Immediate termination of free radical polymerizations

Abstract

Free radical polymerizations are immediately terminated by adding a phenothiazine-containing solution whose solvent comprises at least 50% of its weight of an N-alkylpyrrolidone.

We claim:  
     
       1. A process for immediately terminating a free radical polymerization of at least one monomer comprising adding a phenothiazine-containing inhibitor solution to a system undergoing free radical polymerization, wherein the solvent of the inhibitor solution comprises at least 50% of its weight of an N-alkylpyrrolidone; and 
       wherein the content of phenothiazine in the inhibitor solution is at least 10% by weight based on the solution.  
     
     
       2. A process as claimed in claim  1 , wherein the N-alkylpyrrolidone is N-methylpyrrolidone or N-ethylpyrrolidone. 
     
     
       3. A process as claimed in claim  1 , wherein the phenothiazine content of the inhibitor solution is at least 10% by weight, based on the weight of the inhibitor solution. 
     
     
       4. A process as claimed in claim  1  to  3 , wherein the system undergoing free radical polymerization comprises (meth)acrylic monomers undergoing free radical mass polymerization. 
     
     
       5. A process as claimed in claim  4 , wherein the (meth)acrylic monomer is (meth)acrylic acid. 
     
     
       6. A process as claimed in claim  4 , wherein the (meth)acrylic monomer is a (meth)acrylic ester. 
     
     
       7. Apparatus for immediately terminating a free radical polymerization, said apparatus comprising a spray nozzle, and said apparatus containing a phenothiazine-containing inhibitor solution, wherein the solvent of the inhibitor solution comprises at least 50% of its weight of an N-alkylpyrrolidone. 
     
     
       8. An inhibitor solution containing phenothiazine and at least 50% of its weight of an N-alkylpyrrolidone. 
     
     
       9. A solution as claimed in claim  8 , containing phenothiazine and at least 50% of its weight of N-methylpyrrolidone. 
     
     
       10. The process of claim  1 , wherein the phenothiazine-containing inhibitor solution is introduced to said system by means of a spray nozzle.