JP2017144390A - Composite membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite membrane that exerts stable performance even when being used under a high-pressure, has sufficient durability against various liquid and is excellent in permeability of liquid.SOLUTION: The composite membrane includes: a porous support layer; and a layer having performance of a semi-permeable membrane on the porous support layer. The porous support layer satisfies conditions (1) and (2), where (1) a ratio of pore with an equivalent circle diameter of 1 μm or more is less than 30% and (2) a membrane thickness is 100 μm or more.SELECTED DRAWING: None

Description

  The present invention relates to a composite membrane.

  In recent years, a membrane separation technique using a semipermeable membrane has attracted attention from the viewpoint of energy saving, resource saving, and environmental protection. The semipermeable membrane is used as a nanofiltration membrane, a reverse osmosis membrane, or a forward osmosis membrane, and can be applied to separation, purification, production process and the like of various liquids including water.

The forward osmosis treatment is performed by bringing a solution having different solute concentrations into contact with each other through a semipermeable membrane, and using a osmotic pressure difference resulting from the difference in solute concentration as a driving force, from a dilute solution having a low solute concentration to a concentrated solution having a high solute concentration. Is a process of transmitting the light.
By forward osmosis treatment, the dilute solution can be concentrated or the concentrated solution can be diluted. The generator can also be driven by forward osmotic pressure energy as the fluid penetrates from the dilute solution to the concentrated solution.
The forward osmosis treatment is common to the reverse osmosis treatment in that water is preferentially permeated over the solute using a semipermeable membrane. However, forward osmosis treatment uses osmotic pressure difference to allow water to permeate from the dilute solution side to the concentrated solution side. In this respect, water is concentrated by pressurizing the concentrated solution side against the osmotic pressure difference. This is different from reverse osmosis treatment in which the solution side permeates the dilute solution side. Therefore, even if the semipermeable membrane used in the reverse osmosis treatment is applied to the forward osmosis treatment as it is, it is not necessarily suitable for the forward osmosis treatment.

  In reverse osmosis treatment, concentrated solution is placed on one side across the membrane, diluted solution is placed on the other side, and the concentrated solution side is pressurized against the osmotic pressure difference between the two solutions to concentrate the water. Penetration from the solution side to the dilute solution side. For this reason, the reverse osmosis membrane is required to have a strength sufficient to withstand the pressure on the concentrated solution side. Therefore, it is necessary for the reverse osmosis membrane to ensure strength without increasing the porosity of the support layer so much. As a result, the space in which the solute freely diffuses in the support layer is limited. However, in reverse osmosis membranes, the direction of water permeation and the direction of salt leakage are the same, so internal polarization does not occur in the support layer, so the effect of the structure of the support layer on the water permeability of the membrane (membrane permeation flow rate) It is not definitive. Therefore, as the pressure applied to the concentrated solution side increases, the water permeability of the membrane can be increased as well.

  On the other hand, in the forward osmosis membrane, the internal concentration polarization of the support layer greatly affects the water permeability of the membrane. In forward osmosis treatment, a concentrated solution is placed on one side across the membrane, a dilute solution is placed on the other side, and water is permeated from the dilute solution side to the concentrated solution side using the osmotic pressure difference between the two solutions as the driving force. Let At this time, in order to increase the water permeability of the forward osmosis membrane, it is important to increase the effective osmotic pressure difference of the skin layer by reducing the internal concentration polarization of the support layer as much as possible. If the space in which the solute freely diffuses in the support layer is restricted, the concentration polarization of the solute in the support layer is likely to occur, and it becomes difficult to ensure a sufficient amount of water permeability. Therefore, in the forward osmosis membrane, the support layer is made of a material that does not limit the diffusion of the solute in the interior as much as possible, has a high porosity, and can ensure a predetermined strength even if formed as such. The constitution is important in terms of providing desired film performance.

Until now, various semipermeable membranes have been studied as membranes for forward osmosis treatment (forward osmosis membranes). For example, Patent Document 1 discloses a forward osmosis membrane in which a polyamide skin layer is laminated on a support layer made of polyacrylonitrile, polyacrylonitrile-vinyl acetate copolymer, polysulfone, or the like;
Patent Document 2 discloses a forward osmosis membrane in which a polyamide skin layer is laminated on a support layer made of an epoxy resin;
Patent Document 3 discloses a forward osmosis membrane in which a polyamide skin layer is laminated on a support layer made of polyethylene terephthalate (PET) or polypropylene;
Each is disclosed.
Thus, various forward osmosis membranes have been studied, including the polymer forward osmosis membranes disclosed in Patent Documents 1 to 3 above. However, there are still few forward osmosis membranes having high water permeability, and a high performance forward osmosis membrane is desired.

Conventional polymer forward osmosis membranes have problems in durability against acids, organic solvents, and the like, and heat resistance, and their application range is limited.
On the other hand, Patent Document 4 proposes a forward osmosis membrane flow system using a forward osmosis membrane having excellent durability and containing zeolite which is an inorganic material. However, since the water permeability of the semipermeable membrane of Patent Document 4 is extremely low and durability and water permeability performance cannot be achieved at the same time, there is a problem in practicality as a forward osmosis membrane flow system. In particular, there is a problem in practicality in applications that require high pressure resistance such as osmotic pressure power generation.

  Patent Document 5 proposes a nanofiltration membrane using a polyolefin ketone having a superior organic solvent resistance as a support layer. However, the membrane disclosed in Patent Document 5 has a small pore size and a problem in liquid permeability.

