Multilayer polypropylene film

Abstract

Multilayer film comprising at least a skin layer, a core layer and an inner layer, whereby the inner layer comprises a single site catalyst derived (SSC) random propylene ethylene copolymer having—a melting temperature (Tm) from 120° C. to 144° C., —a content of units derived from ethylene in an amount of 1.5 to 6.0 wt.-%, —the melting temperature (Tm) fulfilling the following equation Tm<156° C.−[5.2×C2 content in wt.-%]° C. wherein C2 content stands for the content of units derived from ethylene; and —a xylene cold soluble content (ISO 16152, 1st ED, 2005 Jul. 1; 25° C.) of preferably below 30 wt.-% wherein the multilayer film is free of phthalic acid esters as well as decomposition products thereof.

Claims

1. A multilayer film comprising at least a skin layer, a core layer and an inner layer, the skin layer comprising a homo polypropylene or a random propylene ethylene copolymer including up to 2.5 wt.-% units derived from ethylene, the homo polypropylene or the random propylene ethylene copolymer having a MFR.sub.2 (ISO1133, 230° C.) of 2.0 to 20 g/10 min and a melting temperature (Tm) of 145 to 170° C.; the core layer comprising a mixture obtainable by melt blending 20 to 80 wt.-% of a random heterophasic copolymer and 20 to 80 wt.-% of styrene based thermoplastic elastomer (TPE), wherein the random heterophasic copolymer comprises a matrix phase and dispersed therein an elastomer phase, whereby the matrix phase is formed by a random propylene ethylene copolymer and wherein the random heterophasic copolymer has a melting temperature (Tm) of 130° C.-145° C. a flexural modulus of 250 to 850 MPa when measured on injection molded specimens (23° C., 50% humidity, ISO 178) and wherein the random heterophasic copolymer includes an ethylene propylene copolymer rubber; and wherein the styrene based thermoplastic elastomer (TPE) has a styrene content of from 5 to 20 wt.-%, and the inner layer comprising a single site catalyst derived (SSC) random propylene ethylene copolymer having a melting temperature (Tm) from 120° C. to 144° C., a content of units derived from ethylene in an amount of 1.5 to 6.0 wt.-%, the melting temperature (Tm) fulfilling the following equation
Tm<156° C.−[5.2×C2 content in wt.-%]° C. wherein C2 content stands for the content of units derived from ethylene; and a xylene cold soluble content (ISO 16152, 1st ED, 2005 Jul. 1; 25° C.) of preferably below 30 wt.-% wherein the multilayer film is free of phthalic acid esters as well as decomposition products thereof.

2. The multilayer film according to claim 1, wherein xylene cold soluble fraction (XCS) of the random heterophasic copolymer contributing to the core layer has an intrinsic viscosity of 1.0 to 2.0 dl/g (DIN ISO 1628/1, 10/1999; Decalin, 135° C.).

3. The multilayer film according to claim 1 having a total thickness of 50 to 250 micrometer.

4. The multilayer film according to claim 1, wherein the core layer has a thickness of 50 to 85% with respect to the thickness of the multilayer film.

5. The multilayer film according to claim 1, wherein the thicknesses of the skin layer is 10 to 25% with respect to the total thickness of the multilayer film and/or wherein the thicknesses of the inner layer is 10 to 25% with respect to the total thickness of the multilayer film.

6. The multilayer film according to claim 1, wherein the skin layer consists of the homo polypropylene or random propylene ethylene copolymer; and/or the core layer consists of the mixture obtainable by melt blending 20 to 80 wt.-% of a random heterophasic copolymer and 20 to 80 wt.-% of styrene based thermoplastic elastomer (TPE); and/or the inner layer consists of the single site catalyst derived (SSC) random propylene ethylene copolymer, or the inner layer consists of a mixture obtainable by blending the single site catalyst derived (SSC) random propylene ethylene copolymer and a propylene ethylene elastomer having an ethylene content of less than 20 wt.-%; or the inner layer consists of a mixture obtainable by blending the single site catalyst derived (SSC) random propylene ethylene copolymer and a styrene ethylene butylene styrene copolymer (SEBS).

