JP2001288146A - Method for purifying (meth)acrylic acid ester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for purifying a (meth)acrylic acid ester, capable of sufficiently eliminating coloration causing impurities contained in the (meth) acrylic acid ester by a simple method. SOLUTION: This method for purifying the (meth)acrylic acid ester is provided by making the (meth)acrylic acid ester containing the coloration-causing impurities in contact with a basic ion exchanging resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying a (meth) acrylate containing a coloring substance, and more particularly to a method for purifying methyl methacrylate containing a coloring substance.

[0002]

2. Description of the Related Art As an industrial production method of methyl methacrylate, there are an ACH method with by-product of ammonium sulfate, an improved ACH method without by-product of ammonium sulfate, a C4 oxidation method, and a method of obtaining an ester directly from methacrolein and methanol. And methods for carbonylation of methylacetylene and the like are known.

[0003] Various (meth) acrylic esters can be produced by a method such as transesterification or esterification of methyl (meth) acrylate or (meth) acrylic acid with an alcohol.

The (meta) obtained by such a method
Acrylic esters contain a large amount of coloring agents generated by exposure to strong oxidizing agents and high temperatures during the production process. Many applications of (meth) acrylic acid esters, particularly methacrylic acid esters, require transparency, and the amount of the color-causing substance greatly affects its commercial value. For example, methacrylic resin containing methacrylic acid ester as a main component has excellent properties such as weather resistance, transparency, surface gloss, mechanical strength, moldability, etc., and is used for optical materials, signboards, lighting covers, and mechanical devices. Windows, aquarium tanks,
Alternatively, it is used for many purposes such as members for various display devices, but coloring of a cut surface or the like may cause a problem in appearance.
In particular, in the case of an optical fiber application or the like, there is an important problem that the presence of a coloring cause substance impairs the transmittance of light of a specific wavelength.

[0005] Adsorbents for removing impurities include:
For example, activated clay obtained by pulverizing acidic clay or bentonite and treating with acid, silica gel obtained by hydrolyzing an alkali silicate solution with an acid, activated alumina obtained by applying a special treatment to aluminum oxide, and molecular sieves. Activated carbons such as synthetic zeolites, naturally occurring zeolites, charcoal-based, fruit-shell-based, and coal-based are exemplified.

[0006] Further, as a method for removing a coloring cause substance contained in methacrylic acid ester, a method of separating by distillation at a high reflux ratio with a high-stage distillation column, a method of performing an adsorption treatment with activated carbon, and Japanese Patent Application Laid-Open No. Sho 60-18964. There are known a method of passing through a solid adsorbent such as alumina described in the publication, a method of treating with an aromatic diamine and the like described in EP-A-206230, and the like. Further, JP-A-7-2380
No. 55, JP-A-7-258160 and JP-A-7-258161 disclose an oxime-forming treatment of hydroxylamine with a mineral acid salt, a reducing treatment with a metal hydride complex compound, and an alkali metal and / or alkaline earth. Methods such as a cleaning treatment with an aqueous solution of a metal-like compound have been proposed.

[0007]

However, the purification method by distillation requires an enormous amount of energy to remove a substance having a small specific volatility such as diacetyl, which is one of coloring substances of methyl methacrylate. There is a problem. The method using a solid adsorbent such as alumina has a problem that an enormous amount is required for the coloring causative substance contained in the object to be purified. In addition, the method using other mineral salts of hydroxylamine, metal hydride complex compounds, alkali (earth) metals, etc., has a problem that the process is complicated even though the removal of coloring substances is not sufficient. There is.

Accordingly, an object of the present invention is to provide a method for purifying a (meth) acrylic ester which can sufficiently remove a coloring cause substance contained in the (meth) acrylic ester by a simple method.

[0009]

SUMMARY OF THE INVENTION The present invention is a method for purifying a methacrylate ester by contacting a basic ion exchange resin with a methacrylate ester containing a coloring substance. The present invention is suitable when the methacrylate is methyl methacrylate.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The (meth) acrylate to be purified in the present invention includes methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and (meth) acrylate. 2-ethylhexyl, ethylene glycol di (meth) acrylate, diethylene glycol (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolethanetri (meth) acrylate, trimethylolentertri (meth) acrylate, pentaerythritol tetra (meth) ) Acrylates, allyl (meth) acrylates,
Esters of (meth) acrylic acid and alcohol, such as 2-hydroxyethyl (meth) acrylate, are exemplified. In particular, the present invention has a remarkable effect on methyl methacrylate. Here, (meth) acrylic ester means acrylic ester and methacrylic ester as commonly used.

