木质素对木质素-脲醛共聚树脂的影响及反应机理

通过调控甲醛与尿素摩尔比, 降低脲醛树脂胶黏剂中游离甲醛的含量, 以生物质玉米芯为原材料, 用碱液提取得到的碱木质素溶液与甲醛和尿素进行三元逐步共聚, 弥补降低醛脲比带来的胶合强度的快速下降问题. 以降低游离甲醛含量同时兼顾胶合强度为原则进行探索, 得到最佳实验条件为甲醛与尿素摩尔比(F/U)为0.91∶1, 木质素添加量为20%(质量分数), 在此条件下木质素-尿素-甲醛共聚树脂(LUF)胶合强度为0.99 MPa, 游离甲醛含量为0.26%. 对共聚树脂进行了结构表征, 表明木质素参与到反应中, 并能提高树脂的热稳定性和耐水性, 同时对反应的机理进行了讨论.

Lignin Impacts on the Lignin-urea-formaldehyde Copolymer Resin and the Reaction Mechanism†

By regulating the molar ratio of formaldehyde and urea to reduce the content of free formaldehyde in urea-formaldehyde resin adhesive, using biomass corn cob as raw material to extract lignin with alkali solution, the alkali lignin solution was gradually copolymerized with formaldehyde and urea to compensate for the problem of rapid decrease in the bonding strength caused by the reduction of aldehyde urea ratio. With reducing the free formaldehyde content and taking into account the bonding strength as a principle to explore, the best experimental conditions were obtained: formaldehyde to urea molar ratio of F/U is 0.91∶1, the amount of lignin added is 20%(mass fraction), under these conditions, the lignin-urea-formaldehyde(LUF) copolymer resin has a bonding strength of 0.99 MPa and a free formaldehyde content of 0.26%. The characterization results of the copolymer resin using HR-MS, XPS, FTIR and TG show that lignin can participate in the reaction and improve the thermal stability and water resistance of the resin. At the same time, the mechanism of the reaction was discussed.