Utilization of 1-hexene in multistage polyolefin production.

Abstract

The present disclosure relates to a method for polymerizing olefins in a multi-stage polymerization process configuration, comprising: a) polymerizing ethylene in a first polymerization step in the presence of a polymerization catalyst, optionally in the presence of at least one other alpha-olefin comonomer, to form a first polymer component (A); and b) polymerizing a predetermined monomer mixture comprising ethylene and 1-hexene in the presence of said first polymer component (A) of step a), optionally in the presence of at least one other alpha-olefin comonomer, in gas phase to form a second polymer component (B), wherein the multimodal polyethylene polymer produced by the process comprises 1-hexene comonomer and at least one further C 4~10 The present disclosure further relates to a method for improving the performance of a single-site polymerization catalyst in a multi-stage olefin copolymerization process, comprising the step of: supplying a predetermined monomer mixture comprising ethylene and 1-hexene to the gas phase polymerization step from the start-up of the gas phase polymerization step. The present disclosure further relates to a method for improving the performance of a single-site polymerization catalyst in a multi-stage olefin polymerization, comprising the step of supplying a predetermined monomer mixture comprising ethylene and 1-hexene to the gas phase polymerization step from the start-up of the gas phase polymerization step.

Description

[Technical field]

[0001] This disclosure relates to the copolymerization of olefins, and more particularly to a multi-stage polyolefin production process for producing an ethylene / 1-butene / 1-hexene terpolymer. This disclosure further relates to the use of 1-hexene in the gas phase polymerization stage to improve the performance of a single-site catalyst in a multi-stage olefin copolymerization process. [Background technology]

[0002] Multi-stage polyolefin production processes (e.g., Borstar PE, PP, and Spheripol PP) consist of multi-stage reactor configurations to provide multimodal capabilities to easily achieve processing of resins with desired mechanical properties. In such processes, multiple slurry loop reactors are combined in series followed by a gas phase reactor to produce all kinds of polyolefin grades.

[0003] One of the important features in multi-stage olefin polymerization processes is to ensure adequate catalyst performance in all stages of the multi-stage polymerization process, and more particularly to properly select gas-phase reactor operating conditions resulting in smooth operability in the GPR. This can be difficult with single-site catalysts, which have superior comonomer incorporation capabilities compared to first generation single-site catalysts. The presence of small size particles (also known as Stocke particles: particles whose buoyancy is greater than gravity in a gas-solid fluidization environment) that tend to be entrained by the fluidization gas can cause problems with reactor fouling (polymer coating on the reactor walls), sheeting and chunking, as well as fouling of cycle gas compressors and heat exchanger units. In this context, optimizing catalyst performance in terms of eliminating the population of small size particles in the GPR is of utmost importance and represents a key aspect for the successful implementation of the catalyst in a multi-stage ethylene copolymerization process. Summary of the Invention [Problem to be solved by the invention]

[0004] It is an object of the present disclosure to provide a method for polymerizing olefins in a multi-stage polymerization process configuration to overcome the above disadvantages.

[0005] The object of the present disclosure is achieved by a method which is characterized by what is stated in the independent claims. Preferred embodiments of the present disclosure are disclosed in the dependent claims.

[0006] The present disclosure is based on the idea of ​​injecting 1-hexene into the gas phase reactor from the gas phase start up onwards, which ensures adequate catalyst performance in all stages of the multi-stage polymerization process and more particularly ensures the proper selection of gas phase reactor operating conditions resulting in smooth operability in the GPR.

[0007] More particularly, the present disclosure establishes a start-up strategy for the gas phase reactor in terms of appropriate comonomer injection aimed at improving catalyst performance, resulting in enhanced reactor operability and process performance, while demanding products (e.g., low density and low MFR) can be produced. [Means for solving the problem]

[0008] The present disclosure provides a method for polymerizing olefins in a multi-stage polymerization process configuration, the method comprising: a) in a first polymerization step, polymerizing ethylene in the presence of a polymerization catalyst, and optionally in the presence of at least one other alpha-olefin comonomer, to form a first polymer component (A); and b) in a second polymerization step, polymerizing in the gas phase a given monomer mixture comprising ethylene and 1-hexene in the presence of said first polymer component (A) of step a), optionally in the presence of at least one other alpha-olefin comonomer, to form a second polymer component (B). Including, wherein the multimodal polyethylene polymer produced by the process comprises 1-hexene comonomer and at least one further C 4~10 Comonomers, and wherein the predetermined monomer mixture containing ethylene and 1-hexene is supplied to the second polymerization step from the start-up of the second polymerization step. Regarding the above method.

[0009] By introducing a predetermined monomer mixture comprising ethylene and 1-hexene into the gas phase reactor, the population of small size particles (less than 80 μm) is reduced from the start of gas phase process operation in the second polymerization step, thus improving catalyst performance during gas phase reactor operation.

[0010] Ensuring proper operating conditions in the gas phase reactor by selecting a start-up strategy that favors the initial particle growth rate of individual polymer particles so as to reduce the population of small size polymer particles during the initial stages of the gas phase reaction is an important aspect towards good catalyst performance and thus smooth GPR operability and reactor performance, thus establishing proper polymerization conditions to produce desired product targets. Effect of the Invention

[0011] Thus, the present method allows the utilization of single-site catalysts (high comonomer sensitive catalysts) that are capable of incorporating large amounts of comonomer while achieving smooth catalyst performance without experiencing process limitations due to sheeting, chunking and reactor fouling caused primarily by the presence of small sized polymer particles (fines). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] process

[0013] The present disclosure relates to a multi-stage polymerization process using a polymerization catalyst, said process comprising an optional but preferred prepolymerization step followed by a first polymerization step and a second polymerization step.

