JPH10176004A - Fluidized bed reaction using unsupported type catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the removal of heat by a polymerization reaction from a fluidized bed reactor and to improve the space time yield of an exothermic polymerization reaction carried out in the fluidized bed reactor by the removal of heat, by maintaining the temperature of the fluidized bed reactor at a fixed level. SOLUTION: A gas flow comprising one or more fluid monomers is continuously fed to a vapor-phase reactor in the presence of a soluble catalyst of unsupported type under a reaction condition. A polymerization product and unreacted fluid monomers are taken out, a part or the whole of the unreacted fluid monomers, are cooled to form a two-phase mixture of the gas and the liquid taken with it. The two-phase mixture together with supplemental monomers in amounts sufficient to supply monomers which are polymerized and taken out as a reaction product are reintroduced into the reactor to maintain the temperature of the reactor at a fixed temperature. For example, a reaction product of methylaminooxane and a cyclopentadienylzirconium trisalkyl carbamate is preferably used as the catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an exothermic polymerization reaction carried out in a fluidized reactor using an unsupported transition metal catalyst, whereby a gas continuously withdrawn from the reactor is cooled to a temperature below the dew point of the gas. Increasing the removal of heat of the polymerization reaction from the reactor by cooling to temperature and returning the resulting two-phase mixture to the reactor to maintain the temperature of the fluidized bed reactor at the desired level;
The present invention relates to a method for improving a space-time yield of an exothermic reaction polymerization reaction performed in a fluidized reactor.

[0002]

BACKGROUND OF THE INVENTION The use of a condensing mode of operation in a continuous gas phase fluidized bed polymerization process is described in U.S. Pat. Nos. 4,543,399 and 4,588,790. According to the method, part or all of the circulation is cooled to form a mixture containing both gas and liquid phases, and the mixture is reintroduced into the reactor to evaporate the liquid part of the circulation. According to this, the production rate and cooling capacity of the gas phase method are greatly improved.

[0003] More recently, US Patent No. 5,352,749.
No. 5,436,304 propose various condensation modes. U.S. Pat. No. 5,317,036 describes a condensation mode suitable for soluble, unsupported catalysts. afterwards,
U.S. Pat. Nos. 5,405,922 and 5,462,999 disclosed condensation modes for use with supported metallocene catalysts. In accordance with the present invention, it has been found that the use of a condensing mode with a soluble unsupported catalyst facilitates the migration of unsupported catalyst components in an unintended manner in the prior art.

[0004]

SUMMARY OF THE INVENTION The present invention relates to an exothermic reaction polymerization carried out in a flow reactor, in which a circulating stream (recycle stream) is cooled below its dew point and the resulting two-phase fluid stream is passed to the reactor. A method is provided for improving the space-time yield of an exothermic reaction polymerization reaction performed in a fluidized reactor by returning and maintaining the temperature of the fluidized bed reactor at a desired level above the dew point of the circulating stream. The cooling capacity of the circulating stream is increased both by the large temperature difference between the incoming circulating stream and the reactor and by the evaporation of the condensed fluid entrained in the circulating stream.

[0005] The improvement in the amount of condensate and consequently the production rate is further increased by modifying the operating conditions to increase the dew point of the circulation.

[0006]

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, there is provided a method of performing a condensation mode in combination with an unsupported catalyst.
While not dependent on the particular type of polymerization reaction as long as it is exothermic, the present invention is particularly suitable for polymerization reactions involving the polymerization of one or more of the following monomers. I. Olefins: ethylene, propylene, butene
1, pentene-1, 4-methylpentene-1, hexene-1, styrene. II. Polar vinyl monomers: vinyl chloride, vinyl acetate, vinyl acrylate, methyl methacrylate, tetrafluoroethylene, vinyl ether, acrylonitrile. III. Diene (conjugated, non-conjugated): butadiene, 1,4-
Hexadiene, isoprene, ethylidene norbornene. IV. Acetylenes: substituted acetylenes such as acetylene and methylacetylene. V. Aldehydes: formaldehyde.

[0007] Unsupported catalysts which can be used for the fluidized-bed polymerization of the above-mentioned monomers will very usually be: I. Coordinating anionic catalyst. II. Cationic catalysts for ethylene homopolymers: others of this type require free radical catalysts. III. Free radical catalysts or coordinating anionic catalysts. IV. Coordinating anionic catalyst. V. Anionic catalyst.

[0008] Preferably, the catalyst is US Pat.
36, 5405922, 5462999, and US patent application Ser. No. 08 / 412,964 (March 1995).
). More preferably, the catalyst is the reaction product of methylaluminoxane or a modification thereof with cyclopentadienyl (or substituted cyclopentadienyl) zirconium trisalkyl carbamate (or carboxylate).

Although the present invention is not limited to a particular type of polymerization reaction, the following description of the process operation relates to the polymerization of olefinic monomers which the present invention has been found to be particularly free. Will be explained.

