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Publication numberUS20050238560 A1
Publication typeApplication
Application numberUS 11/158,827
Publication dateOct 27, 2005
Filing dateJun 22, 2005
Priority dateNov 26, 2002
Also published asCN1738766A, CN1738766B, EP1565400A2, US7572423, US20040156773, WO2004048261A2, WO2004048261A3
Publication number11158827, 158827, US 2005/0238560 A1, US 2005/238560 A1, US 20050238560 A1, US 20050238560A1, US 2005238560 A1, US 2005238560A1, US-A1-20050238560, US-A1-2005238560, US2005/0238560A1, US2005/238560A1, US20050238560 A1, US20050238560A1, US2005238560 A1, US2005238560A1
InventorsYakov Kutsovsky
Original AssigneeCabot Corporation
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Fumed metal oxide particles and process for producing the same
US 20050238560 A1
Abstract
The invention provides a process for producing fumed metal oxide particles comprising providing a stream of a liquid feedstock comprising a volatizable, non-halogenated metal oxide precursor, providing a stream of a combustion gas having a linear velocity sufficient to atomize and combust or pyrolyze the liquid feedstock, and injecting the stream of the liquid feedstock into the stream of combustion gas to form a reaction mixture such that the liquid feedstock is atomized and subjected to a sufficient temperature and residence time in the combination gas stream for fumed metal oxide particles to form before the combustion gas temperature is reduced below the solidifying temperature of the metal oxide particle. The invention further provides fumed silica particles having a relatively small aggregate size and/or narrow aggregate size distribution.
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Claims(24)
1-30. (canceled)
31. A process for producing metal oxide particles, the method comprising:
injecting into a combustion gas stream a liquid feedstock comprising volatizable, non-halogenated precursor for metal oxide; and
in the combustion gas stream, combusting or pyrolyzing the liquid feedstock and forming particles comprising the metal oxide;
wherein the metal oxide is selected from the group consisting of alumina, zirconia, yttria, silica, titania, baria, niobia, rubidia, strontia and calcia.
32. The process of claim 31, wherein the combustion gas stream has a linear velocity of at least Mach 0.2 when the liquid feedstock is injected into the combustion gas stream during the injecting.
33. The process of claim 31, wherein the combustion gas stream has a temperature of from 2200 K to 2300 K when the liquid feedstock is injected into the combustion gas stream during the injecting.
34. The process of claim 31, wherein during the injecting, the liquid feedstock is injected into the combustion gas stream through at least one nozzle.
35. The process of claim 34, wherein the liquid feedstock is fed to the at least one nozzle under pressure and the liquid feedstock exits the at least one nozzle with sufficient force to atomize the liquid feedstock.
36. The process of claim 34, wherein the force of the combustion gas stream atomizes the liquid feedstock injected into the combustion gas stream during the injecting.
37. The process of claim 31, wherein during the injection, the liquid feedstock is injected into the combustion gas stream through two or more nozzles.
38. The process of claim 37, wherein at least one of the nozzles is located downstream of at least one other of the nozzles.
39. The process of claim 31, wherein during the injecting, the liquid feedstock is injected into the combustion gas when the combustion gas is flowing through a constricted portion of a reactor.
40. The process of claim 39, wherein:
the reactor comprises a combustion chamber upstream of the constricted portion and an enlarged portion downstream of the constricted portion, wherein the combustion chamber has a first diameter, the constricted portion has a second diameter and the enlarged portion has a third diameter, the second diameter being smaller than each of the first diameter and the third diameter;
the combustion gas is established in the combustion chamber and flows through the constricted portion and into the enlarged portion; and
the particles form in the enlarged portion.
41. The process of claim 31, wherein the metal oxide is one of two or more different metal oxides in the particles.
42. The process of claim 31, comprising the combusting the liquid feedstock.
43. The process of claim 31, comprising the pyrolyzing the liquid feedstock.
44. The process of claim 31, wherein the metal oxide is alumina.
45. The process of claim 31, wherein the metal oxide is zirconia.
46. The process of claim 31, wherein the metal oxide is yttria.
47. The process of claim 31, wherein the metal oxide is silica.
48. The process of claim 31, wherein the metal oxide is titania.
49. The process of claim 31, wherein the metal oxide is baria.
50. The process of claim 31, wherein the metal oxide is niobia.
51. The process of claim 31, wherein the metal oxide is rubidia.
52. The process of claim 31, wherein the metal oxide is strontia.
53. The process of claim 31, wherein the metal oxide is calcia.
Description
    CROSS-REFERENCE TO RELATED APPLICATIONS
  • [0001]
    This patent application claims the benefit of U.S. Provisional Patent Application No. 60/429,217, filed Nov. 26, 2002.
  • FIELD OF THE INVENTION
  • [0002]
    This invention pertains to metal oxide particles and processes for the production thereof.
  • BACKGROUND OF THE INVENTION
  • [0003]
    Metal oxide particles have found widespread applications in industry. For example, in the semiconductor industry, metal oxide particles have been used as abrasives in polishing compositions. Metal oxide particles also have been used in the preparation of coating compositions, such as paints, and in the production of ink recording media.
