JP2010229250A - Method for producing 2-acrylamido-2-methylpropanesulfonic acid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing 2-acrylamido-2-methylpropanesulfonic acid for obtaining a copolymer having a molecular weight higher than a conventional method. <P>SOLUTION: In the method for producing 2-acrylamido-2-methylpropanesulfonic acid by reacting acrylonitrile with sulfuric acid and isobutylene, the acrylonitrile is separated and recovered from a filtrate slurry of crude reaction liquid and reused in the reaction. The content of N-tertiary-butyl acrylamide in acrylonitrile to be added a reaction is controlled to &le;1,000 ppm. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a method for producing 2-acrylamido-2-methylpropanesulfonic acid (hereinafter referred to as ATBS), and more specifically, in a production method for recovering and reusing acrylonitrile, which is one of production raw materials. The present invention relates to a method for producing 2-acrylamido-2-methylpropanesulfonic acid, characterized in that the content of N-tertiary butyl acrylamide in acrylonitrile to be subjected to is controlled to 1,000 ppm or less.

ATBS is a modifier for acrylic fibers, and water-soluble or water-absorbing polymers obtained by copolymerization with water-soluble monomers such as acrylamide are polymer flocculants, dispersants, thickeners, and crude oils. Used in a wide range of fields such as drugs used for subsequent collection.
ATBS is produced by addition reaction of acrylonitrile, sulfuric acid, and isobutylene, and is normally white needle-like crystals having a melting point of 185 ° C.
In the above addition reaction, acrylonitrile, sulfuric acid, and isobutylene are reacted in equimolar amounts to produce ATBS, but acrylonitrile also serves as a reaction medium and should be used in a large excess compared to sulfuric acid and isobutylene. Is common.

Since ATBS is hardly soluble in acrylonitrile, the reaction product obtained by the above reaction is in a slurry state in which ATBS is precipitated in acrylonitrile. In the production of ATBS, ATBS deposited from this slurry is filtered, washed and dried to become a product. On the other hand, acrylonitrile is recovered from the filtrate slurry, and the recovered acrylonitrile is reused in the addition reaction.
When the recovered acrylonitrile is reused, as a purification method of acrylonitrile, a method of neutralizing an acrylonitrile recovery solution containing an acid as an impurity and removing a generated neutral salt (Patent Document 1), acrylonitrile and a small amount A method of treating a mixture containing acid and acrylamide with a base, removing the salt formed and distilling the treated mixture (Patent Document 2), and an inert gas atmosphere containing a specific amount of oxygen (Patent Document 3) is known.

JP-A-5-230007 Japanese Patent Publication No. 7-59544 Japanese Patent Laid-Open No. 7-70036

However, when acrylonitrile purified by the conventional method is reused in the reaction, there is a problem that the molecular weight of the produced copolymer using ATBS does not increase. In particular, in an industrial plant that continuously manufactures, this deterioration in the quality of ATBS tends to become more prominent over time.
In addition, in recent years, there is a background that higher molecular weight copolymers are required than in the past for applications such as high-order recovery of crude oil, and ATBS from which high molecular weight copolymers can be obtained in industrial production facilities. There is a demand for a method for efficiently producing the above.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that N-tertiary butyl acrylamide represented by the following formula (1), which is a by-product of the reaction, is acrylonitrile to be recovered and reused (hereinafter, It was found that the content of TBAM affects the polymerizability of the final product ATBS. Therefore, in the method for producing ATBS in which acrylonitrile is recovered and reused, by controlling the amount of TBAM in acrylonitrile to be used for the reaction (new product + reuse), a copolymer having excellent polymerizability and high molecular weight can be obtained. The inventors have found that an ATBS that can be obtained can be manufactured, and have completed the present invention.

  That is, according to the first aspect of the present invention, 2-acrylamido-2-methylpropane is prepared by reacting acrylonitrile, sulfuric acid, and isobutylene while mixing acrylonitrile and sulfuric acid and bringing the resulting mixture into contact with isobutylene. In producing sulfonic acid, N-tertiary butyl represented by the following formula (1) in acrylonitrile to be used in the reaction in a production method in which acrylonitrile is separated and recovered from the filtrate slurry of the crude reaction solution and reused in the reaction. It is a method for producing 2-acrylamido-2-methylpropanesulfonic acid, wherein the acrylamide content is controlled to 1,000 ppm or less.