7. The multilayer film according to claim 1, wherein the propylene homopolymer of the skin layer has an MFR (230° C., 2.16 kg, ISO1133) of 4.0 to 13 g/10 min and/or a melting temperature of above 154° C. up to 170° C. and/or a flexural modulus of above 1300 MPa when measured on injection molded specimens (23° C., 50% humidity, ISO 178) or the random propylene ethylene copolymer of the skin layer has an MFR (230° C., 2.16 kg, ISO1133) of 4.0 to 13 g/10 min, an ethylene content of 0.5 to 2.2 wt.-% and/or a melting temperature of 145 to 155° C. and/or a flexural modulus of above 975 MPa when measured on injection molded specimens (23° C., 50% humidity, ISO 178).

8. The multilayer film according to according to claim 1, wherein the random heterophasic copolymer having a melting temperature (Tm) of 130 to 145° C. contributing to the core layer has a MFR.sub.2 of 3.0 to 7.0 g/10 min (ISO 1133, 230° C., 2.16 kg) and/or a total ethylene content of 7.0 to 14.0 wt.-% and/or an amount of the xylene cold soluble fraction (XCS) in the range of 18.0 to 25.0 wt.-% and/or an intrinsic viscosity of 1.0 to 1.6 dl/g (DIN ISO 1628/1, 10/1999; Decalin, 135° C.) of the xylene cold soluble fraction (XCS).

9. The multilayer film according to claim 1, wherein the single site catalyst derived (SSC) random propylene ethylene copolymer of the inner layer has a the melting temperature (Tm) fulfilling the following equation
Tm<154° C.−[5.2×C2 content in wt.-%]° C. wherein C2 content stands for the content of units derived from ethylene; and/or has an ethylene content of 1.5 to 6.0 wt.-%, preferably 1.6 to 4.0 and/or has an melt flow rate of 3.0 to 20 preferably 3.0 to 9.0 g/10 min (230° C., 2.16 kg, ISO1133), and/or a flexural modulus of from 600 to 900 MPa when measured on injection molded specimens (23° C., 50% humidity, ISO 178).

10. The multilayer film according to claim 1, wherein the core layer comprises a mixture obtainable by melt blending 40 to 60 wt.-% of a random heterophasic copolymer and 60 to 40 wt.-% of styrene based thermoplastic elastomer (TPE).

11. The multilayer film according to claim 1, wherein the core layer comprises a mixture obtainable by melt blending 60 to 80 wt.-% of a random heterophasic copolymer and 40 to 20 wt.-% of styrene based thermoplastic elastomer (TPE).

12. A pouch made from the multilayer film of claim 1.

13. A process for preparing a film according to claim 1, wherein the components forming the skin layer, the core layer and the inner layer are extruded on a multi layer cast film line.

14. A process for preparing a film according to claim 1, wherein the single site catalyst derived (SSC) random propylene ethylene copolymer is obtained in the presences of a single site catalysts comprising (i) a complex of formula (I): ##STR00014## wherein M is zirconium or hafnium; each X is a sigma ligand; L is a divalent bridge selected from —R′2C—, —R′2C—CR′2-, —R′2Si—, —R′2Si— SiR′2-, —R′2Ge—, wherein each R′ is independently a hydrogen atom, C1-C20-hydrocarbyl, tri(C1-C20-alkyl)silyl, C6-C20-aryl, C7-C20-arylalkyl or C7-C20-alkylaryl; R2 and R2′ are each independently a C1-C20 hydrocarbyl radical optionally containing one or more heteroatoms from groups 14-16; R5′ is a C1-20 hydrocarbyl group containing one or more heteroatoms from groups 14-16 optionally substituted by one or more halo atoms; R6 and R6′ are each independently hydrogen or a C1-20 hydrocarbyl group optionally containing one or more heteroatoms from groups 14-16; wherein R6′ is preferably a tertiary alkyl group R7 is hydrogen or C1-20 hydrocarbyl group optionally containing one or more heteroatoms from groups 14-16; R7′ is hydrogen; Ar is independently an aryl or heteroaryl group having up to 20 carbon atoms optionally substituted by one or more groups R1; Ar′ is independently an aryl or heteroaryl group having up to 20 carbon atoms Optionally substituted by one or more groups R1; each R1 is a C1-20 hydrocarbyl group or two R1 groups on adjacent carbon atoms taken together can form a fused 5 or 6 membered non aromatic ring with the Ar group, said ring being itself optionally substituted with one or more groups R4; each R4 is a C1-20 hydrocarbyl group; and (ii) a cocatalyst comprising at least one or two compounds of a group 13 metal, such as Al and/or boron compound.

