JP2003212821A - Method of inhibiting (meth)acrylic monomer from being polymerized - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of inhibiting (meth)acrylic monomers from causing undesired polymerization on the heat transfer surface simply and economically when (meth)acrylic monomers are heated. <P>SOLUTION: The solution including (meth)acrylic monomers and polymerization inhibitor is sucked up from the lower part of the agitation blades by the centrifugal force of the agitation blades on the rotary shaft and sprayed down from the upper part of the agitation blades whereby almost all of the heat transfer surface are substantially wetted with the solution. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing polymerization of a (meth) acrylic monomer. More specifically, the present invention relates to a method for preventing unintended polymerization of a (meth) acrylic acid monomer on a heat transfer surface of a gas phase portion of an apparatus when heating a solution containing a (meth) acrylic acid monomer. It is. [0003] The reaction of (meth) acrylic acid monomers,
In operations involving heating such as evaporation, distillation, and mixing and dissolution, a device that is not equipped with a special device for preventing polymerization may be used. In such an apparatus, (meth) acrylic acid-based monomer containing no polymerization inhibitor is heated by agglomeration of vapor on the heat transfer surface, and undesired polymerization occurs on the heat transfer surface. . In order to avoid such undesired polymerization on the heat transfer surface, a solution containing a polymerization inhibitor is sent to an apparatus having a function equivalent to that of a sprinkler or the like by using an external device such as a pump and the like. Is known with a solution containing a polymerization inhibitor. [0005] However, in the above conventional method, the amount of liquid increases or decreases during operations such as reaction, evaporation, distillation, and mixing and dissolution, and a part of the heat transfer surface is reduced during the operation. It is difficult to cope with the case where the compound is exposed, or when the compound is operated in a small amount in a situation where various compounds are operated using the same apparatus such as a multi-plant. In addition, since an external device is used, the device becomes large-scale, and the device becomes expensive.
In addition, there is a problem that labor is required for maintenance of the apparatus. [0006] The inventors of the present invention have conducted various studies to solve the above problems, and as a result, when heating a solution containing a (meth) acrylic acid monomer and a polymerization inhibitor,
By the centrifugal force of the stirring blade attached to the rotating shaft, the solution is sucked up from the lower portion of the stirring blade, and the solution is sprayed from the upper portion of the stirring blade to wet substantially all the heat transfer surfaces with the solution. It has been found that unintended polymerization of a (meth) acrylic acid-based monomer on the heat transfer surface can be prevented simply and economically. DETAILED DESCRIPTION OF THE INVENTION The (meth) acrylic acid-based monomer used in the present invention includes (meth) acrylic acid ester having no vinyl ether group in the ester portion, (meth) acrylic acid, and (meth) acrylic acid. Acid halide, (meth)
Acrylic anhydride and (meth) acrylate. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, sec (meth) acrylate -Butyl, propyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, lauryl (meth) acrylate, benzyl (meth) acrylate, dicyclopentanyl (meth) acrylate, Isobornyl (meth) acrylate, 2- (2′-methoxyethoxy) ethyl (meth) acrylate, 2- (2 ′) (meth) acrylate
-Ethoxyethoxy) ethyl, 2- (meth) acrylate
(Acetoacetoxy) ethyl, phenoxyethyl (meth) acrylate, cyclohexylmethyl (meth) acrylate, trifluoroethyl (meth) acrylate, (meth) acrylate
Octafluoropentyl acrylate, N, N'-dimethylaminoethyl (meth) acrylate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, 1,4-butanediol di (Meta)
Acrylate, 1,6-hexanediol di (meth) acrylate, polypropylene glycol di (meth) acrylate, glycidyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (meth) acrylic acid 3
(Meth) acrylic esters such as -hydroxypropyl, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate; acrylic acid, methacrylic acid; (meth) acrylic chloride, (meth) acrylic acid (Meth) acrylic halides such as bromide; (meth) acrylic anhydride; (meth) acrylic acid such as sodium (meth) acrylate, potassium (meth) acrylate, magnesium (meth) acrylate, and calcium (meth) acrylate ) Acrylates. Among these, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, (meth)
Tert-butyl acrylate, 2- (meth) acrylate
Ethylhexyl, cyclohexyl (meth) acrylate,
Lauryl (meth) acrylate, benzyl (meth) acrylate, isobornyl (meth) acrylate, 2- (2'-methoxyethoxy) ethyl (meth) acrylate, 2- (2'-ethoxyethoxy) (meth) acrylate ) Ethyl, glycidyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, acrylic acid, and methacrylic acid are preferred. These (meth) acrylic acid monomers can be used alone or in an appropriate combination of two or more. [0009] These (meth) acrylic acid monomers may be present from the beginning of the operation, may be formed in the middle, or may be added in the middle. The polymerization inhibitors used in the present invention include:
