JPH05163235A - Production of high-purity 2-acrylamide-2-methylpropanesulfonic acid - Google Patents

Abstract

PURPOSE:To efficiently obtain the high-purity subject compound by washing crude 2-acrylamide-2-methylpropanesulfonic acid with water-containing acrylonitrile having high water content. CONSTITUTION:Excess acrylonitrile which is used as both of a raw material and a reaction solvent is made to react with a prescribed amount of sulfuric acid or fuming sulfuric acid and isobutylene to provide crude acrylamide-2- methylpropanesulfonic acid separated and deposited in a crystalline state from the reaction mixture. The crude crystal is, preferably right after being separated and obtained, washed with acrylonitrile having >=1.0wt.%, preferably >=2.0wt.% acrylonitrile and dried at 30-140 deg.C according to ordinary method to provide the objective compound as a powdery high-purity crystal. An amount of acrylonitrile used for washing is preferably 0.5-5 pts.wt. especially 1-3 pts.wt. based on 1 pts. crude crystal.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Generally, 2-acrylamido-2-methylpropanesulfonic acid is a reaction mixture prepared by using an excess of acrylonitrile, which serves both as a synthetic raw material and a reaction solvent, and adding a predetermined amount of sulfuric acid or fuming sulfuric acid and isobutylene. It is produced by separating more crystalline 2-acrylamido-2-methylpropane sulfonic acid (Japanese Patent Publication No. 50-30059).

2-Acrylamido-2-methylpropanesulfonic acid forms homopolymers and copolymers by polymerization and is used as a polymer electrolyte for various purposes. Among them, a dispersant for papermaking and an aggregating agent are used. For such applications, high-purity 2-acrylamido-2-methylpropanesulfonic acid is required to obtain a water-soluble polymer having a high molecular weight and a high solubility.

However, 2-acrylamido-2-methyl precipitated in a crystalline form from the reaction mixture by using an excess of acrylonitrile, which also serves as a raw material and a reaction solvent, and adding a predetermined amount of sulfuric acid or fuming sulfuric acid and isobutylene to cause a reaction. The above-mentioned Japanese Examined Patent Publication No. 50-3005 for separating propanesulfonic acid
According to the results of the additional tests by the inventors of the method described in 9,
Since the sulfonated product of isobutylene, a sulfate ester, and the like produced as a by-product during the reaction precipitates together with the 2-acrylamido-2-methylpropanesulfonic acid crystal, the obtained 2-
The purity of acrylamido-2-methylpropanesulfonic acid is low, and therefore, the polymer obtained by copolymerizing 2-acrylamido-2-methylpropanesulfonic acid with acrylamide or the like has a low molecular weight or its copolymerization weight. Insoluble gel is generated in the combined aqueous solution,
It could not be used satisfactorily.

As a method for removing impurities in the crystals of crude 2-acrylamido-2-methylpropanesulfonic acid obtained immediately after the synthetic reaction, Japanese Patent Publication No. 56-53306 discloses a method of separating 2-from the reaction mixture. A method has been proposed in which acrylamido-2-methylpropanesulfonic acid crystals are recrystallized with hydrous acetic acid and purified. However, implementation of such recrystallization causes increase in equipment cost, labor cost, and decrease in product acquisition amount, which is not economically preferable. Therefore,
A method for efficiently producing high-purity 2-acrylamido-2-methylpropanesulfonic acid has been desired.

[0006]

The present invention is of high purity
-Acrylamido-2-methylpropanesulfonic acid,
It is intended to provide a method of efficiently manufacturing.

[0007]

Means for Solving the Problems As a result of intensive studies on the above problems, the present inventors have found that crude 2-acrylamido-2-methylpropanesulfonic acid obtained in crystalline form immediately after a synthetic reaction is washed with acrylonitrile having a high water content. Then, impurities adhering to or contained in the crude 2-acrylamido-2-methylpropanesulfonic acid can be removed, and the crude 2
-The present inventors have found that the loss of acrylamido-2-methylpropanesulfonic acid is small and have completed the present invention.

