WO2004039852A1

WO2004039852A1 - Low density ethylene copolymer, a process for making same and blends comprising such copolymer

Info

Publication number: WO2004039852A1
Application number: PCT/US2003/033765
Authority: WO
Inventors: Weiguo Hu; Thomas Chen-Chi Yu
Original assignee: Exxonmobil Chemical Patents, Inc.
Priority date: 2002-10-28
Filing date: 2003-10-28
Publication date: 2004-05-13
Also published as: AU2003286667A1; WO2004039852A9

Abstract

The invention relates to novel low density elastomeric copolymer pellets, a process for making said pellets and blends made from such copolymer pellets. The elastomeric copolymer pellets of this invention have a high proportion of monoclinic crystallites.

Description

LOW DENSITY ETHYLENE COPOLYMER, A PROCESS FOR MAKING SAME AND BLENDS COMPRISING SUCH COPOLYMER

FIELD OF THE INVENTION

This invention relates to processes for preparing pelletized low density elastomeric copolymers of ethylene and a higher alpha olefin monomer, and the novel pelletized resins and blends resulting from such processes.

BACKGROUND

Continuous polymerization processes have been exemplified to make ethylene copolymers having densities of over 0.88 g/cm³ in a solution process using catalysts such as a bis-cyclopentadienyl hafnocene in combination with a non-coordinating anion (NCA). See for example, WO99/41294, WO99/45040, WO99/45041, WO00/24792, WO01/29096 and WO00/24793 which describe metallocene catalyst systems capable of polymerizing ethylene with an alpha- olefin comonomer at relatively - high polymerization temperatures for a given target molecular weight. These disclosures relate to continuous solution processes, in which back mixing provides a substantial absence of concentration gradients of reactants dissolved in the solvent inside the reactor and the formation of polymer chains in a substantially homogeneous environment with approximately randomly distributed short chain branches formed by the comonomer. After polymerization and removal of volatiles, the resin is sometimes subjected to a finishing process by forming the resin into pellets for storage and shipment, such as is disclosed in WO02/34795. However, very low density elastomers crystallize very slowly. Thus pellets made from very low density elastomeric resins have an increased tendency to stick and agglomerate, which adversely affects transportation and subsequent processing. Often costly remedial steps are required to ensure that the pellets remain free-flowing after storage. It is believed that the novel resin of this invention can be produced with reduced stickiness, thereby reducing the need for the costly remedial steps.

For additional background see: WO 02/34795, EP 608369B, U.S. Patent No. 5,278,272, and Macromol. Chem. Rapid Commun. 13, 321-327 (1992), WO 97/26287, U.S. Patent No. 6,403,737, and U.S. Patent No. 6,448,341, the disclosures of which are hereby incorporated herein by reference.

In one embodiment, the invention provides improved, pelletized, very low density ethylene copolymers and processes for their production.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 is a Solid State Nuclear Magnetic Resonance (SSNMR) spectrum of a solidified ethylene-octene copolymer made in accordance with the current invention, in comparison to a similar ethylene-octene copolymer made with a mono-cyclopentadienyl catalyst.

SUMMARY OF THE INVENTION

An aspect of this invention provides an ethylene copolymer pellet comprising 55wt% to 85wt% of ethylene derived units and 15wt% to 45wt% of units derived from C₄ to C₈ alpha-olefin, having a density of from 0.85 g/cm³ to

0.88 g/cm³, a melt index of from 0.1 to 50 dg/min, a reactivity ratio product (rιr ) of between 0.1 to 0.8 and a monoclinic to orthorhombic crystallite ratio of greater than 0.5. Another aspect of the invention provides an ethylene copolymer pellet comprising 55wt% to 85wt% of ethylene derived units and 15wt% to 45wt% of units derived from C₄ to C₈ alpha-olefin, having a density of from 0.85 g/cm³ to

0.88 g/cm³, a melt index of from 0.1 to 50 dg/min, and a monoclinic to orthorhombic crystallite ratio of greater than 0.5, made by the process of polymerizing ethylene and a C₄ to C₈ alpha-olefin with a bis-cyclopentadienyl metallocene in a diluent to form a slurry of molten polymer and diluent, removing at least a portion of the diluent from the slurry, pelletizing the slurry in a pelletizer, and quenching the pellets in a cooling solution.

Another aspect of the invention provides a process for copolymerizing ethylene and at least one alpha-olefin comprising selecting a bis-cyclopentadienyl catalyst having a reactivity ratio product (rιr₂) of between 0.1 to 0.8, polymerizing ethylene and a C₄-C₈ alpha-olefin comonomer with the bis-cyclopentadienyl catalyst, producing a copolymer resin having from 55wt% to 85wt% of ethylene derived units and 15wt% to 45wt% of units derived from the C₄ to C₈ alpha-olefin, the resin having a density in a range of 0.85g/cm³ to 0.88g/cm³ and a melt index of from 0.1 to 50 dg/min, forming pellets from the resin, and quenching the pellets in a cooling solution at a rate of greater than about 10°C per minute.

Another aspect of this invention provides thermoplastic blends of an ethylene copolymer derived from the pellets of this invention and a thermoplastic material having a melting point greater than 120°C.

DETAILED DESCRIPTION OF THE INVENTION

This invention is a novel pelletized low-density elastomer comprising a copolymer of ethylene and a C₄ to C₈ alpha-olefin monomer, and a process for making the novel pelletized elastomer.