15. A process for preparing a film according to claim 1, comprising at least a skin layer, a core layer and an inner layer, wherein the skin layer comprises a homo polypropylene or a random propylene ethylene copolymer including up to 2.5 wt.-% units derived from ethylene, the homopolypropylene or the random propylene ethylene copolymer having a MFR.sub.2 (ISO1133, 230° C.) of 2.0 to 20 g/10 min and a melting temperature (Tm) of 145 to 170° C., wherein the homo polypropylene or the random propylene ethylene copolymer is obtainable by polymerization in the presence of a Ziegler-Natta catalyst (ZN-C) comprising compounds (TC) of a transition metal of Group 4 to 6 of IUPAC, a Group 2 metal compound (MC) and an internal donor (ID), wherein said internal donor (ID) is a selected from optionally substituted malonates, maleates, succinates, glutarates, cyclohexene-1,2-dicarboxylates, benzoates and derivatives and/or mixtures thereof, citraconate; or the combination of two internal donors (IDs) being 1,3-diethers and succinates optionally a co-catalyst (Co), and optionally an external donor (ED).

Description

EXPERIMENTAL PART

1. Measuring Methods

(1) The following definitions of terms and determination methods apply for the above general description of the invention as well as to the below examples unless otherwise defined.

(2) Phthalic acid esters and decomposition products Detection is carried out by gas chromatography coupled with one- or two dimensional mass spectrometry (GC-MS respectively GC-MS/MS) optionally preceded by enrichment on a suitable adsorption material. “Free of phthalic acid esters as well as decomposition products thereof” indicates

(3) a maximum of 10 μg/kg, i.e. 10 ppb by weight. Typical equipment to be used is for example given in H. Fromme, T. Küchler, T. Otto, K. Pilz, J. Müller, A. Wenzel Water Research 36 (2002) 1429-1438 which is incorporated by reference herewith.

(4) Calculation of comonomer content of the second propylene copolymer fraction (R-PP2):

(5) $\begin{array}{cc}\frac{C\left(PP\right)-w\left(PP1\right)xC\left(PP1\right)}{w\left(PP2\right)}=C\left(PP2\right)& \left(I\right)\end{array}$

(6) wherein w(PP1) is the weight fraction [in wt.-%] of the first propylene copolymer fraction (R-PP1), w(PP2) is the weight fraction [in wt.-%] of second propylene copolymer fraction (R-PP2), C(PP1) is the comonomer content [in mol-%] of the first propylene copolymer fraction (R-PP1), C(PP) is the comonomer content [in mol-%] of the random propylene copolymer (R-PP), C(PP2) is the calculated comonomer content [in mol-%] of the second propylene copolymer fraction (R-PP2).

(7) Calculation of the xylene cold soluble (XCS) content of the second propylene copolymer fraction (R-PP2):

(8) $\begin{array}{cc}\frac{XS\left(PP\right)-w\left(PP1\right)xXS\left(PP1\right)}{w\left(PP2\right)}=XS\left(PP2\right)& \left(\mathrm{II}\right)\end{array}$

(9) wherein w(PP1) is the weight fraction [in wt.-%] of the first propylene copolymer fraction (R-PP1), w(PP2) is the weight fraction [in wt.-%] of second propylene copolymer fraction (R-PP2), XS(PP1) is the xylene cold soluble (XCS) content [in wt.-%] of the first propylene copolymer fraction (R-PP1), XS(PP) is the xylene cold soluble (XCS) content [in wt.-%] of the random propylene copolymer (R-PP), XS(PP2) is the calculated xylene cold soluble (XCS) content [in wt.-%] of the second propylene copolymer fraction (R-PP2), respectively.

(10) Calculation of melt flow rate MFR.sub.2 (230° C./2.16 kg) of the second propylene copolymer fraction (R-PP2):

(11) $\begin{array}{cc}MFR\left(PP2\right)={10}^{\left[\frac{\log \left(\mathrm{MFR}\left(\mathrm{PP}\right)\right)-w\left(\mathrm{PP}1\right)\mathrm{xlog}\left(\mathrm{MFR}\left(\mathrm{PP}1\right)\right)}{w\left(\mathrm{PP}2\right)}\right]}& \left(\mathrm{III}\right)\end{array}$

(12) wherein w(PP1) is the weight fraction [in wt.-%] of the first propylene copolymer fraction (R-PP1), w(PP2) is the weight fraction [in wt.-%] of second propylene copolymer fraction (R-PP2), MFR(PP1) is the melt flow rate MFR.sub.2 (230° C./2.16 kg) [in g/10 min] of the first propylene copolymer fraction (R-PP1), MFR(PP) is the melt flow rate MFR.sub.2 (230° C./2.16 kg) [in g/10 min] of the random propylene copolymer (R-PP), MFR(PP2) is the calculated melt flow rate MFR.sub.2 (230° C./2.16 kg) [in g/10 min] of the second propylene copolymer fraction (R-PP2).

