Catalyst conversion process

Abstract

A process for switching between two different catalysts during the production of a polypropylene homopolymer or copolymer in a continuous multi-stage polymerization reaction, the process comprising the steps of: a) in the presence of a first catalyst, in a multi-stage polymerization reactor system comprising a pre-polymerization reactor, a subsequent slurry reactor and a gas phase reactor; polymerizing propylene and optionally a comonomer; b) stopping feeding the first catalyst into the prepolymerization reactor; c) subsequently introducing propylene, optionally a comonomer and a second catalyst into the prepolymerization reactor and introducing aluminum alkyl into the polymerization reactor while introducing the second catalyst; d) polymerizing propylene and optionally a comonomer in the presence of a second catalyst in a multi-stage polymerization reactor system; wherein the first catalyst is a Ziegler-Natta catalyst and the second catalyst is a single site catalyst; and the feed amount of aluminum alkyl in step c) is from 0.5 to 10.0 grams per ton of total propylene fed to the prepolymerization reactor and the slurry reactor in steps c) and d).

Description

[0001] The present invention relates to a method for converting polymerizations occurring in a multi-stage reactor system from polymerizations using Ziegler-Natta catalysts to polymerizations using single-site catalysts, such as metallocene catalysts. Specifically, the present invention addresses the problem of restarting polymerizations after the conversion, as residual catalyst poisons after Ziegler-Natta (ZN) polymerizations can limit the catalytic activity of single-site catalysts. Background Art

[0002] During the production of olefin polymers in commercial reactors, it is usually necessary to convert from a catalyst system that produces a polymer with certain properties and characteristics to another catalyst system that can produce a polymer with different chemical and / or physical attributes. In the past, in order to achieve effective conversion between incompatible catalysts, the first catalytic olefin polymerization process was stopped by various techniques known in the art. The reactor was then emptied, cleaned, recharged, and a second catalyst was introduced into the reactor. Owing to the need to shut down the reactor for a long time during the conversion process, this catalyst conversion was both time-consuming and costly.

[0003] Another conversion method involves interrupting the polymerization of the first catalyst system to stop polymerization and introducing the second catalyst system into the polymerization reactor. However, stopping the first catalyst system from feeding the reactor does not immediately stop the polymerization reaction occurring within the reactor. As a result, both catalysts may produce polymer simultaneously for a period of time, resulting in the formation of "off-spec" product over a potentially prolonged period of time. The production of off-spec product is not only costly but also time-consuming.

[0004] Because active Ziegler-Natta catalysts are known to "poison" active metallocene catalysts, switching from one catalyst system to another is often complex. For example, switching from Ziegler-Natta to metallocene catalysts, or vice versa, typically requires a lengthy transition period. Furthermore, the properties of the polyolefins produced during this transition period will continue to change. If switching from one catalyst system to another requires significant changes in reactor conditions, the risk of encountering production problems and producing polymers with extreme properties is high.

[0005] Therefore, a new conversion method is needed that requires less reactor downtime and enables the transition from ZN to single-site catalysts without reactor fouling and other issues. Such a method should minimize the conversion time to produce the target second polymer product as quickly as possible. Importantly, the effects of catalyst poisons on single-site catalysts should be minimized.

[0006] The possibility of switching between catalysts is described in the literature. EP-A-0751965 describes a method for switching from a polymerization reaction catalyzed by a first catalyst to a polymerization reaction catalyzed by a second catalyst, including a metallocene catalyst, wherein the first and second catalysts are incompatible. This method requires stopping the feed of the first catalyst before using an irreversible catalyst killer to stop the catalytic activity. Examples of catalyst scavengers are CO and CO2.

[0007] A process for switching from a first polymerization reaction carried out in the presence of a first catalyst system to a second polymerization reaction carried out in the presence of a second catalyst system is described in EP-A-1 578 808. In addition to careful control of the fluidized bed set-up, the present invention also employs alkoxylated amides or amines between the steps.

[0008] EP-A-1620472 describes a polymerization process in which a catalyst scavenger is used to terminate a first polymerization reaction, thereby allowing a second catalyst system to be introduced into the polymerization reactor in the presence of a catalyst killer. Exemplary catalyst killers include one or more compounds selected from the group consisting of water, oxygen, alcohols, glycols, phenols, ethers, carbonyl compounds such as ketones, aldehydes, carboxylic acids, esters, fatty acids, hydrocarbons such as acetylene, amines, nitrites, nitrous compounds, pyridine, pyrrole, carbonyl sulfide (COS), mercaptans, derivatives thereof, or any mixture or combination thereof.

[0009] EP-A-3237458 describes a process for switching from a first continuous polymerization reaction to a second polymerization reaction in which the catalysts are incompatible. A catalyst scavenger is used to deactivate the first catalyst.

[0010] EP-A-3394111 claims a process for switching from a first continuous polymerization carried out in a gas phase reactor in the presence of a metallocene catalyst to a second polymerization carried out in a gas phase reactor in the presence of a Ziegler-Natta catalyst, wherein the metallocene catalyst and the Ziegler-Natta catalyst are incompatible. The metallocene catalyst is deactivated using cyclohexylamine before the organometallic compound is introduced and reacted with the cyclohexylamine.

[0011] EP-A-1182216 relates to a process for switching between two different catalysts in olefin polymerization. The process switches between a chromium oxide-based catalyst and a metallocene catalyst in the absence of any substances that deactivate or eliminate the catalyst.

[0012] WO 2010086392 describes a method for switching between two different catalysts during the production of polypropylene homopolymer or copolymer in a continuous slurry / gas phase polymerization reaction, wherein a prepolymerization reaction is previously carried out in the continuous slurry / gas phase polymerization reaction, the method comprising the following steps:

[0013] (a) stopping feeding the first catalyst to the prepolymerization reactor; and then

[0014] (b) introducing a second catalyst into a prepolymerization reactor,

[0015] (c) adjusting the reaction conditions in the prepolymerization reactor, the slurry reactor and the subsequent gas phase reactor,

[0016] wherein the conversion is carried out between a Ziegler-Natta catalyst and a self-supporting solid metallocene catalyst prepared by using an emulsification / solidification technique, or vice versa, whereby the conversion is carried out in the absence of any additional reagents that deactivate or inactivate the catalyst. There is no disclosure of flushing the alkyl aluminum once the ZN catalyst feed is stopped, nor is there any disclosure of flushing the alkyl aluminum once the external donor feed is stopped. A significant problem with the conversion from ZN to single-site catalysis is the slow start-up of the single-site catalytic polymerization after the conversion. The main reason for the slow start-up is the catalyst poisons present in the ZN polymerization. These poisons include the external donor used in the ZN polymerization and any antistatic agent that may be present in the ZN reaction. Other poisons include water and oxygen. Single-site catalysts are very sensitive to catalyst poisons, mainly because the content of active metals in such catalysts is low and no external co-catalyst is used in single-site catalysts.

[0017] The present inventors have realized that the addition of an aluminum alkyl scavenger after the first ZN can significantly reduce the effects of these poisons, allowing for the rapid production of an "on-spec" second polymer product. The presence of this aluminum alkyl additive overcomes the negative effects of any catalyst poisons that may be present.

[0018] In one embodiment, the present invention requires the use of an aluminum alkyl flush between polymerization steps to reduce or eliminate the effects of catalyst poisons on single-site catalysts. In a second embodiment, the present invention utilizes an aluminum alkyl feed shortly before or simultaneously with the addition of the second catalyst to significantly reduce the effects of these poisons. Optionally, these two embodiments can be used together. Summary of the Invention

[0019] Viewed from one aspect, the present invention provides a method for switching between two different catalysts in a continuous multi-stage polymerization process for producing polypropylene homopolymer or copolymer, the method comprising the steps of:

[0020] a) polymerizing propylene and optionally a comonomer in the presence of a first catalyst in a multistage polymerization reactor system comprising a prepolymerization reactor, a subsequent slurry reactor and then a gas phase reactor;

[0021] b) stopping feeding the first catalyst into the prepolymerization reactor;

[0022] c) subsequently introducing propylene, optional comonomers and a second catalyst into a prepolymerization reactor and simultaneously introducing an aluminum alkyl into the polymerization reactor;

[0023] d) polymerizing propylene and optionally a comonomer in the presence of a second catalyst in a multi-stage polymerization reactor system;

[0024] wherein the first catalyst is a Ziegler-Natta catalyst and the second catalyst is a single-site catalyst; and

[0025] The feed amount of the alkyl aluminum in step c) is 0.5 to 10.0 g per ton of total propylene fed to the prepolymerization reactor and the slurry reactor in steps c) and d) (i.e., 0.5 to 10.0 g per 1000 kg).

[0026] Viewed from another aspect, the present invention provides a method for switching between two different catalysts in a continuous multi-stage polymerization process for producing polypropylene homopolymer or copolymer, the method comprising the steps of:

[0027] a) polymerizing propylene and optionally a comonomer in the presence of a first catalyst in a multistage polymerization reactor system comprising a prepolymerization reactor, a subsequent slurry reactor and then a gas phase reactor;

[0028] b) stopping feeding the first catalyst into the prepolymerization reactor;

[0029] c-1) introducing an alkyl aluminum compound into a prepolymerization reactor;

[0030] c-2) subsequently introducing propylene, optional comonomers and a second catalyst into a prepolymerization reactor;

[0031] d) polymerizing propylene and optionally a comonomer in the presence of a second catalyst in a multi-stage polymerization reactor system;

[0032] wherein the first catalyst is a Ziegler-Natta catalyst and the second catalyst is a single-site catalyst; and

[0033] The feed amount of the alkyl aluminum in step c-2) is 0.5 to 10.0 g per ton of total propylene fed to the prepolymerization reactor and slurry reactor in steps c-2) and d) (i.e., 0.5 to 10.0 g per 1000 kg).

[0034] In some embodiments, it may also be considered that the aluminum alkyl is fed in an amount of 0.5 to 10.0 g / hr per ton of total propylene fed to the prepolymerization reactor and slurry reactor in steps c) and d) (ie, 0.5 to 10.0 g / hr per 1000 kg).

[0035] Viewed from a second aspect, the present invention provides a method for switching between two different catalysts in a continuous multi-stage polymerization process for producing polypropylene homopolymer or copolymer, the method comprising the steps of:

[0036] a) polymerizing propylene and optionally a comonomer in the presence of a first catalyst in a multistage polymerization reactor system comprising a prepolymerization reactor, a subsequent slurry reactor and a gas phase reactor;

[0037] b) stopping feeding the first catalyst into the prepolymerization reactor;

[0038] c) subsequently introducing propylene, optional comonomers and a second catalyst into a prepolymerization reactor;

[0039] d) polymerizing propylene and optionally a comonomer in the presence of a second catalyst in a multi-stage polymerization reactor system;

[0040] wherein the first catalyst is a Ziegler-Natta catalyst and the second catalyst is a single-site catalyst;

[0041] wherein between steps b) and c) propylene and an aluminium alkyl are introduced into a prepolymerisation reactor, wherein the amount of the aluminium alkyl is from 100 to 300 g / ton, i.e. from 100 to 300 g per 1000 kg of propylene introduced into this step, i.e. propylene is fed to the prepolymerisation reactor between steps b) and c).

[0042] In this second aspect, the aluminum alkyl is introduced into the prepolymerization reactor only after step b), i.e., after the feed of the first catalyst to the prepolymerization reactor is stopped. In other words, the aluminum alkyl feed is started only after step b). Preferably, the aluminum alkyl is introduced as a flushing liquid after step b) and before step c).

[0043] Preferably, the amount of aluminum alkyl fed after step b) is 0.5 to 10.0 g per ton of total propylene fed to the prepolymerization reactor and slurry reactor in steps c) and d) (ie 0.5 to 10.0 g per 1000 kg).

