MXPA96006589A - Improvement in fluidized bed reaction systems using catalysts without support - Google Patents

Abstract

A process for increasing the space-time yield of polymer production in a fluidized bed reactor employing an exothermic polymerization reaction is described, cooling the recycle stream to lower its dew point and returning the two-phase fluid stream resulting to the reactor to maintain the fluidized bed at a desired temperature above the dew point of the recycle stream

Description

»" IMPROVEMENT IN FLUIDIZED BED REACTION SYSTEMS USING CATALYSTS WITHOUT SUPPORTS " FIELD OF THE INVENTION This invention relates to a method for improving the space time of production of an exothermic polymerization reaction conducted in a fluidized bed reactor using a transition metal catalyst without supports, increasing the removal of heat from polymerization from the reactor by cooling gases, continuously removed from the reactor, to a temperature lower than the dew point temperature of these gases and returning the fluid mixture of two resulting phases to the reactor to maintain the temperature of the fluidized bed at the desired level.

BACKGROUND OF THE INVENTION The use of a condensation mode of operation in a continuous gas fluidized bed polymerization is disclosed in U.S. Patent Nos. 4,543,399 and 4,588,790. That process -provided part of the cooling and the entire recycle stream to form A mixture comprising both a gas phase and a liquid phase before reintroducing the stream into the reactor, wherein the liquid portion of the recycle stream was vaporized. This invention greatly improved the production rate and the cooling capacity of the gas phase process. Recently, U.S. Patent Nos. 5,352,749 and 5,436,304 have disclosed variations in the condensation mode operation. In U.S. Patent Number 5,317,036, the use of condensation mode for soluble catalysts without supports was disclosed. From that time, the condensation mode has also been disclosed for use with metallocene catalysts supported by US Patent Nos. 5,405,922 and 5,462,999. It has now been discovered that the use of the condensation mode with soluble catalysts without supports aids the migration of the catalyst components without supports in a manner not proposed by the prior art.

COMPENDIUM OF THE INVENTION The present invention provides a process for increasing the space-time yield of polymer production in a fluidized bed reactor by employing an exothermic polymerization reaction by cooling the recycle stream to less than its dew point temperature and returning the fluid stream of two phases resulting in the reactor to keep the bed 5 fluidized at a desired temperature above the dew point of the recycle stream. The cooling capacity of the recycle stream is increased both due to the higher temperature differential between the incoming recycle stream and the reactor, and by the vaporization of the condensed liquids retained in the recycle stream. The amount of condensation, and therefore, the increase in the production regime can be improved, also altering the process conditions to increase the dew point of the recycle stream.

DETAILED DESCRIPTION OF THE INVENTION In accordance with the present invention, a process for carrying out a condensation mode with catalysts without supports is provided. Although no specific type or type of polymerization reaction is limited (as long as the reaction is of an exothermic nature), this invention is particularly suitable for polymerization reactions involving the polymerization of one or more monomers that are listed below: I. Type of olefin: ethylene, propylene, buten-1, penten-1,4-methylpenten-1, hexen-1-, styrene. II. Type of polar vinyl monomer: vinyl chloride, vinyl acetate; vinyl acrylate, methyl methacrylate, tetrafluoroethylene, vinyl ether, acrylonitrile. III. Diene type (conjugated and unconjugated): 10 butadiene, 1, 4-hexadiene, isoprene, ethylidene norbornene. IV. Type of acetylene: acetylene, substituted acetylene, such as methyl acetylene. V. Type of aldehyde: formaldehyde. It should be noted that the catalysts without carriers employable in the fluidized bed polymerization of the aforementioned monomer types, respectively, would usually be as follows: I. Coordinated anionic catalyst II. Cationic catalyst for copolymers with ethylene only; others of this type require a free radical catalyst III. Be it a free radical catalyst or a coordinated anionic catalyst.

