Porous structure

Abstract

To provide a porous structure composed mainly of a polyphenylene ether-based resin having high permeation performance and high mechanical durability.SOLUTION: There is provided a porous structure having a spherical structure interconnected by spherical bodies that are mainly composed of a polyphenylene ether-based resin.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a porous structure containing a polyphenylene ether resin as a main component. [Background technology]

[0002] Porous structures such as adsorbents and porous separation membranes such as microfiltration membranes and ultrafiltration membranes are used for purposes such as clarification, concentration, and separation in water treatment, food, and pharmaceutical applications. In recent years, as the range of applications of porous structures has expanded, there has been an increasing demand for porous structures with higher performance (e.g., adsorption, permeability, separation, durability, etc.).

[0003] When used as a porous separation membrane for water treatment applications such as water purification, the porous separation membrane becomes clogged with the substances to be removed as a result of continuous filtration, resulting in a decrease in the throughput, and therefore periodic cleaning is required. Methods for cleaning a clogged porous separation membrane include physical cleaning (air scrubbing), in which air bubbles are blown onto the surface of the membrane while the membrane is vibrated, and chemical cleaning, in which the substances to be removed that are clogged in the pores of the porous separation membrane are decomposed using a chemical solution such as an acid or alkali, so the porous separation membrane is required to have high mechanical durability and high chemical durability.

[0004] In recent years, porous separation membranes using fluororesins such as polyvinylidene fluoride, which have both mechanical and chemical durability, have been widely used, but due to concerns about the burden of organic fluorine compounds on the human body and the environment, alternatives are being sought. One example of a resin that has a small environmental burden and high chemical durability is polyphenylene ether resin.

[0005] Polyphenylene ether resins are lightweight, heat resistant, mechanically durable, acid and alkali resistant, and have excellent dimensional stability, and are widely used in home appliances, office equipment, and the automotive industry. In addition, polyphenylene ether resins are polymerized by the carbon-oxygen coupling method, a process in which only water is discharged, and raw materials that do not contain halogens are used, so the resin manufacturing process is also characterized by its low environmental impact. In recent years, recycling technologies have also been actively developed, and further reductions in environmental impact are expected.

[0006] On the other hand, polyphenylene ether has a problem that it becomes brittle when processed into a porous separation membrane because it is hard. As a porous separation membrane made of polyphenylene ether, there is a method in which polyphenylene ether is dissolved in an organic solvent and a porous membrane is formed by non-solvent thermally induced phase separation (Patent Document 1). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2014 / 054346 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the porous membrane described in Patent Document 1 had insufficient mechanical durability for use in water treatment and food and pharmaceutical applications that require physical cleaning.

[0009] Therefore, an object of the present invention is to provide a porous structure containing as a main component a polyphenylene ether resin having high permeability and high mechanical durability. [Means for solving the problem]

[0010] As a result of intensive research aimed at solving the above problems, the present inventors discovered that the above problems can be solved by providing a spherical structure in a porous structure mainly composed of a polyphenylene ether resin, and thus completed the present invention.

[0011] That is, the present invention comprises the following: [1] A porous structure having a spherical body interconnected structure in which spherical bodies composed mainly of a polyphenylene ether resin are interconnected. [2] The porous structure according to [1] above, wherein the average diameter of the spheres is 0.1 μm or more and 10 μm or less. [3] The porous structure according to [1] or [2] above, having a porosity of 40% or more and 90% or less. [4] A method for manufacturing a porous structure, comprising discharging a polymer solution containing a polyphenylene ether resin and an organic solvent, and cooling and solidifying the solution in a coagulation bath at 10°C or lower at an average cooling rate of 100°C / min to 500°C / min. [5] The method for producing a porous structure according to the above [4], wherein the temperature of the polymer solution when discharged is 100° C. or higher. [6] A method for separating a fluid, which uses the porous structure according to any one of the above items [1] to [3]. [7] A separation device using the porous structure according to any one of the above [1] to [3]. [8] An adsorbent using the porous structure according to any one of the above [1] to [3]. Effect of the Invention

[0012] According to the present invention, it is possible to obtain a porous structure composed mainly of a polyphenylene ether resin which has a low environmental impact and is highly durable against physical cleaning and cleaning with chemicals in water treatment, food, and pharmaceutical applications. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective view of a spherical structure of one embodiment of the present invention. [Diagram 2]FIG. 2-a is a schematic diagram showing the pressure loss at the pore inlet when the wall end is a square end, and FIG. 2-b to FIG. 2-d are schematic diagrams showing the pressure loss at the pore inlet when the wall end is a circular end. [Diagram 3] 1 is an electron microscope photograph of a cross section of a porous separation membrane according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, a porous separation membrane will be described in detail as an embodiment of the porous structure of the present invention, but the present invention is not limited thereto in any way.

