CA2155236C

CA2155236C - Gas phase polymerization process

Info

Publication number: CA2155236C
Application number: CA002155236A
Authority: CA
Inventors: Robert Joseph Noel Bernier; Robert Lorenz Boysen; Robert Cecil Brown; Leonard Sebastian Scarola; Gary Harry Williams
Original assignee: Union Carbide Chemicals and Plastics Technology LLC
Current assignee: Union Carbide Chemicals and Plastics Technology LLC
Priority date: 1994-08-02
Filing date: 1995-08-02
Publication date: 1999-04-13
Anticipated expiration: 2015-08-02
Also published as: DE69519171D1; KR100250842B1; CA2196664A1; BR9503534A; CA2196676A1; PL318526A1; PL318527A1; TW311142B; AU3237395A; KR960007623A; CZ29797A3; US5453471B1; DE69512421T2; EP0856530B1; ZA956458B; DE69530872T2; US5834571A; EP0773963A1; CA2155236A1; PL318524A1

Abstract

A process for producing polymers in a gas phase reactor by continuously introducing a stream of monomer and gas into a polymerization zone while maintaining the temperature within the polymerization zone below the dew point temperature of at least one monomer present in said polymerization zone.

Description

('.A~: P~A~;~ PO~ I~R~7~q'I()N PE20 rMARy OF 1~ ~VF~I'ION
This invention relates to a new gas phase process capable of effecting polymerization re~ctiQnc using liquid monr~mers in an otherwise gas-phase process.

R~CKGROUNT~ OF 1~1; ~V~TIl~N
The discovery of gas-phase fl~ i7Pd bed and stirred reactor processes for the production of polymers, especially polyolefin polymers, made it possible to produce a wide variety of new polymers with highly desirable and improved properties. These gas-phase processes, especially the gas fluidized bed process for producing fiuch polymers provided a means for producing polymers with a drastic reduction in capital investment expense and dr~m~tic savings in energy usage as compared to other then conventional polymerization processes.
In a conventional gas flllitli7erl bed process a gaseous stream cont~ining one or more mQ~omers is p~Cseti into a fluidized bed reactor cont~ining a bed of growing polymer particles in a polymerization zone, while continuously or intermittently introducing a polymerization catalyst into the polymerization zone. The desired polymer product is withdrawn from the polymerization zone, degassed, shhili7e~ and ps3rks~ged for shipmen~ all by well known techniques. Because the polymerization reaction is exothermic, sub6tantial heat i6 generated in the polymerization zone which must be removed to ~,e~,ent the polymer particles from overhe~ting and fusing together. This is accomplished by continuously removing unreacted hot gases from the polymerization zone and repl~cing them with cooler gases. The hot gases removed from the polymerization zone are CGlll~l assed, cooled in a heat e~ch~nger, supplementerl by additional amounts of monomer to replace monomer polymerized and removed from the reaction zone and then recycled into the bottom of the reactor. Cooling of the recycled D-17226 ,~ 7 ~ ~ ~ 3 ~

