Process for preparing vinyl amine-containing water soluble copolymers and their use as wet and dry strength agents for paper

Process for the preparation of vinylamine units water-soluble copolymers containing polymerized by copolymerizing a) from 95 to 10 mol% of N-vinylformamide and (b) 5 to 90 mol% of an ethylenically unsaturated monomer from the group vinyl acetate, vinyl propionate, C₁- to C₄- alkyl vinyl ethers, the esters, nitriles and amides of acrylic acid and methacrylic acid and N-vinylpyrrolidone and subsequent cleavage from 30 to 100 mol% of the formyl groups from the copolymer. Preferably Copolmerisate of N-vinylformamide and vinyl acetate can be considered, whose monomer units are hydrolyzed to each 30 to 100 mol%. The copolymers are used in the manufacture of paper to enhance the dry and wet strength of the paper.