In general, fluidized bed processes of the prior art resins, especially polymers prepared from monomers, involve the formation of a gas phase stream containing one or more monomers under reaction conditions and in the presence of a catalyst. , By continuous flow to a fluidized bed reactor. A gas phase stream containing unreacted gaseous monomers is continuously withdrawn from the reactor, compressed, cooled and circulated to the reactor. The product is withdrawn from the reactor. Also, make-up monomers are added to the circulation.

The reaction forming the polymer is an exothermic reaction,
In some manner, the temperature of the gas stream in the reactor must be maintained below the degradation temperature of the resin and catalyst and below the temperature at which the resin particles formed during the polymerization reaction will fuse and adhere. This is necessary to prevent reactor blockage due to the rapid growth of polymer mass that cannot be continuously removed as a product. Thus, it is understood that the amount of polymer that can be produced in a given size fluidized bed reactor within a particular time period is directly proportional to the amount of heat that can be drawn from the fluidized bed.

According to the present invention, the circulating gas stream is intentionally cooled below the dew point to form a two-phase gas-liquid mixture. Cooling is performed under conditions such that the liquid phase of the gas-liquid mixture is entrained in the gas phase of the gas-liquid mixture at least until it evaporates from the inlet of the fluidized bed or enters the fluidized bed. A considerable increase in space-time yield is obtained according to the invention without having a substantial effect on the product properties and the yield. When implemented as described herein, the entire process proceeds continuously and smoothly without any particular operational difficulties.

In some cases, it is desirable to increase the dew point of the circulating gas stream to further increase heat removal. The dew point can be raised as follows. (1) increasing the operating pressure of the reactants, (2) increasing the concentration of condensable gas in the circulation, and / or (3) decreasing the concentration of non-condensable gas in the circulation.
According to one embodiment of the present invention, the dew point of the recycle stream can be increased by adding a condensable fluid inert to the catalyst, reactants and polymerization reaction products to the recycle stream. This addition of inert condensable fluid can be added with make-up fluid or at any point in the system. Examples of these fluids are saturated hydrocarbons, such as butane, pentane or hexane.

The main limitations on the degree of condensation are the solubility of the condensable components and their softening effect on the polymer particles. This depends on the condensing agent, its concentration, the reaction conditions of the circulating gas composition such as temperature and pressure, the molecular weight, density and branch chain distribution of the polymer. A suitable condensation operation is described in US Pat.
Despite the description of the '52749, low and high flow bulk densities are achieved.

Practical experiments have shown that condensation of more than 20% by weight takes place without exceeding the limits imposed by the softening of the polymer.

The point of entry of the two-phase circulation is preferably below the fluidized bed in order to keep the fluidized bed (polymerization zone) in suspension. A circulating stream containing entrained liquid is introduced at the lower part of the reactor, most preferably at the bottom of the reactor, thereby ensuring the homogeneity of the fluid stream flowing up the fluidized bed. The other inlet points are any number of openings provided along the side of the reactor and directly connected to the fluidized bed, the discharge
This can be done from a wall or from a tube extending to the body part of the fluidized bed. Similarly, the introduction can take place from a tube extending through the distributor plate and into the fluidized bed. It is also possible to use a spray or spray nozzle to distribute the stream in the fluidized bed.

By providing baffles and other means for preventing the formation of low gas velocity regions near the circulating inlet, solids and liquids can be maintained entrained in the rising circulating flow. One such means is described in U.S. Pat. Nos. 4,877,587 and 4,933,149.

With no apparent benefit, the two-phase circulating stream can be split into two or more separate streams, one or more of which can enter the polymerization zone directly. Provided that sufficient gas velocity is provided below and through the bed to maintain the bed in suspension. In all cases, the composition of the gas stream is kept substantially uniform and flows such that no dead space is formed, which forms non-removable solids.

It will be apparent that, if necessary, a two-phase fluid stream may be formed in the reactor at the point of injection by separately injecting the gas and liquid under conditions such as to form a two-phase fluid. However, little benefit is found in such operation of gas and liquid because of the additional burden on separating the gas and liquid phases after cooling. WO 94/28032 (issued December 8, 1994) expresses a contradictory view on this mode of operation. However, it is desirable to inject the replenishment monomer into the reactor in this manner. The injection of liquid or gaseous make-up monomer at the inlet of the two-phase fluid circulation of the reactor, at other points in the reactor, or into the circulation is contemplated by the present invention.

The benefits of the present invention are not limited to the production of polyolefins. The present invention may be practiced in connection with any exothermic reaction polymerization process performed in a gas phase fluidized bed. The advantages over the prior art of the present invention are greater when the dew point of the circulating stream is closer to the reaction temperature inside the fluidized bed.

