羟甲基化对合成木质素改性酚醛胶粘剂性能的影响

Effect of Hydroxymethylation of Lignin on the Properties of Lignin-phenol-formaldehyde Resins

采用羟甲基化技术对碱木质素进行活化,对比了羟甲基化前后木质素改性酚醛树脂胶的粘结强度、残留甲醛、贮存稳定性和热稳定性等性能,为木质素的高值应用探讨新的途径。试验结果表明在木质素对苯酚的替代率低于30%条件下,以分离提纯后的木质素可直接应用于酚醛树脂胶粘剂的改性;而当替代率大于50%后,木质素的羟甲基化展示对木质素改性酚醛树脂的胶结强度、热稳定性具有良好的促进作用。但木质素的羟甲基化作用同时也导致木质素改性酚醛树脂中残留甲醛含量增加,进而导致制备的胶粘剂的贮存稳定性降低,可以通过改变合成过程中甲醛和碱的用量来达到降低酚醛树脂中残留甲醛含量。

lignin was activated by hydroxymethylation for preparation of lignin-phenol-formaldehyde adhesive,and the properties of adhesives synthesized, including adhesive strength, residual formaldehyde content, storagestability and thermostability, were investigated. The results show that under the condition of less than 30% replacement of phenol by lignin,there are little of differences in the properties of adhesives synthesized with lignin and hydroxymethylated ligmin, and hence the purified lignin can be directly used in the lignin modified phenol-formal- dehyde adhesive. However, when the replacement of phenol by lignin is more than 50%, the hydroxymethylated lignin can facilitate the adhe- sive strength and thermostability. Although the use of hydroxymethylated lignin in the adhesive results in the higher contents of residual form- aldehyde and the lower storagstability,this negative effect can be reduced by altering the dosages of formaldehyde and alkali.