MULTILAYER FILM WITH IMPROVED PROPERTIES

Abstract

The present invention relates to a multilayer blown film comprising at least one skin layer (A) comprising a Ziegler Natta catalyzed heterophasic propylene copolymer (HECO) and one inner layer (B) comprising a metallocene catalyzed propylene based random copolymer (PRC), and optionally one core layer (C) comprising either a Ziegler Natta catalyzed heterophasic propylene copolymer (HECO) or a metallocene catalyzed propylene based random copolymer (PRC).

Claims

1. A multilayer blown film comprising at least two layers (A) and (B) and optionally one core layer (C) located between layer (A) and (B), wherein layer (A) comprises a Ziegler Natta catalyzed heterophasic propylene copolymer (HECO) and layer (B) comprises a metallocene catalyzed propylene based random copolymer (PRC), wherein: said heterophasic propylene copolymer (HECO) of Layer A comprises; a) 75.0 to 95.0 wt. % of a polypropylene matrix (PP-M) with an MFR.sub.2 (ISO 1133, 230° C., 2.16 kg) of 0.8 to 10.0 g/10 min being a homopolymer or a copolymer which has an alpha-olefin comonomer content of less than 2.0 wt. %, b) 5.0 to 25.0 wt. % of an elastomeric propylene-ethylene copolymer (EPC) dispersed in said matrix (PP-M) and c) 0.0 to 0.5 wt. % of one or more alpha-nucleating agent(s) (NA), and is produced in the presence of a Ziegler Natta catalyst, the heterophasic propylene copolymer (HECO) having (i) a melt flow rate MFR.sub.2 measured according to ISO 1133 (230° C., 2.16 kg load) in the range of 0.3 to 5.0 g/10 min; (ii) a melting temperature measured with DSC according to ISO 11357-3 in the range of 160° C. to 170° C. (iii) a xylene cold soluble (XCS) fraction determined according to ISO 16152 (25° C.) in the range of 5.0 to 25.0 wt. % based on the total weight of the heterophasic propylene copolymer (HECO); the xylene cold soluble (XCS) fraction having an intrinsic viscosity (IV) of 0.8 to 2.8 dl/g an ethylene content in the range of 10.0 to 45.0 wt. %, (iv) a total ethylene content in the range of 1.0 to 10.0 wt. %, said propylene based random copolymer (PRC) of Layer B comprises (i) alpha-olefin comonomers selected from ethylene and/or 1-butene in a total amount of 2.0 to 8.0 wt. % (ii) a melting temperature measured with DSC according to ISO 11357-3 in the range of 115° C. to 140° C. and is produced in the presence of a metallocene catalyst, and wherein the optional core layer (C) comprises either the Ziegler Natta catalyzed heterophasic propylene copolymer (HECO) or the metallocene catalyzed propylene based random copolymer (PRC).

2. The multilayer blown film according to claim 1, wherein the polypropylene matrix (PP-M) of the Ziegler Natta catalyzed heterophasic propylene copolymer (HECO) is a propylene homopolymer having a melt flow rate MFR2 (ISO 1133; 230° C.; 2.16 kg) in the range of 0.8 to 10.0 g/10 min.

3. The multilayer blown film according to claim 1, wherein the heterophasic propylene copolymer (HECO) comprises 0.0001 to 0.5 wt. % of an alpha-nucleating agent (NA), the alpha-nucleating agent being either a polymeric nucleating agent or an alpha-nucleating agent selected from the group consisting of 1,3:2,4-bis-(3,4-dimethyl-benzylidene)-sorbitol, sodium-2,2′-methylenebis-(4,6-di-tert-butyl-phenyl)-phosphate, hydroxybis-(2,4,8,10-tetra-tert-butyl-6-hydroxy-12h-dibenzo-(d,g)(1,3,2)-dioxaphosphocin-oxidato)-aluminium, 1,2-cyclohexane dicarboxylic acid, Ca-salt; or mixtures thereof.

