Patents by Inventor Ji Y. Chang

Ji Y. Chang 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).

  • Copolyimides and a process for the preparation thereof
    Patent number: 5357032
    Abstract: A diamine compound of the general formula ##STR1## wherein the arrows denote isomerism, R.sub.1 is a divalent aromatic group selected from the group consisting of ##STR2## R.sub.2 is a tetravalent aromatic group selected from the group consisting of ##STR3## and R.sub.4 is a monovalent aliphatic group selected from the group consisting of ethyl and isopropyl; and, a process for preparing same.
    Type: Grant
    Filed: August 17, 1992
    Date of Patent: October 18, 1994
    Assignee: Korea Research Institute of Chemical Technology
    Inventors: Suh Bong Rhee, Ji Y. Chang, Bong S. Moon, Ji-Woong Park