Preparation and process optimization of lignin-based phenolic resin
The enzymatic hydrolysis lignin obtained from biorefinery industry retains the structural characteristics of the original lignin with rich active groups such as alcohol hydroxyl and phenolic hydroxyl,which can be used in the preparation of phenolic resin.The purity,alcohol hydroxylic group and the phenolic hydroxyl group were investigated for the synthesis and application properties of phenol-formaldehyde resin(PF).Limited by the complexity of the lignin structure,the reaction process could not be effectively tracked and optimized.The preparation process of lignin-PF was optimized by online ReactIR equipment,and the change pattern of formaldehyde amount in the system was studied by the infrared absorption peak of 1020cm-1.The results showed that adding formaldehyde and sodium hydroxide in a multistep reaction with the system pH above 10.5 promoted the synthesis of the phenolic resin.When the ideal polymerization temperature was controlled at 88-95℃ and the maximum amount of lignin was added at 60%,the bonding strength of phenolic resin adhesive(0.90MPa)and the lowest formaldehyde release(0.142mg/L)could reach the E0 and I specified standard.