CA1124917A - Elastoplastic blends of cured olefin rubber and polyolefin resin - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

There are disclosed novel thermoplastic elatomeric compositions comprising blends of olefin rubber and polyolefin resin in which the rubber is cured with phenolic curative.
These compositions exibit superior properties including improved compression set and oil resistance. and are useful for making a variety or articles such as tires, homes, moldings, etc.

Description

~3-1002A 11~4~i7 THERMOPLASTIC ELASTOMERIC BLENDS OF
OLEFIN RUBBER AND POLYOLEFIN RESIN
This application relates to thermoplastic elastomeric compositions comprising blends of polyolefin resin and cured olefin rubber.
BACKGRO~ND OF THE INVENTION
It is known that curing EPDM rubber with phenolic curative gives good mechanical properties but, as predicted by Hoffman, infra, the curing of EPDM rubber with phenolic curative has not been accepted commercially.
Thermoplastic elastomeric (elastoplastic) compositions consisting of blends of polyolefin resin and cured EPDM rubber exhibiting superior physical properties including improved tensile strength, are known. Belgium patent 844,318 issued January 20, 1977, and Canadian Patent Application 257,371, filed July 20, 1976. The aforesaid improved compositions are economically attractive because they may be extended with extender oil and carbon black which additives improve properties including processibility and oil resistance while lowering the cost. However, compositions exhibiting better oil resistance are needed to meet high performance specifications where exposure to organic so-vents or oil at high temperature is encountered. Surprisingly, blends of polyolefin resin and EPDM
rubber cured with phenolic curative exhibit superior properties including superior oil resistance as compared with blend com-positions which are identical except for the EPDM rubber being cured with other curatives.
SUMMARY OF THE INVENTION

In accordance to this invention, it has been found that elastoplastic compositions comprising polyolefin resin and EPDM
rubber in which the rubber is cured with phenolic curative are

-2-~,`

1124~7 tough, strong, elastomeric compositions processable as thermoplastics and have improved properties as compared to blends of similar composition but in which the rubber is cured with sulfur or peroxide curatives. Compositions of the inven-tion exhibit improved oil resistance and compression set and articles made thereof have smoother surfaces free of bloom (surface haze). The use of phenolic curative reduces objec-tional odor during manufacture and processing and gives more pleasantly scented products. Compositions of the invention are more easily processed especially in extrusion processes and also exhibit improved paintability, i.e., the surfaces provide better adherance for paint. These and other advantages will become apparent as the description of the invention proceeds.
Elastoplastic compositions of the invention are com-positi~scomprising blends of (a) thermoplastic crystalline polyolefin resin, in an amount sufficient to impart thermo-plasticity to the composition, and (b) cured EPDM rubber, in an amount sufficient to impart rubberlike elasticity to the composition, in which the rubber is cured with phenolic curative to the extent that no more than about five percent of the rubber is extractable in boiling xylene. The relative proportions of polyolefin resin and EPDM rubber are not subject to absolute delineation because the limits vary due to a number of factors including type, molecular weight, or molecular weight distribu-tion of the polyolefin resin or EPDM rubber and are dependent upon the absence or presence of other ingredients in the composi-tion. For example, inert fillers such as carbon black or silica tend to reduce the operative range, whereas, extender oil and plasticizers tend to increase the range of operative proportions.
Typically, the compositions may comprise blends of rubber in an amount below about 75 parts by weight and resin in an amount above about 25 parts by weight per 100 parts total weight of resin and rubber. Generally, the compositions comprise blends

-3-~i249i7 of (a) about 25-75, preferably 30-70 parts by weight of thermo-plastic crystalline polyolefin resin and (b) about 75-25, pre-ferably 70-30 parts by weight of EPDM rubber per 100 total parts by weight of polyolefin resin and rubber. Preferred composi-tions contain polyolefin resin in amounts not exceeding 50 weight percent of the total composition.
The EPDM rubber is fully cured in the compositions of the invention. A convenient procedure for evaluating the state of cure consists of determining the amount of rubber soluble in cyclohexane. The rubber is regarded as fully cured when it is cured to the extent that no more than about three percent of the rubber is extractable in cyclohexane at 23C. The procedure which takes into account the presence of soluble ingredients other than rubber will be described in greater detail later. An alternative means for evaluating the state of cure consists of determining the amount of rubber soluble in boiling xylene.
The rubber is regarded as fully cured when it is cured to the extent that no more than about five percent of the rubber in the blend is extractable in boiling xylene, preferably, no more than about three percent, more preferably, no more than about one percent of the rubber is extractable in boiling xylene. It should be appreciated that the compositions of the invention con-sist essentially of blends of polyolefin resin and cured EPDM
rubber and contain negligible amounts, if any, of grafted co-polymer of polyolefin resin and EPDM rubber. Accordingly, the compositions of the invention should not be confused with the graft copolymers described in Hartman, U.S. patents 3,862,056 and 3,909,463. The absence of graft copolymer is confirmed in the com-positions of the invention because the cured EPDM rubber is essen-tially insoluble in boiling xylene and thereby can be separatedfrom the polyolefin resin in the blend whereas, the Hartman graft copolymers are essentially completely soluble in boiling xylene.

~, ~124'9i7 In the preferred compositions of the invention, essentially all of the polyolefin resin is soluble but no more than about three percent, of the rubber is extractable in boiling xylene. Infrared analysis of the isolated polyolefin resin fraction (soluble in boiling xylene but insoluble in xylene at room temperature) show it to be essentially free of grafted EPDM rubber with less than about two weight percent of grafted EPDM rubber being present.
Vulcanizable rubbers, although thermoplastic in the uncured state, are normally classified as thermosets because they undergo the irreversible process of thermosetting to an unprocessable state. The products of the instant inven-tion, although processable, contain irreversibly thermoset rubber (although of quite small particle size) because they can be prepared from blends of rubber and polyolefin resin which are treated with phenolic curatives in amounts and under time and temperature conditions known to give fully cured products and, indeed, the rubber has undergone gelation (become insoluble in organic solvents) to the extent characteristic of such a state of cure. The thermoset state of the bulk composition can be avoided in the compositions of the invention by simultaneously masticating and curing the blends. Thus, the thermoplastic elastomeric (elastoplastic) compositions of the invention may be prepared by blending a mixture of EPDM rubber, softened or molten polyolefin resi ~ and phenolic curatives, then masticating the blend at a temperature which maintains the melt and promotes curing until cure is complete, using conventional masticating equipment, for example, Banbury*mixers, Brabender*mixers, or certain mixing extruders.

The ingredients except curative are mixed at a tempera-ture sufficient to soften the polyolefin resin or, more commonly, * Trade Mark at a temperature above its melting point if the resin is crystalline at ordinary temperatures. After the molten resin and EPDM rubber are intimately mixed, phenolic curative (i.e., phenolic curing agent and cure activator) is added. Heating and masticating at curing temperatures are generally adequate to complete the cross-linking reaction in a few minutes or less.
The time required to complete the cross-linking reaction varies depending upon the cure temperature and the type of EPDM rubber or phenolic curative system employed. A suitable range of curing temperatures is from about the melting temperature of the poly-olefin resin (about 120C in the case of polyethylene and about 175C in the case of polypropylene) to 250C or more; typically, the range is from about 150C to 225C. A preferred range of curing temperatures is from about 170C to about 200C. To obtain thermoplastic compositions, it is important that mixing continues without interruption until curing occurs. If appre-ciable curing is allowed after mixing has stopped, a thermoset unprocessable composition may be obtained.
The particular results obtained by the aforedescribed dynamic curing process are a function of the particular rubber curing system selected. It has now been found that phenolic curative systems give improved compositions heretofore not obtained. It is essential to select a phenolic curative system which fully cures the rubber which result generally requires using a cure activator along with a phenolic curing resin. Similarly, the process using phenolic curative systems is only applicable to polyolefin terpolymer rubber comprising two monoolefins and at least one diolefin, such as, ethylene, propylene and nonconjugated diene containing residual unsaturation in the side chains commonly referred to as "EPDM rubbers."

