Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Reexamination Certificate
2006-05-09
2006-05-09
Zucker, Paul A. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
Reexamination Certificate
active
07041850
ABSTRACT:
The present invention provides a process for producing purified (meth)acrylic acid by subjecting crude (meth)acrylic acid containing maleic acids and aldehydes as impurities to distillation, the said process comprising, prior to the distillation, the following steps:(A) adding hydrazines to the crude (meth)acrylic acid at a temperature of not less than a melting point of acrylic acid and not more than 50° C. to react the maleic acids with the hydrazines;(B) heat-treating the reaction solution obtained in the above step (A) at a temperature of 60 to 90° C. to convert the reaction product into a substance soluble in the reaction solution; and(C) adding hydrazines to the thus heat-treated reaction solution obtained in the above step (B) at a temperature of not less than the melting point of acrylic acid and not more than 50° C. to react the aldehydes with the hydrazines, thereby producing a substance soluble in the reaction solution.In the process for producing purified (meth)acrylic acid from the crude (meth)acrylic acid containing maleic acids and aldehydes as impurities according to the present invention, not only the maleic acids but also the aldehydes can be removed therefrom to a sufficient extent, and the operation thereof can be continued for a long period of time.
REFERENCES:
patent: 5759358 (1998-06-01), Bauer, Jr. et al.
Ogawa Yasushi
Suzuki Yoshiro
Takasaki Kenji
Yada Shuhei
Mitsubishi Chemical Corporation
Nixon & Vanderhye P.C.
Zucker Paul A.
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