SPRAY DRIED POLYMER FOR CATALYST SUPPORT

Abstract: This invention relates to catalyst supports made by spray drying an emulsion polymerizated latex and the novel supported catalysts utilizing these supports. This invention further relates to a method for forming supported catalysts by spray drying a latex of microparticles containing catalyst or catalyst components.

Description: TITLE OF INVENTION: SPRAY DRIED POLYMER FOR CATALYST SUPPORT. Field of the Invention This invention relates to polymeric macroparticles, a method of utilizing them as catalyst supports, and a method to make the supports by spray drying the microparticles with or without catalyst. Background of the Invention Spray drying offers an opportunity to control the particle size of an inorganic support and a supported catalyst, which in turn is used to control particle size and final polymer product properties in gas phase polymerization. Silica, a favorite catalyst support, is typically spray dried to obtain certain ranges of particle sizes and distributions. Similarly, catalyst systems themselves are spray dried. For example, US 4,424,138 discloses a solution having a solid component, an agglomeration enhancer of dissolved polystyrene and other components spray dried for use as a polymerization catalyst in gas phase. It is also known that polymers can be used as catalyst supports since they are less susceptible to typical catalyst killing impurities such as, for example, water and oxygen. Supported porous polymer particles having pore sizes of 10 angstroms are disclosed as supports in U.S. 5,118,648. (See also U.S. 3,051,484 and U.S. 4,921,825 for polymeric supports.) These "spongy" polymeric supports, however, do not provide uniform pore sizes, which in turn can lead to reactor fouling and other undesired events. There has been a need for a method to produce small particle size organic polymer supports having good pore size distribution for use as catalyst supports. Brief Summary of the Invention This invention relates to porous polymeric catalyst supports comprising agglomerates (macroparticles) of polymer microparticles, said microparticles having an average diameter of about 0.005 to about 5.0 micrometers. This invention further relates to catalyst supports comprising polymeric agglomerates of particles of about 0.005 to about 5.0 micrometers and combinations thereof with catalysts or catalyst components. Likewise, this invention also relates to methods of preparing porous polymeric supports and supported catalysts by spray drying, preferably spray drying an emulsified composition. Brief Description of the Drawings Fig. 1 is an electron micrograph of a polystyrene bead that was emulsion polymerized and then spray dried. Fig. 2 is an electron micrograph of a polystyrene/MgCl 2 bead. The polystyrene was emulsion polymerized, combined with the MgCl2, then spray dried. Fig. 3 is an electron micrograph of CHROMOSORB 101™. Detailed Description of the Invention In a preferred embodiment, this invention relates to a porous polymeric catalyst support comprising agglomerates of polymer microparticles of uniform size, said microparticles having an diameter of about 0.005 to about 5.0 micrometers. Preferred embodiments of this invention relate to porous polymeric supports, preferably spray dried supports and a method for preparing supports comprising spray drying a suspension of 0.005 to 5.0 micrometer polymer particles (microparticles) . In preferred embodiments, the microparticles are combined with catalyst or catalyst components before or after spray drying. Preferred polymer microparticles are about 0.005 to about 5.0 micrometers in diameter, preferred embodiments included diameters as small as 0.1 micrometers, even as small as 0.05 micrometers and diameters as large as 2.0 micrometers, even as large as 3.0 micrometers or even as large as 4.0 micrometers, which when in the liquid media and upon spray drying agglomerate into larger particles (macro- particles) of up to about 300 micrometers, preferably about 10 to about 300 micrometers, more preferably about 10 to 150 micrometers, even more preferably about 20 to about 90 micrometers. In a preferred embodiment, the microparticles are substantially uniform in size, i.e. the particle sizes have a standard deviation of less than about 20 %. If the microparticles are not substantially spherical in nature then the "diameter" is the diameter of the smallest sphere that will contain at least 90% by wt. of the microparticle. Likewise, the microparticles may be formed in situ or may be combined with the liquid media prior to spray drying. The polymer microparticles, can be purchased from chemical suppliers or can be prepared by known emulsion polymerization techniques, such as those disclosed in Principles of Polymerization, by George Odian, McGraw-Hill Publishers, 2nd. ed. 1981, which is incorporated by reference herein. The microparticles can be prepared, for example, by (1) placing a monomer, such as an acrylate, a styrene or the like, into water with a surfactant, and (2) adding a free radical initiator such as a peroxide to begin the polymerization. The different