JPH061749A - Method for purifying (meth) acrylic acid ester - Google Patents

Abstract

PURPOSE:To sufficiently remove impurities, especially free acids in a (meth) acrylic acid ester by a simple operation and to purify the (meth)acrylic acid ester at a low cost without causing the discoloration of the ester. CONSTITUTION:A (meth)acrylic acid ester is made to contact with a metal oxide to remove the impurities existing in the ester. The metal oxide is preferably dehydrated before use. The metal oxide is preferably an oxide of the element of the group 3, group 4 or group 4a and preferably modified with an alkali metal, etc.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for purifying (meth) acrylic acid ester. More specifically, impurities contained in (meth) acrylic acid ester, especially free acid contained in a trace amount, can be removed by a simple operation at low cost, and (meth) acrylic without coloring. It relates to a method for purifying acid esters.

[0002]

2. Description of the Related Art Conventionally, acrylic acid esters and methacrylic acid esters have been widely used as monomer components for producing coating agents, adhesive agents, and optical materials such as contact lenses. Among these, acrylic acid ester is mainly produced by esterifying acrylic acid obtained by catalytic oxidation of propylene, and methacrylic acid ester is an acetone cyanohydrin method, a new acetone cyanohydrin method, Alternatively, it is directly produced by a catalytic oxidation method using isobutene or t-butyl alcohol as a raw material, the methacrylic acid obtained by these methods is esterified, and the methyl methacrylate obtained directly by these methods is transesterified. It is manufactured by

The acrylic acid ester and the methacrylic acid ester obtained by these methods (hereinafter, the two are collectively referred to as (meth) acrylic acid ester) generally have a color number (APHA) of 1 or less and are free. It contains about 5-5,000 ppm of impurities such as (meth) acrylic acid.

However, depending on the use of the (meth) acrylic acid ester, the presence of a free acid is disliked. For example, when manufacturing an optical material such as a contact lens, when the (meth) acrylic acid ester contains a free acid as an impurity, the (meth) acrylic acid ester polymer is colored and used as a raw material of the optical material. There was a problem that I could not do it. Further, when a polymer is produced by ionically polymerizing a (meth) acrylic acid ester, there is a problem that the polymerization initiator is deactivated and a desired polymer cannot be obtained.

Therefore, it has been conventionally practiced to remove impurities contained in the (meth) acrylic acid ester, particularly free acid, to purify the (meth) acrylic acid ester.
Examples of such a purification method are: (1) a method of passing a (meth) acrylic acid ester through an activated carbon bed; (2) a method of adding polyamines to a (meth) acrylic acid ester and distilling (JP-A-5223017). Gazette);
And (3) a method of passing a (meth) acrylic ester through a weakly basic anion exchange resin bed (JP-A-63-2952).
No. gazette) is proposed.

[0006]

However, the method using activated carbon has a problem that the free acid cannot be sufficiently removed. In addition, there is a problem that the cost of recycling the used activated carbon is high.

When distillation is carried out using polyamines, the purified (meth) obtained when the mixture of polyamines and (meth) acrylic acid ester is overheated or when polyamines are excessively added. There is a problem that the acrylic ester is colored and cannot be used for some applications such as optical applications. Further, if it is attempted to avoid this coloring by controlling the refining treatment conditions, there is a problem in that the treatment operation needs to be extremely precise and the treatment operation becomes very complicated.

Even when a weakly basic anion exchange resin is used, the weakly basic anion exchange resin elutes the deteriorated organic amine into the (meth) acrylic acid ester at the initial stage of the purification treatment, and as a result, There is a problem that the (meth) acrylic acid ester is colored. Therefore, there is a problem in that the pretreatment of the weakly basic anion exchange resin requires time and reagents, and the purification cost cannot be reduced. Further, since it takes time and a reagent to regenerate the weakly basic anion exchange resin, there is also a problem that the purification cost cannot be reduced. In addition, purification on such weakly basic anion exchange resins is basically limited to its relatively small exchange capacity to effect removal of the free acid by acid-base reactions,
There has been a problem that many weakly basic anion exchange resins must be used to sufficiently remove impurities. In addition, the weakly basic anion exchange resin deteriorates during purification or storage, so that there is a problem that its life is not so long in practical use.

