Propylene-based copolymer compositions

Abstract

A polyolefin composition comprising: A) from 67% to 94% by weight of a copolymer of propylene and ethylene wherein: i) the content of ethylene derived units measured by NMR is between 2.7% by weight and 5.3% by weight; b) from 6% to 33% by weight of a propylene ethylene copolymer containing from 18.2% to 36.4% by weight of ethylene derived units as measured by NMR; wherein the resulting polyolefin composition has: i) a content of ethylene derived units, measured by NMR, of between 5.4 wt% and 10.0 wt%; ii) the content of ethylene derived units in the fraction soluble in xylene at 25 DEG C, measured by NMR, is between 14.4 wt% and 31.1 wt%; iii) the melt flow rate (ISO 1133 (230 DEG C, 21.6 kg) ranges from 0.5 g / 10 minutes to 7.5 g / 10 minutes; iv) the range of xylene solubles at 25 DEG C is from 13.9 wt% to 30.0 wt%; v) the intrinsic viscosity of the fraction soluble in xylene at 25 DEG C, measured in tetrahydronaphthalene at 135 DEG C, ranges from 4.4 dl / g to 9.4 dl / g; vi) the intrinsic viscosity of the entire composition, measured in tetralin at 135 DEG C, ranges from 4.0 dl / g to 9.4 dl / g; the sum of A and B is 100.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a composition comprising a propylene ethylene copolymer. The composition has a high molecular weight and a high abrasion resistance. The composition is particularly suitable for the production of molded articles. BACKGROUND

[0002] It is well known in the field of polymers that different applications require specially tailored polymers to achieve individually high demanding properties.

[0003] For many applications, abrasion resistance is an important feature of articles made of polymeric materials, in particular for polypropylene. For example, in the automotive industry, where durable plastic products are required as exterior parts and interior parts, especially in case they are part of moving parts such as gears.

[0004] Therefore, there is a need to develop a composition comprising a propylene ethylene copolymer for molded articles with enhanced abrasion resistance. SUMMARY

[0005] A polyolefin composition comprising: A) 67 wt% to 94 wt% of a copolymer of propylene with ethylene, wherein: i) the content of ethylene derived units is between 2.7 wt% to 5.3 wt% as measured by NMR; B) 6 wt% to 33 wt% of a propylene ethylene copolymer containing 18.2 wt% to 36.4 wt% of ethylene derived units as measured by NMR; wherein the resulting polyolefin composition has: i) the content of ethylene derived units is between 5.4 wt% to 10.0 wt% as measured by NMR; ii) the content of ethylene derived units in the fraction soluble in xylene at 25° is between 14.4 wt% to 31.1 wt% as measured by NMR; iii) a melt flow rate (ISO 1133 (230°C, 21.6 kg) ranging from 0.5 g / 10 min to 7.5 g / 10 min; iv) xylene solubles at 25°C ranging from 13.9 wt% to 30.0 wt%; v) the intrinsic viscosity of the fraction soluble in xylene at 25°C measured in tetralin at 135°C ranging from 4.4 dl / g to 9.4 dl / g; vi) the intrinsic viscosity of the whole composition measured in tetralin at 135°C ranging from 4.0 dl / g to 9.4 dl / g; The sum of A+B is 100. DETAILED DESCRIPTION

