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WO2003016362A9 - Procede de polymerisation de l'ethylene - Google Patents

Procede de polymerisation de l'ethylene

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Publication number
WO2003016362A9
WO2003016362A9 PCT/US2002/026314 US0226314W WO03016362A9 WO 2003016362 A9 WO2003016362 A9 WO 2003016362A9 US 0226314 W US0226314 W US 0226314W WO 03016362 A9 WO03016362 A9 WO 03016362A9
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WO
WIPO (PCT)
Prior art keywords
reactor
ethylene
catalyst
polymer
polymerization
Prior art date
Application number
PCT/US2002/026314
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English (en)
Other versions
WO2003016362A1 (fr
Inventor
Ruddy Nicasy
Frederik E Gemoets
Patrick J Schouterden
Jozef J Vandun
Original Assignee
Dow Global Technologies Inc
Ruddy Nicasy
Frederik E Gemoets
Patrick J Schouterden
Jozef J Vandun
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Dow Global Technologies Inc, Ruddy Nicasy, Frederik E Gemoets, Patrick J Schouterden, Jozef J Vandun filed Critical Dow Global Technologies Inc
Publication of WO2003016362A1 publication Critical patent/WO2003016362A1/fr
Publication of WO2003016362A9 publication Critical patent/WO2003016362A9/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F10/00—Homopolymers and copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F110/00—Homopolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
    • C08F110/02—Ethene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F210/00—Copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
    • C08F210/16—Copolymers of ethene with alpha-alkenes, e.g. EP rubbers

Definitions

  • ETHYLENE POLYMERIZATION PROCESS FIELD OF THE INVENTION This invention pertains to a polymerization process for making ethylene polymers characterized as having low or no gels, especially those due to extraneous high molecular weight polymer fractions.
  • BACKGROUND OF THE INVENTION Polymerization processes that utilize Ziegler-Natta catalyst or chromium catalyst systems to manufacture ethylene polymers are well known in the art. With the introduction of new metallocene or single-site catalysts, these new catalysts are increasingly used to manufacture ethylene polymers via polymerization, such as gas phase or slurry polymerization processes.
  • HMW polyethylene polymer chains or fractions that are immiscible with the bulk polymer phase. While a few applications can tolerate gels, for the vast majority of polyethylene applications, gels are undesirable aesthetically or they adversely affect product performance. It is known that polyethylene as produced still contains active catalyst residues. If the catalyst residues are not promptly deactivated, gels and/or extraneous HMW polymer fractions will result. As a result, catalyst kill agents (e.g. water, O 2 , CO and CO 2 ) are routinely added to the polymer post-reactor in a process-finishing step. Also, ethylene polymerization typically involves the use of chain terminating agents (e.g. hydrogen and isobutane) to control the product melt index or molecular weight to target.
  • chain terminating agents e.g. hydrogen and isobutane
  • ethylene polymer producers desire the ability to use Ziegler-Natta catalysts or chromium catalysts in combination with metallocene or single-site catalysts in the same manufacturing facility to make different polymer products. Producers also desire the flexibility to use the different catalysts simultaneously for a single polymer product such as in a tandem polymerization with a different catalyst system being separately injected into different reactors. But experience indicates that for facilities that utilize both catalyst systems even short runtimes before the onset of fouling and sheeting result relative to an equivalent facility dedicated exclusively to using new catalysts.
  • the invention relates to a polymerization process for making a polymer, the polymer comprising ethylene and characterized as having low levels of gels or extraneous high molecular weight (HMW) polymer fractions or both, and the process comprising: (I) providing a polymerization system comprising: (a) at least one by-passable purification unit, (b) at least one catalyst feed vessel, (c) at least one reactor, and (d) post-reactor equipment and vessels, and (II) continuously polymerizing ethylene in the at least one reactor in the presence of an active catalyst which is continuously fed to the reactor, continuously transferring the polymerized ethylene downstream through to the post-reactor part of the system and: (a) providing and maintaining a molar ratio of chain terminator to ethylene of from about 0.001 to about 0.5 throughout the post-reactor part of the polymerization system until all active catalyst is deactivated, or (b) purifying the ethylene by directing the ethylene through the at least one purification unit before entry into
  • FIG. 1 illustrates a slurry polymerization reactor system used in one embodiment of the invention.
