Catalyst component for the prepolymerization of olefins

Abstract

A prepolymer catalyst component for olefin polymerization, characterized in that it comprises: (a) a solid catalyst component comprising Ti, Mg, and a halogen, and a bidentate electron donor compound (BE), wherein the amount of the bidentate electron donor compound is such that the (BE) / Ti molar ratio ranges from 0 to 0.3; and (b) an ethylene (co)polymer, wherein the amount of the ethylene (co)polymer ranges from 0.1 to no more than 30 g per g of the solid catalyst component, and wherein the intrinsic viscosity measured in tetrahydronaphthalene at 135 °C is at least 3.0 dL / g; the prepolymer catalyst component also exhibits a porosity of 0.1 to 1 cm² as measured by the mercury method. 3 Within the range of / g, the prepolymerized catalyst exhibits high morphological stability and produces a small amount of fine particles.

Description

Technical Field

[0001] This disclosure relates to catalyst components for preparing ethylene (co)polymers using gas-phase, slurry, or bulk (co)polymerization processes. Background Technology

[0002] High-yield catalyst components for olefin polymerization, and particularly for ethylene polymerization, are known in the art. They are typically obtained by supporting titanium compounds selected from titanium halides, alkoxides, and halohydrides on magnesium dihalides. These catalyst components are then used together with alkylaluminum compounds for ethylene polymerization. These catalyst components and the catalysts obtained therefrom are primarily used in equipment for the (co)polymerization of ethylene, operating in both liquid (slurry or bulk) and gas phases. However, the use of such catalyst components is not entirely satisfactory. In fact, due to the high reactivity of ethylene, the polymerization kinetics are very high. Therefore, the catalyst is subjected to very strong stress in the initial stages of polymerization, which can lead to uncontrolled breakage of the catalyst itself. This event results in the formation of fine polymer particles, which in turn leads to low polymer packing density and makes the operating process difficult.

[0003] To attempt to address these issues, catalysts are prepolymerized under controlled conditions to obtain prepolymerized catalysts intended to exhibit good morphological stability. Indeed, it has been argued that prepolymerization increases the catalyst's resistance by reducing its tendency to break under polymerization conditions. Prepolymerization conditions are typically particularly mild when carried out batchwise rather than sequentially on polymerization equipment, as reported in WO2013 / 092282. While prepolymerization according to the cited techniques improves the morphological stability of non-prepolymerized catalysts, performance in the main polymerization step for producing ethylene polymers still requires improvement in terms of bulk density and the percentage of fine particles (diameter less than 300 μm), particularly for gas-phase processes.

[0004] Furthermore, preparing prepolymerized catalyst systems using existing technologies is cumbersome due to the very low productivity. In fact, the low temperature at which ethylene enters the reactor and the slow feed rate result in long reaction times, thus leading to low productivity.

[0005] The applicant has now discovered that when the prepolymerized catalyst exhibits specific characteristics in relation to the properties of the ethylene prepolymer, the prepolymerized catalyst possesses high morphological stability, which also allows for the generation of fewer fine particles during the main polymerization step. Furthermore, this prepolymerized catalyst can be obtained using a more efficient preparation process. Summary of the Invention

[0006] Therefore, the object of this disclosure is a prepolymer catalyst component for olefin polymerization, characterized by comprising: (a) a solid catalyst component comprising Ti, Mg, and a halogen, and optionally a bidentate electron donor compound (BE), the amount of which is such that the (BE) / Ti molar ratio ranges from 0 to 0.3; and (b) an ethylene (co)polymer, the amount of which ranges from 0.1 to no more than 30 g per g of the solid catalyst component, and wherein the intrinsic viscosity measured in tetrahydronaphthalene at 135 °C is at least 3.0 dL / g; the prepolymer catalyst component also exhibits a porosity of 0.1 to 1 cm² as measured by the mercury method. 3 Within the range of / g. Detailed Implementation

[0007] The characteristics and components of a prepolymerized catalyst component are not inseparable. This means that a preferred level of one characteristic does not necessarily involve the same preferred level of the remaining characteristics of the same or different components. Rather, the intention of this disclosure is that any preferred range of characteristics of any prepolymerized catalyst component can be combined with each other and with any possible additional components and their preferred characteristics described in this disclosure.

[0008] Throughout this disclosure, the term "non-stereospecific solid catalyst component" refers to a solid catalyst component, either on its own or in a prepolymerized form, that, under the standard polymerization conditions described in the experimental section, produces a propylene homopolymer having an insoluble fraction in xylene of less than 70%, preferably less than 65%, and more preferably less than 60% at 25°C. Under the same testing conditions, a solid catalyst component producing an insoluble fraction in xylene of more than 70% at 25°C is considered a "stereospecific catalyst."

