Propylene polymer composition

Abstract

A polypropylene composition comprising: A) from 90.6% to 97.0% by weight of a propylene homopolymer having a melt flow rate comprised between 40.0 g / 10 min and 100.0 g / 10 min; B) from 3.0% to 9.4% by weight of a propylene-ethylene copolymer having an ethylene content ranging from 22% to 38% by weight; said polypropylene composition having: i) a xylene-soluble fraction ranging from 5% to 13.0% by weight at 25 °C; ii) an ethylene content in the fraction insoluble in xylene at 25 °C ranging from 0.3% to 1.6% by weight; iii) an ethylene content in the fraction soluble in xylene at 25 °C ranging from 17.2% to 27.0% by weight; (iv) a melt flow rate MFR comprised between 80.0 g / 10 min and 150.0 g / 10 min.

Description

Technical Field

[0001] The present disclosure relates to polypropylene copolymer compositions having a combination of improved processability, stiffness and transparency. These compositions can be used to produce molded articles, particularly injection molded articles or thermoformed articles such as containers. Background Art

[0002] Injection molded parts such as food packaging and plastic cups place specific requirements on the polymeric materials used to produce these articles.

[0003] Polymer-based polypropylenes have many properties that make them suitable for applications such as molded articles as well as pipes, fittings and foams.

[0004] Typically, high-rigidity polypropylene products are based on high molecular weight materials, which are usually nucleated by adding nucleating agents, i.e., they start to crystallize at higher temperatures and have a high crystallization rate.

[0005] WO 2008 / 074423 relates to polypropylene compositions comprising a multiphase propylene copolymer, the multiphase propylene copolymer comprising:

[0006] a) a matrix phase (A) comprising a propylene homopolymer and / or a propylene copolymer, and

[0007] b) a dispersed phase (B) comprising a propylene copolymer rubber dispersed in the matrix phase (A),

[0008] wherein

[0009] (i) the polypropylene composition has a melt flow rate MFR2 of 50 g / 10 min or higher,

[0010] (ii) the propylene copolymer rubber of the dispersed phase (B) has a comonomer content of 40 wt% or higher. WO2008 / 074423 does not mention the haze value at all, and in addition, component (ii) contains a large amount of comonomer.

[0011] WO 2018 / 104092 relates to a polypropylene composition comprising:

[0012] A) from 50 wt% to 90 wt% of a propylene homopolymer having an MFR L of from 0.5 g / 10 min to 200 g / 10 min;

[0013] B) from 10 wt% to 50 wt% of a copolymer of propylene and ethylene having from 30.0 wt% to 70.0 wt% of ethylene-derived units;

[0014] The sum of the amounts of components A) and B) is 100;

[0015] The composition has:

[0016] i) an intrinsic viscosity of the fraction soluble in xylene at 25 °C, which is between 2.2 dl / g and 4.0 dl / g;

[0017] ii) MFR L (from 0.5 g / 10 min to 50 g / 10 min);

[0018] iii) a xylene-soluble fraction ranging from 20% by weight to 50% by weight.

[0019] It has now been found that by fine-tuning a polypropylene copolymer composition containing an isotactic polypropylene homopolymer and an ethylene-propylene copolymer, a copolymer having good mechanical properties and good haze can be obtained. SUMMARY OF THE INVENTION

[0020] Accordingly, the present disclosure provides a polypropylene composition comprising:

[0021] A) from 90.6% by weight to 97.0% by weight of an isotactic polypropylene homopolymer having a fraction insoluble in xylene at 25 °C of greater than 90% by weight; and a melt flow rate MFR, measured according to ISO 1133-1 at 230 °C and a load of 2.16 kg, which is between 40.0 g / 10 min and 100.0 g / 10 min;

[0022] B) from 3.0% by weight to 9.4% by weight of an ethylene-propylene copolymer having an ethylene-derived unit content ranging from 22% by weight to 38% by weight as measured by 13 13C NMR;

[0023] The polypropylene composition has:

[0024] i) a xylene-soluble fraction ranging from 5.0% by weight to 13.0% by weight at 25 °C;

[0025] ii) an ethylene-derived unit content in the fraction insoluble in xylene at 25 °C, ranging from 0.3% by weight to 1.6% by weight, as measured by 13 13C NMR;

[0026] iii) an ethylene-derived unit content in the fraction soluble in xylene at 25 °C, ranging from 13.2% by weight to 27.0% by weight, as measured by 13 13C NMR;

[0027] (iv) a melt flow rate MFR, measured according to ISO 1133-1 at 230 °C and a load of 2.16 kg, which is between 35.0 g / 10 min and 70.0 g / 10 min;

[0028] The sum of the amounts of A) and B) is 100% by weight. Detailed Description

[0029] Accordingly, the present disclosure provides a polypropylene composition comprising:

[0030] A) from 90.6% to 97.0% by weight, preferably from 91.0% to 96.0% by weight, more preferably from 91.0% to 95% by weight of a propylene homopolymer having a fraction insoluble in xylene at 25 °C greater than 90% by weight, preferably greater than 94% by weight; and a melt flow rate MFR measured according to ISO 1133-1 at 230 °C and a load of 2.16 kg and included between 40.0 g / 10 min and 100.0 g / 10 min, preferably included between 55.0 g / 10 min and 90.0 g / 10 min, more preferably included between 70.0 g / 10 min and 85.0 g / 10 min;

[0031] B) from 3.0% to 9.4% by weight, preferably from 5.0% to 9.3% by weight, more preferably from 7% to 9.0% by weight of a propylene-ethylene copolymer having an ethylene-derived unit content ranging from 22% to 38% by weight, preferably from 25% to 35% by weight, more preferably 27% to 32% by weight as measured by 13 13C NMR;

[0032] The polypropylene composition has:

[0033] i) a xylene-soluble fraction ranging from 5.0% to 13.0% by weight at 25 °C, preferably from 6.0% to 12.0% by weight, more preferably from 7.0% to 11.0% by weight;

[0034] ii) an ethylene-derived unit content in the fraction insoluble in xylene at 25 °C ranging from 0.3% to 1.6% by weight, preferably from 0.4% to 1.5% by weight, more preferably from 0.5% to 1.4% by weight as measured by 13 13C NMR;

[0035] iii) an ethylene-derived unit content in the fraction soluble in xylene at 25 °C ranging from 13.2% to 27.0% by weight, preferably from 17.8% to 25.2% by weight, more preferably from 18.2% to 23.4% by weight as measured by 13 13C NMR;

[0036] iv) The melt flow rate MFR measured according to ISO 1133-1 at 230 °C and a load of 2.16 kg, which is between 35.0 g / 10 min and 70.0 g / 10 min, preferably between 38.0 g / 10 min and 65.0 g / 10 min, more preferably between 40.0 g / 10 min and 60.0 g / 10 min;

[0037] The sum of the amounts of A) and B) is 100% by weight.

[0038] For the present disclosure, the term "copolymer" refers to a polymer containing only two comonomers (such as propylene and ethylene).

[0039] The polypropylene composition of the present disclosure does not undergo chemical or physical visbreaking, i.e., the MFR is obtained through the polymerization process.

[0040] Preferably in the polypropylene composition, the intrinsic viscosity measured for the fraction soluble in xylene at 25 °C ranges from 0.9 dl / g to 2.3 dl / g, preferably from 1.1 dl / g to 2.0 dl / g, more preferably from 1.2 dl / g to 1.8 dl / g.

[0041] The polypropylene composition according to the present disclosure is preferably characterized by having one or more of the following properties:

[0042] a) The haze measured on a 1 mm plate is less than 32%, preferably less than 31%, more preferably less than 30%, and the higher value is preferably 8%;

[0043] b) The flexural modulus is higher than 1300 MPa, preferably higher than 1350 MPa, more preferably higher than 1400 MPa, and the highest value is preferably 2500 MPa;

[0044] c) The Charpy impact measured at 23 °C is higher than 4.0 kJ / m 2 , preferably higher than 4.2 kJ / m 2 , more preferably higher than 4.0 kJ / m 2 , and the highest value is 50 kJ / m 2 ;

[0045] d) The ductile-brittle transition temperature (M / B TT) is lower than 11 °C, more preferably lower than or equal to 10 °C, and the lowest value is 2 °C.

[0046] e) The fraction soluble in hexane measured on a 100 μm film is less than 2.4%, preferably less than 2.3%, more preferably less than 2.2%, and the lowest value is 0.5%.

[0047] Due to the specific polymerization process used and the specific Ziegler-Natta catalyst used in the polymerization, these features make the polypropylene composition according to the present disclosure particularly suitable for the production of molded articles, especially injection molded articles or thermoformed articles. The polypropylene composition of the present disclosure is obtained by a polymerization process in two or more stages, wherein component A) is obtained in the first stage, and then component B) is obtained in the second stage in the presence of component A). Each stage can be carried out in the gas phase, operating in one or more fluidized or mechanically stirred bed reactors, in the slurry phase using an inert hydrocarbon solvent as a diluent, or in bulk polymerization using a liquid monomer (such as propylene) as the reaction medium. Preferably, component B) is polymerized in the gas phase process in the presence of component A).

[0048] The polymerization is generally carried out at a temperature ranging from 20 °C to 120 °C, preferably from 40 °C to 80 °C. When the polymerization is carried out in the gas phase, the operating pressure is generally between 0.5 MPa and 5 MPa, preferably between 1 MPa and 4 MPa. In bulk polymerization, the operating pressure is generally between 1 MPa and 8 MPa, preferably between 1.5 MPa and 5 MPa. Hydrogen is usually used as a molecular weight regulator.

