Continuous olefin polymerization process in presence of antistatic agent

Abstract

A process for the continuous production of a polyolefin polymer in a gas phase polymerization reactor in the presence of a polymerization catalyst and an antistatic agent, comprising the steps of: providing a mixture of polyolefin particles and a gas; passing the mixture through a conduit at a gas velocity greater than or equal to 2 m / s; and introducing an antistatic agent into the mixture.

Description

Technical Field

[0001] The present disclosure relates to a process for continuously producing a polyolefin polymer in a gas phase polymerization reactor in the presence of a polymerization catalyst and an antistatic agent and an apparatus for carrying out the process. Background Art

[0002] During the production of polymers, polymer particles show a tendency to adhere to the reactor walls due to high levels of electrostatic charge. This not only carries the risk of forming large lumps or wall sheets, which mainly lead to the inevitable shutdown of the polymerization reactor due to blockage, but also hinders the fluid dynamics in the reactor and disturbs the fluidization of the polymer particles.

[0003] Therefore, in the technology for olefin polymerization, use antistatic agent to avoid electrostatic charging, thereby reduce the formation of wall flakes and polymer agglomerates in polymerization reactor or downstream equipment (such as degassing and recovery container).In the context of polyolefin polymerization, antistatic agent is also referred to as antiscalant, polymerization process aid, active inhibitor or kinetic modifier.Antistatic agent comprises the compound that plays antistatic effect, and it has polar functional group, such as acid or ester group, amine or amide group or hydroxyl or ether group.The common example of the compound that plays antistatic effect is polysulfone copolymer, polymerized polyamine, polyvalent alcohol, the hydroxy ester of polyvalent alcohol, the salt of alkyl aryl sulfonic acid, polysiloxane, alkoxy amine and polyethylene glycol ether.

[0004] US 5,410,002 describes a polymerization process in which an antistatic compound is used to eliminate or reduce the accumulation of polymer particles on the walls of a gas phase polymerization reactor. The compound employed is believed to be able to selectively inhibit polymerization on polymer particles smaller than 850 μm, which have been identified as the cause of fouling problems and polymer sheeting.

[0005] In a multi-zone circulation reactor, polymer particles can, for example, adhere to the wall of the riser, and the coverage of the wall of the riser is constantly increasing. If these agglomerated polymer particles fall at a certain point, the amount of polymer particles that can be transported in the riser increases sharply, more polymer is transported to the downcomer, and the polymer particle level in the downcomer rises rapidly. However, with the increase in the number of polymer particles in the riser, not only the density of the reactor contents in the riser changes temporarily, but also the fluid dynamics of the reaction mixture fluctuates. In addition, the change in the polymer particle level in the downcomer also affects the fluid dynamics in the entire multi-zone circulation reactor. Although several antistatic agents are known to those skilled in the art to solve this problem, antistatic agents are only effective when properly dispersed on polymer powders.

[0006] WO 2017 / 108337 discloses a process for preparing polyolefins, the process comprising the step of polymerizing olefins in the presence of an antistatic compound, the antistatic compound comprising a) 0.5 to 50% by weight of a compound of formula R-OH, wherein R represents hydrogen or a linear or branched saturated alkyl group having 1 to 15 carbon atoms; and b) 50 to 99% by weight of an oligomeric or polymeric organic compound having one or more terminal hydroxyl groups and at least 20 mm at 40°C. 2 The antistatic compound can be introduced into the reactor at different locations, for example directly into the reactor, into the line leading to the reactor, into the line of the reactor or into the polymer discharged from the polymerization reactor.

[0007] EP 2 711 379 A1 discloses a process and an apparatus for producing olefin polymers, wherein an antistatic agent is metered via a feed line connected to a dense bed at a feed point, the feed point being located in a feed zone extending upwards from the top of a restriction to a distance of five times the cross-sectional diameter of the dense bed above the restriction.

[0008] WO 2018 / 134007 A1 describes a process in which a fluid is fed into a polymer bed of a fluidized bed gas phase polymerization reactor by introducing the fluid into the polymer bed through a distributor, which protrudes into the fluidized bed zone of the reactor and terminates with a discharge end, which is positioned so that the equation d / D>0.002 is satisfied, where d is the distance of the discharge end of the distributor from the wall of the reactor and D is the diameter of the reactor in the fluidized bed zone.

[0009] WO 2005 / 080449 A2 provides a propylene polymerization process carried out in the presence of an antiscalant. The antiscalant comprises an antiscalant polymer, the antiscalant polymer comprising one or more blocks -(CH 2 -CH 2 -O) k – wherein each k is in the range of 1 to 50, and one or more blocks –(CH 2 -CH(R)-O) n – wherein R comprises an alkyl group having 1 to 6 carbon atoms and each n is in the range of 1 to 50. The scale inhibitor polymer is terminated by R' and R" end groups, wherein R' is PH or an alkoxy group having 1 to 6 carbon atoms, and R" is H or an alkyl group having 1 to 6 carbon atoms, and when added to the polymerization medium, the scale inhibitor polymer is solvated in a solvent comprising cyclohexane.

[0010] In WO 2011 / 029735 A1 a polymerization process is described in which the antiscalant is metered via at least N feed lines placed at different heights of the dense polymer bed.

[0011] WO 2016 / 150997 provides a process for preparing polyolefins by polymerizing olefins in a polymerization reactor in the presence of a polymerization catalyst at a temperature of 20° C. to 200° C. and a pressure of 0.1 MPa to 20 MPa, wherein the polymerization is carried out in the presence of an antistatic agent, the antistatic agent comprising an alkylene oxide-derived polymer comprising, on average, 10 to 200 repeating units –(CH 2 -CHR-O)-wherein R is hydrogen or an alkyl group having 1 to 6 carbon atoms, wherein the alkylene oxide-derived polymer is a random copolymer of ethylene oxide and other alkylene oxides, and the repeating units derived from ethylene oxide-(CH 2 -CH 2 -O)- and repeating units derived from other alkylene oxides –(CH 2 The ratio n:m of CHR'-O)- (wherein R' is an alkyl group having 1 to 6 carbon atoms) is in the range of 6:1 to 1:1, and all the terminal groups of the alkylene oxide-derived polymer are -OH groups. It is recommended to introduce the antistatic agent directly into the reactor or into a pipeline leading to the reactor.

