JP2000034395A - Simultaneously cured rubber-thermoplastic elastomer composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition having a single low-temperature brittle point by including plural functionalized acrylic rubber and a thermoplastic polyester polymer. SOLUTION: This composition comprises (A) a thermoplastic polyester polymer phase and (B) a cross-linked rubber phase comprising (ii) at least two functionalized acrylic rubbers dynamically vulcanized using a curing agent in which (i) at least one rubber is an ethylene-alkyl acrylate-unsaturated carboxylic acid terpolymer. The component A is a polyester, a copolyester, etc., and the amount of the component A is preferably about 5 to about 95 pts.wt. based on 100 pts.wt. of the component (ii). The amount of the component (i) is preferably about 25 - about 75 pts.wt. based on 100 pts.wt. of the component (ii). The composition has preferably at least 80% curing degree. The composition is obtained by mixing at least the two components (ii) in which at least one component is the component (i) with the curing agent and dynamically vulcanizing the component (ii).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a thermoplastic elastomer composition and a method for producing the same.

[0002]

BACKGROUND OF THE INVENTION Thermoplastic elastomers are materials that exhibit both thermoplastic and rubbery elasticity, that is, they can be processed as thermoplastics, but have the same physical properties as elastomers. Moldings can be formed from thermoplastic elastomers by extrusion, injection molding or compression molding without the time-consuming curing steps required with conventional vulcanizates. In addition, thermoplastic elastomers can be reworked without the need for regeneration, and many thermoplastic elastomers can be heat welded.

US Pat. No. 5,300,573 to Patel relates to a thermoplastic elastomer composition comprising a blend of a polyester resin and a single covalently crosslinked acrylic rubber.

[0004]

It is an object of the present invention to provide a thermoplastic elastomer composition having a single low-temperature embrittlement point.

[0005]

SUMMARY OF THE INVENTION The present invention is directed to a thermoplastic elastomer composition made from two or more functionalized acrylic rubbers. Hardeners, which can be used in small or large quantities, generally harden by the formation of conjugated or ionic bonds, and include hardeners with compounds such as various peroxides, magnesium oxide and various epoxidized soybean oils. Is included. The present invention also relates to the dynamic vulcanization of two or more functionalized acrylic rubbers in the presence of a thermoplastic polymer such as an ester polymer. Dynamically vulcanized compositions have a single low temperature embrittlement point.

[0006] The present invention relates to a blend of two or more functionalized acrylic rubber components that are cured in the presence of a curing agent and a thermoplastic ester polymer. The functional groups are the same or different. One of the functionalized acrylic rubbers is
Derived from ethylene, alkyl acrylate and unsaturated carboxylic acid monomers, when cured, the composition has, surprisingly, only a single low temperature embrittlement point. The degree of cure of the two or more acrylic rubbers is generally at least 80%.
When cured, the thermoplastic elastomer composition has a good balance of good low temperature physical properties and low swelling number.

The thermoplastic elastomer composition of the present invention comprises:
Generally, it contains a plastic phase or matrix of a thermoplastic ester polymer that is compatible with two or more functionalized acrylic rubber components.

[0008] Suitable thermoplastic ester polymers include epoxy end-capped derivatives and mixtures thereof, such as polyesters, copolyesters, polyester block copolymers or polycarbonates. The various polyesters are aromatic or aliphatic or a combination thereof and generally include diols such as glycols having a total of from 2 to 12 carbon atoms, desirably from about 2 to about 4 carbon atoms. Direct or indirect from reaction with aliphatic acids having a total of from 2 to 20 carbon atoms, preferably from about 3 to about 15 carbon atoms, or aromatic acids having a total of from about 8 to about 15 carbon atoms It is guided to. Generally, aromatic polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene isophthalate, polynaphthalene phthalate, and the like, and their end-capped epoxy derivatives, for example, monofunctional epoxy polybutylene terephthalate, are preferred. Various polycarbonates are also used, which are esters of carboxylic acids. Suitable polycarbonates are compounds based on bisphenol A, ie poly (carbonyldioxy-1,4-phenyleneisopropylidene-1,4-phenylene). Various ester polymers also include at least one block of polyester,
Block polyesters such as compounds containing at least one rubbery block, such as glycols having 2 to 6 carbon atoms such as polyethylene glycol or polyethers derived from alkylene oxides having 2 to 6 carbon atoms. Is included. Preferred block polyesters are DuPont to Hytr
el) Polybutylene terephthalate-block-polyethylene glycol available as

[0009] The amount of one or more thermoplastic ester polymers is generally from about 5 to about 95 parts by weight, preferably from about 15 to about 95 parts by weight, based on 100 parts by weight of all two or more functionalized acrylic rubbers. 60 parts by weight, and preferably about 20 to about 40
Parts by weight.