  • FIG. 2A and FIG. 2B are schematics of feed gas purification systems used in embodiments of the invention.
  • FIG. 3 are photos showing the extent of reactor fouling and/or sheeting for various examples: 3 A - Inventive Example 2; 3B - Inventive Example 3; 3C - Comparative Run 2A; and 3D - Comparative Run 2B.
  • FIG. 4 is a graph of the heat exchange coefficient across the reactor wall (U' values) vs. run time for various levels of ethylene purity.
  • FIG. 5 is a another graph of U' values vs. run time for various levels of ethylene purity.
  • Embodiments of the invention are based, in part, on one or more of the following discoveries. It has been found that polymerization that utilize metallocene or single-site catalyst systems possesses unique characteristics not typically known for Ziegler-Natta catalysts. Specifically, the chain terminator consumption rate is substantially higher for some metallocene or single-site catalysts relative to Ziegler-Natta catalysts. With regard to reactor fouling and sheeting, some metallocene or single-site catalysts are more sensitive to ethylene feed gas purity levels than Ziegler-Natta catalysts. It has been discovered that gels and/or extraneous HMW fractions can result from mixed catalyst systems due to cross- contamination.
  • the process system comprises at least one catalyst feed vessel, at least one reactor, and post- reactor equipment and vessels.
  • at least one by-passable purification unit is also part of the process system.
  • the polymerization process comprises (a) feeding the reactants and catalysts to the polymerization system; (b) continuously polymerizing monomers or comonomers (such as ethylene and 1-octene) in the reactor in the presence of an active catalyst which is continuously fed to the reactor; and (c) continuously transferring the polymer downstream to the post-reactor vessels.
  • steps or acts are performed as desired: (1) providing a chain terminator in the post-reactor and maintaining a molar ratio of chain terminator to monomer or comonomer from about 0.001 to about 0.5 in the post-reactor until all active catalyst is deactivated; (2) purifying the monomer or comonomer by directing the monomer or comonomer through the at least one purification unit before entry into the at least one reactor; or (3) providing critically clean catalyst feed vessels. In preferred embodiments, all of the three steps or acts are employed.
  • the term "interpolymer" is used herein to indicate a copolymer, a terpolymer, a tetrapolymer, etc.
  • At least one other comonomer is polymerized with ethylene or other olefins to make an interpolymer.
  • Suitable ethylene interpolymers which are produced from the reactor system comprise ethylene with at least one C 3 -C 20 ⁇ -olefin and/or C 4 -Cj 8 diolefin.
  • Preferred comonomers include the one C 3 -C 20 ⁇ -olefins, especially propylene, isobutylene, 1-butene, 1-hexene, 4-methyl-l-pentene, 1-heptene, 1-octene, 1-nonene, and 1- decene, more preferably 1-butene, 1-hexene, heptene and 1-octene.
  • the ethylene interpolymer is a copolymer of ethylene and 1-butene.
  • the process system as shown in Fig. 1, comprises a reactor Rl, a catalyst feed vessel VI, a first post reactor vessel V2, and a second post reactor vessel V3.
  • a first monomer (SI), preferably ethylene, a chain terminating agent (S2), preferably hydrogen, and a solvent (S3), preferably butene, are fed to the reactor Rl.
  • the reactor Rl and the first post reactor vessel V2 are preferably jacketed and equipped with a means for agitation.
  • the catalyst feed vessel VI is also equipped with a means for agitation.
  • the temperature of the reactor Rl ranges from about is from 20 to 115 °C, preferably from 50 to 105 °C. However, the upper limit of the polymerization temperature is a temperature which is highest among temperatures at which the ethylene copolymer produced can maintain substantially a powdery state.
  • the pressure of the reactor Rl ranges from about 1 to about 100 atm, preferably from about 3 to about 30 atm.
  • Catalyst (S4) from the catalyst feed vessel VI is also fed to the reactor Rl.
  • the molar ratio of catalyst/cocatalyst employed preferably ranges from 1:10,000 to 100: 1, more preferably from 1 :5000 to 10: 1, most preferably from 1:1000 to 1: 1.
  • Alumoxane, when used by itself as an activating cocatalyst, is generally employed in large quantity, generally at least 100 times the quantity of metal complex on a molar basis.