[0012] WO 2009 / 010413 describes a process for olefin polymerization, comprising: a) polymerizing at least one liquid olefin monomer in a polymerization reactor to form a polymerization slurry comprising a polyolefin and the liquid monomer; b) continuously transferring the polymerization slurry from the polymerization reactor to a flash chamber via a transfer line comprising a pipeline, in which a turbulent three-phase flow comprising polymer, liquid monomer and gaseous monomer is established; c) separating the evaporated monomer from the polymer in the flash chamber; the process is characterized in that in step b), an antiscalant in liquid form is continuously introduced upstream of the inlet of the pipeline.

[0013] Antistatic agents used in the continuous polymerization of olefins generally do not only have the desired antistatic effect, but also have a negative impact on the activity of almost all olefin polymerization catalysts. In addition, their efficiency is limited; this means that even if these antistatic agents are added to the polymerization, there are sometimes still problems with sheeting and agglomerate formation due to electrostatic charging of certain products, especially when preparing polyolefins with relatively high molecular weights. In addition, long-term reliable operation of the polymerization reactor should be ensured.

[0014] Therefore, there is a need to provide a polymerization process which not only prevents the formation of wall sheets and polymer agglomerates in the polymerization reactor but also provides good operability of the polymerization process. Summary of the invention

[0015] The present disclosure provides a process for continuously producing a polyolefin polymer in a gas phase polymerization apparatus at a temperature of 20° C. to 200° C. and a pressure of 0.5 MPa to 10 MPa in the presence of a polymerization catalyst, the process comprising the following steps:

[0016] Providing a mixture of polyolefin particles and gas;

[0017] conveying the mixture through a pipeline at a gas velocity greater than or equal to 2 m / s; and

[0018] • Introducing an antistatic agent into the mixture.

[0019] In some embodiments, the mixture is conveyed through the conduit at a gas velocity less than or equal to 50 m / s, preferably less than or equal to 40 m / s, more preferably less than or equal to 30 m / s and most preferably less than or equal to 20 m / s.

[0020] In some embodiments, the process is characterized in that the density of the polyolefin particles in the gas is at least 30 kg / m 3 , preferably at least 50 kg / m 3 , more preferably at least 80 kg / m 3 In some embodiments, the process is characterized in that the density of the polyolefin particles in the gas is at most 200 kg / m 3 .

[0021] In some embodiments, the process is characterized in that the conduit is a discharge line and / or a transfer line.

[0022] In some embodiments, the process is characterized in that the process further comprises the following steps:

[0023] Feeding an olefin or an olefin and one or more other ethylenically unsaturated monomers into a gas phase polymerization reactor;

[0024] Homopolymerizing olefins or copolymerizing olefins with one or more other ethylenically unsaturated monomers in a gas phase reactor in the presence of a polymerization catalyst;

[0025] • The formed polyolefin particles are discharged from the gas phase reactor.

[0026] In some embodiments, the process is characterized in that the gas phase polymerization unit includes two or more gas phase polymerization reactors. In some embodiments, the process may be characterized in that a series of fluidized bed reactors and multi-zone circulation reactors.

[0027] In some embodiments, the process is characterized in that the antistatic agent comprises an alkylene oxide derived polymer. In one embodiment, the alkylene oxide derived polymer may contain an average of 10 to 200 -(CH 2-CHR-O)-, wherein R is hydrogen or an alkyl group having 1 to 6 carbon atoms, wherein the alkylene oxide-derived polymer is a random copolymer of ethylene oxide and other alkylene oxides, and the repeating units derived from ethylene oxide -(CH 2 -CH 2 -O)- and repeating units derived from other alkylene oxides -(CH 2 The ratio n:m of -CHR'-O)- (wherein R' is an alkyl group having 1 to 6 carbon atoms) is in the range of 6:1 to 1:1, and all terminal groups of the alkylene oxide-derived polymer are -OH groups.

[0028] In some embodiments, the process is characterized in that the alkylene oxide derived polymer is a random copolymer of ethylene oxide and propylene oxide. In some embodiments, the alkylene oxide derived polymer can be a linear ethylene oxide / propylene oxide copolymer.

[0029] In some embodiments, the process is characterized in that the antistatic agent is introduced into the mixture of gas and polyolefin in the feed of the carrier, wherein the weight ratio of antistatic agent to carrier in the combined stream introduced into the pipeline is in the range of 1:5000 to 1:10.

[0030] In some embodiments, the process is characterized in that the carrier is selected from the group consisting of: water, liquid hydrocarbons, preferably liquid hydrocarbons having 3 to 8 carbon atoms, such as propane.

[0031] In some embodiments, the process is characterized in that the polymerization is carried out in a cascade of polymerization reactors including a fluidized bed reactor and a multi-zone circulation reactor, in which the growing polymer flows upward through the first polymerization zone under fast fluidization or transport conditions, leaves the first polymerization zone and enters the second polymerization zone, and the particles flow downward through the second polymerization zone under the action of gravity, leave the downcomer and are reintroduced into the riser, thereby establishing the circulation of the polymer, and the fluidized bed reactor is arranged upstream of the multi-zone circulation reactor.

[0032] In some embodiments, the process is characterized in that a lower molecular weight polyolefin polymer component is obtained in a fluidized bed reactor, and a higher molecular weight polyolefin polymer component is obtained in a multi-zone circulation reactor.

