Patents by Inventor Gerhard Wiederhoft

Gerhard Wiederhoft 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).

  • Nanodisperse titanium dioxide, process for the production thereof and use thereof
    Patent number: 5840111
    Abstract: The present invention relates to nanodisperse titanium dioxide, to a process for the production thereof and to the use thereof.
    Type: Grant
    Filed: November 8, 1996
    Date of Patent: November 24, 1998
    Assignee: Bayer AG
    Inventors: Gerhard Wiederhoft, Kai Butje, Peter-Joachim Barenthien, Michael Bodiger, Heinrich Alberts
  • Process for the calcination of filter cakes with high solids contents being partly pre-dried in a directly heated rotary kiln
    Patent number: 5174817
    Abstract: A process for calcining a filter cake in a directly heated rotary kiln wherein part of the filter cake is separated from the entire mass of filter cake, the separated portion is predried and recombined with the remainder portion and the combined predried and remainder portion is calcined. The filter cake can be inorganic solids such as oxides of titanium, chromium (III), zinc and iron.
    Type: Grant
    Filed: June 18, 1990
    Date of Patent: December 29, 1992
    Assignee: Bayer Aktiengesellschaft
    Inventors: Bernd-Michael Holle, Peter Beumer, Rolf M. Braun, Hilmar Rieck, Jurgen Kischkewitz, Gerhard Wiederhoft
  • Process for the production of TiO.sub.2 pigments
    Patent number: 5094834
    Abstract: In the production of TiO.sub.2 pigments by the steps of digesting titanium-containing raw materials with sulfuric acid, hydrolyzing the titanyl sulfate obtained, separating the waste acid from the hydrolyzate, bleaching the hydrolyzate and calcining the hydrolyzate after addition of rutilizing nuclei and standardizing chemicals to form TiO.sub.2 pigments, and recovering sulfuric acid from the waste acid, the improvement which comprises employing as the rutilizing nuclei nuclei produced from part of the bleached and then washed hydrolyzate, which nuclei are added to the remainder of the bleached and washed hydrolyzate before calcination.
    Type: Grant
    Filed: October 31, 1990
    Date of Patent: March 10, 1992
    Assignee: Bayer Aktiengesellschaft
    Inventors: Gerhard Wiederhoft, Gunter Lailach
  • Process for the recorvery of sulphuric acid in the production of titanium dioxide
    Patent number: 4988495
    Abstract: A process for the preparation of an improved quality TiO.sub.2 pigment by hydrolysis of titanyl sulphate, isolation of the hydrolysis product form the waste acid produced during the hydrolysis, washing of the hydrolysis product and calcination of the hydrolysis product to form the TiO.sub.2 pigment, wherein the hydrolysis of the titanyl sulphate is carried out using separately produced hydrolysis nuclei which have been produced by a reaction of titanium salts with alkaline reagents, and in which waste acid and/or wash liquid containing waste acid is added after at least 50% of the total duration of the hydrolysis process.
    Type: Grant
    Filed: December 15, 1989
    Date of Patent: January 29, 1991
    Assignee: Bayer Aktiengesellschaft
    Inventors: Gerhard Wiederhoft, Eckhard Bayer, Wolfgang D. Muller, Gunter Lailach
  • Process for the preparation of titanium dioxide
    Patent number: 4663131
    Abstract: In the preparation of titanium dioxide comprising autothermically digestion a titanium-containing raw material with sulphuric acid to form a solid relatively easily soluble digestion cake containing titanyl sulphate, extracting metal sulphates from this cake by water or dilute sulphuric acid, separating the undissolved residues and, optionally after crystallization of iron sulphate heptahydrate, hydrolyzing the titanyl sulphate to produce titanium oxide hydrate, and calcining the titanium oxide hydrate to titanium dioxide, the improvement which comprises adding to the raw material a metal sulphate and effecting the autothermic decomposition with sulphuric acid of about 80 to 88% concentration. Advantageously the acid is obtained by mixing dilute acid with concentrated sulphuric acid or oleum, some of the dilute acid and metal sulphate coming from a by-product filter cake produced in the course of the process.
    Type: Grant
    Filed: November 20, 1984
    Date of Patent: May 5, 1987
    Assignee: Bayer Aktiengesellschaft
    Inventors: Rudolf Gerken, Gerhard Wiederhoft, Gunter Lailach, Walter Gutsche, Wolfgang D. Muller