Special table 2012-519593 JP 2013-013888 A Special table 2013-502323 gazette JP 2014-039915 A Korean Published Patent No. 2015-0084503

  The present invention has been made in view of the conventional situation as described above, and its purpose is to exhibit stable performance even in use under high pressure, having sufficient durability against various liquids, The object is to provide a semipermeable membrane having excellent liquid permeability.

The present inventors have intensively studied in order to solve the above problems. As a result, a porous membrane having a large thickness, a high porosity, and a small number of cavities is used as a semipermeable membrane supporting layer, and a semipermeable membrane skin layer is laminated on one of the front and back surfaces or the inner and outer surfaces. Thus, it was found that the internal polarization of the support layer is effectively reduced. And the system of such a configuration
When used as a forward osmosis treatment system, it has high pressure resistance and can maintain a high water permeability, or
The present inventors have found that high liquid permeability can be maintained even when a liquid containing an organic compound is filtered under high pressure, and the present invention has been completed.
The present invention further reveals advantageous application methods of the forward osmosis treatment system.
That is, the present invention is as follows.

[1] A composite membrane having a porous support layer and a layer having a semipermeable membrane performance on the porous support layer,
The porous support layer has the following conditions (1) and (2):
(1) The ratio of holes having an equivalent circle diameter of 1 μm or more is less than 30%, and (2) the film thickness is 100 μm or more,
The composite film is characterized in that:
[2] The layer having the performance of the semipermeable membrane is at least selected from a cellulose acetate membrane, a polyamide membrane, a polyvinyl alcohol / polypiperazine amide composite membrane, a sulfonated polyethersulfone membrane, a polypiperazine amide membrane, and a polyimide membrane. The composite film according to [1], which is a thin film layer containing one kind.

[3] The composite membrane according to [1] or [2], wherein the porous support layer is a polyketone porous membrane.
[4] A forward osmosis treatment system comprising the composite membrane according to any one of [1] to [3].
[5] A reverse osmosis treatment system comprising the composite membrane according to any one of [1] to [3].

[6] A filtration system comprising the composite membrane according to any one of [1] to [3].
[7] A fresh water generation method using the system according to any one of [4] to [6].
[8] A method for purifying an organic compound, comprising using the system according to any one of [4] to [6].

[9] A method for concentrating a hydrated product, characterized in that the system according to any one of [4] to [6] is used.
[10] A power generation method using the forward osmosis treatment system according to [4].

  The composite membrane of the present invention was able to improve both pressure resistance and water permeability by using a porous membrane having a high porosity and few cavities as a semipermeable membrane support layer. According to a preferred embodiment of the present invention, by using a polyketone porous membrane as a semipermeable membrane support layer, the internal concentration polarization of the support layer can be suppressed, the water permeability can be effectively increased, and an organic compound is included. Since durability against a low osmotic pressure fluid can be improved, it can be used as a forward osmosis treatment system having stable performance even during long-time operation.

Therefore, the forward osmosis treatment system using the composite membrane of the present invention includes, for example, seawater desalination, brine desalination, wastewater treatment, concentration of various valuable materials, treatment of associated water in oil and gas drilling, osmotic pressure Can be suitably used for power generation using two different liquids, saccharides, fertilizer, dilution of refrigerant, and the like.
In addition, it has sufficient durability against organic compounds and high liquid permeability, and also has high removal performance against foreign matters of fine particles or molecules, so it can be used for purification and production of liquids containing organic solvents. It can be used suitably.

  Hereinafter, an example of an embodiment of the present invention will be described in detail. The following description relates to an example of the present invention, and the present invention is not limited thereto.

The composite membrane of the present invention has a porous support layer and a layer having the performance of a semipermeable membrane on the porous support layer, and the porous support layer has the following conditions (1) and (2):
(1) The ratio of holes having an equivalent circle diameter of 1 μm or more is less than 30%, and (2) the film thickness is 100 μm or more,
Satisfied.

<Porous support layer>
The circle equivalent radius of the pores of the porous support layer in the composite membrane of the present invention is the diameter of the pores in the thickness direction cross section of the porous support layer. The shape of the hole is not particularly limited, and may be a circle, an ellipse, a polygon (triangle, quadrangle, etc.), an indefinite shape, or the like.
From the viewpoint of maintaining the strength of the membrane, the proportion of pores having an equivalent circle diameter of 1 μm or more is preferably less than 30%, more preferably less than 20%, still more preferably less than 5%, and most preferably 1%. Is less than. Here, the ratio of the holes is a value represented by (cross-sectional area of holes having an equivalent circle diameter of 1 μm or more) / (cross-sectional area of the entire film) × 100 [%].

  The thickness of the support layer is preferably 100 μm or more. When the film thickness is smaller than 100 μm, the water permeability is improved, but the strength of the film is lowered, so that the pressure resistance is deteriorated and the use pressure is restricted when the composite semipermeable membrane is used. From the viewpoint of strength, it is preferable that the film thickness is large. However, the film thickness of the support layer is preferably less than 900 μm, more preferably because the film volume is compact, the apparatus is downsized, and the water permeability is maintained. It is less than 490 μm, more preferably less than 190 μm.

  In the composite membrane of the present invention, the porous support layer described above is used, and a semipermeable membrane skin layer (a layer having a semipermeable membrane performance) is provided on one of the front and back surfaces or the inner and outer surfaces. By adopting such a configuration, when the composite membrane is used as, for example, a forward osmosis membrane, the internal polarization of the support layer can be effectively reduced, the amount of water permeation can be increased, and the cavity can be reduced. By using the designed material and setting the film thickness to be as thick as 100 μm or more, the pressure resistance becomes high, and a high water permeability can be maintained stably for a long time even when used under high pressure. Specifically, this property can increase power generation efficiency in applications requiring pressure resistance of 1.5 MPa or more, such as osmotic pressure power generation using seawater and fresh water, and can be used for a long time. Will give the advantage.