[0033] In some embodiments, the process is characterized in that the polyolefin polymer is prepared by homopolymerizing ethylene or ethylene with up to 10 wt.%, up to 5 wt.%, or up to 3 wt.% of C 3 -C 8 -1-Polyethylene prepared by copolymerization of olefins.

[0034] In another aspect, the present disclosure provides a gas phase polymerization apparatus for carrying out the process of the present disclosure, comprising a gas phase polymerization reactor and at least one pipeline, characterized in that the pipeline comprises at least one inlet for introducing an antistatic agent into the pipeline.

[0035] In some embodiments, the device is characterized in that the pipeline includes a receiving end for receiving the mixture of polyolefin particles and gas and a discharge end for discharging the mixture of polyolefin particles and gas, wherein at least one inlet for introducing an antistatic agent into the pipeline is located in the front half. In some embodiments, the at least one inlet can be arranged in the front third of the pipeline starting from the receiving end of the pipeline. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 An exemplary setup of a polymerization reactor cascade including a fluidized bed reactor and a multi-zone circulation reactor for use in the polymerization process of the present disclosure is schematically shown. DETAILED DESCRIPTION

[0037] The present disclosure provides a continuous process for producing polyolefins, in particular, a continuous process for polymerizing 1-olefins (i.e., hydrocarbons having terminal double bonds), but not limited thereto. The monomer may be a functionalized olefin unsaturated compound, such as an ester or amide derivative of acrylic acid or methacrylic acid, for example, acrylate, methacrylate, or acrylonitrile. The monomer may be particularly a non-polar olefin compound, including an aromatic substituted 1-olefin. Particularly preferred 1-olefins are linear or branched C 2 -C 12 -1-olefins, especially straight-chain C 2 -C 10 -1-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene or branched C 2 -C 10 -1-olefins such as 4-methyl-1-pentene, conjugated and non-conjugated dienes such as 1,3-butadiene, 1,4-hexadiene or 1,7-octadiene or vinyl aromatic compounds such as styrene or substituted styrene. Mixtures of various 1-olefins can also be polymerized. Olefins can also include olefins in which the double bond is part of a cyclic structure that can have one or more ring systems. Examples are cyclopentene, norbornene, tetracyclododecene or methylnorbornene or dienes such as 5-ethylidene-2-norbornene, norbornadiene or ethylnorbornadiene. Mixtures of two or more olefins can also be polymerized.

[0038] The process is particularly suitable for homopolymerization or copolymerization of ethylene or propylene, and is particularly preferably used for homopolymerization or copolymerization of ethylene. The comonomer in the polymerization of propylene may be, for example, up to 40 wt.% of ethylene and / or 1-butene, preferably 0.5 wt.% to 35 wt.% of ethylene and / or 1-butene, based on the total weight of monomers and comonomers. As comonomer in the polymerization of ethylene, it is preferred to use up to 20 wt.%, more preferably 0.01 wt.% to 15 wt.%, and especially 0.05 wt.% to 12 wt.% of C 3 -C 8 1-olefins, in particular 1-butene, 1-pentene, 1-hexene and / or 1-octene. Particularly preferred is a process in which ethylene is copolymerized with 0.1 wt.% to 12 wt.% of 1-hexene and / or 1-butene, based on the total weight of monomers and comonomers.

[0039] The polymerization of olefins is carried out in the presence of a polymerization catalyst. In the process of the present disclosure, any conventional olefin polymerization catalyst can be used. This means that the polymerization can be carried out using a Phillips catalyst based on chromium oxide, using a titanium-based Ziegler catalyst or a Ziegler-Natta catalyst or using a single-site catalyst. For the purposes of the present disclosure, a single-site catalyst is a catalyst based on a chemically uniform transition metal coordination compound. In addition, a mixture of two or more of these catalysts can also be used for the polymerization of olefins. This mixed catalyst can be referred to as a composite catalyst. The preparation and use of these catalysts for olefin polymerization are generally known.

[0040] The catalyst used in the process of the present disclosure may be, for example, a Phillips-type catalyst, which can be prepared by applying a chromium compound to an inorganic support and then calcining it at a temperature in the range of 350° C. to 950° C., resulting in the conversion of chromium present below hexavalent to a hexavalent state. In addition to chromium, other elements such as magnesium, calcium, boron, aluminum, phosphorus, titanium, vanadium, zirconium or zinc may also be used. Titanium, zirconium or zinc are particularly preferably used. Combinations of the above elements are also possible. The catalyst precursor may be doped with fluoride before or during calcination. As carriers of Phillips catalysts also known to those skilled in the art, aluminum oxide, silicon dioxide (silica gel), titanium dioxide, zirconium dioxide or their mixed oxides or co-gels, or aluminum phosphate may be mentioned. Other suitable carrier materials may be obtained by varying the pore surface area, for example by compounds of the elements boron, aluminum, silicon or phosphorus. In one embodiment, the carrier material may be silica gel. In one embodiment, the silica gel may be spherical or granular silica gel, the former also being capable of spray drying. The activated chromium catalyst may then be prepolymerized or pre-reduced. The prereduction can be carried out in an activator at 250° C. to 500° C., preferably 300° C. to 400° C., with the aid of cobalt or in another way with the aid of hydrogen.

[0041] The catalyst used in the process of the present disclosure may also be a single-site catalyst. Particularly suitable are those comprising bulky σ- or π-bonded organic ligands, such as catalysts based on mono-Cp complexes, catalysts based on bis-Cp complexes, which are generally referred to as metallocene catalysts, or catalysts based on late transition metal complexes, in particular iron-bisimine complexes. Further preferred catalysts are mixtures of two or more single-site catalysts or mixtures of catalysts of different types including at least one single-site catalyst.

