CA1290136C - Process for preparing fine particles of metal oxides - Google Patents
Process for preparing fine particles of metal oxidesInfo
- Publication number
- CA1290136C CA1290136C CA000543440A CA543440A CA1290136C CA 1290136 C CA1290136 C CA 1290136C CA 000543440 A CA000543440 A CA 000543440A CA 543440 A CA543440 A CA 543440A CA 1290136 C CA1290136 C CA 1290136C
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- Prior art keywords
- water
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- emulsion
- perfluoropolyether
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B13/00—Oxygen; Ozone; Oxides or hydroxides in general
- C01B13/14—Methods for preparing oxides or hydroxides in general
- C01B13/32—Methods for preparing oxides or hydroxides in general by oxidation or hydrolysis of elements or compounds in the liquid or solid state or in non-aqueous solution, e.g. sol-gel process
- C01B13/328—Methods for preparing oxides or hydroxides in general by oxidation or hydrolysis of elements or compounds in the liquid or solid state or in non-aqueous solution, e.g. sol-gel process by processes making use of emulsions, e.g. the kerosine process
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/113—Silicon oxides; Hydrates thereof
- C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
- C01B33/126—Preparation of silica of undetermined type
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B35/00—Boron; Compounds thereof
- C01B35/08—Compounds containing boron and nitrogen, phosphorus, oxygen, sulfur, selenium or tellurium
- C01B35/10—Compounds containing boron and oxygen
- C01B35/1027—Oxides
- C01B35/1036—Boric anhydride
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F7/00—Compounds of aluminium
- C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
- C01F7/34—Preparation of aluminium hydroxide by precipitation from solutions containing aluminium salts
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F7/00—Compounds of aluminium
- C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
- C01F7/34—Preparation of aluminium hydroxide by precipitation from solutions containing aluminium salts
- C01F7/36—Preparation of aluminium hydroxide by precipitation from solutions containing aluminium salts from organic aluminium salts
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G23/00—Compounds of titanium
- C01G23/04—Oxides; Hydroxides
- C01G23/047—Titanium dioxide
- C01G23/053—Producing by wet processes, e.g. hydrolysing titanium salts
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G23/00—Compounds of titanium
- C01G23/04—Oxides; Hydroxides
- C01G23/047—Titanium dioxide
- C01G23/053—Producing by wet processes, e.g. hydrolysing titanium salts
- C01G23/0536—Producing by wet processes, e.g. hydrolysing titanium salts by hydrolysing chloride-containing salts
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G25/00—Compounds of zirconium
- C01G25/02—Oxides
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/30—Particle morphology extending in three dimensions
- C01P2004/32—Spheres
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- Oxygen, Ozone, And Oxides In General (AREA)
- Colloid Chemistry (AREA)
- Inorganic Compounds Of Heavy Metals (AREA)
- Polymers With Sulfur, Phosphorus Or Metals In The Main Chain (AREA)
- Silicon Compounds (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
Abstract of the Disclosure A process for preparing spheroidal particles of metal oxides, of average diameter smaller than 3 microns, characterized in that an emulsion is prepared of a hydrolyzable liquid metal compound in: a perfluoropolyether, and the emulsion is reacted with water, water vapor, or with a mixture, in any ratio, of water with a liquid miscible or immiscible with it, which does not interfere with the reaction of the metal compound with water, with the formation of a metal oxide hydrate, which is separated.
The metal oxide hydrate is subsequently dried and calcined to the oxide.
The metal oxide hydrate is subsequently dried and calcined to the oxide.
Description
3 ~
D~scription of the Inverltion . .
'Ill~ present invention relates to Q process for prepar-illg fine p~r~icles of metal oxides. More p~rticul~rly, it re Intes to n process for preparing spheroidal particles of met~l oxides llavillg ~ submicronic aver~ge diameter, or having an QVer-~e di~m~ter ~Inaller tllnn 3 microns. The particles thus produced r~r~ uscd, c.g., in tllc prepnration of cernmic materiRls.
It is nlre~dy known to prep~re fine particles of metal oxides by renction witl~ water vapor of arl nerosol of hydrolyz~ble metal compoullds in an itlert gas. This rnetll~d shows several draw-bnclcs. First of nll, the metal cornpound must be completely evap-orated before forming tlle aerosol, witll ~ consequent high energy consllmption. Furthermore, the method implies the use of large volumes of inert gas, wllich must moreover ha~e a particularly low level of moisture. On the other hand, only hydroly~able metal compounds having a high vapor pressure cnn be used. Fin~lly, the method has a poor potenti~lity9 requlres high investment costs, ~and involves a high produ~tion ~ost.
The present invention provides a process for preparing fine particles of metal oxides which overcomes the above drawbacks. ~
According to the present invention there is provided a process for preparing spheroidal particles of an oxide compound selected from the group consisting of Ti A1, Zr, si and B oxides, having an average diameter o~ less than 3 microns, comprising: preparing an ~mul~ion in a perfluoropolyether of a hydrolyzable liquid compound of an element selected ~rom the group consisting of Ti, Al, zr, Si and B; reacting the emulslon with water, with water vapor or with a mixture, in any ratio, of water with a liquid miscible or immiscible with water, said liquid not interfering with the reaction of the hydrolyzable compound with water, to ~obtain an oxide hydrate, recovering said oxide hydrate, drying and calcining said oxide hydrate to an oxide.
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By the term "hydrolyzable metal compound" is meant a metal compound able to react with water to yield the correspond-ing metal oxide hydrate.
The hydrolyzable metal compound is preferably a com-pound of Ti, Al, Zr, Si, or B.
Ther perfluoropolyethers are per se well known com-pounds described, e.g., in patents to which reference is made hereafter.
Suitable perfluoropolyethers for forming the emulsions or hydroIyzable metal compounds are, particularly, those comply-ing with the following formuIae (A) to tG), and having~ a ViSC09-, ity of~from 4 to 1500 cSt~
(A) CF30 (C3F6O)m(c2F4O)n(cFxojq-cF3 wherein X is equal to -F or ~CF3; m, n~and g are integers; ~the~
ratio n + q~
being within the range of from 1 to iO,;and n/q being within the range of from 1 to~10, w1th the oxyperfluoroa~lkylene; units ran-domly d1stributed al~ong ~the cha~n. The ~preparation~ of ~these~
compounds is descr1bed~in~U.S. Patent No.~ 3,665,04 (B) C3F7OlC3F6O)m ~, ~
; ~ : :;
- - .
:
. ' ' , ~Z9~L36 wherein Rf is -C2F~ or -C3F7 and m is an integer greater than 2. The preparation of these compounds is described in U.S.
