EP0477186A1 - Compatible blends of ethylene-propylene rubber and polychloroprene or nitrile rubbers - Google Patents

Abstract

The invention provides elastomeric compositions and vulcanizates thereof, having increased resistance to chemical attack, comprising a uniform blend of polychloroprene or nitrile rubber elastomer and from about 10 to about 60% by weight. weight, depending on the total elastomer content present in the composition of a carboxylated copolymer of ethylene, a higher alpha-olefin and, optionally, a non-conjugated diene. The elastomer mixture thus obtained is easily covulcanized and produced in the form of heat and oil resistant articles such as transmission belts and automobile hoses, said articles not only having increased resistance to attack. by oxygen or by ozone but also having existing or improved physical properties such as resistance to wear, modulus of elasticity, elongation and tensile strength.

Description

COMPATIBLE BLENDS OF ETHYLENE- PROPYLENE RUBBER AND POLYCHLOROPRENE OR NITRILE RUBBERS

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to compatible blends of ethylene-propylene rubber and polychloroprene and/or nitrile rubber and covulcanizates thereof having improved resistance to the deleterious effects of ozone, oxygen and heat while retaining outstanding tensile strength and abrasion resistance.

2. Description of Related Art

It is known in the art that the resistance of cured u n s aturat ed el a s t ome rs such a s po l ybut a d i en e o r polyisoprene to chemical attack from ozone and oxygen can be enhanced by forming a blend thereof with minor amounts of an ethylene/propylene/diene terpolymer and covulcanizing the blend . This devel opment takes advantage of the inherent resistance of the olefin/diene terpolymer to chemical attack and imparts this property into the covulcanized blend.

However, the use of olefin/diene terpoly ers in blends with other elastomers is often limited to those other elastomers which have a mutual compatibility and

comparable cure-rate behavior with respect to the olefin/diene terpolymer. Thus, whereas highly unsaturated elastomers such as polybutadiene or polyisoprene may be, in some cases reasonably compatible with olefin/diene elastomers and may be readily covulcanized because of the high availability of sites of ethylenic unsaturation, other elastomers such as polychloroprene, butadiene/acrylonitrile copolymers (nitrile) and like materials containing polar groups along the chain and/or a relatively low degree of ethylenic unsaturation are not so readily covulcanized. In the case of blends with these latter elastomers, chemical resistance may be improved due to the influence of the olefin/diene terpolymer, but often at the expense of a lowering of physical properties such as tensile strength, elongation, modulus and/or abrasion resistance of the covulcanizate as compared with the cured elastomer itself.

Ethylene/propylene copolymers and ethylene/ propylene/diene terpolymers which have been chemically treated by free-radical grafting thereon of unsaturated acid monomers are also disclosed in the art as additives in polymeric compositions. For example, European Patent 0183493 to Mitsui Petrochemical Industries, Ltd. discloses liquid olefin copolymers or olefin/diene terpolymers having a molecular weight (Mn) of 200 to 10,000 which have been modified by graft copolymerization with an unsaturated carboxylic acid compound. These graft copolymers are disclosed to be useful as tackifier additives to various resinous compositions or as additives to curable rubbery polymers such as ethylene/propylene/diene elastomers and mixtures thereof with other elastomers. In addition, US Patent 4307204 to DuPont discloses an expandable, curable elastomeric sponge composition based on ethylene/propylene/diene terpolymer (EPDM) elastomer or polychloroprene elastomer, which composition further contains a minor amount of an ionomer resin which is an ethylene polymer or copolymer containing at least about 50 mole percent acid functional groups, which groups are at least about 50% neutralized by metal ions. These acid-modified ethylene polymers, which may also include acid-modified EPDM terpolymers, are disclosed to improve the balance of curing and expanding properties of the polymer composition when used to prepare cured expanded materials.

Neither of the aforementioned disclosures addresses the development of a cured polychloroprene or nitrile rubber formulation which not only exhibits improved resistance to ozone or oxygen attack and improved heat stability, but also exhibits a retention and in some cases improvement of important physical properties such as tensile strength, elongation, modulus and resistance to abrasion.

