Olefin polymer films

Abstract

Disclosed are films or sheets comprising an olefin polymer composition which is comprised of(a) from about 10 to 50 parts of a propylene homopolymer having an isotactic index greater than 80, or a copolymer of propylene with ethylene and/or an another alpha-olefin, containing over 80% propylene and having an isotactic index greater than 80;(b) from about 5 to 20 parts of a semi-crystalline copolymer fraction, which copolymer is insoluble in xylene at room or ambient temperature; and(c) from about 40 to 80 parts of a copolymer fraction of ethylene with propylene and/or another alpha-olefin, and optionally with minor amounts of a diene, said copolymer fraction containing less than 40% ethylene and/or other alpha-olefin, being soluble in xylene at room temperature, and having an intrinsic viscosity from 1.5 to 4 dl/gCoextruded films or sheets and laminates wherein at least one layer is a film or sheet as described above, and films or sheets of blends of the olefin polymer composition and another olefin polymer are also disclosed.

Description

FIELD OF THE INVENTION

This invention relates to thermoplastic films, sheets and laminates and coextruded materials formed therefrom, and films and sheets formed from blends of an olefin polymer composition with other olefin polymer materials.

BACKGROUND OF THE INVENTION

In many film applications, such as packaging of foodstuffs, chemical and hazardous materials and in medical applications, the industry requires films having certain properties. In the packaging of foodstuffs, for example, the films must have high puncture resistance, high clarity and gloss, and reduced permeability to gases and/or vapors. The films used to manufacture containers for chemicals and hazardous waste materials must have a high puncture resistance, high elongation strength, high tear resistance and chemical resistance. Films used in medical applications, such as blood bags, must have a high puncture resistance, low modulus, high tear resistance and autoclavability.

Films made from ethylene polymers, e.g., HDPE and LLDPE, and propylene polymers, such as crystalline homopolymers of propylene and random copolymers of propylene and ethylene, do not provide such a combination of desirable properties.

Attempts have been made to overcome the shortcomings of these polymers by preparing heterophasic mixtures of crystalline propylene polymers and 8 to 25% of an elastomeric propylene-ethylene copolymer by sequential polymerization in the presence of a stereospecific Ziegler-Natta type catalyst. However, films of such heterophasic compositions are subject to the formation of fisheyes, inadequate tear strength or the formation of rough surfaces.

Hence, there is a need for a polymer material which has a lower flexural modulus, high clarity, good tear strength, as well as all of the other desirable properties.

All parts and percentages used in this application are by weight unless otherwise specified. Ambient or room temperature is approximately 25.degree. C.

SUMMARY OF THE INVENTION

This invention provides a thermoplastic film having the desired properties comprising a heterophasic olefin polymer composition which is comprised of

(a) from about 10 to 50 parts of a propylene homopolymer having an isotactic index greater than 80, or a copolymer selected from the group consisting of (i) propylene and ethylene, (ii) propylene, ethylene and a CH.sub.2 --CHR alpha-olefin, where R is a C.sub.2-8 straight or branched alkyl, and (iii) propylene and an alpha-olefin as defined in (a) (ii), said copolymer containing over 80% propylene and having an isotactic index greater than 80; (b) from about 5 to 20 parts of a semi-crystalline, essentially linear copolymer fraction having a crystallinity of about 20 to 60% wherein the copolymer is selected from the group consisting of (i) ethylene and propylene containing over 55% ethylene, (ii) ethylene, propylene, and an alpha-olefin as defined in (a) (ii) containing from 1 to 10% of the alpha-olefin and over 55% of both ethylene and alpha-olefin, and (iii) ethylene and an alpha-olefin as defined in (a) (ii) containing over 55% of said alpha-olefin, which copolymer is insoluble in xylene at room or ambient temperature; and (c) from about 40 to 80 parts of a copolymer fraction is selected from the group consisting of a copolymer of (i) ethylene and propylene wherein the copolymer contains from 20% to less than 40% ethylene and, (ii) ethylene, propylene, and an alpha-olefin as defined in (a) (ii) wherein the alpha-olefin is present in an amount of 1 to 10% and the amount of ethylene and alpha-olefin present is from 20% to less than 40%, and (iii) ethylene and an alpha-olefin as defined in (a) (ii) containing from 20% to less than 40% of the alpha-olefin, and optionally with 0.5 to 10% of a diene, said copolymer fraction being soluble in xylene at ambient temperature, and having an intrinsic viscosity of from 1.5 to 4.0 dl/g; with the total of the (b) and (c) fractions, based on the total olefin polymer composition, being from about 50% to 90%, and the weight ratio of (b)/(c) being less than 0.4.

In another embodiment this invention provides films comprising a layer of the heterophasic olefin polymer composition applied to at least one surface of a thermo-plastic film material or a metallic substrate.

In yet another embodiment films from blends of the olefin polymer composition and a thermoplastic material are provided.

DETAILED DESCRIPTION OF THE INVENTION

Component (a) is preferably present in an amount from 10 to 40 parts, most preferably from 20 to 35 parts. When (a) is a propylene homopolymer, the isotactic index is preferably from about 85 to 98. When (a) is a copolymer, the amount of propylene in the copolymer is preferably from about 90 to 99%.

