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
  • C08F10/02—Ethene

Definitions

• the process of the invention is related to olefins polymerization and the changeover between two incompatible polymerization catalysts.
• the process involves emptying the reactor as part of this changeover.
• the first catalyst may be a Ziegler-Natta catalyst and the second catalyst may be a metallocene catalyst.
• Ziegler-Natta catalysts require operating at high hydrogen concentrations (about 6 mole% in the reactor) while metallocene catalysts must be operated at low hydrogen concentrations (about 500 ppm). If the Ziegler-Natta catalysts are operated at low hydrogen, they produce very high molecular weight (MW) polymers. If the metallocene catalysts are operated at high hydrogen concentrations they produce low molecular weight polymers. Combining the two catalysts and operating at 500 ppm leads to a polymer that contains ultra-high MW chains and hard particles. Processing this polymer mix results in polyethylene films containing gels. The operating conditions for the two catalyst systems are incompatible.
• the comonomer incorporation or uptake rates for the two catalyst systems are very different.
• the Ziegler-Natta catalyst requires a much higher concentration of comonomer in the feed to get the same degree of incorporation in the polymer chains.
• the metallocene catalyst produces very low-density polymer with lower sintering temperature, which may cause sheeting in the bed.
• Agapiou et al. have patented a process for transitioning from one incompatible catalyst to another.
• the process comprises the steps of: a) discontinuing the introduction of one of the incompatible catalysts or catalyst systems into a reactor; b) introducing an irreversible catalyst killer; and c) introducing into the reactor a second catalyst or catalyst system incompatible with the first catalyst system.
• the transition is between a traditional Ziegler-Natta type catalyst system and a metallocene-type catalyst.
• the polymer product from the first catalyst present during the transition results in product made from both catalysts; this mixture may have less than optimum polymer properties (e.g., MWD, density, etc.).
• the first catalyst must be killed by titration. Too much kill agent will inactivate the second catalyst; too little will not meet the process objective.
• a serious disadvantage for the Agapiou et al. process lies in the fact that an overly active metallocene catalyst can generate hot spots and polymer sheets on startup, if the polymer bed is composed of LLDPE.
• Another disadvantage is that any reactor chunks or sheets that have formed and adhered to the reactor wall during operation of the first catalyst cannot be removed during the catalyst change, since the reactor is not opened.
• Borealis in WO 9732905 also teaches a method for transitioning between two different catalysts in olefins polymerizations. The method comprises: (a) discontinuing the feed of the first catalyst into the polymerization reactor; and (b) introducing the second catalyst into the reactor. The transitioning is performed between a chromium-based catalyst and a metallocene catalyst. It is taught that the transition may be performed rapidly without emptying the reactor.
• the reaction may be stopped and the first catalyst deactivated, or a "flying" transition may be performed by stopping the feed of the first catalyst, adjusting the reactor conditions and starting the feed of the second catalyst. None of the above patents are concerned with ways to shorten the turnaround time for catalyst transitions where the reaction is stopped and polymer, along with catalyst, are removed from the reactor.
• the invention is an improved process for changing between two incompatible polymerization catalysts in a commercial-scale olefins polymerization process.
• the invention comprises: polymerizing olefins with a first polymerization catalyst; stopping the polymerization; removing substantially all of the polymer from the reactor, preferably including non-powder polymer chunks; rapidly purging with nitrogen; adding a seedbed of polymer particulates to the reactor, and polymerizing olefins with a second polymerization catalyst.
• the reactor incorporates a fluidization grid plate with a central opening for polymer removal. It is preferred that the reactor also include a man-way that allows for inspection and cleanup of the grid plate.
• a vessel e.g., a silo
• the vessel has a high enough pressure rating to allow using a high pressure N 2 line to quickly transfer the seedbed polymer into the reactor.
• the reactor system also includes a high-pressure nitrogen line to allow for rapidly purging the reactor.
• a seedbed of high melting polymer particulates also called a startup bed, is rapidly added to the reactor.
• This high melting point polymer is selected to eliminate sheeting and chunking of the polymer during start-up. It minimizes the potential for overheating and melting when the catalyst lights off. Compared to using a low melting polymer, the use of a high melting polymer particulates allows the catalyst to be added more rapidly.
