Low modulus thermoplastic olefin compositions

This invention relates to thermoplastic olefin compositions of a low modulus which are suitable for fabrication into flexible skins and liners for applications which heretofore have been serviced by skins and liners produced essentially only from plasticized polyvinyl chloride resin compositions. TPO compositions of this invention comprise an impact modified polypropylene resin and a "plastomer" resin intimately blended in proportions with respect of one to another to provide a blend composition having a 1% secant modulus of less than 40,000 psi, and preferably less than 30,000 psi. Optionally, and preferably, the blend also comprises as a discrete component apart from the impact modified polypropylene an olefin copolymer elastomer or a cross-linked elastomer concentrate. Optionally the blend may contain other polyolefin components to alter its stiffness in desirable ways. In addition to the olefin based polymer components, the blend may further comprise, and preferably does comprise, a coupling agent and activator compound which, during melt compounding of the blend components causes the plastomer to extend to its dimer form and, when a discrete OCE component is present to couple the plastomer thereto.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
 Not Applicable.
 1. Field of the Invention
 This invention relates to thermoplastic olefin compositions of a low
 modulus which are suitable for fabrication into flexible skins and liners
 for applications which heretofore have been serviced by skins and liners
 produced essentially only from plasticized polyvinyl chloride resin
 compositions.
 2. Background of the Invention
 Thermoplastic elastomers (TPEs) are an important class of polymeric
 composition which are particularly useful in producing durable components
 through conventional extrusion or injection molding processes. Typically a
 TPE is a blend of thermoplastic polymer and a cured elastomer (rubber).
 Articles may be produced from a TPE that have a behavior similar to a
 cured elastomer but the composition has the advantage, compared to a
 rubber (elastomer) resin, that the TPE undergoes plastic flow above the
 softening point of the thermoplastic polymer component of the blend. This
 permits TPEs to be used in component fabrication through common polymer
 processing techniques, such as injection molding techniques to produce
 finished articles having resilient rubber-like properties without the need
 for a vulcanizing cure of the finished article. This provides TPEs with an
 advantage compared to conventional curable elastomers because conventional
 curable elastomers are tacky, do not undergo plastic flow at elevated
 temperatures and therefore cannot be fabricated into finished article
 forms by an extrusion or injection molding technique.
 The components for a thermoplastic elastomer (TPE) blend may be formed as a
 reactor blend of a thermoplastic polymer and an uncured elastomer--with
 the thermoplastic polymer and the elastomer being simultaneously formed by
 different catalysts in a single reactor vessel--or the respective
 thermoplastic polymer and elastomer components for the blend may be
 separately prepared and then melt blended, generally by a high shear
 mixing technique. The elastomeric component of a TPE may be precured or
 cured in situ by a curing agent added during its melt blending with the
 thermoplastic polymer component. When the elastomer component of a TPE is
 cured during blending with the thermoplastic polymer component, the TPE
 may also be referred to as an "alloy" and/or as a "dynamically vulcanized
 alloy."
 When both the thermoplastic polymer component and the elastomer component
 are composed of olefin monomeric units, the resulting TPE is often
 referred to as a thermoplastic olefin (TPO). Thermoplastic olefin
 elastomer compositions (TPOs) are a class of TPEs based predominately or
 wholly on olefin polymers. A typical TPO is a melt blend or reactor blend
 of a polyolefin plastic, typically a propylene polymer, with an olefin
 copolymer elastomer (OCE), typically an ethylene-propylene rubber (EPM) or
 an ethylene-propylene-diene rubber (EPDM). The polyolefin plastic imparts
 to the TPO the temperature resistance and rigidity typical of that
 thermoplastic resin while the olefin copolymer elastomer imparts
 flexibility, resilience and toughness to the TPO. For example, a propylene
 homopolymer or random copolymer having at least 95 wt. % propylene content
 with an alpha-olefin comonomer content no greater than about 5 wt. % is a
 thermoplastic polymer which when blended by reactor or melt compounding
 with an ethylene-propylene rubber (EPM) or an ethylene-propylene-diene
 (EPDM) rubber results in a composition that would properly be called a
 thermoplastic olefin. Wherein such EPM or EPDM comprises not more than
 about 20 wt. % of this propylene polymer blend, this TPO composition is
 typically referred to as an impact modified polypropylene (im-PP).
 For many purposes, such as enhanced weatherability, low temperature impact
 strength and reduced material cost, a TPO form of TWE composition may be
 and is preferred, provided that the TPO composition can be formulated to
 have a set of properties which will meet the service needs for its
 intended end use application. For example, TPOs that are impact modified
 polypropylenes are particularly well suited for producing resilient
 structures, such as body parts for automotive applications like bumper
 covers, air dams, and other trim parts, etc. The capability of such TPOs
 to be injection molded makes them particularly attractive for high volume
 production necessary in automotive body part applications. However, for
 other end use applications, such as for production of skin and/or liner
 articles--such as dash board and interior door panel skin surface layers
 in the automotive industry or as geomembranes and/or reinforced roof
 membrane liners--impact modified polypropylenes (im-PP) heretofore known
 have been found wanting in their properties, and have not been adopted for
 applications such as skins and/or liners. Chief among the deficiencies of
 the heretofore known im-PP compositions that has forestalled their
 adoption for use as skins/liners has been the stiffness-flexible
 softness-conformability properties of skins and liners formed of such
 compositions, as indicated by the 1% secant modulus property of the base
 composition (as measured per ASTM D-790 on injection molded test
 specimens). Generally, TPEs, and particularly TPOs in the nature of impact
 modified polypropylenes, have a 1% secant modulus (hereinafter "secant
 modulus") significantly exceeding 30,000 psi (200 MPa). Further, the
 potential expedient of increasing the content of the EPM or EPDM component
 of a polypropylene TPO blend to levels greater than about 20 wt. % to
 further reduce its secant modulus is not viable in practice since higher
 elastomer contents tend to render the blend to be too tacky for convenient
 processing and can even lead to a phase inversion of the blend that
 detracts from the other physical properties of an im-PP.
 Many service applications require a skin and/or liner to be very compliant
 or flexible in order to finally conform or fashion the skin or liner about
 the contours of that substrate to which it must be affixed to form the
 finished article. Hence, many applications require a skin or layer, the
 resin base of which is both resilient while being flexible and compliant.
 This property requirement for such a skin or liner translates to a secant
 modulus not exceeding and generally significantly less than about 30,000
 psi (200 MPa) for the base resin from which the skin or liner is to be
 fabricated. And this low secant modulus must be accomplished without
 sacrificing the other properties that would make the resin seem suitable
 or desirable for production of a skin/liner such as automotive door skins
 and instrument panel skins. In the fabrication process these skins need to
 be embossed with desirable surface patterns, and subsequently formed into
 the final contours by various processes such as low pressure molding or
 vacuum forming. Grain retention of the embossed patterns on such skins
 during fabrication is therefore essential. During thermoforming, the
 heated skin needs to stretch rapidly during deep drawing while maintaining
 the embossed grain patterns. To date, plasticized polyvinyl chloride
 compositions have been essentially the only resin that has been found to
 meet this low secant modulus service requirement while also retaining its
 other properties required for service as a skin/liner.
