JP2014014739A - Method of manufacturing composite semipermeable membrane element and composite semipermeable membrane element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite semipermeable membrane element for reducing a change in a separation characteristic of a membrane when processing high concentration raw water such as seawater, and reducing a change with time of performance when operated under high pressure.SOLUTION: The composite semipermeable membrane element includes a composite semipermeable membrane composed of a porous support and a thin film supported by it, and the composite semipermeable membrane is provided by performing consolidation processing for two hours or more by using liquid in which the temperature T[°C] and pressure P[MPa] satisfy all of the formulas (1) to formula (3). In the composite semipermeable membrane element, T × P ≤ 300 ... the formula (1), 6.0 ≤ P ≤ 8.3 ... the formula (2) and 30 ≤ T ≤ 50 ... the formula (3).

Description

  The present invention relates to a composite semipermeable membrane element that can be stably operated with little change in performance over time even when used under high pressure, and a method for producing the same.

  Currently, an asymmetric membrane type cellulose acetate membrane and a composite semipermeable membrane in which an active separation functional layer is formed on a porous support are known as semipermeable membranes widely used industrially. However, the former cellulose acetate membrane has problems in hydrolysis resistance, microbial resistance, etc., and the salt rejection rate and water permeability are not sufficient. It has not yet been put to practical use.

  On the other hand, in the composite semipermeable membrane, it is possible to select an optimal material for each of the separation functional layer and the porous support, and various methods can be selected for the film forming technique.

  Currently, commercially available composite semipermeable membranes have a separation functional layer obtained by interfacial polycondensation of monomers on a porous support. These composite semipermeable membranes have higher desalting performance than cellulose acetate asymmetric membranes, and these membranes are also being improved in durability against chlorine and hydrogen peroxide used for sterilization, and their applications are expanding.

  When performing separation with a semipermeable membrane, it is necessary to apply a pressure higher than the difference between the osmotic pressure on the supply water side and the osmotic pressure on the permeate side to the supply water side. When the pressure is high, a high pressure is required as the operation pressure. Further, when the ratio of the amount of permeated water to the supply water (this is called the recovery rate) increases, the solute concentration of the concentrated water increases, so a high pressure is required as the operating pressure. For example, in the case of seawater desalination, the osmotic pressure of seawater having a concentration of 3.5% by weight is 2.5 MPa. When desalination is performed at a recovery rate of 40%, the concentration of concentrated water is about 6% by weight. An operating pressure higher than the osmotic pressure (about 4.4 MPa) is required. In order to obtain sufficient quality and quantity of permeated water, it is actually necessary to apply a pressure about 2 MPa higher than the osmotic pressure of concentrated water (this pressure is called effective pressure) to the concentrated water side. . Conventional conventional seawater desalination is operated under conditions of a recovery rate of about 40% under a pressure of about 6 to 6.5 MPa. On the other hand, the semipermeable membrane device may be operated at a pressure of 7 MPa or more, such as when separating and concentrating a high concentration solution.

  Generally, when pressure is applied to the semipermeable membrane, the semipermeable membrane is consolidated, but returns to its original form when the pressure is removed. However, when a pressure higher than the limit pressure is applied, the voids of the asymmetric membrane or the microporous membrane may be crushed or the separation functional layer may be further densified, thereby changing the membrane form and membrane performance. Specifically, when the membrane permeability coefficient of the semipermeable membrane is reduced, the permeation flux may be reduced and stable operation may not be possible.

  Normally, when a design flow rate cannot be obtained due to consolidation in a plant that is designed using semi-permeable membrane elements as specified, the pressure is often increased further to secure the production water volume. It may cause damage to the semipermeable membrane element and failure of piping and equipment.

  It is also possible to adopt a semipermeable membrane element with a high initial permeation flux in anticipation of consolidation during long-term operation, but in this case, in the initial operation where consolidation has not been completed, Compared with the expected value, the operating pressure becomes lower and the quality of the produced water also deteriorates. Since the high-pressure pump is a large-sized pump that can cope with the pressure after consolidation, it is necessary to adjust the pressure by a valve, and the influence on the apparatus itself and the surrounding environment becomes very large due to vibration and noise of the piping.

