MXPA97006989A - A non-sustainable gas phase polymerization - Google Patents

Abstract

The present invention relates to a polymer gas phase polymerization comprising: a) introducing a monomer or monomers into a gas phase reactor, b) introducing a non-supported polymerization catalyst system into the gas phase reactor, wherein the unsupported polymerization catalyst system comprises: i) a fraction of non-volatile materials containing a polymerization catalyst, ii) a fraction of the solvent that is at least partially miscible in the fraction of non-volatile materials and that is sufficiently volatile to allow the formation of polymerization catalyst particles when the mixture of the solvent fraction and the fraction of nonvolatile materials is sprayed into the reactor, iii) a compressed fluid, and iv) optionally a slow vaporization solvent; and c) recover the polymer product

Description

"A POLYMERIZATION OF GAS PHASE USING NON-SUSTAINED CATALYSTS" This application claims the benefit of United States Provisional Application numbered 60/004283 filed on September 25, 1995.

FIELD The present invention relates to a gas phase polymerization using unsupported catalysts. More specifically, this invention relates to the use of supercritical or highly compressed fluids as the means for introducing unsupported catalysts into the gas phase system.

BACKGROUND The introduction of catalysts in a gas phase polymerization reactor is an important complex mechanism in the total process. The mechanism must take into account not only the chemical reactions that start when the catalyst is coupled with the monomers but also the aspects of the way in which this delivery mechanism occurs. In the area of polyolefin chemistry, this has led to discoveries of various methods for supporting the catalyst as well as the design of the supply nozzles. The reason behind these findings is largely based on the assumption that the support provides a template for the growth of the polymer particles leading to desirable product morphology, and that it acts to minimize the operational problems associated with the introduction of non-solid catalyst particles. The catalysts have been impregnated in supports such as silica and introduced into a reactor in which the solid gas polymerization is being carried out. The catalyst support, as well as possibly other solids in the formulation, are permanently incorporated into the resin and can be shown to be detrimental to certain properties of the resin. For example, the clarity of the film can be reduced by the presence of excessive amounts of solids in the resin. In addition, the use of a catalyst support can lead to catalyst sites that have different chemical properties and, therefore, lead to the formation of different polymers as compared to the polymers being formed at other catalyst sites. As a consequence, the resulting resin is a mixture of different polymers produced at different sites. The use of an unsupported catalyst avoids the problems caused by the presence of a catalyst support and represents a new technology for the introduction of catalysts in a polymerization reactor. Recently, in the area of polymerization chemistry, catalysts with very high activity have been discovered, if it is ultimately translated into productivity, they have the potential to improve the polymerization processes. The catalysts formed from the transition metal compounds and aluminoxanes as proposed in these references, have a much higher activity than the polymerization catalyst systems formed of transition metal compounds and organoaluinium compounds, previously used. Most of these catalyst systems are soluble in the reaction systems and are used in a solution polymerization system. As a result, the viscosity of the polymer solution becomes very high, the polymer obtained by the subsequent treatment of the solution has a low bulk density, and it is difficult to obtain polymers having excellent characteristics. On the other hand, attempts have also been made to polymerize olefins in a suspension polymerization system or a gas phase polymerization system using catalysts comprising the aforementioned transition metal compounds, or aluminoxane or both supported on a carrier of porous inorganic oxide such as silica, silica and alumina or alumina. See, for example, U.S. Patent Nos. 4,897,455; 4,937,301; 5,147, 949 and 5, 373, 072. Attempts have also been made to eliminate the inorganic carrier remaining as a foreign matter in the resulting polymer as obtained with conventional catalysts supported on inorganic carriers. See U.S. Patent Number 4,923,833 where a solid catalyst of fine particles is used without a support. Recently, some of these catalysts have been found to retain their high activity when fed as a solution to the reactor (See US Patent Number (5,317,036).) In addition, recent discoveries have indicated that in gas phase polymerizations, not only it is possible to operate in a condensing mode (See US Pat. Nos. 4,543,399 and 4,588,790), but the addition of a liquid monomer can also be advantageously employed under certain circumstances (US Patent Number 5,453,471) .These factors have conspired to make the use of liquid catalysts in the gas phase polymerizations that previously, and therefore the need to overcome the inherent problems associated with the feeding of a catalyst not supported by a gas phase polymerization.The use of compressed fluids for new applications it has become the predominant area for scientific research, mainly in the areas of solvents to effect different separations, formulations and technology for the supply of coatings (See US Patent Numbers 4,916,108; 5,326,835 and 5,391,654). The use of a supercritical fluid or a compressed fluid as part of the catalyst formulation is a superior means of introducing the catalyst into the reactor, which has unexpectedly been found to solve many of the problems associated with the addition of a non-catalytic catalyst. supported by a gas phase polymerization.