[0014] Preferably, the same polymerization catalyst is used in each step, and ideally it is transferred sequentially from the prepolymerization to the subsequent polymerization steps in a well-known manner. One preferred process configuration is the Borstar 登録商標 Type cascade, especially Borstar 登録商標 2G type cascade, preferably Borstar 登録商標 Based on 3G type cascade.

[0015] Thus, the method of polymerizing olefins in a multi-stage polymerization process configuration comprises: a) in a first polymerization step, polymerizing ethylene in the presence of a polymerization catalyst, and optionally in the presence of at least one other alpha-olefin comonomer, to form a first polymer component (A); and b) in a second polymerization step, polymerizing in the gas phase a given monomer mixture comprising ethylene and 1-hexene in the presence of said first polymer component (A) of step a), optionally in the presence of at least one other alpha-olefin comonomer, to form a second polymer component (B). Including, wherein the multimodal polyethylene polymer produced by the process comprises 1-hexene comonomer and at least one further C 4~10 Contains comonomer.

[0016] Prepolymerization process

[0017] A prepolymerization step may be performed before the polymerization step. The purpose of the prepolymerization is to polymerize a small amount of polymer on the catalyst at a low temperature and / or a low monomer concentration. The prepolymerization can improve the performance of the catalyst in the slurry and / or modify the properties of the final polymer. The prepolymerization step is preferably performed in the slurry, and the amount of polymer produced in any prepolymerization step is counted in the amount (wt%) of the ethylene polymer component (A).

[0018] If a prepolymerization step is present, the catalyst components are preferably all introduced into said prepolymerization step, and the reaction product of said prepolymerization step is then preferably introduced into said first polymerization step.

[0019] However, when the solid catalyst component and the cocatalyst can be fed separately, it is possible that only a part of the cocatalyst is introduced into the prepolymerization stage and the remaining part is introduced into the subsequent polymerization stage, and in such a case, it is necessary to introduce into the prepolymerization stage an amount of the cocatalyst sufficient to obtain a sufficient polymerization reaction.

[0020] Within the scope of the present invention, it is understood that the amount of polymer produced in the prepolymerization is in the range of 1-7% by weight relative to the final multimodal (co)polymer, which can be counted as part of the first polymer component (A) produced in the first polymerization step a).

[0021] First polymerization step a)

[0022] In this process, the first polymerization step a) comprises polymerizing ethylene monomer and, optionally, at least one olefin comonomer.

[0023] In one embodiment, the first polymerization step comprises polymerizing ethylene to produce an ethylene homopolymer.

[0024] In another embodiment, the first polymerization step comprises polymerizing ethylene and at least one olefin comonomer to produce an ethylene copolymer.

[0025] The first polymerization step may be carried out in any suitable reactor or series of reactors. The first polymerization step is carried out in one or more slurry polymerization reactors. Preferably, the first polymerization step is carried out in one or more slurry polymerization reactors, more preferably in at least three slurry phase reactors, including a slurry phase reactor for carrying out a prepolymerization.

[0026] The polymerization in the first polymerization zone is preferably carried out in a slurry. The polymer particles formed in the polymerization are then suspended in a fluid hydrocarbon with the catalyst fragmented and dispersed within the particles. The slurry is agitated to allow transfer of reactants from the fluid to the particles.

[0027] The slurry polymerization is usually carried out in an inert diluent, typically a hydrocarbon diluent, such as methane, ethane, propane, n-butane, isobutane, pentane, hexane, heptane, octane, and the like, or mixtures thereof. Preferably, the diluent is a low boiling hydrocarbon having 1 to 4 carbon atoms, or a combination of such hydrocarbons. A particularly preferred diluent is propane, optionally with small amounts of methane, ethane, and / or butane.

[0028] The ethylene content in the fluid phase of the slurry is 2 to about 50 mol%, preferably about 3 to about 20 mol%, particularly about 5 to about 15 mol%. The advantage of having a high ethylene concentration is that the productivity of the catalyst is increased, but the disadvantage is that more ethylene needs to be recycled than if the concentration is lower.

[0029] The temperature in the slurry polymerization is typically from 50 to 115° C., preferably from 60 to 110° C., particularly from 70 to 100° C. The pressure is from 1 to 150 bar, preferably from 10 to 100 bar.

[0030] The pressure in the first polymerization step is typically from 35 to 80 bar, preferably from 40 to 75 bar, in particular from 45 to 70 bar.

[0031] The residence time in the first polymerization stage is typically from 0.15 hours to 3.0 hours, preferably from 0.20 hours to 2.0 hours, particularly from 0.30 hours to 1.5 hours.

[0032] It may be advantageous to carry out the slurry polymerization above the critical temperature and pressure of the fluid mixture. Such an operation is described in US-A-5391654. In such an operation, the temperature is typically 85-110°C, preferably 90-105°C, and the pressure is 40-150 bar, preferably 50-100 bar.

[0033] The slurry polymerization can be carried out in any reactor known for use in slurry polymerization. Such reactors include continuous stirred tank reactors and loop reactors. It is particularly preferred that the polymerization is carried out in a loop reactor. In a loop reactor, the slurry is circulated at high speed along a closed pipe by using a circulation pump. Loop reactors are generally known in the art, and examples are given, for example, in US-A-4582816, US-A-3405109, US-A-3324093, EP-A-479186 and US-A-5391654.

[0034] The slurry can be withdrawn from the reactor continuously or intermittently. A preferred method of intermittent withdrawal is the use of settling legs, in which the slurry is concentrated before withdrawing a batch of the concentrated slurry from the reactor. The use of settling legs is disclosed, inter alia, in US-A-3374211, US-A-3242150, and EP-A-1310295. Continuous withdrawal is disclosed, inter alia, in EP-A-899990, EP-A-1415999, EP-A-1591460, and WO-A-2007 / 025640. Said continuous withdrawal is advantageously combined with suitable concentration methods, as disclosed in EP-A-1310295, EP-A-1591460 and EP 3178853 B1.

