木质素环氧聚合物合成及其改性大豆蛋白胶黏剂的性能

Synthesis of Epoxy Polymer of Lignin and Its Performance for Modified Soy Protein Adhesive

以木质素、乙二醇二缩水甘油醚为材料,在碱性催化剂作用下开环反应合成木质素环氧聚合物(EPL),将木质素环氧聚合物与大豆分离蛋白(SPI)进行交联反应,制备改性大豆蛋白胶黏剂;采用环氧值测定、傅里叶红外光谱、核磁共振、热质量分析等方法,分析木质素环氧聚合物的环氧值、化学结构,探索木质素环氧聚合物对改性大豆蛋白胶黏剂结构、热稳定性、胶合强度的影响,评价木质素环氧聚合物对大豆蛋白胶黏剂结构、胶合性能的改性效果。结果表明:木质素成功接枝环氧基团,合成了高反应活性的木质素环氧聚合物,环氧值为2.92 mol/kg,与商用水性环氧树脂环氧值接近;木质素环氧聚合物可以与大豆蛋白分子发生氢键作用和化学反应,形成交联结构,提高改性大豆蛋白胶黏剂的耐热性能;当木质素环氧聚合物质量分数为5%时,改性大豆蛋白胶黏剂胶合强度达到0.99 MPa,满足国家标准GB/T 9846—2015规定的Ⅱ类胶合板要求。

The epoxy polymer of lignin(EPL)was synthesized by ring-opening reaction of lignin and ethylene glycol diglycidyl ether in alkaline condition,and then used to crosslink with soy protein isolate(SPI)to produce modified soy protein adhesives.Using epoxy value determination,fourier transform infrared spectroscopy,proton nuclear magnetic resonance spectrometry,and thermogravimetric analysis,the epoxy value and chemical structure of epoxy polymer of lignin were analyzed,and the influence of epoxy polymer of lignin on the structure,thermal properties,and bonding strength of modified soy protein adhesives was also investigated,thus the modification effect of epoxy polymer of lignin on the structure and bonding performance of soy protein adhesives were evaluated.The results showed that the lignin was successfully grafted with epoxy groups to synthesize the epoxy polymer of lignin with high reactive activity,and its epoxy value was 2.92 mol/kg,which was close to that of commercial waterborne epoxy resin.The epoxy polymer of lignin can react with soy protein molecules via a hydrogen bonding and chemical reaction to form a crosslinking structure,which can improve the thermal properties of modified soy protein adhesives.Additionally,the wet shear strength of SPI-EPL(5.0%)adhesive reached 0.99 MPa,meeting the requirements of type II plywood specified in the China National Standards(GB/T 9846-2015).