  • the remaining activating cocatalysts are generally employed in approximately equimolar quantity with the metal complex.
  • the polymerization may be accomplished at conditions known in the art for Ziegler-Natta or Kaminsky-Sinn type polymerization reactions, that is, temperatures from -50 to 250 °C, preferably 30 to 200 °C and pressures from atmospheric to 10,000 atmospheres. Suspension, solution, slurry, gas phase, solid state powder polymerization or other process condition may be employed if desired.
  • a support especially silica, alumina, or a polymer (especially polytetrafluoroethylene or a polyolefin) may be employed, and desirably is employed when the catalysts are used in a gas phase or slurry polymerization process.
  • the support is passivated before the addition of the catalyst. Passivation techniques are known in the art, and include treatment of the support with a passivating agent such as triethylaluminum.
  • the support is preferably employed in an amount to provide a weight ratio of catalyst (based on metal): support from about 1: 100,000 to about 1:10, more preferably from about 1 :50,000 to about 1:20, and most preferably from about 1:10,000 to about 1:30.
  • the molar ratio of catalys polymerizable 1 1 compounds employed preferably is from about 10 " : 1 to about 10 " : 1, more preferably from about 10 '9 : 1 to about 10 "5 : 1.
  • Suitable solvents for polymerization are inert liquids.
  • Examples include, but are not limited to, straight and branched-chain hydrocarbons such as isobutane, butane, pentane, hexane, heptane, octane, and mixtures thereof; mixed aliphatic hydrocarbon solvents such as kerosene and ISOPAR (available from Exxon Chemicals), cyclic and alicyclic hydrocarbons such as cyclohexane, cycloheptane, methylcyclohexane, methylcycloheptane, and mixtures thereof; perfluorinated hydrocarbons such as perfluorinated C - ⁇ 0 alkanes, and the like, and aromatic and alkyl-substituted aromatic compounds such as benzene, toluene, xylene, ethylbenzene and the like.
  • straight and branched-chain hydrocarbons such as isobutane, butane, pentane, hexane, heptan
  • Suitable solvents also include, but are not limited to, liquid olefins which may act as monomers or comonomers including ethylene, propylene, butadiene, cyclopentene, 1-hexene, 1 -hexane, 4-vinylcyclohexene, vinylcyclohexane, 3-methyl-l- pentene, 4-methyl-l-pentene, 1,4-hexadiene, 1-octene, 1-decene, styrene, divinylbenzene, allylbenzene, vinyltoluene (including all isomers alone or in admixture), and the like. Mixtures of the foregoing are also suitable.
  • the catalysts may be utilized in combination with at least one additional homogeneous or heterogeneous polymerization catalyst in separate reactors connected in series or in parallel to prepare polymer blends having desirable properties.
  • An example of such a process is disclosed in WO 94/00500, equivalent to U. S. Serial Number 07/904,770, as well as U. S. Serial Number 08/10958, filed January 29, 1993.
  • the disclosures of the patent applications are incorporated by references herein in their entirety.
  • the catalyst system may be prepared as a homogeneous catalyst by addition of the requisite components to a solvent in which polymerization will be carried out by solution polymerization procedures.
  • the catalyst system may also be prepared and employed as a heterogeneous catalyst by adsorbing the requisite components on a catalyst support material such as silica gel, alumina or other suitable inorganic support material.
  • a catalyst support material such as silica gel, alumina or other suitable inorganic support material.
  • silica as the support material.
  • the heterogeneous form of the catalyst system may be employed in a slurry polymerization.
  • slurry polymerization takes place in liquid diluents in which the polymer product is substantially insoluble.
  • the diluent for slurry polymerization is one or more hydrocarbons with less than 5 carbon atoms.
  • saturated hydrocarbons such as ethane, propane or butane may be used in whole or part as the diluent.
  • ⁇ -olefin monomer or a mixture of different ⁇ -olefin monomers may be used in whole or part as the diluent.
  • the major part of the diluent comprises at least the ⁇ -olefin monomer or monomers to be polymerized.
  • Solution polymerization conditions utilize a solvent for the respective components of the reaction.
  • Preferred solvents include, but are not limited to, mineral oils and the various hydrocarbons which are liquid at reaction temperatures and pressures.
