JPS61222503A - Method for preparing desalted water - Google Patents

Abstract

PURPOSE:To prepare desalted water suitable for making ultra-pure water in a high desalting ratio at a high water transmitting speed under low treatment pressure to low concn. brine, by using a semipermeable membrance having a sulfonic acid group. CONSTITUTION:Sulfonated polyaral ether which was obtained by sulfonating polyrayl ether comprising a repeating unit I (wherein R is -CO- or -SO2-) or a linear polyaryl ether copolymer comprising the repeating unit I and a repeating unit II (wherein R' is a C-C bond or a divalent group containing -CO- or -SO2-) with conc. sulfuric acid, is dissolved in ethylene glycol monomethyl ether and a low volatile org. compound such as lactic acid is added to the resulting solution as an additive to prepare a film forming solution which is, in turn, applied to a support membrance such as a polysulfone dry ultrafiltration membrane and the solvent is subsequently evaporated to obtain a composite semipermeable membrane having a membrane like skin layer. For example, relatively low concn. brine, obtained after raw water was partially desalted by using a conventional reverse osmosis membrane, is treated by using this membrane to obtain desalted water.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing desalinated water, and particularly to a method for producing desalted water that can be suitably applied to the production of ultrapure water.

(Prior art) Ultrapure water is essential for the manufacture of semiconductor devices in the electronics industry, and is not only required to have a resistivity close to that of theoretical water, but also to contain as few particles and bacteria as possible. is required.

In recent years, in order to produce such ultrapure water, a method using a membrane treatment method has been put into practical use, for example, as described in "Applications of Membrane Separation Technology", September 1981, No. 304-309. There is. In this method, raw water is subjected to pretreatment such as coagulation sedimentation and filtration to remove suspended solids, then ionic salts are removed using an ion exchange resin, and then filtered through an ultrafiltration membrane or reverse osmosis membrane. It removes fine particles, microorganisms, colloidal substances, etc. If the salt concentration in the raw water is high, pretreatment using a reverse osmosis membrane may be added. In other words, conventionally, ultrafiltration membranes and reverse osmosis membranes have been used to produce ultrapure water, but the removal rate of salts is not high enough for the production of ultrapure water. It is only used to remove particulates and to partially desalinate raw water as a pre-treatment. Furthermore, especially in the conventional method using a reverse osmosis membrane, the osmotic pressure of salt water is high, so high pressure is required for treatment, and the membrane water permeation rate is extremely low, resulting in low treatment efficiency. According to the method, the ion exchange resin must be regenerated again and again.

(Objective of the Invention) As a result of intensive research to solve the above-mentioned problems, the present inventors have discovered that a semipermeable membrane having a sulfonic acid group, particularly a skin layer having solute separation activity, has a sulfonic acid group and According to the composite semipermeable membrane formed in the form of an extremely thin film, it not only shows an extremely high salt removal rate at a relatively low processing pressure, especially for salt water with a relatively low salt concentration. , has found that it has a high water permeation rate, and therefore, it has been found that desalinated water with a salt concentration of about ppb can be easily and efficiently obtained by a method using a composite semipermeable membrane according to N'J'. This led to the present invention.

Therefore, an object of the present invention is to provide a method for producing desalinated water, and in particular, an object of the present invention is to provide a method for producing desalted water that can be suitably applied to the production of ultrapure water.

(Structure of the Invention) The method for producing desalted water according to the present invention is characterized by treating salt water with a semipermeable membrane having sulfonic acid groups. After that, further desalting is carried out using a composite semipermeable membrane consisting of a thin skin layer having a sulfonic acid group and having a solute separation activity, and a support membrane that integrally supports this skin layer. .

The semipermeable membrane having sulfonic acid groups used in the method of the present invention is a semipermeable membrane made of a polymer in which sulfonic acid groups account for most of the total ion exchange groups, preferably 70% or more, particularly preferably 90% or more. be.

As long as the sulfonic acid group is within the above range among all ion exchange groups, the remaining ion exchange group may be an ion exchange group other than the sulfonic acid group, for example, a carboxylic acid group.