[0010] The at least two functionalized acrylic rubber components are generally compatible with each other and with the thermoplastic ester polymer. Nitrile groups, such as acrylonitrile-containing rubbers such as nitrile rubber, are either excluded from the compositions of the present invention or are substantially not included in the compositions of the present invention (ie, 5 to 100 parts by weight of total acrylic rubber). Less than 3% by weight, less than 1% by weight
Less and desirably 0% by weight). The two or more functionalized acrylic rubber components can be derived from alkyl acrylates in which the alkyl moiety has 1 to 10 carbon atoms, preferably 1 to 3 carbon atoms. Particular examples include polymers such as ethyl acrylate, butyl acrylate, ethyl-hexyl acrylate, and the like. Other suitable acrylic rubbers include copolymers of ethylene and the above-described alkyl acrylates, and the amount of ethylene is desirably large, such as ethylene in the copolymer, to produce a rubber having polar and non-polar portions. And about 10 to about 90, based on the total moles of
Mol%, desirably about 30 to about 70 mol%, and preferably about 40 to about 60 mol%.

The two or more acrylic rubbers have functional groups that can be acids, ie, carboxyl groups, epoxy groups, hydroxyl groups, and the like. The two or more acrylic rubbers can have different functional groups, or
They can have the same functional groups. Such functionalized acrylic rubber components are formed by using various comonomers during the polymerization of the acrylic polymer described above. Suitable comonomers for adding hydroxyl groups include unsaturated alcohols having about 2 to about 20, preferably 2 to about 10 carbon atoms. A specific example of a hydroxy-functionalized acrylic rubber is Hytemp 4404, commercially available from Zeon Corporation. Suitable comonomers for adding pendant epoxy groups include:
Unsaturated oxiranes, such as oxirane acrylates, where the oxirane group has about 3 to about 10 carbon atoms and the ester group of the acrylate is an alkyl having 1 to 10 carbon atoms, include glycidyl. Acrylate. Another group of unsaturated oxiranes are the various oxirane alkenyl ethers, where the oxirane group also has about 3 to about 10 carbon atoms and the alkenyl group has about 3 to about 10 carbon atoms, with specific examples Is allyl glycidyl ether. Examples of epoxy-functionalized acrylic rubber include acrylate AR-53 obtained from Zeon Corporation
And acrylate AR-31. Suitable comonomers for adding pendant carboxylic acid groups include:
Unsaturated acids having 2 to about 15 carbon atoms, and preferably 2 to 10 carbon atoms, are included. Examples of acid functionalized acrylic rubbers include terpolymers of ethylene-alkyl acrylate-unsaturated carboxylic acids, such as Vamac G, available from DuPont, and various carboxyls manufactured by Nippon Zeon. Functionalized acrylates and the like are included. The amount of functional groups in the acrylic rubber is
It can be up to about 10 mole%, desirably about 0.5 to about 6 mole%, preferably about 1 to about 4 mole% of the acrylic rubber, ie, of the total repeating groups in the acrylic rubber.

[0012] Unexpectedly, when an ethylene-alkyl acrylate-unsaturated carboxylic acid terpolymer is used, the two or more acrylic rubber blends have only one,
That is, a single low temperature embrittlement point (LTB) (low temperatur
It has been found that the resulting thermoplastic elastomer has good low temperature properties. A single LTB is identified by ASTM test number D-746
Generally, it is -20 ° C or lower, desirably -30 ° C or lower, preferably -40 ° C or lower. Further, such terpolymer blends have good oil resistance, ie, low oil swell values. Its oil swell index is at least 10% lower, preferably at least 20 or 30% lower than the oil swell index of the acrylic terpolymer;
Preferably it is at least 40, 50% or 60% lower. Its oil swell value is 70 hours at 125 ° C,
According to ASTM D-471 when using ASTM Reference Oil # 3, generally from about 20 to about 65, preferably from about 25 to about 40,
45 or 50. The combination of a low oil swell index and a single low temperature brittle point is highly desirable because the thermoplastic elastomer composition can be used in commercially desirable end products. For example, in various seals, gaskets, etc., it is desirable to have a single low-temperature embrittlement point, that is, a low oil swelling index of -20 ° C or lower, and a low oil swelling index of, for example, 40 or lower. .

