Patent Description:
Films of heterophasic propylene copolymers are used in a wide range of areas, e.g. food packaging, such as wrapping films and containers. Such films are known for their well-balanced properties like strength, stiffness, transparency and resistance to impact, among others. Metallized films are also used as a packaging material, for example, in the form of a layered polypropylene film/aluminium foil structure.

Whilst such films have been shown to have well-balanced properties, optimising the balance of mechanical properties, optical properties and sealing properties remains a fine art, with compromises to some properties being required to obtain improvements in other areas.

In order to obtain a good balance of mechanic properties, compositions based upon Ziegler-Natta-catalysed polypropylene are often used; however, such compositions can often have less ideal sealing properties and optical properties, especially after steam sterilization.

<CIT> describes heterophasic polypropylene compositions having optimised optical and mechanical properties as well as low amount of extractables. These compositions are obtainable through the use of Ziegler-Natta catalysis. The heterophasic polypropylene compositions are processed into films, which are said to be useful for food packaging applications.

<CIT> describes a metallocene-based heterophasic polypropylene composition having high stiffness, high toughness and high transparency, wherein the beneficial properties are obtained through blending the metallocene-based heterophasic polypropylene with a minor amount of Ziegler-Natta-based heterophasic polypropylene. The metallocene-based heterophasic polypropylene copolymer component present in the composition has a relatively low ethylene content and soluble fraction content.

Despite developments in this field, there remains a need to provide a simple heterophasic polypropylene composition having improved sealing and optical properties without sacrificing the mechanical performance, in particular for materials that are easy to produce and process, in particular not requiring extra process steps or additional polymer components to achieve the desired properties.

The present invention is based upon the finding that a heterophasic propylene ethylene copolymer composition having specific properties, including melting temperature and crystalline/soluble fraction contents according to CRYSTEX QC analysis and the individual properties of each fraction, has improved sealing properties and optical properties both before and after steam sterilization.

The present invention is directed to a heterophasic propylene ethylene copolymer composition (HECO) having a melt flow rate (MFR<NUM>) measured according to ISO <NUM> at <NUM> and <NUM> in the range from <NUM> to <NUM>/<NUM>, a total ethylene content C(C2), as determined by quantitative IR spectroscopy, in the range from <NUM> to <NUM> mol-%, and a melting temperature (Tm) measured by differential scanning calorimetry (DSC) in the range from <NUM> to <NUM>, comprising:.

wherein the heterophasic propylene ethylene copolymer composition is characterized in terms of its soluble fraction (SF) and crystalline fraction (CF) as determined by CRYSTEX QC analysis:.

In another aspect, the present invention is directed to a film, preferably a cast film, comprising at least <NUM> wt. -% of the inventive heterophasic propylene ethylene copolymer composition (HECO).

A heterophasic polypropylene is a propylene-based copolymer with a crystalline matrix phase, which can be a propylene homopolymer or a random copolymer of propylene and at least one alpha-olefin comonomer, and an elastomeric phase dispersed therein. In case of a random heterophasic propylene copolymer, said crystalline matrix phase is a random copolymer of propylene and at least one alpha-olefin comonomer. The polymers according to the present invention have such morphology.

The elastomeric phase can be a propylene copolymer with a high amount of comonomer that is not randomly distributed in the polymer chain but is distributed in a comonomer-rich block structure and a propylene-rich block structure. A heterophasic polypropylene usually differentiates from a one-phasic propylene copolymer in that it shows two distinct glass transition temperatures Tg which are attributed to the matrix phase and the elastomeric phase.

A propylene homopolymer is a polymer that essentially consists of propylene monomer units. Due to impurities especially during commercial polymerization processes, a propylene homopolymer can comprise up to <NUM> mol-% comonomer units, preferably up to <NUM> mol-% comonomer units and most preferably up to <NUM> mol-% comonomer units. A propylene random copolymer is a copolymer of propylene monomer units and comonomer units, preferably selected from ethylene and C4-C12 alpha-olefins, in which the comonomer units are distributed randomly over the polymeric chain. The propylene random copolymer can comprise comonomer units from one or more comonomers different in their amounts of carbon atoms. In the following amounts are given in % by weight (wt. -%) unless it is stated otherwise.

In a heterophasic propylene copolymer the matrix and elastomeric phases cannot be separated and measured, since the elastomeric phase is dispersed within the crystalline matrix. In order to characterize the matrix and elastomeric phases of a heterophasic propylene copolymer several methods are known. One method is the extraction with xylene of a fraction that contains for the most part the elastomeric phase, thus separating a xylene cold soluble (XCS) fraction from a xylene cold insoluble (XCI) fraction. The XCS fraction contains for the most part the elastomeric phase and only a small part of the matrix phase, whereas the XCI fraction contains for the most part the matrix phase and only a small part of the elastomeric phase.

As an alternative method the separation of a crystalline fraction and a soluble fraction with the CRYSTEX QC method using trichlorobenzene (TCB) as a solvent. This method is described below in the determination methods section. The crystalline fraction (CF) contains for the most part the matrix phase and only a small part of the elastomeric phase and the soluble fraction (SF) contains for the most part the elastomeric phase and only a small part of the matrix phase. In some cases, this method results in more useful data, since the crystalline fraction (CF) and the soluble fraction (SF) more accurately correspond to the matrix and elastomeric phases respectively. Due to the differences in the separation methods of xylene extraction and CRYSTEX QC method the properties of XCS/XCI fractions on the one hand and crystalline/soluble (CF/SF) fractions on the other hand are not exactly the same, meaning that the amounts of matrix phase and elastomeric phase can differ as well as the properties.

