Inhibition of yellowing in papers

Abstract

Lignin-containing papers are rendered light stable when they contain TiO 2 in combination with an amine hindered radical scavenger.

1 . A light stable lignin-containing paper having a content of particulate titanium dioxide and a radical scavenger effective to inhibit yellowing of the paper.  
     
     
         2 . A paper according to  claim 1 , wherein said radical scavenger is a hindered amine radical scavenger.  
     
     
         3 . (Amended) A paper according to  claim 1 , wherein said titanium dioxide is rutile titanium dioxide having a particle size of 0.01 to 1.5 microns and is present in an amount of 0.05 to 10%, by weight, based on the weight of oven dry pulp fibre in the paper.  
     
     
         4 . A paper according to  claim 3 , wherein said titanium dioxide is in an amount of 0.5 to 6%, by weight, based on the weight of oven dry pulp fiber and said particle size is 0.1 to 1.5 microns.  
     
     
         5 . A paper according to  claim 3 , wherein said titanium dioxide is in an amount of 1 to 5%, by weight, based on the weight of oven dry fibre and said particle size is 0.16 to 0.28 microns.  
     
     
         6 . (Amended) A paper according to  claim 1 , wherein said radical scavenger is present in an amount of 0.05 to 5%, by weight, based on the weight of oven dry fibre.  
     
     
         7 . (Amended) A paper according to  claim 1 , wherein said radical scavenger is present in an amount of 0.1 to 2%, by weight, based on the weight of oven dry fibre.  
     
     
         8 . (Amended) A paper according to  claim 1 , wherein said radical scavenger is present in an amount of 0.1 to 1.0%, by weight, based on the weight of oven dry fibre.  
     
     
         9 . (Amended) A paper according to  claim 1 , wherein said radical scavenger is selected from piperidines and pyrolidines of formula A, B, C and D:  
       
         
           
           
               
               
           
         
       
       in which: 
 R 1  is selected from hydrogen, hydroxyl, primary, secondary, tertiary or quaternary amino, alkyl, alkoxy, aminoalkyl alkylene oxide of the general formula [—O—(CH2) n ] N  where n is 1 to 4 and N is 1 to 20. The alkyl or alkyl moiety in R 1  has from 1 to 12 carbons, and may be straight chain or branched. The alkyl and alkyl moieties may be unsubstituted or substituted with hydroxyl (OH), carboxyl (COOH) or carboxylate (COO −   r M r/z   z+ ) groups with M being a metal ion from the 1st, 2nd or 3rd group of the periodic table, or Zn, Cu, Ni or Co; or M is N + (R 6 ) 4  where R 6  is alkyl of 1 to 8 carbon atoms or benzyl; and r and z are each integers of 1, 2 or 3;  
 R 2  and R 3  can be the same or different and are selected from hydrogen, hydroxyl (OH), carboxyl (COOH) or carboxylate (COO −   r M r/z   z+ ) groups with M being a metal ion from the 1st, 2nd or 3rd group of the periodic table, or Zn, Cu, Ni or Co; or M is a group N + (R 6 ) 4  where R 6  is alkyl of 1 to 8 carbon atoms or benzyl, and r and z are each integers of 1, 2 or 3;  
 Y is oxyl or hydroxyl; and  
 X is an inorganic or organic anion,  
 p and m are integers of 1 to 20.  
 
     
     
         10 . (Amended) A paper according to  claim 1 , wherein said titanium dioxide and radical scavenger are present with filler in the paper.  
     
     
         11 . (Amended) A paper according to  claim 1 , wherein said titanium dioxide and said radical scavenger are present in a pigment coating on at least one side of the paper.  
     
     
         12 . (Amended) A paper according to  claim 1 , further including an organic ultra violet absorber with said titanium dioxide and radical scavenger.  
     
     
         13 . (Amended) A paper according to  claim 1 , derived from a lignin-containing pulp having a lignin content of 15 to 35%, by weight, based on the weight of oven dry fibre lignin in the lignin-containing pulp.  
     
     
         14 . (Amended) A paper according to  claim 1 , derived from a pulp which comprises a high yield pulp selected from refiner mechanical pulp, stone groundwood pulp, thermomechanical pulp, chemithermo-mechanical pulp and chemimechanical pulp in an amount of 80 to 100%, by weight, based on the total pulp weight.  
     