  In order to solve such problems, the structure of the porous support is changed (Patent Document 1), the structure of the permeate flow channel material is changed (Patent Documents 2 and 3), and a high pressure is applied to the semipermeable membrane in advance. (Patent Documents 4 and 5) are also proposed, but none of them has sufficient pressure resistance, and stable operation such as changes in initial performance according to operation could not.

JP-A-8-168658 Japanese Patent Laid-Open No. 9-14060 JP-A-9-141067 JP 2000-288368 A Japanese Patent Laid-Open No. 2002-95941

  An object of the present invention is to solve such problems of the prior art, and is a composite semipermeable membrane incorporating a composite semipermeable membrane capable of stable operation even under high pressure, particularly 6 MPa or higher. It is to provide a membrane element.

  The present invention for solving the above problems relates to the following embodiments (1) to (6).

  (1) A method for producing a composite semipermeable membrane element comprising a porous support and a composite semipermeable membrane comprising a thin film supported thereon, wherein the composite semipermeable membrane is subjected to a temperature T [° C.] and a pressure P [MPa. Includes a step of performing a consolidation treatment for 2 hours or more using a liquid satisfying all of the formulas (1) to (3).

T × P ≦ 300 (1)
6.0 ≦ P ≦ 8.3 Expression (2)
30 ≦ T ≦ 50 Formula (3)
(2) The method for producing a composite semipermeable membrane element according to (1), wherein the osmotic pressure of the liquid is 3 MPa or more.

  (3) The porous support is provided with a porous layer on a substrate, and the thickness of the porous layer after the consolidation treatment is 10% compared to the thickness of the porous layer before the consolidation treatment The method for producing a composite semipermeable membrane element according to the above (1) or (2), wherein the consolidation treatment is performed until it is reduced as described above.

  (4) A composite semipermeable membrane element including a porous support and a composite semipermeable membrane comprising a thin film supported by the porous support, wherein the composite semipermeable membrane has a temperature T [° C.] and a pressure P [MPa]. A composite semipermeable membrane element characterized by being subjected to consolidation for 2 hours or more using a liquid satisfying all of the formulas (3) to (1).

T × P ≦ 300 (1)
6.0 ≦ P ≦ 8.3 Expression (2)
30 ≦ T ≦ 50 Formula (3)
(5) The composite semipermeable membrane element according to (4), wherein the osmotic pressure of the liquid is 3 MPa or more.

  (6) The porous support is provided with a porous layer on a substrate, and the thickness of the porous layer after the consolidation treatment is 10% compared to the thickness of the porous layer before the consolidation treatment The composite semipermeable membrane element according to (4) or (5), wherein the composite semipermeable membrane element is reduced as described above.

  The composite semipermeable membrane of the present invention has excellent pressure resistance even when used at high pressure, can suppress a decrease in the amount of permeate during operation, and can stably maintain the amount of permeate. In particular, it is suitable for processing high-concentration stock solutions such as seawater, and can be operated stably. Furthermore, while suppressing the vibration of the apparatus and the like, it is possible to expect an improvement in water quality from that expected at the design stage.

It is a schematic block diagram of the composite semipermeable membrane element used in the Example.

  The porous support used in the present invention supports the separation functional layer of the composite semipermeable membrane and comprises a base material and a porous layer. A woven or non-woven fabric such as polyester is used as a base material, and an organic solvent of a polymer that is a film-forming stock solution is cast on the base material and immersed in a non-solvent coagulation bath with respect to the polymer. By this, a porous support having a porous layer provided on a substrate is obtained.

  The material of the porous layer is not particularly limited, and examples thereof include homopolymers or blends such as polysulfone, polyethersulfone, polyphenylene sulfide sulfone, polyphenylene sulfone, polyimide, and polyvinylidene fluoride. Polysulfone and polyethersulfone which are mechanically and thermally stable are preferably used.

  The stock solution for forming the porous layer may be any solvent that can dissolve the polymer. For example, N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide , Nitrogen-containing compounds such as dimethyl sulfoxide and pyridine, polyhydric alcohols such as diethylene glycol, diethylene glycol dimethyl ether and diethylene glycol diethyl ether and derivatives thereof, ethers such as 1,4-dioxane, tetrahydrofuran and ethyl butyl ether, acetals and the like can be used. . These solvents may be used alone or in combination of two or more. Further, an alcohol such as water, methanol, ethanol or the like as a poor solvent, or an inorganic salt such as sodium chloride, magnesium chloride or lithium chloride may be added.

