Process of bleaching

Abstract

The present invention concerns bleaching of substrates with an aqueous solution of a water soluble salt of a preformed transition metal catalyst together with hydrogen peroxide.

What is claimed is: 
     
         1 . An aqueous solution of a preformed transition metal catalyst salt, which salt is a mononuclear or dinuclear complex of a Mn(III) or Mn(IV) transition metal catalyst having a non-coordinating counter ion selected to provide a preformed transition metal catalyst salt that has a water solubility of at least 30 g/l at 20 ° C. and wherein the ligand of the transition metal catalyst is of formula (I): 
       
         
           
           
               
               
           
         
         wherein: 
       
       
         
           
           
               
               
           
         
         p is 3; 
         R is independently selected from: hydrogen or C1-C6-alkyl; and 
         R1, R2, R3, and R4 are independently selected from: H, C1-C4-alkyl, and C1-C4-alkylhydroxy, 
         which aqueous solution is present in a buffer system that maintains the solution in a pH range of 4 to 6. 
       
     
     
         2 . The solution of  claim 1 , wherein R is independently selected from: CH3 and C2H5. 
     
     
         3 . The solution of  claim 1 , wherein R1, R2, R3, and R4 are independently selected from: H and Me. 
     
     
         4 . The solution of  claim 1 , wherein the catalyst is derived from 1,4,7-trimethyl-1,4,7-triazacyclononane. 
     
     
         5 . The solution of  claim 1 , wherein the preformed transition metal catalyst salt is a dinuclear Mn(III) or Mn(IV) complex with at least one O2-bridge. 
     
     
         6 . The solution of  claim 1 , wherein the preformed transition metal catalyst salt has a water solubility of at least 50 g/l at 20° C. 
     
     
         7 . The solution of  claim 6 , wherein the salt is selected from the group consisting of chloride, acetate, sulphate, and nitrate. 
     
     
         8 . The solution of  claim 7 , wherein the salt is acetate or sulphate. 
     
     
         9 . The solution of  claim 7 , wherein the salt is acetate. 
     
     
         10 . The solution of  claim 1 , wherein the buffer system maintains the solution in a pH range of 4.5 to 5.5. 
     
     
         11 . The solution of  claim 1 , wherein the buffer system is a phosphate- or carboxylate-containing buffer. 
     
     
         12 . The solution of  claim 11 , wherein the buffer system is an acetate, benzoate or citrate buffer.