MODIFICATION OF THERMOPLASTIC VULCANIZATES WITH A THERMOPLASTIC RANDOM COPOLYMER OF ETHYLENE

Abstract: Random thermoplastic ethylene copolymers can be used to increase the elongation to break and toughness of thermoplastic vulcanizates. Polypropylene is a preferred thermoplastic phase. The rubber can be olefinic rubbers. Random thermoplastic ethylene copolymers are different from Ziegler-Natta ethylene copolymers as the compositional heterogeneity of the copolymer is greater with Ziegler-Natta copolymers. This difference results in substantial differences in properties (elongation to break and toughness) between thermoplastic vulcanizates modified with random thermoplastic ethylene and those modified with Ziegler-Natta ethylene copolymers. An increase in elongation to break results in greater extensibility in the articles made from a thermoplastic vulcanizate.

Description: MODIFICATION OF THERMOPLASTIC VULCANIZATES WITH A THERMOPLASTIC RANDOM COPOLYMER OF ETHYLENE FIELD OF INVENTION Thermoplastic random copolymers of ethylene can be used to increase the elongation to break and toughness of thermoplastic vulcanizates made from a thermoplastic polypropylene phase and a crosslinkable rubber. The thermoplastic random copolymers of ethylene are available from several suppliers as polymers from single site catalyst, often referred to as metallocene catalyst polymerized polymers. They differ from other ethylene copolymers in that the comonomer is rather uniformly distributed in substantially all of the polymer chains, while in prior art thermoplastic ethylene copolymers the comonomer was disproportionately increased in a portion of the polymer chains and the comonomer was disproportionately reduced in a portion of the polymer chains resulting in a broad compositional distribution for the polymer. BACKGROUND OF INVENTION Thermoplastic vulcanizates from polypropylene and a rubber have gained wide acceptance as a substitute for thermoset rubbers in a variety of applications. It would be desirable for many of these applications to increase the elongation to break of said thermoplastic vulcanizates and to increase the total toughness (as measured by the area under the stress strain curve) when a thermoplastic vulcanizate is measured in a tensile test. Polyethylene and copolymers of polyethylene are very interesting polymers because they can have both amorphous regions and crystalline regions. Amorphous regions of polyethylene are rubbery at room temperatures having a glass transition temperature well below 0°C. Crystalline regions of polyethylene are more rigid materials having a melting point generally between about 80°C and 135°C depending on the characteristics of the crystals and the densitλ- of the polyethylene. The crystalline regions of polyethylene are more dense, i.e.. have higher densities than the amorphous region of the polymer. . i High density polyethylene has higher relative proportions or cπ stallme poh mer versus amorphous polymer than its low-density counterparts Generalh poh mer chain branching and the incorporation of comonomers decrease the cr> stalhn in poly ethylene due to the fact that the crystal structure cannot accommodate mam comonomers or large chain branches The amorphous regions ol semi- crystal ne polyethylene adds to the toughness of the material as it can undergo elastic and plastic deformation to accommodate stresses or strains thus avoiding fracture of the crystalline regions Ethylene-propylene-diene polymers (EPDM) also know n as lene-prop\ lene-dιene-polymethylene rubber w ith weight ratios ot eth\ lene to prop\ lene of trom 25 75 to about 75 25 e sufficient incorporation ot both ethy lene and propylene in the polymer chain such that these materials are rubber} at room temperature rather than solid, such as polyethylene or poh propylene Copolymers from polyethylene have been made in the past w ith cataly sts other than single site catalysts Various polymerization techniques e been used so that a specified portion of comonomer is present in the copolymer Howe\ er. few polymerization catalysts or poly merization s . stems are known which truh randomly polvmeπze ethylene w ith comonomers into a thermoplastic copolymer Linear low densitλ polyethy lene invoh es the poh meπzation with an ethylene feed and a second olefin feed, generalh 4-8 carbon atoms, keeping a relatively constant feed ratio The cataly sts have several different active sites such that some sites incorporate the second olefin more efficiently than others The different sites also can result in different poh mer chain lengths This results in a broad molecular weight distribution and a broad compositional distribution in the resulting polymer Another method of making low-density polyethylene inv olves using polymerization conditions that encourage branching in the polyethvlene chain, said branching disrupting the cry stalhnity of the polyethylene and causing a reduced amount of cry stalhnm and consequently a reduced density SUMMARY OF INVENTION Thermoplastic vulcanizates from poly prop\ lene. a rubber, and a thermoplastic