Patents by Inventor S. Prabhakara Rao

S. Prabhakara Rao 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).

  • Patent number: 5663024
    Abstract: Polymeric dyes that comprise (a) segments that render the dyes soluble or dispersible in hydrocarbon solvents and (b) segments that impart color. The polymeric dyes can be introduced into hydrocarbon solvents or formed in hydrocarbon solvents to form stable colored dispersions, which can be used as toners for electrophotography. In these toners, the polymeric dye contains macromeric moieties that render the polymeric dye dispersible in hydrocarbon solvents. The polymeric dye may contain either a charge-directing chelating moiety or a surface-release promoting moiety or both of these moieties.
    Type: Grant
    Filed: November 1, 1996
    Date of Patent: September 2, 1997
    Assignee: Minnesota Mining and Manufacturing Company
    Inventors: Terrance P. Smith, S. Prabhakara Rao, David W. Macomber
  • Patent number: 5599886
    Abstract: Polymeric dyes that comprise (a) segments that render the dyes soluble or dispersible in hydrocarbon solvents and (b) segments that impart color. The polymeric dyes can be introduced into hydrocarbon solvents or formed in hydrocarbon solvents to form stable colored dispersions, which can be used as toners for electrophotography. In these toners, the polymeric dye contains macromeric moieties that render the polymeric dye dispersible in hydrocarbon solvents. The polymeric dye may contain either a charge-directing chelating moiety or a surface-release promoting moiety or both of these moieties.
    Type: Grant
    Filed: February 22, 1996
    Date of Patent: February 4, 1997
    Assignee: Minnesota Mining and Manufacturing Company
    Inventors: Terrance P. Smith, S. Prabhakara Rao, David W. Macomber
  • Patent number: 5530067
    Abstract: Electrostatic toners comprising polymeric dyes comprising of (1) discrete segments that are dispersible in highly fluorinated solvents and (2) discrete color-imparting segments. These toners can be prepared by a means of a polymerization process, wherein macromers containing highly fluorinated dispersible segments are grafted onto a polymer having chromophores attached thereto.
    Type: Grant
    Filed: May 17, 1994
    Date of Patent: June 25, 1996
    Assignee: Minnesota Mining and Manufacturing Company
    Inventors: S. Prabhakara Rao, Terrance P. Smith
  • Patent number: 5530053
    Abstract: Electrostatic toners comprising polymeric dyes comprising of (1) discrete segments that are dispersible in highly fluorinated solvents and (2) discrete color-imparting segments. These toners can be prepared by a means of a polymerization process, wherein macromers containing highly fluorinated dispersible segments are grafted onto a polymer having chromophores attached thereto.
    Type: Grant
    Filed: May 24, 1995
    Date of Patent: June 25, 1996
    Assignee: Minnesota Mining and Manufacturing Company
    Inventors: S. Prabhakara Rao, Terrance P. Smith
  • Patent number: 5521271
    Abstract: Polymeric dyes that comprise (a) segments that render the dyes soluble or dispersible in hydrocarbon solvents and (b) segments that impart color. The polymeric dyes can be introduced into hydrocarbon solvents or formed in hydrocarbon solvents to form stable colored dispersions, which can be used as toners for electrophotography. In these toners, the polymeric dye contains macromeric moieties that render the polymeric dye dispersible in hydrocarbon solvents. The polymeric dye may contain either a charge-directing chelating moiety or a surface-release promoting moiety or both of these moieties.
    Type: Grant
    Filed: September 29, 1994
    Date of Patent: May 28, 1996
    Assignee: Minnesota Mining and Manufacturing Company
    Inventors: Terrance P. Smith, S. Prabhakara Rao, David W. Macomber
  • Patent number: 5482809
    Abstract: A liquid toner composition for use in electrographic imaging comprises a non-aqueous solvent and a soluble dispersant made from thermodynamically compatible polymers containing functional groups with good adsorption properties for cyan, magenta, yellow and black pigments. The invention also describes the incorporation of reactive functional groups that crosslink on heat treatment to improve modulus and scratch resistance.
    Type: Grant
    Filed: June 16, 1994
    Date of Patent: January 9, 1996
    Assignee: Minnesota Mining and Manufacturing Company
    Inventors: S. Prabhakara Rao, Valdis Mikelsons
  • Patent number: 5460874
    Abstract: The receptor sheet of the present invention includes a substrate on which is coated an image-receiving layer formed from a water-based coating composition. The water-based coating composition includes a major amount of a latex polymer having a Tg of no greater than about 30.degree. C.; a minor amount of a water-soluble low molecular weight compound or salt having reactive functional groups; and a minor amount of a water-soluble carbodiimide.
    Type: Grant
    Filed: September 30, 1994
    Date of Patent: October 24, 1995
    Assignee: Minnesota Mining and Manufacturing Company
    Inventor: S. Prabhakara Rao
  • Patent number: 4555269
    Abstract: Cementing compositions and methods of using such compositions in oil, gas and water well cementing operations to reduce fluid loss from the composition to the formation are disclosed. Such compositions incorporate certain copolymers and copolymer salts of N,N dimethylacrylamide and 2-acrylamido, 2-methyl propane sulfonic acid having mole ratios of between 1:4 and 4:1 respectively and average molecular weights of between about 75,000 and about 300,000.
    Type: Grant
    Filed: February 20, 1985
    Date of Patent: November 26, 1985
    Assignee: Halliburton Company
    Inventors: S. Prabhakara Rao, John F. Burkhalter
  • Patent number: 4554081
    Abstract: High density well drilling, completion and workover brines having low fluid loss to subterranean formations when in contact therewith are provided comprised of water, one or more inorganic salts, and an additive for reducing fluid loss. The additive is comprised of water soluble binary or ternary copolymers formed from vinyl monomers. Methods of use are also provided.
    Type: Grant
    Filed: May 21, 1984
    Date of Patent: November 19, 1985
    Assignee: Halliburton Company
    Inventors: John K. Borchardt, S. Prabhakara Rao
  • Patent number: 4522653
    Abstract: A dispersant for cement slurries is provided comprised of a copolymers of sodium vinylsulfonate and either acrylic acid or acrylamide. Salt cement slurries and method of use in cementing in subterranean wellbores are also provided.
    Type: Grant
    Filed: April 3, 1984
    Date of Patent: June 11, 1985
    Assignee: Halliburton Company
    Inventors: S. Prabhakara Rao, Lance E. Brothers, Bobby G. Brake
  • Patent number: 4515635
    Abstract: Cementing compositions and methods of using such compositions in oil, gas and water well cementing operations to reduce fluid loss from the composition to the formation are disclosed. Such compositions incorporate certain copolymers of N, N dimethylacrylamide and 2-acrylamido, 2-methyl propane sulfonic acid having mole ratios of between 1:4 and 4:1 respectively and average molecular weights of between about 75,000 and about 300,000.
    Type: Grant
    Filed: March 23, 1984
    Date of Patent: May 7, 1985
    Assignee: Halliburton Company
    Inventors: S. Prabhakara Rao, John F. Burkhalter
  • Patent number: 4500357
    Abstract: Cementing compositions and methods of using same in high temperature oil and gas well cementing operations are disclosed. Such compositions are comprised of fresh or salt water cement slurries, a water-soluble borate and particular terpolymers comprised of a strong acid monomer, a weak acid monomer and a nonionic monomer.
    Type: Grant
    Filed: April 3, 1984
    Date of Patent: February 19, 1985
    Assignee: Halliburton Company
    Inventors: Lance E. Brothers, S. Prabhakara Rao