JPH08173777A - Reverse osmosis membrane and its surface treating method - Google Patents

Abstract

PURPOSE: To enable highly selective separability and high water permeability to be exhibited even in operation under low pressure by a method wherein a membrane surface is treated by irradiation with ultraviolet rays in a reverse osmosis membrane for separating components of a liquid mixture by selective permeation. CONSTITUTION: In a reverse osmosis membrane being a dual membrane wherein in an asymmetrical model used suitably for manufacture of super pure water used for making freshwater from seawater, desalinization of salt water, manufacture of semiconductor, etc., a separating function layer having a membrane-separating function made of a material different from a finely porous support membrane, is covered on the support membrane, a membrane surface is treated by irradiation with 10-400nm ultraviolet rays. Further, the separating function layer forming the dual film is formed of a cross-linked polymer or cross-linked aromatic polyamide. Then, the carboxylic group concentration of the membrane surface -COOH/Ctotal is at least 0.015. When the separating function layer is formed of a cross-linked polyamide, 0.05wt.% of salt water is used. When a reverse osmosis test is carried out under conditions of 0.34MPa pressure and 25 deg.C temperature, permeability of water is made to be at least 0.4m<3> /m<2> .day.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high performance reverse osmosis membrane for selectively permeating and separating the components of a liquid mixture, and a surface treatment method thereof. The reverse osmosis membrane obtained by the present invention can be used particularly for desalination of seawater, desalination of canned water, and production of ultrapure water used for production of semiconductors. Furthermore, softening of hard water, removal of pollutants from river water, and selective removal or recovery of pollutants or useful substances contained therein from dyeing wastewater, electrodeposition paint wastewater, etc. -It can contribute to the conversion.

[0002]

2. Description of the Related Art Conventionally, reverse osmosis membranes which have been industrially used include asymmetric membrane type and composite membrane type.

Of these, a cellulose acetate membrane is a main example of the asymmetric membrane (see, for example, US Pat. No. 3,133,
No. 132, No. 3, 133, 137).
However, this membrane has problems in hydrolysis resistance, microbial resistance, etc., and the salt rejection and water permeability were not sufficient. Therefore, although the cellulose acetate asymmetric membrane is used for some applications, it has not been put to practical use in a wide range of applications.

It was devised to make up for these drawbacks,
It was a composite membrane in which a separation function layer that substantially controls the membrane separation function was coated on a microporous support membrane with a different material. In the composite membrane, it is possible to select the optimum material for each of the separation functional layer and the microporous support membrane, and various methods can be selected for the membrane formation technology.

Most of the composite membranes currently on the market have an active layer obtained by crosslinking a gel layer and a polymer on a microporous support membrane, and an active layer obtained by interfacial polycondensing monomers on the microporous support membrane. There are two types. Specific examples of the former include Japanese Patent Application Laid-Open No. 49-13282 and Japanese Patent Publication No. 55-55.
No. 38164, PB Report 80-18209
0, Japanese Patent Publication No. 59-27202, 61-2710.
There is No. 2 publication, etc. Specific examples of the latter include US Pat. Nos. 3,744,942 and 3,926,798.
No. 4,277,344, JP-A-5
No. 5-147106, No. 58-24303,
No. 62-121603 is available. These composite membranes are attracting attention as membranes with high permeability and high selective separation. In recent years, a loose RO membrane, which is located between the reverse osmosis membrane and the ultrafiltration membrane, has appeared and has come into use. Loose R
The O film has a high exclusion rate of medium to high molecular weight molecules of several hundred to several thousand or more, divalent ions such as calcium and magnesium, and polyvalent ions such as heavy metal ions, but monovalent ions and low molecular weight. The substance is a membrane that has the property of being permeable.
In addition, this loose RO membrane has a high membrane permeation rate, and is 0.
Another feature is that a low-concentration aqueous solution of about 1% can be separated at an ultralow pressure of 10 atm or less. However, the required properties for composite membranes are increasing year by year, and
Some SRO membranes are also commercially available, but a membrane with sufficiently satisfactory performance has not yet been obtained.
In particular, low molecular weight organic substances, such as trihalomethane and its precursors and membranes with excellent performance in removing toxic substances such as pesticides,
Development of higher performance membranes such as membranes capable of separating inorganic salts and organic compounds and membranes having low water pressure and high water permeability is required.