[0049] The polypropylene composition disclosed herein is prepared by a process comprising: homopolymerizing propylene in the first stage, and then copolymerizing propylene with ethylene in the second stage, both stages being carried out in the presence of a catalyst system comprising a product obtained by contacting (a) a solid catalyst component having an average particle size ranging from 15 μm to 80 μm, (b) a hydrocarbyl aluminum compound, and optionally (c) an external electron donor compound, the solid catalyst component comprising magnesium halide, a titanium compound having at least a Ti-halogen bond, and at least one electron donor compound such as a succinate and another selected from 1,3-diether.

[0050] Preferably, the succinate present in the solid catalyst component (a) is selected from succinates of the following formula (I):

[0051]

[0052] wherein the radicals R 1 and R 2 are the same or different from each other and are C 1 to C 20 linear or branched alkyl, alkenyl, cycloalkyl, aryl, aralkyl or alkaryl, optionally containing heteroatoms; and the groups R 3 and R 4 are the same or different from each other and are C 1 to C 20An alkyl, C3-C20 cycloalkyl, C5-C20 aryl, aralkyl or alkaryl group, provided that at least one of them is a branched alkyl group; with respect to the two asymmetric carbon atoms identified in the structure of formula (I), the compound is of the (S,R) or (R,S) stereoisomer type.

[0053] R 1 and R 2 Preferably C 1 to C 8 alkyl, cycloalkyl, aryl, aralkyl and alkaryl groups. Particularly preferred are those in which R 1 and R 2 are selected from primary alkyl groups, and in particular branched primary alkyl groups. Suitable examples of R 1 and R 2 groups are methyl, ethyl, n-propyl, n-butyl, isobutyl, neopentyl, 2-ethylhexyl. Particularly preferred are ethyl, isobutyl and neopentyl.

[0054] Particularly preferred are those in which R 3 and / or R 4 radicals are secondary alkyl groups such as isopropyl, sec-butyl, 2-pentyl, 3-pentyl or cycloalkyl groups such as cyclohexyl, cyclopentyl, cyclohexylmethyl.

[0055] Examples of the above compounds are diethyl 2,3-bis(trimethylsilyl)succinate, diethyl 2,3-bis(2-ethylbutyl)succinate, diethyl 2,3-dibenzylsuccinate, diethyl 2,3-diisopropylsuccinate, diisobutyl 2,3-diisopropylsuccinate, diethyl 2,3-bis(cyclohexylmethyl)succinate, diethyl 2,3-diisobutylsuccinate, diethyl 2,3-dineopentylsuccinate, dicyclopentyl 2,3-dicyclohexylsuccinate in the pure (S,R)(S,R) form or in a mixture form, optionally in the racemic form.

[0056] Among the above 1,3-diether, particularly preferred is the compound of formula (II)

[0057]

[0058] wherein R I and R II are the same or different and are hydrogen or straight-chain or branched C 1 to C 18 hydrocarbon groups which may also form one or more cyclic structures; R III groups, which are the same or different from each other, are hydrogen or C 1 to C 18 hydrocarbon groups; R IV groups are the same or different from each other and have the same as RIII have the same meaning, except that they cannot be hydrogen; R I to R IV groups each may contain a heteroatom selected from halogen, N, O, S, and Si.

[0059] Preferably, R IV is an alkyl radical of 1 to 6 carbon atoms, more particularly methyl, while R III group is preferably hydrogen. In addition, when R I is methyl, ethyl, propyl, or isopropyl, R II can be ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, isopentyl, 2-ethylhexyl, cyclopentyl, cyclohexyl, methylcyclohexyl, phenyl, or benzyl; when R I is hydrogen, R II can be ethyl, butyl, sec-butyl, tert-butyl, 2-ethylhexyl, cyclohexylethyl, diphenylmethyl, p-chlorophenyl, 1-naphthyl, 1-decahydronaphthyl; R I and R II can also be the same and can be ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, neopentyl, phenyl, benzyl, cyclohexyl, cyclopentyl.

