IMPROVED THERMOPLASTIC COMPOSITIONS FOR DURABLE GOODS APPLICATIONS

Abstract: Thermoplastic compositions have been discovered which are suitable for rotational molding. The compositions have improved processability and/or improved physical and mechanical properties. The compositions advantageously often exhibit one or more of the following: reduced low shear viscosity, reduced melt elasticity at low shear rate, reduced cycle times, improved sintering, faster bubble removal, a wide range of processing temperatures, improved low temperature and/or room temperature impact, good or improved environmental stress crack resistance, acceptable heat distortion temperature, and acceptable flexural and secant modulus.

Description: IMPROVED THERMOPLASTIC COMPOSITIONS FOR DURABLE GOODS APPLICATIONS This invention relates to compositions comprising thermoplastic polymers which are suitable for fabrication into products useful for durable goods applications by processes such as rotational molding, in j ection molding, blow molding, calendaring, pulltrusion, cast film, and blown film The products made according to this invention are either flexible or rigid and are suitable for applications such as lawn & garden equipment, building & construction materials, furniture, medical goods, sporting good, toys, storage tanks, boats, kayaks, canoes, sailboats, and crash barriers One of the key fabrication methods covered herein is rotational molding (also known as rotomolding), which is used to manufacture hollow objects from thermoplastics In the basic process of rotational molding, pulverized polymer is placed in a mold While the mold is being rotated, the mold is heated and then cooled The mold can be rotated uniaxially or biaxially and is usually rotated biaxially, that is, rotated about two perpendicular axes simultaneously The mold is typically heated externally and then cooled while being rotated As such, rotomolding is a zero shear process and involves the tumbling, heating and melting of thermoplastic powder, followed by coalescence, fusion or sintering and cooling In this manner, articles may be obtained which are complicated, large in size, and uniform in wall thickness Many compositions have been employed in rotational molding For example, U S Patent No 4,857,257 teaches rotational molding compositions comprising polyethylene, peroxide cross-linker, and a metal cationic compound while U S Patent No 4,587,318 teaches crosshnked compositions comprising ethylene terpolymer and organic peroxide It would be desirable to discover new rotational molding compositions, which exhibit improved processabihty and/or improved properties achievable without necessarily having to crosslink the composition Improved processabihty refers to reduced viscosity or melt elasticity at zero or low shear rates, which in turn results in shorter cycle times, faster sintering, faster bubble removal and/or the ability to fabricate articles over wide ranges of processing temperatures Some of the key properties of rotational molding compositions include impact strength at low temperature (for example, 0, -40 or -20°C) or room temperature (RT), and environmental stress crack resistance (ESCR) Another key process for fabricating durable goods is injection molding The processabihty of an in j ection molding resin is related to its capability to fill the mold easily and without large pressure increase Processabihty can be determined by measuring the viscosity/ shear rate curve, using a rheometer The slope of the viscosity curve provides information about the mechamcal/rheological property balance A polymer having a broad molecular weight distribution exhibits more shear thinning and therefore a relatively low viscosity (good processabihty) at the high shear rates (100-1000 s '), which are typical of injection molding In one aspect of the invention, thermoplastic compositions have been discovered which are especially suitable for rotational and injection molding and have improved physical and/or mechanical properties The compositions comprise one or more polymers and an impact additive In many cases, processabihty is also improved during rotational molding, as reflected in, for example, shorter cycle times, faster sintering, faster bubble removal and/or the ability to fabricate articles over wide ranges of processing temperatures Advantageously, the compositions often exhibit one or more of the following improved low temperature and/or room temperature impact, improved environmental stress crack resistance, and acceptable flexural and secant modulus In the case of rotational molding, the final density and melt index of the compositions is typically a compromise between processabihty and end-product properties Conventional knowledge teaches that increasing polymer density (or modulus) results in decreasing impact, and increasing melt index (or decreasing molecular weight) results in increased processabihty and corresponding decreases in ESCR and impact Furthermore, increased branching has been known to result in inferior processabihty As a result, one typically must choose which property to increase with the expectation that the other property must be decreased In contrast, the compositions of the present invention unexpectedly show that processabihty in rotational molding is improved even when the zero or low shear viscosity or branching is increased, and impact strength is improved without necessarily decreasing the polymer density The compositions of the present invention with improved impact properties can also be utilized in other fabrication processes including, but not limited to, blow molding, calendaring, pulltrusion, cast film, and blown film In another aspect of the present invention, thermoplastic compositions have been discovered which are specifically suitable for rotational molding and have acceptable physical and mechanical properties, but exhibit improved processabihty The compositions comprise one or more thermoplastic polymers and a small amount of a low molecular weight processing additive that is preferably not volatile at the processing conditions These compositions advantageously exhibit reduced melt viscosity or elasticity at zero or low shear rates This results in shorter cycle times, faster sintering, faster bubble removal and/or the ability to fabricate articles over wide ranges of processing temperatures As used herein, "Izod impact strength" (Izod, notched) was measured on compression molded specimens according to ASTM test D-256 conducted at a particular temperature, "2percent secant modulus" was measured according to ASTM test D-790, "flexural modulus" was measured according to ASTM test D-790, "heat distortion temperature" was measured according to ASTM test D-648 (at 66 psi), "low shear viscosity" was measured at 0 1 s ' shear rate using a dynamic mechanical spectrometer, "low shear tan delta" was measured at 0 1 s ' shear rate using a dynamic mechanical spectrometer, "melt index, 12" was measured according to ASTM test D-1238 (190°C, 2 16 kg load), "density" was measured according to ASTM D-792, and "Environmental Stress Crack Resistance" (ESCR-F50) was measured according to ASTM D-1524 using 10 percent Igepal solution The test methods used for measuring sintering times, conducting umaxial or rotational molding experiments and measuring low temperature dart impact strength are described in the examples ahead All references herein to elements or metals belonging to a certain Group refer to the Periodic Table of the Elements published and copyrighted by CRC Press, Inc , 1989 Also any reference to the Group or Groups shall be to the Group or Groups as reflected in this Periodic Table of the Elements using the IUPAC system for numbering groups Any numerical values recited herein include all values from the lower value to the upper value in increments of one unit provided that there is a separation of at least 2 units between any lower value and any higher value As an example, if it is stated that the amount of a component or a value of a process variable such as, for example, temperature, pressure, time is, for example, from 1 to 90, preferably from 20 to 80, more preferably from 30 to 70, it is intended that values such as 15 to 85, 22 to 68, 43 to 51, 30 to 32 etc are expressly enumerated in this specification For values which are less than one, one unit is considered to be 0 0001 , 0 001 , 0 01 or 0 1 as appropriate These are only examples of what is specifically intended and all possible combinations of numerical values between the lowest value and the highest value enumerated are to be considered to be expressly stated in this application in a similar manner The term "hydrocarbyl" as employed herein means any aliphatic, cycloa phatic, aromatic, aryl substituted aliphatic, aryl substituted cycloahphatic, aliphatic substituted aromatic, or aliphatic substituted cycloahphatic groups The term "hydrocarbyloxy" means a hydrocarbyl group having an oxygen linkage between it and the carbon atom to which it is attached The term "interpolymer" is used herein to indicate a polymer wherein at least two different monomers are polymerized to make the interpolymer This includes for example copolymers and terpolymers A Thermoplastic Compositions with Improved Impact Properties One aspect of the invention involves thermoplastic compositions having improved properties, for example, improved low temperature and/or room temperature impact, and improved environmental stress crack resistance The compositions typically comprise one or more polymers as the majority component of the composition and one or more impact-improving additives, that is impact additives 1 Maioπty Component The composition having improved impact properties typically comprises one or more polymers as the "majority component " As used herein the term, "majority component or majority", means a single polymer or mixture of polymers which comprises 50 percent or greater, preferably 60 percent or greater, most preferably 70 percent or greater by weight of the composition having improved impact properties The polymers that are suitable include those polymers or mixtures of polymers that are thermoplastic when employed with the impact additives described herein By "thermoplastic" is meant those substances that soften when heated to temperatures employed in rotational and injection molding and which return to their original condition upon cooling to about room temperature Such polymers include those often employed in rotational molding and injection molding such as ethylene and/or alpha olefin homopolymers or interpolymers, for example, LLDPE, HDPE, LDPE, VLDPE , and mixtures thereof Because of the presence of the impact additives employed in the composition of the invention, other polymers that have not been used extensively in rotational molding and injection molding, may also comprise the majority of the thermoplastic composition For example, polymers such as propylene homopolymers and copolymers, styrene homopolymers and copolymers, polycarbonates, nylon, polyesters, polybutylene, polyethylene terephthalate, and acrylic polymers may also be employed as the one or more polymers that comprise the majority of the composition The ethylene and/oi -olefin homopolymers or interpolymers employed as the majority component in the blends of the present invention are derived from ethylene and/or C r C 2 o α- olefins, and include, but are not limited to, polypropylene, propylene/C 4 -C 2 o α- olefin copolymers, polyethylene, and ethylene/ CvC 2 o α- olefin copolymers In the case of all such homopolymers and tei polymers, with the exception of propylene homopolymers and interpolymers, their densities should be greater than 0 915 g/cm 1 The interpolymers can be either heterogeneous ethylene/α-olefin interpolymers or homogeneous ethylene/α-olefin interpolymers, including the substantially linear ethylene/α-olefin interpolymers Heterogeneous interpolymers are differentiated from the homogeneous interpolymers in that in the latter, substantially all of the interpolymer molecules have the same ethylene/comonomer ratio within that interpolymer, whereas heterogeneous interpolymers are those in which the interpolymer molecules do not have the same ethylene/comonomer ratio The term 'broad composition distribution" used herein describes the comonomer distribution for heterogeneous interpolymers and means that the heterogeneous interpolymers have a "linear" fraction, multiple melting peaks (that is they exhibit at least two distinct melting peaks) by DSC and have a degree of branching less than or equal to 2 methyls/1000 carbons in 10 percent (by weight) or more, preferably more than 15 percent (by weight), and especially more than 20 percent (by weight of the polymer) The heterogeneous interpolymers also have a degree of branching equal to or greater than 25 methyls/1000 carbons in 25 percent or less (by weight of the polymer), preferably less than 15 percent (by weight), and especially less than 10 percent (by weight of the polymer) The Ziegler catalysts suitable for the preparation of the heterogeneous component of the current invention are typical supported, Ziegler-type catalysts, which are particularly useful at the high polymerization temperatures of the solution process Examples of such compositions are those derived from organomagnesium compounds, alkyl hahdes or aluminum hahdes or hydrogen chloride, and a transition metal compound Examples of such catalysts are described in U S Pat Nos 4,314,912 (Lowery, Jr et al ), 4,547,475 (Glass et al ), and 4,612,300 (Coleman, III) Suitable catalyst materials may also be derived from an inert oxide supports and transition metal compounds Examples of such compositions suitable for use in the solution polymerization process are described in U S Pat No 5,420,090 (Spencer et al ) The heterogeneous polymer component can be an ethylene and/or -olefin homopolymer preferably polyethylene or polypropylene, or, preferably, an interpolymer of ethylene with at least one C3-C20 α-olefin and/or C4-Cιg diolefins Heterogeneous copolymers of ethylene and 1-butene, ethylene and 1-pentene, ethylene and 1-hexene and ethylene and 1-octene are especially preferred (with density greater than 0 915 g/cm 3 ) The relatively recent introduction of metallocene-based catalysts for ethylene/α-olefin polymerization has resulted in the production of new ethylene interpolymers Such polymers are known as homogeneous interpolymers and are characterized by their narrower molecular weight and composition distributions relative to, for example, traditional Ziegler catalyzed heterogeneous polyolefin polymers The homogeneous polymer component can be an ethylene and/or α-olefin homopolymer preferably polyethylene or polypropylene, or, preferably, an interpolymer of ethylene with at least one C3-C20 ct-olefm and/or C4-CJ 8 diolefins Homogeneous copolymers of ethylene and one or more C3-C8 α-olefins are especially preferred The substantially linear homogeneous ethylene/α-olefin polymers and interpolymers which can be employed as the majority component of the present invention (subject to the limitation of density greater than 0 915 g/cm 3 ) are herein defined as in U S Patent No 5,272,236 (Lai et al ), and in U S Patent No 5,278,272 Commercially available products to be employed as the majority component include low density polyethylene (LDPE), linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), polyolefin plastomers, such as those marketed by The Dow Chemical Compan> under the AFFINITY™ tradename and by