Patents by Inventor Hans W. Petroll

Hans W. Petroll 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).

  • Stabilization of anionic indole dyestuffs
    Patent number: 4245995
    Abstract: Azo dyestuffs which contain, as the coupling component an indole of the formula ##STR1## wherein R denotes an optionally substituted alkyl radical, an optionally substituted aryl radical or an optionally substituted aralkyl radical, and the benzene ring A can be further substituted,frequently exhibit an undesired irreversible change in the color shade in acid solutions, which surprisingly can be prevented by adding nitrogen-containing complex-forming substances.
    Type: Grant
    Filed: February 9, 1978
    Date of Patent: January 20, 1981
    Assignee: Bayer Aktiengesellschaft
    Inventors: Herbert Hugl, Hans-Gunter Otten, Hans W. Petroll, Karlheinz Wolf