[0044] Thus, viewed from another perspective, the present invention provides a method for switching between two different catalysts in a continuous multi-stage polymerization process for producing polypropylene homopolymer or copolymer, the method comprising the steps of:

[0045] a) polymerizing propylene and optionally a comonomer in the presence of a first catalyst in a multistage polymerization reactor system comprising a prepolymerization reactor, followed by a slurry reactor and a gas phase reactor;

[0046] b) stopping feeding the first catalyst into the prepolymerization reactor;

[0047] c-1) introducing propylene and an aluminum alkyl into the prepolymerization reactor, preferably in the form of a flush, wherein the amount of aluminum alkyl is from 100 to 300 g / ton, i.e. from 100 to 300 g per 1000 kg of propylene introduced into this step, i.e. fed to the prepolymerization reactor between steps b) and c-2);

[0048] c-2) subsequently introducing propylene, optional comonomers and a second catalyst into a prepolymerization reactor;

[0049] d) polymerizing propylene and optionally a comonomer in the presence of a second catalyst in a multi-stage polymerization reactor system;

[0050] The first catalyst is a Ziegler-Natta catalyst and the second catalyst is a single-site catalyst.

[0051] And preferably, the feed amount of the alkyl aluminum in step c-2) is 0.5 to 10.0 g per ton of total propylene fed to the prepolymerization reactor and the slurry polymerization reactor in steps c-2) and d).

[0052] In this embodiment, it is also conceivable to introduce propylene and an aluminum alkyl into the prepolymerization reactor, wherein the amount of aluminum alkyl is from 100 to 300 g / h, based on the tons of propylene introduced per hour in this flushing step c-1).

[0053] Most preferably, the present invention provides a method for switching between two different catalysts during the production of polypropylene homopolymer or copolymer in a continuous multi-stage polymerization reaction, the method comprising the steps of:

[0054] a) polymerizing propylene and optionally a comonomer in the presence of a first catalyst in a multistage polymerization reactor system comprising a prepolymerization reactor, followed by a slurry reactor and a gas phase reactor;

[0055] b) stopping feeding the first catalyst into the prepolymerization reactor;

[0056] c-1) introducing propylene and an aluminum alkyl into a prepolymerization reactor, wherein the amount of the aluminum alkyl is from 100 to 300 g / ton, i.e. from 100 to 300 g per 1000 kg of propylene introduced into this step;

[0057] c-2) adjusting the feed amount of aluminum alkyl so as to provide 0.5 to 10.0 g of aluminum alkyl per ton of total propylene fed to the prepolymerization reactor and the slurry reactor in steps c-3) and d) (i.e., 0.5 to 10.0 g per 1000 kg);

[0058] c-3) subsequently introducing propylene, optional comonomers and a second catalyst into a prepolymerization reactor;

[0059] d) polymerizing propylene and optionally a comonomer in the presence of a second catalyst in a multi-stage polymerization reactor system;

[0060] The first catalyst is a Ziegler-Natta catalyst, and the second catalyst is a single-site catalyst.

[0061] definition

[0062] The term "first polymer product" is used to define the target polypropylene produced in the ZN catalyzed polymerization process, for example a first propylene homopolymer.

[0063] The term "second polymer product" is used to define the target polypropylene produced in a single-site catalytic polymerization process, such as a second propylene homopolymer.

[0064] The method of the present invention is carried out in a multistage polymerization reactor system comprising a prepolymerization reactor, at least one slurry reactor, and at least one gas-phase reactor. Thus, the ZN catalytic process involves a first prepolymerization reaction, a first slurry polymerization reaction, and a first gas-phase polymerization reaction. These reactions occur in the multistage polymerization reactor system, namely, in the prepolymerization reactor, at least one slurry reactor, and at least one gas-phase reactor, respectively.

[0065] Thus, the single-site catalytic process will involve a second prepolymerization reaction, a second slurry polymerization reaction and a second gas phase polymerization reaction. These polymerization reactions take place in the same multi-stage polymerization reactor system, i.e., in a prepolymerization reactor, at least one slurry reactor and at least one gas phase reactor, respectively.

[0066] It will be appreciated that the first and second polymerization reactions actually occur in the same vessel.

[0067] The term "aluminum alkyl" defines a compound consisting of aluminum bonded to three alkyl groups. Alkyl aluminum compounds do not contain halogen groups.

[0068] Detailed Description of the Invention

[0069] The present invention relates to a method for switching between ZN and single-site catalysts in a continuous multistage reaction, in particular in a multistage polymerization process, wherein there is a multistage polymerization reactor system comprising a prepolymerization reactor, a slurry reactor and a gas phase reactor.

[0070] Therefore, it is initially envisaged that the multistage polymerization reactor system will carry out a propylene polymerization reaction catalysed by a ZN catalyst (first polymerization). After the switch, the multistage polymerization reactor system will carry out a propylene polymerization reaction catalysed by a single-site catalyst, in particular a metallocene (second polymerization). The present invention explains how to ensure a smooth switch between the two processes.

[0071] The properties of the two catalysts are first described, followed by the polymerization process before and after the switch and the details of how the switch was achieved.

[0072] catalyst

[0073] Ziegler-Natta (ZN) catalyst

[0074] The Ziegler-Natta catalyst can be any Ziegler-Natta catalyst known in the art. The Ziegler-Natta catalyst typically used in the present invention for propylene polymerization is a stereospecific, solid, high-yield Ziegler-Natta catalyst component comprising compounds of Mg, Ti, and Cl, and an internal donor component. In addition to the solid catalyst component, a cocatalyst and an external donor are typically used in propylene processes.

[0075] The catalyst component can be supported on a particulate support, for example an inorganic oxide such as silica or alumina, or a magnesium halide can form a solid support. The solid catalyst component can also be prepared by emulsion solidification or precipitation.

[0076] The solid catalyst component for propylene polymerization generally consists of an internal electron donor and an aluminum compound as a cocatalyst. Suitable internal electron donors include esters of carboxylic acids or dicarboxylic acids, such as phthalates, unsubstituted or substituted malonates, unsubstituted or substituted maleates, ethers and diethers or oxygen- or nitrogen-containing silicon compounds, or mixtures thereof.

[0077] The optional aluminum cocatalyst used in conjunction with the catalyst preparation is generally selected from aluminum alkyls, aluminum alkyl halides, aluminum alkyl alkoxides or aluminum alkyl halide alkoxide compounds wherein the alkyl group contains 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, and especially 1 to 6 carbon atoms.

[0078] The cocatalyst typically comprises a trialkylaluminum or alkylaluminum halide compound, wherein the alkyl group typically contains 1 to 20 carbon atoms, for example 1 to 10 carbon atoms. The alkylaluminum compound is preferably a trialkylaluminum, such as trimethylaluminum, triethylaluminum (TEAL), triisobutylaluminum, tri-n-octylaluminum. Alkylaluminum halides of interest include dialkylaluminum halides, alkylaluminum dihalides, or alkylaluminum sesquihalides, such as diethylaluminum chloride, dimethylaluminum chloride, ethylaluminum dichloride, or ethylaluminum sesquichloride.

[0079] To activate the catalyst, a cocatalyst is used in combination with the ZN catalyst. Preferably, the cocatalyst is an alkyl aluminum compound. TEAL is particularly preferred.

[0080] External donors are also commonly used in ZN polymerization processes. Suitable external electron donors for propylene polymerization are well known in the art and include ethers, ketones, amines, alcohols, phenols, phosphines, esters, and silanes. Silane-based external donors are typically organosilane compounds containing Si-OCOR, Si-OR, or Si-NR2 bonds, with silicon as the central atom and R being an alkyl, alkenyl, aryl, aralkyl, or cycloalkyl group having 1 to 20 carbon atoms, as known in the art.

[0081] Preferred external donors are silane donors including diisopropyldiethoxysilane (DIPDES), cyclohexylmethyldiethoxysilane (CHMDES), dicyclopentyldimethoxysilane (DCPDMS), cyclohexylmethyldimethoxysilane and dicyclopentadienyldiethoxysilane (DCPDES) and diethylaminotriethoxysilane.

[0082] The amount of external donor used may be from 2 wt ppm to 70 wt ppm, preferably from 5 wt ppm to 50 wt ppm, based on the weight of propylene fed to the first prepolymerization reactor and the first slurry reactor.

[0083] Examples of suitable catalysts and compounds in the catalyst are shown in WO 87 / 07620, WO 92 / 21705, WO 93 / 11165, WO 93 / 11166, WO 93 / 19100, WO 97 / 36939, WO 98 / 12234, WO 99 / 33842, WO 03 / 000756, WO 03 / 000757, WO 03 / 000754, WO 03 / 000755, WO 2004 / 029112, EP 2610271, WO 2012 / 007430, WO 92 / 19659, WO 92 / 19653, WO 92 / 19658, US 4382019, US 4435550, US 4465782, US 4473660, US 4560671, US 5539067, US5618771, EP45975, EP45976, EP45977, WO95 / 32994, US 4107414, US 4186107, US 4226963, US 4347160, US 4472524, US 4522930, US 4530912, US 4532313, US 4657882, US 4581342 and US 4657882.

[0084] The Ziegler-Natta catalyst used is most preferably a solid Ziegler-Natta catalyst selected from the group consisting of a MgCl2-supported titanium Ziegler-Natta catalyst and a self-supported solid Ziegler-Natta catalyst.

[0085] In general, the present invention relates to a method for converting a process catalyzed by a conventional ZN catalyst to a process catalyzed by a conventional single-site catalyst. The specific nature of the ZN catalyst is not critical, but it is preferred if the ZN process involves the use of an alkylaluminum cocatalyst compound. It is also preferred if the single-site process utilizes an alkylaluminum cocatalyst.

[0086] The present inventors have recognized that adding an aluminum alkyl scavenger after the first ZN reaction significantly reduces the effects of poisons, allowing for rapid production of an "on-spec" second polymer product. The presence of this aluminum alkyl additive overcomes the negative effects of any catalyst poisons that may be present. Therefore, these principles are generally applicable to Ziegler-Natta catalysts, and since the poisons have been removed, the use of aluminum alkyls can successfully transition to any single-site catalyst.

[0087] Single-site catalyst

[0088] The single-site catalyst is preferably a metallocene catalyst or a non-metallocene catalyst. The single-site catalyst preferably comprises a transition metal compound containing at least one cyclopentadienyl, indenyl or fluorenyl ligand. Preferably, the single-site catalyst contains two cyclopentadienyl, indenyl or fluorenyl ligands, in particular two bridged cyclopentadienyl, indenyl or fluorenyl ligands. In addition, the ligand may have a substituent, for example, an alkyl, aryl, aralkyl, alkaryl, silyl, siloxy, alkoxy or other heteroatom groups. Examples of suitable metallocene compounds are shown 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.

[0089] The single-site catalyst 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 from the actinides or lanthanides. According to the present invention, the term "organometallic compound (C)" comprises any metallocene compound of a transition metal which carries at least one organic (coordinating) ligand and which exhibits catalytic activity alone or in combination with a cocatalyst. Transition metal compounds are well known in the art, and the present invention encompasses compounds of metals from Groups 3 to 10, e.g., Groups 3 to 7 or Groups 3 to 6, e.g., Groups 4 to 6, of the Periodic Table of the Elements (IUPAC 2007), as well as compounds of lanthanides or actinides.

[0090] In one embodiment, the organometallic compound (C) has the following formula (I):

[0091] (L) m R n MX q (I)

[0092] in

[0093] “M” is a transition metal (M) from Groups 3 to 10 of the Periodic Table of the Elements (IUPAC 2007);

[0094] Each "X" is independently a monoanionic ligand, such as a σ-ligand;

[0095] Each "L" is independently an organic ligand coordinated to the transition metal "M";

[0096] "R" is a bridging group connecting the organic ligand (L);

[0097] "m" is 1, 2 or 3, preferably 2;

[0098] "n" is 0, 1 or 2, preferably 1;

[0099] "q" is 1, 2 or 3, preferably 2; and

[0100] m+q equals the valence of the transition metal (M).