[0035] A cyclone may be placed at the exit of the disengagement zone (recirculation gas line) to collect entrained particles (estimated particle carryover) and to prevent small size particles from passing through the gas compressor and heat exchanger.

[0036] As known in the art, hydrogen may be fed into the reactor to control the molecular weight of the polymer. Additionally, one or more alpha-olefin comonomers may be added to the reactor to control the density of the polymer product. The actual amount of hydrogen and comonomer fed depends on the catalyst used and the desired melt index (or molecular weight) and density (or comonomer content) of the resulting polymer.

[0037] Second polymerization step b)

[0038] From the first polymerization step, the first polymer component (A) is transferred to the second polymerization step.

[0039] In this process, the second polymerization step b) comprises polymerizing ethylene monomer and 1-hexene comonomer, and optionally at least one other alpha-olefin comonomer.

[0040] In one embodiment, the second polymerization step comprises polymerizing ethylene and 1-hexene and at least one olefin comonomer to produce an ethylene terpolymer.

[0041] In another embodiment, the second polymerization step polymerizes ethylene and 1-hexene and 1-butene to produce an ethylene / 1-butene / 1-hexene polymer.

[0042] The second polymerization step is carried out in one or more gas phase polymerization reactors.

[0043] The gas phase polymerization can be carried out in any reactor known for use in gas phase polymerization. Such reactors include fluidized bed reactors, fast fluidized bed reactors, or settled bed reactors, or any combination thereof. When a combination of reactors is used, the polymer is transferred from one polymerization reactor to another. Moreover, some or all of the polymer from a polymerization stage may be returned to a previous polymerization stage.

[0044] The gas phase polymerization is typically carried out in a gas-solids fluidized bed, also known as a gas phase reactor (GPR). Gas solids olefin polymerization reactors are commonly used for the polymerization of alpha-olefins, such as ethylene and propylene, because they allow relatively high flexibility in polymer design and the use of various catalyst systems. A common variation of the gas solids olefin polymerization reactor is the fluidized bed reactor.

[0045] A gas-solid olefin polymerization reactor is a polymerization reactor for heterophase polymerization of one or more gaseous olefin monomers into polyolefin powder particles, which comprises three zones: in the bottom zone, a fluidization gas is introduced into the reactor; in the middle zone, which usually has a generally cylindrical shape, one or more olefin monomers present in the fluidization gas are polymerized to form polymer particles; in the top zone, the fluidization gas is withdrawn from the reactor. In some gas-solid olefin polymerization reactors, a fluidization grid (also named distribution plate) separates the bottom zone from the middle zone. In some gas-solid olefin polymerization reactors, the top zone forms a disengaging zone or entrainment zone where the fluidization gas expands due to its expanding diameter compared to the middle zone, and where the gas disengages from the polyolefin powder.

[0046] Dense phase refers to the region in the intermediate zone of a gas-solid olefin polymerization reactor that has an increased bulk density due to the formation of said polymer particles. In certain gas-solid olefin polymerization reactors, i.e. fluidized bed reactors, said dense phase is formed by the fluidized bed.

[0047] The temperature in the gas phase polymerization is typically 40 to 120°C, preferably 50 to 100°C, and more preferably 65 to 90°C.

[0048] The pressure in the gas phase polymerization is typically from 5 to 40 bar, preferably from 10 to 35 bar, more preferably from 15 to 30 bar.

[0049] The residence time in the gas phase polymerization is typically from 1.0 to 4.5 hours, preferably from 1.5 to 4.0 hours, and particularly from 2.0 to 3.5 hours.

[0050] The molar ratios of reactants can be adjusted as follows: C6 / C2 ratio is 0.0001-0.1 mol / mol, H2 / C2 ratio is 0-0.1 mol / mol.

[0051] The polymer production rate in the gas phase reactor is 10 tn / h to 65 tn / h, preferably 12 tn / h to 58 tn / h, particularly 13 tn / h to 52.0 tn / h, and therefore the total polymer withdrawal rate from the gas phase reactor is 15 tn / h to 100 tn / h, preferably 18 tn / h to 90 tn / h, particularly 20 tn / h to 80.0 tn / h.

[0052] The product split (second polymer component (B) % / first polymer component (A) %) may be 0.65 to 2.5, preferably 0.8 to 2.3, and most preferably 1.0 to 1.65.

[0053] The process requires that 1-hexene is introduced into the second polymerization step b), ie into the first gas phase reactor, from the beginning of the start-up of the gas phase reaction.

[0054] This can be accomplished by introducing a predetermined monomer mixture of ethylene and 1-hexene into the second polymerization step.

[0055] The molar ratio of 1-hexene to ethylene in the second polymerization step is typically in the range of 7 mol / kmol to 80 mol / kmol, preferably 8.0 mol / kmol to 60.0 mol / kmol, particularly 9.0 to 50.0 mol / kmol.

[0056] The feed ratio of the predetermined 1-hexene / ethylene mixture is from 70 kg / ton to 400 kg / ton, preferably from 75 kg / ton to 350 kg / ton, more preferably from 80 kg / ton to 280 kg / ton.

[0057] 1-Hexene may be introduced into the reactor via, for example, a fresh comonomer injection line installed downstream of the cooler, where it is mixed with the recycle gas stream and thus introduced into the gas phase reactor. Thus, 1-hexene is preferably introduced simultaneously with ethylene, and in particular not as a separate mixture of 1-hexene and ethylene.