  The concentration of the polymer in these solvents is preferably 30% by weight or less. More preferably, it is 10 to 20% by weight. If the polymer concentration is higher than this range, the water permeability is remarkably lowered. On the other hand, if it is low, the film-forming stock solution gels or defects are generated in the porous layer, and the membrane performance tends to become unstable.

  The method for applying the film-forming stock solution to the substrate may be a method in which the film-forming stock solution is uniformly and continuously wet on the substrate, and examples include a method of coating the film-forming stock solution on the substrate using a coater. In order to coat the substrate with a constant thickness, the gap between the substrate and the coater is adjusted to be constant.

  The film-forming stock solution coated on the substrate is immersed in a coagulation bath to form a porous layer. As the coagulation bath to be used, water is usually used, but any water that does not dissolve the polymer may be used. The film form of the porous layer changes depending on the composition of the coagulation bath, thereby changing the film forming property of the composite semipermeable membrane.

  Next, the porous support thus obtained is washed with hot water in order to remove the film-forming solvent present in the film. The temperature of the hot water at this time is preferably 50 to 100 ° C, more preferably 60 to 95 ° C. When it is higher than this range, the degree of shrinkage of the porous support increases, and the water permeability decreases. Conversely, if it is low, the cleaning effect becomes small.

  The thickness of the porous support and the thickness of the substrate influence the strength of the composite semipermeable membrane and the packing density when it is used as an element. In order to obtain sufficient mechanical strength and packing density, the thickness of the porous support is preferably in the range of 50 to 300 μm, more preferably in the range of 100 to 250 μm. Moreover, it is preferable that the thickness of the porous layer in a porous support body exists in the range of 20-120 micrometers, More preferably, it exists in the range of 30-100 micrometers.

  Next, a method for producing the composite semipermeable membrane according to the present invention will be described.

  The separation functional layer constituting the composite semipermeable membrane is generally used as a reverse osmosis membrane material such as cellulose acetate polymer, polyester, polyimide, vinyl polymer, etc. The skeleton is formed by interfacial polycondensation of the polyfunctional amine aqueous solution and the polyfunctional acid halide on the surface of the microporous support, that is, the polyfunctional amine is formed on the microporous support. An example is a cross-linked polyamide separation functional layer formed by contacting an aqueous amine solution and then bringing a polyfunctional acid halide into contact with a water-immiscible organic solvent solution to cause interfacial polycondensation.

  Here, the polyfunctional amine refers to an amine having at least two primary and / or secondary amino groups in one molecule. For example, two amino groups are any of ortho, meta, and para positions. Aromatic polyfunctional amines such as phenylenediamine, xylylenediamine, 1,3,5-triaminobenzene, 1,2,4-triaminobenzene and 3,5-diaminobenzoic acid bonded to benzene in the positional relationship of Aliphatic amines such as ethylenediamine and propylenediamine, alicyclic polyfunctional amines such as 1,2-diaminocyclohexane, 1,4-diaminocyclohexane, piperazine, 1,3-bispiperidylpropane and 4-aminomethylpiperazine be able to. Of these, aromatic polyfunctional amines are preferred in view of selective separation, permeability, and heat resistance of the membrane. Examples of such polyfunctional aromatic amines include m-phenylenediamine, p-phenylenediamine, 1, 3,5-triaminobenzene is preferably used. Among these, it is more preferable to use m-phenylenediamine (hereinafter referred to as m-PDA) from the standpoint of availability and ease of handling. These polyfunctional amines may be used alone or in combination.

  The polyfunctional acid halide refers to an acid halide having at least two carbonyl halide groups in one molecule. Examples of trifunctional acid halides include trimesic acid chloride, 1,3,5-cyclohexanetricarboxylic acid trichloride, 1,2,4-cyclobutanetricarboxylic acid trichloride, and bifunctional acid halides include biphenyl dicarboxylic acid. Aromatic difunctional acid halides such as acid dichloride, biphenylene carboxylic acid dichloride, azobenzene dicarboxylic acid dichloride, terephthalic acid chloride, isophthalic acid chloride, naphthalene dicarboxylic acid chloride, aliphatic difunctional acid such as adipoyl chloride, sebacoyl chloride Mention may be made of alicyclic bifunctional acid halides such as halides, cyclopentane dicarboxylic acid dichloride, cyclohexane dicarboxylic acid dichloride, tetrahydrofuran dicarboxylic acid dichloride. Considering the reactivity with the polyfunctional amine, the polyfunctional acid halide is preferably a polyfunctional acid chloride, and considering the selective separation property and heat resistance of the membrane, the polyfunctional aromatic acid chloride is preferable. Preferably there is. Among them, it is more preferable to use trimesic acid chloride from the viewpoint of easy availability and easy handling. These polyfunctional acid halides may be used alone or in combination.