particle sizes (between 0.005 to 5.0 micrometers) can be obtained by varying the amount of surfactant used in the emulsion and other methods known to those of skill in the art. In a preferred embodiment the polymer microparticles are polymers comprising units derived from aromatic monomer, cyclic monomer, vinyl halide monomer, vinyl ester, acrylic acid or ester thereof; and/or alkyl acrylic acid or esters thereof. In another embodiment, preferred monomers used in preparing microparticles of this invention are those that are emulsion polymerizable including but not limited to alkyl styrenes and alkyl (meth)acrylates, wherein the alkyl groups have from about 1 to about 40 carbon atoms, more preferably from 1 to 20 carbon atoms. Examples of preferred monomers include styrene, alpha-methylstyrene, methylstyrene, para-chlorostyrene, para-methylstyrene, acrylic acid, 2-ethyl-hexyl acrylate, vinyl versatate, vinyl chloride, vinyl acetate, methyl acrylate, methyl methacrylate, ethyl acrylate, glycidylmethacrylate, divinylbenzene, butyl acrylate, n-octyl acrylate, vinylidene chloride, acrylamide, 2-hydroxy-ethyl-acrylate, methyl acrylic acid, vinyl cyclohexane, vinyl cyclohexene and the like. The phrase alkyl (meth)acrylates is herein defined to mean both alkyl acrylates and alkyl meth- acrylates. Further, the inclusion of monomers in the polymer making up the microparticles that are capable of crosslinking, such as polyenes or alpha, omega-dienes, is also preferred in some embodiments. These monomers provide the capability of crosslinking the polymer within the microparticles. This may be desirable when the polymeric microparticles and the agglomerations are soluble in the solvent of choice for a particular catalyst. Cross-linking the microparticles results in the polymer becoming insoluble. In preferred embodiments the crosslinkable comonomers are present in the polymer at up to about 25 weight percent, based upon the weight of the polymer, preferably about 2 to about 20 weight percent, even more preferably, 2 to 10 weight percent. Preferred crosslinkable monomers include alpha, omega- dienes, non-conjugated dienes and di- or multi-functional monomers having up to about 200 carbon atoms, and may comprise linear, branched or cyclic structures. Examples of preferred monomers include butadiene, diacrylate, divinyl benzene, triacrylate, 1,5- hexadiene, 1,6-heptadiene, 1,7- octadiene. Likewise any polymer that may be formed into microparticles of an average size of about 0.005 to about 5.0 micrometers, preferably 0.1 to 2.0, may also be used in the practice of this invention. In addition, the microparticles making up the macroparticles are not necessarily made of the same polymer. Different microparticles each comprising a different polymer may be within the same macroparticle. Similarly, each microparticle may contain two or more different polymers. In preferred embodiments the microparticles are suspended in a liquid media, such as water or a hydrocarbon diluent, and spray dried to form the agglomerated support. In a further preferred embodiment, the microparticles are suspended in a liquid media and then combined with one or more catalysts or catalyst components and then spray dried. This forms a supported catalyst, or supported catalyst components, respectively. In another preferred embodiment, the agglomerated support is combined with cyclopentadienyl transition metal compounds, an alumoxane, an aluminum alkyl or a non-coordinating anion and allowed to remain in solution for 1 minute to an hour to allow enough time for the catalyst or component to "load" onto the support and may even be optionally heated. Loading is performed by standard techniques known in the art. In a particularly preferred embodiment the microparticles of polymer are combined in liquid medium with one or more of cyclopentadienyl transition metal compounds, an alumoxane, an aluminum alkyl or a non- coordinating anion and thereafter spray dried. Preferred cyclopentadienyl transition metal compounds, alumoxanes and non-coordinating anions are those disclosed in U.S. 5,055,438; U.S. 5,657,415; 5,096,867; 5,017,714; 5,240,894; 5,153,157; 5,198,401; 5,384,299; EPA 520,732, published Dec. 30, 1992; EPA 129,368, published Dec. 27, 1984; EPA 277,003, and EPA 277,004, both published June 3, 1988, EPA 551,277 published 7/21/93; WO 9403506 published 2/17/94, which are herein incorporated by reference. In general these catalysts comprise two parts: a first component of a bulky ancillary ligand transition metal compound, preferably a cyclopentadienyl derivative of a group 4, 5 or 6 transition metal, even more preferably a mono- or bis-cyclopentadienyl derivative of a group 4 compound; and a second optional component of a cocatalyst or activator such as an alumoxane or a bulky anionic cocatalyst such as a non- coordinating anion. In particularly preferred embodiments the first component is a mono- cyclopentadienyl (mono-Cp) group 4 transition metal compound or a bis-cyclopentadienyl (bis-Cp) group 4 transition metal compound. The cyclopentadienyl portions of the transition metal compounds may be bridged or unbridged, unsubstituted, partially