Propylene-based copolymer composition for pipes

Abstract

A polyolefin composition comprising: A) from 85% to 99.0% by weight of propylene, B) from 1.0% to 15.0% by weight of a propylene, ethylene copolymer comprising: b1) from 13% to 43% by weight of a propylene ethylene copolymer having an ethylene derived unit content ranging from 0.8% to 7.1% by weight; b2) from 57% to 87% by weight of a propylene ethylene copolymer having an ethylene derived unit content ranging from 39.7% to 76.5% by weight.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a composition comprising a propylene homopolymer and a heterophasic propylene ethylene copolymer, which is particularly suitable for the production of sewer pipes having a relatively high impact at low temperatures to ensure installation under low temperature conditions. BACKGROUND

[0002] Propylene ethylene copolymers are known in the art for the production of pipes.

[0003] For example, according to international patent application WO 97 / 33117, pipes of polypropylene plastic material having high creep resistance, high long-term pressure resistance, improved stiffness and resistance to rapid crack propagation can be obtained. According to said document, when a polypropylene plastic pipe is made of several layers of different polypropylene plastic materials, wherein at least one layer consists of a broad molecular weight distribution (MWD) polypropylene providing high creep resistance and at least one layer consists of an elastomer-modified polypropylene providing increased impact strength, catastrophic failure of the pipe can be prevented. Said broad MWD polypropylene is a mixture of a very high molecular weight propylene random copolymer having from 1 wt% to 10 wt% of ethylene or higher a-olefin repeat units and a low molecular weight propylene polymer having low (up to 1 wt%) or zero comonomer.

[0004] It is important to limit the wall thickness of the pipes. This allows to obtain pipes containing less material, lighter in weight, and increases the efficiency of the pipes in terms of feed due to the larger internal diameter, mainly for smaller diameter pipe applications. However, when the wall thickness is reduced, the pipes become brittle, and it is therefore necessary to use materials having high impact resistance, especially at low temperatures. Moreover, the material used for the pipes must have a high flexural modulus in order to obtain rigid pipes. Generally in polypropylene based compositions, when the impact performance is increased, the flexural modulus is reduced. The Applicant found that it is possible to add to the propylene ethylene copolymer a small amount of a heterophasic copolymer having certain characteristics, in order to obtain a good impact / stiffness balance without substantially compromising the stiffness. SUMMARY

[0005] It is an object of the present disclosure a polyolefin composition comprising:

[0006] A) from 85 wt% to 99.0 wt% of a propylene homopolymer having:

[0007] (i) a polydispersity index ranging from 5 to 10

[0008] (ii) from 4.0 wt% to 1.0 wt% of solubles in xylene at 25°C;

[0009] (iii) a melt flow rate (230°C / 5 kg.. ISO 1133) ranging from 0.2 g / 10 min to 3.5 g / 10 min;

[0010] B) 1.0 wt.-% to 15.0 wt.-% of a propylene, ethylene copolymer composition having:

[0011] i) a fraction soluble in xylene at 25°C ranging from 44 wt.-% to 70 wt.-%;

[0012] ii) a melt flow rate (230°C / 2.16 kg.. ISO 1133) ranging from 0.1 g / 10 min to 2.0 g / 10 min

[0013] iii) an intrinsic viscosity measured in decahydronaphthalene of the fraction soluble in xylene at 25°C ranging from 2.6 dl / g to 6.1 dl / g;

[0014] iv) an ethylene derived units content ranging from 31.5 wt.-% to 52.3 wt.-%;

[0015] The propylene, ethylene copolymer composition component B comprises:

[0016] b1 ) 13 wt.-% to 43 wt.-% of a propylene ethylene copolymer having a melt flow rate MFR1 (230°C / 2.16 kg. ISO 1133) ranging from 22.0 g / 10 min to 50.0 g / 10 min;

[0017] and having an ethylene derived units content ranging from 0.8 wt.-% to 7.1 wt.-%;