[0042] Preferred catalysts are other Ziegler-type catalysts, preferably comprising a compound of titanium or vanadium, a compound of magnesium and optionally an electron donor compound and / or a particulate inorganic oxide as a support. It has surprisingly been found that these types of catalysts are particularly suitable in combination with antistatic agents, in particular with antistatic agents comprising copolymers of ethylene oxide and propylene oxide.

[0043] As titanium compounds, halides or alkoxides of trivalent or tetravalent titanium can be used, whereby titanium alkoxyhalogen compounds or mixtures of various titanium compounds are also possible. Examples of such titanium compounds are TiBr 3 、TiBr 4 、TiCl 3 、TiCl 4 、Ti(OCH 3 )Cl 3 、Ti(OC 2 H 5 )Cl 3、Ti(OiC 3 H 7 )Cl 3 、Ti(OnC 4 H 9 )C| 3 、Ti(OC 2 H 5 )Br 3 、Ti(OnC 4 H 9 )Br 3 、Ti(OCH 3 ) 2 Cl 2 、Ti(OC 2 H 5 ) 2 C| 2 、Ti(OnC 4 H 9 ) 2 C| 2 、Ti(OC 2 H 5 ) 2 Br 2 、Ti(OCH 3 ) 3 Cl、Ti(OC 2 H 5 ) 3 Cl、Ti(OnC 4 H 9 ) 3 Cl、Ti(OC 2 H 5 ) 3 Br、Ti(OCH 3 ) 4 、Ti(OC 2 H 5 ) 4 or Ti(OnC 4 H 9 ) 4 In some embodiments, the titanium compound may contain chlorine as halogen. In some embodiments, the titanium compound may be a titanium halide, which contains only halogen in addition to titanium, and among these especially titanium chloride, and in particular titanium tetrachloride. Among the vanadium compounds, mention may be made in particular of vanadium halides, vanadium oxyhalides, vanadium alkoxides and vanadium acetylacetonate. In some embodiments, the vanadium compound may be a vanadium compound in an oxidation state of 3 to 5.

[0044] In the production of solid components, at least one compound of magnesium can be used in addition. This type of compound can be a halogen-containing magnesium compound, such as a magnesium halide, and particularly magnesium chloride or magnesium bromide, and a magnesium compound wherein the magnesium halide can be obtained in a conventional manner (e.g., by reacting with a halogenating agent). For purposes of this disclosure, halogen is a mixture of chlorine, bromine, iodine or fluorine or two or more halogens. In certain embodiments, halogen can be chlorine or bromine, and particularly chlorine.

[0045] Possible halogen-containing magnesium compounds are in particular magnesium chloride or magnesium bromide. Magnesium compounds from which halides can be obtained are, for example, alkyl magnesiums, aryl magnesiums, alkoxy magnesium compounds or aryloxy magnesium compounds or Grignard compounds. The halogenating agent may be, for example, a halogen, a hydrogen halide, SiCl 4 or CCl 4 , and in particular chlorine or hydrogen chloride.

[0046] Examples of magnesium halogen-free compounds are diethylmagnesium, di-n-propylmagnesium, diisopropylmagnesium, di-n-butylmagnesium, di-sec-butylmagnesium, di-tert-butylmagnesium, dipentylmagnesium, n-butylethylmagnesium, n-butylsec-butylmagnesium, n-butyloctylmagnesium, diphenylmagnesium, diethoxymagnesium, di-n-propoxymagnesium, diisopropyloxymagnesium, di-n-butoxymagnesium, di-sec-butoxymagnesium, di-tert-butoxymagnesium, dipentylmagnesium, n-butoxyethoxymagnesium, n-butoxysec-butoxymagnesium, n-butoxyoctyloxymagnesium, and diphenoxymagnesium. Among these, n-butylethylmagnesium or n-butyloctylmagnesium is preferably used.

[0047] Examples of Grignard compounds are methylmagnesium chloride, ethylmagnesium chloride, ethylmagnesium bromide, ethylmagnesium iodide, n-propylmagnesium chloride, n-propylmagnesium bromide, n-butylmagnesium chloride, n-butylmagnesium bromide, sec-butylmagnesium chloride, sec-butylmagnesium bromide, tert-butylmagnesium chloride, tert-butylmagnesium bromide, hexylmagnesium chloride, octylmagnesium chloride, amylmagnesium chloride, isopentylmagnesium chloride, phenylmagnesium chloride and phenylmagnesium bromide.

[0048] As the magnesium compound for producing the granular solid, in addition to magnesium dichloride or magnesium dibromide, it is preferred to use di(C 1 -C 10 Preferably, the Ziegler-Natta catalyst comprises a transition metal selected from titanium, zirconium, vanadium, chromium.

[0049] The electron donor compound used for preparing the Ziegler type catalyst may be, for example, alcohol, diol, ester, ketone, amine, amide, nitrile, alkoxysilane and aliphatic ether. These electron donor compounds may be used alone or in combination with other electron donor compounds.