4. The multilayer blown film according to claim 1, wherein the propylene based random copolymer (PRC) is a propylene-ethylene random copolymer having: (a) a total ethylene content in the range of from 3.0 to 7.0 wt. %, (b) a melt flow rate MFR2 (230° C./2.16 kg) measured according to ISO 1133 in the range of from 0.6 to 5.0 g/10 min, and (c) a melting temperature Tm as determined by DSC according to ISO 11357 of from 115° C. to 135° C.

5. The multilayer blown film according to claim 4, wherein the propylene-ethylene random copolymer consists of: 45.0 to 85.0 wt. % of polymer fraction (PRC-1) having., (i) an ethylene content in the range of from 1.5 to 5.0 wt. % and (ii) a melt flow rate MFR2 (230° C./2.16 kg) measured according to ISO 1133 in the range of from 0.8 to 8.0 g/10 min and 15.0 to 55.0 wt. % of polymer fraction (PRC-2) having, (i) an ethylene content in the range of from 4.0 to 10.0 wt. % and (ii) a melt flow rate MFR2 (230° C./2.16 kg) measured according to ISO 1133 in the range of from 0.1 to 3.0 g/10 min, whereby the melt flow rate MFR2 (230° C./2.16 kg) of polymer fraction (PRC-2) is lower than the MFR2 (230° C./2.16 kg) of polymer fraction (PRC-1).

6. The multilayer blown film according to claim 1, wherein the film comprises a core layer (C), said core layer (C) comprises either a Ziegler Natta catalyzed heterophasic propylene copolymer (HECO) as defined for layer (A) or a metallocene catalyzed propylene based random copolymer (PRC) as defined for layer (B).

7. The multilayer blown film according to claim 1, wherein the multilayer blown film has a total film thickness of from 10 to 2000 μm.

8. The multilayer blown film according to claim 1, wherein layer (A) has a thickness in the range of 35 to 80% with respect to the total thickness of the multilayer film; layer (B) has a thickness in the range of 5 to 40% with respect to the total thickness of the multilayer film; and layer (C) has a thickness in the range of 0 to 45% with respect to the total thickness of the multilayer film.

9. The multilayer blown film according to claim 1, wherein the multilayer blown film has an Elmendorf tear strength (measured on a 50 μm multilayer blown film) determined in accordance with ISO 6383/2 measured in machine direction (MD), in the range from at least 5.0 N/mm up to 25.0 N/mm, and measured in transverse direction (TD) in the range of from at least 15.0 N/mm up to 50.0 N/mm.

10. The multilayer blown film according to claim 1, wherein the multilayer blown film has a sealing initiation temperature (SIT) (determined as described in the experimental part) in the range from 85° C. to below 120° C.

11. The multilayer blown film according to claim 1, wherein the multilayer blown film has a tensile modulus in machine (MD) direction determined acc. to ISO 527-3 on a 50 μm multilayer blown film in the range of from 800 to 1500 MPa.

12. The multilayer blown film according to claim 1, wherein the film has a resistance factor (R-factor) according to formula: $R-\mathrm{factor}=\frac{\mathrm{Tensile}\mathrm{Modulus}\left(\mathrm{MD}\right)\left[\mathrm{MPa}\right]*\mathrm{Tear}\left(\mathrm{MD}\right)\left[N/\mathrm{mm}\right]}{SIT\left[°C.\right]}$ of at least 50 up to 300, wherein the Tensile Modulus in machine direction is measured according to ISO 527-3 at 23° C. on 50 μm multilayer blown film , Tear is the Elmendorf tear strength determined in accordance with ISO 6383/2 measured in machine direction (MD) on a 50 μm multilayer blown film and SIT is the sealing initiation temperature (determined as described in the experimental part) on a 50 μm multilayer blown film.

13. The multilayer blown film according to claim 1, wherein the film has a dart-drop impact strength (DDI) determined according to ASTM D1709, method A on a 50 μm multilayer blown film of at least 20 g up to 300 g.

14. (canceled)

Description

EXPERIMENTAL PART

A. Measuring Methods

[0289] 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.