SUMMARY OF THE INVENTION The present invention provides a process for a gas phase polymerization of polymers whose process comprises introducing the monomer or monomers and a non-supported polymerization catalyst system in a gas phase reactor, wherein the polymerization catalyst system unsupported comprises a fraction of non-volatile materials containing the polymerization catalyst; a fraction of the solvent that is at least partially miscible in the non-volatile fraction is sufficiently volatile to form particles of the polymerization catalyst when sprayed, a highly compressed fluid; and optionally a slow evaporating solvent; and recover the polymer product. It is possible that when a co-catalyst, such as an aluminoxane, is employed, it may be fed into the reactor in a non-highly compressed fluid such as in the monomer feed. The catalyst particles that form can exist either as solid particles or liquid droplets in which the solid particle is wetted with the solvent or even where the catalyst is still in solution. The use of supercritical fluids or compressed fluids as part of the catalyst formulation provides a powerful means to introduce unsupported catalysts for polymerization in a gas phase reactor, such as a UNIPOL (R) polyolefin reactor. It has been discovered that the use of a compressed or supercritical fluid produces a dramatically superior pattern of spray droplets in the gas phase reactor, which form polymer particles as well as intercept the growth of particles thereby adding to their growth. Specifically, the spraying of compressed fluid has a much more critical droplet size distribution. The predominant portion of the droplets are small in size. Surprisingly, these small droplets do not form fine dust particles but rather yield a critical particle size distribution of the polymer.

DETAILED DESCRIPTION OF THE INVENTION In accordance with the present invention, a new and powerful means is provided for introducing unsupported catalysts into the gas phase reactor. As the temperature of a pure liquid rises, this liquid becomes a vapor. In this way, water, when heated to an atmosphere, becomes steam at 100 ° C. If the pressure rises, then the water will not turn into steam until it reaches a higher temperature. Increasing the pressure will additionally produce higher and higher temperatures at which the liquid water will turn into steam. However, this situation has a limit. Under pressure of 225.54 kilograms per absolute square centimeter and temperature of 374.15 ° C, the water reaches what is called its critical point. At this point, the vapor (water vapor) and the liquid densities are equal. Also, if the temperature is increased beyond 374.14 ° C, it is impossible to produce a liquid phase regardless of how much more pressure is applied. The temperature of 374.14 ° C is called the critical water temperature, and the pressure of. 225.54 kilograms per absolute square centimeter is called the critical pressure. As used herein, it will be understood that a "compressed fluid" is a fluid that may be in its gaseous state, its liquid state or a combination thereof, or is a supercritical fluid, depending on (i) the temperature and specific pressure to which it is subjected, (ii) the vapor pressure of the fluid at that specific temperature, and (iii) the critical temperature and the critical pressure of the fluid, but which is in its gaseous state at normal conditions of 0 ° C temperature Celsius and a pressure atmosphere absolute (STP). As used herein, a "supercritical fluid" is a fluid that is at a temperature and pressure such that it remains at or above its critical point. Compounds that can be used as compressed fluids in the present invention include, but are not limited to, carbon dioxide, nitrous oxide, ammonium, xenon, ethane, ethylene, propane, propylene, butane, isobutane, chlorotrifluoromethane, monofluoromethane, and mixtures thereof. Table 1 lists a number of normally gaseous materials along with their critical pressure temperatures. It should be noted that, in general, the lower the normal boiling temperature of the material, the lower its critical temperature. Preferably, the compressed fluid has a critical temperature greater than 273K and less than 505K.

TABLE 1 SUPERCRITICAL FLUID EXAMPLES Compound Temp Temp Pressure Density boiling Critical Critical Critical ° C ° C atm g / m Ethylene -103.7 9.2 49.7 0.22 Xenon -108.2 16.6 57.6 0.12 Chlorotrifluoroethane -31.2 28.0 38.7 0.58 Carbon Dioxide -78.5 31.3 72.9 0.45 Ethane -88.6 32.3 48.1 0.20 Nitrous Oxide -88.6 36.5 71.7 0.45 Monofluoromethane -78.4 44.6 58.0 0.3 Propane -42.1 96.7 41.9 0.22 Ammonia -33.4 132.4 112.5 0.24 Of the compounds listed in Table 1, carbon dioxide is the one most frequently mentioned in the illustrations of the use of compressed fluids in different separation processes and other processes. For example, the UNICARB ™ supercritical spray coating process typically uses carbon dioxide. However, for many catalysts, carbon dioxide can either poison the catalyst partially or completely. Therefore, there may be a case in which another fluid will be used when these catalysts are supplied. The fluid can be either an inert monomer or a reactive or other intermediate. Examples of inert fluids are ethane and propane. Examples of reactive fluids are ethylene and propylene. It should be noted that the catalyst and the cocatalyst, such as metallocene or aluminoxane, can not be together in the reactive fluids without initiating the polymerization. The selected compressed fluid must exist as a vapor at the pressure and at the temperature of the reactor. The utility of any of the compressed fluids mentioned above in the practice of the present invention will depend on the catalyst being supplied, the temperature and pressure of the reactor and the inertia and stability of the compressed fluid.