• the invention is utilized with a continuous polymerization process to make polyethylene, more preferably linear low density polyethylene (LLDPE).
• the process is generally described and exemplified herein as pertaining to ethylene polymerizations, it should be understood that this is merely illustrative, and the invention encompasses polymerization of other olefin or combinations of olefins.
• the high melting polymer is preferably high density polyethylene (HDPE).
• HDPE has a higher melting point (i.e., higher sintering temperature) than the LLDPE.
• reaction gases such as monomer, comonomer, and hydrogen, are then added and circulated. Polymerization is initiated by feeding the second catalyst and adjusting polymerization temperatures and pressures.
• An important aspect of the present invention is to do the whole process rapidly without fouling the reactor during startup with an overactive catalyst.
• the down time is less than 3 days, more preferably less than 2 days.
• the invention further comprises a transition between comonomers.
• a transition between a non- polar and a polar comonomer coincides with the catalyst changeover.
• the invention is a process for changing between two incompatible catalysts, a first catalyst and a second catalyst, during olefins polymerization, said process comprising: (a) operating an olefins polymerization plant which comprises a reactor system having a reactor, means for easy polymer removal and a means for polymer introduction, said plant utilizing a first catalyst at a first set of polymerization conditions; (b) stopping the polymerization; (c) removing substantially all of the polymer from the reactor system; (d) rapidly purging the reactor with nitrogen, preferably using a high pressure purge line; (e) drying the reactor; (f) adding a seedbed of high melting polymer particulates to the reactor; (g) adding reaction gases comprising monomer, comonomer (if desired), hydrogen, nitrogen, and an inert hydrocarbon (preferably n-pentane, isopentane, n-hexane); (h) adding said second polymerization catalyst to the reactor; (i) polymerizing
• the polymerization is stopped without poisoning the catalyst in the reactor. It is also preferred that any non-powder polymer chunks be removed as part of step (c), above. Moreover, it is also preferred that the process is completed in less than 3 days, more preferably in less than 2 days.
• the invention further comprises a transition between comonomers, which coincides with the catalyst change.
• step (g) preferably inert hydrocarbon and nitrogen are also included in the gases.
• comonomer is preferably included if co-polymerization operation is desired.
• the present invention is based on our finding that catalyst changeovers can be accomplished without using catalyst kill agents using a rapid changeover procedure in accordance with the procedure described herein.
• Our time-saving process preferably uses high pressure nitrogen introduced via one or more supply lines, and uses rapid purging, preferably also in addition to using a seedbed of high melting polymer particulates for controlling polymerization light-off.
• the process of the present invention allows for rapid catalyst changeovers with short turnaround times, even though polymer is removed from the reactor.
• the present process also allows for reactor inspection and clean-up before polymerization with the second catalyst begins.
• BRIEF DESCRIPTION OF THE FIGURE The Figure is a schematic of a reactor system useful in the present invention.
• the invention relates to changing between two incompatible catalysts in a commercial scale process operating in olefins polymerization plant.
• a commercial scale olefins polymerization process is one that is primarily operated to produce polymer product for sale to customers, either internal or external customers.
• the process of the invention includes removing polymer from the reactor during the catalyst changeover.
• olefins is used herein to preferably include ethylene; propylene; butene-1 ; hexenes such as 4-methylpentene-1 and hexene-1 ; octene-1 ; and decene-1.
• the olefins polymerization may be a homopolymerization, such as ethylene polymerization, or a co-polymerization, such as ethylene plus butene, propylene, or other olefins such as mentioned above.
• the invention is a process for changing between two incompatible catalysts, a first catalyst and a second catalyst, during olefins polymerization, the process comprising: (a) operating an olefins polymerization plant which comprises a reactor system having a reactor, a grid plate, a means for easy polymer removal, and a means for polymer introduction, said plant utilizing said first catalyst at a first set of polymerization conditions; (b) stopping the polymerization without using a catalyst kill agent; (c) removing substantially all of the polymer from the reactor; (d) shutting down the compressor; (e) opening the reactor, and inspecting and removing non-powder chunks; (f) rapidly purging the reactor with nitrogen; (g) drying the reactor; (h) adding a HDPE seedbed that is at least 40% of the weight of the operational polymer bed to the reactor; (i) adding reaction gases comprisinging monomer, comonomer, hydrogen, nitrogen and an inert hydrocarbon; (j) adding said
