BACKGROUND OF THE INVENTION Many polymeric materials find applications that impose multiple performance requirements on physical properties such as, for instance, tensile strength, elasticity and abrasion resistance, and also require the material to be effective over a wide temperature range. In seeking these desirable properties it is known to blend different polymers. This is not always easy, however. If two polymers will not mix and bond with each other there are formed large domains of one polymer distributed in a continuous phase of the other polymer.

In the absence of bonding between the two polymers, or if bonding occurs to only a limited extent, the discontinuous polymer does not contribute to the properties of the blend, and there is formed a product that has low modulus and low tensile strength.

For example, ethylene/propylene rubber (EPR) is a copolymer of ethylene and propylene usually containing 50 to 75 parts of ethylene and the balance propylene. EPDM is a terpolymer of ethylene, propylene and a diene monomer, the diene monomer being hexadien, dicyclopentadiene or, more commonly, ethyliden norbornene. EPR and EPDM both have good heat resistance, good cold resistance, good ozone resistance and good weather resistance. Both have poor physical, abrasive and adhesive properties, however. Attempts have been made in the past to blend EPR or EPDM with other polymers, seeking to obtain a composition that has the good weather and temperature properties of EPR or EPDM and also good physical properties of the other polymer. Difficulty has been encountered in blending the EPR or

EPDM and other polymers, resulting in compositions that display no useful enhancement of properties.

SUMMARY OF THE INVENTION The present invention provides a method for covulcanizing two or more polymeric materials which comprises admixing the two or more polymeric materials with an, optionally hydrogenated, carboxylated nitrile rubber (XNBR/HXNBR), a multivalent salt of an organic acid and a vulcanizing agent.

In another aspect the present invention provides a composition comprising two or more different polymeric materials that have been admixed with an, optionally hydrogenated, carboxylated nitrile rubber, a multivalent salt of an organic acid and a vulcanizing agent.

DESCRIPTION OF PREFERRED EMBODIMENTS Different polymers have different solubility parameters. Solubility parameters correlate with polarity, and are measured in units of (cal. cm3) t/2.

According to"The Elements of Polymer Science and Engineering", Academic Press Inc. 1982, by Alfred Rudin, Chapter 12 Polymer Mixtures, pages 428 to 445, nitrile rubber of 43% acrylonitrile content, for example, has a solubility parameter of 10.53. Hydrogenated nitrile rubber of 43% acrylonitrile content has a solubility parameter of 10.71. These can be readily blended. EPR has a solubility parameter of about 8.1 EPDM has a solubility parameter of about 8.0, and these do not blend readily with nitrile rubber or hydrogenated nitrile rubber.

Compatibility between polymers reduces as the difference in the solubility parameters of the respective polymers approaches a value of 0.5 or greater, especially 2 or greater, and the invention finds application particularly for blending polymers which differ in solubility parameter by the value of 0.5 or more and in some instances by 2 or greater.

Because EPR and EPDM display good weather resistance, heat resistance and cold resistance, it is desired to blend them with polymers that have good physical properties but whose weather resistance, heat resistance and cold resistance are not as good as desired. For example, accessory drive belts in automobile and trucks, such as alternator belts and the like, may be

made from nitrile rubber or hydrogenated nitrile rubber. These display good physical properties for these applications. It is desired to increase the temperature range over which these can be used, however, so that the high temperature demands imposed by summer in Arizona, Nevada and New Mexico, and the low temperature demands imposed by winter in Alaska and Northern Alberta can be satisfied by the same material. In some embodiments of the invention, therefore, EPR or EPDM polymer is covulcanized with nitrile rubber, and in other embodiments EPR or EPDM is covulcanized with hydrogenated nitrile rubber each time in the presence of an, optionally hydrogenated carboxylated nitrile rubber.