In one embodiment, polymerization of the elastomer is conducted in a single continuous solution reactor to generate a random copolymer. The polymerization reactor may be a liquid filled, continuous flow, stirred tank reactor providing full back mixing for random copolymer production. The reactor may be cooled by a reactor jacket or cooling coils, autorefrigeration, prechilled feeds or combinations of all three to absorb the heat of the exothermic polymerization reaction. Autorefrigerated reactor cooling requires the presence of a vapor phase in the reactor. Adiabatic reactors with prechilled feeds in which the polymerization exotherm is absorbed by permitting a temperature rise of the polymerizing liquid may be used. Hydrogen may be used to control molecular weight. The reactor temperature may also be used to influence the molecular weight of the polymer fraction produced. Examples of particular reactor configurations and processes that may be used for making the compositions of the present invention are described in detail in WO 99/45049, PCT/USO 1/32299 filed October 17, 2001, and U.S. Patent No. 6,319,998, the disclosures of which are hereby incorporated herein by reference. The catalysts useful for this invention are cyclopentadienyl metallocene complexes which have two cyclopentadienyl ring systems for ligands, or bis- cyclopentadienyl metallocenes. The term "bis-cyclopentadienyl metallocene" and "bis-cyclopentadienyl metallocene catalyst precursor" as used herein shall be understood to refer to compounds possessing a transition metal M, with cyclopentadienyl ligands, at least one non-cyclopentadienyl-derived ligand X, and zero or one heteroatom-containing ligand Y, the ligands being coordinated to M and corresponding in number to the valence thereof. The bis-cyclopentadienyl metallocene catalyst precursors are generally neutral complexes but when activated with a suitable co-catalyst yield an active metallocene catalyst which refers generally to an organometallic complex with a vacant coordination site that can coordinate, insert, and polymerize olefins. The metallocene catalyst precursor is a cyclopentadienyl complex which has two cyclopentadienyl ring systems for ligands. The cyclopentadienyl ligands form a sandwich complex with the metal and can be free to rotate (unbridged) or locked into a rigid configuration through a bridging group. The cyclopentadienyl ring ligands can be like or unlike, unsubstituted, substituted, or a derivative thereof such as a heterocyclic ring system which may be substituted, and the substitutions can be fused to form other saturated or unsaturated rings systems such as tetrahydroindenyl, indenyl, or fluorenyl ring systems. These cyclopentadienyl complexes have the general formula

(Cp¹R¹ _m)R³ _n(Cp²R² _p)MX_q

wherein Cp¹ of ligand (Cp^_m) and Cp² of ligand (Cp²R² _p) are the same or different cyclopentadienyl rings R¹ and R² each is, independently, a halogen or a hydrocarbyl, halocarbyl, hydrocarbyl-substituted organometalloid or halocarbyl- substituted organometalloid group containing up to about 20 carbon atoms, m is 0 to 5, p is 0 to 5, and two R¹ and/or R² substituents on adjacent carbon atoms of the cyclopentadienyl ring associated there with can be joined together to form a ring containing from 4 to about 20 carbon atoms, R is a bridging group, n is the number of atoms in the direct chain between the two ligands and is 0 to 8, or 0 to 3, M is a transition metal having a valence of from 3 to 6, preferably from group 4, 5, or 6 of the periodic table of the elements and is preferably in its highest oxidation state, each X is a non-cyclopentadienyl ligand and is, independently, a halogen or a hydrocarbyl, oxyhydrocarbyl, halocarbyl, hydrocarbyl-substituted organometalloid, oxyhydrocarbyl-substituted organometalloid or halocarbyl- substituted organometalloid group containing up to about 20 carbon atoms, q is equal to the valence of M minus 2.

Examples of suitable bis-cyclopentadienyl metallocenes of the type described above are disclosed in U.S. Patent Nos. 5,324,800; 5,198,401; 5,278,119; 5,387,568; 5,120,867; 5,017,714; 4,871,705; 4,542,199; 4,752,597; 5,132,262; 5,391,629; 5,243,001; 5,278,264; 5,296,434; and 5,304,614, all of which are hereby incorporated herein by reference. Illustrative, but not limiting, examples of bis-cyclopentadienyl metallocenes of the type described above are the racemic isomers of: μ-(CH₃)₂Si(indenyl)₂M(Cl)₂ μ-(CH₃)₂Si(indenyl)₂M(CH₃)₂ μ-(CH₃)₂Si(tetrahydroindenyl)₂M(Cl)₂ μ-(CH₃)₂Si(tetrahydroindenyl)₂M(CH₃)₂ μ-(CH₃)₂Si(indenyl)₂M(CH₂CH₃)₂ and μ-(C₆H₅)₂C(indenyl)₂M(CH₃)₂; wherein M is chosen from a group consisting of Zr and Hf.

Examples of unsymmetrical cyclopentadienyl metallocenes are disclosed in U.S. Patent Nos. 4,892,851; 5,334,677; 5,416,228; and 5,449,651; and are described in publication J Am. Chem. Soc. 1988, 110, 6255, all of which are incorporated by reference herein. Examples of unsymmetrical cyclopentadienyl metallocenes of the type described above are: μ-(C₆H₅)₂C(cyclopentadienyl)(fluorenyl)M(R)₂ μ-(C₆H₅)₂C(3-methylcyclopentadienyl)(fluorenyl)M(R)₂ μ-(CH₃)₂C(cyclopentadienyl)(fluorenyl)M(R)₂ μ-(C₆H₅)₂C(cyclopentadienyl)(2-methylindenyl)M(CH₃)₂ μ-(C₆H₅)₂C(3 -methylcyclopentadienyl)(2-methylindenyl)M(Cl)₂ μ-(C₆H₅)₂C(cyclopentadienyl)(2,7-dimethylfluorenyl)M(R)₂ and μ-(CH₃)₂C(cyclopentadienyl)(2,7-dimethylfluorenyl)M(R)₂; wherein M is chosen from a group consisting of Zr and Hf, and R is chosen from a group consisting of CI and CH₃. The metallocene complexes may be activated with a non-coordinating anion (NCA), described further below. Optionally, a scavenger component such as a trialkyl aluminum scavenger may be added to the reactor feed(s) to prevent deactivation of catalyst by poisons and to increase the apparent activity.