• IV. A coordinated anionic catalyst V. An anionic catalyst Preferably, the catalyst is of the type disclosed in U.S. Patent Nos. 5,317,036; 5,405,922; 5,462,999 and U.S. Patent Application Serial No. 08 / 412,964 filed March 29, 1995. Most preferably, the catalyst is the reaction product of modified methylaluminoxane or ftr methylaluminoxane and a carbamate carboxylate of tris-alkyl cyclopentadienyl zirconium or substituted cyclopentadienyl. Even though this invention is not limited to any specific type of polymerization reaction, the following discussions of the operation of the process are directed to polymerizations of the olefin type monomer wherein it has been found that the invention is especially advantageous. In very general terms, a conventional fluidized bed process to produce resins, In particular, polymers produced from monomers are carried out by passing a gaseous stream containing one or more monomers continuously through a fluidized bed reactor under rectifying conditions and in the presence of a catalyst. The gaseous current that contains an unreacted gaseous monomer is continuously removed from the reactor, compressed and cooled and recycled to the reactor. The product is removed from the reactor. The replenishing monomer is added to the recycle stream. The polymer forming reaction is exothermic, making it necessary to maintain to some degree the temperature of the gas stream within the reactor at a temperature not only lower than the degradation temperatures of the resin and the catalyst but at a lower temperature than the melting or adhesion temperature of the resin particles produced during the polymerization reaction. This is necessary in order to prevent the sealing of the reactor due to the rapid growth of pieces of polymer that can not be removed in a certain way. continues as a product. It will be understood, therefore, that the amount of the polymer that can be produced in a fluidized bed reactor of a given size in a specified period of time, is directly related to the amount of heat that can be removed of the fluidized bed. In accordance with this invention, the recycle gas stream is intentionally cooled to a temperature lower than the dew point of the recycle gas stream to produce a two phase liquid gas mixture under conditions such that the liquid phase of the mixture will remain retained in the gas phase of the mixture at least from the point of entry into the fluidized-bed reactor until it volatilizes or until it passes into the fluidized bed. There results a considerable increase in the space-time performance of the practice of this invention with little or no change in the properties or quality of the product. When carried out as described herein, the total process i progresses continuously and uniformly and without unused operating difficulties. It may be desirable, in some cases, to raise the dew point of the recycle gas stream to further increase the heat removal. The dew point of the recycle stream can be increased by: (1) raising the operating pressure of the reaction system; (2) increasing the concentration of the condensable fluids in the recycle stream; and / or (3) reducing the concentration of non-condensable gases in the recycle stream. In a As an embodiment of this invention, the dew point of the recycle stream can be increased by the addition of a condensable fluid in the recycle stream is inert to the catalyst, to the reactants and to the products of the polymerization reaction. The fluid is can be introduced into the recycle stream with the replacement fluid * or by any other means or at any other point in the system. Examples of these fluids are saturated hydrocarbons such as methane, pentane or hexane. A primary limitation on the degree of condensation is the solubility and softening effect of the condensable component in the polymer particles. This is affected by the selection of the condensing agent, its concentration, the reaction conditions of the cycle gas composition such as temperature and pressure, and the molecular weight of density and chain branching distribution of the polymer. Stable condensation operation has been achieved at high and high fluidized bulk densities despite the teachings of U.S. Patent No. 5,352,749. In practical experience, condensation levels of 20 percent by weight and above have been demonstrated while not exceeding the limit of polymer softening. The point of entry of the two phase recycle stream is preferably below the fluidized bed (polymerization zone) to ensure uniformity of the flowing gas stream ascending and to maintain the bed in a suspended cold condition. The recycle stream containing retained liquid is introduced into the reactor at a point in the lower region of the reactor and most preferably at the bottom of the reactor to ensure uniformity of the fluid stream passing up through the fluidized bed . Other entry points include any number of holes along the side of the reactor directly into the fluidized bed, with the release being in the wall or through a pipe or tube to the body of the bed. Also, the entry point can be towards the bed from a pipe extending through the distributor plate. Spray or spray nozzles can be used to distribute the flow to the bed. A baffle or similar means for preventing regions of low gas velocity in the vicinity of the point of entry of the recycle stream can be provided to keep the solids and liquids retained in the recycle stream flowing downwardly. One of these means include an annular disc as disclosed in US Patent Nos. 4,877,587 and 4,933,149. Even though there is no apparent advantage in doing so, the two phase recycle stream can be divided into two or more streams separated one or more of which can be introduced directly into the polymerization zone, as long as a sufficient gas velocity is provided below and through the bed to keep the bed suspended. In all cases, the composition of the gas stream remains essentially uniform, including in such a way that there are no inactive or dead spaces in the bed where non-removable solids can be formed. It will be apparent that if desired, it is possible to form a two-phase fluid stream within the reactor at an injection point, by separately injecting gas and liquid under conditions that will produce a two-phase stream. Little advantage will be seen in operating in this manner due to the added and unnecessary burden and cost to separate the gas and liquid phases after cooling. In Patent Number WO 94/28032 published on December 8, 1994, a view to the contrary is expressed as to the advantage obtained through this mode of operation. However, it may be desirable to inject the replenishing monomer into the reactor in this manner. The injection of the liquid or gaseous replacement monomer at the point of entry of the two-phase recycle stream or elsewhere in the reactor into the recycle stream is proposed by means of this invention.

