Mech. + G/SBK 0 10 — i — 20 — i — 30 To SBK Content, % FIGURE 13, 12-. Density on Semi-Bleached Kraft Content of Simulated Newsprint Handsheets. Cn \ 10- g g 8 - X cu In  u 6 - (TJ QJ EH 4 0 O Gmelina Mech. + WC/SBK A WC/SGW + WC/SBK K Gmelina Mech. + G/SBK - i — 10 - i — 20 —r— 30 - r — 40 50 — r 60 SBK Content, % FIGURE 14 Tear Index of Simulated Newsprint Handsheets. 91. \ 3-1 \ CM e • 2- In  1- + J U Bu  0 —I 1 1—- 10 20 30 SBK C o n t e n t , © G m e l i n a Mech + WC/SBK A WC/SGW and WC/SBK X G m e l i n a Mech + G/SBK 1 40 ~ i — 50 FIGURE 15. B u r s t I n d e x on Semi-Ble a c h e d K r a f t C o n t e n t o f S i m u l a t e d N e w s p r i n t Handsheets -P cn c CD * 3- Cn C •H cd QJ o ffl ot O Gm e l i n a Mech + WC/SBK A WC/SGW and WC/SBK X G m e l i n a Mech + G/SBK — r — 10 20 30 40~ SBK C o n t e n t , % FIGURE 16. B r e a k i n g L e n g t h on Semi-Ble a c h e d K r a f t C o n t e n t o f S i m u l a t e d N e w s p r i n t Handsheets 92. 2.0 1. 5 u -P cu + J 00 1. OH 0. 5H i © Gmelina Mech + WC/SBK 4 WC/SGW and WC/SBK H Gmelina Mech + G/SBK 10 To SBK C o n t e n t , l — 30 — r — 40 50 FIGURE 17. S t r e t c h on Semi-Bleached K r a f t C o n t e n t o f S i m u l a t e d N e w s p r i n t Handsheets 6O-1 Q. re  50 • rH W tfl 0) CD C 40 • •P cn •H CQ t OGmelina Mech + WC/SBK AWC/SGW and WC/SBK & Gmelina Mech + G/SBK "To" FIGURE 18, i 20 — i — 30 40 50 SBK Con t e n t , % B r i g h t n e s s on Semi-Bleached K r a f t C o ntent of S i m u l a t e d N e w s p r i n t Handsheets 100i 0\° >1 + J •H £ 90-1 a, •o i t — i — 10 OGmelina Mech + WC/SBK A WC/SGW and WC/SBK X Gmelina Mech + G/SBK i 20 i 30 40 50 SBK C o n t e n t , FIGURE 19. O p a c i t y on Semi-Bleached K r a f t Content o f S i m u l a t e d N e w s p r i n t Handsheets 600-4 -p c CD •H u •H IH ^ 5 o u C •rH Q) 4 +J +J (0 O CO 00 1 00 0 O Gmelina Mech + WC/SBK A WC/SGW and WC/SBK ¥ Gmelina Mech + G/SBK — i - i — r — 10 20 30 SBK Con t e n t , % — i — 40 5 0 Cn -P CU •H o •H m 0 o u G o •H +J ft rH O CO FIGURE 2.0. S c a t t e r i n g C o e f f i c i e n t on Semi- B l e a c h e d K r a f t Content o f S i m u l a t e d N e w s p r i n t Handsheets 80 6 0 4 4 0 i ,t • Gmelina Mech + WC/SBK AWC/SGW and WC/SBK i 10 — — i 1— 20 30 SBK Con t e n t , \ Gmelina Mech + G/SBK 1— r 40 50 FIGURE ,21. A b s o r p t i o n C o e f f i c i e n t on Semi- B l e a c h e d K r a f t Content : o f S i m u l a t e d Newsprint Handsheets 95. 100 ., 90 1 80 4 Xi -p •H IS g CJ \ in cn cn -p CO 70 1 60 50 1 — t — 10 HIGH PRESSING LOAD LOW PRESSING LOAD O G m e l i n a Mech + WC/SBK R G m e l i n a Mech + G/SBK , — 20 30 SBK C o n t e n t , 40 50 FIGURE ;22 Wet S t r e n g t h C h a r a c t e r i s t i c s ( S t r e s s ) on Semi-Bleached K r a f t C o n t e n t of S i m u l a t e d N e w s p r i n t Handsheets 96. FIGURE 23. Wet S t r e n g t h C h a r a c t e r i s t i