JP2009155324A - 2-acrylamide-2-methylpropane sulfonic acid and process for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide 2-acrylamide-2-methylpropanesulfonic acid with reduced amount of impurities and imparting a polymer with a high molecular weight, and to provide a method for producing the same. <P>SOLUTION: The invention relates to the process for producing 2-acrylamide-2-methylpropanesulfonic acid. During the reaction, the concentration of 2-methyl-2-propenyl-1-sulfonic acid and/or that of 2-methylidene-1, 3-propylenedisulfonic acid in the reaction system are determined. When the 2-methyl-2-propenyl-1-sulfonic acid concentration exceeds 12,000 ppm and/or the 2-methylidene-1,3-propylenedisulfonic acid concentration exceeds 6,000 ppm, then the concentration of sulfur trioxide in the reaction system is reduced. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to 2-acrylamido-2-methylpropanesulfonic acid (hereinafter sometimes abbreviated as ATBS) and a method for producing the same. More specifically, the present invention relates to ATBS with a low specific impurity content and a method for producing the same.

  ATBS is a raw material for pharmaceutical production used as a modifier for acrylic fibers, as a monomer raw material for dispersants and flocculants, or as a monomer raw material for cosmetic thickeners, and for higher-level recovery of crude oil. Used as a monomer in a wide range of fields.

  The polymer produced using the above ATBS as a raw material monomer used for these applications is particularly required to have a high molecular weight. That is, the ATBS used for the above applications is required to reduce the content of a substance that inhibits polymerization as much as possible and to have a stable quality.

    ATBS is usually produced by addition reaction of acrylonitrile, sulfuric acid, and isobutylene, and its properties are normally white needle-like crystals with a melting point of 185 ° C. (for example, Patent Document 1).

  In the above addition reaction, the three components of acrylonitrile, sulfuric acid, and isobutylene react in equimolar amounts, but acrylonitrile also serves as a reaction medium, and is therefore used in a large excess compared to sulfuric acid and isobutylene.

  Since ATBS is hardly soluble in acrylonitrile, the reaction product obtained after the reaction is in the form of a slurry in which ATBS is precipitated in acrylonitrile. Usually, in the production of ATBS, ATBS is separated from this slurry and purified in the next purification step. As a purification method, there is a method of washing with acrylonitrile. (For example, patent document 1).

  Also, a method of recrystallizing crude ATBS with methanol (for example, Patent Document 2), a method for purification using an anion exchange resin (for example, Patent Document 3), and removing water by distilling an aqueous solution of ATBS in the presence of acrylonitrile. Then, after obtaining an ATBS acrylonitrile dispersion, ATBS is filtered from the dispersion (for example, Patent Document 4).

However, there is no clear conclusion as to what is a substance that inhibits polymerization. Therefore, conventionally, a method that meets the above requirements by sufficiently purifying ATBS has been adopted. Since the substance that inhibits the polymerization has not been specified, the above-described method of sufficient purification is not specialized in removing the specific substance that inhibits the polymerization. It has only been done. Therefore, in some cases, it may be excessively purified, and it is difficult to stabilize the quality related to the impurity concentration of ATBS obtained.
Japanese Patent Publication No.50-30059 (Example 1) JP-A-2004-359591 (Claim 1) JP 2004-143078 (Claim 1) JP-A-2004-277363 (Claim 1)

  As a result of various studies to solve the above problems, the present inventor firstly made 2-methyl-2-propenyl-1-sulfonic acid (abbreviated as IBSA) and 2-methylidene- which are reaction by-products. 1,3-propylene disulfonic acid (abbreviated as IBDSA) has a chain transfer action of polymerization, and it is found that the molecular weight of the copolymer of ATBS does not increase when the content of these compounds in ATBS increases. It was. Furthermore, as a result of investigation, the content of the by-product can be accurately quantified by high-performance liquid chromatography, and a high-molecular weight polymer is produced by controlling the by-product to a predetermined value or less in the ATBS production process. It was learned that ATBS can be manufactured. The present invention has been completed as a result of the above studies.