  Here, the concentration of the polyfunctional amine in the polyfunctional amine aqueous solution is preferably in the range of 2.5 to 10% by weight, more preferably in the range of 3 to 5% by weight. In this range, sufficient salt removal performance and water permeability can be obtained. As long as the polyfunctional amine aqueous solution does not interfere with the reaction between the polyfunctional amine and the polyfunctional acid halide, a surfactant, an organic solvent, an alkaline compound, an antioxidant, or the like may be contained. The surfactant has the effect of improving the wettability of the porous support surface and reducing the interfacial tension between the aqueous amine solution and the nonpolar solvent, and the organic solvent may act as a catalyst for the interfacial polycondensation reaction. In some cases, the interfacial double reaction can be efficiently performed by adding them.

  In order to perform interfacial polycondensation on the porous support, first, the above-mentioned polyfunctional amine aqueous solution is brought into contact with the porous support. The contact is preferably performed uniformly and continuously on the surface of the porous support. Specific examples include a method of coating a porous support with a polyfunctional amine aqueous solution and a method of immersing the porous support in a polyfunctional amine aqueous solution. The contact time between the porous support and the polyfunctional amine aqueous solution is preferably within a range of 1 to 10 minutes, and more preferably within a range of 1 to 3 minutes.

  After the polyfunctional amine aqueous solution is brought into contact with the porous support, the liquid is sufficiently drained so that no droplets remain on the surface. By sufficiently draining the liquid, it is possible to prevent the remaining portion of the liquid droplet from becoming a film defect after the film is formed and deteriorating the film performance. As a method of draining, for example, as described in JP-A-2-78428, a method of allowing an excess aqueous solution to naturally flow down by vertically gripping the porous support after contacting with the polyfunctional amine aqueous solution. Alternatively, a method of forcibly draining by blowing air such as nitrogen from an air nozzle can be used. In addition, after draining, the membrane surface can be dried to remove part of the water in the aqueous solution.

  Next, an organic solvent solution containing a polyfunctional acid halide is brought into contact with the support film after contact with the polyfunctional amine aqueous solution, and a skeleton of a crosslinked polyamide separation functional layer is formed by interfacial polycondensation.

  The concentration of the polyfunctional acid halide in the organic solvent solution is preferably in the range of 0.01 to 10% by weight, and more preferably in the range of 0.02 to 2.0% by weight. Within this range, a sufficient reaction rate can be obtained, and the occurrence of side reactions can be suppressed. Further, it is more preferable that an acylation catalyst such as N, N-dimethylformamide is contained in the organic solvent solution because interfacial polycondensation is promoted.

  As the organic solvent, an organic solvent immiscible with water is used. Among organic solvents that are immiscible with water, an organic solvent that dissolves the acid halide and does not destroy the porous support is desirable, and any solvent that is inert to amino compounds and acid halides may be used. Preferable examples include hydrocarbon compounds such as n-hexane, n-octane, and n-decane.

  The method of contacting the organic solvent solution of the polyfunctional acid halide with the amino compound aqueous solution phase may be performed in the same manner as the method of coating the porous support with the polyfunctional amine aqueous solution.

  As described above, after the interface polycondensation is performed by bringing the acid halide organic solvent solution into contact with each other and the separation functional layer containing the crosslinked polyamide is formed on the porous support, the excess solvent may be drained. As a method for draining, for example, a method in which a film is held in a vertical direction and excess organic solvent is allowed to flow down and removed can be used. In this case, the time for gripping in the vertical direction is preferably 1 to 5 minutes, more preferably 1 to 3 minutes. Within this range, the separation functional layer is completely formed, and defects due to overdrying of the organic solvent are less likely to occur.