  • Illustrative examples of useful solvents include, but are not limited to, alkanes such as pentane, iso-pentane, hexane, heptane, octane and nonane, as well as mixtures of alkanes including kerosene and Isopar ETM, available from Exxon Chemicals Inc.; cycloalkanes such as cyclopentane, cyclohexane, and methylcyclohexane; and aromatics such as benzene, toluene, xylenes, ethylbenzene and diethylbenzene. At all times, the individual ingredients, as well as the catalyst components, should be protected from oxygen and moisture.
  • alkanes such as pentane, iso-pentane, hexane, heptane, octane and nonane
  • mixtures of alkanes including kerosene and Isopar ETM
  • the catalyst components and catalysts should be prepared and recovered in an oxygen and moisture free atmosphere.
  • the reactions are performed in the presence of a dry, inert gas such as, for example, nitrogen or argon.
  • the polymerization may be carried out as a batch or a continuous polymerization process.
  • a continuous process is preferred, in which event catalysts, solvent or diluent (if employed), and comonomers (or monomer) are continuously supplied to the reaction zone and polymer product continuously removed therefrom.
  • the polymerization conditions for manufacturing the inte ⁇ olymers according to embodiments of the invention are generally those useful in the solution polymerization process, although the application is not limited thereto.
  • the polymerization is conducted in a continuous solution polymerization system comprising two reactors connected in series or parallel.
  • One or both reactors contain at least two catalysts which have a substantially similar comonomer inco ⁇ oration capability but different molecular weight capability.
  • a relatively high molecular weight product (M w from 100,000 to over 1,000,000, more preferably 200,000 to 1 ,000,000) is formed while in the second reactor a product of a relatively low molecular weight (M w 2,000 to 300,000) is formed.
  • the final product is a mixture of the two reactor effluents which are combined prior to devolatilization to result in a uniform mixing of the two polymer products.
  • Such a dual reactor/dual catalyst process allows for the preparation of products with tailored properties.
  • the reactors are connected in series, that is the effluent from the first reactor is charged to the second reactor and fresh monomer, solvent and hydrogen is added to the second reactor. Reactor conditions are adjusted such that the weight ratio of polymer produced in the first reactor to that produced in the second reactor is from 20:80 to 80:20.
  • the temperature of the second reactor is controlled to produce the lower molecular weight product.
  • the second reactor in a series polymerization process contains a heterogeneous Ziegler-Natta catalyst or chrome catalyst known in the art.
  • Ziegler-Natta catalysts include, but are not limited to, titanium-based catalysts supported on MgCl 2 , and additionally comprise compounds of aluminum containing at least one aluminum-alkyl bond.
  • Suitable Ziegler-Natta catalysts and their preparation include, but are not limited to, those disclosed in US Patent 4,612,300, US 4,330,646, and US 5,869,575. The disclosures of each of these three patents are herein inco ⁇ orated by reference.
  • Suitable catalysts include,, but are not limited to, metallocene or single-site catalyst systems.
  • the single-site or metallocene catalyst is a constrained geometry catalyst system as described in WO 96/16092, WO 98/27119, and WO 96/28480, the disclosures of which are inco ⁇ orated herein by reference. More preferably, the metallocene or single-site catalyst is supported using an inert material such as, for example, silica.
  • the single-site or metallocene catalyst is reacted with a suitable co-catalyst (e.g., a boron- containing compound or an alumoxane) which is bonded or fixed to the support in a prior step such that the single-site or metallocene catalyst is immobilized to the extent that substantially no soluble catalyst species is extracted from the support during polymerization, most preferably the species are fixed or bonded such that there is substantially no extraction when the solid catalyst system is boiled in toluene for 2 hours.
  • a suitable co-catalyst e.g., a boron- containing compound or an alumoxane
  • the supported catalyst systems used in polymerization make inte ⁇ olymers with reverse comonomer distribution ("RCD").
  • RCD reverse comonomer distribution
  • the characteristics of these inte ⁇ olymers, including RCD, are described in U.S. Provisional Application Serial No. 60/313,357, filed on August 17, 2001, entitled "BIMODAL POLYETHYLENE COMPOSITION AND ARTICLE MADE THEREFROM,” in names of Jozef J. Van Dun et al, the disclosure of which is inco ⁇ orated herein by reference.
