Process for making a coupled low vinyl block copolymer composition and the resulting composition

Abstract

This invention relates to a process for making a coupled, low vinyl block copolymer composition, comprising the steps of:

Description

Claims

1. A process for making a coupled, low vinyl block copolymer composition, having a vinyl content of less than 15%, comprising the steps of: a) reacting a living lithium-terminated polymer having the formula P—Li, where P is a copolymer chain having at least one polymer block A composed of one or more mono alkenyl arenes having 8 to 18 carbon atoms and at least one polymer block B composed of one or more conjugated dienes having 4 to 12 carbon atoms, with an alkyltrialkoxysilane coupling agent having the formula R—Si—(OR′)3, where R is selected from branched alkyl radicals having from 3 to 12 carbon atoms, and R′ is a methyl group, and where the molar ratio of Si to Li is between 0.3 and 1.0, thereby forming a coupled block copolymer composition; andb) recovering the resulting coupled block copolymer composition.

2. The process of claim 1 wherein said conjugated diene is selected from butadiene and isoprene and said mono alkenyl arene is styrene.

3. The process of claim 2 wherein P is a block copolymer of styrene and butadiene with the butadiene block being attached to the lithium ion.

4. The process of claim 3 wherein the styrene block has an average molecular weight of from 3 to 60 kg/mole and said butadiene block has an average molecular weight of from 20 to 200 kg/mole.

5. The process of claim 4 wherein said alkyltrialkoxysilane has a branched alkyl radical having from 3 to 8 carbon atoms.

6. The process of claim 4 wherein said alkyltrialkoxysilane has a branched alkyl radical having from 4 to 6 carbon atoms.

7. The process of claim 4 wherein said alkyltrialkoxysilane is isobutyltrimethoxysilane.

8. The process of claim 1 wherein the molar ratio of Si to Li is from 0.35 to 0.7.

9. The process of claim 5 wherein the molar ratio of Si to Li is from 0.35 to 0.7.

10. The process of claim 6 wherein the molar ratio of Si to Li is from 0.35 to 0.7.

11. The process of claim 7 wherein the molar ratio of Si to Li is from 0.35 to 0.7.

12. The process of claim 1 wherein the molar ratio of Si to Li is from 0.4 to 0.5.

13. A coupled, low-vinyl block copolymer having a vinyl content of less than 15% based on the conjugated diene midblock, said block copolymer made by reacting a living lithium-terminated polymer having the formula P—Li, where P is a copolymer chain having at least one polymer block A composed of one or more mono alkenyl arenes having 8 to 18 carbon atoms and at least one polymer block B composed of one or more conjugated dienes having 4 to 12 carbon atoms, with an alkyltrialkoxysilane coupling agent having the formula R—Si—(OR′)3, where R is selected from branched alkyl radicals having from 3 to 12 carbon atoms, and R′ is a methyl group, and where the molar ratio of Si to Li is between 0.3 and 1.0 to obtain a coupled block copolymer composition and recovering the resulting coupled block copolymer composition.

14. The block copolymer of claim 13 wherein said conjugated diene is selected from butadiene and isoprene and said mono alkenyl arene is styrene.

15. The block copolymer of claim 14 wherein P is a block copolymer of styrene and butadiene with the butadiene block being attached to the lithium ion.

16. The block copolymer of claim 15 wherein the styrene block has an average molecular weight of from 3 to 60 kg/mole and said butadiene block has an average molecular weight of from 20 to 200 kg/mole.

17. The block copolymer of claim 16 wherein said alkyltrialkoxysilane has a branched alkyl radical having from 3 to 8 carbon atoms.

18. The block copolymer of claim 16 wherein said alkyltrialkoxysilane has a branched alkyl radical having from 4 to 6 carbon atoms.

19. The block copolymer of claim 16 wherein said alkyltrialkoxysilane is isobutyltrimethoxysilane.

20. The process of claim 1 wherein the molar ratio of Si to Li is from 0.35 to 0.7.