random copolymer of ethylene can be prepared by blending a thermoplastic random copolymer of ethylene w ith the components of a thermoplastic \ ulcanizate or by mixing a thermoplastic random copolymer of ethylene with a preformed thermoplastic vulcamzate from polypropylene and a rubber The thermoplastic random copolymers of ethylene are commercially available as a result of the development of single site catalysts including metallocene catalysts The thermoplastic random copolymers of ethylene currenth have rather narrow molecular weight distributions and rather narrow compositional distributions The av erage comonomer concentration is from about 5 to about 30 weight percent based on the weight of the lene copolymer As is known to the art. thermoplastic \ ulcanizates usually comprise from about 15 to about 75 parts of the thermoplastic phase and from about 25 to about 85 parts by weight of the rubber phase They can further comprise various amounts of curatives, plasticizers. fillers, etc The thermoplastic random copolymer of ethylene is desirably present in amounts of from about 5 to about 150 parts per 100 parts of polypropylene in the thermoplastic \ ulcanizate The rubber can be any hy drocarbon rubber such as but\ l rubbers, halobun 1 rubbers halogenated (e brominated) copolymers of paramethy 1 styrene and ISO- butylene. EPDM rubber, and natural rubber or diene-based homo or copolymer rubber DETAILED DESCRIPTION OF THE INVENTION The thermoplastic random copolymer of ethy lene used to modih thermoplastic \ ulcamzates in this invention is different from other etlr lene copoh mers used in thermoplastic \ ulcamzates m the past it is much more random in terms ot the incorporation of comonomer( s ) in the copoly mer In the past, copolymers w ith more than 2. 5. or 10 weight percent comonomer were either rubbers or were a physical blend of copolymers low in ethylene repeat units and other copolymers significanth richer in ethylene repeat units, which blend would have a relative weight percent of comonomer and ethylene cited in the product literature. The thermoplastic random copolymer of ethylene used in this invention can have very narrow molecular weight distributions (Mw/Mn) of from about 1.5 or 1.7 to 3.5. more desirably from about 1 .8 to about 3.0 and preferably from about 1 .5 or 1 .9 to 2.8 due to the single site catalyst, also referred to as metallocene catalyst, currently used to prepare such polymers. This disclosure is not limited to thermoplastic random copolymers of ethylene made with metallocene catalysts, but rather uses those commercially available polymers as illustrative of a polymerization method capable of making random copolymers operable in this disclosure. Further, the molecular w eight distributions are recited as a method of identifying these polymers, but are not a requirement for operativeness of the copolymer in a thermoplastic vulcanizate. The thermoplastic random copolymer of ethylene can have varying amounts of one or more comonomers therein. In the examples, the thermoplastic random copolymer of ethylene is often referred to as a plastomer indicating that it has some properties of both a plastic and an elastomer. Desirably the amount of repeat units from one or more comonomers is from about 5. 10. 15 or 20 to about 30 or 35 weight percent of the thermoplastic random copolymer of ethylene. More desirably, the amount of repeat units from said one or more comonomers is from about 10 to about 25 weight percent. The amount of ethylene in said thermoplastic random copolymer of ethylene is desirably from about 65 or 70 to about 80. 85. 90 or 95 weight percent, and more desirably from about 65. 70 or 75 to about 80. 85 or 90 weight percent. The one or more comonomers can be any ethylenically unsaturated compound copolymerizable with ethylene using a single site catalvst. The one or more ethylenically unsaturated monomers desirably have from about 3 or 4 to about 12 carbon atoms, more desirably from about 3 or 4 to about 8 carbon atoms, and are preferably monoolefins with the specified range of carbon atoms. Examples of such comonomers include alkylacrylates such as ethylacrylate. buty acrylate: monoolefins such as propylene or octene. etc. The thermoplastic random copolymers of ethylene desirablv have densities of from about 0.85 or 0.86 to about 0.91. 0.92 or 0.93 grams per cubic centimeter, more desirably from about 0.86 or 0.87 to about 0.90. 