  The composite semipermeable membrane obtained by the above-mentioned method is a process of hydrothermal treatment in the range of 50 to 150 ° C, preferably in the range of 70 to 130 ° C for 1 to 10 minutes, more preferably 2 to 8 minutes, etc. By passing through, the exclusion performance and water permeability of the composite semipermeable membrane may be further improved.

  An organic substance and / or an organic polymer, preferably, an organic substance having a nonionic hydrophilic group and / or an organic polymer solution is applied onto such a composite semipermeable membrane surface, and then dried. Obtaining a composite semipermeable membrane is also effective in improving stain resistance and the like.

  In the above, the crosslinked polyamide separation functional layer has been described in detail as the separation functional layer constituting the composite semipermeable membrane according to the present invention. For example, a cellulose acetate-based material has a dense layer on at least one side of the membrane. A semipermeable membrane can be formed by forming an asymmetric membrane having micropores with a large pore diameter gradually from the layer toward the inside of the membrane or the other surface.

  The composite semipermeable membrane element used in the present invention is formed in order to actually use the semipermeable membrane. When the semipermeable membrane is a flat membrane, spiral, tubular, plate Although it can be used by being incorporated in an and frame module, the present invention is not affected by these forms.

  In addition, when the spiral shape is used as a semipermeable membrane element, members such as a channel material for supply water and a channel material for permeate water are incorporated in the module, and particularly designed for high concentration and high pressure. It is preferably used as a semi-permeable membrane element.

  The present invention is characterized in that the composite semipermeable membrane element manufactured as described above is subjected to consolidation treatment on the composite semipermeable membrane incorporated in the composite semipermeable membrane element. The method for consolidation treatment is not particularly limited as long as it is a method in which a liquid such as water is used for 2 hours or more at a pressure of 6 MPa or more and a temperature of 30 ° C. or more using a high-concentration liquid. As a consolidation treatment method at this time, the composite semipermeable membrane before constituting the composite semipermeable membrane element may be subjected to consolidation treatment, or the composite incorporated after constituting the composite semipermeable membrane element. A method of obtaining the composite semipermeable membrane element of the present invention by performing treatment so that a desired consolidation treatment is performed on the semipermeable membrane may be used.

  Consolidation after the composite semipermeable membrane element is configured, the composite semipermeable membrane or composite semipermeable membrane element is sealed in a pressure-resistant container and sealed, and gas or liquid is sealed in it to raise the temperature and pressure. And processing for a certain period of time. After a certain period of time, the temperature and pressure are returned to normal temperature and normal pressure, the pressure vessel is opened, and the compacted composite semipermeable membrane or composite semipermeable membrane element is taken out from the inside.

  From the viewpoint of improving the efficiency of producing the composite semipermeable membrane element, the consolidation treatment is preferably performed after the composite semipermeable membrane element is formed, and in this case, it is preferable to perform liquid such as water as a medium.

  In the present invention, the temperature T [° C.] and the pressure P [MPa] when performing the consolidation treatment are appropriately selected within a range satisfying the formulas (1) to (3).

T × P ≦ 300 (1)
6.0 ≦ P ≦ 8.3 Expression (2)
30 ≦ T ≦ 50 Formula (3)
The setting of temperature and pressure is particularly important in the consolidation process, but not only has a great effect on the composite semipermeable membrane, but is also a component of the composite semipermeable membrane element when both pressure and temperature are high. Therefore, the present invention is characterized in that processing is performed under conditions that satisfy the relationship represented by the expression (1).

  The pressure at the time of the consolidation treatment is preferably high, but if it is too high, the reduction in the amount of permeated water becomes too large due to the consolidation treatment. In the present invention, the consolidation treatment is performed at 6 MPa or more and 8.3 MPa or less. If the pressure is less than 6 MPa, the consolidation effect is small, and if it exceeds 8.3 MPa, the composite semipermeable membrane element itself may be deformed.

  The temperature at which the consolidation process is performed is preferably in a range where the liquid of the medium does not volatilize. In particular, when the consolidation process is performed after the composite semipermeable membrane element is configured, the composite semipermeable membrane element is affected. From the point of view, the present invention is characterized in that it is carried out in the range of 30 ° C. or more and 50 ° C. or less. If the temperature is less than 30 ° C., the consolidation effect is small. If the temperature exceeds 50 ° C., the composite semipermeable membrane element has a great influence on various members, and deformation or breakage may occur.

