EP0713509A1 - Compatibilization of polar and nonpolar elastomer blends using functionalized ethylene/propylene copolymers or ethylene/propylene/diene terpolymers - Google Patents

Abstract

This invention relates to a compatibilized rubber composition and a process for compatibilizing polar/nonpolar rubber blends comprising blending functionalized EPDM or EP rubber with neoprene rubber and at least one nonpolar elastomer selected from the group including, but not limited to, EP and EPDM.

Description

COMPATIBILIZATION OF POLAR AND NONPOLAR ELASTOMER BLENDS USING FUNCTIONALIZED ETHYLENE/PROPYLENE COPOLYMERS OR ETHYLENE/PROPYLENE/DIENE TERPOLYMERS BACKGROUND OF THE INVENTION

1. FIELD OF INVENTION

This invention is related to co-pending application U.S. Serial No. 827,772, filed January 29, 1992. This invention relates to the field of compatibilization technology. In particular, this invention relates to the use of functionalized EP or EPDM rubbers such as carboxylated ethylene/propylene/copolymers, sulfonated or epoxidized ethylene propylene/diene terpolymers as compatibilizers for polar/nonpolar elastomer blends.

2. DESCRIPTION OF THE RELATED ART

A considerable amount of research has been made over the last several years with a view to obtaining new polymeric materials with enhanced specific attributes for specific applications or a better combination of different attributes. Much attention is currently being devoted to the simplest route for combining outstanding properties of different existing polymers, that is, formation of polymer blends. Although increasing numbers of miscible blends are reported in the literature [D.R. Paul et. al. , J. Macromol. Sci., Rev. Macromol. Chem., C- 18:109 (1980)], most polymers are nonetheless immiscible thus leading to heterophase polymer blends. In general, "compatibility (miscibility) is the exception, immiscibility is the rule" [Dobry and Boyer-Kawenski, J. Polymer Science, 2.(1), 90-100 (1947) ] .

There are two widely useful types of elastomer blends: single phase and two phase blends. The single phase blend is miscible. The term miscibility does not imply ideal molecular mixing but suggests that the level of molecular mixing is adequate to yield macroscopic properties expected of a single-phase material. The formation of two-phase elastomer blend is not necessarily an unfavorable event since many useful properties, characteristic of a single phase, may be preserved in the blend composition while other properties may be averaged according to the blend composition. Proper control of overall elastomer blend morphology and good adhesion between the phases are in any case required in order to achieve good mechanical properties. The elastomer blend components that resist gross phase segregation and/or give desirable blend properties are frequently said to have a degree of "compatibility" even though in a thermodynamic sense they are not "miscible". It should be emphasized that "compatibility" and "miscibility" are two different terms. Compatibilization means the absence of separation or stratification of the components of the polymeric alloy during the expected useful lifetime of the product (Gaylord, N.G., in "Copoly ers, Polyblends and Composites", Advances in Chemistry Series 142, American Chemical Society: Washington, D.C., 1975, p. 76). "Technological compatibilization", according to Coran and co- workers [Rubber Chem. Technol. , 56, 1045 (1983)] is "the result of a process or technique for improving ultimate properties by making polymers in a blend less incompatible; it is not the application of a technique which induces "thermodynamic compatibility", which would cause the polymers to exist in a single molecularly blended homogeneous phase".

It is well established that the presence of certain polymeric species, usually block or graft copolymers with the right structure, can indeed result in compatibilization of an immiscible elastomer blend because of their ability to alter the interfacial situation. Such, species as a consequence, are often referred to as

"compatibilizers" or "interfacial agents" which is analogous to the term "solubilization used in the colloid field to describe the effect surfactants have on the ability to mix oil and water (McBain et. al., "Solubilization and Related Phenomena", Academic Press, New York, 1955). Such "compatibilizers" can be either preformed and added to the binary blend or formed "in situ" during the blending process. The role of the compatibilizer in an elastomer blend is manifold: (1) reduce the interfacial energy between the phases, (2) permit a finer dispersion during mixing, (3) provide a measure of stability against gross segr gation, and (4) result in improved interfacial adhesion (G.E. Molau, in