Component (b) is preferably present in an amount from 7 to 15 parts. Typically the crystallinity is about 20 to 60% by differential scanning calorimetry (DSC). Generally, the ethylene or said alpha-olefin content or the combination of ethylene and said alpha-olefin when both are used is over 55% up to 98%, preferably from 80 to 95%.

Component (c) is preferably present in an amount from 50 to 70 parts. The ethylene or said alpha-olefin content or ethylene and said alpha-olefin content of component (c) is preferably from 20 to 38%, most preferably from 25 to 38%. When component (c) is a terpolymer, the said alpha-olefin is typically present in an amount from 1 to 10%, preferably 1 to 5%. The preferred intrinsic viscosity of is from 1.7 to 3 dl/g.

The total amount of (b) and (c), based on the total olefin polymer composition is preferably from 65 to 80% and the weight ratio of (b)/(c) is preferably from 0.1 to about 0.3.

The total amount of ethylene units or said alpha-olefin units, or of ethylene and said alpha-olefin units when both are present, in the olefin polymer composition is from about 15% to about 35%.

The compositions have at least one melt peak, determined by DSC, present at temperatures higher than 120.degree. C., and at least one peak, relative to the vitreous transition, present at temperatures from -10.degree. C. and -35.degree. C.

In addition, these compositions have a flexural modulus of less than 150 MPa, generally from 20 and 100 MPa; a tensile strength at yield of from 10 to 20 MPa, elongation at break over 400%; a tension set, at 75% strain, from 20% to 50%; a Shore D hardness from 20 and 35; and do not break (no brittle impact failure) when an IZOD impact test is conducted at -50.degree. C.

Preferably the haze values are less than 40%, most preferably less than 35%.

Copolymer and terpolymers of propylene and ethylene or an alpha-olefin or of propylene, ethylene and an alpha-olefin are preferred as component (a), and copolymers of propylene with ethylene or an alpha-olefin are most preferred as component (a) since they provide the compositions with higher clarity.

Suitable alpha-olefins of the formula CH.sub.2 --CHR include butene-1, pentene-1, 4-methylpentene-1, hexene-1, and octene-1. When used to prepare component (a) they are present in such quantities that the isotactic index of the resulting polymer is not less than 80%.

When a diene is present during the preparation of components (b) and (c), it is typically a butadiene, 1,4-hexadiene, 1,5-hexadiene, ethylidene norbornene diene monomer and is typically present in amount from 0.5 to 10%, preferably 1 to 5%.

The compositions can be prepared with a polymerization process comprising at least two stages, where in the first stage the propylene or propylene and ethylene or said alpha-olefin or propylene, ethylene or said alpha-olefin are polymerized to form component (a), and in the following stages the mixtures ethylene and propylene or said alpha-olefin or ethylene, propylene and said alpha-olefin, and optionally a diene, are polymerized to form components (b) and (c).

The polymerization can be conducted in liquid phase, gas phase, or liquid-gas phase using separate reactors, all of which can be done either by batch or continuously. For example, it is possible to carry out the polymerization of component (a) using liquid propylene as diluent, and the polymerization of components (b) and (c) in gas phase, without intermediate stages except for the partial degassing of the propylene. This is the preferred method.

The polymerization reactions are carried out in an inert atmosphere in the presence of an inert hydrocarbon solvent or of a liquid or gaseous monomer.

Suitable inert hydrocarbon solvents include saturated hydrocarbons, such as propane, butane, hexane and heptane.

Hydrogen can be added as needed as a chain transfer agent for control of the molecular weight.

The reaction temperature in the polymerization of component (a) and for the polymerization of components (b) and (c), can be the same or different, and is generally from 40.degree. C. to 90.degree. C., preferably 50.degree. to 80.degree. C. for the polymerization of component (a), and 40.degree. to 65.degree. C. for the polymerization of components (b) and (c).

The pressure of the polymerization of component (a), if carried out in liquid monomer, is the one which competes with the vapor pressure of the liquid propylene at the operating temperature used, eventually modified by the vapor pressure of the small quantity of inert diluent used to feed the catalyst mixture, and the overpressure of optional monomers and the hydrogen used as molecular weight regulator.

The pressure of the polymerization of components (b) and (c), if done in gas phase, can be from 5 to 30 atm. The residence times relative to the two stages depend on the desired ratio between fraction (a) and (b) +(c), and are usually from 15 min. to 8 hours.

The catalyst used in the polymerization comprises the reaction product of 1) a solid component containing a halogen-containing titanium compound and an electron-donor compound (internal donor) supported on an activated magnesium chloride, 2) a non-halogen containing Al-trialkyl compound and 3) an electron-donor compound (external donor).

Suitable titanium compounds include those with at least one Ti-halogen bond, such as halides and alkoxy halides of titanium.

In order to obtain these olefin polymer compositions in the form of flowable spherical particles having a high bulk density, the solid catalyst component must have a) a surface area smaller than 100 m.sup.2 /g, preferably between 50 and 80 m.sup.2 /g, b) a porosity from 0.25 to 0.4 cc/g. and c) an X-ray spectrum, where the magnesium chloride reflections appear, showing the presence of a halo between the angles 2 .theta. of 33.5.degree. and 35.degree. and by the absence of the reflection at 2 .theta. of 14.95.degree.. The symbol .theta.=Bragg angle.