[0009] Preferably, the intrinsic viscosity is equal to or greater than 4.0 dl / g, and more preferably in the range of 4.5 to 15 dl / g, particularly in the range of 5 to 12 dl / g.

[0010] Preferably, the ethylene (co)polymer is an ethylene homopolymer or an ethylene copolymer, which contains less than 5 mol%, preferably less than 3 mol%, of an ethylene copolymer selected from the formula CH2=CHR. 1 Those α-olefins, in which R 1 It is a C1-C6 straight-chain alkyl group. Preferably, the α-olefin is selected from propylene, butene-1, hexene-1, and octene-1. More preferably, the ethylene (co)polymer is an ethylene homopolymer.

[0011] In specific embodiments, the amount of ethylene (co)polymer is less than 10 g, and preferably less than 5 g per gram of solid catalyst component. In particularly preferred embodiments, the amount is from 0.5 to 2.5 g per gram of solid catalyst component.

[0012] Preferably, since the pore radius exceeds 1 μm, the prepolymerized catalyst component has a pore size ranging from 0.20 to 0.90, more preferably from 0.30 to 0.80 cm⁻¹. 3 / g mercury porosity.

[0013] Furthermore, the average pore radius associated with the porosity ranges from 100 to 300 nm, preferably from 150 to 280 nm.

[0014] Preferably, the bulk density of the prepolymerized catalyst component ranges from 0.34 to 0.50 g / cm³. 3 More preferably from 0.35 to 0.50, and particularly from 0.36 to 0.50 g / cm³ 3 .

[0015] Preferably, the solid catalyst component is non-stereospecific. It preferably comprises titanium compounds and magnesium dihalides. Magnesium halides, preferably in the active form MgCl2 used as a support for Ziegler-Natta catalysts, are well known in the patent literature. Patents USP 4,298,718 and USP 4,495,338 first described the use of these compounds in Ziegler-Natta catalysis. From these patents, it is known that the active form of magnesium dihalides used as a support or co-support for catalyst components for olefin polymerization is characterized by X-ray spectroscopy, in which the intensity of the strongest diffraction lines appearing in the spectra of inactive halides decreases and broadens to form halogens.

[0016] Preferred titanium compounds used as solid catalyst components in this disclosure are those of the formula Ti(OR). II ) 4-y X y Of those, R II It is C1-C 20 The hydrocarbon group, X is a halogen, and y is a number between 1 and 4. Particularly preferred compounds are TiCl4 and Ti-tetraolides or compounds of the formula Ti(OR) III ) a Cl 4-a Ti-chlorohydrin, where "a" is a number between 1 and 4, and R III It is a C1-C8 alkyl or aryl group. Preferably, R III It is selected from ethyl, propyl, n-butyl, isobutyl, 2-ethylhexyl, n-octyl and phenyl.

[0017] Titanium compounds can be formed in advance, or by titanium tetrahalides, particularly TiCl4, with alcohols R II OH or with the formula Ti(OR) II The product is produced in situ by the reaction of titanium alkoxides with R. II It has the meaning defined above.

[0018] Preferably, prior to prepolymerization, the solid catalyst component comprises more than 70%, more preferably more than 90%, and in particular, all titanium atoms are in the 4-degree position. + Price state.

[0019] Non-stereospecific solid catalyst components may include electron donor compounds (internal donors) selected from ethers, esters, amines, and ketones. However, if present, the electron donor compounds should not have stereotactic power or should be present in an amount insufficient to provide sufficient stereotactic power to the catalyst. As a general indication, electron donors without stereotactic power can be present in a wide range of amounts, but preferably in a molar ratio to Ti of less than 10, more preferably less than 7, and more preferably less than 5. Preferably, bidentate electron donors (BE) are absent or present in an amount such that the (BE) / Ti ratio is from 0 to less than 0.2, and more preferably from 0 to less than 0.1. Most preferably, bidentate electron donors (BE) are absent.

[0020] In bidentate electron donors, preferred bidentate electron donors are derived from esters of aliphatic or aromatic dicarboxylic acids (such as phthalates, succinates, glutarates), esters of monocarboxylic acids with aliphatic or aromatic diols, and 1,3-diethers.

[0021] Electron donors that do not possess stereotactic capability are preferably monodentate (MD) and are preferably selected from esters of aliphatic or aromatic carboxylic acids (such as ethyl acetate, benzoate esters), and cycloalkyl ethers (such as tetrahydrofuran). Monodentate donors may be present in amounts such that the (MD):Ti ratio ranges from 0.1:1 to 25:1, preferably from 0.5:1 to 20:1, and especially from 1:1 to 15:1.