Exxon Chemical under the EXACT™ tradename The C3 α-olefin homopolymers or copolymers employed as the majority component in the blends of the present invention are polypropylenes The polypropylene is generally in the isotactic form of homopolymer polypropylene, although other forms of polypropylene can also be used (for example, syndiotactic or atactic) Polypropylene impact copolymers (for example, those wherein a secondary ln-reactor copolymeπzation step reacting ethylene with the propylene is employed) and random copolymers (also reactor modified and usually containing 1 5-20 percent of ethylene or C4-C8 α-olefin copolymerized with the propylene), however, can also be used A complete discussion of various polypropylene polymers is contained in Modern Plastics Encvclopedιa 89, mid October 1988 Issue, Volume 65, Number 1 1 , pp 86-92 The molecular weight of the majority component for use in the present invention is conveniently indicated using a melt index or melt flow measurement such as ASTM D-1238, Condition 190°C/2 16 kg (formerly known as "Condition (E)" and also known as I 2 ) for ethylenic polymers As one skilled in the art will appreciate, the melt index or melt flow rate is measured at different temperatures and loads for different polymers For instance, the temperatures used are 190°C for ethylenic polymers, 200°C for polystyrene, 230°C for polypropylene, and 300°C for polycarbonate Melt flow late is inversely proportional to the molecular weight of the polymer Thus, the higher the molecular weight, the lower the melt flow rate, although the relationship is not linear Generally, the polymers which comprise the majority component of the thermoplastic composition will have a melt index or melt flow rate of from 0 5 to 5000, preferably from 1 to 2000, more preferably from 2 to 500 g/10 mm 2 Impact Additive The type of impact additive may vary depending upon the type and amount of polymer(s) employed as the majority of the rotational molding or injection molding composition, as well as, the desired properties of the articles to be made via rotational molding or injection molding Generally, for rotational molding, the impact additive is selected from the group consisting of ethylene- vinyl acetate copolymer (EVA), heterogeneous or homogeneous interpolymers of polymer units derived from ethylene and/or one or more C 3 -C 20 α-olefins (with density of 0 915 g/cm or less), or one or more substantially random interpolymers comprising, (1 ) polymer units derived from (1) at least one vinyl or vinyhdene aromatic monomer, or (11) at least one hindered aliphatic or cycloahphatic vinyl or vinyhdene monomer, or (111) a combination of at least one vinyl or vinyhdene aromatic monomer and at least one steπcally hindered aliphatic or cycloahphatic vinyl or vinyhdene monomer, and (2) polymer units derived from (1) ethylene, or (n) C} 20 α-olefin, and mixtures thereof Generally, for injection molding, the impact additive is selected from the group consisting of ethylene - vinyl acetate copolymer (EVA), heterogeneous or homogeneous interpolymers of polymer units derived from ethylene and/or one or more C 3 -C 20 α-olefins (with density of 0 915 g/cm 3 or less), and mixtures thereof The term "substantially random" (in the substantially random interpolymer comprising polymer units derived from ethylene and/or one or more α-olefin monomers with one or more vinyl or vinyhdene aromatic monomers and/or steπcally hindered aliphatic or cycloahphatic vinyl or vinyhdene monomers) as used herein means that the distribution of the monomers of said interpolymer can be described by the Bernoulli statistical model or by a first or second order Markovian statistical model, as described by J C Randall in polymer sequence determination, carbon- 13 NMR method. Academic Press New York. 1977. pp 71-78 Preferably, substantially random interpolymers do not contain more than 15 percent of the total amount of vinyl or vinyhdene monomer in blocks of vinyl or vinyhdene monomer of more than 3 units More preferably, the interpolymer is not characterized by a high degree of either isotacticity or syndiotacticity This means that in the carbon 13 NMR spectrum of the substantially random interpolymer the peak areas corresponding to the main chain methylene and methine carbons representing either meso diad sequences or racemic diad sequences should not exceed 75 percent of the total peak area of the main chain methylene and methine carbons The substantially random interpolymers interpolymers used as the impact additive in the present invention can be prepared by polymerizing l) ethylene and/or one or more α-olefin monomers and n) one or more vinyl or vinyhdene aromatic monomers and/or one or more hindered aliphatic or cycloahphatic vinyl or vinyhdene monomers, and optionally in) other polymeπzable ethylemcally unsaturated monomer(s) Suitable α-olefins include for example, α-olefins containing from 3 to 20, preferably from 3 to 12, more preferably from 3 to 8 carbon atoms Particularly suitable are ethylene, propylene, butene-1, 4-methyl-l- pentene, hexene-1 or octene-1 or ethylene in combination with one or more of propylene, butene-1, 4-methyl-l- pentene, hexene-1 or octene-1 These α-olefins do not contain an aromatic moiety Other optional polymeπzable ethylemcally unsaturated monomer(s) include norbornene and 10 alkyl or C 6 ιo aryl substituted norbornenes, with an exemplary interpolymer being ethylene/styrene/norbornene Suitable vinyl or vinyhdene aromatic monomers include, for example, those represented by the following formula Ar I (CH 2 ) n R l — C = C(R2) 2 wherein R 1 is selected from the group of radicals consisting of hydrogen and alkyl radicals containing from 1 to 4 carbon atoms, preferably hydrogen or methyl, each R 2 is independently selected from the group of radicals consisting of hydrogen and alkyl radicals containing from 1 to 4 carbon atoms, preferably hydrogen or methyl, Ar is a phenyl group or a phenyl group substituted with from 1 to 5 substituents selected from the group consisting of halo, d 4 -alkyl, and Ci 4 -haloaIkyl, and n has a value from zero to 4, preferably from zero to 2, most preferably zero Exemplary vinyl or vinyhdene aromatic monomers include styrene, vinyl toluene, α- methylstyrene, t-butyl styrene, and chlorostyrene, including all isomers of these compounds Particularly suitable such monomers include styrene and lower alkyl- or halogen-substituted derivatives thereof Preferred monomers include styrene, α-methyl styrene, the lower alkyl- (C r C 4 ) or phenyl-πng substituted derivatives of styrene, such as for example, ortho-, meta-, and para-methylstyrene, the ring halogenated styrenes, para- vinyl toluene or mixtures thereof A more preferred aromatic vinyl monomer is styrene By the term " hindered aliphatic or cycloahphatic vinyl or vinyhdene compounds", it is meant addition polymeπzable vinyl or vinyhdene monomers corresponding to the formula A' I R 1 — C = C(R 2 ) 2 wherein A 1 is a steπcally bulky, aliphatic or cycloahphatic substituent of up to 20 carbons, R 1 is selected from the group of radicals consisting of hydrogen and alkyl radicals containing from 1 to 4 carbon atoms, preferably hydrogen or methyl, each R 2 is independently selected from the group of radicals consisting of hydrogen and alkyl radicals containing from 1 to 4 carbon atoms, preferably hydrogen or methyl, or alternatively R 1 and A 1 together form a ring system The aliphatic or cycloahphatic vinyl or vinyhdene compounds are monomers in which one of the carbon atoms bearing ethylenic unsaturation is tertiary or quaternary substituted Examples of such substituents include cyclic aliphatic groups such as cyclohexyl, cyclohexenyl, cyclooctenyl, or ring alkyl or aryl substituted derivatives thereof, tert-butyl,and norbornyl Most preferred aliphatic or cycloahphatic vinyl or vinyhdene compounds are the various lsomeπc vinyl- ring substituted derivatives of cyclohexene and substituted cyclohexenes, and 5-ethyhdene-2-norbornene Especially suitable are 1-, 3-, and 4- v ylcyclohexene Simple linear non-branched α-olefins including for example, α-olefins containing from 3 to 20 carbon atoms such as propylene, butene-1, 4-methyl-l-pentene, hexene-1 or octene-1 are not examples of steπcally hindered aliphatic or cycloahphatic vinyl or vinyhdene compounds One method of preparation of the substantially random interpolymers includes polymerizing a mixture of polymeπzable monomers in the presence of one or more metallocene or constrained geometry catalysts in combination with various cocatalysts, as described in EP-A-0,416,815 by James C Stevens et al and US Patent No 5,703,187 by Francis J Timmers and U S Patent No 5,872201 by Yunwa Cheung et al, Preferred operating conditions for such polymerization reactions are pressures from atmospheric up to 3000 atmospheres and temperatures from -30°c to 200°c Polymerizations and unreacted monomer removal at temperatures above the autopolymeπzation temperature of the respective monomers may result in formation of some amounts of homopolymer polymerization products resulting from free radical polymerization Examples of suitable catalysts and methods for preparing the substantially random interpolymers are disclosed in US Application Serial No 702,475, filed May 20, 1991 (EP-A-514,828), as well as US Patents 5,055,438, 5,057,475, 5,096,867, 5,064,802, 5,132,380, 5, 189,192, 5,321, 106, 5,347,024, 5,350,723, 5,374,696, 5,399,635, 5,470,993, 5,703,187, and 5,721, 185 The substantially random α-olefin/vinyl aromatic interpolymers can also be prepared by the methods described in JP 07/278230 employing compounds shown by the general formula Cp 1 R J / 3 \ / R M \ Cp ' R^ where Cp 1 and Cp 2 are cyclopentadienyl groups, indenyl groups, fluorenyl groups, or substituents of these, independently of each other, R and R " are hydrogen atoms, halogen atoms, hydrocarbon groups with carbon numbers of 1 -12, alkoxyl groups, or aryloxyl groups, independently of each other, M is a group IV metal, preferably Zr or Hf, most preferably Zr, and R 3 is an alkylene group or silanediyl group used to cross-link Cp' and Cp 2 ) The substantially random α-olefin/ vinyl aromatic interpolymers can also be prepared by the methods described by John G Bradfute et al (W R Grace & Co ) in WO 95/32095, by R B Pannell (Exxon Chemical Patents, Inc ) in WO 94/00500, and in Plastics Technology, p 25 (September 1992) Also suitable are the substantially random interpolymers which comprise at least one α-olefϊn/vinyl aromatic/vinyl aromatic/α-olefin tetrad disclosed in US Application No 08/708,869 filed September 4, 1996 and WO 98/09999 both by Francis J Timmers et al These interpolymers contain additional signals in their carbon- 13 NMR spectra with intensities greater than three times the peak to peak noise These signals appear in the chemical shift range 43 70 - 44 25 ppm and 38 0 - 38 5 ppm Specifically, major peaks are observed at 44 1, 43 9, and 38 2 ppm A proton test NMR experiment indicates that the signals in the chemical shift region 43 70 - 44 25 ppm are methine carbons and the signals in the region 38 0 - 38 5 ppm are methylene carbons It is believed that these new signals are due to sequences involving two head-to-tail vinyl aromatic monomer insertions preceded and followed by at least one α-olefin insertion, for example an ethylene/styrene/styrene/ethylene tetrad wherein the styrene monomer insertions of said tetrads occur exclusively in a 1 ,2 (head to tail) manner It is understood by one skilled in the art that for such tetrads involving a vinyl aromatic monomer other than styrene and an α-olefin other than ethylene that the ethylene/vinyl aromatic monomer/vinyl aromatic monomer/ethylene tetrad will give rise to similar carbon- 13 nmr peaks but with slightly different chemical shifts These interpolymers can be prepared by conducting the polymerization at temperatures of from -30°C to 250°C in the presence of such catalysts as those represented by the formula / \ (ER 2 ) m MR' 2 C P wherein each Cp is independently, each occurrence, a substituted cyclopentadienyl group π-bound to M, E is C or Si, M is a group IV metal, preferably Zr or Hf, most preferably Zr, each R is independently, each occurrence, H, hydrocarbyl, silahydrocarbyl, or hydrocarbylsilyl, containing up to 30 preferably from 1 to 20 more preferably from 1 to 10 carbon or silicon atoms, each R' is independently, each occurrence, H, halo, hydrocarbyl, hyrocarbyloxy, silahydrocarbyl, hydrocarbylsilyl containing up to 30 preferably from 1 to 20 more preferably from 1 to 10 carbon or silicon atoms or two R' groups together can be a ]0 hydrocarbyl substituted 1,3-butadιene, m is 1 or 2, and optionally, but preferably in the presence of an activating cocatalyst Particularly, suitable substituted cyclopentadienyl groups include those illustrated by the formula Wherein each R is independently, each occurrence, H, hydrocarbyl, silahydrocarbyl, or hydrocarbylsilyl, containing up to 30 preferably from 1 to 20 more preferably from 1 to 10 carbon or silicon atoms or two R groups together form a divalent derivative of such group Preferably, R independently each occurrence is (including where appropriate all isomers) hydrogen, methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, phenyl or silyl or (where appropriate) two such R groups are linked together forming a fused ring system such as indenyl, fluorenyl, tetrahydroindenyl, tetrahydrofluorenyl, or octahydrofluorenyl Particularly preferred catalysts include, for example, racemιc-(dιmethylsιlanedιyl)-bιs-(2-methyl-4- pheny ndenyl) zirconium dichlonde, racemιc-(dιmethylsιlanedιyl)-bιs-(2-methyl-4-phenylιndenyl) zirconium 1 ,4-dιphenyl- 1 ,3-butadιene, racemιc-(dιmethylsιlanedιyl)-bιs-(2-methyl-4-phenylιndenyl) zirconium di-C 1 -4 alkyl, racernιc-(dιmethylsιlanedιyl)-bιs-(2-methyl-4-pheny_ιndenyl) zirconium di-C 1 -4 alkoxide, or any combination thereof It is also possible to use the following titanium-based constrained geometry catalysts, [N-(l,l- dimethylethyl)- 1 , 1 -dimethyl- 1-[( 1 ,2,3,4,5-η)- 1 ,5,6,7-tetrahydro-s-ιndacen- 1 -yl]sιlanamιnato(2-)-N] titanium dimethyl, (l-ιndenyl)(tert-butylamιdo)dιmethyl- silane titanium dimethyl, ((3-tert-butyl)(l,2,3,4,5-η)-l- ιndenyl)(tert-butylamιdo) dimethylsilane titanium dimethyl, and ((3-ιso-propyl)(l,2,3,4,5-η)-l-ιndenyl)(tert- butyl amιdo)dιmethylsιlane titanium dimethyl, or any combination thereof Further preparative methods for the interpolymers used in the present invention have been described in the literature Longo and Grassi (Makromol Chem . Volume 191 , pages 2387 to 2396 [1990]) and D'Anniello et al (Journal of Applied Polymer Science, volume 58, pages 1701-1706 [1995]) reported the use of a catalytic system based on methylalumoxane (mao) and cyclopentadienyltitanium trichloride to prepare an ethylene-styrene copolymer Xu and Lin (Polymer Preprints, Am Chem Soc , Div Polym Chem ) Volume 35, pages 686,687 [ 1994]) have reported copolymenzation using a MgCl 2 /TιCl /NdCl,/ Al(ιBu catalyst to give random copolymers of styrene and propylene Lu et al (Journal of Applied Polymer Ccience, volume 53, pages 1453 to 1460 [ 1994]) have described the copolymenzation of ethylene and styrene using a TiClJNdCV MgCl 2 /Al(Et), catalyst Sernetz and Mulhaupt, (Macromol Chem Phvs , V 197, pp 1071-1083, 1997) have described the influence of polymerization conditions on the copolymenzation of styrene with ethylene using Me 2 Sι(Me 4 Cp)(n-tert-butyl)TιCl 2 /methylalumιnoxane Ziegler-Natta catalysts Copolymers of ethylene and