0.91 or 0.92 grams per cubic centimeter. As the polymerization systems, e.g.. the single site catalyst polymerization system which includes metallocene catalysts readily- incorporate comonomers with the ethylene in the thermoplastic random copolymer of ethylene. the comonomers are randomly distributed within the individual polymer chains and the individual polymer chains are rather uniform in comonomer composition. Due to the uniform distribution of repeat units from the comonomers within the polymer chains and the uniformity of comonomer distribution within the polymer, as opposed to prior art polyethylene copolymers. the thermoplastic random copolymers of ethylene tend to have rather narrow melting temperature ranges by test methods such as dynamic scanning calorimetry (DSC) as compared to prior art ethylene copolymers. This is due to the fact that the thermoplastic random copolymers of ethylene have a very uniform crystalline structure and thus melt within a narrow temperature range. The random copolymers of ethylene vary from most other ethylene copolymers in that the melting peak in the dynamic scanning calorimetry of the random copolymers decreases as the comonomer content increases. The peak represents the largest amount of endothermic crystal melting at a single temperature. Therefore, desirably the random copolymer of ethylene has a peak melting temperature of less than about 120°C. more desirably from about 50 to about 120°C. still more desirably from about 55. 60. or 65 to about 105 or H OT. and preferably from about 55. 60 or 65 to about 90. 95 or 100°C. Prior art ethylene copolymers melt over a broader temperature range because they have a broader range of copolymer compositions. The thermoplastic random copolymer of ethylene can be incorporated into the components used to form a thermoplastic vulcanizate (TPY ) or blended with a TPV composition prior to vulcanization of the rubber component, or added after said vulcanization. The physical properties of the resulting blend may or may not vary depending upon whether the thermoplastic random copolymer of ethylene was added prior to or subsequent to vulcanization of the rubber phase The thermoplastic random copolymer of ethy lene can be considered a supplement to the polypropy lene of the thermoplastic \ ulcanizate or can be considered to be substituted on a weight basis for the polypropylene in a thermoplastic vulcanizate When the random copolymer is added prior to vulcanization, it is anticipated that a majority of the thermoplastic random copolymers of ethylene are in the thermoplastic phase of the resulting thermoplastic vulcanizate. although it may be disproportionately present at the interface between the rubber phase and the thermoplastic phase Since the melting temperature of the cry stalline portion of the thermoplastic random copolymer of ethylene is lower than that of the semi-cr stalhne poly propy lene, it is readily melt-blendable with the thermoplastic \ ulcamzate or the components thereof at the normal processing/mixing temperatures for the thermoplastic \ ulcanizate The thermoplastic random copolymer of ethylene is desirably present in amounts from about 5 to about 150 parts per 100 parts of polypropylene m the thermoplastic vulcanizate. more desirably in amounts from about 10 to about 120 parts per 100 parts of polypropylene, still more desirably from about 10 or 25 to about 100 parts per 100 parts weight of poly - propylene. and preferably from about 25 to about 80 parts by weight per 100 parts by weight of polypropylene Thus the thermoplastic random copolymer of ethylene may be present m amounts from about 20 to about 60 weight percent of the thermoplastic phase of the thermoplastic \ ulcamzate Since the thermoplastic phase of the thermoplastic vulcanizate can be from about 15 to about 75 percent of the blend of the thermoplastic and rubber phase (w ithout fillers, oils, etc ). the percentage of thermoplastic random copolymer of ethvlene based upon the total weight of the thermoplastic \ ulcanizate can range from 1 or 2 to about 40 or 50 weight percent based upon either the combined weight of the thermoplastic polypropylene and rubber components ( w ithout fillers, oils etc ) or the weight of the thermoplastic \ ulcanizate The major portion of polymers in the thermoplastic vulcanizate are the semi-crystalline polypropylene: the thermoplastic random copolymer of ethylene. and a crosslinkable rubber. Examples of semi-crystalline polypropylene are polypropylene, its copolymers and mixtures thereof. The rubber may be a polyolefin such as EPDM rubber which, because of the random nature of its repeat structure or side groups, tends not to crystallize. Examples of the rubber include EPDM rubber, butyl rubber, halobutyl rubber, halogenated (e.g. brominated) copolymer of p-alkylstyrene and an isomonoolefin of from 4 to 7 carbon atoms (e.g. isobutylene). natural rubber. homo or copolymers of at least one diene monomer, or combinations thereof. Minor amounts of other polymers may be added to modify flow properties, such as fillers or diluents, or as additives, such as polymeric antioxidants. Non- polymeric materials such as oils, fillers, diluents and additives (discussed in a later paragraph) may be present in large amounts. Amounts of most of the components to the blend will be specified either 1 ) per 100 parts by weight of the blend of the semi-crystalline polypropylene and the rubber or 2) per 100 parts by weight of rubber. The semi-crystalline polypropylene is desirably from about 6 to about 85 weight percent, more desirably from about 7 to about 75. and preferably from about 8 to about 60 weight percent of the thermoplastic vulcanizate. Desirably the rubber is from about 5 to about 70. more desirably about 10 to about 50 and preferably from about 15 to 45 weight percent of the thermoplastic vulcanizate. Desirably the other conventional components to TPV. e.g. fillers, oils, curatives, processing aids. etc.. are from about 0. 