WO2017097579A1

WO2017097579A1 - Propylene based polymer composition

Info

Publication number: WO2017097579A1
Application number: PCT/EP2016/078417
Authority: WO
Inventors: Massimo Covezzi; Paola Massari; Claudio Cavalieri; Roberta Marzolla
Original assignee: Basell Poliolefine Italia S.R.L.
Priority date: 2015-12-11
Filing date: 2016-11-22
Publication date: 2017-06-15
Also published as: EP3387066A1; EP3387066B1; CN108431122A; BR112018010717B1; BR112018010717A8; US20180362748A1; US10611901B2; KR102024496B1; RU2729781C2; JP2018536084A; JP6578069B2; BR112018010717A2; RU2018121812A3; RU2018121812A; CN108431122B; KR20180094930A

Abstract

A propylene polymer composition comprising: a) from 40 wt% to 80 wt% of a propylene 1-hexene copolymer containing from 5.5 to 9.0% by weight, of 1-hexene derived units having a Melt Flow Rate (MFR, measured according to ASTM D 1238, 230°C/2.16 kg, i.e. at 230°C, with a load of 2.16 kg) from 3.5 to 12.0 g/10 min; b) from 20 wt% to 60 wt% of a propylene ethylene copolymer containing from 1.5 wt% to 6.5 wt% of ethylene derived units, a having a Melt Flow Rate (MFR, measured according to ASTM D 1238, 230°C/2.16 kg, i.e. at 230°C, with a load of 2.16 kg) from 3.5 to 12.0 g/10 min.

Description

TITLE

PROPYLENE BASED POLYMER COMPOSITION

FIELD OF THE INVENTION

[0001] The present disclosure relates to a composition comprising a copolymers of propylene with 1-hexene and a copolymer of propylene and ethylene particularly suited for preparing films, in particular biaxially oriented polypropylene films (BOPP) and cast films having a low seal initiation temperature (SIT), high transparency and printability.

BACKGROUND OF THE INVENTION

[0002] Copolymer of propylene and 1-hexene are already known in the art, for example WO 2006/002778 relates to a copolymer of propylene and 1-hexene having from 0.2 to 5 wt of 1- hexene derived units. This copolymer have a molecular weight distribution of monomodal type and are used for pipes systems.

[0003] WO 2009/077287 relates to a a copolymer of propylene with hexene-1 containing from 5 to 9% by weight of recurring units derived from hexene-1, said copolymer having a melting temperature from 125°C to 140°C and Melt Flow Rate (ASTM D1238, 230°C/2.16 kg) from 0.1 to 3 g/10 min.

[0004] WO 2015/062787 relates to a multimodal copolymers of propylene and 1-hexene having a content of 1-hexene derived units ranging from 0.6 wt to 3.0 wt especially suitable for the production of industrial sheets.

[0005] The applicant found that it is possible to produce BOPP and cast films having a low value of haze, low seal initiation temperature (SIT) and good dyne retention by using a composition comprising a propylene 1-hexene copolymer and a propylene ethylene copolymer.

SUMMARY OF THE INVENTION

[0006] Thus the present disclosure provides a propylene polymer composition comprising:

[0007] a) from 40 wt to 80 wt of a propylene 1-hexene copolymer containing from 5.5 to 9.0% by weight, of 1-hexene derived units having a Melt Flow Rate (MFR, measured according to ASTM D 1238, 230°C/2.16 kg, i.e. at 230°C, with a load of 2.16 kg) from 3.5 to 12.0 g/10 min;

[0008] b) from 20 wt% to 60 wt% of a propylene ethylene copolymer containing from 1.5 wt% to 6.5 wt% of ethylene derived units, a having a Melt Flow Rate (MFR, measured according to ASTM D 1238, 230°C/2.16 kg, i.e. at 230°C, with a load of 2.16 kg) from 3.5 to 12.0 g/10 min;

[0009] the sum of the amount of a) and b) being 100.