# The advantages of this invention are not limited to the production of polyolefin resins. This invention can be practiced in connection with any exothermic polymerization process carried out in a gas phase fluidized bed. The advantages of this invention in relation to conventional processes, in general, they will increase in direct relation to the proximity of the dew point temperature of the recycle stream, to the reaction temperature within the interior 10 of the fluid bed. The applicability of this invention to the production of any given polymer can be determined by using the following formula: X Hrxn. Gmasa 'GP gas (trxn t limit) P = desired polymer production rate, restricted to regimes that provide X less than 1.0 without the present invention. Hrxn = polymerization heat of the specific polymer that is produced. Gmasa = mass flow regime of the recycle stream; limited to a minimum value by the need for adequate fluidization and mixing in the bed and up to a maximum value by retaining solids. The specific minimums and maximums depend on numerous factors known to those skilled in the art. # CPgas heat capacity of the current recycled. Trxn temperature of the reaction zone (fluid bed); has a maximum value that depends on the adhesion temperature of the polymer at the pressure of the recycle stream and / or the operation of the catalyst, and a minimum value that depends on the operation of the catalyst. limit = Minimum temperature of the current of recycling that enters the reaction zone. This temperature is either the dewpoint of the recycle stream or the cooling limit of the heat exchange zone 25 whichever is higher. If dew point of the recycle stream, the invention is carried out by simply cooling the current to a temperature lower than its spray temperature. If j ^ i ^ g is controlled by the heat exchange zone, the invention is carried out by adding a condensable fluid to increase the dew point of the recycle stream to a temperature above the cooling limit of the zone of thermal exchange. When the value of X is greater than 1, the use of the present invention will provide a benefit and as the valaor of X increases, the greater the benefits that can result from this invention. Generally, the height to diameter ratio of the reaction zone within a reactor varies within the range of about 2.7: 1 to about 4.6: 1. The scale can of course vary to larger or smaller ratios depending on the desired production capacity. The cross-sectional area of the velocity reduction zone typically falls within the range of approximately # 2.6 to approximately 2.8 multiplied by the cross-sectional area of the reaction zone. The reaction zone includes a bed of growing polymer particles, polymer particles formed and a small amount of fluidized catalyst particles by the continuous flow of the polymerizable and gaseous modification components in the form of a replacement feed and a fluid of recycling through the reaction zone. To maintain a bed As the fluidized gas is viable, the velocity of the surface gas through the bed must exceed the minimum flow required for fluidization, and is preferably at least 0.061 meter per second above the minimum flow. In general, the surface gas velocity does not exceed 1.52 meters per second and usually no more than .762 meters per second is enough. It is essential that the bed always contains particles to prevent the formation of localized "hot spots" and to trap and distribute the catalyst in particles through the reaction zone. During initiation or startup, the reactor is usually charged with a polymer particle base before the gas flow starts. These particles can be identical in nature to the polymer to be formed or different from the same. When they are different, they are removed with the desired polymer particles formed as the first product. Eventually, the fluidized bed of desired polymer particles impersonates the starter bed. The partially or fully activated precursor composition and / or the catalyst used in the fluidized bed is preferably stored for service in a reservoir under a blanket of gas that is inert to the stored material such as nitrogen or argon. Is fluidization achieved by a high regime of recycling fluid to and through the bed, typically within the order of about 50 times the rate of supply of the replacement fluid. The fluidized bed has the general appearance of a dense mass of particles that move individually, as creates by percolation of the gas through the bed. The pressure drop across the bed is equal to or slightly greater than the weight of the bed divided between the bed section area. Therefore, it depends on the geometry of the reactor. The replenishment fluid can be fed directly to the bed but is more often fed to the recycling line. When the recycling line is fed, it is usually fed before or after either the heat exchanger or the gas cooler. cycle. The composition of the replenishment current is determined by a gas analyzer. The gas analyzer determines the composition of the recycle stream and the composition of the replenishment stream that is adjusted accordingly in order to maintain a gaseous composition of essentially constant state within the reaction zone. In gas analyzer it may be a conventional gas analyzer which classifies in a conventional manner for G to indicate the composition of the recycle stream and that 0 is adapted to regulate the feed and can be obtained commercially from a wide variety of sources. The gas analyzer may also be one of the most sophisticated rapid gas analyzers as disclosed in U.S. Patent Number 5,437,179. 