  • polymer (S5) is transferred to either the first post reactor vessel V2 or the second post reactor vessel V3. If polymer (S5) is transferred to the second post reactor vessel V3, the unreacted monomers and diluent are removed.
  • hydrogen concentration drops faster than ethylene concentration due to the catalyst's intrinsic high consumption rate of hydrogen vs ethylene, and/or due to venting of the vessel since hydrogen is preferentially vented vs ethylene due to the fact that hydrogen has a lower solubility.
  • the post reactor vessels are not part of the reactor. They are separate from the reactor and have their own operating temperatures and pressures. The operating conditions of the post reactor vessels may be similar to the reactor or they may be different. If polymer (S5) is transferred to the first post-reactor vessel V2, the terminator (S2) concentration is relatively important in metallocene or single-site catalyst systems.
  • the concentration for chain terminator agents in the post-reactor environment is kept in the range of about 0.001 to about 0.5 mole of terminator per mole of ethylene. Below 0.001 mole terminator to mole ethylene, undesirable gel formation occurs and above 0.5 mole terminator to mole ethylene, undesirable oligomer formation occurs. More preferably, the range of from about 0.01 to about 0.4 or about 0.05 to about 0.2 mole of terminator to mole ethylene is maintained.
  • Chain terminators are also know as chain transfer agents or telogens which are used to control the melt flow index in a polymerization process.
  • Chain transfer involves the termination of growing polymer chains, thus limiting the ultimate molecular weight of the polymer material.
  • Chain transfer agents are typically hydrogen atom donors that will react with a growing polymer chain and stop the polymerization reaction of said chain. These agents can be of many different types, from saturated hydrocarbons or unsaturated hydrocarbons to aldehydes, ketones or alcohols.
  • concentration of the selected chain transfer agent By controlling the concentration of the selected chain transfer agent, one can control the length of polymer chains, and, hence, the weight average molecular weight, M w
  • MFI or I 2 The melt flow index (MFI or I 2 ) of a polymer, which is related to M w , is controlled in the same way.
  • chain transfer agent After the donation of a hydrogen atom, the chain transfer agent forms a radical which can react with the monomers, or with already formed oligomers or polymers, to start a new polymer chain.
  • any functional groups present in chain transfer agents for instance, carbonyl groups of aldehydes and ketones, will be introduced in the polymer chains.
  • Any chain terminator agents known or presently unknown in the art may be used in embodiments of the invention. But preferred chain terminator agents include hydrogen, propylene and isobutane, with hydrogen being most preferred.
  • chain terminator agent is used interchangeably in the art with the terms “chain transfer agent” and "telogen".
  • a large number of chain transfer agents for example propylene and 1-butene which have an olefinically unsaturated bond, can also be inco ⁇ orated in the polymer chain, themselves, via a copolymerization reaction. This generally leads to the formation of short chain branching of respectively methyl and ethyl groups, which lowers the density of the polymers obtained.
  • Another process for reducing the amount of HMW gels in the polymer product, is by using a critically clean catalyst feed vessel.
  • critically clean catalyst feed vessel it is meant that only disposable or one-time-use catalyst vessels are used or, when reusable catalyst vessels are used, prior to use they are cleaned by the following exemplary procedure: as in ordinary cleaning, the contents of the catalyst vessel are drained and the vessel is rinsed with hexane or other diluents or solvents until it is visually free of solids. The catalyst vessel is then dried with N 2 .
  • the catalyst vessel is filled with a mixture of hexane and isopropanol (concentration: 1 :1 hexane/alcohol molar ratio) to a liquid level at least as high as the level of the previously contained catalyst system.
  • the alcohol/hexane mixture is then agitated for 2-3 hours and afterwards drained.
  • the drained/empty vessel is then flushed with N 2 for 1 hour and then rinsed with hexane.
  • the vessel is then filled with hexane and stirred for 1 hour and then drained and purged with N 2 for 1 hour.
  • the hexane rinsing steps of stirring for 1 hour and purging with N 2 for 1 hour (or until dry) is then repeated. It should be understood that variations from the above procedure are acceptable so long as substantially similar results are achieved.
  • the critical cleaning procedure involves cleanup of the catalyst holding and feed vessels and catalyst feed lines to the reactors.
  • the process described herein is suitable for use in manufacturing olefin homopolymers or inte ⁇ olymers, especially ethylene homopolymers as well as ethylene inte ⁇ olymers.