  • [0004]
    Various methods have been disclosed for the production of metal oxide particles. For example, U.S. Pat. No. 3,322,499 (Carpenter et al.) discloses a method for the production of pyrogenic metal oxide particles by high-temperature oxidation of volatile metal compounds, such as metal halides or oxyhalides. While such processes yield metal oxide particles of satisfactory quality, they often involve expensive post-production treatment steps, such as removing the acid that results from the combustion of the halogenated feedstock.
  • [0005]
    Thus, a need exists for a process for the production of metal oxide particles that does not involve costly and complicated pre- and post-production treatment steps. A need also exists for metal oxide particles having a relatively small aggregate size and/or a relatively narrow aggregate size distribution. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.
  • BRIEF SUMMARY OF THE INVENTION
  • [0006]
    The invention provides a process for producing fumed metal oxide particles comprising providing a stream of a liquid feedstock comprising a volatizable, non-halogenated metal oxide precursor, providing a stream of a combustion gas having a linear velocity sufficient to atomize and combust or pyrolyze the liquid feedstock, injecting the stream of the liquid feedstock into the stream of combustion gas to form a reaction mixture such that the liquid feedstock is atomized and subjected to a sufficient temperature and residence time in the combustion gas stream for fumed metal oxide particles to form before the combustion gas temperature is reduced below the solidifying temperature of the fumed metal oxide particle.
  • [0007]
    The invention further provides a population or collection of fumed silica particles having a primary particle size d and an aggregate size Dcirc, wherein the average of the primary particle sizes dave, the average of the aggregate sizes Dcirc ave, and the geometric standard derivation of the aggregate sizes σg(Dcirc) satisfy one or both of the following equations:
    D circ ave(nm)<52+2d ave(nm)  (1)
    σg(D circ)<1.44+0.011d ave(nm).  (2)
  • BRIEF DESCRIPTION OF THE DRAWINGS
  • [0008]
    FIG. 1 is a schematic view of a reactor suitable for carrying out the inventive process.
  • DETAILED DESCRIPTION OF THE INVENTION
  • [0009]
    The invention provides a process for producing fumed metal oxide particles. The method comprises (a) providing a stream of a liquid feedstock comprising a volatizable, non-halogenated metal oxide precursor, (b) providing a stream of a combustion gas having a linear velocity sufficient to atomize and combust or pyrolyze the liquid feedstock, and (c) injecting the stream of the liquid feedstock into the stream of combustion gas to form a reaction mixture such that the liquid feedstock is atomized and subjected to a sufficient temperature and residence time in the combustion gas stream for fumed metal oxide particles to form before the combustion gas temperature is reduced below the solidifying temperature of the fumed metal oxide particle.
  • [0010]
    As used herein, the term metal oxide particles refers to discrete particles of metal oxides, which can be represented by the chemical formula MXOY, wherein M represents a metal and X and Y are independently greater than 1. These particles, typically, are aggregates of smaller primary particles, which are held together by relatively strong cohesive forces. Aggregate metal oxide particles can also form larger agglomerate particles, which are held together by relatively weak cohesive forces.
  • [0011]
    The liquid feedstock used in the invention comprises a volatizable, non-halogenated metal oxide precursor. As utilized herein, the term “volatizable” refers to a compound that readily converts to a gas or vapor when introduced into the stream of combustion gas. The metal oxide precursors suitable for use in the invention are not particularly limited, and include any metal oxide precursors known to those of skill in the art, provided that the precursors are non-halogenated and are readily volatizable in a stream of combustion gas. Suitable non-halogenated precursors include, but are not limited to, aluminum(III) n-butoxide, aluminum(III) sec-butoxide, aluminum(III) isopropoxide, trimethylaluminum, and titanium isopropoxide, and mixtures thereof. The metal oxide precursor also can be a silicone compound. Suitable silicone compounds include, but are not limited to, (i) silicates such as tetraethoxyorthosilicate (TEOS) and tetramethoxyorthosilicate; (ii) silanes such as alkoxysilanes, alkylalkoxysilanes, and aryl-alkylalkoxysilanes, for example, tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, trimethylethoxysilane, and diethylpropylethoxysilane; (iii) silicone oil; (iv) polysiloxanes and cyclic polysiloxanes, for example, octamethylcyclotetrasiloxane (OMTS), decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, hexamethyl-cyclotrisiloxane; (v) silazanes such as hexamethyldisilazane; and mixtures thereof. Preferably, the silicone compound is selected from the group consisting of methyltrimethoxysilane, octamethylcyclotetrasiloxane, and mixtures thereof.
  • [0012]
    The liquid feedstock also can comprise two or more volatizable, non-halogenated metal oxide precursors. For example, the liquid feedstock can comprise a silicon-containing metal oxide precursor and an aluminum-containing metal oxide precursor, or the liquid feedstock can comprise a silicon-containing metal oxide precursor and a titanium-containing metal oxide precursor. Preferably, the metal oxide precursor comprises a silicone compound and at least one compound selected from the group consisting of aluminum(III) n-butoxide, aluminum(III) sec-butoxide, aluminum(III) isopropoxide, and trimethylaluminum. When the liquid feedstock comprises two or more volatizable, non-halogenated metal oxide precursors, the two or more metal oxide precursors can be present in the liquid feedstock in any suitable amounts. It will be understood that by varying the relative amounts of the metal oxide precursors the chemical composition of the fumed metal oxide particles can be varied.
