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:
Jun. 16, 1998
Filed:
Jan. 17, 1996
Masaaki Hosoda, Sabae, JP;
Masahiro Makino, Sabae, JP;
Nicca Chemical Co., Ltd., Fukui-ken, JP;
Abstract
A process for producing a high purity 2,4'-dihydroxydiphenylsulfone (2,4'-isomer) comprising separating 2,4'-isomer from 4,4'-dihydroxydiphenylsulfone (4,4'-isomer) by adding a hydroxide of an alkali metal in an amount which is the total of an amount by mol 1.6 to 2.2 times as great as the amount by mol of 2,4'-isomer and an amount by mol 0.8 to 1.2 times as great as the amount by mol of 4,4'-isomer to a solution of a mixture of 2,4'-isomer and 4,4'-isomer containing 15% by weight or more of 2,4'-isomer in water, to allow 2,4'-isomer to remain dissolved in water in the form of a dialkali metal salt thereof and 4,4'-isomer to be precipitated from the solution in the form of a monoalkali metal salt thereof. A carbonate of an alkali metal may also be used. In order to accelerate the operation, an excess amount of the alkali may be added, which is subsequently neutralized. A high purity 2,4'-isomer having a purity of 95 to 99.5% by weight can be obtained easily with a high yield from a mixture of the isomers containing 15% by weight or more of 2,4'-isomer.