JPH04317732A - Anionic charge type semitransparent composite membrane - Google Patents

Abstract

PURPOSE:To obtain a composite membrane excellent in fractionating performance over a medium- to low-molecular weight range by forming a thin layer of sulfonation product of polyaryl ether ketone having a specific repeating unit on the surface of a porous membrane having an anisotropic structure. CONSTITUTION:The sulfonation product of the polyaryl ether ketone having the repeating unit represented by the structural formula is dissolved in an org. solvent such as methyl alcohol and ethyl alcohol to prepare a membrane forming solution. A porous membrane having an anisotropic structure is immersed in an aq. solution of the filler consisting of a water-soluble, and involatile org. compound such as ethylene glycol, diethylene glycol and glycerol to replace the water contained in the membrane with the filler. By the subsequent evaporation and drying, the porous membrane treated with the filler is obtained. After coating the porous membrane having the anisotropic structure with the aforesaid membrane forming solution, the solution is evaporated to obtain an anionic charge type semitransparent composite membrane. The composite membrane thus obtained is extremely effective for separating biological substance such as protein, peptide and amino acid.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anion-charged semipermeable composite membrane useful for selective separation of liquid mixtures, particularly for selective separation of electrically neutral substances and charged substances having similar molecular weights.

0002

[Prior art and its problems] In general, membrane treatment is an energy-saving process that selectively permeates specific components from liquid mixtures such as liquid mixtures to separate, concentrate, and purify them. It is provided. Particularly recently, membrane treatment methods have been applied to various fields such as food processing, pharmaceutical industry, and water treatment.

[0003] In such a membrane treatment method, components with medium and low molecular weights, that is, molecular weights of about 50 to 2000, are selectively separated from liquid mixtures having various molecular weights (hereinafter also referred to as fractionation). There is a strong demand for the development of a charged semipermeable membrane that can separate molecules of similar molecular weight depending on the presence or absence of charge, and various studies are being conducted. One of these is an anion-charged semipermeable membrane in which a negative charge is fixed on the membrane.

Conventionally, anionically charged semipermeable membranes include:
Uniform membranes and non-uniform membranes made of sulfonated substances such as polysulfone and polyetherimide are known. For example, JP-A-50-99973 and JP-A-51-146.
379 publication, the repeating unit of the following formula (B)

A composite semipermeable membrane is disclosed in which a semipermeable membrane made of a sulfonated polysulfone having the following structure is laminated on an ultrafiltration membrane having an anisotropic structure. However, when one of the two benzene rings in the bisphenol A moiety of such polysulfone is monosulfonated, the theoretical ion exchange capacity of the sulfonated polysulfone is as low as 1.9 m equivalent/g of resin. If the sulfonation reaction is carried out so that the ion exchange capacity is 1.5 m equivalent/g of resin or more, the sulfonated product exhibits water-soluble properties, so semi-permeable water is often used to treat aqueous solutions. It cannot withstand use as a membrane. Also, Tokuhei 2-5252
In Publication No. 8, a repeating unit of the following formula (C) is placed on an ultrafiltration membrane having an anisotropic structure made of polysulfone having a repeating unit of the above formula (B).

A composite semipermeable membrane formed by laminating semipermeable membranes made of a sulfonated product of polysulfone having the following formula and a method for producing the same are disclosed. However, 2 of such polysulfones
When a benzene ring sandwiched between two ethers is monosulfonated, the theoretical ion exchange capacity of the sulfonated polysulfone is 2.4 m equivalent/g of resin, which is not sufficient, and the ion exchange capacity is 2.0 m equivalent/g of resin. If the sulfonation reaction is carried out in such a way that the sulfonation reaction is greater than It is clearly stated. Furthermore, the effect of the sulfonic acid groups in these composite membranes is limited to increasing permeation flux by improving hydrophilicity, and separation of ionic substances using the fixed charges of the membrane has not yet been achieved. not present. That is,
Currently, these composite membranes do not satisfy user requirements in terms of fractionation performance, permeation flux, durability, etc.