Thus, the use of an ethylene-alkyl acrylate-unsaturated carboxylic acid terpolymer as one of the functionalized acrylic rubber components is highly preferred. Such terpolymers generally have from about 35 to about 80 mole%, and preferably from about 45 to about 55 mole%, of the ethylene repeat groups, generally about 0.
5 to about 10 mole%, preferably about 2 to about 8 mole% of unsaturated carboxylic acid repeats, and generally about 10 to about 60 mole%, preferably about 37 to about 50 mole% of alkyl acrylate repeats including. Acid repeat groups are generally derived from acrylic acid or methacrylic acid. Certain commercially available compounds generally have about 50 mole% ethylene, about 45 mole% methyl acrylate and about 5 mole% acrylic acid.
Vamac G manufactured by DuPont. The amount of terpolymer is generally important in order to obtain a single low temperature embrittlement point and very desirable properties of good oil swell index. Accordingly, the amount of the terpolymer used is from about 25 to about 75 parts by weight, desirably from about 40 to about 60 parts by weight, and preferably from about 45 to about 50 parts by weight, based on a total of 100 parts by weight of all acrylic rubbers. Is the amount of parts.

[0014] An effective amount of one or more curing agents is used to simultaneously cure the functionalized acrylic rubber and obtain a suitable thermoplastic rubber-like elasticity. With such an effective amount, at least about 80%, desirably at least about 90% or 95% and preferably at least about 97%, 98%, 99% and 100%
%, Ie, full cure. The degree of cure is easily determined by the amount of acrylic rubber insoluble in toluene at 20 ° C. Suitable crosslinkers cure two or more functionalized acrylic rubbers by covalent or ionic bonds with reactive functional groups. Examples of such crosslinking agents include various diisocyanates such as toluene diisocyanate, isocyanate terminated polyester prepolymers and various polyols such as pentaerythritol or diols such as bisphenol A, methylene dianiline and diphenyl guanidine. Such as various polyamines, various epoxides such as diglycidyl ether of bisphenol A, and various epoxidized oils such as soybean oil.

When epoxidized oils are used, they often, but not always, have at least two internal oxirane groups and typically, but not always, have some unsaturation. The term "internal" means that the oxirane group is not attached to a terminal carbon atom of the oil molecule and often is not partially attached to one of the two terminal carbon atoms of each terminal portion of the oil molecule. Upon heating, the ring of the oxirane group opens and reacts with the acrylic rubber to crosslink or cure. Epoxidized oils are generally known in the art or in the literature, and are generally derived from plants, animals, such as vegetables, or petroleum. Epoxidized oils are generally saturated and / or preferably unsaturated fatty acids. Epoxidized oils also include glycerides of various fatty acids, such as linseed oil, which are glycerides of linolenic, oleic and linoleic unsaturated acids, and saturated fatty acids. Various fatty acids generally have about 10 to about 25 carbon atoms, and more desirably about 14 to about 21 carbon atoms. Generally, the iodine value of the epoxidized oil is from about 0.5 to about 12, preferably from about 1 to about 3 or 5 or 9. The weight of oxirane groups in the oil may range from only about 1 or 2% by weight, more preferably from 3 or 4% by weight to about 10, 12 or 15% by weight.
Can vary over a wide range. Preferred oils include C.I. P. Hall Kanenyi (CP Hall Compan)
paraplex manufactured by y)
Epoxidized soybean oils such as G-62 are included.

The amount of curing agent is generally used in an amount of about 0.5 to about 12 parts by weight, based on 100 parts by weight of the two or more functionalized acrylic rubbers. If the functionalized rubber has different functional groups, some self-curing of the rubber will occur (ie, without curing caused by the curing agent), and lesser amounts of curing agent, such as from about 1 to about 3 parts by weight. You only need it. When the functional groups of the acrylic rubber are the same, generally,
Higher amounts of curing agent, such as about 1 to about 5 parts by weight, are required.

