Thermoplastic elastomers having improved low temperature properties
The present invention provides a thermoplastic vulcanizate prepared by a process comprising the steps of dynamically vulcanizing rubber within a blend that includes the rubber and a thermoplastic resin, where the rubber comprises an elastomeric copolymer of ethylene, at least one α-olefin, and optionally one or more diene monomers, where the elastomeric copolymer is characterized by having a crystallinity, as measured by differential scanning calorimetry, of less than 10 J/g, an ethylene content that is less than 90 mole percent based upon the entire copolymer, a weight average molecular weight that is greater than about 20,000 as measured by GPC with polystyrene standards, a molecular weight distribution that is less than 7, and an ethylene compositional distribution that is less than about 4 percent for the closest 90 percent of fractioned samples.
1. A thermoplastic vulcanizate comprising a blend of cured rubber, said cured having a degree of cure where not more than 5 percent of said cured rubber is extractable in boiling xylene or cyclohexane and thermoplastic resin, where said rubber comprises an elastomeric copolymer of ethylene, at least one α-olefin, and optionally one or more diene monomers, where said elastomeric copolymer is characterized by having a crystallinity, as measured by differential scanning calorimetry, of less than 3 J/g, an ethylene content that is less than 70 mole percent based upon the entire copolymer, a weight average molecular weight that is greater than about 40,000 as measured by GPC with polystyrene standards, a molecular weight distribution that is less than 7, and an ethylene compositional distribution that is less than about 4 percent for the closest 90 percent of fractioned samples.
2. The thermoplastic vulcanizate of claim 1 , where said blend further comprises an extender oil including a petroleum processing oil, a synthetic oil, a plasticizer, an organic ester, an alkyl ether ester, or combinations of two or more thereof.
3. The thermoplastic vulcanizate of claim 1 , where said elastomeric copolymer is a terpolymer/tetrapolymer of ethylene, propylene, and 5-ethylidene-2-norbornene and/or 5-vinyl-2-norbornene, and where said thermoplastic resin comprises polypropylene.
4. The thermoplastic vulcanizate of claim 1 , said elastomeric copolymer is characterized by having a Mooney viscosity (ML 1+4 @ 125° C.) of from about 50 to about 150, and an ethylene compositional distribution that is less than about 3 percent for the closest 90 percent of fractioned samples.
5. The thermoplastic vulcanizate of claim 4 , where said elastomeric copolymer is characterized by having a crystallinity of less than 0.2 J/g, an ethylene content that is less than 60 mole percent based upon the entire copolymer, a weight average molecular weight that is greater than about 100,000, and an ethylene compositional distribution that is less than about 2 percent for the closest 90 percent of fractioned samples.
6. The thermoplastic vulcanizate of claim 5 , where said elastomeric copolymer is characterized by having a crystallinity of less than 0.1 J/g, an ethylene content that is less than 50 mole percent based upon the entire copolymer, a weight average molecular weight that is greater than about 250,000, a Mooney viscosity (ML 1+4 @ 125° C.) of from greater than 80 to about 90, and an ethylene compositional distribution that is less than about 1 percent for the closest 90 percent of fractioned samples.
7. The thermoplastic vulcanizate of claim 6 , where said elastomeric copolymer has a Mooney viscosity (ML 1+4 @ 125° C.) of about 70 to about 100.
8. The thermoplastic vulcanizate of claim 1 , where said blend comprises from about 45 to about 85 percent by weight said cured rubber and from about 15 to about 55 percent by weight thermoplastic resin, based upon the total weight of said cured rubber and said thermoplastic resin combined.
9. A thermoplastic vulcanizate comprising: a blend of cured rubber, and thermoplastic resin, where said rubber comprises an elastomeric copolymer of ethylene, at least one α-olefin, and optionally one or more diene monomers, where said elastomeric copolymer is characterized by having a crystallinity, as measured by differential scanning calorimetry, of less than 3 J/g, an ethylene content that is less than 60 mole percent based upon the entire copolymer, a Mooney viscosity (ML 1+4 @ 125° C.) of about 70 to about 100, a molecular weight distribution that is less than 5, and an ethylene compositional distribution that is less than about 4 percent for the closest 90 percent of fractioned samples.
10. The thermoplastic resin of claim 9 , where said cured rubber has a degree of cure where not more that 5 percent of said cured rubber is extractable in boiling xylene or cyclohexane.
11. The thermoplastic vulcanizate of claim 10 , where said blend further comprises an extender oil including a petroleum processing oil, a synthetic oil, a plasticizer, an organic ester, an alkyl ether ester, or a combination of two or more thereof.
12. The thermoplastic vulcanizate of claim 11 , where said elastomeric copolymer is a terpolymer/tetrapolymer of ethylene, propylene, and 5-ethylidene-2-norbornene and/or 5-vinyl-2-norbornene, and where said thermoplastic resin comprises polypropylene.
13. The thermoplastic vulcanizate of claim 12 , where said blend comprises from about 45 to about 85 percent by weight said cured rubber and from about 15 to about 55 percent by weight thermoplastic resin, based upon the total weight of said cured rubber and said thermoplastic resin combined.