The heterophasic propylene ethylene copolymer composition (HECO) of the present invention has a content of crystalline fraction (CF) within the range from <NUM> to <NUM> wt. -%, more preferably <NUM> to <NUM> wt. -%, based on the total weight of the heterophasic propylene ethylene copolymer composition.

The crystalline fraction (CF) of the heterophasic propylene ethylene copolymer composition (HECO) of the present invention has an intrinsic viscosity iV(CF) measured according to DIN ISO <NUM>/<NUM>, October <NUM> (in Decalin at <NUM>) in the range from <NUM> to <NUM> dl/g, more preferably in the range from <NUM> to <NUM> dl/g, most preferably in the range from <NUM> to <NUM> dl/g.

The crystalline fraction (CF) of the heterophasic propylene ethylene copolymer composition (HECO) of the present invention has an ethylene content C2(CF), as determined by quantitative IR spectroscopy, in the range from <NUM> to <NUM> mol-%, more preferably in the range from <NUM> to <NUM> mol-%, most preferably in the range from <NUM> to <NUM> mol-%.

The heterophasic propylene ethylene copolymer composition (HECO) of the present invention has a content of soluble fraction (SF) within the range from <NUM> to <NUM> wt. -%, more preferably <NUM> to <NUM> wt. -%, based on the total weight of the heterophasic propylene ethylene copolymer composition.

The soluble fraction (SF) of the heterophasic propylene ethylene copolymer composition (HECO) of the present invention has an intrinsic viscosity iV(SF) measured according to DIN ISO <NUM>/<NUM>, October <NUM> (in Decalin at <NUM>) in the range from <NUM> to <NUM> dl/g, more preferably in the range from <NUM> to <NUM> dl/g, most preferably in the range from <NUM> to <NUM> dl/g.

The soluble fraction (SF) of the heterophasic propylene ethylene copolymer composition (HECO) of the present invention has an ethylene content C2(SF), as determined by quantitative IR spectroscopy, in the range from <NUM> to <NUM> mol-%, more preferably in the range from <NUM> to <NUM> mol-%, most preferably in the range from <NUM> to <NUM> mol-%.

According to the present invention, the ratio of the intrinsic viscosities of the two fractions, iV(SF)/iV(CF), is preferably in the range from <NUM> to <NUM>, more preferably in the range from <NUM> to <NUM>, most preferably in the range from <NUM> to <NUM>.

The heterophasic propylene ethylene copolymer composition (HECO) of the present invention has a melt flow rate (MFR<NUM>) measured according to ISO <NUM> at <NUM> and <NUM> in the range from <NUM> to <NUM>/<NUM>, more preferably from <NUM> to <NUM>/<NUM>, most preferably in the range from <NUM> to <NUM>/<NUM>.

The heterophasic propylene ethylene copolymer composition (HECO) of the present invention has an ethylene content C(C2), as determined by quantitative IR spectroscopy, preferably in the range from <NUM> to <NUM> mol-%, more preferably in the range from <NUM> to <NUM> mol-%, most preferably in the range from <NUM> to <NUM> mol-%.

The heterophasic propylene ethylene copolymer composition (HECO) of the present invention preferably has an intrinsic viscosity (iV) measured according to DIN ISO <NUM>/<NUM>, October <NUM> (in Decalin at <NUM>) in the range from <NUM> to <NUM> dl/g, more preferably from <NUM> to <NUM> dl/g, most preferably in the range from <NUM> to <NUM> dl/g.

The crystalline matrix component (M) of the heterophasic propylene ethylene copolymer composition (HECO) preferably has a melt flow rate (MFR<NUM>), measured according to ISO <NUM> at <NUM> and <NUM> in the range from <NUM> to <NUM>/<NUM>, more preferably from <NUM> to <NUM>/<NUM>, yet more preferably from <NUM> to <NUM>/<NUM>, most preferably from <NUM> to <NUM>/<NUM>.

It is preferred that the crystalline matrix component (M) of the heterophasic propylene ethylene copolymer composition (HECO) of the present invention is a propylene homopolymer.

When the crystalline matrix component (M) of the heterophasic propylene ethylene copolymer composition (HECO) is a propylene homopolymer, it preferably has an isotactic pentad concentration [mmmm] as determined by <NUM>C-NMR spectroscopy of more than <NUM>%, and a content of <NUM>,<NUM>-regiodefects in the range from <NUM> to <NUM> mol-%. These values are indicative of heterophasic propylene ethylene copolymers that have been produced in the presence of a single-site catalyst.

In many similar heterophasic propylene copolymers, it is necessary to adjust the rheological and mechanical properties of the final composition by treatment of the raw heterophasic propylene copolymer with a radical initiator, often in the extrusion step. This process may be known as visbreaking. The properties of the heterophasic propylene ethylene copolymer composition (HECO) of the present invention are suitably desirable, and therefore no visbreaking (or similar treatment) is necessary to obtain superior properties. It is, therefore, preferred that the heterophasic propylene ethylene copolymer composition (HECO) is free from radical initiators and decomposition products thereof, more preferably the heterophasic propylene ethylene copolymer composition (HECO) has not been visbroken.

