JP3269860B2 - Ion exchange purification system and method for purifying polymer solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system and a method for purifying an acrylonitrile-based polymer solution which is used as a precursor for acrylonitrile-based fibers and a precursor which is a carbon fiber precursor.

[0002]

2. Description of the Related Art Acrylic fiber has properties such as excellent bulkiness, feeling, and clearness of dyeing similar to wool, and is used for a wide range of applications. In order to produce these fibers, a solution prepared by dissolving an acrylonitrile-based polymer as a raw material in an organic solvent or an inorganic solvent is prepared, and is spun by a spinning method such as a wet method, a dry method, or a dry-wet method. It is produced industrially.

The desired acrylonitrile polymer is
Generally, an acrylonitrile monomer as a raw material and a monomer copolymerizable therewith are obtained by a radical polymerization reaction. The acrylonitrile polymer thus obtained is
The polymer is produced as staples or filaments by a wet spinning method, a dry spinning method or a dry-wet spinning method after a step of dissolving the polymer in a solvent for dissolving the polymer. ("Fiber Handbook", 1991 edition, Textile Research Institute) Also, the acrylonitrile-based fiber obtained by the above method is used as a precursor (precursor) of carbon fiber, carbonized through a firing step, and carbonized. Fiberized as fibers. This carbon fiber has high performance in terms of strength, elastic modulus, heat resistance and the like, and is used for various uses including aircraft materials.

The suspension polymerization method, which is a heterogeneous polymerization in an aqueous system, is a method for producing an acrylonitrile-based polymer which has a long history and is widely used. According to this method, there are features such as easy quality control of the polymer, easy recovery of unreacted monomer, and easy control of the entire process. ("Textile Handbook", Raw Materials, edited by The Textile Society of Japan, Maruzen Co., Ltd.) As a method for producing such an acrylonitrile-based polymer,
It is produced by a continuous suspension polymerization method using water as a reaction medium. In this case, an inorganic initiator (such as ammonium persulfate) is generally used as a polymerization initiator. The acrylonitrile-based polymer produced by continuous suspension polymerization is separated by filtration, dried, dissolved in a solvent, and spun by various methods as described above.

[0005] As described above, a monomer mainly composed of an acrylonitrile monomer is used as a reaction solvent by using sulfuric acid-acidified water, and an inorganic initiator (for example, ammonium persulfate-sodium bisulfite-iron redox). When a polymerization reaction is carried out according to (system combination), polymer particles are produced, and an acrylonitrile-based polymer can be obtained in the state of an aqueous dispersion. After completion of the polymerization, an aqueous dispersion of the polymer is separated by filtration, washed and dried to obtain an acrylonitrile-based polymer as a raw material of an acrylic fiber.

[0006] As a reaction vessel for obtaining an acrylonitrile-based polymer by continuous aqueous suspension polymerization, it is preferable to use a reaction vessel made of aluminum. When an acrylonitrile-based polymer is produced by an aqueous continuous suspension polymerization reaction, in a stainless steel reaction vessel or a glass-lined reaction vessel, scale is generated due to the adhesion of the acrylonitrile-based polymer, and it is substantially used continuously. Becomes impossible. When an aluminum-made reaction vessel is used as the reaction vessel, it is said that the formation of scale is prevented by the corrosion and dissolution of the aluminum surface because the inside of the reaction system is an acidic aqueous solution.

[0007] In order to terminate the polymerization reaction, a polymerization terminator is added. As a polymerization terminator when the above polymer is produced by aqueous suspension polymerization, it is necessary to maintain the function of neutralizing the acidic aqueous solution of the reaction system, sodium oxalate,
Ethylenediaminetetraacetate sodium salt and an aqueous electrolyte solution of sodium bicarbonate are mentioned.

As described above, the acrylonitrile-based polymer is produced in the presence of an electrolyte by a polymerization initiator, an electrolyte by corrosion of a polymerization vessel, an electrolyte by a polymerization terminator, and the like. In addition, the acrylonitrile-based polymer forms polymer particles of several tens of microns as described above and becomes dispersed particles in an aqueous system as the polymerization reaction proceeds, but the above-mentioned various electrolytes are mixed into the polymer particles. Will be. Therefore, in order to produce an acrylonitrile-based polymer by aqueous continuous suspension polymerization as described above, it is necessary to wash the produced polymer with a sufficient amount of water. Thus, although the surface of the produced polymer can be washed, it is impossible to wash and remove the electrolyte trapped inside the polymer with water.