  The support layer has a porous structure and allows solute and water to pass through the internal through voids. In order to effectively suppress the internal concentration polarization in the support layer, it is preferable that pores having a larger pore diameter are formed in the support layer. From such a viewpoint, the support layer preferably has pores having a maximum pore diameter of 50 nm or more.

  The maximum pore diameter is measured by a bubble point method (according to ASTM F316-86 or JIS K3832). When a porous membrane having a maximum pore diameter of 50 nm or more is used as the support layer of the forward osmosis membrane, it is possible to reduce internal concentration polarization in the support layer, so that the performance of the forward osmosis membrane can be improved. Since the internal concentration polarization is reduced as the maximum pore diameter is increased, the maximum pore diameter of the support layer is preferably 50 nm or more, more preferably 80 nm or more, further preferably 100 nm or more, and most preferably 130 nm or more. If the maximum pore size is greater than 50 nm, the molecular weight cut-off will be greater than 100,000.

  On the other hand, as the maximum pore size is increased, it becomes difficult to support the semipermeable membrane skin layer, and the pressure resistance may deteriorate. From such a viewpoint, the maximum pore diameter of the support layer is preferably 2 μm or less, more preferably 1.5 μm or less, further preferably 1 μm or less, and most preferably 0.6 μm or less.

The porosity of the support layer is not particularly limited, but the higher the porosity, the easier the diffusion of solutes in the support layer, and it is possible to suppress the internal concentration polarization of the support layer and increase the water permeability of the forward osmosis membrane. Become. Therefore, the porosity of the support layer is preferably 60% to 95%, more preferably 70% to 95%, and further preferably 80% to 95%. The porosity of the polyketone support layer (porous membrane) is calculated by the following formula (1).
Porosity (%) = (1−G / ρ / V) × 100 (1)
[In Formula (1), G is the mass (g) of the support layer, ρ is the mass average density (g / cm ³ ) of the support layer, and V is the volume (cm ³ ) of the support layer. ]

In the above mathematical formula (1), when the support layer is composed of two types of resins having different densities, the mass average density ρ is the sum of values obtained by multiplying the density of each resin by the constituent mass ratio. . For example, when each of the fibers composed of the resin A having a density ρA, the resin B having a density ρB, and the resin P having a density ρp is formed of a mass ratio of GA, GB, and GP, the mass average density ρ is expressed by the following formula (2).
Mass average density ρ = (ρA · GA + ρB · GB + ρP · GP) / (GA + GB + GP) (2)

  The material constituting the porous support layer is not particularly limited. However, it is preferable to use materials with high durability against various liquids. From the viewpoint of high durability against various liquids and good affinity, the porous support layer in the present invention is more preferably a polyketone support layer.

The polyketone polymer (hereinafter referred to as polyketone) constituting the polyketone support layer is composed of a copolymer of carbon monoxide and olefin. By constituting the support layer from polyketone, it is possible to form a support layer having a high porosity while ensuring strength.
Conventionally, a reverse osmosis membrane sometimes requires a supporting substrate such as a nonwoven fabric. However, since the polyketone support layer is highly self-supporting, such a support substrate is also unnecessary. This makes it possible to reduce the thickness of the resulting composite film. Furthermore, since the polyketone can be easily formed into an arbitrary shape such as a flat plate (flat membrane) or a hollow fiber, it can be easily applied to a conventionally known membrane module.

  From the viewpoint of ensuring strength and increasing the porosity, the polyketone support layer contains a polyketone, which is a copolymer of carbon monoxide and one or more olefins, in a proportion of 10% by mass to 100% by mass. It is preferable. The higher the polyketone content in the polyketone support layer, the better. 70 mass% or more is preferable, as for the polyketone content rate in a polyketone support layer, 80 mass% or more is more preferable, and 90 mass% or more is further more preferable. The content of the polyketone in the polyketone support layer is a method of dissolving and removing the polyketone with a solvent that dissolves only the polyketone among the components constituting the support layer, a method of dissolving and removing other than the polyketone with a solvent that dissolves only the polyketone, etc. Can be confirmed.

  In the synthesis of the polyketone, as the olefin to be copolymerized with carbon monoxide, any type of compound can be selected depending on the purpose. Examples of the olefin include chain olefins such as ethylene, propylene, butene, hexene, octene, and decene; alkenyl aromatic compounds such as styrene and α-methylstyrene; cyclopentene, norbornene, 5-methylnorbornene, tetracyclododecene, Examples thereof include cyclic olefins such as tricyclodecene, pentacyclopentadecene and pentacyclohexadecene; halogenated alkenes such as vinyl chloride and vinyl fluoride; acrylic acid esters such as ethyl acrylate and methyl methacrylate; and vinyl acetate. From the viewpoint of securing the strength of the polyketone support layer, the number of olefins to be copolymerized is preferably 1 to 3, more preferably 1 to 2, and even more preferably 1 type.

The polyketone preferably has a repeating unit represented by the following formula (1).
-RC (= O)-(1)
[In Formula (1), R represents a C2-C20 hydrocarbon group which may have a substituent. ]
Examples of the substituent for the hydrocarbon group in R in the above formula (1) include a halogen atom, a hydroxyl group, an ether group, a primary amino group, a secondary amino group, a tertiary amino group, a quaternary ammonium group, and a sulfonic acid. One or more functional groups selected from the group consisting of a group, a sulfonic acid ester group, a carboxylic acid group, a carboxylic acid ester group, a phosphoric acid group, a phosphoric acid ester group, a thiol group, a sulfide group, an alkoxysilyl group, and a silanol group Can give. The ketone unit represented by the above formula (1) may be composed of only one type, or may be a combination of two or more types.

