| abstract |
Described is the use, as additives to paper-making pulp, of copolymers obtained by polymerizing a) 5 to 99 mole % of N-vinyl carboxylic acid amides, b) 95 to 1 mole % of monoethylenically unsaturated carboxylic acids and/or alkali-metal, alkaline-earth metal, ammonium or amine salts thereof, and optionally c) up to 30 mole % of other monoethylenically unsaturated compounds, and optionally d) up to 2 mole % of crosslinking agents, and subsequently splitting off some or all of the formyl groups from the N-vinyl carboxylic acid amide units in the copolymer to form amine or ammonium groups. Such additives increase the water-removal speed and retention during the manufacture of paper, as well as the dry and wet strength of the paper. |