Epoxidized diene elastomers for exterior block crosslinking

Abstract

An epoxidized diene block polymer comprising at least interior and exterior diene blocks wherein the exterior diene blocks contain a greater concentration of di-, tri- and tetrasubstituted olefinic epoxides than the interior blocks and wherein the exterior blocks contain from 0.2 to 10 Meq of olefinic epoxides per gram of exterior blocks and the molecular weights of the exterior blocks are from 3000 to 50,000 and the molecular weights of the interior blocks are from 15,000 to 200,000.

I claim: 
     
       1. A process for the production of a partially hydrogenated conjugated diene block copolymer of the formula   D.sub.n -X-C.sub.r     wherein D is A-B-M p  or (A-B) j  -M p  or A-(B-A) j  -M p  ; and   wherein A is a diene block which has a molecular weight of 3,000 to 50,000; and   wherein B is a diene block which has a molecular weight of from 15,000 to 200,000; and   wherein C is a block or multiblock segment which has a molecular weight of from 100 to 200,000 and comprises A, B or methacrylate or mixtures thereof but is not identical to D; and   wherein the B block may comprise up to 50% of a monoalkenyl aromatic hydrocarbon monomer and the A blocks may comprise up to 99% of a monoalkenyl aromatic hydrocarbon monomer; and   wherein M is a miniblock of a monomer selected from the group consisting of vinyl aromatic hydrocarbons and dienes and which has a molecular weight of 50 to 3000; and   wherein the A blocks contain a greater concentration of di-, tri-, or tetrasubstituted olefinic epoxides than the B blocks; and   wherein X is a coupling agent or coupling monomers or initiator, j is 1 to 6, n≧2, r≧0, n≧r, n+r ranges from 3 to 100 and p is 0 or 1; said process comprising polymerizing the diene which makes up block A under anionic polymerization conditions to form block A, adding the diene which makes up block B to the reaction mixture and polymerizing it to form block B at one end of block A, subsequently coupling AB diblocks together by adding X to the reaction mixture to form a coupled block copolymer, and partially hydrogenatinq the coupled block copolymer such that the ratio of olefinic double bonds in the A blocks to that in the B blocks is at least 3:1.     
     
     
       2. A process for the production of a partially hydrogenated conjugated diolefin block copolymer of the formula   (A-B).sub.k or A-(B-A).sub.j     wherein A is a diene block which has a molecular weight of 3000 to 50,000; and   wherein B is a diene block which has a molecular weight of from 15,000 to 200,000; and   wherein the A blocks contain a greater concentration of di-, tri-, or tetrasubstituted olefinic epoxides than the B blocks; and   wherein j is 1 to 6 and k is 2 to 6; and said process comprising polymerizing the diene which makes up block A under anionic polymerization conditions to form block A, adding the diene which makes up block B to the reaction mixture and polymerizing it under anionic polymerization conditions to form block B at one end of block A, optionally, repeating the sequential addition of said dienes and anionic polymerization of them to form additional blocks to provide the block copolymer, and partially hydrogenating the block copolymer such that the ratio of olefinic double bonds in the A blocks to that in the B blocks is at least 3:1.