substituted or completely substituted and may also be part of a fused ring system such as fluorenyl or indenyl systems. Titanium, zirconium and hafnium are preferred group 4 metals. The second component is preferably an alumoxane or a non-coordinating anion. Preferred alumoxanes include methylalumoxane. Preferred non-coordinating anions include N,N dimethylanilinium tetrakis(pentaflourophenyl)borate. Preferred combinations of catalyst components include: 1) a mono-cyclopentadienyl titanium compound combined with a non-coordinating anion or methylalumoxane; 2) a bridged mono-cyclopentadienyl titanium compound containing a heteroatom combined with a non- coordinating anion or methylalumoxane; 3) a substituted biscyclopentadienyl hafnium or zirconium compound combined with a non-coordinating anion or methylalumoxane; or 4) a substituted biscyclopentadienyl (substituted with groups having 2 or more carbons) hafnium or zirconium compound combined with a non-coordinating anion or methylalumoxane; and/or 5) a bridged biscyclopentadienyl compound combined with a non-coordinating anion or methylalumoxane. In a preferred embodiment, the cyclopentadienyl compound and/or the alumoxane and/or the non- coordinating anion are combined in a hydrocarbon media with the microparticles and thereafter spray dried. Likewise, in another preferred embodiment one or more components of a traditional Ziegler-Natta catalyst is placed in a liquid media with the microparticles prior to spray drying. Traditional Ziegler-Natta catalysts which may be combined with the microparticles before spray drying or combined with the polymer particle agglomerates after polymerization are discussed in "Zieσler-Natta Catalysts and Polymerizations." by John Boor, Jr., Academic Press, New York, 1979, and "Isospecific Polymerization of Olefins: With Heterogeneous Ziegler-Natta Catalysts." by Y.V. Kissin, Springer-Verlag, New York, 1985, both of which are incorporated by reference herein. Typically these catalysts comprise at least two components: a transition metal component and an organo- aluminum component. The transition metal component is typically a group 4, 5 or 6 transition metal component, all references to the periodic table being to the version published in Chemical and Engineering News, 63 (5), 27, 1985. The organo-aluminum component is typically an aluminum alkyl and is preferably an aluminum alkyl halide, having 1 to 40 carbon atoms in the alkyl group. As described above these components may be combined together or separately with the micro- or macro- particles before or after spray drying in any number of combinations that will occur to those of ordinary skill in the art having the benefit of this disclosure. In addition, catalyst precursors can be loaded onto the supports or suspended in the emulsion media prior to spray drying to form a supported composition that can thereafter be treated to form the catalyst or catalyst component. Also the catalyst or catalyst components may be adsorbed or absorbed onto the support. In a preferred embodiment, the 0.005 to 5.0 micrometer size polymeric particles are suspended in a liquid media and then spray dried to remove the liquid. This produces hexagonally close packed macroparticles (agglomerates) on the drying surface. (Examples of drying surfaces are teflon films, walls and any other surface in between.) The macroparticles are preferably about 2 to about 300 micrometer in diameter, more preferably 10 to 150 micrometers, even more preferably 20 to 90 micrometers in diameter. These hexagonally closed packed particles are then exceptionally useful as supports for catalysts or catalyst components. Typically, the pore sizes of the agglomerates are determined by the sizes of the microparticles. Thus, in a preferred embodiment, the pore sizes are substantially uniform across the agglomerate or macroparticle, when the microparticles are of substantially the same size. This of course is not the case in some embodiments when microparticles of more than one size are selected and combined for spray drying together. It is also contemplated by this invention that supports having different pore sizes and/or macroparticles and/or microparticles could be combined to form the catalyst support. One of ordinary skill in the art will recognize the use of the phrase substantially uniform above is meant to exclude wide variations in sizes, while allowing statistical variations, i.e. having a standard deviation of less than about 20%. In a particularly preferred embodiments, the pore sizes are substantially uniform and have an average diameter of between about 50 and about 50,000 nanometers. One of ordinary skill in the art will also recognize that typical supported catalyst procedures may be practiced with the composition disclosed herein. For example one may prepolymerize with these compositions or use them with scavengers or electron donors. The dried polymer can be treated as any other typical catalyst support, for example dehydrated. In a preferred embodiment the microparticles and/or spray dried supports of this invention are substituted for the silica supports in US 