| 摘要 |
A process for preparing a block copolymer. In one embodiment, the block copolymers comprise (A) a poly (vinyl aromatic) block and (B) a poly (vinyl aromatic-co-acrylic) block, said process comprising the steps,(a) polymerizing at an elevated temperature from about 5 to about 95 mole % of a charge comprising at least one vinyl aromatic monomer to prepare a stabilized active polymer block (A), using a free radical polymerization process,wherein a stable free radical agent is employed during the polymerization, thereby preserving the stabilized active polymerization site at the terminus of the poly (vinyl aromatic) block (A);(b) adding at least one acrylic monomer and optionally, additional vinyl aromatic monomer, to the mixture of vinyl aromatic monomer and stabilized active polymer block of (a); and(c) further reacting the mixture of (b) using a free radical process to effect copolymerization of said monomers, thereby preparing a (vinyl aromatic-co-acrylate) block (B).The present invention also relates to block copolymers prepared by the above process, additive concentrates for preparing lubricating oil compositions and lubricating oil compositions. In other embodiments, the present invention relates to block copolymers having more than two blocks.
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