Method for producing polypropylene copolymer

Abstract

The present invention provides a method for producing a polypropylene copolymer, the method comprising the steps of: a) prepolymerizing propylene in a first reactor in the presence of ethylene and a metallocene catalyst to obtain a prepolymer, wherein the ratio of the ethylene feed rate to the propylene feed rate is in the range of 0.1 to 15 mol / kmol; b) transferring the prepolymer to a second reactor; c) polymerizing propylene in the second reactor in the presence of the prepolymer and one or more comonomers selected from alpha-olefins having 2 or 4 to 10 carbon atoms, preferably 2 or 4 carbon atoms, or a mixture thereof to obtain a polypropylene copolymer; and d) removing the polypropylene copolymer from the second reactor or transferring the polypropylene copolymer to a third reactor, wherein the metallocene catalyst comprises a metallocene complex and a support, and the support comprises silica.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a polypropylene copolymer in the presence of a metallocene catalyst, with a specified ethylene to propylene feed ratio. [Background technology]

[0002] Polypropylene-based copolymers, such as propylene-ethylene copolymers, are an interesting class of materials with a wide range of uses in a variety of applications where a good cost-performance ratio is required. The properties of propylene copolymers also depend on the form of the catalyst used in the polymerization process.

[0003] Therefore, controlling the powder morphology is a common concern in such polypropylene copolymer polymerization processes. In polypropylene polymerization processes known in the prior art, the original morphology of the catalyst and the catalyst start-up method are very important to the final polymer powder morphology. If the start-up is not ideal, the final polymer powder morphology may also not be ideal.

[0004] As a result, to avoid abrupt changes in the catalyst environment and avoid early over-reaction, a pre-polymerization step, i.e., a pre-polymerization reactor, is usually installed before the main polymerization reactor. In pre-polymerization, the catalyst is started under mild conditions to maintain the catalyst morphology. This step affects the final catalyst morphology. The mild conditions are specific to the catalyst and the process.

[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 constant need for further improvements in the polypropylene polymerization process with a view to maintaining good polymer powder morphology, especially the specified bulk density. 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] 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]

[0010] Summary of the Invention Surprisingly, the above object can be achieved by the following steps: a) prepolymerizing propylene in the presence of ethylene and a metallocene catalyst in a first reactor to obtain a prepolymer, wherein the ratio of the amount of ethylene fed to the amount of propylene fed is in the range of 0.1 to 15 mol / kmol; b) transferring the prepolymer to a second reactor; c) polymerizing propylene in a second reactor in the presence of said prepolymer and one or more comonomers selected from alpha-olefins having 2 or 4 to 10 carbon atoms, preferably 2 or 4 carbon atoms, or mixtures thereof, to obtain a polypropylene copolymer; d) removing the polypropylene copolymer from the second reactor or transferring the polypropylene copolymer to a third reactor, preferably transferring the polypropylene copolymer to a third reactor. wherein the metallocene catalyst comprises a metallocene complex and a support, and the support comprises silica.

[0011] The present invention is based on the surprising discovery that the morphology or morphology development of the polymerization catalyst and polymer powder is improved by feeding additional ethylene to the prepolymerization reactor.

[0012] Detailed Description of the Invention The polypropylene copolymer is produced in the presence of a metallocene catalyst, 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 complex typically comprises a bridged ligand, a Group IVa to Group VIa transition metal, and an organoaluminum compound. The catalytic metal compound is typically a metal halide.

[0013] The metallocene catalyst according to the present invention may be any supported metallocene catalyst suitable for producing polypropylene copolymers.

[0014] The metallocene catalyst preferably comprises a metallocene complex, a cocatalyst system comprising a boron-containing cocatalyst and / or an aluminoxane cocatalyst, and a support preferably comprising or consisting of silica.

[0015] 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.

[0016] 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 from 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 includes compounds of metals from Groups 3 to 10 of the Periodic Table (IUPAC 2007), such as Groups 3 to 7, or Groups 3 to 6, such as Groups 4 to 6, as well as lanthanides or actinides.

[0017] 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.

[0018] "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).

[0019] 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 belonging to 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, 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 - monodentate, bidentate or polydentate ligands of the formula: -, such ring systems optionally containing one or more heteroatoms selected from groups 15 and 16 of the periodic table.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] C1 to C used in this application 20 The term hydrocarbyl group 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.