The solid catalyst component is prepared by forming an adduct of magnesium dichloride and an alcohol, such as ethanol, propanol, butanol and 2-ethylhexanol, containing generally 3 moles of alcohol per mole of MgCl.sub.2, emulsifying the adduct, cooling the emulsion quickly to cause the adduct to solidify into spherical particles, and partially dealcoholating the particulate adduct by gradually increasing the temperature from 50.degree. C. to 130.degree. C. for a period of time sufficient to reduce the alcohol content from 3 moles to 1-1.5 moles per mole of MgCl.sub.2. The partially dealcoholated adduct is then suspended in TiCl.sub.4 at 0.degree. C., such that the concentration of adduct to TiCl.sub.4 is 40-50 g/l TiCl.sub.4 The mixture is then heated to a temperature of 80.degree. C. to 135.degree. C. for a period of about 1-2 hr. When the temperature reaches 40.degree. C., sufficient electron donor is added so that the desired molar ratio of Mg to electron donor is obtained.

An electron-donor compound selected preferably among the alkyl, cycloalkyl, and aryl phthalates, such as for example diisobutyl, di-n-butyl, and di-n-octyl phthalate, is added to the TiCl.sub.4.

When the heat treatment period has ended, the excess hot TiCl.sub.4 is separated by filtration or sedimentation, and the treatment with TiCl.sub.4 is repeated one or more times. The solid is then washed with a suitable inert hydrocarbon compound, such as hexane or heptane, and dried.

The solid catalyst component typically has the following characteristics:

______________________________________Surface area: less than 100 m.sup.2 /g, preferably between 50 and 80 m.sup.2 /gPorosity: 0.25-0.4 cc/gPore volume distribution: 50% of the pores have a radius greater than 100 angstroms.X-ray spectrum: where the Mg chloride reflections appear, showing a halo with maximum intensity between angles of 2 of 33.5.degree. and 35.degree., and where the reflection at 2 of 14.95.degree. is absent.______________________________________

The catalyst is obtained by mixing the solid catalyst component with a trialkyl aluminum compound, preferably triethyl aluminum and triisobutyl aluminum, and an electron-donor compound.

Various electron donor compounds are known in the art. The preferred electron donor compounds are those silane compounds having the formula R'R"Si(OR).sub.2 where R' and R" may be the same or different and are C.sub.1-18 normal or branched alkyl, C.sub.5-18 cycloalkyl, or C.sub.6-18 aryl radicals, and R is a C.sub.1-4 alkyl radical.

Typical silane compounds which may be used include diphenyldimethoxysilane, dicyclohexyldimethoxysilane, methyl-t-butyldimethoxysilane, diisopropyldimethoxysilane, dicyclopentyldimethoxysilane, cyclohexylmethyldimethoxysilane and phenyltrimethoxysilane.

The Al/Ti ratio is typically between 10 and 200 and the Al/silane molar ratio between 1/1 and 1/100.

The catalysts may be precontacted with small quantities of olefin monomer (prepolymerization), maintaining the catalyst in suspension in a hydrocarbon solvent and polymerizing at a temperature from room temperature to 60.degree. C. for a time sufficient to produce a quantity of polymer from 0.5 to 3 times the weight of the catalyst.

This prepolymerization also can be done in liquid or gaseous monomer to produce, in this case, a quantity of polymer up to 1000 times the catalyst weight.

The content and amount of catalyst residue in the thermoplastic olefin polymers of this invention is sufficiently small so as to make the removal of catalyst residue, typically referred to as deashing, unnecessary.

The thermoplastic olefin polymers prepared with the aforementioned catalyst are in spheroidal particle form, and the particles have a diameter from 0.5 to 7 mm.

Analytical Methods

Unless otherwise specified, the following analytical methods are used to characterize the supported catalyst component, the heterophasic olefin polymer compositions, films prepared therefrom and comparative film materials.

______________________________________Properties Method______________________________________Melt Flow Rate, g/10 min. ASTM-D 1238, condition LEthylene, wt % I.R. SpectroscopyIntrinsic viscosity Determined in tetrahydro- naphthalene at 135.degree. C.Xylene solubles, wt % See description below.Flexural modulus at 23.degree. C. Using a device for dynamic-and Vitreous transition mechanical measurements oftemperature DMTA of Polymer Laboratories at a frequency measure of 1 H.sub.z and a scanning temperature of 2.degree. C./min. A sample plaque (40 .times. 10 .times. 2 mm) of the polymer to be analyzed is cut from a pressure molded sheet prepared with a Carver press at 200.degree. C. with 10 tons of pressure for 10 minutes and then cooling the sheet at 15.degree. C./min.Notched IZOD impact ASTM-D 256Haze ASTM-D 1003Tension set at 75% ASTM-D 412Tensile Strength at yield ASTM-D 638and at breakElongation at yield and ASTM-D 638at breakSurface area B.E.T.Porosity B.E.T.Bulk density DIN-53194Elemendorf tear ASTM-D 1922-78Trouser tear ASTM-D 1938-85Gloss ASTM-D 523Coefficient of friction ASTM-D 1894Moisture vapor transmission ASTM-E 96Dart impact strength ASTM D 4272-83______________________________________

Unless otherwise specified, the samples of the olefin polymer composition to be subjected to the various physical-mechanical analyses are molded by use of a Negri & Bossi 90 injection press, after stabilizing the material with 0.1% Irganox 1010 tetrakis[methylene 3,5-di-tert-butyl-4-hydroxyhydrocinnamate)]methane and 0.1% BHT (2,6-di-tert-butyl-p-cresol), and pelletizing it with a single screw Bandera extruder (cylinder diameter 30 mm) at 210.degree. C. The analytical conditions are as follows:

temperature of the melt 250.degree. C. temperature of the mold 60.degree. C. injection time 20 sec cooling time 25 sec.