In the present invention, as a semipermeable membrane having a sulfonic acid group that can be particularly suitably used, a sulfonated polyarylether obtained by sulfonating a polyarylether consisting of repeating units, or the above repeating unit A and repeating unit B (however, , R represents -CO- or -SO,-, and Ro represents a carbon-carbon bond or a divalent group containing -〇〇- or -5O8-). Examples include a composite semipermeable membrane in which a skin layer made of a sulfonated polyaryl ether formed by a sulfonated polyaryl ether is integrally laminated on an ultrafiltration membrane as a support membrane.

Such a composite semipermeable membrane is preferably produced by sulfonating a polyarylether consisting of the above-mentioned repeating unit A or a linear polyarylether copolymer consisting of the above-mentioned repeating unit A and repeating unit B, respectively. The aryl ether is prepared and mixed with an alkylene glycol alkyl ether such as ethylene glycol monomethyl ether, which may contain a small amount of an aprotic polar organic solvent, and a water-soluble and low-volatility organic compound as an additive or It can be obtained by applying a film-forming solution containing an inorganic salt as an additive onto a dried support film, and then evaporating the organic solvent from this film-forming solution.

The above sulfonated polyaryl ether can be obtained by treating the corresponding polymaryl ether with concentrated sulfuric acid. In the present invention, the sulfonated polyaryl ether obtained in this way is
The logarithmic viscosity measured at a temperature of 30 ° C. of a solution prepared by dissolving g in 100 ml of N-methyl-2-pyrrolidone is 0.2 or more, and the ion exchange capacity is 2.3 milliequivalents/g or less. is desirable. When the ion exchange capacity exceeds 2.3 milliequivalents/g, the sulfonated polyarylether becomes water-soluble and is unsuitable as a material for a semipermeable membrane for desalting salt water. This is because when the logarithmic viscosity is smaller than 0.2, it is difficult to form a uniform skin layer without defects such as pinholes.

In addition, when forming a skin layer using a sulfonated polyaryl ether obtained by sulfonating the linear polyaryl ether copolymer, the linear polyaryl ether copolymer has a repeating content of 10 mol% or more. Unit A and 9
It is preferable that the repeating unit B is 0 mol % or less.

The sulfonic acid group possessed by the above-mentioned sulfonated polyarylether is represented by the formula -So,M, where M is hydrogen,
Indicates an alkali metal or tetraalkylammonium.

For example, by sulfonating a polyaryl ether, washing the sulfonated polyaryl ether with water, and drying it, a sulfonated polyaryl ether having free sulfonic acid groups can be obtained. Furthermore, by suspending and treating this sulfonated polyarylether in an aqueous solution, methanol, ethanol solution, etc. of an alkali metal hydroxide or alkali metal alcoholade, the sulfonic acid group can be converted into an alkali metal salt. As the alkali metal hydroxide, for example, sodium hydroxide, potassium hydroxide, lithium hydroxide, etc. are used, and as the naralkali metal alcoholade, for example, sodium methylate, potassium methylate, potassium ethylate, etc. are used. Furthermore, if a sulfonated polyaryl ether is similarly treated with a solution of a tetraalkylammonium such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, or tetrabutylammonium hydroxide, the sulfonated polyaryl ether can be The acid group can be the corresponding tetraalkylammonium salt.

The composite semipermeable membrane that can be suitably used in the method of the present invention comprises the above-mentioned sulfonated polyarylether, a water-soluble and low-volatility compound as an additive, and a small amount of an aprotic polar organic solvent. It can be obtained by dissolving it in an alkylene glycol alkyl ether that may contain it to form a film-forming solution, applying this onto a dried support film, and then evaporating the organic solvent from this film-forming solution.

As the organic solvent for preparing the film-forming solution, alkylene glycol alkyl ethers in which the alkylene group has 2 to 4 carbon atoms and the alkyl group has 1 to 4 carbon atoms are particularly preferably used.

This solvent has excellent solubility for the sulfonated polyarylether and is highly volatile, and on the other hand, as described later, it is suitable for use as a support membrane in the composite semipermeable membrane used in the present invention. This is because it does not dissolve the polysulfone ultrafiltration membrane that can be used.

Specific examples of such alkylene glycol alkyl ethers include alkylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether, ethylene glycol dimethyl ether, and ethylene glycol monoethyl ether. glycol methyl ethyl ether,
Mention may be made of alkylene glycol dialkyl ethers such as ethylene glycol diethyl ether. In particular, ethylene glycol monomethyl ether is preferably used because it has excellent solubility in sulfonated polyaryl ether and is highly volatile.

