MXPA99007611A - Improved control of solution catalyst droplet size with an effervescent spray nozzle - Google Patents

Abstract

The present invention teaches the use of an effervescent nozzle to deliver liquid catalyst to a gas phase polymerization system.

Description

IMPROVED CONTROL OF CATALYTIC DROP SIZE IN SOLUTION WITH AN EFFERVESCENT SPRAY NOZZLE Field of the Invention A method for controlling the size of liquid catalyst droplets entering a gas phase polymerization reactor to prevent the formation of large scale particles resulting from the use of liquid catalysts is taught herein. effect, using one. effervescent spray nozzle that produces fine catalyst droplet dispersion, resulting in small spherical primal particles and agglomerates of small particles.

Background of the. Invention U.S. Patent A No. 5.31.7..036 teaches the gas phase polymerization of olefins with catalysts in liquid form. In such systems, the particle size of resin can be controlled by spraying the liquid catalyst into an area that is substantially free of resin as described in the US patent application Serial No. 08 / 659,764. which is incorporated herein by reference. This process allows a short period of time for the spraying drops to be subjected to evaporation and polymerization before contacting the polymer particles already in the reactor, thereby reducing the tendency of the droplets to adhere to themselves. The "thin particulate" zone is preferably created by feeding a stream of heated monomer or cyclic gas to the reactor side. Without these arc, these feed systems often provide particle agglomerates that restrict the reactor's operating capacity. particles exhibit a scaly or hollow sphere morphology and result in bulk densities below 160 kg / m3. These particles have a high cross-sectional mass ratio and are easily trapped outside the upper part of the fluidized fleck, and thus they accumulate in the cycler gas cooler, the compressor suction screen and the distributor plate. These particles also restrict the flow of resin out of the reactor and into the downstream transport lines. Avoiding these types of particles is essential for the commercial operation of catalysts in the liquid form.

SUMMARY OF THE INVENTION It has been found that the use of an effervescent nozzle to deliver a catalyst in liquid form eliminates the formation of large catalyst droplets. This reduction in the formation of large catalyst droplets allows control of the catalyst particle size and thus, the polymer particle size, preventing the formation of large agglomerates of flaky resin. This mouthpiece also allows the. control of the final particle size, of resin varying the flow rates of the atomization gas and / or the isopentane catalyst diluent.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates an exemplary effervescent nozzle for use in accordance with the. present invention. Figure 2 is a graph indicating the dependence of the catalyst particle size on the liquid catalyst and the gas flow rates in an effervescent nozzle, Detailed Description of the Invention It is suspected that the large hollow polymer groups that can be produced when a catalyst is used in a liquid form in a gas phase polymerization reactor result from the large catalyst droplets, which are formed either in the injection tube or during the coalescence in the spraying of liquid. Whether in flight, or during contact with resin in the reactor, these large droplets make contact with a large number of small droplets or particles that adhere to the drop surface. The solvent, if any, in the. Catalyst droplet evaporates, depositing the catalyst on the inner surface of the spherical assembly. This deposited catalyst helps the polymerization at this site and in this way cements the small particles towards. the surface of the expanding spherical group, which can eventually break open producing a scaly structure. In this way, the prevention of the formation of these large gofas of catalyst is believed to provide a solution to the excessive agglomeration and scaling problem. Currently, it has been found that the size of the Drops can be controlled through the proper use of an effscent nozzle. With the effscent nozzles, a stream of liquid or gas is passed through an inner tube, while a liquid or gas is passed cocurrently through an annular space defined by the inner tube and a concentric outer tube. The flow direction of the liquid and gas is generally along the central axis of the tubes. The solution of catalyst or atomizing gas are fed through their respective entrances and exit through a common hole in the spraying tip, towards the tip of the inner tube, although not necessarily at the end, holes are found (holes ) that allow the gas to enter the liquid, the gas is introduced into the liquid that flows cocurrently near the common exit orifice. In this way, the pieces of liquid are prevented and the constant formation of drop occurs. The gas bubbles that form are forced through a hole in the tip of the outer tube, forcing the flow of liquid cocurrent along the outer edge of the hole. _The thin film of liquid in the orifice wall is ejected from the orifice in thin sheets that disintegrate into small droplets. The gas bubbles are considered to rapidly increase in volume as they exit the orifice, providing additional energy that breaks down the liquid. in small droplets, This is a distinction over certain delivery systems in which the direction of gas and liquid flow is the same. both driving for the delivery of the catalyst to the reactor, Additionally there is no separate mixing chamber for gas and liquid; rather, the two phases are mixed a. average current, It is observed that the effervescent nozzles do not change the flow direction of the gas and liquid at the point where they have been in combination, instead, the spraying is in the direction of flow of the power lines. However, the effervescent nozzle may be a perpendicular nozzle where the gas and liquid after which they have been combined exit through the orifice in a direction perpendicular to the direction of flow. The nozzle may produce droplets of a desired average size ( 0.005 to 0.30 mm) within a narrow size distribution, the droplet size can be adjusted without disturbing the in-process polymerization reaction by regulating the liquid and gas flow rates. A. Narrow distribution of droplet size, from about 0.005 to about 0.300 mm. preferably around 0.010 to 0.075 mm, it can prevent the formation of large agglomerates resulting from large droplets and the formation of fines resulting from small droplets. Under many conditions, however, a broad droplet size distribution is acceptable since smaller droplets can agglomerate to a certain extent with the resin in the reactor and larger droplets can form particles up to 0.5 cm that can be easily fluidized. as long as the particle fraction is. sufficiently low, preferably less than about 10% and more preferably less than 2% by weight of the total resin in the bed.