The heterophasic propylene ethylene copolymer composition (HECO) of the present invention preferably has a glass transition temperature associated with the amorphous propylene-ethylene elastomer (Tg(E)), measured according to ISO <NUM>-<NUM>, in the range from -<NUM> to -<NUM> more preferably in the range from -<NUM> to -<NUM>, most preferably in the range from -<NUM> to -<NUM>.

The heterophasic propylene ethylene copolymer composition (HECO) of the present invention preferably has a glass transition temperature associated with the crystalline matrix (Tg(M)), measured according to ISO <NUM>-<NUM>, in the range from -<NUM> to <NUM> more preferably in the range from -<NUM> to <NUM>, most preferably in the range from -<NUM> to <NUM>.

The heterophasic propylene ethylene copolymer composition (HECO) of the present invention preferably has a melting temperature (Tm) measured by differential scanning calorimetry (DSC) in the range from <NUM> to <NUM>, more preferably in the range from <NUM> to <NUM>, most preferably in the range from <NUM> to <NUM>. These values are indicative of heterophasic propylene ethylene copolymers that have been produced in the presence of a single-site catalyst.

The heterophasic propylene ethylene copolymer composition (HECO) of the present invention preferably has a crystallisation temperature (Tc) measured by differential scanning calorimetry (DSC) in the range from <NUM> to <NUM>, more preferably in the range from <NUM> to <NUM>, most preferably in the range from <NUM> to <NUM>.

The heterophasic propylene ethylene copolymer composition (HECO) of the present invention preferably has a flexural modulus measured according to ISO <NUM> in the range from <NUM> to <NUM> MPa, more preferably in the range from <NUM> to <NUM> MPa, most preferably in the range from <NUM> to <NUM> MPa.

The heterophasic propylene ethylene copolymer composition (HECO) of the present invention preferably has a Charpy Notched Impact Strength (NIS) measured according to ISO <NUM>-<NUM> eA at <NUM> in the range from <NUM> to <NUM> kJ/m<NUM>, more preferably in the range from <NUM> to <NUM> kJ/m<NUM>, most preferably in the range from <NUM> to <NUM> kJ/m<NUM>.

The heterophasic propylene ethylene copolymer composition (HECO) of the present invention preferably has a Charpy Notched Impact Strength (NIS) measured according to ISO <NUM>-<NUM> eA at -<NUM> in the range from <NUM> to <NUM> kJ/m<NUM>, more preferably in the range from <NUM> to <NUM> kJ/m<NUM>, most preferably in the range from <NUM> to <NUM> kJ/m<NUM>.

In addition to the fractions as discussed above, the heterophasic propylene ethylene copolymer composition of the present invention may comprise additives.

Preferably, the heterophasic propylene ethylene copolymer composition (HECO) comprises from <NUM> to <NUM> wt. -%, more preferably <NUM> to <NUM> wt. -%, still more preferably <NUM> to <NUM> wt. -%, most preferably <NUM> to <NUM> wt. -% of additives, based on the weight of the heterophasic propylene ethylene copolymer composition (HECO).

Such additives are commercially available and for example described in "<NPL>).

The heterophasic propylene copolymer (HECO) of the present invention may be polymerized by sequential polymerization in the presence of a single-site catalyst system, wherein.

In a preferred embodiment, the polymerization process is carried out in the presence of a single-site catalyst system as laid out herein.

The heterophasic polypropylene composition of the present invention is typically and preferably made in a multistep process well known in the art. A preferred multistage process is a loop-gas phase-process, such as developed by Borealis A/S, Denmark (known as BORSTAR(R) technology) described e.g. in patent literature, such as in <CIT> or in <CIT>. An alternative multistage process is the Spheripol process of LyondellBasell, USA.

The invention preferably relates to the copolymerization of propylene, ethylene and optionally further comonomers as defined above and below, in an at least two, optionally three step process so as to form the heterophasic polypropylene composition. Preferably, propylene and ethylene are the only monomers used.

Ideally, the process of the invention employs two, preferably three main reactors, a first reactor operating in bulk, a first gas phase reactor and optionally a second gas phase reactor.

The process may also utilize a prepolymerization step, taking place in a separate reactor before the three main reactors.

The crystalline matrix may preferably be present in the range of <NUM> to <NUM> wt. -%, more preferably in the range of <NUM> to <NUM> wt. -%, most preferably in the range of <NUM> to <NUM> wt. -%, based on the total weight of the heterophasic polypropylene composition.

The elastomeric phase comprised in the heterophasic polypropylene composition and dispersed in above mentioned matrix, may preferably be present in the range of <NUM> to <NUM> wt. -%, more preferably in the range of <NUM> to <NUM> wt. -%, most preferably in the range of <NUM> to <NUM> wt. -%, based on the total weight of the heterophasic polypropylene composition.

The comonomer content, C(C2) (total), of the inventive polymer may be in the range of <NUM> to <NUM> mol-%, more preferably in the range from <NUM> to <NUM> mol-%, most preferably in the range from <NUM> to <NUM> mol-%.

