Method for producing polypropylene homopolymer or copolymer

Abstract

A method for producing a polypropylene homopolymer or copolymer, the method comprising the steps of: a) prepolymerizing propylene in a first reactor in the presence of hydrogen and a metallocene catalyst to obtain a first polypropylene homopolymer or copolymer fraction, wherein the ratio of the hydrogen feed rate to the propylene feed rate is in the range of 0.01 to 0.08 mol / kmol and the temperature in the first reactor is 15 to 29°C; b) transferring the first polypropylene homopolymer or copolymer fraction to a second reactor; c) polymerizing propylene in the second reactor in the presence of the first polypropylene homopolymer or copolymer fraction to obtain a second polypropylene homopolymer or copolymer fraction, wherein the residence time in the second reactor is 10 to 40 minutes; and d) removing the first and second polypropylene homopolymer or copolymer fractions from the second reactor or transferring the first and second polypropylene homopolymer or copolymer fractions to a third reactor.

Description

[Technical Field]

[0001] The present invention relates to a method for producing polypropylene homopolymers or copolymers using a defined temperature and hydrogen (H2) concentration range in the presence of a metallocene catalyst and a propylene homopolymer or copolymer having a defined bulk density. [Background technology]

[0002] Polypropylene copolymers, such as propylene-ethylene copolymers, are an interesting class of materials that can be used in a wide variety of applications where a good cost-performance ratio is required. The properties of propylene-ethylene copolymers depend, inter alia, on the properties and nature, e.g., morphology, of the catalyst used in the polymerization process.

[0003] Therefore, during the polymerization process of polypropylene (co)polymers, it is a general concern to control the powder morphology of the (co)polymer. In prior art polypropylene polymerization processes, the original morphology of the catalyst and the catalyst start-up method are crucial to the final (co)polymer powder morphology. A non-ideal start-up may result in a non-ideal final powder morphology.

[0004] As a result, a prepolymerization reactor is typically installed before the main polymerization reactor to avoid sudden changes in the catalyst environment, such as fluctuations in polymerization conditions, and to avoid the occurrence of early overreaction. During prepolymerization, the catalyst is initiated under mild conditions to maintain the morphology of the growing polymer. The mild conditions are specific to the catalyst and process. Furthermore, the prepolymerization step achieves more controlled catalyst / support decomposition (fragmentation), which has a significant impact on the powder morphology of the formed polymer.

[0005] It is also known that the morphology of polymer particles is determined by the shape of the supported catalyst particles due to the so-called replica effect.

[0006] Therefore, there is a continuing need for further improvements in the polypropylene polymerization process with a view to maintaining good polymer powder morphology. Summary of the Invention [Problem to be solved by the invention]

[0007] Object of the invention It is therefore an object of the present invention to provide a process for the polymerization of propylene which overcomes the above-mentioned problems.

[0008] It is a further object of the present invention to provide a process for the polymerization of propylene which maintains, and preferably improves, the morphology of the polymer powder.

[0009] A further object of the present invention is to provide propylene homopolymers or copolymers obtainable by the process of the present invention and having an improved morphology, in particular a defined bulk density.

[0010] definition As used herein, the term "copolymer of [monomer]" means a polymer that is derived predominantly by weight from [monomer] units (i.e., at least 50% by weight of [monomer], based on the total weight of the copolymer). [Means for solving the problem]

[0011] Summary of the Invention Surprisingly, the above object can be achieved by the following steps: a) prepolymerizing propylene in a first reactor in the presence of hydrogen and a metallocene catalyst to obtain a first polypropylene homopolymer or copolymer fraction, preferably a first polypropylene homopolymer fraction, wherein the ratio of the hydrogen feed rate to the propylene feed rate is in the range of 0.01 to 0.08 mol / kmol and the first reactor is maintained at a temperature of 15 to 29°C; b) transferring the first polypropylene homopolymer or copolymer fraction to a second reactor; c) polymerizing propylene in a second reactor in the presence of the first polypropylene homopolymer or copolymer fraction to obtain a second polypropylene homopolymer or copolymer fraction, preferably to obtain a second polypropylene homopolymer fraction, wherein the average residence time in the second reactor is 10 to 40 minutes; d) removing the polypropylene homopolymer or copolymer comprising said first and second polypropylene homopolymer or copolymer fractions from the second reactor or transferring said polypropylene homopolymer or copolymer to a third reactor, preferably transferring said polypropylene homopolymer or copolymer to a third reactor. Including, The metallocene catalyst comprises a metallocene complex, the metallocene complex being an organic compound (C), and the organometallic compound (C) has the formula (Ia): (L)2R n MX2(Ia) [In the formula, "M" is Zr or Hf; Each "X" is a σ-ligand; each "L" is an optionally substituted cyclopentadienyl, indenyl, or tetrahydroindenyl; "R" is a SiMe2 bridging group that connects the organic ligands (L); "n" is 0 or 1, preferably 1. It has been found that this can be achieved by a process for producing a polypropylene homopolymer or copolymer, preferably a polypropylene homopolymer, having the following formula:

[0012] The present invention is based on the surprising discovery that the morphology or morphology development of the resulting polymer powder can be improved by operating the prepolymerization reactor in a specific temperature range between 15 and 29°C and feeding hydrogen and propylene to the prepolymerization reactor in a ratio of 0.01 to 0.08 mol / kmol.

[0013] The present invention has many advantages. Under the above operating conditions, not only can a degree of prepolymerization of 100-600 g of polypropylene per gram of catalyst be obtained, but also a bulk density of the polypropylene homopolymer or copolymer can be increased to 320 kg / m 3 Furthermore, an optimized morphology of the polymerization catalyst and therefore process stability is achieved in terms of product quality.

[0014] According to the present invention, step a) is a prepolymerization step. The purpose of prepolymerization is to polymerize a small amount of polymer over a catalyst at low temperature and / or low monomer concentration. The prepolymerization step is typically carried out as a slurry polymerization. The use of a prepolymerization step may improve the performance of the catalyst in the slurry and / or modify the properties of the final polymer. The use of a catalyst in the prepolymerization step offers the advantage of minimizing leaching of catalyst components.

[0015] When used, the slurry polymerization in step a) is preferably bulk polymerization. "Bulk polymerization" means that the polymerization is carried out using liquid monomers and, therefore, essentially in the absence of an inert diluent. However, as is well known to those skilled in the art, the monomers used in commercial production are never pure and always contain impurities such as aliphatic hydrocarbons. For example, propylene monomer may contain up to 5% propane as an impurity. As propylene is consumed in the reaction and recycled from the reaction effluent to the polymerization, impurities, which may be inert components, tend to accumulate, and the concentration of said impurities in the reaction medium may reach values ​​of up to 40% by weight. However, it should be understood that such polymerization processes in which impurities are present are still within the meaning of "bulk polymerization" as defined above.