• the process is completed in less than 3 days, more preferably in less than 2 days.
• the process may further comprise a transition between comonomers.
• incompatible catalyst is used in the same way as used in Agapiou et al., USP 5,753,786, bottom of Column 3.
• “Incompatible catalysts” are those that satisfy one or more of the following: (1) those catalysts that in each others presence reduce the activity of at least one of the catalysts by greater than 50%; (2) those catalysts such that under the same reactive conditions one of the catalysts produces polymers having a molecular weight greater than two times higher than any other catalyst in the system; and (3) those catalysts that differ in comonomer incorporation or reactivity ratio under the same conditions by more than about 30%.
• the process of this invention can be used in a gas phase, solution phase, slurry or bulk phase polymerization process.
• a gas phase polymerization process in a fluidized bed reactor is preferred, and may be operated in condensed mode or in 100% gas phase.
• a gaseous stream comprising monomer, with or without entrained liquids, is passed through a fluidized bed reactor in the presence of a catalyst under reactive conditions.
• a polymer product is withdrawn.
• Also withdrawn is a gas stream, which is recycled and usually cooled, and together with additional monomer sufficient to replace the monomer polymerized is returned to the reactor.
• the recycle gas stream is cooled to form a gas and a liquid phase mixture that is then introduced into the reactor.
• a gas phase process see U.S. Pat. Nos. 4,543,399; 4,588,790 and 5,668,228 which are incorporated herein by reference. While the preferred embodiment of the process of the invention is directed to changing between a traditional Ziegler-Natta catalyst and a metallocene catalyst, it is within the scope of this invention that the process of the invention would apply to any change between incompatible catalysts.
• a traditional Ziegler-Natta catalyst and a chromium catalyst or changing between a chromium catalyst and a metallocene catalyst or even change between a traditional Ziegler-Natta titanium catalyst to a Ziegler-Natta vanadium catalyst.
• This invention contemplates that the direction of changing between incompatible catalysts is not limiting. However, it is preferred that the process of the invention involve a change from or to a metallocene catalyst.
• Traditional Ziegler-Natta catalysts typical in the art comprise a transition metal halide, such as titanium or vanadium halide, and an organometallic compound of a metal of Group 1 , 2 or 3, typically trialkylaluminum compounds. The latter serve as an activator for the transition metal halide.
• Some Ziegler-Natta catalyst systems incorporate an internal electron donor that is complexed to the alkyl aluminum or the transition metal.
• the transition metal halide may be supported on a magnesium halide or complexed thereto.
• This active Ziegler-Natta catalyst may also be impregnated onto an inorganic support such as silica or alumina.
• an inorganic support such as silica or alumina.
• Metallocene catalysts are typically those bulky ligand transition metal compounds derivable from the formula: [ ] m M[A] n [B] p where L is a bulky ligand, A is an anionic ligand, B is a neutral donor ligand, p is zero, one, two or three, M is a transition metal, and m and n are such that the total ligand valency corresponds to the transition metal valency; m can be one, two, three or four, and n can be zero or the valency state of the transition metal minus m.
• the ligands L and A may be bridged to each other, and the ligands L and B may be bridged to each other, and if two ligands L and/or A are present, they may be bridged.
• A may be a halide, an alkyl, an amide, or phosphide, etc.
• B may be an oxygen donor such as tetrahydrofuran , pyridine, thiophene, an alkene, or a diolefin.
• the metallocene compound may be a full-sandwich compound having two or more ligands L, which may be cyclopentadienyl ligands or cyclopentadiene derived ligands, or half-sandwich compounds having one ligand L, which is a cyclopentadienyl ligand or a cyclopentadiene derived ligand.
• the metallocene compounds contain a multiplicity of bonded atoms, preferably carbon atoms, forming a group that can be cyclic.
• the bulky ligand can be a cyclopentadienyl ligand or cyclopentadienyl derived ligand, which can be mono- or poly-nuclear or any other ligand capable of .eta.-5 bonding to the transition metal.
• One or more bulky ligands may be .pi.-bonded to the transition metal atom.
• the transition metal atom may be a Group 4, 5 or 6 transition metal and/or a transition metal from the lanthanide and actinide series.
• Other ligands may be bonded to the transition metal, such as those indicated above.
• Non-limiting examples of metallocene catalysts and catalyst systems are discussed in for example, U.S. Pat. Nos.