EPM rubbers essentially free of unsaturation are unsatisfactory, 43-1002A ~2~9i7 not being sufficiently cross-linkable by phenolic curative systems. Moreover, the presence of at least about 25~ by weight of polyolefin resin in the blend is required for the consistent preparation of processable thermoplastic elastomers. It is thus possible to obtain unprocessable dynamically cured composi-tions even before complete gelation has occurred or to obtain only minor improvements in tensile strength by curing. But it is assumed that no one would want to achieve a useless result, and would not be misled by the fact that the interaction of the variables which influence the result is imperfectly understood.
A few simple experiments within the skill of the art utilizing available rubbers and phenolic curative systems will suffice to determine their applicability for the preparation of the improved products of this invention.
The new products are all processable in an internal mixer, to products which, upon transferring at temperatures above the softening or crystallizing points of the resin phases to the rotating rolls of a rubber mill, form continuous sheets.
The sheets are reprocessable in the internal mixer in which, upon reaching temperatures above the softening or melting points of the polyolefin resin phase, are again transformed to the plastic state (molten state of the resin phase) but upon passing the molten product through the rolls of the rubber mill a con-tinuous sheet again forms. In addition, a sheet of thermo-plastic composition of this invention can be cut into pieces and compression molded to give a single smooth sheet with complete knitting or fusion between the pieces. It is in the foregoing sense that "thermoplastic" will be herein understood.
In addition, elastoplastic compositions of the invention are further processable to the extent that articles may be formed therefrom by extrusion, injection molding, blow molding, thermo-forming, etc.

43-1002A ~43i7 The amount of rubber extractable from a blend is used to measure the extent of cure. The improved elastoplastic composi-tions of the invention are produced by curing the blends to the extent that the cured composition contains no more than about three percent by weight of curable rubber extractable in cyclohexane at 23C or no more than about five percent by weight of rubber extractable in boiling xylene. In general, the less extractables the better are the properties and still more pre-ferable are compositions having essentially no extractable rubber (less than l.0 weight percent) in the organic solvent.
The percent of soluble rubber in the cured composition is determined by soaking a nominally 2 mm thick specimen for 48 hours in cyclohexane at 23C or refluxing a thin film specimen in boiling xylene for one half hour, weighing the dried residue and making suitable corrections based upon knowledge of the com-position. Thus, corrected initial and final weights are used by subtracting from the initial weight the weight of the components soluble in the solvent, other than the curable rubber, such as extender oils, plasticizers, low molecular weight polymers and components of the polyolefin resin soluble in cyclohexane. Any insoluble pigments, fillers, etc.,are subtracted from ~oth the initial and final weights. Any materials in the uncured rubber which are soluble in acetone are regarded as being non-cross-linkable components of the rubber which quantities are subtracted from the rubber when calculating the percent of soluble rubber in a cured composition. Up to five weight percent, typically between 0.5-2.0 weight percent, of EPDM rubber is acetone soluble.
Of course, it is understood that enough of phenolic curative must be used to fully cure the rubber. The minimum quantity of phenolic curative necessary to cure the rubber varies llZ~i7 depending upon the type of rubber, phenolic curing agent, type cure promoter and curing conditions such as temperature. Typi-cally, the quantity of phenolic curing agent used to fully cure the EPDM rubber is about 5 parts to 20 parts by weight phenolic curing agent per 100 parts by weight of EPDM rubber. Preferably, the quantity of phenolic curing agent is between about 7 parts to 14 parts by weight phenolic curing agent per 100 parts by weight EPDM rubber. In addition, an appropriate quantity of cure activator is used to assure full cure of the rubber. Satis-factory amounts of cure activator varies from 0.01 parts byweight to ten parts by weight per 100 parts by weight EPDM
rubber, although, higher amounts may be used, if desired and satisfactory cure is obtained. The term "phenolic curative" in-cludes phenolic curing agent (resin) and cure activator. However, it should not be assumed, from the fact that the amount of phenolic curative is based on the EPDM rubber content of the blend that the phenolic curative does not react with the poly-olefin resin or that there is no reaction between the polyolefin resin and EPDM rubber. There may be highly significant reactions involved but of limited extent, i.e., there is no substantial quantity of graft formation between the polyolefin resin and the EPDM rubber. Essentially all of the cured EPDM rubber and polyolefin resin can be separated and isolated from the blend by high temperature solvent extraction, for example, boiling xylene extraction and infrared analysis of the isolated fractions indicated that little, if any, graft copolymer is formed between the EPDM rubber and polyolefin resin.
Any EPDM rubber which can be completely cured (cross-linked) with phenolic curative is satisfactory in the practice of the invention. Suitable monoolefin terpolymer rubber com-prises essentially non-crystalline, rubbery terpolymer of two or _g_ 43-1002A ~24917 more alpha monoolefins, preferably copolymerized with at least one polyene, usually a non-conjugated diene which rubber herein and in the claims is referred to as "EPDM rubber." Satisfactory EPDM rubbers comprise the products from the polymerization of monomers comprising two monoolefins, generally ethylene and propylene, and a lesser quantity of non-conjugated diene. The amount of non-conjugated diene is usually between 2-10 weight percent of the rubber. Any EPDM rubber which has sufficient reactivity with phenolic curative to completely cure is suitable in the practice of the invention. The reactivity of EPDM rubber varies depending upon both the amount of unsaturation and the type of unsaturation present in the polymer. For example, EPDM
rubbers derived from ethylidene norbornene are more reactive toward phenolic curatives than EPDM rubbers derived from dicyclo-pentadiene and EPDM rubbers derived from 1,4 hexadiene are less reactive toward phenolic curatives than EPDM rubbers derived from dicyclopentadiene. However, the differences in reactivity can be overcome by polymerizing larger quantities of less active diene into the rubber molecule. For example, 2.5 weight percent of ethylidene norbornene or dicyclopentadiene may be sufficient to impart sufficient reactivity to the EPDM to make it completely curable with phenolic curative comprising conventional cure activators, whereas, at least 3.0 weight percent or more is re-quired to obtain sufficient reactivity in an EPDM rubber derived from 1,4 hexadiene.
Suitable alpha monoolefins are illustrated by the formula CH2=CHR in which R is hydrogen or alkyl of 1-12 carbon atoms, examples of which include ethylene, propylene, l-butene, l-pentene, l-hexene, 2-methyl-1-propene, 3-methyl-1-pentene, 30 4-methyl-1-pentene, 3,3-dimethyl-1-butene, 2,4,4-trimethyl-1-pentene, 3-methyl-1-hexene, 1,4-ethyl-1-hexene and others.

43-1002A ~2~ 7 Satisfactory non-conjugated dienes include straight chain (acyclic) dienes such as 1,4-hexadiene, 2-methyl-1,4-pentadiene, 1,4,9 decatriene and ll-ethyl-l,ll-tridecadiene; monocyclic dienes such as 1,5-cyclooctadiene! 1,4-cycloheptadiene and 1-methyl-1,5-cyclooctadiene and bridged ring bicyclic dienes such as 5-ethylidenenorbornene, 5-methylene-2-norbornene; 5-isopropyli-dene-2-norbornene and 2-methyl-bicyclo-(2,2,1)-2,5-heptadiene;
fused ring bicyclics such as bicyclo (4.3.0)-3-7-nonadiene;
5-methylbicyclo(4.3.0)-3,7-nonadiene; 5,6-dimethyl-bicyclo-(4.3.0)-3,7-nonadiene and bicyclo(3.2.0)-2,6-heptadiene; alkenyl substituted monocyclics such as 4-vinyl-cyclohexene; 1,2-divinylcyclobutane and 1,2,4-trivinylcyclohexane; ahd tri-cyclics such as dicyclopentadiene. Grades of EPDM rubbers suitable for the practice of the invention are commercially available; Rubber World Blue Book 1975 Edition, Materials and Compounding Ingredients for Rubber, pages 406-410.
Suitable thermoplastic polyolefin resins comprise crystalline, high molecular weight solid products from the poly-merization of one or more monoolefins by either high pressure or low pressure processes. Examples of such resins are the isotactic and syndiotactic monoolefin polymer resins, represen-tative members of which are commercially available. Examples of satisfactory olefins are ethylene, propylene, l-butene, 1-pentene, l-hexene, 2-methyl-1-propene, 3-methyl-1-pentene, 4-methyl-l-pentene, 5-methyl-1-hexene and mixtures thereof.
Commercially available thermoplastic polyolefin resins, and preferably polyethylene or polypropylene, may be advantageously used in the practice of the invention, with polypropylene being preferred.
Any phenolic curative system which fully cures EPDM