[0015] <Polyphenylene ether resin> The term "polyphenylene ether resin" refers to a resin (polymer) containing polyphenylene ether (hereinafter, "PPE") having an aromatic ring and an ether group in the main chain, and examples thereof include a PPE resin represented by the following general formula (I). The PPE resin may be copolymerized with other monomers and may contain other functional groups within the range that does not impair the effects of the present invention. The PPE resin used to form the porous structure may be one type, or two or more types of PPE resins may be mixed together.

[0016] [ka]

[0017] In formula (I), n represents a natural number of 1 or more.

[0018] The number average molecular weight of the PPE is preferably from 5,000 to 500,000. Within this range, the viscosity of the membrane-forming solution is sufficient, and a porous separation membrane having sufficient strength while having formability can be produced.

[0019] The term "major component" refers to a component that accounts for 50% by mass or more of the constituent components. For example, in a porous separation membrane, a component that accounts for 50% by mass or more is the main component of the porous separation membrane.

[0020] From the viewpoint of further improving the strength of the porous separation membrane and optimizing the membrane performance, a polymer blend of the above-mentioned PPE-based resin and various polymers such as polystyrene, which are known to be completely compatible with PPE-based resins, may be used as the raw material of the porous separation membrane. When using a polymer blend, the ratio of the PPE-based resin is preferably 50 mass% or more. In addition, the PPE-based resin may be configured to contain a filler. Furthermore, from the viewpoint of imparting hydrophilicity to a porous separation membrane mainly composed of a hydrophobic polymer, PPE-based resin, the porous separation membrane may contain an ionic surfactant, a nonionic surfactant, or a hydrophilic polymer such as polyethylene glycol or polyvinylpyrrolidone.

[0021] The proportion of the PPE-based resin constituting the porous separation membrane according to this embodiment is 50% by mass or more, preferably 60% by mass or more, and more preferably 80% by mass or more. If it is in this range, the characteristics of the PPE-based resin, which has high mechanical durability and high chemical durability, are maintained, and therefore it is suitable as a porous separation membrane.

[0022] The fact that PPE resin is the main component can be analyzed by various nuclear magnetic resonance measurements.

[0023] <Spheroidal connection structure> The porous separation membrane according to this embodiment has a structure in which spheres are linked together (hereinafter also referred to as a "linked sphere structure").

[0024] The "spherical body linked structure" is a structure in which spherical bodies are partially linked three-dimensionally. The spherical bodies may be approximately spherical or approximately elliptical, and the linked state is not particularly limited, and two or more adjacent spherical bodies may be linked. A specific method for measuring the average diameter of the spherical bodies will be described later.

[0025] A large number of such sphere-connected structures, in which spheres are partially connected three-dimensionally, are gathered together, and voids form between the sphere-connected structures, which are the solid parts, to form a porous structure having a structure in which spheres are connected (sphere-connected structure). The formed voids are supported by the partially connected spheres, so they are less likely to shrink and larger voids are more likely to form than in a mesh-like structure. This allows the porous separation membrane having the sphere-connected structure to maintain high water permeability. Furthermore, the formation of the sphere-connected structure allows the membrane to achieve higher strength than a porous membrane made of a mesh-like structure.

[0026] A schematic diagram of a portion of the spherical body linked structure is shown in Figure 1. In the spherical body linked structure 1 of Figure 1, a plurality of spherical bodies 10 are linked together.

[0027] The spherical body 10 is approximately spherical or approximately ellipsoidal. As shown in Fig. 1, the spherical body 10 is connected to other spherical bodies 10, so the entire spherical or ellipsoidal surface cannot be observed. However, the spherical shape of each spherical body is extrapolated from the shape shown in the outer shape of each spherical body.

[0028] The spheres may be connected by direct adhesion between the spheres or by non-spherical portions between the spheres, for example the waists 11 of the spheres.

[0029] The voids 12 between the spherical-body linked structures are the voids between the solid parts of the spherical-body linked structures described above, i.e., the pores of the porous structure. In Fig. 1, the voids 12 between the spherical-body linked structures are not completely enclosed, but the pores of the porous structure may be any space surrounded by the spherical-body linked structures.

[0030] The average diameter of the spheres in the porous separation membrane according to this embodiment is preferably 0.1 μm to 10 μm, more preferably 0.5 μm to 5 μm, and even more preferably 0.8 μm to 3 μm. If the average diameter of the spheres is within the above range, it is easy to obtain high permeability and fractionation as a porous separation membrane.

