Claims
- 1. A process for preparing a block copolymer corresponding to the formula AB(BA)n wherein A is a block of a monovinylidene aromatic monomer and B is a block of butadiene, and n is a number from 0 to 6, said block copolymer being further characterized in that at least one of the junctions between an A block and a B block is tapered such that the total amount of isolated, polymerized monovinylidene aromatic units in the polymer is from 30 to 75 percent and the 1,2-vinyl content of the polybutadiene block of the copolymer is from 35 to 55 percent comprising polymerizing a monovinylidene aromatic monomer and a conjugated diene under anionic polymerization conditions in the presence of a suitable randomizing agent to prepare said tapered block copolymer.
- 2. A process according to claim 1 wherein the randomizing agent is a tertiary amine.
- 3. A process according to claim 2 wherein the tertiary amine is an aliphatic diamine or triamine.
- 4. A process according to claim 3, wherein the tertiary amine is N,N,N',N',N"-pentamethyl diethylene triamine.
CROSS-REFERENCE TO RELATED APPLICATION
This is a divisional of application Ser. No. 440,850 filed Nov. 24, 1989.
US Referenced Citations (4)
Foreign Referenced Citations (1)
Number |
Date |
Country |
316857 |
May 1989 |
EPX |
Divisions (1)
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Number |
Date |
Country |
Parent |
440850 |
Nov 1989 |
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