[0058] The particle growth rate of individual polymer particles is proportional to the polymerization rate (ie, catalyst activity) and inversely proportional to the particle size and density of the particle polymer phase. Thus, the presence of 1-hexene from the beginning of the GPR operation (GPR start-up) results in the following positive effects on particle growth: i) it increases the solubility of the small penetrant (i.e., ethylene) in the gas phase reactor due to the cosolubility effect (i.e., the high molecular weight olefin acts as a solvent for the low molecular weight olefin), thus increasing the local polymerization rate; ii) it reduces the polymer phase density of the particles due to the swelling effect; iii) it reduces the overall density of the polymer due to the reduced crystallinity, thus the amorphous fraction of the polymer phase in the polymer particles is higher compared to the absence of comonomer in the reactor, further increasing the amount of reactant sorption, thus increasing the local polymerization rate and increasing the particle growth rate; and iv)) it provides the necessary time for the sorption process of 1-hexene within the polymer particles, thereby resulting in a uniform distribution of the sorbed concentration of 1-hexene within the polymer particles (improved reactant uniformity at the particle level).

[0059] Polymerization Catalyst

[0060] The polymerization catalyst utilized in the present process is a metallocene catalyst, which typically comprises (i) a transition metal complex, (ii) a cocatalyst, and, optionally, (iii) a support.

[0061] Preferably, the first polymerization step and the second polymerization step are carried out using, i.e. in the presence of, the same metallocene catalyst.

[0062] The process preferably utilizes a single-site catalyst. Polyethylene copolymers produced with single-site catalysts, in contrast to Ziegler-Natta catalysts, have properties that allow them to be distinguished from Ziegler-Natta materials. In particular, the comonomer distribution is more uniform. This can be shown using the TREF technique or the Crystaf technique. The catalyst residue may also indicate the catalyst used. Ziegler-Natta catalysts do not contain group (IV) metals, for example Zr or Hf.

[0063] Transition metal complexes (i)

[0064] The transition metal complex comprises a transition metal (M) from groups 3 to 10 of the periodic table (IUPAC 2007), or an actinide or lanthanide transition metal (M).

[0065] In accordance with the present invention, the term "transition metal complex" includes any metallocene or non-metallocene compound of a transition metal, which has at least one organic (coordination) ligand and has catalytic activity alone or together with a cocatalyst. Such transition metal compounds are well known in the art, and the present invention covers compounds of metals from groups 3 to 10, such as groups 3 to 7, or groups 3 to 6, such as groups 4 to 6, as well as the lanthanides or actinides of the periodic table (IUPAC 2007).

[0066] In one embodiment, the transition metal complex (i) has the formula (iI): (L) m R n MX q (ii) Where: "M" is a transition metal (M) in groups 3 to 10 of the periodic table (IUPAC 2007), Each "X" is independently a monoanionic ligand, e.g., a σ-ligand; each "L" is independently an organic ligand that coordinates to a transition metal "M"; "R" is a bridging group that links multiple organic ligands (L); "m" is 1, 2 or 3, preferably 2; "n" is 1 or 2, preferably 0 or 1; "q" is 1, 2 or 3, preferably 2, and m+q is equal to the valence of the transition metal (M).

[0067] "M" is preferably selected from the group consisting of zirconium (Zr), hafnium (Hf), or titanium (Ti), and more preferably selected from the group consisting of zirconium (Zr) and hafnium (Hf).

[0068] "X" is preferably a halogen, most preferably Cl.

[0069] Most preferably, the transition metal complex (i) is a metallocene complex, which comprises a transition metal compound as defined above, which comprises a cyclopentadienyl, indenyl or fluorenyl ligand as the substituent "L", which further comprises one or more substituents such as alkyl, aryl, arylalkyl, alkylaryl, silyl, siloxy, alkoxy or other heteroatom groups. Suitable metallocene catalysts are known in the art and are disclosed, inter alia, in WO-A-95 / 12622, WO-A-96 / 32423, WO-A-97 / 28170, WO-A-98 / 32776, WO-A-99 / 61489, WO-A-03 / 010208, WO-A-03 / 051934, WO-A-03 / 051514, WO-A-2004 / 085499, EP-A-1752462 and EP-A-1739103.

[0070] In one embodiment of the invention, the metallocene complex is bis(1-methyl-3-n-butylcyclopentadienyl)zirconium(IV) chloride.

[0071] In another embodiment, the transition metal complex (i) has the following formula (i-II): [ka] where each X is independently a halogen atom, C 1~6 Alkyl group, C 1~6 an alkoxy group, a phenyl group, or a benzyl group; each Het is independently a monocyclic heteroaromatic ring containing at least one heteroatom selected from an O atom or a S atom; L is -R' 2 Si-, where each R' is independently optionally substituted with an alkoxy group having 1 to 10 carbon atoms; 1~20 Hydrocarbyl or C 1~10 is alkyl; M is Ti, Zr or Hf; Each R 1 may be the same or different, C 1~6 Alkyl group or C 1~6 is an alkoxy group; each n is 1 to 2; Each R 2 may be the same or different, C 1~6 Alkyl group, C 1~6 Alkoxy group or -Si(R) 3 It is a base; Each R is C 1~10 Alkyl group or 1 to 3 C 1~6 a phenyl group optionally substituted by an alkyl group; and Each p is an integer from 0 to 1.

[0072] Preferably, the compound of formula (i-II) has the following structure (i-III): [ka] where each X is independently a halogen atom, C 1~6 Alkyl group, C 1~6 an alkoxy group, a phenyl group, or a benzyl group; L is for Me 2 Si- and; Each R 1 may be the same or different, C 1~6 an alkyl group, such as methyl or t-Bu; each n is 1 to 2; R 2 is -Si(R) 3 is an alkyl group; Each p is 1; Each R is C 1~6 It is an alkyl group or a phenyl group.

