Synthesis of Lignin-Based Polyacid in an Acidic Ionic Liquid: A Green Method to Improve the Performance of Lignin as Catalyst in Urea-Formaldehyde Resin

摘要

The aim of this research was to investigate the effect of ionic liquid treated lignin-based polyacid as a catalyst for urea-formaldehyde(UF)resins.Esterification of lignin was carried out,without any catalyst,with anhydride maleic and 1-butyl-3-methylimidazolium hydrogen sulfate[Bmim][HSO 4]as acidic ionic liquid to form maleated lignin-based polyacids(MA-IL).The performance of MA-IL as UF resin catalyst was respectively compared to hyroxymethylated lignin-based polyacid(MA-HL)and to NH 4 Cl.The FTIR analysis indicated that the propor-tion of-COOH and C-O bonds increased due to the esterification of lignin with ionic liquid rather than its hyr-oxymethylation.Physicochemical tests indicated that the gelation time of the UF resin was shorter by adding MA-IL when compared to NH 4 Cl and MA-HL,respectively.DSC analysis showed that the addition of MA-IL significantly decreased the temperature peak(Tp)of the UF resin;as the Tp of the UF resin with 2 wt%MA-IL was lower than with MA-HL and NH 4 Cl,respectively.The panel test results of plywood bonded with a UF resin with a MA-IL level increasing from 1%to 3%,effectively improved the mechanical strength,water resistance and formaldehyde emission even higher than with MA-HL and NH 4 Cl,respectively.