DETAILED DESCRIPTION OF THE INVENTION

[0010] The present disclosure provides a propylene polymer composition comprising:

[0011] a) from 40 wt% to 80 wt%; preferably from 45 wt% to 74 wt%; more preferably from 48 wt% to 63 wt% of a propylene 1-hexene copolymer containing from 5.5 to 9.0% by weight, preferably from 6.0 to 8.5% by weight, more preferably from 6.5 to 8.0% by weight of 1-hexene derived units, having a Melt Flow Rate (MFR, measured according to ASTM D 1238,

230°C/2.16 kg, i.e. at 230°C, with a load of 2.16 kg) from 3.5 to 12.0 g/10 min; preferably from 3.8 to 7.5 g/10 min; more preferably from 4.0 to 6.0 g/10 min;

[0012] b) from 20 wt% to 60 wt% preferably from 26 wt% to 55 wt% more preferably from 37 wt% to 52 wt% of a propylene ethylene copolymer containing from 1.5 wt% to 6.5 wt%; preferably from 2.0 wt% to 6.1 wt%; more preferably from 3.5 wt% to 5.1 wt% of ethylene derived units, a having a Melt Flow Rate (MFR, measured according to ASTM D 1238,

[0013] the sum of the amount of a) and b) being 100.

[0014]

[0015] Preferably the propylene 1-hexene copolymers component a) is endowed with one or more of the following features:

[0016] i) the DSC plot shows at least two peaks having a difference in height ranging from 0 to 5 mW ; preferably from 0 to 3 mW;

[0017] ii) the higher melting temperature, measured by DSC, ranging from 141.0 °C to 151.0 °C; preferably from 142.0°C to 149.0°C; more preferably from 142.5°C to 145.0°C. [0018] Preferably the difference of the melting temperature of the two peaks ranges from 5°C to 20°C; more preferably from 7°C to 15°C; even more preferably from 8°C to 12°C.

[0019] The propylene 1-hexene copolymer of the present disclosure contains only propylene and 1-hexene derived units the copolymer can further contain up to 1.0 wt% by weight of ethylene derived units . The propylene ethylene copolymer of the present disclosure contains only propylene and ethylene derived units. The copolymer can further contain up to 1.0 wt by weight of 1-hexene derived units.

[0020] A peak in the DSC curve (temperature/heat of fusion(mW)) is defined as a point on the DSC curve (temperature/heat of fusion) having the highest value of heat of fusion at a temperature A with respect to the values of heat of fusion (mW) in the range + 5 °C with respect to temperature A.

[0021] The melting temperature values are determined by differential scanning calorimetry, according to ISO 11357-3, with a heating rate of 20 °C/minute.

[0022] The composition of the present disclosure is endowed with a very low HAZE and a low seal initiating temperature (SIT) so that this material can be advantageously used for the production of film in particular cast or BOPP films.

[0023] In particular there is a synergistic effect in the haze of the composition that results lower than the haze of component a) and b) alone.

[0024]

[0025] Components a) and b) of the propylene polymer composition can be obtained with polymerization processes carried out in the presence of stereo specific Ziegler-Natta catalysts supported on magnesium dihalides. By properly dosing the molecular weight regulator

(preferably hydrogen).

[0026] The polymerization process, which can be continuous or batch, is carried out following known techniques and operating in gas phase, or in liquid phase in the presence or not of inert diluent, or by mixed liquid-gas techniques. It is preferable to carry out the

polymerization in gas phase in two reactors.

[0027] Polymerization reaction time, pressure and temperature are not critical, however it is best if the temperature is from 20 to 100°C. The pressure can be atmospheric or higher.

[0028] As previously mentioned, the regulation of the molecular weight is carried out by using known regulators, hydrogen in particular. [0029] The said stereospecific polymerization catalysts comprise the product of the reaction between:

[0030] 1) a solid component, containing a titanium compound and an electron-donor compound (internal donor) supported on magnesium dihalide (preferably chloride);

[0031] 2) an aluminum alkyl compound (cocatalyst); and, optionally,

[0032] 3) an electron-donor compound (external donor).