Catalyst Drop Size Control The predicted droplet size of an effervescent spray can be easily calculated based on the following equations: a = P? sr Eq. 4 1 + pLALR where D32 is the diameter of the drop of liquid that leaves the hole in micrometers; pL is the liquid density in g / cm3; pA is the gas density in g / cm3, or is the surface tension in dyne / cm; uL is the liquid viscosity in cP (1 cP = 100 g / cm s) dt, is the thickness of the liquid film on the orifice wall in cm; dA is the diameter of the gas core in the center of the hole in cm; ALP is the ratio of mass flow from gas to liquid sr is the sliding ratio o_ gas velocity and liquid alpha is the fraction of gas column in the orifice. The results of the sample calculations in the exemplary nozzle described under «< = illustrated in Figure 2 Calculations are based on the system of nitrogen / isopentane at 1962 kPa and 7 SC It can be seen that the average droplet size can be changed through the desired scale very easily by changing the flow rate of liquid and total gas through a regularly narrow scale, For example, if 5 kg / hr of catalyst and cocatalyst were the desired flow rates to the reactor, and if no solvent was used and if the gas supply regime (v. .gr, nitrogen) outside 15 kg / hr, then the calculated drop size would be approximately 0.017 mm, if the gas feed rate were decreased a. 5 kg / hr, and the total liquid regime will increase to 15 kg / hr co-metering 10 kg / hr of isophane, then the calculated drop size would be 0.069 mm, in this way, the drop size is very sensitive to. relatively small changes in gas and liquid feed rates. This drop size control is vital for the control of the final resin particle size. In contrast, control of droplet size between 0.017 and 0.069 millimeters with an injection tube would be possible only with regimes of f 1"O O H H 9 ^ t ab l ^? T10!" 1 t * ^? l owa rí c? ? a o rio a fnm i a r? í? n -10 times higher than those mentioned above, The use of this model of size / flu or drop regime can be linked operationally (through computer, live operator or other means) to specific reactor conditions and controls, which would allow the control of catalyst droplet size relative to the polymer particle size in the reactor. The polymer volume density is known to decrease in the presence of unwanted larger particles. With volume density fluctuations that are commensurate changes in the bed level and the width of the fluidization bands that illustrate the bed oscillations. If the polymer particles are too small, they tend to accumulate in the upper part of the reactor and can be discerned by detecting changes in fluidized volume density, bed level and high bed level. Based on these readings, appropriate changes can be made to the flows of liquid and gas in the nozzle to adjust the particles to within a desired scale to maintain the resin size during the course of the polymerization, Such control can be achieved separately from the catalyst flow rate if a diluent is used liquid for the catalyst, ie, the level of diluent can be controlled separately from the catalyst feed rate. As can be understood by one of experience in this field, this can be done using automated control technology. Additional control of the average particle size can be achieved by using multiple effervescent nozzles or a combination of effervescent and other atomizing devices, each creating a single drop size. Relative catalyst feed rates can then be changed to control the average particle size total, additional, multiple nozzles could be used to atomize different catalysts, of different solvent compatibilities and particle formation tendencies, to produce broad or bimodal molecular weight polymers and comonomer distributions in a single reactor, Catalyst, Any type of polymerization catalyst can be used in the present process, as long as it is stable and sprayable or atomizable when in liquid form, a single liquid catalyst can be used, or a liquid mixture of catalysts can be used if desired. These catalysts are used with cocatalysts and promoters well known in the art Examples of suitable catalysts include; A, Ziegler-Natta catalysts, including titanium-based catalysts such as those described in U.S. Patents. Nos. 4376,062 and 4,379,758. Ziegler-Natta catalysts are typically complex agnesium / titanium / electron donors used in conjunction with an organoaluminum cocatalyst, B, Chromium-based catalysts such as those described in U.S. Patent Nos. 3,709,853; 3,709,954; and 4, 077,904. C, Vanadium-based catalysts such as vanadium oxychloride and vanadium acetylacetonate, such as those described in U.S. Pat. No, 5,317,036, D, Metallocene catalysts, E, Cationic forms of metal halides, such as aluminum trihalides, F, Cobalt catalysts and mixtures thereof, such as those described in U.S. Patents. Nos. 4,472,559 and 4,182,814, G,. Nickel catalysts and mixtures thereof such as those described in U.S. Patent Nos. 4,155,880 and 4,102,817, H. rare earth metal catalysts, ie, those containing a metal that it has an atomic number in the Periodic Table from 57 to 103, such as compounds of cerium, lanthanum, praseodymium. gadolinium and neodymium. Especially useful are carboxylates, alcoholates, acetylacetonates, halides (including ether and alcohol complexes of neodymium trichloride), and allyl derivatives of said metals. Neodymium compounds, particularly neodecanoate, octanoate and neodymium versatate are metal catalysts. of rare earth more preferred. Rare earth catalysts are used to produce polymerized polymers using butadiene or isoprene. Catalyst compositions comprising a metallocene catalyst in liquid form and an activating cocatalyst are preferred among these different catalyst systems. The practice of this invention is not limited to any particular class of metallocene catalyst. Accordingly, the catalyst composition can comprise any unsupported metallocene catalyst useful in polymerization of olefin in suspension, in solution, in volume or in gas phase. One or more of a metallocene catalyst can be used. For example, as described in U.S. Patent, A. No. 4,530, 914, at least two metallocene catalysts can be used in a single catalyst composition to achieve an amplified molecular weight distribution polymer product. Metallocene catalysts with organometallic coordination complexes of one or more fractions // - linked in association with a metal atom from Groups IIIB to VIII or the rare earth metals of the Periodic Table. The mono-, bis-, and tris-cycloalkane-dienyl / bridged metal compounds are the most common metallocene catalysts, they are generally of the formula; lL) and? t z (L ') MH (x-y-l) (II) wherein M is a metal of groups IIIB to VIII of the Periodic Table; L and L 'are identical or different p-linked ligands to M, preferably cycloalkadienyl groups such as cyclopentadienyl, indenyl or fluorenyl groups optionally substituted with one or more hydrocarbyl groups containing 1 to 20 carbon atoms; P1 is a substituted or unsubstituted alkylene radical of Ci-Cf, a radial dialkyl or diaryl germanium or silicon, or an alkyl or aryl phosphine or amine bridging at L and L '; each X is independently hydrogen, an aryl, alkyl, alkenyl, alkylaryl or arylalkyl radical having 1-20 carbon atoms, a hydrocarboxyl radical having 1-20 carbon atoms, a halogen, R2C02-, or R22NC02-, wherein each P2 is a hydrocarbyl group containing 1 to about 20 carbon atoms; n and m are each 0, 1, 2, 3, or 4; and it is O, 1, or 2; x is 1, 2, 3, or 4 depending on the valence state of M; z is 0 or 1 and is O when y is O; and x-y3 1, Illustrative but non-limiting examples of metallocene catalysts represented by formula II are dialkyl metallocenes such as bis (cyclopentadienyl) thio anion dimethyl, bis (cyclopentadienyl) titanium diphenyl, bis (cyclopentadienyl) zirconium dimethyl, bis (cyclopentadienyl) zirconium diphenyl. bis (cyclopentadienyl) hafnium methyl and diphenyl, bis (cyclopentadienyl) titanium di-neopentyl, bis (cyclopentadienyl) zirconium di-neopentyl, bis (cyclopentadienyl) titanium dibenzyl. bis (cyclopentadienyl) zirconium dibenzyl, bis (cyclopentadienyl) vanadium dimethyl, monoalkyl metallocenes such as bis (cyclopentadienyl Jvanadium dimethyl chloride; bis (cyclopentadienyl) titanium ethyl chloride; bis (cyclopentadienyl) titanium phenyl chloride; cyclopentadienyl) zirconium methyl, bis (cyclopentadienyl) zirconium ethyl chloride, bis (cyclopentadienyl) zirconium phenyl chloride, bis (cyclopentadienyl) titanium methyl bromide; trialkyl metallocenes such as cyclopentadienyl titanium trimethyl, cyclopentadienyl zirconium triphenyl and cyclopentadienyl zirconium trineopentyl, cyclopentadienyl zirconium trimethyl, cyclopentadienyl hafnium triphenyl, cyclopentadienyl hafnium trineopentyl and cyclopentadienyl hafnium trimethyl; monocyclopentadienyl titanocenes. such as pentamethylcyclopentadienyl titanium trichloride, pentaethyloxy-pentaethylene-titanium trichloride; bis (pentamethylcyclopentadienyl) titanium diphenyl, the carbene represented by the formula bis (cyclopentadienyl) titanium = CH2 and derivatives of this reagent compounds bis (cyclopentadienyl) titanium substituted (IV) such as diphenyl or dichloride, bis (indenyl) titanium diphenyl or dihalide, bis (methylcyclopentadienyl) ITANIO • compounds cic? opentadienil titanium trialkyl dialkyl, tetraalkyl and pentaalquilo such as diphenyl or dichloride, bis (1, 2-dimethylcyclopentadienyl) titanium diphenyl or dichloride, bis (1, 2-diethylcyclopentadienyl) titanium; complex silicon, phosphine, amine or carbon bridged cyclopentadiene such as diphenyl or dichloride silildiciclopentadienil dimethyl titanium diphenyl or dichloride methyl phosphine diclopentadienil titanium diphenyl or dichloride and other metilendiclopentadienil titanium dihalide complexes, and the like; and bridged metallocene compounds such as isopropyl (cyclopentadienyl) (fluorenyl) zirconium dichloride, isopropyl (cyclopentadienyl) (octahydrofluorenyl) zirconium »diphenylmethylene (cyclopentadienyl) (fluorenyl) zirconium dichloride, diisopropyl-methylenebis ( cyclopentadienyl) (fluorenyl) zirconium, diisobutylmethylene (cyclopentadienyl) (fluorenyl) zirconium dichloride, diisobutylmethylene (cyclopentadienyl) - (fluorenyl) zirconium dichloride, diterbutylmethylene- (cyclopentadienyl) (fluorenyl) zirconium dichloride, cyclohexylidene (cyclopentadienyl) dichloride (fluorenyl) ) zirconium, diisopropylmethylene (2, 5-dimethylcyclopentadienyl) dichloride (fluorenyl J-zirconium, isopropyl- (cyclopentadienyl) (fluorenyl) hafnium dichloride, diisopropylmethylene (cyclopentadienyl) (fluorenyl) hafnium dichloride, diisobutylmethylene dichloride (cyclopentadienyl) - ( fluorenil) hafnium, diterbutylmethylene- (cyclopentadienyl) dichloride (fluorenyl) hafnium, cyclohexylidene (cyclopentadienyl) (fluorenyl) hafnium dichloride, diisopropylmethylene (2, 5-dimethylcyclopentadienyl) (fluorenyl) -hafnium dichloride, isopropyl- (cyclopentadienyl) (fluorenyl) itanium dichloride, diphenylmethylene dichloride (cyclopentadienyl) ( fluorenyl) titanium, diisopropylmethylene (cyclopentadienyl) - (fluorenyl) titanium dichloride, diisobutylmethylene- (cyclopentadienyl) (fluorenyl) titanium dichloride, diterbutylmethylene (cyclopentadienyl) (fluorenyl) titanium dichloride, cyclohexylidene (cyclopentadienyl) (fluorenyl) -titanium dichloride dichloride, diisopropylmethyl), 5-dimethylcyclo-pentadienilfluorenil) titanium dichloride, ethylene racemic bis (4, 5, 6, 7-tetrahydro-l-indenyl) zirconium (IV) dichloride racómico dimethylsilyl bis (4, 5, 6 , -tetra-hydro-1-indenyl) zirconium (V), racemic dimethylsilyl dichloride bis (, 5,, 7-tetrahydro-l-indenyl (zirconium (IV). 1, 1, 2, 2-tetramethylsilanylene bis (1-indenyl) zirconium racemic (IV) dichloride, 1, 1, 2, -tetramethyl-silanylene bis (5, 6, 7-tetrahydro-l-indenyl) dichloride zirconium dichloride (IV) dichloride, ethylidene (1-indenyl tetrame-tilciclopentadienil) zirconium (IV) dichloride, dimethylsilyl bis (2-methyl-4-t-butyl-l-cyclopentadienyl) zirconium (IV) racemic dichloride of ethylene bis (1-indenyl) hafnium (IV), racemic dichloride of ethylene bis (, 5, 6, 7-tetrahydro-l-indenyl) hafnium (IV), racemic dimethylsilyl bis (1-indenyl) hafnium (IV) dichloride , racemic dimethylsilyl bis, (5,6,7-tetrahydro-l-indenyl) hafnium (IV) dichloride, 1,1,2,2-tetramethylsilanylene bis (1-indenyl) hafnium (IV) dichloride racic. 