2-8 are more preferable, as for carbon number of the hydrocarbon group R of the said Formula (1), 2 or -3 is further more preferable, and 2 is the most preferable. The repeating unit constituting the polyketone preferably contains many 1-oxotrimethylene repeating units represented by the following formula (2).
—CH ₂ —CH ₂ —C (═O) — (2)

  From the viewpoint of securing the strength of the polyketone support layer, the proportion of 1-oxotrimethylene repeating units in the repeating units constituting the polyketone is preferably 70 mol% or more, more preferably 90 mol% or more. More preferably, it is 95 mol% or more. The proportion of 1-oxotrimethylene repeating units may be 100 mol%. Here, 100 mol% means that no repeating unit other than 1-oxotrimethylene is observed except for the polymer end groups in known elemental analysis, NMR (nuclear magnetic resonance), gas chromatography and the like. . Typically, the structure of the repeating unit constituting the polyketone and the amount of each structure are confirmed by NMR.

  The polyketone can be obtained, for example, by polymerizing carbon monoxide and olefin using palladium, nickel or the like as a catalyst. For the production of the polyketone support layer, for example, methods described in JP-A Nos. 2002-348401 and 2-4431 can be referred to.

The porous support layer in the present invention may be a symmetric membrane or an asymmetric membrane. When the porous support layer is an asymmetric membrane, a semipermeable membrane skin layer described later is preferably provided on the dense surface of the support layer.
The porous support layer can have any shape. For example, a flat plate shape (flat membrane shape), a hollow fiber shape, or the like.
Such a porous support layer can be produced by a known method. When the porous support layer is a polyketone support layer, for example, the following method is convenient.

  A polyketone is dissolved in a solution containing a metal halide salt (for example, zinc halide salt, alkali metal halide salt, etc.) to prepare a polyketone dope, and this dope is passed through a film die, a double tube orifice, etc. in a coagulation bath. To form a flat plate shape, a hollow fiber shape, or the like. Furthermore, a polyketone support layer can be obtained by washing and drying the molded body. In this case, for example, the porosity and pore diameter of the polyketone support layer can be appropriately adjusted by adjusting the polymer concentration in the dope and the temperature of the coagulation bath.

  Alternatively, the polyketone is dissolved in a good solvent (for example, an aqueous solution containing resorcinol, hexafluoroisopropanol, m-cresol, o-chlorophenol, zinc halide salt, alkali metal halide salt, etc.). From the viewpoint of increasing the surface openness and the porosity, an aqueous solution containing resorcinol is preferably used. The polyketone support layer can also be obtained by casting the obtained solution on a substrate, immersing it in a non-solvent (for example, methanol, isopropanol, acetone, water, etc.), and further washing and drying. In this case, for example, the porosity and pore diameter of the polyketone porous film can be appropriately adjusted by adjusting the mixing ratio of the polyketone and the good solvent, the type of non-solvent, and the like.

<Semipermeable membrane skin layer>
A semipermeable membrane skin layer is formed on the porous support layer in the composite membrane of the present invention.
The semipermeable membrane skin layer is a layer having the performance of a semipermeable membrane, and known materials used in conventional forward osmosis membranes, reverse osmosis membranes, nanofilters and the like may be applied as they are. For example, a cellulose acetate film, a polyamide film, a polyvinyl alcohol / polypiperazine amide composite film, a sulfonated polyether sulfone film, a polypiperazine amide film, a polyimide film, and the like can be exemplified, including one or more selected from these A thin film layer is preferably used. In consideration of the low osmotic pressure solution, the high osmotic pressure solution, the durability against the organic solvent used, the liquid permeability, and the like, the material of the semipermeable membrane skin layer may be selected.
In the present invention, a semipermeable membrane skin layer made of a polyamide membrane is particularly preferred from the viewpoint of easy formation of a thin film on the porous support layer.

Although the thickness of a semipermeable membrane skin layer is not specifically limited, Preferably it is 0.05 micrometer-2 micrometers, More preferably, it is 0.05 micrometer-1 micrometer.
The thickness of the semipermeable membrane skin layer can be measured by observing the cross section of the composite membrane with an SEM.

<Other layers>
In the composite membrane of the present invention, other layers such as a fabric such as a woven fabric and a non-woven fabric, and a membrane may be laminated on one side or both sides for the purpose of suppressing performance deterioration due to adsorption of contaminants. However, it is preferable not to include other layers from the viewpoint of increasing the effective area through which the liquid permeates and from the viewpoint of reducing the size of the apparatus.

<Normal osmosis treatment system>
The composite membrane of the present invention can be used as a semipermeable membrane in a forward osmosis treatment system that utilizes forward osmosis. In this forward osmosis treatment system, a low osmotic pressure solution is disposed on one surface side of the composite membrane of the present invention, and a high osmotic pressure solution having a higher osmotic pressure than the low osmotic pressure solution is supplied to the other surface side. Then, fluid movement from the low osmotic pressure solution side to the high osmotic pressure solution side occurs, thereby increasing the flow rate on the high osmotic pressure solution side.
In this case, whether the side of the semipermeable membrane skin layer of the composite membrane of the present invention is disposed on the low osmotic pressure solution side or the high osmotic pressure solution side depends on the water permeability and fouling resistance of the liquid to be treated. In consideration of the above, it can be appropriately determined by those skilled in the art.

