Propylene-based polymer composition

Abstract

Claimed is: A propylene polymer composition comprising: a) from 20 to 44 wt% of a propylene 1-hexene copolymer containing from 5.0 to 8.3 wt% of 1-hexene derived units; b) from 25 to 45 wt% of a propylene 1-hexene ethylene terpolymer; c) from 25 to 50 wt% of a propylene ethylene copolymer; wherein the melt flow rate of components a) + b) + c) is from 3.5 to 12.0 g / 10 min.

Description

Technical Field

[0001] This disclosure relates to compositions comprising copolymers of propylene and 1-hexene and copolymers of propylene and ethylene, which are particularly suitable for preparing films having low seal initiation temperature (SIT) and high crystallization temperature, especially biaxially oriented polypropylene films (BOPP) and cast films. Background Technology

[0002] Copolymers of propylene and 1-hexene are known in the art; for example, WO 2006 / 002778 relates to copolymers of propylene and 1-hexene having 0.2 to 5 wt% 1-hexene-derived units. These copolymers have a unimodal molecular weight distribution and are used in piping systems.

[0003] WO2017 / 097579 relates to compositions comprising copolymers of propylene and 1-hexene and copolymers of propylene and ethylene, which are particularly suitable for preparing films with low seal initiation temperature (SIT) and high transparency, especially biaxially oriented polypropylene films (BOPP) and cast films. The obtained seal initiation temperature is still unsatisfactory and can be reduced.

[0004] WO 2018 / 202396 relates to propylene polymer compositions comprising: 35 wt% to 65 wt% of a propylene-1-hexene copolymer containing 10.2 to 13 wt% of 1-hexene-derived units and 35 wt% to 65 wt% of a propylene-ethylene copolymer containing 1.5 wt% to 6.5 wt% of ethylene-derived units. Even though the exemplified compositions exhibit very low SIT, the xylene-soluble content is very high, and as shown in the comparative examples, the amount of gel can be reduced.

[0005] The applicant discovered that by using compositions comprising propylene-1-hexene copolymer, propylene, 1-hexene, ethylene terpolymer and propylene-ethylene copolymer, BOPP and cast films with low seal initiation temperature (SIT), high crystallization temperature and good optical properties can be produced. Summary of the Invention

[0006] Therefore, this disclosure provides a propylene polymer composition comprising:

[0007] a) 20 wt% to 44 wt% of propylene-1-hexene copolymer containing 5.0 to 8.3 wt% of 1-hexene-derived units, having a melt flow rate (MFR, measured according to ISO 1133, 230 °C / 2.16 kg, i.e. at 230 °C and 2.16 kg load) of 3.5 to 8.5 g / 10 min.

[0008] b) 25 wt% to 45 wt% of a propylene-1-hexene-ethylene terpolymer containing 7.2 to 12.0 wt% of 1-hexene-derived units and 0.5 to 2.5 wt% of ethylene-derived units, wherein the melt flow rate (MFR, according to ISO 1133, 230 °C / 2.16 kg, i.e., measured at 230 °C and 2.16 kg load) of components a)+b) is 3.5 to 8.5 g / 10 min.

[0009] c) 25 wt% to 50 wt% of a copolymer of propylene and ethylene, containing 3.5 wt% to 8.7 wt% of ethylene-derived units.

[0010] The melt flow rate (MFR, measured according to ISO 1133, 230℃ / 2.16kg, i.e. at 230℃ and 2.16kg load) of components a)+b)+c) is 3.5 to 12.0 g / 10 min.

[0011] The sum of the quantities in a), b), and c) is 100;

[0012] in:

[0013] i) The xylene-soluble content of the composition at 25°C ranges from 16.4 wt% to 35.3 wt%;

[0014] ii) The melting point of the composition is in the range of 122°C to 132°C. Detailed Implementation

[0015] This disclosure provides a propylene polymer composition comprising:

[0016] a) 20 wt% to 44 wt%, preferably 27 wt% to 40 wt%; more preferably 29 wt% to 35 wt% of a propylene-1-hexene copolymer containing 5.0 wt% to 8.3 wt%, preferably 6.3 wt% to 7.8 wt%; more preferably 6.5 wt% to 7.4 wt% of 1-hexene-derived units having a melt flow rate (MFR, according to ISO 1133, 230 °C / 2.16 kg, i.e., measured at 230 °C and 2.16 kg load); more preferably 5.0 to 7.0 g / 10 min.