On the other hand, in Japanese Patent Publication No. 63-51174, a repeating unit of the following formula (A)

A film-forming sulfonated polyaryletherketone resin obtained by sulfonating a polyaryletherketone having the following formula with concentrated sulfuric acid and a method for producing the same are disclosed. When the benzene ring sandwiched between two ethers of such polyaryletherketone is monosulfonated,
The sulfonated polyaryletherketone has a very high theoretical ion exchange capacity of 2.6 m equivalent/g of resin, and also contains a considerable amount of water (for example, 20% by weight of water).
It is described as a characteristic that it possesses considerable strength even when it contains carbon dioxide, and it is mentioned that it is potentially useful as a membrane material in ultrafiltration processes. Also, JP-A-2-237628 or JP-A-3-2
Publication No. 1333 discloses a permselective membrane made of a sulfonated polyaryletherketone having the above-mentioned repeating unit of formula (A) or a mixture of the sulfonated product and various polysulfones, and a method for producing the same. . In each case, a sulfonated polyaryletherketone alone or a mixture of the sulfonated product and various polysulfones is dissolved in an aprotic organic solvent such as N,N,-dimethylformamide or N-methyl-2-pyrrolidone, and then a conventionally known method is used. This is a one-piece permselective membrane obtained by forming a membrane using a phase inversion method (casting method). Therefore, these selectively permeable membranes do not have sufficient densification of the selectively active layer, and are inferior to composite membranes in which a semipermeable membrane of polysulfone sulfonate is laminated on a porous membrane having the above-mentioned anisotropic structure. However, there is a problem that the fractionation performance and solution processing speed in the target medium-low molecular weight region are inferior.

[0006] Therefore, in view of the above-mentioned problems, an object of the present invention is to provide a semipermeable composite membrane that has excellent fractionation properties in the medium and low molecular weight region, as well as excellent water permeability and durability. Another object of the present invention is to provide an anionically charged semipermeable composite membrane that can satisfactorily separate ionic substances.

[0007]

[Means for solving the problem] According to the present invention, repeating units of the following formula (A) are provided on the surface of a porous membrane having an anisotropic structure.

An anionically charged semipermeable composite membrane is provided in which a thin layer is formed of a sulfonated polyaryletherketone having the following formula:

[0008] The porous membrane serving as the base material in the composite membrane of the present invention is an anisotropic membrane having a dense layer having a thickness of about 5 μm or less, preferably 1 μm or less on at least one surface, and having a porous interior. It is a sexual structure (also called an asymmetric structure),
Generally, a separation membrane having properties equivalent to an ultrafiltration membrane is used. Materials for such porous membranes include polysulfones, polyethersulfones, polyimides, polyetherimides, polyamides, polyphenylene oxide, poly(2,6,-dimethylphenylene), etc., which can be formed by a phase conversion method. Condensation polymers such as oxide and polyphenylene sulfide, polymeric polymers such as cellulose acetate, polyacrylonitrile, polyvinyl alcohol, polyvinyl chloride, polystyrene, and polyvinylidene fluoride, or methods that combine phase separation and sol-gel methods. Examples of the material include inorganic ceramics such as silica and alumina, which can be formed into a film by, but are not particularly limited to. Preferably, condensation polymers are used from the viewpoint of ease of film formation, and polysulfones and polyetherimides are particularly preferably used.

[0009] The form of the membrane is flat membrane, tubular membrane,
Conventionally known types such as capillary membrane type and hollow fiber membrane type,
It can be used in any desired form depending on the purpose. In addition, in the case of a flat membrane or a tubular membrane, it is possible to obtain a porous membrane with excellent mechanical strength and dimensional stability by using, for example, woven fabric, nonwoven fabric, net, etc. as a reinforcing backing material. It is valid.

The thin layer serving as the selectively active layer of the anionically charged semipermeable composite membrane according to the present invention has a repeating unit of the following formula (A).