[0101] “M” is preferably selected from zirconium (Zr), hafnium (Hf) or titanium (Ti), and more preferably selected from the group consisting of zirconium (Zr) and hafnium (Hf).

[0102] In a more preferred definition, each organic ligand (L) is independently

[0103] (a) substituted or unsubstituted cyclopentadienyl or a bicyclic or polycyclic derivative of cyclopentadienyl, which optionally carries further substituents and / or one or more heteroatoms from Groups 13 to 16 of the Periodic Table of the Elements (IUPAC); or

[0104] (b) acyclic η composed of atoms from Groups 13 to 16 of the Periodic Table of Elements 1 - to η 4 - or η 6 - ligands, wherein the open-chain ligands may be fused to one or two, preferably two, aromatic or non-aromatic rings and / or carry further substituents; or

[0105] (c) Cyclic η consisting of unsubstituted or substituted monocyclic, bicyclic or polycyclic ring systems 1 - to η 4 - or η 6- a monodentate, bidentate or polydentate ligand, the mono-, bi- or polycyclic ring system being selected from aromatic or 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.

[0106] The organometallic compound (C) preferably used in the present invention has at least one organic ligand (L) belonging to the above-mentioned group (a). Such an organometallic compound is called a metallocene.

[0107] More preferably, at least one organic ligand (L), preferably two organic ligands (L), are selected from the group consisting of cyclopentadienyl, indenyl, tetrahydroindenyl, fluorenyl, which may independently be substituted or unsubstituted.

[0108] Furthermore, in the case where the organic ligand (L) is substituted, it is preferred that at least one organic ligand (L), preferably two organic ligands (L), comprise one or more organic ligands independently selected from C1 to C 20 a substituent of a hydrocarbyl or silyl group, which optionally contains one or more heteroatoms selected from Groups 14 to 16 and / or is optionally substituted by a halogen atom,

[0109] Whenever used in this application, the terms C1 to C 20 The hydrocarbon groups include C1 to C 20 Alkyl, C2 to C 20 Alkenyl, C2 to C 20 Alkynyl, C3 to C 20 Cycloalkyl, C3 to C 20 Cycloalkenyl, C6 to C 20 Aryl, C7 to C 20 Alkyl aryl or C7 to C 20 Aralkyl or mixtures of these groups, for example cycloalkyl substituted by alkyl.

[0110] Furthermore, two substituents attached to adjacent C atoms of a ring of the ligand (L), which may be identical or different, may also together form a further monocyclic or polycyclic ring fused to this ring.

[0111] Preferred hydrocarbon groups are independently selected from linear or branched C1 to C 10 Alkyl, optionally interrupted by one or more Group 14 to 16 heteroatoms, such as O, N or S, and substituted or unsubstituted C6 to C 20 Aryl.

[0112] Straight or branched C1 to C 10 Alkyl, optionally interrupted by one or more heteroatoms from Groups 14 to 16, more preferably selected from methyl, ethyl, propyl, isopropyl, tert-butyl, isobutyl, C 5-6 Cycloalkyl, OR, SR, where R is C1 to C 10alkyl,

[0113] C6 to C 20 Aryl is more preferably phenyl, which is optionally substituted by 1 or 2 C1 to C 10 Alkyl substitution.

[0114] In the present invention, "σ-ligand" refers to a group that bonds to the transition metal (M) through a σ bond.

[0115] Furthermore, the ligand "X" is preferably independently selected from hydrogen, halogen, C1 to C 20 Alkyl, C1 to C 20 Alkoxy, C2 to C 20 Alkenyl, C2 to C 20 Alkynyl, C3 to C 12 Cycloalkyl, C6 to C 20 Aryl, C6 to C 20 Aryloxy, C7 to C 20 Aralkyl, C7 to C 20 The group consisting of aralkenyl, -SR", -Pr"3, -SiR"3, -OSiR"3 and -NR"2, wherein each R" is independently hydrogen, C1 to C 20 Alkyl, C2 to C 20 Alkenyl, C2 to C 20 Alkynyl, C3 to C 12 Cycloalkyl or C6 to C 20 Aryl.

[0116] More preferably, the "X" ligand is selected from halogen, C1 to C6 alkyl, C5 to C6 cycloalkyl, C1 to C6 alkoxy, phenyl and benzyl.

[0117] The bridging group "R" can be a divalent bridge, 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 to C 20 Alkyl, C2 to C 10 Cycloalkyl, tri(C1-C 20 Alkyl)silyl, C6-C 20 Aryl, C7-C 20 Arylalkyl and C7-C 20 Alkylaryl.

[0118] More preferably, the bridging group "R" is a divalent bridge selected from -R'2C-, -R'2Si-, wherein each R' is independently a hydrogen atom, a C1 to C 20 Alkyl, C2 to C 10 Cycloalkyl, C6-C 20 Aryl, C7-C 20Arylalkyl and C7-C 20 Alkylaryl.

[0119] Another subgroup of organometallic compounds (C) of formula (I) are known as non-metallocenes, wherein the transition metal (M), preferably a Group 4 to 6 transition metal, suitably Ti, Zr or Hf, has coordinating ligands other than cyclopentadienyl ligands.

[0120] As used herein, the term "non-metallocene" refers to a compound that does not carry a cyclopentadienyl ligand or a fused derivative thereof, but carries one or more non-cyclopentadienyl η- or σ-monodentate, bidentate or multidentate ligands. Such ligands can, for example, be selected from groups (b) and (c) as defined above, and are described, for example, in WO 01 / 70395, WO 97 / 10248, WO 99 / 41290 and WO 99 / 10353 and VC Gibson et al. in Angew. Chem. Int. Ed., Engl., vol 38, 1999, pp 428-447, the disclosures of which are incorporated herein by reference.

[0121] However, the organometallic compound (C) according to the present invention is preferably a metallocene as defined above.

[0122] Many patents describe metallocenes. Here are just a few examples: 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 WO 00 / 148034, EP 423 101, EP 537 130, 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 disclosure of which is incorporated herein by reference. In addition, metallocenes are extensively described in academic and scientific articles.

[0123] In a preferred embodiment, the organometallic compound (C) has the following formula (Ia):

[0124] (L)2R n MX2(Ia)

[0125] in

[0126] "M" is Zr or Hf;

[0127] Each “X” is a σ ligand;

[0128] each "L" is optionally substituted cyclopentadienyl, indenyl, or tetrahydroindenyl;

[0129] "R" is a SiMe2 bridging group connecting the organic ligand (L);

[0130] "n" is 0 or 1, preferably 1;

[0131] The metallocene catalyst complexes of the present invention are preferably asymmetric. Asymmetric simply means that the two ligands forming the metallocene are different, that is, each ligand carries a chemically different set of substituents.

[0132] Metallocene catalyst complex of the present invention is normally the chirality of anti-configuration, the bridging bis-indenyl C1-symmetric metallocene of racemization.Although this complex is C1-symmetric formally, because they keep C2-symmetry near metal center, rather than in the ligand periphery, so complex ideally keeps false C2-symmetry.According to its chemical property, can form trans and cis enantiomer pair (in the case of C1-symmetrical complex) in complex building-up process.For the present invention, racemization-trans refers to that two indenyl ligands are towards opposite directions with respect to cyclopentadienyl-metal-cyclopentadienyl plane, and racemization-cis refers to that two indenyl ligands are towards same direction with respect to cyclopentadienyl-metal-cyclopentadienyl plane, as shown below.

[0133]

[0134] Formula (I) and any subformulae are intended to encompass both cis and trans configurations.Preferred metallocene catalyst complexes are in the trans configuration.

[0135] The metallocene catalyst complex of the present invention is usually used in the form of racemic-trans isomers. Therefore, ideally, at least 95% mol, for example at least 98% mol, particularly at least 99% mol of the metallocene catalyst complex is in the form of racemic-trans isomers.

[0136] More preferably, the single site catalyst has formula (II)

[0137]

[0138] Mt is Hf or Zr;

[0139] Each X is a σ ligand;

[0140] Each R 1 are independently the same or may be different and are CH2-R 7 Group, where R 7 H or linear or branched C 1-6Alkyl, C 3-8 Cycloalkyl, C 6-10 Aryl,

[0141] Each R 2 are independently -CH=--CY=, -CH2-, -CHY- or -CY2- groups, wherein Y is C 1-10 hydrocarbon group, and n is 2-6,

[0142] Each R 3 and R 4 are independently the same or may be different and are hydrogen, a linear or branched C1-C6 alkyl group, an OY group or a C 7-20 Aralkyl, C 7-20 Alkaryl or C 6-20 Aryl, wherein each phenyl group has at least one R 3 and at least one R 4 is not hydrogen, and optionally two adjacent R 3 or R 4 The groups may be part of a ring including the phenyl carbon atom to which they are bonded,

[0143] R 5 is a straight or branched C1-C6 alkyl group, C 7-20 Arylalkyl, C 7-20 Alkyl aryl or C6-C 20 Aryl,

[0144] R 6 C(R 8 )3 groups, wherein R 8 is a linear or branched C1-C6 alkyl group, and

[0145] Each R is independently C1-C 20 Hydrocarbon group.

[0146] It is preferred if Mt is Zr.

[0147] Preferably, each X is independently a hydrogen atom, a halogen atom, a C 1-6 Alkoxy or R' group, where R' is C 1-6 alkyl, phenyl or benzyl. Most preferably, X is chlorine, benzyl or methyl. Preferably, the two X groups are the same. The most preferred selection is two chlorine, two methyl or two benzyl groups, especially two chlorine.

[0148] Each R is independently C1-C 20 Hydrocarbon groups, such as C6-C 20 Aryl, C7-C 20 Arylalkyl or C7-C 20 Alkylaryl. Term C 1-20 Hydrocarbyl also includes C 1-20Alkyl, C 2-20 Alkenyl, C 2-20 Alkynyl, C 3-20 Cycloalkyl, C 3-20 Cycloalkenyl, C 6-20 Aryl, C 7-20 Alkyl aryl or C 7-20 Unless otherwise specified, preferred C 1-20 The hydrocarbon group is C 1-20 Alkyl, C 4-20 Cycloalkyl, C 5-20 Cycloalkyl-alkyl, C 7-20 Alkyl aryl, C 7-20 Arylalkyl or C 6-20 Aryl.

[0149] Preferably, the two R groups are the same. Preferably, R is C1-C 10 Hydrocarbon or C6-C 10 Aryl, such as methyl, ethyl, propyl, isopropyl, tert-butyl, isobutyl, C 5-6 cycloalkyl, cyclohexylmethyl, phenyl or benzyl, more preferably, both R are C1-C6 alkyl, C 3-8 Cycloalkyl or C6 aryl, such as C1-C4 alkyl, C 5-6 Cycloalkyl or C6 aryl, most preferably, both R are methyl, or one is methyl and the other is cyclohexyl. Most preferably, the bridge is -Si(CH3)2-.

[0150] Each R 1 are independently the same or may be different and are CH2-R 7 Group, where R 7 H or linear or branched C 1-6 Alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl, or C 3-8 Cycloalkyl (e.g. cyclohexyl), C 6-10 Aryl (preferably phenyl).

[0151] Preferably, the two R 1 The groups are the same and are CH2-R 7 Group, where R 7 is H or a linear or branched C1-C4 alkyl group, more preferably, two R 1 The groups are the same and are CH2-R 7 Group, where R 7 is H or a linear or branched C1-C3 alkyl group. Most preferably, the two R 1 All are methyl.

[0152] Each R2 are independently -CH=--CY=, -CH2-, -CHY- or -CY2- groups, wherein Y is C 1-10 Hydrocarbyl, preferably C 1-4 A hydrocarbon group, and n is 2-6, preferably 3-4.