[0050] In some embodiments, the alcohol may be of formula R 1 Those of OH, where R 1 The group is C 1-C 20 In some embodiments, R 1 C 1 -C 20 -alkyl. Specific examples are methanol, ethanol, isopropanol, and n-butanol. In some embodiments, the diols are those with a total number of carbon atoms less than 50. In some embodiments, the diols can be 1,2 or 1,3 diols with a total number of carbon atoms less than 25. Specific examples are ethylene glycol, 1,2-propylene glycol, and 1,3-propylene glycol. In some embodiments, the esters are C 1 -C 20 Alkyl esters of aliphatic carboxylic acids, and in particular C 1 -C 8 -alkyl esters, such as ethyl acetate, methyl formate, ethyl formate, methyl acetate, propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate. In some embodiments, the amine is of formula NR 2 3 Those, among which R 2 The groups are independently hydrogen or C 1 -C 20 -hydrocarbon, provided that R 2 The groups are not simultaneously hydrogen. Preferably, R 2 C 1 -C 10 Specific examples are diethylamine, diisopropylamine and triethylamine. In some embodiments, the amide can be of formula R 3 CONR 4 2 Those, among which R 3 and R 4 are independently hydrogen or C 1 -C 20 Specific examples are formamide and acetamide. In some embodiments, the nitrile is of formula R 1 Those of CN, where R 1 has the same meaning as given above. A specific example is acetonitrile. In some embodiments, the alkoxysilane is of formula R 5 a R 6 b Si(OR 7 ) c Those of, wherein a and b are integers from 0 to 2, c is an integer from 1 to 4, and the sum (a+b+c) is 4; R 5 , R 6 and R 7 is an alkyl, cycloalkyl or aryl group having 1 to 18 carbon atoms which may contain heteroatoms. Particularly preferred are silicon compounds wherein a is 0 or 1, c is 2 or 3, and R 6 is an alkyl or cycloalkyl group optionally containing a heteroatom, and R7 is methyl. Examples of such silicon compounds are methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane and tert-butyltrimethoxysilane. In some embodiments, the electron donor compound is selected from the group consisting of amides, esters and alkoxysilanes.

[0051] Ziegler type catalyst can be polymerized in the presence of a cocatalyst. This cocatalyst can be an organometallic compound of the 1st, 2nd, 12th, 13th or 14th family metal of the periodic table, particularly an organometallic compound of the 13th family metal, and especially an organoaluminum compound. In certain embodiments, the cocatalyst is, for example, an organometallic alkyl, an organometallic alkoxide or an organometallic halide. In certain embodiments, the organometallic compound comprises alkyl lithium, alkyl magnesium or alkyl zinc, alkyl magnesium halide, alkyl aluminum, alkyl silicon, silicon alkoxide and alkyl silicon halide. In certain embodiments, the organometallic compound can include alkyl aluminum and alkyl magnesium. In certain embodiments, the organometallic compound can include alkyl aluminum, such as a trialkyl aluminum compound. Alkyl aluminum can include, for example, trimethyl aluminum, triethyl aluminum, triisobutyl aluminum, tri-n-hexyl aluminum, etc.

[0052] The polyolefin particles obtained have a more or less regular morphology and size, depending on the catalyst morphology and size and the polymerization conditions. Depending on the catalyst used, the polyolefin particles generally have an average diameter of several hundred to several thousand micrometers. In the case of chromium catalysts, the average particle diameter is generally from about 300 to about 1600 μm, and in the case of Ziegler-type catalysts, the average particle diameter is generally from about 500 to about 3000 μm.

[0053] The process of the present disclosure is carried out as a gas phase polymerization, i.e. by a process in which a solid polymer is obtained from a gas phase of one or more monomers. Such a gas phase polymerization can be carried out at a pressure of 0.1 MPa to 20 MPa, preferably 0.5 MPa to 10 MPa and in particular 1.0 MPa to 5 MPa and at a polymerization temperature of 40°C to 150°C and preferably 65°C to 125°C.

[0054] The process of the present disclosure can be carried out, for example, in an apparatus comprising two or more gas phase polymerization reactors, in particular a series of fluidized bed reactors and multizone circulation reactors.

[0055] Fluidized bed polymerization reactor is a reactor in which polymerization occurs in a polymer particle bed, which is maintained in a fluidized state by feeding gas at the lower end of the reactor (usually below a gas distribution grid having the function of distributing gas flow) and discharging gas again at its upper end. The reactor gas is then returned to the lower end of the reactor via a recycle line equipped with a compressor and a heat exchanger. The circulating reactor gas is generally a mixture of olefins to be polymerized, inert gases such as nitrogen and / or lower alkanes such as ethane, propane, butane, pentane or hexane and optional molecular weight regulators such as hydrogen. Preferably, nitrogen or propane is used as an inert gas, if appropriate in combination with other lower alkanes. The speed of the reactor gas must be high enough to first fluidize the mixed bed of finely divided polymers present in the tube used as the polymerization zone, and secondly effectively remove the polymerization heat. Polymerization can also be performed in a condensing or supercondensing mode, in which a portion of the circulating reaction gas is cooled below the dew point and returned to the reactor as a liquid phase and a gas phase or together as a two-phase mixture, so as to additionally use the enthalpy of evaporation to cool the reaction gas.

[0056] A multi-zone circulation reactor is a gas phase reactor in which two polymerization zones are connected to each other and polymer alternately passes through the two zones many times. Such a reactor is described, for example, in WO 97 / 04015 A1 and WO 00 / 02929 A1, and has two interconnected polymerization zones, i.e., a riser and a downcomer, in which the growing polymer particles flow upward under fast fluidization or conveying conditions, and in the downcomer, the growing polymer particles flow in a densified form under gravity. The polymer particles leaving the riser enter the downcomer, and the polymer particles leaving the downcomer are reintroduced into the riser, thereby establishing a circulation of polymer between the two polymerization zones, and the polymer alternately passes through the two zones many times. It is also possible to operate two polymerization zones of a multi-zone circulation reactor with different polymerization conditions by establishing different polymerization conditions in its riser and its downcomer. For this purpose, it is possible to partially or completely prevent a gas mixture leaving the riser and entraining polymer particles from entering the downcomer. This can be achieved, for example, by feeding a spacer fluid in the form of a gas and / or liquid mixture into the downcomer (such as in the upper part of the downcomer). The spacer fluid should have a composition different from that of the gas mixture present in the riser. The amount of spacer fluid added can be adjusted in such a way that an upward gas flow (particularly at its top) countercurrent to the polymer particle flow is generated to act as a spacer for the gas mixture entrained in the particles from the riser. In this way, two different gas composition zones can be obtained in a multi-zone circulation reactor. In addition, additional monomers, comonomers, molecular weight regulators such as hydrogen and / or inert fluids can also be introduced at any point of the downcomer, particularly below the isolation feed point. Therefore, different monomer concentrations, comonomer concentrations and hydrogen concentrations can also be easily produced along the downcomer, resulting in further differences in polymerization conditions.