[0073] More preferred transition metal complexes of formula (i-III) are as follows: [ka]

[0074] Cocatalyst (ii)

[0075] To form the polymerization catalyst, a cocatalyst, also known as an activator, is used, as is well known in the art. Cocatalysts containing Al or B are well known and can be used herein. The use of aluminoxanes (e.g., MAO) or boron-based cocatalysts (e.g., borates) is preferred.

[0076] Suitable cocatalysts are metal alkyl compounds, particularly aluminum alkyl compounds known in the art. Particularly suitable activators for use with metallocene catalysts are alkylaluminumoxy compounds, such as methylalumoxane (MAO), tetraisobutylalumoxane (TIBAO) or hexaisobutylalumoxane (HIBAO).

[0077] Preferably, the cocatalyst is methylalumoxane (MAO).

[0078] Support (iii)

[0079] The polymerization catalyst of the present invention can be used in solid but unsupported form according to the protocol of WO03 / 051934.The polymerization catalyst of the present invention is preferably used in solid supported form.The particle support material used can be an inorganic porous support, such as silica, alumina, or mixed oxide, such as silica-alumina, especially silica.

[0080] The use of a silica support is preferred.

[0081] In particular, the support is a porous material and thus the complex may be supported within the pores of the particulate support using similar processes as described, for example, in WO 94 / 14856, WO 95 / 12622, WO 2006 / 097497, and EP 1828266.

[0082] The average particle size of the support, e.g., silica support, can typically be from 10 to 100 μm. The average particle size (i.e., median particle size, D 50 ) can be determined using a laser diffraction particle size analyzer Malvern Mastersizer 3000 (sample dispersion: dry powder).

[0083] The average pore size of the support, for example a silica support, can range from 10 to 100 nm and the pore volume can be from 1 to 3 mL / g.

[0084] Examples of suitable support materials are, for example, ES757 manufactured and sold by PQ Corporation, Sylopol 948 manufactured and sold by Grace, or SUNSPERA DM-L-303 silica manufactured and sold by AGC Si-Tech Co. The support can optionally be calcined prior to use in the catalyst preparation to reach an optimum silanol group content.

[0085] The catalyst may comprise 5-500 μmol, such as 10-100 μmol, of transition metal per gram of support, eg, silica, and 3-15 mmol of Al per gram of support, eg, silica.

[0086] Multimodal Polyethylene Polymer

[0087] The present invention relates to the preparation of a multimodal polyethylene copolymer, the density of which is between 900 and 980 kg / m 3 , preferably 905 to 940 kg / m 3 , especially 910-935kg / m 3 , it is possible.

[0088] It is preferred that the multimodal polyethylene polymer is a copolymer. More preferably, the multimodal polyethylene copolymer is LLDPE. It has a viscosity of 905 to 940 kg / m 3 , preferably 910 to 935 kg / m 3 , more preferably 915 to 930 kg / m 3 , especially 916-928kg / m 3 In one embodiment, the density may be 910 to 928 kg / m 3 As used herein, "LLDPE" refers to linear low density polyethylene. The LLDPE is preferably multimodal.

[0089] The term "multimodal" includes polymers that are multimodal with respect to MFR, and therefore includes bimodal polymers. The term "multimodal" can also mean multimodality with respect to "comonomer distribution".

[0090] Usually, polymers containing at least two polyethylene fractions are said to be "multimodal" because they are produced under different polymerization conditions and the fractions have different (weight average) molecular weights and molecular weight distributions. The prefix "multi" refers to the number of different polymer fractions present in the polymer. Thus, for example, the term "multimodal polymer" includes so-called "bimodal" polymers consisting of two fractions. The molecular weight distribution curve of a multimodal polymer, e.g. LLDPE, i.e. the graphical appearance of the polymer weight fraction as a function of molecular weight, may show two or more maxima or at least be clearly broadened compared to the curves for the individual fractions. The final MWD curve is often broad, skewered or shows a shoulder.

[0091] Ideally, the molecular weight distribution curve of the multimodal polymer of the present invention will show two distinct maxima. Alternatively, the polymer fractions have similar MFR and are bimodal in comonomer content. Polymers comprising at least two polyethylene fractions are produced under different polymerization conditions, resulting in different comonomer contents of the fractions, also referred to as "multimodal".

[0092] For example, when a polymer is produced in a sequential, multi-stage process using reactors connected in series and using different conditions in each reactor, the polymer fractions produced in the different reactors will have their own molecular weight distributions and weight average molecular weights. When the molecular weight distribution curve of such a polymer is recorded, the individual curves of these fractions are superimposed on the molecular weight distribution curve for the resulting polymer product as a whole, usually giving a curve with two or more distinct maxima.

[0093] In the possible multimodal polymers, there may be a lower molecular weight component (LMW) and a higher molecular weight component (HMW). The LMW component has a lower molecular weight than the high molecular weight component. This difference is preferably at least 5000 g / mol.

[0094] The multimodal polyethylene polymer produced by this process comprises 1-hexene comonomer and at least one further C 4~10 comonomer. 1-hexene comonomer is present in the second polymer component (B). Further comonomers may be present in the HMW component (i.e., second component (B), produced in the second polymerization step) or in the LMW component (i.e., first component (A), produced in the first polymerization step) or in both. Hereinafter, the term "LMW / HMW component" is used, but the described embodiments apply to the first component and the second component, respectively.

[0095] At least one HMW component is C 4~10 The LMW component may then be an ethylene homopolymer or may contain at least one C 4~10 In a preferred embodiment, the multimodal polyethylene polymer comprises at least two, e.g. exactly two, C 4~10 Contains comonomer.