  Accordingly, an object of the present invention is to provide an ATBS having a low content of a compound that inhibits polymerization, and a method for producing the ATBS.

  The present invention for achieving the above object is as follows.

    [1] The following formula (1)

The content of 2-methyl-2-propenyl-1-sulfonic acid represented by the formula is 100 ppm or less, and the following formula (2)

The content of 2-methylidene-1,3-propylene disulfonic acid represented by formula (3) is 100 ppm or less.

2-acrylamido-2-methylpropanesulfonic acid represented by

    [2] A method for producing 2-acrylamido-2-methylpropanesulfonic acid, which comprises reacting acrylonitrile, fuming sulfuric acid and isobutylene, wherein 2-methyl-2-propenyl-1- exists in the reaction system during the reaction When the concentration of sulfonic acid and / or 2-methylidene-1,3-propylene disulfonic acid is measured and the concentration of 2-methyl-2-propenyl-1-sulfonic acid exceeds 12000 ppm, and / or 2-methylidene-1 A process for producing 2-acrylamido-2-methylpropanesulfonic acid, wherein the concentration of sulfur trioxide in the reaction system is reduced when the concentration of 1,3-propylenedisulfonic acid exceeds 6000 ppm.

    [3] A method for producing 2-acrylamido-2-methylpropanesulfonic acid, in which acrylonitrile, fuming sulfuric acid, and isobutylene are continuously supplied to the reaction system and reacted, and is present in the reaction system during the reaction. -When the concentration of methyl-2-propenyl-1-sulfonic acid and / or 2-methylidene-1,3-propylene disulfonic acid is measured and the concentration of 2-methyl-2-propenyl-1-sulfonic acid exceeds 12000 ppm 2-acrylamide-2, characterized by reducing the concentration of sulfur trioxide in the fuming sulfuric acid supplied to the reaction system when the concentration of 2-methylidene-1,3-propylene disulfonic acid exceeds 6000 ppm -A continuous process for producing methylpropanesulfonic acid.

    [4] A process for producing 2-acrylamido-2-methylpropanesulfonic acid, which comprises reacting acrylonitrile, fuming sulfuric acid and isobutylene, wherein 2-methyl-2-propenyl-1- exists in the reaction system during the reaction When the concentration of sulfonic acid and / or 2-methylidene-1,3-propylene disulfonic acid is measured and the concentration of 2-methyl-2-propenyl-1-sulfonic acid exceeds 12000 ppm, and / or 2-methylidene-1 , A method for continuously producing 2-acrylamido-2-methylpropanesulfonic acid, wherein the reaction time is increased when the concentration of propylenedisulfonic acid exceeds 6000 ppm.

    [5] A crude product of 2-acrylamido-2-methylpropanesulfonic acid in the slurry obtained by the production method of any one of [2] to [4] is filtered to obtain a cake, and then acrylonitrile, acetonitrile Of 2-acrylamido-2-methylpropanesulfonic acid, wherein the cake is washed with one solvent selected from the group consisting of ethanol, acetone, methanol, ethanol, 2-propanol, butanol, ethyl acetate, and acetic acid, or a mixed solvent thereof. Production method.

    [6] A crude product of 2-acrylamido-2-methylpropanesulfonic acid in a slurry obtained by the production method according to any one of [2] to [4] is filtered to obtain a cake, and then the cake is obtained. A method for producing 2-acrylamido-2-methylpropanesulfonic acid, which is dried at a temperature of 60 to 130 ° C. for 10 to 300 minutes.

  The ATBS of the present invention has a low content of IBSA and IBDSA. Therefore, the polymer obtained by copolymerizing this ATBS has a high molecular weight.

  In the method for producing ATBS of the present invention, high purity ATBS can be easily produced by measuring the amount of by-products IBSA and IBDSA produced and adjusting the concentration of sulfur trioxide. Therefore, the subsequent purification process is simplified.