Summary of the Invention

The present invention provides for polychloroprene and nitrile rubber compositions and vulcanizates thereof having improved resistance to chemical attack comprising a uniform mixture of polychloroprene or nitrile elastomer and from about 10 to about 60% by weight based on the content of total elastomer in the composition of a carboxylated ethylene-propylene rubber. The blend of this invention may be readily covulcanized and formed into shaped, heat resistant and oil resistant articles such as automotive drive belts and automotive hoses which not only exhibit improved resistance to oxygen and ozone attack but also have retained or enhanced physical properties such as abrasion resistance, modulus, elongation and tensile strength.

Detailed Description of the Invention

The carboxylated ethylene-propylene copolymer rubber (EPR) useful for forming the blends of this invention are prepared from ethylene and ethylenically unsaturated hydrocarbons including cyclic, alicyclic and acyclic, containing from 3 to 28 carbons, e.g. 2 to 18 carbons. These ethylene copolymers may contain from 30 to 85 wt. % ethylene preferably 40 to 80 wt. % of ethylene and 15 to 70 wt. %, preferably 20-60 wt. % of one or more C₃ to C₂g, preferably C₃ to C₁₈ , more preferably C₃ to Cg, alpha olefins. Copolymers of ethylene and propylene are most preferred. Other alpha-olefins suitable in place of propylene to form the copolymer, or to be used in combination with ethylene and propylene, to form a terpolymer, tetrapolymer, etc, include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, etc; also branched chain alpha-olefins , such as 4-methyl-l-pentene, 4-methyl-l-hexene, 5-methylpentene-l, 4, 4-dimethyl-l-pentene, and 6-methylheptene-l, etc. and mixtures thereof.

The term copolymer or EPR as used herein, unless otherwise indicated, includes terpolymers, tetrapolymers , etc. , preferably of ethylene, said C₃_₂₈ alpha-olef in and/or a non-conjugated diolefin or mixtures of such diolefins which may also be used. The amount of the non-conjugated diolefin will generally range from about 0.5 to 20 wt. percent, preferably about 1 to about 7 wt. percent, based on the total amount of ethylene and alpha-olef in present. Representative examples of non-conjugated dienes that may be used as the third monomer in the terpolymer include:

a. Straight chain acyclic dienes such as: 1,4-hexadiene; 1,5-heptadiene; 1,6-octadiene. b. Branched chain acyclic dienes such as: 5-methyl-l, 4-hexadiene; 3 , 7-dimethyl 1, 6-octadiene; 3,7-dimethyl 1,7-octadiene; and the mixed isomers of dihydro-myrcene and dihydro-cymene . c. Single ring alicyclic dienes such as:

1, 4-cyclohexadiene; 1, 5-cyclooctadiene; 1,5-cyclo-dodecadiene; 4-vinylcyclohexene; 1-allyl, 4-isopropylidene cyclohexane ; 3-allyl-cyclopentene; 4-allyl cyclohexene and l-isopropenyl-4- (4-butenyl) cyclohexane. d. Multi-single ring alicyclic dienes such as:

4 , 4 ' -dicyclopentenyl and 4,4' -dicyclo exenyl dienes . e. Multi-ring alicyclic fused and bridged ring dienes such as: tetrahydroindene ; methyl tetrahydroindene; dicyclopentadiene; bicyclo (2.2.1) hepta 2,5-diene; alkyl, alkenyl, alkylidene, σycloalkenyl and cycloalkylidene norbornenes such as: ethyl norbornene ; 5-methylene-6-methyl-2-norbornene; 5-methylene-6 , 6-dimethyl-2-norbornene ; 5-propenyl-2-norbornene ;

5- ( 3-cyclopentenyl) -2-norbornene and 5 -cyclohexylidene-2 -norbornene; norbornadiene; etc.