[0096] In one embodiment, the multimodal polyethylene polymer is a terpolymer and comprises a hexene comonomer and at least one C 4~10 In that scenario, the HMW component may be a terpolymer component, and the low molecular weight (LMW) component may be an ethylene homopolymer or copolymer component. Alternatively, both the LMW and HMW components may contain at least two C 4~10 It may be a copolymer such that a comonomer is present.

[0097] Thus, the multimodal polyethylene polymer has an HMW component consisting of ethylene and at least two other C 4~10 Alpha-olefin monomers, such as 1-butene, and one C 6~10 and alpha-olefin monomers. Ethylene preferably forms the majority of the LMW or HMW component. In a most preferred embodiment, the LMW component may comprise an ethylene 1-butene copolymer, and the HMW component may comprise an ethylene 1-hexene copolymer.

[0098] The total comonomer content in the multimodal polyethylene polymer may be, for example, from 0.2 to 14.0 mol %, preferably from 0.3 to 12 mol %, more preferably from 0.5 to 10.0 mol %, and most preferably from 0.6 to 8.5 mol %.

[0099] The 1-butene may be present in an amount of from 0.05 to 6.0 mol %, for example from 0.1 to 5 mol %, more preferably from 0.15 to 4.5 mol %, and most preferably from 0.2 to 4 mol %.

[0100] C 6 ~C 10 The alpha-olefin may be present in an amount of from 0.2 to 6 mol %, preferably from 0.3 to 5.5 mol %, and more preferably from 0.4 to 4.5 mol %.

[0101] Preferably, the LMW component has a lower comonomer amount (mol %) than the HMW component, for example the amount of comonomer, preferably 1-butene, in the LMW component is 0.05-0.9 mol %, more preferably 0.1-0.8 mol %, while the amount of comonomer, preferably 1-hexene, in the HMW component (B) is 1.0-8.0 mol %, more preferably 1.2-7.5 mol %.

[0102] Thus, the multimodal polyethylene copolymer may be formed from ethylene along with at least one of 1-butene, 1-hexene, or 1-octene. The multimodal polyethylene polymer may be an ethylene butene hexene center polymer, for example, the HMW component is an ethylene butene hexene center polymer and the LMW is an ethylene homopolymer component. The use of terpolymers of ethylene with 1-octene and 1-hexene comonomers is also envisioned.

[0103] In a further embodiment, the multimodal polyethylene copolymer may comprise two ethylene copolymers, such as two ethylene butene copolymers or an ethylene butene copolymer (e.g., as the LMW component) and an ethylene hexene copolymer (e.g., as the HMW component). It would also be possible to combine an ethylene copolymer component with an ethylene terpolymer component, such as an ethylene butene copolymer (e.g., as the LMW component) and an ethylene butene hexene copolymer (e.g., as the HMW component).

[0104] The LMW component of the multimodal polyethylene polymer has an MFR of 0.5 to 3000 g / 10 min, more preferably 1.0 to 1000 g / 10 min. 2 In some embodiments, the MFR of the LMW component may be 2 For example, when the target is a cast film, the loading rate can be 50 to 3000 g / 10 min, more preferably 100 to 1000 g / 10 min.

[0105] The molecular weight (Mw) of the LMW component should preferably be between 20,000 and 180,000, for example between 40,000 and 160,000. The LMW component should have a molecular weight (Mw) of at least 925 kg / m 3 , e.g. at least 940 kg / m 3 , and may have a density of 930 to 950 kg / m 3 , preferably 935 to 945 kg / m 3 , the range of densities is possible.

[0106] The HMW component of the multimodal polyethylene polymer has, for example, an MFR of less than 1 g / 10 min, for example, 0.2 to 0.9 g / 10 min, preferably 0.3 to 0.8 g / 10 min, more preferably 0.4 to 0.7 g / 10 min. 2 The HMW component may have a viscosity of 915 kg / m 3 Less than 910kg / m 3 Less than 905 kg / m 3 The Mw of the high molecular weight component may range from 70,000 to 1,000,000, preferably from 100,000 to 500,000.

[0107] The LMW component may be 30 to 70 wt %, such as 35 to 65 wt %, especially 38 to 62 wt %, of a multimodal polyethylene polymer.

[0108] The HMW component may be from 30 to 70% by weight, such as from 35 to 65% by weight, especially from 38 to 62% by weight, of multimodal polyethylene polymer.

[0109] In one embodiment, there is 40-45 wt.% of the LMW component and 60-55 wt.% of the HMW component.

[0110] In one embodiment, the polyethylene polymer is composed of HMW and LMW components as the only polymer components.

[0111] The multimodal polyethylene polymer of the present invention has an MFR of 0.01 to 50 g / 10 min, preferably 0.05 to 25 g / 10 min, particularly 0.1 to 10 g / 10 min. 2 may have.

[0112] The molecular weight distribution (MWD, Mw / Mn) of the polyethylene terpolymer of the present invention is in the range of 2.0 to 15.0, preferably in the range of 2.2 to 10.0, and more preferably in the range of 2.4 to 4.6.

[0113] Working Example

[0114] Polymer Analysis and Characterization

[0115] Bulk density

[0116] The bulk density of the polymer powder can be determined according to standard methods, such as ISO 60:1977 or ASTM D1895-17.

[0117] MFR

[0118] The melt flow rate (MFR) is determined according to ISO 1133 and is expressed in g / 10 min. MFR is an indicator of the flowability and therefore processability of a polymer. The higher the melt flow rate, the lower the viscosity of the polymer. MFR of polypropylene 2 is the temperature of 230℃ and the load of 2.16kg, and the MFR of polyethylene 5 is a temperature of 190°C, a load of 5 kg, and the MFR of polyethylene. 2 is determined at a temperature of 190°C and a load of 2.16 kg.