 The use of plasticized polyvinyl chloride (PVC) for service as a flexible
 skin or liner is not without its disadvantages. First, the plasticizer
 required to impart compoundability to the PVC resin so that it may in the
 first instance be fabricated into the form of a skin/liner--a high surface
 area article form--tends over time to migrate to the surface of the
 skin/liner and emits therefrom as an odor (i.e., the "new car" smell for
 example) which may or may not be objectionable to a user of the finished
 article. The continued loss over service lifetime of plasticizer from the
 PVC layer promotes hairline cracks, which in time can lead to the eventual
 failure of the PVC skin. By comparison to olefin based resins, a PVC resin
 is of 30-40% greater density; meaning that to fabricate a skin/liner of a
 given dimension of length, width and thickness, 30-40% more mass is
 required with a PVC resin than would be the case if an olefin based resin
 could instead be utilized. Further, to join one skin/liner section to
 another skin/liner section--an installation act often required in the
 field--requires a tedious process of solvent welding when the skin/liner
 is formed of a plasticized PVC resin since PVC is not a heat weldable
 resin. With an olefin based resin, such installation could readily be
 accomplished by heat welding with a portable hot gun if a TPO composition
 could otherwise be used for service as a skin/liner article.
 Unfortunately, skins/liners formed of present day TPO compositions are too
 stiff and lacking in compliability, (as indicated by their high secant
 modulus properties of the TPO resin) to be readily and easily formed about
 the contours of an article as to which they would form the skin/liner
 layer and hence, have not heretofore been adopted for these end use
 applications.
 It is still a desire in the art to develop a TPO composition that has a
 secant modulus similar to that of a flexible plasticized PVC--that is, a
 secant modulus less than about 40,000 psi, and particularly less than
 about 30,000 psi--without otherwise sacrificing the other beneficial
 mechanical/physical/chemical properties of a TPO composition which would
 render it suitable and/or superior in service as a flexible skin/liner for
 those applications where heretofore a plasticized PVC resin has been the
 only acceptable resin for use.
 SUMMARY OF THE INVENTION
 This invention provides a TPO composition which is drop-in replacement for
 flexible PVC, such that the identical calendering equipment can be used to
 fabricate TPO skins and liners with adjustment in processing temperature
 and speed, etc. only, and with minor hardware modifications.
 A TPO composition has been discovered which has a flexural modulus (1%
 secant modulus) of 40,000 psi or less which may be fabricated to have a
 desired melt flow ratio (OR) value within the range of 0.5 to 5 while
 still offering superior properties such as strength, impact and puncture
 resistance, etc. as compared to flexible plasticized PVC compositions of a
 low secant modulus heretofore used for production of skins and liners. The
 TPO compositions of this invention are especially suitable for
 applications which heretofore have been practically serviceable only by a
 plasticized PVC composition and, by comparison to such plasticized PVC
 composition, the TPOs of this invention have the advantage of being: odor
 free in that there is no migration of a plasticizer to the surface of
 articles fabricated therewith; of lower density, to enable production of a
 skin or membrane article of comparable dimensions with less material; and
 able to provide articles that are joinable to each other by heat welding,
 thereby eliminating the need for solvent welding as with flexible PVC
 compositions. The TPO compositions of this invention are particularly
 adapted to serve as automotive interior skins, such as instrument panels
 and door trim panels, and as industrial liners such as in geomembranes and
 reinforced roof membranes.
 TPO compositions of this invention comprise an impact modified
 polypropylene resin and a "plastomer" resin intimately blended in
 proportions with respect of one to another to provide a blend composition
 having a 1% secant modulus of less than 40,000 psi, and preferably less
 than 30,000 psi. Optionally, and preferably so, TPO blend compositions of
 this invention further comprise, as a discrete blend component apart from
 any impact modifying elastomer content of the impact modified
 polypropylene, a discrete olefin copolymer elastomer (OCE) resin
 intimately blended with the impact modified polypropylene and plastomer
 components to further reduce flexural modulus of the resulting blend
 product. To enhance grain retention and deep draw thermoforming, the
 discrete OCE component may be cross-linked to bolster the melt strength of
 the TPO skin during processing. Further, the TPO blend compositions of
 this invention optionally further comprise, and preferably so, a coupling
 agent and activator compound which, upon melt compounding of the plastomer
 with the impact modified polypropylene component, produces an end to end
 coupling of plastomer to produce dimers thereof and, when present, to
 couple the plastomer to the optional discrete OCE, during melt compounding
 of the blend components to yet further significantly reduce the flex
 modulus of the resulting TPO blend.
 By appropriate selection of the melt flow rates of the impact modified
 polypropylene component and of the plastomer component, the resulting TPO
 blend composition may be prepared to have any desired MFR for purpose of
 its subsequent processing into skin and/or liner layers or other finished
 article forms all while having a reduced 1% secant modulus value which
 renders the TPO composition suitable for fabrication into flexible
 skin/liner articles which are of similar compliability and flexibility as
 skin/liners heretofore prepared by plasticized PVC compositions.
 The low secant modulus TPO compositions of this invention essentially
 retain the other superior physical/mechanical/chemical properties of the
 impact modified polypropylene component thereof, yet the TPO of this
 invention remains non-tacky and free flowing when in pelletized form so
 that it may be processed in conventional fashion as if it were a typical
 thermoplastic resin. Particularly, TPO compositions of this invention can
 be directly used in equipment and lines now used to produce flexible PVC
 skins/liners without any difficulties of handling and yet produce
 skins/liners of superior use properties compared to plasticized PVC
 skins/liners. A skin/liner is a sheet-like layer of a thickness of at
 least about 0.005 inch.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
 TPO compositions of this invention are comprised of at least three
 components; a propylene polymer, an OCE and a plastomer. The propylene
 polymer and OCE may be supplied as separate polymeric components, or may
 be preformed as an impact polypropylene resin, to which the plastomer is
 supplied. Optionally, but preferably so when an impact polypropylene resin
 is employed, a further quantity of OCE discrete from and in addition to
 that supplied by the impact polypropylene is employed in preparing TPO
 blends of this invention. When a further quantity of OCE discrete from
 that of the impact polypropylene resin is utilized, it is preferably
 precured or cross-linked as an OCE concentrate in a small quantity of
 propylene polymer and it is this precured OCE-propylene polymer
 concentrate which is added to the impact propylene and plastomer
 components in an amount that supplies the further quantity of OCE that is
 desired, after which the impact polypropylene, plastomer and further
 quantity of OCE are melt compounded to a uniform blend. Optionally, but
 preferably so, a coupling agent and activator compound therefor are added
 in appropriate amounts to the impact polypropylene, plastomer and optional
 additional quantity of discrete OCE so that upon melt compounding of these
 components the plastomer undergoes an end to end coupling with itself to
 form plastomer dimers and/or the plastomer undergoes coupling to the
 further quantity of OCE added.
 However prepared, whether as a blend of individual propylene polymer, OCE
 and plastomer components or as a blend of impact polypropylene resin,
 plastomer and an optional quantity of additional discrete OCE, the final
 TPO blends of this invention will, on a total olefin monomer content
 basis, contain from about 37 to about 51 weight % propylene units (C.sub.3
 H.sub.6); from about 41 to about 52.5 weight % ethylene units (C.sub.2
 H.sub.4); from about zero to about 0.5 weight % diene units; and the
 balance will be from about 8 to about 10 weight % of units derived from a
 C.sub.4-8 .alpha.-olefin.
 Compositions of this invention are TPOs having a relatively low 1% secant
 modulus, namely less than 40,000 and preferably less than 30,000 psi. The
 composition comprises a blend of an impact modified polypropylene
 thermoplastic and a plastomer component. Optionally, and preferably, the
 blend also comprises as a discrete component apart from the impact
 modified polypropylene an olefin copolymer elastomer. Preferably the OCE
 added will ultimately become cross-linked in order to improve the melt
 strength of the final TPO blend. Cross-linking of the OCE to improve melt
 strength can be accomplished in two ways. The correct amount of
 cross-linking agent can be added during the blend mixing step. However, in
 order to complete the cross-linking reaction, a prolonged mixing time
 which would add from two to five minutes cycle time would be required.
