木质素对酚醛/木质素嵌段共聚树脂制备的影响及反应机理

以工业木糖生产残渣为原料, 用不同条件下碱提取得到的碱木质素液与苯酚和甲醛原位反应制备酚醛/木质素嵌段共聚树脂. 以所制备树脂中甲醛释放量最小为原则, 得到木质素的最佳提取条件: 碱浓度5%(质量分数), 固液体积比1:12, 反应时间3 h. 在此条件下树脂中甲醛释放量为0.115%, 相应的胶合强度为1.197 MPa, 均远优于GB/T14074-2006中对于一类胶合板用酚醛胶的要求(甲醛释放量≤0.3%, 胶合强度≥0.7 MPa). 实验结果表明, 碱木质素液能参与到反应中, 提高酚醛/木质素嵌段共聚树脂的热稳定性及胶合强度, 降低甲醛释放量, 有利于树脂的储存及应用. 同时讨论了碱木质素与苯酚和甲醛的可能反应机理.

Lignin Impacts on the Preparation of Phenolic-resin/Lignin Block Copolymer Resin and the Reaction Mechanism†

Phenolic-resin/lignin block copolymer resin was in-situ prepared using alkali lignin under different extraction conditions, phenol and formaldehyde as reactants, industrial xylose production residue as raw material. To obtain the minimum formaldehyde release, the best extraction conditions of alkali lignin are as following:the sodium hydroxide concentration is 5%( mass fraction) , the mass ratio of solid/liquid is 1:12, and the reaction time is 3 h. The formaldehyde release is 0. 115% and boiling water soaked bonding strength is 1.197 MPa, which are superior to the GB/T14074-2006(≤0. 3%,≥0. 7 MPa) . TG, FTIR and SEM results show that alkali lignin involved in the reaction. It improved the thermal stability and bonding strength of phenolic-resin/lignin block copolymer resin, at the same time it decreases the formaldehyde release. All of them improved the storage and application of resin significantly. According to our experimental results, possible reaction mechanism was proposed.