1, 1, 2, 2-tetramethylsilanyl 1,4-racemic bis (4,5,6,7-tetrahydro-1-indeyl) hafnium (IV) dichloride, ethylidene (1-indenyl-1, 2,3,4-tetramethyl) dichloride -l-cyclopenta-dienyl) hafnium (IV), ethylene bis (l-indenyl) -titanium (IV) racemic dichloride, ethylene bis (4,5,6,7-tetrahydro-1-indenyl) titanium dichloride (IV ) racemic, racemic dimethylsilyl bis (1-indenyl) titanium (IV) dichloride. dimethylsilyl dichloride bis (4, 5, 6, 7-tetrahydro-l-inde-nyl) racemic titanium (IV), 1,1,2,2-tetramethylsilanylene bis (1-indenyl) titanium- (IV) dichloride racic, dichloride 1, 1, 2 , 2-tetramethylsilanylene bis (4,5,6,7-tetrahydro-1-indenyl) titanium (IV) racemic and ethylidene (l-indenyl-2, 3,4,5-tetramethyl-l-cyclopentadienyl) titanium dichloride ( IV), Particularly preferred metallocene catalysts have one of the following formulas (III or IV); (IV) where; M is a metal of groups IIIB to VIII, preferably Zr or Hf; L is a ligand '-ligated, substituted or unsubstituted coordinated to M, preferably a substituted cycloalkadienyl ligand; Each Q is independently selected from the group consisting of -0-, -NR3-, -CR32- and -S-, preferably oxygen; And it is C or S, preferably carbon; Z is selected from the group consisting of -OR3, -NR3 ,, -CR33-, -SR3, -SiR33, -PR32, and -H with the proviso that when Q is -NR3-, then Z is selected at starting from the group consisting of -OR3, -NR32, -SR3-, SiR33, -PR32, and -H, preferably Z is selected from the group consisting of -OR3, -CR33, and -NR32; n is 1 or; A is a univalent anionic group when n is 2 or A is a divalent anionic group when n is 1, preferably A is a carbamate, carboxylate or other heteroalyl fraction described by the combination Q, Y and Z; and each R3 is independently a group containing carbon, silicon, nitrogen, oxygen and / or phosphorus and one or more groups R3 is a hydrocarbon group containing from 1 to 20 carbon atoms, more preferably an alkyl, cycloalkyl or aryl group; T is a bridging group selected from the group consisting of alkylene or arylene groups, containing from 1 to 10 carbon atoms, optionally substituted with carbon or heteroatoms, germanium, silicone and alkylphosphine; and m is 1 to 7, preferably 2 to 6, more preferably 2 or 3, The support substituent formed by X, Y and Z is a uni-charged polydentate ligand which exerts electronic effects due to its high polarization capacity, similar to the group cyclopentadienyl, In the most preferred embodiments of this invention, the disubstituted carbamates, And the carboxylates they are used Examples of metallocetium catalysts according to formulas III and IV include indenyl zirconium tris (indenylcarbamate, zirconium indenyl tris (pivalate), indenyl zirconium tris (p-toluate), indenyl zirconium tris (benzoate), tris ( (1-methylindenyl) zirconium pivalate, tris (diethylcarbamate) of (methylcyclopentadienyl Jzirconium, tris (cyclopentadienyl pivalate and (pentamethylcyclopentadienyl) zirconium trisinobenzoate.) Preferred examples of these metallocene catalysts are tris (indenyl zirconium diethylcarbamate and tris (pivalate ) of indenyl zirconium, Another type of metallocene catalyst that can be used in accordance with the invention is a constrained geometry catalyst of the formula; / \ Cp Y1 M (X ') a (V) where; M is a metal of Group IIIB to VIII of the Periodic Table of the Elements; Cp is a substituted cyclopentadienyl or cyclopentadienyl group linked to an H5 mode linked to M; Z 'is a fraction comprising boron, or a member of Group IVB of the Periodic Table the Elements and optionally sulfur or oxygen, the fraction having up to 20 non-hydrogen atoms, and optionally Cp and Z' together form a fused ring system; X1 is an anionic ligand group or a neutral Lewis base ligand group having up to 30 non-hydrogen atoms; a is 0, 1. 2, 3 or 4 depending on the valence of M; and Y 'is an anionic or non-anionic ligand group linked to Z' and M comprising nitrogen, phosphorus, oxygen or sulfur having up to 20 non-hydrogen atoms, and optionally Y 'and Z' together form a fused ring system, Restricted geometry catalysts are well known to those skilled in the art and are described, for example, in US Patents Nos. 5,026,798 and 5,055,438 and published European Application No. 0 416 815 A2. Illustrative but non-limiting examples of substituents Z ', Cp, Y', X 'and M in formula v are; Z 'Cp and' X 'M dimethyl-cyclopentat-butyl-chloride titanium silyl dienyl amido methyl fluorenyl phenylmethyl zirconium phenyl amido silyl defensyl indenyl cyclohexane silyl hexyl amido tetramethyl oxo ethylene ethylene tetramethyl cyclopentadienyl diphenyl-methane The invention is also useful in another class of single-site catalyst precursors, di (imine) metal complexes, as described in the PCT No, WO 96/23010. which is incorporated herein by reference, The activating cocatalyst is capable of activating the metallocene catalyst. Preferably, the activating cocatalyst is one of the following; (a) cyclic or branched poly (hydrocarbyl aluminum oxide) s containing recurring units of the general formula - (A1 (R *) 0) -, where P * is hydrogen, an alkyl radical containing 1 to about 12 carbon atoms, or an aryl radical such as a substituted or unsubstituted phenyl or naphthyl group; (b) ionic salts of the general formula [A +] [BR ** 4 ~], wherein A + is a Lewis or Bronsted cationic acid capable of abstracting an alkyl, halogen or hydrogen from the metallocene catalysts, B is boron, and R ** is a substituted aromatic hydrocarbon, preferably a perflusrofenyl radical; and (c) boron alkyls of the general formula BR ** 3, wherein R ** is as defined above. Preferably, the activating cocatalyst is an aluminoxane such as methylaluminoxane (MAO) or modified methylaluoxane (MMAO), or a boron alkyl. Aluminoxanes are preferred and their method of preparation is well known in the art. The aluminoxanes may be in the form of linear alkyl oligomeric aluminoxanes represented by the formula; or oligomeric cyclic alkyl aluminoxanes of the formula; where s. is 1-40, preferably 10-20; p_ is 3-40, preferably 3-20; and R *** is an alkyl group containing 1 to 12 carbon atoms, preferably methyl or an aryl radical such as a substituted or unsubstituted phenyl or naphthyl radical. In the case of MAO, p *** is methyl, while in MMAO, p *** is a mixture of methyl and C2 to C12 alkyl groups wherein methyl comprises about 20 to 80 weight percent of the R * group **, The amount of metallocene catalyst and activator usefully used in the preparation of the catalyst composition, whether the catalyst composition is formed on site as it is being introduced into the reaction zone, or formed before the introduction to the reaction zone, can vary across a broad scale, When the cocatalyst is a cyclic or branched poly (hydrocarbylaluminum oxide) oligomer, the molar ratio of aluminum atoms contained in the poly (hydrocarbylaluminum oxide) to metal atoms The contents of the metallocene catalyst are generally in the range of about 2: 1 to about 1,000,000: 1, preferably in the range of about 10: 1 to about 10,000: 1. and more preferably on the scale of about 50: 1 to about 2,000: 1. When the cocatalyst is an ionic salt of the formula [A +] [BR * 4-] or a boron alkyl of the formula BR + 3, the molar ratio of boron atoms contained in the ionic salt or boron alkyl to atoms The metal content of the metallocene catalyst is generally in the range of about 0.5: 1 to about 10: 1, preferably from about 1: 1 to about 5: 1, the liquid catalyst may be composed of one or more metal compounds in combination with one or more cocatalysts, Alternatively, all or a portion of the cocatalyst can be fed separately from the metal compounds to the reactor. Promoters associated with any polymerization particularly, are generally added to the reactor separately from the cocatalyst and / or metal compounds, If the metal compound and / or the cocatalyst occurs naturally in the liquid form, it can be introduced "clean" in the thin zone of particle. More likely, the liquid catalyst is introduced into the thin particle zone as a solution (single phase, or "true solution" using a solvent to dissolve the metal compound and / or cocatalyst), an emulsion (partially dissolving the catalyst components in a solvent), suspension, dispersion, or pasta (each having at least two phases). Preferably, the liquid catalyst used is a solution or an emulsion, more preferably a solution, as used herein, "liquid catalyst" or "liquid form" includes clean, solution, colloid emulsion, suspension and dispersions of the transition metal or rare earth metal components of the catalyst and / or cocatalyst. The solvents that can be used to form liquid catalysts are inert solvents, preferably non-functional hydrocarbon solvents, and may include aliphatic hydrocarbons such as butane, isobutane, ethane, propane, pentane, isopentane, hexane, heptane, octane, decane, dodecane, hexadecane, octadecane and the like; alicyclic hydrocarbons such as cyclopentane, methylcyclopentane, cyclohexane. cyclooctane, norbornane, ethylcyclohexane and the like; aromatic hydrocarbons such as benzene, toluene, ethylenebenzene, propylbenzene, butylbenzene, xylene, tetrahydrofuran and the like; petroleum fractions such as gasoline, kerosene, light oils and the like; and mineral oils. Also, halogenated hydrocarbons such as methylene chloride, chlorobenzene, ortho-chlorotoluene and the like may also be used. By "inert" it is meant that the material to which reference is made is non-deactivating in the polymerization reaction zone under the gas phase polymerization conditions and is non-deactivating with the catalyst in or outside the reaction zone . By "non-functional", it is meant that the solvents do not contain groups such as strong polar groups that can deactivate active catalyst metal sites. The concentration of catalyst and / or cocatalyst that is in solution that is provided to the thin particle zone can be as high as the saturation point of the particular solvent that is being used. Preferably, the concentration is on the scale of about 0.01 to about 10,000 millimoles / liter, Of course, if the catalyst and / or cocatalyst is being used in the clean form, ie in its liquid state without solvent, it will be comprised of essentially pure catalyst and / or cocatalyst, respectively . The liquid flow rates of catalyst, cocatalyst and activators vary between 5 and 250 kg / hr for commercial scale gas phase reactors, which require gas flow regimes in the range of 5 to 200 kg / hr, Gas An important benefit of the effervescent nozzle is the low amount of inert gas required to atomize the liquid, it is known from atmospheric experiments (Lefebvre, AH, Atomization and Sprays, (Taylor and Francis),) that effervescent nozzles can produce fine sprays at very low gas-to-liquid ratios, 0.03: 1 to 0.05: 1, unlike other gas-aided nozzles that may require gas-to-liquid ratios as high as 3: 1 to 5: 1. At pressures used for gas phase polymerizations, 1400 to 2800 kPa, a proportionately higher ratio of gas to liquid is required to produce fine atomization, for example, at pressures twenty times higher than atmospheric, the mass flow rate of gas of atomization to the nozzle should be increased by a factor of approximately 20 to maintain the same gas-to-liquid velocities, due to the reduced volume of gas, A commercial polymerization reactor with gas mass flow ratios has been well-functioning. liquid between 0.5: 1 to 2: 1, This represents a very efficient use of atomization gas, The optional gases for use in the effervescent nozzle can be any relatively inert to the catalyst so that there is no blockage in the nozzle. Exemplary gases include N2, Ar, He, CR1, C2H &, C3H8, C02, Hx, cyclar gas, Reactive gases (v gr,, olefins) can be used if the catalyst is activated in the reactor, v.gr , the cocatalyst is fed separately, The gas flow rates at the nozzle should be between approximately 2.5 and 100.0 kg / hr, depending on the size of the reactor and particle size control as discussed above, Other Material The effervescent nozzle can also be used to deliver non-catalytic liquids to the reactor, eg, solvents, anti-fouling agents, scrubbers, monomers, antistatic agents, secondary alkyls, stabilizers or antioxidants. Other specific examples include methanol, vertrol, propylene oxide, glyme, water, Atmer-163. hydrogen, metal alkalies of the general formula M3R5g, wherein M3 is a metal of Group IA, IIA or IIIA, P5 is an alkyl or aryl. and g is 1, 2 or 3; zinc alkyls, CHC13, CFC13, CH3CC13, CF2C1CC13. ethyltrichloroacetate, aluminum alkyls, more preferably triisobutylalu inium. The gas in such situations may be the cyclic gas in a gas phase reactor that is operating in condensing mode or may be another inert gas, as used with the delivery of the catalyst. The addition of this liquid can be anywhere to the reaction system eg to the bed, under the bed, above the bed or the cycle line. The use of these additives is well within the experience of those experienced in the bouquet These additives can be added to the separate reaction zone or independently of the liquid catalyst if they are solid, or as part of the catalyst as long as they do not interfere with the desired atomization. To be part of the catalyst solution, the additives must be liquid and capable of dissolving in the catalyst solution.

