Thermoplastic vulcanizates comprising broad molecular weight distribution polypropylene
Provided herein are thermoplastic vulcanizates that comprise rubber, broad molecular weight distribution polypropylene, and oil, where the rubber forms a rubber phase that is dispersed and at least partially cross-linked within a continuous thermoplastic component that comprises the broad molecular weight distribution polypropylene. The broad molecular weight distribution polypropylene preferably has a molecular weight distribution (Mw/Mn) of greater than 4; a melt flow rate of greater than 1 g/10 min; and a weight average molecular weight (Mw) of greater than 380,000 daltons.
1. A thermoplastic vulcanizate comprising:
(i) a rubber comprising an ethylene-propylene diene rubber and 5-ethylidene-2-norbornene ENB diene content;
(ii) a broad molecular weight distribution polypropylene, where the broad molecular weight distribution polypropylene has:
(a) a molecular weight distribution (Mw/Mn) from 5 to 10;
(b) a melt flow rate (ASTM D1238 Condition L at 230° C. and 2.16 kg) of greater than 1 g/10 min; and
(c) a weight average molecular weight (Mw) of greater than 380,000 daltons; and
(iii) a hydrocarbon oil in the amount of 5 to 300 phr;
wherein the thermoplastic vulcanizate has an ultimate elongation (ASTM D638) of greater than 400%; wherein the thermoplastic vulcanizate has a Shore A hardness of greater than 50; wherein the thermoplastic vulcanizate comprises a rubber phase that is dispersed and at least partially cross-linked within a continuous thermoplastic component that comprises the broad molecular weight distribution polypropylene, wherein the thermoplastic vulcanizate further comprises a propylene-based elastomer comprising propylene and from about 5 to about 30 wt % of one or more comonomers selected from ethylene and/or C 4 -C 12 α-olefins, and wherein the propylene-based elastomer is a propylene-ethylene copolymer that has from about 9 wt % to about 15 wt % ethylene-derived units and has: (i) a melt index of from about 0.5 to about 3.0 g/10 min; (ii) a melt flow rate of from about 0.5 to about 7.0 g/10 min; and (iii) a Mooney viscosity of from about 10 to about 40.
2. The thermoplastic vulcanizate of claim 1 , wherein the thermoplastic vulcanizate comprises from about 7 wt % to about 45 wt % of the rubber, based on the total weight of the thermoplastic vulcanizate.
3. The thermoplastic vulcanizate of claim 1 , wherein the thermoplastic vulcanizate comprises from about 3 wt % to about 60 wt % of the broad molecular weight distribution polypropylene, based on the total weight of the thermoplastic vulcanizate.
4. The thermoplastic vulcanizate of claim 1 , wherein the broad molecular weight distribution polypropylene has a melt strength of at least 20 cN determined using an extensional rheometer at 190° C.
5. The thermoplastic vulcanizate of claim 1 , wherein the broad molecular weight distribution polypropylene has a molecular weight distribution greater than 5.
6. The thermoplastic vulcanizate of claim 1 , wherein the broad molecular weight distribution polypropylene has a viscosity ratio of greater than or equal to 17 as determined at an angular frequency ratio of 0.1 and at an angular frequency ratio of 100 rad/s (at an angular frequency ratio of 0.1 to 100 rad/s) at a fixed strain of 10% at 190° C.
7. The thermoplastic vulcanizate of claim 1 , wherein the broad molecular weight distribution polypropylene has a melt flow rate greater than 2 g/10 min.
8. The thermoplastic vulcanizate of claim 1 , wherein the broad molecular weight distribution polypropylene has a high load MFR (ASTM D1338 at 230° C.; 21.6 kg) of greater than 150 g/10 min.
9. The thermoplastic vulcanizate of claim 1 , wherein the broad molecular weight distribution polypropylene has a zero shear viscosity of greater than 28,000 Pa·s.
