Process for making paper, cardboard and paperboard with great dry and wet resistance and lean resistance

摘要

1. A process for the production of paper, cardboard and board having high dry strength, wet strength and alkali resistance by adding an aqueous polymer solution to the paper stock in an amount of from 0.1 to 5% by weight, based in each case on the solids, and draining the paper stock on a screen to form sheets, wherein the aqueous polymer solution used is a reaction product obtained by reacting (1) a homopolymer of a vinylimidazole of the formula I see diagramm : EP0146000,P6,F1 where R**1 , R**2 and R**3 are each H or CH3 , and R**1 may furthermore be C2 H5 , C3 H7 or C4 H9 , or (2) a water-soluble copolymer of a) at least 5% by weight of a vinylimidazole of the formula I, b) up to 95% by weight of acrylamide and/or methacrylamide and, if desired, c) up to 30% by weight of acrylonitrile, methylenically unsaturated C3 -C5 - carboxylic acid or one of its esters, with epichlorhydrin in a ratio of from 0.02 to 2.9 moles of epichlorhydrin per molar equivalent of basic nitrogen in the homopolymer or copolymer, in the absence of a polyalkyleneimine.