2-Acrylamide-2-methylpropanesulfonic acid (ATBS)
The present invention provides the following formula (1)

The content of 2-methyl-2-propenyl-1-sulfonic acid (IBSA) represented by the formula is 100 ppm or less, and the following formula (2)

The content of 2-methylidene-1,3-propylene disulfonic acid (IBDSA) represented by the formula (3) is 100 ppm or less

2-acrylamido-2-methylpropanesulfonic acid (ATBS).

  This ATBS has a high purity in which the contents of IBSA and IBDSA are each 100 ppm or less (mass basis). As described above, IBSA and IBDSA are compounds by-produced when producing ATBS, and these compounds act as a chain transfer agent in the radical polymerization reaction. Therefore, the presence of these IBSA and IBDSA causes a decrease in the molecular weight of the polymer obtained by homopolymerizing or copolymerizing ATBS or a salt thereof in the radical polymerization reaction. Furthermore, variations in the content of these compounds cause variations in the molecular weight of a polymer obtained by singly or copolymerizing ATBS or a salt thereof.

  The present inventor confirmed that IBSA and IBDSA have a chain transfer action by the following experiment.

  That is, the amount of IBSA added was changed to an aqueous solution of acrylamide and ATBS. A copolymer was obtained by polymerizing the monomer aqueous solution. The result of measuring the viscosity of this aqueous solution by dissolving this copolymer in water is shown in FIG.

  The experiment 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 a 40% by mass acrylamide aqueous solution was added, and 5.2 g of water was further added to adjust the monomer concentration to 35% by mass. Nitrogen was blown into this monomer aqueous solution and the liquid temperature was adjusted to 30 ° C., then 0.7 g of ammonium persulfate, 0.7 g of sodium sulfite, 0.6 g of an aqueous copper chloride solution containing 10 ppm (mass basis) of copper ions, diazo series As a radical polymerization initiator, 0.7 g of a 10 mass% aqueous solution of V-50 (trade name, manufactured by Wako Pure Chemical Industries, Ltd.) 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
As can be seen from FIG. 1, as the amount of IBSA increases, the viscosity decreases and the average molecular weight of the resulting copolymerized polymer decreases. This data confirmed that IBSA acts as a chain transfer agent.

    Experiments similar to IBSA were performed on IBDSA. The results are shown in FIG. From FIG. 2, it was confirmed that IBDSA acts as a chain transfer agent.

    Furthermore, from the results of FIGS. 1 and 2 above, in order to maintain a high polymerizability of ATBS and to obtain a polymer having a high molecular weight when polymerized, ATBS and IBDSA are both 100 ppm (mass basis) or less. It was confirmed that it was necessary.

ATBS Manufacturing Method Hereinafter, the ATBS manufacturing method will be described.

  As shown in the following reaction formula (A), 2-acrylamido-2-methylpropanesulfonic acid (ATBS) represented by the following chemical formula (3) is a raw material acrylonitrile (4), sulfuric acid (5), Prepared by reacting with isobutylene (6). The reaction may be a batch reaction or a continuous reaction.

  In the reaction of acrylonitrile, sulfuric acid, and isobutylene, first, acrylonitrile and sulfuric acid are mixed at a low temperature (about -15 to -10 ° C), and isobutylene is blown into the mixture while stirring the mixture. 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 50 ° C.

  ATBS is generated by an equimolar addition reaction of the above three raw material components, and the reaction liquid becomes a slurry in which ATBS of solid crystals is dispersed with the progress of the reaction. Most of the dispersion medium of this slurry is acrylonitrile mixed in a large excess compared with sulfuric acid and isobutylene.

  Regarding the mixing ratio of the three raw material components, the ratio of isobutylene to sulfuric acid is preferably about equimolar, and the ratio of acrylonitrile to them is preferably 10 to 20 times mol. By making it react using the liquid mixture of such a ratio, the slurry whose solid content concentration is 15-25 mass% is obtained as a reaction product liquid.

