Thermoplastic vulcanizate compositions

1. A thermoplastic vulcanizate comprising an isotactic polypropylene matrix phase in which cross-linked rubber particles are dispersed, the thermoplastic vulcanizate comprising the reaction product of a mixture comprising:

(a) at least 10 wt % of isotactic polypropylene;

(b) at least 25 wt % of an ethylene-propylene-diene terpolymer (EPDM) containing at least 40 wt % of ethylene-derived units;

(c) at least 0.5 wt % of a propylene-ethylene-diene terpolymer (PEDM) containing at least 60 wt % propylene-derived units and less than or equal to 25 wt % of ethylene-derived units and having a heat of fusion (H f ) of 2 to 10 J/g; and

(d) at least 0.015 wt % of at least one curative,

wherein the percentages of components (a) to (d) are based on the total weight of the mixture.

2. The thermoplastic vulcanizate of claim 1 , wherein the PEDM comprises 5 to 18 wt % of ethylene-derived units.

3. The thermoplastic vulcanizate of claim 1 , wherein the PEDM comprises 0.3 to 10 wt % of diene-derived units; where the diene is selected from the group consisting of 5-ethylidene-2-norbornene, 5-vinyl-2-norbornene, divinyl benzene, and dicyclopentadiene.

4. The thermoplastic vulcanizate of claim 1 , wherein the PEDM has a Mooney viscosity of MST (5+4) at 230° C. from 10 to 90.

5. The thermoplastic vulcanizate of claim 1 , in which the amount of PEDM is from 2 to 30 wt % of the amount of EPDM.

6. The thermoplastic vulcanizate of claim 1 , wherein the particle size dispersity index (PSDI) of the rubber particles is less than 3.

7. The thermoplastic vulcanizate of claim 1 and further comprising at least 5 wt % of a diluent based on the total weight of the mixture.

8. A thermoplastic vulcanizate comprising an isotactic polypropylene matrix phase in which cross-linked rubber particles are dispersed, the thermoplastic vulcanizate comprising the reaction product of a mixture comprising:

a) 20 to 30 wt % of isotactic polypropylene (iPP);

b) 35 to 55 wt % of an ethylene-propylene-diene terpolymer (EPDM) containing at least 40 wt % of ethylene-derived units;

c) 0.5 to 15 wt % of a propylene-ethylene-diene terpolymer (PEDM) containing at least 60 wt % propylene-derived units and less than or equal to 25 wt % of ethylene-derived units and having a heat of fusion (H f ) of 2 to 10 J/g;

d) 5 to 25 wt % of a diluent; and

e) 0.015 to 0.03 wt % of at least one curative;

wherein the percentages of components (a) to (e) are based on the total weight of the mixture.

9. The thermoplastic vulcanizate of claim 8 , wherein the PEDM comprises 5 to 18 wt % of ethylene-derived units.

10. The thermoplastic vulcanizate of claim 8 , wherein the PEDM comprises 0.3 to 10 wt % of diene-derived units; where the diene is selected from the group consisting of 5-ethylidene-2-norbornene, 5-vinyl-2-norbornene, divinyl benzene, and dicyclopentadiene.

11. The thermoplastic vulcanizate of claim 8 , wherein the PEDM has a Mooney viscosity of MST (5+4) at 230° C. from 10 to 90.

12. The thermoplastic vulcanizate of claim 8 , in which the amount of PEDM is from 2 to 30 wt % of the amount of EPDM.

13. The thermoplastic vulcanizate of claim 8 , wherein the particle size dispersity index (PSDI) of the rubber particles is less than 3.

14. A process for producing a thermoplastic vulcanizate (TPV) comprising:

i) providing a mixture comprising:

(a) at least 10 wt % of isotactic polypropylene;

(b) at least 25 wt % of an ethylene-propylene-diene terpolymer (EPDM) containing at least 50 wt % of ethylene-derived units;

(c) at least 0.5 wt % of a propylene-ethylene-diene terpolymer (PEDM) containing at least 60 wt % propylene-derived units and less than or equal to 25 wt % of ethylene-derived units and having a heat of fusion (H f ) of 2 to 10 J/g;

(d) at least 5 wt % of a diluent; and

(e) at least 0.015 wt % of at least one curative,

wherein the percentages of components (a) to (e) are based on the total weight of the mixture, and

(ii) reacting the mixture under shear and at a temperature above the melting point of the polypropylene to at least partially cross-link the EPDM and PEDM and produce a polypropylene matrix phase in which cross-linked rubber particles are dispersed.

15. The process of claim 14 , wherein the reacting (ii) is performed in a twin-screw extruder.