[0017] b) 25 wt% to 45 wt%, preferably 35 wt% to 40 wt%; more preferably 36 wt% to 39 wt% of a propylene-1-hexene-ethylene terpolymer containing 7.2 wt% to 12.0 wt%, preferably 7.5 wt% to 9.5 wt%, more preferably 8.2 wt% to 9.1 wt% of 1-hexene-derived units and 0.5 wt% to 2.5 wt%, preferably 0.7 wt% to 2.2 wt%, more preferably 0.8 wt% to 2.0 wt% of ethylene-derived units; wherein the melt flow rate (MFR, according to ISO 1133, 230 °C / 2.16 kg, i.e., measured at 230 °C and 2.16 kg load) of components a) + b) is 3.5 to 8.5 g / 10 min, preferably 4.4 to 8.0 g / 10 min; more preferably 5.0 to 7.0 g / 10 min;

[0018] c) 25 wt% to 50 wt%, preferably 27 wt% to 40 wt%; more preferably 29 wt% to 35 wt% of a copolymer of propylene and ethylene, containing 3.5 wt% to 8.7 wt%; preferably 4.5 wt% to 8.4 wt%; more preferably 4.8 wt% to 8.1 wt% of ethylene-derived units.

[0019] The melt flow rate (MFR, measured according to ISO 1133, 230℃ / 2.16kg, i.e. at 230℃ and 2.16kg load) of components a)+b)+c) is 3.5 to 12.0 g / 10 min.

[0020] The preferred range is 4.4 to 8.0 g / 10 min; the more preferred range is 5.0 to 8.5 g / 10 min.

[0021] The sum of the quantities in a), b), and c) is 100;

[0022] in:

[0023] i) The xylene-soluble content of the composition at 25°C ranges from 16.4 wt% to 35.3 wt%; preferably from 18.3 wt% to 30.1 wt%; more preferably from 22.1 wt% to 28.3 wt%;

[0024] ii) The melting point of the composition is in the range of 122°C to 132°C; preferably 125°C to 131°C; more preferably 126°C to 130°C.

[0025] The propylene-1-hexene copolymer disclosed herein contains only propylene and 1-hexene-derived units. The propylene-ethylene copolymer disclosed herein contains only propylene and ethylene-derived units. The propylene-1-hexene-ethylene terpolymer disclosed herein contains only propylene, 1-hexene, and ethylene-derived units.

[0026] The compositions disclosed herein have a very low seal initiation temperature (SIT), making the material advantageously suitable for the production of films, particularly cast films or BOPP films.

[0027] In particular, for the compositions of this disclosure, the difference between the melting point and the SIT value is particularly large. The relatively high melting point allows the polymer to have better processability, especially when used to obtain films, while the low SIT value improves the use of the film in sealing applications.

[0028] Preferably, the SIT value is between 70°C and 85°C; more preferably, it is between 75°C and 82°C. The difference between the melting point and SIT (Tm-SIT) is preferably in the range of 45°C to 60°C; more preferably, it is in the range of 46°C to 58°C.

[0029] Furthermore, the compositions disclosed herein possess particularly good optical properties, such as a haze value of less than 0.90% when measured on a BOPP film, preferably less than 0.80%, more preferably less than 0.78%. Preferably, the haze is greater than 0.20%.

[0030] The method for preparing the propylene-ethylene copolymer of this disclosure is carried out in the presence of a highly stereoselective multiphase Ziegler-Natta catalyst. The Ziegler-Natta catalyst suitable for preparing the propylene-ethylene copolymer of this disclosure comprises a solid catalyst component comprising at least one titanium compound having at least one titanium-halogen bond and at least one electron donor compound (internal donor), both supported on magnesium chloride. The Ziegler-Natta catalyst system further includes an organoaluminum compound as a necessary cocatalyst and an optional external electron donor compound.

[0031] Suitable catalyst systems are described in European patents EP45977, EP361494, EP728769, EP 1272533 and international patent application WO00163261.

[0032] The organoaluminum compound is preferably alkyl-Al, selected from trialkylaluminum compounds, such as triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, and tri-n-octylaluminum. Mixtures of trialkylaluminum with alkylaluminum halides, alkylaluminum hydrides, or alkylaluminum sesquichlorides (such as AlEt2Cl and Al2Et3Cl3) can also be used.

