Cationic surface sizing agent

Provided herein is， in the presence of a second free radical initiator， a second ethylenically unsaturated monomer blend comprising， in a polymerization solvent comprising C1-6-carboxylic acid and C1-6-carboxylic anhydride， a free radical emulsion An aqueous prepolymer composition (B) obtainable by copolymerizing and adding water to the obtained polymer dispersion to obtain an aqueous prepolymer composition: (i) 5 to 50% by weight of N，N，N-tri(C1-4-alkyl)amino C1-4-alkyl(meth)acrylate with a quaternary salt of a mineral or organic acid and/or N， N，N-tri(C1-4-alkyl)amino C1-4-alkyl(meth)acrylamide with at least one ethylenically unsaturated quaternary amine selected from quaternary salts of mineral or organic acids， and (iii) 10 In the presence of a water-soluble redox system comprising to 95% by weight of at least one optionally substituted styrene， and a first free radical initiator for free radical emulsion copolymerization， a first ethylenically unsaturated monomer blend comprising: a free radical emulsion copolymerization It is an aqueous polymer dispersion (A) obtainable by: (b) 15 to 100% by weight of at least one C1-C4-alkyl (meth)acrylate. Provided herein is an aqueous polymer dispersion (A) obtainable by free radical emulsion copolymerizing a first ethylenically unsaturated monomer blend comprising (b) 15 to 100 % by weight of at least one Cl-C4-alkyl (meth)acrylate， in the presence of a water-soluble redox system comprising a first free radical initiator for the free radical emulsion copolymerization and an aqueous prepolymer composition (B) obtainable by free radical emulsion copolymerizing in a polymerization solvent comprising Cl-6-carboxylic acid and Cl-6-carboxylic acid anhydride a second ethylenically unsaturated monomer blend comprising (i) 5 to 50 % by weight of at least one ethylenically unsaturated quaternary amine selected from quaternary salt of N，N，N-tri(Cl-4-alkyl) amino Cl-4-alkyl(meth)acrylate with a mineral acid or an organic acid and/or quaternary salt of N，N，N-tri(Cl-4-alkyl)amino Cl-4-alkyl(meth)acrylamide with a mineral acid or an organic acid， and (iii) 10 to 95 % by weight of at least one optionally substituted styrene， in the presence of a second free radical initiator， and adding water to the obtained polymer dispersion to obtain the aqueous prepolymer composition. Provided herein is an aqueous polymer dispersion (A) obtainable by free radical emulsion copolymerizing a first ethylenically unsaturated monomer blend comprising (b) 15 to 100 % by weight of at least one Cl-C4-alkyl (meth)acrylate， in the presence of a water-soluble redox system comprising a first free radical initiator for the free radical emulsion copolymerization and an aqueous prepolymer composition (B) obtainable by free radical emulsion copolymerizing in a polymerization solvent comprising Cl-6-carboxylic acid and Cl-6-carboxylic acid anhydride a second ethylenically unsaturated monomer blend comprising (i) 5 to 50 % by weight of at least one ethylenically unsaturated quaternary amine selected from quaternary salt of N，N，N-tri(Cl-4-alkyl) amino Cl-4-alkyl(meth)acrylate with a mineral acid or an organic acid and/or quaternary salt of N，N，N-tri(Cl-4-alkyl)amino Cl-4-alkyl(meth)acrylamide with a mineral acid or an organic acid， and (iii) 10 to 95 % by weight of at least one optionally substituted styrene， in the presence of a second free radical initiator， and adding water to the obtained polymer dispersion to obtain the aqueous prepolymer composition.