Methods for improving discoloration resistance of pulp and pulp improved in discoloration resistance

Abstract

The present invention aims to provide a method for improving discoloration in pulp, characterized by a versatile technique adaptable to any type of pulp, a time-saving process, a great and permanent anti-fading effect, environmental friendliness and other properties, as well as a pulp with greatly improved discoloration obtained by said method for improving discoloration. Discoloration in pulp can be greatly improved by adding one or more additives selected from the group consisting of reducing agents, peroxides and hydrogen-donating organic compounds to one of bleached mechanical pulp, semi-chemical pulps, chemical pulp and deinked pulps or a mixture of two or more of them, and irradiating it with UV and/or visible light.

1 - 4 . (canceled)  
   
   
       5 . A method for improving discoloration in pulp characterized in that a pulp containing a bleached mechanical pulp is irradiated with UV and/or visible light in the presence of at least one compound selected from the group consisting of reducing agents, peroxides and hydrogen-donating organic compounds.  
   
   
       6 . The method for improving discoloration in pulp of  claim 5  characterized in that the pulp containing a bleached mechanical pulp is a mixture with one or more of bleached semi-chemical pulp, bleached chemical pulp and bleached deinked pulp.  
   
   
       7 . The method for improving discoloration in pulp of  claim 5  characterized in that the UV and/or visible light is laser light.  
   
   
       8 . The method for improving discoloration in pulp of  claim 6  characterized in that the UV and/or visible light is laser light.  
   
   
       9 . The method for improving discoloration in pulp of  claim 5  characterized in that the at least one compound selected from the group consisting of reducing agents, peroxides and hydrogen-donating organic compounds is used in the range of 0.05 to 50% solids by weight on the basis of pulp solids.  
   
   
       10 . The method for improving discoloration in pulp of  claim 6  characterized in that the at least one compound selected from the group consisting of reducing agents, peroxides and hydrogen-donating organic compounds is used in the range of 0.05 to 50% solids by weight on the basis of pulp solids.  
   
   
       11 . The method for improving discoloration in pulp of  claim 7  characterized in that the at least one compound selected from the group consisting of reducing agents, peroxides and hydrogen-donating organic compounds is used in the range of 0.05 to 50% solids by weight on the basis of pulp solids.  
   
   
       12 . A pulp with improved discoloration obtained by the method for improving discoloration in pulp of  claim 5 .  
   
   
       13 . A pulp with improved discoloration obtained by the method for improving discoloration in pulp of  claim 6 .  
   
   
       14 . A pulp with improved discoloration obtained by the method for improving discoloration in pulp of  claim 7.