It is formed from a sulfonated polyaryletherketone consisting of: The sulfonated product of polyaryletherketone is generally prepared by adding the polyaryletherketone having the above-mentioned repeating unit A to 97% or more concentrated sulfuric acid, and slowly heating the mixture at room temperature for several hours to several days, preferably for 1 to 3 days. Obtained by stirring. At that time, for 2 to 5 hours immediately after the start of the reaction, the reaction temperature is kept below 0°C using a coolant such as ice water in the reaction vessel to slow down the speed of the initial sulfonation reaction, and also to Suppressing the decomposition of is an effective method for obtaining a uniform sulfonated product. Furthermore, mixing an appropriate amount of a conventionally known sulfonating reagent such as chlorosulfonic acid with concentrated sulfuric acid as a solvent is also effective as a method for increasing the efficiency of sulfonation of the resin. After the reaction, the resulting viscous reaction solution is poured into water or ice water, washed thoroughly with water until the water used for washing becomes neutral, and filtered to obtain the sulfonated polyaryletherketone. Resin can be obtained. The polyaryletherketone used as a raw material may be in the form of powder, sheet, or pellets, but in order to carry out the sulfonation reaction more efficiently, it is preferably in the form of powder with a large surface area. In addition, the molecular weight of the polyaryletherketone used as a raw material is 5,000 to 200,000.
, preferably 10,000 to 50,000.
When all of the aromatic rings sandwiched between two ether groups in the polyaryletherketone consisting of the repeating unit of chemical formula (A) above are monosulfonated, the theoretical ion exchange capacity of the sulfonated polyaryletherketone is 2.6 m equivalent/g of resin, but the sulfonated polyaryletherketone used in the present invention has an ion exchange capacity of 0.5 to 2.5 m equivalent/g of resin. The reason is that the ion exchange capacity is 0.5 m equivalent/
If the sulfonated product is less than 1 g of resin, film formation becomes extremely difficult because the sulfonated product is not soluble in a suitable organic solvent, whereas if the ion exchange capacity is 2.5 m equivalent/g of resin or more, the sulfonated product becomes water-soluble. This is because they are not suitable for use as semipermeable membranes that often treat liquids containing aqueous media. The sulfonated polyaryletherketone particularly preferably used in the present invention has an ion exchange capacity of 1.8.
~2.3 m equivalent/g of resin.

In the present invention, the sulfonic acid group possessed by the sulfonated product of polyaryletherketone has the formula -SO3
It is represented by X, where X represents a hydrogen ion, metal ion or organic ion. By treating the sulfonated polyaryletherketone described above with an aqueous solution containing metal ions, the sulfonic acid group can be converted into a metal salt. Examples of the metal ions include monovalent ions such as sodium ions, potassium ions, and lithium ions, divalent ions such as calcium ions, magnesium ions, and barium ions, or higher polyvalent metal ions. The sulfonic acid group may be converted into a monovalent metal salt either before or after film formation, but it must be converted into a polyvalent metal salt after film formation. This is because if the sulfonic acid group is made into a polyvalent metal salt, the apparent molecular weight increases due to the formation of an ionic crosslinked structure, and it is often insoluble in organic solvents, making film formation extremely difficult. On the other hand, it is useful to convert the sulfonic acid group into a polyvalent metal salt after film formation because it can improve the fractionation properties and durability of the film. Also,
The sulfonic acid groups are treated with an aqueous solution of monovalent organic ions such as tetramethylammonium hydroxide, tetraethylammonium chloride, tetrapropylammonium iodide, and tetrabutylammonium bromide. It can be an ammonium salt. Polyaryletherketones with sulfonic acid groups that are converted into ammonium salts by treatment with an aqueous solution of monovalent organic amines become easily soluble in organic solvents, so it is recommended to perform such treatment before film formation. be done. Furthermore, after film formation, for example, N,N,N',N'-tetramethylmethylenediamine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetraethylpropylenediamine. , N, N, N', N'-
A polyvalent organic ionic compound having two or more quaternized nitrogen atoms in one molecule obtained by quaternizing tetraethylhexanediamine etc. using a quaternizing reagent such as methyl iodide or ethyl iodide is mixed with water or hexane etc. By treating the polyaryletherketone with a solution dissolved in an appropriate organic solvent, the sulfonic acid group of the polyaryletherketone becomes the corresponding ammonium salt, which has a crosslinked structure with the polyvalent organic ionic compound. Similar to the case of salt treatment, this treatment is useful because it can improve the fractionation properties and durability of the membrane.

The anion-charged semipermeable composite membrane of the present invention is prepared by dissolving the sulfonated polyaryletherketone in an organic solvent to obtain a membrane-forming solution, which is then pre-soaked in an aqueous plugging agent solution and dried. It can be manufactured by applying the above membrane forming solution onto a porous membrane having an orthotropic structure and then evaporating the solvent.