[0018] b2) 57 wt.-% to 87 wt.-% of a propylene ethylene copolymer having an ethylene derived units content ranging from 39.7 wt.-% to 76.5 wt.-%;

[0019] wherein the polyolefin composition has: a melt flow rate (230°C / 5 kg ISO 1133) ranging from 0.4 g / 10 min to 4.0 g / 10 min; the amount of A+B is the sum of 100 wt.-% and the amount of b1 +b2 is the sum of 100 wt.-%. DETAILED DESCRIPTION

[0020] It is therefore an object of the present disclosure a polyolefin composition comprising:

[0021] A) 85.0 wt.-% to 99.0 wt.-%; preferably 90 wt.-% to 98.5 wt.-%; more preferably 93 wt.-% to 98 wt.-% of a propylene homopolymer having:

[0022] (i) a polydispersity index in the range of 5 to 10

[0023] (ii) a solubles in xylene at 25°C in the range of 4.0 wt% to 1.0 wt%; preferably 3.0 wt% to 2.0 wt%;

[0024] (iii) a melt flow rate (230°C / 5 kg.. ISO 1133) in the range of 0.2 g / 10 min to 3.5 g / 10 min; preferably 0.6 g / 10 min to 2.0 g / 10 min;

[0025] B) 1.0 wt% to 15.0 wt%; preferably 1.5 wt% to 10.0 wt%; more preferably 2.0 wt% to 7.0 wt% of a propylene, ethylene copolymer composition having:

[0026] i) a fraction soluble in xylene at 25°C in the range of 44 wt% to 70 wt%; preferably 47.0 wt% to 67.0 wt%; more preferably 52.0 wt% to 63.0 wt%;

[0027] ii) a melt flow rate (230°C / 2.16 kg.. ISO 1133) in the range of 0.1 g / 10 min to 1.0 g / 10 min; preferably 0.2 g / 10 min to 1.6 g / 10 min; more preferably 0.3 g / 10 min to 1.4 g / 10 min;

[0028] iii) an intrinsic viscosity in the range of 2.6 dl / g to 6.1 dl / g; preferably 2.8 dl / g to 5.6 dl / g; more preferably 3.1 dl / g to 5.2 dl / g of the fraction soluble in xylene at 25°C measured in decahydronaphthalene;

[0029] iv) an ethylene derived units content in the range of 31.5 wt% to 52.3 wt%; preferably in the range of 33.4 wt% to 49.9 wt%; more preferably in the range of 36.3 wt% to 48.2 wt%;

[0030] said propylene, ethylene copolymer composition comprises:

[0031] b1 ) 13 wt.-% to 43 wt.-%; preferably 18 wt.-% to 38 wt.-%; more preferably 21 wt.-% to 35 wt.-% of a propylene ethylene copolymer having a melt flow rate MFR1 (230°C / 2.16 kg. ISO 1133) in the range of 22.0 g / 10 min to 50.0 g / 10 min; preferably 25.0 g / 10 min to 48.0 g / 10 min; more preferably 27.0 g / 10 min to 45.0 g / 10 min; and having an ethylene derived units content in the range of 0.8 wt.-% to 7.1 wt.-%; preferably in the range of 1.4 wt.-% to 6.2 wt.-%; more preferably in the range of 1.9 wt.-% to 5.1 wt.-%;

[0032] b2) 57 wt.-% to 87 wt.-%; preferably 62 wt.-% to 82 wt.-%; more preferably 65 wt.-% to 79 wt.-% of a propylene ethylene copolymer having an ethylene derived units content in the range of 39.7 wt.-% to 76.5 wt.-%; preferably in the range of 45.8 wt.-% to 70.3 wt.-%; more preferably in the range of 49.8 wt.-% to 66.3 wt.-%;

[0033] wherein the polyolefin composition has a melt flow rate (230°C / 5 kg.. ISO 1133) in the range of 0.4 g / 10 min to 4.0 g / 10 min; preferably 0.7 g / 10 min to 3.2 g / 10 min; more preferably 1.0 g / 10 min to 2.7 g / 10 min; the amount of A+B is the sum of 100 wt.-% and the amount of b1 +b2 is the sum of 100 wt.-%.

