Soft thermoplastic vulcanizate compositions
Disclosed herein are low Shore A Hardness thermoplastic vulcanizate compositions having high Rebound values. In at least one exemplary embodiment, the compositions include a dispersed at least partially vulcanized rubber component; a thermoplastic component; and process oil; wherein the weight ratio of the thermoplastic component to the rubber component ranges from 80:20 to 15:85; and the thermoplastic component comprises more than 80 wt % of a polypropylene (preferably a random propylene copolymer) having a melting point less than about 105° C. The compositions can be used in molded products, consumer goods and the like.
1. A thermoplastic vulcanizate composition, comprising:
a) a dispersed at least partially vulcanized rubber component;
b) a thermoplastic component that includes polypropylene having a melting point greater than 110° C. and a random propylene copolymer having a melting point ranging from 25° C. to 105° C.; and
c) additive oil; wherein:
(i) the weight ratio of the thermoplastic component to the rubber component ranges from 80:20 to 15:85;
(ii) the weight ratio of the random propylene copolymer to the polypropylene is greater than 100:100; and
(iii) the Rebound of the composition is greater than 55%.
2. A thermoplastic vulcanizate composition, comprising:
a) a dispersed at least partially vulcanized rubber component;
b) a thermoplastic component that includes polypropylene having a melting point greater than 110° C. and a polypropylene having a melting point ranging from 25° C. to 105° C.; and
c) additive oil; wherein:
(i) the weight ratio of the thermoplastic component to the rubber component ranges from 80:20 to 15:85;
(ii) the weight ratio of the polypropylene having a melting point ranging from 25° C. to 105° C. to the polypropylene having a melting point greater than 110° C. is greater than 100:100; and
the Rebound of the composition is greater than 55%.
3. The thermoplastic vulcanizate composition of claims 1 or 2 , wherein the thermoplastic component comprises more than 80 wt % of a random propylene copolymer having a melting point of from 25° C. to 105° C.
4. The thermoplastic vulcanizate composition of claims 1 or 2 , wherein the Shore A Hardness of the composition is 45 or less.
5. The composition of claim 1 in which the polypropylene is isotactic polypropylene.
6. The composition of claim 1 in which the polypropylene is syndiotactic polypropylene.
7. The composition of claim 1 in which the polypropylene is atactic polypropylene.
8. The composition of claim 1 in which the random propylene copolymer has a comonomer content of from 10 wt % to 25 wt %.
9. The composition of claim 1 in which the random propylene copolymer has a comonomer content greater than 10 wt %.
10. The composition of claim 1 in which the random propylene copolymer has a comonomer content greater than 12 wt %.
11. The composition of claim 1 in which the random propylene copolymer has a comonomer content greater than 15 wt %.
12. The composition of claims 1 or 2 in which the composition has a tensile strength of from 0.5 to 15 MPa.
13. The composition of claims 1 or 2 in which the composition has a tensile strength of from 2 to 7 MPa.
14. The composition of claims 1 or 2 in which the composition has a Shore A Hardness of 40 or less.
15. The composition of claims 1 or 2 in which the composition has a Shore A Hardness of 35 or less.
16. The composition of claims 1 or 2 in which the composition has a Rebound of 60% or more.
17. The composition of claims 1 or 2 in which the composition has a Rebound of 65% or more.
18. The composition of claims 1 or 2 in which the composition has a Rebound of 70% or more.
19. The composition of claim 1 in which the random propylene copolymer occupies more than 90 wt % of the thermoplastic component.
20. The composition of claim 1 in which the random propylene copolymer occupies more than 95 wt % of the thermoplastic component.
21. The composition of claim 1 in which the thermoplastic component additionally includes isotactic polypropylene having a melting point greater than 110° C.
22. The composition of claims 1 or 2 in which the thermoplastic component further includes an additional polypropylene polymer.
23. The composition of claims 1 or 2 in which the thermoplastic component further includes a polypropylene having a melt flow rate of from 10 to 30 g/10 min.
24. The composition of claims 1 or 2 in which the thermoplastic component further includes a polypropylene having a melt flow of less than 1.0 g/10 min.
25. The composition of claims 1 or 2 in which the thermoplastic component further includes a first polypropylene having a melt flow ranging from 10 to 30 g/10 min and a second polypropylene having a melt flow of less than 1.0 g/10 min.
26. The composition of claim 1 in which the random propylene copolymer consists essentially of from about 80 to about 95 weight percent repeat units from propylene and from about 5 to about 20 weight percent of repeat units from one or more unsaturated olefin monomers having 2 or 4 to 12 carbon atoms.
27. The composition of claim 1 in which the random propylene copolymer is prepared using a metallocene catalyst system.
28. The composition of claim 1 in which the random propylene copolymer has a heat of fusion of less than 75 joules/gram.
29. The composition of claim 1 in which the rubber component is selected from the group consisting of ethylene-propylene-diene rubber, natural rubber, butyl rubber, halobutyl rubber, halogenated rubber copolymer of p-alkystyrene and at least one isomonoolefin having 4 to 7 carbon atoms, a copolymer of isobutylene and divinyl-benzene, a rubber homopolymer of a conjugated diene having from 4 to 8 carbon atoms, a rubber copolymer having at least 50 weight percent repeat units from at least one conjugated diene having from 4 to 8 carbon atoms and a vinyl aromatic monomer having from 8 to 12 carbon atoms, or acrylonitrile monomer, or an alkyl substituted acrylonitrile monomer having from 3 to 8 carbon atoms, or an unsaturated carboxylic acid monomer, or an unsaturated anhydride of a dicarboxylic acid, and combinations thereon.
30. The composition of claim 1 in which the random propylene copolymer has a melting point ranging from 40° C. to 50° C.
31. The composition of claims 1 or 2 in which the rubber component is ethylene-propylene-diene rubber.
32. The composition of claims 1 or 2 in which the rubber component is butyl rubber, halobutyl rubber, or a halogenated rubber copolymer of p-alkylstyrene and isobutylene or a combination thereof.
33. The composition of claims 1 or 2 in which the rubber component is a rubber homopolymer of a conjugated diene having from 4 to 8 carbon atoms, a rubber copolymer having at least 50 weight percent repeat units from at least one conjugated diene having from 4 to 8 carbon atoms, or combinations thereof.