Alcohols are preferably used as the organic solvent for preparing the film forming solution in the present invention. This is because this solvent generally has excellent solubility in sulfonated polyaryletherketones and does not dissolve a porous membrane having an anisotropic structure that serves as a support membrane. Examples of the alcohols include methyl alcohol, ethyl alcohol, n-propyl alcohol, iso-propyl alcohol, ethylene glycol, propylene glycol, diethylene glycol, and the like. In particular, methyl alcohol is preferably used because it not only has excellent solubility of the sulfonated polyaryletherketone but also has high volatility. However, depending on the degree of sulfonation and molecular weight of the sulfonated polyaryletherketone used, it may not dissolve in the alcohol or may only swell. It dissolves well in a mixed solvent made by adding a small amount of aprotic polar organic solvent to alcohol. Examples of the aprotic polar organic solvent include N-methyl-2-pyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide,
N,N-dimethylacetamide and the like are preferably used. In such a mixed solvent, the mixing ratio of the aprotic polar organic solvent is 3 parts by weight per 100 parts by weight of the alcohol.
It is preferably at most 1 part by weight, particularly at most 1 part by weight. When the amount of the aprotic polar organic solvent is more than 3 parts by weight, when the membrane forming solution is applied onto a dried porous membrane having an anisotropic structure, the porous membrane dissolves or swells, This is because it becomes difficult to obtain a semipermeable composite membrane with good membrane performance. The concentration of the sulfonated polyaryletherketone in the film forming solution is related to the thickness of the thin layer formed by this polymer, but is usually 0.01 to 15% by weight.
, preferably in the range of 0.05 to 5% by weight.

[0014] A porous membrane having an anisotropic structure to which a membrane-forming solution is applied needs to be packed in advance. This is because when the sulfonated polyaryletherketone contained in the membrane forming solution permeates into the porous membrane and solidifies the sulfonated polyaryletherketone,
This is because it blocks the micropores in the porous membrane. This packing treatment is usually performed by immersing a porous membrane with an anisotropic structure obtained as a water-containing membrane in an aqueous solution of a packing agent consisting of a water-soluble and non-volatile organic compound. This is done by replacing the water with water and then evaporating the water and drying it. As the above-mentioned plugging agent, polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, and glycerin, or hydroxycarboxylic acids such as lactic acid and hydroxybutyric acid are preferably used. In particular, in the present invention, glycerin, 1,4-butanediol, and lactic acid, which are plugging agents that do not dissolve or swell the sulfonated polyaryletherketone in the membrane forming solution, are preferably used. The concentration of the aqueous plugging agent solution is usually in the range of 1 to 90% by weight, especially 10% by weight.
A range of 30% by weight is preferred.

[0015] A porous membrane having an anisotropic structure in a water-containing state is immersed in the above-mentioned aqueous solution of the packing agent, and after replacing the water in the micropores with the aqueous solution of the packing agent, it is air-dried or heated as necessary. to evaporate the water and dry the porous membrane. By this treatment, the plugging agent is allowed to exist in the micropores of the porous membrane, and the porous membrane can be dried without shrinking the micropores. The drying temperature at that time is not particularly limited, but is usually 0 to 100°C, preferably 20 to 100°C.
The temperature is 80°C. The time required for drying is usually 1 minute to 10 hours, but it was confirmed by visual inspection that the aqueous plugging agent solution was uniformly dry on both the front and back sides of the porous membrane with an anisotropic structure. If possible, there are no particular restrictions.

Next, the membrane-forming solution is applied onto the porous membrane having an anisotropic structure in a dry state, and the solvent is evaporated to form the anion-charged semipermeable composite membrane of the present invention. obtain. The method of applying membrane forming solution to porous membrane is as follows:
Examples include a method of floating the porous membrane on a membrane-forming solution, a method of casting the membrane-forming solution on the porous membrane, a method of spraying the membrane-forming solution, and a method of immersing the porous membrane in the membrane-forming solution for a certain period of time. Next, from the porous membrane coated with the membrane forming solution, most of the solvent in the membrane forming solution is generally evaporated off by air drying, and then, if necessary, the solvent is completely removed by heating. This heating temperature is usually 150°C or lower, preferably 100 to 120°C. The time required for heating is not particularly limited, but is usually from 1 minute to 10 hours or more, preferably from 5 to 60 minutes.

The thickness of the thin layer based on the sulfonated polyaryletherketone in the anionically charged semipermeable composite membrane obtained by the present invention is determined by the concentration of the sulfonated polyaryletherketone in the membrane forming solution and the thickness of the sulfonated polyaryletherketone in the membrane forming solution. Although it depends on the cast thickness, it is better to be thinner to increase the water permeation rate of the membrane, and conversely, thicker is better to increase the mechanical strength of the membrane. Therefore, although it is not particularly limited, it is usually preferably in the range of 0.01 to 5 μm.

[0018]

[Effect] The charged semipermeable composite membrane of the present invention contains charged molecules and uncharged molecules with similar molecular weights or diameters due to the negative charge of the sulfonic acid groups present in the surface layer of the membrane. By filtering the solution, it is possible to separate such that only uncharged molecules pass through and negatively charged molecules remain, or only positively charged molecules pass through and uncharged molecules remain. For example, it is extremely effective in separating biological substances such as proteins, peptides, and amino acids.