The most preferred EPDM elastomer contains from about 60 to about 80% by weight ethylene, from about 15 to about 35% by weight propylene and from about 3 to about 7% by weight of non-conjugated diene. The term "carboxylated" as used herein refers to EPR polymers as described above which have been modified by inclusion into the polymer chain of from about 0.05 to about 10% by weight of an unsaturated polycarboxylic acid or lower alkyl esters or anhydrides thereof. The reaction of the EPR with an unsaturated mono or polycarboxylic acid, and derivatives thereof, can be carried out in the presence of a free radical source. The EPR may be reacted with unsaturated mono or polycarboxylic acids, and derivatives thereof, at temperatures generally less than 300° C. , preferably from about 150°-250° C, in the presence of free radical sources. Suitable free radical sources are, for example peroxides such as ditertiary butyl peroxide, tertiary butyl hydroperoxide, cumene hydroperoxide, p-menthane peroxide, p-menthane hydroperoxide compounds or azo compounds, such as azobis (isobutyronitrile) , or irradiation sources. Suitable irradiation sources include, for example, those from cobalt, uranium, thorium, and the like and ultraviolet light. Preferably, from about 0.05 to about 10 percent organic unsaturated polycarboxylic acid, anhydride or esters thereof, based on the weight of the EPR, can be used. The amount of peroxide or free radical agent used is generally quite low being of the order of about 0.01 to about 0.5 percent based on the weight of the EPR. Suitable unsaturated mono or polycarboxylic acids and derivatives thereof include maleic acid, maleic anhydride, fumaric acid, citaconic anhydride, aconitric anhydride, itaconic anhydride, the half or full esters derived from methyl, ethyl, dimethyl maleate, dimethyl fumarate, methyl ethyl maleate, dibutyl maleate, dipropyl maleate, and the like, or those compounds which form these compounds at elevated reaction temperatures such as citric acid, for example. The reaction may be carried out either in a batchwise or in a continuous manner with contact times in the order of about 10 minutes to about 2 hours. The reaction of the EPR can also be carried out in an extruder or a Banbury mixer. This process can be used for EPR having a melt viscosity greater than 5,000 cp. at 190°C, up to a viscosity of 500,000 cp. at 190° C.

The acid functionality may also be incorporated in the EPR polymer chain by copolymerizing the unsaturated polycarboxylic acid or derivative thereof with the olefin or the olefin and diene monomers during the formation of the EPR. Polymers prepared by copolymerization of ethylene and such acid monomers are disclosed in US Patent 3264272.

The preferred method for preparing the carboxylated EPR for the purposes of this invention is to graft polymerize the unsaturated acid monomer onto the polymer backbone, preferably in the presence of a free radical generator such as an organic peroxide.

As indicated above, the amount of unsaturated polycarboxylic acid monomer or derivative thereof incorporated into the EPR polymer according to this invention may generally range from about 0.05 to 10.0 percent by weight, more preferably from about 0.1 to about 5 percent by weight, and most preferably from about 0.15 to about 1.0 percent by weight, based on the weight of EPR polymer. To insure optimum compatibility of the carboxylated EPR and the polychloroprene or nitrile rubber with which it is blended, it is also important that the acid groups present in the EPR polymer chains are not substantially neutralized, such as by treatment with metal salts, prior to vulcanization of the blend. Partial neutralization of, for example, up to about 25% by weight of the acid groups may be tolerated, but higher levels of neutralization tends to detract from the compatibility of the elastomers and the physical properties of the covulcanizates. The carboxylated EPR polymers used in this invention are solid materials having a number average molecular weight (Mn) in the range of from about 15,000 up to about 150,000, more preferably from about 25,000 to about 90,000, as measured by Gel Permeation Chromatography (GPC) .

The polychloroprene elastomer used as the major component in the elastomer blend in one embodiment of the present invention is a commercially available material, commonly referred to as CR or neoprene rubber. It is available in a number of grades and molecular weights, all of which elastomeric grades are suitable for use in the compositions of this invention. The preferred grade is Neoprene GRT which is more resistant to crystallization and is based on a copolymer of chloroprene and 2,3-dichloro-1,3-butadiene.