[0034] The term copolymer means a polymer containing only two monomers; preferably propylene and ethylene.

[0035] The polyolefin composition of the present disclosure preferably shows a Charpy notched impact strength measured according to ISO 179-1 :2010 at 23°C in the range of 55,0 KJ / m 2 to 80,0 KJ / m 2 ; preferably in the range of 60,0 KJ / m 2 to 75,0 KJ / m 2 ; even more preferably in the range of 63,0 KJ / m 2 to 72,0 KJ / m 2The tensile modulus of the polyolefin composition of the present disclosure is in the range of 1600 MPa to 2500 MPa; preferably 1700 MPa to 2300 MPa; even more preferably 1800 MPa to 2200 MPa, determined according to ISO 527-2. The flexural modulus of the polyolefin composition of the present disclosure is in the range of 1600 MPa to 2400 MPa; preferably 1700 MPa to 2200 MPa; even more preferably 1800 MPa to 2100 MPa, determined according to ISO 178:2019.

[0036] Preferably, component A) has one or more of the following characteristics:

[0037] i) a flexural modulus in the range of 1500 Mpa to 2300 MPa; preferably in the range of 1800 Mpa to 2200 MPa, determined according to method ISO 178:2019;

[0038] ii) an Izod impact test at 0°C in the range of 3.0 kJ / m 2 to 6.0 kJ / m 2 ; preferably in the range of 3.8 kJ / m 2 to 5.3 kJ / m 2 , measured according to ISO 180 / A with a specimen injection moulded according to ISO 1873-2;

[0039] iii) a melting point in the range of 155°C to 170°C, preferably in the range of 160°C to 167°C, measured by DSC.

[0040] With the polyolefin composition of the present disclosure, pipes, in particular sewer pipes, having a high modulus and a high impact resistance can be obtained. In particular, the impact resistance can be increased without reducing the modulus.

[0041] It is therefore another object of the present disclosure a pipe comprising the composition of the present disclosure.

[0042] The term "pipe" as used herein also includes pipe fittings, valves and all components generally required for e.g. hot water pipe systems. Also included in this definition are single- and multi-layer pipes, wherein e.g. one or more layers are metal layers and can include adhesive layers.

[0043] Such articles can be manufactured by various industrial methods well known in the art, such as e.g. moulding, extrusion, etc.

[0044] The composition of the present disclosure can also comprise an inorganic filler in an amount ranging from 0.5 parts by weight to 60 parts by weight, relative to 100 parts by weight of the composition. Typical examples of such fillers are calcium carbonate, barium sulfate, titanium dioxide and talc. Talc and calcium carbonate are preferred. Many fillers can also have a nucleating effect, such as talc which is also a nucleating agent. The amount of nucleating agent is generally 0.2% to 5% by weight, relative to the amount of polymer.

[0045] The composition of the present disclosure is also suitable for providing pipes having walls of any configuration other than those having a smooth inner surface and outer surface. Examples are pipes having a sandwich-like pipe wall, pipes having a hollow wall structure with longitudinally extending cavities, pipes having a hollow wall structure with helical cavities, pipes having a smooth inner surface and a compact or hollow, helical or annular ribbed outer surface, irrespective of the configuration of the respective pipe end.

[0046] The articles, pressure pipes and related fittings according to the present disclosure are produced in a manner known per se, for example by (co)extrusion or molding.

[0047] The extrusion of the articles can be carried out with different types of polyolefin extruders, for example single-screw or twin-screw extruders.

[0048] A further embodiment of the present disclosure is a method of molding the composition into the article.