[0153] Each substituent R 3 and R 4 are independently the same or may be different and are hydrogen, a linear or branched C1-C6 alkyl group, an OY group or a C 7-20 Arylalkyl, C 7-20 Alkyl aryl or C 6-20 Aryl, preferably hydrogen, linear or branched C1-C6 alkyl, or C 6-20 Aryl, and optionally two adjacent R 3 or R 4 The groups may be part of a ring including the phenyl carbon atom to which they are bonded. More preferably, R 3 and R 4 is hydrogen or a linear or branched C1-C4 alkyl group or an OY-group, wherein Y is C 1-4 Even more preferably, each R 3 and R 4 are independently hydrogen, methyl, ethyl, isopropyl, tert-butyl or methoxy, especially hydrogen, methyl or tert-butyl, wherein each phenyl group has at least one R 3 and at least one R 4 Not hydrogen.

[0154] Therefore, it is preferred that there be one or two R 3 is not hydrogen, more preferably R on the two phenyl groups 3 The groups are the same, such as two phenyl groups are 3',5'-dimethyl or 4'-tert-butyl.

[0155] For the indenyl moiety, one or two R 4 Not hydrogen, more preferably two R 4 Not hydrogen, most preferably these two R 4 The same, such as 3',5'-dimethyl or 3',5'-di-tert-butyl.

[0156] R 5 is a linear or branched C1-C6 alkyl group, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl, C 7-20 Arylalkyl, C 7-20 Alkyl aryl or C6-C 20 Aryl. R 5 Preferably a linear or branched C1-C6 alkyl group or a C 6-20Aryl, more preferably linear C1-C4 alkyl, even more preferably C1-C2 alkyl, most preferably methyl.

[0157] R 6 C(R 8 )3 groups, wherein R 8 It is a straight chain or branched C1-C6 alkyl group.

[0158] Each R is independently C1-C 20 Hydrocarbon, C6-C 20 Aryl, C7-C 20 Arylalkyl or C7-C 20 Preferably, each R 8 Same or different, and R 8 is a linear or branched alkyl group, more preferably, R 8 are the same and are C1-C2 alkyl. Most preferably, all R 8 All are methyl.

[0159] In another preferred embodiment, the organometallic compound (C) has the following formula (III):

[0160]

[0161] in

[0162] Mt is Zr or Hf, preferably Zr;

[0163] Each R 3 and R 4 are independently the same or may be different and are hydrogen or a linear or branched C1-C6 alkyl group, wherein at least one R 3 and at least one R 4 Not hydrogen.

[0164] Specific metallocene catalyst complexes include: racemic-trans-dimethylsilanediyl[2-methyl-4,8-bis-(4'-tert-butylphenyl)-1,5,6,7-tetrahydro-s-indan-1-yl][2-methyl-4-(3',5'-dimethylphenyl)-5-methoxy-6-tert-butylinden-1-yl]zirconium dichloride;

[0165] rac-trans-dimethylsilanediyl[2-methyl-4,8-bis-(3',5'-dimethylphenyl)-1,5,6,7-tetrahydro-s-indan-1-yl][2-methyl-4-(3',5'-dimethylphenyl)-5-methoxy-6-tert-butylindan-1-yl]zirconium dichloride;

[0166] Racemic-trans-dimethylsilanediyl[2-methyl-4,8-bis-(3',5'-dimethylphenyl)-1,5,6,7-tetrahydro-s-indan-1-yl][2-methyl-4-(3',5'-di-tert-butylphenyl)-5-methoxy-6-tert-butylinden-1-yl]zirconium dichloride; or its corresponding dimethyl zirconium analog.

[0167]

[0168] synthesis

[0169] The ligands required to form the single-site catalysts of the present invention can be synthesized by any method, and a skilled organic chemist can devise various synthetic schemes to produce the necessary ligand materials. For example, WO2007 / 116034 discloses the necessary chemical processes. Synthetic schemes can also generally be found in WO2002 / 02576, WO2011 / 135004, WO2012 / 084961, WO2012 / 001052, WO2011 / 076780, and WO2015 / 158790.

[0170] In order to form an active single-site catalytic species, it is generally necessary to use a cocatalyst known in the art. According to the present invention, a cocatalyst system comprising a boron-containing cocatalyst and / or an aluminoxane cocatalyst may be used.

[0171] The aluminoxane cocatalyst may be one of formula (X):

[0172]

[0173] wherein n is generally 6 to 20, and R has the following meanings.

[0174] Aluminoxanes are formed by partial hydrolysis of organoaluminum compounds, such as those of the formula AlR3, AlR2Y, and Al2R3Y3, where R can be, for example, C1-C 10 Alkyl, preferably C1-C5 alkyl, or C 3-10 Cycloalkyl, C7-C 12 Aralkyl or alkylaryl and / or phenyl or naphthyl, wherein Y can be hydrogen, halogen, preferably chlorine or bromine, or C1-C10 alkoxy, preferably methoxy or ethoxy. The oxygen-containing aluminoxane obtained is usually not a pure compound, but a mixture of oligomers of formula (X).

[0175] The preferred aluminoxane is methylaluminoxane (MAO).Since the aluminoxanes used as cocatalysts according to the invention are not pure compounds due to the way they are prepared, the molar concentrations of the aluminoxane solutions hereinafter are based on their aluminum content.

[0176] According to the present invention, a boron-containing cocatalyst may also be used instead of the aluminoxane cocatalyst, or the aluminoxane cocatalyst may be used in combination with the boron-containing cocatalyst.

[0177] It will be appreciated by those skilled in the art that when a boron cocatalyst is used, the complex is typically pre-alkylated by reaction with an alkyl aluminum compound, such as TIBA. This process is well known and any suitable aluminum alkyl may be used, such as Al(C 1-6 -alkyl)3.

[0178] Preferred alkylaluminum compounds are triethylaluminum, triisobutylaluminum, triisohexylaluminum, tri-n-octylaluminum and triisooctylaluminum.

[0179] Alternatively, when a borate cocatalyst is used, the metallocene catalyst complex is in its alkylated form, ie, for example, a dimethyl or dibenzyl metallocene catalyst complex may be used.

[0180] Boron-based cocatalysts of interest include those of formula (Z)

[0181] BY3(Z)

[0182] 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 alkylaryl group, an arylalkyl 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 are methyl, propyl, isopropyl, isobutyl, or trifluoromethyl, unsaturated groups such as aryl or haloaryl groups such as phenyl, tolyl, benzyl, p-fluorophenyl, 3,5-difluorophenyl, pentachlorophenyl, pentafluorophenyl, 3,4,5-trifluorophenyl, and 3,5-bis(trifluoromethyl)phenyl.

[0183] Preferred options are 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.

[0184] Tris(pentafluorophenyl)borane is particularly preferred.

[0185] However, preference is given to using borates, i.e. compounds containing borate ions. Such ionic promoters preferably contain non-coordinating anions, such as tetrakis(pentafluorophenyl)borate and tetraphenylborate. Suitable counterions are protonated amines or aniline derivatives, such as methylammonium, aniline, dimethylammonium, diethylammonium, N-methylaniline, diphenylammonium, N,N-dimethylaniline, trimethylammonium, triethylammonium, tri-n-butylammonium, methyldiphenylammonium, pyridine, p-bromo-N,N-dimethylaniline or p-nitro-N,N-dimethylaniline.

[0186] Preferred ionic compounds that can be used according to the present invention include:

[0187] triethylammonium tetra(phenyl)borate,

[0188] Tributylammonium tetra(phenyl)borate,

[0189] trimethylammonium tetra(tolyl)borate,

[0190] Tributylammonium tetra(tolyl)borate,

[0191] Tributylammonium tetrakis(pentafluorophenyl)borate,

[0192] tripropylammonium tetrakis(dimethylphenyl)borate,

[0193] Tributylammonium tetrakis(trifluoromethylphenyl)borate,

[0194] Tributylammonium tetrakis(4-fluorophenyl)borate,

[0195] N,N-dimethylcyclohexyltetrakis(pentafluorophenyl)ammonium borate,

[0196] N,N-dimethylbenzyltetrakis(pentafluorophenyl)ammonium borate,

[0197] N,N-dimethylphenyltetra(phenyl)ammonium borate,

[0198] N,N-diethylphenyltetra(phenyl)ammonium borate,

[0199] N,N-dimethylphenyltetrakis(pentafluorophenyl)ammonium borate,

[0200] N,N-di(propyl)tetrakis(pentafluorophenyl)ammonium borate,

[0201] Di(cyclohexyl)tetrakis(pentafluorophenyl)ammonium borate,

[0202] triphenylphosphonium tetrakis(phenyl)borate,

[0203] triethylphosphonium tetra(phenyl)borate,

[0204] Diphenylphosphonium tetrakis(phenyl)borate,

[0205] tri(methylphenyl)phosphonium tetra(phenyl)borate,

[0206] tris(dimethylphenyl)phosphonium tetra(phenyl)borate,

[0207] triphenylcarbonium tetrakis(pentafluorophenyl)borate,

[0208] Or tetrakis(pentafluorophenyl)ferric borate.

[0209] Preferably triphenylcarbonium tetrakis(pentafluorophenyl)borate,

[0210] N,N-dimethylcyclohexyltetrakis(pentafluorophenyl)ammonium borate, or

[0211] N,N-dimethylbenzyltetrakis(pentafluorophenyl)ammonium borate.

[0212] Surprisingly, it has been found that certain boron cocatalysts are particularly preferred. Thus, preferred borates for use in the present invention include trityl ions. Thus, N,N-dimethyltetrapentafluorophenylammonium borate and Ph3CB(PhF5)4 and their analogs are particularly preferred.

[0213] According to the present invention, preferred cocatalysts are alumoxanes, more preferably methylalumoxane, combinations of alumoxanes with alkylaluminum, boron or borate cocatalysts and combinations of alumoxanes with boron-based cocatalysts.

[0214] According to the most preferred embodiment of the present invention, the preferred cocatalyst is an aluminoxane, most preferably methylaluminoxane.

[0215] Suitable amounts of cocatalyst are known to those skilled in the art.The molar ratio of boron to metal ion of the metallocene may be from 0.5:1 to 10:1 mol / mol, preferably from 1:1 to 10:1, in particular from 1:1 to 5:1 mol / mol.

[0216] The molar ratio of Al in the aluminoxane to the metal ion of the metallocene may be 1:1 to 2000:1 mol / mol, preferably 10:1 to 1000:1, and especially 50:1 to 500:1 mol / mol.

[0217] Catalyst manufacturing

[0218] The single-site (preferably metallocene) catalyst complex can be used in supported or unsupported form. The particulate support material used is preferably an organic or inorganic material, such as silica, alumina or zirconium oxide or a mixed oxide, such as silica-alumina, in particular silica, alumina or silica-alumina. Silica supports are preferably used. Those skilled in the art are aware of the procedures required for supporting such catalysts.

[0219] Particularly preferably, the support is a porous material so that the complex can be loaded into the pores of the support, for example using methods similar to those described in WO 94 / 14856, WO 95 / 12622, and WO 2006 / 097497. The particle size is not critical but is preferably in the range of 5 to 200 μm, more preferably in the range of 20 to 80 μm. The use of such supports is conventional in the art.

[0220] In an alternative embodiment, no support is used at all. Such catalysts can be prepared in solution, for example in an aromatic solvent such as toluene, by contacting the metallocene (as a solid or in solution) with a cocatalyst such as methylaluminoxane or borane or a borate predissolved in an aromatic solvent, or by sequentially adding the dissolved catalyst components to the polymerization medium.

[0221] In one embodiment, no external support is used, but the catalyst is still present in solid particulate form. Thus, there is no need to employ an external support material, such as an inert organic or inorganic support, such as the silica described above.