"Block Copolymers", Ed by S.L. Agarwal, Plenum, New York, 1970, p. 79) . Two elastomers form a compatible mixture when they have at least one of the following characteristics: o Segmental structural identity. For example, a graft or block copolymer of butadiene and styrene is compatible with either polybutadiene or polystyrene, o Miscibility or partial miscibility with each other. Solubility parameter (<S) difference < 1, generally < 0.2 units. For example, poly (vinyl chloride) , PVC, poly (ethylacrylate) , PEA, poly (methylacrylate) , PMMA, have solubility parameters in the 9.4-9.5 range and form compatible mixtures. Although, the structure of nitrile rubber, NBR is entirely different from those of PVC, PMMA, PEA, it has a similar solubility parameter 9.5 and is compatible with these three polymers, o Functional groups capable of generating covalent, ionic, donor-acceptor or hydrogen bonds between the polymers. Compatibilization of dissimilar elastomer blends is an area of active interest from both technological and scientific points of view. Many of the synthetic and natural elastomers have good properties that when combined with other rubbers of similar or complementary properties may yield desirable traits in the products.

Neoprene or polychloroprene rubber (CR) has been the material of choice in most power transmission belts, due to its unique combination of properties: oil resistance, toughness, dynamic flex life, good adhesion to other materials and heat resistance up to 100°C. In the past, CR belts have kept pace with the needs of the automotive industry, but recently there is a need for new materials for more demanding applications. First of all, CR belts are encountering greater heat duress in service due to increasing underhood temperatures (up to 150°C) . Secondly, to meet automotive industry's longer warranty periods ("100,000 mile target"), the CR belts must have a lower failure rate with high mean life, even when high temperatures are not encountered. To meet these emerging needs, improvements in heat, ozone, and cut growth resistance of neoprene belts are desirable. The above requirement for neoprene belts could be satisfied by blending with polyolefin elastomers such as ethylene/propylene rubber (EP) or ethylene/propylene/diene terpolymer (EPDM) which have better heat/ozone and cut growth resistance. As such, however, these neoprene/EPR or EPDM blends are incompatible.

It is known in the art that the resistance of cured unsaturated elastomers such as polybutadiene or 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 co-vulcanizing the blend. This development takes advantage of the inherent resistance of the olefin/diene terpolymer to chemical attack and imparts this property into co- vulcanized blend. However, the use of olefin/diene terpolymers 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 co-vulcanized because of the high availability of sites of ethylenic unsaturation, other elastomers such as polychloroprene, and like materials containing polar groups along the chain and/or a relatively low degree of ethylenic unsaturation are not so readily co-vulcanized. 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 co-vulcanizate as compared with the cured elastomer itself.

Thus, it would be of great importance to the art if a compatibilizer for polar/nonpolar rubber blends such as CR/EPDM, CR/EP could be found. Use of functionalized EP or EPDM such as sulfonated EPDM, epoxidized EPDM and carboxylated EP as a compatibilizer for polar/nonpolar rubber blends is not known.

Use of a maleated EPDM as a modifier for polymer blends is known (see U.S. Patent No.

4,508,411 to Kinoshita) . As a modifier is not necessarily a compatibilizer, the use as a modifier means that the blend produced is binary rather than the preferred ternary blend produced by compatibilization. Modifiers can improve tack and typically improve dynamic properties at room temperature. Indeed, modifiers tend to behave much like plasticizers or lubricants. Compatibilizers, on the other hand, have the ability to alter the interfacial situation of an incompatible blend which results in synergistic improvement of blend properties at both room temperatures and at high end use temperatures. The eff<- t of compatibilizers is similar to that of surfactants having the ability to mix oil and water which is often referred to as "emulsification effect" in the field of colloids. The role of the compatibilizer in an elastomer blend is manifold: (1) reduce the interfacial energy between the phases, (2) permit a finer dispersion during mixing, (3) provide a measure of stability against gross phase segregation, and (4) result in improved interfacial adhesion.