[0033] Said catalysts are preferably capable of producing homopolymers of propylene having an isotactic index higher than 90% (measured as weight amount of the fraction insoluble in xylene at room temperature).

[0034] The solid catalyst component (1) contains as electron-donor a compound generally selected among the ethers, ketones, lactones, compounds containing N, P and/or S atoms, and mono- and dicarboxylic acid esters.

[0035] Catalysts having the above mentioned characteristics are well known in the patent literature; particularly advantageous are the catalysts described in US patent 4,399,054 and European patent 45977.

[0036] Particularly suited among the said electron-donor compounds are phthalic acid esters and succinic acid esters.

[0037] Suitable succinic acid esters are represented by the formula (I):

(I)

[0038]

[0039] wherein the radicals R and R₂, equal to or different from each other, are a C1-C20 linear or branched alkyl, alkenyl, cycloalkyl, aryl, arylalkyl or alkylaryl group, optionally containing heteroatoms; the radicals R₃ to R₆ equal to or different from each other, are hydrogen or a C1-C20 linear or branched alkyl, alkenyl, cycloalkyl, aryl, arylalkyl or alkylaryl group, optionally containing heteroatoms, and the radicals R₃ to R₆ which are joined to the same carbon atom can be linked together to form a cycle. [0040] Ri and R₂ are preferably C1-C8 alkyl, cycloalkyl, aryl, arylalkyl and alkylaryl groups. Particularly preferred are the compounds in which Ri and R₂ are selected from primary alkyls and in particular branched primary alkyls. Examples of suitable Ri and R₂ groups are methyl, ethyl, n-propyl, n-butyl, isobutyl, neopentyl, 2-ethylhexyl. Particularly preferred are ethyl, isobutyl, and neopentyl.

[0041] One of the preferred groups of compounds described by the formula (I) is that in which R₃ to R5 are hydrogen and R₆ is a branched alkyl, cycloalkyl, aryl, arylalkyl and alkylaryl radical having from 3 to 10 carbon atoms. Another preferred group of compounds within those of formula (I) is that in which at least two radicals from R₃ to R₆ are different from hydrogen and are selected from C1-C20 linear or branched alkyl, alkenyl, cycloalkyl, aryl, arylalkyl or alkylaryl group, optionally containing heteroatoms. Particularly preferred are the compounds in which the two radicals different from hydrogen are linked to the same carbon atom. Furthermore, also the compounds in which at least two radicals different from hydrogen are linked to different carbon atoms, that is R₃ and R5 or R₄ and R₆ are particularly preferred.

[0042] Other electron-donors particularly suited are the 1,3-diethers, as illustrated in published European patent applications EP-A-361 493 and 728769.

[0043] As cocatalysts (2), one preferably uses the trialkyl aluminum compounds, such as Al- triethyl, Al-triisobutyl and Al-tri-n-butyl.

[0044] The electron-donor compounds (3) that can be used as external electron-donors (added to the Al-alkyl compound) comprise the aromatic acid esters (such as alkylic benzoates), heterocyclic compounds (such as the 2,2,6,6-tetramethylpiperidine and the 2,6- diisopropylpiperidine), and in particular silicon compounds containing at least one Si-OR bond (where R is a hydrocarbon radical). Examples of the said silicon compounds are those of formula

where a and b are integer numbers from 0 to 2, c is an integer from 1 to 3 and the sum (a+b+c) is 4; R 1 , R2 , and R 3 are alkyl, cycloalkyl or aryl radicals with 1-18 carbon atoms optionally containing heteroatoms.

[0045] Thexyltrimethoxysilane (2,3-dimethyl-2-trimethoxysilyl-butane) is particularly preferred.