[0222] In order to provide the catalyst of the present invention in solid form without the use of an external support, a liquid / liquid emulsion system is preferably used. The method comprises forming a dispersion of catalyst components (i) and (ii) in a solvent and solidifying the dispersed droplets to form solid particles.

[0223] Specifically, the method includes preparing a solution of one or more catalyst components; dispersing the solution in a solvent to form an emulsion, wherein the one or more catalyst components are present in droplets of a dispersed phase; immobilizing the catalyst components in the dispersed droplets in the absence of an external particulate porous support to form solid particles comprising the catalyst, and optionally recovering the particles.

[0224] This method can produce active catalyst particles with improved morphology, such as a predetermined spherical shape, surface properties, and particle size, without the use of any added external porous support material, such as an inorganic oxide, such as silica. The term "preparing a solution of one or more catalyst components" means that the catalyst-forming compounds can be mixed in one solution and then dispersed into an immiscible solvent, or at least two separate catalyst solutions can be prepared for each portion of the catalyst-forming compounds and then dispersed sequentially into the solvent. A complete disclosure of the necessary procedures can be found in WO 03 / 051934.

[0225] It is desirable that the single-site polymerization process be carried out in the presence of an alkylaluminum scavenger, such as a trialkylaluminum compound (TEAL, TMA and / or TIBAL).

[0226] As mentioned above, the key to the present invention is not the specific nature of the single-site catalyst used, so a wide range of choices can be made, however, it is required that the second prepolymerization process can be carried out in the presence of an alkyl aluminum compound. The key to the present invention is how to carry out the conversion process.

[0227] Aggregation Method

[0228] The method according to the present invention is a kind of " flying " conversion, and wherein the change from one type of production polymer (the first polymer product herein) to another kind (the second polymer product) is continuous, that is to say without shutting down the reactor.When converting from the first catalyst to the second catalyst, the feeding of the first catalyst stops.The second catalyst is subsequently introduced.In order to produce the second polymer product, it should be understood that the reactor conditions must be adjusted relative to the conditions used for producing the first polymer product.The change of conditions can be carried out before or after introducing the second catalyst.Or, some conditions may change before introducing the second catalyst, and other conditions may change after introducing the second catalyst.

[0229] The conversion process of the present invention occurs between two multi-stage polymerization processes, particularly in a multi-stage polymerization reactor system comprising a prepolymerization reactor and at least two additional reactors. The reactors are connected in series. Therefore, a prepolymerization reactor, at least one slurry reactor, and at least one gas phase reactor are required. The slurry reactor is typically a loop reactor.

[0230] Borealis has developed a preferred "loop gas phase" polymerization process called technology and is extensively described in the patent literature, for example in EP 0 887 379, WO 92 / 12182 or WO 2005 / 002744.

[0231] Switching from producing one polymer grade to another typically requires a transition period to allow the polymerization reactor to switch to the new resin specification. This time is required to adjust process conditions, such as reaction temperature, reactants, and reactant concentration ratios, to form the desired new polymer. During the transition from a first multi-stage polymerization reaction designed to produce a first resin product meeting a first specification to a second multi-stage polymerization reaction designed to produce a second target resin product meeting a second specification, some "off-spec" polymer may be produced while the transition occurs.

[0232] Unless the changeover is properly implemented, this off-spec product may become viscous under the conditions (including temperature) during the changeover and may cause lumps or sheets (on the reactor walls or dome) and product discharge problems. The formation of sticky polymer may force the reactor to be shut down for cleaning. The method of the present invention minimizes this risk.

[0233] Obviously, the longer the changeover time, the more "off-spec" polymer is likely to be produced, and there is a commercial incentive to make the changeover from the first polymer product to the second polymer product as cleanly and quickly as possible.

[0234] The specific first and second polymerization conditions depend on various factors, such as catalyst activity, the type and amount of optional comonomers, the type of polymer to be produced, and the production equipment. Therefore, the specific conditions during the transition between Ziegler-Natta and single-site catalysts must be determined for each specific product in a specific equipment. This is within the capabilities of those skilled in the art.

[0235] The conversion process of the present invention occurs in a multistage polymerization process involving a multistage polymerization reactor system comprising a prepolymerization reactor and a subsequent slurry reactor and relates to the production of polypropylene homopolymer or polypropylene copolymer. Accordingly, suitable equipment for the continuous production of polypropylene homopolymer or copolymer comprises a feed system for supplying catalyst, monomer, comonomer, additives, etc. to the reactors, i.e. the prepolymerization reactor, the slurry reactor and the gas phase reactor, e.g. a fluidized bed gas phase reactor (GPR).

[0236] In a first embodiment, the present invention relies on the use of an aluminum alkyl scavenger in the second prepolymerization to reduce the concentration of catalyst scavengers (poisons) in the prepolymerization reactor and subsequent reactors by scavenging catalyst killers. The aluminum alkyl may react with the catalyst inhibitor to form compounds that are easily scavenged or removed from the reactor.

[0237] The chemical formula of the aluminum alkyl of the present invention is Al(C1-10-alkyl)3, for example Al(C1-6-alkyl)3. The individual alkyl groups may be the same or different, preferably the same. Mixtures may also be used.

[0238] Preferred aluminum alkyls include triethylaluminum (TEAL), trimethylaluminum (TMA), triisobutylaluminum (TIBAL), and tri-n-hexylaluminum (TNHAL).

[0239] Particular preference is given to using triethylaluminum (TEAL), triisobutylaluminum (TIBA) or mixtures thereof.

[0240] The method for switching from Ziegler-Natta catalyzed polymerization to metallocene catalyzed polymerization according to the present invention may comprise the following steps.

[0241] In step a) of the process, a first prepolymerization is carried out. Preferably, this is carried out as a bulk slurry polymerization, for example in a continuous stirred tank reactor (CSTR) or a loop reactor, in liquid propylene, i.e. the liquid phase comprises mainly propylene with small amounts of other reactants and optionally inert components dissolved therein.

[0242] The first prepolymerization reaction is generally carried out at a temperature of 0°C to 50°C, preferably 10°C to 45°C, more preferably 15°C to 40°C. The pressure in the first prepolymerization reactor is not critical, but must be high enough to maintain the reaction mixture in the liquid phase. Thus, the pressure may be 20 bar to 100 bar, for example 30 bar to 70 bar.

[0243] The residence time is generally in the range of 0.1 hour to 1 hour.

[0244] Preferably, the ZN catalyst components are introduced entirely into the first prepolymerization step. However, when the Ziegler-Natta catalyst, preferably a solid Ziegler-Natta catalyst, and the separate cocatalyst can be fed separately, only a portion of the cocatalyst can be introduced into the first prepolymerization stage, while the remainder is introduced into the subsequent polymerization stage. In this case as well, it is necessary to introduce sufficient separate cocatalyst (if necessary) into the prepolymerization stage in order to obtain a sufficient polymerization reaction therein.

[0245] Other components may also be added during the first prepolymerization stage. Thus, hydrogen may be added during the first prepolymerization stage to control the molecular weight of the prepolymer, as is known in the art. In addition, antistatic additives may be used to prevent catalyst or polymer particles from adhering to each other or to the reactor walls.

[0246] The precise control of the first prepolymerization conditions and reaction parameters is within the capabilities of the skilled artisan.

[0247] The prepolymerized first catalyst thus obtained is then fed to a subsequent slurry reactor, such as a continuous stirred tank reactor, preferably to a loop reactor in step a) of the process. For a slurry reactor, the reaction temperature is generally in the range of 50°C to 110°C (e.g. 60°C to 100°C or 70°C to 110°C) and the reactor pressure is generally in the range of 20 bar to 80 bar (e.g. 30 bar to 70 bar).

[0248] The residence time in the slurry reactor is generally in the range of 0.2 hours to 5 hours (e.g., 0.3 hours to 2 hours). Preferably, the residence time is 0.2 hours to 1 hour, more preferably 0.3 hours to 0.6 hours. As is well known in the art, the average residence time τ can be calculated from the following formula 1:

[0249] Formula 1: Residence time

[0250]

[0251] Where V R is the volume of the reaction space (in a loop reactor, the volume of the reactor, in a fluidized bed reactor, the volume of the fluidized bed), and Q ois the volumetric flow rate of the product stream (comprising polymer product and fluid reaction mixture).

[0252] The diluents used are generally aliphatic hydrocarbons having a boiling point in the range from -70° C. to +100° C. In such reactors, the polymerization can, if desired, be carried out under supercritical conditions.

[0253] Then, in step a) of the process, the polymer produced in the slurry phase reactor is fed to a gas phase reactor. The slurry can be discharged from the reactor continuously or intermittently. A preferred method of intermittent discharge is to use settling legs, wherein the slurry is concentrated before a batch of concentrated slurry is discharged from the reactor.

[0254] For gas phase reactors, the reaction temperature used is generally 50° C. to 130° C. (e.g., 60° C. to 115° C., or 60° C. to 100° C.), the reactor pressure is generally 5 bar to 60 bar, preferably 10 bar to 40 bar, and the residence time is generally 1 hour to 8 hours. The gas used is generally a non-reactive gas, such as nitrogen and monomers.

[0255] Hydrogen can be introduced into any reactor to control the molecular weight of the polymer, as is well known and conventional in the art. In one embodiment, the molar ratio of hydrogen to total olefin monomer in the recycle gas stream is in the range of 0.001 or 0.002 or 0.003 to 0.014 or 0.016 or 0.018 or 0.024, where the desired range may include any combination of any molar ratio upper limit and any molar ratio lower limit described herein. In other words, the amount of hydrogen in the reactor at any time may be in the range of 1000 ppm to 20,000 ppm in one embodiment; in another embodiment, in the range of 2000 ppm to 10,000 ppm; in yet another embodiment, in the range of 3000 ppm to 8,000 ppm; and in yet another embodiment, in the range of from 4000 ppm to 7000 ppm, where the desired range may include any hydrogen upper limit and any hydrogen lower limit described herein.

[0256] In the process of the present invention, the Ziegler-Natta catalyzed polymerization is preferably started in a manner known in the art by introducing the above-mentioned Ziegler-Natta catalyst into the prepolymerization reactor via a catalyst feed tank, preferably via an oil catalyst feed system or via a wax catalyst feed system. In addition, propylene and hydrogen, as well as optional cocatalysts and external donors (all or part) are added to the prepolymerization reactor.

[0257] The prepolymerized catalyst, additional propylene, hydrogen, optionally additional cocatalyst, and external donor are then introduced into a slurry phase reactor, after which the polymer product is recovered from the slurry phase reactor and introduced into a gas phase reactor fluidized bed, optionally additional propylene and optional comonomer are fed into the gas phase reactor, optionally additional hydrogen is fed into the gas phase reactor to control the hydrogen to propylene ratio to provide the desired polymer product molecular weight, and the polymer product is recovered from the gas phase reactor.

[0258] The reaction conditions in the slurry phase and gas phase reactors (such as temperature, pressure, amount of propylene and optional comonomers, amount of hydrogen) are selected according to the desired product parameters of the first product. Generally speaking, such processes are conventional.

[0259] Conversion

[0260] In the Ziegler-Natta catalytic polymerization process of step a) of the present method, a single-site catalyst such as that described above can be introduced into a catalyst feed tank connected to the prepolymerization reactor. Typically, the catalyst is prepared within about 130 minutes to 400 minutes before the catalyst is introduced into the prepolymerization reactor.

[0261] The reaction conditions in the prepolymerization reactor and the slurry reactor can be adjusted to reflect the reaction conditions required to produce the second polymer product before the single site catalyst is introduced into the prepolymerization reactor. If a prepolymerization reactor is used, it is considered to be part of the first reactor (thus, the prepolymerization reactor and the slurry reactor are the first reactor for this purpose).