[0033] Preferred external electron donor compounds include silicon compounds, ethers, esters such as ethyl 4-ethoxybenzoate, amines, heterocyclic compounds, and particularly 2,2,6,6-tetramethylpiperidine, ketones, and 1,3-diethers. Another class of preferred external donor compounds is of formula R. a 5 R b 6 Si(OR 7 )c A silicon compound, wherein a and b are integers from 0 to 2, c is an integer from 1 to 3, and the sum of (a+b+c) is 4; R 5 R 6 and R 7 The external electron donor compound is optionally an alkyl, cycloalkyl, or aryl group having 1-18 carbon atoms and containing a heteroatom. Particularly preferred are methylcyclohexyldimethoxysilane, diphenyldimethoxysilane, methyl tert-butyldimethoxysilane, dicyclopentyldimethoxysilane, 2-ethylpiperidinyl-2-tert-butyldimethoxysilane, and 1,1,1-trifluoropropyl-2-ethylpiperidinyl-dimethoxysilane and 1,1,1-trifluoropropyl-methyl-dimethoxysilane. The amount of the external electron donor compound is such that the molar ratio between the organoaluminum compound and the electron donor compound is 0.1 to 500; preferably 1 to 100; more preferably 2 to 50.

[0034] The polymerization method can be continuous or intermittent, carried out according to known techniques, and operated in the gas phase, or in the liquid phase with or without an inert diluent, or by a mixed liquid-gas technique. Polymerization is preferably carried out in the gas phase in three reactors, one reactor for each component of the composition. Components a) and b) are preferably obtained in the first two reactors, respectively, while component c) is obtained in the third and last reactors.

[0035] The polymerization reaction time, pressure, and temperature are not critical; however, a temperature of 20 to 100°C is optimal. The pressure can be atmospheric pressure or higher.

[0036] As mentioned earlier, the molecular weight is adjusted by using known modifiers, particularly hydrogen.

[0037] The compositions disclosed herein may also contain additives commonly used in olefin polymers, such as nucleating agents, clarifying agents, and processing aids.

[0038] The composition disclosed herein is preferably characterized by a gel number of less than 250; more preferably less than 150 (>0.1 mm). The gel number indicates the uniformity of the product: the lower the number of gels, the higher the uniformity of the polymer.

[0039] The propylene polymer compositions disclosed herein can be advantageously used in the production of films. Preferred are cast or BOPP films, either single-layer or multi-layer, wherein at least one layer comprises the compositions disclosed herein.

[0040] Example

[0041] The following examples are given to illustrate the invention and not to limit it.

[0042] Data related to the polymer materials and films of the examples were determined using the methods reported below.

[0043] Melting and crystallization temperatures (ISO 11357-2013)

[0044] Determined by differential scanning calorimetry (DSC) according to ISO 11357-20133, at a scan rate of 20 °C / min, under cooling and heating conditions, on samples of 5 to 7 mg weight, under an inert N2 flow. The instrument was calibrated using indium.

[0045] Melt flow rate (MFR)

[0046] Measured according to ISO 1133, 230℃, 2.16kg.

[0047] Solubility in xylene at 25°C

[0048] Solubility in xylene at 25°C: 2.5 g of polymer sample and 250 ml of xylene were introduced into a glass flask equipped with a refrigerator and magnetic stirrer. The temperature was raised to 135°C over 30 minutes. The resulting clear solution was kept under reflux and stirred for another 30 minutes. The solution was cooled in two stages. In the first stage, the temperature was lowered to 100°C in air with stirring for 10 to 15 minutes. In the second stage, the flask was transferred to a temperature-controlled water bath at 25°C for 30 minutes. The temperature was lowered to 25°C without stirring for the first 20 minutes and maintained at 25°C with stirring for the next 10 minutes. The solid formed was filtered through rapid filter paper (e.g., Whatman filter paper grade 4 or 541). 100 ml of the filtrate (S1) was poured into a pre-weighed aluminum container and heated to 140°C on a hot plate under a nitrogen stream to remove the solvent by evaporation. The container was then kept under vacuum in an oven at 80°C until constant weight was achieved. The amount of polymer soluble in xylene at 25°C was then calculated. XS(tot) and XSA values ​​were determined experimentally. The fraction (XSB) of component (B) soluble in xylene at 25°C can be calculated using the following formula:

[0049] XS=W(A)×(XS A )+W(B)×(XS B )

[0050] Where W(A) and W(B) are the relative amounts of components (A) and (B) respectively, and W(A) + W(B) = 1.