The crystalline matrix being a propylene homo- or copolymer is produced in a bulk step, then transferred to the second stage in which the amorphous propylene ethylene elastomer is produced in a first gas phase reactor (GPR1) in the presence of the first polypropylene fraction.

The comonomer content of the crystalline matrix may be in the range of <NUM> to <NUM> mol-%, preferably in the range of <NUM> to <NUM> mol-%, more preferably in the range of <NUM> to <NUM> mol-%.

It is particularly preferable that the crystalline matrix (a) is a propylene homopolymer and comprises <NUM> wt. -% of comonomer.

The MFR of the crystalline matrix may be in the range of <NUM> to <NUM>/<NUM>, more preferably in the range from <NUM> to <NUM>/<NUM>, most preferably in the range from <NUM> to <NUM>/<NUM>. This applies regardless of the (bi)-modality of the crystalline matrix.

In case, the crystalline matrix is bimodal, then the first polypropylene fraction is produced in a bulk step, then transferred to the second stage in which the second polypropylene fraction is prepared in a first gas phase reactor (GPR1) in the presence of the first polypropylene fraction. This mixture, being the crystalline matrix and comprising said first and second polypropylene fractions together, is transferred to the third stage in which the amorphous propylene-ethylene elastomer is prepared in a gas phase reactor (GPR2) in the presence of the crystalline matrix.

The MFR<NUM> of the polymer produced in the first stage, being the first polypropylene fraction, may be in the range of <NUM> to <NUM>/<NUM>, more preferably in the range from <NUM> to <NUM>/<NUM>, most preferably in the range from <NUM> to <NUM>/<NUM>.

The MFR<NUM> of the polymer produced in the second stage, being the second polypropylene fraction, may be in the range of <NUM> to <NUM>/<NUM>, more preferably in the range from <NUM> to <NUM>/<NUM>, most preferably in the range from <NUM> to <NUM>/<NUM>.

Given the second polypropylene fraction is produced in the presence of the first polypropylene fraction, it is understood, that it's properties cannot be analysed as such, but have to be determined based on the properties of the first polypropylene fraction and the properties of the crystalline fraction.

In a preferred embodiment, the heterophasic polypropylene composition comprises a1) <NUM> - <NUM> wt. -%, preferably in the range of <NUM> to <NUM> wt. -%, more preferably in the range of <NUM> to <NUM> wt. -% of a first polypropylene fraction having an MFR<NUM> of <NUM> to <NUM>/<NUM>, a2) <NUM> - <NUM> wt. -%, preferably in the range of <NUM> to <NUM> wt. -%, more preferably in the range of <NUM> to <NUM> wt. -% of a second polypropylene fraction having an MFR<NUM> of <NUM> to <NUM>/<NUM>, b) <NUM> to <NUM> wt. -% of the amorphous propylene ethylene elastomer, preferably in the range of <NUM> to <NUM> wt. -%, most preferably in the range of <NUM> to <NUM> wt.

Preferably, the amount of the first polypropylene fraction is equal or higher than the amount of the second polypropylene fraction based on the total weight of the crystalline matrix.

The amount of the first polypropylene fraction may be in the range of <NUM> to <NUM> wt. -%, preferably <NUM> to <NUM> wt. -%, more preferably in the range of <NUM> to <NUM> wt. -% based on the total weight of the crystalline matrix.

The amount of the second polypropylene fraction may be in the range of <NUM> to <NUM> wt. -%, preferably <NUM> to <NUM> wt. -%, more preferably in the range of <NUM> to <NUM> wt. -% based on the total weight of the crystalline matrix.

The ratio of the amount of the first and the second polypropylene fraction may be in the ranges of <NUM>:<NUM> to <NUM>:<NUM>, like <NUM>:<NUM> to <NUM>:<NUM>, preferably <NUM>:<NUM> to <NUM>:<NUM>.

For bulk and gas phase copolymerization reactions, the reaction temperature used will generally be in the range <NUM> to <NUM> (e.g. <NUM> to <NUM>), the reactor pressure will generally be in the range <NUM> to <NUM> bar for gas phase reactions with bulk polymerization operating at slightly higher pressures. The residence time will generally be <NUM> to <NUM> hours (e.g. <NUM> to <NUM> hours).

The comonomer content of the first and second polypropylene fraction may be same or different and independently chosen from each other.

The comonomer content of the polymer produced in the first stage, namely the first polypropylene fraction, may be in the range of <NUM> to <NUM> mol-%, preferably in the range of <NUM> to <NUM> mol-%, more preferably in the range of <NUM> to <NUM> mol-%.

It is particularly preferable that the first polypropylene fraction is a propylene homopolymer and comprises <NUM> wt. -% of comonomer.

The comonomer content of the polymer produced in the second stage, namely the second polypropylene fraction, may be in the range of <NUM> to <NUM> mol-%, preferably in the range of <NUM> to <NUM> mol-%, more preferably in the range of <NUM> to <NUM> mol-%.

It is particularly preferable, that the second polypropylene fraction is a propylene homopolymer and comprises <NUM> wt. -% of comonomer.