[0022] In addition to the characteristics mentioned above, the solid catalyst component (a) can exhibit a porosity P determined by the mercury method. F The range is from 0.2 to 0.80 cm. 3 / g, and more preferably from 0.3 to 0.70cm 3 / g, more preferably 0.35 to 0.60cm 3 Within the range of / g.

[0023] The surface area measured by the BET method is preferably less than 80, and especially between 10 and 70 m². 2The porosity measured by the BET method is typically between 0.10 and 0.50, preferably from 0.10 to 0.40 cm³. 3 / g.

[0024] The above-mentioned catalyst component can be prepared by a method including step (a), wherein the compound MgCl2.mR is made III OH (where 0.3 ≤ m ≤ 1.7 and R) III (It is an alkyl, cycloalkyl, or aryl radical having 1 to 12 carbon atoms) and the formula Ti(OR) I ) n X 4-n Titanium compound reaction, where n, y, X and R I The meaning is the same as the one already defined.

[0025] In this case, MgCl2.mR III OH represents the precursor of magnesium dihalide. These compounds can be obtained by mixing an alcohol and magnesium chloride in the presence of an inert hydrocarbon immiscible with the adduct, under stirring at the melting temperature of the adduct (100 to 130 °C). The emulsion is then rapidly quenched, causing the adduct to solidify into spherical particles. Representative methods for preparing these spherical adducts are reported, for example, in USP 4,469,648, USP 4,399,054, and WO98 / 44009. Another available method for spheroidization is spray cooling, as described, for example, in USP 5,100,849 and 4,829,034. Adducts with the desired final alcohol content can be obtained by directly using a selected amount of alcohol during adduct preparation. However, to obtain adducts with increased porosity, adducts with more than 1.7 moles of alcohol per mole of MgCl2 can be prepared first, followed by thermal and / or chemical dealcoholization processes. The thermal de-alcoholization process is carried out in a nitrogen stream at a temperature between 50 and 150°C until the alcohol content is reduced to a value ranging from 0.3 to 1.7. This type of process is described in EP 395083.

[0026] The dealcohol adducts are also characterized by a porosity (measured by the mercury method) ranging from 0.15 to 2.5 cm⁻¹ due to pore radii exceeding 0.1 μm. 3 / g, preferably from 0.25 to 1.5cm 3 / g.

[0027] In the reaction of step (a), the molar ratio Ti / Mg is a stoichiometric ratio or higher; preferably, this ratio is higher than 3. A large excess of titanium compound is also more preferably used. Preferred titanium compounds are titanium tetrahalides, particularly TiCl4. The reaction with the Ti compound can be carried out by suspending the adduct in cold TiCl4 (typically 0°C); the mixture is heated to 80 to 140°C and held at this temperature for 0.5 to 8 hours, preferably from 0.5 to 3 hours. Excess titanium compound can be separated at high temperature by filtration or precipitation and siphoning. Step (a) can be repeated two or more times. In the case of a catalyst containing an electron-donating compound, this electron-donating compound can be added to the reaction system along with the titanium compound for reaction with MgCl2·mR III OH adduct reaction. However, the electron donor compound can also be contacted with the adduct alone first, and then the product thus formed can be reacted with the titanium compound. Alternatively, the electron donor compound can be added separately in a separate step after the reaction between the adduct and the titanium compound is complete.

[0028] The prepolymerized catalyst component of this disclosure can be obtained by the following steps, including: reacting a solid catalyst component (a) with ethylene and optionally an α-olefin CH2=CHR. 1 The prepolymerization is carried out to the extent that the amount of the resulting ethylene (co)polymer ranges from 0.1 to 50 g per g of the solid catalyst component (a), which comprises Ti, Mg, and halogens and optionally a bidentate electron donor compound (BE) in an amount such that the (BE) / Ti molar ratio ranges from 0 to 0.3. The process is carried out at a temperature ranging from 25 to 100°C and in the presence of an alkylaluminum compound such that the Al / Ti molar ratio is less than 0.5.

[0029] The process can be carried out in the presence of an external electron donor compound (C) in an amount such that the (B) / (C) molar ratio is less than 50, preferably from 0.1 to 20, more preferably from 0.5 to 10, and especially from 0.5 to 8.

[0030] The alkylaluminum compound is preferably selected from trialkylaluminum compounds, such as triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, and tri-n-octylaluminum. Tri-n-octylaluminum is particularly preferred. Mixtures of trialkylaluminum with alkylaluminum halides, alkylaluminum hydrides, or alkylaluminum sesquichlorides such as AlEt2Cl and Al2Et3Cl3 can also be used.

[0031] Preferably, the prepolymerization uses a small amount of alkylaluminum compound. In particular, the amount can be such that the Al / Ti molar ratio is preferably less than 0.4, more preferably less than 0.3, and especially less than 0.2.