The applicability of the present invention to the production of any polymer can be determined using the following equation: X = P · H _rxn / G _mass · CP _gas (T _rxn −T
_limit ) where P = the desired production rate of the polymer, which is 1.0
Limited to speeds that give less. H _rxn = the heat of polymerization of the particular polymer produced. G _mass = mass flow rate of the circulating stream, limited by the minimum due to the need for appropriate fluidization and mixing in the bed and the maximum by entrainment of solids. CP _gas = heat capacity of the circulation. T _rxn = the temperature of the reaction zone (fluidized bed), with a maximum depending on the polymer deposition temperature and / or the performance of the catalyst at the pressure of the circulating stream and a minimum dependent on the performance of the catalyst. T _limit = minimum temperature of the circulating stream entering the reaction zone. This temperature is the higher of the dew point of the circulation stream or the cooling limit of the heat exchanger zone. If T _limit is the dew point of the circulating stream, the invention is implemented simply by cooling the stream to a temperature below the dew point. Where T _limit is controlled in the heat exchanger zone, the invention is practiced by adding a condensable fluid to raise the dew point of the circulating stream above the cooling limit of the heat exchanger zone.

When X is greater than 1, the benefits of the present invention are obtained, and the effect obtained from the present invention increases as the value of X increases.

Generally, the ratio of the height to the diameter of the reaction zone in the reactor will vary from about 2.7: 1 to 4.6: 1. This range can of course vary to larger or smaller values depending on the desired production rate. The cross-sectional area of the deceleration zone above it is typically about 2.6-2.8 multiplied by the cross-sectional area of the reaction zone.

The reaction zone comprises growing polymer particles fluidized by a continuous stream of a polymerizable and reforming gaseous component in the form of a replenishment feed and recycle stream; Particles and a small amount of catalyst particles. To maintain a living fluidized bed, the apparent velocity through the bed must exceed the minimum velocity required for fluidization and is preferably at least 0.2 ft / sec (60 cm / sec) greater than the minimum velocity. Typically, the apparent gas velocity does not exceed 5.0 ft / sec (15.0 m) and is about 2.5 ft / sec (7.5 m / sec).
/ S) or less is sufficient.

It is imperative that the bed always contain particles in order to prevent the formation of local hot spots and to trap and distribute the particulate catalyst throughout the reaction zone. At start-up, the reactor is charged with a basic amount of particulate polymer particles prior to the start of the gas stream. Such particles may be the same as or different from the polymer to be produced. If different, they are withdrawn in a given amount of the produced polymer and mainly as initial product. Ultimately, the desired polymer particles displace the starting bed.

The partially or fully activated precursor composition and / or catalyst used in the fluidized bed may be stored in a reservoir in a gas impregnated with inert gas such as nitrogen or argon. It is preferable to prepare for use.

Fluidization can be achieved by increasing the flow rate of the fluid circulating stream flowing through the bed, typically to about 50 times the feed rate of the make-up fluid. A fluidized bed generally has the appearance of a dense population of moving particles formed by the gas flowing through the fluidized bed. The pressure drop through the bed is equal to or slightly greater than the fluidized bed weight divided by its cross-sectional area. Therefore,
The pressure drop depends on the geometry of the reactor.

Although the replenishment fluid may be supplied directly to the bed, it is more often supplied to the circuit. When supplying to a circulation path, it supplies before or after a heat exchanger or a circulation gas cooler. The makeup of the make-up stream is determined by gas analysis. The gas analyzer analyzes the composition of the recycle stream and the make-up stream to maintain the gas composition in the reaction zone at a substantially steady state.

As the gas analyzer, any commercially available gas analyzer adapted to evaluate and indicate the composition of the circulating stream in a conventional manner to adjust the feed stream can be used. The gas analyzer may be one of the more complex rapid gas analyzers described in US Pat. No. 5,437,179. Generally, the gas analyzer is positioned to receive gas from a point between the deceleration zone and the heat exchanger.

To achieve complete fluidization, a portion of the recycle stream and, if desired, a further make-up stream is returned to the reactor from the bottom of the bed through a circuit. Preferably, a gas distribution plate can be provided above the return point to help fluidize the bed. As it flows through the bed, the circulation stream absorbs the heat of reaction generated by the polymerization reaction.

In some cases, the use of aluminoxane can easily generate static electricity. Inductive and natural condensation mode operation has been found to suppress static electricity. The loss of static electricity is mainly obtained by supplying a condensing medium such as isopentane to the reactor at an instantaneous supply flow rate, and is not considered to be due to the condensation of isopentane already existing in the reactor. Thus, fluctuations in the feed rate of the condensing medium have a dramatic effect on the static electricity of the reactor. By supplying the spray of condensed medium directly to the bottom of the distributor plate, at a given condensed medium concentration throughout the reactor, more liquid is produced than when the condensed medium is introduced into the bottom or circuit. Hit the distribution plate. The advantage of this is that less condensed medium is required, so that flooding of the fluidized bed can be avoided.

The portion of the fluidized bed that is not active in the bed constitutes a recycle stream which is removed from the polymerization zone, preferably via a deceleration zone above which entrained particles are given the opportunity to return to the bed. .