  • the cleaning method described above may be used during startup or when transitioning between different and/or incompatible catalysts.
  • the catalysts are incompatible due to different reactivity ratios for molecular weight regulators and comonomers. They may detrimentally react with each other and reduce the activity of one or both catalysts.
  • the method may be used in gas phase, solution phase or slurry phase polymerization process systems.
  • ethylene (Q3) from a pipeline is fed to a first purification unit PI.
  • a second purification unit P2 may be in series or parallel with the first purification unit PI.
  • the purification units, PI and P2 may be bypassed by a series of valves (all of which are not shown). This gives the operator flexibility on the degree of purity (Q2 or Q3) to be sent to the reactor Rl.
  • the first purification unit PI and the second purification unit P2 are preferably filled with a molecular sieve or activated alumina bed for removing impurities from the ethylene.
  • the molecular sieve may be of the zeolite type.
  • the activated alumina may be of the gel, psuedoboehmite, gamma or bayerite type aluminas .
  • process diluent and solvent as well as comonomer fed streams are also in-situ purified.
  • Process steps described above can be practiced in a gas phase, solution phase or slurry phase polymerization process system but they are particularly suitable for use in gas phase and slurry polymerization. These process steps can be used for a single-reactor polymerization system or a multiple reactor polymerization system either configured in series or in parallel. They can also be used in a multiple reactor system where there is separate fresh catalyst injection in each reactor as well as where there is fresh catalyst injection in the first reactor only. In a multiple reactor polymerization system, post-reactor equipment and vessels exist after each reactor and intermediate to the next subsequent reactor.
  • the extraneous fraction was not formed in the reactor, it was formed in a post-reactor environment.
  • low gels or “low extraneous HMW polymer fraction”
  • the visual gel count on a 10 cm x 10 cm x 25 mm film fabricated at a melt temperature in the range of about 200 to about 212 °C will be less than about 300 gels/gram of film, preferably, less than or equal to about 250 gels/gram of film, more preferably, less than or equal to about 100 gels/gram of film and, most preferably, less than or equal to about 75 gels/gram of film.
  • the second post reactor vessel V3 was designed to collect a slurry polymer sample directly from the reactor.
  • the second post reactor vessel V3 had no insulation or cooling and thus the temperature at the device was lower than the reactor temperature.
  • the pressure at the start of the experiment was about 2 to about 4 barg. During sampling, no venting took place and the pressure increased to about 6 to about 7 bar.
  • the solvent was filtered from the polymer with N 2 pressure. After this step, the second post reactor vessel V3 was purged with N 2 , then depressurized to atmospheric pressure. At these conditions, polymerization could continue.
  • Second post reactor vessel V3 was then opened and the powder was collected in a drum wherein unreacted ethylene and hydrogen were permitted to vent.
  • the reactor level was kept at about 75 % of the total volume by discontinuously dumping the reactor content to the flash vessel.
  • this flash vessel (operating at a pressure of about 1.3 bar and a temperature of about 75 °C), the diluent and unreacted monomers are evaporated and vented, resulting in a dry powder.
  • the reactor was vented continuously to allow for gas analysis using an on-line gas chromatograph (GC).
  • GC on-line gas chromatograph
  • the GC provided an analysis of the reactor head space about every 6 minutes.
  • the production rate was controlled by the catalyst flow and was calculated based on ethylene feed flow minus the vent flow through the vent.
  • the diluent used was hexane.
  • the I 2 melt index of the polymer for the runs was controlled via hydrogen addition to the reactor, the density was controlled via comonomer addition to the reactor, and in all cases the comonomer was 1-butene, if present. Based on the polymer production and catalyst consumption, the catalyst efficiency was also calculated.
  • the catalyst used in this experiment was a supported borate constrained geometry catalyst system prepared as follows: Silica gel (948 grade available from Grace-Davidson) was dehydrated at an elevated temperature to a total volatiles of ca. about 3 wt. %.
  • FIG. 2A shows scheme for ethylene purification.
  • the process conditions including total run time, GC gas analysis and product properties are shown in Table 3 for the various runs. Table 3 indicates that when ethylene purity increases (i.e. improves), the run time increased. Also, catalyst productivity/efficiency substantially increased with increasing ethylene purity, and less fine particles were produced.