U.S. Patent No. 4,397,987 to Cornell discloses Maleated EPDM as a modifier for nitrile rubber. In addition, U.S. Patent 4,307,204 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 copoly er containing at least about 50 mole percent acid functional groups, which groups are at least 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. None of the aforementioned disclosures addresses the development of compatibilized polychloroprene/EPDM or EP which not only exhibit improved resistance to ozone or oxygen attack and improved heat stability, but also exhibit a retention and in some cases improvement of important physical properties such as tensile strength, elongation, modulus and resistance to abrasion at room and end use temperatures. SUMMARY OF THE INVENTION A new family of compatibilizers for polar/nonpolar elastomer blends is disclosed herein. EPDM or EP modified with different functional groups, particularly carboxylated or sulfonated or epoxidized EPDM or EP have been found to compatibilize polar/nonpolar elastomer blends, including, but not limited to, neoprene/EPDM or EP by improving the overall properties of the said blends. The present invention provides for neoprene/EPDM or EP blend compositions and vulcanizates thereof having improved heat, ozone and cut growth resistance comprising: a compatibilized blend of neoprene/EPDM (or EP) , and 1 to about 15 phr of a functionalized EPDM or EP particularly maleated or sulfonated or epoxidized ethylene/propylene/diene terpolymers or ethylene/propylene copolymers. The blends of this invention may be readily co-vulcanized and formed into shaped, heat, ozone, cut growth and oil resistant articles such as automotive drive belts and automotive hoses which not only exhibit improved heat, ozone and cut growth resistance but also have retained or enhanced physical properties such as abrasion resistance, modulus, elongation and tensile strength.

The functionalized EPDM or EP, particularly, EP-MA, EPDM-Epoxy, and EPDM-Sulfonate of this invention, are excellent compatibilizers for neoprene rubber and ethylene/propylene rubber (CR/EP) blends, and neoprene rubber and ethylene/propylene/diene (CR/EPDM) blends.

The compatibilizers of this invention comprise EPDM or EP rubbers modified with functional groups selected from the group consisting of α, β- unsaturated carboxylic acids and anhydrides thereof, epoxy or sulfonic acid and derivatives thereof. "MA" is herein defined to include maleic acid and maleic anhydride. The EPDM is a random copolymer of ethylene/propylene/and a diene, where the ethylene is present at 35-80 wt. %, and the diene is present at 0 to 15 wt.%, based upon the weight of the copolymer. The EPDM polymer can be produced by the well known Zeigler-Natta polymerization method. The dienes useful in producing EPDM copolymers are typically 1,4-hexadiene, cycloalkylidene norbornenes, etc. The EP or EPDM is then typically grafted by any process known in the art with maleic acid, maleic anhydride, or other , β-unsaturated mono- or dicarboxylic acids or anhydrides thereof, or epoxidized or sulfonated following known literature procedures.

The rubbers and the compatibilizer may be blended, formed, or otherwise mixed by any one of a number of suitable methods.

The rubbers useful in this invention include: ethylene/propylene rubber, (EP) , ethylene/propylene/diene terpolymer, (EPDM) , polychloroprene, (neoprene or CR rubber) , butadiene rubber (BR) , styrene/butadiene rubber (SBR) , natural rubber (NR) , and polyisoprene rubber (IR) , butyl, halobutyl, poly(isobutylene-co-4-methyl styrene), and brominated poly(isobutylene-co-4-methyl styrene) rubber. The EP rubbers useful in this invention are random copolymers of ethylene and propylene where the copolymer has an ethylene content of 30 to 85 wt.%, based upon the weight of the copolymer. The EP copolymer can be produced by the well known Zeigler-Natta polymerization method.

The EPDM Rubbers to be compatibilized in this invention are random copolymers of ethylene/propylene/ and a diene, where the ethylene is present at 35-80 wt.%, and the diene is present at 0 to 15 wt.%, based upon the weight of the copolymer. The EPDM polymer can be produced by the well known Zeigler-Natta polymerization method. The dienes useful in producing EPDM copolymers are typically 1,4-hexadiene, alkylidene norbornenes, etc.

The neoprene rubbers useful in this invention are polymers of chloroprene. These can be produced by the well known free radical polymerization method.

In particular, the functionalized EPDM or EP rubbers of this invention are useful for compatibilizing Neoprene/EP and neoprene/EPDM blends. DETAILED DESCRIPTION OF THE INVENTION

This invention provides a process for compatibilizing rubber blends comprising blending a functionalized EP or EPDM with two or more different rubbers. Preferably this invention relates to a process for compatibilizing polar/nonpolar rubber blends comprising:

Blending a functional group grafted EPDM, or EP wherein the functional groups are MA, SO₃ and Epoxy with two or more polar and nonpolar synthetic or natural rubbers. More preferably this invention relates to a process for compatibilizing polar/nonpolar rubber blends comprising blending two or more polar and nonpolar natural or synthetic rubbers, with a modified EP or EPDM wherein the modification includes maleation, sulfonation and epoxidation.

