Process for producing a polypropylene homo- or copolymer

Abstract

This invention relates to a method for manufacturing a polypropylene homopolymer or copolymer, comprising the following steps: a) prepolymerizing propylene in a first reactor in the presence of hydrogen and a metallocene catalyst to produce a first polypropylene homopolymer or copolymer fraction, wherein the ratio of hydrogen feed to propylene feed is in the range of 0.01 to 0.08 mol / kmol, and wherein 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 produce a second polypropylene homopolymer or copolymer fraction, wherein the average residence time in the second reactor is 10 to 40 minutes; and d) discharging a polypropylene homopolymer or copolymer containing the first polypropylene homopolymer or copolymer fraction and the second polypropylene homopolymer or copolymer fraction from the second reactor, or transferring the polypropylene homopolymer or copolymer to a third reactor.

Description

Technical Field

[0001] The present invention relates to a method for producing a polypropylene homopolymer or copolymer, wherein the method uses a specific temperature and hydrogen (H2) concentration range in the presence of a metallocene catalyst and a polypropylene homopolymer or copolymer having a specific overall density. Prior Art

[0002] Polypropylene copolymers, such as propylene-ethylene copolymers, are a group of materials that are attracting attention for a wide range of applications requiring a good cost-benefit ratio. The properties of propylene-ethylene copolymers depend, among other things, on the nature and properties of the catalyst used in the polymerization process, such as its morphology.

[0003] Therefore, controlling the powder morphology of polypropylene (co)polymers during polymerization is of widespread interest. In prior art polypropylene polymerization processes, the initial catalyst morphology and catalyst startup are crucial to the final (co)polymer powder morphology. Unsatisfactory startup can lead to unsatisfactory final powder morphology.

[0004] Therefore, to protect the catalyst from sudden changes in its environment, such as changes in polymerization conditions, and to avoid initial overreaction, a prepolymerization reactor is often installed before the main polymerization reactor. During the prepolymerization process, the catalyst is activated under optimal conditions to maintain the morphology of the growing polymer. These optimal conditions are catalyst- and process-specific. Furthermore, during the prepolymerization step, catalyst / support decomposition (breakdown) is better controlled. This significantly affects the powder morphology of the resulting polymer.

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

[0006] Therefore, further improvements in the polypropylene polymerization process are always needed to maintain good polymer powder morphology. Summary of the Invention

[0007] [Object of the present invention]

[0008] Therefore, an object of the present invention is to provide a propylene polymerization process that overcomes the above-mentioned problems.

[0009] Another object of the present invention is to provide a process for polymerizing propylene while maintaining and preferably improving the polymer powder morphology.

[0010] Another object of the present invention is to provide a polypropylene homopolymer or copolymer obtainable by the process of the present invention, which has improved morphology, in particular a specific overall density. [definition]

[0011] As used herein, the term "copolymer of [monomer]" means a polymer wherein the majority of its weight is derived from [monomer] units (ie, at least 50 wt% of [monomer] relative to the total weight of the copolymer).

[0012] It has now been unexpectedly discovered that the above object can be achieved by a method for producing a polypropylene homopolymer or copolymer, preferably a polypropylene homopolymer, comprising the following steps: a) prepolymerizing propylene in a first reactor in the presence of hydrogen and a metallocene catalyst to produce a first polypropylene homopolymer or copolymer fraction, preferably a first polypropylene homopolymer, wherein the ratio of hydrogen feed to propylene feed is in the range of 0.01 to 0.08 mol / kmol and wherein the temperature in the first reactor is in the range of 15 to 29°C; b) transferring the first polypropylene homopolymer or copolymer fraction to a second reactor; c) polymerizing propylene in the presence of the first polypropylene homopolymer or copolymer fraction in a second reactor to produce a second polypropylene homopolymer or copolymer fraction, preferably a second polypropylene homopolymer fraction, wherein the average residence time in the second reactor is from 10 to 40 minutes; and d) discharging the polypropylene homopolymer or copolymer containing the first polypropylene homopolymer or copolymer fraction and the second polypropylene homopolymer or copolymer fraction from the second reactor, or transferring the polypropylene homopolymer or copolymer to a third reactor, preferably transferring the polypropylene homopolymer or copolymer to the third reactor.

[0013] Wherein, the metallocene catalyst comprises a metallocene complex, and the metallocene complex is an organometallic compound (C), and the organometallic compound (C) is represented by the following chemical formula (Ia): (L) 2R nMX 2(Ia) in, "M" is zirconium or hafnium; Each "X" is a σ-ligand; Each "L" is optionally substituted cyclopentadienyl, indenyl or tetrahydroindenyl; "R" is a SiMe 2 bridging group connecting the organic ligand (L); "n" is 0 or 1, preferably 1.

[0014] The present invention is based on the surprising finding that the morphology or the development of the morphology of the obtained polymer powder can be improved by operating the prepolymerization reactor in a specific temperature range of 15 to 29° C. and feeding hydrogen and propylene into the prepolymerization reactor in a ratio of 0.01 to 0.08 mol / kmol.

[0015] The present invention offers numerous advantages. The aforementioned operating conditions not only produce a prepolymerization degree of 100 to 600 g of polypropylene per gram of catalyst, but also achieve an overall density of polypropylene homopolymer or copolymer exceeding 320 kg / m³. Furthermore, the optimized morphology of the polymerization catalyst is achieved, thereby ensuring process stability and product quality. Implementation Method

[0016] According to the present invention, step a) is a prepolymerization step. The purpose of prepolymerization is to polymerize a small amount of polymer onto a catalyst at low temperature and / or low monomer concentration. The prepolymerization step is typically performed as a slurry polymerization. Using a prepolymerization step can improve the performance of the catalyst in the slurry and / or modify the properties of the final polymer. Using a catalyst in the prepolymerization step offers the advantage of minimizing the dissolution of catalyst components.

[0017] If used, the slurry polymerization in step a) is preferably a bulk polymerization. "Bulk polymerization" refers to polymerization using monomers in liquid form, thus essentially without the presence of inert diluents. However, as is known to those skilled in the art, monomers used in commercial production are never pure but always contain impurities, such as aliphatic hydrocarbons. For example, propylene monomer may contain up to 5% propane as an impurity. Since propylene is consumed in the reaction and also recycled from the reaction effluent back to the polymerization, impurities, which may be inert components, tend to accumulate, and as a result, the concentration of such impurities in the reaction medium may increase to values ​​as high as 40 wt%. However, it should be understood that such polymerization processes in which impurities are present are still considered "bulk polymerization" processes as defined above.

[0018] The slurry polymerization, preferably bulk polymerization, can be carried out in any known reactor for slurry polymerization. Such reactors typically include continuous stirred tank reactors and loop reactors.