styrene produced by bridged metallocene catalysts have been described by Aral, Toshiaki and Suzuki (Polymer Preprints, Am Chem Soc , Div Polym Chem ) Volume 38, pages 349, 350 [1997]) and in US Patent No 5,652,315, issued to Mitsui Toatsu Chemicals, Inc The manufacture of α-olefin/vinyl aromatic monomer interpolymers such as propylene/styrene and butene/styrene are described in US Patent No 5,244,996, issued to Mitsui Petrochemical Industries Ltd or US Patent No 5,652,315 also issued to Mitsui Petrochemical Industries Ltd or as disclosed in DE 197 1 1 339 Al and U S Patent No 5,883,213 both to Denki Kagaku Kogyo KK Also the random copolymers of ethylene and styrene as disclosed in Polymer Preprints Vol 39, No 1 , March 1998 by Toru Ana et al can also be employed as blend components for the present invention While preparing the substantially random interpolymer, an amount of atactic vinyl aromatic homopolymer may be formed due to homopolymeπzation of the vinyl aromatic monomer at elevated temperatures The presence of vinyl aromatic homopolymer is in general not detrimental for the purposes of the present invention and can be tolerated The vmyl aromatic homopolymer may be separated from the interpolymer, if desired, by extraction techniques such as selective precipitation from solution with a non solvent for either the interpolymer or the vinyl aromatic homopolymer For the purpose of the present invention it is preferred that no more than 30 weight percent, preferably less than 20 weight percent based on the total weight of the impact additive of atactic vinyl aromatic homopolymer is present While the improvement in impact properties of the rotational molding and injection molding compositions will vary depending on the types, molecular weights and amounts of polymer(s) present as the ma j ority of the composition, the improvement also vanes according to the monomer content and molecular weights of the polymeric impact additives For example, when EVA copolymers are employed, the vinyl acetate content of the EVA is somewhat important Generally, to optimize the impact properties, the EVA polymers comprise at least 2, preferably at least 3, more preferably at least 5 weight percent vinyl acetate Correspondingly, the EVA polymers typically comprise less than 50, preferably less than 30, more preferably less than 20 weight percent vinyl acetate Similarly, when substantially random interpolymers are employed as the impact additive, the monomer content of the vinyl or vinyhdene aromatic component is important, as the glass transition temperature of the substantially random interpolymers will increase with increasing vinyl or vinyhdene aromatic content Typically, to optimize the impact properties the substantially random interpolymers comprise at least 1 , preferably at least 3, more preferably at least 5 mole percent vinyl or vinyhdene aromatic component Correspondingly, the substantially random interpolymers typically comprise less than 30, preferably less than 25, more preferably less than 20 mole percent vinyl aromatic component A particularly preferred interpolymer is a substantially random ethylene-styrene interpolymer comprising from 1 to 30, preferably from 3 to 25, more preferably from 5 to 20 mole percent styrene When heterogeneous or homogeneous interpolymers with polymer units derived from ethylene and/or one or more -C 20 α-olefins and mixtures thereof, are employed as the impact additive, the interpolymer density will be 0 915 g/cm 3 or less, preferably 0 905 g/cm 1 or less more preferably 0 895 g/cm 3 or less Particularly preferred are heterogeneous or homogeneous copolymers of ethylene and 1 propene, ethylene and 1-butene, ethylene and 1-pentene, ethylene and 1-hexene and ethylene and 1-octene with density of 0 850-0 915 g/cm 3 , preferably 0 860-0 905 g/cm 3 and most preferably 0 870-0 895 g/cm 3 Generally, the polymers which comprise the impact additive of the thermoplastic composition will have a melt index (I at 190°C) of at least 0 001 , preferably at least 0 01 , more preferably at least 0 05 g/10 mm Likewise, the polymers will have a melt index (I 2 at 190°C) less than 5000, preferably less than 1000, more preferably less than 100 g/10 mm The amount of impact additive in the composition will vary depending on the particular additive, the types and amount of the majority of the composition, the desired properties, and the types and amounts of other components Typically, the amount of impact additive is at least the amount at which the rotational molding and injection molding composition exhibits an increase in impact strength, for example, Izod impact strength, as compared to the majority in the absence of additive and may also exhibit an improvement in ESCR-F50 Typically, such an increase is at least a 0 1 ft-lb/in, preferably at least a 0 2 ft-lb/in, more preferably at least a 0 3 ft-lb/in increase in Izod impact strength at room temperature (about 24°C) or low temperatures (for example, 0°C, -20°C, or -40°C) as compared to the composition without impact additive The ESCR-F50 improvement is at least 25 percent, preferably 50 percent, more preferably 75 percent as compared to the composition without impact additive The amount of the impact additives used will be such as to maintain flexural modulus greater than 80,000 psi, a 2percent secant modulus greater than 70,000 psi and a heat distortion temperature greater than 45°C Generally, the amount of the impact additive is from 2 to 50, preferably from 3 to 50, and most preferably from 5 to 50 weight percent based on the total weight of the composition The impact additive may be mixed with the polymers comprising the majority component in any way so long as the additive and the other components become nearly homogeneously dispersed The manner of mixing is not critical so long as the two or more polymers are blended sufficiently to be employed in rotational molding or injection molding Suitable mixing often occurs by employing melt-blending and powder blending If desired, a compatibihzer may be employed to facilitate mixing the polymers Similarly, the time or stage at which the polymers are mixed is not critical so long as the final composition is suitable for rotational molding or injection molding Generally, if two or more polymers are to comprise the majority of the thermoplastic composition, the polymers may be mixed before, during, or after the impact additive has been added Correspondingly, if two or more polymers are to comprise the majority then the two polymers may be formed simultaneously in situ Likewise, the polymer or polymers that are to comprise the majority may even be made from the monomers simultaneously in situ with the impact additive When the impact additive comprises heterogeneous or homogeneous copolymers of ethylene and 1 propene, ethylene and 1-butene, ethylene and 1-pentene, ethylene and 1-hexene and ethylene and 1-octene, the resulting blended resins have novel lmpact/modulus/processabihty relationships These resins are ideally suited for durable molded articles that require superior low and room temperature impact properties, high modulus and equivalent or improved processabihty These resins have demonstrated notched Izod impacts (ASTM D256) up to 4-5 times greater than standard resins of equivalent modulus (>80,000 psi flex modulus - ASTM D790) and processabihty ( 1 5-30 g/10 min I 2 and 6 0-10 I 10 /I 2 - ASTM D1238) In particular, it was found that the novel impact properties are observed when the impact additive comprises homogeneous interpolymers of ethylene and 1 -propene, ethylene and 1-butene, ethylene and 1 -pentene, ethylene and 1-hexene and ethylene and 1-octene having a density < 0 910 g/cm 3 (or percent crystalhnity < 43 percent, as defined by the following equation ), percent Crystalhnity = { (p-p a )/(p c -p a ) } (p c /p) where p is the polymer density in g/cm , where p a is the density of the amorphous fraction = 0 853 g/cm 3 , where p c is the density of the crystalline fraction = 1 000 g/cm and also has the following properties 1 no linear polymer fraction, 2 a single melting peak as measured using differential scanning calonmetry, 3 a single peak elution temperature as measured by Analytical Temperature Rising Elution Fractionation (ATREF) which elutes at a peak temperature of less than or equal to 77°C and has a narrow distribution such that at least 45 weight percent of this component elutes between a range of plus or minus 5°C Alternatively, if the impact additive is a heterogeneous interpolymer of ethylene and 1 -propene, ethylene and 1-butene, ethylene and 1-pentene, ethylene and 1-hexene and ethylene and 1-octene, then it should be added in an amount such that in the final composition, the fraction of the heterogeneous interpolymer eluting at a temperature of less than or equal to 77°C under ATREF conditions, is 2 wt percent or more (based on the weight of the final composition) B Rotational Molding Compositions with Improved Processabihty In another aspect of the present invention, thermoplastic compositions have been discovered which are specifically suitable for rotational molding and have acceptable physical and mechanical properties but exhibit improved processabihty and reduced sintering time The compositions comprise one or more thermoplastic polymers and a small amount of a low molecular weight processing additive that is preferably not volatile at the processing conditions These compositions advantageously exhibit reduced melt viscosity or elasticity at zero or low shear rates This results in shorter cycle times, faster sintering, faster bubble removal and/or the ability to fabricate articles over wide ranges of processing temperatures The compositions typically comprise as Component A, one or more polymers, and in addition, as Component B, one or more processing addιtιve(s) 1 Component A Component A comprises one or more polymers, which in turn comprise 94 percent by weight or more of the rotational molding composition with improved processabihty and reduced sintering time Any suitable polymer or mixture of polymers may be employed In general, the polymers which are suitable include those polymers or mixtures of polymers which, when mixed with the processing additive, are useful for rotational molding Thus, polymers such as those described earlier as being part of the majority component of the rotational molding compositions with improved impact properties may be employed as part of the 94 percent or greater In addition, the impact additives of the rotational molding compositions with improved impact properties described above (such as EVA, heterogeneous or homogeneous interpolymers with polymer units derived from ethylene or one or more C 3 -C 20 α-olefins (and mixtures thereof) with density of 0 915 g/cm 3 or less, and substantially random interpolymers) may be employed as part of the 94 percent or greater Generally, the polymers which comprise more than 94 percent by weight of the rotational molding composition with improved processabihty, have a melt index or melt flow rate of from 0 5 to 99, preferably of from 1 to 60, more preferably of from 2 to 50 g/10 min As one skilled in the art will appieciate, the melt index or melt flow rate is measured at 190°C for ethylenic polymers, at 200°C for polystyrene, at 230°C for polypropylene, and at 300°C for polycarbonate 2 Component B (Processing Additive) The nature of Component B varies depending on the amounts and types of polymers employed as Component A in the composition Component B may be either polar or non-polar However, its polarity may facilitate the dispersion of other ingredients in the final compositions For example, if Component A is non- polar, like polyethylene, and a polar pigment like titanium dioxide is to be employed, then employment of a polar processing additive as Component B may improve dispersion Component B is preferably non- volatile, that is, it does not evaporate from ambient temperature up to the temperature employed in rotational molding Thus, the additive is preferably a liquid or solid at temperatures above 20°C to temperatures below 300, preferably below 280, more preferably below 250, most preferably below 220°C Suitable processing additives as Component B preferably have a molecular weight such that the rotational molding composition's melt viscosity or melt elasticity both at zero or low shear rates (as determined by dynamic mechanical spectrometry) is decreased Melt elasticity is inversely related to measurements of tan delta (= loss modulus divided by storage modulus) Component B, when employed in a suitable amount, can reduce either the viscosity or tan delta, or both (at zero or low shear rate, that is 0 1 s ') of the composition by at least one, more preferably at least two percent as compared to Component A in the absence of the processing additive, Component B Advantageously, the addition of Component B does not lower the weight average molecular weight (Mw) of the composition by no more than 5 percent, preferably no more than 3 percent Component B has a molecular weight of at least 10 and below 30,000, preferably below 20,000, most preferably below 10,000 Decreasing the melt viscosity or melt elasticity both at zero or low shear rates offers many advantages for rotational molding One of the advantages is leduced sintering time, that is, the time it takes for agglomeration or fusion of the particles of the composition during rotational molding Another advantage is faster bubble removal Reduced sintering time and/or faster bubble removal results in improved processabihty such that cycle times and maximum mold temperatures in rotational molding are reduced correspondingly This results in decreased propensity for thermal degradation and a higher throughput rate with the ability to mold articles in a shorter time Thus, production rate may be increased The sintering time of the compositions of the present invention is controlled by factors such as the type and melt rheology of Component A, the nature of Component B and the size of the particles of the final composition The sintering times of the compositions of the present invention will be decreased by at least 5 percent, preferably by at least 7 percent, more preferably by at least 10 percent relative to the sintering time of Component A in the absence of Component B Additives suitable for use as Component B in the present invention include, but are not limited to aromatic or aliphatic hydrocarbon oils, esters, amides, alcohols, acids, and their organic and inorganic salts Examples include mineral oil, natural oils such as lanolin, castor, corn, cottonseed, olive, rapeseed, soybean, sunflower, other vegetable and animal oils, and paraffin, naphthenic and aromatic oils obtained from petroleum refining, and liquid resins from rosin or petroleum feedstocks Exemplary classes of oils useful as processing aids include white mineral oil such as Kaydol™ oil (available from and a registered trademark of Witco), Shellflex™ 371 naphthenic oil (available from and a registered trademark of Shell Oil Company) and Tuflo™ oil (available from and a registered trademark of Lyondell) Also included are esters, alcohols, and acids of the oils, sihcone oils of similar viscosities, and polyether polyols, glycerol monostearate, pentaerythπtol monooleate, erucamide, stearamides, adipic acid, sebacic acid, styrene-alpha-methyl styrene, calcium stearate, zinc stearate, and the phthalates, such as dioctyl phthalate and dnsobutyl phthalate The choice of Component B depends on the nature of