METHOD OF MANUFACTURING PAPER OR CARDBOARD Russian patent published in 2023 - IPC D21H21/18 D21H17/55 

FIELD: manufacturing paper or cardboard.

SUBSTANCE: invention relates to a method for the manufacture of paper or cardboard, including the addition of polymer P to an aqueous suspension of pulp, dehydration of the specified aqueous suspension of pulp containing polymer P on a water-permeable substrate to obtain a wet paper structure with a solids content of 18.5 to 25% by weight, and additional dehydration of the wet paper structure to obtain paper or board. Polymer P is obtained by polymerization (i) between 33 and 83 mol. % of monomer of formula I

in which R¹=H or C₁-C₆-alkyl, (ii) between 6 and 56 mol. % of diallyl dimethylammonium chloride, diallyldiethylammonium chloride, or a salt of a monoethylenically unsaturated monomer containing a quaternized nitrogen atom, which is the only charge-containing group at a pH value of 7, (iii) between 11 and 61 mol. % of monoethylenically unsaturated carboxylic acid, monoethylenically unsaturated sulfonic acid or monoethylenically unsaturated phosphonic acid, or their salts, (iv) between 0 and 50 mol. % of one or more ethylenically unsaturated monomers other than the monomer (i), (ii) and (iii), where the total amount of all monomers (i), (ii), (iii) and (iv) is 100 mol. %, and subsequent hydrolysis of the N-C(=O)R¹ of groups contained in the units of the monomers of formula (I), polymerized to obtain polymer V, with formation of primary amino groups or amide groups in the polymer P, where at least 87% of the units of the monomers of the formula are hydrolysed (I).

EFFECT: resulting paper or paperboard has good dry strength.

10 cl, 6 tbl