According to a second aspect of the present invention, 2-acrylamido-2-methylpropanesulfone according to the first aspect is characterized in that acrylonitrile is separated and recovered from the filtrate slurry of the crude reaction liquid using a distillation apparatus having three or more stages. It is a manufacturing method of an acid.
Furthermore, the third invention of the present invention is the first invention characterized in that, in the distillation operation in the separation and recovery of acrylonitrile from the filtrate slurry of the crude reaction solution, the distillation temperature is operated within the range of 2 ° C. or less from the boiling point of acrylonitrile. A method for producing 2-acrylamido-2-methylpropanesulfonic acid according to the second invention.

  According to the production method of the present invention, a high-purity ATBS capable of obtaining a high-molecular-weight copolymer in a high yield can be produced by an easy method even in an industrial production apparatus for recovering and reusing acrylonitrile. Can do.

Hereinafter, a method for manufacturing the ATBS will be described.
As shown in the following reaction formula (A), 2-acrylamido-2-methylpropanesulfonic acid (ATBS) represented by the following chemical formula (2) is a raw material acrylonitrile (3), sulfuric acid (4), It is produced by reacting with isobutylene (5). The reaction can be carried out by either batch reaction or continuous reaction. In the present invention, a continuous reaction in which acrylonitrile used in excess for the reaction is recovered and reused is employed.

(Reaction process)
In the reaction of acrylonitrile, sulfuric acid, and isobutylene, acrylonitrile and sulfuric acid are first mixed at a low temperature (about −15 to −10 ° C.). The mixture is then blown with isobutylene while stirring. When the reaction starts, the temperature of the mixture increases due to the heat of reaction. Therefore, it is preferable to cool the mixture and maintain the temperature at 40 to 60 ° C.
ATBS is produced by an equimolar addition reaction of the above three raw material components. As the reaction progresses, the reaction solution becomes a slurry in which solid crystalline ATBS is dispersed. The dispersion medium constituting this slurry is acrylonitrile mixed in a large excess compared with sulfuric acid and isobutylene.
The mixing ratio of the three raw material components is as follows. Sulfuric acid and isobutylene are preferably mixed in approximately equimolar amounts. The mixing ratio of acrylonitrile with respect to sulfuric acid or isobutylene is preferably 10 to 20 times mol. By reacting the mixed liquid at this ratio, a slurry having a solid content concentration of 15 to 25% by mass is obtained.
In the above reaction, moisture present in the reaction system is not preferable because it causes a side reaction. It is preferable to use a raw material component that does not contain moisture. Particularly for sulfuric acid, it is preferable to use a mixture of concentrated sulfuric acid and fuming sulfuric acid.

(Solid-liquid separation process)
Next, a crude ATBS is isolated from the slurry obtained as described above. The isolation method can take any separation method such as a filter for solid-liquid separation of a crude product from the resulting slurry, a centrifuge, a centrifugal filter, a tray filter, a belt filter, and the like. By performing solid-liquid separation, a coarse cake containing an ATBS coarse body is obtained. However, since the coarse cake contains a large amount of impurities, it cannot be used for producing a high molecular weight polymer as it is. Therefore, the crude cake is purified in the purification process.

(Solid purification process)
As an example of the purification step, there is a method of washing a crude cake obtained by solid-liquid separation of a slurry with acrylonitrile. Even if a solvent other than acrylonitrile is used, it can be purified in the same manner.
The amount of the cleaning solvent used is preferably 0.2 to 10 times the mass of the solid content of the cake to be cleaned, and more preferably 0.5 to 3 times the mass.
As the washing solvent, acrylonitrile, acetonitrile, acetone, methanol, ethanol, 2-propanol, butanol, ethyl acetate, acetic acid, etc., or a mixed solvent thereof is preferable. Is preferred.

(Solid drying process)
Any system such as heating, decompression, and air flow can be used, and the solvent and impurities such as acrylonitrile impregnated in the cake are removed to obtain ATBS.

(Solvent recovery process)
The present invention relates to recovering acrylonitrile as a solvent from the filtrate after separating a crude product from a reaction slurry in the solid-liquid separation step, and reusing the recovered acrylonitrile for the reaction.
In addition to acrylonitrile, the filtrate contains sulfuric acid, TBAM, acrylamide, isobutylene sulfonic acid, ATBS, and the like, and is transferred to the aqueous layer side while neutralizing acidic impurities in the filtrate. For the operation here, a known method can be adopted (Patent Document 1, etc.). Although there is no limitation in particular in the alkali compound used for preparation of the said aqueous alkali solution, Preferably, it is an alkaline compound which has high water solubility, such as ammonia, sodium hydroxide, potassium hydroxide, sodium carbonate. The preferable concentration of the alkali compound in the alkaline aqueous solution is usually 10 to 30% by mass. A preferred ratio of the filtrate to the alkaline aqueous solution is 1 to 10 parts by mass of alkali per 100 parts by mass of the filtrate. Moreover, it is preferable that the aqueous solution after wash | cleaning a filtrate with alkaline aqueous solution by the following operation is weakly alkaline (PH is about 7.5-8).

