JPH1087553A - Stabilization of (meth)acrylic acid and its ester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable (meth)acrylic acid, etc., to be prevented from polymerization and manifest deterring effects from the polymerization even at the time of long-term storage, by adding an iron chloride, etc., to the (meth)acrylic acid, etc. SOLUTION: Iron(II) chloride or copper(II) chloride or both in an amount of preferably 1-5,000ppm, more preferably 10-500ppm are added to (meth)acrylic acid and its ester to thereby stabilize the (meth)acrylic acid and its ester. Molecular oxygen, as necessary, can be used and may be mixed in the acrylic acid by air bubbling, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for stabilizing (meth) acrylic acid and esters thereof. More specifically, the present invention relates to a method for stabilizing (meth) acrylic acid and its ester, characterized by adding iron (II) chloride and / or copper (II) chloride to (meth) acrylic acid and its ester.

[0002]

2. Description of the Related Art A method for producing (meth) acrylic acid and its ester by gas-phase catalytic oxidation is well known as an industrial production method. However, (meth) acrylic acid and its ester formed by an oxidation reaction are It is usually done to be absorbed and recovered in water. On the other hand, (meth) acrylic acid and its esters have the property of easily and extremely intensely polymerizing due to heat, light, peroxide, etc. Therefore, how to stabilize and store them is one of the major issues. It is.

Heretofore, as one method of stabilizing acrylic acid, addition of a polymerization inhibitor has been proposed and implemented for a long time. Representative polymerization inhibitors include phenols such as hydroquinone and hydroquinone monomethyl ether, amines such as phenothiazine and diphenylamine, copper salts such as copper dibutyldithiocarbamate, manganese salts such as manganese acetate, nitro compounds, and nitroso compounds. ing. Then, a method of using these polymerization inhibitors in a single form, or using a combination of a molecular oxygen-containing gas and these polymerization inhibitors has been proposed. However, a water-soluble compound such as hydroquinone or manganese acetate is often used as a stabilizer for the aqueous solution of acrylic acid.

[0004]

However, the polymerization inhibitor thus proposed is not suitable for use when the (meth) acrylic acid aqueous solution is exposed to a high temperature such as a distillation operation or when it is stored for a long period of time. The effect is not enough and not satisfactory in industrial practice. Under these circumstances, the present inventors have conducted intensive studies for the purpose of finding a method for imparting excellent stability to (meth) acrylic acid and its esters even at high temperatures and even under long-term storage. , Iron (II) chloride and copper chloride (I
It has been found that I) exhibits excellent stability, and the present invention has been completed.

[0005]

That is, the present invention is characterized in that iron (II) chloride and / or copper (II) chloride is added to (meth) acrylic acid and an ester thereof. An object of the present invention is to provide a method for stabilizing the ester.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of the present invention will be described below in detail. The method of the invention can be applied to (meth) acrylic acid and its esters. The (meth) acrylic acid is acrylic acid or methacrylic acid, and the acrylate is methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, 2-methyl acrylate.
Examples of hydroxyethyl, 2-hydroxypropyl acrylate, and the like, and examples of methacrylates include methyl methacrylate, butyl methacrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate.

As a method for stabilizing (meth) acrylic acid and its ester in the method of the present invention, it is essential to add iron (II) chloride and / or copper (II) chloride to these solutions. These addition amounts are about 1 to 5000 pp with respect to (meth) acrylic acid and its ester.
m, preferably 10 to 500 ppm. If the amount of the stabilizer is less than the above range, the polymerization inhibitory effect is not sufficient, and if it exceeds this range, the polymerization inhibitory effect is obtained but is not economical.

The method of adding the stabilizer is not particularly limited as long as it is generally carried out by a known method. In the case of acrylic acid, for example, the method of adding the stabilizer to acrylic acid as it is or dissolving it in an appropriate organic solvent is used. May be added. These can be added immediately after the production of acrylic acid, or may be added immediately before distillation, and are industrially refluxed to the distillation can solution side in the acrylic acid feed material supplied to the distillation apparatus or by distillation. It can also be supplied after being dissolved in a liquid to be prepared. Generally, 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. Polymerization can be sufficiently prevented, and long-term storage can be achieved by adding a stabilizer during storage and transportation of the acrylic acid aqueous solution when acrylic acid is absorbed into water.

In the method of the present invention, iron (II) chloride and / or copper (II) chloride is used as a stabilizer, but other known stabilizers can be further added or used in combination. is there. Such known stabilizers include hydroquinone, phenols such as hydroquinone monomethyl ether, phenothiazine, amines such as diphenylamine,
Examples thereof include copper salts such as copper dibutyldithiocarbamate, manganese salts such as manganese acetate, nitro compounds and nitroso compounds. These can be used in the same manner as the stabilizer applied in the above-mentioned method of the present invention, and in the same range of addition.

[0010] In the method of the present invention, molecular oxygen can be used if necessary. Molecular oxygen may be mixed into acrylic acid by air bubbling, etc., and industrially, acrylic acid distillation tower, acrylic acid and solvent separation tower, acrolein and methacrolein tower, light boiling stripper tower It can be carried out at the place where the distillation operation is performed.

[0011]

According to the method of the present invention described in detail above, the polymerization of (meth) acrylic acid and its ester can be effectively performed only by using inexpensive iron (II) chloride or copper (II) chloride as a stabilizer. It has an effect of preventing polymerization and has an effect of inhibiting polymerization even during long-term storage, and its industrial utility value is extremely large.

[0012]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Example 1 Hydroquinone (100 ppm) was added to a solution obtained by distilling an aqueous solution of acrylic acid produced by gas phase catalytic oxidation under reduced pressure. To this solution was further added 10 ppm of the stabilizers shown in Table 1.
The mixture was added, and 5 g was placed in a test tube with a lid having a capacity of 20 ml and sealed. This was immersed in an oil bath at 80 ° C., heated for 3 hours, taken out and cooled. Dilute this solution with water,
It was reacted with a quaternary ammonium salt, and polyacrylic acid was quantified from the degree of turbidity. Table 1 shows the results. In Table 1, those with a symbol in the column of the stabilizer name are examples in which no stabilizer other than hydroquinone was added.

[0014]

[Table 1] * 1: The measurement could not be performed because the polyacrylic acid concentration was too high.

Claims (2)

[Claims] 1. A method for stabilizing (meth) acrylic acid and its ester, characterized by adding iron (II) chloride and / or copper (II) chloride to (meth) acrylic acid and its ester. 2. The (meth) acrylic according to claim 1, wherein the addition amount of iron (II) chloride and / or copper (II) chloride to (meth) acrylic acid and its ester is 1 to 5000 ppm. Methods for stabilizing acids and their esters.