gases is accomplished in one or more heat exchanger stages. The sequence of compression and cooling is a matter of design choice but it is usually preferable to provide for compression of the hot gases prior to cooling. The rate of gas flow into and through the reactor is maintained at a level such that the bed of polymer particles is maintained in a fLuidized condition. The production of polymer in a stirred bed reactor is very ~imil~r, differing primarily in the use of mechanical stirring means to assist in maint~ining the polymer bed in a fluidized condition.
Conventional gas phase fluidized bed resin production is very well known in the art as shown, for example, by the disclosure appearing in United States Patents Nos. 4,379,758; 4,383,095 and 4,876,320.
The production of polymeric substances in gas phase stirred reactors is also well known in the art as exemplified by the process and equipment descriptions appearing in United States Patent No. 3,256,263.
For many years it was erroneously believed that to allow liquid of any kind to enter into the polymerization region of a gas phase reactor would inevitably lead to agglomeration of resin particles, formation of large polymer chunks and ultimately complete reactor shut-down. This concern caused gas phase polymer producers to carefully avoid cooling the recycle gas stream entering the reactor to a temperature below the condensation temperature of any of the monomers employed in the polymerization reaction.
Comonomers such as hexene-1,4-methyl pentene and octene- 1, are particularly valuable for producing ethylene copolymers-polymers. These higher alpha olefins have relatively high condensation temperatures. Due to the apprehension that liquid monomers in the polymerization zone would lead to agglomeration, chllnking and ultimately shut down the reactor, production rates which depend upon the rate at which heat is removed from the polymerization zone, were severely constrained by the perceived need to maintain the tempe. dlul e of the cycle gas stream entering the reactor at temperature safely above the cor~ nc~tion tçm~~ e of the highest boiling monomer present in the cycle gas 8~ ea~
Even in the case of polymerization reactions cor~ rt&~ in stirred reactors, care was exercised to m~int~in the resin bed t~ alule above the con~l~ns~t;on te~ e~atule ofthe recycle gas stre~m components.
To m~imi7e heat removal it was not unusual to spray or inject liquid into or onto the polymer bed where it would imme~i~tely flash into a gaseous state by exposure to the hotter recycle gas stream. A
limited amount of additional cooling was achieved by this te<~hnique by the Joules-Thompson effect but without ever cooling the recycle gas stream to a level where condensation might occur. This approach typically involved the labonous and energy wasting approach of separately cooling a portion of the cycle gas s~re~ to obtain liquid monomer for storage and subsequent separate introduction into or onto the polymerization bed. ~y~mples of this procedure are found in United States Patent Nos. 3,254,070; 3,300,467; 3,662,527 and 4,012,573.
It was discovered later, CO~t~ to the long held belief that the presence of liquid in the cycle gas stream would lead to agglomeration and reactor shut-down, that it is indeed possible to cool the entire cycle gas stream to a tempel atu, e where conde~c~tio~ of significant amounts of monomer would occur without the expected dire results when these liquid were introduced into the reactor in t~..pe. atule equilibrium with the recycle gas stream. Cooling the entire cycle gas stream produces a two-phase gas-liquid mi~t~lre in tem~e~ture equilibrium with each other so that the liquid contained in the gas stream does not imme~ tely flash into vapor. Instead a subs~nt;~lly greater amount of cooling takes place because the total mass of both gas and liquid enters the polymerization zone at a subst~nti~lly lower temperature than previously thought possible. This process led to substantial iml ~ o\/elllents in the yield of polymers produced in the gas D-17226 ~ 3 phase, especially where comonomers which condense at relatively low temperatures are used. This procedure, commonly referred to as "condensing mode" operation, is described in detail in United States Patent Nos. 4,543,399 and 4,588,790. In condensing mode operation the two-phase gas-liquid mixture entering the polymerization zone is heated quite rapidly and is completely vaporized within very short distance alter entry into the polymerization zone. Even in the largest commercial reactors, all liquid has been vaporized and the temperature of the then totally gaseous cycle gas stream raised substantially by the exothermic nature of the polymerization reaction soon after entry into the polymerization zone. The ability to operate a gas phase reactor in condensing mode was believed possible due to the rapid heating of the two-phase gas liquid stream entering the reactor coupled with efficient constant back mi~ing of the fluidized bed leaving no liquid present in the polymer bed more than a short distance above the entry level of the two-phase gas-liquid recycle stream.
We have now found that liquid monomer may be present throughout the entire polymer bed provided that the liquid monomer present in the bed is adsorbed on or absorbed in solid particulate matter present in the bed, such as the polymer being produced or fluidization aids present in the bed, so long as there is no substantial amount of free liquid monomer present more than a short distance above the point of entry into the polymerization zone, as in the case of condensing mode operation. This discovery makes it possible to produce polymers in a gas phase reactor with the use of monomers having condensation temperatures much higher than the temperatures at which conventional polyolefins are produced in gas phase reactors.
This invention makes possible the gas phase production of classes of polymers which previously were thought not capable of production in a continuous gas phase process.

n~TAlT l; n n~C~l'ION OF '1~ ~VF~I'T(lN ~~
VVhile not limited to any particular type or kind of polymerization reAc~n, this i.lvt~ ion is particularly well suited to olefin polymerization re~c~;on~ involving homopolymeri7~tion and copolymeri7.~tion of relatively bigh boiling mnnnmerE;.
~ .Y~mrles of higher hoiling m~nr~mers cPp~hle of undergoing olefinic polymeri7.~t;or- re~;on~ are the following:
A. higher molecular weight alpha olefins such as ~lec~ne-l, dodecene-1 etc. and styrene.
B. dienes such as hexadiene, vinyl cyclohp~ne~
dicyclopentadiene, butadiene, isobutylene, isoprene, ethylidene norbornene and the like.
C. polar vinyl mn~omers such as acrylonitrile, maleic acid esters, vinyl acetate, acrylate esters, methacrylate esters, vinyl trialkyl ~ nes and the like.
These higher boiling monomers r~n be homopolymerized in accordance with this invention with the use of an inert gas as the gaseous component of the two phase gas-liquid ~ . e cycled through the reactor. Suitable inert materials for this purpose include l~ u~
and saturated hydrocarbons which remain gaseous at a temre. a~ e below the temperature selected to be m~int~inetl in the polymerization zone.
The higher boiling monomers can also be copolymerized with one or more lower boiling m~-nomers such as ethylene, propylene and butene, as well as other higher boiling mo~omers such as those mentioned above, the only rec~ e"~ent being that there be a sufficient difference in the con~nc~tion telllye~at~es ofthe higher boiling monomer and at least one lower boiling monomer or inert substance as will allow enough gas to be present in the cycle gas sll e~ to permit practical, steady state, continuous operation.

