Nippon Shokubai Co., Ltd.

Toyo Kasei Kogyo Company Limited

Satoshi Nakagawa

Kazuhiko Sakamoto

Yoshitake Ishii

Koji Ueno

Hiroshi Yoshida

Hideaki Tsuneki

Harunori Hirao

Toshio Hayashi

Yukihiko Kakimoto

Atsuhiro Onishi

Masatsugu Kitaura

Ritsuo Kitada

Hideyuki Baba

Hiroaki Tanaka

Kunihiko Suzuki

Sunao Mitsui

Takashi Sugimoto

Takahiro Inagaki

Satoshi Yamaguchi

Susumu Ohno

Hideki Ogawa

Kohei Umehara

PROBLEM There is provided a melting method of (meth)acrylic acid crystal which is capable of providing a higher quality of (meth)acrylic acid without carrying out an additional purification treatment to (meth)acrylic acid obtained by a crystallization operation accompanied by melting of (meth)acrylic acid. In addition, there is provided a simple method for adjusting a content of polymerization inhibitor in a product (meth)acrylic acid. SOLUTION In the crystallization method melting (meth)acrylic acid crystal while wetting with the crystalline molten liquid, a polymerization inhibitor is added to a molten liquid melted after initiation of melting, and all of crystal is melted while circulating and feeding the molten liquid containing said polymerization inhibitor to the crystal. In addition, a content of polymerization inhibitor in product (meth)acrylic acid is adjusted by adding a predetermined amount of polymerization inhibitor corresponding to a product specification to the molten liquid melted after initiation of melting.

Method for crystallizing (meth)acrylic acid and method for regulating content of polymerization inhibitor in product (meth)acrylic acid

A process for producing (meth)acrylic acid of the present invention comprises the steps in the following order: a crystallization step of supplying a cooling medium cooled by a heat source device to a crystallizer to obtain a (meth)acrylic acid crystal from a crude (meth)acrylic acid solution; an adjustment step of returning the cooling medium discharged from the crystallizer to the crystallizer without cooling; a sweating step of supplying a heating medium to the crystallizer to partially melt the (meth)acrylic acid crystal, thereby obtaining a melted liquid, and discharging the melted liquid from the crystallizer; and a melting step of supplying the heating medium to the crystallizer to melt the (meth)acrylic acid crystal, thereby obtaining purified (meth)acrylic acid. According to the present invention, purified (meth)acrylic acid with high purity can be obtained.

Process for producing (meth) acrylic acid

The objective of the present invention is to provide a process for production of (meth)acrylic acid with improved production efficiency by efficiently shifting from heating procedure to cooling procedure for a crystallizer. A process for production of (meth)acrylic acid according to the present invention is characterized in comprising the steps of crystallizing (meth)acrylic acid from a crude (meth)acrylic acid solution by using a batch type crystallizer, and melting the obtained (meth)acrylic acid crystal to obtain a (meth)acrylic acid melted liquid; wherein preliminary cooling of the crystallizer for the next crystallization step is started during transferring the (meth)acrylic acid melted liquid from the crystallizer.

Process for production of (meth)acrylic acid

A process for producing (meth)acrylic acid, comprising the step of repeating a crystallization operation 'n' times (providing 'n' is an integer 2 or more) to produce purified (meth)acrylic acid from crude (meth)acrylic acid, wherein a (meth)acrylic acid solution is crystallized and the crystallized (meth)acrylic acid is melted to obtain a (meth)acrylic acid melt in the crystallization operation; wherein a constant amount Aof the (meth)acrylic acid solution is subjected to the kcrystallization operation (providing &#x201c;k&#x201d; is an integer 1 to n&#x2212;1), and the (meth)acrylic acid melt obtained by the kcrystallization operation is utilized as the (meth)acrylic acid solution for the k+1crystallization operation without being discharged from a crystallizer or is transferred from the crystallizer to a k+1storage tank for storing the (meth)acrylic acid solution to be used in the k+1crystallization operation depending on the stored amount of the k+1storage tank.