The term "noncoordinating anion" (NCA) means an anion which either does not coordinate to the transition metal cation or which is only weakly coordinated to the cation thereby remaining sufficiently labile to be displaced by a neutral Lewis base. "Compatible" noncoordinating anions are those which are not degraded to neutrality when the initially formed complex decomposes. Further, the anion will not transfer an anionic substituent or fragment to the cation so as to cause it to form a neutral four coordinate metallocene compound and a neutral byproduct from the anion. Useful noncoordinating anions are those that are compatible, stabilize the metallocene cation in the sense of balancing its ionic charge in a +1 state, yet retain sufficient lability to permit displacement by an ethylenically or acetylenically unsaturated monomer during polymerization. Additionally, useful anions will be large or bulky in the sense of sufficient molecular size to largely inhibit or prevent neutralization of the metallocene cation by Lewis bases other than the polymerizable monomers that may be present in the polymerization process. Typically the anion will have a molecular size of greater than or equal to about 4 angstroms. NCA's are preferred because of their ability to produce a target molecular weight polymer at a higher temperature than tends to be the case with other activation systems such as alumoxane. Descriptions of ionic catalysts for coordination polymerization using metallocene cations activated by non-coordinating anions appear in the early work in EP-A-0 277 003, EP-A-0 277 004, WO92/00333 and U.S. Patent Nos. 5,198,401 and 5,278,119. These references teach a preferred method of preparation wherein metallocenes (bis-cyclopentadienyl and mono- cyclopentadienyl) are protonated by an anionic precursors such that an alkyl/hydride group is abstracted from a transition metal to make it both cationic and charge-balanced by the non-coordinating anion. The use of ionizing ionic compounds not containing an active proton but capable of producing both the active metallocene cation and a noncoordinating anion is also known. See, EP-A- 0 426 637, EP-A- 0 573 403 and U.S. Patent No. 5,387,568. Reactive cations other than Bronsted acids capable of ionizing the metallocene compounds include ferrocenium triphenylcarbonium and triethylsilylinium cations. Any metal or metalloid capable of forming a coordination complex which is resistant to degradation by water (or other Bronsted or Lewis Acids) may be used or contained in the anion of the second activator compound. Suitable metals include, but are not limited to, aluminum, gold, platinum and the like. Suitable metalloids include, but are not limited to, boron, phosphorus, silicon and the like. The description of non-coordinating anions and precursors thereto of these documents are hereby incorporated herein by reference.

An additional method of making the ionic catalysts uses ionizing anionic pre-cursors which are initially neutral Lewis acids but form the cation and anion upon ionizing reaction with the metallocene compounds, for example tris(pentafluorophenyl) boron acts to abstract an alkyl, hydride or silyl ligand to yield a metallocene cation and stabilizing non-coordinating anion, see EP-A-0 427 697 and EP-A-0 520 732. Ionic catalysts for addition polymerization can also be prepared by oxidation of the metal centers of transition metal compounds by anionic precursors containing metallic oxidizing groups along with the anion groups, see EP-A-0 495 375. The description of non-coordinating anions and precursors thereto of these documents are similarly hereby incorporated herein by reference. Examples of activators capable of ionic cationization of the metallocene compounds described herein, and consequent stabilization with a resulting noncoordinating anion include: trialkyl-substituted ammonium salts such as: triethylammonium tetraphenylborate, tripropylammonium tetraphenylborate, tri(n-butyl)ammonium tetraphenylborate, trimethylammonium tetrakis(p-tolyl)borate, trimethylammonium tetrakis(o-tolyl)borate, tributylammonium tetrakis(pentafluorophenyl)borate, tripropylammonium tetrakis(o,p-dimethylphenyl)borate, tributylammonium tetrakis(m,m-dimethylphenyl)borate, fributylammonium tetrakis(p-trifluoromethylphenyl)borate, tributylammonium tetrakis(pentafluorophenyl)borate, and tri(n-butyl)ammonium tetrakis(o-tolyl)borate;

N,N-dialkyl anilinium salts such as:

N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate,

N,N-dimethylaniliniumtetrakis(heptafluoronaphthyl)borate,

N,N-dimethylanilinium tetrakis(perfluoro-4-biphenyl)borate, N,N-dimethylanilinium tetraphenylborate,

N,N-diethylanilinium tetraphenylborate, and .

N,N-2,4,6-pentamethylanilinium tetraphenylborate; dialkyl ammonium salts such as: di-(isopropyl)ammonium tetrakis(pentafluorophenyl)borate, and dicyclohexylammonium tetraphenylborate; and triaryl phosphonium salts such as: triphenylphosphonium tetraphenylborate, tri(methylphenyl)phosphonium tetraphenylborate, and tri(dimethylphenyl)phosphonium tetraphenylborate. Further examples of suitable anionic precursors include those including a stable carbonium ion, and a compatible non-coordinating anion. These include: tropillium tetrakis(pentafluorophenyl)borate, triphenylmethylium tetrakis(pentafluorophenyl)borate, benzene (diazonium) tetrakis(pentafluorophenyl)borate, tropillium phenyltris(pentafluorophenyl)borate, triphenylmethylium phenyl-(trispentafluorophenyl)borate, benzene (diazonium) phenyl-tris(pentafluorophenyl)borate, tropillium tetrakis(2,3,5,6-tetrafluorophenyl)borate, triphenylmemylium tetrakis(2,3,5,6-tetrafluorophenyl)borate, benzene (diazonium) tetrakis(3,4,5-trifluorophenyl)borate, tropillium tetrakis(3,4,5-trifluorophenyl)borate, benzene (diazonium) tetrakis(3,4,5-trifluorophenyl)borate, tropillium tetrakis(3 ,4,5-trifluorophenyl)aluminate, triphenylmethylium tetrakis(3,4,5-trifluorophenyl)aluminate, benzene (diazonium) tetrakis(3,4,5-trifluorophenyl)aluminate, tropillium tetrakis(l ,2,2-trifluoroethenyl)borate, triphenylmethylium tetrakis(l,2,2-trifluoroethenyl)borate, benzene (diazonium) tetrakis(l,2,2-trifluoroethenyl)borate, tropillium tetrakis(2,3,4,5-tetrafluorophenyl)borate, triphenylmethylium tetrakis(2,3,4,5-tetrafluorophenyl)borate, and benzene (diazonium) tetrakis(2,3,4,5-tetrafluorophenyl)borate. Where the metal ligands include halide moieties, for example, (methyl- phenyl) silylene (tetra-methyl-cyclopentadienyl) (tert-butyl-amido) zirconium dichloride), which are not capable of ionizing abstraction under standard conditions, they can be converted via known alkylation reactions with organometallic compounds such as lithium or aluminum hydrides or alkyls, alkylalumoxanes, Grignard reagents, etc. See EP-A-0 500 944, EP-Al-0 570 982 and EP-Al-0 612 768 for processes describing the reaction of alkyl aluminum compounds with dihalide substituted metallocene compounds prior to or with the addition of activating anionic compounds. For example, an aluminum alkyl compound may be mixed with the metallocene prior to its introduction into the reaction vessel. Since the alkyl aluminum is also suitable as a scavenger its use in excess of that normally stoichiometrically required for alkylation of the metallocene will permit its addition to the reaction solvent with the metallocene compound. Normally alumoxane would not be added with the metallocene so as to avoid premature activation, but can be added directly to the reaction vessel in the presence of the polymerizable monomers when serving as both scavenger and alkylating activator. Alumoxanes may also fulfill a scavenging function. Alkylalumoxanes may also be used as catalyst activators, particularly for those metallocenes comprising halide ligands. The alumoxane component useful as catalyst activator typically is an oligomeric aluminum compound represented by the general formula (R-Al-O)^, which is a cyclic compound, or R(R-A1-

O)røAlR2, which is a linear compound. In the general alumoxane formula, R is a Cι to C5 alkyl radical, for example, methyl, ethyl, propyl, butyl or pentyl and "n" is an integer from 1 to about 50. Most preferably, R is methyl and "n" is at least 4, i.e., methylalumoxane (MAO). Alumoxanes can be prepared by various procedures known in the art. For example, an aluminum alkyl may be treated with water dissolved in an inert organic solvent, or it may be contacted with a hydrated salt, such as hydrated copper sulfate suspended in an inert organic solvent, to yield an alumoxane. Generally, however prepared, the reaction of an aluminum alkyl with a limited amount of water yields a mixture of the linear and cyclic species of the alumoxane.

