EP0403473A1 - Procede de preparation de spheres en dioxyde de titane monodispersees - Google Patents

Procede de preparation de spheres en dioxyde de titane monodispersees

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Publication number
EP0403473A1
EP0403473A1 EP19880903035 EP88903035A EP0403473A1 EP 0403473 A1 EP0403473 A1 EP 0403473A1 EP 19880903035 EP19880903035 EP 19880903035 EP 88903035 A EP88903035 A EP 88903035A EP 0403473 A1 EP0403473 A1 EP 0403473A1
Authority
EP
European Patent Office
Prior art keywords
solution
titania
amine
powder
particles
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
EP19880903035
Other languages
German (de)
English (en)
Inventor
William L. Olson
William E. Liss
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Honeywell International Inc
Original Assignee
AlliedSignal Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by AlliedSignal Inc filed Critical AlliedSignal Inc
Publication of EP0403473A1 publication Critical patent/EP0403473A1/fr
Ceased legal-status Critical Current

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Classifications

    • 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
    • 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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/50—Agglomerated particles
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/51—Particles with a specific particle size distribution
    • C01P2004/52—Particles with a specific particle size distribution highly monodisperse size distribution
    • 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

Definitions

  • This invention relates to a method of preparing onosized or monodispersed titania spheres as particles by so-gel chemistry using a size control additive to produce excellent yields of the desired material.
  • This invention relates, more specifically, to a process for reproducibly forming monodisperse titania spheres by the hydrolysis of titanium alkoxides in the presence of an amine-containing size control additive in such a way as to constrain the particle size within a narrow range.
  • Ceramic materials offer a wide variety of possible physicochemical characteristics which are controlled by the inherent atomic structure and microstructure of the material. Their refractory nature and chemical inertness allow for the use of these materials in environments where conventional materials such as polymers do not survive. Although the potential for growth in new application areas is very strong, their use is actually limited by processing technology which cannot adequately meet the purity, strength, homogeneity, and microstructure requirements of high performance ceramic applications.
  • Monodisperse metal oxide powders offer many processing advantages over conventional ceramic powders.
  • the spherical shape and narrow particle size distribution of the monodispersed powders allow for a tight control over the packing of the. owder particles in the green ceramic. Since there are very few agglomerates, the particles pack very uniformly with the residual pore sizes in the green ceramic often being on the order of two particle diameters ( ⁇ 1 micron) . If dispersions of the powder are slowly settled, very high green densities are attainable due to the statistical ordering of the particles with the residual pore size often on the order of one particle diameter.
  • monodisperse powders possess special advantages over conventional powders during the firing of the ceramic. Since the sintering temperature is inversely related to the size of the particles, the sub icron diameter of the powder particles results in lowering, often by several hundred degrees, the temperature required for sintering the material.
  • the tightly controlled particle size eliminates the problems of differential sintering that can occur in conventional powders where the very small particles begin to sinter ahead of the larger particles in the compact. This process, which often results in undesirably large grain growth and grain size distributions and porosity, can have disasterous consequences for the performance and properties of the ceramic material.
  • sintering of the powder particles is rapid and spatially uniform and results in a homogeneous fine grained microstructure in the sintered article.
  • sintering aids if required, can be included in the powder cheaply and uniformly during the synthesis stage and the composition of the powder can be tightly controlled during processing.
  • U.S. Patent 4,543,341 also described the synthesis and characterization of a monodisperse, submicron titania powder possessing a spherical shape, uniform dimensions and low state of aggregation.
  • the powder was prepared by mixing equal volume ethanol solutions of titanium tetraethoxide and water and stirring briefly. It was noted that powder isolation procedures must be initiated within thirty minutes of the onset of precipitation, or hard necked aggregates of the individual powder particles would form. Isolation procedures consisted of centrifuging the freshly prepared powder at low speed followed by decantation of the sol.
  • the powder was washed with ethanol followed by washing with alkaline water to impart a negative charge to the titania particle's surface thereby providing a net repulsive interparticle potential which inhibits flocculation of the powders.
  • an embodiment of this invention is found in a process for making monodisperse titania comprising the steps of: dissolving a titanium tetraalkoxide in a liquid comprising an alcohol to form a solution of said alkoxide; and thereafter adding an amine-containing size control additive and water to the solution to form a precipitate of solid monodisperse spheres of titania.
  • a further embodiment of the invention is found in a process for increasing the internal porosity of the monodisperse titania particles comprising the aging of dispersions of said titania in mediums such as basic water or titanium-alkoxide based sols.