Patent No. 3,242,21~.
(C) CF3O(c2~4O)p(cF2o)q CF3 wherein p and ~ are integers equal to or different from each other, and the p/q ratio is within the range of from 0.5 to 1.5, the oxyperfluoroalkylene units being randomly distributed along the chain. The preparation of these compounds is described in U.S. Patents Nos. 3,715,378 and 3,865,041.
(D) CF30(C3F6O)m(CFXO)n CF2Y
wherein X and Y, equal to or different from each other, are -F or -CF3 m and n are integers and the m/n ratio is within the range of from 5 to 40, the oxyperfluoroalkylene units being rando~ly distributed along the chain. The preparation of these compounds is described in U.K. Patents Nos. 1,104,482 and 1,226,566.
(E~) Perfluoropolye~thers havlng an oxetane str~uct~ure,~
~; ~ as described in Canadian Patént application No. 501,657 ~; ( F ) R ' f O ( CF 2CF 20 ) PR f ~: ~he~ 9 ~ n PI _nd R~ eqUa' to or dlfferent from each other, are~
~-CF3 or -C2F5, and ~ is an integer such that the viscosity is : ~ ~
within the stated ranFe. Products of this type are described in .S. Patent No. 4,523,039.
(G) R'f (CF2cF2 CF2)s Rf wherein Rf and R~f, equal to or different from each other, are -CF3 or ~C2F5, and s is an integer such that the viscosity is within the stated range. Products of this type are described in : ~ :
Canadian Patent No, 1,259,~443.
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~ 29~136 ,".
Usually, the perfluoropolyether used to form the emul-sion has a viscosity within the range of from 4 to 200 cSt.
The hydrolyzable metal compounds used to form the emul-sions are, e.g., the alkoxides and haloalkoxides of Al, Ti, Zr and B (such as the isopropyloxide, sec-butyloxide, n-butyloxlde, and n-propyloxide, halides, such as TiC1~9 BC13 and SiC14, and those halide complexes which are liquid at emulsifying tempera ture: e.g., AlC13-complexes wlth arom~tic esters and TiC14-com-plexes with long-chain aliphatic ethers. These metal compounds must be liquid at the emulsifying temperature. Usually, the emulsion is prepared ~t ambient temperature. However,~one may;
operate at a lower or higher than ambient temperature, e.g., within the range of from -30 to +90C.
The alkoxides may be used as solutions in their corre-sponding alcohol. When Al, Ti, Zr or B oxides are to be pre-pared, the alkoxides are commonly used as the startlng materials.
The ratio, by volume, of the hydrolyznble metal com-pound to the perfluoropolyether in the emulsion is within the rQnge of from 0.01 to 1.
The emulsion is preferably prepared in the presence of an emulsion stabilizer consisting or consisting essentially of a perfluoropolyether having n functionnl end group. Prefernbly, the perfluoropolyether having a funetional end group has the following end groups:
O
- C~
~ ~ H-R
: : :
' ~ :
~ ~ ~ - 5 -:
~ 1;;:90~36 wherein R is a linear, branched or cyclic alkyl of from 1 to 20 carbon atoms, or an alkylaryl of from 7 to 20 carbon atoms; R may also contain heteroatoms, fn particular O and/or Si atoms, and substituents, e.g., Cl.
Examples of suitable emulsion stabilizers are:
CF3-~OC3F6)n(OCF2)m-O-CF2-C3O CH2 1 3 3 (I) 3 (c3F6)n(cP2)m ocF2-coo-cH2-cHoH-o-(c~2)3-si(oMe)3 (Il) CF3 ~oc3F6)ntocF2)m-o-GF2oo-NH-(cH2)3-si(oEt)3 (III) :
The amount of emulsion stabilizer is gensrally with;n the range of from 0.01 to 5% by weight based on perfluoropoly-ether; more usually, from 0.1 to 0.5~ thereof is used.
Any process allowing one to obtain the emulsion may be conveniently used in the process of this invention. ~ -~;
The emulsion may be prepared, e.g., by means of st~rong stirring, e.g., by using an ultraturrax stirrer. The emulslon is prepared under Hn adequate stirring. By increasing the stirring rate, smaller particles of metal oxide hydrate are obtained.
With incre~sing viscosity of the perfiuoropolyether, particles of m~tal oxide hydrate of larger dimensions are ob-tained.
~: ,:
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, ~29C~1~6 A first method for carrying out the hydrolysis consists in adding the emulsion to water, with stirring.
A second method consists in adding, always with stir-ring, the emulsion to water mixed, in ~ny ratio, with a liquid miscible or immiscible with it.
Among the water-miscible liquids which may be used according to the present invention, the alcohols of from I to 8 carbon atoms and ethylene glycol may be mentioned. Among the immiscible liquids, perfluoropolyethers, hydrocarbons, and sili-cone oils may be mentioned. More commonly, water is present in such blends in amounts ranging from 0.1 to 90% by volume.
A third method for carry out the hydrolysis conslsts or ~onsists essenti~lly in adding the emulsion to water ~vapor.
Water vapor may be used as sueh, or contained in a gas, such as, e.g., nitrogen; usually, a gas saturated with water is used. In this case, the sphericity of the oxide hydrate is generally im-proved.
The amount of wat~er relative to the metal compound ma~y vary over a wide range. The minimum amount is that amount which is stoichiometrically required to carry out the hydrolysis reac-tion. However, large excesses of water may be used, and an amount of water equal to 2.5 times the stoichiometric ratio is commonly used.
The emulsion may be prepared ~and introduced into the liquid water phase ~w~ter, or blends thereof with other liquids) by a high-linear~speed stream. ~ For that purpose a homogeneous mixture is prepared of the hydrolyzable metal compound and of the ~ ~ ~ : ; ' ~ ; - 7 - ;
; ~ :, :~ :
: ~. ~ , . , ~
, ~290~l36 :
perfluoropolyether, and the mixture is passed, under pressure, through a tube having a length equal to from 500 to 3000 times its diameter, and wherein the linear speed of the mixture is greater than I meter/second. Such a stream may be introduced into a vessel containing the liquid aqueous phase, or into a recycle circuit wherein the liquid aqueous phase is circulated.
When such a stream is used, the emulsion pressure is generally within the range of from 20 to 90 relative to the atmosphere.
By thus injecting the emulsion, the diameter of the metal oxide hydrate particles is reduced.