However, depending on the sulfonated polyaryl ether used, it may be difficult to dissolve it in the alkylene glycol alkyl ether, or it may simply swell. It was found that it dissolves well in a mixed solvent prepared by adding a polar organic solvent.

As such an aprotic polar organic solvent, for example, dimethyl sulfoxide, N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, etc. are preferably used.

In such a mixed solvent, the proportion of the aprotic polar organic solvent is as follows:
00 parts by weight is preferably 5 parts by weight or less, particularly 3 parts by weight or less. In the mixed solvent, if the amount of the aprotic polar organic solvent is more than 5 parts by weight per 100 parts by weight of the alkylene glycol alkyl ether, use a dry polysulfone ultrafiltration membrane as described below as the support membrane to prepare the membrane forming solution. This is because when applied on this support membrane, the support membrane dissolves or swells, making it impossible to obtain a composite semipermeable membrane with good performance.

In addition, as a solvent for the membrane-forming solution, using alkylene glycol alkyl ether or a mixed solvent of this and a small amount of the aprotic polar organic solvent can be used, as described later, after applying the membrane-forming solution to the support membrane. In the step of evaporating and removing the solvent from the film-forming solution, it is advantageous because all the solvent can be practically removed by heating at room temperature or with a slight amount of heat, and a uniform thin film without defects can be obtained. .

The concentration of the sulfonated polyaryl ether in the membrane forming solution is related to the thickness of the semipermeable membrane made of these polymers in the resulting composite semipermeable membrane, but is usually 0.05 to 1.
A range of 0% by weight is preferred, and a range of 0.1 to 5% by weight is particularly preferred.

When manufacturing a composite semipermeable membrane that can be suitably used in the method of the present invention, the membrane forming solution contains specific additives. Among such additives, at least one selected from the group consisting of polyhydric alcohols, polyalkylene glycols, carboxylic acids, salts thereof, hydroxycarboxylic acids and salts thereof is used as the organic compound. These organic compounds as additives must be water-soluble and have low volatility, and must be dissolved in the film forming solution. Polyalkylene glycols, carboxylic acids, salts thereof, and hydroxycarboxylic acids or salts thereof are preferably used.

Specific examples include ethylene glycol, propylene glycol, glycerin, 1,4-butanediol, etc. as polyhydric alcohols, diethylene glycol, triethylene glycol, dipropylene glycol, etc. as polyalkylene glycols, and citric acid, as carboxylic acids.
Oxalic acid and the like, hydroxycarboxylic acids such as lactic acid and hydroxybutyric acid, and salts of carboxylic acids and hydroxycarboxylic acids include sodium salts and potassium salts.

Furthermore, inorganic salts that are water-soluble and dissolve in the membrane forming solution can also be used as additives. Examples of such inorganic salts include lithium chloride, lithium nitrate, and magnesium perchlorate.

The concentration of these additives in the film forming solution is usually 0.1
~80% by weight. Although the effects of these additives on the formation of composite semipermeable membranes are not necessarily clear,
It is related to the micropore diameter of the semipermeable membrane formed from sulfonated polyaryl ether, and when the membrane forming solution is applied onto the ultrafiltration membrane that is the supporting membrane, the solvent and additives of the membrane forming solution are It appears to modify the surface of the ultrafiltration membrane, and thus, by selecting the type and amount of the additive used, the performance of the resulting composite semipermeable membrane, particularly the salt removal rate and the amount of water permeated through the membrane, can be controlled over a wide range. be able to.

The membrane forming solution prepared as described above is then applied onto a dry ultrafiltration membrane as a support membrane. As is well known, a dry ultrafiltration membrane is produced by heating a wet ultrafiltration membrane prepared by a wet method to an appropriate temperature to evaporate the water contained in the pores of the membrane. It can be obtained by substantially drying.

In the above method, the ultrafiltration membrane as a support membrane for applying the membrane-forming solution is preferably an ultrafiltration membrane made of polysulfone, for example, an ultrafiltration membrane of the following formula C An ultrafiltration membrane consisting of a repeating unit of is preferably used.