This invention further relates to compatibilized compositions of polar and nonpolar rubbers, and a functionalized EPDM or EP. In particular, this invention relates to compatibilized rubber blends comprising a functionalized EPDM or EP wherein the functional groups, preferably are MA, sulfonic acid or epoxy group; at least one polar rubber and at least one nonpolar rubber. In essence, this invention provides a new approach for compounding rubber blends using functionalized, particularly maleated, EP copolymer or EPDM terpolymer as the compatibilizer. The inventors have found that these functionalized EP copolymer or EPDM terpolymers are excellent agents for compatibilizing neoprene/ethylene-propylene rubber and neoprene/ethylene-propylene-diene blends The particular maleated EP or EPDM rubbers useful as compatibilizers in the present invention include those manufactured and sold by EXXON CHEMICAL CO. under the name trade name Exxelor VA 1801 and Exxelor VA 1803.

The compatibilizers of this invention comprise functionalized EP or EPDM. The term EPDM or EP as used herein, unless otherwise indicated, includes terpolymers, tetrapolymers, etc., preferably of ethylene, and a C₃-C₂₈ alpha-olefin, typically propylene, 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-olefin 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-1,4-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- cyclo-hexadiene; 1, 5-cyclooctadiene; 1,5-cyclo- dodecadiene; 4-vinylcyclohexene; 1-allyl, 4- isopropylidene cyclo-hexane; 3-allyl-cyclopentene; 4-allyl cyclohexene and l-isopropenyl-4-(4-butenyl) cyclohexane. d. Multi-single ring alicyclic dienes such as: 4,4 ^■-dicyclo-pentenyl and 4, 4 '-dicyclohexenyl. 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, cycloalkenyl and cycloalkylidene norbornenes such as: ethylidene norbornene; 5-methylene-6- methyl-2- norbornene; 5-methylene-6, 6-dimethyl-2-norbornene; 5-propenyl-2-norbornene; 5-(3-cyclo-pentylidene)-2- norbornene and 5-cyclohexylidene-2-norbornene; 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. Synthesis of EPDM is well known in the art. G. ver Strate, Encyclopedia of Polymer Science and

Engineering, vol. 6, 2nd Ed., 1986, p. 522-564.

To produce the compatibilizers of this invention, the EP or EPDM is grafted with a functional group, typically an acid group, wherein t-tiB functional group may be selected from carboxylic acids (such as maleic acid, fumaric acid, citraconic acid, itaconic acid, acrylic acid, methacrylic acid, himic acid, etc. ... and anhydrides thereof, preferably maleic acid or maleic anhydride) , sulfonic acids and epoxy groups.

The term "carboxylated" as used herein refers to EP or EPDM 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 EP or EPDM with an unsaturated mono or dicarboxylic acids and derivatives thereof, can be carried out in the presence of a free radical source. The EP or EPDM 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 EP or EPDM, 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 EP or EPDM. Suitable unsaturated mono or polycarboxylic acids and derivatives thereof include maleic acid, maleic anhydride, fumaric acid, citraconic anhydride, aconitic anhydride, itaconic anhydride, the half or full esters derived therefrom, such as methyl, ethyl, dimethyl maleate, dimethyl fumaratte, 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 on the order of about 1 minute to about 2 hours. The reaction of the EP or EPDM can be carried out in an extruder or a Banbury mixer. This process can be used for EP or EPDM 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 EP or EPDM 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 EP or EPDM. Polymers prepared by copolymerization of ethylene and such acid monomers are disclosed in US Patent 3264272.

The preferred method for preparing the carboxylated EP or EPDM for the purposes of this invention is to graft 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 EP or EPDM 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 EP or EPDM polymer. The carboxylated EP or EPDM 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 up to about 90,000, as measured by Gel Permeation Chromatography (GPC) . The EPDM-Epoxy, one of the compatibilizers of this invention can be obtained either by direct epoxidation of the unsaturation sites of the EPDM or by grafting a monomer containing an epoxy groups on to EPDM. The use of the term epoxy group hereinafter includes epoxies obtained by either method. Details of these synthetic techniques to prepare EPDM-Epoxy are well known in the art, as disclosed in U.S. Patent Nos.: 4,156,061, 3,842,010, 3,448,174, 3,330,794. In a typical example, the EPDM terpolymer (Vistalon 7000) was reacted with meta- chloroperoxybenzoic acid in toluene solution for six hours and the reaction product was isolated by diluting the reaction mixture with isopropyl alcohol, collecting the precipitated polymer and then drying in a vacuum oven. The presence of epoxy group in the reaction product was confirmed by analyzing the FTIR spectrum for the absorption band at 857 cm^-1 which was characteristic of an epoxy group.

