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:
Oct. 03, 1978
Filed:
Sep. 25, 1974
Simon Pierce Burns, Austin, TX (US);
John Monte Walton, Austin, TX (US);
Texaco Development Corp., New York, NY (US);
Abstract
In a process for purifying and reducing the acidity of a polymethylene polyphenylpolyisocyanate mixture wherein the mixture is subjected to a distillation step, such as by passing a flowing stream of a crude polymethylene polyphenylpolyisocyanate mixture through a distillation column which has a reboiler means consisting of a thin film evaporator apparatus mounted therewith for rapidly heating the stream to about 190.degree. C. to about 250.degree. C. whereby the solvent and impurities are taken overhead, and then allowing the distillation residue of polymethylene polyphenylpolyisocyanate to cool, an improvement is disclosed which comprises maintaining the distillation residue of the polymethylene polyphenylpolyisocyanate at a temperature of about 190.degree. C. to about 250.degree. C. for a time period of from about 1 to about 60 minutes and then recirculating continuously a portion of the distillation residue to the distillation column for admixture with the flowing feed stream of crude polymethylene polyphenylpolyisocyanate at a recirculation rate of from about 1:1 to about 3:1 volumes of isocyanate distillation residue per volume of crude isocyanate feed. The acid level of the polymethylene polyphenylpolyisocyanate mixture treated by the improved process of the invention is substantially reduced without adversely affecting the isocyanate equivalent weight, viscosity or other physical and chemical characteristics of the product.