As mentioned above, when using an alkylene glycol alkyl ether or a mixed solvent containing a small amount of the aprotic polar organic solvent as the solvent for the membrane forming solution, usually
Substantially all of the solvent can be evaporated at room temperature without the need for heating; however, after the coating solution is applied onto the support membrane, it is possible to evaporate the solvent if necessary. May be heated. The heating temperature may be appropriately selected depending on the solvent used, but a temperature of 150° C. or lower is usually sufficient. Incidentally, in order to promote evaporation of the solvent after the film-forming solution is applied onto the support film, the film-forming solution may be heated in advance and then applied onto the support film.

The thickness of the thin semipermeable membrane based on sulfonated polyarylether in the composite semipermeable membrane thus obtained depends on the concentration of these polymers in the membrane forming solution and the coating thickness of the membrane forming solution on the support membrane. Although it depends on the situation, it is better to make the composite semipermeable membrane thinner to increase the water permeation rate, and thicker to increase the strength.

Therefore, although not particularly limited, it is preferable that a semipermeable membrane having a solute separation activity based on sulfonated polyarylether generally has a thickness in the range of 0.01 to 5 μm.

In this way, the thickness is usually less than 108 m,
A sulfonated polyaryl ether composite semipermeable membrane can be obtained in which a skin layer having sulfonic acid groups and separation performance is made of sulfonated polyaryl ether, and this skin layer is integrally laminated on a support membrane. still,
Depending on the type of additive used, additives may remain in the composite semipermeable membrane obtained in this way, but the composite semipermeable membrane obtained is immersed in water, It is easily removed by passing water through it.

For example, the method of the present invention is, for example, the method of removing the raw water partially using a conventional reverse osmotic membrane, and without the above -destroyed salt in the composite semi -permeable membrane, and the partial destroyer described above. This includes a method of immediately desalinating raw water with a relatively high salt concentration using the above-mentioned composite semipermeable membrane, but in particular, the above-mentioned composite semipermeable membrane desalinates extremely high salt water with a low salt concentration of 0.1% or less. In order to take advantage of the characteristics of salt removal rate and high water permeation rate, it is desirable to treat salt water that has been previously desalinated to a salt concentration of 0.1% as raw water. This is because desalinated water having a salt concentration in ppb units can be easily and efficiently obtained by such a two-stage treatment.

In the method of the present invention, the treatment temperature of raw water is usually 0.
-95°C. The higher the temperature, the higher the water permeation rate. Regarding the processing pressure, as described above, according to the method using the above-mentioned composite semipermeable membrane, a high water permeation rate can be obtained at a relatively low processing pressure, and
The higher the treatment pressure, the higher the water permeation rate, so the treatment pressure is not limited in any way, but usually 0.1 to 1
00kg/cJ, preferably 1-60
kg/cd.

(Effects of the Invention) As described above, the composite semipermeable membrane having the skin layer made of the sulfonated polyaryl ether and preferably having a thickness of 10 μm or less has sulfonic acid groups and is highly hydrophilic. In addition, it not only shows an extremely high salt removal rate at a relatively low treatment pressure for salt water with a relatively low salt concentration, but also has a high water permeation rate.
．． By treating salt water desalinated to 1% with the above-mentioned composite semipermeable membrane, desalinated water with a salt concentration in ppb units can be easily and efficiently obtained. It can be suitably used in the production of pure water.

(Examples) The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples in any way. In the examples, the solute removal rate and water permeation rate were determined by the following formulas.

Example 1 (1) Repeating unit A for producing sulfonated polysulfone
.

10 g of polysulfone was added to 80 ml of 97% concentrated sulfuric acid, and the mixture was stirred gently at room temperature for 4 hours to obtain a dark brown viscous reaction liquid. This was placed in a water bath to solidify the sulfonated polysulfone. After washing with water, 0.
The mixture was left overnight in 800 ml of 5N aqueous sodium hydroxide solution. Next, the polymer was washed until the washing solution became neutral, and then vacuum-dried at 30° C. for 7 hours. The pale yellow granular sulfonated polysulfone thus obtained has a logarithmic viscosity of 3.00 and a sulfonic acid group of 10% of the total ion exchange groups.
0%, and the ion exchange capacity was 1.92 meq/g.