The circulating stream is then compressed in a compressor and then sent to a heat exchange zone where heat of reaction is removed and then returned to the bed. The heat exchange zone is typically a heat exchanger which may be horizontal or vertical. The circulating stream is then returned to the fluidized bed from the bottom of the reactor through a gas distribution plate. A gas deflecting member is preferably located at the inlet of the reactor to prevent the particles from settling and solidifying. The previously mentioned annular disk is one means for doing this.

The bed temperature is controlled to a substantially constant temperature at steady state by continuously removing the heat of reaction. With polyethylene, there appears to be no appreciable temperature gradient at the top of the bed. It is not uncommon for polypropylene to have a temperature gradient of about 1-2 ° C across the top of the bed. The temperature gradient is about 6-12 inches (1
5.2-30.5 cm), the gradient between the temperature of the incoming fluid and the temperature of the rest of the bed.

Good gas distribution plays an important role in the operation of the reactor. The fluidized bed includes a growing particulate polymer, a grown particulate polymer, and catalyst particles. Since the polymer particles are hot and possibly active, sedimentation must be prevented. If a static mass is present, the active catalyst contained therein may continue the reaction and cause fusion. It is therefore important to distribute the circulating stream to the bed at a rate sufficient to maintain fluidization through the bed.

The gas distribution plate is one of the preferable means for achieving this good gas distribution, and is, for example, a mesh plate, a slot plate, a perforated plate, a bubble cap plate or the like.
All elements of the distribution plate may be fixed, or US Pat.
It may be a movable type as described in Japanese Patent No. 98192.
In any design, the circulating stream must be diffused through the particles at the base of the bed to keep the bed fluid and also to support a stationary bed of resin particles during reactor shutdown.

The preferred gas distribution plate is of the type generally made of metal and having holes distributed over its surface. Holes are usually about 0.5 inches (1.27 cm) in diameter
It is. The holes extend through the distribution plate, and above each hole is disposed a triangular angle steel fixed to the distribution plate. Angle steel distributes the fluid flow along the surface of the distribution plate to avoid solid stagnation zones. In addition, the angle steel prevents the resin from flowing through the holes as the floor sinks.

Any fluid inert to the catalyst and reactants can be present in the circulation. If an activator (activator) compound is used, it can preferably be introduced into the reaction downstream of the heat exchanger or directly into the fluidized bed. In this case, it may be introduced with a carrier fluid such as a condensing medium or a liquid monomer.

It is important that the fluidized bed reactor be operated at a temperature below the sintering temperature of the polymer particles so that no sintering occurs. Sintering temperature is a function of resin density. Generally, for example, low density polyethylene resins have low sintering temperatures, and low density polyethylene resins have high sintering temperatures. For example, temperatures from about 75 ° C. to 95 ° C. are used to produce polyethylene copolymers having a density of about 0.91 to 0.95 g / cm ³ , and temperatures from about 100 ° C. to about 115 ° C. It is used to produce about 0.95 to 0.97 g / cm ³ of polyethylene copolymer.

The fluidized bed reactor is operated at about 1000 psi (70 k
g / cm ² ), and is preferably about 100-100 psi for polyethylene resin production.
(7.0 kg / cm ² ), and operation at higher pressures within this range is more favorable for heat transfer as increasing the pressure increases the unit heat capacity of the gas.

The partially or fully activated precursor composition and / or catalyst (hereinafter simply referred to as catalyst) comprises:
It is supplied to the floor at a rate corresponding to its consumption. Preferably, the catalyst is injected at a site in the bed where good mixing of the polymer particles occurs. Injecting the catalyst at a point above the distribution plate is an important factor for satisfactory operation of the fluidized bed. Since the catalyst is highly active, injecting the catalyst into the area below the distributor plate will initiate polymerization at that location, which can result in blockage of the distributor plate. Instead, injecting the catalyst into the fluidized bed tends to promote the distribution of the catalyst throughout the bed and prevent the formation of localized high concentration spots of the catalyst that can result in the formation of hot spots. Occurs. When catalyst is injected into the reactor from above the bed, excess catalyst is conveyed to the circuit where polymerization can begin and block tubes and heat exchangers.

The catalyst can be injected into the reactor by various techniques. Not all methods of spraying unsupported catalysts are equally effective. In one mode of operation, in which the catalyst was sprayed directly onto the bed, it grew uncontrollably as the catalyst coated the resin particles. Several preferred methods have been found. In one method, the organometallic complex and the activator are provided separately. Another preferred method resulted from feeding these combined components to the reactor, but allowing sufficient time for the spray particles to start evaporating before coming into contact with the particles in the bed. In yet another method, the two components are fed in a carrier that causes them to begin losing their solubility while they are fed, so that the active catalyst as the feed enters the reactor Nuclei were formed. It is believed that the use of a spray nozzle on the bed with a large oversized support line flow tends to prevent the formation of foul. Similarly, the use of spray nozzles penetrating the distributor plate tends to prevent the formation of deposits as well, since the catalyst is supplied directly above the distributor plate. I don't know which one is best for now.