rubber is suitable in the practice of the invention. A basic ingredient of such system is a phenolic curing resin made by condensation of a substituted or unsubstituted phenol with an aldehyde in an alkaline medium or by condensation of bifunctional phenoldialcohols. The phenolic curing resin may be a non-halogenated dimethylol(alkyl)phenol compound, for example, dimethylol-_-octyl phenol may be used. Halogenated phenol curing resins are especially suitable. Phenolic curative systems comprising phenolic resin, halogen donor and metal com-pound are especially recommended, details of which are des-cribed in Giller, U.S. Patent 3,287,440 and Gerstin et al, U.S. Patent 3,709,840. Ordinarily, halogenated, preferably brominated, phenolic resins containing 2-10 weight percent bromine, do not require halogen donor but are used in con-junction with a hydrogen halide scavanger such as metal oxides such as iron oxide, titanium oxide, magnesium oxide, magnesium silicate, silicon dioxide and preferably zinc oxide, the presence of which promotes the cross-linking function of the phenolic resin, however, with rubbers which do not readily cure with phenolic resins, the con~oint use of a halogen donor and zinc oxide is recommended. The preparation of halogenated phenol resins and their use in a curative system with zinc oxide are described in U.S. Patents 2,972,600, Feb. 21/61, C.A. Braidwood and 3,093,613, June 11/63, J.V. Fusco et al. Examples of suitable halogen donors are stannous chloride, ferric chloride, or halogen donating polymers such as chlorinated paraffin, chlorinated polyethylene, chlorosulfonated polyethylene, and polychlorobutadiene (neoprene rubber). The term "activator"
as used herein means any material which materially increases the cross-linking efficiency of the phenolic curing resin and includes both metal oxides and halogen donors. For further details of phenolic curative systems see "Vulcanization and Vulcanizing Agents", W. Hoffman, Palmerton Publishing Company.
Suitable phenolic curing resins and brominated phenolic curing 43-1002A ~124.~7 resins are commercially available, for example, such resins may be purchased under the trade names SP-1045, CRJ-352, SP-1055 and SP-1056 from Schenectady Chemicals, Inc. Similar functionally equivalent phenolic curing resins may be obtained from other suppliers. As explained above, sufficient quantities of cura-tives are used to achieve essentially complete cure of the rubber.
The properties of the elastoplastic compositions of this invention may be modified, either before or after vulcani-lQ zation, by addition of ingredients which are conventional inthe compounding of EPDM rubber, polyolefin resin and blends thereof. Examples of such ingredients include carbon black, silica, titanium dioxide, colored pigments, clay, zinc oxide, stearic acid, stabilizers, antidegradants, flame retardants, processing aids, adhesives, tackifiers, plasticizers, wax, discontinuous fibers, such as wood cellulose fibers and extender oils. The addition of carbon black, extender oil or both, preferably prior to dynamic curing, are particularly recommended.
Carbon black improves the tensile strength and tends to promote the phenolic curative. Extender oil can improve the resistance to oil swell, heat stability, hysteresis, cost and permanent set of the elastoplastic composition. Aromatic, naphthenic and paraffinic extender oils are satisfactory. The addition of extender oil can also improve processibility. For suitable extender oils, refer to Rubber World Blue Book, supra, pages 145-190. The quantity of extender oil added depends upon the properties desired, with the upper limit depending upon the compatibility of the particular oil and blend ingredients which limit is exceeded when excessive exuding of extender oil occurs.
Typically, 5-300 parts by weight extender oil are added per 100 parts by weight blend of olefin rubber and polyolefin resin.

~1249~7 Commonly about 30 to 250 parts by weight of extender oil are added per 100 parts by weight of rubber present in the blend with quantities of about 70 to 200 parts by weight of extender oil per 100 parts by weight of rubber being preferred. The amount of extender oil depends~ at least in part, upon the type of rubber. High viscosity rubbers are more highly oil extendable.
In the preparation of colorable compositions of the invention, colorless or white pigments (fillers, extenders, or reinforcing pigments) are used in place of carbon black. Silica, aluminum silicate, magnesium silicate and titanium dioxide are suitable for such purpose. Typically, 5-100 parts by weight white pigment are added per 100 parts by weight of rubber in the blend. Typi-cal additions of carbon black comprise about 2-250 parts, preferably about 40-250 parts by weight of carbon black per 100 parts by weight of EPDM rubber and usually about 10-100, preferably 20-100 parts by weight carbon black per 100 parts total weight of EPDM rubber and extender oil. The amount of carbon black which can be used depends, at least in part, upon the type of black and the amount of extender oil to be used.
Methods other than the dynamic curing of rubber/poly-olefin resin blends can be utilized to prepare compositions of the invention. For example, the rubber can be fully cured in the absence of the polyolefin resin, either dynamically or stati-cally, powdered, and mixed with the polyolefin resin at a temper-ature above the melting or softening point of the resin. Provided that the cross-linked rubber particles are small, well dispersed and in an appropriate concentration, the compositions within the invention are easily obtained by blending cross-linked rubber and polyolefin resin. Accordingly, the term "blend" herein means a mixture comprising well dispersed small particles of cross-linked rubber. A mixture which is outside of the invention because it contains poor dispersed or too large rubber particles can be comminuted by cold milling (to reduce particle size to below about 50~) preferably below 20~ and more preferably to below 5~.
After sufficient comminution or pulverization, a composition of the invention is obtained. Frequently, poor dispersion or too large rubber particles is obvious to the naked eye and observable in a molded sheet. This is especially true in the absence of pigments and fillers. In such a case, pulverization and remold-ing gives a sheet in which aggregates of rubber particles or large particles are not obvious or are far less obvious to the naked eye and mechanical properties are greatly improved.
Elastoplastic compositions of the invention are use-ful for making a variety of articles such as tires, hoses, belts, gaskets, moldings and molded parts. They are particularly use-ful for making articles by extrusion, injection molding and compression molding techniques. They also are useful for modifying thermoplastic resins, in particular, polyolefin resins.
The compositions are blended with thermoplastic resins using conventional mixing equipment. The properties of the modified resin depend upon the amount of elastoplastic composition blend-ed. Generally, the amount of elastoplastic composition is such that the modified resin contains about 5 to 25 parts by weight of EPDM rubber per about 95 to 75 parts weight of total resin.
The stress-strain properties of the compositions are determined in accordance with the test procedures set forth in ASTM D638 and ASTMD1566. The term "elastomeric" as used herein and in the claims means a composition which possesses the tension set property of forcibly retracting within a given period of time (1 to 10 minutes) to less than 160~ of its original length after being stretched at room temperature to twice its original length andheld for the same period of time (1 or 10 .~
L~J

43-1002A 1~2~

minutes) before release. Compression set is determined in accordance with ASTM D-395, Method B, by compressing the sample for 22 hours at 100C. Oil swell (percent change in weight) is determined in accordance with the ASTM D-471 by submerging the specimen in ASTM #3 oil for 3 days at 121C. Especially pre-ferred compositions of the invention are rubbery compositions having tension set values of about 50% or less which composi-tions meet the definition for rubber as defined by ASTM Standards, V. 28, page 756 (D1566). More preferred compositions are rubberv compositions having a Shore D hardness of 60 or below or a 100%
modulus of 180 Kg./cm2 or less or a Young's modulus below 2500 Kg./cm2.
DESCRIPTION OF PREFERRED EMBODIMENTS
To illustrate the invention, a masterbatch containing EPDM rubber, paraffinic extender oil, carbon black, zinc oxide, stearic acid and antidegradant (when present) in the indicated proportions (all parts by weight) is mixed with polypropylene at 80 rpm in a Brabender mixer with an oil bath temperature of 180C for 2.5 minutes after which time the polypropylene is melted and a uniform blend is obtained. Hereinafter tempera-ture of a Brabender mixer will be understood to be temperature of the oil bath. Phenolic curative i9 added and mixing is con-tinued for four additional minutes at which time maximum Brabender consistency has been reached. The composition is removed and specimens are compression molded at 210C. The specimens are cooled below 100C under pressure before removal. Properties of the molded sheet are measured and recorded.
Data for various compositions are shown in Table I.
Stocks 1-3 and 4-6 contain different EPDM rubbers as identified in the footnotes. Stocks 1 and 4 are controls containing no curatives. Stocks 2 and 5 illustrate compositions of the invention cured with phenolic curative. Stocks 3 and 6 ~124~i7 TABLE I
Stocks 1 2 3 4 5 6 EP~M r~er 361 361 361 362 362 362 Polypropylene3 64 64 64 64 64 64 Extender Oil 30.6 30.6 30.6 30.6 30.6 30.6 Carbon Black 28.8 28.8 28.8 28.8 28.8 28.8 Zinc CKide 1.8 1.8 1.8 1.8 1.8 1.8 Stearic Acid 0.36 0.36 0.36 0.36 0.36 0.36 Flectol-H* 0.72 0.72 0.72 Antidegradant4 SP-10565 - 3.24 - - 3.24 Sulfur Curative6 - - 1.31 - - 1.31 Hardness, Shore D 43 47 47 35 40 39 100~ modulus, 86 115 101 70 114 87 Kg./cm2 UTS, Kg./cm2 110 176 190 78 179 139 Ult. Elong.,% 460 390 490 460 300 390 #3 ASqM oil swell,~ 131 67 88 88 53 75 Ccmpression Set,% - - - 68 36 52 173 wt.% ethylene, 4.4 wt.% ethylidene norbornene, polydispersity 2.1, SP. gr. 0.86, Mooney Visc., 55 (ML + 121C).
255 wt.% ethylene, 4.4% ethylidene norbornene, polydispersity 5.2,SP. gr. 0.86, Mooney Visc., 40 (ML 1+8 @ 121C).
Low flow, general purpose, SP. g. 0.902, 11~ yield elongation.
4Polymerized 1,2-dihydro-2,2,4-trimethylquinoline.
5Brominated methylol phenolic curing resin.
6Sulfur 17.2 parts, zinc dimethyldithiocarbamate 10.3 parts, tetraethyl thiuram disulfide 10.3 parts, 2-bis(benzothiazolyl) disulfide 34.5 parts and dipentamethylene thiuram hexasulfide 27.7 parts.
* Trade Mark ~ - 17-11242~17 included for comparison are compositions cured with sulfur cura-tive system. The EPDM rubber in Stocks 2, 3, 5 and 6 is fully cured, i.e., the compositions are characterized by less than 3%
by weight of the rubber (based on total weight of rubber present) being extractable in cyclohexane at room temperature or in boil-ing xylene. The cured compositions are elastomeric and process-able as thermoplastics and may be reprocessed without the need for any reclaiming in contrast to static cured compositions which are thermosets not processable as thermoplastics. The data show that compositions prepared from EPDM containing a high ethylene content have higher hardness. The data further show that the compositions prepared with phenolic curing resin have substantially the same stress-strain properties, whereas, the sulfur cure system is more efficient in the composition containing low polydispersity EPDM rubber. The compositions cured with phenolic curing resin exhibit two important advantages compared to compositions cured with sulfur curative, namely, greater oil resistance (low oil swell) and better compression set.
Compositions comprising blends containing EPDM rubber as 2Q the major component are shown in Table II. Stock 1 contains no curatives. Stock 2 illustrates a composition of the invention cured with phenolic curing resin. Stocks 3 and 4 included for comparison are compositions cured with sulfur curative system and peroxide curative, respectively. The polypropylene is the same as in Table I. The EPDM rubber is a terpolymer comprising 69 wt. % ethylene, 8.3 wt. % ethylidene norbornene, and the bal-ance propylene, polydispersity 2.2, Mooney Visc. 51(ML8 @ 100C).
The procedure is the same as in Table I, except in Stock 2, the zinc oxide is added one minute after adding the phenolic curing resin and in Stock 4, 0.6 parts by weight of tris(nonylphenyl)-phosphite, a free radical scavenger, is charged after the maximum 1~24~17 TABLE II