5,240,894, which is herein incorporated by reference. In another embodiment of this invention, a suspension of microparticles in water is freeze dried or mixed with electrophilic hydrocarbons, to remove the water without causing agglomeration into macroparticles. The microparticles may then be suspended in hydrocarbon or the like, with hydrocarbon soluble or suspended catalysts and/or components and then spray dried. In another preferred embodiment of this invention the microparticles form supports that have pore radius sizes that are relatively uniform and may be up to about 100,000 nanometers, preferably from about 50 to about 50,000 nanometers, even more preferably about 1500 to about 5000 nanometers. In a preferred practice of this invention, an emulsion polymerized polymer is suspended in a liquid medium such as water, alcohol, hexane and the like, and is forced at high pressure through a small orifice onto a surface. The deposited polymer is allowed to dry, or otherwise separated from the liquid medium, and the resulting polymer macroparticles, usually of up to 300 micrometers in size, are preferably dried and used as a polymeric catalyst support. Drying techniques include heat, vacuum, freeze drying, evaporation, and the like. The polymer is preferably dried to a free flowing state, collected and used as a support. Preferred liquid media depend on the desired end product and the steps necessary to attain it. For example, MgCl2, a typical Ziegler-Natta catalyst support component, is soluble in water and can be simply added to the products of a preceding emulsion polymerization and then spray dried or added, after the emulsified polymer particles are spray dried, to the macroparticles in water or another liquid media. In contrast, alumoxanes, especially methyl¬ alumoxane, are desirably kept in a water and oxygen- free environment. In this situation, the microparticles may be separated from a water emulsion latex in such a way as to prevent agglomeration into macro-particles (i.e., freeze dried), then resuspended in microparticle form in a hydrocarbon or other non- water medium with the alumoxane, and thereafter spray dried. Preferred liquid media include water, hydrocarbons, and the like. The hydrocarbons may be any linear, cyclic or branched, substituted or unsubstituted C^ to C^ Q O hydrocarbon. Preferred examples include pentane, hexane, toluene, xylene, cyclopentane, methyl cyclopentane, benzene, methyl chloride, and the like. Care should be exercised in selecting media for particular supports and catalyst components. For example, alumoxanes and cyclopentadienyl compounds are sensitive to water and air, and thus are preferably suspended in a hydrocarbon media. In another preferred embodiment, the spray dried polymer support is dehydrated to drive off all moisture and/or residue liquid medium. This dried support is then contacted with a liquid medium containing catalyst, catalyst component or catalyst precursor. This combination may then be dried such that the catalyst and/or catalyst component is deposited on or in the polymeric support. Likewise, this invention also contemplates placing the catalyst, catalyst component or catalyst precursor to be supported into the emulsion prior to polymerization or addition to the emulsion after polymerization but before spray drying. Further, the catalyst, catalyst component or catalyst precursor to be supported may be added onto the aggregate prior to spray drying or addition to the aggregate after spray drying. Likewise, the polymer particle may be "dried" several times. For example, the emulsified polymer is freeze dried to a water free state, suspended in an alcohol then spray dried to achieve a final aggregate form. In another embodiment, the microparticles could be isolated as dry, free flowing powder and slurried in hydrocarbon liquid. The microparticles will then be impregnated with catalyst precursor material by surface absorption or the microparticles could be added to gCl 2 dissolved in an alcohol or an ether and then spray dried to form the macroparticles. The supported catalyst can then be used in the gas phase, slurry phase or high pressure polymerization of olefin. For example, MgCl 2 will be added to the water medium followed by spray drying to form the aggregates. The result will be homogeneous distribution of MgCl 2 in the intersticies of the primary micro-particles comprising the final aggregates. The MgCl 2 loaded aggregates will be isolated as dry, free flowing powder and slurried in hydrocarbon liquid after which Ziegler-Natta catalyst preparation will proceed using techniques well known in the art. In another case, hydrated AI 2 (80 4 ) 3 will be added to the water medium followed by spray drying to form the aggregates. These will be separated and added to a hydrocarbon solution of trimethylaluminum to form methyl-alumoxane (MAO) in situ. The MAO loaded aggregates will be the basis for numerous metallocene catalyst preparations. Spray Drying In general, spray drying is a known technique that can be practiced in a variety of ways. Of the many methods and equipment available to spray dry a substance the