  • [0013]
    The liquid feedstock can be formed by any suitable method. The metal oxide precursor can be prepared by mixing the metal oxide precursor with a suitable solvent therefor. Preferably, the solvent does not leave residual contaminants in the formed metal oxide particles upon combustion or pyrolysis of the liquid feedstock. Suitable solvents include, but are not limited to, one or more organic solvents.
  • [0014]
    The metal oxide precursor can be present in the liquid feedstock in any suitable concentration. Higher metal oxide precursor concentrations generally are preferred to lower metal oxide precursor concentrations in order to maximize fumed metal oxide particle production rates. Metal oxide precursor concentrations that approach saturation in the liquid feedstock are particularly preferred. As will be appreciated by those of ordinary skill in the art, the saturation point of the liquid feedstock will depend upon the particular solvent and metal oxide precursor used, as well as external factors such as pH, temperature, and pressure. Thus, in some preparations, the concentration of the metal oxide precursor in the liquid feedstock typically will be about 20 wt. % or more, preferably about 60 wt. % or more, and more preferably about 80 wt. % or more. Most preferably, the metal oxide precursor is not mixed with a suitable solvent therefore (i.e., the metal oxide precursor is 100 wt. % of the liquid feedstock).
  • [0015]
    The stream of combustion gas can be formed by any suitable method. Preferably, the stream of combustion gas is established by combustion of a preheated oxidant stream and a liquid or gaseous fuel stream. Typically, the oxidant stream comprises any gaseous oxidant which, when mixed in appropriate proportions with the fuel stream, results in an energetically combustible mixture. Suitable oxidant streams include, but are not limited to, air, oxygen, and mixtures thereof. The oxidant stream can also comprise one or more substantially non-oxidizing or inert gases, such as nitrogen, carbon dioxide, argon, etc. When the oxidant stream comprises a mixture of at least one oxidant gas and at least one substantially non-oxidizing or inert gas, the total oxidant gas concentration of the mixture is preferably at least about 20 vol. %.
  • [0016]
    The oxidant stream can be preheated to any suitable temperature. Typically, the oxidant stream is heated to a temperature such that, when mixed with the oxidant stream, the resulting mixture can be readily combusted. In other embodiments, the oxidant stream can be heated to a temperature such that the fuel stream immediately combusts when mixed with the oxidant stream.
  • [0017]
    The fuel stream can comprise one or more of any readily combustible gases, vapors, and/or liquid fuels. Examples of suitable fuels include, but are not limited to, hydrogen (H2), carbon monoxide (CO), methane (CH4), etc. However, it is generally preferred to use fuel streams having a high content of carbon-containing components, such as hydrocarbons. Suitable hydrocarbons include, but are not limited to, natural gas, methane, acetylene, alcohol, kerosene, and mixtures thereof. As used herein, the term “natural gas” refers to a mixture of methane (CH4), ethane (C2H6), propane (C3H8), butane (C4H10), and nitrogen. In some forms, natural gas may further comprise relatively small amounts of helium. As utilized herein, the term “kerosene” refers to a mixture of petroleum hydrocarbons, which is obtained during the fractional distillation of petroleum. In another preferred embodiment, the fuel stream comprises hydrogen.
  • [0018]
    The relative amounts of the oxidant stream and fuel stream used to establish the stream of combustion gas can be varied over a wide range to optimize the temperature and linear velocity of the stream for specific precursors. The relative amounts of oxidant and fuel necessary to produce a stream of combustion gas having a linear velocity sufficient to atomize and pyrolyze or combust the liquid feedstock will depend upon the particular oxidant(s) and fuel(s) being used, as well as the particular feedstock to be atomized and pyrolyzed or combusted. Typically, the mixture of oxidant and fuel can be either fuel rich or fuel lean. As utilized herein, the term “fuel rich” refers to a mixture of fuel and oxidant in which the amount of oxidant present in the mixture is not sufficient to completely oxidize, or combust, the amount of fuel present in the mixture. By way of contrast, the term “fuel lean” refers to a mixture of fuel and oxidant in which the oxidant is present in an amount in excess of that necessary to completely oxidize, or combust, the fuel present in the mixture.
  • [0019]
    The stream of combustion gas has a linear velocity sufficient to atomize and combust or pyrolyze the liquid feedstock. Typically, the stream of combustion gas will have a linear velocity of at least about Mach 0.2. As utilized herein, the term “Mach” refers to the ratio of the linear velocity of the stream of combustion gas to the velocity of sound in the surrounding medium (i.e., the stream of combustion gas). Those of ordinary skill in the art will recognize that, as the speed of sound is dependent upon the temperature and pressure of the medium through which it travels, the Mach velocity is also dependent upon the temperature and pressure of the surrounding medium. Thus, the velocity of the stream of combustion gas, expressed in terms of Mach number, will depend upon the temperature and pressure of the combustion gas. Furthermore, the linear velocity necessary to atomize and pyrolyze or combust the liquid feedstock will depend upon the particular feedstock(s) being used. For example, the optimum linear velocity for the atomization and combustion of a methyltrimethoxysilane feedstock may be different from the optimum linear velocity for the atomization and combustion of an octamethylcyclotetrasiloxane feedstock.