Component A, the rotational molding apparatus and process to be employed, as well as, the desired properties of the articles to be made However, particularly preferred additives for rotational molding compositions comprised of polymers such as LLDPE, polycarbonate and polypropylene include mineral oil, glycerol monostearate, pentaerythitol monooleate, and calcium stearate Most preferred are calcium stearate and mineral oil Typically, the amount of Component B to be added is at least 0 01 , preferably at least 0 03, and more preferably at least 0 05 percent by weight (based on the weight of the final composition) Correspondingly, the amount is 6 or less, preferably 4 or less, most preferably 3 percent or less by weight (based on the weight of the final composition) When Component B is mineral oil, the amount to be added is from 0 1 to 6, preferably from 0 3 to 4, more preferably from 0 5 to 3 percent by weight (based on the weight of the final composition) When Component B is calcium stearate, the amount to be added is 001 to 1 When Component B is glycerol monostearate, the ESCR-F50 of the compositions of the present invention exhibit an improvement in ESCR-F50 of at least 25 percent, preferably 50 percent, more preferably 75 percent as compared to the compositions without impact additive Component B may be mixed with Component A in any manner and at any time so long as they are sufficiently mixed such that the processabihty of the rotational molding composition is improved While such mixing methods may vary depending on the polymers or additives employed, this may include melt blending, tumble blending (for example in a ribbon blender, drum tumbler, or paddle blender ). spraying molten polymer with the additive followed by mechanical distribution and/or drying of some form In this manner, a substantially homogenous mixture of polymer and additive usually results The additives may also be added in the manufacture of the polymers, either in situ or post-reactor C Composition With Improved Impact Properties And The Composition With Improved Processabihty Generally, the degree of crosshnking, if any, of the compositions of the present inventions (or their individual components) to be employed herein is dependent upon the desired properties Typically, the more crosshnking there is, the higher will be the viscosity, ESCR and heat distortion temperature of the final composition Conventional crosshnking agents may be employed including, but not limited to, the use of peroxides, azides, or silanes Crosshnking may be undertaken before, during or after the mixing, so long as the final composition is useful for rotational molding or injection molding D Other Ingredients For The Compositions With Improved Impact Properties And The Compositions With Improved Processabihty Additives such as antioxidants (for example, hindered phenols such as, for example, Irganox™ 1010 a registered trademark of Ciba Geigy), phosphites (for example, Irgafos™ 168 a registered trademark of Ciba Geigy), U V stabilizers, fire retardants, crosshnking agents, blowing agents, compatibihzers, cling additives (for example, polyisobutylene), slip agents (such as erucamide and/or stearamide), antiblock additives, colorants, and pigments, can also be used in the overall blend compositions employed in the present invention For the compositions of the present invention having improved impact properties, processing aids, which are also referred to herein as plasticizers, can also be used in the overall blend compositions These processing aids include, but are not limited to, the phthalates, such as dioctyl phthalate and dnsobutyl phthalate, natural oils such as lanolin, and paraffin, naphthenic and aromatic oils obtained from petroleum refining, and liquid resms from rosin or petroleum feedstocks Exemplary classes of oils useful as processing aids include white mineral oil (such as Kaydol™ oil (available from and a registered trademark of Witco), and Shellflex™ 371 naphthenic oil (available from and a registered trademark of Shell Oil Company) Another suitable oil is Tuflo™ oil (available from and a registered trademark of Lyondell) Tackifiers can also be included in the overall blend compositions employed in the present invention to alter the processing performance of the polymer and thus can extend the available application temperature window of the articles A suitable tackifier may be selected on the basis of the criteria outlined by Hercules in J Simons, Adhesives Age, "The HMDA Concept A New Method for Selection of Resins", November 1996 This reference discusses the importance of the polarity and molecular weight of the resin in determining compatibility with the polymer In the case of substantially random interpolymers of at least one α-olefin and a vinyl aromatic monomer, preferred tackifiers will have some degree of aromatic character to promote compatibility, particularly in the case of substantially random interpolymers having a high content of the vinyl aromatic monomer Tackifying resins can be obtained by the polymerization of petroleum and terpene feedstreams and from the denvatization of wood, gum, and tall oil rosin Several classes of tackifiers include wood rosin, tall oil and tall oil derivatives, and cyclopentadiene derivatives, such as are described in United Kingdom patent application GB 2,032,439A Other classes of tackifiers include aliphatic C5 resins, polyterpene resins, hydrogenated resins, mixed aliphatic-aromatic resins, rosin esters, natural and synthetic terpenes, terpene- phenohcs, and hydrogenated rosin esters Also included as a potential component of the polymer compositions used in the present invention are various organic and inorganic fillers, the identity of which depends upon the type of application for which the molded parts are to be utilized The fillers can also be included in either blend Component A and/or blend Component B or the overall blend compositions employed to prepare the fabricated articles of the present invention Representative examples of such fillers include organic and inorganic fibers such as those made from asbestos, boron, graphite, ceramic, glass, metals (such as stainless steel) or polymers (such as aramid fibers) talc, carbon black, caibon fibers, calcium carbonate, alumina tπhydrate, glass fibers, marble dust, cement dust, clay, feldspar, silica or glass, fumed silica, alumina, magnesium oxide, magnesium hydroxide, antimony oxide, zinc oxide, barium sulfate, aluminum silicate, calcium silicate, titanium dioxide, titanates, aluminum nitride, B203, nickel powder or chalk Other representative organic or inorganic, fiber or mineral, fillers include carbonates such as barium, calcium or magnesium carbonate, fluorides such as calcium or sodium aluminum fluoride, hydroxides such as aluminum hydroxide, metals such as aluminum, bronze, lead or zinc, oxides such as aluminum, antimony, magnesium or zinc oxide, or silicon or titanium dioxide, silicates such as asbestos, mica, clay (kaolin or calcined kaolin), calcium silicate, feldspar, glass (ground or flaked glass or hollow glass spheres or microspheres or beads, whiskers or filaments), nepheline, perlite, pyrophyllite, talc or wollastonite, sulfates such as barium or calcium sulfate, metal sulfides, cellulose, in forms such as wood or shell flour, calcium terephthalate, and liquid crystals Mixtures of more than one such filler may be used as well These additives are employed in functionally equivalent amounts known to those skilled m the art When used in proper quantities such ingredients will typically not render the composition unsuitable for rotational molding or injection molding For example, the amount of antioxidant employed is that amount which prevents the polymer or polymer blend from undergoing oxidation at the temperatures and environment employed during storage and ultimate use of the polymers Such amount of antioxidants is usually in the range of from 0 01 to 10, preferably from 0 05 to 5, more preferably from 0 1 to 2 percent by weight based upon the weight of the polymer or polymer blend Similarly, the amounts of any of the other enumerated additives are the functionally equivalent amounts such as the amount to render the polymer or polymer blend antiblocking, to produce the desired result, to provide the desired color from the colorant or pigment Such additives can suitably be employed in the range of from 0 05 to 50, preferably from 0 1 to 35, more preferably from 0 2 to 20 percent by weight based upon the weight of the polymer or polymer blend When used in proper quantities such ingredients will typically not render the composition unsuitable for rotational molding However, large amounts of some ingredients, in particular conventional fillers such as calcium carbonate, may harm the rotational molding properties of the composition For this reason, it is preferable to add less than 10, preferably less than 5 weight percent filler to the composition E Rotational Molding Processes and Useful Articles The present invention includes a method of rotational molding using the composition with improved impact properties and the composition with improved processabihty Typically the rotational molding process with the above-described compositions comprises the steps of preparing the composition The composition can be manufactured in powder or pellet form For rotational molding, powders are preferably used having a particle size smaller than or equal to 35 mesh The grinding may be done cryogenically, if necessary The composition is heated within the mold as the mold is rotated The mold is usually rotated biaxially, that is rotated about two perpendicular axes simultaneously The mold is typically heated externally (generally with a forced air circulating oven) The process steps include tumbling, heating and melting of thermoplastic powder, followed by coalescence, fusion or sintering and cooling to remove the molded article The composition of the present invention can be processed in most commercial rotational molding machines The oven temperature range during the heating step is from 400°F to 800° F preferably 500°F to 700°F and more preferably from 575 °F to 650° F After the heating step the mold is cooled The part must be cooled enough to be easily removed from the mold and retain its shape Preferably the mold is removed from the oven while continuing to rotate Cool air is first blown on the mold The air can be an ambient temperature After the air has started to cool the mold for a controlled time period, a water spray can be used The water cools the mold more rapidly The water used can be at cold tap water temperature, usually from 4° C (40° F ) to 16°C (60° F ) After the water-cooling step, another air-cooling step may optionally be used This is usually a short step during which the equipment dries with heat removed during the evaporation of the water The heating and cooling cycle times will depend on the equipment used and the article molded Specific factors include the part thickness in the mold material Typical conditions for an % inch thick part in a steel mold are to heat the mold in the oven with air at about 316°C (600° F ) for about 15 minutes The part is then cooled in ambient temperature forced air for about 8 minutes and then a tap water spray at about 10°C (50° F ) for about 5 minutes Optionally, the part is cooled in ambient temperature forced air for an additional 2 minutes During the heating and cooling steps the mold containing the molded article is continually rotated Typically this is done along two perpendicular axes The rate of rotation of the mold about each axis is limited by machine capability and the shape of the article being molded A typical range of operation which can be used with the present invention is to have the ratio of rotation of the major axis to the minor axis of 1 8 to 10 1 with a range of from 1 2 to 8 1 being preferred Rotational molded articles of the present invention can be used where durability is essential in the sense that there is crack and puncture resistance Examples of articles which can be made include gasoline tanks large trash containers, and large bins or silos for fertilizer, etc E Imection Molding Processes The various injection molding processes are well known to those skilled in the art as for example are summarized in for example "Plastics Materials and Processes" by S Schwartz and S Goodman, pgs 527 - 577, Van Nostrand Rheinhold Company Inc New York, 1982 F Other Applications Other processes that can be used to fabricate the above described thermoplastic compositions with improved impact properties include blow molding, calendaring, pulltrusion, cast film, and blown film Test methods A) Melt Flow Measurements The molecular weight of the substantially random interpolymers used in the present invention is conveniently indicated using a melt index measurement according to ASTM D-1238, condition 190°C/2 16 kg (formally known as "Condition (e)" and also known as I2) is determined Melt index is inversely proportional to the molecular weight of the polymer Thus, the higher the molecular weight, the lower the melt index, although the relationship is not linear Also useful for indicating the molecular weight of the substantially random interpolymers used in the present invention is the Gottfert melt index (G, cmVlO mm) which is obtained in a similar fashion as for melt index (I 2 ) using the ASTM D1238 procedure for automated plastometers, with the melt density set to 0.7632, the melt density of polyethylene at 190°C The relationship of melt density to styrene content for ethylene-styrene interpolymers was measured, as a function of total styrene content, at 190°C for a range of 29 8 percent to 81.8 percent by weight styrene Atactic polystyrene levels in these samples was typically 10 percent or less The influence of the atactic polystyrene was assumed to be minimal because of the low levels Also, the melt density of atactic polystyrene and the melt densities of the samples with high total styrene are very similar The method used to determine the melt density employed a Gottfert melt index machine with a melt density parameter set to 0.7632, and the collection of melt strands as a function of time while the I2 weight was in force The weight and time for each melt strand was recorded and normalized to yield the mass in grams per 10 minutes. The instrument's calculated I2 melt index value was also recorded. The equation used to calculate the actual melt density is δ = δ 0 7632 l2 l2 Gottfert where δ 07612 = 0 7632 and 12 Gottfert = displayed melt index A linear least squares fit of calculated melt density versus total styrene content leads to an equation with a correlation coefficient of 0.91 for the following equation: δ = 0.00299 x S + 0.723 where S = weight percentage of styrene in the polymer. The relationship of total styrene to melt density can be used to determine an actual melt index value, using these equations if the styrene content is known. So for a polymer that is 73 percent total styrene content with a measured melt flow (the "Gottfert number"), the calculation becomes δ = 0.00299*73 + 0 723 = 0 9412 where 0.9412/0.7632 = I 2 / G# (measured) = 1 23 B) Styrene Analyses Interpolymer styrene content and atactic polystyrene concentration are determined using proton nuclear magnetic resonance ( H NMR) All proton NMR samples are prepared in 1 , 1, 2, 2-tetrachloroethane-d 2 (tce-d 2 ) The resulting solutions are 1 6 - 3 2 percent polymer by weight Melt index (I 2 ) is used as a guide for determining sample