[0006] It is therefore an object of the present disclosure a polyolefin composition comprising: A) from 67 wt% to 94 wt%; preferably from 76 wt% to 90 wt%; more preferably from 81 wt% to 86 wt% of a copolymer of propylene with ethylene, wherein: i) the content of ethylene derived units, measured by NMR, is between 2.7 wt% and 5.3 wt%; preferably between 2.9 wt% and 5.1 wt%; more preferably between 3.1 wt% and 4.7 wt%; B) from 6 wt% to 33 wt%; preferably from 10 wt% to 24 wt%; more preferably from 14 wt% to 19 wt% of a propylene ethylene copolymer containing from 18.2 wt% to 36.4 wt%; preferably from 19.6 wt% to 33.6 wt%; more preferably from 21.0 wt% to 30.8 wt% of ethylene derived units, measured by NMR; wherein the resulting polyolefin composition has: i) the content of ethylene derived units, measured by NMR, is between 5.4 wt% and 10.0 wt%; preferably between 6.2 wt% and 9.2 wt%; more preferably between 6.5 wt% and 8.5 wt%; ii) the content of ethylene derived units in the fraction soluble in xylene at 25°, measured by NMR, is between 14.4 wt% and 31.1 wt%; preferably between 16.7 wt% and 28.9 wt%; more preferably between 17.8 wt% and 26.6 wt%; iii) the melt flow rate (ISO 1133 (230°C, 21.6 kg) ranges from 0.5 g / 10 min to 7.5 g / 10 min; preferably ranges from 1.5 g / 10 min to 6.4 g / 10 min; more preferably ranges from 2.3 g / 10 min to 5.1 g / 10 min; iv) the xylene solubles at 25°C ranges from 13.9 wt% to 30.0 wt%; preferably ranges from 16.1 wt% to 27.8 wt%; more preferably ranges from 17.1 wt% to 25.7 wt%; v) the intrinsic viscosity of the fraction soluble in xylene at 25°C, measured in tetralin at 135°C, ranges from 4.0 dl / g to 9.9 dl / g; preferably ranges from 4.4 dl / g to 7.4 dl / g; more preferably ranges from 4.7 dl / g to 5.9 dl / g; vi) the intrinsic viscosity of the whole composition measured in tetrahydronaphthalene at 135 °C ranges from 4.4 dl / g to 9.4 dl / g; preferably from 5.0 dl / g to 7.5 dl / g; more preferably from 5.6 dl / g to 6.9 dl / g; A+B is equal to 100. The term copolymer must refer to a binary copolymer containing two monomers (propylene and ethylene).

[0007] Preferably, the polyolefin composition of the present disclosure has an intrinsic viscosity of the fraction insoluble in xylene at 25 °C measured in tetrahydronaphthalene at 135 °C ranging from 3.8 dl / g to 8.1 dl / g; preferably from 4.3 dl / g to 6.5 dl / g; more preferably from 4.9 dl / g to 6.0 dl / g.

[0008] Preferably, the polyolefin composition of the present disclosure has a content of ethylene-derived units in the fraction insoluble in xylene at 25 °C measured by NMR comprised between 2.9 wt% and 6.3 wt%; preferably between 3.4 wt% and 5.0 wt%; more preferably between 3.8 wt% and 4.6 wt%; The polyolefin composition of the present disclosure shows a low abrasion resistance value measured according to ISO 15527: 2007. The average abrasion index value measured on compression moulded plaques according to ISO 15527: 2007 can be lower than 300; preferably lower than 280; more preferably lower than 230. Preferably, the higher value of the average abrasion index measured according to ISO 15527: 2007 is 100.

[0009] Preferably, the propylene copolymer of the present disclosure shows a Charpy impact test at 23 °C ranging from 40 kJ / m2to 70.0 kJ / m2 2 ; preferably from 50.5 kJ / m2 2 to 65.0 kJ / m2 2 .

[0010] Therefore, the polyolefin composition of the present disclosure is particularly suitable for the production of moulded articles, which can be for example injection moulded articles, blow moulded articles or compression moulded articles. Preferably, the moulded articles of the present disclosure are compression moulded articles.

[0011] The low abrasion index value makes the moulded articles of the present disclosure particularly suitable for the production of automotive articles, especially articles subjected to motion.

[0012] The compositions of the present disclosure can also be prepared by blending components A) and B). Components (A) and (B) can also be prepared in a sequential sequence polymerization process, wherein component A) is prepared in a first reactor and component (B) is prepared in a second reactor in the presence of component A) according to known techniques and operating in gas phase or in liquid phase in the presence or absence of inert diluents, or by mixed liquid-gas technology.

[0013] The polymerization of A) and B) can be carried out in the presence of a Ziegler-Natta catalyst. An essential component of said catalyst is a solid catalyst component comprising a titanium compound having at least one titanium-halogen bond and an electron donor compound, both supported on a magnesium halide in active form. Another essential component (cocatalyst) is an organoaluminum compound, such as an alkylaluminum compound.

[0014] An external donor is optionally added.

[0015] The catalysts generally used in the process of the present invention are able to produce polypropylenes having a xylene insoluble value greater than 90%, preferably greater than 95%, at ambient temperature.

