Compatibilized Thermoplastic Vulcanizate Compositions

• US 20190309151A1
• Filed: 03/18/2019
• Published: 10/10/2019
• Est. Priority Date: 04/06/2018
• Status: Active Grant

• Current Assignee: Celanese International Corporation (Celanese Corporation)
• Original Assignee: ExxonMobil Chemical Patents Inc. (Exxon Mobil Corporation)
• Inventors: Datta, Sudhin, Tsou, Andy H., Walker, Ron, Passino, Hillary L.
• Granted Patent: US 11,142,605 B2
• Time in Patent Office: Days
• CPC Class Codes: C08F 210/02 Ethene
• CPC Class Codes: C08F 210/06 Propene
• CPC Class Codes: C08F 210/18 with non-conjugated dienes, e.g. EPT rubbers
• CPC Class Codes: C08F 236/045 conjugated hydrocarbons other than butadiene or isoprene
• CPC Class Codes: C08F 236/20 unconjugated
• CPC Class Codes: C08F 2500/03 Narrow molecular weight distribution, i.e. Mw/Mn < 3
• CPC Class Codes: C08F 2500/12 Melt flow index or melt flow ratio
• CPC Class Codes: C08F 2500/17 Viscosity
• CPC Class Codes: C08F 2500/21 Rubbery or elastomeric properties
• CPC Class Codes: C08F 2500/24 Polymer with special particle form or size
• CPC Class Codes: C08F 2500/27 Amount of comonomer in wt% or mol%
• CPC Class Codes: C08F 4/65908 in combination with an ionising compound other than alumoxane, e.g. (C6F5)4B-X+
• CPC Class Codes: C08F 4/65927 two cyclopentadienyl rings being mutually bridged
• CPC Class Codes: C08J 2323/16 Ethene-propene or ethene-propene-diene copolymers
• CPC Class Codes: C08J 2423/12 Polypropene
• CPC Class Codes: C08J 3/005 Processes for mixing polymers
• CPC Class Codes: C08J 3/212 and solid additives
• CPC Class Codes: C08J 3/24 Crosslinking, e.g. vulcanising, of macromolecules mechanical aspects B29C35/00; crosslinking agents C08K
• CPC Class Codes: C08K 5/0025 Crosslinking or vulcanising agents; including accelerators
• CPC Class Codes: C08L 2205/025 containing two or more polymers of the same hierarchy C08L, and differing only in parameters such as density, comonomer content, molecular weight, structure
• CPC Class Codes: C08L 2205/03 : containing three or more polymers in a blend
• CPC Class Codes: C08L 2205/08 : containing additives to improve the compatibility between two polymers
• CPC Class Codes: C08L 2205/22 : Mixtures comprising a continuous polymer matrix in which are dispersed crosslinked particles of another polymer
• CPC Class Codes: C08L 2207/02 : Heterophasic composition
• CPC Class Codes: C08L 2207/10 : Peculiar tacticity
• CPC Class Codes: C08L 23/12 : Polypropene
• CPC Class Codes: C08L 23/142 : at least partially crystalline copolymers of propene with other olefins
• CPC Class Codes: C08L 23/16 : Elastomeric ethene-propene or ethene-propene-diene copolymers, e.g. EPR and EPDM rubbers
• CPC Class Codes: C08L 2312/00 : Crosslinking
• CPC Class Codes: C08L 2312/02 : with dienes

Abstract

Disclosed is the preparation of compatibilized thermoplastic vulcanizates with reduced crosslinked rubber dispersion sizes and dispersity. A cross-linkable ethylene-propylene-diene terpolymer with majority propylene (PEDM) is used to compatibilize a plastic and rubber blend of a polypropylene (PP) and an ethylene-propylene-diene terpolymer rubber, where the propylene content is less than 50 wt % (EPDM), in dynamic vulcanization and preparation of PP/EPDM thermoplastic vulcanizates. The resulting PP/EPDM thermoplastic vulcanizates typically exhibit a weight average equivalent dispersion diameter of less than 3 microns and a particle size polydispersity index (PSDI), or weight average over number average dispersion diameter, of less than 5. This reduction in crosslinked rubber dispersion size in a PP/EPDM TPV by using PEDM compatibilizers enhances the toughness of the vulcanizate product by raising both elongation to break and break stress.

Claims

1. A thermoplastic vulcanizate comprising an isotactic polypropylene matrix phase in which a cross-linked ethylene-propylene-diene terpolymer (EPDM) is dispersed, the vulcanizate comprising the reaction product of:

a) 35 to 55 wt % of an ethylene-propylene-diene terpolymer (EPDM);

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

c) 10 to 25 wt % of a diluent;

d) 0.5 to 15 wt % of a propylene-ethylene-diene terpolymer (PEDM) compatibilizer; and

e) 0.015 to 0.03 wt % of curatives;

each weight percent is by weight of the combined components.