[0019] Particularly preferably, the prepolymerization of step a) is carried out in a loop reactor.

[0020] Preferably, the first reactor is a loop reactor. In this type of reactor, the slurry is circulated at high speed along a closed pipeline using a circulation pump. Loop reactors are generally known in the art to which the present invention pertains, and examples are provided, for example, in US-A-4582816, US-A-3405109, US-A-3324093, EP-A-479186, and US-A-5391654. Therefore, the prepolymerization stage is preferably carried out in a loop reactor as a slurry polymerization process.

[0021] Typically, polymerization is carried out in the prepolymerization step at an average monomer amount of 0.1 to 1000 g per 1 g of solid catalyst component. As is known to those skilled in the art, not all catalyst particles recovered from a continuous prepolymerization reactor contain the same amount of prepolymer. Instead, each particle has its own characteristic amount, which depends on its residence time in the prepolymerization reactor. Due to variations in the residence time of catalyst particles in the reactor, for example, some particles remain in the reactor for a relatively long time while others remain for a relatively short time, the amount of prepolymer on different particles may vary. It is even possible that some individual particles may contain amounts of prepolymer exceeding the aforementioned limits. However, the average amount of prepolymer on the catalyst is generally within these limits.

[0022] It is understood that within the scope of the present invention the amount of polymer produced in the prepolymerization is generally between 0.1 and 0.3 wt% relative to the polypropylene homopolymer or copolymer.

[0023] Preferably, step a) is carried out under specified conditions so that the production amount of the first polypropylene homopolymer or copolymer fraction is 0.1 to 0.3 wt% relative to the polypropylene homopolymer or copolymer.

[0024] Preferably, in step a), the temperature in the first reactor is 20 to 28°C, more preferably 21 to 27°C, and most preferably 22 to 26°C.

[0025] Preferably, in step a), the pressure in the first reactor is preferably 1 to 150 bar, more preferably 35 to 60 bar, even more preferably 50 to 60 bar, and most preferably 53 to 57 bar.

[0026] Preferably, the ratio of hydrogen feed to propylene feed is in the range of 0.02 to 0.07 mol / kmol.

[0027] In step a), a comonomer is preferably present in the first reactor. Preferably, the comonomer in step a) is ethylene.

[0028] In step a), the average residence time in the first reactor is generally 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 equation (1): Equation (1) in, VR is the volume of the reaction space (the volume of the reactor in the case of a loop reactor or the volume of the fluidized bed in the case of a fluidized bed reactor), Q o is the volume flow rate of the product stream (comprising polymer product and fluid reaction mixture).

[0029] As used herein, the production rate of polypropylene (kg PP / h) is measured by the energy balance of the first or second reactor, respectively. Typically, the production rate of the first reactor is 0.5 to 2.0 kg PP / h.

[0030] The degree of prepolymerization in the first reactor is calculated by dividing the production rate in the first reactor by the catalyst feed to the first reactor. The catalyst feed to the first reactor is typically 1.0 to 3.0 g catalyst / h. Therefore, the degree of prepolymerization is typically and 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.

[0031] The slurry can be discharged from the first reactor continuously or intermittently. A preferred method for intermittent discharge is to use settling legs, wherein the slurry is concentrated before a batch of concentrated slurry is discharged from the reactor. The use of settling legs is disclosed in US-A-3374211, US-A-3242150, and EP-A-1310295. Continuous discharge is disclosed in EP-A-891990, EP-A-1415999, EP-A-1591460, and WO-A-2007 / 025640. As disclosed in EP-A-1310295 and EP-A-1591460, continuous discharge is advantageously combined with a suitable concentration method. Preferably, the slurry is discharged continuously from the first reactor.

[0032] Preferably, the slurry discharged from the first reactor is directly transferred to the second reactor to produce the second polypropylene homopolymer or copolymer fraction. "Directly" means that the slurry is introduced from the first reactor into the second reactor without any separation step (e.g., a flash separation step) in between.

[0033] 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 comprises the first polypropylene homopolymer or copolymer fraction, unreacted monomer, and a metallocene catalyst.

[0034] Similar to 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.

[0035] 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. Respectively, the polymerization in step c) is preferably carried out at a reactor pressure in the range of 1 to 100 bar, more preferably 20 to 80 bar, more preferably 30 to 70 bar.

[0036] Preferably, the metallocene catalyst used in step a) is present in the second reactor during the polymerization process in step c). This is accomplished by transferring the metallocene catalyst used in step a) to the second reactor, preferably via a slurry. If desired, fresh metallocene catalyst may be added to the second reactor in step c).

[0037] In step a) and / or step c), one or more comonomers are preferably present in the reactor, wherein the comonomers are selected from α-olefins having 2 or 4 to 10 carbon atoms or mixtures thereof. Preferably, the one or more comonomers are α-olefins having 2 or 4 carbon atoms, more preferably α-olefins having 2 carbon atoms, and most preferably ethylene.

[0038] In case it is desired to control the MFR2 of the second polypropylene homopolymer or copolymer fraction, hydrogen is typically introduced into the polymerization stage in step c). As will be appreciated by those skilled in the art, the amount of hydrogen required to achieve the desired MFR2 depends on the catalyst used and the polymerization conditions.

[0039] When it is necessary to control the melt index of a polypropylene homopolymer or copolymer, it is often necessary to introduce additional hydrogen into the second reactor, in addition to the amount required to control MFR2. The hydrogen feed to the second reactor is preferably controlled to maintain a constant hydrogen to propylene ratio. Good results have been achieved by maintaining the hydrogen feed to propylene feed ratio within the range of 0.1 to 5.0 mol / kmol.

[0040] Preferably, in step c), the ratio of the hydrogen feed to the propylene feed is in the range of 0.1 to 5.0 mol / kmol, more preferably 0.2 to 2.0 mol / kmol, more preferably 0.3 to 1.0 mol / kmol.

[0041] In step c), the average residence time in the second reactor is typically 10 to 40 minutes, preferably 15 to 35 minutes. This can be determined by referring to equation (1). The production rate is appropriately controlled by the catalyst feed rate. The production rate can also be influenced by selecting an appropriate propylene monomer concentration. The desired monomer concentration can then be achieved by appropriately adjusting the propylene feed rate.

[0042] In a preferred embodiment, the polymerization production method of the present invention does not recover the comonomer.

[0043] 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%.

[0044] In step d), the polypropylene homopolymer or copolymer is discharged from the second reactor or transferred to a third reactor. Preferably, the polypropylene homopolymer or copolymer is transferred to the third reactor.

[0045] The polypropylene homopolymer or copolymer comprises: a first polypropylene homopolymer or copolymer fraction produced in the first reactor, and a second polypropylene homopolymer or copolymer fraction produced in the second reactor.