Stocks 1 2 3 4 EPDM rubber 60 60 60 60 Polypropylene 40 40 40 40 Zinc oxide - 1.25 3.0 Tetraethyl thiuram - - 0.6 disulfide 2-bis(benzothiazolyl) - - 0.3 disulfide Sulfur _ _ o.g 2,5-dimethyl-2,5- - - - 1.2 di(t-butylperoxy)hexane Hardness, Shore D 36 42 43 39 100~ modulus, Kg./c~d2 61 101 110 82 300~ modulus, Kg./cm2 - 221 179 122 UTS, Kg./cm2 64 244 217 164 Ult. Elong., ~ 300 310 370 420 Tension set, ~ 38 32 34 35 Compression set, ~ 91 24 43 32 #3 ASTM oil swell, ~ 133 109 194 225 Wt.~ of sample soluble 48 0 0 in cyclohexane @ R.T.
Wt.~ of rubber soluble 80 0 0 1.7 in cyclohexane @ R.T.
(uncorrected for acetone soluble portion of rubber) 43-1002A ~Z4~7 Brabender consistency has been reached. The data indicate that the composition cured with phenolic curing resin exhibits grea~er oil resistance (low oil swell) and better compression set.
Soft compositions containing high proportions of rubber and extender oil are shown in Table III. The procedure is the same as in Table I except after the curatives are added mixing is continued for five minutes. Stock 1 is a control containing no curatives. Stocks 2, 4 and 6 illustrate compositions of the invention cured with phenolic curing resin. Stocks 3,5 and 7 are la compositions cured with sulfur curative system. The data indicate that the compositions cured with phenolic curing resin have better compression set and higher oil resistance. In addition, the compositions cured with phenolic curing resin give smoother surfaces upon extrusion or injection molding. Surfaces of extrudates and parts molded from compositions cured with phenolic curing resin are bloom-free and non-sticky. Stock 6 containing a high proportion of rubber exhibits superior elastomeric properties such as low tension set and low compression set.
A study of the effect of curative level is shown in Table IV. The procedure and ingredients are the same as Table III. The data show that increasing curative level has less effect upon stress-strain properties with the sulfur curing system than with the phenolic resin curing system. Ten-sile strength is essentially unchanged when the curative con-centration is varied in both curing systems. Modulus increases and elongation decreases with increasing phenolic curing resin concentration, whereas, modulus and elongation are essentially unchanged when the amount of sulfur curative is varied. At all concentrations studied, the compositions cured with phenolic cur-ing resi~ exhibit better compression set and greater oil resis-tance.

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Compositions of the invention cured with a nonhalo-genated phenolic curing resin are illustrated in Table V. The procedure is the same as before. Stock 1 is a control containing no curatives. Stock 2 is a control containing phenolic curing resin but no cure activator. Stock S is another control con-taining sulfur curative. Stock 3 contains dimethylol-p-nonyl phenol (phenolic curing resin sold under the trade name SP-1045).
Stocks 3 and 4 contain stannous chloride and chlorosulfonated polyethylene, respectively, as halogen donors. The data show that it is critical that a cure activator be used in conjunction with nonhalogenated phenolic curative in order to fully cure the rubber. The presence of halogen donor ~cure activator) results in substantial increases in tensile strength and signi-ficant improvement in compression set and oil resistance. The high oil swell for Stock 2 indicates that the rubber is only partially cured. The data also show that the compositions cured with the phenolic curing system containing halogen donor gives better compression set and oil resistance than a similar composi-tion cured with sulfur curative. Stocks 3 and 4 show especially high retention of tensile strength after being swelled by oil.
The experiments shown in Table VI further demonstrate that in order to fully cure the rubber that a cure activator (zinc oxide) must be present. The procedure is the same as in Table I
but a masterbatch is not used since the compositions contain neither carbon black nor extender oil. The composition of Stocks 1 and 2 is the same except Stock 2 contains no zinc oxide. Duplicate runs of stock 2 are made with the average of the values obtained recorded in Table VI. The compositions are extracted with boiling xylene to determine the extent of cure of the rubber (cured rubber being insoluble in boiling xylene). Thin film (about 0.05 mm thick) specimens are placed in boiling xylene.

43-1002A 1~249i7 TABLE V
Stocks l 2 3 4 5 EPDM rubberl 36 36 36 36 36 Polypropylene2 64 64 64 64 64 Extender oil 30.6 30.630.6 30.630.6 Carbon black 28.8 28.8 28.8 28.8 28.8 Zinc oxide 1.8 1.8 1.8 1.8 1.8 Stearic acid 0.36 0.36 0.36 0.36 0.36 SP-10453 - 4.32 4.32 4.32 SnCl2 - -0.72 Chlorosulfonated - - - 1.8 polyethylene Sulfur curative2 - - - - 1.08 Hardness, Shore D 37 4245 45 43 100% modulus, Kg./cm2 72102 146 129 114 UTS, Kg./cm2 95 170226 223 211 Ult. Elong., ~ 510 450260 380 410 Tension set, ~ 48 2927 29 32 Compression set, ~ - 5736 39 49 ASTM #3 oil swell, % 79 86 44 55 66 UTS after oil, Kg./cm2 38 83 157 143 113 % UTS retention 40.0 48.8 69.6 64.0 53.7 1 69 wt.% ethylene, 8.3 wt.% ethylidene norbornene, polydispersity 2.1, Sp.gr. 0.86, Mooney Visc. 50(ML-8, 100C).
2 Same as Table I.
3 Dimethylol-p-nonyl phenol ~nonhalogenated).

43-1002A 11~4~17 TABLE VI
Stocks 1 2 EPDM rubber 1 36 36 Polypropylene 2 64 64 Stearic acid 0.36 0.36 Zinc oxide 1.8 Flectol-H antidegradant2 0.72 0.72 SP-10562 4.05 4-05 10 Hardness, Shore D 53 51 100% modulus, Kg./cm2 141 125 300% modulus, Kg./cm2 157 133 UTS, Kg./cm2 179 165 Ult. Elong., ~ 390 530 Tension set, % 42 52 Compression set, %51 67 ASTM #3, oil swell, % 105 151 Wt. % of sample insoluble 40.2 26.3 in boiling xylene(39.3) (38.6) Wt. % of rubber soluble 0 32.0 in boiling xylene Wt. ~ of sample insoluble 55.0 56.7 in xylene @ R.T.(60.4) (61.4) Wt. % of sample soluble 4.7 17.8 in xylene @ R.T.
% Total 99.9 100.8 1 55 wt.% ethylene, 4.4 wt.% ethylidene norbornene, poly-dispersity 2.5, Sp. gr. 0.86, Mooney Visc., 70 (ML 1+8 @
3Q 121C), sulfur vulcanizable very fast curing.
2 Same as Table I.