Within this application it is understood, that the comonomer content of the crystalline matrix, when available as distinct material sample, is determined via quantitative FT-IR spectroscopy calibrated by <NUM>C-NMR spectroscopy. When the comonomer content of the matrix and the dispersed fraction should be evaluated starting from the final polymer (comprising both the matrix and the dispersed fraction), then the matrix (and its properties) is reflected by the crystalline fraction (CF) determined according to CRYSTEX QC analysis. Accordingly, the dispersed amorphous propylene ethylene elastomer is reflected by the soluble fraction (SF) determined according to CRYSTEX QC analysis.

The heterophasic polypropylene composition according to the invention is preferably obtainable by a catalyst system comprising by a single-site catalyst, more preferably being obtainable by a metallocene catalyst complex and cocatalysts.

Preferred complexes of the metallocene catalyst include:.

Especially preferred is rac-anti-dimethylsilanediyl[<NUM>-methyl-<NUM>,<NUM>-bis-(<NUM>',<NUM>'-dimethylphenyl)-<NUM>,<NUM>,<NUM>,<NUM>-tetrahydro-s indacen-<NUM>-yl] [<NUM>-methyl-<NUM>-(<NUM>',<NUM>'-dimethylphenyl)-<NUM>-methoxy-<NUM>-tert-butylinden-<NUM>-yl] zirconium dichloride.

To form an active catalytic species it is normally necessary to employ a cocatalyst as is well known in the art.

According to the present invention a cocatalyst system comprising a boron containing cocatalyst and an aluminoxane cocatalyst is used in combination with the above defined metallocene catalyst complex.

The aluminoxane cocatalyst can be one of formula (I):
<CHM>
where n is from <NUM> to <NUM> and R has the meaning below.

Aluminoxanes are formed on partial hydrolysis of organoaluminum compounds, for example those of the formula AlR<NUM>, AlR<NUM>Y and Al<NUM>R<NUM>Y<NUM> where R can be, for example, C1- C10-alkyl, preferably C1-C5-alkyl, or C3-C10-cycloalkyl, C7-C12-arylalkyl or -alkylaryl and/or phenyl or naphthyl, and where Y can be hydrogen, halogen, preferably chlorine or bromine, or C1-C10-alkoxy, preferably methoxy or ethoxy. The resulting oxygen-containing aluminoxanes are not in general pure compounds but mixtures of oligomers of the formula (I).

The preferred aluminoxane is methylaluminoxane (MAO). Since the aluminoxanes used according to the invention as cocatalysts are not, owing to their mode of preparation, pure compounds, the molarity of aluminoxane solutions hereinafter is based on their aluminium content.

Also a boron containing cocatalyst is used in combination with the aluminoxane cocatalyst.

The catalyst complex ideally comprises a co-catalyst, certain boron containing cocatalysts are preferred. Especially preferred borates of use in the invention therefore comprise the trityl, i.e. triphenylcarbenium, ion. Thus the use of Ph<NUM>CB(PhF<NUM>)<NUM> and analogues therefore are especially favoured.

The catalyst system of the invention is used in supported form. The particulate support material used is silica or a mixed oxide such as silica-alumina, in particular silica. The use of a silica support is preferred. The skilled practitioner is aware of the procedures required to support a metallocene catalyst.

In a preferred embodiment, the catalyst system corresponds to the ICS3 of <CIT>.

The present invention is further directed to a film comprising at least <NUM> wt. -% of the heterophasic propylene ethylene copolymer composition (HECO) as described in the previous sections.

The film, more preferably the cast film, comprises at least <NUM> wt. -%, more preferably at least <NUM> wt. -%, yet more preferably at least <NUM> wt. -%, still more preferably at least <NUM> wt. -%, of the heterophasic propylene ethylene copolymer composition (HECO).

Other polymeric components in addition to the heterophasic propylene ethylene copolymer composition can be present in the film, more preferably the cast film; however, it is preferred that the heterophasic propylene ethylene copolymer composition (HECO) is the only polymeric component in the film, more preferably the cast film.

In one particularly preferred embodiment, the film, more preferably the cast film, consists of the heterophasic propylene ethylene copolymer composition (HECO).

It is preferred that the film, more preferably the cast film, has a thickness in the range from <NUM> to <NUM>, more preferably in the range from <NUM> to <NUM>, most preferably in the range from <NUM> to <NUM>.

The film, more preferably the cast film, comprising the heterophasic propylene ethylene copolymer composition (HECO) preferably has a seal strength, measured according to the method described herein, in the range from <NUM> to <NUM> N, more preferably in the range from <NUM> to <NUM> N, most preferably in the range from <NUM> to <NUM> N.

It is preferred that the film, more preferably the cast film, has a haze value before steam sterilization, measured according to ASTM D1003, of below <NUM>%, more preferably below <NUM>%, most preferably below <NUM>%.

It is preferred that the film, more preferably the cast film, has a haze value after steam sterilization, measured according to ASTM D1003, of below <NUM>%, more preferably below <NUM>%, most preferably below <NUM>%.

It is preferred that the film, more preferably the cast film, has a tensile modulus in the machine direction (MD), measured according to ISO <NUM>-<NUM>, in the range from <NUM> to <NUM> MPa, more preferably in the range from <NUM> to <NUM> MPa, most preferably in the range from <NUM> to <NUM> MPa.

It is preferred that the film, more preferably the cast film, has a tensile modulus in the transverse direction (TD), measured according to ISO <NUM>-<NUM>, in the range from <NUM> to <NUM> MPa, more preferably in the range from <NUM> to <NUM> MPa, most preferably in the range from <NUM> to <NUM> MPa.