Catalyst killer such as water may be added to the effluent of the reactor or reactors, for example at the last stage prior to finishing, so as to prevent additional, difficult to control polymerization during finishing. It is possible that the catalyst is effectively spent at the end of the polymerization; however, the more active bis-cyclopentadienyl catalysts and NCA's have sufficient stability to remain active even after the polymerization proper has ended. The amount of killer and the manner of its addition are tailored to ensure that just enough is added to ensure a complete kill. Excess killer may have to be removed by scavenger or other means such as atomic sieves or other purification columns to ensure that killers are not recycled and act as poisons in the polymerization process. Optionally, the process also uses a scavenging compound. Trialkyl aluminum may be used as a scavenger, as well as other scavengers known in the art. The term "scavenging compounds" as used in this application and in the claims is meant to include those compounds effective for removing polar impurities from the reaction solvent.

An example of a bis-cyclopentadienyl metallocene for the current invention contains a bridging group R³, for example a single atom bridge (wherein n=l), wherein the single atom bridge may be a methylene unit that bridges the bis aryl substituents. The bis-cyclopentadienyl metallocene may have at least one cyclopentadienyl ring ligand, or a derivative thereof, having a fused ring, such as a fluorenyl ring system. The bis-cyclopentadienyl metallocene may have hafnium as its transition metal (M). The bis-cyclopentadienyl metallocene described above may be activated with an NCA. The NCA may be tetra-aryl fluorinated and may contain a boron-derived group. The tetra-aryl fluorinated NCA may contain at least two perflourinations, and may have at .least one polycyclic aryl group which may be a fused polycyclic group. In general, the reactor temperature can vary between 0-240°C, or 10-

130°C, or 20-110°C. Optimal temperatures can be achieved with progressively increasing polymerization temperature by using a bis-cyclopentadienyl metallocene containing hafnium as the transition metal, especially one having a covalent, single atom bridge coupling the two cyclopentadienyl rings. The reactor may be pressurized up to 120 bar.

The process of this invention involves selecting a bis-cyclopentadienyl catalyst system having a product of the reactivity ratio (rιr ) of less than 1, or within the range of from 0.1 to 0.8, or within the range of from 0.1 to 0.5, to randomly and continuously polymerize ethylene and at least one alpha-olefin to produce an ethylene copolymer having a density of from 0.85 g/cm to 0.88 g/cm . The ethylene copolymer produced by the process of this invention contains about 55 wt% to about 85 wt% ethylene units and from about 15 wt% to about 45 wt% of the C₄ to C₈ alpha-olefin comonomer based upon measurement by C NMR. Examples of alpha olefin monomers include, but are not limited to 1-octene, 1- hexene and 1-butene.

The product of the reactivity ratio (rιr ) of the polymerization is a measure of the distribution of comonomer incorporated along the chain. The product of the reactivity ratio, wherein rl is the reactivity ratio of the comonomer (C), and r2 is the reactivity ratio of ethylene (E), can be calculated from the following formula (M. Kakugo et al., Macromolecules, 15, 1150-1152):

r_ιr2 = 4(EE) (CC)/(EC)²

where EE, CC and EC are diad sequence of monomers, which can be expressed in terms of triads as follows:

EE=EEE+1/2(EEC+CEE)

CC-CCC+1/2(CCE+ECC) EC=ECE+CEC+1/2(EEC+CEE+ECC+CCE)

Triads can be determined from the ¹³C NMR spectrum using the method described in J Macromol. Set, Rev. Macromol. Chem. Phys., C29, 201-317 by J. C. Randall, incorporated herein by reference. The reactivity ratio product of rιr =1 defines a statistically random copolymer. A copolymer with a rιr₂ greater than 1 is "blocky" and a copolymer with a r^₂ less than 1 is said to be "alternating."

Using the disclosed process, a regular dispersion of comonomer along the polymer chain can be obtained combined with high comonomer incorporation. Less alpha-olefin needs to be fed to the polymerization reactor and less alpha- olefin needs to be recycled after polymer isolation.

The process allows for efficient incorporation of the higher alpha-olefin monomer into the polymer chain, for the production of the novel low density elastomer. By efficient incorporation, it is meant that there is low incorporation of higher alpha-olefins in diad and triad sequences in the polymer chain, i.e. the process provides for a highly random distribution of the alpha-olefins along the polymer chain. As a single alpha-olefin monomer is as effective as contiguous alpha-olefin monomers in providing a low density elastomer, the process of the current invention provides a low density elastomer while incorporating less of the more costly comonomer. Surprisingly, the novel low density elastomer also contains a high proportion of monoclinic crystallites. Although the crystallinity in low density elastomers is low, the mechanical properties of the resin may be influenced by its crystallinity because the modulus of crystalline region is much larger than that of the amorphous region. It is expected that the differences between orthorhombic crystallites and monoclinic crystallites will manifest different mechanical properties in elastomers, for example, a higher proportion of monoclinic crystallites is believed to decrease stickiness when pelletizing the resin for storage and transportation. The ratio of monoclinic to orthorhombic crystallites in an elastomer can be determined by Solid State Nuclear Magnetic Resonance (SSNMR). The resins produced by the inventive process preferably have a ratio of monoclinic crystallites to orthorhombic crystallites (m/o) of greater than 0.5 as calculated by dividing the signal area of the peak at 34.0 ppm (corresponding to monoclinic crystallites) by the signal area of the peak at 33.0 ppm (corresponding to orthorhombic crystallites) in the solid state ¹³C NMR spectrum. It is believed that a high MCP/OCP ratio, with a suitable dispersion of short chain branches, can provide benefits in pellet handling and impact performance in an end use blend.