On the other hand, utilization of light energy is being studied as a method for improving the performance of the separation membrane. In the gas separation membrane, there is an example in which the permeation flux and / or the separation coefficient are improved by irradiating the surface of the membrane with ultraviolet rays. Specific examples thereof include those relating to a polyorganosiloxane-acetylene composite film (JP-A-64-67210), those relating to a polymer film comprising a substituted silylacetylene monomer unit (JP-A-64-20239), and the like. ing. Regarding the microfiltration membrane, in Japanese Patent Laid-Open No. 2-59032,
By irradiating a polysulfone porous membrane with ultraviolet rays, the surface of the membrane is hydrophilized and a rapid decrease in filtration rate due to adsorption of proteins is suppressed. However, no application to a reverse osmosis membrane has been found so far.

[0007]

The permeability and selective separability of reverse osmosis membranes are improving year by year. However, the development of separation membranes that have the performance of removing low molecular weight organic substances, the separation of inorganic salts and organic compounds, the membranes that operate at low pressure and have high water permeability, etc., in the intermediate region between the reverse osmosis membrane and the ultrafiltration membrane. With respect to (1), a film with satisfactory performance has not yet been obtained.

It has been difficult to achieve both high selectivity and water permeability, especially when operating at a low pressure of about 0.5 MPa or less. To control the selective separability and water permeability, a method of changing the kind or composition of the monomer forming the separation functional layer of the asymmetric membrane or the composite membrane has been used.
With this method, it was very difficult to balance the two. That is, there is a contradictory relationship between the selective separability and the water permeability, such that the selective separability is significantly lowered when high water permeability is desired, and conversely the water permeability is remarkably lowered when the selective separability is prioritized.

It is an object of the present invention to provide a reverse osmosis membrane which exhibits high selective separation and high water permeability even when operated at low pressure.

[0010]

To achieve the above object, the present invention basically has the following constitution.

That is, "a reverse osmosis membrane characterized in that the membrane surface is subjected to ultraviolet irradiation treatment."

In the present invention, the asymmetric membrane has a dense layer having desalination performance and a porous layer as a support,
Both porous layers are reverse osmosis membranes made of a single material. Cellulose acetate is mainly used as the material for the asymmetric membrane. As a film forming method, for example, there is a method in which a formamide solution of cellulose acetate is cast on a glass plate to a certain thickness to evaporate the solvent, and then the formed film is immersed in hot water for heat treatment. The membrane obtained by this method has a dense layer exhibiting desalination performance on the evaporation surface side of the solvent, and a porous layer having a large number of pores and serving as a support under the dense layer.

In the present invention, the microporous support membrane forming the composite membrane is a layer having substantially no separation performance, and imparts strength to the separation functional layer having substantially separation performance. It is used for. The microporous support membrane has uniform fine pores or dense and fine pores on one side,
It has an asymmetric structure with gradually increasing fine pores to the other side, and the size of the fine pores is 1 on the dense surface of one side.
A structure having a thickness of 00 nm or less is preferable. The thickness of the microporous support film is 1 μm to several mm, preferably 10 μm or more from the viewpoint of film strength, and several 100 μm or less from the viewpoint of ease of handling and module processing. These microporous support membranes may be reinforced with cloth or non-woven fabric.

The above-mentioned microporous support membrane is, for example, "Millipore Filter VSWP" (trade name) manufactured by Millipore, or "Ultra Filter UK10" (trade name) manufactured by Toyo Roshi Kaisha, Ltd.
You can also choose from a variety of commercially available materials, such as "Office of Saline Water Research and Development Progress Report," No. 359 (1968). The material of the microporous support membrane may be a homopolymer or a copolymer of polysulfone, polyamide, polyester, cellulosic polymer, vinyl polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, polyphenylene oxide, etc., alone or in combination with these polymers. Blends can be used. Among these materials, polysulfone is generally used because it has high chemical, mechanical and thermal stability and is easy to mold. For example, polysulfone dimethylformamide (DMF)
The solution is cast on a densely woven polyester cloth or non-woven cloth to a certain thickness, and it is poured into sodium dodecyl sulfate 0.5
By wet coagulation in an aqueous solution containing 2% by weight of DMF and 2% by weight of DMF, a microporous support membrane having most of the surface with fine pores having a diameter of several tens nm or less is obtained.