By operating with a high-linear-speed emulsion stream, the introduction of the emulsion into the liquid aqueous phase requires a short time. When such a procedure is not used, the introduction of the emulsion into the liquid aqueous phase or the introduction of the liquid aqueous phase into the emulsion is preferably gradual; it is carried out, e.g., over a time of from 1 to 30 minutes.
The hydrolysis step may be preceded by a prehydrolysis;
i.e., a small amount of water is introduced into the emulsion before the true hydrolysis is performed. Usually, from 5 to 10%
of the total amount of water used in the process is thus intro-duced with stirring. Usually, this water addition Is instantan-eous. After such an addition, stirring is continued for a cer-tain time, e.g~, for 5 minutes, before the true hydrolysis is carried out. This pre-hydrolysis improves the sphericity of the metal oxide hydrate.
:: :
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~LX90~36 The hydrolysis is commonly carried out at ambient tem-perature. However, operating at a lower o~ higher temperature, e.g~, within the r~nge of from -30 to +90C, is possible. W~en operating below 0C, the water must be in the presence of a sub-stance which lowers its freezing po;nt, such as ethylene glycol.
The separation of the metal oxide hydrate from the liquid phase at the end of the hydrolysis may be carried out by known methods, e.g., by filtration.
The metal oxide hydrate is dried by per se known methods. The calcination is carried out, as is well-known, at different temperatures, depending on the nature of the metal oxide hydrate and its desired crystalline form.
The present invention is also suitable for preparing mixed metal oxides.
The following Examples are given for still ~better i;llustrating the Inventive concept of the present inven~tlon.~
To a 500-cc stainless-steel autoclave equipped~ with an anchor~stirrer, 200~cc of a perfluoropolyether Fomblin Y of vis- ~;
cosity 20 cSt, a To~ rk of ~ontefluos S.p.A., and 200 cc of titanlum tetra~-n-butoxide are add~ed at room temperature. Fombli~n Y ~is~
within the formula~
CF3o-(c3F6o)n(cF2-o)m CP3 (I~) where m and n are as defined above.
; ~ The mixture is stirred for 5 minutes to homoge~nize , it. Then, under an overpressure of 10 atm of nitrogen, which is kept constant thr~oughout~ the duration of test, within~ a ;30-: ~ .
.
,' ~ .
129~136 seconds time the mixture is passed through a stainless-steel 4 meter long tube having an inner diameter of 2 mm, to form the emulsion, which is discharged into a glass flask containing 2 liters of distilled water kept vigorously stirred.
The so-formed suspension is fitered over a Millipore filter with a cut-off of 0.2 microns; the obtained solid is washed with distilled water, and then with trichlorofluoro-methane. The solid is oven-dried and inspected by scanning elec-tron microscope, while its granulometric distribution is analyzed by the sedigrnph technique. The particles have a spheroidal shape and an aYerage diameter of 0.5 microns.
: . : .
Example 2 ~: ~ ::
~ xample 1 is repeated, by using, instead of titanium alkoxide, an equal volume of aluminum sec-butyloxide, and a ;
nitrogen overpressure of 15 atm. ;
The thus-obtained solid has a spheroidal shape and an average diameter of 0.3 microns. ~
: :
Example 3 Example 1 is repeated, by using, instead of titanium alkoxide, an equal volume of Zr n-propyloxide dissolved in pro-panol, and a nitrogen overpressure of 15 atm.
The ttlus-obtained solld has a spherical shape and an average diameter of 0.3 microns.
:: ' :
' ;
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9~l36 Example 4 To the same autoclave of Example 1, 200 cc of per~
fluo~opolyethe~ Galden/D05 (a Trademark) of 5 cS-t viscosit~sold by Mont~luos S.p.A., 5 cc of isopropyl tltanate and 0.2 cc OI an amidosilane of Fomblin Y, having an acidimetric eguivalent weight of 5000, are added. Galden/D05 (a Trad OE k) is within fornula (IV) of Example 1, and . ~
the above Fomblin y(a rrademark) amidosilane is within lormula ;TII) as re-ported in the description.
The whole is stirred for 5 minutes and, under an over-pressures of 30 atmospheres of nitrogen, kept constant throughout the test duration, within a 50-second time, the so-formed mixture is discharged through a l-meter long stainless-steel tube having an inner diameter of 1 mm, into a glass flask9 equipped wlt~an anchor stirrer, containing 800 cc of Galden/D05 (a Tradsmsrk)3.~2 cc of dls-tllled water, and 0.5 cc of Rioklen NF 10 (a Tr dem9rk for ethoxylated alkyl-phenol), with stlrring at~l;500 rpm.
The solid,~ isolated by the same procedure~s~as those ~ofEx mple 1, has a spheroida~l shape and an~average diameter of~0~.5 microns.
Example 5 E~xample 4 Is repeated,~ wlth the~exception of;~the fol~-lowing specifically indicated modifications~
:
5.77 g of aluminum sec-butyloxide and a nitrogen over-~; pressure of 60 atm are used. The mixture is discharged within l5 minutes and 30 seconds through a l-meter long stginless-steel tube~ of 0.75 mm internal di~meter, into & circuit containlng 2.~5 liters of Galden~D05 (a Trademarkj and 3.2 cc of distilIed water.
:
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. . .
L29~36 .' The solid9 isolated by the same procedures as in Exam-ple 1, has a spheroidal shape and Q diameter of 2 microns.
Example 6 Example 5 is repeated, with the exception of the fol-lowing specifically indicated modifications:
7.75 cc of zirconium n-propyloxide in solution in its corresponding alcohol and 150 cc of perfluoropoly.ether are used.
Before discharging the mixture, 0~16 cc of distilled water are added, and the mixture is discharged a few minutes later. The mixture is discharged within 14-minutes time. The ; ~solid, isolQted by the same procedures as of Example ~ has a spheroidal shape and an average diameter of 1.5 microns. ;
Example 7 To a 2-liter glass reactor~ equipped with an anchor stirrer, 200 cc of perfluoropolyether Galden/D20, having a vis-~osity of 18 cSt, sopl~d by Montefluos S.p.A., 5 cc ~of ispropyl titanate and 0.2 cc of the above Pomblin ~ amidosilane r~e chsrged. Galden/D20 is~within formula (IV) of Exsrnple 1.;
The reactor contents are stirred 5 minutes at 600 rpm, and are then discharged by gravity into an underlying flask equipped with an anchor stirrer, containing 800 cc of Galden/D20 and 3.2 cc of distilled water, kept vigorously stirred (1000 rpm).
The solid, isolated by the same procedures as in Exam-ple 1, has a spheroidal shape, and an average diameter of 2 micron5.