10. The thermoplastic vulcanizate of claim 1 , wherein the broad molecular weight distribution polypropylene has a number average molecular weight (Mn) of greater than 55,000 daltons.
11. The thermoplastic vulcanizate of claim 1 , wherein the broad molecular weight distribution polypropylene has a weight average molecular weight (Mw) of greater than 400,000 daltons.
12. The thermoplastic vulcanizate of claim 1 , wherein the broad molecular weight distribution polypropylene has a z-average molecular weight (Mz) of greater than 1,000,000.
13. The thermoplastic vulcanizate of claim 1 , wherein the broad molecular weight distribution polypropylene is made by a process that comprises contacting propylene monomers at a temperature and a pressure in the presence of catalyst system to produce a propylene resin comprising at least 50 mol % propylene, wherein the catalyst system comprises:
a Ziegler-Natta catalyst comprising a non-aromatic internal electron donor;
a first external electron donor having the formula R 1 2 Si(OR 2 ) 2 , wherein each R 1 is independently a hydrocarbyl radical comprising from 1 to 10 carbon atoms in which the carbon adjacent to the Si is a secondary or a tertiary carbon atom, and wherein each R 2 is independently a hydrocarbyl radical comprising from 1 to 10 carbon atoms; and
a second external electron donor having the formula R 3 n Si(OR 4 ) 4-n , wherein each R 3 and R 4 are independently a hydrocarbyl radical comprising from 1 to 10 carbon atoms, and n is 1, 2, or 3; and
where the second external electron donor is different than the first external electron donor.
14. The thermoplastic vulcanizate of claim 1 , wherein the thermoplastic vulcanizate comprises from about 10 wt % to about 55 wt % oil, based on the total weight of the thermoplastic vulcanizate.
15. A thermoplastic vulcanizate comprising a rubber phase dispersed and at least partially cross-linked in a continuous thermoplastic phase, the thermoplastic vulcanizate having:
(a) an ultimate elongation (ASTM D638) of greater than 400%;
(b) a Shore A hardness of greater than 50; and
(c) an ultimate tensile strength (ASTM D638) of greater than 7 MPa;
wherein the rubber phase comprises an ethylene-propylene diene rubber that has about 64 wt % ethylene content (as measured by ASTM D3900) and 4.5 wt % 5-ethylidene-2-norbomene ENB diene content (as measured by ASTM D6047) and the thermoplastic phase comprises a broad molecular weight distribution polypropylene having:
(i) a molecular weight distribution (Mw/Mn) from 5 to 10;
(ii) a melt flow rate (ASTM D1238 Condition L at 230° C. and 2.16 kg) of greater than 2 g/10 min; and
(iii) a weight average molecular weight (Mw) of greater than 410,000 daltons.
16. The thermoplastic vulcanizate of claim 15 , wherein the thermoplastic vulcanizate comprises from about 7 wt % to about 45 wt % of the rubber phase, based on the total weight of the thermoplastic vulcanizate.
17. The thermoplastic vulcanizate of claim 15 , wherein the thermoplastic vulcanizate comprises from about 3 wt % to about 60 wt % of the broad molecular weight distribution polypropylene, based on the total weight of the thermoplastic vulcanizate.
18. The thermoplastic vulcanizate of claim 15 , wherein the broad molecular weight distribution polypropylene has a melt strength of at least 20 cN determined using an extensional rheometer at 190° C.
19. The thermoplastic vulcanizate of claim 15 , wherein the broad molecular weight distribution polypropylene has a viscosity ratio of greater than or equal to 17 as determined at an angular frequency ratio of 0.1 and at an angular frequency ratio of 100 rad/s (at an angular frequency ratio of 0.1 to 100 rad/s) at a fixed strain of 10% at 190° C.
20. The thermoplastic vulcanizate of claim 15 , wherein the broad molecular weight distribution polypropylene has a zero shear viscosity of greater than 28,000 Pa·s.