Any of those generally used as a radical polymerization inhibitor can be used. Typical examples thereof include quinone-based polymerization inhibitors such as hydroquinone, methoxyhydroquinone, benzoquinone, and p-tert-butylcatechol; 2,6-di-tert-butylphenol, and 2,4-di-tert-. Alkylphenol polymerization inhibitors such as butylphenol, 2-tert-butyl-4,6-dimethylphenol, 2,6-di-tert-butyl-4-methylphenol and 2,4,6-tri-tert-butylphenol; alkyl Diphenylamine, N, N'diphenyl-p-phenylenediamine, phenothiazine, 4-hydroxy-2,2,2
6,6-tetramethylpiperidine, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, 1,4
-Dihydroxy-2,2,6,6-tetramethylpiperidine, 1-hydroxy-4-benzoyloxy-2,
Amine polymerization inhibitors such as 2,6,6-tetramethylpiperidine; copper dithiocarbamate polymerization inhibitors such as copper dimethyldithiocarbamate, copper diethyldithiocarbamate and copper dibutyldithiocarbamate; 2,2,6,6-
Such as tetramethylpiperidine-N-oxyl, 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl N-oxyl-based polymerization inhibitors; and the like. Among them, hydroquinone, methoxyhydroquinone, benzoquinone, p-tert-butylcatechol, phenothiazine, 4-hydroxy-2,
2,6,6-tetramethylpiperidine, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine,
1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, 1-hydroxy-4-benzoyloxy-
2,2,6,6-tetramethylpiperidine, 2,2
6,6-tetramethylpiperidine-N-oxyl, 4-
Hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-benzoyloxy-2,2,6
6-Tetramethylpiperidine-N-oxyl is preferably used. These polymerization inhibitors can be used alone or in an appropriate combination of two or more. The amount of the polymerization inhibitor depends on the type of the (meth) acrylic acid monomer used and the purpose of the heating operation, but the lower limit is 0.0001% by mass of the (meth) acrylic acid monomer. % Or more, more preferably 0.001% or more, still more preferably 0.005% or more, particularly preferably 0.01% or more, and the upper limit is preferably 5% or less, and more preferably 1% or less. Is more preferably 0.5% by mass or less, particularly preferably 0.1% by mass or less. In the method of preventing polymerization of the present invention, the reaction raw material, water, organic solvent, catalyst, additives and the like may be contained in any amount in addition to the above (meth) acrylic acid monomer and polymerization inhibitor. Good. The polymerization preventing method of the present invention can be applied to various reactions and various unit operations. Specifically, Diels-Alder reaction, esterification reaction, transesterification reaction,
The present invention can be applied to reactions such as addition reaction, acetalization reaction, oxidation reaction, reduction reaction, and polymerization; distillation; evaporation; Among them, it is preferably applied to a reaction in which the liquid level increases by dropping or the like; a reaction in which the liquid level decreases by reactive distillation; a distillation in which the liquid level decreases; and an evaporation in which the liquid level decreases. Further, the method for preventing polymerization according to the present invention can be performed with a small amount in a situation where various compounds are operated using the same apparatus such as a multi-plant, that is, an operation with a liquid level lower than the heat transfer surface. Is also suitably applied. The above operation may be performed in any of reduced pressure, normal pressure and pressurized conditions, and the temperature is not particularly limited, but the lower limit is usually 40 ° C. or higher, preferably 50 ° C. or higher, more preferably Is performed at 60 ° C. or higher, and the upper limit is 200 ° C. or lower, preferably 180 ° C. or lower, more preferably 170 ° C. or lower. The method of preventing unintended polymerization of a (meth) acrylic acid monomer on the heat transfer surface in the present invention is to attach a solution containing a (meth) acrylic acid monomer and a polymerization inhibitor to a rotating shaft. A method in which the solution is sucked up from the lower portion of the stirring blade by the centrifugal force of the stirring blade and sprayed from the upper portion of the stirring blade to wet substantially all the heat transfer surfaces with the solution. The stirring blade has a cylindrical and / or trough-like shape and is at least 5 °, preferably at least 10 °, more preferably at least 15 ° and at most 75 ° with respect to the rotation axis. Is mounted at an angle of 60 ° or less, more preferably 50 ° or less. In addition, when the stirring blade has a gutter shape,
The opening is attached so as to face upward. The angle attached to the rotating shaft can be such that the solution can be pumped from the lower part based on various factors such as the depth and diameter of the device, the amount of liquid charged inside the device, and the like.
