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己内酰胺在苯甲酸和6-氨基己酸存在下的聚合反应,实验结果表明苯甲酸具有引发 单体聚合、酸解大分子链和酰化大分子的氨基的作用。反应的开始为催化引发单体生成大分子链而不是苯甲酸与单体的加成。随着大分子的增多,酸解和酰化也同时发生。在反应半小时后酸解的影响逐渐显著,到3—4小时以后,酸解影响超过缩聚使聚合物分子量下降羧基含量增加。到反应7—8小时后,聚合物生成量及分子量已达恒定而酰化仍继续进行。到反应达到平衡时,仍然有游离的苯甲酸,聚合物中仍有游离的氨基和羧基,说明酸解、酰化与缩聚都是可逆反应。 在不用苯甲酸的己内酰胺与水的聚合实验中,聚合物虽在常压通氮的情况下在250°,270°或300°加热6小时分子量仍能稳定在一定数值而不升高,即加热15小时(250°)变化也很小。氨基与羧基不再进行缩聚,可能系由于反应系统粘稠,水分子不易扩散除去,大分子不易移动接触,功能基又受本身分子链的空间阻碍,使反应不易继续进行,维持在一定平衡状态。
Caprolactam polymerization in the presence of benzoic acid and 6-aminocaproic acid, the experimental results show that benzoic acid has the role of initiating monomer polymerization, acid hydrolysis of the amino group of the macromolecular chains and acylated macromolecules. The start of the reaction catalyzes the monomer-initiated macromolecular chain rather than the addition of benzoic acid to the monomer. With the increase of macromolecules, acid hydrolysis and acylation also occur simultaneously. After half an hour of reaction, the effect of acidolysis becomes noticeable. After 3-4 hours, the acid hydrolysis affects polycondensation and the molecular weight of the polymer decreases. After 7-8 hours of reaction, the amount and molecular weight of the polymer have been reached and the acylation continues. When the reaction reaches equilibrium, there is still free benzoic acid, and there are still free amino and carboxyl groups in the polymer, indicating that acid hydrolysis, acylation and polycondensation are all reversible reactions. In the polymerization experiment of caprolactam without benzoic acid and water, the molecular weight of the polymer can be stabilized at a certain value without heating by heating at 250 °, 270 ° or 300 ° for 6 hours under atmospheric pressure of nitrogen, that is, heating 15 hours (250 °) change is also small. Amino and carboxyl no longer polycondensation may be due to the reaction system is viscous, water molecules are not easy to remove diffusion, the macromolecule is not easy to move contact, the functional group is hindered by its own molecular chain space, the reaction is not easy to continue to maintain a certain balance .