[0024] Furthermore, two identical or different substituents attached to adjacent C atoms of a ring of the ligand (L) can also together form a further monocyclic or polycyclic ring fused to the ring.

[0025] 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.

[0026] 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.

[0027] In the present invention, the term "σ ligand" refers to a group that is bonded to a transition metal (M) via a sigma bond.

[0028] 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.

[0029] More preferably, the "X" ligand is selected from halogen, C1-C6 alkyl, C5-C6 cycloalkyl, C1-C6 alkoxy, phenyl and benzyl groups.

[0030] 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).

[0031] More preferably, the bridging group "R" is -R'C, -R'Si- (wherein each R' is independently a hydrogen atom, a C1-C 20 Alkyl, C2-C 10 Cycloalkyl, C6-C20 Aryl, C7-C 20 Aryl alkyl and C7-C 20 alkylaryl).

[0032] 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.

[0033] The term "nonmetallocene" as used herein refers to a compound that does not have a cyclopentadienyl ligand or its fused derivatives, but has one or more non-cyclopentadienyl η- or 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.

[0034] However, the organometallic compound (C) of the present invention is preferably a metallocene as defined above.

[0035] Metallocenes are described in numerous patents. Examples of such patents include EP 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, WO00 / 148034, EP 423 101, EP 537 130, WO2002 / 02576, WO2005 / 105863, WO 2006097497, WO2007 / 116034, WO2007 / 107448, WO2009 / 027075, WO2009 / 054832, WO 2012 / 001052, and EP 2532687, the disclosures of which are incorporated herein by reference. Furthermore, metallocenes have been widely described in the academic and scientific literature.

[0036] 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.

[0037] 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.

[0038] 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).

[0039] [ka]

[0040] Formula (I) and subformulas are intended to encompass both the syn and anti configurations. Preferred metallocene catalyst complexes are in the anti configuration.

[0041] The metallocene catalyst complexes of the present invention are typically used as the rac-anti isomer, 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 isomer form.

[0042] 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 are independently the same or different, and CH2-R 7 Group(R 7 is H or linear or branched C 1-6Alkyl 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 straight 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 straight or branched C1-C6 alkyl group, C 7-20 Aryl alkyl, C 7-20 Alkylaryl group or C6-C 20 is an aryl group, R 6 is C(R 8 )3 groups (R 8 is a straight or branched C1-C6 alkyl group, Each R is independently C1-C 20 -hydrocarbyl] It is of the type.

[0043] Preferably, Mt is Zr.

[0044] 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).

[0045] 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.

[0046] 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, C 7-20 Alkylaryl group, C 7-20 Arylalkyl group, or C 6-20 It is an aryl group.

[0047] 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 3-8Preferably, 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)-.

[0048] Each R 1 may 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).

[0049] 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.

[0050] 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.

[0051] Each substituent R 3 and R 4 are independently the same or different and are hydrogen, a straight or branched C1-C6 alkyl group, an OY group, or C7-20 Aryl alkyl, C 7-20 Alkylaryl group, or C 6-20 is an aryl group, preferably hydrogen, a straight 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 straight 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.

[0052] 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.

[0053] 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.

[0054] R 5 is a straight or branched C1-C6 alkyl group such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, tert-butyl, etc., C 7-20 Aryl alkyl, C7-20 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.

[0055] R 6 is C(R 8 )3 groups, R 8 is a straight-chain or branched C1-C6 alkyl group.

[0056] 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.

[0057] 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, whereby there is at least one R per phenyl group. 3 and at least one R 4 is not hydrogen] It has.

[0058] 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.

[0059] TIFF2025540472000004.tif83144

[0060] 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 chemistry. Synthetic protocols can also be found generally in WO 2002 / 02576, WO 2011 / 135004, WO 2012 / 084961, WO 2012 / 001052, WO 2011 / 076780, and WO 2015 / 158790.

[0061] To form an active catalytic species, it is usually necessary to use a cocatalyst, as is well known in the art.

[0062] According to the present invention, a cocatalyst system comprising a boron-containing cocatalyst and / or an aluminoxane cocatalyst is used in combination with the metallocene catalyst defined above.

[0063] The aluminoxane cocatalyst has the formula (IV): [ka] [In the formula, n is usually 6 to 20, and R has the following meaning] It can be of the following type.