[0046] The previously said 1,3- diethers are also suitable to be used as external donors. In the case that the internal donor is one of the said 1,3-diethers, the external donor can be omitted. [0047] The catalysts may be precontacted with small quantities of olefin

(prepolymerization), maintaining the catalyst in supension in a hydrocarbon solvent, and polymerizing at temperatures from room to 60 °C, thus producing a quantity of polymer from 0.5 to 3 times the weight of the catalyst.

[0048] Components a) and b) prepared with the above described processes are then blended by using processes known in the art.

[0049] The composition according to the present disclosure can also be prepared by subsequential polymerization in two or more reactors wherein in the first reactor component a) is prepared and then component b) is prepared in a subsequent reactor in the presence of component a) or vice versa. The polymerization processes that can be used are that one above described.

[0050] The composition of the present disclosure can also contain additives commonly used for olefin polymers like, for example, nucleating and clarifying agents and processing aids.

[0051] The propylene polymer composition of the present disclosure can be advantageously used for the production of films. Preferably cast or BOPP film mono or multilayer wherein at least one layer comprises the composition of the present disclosure.

[0052] The film obtained with the propylene polymer composition of the present disclosure is characterized by a good dyne retention, this renders the film suitable to being printed even after long time that for example plasma or corona treatment have been applied.

[0053] The multilayer films obtained with the propylene polymer composition of the present disclosure are characterized by having at least a skin layer comprising the propylene polymer composition of the present disclosure, the remaining layers can be formed of any material known in the art for use in multilayer films or in film-coated products. Thus, for example, each layer can be formed of a polypropylene homopolymer or copolymer or polyethylene homopolymer or copolymer or other kind of polymers such as EVA, EVOH

[0054] The combination and number of the layers of the multilayer structure is not particularly limited. The number is usually from 3 to 11 layers, preferably 3 to 9 layers, and more preferably 3 to 7 layers, and more preferably 3 to 5 layers and combinations including A/B/A, A/B/C, A/B/C/B/A, A/B/C/D/C/B/A are possible, provided that at least a skin layer A comprises the propylene polymer composition of the present disclosure. [0055] Preferred layers of the multilayer film of the present disclosure are 3 or 5 wherein at least one skin layer comprises the propylene/ethylene copolymer of the present disclosure. The preferred structure is A/B/A or A/B/C wherein A is the propylene polymer composition of the present disclosure.

[0056] For the purpose of the present disclosure the skin layer is the top layer and/or the bottom layer of a multilayer film.

[0057] Preferably in the multilayer film of the present disclosure the top and the bottom layer of the film comprised the propylene/ethylene copolymer of the present disclosure.

EXAMPLES

[0058] The following examples are given to illustrate the present invention without limiting purpose.

[0059] The data relating to the polymeric materials and the films of the examples are determined by way of the methods reported below.

[0060] Melting temperature (ISO 11357-3)

[0061] Determined by differential scanning calorimetry (DSC). A sample weighting 6 ± 1 mg, is heated to 200 ± 1° C at a rate of 20 °C/min and kept at 200 ± 1° C for 2 minutes in nitrogen stream and it is thereafter cooled at a rate of 20° C/min to 40 ± 2° C, thereby kept at this temperature for 2 min to crystallise the sample. Then, the sample is again fused at a temperature rise rate of 20° C/min up to 200° C ± 1. The melting scan is recorded, a thermogram is obtained (°C vs. mW), and, from this, temperatures corresponding to peaks are read. The temperature corresponding to the most intense melting peaks recorded during the second fusion is taken as the melting temperatures.

[0062] Melt Flow Rate (MFR)

[0063] Determined according to ASTM D 1238, at 230° C, with a load of 2.16 kg.