1. 2. or 10 to about 87. 88 or 89 weight percent of the TPV. more desirably from about 0. 1. 2. or 15 to about 81. 82 or 83 and preferably from about 0. 1. 2. or 25 to about 75. 76 or 79 weight percent. The semi-crystalline polypropylene is desirably from about 15 to about 80 parts by weight, more desirably from about 25 to about 75 parts by weight, and preferably from about 25 to about 50 pans by weight per 100 parts of the blend of semi-crystalline polypropylene and the unsaturated rubber. The rubber is desirably from about 20 to about 85 parts b\ w eight, more desirabh from about 25 to about 75 parts by weight and preferably from about 50 to about 75 parts by weight per 100 parts by weight of said blend If the amount of semi-crystalline polypropylene is based on the amount of rubber, it is desirabh from about 17 5 to about 320 parts by weight, more desirably from about 33 to about 300 parts and preferably from about 33 to about 200 parts by weight per 100 parts by weight of the rubber The terms "blend" and "thermoplastic vulcanizate" used herein mean a mixture ranging from small particles of crosslinked rubber well dispersed in a semi-crvstalline polypropylene matrix to co-continuous phases ot the semi-cry stalhne poly propylene and a partialh to fulh crosslinked rubber or combinations thereof The term "thermoplastic \ ulcamzate ' indicates the rubber phase is at least partially vulcanized ( crosslinked) The term "thermoplastic vulcanizate" refers to compositions that may possess the properties of a thermoset elastomer and are reprocessable in an internal mixer Upon reaching temperatures above the softening point or melting point of the semi-crystalline polypropylene phase, they can form continuous sheets and/or molded articles with what \ isually appears to accomplish complete knitting or fusion of the thermoplastic \ ulcamzate under conv entional molding or shaping conditions for thermoplastics Subsequent to dynamic vulcanization (curing) of the rubber phase of the thermoplastic vulcanizate. desirably less than 5 weight percent of the rubber is extractable from the specimen of the thermoplastic v ulcanizate in boiling \ylene Techniques for determining extractable rubber as set forth in L S Patent 4.31 1.628. are herein incorporated by reference The semi-crvstalline polypropylene comprises semi-crystalline thermoplastic polymers from the polymerization of monoolefin monomers ( e g 2 to 10 carbon atoms ) by a high pressure, low pressure, or intermediate pressure process, or bv Ziegler-l atta catalysts, or by metallocene catalvsts It may hav e any tacticity (e g isotactic and syndiotactic) or be a copolymer such as impact modified polypropy lene or a random polypropylene copolvmer Desirabh the monoolefin monomers converted to repeat units are at least 80. 85 or 93 percent monoolefins of the formula CH = C(CH-)-H The poly propylene can be a homopolymer as well as a reactor copolymer poly propylene Desirably it has a melting temperature peak of at least 120°C The rubbei can be any rubber that can react and be crosslinked under cross nking conditions These rubbers can include natural rubber. EPDM rubber, buty 1 rubber, halobutyl rubber, halogenated (e « brominated) copolymers of p-alkylstyrene and an isomonoolefin. homo or copolymers from at least one conjugated diene. or combinations thereof EPDM. butyl and halobuty l rubbers are referred to as rubbers low in residual unsaturation and are preferred when the v ulcanizate needs good thermal stability or o\ιdatιv e stability The rubbers low m residual unsaturation desirably have less than 10 weight percent repeat units having unsaturation Desirably excluded from rubbers are acrylate rubber and epichlorohydπn rubber For the purpose of this invention, copolymers will be used to define polymers from two or more monomers, and polymers can have repeat units from one or more different monomers The rubber is desirably an olefin rubber such as EPDM-type rubber EPDM-type rubbers are generalh terpolymers derived from the polymerization of at least two different monoolefin monomers having from 2 to 10 carbon atoms, preferably 2 to 4 carbon atoms, and at least one poly- unsaturated olefin having from 5 to 20 carbon atoms Said monoolefins desirably have the formula CH : =CH-R where R is H or an alkyl of 1 -12 carbon atoms and are preferably ethylene and propylene Desirably the repeat units from at least two monoolefins (and preferably from ethylene and propy lene) are present in the pohmer in weight ratios of 25 75 to 75 25 ( ethylene. propylene) and constitute from about 90 to about 99 6 weight percent of the polymei The poly unsaturated olefin can be a straight chained, branched, cy clic, bridged ring bicyc c. fused ring bicy c c compound, etc . and preferabh is a nonconjugated diene Desirably repeat units from the nonconjugated