[0016] Slurry polymerization, preferably bulk polymerization, may be carried out in any known reactor used for slurry polymerization, which typically include continuous stirred tank reactors and loop reactors.

[0017] It is particularly preferred that the prepolymerization in step a) is carried out in a loop reactor.

[0018] Preferably, the first reactor is a loop reactor. In such a reactor, the slurry is circulated at high speed along a closed pipe using a circulation pump. Loop reactors are generally continuous reactors known in the art, and examples are shown, for example, in US-A-4582816, US-A-3405109, US-A-3324093, EP-A-479186, and US-A-5391654. Therefore, it is preferred to carry out the prepolymerization step as a slurry polymerization in a loop reactor.

[0019] The average amount of monomer is typically such that 0.1 to 1000 grams of monomer are polymerized in the prepolymerization step per gram of solid catalyst component. As those skilled in the art will appreciate, catalyst particles recovered from a continuous prepolymerization reactor do not all contain the same amount of prepolymer. Rather, each particle has its own characteristic amount depending on the particle's residence time in the prepolymerization reactor. The residence time of catalyst particles in the reactor may vary; for example, some particles may remain in the reactor for a relatively long time, while others may remain in the reactor for a relatively short time, and therefore the amount of prepolymer on various particles may vary. It is even possible for individual particles to contain amounts of prepolymer outside the above limits. However, the average amount of prepolymer on the catalyst is typically within the aforementioned range.

[0020] It is understood within the scope of the present invention that the amount of polymer produced in the prepolymerization is typically in the range of 0.1 to 0.3% by weight relative to the polypropylene homopolymer or copolymer.

[0021] Preferably, step a) is carried out under the conditions indicated above such that the first polypropylene homopolymer or copolymer fraction is produced in an amount of 0.1 to 0.3% by weight relative to the polypropylene homopolymer or copolymer.

[0022] Preferably, in step a), the temperature in the first reactor is between 20 and 28°C, more preferably between 21 and 27°C, most preferably between 22 and 26°C.

[0023] Preferably, in step a), the pressure in the first reactor is preferably from 1 to 150 bar, more preferably from 35 to 60 bar, even more preferably from 50 to 60 bar, most preferably from 53 to 57 bar.

[0024] Preferably, the ratio of the amount of hydrogen supplied to the amount of propylene supplied is in the range of 0.02 to 0.07 mol / kmol.

[0025] In step a), a comonomer is preferably present in the first reactor. Preferably, the comonomer in step a) is ethylene.

[0026] The average residence time in the first reactor in step a) is typically 0.05 to 0.5 hours, preferably 0.1 to 0.4 hours, and more preferably 0.2 to 0.3 hours. As is well known in the art, the average residence time τ can be calculated by the following formula (1):

number

[0027] As used herein, the production rate of polypropylene produced (kg PP / h) is determined by the energy balance for the first or second reactor, respectively. Typically, the production rate in the first reactor is 0.5 to 2.0 kg PP / h.

[0028] The degree of prepolymerization in the first reactor is calculated by dividing the production rate in the first reactor by the catalyst feed rate to the first reactor. The catalyst feed rate to the first reactor is typically 1.0 to 3.0 g catalyst / h. As a result, the degree of prepolymerization is typically preferably 50 to 2000 g PP / g catalyst, more preferably 200 to 1000 g PP / g catalyst, and most preferably 300 to 700 g PP / g catalyst.

[0029] The slurry may be removed from the first reactor continuously or intermittently. A preferred method of intermittent removal is the use of settling legs, which thicken the slurry before removing batches of concentrated slurry from the reactor. The use of settling legs is disclosed, inter alia, in US-A-3,374,211, US-A-3,242,150, and EP-A-1,310,295. Continuous removal is disclosed, inter alia, in EP-A-891,990, EP-A-1,415,999, EP-A-1,591,460, and WO-A-2007 / 025640. Continuous removal is advantageously combined with an appropriate thickening method, as disclosed in EP-A-1,310,295 and EP-A-1,591,460. Continuous removal of the slurry from the first reactor is preferred.

[0030] Preferably, the slurry removed from the first reactor is transferred directly to a second reactor to produce a second polypropylene homopolymer or copolymer fraction, "directly" meaning that the slurry is introduced from the first reactor to the second reactor without an intervening separation step (e.g., a flash separation step).

[0031] In step b), the first polypropylene homopolymer or copolymer fraction obtained in step a) is transferred to a second reactor, preferably directly to the second reactor. Preferably, the first polypropylene homopolymer or copolymer fraction is transferred to the second reactor in the form of a slurry. The slurry preferably contains the first polypropylene homopolymer or copolymer fraction, unreacted monomers, and the metallocene catalyst.

[0032] Like step a), step c) in the second reactor is preferably carried out as a slurry polymerization, which is preferably a bulk polymerization. Preferably, the second reactor is a loop reactor.

[0033] Preferably, the reactor temperature in step c) is in the range of 60 to 100° C., more preferably 65 to 90° C., most preferably 70 to 85° C. The polymerization in step c) is preferably carried out at a pressure in the range of 1 to 100 bar, more preferably 20 to 80 bar, more preferably 30 to 70 bar, respectively.

[0034] Preferably, the metallocene catalyst used in step a) is present in the second reactor during the polymerization in step c). This is achieved by transferring the metallocene catalyst used in step a) to the second reactor, preferably via a slurry. If necessary, fresh metallocene catalyst may be added to the second reactor in step c).

[0035] In steps a) and / or c), one or more comonomers selected from alpha-olefins having 2 or 4 to 10 carbon atoms or mixtures thereof are preferably present in the reactor. Preferably, the one or more comonomers are alpha-olefins having 2 or 4 carbon atoms, more preferably having 2 carbon atoms, and most preferably ethylene.

[0036] If it is desired to control the MFR2 of the second propylene homopolymer or copolymer fraction, hydrogen is usually introduced in step c) of the polymerization stage. The amount of hydrogen required to reach the desired MFR2 depends on the catalyst and polymerization conditions used, as will be understood by those skilled in the art.

[0037] In addition to the amount required to control MFR2, it is often necessary to introduce additional hydrogen into the second reactor if it is necessary to control the melt index of the polypropylene homopolymer or copolymer. Suitably, the hydrogen feed to the second reactor is controlled to maintain a constant hydrogen to propylene ratio. Good results have been obtained by maintaining the ratio of hydrogen feed to propylene feed in the range of 0.1 to 5.0 mol / kmol.

[0038] Preferably, in step c), the ratio of the amount of hydrogen supplied to the amount of propylene supplied is in the range of 0.1 to 5.0 mol / kmol, more preferably 0.2 to 2.0 mol / kmol, and even more preferably 0.3 to 1.0 mol / kmol.

