JPH07196596A - Method for production highly pure 2-acrylamide-2 methylpropanesulfonic acid - Google Patents

Abstract

PURPOSE:To efficiently obtain the subject colorless compound capable of providing high mol.wt. polymers not or extremely slightly forming a water-soluble gel by reacting acrylonitrile, isobutylene and (fuming) sulfuric acid having an iron content of zero or a specific small amount with each other. CONSTITUTION:(A) Sulfuric acid or fuming sulfuric acid having an iron content of 0-20ppm and preferably a concentration of >=95% (preferably 98-102%), (B) acrylonitrile preferably having a water content of <=0.2wt.% (especially <=0.05wt.%), and (C) isobutylene are reacted with each other preferably at a temperature of -10 to 70 deg.C (especially 30-50 deg.C), and the reaction product is subsequently subjected to the separation of the excessive acrylonitrile therefrom by a filtration separation method, etc., to obtain the objective compound. The addition ratio of the component C is 0.8-1.2 moles (especially 0.8-1.0 mole) per mole of the component A. The separated acrylonitrile is preferably recovered and reutilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently producing 2-acrylamido-2-methylpropanesulfonic acid with high purity, which is useful as a monomer for acrylamide copolymers, an acrylic fiber dyeability improving agent and the like. It is a thing.

[0002]

2. Description of the Related Art Generally, 2-acrylamido-2-methylpropanesulfonic acid is obtained by reacting excess acrylonitrile, which also serves as a synthetic raw material and a reaction solvent, with a predetermined amount of sulfuric acid or fuming sulfuric acid, and isobutylene, and crystallizes from a reaction mixture. It is produced by separating 2-acrylamido-2-methylpropanesulfonic acid which is deposited in the form of a solid (Japanese Patent Publication No. 50-30059).

2-Acrylamido-2-methylpropanesulfonic acid itself is used for various purposes, and is made into a fiber as a homopolymer or a copolymer, or is useful as, for example, a dispersant for papermaking, an aggregating agent or the like. Although it is used as a polymer electrolyte for various purposes, it is required to have a high purity for the purpose of obtaining a water-soluble polymer having no coloration, a high molecular weight and a high solubility.

However, the inventors of the present invention described the above Japanese Patent Publication No. 50-
As a result of additional testing of the method described in Japanese Patent No. 30059, a sulfonated product of isobutylene or a sulfate ester produced as a by-product during the reaction is contained as an impurity in 2-acrylamido-2-methylpropanesulfonic acid, and is colored,
Alternatively, when the obtained crystals were copolymerized with acrylonitrile, acrylamide and the like, a gel having a low molecular weight or a water-insoluble gel was formed, and it could not be used satisfactorily.

As a method for removing impurities in crystals of crude 2-acrylamido-2-methylpropanesulfonic acid obtained by a synthetic reaction, Japanese Patent Publication No. 56-53306 discloses 2-acrylamido separated from a reaction mixture. A method has been proposed in which 2-methylpropanesulfonic acid crystals are recrystallized with hydrous acetic acid and purified. However, such recrystallization causes an increase in equipment costs, labor costs, and a decrease in the amount of products to be obtained, which is not economically preferable.

On the other hand, crude 2-acrylamido-2-
There has been proposed a method for producing high-purity 2-acrylamido-2-methylpropanesulfonic acid, which is characterized in that methylpropanesulfonic acid is washed with acrylonitrile having a water content of 1.0 wt% or more (JP-A-3-33264). According to this method, as compared with the above-mentioned recrystallization method, a sulfonated product of isobutylene or a sulfate ester produced as a by-product during the reaction can be more economically removed.

However, although the above-mentioned manufacturing method can remove the sulfonated product of isobutylene, sulfate ester, etc., which are by-products, it still has coloring or has a low molecular weight when formed into a polymer, and also has a low water content. An insoluble gel may form.

[0008]

DISCLOSURE OF THE INVENTION The present inventors have clarified the above points, that is, the reason why a gel which is colored or has a low molecular weight when formed into a polymer and is insoluble in water is formed. As a result of diligent study, it was found that the cause was iron contained as an impurity in 2-acrylamido-2-methylpropanesulfonic acid, and as a result of diligent research on a solution to the problem, the present invention was completed.

[0009]

According to the present invention, when acrylonitrile, sulfuric acid or fuming sulfuric acid and isobutylene are used to produce 2-acrylamido-2-methylpropanesulfonic acid, sulfuric acid having an iron content of 20 ppm or less is used. Or high purity characterized by using fuming sulfuric acid 2
-A method for producing acrylamido-2-methylpropanesulfonic acid.