poh unsaturated olefin is from about 0 4 to about 10 weight percent of the rubber The rubber can be a buty l rubber, halobutv l rubber, or a halogenated (e g brominated) copolymer of p-alkv lsty rene and an lsomonoolefin of 4 to 7 carbon atoms "But l rubber" is defined a poh mer predominantly comprised of repeat units from isobutylene but including a few repeat units of a monomer which provides sites for crosshnking The monomers which provide sites for crosshnking can be a polyunsaturated monomer such as a conjugated diene or divinyl benzene Desirably from about 90 to about 99 5 weight percent of the butyl rubber are repeat units derived from the polymerization of isobutylene. and from about 0 5 to about 10 weight percent of the repeat units are from at least one polyunsaturated monomer hav ing from 4 to 12 carbon atoms Preferably the po unsaturated monomer is isoprene or div inv lbenzene The poh mer may be halogenated to further enhance reactiv ity in crosshnking Preferably the halogen is present in amounts from about 0 1 to about 10 weight percent, more preferably about 0 5 to about 3 0 weight percent based upon the weight of the halogenated polymer, preferably the halogen is chlorine or bromine The brominated copolymer of p-alky styrene. hav ing from about 9 to 12 carbon atoms, and an lsomonoolefin. having from 4 to 7 carbon atoms, desirably has from about 88 to about 99 weight percent lsomonoolefin. more desirably from about 92 to about 98 weight percent, and from about 1 to about 12 weight percent p-alkylstyrene. more desirably from about 2 to about 8 weight percent based upon the weight of the copolymer before halogenation Desirably the alkylstyrene is p-methylstyrene and the lsomonoolefin is isobutylene Desirably the percent bromine is from about 2 to about 8. more desirably from about 3 to about 8. and preferably from about 5 to about 7 5 weight percent based on the weight of the halogenated copolymei The halogenated copolymer is a complementary amount, I e . from about 92 to about 98. more desirabh from about 92 to about 97 and preferably from about 92 5 to about 95 weight percent These polymers are commercialh av ailable from Exxon Chemical Co Other rubber such as natural rubber or homo or copoly mers from at least one conjugated diene can be used in the dv namic v ulcanizate These rubbers are higher in unsaturation than EPDM rubber and butv l rubber The natural rubber and said homo or copolymers ot a diene can optionalh be partialh hv drogenated to increase thermal and oxidam e stabihtv The sy nthetic rubber can be nonpolar or polar depending on the comonomers Desirabh the homo or copolymers of a diene have at least 50 w eight percent repeat units from at least one conjugated diene monomer hav ing from 4 to 8 carbon atoms Comonomers may be used and include vinyl aromatic monomer(s) hav ing from 8 to 12 carbon atoms and acrylomtπle or alkyl-substituted acrylomtπle monomer(s) having from 3 to 8 carbon atoms Other comonomers desirabh used include repeat units from monomers having unsaturated carbow lic acids, unsaturated dicarbox c acids, unsaturated anhv dπdes of dicarboxy lic acids, and include diviny lbenzene. alkvlacrylates and other monomers having from 3 to 20 carbon atoms Examples of synthetic rubbers include sv nthetic poly isoprene poly butadiene rubber, styrene-butadiene rubber, butadiene-acry lonitπle rubber. etc Amine-functionahzed. carboxy-functiona zed or epoxv -functionalized synthetic rubbers mav be used, and examples of these include maleated EPDM. and epoxv -functionalized natural rubbers These materials are commercialh av ailable The thermoplastic v ulcanizates of this disclosure are generalh prepared by melt-mixing the semi-cry stal ne poholefin(s) ( e g poly propv lene) the rubber, and other ingredients (filler, plasticizer. lubricant, stabilizer, etc ) in a mixer heated to above the melting temperature of the semi-crystalline polypropylene The optional fillers, plasticizers. additives etc . can be added at this stage or later Alter sufficient molten-state mixing to form a well mixed blend, v ulcanizing agents (also known as curatives or crosshnkers) are generalh added In some embodiments it is preferred to add the v ulcanizing agent in solution w ith a liquid, for example rubber processing oil or in a mastcrbatch which is compatible with the other components It is conv enient to follow the progress ot v ulcanization bv monitoring mixing torque or mixing energv requirements during mixing The mixing torque or mixing energy curv e "eneralh eoes throush a maximum after which mixing can be continued somewhat longer to improve the fabπcabi ty of the blend If desired, one can add some of the ingredients after the dynamic v ulcanization is complete The random thermoplastic copolymer(s) of ethylene can be added before during, or after v ulcanization After discharge from the mixer, the blend containing v ulcanized rubber and the thermoplastic can be milled, chopped, extruded, pelletized. injection-molded, or processed by any other desirable technique It is usually desirable to allow the