[0060] Specific examples of ethers that can be advantageously used include: 2-(2-ethylhexyl)-1,3-dimethoxypropane, 2-isopropyl-1,3-dimethoxypropane, 2-butyl-1,3-dimethoxypropane, 2-sec-butyl-1,3-dimethoxypropane, 2-cyclohexyl-1,3-dimethoxypropane, 2-phenyl-1,3-dimethoxypropane, 2-tert-butyl-1,3-dimethoxypropane, 2-cumyl-1,3-dimethoxypropane, 2-(2-phenylethyl)-1,3-dimethoxypropane, 2-(2-cyclohexylethyl)-1,3-dimethoxypropane, 2-(p-chlorophenyl)-1,3-dimethoxypropane, 2-(diphenylmethyl)-1,3-dimethoxypropane, 2-(1-naphthyl)-1,3-dimethoxypropane, 2-(p-fluorophenyl)-1,3-dimethoxypropane, 2-(1-decahydronaphthyl)-1,3-dimethoxypropane, 2-(p-tert-butylphenyl)-1,3-dimethoxypropane, 2,2-dicyclohexyl-1,3-dimethoxypropane, 2,2-diethyl-1,3-dimethoxypropane, 2,2-dipropyl-1,3-dimethoxypropane, 2,2-dibutyl-1,3-dimethoxypropane, 2,2-diethyl-1,3-diethoxypropane, 2-dicyclopentyl-1,3-dimethoxypropane, 2,2-dipropyl-1,3-diethoxypropane, 2,2-dibutyl-1,3-diethoxypropane, 2-methyl-2-ethyl-1,3-dimethoxypropane, 2-methyl-2-propyl-1,3-dimethoxypropane, 2-methyl-2-benzyl-1,3-dimethoxypropane, 2-methyl-2-phenyl-1,3-dimethoxypropane, 2-methyl-2-cyclohexyl-1,3-dimethoxypropane, 2-methyl-2-methylcyclohexyl-1,3-dimethoxypropane, 2,2-bis(p-chlorophenyl)-1,3-dimethoxypropane, 2,2-bis(2-phenylethyl)-1,3-dimethoxypropane, 2,2-bis(2-cyclohexylethyl)-1,3-dimethoxypropane, 2-methyl-2-isobutyl-1,3-dimethoxypropane, 2-methyl-2-(2-ethylhexyl)-1,3-dimethoxypropane, 2,2-bis(2-ethylhexyl)-1,3-dimethoxypropane, 2,2-bis(p-methylphenyl)-1,3-dimethoxypropane, 2-methyl-2-isopropyl-1,3-dimethoxypropane, 2,2-diisobutyl-1,3-dimethoxypropane, 2,2-diphenyl-1,3-dimethoxypropane, 2,2-dibenzyl-1,3-dimethoxypropane, 2-isopropyl-2-cyclopentyl-1,3-dimethoxypropane, 2,2-bis(cyclohexylmethyl)-1,3-dimethoxypropane, 2,2-diisobutyl-1,3-diethoxypropane, 2,2-diisobutyl-1,3-dibutoxypropane, 2-isobutyl-2-isopropyl-1,3-dimethoxypropane, 2,2-di-sec-butyl-1,3-dimethoxypropane, 2,2-di-tert-butyl-1,3 - dimethoxypropane, 2,2 - neopentyl - 1,3 - dimethoxypropane, 2 - isopropyl - 2 - isopentyl - 1,3 - dimethoxypropane, 2 - phenyl - 2 - benzyl - 1,3 - dimethoxypropane, 2 - cyclohexyl - 2 - cyclohexylmethyl - 1,3 - dimethoxypropane.,

[0061] In addition, particularly preferred are the 1,3 - diethers of formula (III)

[0062]

[0063] wherein the radical R IV has the same meaning as explained above, and the radicals R III and R V radicals are the same as or different from each other and are selected from the group consisting of: hydrogen; halogen, preferably Cl and F; straight - chain or branched C 1 to C 20 alkyl radicals; C 3 to C 20 cycloalkyl, C 6 to C 20 aryl, C 7 to C 20 alkaryl and C 7 to C 20 aralkyl radicals, and two or more of the R V radicals may be bonded to each other to form a fused ring structure, which is saturated or unsaturated and may optionally be substituted by R VI radicals selected from the group consisting of: halogen, preferably Cl and F; straight - chain or branched C l to C 20 alkyl; C 3 to C 20 cycloalkyl, C 6 to C 20 aryl, C 7 to C 20 alkaryl and C 7 to C 20 aralkyl radicals; the radicals R V and R VI optionally contain one or more heteroatoms as substituents for carbon or hydrogen atoms or both.

[0064] Preferably, in the 1,3 - diethers of formula (I) and (II), all R III radicals are hydrogen and all R IV radicals are methyl. In addition, particularly preferred are the 1,3 - diethers of formula (II) wherein two or more of the R V radicals are bonded to each other to form one or more fused ring structures, preferably benzenoid, optionally substituted by RVI Free radical substitution. Particularly preferred are the compounds of formula (IV):

[0065]

[0066] wherein R VI free radicals are the same or different and are hydrogen; halogen, preferably Cl and F; straight-chain or branched C l to C 20 alkyl radicals; C 3 to C 20 cycloalkyl, C 6 to C 20 aryl, C 7 to C 20 alkaryl and C 7 to C 20 aralkyl radicals, optionally containing one or more heteroatoms as substituents of carbon atoms or hydrogen atoms or both selected from the group consisting of: N, 0, S, P, Si and halogen, especially Cl and F; radicals R III and R IV are as defined above for formula (III).

