JPH0819537B2 - Method for producing polymer acid - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a water-soluble polymeric acid. Specifically, when the salt of the water-soluble polymer acid is released to obtain the polymer acid, the salt of the water-soluble polymer acid is removed by an electrodialysis device in which an amphoteric ion exchange membrane and a cation exchange membrane are alternately arranged. The step of liberating to obtain a polymeric acid, the step of neutralizing the mixed solution of the liberated neutral salt and the acid, the neutralized solution is treated with an electrodialyzer equipped with a bipolar membrane and an anion / cation exchange membrane. The present invention relates to a method for producing a polymeric acid, which comprises the step of regenerating with alkali.

[Prior art and its problems]

Conventionally, as a method of obtaining a free water-soluble polymeric acid, for example, a method of polymerizing a water-soluble unsaturated acid, or a salt of a polymeric acid is electrodialyzed using an acid, an ion exchange resin or an ion exchange membrane. There is a method of converting the polymer acid.

However, in the method of polymerizing a water-soluble unsaturated acid,
It has been difficult to polymerize any desired polymeric acid.

Further, in the method of converting a salt of a polymeric acid with an acid, it is necessary to act an acid stronger than the polymeric acid, so that a strong acid salt is generated as a by-product and separation from the desired polymeric acid is caused. It will be difficult. Furthermore, the method using an ion exchange resin has a problem that the conversion rate to a polymer acid is low and the ion exchange resin needs to be regenerated.

[Problems to be solved by the invention]

In contrast, a method of converting a water-soluble polymer acid salt into a polymer acid by electrodialysis using a cation exchange membrane is disclosed in
As described in JP-A-59-173282, it is possible to solve the problems of the prior art as described above and obtain a desired water-soluble polymeric acid, but the salt of the polymeric acid diffuses through the cation exchange membrane. , The conversion rate to polymer acid is extremely poor because it permeates. Therefore,
In the method by electrodialysis using such a cation exchange membrane, it is necessary to increase the concentration, capacity, etc. of the acid used in order to improve the conversion rate of the salt of the polymer acid into the polymer acid. However, the cost becomes very high, which is not industrially preferable.

[Means for solving problems]

In view of the above, the present invention is an extremely efficient polymer acid that can recover the polymer acid from the salt of the polymer acid at a high conversion rate and a high yield and that can recycle the used waste acid for reuse. The present invention provides a method for manufacturing the same.

That is, in the present invention, when the salt is released from a salt solution of a water-soluble polymer acid to produce the polymer acid, an amphoteric ion exchange membrane and a cation exchange membrane are alternately arranged to form a polymer acid production chamber. The salt solution of the water-soluble polymeric acid is supplied to the polymeric acid production chamber of the electrodialysis device (I) in which the acid chambers are alternately formed, and the acid solution is supplied to the acid chamber for electrodialysis to produce the polymeric acid. Polymeric acid recovery step (A) for recovering a mixed solution of a polymeric acid solution from the chamber and a salt solution released from the salt solution of the water-soluble polymeric acid and an undialyzed acid solution from the acid chamber, the mixing Neutralization step (B) in which the solution is neutralized with an alkaline solution to obtain a neutralized solution, a bipolar membrane, a cation exchange membrane and an anion exchange membrane are sequentially arranged, and an alkali production chamber, a desalination chamber and an acid production chamber are sequentially provided. The neutralization solution obtained in the neutralization step (B) is supplied to the desalting chamber of the electrodialysis device (II) formed in Electrolyzed by passing an alkaline solution through the alkali generation chamber and an acid solution through the acid generation chamber, and electrolyzing the alkali solution corresponding to the cation component of the neutralization solution from the alkali generation chamber, and the anion of the neutralization solution from the acid generation chamber. A regeneration step (C) for recovering an acid solution corresponding to an ionic component and an alkaline solution obtained in the regeneration step (C) as an alkaline solution in the neutralization step (B) and / or an acid solution as an electrodialyzer ( A method for producing a polymeric acid, which comprises a circulation step (D) in which the acid solution of I) is circulated.