: ~ : :
1 ~
1~ .-~ ~; . 1 ;
I
---" I ~ Z90136 ¦ Example 8 Example 5 is repeated, but with the difference that 0.16 cc of distilled water is charged to the autoclave, and that before discharging the autoclave contents, some minutes are allowed to elapse.
The solid, isolated by the same procedures as in Exam-ple 1, has a spheroidal shape, and an average diameter of 2 microns.
.
Example 9 To a glass vessel, 200 cc of perfluoropolyether Galden/D05, 5 cc of isopropyltitanate and 0.2 cc of the above Fomblin Y amidosilane are oharged. The contents of the ve~ssel are stirred 5 minutes by an ultratrrax s~irrer, at a speed of 4500 rpm, and, with the stirring being maintained, 3.2~cc of distilled water are then added dropwise.
The solid, isolated by the same procedures as in ~xam-ple 1, has a spheroidal shape, and an average diameter o~ 0.3 micron ,.' : '.
' : ~ :~ .
. ` ~ ~, .
- 13 - ~
: :
: ~' :
..
. . .
''~'': ' .' , ' '~
D~scription of the Inverltion . .
'Ill~ present invention relates to Q process for prepar-illg fine p~r~icles of metal oxides. More p~rticul~rly, it re Intes to n process for preparing spheroidal particles of met~l oxides llavillg ~ submicronic aver~ge diameter, or having an QVer-~e di~m~ter ~Inaller tllnn 3 microns. The particles thus produced r~r~ uscd, c.g., in tllc prepnration of cernmic materiRls.
It is nlre~dy known to prep~re fine particles of metal oxides by renction witl~ water vapor of arl nerosol of hydrolyz~ble metal compoullds in an itlert gas. This rnetll~d shows several draw-bnclcs. First of nll, the metal cornpound must be completely evap-orated before forming tlle aerosol, witll ~ consequent high energy consllmption. Furthermore, the method implies the use of large volumes of inert gas, wllich must moreover ha~e a particularly low level of moisture. On the other hand, only hydroly~able metal compounds having a high vapor pressure cnn be used. Fin~lly, the method has a poor potenti~lity9 requlres high investment costs, ~and involves a high produ~tion ~ost.
The present invention provides a process for preparing fine particles of metal oxides which overcomes the above drawbacks. ~
According to the present invention there is provided a process for preparing spheroidal particles of an oxide compound selected from the group consisting of Ti A1, Zr, si and B oxides, having an average diameter o~ less than 3 microns, comprising: preparing an ~mul~ion in a perfluoropolyether of a hydrolyzable liquid compound of an element selected ~rom the group consisting of Ti, Al, zr, Si and B; reacting the emulslon with water, with water vapor or with a mixture, in any ratio, of water with a liquid miscible or immiscible with water, said liquid not interfering with the reaction of the hydrolyzable compound with water, to ~obtain an oxide hydrate, recovering said oxide hydrate, drying and calcining said oxide hydrate to an oxide.
.
: ~ : :
'J~7 ~2~13~;
By the term "hydrolyzable metal compound" is meant a metal compound able to react with water to yield the correspond-ing metal oxide hydrate.
The hydrolyzable metal compound is preferably a com-pound of Ti, Al, Zr, Si, or B.
Ther perfluoropolyethers are per se well known com-pounds described, e.g., in patents to which reference is made hereafter.
Suitable perfluoropolyethers for forming the emulsions or hydroIyzable metal compounds are, particularly, those comply-ing with the following formuIae (A) to tG), and having~ a ViSC09-, ity of~from 4 to 1500 cSt~
(A) CF30 (C3F6O)m(c2F4O)n(cFxojq-cF3 wherein X is equal to -F or ~CF3; m, n~and g are integers; ~the~
ratio n + q~
being within the range of from 1 to iO,;and n/q being within the range of from 1 to~10, w1th the oxyperfluoroa~lkylene; units ran-domly d1stributed al~ong ~the cha~n. The ~preparation~ of ~these~
compounds is descr1bed~in~U.S. Patent No.~ 3,665,04 (B) C3F7OlC3F6O)m ~, ~
; ~ : :;
- - .
:
. ' ' , ~Z9~L36 wherein Rf is -C2F~ or -C3F7 and m is an integer greater than 2. The preparation of these compounds is described in U.S.
Patent No. 3,242,21~.
(C) CF3O(c2~4O)p(cF2o)q CF3 wherein p and ~ are integers equal to or different from each other, and the p/q ratio is within the range of from 0.5 to 1.5, the oxyperfluoroalkylene units being randomly distributed along the chain. The preparation of these compounds is described in U.S. Patents Nos. 3,715,378 and 3,865,041.
(D) CF30(C3F6O)m(CFXO)n CF2Y
wherein X and Y, equal to or different from each other, are -F or -CF3 m and n are integers and the m/n ratio is within the range of from 5 to 40, the oxyperfluoroalkylene units being rando~ly distributed along the chain. The preparation of these compounds is described in U.K. Patents Nos. 1,104,482 and 1,226,566.
(E~) Perfluoropolye~thers havlng an oxetane str~uct~ure,~
~; ~ as described in Canadian Patént application No. 501,657 ~; ( F ) R ' f O ( CF 2CF 20 ) PR f ~: ~he~ 9 ~ n PI _nd R~ eqUa' to or dlfferent from each other, are~
~-CF3 or -C2F5, and ~ is an integer such that the viscosity is : ~ ~
within the stated ranFe. Products of this type are described in .S. Patent No. 4,523,039.
(G) R'f (CF2cF2 CF2)s Rf wherein Rf and R~f, equal to or different from each other, are -CF3 or ~C2F5, and s is an integer such that the viscosity is within the stated range. Products of this type are described in : ~ :
Canadian Patent No, 1,259,~443.
::
--', ~
~ 29~136 ,".
Usually, the perfluoropolyether used to form the emul-sion has a viscosity within the range of from 4 to 200 cSt.
The hydrolyzable metal compounds used to form the emul-sions are, e.g., the alkoxides and haloalkoxides of Al, Ti, Zr and B (such as the isopropyloxide, sec-butyloxide, n-butyloxlde, and n-propyloxide, halides, such as TiC1~9 BC13 and SiC14, and those halide complexes which are liquid at emulsifying tempera ture: e.g., AlC13-complexes wlth arom~tic esters and TiC14-com-plexes with long-chain aliphatic ethers. These metal compounds must be liquid at the emulsifying temperature. Usually, the emulsion is prepared ~t ambient temperature. However,~one may;
operate at a lower or higher than ambient temperature, e.g., within the range of from -30 to +90C.
