Papermaking agent system, method for making a papermaking agent system and its use

Abstract

The invention relates to a papermaking agent system in liquid form, which comprises (i) cationic starch solution, prepared by cooking a starch mixture comprising a starch component and a water component, and (ii) polymer composition, which has anionic and cationic groups and a cationic net charge of >0.1 meq/g. The polymer composition comprises or originates from at least one of constituents a), b) or c). Constituent a) contains an amphoteric polymer, which is a copolymer comprising structural units derived from acrylamide and/or methacrylamide monomers, and anionic and cationic groups attached to the copolymer. Constituent b) contains a first polymer, which is a copolymer comprising structural units derived from acrylamide and/or methacrylamide monomers, and anionic or cationic groups attached to the copolymer, as well as a second polymer, which comprises groups with opposite charge than the first polymer. Constituent c) contains a third polymer, which comprises a copolymer comprising structural units derived from acrylamide and/or methacrylamide monomers, as well as hydrolytically unstable cationic groups attached to the copolymer. Constituent a), b) or c) is added to one of the components of the starch mixture or to the starch mixture before the cooking of the starch mixture, and/or constituent a) or b) is added to the cationic starch solution after cooking of the starch mixture. The invention relates also to the use of the papermaking agent system and to a method for its preparation.