[0046] Preferably, the polypropylene homopolymer or copolymer has a melt flow rate MFR 2 measured according to ISO 1133 of 50 to 90 g / 10 min, preferably 60 to 80 g / 10 min.

[0047] As described above, the polypropylene homopolymer or copolymer is preferably discharged from the second reactor or 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 employed is typically in the range of 60 to 100°C, and the reactor pressure is typically in the range of 1 to 100 bar. The gases employed are typically: a non-reactive gas such as nitrogen, or a low-boiling hydrocarbon such as propane; and a monomer (e.g., propylene). Preferably, one or more comonomers are present in the third reactor, selected from α-olefins having 2 or 4 to 10 carbon atoms, or mixtures thereof. Preferably, the one or more comonomers are α-olefins having 2 or 4 carbon atoms, preferably α-olefins having 2 carbon atoms, i.e., ethylene.

[0048] Preferably, the method of the present invention further comprises a third reactor downstream of the second reactor; more preferably, comprises a third reactor downstream of the second reactor and a fourth reactor downstream of the third reactor; and most preferably, comprises 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 further polymerization of the polypropylene homopolymer or copolymer.

[0049] The fourth reactor and / or the fifth reactor are preferably gas-phase reactors, more preferably fluidized-bed gas-phase reactors. The temperature and pressure in the fourth reactor and / or the fifth reactor are preferably the same as those in the third reactor. Furthermore, the residence time in the fourth reactor and / or the one or more comonomers present therein are preferably the same as those in the third reactor.

[0050] A suitable process is the slurry-gas phase process consistent with the above, which has been developed, for example, by Borealis and is known as Borstar® technology. In this respect, reference is made to European patent applications EP 0887379 A1 and EP 0517868 A1.

[0051] It should be understood that the propylene polymer obtained by the production process of the present invention may contain standard polymer additives. These typically constitute less than 5.0 wt%, for example, less than 2.0 wt%, of the polymer material. Thus, additives such as antioxidants, phosphites, adhesion additives, pigments, colorants, fillers, antistatic agents, processing aids, and clarifiers may be added during the polymerization process. These additives are well known in the industry, and their use will be familiar to those skilled in the art. Any additives present may be added as separate raw materials or in admixture with a carrier polymer, i.e., in a so-called masterbatch.

[0052] Polypropylene homopolymers or copolymers are produced according to the manufacturing method of the present invention in the presence of a metallocene catalyst, preferably at least one metallocene catalyst. The metallocene catalyst typically comprises a metallocene / activator reaction product impregnated in a porous support having a maximum internal pore volume. The metallocene catalyst comprises: a ligand, typically a bridged ligand, a transition metal from Group IVa to Group VIa, and an organoaluminum compound. The catalytic metal compound is typically a metal halide.

[0053] The metallocene catalyst used according to the present invention may be any supported metallocene catalyst suitable for producing polypropylene copolymers.

[0054] The metallocene catalyst preferably comprises: a metallocene complex; a cocatalyst system comprising a boron-containing cocatalyst and / or an aluminoxane cocatalyst; and a carrier, preferably a carrier comprising or consisting of silicon dioxide.

[0055] Examples of suitable metallocene compounds are given, 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, WO 99 / 42497, EP 2402353, EP 2729479 and EP 2746289.

[0056] The metallocene complex is ideally an organometallic compound (C) comprising a transition metal (M) from Groups 3 to 10 of the Periodic Table of the Elements (IUPAC 2007), or an actinide or lanthanide. The term "organometallic compound (C)" according to the present invention encompasses any metallocene compound of a transition metal bearing at least one organic (coordinating) ligand and exhibiting catalytic activity, either 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, such as Groups 3 to 7, or Groups 3 to 6, such as Groups 4 to 6 of the Periodic Table (IUPAC 2007), as well as lanthanides or actinides.

[0057] In one embodiment, the organometallic compound (C) is represented by the following chemical formula (I): (L) mR nMX q(I) in, “M” is a transition metal from Group 3 to Group 10 of the Periodic Table of Elements (IUPAC 2007); Each "X" is independently a monoanionic ligand, such as a σ-ligand; Each "L" is independently an organic ligand coordinated to the transition metal "M"; "R" is a bridging group connecting the organic ligand (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; and m+q is equal to the valency of the transition metal (M).

[0058] “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).

[0059] In a more preferred definition, each organic ligand (L) is independently:

[0060] (a) substituted or unsubstituted cyclopentadienyl or bicyclic or polycyclic derivatives of cyclopentadienyl, which optionally carry further substituents and / or one or more heteroatoms from Groups 13 to 16 of the Periodic Table of the Elements (IUPAC); or

[0061] (b) an acyclic η1 to η4 or η6 ligand composed of atoms from Groups 13 to 16 of the Periodic Table of the Elements, wherein the open chain ligand may be fused to one or two, preferably two, aromatic or non-aromatic rings and / or carry further substituents; or

[0062] (c) cyclic n1 to n4 or n6, monodentate, bidentate or multidentate ligands consisting of unsubstituted or substituted monocyclic, bicyclic or polycyclic ring systems selected from aromatic, non-aromatic or partially saturated ring systems, such ring systems optionally containing one or more heteroatoms selected from Groups 15 and 16 of the Periodic Table of the Elements.

[0063] The organometallic compound (C) preferably used in the present invention has at least one organic ligand (L) belonging to the above group (a). Such organometallic compounds are called metallocenes.

[0064] More preferably, at least one organic ligand (L), more preferably two organic ligands (L) are selected from the group consisting of cyclopentadienyl, indenyl, tetrahydroindenyl, and fluorenyl, which may be independently substituted or unsubstituted.

[0065] In addition, when the organic ligand (L) is substituted, preferably, at least one organic ligand (L), preferably both organic ligands (L) comprise one or more substituents independently selected from a C1-C20 hydrocarbon group or a silyl group, wherein the substituents optionally contain one or more heteroatoms selected from Groups 14 to 16 and / or are optionally substituted with halogen atoms.

[0066] Whenever used in the present invention, the term C1-C20 hydrocarbyl includes C1-C20 alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C3-C20 cycloalkyl, C3-C20 cycloalkenyl, C6-C20 aryl, C7-C20 alkaryl, or C7-C20 aralkyl, or mixtures of these groups, for example cycloalkyl substituted by alkyl.

[0067] Furthermore, two substituents, which may be the same or different, attached to adjacent C atoms of the ring of the ligand (L) may also together form another monocyclic or polycyclic ring fused to the ring.

[0068] Preferred hydrocarbon groups are independently selected from: linear or branched C 1-C 10 alkyl groups, which are optionally interrupted by one or more heteroatoms from Groups 14 to 16, such as O, N or S; and substituted or unsubstituted C 6-C 20 aryl groups.

