Patent ID: 7691231

Claim:
Newsprint for offset printing, characterized in that said newsprint for offset printing is obtained by a process in which base paper for newsprint is coated with a surface treating agent mainly comprised of the following component (A) and component (B), dried and subjected to a calender treatment: component (A): at least one water-soluble macromolecular substance selected from the group consisting of starches, polyvinyl alcohols, polyacrylamides, and cellulose derivatives; component (B): a water-soluble surface sizing agent that is a copolymer obtained by the copolymerization of the following component (a) and component (b); a copolymer obtained by the copolymerization of component (a), component (b) and component (c); or a copolymer obtained by quaternizing, by component (d), any of the foregoing copolymers in which component (b) is a vinyl monomer containing a tertiary amine group; component (a): styrene monomer which is at least one styrene monomer selected from the group consisting of styrene, α-methyl styrene, chlorostyrene and cyanostyrene, component (b): cationic monomer which is a vinyl monomer containing any one of primary amino group, secondary amino group, and tertiary amino group, component (c): other hydrophobic monomers which is at least one hydrophobic monomer which is copolymerizable and selected from the group consisting of methacrylic acid esters and acrylic acid esters, component (d): quaternizing agents which is at least one quaternizing agent selected from the group consisting of epichlorohydrin, methyl chloride, ethyl chloride, benzyl chloride, dimethyl sulfate, diethyl sulfate, oxides, epoxy compounds, and organic halogen compounds, wherein the cationization degree of the water-soluble surface sizing agent is 1.4-2.0 meq/g, the average particle size of the water-soluble surface sizing agent is 40 nm or smaller, aluminum sulfate (a 50% by weight Al 2 O 3 .14H 2 O product) is added to the papermaking pulp at a ratio of less than 3.0% by weight relative to oven-dried pulp when manufacturing the base paper for newsprint, and a ratio by solid weight of the styrene monomer of component (a) to the cationic monomer of component (b) is in the range from 80:20 to 20:80.