[0067] Specific examples of the compounds included in formulas (III) and (IV) are:

[0068] 1,1-bis(methoxymethyl)-cyclopentadiene;

[0069] 1,1-bis(methoxymethyl)-2,3,4,5-tetramethylcyclopentadiene;

[0070] 1,1-bis(methoxymethyl)-2,3,4,5-tetraphenylcyclopentadiene;

[0071] 1,1-bis(methoxymethyl)-2,3,4,5-tetrafluorocyclopentadiene;

[0072] 1,1-bis(methoxymethyl)-3,4-dicyclopentylcyclopentadiene;

[0073] 1,1-bis(methoxymethyl)indene; 1,1-bis(methoxymethyl)-2,3-dimethylindene;

[0074] 1,1-bis(methoxymethyl)-4,5,6,7-tetrahydroindene;

[0075] 1,1-bis(methoxymethyl)-2,3,6,7-tetrafluoroindene;

[0076] 1,1-bis(methoxymethyl)-4,7-dimethylindene;

[0077] 1,1-bis(methoxymethyl)-3,6-dimethylindene;

[0078] 1,1-bis(methoxymethyl)-4-phenylindene;

[0079] 1,1-bis(methoxymethyl)-4-phenyl-2-methylindene;

[0080] 1,1-bis(methoxymethyl)-4-cyclohexylindene;

[0081] 1,1-bis(methoxymethyl)-7-(3,3,3-trifluoropropyl)indene;

[0082] 1,1-bis(methoxymethyl)-7-trimethylsilylindene;

[0083] 1,1-bis(methoxymethyl)-7-trifluoromethylindene;

[0084] 1,1-bis(methoxymethyl)-4,7-dimethyl-4,5,6,7-tetrahydroindene;

[0085] 1,1-bis(methoxymethyl)-7-methylindene;

[0086] 1,1-bis(methoxymethyl)-7-cyclopentylindene;

[0087] 1,1-bis(methoxymethyl)-7-isopropylindene;

[0088] 1,1-bis(methoxymethyl)-7-cyclohexylindene;

[0089] 1,1-bis(methoxymethyl)-7-tert-butylindene;

[0090] 1,1-bis(methoxymethyl)-7-tert-butyl-2-methylindene;

[0091] 1,1-bis(methoxymethyl)-7-phenylindene;

[0092] 1,1-bis(methoxymethyl)-2-phenylindene;

[0093] 1,1-bis(methoxymethyl)-1H-benzo[e]indene;

[0094] 1,1-bis(methoxymethyl)-1H-2-methylbenzo[e]indene;

[0095] 9,9-bis(methoxymethyl)fluorene;

[0096] 9,9-bis(methoxymethyl)-2,3,6,7-tetramethylfluorene;

[0097] 9,9-bis(methoxymethyl)-2,3,4,5,6,7-hexafluorofluorene;

[0098] 9,9-Bis(methoxymethyl)-2,3-benzofluorene;

[0099] 9,9-Bis(methoxymethyl)-2,3,6,7-dibenzofluorene;

[0100] 9,9-Bis(methoxymethyl)-2,7-diisopropylfluorene;

[0101] 9,9-Bis(methoxymethyl)-1,8-dichlorofluorene;

[0102] 9,9-Bis(methoxymethyl)-2,7-dicyclopentylfluorene;

[0103] 9,9-Bis(methoxymethyl)-1,8-difluorofluorene;

[0104] 9,9-Bis(methoxymethyl)-1,2,3,4-tetrahydrofluorene;

[0105] 9,9-Bis(methoxymethyl)-1,2,3,4,5,6,7,8-octahydrofluorene;

[0106] 9,9-Bis(methoxymethyl)-4-tert-butylfluorene.

[0107] As explained above, in addition to the above electron donors, the catalyst component (a) comprises a titanium compound having at least one Ti-halogen bond and magnesium halide. The magnesium halide is preferably MgCl 2 , which is widely known from the patent literature as a support for Ziegler-Natta catalysts. Patents USP 4,298,718 and USP 4,495,338 first described the use of these compounds in Ziegler-Natta catalysis. It is known from these patents that the active form of magnesium dihalide used as a support or co-support in the components of catalysts for olefin polymerization is characterized by an X-ray spectrum in which the intensity of the strongest diffraction line appearing in the spectrum of the non-active halide is diminished and replaced by a halo, the maximum intensity of which is displaced towards lower angles relative to the stronger line.

[0108] Preferred titanium compounds used in the catalyst component of the present invention are TiCl 4 and TiCl 3 ; in addition, Ti-haloalcoholates of the formula Ti(OR) n-y X y can also be used, where n is the valence of titanium, y is a number between 1 and n-1, X is a halogen, and R is a hydrocarbon radical having from 1 to 10 carbon atoms.

[0109] Preferably, the catalyst component (a) has an average particle size ranging from 20 μm to 70 μm, and more preferably from 25 μm to 65 μm. As explained, the succinate is present in an amount ranging from 50% to 90% by weight relative to the total amount of the donor. Preferably, the range is from 60% to 85% by weight, and more preferably from 65% to 80% by weight. The 1,3-diether preferably constitutes the balance.

[0110] The hydrocarbyl aluminum compound (b) is preferably a hydrocarbyl aluminum compound in which the hydrocarbyl group is selected from C 3 to C 10 branched aliphatic or aromatic radicals; preferably selected from those in which the branched radical is an aliphatic radical, and more preferably selected from branched trialkylaluminum compounds selected from triisopropylaluminum, triisobutylaluminum, triisohexylaluminum, triisooctylaluminum. Mixtures of branched trialkylaluminum with alkylaluminum halides, alkylaluminum hydrides or alkylaluminum sesquichlorides (such as AlEt 2 Cl and Al 2 Et 3 Cl 3 ) can also be used.