[0019]

[Examples] Examples and comparative examples of the present invention are shown below.
The present invention is not limited to these examples. The water permeability shown in Examples and Comparative Examples is the flux measured using a batch-type ultrafiltration device (effective membrane area 12.5 cm2) manufactured by Toyo Roshi Co., Ltd. using pure water at an operating pressure of 4 kg/cm2. be. In addition, solute permeability was measured using the same device at the same operating pressure in an aqueous solution of monodisperse polyethylene glycol (PEG) having a predetermined weight average molecular weight (concentration 1,000).
0 ppm), and the inhibition rate (%) when the volume of this stock solution reached 1/5 was calculated using the following formula. that time,
The concentrations of permeate and blocking solution were determined by gel permeation chromatography.

Example 1 (1) Production of porous membrane with anisotropic structure Formula (B) below:
repeating unit of

Udel polysulfone (pellet form, manufactured by Amoco Chemical Japan, weight average molecular weight 35,000) having [Chemical formula 7] 30
After stirring a mixture consisting of 5 g, polyvinylpyrrolidone K-30 (manufactured by Wako Pure Chemical Industries, Ltd., weight average molecular weight 10,000) and 150 g of N-methyl-2-pyrrolidone at room temperature for 10 hours, a solution with a viscosity of 30 poise was obtained. . Next, this solution was cast onto a glass plate to a thickness of about 300 μm, and then immersed in pure water at 5° C. to solidify, thereby obtaining a polysulfone membrane with a thickness of about 100 μm. Furthermore, immersion treatment was performed in warm water at 60° C. for 1 hour. When the cross-section of this polysulfone film was observed using a scanning electron microscope, a layer with a dense structure about 2 μm thick was confirmed on the surface layer of the film, and the other parts had a so-called finger-like structure. It was a porous layer.

[0021] Regarding this polysulfone membrane, the permeation flux of pure water was measured and was found to be 1340 l/m2·hr. Further, as a result of measuring the permeability of a monodisperse aqueous solution (concentration 1,000 ppm) of PEG having a weight average molecular weight of 21,000, the rejection rate was 99.1%. Similarly, as a result of measuring the permeability of an aqueous PEG solution having a weight average molecular weight of 2,000, the rejection rate was 5.3%.

(2) Production of sulfonated product of polyaryletherketone Repeating unit of the following formula (A)

A polyaryletherketone having the following formula: Victor
x 450P (powder, manufactured by Sumitomo Chemical) 20g at 97%
The mixture was added to 180 g of concentrated sulfuric acid and gently stirred at 0° C. for 2 hours. Thereafter, the temperature was raised to 25° C., and the mixture was gently stirred for an additional 46 hours to obtain a viscous reaction liquid. This was gradually poured into water to solidify the sulfonated polyaryletherketone. Rinse with water until the cleaning solution becomes neutral.
After repeated washing, it was filtered off. Then air dry,
Further, it was dried under reduced pressure at 60°C.

The sulfonated polyaryletherketone thus obtained has an ion exchange capacity of 2.1.
m equivalent/g of resin.

(3) Production of anionically charged semipermeable composite membrane The above polysulfone membrane was coated with glycerin 1 as a packing material.
0% aqueous solution (25°C) for 1 hour, then about 6
It was dried for 30 minutes in a drying oven at 0°C. Next, the sulfonated polyaryletherketone was dissolved in methyl alcohol to a concentration of 1.0% by weight, and this solution was applied to a thickness of about 100 μm on the polysulfone membrane. This was left at room temperature, and after confirming that most of the solvent had evaporated, it was heated to 60° C. for 5 minutes to obtain an anion-charged semipermeable composite membrane according to the present invention. Observation of the cross section of the membrane using a scanning electron microscope revealed that the resulting anionically charged semipermeable composite membrane had a thin layer of sulfonated polyaryletherketone with a thickness of approximately 1 μm on a dense layer of polysulfone membrane. was observed.

[0025] As a result of measuring the permeation flux of pure water for this anion-charged semipermeable composite membrane, it was found to be 48.5 l/m2.
It was hr. Further, as a result of measuring the permeability of a monodispersed aqueous solution of PEG having a weight average molecular weight of 2,000, the rejection rate was 99.0%. Similarly, the weight average molecular weight is 9
As a result of measuring the permeability of a PEG aqueous solution having a concentration of 60%, the rejection rate was 92.3%.

