植物材料からの新しいポリウレタン

Abstract

New types of polyurethanes were synthesized from kraft lignin, solvolysis lignin and wood meal by polymerization with polyethylene glycol (PEG) and diphenylmethane diisocyanate (MDI). The results obtained are as follows.(1) Polyurethane films were made by solvent casting, and their tensile properties were measured. It was found that kraft and solvolysis lignins contributed effectively to an improvement in the mechanical properties of polyurethanes. Polyurethanes of considerable toughness were obtained, under specific conditions of the isocyanate/hydroxyl group ratio (NCO/OH) and also depending on either kraft or solvolysis lignin content. At high kraft and solvolysis contents, the obtained polyurethanes were hard and brittle, regardless of the NCO/OH ratio used in the experiment.(2) Polyurethane foams were synthesized from a three-component system consisting of PEG, MDI and kraft lignin. Polyurethane foams having kraft lignin contents of up to 40% and apparent densities ranging from 0.04 to 0.22 g/cm3 were prepared by controlling the kraft lignin content, NCO/OH ratio and water content. The compressive strength and elasticity of the polyurethane foams increased with increasing kraft lignin content and NCO/OH ratio.(3) Polyurethane films and foams, which were synthesized by using wood meal as a raw material, generally showed similar mechanical properties to those of polyurethanes which were synthesized from kraft and solvolysis lignins.