The alkoxides may be used as solutions in their corre-sponding alcohol. When Al, Ti, Zr or B oxides are to be pre-pared, the alkoxides are commonly used as the startlng materials.
The ratio, by volume, of the hydrolyznble metal com-pound to the perfluoropolyether in the emulsion is within the rQnge of from 0.01 to 1.
The emulsion is preferably prepared in the presence of an emulsion stabilizer consisting or consisting essentially of a perfluoropolyether having n functionnl end group. Prefernbly, the perfluoropolyether having a funetional end group has the following end groups:
O
- C~
~ ~ H-R
: : :
' ~ :
~ ~ ~ - 5 -:
~ 1;;:90~36 wherein R is a linear, branched or cyclic alkyl of from 1 to 20 carbon atoms, or an alkylaryl of from 7 to 20 carbon atoms; R may also contain heteroatoms, fn particular O and/or Si atoms, and substituents, e.g., Cl.
Examples of suitable emulsion stabilizers are:
CF3-~OC3F6)n(OCF2)m-O-CF2-C3O CH2 1 3 3 (I) 3 (c3F6)n(cP2)m ocF2-coo-cH2-cHoH-o-(c~2)3-si(oMe)3 (Il) CF3 ~oc3F6)ntocF2)m-o-GF2oo-NH-(cH2)3-si(oEt)3 (III) :
The amount of emulsion stabilizer is gensrally with;n the range of from 0.01 to 5% by weight based on perfluoropoly-ether; more usually, from 0.1 to 0.5~ thereof is used.
Any process allowing one to obtain the emulsion may be conveniently used in the process of this invention. ~ -~;
The emulsion may be prepared, e.g., by means of st~rong stirring, e.g., by using an ultraturrax stirrer. The emulslon is prepared under Hn adequate stirring. By increasing the stirring rate, smaller particles of metal oxide hydrate are obtained.
With incre~sing viscosity of the perfiuoropolyether, particles of m~tal oxide hydrate of larger dimensions are ob-tained.
~: ,:
. , ~ - 6 -~ :
~ ' ~
: . , " ,,,.
, ~29C~1~6 A first method for carrying out the hydrolysis consists in adding the emulsion to water, with stirring.
A second method consists in adding, always with stir-ring, the emulsion to water mixed, in ~ny ratio, with a liquid miscible or immiscible with it.
Among the water-miscible liquids which may be used according to the present invention, the alcohols of from I to 8 carbon atoms and ethylene glycol may be mentioned. Among the immiscible liquids, perfluoropolyethers, hydrocarbons, and sili-cone oils may be mentioned. More commonly, water is present in such blends in amounts ranging from 0.1 to 90% by volume.
A third method for carry out the hydrolysis conslsts or ~onsists essenti~lly in adding the emulsion to water ~vapor.
Water vapor may be used as sueh, or contained in a gas, such as, e.g., nitrogen; usually, a gas saturated with water is used. In this case, the sphericity of the oxide hydrate is generally im-proved.
The amount of wat~er relative to the metal compound ma~y vary over a wide range. The minimum amount is that amount which is stoichiometrically required to carry out the hydrolysis reac-tion. However, large excesses of water may be used, and an amount of water equal to 2.5 times the stoichiometric ratio is commonly used.
The emulsion may be prepared ~and introduced into the liquid water phase ~w~ter, or blends thereof with other liquids) by a high-linear~speed stream. ~ For that purpose a homogeneous mixture is prepared of the hydrolyzable metal compound and of the ~ ~ ~ : ; ' ~ ; - 7 - ;
; ~ :, :~ :
: ~. ~ , . , ~
, ~290~l36 :
perfluoropolyether, and the mixture is passed, under pressure, through a tube having a length equal to from 500 to 3000 times its diameter, and wherein the linear speed of the mixture is greater than I meter/second. Such a stream may be introduced into a vessel containing the liquid aqueous phase, or into a recycle circuit wherein the liquid aqueous phase is circulated.
When such a stream is used, the emulsion pressure is generally within the range of from 20 to 90 relative to the atmosphere.
By thus injecting the emulsion, the diameter of the metal oxide hydrate particles is reduced.
By operating with a high-linear-speed emulsion stream, the introduction of the emulsion into the liquid aqueous phase requires a short time. When such a procedure is not used, the introduction of the emulsion into the liquid aqueous phase or the introduction of the liquid aqueous phase into the emulsion is preferably gradual; it is carried out, e.g., over a time of from 1 to 30 minutes.
The hydrolysis step may be preceded by a prehydrolysis;
i.e., a small amount of water is introduced into the emulsion before the true hydrolysis is performed. Usually, from 5 to 10%
of the total amount of water used in the process is thus intro-duced with stirring. Usually, this water addition Is instantan-eous. After such an addition, stirring is continued for a cer-tain time, e.g~, for 5 minutes, before the true hydrolysis is carried out. This pre-hydrolysis improves the sphericity of the metal oxide hydrate.
:: :
. . .
~ ~ ~ - 8 - ~
, .
~LX90~36 The hydrolysis is commonly carried out at ambient tem-perature. However, operating at a lower o~ higher temperature, e.g~, within the r~nge of from -30 to +90C, is possible. W~en operating below 0C, the water must be in the presence of a sub-stance which lowers its freezing po;nt, such as ethylene glycol.
The separation of the metal oxide hydrate from the liquid phase at the end of the hydrolysis may be carried out by known methods, e.g., by filtration.
The metal oxide hydrate is dried by per se known methods. The calcination is carried out, as is well-known, at different temperatures, depending on the nature of the metal oxide hydrate and its desired crystalline form.
The present invention is also suitable for preparing mixed metal oxides.
The following Examples are given for still ~better i;llustrating the Inventive concept of the present inven~tlon.~
To a 500-cc stainless-steel autoclave equipped~ with an anchor~stirrer, 200~cc of a perfluoropolyether Fomblin Y of vis- ~;
cosity 20 cSt, a To~ rk of ~ontefluos S.p.A., and 200 cc of titanlum tetra~-n-butoxide are add~ed at room temperature. Fombli~n Y ~is~
within the formula~
CF3o-(c3F6o)n(cF2-o)m CP3 (I~) where m and n are as defined above.
; ~ The mixture is stirred for 5 minutes to homoge~nize , it. Then, under an overpressure of 10 atm of nitrogen, which is kept constant thr~oughout~ the duration of test, within~ a ;30-: ~ .
.
,' ~ .
129~136 seconds time the mixture is passed through a stainless-steel 4 meter long tube having an inner diameter of 2 mm, to form the emulsion, which is discharged into a glass flask containing 2 liters of distilled water kept vigorously stirred.