The microporous support membrane is coated with a separation functional layer to produce a composite membrane. The separation functional layer is a portion that substantially separates the composite membrane, and as its material, a crosslinked or linear organic polymer can be used. In order for the composite membrane to exhibit high separation performance, the polymer is preferably polyamide, polyurethane, polyether, polyester, cellulose ester, polyimide, polyamic acid, vinyl polymer, more preferably polyamide, especially crosslinked polyamide. .

The cross-linked polyamide is not particularly limited, but cross-linked aromatic polyamide is preferable, and as the cross-linked aromatic polyamide, a polyfunctional aromatic amine selected from aromatic diamine and aromatic triamine and 2
A three-dimensional crosslinked aromatic polyamide obtained by the reaction of a functional and / or trifunctional polyfunctional aromatic acid halide is preferred.

The functional layer is coated by a method of coating a polymer, a method of further crosslinking the coated polymer, a method of polymerizing a monomer on the surface of a microporous support membrane,
Alternatively, it can be performed by a method of interfacial polycondensation on the surface of the microporous support film.

The thickness of the separation functional layer is 5 to 1000 nm, preferably 10 to 800 nm, more preferably 5.
It is 0 to 500 nm. If the thickness of the separation functional layer is too small, many defects will occur during film formation and scratches will be liable to occur during handling, and defects and scratches may occur even when pressure is applied, leading to a reduction in rejection rate. . On the other hand, if the thickness of the separation functional layer is too large, the water permeability becomes low, which is not preferable.

In the present invention, the carboxyl group concentration (-COOH / C _{[tot al]} ) on the membrane surface of the reverse osmosis membrane is 0.015.
Or more, more preferably 0.018 or more, still more preferably 0.020 or more. This value represents the ratio of carbon contained in the carboxyl group in all carbon atoms existing on the film surface. X-ray photoelectron spectroscopy (ESCA) is adopted as a method of analyzing the chemical composition of the film surface. In this analysis method, the binding energy of photoelectrons emitted by X-ray irradiation is measured. Qualitative and quantitative analyzes of elements can be obtained from the positions and intensities of the ESCA spectra of core electrons such as C _1s , O _1s , and N _1s, and information on the bonding state can be obtained from chemical shifts. Specifically, depth profiling from the sample surface to 100 angstrom by the photoelectron escape angle change method and detailed functional group analysis using the gas phase chemical modification method are possible. The quantitative determination of the carboxyl concentration is performed by using the photoelectron escape angle changing method in combination with the gas phase chemical modification method. As the device, for example, ESCA manufactured by Shimadzu Corporation
750 is used, and the X-ray source is MgKα1,2 rays (125
3.6 eV) and set the photoelectron escape angle to 90 °. When the energy correction is performed with the C _1s peak value of neutral carbon being 284.6 eV, the surface composition of the film and the bonding state of atoms can be found. Further, the concentration of the carboxyl group is determined by the gas phase chemical modification method. At this time, trifluoroethanol (TFE) is used for labeling the carboxyl group, and dicyclohexylcarbodiimide (DCC) is used as the dehydration catalyst during the reaction. TF by polyacrylic acid (PAA) standard sample
The reaction rate (r) of E and the residual rate (m) of DCC are obtained, and the carboxyl group concentration can be obtained from the C _1s and F _1s peak area intensities of the respective samples in consideration of r and m. Regarding the reverse osmosis membrane in the present invention, it is considered that the intermolecular or intramolecular bond forming the membrane is cleaved by ultraviolet irradiation to generate a polar group such as a carboxyl group, and the membrane surface is hydrophilized. To be