In addition, the solution may be sprayed from the top toward the heat transfer surface, and the angle may be appropriately determined so that substantially all of the heat transfer surface can be wetted with the solution. The length of the stirring blade and the position of attachment to the rotating shaft are such that when the solution pumped from the lower portion of the stirring blade is sprayed from above onto the heat transfer surface, substantially all of the heat transfer surface is covered with the solution. What is necessary is just to determine suitably so that it can be wet. For example, in the case of the external heating method, the length may be set such that the solution is sprayed at a position higher than the heat transfer surface, that is, the inner surface through which heat is transferred, and the mounting position on the rotating shaft may be sufficient. In the case of an internal heating method such as an internal coil, the length of the stirring blade and the position of attachment to the rotating shaft may be set so that the solution is sprayed on the coil. The number of the stirring blades may be at least one, but it is preferable to use a plurality of stirring blades so that the heat transfer surface is constantly wetted with the solution containing the (meth) acrylic acid monomer and the polymerization inhibitor. . The number of rotations of the rotating shaft is such that the solution can be pumped from the lower part of the stirring blade attached to the rotating shaft,
And the solution is sprayed from the upper part toward the heat transfer surface, and it is sufficient that the rotation speed is such that substantially all of the heat transfer surface can be wet with the solution, and it is not particularly limited. , Usually at least 50 rpm, preferably at least 75 rpm, more preferably at least 100 rpm, even more preferably at least 125 rpm.
pm or more, particularly preferably 150 rpm or more, and the upper limit is 500 rpm or less, preferably 450 rpm or less,
More preferably 400 rpm or less, particularly preferably 35 rpm.
0 rpm or less. [0023] A stirring blade other than the cylindrical and / or trough-shaped stirring blade may be attached to the rotating shaft. In this case, the shape, position, and number of stirring blades may be appropriately set according to the apparatus and purpose. The present invention will be described in more detail with reference to the following examples, which should not be construed as limiting the invention thereto. Example 1 (Production of (meth) acrylic acid ester by transesterification reaction) [0025] Two semi-cylindrical trough-shaped stirring blades having a length of 7 cm and an inner diameter of 8 mm were used.
A stirring blade (hereinafter abbreviated as “gutter-shaped stirring blade”) attached at the lowermost part of the rotation shaft having a diameter of 8 mm and at a 45 ° angle to the rotation shaft at a position facing the two stirring blades, a thermometer, an Oldershaw 268 g of diethylene glycol monoethyl ether, 550 g of ethyl acrylate, 100 mg of phenothiazine and 3.5 g of dibutyltin oxide were added to a 1 L separable flask equipped with a mold rectification tower and a gas introduction tube. While introducing air into the liquid phase from the gas inlet pipe, 3
Rotate the gutter-shaped stirring blade at 00 rpm to mix and stir,
The temperature was raised by placing the flask portion in an oil bath at a temperature of 8 ° C. to a depth of 8 cm. In this case, the heat transfer surface is a portion corresponding to the inner wall surface of the container in contact with the oil bath (heat medium).