concentration Thus when the I 2 is greater than 2 g/10 min, 40 mg of interpolymer is used, with an ι 2 between 1 5 and 2 g/10 mm, 30 mg of interpolymer is used, and when the I 2 is less than 1 5 g/10 min, 20 mg of interpolymer is used The interpolymers are weighed directly into 5-mm sample tubes A 0 75-ml aliquot of tce-d 2 is added by syringe and the tube is capped with a tight-fitting polyethylene cap The samples are heated in a water bath at 85°C to soften the interpolymer To provide mixing, the capped samples are occasionally brought to reflux using a heat gun Proton NMR spectra are accumulated on a Vaπan VXR 300 with the sample probe at 80°c, and referenced to the residual protons of tce-d 2 at 5 99 ppm The delay times are varied between 1 second, and data is collected in triplicate on each sample The following instrumental conditions are used for analysis of the interpolymer samples Vaπan vxr-300, standard 'h Sweep width, 5000 hz Acquisition time, 3 002 sec Pulse width, 8 μsec Frequency, 300 mhz Delay, 1 sec Transients, 16 The total analysis time per sample is about 10 minutes Initially, a Η NMR spectrum for a sample of the polystyrene, having a molecular weight (mw) of about 192,000, is acquired with a delay time of one second The protons are ' labeled" b, branch, a, alpha, o, ortho, m, meta, p, para, as shown in figure 1 Figure 1 Integrals are measured around the protons labeled in figure 1 , the 'a' designates aPS Integral a 7 1 (aromatic, around 7 1 ppm) is believed to be the three ortho/para protons, and integral a 6 6 (aromatic, around 6 6 ppm) the two meta protons The two aliphatic protons labeled a resonate at 1 5 ppm, and the single proton labeled b is at 1 9 ppm The aliphatic region is integrated from about 0 8 to 2 5 ppm and is referred to as a a , The theoretical ratio for a 7 ] a 6 6 a a! is 3 2 3, or 1 5 1 1 5, and correlated very well with the observed ratios for the polystyrene sample for several delay times of 1 second The ratio calculations used to check the integration and verify peak assignments are performed by dividing the appropriate integral by the integral a 6 6 ratio a r is a 7 1 / a 66 Region ag 6 is assigned the value of 1 Ratio al is integral a a! / a 6 6 All spectra collected have the expected 1 5 1 1 5 integration ratio of (o+p) m (α+b) The ratio of aromatic to aliphatic protons is 5 to 3 An aliphatic ratio of 2 to 1 is predicted based on the protons labeled a and b respectively in figure 1 This ratio is also observed when the two aliphatic peaks are integrated separately For the ethylene/styrene interpolymers, the 'h NMR spectra using a delay time of one second, had integrals c 7 ], c 6 6 , and c a! defined, such that the integration of the peak at 7 1 ppm included all the aromatic protons of the copolymer as well as the o <__ p protons of aPS Likewise, integration of the aliphatic region c a | in the spectrum of the interpolymers included aliphatic protons from both the aPS and the interpolymer with no clear baseline resolved signal from either polymer The integral of the peak at 6 6 ppm c 6 6 is resolved from the other aromatic signals and it is believed to be due solely to the aPS homopolymer (probably the meta protons) (the peak assignment for atactic polystyrene at 6 6 ppm (integral a 6 6 ) is made based upon comparison to the authentic sample of polystyrene having a molecular weight (mw) of about 192,000, this is a reasonable assumption since, at very low levels of atactic polystyrene, only a very weak signal is observed here Therefore, the phenyl protons of the copolymer must not contribute to this signal With this assumption, integral a 6 6 becomes the basis for quantitatively determining the aPS content The following equations are then used to determine the degree of styrene incorporation in the ethylene/styrene interpolymer samples (c phenyl) = c 7 , + a 7 , - ( 1 5 x a 6 6 ) (c aliphatic) = c a! - ( 1 5 x ag 6 ) S c = (c phenyl) /5 E c = (c aliphatic - (3 x s c )) / 4 E = e c / (e c + s c ) S c = s c / (e c + s c ) And the following equations are used to calculate the mole percent ethylene and styrene in the interpolymers And Where s c and e c are styrene and ethylene proton fractions in the interpolymer, respectively, and s c and e are mole fractions of styrene monomer and ethylene monomer in the interpolymer, respectively The weight percent of aPS in the interpolymers is then determined by the following equation The total styrene content is also determined by quantitative fouπer transform infrared spectroscopy (FTIR) Catalyst Preparation Preparation of Catalyst A, (dιmethyl[N-( 1 , 1 -dimethylethyl)- 1 , 1 -dimethyl- 1 -[( 1 ,2,3,4,5-η)- 1 ,5,6,7-tetrahydro-3- phenyl-s-ιndacen-l-yl]sιlanamιnato(2-)-N]- titanium) 1) Preparation of 3,5,6,7-Tetrahydro-s-Hydnndacen-l(2H)-one Indan (94 00 g, 0 7954 moles) and 3-chloropropιonyl chloride (10099 g, 07954 moles) were stirred in CH 2 C1 2 (300 mL) at 0°C as A1C1 3 (130 00 g, 0 9750 moles) was added slowly under a nitrogen flow The mixture was then allowed to stir at room temperature for 2 hours The volatiles were then removed The mixture was then cooled to 0°C and concentrated H 2 S0 4 (500 mL) slowly added The forming solid had to be frequently broken up with a spatula as stirring was lost early in this step The mixture was then left under nitrogen overnight at room temperature The mixture was then heated until the temperature readings reached 90°C These conditions were maintained for a 2 hour period of time during which a spatula was periodically used to stir the mixture After the reaction period crushed ice was placed m the mixture and moved around The mixture was then transferred to a beaker and washed intermittently with H 2 0 and diethylether and then the fractions filtered and combined The mixture was washed with H 2 0 (2 x 200 mL) The organic layer was then separated and the volatiles removed The desired product was then isolated via recrystallization from hexane at 0°C as pale yellow crystals (22 36 g, 16 3 percent yield) Η NMR (CDC1 3 ) d2 04-2 19 (m, 2 H), 2 65 (t, 3 J H H=5 7 Hz, 2 H), 2 84-3 0 (m, 4 H), 3 03 (t, 3 J H H=5 5 Hz 2 H), 7 26 (s, 1 H), 7 53 (s, 1 H) C NMR (CDCl . ) d25 71 , 26 01, 32 19, 33 24, 36 93, 1 18 90, 122 16, 135 88, 144 06, 152 89, 154 36, 206 50 GC-MS Calculated for C 12 H 12 0 172 09, found 172 05 2) Preparation of l,2,3,5-Tetrahydro-7-phenyl-s-ιndacen 3,5,6,7-Tetrahydro-s-Hydπndacen-l(2H)-one (12 00 g, 0 06967 moles) was stirred in diethylether (200 mL) at 0°C as PhMgBr (0 105 moles, 35 00 mL of 3 0 M solution in diethylether) was added slowly This mixture was then allowed to stir overnight at room temperature After the reaction period the mixture was quenched by pouring over ice The mixture was then acidified (pH=l) with HC1 and stirred vigorously for 2 hours The organic layer was then separated and washed with H 2 0 (2 x 100 mL) and then dried over MgS0 4 Filtration followed by the removal of the volatiles resulted in the isolation of the desired product as a dark oil (14 68 g, 90 3 percent yield) Η NMR (CDC1 3 ) d2 0-2 2 (m, 2 H), 2 8-3 1 (m, 4 H), 6 54 (s, 1H), 7 2-7 6 ( , 7 H) GC-MS Calculated for C 1 1 S 8H„ 10 232 13, found 232 05 3) Preparation of l,2,3,5-Tetrahydro-7-phenyl-s-ιndacene, dihthium salt l ,2,3,5-Tetrahydro-7-phenyl-s-ιndacen (14 68 g, 0 06291 moles) was stirred in hexane (150 mL) as nBuLi (0 080 moles, 40 00 mL of 2 0 M solution in cyclohexane) was slowly added This mixture was then allowed to stir overnight After the reaction period the solid was collected via suction filtration as a yellow solid which was washed with hexane, dried under vacuum, and used without further purification or analysis (12 2075 g, 81 1 percent yield) 4) Preparation of Chlorodιmethyl(l,5,6,7-tetrahydro-3-phenyl-s-ιndacen-l-yl)sιlane l ,2,3,5-Tetrahydro-7-ρhenyl-s-ιndacene, dihthium salt (12 2075 g, 0 05102 moles) in THF (50 mL) was added dropwise to a solution of Me 2 SιCl 2 (19 5010 g, 0 1511 moles) in THF ( 100 mL) at 0°C This mixture was then allowed to stir at room temperature overnight After the reaction period the volatiles were removed and the residue extracted and filtered using hexane The removal of the hexane resulted in the isolation of the desired product as a yellow oil (15 1492 g, 91 1 percent yield) Η NMR (CDCI 3 ) dO 33 (s, 3 H), 0 38 (s, 3 H), 2 20 (p, 3 JHH=7 5 Hz, 2 H), 2 9-3 1 (m, 4 H), 3 84 (s, 1 H), 6 69 (d, 3 JHH=2 8 Hz, 1 H), 7 3-7 6 (m, 7 H), 7 68 (d, 3 JHH=7 4 Hz, 2 H) B C NMR (CDCI 3 ) dO 24, 0 38, 26 28, 33 05, 33 18, 46 13, 11642, 119 71, 127 51, 128 33, 128 64, 129 56, 136 51, 141 31, 141 86, 142 17, 142 41, 144 62 GC-MS Calculated for C 20 H 2| ClSι 324 11 , found 324 05 5) Preparation of N-( 1 , 1 -Dimethylethyl)- 1 , 1-dιmethyl- 1-(1 ,5,6,7-tetrahydro-3-phenyl-s-ιndacen- 1 - yl)sιlanamιne Chlorodιmethyl(l,5,6,7-tetrahydro-3-phenyl-s-ιndacen-l-yl)sιlane (10 8277 g, 0 03322 moles) was stirred in hexane (150 mL) as NEt 3 (3 5123 g, 0 03471 moles) and .-butylamine (2 6074 g, 003565 moles) were added This mixture was allowed to stir for 24 hours After the reaction period the mixture was filtered and the volatiles removed resulting in the isolation of the desired product as a thick red-yellow oil (10 6551 g, 88 7 percent yield) H NMR (CDCI 3 ) dO 02 (s, 3 H), 0 04 (s, 3 H), 1 27 (s, 9 H), 2 16 (p, 3 JHH=7 2 Hz, 2 H), 2 9-3 0 (m, 4 H), 3 68 (s, 1 H), 6 69 (s, 1 H), 7 3-7 5 (m, 4 H), 7 63 (d, 3 JHH=7 4 Hz, 2 H) l3 C NMR (CDCI 3 ) d-0 32, -0 09, 26 28, 33 39, 34 11 , 4646, 47 54, 49 81, 1 15 80, 119 30, 126 92, 127 89, 128 46, 132 99, 137 30, 140 20, 140 81, 141 64, 142 08, 144 83 6) Preparation of N-( 1 ,1 -Dimethylethyl) l , l -dιmethyl-l-( l ,5,6,7-tetrahydro-3-phenyl-s ιndacen-1-yl) silanamine, dihthium salt N-( 1 , 1 -Dimethylethyl)- 1 , 1 -dimethyl- 1 -( 1 ,5 ,6,7-tetrahydro-3-phenyl-s-ιndacen 1 -yl)sιlanamιne (10 6551 g, 0 02947 moles) was stirred in hexane (100 mL) as nBuLi (0 070 moles, 35 00 mL of 2 0 M solution in cyclohexane) was added slowly This mixture was then allowed to stir overnight during which time no salts crashed out of the dark red solution After the reaction period the volatiles were removed and the residue quickly washed with hexane (2 x 50 mL) The dark red residue was then pumped dry and used without further purification or analysis (9 6517 g, 87 7 percent yield) 7) Preparation of Dιchloro[N-( 1 , 1 -dimethylethyl)- 1 , 1 -dimethyl- 1 -[( 1 ,2,3,4,5-η) 1 ,5,6,7-tetrahydro-3-phenyl-s- ιndacen-l-yl]sιlanamιnato(2-)-N]tιtanιum N-( 1 , 1 -Dimethylethyl)- 1 , 1 -dimethyl- 1 -( 1 ,5,6,7-tetrahydro-3-phenyl-s-ιndacen- 1 -yl)sιlanamιne, dihthium salt (4 5355 g, 0 01214 moles) in THF (50 mL) was added dropwise to a slurry of TιCl 3 (THF) 3 (4 5005 g, 0 01214 moles) in THF (100 mL) This mixture was allowed to stir for 2 hours PbCl 2 (1 7136 g, 0 006162 moles) was then added and the mixture allowed to stir for an additional hour After the reaction period the volatiles were removed and the residue extracted and filtered using toluene Removal of the toluene resulted in the isolation of a dark residue This residue was then slurned in hexane and cooled to 0°C The desired product was then isolated via filtration as a red-brown crystalline solid (2 5280 g, 43 5% yield) H NMR (CDCl j ) dO 71 (s, 3 H), 097 (s, 3 H), 1 37 (s, 9 H), 2 0-2 2 (m, 2 H), 2 9-3 2 ( , 4 H), 6 62 (s, 1 H), 7 35-7 45 (m, 1 H), 7 50 (t, 3 JHH=7 8 Hz, 2 H), 7 57 (s, 1 H), 7 70 (d, JHH=7 1 Hz, 2 H), 7 78 (s, 1 H) H NMR (C 6 D 6 ) dO 44 (s, 3 H), 0 68 (s, 3 H), 1 35 (s, 9 H), 1 6-1 9 (m, 2 H), 2 5-3 9 (m, 4 H), 6 65 (s, 1 H), 7 1-7 2 (m, 1 H), 7 24 (t, 3 JHH= 1 Hz, 2 H), 7 61 (s, 1 H), 7 69 (s, 1 H), 7 77-7 8 (m, 2 H) C NMR (CDC1-) dl 29, 3 89, 26 47, 32 62, 32 84, 32 92, 63 16, 98 25, 118 70, 121 75, 125 62, 128 46, 128 55, 128 79, 129 01, 134 11, 134 53, 136 04, 146 15, 148 93 π C NMR (C 6 D 6 ) dO 90, 3 57, 2646, 32 56, 32 78, 62 88, 98 14, 119 19, 121 97, 125 84, 127 15, 128 83, 129 03, 129 55, 134 57, 135 04, 136 41, 136 51 , 147 24, 148 96 8) Preparation of Dιmethyl[N-( 1 , 1 -dimethylethyl)- 1 , 1-dιmethyl- 1 -[( 1 ,2,3,4,5-η)- 1 ,5,6,7-tetrahydro-3-phenyl-s- indacen- 1 -yl]sιlanamιnato(2-)-N]tιtanιum Dιchloro[N-( 1 , 1 -dimethylethyl)- 1 , 1 -dimethyl- 1 -[( 1 ,2,3 ,4,5-η )- 1 ,5 ,6,7-tetrahydro-3-pheny 1-s-ιndacen- l-yl]sιlanamιnato(2-)-N]tιtanιum (04970 g, 0001039 moles) was stirred in diethylether (50 mL) as MeMgBr (0 0021 moles, 0 70 mL of 3 0 M solution in diethylether) was added slowly This mixture was then stirred for 1 hour After the reaction period the volatiles were removed and the residue extracted and filtered using hexane Removal of the hexane resulted in the isolation of the desired product as a golden yellow solid (0 4546 g, 66 7 percent yield) H NMR (C 6 D 6 ) dO 071 (s, 3 H), 0 49 (s, 3 H), 0 70 (s, 3 H), 0 73 (s, 3 H), 1 49 (s, 9 H), 1 7-1 8 (m, 2 H) 2 5 2 8 (m, 4 H), 6 41 (s, 1 H), 7 29 (t, 3 JHH=7 4 Hz, 2 H), 7 48 (s, 1 H), 7 72 (d, 3 JHH=7 4 Hz, 2 H), 7 92 (s 1 H) "c NMR (C.D 6 ) d2 19, 4 61, 27 12, 32 86, 33 00, 34 73, 58 68, 58 82, 118 62, 121 98, 124 26, 127 32, 128 63, 128 98, 131 23, 134 39, 136 38, 143 19, 144 85 Polymerization Method for ESI #'s 1 -3 ESI #'s 1 -3 were prepared in a 6 gallon (22 7 L), oil jacketed, Autoclave continuously stirred tank reactor (CSTR) A magnetically coupled agitator with Lightning A 320 impellers provided the mixing The reactor ran liquid full at 475 psig (3,275 kPa) Process flow was in at the bottom and out of the top A heat transfer oil was circulated through the jacket of the reactor to remove some of the heat of reaction At the exit of the reactor was a MicroMotion flow meter that measured flow and solution density All lines on the exit of the reactor were traced with 50 psi (344 7 kPa) steam and insulated Toluene solvent was supplied to the reactor at 30 psig (207 kPa) The feed to the reactor was measured by a Micro-Motion mass flow meter A variable speed diaphragm pump controlled the feed rate At the discharge of the solvent pump, a side stream was taken to provide flush flows for the catalyst injection line (1 lb/hr (0 45 kg/hr)) and the reactor agitator (0 75 lb/hr ( 0 34 kg/ hr)) These flows were measured by differential pressure flow meters and controlled by manual adjustment of micro-flow needle valves Uninhibited styrene monomer was supplied to the reactor at 30 psig (207 kpa) The feed to the reactor was measured by a Micro- Motion mass flow meter A variable speed diaphragm pump controlled the feed rate The styrene stream was mixed with the remaining solvent stream Ethylene was supplied to the reactor at 600 psig (4,137 kPa) The ethylene stream was measured by a Micro-Motion mass flow meter just prior to the Research valve controlling flow A Brooks flow meter/controller was used to deliver hydrogen into the ethylene stream at the outlet of the ethylene control valve The ethylene/hydrogen mixture combines with the solvent/styrene stream at ambient temperature The temperature of the solvent/monomer as it enters the reactor was dropped to ~5 °C by an exchanger with -5°C glycol on the jacket This stream entered the bottom of the reactor The three component catalyst system and its solvent flush also entered the reactor at the bottom but through a different port than the monomer stream Preparation of the catalyst components took place in an inert atmosphere glove box The diluted components were put in nitrogen padded cylinders and charged to the catalyst run tanks in the process area From these run tanks the catalyst was pressured up with piston pumps and the flow was measured with Micro-Motion mass flow meters These streams