(13) Calculation of comonomer content of the elastomeric propylene copolymer (E), respectively:

(14) $\begin{array}{cc}\frac{C\left(RAHECO\right)-w\left(PP\right)xC\left(PP\right)}{w\left(E\right)}=C\left(E\right)& \left(\mathrm{IV}\right)\end{array}$

(15) wherein w(PP) is the weight fraction [in wt.-%] of the random propylene copolymer (R-PP), i.e. polymer produced in the first and second reactor (R1+R2), w(E) is the weight fraction [in wt.-%] of the elastomeric propylene copolymer (E), i.e. polymer produced in the third reactor (R3) C(PP) is the comonomer content [in mol-%] of the random propylene copolymer (R-PP), i.e. comonomer content [in mol-%] of the polymer produced in the first and second reactor (R1+R2), C(RAHECO) is the comonomer content [in mol-%] of the propylene copolymer, i.e. is the comonomer content [in mol-%] of the polymer obtained after polymerization in the third reactor (R3), C(E) is the calculated comonomer content [in mol-%] of elastomeric propylene copolymer (E), i.e. of the polymer produced in the third reactor (R3).

(16) MFR.sub.2 (230° C. 12.16 kg) is measured according to ISO 1133 at 230° C. and 2.16 kg load.

(17) Quantification of Microstructure by NMR Spectroscopy

(18) Quantitative nuclear-magnetic resonance (NMR) spectroscopy was used to quantify the comonomer content and comonomer sequence distribution of the polymers.

(19) Quantitative .sup.13C{.sup.1H} NMR spectra were recorded in the solution-state using a Bruker Advance III 400 NMR spectrometer operating at 400.15 and 100.62 MHz for .sup.1H and .sup.13C respectively. All spectra were recorded using a .sup.13C optimised 10 mm extended temperature probehead at 125° C. using nitrogen gas for all pneumatics.

(20) Approximately 200 mg of material was dissolved in 3 ml of 1,2-tetrachloroethane-d.sub.2 (TCE-d.sub.2) along with chromium-(III)-acetylacetonate (Cr(acac).sub.3) resulting in a 65 mM solution of relaxation agent in solvent (Singh, G., Kothari, A., Gupta, V., Polymer Testing 28 5 (2009), 475). 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 1 hour. Upon insertion into the magnet the tube was spun at 10 Hz. This setup was chosen primarily for the high resolution and quantitatively needed for accurate ethylene content quantification. Standard single-pulse excitation was employed without NOE, using an optimised tip angle, 1 s recycle delay and a bi-level WALTZ16 decoupling scheme (Zhou, Z., Kuemmerle, R., Qiu, X., Redwine, D., Cong, R., Taha, A., Baugh, D. Winniford, B., J. Mag. Reson. 187 (2007) 225; Busico, V., Carbonniere, P., Cipullo, R., Pellecchia, R., Severn, J., Talarico, G., Macromol. Rapid Commun. 2007, 28, 1128). A total of 6144 (6k) transients were acquired per spectra.

(21) Quantitative .sup.13C{.sup.1H} NMR spectra were processed, integrated and relevant quantitative properties determined from the integrals using proprietary computer programs. All chemical shifts were indirectly referenced to the central methylene group of the ethylene block (EEE) at 30.00 ppm using the chemical shift of the solvent. This approach allowed comparable referencing even when this structural unit was not present. Characteristic signals corresponding to the incorporation of ethylene were observed Cheng, H. N., Macromolecules 17 (1984), 1950).

(22) With characteristic signals corresponding to 2,1 erythro regio defects observed (as described in L. Resconi, L. Cavallo, A. Fait, F. Piemontesi, Chem. Rev. 2000, 100 (4), 1253, in Cheng, H. N., Macromolecules 1984, 17, 1950, and in W-J. Wang and S. Zhu, Macromolecules 2000, 33 1157) the correction for the influence of the regio defects on determined properties was required. Characteristic signals corresponding to other types of regio defects were not observed.