Here, when an aqueous solution of an organic compound is used as the low osmotic pressure solution, the concentration of the organic compound in the organic compound aqueous solution can be increased by the forward osmosis treatment using the forward osmosis treatment system. Suitable as part of the process.
Similarly, when an aqueous solution (hydrated product) containing a predetermined target is used as the low osmotic pressure solution, the hydrated product can be concentrated by forward osmosis treatment.
Further, depending on the combination of the low osmotic pressure solution and the high osmotic pressure solution, the organic solvent can be fluid-transferred from the low osmotic pressure solution to the high osmotic pressure solution.

<Reverse osmosis treatment system>
The composite membrane of the present invention can be used as a semipermeable membrane in a reverse osmosis treatment system utilizing a reverse osmosis phenomenon. In this reverse osmosis treatment system, a low osmotic pressure solution is arranged on one side of the composite membrane of the present invention, and a high osmotic pressure solution having a higher osmotic pressure than the low osmotic pressure solution is supplied to the other side. When pressure is applied to the pressure solution side, fluid flow occurs from the high osmotic pressure solution side to the low osmotic pressure solution side, thereby increasing the flow rate on the low osmotic pressure solution side.
In this case, it is preferable to arrange the semipermeable membrane skin layer side of the composite membrane of the present invention on the hyperosmotic pressure solution side.
In particular, when the porous support layer is a polyketone support layer, it has high durability against organic solvents and other organic compounds, and is a liquid containing an organic solvent or organic compound in at least one of a low osmotic pressure solution and a high osmotic pressure solution. Also in the treatment, stable performance can be expressed for a long time.

Here, when an organic compound aqueous solution is used as the high osmotic pressure solution, the concentration of the organic compound in the organic compound aqueous solution can be increased by the reverse osmosis treatment using the reverse osmosis treatment system described above, and the purification of the organic compound is possible. Suitable as part of the process.
Similarly, when an aqueous solution (hydrated product) containing a predetermined target is used as the high osmotic pressure solution, the hydrated product can be concentrated by reverse osmosis treatment.

<Power generation method>
The power generation method of the present invention uses the forward osmosis treatment system of the present invention.
In the power generation method of the present invention, the composite membrane of the present invention is used as a forward osmosis membrane, a low osmotic pressure solution is brought into contact with the semipermeable membrane skin layer side, and a high osmotic pressure solution is brought into contact with the opposite side. Alternatively, the high osmotic pressure solution may be brought into contact with the semipermeable membrane skin layer side, and the low osmotic pressure solution may be brought into contact with the opposite side. Then, by allowing water to permeate from the low osmotic pressure solution to the high osmotic pressure solution through the composite membrane of the present invention, the flow rate flowing through the high osmotic pressure solution is increased, and the water current generator is driven at the increased flow rate to generate power. Is done.

Hereinafter, the present invention will be described in more detail with reference to examples. In the following description, specific compounds, numerical values, and the like will be described. However, the scope of the present invention is not limited to these.
The measuring method of each measured value in the following examples is as follows.

(1) Maximum pore diameter and average pore diameter The maximum pore diameter is a PMI palm porometer (model: CFP-1200AEX), and a PMI galwick (surface tension = 15.6 dynes / cm) is used as the immersion liquid. It measured based on JIS K3832 (bubble point method).
The average pore diameter was measured by a half dry method in accordance with ASTM E1294-8.

(2) Average thickness of porous support layer and semipermeable membrane skin layer The composite membrane on which the semipermeable membrane skin layer was laminated was frozen and cleaved to prepare a cross-sectional sample of the membrane, which was used as a sample. This was observed using a scanning electron microscope (manufactured by Hitachi, Ltd., model S-4800) under the conditions of an acceleration voltage of 1.0 kV, a WD of 5 mm standard ± 0.7 mm, and an emission current setting of 10 ± 1 μA. The average thickness of each of the porous support layer and the semipermeable membrane skin layer was measured from the obtained SEM photograph.

(3) Percentage of pores A porous layer (without a semipermeable membrane skin layer) encapsulated in gelatin capsules with ethanol, immersed in liquid nitrogen, cooled, and cleaved with ethanol frozen The cross-section sample was prepared.
About the obtained section | slice sample, the photograph (image) of 500-50,000 times magnification was image | photographed with the electron microscope. The photographed negative image was analyzed by the following method using an image analyzer (IP1000-PC: manufactured by Asahi Kasei Corporation).

The captured image was binarized by particle analysis. The parameters set at this time are
(1) Lightness (darkness) of particles,
(2) threshold (automatic),
(3) Shading correction processing (none),
(4) Shrinkage separation processing (linear separation: shrinkage number 10, non-separation radius 1, separation contact degree 10),
(5) Outer frame correction (present), and (6) Fill hole processing (present)
Met.
From the binarized image obtained above, a hole that contacts the measurement area line (the outer frame of the measured rectangular range), a hole that partially falls out of the measurement range, a resin portion other than polyketone, and the resin are included. After removing the holes, particle analysis was performed to obtain the equivalent circle diameter of the target hole.
The above analysis was performed for five fields of view taken from the front surface to the back surface of the film while shifting in the thickness direction of the film, and then the arithmetic average value was calculated for the circle-equivalent diameters of all the measured holes. Then, the total area of holes having an equivalent circle diameter of 1 μm or more was calculated, and the ratio P of holes having an equivalent circle diameter of 1 μm or more was calculated from the following number (3).
Ratio P = (total area of holes with equivalent circle diameter of 1 μm or more) / (cross-sectional area of the entire film) × 100 [%] (3)

(4) Evaluation of membrane performance By performing both the pressure-driven reverse osmosis treatment test and the forward osmosis-driven forward osmosis treatment test, the value of the structure parameter S representing the index of the degree of internal concentration polarization of the support layer is obtained. Each forward osmosis membrane was evaluated. At the same time, a water permeability coefficient A and a salt permeability coefficient B representing the permeation performance of the semipermeable membrane skin layer were determined.