Example 2 An anionically charged semipermeable composite membrane was obtained in the same manner as in Example 1, except that a 30% aqueous glycerin solution was used as the aqueous plugging agent solution.

[0027] Regarding this semipermeable composite membrane, the permeation flux of pure water was measured and found to be 49.8 l/m2·hr. In addition, as a result of measuring the permeability of a monodisperse aqueous solution of PEG with a weight average molecular weight of 2,000, the rejection rate was 98.6%.
Met. Similarly, PE with a weight average molecular weight of 960
As a result of measuring the permeability of G aqueous solution, the rejection rate was 91.6%.
Met.

Example 3 An anionically charged semipermeable composite membrane was obtained in the same manner as in Example 1, except that a 10% aqueous lactic acid solution was used as the aqueous plugging agent solution.

[0029] Regarding this semipermeable composite membrane, the permeation flux of pure water was measured and found to be 48.7 l/m2·hr. In addition, as a result of measuring the permeability of a monodisperse aqueous solution of PEG with a weight average molecular weight of 2,000, the rejection rate was 98.3%.
Met. Similarly, PE with a weight average molecular weight of 960
As a result of measuring the permeability of G aqueous solution, the rejection rate was 91.2%.
Met.

Example 4 An anionically charged semipermeable composite membrane was prepared in the same manner as in Example 1, except that the solvent type and the concentration of the sulfonated polyaryletherketone in the membrane forming solution were varied. I got it. Table 1 shows the membrane performance of each anion-charged semipermeable composite membrane thus obtained. Note that (Comparative Example) in Table 1 is the polysulfone membrane itself produced in Example 1.

[Table 1]

Example 5 Regarding the anionically charged semipermeable composite membrane obtained in Example 1,
In order to investigate the effect of the negative charge, a permeation test was conducted with an aqueous solution (concentration 1000 ppm) of a quaternary ammonium salt, which is a cationic substance, and an organic acid, which is an anionic substance. Table 2 shows the results.

[Table 2]

Example 6 The anionically charged semipermeable composite membrane obtained in Example 1 was
．． Soaked in 1N sodium chloride aqueous solution for 2 hours at room temperature,
Through an ion exchange reaction, the counter ion of the sulfonic acid group of the membrane was changed from hydrogen ion to sodium ion. Then, it was thoroughly washed with pure water.

[0033] Regarding this membrane, the permeation flux of pure water was measured and found to be 49.8 l/m2·hr. Further, as a result of measuring the permeability of a monodisperse aqueous liquid of PEG having a weight average molecular weight of 2,000, the rejection rate was 97.6%. Similarly, the permeability of a PEG aqueous solution having a weight average molecular weight of 960 was measured, and the rejection rate was 92.6%.

Example 7 The anionically charged semipermeable composite membrane obtained in Example 1 was
．． Soaked in 1N calcium chloride aqueous solution at room temperature for 2 hours,
Through an ion exchange reaction, the counter ions of the sulfonic acid groups of the membrane were changed from hydrogen ions to calcium ions, resulting in ionic crosslinking. Then, it was thoroughly washed with pure water.

[0035] Regarding this membrane, the permeation flux of pure water was measured and found to be 50.2 l/m2·hr. Further, as a result of measuring the permeability of a monodispersed aqueous liquid of PEG having a weight average molecular weight of 2,000, the rejection rate was 99.2%. Similarly, as a result of measuring the permeability of an aqueous PEG solution having a weight average molecular weight of 960, the rejection rate was 95.5%.

Example 8 The calcium-type anion-charged semipermeable composite membrane obtained in Example 7 was immersed in methyl alcohol at room temperature for 2 hours. Then, it was thoroughly washed with pure water.

[0037] Regarding this membrane, the permeation flux of pure water was measured and found to be 48.5 l/m2·hr. Further, as a result of measuring the permeability of a monodispersed aqueous liquid of PEG having a weight average molecular weight of 2,000, the rejection rate was 98.2%. Similarly, as a result of measuring the permeability of an aqueous PEG solution having a weight average molecular weight of 960, the rejection rate was 92.5%.

Example 9 The anionically charged semipermeable composite membrane obtained in Example 1 was
．． The membrane was immersed in a 1N aqueous tetramethylammonium hydroxide solution at room temperature for 2 hours, and the counter ion of the sulfonic acid group of the membrane was changed from hydrogen ion to tetramethylammonium ion through an ion exchange reaction. Then, it was thoroughly washed with pure water.