(23) The comonomer fraction was quantified using the method of Wang et. al. (Wang, W-J., Zhu, S., Macromolecules 33 (2000), 1157) through integration of multiple signals across the whole spectral region in the .sup.13C{.sup.1H} spectra. This method was chosen for its robust nature and ability to account for the presence of regio-defects when needed. Integral regions were slightly adjusted to increase applicability across the whole range of encountered comonomer contents.

(24) For systems where only isolated ethylene in PPEPP sequences was observed the method of Wang et al. was modified to reduce the influence of non-zero integrals of sites that are known to not be present. This approach reduced the overestimation of ethylene content for such systems and was achieved by reduction of the number of sites used to determine the absolute ethylene content to:
E=0.5(Sββ+Sβγ+Sβδ+0.5(Sαβ+Sαγ))

(25) Through the use of this set of sites the corresponding integral equation becomes:
E=0.5(I.sub.H+I.sub.G+0.5(I.sub.C+I.sub.D))

(26) using the same notation used in the article of Wang et. al. (Wang, W-J., Zhu, S., Macromolecules 33 (2000), 1157). Equations used for absolute propylene content were not modified.

(27) The mole percent comonomer incorporation was calculated from the mole fraction:
E[mol %]=100*fE

(28) The weight percent comonomer incorporation was calculated from the mole fraction:
E[wt %]=100*(fE*28.06)/((fE*28.06)+((1−fE)*42.08))

(29) The comonomer sequence distribution at the triad level was determined using the analysis method of Kakugo et al. (Kakugo, M., Naito, Y., Mizunuma, K., Miyatake, T. Macromolecules 15 (1982) 1150). This method was chosen for its robust nature and integration regions slightly adjusted to increase applicability to a wider range of comonomer contents.

(30) The relative content of isolated to block ethylene incorporation was calculated from the triad sequence distribution using the following relationship (equation (I)):

(31) $\begin{array}{cc}I\left(E\right)=\frac{fPEP}{\left(fEEEE+fPEE+fPEP\right)}\times 100& \left(I\right)\end{array}$

(32) wherein

(33) I(E) is the relative content of isolated to block ethylene sequences [in %];

(34) fPEP is the mol fraction of propylene/ethylene/propylene sequences (PEP) in the sample;

(35) fPEE is the mol fraction of propylene/ethylene/ethylene sequences (PEE) and of ethylene/ethylene/propylene sequences (EEP) in the sample;

(36) fEEE is the mol fraction of ethylene/ethylene/ethylene sequences (EEE) in the sample.

(37) Intrinsic viscosity is measured according to DIN ISO 1628/1, October 1999 (in Decalin at 135° C.).

(38) The xylene cold solubles (XCS, wt.-%): Content of xylene cold solubles (XCS) is determined at 25° C. according ISO 16152; first edition; 2005 Jul. 1. The part which remains insoluble is the xylene cold insoluble (XCI) fraction.

(39) Melting temperature (T.sub.m) crystallization temperature (T.sub.c) and heat of crystallization (H.sub.c): measured with Mettler TA820 differential scanning calorimetry (DSC) on 5 to 10 mg samples. DSC is run according to ISO 11357-3:1999 in a heat/cool/heat cycle with a scan rate of 10° C./min in the temperature range of +23 to +210° C. The crystallization temperature is determined from the cooling step, while the melting temperature is determined from the second heating step.

(40) Transparency, haze and clarity were determined according to ASTM D1003-00 on a 200 μmcast film as described herein.

(41) Flexural Modulus: The flexural modulus was determined in 3-point-bending according to ISO 178 on 80×10×4 mm.sup.3 test bars injection molded at 23° C. in line with EN ISO 1873-2.

(42) Charpy notched impact strength is determined according to ISO 179 1 eA at 23°, and at

(43) −20° C. by using an 80×10×4 mm.sup.3 test bars injection molded in line with EN ISO 1873-2.

(44) Tensile modulus in machine and transverse direction was determined according to ISO 527-3 at 23° C. on 200 μm cast films produced as described herein. Testing was performed at a cross head speed of 1 mm/min.