The present invention is intended to solve the above-mentioned problems of the prior art, and when purifying a (meth) acrylic acid ester, impurities contained in the (meth) acrylic acid ester, particularly It is an object of the present invention to provide a method capable of removing a free acid by a simple operation and not coloring a (meth) acrylic acid ester.

[0010]

Means for Solving the Problems The present inventors have noticed that a metal oxide has a property as a Lewis acid or a Lewis base, and by treating a (meth) acrylic acid ester with the metal oxide, The inventors have found that the above-mentioned objects can be achieved, and have completed the present invention.

That is, the present invention provides a method for purifying a (meth) acrylic acid ester, which comprises removing the impurities contained therein by bringing the (meth) acrylic acid ester into contact with a metal oxide. To do.

The present invention will be described in detail below.

A metal oxide is used in the present invention.
By using the metal oxide, the impurities contained in the (meth) acrylic acid ester, especially the free acid contained in a trace amount, can be sufficiently removed, for example, at a rate of about 70% or more.

Further, unlike the weakly basic anion exchange resin, the metal oxide itself is chemically stable, and therefore does not release impurities such as coloring the (meth) acrylic acid ester during purification. Moreover, after using for purification in atmospheric pressure,
By heating in an air atmosphere at a temperature of 250 to 700 ° C. for 1 to 4 hours, it can be chemically stably and easily regenerated, so that it has a longer life than a weakly basic anion exchange resin. Therefore, the purification cost of the (meth) acrylic acid ester can be reduced.

Although the reason why the metal oxide exhibits such characteristics is not clear, it is because the ionic sum is generated between the free acid and the metal or the free acid is chemically adsorbed synergistically. It is believed that there is.

The metal oxide used in the present invention is
It is a metal oxide of elements of Groups 3, 4 and 4a, such as titanium, zirconium, aluminum, gallium, silicon and germanium.

In the present invention, the various metal oxides described above can be used, but they can be used alone, as a mixture or as a composite oxide, and among them, it is preferable to use the composite oxide. Thereby, the durability of the metal oxide can be increased. Examples of preferable metal composite oxides include silica-titania and silica-zirconia.

Further, it is preferable to modify such an oxide with a metal oxide of Group 1 or Group 2 because the ability of the oxide to remove free acid is increased. Sodium, potassium, cesium, magnesium, calcium and the like are preferable as the Group 1 and Group 2 elements for modification.

The shape of the metal oxide is not particularly limited,
The shape is preferably such that the specific surface area is increased in order to increase the rate of removing impurities in the (meth) acrylic acid ester, especially free acid. Regarding the particle size of the metal oxide, if it is too fine, it will be mixed with the purified (meth) acrylic acid ester, or pressure loss will occur when the metal oxide is passed through the (meth) acrylic acid ester for purification. In general, it is preferable that the particle size be about 1 to 64 mesh because the particle size becomes large.

In the present invention, the (meth) acrylic acid ester and the metal oxide are brought into contact with each other, but the means for bringing them into contact is not particularly limited, and a general method such as a fixed bed, a fluidized bed or a moving bed of the metal oxide is used. The bed may be contacted with (meth) acrylic acid ester, or may be contacted with a stirring tank. Above all, it is preferable to bring the metal oxide into contact with the (meth) acrylic acid ester as a fluidized bed, and in this case, the space velocity (hereinafter abbreviated as SV) is preferably 2 to 20 h ⁻¹ . The contact temperature is preferably 1
It is 5-40 degreeC.

Before contacting the (meth) acrylic acid ester with the metal oxide, the metal oxide is added in an amount of 150 to 150
It is preferable to dehydrate by performing a heat treatment at a temperature of 700 ° C. By dehydrating, the removal rate and removal rate of impurities can be improved.

