Patents by Inventor David A. Citron

David A. Citron 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: 6297338
    Abstract: Polyolefins made preferably only from ethylene using a selected ethylene oligomerization catalyst to form &agr;-olefins and a polymerization catalyst which can copolymerize ethylene and &agr;-olefins produces a novel polymer which advantageous rheological properties.
    Type: Grant
    Filed: September 29, 1999
    Date of Patent: October 2, 2001
    Assignee: E. I. du Pont de Nemours and Company
    Inventors: Patricia Metzger Cotts, William Howard Tuminello, Lin Wang, Joel David Citron
  • Patent number: 6252022
    Abstract: The molecular weight of polyolefins produced using iron or cobalt complexes of 2,6-pyridinecarboxaldehyde diimines or a 2,6-diacylpyridine diimines as polymerization catalysts may be lowered by carrying out the polymerization in the presence of hydrogen.
    Type: Grant
    Filed: May 21, 1999
    Date of Patent: June 26, 2001
    Assignee: E. I. du Pont de Nemours and Company
    Inventors: Samuel David Arthur, Joel David Citron
  • Patent number: 6232259
    Abstract: Transition metal imine complexes can be prepared by reacting the imine precursors, a carbonyl compound and a primary amine, in the presence of a selected transition metal compound. The complexes may be used as catalysts for olefin polymerization.
    Type: Grant
    Filed: March 29, 1999
    Date of Patent: May 15, 2001
    Assignee: E. I. du Pont de Nemours and Company
    Inventors: Steven Dale Ittel, Samuel David Arthur, Joel David Citron
  • Patent number: 5928485
    Abstract: A first process involves the partial electrodialysis of a dialkali metal salt of an aromatic hydroxycarboxylic acid or a dicarboxylic acid to produce the approximate monoalkali metal salt and the alkali metal hydroxide. The monoalkali metal salt is then treated with an acid such as a bisulfate to recover the aromatic hydroxycarboxylic acid or dicarboxylic acid. The resulting inorganic salt such as sodium sulfate may then be electrolyzed to sodium bisulfate and NaOH. A second process involves the electrodialysis at elevated temperatures of a (di)alkali metal salt of p-hydroxybenzoic acid produce free p-hydroxybenzoic acid and the alkali metal hydroxide. These are efficient and economical methods for recovering the acid and alkali metal hydroxide values, as well as the parent organic compound, from these dialkali metal salts.
    Type: Grant
    Filed: April 4, 1997
    Date of Patent: July 27, 1999
    Assignee: E. I. du Pont de Nemours and Company
    Inventors: Joel David Citron, Michael Robert Samuels
  • Patent number: 5770678
    Abstract: A process for polymerizing oxiranes, oxetanes, oxepanes, dioxolanes, trioxanes, and tetrahydrofurans to their respective polymers by contacting them with a selected metal compound is disclosed; and also a process for depolymerizing polytetrahydrofurans to monomeric tetrahydrofurans by contacting the polymer with a selected metal compound at a temperature of about 100.degree. C. to about 250.degree. C. The catalysts may be in solution or part of a heterogeneous solid, and selected organic compounds are used as accelerators in the polymerizations. The polymeric products, some of which are novel, may be used as polyether monomers for further polymerization, as by reaction with isocyanates to produce polyurethanes, and other useful polymers. Some of the polymeric products are relatively high in molecular weight and are suitable for direct use, for instance as spandex fibers.
    Type: Grant
    Filed: December 9, 1996
    Date of Patent: June 23, 1998
    Assignee: E. I. du Pont de Nemours and Company
    Inventors: Neville Everton Drysdale, Richard Edmund Bockrath, Norman Herron, Joel David Citron
  • Patent number: 5688895
    Abstract: Disclosed herein are thermotropic liquid crystalline poly(ester-amides) containing repeat units derived from alipatic diamines and other monomers, such as aromatic diols, aromatic dicarboxylic acids, aromatic hydroxycarboxylic acids, and optionally aliphatic diols. The polymers are particularly useful as films and in multilayer structures as barrier layers because of their relatively low permeability to various compounds.
    Type: Grant
    Filed: June 24, 1996
    Date of Patent: November 18, 1997
    Assignee: E. I. Du Pont de Nemours and Company
    Inventors: Irene Greenwald Plotzker, Joel David Citron, Marion Glen Waggoner
  • Patent number: 3978148
    Abstract: Dissolved rhodium compounds are removed from liquid, organic process streams in the manufacture of 1,4-hexadiene from 1,3-butadiene and ethylene by contacting the organic process streams with activated carbon of decolorizing grade for at least about 0.1 hour at about -20.degree. to +120.degree.C. The adsorbed rhodium can be recovered at a reasonable cost and reused. This invention thus provides an economic incentive.
    Type: Grant
    Filed: July 21, 1975
    Date of Patent: August 31, 1976
    Assignee: E. I. Du Pont de Nemours and Company
    Inventor: Joel David Citron
  • Patent number: 3962199
    Abstract: Removal of dissolved vanadium catalyst residues from .alpha.-olefin polymer solutions improves the heat stability of the polymer recovered therefrom. Vanadium residues are removed from .alpha.-olefin polymer solutions in inert solvents by contacting the solutions at 50.degree.-225.degree.C. with one or more active metals, either in their elemental form or as alloys, selected from alkali metals, aluminum, and zinc, and separating the solutions from vanadium residues precipitated thereby. The process can be carried out continuously by passing the polymer solution through a column containing the active metal.
    Type: Grant
    Filed: February 28, 1975
    Date of Patent: June 8, 1976
    Assignee: E. I. Du Pont de Nemours and Company
    Inventor: Joel David Citron