The sulfonated elastomeric polymers which are preferred for the purpose of this invention are water insoluble and include sulfonated terpolymers of ethylene, propylene and a diene, preferably non- conjugated diene (EPDM) . The water insoluble sulfonated polymers of the instant invention will comprise from about 4 to about 200 milli equivalents of pendant sulfonate groups per 100 grams of polymer, more preferably from 10 to 100 meq. pendant sulfonate groups. The sulfonated elastomers utilized in the instant invention are neutralized with elements from Groups I?, and IIA and with transition elements selected from Groups IVB, VB,

VIB, VIIB, VIIIBA, IB, and IIB of the Periodic Table of Elements and lead, tin, and antimony, as well as ammonium and amine counterions. Zinc and sodium neutralizing ions (as ionic salts, e.g., acetate or hydroxide) are preferred. Neutralization of the cited polymers with appropriate metal hydroxides, metal acetates, metal oxides or ammonium hydroxide, etc. can be conducted by means well known in the art. The sulfonated elastomers of the instant invention may vary in number average molecular weight from 1,000 to 10,000,000 preferably 5,000 to 1,000,0000 most preferably from 10,000 to 600,000. These polymers may be prepared by methods known in the art, for example, see U.S. Patent No. 3,642,728, incorporated herein by reference.

The most preferred sulfonated polymers for use in the instant invention are sulfonated ethylene/propylene terpolymers which may be prepared by the procedures described in U.S. Patent Nos. 3,870,841 and 4,119,616 incorporated herein by reference. The rubbers which can be compatibilized using these terpolymers, include, but are not limited to ethylene/propylene rubber, neoprene, nitrile rubber, ethylene/proprylene/diene terpolymers, SBR, Butyl, halobutyl, poly (isobutylene-co-4-methylstyrene) , brominated poly (isobutylene-co-4-methyl styrene) , natural rubber and the like.

The term EPDM or EP as used herein, unless otherwise indicated, includes terpolymers, tetrapolymers, etc. , preferably of ethylene, and a ^c ₃~^c ₂₈ alpha-olefin, preferably propylene 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 7 wt. percent, based on the total amount of ethylene and alpha-olefin 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-1, 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- cycl-hexadiene; 1,5 cyclooctadiene; 1,5-cyclo- dodecadiene; 4-vinylcyclohexene; 1-allyl, 4- isopropylidene cyclo-hexane; 3-allyl-cyclopentene; 4-ally cyclohexene and l-isopropenyl-4-(4-butenyl) cyclohexane. d. Multi-single ring alicyclic dienes such as: 4,4"-dicyclo- pentenyl and 4,4" -dicyclohexenyl. 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, cycloalkenyl and cycloalkylidene norbornenes such as: ethylidene norbornene; 5-methylene-6- methyl-2- norbornene; 5-methylene-6, 6-dimethyl-2-norbornene; 5-propenyl-2-norbornene; 5-(3-cyclo-pentylidene)-2- norbornene and 5-cyclohexylidene-2-norbornene; 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. Synthesis of EPDM is well known in the art. G. ver Strate, Encyclopedia of Polymer Science and Engineering, vol. 6, 2nd Ed., 1986, p. 522-564.

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. Neoprene synthesis is also well known in the art. C. A. Hargraves et al. , Encyclopedia of Polymer Science and Technology, vol. 3, p. 705-730. As indicated above, the polychloroprene 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 30 to 90% 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 other polar rubbers.

The vulcanizable composition of the present invention also includes a conventional mixed vulcanizing system for EP or EPDM and polychloroprene. 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 elastomers blend composition of this invention 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- εtyrene resin, coumarone-indene resin, phenolic resins, lignin, modified elamine 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 Ticinoleic 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 naphthenic oils, phthalic acid esters, adipic acid esters, sebacic acid esters and phosphoric acid-type plasticizers. Examples of tackif.. ars 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'- dinitrosopenta- methylenetetramine, azocarbonamide, azobis-isobutyronitrile, benzeneεulfonyl hydrazide, toluenesulfonyl hydrazide, calcium amide, p-toluenesulfonyl azide, salicyclic acid, phthalic acid and urea. The compatibilized elastomers blend composition of this invention, may be prepared and blended on any suitable mixing device such as an internal mixer (Brabender Plasticorder) , a Banbury Mixer, an extruder, a kneader or a similar mixing device. The EP or EPDM rubber to be compatibilized is typically present at about 1JD to 9_0 phr, more preferably 1_.5 to 5_.0 phr, most preferably 2_0 to ____0_ phr. The modified EPDM or EP is typically present at .1 to 60 phr, more preferably 5 to 30 phr, most preferably 5 to 20 phr. The CR is typically present at 10 to £0 phr, preferably 30 to 80 phr, more preferably 4_0 to 7_0 phr (phr meaning parts per hundred rubber) .

