Chemical improvement in paper making

Abstract

The invention relates to an improvement in the printability of uncoated mechanical pulp paper grades, especially to an improvement in the printability of supercalendered (SC) papers, particularly in rotogravure printing. In the method according to the invention, a mixture of alkyl ketene dimer and styrene maleic acid anhydride co-polymer is applied onto the paper web in connection with supercalendering.

1 . A method for improving printability of mechanical pulp paper which method comprises 
 applying a combination of alkyl ketene dimer and styrene maleic acid anhydride copolymer onto at least one side of a paper web, and    calendering the paper web.    
   
   
       2 . The method according to  claim 1  wherein the combination of alkyl ketene dimer and styrene maleic acid anhydride copolymer is applied before calendering.  
   
   
       3 . The method according to  claim 1  wherein the combination of alkyl ketene dimer and styrene maleic acid anhydride copolymer is a mixture of alkyl ketene dimer and styrene maleic acid anhydride copolymer.  
   
   
       4 . The method according to  claim 3  wherein the mixture of alkyl ketene dimer and styrene maleic acid anhydride copolymer is applied together with moistening water.  
   
   
       5 . The method according to  claim 1  wherein the paper to be treated is uncalendered paper.  
   
   
       6 . The method according to  claim 1  wherein the weight ratio of alkyl ketene dimer to styrene maleic acid anhydride copolymer is 1:5-2:1.  
   
   
       7 . The method according to  claim 1  wherein the combination of alkyl ketene dimer and styrene maleic acid anhydride copolymer is applied onto the paper web in an amount of 0.05-0.8 g/m 2 .  
   
   
       8 . The method according to  claim 1  wherein the combination of alkyl ketene dimer and styrene maleic acid anhydride copolymer is applied onto the paper web 
 at a separate calender before or during calendering, or    at a paper machine before or during on-line calendering, or    at a paper machine before the paper web is passed to a separate calender.    
   
   
       9 . The method according to  claim 1  wherein before applying the combination of alkyl ketene dimer and styrene maleic acid anhydride copolymer the paper web is dried to a a moisture content <15%.  
   
   
       10 . (canceled)  
   
   
       11 . The method according to  claim 1  wherein the improved printable paper is supercalendered paper or newsprint paper.  
   
   
       12 . Paper prepared according to the method of  claim 1 .  
   
   
       13 . The paper according to  claim 12  which paper is a rotogravure printing paper.