combine with each other and the catalyst flush solvent just prior to entry through a single injection line into the reactor Polymerization was stopped with the addition of catalyst kill (water mixed with solvent) into the reactor product line after the MicroMotion flow meter measuring the solution density Other polymer additives can be added with the catalyst kill A static mixer in the line provided dispersion of the catalyst kill and additives in the reactor effluent stream This stream next entered post reactor heaters that provide additional energy for the solvent removal flash This flash occurred as the effluent exited the post reactor heater and the pressure was dropped from 475 psig (3,275 kPa) down to ~250mm of pressure absolute at the reactor pressure control valve This flashed polymer entered a hot oil jacketed devolatihzer Approximately 85 percent of the volatiles were removed from the polymer in the devolatihzer The volatiles exited the top of the devolatihzer The stream was condensed with a glycol jacketed exchanger and entered the suction of a vacuum pump and was discharged to a glycol jacket solvent and styrene/ethylene separation vessel Solvent and styrene were removed from the bottom of the vessel and ethylene from the top The ethylene stream was measured with a Micro- Motion mass flow meter and analyzed for composition The measurement of vented ethylene plus a calculation of the dissolved gasses in the solvent/ styrene stream were used to calculate the ethylene conversion The polymer separated in the devolatihzer was pumped out with a gear pump to a ZSK-30 devolatihzing vacuum extruder The dry polymer exits the extruder as a single strand This strand was cooled as it was pulled through a water bath The excess water was blown from the strand with air and the strand was chopped into pellets with a strand chopper Polymerization Method for Ethylene-Styrene Interpolymers (ESIs) # 4 and 5 ESI's # 4 and 5 were prepared in a continuously operating loop reactor (36 8 gal 139 L) An Ingersoll Dresser twin screw pump provided the mixing The reactor ran liquid full at 475 psig (3,275 kPa) with a residence time of approximately 25 minutes Raw materials and catalyst/cocatalyst flows are fed into the suction of the twin screw pump through injectors and Kemcs™ static mixers The twin screw pump discharged into a 2" diameter line which supplied two Chemineer-Kenics™ 10-68 Type BEM Multi-Tube heat exchangers in series The tubes of these exchangers contained twisted tapes to increase heat transfer Upon exiting the last exchanger, loop flow returned through the injectors and static mixers to the suction of the pump Heat transfer oil is circulated through the exchangers' jacket to control the loop temperature probe located just prior to the first exchanger The exit stream of the loop reactor is taken off between the two exchangers The flow and solution density of the exit stream is measured by a MicroMotion™ flowmeter Solvent feed to the reactor is supplied by two different sources A fresh stream of toluene from an 8480-S-E Pulsafeeder™ diaphragm pump with rates measured by a MicroMotion™ flowmeter is used to provide flush flow for the reactor seals (20 lb/hr (9 1 kg/hr) Recycle solvent is mixed with uninhibited styrene monomer on the suction side of five 8480-5-E Pulsafeeder™ diaphragm pumps in parallel These five Pulsafeeder™ pumps supplied solvent and styrene to the reactor at 650 psig (4,583 kPa) Fresh styrene flow is measured by a MicroMotion™ flowmeter, and total recycle solvent/styrene flow is measured by a separate MicroMotion™ flowmeter Ethylene is supplied to the reactor at 687 psig (4,838 kPa) The ethylene stream is measured by a MicroMotion™ mass flowmeter A Brooks flowmeter/controller is used to deliver hydrogen into the ethylene stream at the outlet of the ethylene control valve The ethylene/hydrogen mixture combined with the solvent/styrene stream at ambient temperature The temperature of the entire feed stream as it entered the reactor loop is lowered to 2°C by an exchanger with -10°C glycol on the jacket Preparation of the three catalyst components took place in three separate tanks fresh solvent and concentrated catalyst cocatalyst premix are added and mixed into their respective run tanks and fed into the reactor via variable speed 680-S-AEN7 Pulsafeeder diaphragm pumps As previously explained, the three component catalyst system entered the reactor loop through an injector and static mixer into the suction side of the twin screw pump The raw material feed stream is also fed into the reactor loop through an injector and static mixer downstream of the catalyst injection point but upstream of the twin screw pump suction Polymerization is stopped with the addition of catalyst kill (water mixed with solvent) into the reactor product line after the MicroMotion™ flowmeter measuring the solution density A static mixer in the line provided dispersion of the catalyst kill and additives in the reactor effluent stream This stream next entered post reactor heaters that provided additional energy for the solvent removal flash This flash occurred as the effluent exited the post reactor heater and the pressure is dropped from 475 psig (3,275 kPa) down to 450 mmHg (60 kPa) of absolute pressure at the reactor pressure control valve This flashed polymer entered the first of two hot oil jacketed devolatihzers The volatiles flashing from the first devolatizer are condensed with a glycol jacketed exchanger, passed through the suction of a vacuum pump, and are discharged to the solvent and styrene/ethylene separation vessel Solvent and styrene are removed from the bottom of this vessel as recycle solvent while ethylene exhausted from the top The ethylene stream is measured with a MicroMotion™ mass flowmeter The measurement of vented ethylene plus a calculation of the dissolved gases in the solvent/styrene stream are used to calculate the ethylene conversion The polymer and remaining solvent separated in the devolatihzer is pumped with a gear pump to a second devolatizer The pressure in the second devolatizer is operated at 5 mm Hg (0 7 kPa) absolute pressure to flash the remaining solvent This solvent is condensed in a glycol heat exchanger, pumped through another vacuum pump, and exported to a waste tank for disposal The dry polymer (< 1000 ppm total volatiles) is pumped with a gear pump to an underwater pelletizer with 6-hole die, pelletized, spin-dried, and collected in 1000 lb boxes The various catalysts, co-catalysts and process conditions used to prepare the various individual ethylene styrene interpolymers (ESI #1-5) are summarized in Table 1 and their properties are summarized in Table 2 Table 1. Preparation Conditions for ESI #'s 1-5 a Catalyst A is dimethyl[N-( 1 , 1 -dimethylethyl)- 1 , 1 -dimethyl- 1-[( 1 ,2,3,4,5-η)- 1 ,5,6,7-tetrahydro-3-phenyl-s-indacen- l-yl]silanaminato(2-)-N]- titanium. b Catalyst B is (t-butylamido)dimethyl(.etramethylcyclopentadienyl)silane-titanium (II) 1,3-pentadiene prepared as in U.S. Patent # 5,556,928, Ex. c Cocatalyst C is tris(pentafluorophenyl)borane, (CAS# 001 109-15-5),. d a modified methylaluminoxane commercially available from Akzo Nobel as MMAO-3A (CAS# 146905-79-5) Table 2. Properties of ESI #'s 1 - 5. The following examples are illustrative of the invention, but should not be construed as to limiting the scope thereof in any manner Example 1 - Rotational Molding Compositions With Improved Processabilitv Low molecular weight additives were tumble blended with polyethylenes and subsequently compounded on a 30 mm twin screw extruder Reference samples were made by extruding the polyethylenes without the additives The melt temperatures were in the range 202-208°C The processing additives used were mineral oil (MO), glycerol monostearate (GMS) and pentaerythπtol monooleate (PEMO) The extruder was set at 400 rpm and the output rates ranged from about 36-71 lb/hr The specifications of the polymers used (all of which were products of The Dow Chemical Company) were as follows The properties of the reference samples and the different blends are given in Table 3 Note "RT" refers to "room temperature" Table 3 - Rotational Molding Compositions with Improved Processabihty Based on Polyethylenes. NJ <C : Not an Example of the present invention The blending of low molecular weight additives with the various polymers generally resulted in decreased viscosity and increased tan delta (that is decreased melt elasticity, since tan delta = loss modulus / storage modulus) at low shear rate These in turn are expected to yield faster sintering, enhanced coalescence and/or faster bubble removal in rotational molding leading to shorter cycle times The physical and mechanical properties of the blends were acceptable, that is secant modulus greater than 70,000 psi, flexural modulii greater than 80,000 psi and heat distortion temperature greater than 45 °C Example 2 -- Rotational Molding Compositions With Improved Processability Low molecular weight additives were tumble blended with DOWLEX™ NG2432 linear low density polyethylene (LLDPE) and subsequently compounded on a 30 mm twin screw extruder Reference samples were made by extruding the LLDPE without the additives The melt temperatures were in the range 185-21 1°C The low molecular weight additives used were mineral oil (MO), GMS, PEMO and SHELLFLEX™ 3131 (a poduct and trademark of Shell) The extruder was set at 375 φm and the output rates ranged from about 44-78 lb/hr Table 4 shows the properties of the reference samples and the different blends Table 4 - Additional Rotational Molding Compositions with Improved Processability Based on Polyethylenes. *Not an Example of the present invention, The blending of low molecular weight additives with polyethylene resulted in decreased "low shear viscosity" and increased "low shear tan delta" (that is, at 0 lsec ' shear rate) Furthermore, the viscosity tended to decrease with increased loadings of the additives Consequently sintering times during rotational molding are expected to be significantly shorter Furthermore, particle coalescence and/or bubble removal is expected to be enhanced The overall effect is expected to be reduced cycle times in rotational molding The physical and mechanical properties of the blends were acceptable, that is, secant modulus greater than 70,000 psi, flexural modulii greater than 80,000 psi and heat distortion temperature greater than 45 °C Suφnsingly, unlike the other additives, GMS did not have deleterious effects on secant and flexural modulus and also improved the ESCR- F50 properties significantly Izod impact strength was not affected significantly by any of the additives Example 3 - Sintering Rates of Rotational Molding Compositions With Improved Processability Some of the samples from Example 2 were evaluated for sintering Sintering is defined as the formation of a homogeneous melt from the coalescence of powder particles During sintering, there is a thermodynamic driving force for the particles to lower their surface energy by reducing their surface area In polymers, the sintering is governed by viscous flow The driving force is the surface tension and the viscosity offers resistance The concept of such a sintering mechanism is illustrated in Figure 2 Figure 2. Schematic sketch of the sintering sequence for two particles Where: a -particle radius ao -initial particle radius a_ -final particle radius y -neck radius L -length of the sintering particles W -width of the sintering particles As the sintering of the two spherical particles progresses, material transport occurs resulting in growth of the contact neck between the particles The sintering rate can be expressed by the rate of the neck growth The quantitative characterization of the process can be described by the following expression which is valid at the initial stages only Where T, η, y, a and t are the surface tension of the polymer, viscosity, neck radius, particles radius, and sintering time, respectively The growth of the neck between the two particles is proportional to the square root of the time The coalescence of the two particles is completed when the two particles have adhered together to form a single particle (y/a = 1) In rotational molding, the overall cycle time depends not only on the rate of oven heating but also on the rate of the sintering of the polymers The sintering time, (time required for the completion of the neck growth, (t s ) ) can be calculated by using an empirical model, called First Order Response The model is y/a=l-A e (t ts) The results of the curve fitting, the sintering time (t s ) was calculated by non-linear regression In rotational molding, sintering or coalescence of the polymer particles is a very important step due to its controlling mechanism in the heating cycle Sintering rate plays a significant role in the heating time and affects the properties of the final part Therefore the sintering behavior of the polymers provides useful information in evaluating their rotomoldabihty For the sintering experiments, polymer cylinders were prepared by compression molding using a plate with holes of diameter 0 32 mm and height of 0 3 mm The cylinders were cut off from the compression molded film The apparatus for measuring sintering consisted of a heat chamber and an optical microscope equipped with a video camera The camera was connected to a VCR & TV in turn was connected to a PC with a frame grabber board where the images were stored as files The two polymer cylinders or particles were selected and positioned at the center of a small glass cup by making point contact between themselves The glass cup was placed in the center of heat chamber which had glass windows on top and bottom for inspection and for taping of the process The temperature was controlled by a thermocouple sitting in the wall of the heat chamber and set at 230 °C The temperature in the glass cup was also measured The conditions were kept identical for all samples and the recording of the sintering experiments started when the temperature in the glass cup reached 90 C To simulate the rotational molding temperature profile the sintering experiments were performed on non-isothermal conditions After the completion of the sintering process (approximately 400 sec), taped images were sampled at intervals of 15 sec in the initial stages and less frequently in the advanced stages From the images, the neck growth between the two particles and the particle radius was measured by using an image analyzer software program called SigmaScan Pro (Jandel Scientific Software, 1992) The neck diameter was measured directly, while the particle diameter was calculated from the measurement of the surface area of the particles Sintering rate was evaluated from the measurement of the neck radius between the particles and the particle radius The sintering time (time required for the 99 percent completion of the neck growth) was calculated based on the sintering rate curves and using an empirical model (First Order Response) Non-isothermal sintering experiments were performed for the different samples The neck formation between the two cylindrical particles was recorded as a function of time The results of the measurements are shown in Tables 5 and 6 All three additives (mineral oil, GMS and PEMO) resulted in significantly faster sintering and coalescence Table 5: Sintering Rates (y/a versus time) *Not an example of the present invention. Table 6 : Other Results from Sintering Measurements *Not an example of the present invention Example 4 - Uniaxial