[0064] 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 Y may be 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).

[0065] 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 their aluminum content.

[0066] 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.

[0067] 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, e.g., Al(C1-C6 alkyl)3. Preferred aluminum alkyl compounds are triethylaluminum, triisobutylaluminum, triisohexylaluminum, tri-n-octylaluminum, and triisooctylaluminum.

[0068] Alternatively, when a borate cocatalyst is used, the metallocene complex may be alkylated, for example, a dimethyl or dibenzyl metallocene complex may be used.

[0069] 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 1 to about 1 carbon atoms, an aryl group having 6 to about 15 carbon atoms, an alkylaryl, arylalkyl, haloalkyl, or haloaryl group 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 unsaturated groups such as aryl or haloaryl, such as methyl, propyl, isopropyl, isobutyl, or trifluoromethyl, 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.

[0070] Particularly preferred is tris(pentafluorophenyl)borane.

[0071] However, borate, i.e., the trivalent borate cation (borate 3 + It is preferred to use a compound containing a cation.

[0072] 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.

[0073] 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 tetrakis(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.

[0074] Triphenylcarbenium tetrakis(pentafluorophenyl)borate, N,N-dimethylcyclohexylammonium tetrakis(pentafluorophenyl)borate or N,N-dimethylbenzylammonium tetrakis(pentafluorophenyl)borate are preferred.

[0075] Surprisingly, it has been found that certain boron cocatalysts are particularly preferred.

[0076] 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.

[0077] 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.

[0078] Suitable amounts of cocatalyst are well known to those skilled in the art.

[0079] The molar ratio of boron to metal ion of the metallocene may range 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.

[0080] 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.

[0081] The metallocene catalysts used in the polymerization process of the present invention are used in supported form. The supports used comprise, and preferably consist of, silica. Those skilled in the art are aware of the procedures required for supporting metallocene catalysts.

[0082] 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.

[0083] 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.

[0084] The particle size distribution of the carrier will be described later. The carrier preferably has a D between 10 and 80 μm, more preferably between 18 and 50 μm. 50 Furthermore, the carrier preferably has a D between 5 and 30 μm. 10 and D between 30 and 90 μm 90 Preferably, the carrier has a SPAN value of 0.1 to 1.1, more preferably 0.3 to 1.0.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] In general, silica-supported polymerization catalysts exhibit very complex polymerization behavior, and the polymerization process can be divided into several stages.

[0090] 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, which in turn affects the process performance and reactor operability.

[0091] The above polymerization kinetics necessitate a new design of the prepolymerization process in terms of temperature, monomer concentration and residence time.

[0092] 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.

[0093] In one embodiment, the polymerization is carried out in the presence of hydrogen. Hydrogen is typically used to help control polymer properties, such as the molecular weight of the polymer. In another embodiment, no hydrogen is added in steps a) or c). However, one skilled in the art will appreciate that hydrogen can be generated during the polymerization process. Thus, hydrogen present in the polymerization reaction mixture produced in steps a) or c) of the process may originate from hydrogen added as a reactant and / or hydrogen produced as a by-product during the polymerization.

[0094] 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. Prepolymerization can be carried out to improve the performance of the catalyst in the slurry and / or to modify the properties of the final polymer. The prepolymerization step is typically carried out as a slurry polymerization. The use of a catalyst prepolymerization step offers the advantage of minimizing leaching of catalyst components.

[0095] In step c) of the present invention, lower catalyst activity aids in more precise control of the polymerization reaction and allows easier fine-tuning of process parameters, thus enabling operation closer to ideal conditions, which would otherwise be more difficult to control due to high catalyst activity and less flexibility in adjusting operating conditions.

[0096] The slurry polymerization in step a) is preferably bulk polymerization. By "bulk polymerization" is meant a process in which polymerization is carried out in liquid monomer in the absence of an essentially inert diluent. However, as is well known to those skilled in the art, the monomers used for commercial production are never pure and always contain aliphatic hydrocarbons as impurities. 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, inert components tend to accumulate, and the reaction medium may contain up to 40% by weight of compounds other than monomers. However, it should be understood that such polymerization processes are also within the meaning of "bulk polymerization" as defined above.

[0097] The slurry polymerization, preferably bulk polymerization, can be carried out in any known reactor used for slurry polymerization, including continuous stirred tank reactors and loop reactors. It is particularly preferred to carry out the polymerization in a loop reactor.