[0031] The average diameter of the spheres that make up the linked sphere structure is determined by taking an electron micrograph of the cross section of the porous structure using a scanning electron microscope or the like at a magnification at which the linked sphere structure can be clearly seen, and measuring the diameters of 10 randomly selected spheres per cross section. The same measurement is performed on 5 randomly selected cross sections, and the arithmetic mean of the obtained diameters is calculated to determine the average diameter.

[0032] When calculating the diameter of each sphere, in the case of spheres that are connected by a spherical constriction 11 (spheres whose outline can be confirmed), straight lines are drawn in the directions of the long and short axes, and the average of the long and short axes is taken as the diameter of the sphere.

[0033] In the case of connected spheres, as shown in Figure 1, a straight line 13 is drawn through the center of the sphere in the direction of the long and short diameters so as not to include the connecting parts of the spheres, and the average of the long and short diameters is taken as the diameter of the sphere. In this case, there are two points on the contour of the sphere where the line drawn in the diameter direction intersects, and the tangents at each intersection point face each other in approximately parallel relation. In the case of connected spheres, if the center of a sphere overlaps with an adjacent sphere, that is, if the contours are not approximately parallel and face each other (corresponding to X1 in Figure 1), the sphere is excluded from the measurement target.

[0034] Furthermore, if two spheres appear to overlap in the depth direction of the electron microscope photograph, the sphere at the back (corresponding to X2 in Figure 1) is excluded from the measurement. Then, the outline of the sphere at the front is used as the boundary between the two spheres at the front and back, and only the diameter of the sphere at the front is measured and calculated.

[0035] In addition, if the spheres are discontinued at the edge of the electron microscope photograph used for measurement, the spheres at that edge are excluded from the measurement.

[0036] The larger the average diameter of the spheres, the larger the sphere-connected structures will be, and the larger the gaps 12 between the sphere-connected structures, i.e., the pores of the porous structure will be.

[0037] The density of the spheres of the porous separation membrane according to this embodiment is 10 3 pieces / mm 2Over 10 8 pieces / mm 2 It is preferable that the ratio is 10 or less, and more preferably 10 4 pieces / mm 2 Over 10 6 pieces / mm 2 The density of the sphere is 10 3 pieces / mm 2 This provides high strength and pressure resistance, and is 10 8 pieces / mm 2 High water permeability can be obtained by satisfying the following conditions.

[0038] The average diameter and density of the spheres can be controlled, for example, by the polymer concentration, temperature and pressure in the polymer solution before molding into the porous separation membrane, and the temperature gradient during molding (solidification).

[0039] The density of the spheroids is calculated by taking an electron microscope photograph, as in the case of measuring the diameter, extrapolating the spherical shape of each spheroid from the outline of each spheroid, and counting the number of spheroids per unit area of ​​the image.

[0040] <Pressure loss reduction effect by spherical body connection structure> The porous separation membrane according to the present embodiment is characterized by having a structure in which spherical body linked structures, the main component of which is a PPE-based resin, are linked. Considering the case where liquid flows from the surface of the separation membrane to the inside during liquid filtration through the porous separation membrane, the flow path narrows suddenly at the pores on the surface of the separation membrane, which is the inlet, causing a pressure loss at the inlet and hindering the flow. In other words, the spherical shape of each sphere constituting the spherical body linked structure and the shape of the pores, which are the voids between the spherical body linked structures, form the shape of the inlet of the pores. The pressure loss at the inlet is expressed by the following formula (1) and is known to depend on the loss coefficient (ζ) of the inlet. ΔP=ζ×(V2) 2 / 2g...Formula (1) Here, ΔP is the pressure loss at the inlet, ζ is the loss coefficient at the inlet, V2 is the flow velocity in the pore, and g is the gravitational acceleration.

[0041] As shown in Figure 2, the loss coefficient (ζ) is a value determined by the shape of the flow passage. When the wall surface of the inlet section is a corner end (90°), ζ = 0.5 (Figure 2-a). However, if the wall end is circular and the radius R increases, the loss coefficient becomes smaller (Figures 2-b to 2-d).

[0042] That is, the porous separation membrane according to the present embodiment has a spherical body connected structure in which spherical bodies are connected, and the wall end is circular, so that the pressure loss at the inlet part is small and the obstruction to the flow of liquid is small. A porous separation membrane having such a spherical body and spherical body connected structure allows liquid to easily flow into the porous separation membrane, and can exhibit high permeability.