[0039] The average residence time in the second reactor in step c) is typically 10 to 40 minutes, preferably 15 to 35 minutes. See equation (1) above. The production rate is appropriately controlled by the catalyst feed rate. The production rate can also be influenced by appropriate selection of the propylene monomer concentration. The desired monomer concentration can then be achieved by appropriately adjusting the propylene feed rate.

[0040] In a preferred embodiment, the polymerization process of the present invention does not recover comonomer.

[0041] The production split between the first polypropylene homopolymer or copolymer fraction of step a) and the second polypropylene homopolymer or copolymer fraction of step c) is preferably in the range of 0.1 to 10 wt.%, more preferably 0.5 to 5 wt.%, most preferably 1 to 3 wt.%.

[0042] In step d), the polypropylene homopolymer or copolymer is either removed from the second reactor or transferred to a third reactor. Preferably, the polypropylene homopolymer or copolymer is transferred to the third reactor.

[0043] The polypropylene homopolymer or copolymer comprises a first polypropylene homopolymer or copolymer fraction produced in a first reactor and a second polypropylene homopolymer or copolymer fraction produced in a second reactor.

[0044] The polypropylene homopolymer or copolymer preferably has a melt flow rate (MFR2), measured according to ISO 1133, of 50 to 90 g / 10 min, preferably 60 to 80 g / 10 min.

[0045] As described above, the polypropylene homopolymer or copolymer removed from the second reactor is preferably transferred to a third reactor. Preferably, the third reactor is a gas-phase reactor, more preferably a fluidized-bed gas-phase reactor. For gas-phase reactors, the reaction temperature is generally in the range of 60 to 100°C, and the reactor pressure is generally in the range of 1 to 100 bar. The gas used is typically a non-reactive gas such as nitrogen, or a low-boiling hydrocarbon such as propane, together with a monomer (e.g., propylene). One or more comonomers, preferably selected from alpha-olefins having 2 or 4 to 10 carbon atoms or a mixture thereof, are preferably present in the third reactor. Preferably, the one or more comonomers are alpha-olefins having 2 or 4 carbon atoms, more preferably alpha-olefins having 2 carbon atoms, i.e., ethylene.

[0046] Preferably, the process of the present invention further comprises a third reactor downstream of the second reactor, more preferably a third reactor downstream of the second reactor and a fourth reactor downstream of the third reactor, and most preferably a third reactor downstream of the second reactor, a fourth reactor downstream of the third reactor and a fifth reactor downstream of the fourth reactor, for polymerization of additional polypropylene homopolymer or copolymer.

[0047] The fourth and / or fifth reactors are preferably gas-phase reactors, more preferably fluidized-bed gas-phase reactors. The temperature and pressure of the fourth and / or fifth reactors are preferably the same as those described above for the third reactor. Also, the residence time and / or the one or more comonomers present in the fourth and / or fifth reactors are preferably the same as those described above for the second reactor.

[0048] A suitable process is the above-mentioned slurry-gas phase process, such as that developed by Borealis and known as Borstar® technology. In this regard, see EP applications EP 0 887 379 A1 and EP 0 517 868 A1.

[0049] It will be understood that the propylene polymer obtained by the process of the present invention may contain standard polymer additives. These typically form less than 5.0% by weight, for example less than 2.0% by weight, of the polymer material. Thus, additives such as antioxidants, phosphites, tackifiers, pigments, colorants, fillers, antistatic agents, processing aids, clarifiers, etc. may be added during the polymerization process. These additives are well known in the industry, and their use is well known to those skilled in the art. Any additives present may be added as a single ingredient or in a mixture with a carrier polymer, i.e., in a so-called masterbatch.

[0050] Polypropylene homopolymers or copolymers are produced according to the process of the present invention in the presence of a metallocene catalyst, more preferably at least one metallocene catalyst. The metallocene catalyst typically comprises a metallocene / activator reaction product impregnated into a porous support at its maximum internal pore volume. The metallocene catalyst typically comprises a bridged ligand, a Group IVa-Group VIa transition metal, and an organoaluminum compound. The catalytic metal compound is typically a metal halide.

[0051] The metallocene catalyst used in accordance with the present invention may be any supported metallocene catalyst suitable for the production of polypropylene copolymers.

[0052] The metallocene catalyst preferably comprises a metallocene complex, a cocatalyst system comprising a boron-containing cocatalyst and / or an aluminoxane cocatalyst, and a support, which preferably comprises or consists of silica.

[0053] Examples of suitable metallocene compounds are described, inter alia, in EP 629631, EP 629632, WO 00 / 26266, WO 02 / 002576, WO 02 / 002575, WO 99 / 12943, WO 98 / 40331, EP 776913, EP 1074557 and WO 99 / 42497, EP 2402353, EP 2729479 and EP 2746289.

[0054] The metallocene complex is ideally an organometallic compound (C) containing a transition metal (M) from Groups 3 to 10 of the Periodic Table (IUPAC 2007) or an actinide or lanthanide. The term "organometallic compound (C)" in the present invention includes metallocene compounds of transition metals having at least one organic (coordinating) ligand and exhibiting catalytic activity alone or in combination with a cocatalyst. Transition metal compounds are well known in the art, and the present invention encompasses compounds of metals from Groups 3 to 10 of the Periodic Table (IUPAC 2007), e.g., Groups 3 to 7, or Groups 3 to 6, e.g., Groups 4 to 6, as well as lanthanides or actinides.

[0055] In one embodiment, the organometallic compound (C) has the following formula (I): (L) m R n MX q (I) [In the formula, "M" is a transition metal (M) from groups 3 to 10 of the periodic table (IUPAC 2007); each "X" is independently a monoanionic ligand, such as a σ-ligand; each "L" is independently an organic ligand that coordinates to a transition metal "M"; "R" is a bridging group connecting the organic ligands (L); "m" is 1, 2 or 3, preferably 2; "n" is 0, 1 or 2, preferably 1; "q" is 1, 2 or 3, preferably 2; m + q is equal to the valence of the transition metal (M). It has.

[0056] "M" is preferably selected from the group consisting of zirconium (Zr), hafnium (Hf), or titanium (Ti), and more preferably selected from the group consisting of zirconium (Zr) and hafnium (Hf).

[0057] In a more preferred definition, each organic ligand (L) is independently: (a) a substituted or unsubstituted cyclopentadienyl, or a bicyclic or polycyclic derivative of cyclopentadienyl, optionally bearing further substituents and / or one or more hetero ring atoms from groups 13 to 16 of the Periodic Table (IUPAC); or (b) Acyclic η atoms composed of atoms from groups 13 to 16 of the periodic table 1 ~η 4 or η 6 ligands, where the open-chain ligands may be fused with one or two, preferably two, aromatic or non-aromatic rings and / or may carry further substituents; or (c) cyclic η rings consisting of unsubstituted or substituted monocyclic, bicyclic or polycyclic ring systems selected from aromatic, non-aromatic or partially saturated ring systems; 1 ~η 4 or η 6 wherein such ring systems optionally contain one or more heteroatoms selected from groups 15 and 16 of the periodic table.