In the present invention, the (meth) acrylic ester to be purified may be produced by any method. As an industrial production method of (meth) acrylic acid ester, for example, acetone cyanohydrin (AC
H) as a raw material, an ACH method with ammonium sulfate by-product, an improved ACH method with acetone cyanohydrin as a raw material, without ammonium sulfate by-product,
C4 oxidation method in which methacrolein obtained by gas-phase catalytic oxidation reaction of a compound having 4 carbon atoms is subjected to esterification reaction of methacrylic acid and alcohol obtained by further gas-phase catalytic oxidation, gas-phase catalytic oxidation of compound having 4 carbon atoms There are known a method of directly reacting methacrolein obtained by the reaction with an alcohol to obtain an ester form, a method of carbonylating methylacetylene using carbon monoxide and an alcohol, and the like.

Examples of the substance causing coloring include diacetyl, 2,5-dimethylfuran, methacrolein, crotonaldehyde, methyl pyruvate and the like. The present invention is suitable for purifying methyl methacrylate containing diacetyl and 2,5-dimethylfuran. Diacetyl and 2,5-dimethylfuran are often contained in, for example, methyl methacrylate produced by a C4 oxidation method.

The basic ion exchange resin used in the practice of the present invention is an insoluble synthetic resin having a basic group capable of ion exchange, for example, a strongly basic gel type ion exchange resin, a strongly basic exchange resin. Porous ion exchange resin,
Examples include a weakly basic gel-type ion exchange resin, a weakly basic porous ion-exchange resin, and the like.

Such a basic ion exchange resin is, for example, a monomer such as styrene as a first component, a crosslinking agent such as DVB as a second component, an organic solvent as a third component, and a linear (non-crosslinked) resin. A polymer, a precipitant, a swelling agent and the like may be added alone or as a combination of two and reacted (copolymerized) to produce a copolymer. Here, the third component is used to impart properties as a synthetic adsorbent, and varies the pore distribution, pore volume, surface area, pore diameter, etc. depending on the method of adding a precipitant, a swelling agent, and a linear polymer. Can be changed. Examples of the method for adding the third component include a precipitant addition method, a linear polymer addition method, a precipitant / swelling agent addition method, a precipitant / linear polymer addition method, and a swelling agent / linear polymer addition method. Can be

In the present invention, the contact of the (meth) acrylic acid ester with the basic ion-exchange resin is carried out by, for example,
The (meth) acrylate is passed through a fixed bed of the resin. The amount of liquid per hour is 0.1 to 1 of the volume of the resin.
The amount is preferably 0 times, and particularly preferably 1 to 5 times. The larger the amount of liquid passing, the less resin is required, and the smaller the amount of liquid passing, the more the coloring cause substance contained in the (meth) acrylate is adsorbed. The temperature of the object to be purified at the time of contact is preferably in the range of room temperature to the boiling point of the methacrylic acid ester as the object to be purified. Regarding the pressure, the operation is preferably performed under the atmospheric pressure.

Although the purification method of the present invention is preferably carried out in combination with a distillation step, the distillation step is not essential. The purification method of the present invention is preferably carried out on the crude (meth) acrylate before distillation obtained in the reaction step, but may be carried out after the distillation step.

[0017]

The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples. In the examples, the concentration of 2,5-dimethylfuran, which is a coloring substance in methyl methacrylate, was determined by gas chromatography with a hydrogen flame type detector (SHIMA manufactured by Shimadzu Corporation).
DZU.GC-17A) was used for the absolute calibration curve method.

As an index showing the effect of the present invention, the light transmission amount of a product obtained by cast polymerization of methyl methacrylate alone was used. Cast polymerization is performed by adding and mixing and dissolving 0.001 part by weight of 2,2'-azobis (isobutyronitrile) to 100 parts by weight of methyl methacrylate, and mixing and dissolving two glass pieces of 600 mm × 600 mm × 5 mm. The gap was filled with a polyvinyl chloride gasket between them, and the gap was poured into a 5 mm glass cell, polymerized in a 50 ° C. water bath for 5 hours, and then heat-treated in a 120 ° C. air oven for 2 hours. The amount of light transmission was 5% for the methyl methacrylate resin cast plate obtained by the cast polymerization.
It was cut into a rod shape of mm (width) x 5 mm (thickness) x 550 mm (length), and each surface was mirror-polished, and measured in the longitudinal direction at predetermined wavelengths shown in Table 1. For this measurement, a parallel beam having a beam diameter of 2 mm obtained by dispersing the light from the halogen lamp was applied to one end surface of the rod (5 mm × 5 mm).
mm surface), and the amount of light emitted from the opposite end surface, that is, the amount of transmitted light, was read by an ammeter connected to a silicon photodiode. In addition,
The light transmission amount in Table 1 is shown by a direct reading value (unit: nA) of the ammeter.