[0098] 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 known in the art, and examples are shown, for example, in US-A-4,582,816, US-A-3,405,109, US-A-3,324,093, EP-A-479,186, and US-A-5,391,654. Therefore, it is preferred to carry out the first polymerization stage as a slurry polymerization in a loop reactor.

[0099] The 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 a characteristic amount that depends on the particle's residence time in the prepolymerization reactor. Because some particles remain in the reactor for a relatively long time and others for a relatively short time, the amount of prepolymer on different particles will vary, and individual particles may contain amounts of prepolymer outside the above-specified limits. However, the average amount of prepolymer on the catalyst typically falls within the ranges specified above.

[0100] The molecular weight of the prepolymer can be controlled by hydrogen, as is known in the art. Additionally, antistatic additives may be used to prevent particles from adhering to each other or to the walls of the reactor, as disclosed in WO-A-96 / 19503 and WO-A-96 / 32420.

[0101] 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 1.0 to 5.0% by weight based on the polypropylene copolymer.

[0102] Preferably, the temperature in the first reactor is between 10 and 40°C, more preferably between 10 and 30°C, and most preferably between 15 and 25°C.

[0103] Preferably, the pressure in the first reactor is preferably from 1 to 150 bar, more preferably from 35 to 60 bar, even more preferably from 40 to 55 bar, and most preferably from 43 to 52 bar.

[0104] In step a), the ratio of the amount of ethylene fed to the amount of propylene fed is preferably in the range of 1 to 14 mol / kmol, more preferably in the range of 2 to 13 mol / kmol.

[0105] The average residence time τ 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

[0106] 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.

[0107] 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 4.0 g catalyst / h, or preferably 2.0 to 4.6 g catalyst / h. As a result, the degree of prepolymerization is typically preferably 50 to 2000 g PP / g catalyst, more preferably greater than 510 to 1000 g PP / g catalyst, and most preferably greater than 520 to 700 g PP / g catalyst.

[0108] In step b), the prepolymer obtained in step a) is transferred to a second reactor, preferably directly to the second reactor. Preferably, the prepolymer is transferred to the second reactor in the form of a slurry. The slurry preferably contains the prepolymer, unreacted monomer, and metallocene catalyst.

[0109] The slurry can be withdrawn from the first reactor continuously or intermittently. A preferred method of intermittent withdrawal is the use of settling legs, which thicken the slurry before withdrawing 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 withdrawal 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 withdrawal is advantageously combined with an appropriate thickening method, as disclosed in EP-A-1,310,295 and EP-A-1,591,460. Continuous withdrawal of the slurry from the first reactor is preferred.

[0110] Preferably, the slurry withdrawn from the first reactor is transferred directly to the second reactor to produce the polypropylene copolymer, "directly" meaning that the slurry is introduced from the first reactor to the second reactor without an intervening separation step.

[0111] Like step a), step c) in the second reactor is carried out as a slurry polymerization, which is preferably a bulk polymerization. Preferably, the second reactor is a loop reactor.

[0112] Preferably, the 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. 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.

[0113] 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).

[0114] In step c), the ratio of the amount of comonomer fed to the amount of propylene fed is preferably in the range of 1 to 15 mol / kmol, preferably 1.5 to 10 mol / kmol, more preferably 2 to 9 mol / kmol.

[0115] In step c), the one or more comonomers are selected from alpha-olefins having 2 or 4 to 10 carbon atoms or mixtures thereof. Preferably, the one or more comonomers are alpha-olefins having 2 or 4 carbon atoms, i.e., ethylene or 1-butene, most preferably alpha-olefins having 2 carbon atoms, i.e., ethylene.

[0116] Hydrogen is typically introduced into the polymerization stage in step c) to control the MFR2 of the propylene copolymer. 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.

[0117] The average residence time in the polymerization stage of step c) is typically 20 to 120 minutes, preferably 30 to 80 minutes, see formula (1) above.

[0118] The production rate is appropriately controlled by the catalyst feed rate. The production rate can also be influenced by the appropriate selection of the monomer concentration. The desired monomer concentration can then be achieved by appropriately adjusting the propylene feed rate.

[0119] It will be appreciated that the propylene polymer may contain standard polymer additives. These typically form less than 5.0% by weight, e.g., 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.