[0057] In the case of two or more gas phase polymerization reactors, the process of the present disclosure may further include a step of transferring polymer particles from one reactor to another reactor. In order to avoid agglomeration or clogging of the pipeline, an antistatic agent may be introduced directly into the transfer pipeline.

[0058] In an exemplary embodiment of the present disclosure, the fluidized bed reactor is arranged upstream of the multi-zone circulation reactor. Such a reactor cascade of gas phase reactors may further include additional polymerization reactors. These additional reactors may be any type of low pressure polymerization reactor, such as a gas phase reactor or a suspension reactor, and may also include a prepolymerization stage.

[0059] In an exemplary embodiment, the process of the present disclosure therefore further comprises the following steps:

[0060] Feeding an olefin or an olefin and one or more other ethylenically unsaturated monomers into a gas phase polymerization reactor;

[0061] Transfer polymer particles from one gas phase reactor to another

[0062] • The formed polyolefin particles are discharged from the gas phase reactor.

[0063] The antistatic agent of the present disclosure can be introduced into the reactor by means of conventional methods. The feed can occur directly into the reactor or into the pipeline leading to the reactor. In the process of the present disclosure, it is surprisingly found that, in addition to the position where the antistatic agent is introduced into the mixture of polyolefin particles and gas, the gas velocity is also critical when the antistatic agent is effectively distributed to obtain the maximum effect. Therefore, the mixture of polyolefin particles and gas is transmitted through the polymerization device at a speed greater than or equal to 2m / s, preferably greater than or equal to 2.5m / s.

[0064] The mode of introducing the antistatic agent into the polymerization reactor may vary depending on the polymer produced. In the case of polyethylene production, the antistatic agent can be introduced into the polymerization reactor, for example, by the flow of a liquid carrier. The flow of the liquid carrier, also referred to as a pick-up flow, can be a flow of liquid hydrocarbons, such as those with 3 to 8 carbons, such as propane. In some embodiments, the weight ratio of the antistatic agent to the liquid carrier in the combined flow introduced into the reactor is less than 1:5, more preferably the weight ratio of the antistatic agent to the liquid carrier in the combined flow is in the range of 1:5000 to 1:10, even more preferably in the range of 1:2000 to 1:20, and most preferably in the range of 1:1000 to 1:50. In some embodiments, the combined feed stream comprising a liquid carrier and an antistatic agent does not contain an organoaluminum compound, such as an alkyl aluminum. In a preferred embodiment of the present disclosure, the feed line for introducing the combined feed stream comprising a liquid carrier and an antistatic agent into a gas phase polymerization reactor is equipped with a static mixer, and the combined feed stream passes through the static mixer before being introduced into the gas phase polymerization reactor.

[0065] In an alternative embodiment, the antistatic agent is introduced with the monomer and / or comonomer stream.

[0066] According to an exemplary embodiment of the present disclosure, the polymerization is a gas phase polymerization, and the density of the solid polymer particles fed into the reactor by the antistatic agent is at least 30 kg / m 3 , preferably at least 50 kg / m 3 and more preferably at least 80 kg / m 3 The antistatic agent is introduced into the gas phase polymerization reactor by feeding the antistatic agent into the gas phase polymerization reactor. In some embodiments, the parts of the gas phase polymerization reactor into which the antistatic agent can be fed are, for example, those parts of the stirred bed or fluidized bed containing polymer particles. According to this embodiment, other parts of the gas phase polymerization reactor into which the antistatic agent can be fed are the riser or downcomer of the multi-zone circulation reactor.

[0067] In one embodiment, except being greater than or equal to 2m / s, preferably being greater than or equal to 2.5m / s speed by antistatic agent being fed in the pipeline of the mixture of transmission polyolefin particles and gas, antistatic agent can also be fed in polymerization reactor.Preferably, pipeline is the transmission line that mixture is transmitted to subsequent polymerization reactor from a polymerization reactor or for example is used for mixture is discharged into the discharge line in collection, degassing and / or recovery container.Due to the high conveying speed greater than or equal to 2m / s, the electrostatic load of polyolefin particles in mixture may increase.However, by additionally antistatic agent is injected into pipeline, antistatic agent is effectively distributed in mixture, and therefore can effectively reduce the electrostatic load of polyolefin particles, prevents wall flakes and blockage at the section contacting with the mixture discharged from described pipeline in pipeline and subsequent container.

[0068] The antistatic agent used in the process of the present disclosure may include an alkylene oxide derived polymer. In one embodiment, the alkylene oxide derived polymer may include an average of 10 to 200 repeating units -(CH 2 -CHR-O)-, wherein R is hydrogen or an alkyl group having 1 to 6 carbon atoms, wherein the alkylene oxide-derived polymer is a random copolymer of ethylene oxide and other alkylene oxides, and the repeating units derived from ethylene oxide -(CH 2 -CH 2 -O)- and repeating units derived from other alkylene oxides -(CH 2 The ratio n:m of -CHR'-O)- (wherein R' is an alkyl group having 1 to 6 carbon atoms) is in the range of 6:1 to 1:1, and all terminal groups of the alkylene oxide-derived polymer are -OH groups.

[0069] In one exemplary embodiment, the alkylene oxide derived polymer is a random copolymer of ethylene oxide and propylene oxide, such as a linear ethylene oxide / propylene oxide copolymer.