The so-formed suspension is fitered over a Millipore filter with a cut-off of 0.2 microns; the obtained solid is washed with distilled water, and then with trichlorofluoro-methane. The solid is oven-dried and inspected by scanning elec-tron microscope, while its granulometric distribution is analyzed by the sedigrnph technique. The particles have a spheroidal shape and an aYerage diameter of 0.5 microns.
: . : .
Example 2 ~: ~ ::
~ xample 1 is repeated, by using, instead of titanium alkoxide, an equal volume of aluminum sec-butyloxide, and a ;
nitrogen overpressure of 15 atm. ;
The thus-obtained solid has a spheroidal shape and an average diameter of 0.3 microns. ~
: :
Example 3 Example 1 is repeated, by using, instead of titanium alkoxide, an equal volume of Zr n-propyloxide dissolved in pro-panol, and a nitrogen overpressure of 15 atm.
The ttlus-obtained solld has a spherical shape and an average diameter of 0.3 microns.
:: ' :
' ;
:, ~
9~l36 Example 4 To the same autoclave of Example 1, 200 cc of per~
fluo~opolyethe~ Galden/D05 (a Trademark) of 5 cS-t viscosit~sold by Mont~luos S.p.A., 5 cc of isopropyl tltanate and 0.2 cc OI an amidosilane of Fomblin Y, having an acidimetric eguivalent weight of 5000, are added. Galden/D05 (a Trad OE k) is within fornula (IV) of Example 1, and . ~
the above Fomblin y(a rrademark) amidosilane is within lormula ;TII) as re-ported in the description.
The whole is stirred for 5 minutes and, under an over-pressures of 30 atmospheres of nitrogen, kept constant throughout the test duration, within a 50-second time, the so-formed mixture is discharged through a l-meter long stainless-steel tube having an inner diameter of 1 mm, into a glass flask9 equipped wlt~an anchor stirrer, containing 800 cc of Galden/D05 (a Tradsmsrk)3.~2 cc of dls-tllled water, and 0.5 cc of Rioklen NF 10 (a Tr dem9rk for ethoxylated alkyl-phenol), with stlrring at~l;500 rpm.
The solid,~ isolated by the same procedure~s~as those ~ofEx mple 1, has a spheroida~l shape and an~average diameter of~0~.5 microns.
Example 5 E~xample 4 Is repeated,~ wlth the~exception of;~the fol~-lowing specifically indicated modifications~
:
5.77 g of aluminum sec-butyloxide and a nitrogen over-~; pressure of 60 atm are used. The mixture is discharged within l5 minutes and 30 seconds through a l-meter long stginless-steel tube~ of 0.75 mm internal di~meter, into & circuit containlng 2.~5 liters of Galden~D05 (a Trademarkj and 3.2 cc of distilIed water.
:
' :' , `' ; , ,~;; '::~' ' : , .
. . .
L29~36 .' The solid9 isolated by the same procedures as in Exam-ple 1, has a spheroidal shape and Q diameter of 2 microns.
Example 6 Example 5 is repeated, with the exception of the fol-lowing specifically indicated modifications:
7.75 cc of zirconium n-propyloxide in solution in its corresponding alcohol and 150 cc of perfluoropoly.ether are used.
Before discharging the mixture, 0~16 cc of distilled water are added, and the mixture is discharged a few minutes later. The mixture is discharged within 14-minutes time. The ; ~solid, isolQted by the same procedures as of Example ~ has a spheroidal shape and an average diameter of 1.5 microns. ;
Example 7 To a 2-liter glass reactor~ equipped with an anchor stirrer, 200 cc of perfluoropolyether Galden/D20, having a vis-~osity of 18 cSt, sopl~d by Montefluos S.p.A., 5 cc ~of ispropyl titanate and 0.2 cc of the above Pomblin ~ amidosilane r~e chsrged. Galden/D20 is~within formula (IV) of Exsrnple 1.;
The reactor contents are stirred 5 minutes at 600 rpm, and are then discharged by gravity into an underlying flask equipped with an anchor stirrer, containing 800 cc of Galden/D20 and 3.2 cc of distilled water, kept vigorously stirred (1000 rpm).
The solid, isolated by the same procedures as in Exam-ple 1, has a spheroidal shape, and an average diameter of 2 micron5.
: ~ : :
1 ~
1~ .-~ ~; . 1 ;
I
---" I ~ Z90136 ¦ Example 8 Example 5 is repeated, but with the difference that 0.16 cc of distilled water is charged to the autoclave, and that before discharging the autoclave contents, some minutes are allowed to elapse.
The solid, isolated by the same procedures as in Exam-ple 1, has a spheroidal shape, and an average diameter of 2 microns.
.
Example 9 To a glass vessel, 200 cc of perfluoropolyether Galden/D05, 5 cc of isopropyltitanate and 0.2 cc of the above Fomblin Y amidosilane are oharged. The contents of the ve~ssel are stirred 5 minutes by an ultratrrax s~irrer, at a speed of 4500 rpm, and, with the stirring being maintained, 3.2~cc of distilled water are then added dropwise.
The solid, isolated by the same procedures as in ~xam-ple 1, has a spheroidal shape, and an average diameter o~ 0.3 micron ,.' : '.
' : ~ :~ .
. ` ~ ~, .
- 13 - ~
: :
: ~' :
..
. . .
''~'': ' .' , ' '~
Claims (14)
1. A process for preparing spheroidal particles of an oxide compound selected from the group consisting of Ti,Al, Zr, Si and B oxides, having an average diameter of less than 3 microns, comprising: preparing an emulsion in a perfluoropolyether of a hydrolyzable liquid compound of an element selected from the group consisting of Ti, Al, Zr, Si and B; reacting the emulsion with water, with water vapor or with a mixture, in any ratio, of water with a liquid miscible or immiscible with water, said liquid not interfering with the reaction of the hydrolyzable compound with water, to obtain an oxide hydrate; recovering said oxide hydrate, drying and calcining said oxide hydrate to an oxide.