One problem experienced with the supply of soluble catalyst is that catalyst droplets impact polymer particles in a fluidized bed,
Coating the polymer particles. Subsequently, the size of the polymer increases steadily due to the polymerization. This tendency is greatly reduced and controlled by forming solid catalyst particles from the reaction of the metallocene compound and the aluminoxane compound as they are fed to the reactor.

The metallocene catalyst is provided as a dilute solution in an aliphatic or aromatic hydrocarbon such as toluene or isopentane. Aluminoxane is also provided as a solution of an aliphatic or aromatic hydrocarbon such as isopentane or toluene. Each being fed to the reactor continuously or intermittently;
Prior to entering the reactor, it is mixed with isopentane or another inert hydrocarbon carrier fluid. Additionally, an inert gas such as nitrogen may be added to act as a carrier gas for spraying or dispersing the catalyst into the reactor.
The metallocene compound and the aluminoxane compound react in this manner to form an active catalyst species that is insoluble in the isopentane carrier. The catalyst precipitates into fine solid particles of only a few microns or less in diameter and is then sent to the reactor as a slurry in isopentane. The reaction and subsequent precipitation are very fast. The adduct dissolves in toluene. Toluene can be present, but isopentane is much more abundant so that it can precipitate. This improves the morphological properties of the polymer produced by feeding the soluble metallocene catalyst to the gas phase reactor. The catalyst and aluminoxane compound react to form particles that are insoluble in the carrier fluid, which act as a polymer template (excipient) to provide good morphological properties, good resin bulk density, and Produces polymer particles with good flow properties. The use of this shaped liquid feed catalyst reduces fouling over the full range of operation in condensation mode.

Similarly, a toluene solution of an aluminoxane or other activator can be used, which can be precipitated by contact with isopentane as a carrier. This contacting can occur at a point prior to where the catalyst is mixed with the isopentane carrier, at a point where the catalyst is added to the carrier, or downstream of where the catalyst is injected into the isopentane carrier. The catalyst particles can be sprayed into the reactor using a spray nozzle using isopentane or nitrogen as the carrier fluid. The spray can be directed upward directly from the bottom of the reactor without the distributor plate in place. Therefore,
The distance that particles have to travel before impacting the floor is very short. During this time, the carrier fluid evaporates, leaving the catalyst particles precipitated in clusters. Even when the carrier does not evaporate, the precipitated catalyst particles have a tendency to disperse. Providing the catalyst in this manner is not the subject of the present invention. If measures are taken to properly disperse the catalyst in the polymer, the catalyst may be introduced directly into the bed.

Alternatively, at least some of the organometallic complexes and the aluminoxane activator do not require pre-contact to provide good productivity or good morphological properties. What is specifically shown is that when the catalyst component is fed to the reactor by a special feeding method, new individually separated resin particles are formed in the fluidized bed, and no agglomeration of the falling resin particles occurs. Operation in agglomeration mode, or even in the presence of high levels of condensable components, but not in condensation mode, is advantageous in that the solvation and migration properties of the catalyst precursor are throughout the polymer formed. (The precursors must recognize each other to form an active polymerization catalyst). A dramatic increase in catalyst productivity is obtained when the isopentane concentration is increased such that the dew point of the circulating gas increases from 20 ° C to 33 ° C. Very high levels of condensation, e.g., greater than 25% by weight, are advantageous in that they promote catalyst precursor migration and active site formation.

As mentioned above, the reaction of the catalyst precursor to form a soluble adduct in the condensation mode can provide a template for polymer growth and particle replication. Experience has shown that primary resin particles are generally spherical, with
It is a solid having a diameter in the range of 100 microns. These particles can aggregate into larger particles. One of the advantages of spraying the catalyst into the reactor is that the size of the resulting particles can be controlled. By controlling the size of the spray nozzle and the speed of the carrier, the particle size can be adjusted over a wide range. This is particularly advantageous when the productivity of the catalyst needs to be coordinated with the heat sensitivity of the catalyst. Increasing the particle size of the polymer is advantageous when reducing bed volume when switching between products during the manufacturing process.

There are several additional advantages over soluble adducts. One is that as the solvent of the sprayed particles evaporates, the unsolubilized components can form a template leading to improved morphological properties.
Further, the prepolymer tends to form a rigid frame that can serve as a template for the resin particles.

[0049] Unsupported catalysts do not need to bind to fixed deposits as do supported catalysts. The mobility of the unsupported catalyst is improved by operating in the condensation mode. This is because the liquid helps disperse the catalyst components, promotes mixing of the components, and forms the catalyst with high efficiency. Further diffusion of the catalyst into the particles is facilitated by swelling the polymer with a condensing agent. The organometallic complex and activator are more evenly dispersed throughout the resin particles to provide improved catalyst productivity and product uniformity. If the individual components that must react to form the insoluble catalyst are themselves soluble in the condensing medium, this swelling concept that helps disperse the catalyst and activator is also applicable to insoluble adduct catalysts .