[0043] Moreover, the greater the curvature of each sphere, that is, the greater the average diameter of the spheres, the larger the pores, which are the gaps between the sphere-connected structures, and the higher the water permeability of the porous separation membrane. On the other hand, the fractionation performance of the porous separation membrane is lowered. Furthermore, if the average diameter of the spheres is small, the pores, which are the gaps between the sphere-connected structures, are smaller, and the water permeability of the porous separation membrane is lowered. Therefore, from the viewpoint of obtaining high water permeability and appropriate fractionation performance, the pore diameter of the porous structure is preferably 0.1 μm or more and 10 μm or less, more preferably 0.3 μm or more and 7 μm or less, and even more preferably 0.5 μm or more and 5 μm or less. The pore diameter of the porous structure can be calculated by measuring the diameters of 50 randomly selected pores in an image of the surface of the porous structure taken at a magnification of, for example, 1,000 times or 10,000 times using a scanning electron microscope, and calculating the arithmetic average. If the number of pores in one image is less than 50, multiple images are used to calculate so that the number of pores becomes 50.

[0044] <Porosity> In order to obtain high water permeability and to suppress deformation of the porous separation membrane during use, such as breakage, folding, or crushing, the porous separation membrane of this embodiment preferably has a porosity of 40% or more and 90% or less, and more preferably 50% or more and 80% or less.

[0045] The pore diameter and porosity of the porous structure, like the average diameter and density described above, can be controlled, for example, by the polymer concentration, temperature and pressure in the polymer solution before molding into the porous separation membrane, the temperature gradient during molding (solidification), and the magnification and temperature in the stretching described below.

[0046] The porosity can be calculated from the following formula (2) by measuring the volume of a test piece of the porous separation membrane using Archimedes' principle. At this time, liquid A, which keeps the porous separation membrane in a wet state, and liquid B, which is used to measure the buoyancy using Archimedes' principle, must be incompatible, and liquid B must not dissolve the resin that forms the porous separation membrane. Porosity (%) = (1 - volume of test specimen in bone dry state / volume of test specimen in wet state) × 100...Equation (2).

[0047] <Fractional particle size> The fractional particle size of the porous separation membrane according to this embodiment is preferably 0.05 μm or more and 2.0 μm or less, more preferably 0.10 μm or more and 1.5 μm or less, and even more preferably 0.15 μm or more and 1.0 μm or less. By making the fractional particle size 0.05 μm or more, the permeation resistance of the membrane pores is reduced, and a porous membrane with high permeability suitable for practical use is obtained. On the other hand, by making the fractional particle size 2.0 μm or less, the possibility of components such as turbidity leaking into the treated water is reduced.

[0048] The fractional particle size, like the average diameter and density described above, can be controlled by the resin concentration, temperature and pressure in the polymer solution before molding into the porous separation membrane, the temperature gradient during molding (solidification), and the magnification and temperature in the stretching described below.

[0049] <Pure water permeability, breaking strength, breaking elongation> The porous separation membrane according to this embodiment has a pure water permeability of 0.05 m at 25° C. under a pressure of 100 kPa. 3 / m 2 / hr or more 5.0m 3 / m 2 / hr or less, and more preferably 0.10 m 3 / m2 / hr or more 4.0m 3 / m 2 / hr or less, and more preferably 0.15 m 3 / m 2 / hr or more 3.0m 3 / m 2 / hr or less.

[0050] The porous separation membrane according to this embodiment preferably has substantially no macrovoids.

[0051] "Macrovoid" refers to a void having a major axis of 50 μm or more observed in the cross section of a porous separation membrane.

[0052] "Substantially free of macrovoids" means that the number of macrovoids in the cross section of the porous separation membrane is 10 / mm 2 This means that the number of macrovoids in the cross section of the porous separation membrane is 5 / mm 2 Preferably it has less than 100% and most preferably none at all.

[0053] The breaking strength of the porous separation membrane according to this embodiment is 50 g / mm 2 More than 1000g / mm 2 It is preferable that the content is less than 100 g / mm 2 More than 800g / mm 2 More preferably, it is 150 g / mm 2 More than 600g / mm 2 The following is the result.

[0054] The breaking elongation of the porous separation membrane according to this embodiment is preferably 5% or more and 100% or less, more preferably 10% or more and 90% or less, and even more preferably 15% or more and 80% or less.

[0055] When the breaking strength and breaking elongation are within the above ranges, sufficient water permeability is exhibited under normal use conditions, and breakage of the porous separation membrane can be suppressed.