Melt Flow Rate

[0290] The melt flow rate (MFR) was determined according to ISO 1133—Determination of the melt mass-flow rate (MFR) and melt volume-flow rate (MVR) of thermoplastics—Part 1: Standard method and is indicated in g/10 min. 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.sub.2 of polyethylene is determined at a temperature of 190° C. and a load of 2.16 kg. The MFR.sub.2 of polypropylene is determined at a temperature of 230° C. and a load of 2.16 kg.

[0291] Calculation of melt flow rate MFR.sub.2 (230° C.) of the polymer fraction (PRC-2):

[00002]$\mathrm{MFR}\left(\mathrm{PRC}-2\right)={10}^{\left[\frac{\log \left(\mathrm{MFR}\left(\mathrm{PRC}\right)\right)-w\left(\mathrm{PRC}-1\right)\times \log \left(\mathrm{MFR}\left(\mathrm{PRC}-1\right)\right)}{w\left(A2\right)}\right]}$ [0292] wherein [0293] w(PRC-1) is the weight fraction [in wt.-%] of the polymer fraction PRC-1 [0294] w(A2) is the weight fraction [in wt.-%] of the polymer fraction PRC-2, [0295] MFR(PRC-1) is the melt flow rate MFR.sub.2 (230° C.) [g/10 min] of the polymer fraction PRC-1, [0296] MFR(PRC) is the melt flow rate MFR.sub.2 (230° C.) [g/10 min] of the propylene random copolymer (PRC), [0297] MFR(PRC-2) is the calculated melt flow rate MFR.sub.2 (230° C.) [g/10 min] of the polymer fraction PRC-2.

Quantification of Microstructure by NMR Spectroscopy

[0298] Quantitative nuclear-magnetic resonance (NMR) spectroscopy was further used to quantify the comonomer content and comonomer sequence distribution of the polymers. 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. Approximately 200 mg of material was dissolved in 3 ml of 1,2-tetrachloroethane-d.sub.2 (TCE-d2) 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.

[0299] 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. 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).

[0300] 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.

[0301] 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.

[0302] 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))

[0303] 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))

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.

[0304] The mole percent comonomer incorporation was calculated from the mole fraction:

E[mol %]=100*fE

[0305] The weight percent comonomer incorporation was calculated from the mole fraction:

E[wt %]=100*(fE*28.06)/((fE*28.06)+((1−fE)*42.08))

[0306] 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.

Calculation of Comonomer Content of the Second Polymer Fraction (PRC-2)

[0307]
(C(PRC)−w(PRC-1)×C(PRC-1))/(w(PRC-2))=C(PRC-2)

wherein
w(PRC-1) is the weight fraction [in wt.-%] of the first polymer fraction (PRC-1),
w(PRC-2) is the weight fraction [in wt.-%] of second polymer fraction (PRC-2),
C(PRC-1) is the comonomer content [in wt.-%] of the first polymer fraction (PRC-1),
C(PRC) is the comonomer content [in wt.-%] of the propylene random copolymer (PRC),
C(PRC-2) is the calculated comonomer content [in wt.-%] of the second polymer fraction (PRC-2).

Xylene Cold Solubles (XCS)

[0308] The xylene soluble (XS) fraction as defined and described in the present invention is determined in line with ISO 16152 as follows: 2.0 g of the polymer were dissolved in 250 ml p-xylene at 135° C. under agitation. After 30 minutes, the solution was allowed to cool for 15 minutes at ambient temperature and then allowed to settle for 30 minutes at 25+/−0.5° C. The solution was filtered with filter paper into two 100 ml flasks. The solution from the first 100 ml vessel was evaporated in nitrogen flow and the residue dried under vacuum at 90° C. until constant weight is reached. The xylene soluble fraction (percent) can then be determined as follows:

XS %=(100*m*V.sub.0)/(m.sub.0*v);m.sub.0=initial polymer amount(g);m=weight of residue(g);V.sub.0=initial volume (ml);v=volume of analysed sample(ml).