(2) Preparation of composite semipermeable membrane Consisting of repeating units of the above formula C, with an average molecular weight of 20,000
An anisotropic ultrafiltration membrane having a removal rate of 10% for polyethylene glycol was dried at a temperature of 60° C. to obtain a dry ultrafiltration membrane for a support membrane.

0.8 g of the sulfonated polysulfone obtained above was mixed with 89.9 g of ethylene glycol monomethyl ether. 10 g of lactic acid was added thereto, and the resulting polymer solution was filtered through a 108 m filter paper and used as a membrane forming solution.

This membrane-forming solution was applied onto the dry ultrafiltration membrane, and after volatilizing most of the solvent at room temperature, it was heat-treated at 60°C for 5 minutes to form a composite film with a skin layer of 0.5 μm in thickness. A semipermeable membrane was obtained.

(3) Production of desalinated water Using the composite semipermeable membrane described above, aqueous solutions containing sodium chloride at various concentrations were treated at 25° C. and 10 kg/crA. The relationship between salt concentration and salt removal rate is shown in the table and drawings. Composite semipermeable membrane has a salt concentration of 0.1%, especially 0.01%
It is clear that the salt removal rate is extremely high when: Moreover, the water permeation rate was 4 m'/m''/day.

Example 2 (1) Production of sulfonated polysulfone copolymer 57 mol % of repeating units of formula A, and 2B.

10 g of a linear polysulfone copolymer consisting of 43 mol% of repeating units of
was added to 80ml of 97% concentrated sulfuric acid, dissolved, and dissolved at room temperature for 4 hours.
The reaction was stirred for a period of time to obtain a blackish brown viscous reaction liquid. This was placed in a water bath to solidify the sulfonated polysulfone copolymer. After washing with water, it was left overnight in 800 ml of a 0.5N aqueous sodium hydroxide solution. Next, the polymer was washed until the washing solution became neutral, and then vacuum-dried at 60° C. for 5 hours.

The sulfonated polysulfone copolymer thus obtained had a logarithmic viscosity of 0.84, sulfonic acid groups accounted for 100% of the total ion exchange groups, and an ion exchange capacity of 1.2 meq/g. .

(2) 0.8 g of linear sulfonated polysulfone copolymer obtained in the preparation of composite semipermeable membrane
79.2 g of ethylene glycol monomethyl ether
After dissolving in the solution, 20 g of glycerin was added, and the resulting polymer solution was filtered through a 10 μm filter paper, and the resulting polymer solution was used as a membrane forming solution.

This membrane forming solution was applied onto the same polysulfone dry ultrafiltration membrane as in Example 1, and after volatilizing most of the solvent at room temperature,
A heat treatment was performed at a temperature of 60° C. for 5 minutes to obtain a composite semipermeable membrane having a skin layer with a thickness of 0.5 μm.

(3) Production of desalinated water Salt water was treated under the same conditions as in Example 1 using the above composite semipermeable membrane. The relationship between salt concentration and salt removal rate is shown in the table and drawings. This composite semipermeable membrane also has a salt concentration of 0.1%, especially 0.0%.
It is clear that when it is 1% or less, it has an extremely high salt removal rate. Moreover, the water permeation rate was 4 m'/m''7 days.

For comparison, the figure shows the relationship between salt concentration and salt removal rate when salt water is similarly treated using a reverse osmosis membrane made of cellulose acetate. Further, the water permeation rate was 1 m''/m''/day.

Example 3 (1) Production of sulfonated polyaryletherketone) Polyaryletherketone (1 (manufactured by 1 company) consisting of repeating unit A2)
10 g of EK 45G) was added to 80 ml of 97% concentrated sulfuric acid, reacted at room temperature for 8 hours, and then left at room temperature for an additional 17 hours to obtain a concentrated sulfuric acid solution of the above polymer.

The above solution was poured into a thin thread onto pure water cooled in a water bath to solidify the polymer, collected by filtration, and poured with pure water for 50 minutes.
Washed twice. IN sodium hydroxide aqueous solution 600a+1 was added to this polymer, and after leaving it for 3 hours, the pH of the cleaning solution was
It was washed until the value was 7.