The catalyst formulation is essentially a composition carried by the solvent. The catalyst carried by the solvent usually comprises (1) a fraction of non-volatile materials containing the polymerization catalyst system which is capable of forming particles when sprayed; and (2) a fraction of the solvent that is at least partially miscible in the fraction of non-volatile materials and that is sufficiently volatile to cause the catalysts carried by the solvent to be capable of forming particles when sprayed. Typically, this occurs through evaporation of the solvent, however, there are times when at least 100 percent of the solvent evaporates, that is, the polymerization catalyst remains as a droplet of fine liquid. The desired spraying is a decompressive spraying, even when it is not strictly critical to obtain the advantages of the present invention. In general, the fraction of non-volatile materials is the fraction of the catalyst carried by the solvent and remains after the fraction of the solvent has evaporated and therefore, is the fraction that forms the particles. Fractions of the appropriate non-volatile materials may include but need not be limited to metallocene catalysts, other single-site catalysts, Ziegler Natta catalysts, aluminoxanes, borates, organoaluminium cocatalysts, and other components generally present in a catalyst system. An illustrative list of these suitable catalysts includes: bis (cyclopentadienyl) zirconium dichloride / methylaluoxano; dichloride / methylalumoxane of bis (indenyl) zirconium; dichloride / methylalumoxane of bis (butylcyclopentadienyl) zirconium titanium trichloride / triethylaluminum. The fraction of non-volatile materials can be supplied as a solution, emulsion, dispersion or suspension in the solvent fraction. Preferably, the fraction of the non-volatile materials will be supplied as a solution. In general, divided solids that are dispersed must have particle sizes that are small enough to maintain the dispersed state and to easily pass through the orifice of the supply nozzle. Solids divided with particle sizes too large to maintain a stable dispersion, they can be used if a dispersion or suspension can be formed and maintained by agitation. The fraction of non-volatile materials should generally be greater than about 0.01 weight percent of the catalyst carried by the solvent, preferably greater than about 0.05 percent, and more preferably greater than about 0.1 percent, and so especially preferred greater than about 1 percent. The fraction of non-volatile materials should not be an excessively high fraction that causes the catalyst carried by the solvent to be incapable of forming an essentially decompressive spray or forming an appropriate particle size. The appropriate upper limit will depend on the physical and chemical characteristics, such as molecular weight and solubility, of the specific non-volatile fraction selected. The fraction of non-volatile materials should generally be less than about 70 percent, more preferably less than about 50 percent, and especially preferably less than about 40 percent. Generally, the fraction of the solvent is preferably less than about 99 weight percent of the catalyst carried by the solvent, more preferably less than 60 percent, and most preferably less than 50 percent. The solvent should evaporate quickly. A solvent that evaporates quickly usually has a boiling temperature between 225K and 400K. The solvent is selected to be at least partially miscible in the fraction of the non-volatile materials and to be sufficiently volatile. A higher solubility is preferred. The solvents are preferably compatible with the preservation of the catalyst activity and the stability of the catalyst material. Suitable solvents include, but are not limited to, i-pentane, higher boiling temperature monomers such as hexanes and octanes, and solvents (other than oxygenated solvents) with carbon numbers up to 8. In some cases, there is a catalyst in a hyperactive state in the first seconds or minutes of its duration. Typically, the compressed fluid will have completely evaporated from the droplet before this early hyper-activity stage has been completed, leaving the catalyst particle susceptible to overheating and deactivation. This problem can be overcome by adding the formulation a relatively slow evaporation solvent. A slow evaporating solvent usually has a boiling temperature of about 400K. Typical slow evaporation solvents include, but are not limited to, solvents with carbon numbers greater than 8, oxo-alkanes with two carbon atoms or a larger number, monomers of higher boiling temperature and mineral oil. This solvent forms a diffusion barrier for the monomer to reach the catalyst and also increases the external area of the droplet. These effects slow down the reaction and increase the rate of heat transmission from the droplet, thus mitigating the hyperactivity problem. The amount of the slow solvent, if any, may vary up to about 70 weight percent, based on the total weight of the compressed fluid, the catalyst carried by the solvent and the slow solvent, preferably from about 0 percent to 60 percent. percent and especially preferably from 0 percent to 50 percent. For spraying, the catalyst carried by the solvent is first mixed with at least one compressed fluid to form a liquid mixture in a closed system, the compressed fluid being present in an amount that causes the liquid mixture to be capable of spraying essentially decompressive. In general, the catalyst carried by the solvent is between 0.01 to 99.99 percent by weight of the total weight of the compressed fluidand the catalyst carried by the solvent, preferably from 0.05 percent to 75 percent by weight, especially preferably from 0.1 percent to 40 percent by weight. The liquid mixture is then sprayed at temperature and pressure which provides an essentially decompressive spray by passing the mixture through an orifice into the reactor where the particles are formed. As mentioned above, a certain amount of the liquid solvent can remain either to moisten the surface of the solid particle or even to place the catalyst in solution in a fine particle droplet. The essentially de-pressurized sprays are usually formed within a relatively critical combination scale of compressed fluid concentration and spraying temperature and pressure, which varies with the characteristics of the catalyst carried by the particular solvent. The important characteristics are the composition and quantity of the fraction of non-volatile materials, the composition of the solvent and the composition of the compressed fluid used. Therefore, the appropriate conditions for forming the essentially decompressive spray should generally be determined experimentally for any given spray and orifice mixture. However, the region of the decompressive spraying generally must be less than the solubility limit of the compressed fluid in the catalyst carried by the solvent, as it changes with temperature and pressure as disclosed in the Patent Application. North American Serial Number 129,256, filed September 29, 1993. At a constant pressure, the solubility decreases at a higher temperature. The solubility increases with higher pressure. The decompressive spraying region usually occurs at a concentration of compressed fluid that is somewhat lower than the solubility limit, frequently being about a weight percentage of five points the same or less. Frequently, the spraying is carried out just below the solubility limit. A sufficiently high spraying pressure is used to obtain a sufficiently high solubility. The spraying temperature and the concentration of the compressed fluid are then adjusted to provide a decompressive spray having the desired droplet size. The solubility will also change with the compressed fluid used. The solubility will also change with the level of the fraction of non-volatile materials being lower for a higher solids content. At concentrations of compressed fluid greater than the solubility limit, at higher pressures, the liquid mixture will usually comprise a phase of liquid non-volatile materials and a liquid compressed fluid phase containing the extracted solvent, while at lower pressures , the excess of the compressed fluid forms a gaseous phase. In general, the amount of the compressed fluid used will be from about 1 percent to 99.99 percent by weight, based on the total weight of the compressed fluid and the catalyst carried by the solvent, preferably from about 3 percent to 99.95 percent. and especially preferably from about 5 percent to 99.9 percent. The amount of the compressed fluid may exceed the solubility limit if desired but should not be so excessively high so that the excess of the phase of the compressed fluid interferes unduly with the formation of the spray, for example by not remaining well dispersed in the liquid mixture or providing a poor atomization. If desired, an excess of the compressed fluid can be used to separate a portion of the solvent from the spray mixture before spraying, using the methods disclosed in US Patent Number 5,290,604. Generally, the liquid mixture will contain less than about 60 weight percent of the compressed fluid. Even when spraying pressures up to approximately 703.00 kilograms per square centimeter gauge and higher, preferably, the pressure of the spraying of the liquid mixture is less than about 351.50 kilograms per square centimeter gauge, more preferably less than about 210.90 kilograms per square centimeter gauge. A very low pressure is generally not compatible with the high solubility of the compressed fluid in the catalyst carried by the solvent, and with the superatmospheric pressures generally found in the gas phase polymerizations. The compressed fluid is preferably a supercritical fluid at the temperature and pressure at which the liquid mixture is sprayed. Even when a higher spraying temperature is favored for evaporation of the faster solvent from the spraying, the temperature must be compatible with the maintenance of catalyst activity because some catalyst materials are sensitive to heat, particularly when in the solvent . Therefore, the lowest spraying temperature which provides a desirable decompressive spraying and proper evaporation of the solvent is generally preferred. The level of temperature that can be used will generally depend on the characteristics of the catalyst carried by the solvent, such as stability and sensitivity to heat. Reactive systems will usually be sprayed at a lower temperature than non-reactive systems. Preferably, the spraying temperature of the liquid mixture is between about 0 ° C and 130 ° C more preferably between about 20 ° C to 100 ° C, and especially preferably between about 30 ° to 85 ° C. In order to increase the evaporation rate of the solvent from the spraying, the liquid mixture is preferably heated to a temperature that substantially compensates for the drop in spraying temperature that occurs due to expansion cooling of the compressed fluid decompression. Essentially decompressive sprays can be formed through a temperature scale by varying the amount of the compressed fluid accordingly, as the solubility varies. In order to evaporate the solvent more rapidly from spraying to form the particles, it is desirable that a higher spraying temperature be used. The spraying temperature must be high enough to provide sufficiently rapid evaporation of the solvent and compressed fluid for the average relative evaporation rate of the solvent fraction used and the quality of the solvent to be evaporated. In general, a higher spraying temperature is preferred for a lower average relative evaporation rate. The particles of the catalysts that are formed by the methods of the present invention desirably have an average particle size within the range of about 0.1 to 20 microns, preferably within the range of about 5 to 15 microns. The most favorable particle size will depend on the specific polymerization being carried out and the selected catalyst system. In general, critical particle size distributions are preferred. Typically, the catalyst contains at least one compound of a transition metal. It is believed that the present invention found exceptional utility with the class of catalysts known as metallocenes. Some preferred catalyst systems include: bis-n-butylcyclopentadienyl zirconium dichloride, indenyl zirconium diethylene carbamate or indenyl zirconium pivalate. Preferred co-catalysts include MAO (methyl alumoxane) or modified MAO, which consists of the methyl alumoxane with a fraction of the methyl-alkyl groups which have been replaced by isobutyl groups. The preferred solvent for MAO is toluene and that for MMAO is isopentane. The preferred slow solvent is propylene or a mineral oil. The compressed fluid is preferably ethane or propane. Preferably, the catalyst system must consist of only one phase at a pressure and temperature at the inlet to the supply nozzle, but as it passes through the supply nozzle it is possible for a second phase to form, as well as the desired gas. A hole is a hole or opening in a wall or housing, such as in a supply nozzle. Spraying orifices, spraying tips, spraying nozzles, spraying guns and capillary tubing are generally suitable for spraying the liquid mixtures of the present invention. Supply nozzles are preferred that do not have an excessive flow volume between the orifice and the valve that connects and disconnects the spraying and that do not obstruct the wide angle to which the spray typically leaves the spraying orifice. Orifice sizes of approximately 0.254 millimeter to approximately 1.59 millimeters in nominal diameter are preferred, although smaller or larger orifice sizes can be used. At present, commercial products only reach diameters of 0.762 millimeters, but it is believed that smaller diameters will also be useful. Flow devices and designs such as pre-orifices or turbulence activators that activate a turbulent or agitated flow in the liquid mixture before passing the mixture through the orifice can also be used. The pre-orifice preferably does not create an excessively large pressure drop in the flow of the liquid mixture. The spraying pattern may be a circular spray such as that which is produced from a round hole or may be an oval or flat spray as is produced by a slot cut through the hole, as mentioned above.

