Plastic elastomer compositions and air bag cover

Abstract

A resin composition for impact-resistant moldings with high low-temperature impact strength, and an air bag cover made of this resin composition are provided. The resin composition, or a thermoplastic elastomer composition for impact-resistant moldings, is produced by a process comprising subjecting 15 to 40% by weight of component (A), 15 to 40% by weight of component (B) and 20 to 70% by weight of component (C) (taking the total of the components (A), (B) and (C) as 100% by weigh) to a dynamic heat treatment in the presence of a crosslinking agent, said components being as specified below:

Description

Claims

1. A thermoplastic elastomer composition obtained by mixing, at least, 15 to 40% by weight of a component (A1), 15 to 40% by weight of a component (B1) and 20 to 70% by weight of a component (C) (taking the total of the components (A1), (B1) and (C) as 100% by weight), said components being as specified below: (A1): an ethylene-α-olefin-non-conjugated diene copolymer rubber having a density of 850 to 900 kg/m3, a Mooney viscosity (ML1+4(100° C.)) of 30 to 150, an iodine value of 0.1 to 40, and an ethylene unit content of 30 to 90% by weight;(B1): an ethylene-α-olefin-non-conjugated diene copolymer rubber having a density of 850 to 900 kg/m3, a Mooney viscosity (ML1+4(100° C.)) of 30 to 150, an iodine value of 0.1 to 40, and an ethylene unit content which is 0.50 to 0.95 time that of the component (A1);(C): a polypropylene resin.

2. A thermoplastic elastomer composition obtained by mixing, at least, 15 to 40% by weight of a component (A2), 15 to 40% by weight of a component (B2) and 20 to 70% by weight of a component (C) (taking the total of the components (A2), (B2) and (C) as 100% by weight), said components being as specified below: (A2): an ethylene-α-olefin-non-conjugated diene copolymer rubber having a density of 850 to 900 kg/m3, a Mooney viscosity (ML1+4(100° C.)) of 30 to 150, an ethylene unit content of 30 to 90% by weight, and an iodine value of 0.1 to 40;(B2): an ethylene-α-olefin-non-conjugated diene copolymer rubber having a density of 850 to 900 kg/m3, a Mooney viscosity (ML1+4(100° C.)) of 30 to 150, an ethylene unit content of 30 to 90% by weight, and an iodine value which is 0.25 to 0.95 time that of the component (A2);(C): a polypropylene resin.

3. A thermoplastic elastomer composition according to claim 1 wherein the ethylene-α-olefin-non-conjugated diene copolymer rubbers of the components (A1), (A2), (B1) and (B2) are an oil-extended ethylene-α-olefin-non-conjugated diene copolymer rubber having an ethylene unit content of 40 to 80% by weight, an iodine value of 1 to 30, and an oil extension rate of 20 to 120 phr.

4. A thermoplastic elastomer composition according to claim 1 obtained by subjecting the component materials to a dynamic heat treatment in the presence of a crosslinking agent.

5. A thermoplastic elastomer composition according to claim 4 wherein the dynamic heat treatment is carried out in the presence of an organic peroxide or in the presence of an organic peroxide and a crosslinking assistant.

6. An air bag cover obtained by molding a thermoplastic elastomer composition set forth in claim 1.

7. A method of producing a thermoplastic elastomer composition of claim 1, which comprises the steps of: using two polymerization reactors connected in series or parallel to each other;forming the component (A1) in one of said polymerization reactors while forming the component (B1) in the other polymerization reactor;forming a mixed solution of the components (A1) and (B1) being mixed in a solvent; thenremoving the solvent from said mixed solution to obtain a mixture of the components (A1) and (B1); andcompounding and kneading the component (C) in this mixture so that the content of the component (A1) will become 15 to 40% by weight, the content of the component (B1) 15 to 40% by weight and the content of the component (C) 20 to 70% by weight.

8. A method of producing a thermoplastic elastomer composition of claim 2, which comprises the steps of: using two polymerization reactors connected in series or parallel to each other;forming the component (A2) in one of said polymerization reactors while forming the component (B2) in the other polymerization reactor;forming a mixed solution of the components (A2) and (B2) being mixed in a solvent; thenremoving the solvent from said mixed solution to obtain a mixture of the components (A2) and (B2); andcompounding and kneading the component (C) in this mixture so that the content of the component (A2) will become 15 to 40% by weight, the content of the component (B2) 15 to 40% by weight and the content of the component (C) 20 to 70% by weight.