fillers and a portion of any plasticizer to distribute themselves in the rubber or semi-crystalline polypropylene phase before the rubber phase or phases are crosslinked Crosshnking (v ulcanization) of the rubber can occur in a few minutes or less depending on the mix temperature shear rate, and activators present tor the curativ e Suitable curing temperatures include from about 120°C or 150°C for a semi-cry stal ne polypropylene phase to about 250°C. more preferred temperatures are from about 150°C or 1 70°C to about 225°C or 250°C The mixing equipment can include Banbury * " mixers. Brabender™ mixers, and certain mixing extruders The thermoplastic vulcanizate can include a v ariety of additives The additiv es include particulate fillers such as carbon black, silica, titanium dioxide, colored pigments, clay , zinc oxide, steaπc acid, stabilizers, anti- degradants. flame retardants. processing aids, adhesiv es. tackifiers plasticizers wax. discontinuous fibers (such as wood cellulose fibers ) and extender oils When extender oil is used it can be present in amounts from about 5 to about 300 parts by weight per 100 parts by weight of the blend of semi-crystalline polypropy lene and rubber The amount of extender oil (e . hydrocarbon oils and ester plasticizers) may also be expressed as from about 30 to 250 parts, and more desirably from about 70 to 200 parts bv weight per 100 parts bv weight of said rubber When non-black fillers are used, it is desirable to include a coupling agent to compatibi ze the interface between the non-black filleis and polv mers Desirable amounts of carbon black, when present, are from about 5 to about 250 parts bv weight per 100 parts by weight of rubber Thermoplastic v ulcanizate compositions of the invention are useful for makine a vaπetv of articles such as tires, hoses belts caskets moldings and molded parts They are particularly useful for making articles bv extrusion, injection molding, blow molding, and compression molding techniques They also are useful for modifying thermoplastic resins and in particular polyolefin resins The compositions can be blended with fhermo- plastic lesins using conventional mixing equipment making a rubber modified thermoplastic resin The properties of the modified thermoplastic resin depend upon the amount of thermoplastic vulcanizate composition blended The stress-strain properties of the compositions are determined in accordance with the test procedures set forth in ASTM D412 These properties include tension set (TS), ultimate tensile strength (UTS). 50° o modulus (M50) 100° o modulus (Ml 00). and ultimate elongation at break (UE ) The tear strength is measured according to ASTM D623 1 he hardness is measured according to ASTM D2240 with a 5 second delav using either the Shore A or Shore D scale Compression set (CS) is determined in accordance with ASTM D-395. Method B. by compressing the sample for 22 hours at 100 ϋ C Oil swell (OS) (percent change in weight) is determined in accordance with the ASTM D-471 by submerging the specimen in IRM 903 oil and unless otherwise specified is for 24 hours at 125±2 α C Especially preferred compositions of the inv ention are rubberv compositions having tension set values of about 50% or less which compositions meet the definition for rubber as defined by Λ.STM Standards. V 28. page 756 (D1566) More preferred compositions are rubbery compositions having a Shore D hardness of 60 or below, or a 100% modulus of 18 MPa or less, or a Young ' s modulus below 250 MPa EXAMPLES Tables I through XI provide additional experimental data on pol ethv lenes and thermoplastic random ethvlene copoly mers blended w ith either thermoplastic v ulcanizates or the precursors to thermoplastic v ulcanizates The ethy lene homopolvmers and some of the ethylene copoh mers which aie not truly random when blended with the thermoplastic v ulcanizates or then precursors are control examples The examples of thermoplastic random copolymers of ethylene blended with thermoplastic vulcanizates or their precursors are examples of the invention. Tables I and II show the composition of several ethvlene copolymers and the composition of several thermoplastic vulcanizates used in later tables. Table X also shows several ethylene polymers or copolymers. The trade name Exact™ is being used by Exxon for some of their metallocene polymerized ethylene copolymers. The trade name Engage™ is being used by DuPont Dow Elastomers. In Table I several experimental polymers (e.g. those with SLP prefixes) from Exxon were used in the experimentation, but similar commercially available ethylene copolvmers are currently available under the Exact trade name. Table III shows the variation in physical properties achieved with varying amounts of four different thermoplastic random ethylene copolymers of ethylene and 1 -butene. The Shore A hardness may increase or decrease from the addition of the thermoplastic random ethylene copolymers depending upon the particular thermoplastic random ethylene copolymer used. Tensile strength usually increases along with ultimate elongation