For compositions carried by the solvent, particularly viscous or for high relative evaporation rates, a more oval or circular spray may be desirable to minimize polymer accumulation in the spray tip. Another design that has two intersecting grooves cut through the outlet of the hole at right angles to each other. This produces two intersecting spraying fans that produce a more spindle-symmetrical spray pattern that provides better mixing of the ambient gas into the spray than a circular orifice. The pressure in the gas phase reactor must be considerably less than the spraying pressure in order to obtain sufficient decompression of the compressed fluid to form the decompressive spraying. The reactor must contain sufficiently low partial pressures for the highly compressed fluid contained in the composition carried by the solvent in order to activate an evaporation of the solvent fast enough from the spraying. Very low partial pressures are preferred. However, the present invention can be operated in the condensed mode in the supercondensing mode. The decompressive spraying produces a uniform spraying pattern with a critical particle size distribution. Not only can the particle size distribution be critical at a point in the spraying but an average particle size can be very uniform throughout the spraying pattern which provides a critical total particle size distribution for the entire spraying, because some of the regions are not over-atomized or sub-atomized. Non-uniform atomization is often a problem with conventional spraying methods. The gas phase polymerization reaction is carried out by contacting a stream of the monomer (s), in a gas phase process, such as in the fluid bed process that will be described below, essentially in the absence of contamination or poison of the catalyst at a temperature and at a pressure sufficient to initiate the polymerization reaction. While it is believed that the present invention will be suitable for all gas phase polymerizations, it is considered to be particularly useful when the monomer or monomers are linear or branched alkenes, dialkenes or trialkenes of 2 to 10 carbon atoms. More preferably, the monomers are selected from the group consisting of ethene, propene, butene, pentene, hexene, octene and 1,3-butadiene.