Another way to achieve the benefits of the present invention is to use an activator that precipitates or gels in the polymerization reactor (or before charging to the reactor) before reacting with the catalyst precursor. It is. This precipitation can be caused by the formation of a discontinuous layer by the condensing medium. For example, normal aluminoxane is supplied in toluene and is soluble in isopentane. This can be precipitated in the feed line, for example, by mixing with a stream of isopentane. It also precipitates in the reactor as toluene is dispersed by mixing with a condensing agent, often isopentane. Operation in the condensing mode results in precipitation of the aluminoxane. Other methods of performing aluminoxane precipitation include disfunctional molecules, polar materials (eg, MgCl 2).
₂ ) or reaction with surfactants. The precipitated aluminoxane then acts as an excellent template for polymer replication and growth. Operation at high condensation levels assists in swelling of the polymer and assists in diffusion of the metallocene procatalyst into the aluminoxane particles.

Although the modified aluminoxanes are somewhat soluble in isopentane, they can still lose solubility rapidly in the absence of a condensing medium such as liquid isopentane. This condition may be present in the fluidized bed of polymer particles even during operation in the condensation mode. Since the condensed liquid does not necessarily penetrate the full height of the bed, there is a dry area from the top down a certain distance towards the interior of the bed. The continuous entry and exit of the catalyst precursor, activator, and newly formed resin particles into the dry and wet areas improves the dispersion of the catalyst components throughout the particles, and furthermore ensures stable particle growth without drop aggregation. Provide a template. In theory, the degree of condensation can be used to control the particle size and morphology of the resin.

[0052] The addition to the dry zone provides rapid nucleation and good particle properties. The addition to the wet zone improves catalyst productivity, cooling to prevent hot spots of particles, reduced deposits, and reduced resin aggregation.

The aluminoxane can also be supplied in a supercritical solvent such as ethylene or ethane (the use of ethylene being a monomer gives obvious benefits). Aluminoxane precipitates very quickly to form a template for polymer replication.

Aluminoxane can be added to the bottom cone by removing the distribution plate through a spray nozzle, and the metallocene cocatalyst can be introduced into the bed by an injection tube from the side of the reactor. The aluminoxane feed stream may also be fed directly to a fluidized bed with a distribution plate in place. The catalyst feed tube may preferably be located about 6 inches (15.4) below the aluminoxane feed tube, but their relative positions may be interchanged or further spaced. These can be inverted, spaced apart, or close together to favor the process or catalyst. It is also possible to simply provide a plurality of injection tubes with constrictions to supply a suitable carrier liquid and gas flow to each. It should be noted that if the injection tube is inserted directly into the fluidized bed, the pre-contacted catalyst and aluminoxane often cause plugging of the injection tube.

Furthermore, the aluminoxane can be added directly to the circuit before the distributor. When fed to the circuit, operation in condensing mode helps to flush the aluminoxane to the reactor.

The supply of the homogeneous polymerization catalyst solution to the fluidized bed is complicated by the coating of the particles present with the new polymer or by the skinning over of the droplets leading to a low activity. This problem can be circumvented by creating catalytically active sites in discrete regions separated by regions without catalytic activity. This results in a maximum surface area-to-volume ratio relative to the initial catalyst point, and thus a maximum contact speed.

The separation of the catalyst can be achieved in several ways. One method is to use an emulsion of a given catalyst component, such as an emulsion of methylaluminoxane in a saturated hydrocarbon. Emulsions can be made and stabilized by a variety of techniques that have a favorable effect on the nature of the polymerization. One example of emulsion formation is to add a mineral oil to a toluene solution of aluminoxane and then drive off (strip) the toluene.

Another method of achieving catalyst separation is to premix the catalyst components and then add a cosolvent to render the resulting mixture insoluble. One example of this is to mix the metallocene with an aluminoxane-toluene mixture and mineral oil.

Another way to achieve catalyst separation is to add components that react with one of the catalyst components and make them insoluble. Examples of this component are bifunctional or trifunctional molecules that lead to cross-linking and insolubilization with aluminoxane, such as ethylene glycol.

Another method of achieving catalyst separation is to add a small amount of suction component that collects one or more catalyst components around itself by intermolecular interactions.

The catalyst is preferably reacted from about 20 to 50% of the reactor diameter from the reactor wall and from the bottom of the reactor or from a height of up to about 50% of the bed height. Supplied to the vessel. The catalyst is likewise located at or just above the distribution plate and from the reactor wall about 20-50% of the reactor diameter
It may be introduced at a remote location, or may be introduced from a number of locations in or on the distribution plate.

The catalyst is fed to the bed, preferably using a carrier inert gas such as ethane, nitrogen or argon as the carrier.

The rate of polymer formation in the bed depends, inter alia, on the catalyst injection flow rate, the amount of condensing medium, and the monomer concentration of the recycle stream. The production rate can be conveniently adjusted simply by adjusting the catalyst injection flow rate.