Blending temperatures and times may range from about 45 to 180°C and from about 1 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 including but not limited to belts, hoses, air springs & power transmission belts are prepared by shaping the prevulcanized formulation using an extruder or a mold, and subjecting the composition to temperatures and curing times as set forth above.

The materials utilized in the examples are described below: (A) Neoprene (CR) GRT is a polychloroprene made by DuPont.

(B) Vistalon 7000 (abbr. V 7000) is a fast curing, high diene ethylene-propylene terpolymer (EPDM) , available from EXXON CHEMICAL COMPANY, with a Mooney viscosity ML(1+4) @ 125°C of 60 and an ethylene content of 70 wt. %.

(C) EXXELOR VA 1801 is maleated EP rubber with ethylene content of 77 wt.%, melt flow rate: 9 g/10 minutes (10 Kg load at 230°C) and maleic anhydride content of 1 0.7 wt.%.

(D) N650 and N762 are two well known, general purpose, moderately reinforcing carbon blacks. They are standard as defined by ASTM D 1765-89 and are manufactured by a number of different companies including: Continental Carbon, J. M. Huber,

Phillips Chemical, Columbian Chemicals, Cabot, and Ashland Chemical.

(E) Sundex 790 is a standard aromatic processing aid (oil) used for compounding of a variety of rubbers: NR, SBR, CR, IIR, BR, EP, EPDM. Similar to the carbon blacks, it is manufactured by a number of companies: Harwick, Matrochem, R. E. Carroll.

(F) Octa ine is an antioxidant used primarily with CR, NR, and SBR. It gives excellent protection against heat, oxygen, and flexing. Chemically, it is a reaction product of diphenyl-amine and diisobutylene. It is manufactured by Uniroyal Chemical.

(G) AgeRite HP-S is an antioxidant used in rubber compounding (similarly to Octamine) . It is a blend of dioctylated diphenylamines and diphenyl-p- phenylene-diamine and is manufactured by R. T. Vanderbilt.

(H) Maglite D is a magnesium oxide, which is used as a curing agent in our compound. It is manufactured by CP. Hall and Merck Chemical.

The foregoing more general discussion this invention will be further exemplified by the following specific examples offered by way of illustration and not limitation of the above- described invention.

The testing conditions and procedures used are set forth in Table 1 below.

TABLE 1

Testing

Test Conditions Procedure

1. Mooney Viscosity (1+8)§100'C ASTM D 1646 (ML)

2. Mooney Scorch 132*C ASTM D 1646 (MS)

3. Oscilating Disk Rheometer (O K) 160'C ASTM D 2084-88

+3* arc

No preheat

100 cycles/min

30 min rotor . Procedures for Pads Cured for ASTM D 3182-89 mixing standard 20 min § 160*C compounds and preparing standard vulcanized sheets

5. Modulus, Tensile, Elongation ASTM D 412

6. Hardness (Durometer) Shore A ASTM D 2240

7. Air Oven Age 140'C for 48 ASTM D 573

96 hr.

8. Static Ozone Bent Loop ASTM D 1149-86 Resistance 100 pphm ozone

37.8'C

9. Dynamic Ozone 100 pphm ozone ASTM D 3395-86 Resistance 37.8*

Methe A

30 cycles/min

0-25% extension

10. Dynamic Crack 120'C flex ASTM D 813-87 Growth angle (De Mattia)* Room temp.

90*C flex angle

100'C

♦Specimens cured 25 min§160*C

11. Tel-Tak 24 oz.,60 sec, Instruction

Room temp. Manual

Monsanto Tel-Tak Tester, July 1969

12. Melt Flow Rate (10kg 230*C) ASTM D 1238

13. Density ASTM D 792 - 26 -

;0

.0

EXAMPLES I Example 1

In an internal mixer (Banbury Intensive Mixer) were charged 100 parts polychloroprene (neoprene GRT) and all other ingredients listed in Table 2 Example 1 except for t " magnesium oxide and zinc oxide curing agents. T\e temperature of the mixture was maintained at 100°C - 120°C and mixing was continued for a period of about 5 minutes. This intensive mixing included 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 elasto eric 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 0.075 inch mold and cured at a temperature of about 160°C for a period of 20 minutes. The property evaluation of the molded samples were done using standard test procedures shown in Table 1. Example 2

