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:
Mar. 10, 1992
Filed:
Aug. 16, 1990
Sumikin Chemical Co., Ltd., Tokyo, JP;
Abstract
A purified desired isomer which is either 3,4- or 3,5-dimethylphenol is separated with a high yield from a dimethylphenol-containing fraction which contains both 3,4- and 3,5-dimethylphenols. The fraction is distilled so as to give a distillate which is enriched with the desired dimethylphenol isomer to be separated and which contains at least 35% by weight of the desired isomer. The desired DMP isomer is crystallized from a melt of the enriched distillate in two stages with at least part of the filtrate separated from the precipitated crystals in the second crystallization stage being circulated to the first crystallization stage. The enriched distillate is introduced into the first crystallization stage when it contains the desired isomer in a concentration of from 35% to less than 70% by weight, or it is introduced into the second crystallization stage when it contains the desired isomer in a concentration of 70% by weight or higher.