2. The thermoplastic vulcanizate of claim 1, in which the EPDM comprises 55 to 75 wt % ethylene, 2 to 10 wt % ethylene norbornene.

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

4. The thermoplastic vulcanizate of claim 1, in which the MFR₂ 16 at 230°

C. of the PEDM is from 0.5 to 20 g/10 min.

5. The thermoplastic vulcanizate of claim 1, in which the PEDM comprises 5 to 20 wt % ethylene and 2 to 15 wt % ethylene norbornene.

6. The vulcanized rubber dispersions in the thermoplastic vulcanizate of claim 1 that has a particle size dispersity index (PSDI) of rubber particle size distribution less than 3.

7. A method for preparing a thermoplastic vulcanizate (TPV) comprising:

i) mixing an iPP, EPDM, and PEDM, and a diluent to prepare a TPV formulation;

ii) adding a diluent to the TPV formulation and continuing mixing;

iii) adding one or more curatives to the TPV formulation and continuing mixing to perform dynamic vulcanization;

iv) adding a further portion of diluent and continuing mixing and dynamic vulcanization to form a TPV composition; and

v) recovering the TPV composition.

8. The method of claim 7, in which the curatives are a resin in oil (RIO) composition, stannous chloride and zinc oxide and the RIO composition is added first, followed by additional mixing, then the stannous chloride and zinc oxide are added.

9. The method of claim 7, in which the ethylene-propylene-diene terpolymer (EPDM) is added in an amount from 35-55 wt % of the TPV formulation, the isotactic polypropylene (iPP) is added in an amount from 20 to 30 wt % of the TPV formulation;

diluent is added in an amount from 13 to 21 wt % of the TPV formulation, a propylene-ethylene-diene terpolymer (PEDM) compatibilizer is added in an amount from 0.5-15 wt % of the TPV formulation.

10. The method of claim 7 that is performed at a temperature of from 150 to 200°

C. in a batch internal mixer running at from 80 to 120 rpm and mixing continues for about 1 minute between i) and ii), for about 2 minutes between ii) and iii), for about 5 minutes between iii) and iv) and for about 3 minutes after v).

11. The method of claim 7 is performed at a temperature from 200 to 250°

C. in a continuous twin-screw extruder running at from 50 to 200 RPM with 1 to 5 minutes of residence time wherein the iPP, EPDM, and PEDM, and first portion of a diluent are added to the extruder at a first position of the extruder, and at least one of the second portion of diluent, the curatives and the third portion of diluent are added to the extruder at least a second position downstream from the first position.

12. The method of claim 8, that is performed at a temperature of from 150 to 200°

C. in an internal mixer running at from 80 to 120 rpm and mixing continues for about 1 minute between i) and ii), for about 2 minutes between ii) and iii), for about 5 minutes between iii) and iv) and for about 3 minutes after v); and

the mixing is performed for about 1 minute between addition of the RIO composition and addition of the stannous chloride and the zinc oxide.

13. The method of claim 8, that is performed at a temperature from 200 to 250°

C. in a continuous twin-screw extruder running at from 50 to 200 RPM with 1 to 5 minutes of residence time; and

in which the RIO composition is added to the extruder at a first position, followed by additional mixing, then the stannous chloride and zinc oxide are added to the extruder at a second, downstream position.

14. A TPV composition made by a method comprising:

i) mixing an iPP, EPDM, and PEDM, and a diluent to prepare a TPV formulation;

ii) adding a diluent to the TPV formulation and continuing mixing;

iii) adding one or more curatives to the TPV formulation and continuing mixing to perform dynamic vulcanization;

iv) adding a further portion of diluent and continuing mixing and dynamic vulcanization to form a TPV composition; and

v) recovering the TPV composition;

in which the ethylene-propylene-diene terpolymer (EPDM) is added in an amount from 35 to 55 wt % of the TPV formulation, the isotactic polypropylene (iPP) is added in an amount from 20 to 30 wt % of the TPV formulation;

diluent is added in an amount from 13 to 21 wt % of the TPV formulation, and a propylene-ethylene-diene terpolymer (PEDM) compatibilizer is added in an amount from 0.5-15 wt % of the TPV formulation.

15. The TPV composition of claim 14, in which the addition and mixing steps are performed at a temperature of from 150 to 200°

C. in an internal mixer running at from 80 to 120 rpm and mixing continues for about 1 minute between i) and ii), for about 2 minutes between ii) and iii), for about 5 minutes between iii) and iv) and for about 3 minutes after v); and

the mixing is performed for about 1 minute between addition of the RIO composition and addition of the stannous chloride and the zinc oxide.

16. The method of claim 14 that is performed at a temperature from 200 to 250°

C. in a continuous twin-screw extruder running at from 50 to 200 RPM with 1 to 5 minutes of residence time; and

in which the RIO composition is added at a first position, followed by additional mixing, then the stannous chloride and zinc oxide are added to the extruder at a second, downstream position.