  • [0020]
    The stream of combustion gas can have any suitable temperature. Typically, the temperature of the stream of combustion gas will be about 2200 K to about 3000 K. The temperature of the stream of combustion gas can be measured by methods known in the art, such as by thermocouples as described in Hung et al., J. Mater. Res., 7, 1861-1869 (July 1992).
  • [0021]
    The oxidant stream and the fuel stream can be combined in any suitable apparatus to render the stream of combustion gas. Typically, the oxidant stream and fuel stream are combined and combusted in a combustion chamber, which is connected to a reaction zone where the liquid feedstock is injected into the stream of combustion gas. In one embodiment, the combustion chamber comprises an enclosure wherein the internal cross-sectional area of the enclosure decreases along the path of the combustion gas. In this embodiment, the combustion gas travels through the enclosure and enters a reaction zone having an internal cross-sectional area greater than the internal cross-sectional area of the combustion chamber.
  • [0022]
    The liquid feedstock can be introduced at any suitable point in the stream of combustion gas. However, the feedstock must be introduced into the stream of combustion gas at a point which ensures that the feedstock is subject to a temperature, linear velocity, and residence time sufficient to atomize and convert the feedstock, either by combustion or pyrolysis, to the desired metal oxide. As noted above, the necessary temperature, linear velocity, and residence time will depend upon the particular feedstock being used, and, accordingly, the necessary point of introduction may vary depending upon the particular feedstock.
  • [0023]
    The stream of the liquid feedstock can be injected into the combustion gas stream by any suitable method. Typically, the stream of the feedstock is injected into the combustion gas through at least one nozzle. The type of nozzle suitable for use in the invention is not particularly limited. Preferably, the nozzle is a single fluid or a bi-fluid nozzle. As utilized herein, the term “single fluid” refers to a nozzle in which a single fluid is introduced into and emanates from the nozzle, and the term “bi-fluid nozzle” refers to a nozzle in which two fluids are introduced into the nozzle, mixed, and the mixture then emanates from the nozzle. Preferably, several (e.g., two or more, or three or more, or four or more) nozzles are used to inject the stream of the liquid feedstock into the stream of combustion gas, thereby ensuring that the liquid feedstock is rapidly and evenly mixed with the combustion gas. Furthermore, when several nozzles are used, one or more of the nozzles is preferably located downstream (i.e., along the path of the combustion gas) of the other nozzle(s).
  • [0024]
    When at least one single fluid nozzle is used, the liquid feedstock can be atomized in two ways. First, the liquid feedstock can be fed to the nozzle under pressure, which ensures that the stream of the liquid feedstock exits the nozzle with sufficient force to atomize the liquid feedstock. Second, the stream of the liquid feedstock can be injected directly into the stream of combustion gas, in which case, the force of the combustion gas stream atomizes the liquid feedstock. Typically, when a bi-fluid nozzle is used, the liquid feedstock is primarily atomized using a pressurized fluid, such as steam or air, and further atomized by the force of the stream of combustion gas.
  • [0025]
    In certain embodiments, one or more additional liquid feedstocks can be introduced into the stream of combustion gas. The additional feedstock(s) can be introduced into the stream of combustion gas at the same point as the first feedstock, or the additional feedstock(s) can be introduced at one or more points downstream of the point where the first feedstock is introduced into the stream of combustion gas. When multiple feedstocks are introduced into the stream of combustion gas, each feedstock can comprise the same precursor, or each feedstock can comprise a different precursor.
  • [0026]
    In the above-described process, the metal oxide particles can be formed in one of two ways. First, the precursor contained in the liquid feedstock can be combusted to form the corresponding metal oxide particle. Second, the precursor contained in the liquid feedstock can be pyrolyzed to form the corresponding metal oxide particle. As utilized herein, the term “pyrolysis” refers to the thermal decomposition of a carbonaceous compound, such as a silicon-containing feedstock.
  • [0027]
    When the metal oxide particles are formed by pyrolysis, the reaction mixture can be contacted with additional components to ensure that the metal oxide precursor has been oxidized. These additional components can be any suitable chemical that increases the oxidation of the metal oxide precursor in the absence of oxygen. Suitable chemicals include, but are not limited to, CO2 and H2O. In certain embodiments, the fuel to oxidant ratio should be maintained at or below a level low enough to ensure that carbon black does not form in the stream of combustion gas. This level is commonly referred to as the “critical equivalence ratio,” and, for the feedstocks suitable for use in the invention, it is equal to approximately 1.7. The equivalence ratio is defined as the ratio of the fuels to oxidizers present in a system divided by the stoichiometric ratio of fuels to oxidizers required for complete combustion of the same system. See I. Glassman, “Combustion,” AP, 1987.
