Thermoplastic compositions and process for the preparation thereof

Claim 2

A thermoplastic composition which comprises:- (a) 80 to 20 parts by weight of a normal vinyl content selectively hydrogenated elastomeric block copolymer having the general configuration A-B-A, wherein: (i) each A block is a polymerized monoalkenyl aromatic hydrocarbon block having an average molecular weight of 4000 to 115,000; (ii) said A blocks, in combination, comprise 5 to 35% by weigh of the entire normal vinyl content elastomeric block copolymer; (iii) the B block is a polymerized selectively hydrogenated block of a conjugated alkadiene having in the range of from 4 to 8 carbon atoms per molecule consisting, before the selective hydrogenation, of 35 to 50 mol per cent condensed alkadiene units in the 1,2 configuration and said B block has an average molecular weight of between 20,000 and 450,000; (b) 20 to 80 parts by weight of a selectively hydrogenated low vinyl content elastomeric block copolymer having the general configuration A-B-A wherein: (i) each A block is a polymerized monoalkenyl aromatic hydrocarbon block having an average molecular weight of 4000 to 115,000; (ii) said A blocks, in combination, comprise 5 to 35% by weight of the entire low vinyl content elastomeric block copolymer; (iii) the B block is a polymerized selectively hydrogenated block of a conjugated alkadiene having in the range of from 4 to 8 carbon atoms per molecule consisting, before the selective hydrogenation, of 18 to 34 mol per cent condensed alkadiene units in the 1,2 configuration, and said B block has an average molecular weight of between 20,000 and 450,000; and (c) 0.001 to 50 phr of a polyolefin, the term "phr" referring to parts by weight per hundred parts by weight of the total elastomeric block copolymer.

Claim 3

A composition as claimed in claim 1, wherein the monoalkenyl aromatic hydrocarbon is styrene.

Claim 4

A composition as claimed in claim 1 or 2, wherein the conjugated diene is 1,3-butadiene.

Claim 5

A composition as claimed in any one of the preceding claims, wherein the polyolefin is a high density polyethylene.

Claim 6

A composition as claimed in any one of the preceding claims, wherein block B in (b) (iii) consists, before the selective hydrogenation, of 21-31 mol per cent condensed butadiene units in the 1,2-configuration.

Claim 7

A composition as claimed in any one of the preceding claims which further comprises:- (a) up to 125 phr of an oil; (b) up to 50 phr of an anionic polystyrene; and (c) up to 25 phr of a member of a stabilizer, a slip-agent, an antioxidant, an antistatic agent, a plasticizer, a preservative, a colorant, a processing aid, and/or a lubricant; (d) up to 1500 phr of a filler, the term "phr" referring to parts by weight per hundred parts by weight of the total elastomeric block copolymer.

Claim 8

A process for the preparation of a thermoplastic composition as claimed in any one of the preceding claims which process comprises:- (a) forming a low vinyl content selectively hydrogenated elastomeric block copolymer by the following steps (i) to (iv): (i) polymerizing a monoalkenyl arene in the presence of an inert hydrocarbon solvent and a lithium-­based catalyst whereby a polymer block A is formed and said polymer block A has an average molecular weight of between 4,000 and 115,000 and said block A is terminated with a lithium ion; (ii) adding a conjugated alkadiene having in the range of from 4 to 8 carbon atoms per molecule to the lithium terminated block and block copolymerizing it with said first block in the presence of a polar compound of the group consisting of ethers, thioethers, and tertiary amines, the molar ratio of said polar compound to lithium-alkyl catalyst being between 7 and 70, to thereby form a block copolymer terminated with lithium having 18 to 34 mol per cent of 1,2 configuration condensed alkadiene units in said B block and said alkadiene polymer B block having an average molecular weight of between 20,000 and 450,000; (iii) adding thereto a monoalkenyl arene and block polymerizing it with the block copolymer of (ii) to form a block copolymer having the general configuration A-B-A or, alternatively, adding thereto a coupling agent to the A-Bʹ block copolymer formed in step (ii) where Bʹ is about one-half the molecular weight of B, thereby forming a polymer of the type A-Bʹ. (Bʹ-A) n , where n is an integer from 1 to 5, (iv) selectively hydrogenating the block copolymer, whereby the unsaturation of the diene block copolymer block B is reduced to less than 10% of its original value and therein forming a low vinyl content elastomeric block copolymer; (b) forming a normal vinyl content elastomeric block copolymer having the general configuration A-B-A, wherein: (i) each A block is a polymerized monoalkenyl aromatic hydrocarbon block having an average molecular weight of 4000 to 115,000; (ii) said A blocks, in combination, comprise 5 to 35% by weight of the entire normal vinyl content elastomeric block copolymer; (iii) the B block is a polymerized block of a conjugated alkadiene having in the range of from 4 to 8 carbon atoms per molecule consisting of 35 to 50 mol per cent condensed alkadiene units in the 1,2 configuration and said B block has an average molecular weight of between 20,000 and 450,000; (iv) selectively hydrogenating the block copolymer, whereby the unsaturation of the diene block copolymer block B is reduced to less than 10% of its original value and therein forming a normal vinyl content elastomeric block copolymer; (c) blending together 20 and 80 parts by weight of said low vinyl content elastomeric block copolymer with 80 to 20 parts by weight of said normal vinyl content elastomeric block copolymer and from 0.001 to 50 phr of a polyolefin; and (d) optionally adding to said blend up to 125 phr of an oil; (e) optionally adding to said blend up to 25 phr of a heat stabilizer, a slip-agent, an antioxidant, an anti-static agent, a plasticizer, a preservative, a colorant, a processing aid and/or a lubricant; (f) optionally adding to said blend up to 1500 phr of a filler, the term "phr" referring to parts by weight per hundred parts by weight of the total elastomeric block copolymer.

Claim 9

A process as claimed in claim 7 wherein said polyolefin of step (c) is a high density polyethylene.

Claim 10

A process claimed in claim 7 or 8, wherein said coupling agent in step (a) (iii) is a dihaloethane, a chlorosilane, an alkoxy silane, a diester or carbon dioxide.

Claim 11

Shaped articles containing a thermoplastic composition as claimed in any one of claims 1 to 6.