and relative toughness. The oil swell and the compression set at 100°C typically increase with the addition of thermoplastic random ethylene copolymer. Control samples (with a C suffix ) are generally a thermoplastic vulcanizate without a thermoplastic random ethylene copolymer. Table IV illustrates blends of a thermoplastic vulcanizate and thermoplastic random ethylene copolymers and their physical properties. These copolymers vary from those in Table III in that they are copolymers of ethylene with 1 -octene. Tables V and VI illustrate further blends of ethylene or ethylene copolvmers with thermoplastic vulcanizates. In these examples, ultimate elongation increases. Table VII lists several conventional ethylene copolymers used in later tables. Table VIII illustrates blends of conv entional ethylene copoly mers and thermoplastic vulcanizates The elongation to break ot the blends and the toughness are generalh less than the control w ithout eth lene copolymers There are increases in elongation and toughness w ith Vιstalon ' 808 and 4709. 5 but they adverseh affect other properties such as increasing oil swell Table IX shows blends of the precursors of a thermoplastic vulcanizate or a thermoplastic vulcanizate with a thermoplastic random ethylene copolymer The purpose of this table is to demonstrate that the thermoplastic random ethylene copolymer can be added before or after curing and some 10 changes in the physical properties can be anticipated Generally if added after cure, it is believ ed the thermoplastic random ethv lene copoly mer causes low er final Brabender torque, slightly higher elongation to break and. as a result ot the higher elongation, a slightly higher toughness The oil sw ell is expected to decrease from adding the thermoplastic random ethylene copolymer after 15 vulcanization Table X show s several additional ethylene polymers oi copolymers both within and outside of the definition of the thermoplastic random ethylene copolymer Table XI show s the physical properties of blends ot a 20 thermoplastic v ulcanizate and the ethylene copohmers and thermoplastic random ethylene copolymers The ultimate elongation increases more dramatically for the thermoplastic random ethylene copolymers than for the other copolymers and homopolvmers To better illustrate the difference between the thermoplastic i random ethylene copolymers and other copolymers of similar total comonomer concentration. Table XII w as prepared The phy sical properties show n are the ultimate elongation and 100 percent modulus for blends ot thermoplastics and the ethy lene homopolv mers or copolymers The first and third examples aie thermoplastic random ethy lene copolymers according to this disclosuie The second and fourth examples are not within the description of a thermoplastic random ethylene copolymer of this disclosure As can be seen from the data. the ultimate elongation is dramatically better for the first and third examples than for the other examples outside the scope of this disclosure. As can be seen by the 100 percent modulus data, the first and third compositions have lower modulus, i.e.. are softer than the second and fourth compositions which are outside the scope of this disclosure. Table XIII was prepared to illustrate that a TPV using butyl rubber, nitrile rubber or natural rubber instead of EPDM rubber would have improved ultimate elongation and tensile strength when blended with a random ethylene copolymer (plastomer). * Available from Exxon ** Available from DuPont Dou Elastomers *** Melt index is ASTM D-1238 (E) The residual of the thermoplastic vulcanizates being conventional TPV components including oils, fillers, processing aids, curatives, etc. C 03 (0 H H C H m n x rπ m H c r- I m t CD c CD 0) H H C H rπ en x m rπ H I c O I m O) ω c CD 0) H H C H m CO x m rπ H c r- m Nϊ O) O c 09 CO H C m O x m m H ro c I m r CO c 03 CO H H C H m en x rπ m H I UJ c rπ ro en Table V Physical Pioperties of Blends of a TPV with Plastomer 32( 31 35 ll'V 1000 u 1000 1000 1000 O c 03 I \aet SI P-0566 I 2 249 439 O H Poly pi opy lene Plaslomei Ratio 1000 100 19 10043 10074 H C H Physical Piopeitics, Unaged m CO llaidness S oie I) 555 52 49 x m m 50° « Modulus MPa 1507 1331 81 1086 H I 100% Modulus MPa 1451 1293 I I 60 1084 c r I ensile Sticimth MPa 1686 2066 2077 m t σ> Ultimate I lomiation 438 548 589 625 l neliness Ml/m' 649 798 792 846 ϋ „ I ension set 1 0 % L, 10 mm, 605 570 470 445 21 C O c 03 O H H C H m ω x rπ rπ H I c rπ ro Table VI I Conventional Ethylene Copolymers PDM/EPR Samples C2 (wt.%) ML (1 14) β 125T Mol. Wt. Dist. Vistalon™ 2504 52 26 O Broad c 03 Vistalon™ 85 10 51 49 Narrow O H Vistalon™ 606 48 65 Broad H C H Vistalon™ 7500 50 m Narrow/Tailored Ends CO Vistalon™ 808 77 6 Medium x m m Vistalon™ 4709 75 H I M Vistalon 1 M is avai lable from Exxon. c σ. r- rπ ro I to ^1 I . c u _ > " ■ 5A ° ET. < 9 r > to l\J I I While in accordance with the patent statutes the best mode and preferred embodiment has been set forth, the scope of the invention is not limited thereto, but rather by the scope of the attached claims.

