JPH0634912B2 - Method for manufacturing selective permeable membrane - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a selectively permeable membrane made of a sulfonated polyaryletherketone.

(Prior art and its problems) Repeating unit A A sulfonated polyaryl ether ketone obtained by sulfonation of a polyaryl ether ketone represented by is already known as described in JP-A-55-36296, and the polyaryl ether ketone is converted into concentrated sulfuric acid. It is obtained by sulfonation.

Further, a semipermeable membrane using the obtained sulfonated polyaryl ether ketone is described in JP-A-61-222503, JP-A-61-222508, and JP-A-63-248409. . These examples are composite membranes composed of a skin layer having separation activity and a support membrane integrally supporting the skin layer. As a manufacturing method, a skin forming layer having a solute separation activity is obtained by applying a membrane forming solution containing a sulfonated polyaryl ether ketone onto a support such as an ultrafiltration membrane and evaporating a solvent in the membrane forming solution. .

(Means for Solving the Problem) The present inventors sulfonated a polyaryletherketone composed of the repeating unit of the above formula A, and selected from among the sulfonated polyaryletherketone and monohydric alcohols, carboxylic acid esters and ketones. A selective permeable membrane having a practical water permeation rate can be obtained by coagulating a film-forming solution containing at least one additive selected from among water, an inorganic salt aqueous solution or an inorganic acid solution. ,
It was found that this selective permeable membrane is particularly useful as an ultrafiltration membrane having excellent pH resistance, and further, by changing the type of additive of the membrane forming solution or the type of coagulating liquid, various solutes can be obtained. It was found that the removal rate and the permeation flux with respect to can be controlled arbitrarily. Therefore, an object of the present invention is to provide a method for producing an effective selective permeable membrane by using a membrane forming solution of a special solvent.

That is, according to the present invention, the repeating unit A Consisting of a hydrophilic polymer obtained by sulfonation of a polyaryletherketone represented by, an aprotic polar organic solvent, and at least one additive selected from monohydric alcohols, carboxylic acid esters and ketones. There is provided a method for producing a selective permeable membrane, which comprises coagulating a membrane forming solution with water, an inorganic salt aqueous solution or an inorganic acid aqueous solution.

In particular, according to the present invention, such a selective permeable membrane is a selective permeable membrane by containing the above-mentioned additive in the membrane forming solution, while arbitrarily controlling the removal rate and the permeation flux for various solutes. Obtainable.

The sulfonated polyaryletherketone used in the present invention is a hydrophilic polymer obtained by sulfonation of the polyaryletherketone having the repeating unit represented by the formula A. The sulfonated polyaryletherketone can be obtained by adding the polyaryletherketone having the repeating unit represented by A to 97% or more concentrated sulfuric acid and gently stirring at room temperature for several hours to several days. After the reaction, the resulting viscous reaction solution was poured into water, and then filtered to obtain
The sulfonated polyaryl ether ketone can be easily separated. The molecular weight of the polyaryl ether ketone used as a raw material for sulfonation is 10,000 to 100,000,
It is preferably 20,000 to 40,000.

In the present invention, such a sulfonated polyallyl ether ketone has an ion exchange capacity of 1 g of dry resin.
It is 2.5 meq / g or less.

In the polyaryl ether ketone composed of the repeating unit A, when all the aromatic rings sandwiched by two ether groups are monosulfonated, the theoretical ion exchange capacity of the sulfonated polyaryl ether ketone is 2.6 meq / g. However, the sulfonated polyaryl ether ketone used in the present invention has an ion exchange capacity of 2.
It should be 5 meq / g or less. When the ion exchange capacity exceeds 2.5 meq / g, the sulfonated polyaryl ether ketone has water solubility and is not suitable for use as a semipermeable membrane which often treats a liquid containing an aqueous medium. The preferred sulfonated polyaryl ether ketones used in the present invention are those that exhibit an ion exchange capacity of 0.5 to 2 meq / g.