[0120] In a further preferred embodiment of the present invention, the polymerization process does not include a step of recovering the comonomer.

[0121] The production split between the prepolymer of step a) and the polypropylene copolymer 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%.

[0122] In step d), the polypropylene copolymer obtained in step c) is either withdrawn from the second reactor or transferred to a third reactor, preferably the polypropylene copolymer obtained in step c) is transferred to the third reactor.

[0123] Preferably, the third reactor is a gas phase reactor, more preferably a fluidized bed gas phase reactor.

[0124] Preferably, the third reactor is a gas phase reactor, more preferably a fluidized bed gas phase reactor. Any suitable gas phase reactor known in the art may be used, such as a fluidized bed gas phase reactor.

[0125] For gas-phase reactors, the reaction temperature used is generally in the range of 65-90°C, and the reactor pressure is generally in the range of 10-40 bar. The gas used is generally a non-reactive gas such as nitrogen, or a low-boiling hydrocarbon such as propane together with a monomer (e.g., ethylene). Preferably, the temperature is in the range of 65-90°C, more preferably 70-85°C. Preferably, the pressure is in the range of 15-26 bar, more preferably 20-25 bar.

[0126] Also, the residence time and / or the comonomer(s) present in the third reactor are preferably the same as those described for the second reactor above.

[0127] The process according to the present invention can not only use the first reactor as a prepolymerization reactor followed by the second reactor, but also preferably 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, 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 further polymerization.

[0128] 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 third reactor.

[0129] 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 0887379 A1 and EP 0517868 A1. [Example]

[0130] Experimental Part Measurement method All of the parameters mentioned above in the detailed description of the invention are measured according to the tests set out below.

[0131] a) Melt flow rate Melt flow rate (MFR) is measured according to ISO 1133 and is expressed in units of g / 10 min. MFR indicates the melt viscosity of the polymer. MFR is measured at 190°C for PE and 230°C for PP. The load at which the melt flow rate is measured is usually indicated by a subscript, e.g., MFR2 is measured under a 2.16 kg load (condition D).

[0132] b) Particle size and particle size distribution Particle size distribution was determined by laser diffraction measurement 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 obtained by dividing a given percentage of the sample mass when the particles are arranged in ascending order of mass. For example, D10 is the diameter at which 10% of the sample mass is made up of particles with a diameter less than this value. D50 is the diameter at which 50% of the sample mass is smaller than this value and 50% is larger than this value. D90 is the diameter at which 90% of the sample mass is made up of particles with a diameter less than this value. The D50 value is also called the median particle size. The volumetric D values ​​based on the volume distribution can be obtained from laser diffraction measurements according to ISO 13320.

[0133] The distribution width or span of the particle size distribution is given by equation (3):

number

[0134] The sieve fraction is determined by digital image analysis on a Camsizer P4 from the company Retsch Technology GmbH. The measurement principle is dynamic image analysis according to ISO 13322-2.

[0135] c) density The density of the polymers was measured according to ISO 1183 / 1872-2B. For the purposes of this invention, the density of the blend is calculated from the densities of the components as follows:

number

[0136] d) Differential Scanning Calorimetry (DSC) Differential scanning calorimetry (DSC) analysis, melting temperature (T m ) and enthalpy of fusion (H m ), crystallization temperature (T c ), and heat of crystallization (H c , H cr ) is measured on 5-7 mg samples using a TA Instruments Q200 Differential Scanning Calorimeter (DSC). DSC is performed in accordance with ISO 11357 / Part 3 / Method C2 in the temperature range of -30 to +225°C, with a scan rate of 10°C / min, using heat / cool / heat cycles.

[0137] Crystallization temperature (T c ) and heat of crystallization (H c ) is measured from the cooling process, and the melting temperature (T m ) and enthalpy of fusion (H m ) is measured from the second heating step.

[0138] Throughout this patent, T c or (T cr The term ) is understood as the crystallization peak temperature measured by DSC at a cooling rate of 10 K / min (i.e. 0.16 K / s).

[0139] e) Quantification of microstructure by NMR spectroscopy Quantitative nuclear magnetic resonance (NMR) spectroscopy was used to quantify the comonomer content, comonomer dyad sequence distribution, and sequence order parameter quantification of the polymers.

