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:
Dec. 20, 1994
Filed:
Sep. 30, 1993
Chester A Thayer, Wilmington, DE (US);
Harold E Bellis, Wilmington, DE (US);
E. I. Du Pont de Nemours and Company, Wilmington, DE (US);
Abstract
A process for preparing lactide or glycolide from a lactic acid oligomer or glycolic acid oligomer is disclosed where the molecular weight of the synthesis reactor residue is controlled to no more than 1.2 times that in the feed. The process is carried out at 130.degree. to 280.degree. C. and preferably 180.degree. to 210.degree. C. using from 1 to 6 weight percent catalyst in the oligomer feed to the synthesis reactor. The catalysts are tin or tin compounds, yttrium or rare earth metal compounds, or antimony compounds which are known as alphahydroxycarboxylic acid cyclic dimerization or polymerization catalysts.