[0051] The content of 1-hexene was determined by NMR.

[0052] The results were obtained on an AV-600 spectrometer operating in Fourier transform mode at 150.91 MHz at 120 °C. 13 C10 NMR spectrum. The peak of propylene CH at 28.83 was used as an internal reference. Obtained using the following parameters. 13C NMR spectrum:

[0053] Spectral center (O1) 30ppm Decoupling sequence WALTZ 65_64pl Pulse program ZGPG Pulse length (P1) For 90° Total Points (TD) 32K Relaxation delay 15s Transient number 1500

[0054] The total amount of 1-hexene as a molar percentage was calculated from the binary unit group using the following relationship:

[0055] [P] = PP + 0.5PH

[0056] [H] = HH + 0.5PH

[0057] propylene / 1-hexene copolymer 13 The assignment of C NMR spectra is calculated according to the table below:

[0058] 1 46.93-46.00 <![CDATA[S αα ]]> PP 2 44.50-43.82 <![CDATA[S αα ]]> PH 3 41.34-4.23 <![CDATA[S αα ]]> HH 4 38.00-37.40 <![CDATA[S αγ +S αδ ]]> PE 5 35.70-35.0 <![CDATA[4B4]]> H 6 35.00-34.53 <![CDATA[S αγ +S αδ ]]> HE 7 33.75 33.20 CH H 8 33.24 <![CDATA[T δδ ]]> EPE 9 30.92 <![CDATA[T βδ ]]> PPE 10 30.76 <![CDATA[S γγ ]]> XEEX 11 30.35 <![CDATA[S γδ ]]> XEEE 12 29.95 <![CDATA[S δδ ]]> EEE 13 29.35 <![CDATA[3B4]]> H 14 28.94-28.38 CH P 15 27.43-27.27 <![CDATA[S βδ ]]> XEE 16 24.67-24.53 <![CDATA[S ββ ]]> XEX 17 23.44-23.35 <![CDATA[2B4]]> H 18 21.80-19.90 <![CDATA[CH3]]> P 19 14.22 <![CDATA[CH3]]> H

[0059] Ethylene (C2) content

[0060] propylene / ethylene copolymer 13 C NMR

[0061] 13 C10 NMR spectra were obtained on a Bruker Av-600 spectrometer equipped with a cryoprobe, operated at 160.91 MHz in Fourier transform mode at 120 °C.

[0062] S at 29.9 ppm ββ Carbon peaks (according to the nomenclature of "Monomer sequence distribution in ethylene-propylene rubber by 13C NMR. 3. Use of reaction probability mode" CJ Carman, RA Harrington, and CE Wilkes, Macromolecules, 1977, 10, 536) were used as an internal reference. Samples were dissolved at 120 °C in 1,1,2,2-tetrachloroethane-d2 at a concentration of 8 wt / v%. Each spectrum was obtained with a 90° pulse, with a 15-second delay between the pulse and CPD to remove 1H-13C coupling. 512 transients were stored in 32K data points using a 9000 Hz spectral window.

[0063] The spectral distribution, triplet state distribution, and compositional assessment were performed 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:

[0064] PPP = 100T ββ / S PPE=100T βδ / S EPE=100T δδ / S

[0065] PEP = 100S ββ / S PEE=100S βδ / S EEE=100(0.25S γδ +0.5S δδ ) / S

[0066] S = T ββ +T βδ +T δδ +S ββ +S βδ +0.25S γδ +0.5S δδ

[0067] The molar percentage of ethylene content is evaluated using the following equation: E%mol = 100 * [PEP + PEE + EEE]. The weight percentage of ethylene content is evaluated using the following equation:

[0068]

[0069] Where P mol% is the molar percentage of propylene content, and MW E and MW P These are the molecular weights of ethylene and propylene, respectively.

[0070] According to Carman (CJCarman, R.A. Harrington, and C.E. Wilkes, Macromolecules 1977; 10, 536), the product of the reaction ratios r1 and r2 is calculated as follows:

[0071]

[0072] The stereoregularity of the propylene sequence is determined by PPP mmT ββ (28.90-29.65ppm) and the entire T ββ The ratio of (29.80-28.37ppm) is calculated as mm content.