  • Table 4 provides the visual assessment of the various runs and FIGS. 3A - 3D show photos of the reactor taken just after the various runs. These results illustrate that substantial reductions in the onset of reactor fouling and sheeting result with increased ethylene purity.
  • Table 3 indicates that the inventive process provides runtimes of greater than or equal to about 12 hours (preferably greater than or equal about 15 hours, more preferably greater than or equal to about 20 hours) per 600 pounds of produced polymer/hour per 10 liters of reactor volume before the onset of reactor fouling and sheeting.
  • the vessel was filled with the mixture such that the liquid level of alcohol/hexane mixture was higher than the original catalyst/hexane slurry.
  • the alcohol/hexane mixture was then agitated at ambient for about 2 to about 3 hours. Afterwards, the alcohol/hexane mixture was drained from the catalyst vessel and the vessel was flushed with N 2 for about 1 hour.
  • the catalyst vessel was then rinsed with hexane by filling the vessel with hexane and agitating the hexane for about 1 hour, and then draining the vessel and purging it with N 2 for about 1 hour. This hexane rinsing procedure was then repeated and provided a dry, critically clean catalyst feed vessel.
  • the solid metallocene catalyst was used to produce a single-reactor, butene copolymer having a melt index I 2 of about 1.5 g/10 min and a density of about 0.944 g/cm 3 .
  • all transfer lines and vessels of the polymerization system were cleaned to avoid contamination of subsequent runs.
  • the catalyst feed vessel was loaded with a standard solid Ziegler-Natta catalyst system at a concentration of about 3 g catalyst/kg hexane.
  • the catalyst system was stored for about 1 week.
  • the contents of the catalyst vessel were drained and the vessel was rinsed with hexane until it was visibly free of solids.
  • the catalyst vessel was then dried with N 2 and loaded with the same constrained geometry catalyst system (concentration was about 25 g catalyst/ ml hexane) and stored overnight. After overnight storage, this catalyst system was used to produce a single-reactor, butene copolymer of having an I 2 melt index of about 1.5 g/10 min. and a density of about 0.944 g/cm 3 .
  • a second purification unit (P3) can be used, in series with the P2 unit filled.
  • Unit P3 consists of a same size purification bed as P2, filled with Selexsorb CD or Selexsorb COS. In this way, the purity of ethylene with quality Q4A can be improved to quality Q5A (with molesieve 3A in P2 and
  • the U'-value was monitored during the runs.
  • the U'-value is the heat transfer coefficient across the reactor wall and is defined by the heat transferred through the reactor wall divided by the temperature difference over the reactor wall and is expressed in units [kJ/K/hr].
  • the U'-value is a measure of the fouling on the wall of the reactor.
  • Figure 4 shows the U'-value of the reactor wall during the 4 experiments.
  • the vertical lines show the times at which the PI purification units have been swapped in experiment 6.
  • the U'-value plots in this graph clearly show that the fouling rate is lower with better purification.
  • ethylene is used that comes from the pipeline (pipeline quality). In this example, this is called Q3 quality ethylene and contains the highest concentration of impurities.
  • the ethylene can be purified by using an adso ⁇ tion bed (PI) filled with either Molesieve 3A (from UOP), Selexsorb CD (activated alumina from Alcoa) or Selexsorb COS (activated alumina from Alcoa).
  • this purification unit (PI) When this purification unit (PI) is put into service, the ethylene quality is improved from level Q3 (Before the purification unit PI) to quality Q4A (when PI is filled with Molesieve 3 A), Q4B (when PI is filled with Selexsorb CD) or Q4C (when PI is filled with Selexsorb COS) after the purification unit PI .
  • a second purification unit (P2) can be used, in series with the PI unit filled. Unit P2 consists of a same size purification bed as PI, filled with Selexsorb CD or Selexsorb COS.
  • the purity of ethylene with quality Q4A can be improved to quality Q5A (with molesieve 3 A in PI and Selexsorb CD in P2) or to quality Q5B (with molesieve 3 A in PI and Selexsorb COS in P2).
  • the ethylene with quality Q4B can be improved to quality Q5C (with Selexsorb CD in PI and Selexsorb COS in P2).
  • the U'-value was monitored during the runs.
