METHOD FOR PRODUCING PAPER OR CARDBOARD

The invention relates to a method for producing paper or cardboard containing the steps (A) adding a final polymer A to a first aqueous fibrous material suspension， whereby a second aqueous fibrous material suspension containing final polymer A is created， wherein the final polymer A is obtainable by - radical polymerisation of the monomers (i) 30 to 90 mol % of a monomer of formula (I) in which R 1 = H or means C1-C6 alkyl， (ii) 3 to 60 mol % of a C1-C4 alkyl ester of acrylic acid or of a C1-C4 alkyl ester of methacrylic acid， (iii) 0 to 45 mol % of a monoethylenically un saturated carboxylic acid， a monoethylenically unsaturated sulfonic acid， or a monoethylenically unsaturated phosphonic acid， or salt forms thereof， (iv) 0 to 9 mol % acrylonitrile or methacrylonitrile， (v) 0 to 35 mol % of one or more ethylenically unsaturated monomers which are different from a monomer (i)， (ii)， (iii) and (iv)， wherein the total amount of all monomers (i)， (ii)， (iii)， (iv) and (v) is 100 mol %， in order to obtain a starting polymer V， and - hydrolysing the starting polymer V in order to obtain the final polymer A， wherein the N-C(=O)R1 groups of formula (I) of the monomers (i) polymerised into the starting polymer V hydrolyse at least in part and in so doing form primary amino groups， wherein the ester groups of the monomers (ii) polymerised into the starting polymer V are converted at least in part and at least part of the conversion 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， (B) dewatering the second aqueous fibrous material suspension containing final polymer A on a water-permeable substrate to form a wet paper structure， (C) dewatering the wet paper structure， whereby the paper or the cardboard is formed. The formed paper or cardboard has a good dry strength. Further subjects of the invention are a paper or cardboard obtainable by the method and a final polymer A and a starting polymer V.