Rotomolding of Compositions With Improved Processability Powders of the samples from Example 3 were further studied on a lab scale uniaxial rotational molding machine. In this machine the mold rotates on the horizontal axis. The set-up consisted of an electrical heated oven, an aluminum mold and a controller panel A table fan provided the cooling The oven was made of two infra-red heating panels During the experiments, a 9 5 x 9 5 x l0 cm cube shaped aluminum mold was used The outside surface of the mold was painted black and the inside surface of the mold was coated with a water based mold release A glass window to permit visual observation covered the front of the mold The air temperature inside the mold was measured by a thermocouple, which was connected to the controller panel through a slip ring The shotweight (polymer sample) was lOOg, which produced a molded part of about 3 mm thickness The speed of the rotation was set to 4 revolutions per minute (rpm), which is a commonly used ma j oi axis speed in biaxial rotational molding The oven controller temperature was preset at 427°C During the molding experiments the pre-weighed powder was loaded into the mold and the rotation was started After the oven was placed over the mold the inside air temperature was recorded every 30 seconds The heating was stopped when the inside air temperature reached 190, 210, 220, 225, 230 and/or 245 °C respectively with most of the samples Stopping the heating at different inside air temperatures varied the heating cycle time After removing the oven, the cooling took place by the aid of a fan The molded parts of about 3 mm thickness were unloaded when the temperature in the mold reached room temperature The molded parts were cut and prepared for further impact tests In rotational molding, as the layer of plastics build up, some air is trapped in the melt and bubbles are formed As the temperature increases in the mold, the bubbles decrease in diameter and finally disappear The layers closer to the mold wall have higher temperature and the bubbles disappear there first Therefore, the density of bubbles is greater near the inner surface of the molded part The presence of bubbles in molded parts depends not only on material properties, but also on process conditions If the cycle time is not enough long, the molded part will have lots of bubbles Therefore, inspection of the part for bubble content can provide good information on the progress of the process Bubble content in the molded parts was studied by using an optical microscope (Olympus SZ 4045) equipped with video camera Samples of approximately 1mm thickness were cut from the cross section parallel with the surface of the molded parts Figure 3 shows photographs of the cross-sections parallel to the surface of rotomolded parts made by uniaxial rotational molding of different samples at a maximum inside air temperature (T max ) of 210°C The parts made from the sample containing 3 wt percent MO were almost bubble free, indicating that the densification process was completed The large number of bubbles in the reference sample ("no additive") suggest that the densification process was still at the early stage In summary, the use of MO resulted in much faster bubble removal, as predicted earlier from the viscosity and Tan Delta measurements on the blends (Example 2, Table 4) No additive 3 wt% mineral oil Figure 3 : Cross-section parallel to the surface of rotomolded part made @ T max = 210°C Measurement of the thickness distribution is a good test to check the quality of the molded parts. The thickness of parts is affected by surface leveling. The degree of smoothness is measured by the standard deviation of the thickness, and depends not only on the properties of the polymer, but also on the process parameters. The heating time is one of the most important controlling factors in surface leveling. For example, if the heating time is not long enough, the surface of the molded part will be uneven. The thickness distribution of the molded parts was measured with a digital micrometer. The average thickness and standard deviation was calculated for each sample. The standard deviation is a measure of thickness uniformity. The data are presented in Table 7. It can be seen that the molded parts produced from the samples containing 3 wt percent MO exhibited more uniform thickness than the parts made from the reference sample ("no additive"). Increasing the maximum inside air temperature improved the thickness uniformity. Densification is one of the most important aspects of the rotational molding process and significantly affects the part properties. The degree of densification is characterized by measuring the density of the part. The density of the molded parts made at different maximum air temperatures was measured and has been reported in Table 7. The density of the molded parts was measured using MD-200S high precision electronic densimeter. The method is based on Archimedes principle. The equipment contains a precision balance that supports a water tank and sample testing stand. The specimens (4 x 4 cm) for this measurements were cut out from the molded parts. First, the mass of the dry sample was measured on the top of the test stand. Then the sample was immersed in the water and measured again on the test stand's submerged platform. The density was calculated by the data-analysis unit. The sample containing 3 wt percent MO started densifying earlier than the reference sample. Low temperature dart impact tests were performed to characterize the mechanical property of the rotomolded parts. This test determined the energy required to cause a failure in the rotomolded part by a free falling dart (weight of the dart is 10 lb = 4.53 kg). Before the tests, the specimens were conditioned in the freezer for 8 hours at -40°C. The frozen samples were placed into the sample holder with the inside surface of the part facing down. The dart was raised to a height expected to cause half of the samples to fail. The dart was released and the results of pass or fail and the type of the failure were recorded. If the specimen failed, the dropping height was lowered by 0 25 or 0 5 ft and the test was repeated with a new sample If the new sample failed, again the height was continuously decreased until the part passed When the part was passed the height was increased again by 0 25 or 0 5 ft until failure occurred The procedure continued until all of the specimens were tested The main failure energy was calculated using the following equations h = h o + Δh (A/N ±0 5) where h mean failure height, m (or feet) h () shortest height at which a failure occurred, m (or feet) Δh increment of the change in dart height used (cm) (or in) N total number of events (failures or non- failures), whichever is smaller A ∑ ιm (ι=countιng index, n^number of events) The counting index assigns the first event a value of zero, the second event a value of 1 and so on until the total of failures are accounted for The negative sign is used when the events are failures and the positive sign is used when the events are non- failures The mean failure energy, MFE, in ft lb (or mkg) was calculated as follows MFE = h x w Where w dart weight in lb (or kg) The MFE data and type of failure of the parts molded at different maximum inside air temperatures in uniaxial rotation are given in Table 7 The main failure energy (MFE), which represents the impact strength of the material, varied with the maximum inside air temperature (T max ) As the T max increased, the MFE increased up to a maximum value and then dropped The sample containing 3 weight percent mineral oil exhibited peak MFE identical to that obtained without mineral oil, but at significantly lower operating window (that is, lower values of T max ) In summary, the cycle time in rotational molding was significantly reduced by adding 3 wt percent mineral oil to the polyethylene and peak impact strength was essentially unchanged Table 7 Properties of Molded Parts from Uniaxial Rotational Molding as a function of Maximum Inside AirTemperature (T maΛ ) *not an example of the present invention a True resin density = 0.94 g/cm Example 5 - Biaxial Rotomolding of Compositions With Improved Processability Biaxial rotational molding experiments were performed on a carousel type McNeil/Femco rotational molding machine using the samples from Example 4 This machine has two arms One arm is typically used in the oven and the other in the cooling chamber (alternating), but for these experiments, only one arm was used (ARM 2) The mold, made from steel, had a box shape (30 x 30 x 20 5 cm) The mold sits on a plate, which in turn was connected to the arm, but not rigidly, such that the assembly could move The arm rotated vertically (outer or main axis) and the plate rotated horizontally The oven was heated by forced air circulation, the air being heated by natural gas The oven temperature was set to 600 °F The rotation speed was set on the controller panel as follows Outer axis (ARM speed) 8 m Inner axis (plate speed) 10 φm The test resin ( 1 4 kg) was placed into the mold and after closing the mold, it was transported to the oven using ARM 2 At the completion of the preset oven time (which varied from 1260 to 1440 seconds) the mold was moved to the cooling chamber and pre-cooled by the surrounding air for 300 seconds More intensive cooling by using a fan for 1800 seconds then followed The rotomolded parts were cut and prepared for impact tests using the method described in Example 4 Impact measurements were conducted on the top and bottom parts The top parts were about 2 9 mm thick and the bottom parts were about 2 5 mm thick The MFE values (in ft lb) of the top and bottom parts, and the types of failure, were as shown in Table 8 Table 8 : MFE and Type of Failure as a Function of Cycle Time in Biaxial Rotational Molding Using The Samples from Example 4. • ■ not an example of the present invention With 3 weight percent MO, the MFE decreased with increasing oven time and the brittle failure at longer cycle times indicated that the parts were over-cured This suggests that the operating window for this resin had shifted to shorter oven times That is, in the case of the sample containing 3 wt percent mineral oil, the cycle time required to achieve peak MFE (about 65 ft lb or greater for the top) was about 180 seconds less than that required without mineral oil This result confirmed the earlier findings in uniaxial rotation (Example 4) and sintering experiments (Example 3) Example 6 — Molding Composition With Improved Impact Strength A blend of ethylene vinyl acetate (EVA) with DOWLEX™ 2027A linear low density polyethylene (LLDPE) was tumble blended and subsequently compounded on a 30 mm twin screw extruder Reference samples were made by extruding two different lots of DOWLEX™ NG2432N (a commercial rotomolding resin) The melt temperatures were in the range 202-208°C The output rates ranged from 51-72 lb/hr, with the extruder set at 375 or 400 φm The specifications of the polymers used were as follows The physical and mechanical properties of the different samples are summarized in Table 9 Table 9 : Molding Compositions with Improved Impact Strength Based on Polyethylenes and EVA "not an example of the present invention. The blend made with EVA copolymer had greatly improved impact properties at both -40°C and room temperature (RT), with modulus equivalent to that of LLDPE, even though the EVA loading was only about 10 percent Thus, conceivably the modulus could be increased further while maintaining acceptable impact properties Furthermore, the heat distortion temperature of the LLDPE/EVA blend was not adversely affected by the addition of 10 weight percent EVA, which had a relatively low softening point Example 7 - Molding Compositions With Improved Impact Strength Blends of ethylene styrene Inteφolymers (ESI) with DOWLEX™ 2027A linear low density polyethylene (LLDPE) were tumble blended and subsequently compounded on a 30 mm twin screw extruder Reference samples were made by extruding two different lots of DOWLEX ™ NG2432 (which is a commercially used LLDPE resin for rotational molding) The melt temperatures were in the range 202-208°C The output rates ranged from 51 -67 lb/hr, with the extruder set at 375 or 400 rpm The specifications of the LLDPE polymers used were as follows The physical and mechanical properties of the different samples are shown in Table 10 Table 10: Molding Compositions with Improved Impact Strength Based on Polyethylenes and ESI *Not an example of the claimed invention The blends made with ESI resins 1 and 2 had superior impact properties at room temperature (RT), at modulus equivalent to that of the LLDPE resins Hence, it is conceivable that the modulus could be increased further while maintaining acceptable impact properties at room temperature The improvements in room temperature impact were more than expected, considering the fact that the loadings of ESI resins in the formulations were only 10 percent. Furthermore, the blend impact properties correlated with the differences in glass transition temperatures of the ESI resins It was also surprising that the heat distortion temperatures of the blends were not adversely affected by the addition of 10 weight percent of the ESI resins, all of which had low softening points compared with DOWLEX™ linear low density polyethylene. Example 8 -Molding Compositions Based on Blends of Polyethylene with EVA or ESI Blends containing 90 wt percent DOWLEX™ NG2432 linear low density polyethylene (LLDPE) and 10 wt percent of EVA or ESI were made by tumble blending and subsequently compounding on a 30 mm twin screw extruder. Reference samples were made by extruding DOWLEX™ NG2432 (a commercialy used rotomolding resin). The melt temperatures were in the range 204-210°C. The output rates ranged from 44-72 lb/hr, with the extruder set at 375 φm. The specifications of the LLDPE and EVA resins used were as follows: The physical and mechanical properties of the different samples are shown in Table 11 : Table 11 : Molding Compositions Based on Blends of Polyethylene with EVA or ESI *Not an example of the present invention. + low shear viscosity and low shear tan delta were measured at 0.1 s ' shear rate. The secant modulii, flexural modulii and heat distortion temperatures of the blends made with EVA and ESI were acceptably high, that is, secant modulus greater than 70,000 psi, flexural modulii greater than 80,000 psi and heat distortion temperature greater than 45 °C Impact strength at room temperature and ESCR- F50 were significantly improved by the blending of EVA and ESI with LLDPE Example 9 - Sintering Rates of Rotational Molding Compositions With Improved Impact The test method described in Example 3 was used to measure the sintering rates of the samples described in Example 8. The results of the measurements shown in Tables 12 and 13 The blends made with EVA and ESI all exhibited significantly lower sintering times than the unmodified LLDPE, even when the low shear viscosity and/or elasticity (at 0.1 s ' shear rate) was increased and/or it look longer for the onset of sintering to occur (see viscosity and tan delta data in Table 11 and onset of sintering data in Table 13) This could possibly be attributed to the increased adhesion obtained with EVA and ESI Table 12: Sintering Rates (y/a versus time) *Not an example of the present invention. Table 13 : Results of Other Sintering Measurements ^Not an example of the present invention. Example 10 -Uniaxial Rotomolding