Tapered block styrene/butadiene copolymers
AssigneePhillips Petroleum Company
InventorsWilliam J. Trepka, George A. Moczygemba, Ralph C. Farrar, Jr.
Life of this patent
Estimating the term…
Abstract
A method for preparing tapered block copolymers in a polymerization process by charging an initiator and monomers sequentially with one or more charges of first one of the monomers, then with a mixture of the two monomers, and then with one or more charges of the second monomer alternating with one or more charges of the first monomer with subsequent coupling, to produce a polymodal tapered block copolymer. Suitable monomers include conjugated dienes and monovinylaromatic compounds. The copolymers are suitable for use in injection and blow molding equipment; the copolymers are particularly useful for shrink films, containers, tubes, fibers and other packaging applications.
Claims22
A method of preparing a polymer comprising:
- (1) charging a monovinylaromatic monomer and an initiator and in the presence of a randomizer and allowing polymerization to occur until essentially no free monomer is present;
- thereafter
- (2a) charging additional monovinylaromatic monomer and initiator, and allowing polymerization to occur until essentially no free monomer is present;
- (2b) charging a mixture of monovinylaromatic monomer and conjugated diene monomer, and allowing polymerization to occur until essentially no free monomer is present;
- (2c) charging additional monovinylaromatic monomer and additional initiator, and allowing polymerization to occur until essentially no free monomer is present;
- thereafter
- (3) charging conjugated diene monomer and allowing polymerization to occur until essentially no free monomer is present;
- and finally
- (4) charging the reaction mixture with a coupling agent.
Dependencies are inferred from the claim text.