Nozzle Design The effervescent nozzle for use in the present must be capable of withstanding high pressures (up to 4200 kPa) and temperatures (up to 300aC), and a harsh chemical environment (eg, aluminum alkyls HCl, etc.) , The nozzle should be easily and safely inserted and separated from a reactor without interrupting the operation of the reactor. The nozzle should not be easily plugged by suspended solid contaminants. The nozzle should not allow the return flow of reactive monomer. The nozzle should not allow fouling of the polymer in the reactor. This can be achieved through the use of a bypass gas, that is, gas that is used to reduce the particle density at or near the nozzle inlet, which allows the catalyst to enter the reactor in a thin particle zone at the reactor, or preferably, entering a substantially free area of the polymer. If this bypass gas flows past the nozzle orifice, it will sweep away any resin, keeping the orifice clear, as a bypass gas can be configured - it is described in the E, U, A, No, Series 08 Patent Application / 659,764, The nozzle is constructed of any material that is non-reactive under the selected polymerization conditions, including, but not limited to, aluminum, bronze aluminum, Hastalloy, Inconel, Incoloy, monel, chromium carbide, boron carbide, cast iron , ceramics, copper, nickel, silicon carbide, tantalum, titanium, zirconium, tungsten carbide, as well as certain polymorphic compositions. Stainless steel is particularly preferred.