[0016] Catalysts having the above characteristics are well known in the patent literature; particularly advantageous are the catalysts described in U.S. Patent 4,399,054 and European Patent 45977. Other examples can be found in U.S. Patent 4,472,524.

[0017] The solid catalyst component used in said catalysts comprises, as electron donor (internal donor), a compound selected from the group consisting of ethers, ketones, lactones, compounds containing N, P and / or S atoms, and esters of mono- and di-carboxylic acids.

[0018] A particularly suitable electron donor compound is an ester of succinic acid (succinate). Preferably, the succinate present in the solid catalyst component is selected from succinates of formula (I) wherein the groups R1and R2, equal to or different from each other, are C1-C20 linear or branched alkyl, alkenyl, cycloalkyl, aryl, aralkyl or alkylaryl, optionally containing heteroatoms; and the groups R3and R4, equal to or different from each other, are C1-C20 alkyl, C3-C20 cycloalkyl, C5-C20 aryl, aralkyl or alkylaryl, provided that at least one of them is branched alkyl; said compound being a (S,R) or (R,S) type stereoisomer with respect to the two asymmetric carbon atoms identified in the structure of formula (I).

[0019] R1and R2are preferably Ci-C8alkyl, cycloalkyl, aryl, aralkyl and alkaryl groups. Particularly preferred are compounds in which R1and R2are selected from primary alkyl groups, in particular branched primary alkyl groups. Examples of suitable R1and R2groups are methyl, ethyl, n-propyl, n-butyl, isobutyl, neopentyl, 2-ethylhexyl. Particularly preferred are ethyl, isobutyl and neopentyl groups.

[0020] Particularly preferred are compounds in which the R3and / or R4groups are secondary alkyl groups such as isopropyl, sec-butyl, 2-pentyl, 3-pentyl or cycloalkyl groups such as cyclohexyl, cyclopentyl, cyclohexylmethyl.

[0021] Examples of the above compounds are (S,R) (S,R) pure or mixed forms, optionally in racemic form, of 2,3-bis(trimethylsilyl)succinic acid diethyl ester, 2,3-bis(2- ethylbutyl)succinic acid diethyl ester, 2,3-dibenzylsuccinic acid diethyl ester, 2,3- diisopropylsuccinic acid diethyl ester, 2,3-diisopropylsuccinic acid diisobutyl ester, 2,3- bis(cyclohexylmethyl)succinic acid diethyl ester, 2,3-diisobutylsuccinic acid diethyl ester, 2,3-dineopentylsuccinic acid diethyl ester, 2,3-dicyclopentylsuccinic acid diethyl ester, 2,3-dicyclohexylsuccinic acid diethyl ester.

[0022] Particularly suitable electron donor compounds are esters of phthalic acid and 1,3-diethers of the formula: wherein R1and R11are identical or different and are C1-C18alkyl, C3-C18cycloalkyl or C7-C18aryl groups; R111and RIVare identical or different and are C1-C4alkyl groups; or are 1,3-diethers, wherein the carbon atom in position 2 belongs to a cyclic or polycyclic structure consisting of 5, 6 or 7 carbon atoms or 5-n or 6-n' carbon atoms and n nitrogen atoms and n' heteroatoms selected from the group consisting of N, O, S and Si, respectively, wherein n is 1 or 2 and n' is 1, 2 or 3, said structure containing two or three unsaturations (cyclopolyene structure) and optionally condensed with other cyclic structures, or substituted by one or more substituents selected from the group consisting of linear or branched alkyl groups, cycloalkyl, aryl, aralkyl, alkaryl groups and halogens, or condensed with other cyclic structures and substituted by one or more of the above mentioned substituents, one or more of the above mentioned alkyl, cycloalkyl, aryl, aralkyl or alkaryl groups and optionally condensed cyclic structures containing one or more heteroatoms as substituents for carbon atoms or hydrogen atoms or both.

[0023] Ethers of this type are described in published European patent applications 361493 and 728769.

[0024] Representative examples of said diethers are 2-methyl-2-isopropyl-1,3-dimethoxypropane, 2,2-diisobutyl-1,3-dimethoxypropane, 2-isopropyl-2-cyclopentyl-1,3-dimethoxypropane, 2-isopropyl-2-isopentyl-1,3-dimethoxypropane, 9,9-bis(methoxymethyl)fluorene.