5 In general, the gas analyzer can be placed in order to receive the gas from a point between the speed reduction zone and the heat exchanger. To ensure complete fluidization, the recycle stream and when desired part of the replenishment stream is returned through the recycle line to the reactor below the bed. It may preferably be a gas distributor plate above the return point to assist fluidization of the bed. When passing through the bed, the recycle stream absorbs the heat of the reaction generated by the polymerization reaction. Sometimes, the use of aluminoxane seems to be contributing to the generation of static electricity. It has been shown that the operation mode of induced and natural condensation controls the static. It is believed that this static "dissipation" results mainly from the instantaneous feed regime of the condensation medium, such as isopentane, into the reactor instead of from the condensation of the isopentane already in the reactor. Therefore, changes in the rate of feed of the condensation medium can dramatically affect the static of the reactor. By feeding a spray of the condensing medium directly to the fluid of the distributor plate, a greater quantity of liquid hits the plate at a concentration of the condensing medium of the determined total reactor than would hit the plate if the condensing medium were fed towards the lower head or recycling line. The advantage of doing this is that a smaller amount of the condensation medium is required and therefore, it is easier to prevent flooding of the fluidized bed. The portion of the fluidization current that does not act on the bed constitutes the recycle stream that is removed from the polymerization zone that passes preferably to the zone of velocity reduction above the bed where an opportunity is provided to the particles retained to fall back towards the bed. The recycle stream is then compressed in a compressor and then passed through a heat exchange zone where the heat of the reaction is removed before it is returned to the bed. The heat exchange zone is typically a heat exchanger that can be of the type horizontal or vertical. The recycle stream is then returned to the reactor at its base and to the fluidized bed through a gas distributor plate. A gas baffle is preferably installed at the inlet to the reactor to prevent the contained polymer particles from settling and agglomerating in a solid mass. The annular disc referred to above is a means to achieve this. The temperature of the bed is controlled at an essentially constant temperature under constant state conditions by constantly stirring the heat of the reaction. No perceptible temperature gradient appears as existing within the upper portion of the bed in the polyethylene. In polypropylene, a small temperature gradient across the upper bed of about 1 ° C to 2 ° C is not unusual. There will be a # temperature gradient at the bottom of the bed in the layer of approximately 15.24 to 30.48 centimeters between the temperature of the inlet fluid and the temperature of the remainder of the bed. Good gas distribution plays an important role in the operation of the reactor. The fluidized bed contains particles of polymer in growth and formed into particles as well as the particles of the # catalyst Since the polymer particles are hot and possibly active, should be prevented from settling because if a quiet dough is left; any active catalyst contained in it can continue to react and cause fusion. Spreading the recycling fluid through the bed to a regime sufficient to maintain fluidization through the bed, therefore it is important. A gas distribution plate is a preferred means for achieving good gas distribution and can be a screen; a slotted plate, a perforated plate, a plate type bubble cap and the like. The elements of the plate may all be stationary or the plate may be of the movable type disclosed in US Patent Number 3,298,192. Whatever your design, you must spread the recycling fluid through The particles in the base of the bed in order to maintain the bed in a fluidized condition, and also serves to hold a bed of still resin particles when the reactor is not in operation. The gas-distributing plate of the preferred type is generally of the type that is made of metal and has holes distributed through its surface. The holes are usually about 1.27 centimeters in diameter. The holes extend through the j * plate and an iron is placed above each hole triangular angle that is fixedly mounted on the plate. The angle irons serve to distribute the flow of fluid along the surface of the plate in order to avoid stagnant areas of solids. They also prevent the resin from flowing through the holes when the bed is sedimented. Any fluid inert to the catalyst and to the reactants may also be present in the recycle stream. An activating compound, if used, is preferably added to the reaction system downstream from the heat exchanger or directly to the bed of fluid possibly with a carrier fluid such as a condensing agent or a liquid monomer. It is essential to operate the fluid bed reactor at a temperature lower than the sintering temperature of the polymer particles to ensure that sintering does not occur. The # sintering temperature is a function of the density of the resin. Generally, low density polyethylene resins, for example, have a low sintering temperature and high density polyethylene resins, for example, have a higher sintering temperature. For example, temperatures of about 75 ° C to about 95 ° C are used to prepare the ethylene copolymers having a density of about 0.91 gram per centimeter cubic to about 0.95 gram per cubic centimeter, while temperatures of about 100 ° C to about 115 ° C are used to prepare ethylene copolymers or homopolymers having a density of about 0.95 gram per cubic centimeter to about 0.97 gram per cubic centimeter. The fluid bed reactor can be operated at pressures up to about 70.30 kilograms per square centimeter and is for the production of polyolefin resin which is operated from preference at a pressure of about 7.03 kilograms per square centimeter to about 70.30 kilograms per square centimeter with operation at the highest pressures at these scales favoring heat transmission since an increase in pressure increases the thermal capacity of the unit volume of the gas . The partially or fully activated precursor composition and / or the catalyst (which is jointly referred to below as the catalyst) is injected into the bed at a rate equal to its consumption. Preferably the catalyst is injected at a point in the bed where good mixing of the polymer particles occurs. The injection of the catalyst at a point above the distribution