  In addition, it is preferable to implement the consolidation process in this invention until the thickness of the porous layer after a consolidation process reduces 10% or more compared with the thickness of the porous layer before a consolidation process.

  Moreover, it is preferable to set the reduction rate so that the reduction rate of the thickness of the porous layer satisfies the following formula.

Reduction rate [%] ≦ 40 × Ln (porous layer thickness before consolidation treatment [μm]) − 102 (4)
If the reduction rate is greater than this, the water permeability will be greatly reduced.

  Since the porous layer has a spongy gap in the porous layer, it undergoes compressive deformation due to continuation of high-pressure operation and causes a decrease in water permeability. By reducing it by 10% or more, the gap between the porous layers is reduced, and the reduction in water permeability can be reduced even in the subsequent high-pressure operation, and stable operation can be achieved.

  The thickness of the porous layer can be determined by observing a cross section with a scanning electron microscope or a transmission electron microscope. For example, in the case of a cross-sectional photograph of a scanning electron microscope, a membrane sample immersed in liquid nitrogen and frozen is cleaved perpendicularly to the direction in which the film-forming stock solution was cast and dried, and then the membrane cross-section Then, platinum / palladium or ruthenium tetroxide, preferably ruthenium tetroxide, is coated thinly and observed with a high resolution field emission scanning electron microscope (UHR-FE-SEM) at an acceleration voltage of 1 to 6 kV. Although the optimal observation magnification should just be a magnification which can observe the whole film cross section, for example, if the film thickness of a porous layer is 60 micrometers, 100-5,000 times are preferable.

  The liquid used in the consolidation treatment is appropriately selected as long as it does not affect the composite semipermeable membrane. However, water or an aqueous solution of an inorganic salt such as NaCl or KCl, or an aqueous alcohol solution such as methanol or ethanol can be used. It is preferred to use.

  In the consolidation process, liquid is supplied to the composite semipermeable membrane element at a pressure of 6 MPa or more. However, if the concentration of the liquid used is too low, the amount of liquid that passes through the composite semipermeable membrane element increases, and the composite semipermeable membrane element However, there is a possibility that the performance deteriorates due to impurities in the apparatus.

  As one method for preventing this, it is effective to increase the concentration of the liquid used in the consolidation treatment, and the osmotic pressure of the liquid used in the consolidation treatment is preferably 3 MPa or more.

  The osmotic pressure is calculated by the Phanto-Hoff equation, and the osmotic pressure and the concentration of the liquid are correlated, and it is necessary to increase the concentration of the liquid in order to obtain an osmotic pressure of 3 MPa or more. Examples of the osmotic pressure of 3 MPa include a 3.8% NaCl aqueous solution and a 4.9% KCl aqueous solution.

  Normally, the consolidation process is performed in the circulation system by returning the permeated water and concentrated water from the element to the raw water. However, if all the consolidation processes cannot be performed by circulation, impurities such as turbidity are in advance. It is also possible to carry out by partially circulating the concentrated water using a high-concentration liquid such as seawater from which water has been removed. Normally, the osmotic pressure of seawater with a concentration of 3.5% is about 2.4 MPa, but the concentration of raw water flowing into the element is increased by circulating part of the concentrated water that has passed through the element back to the raw water side. And the osmotic pressure can be increased to 3 MPa or more. The concentration adjustment method at this time can be carried out by appropriately adjusting the amount of concentrated water to be circulated.

  The SDI of the liquid used in the consolidation process is preferably 3.0 or less. This SDI is a water quality index determined by ASTM (American Standard Test Method) according to D4189-95. Water is passed through a microfiltration filter having a pore diameter of 0.45 μm at a constant pressure of 30 psi (207 kPa), and the water permeability is measured after a certain time. The degree of deterioration of the property is expressed as a numerical value represented by the following formula.

Here, _{t i} is the time immediately after the start filtered to obtain filtered water 500 ml (sec), the _{t s} is the time from the start of filtration s seconds to obtain a filtered water 500 ml (sec).

  If the SDI is high, it can be determined that the amount of impurities in the liquid is large, and if a liquid having an SDI of more than 3.0 is used, the element becomes dirty and the performance deteriorates.