The nitrile rubber used as the major component in the elastomer blend in another embodiment of this invention is also a commercial material available in a number of grades. Nitrile rubber is a random copolymer of a major proportion of butadiene and a minor proportion of acrylonitrile and is generally produced by free radical catalysis.

As indicated above, the polychloroprene or nitrile rubber preferably constitutes the major component of the mixture of elastomers of the present invention, but may be generally present in a range of from about 40 about 90% by weight based on total elastomer content. The carboxylated EPR polymer is correspondingly present at a level of from about 10 to about 60% by weight based on total elastomer content. It is also within the scope of the present invention to provide elastomer compositions based on blends of the polychloroprene and nitrile rubber components.

The vulcanizable composition of the present invention also includes a conventional mixed vulcanizing system for EPR, polychloroprene and nitrile rubber. Generally such vulcanizing systems include a metal oxide such as zinc oxide, magnesium oxide and mixtures thereof, used either alone or mixed with one or more organic accelerators or supplemental curing agents such as an amine, a phenolic compound, a sulfonamide, thiazole, a thiuram compound, thiourea or sulfur. Organic peroxides may also be used as curing agents. The zinc or magnesium oxide is normally present at a level of from about 1 to about 10 parts by weight per 100 parts by weight of elastomer blend, and the sulfur and supplemental curing agents or curing accelerators, where used, may be present at a level of from about 0.1 to about 5 parts by weight per 100 parts by weight of elastomer blend.

The elastomer polymer composition may also contain other additives such as lubricants, fillers, plasticizers, tackifiers, coloring agents, blowing agents, and antioxidants.

Examples of fillers include inorganic fillers such as carbon black, silica, calcium carbonate, talc and clay, and organic fillers such as high-styrene resin, σoumarone-indene resin, phenolic resins, lignin, modified melamine resins and petroleum resins.

Examples of lubricants include petroleum-type lubricants such as oils, paraffins and liquid paraffins, coal tar-type lubricants such as coal tar and coal tar pitch; fatty oil-type such as castor oil, linseed oil, rapeseed oil and coconut oil; tall oil; waxes such as beeswax, carnauba wax and lanolin; fatty acids and fatty acid salts such as licinoleic acid, palmitic acid, barium stearate, calcium stearate and zinc laurate; and synthetic polymeric substances such as petroleum resins.

Examples of plasticizers include hydrocarbon oils, e.g. paraffin, aromatic and naphtheniσ oils, phthalic acid esters, adipic acid esters, sebacic acid esters and phosphoric acid-type plasticizers.

Examples of tackifiers are petroleum resins, coumarone-indene resins, terpene-phenol resins, and xylene/ formaldehyde resins .

Examples of coloring agents are inorganic and organic pigments.

Examples of the blowing agents are sodium bicarbonate, ammonium carbonate, N, N' -dinitrosopentamethylenetetramine, azocarbonamide, azobis isobutyronitrile, benzenesulf onyl hydrazide, toluenesulfonyl hydrazide, calcium amide, p-toluenesulfonyl azide, salicylic acid, phthalic acid and urea.

The vulcanizable composition may be prepared and blended on any suitable mixing device such as an internal mixer (Brabender Plasticorder) , a Banbury Mixer, a kneader or a similar mixing device. Blending temperatures and times may range from about 45 to 180 °C and from about 4 to 10 minutes respectively. After forming a homogeneous mixture of the elastomers and optional fillers, processing aids, antioxidants and the like, the mixture is then vulcanized by the further mixing-in of crosslinking agents and accelerators followed by heating the resulting blend to a temperature of from about 100° to 250°C, more preferably from about 125 to 200°C for a period of time ranging from about 1 to 60 minutes. Molded articles such as belts and hoses are prepared by shaping the pre-vulcanized formulation using an extruder or a mold, and subjecting the composition to temperatures and curing times as set forth above.

