Patents by Inventor Sadao Hagita

Sadao Hagita 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 preparing hydrogen fluoride
    Patent number: 5219551
    Abstract: A process for preparing hydrogen fluoride, which comprises (i) reacting calcium fluoride with sulfuric acid to produce a gypsum and a gas containing hydrogen fluoride, (ii) separating hydrogen fluoride from said gas containing hydrogen fluoride, (iii) absorbing said hydrogen fluoride-separated gas with water to obtain an aqueous solution containing hydrogen fluoride and silicofluoric acid, (iv) reacting calcium carbonate with said aqueous solution to obtain a suspension containing silicic acid and calcium fluoride, (v) adding an alkaline substance to said suspension to make pH at least 8, thereby stabilizing the silicic acid as a colloidal solution, (vi) separating a calcium fluoride solid and the colloidal solution of silicic acid from said suspension, and (vii) recycling the separated calcium fluoride as a starting calcium fluoride.
    Type: Grant
    Filed: May 30, 1991
    Date of Patent: June 15, 1993
    Assignee: Asahi Glass Company Ltd.
    Inventors: Kunihiko Terase, Sadao Hagita, Kouichi Yokoyama, Yasuhiro Sanada, Michiomi Nagase, Suekazu Hirata