(45) Steam sterilization was performed in a Systec D series machine (Systec Inc., USA). The samples were heated up at a heating rate of 5° C./min starting from 23° C. After having been kept for 30 min at 121° C., they were removed immediately from the steam sterilizer and stored at room temperature till processed further.

(46) Sealing Initiation Temperature (SIT); (Sealing End Temperature (SET), Sealing Range)

(47) The method determines the sealing temperature range (sealing range) of polypropylene films, in particular blown films or cast films. The sealing temperature range is the temperature range, in which the films can be sealed according to conditions given below. The lower limit (heat sealing initiation temperature (SIT)) is the sealing temperature at which a sealing strength of >3 N is achieved. The upper limit (sealing end temperature (SET)) is reached, when the films stick to the sealing device. The sealing range is determined on a J&B Universal Sealing Machine Type 3000 with a film of 50 μm thickness with the following further parameters:

(48) Specimen width: 25.4 mm

(49) Seal Pressure: 0.1 N/mm2

(50) Seal Time: 0.1 sec

(51) Cool time: 99 sec

(52) Peel Speed: 10 mm/sec

(53) Start temperature: 80° C.

(54) End temperature: 150° C.

(55) Increments: 10° C.

(56) Specimen is sealed A to A at each sealbar temperature and seal strength (force) is determined at each step. The temperature is determined at which the seal strength reaches 3 N.

2. Examples

Preparation of the Phthalate Free Catalyst

(57) The phthalate free catalyst used in the polymerization processes for the inventive resins (IE) was prepared as follows:

(58) Used Chemicals:

(59) 20% solution in toluene of butyl ethyl magnesium (Mg(Bu)(Et), BEM), provided by

(60) Chemtura

(61) 2-ethylhexanol, provided by Amphochem

(62) 3-Butoxy-2-propanol—(DOWANOL™ PnB), provided by Dow

(63) bis(2-ethylhexyl)citraconate, provided by SynphaBase

(64) TiCl.sub.4, provided by Millenium Chemicals

(65) Toluene, provided by Aspokem

(66) Viscoplex® 1-254, provided by Evonik

(67) Heptane, provided by Chevron

Preparation of a Mg Alkoxy Compound

(68) Mg alkoxide solution was prepared by adding, with stirring (70 rpm), into 11 kg of a 20 wt-% solution in toluene of butyl ethyl magnesium (Mg(Bu)(Et)), a mixture of 4.7 kg of 2-ethylhexanol and 1.2 kg of butoxypropanol in a 20 l stainless steel reactor. During the addition the reactor contents were maintained below 45° C. After addition was completed, mixing (70 rpm) of the reaction mixture was continued at 60° C. for 30 minutes. After cooling to room temperature 2.3 kg g of the donor bis(2-ethylhexyl)citraconate was added to the Mg-alkoxide solution keeping temperature below 25° C. Mixing was continued for 15 minutes under stirring (70 rpm).

Preparation of Solid Catalyst Component

(69) 20.3 kg of TiCl.sub.4 and 1.1 kg of toluene were added into a 20 l stainless steel reactor. Under 350 rpm mixing and keeping the temperature at 0° C., 14.5 kg of the Mg alkoxy compound prepared in example 1 was added during 1.5 hours. 1.7 l of Viscoplex® 1-254 and 7.5 kg of heptane were added and after 1 hour mixing at 0° C. the temperature of the formed emulsion was raised to 90° C. within 1 hour. After 30 minutes mixing was stopped catalyst droplets were solidified and the formed catalyst particles were allowed to settle. After settling (1 hour), the supernatant liquid was siphoned away. Then the catalyst particles were washed with 45 kg of toluene at 90° C. for 20 minutes followed by two heptane washes (30 kg, 15 min). During the first heptane wash the temperature was decreased to 50° C. and during the second wash to room temperature.

(70) The thus obtained catalyst was used along with triethyl-aluminium (TEAL) as co-catalyst and dicyclopentyl dimethoxy silane (D-Donor) as donor.

(71) The aluminium to donor ratio, the aluminium to titanium ratio and the polymerization conditions are indicated in the respective tables

Preparation of the Skin Layer Material

(72) The polypropylene used for the skin layer material was prepared in a loop reactor using the catalyst as described above.

(73) TABLE-US-00001 TABLE 1 Polymerization conditions used for preparation of the material for the skin layer. Donor dicyclopentyl dimethoxy silane Teal/donor 12.5/1 (wt./wt.) Teal/C3 0.15 kg/ton loop temperature 75° C. loop pressure 35 Bar

(74) The properties of the materials are shown in Table 2.