The contact between the filtrate and the aqueous alkaline solution is preferably carried out continuously with a tube mixer such as a static mixer. The liquid in which the organic layer and the aqueous layer are mixed is subjected to liquid-liquid separation, the aqueous layer side is removed, and the organic layer side is subjected to an acrylonitrile recovery operation. As a liquid-liquid separation operation, a known method can be used. For example, the liquid may be left in a tank and separated by gravity. Furthermore, the organic layer side after washing with the alkaline aqueous solution may be further washed with water and liquid-liquid separated, and then the aqueous layer side may be removed and the organic layer side may be subjected to an acrylonitrile recovery operation.
Since the organic layer side contains acrylonitrile-soluble TBAM, acrylamide, etc., it is necessary to separate acrylonitrile by a method such as distillation. As this separation method, a conventionally known method can be applied, but a distillation operation which is widely applied industrially as a general separation method is preferably applied.

  In the present invention, since it is necessary to reduce TBAM contained in acrylonitrile to be recovered as much as possible in the distillation operation, it is preferable to use a distillation apparatus having three or more stages. When a distillation apparatus having two or less stages is used, the amount of TBAM contained in acrylonitrile may increase.

  In the above distillation operation, in order to reduce the amount of TBAM contained in acrylonitrile, it is preferable to control the distillation temperature to be constant, and in particular, the operation is performed within the range of 2 ° C. from the boiling point of acrylonitrile under the distillation pressure condition. It is preferable. When the distillation operation is performed at a temperature exceeding 2 ° C. from the boiling point of acrylonitrile, the amount of TBAM contained in the recovered acrylonitrile tends to increase.

  In the present invention, acrylonitrile to be used for the reaction means the total of acrylonitrile recovered from the filtrate slurry and new acrylonitrile. Normally, new acrylonitrile used industrially does not contain TBAM. Therefore, in the present invention, it is important to reduce the amount of TBAM in acrylonitrile recovered from the filtrate as much as possible.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.
(Manufacture of ATBS)
Two reactors equipped with a mixing stirrer were connected, and under the reaction conditions shown below, acrylonitrile and fuming sulfuric acid were introduced into the first-stage reactor, and a mixing step of acrylonitrile and sulfuric acid was performed. The mixture in the first-stage reactor was introduced into the second-stage reactor, and isobutylene gas was introduced into the second-stage reactor to carry out the reaction continuously. The raw material charge ratio was such that 10 mol of acrylonitrile and 0.95 mol of isobutylene containing various concentrations of TBAM shown in Table 1 below were supplied per 1 mol of fuming sulfuric acid. The concentration of fuming sulfuric acid is 3%. The first-stage reactor was maintained at -5 to -15 ° C, and the second-stage reactor was maintained at 40 to 60 ° C.
The reaction slurry flowing out from the second-stage reactor was filtered, and the resulting ATBS crude cake was washed with acrylonitrile and dried by heating to obtain ATBS.

(Evaluation of polymerization performance)
The polymerization performance evaluation of ATBS shown in each example and comparative example was performed according to the following procedure. First, 40 g of ATBS was dissolved in 60 g of water, and a 48 mass% NaOH aqueous solution was added to adjust the pH to 8. Water was added thereto to adjust the concentration to 35% by mass. 55.6 g of 40 mass% acrylamide aqueous solution was added, and 5.2 g of water was further added to make the total concentration of monomers 35 mass%. Nitrogen was blown into the aqueous monomer solution, and the liquid temperature was adjusted to 30 ° C. Thereafter, 0.7 g of ammonium persulfate, 0.7 g of sodium sulfite and 0.6 g of an aqueous solution of copper chloride containing 10 mass ppm of copper ions in this monomer aqueous solution, V-50 (trade name of Wako Pure Chemical Industries, Ltd. as a diazo radical polymerization initiator) 0.7 g of a 10% by weight aqueous solution (made by company) was added. After 2 hours, the reaction was terminated and the copolymer was taken out.
After 1.15 g of this copolymer was dissolved in 393 g of water, 23.4 g of sodium chloride was added to obtain a sample solution for viscosity measurement (copolymer concentration 0.25% by mass). Viscosity measurement was performed under the following conditions.
Viscometer: Brookfield digital viscometer, rotor rotation speed: 60 rpm,
Measurement temperature: 25 ° C