A fluidized bed reaction system that can be used in practice of the process of the present invention has a reactor consisting of a reaction zone and a rate reduction zone. The reaction zone comprises a bed of growing polymer particles, polymer particles formed and a small amount of catalyst particles fluidized by the continuous flow of the polymerizable and modified gaseous components in the form of replenishment feed and feed gas. recycled through the reaction zone. To maintain a viable fluidized bed, the flow rate of the mass gas through the bed should be above the minimum flow required for fluidization, and preferably from about 1.5 to about 10 times Gmf and more preferably from about 3 to about 6 times Gm-f. Gm-f is used in the accepted form as the abbreviation for the flow of gas of minimum mass to achieve fluidization, the article of C.Y. Wen and Y.H. Yu, "Mechanics of Fluidization", Chemical Engineering Progress Symposium Series, Volume 62, pages 100 to 111 (1966). It is essential that the bed always contains particles to prevent the formation of localized "hot spots" and trap and distribute the catalyst through the reaction zone. During the initiation, the reactor is usually charged with a particulate polymer particle base before the gas flow starts. These particles may be identical in nature to the polymer to be formed or different therefrom. When they are different, are removed from the desired formed polymer particles as the first product. Optionally, a fluidized bed of the desired polymer particles replaces the initiation bed. Fluidization is achieved by a high rate of gas recycling to and through the bed, typically within the order of about 50 times the rate of replacement gas feed. The fluidized bed has the general appearance of a dense mass of viable particles in a possible free vortex flow as created by percolation of the gas through the bed. The pressure drop across the bed is equal to or slightly greater than the mass of the bed divided by the cross-sectional area. Therefore, it depends on the geometry of the reactor. The replacement gas is fed to the bed at a rate equal to the rate at which the particulate polymer product is removed. The composition of the replacement gas is determined by a gas analyzer placed above the bed. The gas analyzer determines the composition of the gas being recycled and the composition of the replacement gas is adjusted accordingly to maintain a gaseous composition of essentially constant state within the reaction zone. To ensure complete fluidization, the recycle gas and when desired part of the replacement gas is returned through a gas recycle line to the reactor at a point below the bed. It can be used to help the fluidization of the bed, a gas distribution plate above the return point. The portion of the gas stream that does not react in the bed constitutes the recycle gas that is removed from the polymerization zone preferably by passing into a velocity reduction zone above the event where it provides the retained particles with an opportunity to fall back to the bed. The recycle gas is then compressed in a compressor and then pumped through a heat exchanger where the heat of adhesion is purified before the bed is returned. Observe the condensation mode (appointment). The temperature of the bed is controlled at an essential temperature constant under conditions of constant state constantly stirring the heat of the reaction. There does not appear to be any discernible temperature gradient within the upper portion of the bed. There will be a temperature gradient at the bottom of the bed between the temperature of the inlet gas and the temperature and the rest of the bed. The recycling is then returned to the reactor at its base and to the fluidized bed through a distribution plate. The compressor can also be placed downstream of the heat exchanger. The distribution plate plays an important role in the operation of the reactor. The fluidized bed contains particulate polymer particles that grow and form as well as the catalyst. Because the polymer particles are hot and possibly active, they should be prevented from settling, because if a standing or standing mass is allowed to exist, any active catalyst content in it can continue to react and cause fusion. The diffusion of the recycle gas through the bed to a sufficient regime to maintain the fuidization through the bed is therefore important. The distribution plate serves for this purpose and may be a screen, a slotted plate, a perforated plate, a bubble cover type plate and the like. The elements of the plate can all be stationary or the plate can be of the movable type as disclosed in US Patent Number 3,298,792.