• the metallocene catalyst of this invention is supported on support materials known in the art, for example, inorganic oxides, like silica, alumina or magnesia or polymeric, such as polyethylene.
• the metallocene catalyst of the invention can be supported on a single support or separately supporting the metallocene on one support and an activator on another support.
• the first polymerization catalyst may be any olefins polymerization catalyst including those described hereinabove.
• the second polymerization catalyst may also be any olefins polymerization catalyst including those described above, with the proviso that the second catalyst be incompatible with the first catalyst.
• the first and second catalysts may be added to the reactor system in various ways.
• U.S. Patent No. 5,028,669 to Rowley et al. which is incorporated herein by reference in its entirety, shows a variety of ways to add catalyst that can be advantageously employed in this invention.
• the catalyst is added to the reactor by a method described in U.S. Pat. No. 5,851 ,493 to Lawson et al., which is incorporated herein by reference in its entirety.
• This patent describes an injection system that includes a valve with at least one cavity for receipt of particulate, and a sweep stream source for providing a sweep stream to remove substantially all the particulate from the cavity of the valve.
• the invention utilizes a reactor system that includes a reactor, at least one heat exchanger, at least one compressor and associated piping.
• the reactor system further comprises a gas distribution grid plate.
• a reactor system useful in this invention is shown schematically in FIG. 1. It includes a fluidized-bed reactor (1 ) consisting of a vertical cylinder (2) surmounted by an expanded chamber, also known as the disengaging section (3) and provided at its bottom part with a fluidization grid (4).
• the grid has small openings for distributing the entering reactant mixture and a larger opening (5) for polymer withdrawal.
• the reactor system also comprises a line (6) for recycling the reaction mixture, which joins the top of the fluidized-bed reactor to its bottom part.
• the recycling line (6) includes, in succession in the direction of flow of the gaseous reaction mixture, a cyclone (7), a first tube heat exchanger (8), a compressor (9) and a second tube heat exchanger (10).
• Ethylene and hydrogen are added through lines (11 ) and (12), respectively.
• Comonomer is added through line (13).
• Line (14) makes it possible to feed the reactor (1 ) with solid catalyst.
• Lines (24) and (25) are the feed lines for the different catalysts.
• Line (14) needs to be clear of the first catalyst before it is used to feed the second catalyst to the reactor.
• the produced polyolefin polymer particulates (27) are discharged from the reactor (1 ) into line (15).
• fines are reinjected into the reactor via line (16).
• Line (23) is a purge line for removing gases from the reactor loop.
• residual polymer particulates are removed through grid withdrawal line (17).
• line (17) is nitrogen purged.
• Portal (18) is a man-way that may be opened to inspect the grid and reactor walls. Non-powder polymer chunks can be manually removed during inspection of the grid plate (4) after entry through the man-way (18). Residual particulates can also be vacuumed out during this inspection.
• the high- pressure nitrogen inlet line (19) is used to purge the reactor. High melting polymer particulates (20), which are blanketed with nitrogen, from the seedbed silo (21 ) are transferred into the reactor (1 ) through the seedbed inlet line (22). Line (26) is used to fill the seedbed silo with polymer. Line (27) represents the polymer in the bed.
• the polymerization may be stopped in a variety of ways, such as stopping catalyst feed, introducing a catalyst poison, or dropping the temperature or pressure or monomer concentration below the minimums necessary to sustain a polymerization reaction. It is preferred that the polymerization be stopped by stopping the addition of the first catalyst. After the polymerization is stopped, substantially all of the polymer is removed from the reactor. First powder is removed via line (15) and then via the grid opening (5). More preferably, before the compressor is turned off, the bed is maintained above 150°F and olefins are purged through purge line (23). It is preferred that the grid opening be located at the center of the grid plate. It is small relative to the size of the grid plate, for example, about 4 to 6 inches compared to about 16 feet.
• substantially all the polymer is meant at least 90%, preferably at least 95%, more preferably at least 98%, and most preferably at least 99.5 wt. % of the polymer.
• One objective of the invention is to achieve a rapid turnaround time for the catalyst changeover.
• the turnaround time is the time between when the first catalyst is no longer added and the second catalyst lights off, i.e., begins sustained olefins polymerization. It is desirable that this is done in less than 3.5 days, preferably in less than 3 days, and more preferably in less than 2 days.