Optionally, an accelerator may be used to reduce the cure time of the two or more functionalized acrylic rubbers. Suitable accelerators include various salts of fatty acids that do not crosslink the functionalized rubber compound. Often, such compounds also serve as lubricants. These fatty acid salts generally have from 12 or 14 to 20 or 25 carbon atoms. Suitable cations include various transition metals, for example, alkali metals and alkaline earth metals from Groups 1 and 2 of the Periodic Table, as well as Groups 11 and 12 of the Periodic Table. Particular examples of accelerators include sodium, potassium, magnesium, calcium, zinc and the like salts of fatty acids such as palmitic acid, stearic acid, oleic acid, and the like, and mixtures thereof, potassium stearate and magnesium stearate. Is preferred. The amount of accelerator is small and can vary up to 10 parts by weight, based on 100 parts by weight of all functionalized acrylic rubber, desirably from about 0.1 to about 4 or 5 parts by weight, often from about 0.5 to about 5 parts by weight.
1.5 parts by weight.

The compositions of the present invention may also contain various additives in conventional or suitable amounts. To prevent extremely rapid curing, various inhibitors are used, such as, for example, quaternary ammonium salts when epoxidized oils are used as curing agents. Other additives include various antioxidants, various UV stabilizers such as various hindered amines, various processing aids, various colorants or pigments such as titanium dioxide, clay, silica, carbon black, Includes various reinforcing agents or fillers, such as talc, zinc oxide, etc., various flame retardants, and various plasticizers, such as sulfonamides and trimellitates, which are non-reactive as well as various phthalate esters, e.g., dioctyl phthalate. It is.

The co-cured thermoplastic rubber composition of the present invention comprises:
Cured by dynamic vulcanization. Dynamic vulcanization, at the curing temperature,
It means vulcanizing the acrylic rubber of the composition of the present invention under high shear. As a result, acrylic rubber is generally crosslinked when blended with a thermoplastic polyester polymer. Thus, the acrylic rubber is simultaneously crosslinked and dispersed as fine particles of a "microgel" within a matrix of a thermoplastic, such as a polyester, or with a plastic phase, together with a crosslinked co-continuous phase.
phase) or a combination thereof.
High shear devices include extruders, including Brabender mixers, Banbury mixers, and twin screw extruders. The unique property of the composition of the present invention is that the elastomeric rubber portion is crosslinked, but nevertheless, the composition is made of conventional thermoplastic processing techniques and equipment such as extrusion, injection molding, compression molding, etc. Can be processed and reworked. An advantage of the thermoplastic elastomer of the present invention is that flushing, scrap, etc. can be recovered and reworked. However, the two or more acrylate polymers are not phase separated and, for example, do not include an internal phase and an external phase with or without graft-linking monomers. That is, the present invention is substantially free of such geometric (eg, shell-inner core) acrylic compounds (ie, 100% of all acrylic rubbers).
Less than 5% by weight, less than 3% by weight, less than 1% by weight and preferably free of such compounds per part by weight).

Dynamic vulcanization generally involves placing at least two functionalized acrylic rubber components, a curing agent, various additives and a thermoplastic ester polymer into a high shear mixing device such as a Brabender mixer. Heating the composition to a temperature above the melting point of the thermoplastic and mixing. The mixing temperature is generally between 180 ° C and about 260 ° C, preferably between about 220 ° C and about 240 ° C. The composition is mixed until the torque curve levels off and is further mixed for a shorter time, for example about 2 minutes. After mixing and curing, the thermoplastic elastomer composition was removed from the Brabender mixer, cold pressed into a pancake, and then compression molded into plaques for testing.

Suitable uses for the thermoplastic elastomers of the present invention include molded, extruded or molded articles useful as vehicle (eg, automotive) components such as seals, turbines, hoses, gaskets, diaphragms, bellows, and the like. included.

The present invention will be better understood from the following examples, which are intended to illustrate, but not limit, the scope of the invention.

[0023]

EXAMPLES A blend of two acid-functionalized acrylic rubbers of polybutylene terephthalate was prepared and cured. Three controls as well as a blend of at least two functionalized cured acrylic polymers of the present invention were made with the formulations described in Table 1.

[0024]

[Table 1]

The above composition was manufactured using a Brabender mixer. The indicated functionalized acrylic rubber and various additives were kneaded, melt mixed, and then the thermoplastic ester polymer was added. Once the thermoplastic ester polymer had melted, the accelerator was added and mixed. Next, a magnesium oxide hardener was added and mixed until the torque curve became flat. Mixing was then continued for another 1 or 2 minutes.