[0058] The organometallic compound (C) preferably used in the present invention has at least one organic ligand (L) belonging to the above group (a). Such an organometallic compound is called a metallocene.

[0059] More preferably, at least one of the organic ligands (L), and preferably both organic ligands (L), is selected from the group consisting of cyclopentadienyl, indenyl, tetrahydroindenyl, fluorenyl, which can independently be substituted or unsubstituted.

[0060] Furthermore, when the organic ligands (L) are substituted, at least one of the organic ligands (L), preferably both of the organic ligands (L), is a C1-C 20 It preferably contains one or more substituents independently selected from hydrocarbyl or silyl groups, which optionally contain one or more heteroatoms selected from Groups 14 to 16 and / or are optionally substituted with halogen atoms.

[0061] C1~C 20 The term hydrocarbyl group, whenever used in this application, refers to a C1-C 20 Alkyl, C2-C 20 Alkenyl, C2-C 20 Alkynyl, C3-C 20 Cycloalkyl, C3-C 20 Cycloalkenyl, C6-C 20 Aryl, C7-C 20 Alkylaryl or C7-C 20 It includes mixtures of these groups such as arylalkyl groups or alkyl-substituted cycloalkyl groups.

[0062] Furthermore, two substituents, which may be the same or different, attached to adjacent C atoms of the ring of the ligand (L) can also together form a further monocyclic or polycyclic ring fused to the ring.

[0063] Preferred hydrocarbyl groups are linear or branched C1-C optionally interrupted independently by one or more heteroatoms of Groups 14-16 such as O, N, or S. 10 Alkyl groups and substituted or unsubstituted C6-C 20 aryl groups.

[0064] Straight or branched C1-C optionally interrupted by one or more heteroatoms of Groups 14-16 10 The alkyl group is more preferably methyl, ethyl, propyl, isopropyl, tertbutyl, isobutyl, C 5-6 Cycloalkyl, OR, SR (R is C1-C 10 alkyl group; C6~C 20 The aryl group is more preferably one or two C1-C6 alkyl groups as defined above. 10 It is a phenyl group optionally substituted with an alkyl group.

[0065] Throughout the present invention, "σ-ligand" means a group that is bonded to a transition metal (M) via a sigma bond.

[0066] Furthermore, the ligand "X" is preferably hydrogen, halogen, C1-C 20 Alkyl, C1-C 20 Alkoxy, C2-C 20 Alkenyl, C2-C 20 Alkynyl, C3-C 12 Cycloalkyl, C6-C 20 Aryl, C6-C 20 Aryloxy, C7-C 20 Aryl alkyl, C7-C 20 Arylalkenyl, -SR'', -Pr'', -SiR'', -OSiR'', and -NR'', where each R is independently hydrogen, C1-C 20 Alkyl, C2-C 20 Alkenyl, C2-C 20 Alkynyl, C3-C 12 Cycloalkyl or C6-C 20 and aryl.

[0067] More preferably, the "X" ligand is selected from halogen, C1-C6 alkyl, C5-C6 cycloalkyl, C1-C6 alkoxy, phenyl and benzyl groups.

[0068] The bridging group "R" may be a divalent bridging group, preferably -R'C-, -R'C-CR'-, -R'Si-, -R'Si-SiR'-, -R'Ge- (wherein each R' is independently a hydrogen atom, a C1-C 20 Alkyl, C2-C 10 Cycloalkyl, tri(C1-C 20 Alkyl)silyl, C6-C 20 Aryl, C7-C 20 Aryl alkyl and C7-C 20 alkylaryl).

[0069] More preferably, the bridging group "R" is -R'2C-, -R'2Si- (wherein each R' is independently a hydrogen atom, a C1-C 20 Alkyl, C2-C 10 Cycloalkyl, C6-C 20 Aryl, C7-C 20 Aryl alkyl and C7-C 20 alkylaryl).

[0070] Another subgroup of organometallic compounds (C) of formula (I) is known as nonmetallocene compounds in which the transition metal (M), preferably a transition metal of groups 4 to 6, suitably Ti, Zr or Hf, has a ligand other than a cyclopentadienyl ligand.

[0071] As used herein, the term "nonmetallocene" refers to a compound that does not have a cyclopentadienyl ligand or a fused derivative thereof, but has one or more non-cyclopentadienyl η-, σ-, monodentate, bidentate, or polydentate ligands. Such ligands can be selected, for example, from groups (b) and (c) defined above and are described, for example, in WO 01 / 70395, WO 97 / 10248, WO 99 / 41290, and WO 99 / 10353, as well as in V.C. Gibson et al., Angew. Chem. Int. Ed., engl., vol. 38, 1999, pp. 428-447, the disclosures of which are incorporated herein by reference in their entirety.

[0072] However, the organometallic compound (C) of the present invention is preferably a metallocene as defined above.

[0073] Metallocenes are disclosed in EP 0 260 130, WO 97 / 28170, WO 98 / 46616, WO 98 / 49208, WO 98 / 040331, WO 99 / 12981, WO 99 / 19335, WO 98 / 56831, WO 00 / 34341, WO 00 / 148034, EP 423 101, EP 537 130, WO2002 / 02576, WO2005 / 105863, WO Nos. 2006097497, 2007 / 116034, 2007 / 107448, 2009 / 027075, 2009 / 054832, 2012 / 001052, and EP 2 532 687, the disclosures of which are incorporated herein by reference in their entirety.

[0074] In a preferred embodiment, the organometallic compound (C) has the following formula (Ia): (L)2R n MX2(Ia) [In the formula, "M" is Zr or Hf; each "X" is a σ ligand; each "L" is an optionally substituted cyclopentadienyl, indenyl, or tetrahydroindenyl; "R" is a SiMe2 bridging group that links the organic ligands (L), "n" is 0 or 1, preferably 1. It has.

[0075] The metallocene catalyst complexes of the present invention are preferably asymmetric, meaning simply that the two ligands forming the metallocene are different, i.e., each ligand has a chemically different set of substituents.

[0076] The metallocene catalyst complexes of the present invention are typically racemic bridged bisindenyl C1-symmetric metallocenes chiral in the anti configuration. While such complexes are formally C1-symmetric, they ideally possess pseudo-C2 symmetry, since they maintain C2 symmetry near the metal center rather than at the periphery of the ligands. Due to their chemical nature, both anti and syn enantiomeric pairs (in the case of C1-symmetric complexes) are formed during the synthesis of the complexes. For purposes of the present invention, racemic anti means that the two indenyl ligands are oriented in opposite directions relative to the cyclopentadienyl-metal-cyclopentadienyl plane, and racemic syn means that the two indenyl ligands are oriented in the same direction relative to the cyclopentadienyl-metal-cyclopentadienyl plane (see diagram below).