A preferred embodiment of an effervescent nozzle is illustrated in Figure 1. There is an outer tube 1 and an internal concentric tube 2, the tip 4 of the outer tube is tapered to a point, with a hole 3, which is present at this point The inner tube is sealed at the tip 5, but it has holes 6 along its length. It is observed, however, that the end of the smaller internal tube 5 may be open in certain cases. It is intended that the gas from the nozzle be fed to the inner tube 2 and the liquid catalyst in the outer tube 1, (although this can be reversed) both being fed in the same direction, flowing towards the orifice 3. The gas can form bubbles in the liquid as it exits through the holes 6, The gas forces the liquid out of the hole like a thin film on the walls, leading to thin ligaments and breaking into fine droplets after leaving the hole. It is observed, even when not shown, that there are elements to deliver the liquid to the inlet of the external tube 1 and gas to the inlet of the inner tube 2. The inner tube could vary from approximately 0.159 cm to 1.27 cm, preferably around from 0.3175 cm to 0.635 cm, the outer tube could be as large as about 2.54 cm, preferably about 1.27 cm, and more preferably 0.635 cm, the hole may be between about 0.050 cm to 0.6 cm, preferably between about 0.1 cm and 0.25 cm, The holes in the inner tube could be between about 0.025 cm to 0.3 cm in diameter, preferably between about 0.05 and 0.125 cm. They should be present approximately 1 to 1000, preferably 10 to 100, holes 6 in the inner tube 2, the length of the inner tube, through which the holes are drilled, could be between approximately 0.5 and 25 cm, yet when preferably, the holes are present in the last about 1 to 3 cm of the inner tube. The tip of the inner tube should preferably be about 0.25 to 0.75 cm from the hole, even though, the tip could move closer to the hole or it could move back several centimeters. The spraying tip of the outer tube may have a variety of configurations, v.gr ,, spherical, conical or parabolic; however, the spraying tip of the outer tube preferably has a taper which is preferably about 5 to 15 degrees off the horizontal and allows the gas to flow uniformly around the nozzle tip with minimal turbulence. Turbulence creates flow backward which can deposit liquid catalyst on the external nozzle body, which may subsequently be subjected to polymerization and fouling the nozzle. The high taper angles can be tolerated since the taper outside the horizontal is gradual. The small tip also prevents fouling by not providing a large area for the catalyst and polymer to accumulate. As is known in the industry, these effervescent nozzles can be made by other means and in other configurations, See, v.gr, Lefebvre. A.H. , Ato ization and Sprays, (Taylor and Francis), The only requirement here is that the gas flowing with the stream is forcing the liquid to separate as they both come out of the nozzle, in a particular mode as illustrated in Figure 1, tip 1 of external tube is 0.635 cm outside diameter and the inner diameter of this outer tube 1 is 0.508 cm, This tube 1 is machined to be approximately eight centimeters long, Tip 8 is tapered towards down to a point of 0.15 cm, a 0.10 cm hole 3 is drilled in the tip, a second internal tube 2 is located inside the nozzle tip, which is made of a length of 3.5 m of conventional stainless steel pipe of 0.3175 cm, the end 5 is closed with welding, towards a hemispherical point, and twenty holes are drilled 6 of 0, 05 cm in diameter towards the end of this internal tube. The holes 6 are drilled in two lines of ten holes each. The holes 6 within a line are spaced through a distance of five centimeters, each of the two lines of holes 6 is wrapped around the nozzle tip in a helical pattern through a quarter of the circumference the two rows of holes 6 are deflected by 90E, The outer tube 1 of the nozzle is welded to a 3 m section of conventional 0.635 cm stainless steel pipe. The 0.3175 and 0.635 cm tubes are connected with a 0.635 cm conventional SWAGELOCK pipe (R '), the 0.635 cm tube (with the 0.3175 cm tube mounted inside) connects to the race of the tee , An adapter of 0.635 to 0.3175 cm is used for the extension of 0.3175 cm out of the opposite stroke of the tee, A line of 0.635 cm flows towards the branching of the tee The gas enters the interior of the line from 0 3175 cm through the return of the te and passes to the tip of the tube 2 of 0 3175 cm, where it is dispersed to the liquid and subsequently discharged through the orifice 3 The catalyst solution and cocatalyst is fed through of the annular space between the two tubes 1, 2, through the branching of the te.The catalyst solution is forced into a thin film in the hole 4 and then atomized efficiently as it leaves the hole 4, The tip is placed inside a jet of tip cleaning gas from 450 to 1360 kg / hr of ethylene, which can preferably be heated, which in turn is placed inside a jet of cycle gas of 4,000 to 30,000 kg / hr.