21~5236 -In accordance with our ~ven~ion the higher hoiling mon~m~rs can be directly intro-lnce~ into the polymeris~ti~n zone or ca~ied into -the polymerization zone as with the recycle ga6 sLIea~.
The practice of this in~,el,tion is not limite~ to any particular clas6 or kind of catalyst. Any catalyst useful in the conduct of gas phase polymeri7~io~ reactions is 6uitable for use in the practice of this invention.
The convent;o~l Ziegler-Natta cataly6t6, by which i6 meant those formed by re~c~ing a metal alkyl or hydride with a transition metal salt, are preferred in the practice of this in~e-.t,;on Those formed by re~cting an alu~llu~ alkyl with salt6 of metals of groups I
to III of the periodic table are particularly useful.
Illustrative of the catalysts useful in the practice of this invention are the following:
A. Titaniu_ based catalysts such as those described in U.S.
Patents Nos. 4,376,062; 4,379,758.
B. Ch~ m based catalysts such as those described in U.S. Patents Nos.3,709,853; 3,709,954 and 4,077,904.
C. Vanadiu_ based catalyst6 6uch as vanadium oxychloride, vanadillm acetyl acetonate.
D. Metallocene catalyst6 such as those described in U.S.
Patents Nos. 4,530,914; 4,665,047; 4,762,597; 5,218,071, 5,272,236 and 5,278,272.
E. Cationic forms of metal h~licle6~ 6uch as al!-.l)l...-.
trih~ les.
- A fluidized bed reaction sy6tem which is particularly suited to production of polymeric materials in accordance with the present invention is illustrated in the drawing. With reference thereto, the reactor 10 consists of a reaction zone 12 and a velocity reduction zone 14.
In general, the height to di~meter ratio of the re~ction zone can vary in the range of about 2.7:1 to about 4.6:1. The range, of course, can vary to larger or sm~ller ratios and depends upon the desired production capacity. The cross-sec~;n~ area of the velocity reductl~on zone 14 is typically within the range of about 2.6 to about 2.8 multiplied by the cross-section~l area of the reac~on zone 12.
The re~ n zone 12 includes a bed of ~ WiL~g polymer - -particles, fonned polymer particles and a minor amount of catalyst particles fl~ i7e~1 by the collt~uous flow of polymerizable and modifying gaseous cc~ o~-ents in the fo~m of m ke-up feed and recycle fluid through the react;on zone. To m~int~in a viable fluidized bed, the superficial gas velocity through the bed must eyr~ee~i the .. ;.-;.. flow required for fluidization, and preferably is at least 0.1 fl;/sec above minimllm flow. Ordinarily, the superficial gas velocity does,not exceed 5.0 f~lsec and usually no more than 2.5 f~sec is sufficient.
It is essential that the bed always colltaill particles to ~l~vellt the fonnation of localized "hot spots" and to entrap and distribute catalyst throughout the reaction zone. On start up, the reactor is usually charged with a base of particulate polymer particles before gas flow is initiated. Such particles may be identical in nature to the polymer to be fonned or they may be different. When different, they are withdrawn with the desired formed polymer particles as the first product. Eventually, a fluidized bed of desired polymer particles supplants the start-up bed.
A partially or totally activated precursor compoeition and/or catalyst used in the fluidized bed is l,lefelably stored for service in a reservoir 16 under a bl~nket of a gas which is inert to tbe stored material, such as nitrogen or argon.
Fluidization is achieved by a high rate of fluid ,ec~elc to and through the bed, typically in the order to about 50 times the rate of feed of make-up fluid. The fl~ i7e~ bed has the general appearance of a dense mass of individually moving particles as created by the percolation of gas through the bed. The pressure drop through the bed is equal to or slightly greater than the weight of the bed divided by the cross-sectional area. It is thus dependent on the geometry of the reactor.