EPR's are well known. They are commercially available from Bayer under the trademark Buna and include examples bearing the designations EP T 2070 and EP G 5050. EP T 2070 is a copolymer of ethylene and propylene with an ethylene content of 70%, the balance propylene, a Mooney viscosity of 20 and containing no processing oil. EP G 5050 is a copolymer of ethylene and propylene with an ethylene content of 50%, balance propylene, a Mooney viscosity of 50 and containing no processing oil. EPR's with or without processing oil can be used in the invention but, for the most part, EPR's without processing oil are preferred.

Terpolymers of ethylene, propylene and ethyliden norbornene are commercially available, for example under the designations EP T 3950, EP T 6470 and EP T 2450. EP T 3950 has a viscosity in Mooney units of 30, a content of ethyliden norbornene of 9%, an ethylene content of 50% and contains no processing oil. EP T 6470 has a Mooney Viscosity of 60, a content of ethyliden norbornene of 4%, an ethylene content of 70% and no processing oil. EP T 2450 has a Mooney viscosity of 20, a content of ethyliden norbornene of 4%, an ethylene content of 50% and no processing oil. EPDM's with or without processing oil can be used in the invention but, for the most part EPDM's without processing oil are preferred. Commercially available are EPDM's with oil contents of 30,50 and 100 per hundred parts by weight of rubber (phr).

As used throughout this specification, the term"nitrile polymer'or NBR is intended to have a broad meaning and is meant to encompass a copolymer

having repeating units derived from at least one conjugated diene, at least one unsaturated nitrile and optionally further one or more copolymerizable monomers.

The conjugated diene may be any known conjugated diene, in particular a C4-C6 conjugated diene. Preferred conjugated dienes are butadiene, isoprene, piperylene, 2, 3-dimethyl butadiene and mixtures thereof. Even more preferred C4-C6 conjugated dienes are butadiene, isoprene and mixtures thereof. The most preferred C4-C6 conjugated diene is butadiene.

The ,--unsaturated nitrile may be any known alpha, beta-unsaturated nitrile, in particular a C3-C5 alpha, beta-unsaturated nitrile. Preferred C3-C5 alpha, beta-unsaturated nitriles are acrylonitrile, methacrylonitrile, ethacrylonitrile and mixtures thereof. The most preferred C3-C5 alpha, beta- unsaturated nitrile is acrylonitrile.

Preferably, the optionally hydrogenated NBR comprises in the range of from 40 to 85 weight percent of repeating units derived from one or more conjugated dienes and in the range of from 15 to 60 weight percent of repeating units derived from one or more unsaturated nitriles. More preferably, the copolymer comprises in the range of from 60 to 75 weight percent of repeating units derived from one or more conjugated dienes and in the range of from 25 to 40 weight percent of repeating units derived from one or more unsaturated nitriles. Most preferably, the copolymer comprises in the range of from 60 to 70 weight percent of repeating units derived from one or more conjugated dienes and in the range of from 30 to 40 weight percent of repeating units derived from one or more unsaturated nitriles.

Optionally, the optionally hydrogenated NBR may further comprise repeating units derived from one or more copolymerizable monomers, such as unsaturated carboxylic acids. Non-limiting examples of suitable unsaturated carboxylic acids are fumaric acid, maleic acid, acrylic acid, methacrylic acid and mixtures thereof. Repeating units derived from one or more copolymerizable monomers will replace either the nitrile or the diene portion of the nitrile rubber and it will be apparent to the skilled in the art that the above mentioned figures will have to be adjusted to result in 100 weight percent. In case of the mentioned unsaturated carboxylic acids, the nitrile rubber preferably comprises

repeating units derived from one or more unsaturated carboxylic acids in the range of from 1 to 10 weight percent of the rubber, with this amount displacing a corresponding amount of the conjugated diolefin.

Other preferred optionally further monomers are unsaturated mono-or di-carboxylic acids or derivatives thereof (e. g. , esters, amides and the like) including mixtures thereof.

Hydrogenated in this invention is preferably understood by more than 50 % of the residual double bonds (RDB) present in the starting nitrile polymer/NBR being hydrogenated, preferably more than 90 % of the RDB are hydrogenated, more preferably more than 95 % of the RDB are hydrogenated and most preferably more than 99 % of the RDB are hydrogenated.