The samples to be subjected to the Haze analysis are molded into 75.times.75.times.1 mm plaques using a GBF F 235/90 injection press under the following conditions:

temperature of the melt 260.degree. C. temperature of the mold 40.degree. C. injection time 20 sec cooling time 10 sec.

The samples of the film materials were 1 mil in thickness and were cut from the film sheet in the size provided in the particular ASTM test method being used.

The weight percentage of the sum of the (b) and (c) fractions, indicated by % (b)+(c), is calculated by determining the weight of the mixture fed during the second stage, and comparing it with the weight of the final product.

The weight percentage (%) of the (a), (b), and (c) fractions described herein are determined as follows:

% (a)=100%-[(b)+(c)] % (c)=S.sub.f -P.sub.a S.sub.a where S.sub.f and S.sub.a are the percentage by weight of the portion soluble in xylene of the final product and the polypropylene fraction (a), respectively; P.sub.a is the weight ratio between said fraction and the final product. % (b)=100-% (a)-% (c)

The percentage by weight of ethylene or said alpha-olefin or ethylene and said alpha-olefin contained in copolymer fraction (c) soluble in xylene is calculated using the following formula: ##EQU1## where: C.sub.f =% ethylene and/or said alpha-olefin in the xylene solubles of the final product;

C.sub.a =% ethylene and/or said alpha-olefin in the xylene solubles of fraction (a); X=S.sub.z .multidot.P.sub.a /S.sub.f

The intrinsic viscosity of fraction (c), (I.V..sub.(c)), is calculated using the following formula:

(I.V. .sub.(c))=(I.V..sub.Sf -I.V..sub.(a) .multidot.X)/(1-X) where I.V..sub.Sf is the intrinsic viscosity of the xylene soluble fraction of the final composition and I.V..sub.(a) is the intrinsic viscosity of the xylene soluble portion of fraction (a).

The weight percent of olefin polymer composition soluble in xylene at room temperature is determined by dissolving 2.5 g of the polymer in 250 ml of xylene in a vessel equipped with a stirrer which is heated at 135.degree. C. with agitation for 20 minutes. The solution is cooled to 25.degree. C. while continuing the agitation, and then left to stand without agitation for 30 minutes so that the solids can settle. The solids are filtered with filter paper, the remaining solution is evaporated by treating it with a nitrogen stream, and the solid residue is vacuum dried at 80.degree. C. until a constant weight is reached. The percent by weight of polymer insoluble in xylene at room temperature is the isotactic index of the polymer. The value obtained in this manner corresponds substantially to the isotactic index determined via extraction with boiling n-heptane, which by definition constitutes the isotactic index of the polymer.

Examples illustrative of the heterophasic olefin polymer composition, physical properties thereof, a process for preparing same, a film based on said olefin polymer composition and a method of preparing said film are set forth below.

SOLID CATALYST COMPONENT

A) Preparation of MgCl.sub.2 /Alcohol Adduct

Under an inert atmosphere, 28.4 g anhydrous MgCl.sub.2, 49.5 g of an anhydrous ethanol, 100 ml of ROL OB/30 vaseline oil and 100 ml of silicone oil having a viscosity of 350 cs are introduced into a reaction vessel equipped with a stirrer and heated at 120.degree. C. with an oil bath and stirred until the MgCl.sub.2 is dissolved. The hot reaction mixture is then transferred under inert atmosphere to a 1500 ml vessel equipped with an Ultra Turrax T-45 N stirrer and a heating jacket and containing 150 ml of vaseline oil and 150 ml of silicone oil. The temperature is maintained at 120.degree. C. with stirring for 3 minutes at 3,000 rpm. The mixture is then discharged into a 2 liter vessel equipped with a stirrer containing 1,000 ml of anhydrous n-heptane cooled at 0.degree. C. with a dry ice/isopar bath and stirred at a tip speed of 6 m/sec for about 20 minutes while maintaining the temperature at 0.degree. C. The adduct particles thus formed are recovered by filtering, are washed 3 times at room temperature with 500 ml aliquots of anhydrous hexane and gradually heated by increasing the temperature from 50.degree. C. to 100.degree. C. under nitrogen for a period of time sufficient to reduce the alcohol content from 3 moles to 1.5 moles per mole of MgCl.sub.2. The adduct has a surface area of 9.1 m.sup.2 /g and a bulk density of 0.564 g/cc.

