Gels from controlled distribution block copolymers
View Patent ↗The present invention relates to gels prepared from novel anionic block copolymers of mono alkenyl arenes and conjugated dienes, and to blends of such block copolymers with other polymers. The block copolymers are selectively hydrogenated and have mono alkenyl arene end blocks and controlled distribution blocks of mono alkenyl arenes and conjugated dienes. The block copolymer may be combined with tackifying resins, oils and other components to form the gels of the present invention.
1. An oil gel composition comprising 100 parts by weight of at least one hydrogenated block copolymer and from about 400 to about 2000 parts by weight of an extending oil, wherein said hydrogenated block copolymer has at least one polymer block A and at least one polymer block B, and wherein:
a. prior to hydrogenation each A block is a mono alkenyl arene homopolymer 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 20,000 and about 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; and
f. the weight percent of mono alkenyl arene in each B block is between about 10 percent and about 75 percent.
2. The oil gel composition according to claim 1 wherein said mono alkenyl arene is styrene and said conjugated diene is selected from the group consisting of isoprene and butadiene.
3. The oil gel composition according to claim 2 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.
4. The oil gel composition according to claim 3 wherein the styrene blockiness of the block B is less than about 40 mol percent.
5. The oil gel composition according to claim 4 wherein the polymer is an ABA polymer and each block B has a center region with a minimum ratio of butadiene units to styrene units.
6. The oil gel composition according to claim 3 wherein the weight percent of styrene in each B block is between about 10 percent and about 30 percent, and the styrene blockiness index of each block B is less than about 10 percent, said styrene blockiness index being defined to be the proportion of styrene units in the block B having two styrene neighbors on the polymer chain.
7. The oil gel composition according to claim 3 wherein said hydrogenated block copolymer has a general configuration AB, ABA, (A-B) n , (A-B) n A, (A-B) n X or mixtures thereof where n is an integer from 2 to about 30, and X is the coupling agent residue.
8. The oil gel composition according to claim 7 wherein said hydrogenated block copolymer is a linear hydrogenated ABA styrene/butadiene block copolymer having a total number average molecular weight of about 80,000 to about 140,000.
9. The oil gel composition according to claim 8 wherein said extending oil is a paraffinic processing oil.
10. The oil gel composition according to claim 9 wherein the amount of extending oil is between about 400 and about 1000 parts by weight.
11. The oil gel composition according to claim 8 wherein said extending oil is a naphthenic oil.
12. The oil gel composition according to claim 8 wherein said extending oil is selected from the group consisting of oligomers of randomly or sequentially polymerized styrene and conjugated diene, oligomers of conjugated diene, liquid polybutene-1 and ethylene-propylene-diene rubber.
13. The oil gel composition according to claim 12 wherein said oligomers of conjugated dienes comprise butadiene or isoprene.
14. The oil gel composition according to claim 12 wherein said extending oil has a weight average molecular weight from 300 to 35,000.
15. The oil gel composition according to claim 1 further comprising a filler or pigment.
16. The oil gel composition according to claim 15 wherein said filler is selected from the group consisting of calcium carbonate, clay, talc, silica, zinc oxide and titanium dioxide.
17. The oil gel composition according to claim 1 wherein said extending oil has an aromatic content less than 50%.
18. The oil gel composition according to claim 1 wherein said extending oil has an initial boiling point above about 500° F.