(4-1) Reverse Osmosis Treatment Test In the reverse osmosis treatment test, ultrapure water or 0.1 M NaCl aqueous solution is pressurized in the range of 0 MPa to 2 MPa to perform reverse osmosis treatment, and the water permeability J _w ^{water RO} or J _w ^{NaCl RO} (unit: L · m ⁻² · h ⁻¹ ) and salt rejection ratio R (unit:%) (= 1− (NaCl concentration in the feed solution / NaCl concentration in the permeate)) were calculated and based on the following formula The water permeability coefficient A and the salt permeability coefficient B of the semipermeable membrane skin layer were calculated. In calculating both coefficients, Sidney Loeb et al. , J .; Membr. Sci., 129 1 (1997) 243-249, and K. Sci. L. Lee et al. , J .; Membr. Sci. , 8 (1981) 141-171.
A = J _w ^{water RO} / ΔP
^{_{B = J w NaCl RO ((}} 1-R) / R) exp (-J w NaCl RO / k f)
P: Applied pressure
R: rejection rate (= 1−C _p / C _b )
C _p : Permeate concentration
C _b : Bulk solution concentration of the supply liquid
k _f : mass transfer coefficient (= J _w ^{NaCl RO} / ln [ΔP (1−J _w ^{NaCl RO} / J _w ^{water RO} ) / (π _b −π _p )]
π _p : osmotic pressure of permeated water
π _b : osmotic pressure of bulk solution

(Pressure resistance)
In the above reverse osmotic pressure test, when the pressure applied by ultrapure water or NaCl aqueous solution was changed, the maximum pressure at which osmotic pressure breakage did not occur was defined as the pressure resistance value of the osmotic membrane.

(4-2) Forward osmosis test In the forward osmosis test, a 0.3M to 1.2M NaCl aqueous solution is used as a concentrated solution (Draw solution), and an ultrapure water is used as a diluted solution (Feed Solution). Went. At this time, forward osmosis treatment was performed with the semipermeable membrane skin layer facing the dilute solution, the water permeability J _w ^FO (unit: L · m ^-2 · h ^-1 ) was measured, and the water permeability coefficient obtained above The structural parameter S of the porous support layer was calculated by substituting A and the salt permeability coefficient B into the following equation. In calculating the structural parameter S, A. Tiraferri et al., J. MoI. Membr. Sci., 367, (2011) 340-352.
^{_{J w FO = (D / S}} ) ln [(B + Aπ DS) / (Aπ FS + B + J w FO)]
D: Diffusion coefficient of solute
π _DS : concentrated solution bulk osmotic pressure
π _FS : Bulk osmotic pressure of dilute solution

  Composite films were prepared according to Examples 1 to 3 and Comparative Examples 1 to 5 below, respectively, and evaluated by the above methods.

<Example 1>
A polymer solution composed of 10% by mass of polyketone, 58.5% by weight of resorcinol, and 31.5% by weight of water is obtained by completely polycopolymerizing ethylene and carbon monoxide and having an intrinsic viscosity of 3.0 dl / g. The film was cast on a glass substrate with a coating thickness of 400 μm using an applicator. Then, it was immersed in the coagulation bath which consists of a water / methanol mixed solvent (70/30 (w / w)), and the polyketone porous membrane (asymmetric membrane) was formed. The obtained polyketone porous membrane was peeled from the glass plate and fixed to a metal frame, then washed with water, acetone and hexane in order and air-dried to obtain a polyketone support layer having a thickness of 137 μm. The proportion of pores with an equivalent circle diameter of 1 μm or more measured for the obtained support layer was 0%, and the maximum pore size was 157 nm. The porosity of the support layer was 81.2%.

On the polyketone support layer (the side that was not in contact with the glass plate when cast on the glass plate), 1,3-phenylenediamine 2 mass%, camphorsulfonic acid 2.3 mass%, triethylamine 1.1 mass %, An amine aqueous solution containing 0.15% by weight of sodium dodecyl sulfate and 3.0% by weight of hexamethylphosphoric triamide was applied, and allowed to stand for 300 seconds. Thereafter, in order to remove excess amine aqueous solution, the membrane was left vertical for 60 seconds.
Thereafter, a hexane solution of 1,3,5-trimesoyl chloride (trimesic acid trichloride 0.15% by mass) was applied from above and allowed to stand for 120 seconds. In order to remove excess chloride solution, the membrane was left vertical for 60 seconds.
The laminated body thus obtained was annealed at 90 ° C. for 600 seconds and then sufficiently washed with water to obtain a composite film 1 having a polyamide skin layer formed on a polyketone support layer.
J _w ^FO of the composite film 1 was 24.8 L · m ⁻² · h ⁻¹ , and the withstand voltage was 1.9 MPa, which showed high withstand pressure.
As described above, even when the maximum pore diameter of the support layer is as large as 157 nm, by reducing the ratio of holes having an equivalent circle diameter of 1 μm or more and setting the support layer thickness to 100 μm or more, high water permeability It was verified that a composite film having both performance and pressure resistance can be obtained. In this case, by using a support layer having a high porosity and a uniform structure, it is possible to suppress the internal concentration polarization even when the thickness of the support layer is increased, thus maintaining high water permeability. It is thought that it was possible.