[0049] When the pipe is multilayer, at least one layer is made of the above polyolefin composition. The further layers are made of amorphous or crystalline polymers of R-CH=CH2 olefins, such as homopolymers and copolymers or terpolymers, wherein R is a hydrogen atom or a C1-C6 alkyl radical. Particularly preferred are the following polymers:

[0050] Isotactic or predominantly isotactic propylene homopolymers;

[0051] Random copolymers and terpolymers of propylene with ethylene and / or C4-C8 a-olefins, such as 1-butene, 1-hexene, 1-octene, 4-methyl-1-pentene, wherein the total comonomer content ranges from 0.05% to 20% by weight, or mixtures of said polymers with isotactic or predominantly isotactic propylene homopolymers;

[0052] Heterophasic polymer blends comprising: (a) a propylene homopolymer, and / or one of the copolymers and terpolymers of item (2); and an elastomeric fraction (b) comprising copolymers and terpolymers of ethylene with propylene and / or C4-C8 a-olefins (optionally containing traces of dienes, the same substances disclosed for polymer (2) (a)); and

[0053] Amorphous polymers, for example, such as fluorinated polymers, polyvinylidene fluoride (PVDF).

[0054] In multilayer pipes, the layers of the pipe can have the same or different thicknesses.

[0055] The composition of the present disclosure can be prepared by blending the various components A), b1 ) and b2), or by preparing component A) and blending this component with component B) prepared in a single polymerization process by sequential polymerization steps.

[0056] The polymerization of A) and B) can be carried out in the presence of a Ziegler-Natta catalyst. An essential component of the catalyst is a solid catalyst component comprising a titanium compound having at least one titanium-halogen bond and an electron donor compound, both supported in active form on a magnesium halide. Another essential component (cocatalyst) is an organoaluminum compound, such as an aluminum alkyl compound.

[0057] An external donor is optionally added.

[0058] The catalyst typically used in the process of the present disclosure is able to produce polypropylene having a xylene insoluble value greater than 90%, preferably greater than 95%, at ambient temperature.

[0059] 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.

[0060] The solid catalyst component used in the catalyst 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.

[0061] Particularly suitable electron donor compounds are esters of phthalic acid and 1,3-diethers of the formula:

[0062]

[0063] wherein R1and R11are identical or different and are C1-C18alkyl, C3-C18cycloalkyl or C7-C18aryl radicals; R111and RIVare identical or different and are C1-C4alkyl radicals; 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 radicals, cycloalkyl, aryl, aralkyl, alkylaryl radicals 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 alkylaryl radicals and optionally condensed cyclic structures containing one or more heteroatoms as substituents for carbon atoms or hydrogen atoms or both.

[0064] Such type of ethers is described in published European patent applications 361493 and 728769.

[0065] 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.

[0066] Other suitable electron donor compounds are phthalic acid esters such as diisobutyl phthalate, dioctyl phthalate, diphenyl phthalate and benzyl butyl phthalate.

[0067] The preparation of the above mentioned catalyst components is performed according to various methods.

[0068] For example, MgCl2-nROH adducts (in particular in the form of spherical particles) where n is generally from 1 to 3 and ROH is ethanol, butanol or isobutanol, are 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 TiCl4in the presence or absence of the electron donor compound, after which it is separated and washed with aliquots of hydrocarbons until all the chloride ions have disappeared.

[0069] In the solid catalyst component, the titanium compound, indicated as Ti, is generally present in an amount of 0.5% to 10% by weight. The amount of the electron donor compound, which remains fixed on the solid catalyst component, with respect to the magnesium dihalide, is generally comprised between 5 and 20 moles%.

[0070] The titanium compounds that can be used for the preparation of the solid catalyst component are halides and halogeno-alcohols of titanium. Titanium tetrachloride is the preferred compound.

[0071] The above reaction forms the magnesium halide in active form. Other reactions are known in the literature, which form the magnesium halide in active form starting from magnesium compounds other than halides, such as magnesium carboxylates.