[0119] density

[0120] The density of the polymer is measured according to ISO 1183-2 / 1872-2B.

[0121] GPC

[0122] The molecular weight averages (Mz, Mw and Mn), the molecular weight distribution (MWD) and its broadness, expressed by the polydispersity index PDI=Mw / Mn, where Mn is the number average molecular weight and Mw is the weight average molecular weight, were determined by Gel Permeation Chromatography (GPC) according to ISO 16014-1:2003, ISO 16014-2:2003, ISO 16014-4:2003 and ASTM D 6474-12 using the following formula:

number

[0123] Fixed elution interval ΔV i , where A i and M i are the elution volumes, V i and the polyolefin molecular weight (MW) associated with the chromatogram peak slice area, where N is equal to the number of data points obtained from the chromatogram between the integration limits.

[0124] A high temperature GPC instrument was used, equipped with an infrared (IR) detector (IR4 or IR5 from PolymerChar, Valencia, Spain) and equipped with 3x Agilent-PLgel Olexis and 1x Agilent-PLgel Olexis Guard columns. As solvent and mobile phase, 1,2,4-trichlorobenzene (TCB) stabilized with 250 mg / L 2,6-ditert-butyl-4-methylphenol was used. The chromatographic system was operated at 160°C and a constant flow rate of 1 mL / min. 200 μL of sample solution was injected per analysis. Data collection was performed using either Agilent Cirrus software version 3.3 or PolymerChar GPC-IR control software.

[0125] The column set was calibrated using universal calibration (according to ISO 16014-2:2003) with 19 narrow MWD polystyrene (PS) standards ranging from 0.5 kg / mol to 11,500 kg / mol. The PS standards were dissolved at room temperature for several hours. Conversion of the polystyrene peak molecular weights to polyolefin molecular weights was accomplished by using the Mark Houwink equation and the Mark Houwink constants:

number

[0126] A third order polynomial fit was used to fit the calibration data.

[0127] All samples were prepared in the concentration range of 0.5–1 mg / mL and dissolved at 160 °C with continuous gentle shaking for 2.5 h for PP and 3 h for PE.

[0128] catalyst

[0129] SiO 2 Loading: 10 kg of silica (PQ Corporation ES757, calcined at 600° C.) was added from a feed drum and O 2 It was inerted in the reactor until the level was below 2 ppm.

[0130] Preparation of MAO / tol / MC: 30 wt% MAO in toluene (14.1 kg) was added from a balance into a separate reactor followed by toluene (4.0 kg) at 25°C (oil circulation temperature) and stirred at 95 rpm. After toluene addition, the stirring speed was increased from 95 rpm to 200 rpm (stirring time 30 min). 477 g of the metallocene Rac-dimethylsilanediylbis{2-(5-(trimethylsilyl)furan-2-yl)-4,5-dimethylcyclopentadiene-1-yl}zirconium dichloride was added from a metal cylinder and then flushed with 4 kg toluene (total toluene 8.0 kg). The stirring speed of the reactor was changed to 95 rpm for MC feed and then back to 200 rpm for a reaction time of 3 hours. After the reaction time, the MAO / tol / MC solution was transferred to the feed vessel.

[0131] Preparation of catalyst: The reactor temperature was set to 10°C (oil circulation temperature) and agitated at 40 rpm for the MAO / tol / MC addition. The MAO / tol / MC solution (target 22.5 kg, actual 22.2 kg) was added within 205 minutes, followed by 60 minutes of agitation (oil circulation temperature set to 25°C). After agitation, the "dry mix" was stabilized at 25°C (oil circulation temperature) and 0 rpm agitation for 12 hours. The reactor was rotated 20° (back and forth) and agitation was performed at 5 rpm for several rounds per hour.

[0132] After stabilization, the catalyst was dried at 60°C (oil circulation temperature) under nitrogen flow of 2 kg / h for 2 hours, followed by drying under vacuum for 13 hours (same nitrogen flow, stirring at 5 rpm). The dried catalyst was sampled and the HC content was measured by thermogravimetry using a Sartorius Moisture Analyser (Model MA45) in a glove box. The target HC level was less than 2% (actual value 1.3%).

[0133] Experimental Example 1 (Comparative Example)

[0134] Initial size 25 microns, span (i.e. (d 90 -d 10 ) / d 50 ) 1.6 single-site catalyst LLDPE film (target MFR 2 =1.3, target density=912~920kg / m 3 The catalyst was first prepolymerized in a prepolymerization reactor at T=50° C. and P=56 barg. More specifically, 40.7 g / h of catalyst, 4 kg / h of ethylene, 85 g / h of 1-butene, 0.03 g / h of hydrogen, and 46 kg / h of propane (diluent) were fed into the prepolymerization reactor, and the average residence time was 23 minutes. The product split was 3.0 wt.%.

[0135] The product was transferred to a split loop reactor configuration, where in the first loop reactor, ethylene (C2), propane (C3), 1-butene (C4) and hydrogen (H2) were fed to the reactor at polymerization conditions of T=85° C., P=54 barg, and the average residence time was 0.31 hours. The C2 concentration in the liquid phase was 3.9 mol %, the H2 / C2 and C4 / C2 molar ratios were 0.38 mol / kmol and 35 mol / kmol, respectively. The product split in the first loop reactor of the split loop configuration was 18.5 wt %, and the product material had an MFR of 0.28 mol / kmol. 2 (g / 10min) = 4.7 and density = 940.7kg / m 3 had the following characteristics:

[0136] The product was then transferred to a second loop reactor in a split loop reactor configuration, where the polymerization conditions were T=85° C. and P=52 barg and the average residence time was 0.60 h. The C2 concentration in the liquid phase was 4.3 mol %, the H2 / C2 and C4 / C2 molar ratios were 0.76 mol / kmol and 29 mol / kmol, respectively. The product split in the second loop reactor in the split loop configuration was 21.6 wt %, the MFR2 (g / 10 min)=5.8 and the density of the material collected after the second loop reactor=940.2 kg / m 3 and the overall catalyst productivity in the loop reactor configured process was 1.0 kg PE / gcat.