[0073] propylene / ethylene copolymer 13 C NMR:

[0074] 13 C10 NMR spectra were obtained on a Bruker Av-600 spectrometer equipped with a cryoprobe, operated at 160.91 MHz in Fourier transform mode at 120 °C.

[0075] S at 29.9 ppm ββ Carbon peaks (according to the nomenclature of "Monomer sequence distribution in ethylene-propylene rubber by 13C NMR. 3. Use of reaction probability mode" CJ Carman, RA Harrington, and CE Wilkes, Macromolecules, 1977, 10, 536) were used as an internal reference. Samples were dissolved at 120 °C in 1,1,2,2-tetrachloroethane-d2 at a concentration of 8 wt / v%. Each spectrum was obtained with a 90° pulse, with a 15-second delay between the pulse and CPD to remove 1H-13C coupling. 512 transients were stored in 32K data points using a 9000 Hz spectral window.

[0076] The spectral distribution, triplet state distribution, and compositional assessment were performed 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:

[0077] PPP = 100T ββ / S PPE=100T βδ / S EPE=100T δδ / S

[0078] PEP = 100S ββ / S PEE=100S βδ / S EEE=100(0.25S γδ +0.5S δδ ) / S

[0079] S = T ββ +T βδ +T δδ +S ββ +S βδ +0.25S γδ +0.5S δδ

[0080] The molar percentage of ethylene content is evaluated using the following equation:

[0081] E%mol = 100 * [PEP + PEE + EEE] The weight percentage of ethylene content is evaluated using the following equation:

[0082]

[0083] Where P mol% is the molar percentage of propylene content, and MW E and MW P These are the molecular weights of ethylene and propylene, respectively.

[0084] According to Carman (CJCarman, R.A. Harrington, and C.E. Wilkes, Macromolecules 1977; 10, 536), the product of the reaction ratios r1 and r2 is calculated as follows:

[0085]

[0086] The stereoregularity of the propylene sequence is determined by PPP mmT ββ (28.90-29.65ppm) and the entire T ββ The ratio (29.80-28.37ppm) is calculated as the mm content.

[0087] 1-Hexene and ethylene content:

[0088] pass 13 C-NMR spectroscopy was performed on terpolymers:

[0089] NMR analysis was performed on an AV-600 spectrometer operating in Fourier transform mode at 150.91 MHz at 120 °C. 13C10 NMR spectrum. The peak of propylene CH at 28.83 was used as an internal reference. Obtained using the following parameters. 13 C NMR spectrum:

[0090] Spectral width (SW) 60ppm

[0091] Spectral center (O1) 30ppm

[0092] Decoupling sequence WALTZ 65_64pl

[0093] Pulse program (1) ZGPG

[0094] Pulse length (P1) (2)\ For 90°

[0095] Total Points (TD) 32K

[0096] Relaxation delay (2) 15s

[0097] Transient number (3) 1500

[0098] The total amount of 1-hexene and ethylene as molar percentages is calculated from the binary unit group using the following relationship:

[0099] [P] = PP + 0.5PH + 0.5PE

[0100] [H] = HH + 0.5PH

[0101] [E] = EE + 0.5PE

[0102] propylene / 1-hexene / ethylene copolymer 13 The assignment of C NMR spectra is calculated according to the table below:

[0103] 1 46.93-46.00 <![CDATA[S αα ]]> PP 2 44.50-43.82 <![CDATA[S αα ]]> PH 3 41.34-4.23 <![CDATA[S αα ]]> HH 4 38.00-37.40 <![CDATA[S αγ +S αδ ]]> PE 5 35.70-35.0 <![CDATA[4B4]]> H 6 35.00-34.53 <![CDATA[S αγ +S αδ ]]> HE 7 33.75 33.20 CH H 8 33.24 <![CDATA[T δδ ]]> EPE 9 30.92 <![CDATA[T βδ ]]> PPE 10 30.76 <![CDATA[S γγ ]]> XEEX 11 30.35 <![CDATA[S γδ ]]> XEEE 12 29.95 <![CDATA[S δδ ]]> EEE 13 29.35 <![CDATA[3B4]]> H 14 28.94-28.38 CH P 15 27.43-27.27 <![CDATA[S βδ ]]> XEE 16 24.67-24.53 <![CDATA[S ββ ]]> XEX 17 23.44-23.35 <![CDATA[2B4]]> H 18 21.80-19.90 <![CDATA[CH3]]> P 19 14.22 <![CDATA[CH3]]> H

[0104] By using formula C6 总 =C6 a xW a+ The 1-hexene content of component b is calculated from the total 1-hexene content of the composition, where C6 is the 1-hexene content, and Wa and Wb are the amounts of components a and b, respectively.