[0070] In a preferred embodiment of the present disclosure, polymerization is carried out in a cascade of a fluidized bed reactor and a multi-zone circulation reactor, and the polymerization reactor is operated under different polymerization conditions, and in particular, under different concentrations of molecular weight regulators (such as hydrogen). Therefore, a polyolefin polymer component of lower molecular weight is obtained in the polymerization using a higher hydrogen concentration reactor, and a polyolefin polymer component of higher molecular weight is obtained in the polymerization using a lower hydrogen concentration reactor. Preferably, a polyolefin polymer component of lower molecular weight is obtained in a fluidized bed reactor, and a polyolefin polymer component of higher molecular weight is obtained in a multi-zone circulation reactor. Therefore, a fluidized bed reactor can be operated with a higher concentration of hydrogen to produce a polyolefin polymer component of lower molecular weight, while a multi-zone circulation reactor can be operated with a lower concentration of hydrogen to produce a polyolefin polymer component of higher molecular weight. The polyolefin polymer prepared in the process of the present disclosure may have an MFR in the range of 0.5 g / 10 min to 350 g / 10 min, more preferably in the range of 1.0 g / 10 min to 40 g / 10 min or 120 g / 10 min to 250 g / 10 min at a temperature of 190° C. under a load of 21.6 kg according to DIN EN ISO 1133:2005. 21.6 The polyethylene of the present invention is preferably a polyethylene having an MFR in the range of 1.2 g / 10 min to 35 g / 10 min, and in particular in the range of 1.5 g / 10 min to 10 g / 10 min. 21.6 Polyethylene. The density can be 0.935g / cm 3 Up to 0.970g / cm 3 In some embodiments and more preferably at 0.945 g / cm 3 Up to 0.968g / cm 3 within the range.

[0071] The process disclosed herein can be used for the homopolymerization of ethylene or ethylene with up to 20 wt.-% C 3 -C 8 -Copolymerization of 1-olefins.

[0072] The process disclosed herein can be used for the preparation of polyethylene in a polymerization reactor cascade, wherein a fluidized bed reactor is arranged upstream of a multizone circulation reactor, and wherein an ethylene homopolymer or ethylene copolymer is produced in the fluidized bed reactor, which has an MFR in the range of 0.1 g / 10 min to 300 g / 10 min, and more preferably in the range of 1 g / 10 min to 100 g / 10 min, at a temperature of 190° C. and a load of 2.16 kg according to DIN EN ISO 1133:2005. 2.16 .

[0073] The process disclosed herein provides the possibility of preparing polyolefin polymers by gas phase polymerization in a polymerization reactor cascade comprising a fluidized bed reactor and a multizone circulation reactor, wherein the formation of polymer agglomerates in the polymerization reactor and fluctuations in the fluid dynamics of the multizone circulation reactor are prevented or at least greatly reduced.

[0074] In another aspect, the present disclosure provides a gas phase polymerization apparatus for carrying out the process of the present disclosure, the gas phase polymerization reactor comprising a gas phase polymerization reactor and at least one pipeline equipped with at least one inlet for introducing an antistatic agent into the pipeline.

[0075] In an exemplary embodiment, the conduit comprises a receiving end for receiving the mixture of polyolefin particles and gas and a discharge end for discharging the mixture of polyolefin particles and gas, wherein at least one inlet is within the first half of the conduit starting from the receiving end of the conduit, in particular within the first third. It was found that such a distance between the receiving end and the inlet results in a particularly good distribution of the antistatic agent on the polymer particles, resulting in reduced wall sheeting and agglomeration of the polymer particles.

[0076] Reference Figure 1 The present disclosure is described in more detail but is not construed as limiting the scope and spirit of the present disclosure.

[0077] Figure 1 An exemplary embodiment of an assembly of a polymerization reactor cascade including a fluidized bed reactor and a multi-zone circulation reactor for carrying out the process of the present disclosure is schematically shown, with arrows depicting exemplary introduction points for antistatic agents.

[0078] The first gas phase reactor, a fluidized bed reactor (1), comprises a fluidized bed (2) of polyolefin particles, a gas distribution grid (3) and a speed reduction zone (4). The speed reduction zone (4) has an increased diameter compared to the diameter of the fluidized bed portion of the reactor. The polyolefin bed is maintained in a fluidized state by an upwardly flowing gas, which is fed through a gas distribution grid (3) placed in the bottom part of the reactor (1). The gaseous stream of reaction gas leaving the top of the speed reduction zone (4) via a recycle line (5) is compressed by a compressor (6), conveyed to a heat exchanger (7), where the stream is cooled and then recirculated to the bottom of the fluidized bed reactor (1) at a point below the gas distribution grid (3) at position (8). If appropriate, the recycle gas can be cooled in the heat exchanger to below the dew point of one or more recycle gas components in order to operate the reactor with condensed material, i.e. in a condensing mode. In addition to unreacted monomers, the recycle gas may also contain inert condensable gases, such as alkanes, and inert non-condensable gases, such as nitrogen. Make-up monomer, molecular weight regulator and optional inert gas or process additives can be fed into the reactor (1) at various locations, for example into the recycle line (5) upstream of the compressor (6) via one or more lines (9) or into the polymer bed in the fluidized bed reactor (1) via line (9a); this does not limit the scope of the present disclosure. The catalyst can be fed into the reactor (1) via line (10), which can be placed in the lower part of the fluidized bed (2).

[0079] The polyolefin particles obtained in the fluidized bed reactor (1) are discontinuously discharged via pipeline (11) and fed to a solid / gas separator (12) to avoid the gaseous mixture from the fluidized bed reactor (1) entering the second gas phase reactor. Pipeline (11) was found to be a good introduction point for antistatic agents. The gas leaving the solid / gas separator (12) leaves the reactor as waste gas via pipeline (13), while the separated polyolefin particles are fed to the second gas phase reactor via pipeline (14).

[0080] The second gas phase reactor is a multi-zone circulating gas phase reactor (31) having two reaction zones, namely a riser (32) and a downcomer (33), through which the polyolefin particles repeatedly pass. In the riser (32), the polyolefin particles flow upward in the direction of arrow (34) under fast fluidization conditions. In the downcomer (33), the polyolefin particles flow downward in the direction of arrow (35) under the action of gravity. The riser (32) and the downcomer (33) are suitably interconnected by interconnecting bends (36) and (37).