A reverse osmosis membrane having a separation functional layer made of crosslinked polyamide was subjected to ultraviolet irradiation treatment and then subjected to a reverse osmosis test using 0.05% by weight saline at a pressure of 0.34 MPa and a temperature of 25 ° C. Has a permeability of 0.4 m ³ / m ² · day or more, preferably 0.7 m ³ / m ² · day or more, more preferably 1.5 m ³ / m ² · day or more. Further, regarding the reverse osmosis membrane whose separation functional layer is composed of cross-linked aromatic polyamide, when the reverse osmosis test is conducted under the conditions of pressure of 1.47 MPa and temperature of 25 ° C. using 0.15 wt% saline solution after irradiation with ultraviolet rays, Has a permeability of 1 m ³ / m ² · day or more, preferably 1.5 m ³ / m ² · day or more, more preferably 2 m ³
/ M ² · day or more. It is conceivable that the permeability of water will increase with the decomposition of the cross-linked portion of the separation functional layer after the ultraviolet irradiation treatment and the increase of hydrophilic groups such as carboxyl groups. Therefore, from the correlation between the carboxyl group concentration after the UV irradiation treatment and the water permeability, it is possible to select the UV irradiation condition by using the carboxyl group concentration as an index of the water permeability.

In the present invention, the surface of the reverse osmosis membrane is irradiated with ultraviolet rays. The surface to be irradiated is a side having desalination performance, for example, a dense layer side in an asymmetric membrane and a separation functional layer side in a composite membrane.

The wavelength of ultraviolet rays is 10 to 400 nm, preferably 100 to 365 nm, more preferably 160 to 2 nm.
It is 60 nm. In general, the photon energy of electromagnetic radiation including ultraviolet rays is inversely proportional to the wavelength λ, so that the photon energy of ultraviolet rays is stronger on the shorter wavelength side and weaker on the longer wavelength side. Further, the longer the wavelength side is, the more the film dries due to the influence of the heat energy of light and the water permeability decreases. Further, if the wavelength is too short, it becomes difficult to obtain an efficient light source. The types of light source lamps used include low pressure, high pressure, ultra high pressure mercury lamps and excimer lamps. A mercury lamp emits light having a wavelength range of about 100 to 300 nm, and has a particularly strong line spectrum of one to a few lines in the range. A low pressure mercury lamp has a high pressure mercury lamp at 184.9 nm and 253.7 nm. Is 365-579 nm, and ultra-high pressure mercury lamps are 365, 40 nm.
It has a strong line spectrum at 5,436 nm. On the other hand, the excimer lamp can obtain a spectrum in a relatively narrow band with high efficiency, and the wavelength of the spectrum can be arbitrarily selected by selecting the type of discharge gas to be used. Since the high-pressure mercury lamp and the ultra-high-pressure mercury lamp have a line spectrum even in the visible region, they generate a large amount of heat during irradiation and may cause the film to dry. Therefore, a low-pressure mercury lamp having a line spectrum on the relatively short wavelength side, or 172
It is preferable to use a xenon excimer lamp having a spectrum in nm, but the surface treatment method of the present invention is not limited to these light sources.

A relation A (sec / sec) of the square of the irradiation time t (sec) of the ultraviolet ray and the distance 1 (cm) from the light source to the film surface.
cm ² ) = t / l ² is 0.001 ≦ A ≦ 500,000,
It is preferably 0.01 ≦ A ≦ 10000, and more preferably 1 ≦ A ≦ 100. Since the intensity of light is inversely proportional to the square of the irradiation distance, if the irradiation distance is long, the photon energy of ultraviolet rays is attenuated and the irradiation process takes a long time. Further, when the irradiation distance is short, when the ultraviolet irradiation is carried out for a long time, the polymer forming the dense layer or the separation functional layer is decomposed, and as a result, the rejection rate of salts and organic substances in the membrane is remarkably lowered. Since there is a correlation between the irradiation time and the irradiation distance in this way, it is necessary to select the conditions of time and distance that give the optimum value of A = t / l ² . For example, the distance from the light source is 2 cm (=
l), when the ultraviolet ray is irradiated with the irradiation time of 100 seconds (= t), A = 25. When the value of A is too large, the rejection rate of the membrane becomes small, and when the value of A is too small, the water permeability is insufficient.