As used throughout this specification, the term"carboxylated nitrile polymer"or XNBR is intended to have a broad meaning and is meant to encompass a copolymer having repeating units derived from at least one conjugated diene, at least one alpha, beta-unsaturated nitrile, at least one copolymerizable monomer having at least one carboxy function and optionally further one or more copolymerizable monomers.

The conjugated diene may be any known conjugated diene, in particular those already specified above.

The alpha, beta-unsaturated nitrile may be any known alpha, beta- unsaturated nitrile, in particular those already specified above.

The invention is not limited to a special copolymerizable monomer having at least one carboxy function. However, unsaturated carboxylic acids such as fumaric acid, maleic acid, acrylic acid, methacrylic acid and mixtures <BR> <BR> thereof, or derivatives of unsaturated (e. g. , esters, amides and the like, for example, an ester of an unsaturated acid, say ethyl, propyl or butyl acrylate or methacrylate) are preferred.

Preferably, the optionally hydrogenated XNBR comprises in the range of from 30 to 84.99 weight percent of repeating units derived from one or more conjugated dienes and in the range of from 15 to 60 weight percent of repeating units derived from one or more unsaturated nitriles and in the range of from 0.01 to 10 weight percent of repeating units derived from one or more copolymerizable monomers having at least one carboxy function. More

preferably, the copolymer comprises in the range of from 50 to 74.99 weight percent of repeating units derived from one or more conjugated dienes and in the range of from 25 to 40 weight percent of repeating units derived from one or more unsaturated nitriles and in the range of from 0.01 to 10 weight percent of repeating units derived from one or more copolymerizable monomers having at least one carboxy function. Most preferably, the copolymer comprises in the range of from 50 to 69.99 weight percent of repeating units derived from one or more conjugated dienes and in the range of from 30 to 40 weight percent of repeating units derived from one or more unsaturated nitriles and in the range of from 0.01 to 10 weight percent of repeating units derived from one or more copolymerizable monomers having at least one carboxy function.

Optionally, the optionally hydrogenated XNBR may further comprise repeating units derived from one or more copolymerizable monomers, such as a vinyl compound, for example, styrene, alpha-methylstyrene or a corresponding compound bearing an alkyl substituent on the phenyl ring, for instance, a p-alkylstyrene such as p-methylstyrene) including mixtures thereof.

Repeating units derived from one or more copolymerizable monomers will replace either the nitrile or the diene portion of the nitrile rubber and it will be apparent to the skilled in the art that the above mentioned figures will have to be adjusted to result in 100 weight percent.

The XNBR can be hydrogenated in known manner. Hydrogenation is not always complete, however, and the degree of remaining unsaturation is expressed in terms of residual double bonds, or"RDB", being the number of carbon-carbon double bonds that remain in the copolymer after hydrogenation, expressed as a percentage of the carbon-carbon double bonds present in the copolymer prior to hydrogenation.

Hydrogenated in this invention is preferably understood as already defined above.

The Mooney viscosity of the rubber was determined using ASTM test D 1646.

Past attempts to covulcanize an EPR or an EPDM and a nitrile rubber or a hydrogenated nitrile rubber have been unsuccessful. In accordance with the present invention, however, it is possible to covulcanize in the presence of a

optionally hydrogenated carboxylated nitrile rubber, a multivalent salt of an organic acid and a vulcanizing agent.

A optionally hydrogenated carboxylated nitrile rubber, and a process for preparing it, are the subject of Canadian Patent Application Serial No.

2,304, 501, filed April 10,2000, which for the purpose of jurisdictions allowing for this procedure is hereby incorporated by reference. It is preferred that the optionally hydrogenated carboxylated nitrile rubber used in the present invention is in accordance with Patent Application Serial No. 2,304, 501.