The type of acrylonitrile is not particularly limited, and may be industrial products that are generally commercially available.
Use of acrylonitrile having a water content of 0.2% by weight or less, more preferably 0.05% by weight or less suppresses by-products such as sulfuric acid ester and enhances the yield of 2-acrylamido-2-methylpropanesulfonic acid. It is possible to do so, which is preferable.

The reaction of acrylonitrile with sulfuric acid or fuming sulfuric acid proceeds even with equimolar amounts, but the slurry concentration increases with the progress of the reaction, and stirring may become difficult. Therefore, acrylonitrile also functions as a reaction solvent. Desirably, in this case, it is preferable to use 4.0 mol or more of acrylonitrile with respect to 1 mol of sulfuric acid or fuming sulfuric acid.

The sulfuric acid or fuming sulfuric acid used in the present invention must have an iron content of 0 to 20 ppm, and it is desirable that the iron content be as low as possible. When the content exceeds 20 ppm, the iron content in the obtained 2-acrylamido-2-methylpropanesulfonic acid becomes about 10 ppm or more, which causes a coloring problem, and when polymerized with acrylonitrile, acrylamide, etc., the molecular weight becomes low, or An insoluble gel is formed.

Generally, sulfuric acid has an iron content of 3 according to the JIS standard.
It is sold at less than 00 ppm, and as a particularly purified sulfuric acid, there is purified sulfuric acid having less than 1 ppm of iron. In addition, the manufacturing method of fuming sulfuric acid is generally manufactured by absorbing sulfur trioxide with sulfuric acid, but in that case, the amount of iron in fuming sulfuric acid is basically the same as the amount of iron in absorbing sulfuric acid. Dependent.

The inventors of the present invention are responsible for the coloring of 2-acrylamido-2-methylpropanesulfonic acid, the reduction of the molecular weight when formed into a polymer, and the formation of a water-insoluble gel in the compound. Not only is it due to iron as an impurity, but its content has a correlation with the content of iron in sulfuric acid or fuming sulfuric acid, which is one of the raw materials, and the content of iron in other raw materials is controlled. The present invention has been completed by finding an unexpected fact that it does not become a physical factor.

More specifically, based on 1 mol of isobutylene, B mol of sulfuric acid or fuming sulfuric acid containing iron Ag is used to react excess acrylonitol as a raw material and a reaction solvent, and the resulting reaction slurry is separated. When 2-acrylamido-2-methylpropanesulfonic acid obtained by drying is C mol, iron in 2-acrylamido-2-methylpropanesulfonic acid is roughly (A × C) / (B ×
It is represented by C × 207.2) = A / (B × 207.2). Therefore, by controlling the iron content in sulfuric acid or fuming sulfuric acid, the iron content of the obtained 2-acrylamido-2-methylpropanesulfonic acid can be controlled, and various problems as described above can be solved at once. It became clear that they could do it.

The concentration of the sulfuric acid or fuming sulfuric acid is preferably 95% or more, more preferably 98 to 102%, in terms of sulfuric acid concentration. When the sulfuric acid concentration is less than 95%, the yield of 2-acrylamido-2-methylpropanesulfonic acid is reduced due to by-products such as sulfuric acid ester, and when the sulfuric acid concentration is higher than 102%, the sulfonated product of isobutylene is by-produced. However, the 2-acrylamido-2-methylpropanesulfonic acid crystal may be colored.

The preferred addition ratio of isobutylene is 0.8 to 1.2 mol per mol of sulfuric acid, and more preferably 0.1.
It is 8 to 1.0 mol. If the addition ratio of isobutylene is less than 0.8 mol per mol of sulfuric acid, 2-acrylamido-2-methylpropanesulfonic acid crystals may be colored, and if it exceeds 1.2 mol, by-products such as tert-butylacrylamide may be generated. May generate.

Reaction conditions of acrylonitrile, sulfuric acid or fuming sulfuric acid and isobutylene are not particularly limited. A one-step continuous reaction in which the components are mixed and reacted at one time is mentioned, and a preferable reaction temperature is -10.
C to 70 ° C, more preferably 30 to 50 ° C. When the reaction temperature is higher than 70 ° C., the amount of the by-product of isobutylene sulfonate increases, and the product tends to be colored. On the contrary, when the reaction temperature is lower than −10 ° C., a sulfate ester is by-produced, so that the yield is high. It tends to decrease.

From the reaction slurry containing crystalline 2-acrylamido-2-methylpropanesulfonic acid obtained by the reaction, excess acrylonitrile is separated by usual filtration separation or centrifugation, and crystals are formed if necessary. It is possible to obtain 2-acrylamido-2-methylpropanesulfonic acid as powdery high-purity crystals by washing with acrylonitrile or hydrous acrylonitrile and then drying under normal pressure or reduced pressure by a conventional method.