[0069] The linear or branched C 1-C 10 alkyl group, which is optionally interrupted by one or more heteroatoms from Groups 14 to 16, is more preferably selected from methyl, ethyl, propyl, isopropyl, tert-butyl, isobutyl, C 5-C 6 cycloalkyl, OR, SR, wherein R is C 1-C 10 alkyl;

[0070] The C 6 -C 20 aryl group is more preferably a phenyl group, which is optionally substituted with 1 or 2 C 1 -C 10 alkyl groups as defined above.

[0071] In the present invention, "σ-ligand" refers to a group that bonds to the transition metal (M) through a σ bond.

[0072] In addition, the ligand "X" is preferably independently selected from the group consisting of hydrogen, halogen, C1-C20 alkyl, C1-C20 alkoxy, C2-C20 alkenyl, C2-C20 alkynyl, C3-C12 cycloalkyl, C6-C20 aryl, C6-C20 aryloxy, C7-C20 arylalkyl, C7-C20 arylalkenyl, -SR", -Pr", -SiR", -OSiR", and -NR", wherein each R" is independently hydrogen, C1-C20 alkyl, C2-C20 alkenyl, C2-C20 alkynyl, C3-C12 cycloalkyl, or C6-C20 aryl.

[0073] The ligand "X" is more preferably selected from halogen, C1-C6 alkyl, C5-C6 cycloalkyl, C1-C6 alkoxy, phenyl, and benzyl.

[0074] The bridging group "R" can be a divalent bridge group, preferably selected from -R'2C-, -R'2C-CR'2-, -R'2Si-, -R'2Si-SiR'2-, and -R'2Ge-, wherein each R' is independently a hydrogen atom, a C1-C20 alkyl group, a C2-C10 cycloalkyl group, a tri(C1-C20 alkyl)silyl group, a C6-C20 aryl group, a C7-C20 aralkyl group, and a C7-C20 alkylaryl group.

[0075] More preferably, the bridging group "R" is a divalent bridging group selected from -R'2C-, -R'2Si-, wherein each R' is independently a hydrogen atom, a C1-C20 alkyl group, a C2-C10 cycloalkyl group, a C6-C20 aryl group, a C7-C20 aralkyl group, and a C7-C20 alkaryl group.

[0076] Another subgroup of organometallic compounds (C) of formula (I) are known as non-metallocenes, in which the transition metal (M), preferably a transition metal from Group 4 to Group 6, suitably Ti, Zr or Hf, has ligands other than cyclopentadienyl ligands.

[0077] As used herein, the term "non-metallocene" refers to compounds that do not have a cyclopentadienyl ligand or a fused derivative thereof, but instead have one or more non-cyclopentadienyl η- or σ-, monodentate, bidentate, or polydentate ligands. Such ligands can be selected from the 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, and further described in V.C. Gibson et al., Angew. Chem. Int. Ed., Engl., vol. 38, 1999, pp. 428-447, the entire contents of which are incorporated herein by reference.

[0078] However, the organometallic compound (C) of the present invention is preferably a metallocene as defined above.

[0079] Metallocenes are described in many patents, including: EP 0260130, 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 423101、EP 537130、WO 2002 / 02576、WO 2005 / 105863、WO 2006097497、WO 2007 / 116034、WO 2007 / 107448、WO 2009 / 027075、WO 2009 / 054832、WO 2012 / 001052 and EP 2532687, the entire disclosures of which are incorporated herein by reference.

[0080] In a preferred embodiment, the organometallic compound (C) is represented by the following chemical formula (Ia): (L) 2R nMX 2(Ia) in, "M" stands for zirconium or hafnium; Each "X" is a σ-ligand; Each "L" is optionally substituted cyclopentadienyl, indenyl or tetrahydroindenyl; "R" is a SiMe 2 bridging group connecting the organic ligand (L); "n" is 0 or 1, preferably 1.

[0081] The metallocene catalyst complex of the present invention is preferably asymmetric. Asymmetric simply means that the two ligands forming the metallocene are different, that is, each ligand carries a set of chemically different substituents.

[0082] The metallocene catalyst complexes of the present invention are typically chiral, racemic bridged, bis-indenyl C1-symmetric metallocenes in their anti-configuration. Although such complexes are formally C1-symmetric, ideally, they retain pseudo-C2-symmetry because they maintain C2-symmetry near the metal center rather than at the periphery of the ligands. Due to their chemical nature, pairs of trans and cis mirror isomers (in the case of C1-symmetric complexes) are formed during the synthesis of the complexes. For the purposes of this invention, racemic-anti refers to the two indenyl ligands being oriented in opposite directions relative to the cyclopentadienyl-metal-cyclopentadienyl plane, while racemic-syn refers to the two indenyl ligands being oriented in the same direction relative to the cyclopentadienyl-metal-cyclopentadienyl plane, as shown in the figure below.

[0083] Formula (I) and any subformulae are intended to encompass both cis and trans configurations. Preferred metallocene catalyst complexes are in the trans configuration.

[0084] The metallocene catalyst complex of the present invention is usually in the racemic-trans isomer form. Therefore, ideally, at least 95% mol, such as at least 98% mol, and especially at least 99% mol of the metallocene catalyst complex is in the racemic-trans isomer form.

[0085] More preferably, the metallocene catalyst is represented by chemical formula (II): Chemical formula (II)

[0086] Mt is hafnium or zirconium;

[0087] Each X is a σ-ligand;

[0088] Each R 1 is independently the same or different and is a CH 2 -R 7 group, wherein R 7 is hydrogen, a linear or branched C 1 -C 6 alkyl group, a C 3 -C 8 cycloalkyl group, or a C 6 -C 10 aryl group,

[0089] Each R 2 is independently a -CH=, -CY=, -CH 2-, -CHY- or -CY 2- group, wherein Y is a C 1-C 10 hydrocarbon group, and n is 2 to 6,

[0090] Each R 3 and R 4 may independently be the same or different and is hydrogen, a linear or branched C 1 -C 6 alkyl group, an OY group, a C 7 -C 20 aralkyl group, a C 7 -C 20 alkaryl group, or a C 6 -C 20 aryl group, wherein at least one R 3 and at least one R 4 on each phenyl group is not hydrogen, and optionally, two adjacent R 3 or R 4 groups may be part of a ring containing the phenyl carbon to which they are bonded,

[0091] R 5 is a linear or branched C 1-C 6 alkyl group, a C 7-C 20 aralkyl group, a C 7-C 20 alkaryl group, or a C 6-C 20 aryl group,

[0092] R6 is a C(R8)3 group, wherein R8 is a linear or branched C1-C6 alkyl group, and

[0093] Each R is independently a C 1 -C 20 hydrocarbon group.