• the term “rapid purge” or “rapidly purging” or the like are intended to mean the quick dilution of catalyst poisons in a minimum time.
• This rapid purging can be accomplished, for example, by using large diameter nitrogen lines and nozzles, or more preferably with high-pressure nitrogen lines supplied at pressures greater than 50 psig, for example at pressures of 100 psig and higher. Preferred pressures are between 125 and 400 psig, more preferably between about 150 and 350 psig, and most preferably at a pressure of between about 300 and 350 psig.
• a rapid purge which includes filling and emptying the reactor with nitrogen takes less than an hour, preferably less than about 40 minutes, more preferably less than about 30 minutes, and still more preferably less than about 20 minutes.
• Rapidly purging the reactor with nitrogen significantly reduces the turnaround time for the catalyst changeover.
• rapid purge means a nitrogen addition rate of at least 340 moles per hour and the subsequent purging of at least that rate, more preferably at least 400 moles per hour, still more preferably at least 500 moles per hour, and most preferably at least 600 moles per hour.
• Temperature for purging operation is preferably between 0°F and 150°F, more preferably between 40°F and 85°F.
• the water level in the nitrogen purge gas should be below 1 ppm.
• a drying agent such as a trialkylaluminum compound may be added to reduce the water level to less than 1 ppm.
• a drying agent such as a trialkylaluminum compound
• Any of the well-known drying agents may be used in this step.
• Preferred drying agents include trialkyl aluminum compounds, such as trimethyl aluminum or more preferably triethyl aluminum (TEA).
• TAA triethyl aluminum
• This portion of the start-up procedure may be accomplished by circulating the gases containing drying agent through the empty bed for about one hour, followed by about three low-pressure N 2 purges to facilitate removal of TEA and water reaction products. The reactor may then be repressured to 150 psig with N 2 .
• a high melting seedbed is introduced to reduce bed sheeting on startup after the LLDPE bed is withdrawn.
• Complete elimination of bed sheeting and chunking on startup has been observed by using, for example, a high melting polyethylene seedbed.
• a high melting polyethylene seedbed It is important to use a high melting polymer as the seedbed, since low-melting polymers can cause problems on start-up.
• the temperature may increase above the target temperature, due to the rapidly accelerating reaction, and localized hot spots may be generated. This can soften or melt the seedbed polymer and block the grid plate openings or polymer withdrawal lines. For example, it has been found that using LLDPE as a seedbed polymer often results in operational problems.
• the high melting polymer powder also known as particulates or fluff
• the powder can be transferred into the reactor by suction or aspiration from a storage silo.
• the silo is appropriately pressure-rated and the polymer is transferred by blowing it into the reactor using a high pressure nitrogen line.
• the high melting polymer should not deactivate the polymerization catalyst.
• HDPE is an especially preferred high melting polymer.
• HDPE having a density of >0.940 g/cc may be used.
• HDPE with a density of >0.950 g/cc is preferred, and Ml above 6 is preferred for the HDPE selected for this use.
• the amount of polymer seedbed should be sufficient to cover the fines re-injection inlet line. This amount is at least 40% of the weight of the operational polymer bed, more preferably at least 50%, and most preferably about 60%.
• the term "operational polymer bed” means the amount of polymer particulates in the reactor when it is operated commercially.
• an antistatic agent is introduced to the reactor after the seedbed, such as HDPE seedbed is introduced, and prior to introducing the second catalyst, such as the metallocene catalyst.
• the second catalyst such as the metallocene catalyst.
• antistatic agent is another factor that aids in successful transition and "light-off, including aiding in avoiding of sheeting and/or chunking.
• Preferred amounts of antistat agent are between about 1 ppm and 1000 ppm by weight based on polyethylene production, more preferably between 5 ppm and 500 ppm, and most preferably between 10 ppm and 80 ppm.
• Preferred antistat agents include those types as described in USP 5,283,278, which is incorporated herein by reference.
• the feed or gas in the reactors is adjusted so that the catalyst will produce a given product of a certain density and melt index. This generally depends on how well a catalyst incorporates comonomer and its rate of reaction with hydrogen.
• the gas composition also contains an amount of hydrogen to control the melt index of the polymer to be produced.
• the gas also contains an amount of dew point increasing component with the balance of the gas composition made up of a non-condensable inerts, for example, nitrogen.