[0032] The external electron donor compound can be selected from alcohols, glycols, esters, ketones, amines, amides, nitriles, alkoxysilanes, and ethers.

[0033] Among alkoxysilanes, the preferred alkoxysilane is of formula (R7). a (R8) b Si(OR9) c Those, where a and b are integers from 0 to 2, c is an integer from 1 to 4, and the sum of (a+b+c) is 4; R7, R8, and R9 are free radicals having 1 to 18 carbon atoms, optionally containing heteroatoms. Particularly preferred are silicon compounds where a is 1, b is 1, c is 2, at least one of R7 and R8 is selected from branched alkyl, cycloalkyl, or aryl groups having 3 to 10 carbon atoms, optionally containing heteroatoms, and R9 is C1-C2. 10 Alkyl groups, particularly methyl groups. Examples of such preferred silicon compounds are methylcyclohexyldimethoxysilane (C donor), diphenyldimethoxysilane, methyl tert-butyldimethoxysilane, dicyclopentyldimethoxysilane (D donor), diisopropyldimethoxysilane, (2-ethylpiperidinyl)-tert-butyldimethoxysilane, (2-ethylpiperidinyl)tert-hexyldimethylchlorosilane, (3,3,3-trifluoro-n-propyl)(2-ethylpiperidinyl)dimethoxysilane, methyl(3,3,3-trifluoro-n-propyl)dimethoxysilane, and N,N-diethylaminotriethoxysilane. Furthermore, silicon compounds in which a is 0, c is 3, R8 is optionally a branched alkyl or cycloalkyl group containing a heteroatom, and R9 is methyl are preferred. Examples of such preferred silicon compounds are cyclohexyltrimethoxysilane, tert-butyltrimethoxysilane, and tert-hexyltrimethoxysilane. The aminosilanes disclosed in EP-A-1538167 may also be used.

[0034] In the ether, preferred ethers are alkoxybenzenes, cycloalkyl ethers (such as tetrahydrofuran), and 1,3-diethers (such as those described in EP362705 and EP728769) as described in WO2011 / 015553.

[0035] Preferred esters may be selected from monoesters of aromatic carboxylic acids, such as benzoic acid esters, especially C1-C benzoic acid. 10 Alkyl esters; and monoesters of aliphatic carboxylic acids, such as C1-C8 alkyl esters of aliphatic monocarboxylic acids, for example, ethyl acetate.

[0036] Another category of interest is the C1-C of aromatic dicarboxylic acids. 10 Alkyl esters, such as phthalates; and C1-C of aliphatic dicarboxylic acids. 10Alkyl esters, such as malonate, succinate, and glutarate. Alternatively, diesters of diols, such as those disclosed in USP 7,388,061 and WO2010 / 078494, may also be used.

[0037] Preferred esters are ethyl acetate, diisobutyl phthalate, ethyl p-ethoxybenzoate, and diethyl 2,3-diisopropylsuccinate.

[0038] The preferred alcohol is of formula R 3 Those of OH, among which R 3 The group is C1-C 20 Hydrocarbon group. Preferably, R 3 It is C1-C 10 Alkyl groups. Specific examples are methanol, ethanol, isopropanol, and butanol.

[0039] Prepolymerization can be carried out in the liquid phase (slurry or solution) or in the gas phase at a temperature ranging from 25 to 100°C, preferably from 30 to 80°C, and more preferably from 30 to 70°C. Furthermore, it is preferably carried out in a liquid diluent, particularly selected from liquid hydrocarbons. Pentane, hexane, and heptane are preferred. The ethylene feed is preferably above 0.08 g C2. - / gcat / h, more preferably in the range of 0.16gC2 - / gcat / h to 1.6gC2 - / gcat / h.

[0040] The prepolymerized catalyst component has a generally spherical morphology and an average diameter between 15 and 200 μm, preferably from 20 to 150 μm, and more preferably from 25 to 100 μm. As for particles having a generally spherical morphology, those refer to particles in which the ratio between the larger and smaller axes is equal to or less than 1.5, and preferably less than 1.3.

[0041] The prepolymerized catalyst thus obtained can be used as is for polymerization or it can undergo further processing. Particularly when the solid catalyst component used for prepolymerization does not contain an internal electron donor, this solid catalyst component constitutes a preferred embodiment of prepolymer processing, which includes loading an electron donor onto the prepolymer. The electron donor can be selected from among the internal donors already described, and can be carried out by contacting the prepolymer and the electron donor in a suitable liquid hydrocarbon medium, which is then removed by drying. Alternatively, the electron donor compound can be contacted with the prepolymer by contacting it with an airflow containing the electron donor compound. This technique is also applicable to non-prepolymerized catalyst components disclosed in PCT / EP2020 / 081034, the relevant portions of which are incorporated herein by reference.