That is, the present invention is characterized in that in the method for producing crude 2-acrylamido-2-methylpropanesulfonic acid, washing is carried out with acrylonitrile having a water content of 1.0 wt% (hereinafter simply abbreviated as%) or more. High purity 2
A method for producing acrylamido-2-methylpropanesulfonic acid.

The present invention will be described in more detail below. ○ Crude 2-acrylamido-2-methylpropanesulfonic acid The crude 2-acrylamido-2-methylpropanesulfonic acid in the present invention is not particularly limited in its synthetic method, but as a preferable synthetic method, for example, a raw material and a reaction are used. Using excess acrylonitrile also serving as a solvent, by reacting this with a predetermined amount of sulfuric acid or fuming sulfuric acid and isobutylene, to obtain crude 2-acrylamido-2-methylpropanesulfonic acid which is separated and precipitated in a crystalline form from the reaction mixture, There is a known method.

The crude 2-acrylamido-2-methylpropanesulfonic acid obtained in crystalline form by carrying out the reaction of the three components consisting of acrylonitrile, sulfuric acid or fuming sulfuric acid and isobutylene as a continuous reaction, is By copolymerization with the above monomer or a homopolymer of itself, a polymer having a high molecular weight and good physical properties can be obtained. Preferred specific examples of the continuous reaction include, for example, a two-step continuous reaction in which acrylonitrile and sulfuric acid are mixed and then isobutylene is added and reacted, and a three-step continuous reaction in which three components are mixed and reacted at once.

Acrylonitrile Generally, commercially available acrylonitrile contains about 0.4% of water. Regarding the water content in the hydrous acrylonitrile used as a cleaning agent in the present invention, the upper limit value is the saturation solubility and the lower limit value must be 1.0%, and preferably 2.0% or more of water is contained. It is desirable to let When the water content of the water-containing acrylonitrile is less than 1.0%, the impurities are not sufficiently removed by washing, and when 2-acrylamido-2-methylpropanesulfonic acid obtained after washing is used, the co-polymerization with acrylamide and the like is reduced. There is a problem that the molecular weight of the polymer is low or a gel insoluble in the aqueous solution of the polymer is formed. On the other hand, when the product is washed with a water-containing acrylonitrile having a saturated solubility of water and a detergent composed of water, the purity of crystals is improved, but the problem that the amount of crystals to be obtained is lowered occurs.

Washing Method The washing in the present invention is also effective for those which have been dried and stored after the crude 2-acrylamido-2-methylpropanesulfonic acid precipitated in a crystalline state by the synthetic reaction is separated and stored for a certain period of time. However, in order to efficiently remove impurities attached to or contained in crude 2-acrylamido-2-methylpropanesulfonic acid, crude 2-acrylamido-2-
It is preferable to wash immediately after the methylpropanesulfonic acid is separated and obtained from the reaction system. The washing method may be substitution washing by filtration such as general suction filtration, pressure filtration or centrifugation, or stirring and mixing washing in which crude crystals are dispersed in hydrous acrylonitrile and then separated. Water content is 1.0%
The method for preparing the above water-containing acrylonitrile is not particularly limited, and specifically, for example, a commercially available acrylonitrile containing about 0.4% of water, so that a desired water content is obtained, water is appropriately added. There is a method of adding. or,
In the case of washing with stirring and mixing, the crude crystals may be dispersed in generally commercially available hydrous acrylonitrile containing about 0.4% of water, and then a predetermined amount of water may be added thereto with stirring. The content of water in the hydrous acrylonitrile can be measured with sufficient accuracy in carrying out the method of the present invention by a general analysis method such as the Karl Fischer method. The amount of hydrous acrylonitrile used for washing is preferably 0.5 part or more and 5 parts or less, and more preferably 1 part or more with respect to 1 part by weight of crude 2-acrylamido-2-methylpropanesulfonic acid (hereinafter simply referred to as "part"). 3 parts or less. If the amount of washing is less than 0.5 part, the removal of impurities by washing is insufficient, and if the crystals obtained after washing are used, the molecular weight of the copolymer with acrylamide or the like may be low,
Alternatively, an insoluble gel may be produced in the aqueous solution of the polymer, while if the washing amount exceeds 5 parts, the amount of the washing waste liquid is increased, which is not economical. It should be noted that in cleaning, the hydrous acrylonitrile and / or the crude 2-acrylamido-2-methylpropanesulfonic acid may be heated in order to improve the cleaning efficiency, but the apparatus and heating energy are required for heating. Therefore, there is a risk of increasing the production cost, and on the other hand, the cleaning agent and the object to be cleaned have a sufficient cleaning effect even at room temperature. Further, it may be washed with a predetermined amount of hydrous acrylonitrile at once or may be washed twice or more times.