The UV irradiation amount (UV illuminance × time) on the surface of the reverse osmosis membrane is the same as that of a UV light when a linear light source having a strong line spectrum at wavelengths of 184 nm and 254 nm and an electric power of 220 W is attached to a reflecting plate. As for the irradiation time and the distance from the light source to the film surface, the value of A is 0.001 ≦ A ≦ 500.
It is preferable that the irradiation amount is equal to the ultraviolet irradiation amount under the condition set to be 000. However, this is not intended to limit the light source in any way, and is merely an example to show a preferable range of the ultraviolet irradiation amount. Therefore,
If the same UV irradiation dose can be obtained, the UV irradiation dose will be the same even if the light source conditions such as line spectra of different wavelengths or power wattages or other point or surface light sources or no reflector are changed. If it falls within the range, it is not affected in this case.

More preferably, it is 0.01 ≦ A ≦ 10000, more preferably 1 ≦ A ≦, calculated under the same light source conditions.
This is equivalent to the ultraviolet irradiation amount when the irradiation condition is set to 100. The ultraviolet irradiation amount is a unit of the ultraviolet exposure amount required to change the performance of the reverse osmosis membrane, and for example,
Ultraviolet illuminance (mW / cm ² ) × irradiation time (sec) = UV irradiation amount (mJ). Therefore, it is considered that the irradiation conditions can be determined irrespective of the power and shape of the light source if the amount of UV irradiation required to obtain a reverse osmosis membrane having a certain desired performance is known in advance. As an example,
1 and 2 are schematic diagrams of a low pressure mercury lamp part of a light source of an ultraviolet irradiation experimental device (PL11-1102WS) manufactured by Sen Special Light Source Co., Ltd. and the entire device. The device has two 110 W linear light sources, and a reflector is attached to the upper surface of the light source. The linear light source includes a straight tube type, a U-shaped type, an annular type and the like, but the light source of the device is a U-shaped type.

The power of the ultraviolet light source lamp is 1 to 3000
W, preferably 10 to 500 W, more preferably 20 to
It is 300W. If the lamp output is too low, the intensity of light will be weak, and thus irradiation will take a long time. On the contrary, if the output is too high, the heat generated from the lamp will be large, and the film will dry and the water permeability will decrease.

The ambient temperature when irradiating with ultraviolet rays is 10 to 10.
60 ° C, preferably 15-40 ° C, more preferably 20
~ 30 ° C. If the ambient temperature is too high, the membrane undergoes heat shrinkage during irradiation, and the surface of the dense layer or the separation functional layer is blocked, resulting in a decrease in water permeability. If the output of the light source lamp used is large or the irradiation time is long,
The temperature in the system rises gradually during irradiation, so a cold mirror, cold filter, air blower, etc. can be used as necessary.
It is preferable to install a cooling device such as to suppress the temperature rise.

The atmosphere for irradiation with ultraviolet rays preferably has an oxygen concentration of ≤20%, and more preferably an inert gas. Examples of the inert gas include nitrogen, helium, argon, etc., which are easily available.
Nitrogen is preferable in terms of price. Oxygen absorbs short wavelength ultraviolet rays and produces ozone. Ozone further absorbs ultraviolet rays and produces excited oxygen atoms. This reaction is represented by formula (4) when a low-pressure mercury lamp is used as a light source. The reaction mechanism of the ultraviolet irradiation treatment of the reverse osmosis membrane in the present invention is not clear so far, but it is considered to be due to the generation / breakage of a chemical bond by light energy and the oxidizing action of this atomic oxygen. Due to these effects, the crosslink density of the dense layer or the separation functional layer and the charge state of the membrane surface change,
As a result, it is considered that salt permeability and water permeability change. Since the irradiation atmosphere does not interfere with the oxidizing action of atomic oxygen, it is considered efficient to perform the ultraviolet irradiation treatment in a deoxygenated atmosphere.