[0262] Thus, the hydrogen concentration in the prepolymerization reactor and the slurry reactor can be adjusted. The temperature within the prepolymerization reactor and the slurry reactor can be adjusted, among other things. Such adjustments within the prepolymerization and slurry reactors can occur approximately 15 to 100 minutes before the single-site catalyst is introduced into the slurry reactor. Preferably, the hydrogen feed to the prepolymerization and slurry reactors is adjusted to reflect the amount of hydrogen required to produce the second polymer product prior to the introduction of the single-site catalyst.

[0263] Preferably, any other polymerization conditions (eg monomer content, temperature) required to reach the second polymer product are adjusted after the single site catalyst is introduced into the prepolymerization reactor in step c).

[0264] When both the prepolymerization reactor and the slurry reactor need to be adjusted, the order of adjustment is not important. The prepolymerization conditions can be adjusted first, the slurry reactor conditions can be adjusted first, or both can be adjusted simultaneously.

[0265] Preferably, the antistatic agent is introduced into the prepolymerisation reactor prior to the introduction of the second catalyst. This may occur 30 minutes to 120 minutes before the introduction of the single site catalyst.

[0266] It is best to stop the feed of the external electron donor in the ZN catalytic process shortly before introducing the single-site catalyst into the prepolymerization reactor. Ideally, this occurs 5 to 30 minutes before the introduction of the single-site catalyst. It is also desirable to stop the ZN catalyst feed itself at this time, for example 5 to 30 minutes before the introduction of the single-site catalyst (step b).

[0267] Conveniently, the feed of the ZN catalyst is stopped at the same time as the feed of the external electron donor is stopped.

[0268] The ZN catalyst includes a cocatalyst. The cocatalyst may be an alkylaluminum cocatalyst. Alternatively, a different cocatalyst may be used in the ZN polymerization. When a different cocatalyst is used instead of an alkylaluminum cocatalyst, the feed of the different cocatalyst may be stopped, preferably at the same time as the ZN catalyst feed is stopped, for example, 5 to 30 minutes before the introduction of the single-site catalyst.

[0269] If the cocatalyst used with the ZN catalyst is an aluminum alkyl, the feed need not be stopped completely but can be adjusted as described below.

[0270] Preferably, if the ZN catalyst includes an aluminum alkyl cocatalyst, and therefore to meet the requirements of the present invention, the amount of the aluminum alkyl must be adjusted, typically reduced. The feed concentration of the aluminum alkyl cocatalyst in a ZN catalyzed polymerization is likely to be much higher than the concentration required in the single-site catalyst polymerization step, and therefore, if the aluminum alkyl is used as a cocatalyst in the ZN polymerization process, its concentration may need to be reduced.

[0271] Preferably, the total feed amount of aluminium alkyl to the prepolymerisation reactor and the slurry reactor of step a) is at least 20 g of aluminium alkyl (e.g. TEAL), i.e. at least 20 g per 1000 kg of total propylene fed to the prepolymerisation reactor and the slurry reactor of step a), preferably from 150 to 200 g of aluminium alkyl per tonne, i.e. from 150 to 200 g per 1000 kg of total propylene.

[0272] The goal is to adjust the aluminum alkyl feed or start the aluminum alkyl feed so that the aluminum alkyl feed amount to the prepolymerization reactor is 0.5 g / ton to 10.0 g / ton, that is, 0.5 g / 1000 kg to 10.0 g / 1000 kg of the total propylene fed to the prepolymerization reactor and the slurry reactor during the second polymerization. Please note that if a mixture of aluminum alkyl compounds is used, then this figure refers to the total content of all aluminum alkyls used.

[0273] This aluminum alkyl level is typically established 5 to 30 minutes before the single-site catalyst is introduced into the prepolymerization reactor. That is, the target aluminum alkyl concentration is preferably established before the single-site catalyst is introduced. However, the reduction in aluminum alkyl concentration can be initiated simultaneously with the introduction of the single-site catalyst. If the aluminum alkyl supply is established prior to the introduction of the single-site catalyst, the aluminum alkyl supply should still be maintained during the introduction of the single-site catalyst.

[0274] Preferably the aluminum alkyl is fed in an amount of 0.5 to 5.0 g per tonne, i.e. 0.5 to 5.0 g aluminum alkyl per 1000 kg, e.g. 1.0 to 3.0 g per tonne, i.e. 1.0 to 3.0 g per 1000 kg of total propylene fed to the prepolymerization reactor and the slurry reactor in steps c) and d).

[0275] In other words, the feed amount of aluminum alkyl is 0.5 to 5.0 g per hour, for example 1.0 to 3.0 g per hour per ton, i.e. 1000 kg of the total amount of polypropylene fed per hour in the prepolymerization reactor and the slurry reactor in steps c) and d).

[0276] Therefore, if the prepolymerization reactor and the slurry reactor are fed with 4000 kg C3 per hour during the conversion and the second polymerization process, the feed amount of aluminum alkyl in the prepolymerization reactor will be in the range of 2 g to 40 g per hour.

[0277] The adjustment of the aluminium alkyl feed is preferably carried out after step b), ie after the first catalyst feed has been stopped.The aluminium alkyl feed can be adjusted shortly before the simultaneous addition of the single site catalyst and the aluminium alkyl.

[0278] It is also preferred if the aluminum alkyl feed is adjusted after stopping the feed of the external donor.

[0279] The aluminum alkyl is preferably introduced into the prepolymerization reactor via a catalyst feed line. Thus, once the catalyst addition is started, the catalyst and the aluminum alkyl are added together. The aluminum alkyl can be added via the upper or lower portion of the catalyst feed line.

[0280] It should be understood that all catalyst and aluminum alkyl are fed through the prepolymerization reactor.In contrast, propylene can be fed to the prepolymerization reactor and directly fed to the slurry reactor and gas phase reactor.

[0281] The single-site catalyst is then introduced into the prepolymerization reactor. Preferably, after the single-site catalyst is introduced into the prepolymerization reactor, the reaction conditions in the prepolymerization reactor and the slurry reactor are adjusted to reflect the reaction conditions required to produce the second polymer product. Thus, the temperature, pressure, monomer feed, comonomer feed, and hydrogen levels within the prepolymerization and slurry reactors can be adjusted. Such adjustments within the prepolymerization and slurry reactors can occur between approximately 0 and 40 minutes after the single-site catalyst is introduced into the polymerization reactor.

[0282] When both the prepolymerization reactor and the slurry reactor need to be adjusted, the order of adjustment is not important. The prepolymerization conditions may be adjusted first, the slurry reactor conditions may be adjusted first, or both may be adjusted simultaneously. However, it is preferred that the prepolymerization conditions be adjusted before the conditions in the slurry reactor to reflect the conditions required to produce the second polymer product.

[0283] The conditions for the second prepolymerization are similar to those described above for the first prepolymerization. Preferably, this is carried out as a bulk slurry polymerization, for example in a continuous stirred tank reactor (CSTR) or a loop reactor, in liquid propylene, i.e. the liquid phase comprises mainly propylene with small amounts of other reactants and optionally inert components dissolved therein.

[0284] The second prepolymerization reaction is generally carried out at a temperature of 0°C to 50°C, preferably 10°C to 45°C, more preferably 15°C to 40°C. The pressure in the prepolymerization reactor is not critical, but must be high enough to maintain the reaction mixture in the liquid phase. Thus, the pressure may be 20 bar to 100 bar, for example 30 bar to 70 bar.

[0285] The residence time is generally in the range of 0.1 hour to 1 hour.

[0286] The prepolymerized second catalyst thus obtained is then fed into a slurry reactor, preferably a loop reactor. For a slurry reactor, the reaction temperature is typically in the range of 50°C to 110°C (e.g., 60°C to 100°C or 70°C to 110°C). The reactor pressure is typically in the range of 20 bar to 80 bar (e.g., 30 bar to 70 bar).

[0287] The residence time in the slurry reactor is generally in the range of 0.2 hours to 5 hours (e.g. 0.3 hours to 2 hours). Preferably, the residence time is 0.2 hours to 1 hour, more preferably 0.3 hours to 0.6 hours.

[0288] The diluents used are generally aliphatic hydrocarbons having a boiling point in the range from -70° C. to +100° C. In such reactors, the polymerization can, if desired, be carried out under supercritical conditions.

[0289] About 20 to 120 minutes after the single site catalyst is introduced into the prepolymerisation reactor, the gas phase reactor conditions are adjusted to reflect the desired second product parameters. This preferably occurs after the conditions in the slurry reactor have been adjusted.

[0290] The polymer produced in the slurry phase reactor is then fed to a gas phase reactor. For the gas phase reactor, the reaction temperature used is typically 50°C to 130°C (e.g., 60°C to 115°C, or 60°C to 100°C), the reactor pressure is typically 5 bar to 60 bar, preferably 10 bar to 40 bar, and the residence time is typically 1 hour to 8 hours. The residence time is 1 hour to 8 hours.

[0291] The gases used are generally non-reactive gases such as nitrogen and monomers.

[0292] Hydrogen can be introduced into any reactor to control the molecular weight of the polymer, as is well known and conventional in the art. In one embodiment, the molar ratio of hydrogen to total olefin monomer in the recycle gas stream is in the range of 0.001 or 0.002 or 0.003 to 0.014 or 0.016 or 0.018 or 0.024, where the desired range may include any combination of any molar ratio upper limit and any molar ratio lower limit described herein. In other words, the amount of hydrogen in the reactor at any time may be in the range of 1000 ppm to 20,000 ppm in one embodiment; in another embodiment, in the range of 2000 ppm to 10,000 ppm; in yet another embodiment, in the range of 3000 ppm to 8,000 ppm; and in yet another embodiment, in the range of from 4000 ppm to 7000 ppm, where the desired range may include any hydrogen upper limit and any hydrogen lower limit described herein.

[0293] The monomer propylene and any comonomers may be introduced into any of the prepolymerisation, slurry polymerisation or gas phase polymerisation. If present, comonomers are preferably added only to the gas phase reactor.

[0294] The amount of propylene fed to the prepolymerization reactor and the slurry reactor is calculated from the time when the single-site catalyst is added to the prepolymerization reactor.

[0295] Preferably, the amount of propylene fed to the prepolymerization reactor and the slurry reactor is calculated based on the amount required to produce the second polymer product, i.e., after any conversion adjustments have occurred. Therefore, for purposes of determining the aluminum alkyl to propylene ratio, it can be assumed that the amount of C3 supplied to the prepolymerization reactor and the slurry reactor is calculated from the time the single-site catalyst was supplied, and that the amount of C3 supplied from the time the single-site catalyst was supplied is the target amount required to produce the second polymer product. Any conversion adjustments can be ignored.

[0296] However, it is preferred that in the presence of a single site catalyst the propylene levels in the prepolymerisation and slurry reactors do not change during the polymerisation. It should also be noted that the supply of propylene to the polymerisation reaction may be linked to the aluminium alkyl feed to ensure that any fluctuations are accounted for.

[0297] For example, if the amount of C3 fed to the slurry reactor required to produce the second polymer product is 1000 kg / h, it can be considered that this amount of C3 is supplied to the slurry reactor from the time the single-site catalyst is introduced into the prepolymerization reactor.

[0298] The amount of aluminum alkyl added to the prepolymerization reactor can be calculated from the time the second catalyst is added. Before the second catalyst is added, a small amount of aluminum alkyl and propylene may be introduced into the prepolymerization reactor, but these amounts are very low and can be ignored.

[0299] Preferably, the majority of the second polymer product comes from the slurry phase stage, for example the split may be 50 wt% to 80 wt% slurry and 50 wt% to 20 wt% gas phase.Any prepolymerisation step contribution is considered part of the slurry phase step.