[0094] Mt is preferably zirconium.

[0095] Preferably, each X is independently a hydrogen atom, a halogen atom, a C1-C6 alkoxy group, or an R' group, wherein R' is a C1-C6 alkyl group, a phenyl group, or a benzyl group. Most preferably, X is chlorine, a benzyl group, or a methyl group. Preferably, the two X groups are the same. The most preferred selections are two chlorine groups, two methyl groups, or two benzyl groups, particularly two chlorine groups.

[0096] Each R is independently a C1-C20 hydrocarbon group, such as a C6-C20 aryl group, a C7-C20 aralkyl group, or a C7-C20 alkaryl group. The term C1-C20 hydrocarbon group also includes C1-C20 alkyl groups, C2-C20 alkenyl groups, C2-C20 alkynyl groups, C3-C20 cycloalkyl groups, C3-C20 cycloalkenyl groups, C6-C20 aryl groups, C7-C20 alkaryl groups, or C7-C20 aralkyl groups, or mixtures of these groups, such as cycloalkyl groups substituted with alkyl groups. Unless otherwise specified, preferred C1-C20 hydrocarbon groups are C1-C20 alkyl, C4-C20 cycloalkyl, C5-C20 cycloalkyl-alkyl, C7-C20 alkaryl, C7-C20 aralkyl, or C6-C20 aryl.

[0097] Preferably, both R groups are the same. Preferably, R is a C1-C10 hydrocarbyl group or a C6-C10 aryl group, such as methyl, ethyl, propyl, isopropyl, tert-butyl, isobutyl, C5-C6 cycloalkyl, cyclohexylmethyl, phenyl, or benzyl group; more preferably, both R groups are C1-C6 alkyl, C3-C8 cycloalkyl, or C6 aryl groups, such as C1-C4 alkyl, C5-C6 cycloalkyl, or C6 aryl groups; and most preferably, both R groups are methyl, or one is methyl and the other is cyclohexyl. Most preferably, the bridging group is a -Si(CH3)2- group.

[0098] Each R 1 is independently the same or different and is a CH 2 -R 7 group, wherein R 7 is hydrogen; a straight-chain or branched C 1 -C 6 alkyl group, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl; a C 3 -C 8 cycloalkyl group (such as cyclohexyl); or a C 6 -C 10 aryl group (preferably phenyl).

[0099] Preferably, both R1 groups are the same and are CH2-R7 groups, wherein R7 is hydrogen or a linear or branched C1-C4 alkyl group. More preferably, both R1 groups are the same and are CH2-R7 groups, wherein R7 is hydrogen or a linear or branched C1-C3 alkyl group. Most preferably, both R1 groups are methyl groups.

[0100] Each R 2 is independently a —CH=, —CY=, —CH 2—, —CHY— or —CY 2— group, wherein Y is a C 1-C 10 hydrocarbon group, preferably a C 1-C 4 hydrocarbon group, and wherein n is 2 to 6, preferably 3 to 4.

[0101] Each substituent R3 and R4 can independently be the same or different and is hydrogen, a linear or branched C1-C6 alkyl group, an OY group, a C7-C20 aralkyl group, a C7-C20 alkaryl group, or a C6-C20 aryl group, preferably hydrogen, a linear or branched C1-C6 alkyl group, or a C6-C20 aryl group. Optionally, two adjacent R3 or R4 groups can be part of a ring containing the phenyl carbon to which they are bonded. More preferably, R3 and R4 are hydrogen, a linear or branched C1-C4 alkyl group, or an OY group, where Y is a C1-C4 hydrocarbon group. Even more preferably, each R3 and R4 is independently hydrogen, methyl, ethyl, isopropyl, tert-butyl, or methoxy, especially hydrogen, methyl, or tert-butyl, wherein at least one R3 and at least one R4 of each phenyl group is not hydrogen.

[0102] Therefore, preferably, one or two R 3 on each phenyl group is not hydrogen; more preferably, R 3 on the two phenyl groups are the same, for example, R 3 on the two phenyl groups are both 3',5'-dimethyl or 4'-tert-butyl.

[0103] For the indenyl moiety, preferably, one or both R 4 on the phenyl group are not hydrogen; more preferably, both R 4 are not hydrogen; most preferably, both R 4 are the same, such as 3',5'-dimethyl or 3',5'-di-tert-butyl.

[0104] R5 is a linear or branched C1-C6 alkyl group, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, C7-C20 aralkyl, C7-C20 alkaryl, or C6-C20 aryl. R5 is preferably a linear or branched C1-C6 alkyl group or a C6-C20 aryl group, more preferably a linear C1-C4 alkyl group, even more preferably a C1-C2 alkyl group, and most preferably a methyl group.

[0105] R 6 is a C(R 8) 3 group, wherein R 8 is a straight-chain or branched C 1-C 6 alkyl group.

[0106] Each R is independently a C1-C20 hydrocarbon group, a C6-C20 aryl group, a C7-C20 aralkyl group, or a C7-C20 alkaryl group. Preferably, each R8 is the same or different, wherein R8 is a linear or branched C1-C4 alkyl group; more preferably, each R8 is the same and is a C1-C2 alkyl group. Most preferably, all R8 groups are methyl groups.

[0107] In another preferred embodiment, the organometallic compound (C) is represented by the following chemical formula (III): Chemical formula (III) in, Mt is hafnium or zirconium, preferably zirconium; Each R 3 and R 4 may independently be the same or different and is hydrogen or a linear or branched C 1 -C 6 alkyl group, wherein at least one R 3 and at least one R 4 of each phenyl group is not hydrogen.

[0108] Specific metallocene catalyst complexes include: rac-trans-dimethylsilanediyl[2-methyl-4,8-bis-(4'-tert-butylphenyl)-1,5,6,7-tetrahydro-s-dicyclopentadien-1-yl][2-methyl-4-(3',5'-dimethylphenyl)-5-methoxy-6-tert-butylinden-1-yl]zirconium dichloride; rac-trans-dimethylsilanediyl[2-methyl-4,8-bis-(3',5'-dimethylphenyl)-1,5,6,7-tetrahydro-s-dicyclopentadien-1-yl][2-methyl-4-(3',5'-dimethylphenyl)-5-methoxy-6-tert-butylinden-1-yl]zirconium dichloride; rac-trans-dimethylsilanediyl[2-methyl-4,8-bis-(3',5'-dimethylphenyl)-1,5,6,7-tetrahydro-s-dicyclopentaphen-1-yl][2-methyl-4-(3',5'-di-tert-butylphenyl)-5-methoxy-6-tert-butylinden-1-yl]zirconium dichloride; or Its corresponding dimethyl zirconium analogue. MC-1 MC-2 MC-3

[0109] The ligands required to form the metallocene catalysts of the present invention can be synthesized by any method, and an organic chemist with ordinary skill can devise various synthetic schemes to produce the necessary ligand materials. For example, WO 2007 / 116034 discloses the necessary chemistry. General synthetic schemes can also be found in WO 2002 / 02576, WO 2011 / 135004, WO 2012 / 084961, WO 2012 / 001052, WO 2011 / 076780, and WO 2015 / 158790.

