Polymerisation process

Abstract

A process of preparing water soluble or water swellable polymer comprising the steps, (a) forming an aqueous mixture comprising, (i) a water soluble ethylenically unsaturated monomer or blend of monomers and, (ii) an ultra violet initiator, (b) effecting polymerization by subjecting the aqueous mixture formed in step (a) to polymerization conditions to form a polymer of said monomer or monomer blend, (c) subjecting the polymer formed in step (b) to ultra violet light radiation, characterized in that the polymerization step (b) is conducted substantially in the absence of ultra violet radiation. In one preferred aspect the ultra violet initiator is distributed throughout the polymer formed in step (b). In another preferred aspect the step (c) is conducted ultra violet light at an intensity of up to 500 milli Watts/cm 2 . Also claimed is a method of reducing the residual monomer content in a water soluble or water swellable polymer by subjecting the polymer to ultra violet irradiation in the presence of an ultra violet initiator. The process is particularly suitable for making highly effective water soluble and water swellable polymers useful as flocculants, coagulants, rheology modifiers, dispersants, superabsorbents and binders etc.

1 . A process of preparing water soluble or water swellable polymer comprising the steps, 
 (a) forming an aqueous mixture comprising, 
 (i) a water soluble ethylenically unsaturated monomer or blend of monomers and,  
 (ii) an ultra violet initiator,  
   (b) effecting polymerisation by subjecting the aqueous mixture formed in step (a) to polymerisation conditions to form a polymer of said monomer or monomer blend, wherein ultra violet initiator is distributed throughout the polymer,    (c) subjecting the polymer formed in step (b) to ultra violet light radiation, characterised in that the polymerisation step (b) is conducted substantially in the absence of ultra violet radiation.    
     
     
         2 . A process according to  claim 1  in which the polymerisation step (b) is effected by suitable polymerisation initiators, selected from the group consisting of redox initiators and thermal initiators.  
     
     
         3 . A process according to  claim 1  or  claim 2  in which the polymer in step (c) is subjected to ultraviolet light radiation at an intensity of up to 500 milliWatts.  
     
     
         4 . A process according to any of  claims 1  to  3  in which the polymer is formed from acrylamide.  
     
     
         5 . A process according to any of  claims 1  to  4  in which the polymer has an intrinsic viscosity of at least 4 dl/g.  
     
     
         6 . A process according to any of  claims 1  to  5  in which the polymer formed by solution polymerisation.  
     
     
         7 . A process according to any of  claims 1  to  6  in which the ultra violet initiator is soluble or dispersible in the aqueous monomer or monomer blend.  
     
     
         8 . A process according to any of  claims 1  to  7  in which the ultra violet initiator is a compound of formula:  
       
         
           
           
               
               
           
         
       
       wherein R 1  and R 2  are each independently C 1-3  alkyl or together form a C 4-8  cycloaliphatic ring, R 3  is H, C 1-2  alkyl or —O(CH 2 CH 2 ) n OH and n is 1-20.  
     
     
         9 . A process according to  claim 8  in which the ultra violet initiator is a compound of formula:  
       
         
           
           
               
               
           
         
       
     
     
         10 . A process according to  claim 8  in which the ultra violet initiator is a compound of formula:  
       
         
           
           
               
               
           
         
       
     
     
         11 . A process according to any of  claims 1  to  10  in which step (c) is conducted simultaneous with a drying stage.  
     
     
         12 . A method of reducing the residual monomer content in a water soluble or water swellable polymer by subjecting the polymer to ultra violet irradiation in the presence of an ultra violet initiator.  
     
     
         13 . A method according to  claim 12  in which the polymer is a polymer of acrylamide of intrinsic viscosity above 4 dl/g.  
     
     
         14 . A method according to  claim 12  or  claim 13  in which the ultra violet initiator is a compound of formula:  
       
         
           
           
               
               
           
         
       
       wherein R 1  and R 2  are each independently C 1-3  alkyl or together form a C 4-8  cycloaliphatic ring, R 3  is H, C 1-2  alkyl or —O(CH 2 CH 2 ) n OH and n is 1-20.  
     
     
         15 . A method according to  claim 14  in which the ultra violet initiator is a compound of formula:  
       
         
           
           
               
               
           
         
       
     
     
         16 . A method according to  claim 15  in which the ultra violet initiator is a compound of formula:  
       
         
           
           
               
               
           
         
       
     
     
         17 . A process of preparing water soluble or water swellable polymer comprising the steps, 
 (a) forming an aqueous mixture comprising, 
 (i) a water soluble ethylenically unsaturated monomer or blend of monomers and,  
 (ii) an ultra violet initiator,  
   (b) effecting polymerisation by subjecting the aqueous mixture formed in step (a) to polymerisation conditions to form a polymer of said monomer or monomer blend,    (c) subjecting the polymer formed in step (b) to ultra violet light radiation at an intensity of up to 500 milli Watts,    characterised in that the polymerisation step (b) is conducted substantially in the absence of ultra violet radiation.    
     
     
         18 . A process according to  claim 17  in which the ultra violet light radiation is at an intensity of up to 50 milli Watts.  
     
     
         19 . A water soluble or water swellable polymer obtainable by a process defined by any of  claims 1  to  11 ,  17  or  18  or by a method according to anyone of  claims 12  to  16  in which the amount of residual monomer is below 100 ppm.