Ethyl acrylate from the top of the Oldershaw type rectification column-
The reaction was continued for 10 hours while distilling off the ethanol azeotropic composition to produce 2- (2'-ethoxyethoxy) ethyl acrylate. As the acrylate / ethanol azeotropic composition is distilled off as the reaction proceeds, the amount of the liquid decreases. However, due to the centrifugal force of the trough-shaped stirring blade, acrylic acid (meth) acrylate 2 -(2'-ethoxyethoxy)
A solution containing ethyl and phenothiazine, which is a polymerization inhibitor, was sucked up from the lower part of the gutter-shaped stirring blade and sprayed from the upper part of the gutter-shaped stirring blade, and the polymer was confirmed on the inner wall of the apparatus because all the heat transfer surfaces were wetted by the solution. Did not. Example 2 (Production of (meth) acrylate by transesterification) The same operation as in Example 1 was carried out except that ethyl acrylate was changed to methyl methacrylate, to give 2- (2'-ethoxyethoxy) methacrylate. ) Ethyl was prepared. As the reaction proceeds, the azeotropic composition of methyl methacrylate-methanol is distilled off, so that the amount of the liquid decreases. However, the methacrylic acid ester of (meth) acrylic acid ester A solution containing-(2'-ethoxyethoxy) and phenothiazine as a polymerization inhibitor was sucked up from the lower part of the gutter-shaped stirring blade and sprayed from the upper part of the gutter-shaped stirring blade, and all the heat transfer surfaces were wetted by the solution. No polymer was found on the inner wall. Embodiment 3 (1/3 using the same apparatus as in Embodiment 1)
Operation on a 5-liquid scale) In the same apparatus as in Example 1, 54 g of diethylene glycol monoethyl ether, 110 g of ethyl acrylate, 20 mg of phenothiazine and 0.7 g of dibutyltin oxide were used.
g was added. While introducing air into the liquid phase from the gas introduction pipe, the gutter-shaped stirring blade is rotated at 300 rpm to mix and stir,
The temperature was raised by placing the flask portion in a 130 ° C. oil bath to a depth of 8 cm. 2- (2′-ethoxyethoxy) ethyl acrylate was produced by continuing the reaction for 10 hours while distilling off the ethyl acrylate-ethanol azeotropic composition from the top of the Oldershaw type rectification column. As the reaction proceeds, the azeotropic composition of ethyl acrylate-ethanol is distilled off, so that the amount of the liquid decreases. However, due to the centrifugal force of the trough-shaped stirring blade, acrylic acid (meth) acrylate 2 -(2'-ethoxyethoxy)
A solution containing ethyl and phenothiazine, which is a polymerization inhibitor, was sucked up from the lower part of the gutter-shaped stirring blade and sprayed from the upper part of the gutter-shaped stirring blade, and the polymer was confirmed on the inner wall of the apparatus because all the heat transfer surfaces were wetted by the solution. Did not. Example 4 (Distillation and Purification of (Meth) Acrylic Ester) A 1-L separable flask equipped with a gutter-shaped stirring blade, a thermometer, an Oldershaw-type rectification column, a gas inlet tube, and a depressurizing device was prepared in the same manner as in Example 1. The reaction solution obtained by the same operation (acrylic acid 2- (2′-
Ethoxyethoxy) ethyl and a solution containing the polymerization inhibitor phenothiazine). While introducing air into the liquid phase from the gas inlet tube, the gutter-shaped stirring blade is rotated at 300 rpm to mix and stir, and the pressure is reduced so that the top of the Oldershaw type rectification tower becomes 666 hPa. Was applied to a depth of 8 cm to start heating. Ethyl acrylate and ethanol were distilled off from the top of the Oldershaw type rectification column and the pressure at the top was gradually increased to 27.