Drying Method The crystals washed as described above are then dried under normal pressure or under reduced pressure by a conventional method to obtain powdery high-purity crystals. The drying temperature is preferably 30 ° C to 140 ° C. High-purity 2-acrylamido-2-methylpropanesulfonic acid is partially decomposed during drying when the drying temperature is high, and the purity tends to decrease. When the drying temperature is low, it takes a long time to remove acrylonitrile and water. Not economical.

[0014]

A well-known 2-acrylamido-2-methylpropane in which acrylonitrile is used in excess as both a synthetic raw material and a reaction solvent, a predetermined amount of sulfuric acid or fuming sulfuric acid and isobutylene are added, and crystals precipitated from the reaction mixture are separated. In the method for producing a sulfonic acid, a sulfonated product of isobutylene produced as a by-product during the reaction, a sulfate ester, and the like precipitate together with 2-acrylamido-2-methylpropanesulfonic acid,
The purity of 2-acrylamido-2-methylpropanesulfonic acid separated and obtained in crystalline form is low, and as a result, the molecular weight of the copolymer with acrylamide or the like is low, or a gel insoluble in an aqueous solution of the polymer is formed. .. Many of these by-products are insoluble or poorly soluble in acrylonitrile,
For example, it cannot be removed by washing with commercially available acrylonitrile having a water content of about 0.4%. As in the present invention, by washing the crude 2-acrylamido-2-methylpropanesulfonic acid obtained after the synthesis reaction with a water-containing acrylonitrile having a high water content, by-products can be removed, and the amount of crystal loss due to the washing can be reduced. Since the amount is small, highly pure 2-acrylamido-2-methylpropanesulfonic acid can be efficiently obtained.

[0015]

The present invention will be specifically described with reference to the following examples.
The percentages shown in the examples are weight percentages, and high-performance liquid chromatography L-6000 (manufactured by Hitachi Ltd.) was used for the purity analysis of 2-acrylamido-2-methylpropanesulfonic acid.

Further, the viscosity and the amount of insolubles of the copolymers shown in the examples are values measured for the copolymer of 2-acrylamido-2-methylpropanesulfonic acid and acrylamide obtained by the following method. ..

Polymerization method 2-acrylamido-2-methylpropanesulfonic acid crystal (40 g) is dissolved in water (60 g), and 16% NaOH aqueous solution is added to adjust the pH to 8. Then, acrylamide (123 g) is mixed, and water is added to obtain a monomer concentration. Was adjusted to 20%. After substituting this aqueous solution with nitrogen, potassium persulfate 200 pp
m and 200 ppm of sodium sulfite were added, and polymerization was initiated at 20 ° C. After 10 hours, the copolymer was taken out and
It was vacuum dried at 00 ° C. for 4 hours and then pulverized.

Viscosity The copolymer powder obtained as described above is made into an aqueous solution,
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 the powder of the copolymer obtained as described above was added to 30 g of water.
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.