The sulfonic acid group contained in the sulfonated polyaryl ether ketone used in the present invention is represented by the formula —SO ₃ M, where M represents a cation such as hydrogen, an alkali metal or tetraalkylammonium.

For example, after sulfonation of a polyaryletherketone consisting of repeating units represented by formula A, washing the sulfonated polyaryletherketone with water and drying,
Sulfonated polyaryl ether ketones having free sulfonic acid groups can be obtained. Further, this sulfonated polyaryl ether ketone is treated with an aqueous solution of alkali metal hydroxide or alkali metal alcoholate or methanol,
The sulfonic acid group can be converted to an alkali metal salt by suspending it in an ethanol solution or the like and treating it. Examples of the alkali metal hydroxide include sodium hydroxide, potassium hydroxide and lithium hydroxide, and examples of the alkali metal alcoholate include sodium methylate and
Potassium methylate, potassium ethylate and the like are used. Further, if the sulfonated polyaryl ether ketone is similarly treated with a solution of tetraalkylammonium, for example, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, etc. The sulfonic acid group can be the corresponding tetraalkylammonium salt.

As the organic solvent for preparing the film-forming solution, in the present invention, an aprotic polar organic solvent, for example, dimethyl sulfoxide, N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethyl Acetamide and the like are preferably used.

The concentration of the sulfonated polyaryl ether ketone in the membrane forming solution is also related to the thickness of the semipermeable membrane of these polymers in the resulting selectively permeable membrane, but is usually 0.1 to 50.
The range of wt% is preferable, and the range of 10 to 30 wt% is particularly preferable.

The selectively permeable membrane according to the present invention is formed using a membrane forming solution containing a specific additive. Among such additives, the organic compound is water-soluble and needs to be dissolved in the film-forming solution. Specific examples include monohydric alcohols such as methyl alcohol, ethyl alcohol and isopropyl alcohol; ketones such as acetone and methyl ethyl ketone; and carboxylic acid esters such as methyl acetate. These additives are usually used for the purpose of improving the rejection rate and the permeation flux. The cause of the performance change due to the additive is not clear, but it is considered that it affects the dissolution state of the film forming solution and the film formation.

Further, in the present invention, an inorganic salt that is water-soluble and is soluble in the film-forming solution can also be used as an additive. Examples of such an inorganic salt include lithium chloride, lithium sulfate, and magnesium perchlorate.

The concentration of these additives in the film forming solution is usually 0.1
The range is up to 80% by weight. These are related to the pore size of the micropores possessed by the selective permeable membrane formed from the sulfonated polyaryletherketone, and by selecting the kind and amount of the additive to be used, the performance of the selective permeable membrane, particularly the solute The removal rate and the permeation flux can be controlled over a wide range.

When the selective permeable membrane is obtained from the above membrane-forming solution, it can be formed into a flat membrane, a hollow fiber, a tubular shape, or the like, and the form is not particularly limited. A flat membrane, hollow fiber or tubular membrane is formed by a well-known method such as a wet method, but the performance of the selective permeable membrane can be widely varied by changing the type of coagulating liquid. Can be varied over time. As the coagulating liquid of the film forming solution, water, an aqueous solution of an inorganic salt, or an inorganic acid solution can be used. Specifically, as inorganic acids and salts thereof, HCl, CaCl ₂ , MgCl ₂ , NH ₄ NO
₃ , NH ₄ CI, NaCl and the like.

By selecting the type and concentration of these coagulating liquids, it is possible to control the performance of the selective permeable membrane of the present invention, in particular, the solute rejection rate and the permeation flux.

(Effects of the Invention) The method for producing a selectively permeable membrane according to the present invention is good in selecting the type and concentration of the additive and coagulating liquid of the membrane forming solution. The flux can be controlled over a wide range, and it is possible to design a membrane suitable for the purpose.

In addition, the selective permeation membrane according to the method of the present invention has an asymmetric membrane structure, and a higher permeation flux can be obtained as compared with a homogeneous membrane having the same thickness.

