The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 06, 2002
Filed:
May. 05, 2000
Applicant:
Inventors:
Shenghong A. Dai, Lake Jackson, TX (US);
Duane S. Treybig, Sugarland, TX (US);
Kathryn Hock, Lake Jackson, TX (US);
Van A. Kent, Lake Jackson, TX (US);
Assignee:
The Dow Chemical Company, Midland, MI (US);
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
C07C / ; C07C / ; C07C / ;
U.S. Cl.
CPC ...
C07C / ; C07C / ; C07C / ;
Abstract
Residues from the distillation of a toluene diamine phosgenation mixture are hydrolyzed by mixing them with water and subjecting the mixture to a temperature of 200-350 ° C. The hydrolysis is performed in the presence of a sufficient amount of a base to maintain the pressure in the reactor to no more than a predetermined operating level. The product mixture is then extracted to recover TDA, which can be recycled. This provides an efficient process whereby nearly quantitative conversion of the residues to TDA can be achieved.