Nevertheless, in the production of acrylonitrile-based polymers by the current aqueous suspension polymerization, the process proceeds to a drying step with insufficient washing, and is dissolved in a solvent that dissolves the acrylonitrile-based polymer. An acrylonitrile-based polymer dope is used, and spinning is performed in a wet, semi-dry, or dry manner, and then acrylic fibers are produced. As described above, the acrylonitrile-based polymer dope solution in which the impurities such as the electrolyte are mixed causes various problems in recent production of high-quality acrylic fibers.

For example, when a dope solution used for producing an acrylic fiber is heated (about 100 ° C.) for a long time, yellow coloring becomes remarkable, and the dope solution itself gels to lower the fluidity of the solution. This is considered to be due to the impurities contained in the acrylonitrile-based polymer. It is also believed that the impurities cause yellowing of the acrylic fiber itself as a product, which has a great effect on the quality of high-quality acrylic fiber. Similarly, when the dope solution itself gels and lowers the fluidity of the solution, stable spinnability cannot be secured,
As a result, a yarn breakage phenomenon occurs.

[0011]

When an acrylonitrile-based polymer obtained by the aqueous suspension polymerization method is used as a raw material to produce an acrylic fiber or a carbon fiber obtained by firing the acrylic fiber, the aqueous suspension polymerization method has The problem is,
Impurities that cannot be avoided when the polymer is produced in the same manner remain in the polymer. These impurities cause problems in spinning and quality when producing acrylic fibers as products or carbon fibers obtained by firing acrylic fibers.

An object of the present invention is to solve the problems of the aqueous suspension polymerization system and to obtain acrylonitrile which is industrially advantageous and suitable for producing acrylic fibers or carbon fibers obtained by firing acrylic fibers. An object of the present invention is to provide an apparatus for purifying a polymer dope solution.

[0013]

The gist of the present invention is to provide an acrylonitrile polymer obtained by aqueous suspension polymerization using an inorganic redox initiator, and an organic solvent capable of dissolving the polymer. From a solution consisting of
An object of the present invention is to provide a system and a method for purifying and removing impurities such as an iron compound or an ion thereof, an aluminum compound or an ion thereof, which are inorganic electrolytes mixed into the polymer, by using a substance having an ion exchange function that is not dissolved in the organic solvent. .

The dope solution has a viscosity of several hundred poise in order to make the acrylonitrile polymer concentration suitable for spinning. Therefore, it is the gist of the present invention to remove low molecular compounds such as inorganic electrolytes as impurities from such a high viscosity solution.

Hereinafter, the present invention will be described in detail.

According to the present invention, there is provided a storage tank for storing a polymer solution, a supply tank for supplying an ion-exchangeable substance,
A strainer with a scraper internally provided with a scraper and partially provided with a purified solution discharge part for separating the purified solution and the substance and discharging the separated solution to the outside of the apparatus; And an ion exchange purification system for a polymer solution, characterized by comprising at least a solution circulation system between the strainer with the scraper and the storage tank. Between the discharge tank and the strainer, actively circulating a solution obtained by dissolving an acrylonitrile-based polymer in an organic solvent obtained by aqueous suspension polymerization using at least an inorganic redox initiator. At the same time, a substance capable of ion exchange is continuously supplied from the supply tank to the inside of the strainer, and necessary for the next step. While the Purified solution is separated from the material consists method for discharging a next step, it is to reliably purify remove inorganic electrolyte or ions as an impurity from the acrylonitrile-based polymer solution.

Examples of the inorganic redox initiator include commonly used inorganic peroxides such as ammonium persulfate and potassium persulfate. As a reducing agent used as a polymerization aid, sodium sulfite, ammonium sulfite,
Representative examples include sodium bisulfite, ammonium bisulfite, sodium thiosulfate, the same ammonium, sodium dithionite, sodium formaldehyde sulfoxylate, L-ascorbic acid, dextrose, etc., such as ferrous sulfate or copper sulfate Can also be used in combination. Among them, a combination of ammonium sulfite-sodium hydrogen sulfite (ammonium) -ferrous sulfate is preferable.