1~4~ ~7 After about 30 minutes, the film is usually disintegrated. The xylene suspension is then filtered through a glass fiber filter of 0.3 micron pore size. All of the ingredients except the polypropylene are regarded as being part of the cured rubber.
The filtrate is cooled to room temperature (R.T.) which causes the polypropylene (or crystalline graft copolymer) to precipitate which material is recovered by filtration. The second filtrate is then evaporated to recover the material which is soluble in xylene at room temperature (atactic polypropylene, low molecular weight polypropylene, amorphorus ethylene-propylene copolymer, uncured EPDM rubber or non-crystalline polypropylene-EPDM rubber graft copolymer). The weight percent of the various materials recovered are recorded with the calculated theoretical values for cured EPDM rubber and polypropylene shown in parenthesis.
The calculated value for cured rubber is corrected to take into account materials present in the uncured rubber which upon curing remain soluble in boiling xylene. The correction (1.6 weight per-cent of the rubber) is the sum of the acetone soluble portion of the uncured rubber, 0.9 wt. ~, and the room temperature cyclo-hexane insoluble portion of the uncured rubber, 0.7 wt. %. Theacetone soluble material is regarded as non-crosslinkable. The room temperature cyclohexane insoluble material is regarded as being polyolefin homopolymer. For example, in Stock 1, the calculated value indicated in parenthesis for insoluble rubber is 39.3 wt. %, which value would be 39.6 wt. percent if not corrected as indicated above. A similar correction is applied to the calculated values (in parenthesis in Tables VII-IX).
The data show that Stock 1, the composition containing zinc oxide, has better tension set and compression set and lower oil swell and that none of the rubber is extractable in boiling 43-1002A 1~24~17 xylene. This indicates that the rubber is fully cured. It further confirms the absence of graft copolymer; where, in the composition containing no zinc oxide 32 percent of the rubber is extractable in boiling xylene. This indicates either the presence of graft copolymer or that the rubber is only partially cured. The data demonstrate that in order to obtain a composition of the invention containing fully cured rubber, it is critical that a cure activator is used to promote the reaction essentially entirely between the EPDM rubber and the phenolic curing resin.
Compositions of the invention of high hardness containing carbon black and high proportions of polypropylene are illustra-ted in Table VII. A masterbatch of EPDM rubber, carbon black, zinc oxide and stearic acid is mixed with polypropylene at 80 rpm in a Brabender mixer at 180C until the polypropylene melts and a uniform blend is obtained. Phenolic curing resin is added and mixing is continued until the maximum Brabender con-sistency is _eached and three minutes thereafter. The composition is removed, sheeted, returned to the Brabender and mixed at 180C for two minutes. The data show that the compositions are harder and stiffer than compositions of the previous tables con-taining higher proportions of rubber. The tension set values indicate that the compositions have reduced elasticity. The solubility data show that the rubber is fully cured with none of the rubber being soluble in boiling xylene.
The order of addition of the ingredients is important, especially the sequence in which cure activator such as zinc oxide is added. This is especially true with adding large amounts of zinc oxide in the absence of a filler. This is illustrated in Table VIII. The procedure is the same as in Table I but no masterbatch is used since no carbon black and extender oil are present. The ingredients are added in the order listed. In 43-1002A l~Z4~17 TAaLE VII
Stocks 1 2 3 EPDM rubber 1 25 30 35 Polypropylene 1 75 70 65 Carbon black 20 24 28 Stearic acid 0.25 0.3 0.35 Zinc oxide 1.25 1.5 1.75 SP-1056 1 2.75 3.3 3.85 Hardness Shore A 97 99 99 Shore D 60 60 59 100% modulus, Kg./cm2196 183 179 300% modulus, Kg./cm2235 234 246 UTS, Kg./cm2 275 240 257 Ult. Elong., % 440 320 350 Tension set, % 54 54 47 20 ~t. % of Sample 40.1 45.4 51.9 insoluble in boiling xylene (39.3) (45.4) (51.0) l Same as Table VI.

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43-1002A ~ 12 4g 17 Stocks 1-5, the zinc oxide is added prior to the adding of the phenolic curing resin, whereas, in Stocks 6-9, the zinc oxide is added after the phenolic curing resin. The data show that the stress-strain properties decrease with increasing amounts of zinc oxide when the zinc oxide is added before the phenolic curing resin but that the amount of zinc oxide has little effect on stress-strain properties when the zinc oxide is added last. Also, the data indicate that superior compositions are obtained when the zinc oxide is added last. Such compositions exhibit higher stress-strain properties, better tension set and compression set and greater oil resistance. The solubility data indicate that the order of zinc oxide addition has a significant effect upon the extent of cure of the rubber. The amount of rubber soluble in boiling xylene varies from 0 to 23 percent depending upon the amount of zinc oxide in the composi-tions (Stocks 1-5) when the zinc oxide is added before the phenolic curing resin, whereas, the amount of rubber soluble in boiling xylene is one weight percent or less of the rubber in composition Stocks 6-9, when the zinc oxide is added last. The cyclohexane soiubility data at room temperature also show that a greater portion of the rubber is soluble in compositions when the zinc oxide is present before the phenolic curing resin is added. The weight percent of rubber soluble in cyclohexane is corrected to take into account of the acetone soluble portion of the uncured rubber, 0.9 wt. percent. The correction perhaps should be greater to take into account the stearic acid which could also be extractable in cyclohexane.
A study in which the proportions of EPDM rubber and poly-propylene are varied is shown in Table IX. The compositions con-tain only EPDM rubber,polypropylene,phenolic curing resin and zinc 43-1002A ~124917 TABLE IX
Stock 1 2 3 4 5 6 EPDM rubberl 60 50 40 30 20 10 Polypropylenel 40 50 60 70 80 90 Zinc oxide 1.2 1.0 0.8 0.6 0.4 0.2 100% modulus, Kg./cm2 99121 141 170 180 205 UTS, Kg./cm2 261 241284 248 264 234 10 E, Kg./cm2 496 787242735664872 7577 Ult. Elong., % 380 430460 440 510 570 Hardness Shore A 89 9298 95 97 97 Shore D 44 4852 60 65 71 Tension set, ~ 18 2743 49 60 85 (necked~necked) Wt. % of sample insol- 62.8 51.7 44.0 31.4 21.7 12.0 uble boiling xylene (61.7) (52.0) (42.2) (31.5) (21.6) (11.0) Wt. ~ of rubber sol- 0 0.6 0 0.3 0.5 0 uble boiling xylene Same as Table VI.

43-1002A 1 12 4C~1 7 oxide. The amounts of zinc oxide and phenolic curing agent are varied to maintain a constant curative to rubber ratio of 2 parts by weight zinc oxide and 10 parts by weight phenolic curing resin per 100 parts by weight of rubber. The EPDM rubber and polypropylene are charged to a Brabender mixer at 180C and mixed at lO0 rpm. Three minutes after the polypropylene melts, phenolic curing resin is added and mixing is continued for one minute. Zinc oxide is then added and mixing is continued for another four minutes. The composition is removed, sheeted, returned to the Brabender mixer and mixed for two additional minutes. The composition is again removed from the mixer and formed into sheets and compression molded at 220C. All the compositions are thermoplastic and Stocks 1-4 ar~ elastomeric.
Stocks 5 and 6 containing high proportions of polypropylene are non-elastomeric with necking occurring when test specimens are pulled, i.e., the test specimen goes through a yield preventing its return to its original form. Over the entire range of proportions, the rubber is fully cured with the amount of the rubber soluble in boiling xylene being less than one weight percent of the rubbe~ present in the composition.
A colorable composition of the invention containing a white pigment (magnesium silicate) and a composition of the invention containing polyethylene are illustrated in Table X.
The composition of Stock 1 contains (all parts by weight) 50 parts EPDM rubber, 50 parts polypropylene, 40 parts magnesium silicate (filler grade), 0.5 parts stearic acid and 5.6 parts phenolic curative, SP-1056. The preparation procedure is the same as in Table VIII, except the magnesium silicate is com-pletely dispersed before the phenolic curative is added. No zinc oxide is required when magnesium silicate is used. The ~1;24917 TAsLE ~.
Stocks 1 2 EPDM rubberl 50 40 Polypropylenel 50 Polyethylene2 - 60 Magnesium silicate 40 Stearic acid 0.5 0-4 Zinc oxide - 0.8 SP-10561 5.6 4.5 Hardness, Shore D 46 44 100% modulus, Kg./cm2133 102 300% modulus, Kg./cm2166 158 UTS, Kg./cm2 190 190 Ult. Elong., % 420 370 Tension set, % 26 32 Compression set, % 28 27 Wt. % of sample 64.0 46.8 insoluble boiling (64.0) (42.6) xylene Wt. % of rubber 0 0 soluble Wt. % of sample 0.1 0.2 soluble in cyclo-hexane @ R. T.

