Water-dispersible polysaccharide derivatives of reduced glyoxal content, and a process for decreasing the glyoxal content in glyoxal-crosslinked polysaccharide derivatives

Abstract

A description is given of glyoxal-treated polysaccharide derivatives which, to decrease the unbound glyoxal, are treated with an aqueous solution of one or more water-soluble aluminium salts, or one or more water-soluble borates, or a combination of one or more water-soluble aluminium salts and one or more water-soluble borates, and, if appropriate, with suitable buffer substances to set the pH, and then dried. A description is likewise given of a process for decreasing the content of unbound glyoxal in glyoxal-treated polysaccharide derivatives.

What is claimed is:  
     
         1 . Glyoxal-treated polysaccharide derivatives, characterized by decrease in the amount of unbound glyoxal, wherein the glyoxal treated polysaccharide derivatives are treated with an aqueous solution of one or more water-soluble aluminium salts, or one or more water-soluble borates, or a combination of one or more water-soluble aluminium salts and one or more water-soluble borates and, optionally, with suitable buffer substances to set pH of the glyoxal treated polysaccharide derivative, and dried.  
     
     
         2 . Glyoxal-treated polysaccharide derivatives according to  claim 1 , characterized in that the pH of a 2% strength solution of the glyoxal-treated polysaccharide derivative is between 4 and 8.  
     
     
         3 . Glyoxal-treated polysaccharide derivatives according to  claim 1 , characterized in that the polysaccharide derivative was treated with more than 0.4% by weight of glyoxal, based on the polysaccharide derivative.  
     
     
         4 . Glyoxal-treated polysaccharide derivatives according to  claim 1 , characterized in that the ratio of water-soluble borate to glyoxal is less than 0.5:1, based on the weight of the two substances used.  
     
     
         5 . Glyoxal-treated polysaccharide derivatives according to  claim 1 , characterized in that the content of extractable, unbound glyoxal is less than 0.1% by weight.  
     
     
         6 . Glyoxal-treated polysaccharide derivatives according to  claim 1 , characterized in that the polysaccharide derivative is cellulose ether.  
     
     
         7 . Glyoxal-treated polysaccharide derivatives according to  claim 1 , characterized in that the polysaccharide derivative contains alkyl groups.  
     
     
         8 . Glyoxal-treated polysaccharide derivatives according to  claim 1 , characterized in that the polysaccharide derivative is methyl hydroxyethyl cellulose or methyl hydroxypropyl cellulose, methyl cellulose or mixtures of these substances.  
     
     
         9 . Process for decreasing the unbound glyoxal in glyoxal-treated polysaccharide derivatives, comprising: 
 a) mixing the polysaccharide derivative at a temperature between 20 and 70° C. with an aqueous solution of one or more water-soluble aluminium salts, or one or more water-soluble borates, or a combination of one or more aluminium salts and one or more water-soluble borates, wherein the resulting mixture optionally contains further buffer substances to set the pH, and then    b) drying the mixture.    
     
     
         10 . Process according to  claim 9 , characterized in that the buffer substance is one or more salts of citric acid or one or more salts of phosphoric acid.