[0042] The prepolymerized catalyst retains its non-sterile specificity after contact with the electron donor compound, which constitutes a preferred embodiment. Preferably, the electron donor is selected from esters of aliphatic or aromatic carboxylic acids (such as ethyl acetate) and cycloalkyl ethers, such as tetrahydrofuran. More preferably, the electron donor comprises a mixture of the above-described substances as described in WO2018 / 114453, the relevant portion of which is incorporated herein by reference.

[0043] Additional possible treatments include further reaction with titanium compounds containing at least one Ti-halogen bond, treatment with a halogenating agent, and treatment with alkyl aluminum.

[0044] As explained, the prepolymerized catalyst component thus obtained possesses a specific combination of donor composition, porosity, and intrinsic viscosity, which can be used for the (co)polymerization of ethylene, thereby allowing for the high-yield production of polymers with regular morphologies, particularly characterized by high packing density and low content of fine polymer particles. Specifically, in gas-phase polymerization, the fraction of polymer particles with particle sizes below 500 μm, and particularly below 300 μm, is reduced due to prior art prepolymerized catalysts. In one specific embodiment, the fraction of polymer particles with a particle size below 500 μm is reduced by more than 25% by weight, and the fraction of polymer particles below 300 μm can be reduced by more than 50%, preferably more than 70%. Furthermore, the prepolymerized catalyst is produced in the copolymerization of ethylene and α-olefins, making it possible to produce LLDPE polymers with low content of xylene-soluble fractions for a given polymer density.

[0045] Specifically, the ethylene (co)polymerization process can be carried out in the presence of a catalyst, comprising (A) the prepolymerization catalyst component described above and (B) an alkylaluminum compound of the type described above. In the main polymerization process, the amount of Al is higher than the amount of Al used in the prepolymerization step. Preferably, the Al compound is used in an amount such that the Al / Ti ratio is greater than 1 and typically between 20 and 800. The external electron donor compound (C) described above can be used in the ethylene polymerization step.

[0046] The catalysts disclosed herein can be used in any olefin polymerization process known in the art. They can be used, for example, in slurry polymerization using inert hydrocarbon solvents as diluents or in bulk polymerization using liquid monomers as the reaction medium. In particular, they are suitable for polymerization processes carried out in the gas phase. The gas phase process can be carried out in a fluidized or stirred fixed-bed reactor or in a gas phase reactor comprising two interconnected polymerization zones, one of which operates under rapid fluidization conditions, while in the other, the polymer flows under gravity. Furthermore, combinations of two types of gas phase reactors can be used. In a preferred embodiment, the catalyst is used to polymerize ethylene in a multi-step gas phase process, wherein the first step is carried out in a fluidized bed gas phase reactor, and subsequent steps are carried out in a second gas phase reactor comprising two interconnected polymerization zones, one of which operates under rapid fluidization conditions, while in the other, the polymer flows under gravity.

[0047] While not mandatory, they are primarily used in polymerization equipment that does not include a prepolymerization section. In fact, because the catalysts do not have aging issues, they can be prepolymerized on a batch scale and then used in liquid-phase or gas-phase olefin polymerization equipment that does not require a prepolymerization line to operate.

[0048] As mentioned above, in the main polymerization process, the amount of Al is higher than the amount of Al used for prepolymerization. Preferably, the Al compound is used in an amount such that the Al / Ti ratio is greater than 20 and typically between 50 and 800.

[0049] The above-described polymerization process can be carried out under polymerization conditions generally known in the art. Therefore, polymerization is typically carried out at temperatures ranging from 20 to 120°C, preferably from 40 to 90°C.

[0050] In any polymerization process (liquid-phase or gas-phase polymerization) used, the catalyst-forming components (A) and (B) can be pre-contacted before being added to the polymerization reactor. The catalyst-forming components can be contacted with a liquid inert hydrocarbon solvent, such as propane, n-hexane, or n-heptane, at a temperature below about 60°C and preferably from about 0°C to 30°C for a period of time from 10 seconds to 60 minutes.

[0051] The above method is applicable to the preparation of a wide range of polyethylene products. As an example, the following product can be prepared: high-density ethylene polymer (HDPE, with a density higher than 0.940 g / cm³). 3 (density), including ethylene homopolymers and copolymers of ethylene with α-olefins having 3 to 12 carbon atoms; linear low-density polyethylene (LLDPE, with a density below 0.940 g / cm³). 3 (low density) and very low density and ultra-low density (VLDPE and ULDPE, with densities below 0.920 g / cm³) 3Its density reaches 0.880 g / cm³. 3 ), consisting of ethylene and one or more α-olefins having 3 to 12 carbon atoms, having a molar content of more than 80% of ethylene-derived units.