c s ( S t r a i n ) on S e m i - B l e a c h e d K r a f t C o n t e n t o f S i m u l a t e d N e w s p r i n t Handsheets APPENDIX FORMULAS APPLIED IN THE CALCULATIONS Horse Power Day P e r Ton, = Min x KW x 1.8 6 HPD/T O.D., l b Min = minutes o f run KW = average K i l o Watt r e a d i n g o v er the r u n O.D. l b = Oven d r y w e i g h t o f p u l p r e f i n e d , i n l b . F a c t o r 1.8 6 = Min t o days = m i n J 6 0 X 2.4 KW t o Horse Power O.D. l b t o Tons KW 0. 746 P.P., l b 2, 000 2. B a s i s Weight, g/m 2 , , _ 50 x Sample wt i n g 100 - % m o i s t u r e Handsneet - N o o f s h e e t s i n Sample x iOO Paper wt o f one sheet x 50 x % s o l i d s Sample wt i n g A r e a o f sample i n m 2 D e n s i t y , g/cm 3 = B a s i s Weight C a l i p e r 16* Tear S t r e n g t h , = 9.807 x „ f . _ x s c a l e r e a d i n g _ M m j_ ff °r s n e e r s mN per Sheet 32, i f heavy pendulum i s used 8, i f l i g h t pendulum i s used 5. Tear Index, = Tear i n mN mN.m2/g B a s i s Weight i n g/m2 6. B u r s t S t r e n g t h , = B u r s t i n p s i x 6.90 kPa 7. B u r s t Index, = B u r s t s t r e n g t h i n kPa kPa.m 2/g B a s i s w e i g h t i n g/m2 97 98. 8. T e n s i l e S t r e n g t h , = 0.65378 x average l o a d i n Kg kN/m T e n s i l e Index, N.m/g 653.78 , , - •. =—T-r—•—:—y—r x average l o a d B a s i s w e i g h t i n g/mz . 3 Tjr 3 J i n Kg 10. B r e a k i n g L e n g t h , m 66667 - : :—=-r—• 7—3- x average l o a d B a s i s w e i g h t i n g/m2 . 3 T, J i n Kg 11. T e n s i l e Rupture Modulus, Pa ( p a s c a l s ) 6.5378 x average l o a d i n Kg x I Q 1 0 C a l i p e r i n x S t r e t c h i n % 12. S t r e t c h , % 0.0277778 x average d i s t a n c e i n mm 13. T e n s i l e Energy A b s o r p t i o n , (TEA), J/m 2 0.196 x c o u n t s x l o a d x span span x w i d t h 14. TEA Index, mJ/g = 1000 x TEA i n J/m; B a s i s wt i n g/m2 15. O.D. B a s i s Wt., g/m2 = Dry wt o f sample x 3 33. 65 No. o f s t r i p s 16. B a s i s Wt. C o r r e c t i o n F a c t o r T a r g e t b a s i s w e i g h t C a l c u l a t e d b a s i s w e i g h t 49 C a l c u l a t e d b a s i s w e i g h t 17. S t r e s s , g/specimen = Average s c a l e r e a d i n g x b ± a b = s l o p e a = i n t e r c e p t 18. C o r r e c t e d g/specimen S t r e s s i n g/specimen x b a s i s wt c o r r e c t i o n f a c t o r 99. 19. S t r a i n , = S c a l e r e a d i n g x 1.32 x 0.07 mm s t r a i n / g cm 20. S t r a i n , % = S t r a i n x ^~ 21. O p a c i t y , % = |°r x 100 22. S c a t t e r i n g = 1 10 C o e f f i c i e n t , O.D. b a s i s wt i n g/m2 x l/R^-R 0 0 cm 2/g (I-RQRQO) ± n l-RoR») 23. A b s o r p t i o n = S (1-R°°) C o e f f i c i e n t , 2 R°° cm 2/g

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{[{ mDataHeader[type] }]} {[{ month[type] }]} {[{ tData[type] }]}

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