Patent ID: 8029647

Claim:
A process for producing paper, board or cardboard comprising: draining a paper stock on a wire with sheet formation which is carried out in the absence of a finely divided inorganic flocculant and in the presence of a retention aid to obtain a sheet, wherein the retention aid comprises: (a) at least one hydrolyzed polyvinylformamide having a degree of hydrolysis of 0.5-50% and a weight average molar mass M w of at least 1,200,000, which is prepared by homopolymerizing N-vinylformamide to give poly-N-vinylformamide and subsequently hydrolyzing 0.5-50% of the vinylformamide units to vinylamine units, which is cationic, and which has a charge density of 0.2-4 meq/g; and (b) at least one cationic poly(meth)acrylamide copolymer having a weight average molar mass M w of at least 3,000,000 and comprising 70-93 mol. % of acrylamide and 7-30 mol. % of at least one cationic monomer, wherein the cationic monomer is selected from the group consisting of dimethylaminoethyl acrylate and dimethylaminoethyl methacrylate, including free bases, salts and/or quaternized forms thereof, wherein a weight ratio of component (b) to component (a) is 0.25-0.4; and drying the sheet obtained from said sheet formation.