Patents Assigned to Harmon Colors
  • Process for preparing gamma quinacridone from polyphosphoric acid and alcohol
    Patent number: 4100162
    Abstract: A method is provided for the direct production of gamma quinacridone pigment comprising ring closure of 2,5-dianilinoterephthalic acid in polyphosphoric acid and diluting the mixture by addition thereof into a water-miscible alcohol containing 1-3 carbon atoms, e.g. methanol, while maintaining the temperature of the alcohol-acid at between 0.degree. and 25.degree. C.
    Type: Grant
    Filed: January 17, 1977
    Date of Patent: July 11, 1978
    Assignee: Harmon Colors
    Inventor: Robert Jarl North