The filtrate from which the crystals have been separated contains acrylonitrile as a main component, and contains unreacted sulfuric acid and by-products at the time of reaction. Although this filtrate can be directly processed as waste liquid,
It is not economical and it is desirable to recover and reuse acrylonitrile. The acrylonitrile can be recovered by a conventional method. For example, the acid component in the filtrate is appropriately neutralized and reused as it is, or in order to prevent the polymerization of acrylonitrile, it is purified by distillation while adding a polymerization inhibitor and reused.

[0021]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples. The unit shown in the examples is% by weight, and
The iron content, APHA, the viscosity of the copolymer and the insoluble matter were measured by the following methods, and the polymerization method is as follows.

Iron content was measured by the atomic absorption method. -APHA It measured with the 25% aqueous solution of 2-acrylamido-2-methylpropanesulfonic acid according to the usual APHA measuring method (JIS-K-1557). The larger the value, the more intense the index. -Viscosity of copolymer: An aqueous solution of the powder of the copolymer obtained by the following polymerization method,
The viscosity was measured under the following conditions. (Conditions) Viscometer: B-type viscometer Rotor rotation speed: 6 rpm Concentration of aqueous solution: 0.1% aqueous solution Temperature of aqueous solution: 25 ° C ・ Amount of insoluble matter 0.3 g of copolymer powder obtained by the following polymerization method Water 30
It was dissolved in 0 ml, and when this was filtered through a mesh of 80 mesh, the volume remaining in the mesh was measured to determine the amount of insoluble matter. -Polymerization method 2-acrylamido-2-methylpropanesulfonic acid crystal 40g is melt | dissolved in water 60g, 16% NaOH aqueous solution is added, and after adjusting to pH 8, 123 g of acrylamide is mixed, and also water is added and monomer concentration is 20%. Adjusted to. After replacing this aqueous solution with nitrogen, potassium persulfate 200 p
pm and 200 ppm of sodium sulfite were added, and polymerization was started at 20 ° C. After 10 hours, the copolymer was taken out, vacuum dried at 100 ° C. for 4 hours, and then pulverized.

(Examples 1 to 4 and Comparative Examples 1 and 2) Two glass reactors equipped with a stirrer and an inlet pipe and an outlet pipe were connected, and acrylonitrile and fuming sulfuric acid were added to the first reactor under the following conditions. After the introduction, a step of mixing acrylonitrile and sulfuric acid was performed, the mixture in the first reactor was introduced into the second reactor, and isobutylene gas was introduced into the second reactor to continuously carry out the reaction.

As shown in Table 1, fuming sulfuric acid containing various irons was used, and 10 mol of acrylonitrile was added to 1 mol of the fuming sulfuric acid.
Mol and isobutylene were supplied at a ratio of 0.9 mol. The concentration of fuming sulfuric acid is 9% (10% when converted to sulfuric acid concentration).
2%). The first reactor was maintained at -5 ° C to -15 ° C, the residence time was 10 minutes, and the second reactor was 30 ° C to -15 ° C.
The temperature was maintained at 50 ° C and the residence time was 40 minutes.

The obtained reaction product is suction-filtered from the second reactor to obtain 2-acrylamido-2-methylpropanesulfonic acid to which the reaction solution is attached, washed with an equal amount of acrylonitrile as the crystals, and then dried under reduced pressure. 2-acrylamide-
2-Methylpropanesulfonic acid was obtained.

Further, each of the above-obtained 2-acrylamido-
The polymer was prepared as above using 2-methylpropanesulfonic acid.

Yield of 2-acrylamido-2-methylpropanesulfonic acid, iron content in fuming sulfuric acid and 2-acrylamido-2-methylpropanesulfonic acid crystals, APHA, copolymer in each of Examples and Comparative Examples. The viscosity of the aqueous solution and the insoluble matter are as shown in Tables 1 and 2.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

EFFECTS OF THE INVENTION According to the present invention, it is possible to obtain high-purity 2 which is not colored.
-Acrylamido-2-methylpropanesulfonic acid can be easily and efficiently produced, and when this 2-acrylamido-2-methylpropanesulfonic acid is used, a gel having a high molecular weight and insoluble in water is produced. It is possible to produce polymers which do not form or produce only small amounts.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Teruo Yoshida 1-1 Funami-cho, Minato-ku, Nagoya, Aichi Toagosei Chemical Industry Co., Ltd. Nagoya Research Institute

Claims (1)

[Claims] 1. Acrylonitrile, sulfuric acid or oleum, and isobutylene are used for 2-acrylamido-
High-purity 2-acrylamido-2-, characterized in that sulfuric acid or fuming sulfuric acid having an iron content of 0 to 20 ppm is used in the production of 2-methylpropanesulfonic acid.
Method for producing methylpropanesulfonic acid.