[0137] The material was then flashed in a high pressure separator and the polymer particles were subsequently transferred to a gas phase reactor (GPR) operated at a total pressure of 19 barg and a temperature of 75°C. The feed rates of the components at steady state were 0.007 kg / h H2, 103.9 kg / h C2 and 3.37 kg / h C6, with H2 / C2 = 0.78 mol / kmol and C6 / C2 = 4.18 mol / kmol, respectively. The total residence time in the GPR was 2.8 hours and the superficial gas velocity was chosen to be 0.32 m / s. The product split in the GPR was 56.9 wt% and the MFR of the final pellet material collected after the GPR was 0.007 kg / h H2, 0.007 kg / h C2 and 0.007 kg / h C6, respectively.2 (g / 10min) = 1.1 and density = 932.1 kg / m 3 and the overall catalyst productivity including the loop and GPR reactor configured processes was 2.3 kg PE / gcat.

[0138] In the above example, C6 was fed into the GPR a few hours after the GPR started up.

[0139] After 2.5 days of 1-hexene feed, serious operability problems related to sheeting and chunking occurred, resulting in the GPR being shut down. A GPR spot sample just before the GPR was shut down had an MFR of 0.55 g / 10 min. 2 , 926.8 kg / m with 58.7 wt% GPR split 3 The highest C6 / C2 feed ratio to the GPR was only 47.5 kg / ton.

[0140] Experimental Examples 2 and 3 (Invention)

[0141] The CE1 procedure was repeated, but with C6 inserted into the GPR during start-up.

[0142] In this case, no operability issues were observed, and smooth operation and good performance of the GPR was observed for about 10 days, thus achieving the targeted material properties as described in IE1 and IE2. The maximum C6 / C2 feed ratio to the GPR was 162.8 kg / ton.

[0143] [Table 1] JPEG2024525007000007.jpg238170

Claims

1. A process for polymerizing olefins in a multi-stage polymerization process configuration, the process comprising: a) in a first polymerization step, polymerizing ethylene in the presence of a polymerization catalyst to form a first polymer component (A); and b) in a second polymerization step, polymerizing a predetermined monomer mixture comprising ethylene and 1-hexene in the gas phase in the presence of the first polymer component (A) of step a) to form a second polymer component (B). wherein Here, the multimodal polyethylene polymer produced by the present method contains 1-hexene comonomer and at least one further C 4～10 comonomer, and a predetermined monomer mixture comprising ethylene and 1-hexene is fed to the second polymerization step from the start-up of the second polymerization step; said method.

2. The method according to claim 1, wherein the polymerization catalyst is a single-site catalyst.

3. The method according to claim 1, wherein the polymerization catalyst is a metallocene catalyst.

4. The method according to claim 1 or 2, wherein the polymerization catalyst comprises (i) a transition metal complex, (ii) a cocatalyst, and (iii) a support.

5. The method according to claim 1, wherein the molar ratio of 1-hexene to ethylene in the second polymerization step is in the range of 7 mol / kmol to 80 mol / kmol.

6. The method according to claim 1, wherein the temperature in the gas phase polymerization is typically 40 to 120 °C.

7. The method according to claim 1, wherein the pressure in the gas phase polymerization is 5 to 40 bar.

8. The method according to claim 1, wherein the residence time in the gas phase polymerization is 1.0 hour to 4.0 hours.

9. The method according to claim 1, wherein step a) comprises polymerizing ethylene in the presence of at least one other alpha-olefin comonomer and in the presence of a polymerization catalyst to form a first polymer component (A).

10. The method according to claim 1, wherein step b) comprises polymerizing ethylene and 1-hexene in the gas phase in the presence of at least one other alpha-olefin comonomer to form a second polymer component (B).

11. A method of using 1-hexene in a gas phase olefin polymerization step to improve the performance of a single-site polymerization catalyst in a multi-stage olefin copolymerization process.

12. The method according to claim 11, wherein a predetermined monomer mixture comprising ethylene and 1-hexene is fed to the gas phase polymerization step from the start-up of the gas phase polymerization step.

13. The method according to claim 11 or 12, wherein the molar ratio of 1-hexene to ethylene in the gas-phase olefin polymerization step is in the range of 7 mol / kmol to 40 mol / kmol.

14. The method according to claim 11 or 12, wherein the supply ratio of the predetermined 1-hexene / ethylene mixture is 70 kg / ton to 400 kg / ton.

15. A method for improving the performance of a single-site polymerization catalyst in multi-stage olefin polymerization, the method comprising supplying a predetermined monomer mixture containing ethylene and 1-hexene to the gas-phase polymerization step from the start-up of the gas-phase polymerization step.

16. The method according to claim 15, wherein the molar ratio of 1-hexene to ethylene in the second polymerization step is typically in the range of 7 mol / kmol to 40 mol / kmol.

17. The method according to claim 15, wherein the supply ratio of the predetermined 1-hexene / ethylene mixture is 70 kg / ton to 400 kg / ton.

18. The method according to claim 15, wherein the single-site catalyst comprises (i) a transition metal complex, (ii) a cocatalyst, and (iii) a support.