  In the above reaction, moisture present in the reaction system causes a side reaction, which is not preferable. 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.

  The slurry produced as described above is then solid-liquid separated by a centrifugal operation or the like to take out ATBS crystals, and further subjected to post-treatment such as washing and drying to obtain a product (ATBS).

(First control method)
In the present invention, in the above reaction for producing ATBS, the abundances of by-products IBSA and IBDSA present in the reaction system are measured, and the reaction conditions are controlled based on the measured values. The control method measures the concentration of either or both of IBSA and IBDSA, and when the concentration of IBDSA exceeds 12000 ppm and / or when the concentration of IBDSA exceeds 6000 ppm, the concentration of sulfur trioxide in the reaction system It is intended to reduce. As a method of reducing the concentration of sulfur trioxide, there is a method of decreasing the supply amount of sulfur trioxide supplied to the reaction system together with sulfuric acid or stopping the supply.

  Any measurement method may be used for measuring the abundance of IBSA and IBDSA. However, a method of measuring using a high performance liquid chromatograph (abbreviated as HPLC) is preferable in terms of simplicity of measurement and accuracy of measurement values.

  FIG. 3 shows a graph obtained by actually measuring the relationship between the excess amount of sulfur trioxide present in the reaction system and the concentrations of IBSA and IBDSA in the ATBS production reaction. From this graph, it can be seen that when sulfur trioxide increases in the reaction system, IBSA and IBDSA increase. The excess amount of sulfur trioxide refers to the amount of sulfur trioxide present in excess with respect to this 100% sulfuric acid in% based on 100% sulfuric acid.

  By controlling the reaction conditions as described above, a reaction slurry is usually obtained in which the concentration of IBSA in ATBS is 12000 ppm (mass basis) or less and the concentration of IBDSA is 6000 ppm (mass basis) or less.

(Second control method)
The second control method measures the amount of by-product IBSA and IBDSA present in the reaction system. If the concentration of IBSA exceeds 12000 ppm and / or if the concentration of IBDSA exceeds 6000 ppm, It is controlled so as to lengthen the time.

    FIG. 4 shows a graph obtained by actually measuring the relationship between IBSA and IBDSA present in the reaction system and the reaction time. According to this graph, it can be seen that as the reaction time is increased, the concentration of IBSA decreases, and the concentration of IBDSA increases temporarily and then decreases. Therefore, it can be seen that when the concentration of IBSA and IBDSA in the reaction system is high, the reaction time may be controlled to be long. As a method for increasing the reaction time, for example, in the case of a continuous production apparatus, there is a method for increasing the residence time of the reaction liquid in the reactor.

  By controlling the reaction conditions as described above, a reaction slurry is usually obtained in which the concentration of IBSA in ATBS is 12000 ppm (mass basis) or less and the concentration of IBDSA is 6000 ppm (mass basis) or less.

  Next, ATBS is isolated from the reaction slurry containing ATBS obtained by reacting acrylonitrile, fuming sulfuric acid, and isobutylene with the above-mentioned control group. The isolation method includes a method in which the ATBS crude product is solid-liquid separated from the resulting reaction slurry to obtain a cake containing ATBS, and then the cake is dried. The obtained ATBS contains a large amount of impurities such as IBSA and IBDSA, and thus cannot be used for production of a high molecular weight polymer as it is. Therefore, the cake needs to be purified in the purification process.

    As an example of the purification step, there is a method in which a cake obtained by solid-liquid separation of the reaction slurry is further washed with acrylonitrile. In this case, changes in the concentrations of IBSA and IBDSA were examined in detail. The result is shown in FIG. When the amount of acrylonitrile in the cleaning solvent is increased, IBSA and IBDSA in ATBS are cleaned and removed. Even if a solvent other than acrylonitrile is used, it can be similarly purified.

