Polymerization process

Abstract

A staged method of forming vinyl (e.g. acrylate) copolymer by solution polymerization which involves a) charging up to 90% of at least two vinyl monomers of the vinyl copolymer to a first stage reaction zone, b) polymerizing the at least two vinyl monomers to about 10 to 90% conversion in the presence of an initiator at an initiator to monomers mole ratio within a specified range, the monomer content of one of the at least two vinyl monomers of the copolymer formed in the first stage being higher than the content of another of the at least two vinyl monomers in the first stage polymer, the weight average molecular weight of the first stage copolymer being about 2000 to 500,000 Daltons; and c) continuing polymerization in the presence of an initiator in a second stage while continuously adding the balance of the monomers of said vinyl copolymer to the polymerization reaction mixture of the first stage at a monomers ratio lower in the one monomer than in the first stage monomers ratio, the initiator to monomers mole ratio in the second stage being different than in the first stage; the vinyl copolymer formed gradually continuously changing in molecular weight from the first stage and increasing in concentration of the one monomer during the second stage, the weight average molecular weight of the total copolymer of both stages being about 2,000 to 250,000 Daltons.

We claim:  
     
         1 . A staged method of forming vinyl copolymer by solution polymerization which comprises: 
 a) charging a positive amount up to 90% of at least two vinyl monomers of said vinyl copolymer to a first stage reaction zone;    b) polymerizing said at least two vinyl monomers in the first stage reaction zone to about 10 to 90% conversion in the presence of an initiator at an initiator to monomers mole ratio of about 1×10 −4 :1 to 5×10 −2 :1, the monomer content of one of the at least two vinyl monomers of the copolymer formed in the first stage being higher than the content of another of the at least two vinyl monomers in said first stage polymer, the weight average molecular weight of the first stage copolymer being about 2000 to 500,000 Daltons; and    c) continuing polymerization in the presence of an initiator in a second stage while continuously adding the balance of the monomers of said vinyl copolymer to the polymerization reaction mixture of the first stage at a monomers ratio lower in said one monomer than in the first stage monomers ratio, the initiator to monomers mole ratio in the second stage being different than in the first stage;    the vinyl copolymer formed gradually continuously changing in molecular weight from the first stage and increasing in concentration of said one monomer during the second stage, the weight average molecular weight of the total copolymer of the first stage and the second stage being about 2000 to 250,000 Daltons.    
     
     
         2 . The process of  claim 1  wherein the initiator to monomers ratio in the first stage is between 5×10 −4 :1 and 2×10 −2 :1.  
     
     
         3 . The process of  claim 2  wherein the vinyl copolymer is an acrylate copolymer, said at least two monomers comprise ethyl acrylate and 2-ethylhexyl acrylate and said one monomer is 2-ethylhexyl acrylate.  
     
     
         4 . The process of  claim 3  wherein the monomers in the first stage are charged to the first stage at one time.  
     
     
         5 . The process of  claim 4  wherein said at least two monomers includes fluorinated acrylate monomer.  
     
     
         6 . The acrylate copolymer product of the process of  claim 3 .  
     
     
         7 . The acrylate copolymer product of the process of  claim 5 .  
     
     
         8 . The acrylate copolymer of  claim 6  wherein the monomers in the copolymer comprise 10 to 20 wt. % ethyl acrylate and 90 to 20 wt. % 2-ethylhexyl acrylate.  
     
     
         9 . The acrylate copolymer product of  claim 7  comprising 10 to 80 wt. % ethyl acrylate, 20 to 90 wt. % 2-ethylhexyl acrylate and 0 to 20 wt. % fluorinated acrylate.