Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
2001-09-25
2003-09-16
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C428S404000, C423S611000, C423S612000, C423S613000, C106S437000, C106S442000, C106S443000, C106S444000, C106S446000
Reexamination Certificate
active
06620508
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an oxide powder obtained by coating, for a powder matrix, the surface of each powder particle of the matrix comprising one or both of a metal oxide and a semi-metal oxide, or of a composite oxide or a mixed oxide prepared from the above metal and semi-metal oxides, with a coat of a metal oxide or semi-metal oxide identical with or different from the above metal or semi-metal oxide, a method for manufacturing thereof, and a product based on the use thereof.
BACKGROUND ART
As a conventional method for manufacturing such an oxide powder, a method for manufacturing composite particles whereby a powder matrix undergoes surface reformation through moisturization by a metal alkoxide so that the surface of its powder particle may receive a coating layer is disclosed (Japanese Patent Laid-Open No. Hei 5-170425). This method for manufacturing composite particles consists of uniformly dispersing silica particles (powder matrix) into an aqueous solution of a metal salt, the metal being chosen from the group comprising hydrolytic metals such as copper, iron, zirconium, aluminum, chromium and yttrium; forming a coat made of a metal compound on the surface of a silica particle through hydrolytic reaction; and thereby obtaining an oxide powder, each powder particle of which has its surface reformed.
The oxide powder obtained by the above method is highly pure, ensures a high quality because its coating layer hardly detach, and may be used in a wide field of applications as a catalyst, catalyst carrier or absorbent.
On the other hand, a slurry for CMP (Chemical Mechanical Polishing) comprising an abrasive composed of mixed crystal particles of silica and alumina is disclosed (Japanese Patent Laid-Open No. Hei 12-265161). This slurry is composed of silica and alumina mixed at a ratio (silica/alumina) of 1/9 to 1/1, and has a pH of 4 to 9.
The slurry having such a composition as described above, i.e., being composed of mixed crystal particles of silica and alumina as an abrasive agent, ensures a stable polishing activity because of its pH being stabilized close to neutrality, and a highly selective affinity between the insulating membrane and the metal membrane.
Moreover, the powder matrix here concerned, when it is incorporated in a printing sheet for a printer for an electronic device or in a printing material used as an OHP film, receives a further coat, i.e., an ink-receiving layer on the surface of its powder particle to enhance the visibility and adsorption of printed ink. Fine silica powder particles and alumina powder particles are used as a material of such an ink-receiving layer (for example, see Japanese Patent Laid-Open Nos. 2000-6513 and 2000-141877).
However, the method for manufacturing composite particles as disclosed in the above Japanese Patent Laid-Open No. Hei 5-170425 requires drying and pulverizing steps, which may raise the production cost. Further, with the aforementioned conventional methods for manufacturing composite particles, silica particles, after drying, tend to aggregate by capillary actions, which will require an additional step for pulverization. Therefore, the number of steps required for the manufacture of those particles will increase.
The oxide powder manufactured by the above conventional methods is used as an additive to a toner for electronic photography. The oxide powder comprising silica each powder particle of which has its surface reformed is added to a toner to provide the toner with fluency. In some cases, titania powder having its surface reformed may be added in combination with the silica powder, to further enhance charge stability and environment stability of the toner. However, there is a problem in that it is difficult to effectively control each activity of these powders. In addition, each powder may tend to detach from the surface of toner particles as a result of mixture.
The CPM slurry as disclosed in the Japanese Patent Laid-Open No. Hei 12-265161 may be disturbed in the dispersion of its particles if its pH shifts from neutrality, and thus its abrasive activity will be impaired.
Further, if silica powder is used as an ink-receiving layer as described in the Japanese Patent Laid-Open Nos. 2000-6513 and 2000-141877, although it certainly confers transparency to the printing material, it only thinly permits the adsorption of ink. Therefore, with the printing material incorporating such a silica powder, ink may spread on the surface of the printing material to blur the print, or the photo-resistance of the material may be impaired. If alumina powder is used instead as a material of the ink-receiving layer, adsorption of ink to the printing material may be improved but the transparency of the material will be impaired. In addition, if silica powder or alumina powder is used, the resulting slurry that is to serve as a material of the ink-receiving layer will become so unstable that it will become impossible to obtain a highly concentrated slurry from them.
The object of this invention is to provide an oxide powder and a method for manufacturing thereof, which comprises taking a powder matrix consisting of an oxide; and uniformly and at a low cost forming a coating layer consisting of an oxide identical with or different from the above oxide, on the surface of the powder matrix, and wherein both of the powder matrix and the coating layer can develop their respective physical and chemical characteristics satisfactorily.
A further object of this invention is to provide an oxide powder, a method for manufacturing thereof, and a product utilizing thereof whereby the oxide powder or the product is provided with or improved in:
fluency, charge controllability, charge stability, electric conductivity, mechanical strength, tackiness, dispersibility, dispersion stability, transparency, anti-precipitation, anti-blocking, rheologic performance, ultra-violet ray absorption, catalytic activity, inhibition of photocatalytic activity, abrasion activity, heat insulation, heat resistance, anion adsorption, etc.
DISCLOSURE OF INVENTION
The invention according to claim
1
provides a method for manufacturing an oxide powder comprising the steps of:
keeping a powder matrix in a fluent state, said powder matrix consisting of a first oxide composed of one or both of a metal oxide and a semi-metal oxide, or a composite or mixed oxide from those oxides, and having an absorbed water amount of 0.1 to 50%, an averaged particle diameter of 0.005 to 0.5 &mgr;m and a surface hydroxyl group number of 0.1 to 25 &mgr;mol/m
2
;
contacting, one or both of a halide and an alkoxide including metal or semi-metal identical with or different from the metal or semi-metal constituting said first oxide, with said powder matrix kept in the fluent state, by means of an inert carrier gas, and then heating them at a temperature of from 25 to 800° C., to thereby coat said powder matrix by a coating layer consisting of a second oxide; and
heating a reaction by-product consisting of one or both of a hydrogen halide or an alcohol generated by said contacting, at a temperature of from 200 to 1000° C. within the inert carrier gas to thereby eliminate the reaction by-product.
The invention according to claim
2
provides a method for manufacturing an oxide powder comprising the steps of:
keeping a powder matrix in a fluent state, said powder matrix consisting of a first oxide having an absorbed water amount of 0.1 to 50%, an averaged particle diameter of 0.005 to 0.5 &mgr;m and a surface hydroxyl group number of 0.1 to 25 &mgr;mol/m
2
,
contacting, a halide including metal or semi-metal identical with or different from the metal or semi-metal constituting said first oxide, with said powder matrix kept in the fluent state, by means of an inert carrier gas, and then heating them at a temperature of from 25 to 800° C., to thereby coat said powder matrix by a coating layer consisting of a second oxide; and
heating a reaction by-product consisting of a hydrogen halide generated by said contacting, at a temperature of from 200 to 1000° C. within the atm
Inoue Akira
Komai Eiji
Shibasaki Takeyoshi
Shirono Hirokuni
Kiliman Leszek
Nippon Aerosil Co., Ltd.
Reed Smith LLP
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