Hydrogenated carboxylated nitrile rubbers in accordance with Application Serial No. 2,304, 501 are commercially available from Bayer under the trademark Therban XT. The amount of the optionally hydrogenated carboxylated nitrile rubber used in the method of this invention can vary between wide limits, say between 1.0 and 40 parts per hundred parts of rubber (phr), preferably between 5 and 25phr. The HXNBR is counted as part of the rubber. In the present invention it is preferred that the optionally hydrogenated carboxylated nitrile rubber is indeed partially or fully hydrogenated.

For use in the present invention it is in particular preferred that the HXNBR has a nitrile content in the range 18 to 45wt%, an acid monomer content in the range 0.3 to 9wt%, an RDB not greater than 9.0% and a Mooney viscosity in the range 35 to 120 (ML 1+4'W100°C). In one preferred HXNBR the nitrile is acrylonitrile, the diene is 1,3-butadiene and the acid is acrylic acid.

Another ingredient used in the method of this invention is a multivalent salt of an organic acid. Suitable multivalent cations are derived from metals, of which zinc, magnesium, calcium and aluminum are mentioned. As organic acids there are mentioned saturated and unsaturated acids having up to 8 carbon atoms, preferably up to 6 carbon atoms. The preferred organic acids are acrylic and methacrylic acids and the preferred salts are zinc diacrylate and zinc dimethacrylate. It is possible to form the salt in situ, but this is not normally preferred. The amount of the salt used can vary between wide limits, preferably in the range of from 5 to 80 phr (= per hundred rubber), more preferably between 10 and 50phr.

The invention is not limited to any specific vulcanizing agent. The vulcanizing agent is preferably a peroxide vulcanizing agent. Suitable organic

peroxide crosslinking agents include dicumyl peroxide, di-t-butyl peroxide, benzoyl peroxide 2, 5-dimethyl-2, 5-di (t-butylperoxy)-hexyne-3 and 2, 5-dimethyl- 2,5-di (benzoylperoxy) hexane and the like. A preferred peroxide curing agent is alpha, alpha-bis (tertiary butylperoxy) diisopropylbenzene, available under the trademark Vulcup 40KE. The peroxide curing agent is suitably used in an amount in the range of from 0.2 to 20phr, preferably 1 to 10phr.

Other polymeric materials that can be covulcanized include, for example, ethylene/vinyl acetate copolymers. A suitable ethylene/vinyl acetate copolymer is available from Bayer under the trademark Levapren. Mention is also made of ethylene/methylacrylate copolymers available, for instance, from DuPont under the trademark Vamac.

As examples of polymeric materials to be blended in accordance with the present invention there are mentioned the following: ethylene-propylene copolymer + NBR ethylene-propylene copolymer + HNBR ethylene-propylene copolymer + NBR + HNBR EPDM + NBR EPDM + HNBR EPDM + NBR + HNBR EPDM + ethylene-vinyl acetate copolymer EPDM + NBR + ethylene/vinyl acetate copolymer EPDM + HNBR + ethylene/vinyl acetate copolymer EPDM + ethylene/methyl acrylate copolymer EPDM + NBR + ethylene/methyl acrylate copolymer EPDM + HNBR + ethylene/methyl acrylate copolymer.

The ratio of two polymeric materials to be covulcanized can vary over wide limits, e. g. in the range of from 90: 10 to 10: 90. The ratio will depend upon the properties of the individual polymers and the desired properties of the covulcanized product, and some experimentation of a routine nature may be required to arrive at optimum proportions. Usually the ratio will be in the range from 80: 20 to 20: 80 and for some purposes ratios of 50: 50 may be appropriate.

If a third or a fourth polymeric material is present, it is anticipated that each material will be present in an amount of at least 1 Ophr.

The method of the invention can be carried out by mixing the various ingredients, initially at room temperature. Another factor that influences the covulcanization process is the speed at which the polymeric materials cure.