  The consolidation treatment is preferably carried out for at least 2 hours. If it is 2 hours or less, the treatment is insufficient, and the performance change during operation may become large.

  The RO element thus obtained is expected to contribute to stable operation with little decrease in performance in desalination of seawater and the like where high pressure is required. Due to alkaline hydrolysis with a strong alkaline liquid, the film may be deteriorated continuously or suddenly for a long time, and the removal rate may be lowered.

  As a performance recovery method for improving the removal rate in such a case, for example, a method for improving the removal rate by bringing a nonionic surfactant or a cationic surfactant into contact with the semipermeable membrane after the start of operation, Examples thereof include a method in which iodine is brought into contact with the semipermeable membrane, a method in which polyethylene glycol having a molecular weight of 4000 to 50000 is brought into contact, and a method in which tannic acid is brought into contact with the semipermeable membrane.

  The present invention will be described below with reference to specific examples, but the present invention is not limited to these examples.

Example 1
As a porous support, a 15.7 wt% dimethylformamide (DMF) solution of polysulfone on a polyester nonwoven fabric having a thickness of 95 μm (air permeability 0.5 to 1 cc / cm ² / sec) as a porous support at a thickness of 200 μm at room temperature (25 ° C. ), And immediately immersed in a pure water coagulant and left for 5 minutes to prepare a porous support (porous layer thickness 60 μm). The porous support thus obtained was immersed in a 3.8% by weight aqueous solution of m-phenylenediamine for 2 minutes. Next, the porous support was pulled up, nitrogen was blown off to remove excess aqueous solution from the surface of the porous support, and then an n-decane solution of trimesic acid chloride 0.175 wt% was applied so that the surface was completely wetted. The membrane was left standing and then drained to remove excess solution from the membrane. Thereafter, the composite semipermeable membrane was obtained by washing with hot water at 90 ° C. for 2 minutes.

  Using the obtained composite semipermeable membrane, this was wrapped in a bag shape in a spiral shape to obtain a composite semipermeable membrane element. FIG. 1 shows a composite semipermeable membrane element of the present invention. In the composite semipermeable membrane element 1, a membrane unit 7 including a composite semipermeable membrane 4, a permeate channel material 5, and a stock solution channel material 6 is spirally wound around a water collection pipe 3 having a water collection hole 2. The exterior body 8 is formed outside the membrane unit 7 to form a fluid separation element 9. A telescope prevention plate 10 for preventing the fluid separation element 9 from being deformed into a telescope shape is attached to the end face of the fluid separation element 9, thereby forming the composite semipermeable membrane element 1.

The performance of this composite semipermeable membrane element was as follows: the pressure was 5.5 MPa, the raw water was 3.2% saline, the recovery was 8%, the temperature was 25 ° C., the pH was 7, and the desalination rate was 99.8%, and the water production was 30 m ³ / d. At this time, the thickness of the porous layer was 60 μm.

This composite semipermeable membrane element is consolidated for 3 hours at a temperature of 35 ° C. and a pressure of 8 MPa (temperature T [° C.] × pressure P [MPa] = 280 ≦ 300) using a saline solution having a concentration of 5.3% (osmotic pressure 4.2 MPa). Then, the performance was evaluated again under the same conditions. As a result, the desalination rate was 99.8% and the amount of water produced was 25 m ³ / d. Further, the thickness of the porous layer after the consolidation treatment was 35 μm, which was 42% smaller than the thickness of the porous layer before the consolidation treatment.

When this element was used for continuous operation for about 1 month at 5.5MPa and 25 ° C using seawater as raw water, the performance after 1 month was 99.7% with a desalination rate of 24m ³ / d. I couldn't see it. The results are shown in Table 1.

(Example 2)
The test was performed under the same conditions as in Example 1 except that the pressure during the consolidation treatment was changed to 6.0 MPa (temperature T [° C.] × pressure P [MPa] = 210 ≦ 300). The results are shown in Table 1. At this time, the thickness of the porous layer was 38 μm, which was 37% less than the thickness of the porous layer before the consolidation treatment.