Furthermore, since the sulfonated polyaryletherketone has a chargeability, the selective permeation membrane according to the method of the present invention is a membrane that is judged to be an ultrafiltration membrane when evaluated with an uncharged polyethylene glycol or the like. However, it was found that even when evaluated with an inorganic salt or protein that dissociates in an aqueous solution, the separation property is exhibited.

(Examples) The present invention will be described with reference to examples, but the present invention is not limited to these examples. still,
In the examples, the rejection rate of the obtained permselective membrane and the permeation flux are 0.1% of sodium sulfate unless otherwise specified.
Aqueous solution, polyethylene glycol 0.3% aqueous solution, etc. at temperature 25
The values are obtained by the following equations after processing at a temperature of 3 ° C and a pressure of 3 kg / cm ² .

Reference Example 1 [Production of sulfonated polyaryl ether] Repeating unit A Polyaryletherketone (ICI, Victr
ex PEEK 308P) (18 g) was added to 182 g of 97% concentrated sulfuric acid, and the mixture was slowly stirred and reacted at room temperature for 48 hours to obtain a viscous reaction solution. This was put into water to coagulate the sulfonated polyaryl ether ketone. It was washed with water, washed repeatedly until the washing liquid became neutral, and then filtered. Then, it dried at 50 degreeC.

The sulfonated polyaryl ether ketone thus obtained had an ion exchange capacity of 1.7 meq / g.

Example 1 The sulfonated polyaryletherketone obtained in Reference Example 1 was dissolved in N-methyl-2-pyrrolidone, methyl alcohol was added as an additive, the sulfonated polyaryletherketone concentration was 20% by weight, and methyl alcohol was 20% by weight. %, And N-methyl-2-pyrrolidone 60% by weight to obtain a film forming solution. This film-forming solution was cast on a glass plate to a thickness of 180 μm and immediately immersed in a 10 wt% NaCl aqueous solution at room temperature to obtain a film. Then, the obtained membrane was thoroughly washed with water. When this membrane was measured, the performance of this selectively permeable membrane was a sodium sulfate rejection of 56% and a permeation flux of 1.77 m ³ / m ² days.

Example 2 A selective permeable membrane was obtained in the same manner as in Example 1 except that the additive in the membrane forming solution was changed to that shown in Table 1.
The performance of this selectively permeable membrane is shown in Table 1.

Example 3 In Example 1, 50% by weight of hydrochloric acid was used as the coagulating solution of the film forming solution.
A selectively permeable membrane was obtained in the same manner as in Example 1 except that the aqueous solution was used. The performance of this selective permeable membrane was a sodium sulfate rejection of 10% and a permeation flux of 4.5 m ³ / m ² days.

Comparative Example Selectivity was the same as in Example 1 except that the film forming solution (20% by weight of sulfonated polyaryletherketone, 80% by weight of N-methyl-2-pyrrolidone) was prepared by removing the additives. A permeable membrane was obtained. The performance of this selective permeable membrane is that the rejection rate of sodium sulfate is 55% and the permeation flux is 0.7.
m ³ / m ² days, polyethylene glycol 20,000 inhibition rate 91
%, The permeation flow rate was 0.47 m ³ / m ² days.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsumori Nagura 1-2-1 Shimohozumi, Ibaraki City, Osaka Prefecture Yasuyuki Yamada Examiner, Nitto Denko Corporation (56) Reference JP-A-63-248409 (JP, A) ) JP-A-61-222503 (JP, A) JP-A-61-222508 (JP, A)

Claims (1)

[Claims] 1. Repeating unit A Consisting of a hydrophilic polymer obtained by sulfonation of a polyaryletherketone represented by, an aprotic polar organic solvent, and at least one additive selected from monohydric alcohols, carboxylic acid esters and ketones. A method for producing a selective permeable membrane, which comprises coagulating a membrane forming solution with water, an inorganic salt aqueous solution or an inorganic acid aqueous solution.