木质素的水热降解及其在酚醛树脂中的应用

Hydrothermal degradation of lignin and its application to phenolic resins

关键词:  木质素  水热降解  酚醛树脂  胶粘剂

Key Words:Lignin  Hydrothermal degradation  Phenolic resins  Adhesives

摘要:本文以乙酸木质素(AAL)为原料,旨在通过水热处理法调控其相对分子量的同时,提高其活性官能团含量,并以改性木质素(DL)替代部分苯酚制备木质素基酚醛树脂胶粘剂(DLPF)。研究了水热处理条件,如温度、水热反应时间以及碱用量等因素对乙酸木质素分子量及其分布、酚羟基、甲氧基等活性基团的影响。在水热降解条件为200℃,150min,碱含量为20wt%(相对于木质素质量)时,改性木质素中酚羟基含量较高,甲氧基含量变低,而木质素分子量从9789降低至4339,木质素中醚键等发生断裂。木片粘接实验检测的结果显示,水热降解木质素制备的DLPF性能最佳时,胶合强度为1.5MPa,游离甲醛含量0.11%,游离苯酚含量为0.54%。

Abstract:This study uses acetic acid lignin (AAL) as the raw material, aiming to regulate its relative molecular weight and increase the content of active functional groups through hydrothermal treatment. Modified lignin (DL) was used to replace part of phenol in the preparation of lignin-based phenolic resin adhesive (DLPF). The effects of hydrothermal treatment conditions, such as temperature, reaction time, and alkali dosage, on the molecular weight and distribution of acetic acid lignin, as well as active groups like phenolic hydroxyl and methoxyl groups, were investigated. Under the hydrothermal degradation conditions of 200 °C, 150 min, and 20 wt% alkali content (relative to lignin mass), the modified lignin exhibited a higher content of phenolic hydroxyl groups, lower methoxyl group content, and its molecular weight decreased from 9789 to 4339, indicating the cleavage of ether bonds in lignin. Wood chip bonding tests showed that when the DLPF prepared from hydrothermally degraded lignin had optimal performance, the glue bond strength was 1.5 MPa, the free formaldehyde content was 0.11%, and the free phenol content was 0.54%.