Patents by Inventor Chiraranjan Podder

Chiraranjan Podder 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).

  • Stabilization of organic polyisocyanates
    Patent number: 5175349
    Abstract: The present invention relates to the use of nucleus-substituted 4-hydroxyphenyl propionic acid compounds for stabilizing organic polyisocyanates.
    Type: Grant
    Filed: March 1, 1991
    Date of Patent: December 29, 1992
    Assignee: Bayer Aktiengesellschaft
    Inventors: Pramod Gupta, Christian Konig, Hans-Jurgen Rabe, Hans-Wilhelm Engels, Wilfried Nolte, Chiraranjan Podder
  • Process for the production of 4-nitrodiphenylamines
    Patent number: 4771067
    Abstract: 4-nitrodiphenylamines may be produced by an improved process from 4-halo nitrobenzenes and primary aromatic amines in the presence of potassium carbonate and copper compounds, wherein(1) mono- and di-carboxylic acid amides or nitriles are added;(2) from 3 to 5 mol of amine are introduced per mol of halo nitrobenzene; and(3) from 1.2 to 2 mol of the amine are added prior to the reaction and the remainder during the reaction so that the molar excess of amine relative to halo nitrobenzene is always from 100 to 400%.
    Type: Grant
    Filed: August 26, 1987
    Date of Patent: September 13, 1988
    Assignee: Bayer Aktiengesellschaft
    Inventors: Chiraranjan Podder, Harro Schlesmann
  • Process for the production of 4-nitrodiphenylamines
    Patent number: 4670595
    Abstract: The reaction of 4-nitrohalogenbenzenes with primary aromatic amines in the presence of potassium carbonate and copper compounds to 4-nitrodiphenylamines gives better yield of purer products when synthetic polyamides are added.
    Type: Grant
    Filed: February 3, 1986
    Date of Patent: June 2, 1987
    Assignee: Bayer Aktiengesellschaft
    Inventors: Chiraranjan Podder, Harro Schlesmann
  • Process for the preparation of 4-nitrodiphenylamines
    Patent number: 4665232
    Abstract: The reaction of 4-nitrohalobenzenes with primary aromatic amines in the presence of potassium carbonate and copper compounds to produce 4-nitrodiphenylamine results in products with improved purity and yield if (1) carbonic acid amides or their derivatives are added, (2) 3 to 5 mol of amine are used per mole of halonitrobenzene and (3) 1.2 to 2 mol of the amine are added before the beginning of the reaction and the remainder during the reaction at such a rate that the molar excessive amine over halonitrobenzene is always from 100 to 400%.
    Type: Grant
    Filed: January 9, 1986
    Date of Patent: May 12, 1987
    Assignee: Bayer Aktiengesellschaft
    Inventors: Chiraranjan Podder, Harro Schlesmann
  • Process for the preparation of 4-nitrodiphenylamines
    Patent number: 4665233
    Abstract: An improved process for the preparation of 4-nitrodiphenylamines by the reaction of 4-nitrohalobenzenes with primary aromatic amines in the presence of potassium carbonate and copper compounds is characterized in that sulpholane dimethylsulphone, dimethylacetamide, diethylacetamide, tetramethylurea, tetraethylurea or mixtures thereof are used as solvents and 3 to 5 mol of amine are used per mol of halogenated nitrobenzene, from 1.2 to 2 mol of said amine being added before the beginning of the reaction and the remainder during the reaction at such a rate that the molar excess of unreacted amine over unreacted halogenated nitrobenzene is constantly at least 100%.
    Type: Grant
    Filed: November 18, 1985
    Date of Patent: May 12, 1987
    Assignee: Bayer Aktiengesellschaft
    Inventors: Chiraranjan Podder, Harro Schlesmann