Block copolymers and method for making same
The present invention is a novel block copolymer containing a controlled distribution copolymer block of a conjugated diene and a mono alkenyl arene, where the controlled distribution copolymer block has terminal regions that are rich in conjugated diene units and a center region that is rich in mono alkenyl arene units. Also disclosed is a method for manufacture of the block copolymer.
1. A functionalized, selectively hydrogenated block copolymer having the general configuration A-B, A-B-A, (A-B) n , (A-B-A) n , (A-B-A) n X, (A-B) n X or mixtures thereof, which has been grafted with an acid compound or its derivative, where n is an integer from 2 to about 30, and X is a coupling agent residue and wherein:
a. prior to hydrogenation each A block is a mono alkenyl arene polymer block and each B block is a controlled distribution copolymer block of at least one conjugated diene and at least one mono alkenyl arene;
b. subsequent to hydrogenation about 0–10% of the arene double bonds have been reduced, and at least about 90% of the conjugated diene double bonds have been reduced;
c. each A block having a number average molecular weight between about 3,000 and about 60,000 and each B block having a number average molecular weight between about 30,000 and 300,000;
d. each B block comprises terminal regions adjacent to the A blocks that are rich in conjugated diene units and one or more regions not adjacent to the A blocks that are rich in mono alkenyl arene units;
e. the total amount of mono alkenyl arene in the hydrogenated block copolymer is about 20 percent weight to about 80 percent weight;
f. the weight percent of mono alkenyl arene in each B block is between about 10 percent and about 75 percent; and
g. the styrene blockiness index of the B block is less than about 40 percent.
2. The block copolymer of claim 1 wherein said acid compound or it derivative is selected from the group consisting of maleic anhydride, maleic acid, fumaric acid, and their derivatives.
3. The copolymer of claim 1 wherein said mono alkenyl arene is styrene and said conjugated diene is selected from the group consisting of isoprene and butadiene.
4. The copolymer of claim 1 wherein said conjugated diene is butadiene, and wherein about 20 to about 80 mol percent of the condensed butadiene units in block B have 1,2-configuration prior to hydrogenation.
5. The copolymer of claim 1 wherein the coupling agent is divinyl benzene.
6. The copolymer of claim 1 wherein n is between about 2 and about 6 and said coupling agent is a tetra alkoxy silane.
7. The copolymer of claim 1 wherein the coupling agent is tetra ethoxy silane.
8. The copolymer of claim 1 wherein n is between about 2 and about 6 and said coupling agent is a diester of a carboxylic acid.
9. The copolymer of claim 1 wherein the coupling agent is dimethyl adipate.