 Another method is the employment of a cross-linked concentrate of the OCE
 which is produced in a separate operation. The concentrate contains a
 minor amount or propylene polymer in order to facilitate the dispersion of
 the cross-linked OCE in the basic impact modified polypropylene and
 plastomer mixture.
 In addition to the olefin based polymer components, the blend may further
 comprise, and preferably does comprise, a coupling agent and activator
 compound which, during melt compounding of the blend components causes the
 plastomer to extend to its dimer form and, when a discrete OCE component
 is present to couple the plastomer thereto. Inclusion of a coupling agent
 and activator compound to produce coupling of the plastomer to itself
 and/or to the discrete OCE component has been found to further
 significantly reduce the 1% secant modulus of the TPO blend compared to an
 otherwise comparable blend not including a coupling agent and activator
 compound.
 The final TPO blend may be produced to have an MFR value desired for its
 fabrication by selection of impact modified polypropylene and plastomer
 components of appropriate MFR values such that in the proportions that one
 is blended with the other to produce the desired 1% secant modulus value
 of the TPO blend the MFR value desired for the final blend is achieved.
 The Impact Modified Polypropylene Thermoplastic Component
 The impact modified polypropylene component for the blend is itself a TPO
 blend of a propylene polymer and an elastomer, preferably an olefin
 copolymer elastomer, wherein the elastomer content is less than 20 wt. %
 of the impact modified polypropylene blend. The propylene polymer
 constituent of the impact modified polypropylene is a homopolymer or a
 random copolymer of propylene having a propylene content of at least 95
 wt. % and a weight average molecular weight of at least 70,000. The
 propylene polymer, when a random copolymer is a copolymer of propylene
 with an ethylene or a C.sub.4 -C.sub.6 alpha-olefin comonomer wherein the
 comonomer content does not exceed about 7 wt. % of the random copolymer.
 As a constituent apart from the OCE with which it is blended for impact
 modification, the propylene polymer is highly stereoregular, either
 isotactic or syndiotactic regularity, with isotactic regularity being
 preferred. The OCE component of the impact modified polypropylene is
 preferably an ethylene-propylene rubber/elastomer of an ethylene content
 of from about 30 to about 70 wt. %, and density of from about 0.86 to
 about 0.89 g/cc and a Mooney viscosity (1+4 at 125.degree. C.) from about
 20 to 70. Other OCE elastomers which can withstand the high compounding
 and subsequent processing temperature for TPO compounds may be used. Two
 examples of heat stable OCEs are isobutylene-paramethylstyrene copolymer
 elastomers or the brominated isobutylene-paramethylstyrene copolymer
 elastomers detailed descriptions of which are given in U.S. Pat. No.
 5,162,445. The preferred brominated isobutylene-paramethylstyrene
 copolymer elastomer should have a bromine content of 0.3 to 1% by weight,
 and a Mooney viscosity (1+8 at 125.degree.) from about 35 to 55, and a
 paramethylstyrene content from about 5 to about 10 wt. %.
 The impact modified polypropylene may be prepared as a reactor blend
 wherein the isotactic propylene polymer or random propylene copolymer and
 impact modifying OCE constituents are simultaneously formed by
 polymerization of propylene with another appropriate olefin comonomer in
 different zones of the same reactor or in a single reaction zone in the
 presence of differing catalysts, one of which is appropriate to formation
 of the propylene polymer constituent, while the other is appropriate to
 the formation of the OCE constituent--as is known in the art.
 Alternatively, the impact modified polypropylene may be formed by melt
 compounding of a propylene polymer with an OCE, each of which were
 separately formed prior to blending. Generally, for reasons of economy,
 impact modified polypropylenes are prepared as reactor blends and for this
 reason generally have an impact modifying OCE content not exceeding about
 20 wt. % of the reactor blend, and more typically not exceeding about 12
 wt. % of the reactor blend. Further discussion of the particulars of an
 impact modified polypropylene may be found in U.S. Pat. No. 4,521,566.
 However the impact modified polypropylene is formed, it generally comprises
 from about 80 to about 90 wt. % of a propylene polymer and from about to
 about 20 wt. % of an OCE such that the propylene content of the blend is
 at least about 80 wt. %; it has a 1% secant modulus of from about 60,000
 psi to about 130,000 psi; and a MFR of from about 0.5 to about 5.0 and
 preferably from about 0.5 to about 3.
 THE PLASTOMER COMPONENT
 The plastomer component for the TPO blends of this invention is an ethylene
 based copolymer, meaning that its major constituent by weight or mole % is
 ethylene, and is prepared with a single sited catalyst, i.e., a catalyst
 the transition metal components of which is an organometallic compound at
 least one ligand of which has a cyclopentadienyl anion structure through
 which such ligand bondingly coordinates to the transition metal cation.
 Such a catalyst system, now commonly known as "metallocene" catalyst,
 produces ethylene copolymers in which the comonomer is more randomly
 distributed within a molecular chain and also more uniformly distributed
 across the different molecular weight fractions comprising the copolymer
 than has heretofore generally been possible to obtain with traditional
 types of heterogeneous multi-sited Ziegler-Natta catalysts. Metallocene
 catalysts are further described in U.S. Pat. Nos. 5,017,714 and 5,324,820.
 In its polymeric properties, a plastomer is neither completely like a
 thermoplastic nor completely like an elastomer, nor is it totally unlike
 either. An ethylene based polymer may exhibit thermoplastic properties or
 elastomeric properties dependent upon its degree of crystallinity, density
 and molecular weight. For example, homopolyethylene is a thermoplastic and
 has a density of between about 0.940 to about 0.965 g/cc depending upon
 its particular degree of crystallinity which in turn relates to its degree
 of chain branching. A substantially linear polyethylene is one essentially
 free of any long chain branching and when substantially free of short
 chain branching is the most crystalline and of highest density. As short
 chain branching of a polyethylene structure increases, its crystallinity
 and density decreases. Polymerization of ethylene with a comonomer, such
 as a C.sub.3 -C.sub.8 alpha-olefin, adds short chain branching to the
 polymer chain, hence decreases the crystallinity and density of the
 resulting copolymer as the content of incorporated comonomer increases.
 Wherein the comonomer content reaches and exceeds about 10 wt. %, the
 ethylene copolymer product, if of sufficient molecular weight, exhibits
 both plastic and elastomeric characteristics. In the continuum of
 increasing comonomer content, a region exists defined by the comonomer
 content and molecular weight wherein an ethylene copolymer which is
 produced with a metallocene catalyst is neither totally thermoplastic-like
 nor elastomer-like in respect to its properties but is partially like a
 thermoplastic and partially like an elastomer. For purposes of this
 application, an ethylene copolymer produced with a metallocene catalyst
 which has a comonomer content and molecular weight that falls within this
 region--hence has a density lower than that of a linear low density
 polyethylene (LLDPE) thermoplastic polymer and approaching and/or even
 somewhat overlapping with that of an ethylene containing copolymer
 elastomer/rubber--is referred to as a "plastomer. "
 Heretofore some ethylene based thermoplastic copolymers have been produced
 with a Ziegler-Natta type catalyst within this density range, such as very
 low density polyethylene (VLDPE), that have some attributes in common or
 overlapping with those of a plastomer--such as commonality of comonomer,
 such as butene-1, and densities in the region of 0.880 to 0.910 g/cc--yet
 are distinctly different from a plastomer due to distinctly differing
 distribution of comonomer between the two types of resin. Hence the
 behavior of the peak melting point temperature (Tmp) as this relates to
 comonomer content and density of the prior Ziegler-Natta made VLDPE resins
 compared to a plastomer are distinctly different. Unlike such prior VLDPE
 resin, the Tmp of a plastomer resin is substantially linearly related to
 the comonomer content and density of the plastomer resin such that
 .DELTA.Tmp/.DELTA.d.gtoreq.900 (.degree. C./g/cm.sup.3) and/or
 .DELTA.Tmp/.DELTA.(comonomer mole %) is about -5.5(.degree. C./mole %).