O ₂ ^{185 nm} > O ₃ ^{254 nm} > O ₂ + O ( ¹ D) excited oxygen atom (4) Before ultraviolet irradiation, the surface of the film to be irradiated may be washed with distilled water or the like. After that, the irradiation treatment may be carried out in the presence of moisture on the film surface, or the moisture may be removed from the film surface by nitrogen gas, an air gun or the like, and then the film may be irradiated with ultraviolet rays. When ultraviolet rays are irradiated with water on the surface of the film, the effect of ultraviolet rays is lessened and the change in the performance of the film is smaller than that in the case of irradiation with water removed.

After the irradiation treatment with ultraviolet rays, the surface of the membrane may be washed with distilled water or the like, or the treatment may be terminated by washing with warm water of about 50 ° C. to 95 ° C. or heat treatment.

The irradiation conditions have been described above. Conditions such as the optimum irradiation time and the distance from the light source to the film surface are determined according to the film material of the reverse osmosis film that is the object to be irradiated and the output and wavelength of the light source lamp used. Must be selected.

The surface treatment represented by the plasma discharge treatment is complicated and the treatment operation such as the treatment under vacuum is complicated and it is difficult to introduce it into the industrial production. The surface treatment of the membrane is carried out under normal pressure, and the treatment equipment and treatment steps are very simple.

The form of the reverse osmosis membrane in the present invention may be a flat membrane or a hollow fiber. The obtained reverse osmosis membrane can be used by incorporating a flat membrane into a spiral, tubular, or plate-and-frame module, or by bundling hollow fibers into a module and then incorporating them.
The present invention does not depend on the usage of these membranes.

The reverse osmosis membrane of the present invention is most suitable for applications requiring high water permeability at low pressure operation. However,
The present invention is not limited to such use.

[0035]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto.

Regarding the performance of the reverse osmosis membrane in the examples, the concentration of the inorganic salt (mainly salt) was determined as the selective separation performance by measuring the electric conductivity, and then the desalination rate was calculated from the following equation.

Desalination ratio = (1-concentration of inorganic salt in permeate / concentration of inorganic salt in supply liquid) × 100 [%] Further, the amount of water produced as permeation performance is the amount of water permeation per unit area and unit time. Decided.

Reference Example 1 Taffeta (vertical yarn, multifilament yarn of 150 denier weft weft friend, length of 30 cm, weft of 20 cm), weft density 90 yarns / inch, weft 6
7 pieces / inch, thickness 160μ) is fixed on the glass plate,
Polysulfone (Udel P-3 manufactured by Amoco Co., Ltd.
500) 15% by weight of dimethylformamide (DMF)
Cast the solution at a thickness of 200μ at room temperature (20 ° C),
Immediately, it is immersed in pure water and left for 5 minutes to prepare a fiber-reinforced polysulfone support membrane (hereinafter abbreviated as FR-PS support membrane). FR-PS thus obtained
The pure water permeation coefficient of the support membrane (thickness 210 to 215μ) was 0.005 to 0.0.5 when measured at a pressure of 1 kg / cm ² and a temperature of 25 ° C.
It was 01 g / cm ² · sec · atm.

Reference Example 2 The FR-PS support film obtained in Reference Example 1 was immersed in an aqueous solution containing 1.34% by weight of metaphenylenediamine and 0.66% by weight of triaminobenzene for 1 minute. F
After removing the excess aqueous solution from the surface of the R-PS support membrane, the membrane was coated with n-decane and trimesic acid chloride 0.0.
A solution in which 675% by weight and 0.0825% by weight of terephthaloyl chloride were coated was coated so that the surface was completely wet and allowed to stand for 1 minute, then the membrane was made vertical and drained, and the wind speed was 10 to 15 m. / S, a temperature of 30 to 35 ° C was applied to remove excess solution. Next, the membrane was washed and then immersed in a sodium hypochlorite aqueous solution having a pH of 7 for 2 minutes.

Examples 1 to 4 and Comparative Example 1 The composite reverse osmosis membrane obtained in Reference Example 2 was coated with UV surface processor PC11-1102WS (made by Sen Special Light Source,
(110 W × 2 lamps) was used, and ultraviolet rays having central wavelengths of 185 nm and 254 nm were irradiated at a temperature of 25 ° C. in nitrogen gas at a distance of 5 cm from the light source. The composite membrane thus obtained was treated with 0.15% by weight saline to a pressure of 1.47MP.
As a result of a reverse osmosis test under the conditions of a and a temperature of 25 ° C., a film having the performance shown in Table 1 was obtained depending on the irradiation time.