Melting Temperature T.SUB.m .and Crystallization Temperature T.SUB.c

[0309] The parameters are determined with a TA Instrument Q2000 differential scanning calorimetry (DSC) on 5 to 7 mg samples. DSC is run according to ISO 11357/part 3/method C2 in a heat/cool/heat cycle with a scan rate of 10° C./min in the temperature range of −30 to +225° C. Crystallization temperature (T.sub.c) is determined from the cooling step, while the melting temperature (T.sub.m) is determined from the second heating step. Melting and crystallization temperatures were taken as the peaks of endotherms and exotherms.

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

[0310] The method determines the sealing temperature range (sealing range) of polypropylene films, in particular blown 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 5+/−0.5 N is achieved. The upper limit (sealing end temperature (SET)) is reached, when the films stick to the sealing device.

[0311] The sealing range was determined on a J&B Universal Sealing Machine Type 3000 of the multilayer films as produced indicated below with the following parameters: [0312] Specimen width: 25.4 mm [0313] Seal Pressure: 0.1 N/mm.sup.2 [0314] Seal Time: 0.1 sec [0315] Cool time: 99 sec [0316] Peel Speed: 10 mm/sec [0317] Start temperature 80° C. [0318] End temperature: 150° C. [0319] Increments: 10° C.
specimen is sealed A to A at each seal bar temperature and seal strength (force) is determined at each step. The temperature is determined at which the seal strength reaches 5 N.

Flexural Modulus

[0320] 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.

[0321] Tear resistance (determined as Elmendorf tear (N)): Applies both for the measurement in machine direction (MD) and transverse direction (TD). The tear strength is measured using the ISO 6383/2 method. The force required to propagate tearing across a film sample is measured using a pendulum device. The pendulum swings under gravity through an arc, tearing the specimen from pre-cut slit. The film sample is fixed on one side by the pendulum and on the other side by a stationary clamp. The tear resistance is the force required to tear the specimen. The relative tear resistance (N/mm) is then calculated by dividing the tear resistance by the thickness of the film.

Tensile Modulus

[0322] Tensile modulus in machine and transverse direction were determined according to ISO 527-3 at 23° C. on the multilayer films as produced indicated below. Testing was performed at a cross head speed of 1 mm/min.

Dart Drop Strength (DDI)

[0323] Dart-drop was measured using ASTM D1709, method A (Alternative Testing Technique) from the multilayer films as produced indicated below. A dart with a 38 mm diameter hemispherical head is dropped from a height of 0.66 m onto a multilayer film clamped over a hole. Successive sets of twenty specimens are tested. One weight is used for each set and the weight is increased (or decreased) from set to set by uniform increments. The weight resulting in failure of 50% of the specimens is calculated and reported.

[0324] Haze was determined according to ASTM D 1003-00 on multilayer films as produced indicated below.

[0325] 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 until being processed further.

B. EXAMPLES

Heterophasic Propylene Copolymer (HECO) for Layer (A) and Optional Layer (C)

[0326] The catalyst used in the polymerization process for the heterophasic propylene copolymer (HECO) of the inventive example (IE1), (IE2) and CE2 was prepared as described below and was used together with triethyl-aluminium (TEA) as co-catalyst and dicyclopentyl dimethoxy silane (donor D) as donor.

1a) Catalyst Preparation

[0327] 3.4 litre of 2-ethylhexanol and 810 ml of propylene glycol butyl monoether (in a molar ratio 4/1) were added to a 20 I reactor. Then 7.8 litre of a 20% solution in toluene of BEM (butyl ethyl magnesium) provided by Crompton GmbH were slowly added to the well stirred alcohol mixture. During the addition the temperature was kept at 10° C. After addition the temperature of the reaction mixture was raised to 60° C. and mixing was continued at this temperature for 30 minutes. Finally after cooling to room temperature the obtained Mg-alkoxide was transferred to storage vessel.

[0328] 21.2 g of Mg alkoxide prepared above was mixed with 4.0 ml bis(2-ethylhexyl) citraconate for 5 min. After mixing the obtained Mg complex was used immediately in the preparation of catalyst component.