The dynamically vulcanized rubber composition was pressed into a pancake shape and compression-molded into plaque. Various physical tests were performed, and their properties are shown in the lower part of Table 1.

As is evident from Table 1, the compositions of the present invention generally provided improved ultimate tensile strength. The compositions obtained in Examples 1 to 5 unexpectedly had only one low temperature embrittlement point (LTB).

In a manner similar to that described above for Table 1, a thermoplastic elastomer composition was prepared with the formulation set forth in Table 2.

[0029]

[Table 2]

As is evident from Table 2, good physical properties were obtained for the functionalized acrylic rubber blends, ie, Examples 6-11. In addition, Example 6 had a very low temperature embrittlement point, ie, -38 ° C, and Examples 7-11 had a very low temperature single embrittlement point. The oil swelling indices of Examples 6 to 11 were very low compared to the use of only the ethylene-alkyl acrylate-unsaturated carboxylic acid terpolymer, ie, Comparative Example 5.

In a manner similar to that described for Table 1, various thermoplastic elastomer compositions were prepared with the formulations described in Table 3 and tested.

[0032]

[Table 3]

As is evident from Table 3, Comparative Examples 6 and 7, which did not contain the ethylene-ethyl acrylate-unsaturated carboxylic acid terpolymer, did not have a low temperature embrittlement point of -40 ° C. Rather, it decomposed before reaching that temperature. Examples 12 to 15 and 16 and 17 had a single low temperature embrittlement point. The oil swelling indices of Examples 12 to 15, like Examples 16 and 17, were very low.

 ────────────────────────────────────────────────── ─── Continuation of the front page (71) Applicant 591162239 388 South Main Street, Akron, Ohio 44311-1059, United States of America (72) Inventor Raman Patel San Barley, Ohio 44313, United States of America Drive 578 (72) Inventor Sabet Abdu-Sabet Knollwood Lane, Acron, United States 44313, Acron 3568 (72) Inventor Krishna Venkaswamy, United States, 44333, Ohio, Acron, Ira Road 3080F Term (reference) 4J002 BB04W BB04X BB041 BB07W BB07X BB071 BB08W BB08X BB081 BG04W BG04X BG041 BG07W BG07X BG071 CD054 CD164 CD19W CD19X CD191 CF042 CF043 CF062 CF063 CF072 73 CF082 CF083 CF102 CF103 CF272 CF273 CG012 CG013 EC056 EJ036 EN076 ER006 FD010 FD020 FD050 FD134 FD136 FD140

Claims (15)