Whatever its design, it must diffuse the recycle gas through the particles in the bed base to maintain the bed in a fluidized condition, and it can also serve to support a bed of still resin particles when the reactor is not in place. functioning. The movable elements of the plate can be used to dislodge any of the polymer particles trapped in or on the plate. It is essential to operate the fluid bed reactor at a temperature lower than the calcination temperature of the polymer particles to ensure that calcination does not occur. For the production of ethylene homopolymers and copolymers, an operating temperature of from about 0 ° C to 150 ° C, preferably from about 10 ° C to 140 ° C, and especially preferably from about 30 ° C to 115 ° C. The fluid bed reactor is operated at pressures up to about 70.30 kilograms per square centimeter and preferably operated at a pressure of about 3.52 to 49.21 kilograms per square centimeter, preferably about 7.03 to 42.18 kilograms per square centimeter and especially preferred way of about 10.55 to 24.10 kilograms per square centimeter, with operation at higher pressures in these scales favoring heat transmission since an increase in pressure, increases the unit volume heat capacity of the gas. The catalyst is injected into the reactor at a rate equal to its consumption. The catalyst can be injected either into the fluidized bed or above or below the bed, depending on the nature of the catalyst system being sprayed. The placement of the injection should be such that it does not interfere with the flow pattern in the bed. Preferably, this will be in a place above the distributor plate. Approximately one fourth to one half of the catalyst particles should form primary or new resin particles to maintain the desired distribution of the resin particle size. The feeding of the catalyst above the bed provides a longer time for the catalyst particles to dry before intercepting the already existing resin particles. In addition, the feed of the catalyst to the bed can also be used but first through a tube leading to the reactor which provides time for the particles to become essentially free of the solvent. The bed production rate is controlled by the injection regime of the catalyst. The production rate can be increased by simply increasing the rate of catalyst injection and decreasing by reducing the rate of catalyst injection. Since any change in the rate of injection of the catalyst will change the rate of heat generation of the reaction, the temperature of the recycle gas entering the reactor is adjusted up or? Down to accommodate the change in the regime of heat generation. This ensures the maintenance of a essentially constant temperature in the bed. The complete instruments of both fluidized bed and the cooling system of the recycle gas are, of course, necessary to detect any change in the temperature in the bed in order to allow the operator Make an appropriate adjustment in the temperature of the recycle gas. Under a set of connections of certain operation, the fluidized bed is maintained at an essentially constant height by removing a portion of the bed as a product at a rate equal to the rate of formation of the polymeric particulate product. Since the heat generation regime is directly related to the formation of the product, a measurement of the temperature rise of the gas through the reactor (the difference between the inlet gas temperature and the outlet gas temperature) is determinative of the rate of particulate polymer formation at a constant gas velocity. The particulate polymer product is preferably continuously withdrawn at a point on or near the suspension distribution plate with a portion of the gas stream discharging as the particles settle to minimize further polymerization and calcination. when the particles reach their final collection area. The suspension gas can also be used to propel the product from one reactor to another reactor.

