Bulk polymerization of silicone-containing copolymers

Abstract

Methods for preparing silicone-containing polymers by essentially adiabatic polymerization methods are disclosed. The polymerization system includes free radically polymerizable monomers. The monomers include ethylenically unsaturated cone-containing monomers and/or mercapto-functional silicones as well as additional free radically polymerizable monomers. The silicone-containing polymers are useful as adhesives or release materials.

1 . A method comprising:
 providing a first reaction mixture comprising:
 an ethylenically unsaturated silicone-containing monomer; 
 at least one additional ethylenically unsaturated monomer; 
 a chain transfer agent; and 
 a thermal initiator; 
   deoxygenating the first reaction mixture;   heating the first reaction mixture to a temperature above the activation temperature of the thermal initiator;   allowing the first reaction mixture to polymerize under essentially adiabatic conditions to yield an at least partially polymerized mixture;   cooling the at least partially polymerized mixture;   adding an additional thermal initiator, and a chain transfer agent to the partially polymerized mixture to form a second reaction mixture;   deoxygenating the second reaction mixture;   heating the second reaction mixture to a temperature above the activation temperature of the additional thermal initiator;   allowing the second reaction mixture to polymerize under essentially adiabatic conditions to form a polymer.   
     
     
         2 . The method of  claim 1  wherein the ethylenically unsaturated silicone-containing monomer comprises a silicone macromer with the structure:
   W-(A) n -Si(R 7 ) 3-m Q m    
 wherein W is a vinyl group; 
 A is a divalent linking group; 
 n is zero or 1; 
 m is an integer of from 1 to 3; R 7  is hydrogen, alkyl, aryl, or alkoxy; and 
 Q is a monovalent siloxane polymeric moiety having a number average molecular weight above about 500 and is essentially unreactive under copolymerization conditions. 
 
     
     
         3 . The method of  claim 2  wherein the ethylenically unsaturated silicone-containing monomer comprises a silicone (meth)acrylate macromer. 
     
     
         4 . The method of  claim 2  wherein the first reaction mixture comprises at least one alkyl (meth)acrylate monomer. 
     
     
         5 . The method of  claim 4  further comprising at least one polar ethylenically unsaturated monomer. 
     
     
         6 . (canceled) 
     
     
         7 . (canceled) 
     
     
         8 . (canceled) 
     
     
         9 . (canceled) 
     
     
         6 . The method of  claim 2  wherein the at least one additional ethylenically unsaturated monomer comprises an alkyl (meth)acrylate which as a homopolymer has a Tg above about 30° C. 
     
     
         11 . (canceled) 
     
     
         7 . The method of  claim 1  further comprising the steps of:
 isolating the polymer; and 
 coating the polymer on a substrate. 
 
     
     
         8 . The method of  claim 7  wherein the coating step comprises hot melt coating, solvent coating or coextrusion. 
     
     
         9 . The method of  claim 7  wherein the polymer comprises a pressure sensitive adhesive and the substrate comprises a film, a tape backing, or a release liner. 
     
     
         10 . The method of  claim 7  further comprising the step of photochemically curing the coated pressure sensitive adhesive polymer. 
     
     
         11 . The method of  claim 7  wherein the polymer comprises a release material and the substrate comprises a film or a tape backing. 
     
     
         17 . (canceled) 
     
     
         12 . The method of  claim 11  further comprising the step of blending the release polymer with a thermoplastic polymer prior to coating. 
     
     
         13 . The method of  claim 11  wherein the coating step comprises is hot melt coating on a pre-tentered film and further comprising the step of stretching the coated film. 
     
     
         14 . A method comprising:
 providing a first reaction mixture comprising:
 an mercapto-functional silicone; 
 at least one ethylenically unsaturated monomer; and 
 a thermal initiator; 
   deoxygenating the first reaction mixture;   heating the first reaction mixture to a temperature above the activation temperature of the thermal initiator;   allowing the first reaction mixture to polymerize under essentially adiabatic conditions to yield an at least partially polymerized mixture;   cooling the at least partially polymerized mixture;   adding an additional thermal initiator to the partially polymerized mixture to form a second reaction mixture;   deoxygenating the second reaction mixture;   heating the second reaction mixture to a temperature above the activation temperature of the additional thermal initiator;   allowing the second reaction mixture to polymerize under essentially adiabatic conditions to form a polymer.   
     
     
         15 . The method of  claim 14  wherein the mercapto-functional silicone has the structure:
   (R 1 ) 3-x (HSR 2 ) x Si—(OSiR 5 R 6 ) y —OSi(R 3 ) 3-q R 4 SH) q  
 
 wherein each R 1  is independently an alkyl, aryl, alkaryl, alkoxy, alkylamino, hydroxyl, hydrogen, or fluoroalkyl group; 
 each R 2  is a divalent linking group; 
 each R 3  is an alkyl, aryl, alkaryl, alkoxy, alkylamino, hydroxyl, hydrogen, or fluoroalkyl group; 
 each R 4  is a divalent linking group; 
 each R 5  is an alkyl, aryl, alkaryl, alkoxy, alkylamino, hydroxyl, fluoroalkyl, hydrogen, or —ZSH, wherein Z is a divalent linking group; 
 each R 6  is an alkyl, aryl, alkaryl, alkoxy, alkylamino, hydroxyl, fluoroalkyl, hydrogen, or —ZSH, wherein Z is a divalent linking group; 
 x is an integer of 0-3; 
 y is an integer of 10 or greater; and 
 q is an integer of 0-3. 
 
     
     
         16 . The method of  claim 14  wherein the mercapto-functional silicone has a number average molecular weight of from 2,000-20,000 grams/mole and from 1-20 mole % —CH 2 CH 2 CH 2 SH groups. 
     
     
         23 . (canceled) 
     
     
         17 . The method of  claim 14  wherein the ethylenically unsaturated monomer comprises an alkyl (meth)acrylate which as a homopolymer has a Tg above about 30° C. 
     
     
         25 . (canceled) 
     
     
         18 . The method of  claim 14  further comprising the steps of:
 isolating the polymer; and 
 coating the polymer on a substrate. 
 
     
     
         27 . (canceled) 
     
     
         19 . The method of  claim 18  wherein the polymer comprises a release material and the substrate comprises a film or a tape backing. 
     
     
         20 . The method of  claim 14  further comprising the steps of:
 isolating the polymer; 
 blending the isolated polymer with a thermoplastic resin; and 
 hot melt coating or coextruding the blend. 
 
     
     
         30 . (canceled)