Patents by Inventor Akihiro Ohba

Akihiro Ohba 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 meta-aromatic polyamide fiber
    Patent number: 6569987
    Abstract: To produce meta aramid filaments having a good quality from a polymer solution of a meta aramid produced by a solution polymerization method, with high efficiency, (1) a meta aramid is prepared by polymerization-reacting a aromatic meta-diamine with a aromatic meta-dicarboxylic acid chloride in a polar organic solvent; (2) hydrogen chloride contained in the resultant polymer solution is neutralized with a neutralizing agent containing an alkali metal hydroxide which can react with hydrogen chloride to produce a salt thereof insoluble in the polymerization solvent; (3) the salt deposited from the polymer solution is removed by filtration; (4) the resultant polymer solution is mixed with water and a polar organic amide solvent to prepare a spinning solution; (5) the resultant meta aramid spinning solution is directly extruded in the form of filamentary streams into an aqueous coagulation liquid, to coagulate the extruded filamentary streams of the polymer solution into the form of filaments; (6) the coagulated
    Type: Grant
    Filed: June 21, 2001
    Date of Patent: May 27, 2003
    Assignee: Teijin Limited
    Inventors: Akihiro Ohba, Takashi Yoshitomi, Hirozumi Iwasaki, Kotaro Takiue
  • Easily dyeable meta-linkage-containing aromatic polyamide fibers
    Patent number: 5852087
    Abstract: Easily dyeable meta-linkage-containing aromatic polyamide fibers consisting of a composition which comprises a meta-linkage-containing aromatic polyamide incorporating a quaternary onium salt of an alkylbenzenesulfonic acid. They are easily dyeable with cationic dyes, and thus may be used in the fields of bedding, clothing and interior decoration.
    Type: Grant
    Filed: December 20, 1996
    Date of Patent: December 22, 1998
    Assignee: Teijin Limited
    Inventors: Akihiro Ohba, Koki Sasaki
  • Process for the preparation of pitch-based carbon fiber
    Patent number: 5145616
    Abstract: A process is provided for the preparation of a pitch-based carbon fiber having a microstructure consisting of strip-like structural units extended in the longitudinal direction of the fiber, wherein the fractal dimension D of the arrangement of the strip-like structural units in the cross-section of the fiber has a fractal structure satisfying the requirement of the following formula (2) relatively to the observation scale r satisfying the requirement of the following formula (1) with respect to the cross-section of the fiber:E/2.5>r>E/25 (1)2.0>D>1.05 (2)wherein E in the formula (1) stands for a smallest principal radius of gyration of cross-sectional area of the cross-section of the fiber.
    Type: Grant
    Filed: January 23, 1991
    Date of Patent: September 8, 1992
    Assignee: Teijin Limited
    Inventors: Jiro Sadanobu, Akihiro Ohba, Tsutomu Nakamura
  • Pitch-based carbon fiber and process for preparation thereof
    Patent number: 5047292
    Abstract: A pitch-based carbon fiber having a microstructure consisting of strip-like structural units extended in the longitudinal direction of the fiber, wherein the fractal dimension D of the arrangement of the strip-like structural units in the cross-section of the fiber has a fractal structure satisfying the requirement of the following formula (2) relatively to the observation scale r satisfying the requirement of the following formula (1) with respect to the cross-section of the fiber:E/2.5>r>E/25 (1)2.0>D>1.05 (2)wherein E in the formula (1) stands for a smallest principal radius of gyration of cross-sectional area of the cross-section of the fiber.
    Type: Grant
    Filed: December 7, 1988
    Date of Patent: September 10, 1991
    Assignee: Teijin Limited
    Inventors: Jiro Sadanobu, Akihiro Ohba, Tsutomu Nakamura