Method for the hydrolysis of a polymer

A method of producing paper or cardboard comprising the following steps:

• (AC) adding a final polymer A to a first aqueous pulp suspension whereby a second aqueous pulp suspension comprising final polymer A is created,
• wherein the final polymer A is obtained by
• radical polymerization of the monomers
• (i) 58 to 90 mol % of a monomer of the formula I
• in which R1 denotes H or C1-C6 alkyl,
• (ii) 3 to 39 mol % of a C1-C4 alkyl ester of acrylic acid or of a C1-C4 alkyl ester of methacrylic acid,
• (iii) 1 to 25 mol % of a monoethylenically unsaturated carboxylic acid, a monoethylenically unsaturated sulfonic acid or a monoethylenically unsaturated phosphonic acid, or salt forms thereof,
• (iv) 0 to 35 mol % of one or more ethylenically unsaturated monomers which are different from a monomer (i), (ii), (iii) and (iv),
• wherein acrylonitrile or methacrylonitrile are used in an amount of 0 to 9 mol %, wherein the total amount of all monomers (i), (ii), (iii) and (iv) is 100 mol % to obtain a starting polymer V, and
• hydrolyzing the provided starting polymer V under alkaline conditions to obtain the final polymer A,
• wherein the N—C(═O)R1 groups of the formula (I) of the monomers (i) polymerized into the starting polymer V at least partially hydrolyze to form primary amino groups,
• wherein the ester groups of the monomers (ii) polymerized into the starting polymer V are at least partially reacted and at least part of the reaction is the formation of five-membered lactam structural units with the obtained primary amino groups or the formation of carboxylic acid groups or salt forms thereof, and wherein a viscosity peak during hydrolyzing of the provided starting polymer V is low to none,
• (BC) dewatering the second aqueous pulp suspension containing final polymer A on a water-permeable substrate to a wet paper structure,
• (CC) dewatering the wet paper structure, resulting in the paper or cardboard.