A process for producing (meth)acrylic acid, comprising a crystallizing step of supplying a cooling medium from a refrigerator to a crystallizer and returning the cooling medium from the crystallizer to the refrigerator, thereby obtaining a (meth)acrylic acid crystal from a (meth)acrylic acid-containing solution; and a melting step of supplying a heating medium from a refrigerator to the crystallizer and returning the heating medium from the crystallizer to the refrigerator, thereby melting the (meth)acrylic acid crystal; wherein the crystallizing step and the melting step are respectively performed at least once, thereby producing purified (meth)acrylic acid from a crude (meth)acrylic acid solution; temperature of the cooling medium discharged from the refrigerator is maintained constant at temperature T; temperature of the cooling medium to be returned to the refrigerator is maintained constant at temperature T; the temperature Tis adjusted depending on a production amount of the purified (meth)acrylic acid per unit time.

Process for producing (meth)acrylic acid

In a production method in which an acrylic acid-containing solution obtained from an acrylic acid-containing gas (or an acrylic acid-containing liquid obtained simply by subjecting the acrylic acid-containing solution to a separation process of reaction by-products) is directly subjected to a crystallization process, the crystallization process can't be carried out smoothly in an unsteady state (when the concentration of water in the acrylic acid-containing solution is high). The present invention aims to provide a method for collecting the purified acrylic acid having high purity in good yield even in an unsteady state. When the acrylic acid-containing solutionsandhave a concentration of water higher than 10 mass % (unsteady state), the purified acrylic acidandor the acrylic acid-containing solutioncontaining 10 mass % or less of water is mixed therewith to make the concentration of water 10 mass % or less [a] [b]. Alternatively, when the acrylic acid-containing solutionsandhave a concentration of water higher than 10 mass %, it is used as an absorption liquid [c]. Thereafter, the crystallization process is carried out.

Method for producing (meth) acrylic acid

The present invention provides a process for more efficiently producing an &#x3b1;-hydroxycarboxylic acid ester wherein side reactions due to the &#x3b1;-hydroxycarboxylic acid ester are inhibited or prevented in comparison with prior art production processes. The invention provides a process for producing an &#x3b1;-hydroxycarboxylic acid ester comprising Steps 1 to 3: Step 1. reacting, in the presence of oxygen, (i) a 1,2-diol with a 1,2-diol or (ii) a 1,2-diol with an alcohol to obtain a reaction product containing an &#x3b1;-hydroxycarboxylic acid ester; Step 2. separating the &#x3b1;-hydroxycarboxylic acid ester from the reaction product obtained in Step 1 by distillation under reduced pressure; and Step 3. feeding Step 1 with a mixture obtained by partially or entirely removing water from the reaction product, wherein the mixture contains an unreacted 1,2-diol and/or alcohol.

Method for producing &#x3b1;-hydroxycarboxylate

This invention is directed to 2,5-dimercapto-1,3,4-thiadiazole dilithium salt and its dihydrate and methods of their manufacture, and a secondary lithium battery and positive electrode-active material comprising the same.

2,5-Dimercapto-1,3,4-thiadiazole dilithium salt and its dihydrate and their manufacture, and a secondary lithium battery and positive electrode-active material comprising the same

Disclosed is a novel blowing agent of tetrazoles and their derivatives. The blowing agent comprising tetrazole derivatives is harmless, odorless and inexpensive. Moreover, the agent is low in physical sensitivities and safe in use, and generates clean gas by being sharply decomposed only due to temperature. The blowing agent of tetrazoles and their derivatives employs aminotetrazole derivatives represented by the general formula (1). The blowing agent offers foaming agents for resin molded bodies having good thermal properties, inflators for air bags serving as automobile safety protection, or smoking agents for diffusing chemicals by a low-cost inexpensive synthetic process.

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Himeji, Japan

Satoshi Nakagawa