[0077] [ka]

[0078] Formula (I) and subformulas are intended to encompass both the syn and anti forms, with the preferred metallocene catalyst complex being the anti form.

[0079] The metallocene catalyst complexes of the present invention are typically used as the rac-anti isomers, and therefore ideally at least 95 mol %, such as at least 98 mol %, especially at least 99 mol % of the metallocene catalyst complex is in the rac-anti isomeric form.

[0080] More preferably, the metallocene catalyst has the formula (II): [ka] [In the formula, Mt is Hf or Zr; each X is a sigma ligand; Each R 1 can be independently the same or different, and CH-R 7 Group (R 7 is H or linear or branched C 1-6 Alkyl group, C 3-8 Cycloalkyl groups, C 6-10 an aryl group), Each R 2 are independently a -CH=, -CY=, -CH2-, -CHY- or -CY2- group (Y is C 1-10 a hydrocarbyl group, and n is 2 to 6; Each R 3 and R 4 are independently the same or different and are hydrogen, a linear or branched C1-C6 alkyl group, an OY group, or C 7-20 Aryl alkyl, C 7-20 Alkylaryl group or C 6-20 Aryl groups, with at least one R per phenyl group 3 and at least one R 4 is not hydrogen, and any two adjacent R 3 or R 4 The groups may be part of a ring that includes the phenyl carbon to which they are attached; R 5 is a linear or branched C1-C6 alkyl group, C 7-20 Aryl alkyl, C 7-20 Alkylaryl group or C6-C 20is an aryl group, R 6 is C(R 8 )3 groups (R 8 is a straight-chain or branched C1-C6 alkyl group, Each R is independently C1-C 20 -hydrocarbyl] It is of the type.

[0081] Preferably, Mt is Zr.

[0082] Preferably, each X is independently a hydrogen atom, a halogen atom, C 1-6 an alkoxy group, or an R' group (where R' is C 1-6 alkyl, phenyl, or benzyl groups). Most preferably, X is a chlorine, a benzyl group, or a methyl group. Preferably, both X groups are the same. The most preferred options are two chlorides, two methyl groups, or two benzyl groups, especially two chlorides.

[0083] Each R is independently C1-C 20 Hydrocarbyl, e.g., C6-C 20 -Aryl, C7-C 20 -arylalkyl, or C7-C 20 -alkylaryl. 1-20 The term hydrocarbyl group includes C 1-20 Alkyl, C 2-20 Alkenyl, C 2-20 Alkynyl, C 3-20 Cycloalkyl, C 3-20 Cycloalkenyl, C 6-20 Aryl group, C 7-20 Alkylaryl group, or C 7-20 Arylalkyl groups, or mixtures of these groups (e.g., alkyl-substituted cycloalkyl) are also included. 1-20 The hydrocarbyl group is C 1-20 Alkyl, C 4-20 Cycloalkyl, C 5-20 Cycloalkyl-alkyl groups, C7-20 Alkylaryl group, C 7-20 Arylalkyl group, or C 6-20 It is an aryl group.

[0084] Preferably, both R groups are the same. R is methyl, ethyl, propyl, isopropyl, tertbutyl, isobutyl, C 5-6 C1-C such as cycloalkyl, cyclohexylmethyl, phenyl, or benzyl 10 -hydrocarbyl group or C-C 10 Preferably, R is a C1-C6-aryl group, more preferably both R are C1-C6-alkyl, C 3-8 Preferably, R is a cycloalkyl, or C-aryl group, such as a C-C-alkyl, C-cycloalkyl, or C-aryl group, and most preferably, both R are methyl, or one is methyl and the other is cyclohexyl. Most preferably, the bridging group is -Si(CH)-.

[0085] Each R 1 can independently be the same or different, and CH-R 7 Group (R 7 is H or linear or branched C 1-6 -Alkyl groups (e.g., methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, tert-butyl), or C 3-8 cycloalkyl groups (e.g., cyclohexyl), C 6-10 It is an aryl group (preferably phenyl).

[0086] Preferably, both R 1 The groups are identical and are CH2-R 7 Group (R 7 is H or a linear or branched C1-C4-alkyl group), more preferably both R 1 The groups are identical and are CH2-R 7 Group (R 7 is H, or a linear or branched C1-C3-alkyl group). Most preferably, both R 1 are both methyl.

[0087] Each R 2 are independently -CH=-, -CY=, -CH2-, -CHY- or -CY2- groups, where Y is C 1-10 Hydrocarbyl groups, preferably C 1-4 It is a hydrocarbyl group, and n is 2 to 6, preferably 3 to 4.

[0088] Each substituent R 3 and R 4 can be independently the same or different and are hydrogen, a linear or branched C1-C6 alkyl group, an OY group, or C 7-20 Aryl alkyl, C 7-20 Alkylaryl group, or C 6-20 is an aryl group, preferably hydrogen, a linear or branched C1-C6 alkyl group, or C 6-20 An aryl group, and two adjacent R 3 or R 4 The groups can be part of a ring that includes the phenyl carbon to which they are attached. More preferably, R 3 and R 4 is hydrogen, a linear or branched C1-C4 alkyl group, or an OY group (where Y is C 1-4 Even more preferably, each R 3 and R 4 are independently hydrogen, methyl, ethyl, isopropyl, tert-butyl or methoxy, in particular hydrogen, methyl or tert-butyl, and at least one R 3 and at least one R 4 is not hydrogen.

[0089] Therefore, preferably, one or two R 3 is not hydrogen, and more preferably, R 3 The groups are the same, for example 3',5'-dimethyl or 4'-tert-butyl for both phenyl groups.

[0090] For the indenyl moiety, preferably one or two R on the phenyl group 4 is not hydrogen, and more preferably two R 4 is not hydrogen, and most preferably these two R 4 are identical, such as 3',5'-dimethyl or 3',5'-di-tert-butyl.

[0091] R 5 is a linear or branched C1-C6 alkyl group such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, and tert-butyl; 7-20 Aryl alkyl, C 7-20 Alkylaryl group, or C6-C 20 is an aryl group. 5 is preferably a linear or branched C1-C6 alkyl group or C 6-20 It is an aryl group, more preferably a straight chain C1-C4 alkyl group, even more preferably a C1-C2 alkyl group, and most preferably methyl.

[0092] R 6 is C(R 8 )3 groups (R 8 is a straight-chain or branched C1-C6 alkyl group).

[0093] Each R is independently C1-C 20 - Hydrocarbyl, C6-C 20 -Aryl, C7-C 20 -arylalkyl or C7-C 20 -alkylaryl. Preferably, each R 8 are the same or different (R 8 is a linear or branched C1-C4-alkyl group, more preferably R 8 are the same and are C1-C2-alkyl groups). Most preferably, all R 8 The group is methyl.