  The cake obtained by solid-liquid separation of the reaction slurry is washed with a solvent such as acrylonitrile, and the resulting washed cake is dried to remove the solvent to obtain an ATBS product. The amount of the cleaning solvent used is preferably 0.5 to 10 times, more preferably 1 to 3 times the solid mass of the cake to be cleaned. As the cleaning solvent, acrylonitrile, acetonitrile, acetone, methanol, ethanol, 2-propanol, butanol, ethyl acetate, acetic acid and the like, or a mixed solvent thereof is preferable. Particularly preferred is acrylonitrile.

  By washing the cake separated from the reaction slurry with a washing solvent, the cake is purified, and the concentration of IBSA and IBDSA becomes 100 ppm (mass basis) or less.

    The drying process has been performed for the purpose of removing the solvent impregnated in the conventional cake.

    The inventor examined the concentration of impurities such as IBSA and IBDSA in the drying process. As a result, it was found that by controlling the drying conditions in this drying step, these IBSA and IBDSA can be reduced and the product quality can be improved.

    FIG. 6 is a graph showing the relationship between the drying temperature and drying time of the washed cake and the IBSA concentration in the product cake. These compounds are thought to decrease due to thermal decomposition.

    From this graph, it can be seen that the IBSA and IBDSA concentrations in the washed cake can be reduced by drying the washed cake at 60 to 130 ° C. for 10 to 300 minutes, preferably 10 to 130 minutes.

    For example, when the amount of sulfur trioxide is excessive in the reaction and the IBSA content is increased, or when the cake is not sufficiently washed in the solid-liquid separation process and the IBSA content cannot be reduced, or When the cake washing process is omitted, the IBSA and IBDSA concentrations in the product can be reduced by taking measures such as (1) increasing the drying temperature and (2) extending the drying time according to the data in the graph of FIG. .

Hereinafter, the present invention will be described specifically by way of examples. The concentration shown in each example is a concentration determined by HPLC.
HPLC conditions; Waters high performance liquid chromatograph column; GL Science ODS-3
Eluent: 0.03% aqueous trifluoroacetic acid / acetonitrile eluent flow rate: 0.8 ml / min
Detection wavelength: 200 nm

Example 1
Two glass reactors equipped with a stirrer and an inlet pipe and an outlet pipe were connected, acrylonitrile and fuming sulfuric acid were charged into the first reactor under the following conditions, and after mixing acrylonitrile and fuming sulfuric acid, Two reactors were fed. In the second reactor, isobutylene gas was blown into the mixture to synthesize ATBS. The above reaction was carried out continuously.

  The amount of acrylonitrile supplied was 11 mol and the amount of isobutylene supplied was 0.9 mol per mol of fuming sulfuric acid. The supply amount of fuming sulfuric acid was 1.6 mol / hour, and the reaction was continuously performed for 12 hours. During the reaction, the reaction solution was collected, the concentrations of IBSA and IBDSA were measured by HPLC, and the supply amount of fuming sulfuric acid was adjusted as shown in Table 1.

    In addition, the concentration of sulfur trioxide in fuming sulfuric acid is 0.6%, and the concentration is adjusted by mixing concentrated sulfuric acid after adding moisture brought from raw materials such as acrylonitrile to commercially available 20% fuming sulfuric acid. Did. The first reactor was maintained at -5 to -15 ° C and the residence time was 10 minutes. The second reactor was maintained at 30-50 ° C. and the residence time was 90 minutes.

  The ATBS slurry obtained in the above production was suction filtered with a glass filter to obtain a cake on the glass filter. The amount of acrylonitrile described in Table 1 with respect to the cake mass was poured into the cake and suction filtered again to wash the cake.

  The cake was transferred to a tray and dried at a drying temperature of 80 ° C. for 90 minutes.

  The obtained ATBS powder was subjected to HPLC analysis, and the concentrations of IBSA and IBDSA were measured.