[0025] Other suitable electron donor compounds are phthalic esters such as diisobutyl phthalate, dioctyl phthalate, diphenyl phthalate and benzyl butyl phthalate.

[0026] The preparation of the above catalyst components is carried out according to various methods.

[0027] For example, a MgCl2.nROH adduct, in particular in the form of spherical particles, where n is generally from 1 to 3 and ROH is ethanol, butanol or isobutanol, is reacted with an excess of TiCl4containing the electron donor compound. The reaction temperature is generally from 80°C to 120°C. The solid is then separated and re-reacted once more with TiCl4, in the presence or absence of the electron donor compound, after which it is separated and washed with aliquots of hydrocarbon until all the chloride ions have disappeared.

[0028] In the solid catalyst component, the titanium compound, indicated as Ti, is generally present in an amount from 0.5% to 10% by weight. The amount of electron donor compound, with respect to the magnesium dihalide, which remains fixed on the solid catalyst component is generally from 5% to 20% by moles.

[0029] The titanium compounds which can be used for the preparation of the solid catalyst component are halides and halogeno-alcohols of titanium. Titanium tetrachloride is the preferred compound.

[0030] The above reaction forms the active form of the magnesium halide. Other reactions are known in the literature which form the active form of the magnesium halide starting from magnesium compounds other than halides, such as magnesium carboxylates.

[0031] The alkyl aluminium compounds used as co-catalysts include trialkylaluminium such as triethylaluminium, triisobutylaluminium, tri-n-butylaluminium, and linear or cyclic alkyl aluminium compounds containing two or more Al atoms bonded to each other through O or N atoms or SO4 or SO3 groups.

[0032] The alkyl aluminium compounds are generally used in such an amount that the Al / Ti ratio is from 1 to 1000.

[0033] The electron donor compounds which can be used as external donors include aromatic acid esters such as alkyl benzoates, and in particular silicon compounds containing at least one Si-OR bond, where R is a hydrocarbon group.

[0034] Examples of silicon compounds are (tert-butyl)2Si(OCH3)2, (cyclohexyl)(methyl)Si(OCH3)2, (cyclopentyl)2Si(OCH3)2and (phenyl)2Si(OCH3)2and (1,1,2-trimethylpropyl)Si(OCH3)3.

[0035] It can also be advantageous to use 1,3-diethers of the above formula. If the internal donor is one of these diethers, the external donor can be omitted.

[0036] In particular, even though many other combinations of the aforementioned catalyst components can allow obtaining a composition according to the present application, it is preferred to prepare component A) by using a catalyst containing phthalate as internal donor and (cyclopentyl)2Si(OCH3)2as external donor, or said 1,3-diether as internal donor.

[0037] In addition, a Ziegler-Natta catalyst that can be used for preparing the propylene polymers of the present application is a solid catalyst component comprising a magnesium halide, a titanium compound having at least one titanium-halogen bond as described above and at least two electron donor compounds, wherein one is selected from succinates and the other is selected from 1,3-diethers.

[0038] The following examples are given in order to illustrate the present application and are not intended to limit the scope of the application.

[0039] Examples Characterization methods Melting and crystallization temperatures: Determination by differential scanning calorimetry (DSC) A sample of 6 ± 1 mg is weighed, heated to 220 ± 1 °C at a rate of 20 °C / min under a nitrogen stream and kept at 220 ± 1 °C for 2 minutes, then cooled to 40 ± 2 °C at a rate of 20 °C / min, whereby the sample is crystallized at this temperature for 2 minutes. Then, the temperature is raised to 220 °C ± 1 at a rate of 20 °C / min to melt the sample again. The melting scan is recorded, a thermogram is obtained and from this the melting and crystallization temperatures are read.

[0040] Melt flow rate: determined according to method ISO 1133 (230 °C, 21.6 kg).

[0041] Xylene soluble fraction at 25 °C (XS) The xylene solubles at 25 °C were determined according to ISO 16152: 2005; the solution volume was 250 ml, the precipitation at 25 °C was for 20 minutes, with 10 minutes of solution under stirring (magnetic stirrer) and drying at 70 °C.