[0072] 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.

[0073] The Al-alkyl compounds are generally used in such an amount as to give an Al / Ti ratio comprised between 1 and 1000.

[0074] The electron donor compounds that 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, wherein R is a hydrocarbon radical.

[0075] 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.

[0076] It is also possible to advantageously use 1,3-diethers having the above chemical formula. If the internal donor is one of these diethers, the external donor can be omitted.

[0077] In particular, even if many other combinations of the aforementioned catalyst components can allow to obtain compositions according to the present disclosure, it is preferred to prepare components A) and B) by using a catalyst containing phthalate as internal donor and (cyclopentyl)2Si(OCH3)2as external donor, or said 1,3-diether as internal donor.

[0078] In addition, the Ziegler-Natta catalysts that can be used for the preparation of the propylene polymers of the present disclosure are solid catalyst components comprising a magnesium halide, a titanium compound having at least one titanium-halogen bond, as described above, and at least two electron donor compounds, one of which is selected from succinates and the other one is selected from 1,3-diethers.

[0079] Component A) is preferably produced with the polymerization process shown in EP application 1 012 195.

[0080] In detail, the process comprises feeding monomers to the polymerization zone in the presence of a catalyst under reaction conditions, and collecting the polymer product from the polymerization zone. In the process, the growing polymer particles flow upwards through one (first) of the polymerization zones (riser) under fast fluidization conditions, leave the riser and enter another (second) polymerization zone (downcomer) in which they flow downwards under the action of gravity in a densified form, leave the downcomer and are reintroduced into the riser, thus establishing a circulation of the polymer between the riser and the downcomer.

[0081] In the downcomer, high solid density values are reached, which are close to the bulk density of the polymer. A positive pressure gain can thus be obtained along the flow direction, making it possible to reintroduce the polymer into the riser without the aid of special mechanical devices. In this way, a "loop" circulation is established, which is defined by the pressure balance between the two polymerization zones and the head loss in the introduction system.

[0082] Generally, the fast fluidization conditions in the riser are established by feeding a gaseous mixture comprising the relevant monomers to the riser. Preferably, the feeding of the gaseous mixture is effected below the point at which the polymer is reintroduced into the riser, by using gas distributor means, where appropriate. The velocity of the conveying gas entering the riser is higher than the conveying velocity under the operating conditions, preferably from 2 m / s to 15 m / s.

[0083] Generally, the polymer and the gaseous mixture leaving the riser are conveyed to a solid / gas separation zone. The solid / gas separation can be effected by using conventional separation means. The polymer enters the downcomer from the separation zone. The gaseous mixture leaving the separation zone is compressed, cooled and transferred to the riser, if appropriate, with the addition of make-up monomers and / or molecular weight regulators. The transfer can be effected by means of a circulation line for the gaseous mixture.

[0084] The control of the polymer circulating between the two polymerization zones can be effected by metering the amount of polymer leaving the downcomer by using means suitable for controlling the flow of solids, such as mechanical valves.

[0085] The operating parameters, such as the temperature, are those commonly used in olefin polymerization processes, for example between 50°C and 120°C.

[0086] The first stage process can be carried out at an operating pressure between 0.5 MPa and 10 MPa, preferably between 1.5 MPa and 6 MPa.

[0087] Advantageously, one or more inert gases are maintained in the polymerization zone in an amount such that the sum of the partial pressures of the inert gases is preferably between 5% and 80% of the total pressure of the gases. The inert gas can be, for example, nitrogen or propane.

[0088] The various catalysts are fed up the riser at any point in the riser. However, they can also be fed at any point in the downcomer. The catalysts can be in any physical state, so catalysts in solid or liquid state can be used.

[0089] The following examples are given for illustrative purposes and not by way of limitation.

[0090] Examples

[0091] Characterization methods

[0092] Xylene soluble (XS) fraction at 25°C

[0093] The xylene solubles at 25°C have been determined according to ISO 16152.

