Abstract: The present invention relates to a polymer dispersion, which comprises polymer particles dispersed in an aqueous continuous phase. The polymer particles are obtainable by a radical polymerisation of one or more vinyl monomers comprising alkyl (meth)acrylates. A rosin component is dissolved into at least one of the vinyl monomers before the radical polymerisation of the vinyl monomers, and the radical polymerisation is conducted in the presence of the rosin component. The invention relates also to the use of the polymer dispersion for surface sizing of a cellulosic fibre web and to a method for producing a polymer dispersion.

Abstract: The present invention relates to a process for bleaching a cellulosic fibre material with a peroxide compound in an aqueous alkaline medium, comprising a bleaching step wherein: a) a first polymer (A) comprising a homopolymer of acrylic acid, methacrylic acid or maleic acid, or a copolymer of acrylic acid and/or methacrylic acid with an unsaturated dicarboxylic acid, and a solution of a second polymer (B) comprising a poly-alpha-hydroxyacrylic acid or a salt thereof, are added to a cellulosic fibre material, and b) thereafter adding a peroxide compound and an alkaline substance and carrying out the bleaching.

Abstract: The present invention relates to a process for bleaching a cellulosic fibre material with a peroxide compound in an aqueous alkaline medium, comprising a bleaching step wherein: a) a first polymer (A) comprising a homopolymer of acrylic acid, methacrylic acid or maleic acid, or a copolymer of acrylic acid and/or methacrylic acid with an unsaturated dicarboxylic acid, and a solution of a second polymer (B) comprising a poly-alfa-hydroxyacrylic acid or a salt thereof, are added to a cellulosic fibre material, and b) thereafter adding a peroxide compound and an alkaline substance and carrying out the bleaching.

Abstract: The invention relates to a process for preparing a cationically modified (meth)acrylamide polymer by the Mannich reaction. There is prepared in advance a stable aldehyde-secondary amine adduct, which is obtained as a reaction product of an aqueous solution of the secondary amine and an aqueous solution of the aldehyde, and which, after the formation of the adduct, is stabilized to endure storage, by lowering the pH of the mixture of 7 or below and/or by adding methanol, and the adduct thus prepared is added to an aqueous solution of the (meth)acrylamide polymer and the pH is adjusted to an alkaline level, whereupon modification occurs. The invention also relates to the use of the modified (meth)acrylamide polymer as a flocculation, retention or dewatering agent.