[0300] advantage

[0301] Adjusting the aluminum alkyl feed to the prepolymerization reactor to provide 0.5 to 10.0 grams of aluminum alkyl per ton of propylene feed in the second prepolymerization and second slurry stage polymerizations provides various benefits. The overall productivity of the second polymer product is improved compared to processes without an aluminum alkyl. The balance between reactors is better, allowing for better control of reactor shares. In processes involving the second polymer product without an aluminum alkyl, the amorphous fraction (xylene soluble fraction) is reduced.

[0302] Compared to processes without aluminum alkyls, the final polymer powder has a narrower mean particle size (PSD), meaning it is more monodisperse. Overall, there are fewer large polymer particles.

[0303] The bulk density of the second polymer product is increased, accelerating the time to normal production. The polymer product also has ideal thermal properties.

[0304] Changeovers occur smoothly without process disruptions such as clogging or scaling.

[0305] Without wishing to be bound by theory, it is conceivable that when the aluminum alkyl is supplied in the concentrations defined herein, poisons from the first stage polymerization, such as external donors and antistatic agents, water, and oxygen, react with the aluminum alkyl and do not harm the novel single-site catalyst, which is notoriously sensitive to poisons.

[0306] Once the second polymerization process is established, i.e., when the second polymerization process produces a second polymer product within the target range, the conversion process is complete and the aluminum alkyl feed can be stopped as needed, but it is also possible to continue to feed the aluminum alkyl at a lower concentration to act as a scavenger for any residual catalyst poisons.

[0307] Any off-spec polymer produced during the conversion process can be discarded.

[0308] Alkyl aluminum flushing solution

[0309] In an alternative embodiment, propylene and an aluminum alkyl are introduced as a flush into the prepolymerization reactor between stopping the ZN catalyst supply and starting the single site catalyst supply.

[0310] Therefore, in this embodiment, the ZN catalyst feed is stopped. Subsequently (e.g., after 5 to 30 minutes), an aluminum alkyl and propylene are introduced into the prepolymerization reactor as a flushing liquid. The amount of aluminum alkyl introduced is 100 to 300 g / ton, i.e., 100 to 300 g / 1000 kg of propylene, for example, 150 to 200 g / ton, i.e., 150 to 200 g / 1000 kg of propylene in the flushing liquid, i.e., propylene fed to the prepolymerization reactor between steps b) and c).

[0311] Flushing may last from 30 minutes to 10 hours, from 0.5 to 4 hours, such as from 1 to 3 hours.

[0312] The propylene / aluminum alkyl flush is preferably introduced into the prepolymerization reactor from the lower portion of the catalyst feed line. Although the location of the aluminum alkyl feed into the catalyst feed line is not critical, it may be useful to minimize the time the aluminum alkyl is in contact with the catalyst in the feed line, so the preferred location for the feed is the end of the catalyst feed line.

[0313] Ideally, the flushing liquid consists of propylene and the aluminum alkyl component and no other feeds are introduced into the prepolymerization reactor during the flushing period.

[0314] Thereafter, the single-site catalyst can be introduced according to the above-described protocol. Thus, in particular, once flushing is complete, the amount of aluminum alkyl fed can be adjusted to 0.5 to 10.0 g of aluminum alkyl per ton, i.e., 1000 kg, of propylene fed in the second prepolymerization and second slurry stage polymerizations. This target range can be established prior to the introduction of the single-site catalyst, for example, 5 to 30 minutes in advance, or the single-site catalyst can be introduced simultaneously with the aluminum alkyl adjustment.

[0315] The second polymerization was then continued according to the above protocol.

[0316] Flushing Advantages

[0317] The advantages of this flushing process are similar to those described above. Compared to a process that does not use a flushing liquid and an aluminum alkyl, and relative to the method of the first embodiment, the overall productivity of the second polymer product is improved. In a process that does not use a flushing liquid and an aluminum alkyl, the amorphous fraction (xylene soluble fraction) is reduced.

[0318] Compared to the process without using a flushing liquid and an aluminum alkyl or compared to the first embodiment, the average particle size (PSD) of the final polymer powder is narrower, ie, more monodisperse.

[0319] Changeovers occur smoothly without process disruptions such as clogging or scaling.

[0320] Without wishing to be bound by theory, it is conceivable that when the aluminum alkyl is supplied in the concentrations defined herein or when a flushing step is used, poisons from the first stage polymerization, such as external donors and antistatic agents, water and oxygen, react with the aluminum alkyl and do not harm the novel single-site catalysts which are notoriously sensitive to poisons.

[0321] Once the second polymerization process is established, i.e., when the second polymerization process produces a second polymer product within the target range, the transition process is complete and the aluminum alkyl feed can be stopped as needed, but it is also possible to continue to feed the aluminum alkyl at a lower concentration to act as a purge for any residual catalyst poisons.

[0322] Advantageously, the single-site catalysts used according to the invention are insensitive to poisons.

[0323] In a preferred embodiment, no catalyst killer, such as carbon monoxide, is required. Thus, it is particularly preferred that the process of the present invention does not involve the addition of a catalyst killer to stop the activity of the ZN catalyst.

[0324] The polypropylene produced before and after the conversion may be a homopolymer or a copolymer. The polypropylene produced before the conversion may be a homopolymer or a copolymer. Suitable comonomers are ethylene and C4-C10 olefins. If a comonomer is present, ethylene is preferably used. Furthermore, the polypropylene produced may have a unimodal or bimodal molecular weight distribution. Preferably, the first polymer product is a homopolymer.

[0325] The second polymer product can be a copolymer or a homopolymer. Suitable comonomers are ethylene and C4-C10 olefins. If a comonomer is present, ethylene is preferably used. Preferably, the polypropylene prepared with a single-site catalyst is a polypropylene homopolymer, for example, a polypropylene homopolymer suitable for preparing biaxially oriented films.

[0326] It is generally observed that when the process of the present invention is employed, the MFR2 of the polypropylene formed is higher (possibly in the range of 0.5 g / 10 min to 50 g / 10 min) than when the process of the present invention is not employed. Therefore, the hydrogen concentration may need to be adjusted to take into account this change in molecular weight.

[0327] poison

[0328] For the second catalyst, the primary poisons are the external donor used in the ZN catalysis process and any antistatic agents used to prevent particle agglomeration during polymerization. Typical antistatic agents include glycerol monostearate (GMS), ethoxylated fatty acid amines, sorbitan monooleate, and diethanolamide. Other poisons include H2O and O2. Single-site catalysts are known to be very sensitive to catalyst poisons (primarily due to their low active metal content and the absence of external cocatalysts in the process). The present invention addresses the problems caused by these poisons by using aluminum alkyls to remove them.

[0329] The invention is further described with reference to the following non-limiting examples and accompanying figures.

[0330] Figure 1 A prepolymerization reactor is shown with an agitator and feed lines into the reactor. The feed lines allow the introduction of catalyst, flushing liquid, or aluminum alkyl into the prepolymerization reactor. The aluminum alkyl can be introduced from the bottom or top of the catalyst feed line.

[0331] Aluminum alkyl and propylene flushing liquid can also be introduced into the prepolymerization reactor through the catalyst feed line.

[0332] Analysis and Testing

[0333] Unless otherwise defined, the following term definitions and determination methods apply to the above general description of the invention as well as the following examples.

[0334] MFR2 (230°C) is measured according to ISO 1133 (230°C, 2.16 kg load).

[0335] Bulk density: The bulk density of the polymer powder was determined according to ASTM D1895-96 Method A.

[0336] Particle size (PS) and average particle size (APS) were measured according to ISO 13322-2 using the image analysis method using a Camsizer P4 analyzer.

[0337] Xylene solubles

[0338] The xylene soluble fraction (XS), as defined and described herein, is determined as follows: 2.0 g of polymer is dissolved in 250 mm p-xylene at 135° C. with stirring. After 30 minutes, the solution is allowed to cool at ambient temperature for 15 minutes and then allowed to stand at 25±0.5° C. for 30 minutes. The solution is filtered with filter paper into two 100 mm flasks. The solution in the first 100 mm container is evaporated in a stream of nitrogen, and the residue is dried under vacuum at 90° C. until a constant weight is reached. The xylene soluble fraction (percentage) can then be determined as follows:

[0339] XS%=(100x m1 X v0) / (m0 x v1),

[0340] where m0 represents the initial polymer amount (g), m1 defines the weight of the residue (g), v0 defines the initial volume (ml), and v1 defines the volume of the analyzed sample (ml).

[0341] DSC analysis

[0342] Melting temperature (Tm) and crystallization temperature (Tcr) were measured on approximately 5 mg of sample using a Mettler-Toledo 822e differential scanning calorimeter (DSC) in accordance with ISO 11357-3, using a heating / cooling / heating cycle at a scan rate of 10°C / min over the temperature range of +23 to +225°C, under a nitrogen flow rate of 50 ml min⁻¹. The melting temperature during the second heating step was taken as the endothermic peak. The instrument was calibrated using H₂O, lead, tin, and indium according to ISO 11357-1. Example

[0343] Example 1

[0344] Example 1 demonstrates the change from ZN to a single-site catalyst with a small amount of TEAL feed as a scavenger.

[0345] CE01 comparative example, no TEAL was added during the second catalyst feed

[0346] IE01 TEAL feed to the lower part of the catalyst feed line

[0347] IE 02: TEAL feed to the upper part of the catalyst feed line

[0348] The present invention uses the following catalysts:

[0349] Single-site catalyst

[0350] The single-site catalyst used in the polymerization process of all examples is

[0351] trans-disilylidene[2-methyl-4,8-bis(3,5-dimethylphenyl)-1,5,6,7-tetrahydro-s-indacene-1-yl][2-methyl-4-(3,5-dimethylphenyl)-5-methoxy-6-tert-butylindene-1-yl]zirconium dichloride, such as MC-2 disclosed in WO2019 / 179959A1.

[0352] The production method of the supported metallocene catalyst is similar to IE2 in WO2019 / 179959A1.

[0353] Ziegler-Natta catalyst

[0354] The production process of the Ziegler-Natta catalyst used in the embodiment is as follows:

[0355] raw material

[0356] TiCl4 (CAS 7550-45-90) was provided by a commercial source.

[0357] 20% toluene solution of butylethylmagnesium (Mg(Bu)(Et)) supplied by Crompton

[0358] 2-Ethylhexanol, supplied by Merck Chemicals

[0359] 3-Butoxy-2-propanol, provided by Sigma-Aldrich

[0360] Bis(2-ethylhexyl)citraconate (internal donor), supplied by Contract Chemicals

[0361] Dicyclopentyldimethoxysilane (DCPDMS) - external donor

[0362] 1-254, provided by Evonik

[0363] Heptane, provided by Chevron

[0364] Preparation of magnesium complexes

[0365] 3.4 liters of 2-ethylhexanol and 810 milliliters of propylene glycol butyl monoether (4 / 1 molar ratio) were added to a 20-liter reactor. 7.8 liters of a 20% BEM (butylethylmagnesium) solution in toluene (supplied by Crompton GmbH) were then slowly added to the well-stirred alcohol mixture. The temperature was maintained at 10°C during the addition. After the addition was complete, the reaction mixture was heated to 60°C and stirred at this temperature for 30 minutes. Finally, after cooling to room temperature, the resulting magnesium alkoxide was transferred to a storage container.

[0366] 21.2 g of the magnesium alkoxide prepared above was mixed with 4.0 ml of bis(2-ethylhexyl)citraconate for 5 minutes. After mixing, the resulting magnesium complex was immediately used to prepare the catalyst component.

[0367] Preparation of catalyst components

[0368] 19.5 ml of titanium tetrachloride was added to a 300 ml reactor equipped with a mechanical stirrer at 25°C and 170 rpm. 26.0 g of the magnesium complex prepared above was added over 30 minutes, maintaining the temperature at 25°C. 3.0 ml of Viscoplex 1-254 and 24.0 ml of heptane were added to form an emulsion. Mixing was continued at 25°C for 30 minutes. The reactor temperature was then raised to 90°C over 30 minutes. The reaction mixture was stirred at 90°C for another 30 minutes. Stirring was then stopped, and the reaction mixture was allowed to stand at 90°C for 15 minutes.