     
         15 . A method of rendering a lignin-containing paper light stable comprising: 
 a) incorporating in said paper a content of particulate titanium dioxide and a radical scavenger, in an amount effective to inhibit yellowing of the paper, or    b) coating the paper with a coating formulation having a content of particulate titanium dioxide and a radical scavenger, in an amount effective to inhibit yellowing of the paper.    
     
     
         16 . A method according to  claim 15 , wherein said radical scavenger is a hindered amine.  
     
     
         17 . (Amended) A method according to  claim 15 , wherein said titanium dioxide is rutile titanium dioxide having a particle size of 0.01 to 1.5 microns and is present in an amount of 0.05 to 10%, by weight, based on the weight of oven dry pulp fiber in the paper.  
     
     
         18 . A method according to  claim 17 , wherein said titanium dioxide is in an amount of 0.5 to 6%, by weight, based on the weight of oven dry pulp fiber.  
     
     
         19 . A method according to  claim 17 , wherein said titanium dioxide is in an amount of 1 to 5%, by weight, based on the weight of oven dry fibre and said particle size is 0.16 to 0.28 microns.  
     
     
         20 . (Amended) A method according to  claim 15 , wherein said radical scavenger is present in an amount of 0.05 to 5%, by weight, based on the weight of oven dry fibre.  
     
     
         21 . (Amended) A method according to  claim 15 , wherein said radical scavenger is present in an amount of 0.1 to 1.0%, by weight, based on the weight of oven dry fibre.  
     
     
         22 . (Amended) A method according to  claim 15 , wherein said radical scavenger is selected from piperidines and pyrrolidines of formula A, B, C and D:  
       
         
           
           
               
               
           
         
       
       in which: 
 R 1  is selected from hydrogen, hydroxyl, primary, secondary, tertiary or quaternary amino, alkyl, alkoxy, aminoalkyl alkylene oxide of the general formula [—O—(CH2) n ] N  where n is 1 to 4 and N is 1 to 20. The alkyl or alkyl moiety in R 1  has from 1 to 12 carbons, and may be straight chain or branched. The alkyl and alkyl moieties may be unsubstituted or substituted with hydroxyl (OH), carboxyl (COOH) or carboxylate (COO −   r M r/z   z+ ) groups with M being a metal ion from the 1st, 2nd or 3rd group of the periodic table, or Zn, Cu, Ni or Co; or M is N + (R 6 ) 4  where R 6  is alkyl of 1 to 8 carbon atoms or benzyl; and r and z are each integers of 1, 2 or 3;  
 R 2  and R 3  can be the same or different and are selected from hydrogen, hydroxyl (OH), carboxyl (COOH) or carboxylate (COO −   r M r/z   z+ ) groups with M being a metal ion from the 1st, 2nd or 3rd group of the periodic table, or Zn, Cu, Ni or Co; or M is a group N + (R 6 ) 4  where R 6  is alkyl of 1 to 8 carbon atoms or benzyl, and r and z are each integers of 1, 2 or 3;  
 Y is oxyl or hydroxyl; and  
 X is an inorganic or organic anion,  
 p and m are integers of 1 to 20.  
 
     
     
         23 . (Amended) A method according to  claim 15 , wherein said titanium dioxide and scavenger are incorporated with filler in the paper in accordance with a).  
     
     
         24 . (Amended) A method according to  claim 15 , wherein said titanium dioxide and said radical scavenger are present in said coating formulation in accordance with b).  
     
     
         25 . (Amended) A method according to  claim 15 , further including an organic ultraviolet absorber with said titanium dioxide and radical scavenger.  
     
     
         26 . (Amended) A method according to  claim 15 , wherein said paper is derived from a lignin-containing pulp having a lignin content of 15 to 35%, by weight, based on the weight of oven dry fibre lignin in the lignin-containing pulp.  
     
     
         27 . (Amended) A method according to  claim 15 , wherein said paper is derived from a pulp which comprises a high yield pulp selected from refiner mechanical pulp, stone groundwood pulp, thermomechanical pulp, chemithermomechanical pulp and chemimechanical pulp in an amount of at least 10%, by weight, based on the total pulp weight.  
     
     
         28 . (Cancel) Use of particulate titanium dioxide in conjunction with a radical scavenger in a lignin-containing paper to inhibit yellowing.  
     
     
         29 . (Cancel) Use according to  claim 28 , wherein said radical scavenger is a hindered amine radical scavenger.