[0064] Solubility in xylene at 25°C

[0065] 2.5 g of polymer and 250 ml of xylene are introduced in a glass flask equipped with a refrigerator and a magnetical stirrer. The temperature is raised in 30 minutes up to the boiling pint of the solvent. The so obtained clear solution is then kept under reflux and stirring for further 30 minutes. The closed flask is then kept for 30 minutes in a bath of ice and water and in thermostatic water bath at 25° C for 30 minutes as well. The so formed solid is filtered on quick filtering paper. 100 ml of the filtered liquid is poured in a previously weighed aluminium container, which is heated on a heating plate under nitrogen flow, to remove the solvent by evaporation. The container is then kept on an oven at 80° C under vacuum until constant weight is obtained. The weight percentage of polymer soluble in xylene at room temperature is then calculated.

[0066] Intrinsic viscosity (IV)

[0067] Determined in tetrahydronaphthalene at 135° C.

[0068] Determination of 1-hexene content by NMR

[0069] 13 C NMR spectra are acquired on an AV-600 spectrometer operating at 150.91 MHz in the Fourier transform mode at 120 °C. The peak of the propylene CH was used as internal reference at 28.83. The 13 C NMR spectrum is acquired using the following parameters:

[0070] The total amount of 1-hexene as molar percent is calculated from diad using the following relations:

[0071] [P] = PP + 0.5PH

[0072] [H] = HH + 0.5PH

[0073] Assignments of the 13 C NMR spectrum of propylene/ 1-hexene copolymers have been calculated according to the following table:

[0074] C NMR of propylene/ethylene copolymers

[0075] 1¹3^JC NMR spectra were acquired on a Bruker AV-600 spectrometer equipped with cryoprobe, operating at 160.91 MHz in the Fourier transform mode at 120°C.

[0076] The peak of the Spp carbon (nomenclature according to "Monomer Sequence Distribution in Ethylene-Propylene Rubber Measured by 13C NMR. 3. Use of Reaction Probability Mode " C. J. Carman, R. A. Harrington and C. E. Wilkes, Macromolecules, 1977, 10, 536) was used as internal reference at 29.9 ppm. The samples were dissolved in 1,1,2,2- tetrachloroethane-d2 at 120°C with a 8 % wt/v concentration. Each spectrum was acquired with a 90° pulse, 15 seconds of delay between pulses and CPD to remove 1H-13C coupling. 512 transients were stored in 32K data points using a spectral window of 9000 Hz.

[0077] The assignments of the spectra, the evaluation of triad distribution and the composition were made according to Kakugo ("Carbon- 13 NMR determination of monomer sequence distribution in ethylene-propylene copolymers prepared with δ-titanium trichloride- diethylaluminum chloride" M. Kakugo, Y. Naito, K. Mizunuma and T. Miyatake, Macromolecules, 1982, 15, 1150) using the following equations:

[0078]

[0079] PPP = 100 Tpp/S PPE = 100 T_p8/S EPE = 100 T₈₈/S

[0080] PEP = 100 S_PP/S PEE= 100 S_p8/S EEE = 100 (0.25 S_y8+0.5 Sss)/S

[0081] S = T_pp + T_P5 + Τ_δδ + S_pp + S_P8 + 0.25 S_≠ + 0.5 S₈₈

[0082]

[0083] The molar percentage of ethylene content was evaluated using the following equation:

[0084] E% mol = 100 * [PEP+PEE+EEE]The weight percentage of ethylene content was evaluated using the following equation:

[0085]

[0086] 100 * E% mol * MW_E

[0087] E Wt. =

[0088] E% mol * MW_{E +} P% mol * MW_P

[0089]

[0090] where P% mol is the molar percentage of propylene content, while MWE and MWp are the molecular weights of ethylene and propylene, respectively.