Moreover, it is unexpectedly found that rapidly quenching the resin during the pelletization process further enhances the monoclinic/orthorhombic ratio of the novel resin. The pelletization process can occur, for example, by the direct devolatization process system disclosed in WO02/34795, the disclosure of which is hereby incorporated herein by reference. For ethylene-butene copolymers of the current invention, the m/o ratio may be greater than 1 when the resin is quenched at a rate of greater than about 20°C/minute. For ethylene-octene copolymers of the current invention, the m/o ratio may be greater than 1, or greater than 1.25, when the resin is quenched at a rate of greater than about 20°C/minute.

Under the direct devolatization process, the solvent or diluent is removed from the slurry of molten polymer and diluent by squeezing, evaporating or flashing in the devolatization equipment, and the diluent-free molten polymer is then extruded or pushed through a die plate with a cutting device to produce the dense pellets. For the purposes of the current invention, diluent-free means that the diluent constitutes less than about 0.5% of the total weight of the slurry. An underwater pelletizer may be used for pelletization. The devolatilized polymer may be advanced to a pelletizer die by a screw. The pelletized die outlet is suitably located underwater. The strands emerging from the die may be cut and the cut pellets slurried in the water diluent.

Chilled water is used for pelletizing the resin. The water temperature is selected so that the resin is quenched at a rate of greater than 10°C per minute, or greater than 20°C per minute. Typical dimensions of these pellets range from about 2 mm diameter up to 2 cm diameter and a height or length ranging from about 2 mm to about 2 cm.

Accordingly, in another embodiment of the invention, this invention comprises the novel pelletized elastomeric copolymer of this invention that has been rapidly quenched. It is believed that by rapidly quenching the novel resin of the current invention during pelletization, a higher proportion of the faster forming monoclinic crystallites are generated which solidifies the elastomer pellet surface, which provides reduced stickiness in the pelletized resin and allows the pellets to flow freely.

The novel elastomeric copolymer of this invention can be used in blends such as TPO (thermoplastic polyolefin) or TPN (thermoplastic vulcanizate) where the matrix phase surrounds the impact modifier. The elastomer is typically blended with a thermoplastic material having a melting temperature over 120°C. The thermoplastic material may be, for example, polypropylene, such as isotactic polypropylene having a melt flow rate (dg/min) in a range of about 1.5 - 40. The polypropylene may contain minor amounts of ethylene and/or an alpha-olefin of 4-12 carbon atoms ranging from 1 wt% to 40 wt% of the polymer. The blend may comprise about 25 to 97 parts by weight of the thermoplastic material, and about 3 to 75 parts by weight of the elastomeric copolymer of this invention.

Suitably the pelletized ethylene copolymer of this invention has an MIR value of from 15-40, or from 17-32, or from 20-30, and a molecular weight distribution of from 1.5 to 3 as determined by GPC LALLS. The pelletized ethylene copolymer may have a melt index [MI] within the range of from 0.1 to 50 dg/min, or within the range of from 0.1 to 15 dg/min, or within the range of from 0.1 to 10 dg/min, or within the range of from 0.5 to 5 dg/min.

The following examples are intended to be illustrative of the novel process and product of the current invention. However, it should be understood that the invention is not intended to be limited in any way to the specific details of the following examples.

Table 1 provides a list of the test methods employed in the following examples.

TABLE 1

EXAMPLES

In the following, an ethylene-octene copolymer will be used as example to demonstrate calculation of sequence distribution. One method to describe the molecular features of an ethylene-octene copolymer is sequence distribution of monomers along the polymer molecule. As is well known, single site catalyst in a single continuous reactor makes copolymer of narrow composition distribution. Therefore, the monomer sequence distribution of the present invention can be determined using spectroscopic analysis. Carbon 13 nuclear magnetic resonance spectroscopy ( C NMR) is highly preferred for this purpose, and is used to establish diad and triad distribution via the integration of spectral peaks.

The following polymerization reactions were performed in a stirred, liquid filled 2L jacketed steel reactor equipped to perform continuous insertion polymerization in presence of an inert hydrocarbon (naphtha) solvent at pressures up to 120 bar and temperatures up to 240 °C. The reactor was typically stirred at 1000 rpm during the polymerization. The reaction system was supplied with a thermocouple and a pressure transducer to monitor changes in temperature and pressure continuously, and with means to supply continuously purified ethylene, 1-octene, and solvent. In this system, ethylene dissolved in the hydrocarbon solvent, 1-octene, tri-n-octyl aluminum (TO A) used as a scavenger, and optionally H₂, are pumped separately, mixed, and fed to the reactor as a single stream. The stream is refrigerated to below 0 °C. The transition metal component (TMC) bis(4-triethylsilylphenyl) methylidene (cyclopentadienyl) (2,7-tertbutyl-fluorenyl) hafnium dimethyl was dissolved in a solvent/toluene mixture (9/1 vol/vol) whereas the ionic precursor of the non-coordinating anion (NCA) activator, which is dimethyl anilinium hydride tetrakis(pentafluorophenyl)boron, was dissolved in toluene/solvent mixture (1/1 vol/vol). Both components were pumped separately, mixed at ambient temperature, and cooled to below about 0 °C prior to entering the reactor. The reactor temperature was set by adjusting the temperature of an oil bath used as a reservoir for the oil flowing through the reactor wall jacket to 110 °C. Next, the polymer molecular weight (MW) or MI was controlled independently by adjusting the ethylene conversion in the reactor via the catalyst flow rate. Finally, the polymer density was controlled by adjusting the ethylene/1- octene weight ratio in the feed.

For comparison commercial Engage™ samples from Dupont Dow Elastomers were used. The composition and reactivity ratio product rιr₂ of the polymer were measured using C solution NMR. The NMR measurements were conducted on a Narian 500 ΝMR spectrometer at 120°C, with orthodichlorobenzene-d4 as the solvent. Triads were determined from the ¹³C ΝMR spectrum using the method as described in J Macromol. Sci., Rev. Macromol. Chem. Phys., C29, 201-317 by J. C. Randall, see Table 2. From the triad intensities, r^₂ can be determined according to Equations (1) to (4).

