Printability Improving Agents And Papers Coated With Them

Abstract

The present invention aims to provide printability improving agents and surface-treating agents capable of improving offset printability of papers, especially newsprint papers to be printed with offset inks as well as papers, especially newsprint papers that can be successfully printed with offset inks. According to a first aspect of the present invention, a printability improving agent comprising a cationic copolymer consisting of one or more hydrophobic monomer unit(s) selected from a specific group and a quaternary ammonium salt-containing monomer unit or a surface-treating agent comprising the printability improving agent and a water-soluble polymer material selected from a specific group is applied on the surface of a base paper, especially a newsprint base paper. According to a second aspect of the present invention, a hydrophobic monomer unit selected from a specific group and a quaternary ammonium salt-containing monomer unit is polymerized to give a cationic copolymer, which is then further polymerized with a hydrophobic monomer to give a copolymer. Alternatively, a hydrophobic monomer unit selected from a specific group and a quaternary ammonium salt-containing monomer unit is polymerized to give a cationic copolymer, which is further polymerized with a hydrophobic monomer in the presence of a surfactant to give a copolymer. A printability improving agent comprising the copolymer or a surface-treating agent comprising the printability improving agent and a water-soluble polymer material selected from a specific group is applied on the surface of a base paper, especially a newsprint base paper.

1 . A printability improving agent characterized in that it comprises a cationic copolymer comprising one or more hydrophobic monomer unit(s) selected from the group consisting of: 
 (1) alkyl acrylates and/or alkyl methacrylates    (2) dialkyl diesters    (3) vinyl esters    (4) N-alkyl acrylamides and/or N-alkyl methacrylamides    (5) methyl vinyl ethers    and a quaternary ammonium salt-containing monomer unit.    
   
   
       2 . A surface-treating agent characterized in that it comprises the printability improving agent of  claim 1  and one or more water-soluble polymer material(s) selected from the group consisting of: 
 (1) various modified starches    (2) polyvinyl alcohols    (3) cellulose derivatives.    
   
   
       3 . A paper characterized in that it is obtained by applying the printability improving agent of  claim 1  or the surface-treating agent on the surface of a base paper.  
   
   
       4 . The paper of  claim 3  characterized in that the base paper is a newsprint base paper prepared by a neutral papermaking process.  
   
   
       5 . A printability improving agent comprising (I) a copolymer obtained by polymerizing one or more hydrophobic monomer unit(s) selected from the group consisting of: 
 (1) styrenes    (2) alkyl acrylates and/or alkyl methacrylates    (3) dialkyl diesters    (4) vinyl esters    (5) N-alkyl acrylamides and/or N-alkyl methacrylamides    (6) methyl vinyl ethers    and a quaternary ammonium salt-containing monomer unit to give a cationic copolymer, which is further polymerized with one or more hydrophobic monomer(s) selected from the group shown above, or (II) a copolymer obtained by polymerizing the cationic copolymer obtained by polymerization of the hydrophobic monomer unit(s) and a quaternary ammonium salt-containing monomer unit with one or more hydrophobic monomer(s) selected from the group shown above in the presence of a surfactant.    
   
   
       6 . A surface-treating agent comprising the printability improving agent of  claim 5  and one or more water-soluble polymer material(s) selected from the group consisting of: 
 (1) various modified starches    (2) polyvinyl alcohols    (3) cellulose derivatives.    
   
   
       7 . A paper characterized in that it is obtained by applying the printability improving agent of  claim 5  or the surface-treating agent on the surface of a base paper.  
   
   
       8 . The paper of  claim 7  characterized in that the base paper is a newsprint base paper prepared by a neutral papermaking process.