Method for the treatment of paper surfaces

Abstract

A method for the treatment of paper surfaces is described.

1 . A process for the treatment of paper surfaces, wherein the surface of the paper is coated with particles (composite particles) which are composed of polymer and finely divided inorganic solid, the weight average particle size of the finely divided inorganic solid being ≦100 nm.  
   
   
       2 . The process as claimed in  claim 1 , wherein the composite particles are applied in the form of an aqueous composite particle dispersion to the paper.  
   
   
       3 . The process as claimed in  claim 2 , wherein the aqueous composite particle dispersion was prepared by a process in which at least one ethylenically unsaturated monomer is dispersed in an aqueous medium and polymerized by means of at least one free radical polymerization initiator in the presence of at least one dispersed, finely divided inorganic solid and at least one dispersant by the aqueous free radical emulsion polymerization method, 
 a) a stable aqueous dispersion of the at least one inorganic solid being used, which dispersion, with an initial solids concentration of ≧1% by weight, based on the aqueous dispersion of the at least one inorganic solid, still contains more than 90% by weight of the originally dispersed solid in dispersed form one hour after its preparation and whose dispersed solid particles have a weight average diameter of ≦100 nm,    b) the disperse solid particles of the at least one inorganic solid having an electrophoretic mobility which differs from zero in an aqueous standard potassium chloride solution at a pH which corresponds to the pH of the aqueous dispersing medium before the beginning of the addition of the dispersants,    c) at least one anionic, cationic and nonionic dispersant being added to the aqueous solid particle dispersion before the beginning of the addition of the at least one ethylenically unsaturated monomer,    d) thereafter from 0.01 to 30% by weight of the total amount of the at least one monomer being added to the aqueous solid particle dispersion and being polymerized to a conversion of at least 90%    and    e) the remaining amount of the at least one monomer then being added continuously under polymerization conditions at the rate at which it is consumed.    
   
   
       4 . A process for the treatment of paper surfaces, wherein the surface of the paper is treated with an aqueous dispersion which is obtained by mixing an aqueous polymer dispersion with at least one dispersed, finely divided inorganic solid which has a weight average particle diameter of ≦100 nm.  
   
   
       5 . The process as claimed in  claim 1 , wherein the amount of composite particles or of a mixture of dispersion polymer and finely divided inorganic solid is from 0.1 to 100 g/m 2  of paper.  
   
   
       6 . The process as claimed in  claim 1 , wherein the polymer can be formed into a film.  
   
   
       7 . The process as claimed in  claim 1 , wherein the paper used is a base paper.  
   
   
       8 . The process as claimed in  claim 1 , wherein the paper used is a coated or sized paper.  
   
   
       9 . The process as claimed in  claim 1 , wherein the finely divided inorganic solid is at least one selected from the group consisting of silica, alumina, hydrated aluminum oxide, calcium carbonate, magnesium carbonate, calcium orthophosphate, magnesium orthophosphate, iron(II) oxide, iron(III) oxide, iron(II/III) oxide, tin oxide, cerium dioxide, yttrium(III) oxide, titanium dioxide, hydroxyapatite, zinc oxide and zinc sulfide.  
   
   
       10 . The process as claimed in  claim 1 , wherein the treated paper is subjected to pressures and/or temperatures such that the polymer forms a film.  
   
   
       11 . A paper obtained by the process as claimed in  claim 1 .  
   
   
       12 . A method of printing paper in the offset, flexographic and gravure printing process comprising utilizing the paper as claimed in  claim 11 .  
   
   
       13 . A printed paper obtained by the method as claimed in  claim 12 .  
   
   
       14 . A method of coating paper comprising utilizing an aqueous dispersion of particles which are composed of polymer and finely divided inorganic solid, the weight average particle size of the finely divided inorganic solid being ≦100 nm.  
   
   
       15 . A method of coating paper comprising utilizing an aqueous dispersion which is obtained by mixing an aqueous polymer dispersion with at least one dispersed, finely divided inorganic solid which has a weight average particle diameter of ≦100 nm for the coating of paper.  
   
   
       16 . The process as claimed in  claim 4 , wherein the amount of composite particles or of a mixture of dispersion polymer and finely divided inorganic solid is from 0.1 to 100 g/m 2  of paper.  
   
   
       17 . The process as claimed in  claim 4 , wherein the polymer can be formed into a film.  
   
   
       18 . The process as claimed in  claim 4 , wherein the paper used is a base paper.  
   
   
       19 . The process as claimed in  claim 4 , wherein the paper used is a coated or sized paper.  
   
   
       20 . The process as claimed in  claim 4 , wherein the finely divided inorganic solid is at least one selected from the group consisting of silica, alumina, hydrated aluminum oxide, calcium carbonate, magnesium carbonate, calcium orthophosphate, magnesium orthophosphate, iron(II) oxide, iron(III) oxide, iron(II/III) oxide, tin oxide, cerium dioxide, yttrium(III) oxide, titanium dioxide, hydroxyapatite, zinc oxide and zinc sulfide.  
   
   
       21 . The process as claimed in  claim 4 , wherein the treated paper is subjected to pressures and/or temperatures such that the polymer forms a film.  
   
   
       22 . A paper obtained by a process as claimed in  claim 4 .  
   
   
       23 . A method of printing paper in the offset, flexographic and gravure printing process comprising utilizing the paper as claimed in  claim 22 .  
   
   
       24 . A printed paper obtained by the method as claimed in  claim 23.