Reference Example 3 The FR-PS support membrane obtained in Reference Example 1 was immersed in an aqueous solution containing 1.0% by weight of piperazine and 0.2% by weight of 1,3-bis (4-piperidyl) propane for 1 minute. did.
After the excess aqueous solution was removed from the surface of the FR-PS support film, it was dried with a hot air dryer at 80 ° C for 1 minute. 1,1,
After coating a solution prepared by dissolving 0.90% by weight of trimesic acid chloride in 2-trichloro-1,2,2, -trifluoroethane and coating the solution so that the surface was completely wet, and leaving it for 1 minute,
The membrane was made vertical and drained to remove the excess solution. Next, the membrane was washed and then immersed in a sodium hypochlorite aqueous solution having a pH of 6 for 2 minutes.

Examples 5 to 7 and Comparative Example 2 The composite reverse osmosis membrane obtained in Reference Example 3 was coated with UV surface processor PC11-1102WS (made by Sen Special Light Source,
(110 W × 2 lamps) was used, and ultraviolet rays having central wavelengths of 185 nm and 254 nm were irradiated at a temperature of 25 ° C. in nitrogen gas at a distance of 5 cm from the light source. The ultraviolet irradiation film thus obtained was adjusted to a pressure of 0.3 by using 0.05 wt% saline.
As a result of a reverse osmosis test under the conditions of 4 MPa and a temperature of 25 ° C., a film having the performance as shown in Table 1 was obtained according to the irradiation time.

[0043]

[Table 1] Examples 8 to 10 and Comparative Example 3 An ultraviolet irradiation film treated in the same manner as in Examples 5 to 7 was treated with 0.05 wt% magnesium chloride, 0.1 wt% sodium sulfate and 0.1 wt% magnesium sulfate aqueous solution. As a result of performing reverse osmosis test under conditions of a pressure of 0.34 MPa and a temperature of 25 ° C., the performance as shown in Table 2 was obtained.

[0044]

[Table 2] Examples 11 to 15 and Comparative Example 4 The composite reverse osmosis membrane obtained by the same method as in Reference Example 2 was UV-coated.
Using Fes Processor-PC11-1102WS (made by Sen Special Light Source, 110 W × 2 lamps), ultraviolet rays with wavelengths of 185 nm and 254 nm were irradiated for 80 seconds in nitrogen gas at a temperature of 25 ° C. The ultraviolet irradiation film thus obtained was washed with 0.15% by weight of saline solution at a pressure of 1.47MP.
As a result of reverse osmosis test under the conditions of a and temperature of 25 ° C., a film having performance as shown in Table 3 was obtained according to irradiation distance.

Examples 16 to 20 A composite reverse osmosis membrane obtained by the same method as in Reference Example 3 was UV-coated.
Fes Processor-PC11-1102WS (made by Sen Special Light Source, 110 W × 2 lamps) was used and irradiated with ultraviolet rays having wavelengths of 185 nm and 254 nm for 60 seconds in nitrogen gas at a temperature of 25 ° C. The ultraviolet irradiation film thus obtained was used with 0.05 wt% saline, and the pressure was 0.34MP.
As a result of reverse osmosis test under the conditions of a and temperature of 25 ° C., a film having performance as shown in Table 3 was obtained according to irradiation distance.

[0046]

[Table 3] Examples 21 to 25 On a composite reverse osmosis membrane obtained by the same method as in Reference Example 2, an excimer light irradiation device UER20-172 (172) manufactured by Ushio Inc.
nm single wavelength, 20 W) and UER20-222 (2
A single wavelength of 22 nm, 20 W) was used, and the ultraviolet rays were irradiated at a temperature of 25 ° C. in a nitrogen gas at a distance of 3 cm from the light source.
The ultraviolet irradiation film thus obtained was added in an amount of 0.15% by weight.
As a result of reverse osmosis test using saline solution under the conditions of pressure of 1.47 MPa and temperature of 25 ° C., the results are shown in Table 4 according to irradiation time.
A film having the performance as shown in was obtained.