[0052] The following examples are given to better illustrate the invention and not to limit it.

[0053] Characterization

[0054] The characteristics were determined using the following method:

[0055] Bulk density ASTM D 1895 / 96 Method A

[0056] MIE Flow Index: ASTM-D 1238 Condition E

[0057] Intrinsic viscosity : Determined in tetrahydronaphthalene at 135℃.

[0058] 5g of prepolymerized catalyst was treated with stirring for 30 minutes. It was washed with a mixture of water (50ml), acetone (50ml) and HCl (20ml), then filtered. After washing with water and acetone, the residue was dried in a vacuum oven at 70°C for 2 hours.

[0059] The sample thus obtained was dissolved in tetrahydronaphthalene at 135 °C, and the solution was then poured into a capillary viscometer. The viscometer tube (Ubbelohde type) was surrounded by a cylindrical glass jacket; this setup allowed for temperature control using a circulating thermostatic liquid. The meniscus passed in front of the upper light source, activating a counter with a quartz crystal oscillator. When the meniscus passed the lower light source, the counter stopped, and the outflow time was recorded: knowing the flow time of the pure solvent under the same experimental conditions (same viscometer and same temperature), this was converted to an intrinsic viscosity value using the Huggins' equation. [η] was determined using a single polymer solution.

[0060] General Procedure for Standard Propylene Polymerization Test

[0061] A 4-liter steel autoclave equipped with a stirrer, pressure gauge, thermometer, catalyst feed system, monomer feed line, and thermostatic jacket was used. 0.01 g of solid catalyst component and 6.6 mmol of TEAL were charged into the reactor. Additionally, 1.6 kg of propylene and 1.5 NL of hydrogen were added. The system was heated to 70 °C within 10 minutes with stirring and maintained under these conditions for 120 minutes. At the end of polymerization, the polymer was recovered by removing any unreacted monomers and dried under vacuum.

[0062] 2.5 g of the polymer thus produced and 250 ml of o-xylene were placed in a round-bottom flask equipped with a cooler and a reflux condenser and kept under nitrogen atmosphere. The resulting mixture was heated to 135 °C and maintained with stirring for about 60 minutes. The final solution was cooled to 0 °C with continuous stirring, and then the insoluble polymer was filtered at 0 °C. The filtrate was then evaporated at 140 °C under a nitrogen stream to constant weight. The content of the xylene soluble fraction is expressed as a percentage of the original 2.5 g, and then expressed as XI by the difference.

[0063] General procedures for gas-phase ethylene polymerization (HDPE)

[0064] The polymerization was carried out in a 16.0-liter stainless steel fluidized bed reactor equipped with a gas circulation system, a cyclone separator, a heat exchanger, temperature and pressure indicators, feed lines for ethylene, propane, and hydrogen, and a 0.6-liter steel reactor for injecting the catalyst of the catalytic system into the fluidized bed reactor.

[0065] In all experiments, the composition of the gas phase in the fluidized bed reactor was as follows: propane (63 mol%), ethylene (12 mol%), and hydrogen (25 mol%) at a total pressure of 24 bar at 80 °C.

[0066] In a 100 mL three-necked glass flask, 20 mL of anhydrous hexane, 0.6 g of TEA, and 0.20 g of catalyst component were introduced in the following order. They were stirred together at room temperature for 5 minutes, and then introduced into a 0.6 L reactor along with 100 g of propane. The reactor was maintained at 30 °C for 15 minutes before introducing the catalytic system into the fluidized bed reactor. Polymerization tests were conducted at 80 °C for 2 hours. After this, polymerization was stopped, and the polymer was drained, dried, and sent for characterization.

[0067] Example

[0068] Example 1

[0069] Procedure for preparing spherical supports (MgCl2 / EtOH adducts)

[0070] Magnesium chloride and alcohol adduct were prepared according to the method described in Example 2 of USP 4,399,054, but at 2000 RPM instead of 10000 RPM. The adduct contained about 3 mol of alcohol and about 2.5% by weight of H2O and had an average size of about 55 μm. The adduct was heat-treated under a nitrogen flow at a temperature range of 50 to 150 °C until an alcohol content of 25% by weight was achieved.

[0071] Procedure for preparing non-stereospecific catalyst components

[0072] At 0°C, 1 L TiCl4 was introduced into a 2 L reaction vessel purged with nitrogen. Then, at the same temperature, 70 g of the spherical MgCl2 / EtOH adduct containing 25 wt% ethanol prepared as described above was added with stirring.