The (meth) acrylic acid ester to which the present invention can be applied is not limited to the kind of the compound or the method used to produce it, and can be obtained by various production methods. Various (meth) acrylic acid esters used may be used.

[0023]

In the present invention, since the (meth) acrylic acid ester is brought into contact with the metal oxide, impurities contained in the (meth) acrylic acid ester, particularly free acid, can be treated by a simple operation without coloring the (meth) acrylic acid ester. Can be removed.

[0024]

The present invention will be described in more detail by the following examples.

In the examples, the amount of free acid contained in the (meth) acrylic acid ester is JIS 6716.
It measured based on 3.4. Also, the number of colors (APHA)
For, a standard curve prepared according to JIS 6716 3.2 was used to prepare a calibration curve at a wavelength of 370 nm, the absorbance of the test solution at this wavelength was measured, and the number of colors was determined from the calibration curve. The removal rate of free acid was calculated according to the equation (1).

Removal rate (%) = [(A−B) / A] × 100 (1) (where A is the concentration of free acid before purification, and B is the concentration of free acid after purification)

Example 1 20 ml of activated alumina (GB-13, manufactured by Mizusawa Chemical Co., Ltd.) calcined at 450 ° C. for 2 hours had a diameter of 10 mm.
A glass column having a length of 300 mm was packed with 100 ml of methyl methacrylate from which free acid had been previously removed. From the bottom of this column, methyl methacrylate containing APHA of 1 or less and containing free acid (as methacrylic acid) at a concentration of 40 ppm was poured at SV = 10 h ⁻¹ and a temperature of 25 ° C.

The free acid concentration in the methyl methacrylate after passing 500 ml was 11 ppm (removal rate 72.5%), and the free acid could be sufficiently removed. Moreover, APHA is 1
It was below and was not colored.

Example 2 20 ml of activated alumina (GB-13, manufactured by Mizusawa Chemical Co., Ltd.) which had been calcined at 450 ° C. for 2 hours had a diameter of 10 mm.
The glass column having a length of 300 mm was packed with 100 ml of 2-hydroxyethyl methacrylate from which the free acid had been previously removed. 2-Hydroxyethyl methacrylate containing APHA of 24 and 0.67% of free acid (as methacrylic acid) was poured from the bottom of this column at SV = 10 h ^{−1 at} a temperature of 25 ° C.

Methacrylic acid 2-after passing 500 ml
Hydroxyethyl concentration is 0.13% (removal rate 80.65
%), And APHA was 21, which was not colored.

Example 3 Activated titania 2 baked at 450 ° C. for 2 hours
0 ml was packed in a glass column having a diameter of 10 mm and a length of 300 mm in the same manner as in Example 1. From the bottom of this column, methyl methacrylate containing APHA of 1 or less and containing free acid (as methacrylic acid) at a concentration of 40 ppm was poured at SV = 10 h ⁻¹ and a temperature of 25 ° C.

The measurement result of methyl methacrylate after passing 500 ml of liquid was 9 ppm (removal rate 77.5%).
It was possible to remove the free acid sufficiently. Moreover, APHA was 1 or less, and it was not colored.

Example 4 20 ml of activated silica-titania calcined at 450 ° C. for 2 hours was packed in a glass column having a diameter of 10 mm and a length of 300 mm in the same manner as in Example 1. From the bottom of this column, methyl methacrylate containing APHA of 1 or less and containing free acid (as methacrylic acid) at a concentration of 40 ppm was poured at SV = 10 h ⁻¹ and a temperature of 25 ° C.

As a result of measurement of methyl methacrylate after passing 500 ml of liquid, 8 ppm (removal rate 80.0%)
It was possible to remove the free acid sufficiently. Moreover, APHA was 1 or less, and it was not colored.