[0111] Preferred external electron donor compounds include silicon compounds, ethers, esters (such as ethyl 4-ethoxybenzoate), amines, heterocyclic compounds, and especially 2,2,6,6-tetramethylpiperidine, ketones and 1,3-diether. Another class of preferred external donor compounds is the silicon compound of the formula R a 5 R b 6 Si(OR 7 ) c , where 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 are alkyl, cycloalkyl or aryl radicals having 1 to 18 carbon atoms, optionally containing heteroatoms. 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 from 5 to 500, preferably from 5 to 400, and more preferably from 10 to 200.

[0112] In step (i), the catalyst-forming components are contacted with a liquid inert hydrocarbon solvent such as, for example, propane, n-hexane or n-heptane for a period of from about 6 seconds to 60 minutes at a temperature below about 60 °C, and preferably from about 0 °C to 30 °C.

[0113] The above catalyst components (a), (b) and optionally (c) are fed to a pre-contact vessel in amounts such that the weight ratio (b) / (a) is in the range of 0.1 to 10, and if compound (c) is present, the weight ratio (b) / (c) is the weight ratio corresponding to the molar ratio defined above. Preferably, the components are pre-contacted at a temperature from 10 °C to 20 °C for 1 minute to 30 minutes. The pre-contact vessel can be a stirred tank or a loop reactor.

[0114] Thus, high transparency and good mechanical properties can be obtained.

[0115] The polypropylene composition of the present disclosure may contain additives commonly used in the art, such as antioxidants, processing stabilizers, slip agents, antistatic agents, anti-caking agents, anti-fogging agents and nucleating agents.

[0116] The following examples are given to illustrate and not limit the present disclosure.

[0117] Examples

[0118] Xylene soluble (XS) fraction at 25 °C

[0119] The xylene soluble matter at 25 °C is determined according to ISO 16 152; the solution volume is 250 ml, precipitated for 20 minutes at 25 °C, with the solution being stirred for 10 minutes (magnetic stirrer), and dried at 70 °C.

[0120] Melt flow rate (MFR)

[0121] Unless otherwise specified, it is measured according to ISO 1133-1 at 230 °C and a load of 2.16 kg.

[0122] Intrinsic viscosity (IV)

[0123] The sample is dissolved in tetralin at 135 °C and then poured into a capillary viscometer. The viscometer tube (Ubbelohde type) is surrounded by a cylindrical glass jacket; this setup allows temperature control with a circulating thermostatic liquid. The downward passage of the meniscus is timed by an optoelectronic device.

[0124] The meniscus is in front of the upper lamp. By activating a counter which has a quartz crystal oscillator. When passing the lower lamp, the meniscus stops the counter and the outflow time is recorded: this is converted into an intrinsic viscosity value by Huggins' equation (Huggins, M.L., J. Am. Chem. Soc., 1942, 64, 2716), provided that the flow time of the pure solvent is known under the same experimental conditions (same viscometer and same temperature). A single polymer solution is used to determine [η].

[0125] Measurement of haze

[0126] Injection molded specimens prepared according to ISO 1873-2 and ISO 294 are used. The haze value is measured using a Gardner photometer unit connected to a haze meter of type UX-10 or an equivalent instrument having a G.E. 1209 light source with filter "C". A reference sample of known haze is used to calibrate the instrument.

[0127] Flexural modulus

[0128] Determination is carried out using injection molded specimens according to ISO 178 and the supplementary conditions according to ISO 1873-2.

[0129] Ethylene content in the copolymer

[0130] 13 13C NMR spectra are obtained on a Bruker AV-600 spectrometer equipped with a cryoprobe, operating at 160.91 MHz in Fourier transform mode at 120 °C.

[0131] The Sββ carbon (nomenclature according to "By 13 13C NMR Measurement of Monomer Sequence Distribution in Ethylene-Propylene Rubber. 3. Use of Reaction Probability Mode)" C.J. Carman, R.A. Harrington and C.E. Wilkes, Macromolecules 1977, 10, 536) peak at 29.9 ppm is used as an internal reference. The sample is dissolved at 8 weight / volume % concentration in 1,1,2,2-tetrachloroethane-d2 at 120 °C. Each spectrum is acquired with a 90° pulse and with a 15 s delay between pulses and CPD to remove 13 1 ​H- 13 C coupling. 512 transients were stored in 32K data points using a spectral window of 9000 Hz.