 See FIGS. 1-3. Such dramatic effects upon the Tmp based upon a change in
 comonomer content or density have not heretofore been generally observed
 in VLDPE produced with non-metallocene transition metal catalyst. Further,
 in contrast to an elastomer resin containing ethylene, regardless of the
 nature of the catalyst from which the elastomer resin is produced, a
 plastomer has a higher degree of crystallinity than is typical for an
 elastomer. Again, see FIGS. 1-3. Unlike an elastomer, a plastomer is
 relatively non-tacky--that is, it may be formed into pellets that are
 non-adhesive and relatively free flowing and so are susceptible to dry
 blending.
 For purposes of this application and the claims hereof, a "plastomer" is a
 copolymer of ethylene and an alpha-olefin comonomer wherein ethylene
 comprises from about 87 mole % to about 97.5 mole % of the plastomer
 copolymer; the alpha-olefin comonomer content comprises from about 13 to
 about 2.5 mole % of the plastomer copolymer and is incorporated into the
 copolymer in an amount that provides for a density of 0.92 g/cc or less
 and is limited in an amount so as not to reduce the density to a value
 less than 0.865 g/cc; and the distribution of the alpha-olefin comonomer
 within the copolymer is substantially random and also uniform among the
 differing molecular weight fractions that comprise the ethylene copolymer.
 This uniformity of comonomer distribution within the plastomer, when
 expressed as a comonomer distribution breadth index value (CDBI), provides
 for a CDBI&gt;60, preferably&gt;80 and more preferably&gt;90. Further, the
 plastomer is characterized by a DSC melting point curve that exhibits the
 occurrence of a single melting point peak occurring in the region of 50 to
 110.degree. C. (second melt rundown), said plastomer copolymer has a
 weight average molecular value no less than 70,000 and no greater than
 130,000, and the plastomer has a molecular weight distribution (M.sub.w
 /M.sub.n) value of.ltoreq.4.0 and preferably.ltoreq.3.5. Said ethylene
 copolymer plastomer has a 1% secant modulus not exceeding about 15,000 and
 as low as about 800 psi or even less.
 The preferred plastomers for use in the present invention are those
 ethylene-based copolymer plastomers sold under the trademark EXACT.TM.,
 available from Exxon Chemical Company of Houston, Texas. These plastomers
 are a copolymer of ethylene with a C.sub.4-8 alpha-olefin comonomer and
 have a plastic-like molecular weight for better dispersion in the impact
 modified polypropylene compound of the TPO blend of the invention. Such
 plastomers, since they are of low tack and form free flowing pellets, are
 also free of exterior dusting agents and interior processing aids which
 could adversely affect the properties of the TPO blend. This invention,
 however, can also be practiced using ENGAGE.TM. polymers, a line of
 metallocene catalyzed plastomers available from Dow Chemical Company of
 Midland, Mich.
 As noted, the plastomer component is an ethylene copolymer which is
 produced with a metallocene catalyst and as such, a plastomer copolymer
 contains a terminal site of unsaturation, of which advantage can be made
 through the use of a coupling agent and activator compound, as further
 explained later. The preferred plastomers have a molecular weight
 distribution (MWD) in the range of 1.7 to 3.5, and more preferably in the
 range of 1.8 to 3.0 and most preferably in the range of 1.9 to 2.8. The
 preferred plastomers have a density in the range of 0.865 to 0.900 g/cc,
 more preferably in the range of 0.870 to 0.890 g/cc and most preferably in
 the range of 0.870 to 0.880 g/cc. The comonomer of the plastomer is
 preferably an acyclic monoolefin such as butene-1, pentene-1, hexene-1,
 octene-1, or 4-methyl-pentene-1. In some respects, it is desirable for the
 plastomer to be an ethylene-alpha-olefin-diene terpolymer since
 incorporation of a quantity of diene monomer into the plastomer provides
 the plastomer with further residual unsaturation to allow further
 functionalization and/or cross-linking reactions or coupling of the
 plastomers in the finished TPO product. In the case of a non-diene
 containing plastomer the residual or chain end unsaturation, on the basis
 of the quantity of terminal double bonds per 1,000 carbon atoms, would be
 of the vinyl type 0.05 to 0.12, of the trans-vinylene type 0.06 to 0.15,
 and of the vinylene type 0.05 to 0.12.
 The Basic Blend Of Impact Modified Polypropylene And Plastomer
 The manner in which the plastomer is incorporated into the impact modified
 polypropylene is not critical, provided it is well dispersed throughout
 the same. For impact polypropylenes that are prepared as a reactor blend,
 the plastomer can be incorporated into the resulting impact modified
 polypropylene by addition of plastomer pellets immediately upstream of the
 pelletizing extruder. Alternatively, the plastomer may be added to an
 already pelletized stock of impact modified polypropylene by a converter
 in a blending process prior to fabricating an end product. Wherein the
 impact modified polypropylene is itself formed by melt blending of a
 propylene polymer with an appropriate impact modifying OCE, the plastomer
 component may also be added at this time and incorporated into the impact
 modified polypropylene at the time that it itself is prepared by melt
 blending. Alternatively, the plastomer can be preblended with the impact
 modifying OCE and the rubber-plastomer pre-blend may later be compounded
 with the propylene polymer in producing the TPO blend compositions of this
 invention.
 Most generally, in preparing TPO blend compositions of this invention, the
 impact modified polypropylene resin--which comprises the thermoplastic
 propylene polymer and its impact modifying olefin copolymer
 elastomer--comprise from about 60 to about 40 wt. % of the olefin based
 polymeric resin components of the blend and the plastomer component
 comprising the ethylene-based copolymer comprises the balance of the
 olefin-based polymeric resin components of a binary imPP-plastomer TPO
 blend composition. The proportion of impact modified polypropylene resin
 component to the plastomer component provides the resulting TPO blend
 composition with a 1% secant modulus of 40,000 psi or less, preferably
 30,000 psi or less, and most preferably 20,000 psi or less.
 Optional Discrete OCE Component
 Optionally, and preferably so, the TPO blend composition of this invention
 also incorporates as a third component an olefin copolymer elastomer (OCE)
 constituent which is discrete from that of the impact modifying OCE for
 the polypropylene polymer. The discrete olefin copolymer elastomer
 component may comprise any elastomer having good heat or thermal stability
 properties and is preferably an ethylene-olefin copolymer elastomer such
 as ethylene-propylene rubber (EPM) or ethylene-propylene-diene rubber
 (EPDM); or an isobutylene-paraalkylstyrene copolymer elastomer such as an
 isobutylene-paramethylstyrene copolymer and its halogenated counterparts
 such as brorninated isobutylene-paramethylstyrene copolymer elastomer. The
 requirement for the discrete OCE are thermally stable elastomers which can
 withstand processing temperatures for TPOs, i.e., 330 to 480.degree. F. In
 addition, these elastomers need to be miscible or compatible with the
 polypropylene polymer. Examples of elastomers which, although are
 compatible with polypropylenes, but themselves do not possess sufficient
 thermal stability are isobutylene-isoprene elastomers and brominated
 isobutylene-isoprene elastomers (i.e., butyl and halobutyl rubbers). The
 polyisobutylene elastomer on the other hand can also be utilized.
