Patents by Inventor Siegfried Keifer

Siegfried Keifer 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).

  • Thermostable zinc ferrite color pigments containing 0.05-0.5 wt % lithium, a process for their preparation and their use
    Patent number: 4985078
    Abstract: Thermostable pigments for coloring stoving lacquers, coil coat lacquers, plastics, sand granulates, lime sandstone, enamel or ceramic glazes are zinc ferrite color pigments containing from 0.01 to 0.5% by weight of lithium.
    Type: Grant
    Filed: May 30, 1989
    Date of Patent: January 15, 1991
    Assignee: Bayer Aktiengesellschaft
    Inventors: Jakob Rademachers, Volker Wilhelm, Siegfried Keifer, Wilfried Burow
  • Air pore lacquers containing white pigments or white fillers
    Patent number: 4249953
    Abstract: An air pore lacquer comprising a solvent, a binder and at least one additive which is a white pigment or white filler, the additive having an average particle size D.sub.zv which is at least about 10% smaller than the optimum average particle size for the same binder free from air pores. When the additives are pigments they are preferably 20 to 50% smaller, and when they are fillers preferably 20 to 80% smaller, than the optimum particle size for the air pore-free binder. Rutile and anatase TiO.sub.2 are preferred.
    Type: Grant
    Filed: January 17, 1977
    Date of Patent: February 10, 1981
    Assignee: Bayer Aktiengesellschaft
    Inventors: Siegfried Keifer, Hans G. Volz
  • Modified chromium oxide pigment
    Patent number: 3960590
    Abstract: Chromium oxide pigments intimately admixed with an alkoxylated alkyl sulphonamide to obtain a pigment having a low degree of flocculation.
    Type: Grant
    Filed: November 14, 1974
    Date of Patent: June 1, 1976
    Assignee: Bayer Aktiengesellschaft
    Inventors: Birger Knickel, Siegfried Keifer, Hermann Perrey, Hans Rudolph, Hans Jurgen Rosenkranz, Reinhold Rudisch