Thereafter, the polymer was dried at 60° C. for 16 hours to obtain 11.6 g of sulfonated polyaryletherketone. This polymer is sulfonated.

This was confirmed by its infrared absorption spectrum and nuclear magnetic resonance spectrum.

The ion exchange capacity of this polymer is 1.5 meq/g, and the logarithmic viscosity measured at 30°C for a solution of 0.5 g of polymer dissolved in 100 ml of N-methylpyrrolidone is 1.
．． It was 30.

(2) After dissolving 9 g of the sulfonated polyaryletherketone obtained in the preparation of the composite semipermeable membrane in 89.1 g of ethylene glycol monomethyl ether, 10 g of glycerin was added, and the solution was obtained by filtering through a 10 μm filter paper. was used as a film forming solution.

The above membrane forming solution was applied onto the same dry polysulfone ultrafiltration membrane as used in Example 1, and after volatilizing most of the solvent at room temperature, it was heat treated at a temperature of 60 ° C. for 5 minutes. A composite semipermeable membrane was obtained.

(3) Production of desalinated water Salt water was treated under the same conditions as in Example 1 using the above composite semipermeable membrane. The figure shows the relationship between salt concentration and salt removal rate.

It is clear that this composite semipermeable membrane also has an extremely high salt removal rate when the salt concentration is 0.1%, especially 0.01% or less. In addition, the water permeation rate was 4 m3/m''/day.

Example 4 Commercially available semipermeable membrane module (NTR71 manufactured by Nitto Electric Industry Co., Ltd.)
97S4) was used to treat a 0.2% aqueous sodium chloride solution at 30 kg/aJ and 25° C. to obtain demineralized water with a sodium chloride concentration of 20 ppa+. The water permeability rate is 2
01/min.

Subsequently, this demineralized water was treated using the same composite semipermeable membrane as used in Example 2 under the same conditions as in Example 2 to obtain demineralized water with a sodium chloride concentration of 20 ppb. The water permeation rate was 3.97 m3/m2/day.

[Brief explanation of drawings]

The drawing shows that using the composite semipermeable membrane according to the present invention, aqueous sodium chloride solutions of various concentrations were heated at 25°C at 201 g/ai.
1 is a graph showing the relationship between salt concentration and salt removal rate when treated under conditions of 1.

Claims (5)

[Claims] (1) A method for producing demineralized water, which comprises treating salt water with a semipermeable membrane having sulfonic acid groups. (2) a thin film-like skin layer in which the semipermeable membrane has a sulfonic acid group and has a solute separation activity;
2. The method for producing demineralized water according to claim 1, which is a composite semipermeable membrane comprising a support membrane that integrally supports the demineralized water. (3) A composite semipermeable membrane having a sulfonic acid group is a sulfonated polyaryl ether made by sulfonating a polyaryl ether consisting of the repeating unit A ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ A or the above repeating unit A
and repeating unit B ▲There are mathematical formulas, chemical formulas, tables, etc.▼ B (However, R represents -CO- or -SO_2-, and R' represents a carbon-carbon bond or a divalent group.) A linear polyaryl consisting of Claim No. 1, characterized in that a skin layer having a solute separation activity and made of a sulfonated polyarylether obtained by sulfonating an ether copolymer is integrally laminated on an ultrafiltration membrane as a support membrane. The method for producing desalinated water according to item 2. (4) After desalting the salt concentration in salt water to 0.1% in advance, a thin film-like skin layer that has sulfonic acid groups and has solute separation activity, and a support film that integrally supports this skin layer. A method for producing desalinated water characterized by further desalination using a composite semipermeable membrane consisting of: (5) A composite semipermeable membrane having a sulfonic acid group is a sulfonated polyaryl ether made by sulfonating a polyaryl ether consisting of the repeating unit A ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ A or the above repeating unit A
and repeating unit B ▲There are mathematical formulas, chemical formulas, tables, etc.▼ B (However, R represents -CO- or -SO_2-, and R' represents a carbon-carbon bond or a divalent group.) A linear polyaryl consisting of Claim No. 1, characterized in that a skin layer having a solute separation activity and made of a sulfonated polyarylether obtained by sulfonating an ether copolymer is integrally laminated on an ultrafiltration membrane as a support membrane. The method for producing desalinated water according to item 4.