 Particularly preferred as an optional discrete olefin copolymer elastomer
 component of the TPO blend compositions of this invention is a
 isobutylene-paramethylstyrene copolymer elastomer and its brominated
 counterparts as described in U.S. Pat. No. 5,162,445. Various grades of
 such preferred isobutylene-paramethylstyrene copolymer elastomers and
 brominated isobutylene-paramethylstyrene copolymer elastomers are now
 available commercially from Exxon Chemical Company of Houston, Tex. In
 addition, divinylbenzene butyl rubber may be used.
 Those grades of isobutylene-paramethylstyrene copolymer elastomer and
 brominated derivatives thereof most preferred for use as the discrete OCE
 for forming TPO blends of this invention are the brominated derivatives
 wherein the paramethylstyrene comonomer is present in an amount of from
 about 5 to about 10 wt. % and bromine content ranges from about 0.8 to
 about 2 wt. % of the copolymer elastomer.
 Addition of Rubber
 Partial replacement of plastomer with a temperature resistant rubber can be
 practiced to produce low modulus compound. The desirable rubber needs to
 have good temperature resistance and good degree of compatibility with
 both polypropylene and plastomer. For example isobutylene-isoprene rubber,
 although meeting the compatibility requirement, cannot withstand the TPO
 processing temperature. One rubber which is suitable as a partial
 replacement of the plastomer is the brominated
 isobutylene-paramethylstyrene rubber (EXXPRO 89-1). Due to its lack of
 backbone unsaturation, it will withstand the TPO processing temperature,
 and its compatibility is excellent with polypropylene as evident by the
 sub-micron dispersion of such a rubber in a polypropylene matrix resin.
 The compatibility between plastomer and this rubber can be improved
 through grafting of the plastomer through terminal unsaturation to the
 paramethylstyrene portion of the rubber. Another polymer which may be used
 as a partial replacement of plastomer is elastic polypropylene. One such
 polymer is sold under the tradename Rexflex available from Rexene.
 Table 1 below illustrates the effect on the final TPO blend of partial
 replacement of the plastomer component of the blend with a brominated
 isobutylene-paramethylstyrene copolymer rubber. In Table 1 compositions A,
 B, C show that replacement of EXACT 4033 with EXXPRO rubber maintained the
 same amount of stiffness. Due to the incompatibility between EXACT 4033
 and EXXPRO, the knitline properties are rather poor. Compositions AA, BB,
 CC are identical to Compositions A, B and C respectively except proper
 amount of zinc oxide and zinc stearate (1 parts each per hundred part of
 EXXPRO) to trigger a grafting reaction. It is evident from the substantial
 reduction in melt flow rate of Compositions AA, BB, CC that grafting
 reaction indeed occurred. The main benefit of the grafting reaction is to
 produce compounds with improved knitline strength, and slight reduction in
 stiffness was also noticed. Knitline integrity is important in injection
 molding applications.
 TABLE 1
 Effect of Rubber Acidition
 A B C AA BB CC
 Composition
 Escorene PD 8191 40 40 40 40 40 40
 EXACT 4033 40 47.5 55 40 47.5 55
 EXXPRO 89-1 20 12.5 5 20 12.5 5
 Zinc Oxide 0.2 0.12 0.05
 Zinc Stearate 0.2 0.12 0.05
 Property
 Melt Flow Rate, dg/min. 1.1 1 1 0.2 0.1 0.9
 1% Secant Modulus, psi 26630 22440 23900 21630 20530 22000
 Knitline Break Strength, 625 660 830 1208 1706 1146
 psi
 Knitline Elongation, % 15.2 52.7 122.1 548.3 964.7 547.1
 Knitline Energy, In-lbs 9.5 44 119 620 1302 584
 Optional Cross-linked Elastomer Concentrate
 A good thermoformable material is required to have a high melt strength to
 permit flow under applied stress, and a sufficient elastic memory to
 resist flow and to retain the embossed grain patterns upon the formed
 article. Ideally these properties should extend over a wide temperature
 range to provide a large thermoforming window. However, a basic two
 component blend of impact modified polypropylene and metallocene plastomer
 may in some circumstances not have a sufficient melt strength and grain
 retention capability. Addition of a cross-linked elastomer concentrate is
 therefore preferred to make a basic two component TPO even more
 satisfactorily thermoformable.
 the same type of TPO skins are sometimes used in a so-called low pressure
 molding process to produce passenger car doors. In this operation, an
 embossed TPO skin is first laid inside a door panel mold. Molten
 polypropylene is next injection molded to fill the back side of the skin.
 Due to the low pressure nature of this operation, there is a lesser degree
 of drawing of the TPO skin than thermoforming. A small amount of
 cross-linked elastomer concentrate would then be sufficient grain pattern
 wash off in stretched corners.
 One such commercially available concentrate is called RC8001, available
 from advanced Elastomer Systems, L. P. Dynamic mechanical thermal analysis
 can be used to obtain the complex modulus at a 1 Hz frequency over a
 70.degree. C. to 150.degree. C. temperature range as shown in Table A. Due
 to the cross-linking nature of this material, its storage modulus (E) is
 found to be rather insensitive to temperature. In contrast to
 polypropylene or TPO sheeting, softening of this RC 8001 material is
 accompanied by a retention of its storage modulus. Another compound which
 can be used is fully compounded, fully cured Santoprene, available from
 Advanced Elastomer Systems.
 TABLE A
 Storage Modulus Versus Temperature for RC8001
 Temperature, .degree. C. Storage Modulus, Dynes/cm.sup.2
 (.times.10.sup.7)
 70 8.2
 80 6.1
 90 5.2
 100 4.6
 110 4.0
 120 3.7
 130 3.1
 140 2.8
 150 2.0
 Examples of crosslinked plastomer concentrates are shown in Table B as
 Examples E-H.
 TABLE B
 Examples of Elastomer Concentrates
 Examples
 Raw Materials E F G H
 Escorene PP 1042 20 20 25 20
 EXACT 4033 40 60 60 40
 Vistalon MDV 94-2 30 10 5 --
 EXXPRO 89-l -- -- 30
 Drakeol 35 10 10 10 10
 Varox DBPH-50 2 2 2 1
 Irganox 1010 0.1 0.1 0.1 0.1
 Irgafos 168 0.1 0.1 01 0.1
 Maglite D 0.1 0.1 0.1 0.1
 Zinc Oxide -- -- -- 0.3
 Zinc Stearate -- -- -- 0.3
 These example concentrates were produced using an intensive mixer such as a
 Stewart Bolling #10. The Escorene PP 1042 (a propylene homopolymer of 1.7
 melt flow rate); EXACT 4033 (a plastomer of ethylene-butene of 0.880
 g/cm.sup.3 density and 0.8 melt index) and Vistalon MDV 94-2 (an
 ethylene-propylene rubber of 0.865 g/cm.sup.3 density and 35 Mooney
 determined at ML(1+4) at 125.degree. C.) were first brought to a flux for
 two minutes. Drakeol 35, a white mineral oil, was next added to the batch
 and fluxed for another minute. Varox DBPH-50, a peroxide crosslinking
 agent [50% 2,5-dimethyl-2,5-di(t-butyl-peroxyl) hexane] was next added and
 the batch was mixed for another four minutes to complete the crosslinking
 reaction. In composition H, Varox together with zinc oxide and zinc
 stearate was added. Finally additives such as Irganox 1010, Irgafos 168
 and Maglite D were added and the entire mass was transferred to a
 downstream extruder, and the batch was reduced into 1/8 inch by 1/8 inch
 free flowing pellets. The presence of a small quantity of polypropylene
 (Escorene PP 1042) in the concentrate insured good and quick dispersion of
 this concentrate into the matrix resin.