21552~6 Make-up fluid is fed to the bed at point 18. The composition of the make-up stre~m i8 determined by a gas analyzer 21. The gas analyzer determines the c~ o~;l ;on of the recycle ~ and the composition of the make-up ~l~eh.ll is adjusted accordillgly to m~;..t~
an e6sçnt~ y steady state ga6eous compo6ition within the re~;on zone.
The gas analyzer is a ~v~ ;onS~l gas analyzer which operates in a conventionAl mAnner to determine the recycle 6tream comrosition to facilitate m~;nt~ining the ratios of feed stream ~ ents. Such eqllirment is commerically av~ hle from a wide variety of 60urces.
The gas analyzer 21 is typically positioned to receive gas from a sAmpling point located between the velocity reduction zone 14 and heat eYçhAnger 24.
The higher boiling monomers can be introduced into the polymerization zone in various ways including direct injection through a nozzle (not shown in the drawing) into the bed or by 6l.. ayhlg onto the top of the bed through a nozzle (not shown) positioned above the bed, which may aid in eliminAting some c&l~ovel- of fines by the cycle gas stream. If the rate of con~ ,lion is relatively small, heavier momomer6 can be introduced into the polymerization zone simply by suspension in the cycle gas stream entering the bottom of the reactor.
To ensure complete flUi~i7Ation~ the recycle sl e~ and, where desired, part of the make-up stream are returned through recycle line 22 to the reactor at point 26 below the bed. There is l,lefe.ably a gas distributor plate 28 above the point of return to aid in fl~ ii7.ing the bed. In pAcsing t~rough the bed, the recycle stream absorbs the heat of reaction generated by the polymerization reaction.
A portion of the fluidizing stream which has not reacted in the bed is removed from the polymeri7Ation zone, preferably by pAs.sing it into velocity reduction zone 14 above the bed where entrained particles can drop back into the bed.
The recycle stream is collll.lessed in a compressor 30 and then p~sse~ through a heat eYchAnge zone where heat is removed before it is returned to the bed. The heat eYrhAnge zone is typically a heat ~~
eYth~nger 24 which can be of the hori~ont~l or vertical type. If desired, several heat eyrh~n~ers can be employed to lower the tempe~ e of the cycle gas stream in stages. It is also poss;ble to locate the coml,,e6sor down~Laam from the heat eyrh~nger or at an interme-liAte point between several heat çychA~ers. After cooling~ the recycle stream is returned to the reactor at its base 26 and to the fl~ e~ bed through gas distributor plate 28. A gas deflector 32 is lJ,ef~.ably installed at the inlet to the reactor to ~ ~veut cont~qine~
polymer particles from sett1ing out and agglomerating into a solid mass and to ~l~vel~t liquid accl-m~ t;Qn at the bottom ofthe reactor as well to facilitate easy transitions between processes which cont~in liquid in the cycle gas stream and those which do not and vice versa.
Illustrative of gas ~eflectors suitable for this purpose is the apparatus described in U.S. Patent No. 4,933,149.
The selected temperature of the bed is maintained at an essentially constant temperature under steady state conditions by constantly removing the heat of reaction. No noticeable temperature gradient appears to exist within the upper portion of the bed. A
temperature gradient will exist in the bottom of the bed in a layer of about 6 to 12 jnrhPs, between the tempeldlule of the inlet fluid and the temperature of the rem~in~ler of the bed.
Good gas distribution plays an important role in the ~.~e.alion of the reactor. The fluidized bed cont~in~ Kl~ wing and formed particulate polymer particles, as well 8S catalyst particles. As the polymer particles are hot and possibly active, they must be ~l~ve~ted from settling, for if a quiescent mass is allowed to exist, any active catalyst contained therein may continue to react and cause fusion. Diffusing recycle fluid through the bed at a rate sufficient to maintain fluidization throughout the bed is, thelefo~e, i~Gl laut.
Gas distribution plate 28 is a preferred means for achieving good gas distribution and may be a ficreen, slotted plate, perforated plate, a plate of the bubble-cap type and the like. The elçments of the plate ' . ' 21 S523~

may all be stationary, or the plate may be of the mobile type disclosed in U.S. 3,298,792. Whatever its ~l~Eign, it must diffuse the recycle fluid through the particles at the base of the bed to keep the bed in a fl~ i7et1 condition, and al60 serve to ~uy~u~ l a quiescent bed of resin particles when the reactor is not in operation.
The preferred type of gas distributor plate 28 is metal and has holes distributed across its 6urface. The holes are norm~lly of a diameter of about V2 inch. The holes e~t~?nd through the plate. Over each hole there is positioned a triangular angle iron i-lent;fied as 36 which is mounted on plate 28. The angle irons 6erve to distribute the flow of fluid along the surface of the plate so as to avoid 6t~gn~nt zones of solids. In addition they ~levellt the polymer from flowing through the holes when the bed is settled.
Any fluid inert to the catalyst and reactants rqn also be present in the recycle stream. An activator col,lyound, if utilized, is yl efel ably added to the reaction system downstream from heat eYl~hqnger 24, in which case the activator may be fed into the recycle system from dispenser 38 through line 40.
In the practice of this i~lvelltion uye-aling te...l.~- atl,les can extend over a range of from about -100~C to about 150~C with temperatures r~qn~ing from about 40~C to about 120~C being l lefel.ed.
The fluid-bed reactor can be operated at pressures up to~about 1000 psi and ~, efelably at a pressure of from about 100 psi to about 350 psi, for polyolefin resin production. Operation at higher pressures favors heat transfer as an increase in IJ 2ssu~e incresses the unit volume heat capacity of the gas.
The partially or totally activated plecu~SO~ co~ Jo~ilion and/or catalyst (hereinafter collectively ~efe.. ed to as catalyst) is injected into the bed at a rate equal to its consumption at a point 42 which is above distributor plate 28. E~ efefably, the catalyst is injected at a point in the bed where good mi~in~ of polymer particles occurs. Injecting the catalyst at a point above the distribution plate is an important feature for satisf~tory operation of a fluidized bed polymerization reactor.