• the gas contains at least one alpha-olefin having from 2 to 20 carbon atoms, preferably 2-15 carbon atoms.
• alpha-olefins examples include alpha-olefins of ethylene, propylene, butene-1 , pentene-1 , 4-methylpentene-1 , hexene-1 , octene-1 , decene-1 , and aromatic containing olefins such as styrene.
• Other monomers can include dienes, norbomene, acetylene, and polar vinyl compounds such as vinyl esters, vinyl ethers, vinyl halides, vinyl amines and vinyl sulfides.
• Vinyl acetate is a preferred polar comonomer.
• the gas composition contains ethylene and at least one alpha-olefin having 3 to 15 carbon atoms.
• a second, third or fourth comonomer may be added to make terpolymers, tetramers and quintamers.
• a second, third or fourth comonomer may be added to make terpolymers, tetramers and quintamers.
• comonomers include non-polar comonomers such as alpha-olefins, i.e., transitions between butene and hexene, and especially between polar comonomers containing elements other than carbon and hydrogen, such oxygen, nitrogen, halogen or sulfur atoms, such as vinyl acetate and vinyl chloride, or between polar and non-polar comonomers. It is envisioned that the catalyst changeover process of the invention will, in some instances, also include a transition between comonomers. Depending on the second catalyst to be introduced into the reactor, the concentration of reactants, such as monomer, comonomer and hydrogen gas, can be increased or decreased.
• reactants such as monomer, comonomer and hydrogen gas
• the concentrations of comonomer and hydrogen are decreased, particularly when a metallocene catalyst is utilized as the second catalyst in the process of the invention.
• the reactant gas composition is diluted as above, for example, by either pressure purging or flow purging, procedures well known in the art. Once the reactant concentrations are sufficiently diluted to accommodate the second catalyst and substantially all poisons are removed, the next step in the invention is to introduce the second catalyst. Once the bed is fluidized and the new gas composition is introduced into the reactor, the second catalyst is introduced into the reactor under reactive conditions.
• Example 1 uses an LLDPE seedbed (added by aspiration from a storage silo). It uses a conventional nitrogen supply line at 50 psig.
• Example 2 of the invention a high-pressure nitrogen purge system (at about 325 psig) is used with an HDPE seedbed, which is blown into the reactor using nitrogen pressure.
• the HDPE seedbed allows more rapid catalyst start-up since concerns about polymer sintering are reduced.
• Example 2 The specifics for Example 2 are described in detail below. These two examples both include the same 21 steps. 1. Stop feeding the Ziegler-Natta catalyst. 2. Reduce the reactor pressure from about 325 to about 150 psig. 3. Draw down the polymer bed, thus also removing the bulk of the catalyst. Add nitrogen to displace the hydrocarbons. 4. Empty remaining polymer and catalyst from reactor through grid plate port. 5. Stop gas circulation (i.e., stop the compressor). 6. Close valves to block off feed lines and put blinds in place (for safety). 7. Open reactor and preferably inspect reactor, especially grid. Remove any sheets or chunks on grid or along walls, and ensure grid is good and clean. 8. Close reactor and remove blinds on feed lines. 9.
• TSA triethyl aluminum
• Example 1 the reactor pressure is dropped to 130 psig. In Example 2, the reactor pressure is dropped to 5-10 psig in order to facilitate transferring the polymer powder with high-pressure nitrogen from the seedbed silo. 18. Transfer the seedbed polymer into the reactor. The amount transferred is equal to about 1/2 the weight of the operational bed. The transfer can be done by various means such as by aspiration of polymer powder from a nitrogen-blanketed storage silo, or preferably by blowing the powder from a storage silo using nitrogen. 19.
• Make polymerization composition by adding feed and other gases, e.g., ethylene monomer, hexene or butene comonomer, and H 2 and then heat reactor to 180°F.
• an antistatic agent can be added in an amount of 5 to 500 ppm by weight based on the polymer production rate. 20. Start feeding the metallocene catalyst; the reactor will light, i.e., polymerization will begin, within four to ten hours. 21. Adjust polymerization conditions to make product meeting LLDPE polymer specifications.
• Table 1 shows the approximate times for each step.

Applications Claiming Priority (3)

Publications (1)

Family

ID=22429097

Family Applications (1)

Country Status (5)

Cited By (1)

Families Citing this family (19)

Family Cites Families (6)

• 2000
  • 2000-03-22 WO PCT/US2000/007573 patent/WO2000058377A1/en not_active Application Discontinuation
  • 2000-03-22 CN CN 00806676 patent/CN1352657A/zh active Pending
  • 2000-03-22 AU AU40195/00A patent/AU4019500A/en not_active Abandoned
  • 2000-03-22 EP EP00919524A patent/EP1171486A1/de not_active Withdrawn
  • 2000-03-22 JP JP2000608669A patent/JP2002540266A/ja active Pending

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events