[0094] DSC method for melting point

[0095] The melting point of samples weighing between 5 and 7 mg was measured according to ISO 11357-3, with a scan rate of 20 C / min, under cooling and heating, under an inert N2 flow. The instrument was calibrated using indium

[0096] Melt flow rate: determined according to method ISO 1133 (230°C, 5 kg or 2.16 kg).

[0097] Ethylene content in the copolymer

[0098] The1H NMR spectra were acquired on a Bruker AV-600 spectrometer equipped with a cryoprobe 13 The C NMR spectra were operated at 160.91 MHz at 120°C in Fourier transform mode.

[0099] Sββ carbon (according to "by 13C NMR measures monomer sequence distribution in ethylene propylene rubber. The peak of the reaction probability mode (Monomer Sequence Distribution in Ethylene-Propylene Rubber Measured by13C NMR. 3. Use of Reaction Probability Mode” C. J. Carman, R. A. Harrington and C. E. Wilkes, Macromolecules, 1977, Vol. 10, p. 536) was used as an internal reference with a value of 29.9 ppm. The sample was dissolved in 1,1,2,2-tetrachloroethane-d2 at 8% wt / v at 120 °C. Each spectrum was acquired with a 90° pulse with a 15 second delay between pulse and CPD to eliminate 1 H- 13 C coupling. A spectral window of 9000 Hz was used with 512 transients stored in 32K data points.

[0100] 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 spectra were assigned using the following equations and the triad distribution and composition were evaluated:

[0101] PPP = 100 Tββ / S PPE = 100 Tβδ / S EPE = 100 Tδδ / S

[0102] PEP = 100 Sββ / S PEE = 100 Sβδ / S EEE = 100 (0.25 Sγδ + 0.5 Sδδ) / S

[0103] S = Tββ + Tβδ + Tδδ + Sββ + Sβδ + 0.25 Sγδ + 0.5 Sδδ

[0104] The mole percent of ethylene content was evaluated using the following equation:

[0105] E mol% = 100 * [PEP + PEE + EEE]

[0106] The weight percent of ethylene content was evaluated using the following equation:

[0107] 100 * E% mol * MWE

[0108] E% wt. = E% mol * MWE + P% mol * MWP

[0109] where P mol% is the mole percent of propylene content, and MWE and MWP are the molecular weight of ethylene and propylene, respectively.

[0110] Preparation of injection molded test specimens: Test specimens of 80 x 10 x 4 mm were obtained according to method ISO 1873-2:2007.

[0111] Flexural modulus: Determined on injection molded test specimens according to method ISO 178:2019.

[0112] Tensile modulus: Determined on injection molded test specimens according to method ISO 527-2.

[0113] Charpy impact test: Measured on injection molded test specimens according to ISO 179-1 :2010.

[0114] Izod impact test, measured on injection molded specimens according to ISO 180 / A, according to ISO 1873-2.

[0115] Polydispersity index (PI): Determined at a temperature of 200 °C by using a parallel plate rheometer of the type RMS-800 sold by RHEOMETRICS (USA) operated at an oscillation frequency increasing from 0.1 rad / sec to 100 rad / sec. According to the cross-over modulus, the P.I. can be derived by the following equation:

[0116] P.I. = 105 / Gc

[0117] where Gcis the cross-over modulus, defined as the value at which G’ = G” (expressed in Pa), where G’ is the storage modulus and G” is the loss modulus.