[0056] Like the average diameter and density, the breaking strength and breaking elongation can be controlled by the polymer concentration, temperature, and pressure of the polymer solution before molding into the porous separation membrane, and the temperature gradient during molding (solidification), and can also be controlled by the magnification and temperature in the stretching described below.

[0057] <Method of manufacturing porous separation membrane> A method for obtaining a porous separation membrane containing a PPE resin as a main component according to this embodiment will be described, but the present invention is not limited to these manufacturing method examples.

[0058] Methods for producing a porous separation membrane from a PPE-based resin include, for example, a thermally induced phase separation method, a non-solvent induced phase separation method, a melt extraction method, a stretching hole opening method, etc. Among these, in this embodiment, it is preferable to use a thermally induced phase separation method.

[0059] Thermally induced phase separation is a phase separation in which a polymer solution dissolved at high temperature is solidified by cooling. When a porous separation membrane is produced using the thermally induced phase separation method, a poor solvent capable of dissolving the PPE resin at 60° C. or higher is preferred as the solvent for the PPE resin, and for example, aprotic polar solvents such as N-methyl-2-pyrrolidone (hereinafter, “NMP”), N,N-dimethylacetamide, N,N-dimethylformamide, and limonene are preferably used.

[0060] There are two main types of phase separation mechanisms in thermally induced phase separation. One is liquid-liquid phase separation, in which a polymer solution that is uniformly dissolved at high temperatures separates into a polymer-rich phase and a polymer-dilute phase as the temperature decreases due to a decrease in the dissolving ability of the solution. The other is solid-liquid phase separation, in which a polymer solution that is uniformly dissolved at high temperatures separates into a polymer solid phase and a polymer-dilute solution phase as the temperature decreases due to crystallization of the resin. In the former method, mainly three-dimensional network structures are formed, while in the latter method, spherical structures are formed.

[0061] In the manufacturing method of the porous separation membrane according to the present embodiment, the spheres and the sphere-connected structure are formed by the latter phase separation mechanism. In the case of the sphere-connected structure, the solid portion is bulky, so that the voids between the solid portions are unlikely to shrink, and high pure water permeability can be maintained, which is preferable. For this reason, it is preferable to select a polymer concentration and a solvent that induce solid-liquid phase separation.

[0062] The inventors discovered that the spherical structures that are generally formed by solid-liquid thermally induced phase separation in crystalline polymers can also be formed by thermally induced phase separation in PPE-based resins, which are amorphous polymers, and that the connectivity of the spherical structure is improved and strength is increased by setting the coagulation bath that induces thermally induced phase separation to 10°C or less and rapid cooling conditions with an average cooling rate Vt of 100°C / min or more and 500°C / min or less.

[0063] In the method for producing a porous separation membrane according to the present embodiment, in the coagulation step for producing a porous separation membrane having a sphere-linked structure, it is preferable to use a coagulation bath with a sufficient volume of 100 times or more the amount of the polymer solution added. In addition, the specific temperature of the coagulation bath is 10° C. or less, preferably 5° C. or less, and more preferably 0° C. or less.

[0064] The temperature of the polymer solution is preferably 100°C or higher, more preferably 120°C or higher. The upper limit of the temperature is preferably the boiling point or lower of the solvent used in the polymer solution, more preferably 200°C or lower, and even more preferably 190°C or lower. By setting the temperature of the polymer solution at 100°C or higher, the precipitation of the polymer can be suppressed, and the connectivity of the spherical structure can be easily controlled. On the other hand, by setting the temperature of the polymer solution at 200°C or lower, the viscosity of the film-forming solution can be made easy to mold, and the evaporation of the solvent in the polymer solution can also be suppressed.

[0065] The quenching conditions for inducing thermally induced phase separation in the manufacturing method of the porous separation membrane according to this embodiment are expressed as an average cooling rate (Vt) and are calculated from the temperature of the polymer solution (Ts), the coagulation bath temperature (Tc), and the coagulation time (t) according to the following formula (3). Vt(℃ / min)=(Ts-Ta) / t...Equation (3).

[0066] In order to obtain a porous separation membrane having a high connectivity of the spherical body connection structure and high mechanical strength, it is important to increase the average temperature decreasing rate (Vt), which is preferably 100°C / min or more and 500°C / min or less, more preferably 150°C / min or more and 450°C / min or less, and even more preferably 200°C / min or more and 400°C / min or less.