inventors will only list a few here for convenience and brevity. However this in no way should be construed as limiting the invention. Some known commercial spray dryers are manufactured by Niro Atomizer, Inc. , Beckman, Stork-Bowen Engineering, Inc. and Swenson Process Equipment. Further information on spray drying techniques is located at page 96 to 99 in volume 21 of the Kirk-Othmer Encyclopedia of Chemical Technology, 3rd Ed. published by John Wiley and Sons, New York; and in Impact of Spray Dryer Design on Powder Properties. Masters, Keith (Niro/Soeborg DK-2860, Den.) Drying 91, [Sel. Pap. Int. Drying Symp.] 7th meeting date 1990, 56-73; Analysis of Spray Drying Systems. Holm Petersen, J.E., Agarwal, H.C. (Larsen and Toubro Ltd, Bombay India) Chem Age India, 21(3) 227-34, 1970; and Spray Drying: A Traditional Process for Advanced Applications. Shaw, Fred, AM.Ceram. Soc. Bull., 69(9) 1484-9, 1990, all of which are incorporated by reference herein. The size of the agglomeration particle, i.e., the dried particle of emulsion polymerized polymer, can be controlled by varying the nozzle size, pressure, and shear rates and the like, of the spraying apparatus. Similarly, the emulsion polymer microparticle size can be controlled by manipulating the polymerization conditions, such as surfactant concentration, polymerization rate, catalyst or initiator concentration, reaction temperature and the like. Specifically, one of ordinary skill in the art will appreciate that the many known emulsion polymerization techniques, such as emulsion, micro-emulsion, mini- emulsion and the like can all be used in the practice of this invention. Both conventional hot air drying and fluid energy mill drying can be used. The supports of this invention have the advantage of producing polymer with extremely good composition distribution, particle size, particle morphology and particle size distribution. In preferred embodiments the polymer product has a composition distribution breadth index (CDBI) of greater than 50 %, preferably greater than 60 %, even more preferably greater than 80%. Further, the polymer products have good morphology, granular, powdery or better and high bulk density. Further, the particle size distribution is narrow. Indeed, the use of emulsion polymerized polymers, which characteristically have very small and controlled particle sizes when compared to silica gel or metal oxide supports leads to exceptional final product properties. Composition distribution and CDBI are defined and described in PCT Publication WO 930393, published Feb. 18, 1993, which is incorporated by reference herein. An advantage of using the supported catalyst of current invention is to have better control of the physical properties of the olefin polymerization catalyst and the final polymer products. Loading each primary particle with catalyst precursor will ensure a homogeneous physical distribution of active catalyst to yield product particles without internal voids and having high internal bulk density. Furthermore, the ability to synthesize the final catalyst on/in the primary particles prior to forming the aggregates could reduce the chemical diversity of catalyst active sites and improve the composition distribution of copolymer products. Additionally, the ability to control the shape, particle size and size distribution of the aggregates will yield spherical product particles free of fines and with excellent flow, packing and bulk density properties. Elimination of pelletizing could also be possible. The thus supported catalysts may be used to polymerize olefins, preferably C2 to C 3 0 α-olefins, even more preferably ethylene, propylene, butene, hexene, octene alone or in combination with other monomers in gas, bulk, solution, slurry and high pressure phases, preferably in gas phase. The examples below are for illustration purposes only and are not meant to limit the scope of this invention. EXAMPLES 35 g of styrene, 0.8g of Vinol 523™ (a polyvinyl alcohol manufactured by Air Products, Allentown, Pa.), 0.26g of Aerosol OT and 0.1 g of 2,2'-azobis (2-methyl- propionitrile) (AMPN) initiator were placed in 65g of water in a one liter reactor and allowed to react for 5 hours at 50 degrees C. A latex emulsion of 0.05 to 2.0 micrometer particles was formed. The sample was divided in half. The first component was spray dried using a Buchi laboratory spray drier set at a chamber temperature of 150°C. 6 weight percent of MgC12 was dissolved into the second sample with mild agitation until completely dissolved. The second sample was then spray dried in the same manner as the first. Figure 1 is an electron micrograph of the first sample and figure 2 is an electron micrograph of the second sample. Note the uniformity of the microparticles and their agglomeration into larger macro-particles in figure 1. As is apparent from the foregoing general description and the specific embodiments, while forms of the invention have been illustrated and described, various modifications can be made without departing from the spirit and scope of the invention. Accordingly, it is not intended that the invention be limited thereby.