[0140] quantitative 13 C{ 1 The {H} NMR spectrum 1 H and 13All spectra were recorded in solution using a Bruker Avance III 400 NMR spectrometer operating at 400.15 and 100.62 MHz for C, respectively. 13 Recordings were made at 125 °C using a 10 mm extended temperature probe head optimized for C, with nitrogen gas used for all pneumatic systems. Approximately 200 mg of material was dissolved in 3 ml of 7,2-tetrachloroethane-d / 2 (TCE-d / 2) along with chromium(III) acetylacetonate (Cr(acac)3) to obtain a 65 mM solvent solution of the relaxation agent (Singh, G., Kothari, A., Gupta, V., Polymer Testing 28 5 (2009), 475). After initial sample preparation in a heat block to ensure a homogeneous solution, the NMR tube was further heated in a rotary oven for at least 1 h. After insertion into the magnet, the tube was spun at 10 Hz. This setup was chosen primarily for its high resolution and the need for accurate ethylene content quantification. Standard single-pulse excitation was used without NOE, using an optimized tip angle, a 1-second recycle delay, and bilevel WALTZ16 decoupling (Zhou, Z., Kuemmerle, R., Qiu, X., Redwine, D., Cong, R., Taha, A., Baugh, D., Winniford, B., J. Mag. Reson. 187 (2007) 225; Busico, V., Carbonniere, P., Cipullo, R., Pellecchia, R., Severn, J., Talarico, G., Macromol. Rapid Commun. 2007, 28, 1 128). A total of 6144 (6k) transients were acquired per spectrum.

[0141] Quantification of the comonomer content of poly(propylene-co-ethylene) copolymers quantitative 13 C{ 1The {H} NMR spectra were processed and integrated using a proprietary computer program, and relevant quantitative properties were determined from the integrals. All chemical shifts were indirectly referenced to the central methylene group of the ethylene block (EEE) at 30.00 ppm using the chemical shift of the solvent. This method allowed for comparative reference even in the absence of this structural unit. Characteristic signals corresponding to the incorporation of ethylene were observed (Cheng, HN, Macromolecules 17 (1984), 1950), and the comonomer fraction was calculated as the fraction of ethylene and propylene in the polymer relative to the total monomers in the polymer:

[0142] The comonomer fraction was calculated using the method of Wang et al. (Wang, WJ., Zhu, S., Macromolecules 33 (2000), 1157). 13 C{ 1 Quantification was performed by integration of multiple signals over the entire spectral range of the {H} spectrum. This method was chosen due to its robust nature and ability to take into account the presence of regio-defects when necessary.

[0143] The molar percentage of comonomer incorporation was calculated from the mole fraction.

number

[0144] The weight percentage of comonomer incorporation was calculated from the mole fraction.

number

[0145] Determination of comonomer dyad sequences The distribution of comonomer sequences was quantified at the dyad level using the characteristic signal corresponding to the incorporation of ethylene into propylene-ethylene copolymers (Cheng, HN, Macromolecules 17 (1984), 1950). Integration of each site was performed separately, and the integration area described in Wang et al. was not applied to quantify the dyad sequences.

[0146] Since the Tβδ and Sγγ signals overlap, the integral range of these signals is corrected using the Sβδ and Sγδ regions using the formula:

number

[0147] Since characteristic signals corresponding to regio-defects were observed (Resconi, L, Cavallo, L, Fait, A., Piemontesi, F., Chem.REV. 2000, 100, 1253; Cheng, HN, Macromolecules 17 (1984), 1950; Wang, WJ., Zhu, S., Macromolecules 33 (2000), 1157), it was necessary to correct for the effect of regio-defects on the comonomer content.

[0148] In the presence of a 2,1-erythro misinsertion, the signal from the ninth carbon (S2ie 9) of this fine structure element (Resconi, L., Cavallo, L., Fait, A., Piemontesi, F., Chem.Rev. 2000, 100, 1253) was selected for correction.