1 Same as Table VI.
2 Medium molecular wt. distribution polyethylene, ASTM D1248-72, Type III, Class A, category 5, melt index 0.3g/10 min., density 0.950 g/cm .

43-1002A ~1249.17 cyclohexane solubility data indicate that the rubber is fully cured. The composition of Stock 2 contains (all parts by weight) 40 parts EPDM rubber, 60 parts polyethylene, 0.4 parts stearic acid, 0.8 parts zinc oxide and 4.5 parts phenolic curing resin, SP-1056. The rubber and polyethylene are charged to a Brabender mixer at 180C and masticated at 80 rpm until the polyethylene melts. Stearic acid and phenolic curative are added with mixing continuing until a uniform mass is obtained. Zinc oxide is added and mixing is continued for 2 minutes beyond the time (about 3-4 minutes) when maximum consistency is reached. The composition obtained is thermoplastic and elastomeric. The solubility data indicate that the rubber is fully cured.
Compositions of the invention using different cure activators are illustrated in Table XI. The EPDM rubber contains 55 weight percent ethylene, 40.6 weight percent propylene and 4.4 weight perce~t dicyclopentadiene and has a polydispersity of 6Ø The polypropylene is the same as in Table I. The phenolic curing resin is added last. Stock 1, a control, contains no cure activator. The properties of the composition show that the rubber is incompletely cured (or possibly a graft copolymer is obtained). This is confirmed by the cyclohexane solubility data. Stocks 2, 3 and 4 contain zinc oxide, zinc stearate and stannous chloride, respectively, as cure activators. The data indicate that the rubber in the blends is essentially completely cured. The percent of the rubber soluble in cyclohexane is corrected to take into account that 1.38 weight percent of the uncured rubber is soluble in acetone. The corrected value is indicated by asterisk. Stocks 4 and 5 show that a non-halogenated phenolic curing resin may be substituted in place of halogenated phenolic curing resin when using stannous chloride as activator and that the resulting elastoplastic compositions exhibit sub-stantially the same properties.

43-1002A ~1249~7 TABLE XI
Stocks 1 2 3 4 5 EPDM rubber 50 50 50 50 50 Polypropylene 50 50 50 50 50 Stearic acid 0.5 0.5 0.5 0.5 0.5 ZnO - 0-5 Zinc stearate - - 0.2 SnC12-2H20 Phenolic curing resin 5.631 5.631 5.6315.631 5.532 Hardness, Shore D29 41 41 40 44 100% modulus,Xg./cm2 72 95 93 100 102 300% modulus,Kg./cm2 - 148 140 147 137 UTS, Kg./cm2 70 214 212 221 190 Ult. Elong.,% 100 450 470 480 470 Tension set, % 57 32 32 30 32 Compression set,~83 38 39 46 45 ASTM #3 oil swell, % 212 133 134 140 147 Wt.~ of sample 21 2.2 1.6 0.4 0 soluble in cyclohexane @ R.T.
Wt.% of rubber soluble 40 4.2 3.0 0.8 0 in cyclohexane38.6* 2.8* 1.6* 0* 0 @ R.T.

1 halogenated phenol curing resin same as Table I.
2 non-halogenated phenol curing resin same as Table IV.

43-1002A 1~%4~7 It is important that cure activator(s) is present and that the proper concentration is used; without cure activator or at improper concentrations the rubber is not completely cured.
Incomplete cure results in diminution of properties of the blend. High concentrations of activators, especially when added prior to the phenolic curing resin, are believed to cause the curing resin to react with itself (homopolymerization), thus depleting the system of curative. The proper activator concentration varies depending upon type of activator, phenolic curing resin or rubber, order of addition of phenolic curing resin and activator, and processing temperature but the proper level may be readily ascertained by trial.
Compositions of the invention in which the EPDM rubber contains different monomers are illustrated in Table XII.
Stocks 1 and 2 illustrate compositions containing EPDM rubber wherein the unsaturation is derived from ethylidene norbornene ~ENB). Stocks 3-6 illustrate compositions containing EPDM
rubber containing unsaturation derived from 1,4-hexadiene (1,4HD). Stock 7 illustrates a composition containing EPDM
2Q rubber containing unsaturation derived from dicyclopentadiene ~DCPD). The compositions are prepared in accordance to the procedure of Table I except for Stock 7 the Brabender temperature is 170C. The cure activator is added last in Stocks 1-6. In Stock 7, the stannous chloride i9 added before the phenolic curing resin is added after which the zinc oxide is added. The uncorrected calculated value for insoluble rubber; calculated assuming that all ingredients excPpt polypropylene become insoluble upon curing are shown in parenthesis. Values desig-nated by asterisk are corrected as follows: In Stocks 4 and 7, 4.13 and 1.38 weight percent of the uncured rubber, respectively, are acetone soluble. The uncured EPDM rubber used in Stock 6 ~3- 1002A 1124917 A A A

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contains no acetone soluble material but, 2.52 weight percent of the uncured rubber is insoluble in cyclohexane at 50C which indicates the presence of that much non-crosslinkable polyolefin polymer. The data show that all the compositions exhibit good stress-strain properties and that the polydispersity of the rubber has no pronounced effect upon extent of cure. All com-positions exhibit satisfactory oil swell and compression set.
The solubility data show that the rubber in all the compositions is completely cured.
Improved processability of compositions of the invention is illustrated by comparing the extrusion characteris-tics of blends cured with phenolic curatives with blends cured with sulfur curatives. For example, 12.7 mm O.D. tubing is prepared by extruding compositions similar to stocks 2 and 3 of Table I through 12.7 mm OD X 9.53 mm ID die (20:1 L/D) at 381 cm/min take off rate using a 3.81 cm diameter Davis-Standard extruder equipped with 24:1 L/D general purpose screw operated at 70 rpm. Tubing size is maintained by slight internal air pressure and a water quench. Barrel temperature is varied over a practicable processing range - from a temperature sufficient to completely melt the polypropylene, 193C, to a temperature where excessive fuming occurs, 232C. An intermediate temperature condition of 216C is also studied. Another variable studied is draw down ratio which measures the integrity of the composition by its extensibility at processing temperature. Draw down ratio is the ratio of the die annulus area to the cross-sectional area of the tubing drawn down in diameter to failure by progressively increasing the take off rate. The results of the study are summarized in Table XIII.

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43-1002A ~24~17 The data show that the composition prepared with phenolic curative is more processable than the composition prepared with sulfur curative. In particular, the data show that phenolic resin cured composition may be extruded over a wide temperature range and permits preparation of a broad range of tube sizes as indicated by the area ratio.
Improved processability of compositions of the invention is further illustrated by comparing the extrusion characteristics of compositions similar to stocks 6 and 7 of Table III. For 10 example, 5 mm rod is prepared by extruding the aforesaid composi-tions through a 5.08 mm rod die using a 2.54 cm diameter NRM
extruder equipped with 16:1 L/D general purpose screw operated at 60 rpm. Barrel temperature is varied from 180-190C to 210-220C. The results are shown in Table XIV. The data show that the composition prepared with phenolic curative may be extruded at higher rates giving tubing with smoother surfaces than the composition prepared with sulfur curatives.
TABLE XIV
Barrel temp., 180-190C Barrel temp.,210-220C

Sample Phenolic Sulfur Phenolic Sulfur Type Curative Curative Curative Curative Output Rate g.jmin. 43.5 39.2 41.5 34.1 Surface smooth rough- smooth rough-Appearance knobby, knobby, many many 0.13-.2; 0.13-.25 mm mm protru- protru-sions sions It is understood that compositions of the invention com-prise blends of polyolefin resin and dispersed sufficiently small 30 particles of cross-linked rubber to give strong compositions processable as thermoplastics. Rubber particle size of 5011 112~9~L7 number average are satisfactory with particle size of 50~
weight average being preferred. In more preferred compositions, the rubber particle size is 5~ or less number average.
Although the invention has been illustrated by typical examples, it is not limited thereto. Changes and modifications of the examples of the invention herein chosen for purposes of disclosure can be made which do not constitute departure from the spirit and scope of the invention.

Claims (92)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In an elastoplastic composition comprising a blend of thermoplastic crystalline polyolefin resin in an amount suf-ficient to impart thermoplasticity to the composition, and cured EPDM rubber, the improvement comprising a composition in which the rubber is cured with phenolic curative comprising phenolic curing resin and cure activator.