The film, more preferably the cast film, may be a monolayer film. Alternatively, the film, more preferably the cast film, may be present as a single layer in a multilayer film.

When the film is present as a single layer in a multilayer film the film can be produced by any means known in the art. It is preferred that the multilayers films are prepared by means of cast film co-extrusion.

The melt flow rate (MFR) is determined according to ISO <NUM> and is indicated in g/<NUM>. The MFR is an indication of the flowability, and hence the processability, of the polymer. The higher the melt flow rate, the lower the viscosity of the polymer. The MFR<NUM> of polypropylene is determined at a temperature of <NUM> and a load of <NUM>.

Quantitative nuclear-magnetic resonance (NMR) spectroscopy was used to quantify the stereo-regularity (tacticity) and regio-regularity of the crystalline matrix of the polymers. Quantitative <NUM>C {<NUM>H} NMR spectra were recorded in the solution-state using a Bruker Advance III <NUM> NMR spectrometer operating at <NUM> and <NUM> for <NUM> and 13C respectively. All spectra were recorded using a <NUM>C optimised <NUM> extended temperature probe head at <NUM> using nitrogen gas for all pneumatics.

For polypropylene homopolymers approximately <NUM> of material was dissolved in <NUM>,<NUM>-tetrachloroethane-d2 (TCE-d2). To ensure a homogenous solution, after initial sample preparation in a heat block, the NMR tube was further heated in a rotatary oven for at least <NUM> hour. Upon insertion into the magnet, the tube was spun at <NUM>. This setup was chosen primarily for the high resolution needed for tacticity distribution quantification (<NPL>; <NPL>). Standard single-pulse excitation was employed utilising the NOE and bi-level WALTZ <NUM> decoupling scheme (<NPL>; <NPL>). A total of <NUM> (<NUM>) transients were acquired per spectra.

Quantitative 13C{<NUM>} NMR spectra were processed, integrated and relevant quantitative properties determined from the integrals using proprietary computer programs. For polypropylene homopolymers all chemical shifts are internally referenced to the methyl isotactic pentad (mmmm) at <NUM> ppm. The tacticity distribution was quantified through integration of the methyl region between <NUM>-<NUM> ppm correcting for any sites not related to the stereo sequences of interest (<NPL>; <NPL>).

Specifically the influence of regio defects and comonomer on the quantification of the tacticity distribution was corrected for by subtraction of representative regio defect and comonomer integrals from the specific integral regions of the stereo sequences. The isotacticity was determined at the pentad level and reported as the percentage of isotactic pentad (mmmm) sequences with respect to all pentad sequences: <MAT>.

The presence of <NUM>,<NUM> erythro regio defects was indicated by the presence of the two methyl sites at <NUM> and <NUM> ppm and confirmed by other characteristic sites.

Characteristic signals corresponding to other types of regio defects were not observed (<NPL>). The amount of <NUM>,<NUM> erythro regio defects was quantified using the average integral of the two characteristic methyl sites at <NUM> and <NUM> ppm: <MAT>.

The total amount of propene was quantified as the sum of primary inserted propene and all other present regio defects: <MAT>.

The mole percent of <NUM>,<NUM> erythro regio defects was quantified with respect to all propene: <MAT>.

The glass transition temperature Tg is determined by dynamic mechanical thermal analysis (DMTA) according to ISO <NUM>-<NUM>. The measurements are done in torsion mode on compression moulded samples (40x10x1 mm3) between -<NUM> and +<NUM> with a heating rate of <NUM>/min and a frequency of <NUM>. Storage modulus G' is determined at +<NUM> according ISO <NUM>-<NUM>:<NUM>. The measurements are done in torsion mode on compression moulded samples (40x10x1 mm3) between -<NUM> and +<NUM> with a heating rate of <NUM>/min and a frequency of <NUM>.

The flexural modulus was determined in <NUM>-point-bending at <NUM> according to ISO <NUM> on 80x10x4 mm<NUM> test bars injection moulded in line with EN ISO <NUM>-<NUM>.

The Charpy notched impact strength (NIS) was measured according to ISO <NUM>1eA at +<NUM> or -<NUM>, using injection moulded bar test specimens of 80x10x4 mm<NUM> prepared in accordance with EN ISO <NUM>-<NUM>.

The crystalline (CF) and soluble fractions (SF) of the polypropylene (PP) compositions as well as the comonomer content and intrinsic viscosities of the respective fractions were analyzed by the CRYSTEX QC, Polymer Char (Valencia, Spain).

A schematic representation of the CRYSTEX QC instrument is shown in <FIG>. The crystalline and amorphous fractions are separated through temperature cycles of dissolution at <NUM>, crystallization at <NUM> and re-dissolution in a1,<NUM>,<NUM>-trichlorobenzene (<NUM>,<NUM>,<NUM>-TCB) at <NUM> as shown in <FIG>. Quantification of SF and CF and determination of ethylene content (C2) are achieved by means of an infrared detector (IR4) and an online <NUM>-capillary viscometer, which is used for the determination of the intrinsic viscosity (iV).