[0369] The solid material was washed with 100 ml of toluene, 30 ml of TiCl₄, 100 ml of toluene, and twice with 60 ml of heptane. 1 ml of donor (i.e., bis(2-ethylhexyl)citraconate) was added to the first two washes. The washes were performed at 80°C with stirring at 170 rpm for 30 minutes. After stopping stirring, the reaction mixture was allowed to stand for 20 to 30 minutes and then siphoned.

[0370] Then, the stirring was stopped and the reaction mixture was allowed to stand for 10 minutes. The temperature was lowered to 70° C., followed by siphoning and then purging with N 2 for 20 minutes to obtain an air-sensitive powder.

[0371] The surface area of ​​the catalyst was measured by BET method and was less than 5 m 2 / g, which is below the detection limit.

[0372] Polymerization Example

[0373] These examples were all performed on a pilot scale.

[0374] The first polymerization was carried out in a conventional manner for 24 hours in the presence of the ZNPP catalyst as described above, wherein an external donor (dicyclopentyldimethoxysilane (DCPDMS)) was supplied to the process at 30 to 50 g / t propylene.

[0375] The ZN catalyst contains TEAL as an alkylaluminum cocatalyst. It is supplied to the prepolymerization reactor and the first slurry reactor at a concentration of 170 grams per ton of propylene. The conversion process is as follows. During the conversion period, both single-site polymer and Ziegler-Natta-catalyzed polymer are produced.

[0376] Universal conversion time scheme for single-site catalyst addition relative to time zero

[0377] -5.0 hours Single-site catalyst is ready in the catalyst feed tank

[0378] -1.0 hour start feeding antistatic agent into prepolymerization reactor (SPAN 80)

[0379] -0.5 hours to adjust the hydrogen feed for the second polymerization to reflect the amount of hydrogen required for the target second polymer product;

[0380] -0.1 hour stop external donor (dicyclopentyldimethoxysilane (DCPDMS)) feed

[0381] -0.1 hour to stop ZN catalyst feeding;

[0382] -0.1 hour: Change the TEAL feed from 170g / tC3 to 2.5g / tC3 based on the C3 feed to the prepolymerization and slurry reactors

[0383] ·0 hour single-site catalyst feed starts

[0384] +0.1 hour to adjust the second prepolymerization conditions to reflect the requirements of the second polymer product

[0385] +0.2 hours to adjust the second slurry phase conditions to reflect the requirements of the second polymer product

[0386] +0.3 hours to adjust the second gas phase conditions to reflect the requirements of the second polymer product

[0387] +0,5-2 hours When the circuit production exceeds 25% of the maximum production, start running GPR.

[0388] The conditions within the polymerization reactor are detailed in Table 1. Polymer properties were measured at the end of the above process, ie after the GPR operation was established.

[0389] Table 1

[0390]

[0391] By using 2.5 wt-ppm TEAL as a scavenger, the following improvements were seen:

[0392] Higher overall productivity.

[0393] Better reactor balance, i.e. better distribution of production between reactors.

[0394] · Fewer amorphous parts and lower XS.

[0395] The final PP powder has good average particle size and PSD.

[0396] The final PP powder has a better bulk density.

[0397] Shorter time to reach normal production.

[0398] Example 2

[0399] In Example 2, a TEAL flush was used between stopping the ZN catalyst feed and starting the single-site catalyst feed. The same catalyst as in Example 1 was used.

[0400] CE 02: No TEAL flushing

[0401] IE 03: flush with large amount of TEAL for 2 hours, then feed TEAL as in Example 1

[0402] The first polymerization was carried out in a conventional manner for 24 hours in the presence of the ZNPP catalyst as described above, wherein an external donor (dicyclopentyldimethoxysilane (DCPDMS)) was supplied to the process at 30 to 50 g / t propylene.

[0403] The ZN catalyst contained TEAL as an aluminum alkyl cocatalyst and was fed to the prepolymerization reactor and the first slurry reactor at a concentration of 170 g per ton of propylene. The conversion process was as follows.

[0404] Universal transition timing scheme for flushing solution addition relative to time zero

[0405] -5.0 hours Single-site catalyst is ready in the catalyst feed tank

[0406] -1.0 hour start feeding antistatic agent into prepolymerization reactor (SPAN 80)

[0407] -0.5 hours to adjust the hydrogen feed for the second polymerization to reflect the amount of hydrogen required for the target second polymer product;

[0408] -0.1 hour stop external donor (dicyclopentyldimethoxysilane (DCPDMS)) feed

[0409] -0.1 hour to stop ZN catalyst feeding;

[0410] 0 hour TEAL flushing, 170 g / t C3 is fed to the lower part of the catalyst feed line and flushed to the prepolymerization reactor, then through the loop and gas phase reactor;

[0411] +2.0 hours Based on the C3 feed amount of the prepolymerization and slurry reactors, change the TEAL feed to 2.5g / tC3

[0412] +2.1 hours Single-site catalyst feed starts

[0413] +2.2 hours to adjust the second prepolymerization conditions to reflect the requirements of the second polymer product

[0414] +2.3 hours to adjust the second slurry phase conditions to reflect the requirements of the second polymer product

[0415] +2.4 hours to adjust the second gas phase conditions to reflect the requirements of the second polymer product

[0416] +2,6-4.1 hours When the circuit production exceeds 25% of the maximum production, put the GPR into operation.

[0417] The conditions within the polymerization reactor are detailed in Table 2. Polymer properties were measured at the end of the above process, i.e. after the GPR operation was established.

[0418] Table 2

[0419]

[0420] The following improvements were seen between the use of ZN and single site catalysts by flushing with TEAL at a rate of 170 g / t propylene / h for 2 hours:

[0421] Higher overall productivity.

[0422] Better reactor balance, i.e. better distribution of production between reactors.

[0423] · Fewer amorphous parts and lower XS.

[0424] The final PP powder has good average particle size and PSD.

[0425] The final PP powder has a better bulk density.

[0426] Shorter time to reach normal production.

[0427] There are no significant changes in thermal characteristics.

Claims

1. A method for switching between two different catalysts in the production of polypropylene homopolymer or copolymer in a continuous multistage polymerization reaction, the method comprising the steps of: a) polymerizing propylene and optionally a comonomer in the presence of a first catalyst in a multistage polymerization reactor system comprising a prepolymerization reactor, a subsequent slurry reactor and then a gas phase reactor; b) stopping feeding the first catalyst into the prepolymerization reactor; c) subsequently introducing propylene, optional comonomers and a second catalyst into a prepolymerization reactor and simultaneously introducing an aluminum alkyl into the polymerization reactor; d) polymerizing propylene and optionally a comonomer in the presence of a second catalyst in a multi-stage polymerization reactor system; wherein the first catalyst is a Ziegler-Natta catalyst and the second catalyst is a single-site catalyst; and The feed amount of the alkyl aluminum in step c) is 0.5 to 10.0 g per ton of total propylene fed to the prepolymerization reactor and the slurry reactor in steps c) and d).

2. A method for switching between two different catalysts in the production of polypropylene homopolymer or copolymer in a continuous multistage polymerization reaction, the method comprising the steps of: a) polymerizing propylene and optionally a comonomer in the presence of a first catalyst in a multistage polymerization reactor system comprising a prepolymerization reactor, a subsequent slurry reactor and then a gas phase reactor; b) stopping feeding the first catalyst into the prepolymerization reactor; c) subsequently introducing propylene, optional comonomers and a second catalyst into a prepolymerization reactor; d) polymerizing propylene and optionally a comonomer in the presence of a second catalyst in a multi-stage polymerization reactor system; wherein the first catalyst is a Ziegler-Natta catalyst and the second catalyst is a single-site catalyst; wherein between steps b) and c), propylene and an aluminum alkyl are introduced into a prepolymerization reactor, wherein the amount of the aluminum alkyl is from 100 to 300 g per ton of propylene introduced into this step; And preferably, the feed amount of the alkyl aluminum in step c) is 0.5 to 10.0 g per ton of total propylene fed to the prepolymerization reactor and the slurry polymerization reactor in steps c) and d).

3. The process according to claim 1 , wherein the feed amount of the aluminum alkyl in step c) is 0.5 to 5.0 g, for example 1.0 to 3.0 g, per ton of total propylene fed to the prepolymerization reactor and the slurry polymerization reactor from the time the second catalyst is introduced into the prepolymerization reactor.

4. The process according to claim 2, wherein the amount of aluminum alkyl fed between steps b) and c) is 150 to 200 g per ton of propylene fed between steps b) and c).

5. The process according to claim 2 or 4, wherein the step of introducing propylene and aluminum alkyl as flushing liquid into the prepolymerization reactor between steps b) and c) lasts for 0.5 to 4 hours, such as 1 to 3 hours.

6. The process according to any one of the preceding claims, wherein the aluminum alkyl is triethylaluminum (TEAL), triisobutylaluminum (TIBA) or a mixture thereof.

7. The process according to any one of the preceding claims, wherein the switch from the first catalyst to the second catalyst is carried out in the absence of any additional reagents that deactivate or eliminate the Ziegler-Natta catalyst, such as carbon monoxide.

8. The process according to claim 1 , wherein the Ziegler-Natta catalyst used is a solid Ziegler-Natta catalyst selected from MgCl2-supported titanium Ziegler-Natta catalysts and self-supported solid Ziegler-Natta catalysts.

9. The process according to claim 1 , wherein an external donor of the first catalyst is used in step a), for example an external donor selected from the group consisting of diisopropyldiethoxysilane (DIPDES), cyclohexylmethyldiethoxysilane (CHMDES), dicyclopentyldimethoxysilane, cyclohexylmethyldimethoxysilane and dicyclopentadienyldiethoxysilane (DCPDES) and diethylaminotriethoxysilane.

10. The process according to any one of the preceding claims, wherein the first catalyst of step a) is used in combination with the cocatalyst triethylaluminium (TEAL), in particular wherein the amount of TEAL used in the prepolymerisation reactor of step a) is at least 20 g per ton of total propylene added to the prepolymerisation reactor and the slurry reactor of step a).

11. The process according to any one of the preceding claims, wherein the single site catalyst is a metallocene catalyst.

12. The process according to claim 11, wherein the metallocene catalyst comprises a transition metal organometallic compound of formula (I) as catalyst component: (L) m R n MX q (I) in "M" is a transition metal (M) from Groups 3 to 10 of the Periodic Table of the 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 equals the valence of the transition metal (M); and co-catalysts.

13. The process according to claim 9, wherein the external donor feed to the first prepolymerization reactor in step a) is stopped before or simultaneously with the first catalyst feed.

14. The process according to any one of the preceding claims, wherein the second catalyst is fed to the prepolymerization reactor together with the aluminum alkyl through a catalyst feed line.

15. The process according to claim 1 , wherein the amount of aluminum alkyl introduced into the prepolymerization reactor is reduced from 150 to 200 g / ton of propylene (based on the propylene feed amount to the prepolymerization reactor and the slurry polymerization reactor in step a)) to 0.5 to 10 g / ton of propylene (based on the propylene feed amount to the prepolymerization reactor and the slurry polymerization reactor in steps c) and d) before the introduction of the second catalyst and preferably after step b).

16. The process according to any of the preceding claims, wherein the polypropylene is a propylene homopolymer.

17. The process according to any one of the preceding claims, wherein the polymerization conditions in the prepolymerization and slurry reactor of step a) are adjusted to reflect the conditions desired in the prepolymerization and slurry reactor of step d) after the feed of the first catalyst has been stopped.

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