Claims: WHAT IS CLAIMED IS: 1. A thermoplastic vulcanizate composition, comprising: from about 20 to about 85 parts by weight rubber and from about 15 to about 80 parts by weight of semi-crystalline polypropylene wherein said parts by weight are based upon 100 parts by weight of said rubber and said polypropylene, and a thermoplastic random ethylene copolymer wherein the weight ratio of said polypropylene to said random ethylene copolymer is from about 100:5 to 100: 150 and wherein said random ethylene copolymer comprises from about 70 to about 95 weight percent repeat units from ethylene and from about 5 to about 30 weight percent of repeat units from one or more other ethylenically unsaturated monomers based upon the weight of said random ethylene copolymer. wherein said rubber comprises an ethylene-propylene-diene rubber, natural rubber, butyl rubber, halobutyl rubber, halogenated rubber copolymer of p-alkylstyrene and at least one isomonoolefϊn having 4 to 7 carbon atoms, a rubber homopolymer of a conjugated diene having from 4 to 8 carbon atoms, or a rubber copolymer having at least 50 weight percent repeat units from at least one conjugated diene having from 4 to 8 carbon atoms or combinations thereof. 2. A composition according to claim 1. wherein said rubber was dynamically vulcanized in the presence of at least said semi-crystalline polypropylene thereby forming said thermoplastic vulcanizate. 3. A composition according to claim 2. wherein said random ethvlene copolymer has a peak melting temperature between about 50°C and about 120°C. 4. A composition according to claim 3. wherein said random ethylene copolymer comprises from about 70 to about 90 weight percent repeat units from ethylene and from about 10 to about 30 weight percent repeat units from at least one monoolefin having from 3 to 8 carbon atoms. 5. A thermoplastic vulcanizate composition according to claim 3, wherein said peak melting temperature is from about 55 to about 1 10°C. 6. A composition according to claim 3. wherein said peak melting temperature is from about 55 to about 100°C. 7. A composition according to claim 3. wherein said peak melting temperature is from about 55 to about 90°C. 8. A composition according to claim 5. wherein said random ethylene copolymer comprises from about 70 to about 90 weight percent repeat units from ethylene and from about 10 to about 30 weight percent repeat units from at least one monoolefin having from 3 to 8 carbon atoms. 9. A composition according to claim 7. wherein said random ethylene copolymer comprises from about 65 to about 85 weight percent repeat units from ethylene and from about 15 to about 35 weight percent repeat units from at least one monoolefin having from 3 to 8 carbon atoms. 10. A composition according to claim 1. wherein said rubber comprises ethylene-propylene-diene rubber. 1 1. A composition according to claim 1. wherein said rubber comprises butyl rubber, halobutyl rubber, or a halogenated rubber copolymer of p-alkylstyrene and isobutylene. 12. A composition according to claim 1. wherein said rubber comprises natural rubber. 13. A composition according to claim 1. wherein said rubber comprises a rubber homopolymer of a conjugated diene having from 4 to 8 carbon atoms or a rubber copolymer having at least 50 weight percent repeat units from at least one conjugated diene having from 4 to 8 carbon atoms or combinations thereof. 14. A process for making a thermoplastic vulcanizate composition, comprising: blending from about 20 to about 85 parts by weight rubber and from about 15 to about 80 parts by weight of a semi-crystalline polypropylene wherein said parts by weight are based upon 100 parts by weight of said rubber and said semi-crystalline polypropylene, and a thermoplastic random ethylene copolymer. wherein the weight ratio of said polypropylene to said random ethylene copolymer is from about 100:5 to 100:150 and wherein said random ethylene copolymer comprises from about 70 to about 95 weight percent repeat units from ethylene and from about 5 to about 30 weight percent of repeat units from one or more other ethylenically unsaturated monomers based upon the weight of said random ethylene copolymer. and dynamically vulcanizing said rubber after blending with said semi-crystalline polypropylene, or said random ethylene copolymer. or combinations thereof. 15. A process according to claim 14. wherein said random ethylene copolymer has a peak melting temperature from about 50 to about 120°C. 16. A process according to claim 14. wherein said random ethylene copolymer has a peak melting temperature from about 55 to about 100°C. 17. A process according to claim 14. wherein said random ethylene copolymer has a peak melting temperature from about 55 to about 90°C. 18. A process according to claim 14. wherein said thermoplastic ethylene copolymer is added and blended after said rubber is vulcanized.

Inventors: ABDOU-SABET SABET, ELLUL MARIA D, FINERMAN TERRY M, ABDOU-SABET, SABET, ELLUL, MARIA, D., FINERMAN, TERRY, M.
Applicants: ABDOU SABET SABET, ADVANCED ELASTOMER SYSTEMS, ELLUL MARIA D, FINERMAN TERRY M, ABDOU-SABET, SABET, ADVANCED ELASTOMER SYSTEMS, L.P., ELLUL, MARIA, D., FINERMAN, TERRY, M.
Application year: 1998
Main classification: C08J5
IPC codes: C08J5, C08L21, C08L23