The following examples are illustrative of the invention. In these examples, the EPR polymer employed is a terpolymer comprising about 70 weight percent ethylene, 25 weight percent propylene and 5 weight percent 5-ethylidene-2-norbomene. This terpolymer has a number average molecular weight (Mn) of about 70,000 as measured by Gel Permeation Chromatography (GPC) , a dispersity (Mw/Mn) of less than 4, and a Mooney Viscosity at 1+4, 125°C of 60. The EPDM terpolymer identified as "Modified EPDM" is the same terpolymer except that it also contains 0.25% by weight of maleic anhydride grafted along the polymer chain by the free radical grafting technique described above. The polychloroprene rubber employed is a commercially available material resistant to crystallization sold by DuPont under the trade name Neoprene GRT and is a copolymer of chloroprene and 2,3-dichloro-l,3-butadiene. The nitrile rubber employed is a commercially available copolymer of butadiene and acrylonitrile sold by Uniroyal under the trademark PARACRIL B and may be characterized by an acrylonitrile content of about 29 mole percent and a nominal Mooney Viscosity ML-4 at 212°F of 82.

Example 1

In an internal mixer (Banbury Intensive Mixer) were charged polychloroprene and all ingredients listed in Table 1, Ex. 1 except for the magnesium oxide/zinc oxide curing agents. The temperature of the mixture was maintained at 100 to 120°C and mixing was continued for a period of about 5 minutes. This intensive mixing includes kneading, shearing and cross-over blending. The uniform admixture was then discharged from the Banbury and placed on a two roll mill and milled at a temperature of 80 to 90°C. The zinc oxide/magnesium oxide curing agents were added to the plastic mass and milling was continued for about 15 to 20 minutes.

The milled elastomer composition was then sheeted off the mill at a thickness of about 0.1 inch, placed in a 6 inch by 6 inch by .075 inch mold and cured at a temperature of about 160°C for a period of 20 minutes.

Example 2

The process of Example 1 was repeated except that the elastomer compos ition consisted of a mixture of polychloroprene and unmodified EPDM. Other ingredients are as set forth in Table 1, Ex. 2.

Example 3

The process of Example 1 was repeated except that the elastomer composition consisted of a mixture of polychloroprene and the modified EPDM of this invention. Other ingredients are as set forth in Table 1, Ex. 3.

Example 4

The process of Example 1 was repeated except that the elastomer composition consisted of a mixture of polychloroprene and unmodified EPDM. The other ingredients are as set forth in Table 1, Ex. 4. The sulfur and vulcanization accelerators additionally present in this formulation were added to the elastomer mixture at the same time as the zinc oxide/magnesium oxide mixture. Example 5

The process of Example 1 was repeated except that the el astomer compos it ion consisted of a mixture of polychloroprene and the modified EPDM elastomer of this invention. Other ingredients are as set forth in Table

Table 1

Ex 1 Ex 2. Ex 3 Ex 4 E 5

Neoprene GRT 100 70 70 70 70 EPDM 30 - SO - Modified EPDM SO - 30

Furnace Carbon black (N550) 50 50 50 50 50

Aromatic hydrocarbon process oil 12.5 12.5 12.5 12.5 12.5

Octamine (1) 2.5 2.5 2.5 2.5 2.5

AgeRite HPS (2) 0.5 0.5 0.5 0.5 0.5

Polyethylene AC-617 wax 1.5 1.5 1.5 1.5 1.5

Stearic Acid 1.5 1.5 1.5 1.5 1.5

Magnesium oxide 4.0 4.0 4.0 4.0 4.0

Zinc Oxide 5.0 5.0 5.0 5.0 5.0

Sulfur 0.5 0.5 benzothiazole disulfide 0.2 0.2 tetramethylthiarum disulfide - 0.2 0.5

Original Physical Properties

20 minute/160°C

Hardness Shore A (ASTM D-2240) 70 75 73 75 73

100% Modulus, MPa (ASTM D-412) 4.6 4.6 5.0 4.8 5.0

Tensile Strength, MPa (ASTM D-412) 19.0 14.2 17.6 16.4 19.2

Elongation, % (ASTM D-412) 380 310 350 360 350

Heat Aged-Air Oven

48 hour/125°-C CASTM D-573)