[0110] In order to form an active catalytic species, it is generally necessary to use a co-catalyst which is well known in the art.

[0111] According to the present invention, it is preferred to use a cocatalyst system comprising a boron-containing cocatalyst and / or an aluminoxane cocatalyst in combination with the metallocene catalyst defined above.

[0112] The aluminoxane cocatalyst may be one of formula (IV): (IV) wherein n is generally 6 to 20, and R has the following meanings.

[0113] Aluminoxanes are formed when organoaluminum compounds are partially hydrolyzed, such as those of the formulae AlR3, AlR2Y, and Al2R3Y3, wherein R can be, for example, a C1-C10 alkyl group, preferably a C1-C5 alkyl group, a C3-C10 cycloalkyl group, a C7-C12 aralkyl group or an alkaryl group, and / or a phenyl or naphthyl group, and wherein Y can be: hydrogen; a halogen group, preferably a chlorine or bromine group; or a C1-C10 alkoxy group, preferably a methoxy or ethoxy group. The resulting oxygen-containing aluminoxane is typically not a pure compound but rather a mixture of oligomers of formula (III).

[0114] The preferred aluminoxane is methylaluminoxane (MAO). Since the aluminoxane used as a cocatalyst according to the present invention is not a pure compound due to its preparation method, the volume molar concentration of the aluminoxane solution hereinafter is based on its aluminum content.

[0115] Additionally, according to 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 the boron-containing cocatalyst.

[0116] Those skilled in the art will appreciate that when a boron-based cocatalyst is used, the complex is typically pre-alkylated by reacting it with an alkylaluminum compound, such as TIBA. This procedure is well known, and any suitable aluminum alkyl, such as Al(C1-C6 alkyl)3, can be used. Preferred aluminum alkyl compounds include triethylaluminum, triisobutylaluminum, triisohexylaluminum, tri-n-octylaluminum, and triisooctylaluminum.

[0117] Alternatively, when a borate cocatalyst is used, the metallocene complex is in its alkylated form, ie, for example, a dimethyl metallocene complex or a benzhydryl metallocene complex may be used.

[0118] Boron-based co-catalysts of note include those represented by formula (V): BY 3(V)

[0119] Wherein, Y is the same or different and is: a hydrogen atom; an alkyl group having 1 to about 20 carbon atoms; an aryl group having 6 to about 15 carbon atoms; an alkaryl group, an aralkyl group, a haloalkyl group, or a haloaryl group, each having 1 to 10 carbon atoms in the alkyl group and 6 to 20 carbon atoms in the aryl group; or fluorine, chlorine, bromine, or iodine. Preferred examples of Y include: a methyl group, a propyl group, an isopropyl group, an isobutyl group, or a trifluoromethyl group; an unsaturated group, such as an aryl group or a haloaryl group, such as a phenyl group, a tolyl group, a benzyl group, a p-fluorophenyl group, a 3,5-difluorophenyl group, a pentachlorophenyl group, a pentafluorophenyl group, a 3,4,5-trifluorophenyl group, and a 3,5-bis(trifluoromethyl)phenyl group. Preferred options include trifluoroborane, triphenylborane, tri(4-fluorophenyl)borane, tri(3,5-difluorophenyl)borane, tri(4-fluoromethylphenyl)borane, tri(2,4,6-trifluorophenyl)borane, tri(pentafluorophenyl)borane, tri(tolyl)borane, tri(3,5-dimethylphenyl)borane, tri(3,5-difluorophenyl)borane, and / or tri(3,4,5-trifluorophenyl)borane.

[0120] Particularly preferred is tris(pentafluorophenyl)borane.

[0121] However, preference is given to using borates, ie compounds containing borate 3+ ions.

[0122] Such ionic cocatalysts preferably contain non-coordinating anions such as tetrakis(pentafluorophenyl)borate and tetraphenylborate. Suitable counterions are protonated amines or aniline derivatives such as methylamine, aniline, dimethylamine, diethylamine, N-methylaniline, diphenylamine, N,N-dimethylaniline, trimethylamine, triethylamine, tri-n-butylammonium, methyldiphenylamine, pyridinium, p-bromo-N,N-dimethylaniline, or p-nitro-N,N-dimethylaniline.

[0123] According to the present invention, preferred ionic compounds that can be used include: triethylammonium tetra(phenyl)borate, Tributylammonium tetra(phenyl)borate, trimethylammonium tetra(tolyl)borate, Tributylammonium tetra(tolyl)borate, Tributylammonium tetrakis(pentafluorophenyl)borate, tripropylammonium tetrakis(dimethylphenyl)borate, Tributylammonium tetrakis(trifluoromethylphenyl)borate, Tributylammonium tetrakis(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 tetrakis(pentafluorophenyl)borate, triphenylphosphonium tetrakis(phenyl)borate, triethylphosphonium tetra(phenyl)borate, Diphenylphosphonium tetrakis(phenyl)borate, tri(methylphenyl)phosphonium tetra(phenyl)borate, tris(dimethylphenyl)phosphonium tetra(phenyl)borate, triphenylcarbonium tetrakis(pentafluorophenyl)borate (triphenylcarbeniumtetrakis(pentafluorophenyl)borate), or Ferrocene tetrakis(pentafluorophenyl)borate.

[0124] Preferably: triphenylcarbonium tetrakis(pentafluorophenyl)borate, N,N-dimethylcyclohexylammonium tetrakis(pentafluorophenyl)borate, or N,N-dimethylbenzylammonium tetrakis(pentafluorophenyl)borate.

[0125] Surprisingly, it has been found that certain boron promoters are particularly preferred.

[0126] Therefore, preferred borates for use in the present invention include trityl ions. Therefore, the use of N,N-dimethylammonium tetrakis(pentafluorophenyl)borate and Ph 3CB(PhF 5) 4 and their analogs is particularly favored.

[0127] According to the present invention, the preferred cocatalyst is aluminoxane, more preferably methylaluminoxane; a combination of aluminoxane with an alkylaluminum, boron or borate cocatalyst; and a combination of aluminoxane with a boron-based cocatalyst.

[0128] Suitable amounts of promoters are well known to those of ordinary skill in the art.

[0129] The molar ratio of boron to the metal ion in the metallocene may be in the range of 0.5:1 to 10:1 mol / mol, preferably 1:1 to 10:1 mol / mol, in particular 1:1 to 5:1 mol / mol.

