Study on Paper Wet Strength Agent of PAE Modified with Blocked Polyurethane

The paper wet strength agents of PAE modified with imidazole-blocked polyurethane were prepared by the reaction of polyaminamide 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.