<Example 2>
A composite membrane 2 was obtained in the same manner as in Example 1 except that the composition of the water / methanol mixed solvent in the coagulation bath was changed to water / methanol = 65/35 (w / w). . The thickness of the polyketone support layer in the composite membrane 2 was 150 μm. The proportion of pores with an equivalent circle diameter of 1 μm or more measured for the support layer was 0%, and the maximum pore size was 182 nm. The porosity of the support layer was 83.0%.
J _w ^FO of the composite membrane 2 is 25.1L · m ^-2 · h ^-1, the breakdown voltage is 1.8 MPa, showed high pressure resistance.
As described above, even when the maximum pore diameter of the support layer is as large as 182 nm, by reducing the proportion of holes having an equivalent circle diameter of 1 μm or more and setting the support layer thickness to 100 μm or more, high water permeability It was verified that a composite film having both performance and pressure resistance can be obtained.

<Example 3>
A composite membrane 3 was obtained in the same manner as in Example 1 except that the composition of the water / methanol mixed solvent in the coagulation bath was changed to water / methanol = 55/45 (w / w). . The thickness of the polyketone support layer in the composite membrane 3 was 167 μm. The proportion of pores with an equivalent circle diameter of 1 μm or more measured for the support layer was 0%, and the maximum pore size was 234 nm. The porosity of the support layer was 85.1%.
J _w ^FO of the composite film 3 was 25.1 L · m ⁻² · h ⁻¹ , and the pressure resistance was 1.5 MPa, which showed high pressure resistance.
As described above, even when the maximum pore diameter of the support layer is as large as 234 nm, by reducing the proportion of holes having an equivalent circle diameter of 1 μm or more and setting the support layer thickness to 100 μm or more, high water permeability It was verified that a composite film having both performance and pressure resistance can be obtained.

<Comparative Example 1>
A composite membrane 4 was obtained in the same manner as in Example 1 except that the composition of the water / methanol mixed solvent in the coagulation bath was changed to water / methanol = 75/25 (w / w). . The thickness of the polyketone support layer in the composite membrane 4 was 145 μm. The ratio of the holes having an equivalent circle diameter of 1 μm or more measured for the support layer was 30%, and the maximum hole diameter was 94 nm. The porosity of the support layer was 81.9%.
The composite film 4 had a J _w ^FO of 19.2 L · m ⁻² · h ⁻¹ and a withstand pressure of 0.8 MPa. The water permeability was less than 20.0 L · m ⁻² · h ⁻¹ , and the pressure resistance decreased.
As described above, when a support layer having a circle-equivalent diameter of 1 μm or more and a pore ratio of 30% is used, even if the support layer film thickness is set to 100 μm or more, the water resistance of the obtained composite membrane is It was insufficient. Further, the composite membrane of this comparative example has a comparatively large maximum pore size of 94 nm used, but the water permeability when the support layer thickness is 145 μm is less than 20.0 L · m ⁻² · h ^−1. Met.

<Comparative example 2>
A composite film 5 was obtained in the same manner as in Comparative Example 1 except that the film was cast with a coating thickness of 200 μm in Comparative Example 1. The thickness of the polyketone support layer in the composite membrane 5 was 69 μm. The ratio of the holes having an equivalent circle diameter of 1 μm or more measured for the support layer was 26%, and the maximum hole diameter was 115 nm. The porosity of the support layer was 80.6%.
The composite film 5 had a J _w ^FO of 22.3 L · m ⁻² · h ⁻¹ , a pressure resistance of 0.6 MPa, and the pressure resistance was low.
As described above, the proportion of holes having an equivalent circle diameter of 1 μm or more is 26%, and when a support layer having a film thickness of 69 μm is used, the resulting composite membrane may have insufficient pressure resistance. confirmed.

<Comparative Example 3>
A composite film 6 was obtained in the same manner as in Example 1 except that in Example 1 above, casting was performed with a coating thickness of 200 μm. The thickness of the polyketone support layer in the composite membrane 6 was 77 μm. The proportion of pores with an equivalent circle diameter of 1 μm or more measured for the obtained support layer was 0%, and the maximum pore size was 123 nm. The porosity of the support layer was 83.8%.
The composite membrane 6 had a J _w ^FO of 27.9 L · m ⁻² · h ⁻¹ and a pressure resistance of 0.6 MPa. Although the water permeability was high, the pressure resistance was low.
As described above, when a support layer having a circle-equivalent diameter of 1 μm or more having a pore ratio of 0% and a film thickness of 77 μm is used, the resulting composite film may have insufficient pressure resistance. confirmed.

<Comparative Example 4>
A composite film 7 was obtained in the same manner as in Example 2 except that in Example 2 above, casting was performed with a coating thickness of 200 μm. The thickness of the polyketone support layer in the composite membrane 7 was 83 μm. The proportion of pores having an equivalent circle diameter of 1 μm or more measured for the support layer was 0%, and the maximum pore size was 155 nm. The porosity of the support layer was 84.5%.
The composite membrane 7 had a J _w ^FO of 30.8 L · m ⁻² · h ⁻¹ and a pressure resistance of 0.4 MPa. Although the water permeability was high, the pressure resistance was low.
As described above, when a support layer having a circle-equivalent diameter of 1 μm or more with a pore ratio of 0% and a film thickness of 83 μm is used, the resulting composite membrane may have insufficient pressure resistance. confirmed.

