US 5,393,838 AGranted

Conjugated diene/monovinylarene block copolymers with multiple tapered blocks

AssigneePhillips Petroleum Company

InventorsGeorge A. Moczygemba, Nathan E. Stacy, Nancy R. Knight

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Abstract

A method for preparing polymodal tapered block copolymers in a polymerization process by sequentially charging: (a) an initiator and monovinylaromatic monomers in the presence of a randomizer; (b) an initiator and monovinylaromatic monomers; (c) a mixture of monovinylaromatic and conjugated diene monomers; (d) a mixture of monovinylaromatic and conjugated diene monomers; (e) an initiator and monovinylaromatic monomers; (f) a mixture of monovinylaromatic and conjugated diene monomers; (g) a mixture of monovinylaromatic and conjugated diene monomers; (h) conjugated diene monomers; and (i) a coupling agent. The copolymers and blends thereof are particularly useful for packaging applications which require good environmental stress crack resistance.

Claims5

Dependent claims

Blends of polystyrene with polymodal block copolymers in which the block copolymer contains from about 55 to about 95 weight percent of monovinylaromatic monomer based upon total weight of the copolymer and the copolymer is produced in accordance with a method comprising:

(a) charging into a polymerization zone an initiator and a monovinylaromatic monomer in the presence of a randomizer and allowing polymerization to occur until essentially no free monomer is present;
thereafter
(b) charging into said polymerization zone a monovinylaromatic monomer and an initiator and allowing polymerization to occur until essentially no free monomer is present;
thereafter
(c) charging into said polymerization zone a mixture of monovinylaromatic monomer and conjugated diene monomer and allowing polymerization to occur until essentially no free monomer is present;
thereafter
(d) charging into said polymerization zone a mixture of monovinylaromatic monomer and conjugated diene monomer and allowing polymerization to occur until essentially no free monomer is present;
thereafter
(e) charging into said polymerization zone a monovinylaromatic monomer and an initiator and allowing polymerization to occur until essentially no free monomer is present;
thereafter
(f) charging into said polymerization zone a mixture of monovinylaromatic monomer and conjugated diene monomer and allowing polymerization to occur until essentially no free monomer is present;
thereafter
(g) charging into said polymerization zone a mixture of monovinylaromatic monomer and conjugated diene monomer and allowing polymerization to occur until essentially no free monomer is present;
thereafter
(h) charging into said polymerization zone a conjugated diene monomer and allowing polymerization to occur until essentially no free monomer is present;
and thereafter
(i) charging the reaction mixture with a coupling agent.

14 more elements

Dependencies are inferred from the claim text.