  • [0028]
    After the solid metal oxide particles have formed, the reaction can be arrested by quenching the reaction mixture (i.e., the liquid feedstock and the combustion gas). Typically, the reaction mixture is quenched by spraying a quenching agent into the stream of newly formed solid metal oxide particles. Any suitable quenching agent can be used to quench the reaction mixture. Suitable quenching agents include, but are not limited to, air, steam, carbon dioxide, and water. Alternatively, or in addition, when the liquid feedstock is injected into the stream of combustion gas inside a reactor having walls, the reaction mixture can be quenched by heat transfer to the walls of the reactor. The quench serves to cool the metal oxide particles and reduce the temperature of the gaseous stream, thereby decreasing the reaction rate. Optionally, quenching can be staged, or take place at several points in the reactor.
  • [0029]
    After the reaction mixture is quenched, the cooled gases and metal oxide particles pass downstream into any conventional cooling and separating means whereby the metal oxide particles and any co-produced carbon black are recovered. The separation of the metal oxide particles from the gas stream is readily accomplished by conventional means such as a precipitator, cyclone separator, bag filter, or other means known to those skilled in the art.
  • [0030]
    The process of the invention can be carried out in any suitable apparatus. Preferably, the process is carried out in a reactor such as that depicted in FIG. 1. In particular, the reactor depicted in FIG. 1 incorporates a combustion chamber 10 having an internal diameter D1 in which the stream of combustion gas is established by injection, for example, of gases A and B (e.g., air and hydrogen). The internal diameter of the combustion chamber 10 decreases along the path 12 of the combustion gas stream until it reaches a constricted portion 14 of the reactor having an internal diameter D2 (which is smaller than D1). Preferably, the liquid feedstock C is injected into the stream of combustion gas at one or more points in the constricted portion 14 of the reactor. While not wishing to be bound to any particular theory, it is believed that injecting the liquid feedstock into the stream of combustion gas in the constricted portion of the reactor ensures that the stream of combustion gas has a velocity and temperature sufficient to atomize and combust or pyrolyze the liquid feedstock. The internal diameter of the reactor then increases along the path 12 of the combustion gas and liquid feedstock streams until it reaches an enlarged portion 16 having an internal diameter D3 (which is larger than the diameter D2), in which the fumed metal oxide particles form, and, optionally, the reaction mixture is quenched by injection of quenching agent D (e.g., water).
  • [0031]
    The temperature of the stream of combustion gas determines the surface area of the metal oxide particles. The surface area of the metal oxide particles generally is related to the size of the primary particles. Preferred metal oxide particles have a surface area, as calculated from the method of S. Brunauer, P. H. Emmet, and I. Teller, J. Am. Chemical Society, 60, 309 (1938), and commonly referred to as BET, of at least about 10 m2/g, preferably at least about 15 m2/g, more preferably at least about 20 m2/g, and most preferably at least about 25 m2/g. The metal oxide particles typically have a BET surface area of less than about 500 m2/g, preferably less than about 475 m2 μg, more preferably less than about 450 m2/g, and most preferably less than about 400 m2/g.
  • [0032]
    The process of the invention can advantageously be used to produce particles of any suitable metal oxide. Suitable metal oxides include, but are not limited to, alumina, zirconia, ceria, yttria, silica, titania, baria, niobia, rubidia, strontia, and calcia. The process of the invention also can be used to produce fumed metal oxide particles comprising two or more metal oxides (e.g., fumed metal oxide particles comprising silica and alumina).
  • [0033]
    The invention further provides a population or collection of (e.g., a composition comprising, consisting essentially of, or consisting of) fumed silica particles having a primary particle size d and an aggregate size Dcirc, wherein the average of the primary particle sizes dave, the average of the aggregate sizes Dcirc ave, and the geometric standard derivation of the aggregate sizes σg (Dcirc) satisfy one or both of the following equations:
    D circ ave(nm)<52+2d ave(nm)  (1)
    σg(D circ)<1.44+0.011d ave(nm).  (2)
    The average of the primary particle sizes, dave, is related to the BET surface area, SA, of the fumed silica particles and can be calculated using the following formula:
    d ave(nm)=1941/SA(m 2 /g).
    The aggregate size, Dcirc, is defined as the diameter of a circle having the same area as the aggregate, A, which can be measured by any suitable method, such as TEM image analysis according to ASTM Standard D3849. Once the area of the aggregates, A, has been determined, the aggregate size, Dcirc, can be calculated using the following equation:
    D circ={square root}{square root over (4A/π)}.
    As utilized herein, the geometric standard deviation of the aggregate sizes, σg (Dcirc), is the geometric standard deviation of the aggregate sizes, Dcirc, for the fumed silica particles of the population, collection, or composition as described below (e.g., about 2000 or more aggregates) and represents the aggregate size distribution for the fumed silica particles. The Dcirc ave values for the fumed silica particles are geometric number averages. The geometric number averages as well as the geometric standard deviation can be calculated by any suitable method, such as the method described in T. Kodas and M Hampden-Smith, Aerosol Processing of Materials, 28-31 (John Wiley & Sons 1999).