The salt of the water-soluble polymeric acid used in the present invention is a polymer having a part or all of a salt in the molecule, for example, an acid group such as a carboxylic acid group, a sulfonic acid group, a phosphoric acid group or a sulfuric acid group. . For example, sodium alginate obtained from nature, or a water-soluble polymer acid obtained by partially or completely converting a polymerizable monomer having an acid group as described above into a salt such as Na, K, Ca, Ba before or after the polymerization. For example, salt.

As the polymer having a carboxylic acid group as described above,
For example, it is a polymer of a monomer such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, and itaconic acid. Further, the polymer having sulfonic acid is, for example, a polymer of monomers such as vinyl sulfonic acid, parasterene sulfonic acid, and 2-hydroxy-3-allyloxypropyl sulfonic acid.
Examples of the polymer having a phosphate group include mono (2
Hydroxyethyl methacrylate), mono (3chloro-
It is a polymer of monomers such as 2-hydroxypropyl methacrylate) and acid phosphate. The polymer having a sulfate group is, for example, a polymer of monomers such as allyl sulfuric acid and ester. Furthermore, monomers capable of polymerizing with monomers having these acid groups, such as acrylic acid ester, methacrylic acid ester, acrylonitrile, methacrylonitrile, styrene, α-methylstyrene, vinyl acetate, acrylamide, N-methylol acrylamide, NN ^1-
Examples thereof include copolymers with dimethyl, aminoethyl methacrylate and the like.

The amphoteric ion exchange membrane constituting the electrodialysis device (I) of the present invention is one in which a cation exchange group and an anion exchange group are uniformly mixed. For example, as a cation exchange group, a conventionally known sulfonic acid is used. , Carboxylic acid groups and the like are preferable, and anion exchange groups are quaternary ammonium bases such as quaternary pyridinium bases, sulfonium bases, and phosphonium bases, and onium bases, and primary, secondary, and tertiary bases. A weak base such as an amino group is preferably used. These amphoteric ion exchange membranes are so-called hydrogen ion selective permeable membranes, and any conventionally known membrane can be used as long as it is a membrane having such properties. Further, as the cation exchange membrane, a membrane that selectively permeates only cations, and a generally known membrane having a sulfonic acid group, a carboxylic acid group or the like can be generally used. The cation exchange membrane constituting the electrodialysis device (II) is preferably a monovalent selective cation exchange membrane having an anion exchange base layer on at least one surface of the cation exchange membrane.

Further, the anion exchange membrane constituting the electrodialysis device (II) of the present invention may be any conventionally known one capable of selectively permeating anions, but particularly preferable is a weakly basic anion exchange membrane. Is. Furthermore, the bipolar membrane is a composite membrane having a cation exchange base layer on one side and an anion exchange base layer on the other side, and in particular, the cation exchange base layer has 10% to 60% of the total thickness. Any known membrane such as a conventionally known bipolar membrane, composite ion exchange membrane, amphoteric membrane, etc. can be used.

The dialysis conditions of the electrodialyzers (I) and (II) of the present invention are preferably current density of 0.5 to 20 A / dm ² and temperature of 10 to 50 ° C.
Thus, by electrodialysis, a polymeric acid can be produced with a high conversion rate. The operation of the electrodialyzers (I) and (II) in the present invention is not particularly limited, and known means and operations can be adopted as they are. For example, an acid solution is supplied to the acid chamber of the electrodialyzer (I), and as the acid solution, it is most industrial to circulate and use the acid solution recovered in the acid generator of the electrodialyzer (II). This is the most preferable process. As the acid solution, generally known strong organic and inorganic acids are preferably used, and for example, sulfuric acid, nitric acid, alkylsulfonic acid and the like are preferable. Further, it is preferable that an acid solution of the same kind as the acid solution to be recovered be passed through the acid generation chamber of the electrodialyzer (II).

Further, it is most industrially preferable that the alkaline solution supplied to the neutralization step (B) of the present invention is an alkaline solution recovered from the alkaline generation chamber of the electrodialyzer (II),
Generally, an alkaline solution such as sodium hydroxide or potassium hydroxide is suitable. Therefore, it is preferable to circulate these alkaline solutions in the alkaline generating chamber of the electrodialysis device (II).

The method of the present invention will be described with reference to the drawings. However, the drawings show only one example of an apparatus used by the method of the present invention, and the present invention is not limited thereby.