[0329] 19.5 ml titanium tetrachloride was placed in a 300 ml reactor equipped with a mechanical stirrer at 25° C. Mixing speed was adjusted to 170 rpm. 26.0 of Mg-complex prepared above was added within 30 minutes keeping the temperature at 25° C. 3.0 ml of Viscoplex 1-254 and 1.0 ml of a toluene solution with 2 mg Necadd 447 was added. Then 24.0 ml of heptane was added to form an emulsion. Mixing was continued for 30 minutes at 25° C. Then the reactor temperature was raised to 90° C. within 30 minutes. The reaction mixture was stirred for further 30 minutes at 90° C. Afterwards stirring was stopped and the reaction mixture was allowed to settle for 15 minutes at 90° C.

[0330] The solid material was washed 5 times: Washings were made at 80° C. under stirring 30 min with 170 rpm. After stirring was stopped the reaction mixture was allowed to settle for 20-30 minutes and followed by siphoning. [0331] Wash 1: Washing was made with a mixture of 100 ml of toluene and 1 ml donor [0332] Wash 2: Washing was made with a mixture of 30 ml of TiCl4 and 1 ml of donor. [0333] Wash 3: Washing was made with 100 ml toluene. [0334] Wash 4: Washing was made with 60 ml of heptane. [0335] Wash 5. Washing was made with 60 ml of heptane under 10 minutes stirring.

[0336] Afterwards stirring was stopped and the reaction mixture was allowed to settle for 10 minutes decreasing the temperature to 70° C. with subsequent siphoning, and followed by N2 sparging for 20 minutes to yield an air sensitive powder.

1b) VCH Modification of the Catalyst

[0337] 35 ml of mineral oil (Paraffinum Liquidum PL68) were added to a 125 ml stainless steel reactor followed by 0.82 g of triethyl aluminium (TEAL) and 0.33 g of dicyclopentyl dimethoxy silane (donor D) under inert conditions at room temperature. After 10 minutes 5.0 g of the catalyst prepared in 1a (Ti content 1.4 wt.-%) was added and after additionally 20 minutes 5.0 g of vinylcyclohexane (VCH) was added. The temperature was increased to 60° C. during 30 minutes and was kept there for 20 hours. Finally, the temperature was decreased to 20° C. and the concentration of unreacted VCH in the oil/catalyst mixture was analysed and was found to be 120 ppm weight.

[0338] The HECO was produced in a Borstar pilot plant with a prepolymerization reactor, one slurry loop reactor and two gas phase reactors.

[0339] The solid catalyst was used in all cases along with triethyl-aluminium (TEAL) as cocatalyst and dicyclo-pentyl-dimethoxysilane (D-donor) as donor. The aluminium to donor ratio was 5 mol/mol, the TEAL/Ti-ratio was 90 mol/mol.

[0340] Polymerization data is shown in Table 1.

TABLE-US-00001 TABLE 1 Polymerization data for HECO Unit HECO Prepolymerization Temperature ° C. 30 TEAL/Ti ratio mol/mol 173 TEAL/Donor ratio mol/mol 8.0 Loop reactor Temperature ° C. 80 Split wt.-% 39 H2/C3 mol/kmol 0.4 XCS wt.-% 2.4 MFR g/10 min 2.4 GPR 1 Temperature ° C. 80 Split wt.-% 50 H2/C3 mol/kmol 7 XCS wt.-% 1.7 MFR.sub.M g/10 min 2.4 GPR 2 Temperature ° C. 75 Split wt.-% 11 C2/C3 mol/kmol 223 H2/C2 mol/kmol 551 C2 total wt.-% 4.2 XCS wt.-% 15.0 C2(XCS) wt.-% 28.0 IV(XCS) dl/g 2.2 MFR.sub.T g/10 min 3.0

[0341] The HECO was stabilized by melt mixing on a co-rotating twin-screw extruder at 200-230° C. with 0.2 wt.-% of Irganox B225 (1:1-blend of Irganox 1010 (Pentaerythrityltetrakis(3-(3′,5′-di-tert.butyl-4-hydroxytoluyl)-propionate, CAS-no. 6683-19-8, and tris (2,4-di-t-butylphenyl) phosphate) phosphite), CAS-no. 31570-04-4, of BASF AG, Germany), 0.1 wt.-% calcium stearate (CAS-no.1592-23-0, commercially available from Faci, Italy) and 0.05 wt.-% of Hyperform HPN-20E (comprising 1,2-cyclohexane dicarboxylicacid, Ca-salt, commercially available from Milliken, USA).