 Table C shows the storage modulus for these compositions. It is evident
 from Table C compositions of Examples F and H show higher modulus than
 RC8001 from 70.degree. C. to 125.degree. C. In the thermoforming
 temperature range from 120 to 150.degree. C. the modulus of all four
 elastomer concentrates are essentially the same.
 TABLE C
 Storage Modulus for Elastomer Concentrates
 Dynes/cm.sup.2 .times. 10.sup.7
 Temp., .degree. C. RC 8001 E F G H
 70.0 8.2 8.2 13.0 8.2 12.0
 80.0 6.1 6.0 1.0 6.0 9.0
 90.0 5.2 5.2 8.5 5.2 7.2
 100.0 4.6 4.5 7.3 4.5 6.0
 110.0 4.0 4.0 6.4 3.9 5.0
 120.0 3.7 3.5 5.5 3.4 4.3
 130.0 3.1 3.1 5.0 2.9 3.7
 140.0 2.8 2.7 4.1 2.5 3.0
 150.0 2.0 2.2 3.0 1.8 2.2
 The compositions as described in Table D which follows have been found to
 produce TPO skins for low pressure molding and thermoforming applications
 with good grain retention.
 TABLE D
 Low
 Geomem- Pressure
 Composition brane Molding Thermoforming
 Escorene PD 8191 50 50 50 50
 EXACT 4033 50 40 25 20
 RC8001 10 25 30
 Property
 Tensile at Break, MD, psi 7107 4440 4454 2414
 Tensile at Break, TD, psi 8655 3580 4071 2401
 Elongation at Break, MD, psi 649 669 726 728
 Elongation at Break, TD, psi 690 693 752 689
 100% Tensile Modulus, MD, psi 1471 1443 1859 1082
 100% Tensile Modulus, TD, psi 1423 1198 1790 1066
 300% Tensile Modulus, MD, psi 1798 1550 2031 1255
 300% Tensile Modulus, TD, psi 1648 1336 1960 1234
 Tear Strength, MD, Lbs/in 577 363 390 273
 Tear Strength, TD, Lbs/in 577 432 373 304
 *MD = Machine Direction *TD = Transverse Direction
 Both tensile strength and tear strength show reductions with increased
 amount of crosslinked rubber concentrate when compared with the basic
 two-component equal blend of Escorene PD 8191 and EXACT 4033.
 Elastomer concentrates such as Examples E, F, G and/or H as described in
 Table B could be used in part or in whole replacement of the RC 8001
 concentrate.
 Coupling Agents and Activator Compounds
 Optionally, and preferably so, the TPO blend composition of this invention
 will further comprise a small but effective amount of a multifunctional
 chemical coupling agent and an activator compound to activate the chemical
 coupling agent to cause intramolecular coupling of the plastomer component
 through the coupling agent as a medium and, when present, intermolecular
 coupling of the plastomer with the optional discrete OCE component, such
 coupling reactions occurring during melt compounding of the TPO components
 to form the final TPO blend composition. As previously noted, a
 metallocene catalyst produced plastomer contains a terminal site of
 unsaturation and it is through this unsaturation site that the plastomer
 couples to the coupling agent. Difunctional coupling agents thus yield
 reaction compositions of the plastomer that are essentially plastomer
 dimers. Higher functional coupling agents yield higher oligomers of the
 plastomer.
 Chemical coupling agents suitable for use in preparing TPO blend
 compositions of this invention are alkylphenol-formaldehyde resins such as
 "SP-1045" by Schenectady Chemicals, 2, 6 bis(hydroxymethyl) cresol
 supplied by Aldrich Chemical and 2,6,2',6' tetrabismethylol bisphenol A.
 Suitable activator compounds to activate the coupling agent are stannous
 chloride. Zinc oxide and zinc stearate combinations may be used to graft
 plastomers to Exxpol elastomers as well as vulcanizing agents for Exxpol
 elastomers.
 Optional Polyolefin Component
 It has further been found that a quantity of low density polyethylene
 thermoplastic, up to about 30 wt. % of the total TPO blend, may be
 incorporated to extend the mass of the TPO composition without degrading
 its desirable properties. Table 2 below illustrates this with respect to a
 three component blend of imPP/plastomer/LDPE wherein the imPP is Escorene
 PD 8191 (1% seant modulus 62,500 psi); the plastomer is EXACT 4033
 (density of 0.880 g/cm.sup.3); and the low density polyethylene is
 Escorene LD 201.48 (density of 0.923 gtcm.sup.3).
 TABLE 2
 Escorene PD 8191/EXACT 4033/Escorene LD 201.48 Blends
 wt. % of imPP/plastomer/LDPE
 Sheet properties* 60/40/0 50/50/0 50/40/10 40/40/20 30/40/30
 Tensile at Break, MD, psi 9475 7107 8105 7504 5333
 Tensile at Break, TD, psi 8704 8655 7298 7325 4313
 Elongation at Break, MD, % 701 649 679 700 651
 Elongation at Break, TD, % 697 690 688 715 653
 100% Tensile Modulus, MD, 1713 1471 1865 1786 1329
 psi
 100% Tensile Modulus, TD, 1654 1423 1839 1663 1084
 psi
 300% Tensile Modulus, MD, 1992 1798 2117 2068 1624
 psi
 300% Tensile Modulus, TD, 1840 1648 1976 1921 1434
 psi
 Tear Strength, MD, Lbs/in 691 577 638 627 486
 Tear Strength, TD, Lbs/in 700 577 593 618 514
 1% Secant Modulus, psi** 34323 26057 30831 24967 22040
 *The property values shown were measured on 20 mils thickness unsupported
 sheet samples produced on a Black Clawson cast line
 **Injection molded ASTM Flex Bars
 MD = Machine Direction
 TD = Transverse Direction
 Addition of 30% LDPE in formulation still maintains good mechanical
 properties. Note in the last three columns of data in Table 2, replacement
 of PD8191 with the less stiff LD 201 in the composition reduces the 1%
 secant modulus of the material. Since it is not possible to determine 1%
 secant modulus for sheet samples either the 100% or 300% tensile modulus
 is used to measure the stiffness of the sheeting. The same conclusions are
 valid for the compositions illustrated in Table 3 below, wherein the
 plastomer component employed was EXACT 4049 (density 0.873 g/cm.sup.3),
 and Table 4 below, wherein the plastomer component employed was EXACT
 SLP9053 (density 0.865 g/cm.sup.3).