(Comparative Example 1)
The test was performed under the same conditions as in Example 1 except that the pressure during the consolidation treatment was changed to 4.0 MPa (temperature T [° C.] × pressure P [MPa] = 140 ≦ 300). The results are shown in Table 1. At this time, the thickness of the porous layer was 55 μm, which was only 8% less than the thickness of the porous layer before the consolidation treatment.

(Example 3)
The test was performed under the same conditions as in Example 1 except that the temperature during the consolidation treatment was changed to 30 ° C. (temperature T [° C.] × pressure P [MPa] = 240 ≦ 300). The results are shown in Table 1. At this time, the thickness of the porous layer was 41 μm, which was 32% less than the thickness of the porous layer before the consolidation treatment.

Example 4
The conditions were the same as in Example 1 except that the temperature during the consolidation treatment was changed to 45 ° C. and the pressure was changed to 6.0 MPa (temperature T [° C.] × pressure P [MPa] = 270 ≦ 300). The results are shown in Table 1. At this time, the thickness of the porous layer was 40 μm, which was 33% less than the thickness of the porous layer before the consolidation treatment.

(Comparative Example 2)
The test was performed under the same conditions as in Example 1 except that the temperature during the consolidation treatment was changed to 25 ° C. (temperature T [° C.] × pressure P [MPa] = 200 ≦ 300). The results are shown in Table 1. At this time, the thickness of the porous layer was 56 μm, which was only 7% less than the thickness of the porous layer before the consolidation treatment.

(Example 5)
The test was carried out under the same conditions as in Example 1 except that the NaCl concentration during the consolidation treatment was changed to 4.0% (osmotic pressure 3.2 MPa) (temperature T [° C.] × pressure P [MPa] = 280 ≦ 300). The results are shown in Table 1. At this time, the thickness of the porous layer was 39 μm, which was reduced by 35% compared to the thickness of the porous layer before the consolidation treatment.

(Comparative Example 3)
The conditions were the same as in Example 1 except that the treatment time during the consolidation treatment was 0.5 hr (temperature T [° C.] × pressure P [MPa] = 280 ≦ 300). The results are shown in Table 1. At this time, the thickness of the porous layer was 56 μm, which was only 7% less than the thickness of the porous layer before the consolidation treatment.

1: Composite semipermeable membrane element 2: Water collecting hole 3: Water collecting pipe 4: Composite semipermeable membrane 5: Permeate flow channel material 6: Stock solution flow channel material 7: Membrane unit 8: Exterior body 9: Fluid separation element 10: Telescope prevention plate

Claims (6)

A method for producing a composite semipermeable membrane element comprising a porous support and a composite semipermeable membrane comprising a thin film supported by the porous support, wherein the composite semipermeable membrane is expressed by a temperature T [° C.] and a pressure P [MPa]. The manufacturing method of the composite semipermeable membrane element characterized by including the process of performing a compaction process for 2 hours or more using the liquid which satisfy | fills all of Formula (3) from (1).
T × P ≦ 300 (1)
6.0 ≦ P ≦ 8.3 Expression (2)
30 ≦ T ≦ 50 Formula (3) The method for producing a composite semipermeable membrane element according to claim 1, wherein the osmotic pressure of the liquid is 3 MPa or more. The porous support is provided with a porous layer on a substrate, and the thickness of the porous layer after the consolidation treatment is reduced by 10% or more compared to the thickness of the porous layer before the consolidation treatment. The method for producing a composite semipermeable membrane element according to claim 1, wherein the compaction treatment is performed until the material is compacted. A composite semipermeable membrane element including a porous support and a composite semipermeable membrane comprising a thin film supported by the porous support, wherein the composite semipermeable membrane has a temperature T [° C.] and a pressure P [MPa] of formula (1). To a composite semipermeable membrane element that has been subjected to consolidation for 2 hours or more using a liquid that satisfies all of the formula (3).
T × P ≦ 300 (1)
6.0 ≦ P ≦ 8.3 Expression (2)
30 ≦ T ≦ 50 Formula (3) The composite semipermeable membrane element according to claim 4, wherein the osmotic pressure of the liquid is 3 MPa or more. The porous support is provided with a porous layer on a substrate, and the thickness of the porous layer after the consolidation treatment is reduced by 10% or more compared to the thickness of the porous layer before the consolidation treatment The composite semipermeable membrane element according to claim 4 or 5, wherein the composite semipermeable membrane element is.

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