If the catalyst injection flow rate fluctuates, the reaction rate and thereby the reaction heat generation rate fluctuate. Therefore, the fluctuation of the reaction heat generation rate is achieved by adjusting the temperature of the circulating flow flowing into the reactor in the vertical direction. Absorb. This ensures a substantially constant temperature of the floor. Complete metering of the fluidized bed and circulating flow cooling system allows the operator or a conventional automatic controller to detect temperature fluctuations in the bed and to properly adjust the temperature of the circulating flow.

Under a given set of operating conditions, the fluidized bed is maintained at a substantially constant height and weight by withdrawing a portion of the fluidized bed as a product at the rate of formation of the particulate polymer product. Is done. Because the rate of heat generation is proportional to the rate of product formation, measuring the temperature rise across the reactor (ie, the difference between inlet and outlet fluid temperatures) assumes that no volatile liquid is present in the inlet fluid. Is an indicator of the rate of formation of the particulate polymer at a constant fluid velocity.

As the particulate polymer product is withdrawn from the reactor, it is desirable to separate the fluid from the product and return it to the circuit. There are many known methods for this. See U.S. Patent No. 4,543,399. Another preferred product withdrawal device is described in U.S. Patent No. 4,621,952.
These devices use at least one pair of (parallel) tanks including a settling tank and a transfer tank connected in series with the gas phase separated from the top of the settling tank and returned to the reactor at a location near the top of the fluidized bed. ing.

The fluidized bed reactor has a suitable evacuation system, whereby evacuation is performed during start-up and rest periods. The reactor does not require a stirrer or wall scraper. The circuit and its components do not impede the circulation or the flow of particles entrained therein. It should have a smooth surface and be free of unwanted obstacles.

The polymer that can be produced by the method of the present invention includes ethylene, propylene, butene, or a copolymer containing ethylene, propylene or butene as a major part and a C _{2 to} C ₈ alpha-olefin as a minor part. is there.
The C ₂ -C ₈ alpha-olefin preferably has no branch at a position closer to 4 carbons. Preferred C
The ₂ -C ₈ alpha-olefin, ethylene, propylene, butene-1, pentene-1, hexene-1, 4-methylpentene-1 and octene-1.

For example, the ethylene copolymer has a melt flow rate of about 22 or more. Melt flow rate is one of the other methods for expressing the molecular weight of a polymer. For example, a melt flow rate (MFR) of 22 corresponds to a Mw / Mn (measured by conventional size exclusion chromatography) of about 2.7.

The ethylene homopolymer is used in an amount of about 0.958 to 0.5.
It has a specific gravity of 972 g / cc.

The ethylene copolymer has a specific gravity of about 0.96 g / cc. The density of the ethylene copolymer primarily regulated by the amount of comonomer of C ₃ -C ₈ which is copolymerized with ethylene in the melt index given copolymer. In the absence of a comonomer, ethylene homopolymerizes to produce a polymer having a density of about 0.96 or less. Therefore,
When a copolymer is formed with progressively greater amounts of comonomer added, the density of the copolymer progressively decreases. Various C ₃ to C required to achieve the same result under the same reaction conditions
The amount of each of the C ₈ comonomer varies from monomer.

As described above, in order to produce a binary copolymer of ethylene having the same density and melt index,
The different comonomers are C ₃ > C ₄ > C ₅ > C ₆ > C ₇ > C
_{Increase in} the order of ₈ .

The ethylene polymer produced by the fluidized bed process described herein is about 15-32 lb / f ³ (0.241
０．５0.514 g / cc) with an average particle size of about 0.005-0.1 inch (0.127 mm-2.5
4 mm), preferably about 0.06 to 0.10 inch (1.524 to 2.54 mm). Particle size is important for the purpose of easily fluidizing the polymer particles in a fluidized bed reactor as described herein.

While the exact scope of the invention is set forth in the appended claims, the following examples illustrate certain aspects of the present invention, and more specifically describe methods for evaluating it. However, the examples are described for illustrative purposes only and should not be construed as limiting the invention except as defined in the appended claims. All parts and percentages are by weight unless otherwise indicated.

[0075]

【Example】

Example 1,1A catalyst eta ⁵ - indenyl zirconium tris (diethyl carbamate) 0.025 molar toluene solution of the catalyst. About 1 L of catalyst is prepared and charged to a continuous stirred vessel filled with pure nitrogen at a pressure of 400 psi (28 kg / cm ² ). The catalyst is withdrawn from the vessel and continuously added to the reactor using a high pressure syringe pump. 7.5cc of catalyst supply flow rate with catalyst solution
/ Hr with a syringe pump. 0.8 lb / hr (0.362 kg / hr) and 7.0, respectively.
The catalyst is supported in a stream of lb / hr (3.18 kg / hr) of isopentane and nitrogen and sent to the reactor. The catalyst and carrier enter the reactor via a reduced tip diameter of 0.041 inch (1.041 mm) of the 1/8 inch (3.18 mm) injection nozzle and aid in atomization and dispersion. The injection tube extends about 3 inches (7.6 cm) into the floor at 2.0 feet (60 cm) above the distribution plate.