  • [0034]
    The population or collection of, or the composition comprising, the fumed silica particles can comprise any suitable number of fumed silica particles. For example, the population, collection, or composition can comprise about 2000 or more aggregates, about 5000 or more aggregates, or even about 10,000 or more aggregates, of the fumed silica particles. The population, collection, or composition also can comprise about 10 g or more, about 100 g or more, or about 1 kg or more of the fumed silica particles.
  • [0035]
    The metal oxide particles of the invention are advantageously suited for a variety of applications. For instance, the metal oxide particles can be used as an abrasive in chemical-mechanical polishing processes. While not wishing to be bound to any theory, it is believed that the smaller aggregate size and/or narrow aggregate size distribution of the metal oxide particles reduces, at least in part, the occurrence of surface defects caused by the polishing processes. The metal oxide particles also can be used in the preparation of coating compositions, such as paints. These coating compositions also can be used to coat a substrate, such as a polymer film or paper, to produce ink recording media.
  • [0036]
    The following examples further illustrate the invention but, of course, should not be construed as in any way limiting its scope.
  • EXAMPLES 1-4
  • [0037]
    These examples demonstrate the process of producing fumed metal oxide particles according to the invention. In particular, these examples demonstrate four processes used to produce fumed silica particles having different surface areas. The following processes were carried out using a pilot scale reactor as described above and as depicted in FIG. 1. The approximate dimensions of the pilot scale reactor, with reference to FIG. 1, were as follows: D1=18.4 cm, D2=9.7 cm, D3=69 cm, and L1=213 cm. The liquid feedstock was a commercially available octamethylcyclotetrasiloxane (OMTS), and the stream of combustion gas was established by combusting a mixture of air and natural gas. The quantities of air, natural gas, and OMTS utilized in each of the processes are set forth in Table 1. The liquid feedstock (i.e., OMTS) was injected into the stream of combustion gas at the constricted portion 14 of the reactor (i.e., the portion with diameter D2 in FIG. 1), and the reaction mixture was quenched using water (which was introduced into the reactor at position D in FIG. 1).
    TABLE 1
    Quantities of air, natural gas, and OMTS.
    EX- EX- EX- EX-
    AMPLE 1 AMPLE 2 AMPLE 3 AMPLE 4
    Air (Nm3/h) 1605 1605 1605 1605
    Natural Gas (Nm3/h) 101 215 181 151
    OMTS (kg/h) 50 150 100 100
  • [0038]
    The surface area of the fumed silica particles produced by each of the processes was measured in accordance with the BET procedure. The average surface area of the fumed silica particles resulting from each of the processes is set forth in Table 2.
    TABLE 2
    Average BET surface area for the fumed silica particles.
    EX- EX- EX- EX-
    AMPLE 1 AMPLE 2 AMPLE 3 AMPLE 4
    BET Surface Area (m2/g) 258 173 82 46
  • [0039]
    As demonstrated by these results, the process of the invention can be used to produce fumed metal oxide particles from a non-halogenated metal oxide precursor. Moreover, the process of the invention can be used to produce fumed metal oxide particles having a wide range of surface areas.
  • EXAMPLE 5
  • [0040]
    This example demonstrates the unique particle size features of the finned silica particles of the invention. The fumed silica particles of Examples 1-4 were analyzed in accordance with the methods described herein to determine the primary particle sizes d and the aggregate sizes Dcirc for 2000 aggregates from each sample of the fumed silica particles (i.e., the silica particles produced by each of Examples 14). The average of the primary particle sizes dave, the average of the aggregate sizes Dcirc ave, and the geometric standard deviation of the aggregate sizes σg (Dcirc) then were calculated. In particular, the average of the primary particle sizes dave of the fumed silica particles was determined using the BET surface area (SA) measurements and the equation: dave(nm)=1941/SA (m2/g). Aggregate size Dcirc was determined using TEM image analysis to measure the area, A, of each aggregate and calculating the aggregate size Dcirc, using the equation Dcirc={square root}{square root over (4A/π)}. From these Dcirc determinations, the geometric number average of the aggregate sizes Dcirc ave and the geometric standard deviation of the aggregate sizes σg (Dcirc) were calculated for each sample of the fumed silica particles (i.e., the silica particles produced by each of Examples 14). The average of the primary particle sizes dave, the average of the aggregate sizes Dcirc ave, and the geometric standard deviation of the aggregate sizes (i.e., the aggregate size distribution) σg (Dcirc) are set forth in Table 3 for each sample of fumed silica particles.
    TABLE 3
    Primary particle size, aggregate size, and aggregate size
    distribution measurements for the fumed silica particles.
    EX- EX-
    AMPLE 1 EXAMPLE 2 EXAMPLE 3 AMPLE 4
    dave (nm) 7.5 11.2 23.7 42.2
    Dcirc ave (nm) 70 67 68 101
    σg (Dcirc) 1.55 1.62 1.6 1.56
  • [0041]
    As demonstrated by these results, the average of the primary particle sizes dave, the average of the aggregate sizes Dcirc ave, and the geometric standard deviation of the aggregate sizes σg (Dcirc) of the silica particles of Example 1 do not satisfy either of the following equations, while those same physical characteristics of the silica particles of Examples 2-4 satisfy one or both of the following equations:
    D circ ave(nm)<52+2d ave(nm)  (1)
    σg(D circ)<1.44+0.011d ave(nm).  (2)
    In particular, while the fumed silica particles of Example 1 do not satisfy equation (1) or (2), the fumed silica particles of Examples 2, 3, and 4 satisfy equation (1), and the fumed silica particles of Examples 3 and 4 satisfy equation (2).