plate in a particularity important for the satisfactory operation of a polymerization reactor of the fluidized bed. Since the catalysts are highly active, the injection of the catalyst in the area below the distributor plate may cause the polymerization to start at that site and eventually cause the distributor plate to clog. The injection into the fluidized bed instead helps to distribute the catalyst through the bed and tends to avoid the formation of localized areas of high concentration of the catalyst which can result in the formation of "hot zones". Injecting the catalyst into the reactor above the bed can result in excessive carryover of the catalyst to the recycle line where polymerization can begin and eventually the line and heat exchanger can be clogged. The catalyst can be injected into the reactor by various techniques. Not all spraying modes of the catalysts without supports were found to be equally effective. In some operating modes, spraying the catalyst directly into the bed coated the resin particles and caused them to grow uncontrollably. Several modes of preferred operation 10 were found. One way involved feeding the organometallic complex and the activator separately. Still another preferred mode was to feed the combined components into the reactor but allowing sufficient time for the sprayed particles begin evaporation before coming into contact with the bed particles. In yet another preferred mode, the two components were aliquoted into a carrier that allowed them to begin to lose solubility while they were being fed and gave result active nucleation catalysts as the feed was entering the reactor. It is believed that the use of an atomization nozzle towards the bed with a large oversize support tube flow tends to avoid fouling. Similarly, the use of a The atomization nozzle through the distributor plate so that the catalyst is fed just above the plate, also tends to avoid fouling. At this stage it has not been clarified which is better. A problem encountered with soluble catalyst feed is that the droplets of the catalyst collide with the polymer powder in the fluid bed and coat the polymer particles. Subsequent JF polymerization leads to powder particles of more size and biggest. This effect is greatly attenuated and handled by forming a solid catalyst particle from the reaction of the metallocene compound and the aluminoxane compound as they are fed to the reactor. The metallocene catalyst is often provides as a solution diluted in aliphatic or aromatic hydrocarbon, such as toluene or isopentane. The aluminoxane can also be an aliphatic hydrocarbon or • aromatic such as isopentane or toluene. Each is added continuously to the reactor (or intermittently) and premix before entering with a carrier fluid of isopentane or other inert hydrocarbon. In addition, an inert gas such as nitrogen can be added to act as a carrier gas to spray or disperse the catalyst to the reactor vessel. The metallocene compound and the aluminoxane compound react under this scenario to form the active catalyst species which may be insoluble in the isopentane carrier. This precipitates as a fine solid of only a few microns in diameter (or less) which is transported to the rest of the path to the reactor as a slurry thick in isopentane. The reaction and subsequent precipitation seems to be very fast. The adduct is soluble in toluene and although there may be toluene present, there is much more isopentane so that it precipitates. This improves the morphology of the polymer prepared by soluble metallocene catalysts fed to the gas phase reactors. The catalyst and the aluminoxane compound can react to form an insoluble particle in a carrier fluid and this particle acts as a template for the polymerization leading to polymer powder having good morphology, good bulk density of resin and good flow characteristics. The soiling of the reactor is also reduced. The use of this liquid feeding catalyst with template reduces the 0 fouling when operating through the full scale of the condensation mode. Similarly, the aluminoxane or other activator in a toluene solution can be used and can be precipitated by contacting the carrier isopentane. This can be carried out before the site where the catalyst is mixed with the isopentane carrier, at the same site where the catalyst is added to the carrier or downstream from where the catalyst is injected into the carrier isopentane. The catalyst particles can be sprayed into the reactor using an atomization nozzle with isopentane and nitrogen as the carrier fluids. The spraying can be directed upwards from the bottom of the reactor without the distributor plate in place. Therefore, there is only a small distance that the particles must travel before hitting the bed. During this moment, the carrier fluid has evaporated leaving the precipitated catalyst particles in clusters. Even when the carrier does not evaporate, the precipitated catalyst particles tend to disperse. Feeding the catalyst in this manner is not a critical factor for this invention. If it can also be fed directly into the bed in case means are provided to properly disperse the catalyst at the tip of the polymer. Alternatively, at least some of the organometallic complexes and aluminoxane activators do not need to be contacted in advance to provide good catalyst and resin productivity or good morphology. Specifically, what has been demonstrated is that by means of a specialized feed of the catalyst components into the reactor, discrete resin particles are formed in the fluidized bed without agglomeration of resin particles. The operation in the condensing mode or even with high levels of condensable components, although they do not condense, is beneficial because it allows the solvation and migration of the catalyst presurers through the polymer that? It is forming. (The precursors must meet one at Another one to make the catalyst active for polymerization). A dramatic increase in catalyst productivity can be obtained as the concentration of the isopentane is increased so that the dew point of the cycle gas increases from 20 ° C to 33 ° C.