EXAMPLES Although the 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 disclosed for illustration only and should not be construed as limitations on the present invention except as set forth in the appended claims. All parts and percentages are by weight unless otherwise specified.

Example 1. Use of a Spraying Cannon as the Spraying Supply Nozzle. Example of the compressed fluid A spraying gun, model AA24AUA-8930-36 from Spraying Systems Co., in Wheaton, IL, with a .178 mm hole, model TP400008TC, as installed on one side of the gas phase reactor with a diameter of 35.56 centimeters , approximately 10.14 centimeters around the distributor plate and projecting from 2.54 to 7.62 centimeters towards the reactor with a fan spray perpendicular to the flow direction of the monomer, that is, the fan spray was horizontal with the flow of the monomer vertical through the bed. The reactor was initially filled with an initiated bed of polyethylene resin at a partial pressure of 15.43 kilograms per square centimeter of monomer and .281 kilogram per square centimeter of hexene. The spraying supply apparatus was initially filled with 0.004 weight percent zirconium of indenyl tertiary butyl carboxylate and 0.21 weight percent of a modified methyl alumoxane catalyst, 0.1 weight percent hexane, 2.6 percent in weight of ethane and ispentane in bulk. As the test progressed, the initial catalyst charge was delivered to the reactor, and subsequent charges were added to the spraying supply apparatus with approximately the initial charge. The pressure of the spraying supply apparatus was graduated at 70.30 kilograms per square centimeter gauge and the temperature was not controlled at room temperature and was between 298K and 308K during the test. The resin that was produced had a melt index of 0.481 degrees per minute, a volume density of 296 grams per cubic centimeter, a resin density of 0.917 gram per cubic centimeter, an average particle size of .457 millimeter. The test showed a surprisingly decreased fine level of 2.1 weight percent when the test was stopped.

Example 2. Use of a Spray Capillary Tube as the Spraying Nozzle. Example of Supercritical Fluid A 20-centimeter long piece of stainless steel tubing with an outer diameter of 1.59 millimeters per internal diameter of .127 millimeters was welded with silver inside a piece of 3.18 millimeter external diameter stainless steel tubing for extra support. This pipe system of 3.18 millimeters by 1.27 millimeters was placed at a distance of approximately 7.62 centimeters to 12.70 centimeters to a gas phase reactor that is approximately 26.67 centimeters away from the distribution plate. Around this point between .908 and 2.27 kilograms per hour of nitrogen were flowed down the annular space between the capillary and a stainless steel pipe of 1.90 centimeters. The 1.1.90-centimeter pipe extended at a distance of 6.99 centimeters to the reactor. Around the 1.90 centimeter pipe, flow gas was flowed at 817.2 kilograms per hour in the annular space between the 1.90-centimeter pipe and a stainless steel pipe with an internal diameter of 2.54 centimeters. The 2.54-centimeter pipe extended a distance of 5.08 centimeters to the reactor. The spraying supply apparatus was initially charged with 0.063 weight percent zirconium of indenyl tertiary butyl carboxylate and 5.5 weight percent of a modified methyl alumoxane catalyst, 7.6 weight percent of ethane and isopentane a Bulk The fluid temperature in the spraying supply system was graduated at 46 ° C and the pressure graduated to 70.30 kilograms per square centimeter gauge. The reactor was initially started in the same manner as mentioned in Example 1.