[0130] The molar ratio of Al in the aluminoxane to the metal ion in 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.

[0131] The metallocene catalyst used in the polymerization method of the present invention is preferably used in a supported form. The supported form comprises, and preferably consists of, silicon dioxide. The procedures required to support the metallocene catalyst are generally understood by those skilled in the art.

[0132] Particularly preferably, the support is a porous material so that the complex can be loaded into the pores of the support, for example, using processes similar to those described in WO 94 / 14856 (Mobil), WO 95 / 12622 (Borealis), and WO 2006 / 097497.

[0133] The average particle size of the carrier can generally be from 10 to 100 μm. However, it has proven particularly advantageous if the average particle size of the carrier is from 15 to 80 μm, preferably from 18 to 50 μm.

[0134] The particle size distribution of the carrier will be described in detail below. Preferably, the carrier has a D50 of 10 to 80 μm, more preferably 18 to 50 μm. Furthermore, preferably, the carrier has a D10 of 5 to 30 μm and a D90 of 30 to 90 μm. Preferably, the carrier has a SPAN value of 0.1 to 1.1, more preferably 0.3 to 1.0.

[0135] 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.

[0136] The particle size distribution of the metallocene catalyst will be described in detail below. The D50 of the metallocene catalyst is preferably 30 to 80 μm, more preferably 32 to 50 μm, and optimally 34 to 40 μm. Furthermore, the D10 of the metallocene catalyst is preferably at most 29 μm, more preferably 15 to 29 μm, even more preferably 20 to 28 μm, and optimally 25 to 27 μm. The D90 of the metallocene catalyst is preferably at least 45 μm, more preferably 45 to 70 μm, and optimally 40 to 60 μm.

[0137] The average pore size of the support can be in the range of 10 to 100 nm, preferably 20 to 50 nm, and the pore volume can be 1 to 3 ml / g, preferably 1.5 to 2.5 ml / g. The BET surface area of ​​the silica support material is determined according to ASTM D3663 and the porosity parameter based on BJH 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.

[0138] All or part of the preparation steps can be carried out in a continuous process. The catalyst formed preferably has good stability / kinetics in terms of reaction life, high activity, and the catalyst is capable of achieving a low ash content.

[0139] Generally speaking, polymerization catalysts supported on silica exhibit very complex polymerization behavior, and the polymerization process can be divided into multiple stages.

[0140] During the first few minutes of polymerization, catalyst activity can reach very high values, leading to uncontrolled cracking processes and, in turn, reduced catalyst activity due to increased external mass and heat transfer phenomena. More specifically, the exothermic heat generated by the polymerization reaction cannot be properly dissipated, resulting in localized particle overheating (i.e., a high temperature difference between the surface and bulk temperature of the growing polymer particle). As a result, the polymer produced on the surface of the growing polymer particle becomes sticky, increasing the risk of particle agglomeration and impacting process performance and reactor operability.

[0141] The above-mentioned polymerization kinetics require a new design of the prepolymerization process in terms of temperature, monomer concentration and residence time.

[0142] In a preferred embodiment of the present invention, during the initial stage (first activity peak), the temperature and monomer concentration must be as low as possible to prevent overheating of the formed polymer and the formation of agglomerates. During the second stage, the monomer concentration and temperature must be as high as possible to accelerate the catalyst cracking process. [Experimental part] [Measurement method]

[0143] Any parameters mentioned in the detailed description of the invention are measured according to the tests given below. a) Melt flow rate

[0144] Melt flow rate (MFR) is measured according to ISO 1133 and expressed in g / 10 min. MFR is an indicator of the melt viscosity of a polymer. The MFR of polyethylene is measured at 190°C, and the MFR of polypropylene is measured at 230°C. The load under which the melt flow rate was measured is usually indicated by a subscript; for example, MFR 2 is measured under a load of 2.16 kg (state D). b) Average particle size and particle size distribution

[0145] Particle size distribution is measured using laser diffraction measurements using a Coulter LS 200. Particle size and particle size distribution are measures of particle size. The D values ​​(D 10 (or d 10), D 50 (or d 50), and D 90 (or d 90)) represent the intercepts at 10%, 50%, and 90% of the sample's cumulative mass. The D value can be thought of as the diameter of a sphere; when the particles are arranged based on increasing mass, the D value divides the sample's mass into specific percentages. For example, D 10 is the diameter at which 10% of the sample's mass consists of particles with a diameter less than the D 10 value. D 50 is the diameter at which 50% of the sample's mass has a diameter less than the D 50 value, and 50% of the sample's mass has a diameter greater than the D 50 value. D 90 is the diameter at which 90% of the sample's mass consists of particles with a diameter less than the D 90 value. The D 50 value is also known as the median particle size. Laser diffraction measurements are performed according to ISO 13320 to obtain volumetric D values ​​based on volume distribution.

[0146] The distribution width or span of the particle size distribution is calculated from the D values ​​D10, D50 and D90 according to equation (2): Span = (D 90 - D 10) / D 50 Equation (2)

[0147] The sieve fraction was determined using a Camsizer P4 from Retsch Technology GmbH using digital image analysis. The measurement principle is dynamic image analysis according to ISO 13322-2. c) Xylene soluble fraction

[0148] The xylene-soluble fraction content (XS) is determined according to ISO 16152 at 25°C. d) Overall density

[0149] Bulk density is determined according to ASTM D1895. [Material]

[0150] The following catalysts were used in the processes according to the comparative examples and inventive examples described in Table 1 .

[0151] The metallocene catalyst described in WO 2019 / 179959 A1 was used, and its preparation method is described in detail as follows.

[0152] A steel reactor equipped with a mechanical stirrer and filter was flushed with nitrogen and set to a temperature of 20°C. Next, 10 kg of silica grade DM-L-303 from AGC Si-Tech Co. was added from a feed drum and precalcined at 600°C. The mixture was then 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, a 30 wt% solution of MAO in toluene from Lanxess (17.5 kg) was added over 140 minutes through a 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 two hours. The slurry was allowed to settle, and the mother liquor was filtered off. The catalyst was washed twice with 43.5 kg of toluene at 90°C, then precipitated and filtered.