Polymers Illustrative of the polymers that can be produced according to the invention are the following; ethylene homopolymers and ethylene polymers employing one or more C3-C alpha olefins ?; propylene homopolymers and propylene copolymers employing one or more G1-C12 alpha olefins; polyisoprene; polystyrene; polybutadiene; polymers of butadiene copolymerized with styrene; butadiene polymers copolymerized with acrylonitrile; copolymerized isobutylene polymers with isoprene; ethylene propylene rubbers and ethylene propylene diene rubbers; polychloroprene and the like. Preferably, polyethylene is made from 240 to 416 kg / m 3.

Polymerization, The present invention is not limited to any specific type of gas phase polymerization reaction and can be carried out in a stirred or fluidized bed reactor. The invention can be carried out in a single reactor or in multiple reactors (two or more series reactors), In addition to conventional well-known gas phase polymerization processes, the "condensed mode" can be employed. which includes the so-called "induced condensate mode" and "liquid monomer" operation of a gas phase polymerization. The conventional fluidized bed process for producing resins is practiced by passing a gaseous stream containing one or more monomers continuously through a fluidized bed reactor under reactive conditions in the presence of a polymerization catalyst. The product is removed from the reactor. A gaseous stream of unreacted monomer is continuously removed from the reactor and recirculated to the reactor together with the formation monomer added to the recirculation stream. Condensed mode polymerizations are described in US Pat. , Nos. 4,532,399; 4.5898,790; 5,352,749; and 5,462,999. Condensation mode processes are used to achieve higher cooling capacities and, therefore, higher reactor productivity. In these polymerizations a recirculation stream, or a portion thereof, can be cooled to a temperature below the fogging point. in a fluidized bed polymerization process, resulting in condensation of all or a portion of the recirculation stream, the recirculation current is returned to the reactor, the nebulization point of the recirculation stream can be increased by increasing the operating pressure of the system of reaction / recirculation and / or increasing the percentage of condensable fluids and decreasing the percentage of non-condensable gases in the recirculation stream, The condensable fluid can be inserted into the catalyst, reactants and the polymer product produced; it can also include monomers and comonomers. Condensation fluid can be introduced into the reaction / recirculation system at any point in the system. Condensable fluids include saturated or unsaturated hydrocarbons. In addition, the condensable fluids of the polymerization process itself, other condensable fluids, inert to the polymerization, can be introduced to "induce" the condensation mode operation. Examples of suitable condensable fluids can be selected from liquid saturated hydrocarbons containing 2 to 8 carbon atoms (e.g., propane, n-butane, isobutane, n-pentane, isopentane, neopentane, n-hexane, isohexane and other unsaturated C6 hydrocarbons, n-heptane, n-octane and other C7 and Cs hydrocarbons, and mixtures thereof), The condensable fluids may also include polymerizable, condensable comonomers such as olefins, alpha-olefins, diolefins, diolefins containing at least one alpha olefin and mixtures thereof. In the condensation mode, it is desirable that the liquid entering the fluidized bed be dispersed and vaporized rapidly. The polymerization mode of liquid monomer is described in the Patent of E, U, A, No, 5,453, 471, No, Serial of E.U.A. No. 510,375, PCT 95/09826 (US) and PCT 95/09827 (US). when operating in the liquid monomer mode, the liquid may be present throughout the entire polymer bed as long as the liquid monomer present in the bed is adsorbed on or adsorbed onto the solid particulate matter present in the bed, such such as the polymer being produced or fluidization aids (eg, carbon black) present in the bed, as long as there is no substantial amount of free liquid monomer present more than a short distance above the point of entry to the polymerization zone. The liquid mode makes it possible to produce polymers in a gas phase reactor using monomers having condensation temperatures well above the temperatures at which conventional polyolefins are produced. In general, the liquid monomer process is conducted in a light agitated or gas fluidized bed reaction vessel having a polymerization zone containing a bed of growing polymer particles. The process comprises continuously introducing a stream of one or more monomers and optionally one or more inert gases or liquids towards the polymerization zone; continuously or intermittently introducing a polymerization catalyst into the polymerization zone, continuously or intermittently removing polymer product from the polymerization zone; and continuously withdraw unreacted gases from the zone; compress and cool the gases while keeping the temperature within the area below the point of nebulization of at least one monomer present in the area, if only one monomer is present in the gas-liquid stream, is also present at least an inert gas. Typically, the temperature within the zone and the velocity of gases passing through the zone are such that essentially no liquid is present in the polymerization zone that is not adsorbed onto or adsorbed to particulate solid matter, In a preferred embodiment of the present invention, the liquid catalyst in a carrier gas (v.gr ,, nitrogen, argon, alkane or mixtures thereof) is surrounded by at least one gas which serves to move or divert resin particles from the bed outside the trajectory of the liquid catalyst as it enters the fluidization zone and away from the catalyst entry area, thus providing a thin particle zone, The first or particle deviation gas can be selected from the group consisting of gas of recirculation, monomer gas, chain transfer gas (e.g., hydrogen), inert gas or mixtures thereof. Preferably, the gas that bypasses particles is all or a portion of the recirculating gas and the tip cleaning gas is all or a portion of the monomer (e.g., ethylene or propylene) used in the process, EXAMPLES The examples below demonstrate the use of the effervescent nozzle during the production of ethylene-hexene copolymer in a commercial scale reactor. A comparative example shows that hollow, squamous particles can be formed when conventional injection tubes are used to spray catalyst into the reactor. The catalyst used for all the examples was a metallocene based on Zr in a 2% by weight solution in n-hexane. The solution was used as received for Example 1, For Example 2, 50% was added to this material by weight of l-hexene, so that the final catalyst concentration was 1.33 weight percent. The catalyst was mixed in line with MMAO 3A (modified methyl alumumoxane) from Akzo Nobel at 7.15 wt.%, The additional dilution was performed by adding isopentane to the mixture before introducing it into the reactor, the catalyst feed rates MMAO were adjusted to provide a final Al: Zr molar ratio between 330 and 340, The reactor was 2.4 m in diameter and operated with a bed height of 11.6 m and a surface gas velocity of approximately 0.6 m. / sec, The total reactor pressure was 1962 kPa, ATMER-163 anti-stat (ICI Chemicals) was added, as was necessary to the reactor to control the accumulation of electrostatic charge. The catalyst atomization devices used in all the examples were placed at the end of the 0.635 cm outer diameter stainless steel tube, and could be separated from the reactor during the operation. This tube passes through a program tube 40 of 1.91. cm (2.1 cm inner diameter), A current of 1000 to 1180 kg / hr of ethylene monomer at a temperature between 85aC and 952C was fed through the annular space between the 0.635cm tube and the 1.91cm tube This monomer stream is referred to as the nozzle cleaning gas. The tube of 1.91 cm, was placed in the center of the 15.24 cm tube (internal diameter of 15.4 cm), through which were fed between 22,700 and 29,500 kg / hr of cyclar gas, known as gas from particle deviation. The 15.24 cm tube extended 53 centimeters in the reactor, the 1.91 cm tube extended 61 centimeters in the reactor, and the spray nozzle extended 66 centimeters to the reactor, in a location 2, 4 m above the distributor plate.