[0067] The composition of the coagulation bath in the method for producing a porous separation membrane according to this embodiment may be the same as the solvent of the polymer solution or may contain a low concentration of a non-solvent for the resin to suppress and smooth the unevenness of the separation membrane surface, and it is preferable to control the occurrence of non-solvent-induced phase separation. The amount of the non-solvent for the resin added to the coagulation bath is preferably 0% by mass or more and 50% by mass or less, more preferably 5% by mass or more and 45% by mass or less, and even more preferably 10% by mass or more and 40% by mass or less.

[0068] The shape of the porous separation membrane according to this embodiment is not particularly limited, but a flat membrane or a hollow fiber membrane is preferred. Both of these membranes can be formed by methods conventionally known to those skilled in the art. For example, in the case of a flat membrane, a polymer solution can be cast on a substrate and immersed in a coagulation bath to produce it. In the case of a hollow fiber membrane, a polymer solution is discharged from the outer circumferential slit of a double tubular nozzle so as to form a hollow cylinder, and a fluid selected from a non-solvent, a poor solvent, a good solvent, a mixed solvent thereof, or a liquid incompatible with the polymer solution, or a gas such as nitrogen or air is extruded from the inner nozzle hole together with the polymer solution, and the membrane can be produced by immersing the membrane in a coagulation bath.

[0069] The concentration of the PPE resin in the polymer solution is preferably 5% by mass or more and 60% by mass or less, and more preferably 10% by mass or more and 50% by mass or less, from the viewpoint of ensuring sufficient mechanical strength while optimizing the water permeability and fractionation performance of the porous separation membrane.

[0070] The porous separation membrane according to the present embodiment may be stretched to expand the pores and improve the water permeability. The temperature conditions during stretching are preferably 50°C or higher and 200°C or lower, more preferably 60°C or higher and 180°C or lower. The stretching ratio is preferably 1.01 times or higher and 2 times or lower. By setting the temperature at 50°C or higher, it is possible to stably and uniformly stretch the membrane, and by setting the temperature at 200°C or lower, it is possible to prevent the porous separation membrane from softening and the pores and hollow parts, which are the voids between the sphere-linked structures, from collapsing. In addition, since the temperature control is easy, stretching is preferably performed in a liquid, and may be performed in a gas such as steam. As the liquid used for stretching, a method of using water or an aqueous solution of a solvent for the polymer solution is simple and preferable, and when stretching at 90°C or higher, it is also preferable to use low molecular weight polyethylene glycol or the like.

[0071] A separation device using the porous structure of the present invention obtained as described above can separate various fluids (for example, separation of liquid, separation of gas, separation of solid from liquid, separation of gas from liquid, etc.) Examples of liquid separation devices include, but are not limited to, a raw liquid tank, a booster pump, a module filled with a porous structure, a treatment liquid tank, a cleaning pump, etc.

[0072] The term "module" refers to a porous structure housed in a container so that a treatment liquid can be collected by separation. For example, a plurality of hollow fiber-shaped porous structures are packed in a cylindrical housing and fixed at one or both ends with polyurethane, epoxy resin, or the like so that a treatment liquid can be collected, or a flat porous structure is attached to a support plate and the ends are sealed so that a treatment liquid can be collected, are generally exemplified, but are not limited to these.

[0073] Examples of methods for separating liquids include, but are not limited to, a method in which raw liquid such as industrial wastewater, fermentation liquid, or culture liquid is treated using a separation device equipped with a porous structure at an operating pressure of 10 kPa or more and 1 MPa or less to remove organic matter and the like contained in the raw liquid.

[0074] The porous structure of the present invention can also be suitably used as an adsorbent having excellent durability, for example, a gas adsorbent, an adsorbent for water purification, an adsorbent for wastewater purification, etc. EXAMPLES

[0075] The present invention will be specifically described below by way of examples, but the present invention is not limited to these in any way.

[0076] (1) Pure water permeability of separation membrane <Hollow fiber membrane> A small module of about 20 cm in length was prepared, consisting of five hollow fiber membranes. Distilled water was pumped from the surface side having a spherical structure at a temperature of 25°C and a filtration differential pressure of 16 kPa. The amount of permeated water (m 3 ) and the value obtained is expressed as unit time (hr) and unit effective membrane area (m 2 ) and calculated per 100 kPa.

[0077] <flat membrane> The flat membrane was cut into a circle with a diameter of 50 mm and set in a cylindrical filtration holder. Distilled water was fed from the surface side having the sphere-connected structure under the conditions of a temperature of 25°C and a filtration differential pressure of 10 kPa, and the amount of permeated water (m 3 ) and the value obtained is expressed as unit time (hr) and unit effective membrane area (m 2 ) and calculated per 100 kPa.