[0118] Component A)

[0119] Preparation of the solid catalyst component for component A)

[0120] Into a 2000 mL five necked glass reactor, equipped with mechanical stirrer, jacket and thermocouple, purged with nitrogen, 1000 mL of TiCl4were introduced and the reactor was cooled to -5°C. While stirring, 60.0 g of microspheres MgCl2.1.7C2H5OH with an average particle size of 58 pm (prepared according to the method described in example 1 of EP728769) were added at -5°C. The temperature was raised to 40°C and an amount of diethyl 2,3-diisopropylsuccinate was added to have a Mg / succinate molar ratio of 13. The temperature was raised to 100°C and this value was maintained for 60 minutes. After this time, the stirring was stopped for 15 minutes and the solid was allowed to settle. The liquid was siphoned off. After siphoning, fresh TiCl4and an amount of 9,9-bis(methoxymethyl)fluorene were added to have a Mg / diether molar ratio of 26. The temperature was raised to 110°C under stirring and maintained for 30 minutes. Then the reactor was cooled to 75°C and the stirring was stopped for 15 minutes. After precipitation and siphoning, fresh TiCl4was added. Then the temperature was raised to 90°C and the suspension was stirred for 15 minutes. Then the temperature was decreased to 75°C and the stirring was stopped for 15 minutes. After precipitation and siphoning, the solid was washed six times with anhydrous hexane (6 x 1000 ml) at 60°C and once with hexane at 25°C. The solid was dried in a rotary evaporator.

[0121] Preparation of the catalyst system

[0122] The above described solid catalyst component was contacted with triethylaluminium (TEAL) and dicyclopentyl dimethoxysilane (DCPMS) at a temperature of 15°C before introducing it into the polymerization reactor.

[0123] Pre-polymerization

[0124] The catalyst system was then subjected to a pre-polymerization treatment at 20°C by keeping it suspended in liquid propylene for a residence time of 9 minutes before introducing it into the polymerization reactor.

[0125] The polymerization run was carried out continuously in a polymerization plant as described in EP 1 012 195.

[0126] The catalyst was sent to a polymerization plant comprising two cylindrical reactors (riser and downer) connected to each other. Fast fluidization conditions were established in the riser by recycling the gas coming from the gas-solid separator. Hydrogen was used as molecular weight regulator. The polymerization conditions are reported in Table 1. Component A is the component A used in example 1 of WO2016 / 050461.

[0127] Table 1

[0128] Component A) TEAL / external donor wt / wt 6 TEAL / catalyst wt / wt 6 Temperature ℃ 73 Pressure bar-g 27 segregated riser wt% 40 downer wt% 60 C3 - riser mole% 80 mole% 1.3 H2 / C3 - riser mol / mol 0.028 H2 / C3 - downcomer mol / mol 0.016

[0129] C3 - = propylene

[0130] The properties of Component A have been reported in Table 2

[0131] Table 2

[0132] Component A MFR 5 Kg / 230°C g / 10 min 1.3 polydispersity (PI) 6.0 xylene solubles at 25°C. ％ <2 flexural modulus MPa 2050 tensile modulus MPa 1960 Ezodol at 0°C kJ / m 2 ]] 4.3 yield stress ％ 36 elongation at break kJ / m 2 ]] 28 Tm ℃ 164

[0133] Component B)

[0134] Component B1 ) is a commercial heterophasic polymer obtained by sequential gas phase polymerization used as Component B) in Example 1 of WO2016 / 050461.

[0135] Component B2) is a commercial heterophasic polymer obtained by sequential gas phase polymerization. The characteristics of the polymer sold by LyondellBasell under the trade name CA7469A are reported in Table 3

[0136] Table 3

[0137]

[0138] *C2 = ethylene derived units

[0139] Component A and Component B have been blended. The properties of the resulting blend are reported in Table 4 for comparison with the properties of Comparative Example 2.

[0140] Table 4

[0141]

[0142]

[0143] * the remaining amount is Component A. Comparative Example 3 is Component A only

[0144] From Table 4 it is clear that the impact properties of Blend 1 are higher with respect to Comparative Blend 2 and Component A only, while the flexural modulus and tensile modulus are substantially unchanged.