[0073] The temperature was raised to 130°C and maintained for 60 minutes over 2 hours. Then, stirring was stopped, allowing the solid product to settle (while maintaining 130°C for 1 hour) and the supernatant to be siphoned off. A certain volume of fresh TiCl4 was introduced into the reactor to again have 1 L of total slurry, and the temperature was raised to 130°C with stirring. This temperature was maintained for 15 minutes, then stirring was stopped, allowing the solids to settle (at 130°C for 1 hour) and the supernatant to be siphoned off.

[0074] The solid residue was then washed twice with hexane at 50°C, three times at 25°C, and dried under vacuum at 30°C before analysis.

[0075] The spherical solids have a magnesium content of 19.0% by weight and an average particle size of 57 micrometers (P50).

[0076] The intermediate solids composition in propylene polymerization was tested using the general method described above. The polymer obtained by this test had a xylene-insoluble fraction of 48.1 wt%.

[0077] Ethylene prepolymerization

[0078] 2 L of hexane was introduced into a 1.5 L glass reactor equipped with a stirrer at 30 °C, and 100 g of the catalyst component prepared as described above was introduced simultaneously at 30 °C with stirring. While maintaining a constant internal temperature, 3.2 g of tri-n-octyl aluminum (TnOA), premixed with 0.32 g of cyclohexylmethyldimethoxysilane in isohexane, was slowly introduced into the reactor. After stirring for 30 minutes, 110 g of ethylene was introduced into the reactor at a constant flow rate over 2 hours at 50 °C. Ethylene consumption in the reactor was monitored, and the monomer feed was interrupted when the theoretical conversion of 1.1 g of polymer per g of catalyst was considered to have been reached. The reaction was continued for another hour (curing step) to ensure that all fed monomers were converted. The prepolymer particles were allowed to settle, washed twice with hexane (60 g / L) at 50 °C, washed once with hexane at room temperature (rt), and vacuum dried at 30 °C. The porosity and average molecular weight (intrinsic viscosity) of the prepolymerized catalyst were analyzed. Data on prepolymerization conditions and prepolymer characterization are reported in Table 1. The prepolymerized solid catalyst component thus obtained was used for gas-phase ethylene polymerization (HDPE), and the results of the gas-phase ethylene polymerization are reported in Table 2.

[0079] Comparison Example C1

[0080] The catalyst was prepared according to the procedure described in Example 1, but the prepolymerization process was carried out without the addition of an external electron donor compound. The prepolymerization step was performed at a temperature of 20°C, with TnOA added in an amount such that the Al / Ti molar ratio was 0.5, and 110 g of ethylene was fed over a total time of 3 hours. The catalyst composition and characterization are also reported in Table 1. The prepolymerized solid catalyst composition thus obtained was used for gas-phase ethylene polymerization, and the results of the gas-phase ethylene polymerization are reported in Table 2.

[0081] Example 2

[0082] The catalyst was prepared according to the procedure described in Example 1, except that 1.65 g of cyclohexylmethyldimethoxysilane was introduced into the reactor and 110 g of ethylene was introduced into the reactor at a constant flow rate for 40 minutes at 30 °C, while the reactor temperature was maintained at 30 °C for the prepolymerization step. The catalyst composition and characterization are also reported in Table 1. The prepolymerized solid catalyst composition thus obtained was used for ethylene polymerization according to a gas-phase procedure, and the results of the ethylene polymerization are reported in Table 2.

[0083] Example 3

[0084] The catalyst was prepared according to the procedure described in Example 2, except that the reactor temperature was 50°C. The catalyst composition and characterization are also reported in Table 1. The prepolymerized solid catalyst composition thus obtained was used for ethylene polymerization according to a gas-phase procedure, and the results of the ethylene polymerization are reported in Table 2.

[0085] Example 4

[0086] The catalyst was prepared according to the procedure described in Example 2, except that 0.63 g of THF was used instead of cyclohexylmethyldimethoxysilane. The catalyst composition and characterization are also reported in Table 1. The prepolymerized solid catalyst composition thus obtained was used for ethylene polymerization according to a gas-phase procedure, and the results of the ethylene polymerization are reported in Table 2.

[0087] Example 5

[0088] The catalyst was prepared according to the procedure described in Example 2, except that 3.9 g of sodium dioctyl sulfosuccinate (DOSS) was used instead of cyclohexylmethyldimethoxysilane. The catalyst composition and characterization are also reported in Table 1. The prepolymerized solid catalyst composition thus obtained was used for ethylene polymerization according to a gas-phase procedure, and the results of the ethylene polymerization are reported in Table 2.