For best results it is desirable that the polymeric materials cure at about the same speed; otherwise it is possible that substantially all the one polymeric material will cure before any significant curing of the other polymeric material occurs. In such a case little or no covulcanization will occur. Curing speed can be controlled to some extent by selection of the polymeric material. For example, EPDM's with higher content of ethyliden norbornene cure more quickly than EPDM's with low content. If it is desired to accelerate the curing of EPDM, therefore, an EPDM with a higher content of ethyliden norbornene is used. Conversely, if it is desired to slow the curing rate an EPDM with lower content of ethyliden norbornene is used. HNBR's with low RDB cure more slowly than those with high RDB, so if accelerated curing is required an HNBR with a higher RDB is used, and vice versa.

The compositions of the invention may also include usual compounding ingredients such as active and/or inactive fillers, for example carbon black, calcium carbonate, silica, clay or talc, antioxidants, plasticizers, processing oils processing aids, waxes, antiozonants, antidegradants, ultra violet absorbers, co-agents, and the like.

The compositions of the invention find many applications including, for example in accessory drive belts such as alternator drive belts for automobiles and trucks, and also in seals particularly for low temperature applications.

The invention is further illustrated in the following examples.

EXAMPLES Example 1: Six runs were carried out, four comparative and two in accordance with the invention. In Run 1, an EPDM (BUNAO EP T 6470 (EPDM 847X) ) was the sole elastomer that was admixed and cured with zinc diacrylate (Sartomer@ 633) and peroxide curing agent (Vulcup0 40KE). Run 2 was identical, except that the sole elastomer was a hydrogenated nitrile rubber (TherbanS) C 3446). Run 3 was identical except that the sole elastomer was an HXNBR, which had a bound acrylonitrile content of 33wt% an acrylic acid monomer content of 5. Owt%, balance 1,3-butadiene, an RDB of 3.5% and a Mooney viscosity of 77 (ML 1+4'@100°C). Run 4 was identical, except that the elastomer was a 50: 50 mixture of BUNAO EP T 6470 (EPDM 847X) and Therban0 C 3446.

Runs 5 and 6 were in accordance with the invention. In Run 5 the elastomer was a mixture of 40 parts BUNA@ EP T 6470 (EPDM 847X) 40 parts Therban0 C 3446 and 20 parts of the HXNBR. In Run 6 the elastomer was a mixture of 50 parts BUNA@ EP T 6470 (EPDM 847X), 30 parts Therban0 C 3446 and 20 parts of the HXNBR. Compositions, mixing conditions and results in moving die rheometer, stress strain and Gehman low temperature stiffness tests are given in Table 1.

Table 1 RUN 1 2 3 4 5 6 BUNA) EP T 6470 100 50 40 50 (EPDM 847X) THERBANO C 3446 100 50 40 30 HXNBR 100 0 20 30 SARTOMERO 633 (SR 30 30 30 30 30 30 633) VULCUPO 40KE 5 5 5 5 5 5

Table 1 cont.

MIXING CONDITIONS MIXER : 6 X 12 inch Mill (Capacity: 1000) Set to 30oC MIXING INSTRUCTIONS : 0'-Band rubber. Make 3/4 cuts.

2'-slowly add"1 B" (SR633); make 3/4 cuts.

8'-slowly add"1 C"; make 3/4 cuts..

11'-remove and refine (6 passes).