Hardness Shore A (ASTM D-2240) 79 80 79 81 80

Tensile Strength, MPa (ASTM D-412) 16.5 13.7 17.0 15.8 18.7

Elongation, % (ASTM D-412) 215 225 260 240 260

Ozone Resistance 100 pphm 0₃, 37.8°C Bent Loop (^"ASTM D-1149 Hour to Craze 24 >500 >500 >500 >500 Hour to Crack 168 >500 >500 >500 >500

Notes: (1) antioxidant reaction product of diphenyl am and diisobutylene.

(2) antioxidant blend of dioctylated diphenyl amine and diphenyl para phenylene diamine. 1, Ex. 5. The sulfur and vulcanization accelerators additionally present in this formulation were added to the elastomer mixture at the same time as the zinc oxide/magnesium oxide mixture.

As can be seen from the data contained in Table 1, the formulations of Examples 2 and 4 which are based on the blend of polychloroprene and unmodified EPDM elastomer (outside of the scope of this invention) show a significant tensile strength loss and lower physical properties after heat aging as compared with the control formulation of Example 1 containing 100% polychloroprene as the cured elastomeric component. However, the formulation of Example 3 which contains the modified EPDM of this invention yields only a small decrease in tensile strength with slightly higher physical properties after heat aging. Adding a small amount of sulfur and accelerators to these blends further increases the tensile strength of the covulcanizate as demonstrated in Examples 4 and 5, but the physical properties of the formulation of Example 5 containing the modified EPDM of this invention are generally superior both before and after exposure to heat to the physical properties of the formulations of Examples ^' 2 and 4 which contain the unmodified EPDM elastomer and which remain deficient in these properties with respect to the formulation of Example 1 containing 100% polychlorprene as the cured elastomeric component. All blend compositions of Examples 2-5 exhibit superior ozone resistance compared with control Example 1 containing 100% polychloroprene as the cured elastomeric component.

As indicated above, the vulcanized composition of the present invention also exhibits both good abrasion resistance and dynamic ozone resistance. The enhancement of these properties is demonstrated in the following Examples. TABLE 2

Ex 6. Ex 7 Ex 8.

Neoprene GRT 100 70 70 EPDM 30 Modified EPDM 30

N650 (GPF-HS) Carbon black 40 40 40

N762 (SRF-LM) Carbon black 30 30 30

Aromatic hydrocarbon process oi 10 10 10

Stearic Acid 2 2 2

Octamine 2.5

AgeRite HPS 0.5

Magnesium Oxide 4.0 4.0 4.0

Zinc Oxide 5.0 5.0 5.0

Original Physical Properties

20 minute/160"C

Hardness, Shore A (ASTM D-2240) 74 80 80 100% Modulus, MPa (ASTM D-412) 6.7 7.5 7.5 Tensile Strength, MPa (ASTM D-412) 19.3 15.3 17.3 Elongation, % (ASTM D-412) 260 205 225

Heat Age — ASTM D-573 48 hour/125°C

Hardness Change, point +9 +9 +9 Tensile Change, % -5 -1 -2 Elongation Change, % ^■42 -45 -45

Ozone Resistance 100 pphm 0₃, 37.8°C Bent LOOP CASTM D-1149

Hour to craze 48 >500 >500 Hour to crack 96 >500 >500

Dynamic Ozone Resistance 0-25% Extension, 30 cycle/min. 100 PPhm 0₂ . 37.8-C fASTM D-1149)

Hour to crack 72 336 >500

Abrasion Resistance ASTM D-2228 4.5kα. 80 rev. 1Hz

Pico Index 139 99 132 Examples 6 - 8

Three additional formulations based on ingredients as set forth in Table 2 were prepared and cured by the process set forth in Example 1. The formulation of Example 6 contains no added EPDM terpolymer elastomer; the formulation of Example 7 contains the unmodified EPDM terpolymer; and the formulation of Example 8 contains the modified (carboxylated) EPDM terpolymer of this invention.