215~236 ::

Injection of the catalyst into the area below the distnbutor plate could cause polymerization to begin there and evçnt~ y cause plu~in~ of the distributor plate. ~jec~;on d;l.:cLly into the fl~ liz~ bed aids in distributing the catalyst ullifol~ly throughout the bed and tends to avoid the forTn~t;on of locpli7erl spot6 of high cataly6t conc~ ation which can cause "hot 6pots" to form. Injection of the catalyst into the reactor above the bed can result in PYGeSRive catalyst Call~UVel into the recycle line where polymeri7At;on can occur lç~ling to plllg~ing of the line and heat çyrh~nger may l:ve~ lly occur.
The catalyst can be injected into the reactor by various techniques. It is preferred, however, to c~-linuously feed the cataly6t into the reactor utili7ing a catalyst feeder as disclosed; e.g., in U.S.
patent 3,779,712. The catalyst is preferably fed into the reactor at a point 20 to 40 percent of the reactor ~ met~r away from the reactor wall and at a height of about 5 to about 30 percent of the height of the bed.
A ga6 which is inert to the catalyst, 6uch as nitrogen or argon, is preferably used to carry the cataly6t into the bed.
The rate of polymer pro~lllction in the bed depends on the rate of catalyst injection and the conrçntration of monomçr(s) in the r~- ycle stream. The pro~ ct;on rate is ~ll~/el~iently controlled by simp, ~ -adjusting the rate of catalyst injection.
Since any change in the rate of cataly6t injection will change the reaction rate and thus the rate at which heat is generated in the bed.
The t~mperature of the recycle ~Lea~ entering the reactor is adjusted upwards and dowll-w~ds to ~c~mmn~l~te any change in the rate of heat generation. This ensure6 the m~inten~nce of an essenti~lly constant temperature in the bed. Complete instrumentation of both the fluidized bed and the recycle stre~m coolir~ sy6tem is, of course, useful to detect any te~l at.ue change in the bed so as to enable either the operator or a collvelltional automatic control system to make a suitable adjusttnçnt in the temperature of the recycle stream.

