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Chemical modification of bark tannins for adhesive formulation

University of British Columbia

A reaction is described that cleaves catechin (I) or conifer tannins (II) into catechol (III) and quinoline derivatives (IV and V). The reagent and conditions required for this reaction were 30% ammonium sulphite in concentrated ammonium hydroxide solution heated to 175° C for 1 to 3 hours. The optimization of these conditions is described along with a quick gas chromatography-based assay procedure for catechol. A mechanism for the reaction of catechin under these reaction conditions is proposed based on the structure of the end products, and the behavior of compounds related to the starting material. It was found that an understanding of the classic Bucherer reaction was necessary for elucidation of the cleavage reaction, so a discussion of the former is presented. The production of catechol and other simple phenolics from tree bark tannins could be important in the utilization of the latter materials as adhesives in the forest product industry. A review of the literature on tannin-based adhesives is presented. Adhesive formulations based on the mixture of organic compounds produced from the cleavage of western hemlock (Tsuga heterophylla (Raf.) Sarg.) bark tannins were qualitatively and quantitatively evaluated for strength- Although early indications were promising, the quality of the bark used, and its ability to produce catechol, degraded rapidly during storage. Adhesives made with bark stored for more than two months did not produce good bond strengths. [See Thesis for Diagram]

Text

2010-06-13

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http://hdl.handle.net/2429/25620

Forestry

University of British Columbia

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