Activator A 13% by weight solution of modified methylaluminoxane (MMAO-3A) in isopentane (Akzo Nobel,
Diluted from a 6% by weight solution) at a flow rate of 100 cc / hr.
Add to reactor via reduced tip diameter of 0.041 inch (1.041 mm) of / 8 inch (3.18 mm) injection nozzle. 0.8lb / hr (0.362k
g / hr) and 5.0 lb / hr (2.27 kg / h)
The flow of isopentane carrier and nitrogen carrier in r) assists in dispersing and atomizing MMAO-3A in the reactor. MMAO-3A is 1.5f (45cm) from the distribution plate
Upper position (5 inches (12.7c
m) Bottom) is added to the reactor and the injection tube is about 4
Extends into the inch (10.2 cm) floor.

The reactor has a bed weight of 85 lb (3.86 kg) and about 8 f (2.4
A 14 inch (34.3 cm) diameter reactor having a height of m) is used. Monomer and other circulating gas components are added to the reactor from a compression case behind the propeller. The additional isopentane allows the dew point of the circulating gas to be adjusted independently of the catalyst carrier stream and the activator stream.

Start-up The reactor is opened before the experiment. To prepare for the polymerization, the reactor and the LLDPE seed bed are dried to about 10 ppm of moisture in the circulating gas using hot nitrogen. 5 in isopentane
About 500 cc of weight percent TiBA is circulated for one hour, and the reactor is evacuated and burned prior to monomer introduction. MMAO-3A
Is started about 30 minutes before the start of the catalyst feed.

Conditions Total pressure, psig (kg / cm ² g) 375 (26.25) Ethylene partial pressure, psi (kg / cm ² ) 180 (12.6) Hydrogen partial pressure, psi (kg / cm ² ) 0 Hexene partial pressure, psi (kg / cm ² ) 5.9 (0.41) Isopentane partial pressure, psi (kg / cm ² ) 22.0 (1.54) (5.65 mol%) Nitrogen partial pressure, psi ( kg / cm ² ) 182 (12.7) H ₂ / C ₂ molar ratio 0.0 C ₆ / C ₂ molar ratio 0.015 Bed temperature, ° C 70 Inlet gas temperature, ° C 69.5 Circulating gas dew point, ° C 41 .2 Circulating gas velocity, f / sec (m / sec) 1.20 (0.36) Production rate, lb / hr (kg / hr) 16 (0.72) Average residence time, hr 5.3 STY, lb / Hr / f ³ (kg / hr / m ³ ) 2.0 (32) Balatrol ( 1,2-dimethoxybenzene) is added to the compressor inlet of the circulating gas path to reduce fouling in the circulating gas path. The feed rate is about 50 cc / hr of a 0.01% by weight solution in isopentane.

Resin I2 melt index 0.86 dg / min, I21 flow index 16.2 dg / min, density 0.926
A 5 g / cc polymer is produced. Resin particle size is 0.0
75 inches (1.91 mm), the bulk density of the resin is 18.5 lb / f ³ (0.296 g / cm ³ ),
The fluidized bulk density is 9.5 lb / f ³ (0.152 g / c
m ³ ).

The comparative commercial performance at an inlet gas temperature of 30 ° C. is 8.
This corresponds to a condensation level of 7% by weight. Condensation levels for a range of inlet gas temperatures are summarized below.

When the isopentane concentration was 5.65 mol% (22
psi = 1.54 kg / cm ² ) to 8 mol% (3
1.2 psi = 2.18 kg / cm ² )
At 10 ° C. inlet gas temperature, 20.4% by weight of condensation is possible. Further, 11 mol% (42.9 psi = 3.0 kg /
cm ² ) at an inlet gas temperature of 25 ° C.
A 6% by weight condensation is achieved. This temperature is within the capability of a commercially available UNIPOL ™ with refrigeration and cooling means. For the conditions used in the previous two examples, as the amount of nitrogen is reduced to allow for additional isopentane, the bulk properties of the resin will fluctuate slightly and the dew point will increase.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Timothy Todd Benzel Poplar Road, Charleston, West Virginia, USA 888 (72) Inventor Mark Gregory Good Meadowbrook Circle, 17 Hurricane, West Virginia, USA (72) Inventor Clark Curtis Williams Skytop Circle 1105, Charleston, West Virginia, USA

Claims (1)

[Claims] 1. A gas stream comprising one or more fluid monomers is formed under the reaction conditions in the presence of a soluble, unsupported catalyst.
Continuously flowing through the gas phase reactor, drawing out the polymerization product and unreacted fluid, cooling a part or all of the unreacted fluid to form a two-phase mixture of gas and liquid entrained therein,
Re-introducing the biphasic mixture into the reactor with a sufficient amount of replenishment monomer to replenish the monomer withdrawn as a product from the polymerization, thereby bringing the temperature of the reactor to the desired temperature Continuously producing a polymer from one or more fluid monomers.