of Compositions with Improved Impact Strength The test method described in Example 4 was used to conduct uniaxial rotational molding of powder forms of the samples described in Example 9 and to measure the mean failure energy (ft lb) The results of the measurements are given below Bubble content in the molded parts was studied using the procedure described in Example 4 Figure 4 shows photographs of the cross-sections parallel to the surface of rotomolded parts made by uniaxial rotational molding of different samples at a maximum inside air temperature (T max ) of 210°C The parts made from the samples containing EVA or ESI had fewer bubbles, indicating that the densification process was proceeding faster This is suφπsing since, in some cases, the melt viscosity and elasticity of the blends was greater than that of the reference LLDPE which would normally be expected to slow down bubble removal (Example 8, Table 11) The thickness distribution of the molded parts was measured using the procedure described in Example 4 The data are presented in Table 14 It can be seen that the molded parts produced from the samples containing EVA or ESI, at T max of 210°C, exhibited average thickness similar to that of the parts made from the reference LLDPE sample ("no additive"), but the standard deviation was less The density of the molded parts made at different maximum air temperatures was measured using the procedure described in Example 4 and has been reported in Table 14 The samples containing EVA or ESI started densifying earlier than the reference sample The mean failure energy (MFE) was measured at -40°C using the procedure described in Example 4 The blending of EVA or ESI with LLDPE generally resulted in improved ductility in parts fabricated at lower processing temperatures and similar or increased impact strength The highest peak MFE was obtained with the blend containing 10 wt percent of ESI#4 Cycle times necessary to achieve about 70 ft lb mean failure energy were significantly reduced by blending 10 wt percent of ELVAX 770 or ESI #4 with the polyethylene LLDPE LLDPE with ELVAX 770 AX Figure 4 : Cross-Section Parallel To The Surface Of Uniaxial Rotomolded Parts Made From LLDPE And Blends With Impact Additives @ T max = 210°C ot an examp e o t e present invention Example 11 -Biaxial Rotomolding of Compositions with Improved Impact Strength The test method described in Example 5 was used to conduct biaxial rotational molding of the samples described in Example 10 and to measure the mean failure energy (ft lb) The results of the measurements (top values) are given below At short oven times (1320 and/or 1380 seconds), the top of the boxes made from the reference LLDPE were under-cured and exhibited low impact resistance in comparison with the blends comprising 10 wt percent of EVA or ESI. At longer heating time (1440 seconds), the blend comprising ESI#4 resulted in higher MFE than the reference LLDPE, while the blends containing EVA resulted in similar MFE, all with ductile failure. In general, cycle times necessary to achieve greater than 60 ft lb mean failure energy were significantly reduced by blending 10 wt percent of EVA or ESI with the polyethylene These results were generally consistent with the earlier findings in uniaxial rotation (Example 10) and sintering experiments (Example 9) Table 15 : Mean Failure Energy (MFE) and Type of Failure in Biaxial Rotational Molding of Blends of LLDPE with EVA or ESI *Not an example of the present invention Example 12 — Molding Compositions With Improved Impact Strength Blends of AFFINITY™ polyolefins with DOWLEX™ 2027A linear low density polyethylene were tumble blended and subsequently compounded on a 30 mm twin screw extruder Reference samples were made by extruding two different lots of DOWLEX™ NG2432N (a commercial rotomolding resin) The melt temperatures were in the range 202-207°C The output rates ranged from 51-72 lb/hr, with the extruder set at 375 or 400 φm The specifications of the polymers used were as follows The physical and mechanical properties of the different samples are shown in Table 16 Table 16 : Molding Compositions with Improved Impact Strength Based on Polyethylenes and AFFINITY TM *Not an example of the present invention The blend made with AFFINITY 7 EG8100 had significantly improved impact properties at both -40°C and room temperature The blend made with AFFINITY™ FM 1570 exhibited improved impact properties at room temperature The other properties of both blends were acceptable, that is, secant modulus greater than 70,000 psi, flexural modulus greater than 80,000 psi and heat distortion temperature greater than 45°C Note that the heat distortion temperatures of these blends were not adversely affected even though the AFFINITY™ components both had relatively low softening points Example 13- Molding Compositions with Improved Impact Strength Based on Polypropylene and ESI Blends of INSPIRE™ H700-12 homopolymer polypropylene (PP) and ethylene styrene Inteφolymi (ESI) were made by tumble blending and subsequently compounding on a 30 mm twin screw extruder A reference sample was made by extruding INSPIRE™ H700-12 PP The melt temperatures were in the range 230-232°C The output rates ranged from 70-78 lb/hr, with the extruder set at 375 φm The specification of the polypropylene used was as follows The following were the physical and mechanical properties of the different samples Table 17 :Molding Compositions with Improved Impact Strength Based on Polypropylene and ESI. Blending of ESI with PP resulted in increased impact strength and ESCR with the other properties remaining acceptably high, that is, secant modulus greater than 70,000 psi, flexural modulus greater than 80,000 psi and heat distortion temperature greater than 45 °C

Claims: CLAIMS 1 A rotational molding composition comprising, A) a majority component of one or more homopolymers or interpolymers, B) one or more impact additives selected from the group consisting of ethylene-vinyl acetate copolymers (EVA), heterogeneous or homogeneous inteφolymers with polymer units derived from ethylene and/or one or more C-j -C 20 α-olefins having a density of 0 915 g/cm 3 or less, and one or more substantially random inteφolymers comprising, (1 ) polymer units derived from (l) at least one vinyl or vinyhdene aromatic monomer, or (n) at least one hindered aliphatic or cycloahphatic vinyl or vinyhdene monomer, or (in) a combination of at least one vinyl or vinyhdene aromatic monomer and at least one hindered aliphatic or cycloahphatic vinyl or vinyhdene monomer, and (2) polymer units derived from (l) ethylene, or (n) 20 α-olefin, and mixtures thereof, wherein the impact strength of the composition at a fixed temperature is increased by at least 0 1 ft-lb/in from that of the majority component in the absence of the impact additive 2 The composition of Claim 1 wherein the majority component, Component A, comprises 70 percent or greater by weight of the composition 3 The composition of Claim 1 wherein the majority component, Component A, is selected from polyethylene, propylene homopolymers and copolymers, styrene homopolymers and copolymers, polycarbonates, nylon, polyesters, polybutylene, polyethylene terephthalate, and acrylic polymers, and mixtures thereof 4 The composition of Claim 1 wherein the majority component, Component A, is selected from ethylene and/or alpha olefin homopolymers or interpolymers, with the density of the ethylene homopolymers or copolymers being greater than 0 915 g/cm The composition of Claim 1 wherein the majority component, Component A, is linear low density polyethylene The composition of Claim 1 wherein the majority component, Component A, is polypropylene The composition of Claim 1 wherein the impact additive, Component B, comprises from 2 to 50 percent by weight of the composition The composition of Claim 1 wherein the impact additive, Component B, comprises ethylene-vinyl acetate copolymer comprising from 2 to 50 weight percent vinyl acetate The composition of Claim 1 wherein the impact additive, Component B, comprises substantially random inteφolymer comprising from 1 to 30 mole percent vinyl aromatic monomer The composition of Claim 1 wherein the impact additive, comprises heterogeneous or homogeneous copolymers of ethylene and 1 -propene, ethylene and 1-butene, ethylene and 1-pentene, ethylene and 1- hexene and ethylene and 1-octene of 0 850-0 915 g/cm 3 density The composition of Claim 9 wherein the vinyl aromatic monomer is styrene The composition of Claim 1 which comprises from 85 to 95 percent by weight of linear low density polyethylene as Component A, and from 5 to 15 percent by weight of ethylene-styrene interpolymer having from 5 to 20 mole percent styrene as Component B, wherein the composition is in the form of a powder which is smaller than or equal to35 mesh The composition of Claim 1 which comprises from 85 to 95 percent by weight of linear low density polyethylene as Component A, and from 5 to 15 percent by weight of ethylene-vinyl acetate copolymer having from 5 to 20 weight percent vinyl acetate as Component B, wherein the composition is in the form of a powder which is smaller than or equal to 35 mesh The composition of Claim 1 which comprises from 85 to 95 percent by weight of linear low density polyethylene as Component A, and from 5 to 15 percent by weight of heterogeneous or homogeneous copolymers of ethylene and 1 -propene, ethylene and 1-butene, ethylene and 1-pentene, ethylene and 1- hexene and ethylene and 1-octene of 0 850-0 915 g/cm 3 density as Component B, wherein the composition is in the form of a powder which has a particle size smaller than or equal to 35 mesh A rotational molding composition comprising, A) 94 percent by weight or more of one or more thermoplastic polymers, and B) 6 percent by weight or less of one or more processing additives, wherein the sintering time of said composition will be decreased by at least 5 percent relative to the sintering time of Component A in the absence of Component B The composition of Claim 15 wherein the one or more thermoplastic polymers are selected from the group consisting of substantially random ethylene-styrene interpolymers, ethylene and/or C 3 - C 2 o oc olefin homopolymers or inteφolymers, nylon, polyethylene terephthalate, polycarbonate, acrylic polymer, polystyrene, and mixtures thereof The composition of Claim 15 wherein the amount of processing additive, Component B, is from 0 01 to 6 weight percent of the composition The composition of Claim 15 wherein the processing additive, Component B, is a solid or liquid at from 20 to 300°C The composition of Claim 15 wherein the processing additive, Component B, has a molecular weight below 10,000 The composition of Claim 15 wherein the processing additive, Component B, is selected from the group consisting of mineral oil, naphthenic oil, paraffinic oil, glycerol monostearate, pentaerythntol monooleate, adipic acid, sabacic acid, styrene-alpha-methyl-styrene, calcium stearate and mixtures thereof The composition of Claim 15 wherein the processing additive, Component B, is mineral oil The composition of Claim 20 which comprises from 94 to 99 9 weight percent of linear low density polyethylene as Component A, and from 0 1 to 6 weight percent of mineral oil as Component B, wherein said mineral oil is dispersed within the polyethylene and the composition is in the form of a powder which has a particle size smaller than or equal to 35 mesh The composition of Claim 20 which comprises from 99 to 99 99 weight percent of linear low density polyethylene as Component A, and from 0 01 to 1 weight percent of calcium stearate as Component B, wherein said calcium stearate is dispersed substantially homogeneously within the polyethylene and the composition is in the form of a powder which has a particle size smaller than or equal to 35 mesh An injection molding composition, comprising A) a majority component of one or more homopolymers or interpolymers, and B) one or more impact additives selected from the group consisting of ethylene-vinyl acetate copolymers (EVA), heterogeneous or homogeneous interpolymers with polymer units derived from ethylene and/or one or more C 3 -C 2 o α-olefins having a density of 0 915 g/cm 3 or less, and mixtures thereof, wherein the impact strength of the composition at a fixed temperature is increased by at least 0 1 ft-lb/in from that of the majority component in the absence of the impact additive The composition of Claim 24 wherein the majority component, Component A comprises 70 percent or greater by weight of the composition The composition of Claim 24 wherein the majority component, Component A, is selected from polyethylene, propylene homopolymers and copolymers, styrene homopolymers and copolymers, polycarbonates, nylon, polyesters, polybutylene, polyethylene terephthalate, and acrylic polymers, and mixtures thereof The composition of Claim 24 wherein the majority component, Component A, is selected from ethylene and/or alpha olefin homopolymers or inteφolymers, with the density of the ethylene homopolymers or copolymers being greater than 0 915 g/cm The composition of Claim 24 wherein the majority component, Component A, is linear low density polyethylene The composition of Claim 24 wherein the majority component, Component A, is polypropylene The composition of Claim 24 wherein the impact additive, Component B, comprises from 2 to 50 percent by weight of the composition The composition of Claim 24 wherein the impact additive, Component B comprises ethylene-vinyl acetate copolymer comprising from 2 to 50 weight percent vinyl acetate The composition of Claim 24 wherein the impact additive, comprises heterogeneous or homogeneous copolymers of ethylene and 1 -propene, ethylene and 1-butene, ethylene and 1-pentene, ethylene and 1- hexene and ethylene and 1 -octene of 0 850-0 915 g/cm 3 density The composition of Claim 24 which comprises from 85 to 95 percent by weight of linear low density polyethylene as Component A, and from 5 to 15 percent by weight of ethylene-vinyl acetate copolymer having from 5 to 20 weight percent vinyl acetate as Component B, wherein the composition is in the form of a powder which is smaller than or equal to 35 mesh The composition of Claim 24 which comprises from 85 to 95 percent by weight of linear low density polyethylene as Component A, and from 5 to 15 percent by weight of heterogeneous or homogeneous copolymers of ethylene and 1-proρene, ethylene and 1-butene, ethylene and 1-pentene, ethylene and 1- hexene and ethylene and 1-octene of 0 850-0 915 g/cm 3 density as Component B, wherein the composition is in the form of a powder which has a particle size smaller than or equal to 35 mesh A rotationally molded or injection molded article prepared using the composition of any one of the preceding claims A cast film or blown film prepared using the composition of any one of the preceding claims An article prepared by blow molding, calendaring, or pulltrusion, and prepared from the composition of any one of the preceding claims

Inventors: CHAUDHARY BHARAT I, LAUBACH ADAM E, MARKOVICH RONALD P, NIETO JESUS, CHAUDHARY, BHARAT, I., LAUBACH, ADAM, E., MARKOVICH, RONALD, P., NIETO, JESUS
Applicants: CHAUDHARY BHARAT I, DOW CHEMICAL CO, LAUBACH ADAM E, MARKOVICH RONALD P, NIETO JESUS, CHAUDHARY, BHARAT, I., LAUBACH, ADAM, E., MARKOVICH, RONALD, P., NIETO, JESUS, THE DOW CHEMICAL COMPANY
Application year: 2000
Main classification: C08L23
IPC codes: B29C41, C08J5, C08L23, C08L25, C08L45, C08L67, C08L69, C08L77, C08L101