Comparative Example No. 1 A seed bed was charged to the reactor and dried to 45 ppm of water. It was pressurized to 790 kPa of nitrogen and then 36 kg / hr of 10 wt.% TEAL in isopentane were fed to the reactor for two hours and were allowed to circulate for 1 hour. The reactor was filled with 1633 kPa of ethylene with a hexene ratio of 0.033, and the temperature of the fluidized bed was adjusted to 76SC, The catalyst and MMAO were contacted with a static mixer near the injection point in the reactor so that their contact time before dilution with isopentane out about 30 seconds. Catalyst and cocatalyst solution were fed to the reactor through an internal tip diameter 0.30 cm injection tube with a current of 54.5 kg / hr of nitrogen atomization gas. The reaction started immediately after the solution of catalyst reached the reactor, During the next 3 hours it was observed that hollow and squamous particles were being formed in the reactor with this atomization configuration, These particles were approximately 3 to 6 mm, during the first three hours of operation, these particles they grew in number so that they reached 1% by weight of all the resin in the reactor. Previous experience had shown that they could be expected to continue to grow in size and number until they caused operational difficulties. The average particle size decreased slightly from 0.704 to 0.648 mm during this period. indicative of the ability of the nozzle to form a large fraction of new particles, it would be expected, however, that the average particle size would eventually increase above an acceptable threshold with continued formation of particles with scaly or hollow morphology.