, Under a given set of ~elaLillg contlit;ons) the fl~ e~ bed i8 maintained at esser t;o11y a cQnctont height by withLc.w~g a portion of the bed as product at the rate of formo-~;nn of the particulate polymer product. Since the rate of heat generation i8 directly related to the rate of product formation, a measurement of the te~ e rise of the fluid across the reactor (the ~ elcllce I~L., ~cn inlet fluid te...l~e,s~uLe and exit fluid temre~ e) is in~1ic-t;ve of the rate of particular polymer form,o.~ion at a constant fluid velocity if no vaporizable liquid is present in the inlet fluid.
On ~lisrh~rge of particulate polymer product from reactor 10, it is desirable and ylefelsble to separate fluid from the product and to return the fluid to the recycle line 22. lhere are numerous ways known to the art to ~ccompli.ch this. One l,iefelled system is shown in the drawings. Thus, fluid and product leave reactor 10 at point 44 and enter product ~iic,ch~rge tank 46 through valve 48, which may be a ball valve which is designed to have mi--;-------~ restriction to flow when opened. Po'sitioned above and below product ~icrh~rge tank 46 are conventional valves 50,62 with the latter being adapted to provide p~Csiqge of product into product surge tank 54. Product surge tank 54 has venting means illustrated by line 56 and gas entry means illustrated by line 68. Also positioned at the base of product surge tank 64, is a ~li,c( h~rge valve 60 which when in the open position tii~c,ch~rges product for ~llve~illg to storage. Valve 50 when in the open posi~io~
releases fluid to surge tank 62. Fluid from surge tank 62 is-directed through a filter absorber 64 and thence through a co ~l lessor 66 and into recycle line 22 through line 68.
In a typical mode of operation, valve 48 is open and valves 50, 52 are in a closed position. Product and fluid enter product discharge tank 46. Valve 48 closes and the product is allowed to settle in product discharge tank 46. Valve 50 is then opened ~el~tlillg fluid to flow from product tiisch~rge tank 46 to surge tank 62 from which it is continually compressed back into recycle line 22. Valve 50 is then closed and valve 62 is opened and any product in product llic~h~rge D-17226 ~ 7 tank 46 flows into product surge tank 54. Valve 52 is then closed. The product is purged with inert gas, preferably nitrogen, which enters product surge tank 54 through line 58 and is vented through line 56.
Product is then discharged from product surge tank 54 through valve 60 and conveyed through line 20 to storage.
The particular timing sequence of the valves is accomplished by the use of conventional progr~mm~qhle controllers which are well known in the art. Moreover, the valves can be kept substantially free of agglomerated particles by directing a stream of gas periodically through the valves and back to the reactor.
Another preferred product discharge system employs at least one (parallel) pair of tanks comprising a settling tank and a transfer tank arranged in series and having the separated gas phase returned from the top of the settling tank to a point in the reactor near the top of the fluidized bed. Such alternative preferred product discharge system obviates the need for a recompression line 64, 66, 68, as shown in the system of the drawing.
The fluidized-bed reactor is equipped with an adequate venting system (not shown) to allow venting the bed during start up and shut down. The reactor does not require the use of stirring and/or wall scraping. The recycle line 22 and the elements therein (compressor 30, heat exch~nger 24) should be smooth surfaced and devoid of unnecessary obstructions so as not to impede the flow of recycle fluid or entrained particles.
Illustrative of the polymers which can be produced in accordance with the invention are the following:
Polyisoprene (cis-1, 4 - Polyisoprene) Polystyrene Polybutadiene SBR (polymer of butadiene copolymerized with sytrene) ABS (polymer of acrylonitrile, butadiene and styrene) Nitrile (polymer of butadiene copolymerized with acrylonitrile) Butyl (polymer of isobutylene copolymerized with isoprene) EPR (polymer of ethylene copolymerized with propylene) EPDM (polymer of ethylene copolymerized with propylene and a diene such as h~Y~Iiiene~
dicyclopentadiene, or ethylidene norbornene) Neoprene (polychlo,~op elle) Silicone (polydimethyl siloxane) Copolymer of ethylene and vinyltrimethoxy silane Copolymer of ethylene and one or more of acryonitrile, maleic acid esters, vinyl Aoet~te, acrylic and methacrylic acid esters and the like When it is desired to produce polymers or copolymers using one or more nlonomers which are all relatively high boilin~ and which are liquids under the temre, atu~e and pressure conditions which are preferred for gas phase fl~ i7ed bed production in accordance with the invention, it is necess~ry to employ an inert subst~rce which will remain gaseous under the conditions selected for polymerization in the fluidized bed. Suitable for this purpose are inert gases such as nitrogen, argon, neon, krypton and the like. Also usefill are saturated hydroc~l,ons such as et~ ~qne~ y2~le, butane and the like a6 well as halogen sub6tituted alkanes such as freon. Other materials which remain gaseous under the desired conditions, such as carbon dioxide, ~ D-17226 2155~3~

provided they are essentially inert and do not affect catalyst perform~nce, ~qn also be employed.
Nitrogen, ber~lse of its physical l,ropel ~ies and relatively low cost is a preferred medium for the mq-mlf~ct~lre of polymers from higher boiling mono~ers such as styrene, vinyl acetic acid, acrylonitrile, methylacrylate, methylmet~ crylate and the like.
Alkanes such as ethane and ~-o~ e which remain gaseous at relatively low tempe,a~ules are also ~.~e~l~ed.
Co~ve~.l;o~ql techniques for the ~.e-vt,l~Lon offouling of the reactor and polymer agglomeration can be used in the prsctice of our invention. Illu~lla~ive ofthese techniques are the introduction of finely divided particulate m~ttPr to ~ Vellt agglomeration, as described in U.S. Patent Nos. 4,994,534 and 5,200,477; addition of negative charge generating ~~hpmir~ls to balance positive voltages or by addition of positive charge generating chemicals to neutralize negative voltage poter~ti~l~ as described in U.S. Patent No. 4,803,251. Antistat substances may also be added, either contimlously or intermittently to prevent or neutralize static charge generation.

The following eY~mples are provided to illustrate our invention.

T~le 1 -In an eY~mple of the process of the invention a fl~ i7etl bed reaction fiystem as described above, was operated as described below to produce ethylene-propylene diene terpolymer. The polymer was produced under the following re~ction conditions: 40~C reactor tempe~ature and 290 psia reactor pressure. The partial pressurefi (dew points) of the mor nmers and comonomers inside the reactor were 90 psia for ethylene and 198 psia for propylene. The partial pressure of hydrogen was 2.0 psia. The monomer ethylidene-norbornene (ENB) was injected into the polymeriza~on zone of the reactor at the rate of 0.53 lb/h. The volume of the reactor was 65 ft3; the resin's weight inside the reactor was 112 lbs. The catalyst system employed in this ~y~mple was vanadium acetyl acetonate with diethylalllmin~lm _ D-17226 2155236 chloride as coc~tPlyst and ethyl tri~hloro~cetpte as the promoter . The production rate was 20 lb/h. The product had a Mooney value of 55.