[0094] In a further preferred embodiment, the organometallic compound (C) has the following formula (III): [ka] [In the formula, Mt is Zr or Hf, preferably Zr; Each R 3 and R 4 are independently the same or different and are hydrogen or a linear or branched C1-C6-alkyl group, and there is at least one R per phenyl group. 3 and at least one R 4 is not hydrogen] It has.

[0095] Specific metallocene catalyst complexes include: rac-anti-dimethylsilanediyl[2-methyl-4,8-bis-(4'-tert-butylphenyl)-1,5,6,7-tetrahydro-s-indacen-1-yl][2-methyl-4-(3',5'-dimethyl-phenyl)-5-methoxy-6-tert-butylinden-1-yl]zirconium dichloride; rac-anti-dimethylsilanediyl[2-methyl-4,8-bis-(3',5'-dimethylphenyl)-1,5,6,7-tetrahydro-s-indacen-1-yl][2-methyl-4-(3',5'-dimethylphenyl)-5-methoxy-6-tert-butylinden-1-yl]zirconium dichloride; rac-anti-dimethylsilanediyl[2-methyl-4,8-bis-(3',5'-dimethylphenyl)-1,5,6,7-tetrahydro-s-indacen-1-yl][2-methyl-4-(3',5'-di-tert-butyl-phenyl)-5-methoxy-6-tert-butylinden-1-yl]zirconium dichloride or their corresponding zirconium dimethyl analogues. TIFF2025541913000005.tif47149

[0096] The ligands required to form the metallocene catalysts of the present invention can be synthesized by any process, and a skilled organic chemist will be able to devise a variety of synthetic protocols for the preparation of the necessary ligand materials. For example, WO 2007 / 116034 discloses the necessary chemical methods. Synthetic protocols are also generally described in WO 2002 / 02576, WO 2011 / 135004, WO 2012 / 084961, WO 2012 / 001052, WO 2011 / 076780, and WO 2015 / 158790.

[0097] To form an active catalytic species, it is usually necessary to use a cocatalyst, as is well known in the art.

[0098] According to the present invention, a cocatalyst system comprising a boron-containing cocatalyst and / or an aluminoxane cocatalyst is preferably used in combination with the metallocene catalyst defined above.

[0099] The aluminoxane cocatalyst has the formula (IV): [ka] [wherein n is usually 6 to 20, and R has the following meaning] It can be of the following type.

[0100] Aluminoxanes are formed upon partial hydrolysis of organoaluminum compounds and are, for example, of the formula AlR3, AlR2Y and Al2R3Y3 (where R is, for example, C1-C 10 Alkyl, preferably C1-C5 alkyl, or C3-C 10 Cycloalkyl, C7-C 12 arylalkyl or alkylaryl, and / or phenyl or naphthyl, and Y is hydrogen, halogen, preferably chlorine or bromine, or C-C 10 (The alkyl group may be alkoxy, preferably methoxy or ethoxy.) The resulting oxygen-containing aluminoxanes are generally not pure compounds but are mixtures of oligomers of formula (III).

[0101] A preferred aluminoxane is methylaluminoxane (MAO). Since the aluminoxanes used according to the invention as cocatalysts are not pure compounds due to the method of their preparation, the molar concentrations of the aluminoxane solutions are hereinafter based on the aluminum content.

[0102] In accordance with the present invention, a boron-containing cocatalyst may be used in place of the aluminoxane cocatalyst, or an aluminoxane cocatalyst may be used in combination with a boron-containing cocatalyst.

[0103] Those skilled in the art will appreciate that when using boron-based cocatalysts, the complex is typically pre-alkylated by reaction with an aluminum alkyl compound such as TIBA. This procedure is well known, and any suitable aluminum alkyl can be used, such as Al(C1-C6 alkyl). Preferred aluminum alkyl compounds are triethylaluminum, triisobutylaluminum, triisohexylaluminum, tri-n-octylaluminum, and triisooctylaluminum.

[0104] Alternatively, when a borate cocatalyst is used, the metallocene complex may be alkylated, ie, for example, a dimethyl or dibenzyl metallocene complex may be used.

[0105] Interesting boron-based cocatalysts include those of formula (V): [ka] wherein Y's are the same or different and each represents a hydrogen atom, an alkyl group having from 1 to about 15 carbon atoms, an aryl group having from 6 to about 15 carbon atoms, an alkylaryl, arylalkyl, haloalkyl, or haloaryl group having from 1 to 10 carbon atoms in the alkyl group and from 6 to 20 carbon atoms in the aryl group, or fluorine, chlorine, bromine, or iodine. Preferred examples of Y include unsaturated groups such as methyl, propyl, isopropyl, isobutyl, or trifluoromethyl, aryl, or haloaryl, such as phenyl, tolyl, benzyl, p-fluorophenyl, 3,5-difluorophenyl, pentachlorophenyl, pentafluorophenyl, 3,4,5-trifluorophenyl, and 3,5-di(trifluoromethyl)phenyl. Preferred choices are trifluoroborane, triphenylborane, tris(4-fluorophenyl)borane, tris(3,5-difluorophenyl)borane, tris(4-fluoromethylphenyl)borane, tris(2,4,6-trifluorophenyl)borane, tris(pentafluorophenyl)borane, tris(tolyl)borane, tris(3,5-dimethyl-phenyl)borane, tris(3,5-difluorophenyl)borane, and / or tris(3,4,5-trifluorophenyl)borane.

[0106] Particularly preferred is tris(pentafluorophenyl)borane.

[0107] However, borate, i.e., borate 3 + Ion (borate 3 + It is preferred to use a compound containing a cation.

[0108] Such ionic cocatalysts preferably contain non-coordinating anions such as tetrakis(pentafluorophenyl)borate and tetraphenylborate. Suitable counterions are protonated amine or aniline derivatives such as methylammonium, anilinium, dimethylammonium, diethylammonium, N-methylanilinium, diphenylammonium, N,N-dimethylanilinium, trimethylammonium, triethylammonium, tri-n-butylammonium, methyldiphenylammonium, pyridinium, p-bromo-N,N-dimethylanilinium, or p-nitro-N,N-dimethylanilinium.