[0047]

[Table 4] Example 26 and Comparative Example 6 The carboxyl group concentration of the composite reverse osmosis membrane obtained in Reference Example 2 and the ultraviolet irradiation membrane of Example 11 was quantified by the gas phase chemical modification method. TFE for labeling carboxyl groups
Was used as a dehydration catalyst in the reaction. The reaction rate (r) of TFE and the residual rate (m) of DCC were determined using a polyacrylic acid (PAA) standard sample (r = 1.0, m = 0.1).
8), the carboxyl group concentration was calculated from the C _1s and F _1s peak area intensities of each sample in consideration of r and m. As a result, as shown in Table 7, it was found that the concentration of carboxyl groups on the surface of the semipermeable membrane increased after the irradiation of ultraviolet rays.

Example 27 and Comparative Example 7 For the composite reverse osmosis membrane obtained in Reference Example 3 and the ultraviolet irradiation membrane in Example 17, the carboxyl group concentration was quantified in the same manner as in Example 26 and Comparative Example 6. . As a result, Table 5
As shown in, it was found that the concentration of carboxyl groups on the surface of the semipermeable membrane increased after ultraviolet irradiation.

[0049]

[Table 5]

[0050]

According to the present invention, it is possible to provide a membrane exhibiting high water permeability even when used at a low pressure, as compared with a conventional reverse osmosis membrane. Further, by adopting a surface treatment by ultraviolet irradiation as a method for improving water permeability, the performance of the reverse osmosis membrane can be improved by a method that is simple in both treatment equipment and steps and inexpensive in cost.

[Brief description of drawings]

[Figure 1] Schematic diagram of a low-pressure mercury lamp (viewed from below)

FIG. 2 is a schematic diagram of an ultraviolet irradiation device (side view)

[Explanation of symbols]

 1: Constant pressure mercury lamp 2: Reflector 3: Membrane sample 4: Lab jack

Claims (11)

[Claims] 1. A reverse osmosis membrane characterized in that the membrane surface is subjected to ultraviolet irradiation treatment. 2. The reverse osmosis membrane according to claim 1, wherein the reverse osmosis membrane is an asymmetric membrane. 3. The reverse osmosis membrane according to claim 1, wherein the reverse osmosis membrane is a composite membrane composed of a microporous support membrane and a separation functional layer. 4. The reverse osmosis membrane according to claim 1, wherein the separation functional layer forming the composite membrane is composed of a crosslinked polymer. 5. The reverse osmosis membrane according to claim 1, wherein the separation functional layer forming the composite membrane is made of a crosslinked aromatic polyamide. 6. The carboxyl group concentration (-COO on the surface of the film
H / C _[total] ) is 0.015 or more, The reverse osmosis membrane according to claim 1. 7. The separation functional layer comprises a crosslinked polyamide,
Pressure of 0.34 MPa using 0.05 wt% saline,
The reverse osmosis membrane according to claim 1, which has a water permeability of 0.4 m ³ / m ² · day or more when subjected to a reverse osmosis test at a temperature of 25 ° C. 8. A method for treating a surface of a reverse osmosis membrane, which comprises irradiating ultraviolet rays having a wavelength of 10 to 400 nm. 9. A linear light source having a strong line spectrum with wavelengths of 184 nm and 254 nm and an electric power of 220 W with respect to the amount of ultraviolet irradiation (UV illuminance × irradiation time) on the surface of the reverse osmosis membrane is attached with a reflector to perform ultraviolet irradiation treatment. When used for, the value of A calculated from the UV irradiation time and the distance from the light source to the film surface should be equivalent to the UV irradiation amount under the condition that 0.001 ≦ A ≦ 500,000 is set. 9. The surface treatment method for a reverse osmosis membrane according to claim 8. 10. The ambient temperature when irradiating with ultraviolet rays is 1
9. The surface treatment method for a reverse osmosis membrane according to claim 8, wherein the temperature is 0 to 60 ° C. 11. The method for surface treatment of a reverse osmosis membrane according to claim 8, wherein the oxygen concentration in the atmosphere when irradiating with ultraviolet rays is 20% or less.