[0089] Example 6

[0090] The catalyst was prepared according to the procedure described in Example 2, except that no external donor was used. The catalyst composition and characterization are also reported in Table 1. The prepolymerized solid catalyst composition thus obtained was used for ethylene polymerization according to a gas-phase procedure, and the results of the ethylene polymerization are reported in Table 2.

[0091] Example 7

[0092] The catalyst was prepared according to the procedure described in Example 2, except that 110 g of ethylene was introduced into the reactor at a constant flow rate for 360 minutes at 30 °C, and the reactor temperature was maintained at 30 °C for the prepolymerization step. The catalyst composition and characterization are also reported in Table 1. The prepolymerized solid catalyst composition thus obtained was used for ethylene polymerization according to a gas-phase procedure, and the results of the ethylene polymerization are reported in Table 2.

[0093] Table 1 - Prepolymerization conditions and characterization.

[0094]

[0095] Table 2 - Vapor-phase polymerized HDPE

[0096]

Claims

1. A catalyst component for the prepolymerization of olefins, characterized in that, include: (a) A solid catalyst component comprising Ti, Mg and halogens and optionally a bidentate electron donor compound (BE), wherein the amount of the bidentate electron donor compound is such that the (BE) / Ti molar ratio ranges from 0 to 0.3; and (b) an ethylene (co)polymer in an amount ranging from 0.1 to no more than 30 g per g of the solid catalyst component and characterized by an intrinsic viscosity measured in tetraline at 135°C ranging from 4.5 to 15 dl / g; the prepolymerized catalyst component also shows a porosity in the range of 0.1 to 1.0 cm 3 / g measured by mercury method.

2. The prepolymerized catalyst component according to claim 1, wherein the ethylene (co)polymer is an ethylene homopolymer or an ethylene copolymer, the ethylene copolymer containing less than 5 mol% of an ingredient selected from the formula CH2=CHR. 1 Those α-olefins, where R 1 It is a C1-C6 straight-chain alkyl group.

3. The prepolymerized catalyst component of claim 2, wherein the ethylene copolymer contains less than 3 mol% of alpha-olefins selected from those of the formula CH2=CHR 1 wherein R 1 is a C1-C6 linear alkyl group.

4. The prepolymerized catalyst component according to claim 1, wherein the ethylene (co)polymer is an ethylene homopolymer.

5. The prepolymerized catalyst component of claim 1, wherein the mercury porosimetry ranges from 0.2 to 0.9 cm3 / g due to pores over 1 pm. 3 / g.

6. The prepolymerized catalyst component according to claim 1, having a concentration ranging from 0.34 to 0.50 g / cm³. 3 The packing density.

7. The prepolymerized catalyst component according to claim 1, wherein the amount of the ethylene (co)polymer is from 0.5 to 2.5 g per g of solid catalyst component.

8. The prepolymerized catalyst component according to claim 1, wherein magnesium is obtained from magnesium chloride and titanium atoms are obtained from the formula Ti(OR) II ) 4-y X y Titanium compounds were obtained, wherein R II It is C1-C 20 The hydrocarbon group, X is a halogen and y is a number between 1 and 4.

9. The prepolymerized catalyst component according to claim 1, wherein the solid catalyst component further comprises one or more monodentate (MD) electron donor compounds selected from esters and cycloalkyl ethers of aliphatic or aromatic carboxylic acids.

10. The prepolymerized catalyst component according to claim 9, wherein the monodentate donor is present in an amount such that the (MD):Ti ratio ranges from 0.1:1 to 25:

1.

11. A process for the preparation of a prepolymerized catalyst component comprising: The solid catalyst component (a) is reacted with ethylene and optionally α-olefin CH2=CHR. 1 The prepolymerization is carried out to the extent that the amount of the resulting ethylene (co)polymer ranges from 0.1 to 50 g per g of the solid catalyst component (a), which comprises Ti, Mg, and halogens, and optionally a bidentate electron donor compound (BE), in an amount such that the (BE) / Ti molar ratio ranges from 0 to 0.

3. The process is carried out at a temperature ranging from 25 to 100 °C and in the presence of an alkylaluminum compound such that the Al / Ti molar ratio is less than 0.

5. The intrinsic viscosity of the resulting ethylene (co)polymer, measured in tetrahydronaphthalene at 135 °C, ranges from 4.5 to 15 dl / g.

12. A catalyst system for olefin polymerization, comprising a product obtained by contacting (A) a prepolymerized catalyst component according to any one of claims 1-10; and (B) an alkylaluminum compound.

13. A process for the (co)polymerization of ethylene, characterized in that, The process is carried out in the presence of a catalyst comprising: (A) a prepolymerized catalyst component according to any one of claims 1-10; and (B) an alkylaluminum compound.

14. The process for ethylene (co)polymerization according to claim 13, wherein the process is carried out in the gas phase.

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