中文摘要：

以咪唑为封闭剂制备出封闭聚氨酯（BPU），用BPU代替部分环氧氯丙烷（ECH）与聚酰胺多胺反应得到改性PAE纸张增湿强剂（MPAE）。研究rBPU封闭率、ECH添加量、助留剂及抄造系统pH值等因素对纸张性能的影响。结果表明，异氰酸酯基团比PAE分子中活性基团对提高纸张湿强性能更有效；w（ECH）为25．71％时，纸张湿抗张指数和湿强度保留率分别达到7．08N·m／g和33．6％；助留剂CPAM可间接提高MPAE的留着率；抄造系统的中（弱）碱性有利于发挥增湿强剂的应用性能。

英文摘要：

The paper wet strength agents of PAE modified with imidazole-blocked polyurethane were prepared by the reaction of polyami- namide and epichlorohydrin （ECH） in BPU N-methyl pyrrolidone solution. The influence of the blocked ratio of BPU, the dosages of ECH, the charge and adding process of retention agent, and the pH value of pulp on the physical properties of the treated paper was studied. The results showed that isocyanate groups are more efficient than the active groups in the PAE molecular in increasing the wet tensile index of paper. When the dosage of ECH is 25.71%, the wet tensile index and the wet strength can reach as high as 7.08 N.m/g and 33.57% respectively. CPAM can indirectly increase the retention of MPAE. It is advantageous of pulp under neutral-weak alkaline condition to increase the application performance of the wet strength agents.