The acrylonitrile polymer used in the present invention is obtained from an acrylonitrile monomer or a monoolefinic monomer copolymerizable with the monomer. Here, the acrylonitrile-based polymer needs to contain at least 60% by weight of an acrylonitrile monomer. If the content of the acrylonitrile monomer is less than 60% by weight, the acrylonitrile-based synthetic fiber cannot have the inherent fiber function. Here, as the copolymerizable monoolefinic monomer, for example, acrylic acid, methacrylic acid, itaconic acid, acrylamide, vinyl acetate, styrene, vinyl chloride, vinylidene chloride, maleic anhydride, N-substituted maleimide, butadiene, Isoprene and the like can be mentioned.

The organic solvent used in the present invention must be a solvent that dissolves the acrylonitrile polymer. Among them, dimethylformamide, dimethylacetamide, and dimethylsulfoxide are preferred. The acrylonitrile polymer 5 obtained by aqueous suspension polymerization
The dope solution is preferably composed of 35% by weight and 95 to 65% by weight of the organic solvent capable of dissolving the acrylonitrile-based polymer. Acrylonitrile polymer 5-35
If the content is less than 5% by weight, satisfactory spinnability of acrylic fiber cannot be secured because the concentration of the polymer is too low. On the other hand, if it exceeds 35% by weight, the viscosity of the polymer solution becomes too high, and the spinning property cannot be ensured.

Examples of the substance having an ion exchange ability which is not dissolved in the organic solvent include a cross-linked ion exchange resin or ion exchange fiber.
A crosslinked ion exchange resin composed of styrene is generally and preferably used. In the state of a dope solution in which the acrylonitrile-based polymer is dissolved in an organic solvent, in order to purify and remove impurities of the polymer with a cross-linked ion exchange resin, the cross-linked ion exchange resin has an affinity with an organic solvent. This is because it is necessary that the resin be a crosslinked resin that does not dissolve in the organic solvent.

Examples of the functional group having ion exchange ability include a strong cation exchange resin having a sulfonic acid group. When the ionic species purified by ion exchange are both cation species and anion species, the cation species comprises a strong cation exchange resin having a sulfonic acid group and a strong anion exchange resin having a quaternary amino group. It is preferred to use both ion exchange resins. For capturing heavy metals, chelating resins of iminodiacetic acid type and polyamine type are mentioned. Further, a weak cation exchange resin composed of methacrylic acid and acrylic acid, and a weak anion exchange resin composed of primary, secondary, and tertiary amines can be used. Further, both of these weak cation exchange resins and the same weak anion exchange resins can be used.

Among them, a strong cation exchange resin having a sulfonic acid group, or both a strong cation exchange resin having a sulfonic acid group and a strong anion exchange resin having a quaternary amino group are used. It is particularly preferred to do so.

The ion exchange resin used in the present invention is preferably used in an amount of 0.01 to 100% by weight based on 100% by weight of the acrylonitrile polymer solution.
If the amount is less than 0.01% by weight, the ion exchange capacity will be significantly reduced, making it impractical. If it exceeds 100% by weight, it is not practical because it is economically disadvantageous and it takes more time than necessary to recover the ion exchange resin.

The purification of the acrylonitrile polymer solution with an ion exchange resin is preferably carried out at a temperature in the range of 30 to 150 ° C. If the temperature is lower than 30 ° C., the viscosity of the acrylonitrile-based polymer solution increases, the fluidity becomes poor, and the ion exchange reaction hardly proceeds. Also, 150
When the temperature exceeds ℃, the heat stability of the ion exchange resin used is insufficient, and it is practically impossible to use the resin for a long time.

In the purification of the acrylonitrile-based polymer solution by the ion-exchange resin according to the present invention, the ion-exchange substance is added to the acrylonitrile-based polymer solution, and the mixture is dispersed while the mixed dispersion dope solution is circulated and mixed. An object of the present invention is to continuously separate a potential substance from a dope solution and to purify and remove an inorganic electrolyte or an ion thereof as an impurity from the acrylonitrile-based polymer solution.

