Stock material or miscellaneous articles – All metal or with adjacent metals – Composite powder
Patent
1997-09-10
1999-11-16
Jenkins, Daniel J.
Stock material or miscellaneous articles
All metal or with adjacent metals
Composite powder
148513, 427127, 427216, 427217, 427229, 4273837, 427405, 4274192, B22F 102
Patent
active
059854669
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a powder having at least a multilayered metal oxide film on the surface thereof and a process for producing the powder. More particularly, the present invention relates to a powder which has at least a multilayered metal oxide film on the surface thereof and is suitable for use as a magnetic coloring material in magnetic color toners, magnetic color inks, etc., and to a process for producing the powder.
BACKGROUND ART
The technique of coating powder particles with another substance for using the powder in various applications is known. With progress in various technical fields, there is a growing desire for a powder having singular properties, in particular, a metal powder or a metal compound powder. Specifically, there is a desire for a powder which combines the properties characteristic of a powder, in particular a metal or metal compound powder, and other properties and hence has multiple functions.
For example, magnetic metal powders as they are cannot be used as raw materials for magnetic color toners because of the color thereof, although their color has not posed any problem in conventional black magnetic toners. Coated powders obtained by the conventional known technique in which a thin metal oxide film is formed on the surface of powder particles to modify the surface for the purpose of, for example, protecting the powder or facilitating the mixing of the powder with synthetic resins or other substances cannot satisfy new requirements in such fields. From this standpoint, it is necessary to provide a powder having a novel constitution not seen in any prior art powder.
The present inventors previously invented a powder having on the surface thereof at least one metal oxide film which has a uniform thickness of from 0.01 to 20 .mu.m and in which the metal contained is different from the metal constituting the base particles, in order to provide a powder, in particular a metal or metal compound powder, which has multiple properties and performs multiple functions so as to satisfy those new requirements (JP-A-6-228604).
If the above powder has two or more layers of the metal oxide film, a special function can be imparted thereto by regulating the thicknesses of the individual layers. For example, when coating films which differ in refractive index are formed on the surface of powder particles each in a thickness corresponding to 1/4 of the wavelength of a light, the coated powder reflects all the light. By applying this technique to a powder comprising magnetic core particles, e.g., a powder of a metal such as iron, cobalt, or nickel or an alloy of such a metal or a powder of iron nitride, it is possible to produce a magnetic powder for magnetic toners which reflects all light and has a bright white color.
A magnetic color toner can be produced from the above powder by forming a colored layer on the powder particles and further forming a resin layer thereon.
The present inventors improved the above powder and invented a powder having a multilayered coating which comprises not metal oxide films alone but metal oxide films stacked alternately with metal films (JP-A-7-90310). This powder has excellent properties which render the powder suitable for use in magnetic color toners, etc.
For producing these powders, it is necessary to form, on powder particles, metal oxide films which each is uniform in thickness. Although this may be attained by precipitating a metal oxide or a metal compound as a precursor therefor from an aqueous solution of a metal salt, this technique is difficult. Hence, the present inventors developed a method which comprises dispersing particles of the above-described powder into a solution of a metal alkoxide and then hydrolyzing the metal alkoxide to form a metal oxide film on the powder particles. By the use of this method, it has become possible to form a metal oxide film which is thin and uniform in thickness, in particular to form a multilayered metal oxide film.
Specifically, the above method is carried out as follows. Powder
REFERENCES:
patent: 5763085 (1998-06-01), Atarashi et al.
Patent Abstracts of Japan vol. 015, No. 300 (P-1232), Jul. 30, 1991 & JP 03 103865 A (Toppan Printing Co. Ltd), Apr. 30, 1991 abstract.
International Search Report.
Atarashi Takafumi
Nakatsuka Katsuto
Jenkins Daniel J.
Nakatsuka Katsuto
Nittetsu Mining Co., Ltd.
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