Preparation of Polyurethane Based on Lignin Isolated from Alkali-Oxygen Pulping Wheat Straw Waste Liquor

摘要

Lignin-based polyurethane was prepared by replacing part of polyols with alkali-oxygen pulping wheat straw lignin (AOL) recovered from the pulping waste liquor, or hydroxyalkylated AOL (H-AOL). Their content of reactive function groups, aliphatic hydroxyl (Alc-OH) groups, was 7.07% and 10.1%, respectively. Polyurethane films (PUs) with various NCO/OH ratios and lignin contents were synthesized with AOL or H-AOL, polyethylene glycol (PEG) and crude diphenylmethanc diisocyanate (MDI). AOL based PUs with NCO/OH ratios (<1.8) had the thermal and mechanical properties lower than those with intermediate NCO/OH ratios (1.8-2.4). Greater NCO/OH ratios (>2.6) made PUs rigid and brittle. H-AOL based PUs could been acquired with lower NCO/OH ratios (1.39-1.83). Adding plasticizer diisobutyl phthalate could raise the ultimate elongation of PUs greatly.