Therefore, the ion exchange purification system of the present invention comprises a tank for the dope solution, a strainer with a scraper, and a supply tank for the ion exchange resin, and the tank for the dope solution and the strainer are actively circulated. The strainer is connected to a supply tank for ion exchange resin. In the dope solution circulating between the dope solution tank and the scraper, a predetermined amount of ion-exchangeable substance is supplied from the ion exchange resin supply tank into the scraper, and the dope is mixed and stirred in the scraper. The inorganic electrolyte, which is an impurity present in the solution, is purified by ion exchange. Most of the dope solution in the scraper returns to the dope solution tank via the circulation path, and the dope solution required for the spinning section, which is the next step, is separated from the ion exchange resin through a filter material such as a wire mesh. Is positively sent to the spinning section of the next step by the supply pump. By repeating such a circulating flow, the inorganic electrolyte which is an impurity present in the dope solution is sufficiently ion-exchanged and purified. In such a system, the more the circulation amount of the dope solution, the more efficiently the ion exchange is performed. In the case of continuous ion exchange purification, it is necessary to periodically remove the ion exchange resin accumulated in the scraper. For this purpose, it is useful as a practical industrial facility to operate the strainer intermittently to periodically separate and remove substances having ion exchange ability.

After the acrylonitrile polymer dope solution is purified by the method of the present invention, the acrylonitrile fiber produced by spinning by a wet, semi-dry or dry method is added to an iron compound as an impurity as an inorganic electrolyte. Or 0 to 3 ppm of the ion, preferably 0 to 1 ppm
ppm, aluminum compound or its ion is 0 to 10
ppm, preferably 0-5 ppm. Here, the iron compound or its ion, or the aluminum compound or its ion, is that ferrous sulfate is used as a polymerization initiator used in the aqueous suspension polymerization defined by the present invention, and that the aqueous suspension Since the aluminum kettle is used as a reaction kettle in the polymerization reaction and the reaction system is an acidic aqueous solution, the aluminum kettle corrodes and dissolves, so that the above-mentioned metals or their ions always exist as impurities in the purified acrylonitrile-based polymer. To do that.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings and embodiments. 1 and 2 show a typical embodiment of the present invention. FIG. 1 is a schematic diagram of an ion exchange purification system of a dope solution of the present invention, and FIG. 2 is a diagram of a strainer with a scraper employed in the system. It is a longitudinal cross-sectional view which shows a schematic structure.

The dope solution ion-exchange refining apparatus constituting the system of the present invention comprises a dope solution storage tank 1, a strainer 2 having a scraper 3 therein, and an ion exchange resin supply tank 4 as main components. Consists of Here, since the storage tank 1 for the dope solution and the supply tank 4 for the ion exchange resin do not have a special configuration, detailed description thereof will be omitted.

As shown in FIG. 2, in the strainer 2, a rotary scraper 3 rotating around a vertical axis is provided in two stages vertically inside a strainer main body 2a formed of a cylindrical closed container. The rotating scraper 3 is an electric motor 5
Driven by On the inner peripheral wall surface of the strainer main body 2a, a 100-mesh stainless steel wire net 6 is provided at a predetermined interval from the inner peripheral wall surface and close to the rotational outer peripheral surface of the rotary scraper 3. A dope solution inlet 2 is provided at the upper end of the cylindrical side wall of the strainer body 2a.
b, a dope solution outlet 2c is formed at the bottom of the strainer body 2a, and a purified dope solution outlet 2d is formed at the lower end of the cylindrical side wall. Further, an ion exchange resin addition port 2e is formed in the upper surface of the strainer main body 2a. A jacket 7 is provided around the cylindrical side wall of the strainer main body 2a and around the dope solution inlets / outlets 2b to 2d to heat the dope solution to a predetermined temperature.

According to the dope solution ion exchange purification system shown in FIG. 1, the dope solutions are connected to each other by piping so as to circulate between the storage tank 1 and the strainer 2. 1 and 2, the dope solution inlet 2b of the strainer 2 and the outlet 1 of the dope solution storage tank 1
a is connected via a pipe 8a, and the dope solution outlet 2c of the strainer 2 and the inlet 1b of the dope solution storage tank 1 are connected via a pipe 8b.

According to the illustrated example, the dope solution inlet 2
b and a pipe 8a connecting the outlet 1a of the dope solution storage tank 1 with an on-off valve 10a and a filter 10 respectively.
The two rows of bypass passages 9a and 9b in which b are interposed are provided in parallel. In this embodiment, the filter 10b employs a 100-mesh stainless steel wire mesh. The bypass passages 9a and 9b may be provided in the pipe 8b connecting the dope solution outlet 2c and the inlet 1b of the dope solution storage tank 1 instead of being provided in the pipe 8a. A screw pump 11 for actively returning the dope solution present inside the strainer 2 to the dope solution storage tank 1 is provided in the middle of the pipe 8b.

