Patents by Inventor Sivaram Krishnan

Sivaram Krishnan 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: 4471104
    Abstract: The present invention relates to the preparation of aromatic polycarbonates by the known two-phase interface process, from diphenols characterized in that aromatic sulfonanilides are used as chain terminators in amounts of about 2 mol % to 20 mol %, preferably in amounts of about 2.5 mol % to 10 mol %, relative to mols of diphenols employed. In addition, the present invention relates to the aromatic polycarbonates obtainable by the process according to the invention. The products of this invention have been found to have better self extinguishing property compared to polycarbonates without sulfonamide end groups.
    Type: Grant
    Filed: November 4, 1982
    Date of Patent: September 11, 1984
    Assignee: Bayer Aktiengesellschaft
    Inventors: Sivaram Krishnan, Wolfgang Cohnen, Dieter Neuray
  • Patent number: 4463163
    Abstract: The present invention relates to the novel monomer 4,4'-bis(4-hydroxyphenyl thio)biphenyl, to a process for its production and to its use in the preparation of polycarbonates, polyurethanes, polyesters, polysulfones and polyethers which polymer resins are useful in the preparation of films, fibers and molded parts.
    Type: Grant
    Filed: June 1, 1982
    Date of Patent: July 31, 1984
    Assignee: Mobay Chemical Corporation
    Inventors: Sivaram Krishnan, John R. Sanderson
  • Patent number: 4448930
    Abstract: Thermoplastic molding compositions characterized by their improved impact performance and deformation under load are disclosed comprising a homogeneous, intimate blend of a polycarbonate resin and a nuclear alkylated polycarbonate resin wherein blend dispersed is a polymeric modifier.
    Type: Grant
    Filed: August 2, 1982
    Date of Patent: May 15, 1984
    Assignee: Mobay Chemical Corporation
    Inventors: Sivaram Krishnan, Nelson R. Lazear
  • Patent number: 4446297
    Abstract: Polycarbonates are provided having improved critical thickness values and flame retardant characteristics based upon an aromatic diol and a halogenated thiodiphenol represented by the structural formula ##STR1## wherein X.sub.1 and X.sub.2 are halogen and "a"+"b"=1 to 8; Y.sub.1 and Y.sub.2 are alkyl groups having 1 to 4 carbon atoms; and "c"+"d"=0 to 7. By incorporating an effective amount of the aromatic halogenated thiodiphenol, based upon the total aromatic diol content, into the polymer the critical thickness and flame retardant characteristics of the polycarbonate are substantially improved, a process for the preparation of the monomer of said structural formula is likewise provided.
    Type: Grant
    Filed: April 7, 1982
    Date of Patent: May 1, 1984
    Assignee: Mobay Chemical Corporation
    Inventors: Sivaram Krishnan, Arthur L. Baron
  • Patent number: 4430475
    Abstract: The invention is directed to a thermoplastic molding composition comprising alkylated polycarbonate and a dispersed polymeric phase which composition is characterized by an improved level of impact strength.
    Type: Grant
    Filed: December 31, 1981
    Date of Patent: February 7, 1984
    Assignee: Mobay Chemical Corporation
    Inventor: Sivaram Krishnan
  • Patent number: 4426514
    Abstract: The invention is directed to copolycarbonates of thiodiphenol characterized by high melt flow rate and good mechanical properties, particularly suitable for molding at temperatures lower than 500.degree. F.
    Type: Grant
    Filed: July 14, 1980
    Date of Patent: January 17, 1984
    Assignee: Mobay Chemical Corporation
    Inventors: Sivaram Krishnan, Arthur L. Baron
  • Patent number: 4425456
    Abstract: A copolycarbonate molding composition comprising the reaction product of an aromatic diphenol, a bis(4-hydroxyphenyl)biphenyl disulfone and a carbonate source is characterized by its high glass transition temperature. A blend thereof containing an organic acid salt is characterized by its improved flame retardance.
    Type: Grant
    Filed: September 28, 1981
    Date of Patent: January 10, 1984
    Assignee: Mobay Chemical Corporation
    Inventors: Arthur L. Baron, Sivaram Krishnan, Mark W. Witman, Roger J. White
  • Patent number: 4346211
    Abstract: Copolycarbonate resins are prepared from an aromatic diol and a carbonic acid derivative. 2,2-bis(p-hydroxy-phenyl) 1,1,1,3,3,3-hexafluoropropane is co-reacted in a minor amount with the aromatic diol and carbonic acid derivative to form a polycarbonate having improved heat distortion characteristics.
    Type: Grant
    Filed: October 6, 1980
    Date of Patent: August 24, 1982
    Assignee: Mobay Chemical Corporation
    Inventors: Sivaram Krishnan, Arthur L. Baron
  • Patent number: 4320049
    Abstract: A sufficient amount of a novel halogenated aromatic imide sulfonate, represented by the structural formula: ##STR1## wherein X is a halogen, n is 1 to 4, Y is a lower alkyl having 1 to 4 carbon atoms, a halogen or a hydrogen atom, "a" is 0 to 4, M is an alkali metal and T is either 0 or 1, is incorporated into an aromatic polycarbonate to provide flame resistance thereto.
    Type: Grant
    Filed: July 14, 1980
    Date of Patent: March 16, 1982
    Assignee: Mobay Chemical Corporation
    Inventors: Sivaram Krishnan, Russell P. Carter, Jr., Robert D. Kroshefsky
  • Patent number: 4306055
    Abstract: Polycarbonate resins are based upon the reaction of an aromatic diol and a carbonic acid derivative. A sulfur containing difunctional phenolic compound represented by the structural formula: ##STR1## wherein R.sub.1 is a lower alkyl having 1 to 4 carbon atoms and "n" equals 0 to 4 and X is S or SO.sub.2 either totally or partially substitutes for said aromatic diol. Polycarbonates prepared in accordance with the invention exhibit good heat distortion characteristics and long term aging properties.
    Type: Grant
    Filed: June 9, 1980
    Date of Patent: December 15, 1981
    Assignee: Mobay Chemical Corporation
    Inventors: Arthur L. Baron, Sivaram Krishnan, Joseph R. Thomas