Claims

1. A) 85 to 99.0 wt.% of a propylene homopolymer having: (i) a polydispersity index ranging from 5 to 10 (ii) solubles in xylene at 25° C. in the range of 4.0 wt % to 1.0 wt %; (iii) a melt flow rate (230°C / 5kg, ISO 1133) ranging from 0.2 g / 10 min to 3.5 g / 10 min; B) 1.0 to 15.0 wt% of a propylene, ethylene copolymer composition having: i) a fraction soluble in xylene at 25° C. in the range of 44% to 70% by weight; ii) said melt flow rate (230°C / 2.16 kg..ISO 1133) ranging from 0.1 g / 10 min to 2.0 g / 10 min; iii) an intrinsic viscosity of said fraction soluble in xylene at 25°C, as measured in tetralin, in the range of 2.6 dl / g to 6.1 dl / g; iv) an ethylene-derived unit content ranging from 31.5% to 52.3% by weight; The propylene and ethylene copolymer composition component B comprises: b1) 13 to 43 wt% of a propylene ethylene copolymer having a melt flow rate MFR1 (230° C. / 2.16 kg, ISO 1133) in the range of 22.0 to 50.0 g / 10 min; and having an ethylene-derived unit content ranging from 0.8 wt% to 7.1 wt%; b2) 57 to 87 wt% of a propylene ethylene copolymer having an ethylene-derived unit content in the range of 39.7 to 76.5 wt%; The polyolefin composition has a melt flow rate (230°C / 5kg ISO 1133) ranging from 0.4 to 4.0 g / 10 min; the total amount of A+B is 100 wt% and the total amount of b1+b2 is 100 wt%.

2. The polyolefin composition according to claim 1, wherein component A) ranges from 90 wt% to 98.5 wt%, and component B) ranges from 1.5 wt% to 10.0 wt%.

3. The polyolefin composition according to claim 1, wherein in component B), b1) ranges from 18 wt% to 38 wt%; and b2) ranges from 62 wt% to 82 wt%. The polyolefin composition according to claim 1 , having a melt flow rate (230° C. / 5 kg.. ISO 1133) ranging from 0.7 g / 10 min to 3.2 g / 10 min.

5. The polyolefin composition according to claim 1, wherein in the component B), component b1) has an ethylene-derived unit content in the range of 1.4 wt% to 6.2 wt%.

6. The polyolefin composition according to claim 1, wherein in said component B) the intrinsic viscosity of the fraction soluble in xylene at 25°C, measured in decahydronaphthalene, ranges from 2.8 dl / g to 5.6 dl / g.

7. The polyolefin composition according to claim 1, wherein in said component B) the fraction soluble in xylene at 25°C ranges from 47 wt% to 67 wt%.

8. The polyolefin composition according to claim 1, wherein in said component B) component b1) has a melt flow rate MFR1 (230°C / 2.16 kg. ISO 1133) ranging from 25.0 g / 10 min to 48.0 g / 10 min.

9. The polyolefin composition according to claim 1, wherein in said component B) component b2) has an ethylene derived units content ranging from 45.8 wt% to 70.3 wt%.

10. The polyolefin composition according to claim 1, wherein component B) has an ethylene derived units content ranging from 33.4 wt% to 49.9 wt%.

11. The polyolefin composition according to claim 1, wherein in component A) the solubles in xylene at 25°C range from 3.0 wt% to 2.0 wt%.

12. The polyolefin composition according to claim 1, wherein component A) ranges from 93 wt% to 98 wt% and component B) ranges from 2.0 wt% to 7.0 wt%.

13. The polyolefin composition according to claim 1, wherein component B) has the fraction soluble in xylene at 25°C ranging from 52.0 wt% to 63.0 wt%.

14. The polyolefin composition according to claim 1, wherein component B) has the fraction soluble in xylene at 25°C an intrinsic viscosity, measured in decahydronaphthalene, ranging from 3.1 dl / g to 5.2 dl / g.

15. A pipe comprising the polyolefin composition according to claim 1.

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