B) Solid Catalyst Component Preparation

The adduct (25 g) is transferred under nitrogen into a reaction vessel equipped with a stirrer and containing 625 ml of TiCl.sub.4 at 0.degree. C. under agitation. It is then heated to 100.degree. C. in 1 hr. When the temperature reaches 40.degree. C., diisobutylphthalate is added in an amount such that the molar ratio of Mg to diisobutylphthalate is 8. The contents of the vessel are heated at 100.degree. C. for 2 hours with agitation, the agitation is stopped and the solids are allowed to settle. The hot liquid is removed by siphon. 550 ml of TiCl.sub.4 is added to the solids in the vessel and the mixture heated at 120.degree. C. for 1 hr. with agitation. The agitation is stopped and the solids are allowed to settle. The hot liquid is then removed by siphon. The solids are washed 6 times at 60.degree. C. with 200 ml aliquots of anhydrous hexane, and then 3 times at room temperature. The solids, after being vacuum dried, have a porosity of 0.261 cc/g, a surface area of 66.5 m.sup.2 /g and a bulk density of 0.44 g/cc.

EXAMPLES 1-3

These examples illustrate the heterophasic olefin polymer composition and a method for preparing the polymers.

GENERAL OPERATING CONDITIONS

The polymerization runs are conducted under nitrogen in a 22 liter stainless steel autoclave equipped with a helicoid magnetic stirrer and operated at about 90 rpm. All temperatures, pressures and concentrations of olefin monomers and hydrogen, when present, are constant unless otherwise indicated. The concentration of hydrogen and of the relative monomers is analyzed continuously in gas phase with a process gas chromatograph and fed in order to maintain constant the desired concentration of same.

The polymerization is a batch process conducted in two stages. The first stage comprising the polymerization of the relevant monomer or monomers in liquid propylene and the second stage the copolymerization of ethylene and propylene in gas phase.

In the first stage, the following ingredients in the order in which they are listed are fed into the autoclave at 20.degree. C. over a period of about 10 minutes: 16 l of liquid propylene, appropriate quantities of ethylene and hydrogen, and the catalyst system consisting of 1) the solid catalyst component (about 0.15g) prepared as described above, and 2) a mixture of 75 ml of triethyl aluminum (TEAL) at a 10% concentration in hexane and an appropriate quantity of cyclohexylmethyldimethoxysilane (CMMS) electron donor such that the Al/CMMS molar ratio is 7.5. The catalyst system is pressure fed into the autoclave with propylene.

The temperature is brought to the desired level in about 10 minutes and maintained constant throughout the entire polymerization reaction period. After the established reaction time has passed, essentially all of the unreacted monomer(s) is/are eliminated by degassing at 60.degree. C. at essentially atmospheric pressure.

In the second stage, the polymer product (a) of the first stage, after taking a sample for the various analyses, is brought to the established temperature for the second stage. Propylene and ethylene are then fed into the autoclave at the ratio and in the quantities established in order to achieve the pressure and the gas phase composition desired. During the polymerization the pressure and gas phase composition are maintained by feeding the propylene and ethylene mixture established by way of instruments which regulate or measure or both regulate and measure the flow rate. The length of the feed varied according to the catalyst system employed and the amount of components b) and c) desired in the particular heterophasic olefin polymer product.

At the end of the second stage polymerization reaction the powder is discharged, stabilized and then oven dried under a nitrogen stream at 60.degree. C.

The ingredients and relative operating conditions are set forth in Table IA and the tests results are set forth in Table IB.

TABLE 1A______________________________________Examples 1 2 3______________________________________1st PhaseTemperature, .degree.C. 70 70 70Pressure, atm. 31 31 31Time, min. 30 20 30H.sub.2 in gas phase, mol % 0.58 0.10 0.30Ethylene in gas 1.45 2.60 2.50phase, mol %Ethylene in pol., wt. % 3.0 4.3 4.1Intrinsic Visc., dl/g 2.18 3.09 2.31Xylene Sol. (S.sub.a), wt. % 9.4 9.0 10.7Ethylene in Xylene Sol. 11 16 17(C.sub.a), wt. %Intrinsic Visc. Xylene 1.15 1.39 1.19Sol. (I.V..sub.a), dl/g2nd PhaseTemperature, .degree.C. 50 50 50Pressure, atm. 11.3 11.5 11.3Time, min. 335 500 250H.sub.2 in gas phase, mol % 2.23 3.0 2.05Ethylene in gas phase, 15.9 16.9 22.54mol %______________________________________ TABLE 1B______________________________________Examples 1 2 3______________________________________Final ProductYield, Kg Pol/g Cat 11 16.3 9.9Comonomer, wt. % 24.6 22.7 29.0Bipolymer (b) + (c), wt. % 70 67 71.8Intrinsic Visc., dl/g 2.05 2.3 2.34Xyl. Sol. (S.sub.f), wt. % 63.4 60.5 63.5Ethylene Xyl. Sol., wt. % 30.2 27.0 34.8(C.sub.f)Intrinsic Vis. Xyl. Sol. 1.83 2.02 2.12I.V..sub.Sf, dl/gFraction (b), wt. % 9.45 9.37 11.34Fraction (c), wt. % 60.55 57.63 60.46Ethylene frac. (b), wt. % 51.9 57.1 53.7Ethylene frac. (c), wt. % 31.1 27.6 35.7Intrinsic Vis. frac. (c) 1.86 2.05 2.18(I.V..sup.c), dl/gMelt Index, .degree.C. 150 147 145Flexural modulus, MPa 30 77 82R.C.I. IZOD at -50.degree. C., J/m NB.sup.1 NB NBShore D hardness 24 25 20Tension Set at 75%, % 41 28 36Tensile strength, MPa 13.8 15.8 15.4Tensile strength at yield, MPa 5.0 5.8 4.6Elongation at break, % 517 925 940Haze, % 31 34 35Vitreous transition.sup.2, .degree.C. -25 (P) -23 (P) -28 (P) -75 -119 -81 -128 -121 -125______________________________________ .sup.1 NB = no break .sup.2 (P) = main peak