    Next, a copolymer of ATBS and acrylamide was produced using ATBS obtained by the above method.

  The copolymer was produced 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% by mass acrylamide aqueous solution was added, and 5.2 g of water was further added to adjust the monomer concentration to 35% by mass. After adjusting the liquid temperature to 30 ° C. while blowing nitrogen into the monomer aqueous solution, 0.7 g of ammonium persulfate, 0.7 g of sodium sulfite, 0.6 g of an aqueous copper chloride solution containing 10 ppm (mass basis) of copper ions, a diazo radical As a polymerization initiator, 0.7 g of a 10 mass% aqueous solution of V-50 (manufactured by Wako Pure Chemical Industries, Ltd.) 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).

    The viscosity of the sample liquid for viscosity measurement was measured with a UL viscosity measuring device. The results are shown in Table 1.

Example 2
In Example 1, the amount of acrylonitrile for washing the cake was halved. From the data shown in FIG. 5, IBSA could be expected to remain, and in order to reduce this, drying was performed at 110 ° C., which is higher than the normal drying temperature, for 90 minutes. The obtained ATBS powder was analyzed by HPLC. In the same manner as in Example 1, a copolymer of ATBS and acrylamide was produced. In the same manner as in Example 1, the viscosity of the copolymer was measured. The results are shown in Table 1.

Example 3
The same operation was performed except that the drying temperature of the cake was 110 ° C. in Example 1. The obtained ATBS powder was analyzed by HPLC. In the same manner as in Example 1, a copolymer of ATBS and acrylamide was produced. In the same manner as in Example 1, the viscosity of the copolymer was measured. The results are shown in Table 1.

Example 4
The same operation was performed except that the solvent for washing the cake in Example 3 was changed to acetic acid. The obtained ATBS powder was analyzed by HPLC. In the same manner as in Example 1, a copolymer of ATBS and acrylamide was produced. In the same manner as in Example 1, the viscosity of the copolymer was measured. The results are shown in Table 1.

Example 5
In Example 1, the synthesis reaction was carried out with the sulfur trioxide concentration changed to 2% and the reaction residence time changed to 120 minutes. The cake was dried at 110 ° C. for 180 minutes. The obtained ATBS powder was analyzed by HPLC. In the same manner as in Example 1, a copolymer of ATBS and acrylamide was produced. In the same manner as in Example 1, the viscosity of the copolymer was measured. The results are shown in Table 1.

Comparative Example 1
ATBS was continuously synthesized in the same manner as in Example 1. However, the initial charge ratio was maintained without analyzing the concentrations of IBSA and IBDSA by HPLC during the reaction. After the completion of the reaction, the reaction solution was collected, and the concentrations of IBSA and IBDSA were measured by HPLC analysis. The IBSA concentration was 15,000 ppm and the IBDSA concentration was 2,000 ppm. The obtained ATBS slurry was suction filtered through a glass filter to obtain a cake on the glass filter. The cake was washed by pouring acrylonitrile twice the cake solid mass on the cake and suction filtering again. The cake was transferred to a tray and dried at a drying temperature of 80 ° C. for 90 minutes. The obtained ATBS powder was analyzed by LC and the concentrations of IBSA and IBDSA were measured. As a result, the IBSA concentration was 150 ppm and the IBDSA concentration was 80 ppm.

    When the polymerization evaluation was performed in the same manner as in Example 1, the UL viscosity was 2.6 mPa · s.

Although the setting of the SO ₃ excess was the same as in Example 1, the SO ₃ excess actually fluctuates due to slight variations in the fuming sulfuric acid concentration, the concentrated sulfuric acid concentration, and the water content brought in during the production. Where the impurity concentration was measured in the reaction solution and the conditions were to be corrected, the reaction was continued with the initial SO ₃ setting without performing the measurement. As described in Comparative Example 1 above, the results of IBSA and IBDSA The concentration increased and decreased and the quality decreased. Further, the variation in the impurity concentration between production lots increases.

