JPH0952861A - Inhibition of (meth)acrylic acid polymerization - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit polymerization of (meth)acrylic acid which polymerizes easily and violently by heat, a light, a peroxide, etc. at a high temperature. SOLUTION: The polymerization of (meth)acrylic acid is inhibited by using preferably 10-5000ppm N-nitrosodiphenylamine together with preferably 50-1000ppm one compound selected from or a mixture of phenothiazine, hydroquinone and hydroquinone monomethyl ether as a polymerization inhibitor. It is preferable to use N-nitrosodiphenylamine and the other polymerization inhibitors in the ratio of (1:10)-(1:1). The polymerization inhibitor can be added directly in solid or powdery form or in the form of a solution of a solvent.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for inhibiting polymerization of (meth) acrylic acid (where (meth) acrylic acid means acrylic acid or methacrylic acid).

[0002]

2. Description of the Related Art (Meth) acrylic acid has the property of easily and extremely violently polymerizing due to heat, light, peroxides, etc., so that a large amount of (meth) acrylic acid is required when purifying them in a distillation column. The capacity of the distillation column is reduced due to the generation of polymer,
It is known that not only the heat transfer performance is deteriorated due to the adhesion of the polymer on the heat transfer surface of the distillation column reboiler, but also the blockage by the polymer occurs in the distillation column. These phenomena are extremely serious obstacles in the process of producing (meth) acrylic acid, and how to suppress the polymerization is industrially important.

Conventionally, as one of the methods for preventing the polymerization of (meth) acrylic acid, the addition of a polymerization inhibitor has been proposed and implemented for a long time. As a typical polymerization inhibitor,
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 are known. 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.

N as a polymerization inhibitor of (meth) acrylic acid
Examples of the use of a nitroso compound include JP-A-52
-5709 discloses N-nitrosodiphenylamine,
JP-B-39-220, JP-A-64-42443, JP-A-3-503896, JP-A-7-11
No. 8307 discloses N-nitrosophenylhydroxylamine.

[0005]

However, such a polymerization inhibitor has a small effect in a high temperature state such as a distillation step of a (meth) acrylic acid production process, and therefore, it has to be added in a large amount. Is not always satisfactory. In particular, when a nonpolar solvent such as toluene or xylene is contained, it is considered that the solubility of polyacrylic acid is lowered, but the adhesion of the polymer becomes a more serious problem.

[0006]

Means for Solving the Problems The present inventors have proposed (meth)
As a result of intensive studies on a method for preventing polymerization of acrylic acid, by using N-nitrosodiphenylamine as a polymerization inhibitor together with at least one compound selected from the group consisting of phenothiazine, hydroquinone and hydroquinone monomethyl ether, The present invention has been completed by finding that the effect of preventing polymerization increases synergistically.

That is, the present invention is as follows. (1) In a method for preventing the polymerization of (meth) acrylic acid by adding a polymerization inhibitor to (meth) acrylic acid, N-nitrosodiphenylamine as a polymerization inhibitor,
Characterized by the combined use of at least one compound selected from the group consisting of phenothiazine, hydroquinone and hydroquinone monomethyl ether (meth)
Acrylic acid polymerization prevention method. (2) The method for preventing polymerization according to the item (1), which prevents polymerization of a (meth) acrylic acid distillation column or an azeotropic dehydration distillation column. (3) The method for preventing polymerization according to the above item (1), wherein the amount of N-nitrosodiphenylamine is 1 to 5000 ppm relative to (meth) acrylic acid. (4) The method for preventing polymerization according to the above item (1), wherein the amount of at least one compound selected from the group consisting of phenothiazine, hydroquinone and hydroquinone monomethyl ether is 1 to 5000 ppm based on (meth) acrylic acid.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. N-nitrosodiphenylamine is 1 to 5000 ppm, preferably 10 ppm, based on (meth) acrylic acid.
~ 500 ppm is added.

For phenothiazine, hydroquinone and hydroquinone monomethyl ether, one of
Only the seeds may be added, or they may be used in combination. The amount used is 1 to 5 with respect to (meth) acrylic acid.
000 ppm, preferably 50 to 1000 ppm.