[0078] (2) Breaking strength and breaking elongation Using a tensile tester (TENSILON (registered trademark) / RTM-100, manufactured by Toyo Baldwin Co., Ltd.), a sample with a measurement length of 50 mm was measured five times at a tensile speed of 10 mm / min in an atmosphere of 25°C, using different samples, and the arithmetic averages of the breaking strength and breaking elongation were calculated.

[0079] (3) Diameter of the sphere For the porous separation membranes produced in Examples 1 to 4 and Comparative Examples 1 to 2 described later, a cross section perpendicular to the surface of the porous separation membrane was photographed at 3000 times using a scanning electron microscope. From the photographed image, 10 spheres forming a sphere-connected structure present in a region from the surface to 20 μm in the thickness direction were randomly selected, and the long and short diameters of each were measured. The above photographing was performed at 5 locations, and the long and short diameters of 10 randomly selected spherical structures were determined, resulting in a total of 50 long diameters and 50 short diameters. Next, the average value of the diameters of the total of 100 was calculated, which was taken as the diameter of the spheres. The spheres to be measured are as described above.

[0080] (4) Porosity The porosity was calculated by measuring the volume of a test piece of the porous separation membrane using Archimedes' principle. The measurement was performed using a specific gravity measurement kit AD-1653 manufactured by A&D Co., Ltd., following the steps (a) to (e). The test piece was 3 cm long for hollow fiber membranes and 2 cm x 2 cm for flat membranes. (a) Place a wet test piece on the weighing dish of the specific gravity measurement kit in the air and set the zero point. The wet test piece was prepared by immersing it in ethanol for 30 minutes or more, and then immersing it in water for 1 hour or more. (b) Using a liquid with a known density, a wet test piece was placed on the weighing dish of the specific gravity measurement kit in the liquid, and the buoyancy (A) was measured. Note that (A) was an absolute value. (c) The volume (B) of the wet test piece was calculated using (A) / liquid density. (d) The wet test piece was dried to measure the bone-dry mass, and the bone-dry volume (C) was calculated from the density of the resin used in the porous separation membrane. (e) The porosity was calculated by (1-(C) / (B)) x 100. Here, water was selected as the liquid for creating a wet state, and decane was selected as the liquid for measuring buoyancy.

[0081] (5) Particle size fraction Rejection rate measurements (filtration pressure 5 kPa, cross-flow velocity 0.5 m / sec) were performed on at least three different sizes of microparticles using a dispersion of polystyrene latex microparticles (concentration 20 ppm). A linear approximation was performed on each measurement value, and the particle size at which the rejection rate was 90% was determined as the fractional particle size.

[0082] [Example 1] 30% by mass of PPE resin (PX100L, manufactured by Global Polyacetal Co., Ltd.) and 70% by mass of NMP (manufactured by Mitsubishi Chemical Co., Ltd.) were dissolved at 150°C to obtain a uniform polymer solution. The obtained polymer solution was left to stand at 130°C, degassed, and then discharged from the outer tube of a double tubular die for hollow fiber molding with a discharge outlet temperature of 100°C. Furthermore, a 35% by mass NMP aqueous solution was discharged from the inner tube of the double tubular die. The solution was passed through a dry length of 5 cm in 1 second, solidified in a coagulation bath at a temperature of -5°C consisting of an aqueous solution of 35% by mass of NMP and 65% by mass of water, and then washed with water to obtain a porous hollow fiber membrane of Example 1. The evaluation results and performance of the obtained porous hollow fiber membrane, such as the structure, are shown in Table 1. An electron microscope photograph of the cross section of the porous hollow fiber membrane is also shown in FIG. 3.

[0083] [Example 2] A homogeneous polymer solution was obtained by dissolving 35% by mass of PPE resin and 65% by mass of (R)-(+)-limonene (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) at 150°C. The obtained polymer solution was left to stand at 130°C, degassed, and then discharged from a slit die with a discharge outlet temperature of 110°C, passed through a dry length of 5 cm in 1 second, solidified in a coagulation bath at a temperature of 0°C consisting of 100% by mass of (R)-(+)-limonene, and then washed with ethanol to obtain a porous flat membrane of Example 2. The evaluation results of the structure and performance of the obtained porous flat membrane are shown in Table 1.

