JPH09316022A - Prevention of polymerization of (meth)acrylic acid and its ester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preventing the polymerization of the subject compound, capable of exhibiting extremely excellent polymerization preventing effects by addition of a small amount of a polymerization inhibitor even in a high-temperature state in distillation, by using a specific polymerization inhibitor and hydroquinone. SOLUTION: (A) At least one of benzoquinone, 1,2-naphtoquinone and its derivative and (B) hydroquinone are used. The amounts of the components A and B are 1-5,000ppm based on the objective compound, respectively and the ratio of the components A to B is preferably (1:100) to (100:1). For example, potassium 1,2-naphtoquinone-4sulfonate is preferably used as the component B.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for preventing polymerization of (meth) acrylic acid and its ester. More specifically, the present invention relates to a method for preventing polymerization in a system containing (meth) acrylic acid and its ester, in which at least one of benzoquinone, 1,2-naphthoquinone and its derivative is used in combination with hydroquinone as a polymerization inhibitor. .

[0002]

2. Description of the Related Art (Meth) acrylic acid and its esters have the property of easily and extremely violently polymerizing due to heat, light, peroxides, etc., and therefore, when they are purified by a distillation column. Not only does the capacity of the distillation column decrease due to the generation of a large amount of polymer, and the heat transfer performance decreases due to the adhesion of the polymer to the heat transfer surface of the distillation column reboiler, but also clogging by the polymer in the distillation column occurs. Known to cause. These phenomena are extremely serious obstacles in the process of producing (meth) acrylic acid and its ester, and how to control the polymerization is important for industrial production.

Conventionally, addition of a polymerization inhibitor has been proposed and practiced for a long time as one of methods for preventing polymerization of (meth) acrylic acid and its ester. Representative polymerization inhibitors include hydroquinone, phenols such as hydroquinone monomethyl ether, phenothiazine,
Known are amines such as diphenylamine, copper salts such as copper dibutyldithiocarbamate, manganese salts such as manganese acetate, nitro compounds and nitroso compounds. Various proposals have been made on the method in which these polymerization inhibitors are used alone or in combination with the molecular oxygen-containing gas and these polymerization inhibitors.

[0004]

However, the polymerization inhibitor proposed in this way has a small effect of inhibiting polymerization at high temperatures such as in the distillation step of the (meth) acrylic acid production process, so that a large amount should be added. Must be satisfied in industrial practice.

[0005]

Means for Solving the Problems The present inventors have proposed (meth)
As a result of diligent studies on a method for preventing polymerization of acrylic acid and its ester, when hydroquinone, which is known as a polymerization inhibitor of acrylic acid, and a specific polymerization inhibitor are used in combination, they cannot be obtained alone. It has been found that a remarkable polymerization inhibiting effect can be exhibited as a synergistic effect, and the present invention has been completed. That is, the present invention provides a method for preventing polymerization of (meth) acrylic acid and its ester, which comprises using at least one of benzoquinone, 1,2-naphthoquinone and its derivative and hydroquinone as a polymerization inhibitor.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The method of the present invention will be described in detail below. The method of the invention can be applied to (meth) acrylic acid and its esters. As acrylic acid ester,
Methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, etc. As the methacrylic acid ester, methyl methacrylate, ethyl methacrylate, methacrylic acid Butyl, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate and the like can be mentioned.

In the method of the present invention, the method for preventing the polymerization of (meth) acrylic acid and its ester is as follows: Hydroquinone, benzoquinone, 1,2-naphthoquinone and its derivative (hereinafter referred to as 1,2-naphthoquinones) as a polymerization inhibitor. In some cases), it is essential to use at least one of them together. Hydroquinone as a polymerization inhibitor,
About 1 to (meth) acrylic acid and its ester
About 5000 ppm, preferably about 10 to about 500 pp
m is added. Benzoquinone or 1,2-naphthoquinones are added in an amount of about 1 to about 5000 ppm, preferably about 10 to about 500 ppm, based on (meth) acrylic acid and its ester. At this time, both are used together, but the ratio (weight ratio) is about 1: about 100 to about 1.
00: about 1, preferably about 1: about 10 to about 10: about 1. If the amount of the polymerization inhibitor added is less than this range, the polymerization inhibitory effect is not sufficient, and if it exceeds this range, a sufficient polymerization inhibitory effect is obtained, but it is not economical.

