Patents by Inventor Kokichi Miyazawa

Kokichi Miyazawa has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Process for producing magnetic metal powder for magnetic recording
    Patent number: 5143542
    Abstract: The present invention provides a process for producing magnetic metal powder for magnetic recording using a metal compound mainly composed of a hydrous iron oxide on an iron oxide, characterized in that prior to subjecting the metal compound mainly composed of a hydrous iron oxide or an iron oxide to a reduction treatment, addition of a boron compound and a heat treatment at 350.degree.-750.degree. C. in a gas atmosphere having a water vapor partial pressure of 10 mmHg or higher are carried out. When a heat treatment at 550.degree.-900.degree. C. in a non-reducing atmosphere is carried out in combination with the above heat treatment, the effect of the present invention is further increased.
    Type: Grant
    Filed: December 20, 1990
    Date of Patent: September 1, 1992
    Assignee: Ishihara Sangyo Kaisha, Ltd.
    Inventors: Kokichi Miyazawa, Masatsuyo Maruo, Toshihiko Kawamura
  • Process for the production of cobalt-containing magnetic iron oxide powder
    Patent number: 4501774
    Abstract: A process is provided for coating the particle surfaces of a phosphor-containing magnetic iron oxide powder with a cobalt compound after subjecting said powder to an activation treatment with an aqueous alkaline and/or acidic medium. The cobalt-containing magnetic iron oxide powder obtained according to this process has excellent coercivity and thermal stability, and the magnetic tape produced by using said powder has not only high coercivity but also excellent squareness, orientability and remanent induction.
    Type: Grant
    Filed: September 29, 1982
    Date of Patent: February 26, 1985
    Assignee: Ishihara Sangyo Kaisha, Ltd.
    Inventors: Kokichi Miyazawa, Kazuo Nakata, Tsuneo Ishikawa, Ichiro Honma, Masaharu Hirai, Makoto Ogasawara, Toshihiko Kawamura
  • Process for producing cobalt containing ferromagnetic iron oxides
    Patent number: 4414245
    Abstract: A process which comprises coating a cobalt compound or a combination of a cobalt compound and a ferrous compound on the surface of magnetic iron oxide particles and then heating the coated particles in the presence of water vapor. The cobalt containing ferromagnetic iron oxide produced by this process is excellent in coercivity and thermal stability. Further, magnetic tape produced from this iron oxide has a high coercivity and is excellent in squareness, orientability and remanent induction.
    Type: Grant
    Filed: July 23, 1982
    Date of Patent: November 8, 1983
    Assignee: Ishihara Sangyo Kaisha, Ltd.
    Inventors: Kokichi Miyazawa, Kazuo Nakata, Tsuneo Ishikawa, Ichiro Honma, Arata Koyama, Masatoshi Amano
  • Producing gypsum and magnetite from ferrous sulfate and separating
    Patent number: 4137293
    Abstract: Gypsum and magnetite which are both coarse and of good quality can simultaneously be produced by introducing calcium carbonate into an aqueous solution containing ferrous sulfate while an oxidizing gas is blown, and then carrying out a neutralizing and oxidizing operation at a pH of 5-6 and a temperature of 60-80.degree. C, and can be separately recovered by magnetic separation.
    Type: Grant
    Filed: December 16, 1977
    Date of Patent: January 30, 1979
    Assignee: Ishihara Sangyo Kaisha, Ltd.
    Inventors: Koichi Nagata, Kokichi Miyazawa, Takeshi Sato, Masashi Tsuchimoto, Junichi Kawashima