[0105] Sealing start temperature (SIT)

[0106] Preparation of membrane samples

[0107] Films with a thickness of 50 μm were prepared by extruding the test compositions in a single-screw Collin extruder (screw length / diameter ratio of 1:25) at a film stretching speed of 7 m / min and a melt temperature of 210–250 °C. Each resulting film was stacked on a 1000 μm thick propylene homopolymer film having a xylene-insoluble fraction of 97 wt% and an MFR L of 2 g / 10 min. The stacked films were bonded together in a Carver press at 200 °C under a 9000 kg load and held for 5 minutes. The resulting laminates were stretched 7 times longitudinally and transversely (i.e., biaxially) at 160 °C using a Karo 4 Brueckener film stretching machine, thereby obtaining films with a thickness of 20 μm (18 μm homopolymer + 2 μm test).

[0108] The determination of SIT.

[0109] Cut a 6 cm wide and 35 cm long strip from the center of the BOPP film and stack it with another BOPP film made of PP homopolymer. Seal the stacked specimens along one of the 2 cm sides using a Brugger Feinmechanik sealing machine (model HSG-ETK 745). The sealing time is 5 seconds at a pressure of 0.14 MPa (20 psi). The initial sealing temperature is approximately 10 °C lower than the melt temperature of the test composition. Cut the sealing strip into six 15 mm wide specimens, long enough to be protected in the tensile testing machine fixtures. Test the seal strength with a force sensor capacity of 100 N, a lateral speed of 100 mm / min, and a clamping distance of 50 mm. The results are expressed as the average of the maximum seal strength (N). Cool from left to right, then attach their unsealed ends to an Instron machine, where they are tested at a traction speed of 50 mm / min.

[0110] Then repeat the test by changing the temperature as follows:

[0111] If the seal strength is less than 1.5 N, increase the temperature.

[0112] If the seal strength is >1.5N, then reduce the temperature.

[0113] If the sealing strength is close to the target, select a step size of 1°C; if the strength is far from the target, select a step size of 2°C. Then the temperature change must be adjusted gradually.

[0114] The target seal strength (SIT) is defined as the lowest temperature at which a seal strength of 1.5 N or higher is achieved.

[0115] Preparation of copolymers

[0116] catalyst system

[0117] Procedure for preparing spherical adducts

[0118] Microspherical MgCl2·pC2H5OH adducts were prepared according to the method described in Comparative Example 5 of WO98 / 44009, except that BiCl3 in powder form at a concentration of 3 mol% relative to magnesium was added before the feed oil.

[0119] Procedure for preparing solid catalyst components

[0120] The solid catalyst components prepared according to Example 1 of EP 728769 have the following differences:

[0121] The second and third titanate esterifications were carried out at 110°C to 120°C;

[0122] Use MgCl2.3C2H50H in the form of spherical solid particles with a maximum diameter of 65 micrometers or less, instead of 50 micrometers.

[0123] Catalyst system and prepolymerization treatment

[0124] Before introducing it into the polymerization reactor, the above solid catalyst component was contacted with triethylaluminum (TEAL) and dicyclopentyldimethoxysilane (DCPMS) as external donors at 15°C for about 6 minutes.

[0125] The catalyst system was then prepolymerized by maintaining it in a liquid propylene suspension at 20°C for about 20 minutes before being introduced into the polymerization reactor.

[0126] polymerization

[0127] A propylene-1-hexene copolymer (component (a)) is prepared by feeding a prepolymerized catalyst system, hydrogen (used as a molecular weight regulator), gaseous propylene, and 1-hexene into a first gas-phase polymerization reactor in a continuous and constant flow. The polypropylene copolymer prepared in the first reactor is discharged in a continuous flow and introduced into a second gas-phase polymerization reactor in a continuous flow along with a metered and constant flow of gaseous hydrogen, 1-hexene, and propylene.

[0128] The polypropylene copolymer produced in the second reactor is discharged in a continuous flow and, after the removal of unreacted monomers, is introduced in a continuous flow along with a constant amount of gaseous hydrogen, 1-hexene, and propylene into the third gas-phase polymerization reactor.