[0091] The product of reactivity ratio r_\r₂ was calculated according to Carman (C.J. Carman,

[0093] The tacticity of Propylene sequences was calculated as mm content from the ratio of the PPP mmTpp (28.90-29.65 ppm) and the whole Tpp (29.80-28.37 ppm)

[0094] Seal Initiation Temperature (SIT)

[0095] Preparation of the film specimens [0096] Some films with a thickness of 50 μιη are prepared by extruding each test composition in a a single screw Collin extruder (length/diameter ratio of screw 1:25) at a film drawing speed of 7 m/min and a melt temperature do 210-250 °C. Each resulting film is superimposed on a 1000 μιη thick film of a propylene homopolymer having a xylene insoluble fraction of 97 wt% and a MFR L of 2 g/10 min. The superimposed films are bonded to each other in a Carver press at 200°C under a 9000 kg load, which is maintained for 5 minutes. The resulting laminates are stretched longitudinally and transversally, i.e. biaxially, by a factor 6 with a TOM Long film stretcher at 150°C, thus obtaining a 20 μιη thick film (18 μιη homopolymer+2 μιη test). 2x5 cm specimens are cut from the films.

[0097] Determination of the SIT.

[0098] For each test two of the above specimens are superimposed in alignment, the adjacent layers being layers of the particular test composition. The superimposed specimens are sealed along one of the 2 cm sides with a Brugger Feinmechanik Sealer, model HSG-ETK 745. Sealing time is 5 seconds at a pressure of 0.1 N/mm . The sealing temperature is increased of 2°C for each seal, starting from about 10 °C less than the melting temperature of the test composition. The sealed samples are left to cool and then their unsealed ends are attached to an Instron machine where they are tested at a traction speed of 50 mm/min.

[0099] The SIT. is the minimum sealing temperature at which the seal does not break when a load of at least 2 Newtons is applied in the said test conditions.

[0100] Determination of the Haze

[0101] 50 μιη film speciments prepared as described above for the SIT measure have been used. The haze value is measured using a Gardner photometric unit connected to a Hazemeter type UX-10 or an equivalent instrument having G.E. 1209 light source with filter "C". Reference samples of known haze are used for calibrating the instrument.

[0102] PREPARATION OF THE COPOLYMER OF PROPYLENE WITH 1- HEXENE

[0103] The copolymer is prepared as follows.

[0104] The solid catalyst component used in polymerization is a highly stereo specific Ziegler-Natta catalyst component supported on magnesium chloride, containing about 2.2% by weight of titanium and diisobutylphthalate as internal donor, prepared by analogy with the method described in WO03/054035 for the preparation of catalyst component A . [0105] CATALYST SYSTEM AND PREPOLYMERIZATION TREATMENT

[0106] Before introducing it into the polymerization reactor, the solid catalyst component described above is contacted at 15 °C for about 6 minutes with aluminum triethyl (TEAL) and thexyltrimethoxysilane (2,3-dimethyl-2-trimethoxysilyl-butane), in a TEAL/ thexyltrimethoxysilane weight ratio equal to about 7 and in such quantity that the TEAL/solid catalyst component weight ratio be equal to about 6.

[0107] The catalyst system is then subjected to prepolymerization by maintaining it in suspension in liquid propylene at 20 °C for about 20 minutes before introducing it into the polymerization reactor.

[0108] Polymerization

[0109] The polymerization is carried out in a two gas phase polymerization reactors by feeding in a continuous and constant flow the prepolymerized catalyst system, hydrogen (used as molecular weight regulator), propylene and 1-hexene in the gas state.

[0110] The main polymerization conditions are reported in table 1

[0111] Table 1

C3 = propylene; C6 = 1-hexene H2 = hydrogen

[0112] The polymer particles exiting the reactor are subjected to a steam treatment to remove the reactive monomers and volatile substances, and then dried.

[0113] The property of the copolymer obtained in example 1 are reported in table 2. [0114] Table 2

[0115] Propylene ethylene copolymers

[0116] Two commercial propylene ethylene copolymers sold by Lyondellbasell have been used to prepare the composition. The feature of the propylene copolymers are reported in table 3

[0117] Table 3

Nm not measured

[0118] Examples 1-5

[0119] Component a) has been blended with various amount of components bl) and b2). The features of the obtained composition are reported on table 4 [0120] Table 4

[0121] From table 4 clearly results that the resulting composition maintains a good value of SIT with respect to the original components and above all the resulting haze is lower than the haze of the original components. Thus the resulting cast film is improved in transparency retaining the low seal initiating temperature.