TABLE-US-00002 TABLE 2 properties of HECO Final product HECO MFR.sub.2 [g/10 min] total 3.0 C.sub.2 content [wt.-%] total 4.2 XCS [wt.-%] 14.0 C.sub.2 of XCS [wt.-%] 28.0 Intrinsic viscosity of XCS [dl/g] 2.2 T.sub.m (DSC) [° C.] 167 T.sub.c (DSC) [° C.] 128 Flexural Modulus [MPa] 1400

Propylene-Ethylene Random Copolymer (PRC) for Layer (B) and Optional Layer (C)

[0342] The catalyst used in the polymerization processes for the 0203 random copolymer of the inventive examples (IE1, IE2) and (CE1) was prepared as follows:

[0343] The metallocene (MC1) (rac-anti-dimethylsilandiyl(2-methyl-4-phenyl-5-methoxy-6-tert-butyl-indenyl)(2-methyl-4-(4-tert-butylphenyl)indenyl)zirconium dichloride)

##STR00008##

has been synthesized according to the procedure as described in WO2013007650, E2.

Preparation of MAO-Silica Support

[0344] A steel reactor equipped with a mechanical stirrer and a filter net was flushed with nitrogen and the reactor temperature was set to 20° C. Next silica grade DM-L-303 from AGC Si-Tech Co, pre-calcined at 600° C. (7.4 kg) was added from a feeding drum followed by careful pressuring and depressurising with nitrogen using manual valves. Then toluene (32 kg) was added. The mixture was stirred for 15 min. Next 30 wt.-% solution of MAO in toluene (17.5 kg) from Lanxess was added via feed line on the top of the reactor within 70 min. The reaction mixture was then heated up to 90° C. and stirred at 90° C. for additional two hours. The slurry was allowed to settle and the mother liquor was filtered off. The MAO treated support was washed twice with toluene (32 kg) at 90° C., following by settling and filtration. The reactor was cooled off to 60° C. and the solid was washed with heptane (32.2 kg). Finally MAO treated SiO2 was dried at 60° C. under nitrogen flow for 2 hours and then for 5 hours under vacuum (-0.5 barg) with stirring. MAO treated support was collected as a free-flowing white powder found to contain 12.6% Al by weight.

Catalyst System Preparation

[0345] 30 wt.-% MAO in toluene (2.2 kg) was added into a steel nitrogen blanked reactor via a burette at 20° C. Toluene (7 kg) was then added under stirring. Metallocene MC1 (286 g) was added from a metal cylinder followed by flushing with 1 kg toluene. The mixture was stirred for 60 minutes at 20° C. Trityl tetrakis(pentafluorophenyl) borate (336 g) was then added from a metal cylinder followed by a flush with 1 kg of toluene. The mixture was stirred for 1 h at room temperature. The resulting solution was added to a stirred cake of MAO-silica support prepared as described above over 1 hour. The cake was allowed to stay for 12 hours, followed by drying under N2 flow at 60° C. for 2h and additionally for 5 h under vacuum (-0.5 barg) under stirring. Dried catalyst was sampled in the form of pink free flowing powder containing 13.9 wt.-% Al and 0.26 wt.-% Zr

[0346] The polymerization for preparing the inventive C.sub.2C.sub.3 random copolymer (PRC) was performed in a Borstar pilot plant with a 2-reactor set-up (loop—gas phase reactor (GPR 1)). In Table 3 the polymerization conditions are given.

