Patent ID: 8349134

Claim:
A process for producing paper, board and cardboard of high dry strength by separately adding a polymer comprising vinylamine units and a polymeric anionic compound to a paper pulp, dewatering the pulp and drying the paper products, wherein said polymeric anionic compound consists of the following monomers which are copolymerized: (a) at least one N-vinylcarboxamide of the formula in which R 1 and R 2 are H or C 1 to C 6 alkyl, (b) at least one acidic monoethylenically unsaturated monomer and/or the alkali metal, alkaline earth metal or ammonium salts thereof, and, optionally, (c) at least one other monoethylenically unsaturated monomer selected from the group consisting of methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, vinyl ester, N-vinylpyrrolidone, N-vinylimidazole, acrylamide and methacrylamide.