As can be see from an analysis of the data present in Table 2, the composition of this invention (Example 8) exhibited both improved hardness and 100% Modulus when compared with the composition of Example 6 which does not contain EPDM elastomer, and also exhibited better tensile strength and elongation than the composition of Example 7 which contains the unmodified EPDM. The dynamic ozone resistance and abrasion resistance of the composition of Example 8 were also superior to those properties for the composition of Example 7. It is also noteworthy that the static and dynamic ozone resistance of the EPDM blends are superior to the polychloroprene composition compounded with antioxidants, even though the antioxidants were not included in he blend formulations of the invention.

TABLE 3

E . 9 Ex. 10 E . 11

Paracril B (UniRoyal) 100 70 70

EPDM _=>___ 30 —

Modified EPDM __ — 30

N650 (GPF-HS) carbon black 35 35 35

N762 (SRF-LM) carbon black 30 30 30

Dioctylsebacate 15 15 15

Aminox (1) 1.5 1.5 1.5

Zinc Oxide 5.0 5.0 5.0

Stearic Acid 1.5 1.5 1.5

Sulfur 1.5 1.5 1.5

MBTS (2) 1.5 1.5 1.5

Original Physical Properties 20 minute/160°C

Hardness, Shore A (ASTM D-2240) 58 69 69 100% Modulus, MPa (ASTM D-412) 2.7 4.3 5.1 200% Modulus, MPa (ASTM D-412) 7.6 10.0 11.5 Tensile Strength, MPa

(ASTM D-412) 18.9 14.4 17.9 Elongation, % (ASTM D-412) 415 290 340

Ozone Resistance 100 pphm 0₃, 37.8°C Bent LOOP ASTM D-1149

Hour to crack 48 >500 >500

Dynamic Ozone Resistance 0-25% Extension, 30 cycle/min 100 PPh 0₂. 37.8"C fASTM D-1149)

Hour to crack 16 48 96

Note

(1) antioxidant based on the reaction product of diphenyl amine and acetone.

(2) benzothiazyl disulfide Examples 9-11

Three additional formulations based on a mixture of nitrile rubber (PARACRIL B) and other ingredients as set forth in Table 3 were prepared and cured by the process set forth in Example 1. The formulation of Example 9 contains no added EPDM terpolymer elastomer; the formulation of Example 10 contains the unmodified EPDM terpolymer; and the formulation of Example 11 contains the modified (carboxylated) EPDM terpolymer of this invention.

As can be seen from an analysis of the data present in Table 3, the composition of this invention (Example 11) exhibited improved hardness, modulus and resistance to crack when compared with the composition of Example 9 which does not contain EPDM elastomer, and also exhibited better tensile strength, elongation, modulus and resistance to crack than the composition of Example 10 which contains the unmodified EPDM.

It is to be understood that the above described embodiments of the invention are illustrative only and that modifications throughout may occur to those skilled in the art. Accordingly, this invention is not to be regarded as limited to the embodiments disclosed herein, but is to be limited as defined by the appended claims.

Claims

CLAIMS :

1. A vulcanizable elastomer composition comprising an admixture of:

a) an elastomer selected from the group consisting of polychloroprene and nitrile rubber; and

b) a copolymer elastomer of at least ethylene and a C₃ to C₁₀ alpha-olefin, said copolymer further characterized as containing from about 0.05 to about 10% by weight of said copolymer of acid functional groups, which groups are substantially non neutralized.

2. The composition of claim 1 wherein said acid functional groups comprise an unsaturated polycarboxylic acid, ester or anhydride thereof.

3. The composition of claim 2 wherein said acid functional groups are grafted along the copolymer chain by a free radical grafting technique.

4. The composition of claim 2 wherein said acid, ester or anhydride is based on a carboxylic acid selected from the group consisting of maleic acid, fumaric acid, itaconic acid, citraconic acid and lower alkyl esters and anhydrides thereof.