The process of Example 1 was repeated except that the elastomer composition consisted of a mixture of 70 parts polychloroprene and 30 parts EPDM (V7000) . All other ingredients are as set forth in Table 2, Ex. 2. Example 3 The process of Example 1 was repeated except that the elastomer composition consisted of a mixture of 70 parts polychloroprene, 30 parts EPDM and 10 parts EP-MA (EXXELOR VA 1801) the compatibilizer of this invention. Other ingredients are set forth in Table 2, Ex. 3.

As can be seen from the data included in Table 2, the beneficial effects of compatibilization of CR/EPDM/EP-MA (EXXELOR VA 1801), 70/30/10 alloys is evident in terms of significant improvements in heat ageing (both tensile strength and elongation change) , ozone resistance, cut growth resistance and other physical properties. Addition of just EPDM alone (i.e., Ex 2 in Table 2) decreased the tensile, and elongation, because of incompatibility of CR and EPDM. However, adding small amounts (10 parts by weight) of the compatibilizer of this invention, EXXELOR VA 1801, helped to bring these properties back up. In other words, the physical properties of the compatibilized blend (Ex. 3 in Table 2) are generally superior both before and after exposure to heat, compared with that of the non-compatibilized blend (Ex. 2 in Table 2) . Addition of EPDM to neoprene, in general, improved the ozone resistance. However, addition of the compatibilizer of this invention, EXXELOR VA 1801, to CR/EPDM, 70/30 blend, (Ex. 3 in Table 2) improved further the ozone resistance, specifically the dynamic ozone resistance. In the cut growth resistance tests, the compatibilized blend (Ex. 3 in Table 2) had vast improvement (lower the numerical value, the better) compared with that of neoprene (Ex. 1 in Table 2) and the binary blend (Ex. 2 in Table 2) . This is a key property for power transmission belt application.

- B O -

II Neoprene GRT/EPDM/Epoxy EPDM or Sulfonated EPDM Blends

Examples 1 through 5 The procedure for this study used the same ratio of curing agents, antioxidants and stearic acid, but excluded the fillers, carbon black and oil from a typical compounding recipe (Table 2) for neoprene belts application as discussed earlier. The blends (Table 3) were compounded with antioxidants and stearic acid in a small scale (45 cc) C. . Brabender at 110°C for 5 minutes. The blended material was cooled to 50°C and the curing agents (Maglite D and zinc oxide) were added and mixed for an additional 5 minutes. The accelerated material was then cured by placing it into a mold and pressing for 20 minutes at 160°C. Tensile dumbbells were died out from the material; the tensile properties at room temperature, heat ageing, and dynamic ozone resistance were measured. The results are included in Table 3.

The beneficial effect of adding small amounts of these functionalized EPDM (both Epoxy EPDM and sulfonated EPDM SO3) was evident in terms of significant improvements in tensile properties

(tensile, % elongation) , heat ageing and dynamic ozone resistance. In the case of EPDM-Epoxy, the results .clearly indicated that there was no need to replace V 7000 completely by V 7000- Epoxy to improve the heat ageing and ozone resistance of

Neoprene in Neoprene/EPDM blends. A small amount (10 wt.%) of the V 7000 Epoxy was sufficient to bring out the synergistic effect in the properties of the above blends. It was even better in the case of sulfonated EPDM, - as shown in Table 3, example 5, 5 wt.% of sulfonated EPDM was all that was needed to improve the properties of Neoprene/EPDM blends.

These results were in agreement with our previous findings, - improved compatibility of Neoprene/EPDM/EP-MA blends. It is reasonable to extrapolate these results to other, similar functionalized EPDM which, in theory, could act as compatibilizers for Neoprene/EPDM blends. Such functionalized EPDM can be: EPDM-Amine, EPDM- Hydroxy, EPDM-SH, EPDM-C0₂H.