[Claims] 1. A thermoplastic ester polymer phase and at least two functionalized acrylic rubbers dynamically vulcanized with a curing agent, one of which is an ethylene-alkyl acrylate-unsaturated carboxylic acid terpolymer. A thermoplastic elastomer composition comprising a crosslinked rubber phase comprising: having a single low-temperature embrittlement point. 2. The method according to claim 1, wherein the ester polymer is a polyester,
A copolyester, a polyester block copolymer, a polycarbonate, an epoxy end-capped derivative thereof or a mixture thereof, wherein the amount of said ester polymer is at least two of said acrylic rubber 100
From about 5 to about 95 parts by weight per 100 parts by weight of said at least two acrylic rubbers, and from about 5 to about 95 parts by weight of said thermoplastic elastomer composition. Is at least 80%. 3. The functionalized rubber wherein at least one of the functionalized rubbers is derived from an alkyl acrylate wherein the alkyl groups have from 1 to 10 carbon atoms and the functionalized acrylic rubber has a functional group such as carboxyl, epoxy, hydroxyl or a combination thereof. 3. The combination of claim 2, wherein the terpolymer has about 35 to about 80 mole% ethylene, about 10 to about 60 mole% alkyl acrylate has a previous and about 0.5 to about 10 mole% unsaturated carboxylic acid. 5. The thermoplastic elastomer composition according to item 1. 4. The thermoplastic elastomer composition according to claim 3, wherein said thermoplastic elastomer composition has an oil swell index lower than that of said terpolymer. 5. The method of claim 1, wherein said ester polymer is said polyester and said amount of said ester polymer is about 100 parts by weight per said at least two functionalized acrylic rubbers.
20 to about 40 parts by weight, wherein the terpolymer has about 45 to about 55 mole% ethylene, about 37 to about 50 mole% alkyl acrylate, and about 2 to about 8 mole% unsaturated carboxylic acid. The amount of the terpolymer is about 40 parts per 100 parts by weight of the at least two functionalized acrylic rubbers.
5. The thermoplastic elastomer composition of claim 4, wherein the thermoplastic elastomer composition has a degree of cure of at least 90% by weight of the thermoplastic elastomer composition. 6. The thermoplastic elastomer composition according to claim 2, wherein the single low-temperature embrittlement point is −20 ° C. or lower. 7. The method according to claim 5, wherein the single low-temperature embrittlement point is −40 ° C. or lower, and the oil swelling index of the thermoplastic elastomer composition is 30% lower than the oil swelling index of the terpolymer. Thermoplastic elastomer composition. 8. Blending at least two functionalized acrylic rubbers, at least one of which is an ethylene-alkyl acrylate-unsaturated carboxylic acid terpolymer, with a thermoplastic ester polymer and a curing agent, wherein the acrylic rubber is dynamically A method of producing a thermoplastic elastomer composition, comprising the step of vulcanizing to produce a thermoplastic elastomer composition having a single low temperature embrittlement point. 9. The method of claim 1, further comprising: curing the thermoplastic elastomer composition to have a degree of cure of at least 80%; and forming the thermoplastic elastomer composition to have a thermoplastic phase and a rubber phase. The polymer is a polyester, copolyester, polyester block copolymer, polycarbonate, an epoxy end-capped derivative thereof or a mixture thereof, and the amount of the ester polymer is at least 2%.
9. The composition of claim 8, wherein the amount is from about 15 to about 60 parts by weight per 100 parts by weight of acrylic rubber and the amount of the terpolymer is from about 25 to about 75 parts by weight per 100 parts by weight of the at least two acrylic rubbers. the method of. 10. The method according to claim 10, wherein the degree of cure is at least 90%.
The terpolymer comprises about 35 to about 80 mole% ethylene;
About 10 to about 60 mole% acrylate and about 0.5 to about 10
Mole percent unsaturated carboxylic acid and the amount of the curing agent is about 100 parts by weight of the at least two acrylic rubbers.
The method of claim 9, comprising producing the thermoplastic elastomer composition having an oil swell index of 0.5 to about 12 parts by weight and at least 30% lower than the oil swell index of the terpolymer. 11. The polymer is the polyester, the single low-temperature embrittlement point is −20 ° C. or less, and the acrylic rubber has an alkyl moiety having 1 to 10 carbon atoms, 11. The method of claim 10, wherein the group is a functionalized alkyl acrylate where the group is carboxyl, epoxy, hydroxyl, or a combination thereof. 12. The method according to claim 11, wherein said single low temperature embrittlement point is −40 ° C. or less. 13. A blend of a dynamically vulcanized acrylic rubber and a thermoplastic ester polymer, wherein said acrylic rubber has been cured by a curing agent and has at least two functional groups, carboxyl group, epoxy group, hydroxyl group. Or the combination thereof, wherein the amount of the functional group is 10 mol% or less based on the total number of the repeating units in the functionalized acrylic rubber, and the cured rubber is prepared in toluene at 20 ° C. % By weight that is insoluble
A thermoplastic elastomer composition having a single low temperature embrittlement point having a degree of cure measured as from about 80 to about 100%. 14. The thermoplastic elastomer composition has a temperature of -20 ° C.
Having the following single low temperature embrittlement point, wherein the ester polymer is a polyester, copolyester, polyester block copolymer, polycarbonate, epoxy end-capped derivative thereof or a mixture thereof;
The amount of the ester polymer is from about 15 to about 60 parts by weight based on 100 parts by weight of the at least two acrylic rubbers, and at least one of the acrylic rubbers is an ethylene-alkyl acrylate-unsaturated carboxylic acid terpolymer. Wherein the amount of the terpolymer is at least 2
About 25 to about 75 based on 100 parts by weight of one acrylic rubber
14. The thermoplastic elastomer composition of claim 13, wherein the thermoplastic rubber composition is in parts by weight and one of the acrylic rubbers is an alkyl acrylate wherein the alkyl group has 1 to 10 carbon atoms. 15. The ester polymer is a polyester, and the terpolymer comprises about 35 to about 80 mole% ethylene, about 10 to about 60 mole% acrylate and about 0.5 to about 10 mole% unsaturated carboxylic acid. 15. The thermoplastic elastomer composition of claim 14, having a degree of cure of from about 90 to about 100%.