  • a still further emdobiment of this invention is found in a process for producing green body compacts comprising the addition of a dispersion of said titania particles to a porous mold and the recovery therefrom of said solid green body compact.
  • This invention is concerned with the production of monodisperse titania particles from an alcoholic solution of titanium tetraalkoxide using an amine-containing addi- tive and water to hydrolyze said titanium alkoxide solution thereby producing the desired titania particles with subsequent separation and recovery of said monodisperse titania particles.
  • a solution of titanium tetraethoxide may be dissolved in ethanol, sec-butyl amine may be added, following which aqueous ethanol may be added to the resultant solution, to afford a precipitation of the desired monodisperse titania particles which can be separated from the solu ⁇ tion and recovered as spherical solids.
  • hydroxypropyl cellulose can be added to the alcohol when mixing with the alkoxide or with the water although it is preferred to be added to the alcohol-water mixture.
  • the monodisperse titania particles may be redispersed in a redispersing medium and recovered as a dispersion of said titania particles.
  • the redispersal of the monodisperse titania powder can be effected in any manner known to a person skilled in the arts though it is preferable to redisperse using a high frequency sonication device such as, for example, Vibra Cell made by Sonics Materials, and to utilize a dispersing medium chosen from the group including, but not limited to, ketones, alcohols of from one to four carbon atoms, aldehydes, water, chlorinated hydrocarbons, carboxylic acids, and amides.
  • a dispersing medium chosen from the group including, but not limited to, ketones, alcohols of from one to four carbon atoms, aldehydes, water, chlorinated hydrocarbons, carboxylic acids, and amides.
  • the redispersed material can be used in a variety of ways.
  • the redispersed material can then be charged into a porous mold and a compact, green body ceramic formed, the material can be cast in the form of a tape, settled slowly into a uniformly packed green ceramic, or the material can be aged from 1 day to 14 days in a medium such as basic water with a pH range of from about 8 to about 11 wherein the preferable base is ammonium hydroxide.
  • the aging conditions include a temperature from 15°C to about 90°C and a pressure in the range of from about 1 to about 10 at and result in a recovered product with a surface area increase that is in a range of from about 100 m /g to about 300 m 2 /g.
  • the typical unaged product has a surface area of about 5 m 2 /g and the aging process increases the surface area to about 200 m 2 /g.
  • the titanium tetraalkoxide used in this invention having a formula Ti(OR) 4 wherein R represents a lower alkyl group of from one to four carbon atoms, can be selected from the group including, but not limited to, titanium tetramethoxide, titanium tetraethoxide, titanium tetrapropoxide, titanium tetrabutoxide, titanium tetrasecbutoxide; titanium tetraisopropoxide, titanium ethoxytriethoxide, titanium ethoxypropoxydibutoxide, titanium dimethoxydiethoxide and titanium methoxyethoxypropoxybutoxide.
  • the alcohol (ROH) used in this invention can be selected from the group including, but not limited to, methanol, ethanol, 1-propanol, 1-butanol, 2-propanol, 2- butanol, 2-methyl-2-propanol. It is important to realize that the alcohol, of formula ROH, can have its R group selected from lower alkyl groups of from one to four carbon atoms.
  • the titanium tetraalkoxide is present in the alcohol solution at a concentration in the range of from 0.05 M to 1.0 M.
  • the water content of the final hydrolysis mixture should not exceed a molarity of water in the range of from .2 M to 1.5 M and that the starting alcohol solution should have no more water than 500 parts per million (ppm) with a preferable level of 200 ppm.
  • the water content of the titanium tetraalkoxide alcohol is preferably in a range of from 100 ppm to 300 ppm.
  • This invention concerns new size control additive systems which produce onosized titania by sol gel chemistry.
  • Sec-butyl amine and triethyl amine/hydroxypropylcellulose are two such preferred additive systems that are capable of preventing flocculation of the powder particles during precipitation/formation and of giving monodisperse spherical powders directly upon hydrolysis of the titanium alkoxide.
  • These additives represent a significant advance beyond the described prior art since they provide a method by which highly uniform dispersions of monosize titania particles can be produced in a very reproducible manner.
  • the additive is used in an amount sufficient to result in the solution containing from 0.001 M to 0.1 M.
  • amines with alkyl groups of from 1 to 7 carbon atoms in length may be employed to effect the process of this invention.
  • the best results may be obtained for mono- and di-substituted amines when used in the absence of hydroxypropylcellulose (HPC) whereas the best results may be obtained for trialkyla ines in the presence of HPC.
  • HPC hydroxypropylcellulose
  • the mono- and di-substituted amines for use in this invention can be selected from the group including, though not limited to, ethylamine, diethylamine. methylamine, dimethylamine, propylamine, dipropylamine, butylamine, dibutylamine, pentylamine, dipentylamine, hexylamine, dihexyla ine, heptylamine, diheptylamine, isopropyla ine, diisopropylamine, isobutylamine, diiosobutylamine, sec-butylamine, disec-butylamine, tert- butylamine, ditert-butylamine, isopentylamine, tert- heptylamine, ethylpropylamine, hexylbutylamine, etc.
  • Trialkyl amines for use in this invention can be selected from the group including, but not limited to, triethyla ine. trimethylamine, triisopropylamine, tributyla ine, triisobutylamine, tri-sec-butylamine, tri- tert-butylamine, tripentylamine, triisopentylamine, trihexylamine, triheptyla ine, methyldiethylamine, ethylmethylpropylamine, propyldiethylamine, hexylmethylpentylamine, propylethylheptylamine, pentyldibutylamine, etc.
