Patents by Inventor Hirobumi Ishikawa

Hirobumi Ishikawa 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).

  • Method of making vacuum-packaged, capacitor-grade tantalum powder
    Patent number: 6079186
    Abstract: The performance of capacitor-grade tantalum powder that is vacuum packaged is enhanced. Preventing contact with air reduces the quantity of oxygen that passes through the oxide film and dissolves in the substrate. Lower oxygen in the powder can lower DC leakage in the capacitor made from the powder. Over a 4-month period, vacuum/argon packaging reduces oxygen pick-up in a 50K-class powder by over 200 ppm compared with the same powder stored in conventional packaging.
    Type: Grant
    Filed: June 7, 1995
    Date of Patent: June 27, 2000
    Assignee: H.C. Starck, Inc.
    Inventors: Ross W. Simon, Katsuo Iwabuchi, Hirobumi Ishikawa, Dieter Behrens
  • Process for purification of polyphenylene-sulfide
    Patent number: 4728723
    Abstract: Polyphenylene-sulfide having a much reduced content of impurities is prepared by adding an inorganic acid or organic acid to a slurry of polyphenylene-sulfide as-obtained by condensation reaction of an aromatic polyhalide compound with an alkali metal sulfide in the presence of a polar organic solvent, to adjust the pH of the slurry to a value not higher than 6, stirring the pH-adjusted slurry, filtering the slurry, and washing and drying the recovered solid.
    Type: Grant
    Filed: March 20, 1987
    Date of Patent: March 1, 1988
    Assignee: Tohpren Co., Ltd.
    Inventors: Yoshiaki Nakamura, Kazuo Tedori, Hirobumi Ishikawa