Thermoplastic polyurethane silicone elastomers
The invention relates to thermoplastic elastomer compositions comprising a blend of a thermoplastic urethane polymer and a silicone composition, and to a process for forming a vulcanized thermoplastic elastomer composition. The thermoplastic elastomer composition comprises a blend of a thermoplastic organic polymer comprising a urethane polymer and (B) a silicone composition comprising (B1) a silicone base comprising (B1a) a diorganopolysiloxane gum having an average of at least 2 alkenyl groups per molecule and (B1b) from 1 to 50% by weight based on the diorganopolysiloxane gum (B1a) of a reinforcing filler, and (B2) an organohydrido silicone compound which contains an average of at least 2 silicon-bonded hydrogen groups per molecule, wherein the weight ratio of the thermoplastic organic polymer (A) to the silicone composition (B) is in the range 55:45 to 80:20.
1. A thermoplastic elastomer composition comprising a blend of:
(A) a thermoplastic organic polymer comprising a urethane polymer; and
(B) a silicone composition comprising:
(B1) a silicone base comprising;
(B1a) a diorganopolysiloxane gum having an average of at least 2 alkenyl groups per molecule, and
(B1b) from 1 to 50% by weight based on the diorganopolysiloxane gum (B1a) of a reinforcing filler; and
(B2) an organohydrido silicone compound which contains an average of at least 2 silicon-bonded hydrogen groups per molecule;
wherein the weight ratio of the thermoplastic organic polymer (A) to the silicone composition (B) is in the range of from 55:45 to 80:20.
2. The thermoplastic elastomer composition according to claim 1 , wherein the reinforcing filler (B1b) is silica.
3. The thermoplastic elastomer composition according to claim 2 , wherein the silica reinforcing filler (B1b) is present at from 2 to 10% by weight based on the diorganopolysiloxane gum (B1a) and the weight ratio of the thermoplastic urethane polymer (A) to the silicone composition (B) is in the range of 55:45 to 65:35.
4. The thermoplastic elastomer composition according to claim 2 , wherein the silica reinforcing filler (B1b) is present at from 6 to 20% by weight based on the diorganopolysiloxane gum (B1a) and the weight ratio of the thermoplastic urethane polymer (A) to the silicone composition (B) is in the range of 65:35 to 80:20.
5. The thermoplastic elastomer composition according to claim 1 , wherein the thermoplastic organic polymer (A) comprises 50 to 100% by weight thermoplastic polyurethane, 0 to 50% by weight of a styrene-based non-crosslinked elastomer, and 0 to 20% of an acrylic styrene copolymer.
6. The thermoplastic elastomer composition according to claim 1 , further comprising (C) a hydrosilylation catalyst.
7. A process for forming a vulcanised thermoplastic elastomer comprising vulcanizing the thermoplastic elastomer composition of claim 6 to obtain the vulcanized thermoplastic elastomer.
8. The process according to claim 7 , wherein the thermoplastic organic polymer (A), the silicone base (B1), the organohydrido silicone compound (B2) and the hydrosilylation catalyst (C) are contacted at a temperature in the range of 100° C. to 250° C.
9. The process according to claim 7 , wherein the thermoplastic organic polymer (A), the silicone base (B1), the organohydrido silicone compound (B2) and the hydrosilylation catalyst (C) are blended in an extruder.