  • monodisperse and monosize will be used interchangeably and mean that the particle size distribution is such that the standard deviation of the particle size distribution is less than one-half of the average particle diameter.
  • the concentration of sec- butylamine is to be in a range of from about .001 M to about .1 M
  • the concentration of hydroxypropylcellulose to be in the range of from about 0.5 to 5 weight percent based on alkoxide is to be present in an amount in the range of about 1 to about 6 mole percent based on titanium metal.
  • hydrolysis reactions proceed at a rate sufficient to assure the rapid growth and precipitation of the material, yet not too rapid that precipitation occurs immediately upon reagent addition. If the reaction is extremely rapid, local areas of supersaturation develop in the sol with the concomitant formation of non-uniform precipitates. Thus the solution must be uniform with no local supersaturation, and particle growth must proceed at an appreciable rate following the initial precipitation.
  • Another aspect which must be incorporated into any successful reaction scheme is to stabilize the particles during their growth in the sol, a very critical factor in the nonreproducibility of the reaction chemistry for titania.
  • the particle's surface must be sufficiently charged, or otherwise sterically stabilized such that interparticle forces are of a repulsive nature and provide a barrier to hard aggregate formation.
  • "agglomeration" processes are certain to occur in concentrated dispersions of the powders, unless they have been stabilized in some manner.
  • the process of this invention can be effected in a batch manner whereby the titanium tetraalkoxide is mixed with the alcohol in a suitable vessel, followed by subsequent addition of the amine containing additive and the aqueous alcohol medium. After a suitable period of mixing, the resultant solid monodisperse titania particles are separated from the reaction mixture, washed with a suitable washing medium, and recovered as solid particles.
  • the separation and recovery of the monodispersed titania particles can be carried out by any means known to those skilled in the art, including such means as gravity settling, batch or continuous centrifugation, and filtration. Precipitation times in the range of from about .1 to about 30 minutes are preferred.
  • the redispersing medium can be selected from the group including, but not limited to, ketones, water, alcohols of from one to four carbon atoms, aldehydes, chlorinated hydrocarbons, carboxylic acids, amines, and solutions of acids or bases.
  • the reaction liquid Prior to the final separation of the monodisperse powder body from the liquid, the reaction liquid can be separated and the body can be washed several times with a liquid taken from the group including, but not limited to, water and alcohols of from one to four carbon atoms.
  • the precipitation reaction may be effected in a continuous manner of operation.
  • a quantity of solution A comprising titanium tetraalkoxide, ethanol and the amine additive
  • a quantity of solution B comprising water and ethanol
  • effluent is continuously withdrawn and subjected to conventional means of separation whereby the desired titania powder is recovered, and the withdrawn stream can be recycled, if so desired.
  • the recovered titania can be redispersed as in the batch reaction or recovered as a solid product.
  • the monodisperse titania particles are produced in a relatively narrow range of particle size corresponding to a standard deviation of the particle size distribution of less than one-half of the average particle diameter whereas the prior work produced particle size markedly exceeding 1 micron, poor uniformity, with standard deviations no less than the average particle diameter.
  • the present invention produces spherical uniform particles in a particle size range of from about .1 to about l.0 micron in contradistinction to the prior work where experiments produce particle sizes in excess of 1 micron.
  • the well defined, spherical shape and narrow range of particle size which is obtainable when employing the process of the present invention, fulfills a long felt need in the ceramic industry for a powder capable of forming high density, microstructurally uniform, green body compacts.
  • the titania particles which are obtained from processes known in the literature are not reproducible and that the product of said known processes was found by scanning electron microscopy (SEM) to be highly agglomerated with an average particle size of 1.2 microns as determined by the Leeds and Northrup small particle analyzer (SPA) .
  • SEM scanning electron microscopy
  • SPA Leeds and Northrup small particle analyzer
  • the prior work reported a particle size of 0.3-0.7 microns whereas, despite extensive and exhaustive attempted replication of this work, the disclosed procedure produced resultant particles which were hard, necked inseparable aggregates with a 1.2 micron size and made up of approximately spherical .3 micron particles of titania.
  • the term "compact” will be defined to include both the separated, non-redispersed titania as well as the formed solid titania resulting from the action of a porous mold on the dispersion of monodisperse titania, or by other forming procedures known to a person skilled in the art. Additionally the term “green body” will be defined to mean an unfired, preceramic compact. The following examples are given for purposes of illustration. However, it is to be understood that these examples are only illustrative in nature and that this invention is not necessarily limited thereto.
  • the particle size distribution values were obtained on a Leeds and Northrup Small Particle Analyzer (SPA) .
  • SPA Leeds and Northrup Small Particle Analyzer
  • This instrument measures the particle size distributions over a range of 0.1-35 microns by laser light scattering.
