Process for the preparation of random copolymers of conjugated dienes and vinyl aromatic compounds

Abstract

Random copolymers of a conjugated diene and at least 50% by weight of a vinyl aromatic compound are prepared by slowly reacting the monomers in a non-polar solvent in the presence of a chelating modifier such as ethylene glycol diethyl ether which results in at least 50% 1,2-polymerization of the conjugated diene.

What is claimed is:  
     
       1. An improved process for the preparation of a random copolymer of at least one conjugated diene and at least 50% by weight of a vinyl aromatic compound wherein the monomers are polymerized with a lithium initiator, the improvement comprising polymerizing at least 5% by weight of the monomers in a non-polar solvent prior to addition of a sufficient amount tetramethylethylenediamine to achieve 1,2-addition of at least 60%, and them slowly adding the remaining portion of the monomers to maintain a reaction temperature from 10° C. to 40° C. 
     
     
       2. The process of  claim 1  wherein the conjugated diene is 1,3-butadiene and the vinyl aromatic compound is styrene. 
     
     
       3. The process of  claim 2  wherein the monomers are premixed and the mixture of the monomers comprises at least 70 percent by weight of the styrene.