[0109] Preferred ionic compounds that can be used in accordance with the present invention include: triethylammonium tetra(phenyl)borate, tributylammonium tetra(phenyl)borate, trimethylammonium tetra(tolyl)borate, tributylammonium tetra(tolyl)borate, tributylammonium tetra(pentafluorophenyl)borate, tripropylammonium tetra(dimethylphenyl)borate, tributylammonium tetra(trifluoromethylphenyl)borate, tributylammonium tetra(4-fluorophenyl)borate, N,N-dimethylcyclohexylammonium tetrakis(pentafluorophenyl)borate, N,N-dimethylbenzylammonium tetrakis(pentafluorophenyl)borate, N,N-dimethylanilinium tetra(phenyl)borate, N,N-diethylanilinium tetra(phenyl)borate, N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, N,N-di(propyl)ammonium tetrakis(pentafluorophenyl)borate, di(cyclohexyl)ammonium tetraquinoline(pentafluorophenyl)borate, triphenylphosphonium tetrakis(phenyl)borate, triethylphosphonium tetrakis(phenyl)borate, diphenylphosphonium tetrakis(phenyl)borate, tri(methylphenyl)phosphonium tetrakis(phenyl)borate, tri(dimethylphenyl)phosphonium tetrakis(phenyl)borate, triphenylcarbenium tetrakis(pentafluorophenyl)borate, or ferrocenium tetrakis(pentafluorophenyl)borate.

[0110] Triphenylcarbenium tetrakis(pentafluorophenyl)borate, N,N-dimethylcyclohexylammonium tetrakis(pentafluorophenyl)borate or N,N-dimethylbenzylammonium tetrakis(pentafluorophenyl)borate are preferred.

[0111] Surprisingly, it has been found that certain boron cocatalysts are particularly preferred.

[0112] Thus, preferred borates for use in the present invention contain a trityl ion, and therefore the use of N,N-dimethylammonium-tetrakispentafluorophenylborate and PhCB(PhF) and analogs thereof is particularly preferred.

[0113] According to the present invention, preferred cocatalysts are aluminoxanes, more preferably methylaluminoxane, combinations of aluminoxanes with Al-alkyls, boron or borate cocatalysts, and combinations of aluminoxanes with boron-based cocatalysts.

[0114] Suitable amounts of cocatalyst are well known to those skilled in the art.

[0115] The molar ratio of boron to the metal ion of the metallocene may be from 0.5:1 to 10:1 mol / mol, preferably from 1:1 to 10:1 mol / mol, in particular from 1:1 to 5:1 mol / mol.

[0116] The molar ratio of Al in the aluminoxane to the metal ion of the metallocene may be in the range of 1:1 to 2000:1 mol / mol, preferably 10:1 to 1000:1 mol / mol, more preferably 50:1 to 900:1 mol / mol, and most preferably 600:1 to 800:1 mol / mol.

[0117] The metallocene catalyst used in the polymerization process of the present invention is preferably used in supported form. The support used comprises, and preferably consists of, silica. Those skilled in the art are aware of the procedures required for supporting the metallocene catalyst.

[0118] Particularly preferably, the support is a porous material so that the complex can be loaded into the pores of the support using processes similar to those described, for example, in WO 94 / 14856 (Mobil), WO 95 / 12622 (Borealis) and WO 2006 / 097497.

[0119] The average particle size of the support may typically be 10 to 100 μm, but it has been found that particular advantages are obtained when the average particle size of the support is 15 to 80 μm, preferably 18 to 50 μm.

[0120] The particle size distribution of the carrier will be described later. The carrier preferably has a D of 10 to 80 μm, preferably 18 to 50 μm. 50 Furthermore, the carrier preferably has a D of 5 to 30 μm. 10 and D of 30 to 90 μm 90 Preferably, the carrier has a SPAN value of 0.1 to 1.1, preferably 0.3 to 1.0.

[0121] The average particle size of the metallocene catalyst is preferably 20 to 50 μm, more preferably 25 to 45 μm, and most preferably 30 to 40 μm.

[0122] The particle size distribution of the metallocene catalyst is shown below. The metallocene catalyst preferably has a D50 of 30 to 80 μm, preferably 32 to 50 μm, and most preferably 34 to 40 μm. Furthermore, the metallocene catalyst preferably has a D10 of at most 29 μm, more preferably 15 to 29 μm, more preferably 20 to 28 μm, and most preferably 25 to 27 μm. The metallocene catalyst preferably has a D90 of at least 45 μm, more preferably 45 to 70 μm, and most preferably 40 to 60 μm.

[0123] The average pore diameter of the support can be in the range of 10 to 100 nm, preferably 20 to 50 nm, and the pore volume can be in the range of 1 to 3 ml / g, preferably 1.5 to 2.5 ml / g. The BET specific surface area of ​​the silica support material is measured according to ASTM D3663, and the BJH porosity parameter is determined according to ASTM D4641. Examples of suitable support materials include ES757 manufactured and sold by PQ Corporation, Sylopol 948 manufactured and sold by Grace, or SUNSPERA DM-L-303 silica manufactured by AGC Si-Tech Co. The support can optionally be calcined before use in catalyst preparation to achieve an optimal silanol group content.

[0124] All or part of the preparation process can be carried out continuously. The catalyst formed preferably has good stability / kinetics in terms of reaction life, high activity, and the catalyst allows for low ash content.

[0125] In general, silica-supported polymerization catalysts exhibit very complex polymerization behavior, and the polymerization process can be divided into several stages.

[0126] During the first few minutes of polymerization, the catalyst activity can reach a high value, resulting in an uncontrollable fragmentation process and a decrease in catalyst activity due to increased external mass and heat transfer phenomena. More specifically, the heat generated by the polymerization reaction cannot be properly dissipated, leading to local particle overheating (i.e., the temperature difference between the surface and bulk temperature of the growing polymer particles reaches a high value). Therefore, the polymer produced on the surface of the growing polymer particles becomes sticky, increasing the risk of particle agglomeration, and thereby affecting the process performance and reactor operability.

[0127] The above polymerization reaction kinetics necessitates a new design of the prepolymerization process in terms of temperature, monomer concentration, and residence time.

[0128] In a preferred embodiment of the present invention, in the initial stage (first activity peak), the temperature and monomer concentration should be as low as possible to avoid overheating of the polymer produced and to prevent the formation of aggregates, while in the second stage, the monomer concentration and temperature should be as high as possible to promote the catalyst fragmentation process. [Example]

[0129] Experimental part Measurement method All of the parameters mentioned above in the detailed description of the present invention are measured according to the tests set out below.

[0130] a) Melt flow rate Melt flow rate (MFR) is measured according to ISO 1133 and is given in units of g / 10 min. MFR is a measure of the melt viscosity of a polymer. MFR is measured at 190°C for polyethylene and 230°C for polypropylene. The load at which the melt flow rate is measured is usually given as a subscript, e.g., MFR2 is measured under a 2.16 kg load (condition D).

[0131] b) Average particle size and particle size distribution Particle size distribution was determined by laser diffraction measurements using a Coulter LS 200. Particle size and particle size distribution are measures of particle size. The D values ​​(D10 (or d10), D50 (or d50), and D90 (or d90)) represent the intercepts at 10%, 50%, and 90% of the cumulative mass of a sample. The D values ​​can be thought of as the diameter of a sphere that divides the mass of a sample into a given fraction when the particles are arranged in ascending order of mass. For example, D10 is the diameter at which 10% of the mass of the sample is made up of particles with a diameter less than this value. D50 is the diameter at which 50% of the mass of the sample is smaller than this value and 50% is larger than this value. D90 is the diameter at which 90% of the mass of the sample is made up of particles with a diameter less than this value. The D50 value is also called the median particle size. Laser diffraction measurements according to ISO 13320 provide volumetric D values ​​based on the volume distribution.