TABLE 3

Sulfonated EPDM 05 Physical Properties Cure 20 Min.. 160°C Tensile MPa 16.2 Elongation % 278 Heat Aaed. 48 Hr. , 148"C Tensile MPa 4.8 Elongation % 278 Dynamic Ozone Resistance 100 ppm 0₃, 37.8°C 0-25% Extension

30 Cycle/Min. ,

Hours to Crack 144 168 >500 336 >500

Note: All blends contained the curing agents and antioxidants: Maglite D = 4 phr, Zinc Oxide = 5 phr, Steric Acid = 2 phr, Octamine = 2.5 phr, Agerite HPS = 0.5 phr

It is apparent from the foregoing description, the materials prepared and the procedures followed relate to specific embodiments of the broad invention. It is apparent from the foregoing general description and the specific embodiments that, while forms of the invention have been illustrated and described, various modifications can be made without departing from the spirit and scope of this invention. Accordingly, it is not intended that the invention be limited thereby.

Claims

IN THE CLAIMS

What is claimed is: 1. A process for compatibilizing rubber blends comprising polar and non-polar elastomers said process comprising: blending an EPDM modified by a sulfonate or an EPDM or EP modified with functional groups selected from the group consisting of , β-unsaturated carboxylic acids, anhydrides of , -unsaturated carboxylic acids, or epoxies with at least one polar elastomer and at least one nonpolar elastomer. 2. The process of claim 1 where the polar elastomer is polychloroprene and the nonpolar elastomer is selected from the group consisting of ethylene-propylene rubber and ethylene-propylene- diene rubber. 3. The process of claim 1 wherein the functional group of the modified EPDM or EP is present from 0.1 to 10 wt%, based upon the weight of the modified EP or EPDM. 4. The process of claim 1 wherein the functional group is selected from the group consisting of α, β- unsaturated mono- or dicarboxylic acids or anhydrides thereof. 5. The process of claim 4, wherein the functional group is maleic acid or maleic anhydride. 6. The process of claim 1 wherein the functional group of the modified EPDM or EP is an epoxy group. 7. The process of claim 6, wherein the epoxy group is glycidyl methacrylate. 8. The process of claim 1 wherein the functional group of the modified EPDM is a sulfonic acid group or a derivative thereof. 9. The process of claim 8, wherein the functional group is a zinc or sodium salt of a sulfonic acid. 10. The process of claim 1 wherein the functionalized EPDM or EP is present in the blend from 1 to 65 phr. 11. The process of claim 1 wherein the functionalized EPDM or EP is present from 5 to 20 phr. 12. A compatibilized blend comprising at least one polar elastomer (a) and at least one nonpolar elastomer (b) and a functionalized EPDM or EP rubber (c). 13. The composition of claim 12 where the polar elastomer is neoprene rubber and the nonpolar elastomer is selected from the group consisting of ethylene-propylene rubber and ethylene-propylene- diene rubber. 14. The compatibilized rubber blend of claim 12 wherein the polar elastomer is polychloroprene, the non-polar elastomer blend is EP or EPDM. 15. The composition of claim 14 wherein the polychloroprene is present from about 10 to about 90 phr. 16. The composition of claim 14, wherein the polychloroprene is present from about 30 to about 80 phr. 17. The composition of claim 14, wherein the polychloroprene is present from about 40 to about 70 phr. 18. The composition of claim 14 wherein the EP or EPDM rubber (B) is present frora about 10 to about 90 phr. 19. The composition of claim 14 wherein the EP or EPDM rubber (B) is present from about 15 to about 50 phr. 20. The composition of claim 14, wherein the EP or EPDM rubber (B) is present from about 20 to about 40 phr. 21. The composition of claim 14 wherein the functionalized EP or EPDM (C) is present from about 0.1 to about 60 phr. 22. The composition of claim 14 wherein the functionalized EP or EPDM (C) is present from about 5 to about 30 phr. 23. The composition of claim 14 wherein the functionalized EP or EPDM (C) is present from about 5 to about 70 phr. 24. The composition of claim 14 wherein the EP or EPDM is functionalized with an a , /3-unsaturated carboxylic acid. 25. The composition of claim 4 wherein the EP or EPDM is functionalized with α, /3-unsaturated carboxylic acid derivatives such as anhydrides, etc. 26. The composition of claim 14 wherein the functionalized EPDM is epoxidized EPDM. 27. The composition of claim 14 wherein the functionalized EPDM is sulfonated EPDM. 28. The composition of claim 14 wherein the EP or EPDM is functionalized with an acid. 29. The composition of claim 14 further comprising carbon black. 30. The composition of claim 12, formed into an article. 31. The composition of the claim 12 formed into a power transmission belt, tire portion, hose or air spring.