The pressure was reduced to hPa. After the distillate disappeared, unreacted diethylene glycol monoethyl ether was distilled off by setting the pressure at the top of the column at 17 hPa and the oil bath at 130 ° C. Thereafter, the temperature of the oil bath was raised to 160 ° C.
(2'-ethoxyethoxy) ethyl was distilled off from the top of the column. Although the liquid volume decreases with the distillation operation, 2- (2'-ethoxyethoxy) ethyl acrylate as a (meth) acrylate and phenothiazine as a polymerization inhibitor are contained by a trough-shaped stirring blade. The solution was sucked up from the lower part of the gutter-shaped stirring blade and sprayed from the upper part of the gutter-shaped stirring blade, and no polymer was found on the inner wall of the apparatus because all the heat transfer surfaces were wetted by the solution. Comparative Example 1 The same operation as in Example 1 was carried out except that the gutter-shaped stirring blade was changed to a turbine blade having a blade diameter of 7 cm.
(2′-ethoxyethoxy) ethyl was prepared. As the reaction proceeds, an azeotropic composition of ethyl acrylate-ethanol is distilled off, so that the liquid volume decreases.
The centrifugal force of the turbine blades makes it impossible to suck up and disperse a solution containing 2- (2'-ethoxyethoxy) ethyl acrylate (meth) acrylate and phenothiazine as a polymerization inhibitor, so that some of the transfer is not possible. At the end of the reaction, a white polymer was observed on the inner wall of the apparatus (heat transfer surface of the gas phase) at the end of the reaction. Comparative Example 2 The same operation as in Example 3 was carried out except that the gutter-shaped stirring blade was changed to a turbine blade having a blade diameter of 7 cm.
(2′-ethoxyethoxy) ethyl was prepared. In the turbine blade, a solution containing 2- (2'-ethoxyethoxy) ethyl acrylate (meth) acrylate and phenothiazine as a polymerization inhibitor cannot be sucked up and dispersed by centrifugal force. Part of the heat transfer surface is exposed from the beginning, and the amount of liquid is reduced because the ethyl acrylate-ethanol azeotropic composition is distilled off with the progress of the reaction, and the heat transfer surface is further exposed, and at the end of the reaction. A white polymer was confirmed on the inner wall of the apparatus (heat transfer surface of the gas phase). Comparative Example 3 The same operation as in Example 4 was carried out except that the gutter-shaped stirring blade was changed to a turbine blade having a blade diameter of 7 cm.
(2′-ethoxyethoxy) ethyl was purified by distillation. With the distillation operation, the liquid volume decreases, and the turbine blade contains 2- (2'-ethoxyethoxy) ethyl acrylate as a (meth) acrylate and phenothiazine as a polymerization inhibitor due to centrifugal force. Since the solution could not be sucked up and sprayed, a part of the heat transfer surface was exposed, and at the end of distillation, a white polymer was confirmed on the inner wall of the apparatus (heat transfer surface in the gas phase). According to the present invention, when a solution containing a (meth) acrylic acid-based monomer and a polymerization inhibitor is heated, the centrifugal force of the stirring blade attached to the rotating shaft causes the stirring blade to move from the lower part of the stirring blade. By sucking up the solution and spraying the solution from the top of the stirring blade, substantially all of the heat transfer surfaces are wetted by the solution, thereby increasing or decreasing the amount of the solution during operations such as reaction, evaporation, distillation, and mixing and dissolution. In some cases, or even when operating in a small amount in a situation where various compounds are operated using the same apparatus such as a multi-plant or the like, it is possible to wet substantially all of the heat transfer surfaces with the solution, which is simple and convenient. Unintended polymerization of a (meth) acrylic acid-based monomer which is economically insufficient in heat transfer stability can be prevented.

Claims (1)

Claims 1. When heating a solution containing a (meth) acrylic acid-based monomer and a polymerization inhibitor, the solution is stirred from the lower part of the stirring blade by a centrifugal force of a stirring blade attached to a rotating shaft. By spraying the solution from the top of the stirring blade,
A method for preventing polymerization of a (meth) acrylic acid monomer, wherein substantially all of the heat transfer surfaces are wetted with the solution.