EXAMPLES 4

These examples illustrate a film material comprising the heterophasic olefin polymer composition and a method for preparing the same.

An air quenched blown film of the heterophasic olefin polymer composition of Example 2 stabilized with 0.25 parts per hundred parts of the olefin polymer composition (pph) octadecyl-3.5-bis(1,1-dimethylethyl)-4-hydroxybenzene propanoate, 0.05 pph tetrakis[methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)]methane, 0.06 pph Sandostab P-EPQ composition, the main component of which is tetrakis(2,4-ditert-butylphenyl)-4-4'-biphenylene diphosphonite and 0.05 calcium stearate is prepared by charging the composition into a single screw extruder, extruding it through a circular die and blowing it into a film form with a sufficient amount of air to provide a film of 1 mil thickness using the following equipment and processing conditions:

______________________________________Screw: Compression ratio 3:1 to 4:1. Polyolefin barrier type L/D ratio = 24:1 to 30:1. Blow up ratio = 2.5 to 4.1. Die gap: 40 mils for a thickness of 0.5 to 5 mils.Extruder barrel profile: 380 to 430.degree. F. going from zone 1 to zone 6.Adapter and die temperatures: 450.degree. F. except upper and lower die zones which are 460.degree. F.Screw speed: 20 rpm.Pressure: 3000 psi.______________________________________

The properties of the resulting film are set forth in Table 2 below.

TABLE 2______________________________________ ResinsProperties Example 2 HDPE.sup.1 LLDPE.sup.2______________________________________Yield Strength 1347/1126 3757/3145 1749/1739(MD/CD.sup.3), psiBreak Strength (MD/CD), 3096/1643 3960/3216 2092/1898psiElongation at yield 65/40 30/7 80/17(MD/CD), %Elongation at break 361/417 120/350 317/425(MD/CD), %Elemendorf tear, No tear 10/282 350/790(MD/CD), g/plyTrouser tear, (MD/CD) 152/530 147/1026 503/758Haze 65.7 76.8 8.7Gloss 6 10 70Coefficient of 1.22/0.815 0.241/0.192 0.688/0.650friction (static/kinetic)Moisture vapor trans- 1.340 1.300 --mission rates at100.degree. F. & 100 relativehumidity, g/100 sq.in/24 hrs.Dart impact strength, 0.980 0.720 1.020ft-lb/mil______________________________________ .sup.1 Quantum LR 732 HDPE having a density of 0.953 g/cc.sup.3. .sup.2 Dowlex 2045 LLDPE containing hexene1 and having a density of 0.920 g/cc.sup.3. .sup.3 MD/CD = machine direction/cross direction.

From the above Table one can see that the olefin polymer composition of this invention provides an air quenched blown film with improved elongation at break and Elemendorf tear properties and a better balance of properties. Further, polymer materials, the major portion of which comprise propylene units, generally do not run well, if at all, on air quenched blown film equipment.

EXAMPLE 5

This example illustrates an cast film material of the heterophasic olefin polymer composition, of a coextruded film of the heterophasic olefin polymer composition and a random copolymer of propylene and ethylene and a method for preparing same.

A cast film of the heterophasic olefin polymer composition of Example 2 stabilized as set forth in Example 4 is prepared by charging the composition into an extruder, extruding it through a flat film die and quenching onto a chill roll to produce a film of 1 mil thickness using the following equipment and processing conditions:

Screw design: Compression ratio: 4:1 to 3:1 Feed zone depth: 0.435 to 0.490" (3.5" extruder with 3.5:1 compression ratio) Metering zone depth: 0.125 to 0.140.increment. for 3.5.increment. extruder Die Convention center-fed coathanger manifold. Extruder operating conditions: Melt temperature: 430.degree.-500.degree. F. Extruder Barrel: 350.degree.-420.degree. F. going from zone 1 to zone 6. Adapter and die temperatures: 420.degree. F.

A coextruded film 1.25 mils thick comprising a film layer of the heterophasic olefin polymer composition of Example 2 stabilized as set forth in Example 4 as the center layer, and two film layers of Pro-fax SA 861 propylene-ethylene random copolymer with an ethylene content of 3.0%, one layer of said copolymer on each surface of the center layer is prepared by the cast film technique.

The properties of the resulting film are set forth in Table 3 below.