Claims: Claims : 1. A method for forming polymeric catalyst supports comprising spray drying an emulsion latex. 2. A method for forming polymeric catalyst supports comprising: 1) combining monomer, surfactant and free radical initiator in water to form polymeric microparticles having and average diameter of 0.005 to 5.0 micrometers, and 2) spray drying the particles. 3. A method for forming polymeric catalyst supports comprising suspending polymer microparticles having an average diameter of 0.005 to 5.0 micrometers in a liquid media and spray drying the media containing the microparticles. 4. The method of any of the preceding claims wherein the polymer microparticles are polymers of one or more of styrene, alpha-methylstyrene, methylstyrene, para-chlorostyrene, para-methylstyrene, acrylic acid, 2-ethyl-hexyl acrylate, vinyl versatate, vinyl chloride, vinyl acetate, methyl acrylate, methyl methacrylate, ethyl acrylate, glycidylmethacrylate, divinylbenzene, butyl acrylate, n-octyl acrylate, vinylidene chloride, acrylamide, 2-hydroxy-ethyl- acrylate or methyl acrylic acid; and optionally further include a crosslinkable comonomer, preferably at up to 25 weight percent, based upon the weight of the copolymer. 5. The method of any of the preceding claims where the microparticles from into macroparticles having an average diameter of up to 300 micrometers, preferably 10 to 150 micrometers. 6. The method of any of the preceding claims wherein a catalyst or catalyst component is combined with the microparticles or suspended in latex prior to spray drying. 7. The method of claim 6, wherein the catalyst or catalyst component is an alumoxane, a non-coordinating anion a metal oxide, an organoaluminum compound or a cyclopentadienyl transition metal compound. 8. A supported catalyst or catalyst component comprising polymeric micro-particles having an average diameter of 0.005 to 5.0 micrometers and catalyst or catalyst component. 9. The supported catalyst of claim 8 wherein the polymeric micro-particles have agglomerated into macroparticles having an average diameter of 10 to 300 micrometers. 10. A process for polymerizing olefins comprising contacting monomer and the supported catalyst or supported catalyst component produced by any of the above claims in gas phase, slurry phase, or high pressure in a polymerization zone under polymerization conditions. 11. A supported catalyst comprising a spray dried emulsion polymerized latex and catalyst. 12. The supported catalyst of claim 11 wherein the latex comprises polymer particles having an average diameter of about 0.005 to about 5.0 micrometers. 13. The supported catalyst of claim 11 wherein the polymer particles are polymers of one or more of styrene, alpha-methylstyrene, methylstyrene, para- chlorostyrene, para-methylstyrene, acrylic acid, 2- ethyl-hexyl acrylate, vinyl versatate, vinyl chloride, vinyl acetate, methyl acrylate, methyl methacrylate, ethyl acrylate, glycidylmethacrylate, divinylbenzene, butyl acrylate, n-octyl acrylate, vinylidene chloride, acrylamide, 2-hydroxy-ethyl-acrylate, vinyl cyclohexane, vinyl cyclohexene or methyl acrylic acid. 14. The supported catalyst of claim 11 wherein the catalyst comprises one or more of: 1) a cyclopentadienyl transition metal compound; 2) an alumoxane; 3) a non-coordinating anion; 4) a metal halide: or 5) a metal oxide.

Inventors: SPECA ANTHONY NICHOLAS, YANG HENRY WU-HSAING, SPECA, ANTHONY, NICHOLAS, YANG, HENRY, WU-HSAING
Applicants: EXXON CHEMICAL PATENTS INC, EXXON CHEMICAL PATENTS INC.
Application year: 1995
Main classification: C08F4
IPC codes: B01J31, B01J32, B01J37, C08F4, C08F10