No, 2 The reactor was operated for 10 days using a different nozzle for comparison, then. the effervescent nozzle as described as an exemplary model above was installed within the pipeline of the tip cleaning and particle deviation gases, the catalyst and MMAO were contacted for approximately 30 minutes before being diluted with isopentane and transported To the nozzle, the effervescent nozzle was more efficient in its use of atomization gas, so that only 6.3 to 8.1 kg / hr of nitrogen was required for fine droplet formation. The reactor was operated for two days with this nozzle without the formation of the hollow squamous particles described in Example 1. The particle morphology with the effervescent nozzle was a combination of spheres or small groups of solid spherical particles, resulting in desirable average particle sizes between 0.50 to 0.76. mm, with densities of volume sedimented from 318 to 373 kg / m3, Average Particle Size Control During the operation with the effervescent nozzle, the ability to control the average particle size was demonstrated as shown in Table 1. The proper handling of the nitrogen atomizing gas and the isopentane diluent allowed corrections in APS when it is either too small or too large, the effervescent nozzle was first operated with a nitrogen carrier rate of 6.4 kg / hr and an isopentane feed rate of 7.7 kg / hr, This caused the APS will decrease from 0.610 to 0.508 mm (Example 2A), This downward trend was arrested by decreasing the amount of isopentane diluent in the catalyst from 7.7 to 3.6 kg / hr (Example 2B), This concentrated to the catalyst so that each drop grew more in size. Agglomeration was also more likely with the catalyst concentration increased. As a result the APS increased to 0.599 mm, the reactor was then -changed so that the resin density decreased from 0.915 to 0.908 g / cm3. The tendency is for increased agglomeration at lower densities, so that the APS tended upwards to 0.762 mm (Example 2C), This is still a desirable APS, but the APS control was shown to increase the N2 flow rate of 6. 6 to 8.1 kg / hr, which decreased the drop size, and increasing the amount of isopentane from 3.6 to 5.4 kg / hr, which diluted the amount of catalyst in each new resin particle, thereby reducing its final size. The APS was decreased to 0.584 mm (Example 2D).

Table 1 Example 2A 2B 2C 2D Device Nozzle Tube Nozzle Nozzle Atomiza Nozzle- Inyec- Eferves- Eferves- Eferves- Efferves- tion cente cente cente cente Catalyst feed rate (kg / hr) 0.66 0.30 0.30 0.43 0.36 MMAO feed rate (kg / hr) 3.3 1.1 1.1 1.5 1.3 Isopentane feed rate (kg / hr) 5.9 7.7 3.6 3.6 5.4 Table 1 (continued) Example 1 2A 2B 2C 2D Nitrogen feed rate (kg / hr) 54.5 6.4 6.3 6.6 Reactor temperature (aC) 76 75 75 70 70 Partial pressure of ethylene (kPa) 1585 1448 1448 1516 1516 C6 / C2 molar ratio 0.033 0.0285 0.0289 0.0318 0 0327 Resin density (g / cc) 0.91 0.915 0.915 0.908 0.090? Average particle size (mm) Initial 0.704 0.610 0.457 0.533 0.762 Final 0.648 0.508 0.559 0.762 0.584 Volume density (kg / m3) 358 373 362 346 318 Morphology Groups Spheres Spheres Spheres Spheres of group- and group- and group- and group- after small positions 1% by weight scales and hollow particles of 3 to 6 mm

Claims (1)

1. - A method comprising using an effervescent nozzle to deliver a liquid catalyst to a gas phase polymerization reactor in a catalytically effective amount, 2 - A method according to claim 1, wherein the effervescent nozzle has a stream of gas supply and a liquid catalyst feed stream. 3 - A method according to claim 2, wherein the flow rates of the liquid and gas streams are operationally linked to changes in the bed fluidization characteristics. 4. A method according to claim 2, wherein the stream additionally contains a liquid other than a catalyst. 5 - A method according to claim 2, wherein the gas is selected from the group consisting of: N2, Ar, He, CH4, C2H6, C3HB, C02 and H2 6, - A process in accordance with claim 1, wherein the particle bypass gas allows the catalyst to enter the reactor in a zone of low polymer density. 7, - A method according to claim 3, wherein the liquid catalyst is fed through multiple effervescent nozzles, each controlled nozzle to deliver different sizes of catalyst droplet. 8, - A method according to claim 2, wherein the polymerization process has a recirculation line and operates in condensation mode, 9 - A method according to claim 2, wherein the liquid is a suspension of sustained catalyst, prepolymerized catalyst or a suspension of particulate matter, 10 - A method according to claim 1, further comprising feeding a cocatalyst to the reactor other than via the effervescent nozzle. 11. A method for controlling the particle size of catalyst delivered to a gas phase polymerization reactor comprising delivering the catalyst with a gas and a liquid, the gas and liquid being selected so that the viscosity, surface tension and The density of the liquid, the density of the gas and its relative flux ratios approximate the desired particle size in accordance with the following equations: a = 1 + ALA * where D32 is the diameter of the. drop of liquid coming out of the hole in micrometers; pL is the liquid density in g / c3; pA is the gas density in g / cm3 or is the surface tension in dyne / cm; uL is the. liquid viscosity in cP (1 cP = 100 g / cm s) dL is the thickness of the liquid film on the orifice wall in cm; dA is the diameter of the gas core in the center of the hole in cm; ALR is the ratio of mass flow from gas to liquid; sr is the sliding or velocity ratio of gas and liquid; and alpha is the volume fraction of gas in the hole,