Electrodialysis device (I) used in high-molecular acid recovery step (A)
1, the cation exchange membranes 15 and the amphoteric ion exchange membranes 16 are alternately arranged, and the polymer acid generating chambers 7 and the acid chambers 8 are alternately formed. A salt solution 4 of a polymeric acid, which is an electrodialysate, is supplied to a polymeric acid production chamber 7, and an acid solution 14 is supplied to an acid chamber 8. Then, only H ⁺ is permeated by the amphoteric ion exchange membrane 16, and the salt of the water-soluble polymeric acid is converted into the polymeric acid 5 at a high conversion rate and recovered. On the other hand, the released salt is the cation exchange membrane15.
Permeate to form a neutral salt in the acid chamber 8 and is supplied to the acid chamber 8 and recovered as a mixed solution 6 with an undialyzed acid solution which has not been subjected to electrodialysis.

The mixed solution 6 recovered in the polymer recovery step (A) is neutralized in the neutralization step (B) with the undialyzed acid solution contained therein to obtain a neutralized solution. Then, the neutralization solution 9 is liquid-fed to the electrodialysis device (II) in the regeneration step (C). As the neutralizing device 3 used in the neutralizing step (B), a known device is used, and a known method for neutralizing means is not particularly limited and may be used.

The electrodialyzer (II) 2 used in the regeneration step (C) has a bipolar membrane 18, a cation exchange membrane 19 and an anion exchange membrane 17, which are sequentially arranged, and has an alkali production chamber 11, a desalination chamber 12 and an acid production chamber 10.
Are sequentially formed. The desalting chamber 12 is supplied with the neutralization solution obtained in the neutralization step (B), and the alkaline solution is passed through the alkali producing chamber 11 and the acid producing chamber 10 to perform electrodialysis. The cations in the salt chamber 12 permeate the cation exchange membrane 19 and proceed to the alkali generation chamber 11 where the bipolar membrane 18
By combining with the more generated hydroxyl group, caustic is generated in the alkali generation chamber 11. Further, the anions in the desalting chamber 12 permeate the anion exchange membrane 17 and proceed to the acid generating chamber 10, where
At 10, it combines with H ⁺ generated from the bipolar film 18 to generate an acid corresponding to the anion. The rest of the solution electrodialyzed in the desalting chamber 12 is discharged from the electrodialyzer (II) as a waste liquid, and the alkali solution produced in the alkali producing chamber 11 and the acid solution produced in the acid producing chamber 10 are medium if necessary. Japanese process (B)
Can be circulated and used as the alkaline solution of the above or as the acid solution of the electrodialyzer (I).

Example 1 A 20% aqueous sodium polyacrylate solution (Na content 58 g /) obtained by polymerizing an aqueous sodium acrylate solution and an aqueous ammonium persulfate solution was treated according to the flow sheet of FIG. 1 to give polyacrylic acid, an acid and an alkali. Was recovered.

Electrodialysis device (I) used in polymer recovery step (A)
Is an electrodialysis tank in which Neoceptor CSV (Tokuyama Soda Co., Ltd. amphoteric ion exchange membrane) and Neoceptor CM (the same strong acidic cation exchange membrane) are alternately arranged to divide into a polymer acid production chamber and an acid chamber. TS-2 type (manufactured by Tokuyama Soda Co., Ltd .: effective film area ² dm ² / pair)
It was used. The electrodialyzer (II) used in the regeneration step (C) was a bipolar BPM (manufactured by Tokuyama Soda Co., Ltd., a bipolar membrane having a strong acid cation exchange group and a strong acid group anion exchange group), Neoceptor CMS ( Tokuyama Soda Co., Ltd. monovalent selective cation exchange membrane) and Neosepta ACM (weakly acid-based anion exchange membrane) are alternately arranged to form an alkali generation chamber,
An electrodialysis tank with a desalting chamber and an acid generating chamber formed sequentially (manufactured by Tokuyama Soda Co., Ltd .; 3 chambers for double decomposition, effective membrane area ² dm ² / pair)
It was used. A neutralization precipitation tank was provided as the neutralization device in the step (B).