  • the U'-value is the heat transfer coefficient across the reactor wall and is defined by the heat transferred through the reactor wall divided by the temperature difference over the reactor wall and is expressed in units [kJ/K/hr].
  • the U'-value is a measure of the fouling on the wall of the reactor.
  • Fig. 5 shows the U'-value of the reactor wall during the above described experiments.
  • the reactor system when operated in accordance with embodiments of the invention, exhibits a reduced level of reactor fouling and/or sheeting. As a result, the runtime and thus the efficiency of the reactor system has increased.
  • Other advantages are apparent to those skilled in the art. While the invention has been described with respect to a limited number of embodiments, the specific features of one embodiment should not be attributed to other embodiments of the invention. No single embodiment is representative of all aspects of the inventions. Moreover, variations and modifications therefrom exist. For example, while the production of ethylene inte ⁇ olymers is preferred use of the processes described herein, the processes can be applied to manufacture any polymer.

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  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)

Abstract

La présente invention concerne un procédé de polymérisation destiné à la fabrication de polymères d'éthylène se présentant sous forme de gels réduits ou de fractions polymères étrangères à poids moléculaire élevé réduites. Le procédé de l'invention est caractérisé en ce que l'on effectue la polymérisation à des rapports relativement élevés entre l'agent de terminaison de chaîne et l'éthylène dans le système de polymérisation post-réacteur, ou en ce que l'on utilise une charge d'éthylène de plus grande pureté, ou en ce que l'on évite la contamination croisée entre les systèmes de catalyseurs Ziegler-Natta ou chrome et les systèmes de catalyseurs métallocènes en veillant à ce qu'une propreté critique déterminée soit maintenue dans les récipients et tubes de transfert des catalyseurs. Selon des formes de mise en oeuvre préférées, on peut recourir à certaines étapes ou à la totalité des trois étapes précitées.
PCT/US2002/026314 2001-08-17 2002-08-16 Procede de polymerisation de l'ethylene WO2003016362A1 (fr)

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WO2003016396A1 (fr) 2001-08-17 2003-02-27 Dow Global Technologies Inc. Composition de polyethylene bimodal et articles fabriques a partir de celle-ci
EP1380602A1 (fr) * 2002-07-11 2004-01-14 BP Lavéra SNC Procédé de (co-)polymérisation d'oléfines en phase gazeuse
GB0329348D0 (en) * 2003-12-18 2004-01-21 Bp Chem Int Ltd Polymerisation process
US8114946B2 (en) 2008-12-18 2012-02-14 Chevron Phillips Chemical Company Lp Process for producing broader molecular weight distribution polymers with a reverse comonomer distribution and low levels of long chain branches
WO2011073369A1 (fr) 2009-12-18 2011-06-23 Total Petrochemicals Research Feluy Procédé de remplacement de catalyseurs de polymérisation d'éthylène incompatibles
RS54300B1 (en) 2009-12-18 2016-02-29 Total Research & Technology Feluy PROCEDURE FOR NEUTRALIZATION OF POLYMERIZATION CATALYST
US8653208B2 (en) 2012-05-18 2014-02-18 Union Carbide Chemicals & Plastics Technology Llc Process for preparing catalysts and catalysts made thereby
CN109957056B (zh) * 2017-12-14 2021-07-02 中国石油化工股份有限公司 卤化单烯烃-共轭二烯烃共聚物的制备方法

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US5326855A (en) * 1983-10-06 1994-07-05 Henry Kahn Process for the manufacture of elastomers in particulate form
NO301331B1 (no) * 1996-03-05 1997-10-13 Borealis As Fremgangsmåte for skifting av katalysator ved suspensjonspolymerisasjon av olefiner
US6214903B1 (en) * 1998-06-16 2001-04-10 Union Carbide Chemicals & Plastics Technology Corporation Post-reactor process for treating polymers prepared in a gas phase polymerization in the presence of an inert particulate material
US6022946A (en) * 1998-12-23 2000-02-08 Union Carbide Chemicals & Plastics Technology Corporation Process for deactivation of polyolefin compositions utilizing carbon dioxide as a deactivation agent
JP2002535457A (ja) * 1999-01-27 2002-10-22 イー・アイ・デュポン・ドウ・ヌムール・アンド・カンパニー 水素を使用するオレフィン重合の分子量制御

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