75 ~er~ t ofthe injected ENB was incol~oldted into polymers by polymeri7~tion The unreacted re--~inrler of ENB, dissolved into polymers and was equal to 0.66 percent of the polymer's weight. With 112 lbs. of resins inside the reactor, the total unreacted ENB was 0.74 lbs. If the unreacted ENB were completely ~v~ol~ted inside the reactor, its partial pressure would be 0.6764 psia.

At 40~C the saturation pressure is 2187.7 psia for ethylene, 337.1 psia for propylene and 0.262 psia for ENB. Since the partial pressures of ethylene and propylene inside the reactor were much less than their saturation pressures, there was no con~l~nsed ethylene or propylene. The calculated partial pressure of unreacted ENB inside the reactor, howevel, is much higher than its saturation pressure. Theleîore, the ENB must have remained in a liquid state and been absorbed by the polymers.

F~Y~ e ~
Ethylene-propylene diene terpolymer was made in a fl~ i7.e-1 bed reaction system as described above under the following reaction conditions: -40~C reactor tempela~ule and 363.4 psia. reactor pressure. The partial pressures of tbe monomprs and coTnnnnmers inside the reactor were 90 psia.
for ethylene and 198.2 psia. for propylene. The partial pressure of hydrogen was 2.2 psia., and tbe partial pressure of ~Lot t:l- was 72.6. The monoIner ethyli~lPnq~orbornene (ENB) was injected into the polymerization zone of the reactor at the rate of 0.53 lb/h. The volume of the reactor was 55 ft3; the resin's weight inside the reactor was 112 lbs. The catalyst system employed in this ~ mrle was vanadium acetyl acetonate with diethylalumi~
chloride as coc~t~lyst and ethyl trichloroacetate as the promoter. The production rate was 20 lblh. The product had a Mooney value of 55.

D-17226 21 5 5 2 3 ~
.~

75 percent of the in~ected ENB was incoll o.ated into polyme-rs by polymerization. The unreacted ~e.l.A; ~ .~er of ENB, dissolved into polymers and was equal to 0.66 percent of the polymer's weight. With 112 lbs. of resins inside the reactor, the total unreacted ENB was 0.74 lbs. If the unreacted ENB comrletely evaporated inside the reactor, its partial pressure would be 0.6764 psia.

At 40~C the sa~u~a~ion pressure is 2187.7 psia. for ethylene, 337.1 psia. for propylene and 0.262 psia, for ENB. Sinoe the partial pressures of ethylene and propylene inside the reactor were much less than their saturation pressures, there was no contl~n~e~l ethylene or propylene. The calculated par~al pressure of unreacted ENB inside the reactor, however, is much higher than its saturation pressure. Th0refole, the ENB must have remained in a liquid state and been absorbed by the polymers.

~Y~les 3-6 The following eY~mples set forth in tabular form, operating conditions for producing a variety of different polymers in accordance with the invention. They illustrate the practice of the invention using different catalyst systems and differing cycle gas compositions.

,._ EXAMPLE NO. POLYBUTADIENE SB4R ABS POLYSlYRENE

Reaction Cn~ nc Te ~ re (~C) 40 40 40 40 Pressure (psi) 100 110 200 100 S_. ri~l Velocity 1.75 2.0 1.5 1.5 P~lu.,lioll Rate30 25 20 40 (Ib/h) Total Reactor Volume (ft3) 55 55 55 5S
Reaction ZoneVolume 7 5 7.5 7.5 Bed Hei~ht (ft) 7.0 7.0 7.0 7.0 Bed Diameter (h)1.17 1.17 1.17 1.17 Bed Wei~ht (Ibs) 112 112 112 112 Cycle Gas Composition:
N2 20 27.3 58.0 99.7 Butadiene 80 72 2 39 9 Acrylonitrile - - 1.95 Catalyst: Co(acac)3* Co(acac)3* Co(acac)3* Cp2ZrMe2 Co-catalyst: Triethylql.. nir.lm Triethy~?ll ~Triethy'-' MAO***
Heavy Monomer Feed Rate (Ib/h) Eu~ -e 46.2 9.62 2.46 St~rrene - 20.83 15.33 44.4 Acrylonitrile - 7.08 Polymer C. . ~ ~
But~ ne 100 25 8 Styrene 75 69 100 Acrylonitrile - 23 * Cobalttriacetylacele- --** Dicycl.J~ ~ ku. limr~y *** Methyl ~I~mc~