This demonstrates the benefit of the invention at higher isopentane levels, particularly when operating in a condensing mode. Very high levels of condensation, say, above 25 percent by weight, can be of additional benefit to help the migration of the catalyst precursor and the establishment of active site. As mentioned above, the reaction of the catalyst precursors to form an adduct insoluble in the condensation component can provide the template for polymer growth and duplication of the particle. Experience shows that the primary resin particles are generally spherical in shape and are solid with a diameter ranging from about 10 to 100 microns. These particles can agglomerate into larger particles. An advantage of spraying the catalyst into the reactor is the ability to control the size of the generated particles. Through the control of the design of the spraying nozzle and the speed of the carrier or carriers, a wide scale of particle sizes can be achieved. This is especially advantageous when balancing the productivity needs of the catalyst with the thermal sensitivity aspects of the catalysts. It is also beneficial to increase the size of the polymer particles when the bed volume decreases when there is a transition between the products during the production run periods. There are several additional advantages for adducts that are soluble. One is that the solvent in the sprayed particle evaporates the solubilized components, which can form a template that can lead to improved morphology. In addition, the initial polymerization tends to form a rigid framework that can also serve as a template for the resin particle.

Catalysts without supports are not required to be attached to a non-mobile accessory, such as a supported catalyst. The mobility of the unsupported catalyst is improved by operating in the condensed mode since the liquid helps to disperse the catalyst components allowing improved mixing of the high efficiency components of the catalyst formation. Further diffusion of the catalyst within the particle is aided by swelling the polymer by means of the condensing agent. The organometallic complex and the activator are dispersed more uniformly through the resin particles resulting in improved catalyst productivity and product uniformity (homogeneity). The concept of Swelling of the polymer that aids the dispersion of the catalyst / activator is also applied to an insoluble adduct catalyst if the individual components that must react to form the insoluble catalyst, in themselves are soluble in the condensation medium. Another way to achieve the benefit of this invention is to use an activator that precipitates or gels in the polymerization vessel (or prior to placement in the reactor) prior to the reaction with the procatalyst. This precipitation can be caused by the formation of a discontinuous phase by the condensing medium. For example, regular aluminoxane is frequently provided in toluene and is insoluble in isopentane. It can be precipitated in the feed line by mixing, for example, with an isopentane stream, it can also be precipitated in the reactor as the toluene is dispersed through mixing with the condensing agent which is frequently isopentane. Operation in the condensation mode will lead to the precipitation of aluminoxane. Other ways to precipitate in the aluminoxane include reaction with a flocculating agent such as a dysfunctional molecule, a polar substance (e.g., MgCl) or a surfactant. The precipitated aluminoxane will then act as an excellent template for polymer duplication and growth. Operation at high levels of condensation aids swelling of the polymer and dispersion of the metallocene procatalyst through the aluminoxane particle. The modified aluminoxane is soluble to some extent in isopentane, however, it can rapidly lose solubility in the absence of the condensing medium such as liquid isopentabo. This condition may exist in the fluid bed of the polymer particles even during operation in the condensation mode. The condensed liquid does not necessarily penetrate through the entire height of the bed so that there is a "dry" region at the top and a certain length down in the bed. The constant movement of the procatalyst, activator and the newly formed resin particle in and out of the "dry" and "wet" zones can improve the dispersion of catalyst components through the particle and also provide a stable template for growth of particles without agglomeration of bleed. In theory, the degree of condensation can be used to control the particle size of the resin and the morphology. Addition to a "dry" zone should provide fast nucleation and better particle characteristics. Addition to a "wet" zone should provide improved catalyst productivity, cooling of the particle to avoid hot zones, reduction of fouling and control of resin agglomeration. The aluminoxane can also be provided in a supercritical solvent such as ethylene or ethane (there is an obvious advantage to using ethylene since it is a monomer). The aluminoxane would precipitate very quickly forming a template for duplication of the polymer. The aluminoxane can first be added through an atomization nozzle to the lower cone with the distributor or stirring plate, and the metallocene co-catalyst can be added via an injection tube through the reactor side to the bed. The aluminoxane feed can also move directly to the fluid bed with a distributor plate in place. The catalyst feed tube is preferably fed to the distance bed approximately 15.24 centimeters below the aluminoxane feed tube but its locations can be inverted or moved further. These can be inverted, separated further or brought together more to make advantages of the process or the catalyst. The simple injection tubes produced can also be used with the carrier liquid and appropriate gas flows each. It is important to note that the procatalyst and the aluminoxane which have been contacted previously frequently lead to massive fouling of these injection tubes when they are inserted directly into the fluid bed. In addition, the aluminoxane could be added directly to the cycle line before the distributor board 0. The condensation operation can help wash the aluminoxane into the reactor if it is added to the cycle line. The feeding of the solution of the homogeneous polymerization catalysts to a fluidized bed can be complicated by coating the existing particles with a new polymer growth or by "increasing the size" of the droplets which leads to less activity. This can be avoided by segregating the catalytically active sites into discrete domains separated by regions that are catalytically inactive. This results in a maximum surface to volume ratio for the incipient catalyst sites leading to maximum regimes. The segregation of the catalyst can be achieved in several ways. One way is to use emulsions of a given catalyst component such as a methylaluminoxane emulsion in a saturated hydrocarbon. The emulsions can be created and stabilized by a number of techniques in order to have favorable influence on the nature of the subsequent polymerization. An example of the creation of an emulsion would be to add mineral oil to a toluene solution of aluminoxane and then purify the toluene. Another way to achieve catalyst segregation would be to premix the catalyst components and then add a co-solvent where the resulting mixture is insoluble. An example of this is, when the metallocene is mixed with the aluminoxane / toluene and the mineral oil.