The resin that was produced had a melt index of 0.404 degree per minute, a bulk density of 196.8 grams per cubic centimeter, a resin density of 0.930 gram per cubic centimeter, an average particle size of .650 millimeter. Again this test showed a surprisingly diminished level of fines of 0.2 weight percent.

Example 3 Use of Spray Capillary as the Spraying Nozzle Example of Supercritical Fluid A 20-centimeter-long piece of a 1.59-millimeter external diameter stainless steel pipe with an internal diameter of .178 millimeter was welded with silver into a piece of 3.18 millimeter outer diameter stainless steel pipe for extra support. This pipe system of 3.18 millimeters per .178 millimeter was placed around 6.99 centimeters in a gas phase reactor at a distance of approximately 26.67 centimeters above the distributor plate. Around this point between .908 and 2.27 kilograms per hour of nitrogen flowed down the annular space between the capillary and a stainless steel pipe of 1.90 centimeters. The 1.90-centimeter pipe extended 5.08 centimeters away to the reactor. Around the 1.90-centimeter pipe, 817.2 kilograms per hour of cycle gas were flowed into the annular space between the 1.90-centimeter pipe and a stainless steel pipe of 2.54 centimeters in internal diameter. The 2.54-centimeter pipe extended a distance of 5.08 centimeters to the reactor. The spraying supply apparatus was initially charged with 0.16 weight percent zirconium of indenyl tertiary butyl carboxylate and 8.9 weight percent of a modified methyl alumoxane catalyst, 31 weight percent of ethane and isopentane in bulk . The temperature of the fluid in the spraying supply system was graduated at uncontrolled ambient temperatures and then between 298K and 308K and the pressure graduated to 70.30 kilograms per square centimeter gauge. The reactor was initially started in the same manner as mentioned in Example 1. The resin produced had a melt index of 0. 833 degree per minute, a volumetric density of 236.8 grams per cubic centimeter, a resin density of 0.926 gram per cubic centimeter, an average particle size of 8.56 millimeters and surprisingly showed a diminished level of fines of 0.7 weight percent.

Claims (16)

CLAIMS:

1. A polymer gas phase polymerization comprising: a) introducing a monomer or monomers into a gas phase reactor, b) introducing a non-supported polymerization catalyst system into the gas phase reactor, wherein the catalyst system of Unsupported polymerization comprises: (i) a fraction of non-volatile materials containing a polymerization catalyst; (ii) a fraction of the solvent that is at least partially miscible in the fraction of the non-volatile materials and that is sufficiently volatile to allow the formation of polymerization catalyst particles when the mixture of the solvent fraction and the fraction of the Non-volatile materials are sprayed into the reactor; (iii) a compressed fluid; and (iv) optionally a slow vaporizing solvent; and c) recovering the polymer product.

2. The polymerization according to claim 1, wherein the monomer or monomers consist of linear or branched alkenes and dialkenes and trialkenes of 2 to 10 carbon atoms.

3. The polymerization according to claim 2, wherein the monomers are ethene, propene, butene, pentene, hexene, octene and 1,3-butadiene. The polymerization according to claim 1, wherein the catalyst system contains at least one transition metal compound. 5. The polymerization according to claim 4, wherein the catalyst system is a metallocene. 6. The polymerization according to claim 1, wherein the solvent is one of the normal or branched alkanes less than 8 carbon atoms. The polymerization according to claim 1, wherein the slow vaporization is a normal solvent and branched alkanes greater than 8 carbon atoms, or oxo-alkanes greater than 2 carbon atoms. The polymerization according to claim 1 wherein the compressed fluid or mixture of fluids, wherein the critical temperature is greater than 273K and less than 505K. 9. The polymerization according to claim 1, wherein the compressed fluid is selected from the group consisting of carbon dioxide, nitrous oxide, ethane, propane, ethene, chlorotrifluoroethane, monofluoromethane, ammonia and xenon. 10. The polymerization according to claim 1, wherein the catalyst system is 5 introduced into the reactor under pressure of less than 703 kilograms per square centimeter gauge. 11. Polymerization according to claim 1, wherein the pressure is less than 210.90 kilograms per square centimeter gauge. 12. The polymerization according to claim 1, wherein the fraction of non-volatile materials is greater than 0.01 percent by weight and less than 70 percent by weight of the polymerization catalyst system. 15 13. Polymerization in accordance with the. claim 12, wherein, the fraction of non-volatile materials is greater than 1.0 percent and less than 40 percent. 1

4. The polymerization according to claim 1, wherein the fraction of the solvent in the polymerization catalyst system is less than 95 percent by weight. 1

5. The polymerization according to claim 1, wherein the amount of fluid compressed in the polymerization catalyst system is between 1 percent and 99.99 percent by weight. 1

6. The polymerization according to claim 15, wherein the amount of fluid compressed in the polymerization catalyst system is between 5 percent and 99.9 percent by weight.