[0129] The aggregation conditions are reported in Table 1.

[0130] Table 1

[0131]

[0132] C3 = propylene; C6 = 1-hexene; C2 = ethylene; H2 = hydrogen

[0133] The polymer obtained according to Table 1 was added with 0.05% Irg.1010; then 0.1% Irg.168 and 0.05% CaSt were granulated. The characteristics of the composition are reported in Table 2.

[0134] Table 2

[0135]

[0136] C3 = propylene; C6 = 1-hexene; C2 = ethylene;

[0137] *Calculated using the formula Ytotal = XaYa + XbYb, where Y is the comonomer content, and Xa and Xb are the splitting monomers (Xa + Xb = 1).

[0138] As can be seen from the results in Table 2, a lower SIT with good haze is obtained using the composition according to the present invention.

Claims

1. A propylene polymer composition comprising: a) 20 wt% to 44 wt% of a propylene 1-hexene copolymer containing 5.0 to 8.3 wt% of 1-hexene derived units, by 13 C NMR measurement, having a melt flow rate, i.e. MFR, according to ISO 1133, 230 °C / 2.16 kg, i.e. measured at 230 °C, under a load of 2.16 kg, of 3.5 to 8.5 g / 10 min; b) 25 wt% to 45 wt% of a propylene-1-hexene ethylene terpolymer containing 7.2 to 12.0 wt% of 1-hexene-derived units, through... 13 C NMR measurements, and 0.5 to 2.5 wt% ethylene-derived units, were obtained through... 13 C NMR measurements, in which the melt flow rate, or MFR, of components a) + b) is 3.5 to 8.5 g / 10 min, according to ISO 1133, 230 °C / 2.16 kg, i.e., measured at 230 °C and 2.16 kg load. c) A copolymer of propylene and ethylene containing 25 wt% to 50 wt% of ethylene-derived units, obtained by... 13 C NMR measurement; The melt flow rate, or MFR, of components a) + b) + c) is 3.5 to 12.0 g / 10 min, as measured according to ISO 1133, 230 °C / 2.16 kg, i.e., at a load of 2.16 kg at 230 °C. The sum of the quantities in a), b), and c) is 100; in: The composition has a xylene-soluble content ranging from 16.4 wt% to 35.3 wt% at 25°C. The melting point of the composition is in the range of 122°C to 132°C.

2. The propylene polymer composition according to claim 1, wherein component a) ranges from 27 wt% to 40 wt%; component b) ranges from 35 wt% to 40 wt%; and component c) ranges from 27 wt% to 40 wt%.

3. The propylene polymer composition according to claim 1, wherein component a) ranges from 29 wt% to 35 wt%; component b) ranges from 36 wt% to 39 wt%; and component c) ranges from 29 wt% to 35 wt%.

4. The propylene polymer composition according to claim 1, wherein component a) contains 6.3 wt% to 7.8 wt% of 1-hexene derivative units.

5. The propylene polymer composition according to claim 1, wherein component b) contains 7.5 wt% to 9.5 wt% of 1-hexene-derived units and 0.7 wt% to 2.2 wt% of ethylene-derived units.

6. The propylene polymer composition according to claim 1, wherein component c) contains 4.5 wt% to 8.4 wt% of ethylene-derived units.

7. The propylene polymer composition according to claim 1, wherein component a) contains 6.5 wt% to 7.4 wt% of 1-hexene derivative units.

8. The propylene polymer composition according to claim 1, wherein component b) contains 8.2 wt% to 9.1 wt% of 1-hexene-derived units and 0.8 wt% to 2.0 wt% of ethylene-derived units.

9. The propylene polymer composition according to claim 1, wherein component c) contains 4.8 wt% to 8.1 wt% of ethylene-derived units.

10. The propylene polymer composition according to claim 1, wherein the melting point of the composition is in the range of 125°C to 131°C.

11. The propylene polymer composition according to claim 1, wherein the xylene-soluble content of the composition at 25°C ranges from 18.3 wt% to 30.1 wt%.

12. The propylene polymer composition according to claim 1, wherein the xylene-soluble content of the composition at 25°C ranges from 22.1 wt% to 28.3 wt%.

13. A membrane comprising the propylene polymer composition according to claim 1.

14. The film according to claim 13 is a cast film.

15. The membrane according to claim 13, wherein it is a BOPP membrane.

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