Reference Test Examples 1 and 2, Comparative Reference Test Example 1
40 g of ATBS was dissolved in 40 g of pure water, and a 16.25% by mass aqueous caustic soda solution was added to adjust the pH to 8 to 8.5. At this time, the liquid temperature was measured and cooled as necessary so as not to exceed 25 ° C. After adjusting the pH, pure water was added to obtain 146 g of an ATBS neutralized aqueous solution (30.3 wt%). In a separate container, 370.2 g of a 40% by mass acrylamide aqueous solution, 66.5 g of the ATBS neutralized aqueous solution, and 363.4 g of pure water were mixed. The measured pH of this monomer mixture was 6.8. This monomer mixture was transferred to a polymerization vessel and nitrogen 2 L / min was blown into the vessel. After 1 hour, the liquid temperature was adjusted to 20 ° C. while continuing to blow nitrogen.

    To this monomer solution, 0.39 ml of 100 ppm aqueous copper solution, 3.02 ml of 10 mass% V-50 aqueous solution and 2.02 ml of 1 mass% ammonium persulfate were added. After 15 minutes, the blowing of nitrogen into the monomer solution was stopped, and a change was made to blow nitrogen of 40 ml / min into the gas phase part of the polymerization vessel. The temperature gradually increased due to the polymerization heat, and after reaching 70 ° C. after 2 hours, the temperature gradually decreased. After 8 hours, the polymer gel was taken out and the produced polymer gel was cooled. The resulting gel was cut using a meat chopper. The cut gel was dried at 80 ° C. for 3 hours. Further, the dried gel was applied to a pulverizer. The obtained powder was dissolved in water according to the following method, and its physical properties were measured.

(Salt viscosity)
2.26 g of the powder obtained by the above operation was placed in a 500 ml container, and 400 ml of pure water was added. After dissolving the powder using a jar tester (rotation speed 200 rpm, stirring time 5 hours), 16 g of sodium chloride was added. The mixture was further stirred for 30 minutes to obtain a salt viscosity measurement solution.

    Viscosity was measured using a B-type viscometer with the solution temperature adjusted to 25 ° C. The measurement results are shown in Table 2.

(Amount of water insoluble matter)
0.5 g of the powder obtained by the above operation was placed in a 500 ml container, and 500 ml of pure water was added. The powder was dissolved using a jar tester (rotation speed: 200 rpm, stirring time: 5 hours) to obtain an insoluble matter amount measurement solution.

For the measurement of the amount of insoluble matter, the solution was poured into an 80 mesh sieve, and after 10 minutes, the gel remaining on the sieve was transferred to a measuring cylinder and its volume was measured. The measurement results are shown in Table 2.
(Spinning)
1.5 g of the powder obtained by the above operation was placed in a 500 ml container, and 500 ml of pure water was added. It melt | dissolved with the jar tester (rotation speed 200rpm, stirring time 5 hours), and it was set as the spinnability measurement solution.

  In the measurement of the spinnability, the solution temperature was adjusted to 25 ° C., and the pulling-down rate was measured at 5 mm / second. The measurement results are shown in Table 2.

  The spinnability measurement method used was to place a sample container on a pedestal whose descent rate was adjusted to 5 mm / second, while the lower end of a crow ball (diameter 10 mm) suspended from above the sample container was below the sample liquid level. Immerse to 27 mm. In this state, the pedestal is lowered at a speed of 5 mm / sec. Measure the time required from when the lower end of the glass ball leaves the sample surface to when the kite thread breaks from the glass ball, and multiply the time by the descent speed of the pedestal (5 mm / sec). Thread property (mm).

    As is apparent from the values of salt viscosity and spinnability, it is understood that a polymer having a high molecular weight can be produced by measuring the concentrations of IBSA and IBDSA and controlling the reaction so as to reduce it to 100 ppm or less.

