Patents by Inventor Theodorus A. van't Zelfde

Theodorus A. van't Zelfde 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).

  • Quaternary nitrogen containing amphoteric water soluble polymers and their use in drilling fluids
    Patent number: 6281172
    Abstract: Water based drilling fluid compositions which contain at least one viscosity builder and at least one rheological control agent wherein the rheological control agent is an amphoteric polymer, the cationic groups of the amphoteric polymer being quaternary ammonium groups.
    Type: Grant
    Filed: April 7, 1999
    Date of Patent: August 28, 2001
    Assignee: Akzo Nobel NV
    Inventors: Brent Warren, Peter M. van der Horst, Theodorus A. van't Zelfde