Multilayer film

The polymers of examples 1, 3 and 4 have been used to produce a A/B/A multilayer film wherein the A layer are the polymers of the examples and the B layer is a propylene homopolymer MOPLEN HP515M sold by Lyondellbasell. The film is 50 micron thick wherein layer A is 20 % of the overall thickness and layer B is 60 % of the overall thickness the processing parameters are reported in table 5.

Table 5

Sample of the obtained films have been subjected to a corona treatment and then the surface tension has been measured after one week and after one month. The results are reported in table

6.

Table 6

From table 6 clearly results that the films of the present disclosure maintains an high surface tension even after 150 days. This allow a better printability of the films even after long time, thus the films have a long shelf life after the corona treatment.

Claims

CLAIMS What is claimed is:

1. A propylene polymer composition comprising:

a) from 40 wt% to 80 wt% of a propylene 1-hexene copolymer containing from 5.5 to 9.0% by weight, of 1-hexene derived units having a Melt Flow Rate (MFR, measured according to ASTM D 1238, 230°C/2.16 kg, i.e. at 230°C, with a load of 2.16 kg) from 3.5 to 12.0 g/10 min;

b) from 20 wt% to 60 wt% of a propylene ethylene copolymer containing from 1.5 wt% to 6.5 wt% of ethylene derived units, a having a Melt Flow Rate (MFR, measured according to ASTM D 1238, 230°C/2.16 kg, i.e. at 230°C, with a load of 2.16 kg) from 3.5 to 12.0 g/10 min;

the sum of the amount of a) and b) being 100.

2. The propylene polymer composition according to claim 1 wherein component a) ranges from from 45 wt% to 74 wt%; and component b) ranges from 26 wt% to 55 wt%.

3. The propylene polymer composition according to claim 2 wherein component a) ranges from from preferably from 48 wt% to 63 wt% and component b) ranges from 37 wt% to 52 wt%.

4. The propylene polymer composition according to anyone of claims 1- 3 wherein component a) contains from 6.0 to 8.5% by weight of 1-hexcene derived units.

5. The propylene polymer composition according to anyone of claims 1-4 wherein component b) contains from 2.0 wt% to 6.1 wt%; of ethylene derived units.

6. The propylene polymer composition according to anyone of claims 1-5 wherein in component a) the DSC plot shows at least two peaks having a difference in height ranging from 0 to 5 mW ; preferably from 0 to 3 mW.

7. The propylene polymer composition according to anyone of claims 1-6 wherein in component a) the higher melting temperature, measured by DSC, ranges from 141.0 °C to 151.0 °C.

8. The propylene polymer composition according to anyone of claims 1-7 wherein in component a) the difference of the melting temperature of the two peaks ranges from 5°C to 20°C.

9. The propylene polymer composition according to anyone of claims 1-8 wherein in component a) the Melt Flow Rate (MFR, measured according to ASTM D 1238, 230°C/2.16 kg, i.e. at 230°C, with a load of 2.16 kg) ranges from 3.8 to 7.5 g/10 min.

10. The propylene polymer composition according to anyone of claims 1-9 wherein in component b) the Melt Flow Rate (MFR, measured according to ASTM D 1238, 230°C/2.16 kg, i.e. at 230°C, with a load of 2.16 kg) ranges from 3.8 to 7.5 g/10 min

11. A film comprising the propylene polymer composition according to anyone of claims 1-10.

12. The film of claim 11 being a cast film or a BOPP film.

13 the multilayer film comprising the propylene polymer composition according to anyone of claims 1-10

14 The multilayer film according to claim 13 having from 3 to 11 layers

15. The multilayer film according to claim 13 having an A/B/A or A/B/C structure wherein the A layer comprises the propylene polymer composition according to anyone of claims 1-10