An ion-exchange resin supply tank is connected to the ion-exchange resin addition port 2e of the strainer 2 via a pipe 8c, and a dope solution drain provided at the lower end of the cylindrical side wall of the strainer body 2a. The outlet 2d is connected via a dope solution supply pump 12 to a pipe connected to a spinning section in a next step (not shown).

Now, the ion exchange purification method according to the system of the present invention having such a configuration will be specifically described. The dope solution sent from the dope solution storage tank 1 to the strainer 2 is supplied to the ion exchange resin supply tank 4 through the ion exchange resin supply tank 4. Agitated by the scraper 3 rotating inside the strainer 2 together with the exchange resin. At this time, the scraper 3 is driven and rotated at 30 to 50 rpm by the electric motor 6, and at the same time, the ion exchange resin is continuously supplied from the ion exchange resin addition port 2e of the strainer 2.

The dope solution and the ion-exchange resin stirred inside the strainer 2 flow out from a dope solution outlet 2c provided at the bottom of the strainer 2, and are positively moved to the dope solution storage tank 1 by a screw pump 11. Will be returned. The dope solution stored in the dope solution storage tank 1 is sent again to the strainer 2 through the pipe 8a together with the ion exchange resin mixed inside the strainer 2, but at this time, excess ion exchange resin is bypassed in two stages. The on-off valves 10a of the passages 9a and 9b are opened to separate and collect through the filter 10b.

On the other hand, of the dope solution ion-exchanged inside the strainer 2, the purified dope solution in an amount required to be supplied to the spinning section in the next step is made of a stainless steel wire mesh mounted inside the strainer 2. The ion exchange resin is separated through 6 and supplied to the spinning section (not shown) from the dope solution outlet 2 d by the dope solution supply pump 12.

Now, the present invention will be described in further detail with reference to Examples. In addition, in the following description, a part and% show a weight part and weight%.

(Example 1) 35 parts of ion-exchanged water (set to PH3) were placed in a polymerization reactor having a capacity of 80 L with stirring (the container was made of aluminum and the stirring blade was an aluminum-coated turbine type).
L were charged 98.5 parts of acrylonitrile, 1.5 parts of methacrylic acid, 1.5 parts of ammonium persulfate, 4.5 parts of ammonium bisulfite, ferrous sulfate (FeSO ₄ · 7H ₂
O) Each was dissolved in ion-exchanged water so that 0.00005 part and 0.085 part of sulfuric acid were obtained, and the supply was continuously started. Further, ion-exchanged water was separately supplied so that the total amount was 400 parts. The polymerization temperature was maintained at 60 ° C., sufficient stirring was performed, the raw materials were continuously supplied for an average staying time of 80 minutes, and the polymerization reaction was performed. A polymer aqueous dispersion was continuously taken out from the overflow port of the reactor, and 0.5 parts of ammonium oxalate and 1.5 parts of ammonium bicarbonate were dissolved in 100 parts of ion-exchanged water to terminate polymerization. 0.2% aqueous solution
After adding further at the speed of the part, and further adding ion-exchanged water,
The unreacted monomer and the residue of the excessive polymerization aid were washed and removed with a rotary filter. The obtained wet polymer was formed into pellets by a screw type extruder, and then dried by a through-air drier to obtain an acrylonitrile polymer shown in Table 1. 22 parts of the dried acrylonitrile polymer was dissolved in 78 parts of dimethylformamide to prepare a polymer solution (dope solution).