[0039] Regarding this membrane, the permeation flux of pure water was measured and found to be 47.5 l/m2·hr. Further, as a result of measuring the permeability of a monodispersed aqueous liquid of PEG having a weight average molecular weight of 2,000, the rejection rate was 98.8%. Similarly, as a result of measuring the permeability of a PEG aqueous solution having a weight average molecular weight of 960, the rejection rate was 92.3%.

Example 10 The anionically charged semipermeable composite membrane obtained in Example 1 was
．． The membrane was immersed in an aqueous solution of 2 mol of N,N,N',N'-tetramethylethylenediamine and 0.1 mol of methyl iodide dissolved in 1 L of water at room temperature for 2 hours to cause an ion exchange reaction. The sulfonic acid groups contained therein were ionically crosslinked with the quaternized organic ion. Then, it was thoroughly washed with pure water.

[0041] Regarding this membrane, the permeation flux of pure water was measured and found to be 49.5 l/m2·hr. Further, as a result of measuring the permeability of a monodispersed aqueous liquid of PEG having a weight average molecular weight of 2,000, the rejection rate was 99.4%. Similarly, as a result of measuring the permeability of an aqueous PEG solution having a weight average molecular weight of 960, the rejection rate was 94.6%.

Example 11 The anion-charged semipermeable composite membrane having an ionic crosslinked structure with quaternized organic ions obtained in Example 10 was immersed in methyl alcohol at room temperature for 2 hours. Then, it was thoroughly washed with pure water.

[0043] Regarding this membrane, the permeation flux of pure water was measured and found to be 49.8 l/m2·hr. Further, as a result of measuring the permeability of a monodisperse aqueous liquid of PEG having a weight average molecular weight of 2,000, the rejection rate was 98.9%. Similarly, as a result of measuring the permeability of an aqueous PEG solution having a weight average molecular weight of 960, the rejection rate was 91.7%.

Example 12 In order to examine the heat resistance of the anionically charged semipermeable composite membrane obtained in Example 1, it was soaked in hot water at 95°C for 30 minutes.
The permeation flux of pure water and the weight average molecular weight of 96
The inhibition rate of 0 PEG was measured. Furthermore, the same treatment was repeated and the membrane performance was measured in the same manner. The results are shown in Table 3.

[Table 3]

Example 13 In order to examine the acid resistance of the anionically charged semipermeable composite membrane obtained in Example 1, it was immersed in 0.5N hydrochloric acid at 25° C. for two days. Then, it was thoroughly washed with pure water.

[0046] Regarding this membrane, the permeation flux of pure water was measured and found to be 47.9 l/m2·hr. Further, as a result of measuring the permeability of a monodisperse aqueous liquid of PEG having a weight average molecular weight of 2,000, the rejection rate was 98.6%. Similarly, as a result of measuring the permeability of a PEG aqueous solution having a weight average molecular weight of 960, the rejection rate was 91.8%.

Example 14 The anionically charged semipermeable composite membrane obtained in Example 1 was
In order to examine the base resistance at 5°C, it was immersed in a 0.5N aqueous sodium hydroxide solution for 2 days. Then, it was thoroughly washed with pure water.

[0048] Regarding this membrane, the permeation flux of pure water was measured and found to be 48.6 l/m2·hr. Further, as a result of measuring the permeability of a monodisperse aqueous liquid of PEG having a weight average molecular weight of 2,000, the rejection rate was 98.9%. Similarly, as a result of measuring the permeability of a PEG aqueous solution having a weight average molecular weight of 960, the rejection rate was 91.2%.

Comparative Example 1 A semipermeable membrane of sulfonated polyaryletherketone was produced according to the method described in JP-A-2-23768. That is, 18 g of polyaryletherketone consisting of the repeating unit of formula (A) above was added to 97% concentrated sulfuric acid,
The reaction was allowed to proceed at room temperature for 48 hours with gentle stirring, and then the reaction solution was poured into water to coagulate the resin, thoroughly washed until the washing solution became neutral, and dried at 50°C. The sulfonated polyaryletherketone thus obtained had an ion exchange capacity of 1.6 milliequivalents/g of resin. Next, the sulfonated polyaryletherketone was dissolved in N-methyl-2-pyrrolidone to obtain a uniform film-forming solution with a resin concentration of 20% by weight,
This was cast onto a glass plate to a thickness of 180 μm, and immediately immersed in a 10% by weight aqueous solution of sodium chloride at room temperature to obtain a film.