(75) TABLE-US-00002 TABLE 2 Properties skin layer material MFR (2.16kg, 230° C., ISO 8.0 g/10 min 1133) Tm (ISO 11357-3) 163° C. Tcr (ISO 11357-3) 122 Flexural modulus (+23° C., 1350 MPa ISO 178)

(76) TABLE-US-00003 TABLE 3 Preparation of the random heterophasic copolymer (RAHECO) for the core layer RAHECO for core layer inventive Catalyst as described above Donor dicyclopentyl dimethoxy silane TEAL/Ti [mol/mol] 220 TEAL/donor [mol/mol] 6.1 Temperature [° C.] 31 Loop Temperature [° C.] 70 Split [%] 33 H2/C3 ratio [mol/kmol] 0.5 C2/C3 ratio [mol/kmol] 5.7 MFR.sub.2 [g/10 min] 4 XCS [wt.-%] 9.8 C2 content [mol-%] 4.4 GPR 1 Temperature [° C.] 80 Pressure [kPa] 2500 Split [%] 54 H2/C3 ratio [mol/kmol] 7.8 C2/C3 ratio [mol/kmol] 26.3 MFR.sub.2 [g/10 min] 6.3 XCS [wt.-%] 8.1 C2 content [mol-%] 6 GPR 2 Temperature [° C.] 75 Split [%] 13 C2/C3 ratio [mol/kmol] 555 H2/C2 ratio [mol/kmol] 502 MFR.sub.2 [g/10 min] 4.9 XCS [wt.-%] 20.5 C2 content [mol-%] 13.2 IV (XCS) dl/g 1.3 Tm ° C. 141

(77) The polypropylenes powders were compounded with the desired amount of additives (333 ppm of Irganox 1010 (FF); 667 ppm of Irgafos 168, 150 ppm of Magnesium oxide) in a ZSK 57 twin screw extruder with melt temperature of 200° C.

Preparation of Core Layer Material

(78) The core layer material was made by compounding the RAHECO as obtained above with 25.0 and 50.0 wt.-% of Kraton G1645MO based on the total amount of the core-layer material in a ZSK 57 twin screw extruder with melt temperature of 200° C. Kraton G1645MO is a linear triblock copolymer based on styrene and ethylene/butylene (SEBS) having a melt flow rate (230° C., 2.16 kg) of about 3 g/10 min, a polystyrene content (KM 03 test method) of 11.5 to 13.5 wt. % measured on the polymer.

(79) The random copolymer used in inner layer is made with a SSC catalyst as described in the following and the process parameters are shown in Table 5.

(80) SSC Catalyst

(81) The metallocene D1 (rac-anti-dimethylsilandiyl(2-methyl-4-phenyl-5-methoxy-6-tert-butyl-indenyl)(2-methyl-4-(4-tert-butylphenyl)indenyl)zirconium dichloride) [shown below] was synthesized as described in WO 2013/007650.

(82) ##STR00013##

(83) The SSC-Catalyst was prepared using metallocene D1 and a catalyst system of MAO and trityl tetrakis(pentafluorophenyl)borate according to Catalyst 3 of WO 2015/11135 with the proviso that the surfactant was 2,3,3,3-tetrafluoro-2-(1,1,2,2,3,3,3-heptafluoropropoxy)-1-propanol.

(84) TABLE-US-00004 TABLE 5 Preparation of the SSC random heterophasic copolymer for the inner layer IE1 IE2 Catalyst as described as described above above Loop Temperature [° C.] 70 70 Split [%] 57 46 Feed H2/C3 ratio [mol/kmol] 0.3 0.4 Feed C2/C3 ratio [mol/kmol] 25.4 38.6 MFR.sub.2 [g/10 min] 8 7 XCS [wt.-%] n.m. 1.3 C2 content [mol-%] 2 2.4 GPR 1 Temperature [° C.] 80 80 Pressure [kPa] 2500 2500 Split [%] 43 54 H2/C3 ratio [mol/kmol] 3.3 5.3 C2/C3 ratio [mol/kmol] 117.8 178 MFR.sub.2 [g/10 min] 8 5 XCS [wt.-%] 1.3 2.5 C2 content [mol-%] 2.5 3.3

(85) The polypropylenes powders were compounded with the desired amount of additives (333 ppm of Irganox 1010 (FF); 667 ppm of Irgafos 168, 500 ppm of calcium stearate) in a ZSK 57 twin screw extruder with melt temperature of 200° C. The properties are shown in Table 6.

