Use of hydroxyl-functional polyalkylorganosiloxanes as solvents for cationic photoinitiators for use in radiation-curable silicones

Abstract

The invention provides for the use of hydroxyl-functional polyalkylorganosiloxanes of the general formula (IV) as solvents for cationic photoinitiators and for the use of these solutions in cationically curable silicones.

1 . A mixture consisting: 
 A) at least one hydroxyl-functional polyalkylorganosiloxanes of the formula (IV)                          where    a is from 0 to 200,    b is from 0 to 50,    R 1  is identical or different at each occurrence in the molecule and denotes alkyl radicals,    R 2 , R 2  and R 2  are identical or different and have the following definition:    R 2a  independently at each occurrence denotes optionally substituted alkyl radicals, optionally substituted aryl radicals, or optionally substituted aralkyl radicals,    R 2b  independently at each occurrence denotes selected radicals of the general formula      —R 3 [—O—(C n H 2n O—) x H] z     where    R 3  is a z+1-valent hydrocarbon radical which optionally is substituted and/or contains ether bridges or is an aryl radical or aralkyl radical which optionally is substituted and/or contains ether bridges,    n is 2, 3 or 4,    x is from 0 to 100,    z is from 1 to 6,    with the proviso that in the average molecule in each case at least one radical R 2 , R 2 * , R 2 ** has the definition R 2b , and    B) at least one cationic photoinitiator.    
     
     
         2 . The mixture according to  claim 1  wherein the hydroxyl-functional polyalkylorganosiloxane is as follows: 
 a is a number in the range from 5 to 100,    b is a number in the range from 0 to 10,    n is a number in the range from 2 to 3,    x is a number in the range from 0 to 30,    z is a number from 1 to 3.    
     
     
         3 . The mixture according to  claim 2 , wherein 
 a is a number in the range of 5 to 80,    b is a number in the range of 0 to 5, and;    v is a number in the range of 0 to 10.    
     
     
         4 . The mixture according to  claim 1  wherein R 1  in the hydroxyl-functional polyalkylorganosiloxane is a methyl radical.  
     
     
         5 . The mixture according to  claim 1 , wherein at least one radical R 2a  in the hydroxyl-functional polyalkylorganosiloxane is a radical selected from the group consisting of methyl, ethyl, butyl, dodecyl, hexadecyl, aryl, and (methyl)ethylphenyl.  
     
     
         6 . The mixture according to  claim 1  wherein at least one radical R 3  is a hydroxyl-functional polyalkylorganosiloxane as set forth radical selected from the group consisting of —CH 2 —, —(CH 2 ) 2 —, —(CH 2 ) 3 —, —(CH 2 ) 4 —, —(CH 2 ) 6 —, —(CH 2 ) 10 —, —CH 2 CH 2 CH(OCH 3 )CH 2 —, phenyl, naphthyl, anthryl,  
       
         
           
           
               
               
           
         
       
     
     
         7 . The mixture as claimed in  claim 1 , wherein the cationic photoinitiator is a diaryliodonium salt.  
     
     
         8 . The mixture as claimed in  claim 7 , wherein the diaryliodonium salts is a compound selected from the group consisting of  
       
         
           
           
               
               
           
         
       
     
     
         9 . The mixture as claimed in  claim 1 , wherein the hydroxyl-functional polyalkylorganosiloxane is selected from the group consisting of  
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
       
     
     
         10 . The mixture as claimed in  claim 1 , wherein the cationic photoinitiator is a triarylsulfonium salt.  
     
     
         11 . (canceled)  
     
     
         12 . A method for increasing the storage shelf life of a solution comprising of at least one cationic photoinitiator which comprises dissolving the cationic photoinitiator in a solvent comprising at least one hydroxyl-functional polyalkylorganosiloxanes of the formula  
       
         
           
           
               
               
           
         
       
       where 
 a is from 0 to 200,  
 b is from 0 to 50,  
 R 1  is identical or different at each occurrence in the molecule and denotes alkyl radicals,  
 R 2 , R 2 * and R 2 ** are identical or different and have the following definition:  
 R 2a  independently at each occurrence denotes selected, optionally substituted alkyl radicals, optionally substituted aryl radicals, or aralkyl radicals,  
 R 2b  independently at each occurrence denotes selected radicals of the general formula  
   —R 3 [—O—(C n H 2n O—) x H] z   
 where  
 R 3  is a z+1-valent hydrocarbon radical which optionally is substituted and/or contains ether bridges or is an aryl radical or aralkyl radical which optionally is substituted and/or contains ether bridges,  
 n is 2, 3 or 4,  
 x is from 0 to 100,  
 z is from 1 to 6,  
 with the proviso that in the average molecule in each case at least one radical R 2 , R 2 *, R 2 ** has the definition R 2b , as solvents for cationic photoinitiators, to form the mixture of  claim 1  whereby the solution is stable for at least six months.  
 
     
     
         13 . A cationically curable composition which comprises at least one organopolysiloxanes, which contains at least one UV reactive group and that cures cationically under UV radiation, and the mixture according to  claim 1 .  
     
     
         14 . An adhesive coating which is obtained by reacting the cationically curable composition according to  claim 1  with UV light.