Derivatives of 1,2-naphthoquinone include potassium 1,2-naphthoquinone-4-sulfonate, 1,
Examples thereof include sodium 2-naphthoquinone-4-sulfonate, bromo-1,2-naphthoquinone, and chloro-1,2-naphthoquinone.

In the present invention, the method of adding the polymerization inhibitor is not particularly limited. For example, in the case of producing acrylic acid, each polymerization inhibitor may be solid or powder. It may be added directly to acrylic acid as it is, or may be added by dissolving each or both in an appropriate organic solvent. These can be added, for example, immediately after the production of acrylic acid, but it is preferable to add them immediately before carrying out the distillation. Industrially, the acrylic acid is fed to the distillation apparatus in the stock solution or by distillation. It can also be supplied by dissolving it in a liquid refluxed. Generally, the distillation of acrylic acid or a system containing acrylic acid is carried out under the conditions of about 50 to about 150 ° C. and about 100 to about 500 mmHg, but according to the method of the present invention, the treatment at such a high temperature is sufficient. Moreover, polymerization can be prevented, and long-term continuous operation becomes possible.

In the method of the present invention, by using at least one of benzoquinone, 1,2-naphthoquinone and its derivative in combination with hydroquinone as a polymerization inhibitor, an excellent polymerization inhibiting effect can be obtained. It is also possible to further add / combine the polymerization inhibitor. Such known polymerization inhibitors include phenols such as hydroquinone monomethyl ether, phenothiazine, amines such as diphenylamine, copper salts such as copper dibutyldithiocarbamate, manganese salts such as manganese acetate, nitro compounds,
A nitroso compound etc. are mentioned. These can be used in the same manner as the polymerization inhibitor applied in the above-mentioned method of the present invention.

Further, in the method of the present invention, molecular oxygen can be used if necessary. Molecular oxygen may be mixed with acrylic acid by air bubbling or the like, and industrially, a rectification column for acrylic acid, a separation column for acrylic acid and a solvent, a stripper for light boiling components such as acrolein and methacrolein, etc. It can be carried out at the place where the distillation operation is performed.

[0012]

According to the method of the present invention described in detail above, it is possible to effectively prevent the polymerization of (meth) acrylic acid and its ester with a small amount of a polymerization inhibitor, especially in a high temperature state during distillation. Also, compared with the case where a polymerization inhibitor is used individually, it exhibits an extremely excellent polymerization inhibiting effect of (meth) acrylic acid and its ester, and its industrial utility value is extremely large.

[0013]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 100 pp of hydroquinone was added to a 50% acrylic acid aqueous solution.
m was added, and 5 g of a solution to which the polymerization inhibitor shown in Table 1 was added was placed in a test tube with a lid having an internal volume of 20 ml, and after bubbling with nitrogen containing 100 ppm of oxygen in a nitrogen box for 5 minutes, the test tube Was sealed under the atmosphere. Then, the test tube was immersed in an oil bath at 100 ° C. for 30 minutes, taken out, and cooled. The cooled solution was diluted with water and reacted with a quaternary ammonium salt, and the amount of polyacrylic acid in the solution was determined from the degree of turbidity.

[0015]

[Table 1] (PA in the table indicates polyacrylic acid)

As is apparent from Table 1, the method of the present invention in which hydroquinone and benzoquinone, or hydroquinone and 1,2-naphthoquinone and its derivatives are used in combination as a polymerization inhibitor is a combination of hydroquinone alone or hydroquinone and a polymerization inhibitor other than the method of the present invention. It can be seen that the effect of preventing polymerization is superior to that of the combined use.

Claims (4)

[Claims] 1. Benzoquinone, 1,2 as a polymerization inhibitor
A method for preventing polymerization of (meth) acrylic acid and its ester, which comprises using at least one of naphthoquinone and its derivative and hydroquinone. 2. The (meth) acrylic acid according to claim 1, wherein the amount of benzoquinone, 1,2-naphthoquinone and its derivative used is 1 to 5000 ppm based on (meth) acrylic acid and its ester. And a method for preventing the polymerization of the ester thereof. 3. The amount of hydroquinone used is 1 to 5000 ppm based on (meth) acrylic acid and its ester.
The method for preventing polymerization of (meth) acrylic acid and its ester according to claim 1, wherein 4. The (meth) acrylic acid according to claim 1, wherein the use ratio of at least one of benzoquinone, 1,2-naphthoquinone and its derivative and hydroquinone is 1: 100 to 100: 1. And a method for preventing the polymerization of the ester thereof.