The dope solution was continuously passed through the dope solution ion exchange purification system shown in FIG. Here, the ion exchange resin used in the dope solution purification apparatus is a strong ion exchange resin having a sulfonic acid group (Diaion PK2
28LH, manufactured by Mitsubishi Kasei Corporation). The scraper installed in the dope solution refining device is driven by a stirring drive.
Stir and rotate at 50 rpm. At the same time, the ion exchange resin is continuously supplied into the scraper. 10 strainers
It is composed of a 0 mesh wire mesh. Circulation between the dope solution storage tank and the strainer was performed by a screw pump. Excess ion exchange resin was separated and collected through a filter through a bypass passage. The required amount of the purified dope solution required for spinning was passed through a wire mesh in a scraper to separate the ion-exchange resin, and then guided to a spinning unit by a supply pump. The ion-exchange resin to be added here is a sulfonic acid type, washed sufficiently with water, dried, and immersed and swollen with dimethylformamide. Hot water at 60 ° C. was flowed through each jacket of the strainer to heat the dope solution flowing inside the strainer. After continuously supplying the dope solution to the dope solution purification device at a rate of 250 g / min, 100 holes,
It is spun into a 55% aqueous dimethylformamide solution (30 ° C.) by a dry-wet spinning method (liquid surface space distance: 5 mm) through a 0.13 mmφ die, stretched 5 times, and heat-set at 115 ° C. 5 denier acrylic fibers shown in Table 1 were obtained. As is clear from this table, the ion exchangeability was good, and the aluminum ions and iron ions in the dope solution could be sufficiently removed.

[0040]

[Table 1]

[0041]

As is apparent from the above description, according to the ion exchange purification system of the present invention, the dope solution, which is an acrylonitrile-based polymer solution obtained by aqueous suspension polymerization using an inorganic redox initiator, Actively circulating and exchangeable substances in a stirring state and actively supply the necessary amount of the purified dope solution to the spinning unit in the next step on the way, so that the inorganic electrolyte mixed in the dope solution or The ions are sufficiently exchanged and removed, and it is possible to realize a high quality acrylic fiber or a carbon fiber obtained by firing the fiber as a final product.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an outline of an ion exchange purification system for an acrylonitrile polymer solution which is a preferred embodiment of the present invention.

FIG. 2 is a longitudinal sectional view schematically showing an example of a strainer applied to the system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dope solution storage tank 2 Strainer with a scraper 2a Strainer main body 2b Dope solution inlet 2c Dope solution outlet 2d Purified dope solution outlet 2e Ion exchange resin addition port 3 Scraper 4 Ion exchange resin supply tank 5 Electric motor 6 Wire mesh 7 Jacket 8a , 8b piping 9a, 9b bypass passage 10a opening / closing valve 10b filter 11 screw pump 12 supply pump

──────────────────────────────────────────────────続 き Continuing on the front page (72) Katsuhiko Ikeda 20-1, Miyukicho, Otake City, Hiroshima Prefecture Mitsubishi Rayon Co., Ltd. Otake Works (72) Inventor Yoshio Manabe 20-1, Miyukicho, Otake City, Hiroshima Prefecture Mitsubishi (56) References JP-A-5-39313 (JP, A) JP-A-3-210304 (JP, A) JP-A-63-286405 (JP, A) JP-A-56- 159317 (JP, A) JP-A-5-237399 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08F 6/00-6/28

Claims (7)

(57) [Claims] 1. An apparatus comprising: a storage tank for storing a polymer solution; a supply tank for supplying a substance having an ion exchange ability; and a scraper therein, wherein the partially purified solution and the substance are separated. And a strainer with a scraper provided with a purified solution discharge section to be discharged to the outside, and connecting the inside of the strainer with the scraper and the supply tank, and at least between the strainer with the scraper and the storage tank. An ion exchange purification system for an acrylonitrile-based polymer solution, comprising a circulation system for the solution. 2. The ion exchange purification system according to claim 1, wherein filtration means for separating and recovering the ion exchangeable substance is provided in the circulation system. 3. The ion exchange purification system according to claim 1, wherein said strainer is provided with heating means for heating the inside to a predetermined temperature. 4. The ion exchange purification system according to claim 1, wherein the scraper is a rotary scraper. 5. An ion exchange purification system according to claim 1, wherein said storage tank and said strainer are
At the same time as actively circulating the acrylonitrile-based polymer solution obtained by aqueous suspension polymerization using at least an inorganic redox initiator, the ion-exchangeable substance is continuously supplied from the supply tank to the inside of the strainer. ,
A method for ion-exchanging an acrylonitrile-based polymer solution, comprising discharging a purified solution in an amount required for the next step while separating the purified solution from the substance. 6. The method according to claim 1, wherein the ion-exchangeable substance is an organic compound.
Crosslinking that has affinity with solvent and does not dissolve in the same organic solvent
6. The ion exchange according to claim 5, which is a type ion exchange resin.Exchange
Law. 7. The temperature of the solution during purification is from 30 to
Ion exchange of actuation method according to claim 5, wherein 0.99 ° C..