(86) TABLE-US-00005 TABLE 4 Properties inner layer material CE1 IE1 IE2 Catalyst ZN, citraconate ssc ssc donor as described above as described above Phthalate free yes yes yes MFR (2.16 kg, 230° C., 8 8 5 ISO 1133) g/1 min C2 wt.-% 4.5 2.5 3.3 XS 8.5 wt.-% nd nd Tm (ISO11357-3) 141° C. 140° C. 130° C. Tm requirement Tm < 156° C. - 5.2 × Tm < 156° C. - 5.2 × Tm < 156° C. - 5.2 × according to C2 (wt.-%)° C. C2 (wt.-%)° C. C2 (wt.-%)° C. claim 1 (for Tm < 156° C. - (5.2 × Tm < 156° C. - (5.2 × Tm < 156° C. - (5.2 × given C2) 4.5)° C. 2.5)° C. 3.3)° C. Tm < 133° C. Tm < 143° C. Tm < 139° C. requirement not requirement met requirement met met More specific Tm < 154° C. - 5.2 × Tm < 154° C. - 5.2 × Tm < 154° C. - 5.2 × Tm requirement C2 (wt.-%)° C. C2 (wt.-%)° C. C2 (wt.-%)° C. Tm < 131° C. Tm < 141° C. Tm < 137° C. Not met met met

(87) It can be seen a ZN catalyst such as the citraconate donor including ZN catalyst as used in the comparative example cannot provide the melting temperature—(content of units derived from ethylene)-relation.

(88) The pelletization was done in a conventional way as well known in the art.

Preparation of the Film

(89) The films according to the present invention have been produced on a multi layer cast film line equipped with 3 extruders. All three extruders were equipped with a notched feeding zone and a 3 zone screw with mixing and shear parts. The diameter of the cylinder of extruder A is 40 mm and the screw length 25 D. Extruder B has a cylinder diameter of 60 mm and a screw length of SOD and extruder C a cylinder diameter of 45 mm and a screw length of 25 D. Each extruder is fed by a gravimetric dosing system. A feed block with lamellas and following distribution was used as co-extrusion adapter Extruder A 10% (skin layer), extruder C 80% (core layer) and extruder B 10% (inner layer). A coat hanger die with automatic die gap regulation was used, die width 800 mm and die gap 0.5 mm. The chill roll unit has a diameter of 450 mm and the 2nd cooling roll 250 mm. The detailed processing parameters are shown in tables 6 below.

(90) TABLE-US-00006 TABLE 5 processing conditions for three layer cast film Extruder A Extruder C Extruder B Layer thickness micron 20 160 20 Layer function Skin layer Core layer Inner layer and functionality Outer protection mainly sealing vs. sterilization Melttemperature ° C. 250 260 250 Melt pressure Bar 45 45 45 Screw speed U/min 8 45 6 output Kg/h 6 48 6 Coex adapter 260 temperature Die temperature 250 Chill roll ° C. 12 temperature 2.sup.nd cooling roll ° C. 21 temperature Take off speed m/min 7.4 winder

(91) The core layer material was not varied, i.e. the amounts of Raheco and SEBS were 50 wt.-% Raheco and 50 wt.-% SEBS (Kraton G1645MO).

(92) The comparative example was made with an inner layer made by the ZN catalyst as used for the core layer and the skin layer.

(93) TABLE-US-00007 TABLE 6 Film properties determined on 200 μm films . . . IE1 IE2 CE1 SIT 122 113 123 Tensile Modulus/MD MPa 157 159 155 Tensile Modulus/TD MPa 135 138 130 Haze/b.s. % 3.9 4.4 3.3 Haze/a.s. % 7.0 7.0 9.1 clarity % 98.7 98.2 96.9 free of phthalic acid esters/ yes yes yes decomposition products b.s = before sterilization; a.s. = after sterilization

(94) All inventive examples surprisingly showed improved haze after sterilization while tensile properties, haze before sterilization (less important) stayed on an excellent level. All inventive examples also surprisingly showed improved clarity. SIT was also lower for the inventive examples.

(95) It has been surprisingly found, that optical properties before and after sterilization can be significantly improved. Moreover, still some SIT improvement has been possible.