The ratio of N-nitrosodiphenylamine to the other polymerization inhibitor is selected from the range of 1: 100 to 10: 1, preferably 1:10 to 1: 1. At this time, if the addition amount of the polymerization inhibitor is less than this range, the polymerization inhibiting effect is not sufficient, and if it is more than this range, a sufficient polymerization inhibiting effect is obtained but it is not economical.

The method of adding the polymerization inhibitor is not particularly limited, but for example, the solid or powder of the polymerization inhibitor may be added directly, or may be added as a solution in an appropriate solvent. In the method of the present invention, a polymerization inhibitor other than N-nitrosodiphenylamine, phenothiazine, hydroquinone and hydroquinone monomethyl ether may be included.

Generally, distillation of (meth) acrylic acid or a solution containing (meth) acrylic acid is carried out at 50 to 150 ° C.
Although it is carried out under the condition of 10 to 500 mmHg, according to the present invention, the polymerization of (meth) acrylic acid can be sufficiently prevented even in such a high temperature distillation column, and a long-term continuous operation becomes possible. . Furthermore, when a non-polar solvent such as toluene or xylene is contained, the adhesion of the polymer becomes a more serious problem. However, the method of the present invention is sufficient even in such a distillation column to produce (meth) acrylic acid. Polymerization can be prevented, and long-term continuous operation becomes possible.

[0013]

The method of the present invention can effectively prevent the polymerization of (meth) acrylic acid with a small amount. In particular, even in a high temperature state at the time of distillation, even in the state of containing a non-polar solvent such as toluene and xylene, it is possible to effectively prevent the polymerization of (meth) acrylic acid, and the method of the present invention is very useful. It is a method of preventing polymerization of (meth) acrylic acid.

[0014]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited to these examples. In the table, NNDA is N-nitrosodiphenylamine, PTZ is phenothiazine, MQ is hydroquinone monomethyl ether, and HQ is hydroquinone.

Example 1 A solution prepared by adding a predetermined amount of various polymerization inhibitors shown in Table 1 to purified acrylic acid was placed in a test tube with a lid having an internal volume of 20 ml.
Into a nitrogen box, nitrogen containing 100 ppm of oxygen was bubbled for 5 minutes, and the test tube was sealed under the atmosphere. This was immersed in an oil bath at 80 ° C., and when the solution became slightly cloudy, it was taken out and cooled. The heating at 80 ° C. was carried out for up to 1 hour, and those which were not cloudy at that time were taken out and cooled. This solution was diluted with water, reacted with a quaternary ammonium salt, and polyacrylic acid was quantified from the degree of turbidity. The results are shown in Table 1.

[0016]

[Table 1] #: Polyacrylic acid could not be quantified due to excessive progress of polymerization.

Example 2 A solution prepared by adding 50% of toluene to acrylic acid and then adding a predetermined amount of each type of polymerization inhibitor shown in Table 2 was prepared.
Put 5 g in a test tube with a lid of 10 ml and put it in a nitrogen box for 10
Bubble nitrogen for 5 minutes with 0 ppm oxygen,
The test tube was sealed under the atmosphere. This was immersed in an oil bath at 60 ° C., and when the solution became slightly cloudy, it was taken out and cooled. The heating at 60 ° C. was carried out for up to 2 hours, and those which were not cloudy at that time were taken out as they were and cooled. This solution was diluted with water, reacted with a quaternary ammonium salt, and polyacrylic acid was quantified from the degree of turbidity. Table 2 shows the results.

[0018]

[Table 2]

Example 3 A solution prepared by adding 50% of toluene to acrylic acid and further adding a predetermined amount of each type of polymerization inhibitor shown in Table 3 had an internal volume of 20.
Put 5 g in a test tube with a lid of 10 ml and put it in a nitrogen box for 10
Bubble nitrogen for 5 minutes with 0 ppm oxygen,
The test tube was sealed under the atmosphere. This was immersed in an oil bath at 90 ° C., and when the solution became slightly cloudy, it was taken out and cooled. The heating at 90 ° C. was carried out for up to 2 hours, and those which were not cloudy at that time were taken out and cooled. This solution was diluted with water, reacted with a quaternary ammonium salt, and polyacrylic acid was quantified from the degree of turbidity. The results are shown in Table 3.

