低黏度大豆蛋白胶黏剂制备及其在刨花板应用

Development of Low Viscosity Soy Protein Adhesive for Particleboard Manufacturing

常规大豆蛋白胶黏剂在刨花板应用中存在黏度高、无法喷胶、固体含量低及耐水胶接性能差等问题。为解决上述问题,本研究通过破坏大豆蛋白分子结构及分子间作用力降低胶黏剂黏度,提高胶黏剂固体含量,以满足刨花板生产工艺要求;利用环氧类交联剂与大豆蛋白交联反应形成交联网络,提高胶黏剂的耐水性和刨花板的力学性能。改性大豆蛋白胶黏剂固体含量提高至30.95%,比未改性大豆蛋白胶提高31.9%;黏度降低至35 s(涂-4杯,25℃),且储存240 h后仍然低于60 s(涂-4杯,25℃),可实现喷涂施胶,板坯预压成型性能良好,可替代表层异氰酸酯胶制备低成本无醛刨花板产品。当表层刨花加入19.8%改性大豆蛋白胶黏剂,芯层刨花加入2.6%改性大豆蛋白胶黏剂和1.7%异氰酸酯时,制备密度654 kg/m^(3)的刨花板,其2 h吸水厚度膨胀率(2.20%)、静曲强度(12.16 MPa)、弹性模量(2163 MPa)、内胶合强度(0.53 MPa)、表面胶合强度(0.85 MPa)等性能指标满足GB/T 4897—2015《刨花板》P2型刨花板的要求。

The application of soy protein adhesives in particleboard manufacturing has some challenges,such as high viscosity,inability to spray glue,low solid content,and poor water resistance.To solve the above problems,in this project the viscosity of the adhesive was reduced,and the solid content of the soy protein adhesive was increased through destroying the molecular structure of soy protein and the intermolecular force to meet the requirements of the particleboard production process.The epoxy crosslinked with the soy protein forming a network to improve the water resistance of the adhesive and the mechanical properties of the particleboard.The solid content of modified soy protein adhesive increased to 30.95%,which was 31.9%higher than that of unmodified soy protein adhesive.The viscosity was reduced to 35 s(coating-4 cup,25°C),while the viscosity was less than 60 s after 240-h(coating-4 cup,25°C)storage,so that the spray sizing was achieved.The laboratory-made particleboards had good preloading performance,which solved the problems of low solid content,high viscosity,and inability of spraying glue of the soy protein adhesive.The results showed the low viscosity soy protein adhesive could replace the surface layer isocyanate adhesive to prepare low-cost formaldehyde-free particleboard products.When 19.8%modified soy protein adhesive was added to the surface layer of shavings,2.6%modified soy protein adhesive and 1.7%isocyanate were added to the core layer of shavings,the particleboard sample with a density of 654 kg/m^(3)was prepared,and its the physical and mechanical properties including 2-h water absorption thickness expansion rate(2.20%),the static flexural strength(12.16 MPa),the elastic modulus(2163 MPa),the internal bonding strength(0.53 MPa)and the surface bonding strength(0.85 MPa),met the specifications of P2 type according to National Standard GB/T 4897—2015 for particleboard.