[0149] In the case of 2,1-regioirregular propene units in structures with one consecutive ethylene unit, the signal from Tγγ (Cheng, HN, Macromolecules 17 (1984), 1950; Wang, WJ., Zhu, S., Macromolecules 33 (2000), 1157) was selected for the calibration. The constitutive formula is:

number

[0150] Note that for simplicity, the two indistinguishable, reversible PE and EP dyads are referred to as EP, i.e., EP = PE + EP. The mole fraction of each dyad was determined by normalizing it to the sum of all dyads.

number

[0151] Description and quantification of sequence order parameters The sequence order parameter X, as defined by Koenig (Koenig92: Spectroscopy of Polymers, Lack. L Koenig. American Chemical Society, Washington, DC 1992) (or named "Koenig-B value" in WO 2010 / 078479 A1), provides information on whether the distribution of structures is random, i.e., can be described by Bernoulli statistics, and whether it tends towards an alternating or block distribution. This parameter is given by the following formula:

number

[0152] f) Cold xylene soluble fraction The xylene cold soluble fraction (XCS) is determined at 25°C according to ISO 16152.

[0153] material The following catalysts were used in the comparative and inventive processes listed in Table 1:

[0154] A metallocene catalyst as described in WO 2019 / 179959 A1 was used. [ka]

[0155] A steel reactor equipped with a mechanical stirrer and 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 43.5 kg of toluene at 90°C, then settled and filtered.

[0156] Finally, the MAO-treated SiO2 was dried under a nitrogen stream at 60°C for 2 hours and then under vacuum (~0.5 barg) with stirring for 14 hours. The MAO-treated support was recovered as a free-flowing white powder and was found to contain 15.0 wt% Al. A 30 wt% MAO solution in toluene (2 kg) was added via burette to a nitrogen-blanked steel reactor at 20°C. Toluene (12.8 kg) was then added with stirring. 129 g of the 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 to the stirred cake of MAO-silica support prepared above over 2 hours. 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.

[0157] example The following examples were carried out in a pilot plant containing a reactor arrangement consisting of a prepolymerization reactor and a loop reactor. The process and properties are shown in Table 1.

[0158] [Table 1]

[0159] As can be seen from the table, the bulk density improved stepwise with increasing ethylene feed rate to the prepolymerization reactor.

Claims

1. 1. A method for producing a polypropylene copolymer, the method comprising the steps of: a) prepolymerizing propylene in the presence of ethylene and a metallocene catalyst in a first reactor to obtain a prepolymer, wherein the ratio of the ethylene feed rate to the propylene feed rate is in the range of 0.1 to 15 mol / kmol; b) transferring the prepolymer to a second reactor; c) polymerizing propylene in a second reactor in the presence of said prepolymer and one or more comonomers selected from alpha olefins having 2 or 4 to 10 carbon atoms or mixtures thereof to obtain a polypropylene copolymer; d) removing the polypropylene copolymer from the second reactor or transferring the polypropylene copolymer to a third reactor. Including, the metallocene catalyst comprises a metallocene complex and a support, the support comprising silica; The metallocene complex is an organometallic compound (C), and the organometallic compound (C) has the formula (I): (L) mRnMXq (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 that links 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). A method comprising:

2. The method of claim 1, wherein the carrier has an average particle size of 10 to 100 μm as determined in accordance with the present specification.

3. 3. The method of claim 1, wherein the support has an average pore size determined in accordance with the present specification of between 10 and 100 nm.

4. 4. The method according to claim 1, wherein the ratio of the amount of ethylene fed to the amount of propylene fed in step a) is in the range of 1 to 14 mol / kmol.

5. 5. The process according to claim 1, wherein the average residence time in the first reactor in step a) is from 0.05 to 0.5 hours.

6. 6. The process according to claim 1, wherein the ratio of the comonomer feed rate to the propylene feed rate in step c) is in the range of 1 to 15 mol / kmol.

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

8. The process according to any one of claims 1 to 7, wherein step a) is carried out as a prepolymerization step and is carried out in a slurry.

9. The process according to any one of claims 1 to 8, wherein the first reactor is a loop reactor.

10. 10. The process according to any one of claims 1 to 9, wherein step c) is carried out as a slurry polymerization and / or the second reactor is a loop reactor.

11. 11. The process according to any one of claims 1 to 10, wherein in step a) the temperature in the first reactor is between 10 and 40°C, and / or in step a) the pressure in the first reactor is between 1 and 150 bar.

12. 12. The method according to any one of claims 1 to 11, wherein in step c) the temperature in the second reactor is between 60 and 90°C, and / or in step c) the pressure in the second reactor is between 1 and 150 bar.

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. The process of any one of claims 1 to 13, further comprising a fourth reactor downstream of the third reactor.

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