The reactivity ratio product r (where ri is the reactivity of ethylene and r₂ is the reactivity of octene) can be calculated from the following formulae (M. Kakugo et al., Macromolecules 15, 1150-1152):

nr₂ = 4 (EE)(OO)/(EO)², (1)

Where EE, OO, and EO are diad sequence of monomers, which can be expressed in terms of triad as follows:

EE=EEE+l/2(EEO+OEE) (2)

OOOOO+1/2(OOE+EOO) (3) EO=EOE+OEO+l/2(EEO+OEE+EOO+OOE) (4)

Various ethylene/octene copolymer compositions were made in accordance with the process described above in a solution continuous reactor at a polymerization temperature of 110°C. Results are provided in Table 2. TABLE 2

Table 3 provides a summary of the ethylene-octene copolymers made in accordance with this invention. The comonomer weight percentages are determined by Carbon NMR. Table 4 provides a summary of comparative ethylene-octene copolymers sold under the tradename Engage™ by DupontDow Elastomers, which are believed to be made with mono-cyclopentadienyl catalysts.

TABLE 3

TABLE 4

Table 5 shows a comparison between sample 1, sample 2 and comparative sample 6. The samples were selected for comparison because of the similarities in their melt index (MI) and densities. All test specimens were cut from compression molded 1/8 inch plaque. Test specimens were conditioned according to ASTM D-618 for 40 hours in an ASTM room.

Samples 1 and 2 have comparable properties to comparative sample 6, and are able to achieve these properties with incorporation of less comonomer. Samples 1 and 2 incorporate 37.4 wt% and 37.3 wt% of octene, respectively, while the control sample incorporates 38.9 wt% of octene. Because one octene is similarly effective in disrupting ethylene crystallinity as do several consecutive octene monomers, the polymer of the present invention achieves comparable mechanical properties by using less octene, which is a more expensive raw material than ethylene.

TABLE S

Similarly, comparison of properties of the ethylene-octene copolymers of the present invention embodied in Samples 3 and 4 and Comparative Sample 7 are shown in Table 6. Again, all test specimens were cut from compression molded 1/8 inch plaque. Test specimens were conditioned according to ASTM D-618 for 40 hours in an ASTM room. These samples were selected for comparison based upon the similarity of their Melt Indexes (~1) and densities (~0.870g/cm³). Similar to the results of Table 5, Table 6 shows that the Samples of the present invention have similar physical properties to the comparative sample while incorporating less of the costly comonomer. For example Sample 3 incorporates 36.2 wt% comonomer compared with the Comparative Sample 7, which incorporates 37.7 wt% comonomer. Accordingly, comparable properties are achieved while using less of the more costly octene comonomer.

TABLE 6

A comparison was made between Sample 5 and Comparative Sample 8 because of the similarities between their melt index (~5) and densities (~0.870g/cm³). As is indicated in Table 7, Sample 5 achieves similar physical properties at lower comonomer incorporation, i.e. 36.8 wt% octene of Sample 5 as compared with 38.9 wt% octene of the Comparative Sample 8.

TABLE 7

Determination of MCP/OCP ratio

The solid-state NMR (SSNMR) experiments were performed on a Bruker

DSX-500 Nuclear Magnetic Resonance (NMR) spectrometer, with a 1H frequency of 500.13 MHz and ¹³C frequency of 125.75 MHz. The pulse sequence was a 90°(1H) pulse followed by cross polarization and ±z ¹³C Tι filter. The spinning speed was 2-4 kHz, 90° pulse length 4.5 μs, contact time 100-500 μs, and ¹³C Ti

1 ^ filter time 1-2 s. Due to the short C Ti of the amorphous regions in the copolymers, most amorphous signals are suppressed by the filter so that the crystalline signals are the prominent peaks on the spectra. All spectra were calibrated with reference to the crystalline signal in high density polyethylene set at 32.8 ppm. Samples were tested either as pellets or as plaques. Plaques were made in accordance with ASTM D4703-00, with a cooling rate used is method A in table 1.

Figures la and lb compare the SSNMR results from Sample 2 (Figure la) with Comparative Sample 6 (Figure lb). The spectra in Figures la and lb were acquired under the same spectrometer conditions, and the samples were cooled at the same rate.

The signal at 32.8 - 33.0 ppm represents the orthorhombic ethylene crystal, while the signal at 34 - 34.2 ppm represents the monoclinic form. The monoclinic to orthorhombic crystallinity ratio in the polymer was established from the NMR measurements by dividing the signal area of the peak at 34.0 ppm (corresponding to monoclinic crystallites) by the signal area of the peak at 33.0 ppm (corresponding to orthorhombic crystallites) in the solid state 13C NMR spectrum. As is shown in Figure 1, Sample 2 of the current invention made with a bis- cyclopentadienyl catalyst has a higher proportion of monoclinic crystallites than a corresponding resin made with a mono-cyclopentadienyl catalyst.

As is shown in Table 8, the monoclinic/orthorhombic crystallite ratio (m/o) increases at a higher rate of cooling. Accordingly, the m/o ratio and the beneficial physical properties that arise from an enhanced m/o ratio, for example, decreased stickiness of the pellets, can be controlled using the process of this invention and by controlling the rate of cooling. TABLE 8

Ethylene-butene copolymer pellets were made in accordance with the above described invention. Properties of the pellets, which were quenched at a rate of greater than 20°C/minute are provided in Table 9.

TABLE 9

Properties of Blends

The properties of the blend of polypropylene and elastomers of the current invention are shown in Table 10. As seen from the table, blends made from polypropylene and elastomers of the current invention, and blends made from polypropylene and Comparative Sample 8 exhibit very comparable properties. Again, the blends made with the elastomeric copolymer of the current invention is able to achieve these similar properties with less incorporation of the costly comonomer. TABLE 10

Escorene AX05B (Impact Polypropylene Copolymer, 35 MFR) Cimpact™ is a talc sold by Luzenac America Inc.

Claims

IN THE CLAIMS We claim:EP Claims

1. An ethylene copolymer pellet comprising 55wt% to 85wt% of ethylene derived units and 15wt% to 45wt% of units derived from C to C₈ alpha-olefin, having a density in the range of from 0.85 g/cm³ to 0.88 g/cm³, a melt index of from 0.1 to 50 dg/min, a reactivity ratio product

of between 0.1 to 0.8 and a monoclinic to orthorhombic crystallite ratio of greater than 0.5, or greater than 1.0.