Example 1 Two glass reactors each equipped with a stirrer and an inlet pipe and an outlet pipe were connected to each other, and a reaction of mixing acrylonitrile and sulfuric acid and a process of adding isobutylene were continuously performed. The first reactor has acrylonitrile and fuming sulfuric acid inlet tubes,
The second reactor has an isobutylene gas blowing tube. The first reactor is maintained at -5 to -15 ° C and the residence time is 10 minutes. The second reactor is maintained at 30-50 ° C and the residence time is 40 minutes. Acrylonitrile and fuming sulfuric acid are mixed in the first reactor and isobutylene is added in the second reactor. To 1 mol of fuming sulfuric acid,
10 mol of acrylonitrile and 0.9 mol of isobutylene are supplied. The concentration of fuming sulfuric acid was 9%. The obtained reaction product is filtered to obtain crude 2-acrylamido-2-methylpropanesulfonic acid containing the reaction solution. The purity of this crude 2-acrylamido-2-methylpropanesulfonic acid is 97.0%, the viscosity of the aqueous copolymer solution obtained using this crude 2-acrylamido-2-methylpropanesulfonic acid is 50 cp, The amount of insoluble matter was 2 ml. 100 g of crude 2-acrylamido-2-methylpropanesulfonic acid was washed with 100 g of hydrous acrylonitrile containing 3.0% of water, and then washed at 100 ° C. for 3 days.
After vacuum drying for 9 hours, 97.5 g of powdery crystalline high-purity 2-acrylamido-2-methylpropanesulfonic acid was obtained. The purity of this high-purity crystal was 99.3%, the viscosity of the copolymer aqueous solution obtained using this high-purity crystal was 360 cp, and the amount of insoluble matter was 0 ml.

EXAMPLE 2 100 g of crystals of crude 2-acrylamido-2-methylpropanesulfonic acid were washed with 300 g of hydrous acrylonitrile containing 1.5% water, and the same procedure as in Example 1 was carried out to obtain high purity. 97.7 g of crystals of 2-acrylamido-2-methylpropanesulfonic acid were obtained. The purity of this high-purity crystal was 99.1%, the viscosity of the aqueous copolymer solution obtained using this high-purity crystal was 390 cp, and the amount of insoluble matter was 8 ml.
Met.

COMPARATIVE EXAMPLE 1 100 g of crude 2-acrylamido-2-methylpropanesulfonic acid crystals were washed with 300 g of hydrous acrylonitrile containing 0.4% water, and the same procedure as in Example 1 was repeated. 98.5 g of crystals of acrylamido-2-methylpropanesulfonic acid were obtained. The purity of this crystal is 98.
It was 5%, the viscosity of the aqueous copolymer solution obtained by using this crystal was 500 cp, and the amount of insoluble matter was 150 ml.

Comparative Example 2 Crystals of 2-acrylamido-2-methylpropanesulfonic acid 42 were prepared in the same manner as in Example 1 except that 100 g of crystals of crude 2-acrylamido-2-methylpropanesulfonic acid were washed with 50 g of water. Obtained 0.5 g. The purity of this crystal was 99.5%, the viscosity of the aqueous copolymer solution obtained using this crystal was 390 cp, and the amount of insoluble matter was 1 ml.

Examples 3 to 6 Crystal purity of high-purity 2-acrylamido-2-methylpropanesulfonic acid in the same manner as in Example 1 except that the water content in the hydrous acrylonitrile and the washing amount were changed.
The viscosity and the amount of insoluble matter in the aqueous copolymer solution are shown in Table 1 below.

[0025]

[Table 1]

[0026]

Industrial Applicability According to the present invention, high-purity 2-acrylamido-2-methylpropanesulfonic acid can be easily produced, and high-purity 2-acrylamido-2-methyl-2-acrylo
As an economical new production method of methylpropanesulfonic acid, its influence on the field is immeasurable.

Claims (1)

[Claims] 1. A method for producing high-purity 2-acrylamido-2-methylpropanesulfonic acid, which comprises washing crude 2-acrylamido-2-methylpropanesulfonic acid with acrylonitrile having a water content of 1.0 wt% or more. ..