  • a scanning electron microscope (SEM) was used to check the SPA-determined particle size values and to examine the morphology of the powder particles. Excellent agreement was always obtained between the SEM and SPA size data providing that proper precautions were taken to insure that proper powder sampling procedures were followed.
  • a dilute, 0.2 molar (M) solution of titanium tetraethoxide in anhydrous ethanol was added to a solution of water in ethanol [0.83 M] to give a precipitation time for this experiment of about 10 seconds.
  • the resultant powder was washed with ethanol, redispersed in a pH 10 solution of deionized water, and the particle size was determined by SPA.
  • the average SPA particle size of 1.3 microns is several times greater than that claimed in the prior work for this material.
  • An SEM micrograph of the powder clearly shows the particle surfaces to be curved or spherical with most of the particles in the 0.3 micron size range present in hard necked aggregates.
  • the surface at 30,000 magnification appears to be fairly smooth, exhibiting very little microstructure.
  • the particle size is not correct, the surface appearance of the powder closely matches the description of the powder reported for this material. This observation is important since the powders prepared utilizing a variety of different additives have surface microstructures markedly different from those of the prior work.
  • the precipitation times observed for comparable reagent concentrations were very close to the literature values. In general, a decrease in either the water or alkoxide concentrations resulted in a longer precipitation time, but the key product discrepancies entailed the morphologies and sizes of the powder particles.
  • the material obtained upon duplication of the prior procedures consistently gave non-uniform, agglomerated powders with average particle diameters of over one micron as determined by SPA and independently verified by SEM.
  • an alkoxide solution (A) was prepared by mixing 4mL of freshly distilled titanium tetraethoxide (Ti(0Et) 4 ), 10 microliters of sec-butyl amine and 100 mL of dry ethanol together under an inert atmosphere of dry nitrogen.
  • the hydrolysis solution (B) was prepared by adding 3mL of distilled water to lOOmL of absolute ethanol. Both solutions were then individually filtered through a 0.4 micron Millipore nylon filter under nitrogen to remove fine particulates from the solutions. The hydrolysis was carried out by taking equal volume portions of both solutions and mixing them vigorously for several seconds, after which the well-mixed solution was allowed to remain undisturbed for 30 minutes.
  • the resulting milky dispersion of titania powder was centrifuged for 20 minutes, the ethanol was decanted from the powder compacts, and the powder was ultrasonically dispersed in a small quantity of ethanol.
  • the powder was then again isolated by centrifugation, redispersed in pH 10 water and the particle size distribution measured by light scattering using a Leeds and Northrup Small Particle Analyzer (SPA) .
  • SEM micrographs of a dried portion of the powder dispersion independently confirmed the uniform, spherical particle morphology and particle size distribution of the precipitate.
  • Example II This example was run as a control experiment in tandem with Example II utilizing the same stock solutions of water and alkoxide.
  • a Millipore filtered solution of 4mL of freshly distilled Ti(0Et) 4 in lOO L absolute ethanol was added to a similarly filtered solution of 1.5 mL distilled water in lOOmL ethanol under an atmosphere of dry nitrogen.
  • the resulting solution was swirled briefly and then allowed to remain undisturbed for twenty minutes.
  • the initially transparent reaction solution became cloudy 28 seconds after mixing, and, after equilibrating for thirty minutes, the solution was examined visually. Large clumps of powder particles were seen in the sol and were clear evidence that flocculation had occurred.
  • the average size of the precipitate measured by laser light scattering was 9.56 microns and in agreement with the visual observation of clumping. Attempts to reduce the average particle size of the precipitate by ultrasonically redispersing a centrifuged compact at high power in either ethanol or pH 10 water was only moderately successful. While the average size of the redispersed material was smaller, it was always greater than 1 micron in diameter. Examination of the powder by SEM revealed that the powder particles largely consisted of hard, necked aggregates of 0.3 micron titania particles. From the average SPA determined particle size of 1.3 microns, it is estimated from the SEM micrographs that the "average titania particle" in this sample consisted of an agglomerate of 3 or more 0.3 micron primary particles of titania.
  • This example demonstrates the effect of increasing the concentration of the amine of the present invention.
  • 4mL of distilled Ti(OEt) 4 was dissolved in 100 mL of absolute ethanol and 57 microliters of sec-butyl amine was added to form Solution A. After filtering through a Millipore filter. Solution A was mixed with filtered Solution B, comprising 1.5 L of water in 100 mL absolute ethanol. The resulting solution became turbid in 55 seconds.
  • the average particle size of the precipitated titania particles was 0.47 microns and was highly uniform in size and particle morphology.
  • EXAMPLE IV In like manner as in Control Example IV, except that Solution A now contained 106 microliters of triethyl amine. Solutions A and B were mixed and the resultant powder compact treated as before to give an average particle size of 0.59 microns for the highly spherical titania powder. A comparison of the results of these two examples shows that the addition of triethylamine, in accord with the present invention, to the HPC increased the average size of the titania powder from 0.21 microns to 0.59 microns while preserving the sphericity of the particles.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Environmental & Geological Engineering (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Inorganic Chemistry (AREA)
  • Inorganic Compounds Of Heavy Metals (AREA)

