| Research Abstract |
Wood adhesives added with lignocellulosic materials were investigated using isolated lignin, steam-exploded wood flours (SE), or steam-exploded wood flours modified with microbes (BMSE) as the additives, and phenol-formaldehyde resin, urea-formaldehyde resin, or thermoplastic polymers (for wood/plastic composites) as the base adhesives. SE was superior to lignin as an additive throughout the experiments. Especially, the effect was remarkable for phenol/formaldehyde resin, which was analyzed to come from a physical, rather than a chemical origin. Good results were also obtained when SE was added to wood/plastic composites.
To increase the aromatic reaction sites for formaldehyde, the transition-metal catalyzed oxidative demethylation of phenyl methyl ether bond in lignin was attempted, and we fund a successful catalytic cleavage of CHィイD23ィエD2-O bond with molecular oxygen under mild conditions. Then, it may be possible to replace CHィイD23ィエD2-O bonds in lignin into HO bonds by biological oxidation. In this context, we examined the biological oxidation of SE with several wood-decay fungi and the performance of products as the additive of phenolic adhesive formulations. The results were, however, disappointing ; the performance of BMSE-added formulations were as good as, or rather poorer than, the SE-added formulations. The biological oxidation was further examined by the addition of inducer(s) in the preincubation stage. Then, the results using MnSOィイD24ィエD2 as the inducer were encouraging. SEs treated with several fungi, such as COV, PHC, and TYP, for example, showed excellent performance as the additive to phenolic resin.
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