It is a graph which shows the relationship between the ISBA density | concentration in ATBS, and the viscosity of the obtained polymer. It is a graph which shows the relationship between the IBSA density | concentration in ATBS, and the viscosity of the obtained polymer. It is a graph which shows the relationship between sulfur trioxide amount density | concentration and IBSA and IBDSA density | concentration byproduced in manufacture of ATBS. It is a graph which shows the relationship between reaction residence time and IBSA and IBDSA density | concentration byproduced. It is a graph which shows the relationship between the washing | cleaning solvent amount of a cake, and IBSA. It is a graph which shows the relationship between the drying time of cake, temperature, and the IBSA density | concentration in a cake.

Claims (6)

Following formula (1)

The content of 2-methyl-2-propenyl-1-sulfonic acid represented by the formula is 100 ppm or less, and the following formula (2)

The content of 2-methylidene-1,3-propylene disulfonic acid represented by formula (3) is 100 ppm or less.

2-acrylamido-2-methylpropanesulfonic acid represented by A process for producing 2-acrylamido-2-methylpropanesulfonic acid, which comprises reacting acrylonitrile, fuming sulfuric acid and isobutylene, wherein 2-methyl-2-propenyl-1-sulfonic acid present in the reaction system during the reaction and The concentration of 2-methylidene-1,3-propylene disulfonic acid is measured and the concentration of 2-methyl-2-propenyl-1-sulfonic acid exceeds 12000 ppm and / or 2-methylidene-1,3- A method for producing 2-acrylamido-2-methylpropanesulfonic acid, wherein the concentration of sulfur trioxide in the reaction system is reduced when the concentration of propylene disulfonic acid exceeds 6000 ppm. A process for producing 2-acrylamido-2-methylpropanesulfonic acid, in which acrylonitrile, fuming sulfuric acid, and isobutylene are continuously supplied to the reaction system and reacted, and the 2-methyl- existing in the reaction system during the reaction When the concentration of 2-propenyl-1-sulfonic acid and / or 2-methylidene-1,3-propylene disulfonic acid is measured and the concentration of 2-methyl-2-propenyl-1-sulfonic acid exceeds 12000 ppm, and / or Or 2-acrylamido-2-methylpropane characterized by reducing the concentration of sulfur trioxide in fuming sulfuric acid supplied to the reaction system when the concentration of 2-methylidene-1,3-propylene disulfonic acid exceeds 6000 ppm A continuous process for producing sulfonic acid. A process for producing 2-acrylamido-2-methylpropanesulfonic acid, which comprises reacting acrylonitrile, fuming sulfuric acid and isobutylene, wherein 2-methyl-2-propenyl-1-sulfonic acid present in the reaction system during the reaction and The concentration of 2-methylidene-1,3-propylene disulfonic acid is measured and the concentration of 2-methyl-2-propenyl-1-sulfonic acid exceeds 12000 ppm and / or 2-methylidene-1,3- A continuous process for producing 2-acrylamido-2-methylpropanesulfonic acid, characterized in that the reaction time is increased when the concentration of propylene disulfonic acid exceeds 6000 ppm. A crude product of 2-acrylamido-2-methylpropanesulfonic acid in the slurry obtained by the production method according to any one of claims 2 to 4 is separated by filtration to obtain a cake, and then acrylonitrile, acetonitrile, acetone, methanol, A method for producing 2-acrylamido-2-methylpropanesulfonic acid, wherein the cake is washed with one solvent selected from the group consisting of ethanol, 2-propanol, butanol, ethyl acetate, and acetic acid, or a mixed solvent thereof. A crude product of 2-acrylamido-2-methylpropanesulfonic acid in the slurry obtained by the production method according to any one of claims 2 to 4 is filtered to obtain a cake, and then the cake is heated to 60 to 130 ° C. A method for producing 2-acrylamido-2-methylpropanesulfonic acid, which is dried for 10 to 300 minutes.

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