Abstract

Cette invention concerne un procédé permettant de former de manière reproductible des sphères en dioxyde de titane monodispersées par l'hydrolyse d'alkoxydes de titane, en présence d'un additif de régulation de taille contenant des amines, de manière à limiter la taille des particules dans une plage de tailles étroite.
EP19880903035 1988-03-03 1988-03-03 Procede de preparation de spheres en dioxyde de titane monodispersees Ceased EP0403473A1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US1988/000649 WO1989008078A1 (fr) 1988-03-03 1988-03-03 Procede de preparation de spheres en dioxyde de titane monodispersees

Publications (1)

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EP0403473A1 true EP0403473A1 (fr) 1990-12-27

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EP19880903035 Ceased EP0403473A1 (fr) 1988-03-03 1988-03-03 Procede de preparation de spheres en dioxyde de titane monodispersees

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EP (1) EP0403473A1 (fr)
JP (1) JPH03503045A (fr)
WO (1) WO1989008078A1 (fr)

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JP4105971B2 (ja) * 2003-03-27 2008-06-25 株式会社資生堂 多孔質酸化チタン粉体及びその製造方法
ITFI20040252A1 (it) * 2004-12-06 2005-03-06 Colorobbia Italiana Spa Processo per la preparazione di dispersioni di ti02 in forma di nanoparticelle, e dispersioni ottenibili con questo processo
ITFI20060030A1 (it) * 2006-02-01 2007-08-02 Colorobbia Italiana Spa Processo per la preparazione di dispersioni acquose di ti02 in forma nanoparticelle e dispersioni ottenibili con questo processo
US7820724B2 (en) * 2008-02-14 2010-10-26 Millennium Inorganic Chemicals, Inc. Colloidal titanium dioxide sols
KR101160928B1 (ko) * 2010-05-26 2012-07-02 서강대학교산학협력단 이산화티타늄 입자의 신규 제조방법 및 이에 의한 이산화티타늄 입자

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JPS6168314A (ja) * 1984-09-07 1986-04-08 Agency Of Ind Science & Technol 多孔性シリカ、アルミナ、チタニアおよびジルコニアの製造方法
US4619908A (en) * 1984-12-24 1986-10-28 Stauffer Chemical Company Non-aged inorganic oxide-containing aerogels and their preparation
GB8501882D0 (en) * 1985-01-25 1985-02-27 Atomic Energy Authority Uk Materials
US4732750A (en) * 1986-08-11 1988-03-22 Allied-Signal Inc. Preparation of monodisperse titania by titanium alkoxide hydrolysis

Non-Patent Citations (1)

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Title
See references of WO8908078A1 *

Also Published As

Publication number Publication date
JPH03503045A (ja) 1991-07-11
WO1989008078A1 (fr) 1989-09-08

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