Abstract: A method for producing a sheet of paper or cardboard from a fibrous suspension, includes injection of a polymer P2 into a fibrous suspension, forming of a sheet of paper or cardboard, and drying the sheet of paper or cardboard. The polymer P2 is prepared, before injection of the polymer P2, from a water-soluble polymer P1 in the form of solid particles. Polymer P1 consists of at least one nonionic monomer selected from acrylamide, methacrylamide, N,N-dimethylacrylamide, and acrylonitrile. Polymer P1 is subjected to a reaction Re to yield polymer P2. The reaction Re includes the addition and the dissolution of solid particles of polymer P1 in an aqueous solution M1 of an alkali hydroxide and/or an alkaline earth hydroxide, and an alkali hypohalide and/or an alkaline earth hypohalide, prior to a reaction time of 10 seconds to 5 hours.

Abstract: A method for producing a sheet of paper or cardboard from a fibrous suspension includes injection of a polymer P2 into a suspension of cellulosic fibers, forming of a sheet of paper or cardboard, and drying of the sheet of paper or cardboard. The polymer P2 is prepared, before the injection, from a water-soluble polymer P1 in inverse emulsion form. P1 consists of at least one nonionic monomer selected from acrylamide, methacrylamide, N,N-dimethylacrylamide, and acrylonitrile. The polymer P1 is subjected to a reaction Re to yield a polymer P2. The reaction Re includes adding the polymer P1 in inverse emulsion form to an aqueous solution M1 of an alkali hydroxide and/or an alkaline earth hydroxide, and an alkali hypohalide and/or an alkaline earth hypohalide, prior to a reaction time of 10 seconds to 5 hours.

Abstract: A process for making a sheet of paper or cardboard from a fiber suspension, includes injection of a polymer P3 into a cellulosic fiber suspension, formation of a sheet of paper or cardboard, and drying of the sheet of paper or cardboard. The P3 polymer is prepared, prior to the injection, from a water-soluble P1 polymer of at least one nonionic monomer, such as acrylamide, methacrylamide, N,N-dimethylacrylamide, and acrylonitrile. The P1 polymer is subjected to a Re1 reaction to give a P2 polymer, which is then subjected to a Re2 reaction to give the P3 polymer, which is injected into the fibrous suspension within 24 hours of the start of the Re1 reaction.