Treatment of a mixture containing cellulose

Abstract

The present invention relates to a method for treating a mixture containing cellulose, comprising at least one step of adding at least one agent capable of reducing carbonyl groups. The invention further relates to a specialty cellulose pulp, obtained by a method comprising said treatment. Furthermore, the invention relates to the use of the specialty cellulose pulp according to the invention or the specialty cellulose pulp obtained by a method according to the invention for the production of cellulose derivatives or materials containing cellulose molecules, including but not limited to, cellulose ethers or cellulose esters. Cellulose derivatives obtained from the specialty cellulose pulp according to the invention display increased viscosity and/or improved brightness over cellulose derivatives obtained from specialty cellulose pulp not subjected to the inventive treatment.

We claim:  
     
         1 . A method for treating a mixture containing cellulose that has not been pulped or that has been pulped chemically or chemically and mechanically, characterized in that the treatment comprises at least one step of adding at least one agent capable of reducing carbonyl groups.  
     
     
         2 . A method according to  claim 1 , characterized in that the at least one agent capable of reducing carbonyl groups is added during at least one step of a multi-stage bleaching process.  
     
     
         3 . A method according to  claim 2 , characterized in that the at least one agent capable of reducing carbonyl groups is added after or as the last stage of a multi-stage bleaching process.  
     
     
         4 . A method according to any of the preceding claims, characterized in that the mixture containing cellulose is obtained from (i) chemically or chemically and mechanically pulping wood or is obtained from (ii) unpulped cotton linters or from any combination of (i) and (ii).  
     
     
         5 . A method according to any of the preceding claims, characterized in that the mixture containing cellulose is an aqueous slurry of cellulose leading to a specialty cellulose pulp.  
     
     
         6 . A method according to  claim 5 , characterized in that the cellulose content in the aqueous slurry is from 1 to 40% by weight, with respect to the total weight.  
     
     
         7 . A method according to any of the preceding claims, characterized in that the at least one agent capable of reducing carbonyl groups is selected from the group of borohydrides, DMAB, LiAlH and mixtures thereof.  
     
     
         8 . A method according to any of the preceding claims, characterized in that the overall content of agent capable of reducing carbonyl groups added to the mixture containing cellulose is from 0.1 to 200 g·moles per ton of the dry mixture containing cellulose.  
     
     
         9 . A method according to any of the preceding claims, characterized in that the step of adding at least one agent capable of reducing carbonyl groups is performed at temperatures from ambient temperature to 90° C.  
     
     
         10 . A method according to any of the preceding claims characterized in that the step of adding at least one agent capable of reducing carbonyl groups is performed at a pH value from 8 to 14.  
     
     
         11 . An integrated method for producing specialty cellulose pulp comprising at least the following steps: 
 (I) Chemical or chemical and mechanical pulping of a raw material containing cellulose resulting in a mixture (I) containing cellulose;    (II) treating an unpulped mixture containing cellulose or treating a mixture (I) containing cellulose wherein the treatment comprises at least one step of adding at least one agent capable of reducing carbonyl groups, resulting in a treated specialty cellulose pulp (II);    (III) at least one step of post-processing of the specialty cellulose pulp (II);    wherein the steps (I) and (III) are optional.    
     
     
         12 . An integrated method according to  claim 11 , characterized in that the at least one step of post-processing is a step of drying.  
     
     
         13 . Specialty cellulose pulp, obtainable by a process comprising at least one step of treating a mixture containing cellulose that has not been pulped or that has been pulped chemically or chemically and mechanically, characterized in that the treatment comprises at least one step of adding at least one agent capable of reducing carbonyl.  
     
     
         14 . Specialty cellulose pulp according to  claim 13 , characterized in that the viscosity or the brightness, or both, of cellulose derivatives obtained from said specialty cellulose pulp are increased over the viscosity or the ISO brightness, or both, obtained from a specialty cellulose pulp that has not been treated with the at least one step of adding at least one agent capable of reducing carbonyl groups.  
     
     
         15 . Use of the specialty cellulose pulp according to the claims  13  or  14  or of the specialty cellulose pulp produced according to any of the  claims 1  to  10  or of the specialty pulp produced according to claims  11  or  12 , for the production of cellulose derivatives, including cellulose ethers or cellulose esters.  
     
     
         16 . Use of the pulp according to the claims  13  or  14  or of the specialty cellulose pulp produced according to any of the  claims 1  to  10  or of the specialty pulp produced according to  claim 11  or  12  for the production of viscose, composite materials, micro-crystalline cellulose formulations for food, cosmetics and pharmaceutical applications, technical filters, special photographic paper, as an additive during plastic molding, high-tenacity rayon yarn for tires and industrial hoses, paints, printing inks, LCD screens, high value specialty paper applications, battery separators, circuit boards and non-woven fabrics.