In the electrodialysis device in the step (A), a sodium polyacrylate aqueous solution (Na content 58 g /) having a polymerization rate of 20% is produced as a salt of a water-soluble polymer acid, and 3 N sulfuric acid is produced as a conversion acid. Supply to chamber and acid chamber, average current density 4A
It was dialyzed at / dm ² , 27 ° C. As a result, the conversion rate from sodium polyacrylate to polyacrylic acid was 96%, and H ⁺
The current efficiency was 99%. The mixed solution (waste liquid) of the salt solution recovered from the acid chamber and the undialyzed acid solution was an acid and a neutral salt, the concentrations of which were 0.54N sulfuric acid and 1.2N neutral salt. The waste liquid was supplied to a neutralization tank and was first neutralized with sodium hydroxide. The neutralized filtrate is supplied to the desalting chamber of the electrodialyzer (II) in the step (C), and diluted sodium hydroxide and diluted sulfuric acid are supplied to the alkali generation chamber and the acid generation chamber, respectively, at a temperature of 35 ° C and an average current. It was electrodialyzed at a density of 5 A / dm ² . As a result, a regenerated solution of 3.1 normal sulfuric acid and 3.0 normal sodium hydroxide was obtained.

Then, the regenerated acid was supplied to the acid chamber of the electrodialysis tank in the step (A) and used as a regenerated acid, and the regenerated alkali was used as a neutralizing agent in the neutralization step.

Example 2 Sodium polystyrene sulfonate aqueous solution (Na content 25 g /
) Was treated according to the flow sheet of FIG. 1 to recover polystyrene sulfonic acid, acid and alkali.

The electrodialysis method was performed under the same conditions and steps as in Example 1. As a result, a polystyrene sulfonic acid having a conversion of 98% was obtained, and 3.2N of sulfuric acid and 3.1N of sodium hydroxide were obtained.

[Brief description of drawings]

FIG. 1 is a flow chart showing a typical manufacturing method of the present invention. In FIG. 1, 1 is an electrodialyzer (I) for obtaining a polymeric acid, 2 is an electrodialyzer (I) for regenerating acid and alkali.
I), 3 is a neutralization tank, 4 is a polymeric acid salt solution, 5 is a polymeric acid solution, 6 is a mixed solution of a salt solution and an undialyzed acid solution, 9
Is a neutralized solution, 13 is a regenerated alkaline solution, and 14 is a regenerated acid solution. Further, in the electrodialysis device 1 , 7 is a high molecular acid production chamber, 8 is an acid chamber, and 10 in the electrodialysis device 2 . Is an acid production chamber, 11 is an alkali production chamber, and 12 is a desalination chamber. In the electrodialyzers (I) and (II), 15 is a cation exchange membrane, 16 is an amphoteric ion exchange membrane, and 17
Is an anion exchange membrane, 18 is a bipolar membrane, and 19 is a monovalent ion-permeable cation exchange membrane.

Claims (1)

[Claims] 1. When a polymeric acid is produced by releasing the salt from a salt solution of a water-soluble polymeric acid, an amphoteric ion exchange membrane and a cation exchange membrane are alternately arranged to produce a polymeric acid generating chamber and an acid. A salt solution of a water-soluble polymeric acid and an acid solution into the acid chamber of the electrodialysis apparatus (I) in which the chamber and the chamber are alternately formed and electrodialyzed. From the acid chamber, the mixed solution of the salt solution released from the salt solution of the water-soluble polymeric acid and the undialysed acid solution from the acid chamber, (A), the mixed solution Step (B) of neutralizing the solution with an alkali solution to obtain a neutralization solution, a bipolar membrane, a cation exchange membrane and an anion exchange membrane are sequentially arranged, and an alkali production chamber, a desalination chamber and an acid production chamber are sequentially provided. The neutralization solution obtained in the neutralization step (B) is supplied to the desalting chamber of the electrodialyzer (II) thus formed, By circulating an acid solution to the alkaline solution and the acid product compartment by electrodialysis Li generating chamber, an alkaline solution corresponding to the cation component of the neutralizing solution from the alkali generating chamber,
Also, a regeneration step (C) for recovering an acid solution corresponding to the anionic component of the neutralization solution from the acid generation chamber, and the alkaline solution obtained in the regeneration step (C) are used as the alkaline solution in the neutralization step (B). And / or acid solution for electrodialysis (I)
The method for producing a polymeric acid, which comprises the circulation step (D) of circulating the acid solution as described above.