The IR4 detector is a multiple wavelength detector detecting IR absorbance at two different bands (CH3 and CH2) for the determination of the concentration and the Ethylene content in Ethylene-Propylene copolymers. IR4 detector is calibrated with series of <NUM> EP copolymers with known Ethylene content in the range of <NUM> wt. -% to <NUM> wt. -% (determined by <NUM>C-NMR spectroscopy) and various concentration between <NUM> and <NUM>/ml for each used EP copolymer used for calibration.

The amount of Soluble fraction (SF) and Crystalline Fraction (CF) are correlated through the XS calibration to the "Xylene Cold Soluble" (XCS) quantity and respectively Xylene Cold Insoluble (XCI) fractions, determined according to standard gravimetric method as per ISO16152. XS calibration is achieved by testing various EP copolymers with XS content in the range <NUM>-<NUM> wt.

The intrinsic viscosity (iV) of the parent EP copolymer and its soluble and crystalline fractions are determined with a use of an online <NUM>-capillary viscometer and are correlated to corresponding iV's determined by standard method in decalin according to ISO <NUM>. Calibration is achieved with various EP PP copolymers with iV = <NUM>-<NUM> dL/g.

A sample of the PP composition to be analyzed is weighed out in concentrations of <NUM>/ml to <NUM>/ml. After automated filling of the vial with <NUM>,<NUM>,<NUM>-TCB containing <NUM>/l <NUM>,<NUM>-tert-butyl-<NUM>-methylphenol (BHT) as antioxidant, the sample is dissolved at <NUM> until complete dissolution is achieved, usually for <NUM>, with constant stirring of 800rpm.

As shown in a <FIG>, a defined volume of the sample solution is injected into the column filled with inert support where the crystallization of the sample and separation of the soluble fraction from the crystalline part is taking place. This process is repeated two times. During the first injection the whole sample is measured at high temperature, determining the iV[dl/g] and the C2[wt. -%] of the PP composition. During the second injection, the soluble fraction (at low temperature) and the crystalline fraction (at high temperature) with the crystallization cycle are measured (wt. -% C2, iV).

The intrinsic viscosity (iV) is measured according to DIN ISO <NUM>/<NUM>, October <NUM>, in Decalin at <NUM>.

Haze was determined according to ASTM D1003-<NUM> on 60x60x1 mm<NUM> plaques injection moulded in line with EN ISO <NUM>-<NUM> or directly on the <NUM> cast film produced in the experimental section.

The heat-seal experiments were performed on at least <NUM> film specimens of <NUM> wide by <NUM> length cut in the machine direction. The <NUM> x <NUM> Teflon coated steel heating bars were set to a temperature of <NUM>. Two films were sealed by positioning, one on top of the other using a <NUM> sealing time and <NUM> N/ mm<NUM> pressure. The resulting sealed area was <NUM> x <NUM>. The specimens were then conditioned for <NUM> days (± <NUM>) at <NUM> (± <NUM>) / <NUM> % RH (± <NUM>%). <NUM> specimens of <NUM> width were cut and tested in tensile mode at <NUM> (± <NUM>) / <NUM> % RH (± <NUM>%) on a Universal Testing Machine (Zwick Z005). The clamping distance used was <NUM>, and a test speed of <NUM>/min. The yielding force and maximum force were measured for each test specimen.

Tensile modulus in machine and transverse direction was determined according to ISO <NUM>-<NUM> at <NUM> on cast films of <NUM> thickness produced on a monolayer cast film line with a melt temperature of <NUM> and a chill roll temperature of <NUM>. Testing was performed at a cross-head speed of <NUM>/min.

Steam sterilization was performed in a Systec D series machine (Systec Inc. The samples were heated up at a heating rate of <NUM>/min starting from <NUM>. After having been kept for <NUM> at <NUM>, they were removed immediately from the steam sterilizer and stored at room temperature till processed further.

The catalyst used was Anti-dimethylsilanediyl[<NUM>-methyl-<NUM>,<NUM>-di(<NUM>,<NUM>-dimethylphenyl)-<NUM>,<NUM>,<NUM>,<NUM>-tetrahydro-s-indacen-<NUM>-yl] [<NUM>-methyl-<NUM>-(<NUM>,<NUM>-dimethylphenyl)-<NUM>-methoxy-<NUM>-tert-butylinden-<NUM>-yl] zirconium dichloride as disclosed in <CIT> as ICS3.

A steel reactor equipped with a mechanical stirrer and a filter net was flushed with nitrogen and the reactor temperature was set to <NUM>. Next silica grade DM-L-<NUM> from AGC Si-Tech Co, pre-calcined at <NUM> (<NUM>) was added from a feeding drum followed by careful pressurising and depressurising with nitrogen using manual valves. Then toluene (<NUM>) was added. The mixture was stirred for <NUM>. Next <NUM> wt. -% solution of MAO in toluene (<NUM>) from Lanxess was added via feed line on the top of the reactor within <NUM>. The reaction mixture was then heated up to <NUM> and stirred at <NUM> for additional two hours. The slurry was allowed to settle and the mother liquor was filtered off. The catalyst was washed twice with toluene (<NUM>) at <NUM>, following by settling and filtration. The reactor was cooled off to <NUM> and the solid was washed with heptane (<NUM>). Finally MAO treated SiO2 was dried at <NUM>° under nitrogen flow for <NUM> hours and then for <NUM> hours under vacuum (-<NUM> barg) with stirring. MAO treated support was collected as a free-flowing white powder found to contain <NUM>% Al by weight.