[0153] Finally, the MAO-treated SiO₂ was dried at 60°C under a nitrogen stream for 2 hours, then dried under vacuum (~0.5 barg) with stirring for 14 hours. The MAO-treated support was collected as a free-flowing white powder and found to contain 15.0 wt% aluminum. A 30 wt% solution of MAO in toluene (2 kg) was added via a burette to a nitrogen-purged steel reactor at 20°C. Toluene (12.8 kg) was added with stirring. 129 g of the metallocene was added from a metal cylinder, followed by a 1 kg toluene rinse. The mixture was stirred at 20°C for 60 minutes. Trityltetrakis(pentafluorophenyl)borate (127.2 g) was then added from 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 to the stirred filter cake of the MAO-silica support prepared as described above over 12 hours. The filter cake was stirred for 30 minutes and then allowed to stand without stirring for 30 minutes before being dried under a stream of nitrogen at 60°C for 2 hours and further dried under vacuum (~0.5 barg) with stirring for 15 hours. [Example]

[0154] The following examples were conducted in a pilot plant consisting of a reactor train consisting of a prepolymerization loop reactor and a loop reactor. The methods and properties are shown in Table 1 below. [ , , ]

[0155] [surface] [1] Example [CE1] [CE2] [IE1] [IE2] [IE3] [IE4] [IE5] [IE6] [IE7] [Prepolymerization reactor] temperature [°C] 30 10 25 25 25 25 25 20 15 pressure [kPa] 5180 5155 5219 5193 5206 5202 5227 5177 5165 Catalyst feed [g / h] 2.1 2.0 2.2 2.1 2.4 2.7 2.9 1.9 2.1 H2 feed (g / h) [g / h] 0.12 0.12 0.12 0.07 0.15 0.18 0.03 0.12 0.12 C3 feed (kg / h) [kg / h] 65.4 65.5 65.6 65.4 65.4 65.4 65.6 65.7 65.5 H2 / C3 feed ratio [mol / kmol] 0.04 0.04 0.04 0.02 0.05 0.06 0.01 0.04 0.04 Production rate (kg / h) [kg / h] 1.2 1.4 1.0 1.1 1.1 1.2 0.6 1.0 1.2 Prepolymerization degree [gPP / g catalyst] 559 698 471 500 447 429 215 504 564 [Loop Reactor] temperature [°C] 75 75 75 75 75 75 75 75 75 pressure [kPa] 5068 5045 5094 5079 5078 5106 5104 5054 5039 H2 / C3 feed ratio [mol / kmol] 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 Production rate [kg / h] 31.3 29.7 32.3 29.9 29.0 29.1 26.6 29.2 30.1 Catalyst productivity [kg / g] 15.1 15.1 15.0 14.7 12.5 11.4 9.9 15.6 14.5 Catalyst activity [kg / g / h] 38.8 39.3 40.4 37.6 32.2 29.0 24.8 42.5 37.8 [Final polymer] MFR 2 [g / 10 min] 82.60 64.60 62.00 72.00 78.20 72.00 60.50 66.60 69.80 Total XS [wt%] 0.84 1.05 0.78 1.00 0.90 0.86 0.64 0.55 0.74 Overall density [kg / m 3] 346.00 319.00 355.00 342.00 346.00 354.00 339.00 333.00 340.00 Sieve bottom [%] 0.02 0.04 0.01 0.01 0.03 0.02 0.02 0.02 0.03 Screening particle size 0.106 mm [%] 0.08 0.15 0.15 0.10 0.15 0.14 0.11 0.11 0.15 Screening particle size 0.250 mm [%] 0.34 0.38 0.69 0.33 0.74 0.74 0.48 0.41 0.56 Screening particle size 0.355 mm [%] 15.67 10.68 18.53 12.85 24.24 26.30 13.84 8.42 13.91 Screening particle size 0.820 mm [%] 78.70 81.53 73.65 80.29 70.24 68.85 77.90 77.80 79.34 Screening size 2.000 mm [%] 4.73 7.20 6.93 6.40 4.57 3.95 7.48 13.20 5.91 Screening size > 4.000 mm [%] 0.46 0.02 0.04 0.02 0.03 0.00 0.17 0.12 0.10

[0156] When the process was run at 30°C for CE1, although fairly good overall density was achieved, the process was stopped due to blockage in the transfer line between the prepolymerization reactor and the loop reactor and larger particles (4 mm or larger, agglomerates).

[0157] However, if the prepolymerization is carried out at too low a temperature, as in Comparative Example CE2, the overall density is low, indicating poor morphology.

[0158] It can be seen from IE1 to IE7 that the optimal conditions for the production method of the present invention are: the temperature in the prepolymerization reactor is 15 to 29°C, and the H2 / C3 feed ratio is 0.01 to 0.08 mol / kmol.

Claims

1. 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 produce a first polypropylene homopolymer or copolymer fraction, wherein, The ratio of hydrogen feed to propylene feed is in the range of 0.01 to 0.08 mol / kmol, and the temperature in the first reactor is 20 to 29°C; b) the first polypropylene homopolymer or copolymer fraction is transferred to a second reactor; c) propylene is polymerized in the second reactor in the presence of the first polypropylene homopolymer or copolymer fraction to produce a second polypropylene homopolymer or copolymer fraction, wherein the average residence time in the second reactor is 10 to 40 minutes; and d) a polypropylene homopolymer or copolymer containing the first polypropylene homopolymer or copolymer fraction and the second polypropylene homopolymer or copolymer fraction is discharged from the second reactor, or the polypropylene homopolymer or copolymer is transferred to a third reactor, wherein the metallocene catalyst comprises a support, a metallocene complex, and a cocatalyst system, wherein the support comprises silicon dioxide, and the cocatalyst system comprises a boron-containing cocatalyst and / or an aluminoxane cocatalyst. Furthermore, the metallocene complex is an organometallic compound (C), which is represented by the following chemical formula (Ia): (L)2RnMX2 (Ia) where M is zirconium or hafnium; each X is a σ-coordinating group; each L is optionally substituted cyclopentadienyl, indenyl or tetrahydroindenyl; R is a SiMe2 bridging group connecting the organic coordinating group (L); and n is 0 or 1.

2. The manufacturing method as described in claim 1, wherein, In step a), the temperature in the first reactor is 20 to 28°C.

3. The manufacturing method as described in claim 1, wherein, In step a), the pressure in the first reactor is 1 to 150 bar.

4. The manufacturing method as described in claim 1, wherein, In step c), the temperature in the second reactor is 60 to 100°C.

5. The manufacturing method as described in claim 1, wherein, In step c), the pressure in the second reactor is 1 to 150 bar.

6. The manufacturing method as described in claim 1, wherein, In step a), a comonomer is present in the first reactor.

7. The manufacturing method as described in claim 1, wherein, In step c), a comonomer is present in the second reactor.

8. The manufacturing method as described in claim 6, wherein, In step a), the comonomer is ethylene.

9. The manufacturing method as described in claim 7, wherein, In step c), the comonomer is ethylene.

10. The manufacturing method as described in claim 1, wherein, The first reactor is a circulating reactor, and / or the second reactor is a circulating reactor.

11. The manufacturing method as described in claim 1, wherein, In step d), the third reactor is a gas-phase reactor.