2. The composition of Claim 1 comprising a blend of about 25-75 parts by weight polyolefin resin and about 75-25 parts by weight of cured EPDM rubber per 100 parts total weight of resin and rubber.

3. The composition of Claim 2 comprising a blend of about 30-70 parts by weight polypropylene, about 30-70 parts by weight rubber, and 5-300 parts by weight extender oil per 100 parts total weight of polypropylene and rubber, and 20-100 parts by weight carbon black per 100 parts total weight of rubber and extender oil.

4. The composition of Claim 2 containing about 30-250 parts by weight of extender oil per 100 parts by weight of rubber.

5. The composition of Claim 4 containing about 2-250 parts by weight carbon black per 100 parts by weight rubber.

6. The composition of Claim 2 wherein the cure activator is a metal halide.

7. The composition of Claim 2 wherein the cure activator is a halogen-donating polymer.

8. The composition of Claim 2 wherein the cure activator is chlorosulfonated polyethylene.

9. The composition of Claim 2 in which the phenolic curative comprises a brominated phenolic curing resin and a metal oxide cure activator.

10. The composition of Claim 9 in which the metal oxide is zinc oxide.

11. The composition of Claim 2 in which the poly-olefin resin is polypropylene.

12. The composition of Claim 11 in which the EPDM
rubber is a terpolymer of ethylene, propylene and ethylidene norbornene.

13. The composition of Claim 2 in which the rubber is cured to the extent that no more than about five weight percent of the rubber is extractable in boiling xylene.

14. The composition of Claim 13 in which the rubber is cured to the extent that no more than about three weight percent of the rubber is extractable in boiling xylene.

15. The composition of Claim 12 in which the rubber is cured to the extent that no more than about five weight percent of the rubber is extractable in boiling xylene.

16. The composition of Claim 2 in which the rubber is cured to the extent that no more than about three percent of the rubber in the blend is extractable in cyclohexane at 23°C.

17. The composition of Claim 1 prepared by masticating the blend and phenolic curative, in an amount sufficient to cure the rubber, at curing temperature until the rubber is cured to the extent that no more than about five percent of the rubber is extractable in boiling xylene.

18. An elastoplastic composition comprising a blend of thermoplastic crystalline high molecular weight iso-tactic or syndiotactic polyolefin resin, in an amount sufficient to impart thermoplasticity to the composition, and cured EPDM
rubber, in an amount sufficient to impart rubber-like elasticity to the composition, in which the rubber is cured with phenolic curative comprising phenolic curing resin and cure activator.

19. The composition of Claim 18 in which the rubber is cured to the extent that no more than about three percent of the rubber in the blend is extractable in cyclo-hexane at 23°C.

20. The composition of Claim 18 in which the rubber is cured to the extent that no more than about five percent of the rubber is extractable in boiling xylene.

21. The composition of Claim 20 comprising a blend of about 25-75 parts by weight polyolefin resin and about 75-25 parts by weight of cured EPDM rubber per 100 parts total weight of polyolefin resin and rubber.

22. The composition of Claim 21 in which the poly-olefin resin is polypropylene.

23. The composition of Claim 22 in which the rubber is a terpolymer of ethylene, propylene and ethylidene norbornene.

24. The composition of Claim 18 containing about 30 to 250 parts by weight of extender oil per 100 parts by weight of rubber.

25. The composition of Claim 18 in which the rubber is cured with a brominated phenolic curing resin.

26. The composition of Claim 23 in which the rubber is cured with a brominated phenolic curing resin.

27. The composition of Claim 24 containing 2 to 250 parts by weight carbon black per 100 parts by weight rubber.

28. The composition of Claim 24 containing 5 to 100 parts by weight white pigment per 100 parts by weight rubber.

29. The composition of Claim 22 comprising a blend of about 30 to 70 parts by weight polypropylene, about 30 to about 70 parts by weight of rubber, and 5-300 parts by weight extender oil per 100 parts total weight of polypropylene and rubber, and 20-100 parts by weight carbon black per 100 parts total weight of rubber and extender oil.

30. The composition of Claim 18 prepared by masti-cating the blend and phenolic curative, in an amount sufficient to cure the rubber, at curing temperature until the rubber is cured to the extent that no more than about five percent of the rubber is extractable in boiling xylene.

31. A process for preparing elastoplastic composi-tions which comprises (1) masticating about 25-75 parts by weight of EPDM rubber and 75-25 parts by weight thermoplastic crystalline polyolefin resin per 100 total parts by weight of rubber and polyolefin resin, and phenolic curing agent, in an amount sufficient to cure the rubber, at a temperature sufficient to soften or melt the polyolefin resin; and, for a time sufficient to obtain a homogeneous mixture, (2) adding cure activator while continuing to masticate the mixture, (3) continuing masticating the mixture at curing temperature until the rubber is cured to the extent that no more than about five percent of the rubber is extractable in boiling xylene.

32. The process of Claim 31 wherein the phenolic curing agent is brominated phenolic curing resin.

33. The process of Claim 32 wherein the cure activator is zinc oxide.

34. A process for preparing elastoplastic composi-tions which comprises masticating about 25-75 parts by weight of EPDM rubber and 75-25 parts by weight thermoplastic cry-stalline polyolefin resin per 100 total parts by weight of rubber and polyolefin resin, and phenolic curative comprising phenolic curing resin and cure activator, in an amount sufficient to cure the rubber, at a temperature sufficient to soften or melt the polyolefin resin; and, for a time sufficient to obtain a homogeneous mixture, and continuing masticating the mixture at curing temperature until the rubber is cured to the extent that no more than about five percent of the rubber is extractable in boiling xylene.

35. In an elastoplastic composition comprising a blend of thermoplastic crystalline polyolefin resin and fully cured EPDM rubber in the form of small dispersed particles essentially of a size of about 50 microns number average or below, the improvement comprising a composition in which the rubber is cured with phenolic curative com-prising phenolic curing resin and cure activator to the extent that the cured composition contains no more than about three percent by weight of curable rubber extractable in cyclohexane at 23°C. or no more than about five percent by weight of curable rubber extractable in boiling xylene.

36. The composition of claim 35 wherein said rubber is present in an amount below about 75 parts by weight and said resin is present in an amount above about 25 parts by weight per 100 parts total weight of resin and rubber.

37. The composition of claim 35 comprising a blend of about 25-75 parts by weight polyolefin resin and about 75-25 parts by weight of cured EPDM rubber per 100 parts total weight of resin and rubber.

38. The composition of claim 35, 36, or 37 in which the polyolefin resin is polypropylene.

39. The composition of claim 35, 36 or 37 con-taining about 30 - 250 parts by weight of extender oil per 100 parts by weight of rubber, and in which the polyolefin resin is polypropylene.

40. The composition of claim 35, 36 or 37 con-taining about 30 - 250 parts by weight of extender oil per 100 parts by weight of rubber, and in which the polyolefin resin is polypropylene and containing about 2 - 250 parts by weight carbon black per 100 parts by weight rubber.

41. The composition of claim 35, 36 or 37 in which the polyolefin resin is polypropylene and in which the phenolic curing resin is a non-halogenated dimethylol(alkyl) phenol compound.

42. The composition of claim 35, 36 or 37 in which the polyolefin resin is polypropylene and in which the phenolic curing resin is a non-halogenated dimethylol(alkyl) phenol compound, and in which the cure activator is selected from the group consisting of metal halide and halogen-donating polymer.

43. The composition of claim 35, 36 or 37 in which the polyolefin resin is polypropylene and in which the phenolic curing resin is a non-halogenated dimethylol(alkyl) phenol compound, and in which the cure activator is selected from the group consisting of metal halide and halogen-donating polymer, the halogen-donating polymer being a chlorosulfonated polyethylene.

44. The composition of claim 35, 36 or 37 in which the polyolefin resin is polypropylene and in which the phenolic curing resin is a non-halogenated dimethylol(alkyl) phenol compound, and in which the cure activator is selected from the group consisting of metal halide and halogen-donating polymer, the halogen-donating polymer being a chlorosulfonated polyethylene, the cure activator system including zinc oxide.

45. The composition of claim 35, 36 or 37 in which the polyolefin resin is polypropylene and in which the phenolic curative comprises a brominated phenolic curing resin and a metal oxide cure activator.

46. The composition of claim 35, 36 or 37 in which the polyolefin resin is polypropylene and in which the phenolic curative comprises a brominated phenolic curing resin and a metal oxide cure activator, the metal oxide being zinc oxide.

47. The composition of claim 35, 36 or 37 in which the polyolefin resin is polyethylene.

48. The composition of claim 35, 36 or 37 in which the polyolefin resin is polypropylene and in which the EPDM rubber is a terpolymer of ethylene, propylene and ethylidene norbornene.