<Comparative Example 5>
A composite film 8 was obtained in the same manner as in Example 3 except that in Example 3 above, casting was performed with a coating thickness of 200 μm. The thickness of the polyketone support layer in the composite membrane 8 was 97 μm. The proportion of pores having an equivalent circle diameter of 1 μm or more measured for the support layer was 0%, and the maximum pore size was 290 nm. The porosity of the support layer was 87.1%.
The composite membrane 8 had a J _w ^FO of 32.7 L · m ⁻² · h ⁻¹ and a withstand pressure of 0.2 MPa. Although the water permeability was high, the withstand pressure was extremely low.
As described above, when a support layer having a circle-equivalent diameter of 1 μm or more with a pore ratio of 0% and a film thickness of 97 μm is used, the resulting composite membrane may have insufficient pressure resistance. confirmed.

  All the above results are shown in Table 1 together with the water permeability coefficient A and the salt permeability coefficient B.

[Liquid permeability evaluation for various organic solvents]
<Examples X1 to X10>
Through the composite membrane 1 obtained in the same manner as in Example 1, various kinds of stock solutions (water and organic solvents) shown in Table 2 were used for pressure filtration under the condition of 0.5 MPa, and after pressurization for 2 hours. The amount of liquid permeation for 3 hours was measured. Then, the permeation coefficient A (L · m ⁻² · h ⁻¹ ) was calculated by dividing the liquid permeation amount by the area of the portion through which the liquid permeates. The results are shown in Table 2.

According to Table 2 above, aprotic polar organic solvents such as DMF, DMSO, and NMP have better liquid permeability than protic polar organic solvents such as alcohol. In the case of an aprotic polar organic solvent such as DMF, DMSO, and NMP, the semipermeable membrane skin layer after liquid permeation was slightly swollen.
When the support layer after filtration was observed with the naked eye, neither contraction nor swelling was observed, and no deterioration was observed. This is a result showing that the composite membrane of the present invention using a polyketone porous membrane as a support layer is suitable as a membrane for filtering various organic solvents.
From the results in Table 2, when the composite membrane of the present invention is used, one organic solvent is selectively extracted from a solution in which two or more solvents are mixed, utilizing the difference in permeability between water and the organic solvent. It is understood that it is also possible to do this.

[Evaluation of rejection rate in various organic solvents]
<Examples Y1-Y5>
Through the composite semipermeable membrane 1 obtained in the same manner as in Example 1, various stock solutions shown in Table 3 (water and organic solvents including methyl orange (Mw = 327)) were filtered under pressure at 0.5 MPa. 10 mL of permeate after 3 hours or more had passed after pressurization. The concentration of methyl orange in the stock solution before filtration and in the permeate after filtration was compared with an ultraviolet-visible absorptiometer to determine the blocking rate.
The results are shown in Table 3.

表３に示すとおり、ＤＭＦ、ＤＭＳＯ、およびアルコールを用いたときには高い阻止率であった。このことから、有機溶媒を含む液体を、本発明の複合膜を用いる逆浸透方式によって精製できることが示唆された。

As shown in Table 3, the rejection was high when DMF, DMSO, and alcohol were used. From this, it was suggested that the liquid containing the organic solvent can be purified by the reverse osmosis method using the composite membrane of the present invention.

<Example Z1>
Through a composite membrane 1 obtained in the same manner as in Example 1, a DMF solution mixed with 10 nm colloidal silica (1 ppm) was subjected to pressure filtration under the condition of 0.5 MPa, and the permeation after 3 hours or more had passed after pressurization. 100 mL of the liquid was collected.
The concentration of colloidal silica in the stock solution before filtration and in the permeate after filtration was measured by ICP-MS and compared to obtain the blocking rate of colloidal silica. The rejection of colloidal silica was 99% or more.

  The embodiments of the present invention have been described above. However, the present invention is not limited to these, and can be changed as appropriate without departing from the spirit of the invention.

  The composite membrane of the present invention has high pressure resistance and excellent water permeability. It can be suitably used for power generation using two liquids having different osmotic pressures, dilution of sugars, fertilizers, refrigerants, and the like. The composite membrane of the present invention exhibits sufficient durability and high liquid permeability with respect to organic compounds, and has high removal performance even with respect to fine particles or foreign matters having a molecular size. It can be suitably used for purification, production, etc.

Claims (10)

A composite membrane having a porous support layer and a layer having a semipermeable membrane performance on the porous support layer,
The porous support layer has the following conditions (1) and (2):
(1) The ratio of holes having an equivalent circle diameter of 1 μm or more is less than 30%, and (2) the film thickness is 100 μm or more,
The composite film is characterized in that:   The layer having the performance of the semipermeable membrane is at least one selected from a cellulose acetate membrane, a polyamide membrane, a polyvinyl alcohol / polypiperazine amide composite membrane, a sulfonated polyethersulfone membrane, a polypiperazine amide membrane, and a polyimide membrane. The composite film according to claim 1, wherein the composite film is a thin film layer.   The composite membrane according to claim 1 or 2, wherein the porous support layer is a polyketone porous membrane.   A forward osmosis treatment system comprising the composite membrane according to any one of claims 1 to 3.   A reverse osmosis treatment system comprising the composite membrane according to any one of claims 1 to 3.   A filtration system comprising the composite membrane according to any one of claims 1 to 3.   A fresh water generation method using the system according to any one of claims 4 to 6.   A method for purifying an organic compound, wherein the system according to any one of claims 4 to 6 is used.   A method for concentrating a hydrated product, comprising using the system according to any one of claims 4 to 6.   A power generation method using the forward osmosis treatment system according to claim 4.