Example 1 Methacrolein obtained by the gas-phase catalytic oxidation reaction of isobutylene was further subjected to a gas-phase catalytic oxidation reaction to obtain an esterification reaction of methacrylic acid and methanol to obtain methyl methacrylate. The concentration of 2,5-dimethylfuran in this methyl methacrylate is 38.6 p.
pm.

The porous weakly basic ion exchange resin XE-
When 5 times the volume of the above-mentioned methyl methacrylate was passed through a fixed bed filled with 583 (manufactured by Organo Co., Ltd.) per hour, the amount of 2,2 in the methyl methacrylate after the passing was passed.
The concentration of 5-dimethylfuran was 15.1 ppm.
Table 1 shows the light transmission amount of the purified methyl methacrylate before and after the passage, which was cast-polymerized singly.

Example 2 The procedure of Example 1 was repeated, except that the flow rate of methyl methacrylate was changed to twice the volume of the resin per hour. The concentration of 2,5-dimethylfuran after the passage was 5.1 ppm. Table 1 shows the measurement results of the light transmission amount.

Example 3 In Example 1, methacrolein obtained by the gas-phase catalytic oxidation reaction of isobutylene was reacted with methanol using a palladium-containing compound to obtain methyl methacrylate. The procedure was performed in the same manner as in Example 1 except that this methyl methacrylate was used as a purification target. The concentration of 2,5-dimethylfuran before the passage was 41.4 ppm, and the concentration of 2,5-dimethylfuran after the passage was 14.
It was 4 ppm. Table 1 shows the measurement results of the light transmission amount.

Example 4 Methyl methacrylate was obtained by an ACH method using acetone cyanohydrin obtained from acetone and hydrocyanic acid as a raw material. The procedure was performed in the same manner as in Example 1 except that this methyl methacrylate was used as a purification target. The concentration of 2,5-dimethylfuran before passing was 9.1 ppm, and the concentration of 2,5-dimethylfuran after passing was 5.3 p.
pm. Table 1 shows the measurement results of the light transmission amount.

Example 5 As a basic ion exchange resin, a porous weak basic ion exchange resin XT-6050RF was used.
The procedure was performed in the same manner as in Example 1 except that (manufactured by Organo) was used. After passing through, the concentration of 2,5-dimethylfuran is 1
It was 0.1 ppm. Table 1 shows the measurement results of the light transmission amount.

Example 6 The same procedure as in Example 1 was carried out except that a gel-type neutral basic ion exchange resin IRA-478RF (manufactured by Organo) was used as the basic ion exchange resin. The concentration of 2,5-dimethylfuran after passing the solution was 15.9.
ppm. Table 1 shows the measurement results of the light transmission amount.

Example 7 The same operation as in Example 1 was carried out except that a gel type weakly basic ion exchange resin IRA-67 (manufactured by Organo Corporation) was used as the basic ion exchange resin. The concentration of 2,5-dimethylfuran after passing through is 17.8 ppm.
Met. Table 1 shows the measurement results of the light transmission amount.

Example 8 The same procedure as in Example 1 was carried out except that a porous weak basic ion exchange resin WA30 (manufactured by Mitsubishi Chemical Corporation) was used as the basic ion exchange resin. The concentration of 2,5-dimethylfuran after passage is 13.1 ppm.
Met. Table 1 shows the measurement results of the light transmission amount.

[0028]

[Table 1]

[0029]

The method for purifying a (meth) acrylate according to the present invention is simpler than the conventional method. Further, according to the present invention, since impurities contained in the (meth) acrylate can be sufficiently removed, a (meth) acrylate having excellent transparency can be obtained. The present invention is particularly effective in purifying methyl methacrylate.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshiaki Kobayashi 20-1 Miyukicho, Otake City, Hiroshima Prefecture Inside Mitsubishi Rayon Co., Ltd. Otake Works (72) Inventor Mohammed 201-1 Miyukicho, Otake City, Hiroshima Prefecture Mitsubishi Rayon Co., Ltd. Central Research Laboratory F-term (reference) 4H006 AA02 AD17

Claims (2)

[Claims] 1. A method for contacting a (meth) acrylic ester containing a coloring substance with a basic ion exchange resin.
A method for purifying an acrylate ester. 2. The method for purifying (meth) acrylate according to claim 1, wherein the (meth) acrylate is methyl methacrylate.