[0042] Intrinsic viscosity (I.V.) The sample was dissolved at 135 °C by tetralin and then poured into the capillary viscometer.

[0043] The viscometer tube (Ubbelohde type) was surrounded by a cylindrical glass jacket; this setup allowed temperature control with a circulating thermostated liquid.

[0044] The downward passage of the meniscus was timed by a photoelectric device. The passage of the meniscus in front of the upper lamp started a counter with a quartz crystal oscillator. When passing the lower lamp, the meniscus stopped the counter and the efflux time was recorded: it was converted into the intrinsic viscosity value by the following method Ethylene content in the copolymer 13C NMR spectra were acquired on a Bruker AV-600 spectrometer equipped with a cryoprobe, operating at 120 °C in Fourier transform mode at 160.91 MHz.

[0045] The peak of the Sββ carbon at 29.9 ppm (nomenclature according to Monomer Sequence Distribution in Ethylene-Propylene Rubber Measured by 13C NMR. 3. Use of Reaction Probability Mode by C. J. Carman, R. A. Harrington and C. E. Wilkes, Macromolecules, 1977, Volume 10, page 536) was used as internal reference. The sample was dissolved at 120 °C in 1,1,2,2-tetrachloroethane-d2 at 8 wt / v% concentration. Each spectrum was acquired with 90° pulses, with a delay of 15 seconds between pulses and CPD to remove H-13C coupling. 512 transients were stored in 32K data points using a spectral window of 9000 Hz.

[0046] According to Kakugo ("Carbon-13 NMR determination of monomer sequence distribution in ethylene-propylene copolymers prepared with δ-titanium trichloride-diethyl-aluminum chloride", M. Kakugo, Y. Naito, K. Mizunuma and T. Miyatake, Macromolecules, 1982, Vol. 15, p. 1150), the assignment of the spectra, the evaluation of the triad distribution and the composition determination were performed using the following equations: PPP = 100 Tββ / SPPE=100 Tβδ / SEPE=100 Tδδ / S PEP = 100 Sββ / SPEE= 100 Sβδ / SEEE = 100 (0.25 Sγδ+0.5 Sδδ) / S S = Tββ + Tβδ + Tδδ + Sββ + Sβδ + 0.25 Sγδ + 0.5 Sδδ The mole percentage of ethylene content was evaluated using the following equation: E% mol = 100 * [PEP+PEE+EEE] The weight percentage of ethylene content was evaluated using the following equation: where P mol% is the mole percentage of propylene content, and MWE and MWP are the molecular weights of ethylene and propylene, respectively.

[0047] The product of the reactivity ratios r1r2 was calculated according to Carman (C.J. Carman, R.A. Harrington and C.E. Wilkes, Macromolecules, 1977; Vol. 10, p. 536) as: The meso content of the propylene sequences was calculated as mm content by the ratio of PPP mmTββ (28.90 ppm to 29.65 ppm) to total Tββ (29.80 ppm to 28.37 ppm).

[0048] The ethylene content of component B) was calculated from the following relationship: where C2tot is the amount of ethylene in the entire composition, C2A and C2B are the amount of ethylene in component A and the amount of ethylene in component B, and XA and XB are the amount of component A and component B, which amounts add up to (A+B=1) Preparation of injection molded test specimens: Test specimens of 80 x 10 x 4 mm were obtained according to method ISO 1873-2:2007.

[0049] Charpy impact test at 23 °C: Measured on injection molded test specimens according to ISO 179-1 :2010.

[0050] Example 1 Procedure for the preparation of the solid catalyst component The solid catalysts used in the following examples were prepared according to example 10 of the international patent application WO 00 / 63261. Triethylaluminium (TEAL) was used as co-catalyst and dicyclopentyl dimethoxysilane as external donor, the weight ratios are shown in table 1.

[0051] Polymerization The polymerization run was carried out in a series of three reactors equipped with means to transfer the product from one reactor to the next one in a continuous mode. The first two reactors were liquid phase reactors and the third one was a fluidized bed gas phase reactor. Component (A) was prepared in the first and second reactors, which had the same polymerization parameters, while component (B) was prepared in the third reactor.