2. Process according to Claim 1, characterized in that the perfluoropolyether has a viscosity of from 4 to 1500 cSt, and is selected from the group consisting of:
(A) CF3O-(C3F6O)m(C2F4O)n(CFXO)q-CF3 wherein X is equal to -F or -CF3; m, n and q are integers; the ratio being within the range of from 1 to 50 and n/q is within the range of from 1 to 10; the oxyperfluoroalkylene units being ran-domly distributed along the chain;
(B) C3F7O(C3F6O)m-Rf wherein Rf is -C2F5 or -C3F7 and m is an integer greater than 2;
(C) CF3O(C2F4O)p(CF2O)q-CF3 wherein p and q are integers equal to or different from each other and the p/q ratio is within the range of from 0.5 to 1.5;
the oxyperfluoroalkylene units being randomly distributed along the chain;
(D) CF3O(C3F6O)m(CFXO)n-CF2Y
wherein X and Y, equal to or different from each other, are -F or -CF3; m and n are integers and the m/n ratio is within the range of from 5 to 40; the oxyperfluoroalkylene units being randomly distributed along the chain;
(E) perfluoropolyethgers having an oxetane struc-ture;
(F) R'f O(CF2CF2O)pRf wherein Rf and R'f equal to or different from each other, are -CF3 or -C2F5 and p is an integer such that the viscosity is within the stated range; and (G) R'f O(CF2CF2CF2O)sRf wherein Rf and R'f, equal to or different from each other, are -CF3 or -C2F5 and s is an integer such that the viscosity is within the stated range.
(A) CF3O-(C3F6O)m(C2F4O)n(CFXO)q-CF3 wherein X is equal to -F or -CF3; m, n and q are integers; the ratio being within the range of from 1 to 50 and n/q is within the range of from 1 to 10; the oxyperfluoroalkylene units being ran-domly distributed along the chain;
(B) C3F7O(C3F6O)m-Rf wherein Rf is -C2F5 or -C3F7 and m is an integer greater than 2;
(C) CF3O(C2F4O)p(CF2O)q-CF3 wherein p and q are integers equal to or different from each other and the p/q ratio is within the range of from 0.5 to 1.5;
the oxyperfluoroalkylene units being randomly distributed along the chain;
(D) CF3O(C3F6O)m(CFXO)n-CF2Y
wherein X and Y, equal to or different from each other, are -F or -CF3; m and n are integers and the m/n ratio is within the range of from 5 to 40; the oxyperfluoroalkylene units being randomly distributed along the chain;
(E) perfluoropolyethgers having an oxetane struc-ture;
(F) R'f O(CF2CF2O)pRf wherein Rf and R'f equal to or different from each other, are -CF3 or -C2F5 and p is an integer such that the viscosity is within the stated range; and (G) R'f O(CF2CF2CF2O)sRf wherein Rf and R'f, equal to or different from each other, are -CF3 or -C2F5 and s is an integer such that the viscosity is within the stated range.
3. Process according to Claim 1 in which the hydrolyzable metal comound is a compound of Ti, Al, Zr, Si or B.
4. Process according to Claim 3, characterized in that the hydrolyzable metal compound of Ti, Al, Zr, Si or B is an alkoxide.
5. Process according to Claims 1 or 2, characterized in that the ratio by volume of the hydrolyzable metal compound to the perfluoropolyether in the emulsion is within the range of from 0.01 to 1.
6. Process according to Claims 1 in which the emulsion of the hydrolyzable metal compound in the perfluoropoyether is prepared in the presence of an emulsion stabilizer consisting essentially of a perfluoropolyether having a functional end group.
7. Process according to Claim 6, characterized in that the functional end group of the perfluoropolyether is selected from the group consisting of:
and wherein R is a linear, branched or cyclic alkyl of from 1 to 20 carbon atoms, or an alkylaryl of from 7 to 20 carbon atoms; and R
may also contain heteroatoms as well as other substituents.
and wherein R is a linear, branched or cyclic alkyl of from 1 to 20 carbon atoms, or an alkylaryl of from 7 to 20 carbon atoms; and R
may also contain heteroatoms as well as other substituents.
8. Process according to Claim 7, in which the amount of emulsion stabilizer is within the range of from 0.01 to 5% by weight based on the perfluoropolyether.
9. Process according to Claim 8, characterized in that the liquid miscible with water is an alcohol of from 1 to 8 carbon atoms, or ethylene glycol.
10. Process according to Claim 1 or 2, characterized in that the liquid immiscible with water is a perfluoropolyether, a hydrocarbon, or a silicone oil.
11. Process according to Claim 1 or 2, characterized in that in the mixture of water with a liquid miscible or immisc-ible with it, water is present in an amount ranging from 0.1 to 90% by volume.
12. Process according to Claim 1 or 2, characterized in that the emulsion of the hydrolyzable metal compound in the perfluoropolyether is obtained by passing a homogeneous mixture of said compounds, under pressure, through a tube having a length from 500 to 3000 times its diameter, and wherein the linear speed of the mixture is greater than 1 meter/second.
13. Process according to Claim 1 in which before reacting the emulsion with water, with water vapor, or with the water-liquid mixture, a small amount of water is added to the emulsion.