2. The ethylene copolymer pellet of claim 1 obtainable by polymerizing ethylene and a C₄ to C₈ alpha-olefin with a bis-cyclopentadienyl metallocene in a diluent to form a slurry of molten polymer and diluent, removing at least a portion of said diluent from said slurry, pelletizing the slurry and quenching the pellets in a cooling fluid.

3. The ethylene copolymer pellet of claim 2, wherein said bis- cyclopentadienyl metallocene has a hafnocene transition metal.

4. The ethylene copolymer pellet of claim 2 or 3, wherein said bis- cyclopentadienyl metallocene has a single atom bridging group comprising a methylene unit.

5. The ethylene copolymer pellet of claim 2, 3, or 4, wherein said bis- cyclopentadienyl metallocene has at least one cyclopentadienyl ring further comprising a fluorenyl ring.

6. The ethylene copolymer pellet of claim 2, 3, 4, or 5, wherein said pellet is quenched at a rate of greater than 10°C per minute, preferably at a rate of greater than 20°C per minute.

7. The ethylene copolymer pellet of any of the preceding claims, wherein said units derived from C₄ to C₈ alpha-olefin comprise butene or octene.

8. The ethylene copolymer pellet of any of the preceding claims, wherein said pellets have an MIR value of from 15 to 40.

9. The ethylene copolymer pellet of any of the preceding claims, wherein said pellets have a molecular weight distribution of from 1.5 to 3 as determined by GPC LALLS.

10. The ethylene copolymer pellet of any of claims 2-9, wherein said diluent is removed to be less than 0.5wt% of the total weight of the slurry.

11. The ethylene copolymer pellet of any of the preceding claims made by the process of: ^>

(a) polymerizing ethylene and a C₄ to C₈ alpha-olefin with a bis- cyclopentadienyl metallocene in a diluent to form a slurry of molten polymer and diluent,

(b) removing at least a portion of said diluent from said slurry, (c) pelletizing said slurry in a pelletizer, and

(d) quenching said pellets in a cooling solution.

12. A thermoplastic blend of an ethylene copolymer derived from pellets according to any of claims 1 to 11, and a thermoplastic material having a melting temperature of over 120°C.

13. The thermoplastic blend of claim 12 in which said thermoplastic material comprises isotactic polypropylene, and optionally comprises units of an alpha- olefin having 4-12 carbon atoms, preferably ethylene.

14. The thermoplastic blend of claim 12 or 13, wherein said blend comprises about 25 to 97 parts by weight of said thermoplastic material, and about 3 to 75 parts by weight of said ethylene copolymer.

15. The thermoplastic blend of any of claims 12-14, wherein said polypropylene has a melt flow rate in the range of about 1.5 to 40 dg/min.

16. A process for copolymerizing ethylene and at least one alpha-olefin, the process comprising: (a) selecting a bis-cyclopentadienyl catalyst having a reactivity ratio product (rιr₂) of between 0.1 to 0.8,

(b) polymerizing ethylene and a C₄-C₈ alpha-olefin comonomer with said bis-cyclopentadienyl catalyst,

(c) producing a copolymer resin having from 55wt% to 85wt% of ethylene derived units and 15wt% to 45wt% of units derived from said C₄ to C₈ alpha-olefin comonomer, said copolymer resin having a density in the range of from 0.85 g/cm³ to 0.88 g/cm³ and a melt index of from 0.1 to 50 dg/min,

(d) forming pellets from said copolymer resin, and (e) quenching said pellets in a cooling solution at a rate of greater than about 10°C per minute.

17. The process of claim 16, wherein said quenched pellets have a monoclinic to orthorhombic crystallite ratio of greater than 0.5, or greater than 1.0.

18. The process of claim 16 or 17, wherein said step of quenching said pellets is at a rate of greater than 20°C per minute.

19. The process of any of claims 16-18, wherein said C₄ to C₈ alpha-olefin comonomer is butene or octene.

20. The process of any of claims 16-19, wherein said quenched pellets have an MIR value of from 15 to 40.

21. The process of any of claims 16-20, wherein said quenched pellets have a molecular weight distribution of from 1.5 to 3 as determined by GPC LALLS.

22. The process of any of claims 16-21, wherein said bis-cyclopentadienyl metallocene has a hafnocene transition metal.

23. The process of any of claims 16-22, wherein said bis-cyclopentadienyl metallocene has a single atom bridging group comprising a methylene unit.

24. The process of any of claims 16-23, wherein said bis-cyclopentadienyl metallocene has at least one cyclopentadienyl ring further comprising a fluorenyl ring.

US Claims

1. An ethylene copolymer pellet comprising 55wt% to 85wt% of ethylene derived units and 15wt% to 45wt% of units derived from a C₄ to C₈ alpha-olefin, having a density of from 0.85 g/cm³ to 0.88 g/cm³, a melt index of from 0.1 to 50 dg/min, a reactivity ratio product (rιr ) of between 0.1 to 0.8 and a monoclinic to orthorhombic crystallite ratio of greater than 0.5.

2. The ethylene copolymer pellet of claim 1 obtainable by polymerizing ethylene and said C to C₈ alpha-olefin with a bis-cyclopentadienyl metallocene in a diluent to form a slurry of molten polymer and diluent, removing at least a portion of said diluent from said slurry, pelletizing the slurry and quenching the pellets in a cooling fluid.

3. The ethylene copolymer pellet of claim 2, wherein said pellet is quenched at a rate of greater than 10°C per minute.

4. The ethylene copolymer pellet of claim 2, wherein said pellet is quenched at a rate of greater than 20°C per minute.

5. The ethylene copolymer pellet of claim 4, wherein said C₄ to C₈ alpha- olefin comprises butene.

6. The ethylene copolymer pellet of claim 5, wherein said pellets have a monoclinic to orthorhombic ratio of 1.0 or more.

7. The ethylene copolymer pellet of claim 4, wherein said C₄ to C₈ alpha- olefin comprises octene.

8. The ethylene copolymer pellet of claim 7, wherein said pellets have a monoclinic to orthorhombic ratio greater than 1.0.

9. The ethylene copolymer pellet of claim 1 or claim 2, having an MIR value offrom l5 to 40.

10. The ethylene copolymer pellet of claim 1 or claim 2, having a molecular weight distribution of from 1.5 to 3 as determined by GPC LALLS.

11. The ethylene copolymer pellet of claim 2, wherein said bis- cyclopentadienyl metallocene has a hafnocene transition metal.

12. The ethylene copolymer pellet of claim 2, wherein said bis- cyclopentadienyl metallocene has a single atom bridging group comprising a methylene unit.

