Block copolymers of conjugated dienes and lactones as modifiers of unsaturated polyesters

A stable composition formed from a process comprising the steps of:

• (a) providing a lithium-terminated polymer of the form A(DLi).sub.y wherein A is a polymer segment comprising one or more polymer blocks formed at least in part from one or more conjugated diene monomers, D is a polymer segment comprising one or more polymer blocks formed from one or more lactone monomers, and y is1, 2, 3, or 4;
• (b) contacting the lithium-terminated polymer A(D-Li).sub.y with a terminating agent selected from the group consisting of water, a mineral acid and a carboxylic acid, thus producing a block copolymer of the form A(D).sub.y ;
• and
• (c) mixing, in a vinyl monomer, the block copolymer of the form A(D).sub.y and an unsaturated polyester.

A process for preparing a composition comprising the steps of

• (1) polymerizing styrene in a hydrocarbon diluent at a temperature of about 40.degree. to about 125.degree. C. using an initiator represented by the formula R"(Li).sub.y wherein R" is a hydrocarbon radical selected from aliphatic, cycloaliphatic and aromatic radicals and combinations thereof and y is an integer from 1 to 4;
• (2) adding 1,3-butadiene monomer to the polystyrene-containing hydrocarbon diluent and allowing the 1,3-butadiene monomer to polymerize so as to form a lithium-terminated styrene-butadiene block copolymer;
• (3) adding a capping agent to the hydrocarbon diluent containing the lithium terminated styrene-butadiene block copolymer and allowing the capping agent to react therewith;
• (4) adding to the hydrocarbon diluent containing the capped copolymer an amount of epsilon-caprolactone monomer within the range of about 8 to about 50 weight percent based on the weight of the total monomers, and allowing the epsilon-caprolactone monomer to polymerize at a temperature within the range of about 0.degree. to about 70.degree. C.;
• (5) contacting the thus-formed lithium-terminated styrene-butadiene-caprolactone block copolymer with a terminating agent selected from the group consisting of water, a mineral acid and a carboxylic acid;
• (6) recovering the thus-formed block copolymer from the hydrocarbon diluent;
• and
• (7) blending, in styrene solution, the block copolymer and an unsaturated polyester at a temperature less than 30.degree. C. and in a weight ratio of unsaturated polyester to block copolymer of about 15:1 to about 0.5 to 1.