Claims

1. A process for producing polymers in a stirred bed or gas fluidized bed reaction vessel having a polymerization zone containing a bed of growing polymer particles which comprises:
1) continuously introducing a stream comprised of one or more monomers and optionally one or more inert gases or liquids into said polymerization zone;

2) continuously or intermittently introducing a polymerization catalyst into said polymerization zone;

3) continuously or intermittently withdrawing polymer product from said polymerization zone;

4) continuously withdrawing unreacted gases from said polymerization zone, compressing and cooling said gases while maintaining the temperature within said polymerization zone below the dew point of at least one monomer present in said polymerization zone;
with the proviso that if there is only one monomer present in said gas-liquid stream there is also present at least one inert gas.

2. A process for producing polymers from two or more monomers by an exothermic polymerization reaction in a stirred bed or gas fluidized bed reaction vessel having a polymerization zone containing a bed of growing polymer particles, which comprises:
1) continuously introducing a fluid stream comprised at least two monomers and optionally one or more inert gases or liquids;
2) continuously or intermittently introducing a polymerization catalyst into said polymerization zone;

3) continuously or intermittently withdrawing polymer product from said polymerization zone;
4) continuously withdrawing unreacted gases from said polymerization zone, compressing and cooling said gases; and

5) maintaining the temperature within said polymerization zone below the dew point of at least one of said monomers.

3. A process according to claim 1 wherein the velocity of said fluid stream entering said polymerization zone, the rate of introduction of said polymerization catalyst into said polymerization zone and the concentration of monomer in said fluid stream are such that the temperature within said polymerization zone is maintained below the dew point of at least one monomer present in said fluid stream.

4. A process according to claim 1 wherein the temperature within said polymerization zone and the velocity of gases passing through the said polymerization zone are such that essentially no liquid is present in the said polymerization zone that is not absorbed on or absorbed in solid particulate matter.

5. A process for producing polymers from two or more monomers by an exothermic polymerization reaction in a stirred bed or gas fluidized bed reactor having a polymerization zone containing a bed of growing polymer particles which comprises:
1) continuously introducing a fluid stream containing at least two monomers and optionally one or more inert gases into said polymerization zone;
2) continuously or intermittently introducing a polymerization catalyst into said polymerization zone;

3) continuously or intermittently withdrawing polymer product from said polymerization zone;
4) continuously withdrawing unreacted gases from said polymerization zone, compressing and cooling said gases; and 5) maintaining the temperature within said polymerization zone below the dew point of at least one of said monomers and above the vaporization temperature of at least one of said monomers.

6. In a continuous fluidized bed polymerization process for the production of polymer from two or more fluid monomers by passing a gaseous stream through a fluidized bed reactor in the presence of catalyst under reactive conditions, withdrawing polymeric product and unreacted fluids, cooling said unreacted fluids and returning said cooled fluids into said reactor together with sufficient additional monomers to replace those monomers polymerized and withdrawn as product, the improvement which comprises; controlling the concentration of monomers in the gas stream passing through said reactor; the temperature of the cooled fluids returned to said reactor and the amount of catalyst present in said reactor so that the temperature within said reactor is maintained below the dew point of at least one of said monomers and above the vaporization level of at least one of said monomers.

7. A process according to claim 1 wherein said polymerization process is conducted in the presence of inert particulate matter.

8. A process according to claim 1 wherein said process is conducted in the presence of an agent or device for controlling the level of static in said reactor.

9. A process according to claim 1 wherein the static voltage in said reactor is maintained essentially neutral.

10. A process for producing polymers in a stirred bed or gas fluidized bed reactor vessel having a polymerization zone containing a bed of growing polymer particles which comprises;
1) continuously introducing a fluid stream comprised of one or more monomers and one or more inert gases into said polymerization zone;
2) continuously or intermittently introducing a polymerization catalyst into said polymerization zone;
3) continuously or intermittently withdrawing polymer product from said polymerization zone;
4) continuously withdrawing unreacted gases from said polymerization zone, compressing and cooling said gases while maintaining the temperature within said polymerization zone below the dew point temperature of at least one of said inert gases.

11. A process according to claim 10 wherein said fluid stream is a two-phase gas-liquid stream comprised of an inert gas and one or more liquid monomers.

12. A process according to claim 11 wherein said inert gas is nitrogen and said liquid monomer is butadiene or chloroprene.

13. A process according to claim 11 wherein said inert gas is nitrogen and said liquid monomer is styrene.

14. A process according to claim 11 wherein said inert gas -is nitrogen and said liquid monomer is a mixture of butadiene, styrene and acrylonitrile.