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.

1 . A method of catalytically treating a substrate, the substrate being a cellulose-containing substrate or starch containing substrate, with a preformed transition metal catalyst salt, the preformed transition metal catalyst salt having a non-coordinating counter ion, the method comprising the following steps:
 (i) optionally dissolving a concentrate or solid form of a preformed transition metal catalyst salt in an aqueous medium to yield an aqueous solution of the preformed transition metal catalyst salt;   (ii) adding the aqueous solution of the preformed transition metal catalyst salt to a reaction vessel; and,   (iii) adding hydrogen peroxide to the reaction vessel,   
     wherein the preformed transition metal catalyst salt is a mononuclear or dinuclear complex of a Mn(III) or Mn(IV) transition metal catalyst for catalytically treating the substrate with hydrogen peroxide, the non-coordinating counter ion of said transition metal 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, C1-C6-alkyl, CH2CH2OH, and CH2COOH, or one of R is linked to the N of another Q via an ethylene bridge; 
       R1, R2, R3, and R4 are independently selected from: H, C1-C4-alkyl, and C1-C4-alkylhydroxy, and the substrate is brought into contact with a mixture of the aqueous solution of the preformed transition metal catalyst salt and the hydrogen peroxide. 
     
   
   
       2 . A method according to  claim 1 , wherein R is independently selected from: CH 3 , C 2 H 5 , CH 2 CH 2 OH and CH 2 COOH. 
   
   
       3 . A method according to  claim 1 , wherein R1, R2, R3, and R4 are independently selected from: H and Me. 
   
   
       4 . A method according to  claim 1 , wherein the catalyst is derived from a ligand selected from the group consisting 1,4,7-Trimethyl-1,4,7-triazacyclononane (Me 3 -TACN) and 1,2,-bis-(4,7,-dimethyl-1,4,7,-triazacyclonon-1-yl)-ethane (Me 4 -DTNE). 
   
   
       5 . A method according to  claim 1 , wherein the preformed transition metal catalyst salt is a dinuclear Mn(III) or Mn(IV) complex with at least one O 2−  bridge. 
   
   
       6 . A method according to  claim 1 , wherein the preformed transition metal catalyst salt has a water solubility of at least 50 g/l at 20° C. 
   
   
       7 . A method according to  claim 6 , wherein the salt is that selected from the group consisting of chloride, acetate, sulphate, and nitrate. 
   
   
       8 . A method according to  claim 7 , wherein the salt is acetate. 
   
   
       9 . A method according to  claim 1 , wherein the aqueous solution of the preformed transition metal catalyst salt is in a buffer system that maintains the solution in the pH range 2 to 7. 
   
   
       10 . A method according to  claim 1 , wherein the preformed transition metal catalyst salt is present at a concentration in the range from 0.1 to 10 wt % in the aqueous solution in step (ii). 
   
   
       11 . A method according to  claim 9 , wherein the concentration is in the range from 0.5 to 8 wt %. 
   
   
       12 . A method according to  claim 1 , wherein during treatment of the substrate the aqueous solution comprises at least 80 wt % water. 
   
   
       13 . A method according to  claim 12 , the aqueous solution comprises at least 90 wt % water. 
   
   
       14 . A method according to  claim 13 , wherein the aqueous solution comprises at least 95 wt % water. 
   
   
       15 . A method according to  claim 1 , wherein the pH of the aqueous solution of the preformed transition metal catalyst salt aqueous solution in step (ii) in the range from 2 to 7. 
   
   
       16 . A method according to  claim 15 , wherein the pH is in the range from 4 to 6. 
   
   
       17 . A method according to  claim 16 , wherein the pH is in the range from 4.5 to 5.5. 
   
   
       18 . A method according to  claim 1 , wherein the substrate is selected from the group consisting of woven or knitted cotton cloths, industrial laundering and wood pulp. 
   
   
       19 . A method according to  claim 1 , wherein the substrate is wood pulp. 
   
   
       20 . A method according to  claim 1 , wherein the preformed transition metal catalyst salt has been formed by a contact and oxidation step that is carried out at least 24 hours before use. 
   
   
       21 . Use of a preformed transition metal catalyst salt in an aqueous medium to bleach a substrate, the substrate being a cellulose-containing substrate or starch containing substrate, with hydrogen peroxide, wherein the preformed transition metal catalyst salt is a dinuclear Mn(III) or Mn(IV) complex with at least two O 2−  bridges for catalytically treating the substrate with hydrogen peroxide, said transition metal catalyst a salt, wherein the preformed transition metal catalyst salt 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, C1-C6-alkyl, CH 2 CH 2 OH, and CH 2 COOH, or one of R is linked to the N of another Q via an ethylene bridge; 
       R1, R2, R3, and R4 are independently selected from: H, C1-C4-alkyl, and C1-C4-alkylhydroxy. 
     
   
   
       22 . Use according to  claim 21 , wherein R is independently selected from: CH 3 , C 2 H 5 , CH 2 CH 2 OH and CH 2 COOH. 
   
   
       23 . Use according to  claim 21 , wherein R1, R2, R3, and R4 are independently selected from: H and Me. 
   
   
       24 . Use according to  claim 23 , wherein the catalyst is derived from a ligand selected from the group consisting 1,4,7-Trimethyl-1,4,7-triazacyclononane (Me3-TACN) and 1,2,-bis-(4,7,-dimethyl-1,4,7,-triazacyclonon-1-yl)-ethane (Me4-DTNE). 
   
   
       25 . A cellulose-containing substrate or a starch containing substrate, wherein the cellulose-containing substrate or the starch containing substrate has been treated by the method defined in  claim 1 .