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:
Jan. 19, 1999
Filed:
Jun. 17, 1997
Hans-Josef Buysch, Krefeld, DE;
Gerd Fengler, Krefeld, DE;
Karl-Heinz Neumann, Sankt Augustin, DE;
Paul Wagner, Dusseldorf, DE;
Martin Melchiors, Aachen, DE;
Wieland Hovestadt, Krefeld, DE;
Bayer Aktiengesellschaft, Leverkusen, DE;
Abstract
The invention relates to a process for the preparation of carbonates having a six-membered ring, of the formula ##STR1## by transesterification of 1,3-propanediol compounds with carbonic acid esters and subsequent distillative depolymerization of the oligo- or polycarbonate initially formed, one or more catalysts from the group consisting of compounds of Sn, Ti or Zr being employed both for the transesterification and for the depolymerization and, if appropriate, the distillation residue is at least partly recycled into the transesterification. Such carbonates having a six-membered ring can furthermore be stabilized against undesirable polymerization by addition of small amounts of acids of sulfur or phosphorus or esters or salts thereof.