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. 21, 1995
Filed:
Dec. 10, 1993
Masaaki Hosoda, Fukui, JP;
Mikihiko Kurose, Fukui, JP;
Yoshihiro Sasada, Takefu, JP;
Hajime Saito, Sabae, JP;
Masahiro Makino, Sabae, JP;
Nicca Chemical Co., Ltd., Fukui, JP;
Abstract
High purity 2,4'-dihydroxydiphenylsulfones useful as developers for thermal recording paper can be produced efficiently and with high selectivity by reacting one or more phenols and sulfuric acid in the presence as of at least one of phosphonic acid, phosphinic acid and salts thereof, in the absence of a solvent or in the presence of an aromatic hydrocarbon solvent having a boiling point at atmospheric pressure of 130.degree. to 200.degree. C., and then purifying the thus-produced crude 2,4'-dihydroxydiphenylsulfones using a mixed solvent containing (1) 5 to 20 weight % of at least one lower aliphatic alcohol and 95 to 80 weight % of at least one aromatic hydrocarbon which does not contain halogen, (2) 10 to 40 weight % of at least one ketone and 90 to 60 weight % of at least one aromatic hydrocarbon which does not contain halogen or (3) 10 to 40 weight % of at least one ester of acetic acid and 90 to 60 weight % of at least one aromatic hydrocarbon which does not contain halogen.