  • [0042]
    All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.
  • [0043]
    The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.
  • [0044]
    Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.
Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2631083 *Jan 19, 1952Mar 10, 1953Cabot Godfrey L IncProduction of calcium fluoride and silica
US2693406 *Apr 28, 1950Nov 2, 1954Godrey L Cabot IncProcess of making aluminum oxide
US2771344 *Aug 5, 1954Nov 20, 1956Cabot Godfrey L IncManufacture of iron oxide pigment
US2773741 *Nov 25, 1952Dec 11, 1956Cabot Godfrey L IncProcess for the production of aluminum oxide
US2780525 *Oct 8, 1953Feb 5, 1957Cabot Godfrey L IncProcess and apparatus for the production of aluminum oxide from aluminum chloride
US2801901 *Mar 23, 1953Aug 6, 1957Cabot Godfrey L IncProcess for making aluminum oxide from hydrated aluminum
US2803038 *Jan 12, 1954Aug 20, 1957Edward J HollandPelletizing apparatus
US2828186 *Mar 2, 1956Mar 25, 1958Cabot Godfrey L IncProcess and apparatus for the production of aluminum oxide
US2829949 *Sep 20, 1952Apr 8, 1958Cabot Godfrey L IncApparatus for making aluminum oxide
US2847316 *Sep 29, 1954Aug 12, 1958Cabot Godfrey L IncProcess for production of mixed metal oxides
US3006738 *Oct 10, 1957Oct 31, 1961DegussaBurner for production of finely divided oxides
US3007774 *Apr 14, 1955Nov 7, 1961Cabot CorpProduction of finely-divided aluminum oxide from bauxite
US3024089 *May 10, 1957Mar 6, 1962Cabto CorpProcess for producing high surface area metal oxides
US3065093 *Apr 7, 1959Nov 20, 1962Berstein GregorNovel pigment compositions
US3112210 *Jul 21, 1961Nov 26, 1963Cabot CorpProcess for the manufacture of ceramic grade titanium dioxide
US3130008 *Nov 23, 1949Apr 21, 1964Cabot CorpMethod of preparing metallic oxides by hydrolysis of metallic halides
US3166542 *Feb 3, 1961Jan 19, 1965Cabot CorpSurface treated inorganic solid polymerization catalyst and method of polymerization therewith
US3203762 *Nov 30, 1962Aug 31, 1965Cabot CorpApparatus and process for the production of titanium dioxide
US3205177 *Sep 10, 1963Sep 7, 1965Cabot CorpSurface treated metal oxide polymerization catalysts and method of preparation
US3205178 *Sep 30, 1963Sep 7, 1965Cabot CorpSurface treated metal oxide polymerization catalyst and method of preparation
US3212911 *Sep 18, 1961Oct 19, 1965Cabot CorpTitanium dioxide pigments
US3322499 *Jan 13, 1964May 30, 1967Cabot CorpApparatus and process for the production of metal oxides
US3363980 *Mar 29, 1965Jan 16, 1968Cabot CorpMixing control during metal and metalloid oxide production
US3365274 *Jul 13, 1964Jan 23, 1968Cabot CorpMetal and metalloid oxide production
US3372001 *Dec 6, 1963Mar 5, 1968Cabot CorpApparatus for producing metal oxides
US3406228 *Jun 17, 1964Oct 15, 1968Cabot CorpMethod of producing extremely finely-divided oxides
US3455653 *Mar 23, 1966Jul 15, 1969Cabot CorpProcess for the production of titanium dioxide
US3488204 *Aug 14, 1967Jan 6, 1970Cabot CorpNonfloating pigments
US3493342 *Feb 16, 1968Feb 3, 1970Cabot CorpCollection of pyrogenic titanium dioxide pigments
US3510291 *Nov 10, 1966May 5, 1970Westinghouse Electric CorpVapor phase conversion of molybdenum or tungsten compound to form the oxide or metal
US3510292 *Jan 11, 1967May 5, 1970Cabot CorpProcess for making metal/metal oxide compositions
US3607049 *Jan 22, 1970Sep 21, 1971Cabot CorpCooling of pyrogenic titanium dioxide pigment containing gas streams
US3619140 *Jan 3, 1967Nov 9, 1971Cabot CorpProcess for making carbon black
US3639100 *Jul 24, 1969Feb 1, 1972Du PontMOLTEN SALT PRE-TREATMENT OF REACTANTS FOR TiC1{11 {0 OXIDATION
US3663283 *Oct 2, 1969May 16, 1972Moynihan Daniel JProcess and apparatus for the production of finely-divided metal oxides
US3922335 *Feb 25, 1974Nov 25, 1975Cabot CorpProcess for producing carbon black
US4023961 *Feb 12, 1975May 17, 1977Plessey IncorporatedMethod of producing powdered materials
US4145403 *Sep 29, 1977Mar 20, 1979Fey Maurice GArc heater method for producing metal oxides
US4857076 *Mar 23, 1987Aug 15, 1989The Dow Chemical CompanyAnnular nozzle