Another way to achieve segregation of the catalyst is to add a component that reacts with one of the catalyst components and causes them to become insoluble. An example of this component could be a di- or tri-functional molecule, for example, ethylene glycol, which would lead to subsequent crosslinking and insolubility of the aluminoxane. Another way to achieve catalyst segregation would be to add small amounts of a The component of attraction that through favorable intermolecular interactions causes one or more of the components of the catalyst to agglomerate around this component. The catalyst is preferably fed towards the reactor at a point from about 20 percent to 50 percent of the diameter of the reactor away from the reactor wall and below the fluidized bed in the bed at a height up to about 50 percent of the bed height. The catalyst can also is fed into or directly above the distributor plate at a point of about 20 percent to 50 percent of the diameter of the reactor remote from the reactor wall and at any of a multiple of locations on or above the distributor plate.

Preferably, it is used to carry the catalyst into the bed, a gas that is inert to catalysts such as ethane, nitrogen or argon. The rate of production of the polymer in the bed depends, inter alia, on the rate of injection of the catalyst, the amount of the condensation medium and the concentration of the monomer (s) in the recycle stream. The production rate is conveniently controlled by simply adjusting the rate of catalyst injection. Since any change in the rate of injection of the catalyst will change the rate of reaction and, therefore, the rate of heat generation of the reaction, the temperature of the recycle stream entering the reactor is adjusted upwardly or downwardly to accommodate any change in the heat generation regime. This ensures the maintenance of an essentially constant temperature in the bed. The complete instruments of both the fluidized bed and the cooling system of the recycle stream are of course useful for detecting any temperature change in the bed in order to allow either the operator or a conventional automatic control system to make an adjustment appropriate in the temperature of the recycle stream.

Under a given set of operating conditions, the fluidized bed is maintained at an essentially constant height or weight by removing a portion of the bed as a product at the rate of formation of the particulate polymer product. Since the rate of heat generation is directly related to the rate of product formation, a measurement of the temperature rise of the fluid through the reactor (the difference between the temperature of the inlet fluid and the output fluid temperature) is indicative of the rate of formation of the particulate polymer at a constant fluid velocity if a vaporizable liquid is not present in the input fluid. During the discharge of the polymer product into Particles from the reactor are desirable and it is preferred to separate the fluid from the product to return the fluid to the recycle line. There are numerous ways known in the art to achieve this. See U.S. Patent Number 4,543,399. Other download system The preferred product that can be used alternatively is that disclosed in US Pat. No. 4,621,952. This system employs at least one pair (in parallel) of tanks comprising a settling tank and a transfer tank placed in series and they have a separate gas phase returned from the top of the sedimentation tank to a point in the reactor near the upper part of the fluidized bed. The fluidized bed reactor is equipped with a suitable ventilation system to allow the bed to be discharged during the drive and the standstill. The reactor does not require the use of agitation and / or scraping of the wall. The recycling line and the elements therein should have a smooth surface and be free from unnecessary obstructions in order not to impede the flow of the recycled fluid or the particles retained. Among the polymers that can be produced in the process of the present invention are the ethylene homopolymers, propylene, butene or the copolymers of a predominant molar percentage of ethylene-propylene or butene and a small molar percentage of one or more of the alpha-olefins of 2 carbon atoms to 8 carbon atoms. The alpha-olefins of 2 carbon atoms to 8 carbon atoms preferably must not contain any branching at any of their carbon atoms that are closer than the fourth carbon atom. The preferred 2-carbon-C-alpha olefins at 8 carbon atoms are ethylene, propylene, buten-1. penten-1, hexen-1, 4- methylpenten-1 and octen-1.

Ethylene polymers, for example, have a melt flow ratio of greater than about 22. The value of the melt flow ratio is another means of indicating the molecular weight distribution of a polymer. A melt flow ratio (MFR) of 22 plus, for example, corresponds to a value of Mw / Mn (as determined by conventional size exclusion chromatography) of about 2.7. W / f Ethylene homopolymers have a density approximately > 0.958 to < 0.972 gram per cubic centimeter. The ethylene copolymers have a density less than about 0.96 gram per cubic centimeter. The density of the ethylene copolymer or a level The determined melting index for the copolymer is mainly regulated by the amount of the comonomer # of 3 carbon atoms to 8 carbon atoms that is copolymerized with ethylene. In the absence of the comonomer, ethylene would homopolymerize to provide polymers having a density of about < 0.96. Therefore, the addition of progressively larger amounts of comonomers to the copolymers results in the progressive reduction of the density of the copolymer. The amount of each of the different comonomers of 3 carbon atoms to 8 carbon atoms needed for. To achieve the same result, it will vary from monomer to monomer, under the same reaction conditions. Therefore, to produce binary ethylene copolymers with the same density and melt index, larger molar amounts of the different comonomers would be needed in the order of C3 > C4 > C5 > CQ > C? > Cg. When they are made in the fluid bed process ß described herein, the ethylene polymers are granulated materials having a settled bulk density of about 240 to 512 grams per cubic centimeter and an average particle size in the order of about .127 millimeter to about 2.54 millimeters, preferably of approximately 1.52 millimeters to 2.54 millimeters. The particle size is important for the purposes of easily fluidizing the polymer particles in the fluid bed reactor as described herein. Although the exact scope of the present invention is set forth in the appended claims, the following specific examples illustrate certain aspects of the present invention and, more particularly, indicate the methods for evaluating same. However, the examples are indicated for illustration only and should not - - be construed as limitations in the present invention, except as set forth in the appended claims. All parts and percentages are by weight unless otherwise specified.