TABLE-US-00003 TABLE 3 IE1 Prepoly reactor Temperature [° C.] 25 Pressure [Pa] 5149 Catalyst feed [g/h] 2.0 C.sub.3 feed [kg/h] 52 H.sub.2 feed [g/h] 0.3 Residence time [h] 0.4 loop reactor Temperature [° C.] 68 Pressure [Pa] 5385 Feed H.sub.2/C.sub.3 ratio [mol/kmol] 0.24 Feed C.sub.2/C.sub.3 ratio [mol/kmol] 48.3 Polymer Split [wt.-%] 67 MFR.sub.2 [g/10 min] (MFR of PRC-1) 2.0 Total C.sub.2 loop [wt.-%] (C.sub.2 of PRC-1) 3.7 XCS loop [wt.-%] 3.5 Residence time 0.4 GPR1 Temperature [° C.] 75 Pressure [Pa] 2500 H.sub.2/C.sub.3 ratio [mol/kmol] 2.0 C.sub.2/C.sub.3 ratio [mol/kmol] 224 Polymer residence time [h] 1.8 Polymer Split [wt.-%] 33 Total MFR.sub.2 [g/10 min] 1.1 MFR.sub.2 [g/10 min] in GPR1 (MFR of PRC-2) 0.3 Total C.sub.2 [wt.-%] (loop + GPR1) 4.1 C.sub.2 in GPR1 [wt.-%] (C.sub.2 of PRC-2) 4.9 Total XCS [wt.-%] 4.7

[0347] The polymer powder was compounded in a co-rotating twin-screw extruder Coperion ZSK 57 at 220° C. with 0.2 wt.-% antiblock agent (synthetic silica; CAS-no. 7631-86-9); 0.1 wt.-% antioxidant (Irgafos 168FF); 0.1 wt.-% of a sterical hindered phenol (Irganox 1010FF); 0.02 wt.-% of Ca-stearat) and 0.02 wt.-% of a non-lubricating stearate (Synthetic hydrotalcite; CAS-no. 11097-59-9).

TABLE-US-00004 TABLE 4 polymer properties Pellet IE1 XCS [wt.-%] 4.6 Total C.sub.2 [wt.-%] 4.1 MFR2 [g/10 min] 1.1 Tm [° C.] 125 Tc [° C.] 85

Manufacturing of Multilayer Films

[0348] Three layer blown polymer films were produced on a three layer Collin lab scale blown film line. The melt temperature of the layer (A) and layer (B) was 185° C. to 195° C. The melt temperature of the core layer (C) was in the range of 205° C. to 215° C. The throughput of the extruders was in sum 80 kg/h. The film structure was A-C-B with a core layer of 15 μm (C), layer (A) of 25 μm and layer (B) of 10 μm. Layer thickness has been determined by Scanning Electron Microscopy. The material used for the layers multilayer films is indicated in the table 5. The properties of the multilayer films are indicated in table 6.

TABLE-US-00005 TABLE 5 Produced multilayer films. IE1 IE2 CE1 CE2 Layer (A) HECO HECO PRC HECO Amount [wt.-%] 100 100 100 100 Layer (B) PRC PRC PRC HECO Amount [wt.-%] 100 100 100 100 Layer (C) PRC HECO PRC HECO Amount [wt.-%] 100 100 100 100 Total Thickness [μm]  50  50  50  50

TABLE-US-00006 TABLE 6 Properties of the 50 μm multilayer blown films. Unit IE1 IE2 CE1 CE2 SIT ° C. 110 109 109 144 Tensile Modulus MD MPa 988 1223 638 1572 Tensile Modulus TD MPa 946 1054 664 1314 Tear MD N/mm 18.1 7.4 6.6 4.2 Tear TD N/mm 16.7 20.6 21.2 13.8 DDI g 44 109 43 161 Haze b.s. % 9.0 18.4 4.9 18.1 Haze a.s. % 9.3 9.3 4.9 17.8 R-factor 162 82 38.6 46 b.s. before steam sterilization a.s. after steam sterilization

[0349] As can be seen from the above table, the inventive multilayer blown films have a more balanced combination of mechanical—optical—sealing properties.