Patents by Inventor Yuichiro Shiro

Yuichiro Shiro 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).

  • Patent number: 5071949
    Abstract: Disclosed is a process for the preparation of polyphenylene-sulfide resins, wherein an aromatic polyhalide compound is reacted with an alkali metal sulfide, or hydrogen sulfide and an alkali metal base, or an alkali metal hydrosulfide and an alkali metal base in the presence of an amide polar solvent. A polyphenylene-sulfide resin having a cyclic oligomer content lower than 1.5% by weight, as determined according to the methylene chloride extraction method, is obtained by (a) carrying out the reaction in the absence a polymerization assistant, (b) using the amide polar solvent in an amount not larger than 400 g per mole of the aromatic polyhalide compound, and (c) subjecting the polymerization liquid obtained by the reaction to hot solid-liquid separation at a temperature at least 50.degree. C. but lower than the boiling point of the solvent used, and washing the separated solid with the solvent used for the reaction, which is heated at a temperature at least 50.degree. C.
    Type: Grant
    Filed: October 16, 1989
    Date of Patent: December 10, 1991
    Assignee: Tohpren Co., Ltd.
    Inventors: Yoshiaki Nakamura, Kazuyoshi Nagaki, Yuichiro Shiro, Kazuhiro Kawamata