Example 5 20 ml of activated magnesia-silica calcined at 450 ° C. for 2 hours was packed in a glass column having a diameter of 10 mm and a length of 300 mm in the same manner as in Example 1. From the bottom of this column, methyl methacrylate containing APHA of 1 or less and containing free acid (as methacrylic acid) at a concentration of 40 ppm was poured at SV = 10 h ⁻¹ and a temperature of 25 ° C.

As a result of measuring methyl methacrylate after passing 500 ml of liquid, 9 ppm (removal rate 77.5%)
It was possible to remove the free acid sufficiently. Moreover, APHA was 1 or less, and it was not colored.

EXAMPLE 6 The deactivated silica-titania used in Example 4 was removed with dry nitrogen to remove methyl methacrylate, then 45
It was regenerated by firing at 0 ° C. for 2 hours. 20 ml of this regenerated activated silica-titania is 10 mm in diameter and 300 m in length.
m glass column was packed as in Example 1. From the bottom of this column, methyl methacrylate containing APHA of 1 or less and containing free acid (as methacrylic acid) at a concentration of 40 ppm was poured at SV = 10 h ⁻¹ and a temperature of 25 ° C.

As a result of measurement of methyl methacrylate after passing 500 ml, 5 ppm (removal rate 75.0%)
It was possible to remove the free acid sufficiently. Moreover, APHA was 1 or less, and it was not colored.

Comparative Example 1 20 ml of 20-32 mesh activated carbon was used, and the diameter was 10 mm.
A glass column having a length of 300 mm was packed in the same manner as in Example 1. Methyl methacrylate containing APHA of 1 or less and containing free acid (as methacrylic acid) at a concentration of 40 ppm was poured from the bottom of this column at SV = 10 h ⁻¹ and a temperature of 25 ° C.

As a result of measurement of methyl methacrylate after passing 500 ml, 35 ppm (removal rate 12.5
%), And almost no free acid was removed.
The APHA was 1 or less.

Comparative Example 2 20 ml of a 20-32 mesh weakly basic anion exchange resin (Amberlyst A21, manufactured by Ardrich) was packed in a glass column having a diameter of 10 mm and a length of 300 mm in the same manner as in Example 1. From the bottom of this column,
Is less than 1 and 40 pp of free acid (as methacrylic acid)
SV = 10 h containing methyl methacrylate contained at a concentration of m
^-1 , at a temperature of 25 ° C.

After passing 500 ml of the solution, the concentration of free acid in methyl methacrylate was 9 ppm (removal rate 77.5%), and APHA was considerably colored with 16, so that the purification was insufficient.

[0043]

EFFECTS OF THE INVENTION According to the present invention, impurities (particularly free acid) contained in a (meth) acrylic acid ester can be sufficiently removed by a simple operation without coloring, and the (meth) acrylic acid ester can be produced at low cost. Can be purified.

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] April 2, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction content]

Before contacting the (meth) acrylic acid ester with the metal oxide, the metal oxide is added in an amount of 150 to 150
It is preferably allowed to dehydrated by heating at a temperature of 700 ° C.. By dehydrating, the removal rate and removal rate of impurities can be improved.

Claims (5)

[Claims] 1. A method for purifying a (meth) acrylic acid ester, which comprises contacting the (meth) acrylic acid ester with a metal oxide to remove impurities contained therein. 2. The method for purifying a (meth) acrylic acid ester according to claim 1, wherein the metal oxide is dehydrated before contacting the (meth) acrylic acid ester with the metal oxide. 3. The method for purifying a (meth) acrylic acid ester according to claim 1, wherein metal oxides of Group 3, 4 and 4a elements are used alone or as a mixture. 4. The method for purifying a (meth) acrylic acid ester according to claim 1, wherein a complex metal oxide of elements of groups 3, 4, and 4a is used as the metal oxide. 5. The (meth) acrylic acid according to claim 1, wherein a metal oxide of a group 3, group 4 or group 4a element is modified with a group 1 or group 2 metal oxide. Method for purifying ester.