[0052] Hydrogen was used as molecular weight regulator.

[0053] The gas phase (propylene, ethylene and hydrogen) was continuously analyzed via gas chromatography.

[0054] At the end of the run, the powder was discharged and dried under nitrogen flow.

[0055] The main polymerization conditions are reported in table 1. C2 = ethylene; C3 = propylene; H2 = hydrogen Wear tests have been measured according to ISO 15527:2007 at 250 °C on compression molded plaques produced with the polymers of example 1 and comparative example 2. The results are reported in table 3 Comparative example 2 is PP H2150, a nucleated propylene homopolymer, sold by LyondellBasell.

Claims

1. A polyolefin composition comprising: A) from 67 to 94 wt% of a copolymer of propylene with ethylene, wherein: i) the content of ethylene derived units measured by NMR is between 2.7 and 5.3 wt%; B) from 6 to 33 wt% of a propylene ethylene copolymer containing from 18.2 to 36.4 wt% of ethylene derived units measured by NMR; wherein the resulting polyolefin composition has: i) the content of ethylene derived units measured by NMR is between 5.4 and 10.0 wt%; ii) the content of ethylene derived units in the fraction soluble in xylene at 25° measured by NMR is between 14.4 and 31.1 wt%; iii) a melt flow rate (ISO 1133 (230°C, 21.6 kg) ranging from 0.5 to 7.5 g / 10 min; iv) xylene solubles at 25°C ranging from 13.9 to 30.0 wt%; v) the intrinsic viscosity of the fraction soluble in xylene at 25°C measured in tetralin at 135°C ranging from 4.4 to 9.4 dl / g; vi) the intrinsic viscosity of the whole composition measured in tetralin at 135°C ranging from 4.0 to 9.4 dl / g; the sum of A+B is 100.

2. The polyolefin composition according to claim 1, wherein the content of ethylene derived units measured by NMR in component A) ranges from 2.9 to 5.1 wt%.

3. The polyolefin composition according to any one of claims 1 to 2, wherein component A) ranges from 76 to 90 wt% and component B) ranges from 10 to 24 wt%.

4. The polyolefin composition according to any one of claims 1 to 4, wherein the content of ethylene derived units measured by NMR in component B) ranges from 19.6 to 33.6 wt%.

5. The polyolefin composition according to any one of claims 1 to 5, wherein the content of ethylene derived units measured by NMR is between 6.2 and 9.2 wt%.

6. The polyolefin composition according to any one of claims 1 to 5, wherein the content of ethylene derived units in the fraction soluble in xylene at 25° measured by NMR is between 16.7 and 28.9 wt%.

7. The polyolefin composition according to any one of claims 1 to 6, wherein the content of ethylene derived units in the fraction soluble in xylene at 25°C measured by NMR is between 17.8 and 26.6 wt%.

8. The polyolefin composition according to any one of claims 1 to 7, wherein the melt flow rate (ISO 1133 (230°C, 21.6 kg) ranges from 1.5 g / 10 min to 6.4 g / 10 min.

9. The polyolefin composition according to any one of claims 1 to 8, wherein the xylene soluble at 25°C ranges from 16.1 wt% to 27.8 wt%.

10. The polyolefin composition according to any one of claims 1 to 9, wherein the intrinsic viscosity of the fraction soluble in xylene at 25°C measured in tetralin at 135°C ranges from 4.4 dl / g to 7.4 dl / g.

11. The polyolefin composition according to any one of claims 1 to 10, wherein the intrinsic viscosity of the whole composition measured in tetralin at 135°C ranges from 5.0 dl / g to 7.5 dl / g.

12. The polyolefin composition according to any one of claims 1 to 11, wherein the intrinsic viscosity of the fraction not soluble in xylene at 25°C measured in tetralin at 135°C ranges from 3.8 dl / g to 8.1 dl / g.

13. The polyolefin composition according to any one of claims 1 to 12, wherein the content of ethylene derived units in the fraction not soluble in xylene at 25°C measured by NMR is comprised between 2.9 wt% to 6.3 wt%.

14. A molded article comprising the polyolefin composition according to any one of claims 1 to 13.

15. A compression molded article comprising the polyolefin composition according to any one of claims 1 to 13.

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