| abstract |
It is an object to improve sizing performance and anti-plate-soiling property in offset printing, for example, in a cationic surface sizing agent to be used for coating base paper of newsprint paper, and as a means for solving the object, a cationic surface sizing agent is produced by quaternizing a copolymer having a weight average molecular weight ranging from 30,000 to 60,000 obtained by polymerizing (a) 20 to 40% by weight of a monomer containing tertiary amino group; (b) 10 to 80% by weight of a C4 to C18 alkyl ester of (meth) acrylic acid; and (c) 0 to 70% by weight of a styrene or derivative thereof, using an azoic polymerization initiator in the presence of a chain transfer agent. In this manner, it is possible to improve sizing performance without reducing the hydrophobic level of copolymer and to suppress sensitization of printing plate such as PS plate by specifying the monomer composition ratio, using an azoic polymerization initiator, and specifying molecular weight of the copolymer. |