[0132] The evaluation of spectral assignments, triplet distributions, and compositions was carried out 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, 15, 1150) using the following equations:

[0133] PPP = 100Tββ / S PPE = 100Tβδ / S EPE = 100Tδδ / S

[0134] PEP = 100Sββ / S PEE = 100Sβδ / S EEE = 100(0.25Sγδ + 0.5Sδδ) / S

[0135] S = Tββ + Tβδ + Tδδ + Sββ + Sβδ + 0.25Sγδ + 0.5Sδδ

[0136] The mole percentage of ethylene content was evaluated using the following equation:

[0137] E%mol = 100 * [PEP + PEE + EEE] The weight percentage of ethylene content was evaluated using the following equation:

[0138] E%mol * MWE

[0139] E%wt. = E%mol * MWE + P%mol * MWP

[0140] where P%mol is the mole percentage of propylene content, and MWE and MWP are the molecular weights of ethylene and propylene, respectively.

[0141] According to Carman (C. J. Carman, R. A. Harrington, and C. E. Wilkes, Macromolecules, 1977; 10, 536), the product of the reaction ratios r1r2 was calculated as:

[0142]

[0143] The tacticity of the propylene sequence is from PPP mmT ββ (28.90 ppm to 29.65 ppm) and all T ββ (29.80 ppm to 28.37 ppm) and the ratio is calculated as the mm content.

[0144] Charpy impact test

[0145] The Charpy impact test is measured according to ISO 179-1eA, e ISO 1873-2

[0146] Tensile modulus

[0147] The tensile modulus is measured on injection-molded samples according to ISO 527-2 and ISO 1873-2

[0148] Hexane extractable matter on 100 μm film

[0149] Determination is carried out according to FDA 177,1520 by suspending the composition specimen in excess hexane. Films are prepared by extrusion. The suspension is placed in an autoclave at 50 °C for 2 hours, then the hexane is removed by evaporation and the dried residue is weighed.

[0150] The ductile-brittle temperature is determined by DSC

[0151] According to ISO 11357-3, at a scanning rate of 20 °C / min, under cooling and heating, the temperature of samples with a weight between 5 mg and 7 mg is measured under an inert N2 flow. Instrument calibration is carried out using indium.

[0152] Determination of Mg and Ti

[0153] The contents of Mg and Ti in the solid catalyst component were determined by inductively coupled plasma emission spectrometry on an “I.C.P Spectrometer ARL Accuris”.

[0154] Samples are prepared by analyzing and weighing 0.1÷0.3 g of catalyst and 2 g of a lithium metaborate / lithium tetraborate 1 / 1 mixture in a “Fluxy” platinum crucible. After adding a few drops of KI solution, the crucible is inserted into a special device “Claisse Fluxy” for complete combustion. The residue is collected and then analyzed by ICP at the following wavelengths: magnesium, 279.08 nm; titanium, 368.52 nm; 3 collect the residue, and then analyze by ICP at the following wavelengths: magnesium, 279.08 nm; titanium, 368.52 nm;

[0155] Determination of Bi

[0156] The content of Bi in the solid catalyst component was determined by inductively coupled plasma emission spectrometry on an “I.C.P Spectrometer ARL Accuris”.

[0157] Samples were prepared by analyzing and weighing 0.1÷0.3 g of the catalyst in a 200 cm 3 volumetric flask. After slowly adding ca. 10 mL of 65 v / v% HNO 3 solution and ca. 50 cm 3 of distilled water, the samples were digested for 4÷6 hours. Then the volumetric flask was diluted to the mark with deionized water. The resulting solution was directly analyzed by ICP at the following wavelengths: bismuth, 223.06 nm.

[0158] Determination of internal donor content

[0159] The determination of the internal donor content in the solid catalytic compound was carried out by gas chromatography. The solid component was dissolved in acetone, an internal standard was added, and the sample of the organic phase was analyzed in a gas chromatograph to determine the amount of the donor present in the starting catalyst compound.

[0160] Example 1 - Preparation of Ziegler-Natta solid catalyst

[0161] Preparation of solid catalyst component

[0162] At 0 °C, 250 mL of TiCl 4 was introduced into a 500 mL four-necked round-bottom flask purged with nitrogen. While stirring, 10.0 g of microspherical MgCl 2 ·2.5C 2 H 5 OH (prepared by thermal dealcoholization of the starting adduct obtained according to the procedure of Example 1 of WO2012 / 084735), a certain amount of the racemic form of diethyl 2,3-diisopropyl succinate was added such that the Mg / succinate ester molar ratio was 12. The temperature was raised to 100 °C and maintained at this value for 60 minutes. After siphoning, fresh TiCl 4 and a certain amount of 9,9-bis(methoxymethyl)fluorene (bMMF) were added such that the Mg / (bMMF) molar ratio was 12. Then the temperature was raised to 90 °C and maintained at this value for 30 minutes. After siphoning, the treatment was repeated with TiCl 4 at 90 °C for 30 minutes, the solid was washed six times with anhydrous hexane (6 x 100 ml) at 60 °C, and finally dried.

[0163] Prepolymerization treatment

[0164] Before introducing it into the polymerization reactor, the above solid catalyst component has been contacted with triethylaluminum (TEAL) without using an external donor. Then the resulting mixture is prepolymerized by maintaining it in a liquid propylene suspension at 20 °C for about 5 minutes, after which it is introduced into the polymerization reactor.