TABLE 3______________________________________ ResinsProperties Ex. 2 Coex.sup.1 P-E Co.sup.2______________________________________Yield Strength 1185/865 1095/817 2523/2452(MD/CD.sup.3), psiBreak Strength 3899/1708 3637/1693 4120/3363(MD/CD), psiElongation at yield 34/19 32/22 15/10(MD/CD), %Elongation at break >450/>550 >530/>550 522/584(MD/CD), %Elemendorf tear, 192/No Tear 657/544 49/102(MD/CD), g/plyHaze 49.0 5.2 2.3Gloss 20.0 57.0 78.1______________________________________ .sup.1 Propyleneethylene random copolymer/Heterophasic olefin polymer composition of Ex. 2/Propyleneethylene random copolymer. .sup.2 Profax 861 propyleneethylene random copolymer with an ethylene content of 3.0%. .sup.3 MD/CD = machine direction/cross direction.

From the above Table one can see that the olefin polymer composition of this invention provides an cast film and a coextruded cast filme with improved elongation at yield and Elemendorf tear properties.

Various types of film materials of conventional thickness and thin films less than 20 mils thick to as thin as about 0.5 mils can be prepared using the heterophasic olefin polymer composition described herein as well as heavy film materials, typically referred to as sheets, from to 100 mils thick. For example, it can be used to prepare cast films, uniaxially and biaxially oriented films and extruded or calendared sheets. In addition, a layer comprising the heterophasic olefin polymer composition can be applied to, e.g. by lamination or coextrusion techniques, at least one surface of a thermoplastic film material or a metallic sheet or foil substrate. Typical thermoplastic materials include crystalline homopolymers of a C.sub.2-10 alpha-olefin monomer, such as propylene or ethylene, or copolymers of propylene with ethylene or with a C.sub.4-10 alpha-olefin monomers or of propylene with both ethylene and a C.sub.4-10 alpha-olefin monomers, provided that, when the comonomer is ethylene, the maximum polymerized ethylene content is about 10%, preferably about 4%, and when the comonomer is a C.sub.4-10 olefin, the maximum polymerized content thereof is about 20 %, preferably about 16%, and when both ethylene and an alpha-olefin are used the maximum polymerized content of both is 30%, preferably 20%, as well as polyesters, polyamides, ethylene-vinyl alcohol copolymers and ethylene-vinyl acetate copolymers. Aluminum is a suitable metallic substrate.

In addition, film materials can be prepared from blends of from about 5 to 45% of the heterophasic olefin polymer composition described herein with from about 95 to 55% of a crystalline homopolymer of a C.sub.2-10 alpha-olefin monomer or copolymer of propylene with ethylene or with a C.sub.4-10 alpha-olefin monomer or of propylene, ethylene and a C.sub.4-10 alpha-olefin monomer, said copolymer having the maximum polymerized content of ethylene or alpha-olefin or both as described in the preceding paragraph. Preferably the amount of the heterophasic olefin polymer composition present in such blends is from 10 to 30%.

The olefin polymer composition of this invention is such that one can achieve the proper balance of properties in the resulting product when a film layer of same is the material applied to at least one surface of another thermoplastic material or to a metallic substrate and when it is blended with another thermoplastic material and the blend is used to make film materials.

Other features, advantages and embodiments of the invention disclosed herein will be readily apparent to those exercising ordinary skill after reading the foregoing disclosures. In this regard, while specific embodiments of the invention have been described in considerable detail, variations and modifications of these embodiments can be effected without departing from the spirit and scope of the invention as described and claimed.

Claims

1. A film or sheet article comprising a base film or sheet of a crystalline homopolymer of a C.sub.2-10 alpha-olefin monomer or of a copolymer selected from the group consisting of (i) propylene with ethylene, (ii) propylene with ethylene and a C.sub.4-10 alpha-olefin monomer, and (iii) propylene with a C.sub.4-10 alpha-olefin monomer, provided that, when the comonomer is ethylene, the maximum polymerized ethylene content is about 10%, when the comonomer is a C.sub.4-10 olefin, the maximum polymerized content thereof is about 20%, and when both ethyelen and a C.sub.4-10 olefin are used the maximum polymerized content is about 30%; and applied to at least one surface of the base film or sheet, a layer of a film or sheet material comprising an olefin polymer composition which is prepared by polymerization in at least two stages, has a flexural modulus of less than 150 MPa, and is comprised of

(a) from about 10 to 50 parts of a propylene homopolymer having an isotactic index greater than 80, or a copolymer selected from the group consisting of (i) propylene and ethylene, (ii) propylene, ethylene and a CH.sub.2 --CHR alpha-olefin, where R is a C.sub.2-8 straight or branched alkyl, and (iii) propylene and an alpha-olefin as defined in (a) (ii), said copolymer containing over 80% propylene and having an isotactic index greater than 80;

(b) from about 5 to 20 parts of a semi-crystalline, essentially linear copolymer fraction having a crystallinity of about 20 to 60% wherein the copolymer is selected from the group consisting of (i) ethylene and propylene containing over 55% ethylene, (ii) ethylene, propylene, and an alpha-olefin as defined in (a) (ii) containing from 1 to 10% of the alpha-olefin and over 55% of both ethylene and alpha-olefin, and (iii) ethylene and an alpha-olefin as defined in (a) (ii) containing over 55% of said alpha-olefin, which copolymer is insoluble in xylene at room or ambient temperature; and