49. The composition of claim 35, 36 or 37 in which the polyolefin resin is polypropylene and in which the rubber is cured to the extent that no more than about five weight percent of the rubber is extractable in boiling xylene.

50. The composition of claim 35, 36 or 37 in which the polyolefin resin is polypropylene and in which the rubber is cured to the extent that no more than about three weight percent of the rubber is extractable in boiling xylene and the rubber is of the size of about 5 microns number average or below.

51. The composition of claim 35, 36 or 37 in which the polyolefin resin is polypropylene and in which the EPDM rubber is a terpolymer of ethylene, propylene and ethylidene norbornene and in which the rubber is cured to the extent that no more than about five weight percent of the rubber is extractable in boiling xylene.

52. The composition of claim 35, 36 or 37 in which the polyolefin resin is polypropylene and in which the rubber is cured to the extent that no more than about three percent of the rubber in the blend is extractable in cyclohexane at 23°C.

53. The composition of claim 35, 36 or 37 pre-pared by masticating the blend and phenolic curative, in an amount sufficient to cure the rubber, at curing temperature until the rubber is cured to the extent that no more than about five percent of the rubber is extractable in boiling xylene.

54. The composition of claim 35 comprising a blend of about 30-70 parts by weight polypropylene, about 30-70 parts by weight EPDM rubber, and 5-300 parts by weight extender oil per 100 parts total weight of polypropylene and rubber, and 10-100 parts by weight particulate filler per 100 parts total weight of rubber and extender oil.

55. The filled composition of claim 54 in which the particulate filler is carbon black.

56. The filled composition of claim 54 in which the particulate filler is non-black filler.

57. The filled composition of claim 56 in which the filler is clay.

58. The composition of claim 35, 36 or 37 in which the polyolefin resin is polypropylene and in which the cure activator is selected from the group consisting of metal halide and halogen-donating polymer, the halogen-donating polymer being a chlorosulfonated polyethylene, the cure activator system including zinc oxide and the phenolic curing resin being dimethylol-p-octyl phenol.

59. An elastoplastic composition comprising a blend of thermoplastic crystalline polyolefin resin, in an amount sufficient to impart thermoplasticity to the composition, and cured EPDM rubber in the form of small dispersed particles essentially of a size of about 50 microns number average or below, in an amount sufficient to impart rubber-like elasticity to the composition, in which the rubber is cured with phenolic curative comprising phenolic curing resin and cure activator to the extent that no more than about five percent of the curable rubber is extractable in boiling xylene.

60. The composition of claim 59 in which the rubber is cured to the extent that no more than about three percent of the rubber in the blend is extractable in cyclo-hexane at 23°C.

61. The composition of claim 59 wherein said rubber is present in an amount below about 75 parts by weight and said resin is present in an amount above about 25 parts by weight per 100 parts total weight of resin and rubber, and in which the rubber is cured to the extent that no more than about three percent of the rubber in the blend is extractable in cyclohexane at 23°C.

62. The composition of claim 59 comprising a blend of about 25-75 parts by weight polyolefin resin and about 75-25 parts by weight of cured EPDM rubber per 100 parts total weight of polyolefin resin and rubber and in which the rubber is cured to the extent that no more than about three percent of the rubber in the blend is extractable in cyclohexane at 23°C.

63. The composition of claim 59, 61 or 62 in which the polyolefin resin is polypropylene.

64. The composition of claim 59, 61 or 62 in which the polyolefin resin is polypropylene and in which the rubber is a terpolymer of ethylene, propylene, and ethylidene norbornene.

65. The composition of claim 59, 61 or 62 con-taining about 30 to 250 parts by weight of extender oil per 100 parts by weight of rubber.

66. The composition of claim 59, 61 or 62 in which the rubber is cured with a brominated phenolic curing resin.

67. The composition of claim 59, 61 or 62 in which the rubber is cured with a brominated phenolic curing resin and zinc oxide cure activator.

68. The composition of claim 59, 61 or 62 contain-ing halogen-donating polymer and in which the rubber is cured with a brominated phenolic curing resin.

69. The composition of claim 59, 61 or 62 in which the phenolic curing resin is a non-halogenated dimethylol (alkyl)phenol compound.

70. The composition of claim 59, 61 or 62 in which the phenolic curing resin is a non-halogenated dimethylol(alkyl)phenol compound and wherein the cure activator is selected from the group consisting of metal halide and halogen-donating polymer.

71. The composition of claim 59, 61 or 62 in which the phenolic curing resin is a non-halogenated dimethylol (alkyl)phenol compound and wherein the cure activator is selected from the group consisting of metal halide and halogen-donating polymer, the halogen-donating polymer being a chlorosulfonated polyethylene.

72. The composition of claim 59, 61 or 62 in which the phenolic curing resin is a non-halogenated dimethylol (alkyl)phenol compound and wherein the cure activator is selected from the group consisting of metal halide and halogen-donating polymer, the halogen-donating polymer being a chlorosulfonated polyethylene, and in which the cure activator system includes zinc oxide.

73. The composition of claim 59 comprising a blend of about 30 to 70 parts by weight polypropylene, about 30 to about 70 parts by weight of EPDM rubber, and 5-300 parts by weight extender oil per 100 parts total weight of poly-propylene and rubber, and 10-100 parts by weight particulate filler per 100 parts total weight of rubber and extender oil, and in which the rubber is cured to the extent that no more than about three percent of the rubber in the blend is extractable in cyclohexane at 23°C.

74. The filled composition of claim 73 in which the particulate filler is carbon black.

75. The filled composition of claim 73 in which the particulate filler is a non-black filler.

76. The filled composition of claim 73 in which the filler is clay.

77. The composition of claim 59, 61 or 62 in which the cured EPDM rubber is of the size of about 5 microns number average or below and in which the polyolefin resin is polypropylene.

78. The composition of claim 73 in which the cured EPDM rubber is of the size of about 5 microns number average or below.

79. The composition of claim 59, 61 or 62, prepared by masticating the blend and phenolic curative, in an amount sufficient to cure the rubber, at curing temperature until the rubber is cured to the extent that no more than about five percent of the rubber is extractable in boiling xylene.

80. A process for preparing elastoplastic composi-tions which comprises (1) masticating below about 75 parts by weight of EPDM rubber and above about 25 parts by weight thermoplastic crystalline polyolefin resin per 100 total parts by weight of rubber and polyolefin resin, and phenolic curing resin, in an amount sufficient to cure the rubber, at a temperature sufficient to soften or melt the polyolefin resin;

and for a time sufficient to obtain a homogeneous mixture in which the rubber is in the form of small dispersed particles essentially of a size of about 50 microns number average or below, (2) adding cure activator and (3) continuing masticating the mixture at curing temperature until the rubber is cured to the extent that no more than about five percent of the curable rubber is extractable in boiling xylene.

81. The process of claim 80 in which the phenolic curing agent is brominated phenolic curing resin.

82. The process of claim 81 in which the cure activator is zinc oxide.

83. The process of claim 80 in which the phenolic curing resin is a non-halogenated dimethylol(alkyl) phenol compound.

84. The process of claim 83 in which the cure activator comprises chlorosulfonated polyethylene and zinc oxide.

85. The process of claim 84 in which the phenolic curing resin is dimethylol-p-octyl phenol.

86. The process of claim 80 in which the polyolefin resin is polypropylene.

87. An elastoplastic composition comprising a blend of thermoplastic crystalline polyolefin resin, in an amount sufficient to impart thermoplasticity to the composition, and EPDM rubber, in an amount sufficient to impart rubber-like elasticity to the composition, in which the EPDM rubber is cured with phenolic curative comprising about 5 parts to 20 parts by weight phenolic curing resin and about 0.01 to 10 parts by weight cure activator per 100 parts by weight of EPDM rubber.

88. The composition of claim 87 wherein said rubber is present in an amount below about 75 parts by weight and said resin is present in an amount above about 25 parts by weight per 100 parts total weight of resin and rubber.

89. The composition of claim 87 comprising a blend of about 25-75 parts by weight of polyolefin and about 75-25 parts by weight of EPDM rubber per 100 total parts by weight of polyolefin resin and EPDM rubber.

90. The composition of claim 87, 88 or 89 in which the polyolefin resin is polypropylene.

91. The composition of claim 87, 88 or 89 in which the polyolefin resin is polypropylene and in which the phenolic curative comprises about 7 to 14 parts by weight of phenolic curing agent per 100 total parts by weight of EPDM rubber.

92. The composition of claim 87, 88 or 89, in which the polyolefin resin is polypropylene and in which the phenolic curative comprises about 7 to 14 parts by weight of phenolic curing agent per 100 total parts by weight of EPDM rubber, the phenolic curing resin being dimethylol-p-octyl phenol.