13. The ethylene copolymer pellet of claim 2, wherein said bis- cyclopentadienyl metallocene has at least one cyclopentadienyl ring further comprising a fluorenyl ring.

14. The ethylene copolymer pellet of claim 11, wherein said bis- cyclopentadienyl metallocene has a single atom bridging group comprising a methylene unit, and wherein said bis-cyclopentadienyl metallocene has at least one cyclopentadienyl ring further comprising a fluorenyl ring.

15. The ethylene copolymer pellet of claim 2, wherein said diluent is removed to be less than 0.5wt% of the total weight of the slurry.

16. An ethylene copolymer pellet comprising 55wt% to 85wt% of ethylene derived units and 15wt% to 45wt% of units derived from a C₄ to C₈ alpha-olefin, having a density of from 0.85 g/cm³ to 0.88 g/cm³, a melt index of from 0.1 to 50 dg/min, and a monoclinic to orthorhombic crystallite ratio of greater than 0.5, made by the process comprising:

(a) polymerizing ethylene and said C₄ to C₈ alpha-olefin with a bis- cyclopentadienyl metallocene in a diluent to form a slurry of molten polymer and diluent,

(b) removing at least a portion of said diluent from said slurry,

(c) pelletizing said slurry in a pelletizer, and

(d) quenching said pellets in a cooling solution.

17. The ethylene copolymer pellet of claim 16, wherein said step of quenching said pellets is at a rate of greater than 10°C per minute.

18. The ethylene copolymer pellet of claim 16, wherein said step of quenching said pellets is at a rate of greater than 20°C per minute.

19. The ethylene copolymer pellet of claim 16, wherein said C₄ to C₈ alpha- olefin comprises butene.

20. The ethylene copolymer pellet of claim 19, wherein said pellets have a monoclinic to orthorhombic ratio of 1.0 or more.

21. The ethylene copolymer pellet of claim 16, wherein said C to C₈ alpha- olefin comprises octene.

22. The ethylene copolymer pellet of claim 21, wherein said pellets have a monoclinic to orthorhombic ratio of 1.0 or more.

23. The ethylene copolymer pellet of claim 16 having an MIR value of from 15 to 40.

24. The ethylene copolymer pellet according to claim 16 having a molecular weight distribution of from 1.5 to 3 as determined by GPC LALLS.

25. The ethylene copolymer pellet according to claim 16, wherein said bis- cyclopentadienyl metallocene has a hafnocene transition metal.

26. The ethylene copolymer pellet according to claim 16, wherein said bis- cyclopentadienyl metallocene has a single atom bridging group comprising a methylene unit.

27. The ethylene copolymer pellet according to claim 16, wherein said bis- cyclopentadienyl metallocene has at least one cyclopentadienyl ring further comprising a fluorenyl ring.

28. The ethylene copolymer pellet of claim 25, wherein said bis- cyclopentadienyl metallocene has a single atom bridging group comprising a methylene unit, and wherein said bis-cyclopentadienyl metallocene has at least one cyclopentadienyl ring further comprising a fluorenyl ring.

29. The ethylene copolymer pellet of claim 16 having a reactivity ratio product (nr₂) of between 0.1 to 0.8.

30. The ethylene copolymer pellet according to claim 16, wherein said diluent is removed to be less than 0.5wt% of the total weight of the slurry.

31. A process for copolymerizing ethylene and at least one alpha-olefin, the process comprising:

(a) selecting a bis-cyclopentadienyl catalyst having a reactivity ratio product (rιr₂) of between 0.1 to 0.8,

(b) polymerizing ethylene and a C₄-C₈ alpha-olefin comonomer with said bis-cyclopentadienyl catalyst, (c) producing a copolymer resin having from 55wt% to 85wt% of ethylene derived units and 15wt% to 45wt% of units derived from said C to C₈ alpha-olefin, said copolymer resin having a density in a range of 0.85 g/cm³ to 0.88 g/cm³ and a melt index of from 0.1 to 50 dg/min, (d) forming pellets from said copolymer resin, and

(e) quenching said pellets in a cooling solution at a rate of greater than about 10°C per minute.

32. The process of claim 31, wherein said quenched pellets have a monoclinic to orthorhombic ratio of greater than 0.5.

33. The process of claim 31, wherein said step of quenching said pellets is at a rate of greater than 20°C per minute.

34. The process of claim 31, wherein said C₄ to C₈ alpha-olefin comprises butene.

35. The process of claim 34, wherein said quenched pellets has a monoclinic to orthorhombic ratio of 1.0 or more.

36. The process of claim 31, wherein said C₄ to C₈ alpha-olefin comprises octene.

37. The process of claim 36, wherein said pellets have a monoclinic to orthorhombic ratio greater than 1.0.

38. The process of claim 31 , wherein said quenched pellets have an MIR value offrom l5 to 40.

39. The process of claim 31, wherein said quenched pellets have a molecular weight distribution of from 1.5 to 3 as determined by GPC LALLS.

40. The process of claim 31, wherein said bis-cyclopentadienyl metallocene has a hafnocene transition metal.

41. The process of claim 31, wherein said bis-cyclopentadienyl metallocene has a single atom bridging group comprising a methylene unit.

42. The process of claim 31, wherein said bis-cyclopentadienyl metallocene has at least one cyclopentadienyl ring further comprising a fluorenyl ring.

43. The process of claim 40, wherein said bis-cyclopentadienyl metallocene has a single atom bridging group comprising a methylene unit, and wherein said bis-cyclopentadienyl metallocene has at least one cyclopentadienyl ring further comprising a fluorenyl ring.

44. A thermoplastic blend of an ethylene copolymer derived from the pellets of claim 1 and a thermoplastic material having a melting temperature of over 120°C.

45. The thermoplastic blend of claim 44, wherein said thermoplastic material comprises isotactic polypropylene.

46. The thermoplastic blend of claim 45, wherein said thermoplastic material further comprises units derived from an alpha-olefin having from 4-12 carbon atoms.

47. The thermoplastic blend of claim 45, wherein said thermoplastic material further comprises units derived from ethylene.

48. The thermoplastic blend of claim 44, wherein said blend comprises about 25 to 97 parts by weight of said thermoplastic material, and about 3 to 75 parts by weight of said ethylene copolymer.

49. The thermoplastic blend of claims 45, wherein said polypropylene has a melt flow rate in the range of about 1.5 to 40 dg/min.