US4879104 *Jun 16, 1987Nov 7, 1989Cabot CorporationProcess for producing carbon black
US4937062 *Mar 7, 1988Jun 26, 1990Cabot CorporationHigh surface area metal oxide foams and method of producing the same
US5075090 *Nov 13, 1989Dec 24, 1991Vista Chemical CompanyProcess for preparing small particle size mixed metal oxides
US5152819 *Aug 26, 1991Oct 6, 1992Corning IncorporatedMethod of making fused silica
US5256389 *May 22, 1991Oct 26, 1993Cabot CorporationHigh surface area metal oxide foams
US5340560 *Apr 30, 1993Aug 23, 1994General Electric CompanyMethod for making fumed silica having a reduced aggregate size and product
US5447708 *May 10, 1993Sep 5, 1995Physical Sciences, Inc.Apparatus for producing nanoscale ceramic powders
US5599511 *May 24, 1995Feb 4, 1997Physical Sciences, Inc.Apparatus for producing nanoscale ceramic powders
US5614472 *May 12, 1995Mar 25, 1997Merck Patent Gesellschaft Mit Beschrankter HaftungSpray-pyrolysis process of preparing superconductor precursors
US5876683 *Nov 2, 1995Mar 2, 1999Glumac; NicholasCombustion flame synthesis of nanophase materials
US5904762 *Apr 18, 1997May 18, 1999Cabot CorporationMethod of making a multi-phase aggregate using a multi-stage process
US5958361 *Nov 22, 1995Sep 28, 1999Regents Of The University Of MichiganUltrafine metal oxide powders by flame spray pyrolysis
US6086841 *Jan 25, 1993Jul 11, 2000Cabot CorporationProcess for producing carbon blacks
US6110437 *Dec 12, 1996Aug 29, 2000Comurhex (S.A.)Method for preparing a mixture of powdered metal oxides from nitrates thereof in the nuclear industry
US6312656 *Jul 30, 1997Nov 6, 2001Corning IncorporatedMethod for forming silica by combustion of liquid reactants using oxygen
US6364944 *Dec 2, 1999Apr 2, 2002Cabot CorporationMethod of making a multi-phase aggregate using a multi-stage process
US6551567 *Aug 15, 2001Apr 22, 2003Shin-Etsu Chemical Co., Ltd.Spherical silica particles and method of production
US6565823 *Dec 17, 1996May 20, 2003Corning IncorporatedMethod and apparatus for forming fused silica by combustion of liquid reactants
US6602820 *Nov 15, 2000Aug 5, 2003Degussa-Huls AktiengesellschaftMethod for producing a nitrogen oxide storage material and a storage material made with it
US6627173 *Mar 27, 2001Sep 30, 2003Degussa AgDoped titanium dioxide
US6630084 *Oct 6, 2000Oct 7, 2003Sumitomo Special Metals Co., Ltd.Method of making ferrite material powder by spray pyrolysis process and method of producing ferrite magnet
US6887566 *Nov 17, 2000May 3, 2005Cabot CorporationCeria composition and process for preparing same
US20020041963 *Aug 15, 2001Apr 11, 2002Yoshiharu KonyaSpherical silica particles and method of production
US20040156773 *Nov 24, 2003Aug 12, 2004Cabot CorporationFumed metal oxide particles and process for producing the same
USRE28974 *Nov 2, 1973Sep 21, 1976Cabot CorporationProcess for making carbon black
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US7572423Nov 24, 2003Aug 11, 2009Cabot CorporationFumed metal oxide particles and process for producing the same
US8038971Sep 5, 2008Oct 18, 2011Cabot CorporationFumed silica of controlled aggregate size and processes for manufacturing the same
US8729158Mar 4, 2011May 20, 2014Cabot CorporationFumed silica of controlled aggregate size and processes for manufacturing the same
US20040156773 *Nov 24, 2003Aug 12, 2004Cabot CorporationFumed metal oxide particles and process for producing the same
US20100059704 *Sep 5, 2008Mar 11, 2010Cabot CorporationFumed silica of controlled aggregate size and processes for manufacturing the same
US20110204283 *Mar 4, 2011Aug 25, 2011Cabot CorporationFumed silica of controlled aggregate size and processes for manufacturing the same
US20110222896 *Mar 4, 2011Sep 15, 2011Canon Kabushiki KaishaSerial communication apparatus and image forming apparatus including the same
Classifications
U.S. Classification423/335
International ClassificationC01B13/20, C01B33/18, C01B13/24, C01B13/30
Cooperative ClassificationC01B13/24, C01P2004/50, C01P2006/12, C01B13/30, C01P2002/60, C01B13/20, C01B33/183, C01P2004/62, C01P2004/64, B82Y30/00
European ClassificationB82Y30/00, C01B13/20, C01B13/30, C01B33/18B4, C01B13/24