Examples 1 and 1A Catalyst ß 10 Catalyst of tris (diethyl carbamate) of? 5 indenyl zirconium as a molar solution of 0.025 in toluene. Approximately one liter of the catalyst was prepared and placed in a continuously stirred vessel under a blanket of pressure-purified nitrogen. 28.12 kilograms per square centimeter. The catalyst was removed from the vessel and continuously added to the reactor using a high pressure syringe pump. The catalyst feed rate of 7.5 cubic centimeters per hour of catalyst solution is controlled by a syringe pump. The isopentane and nitrogen flows at a rate of .36 kilogram per hour and 3.18 kilograms per hour, respectively, take the catalyst to the reactor. The catalyst and the carriers entered the reactor through an injection tube of 3.18 mm k with the diameter of the tip reduced to 10.41 mm to help atomization and dispersion. The injection tube was inserted at a distance of .610 meter above the plate and at a distance of approximately 7.62 centimeters towards the bed.

Activator M Modified methyl aluminoxane (MMAO-3A) as a 13 weight percent solution in isopentane (Akzo Nobel, diluted from a 26 weight percent solution) was added at a rate of 100 cubic centimeters per hour to the reactor through a 3.18 millimeter injection tube with reduced tip diameter to 10.41 centimeters The carrier of isopentane at a rate of .36 kilogram per hour and the carrier of nitrogen at the rate of 2. 27 kilograms per hour helped the dispersion and atomization of MMAO-3A in the reactor. The MMAO-3A is added to the remote bed of .457 meter above the plate distributor (15.24 centimeters below the catalyst feed tube) and approximately 10.16 centimeters towards the bed.

Reactor 25"^ .- ^ w 'The diameter reactor of 35.56 centimeters was used with a bed weight of 38.59 kilograms and an approximate bed height of 2.44 meters.The monomers and other cycle gas components are added to the reactor in the compressor housing behind the propellant An additional isopentane allows control of the dew point of the cycle gas independently of the flows of the catalyst and the activating carrier. 0 Start The reactor opens before the experiment. To prepare it for polymerization the LLDPE seed bed reactor is dried to about 10 parts 5 per million water in the cycle gas using hot nitrogen. Approximately 500 cubic centimeters of TiBA at 5 weight percent is circulated for one hour and the reactor is discharged before introducing the monomer. The addition of MMA0-3A is started at approximately 30 minutes or before the catalyst feed begins.

Terms Total pressure, kilograms per 5 square centimeter gauge 26.36 ^ R. Partial Pressure of Ethylene, kilograms per square centimeter 12.65 Hydrogen Partial Pressure, kilograms per square centimeter Hexeno Partial Pressure, kilograms per square centimeter .415 Isopentane Partial Pressure, 1.55 (5.65% kilograms per square centimeter molar) ß "Partial Pressure of Nitrogen, 10 kilograms per square centimeter 12.79 Molar ratio of H2 / C2 0.0 Molar ratio of Cg / C2 0.015 Bed temperature, ° C 70 Entrda gas temperature, ° C 69.5 15 Gas cycle dew point, ° C 41.2 Cycle Gas Speed, * meters per second .366 Production rate meters per hour 16 20 Retention Time Average hours 5.3 STY kilogram / second / cubic centimeter 115.5 Veratrole (1,2-dimethoxybenzene) is added to the cycle gas line in the suction of the compressor to reduce fouling of the cycle gas line, the compressor and the cycle gas cooler. The feeding regime is approximately 50 cubic centimeters per hour of a 0.01 percent pentane solution.

Resin A polymer with a melt index of 12 is produced •? - of 0.86 dg / minute, a flow index of 121 of 16.2 dg / minute and a density of 0.9265 gram per cubic centimeter. The particle size of the resin is 1.91 millimeters, the volumetric density of the resin is 296 ~ grams per cubic centimeter and the fluidized volumetric density is 152 grams per cubic centimeter. 15 The commercial comparison operation at an inlet gas temperature of 30 ° C corresponds to a * Condensation level of 8.7 percent by weight. The condensation levels for a range of inlet gas temperatures are summarized below: Condensed Liquid Gas Temperature, * Input, ° C percentage by weight 30 8.7 20 12.0 -10 19.3 ?, Increased isopentane concentration of 5.65 mole percent (1.55 kilograms per square centimeter) to 8 mole percent (2.19 kilograms per square centimeter) allows 20.4 percent by weight condensation with an inlet gas temperature of? O ° c; Further increasing the concentration of isopentane to 11 mole percent (3.02 kilograms per square centimeter) achieves 22.6 percent by weight condensation with an inlet gas temperature of 25 ° C. This temperature is within the capacity of a plant UNIPOL (R) commercial with refrigerated cooling. For the conditions used in both previous examples, the nitrogen level is decreased to accommodate the additional isopentane, the volumetric properties of the resin that change slightly and the highest dew point.

Claims (1)

R E I V I N D I C A C I O N *

1. A continuous process for the production of polymer in a gas phase reactor of one or more fluid monomers by continuously passing a gaseous stream through the reactor in the presence of a soluble catalyst without supports under reactive conditions, removing the polymer product and the fluids without: reacting, cooling part or all of the fluids without reacting to form a mixture of two gas phases and the retained liquid and re-introducing the two-phase mixture into the reactor together with additional monomers sufficient to replace those removed polymerized monomers as a product, the improvement comprising: cooling.