[0132] The distribution width or span of the particle size distribution is given by equation (3):

number

[0133] The sieve fraction is measured by digital image analysis on a Camsizer P4 from Retsch Technology GmbH. The measurement principle is dynamic image analysis according to ISO 13322-2.

[0134] c) Xylene-soluble fraction The xylene soluble fraction (XS) is determined according to ISO 16152 at 25°C.

[0135] d) Bulk density Bulk density is measured according to ASTM D1895.

[0136] material The following catalysts were used in the comparative and inventive processes listed in Table 1:

[0137] The metallocene catalyst described in WO 2019 / 179959 A1 was used, and its preparation method is detailed below. [ka]

[0138] A steel reactor equipped with a mechanical stirrer and a filter net was flushed with nitrogen and the reactor temperature was set to 20°C. Next, 10 kg of silica grade DM-L-303 (manufactured by AGC Si-Tech Co.), pre-calcined at 600°C, was added through a feed drum and carefully pressurized and depressurized with nitrogen using a manual valve. Toluene (43.5 kg) was then added. The mixture was stirred for 30 minutes. Next, within 140 minutes, a 30 wt% MAO solution in toluene (17.5 kg) manufactured by Lanxess was added through the feed line at the top of the reactor. The reaction mixture was then heated to 90°C and stirred at 90°C for an additional 2 hours. The slurry was allowed to settle, and the mother liquor was filtered. The catalyst was washed twice with toluene (43.5 kg) at 90°C, then settled and filtered.

[0139] Finally, the MAO-treated SiO2 was dried under a nitrogen stream at 60°C for 2 hours, followed by drying under vacuum (~0.5 barg) with stirring for 14 hours. The MAO-treated support was recovered as a free-flowing white powder found to contain 15.0 wt% Al. A 30 wt% MAO solution in toluene (2 kg) was added via burette to a steel nitrogen-blanked reactor at 20°C. Toluene (12.8 kg) was then added with stirring. 129 g of metallocene was added via a metal cylinder, followed by a 1 kg toluene rinse. The mixture was stirred at 20°C for 60 minutes. Trityl tetrakis(pentafluorophenyl)borate (127.2 g) was then added via a metal cylinder, followed by a 1 kg toluene rinse. The mixture was stirred at room temperature for 1 hour. The resulting solution was added over 2 hours to the stirred cake of MAO-silica support prepared above. The cake was stirred for 30 min, then left without stirring for 30 min, then dried under a stream of N2 at 60 °C for 2 h, and further dried under vacuum (~0.5 barg) with stirring for 15 h.

[0140] example The following examples were carried out in a pilot plant containing a reactor arrangement consisting of a prepolymerization loop reactor and a loop reactor, the process and properties of which are shown in Table 1.

[0141] [Table 1]

[0142] For CE1, when the process was carried out at 30°C, the bulk density was quite good, but the process was stopped due to clogging of the transfer line between the prepolymerization reactor and the loop reactor and due to the presence of more larger particles (greater than 4 mm, agglomerates).

[0143] However, when the prepolymerization is carried out at a considerably low temperature as in Comparative Example CE2, the bulk density becomes low and the morphology becomes poor.

[0144] As can be seen from IE1-IE7, the best conditions of the process are the temperature of 15-29 °C and the H2 / C3 ratio of 0.01-0.08 mol / kmol in the prepolymerization reactor.

Claims

1. 1. A method for producing a polypropylene homopolymer or copolymer, said method comprising the steps of: a) prepolymerizing propylene in a first reactor in the presence of hydrogen and a metallocene catalyst to obtain a first polypropylene homopolymer or copolymer fraction, wherein the ratio of the hydrogen feed rate to the propylene feed rate is in the range of 0.01 to 0.08 mol / kmol and the temperature in the first reactor is 15 to 29°C; b) transferring the first polypropylene homopolymer or copolymer fraction to a second reactor; c) polymerizing propylene in a second reactor in the presence of said first polypropylene homopolymer or copolymer fraction to obtain a second polypropylene homopolymer or copolymer fraction, wherein the residence time in the second reactor is from 10 to 40 minutes; d) removing the polypropylene homopolymer or copolymer comprising said first and second polypropylene homopolymer or copolymer fractions from the second reactor or transferring said polypropylene homopolymer or copolymer to a third reactor. Including, The metallocene catalyst comprises a metallocene complex, the metallocene complex being an organometallic compound (C), and the organometallic compound (C) has the formula (Ia): (L) ２ R ｎ MX ２ (Ia) [In the formula, "M" is Zr or Hf; Each "X" is a σ-ligand; each "L" is an optionally substituted cyclopentadienyl, indenyl, or tetrahydroindenyl; "R" is a SiMe bond that connects the organic ligand (L). ２ is a bridging group; "n" is 0 or 1, preferably 1. A method comprising:

2. 2. The process of claim 1, wherein the temperature in the first reactor in step a) is between 20 and 28°C.

3. 3. The process according to claim 1 or 2, wherein the pressure in the first reactor in step a) is between 1 and 150 bar.

4. The process according to any one of claims 1 to 3, wherein the temperature in the second reactor in step c) is between 60 and 100°C.

5. The process according to any one of claims 1 to 4, wherein the pressure in the second reactor in step c) is between 1 and 150 bar.

6. The process according to any one of claims 1 to 5, wherein in step a) the comonomer is present in the first reactor.

7. The process according to any one of claims 1 to 6, wherein in step c) the comonomer is present in the second reactor.

8. 7. The method of claim 6, wherein in step a) the comonomer is ethylene.

9. 8. The method of claim 7, wherein in step c) the comonomer is ethylene.

10. The method of any of claims 1 to 9, wherein the metallocene catalyst further comprises a support, the support comprising silica.

11. The method of any of claims 1 to 10, wherein the metallocene catalyst further comprises a co-catalyst system, the co-catalyst system comprising a boron-containing co-catalyst and / or an aluminoxane co-catalyst.

12. The process according to any one of claims 1 to 11, wherein the first reactor is a loop reactor and / or the second reactor is a loop reactor.

13. The method according to any one of claims 1 to 12, wherein in step d) the third reactor is a gas phase reactor.

14. A propylene homopolymer or copolymer obtainable by the process according to any one of claims 1 to 13.

15. Bulk density measured according to ASTM D1895 is 320 kg / m ３ The propylene homopolymer or copolymer according to claim 14, wherein

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