[0165] Polymerization

[0166] The polymerization of component A) is carried out continuously in a series of two reactors equipped with means for transferring the product from the first reactor to the second reactor. The polymerization is carried out in a gas-phase polymerization reactor comprising two interconnected polymerization zones (riser and downcomer) without using a "barrier flow".

[0167] The polymer (A) from the first reactor is discharged in a continuous stream and, after purging unreacted monomers, is introduced into the second stirred-bed gas-phase reactor in a continuous stream. An ethylene copolymer (B) is produced in the second reactor.

[0168] The amounts of monomers and hydrogen fed to the polymerization reactor are reported in Table 1.

[0169] Table 1

[0170]

[0171]

[0172] C3 Propylene, C2 Ethylene, H2 Hydrogen

[0173] The polymers of Example 1 and Example 3 and Comparative Example 2 have been characterized as reported in Table 2.

[0174] Table 2

[0175]

[0176]

[0177] Example 1 and Example 3 show better haze hexane extractables and M / B TT compared to Comparative Example 2.

Claims

1. A polypropylene composition, comprising: A) from 90.6% to 97.0% by weight of a propylene homopolymer having a fraction insoluble in xylene at 25 °C greater than 90% by weight; and a melt flow rate MFR measured according to ISO 1133-1 at 230 °C and a load of 2.16 kg and included between 40.0 g / 10 min and 100.0 g / 10 min; B) An ethylene-propylene copolymer from 3.0% to 9.4% by weight, the ethylene-propylene copolymer having an ethylene-derived unit content in the range from 22% to 38% by weight as measured by 13 13C NMR; The polypropylene composition has: i) a xylene-soluble fraction ranging from 5.0% to 13.0% by weight at 25 °C; ii) The content of the ethylene-derived units in the fraction insoluble in xylene at 25°C, which ranges from 0.3 wt% to 1.6 wt% as measured by 13 13C NMR; iii) The 13 content of the ethylene-derived units in the fraction soluble in xylene at 25 °C, measured by 13C NMR, ranges from 17.2% by weight to 27.0% by weight; (iv) a melt flow rate MFR measured according to ISO 1133-1 at 230 °C and a load of 2.16 kg and included between 35.0 g / 10 min and 70.0 g / 10 min; The sum of the amounts of A) and B) is 100% by weight.

2. The polypropylene composition according to claim 1, wherein the propylene composition comprises from 91.0% to 96.0% by weight of component A) and from 5.0% to 9.3% by weight of component B).

3. The polypropylene composition according to claim 1, wherein the xylene-soluble fraction ranges from 6.0% to 12.0% by weight at 25 °C.

4. The polypropylene composition according to claim 1, wherein in component A), the melt flow rate MFR measured according to ISO 1133-1 at 230 °C and a load of 2.16 kg is included between 38.0 g / 10 min and 65.0 g / 10 min.

5. The polypropylene composition according to claim 1, wherein the intrinsic viscosity measured for the fraction soluble in xylene at 25 °C ranges from 0.9 dl / g to 2.3 dl / g.

6. The polypropylene composition according to claim 1, wherein the ethylene-derived unit content in the fraction insoluble in xylene at 25 °C ranges from 0.4% to 1.5% by weight.

7. The polypropylene composition according to claim 1, wherein the ethylene-derived unit content in the fraction soluble in xylene at 25 °C ranges from 17.8% to 25.2% by weight.

8. The polypropylene composition according to claim 1, wherein the intrinsic viscosity measured for the fraction soluble in xylene at 25 °C ranges from 1.1 dl / g to 2.0 dl / g.

9. The polypropylene composition according to claim 1, wherein the melt flow rate MFR measured according to ISO 1133-1 at 230 °C and a load of 2.16 kg is included between 38.0 g / 10 min and 65.0 g / 10 min.

10. The polypropylene composition according to claim 1, wherein the propylene composition comprises from 91.0% to 95% by weight of component A) and from 7% to 9.0% by weight of component B).

11. The polypropylene composition according to claim 1, wherein the xylene-soluble fraction ranges from 7% to 11% by weight at 25 °C.

12. The polypropylene composition according to claim 1, wherein the melt flow rate MFR measured according to ISO 1133-1 at 230 °C and a load of 2.16 kg is included between 40.0 g / 10 min and 60.0 g / 10 min.

13. The polypropylene composition according to claim 1, wherein in component A), the melt flow rate MFR measured according to ISO 1133-1 at 230 °C and a load of 2.16 kg ranges from 70.0 g / 10 min to 85.0 g / 10 min.

14. The polypropylene composition according to claim 1, wherein the intrinsic viscosity measured for the fraction soluble in xylene at 25 °C ranges from 1.2 dl / g to 1.8 dl / g.

15. An injection molded article, the injection molded article comprising the propylene composition according to claim 1.

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