-% MAO in toluene (<NUM>) was added into a steel nitrogen blanked reactor via a burette at <NUM>. Toluene (<NUM>) was then added under stirring. The catalyst as cited above (<NUM>) was added from a metal cylinder followed by flushing with <NUM> toluene. The mixture was stirred for <NUM> minutes at <NUM>. Trityl tetrakis(pentafluorophenyl) borate (<NUM>) was then added from a metal cylinder followed by a flush with <NUM> of toluene. The mixture was stirred for <NUM> at room temperature. The resulting solution was added to a stirred cake of MAO-silica support prepared as described above over <NUM> hour. The cake was allowed to stay for <NUM> hours, followed by drying under N<NUM> flow at <NUM> for <NUM> and additionally for <NUM> under vacuum (-<NUM> barg) under stirring. Dried catalyst was sampled in the form of pink free flowing powder containing <NUM>% Al and <NUM>% Zr.

The inventive HECO IE1 was polymerized according to the conditions in Table <NUM>.

The resulting polymer powder was compounded with <NUM> ppm of Calcium cis-<NUM>,<NUM>-cyclohexanedicarboxylate (Hyperform HPN-20E), supplied by Milliken, USA, <NUM> ppm of Irganox <NUM> (<NUM>:<NUM>-blend of Pentaerythrityl-tetrakis(<NUM>-(<NUM>',<NUM>'-di-tert. butyl-<NUM>-hydroxytoluyl)-propionate and tris (<NUM>,<NUM>-di-t-butylphenyl) phosphite), supplied by BASF.

AG, Germany, and <NUM> ppm of calcium stearate, supplied by Croda, UK.

For the polymerization process of the comparative HECO CE1, a Ziegler-Natta type catalyst as used for the inventive examples of <CIT> and pre-polymerized with vinylcyclohexane to achieve nucleation with poly(vinylcyclohexane) was used. Nucleation by prepolymerization with vinylcyclohexane is described in <CIT> and <CIT> in detail. The comparative HECO CE1 was polymerized according to the conditions in Table <NUM>, using dicyclopentyl dimethoxy silane (donor D) as external donor and triethyl aluminium (TEAL) as co-catalyst. The resulting polymer powder was compounded with <NUM> ppm of Calcium cis-<NUM>,<NUM>-cyclohexanedicarboxylate (Hyperform HPN-20E, supplied by Milliken, USA), <NUM> ppm of Irganox <NUM> (<NUM>:<NUM>-blend of Pentaerythrityl-tetrakis(<NUM>-(<NUM>',<NUM>'-di-tert. butyl-<NUM>-hydroxytoluyl)-propionate and tris (<NUM>,<NUM>-di-t-butylphenyl) phosphite), supplied by BASF AG, Germany, and <NUM> ppm of calcium stearate, supplied by Croda, UK.

Films were produced on a Barmag CAST-Coex pilot line, equipped with an extruder of <NUM> diameter and an L/D ratio of <NUM>. A coathanger die with a die width of <NUM> and a die gap of <NUM> was used.

The <NUM> films were produced in cast mode with an output of <NUM>/h, a line speed of <NUM>/min and a melt temperature of <NUM>.

Roll settings: <NUM>st roll: diameter <NUM> and <NUM>; <NUM>nd roll: diameter <NUM> and <NUM>. Electric pinning via electrostatic charging was applied.

Claim 1:
A heterophasic propylene ethylene copolymer composition (HECO) having a melt flow rate (MFR<NUM>) measured according to ISO <NUM> at <NUM> and <NUM> in the range from <NUM> to <NUM>/<NUM>, a total ethylene content C(C2), as determined by quantitative IR spectroscopy, in the range from <NUM> to <NUM> mol-%, and a melting temperature (Tm) measured by differential scanning calorimetry (DSC) in the range from <NUM> to <NUM>, comprising:
a) a crystalline matrix (M) being a propylene homo- or copolymer, preferably a homopolymer; and
b) an amorphous propylene-ethylene elastomer (E);
wherein the heterophasic propylene ethylene copolymer composition is characterized in terms of its soluble fraction (SF) and crystalline fraction (CF) as determined by CRYSTEX QC analysis:
i) from <NUM> to <NUM> wt.-%, based on the total weight of the heterophasic propylene ethylene copolymer composition, of a crystalline fraction (CF) having an intrinsic viscosity iV(CF) measured according to DIN ISO <NUM>/<NUM>, October <NUM> (in Decalin at <NUM>) in the range from <NUM> to <NUM> dl/g, an ethylene content C2(CF), as determined by quantitative IR spectroscopy, in the range from <NUM> to <NUM> mol-%; and
ii) from <NUM> to <NUM> wt.-%, based on the total weight of the heterophasic propylene ethylene copolymer composition, of a soluble fraction (SF) having an intrinsic viscosity iV(SF) measured according to DIN ISO <NUM>/<NUM>, October <NUM> (in Decalin at <NUM>) in the range from <NUM> to <NUM> dl/g and an ethylene content C2(SF), as determined by quantitative IR spectroscopy, in the range from <NUM> to <NUM> mol-%.