[0081] After flowing through the riser (32), the polyolefin particles and the gaseous mixture leave the riser (32) and are conveyed to a solid / gas separation zone (38). This solid / gas separation can be achieved by using conventional separation devices such as, for example, a centrifugal separator like a cyclone separator. From the separation zone (38), the polyolefin particles enter the downcomer (33).

[0082] The gaseous mixture leaving the separation zone (38) is recycled to the riser (32) via a recycle line (39) equipped with a compressor (40) and a heat exchanger (41). Downstream of the heat exchanger (41), the recycle line (39) splits and the gaseous mixture is divided into two separate streams: the line (42) conveys a portion of the recycle gas into the interconnecting bend (37), while the line (43) conveys another portion of the recycle gas to the bottom of the riser (32) in order to establish fast fluidization conditions therein. The polyolefin particles coming from the first gas phase reactor via the line (14) enter the multi-zone circulating gas phase reactor (31) at the interconnecting bend (37) at the position (44).

[0083] Make-up monomer, make-up comonomer and optionally inert gas or process additives can be fed to the multizone circulation reactor (31) via one, two or more lines (45) or (46) which are appropriately placed at any point of the gas recycle line (39) or the downcomer (33). A possible way to feed process additives such as antistatic agents is to further feed additives via line (47).

[0084] A portion of the gaseous mixture leaving the separation zone (38) leaves the recirculation line (39) after the compressor (40) and is sent via the line (48) to the heat exchanger (49), where the mixture is cooled to a temperature at which the monomers and optionally the inert gases partially condense. A separation vessel (50) is placed downstream of the heat exchanger (49). The separated gaseous mixture is recirculated to the recirculation line (39) via the line (51), and the separated liquid is fed to the downcomer (33) via the line (52) by means of a pump (53).

[0085] The polyolefin particles obtained in the multi-zone circulation reactor (31) are continuously discharged from the bottom of the downcomer (33) via a discharge line (54), which is found to be another good introduction point for the antistatic agent.

[0086] By selecting the discharge line (11) and / or (54) as the point of introduction of the antistatic agent, combined with conveying the mixture of polyolefin particles and gas at a speed greater than or equal to 2 m / s, the formation of wall sheets and polymer agglomerates can be avoided without affecting the operability of the polymerization process.

Claims

1. A process for continuously producing a polyolefin polymer in a gas phase polymerization apparatus at a temperature of 20° C. to 200° C. and a pressure of 0.5 MPa to 10 MPa in the presence of a polymerization catalyst, the process comprising the following steps: Providing a mixture of polyolefin particles and gas; conveying the mixture through a pipeline at a gas velocity greater than or equal to 2 m / s; and - Introducing an antistatic agent into the mixture.

2. The process according to claim 1, characterized in that The density of the polyolefin particles in the gas is at least 30 kg / m 3 , preferably at least 50 kg / m 3 , more preferably at least 80 kg / m 3 .

3. A process according to any one of the preceding claims, characterised in that The pipeline is a discharge line and / or a transfer line.

4. A process according to any one of the preceding claims, characterised in that The process also includes the following steps: Feeding an olefin or an olefin and one or more other ethylenically unsaturated monomers into a gas phase polymerization reactor; homopolymerizing the olefin or copolymerizing the olefin with the one or more other ethylenically unsaturated monomers in the gas phase reactor in the presence of a polymerization catalyst; • The formed polyolefin particles are discharged from the gas phase reactor.

5. Process according to any one of the preceding claims, characterised in that The gas phase polymerization apparatus comprises two or more gas phase polymerization reactors, preferably a series of fluidized bed reactors and multi-zone circulation reactors.

6. Process according to any one of the preceding claims, characterised in that The antistatic agent comprises an alkylene oxide derived polymer.

7. The process according to claim 6, characterized in that The alkylene oxide derived polymer is a random copolymer of ethylene oxide and propylene oxide, preferably a linear ethylene oxide / propylene oxide copolymer.

8. Process according to any one of the preceding claims, characterised in that The antistatic agent is introduced into the mixture of gas and polyolefin in the feed of a liquid carrier, wherein the weight ratio of antistatic agent to liquid carrier in the combined stream introduced into the pipeline is preferably in the range of 1:5000 to 1:

10.

9. The process according to claim 8, characterized in that The liquid carrier is selected from the group consisting of water, liquid hydrocarbons, preferably liquid hydrocarbons having 3 to 8 carbon atoms, such as propane.

10. Process according to any one of the preceding claims, characterised in that The polymerization is carried out in a cascade of polymerization reactors comprising a fluidized bed reactor and a multi-zone circulation reactor, in which the growing polymer flows upward through a first polymerization zone under fast fluidization or transport conditions, leaves the first polymerization zone and enters a second polymerization zone, and the particles flow downward through the second polymerization zone under the action of gravity, leave the downcomer and are reintroduced into the riser, thereby establishing a circulation of the polymer, and the fluidized bed reactor is arranged upstream of the multi-zone circulation reactor.

11. The process according to claim 10, characterized in that A polyolefin polymer component with a lower molecular weight is obtained in the fluidized bed reactor, and a polyolefin polymer component with a higher molecular weight is obtained in the multi-zone circulation reactor.

12. Process according to any one of the preceding claims, characterised in that The polyolefin polymer is a polyethylene prepared by homopolymerizing ethylene or copolymerizing ethylene with up to 10 wt.% of a C3-C8-1-olefin.

13. Process according to any one of the preceding claims, characterised in that In addition to feeding the antistatic agent into the pipe conveying the mixture at a gas velocity greater than or equal to 2 m / s, the antistatic agent is also fed into at least one gas phase polymerization reactor.

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