Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
2001-02-08
2002-09-17
Shah, Mukund J. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
Reexamination Certificate
active
06452040
ABSTRACT:
BACKGROUND OF THE INVENTION
A. TECHNICAL FIELD
The present invention relates to a production process for a hydroxyalkyl (meth)acrylate which comprises the step of carrying out a reaction between (meth)acrylic acid and an alkylene oxide.
B. BACKGROUND ART
An alkylene oxide forms an explosive mixed gas under certain conditions in the presence of oxygen. Therefore, when a hydroxyalkyl (meth)acrylate is produced by carrying out a reaction between (meth)acrylic acid and the alkylene oxide, it is desirable that this production is carried out under an atmosphere in which oxygen does not exist in consideration of safety. On the other hand, however, raw materials or products polymerize under an atmosphere in which oxygen does not exist at all. Therefore, it is proposed to carry out the production under an atmosphere of a gas which contains oxygen as a polymerization inhibitor.
However, when the production is carried out under an atmosphere of a mixed gas which contains oxygen in a comparatively high concentration such as air, there is a particularly high possibility that an explosive mixed gas might be formed when adding the alkylene oxide into a reactor, therefore such production is very dangerous.
In addition, when the production is carried out under an atmosphere of a mixed gas which contains oxygen in a comparatively low concentration, an inert gas (e.g. nitrogen) (which is a sealing gas (e.g. a pressured or replaced sealing gas for such as a raw material storage tank)) or oxygen is dissolved in the raw materials such as the (meth)acrylic acid and the alkylene oxide, therefore, every time these raw materials are added, the oxygen concentration of a gas phase portion of the reactor varies and, if the oxygen concentration becomes high, there occurs a danger of explosion and, if the oxygen concentration lowers near 0 vol %, there occurs a possibility of polymerization. In addition, there is a case where the oxygen concentration of the gas phase portion of the reactor varies also in the progress of the reaction.
SUMMARY OF THE INVENTION
A. OBJECT OF THE INVENTION
An object of the present invention is to provide a production process for a hydroxyalkyl (meth)acrylate wherein, when a reaction between (meth)acrylic acid and an alkylene oxide is carried out to produce the hydroxyalkyl (meth)acrylate, the process enables to maintain the oxygen concentration of a gas phase portion of a reactor within a specific low concentration range in any stage of before adding raw materials, during the reaction, and after the reaction.
B. DISCLOSURE OF THE INVENTION
The present inventors diligently studied to solve the abovementioned problems. As a result, the inventors have hit on an idea that, if a mixed gas, having an oxygen concentration as beforehand adjusted into a specific low concentration range, and/or an inert gas is used to make a concentration adjustment to maintain the oxygen concentration of a gas phase portion of a reactor within a specific low concentration range before adding raw materials, during the reaction, or after the reaction, then the above-mentioned problems can be solved. The present invention has been completed in this way.
That is to say, a production process for a hydroxyalkyl (meth)acrylate, according to the present invention, comprises the step of carrying out a reaction between (meth)acrylic acid and an alkylene oxide in the presence of a catalyst in order to produce the hydroxyalkyl (meth)acrylate, wherein an inert gas and/or a mixed gas of oxygen and an inert gas with a beforehand adjusted oxygen concentration of 0.1 to 14 vol % is used to maintain the oxygen concentration of a gas phase portion of a reactor in the range of 0.1 to 14 vol % before adding the alkylene oxide.
In addition, another production process for a hydroxyalkyl (meth)acrylate, according to the present invention, comprises the step of carrying out a reaction between (meth)acrylic acid and an alkylene oxide in the presence of a catalyst in order to produce the hydroxyalkyl (meth)acrylate, wherein an inert gas and/or a mixed gas of oxygen and an inert gas with a beforehand adjusted oxygen concentration of 0.1 to 14 vol % is used to maintain the oxygen concentration of a gas phase portion of a reactor in the range of 0.1 to 14 vol % during the above reaction.
In addition, yet another production process for a hydroxyalkyl (meth)acrylate, according to the present invention, comprises the step of carrying out a reaction between (meth)acrylic acid and an alkylene oxide in the presence of a catalyst in order to produce the hydroxyalkyl (meth)acrylate, wherein an inert gas and/or a mixed gas of oxygen and an inert gas with a beforehand adjusted oxygen concentration of 0.1 to 14 vol % is used to maintain the oxygen concentration of a gas phase portion of a reactor in the range of 0.1 to 14 vol % between completion of the above reaction and charge for the next reaction.
In addition, yet another production process for a hydroxyalkyl (meth)acrylate, according to the present invention, comprises the step of carrying out a reaction between (meth)acrylic acid and an alkylene oxide in the presence of a catalyst in order to produce the hydroxyalkyl (meth)acrylate, wherein the oxygen concentration of a gas phase portion of a reactor is maintained in the range of 0.1 to 14 vol % throughout the production steps.
These and other objects and the advantages of the present invention will be more fully apparent from the following detailed disclosure.
DETAILED DESCRIPTION OF THE INVENTION
First, the production process for a hydroxyalkyl (meth)acrylate to which the characteristic production process according to the present invention is preferably applicable is roughly explained as follows.
First, a reaction between (meth)acrylic acid and an alkylene oxide is carried out in the presence of a catalyst. The conversion in this reaction is often less than 100%, therefore generally such as an unreacted residue of the (meth)acrylic acid or alkylene oxide is present in the resultant reaction liquid at the end of the reaction. Thus, the above resultant reaction liquid is led to the step to remove such as these unreacted residues of the raw materials from the reaction liquid, and then purified by such as distillation as the subsequent final step, with the result that the aimed hydroxyalkyl (meth)acrylate is obtained.
The production process according to the present invention involves controlling the atmosphere of the gas phase portion of the reactor in the above-mentioned series of production steps.
The alkylene oxide, usable in the present invention, preferably has 2 to 6 carbon atoms, more preferably 2 to 4 carbon atoms. Examples thereof include ethylene oxide, propylene oxide, and butylene oxide. Among them, ethylene oxide or propylene oxide is preferable. In addition, the (meth)acrylic acid, as used in the present invention, means acrylic acid or methacrylic acid.
The catalyst, usable for the reaction in the present invention, is not especially limited, but preferable examples thereof include at least one member selected from the group consisting of: chromium compounds such as chromium chloride, chromium acetylacetonate, chromium formate, chromium acrylate, chromium methacrylate, sodium dichromate, and chromium dibutyldithiocarbamate; iron compounds such as iron powder, iron chloride, iron formate, iron acrylate, and iron methacrylate; and amine compounds such as trialkylamines, cyclic amines (e.g. pyridine) and their quaternary salts, and resins having a basic functional group (e.g. tertiary amino groups, quaternary ammonium salts, and pyridinium groups).
The amount of the above catalyst is not especially limited, but, in the case where the catalyst is a homogeneous catalyst, the catalyst is usually used in the range of 0.05 to 10 weight %, particularly preferably 0.1 to 3 weight %, of the raw (meth)acrylic acid. In addition, in the case where the catalyst is a heterogeneous catalyst, the catalyst is usually used in the range of 5 to 50 weight %, particularly preferably 10 to 30 weight %, of the raw (meth)acrylic acid.
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Asami Masakazu
Nakahara Sei
Shingai Yasuhiro
Ueoka Masatoshi
Yoneda Yukihiro
Haugen Law Firm PLLP
Nippon Shokubai Co. , Ltd.
Shah Mukund J.
Tucker Zachary C.
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