Example 1
The filtrate after filtering the reaction slurry was washed with an alkaline aqueous solution, the aqueous layer was sufficiently removed by liquid-liquid separation, and further washed with water and the aqueous layer was separated and removed to obtain an organic layer. From the organic layer, acrylonitrile is recovered by distillation using a three-stage distillation apparatus, and the recovered acrylonitrile containing 800 ppm of TBAM obtained by maintaining the fluctuation width of the distillation temperature of the final distillation purification equipment within 4 ° C is used. According to the ATBS production conditions, ATBS was obtained. The obtained ATBS was measured for the viscosity of the copolymer by the polymerization performance evaluation method, and the polymerization performance was evaluated. As a result, it was found to have a high polymerization performance of 3.10 mPa · s.

Examples 2-5
The recovered acrylonitrile containing various concentrations of TBAM obtained by acrylonitrile distillation and recovery using a three-stage distillation apparatus was reused under the conditions of the fluctuation temperature of the distillation temperature of the final distillation purification equipment shown in Table 1. Then, ATBS was produced in the same manner as in Example 1, and the viscosity of the copolymer was measured for the obtained ATBS by the above-described polymerization performance evaluation method to evaluate the polymerization performance. The viscosity values were as shown in Table 1.

Comparative Example 1
Using the recovered acrylonitrile containing 3000 ppm TBAM obtained by carrying out distillation recovery of acrylonitrile while maintaining the fluctuation width of the distillation temperature of the final distillation purification equipment within 7 ° C. using a two-stage distillation apparatus, Example 1 and ATBS was obtained according to the same ATBS production conditions. The obtained ATBS was measured for the viscosity of the copolymer by the above-described polymerization performance evaluation method, and the polymerization performance was evaluated. The polymerization performance was as low as 2.70 mPa · s.

Comparative Example 2
Using the recovered acrylonitrile containing 1500 ppm of TBAM obtained by carrying out distillation recovery of acrylonitrile while maintaining the fluctuation width of the distillation temperature of the final distillation purification equipment within 6 ° C. using a two-stage distillation apparatus, Example 1 and ATBS was obtained according to the same ATBS production conditions. The obtained ATBS was measured for the viscosity of the copolymer by the above-described polymerization performance evaluation method, and the polymerization performance was evaluated. As a result, the polymerization performance was as low as 2.85 mPa · s.

Reference Example Using a new acrylonitrile not containing TBAM, ATBS was obtained in accordance with the ATBS production conditions. The obtained ATBS was measured for the viscosity of the copolymer by the above-described polymerization performance evaluation method, and the polymerization performance was evaluated. As a result, the polymerization performance was as high as 3.20 mPa · s. However, since the raw material acrylonitrile is not purified, recovered, and repeatedly reused, the purchase cost of the raw material acrylonitrile and the disposal cost of the filtrate are increased, and it does not mean that the environmental load is increased.

According to the method for producing ATBS of the present invention, ATBS with few impurities that inhibit the polymerizability can be obtained by an industrially easy method. Since the copolymer using the ATBS can obtain a copolymer having a very high molecular weight than before, a copolymer having a higher molecular weight than conventional ones is required for high-order recovery of crude oil. It can also be used in certain fields.

Claims (3)

In producing 2-acrylamido-2-methylpropanesulfonic acid by mixing acrylonitrile and sulfuric acid and reacting acrylonitrile, sulfuric acid and isobutylene while bringing the resulting mixture into contact with isobutylene, In the production method in which acrylonitrile is separated and recovered from the filtrate slurry and reused in the reaction, the content of N-tertiary butylacrylamide represented by the following formula (1) in the acrylonitrile to be subjected to the reaction is controlled to 1,000 ppm or less. A process for producing 2-acrylamido-2-methylpropanesulfonic acid, which comprises:

The method for producing 2-acrylamido-2-methylpropanesulfonic acid according to claim 1, wherein the acrylonitrile is separated and recovered from the filtrate slurry of the crude reaction liquid using a distillation apparatus having three or more stages. The 2-acrylamido-2 according to claim 1 or 2, wherein in the distillation operation in the separation and recovery of acrylonitrile from the filtrate slurry of the crude reaction liquid, the distillation temperature is controlled within the range of 2 ° C from the boiling point of acrylonitrile. -Method for producing methylpropanesulfonic acid.