[0020]

[Table 3]

Example 4 5 g of a solution prepared by adding a predetermined amount of each of the various polymerization inhibitors shown in Table 4 to purified methacrylic acid was placed in a test tube with a lid having an internal volume of 20 ml and charged with nitrogen containing 100 ppm of oxygen in a nitrogen box. After bubbling for 5 minutes, the test tube was sealed under the atmosphere. This was immersed in an oil bath at 80 ° C., and when the solution became slightly cloudy, it was taken out and cooled. The heating at 80 ° C. was carried out for up to 1 hour, and those which were not cloudy at that time were taken out as they were and cooled. This solution was diluted with water, reacted with a quaternary ammonium salt, and polyacrylic acid was quantified from the degree of turbidity. The results are shown in Table 4.

[0022]

[Table 4]

Comparative Example 1 A solution containing 20% of toluene added to acrylic acid and 50 ppm of various polymerization inhibitors shown in Table 5 was placed in a test tube with a lid having an inner volume of 20 ml, 5 g, and 100 ppm of which was added in a nitrogen box. After bubbling with nitrogen containing oxygen for 5 minutes, the test tube was sealed under the atmosphere. This is 100
The solution was soaked in an oil bath at ℃, and when the solution became slightly cloudy, it was taken out and cooled. The heating at 100 ° C. was carried out for up to 1 hour, and those which were not cloudy at that time were taken out and cooled. This solution was diluted with water, reacted with a quaternary ammonium salt, and polyacrylic acid was quantified from the degree of turbidity. Table 5 shows the results.

[0024]

[Table 5]

Example 5 A distillation column having a 300 ml flask equipped with a packed portion of 30 mmφ × 300 mmH was used. Hydroquinone monomethyl ether 70 pp was added as a polymerization inhibitor from the top of the distillation column.
m, containing 200 ppm of phenothiazine, toluene 20
% Acrylic acid solution was fed at a rate of 400 g / H. In addition, 6 ml / min of air in the can liquid, and N-
An acrylic acid solution containing 1000 ppm of nitrosodiphenylamine was continuously fed at 20 g / H, and continuously distilled from the top of the distillation column. On the other hand, the can liquid was continuously withdrawn at a rate of 100 g / H to keep the liquid surface constant. The operating conditions were a pressure of 200 torr and a bath temperature of 140 to 150 ° C. The operation was stopped after 7 hours, and the amount of polymer in the filling part and the can solution was measured. As a result, in the filled portion, the polymer content was 0.
02 g and 0.08 g of polymer in the can portion.

Comparative Example 2 1000 ppm of N-nitrosodiphenylamine in a can solution
Continuous distillation was carried out for 7 hours in the same manner as in Example 5 except that the supply of the acrylic acid solution containing was stopped. As a result, there was 0.68 g of polymer in the filled portion and 1.0 g of polymer in the can portion.

Claims (4)

[Claims] 1. A method for preventing polymerization of (meth) acrylic acid by adding a polymerization inhibitor to (meth) acrylic acid, comprising phenothiazine, hydroquinone and hydroquinone monomethyl ether together with N-nitrosodiphenylamine as a polymerization inhibitor. A method for preventing polymerization of (meth) acrylic acid, which comprises using at least one compound selected from the group. 2. The method for preventing polymerization according to claim 1, which prevents polymerization of (meth) acrylic acid in the distillation column. 3. The amount of N-nitrosodiphenylamine is
The method for preventing polymerization according to claim 1, wherein the amount is 1 to 5000 ppm with respect to (meth) acrylic acid. 4. The method for preventing polymerization according to claim 1, wherein the amount of at least one compound selected from the group consisting of phenothiazine, hydroquinone and hydroquinone monomethyl ether is 1 to 5000 ppm based on (meth) acrylic acid.