 TABLE 3
 Escorene PD 8191/EXACT 4049/Escorene LD 201.48 Blends
 Wt % imPP/plastomer/LDPE
 Sheet Properties* 60/40/0 50/50/0 50/40/10 40/40/20
 Tensile at Break, MD, psi 5481 5232 4997 5678
 Tensile at Break, TD, psi 5136 5337 5145 4955
 Elongation at Break, MD, % 730 768 942 830
 Elongation at Break, TD, % 744 824 827 839
 100% Tensile Modulus, MD, 1648 1387 1755 1693
 psi
 100% Tensile Modulus, TD, 1574 1332 1579 1483
 psi
 300% Tensile Modulus, MD, 1900 1620 1879 1806
 psi
 300% Tensile Modulus, TD, 1760 1542 1704 1697
 psi
 Tear Strength, MD, Lbs/in 599 506 558 559
 Tear Strength, TD, Lbs/in 552 462 536 533
 *The property values shown were measured on 20 mils thickness unsupported
 sheet samples produced on a Black Clawson cast line
 MD = Machine Direction
 TD = Transverse Direction
 TABLE 4
 Escorene PD 8191/EXACT SLP 9053/Escorene LD 201.48 Blends
 Wt. % imPP/plastomer/LDPE
 Sheet Properties* 60/40/0 50/50/0 50/40/10 40/40/20
 Tensile at Break, MD, psi 4827 3704 4441 4517
 Tensile at Break, TD, psi 4301 3940 4377 4394
 Elongation at Break, MD, % 744 713 759 779
 Elongation at Break, TD, % 762 902 839 848
 100% Tensile Modulus, MD, 1516 1284 1608 1552
 psi
 100% Tensile Modulus, TD, 1419 1121 1388 1348
 psi
 300% Tensile Modulus, MD, 1653 1442 1759 1709
 psi
 300% Tensile Modulus, TD, 1607 1271 1510 1528
 psi
 Tear Strength, MD, Lbs/in 648 481 584 532
 Tear Strength, TD, Lbs/in 553 437 488 464
 *The property values shown were measured on 20 mils thickness unsupported
 sheet samples produced on a Black Clawson cast line
 MD = Machine Direction
 TD = Transverse Direction
 Instead of LDPE, other polyethylenes, such as linear low density
 polyethylene (LLDPE) or high density polyethylene (HDPE), can be used as a
 replacement for the LDPE in order to adjust the stiffness of the TPO
 composition. Polyethylene copolymers, such as ethylene vinyl acetate,
 ethylene methylacrylate and even metal oxide neutralized polyethylene acid
 copolymers (polyethylene ionomers) can be used to adjust the stiffness of
 the TPO composition. Further, the impact polypropylene can be partially
 replaced with a polypropylene homopolymer or a polypropylene random
 copolymer for stiffness adjustment purposes.
 Secant Modulus Effect Of Components
 It has been found that by intimately incorporating a plastomer of a low 1%
 secant modulus within an impact modified polypropylene (im PP) having a
 high 1% secant modulus that the 1% secant modulus of the resulting TPO
 blend is substantially reduced in essentially direct proportion with the
 quantity of incorporated plastomer. Further, it has been found that as the
 density of the plastomer decreases the magnitude by which a given quantity
 of such plastomer reduces the 1% secant modulus of the final TPO
 composition increases. Further, as illustrated by FIG. 4, it has been
 found that when an effective amount of coupling agent and activator
 compound are incorporated in a blend of impact modified polypropylene and
 plastomer prior to melt blending of these components that the 1% secant
 modulus value of the resulting melt compounded TPO blend is still further
 significantly reduced by comparison to a comparable blend of im-PP and
 plastomer without coupling agent and activator compound included, as
 illustrated by FIG. 8. As yet a further means for reducing the 1% secant
 modulus of the TPO composition a discrete OCE, such as a brominated
 isobutylene-para-methylstyrene copolymer rubber, when incorporated with
 the plastomer and coupling agent-activator compound will reduce the 1%
 secant modulus.
 As illustrated by FIG. 4, the percentage by which the 1% secant modulus
 value of an impact modified polypropylene may be reduced by melt
 compounding it with a quantity of a plastomer component depends in part
 upon the density of the plastomer component. At similar weight percentages
 of a plastomer component, the lower the density of the plastomer, the
 greater is the percentage of 1% secant modulus value reduction that is
 accomplished for the resulting blend as compared to the initial 1% secant
 modulus value of the impact modified polypropylene component of the blend.
 In the weight percent region of about 10 to about 70 weight percent
 plastomer, the reduction in 1% secant modulus value is substantially
 linear.
 As further illustrated by FIGS. 5 to 7, as a percentage of the 1% secant
 modulus value of the impact modified polypropylene component for the
 blend, the 1% secant modulus value of the resulting blend itself is
 essentially a function only of the quantity of the plastomer component
 regardless of the lower or higher nature of the 1% secant modulus value of
 the impact modified polypropylene component. Accordingly, to achieve a
 targeted 1% secant modulus value for the final blend resin of 40,000 psi,
 or more preferably of 30,000 psi or a lesser value as may be desired, the
 weight percentage quantity of plastomer required to achieve the targeted
 value may readily be determined given the particulars of the impact
 modified polypropylene and the plastomer selected for production of the
 TPO blend. In other words, as illustrated by these FIGS. 4-7, with
 plastomers of lower densities and impact modified polypropylene components
 of lower 1% secant modulus values, the lowest wt. % of plastomer component
 will yield melt compounded blends of the targeted 1% secant modulus value,
 such as 30,000 psi or even less. On the other hand, with plastomers of the
 highest densities and impact modified polypropylenes of the highest 1%
 secant modulus value, the highest weight percentage of plastomer are
 required to achieve TPO blends of the targeted 1% secant modulus value.
 As illustrated by FIG. 8, within a range of 5-40 wt. % of a given plastomer
 for a given impact modified polypropylene component, the 1% secant modulus
 value of a resulting melt compounded TPO blend can be significantly
 reduced in value by employment of a quantity of coupling agent--activator
 compound during melt compounding of the blend components compared to a
 blend of the same impact modified polypropylene and plastomer components
 alone. Table 5 below illustrates this further.
 TABLE 5
 Effect of Chemical Coupling
 Unmodified Chemically Coupled
 EXACT 4033 EXACT 4033
 1% Secant Modulus 1% Secant Modulus psi
 EXACT 4033, psi (percent of (percent of
 Wt. % PD 8191 Modulus) PD 8191 Modulus)
 0 62525(100) 62525(100)
 10 60475(96.72) 47454(75.90)
 20 50967(81.51) 41129(65.78)
 30 43533(69.63) 34253(54.78)
 40 34323(54.89) 30491(48.77)
 50 26057(41.67) 24430(39.07)
 60 18679(29.87) 17684(28.28)
 Fabrication of Skins And Liners Comprised Of The TPO Compositions Of The
 Invention
 The compositions of this invention are specially suited for processing on
 conventional PVC calendering lines with minor adjustments in processing
 temperatures and rotation speed of calendering rolls. FIG. 10 shows a
 schematics of a calendering line equipped with a set of so-called inverted
 L calenders. Raw materials together with heat stabilizers and UV
 stabilizer and pigment are first dry-blended in a ribbon blender. After a
 preset mixing time the dry blend is discharged into a hold tank, from
 which a metered amount of the dry blend is discharged into an intensive
 mixer to produce a molten batch. The fluxed batch is next conveyed into
 one or two sets of holding mills in which several batches were homogenized
 to about 360.degree. F. Afterwards the homogenized batch is forced through
 a filtering extruder to produce a continuous rod-like feed for the
 calendering operation. A feed elevator with a swivel feed head is used to
 feed the molten TPO to the top two calender rolls. The approximate
 temperatures settings for these calendering rolls may be 280 to
 340.degree. F. as shown in FIG. 10. A set of takeoff rolls at about
 250.degree. F. are used to strip off the calendered sheeting from the
 calender stack and feed to a bank of 90 to 100.degree. F. cooling rolls
 before collection on a continuous winder. The pair of takeoff rolls
 sometimes are also used to emboss grain patterns or trademarks on the
 finished sheeting.