5. The composition of claim l wherein said elastomer (a) is present at a level of from about 40 to about 90% by weight and said copolymer is present at a level of from about 10 to about 60 % by weight, based on the total weight of elastomers present in the composition.

6. The composition of claim 5 wherein said copolymer contains from about 30 to about 85% by weight ethylene, from about 15 to about 70% by weight propylene and from a 0 to about 10% by weight non-conjugated diene.

7. The composition of claim 6 wherein said copolymer is a terpolymer containing at least about 0.5% by weight of non-conjugated diene.

8. The composition of claim 7 wherein said terpolymer has a number average molecular weight within the range of from about 15,000 to about 150,000.

9. The composition of claim 8 wherein said non-conjugated diene is 5-ethylidene-2-norbornene.

10. The composition of claim 6 wherein said acid functional groups comprise an unsaturated polycarboxylic acid, ester or anhydride thereof.

11. The composition of claim 10 wherein said acid functional groups are grafted along the terpolymer chain by free-radical grafting techniques.

12. The composition of claim 11 wherein said acid, ester or anhydride is a dicarboxylic acid selected from the group consisting of maleic acid, fumaric acid, itaconic acid, citraconic acid and lower alkyl esters and anhydrides thereof.

13. The composition of claim 12 wherein said copoloymer contains from about 0.15 to about 1.0% by weight of said acid functional groups.

14. The composition of claim 13 wherein said acid, ester or anhydride is maleic anhydride.

15. The composition of claim 13 wherein said copolymer is a terpolymer comprising from about 60 to about 80% by weight of ethylene, from about 15 to about 35% by weight propylene and from about 3 to about 8% by weight non-conjugated diene.

16. The composition of claim 15 wherein said non-conjugated diene is 5-ethylidene-2- norbornene.

17. The composition of claim 5 wherein said elastomer (a) is polychloroprene.

18. The composition of claim 5 wherein said elastomer (a) is nitrile rubber.

19. The composition of claim 1 further containing an effective amount of a vulcanizing system.

20. The composition of claim 19 further containing one or more additives selected from the group consisting of vulcanization accelerators, lubricants, fillers, plasticizers, tackifiers, coloring agents, blowing agents and antioxidants.

21. A vulcanized elastomer composition having improved resistance to ozone attack comprising a compatible blend of:

a) from about 40 to about 90% by weight of an elastomer selected from the group consisting of polychloroprene and nitrile rubber, and b) from about 10 to about 60% by weight of a copolymer elastomer comprising from about 40 to about 80% by weight of ethylene and from about 20 to about 60% by weight propylene, said copolymer further characterized as containing from about 0.1 to about 10% by weight of said copolymer of acid functional groups grafted by free radical grafting along the polymer chain, which groups are substantially non-neutralized prior to vulcanization, said acid functional groups comprising an unsaturated dicarboxylic acid, ester or anhydride selected from the group consisting of maleic acid, fumaric acid, itaconic acid, citraconic acid and lower alkyl esters and anhydrides thereof.

22. The vulcanized composition of claim 21 wherein said unsaturated dicarboxylic acid, ester or anhydride is maleic anhydride.

23. The vulcanized composition of claim 22 wherein said copolymer elastomer additionally comprises from about 1 to about 7% by weight of non-conjugated diene.

24. The vulcanized composition of claim 22 wherein said terpolymer has number average molecular weight within the range of from about 25,000 to about 90,000.

25. The vulcanized composition of claim 22 wherein said maleic anhydride is present at a level of about 0.25% by weight of said terpolymer.

26. The vulcanized composition of claim 21 wherein said elastomer (a) is polychloroprene.

27 . The vulcanized composition of claim 21 wherein said elastomer (a) is nitrile rubber.

28 . The vulcanized composition of claim 23 wherein said non-conj ugated diene is 5-ethylidene-2- norbornene .

29. The vulcanized composition of claim 23 wherein said elastomer (a) is polychloroprene.

30. The vulcanized composition of claim 23 wherein said elastomer (a) is nitrile rubber.