[0084] [Example 3] A homogeneous polymer solution was obtained by dissolving 30% by mass of PPE resin (manufactured by Asahi Kasei Corporation, S201A) having a number average molecular weight of 19,000 and 70% by mass of NMP at 150 ° C. The obtained polymer solution was left to stand at 130 ° C., degassed, and then discharged from the outer tube of a double tubular die for hollow fiber molding with a discharge outlet temperature of 120 ° C. Furthermore, a 35% by mass NMP aqueous solution was discharged from the inner tube of the double tubular die. It was passed through a dry length of 5 cm in 1 second, solidified in a coagulation bath at a temperature of -10 ° C. consisting of an aqueous solution of 35% by mass of NMP and 65% by mass of water, and then washed with water to obtain a porous hollow fiber membrane of Example 3. The evaluation results of the structure and performance of the obtained porous hollow fiber membrane are shown in Table 1.

[0085] [Example 4] A homogeneous polymer solution was obtained by dissolving 30% by mass of modified PPE resin (NX7000, PPE / polyamide alloy manufactured by Global Polyacetal Co., Ltd.) and 70% by mass of NMP at 190°C. The obtained polymer solution was left to stand at 180°C, degassed, and then discharged from the outer tube of a double tubular die for hollow fiber molding with a discharge outlet temperature of 180°C. Furthermore, a 50% by mass aqueous solution of NMP was discharged from the inner tube of the double tubular die. The solution was passed through a dry length of 5 cm in 1 second, solidified in a coagulation bath at a temperature of 0°C consisting of an aqueous solution of 50% by mass of NMP and 50% by mass of water, and then washed with water to obtain a porous hollow fiber membrane of Example 4. The evaluation results of the structure and performance of the obtained porous hollow fiber membrane are shown in Table 1.

[0086] [Comparative Example 1] 30% by mass of PPE resin and 70% by mass of NMP were dissolved at 130°C to obtain a homogeneous polymer solution. The obtained polymer solution was left to stand at 70°C, degassed, and then discharged from the outer tube of a double tubular die for hollow fiber molding with a discharge port temperature of 70°C, and a 35% by mass NMP aqueous solution was further discharged from the inner tube of the double tubular die. After idling in a dry section at 20°C for 10 seconds, the mixture was solidified in a bath at a temperature of 40°C consisting of an aqueous solution of 35% by mass of NMP and 65% by mass of water, and then washed with water to obtain a porous hollow fiber membrane of Comparative Example 1. The evaluation results of the structure and performance of the obtained porous hollow fiber membrane are shown in Table 1.

[0087] [Comparative Example 2] 20% by mass of PPE resin and 80% by mass of NMP were dissolved at 130°C to obtain a uniform polymer solution. The obtained polymer solution was left to stand at 130°C, degassed, and then discharged from the outer tube of a double tubular die for hollow fiber molding with a discharge port temperature of 130°C, and a 20% by mass NMP aqueous solution was further discharged from the inner tube of the double tubular die. After idling in a dry section at 20°C for 10 seconds, the mixture was solidified in a bath at a temperature of 25°C consisting of an aqueous solution of 10% by mass of NMP and 90% by mass of water, and then washed with water to obtain a porous hollow fiber membrane of Comparative Example 2. The evaluation results of the structure and performance of the obtained porous hollow fiber membrane are shown in Table 1.

[0088] [Comparative Example 3] 30% by mass of PPE resin and 70% by mass of γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation) were heated at 150° C., but undissolved PPE resin remained, and a homogeneous polymer solution was not obtained.

[0089] [Table 1] [Explanation of symbols]

[0090] 1 Spherical body connection structure 10 Spherical body 11 Constriction of a spherical body 12. Gaps between sphere-connected structures 13 A straight line passing through the center of a sphere in the direction of its major axis 20 Pore inlet 21 Porous structure 22 Wall end with small radius R 23 Wall end with large radius R 24 Wall end with very large radius R V1 Primary side flow velocity V2 Pore flow velocity X1 Spherical object with no mean diameter measured X2 Spherical object with no mean diameter measured

Claims

1. A porous structure having a spherical body connected structure in which spherical bodies composed mainly of a polyphenylene ether resin are connected.

2. 2. The porous structure according to claim 1, wherein the average diameter of the spheres is from 0.1 μm to 10 μm.

3. The porous structure according to claim 1 or 2, having a porosity of 40% or more and 90% or less.

4. A method for producing a porous structure, comprising discharging a polymer solution containing a polyphenylene ether resin and an organic solvent, and cooling and solidifying the polymer solution in a coagulation bath at 10°C or lower at an average temperature drop rate of 100°C / min to 500°C / min.

5. The method for producing a porous structure according to claim 4 , wherein the temperature of the polymer solution when discharged is 100° C. or higher.

6. A method for separating a fluid, which uses the porous structure according to claim 1 or 2.

7. A separation device using the porous structure according to claim 1 or 2.

8. An adsorbent comprising the porous structure according to claim 1 or 2.

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