Organic compounds -- part of the class 532-570 series – Organic compounds – Sulfur containing
Patent
1991-05-01
1993-02-23
Cintins, Marianne M.
Organic compounds -- part of the class 532-570 series
Organic compounds
Sulfur containing
568 34, C07C31714, C07C31722
Patent
active
051892235
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a process for preparing 4,4'-dihydroxydiphenylsulfone (hereinafter referred to as "4,4'-DDS").
BACKGROUND ART
In recent years, a demand for 4,4'-DDS has been increased in the chemical industry, e.g. fields of fibers, resins or the like. Furthermore a demand for an extremely high-purity 4,4'-DDS has arisen to improve the quality of products in each field. Currently desired is the production of high-purity 4,4'-DDS in high yields as well as the provision of large-size manufacturing apparatus.
A process for preparation of 4,4'-DDS is known in which a phenol and a sulfonating agent are subjected to dehydration reaction in the presence of a solvent such as dichlorobenzene which is capable of dissolving the foregoing materials and the produced 4,4'-DDS. However, when the dehydration reaction is conducted in a solvent as in said process, the desired 4,4'-DDS as dissolved in the reaction product has an isomerization equilibrium with an isomer, i.e. 2,4'-dihydroxydiphenylsulfone (hereinafter referred to as "2,4'-DDS") produced as a by-product so that the obtained crude product contains 20 to 30% by weight of 2,4'-DDS as the impurity which decreases the purity and the yield of 4,4'-DDS. Further, it has been recently recognized that trihydroxytriphenyldisulfone (hereinafter referred to as "tri-compound") is produced as a by-product along with 2,4'-DDS.
In view of the above problems, the present inventors proposed a process for preparing a high-purity 4,4'-DDS in a high yield in which a phenol and a sulfuric acid undergo dehydration reaction in the presence of a solvent, and the 2,4'-DDS produced as a by-product is isomerized into 4,4'-DDS while gradually removing the solvent from the reaction mixture (Japanese Examined Patent Publication No.55-8972). The proposed process is intended to increase the purity and the yield of 4,4'-DDS in the following manner. In the process, only the 4,4'-DDS is precipitated from the reaction system by gradually removing the solvent utilizing the difference between 4,4'-DDS and 2,2'-DDS in the solubility in the solvent, whereby the isomerization equilibrium is shifted in the solution to induce the isomerization of 2,4'-DDS into 4,4'-DDS. However, the process causes the solidification of the reaction product solution on removal of the solvent into a viscous solid having no fluidity, and thus necessitates a special type of stirrer of high mechanical strength in the manufacture, resulting in difficulty in provision of a large-size manufacturing apparatus for mass production.
The present inventors also proposed processes involving the use of an aromatic sulfonic acid as a catalyst for the dehydration reaction or for the dehydration and isomerization reactions (Japanese Unexamined Patent Publications Nos.61-243059 and 61-243060). The proposed processes not only can reduce the time for the dehydration reaction and/or the isomerization reaction, but can prevent the production of 2,4'-DDS as a by-product in the dehydration reaction and the production of a tri-compound as a by-product in the dehydration and isomerization reactions. Yet the processes need to more markedly prevent the production of by-products and to further shorten the reaction time. Moreover, even the processes can not overcome the difficulty in handling the viscous product in the isomerization reaction.
Recently proposed is a process in which while a phenol and a sulfuric acid are subjected to dehydration reaction with heating in the presence of an aliphatic hydrocarbon-type suspending agent and an azeotropic agent, the 2,4'-DDS produced in the reaction is isomerized into 4,4'-DDS (Japanese Unexamined Patent Publication No.64-9970). The process, however, tends to be slow in the progress of dehydration reaction, and exhibits this tendency pronouncedly in the latter period of the reaction, consequently involving a prolonged period of reaction. Furthermore the process entails difficulties in completing the reaction even after a prolonged period of time, and insufficiently
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Nate Nobuyuki
Ogata Eiji
Cintins Marianne M.
Konishi Chemical Ind. Co., Ltd.
Page Margaret
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