14. Process according to Claim 13, characterized in that the amount of water is from 5 to 10% of the total amount of water used in the process.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IT21335A/86 | 1986-07-31 | ||
| IT21335/86A IT1197794B (en) | 1986-07-31 | 1986-07-31 | PROCEDURE FOR THE PREPARATION OF FINE METALLIC OXIDE TROUSERS |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1290136C true CA1290136C (en) | 1991-10-08 |
Family
ID=11180280
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000543440A Expired - Fee Related CA1290136C (en) | 1986-07-31 | 1987-07-30 | Process for preparing fine particles of metal oxides |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US4808397A (en) |
| EP (1) | EP0255702A3 (en) |
| JP (1) | JPS6340706A (en) |
| AU (1) | AU587339B2 (en) |
| CA (1) | CA1290136C (en) |
| IT (1) | IT1197794B (en) |
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| FR2629071B1 (en) * | 1988-03-22 | 1991-03-15 | Produits Refractaires | REACTIVE ZIRCONIUM OXIDE AND ITS PREPARATION |
| FR2629072B1 (en) * | 1988-03-22 | 1990-11-30 | Produits Refractaires | PROCESS FOR THE MANUFACTURE OF HYDRATED ZIRCONIUM OXIDE FROM GRANULAR CRYSTALLIZED ZIRCONIUM OXIDE |
| CA1326122C (en) * | 1988-10-05 | 1994-01-18 | Fawzy Gamaleldin Sherif | Process for forming metal oxide powders from the metal alkoxide |
| DE3834773A1 (en) * | 1988-10-12 | 1990-04-19 | Fraunhofer Ges Forschung | PARTICULAR POLYCONDENSATES, METHOD FOR THE PRODUCTION AND USE THEREOF |
| IT1227185B (en) * | 1988-10-19 | 1991-03-21 | Eniricerche Spa | PROCEDURE FOR THE PREPARATION OF A ZIRCONIUM DIOXIDE PRECURSOR |
| IT1230630B (en) * | 1988-11-11 | 1991-10-28 | Eniricerche Spa | PROCEDURE FOR THE PREPARATION OF A Zirconium Zirconium Precursor |
| KR950001660B1 (en) * | 1989-04-07 | 1995-02-28 | 니혼 쇼꾸바이 가가꾸 고오교 가부시기가이샤 | Method for production of inorganic oxide particles |
| US5876686A (en) * | 1995-06-28 | 1999-03-02 | E. I. Du Pont De Nemours And Company | Process for making inorganic oxide gels in fluorocarbon solvents |
| US6387531B1 (en) | 1998-07-27 | 2002-05-14 | Nanogram Corporation | Metal (silicon) oxide/carbon composite particles |
| US20090255189A1 (en) * | 1998-08-19 | 2009-10-15 | Nanogram Corporation | Aluminum oxide particles |
| US20060147369A1 (en) * | 1997-07-21 | 2006-07-06 | Neophotonics Corporation | Nanoparticle production and corresponding structures |
| US6099798A (en) * | 1997-10-31 | 2000-08-08 | Nanogram Corp. | Ultraviolet light block and photocatalytic materials |
| US6290735B1 (en) | 1997-10-31 | 2001-09-18 | Nanogram Corporation | Abrasive particles for surface polishing |
| US7384680B2 (en) * | 1997-07-21 | 2008-06-10 | Nanogram Corporation | Nanoparticle-based power coatings and corresponding structures |
| US20090075083A1 (en) * | 1997-07-21 | 2009-03-19 | Nanogram Corporation | Nanoparticle production and corresponding structures |
| JP4184487B2 (en) * | 1997-08-15 | 2008-11-19 | 昭和電工株式会社 | Method for producing titanium dioxide fine particles |
| US6991773B2 (en) * | 2002-08-19 | 2006-01-31 | Nanomix, Inc. | Boron-oxide and related compounds for hydrogen storage |
| EP1730074A1 (en) | 2004-03-30 | 2006-12-13 | Pirelli & C. S.p.A. | Process for manufacturing an electrochemical device |
| US7655212B2 (en) * | 2008-04-11 | 2010-02-02 | Eastman Kodak Company | Production of silver sulfate grains using a fluorinated additive |
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|---|---|---|---|---|
| US3242218A (en) * | 1961-03-29 | 1966-03-22 | Du Pont | Process for preparing fluorocarbon polyethers |
| GB1104482A (en) * | 1964-04-09 | 1968-02-28 | Montedison Spa | Perfluoro-olefin derivatives |
| US3715378A (en) * | 1967-02-09 | 1973-02-06 | Montedison Spa | Fluorinated peroxy polyether copolymers and method for preparing them from tetrafluoroethylene |
| GB1226566A (en) * | 1967-04-04 | 1971-03-31 | ||
| US3665041A (en) * | 1967-04-04 | 1972-05-23 | Montedison Spa | Perfluorinated polyethers and process for their preparation |
| FR1587066A (en) * | 1968-07-15 | 1970-03-13 | ||
| US4011096A (en) * | 1975-06-10 | 1977-03-08 | E. I. Du Pont De Nemours And Company | Vesiculated silica microspheres |
| US4090887A (en) * | 1975-11-25 | 1978-05-23 | E. I. Du Pont De Nemours And Company | Pigmented microporous silica microspheres produced by a water in oil emulsion |
| SU865791A1 (en) * | 1978-08-11 | 1981-09-23 | Ордена Ленина Институт Общей И Неорганический Химии Им. Н.С.Курнакова Ан Ссср | Method of producing spherical silicagel |
| JPS5532775A (en) * | 1978-08-31 | 1980-03-07 | Pola Chem Ind Inc | Colored fine spherical silica gel and production thereof |
| JPS5637207A (en) * | 1979-09-05 | 1981-04-10 | Kazutaka Kojima | Manufacture of metal oxide fine powder |
| US4523039A (en) * | 1980-04-11 | 1985-06-11 | The University Of Texas | Method for forming perfluorocarbon ethers |
| CA1261589A (en) * | 1981-05-18 | 1989-09-26 | Bulent E. Yoldas | Predetermined and enhanced densification in sintered metal oxides |
| US4543341A (en) * | 1983-12-23 | 1985-09-24 | Massachusetts Institute Of Technology | Synthesis and processing of monosized oxide powders |
| JPS60137827A (en) * | 1983-12-23 | 1985-07-22 | Shin Etsu Chem Co Ltd | Production of fine zirconia powder |
| DE3486428T2 (en) * | 1983-12-26 | 1996-10-10 | Daikin Ind Ltd | Halogen containing polyether |
| DK251984D0 (en) * | 1984-05-22 | 1984-05-22 | Niro Atomizer As | PROCEDURE FOR THE PREPARATION OF POLYMER PARTICLES |
| GB8501882D0 (en) * | 1985-01-25 | 1985-02-27 | Atomic Energy Authority Uk | Materials |
| IT1200385B (en) * | 1985-02-13 | 1989-01-18 | Montefluos Spa | OXETANIC STRUCTURE FLUIDS HAVING IMPROVED CHARACTERISTICS FOR SPECIAL APPLICATIONS |
| FR2593166A1 (en) * | 1986-01-20 | 1987-07-24 | Solvay | PROCESS FOR PRODUCING A METAL OXIDE POWDER FOR CERAMIC MATERIALS AND ZIRCONIA POWDER OBTAINED THEREBY |
-
1986
- 1986-07-31 IT IT21335/86A patent/IT1197794B/en active
-
1987
- 1987-07-27 AU AU76148/87A patent/AU587339B2/en not_active Ceased
- 1987-07-27 US US07/078,088 patent/US4808397A/en not_active Expired - Fee Related
- 1987-07-28 JP JP62186782A patent/JPS6340706A/en active Pending
- 1987-07-30 CA CA000543440A patent/CA1290136C/en not_active Expired - Fee Related
- 1987-07-30 EP EP87111059A patent/EP0255702A3/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| EP0255702A2 (en) | 1988-02-10 |
| AU7614887A (en) | 1988-02-04 |
| JPS6340706A (en) | 1988-02-22 |
| IT8621335A1 (en) | 1988-01-31 |
| EP0255702A3 (en) | 1989-10-11 |
| IT8621335A0 (en) | 1986-07-31 |
| IT1197794B (en) | 1988-12-06 |
| AU587339B2 (en) | 1989-08-10 |
| US4808397A (en) | 1989-02-28 |
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