 Continuous TPO sheeting can also be produced using an extruder to melt the
 TPO feed. The molten material is forced through a slot die which is placed
 adjacent to a chrome polished three stack roll to convert TPO into
 continuous sheeting. The similar TPO composition can also be reduced into
 10 to 30 mesh average particle size powders for rotational molding.
 Finally the rubber concentrate containing compounds show enhanced melt
 strength over the basic im-PP/EXACT plastomer compounds. They can be used
 to produce products via either extrusion or extrusion blow molding
 process.
 Either calendered or extruded sheeting can be to produce scrim reinforced
 industrial liners such as containment liners, or roof membranes on a
 typical PVC laminator as shown in FIG. 11. Two separate rolls of TPO
 sheeting are heated by two heated drums and fed through a pair of
 pressurized lamination rolls. A heated continuous fiberglass or polyester
 scrim is placed between the TPO sheeting so that the scrim layer is
 interlocked through thermal bonding by the two TPO sheeting at the
 lamination rolls.
 EXAMPLES
 The following tabular data illustrate TPO blend compositions prepared in
 accordance with this invention. Table 6 hereafter identifies the test
 method utilized for determining the property of a given blend component or
 of the TPO blend itself Table 7 hereafter identifies by trade name the
 propylene based impact modified polypropylene resins utilized in
 production of Example TPO blend compositions and for each gives the MFR,
 density and 1% secant modulus values of such impact modified
 polypropylene. Table 7 hereafter also identifies by trade name the
 ethylene based plastomer resins utilized in preparing Example TPO blend
 compositions of this invention and also a LDPE diluent and for each gives
 the MFR, density and 1% secant modulus values of such plastomers and also
 identifies the chemical composition, properties and nature of the chain in
 unsaturation of such plastomers. Table 7 also identifies various
 elastomers utilized. Table 8 hereafter identifies by trade name or
 chemical type the coupling agent and activator compound used therefore and
 supplier thereof for coupling agents and activator compound used in
 preparing Example TPO blend compositions of this invention. Table 8 also
 identifies other additives utilized.
 TABLE 6
 Test Method
 Injection Molded Test Test Method
 Specimen Property
 Melt flow Rate, dg/min ASTM D-1238 Condition L
 Melt Index, dg/min ASTM D-1238 Condition E
 Density, g/cm.sup.3 ASTM D-792
 Hardness, 5 second Shore A ASTM D-2240
 Tensile Strength, psi ASTM D-638
 Elongation, % ASTM D-638
 Knitline Energy, In-lbs ASTM D-638
 Flexural (1% Secant) Modulus, psi ASTM D-790
 Sheeting Property
 Tensile Strength, psi ASTM D-412
 Elongation, % ASTM D-412
 Tensile Modulus, psi ASTM D-412
 Tear Strength, lb/in ASTM D-624
 Rubber Property
 Mooney Viscosity ASTM D-1646
 TABLE 7
 Melt Flow Comonomer % Secant DSC
 PeakMelting
 Trade Name Density, g/cm.sup.3 Rate, dg/min Type Modulus,
 psi Point, .degree. C. Supplier
 POLYPROPYLENE
 Escorene PD 8191 0.9 1 Ethylene 62530 141.6
 Exxon Chemical
 Escorene PP 8092 0.9 2 Ethylene 120400 161.5
 Exxon Chemical
 Escorene PP 1042 0.9 1.7 None 182400 160.5
 Exxon Chemical
 POLYETHYLENE
 EXACT 4033 0.88 0.8 Butene 3300 60
 Exxon Chemical
 EXACT 4049 0.873 4.5 Butene 3000 55
 Exxon Chemical
 EXACT 5008 0.865 10 Butene 780 45
 Exxon Chemical
 EXACT SLP 9053 0.865 4.0 Butene 780 46
 Exxon Chemical
 Escorene LD201.48 0.923 4.1 None 34,600 112
 Exxon Chemical
 RUBBER
 Trade Name Density, g/cm.sup.3 Mooney Comonomer Type
 Bromine, Wt. % Supplier
 EXXPRO 89-1 0.93 35 ML (1 + 8) @ Paramethylstyrene 1.2
 Exxon Chemical
 125.degree. C.
 Vistalon MDV 94-2 0.865 35 ML (1 + 4) @ Ethylene None
 Exxon Chemical
 125.degree. C.
 RUBBER
 CONCENTRATE
 Tensile 100%
 Tensile
 Trade Name Hardness, 5 Sec. Density, g/cm.sup.3 Strength, psi
 Elongation, % Modulus, psi Supplier
 RC 8001 48 Shore A 0.93 526 367 221
 Advanced Elastomer

Systems
 TABLE 8
 Additive and Chemicals
 Trade Name Chemical Description Supplier
 SP-1045 Alkyl phenol-formaldehyde Schenectady Chemical
 resin
 2,6 Dimethyl Cresol 2,6 bis(hydroxymethyl) Aldrich Chemical
 Crasol
 Stannous Chloride Stannous Chloride Aldrich Chemical
 Zinc Oxide Zinc Oxide C. P. Hall
 Zinc Stearate Zinc Stearate Harwick
 Drakeol 35 White mineral oil Penreco
 Varox DBPH-50 2,5-dimethyl-2,5- R. T. Vanderbilt
 di(t-butyl-peroxy) hexane
 Irganox 1010 Tetrakis methylene (3.5-di- Ciba-Geigy
 t-butyl-4-hydroxygydro-
 cinnamate) methane
 Irgafos 168 Tris (2,4-di-t-butylphenyl) Ciba-Geigy
 phosphate
 Maglite D Magnesium Oxide C. P. Hall
 Example 1
 A melt compounded blend of an impact modified polypropylene copolymer
 (ESCORENE PD8191) and a plastomer (EXACT 4033) in various wt. %
 proportions of impact modified polypropylene ranging from 90 wt. % to 40
 wt. % with plastomer as the balance of the polymeric component of the TPO
 blend were prepared by melt compounding of the respective resins. The
 exact identity of the components and the proportions thereof for these
 blends are reported in Table 5.
 Example 2
 Blends analogous to those reported above in Example 1, but further
 incorporating a coupling agent (SP-1045) and an activator compound
 (Stannous Chloride) with the blend components during melt compounding
 thereof are also reported in Table 5.
 Example 3
 Blends analogous to those reported in Example I were prepared wherein as
 compared to a 60/40 blend of ESCORENE PD8191/EXACT 4033, a LDPE was used
 to partially replace a portion of the ESCORENE PD8191, and the physical
 properties of 20 mil thickness sheet samples thereof are reported in Table
 2.
 Example 4
 Blends analogous to those of Example 3 were prepared wherein EXACT 4049 was
 used instead of EXACT 4033, and the physical properties of 20 mil
 thickness sheet samples thereof are reported in Table 3.
 Example 5
 Blends analogous to those of Example 3 were prepared wherein EXACT SLP 9053
 replaced EXACT 4033 and results are reported in Table 4.
 Example 6
 Blends analogous to a 40/60 blend of ESCORENE PD8191 and EXACT 4033 as in
 Example I were prepared wherein a portion of the EXACT 4033 was
 progressively replaced with a corresponding quantity of brominated
 isobutylene-paramethyl(styrene copolymer rubber (EXX PRO 89-1), both with
 and without the presence of a vulcanizing agent, and the physical
 properties for such blends are reported in Table 1.
 Although the invention has been described by reference to its preferred
 embodiments those of skill in the art may appreciate from this description
 changes, modifications or additions that can be made to this invention
 which do not depart from the scope and spirit of the invention described
 above or claimed hereafter.