MOVING DIE RHEOMETER (MDR) CURE CHARACTERISTICS 1.7 HZ 0. 5° arc 170°C, 30 min, 200 dNm MH (dN. m) 54.7 29.94 46.37 43.06 63.11 67.72 ML (dN. m) 0.9 0.62 1.46 0.73 1.03 1.14 Delta MH-ML (dN. m) 53.8 29.32 44.91 42.33 62.08 66.59 ts 1 (min) 0.96 0.92 1.02 0.99 1.08 1.12 t'50 (min) 2.18 2.40 1.44 2.34 2.17 2.18 t'90 (min) 8.26 9.54 4.58 9.03 7.83 7.50 STRESS STRAIN (DUMBELLS) Cure time at 170°C, (min) 15 17 12 16 15 15 Tested @ 23°C Stress @ 100 (MPa) 6.15 4.40 9.90 5.36 8.60 9.37 Stress @ 200 (MPa) 10.90 19.81 13.15 17.16 18.09 Stress @ 300 (MPa) 21.96 37.05 Ultimate Tensile (MPa) 12.04 29.13 38.75 19.52 21.97 20.35 Ultimate Elongation (%) 165 351 319 255 243 221 <BR> <BR> Hard. Shore A2 Inst. (pts. ) 69 67 79 72 81 82 GEHMAN LOW TEMP STIFFNESS Cure time @ 170OC (min) 15 17 12 16 15 15 Start Temperature :-60oC. <BR> <BR> <P>Temperature @ T2 (oC) -9-17-11-9-13-13<BR> Temperature @ T5 (oC) -25-22-17-22-22-23<BR> Temperature @ T10 (oC) -32-23-19-24-25-27<BR> Temperature @ T100 (oC) -60-30-41-39-55-60 In the moving die rheometer test it is noteworthy that in Runs 5 and 6 in accordance with the invention Delta MH-ML is high, which suggests that

crosslinking is occurring. In the stress strain tests it is noteworthy that the ultimate tensile strength, ultimate elongation and Shore hardness of the products of Runs 5 and 6 are markedly superior to that of EPDM alone, and in the Gehman low temperature stiffness test the products of Runs 5 and 6 are markedly superior to hydrogenated nitrile rubber alone. The products of the invention are superior in physical properties to EPDM alone and are superior in low temperature properties to hydrogenated nitrile rubber alone.

Example 2: Runs 7 to 10 were carried out in similar manner to Example 1, but using BUNA EP T 3950 (EPDM 585) as the EPDM. Run 7 is comparative, with the EPDM as the sole elastomer. Run 8 is comparative, the elastomer being a 50: 50 blend of the EPDM and TherbanG) C 3446, with no HXNBR.

Runs 9 and 10 are in accordance with the invention, Run 9 with 40 parts EPDM, 40 parts Therban@ C 3446 and 20 parts of the HXNBR and Run 4 with 50 parts EPDM, 30 parts Therban0 C 3446 and 20 parts of the HXNBR. The mixing conditions were the same as in Example 1. Compositions and results are given in Table 2.

Table 2 RUN 7 8 9 10 BUNA EPT 3950 100 50 40 50 (EPDM 585) THERBAN C 3446 50 40 30 HXNBR 0 20 20 SARTOMER 633 30 30 30 30 VULCUP 40KE 5 5 5 5 MDR CURE CHARACTERISTICS 1.7 Hz, 0. 5oarc, 170oC, 30 min, 200 dNm MH (dN. m) 66.07 44.53 65.13 69.75 ML (dN. m) 0. 53 0.80 0.80 Delta MH-ML (dN. m) 65.56 44.00 64.33 68.95 ts 1 (min) 1.13 1.08 1.16 1.21 t'50 (min) 3.48 2.83 2.53 2.60 t'90 (min) 10.85 10.43 8.90 9.06 Table 2 cont.

STRESS STRAIN (DUMBELLS) Cure Time at 170oC, (min) 18 17 16 16 Tested @ 23oC Stress @ 100 (MPa) 11.05 6.71 9.12 10.45 Stress @ 200 (MPa) 16.29 18.19 Stress @ 300 (MPa) Ultimate Tensile (MPa) 11.51 16.42 19.60 17.24 Ultimate Elongation (%) 103 201 213 170 Hard. Shore A2 Inst. (pts. ) 77 71 81 81 GEHMAN LOW TEMP STIFFNESS Cure time @170oC (min) 18 17 16 16 Start Temperature :-60oC Temperature @ T2 (oC) -30-20-17-18 Temperature @ T5 (oC)-34-24-24-25 Temperature @ T10 (oC) -36-26-27-30<BR> Temperature @ T100 (oC) -51-40-55-55