[0050] Regarding this membrane, the permeation flux of pure water was measured and found to be 38.9 l/m2·hr. Further, as a result of measuring the permeability of a monodispersed aqueous solution of PEG having a weight average molecular weight of 2,000, the rejection rate was 59%. Similarly, as a result of measuring the permeability of an aqueous PEG solution having a weight average molecular weight of 960, the rejection rate was 32%.

Comparative Example 2 A sulfonated product of polysulfone having a repeating unit of formula (C) described above was applied to the surface of an ultrafiltration membrane having an anisotropic structure made of polysulfone having a repeating unit of formula (B) described above. A composite semipermeable membrane in which homogeneous semipermeable membranes were laminated was manufactured according to the method described in Japanese Patent Publication No. 2-52528.

That is, first, in order to produce polysulfone consisting of repeating units of formula (C), hydroquinone 1
Put 3.2 g into a flask equipped with a stirrer, nitrogen gas inlet tube, water drain tube, and thermometer, and add 100 m of sulfolane.
1 and 50 ml of xylene were added. Refluxing was carried out at 150° C. for 1 hour while stirring and heating with a mantle heater, and about 3 ml of water was extracted at this time. Then, the temperature is reduced to 1
The temperature was lowered to 10°C, and 34.5 g of 4,4'-dichlorodiphenylsulfone and 20.7 g of potassium carbonate were added to start the polymerization reaction. After refluxing at 155°C for 50 minutes, the temperature was raised to 200°C while removing water during 50 minutes, and refluxing was continued at 200 to 215°C for 30 minutes. The amount of water drawn off during this reaction was 3.6 ml. Next, 80 ml of sulfolane was added to the reaction solution, the temperature was lowered to 100° C., and 20 ml of dichloromethane was added. The reaction mixture thus obtained was poured into pure water to solidify the polysulfone and left overnight. This was filtered, pulverized with a mixer, washed with pure water and isopropyl alcohol, and then
It was dried for 6 hours at a temperature of °C. 10 g of the polysulfone consisting of repeating unit C obtained as above was added to 80 ml of 97% concentrated sulfuric acid, and the mixture was allowed to react with gentle stirring at room temperature for 4 hours.Then, the reaction solution was poured into water to remove the resin content. Let it solidify, wash thoroughly until the washing solution becomes neutral, and
It was vacuum dried at 0°C for 7 hours. The sulfonated polysulfone thus obtained has an ion exchange capacity of 1.
The amount was 9 m equivalent/g of resin.

On the other hand, the anisotropic ultrafiltration membrane made of polysulfone having the repeating unit of formula (B) obtained in Example 1 was immersed in warm water at 80°C for 1 hour, and then heated at 25°C for 1 hour.
It was immersed in a 0% by weight aqueous 1,4-butanediol solution for 1 hour, and then left in a dryer at about 60° C. for 5 minutes to dry.

A sulfonated product of polysulfone having the repeating unit of formula (C) described above is dissolved in ethylene glycol monomethyl ether to obtain a 1.0% by weight uniform film-forming solution, which is then mixed with the repeating unit of formula (B). It was coated on an anisotropic ultrafiltration membrane made of polysulfone, left at room temperature to evaporate almost all the solvent, heated at 60°C for 5 minutes to form an anionically charged semipermeable membrane. A composite membrane was obtained.

[0055] As a result of measuring the permeation flux of pure water for this anion-charged semipermeable composite membrane, it was found to be 19.7 l/m2.
It was hr. Further, as a result of measuring the permeability of a monodisperse aqueous solution of PEG having a weight average molecular weight of 2,000, the rejection rate was 92.6%. Similarly, the weight average molecular weight is 9
As a result of measuring the permeability of a PEG aqueous solution having a concentration of 60%, the blocking rate was 82.8%.

Comparative Example 3 In order to investigate the effect of negative charge on the anionically charged semipermeable composite membrane obtained in Comparative Example 2, a quaternary ammonium salt as a cationic substance and an organic acid as an anionic substance were used. Table 4 shows the results of a permeation test for an aqueous solution (concentration 1000 ppm).

[Table 4]

Claims (1)

[Claims] Claim 1: An anion-charged film in which a thin layer of a sulfonated polyaryletherketone having a repeating unit A of the following formula (A) is formed on the surface of a porous membrane having an anisotropic structure. type semipermeable composite membrane