(c) from about 40 to 80 parts of a copolymer fraction wherein the copolymer is selected from the group consisting of (i) ethylene and propylene containing from 20% to less than 40% ethylene, (ii) ethylene, propylene, and an alpha-olefin as defined in (a) (ii) wherein the alpha-olefin is present in an amount of 1 to 10% and the amount of ethylene and alpha-olefin present is from 20% to less than 40%, and (iii) ethylene and an alpha-olefin as defined in (a) (ii) containing from 20% to less than 40% of said alpha-olefin, and optionally with 0.5 to 10% of a diene, said copolymer fraction being soluble in xylene at ambient temperature, and having an intrinsic viscosity of from 1.5 to 4.0 dl/g;

with the total of the (b) and (c) fractions, based on the total olefin polymer composition, being from about 50% to 90%, and the weight ratio of (b)/(c) being less than 0.4.

2. A film or sheet article comprising a base film or sheet of a crystalline homopolymer of a C.sub.2-10 alpha-olefin monomer or of a copolymer selected from the group consisting of (i) propylene with ethylene, (ii) propylene with ethylene and a C.sub.4-10 alpha-olefin monomer, and (iii) propylene with a C.sub.4-10 alpha-olefin monomer, provided that, when the comonomer is ethylene, the maximum polymerized ethylene content is about 10%, when the comonomer is a C.sub.4-10 olefin, the maximum polymerized content thereof is about 20%, and when both ethyelen and a C.sub.4-10 olefin are used the maximum polymerized content is about 30%; and applied to at least one surface of the base film or sheet, a layer of the material of claim 1 wherein (a) is a copolymer of propylene and butene-1 and (c) is a copolymer of propylene and ethylene.

3. A film or sheet article comprising a base film or sheet of a crystalline homopolymer of a C.sub.2-10 alpha-olefin monomer or of a copolymer selected from the group consisting of (i) propylene with ethylene, (ii) propylene with ethylene and a C.sub.4-10 alpha-olefin monomer, and (iii) propylene with a C.sub.4-10 alpha-olefin monomer, provided that, when the comonomer is ethylene, the maximum polymerized ethylene content is about 10%, when the comonomer is a C.sub.4-10 olefin, the maximum polymerized content thereof is about 20%, and when both ethyelen and a C.sub.4-10 olefin are used the maximum polymerized content is about 30%; and applied to at lest one surface of the base film or sheet, a layer of the material of claim 1 wherein (a) is a copolymer of propylene and butene-1 and (c) is a terpolymer of propylene, ethylene and butene-1.

4. A film or sheet article comprising a base film or sheet of a metallic substrate having applied to at least one surface thereof a layer of a film or sheet material comprising an olefin polymer composition which is prepared by polymerization in at least two stages, has a flexural modulus of less than 150 MPa, and is comprised of

(a) from about 10 to 50 parts of a propylene homopolymer having an isotactic index greater than 80, or a copolymer selected from the group consisting of (i) propylene and ethylene, (ii) propylene, ethylene and a CH.sub.2 --CHR alpha-olefin, where R is a C.sub.2-8 straight or branched alkyl, and (iii) propylene and an alpha-olefin as defined in (ii), said copolymer containing over 80% propylene and having an isotactic index greater than 80;

(b) from about 5 to 20 parts of a semi-crystalline, essentially linear copolymer fraction having a crystallinity of about 20 to 60% wherein the copolymer is selected from the group consisting of (i) ethylene and propylene containing over 55% ethylene, (ii) ethylene, propylene, and an alpha-olefin as defined in (a) (ii) containing from 1 to 10% of the alpha-olefin and over 55% of both ethylene and alpha-olefin, and (iii) ethylene and an alpha-olefin as defined in (a) (ii) containing over 55% of said alpha-olefin, which copolymer is insoluble in xylene at room or ambient temperature; and

(c) from about 40 to 80 parts of a copolymer fraction wherein the copolymer is selected from the group consisting of (i) ethylene and propylene containing from 20% to less than 40% ethylene, (ii) ethylene, propylene, and an alpha-olefin as defined in (a) (ii) wherein the alpha-olefin is present in an amount of 1 to 10% and the amount of ethylene and alpha-olefin present is from 20% to less than 40%, and (iii) ethylene and an alpha-olefin as defined in (a) (ii) containing from 20% to less than 40% of said alpha-olefin, and optionally with 0.5 to 10% of a diene, said copolymer fraction being soluble in xylene at ambient temperature, and having an intrinsic viscosity of from 1.5 to 4.0 dl/g;

with the total of the (b) and (c) fractions, based on the total olefin polymer composition, being from about 50% to 90%, and the weight ratio of (b)/(c) being less than 0.4.

5. A film or sheet article comprising a base film or sheet of a metallic substrate having applied to at least one surface thereof a layer of the material of claim 1 wherein (a) is a copolymer of propylene and butene-1 and (c) is a copolymer of propylene and ethylene.

6. A film or sheet article comprising a base film or sheet of a metallic substrate having applied to at least one surface thereof a layer of the material of claim 1 wherein (a) is a copolymer of propylene and butene-1 and (c) is a terpolymer of propylene, ethylene and butene-1.