JP4626319B2 - Porous membrane, method for producing the same, and solid-liquid separator - Google Patents

Description

  The present invention relates to a porous membrane suitable for water treatment such as drinking water production, water purification treatment, wastewater treatment, and the food industry. In particular, the present invention relates to a porous membrane which is immersed in an activated sludge tank and suitably used for solid-liquid separation in wastewater treatment.

  In recent years, porous membranes have been used in various fields such as water treatment fields such as drinking water production, water purification, and wastewater treatment, and food industry. In the field of water treatment such as drinking water production, water purification treatment, and wastewater treatment, porous membranes have been used to remove impurities in water as an alternative to conventional sand filtration and coagulation sedimentation processes. In the wastewater treatment field, an activated sludge treatment process for separating flocified sludge and treated water by a microorganism aggregate called activated sludge is widely used. In the food industry field, porous membranes are used for the purpose of separating and removing yeasts used for fermentation and concentrating treatment stock solutions.

  In the wastewater treatment field, an activated sludge treatment process for separating flocified sludge and treated water by a microorganism aggregate called activated sludge is widely used. In this case, when solid-liquid separation is performed by the precipitation method, increasing the activated sludge concentration and proceeding the decomposition process to increase the treatment efficiency may result in poor sedimentation of the sludge in the subsequent sedimentation basin. The management work to prevent the deterioration is complicated. Therefore, by using membrane separation technology for the solid-liquid separation between the sludge and the treated water, even when the high concentration activated sludge treatment is performed, the water quality is not deteriorated and the space is saved.

  As described above, porous membranes that are used in various ways have a large amount of treated water in the field of water treatment such as water purification treatment and wastewater treatment, and are therefore required to improve water permeability. If the water permeation performance is excellent, the membrane area can be reduced, and the equipment becomes compact, so that the equipment cost can be saved, which is advantageous from the viewpoint of membrane replacement cost and installation area. In addition, if water permeability decreases (fouling) due to deposition, adhesion, blockage, etc. of the separation target substance, the stability of operation is hindered, and it is necessary to increase the amount of aeration and the frequency of chemical cleaning. There is a need for a low fouling membrane because it leads to high operating costs. In addition, in the water purification treatment, a disinfectant such as sodium hypochlorite is added to the membrane module part for the purpose of sterilizing the permeated water and preventing biofouling of the membrane, or the membrane with acid, alkali, chlorine, surfactant, etc. In order to clean itself, the porous membrane is required to have chemical durability (chemical resistance). Furthermore, in tap water production, pathogenic microorganisms resistant to chlorine such as Cryptosporidium derived from livestock manure cannot be treated at the water purification plant, and accidents mixed into the treated water have become apparent since the 1990s. Therefore, in order to prevent such an accident, the porous membrane is required to have sufficient separation characteristics and high physical durability so that raw water is not mixed into the treated water.

  Thus, the porous membrane is required to have excellent separation characteristics, chemical durability (chemical resistance), physical durability, permeation performance, and low fouling properties.

  Therefore, in order to satisfy chemical durability and physical durability among these required performances, porous membranes using polyvinylidene fluoride resins have been used. However, it cannot be said that the polyvinylidene fluoride resin has sufficient low fouling properties as it is. As a method for suppressing fouling on the membrane surface, there is a report that a microorganism having a larger hydrophobicity has a higher adsorption ability due to hydrophobic interaction, and a hydrophobic substance is more likely to be adsorbed on a hydrophobic solid surface (Non-patent Document 1). ), Hydrophilicity of the hydrophobic polyvinylidene fluoride film can suppress adsorption and provide low fouling properties. As a method for hydrophilizing a polyvinylidene fluoride membrane, there is a method of coating a hydrophilic polymer on the membrane surface and the pore inner surface as in Patent Document 1, but it is considered that low fouling properties cannot be maintained if the hydrophilic polymer is peeled off. It is done. Therefore, it is considered that if blending without coating the hydrophilic polymer, the hydrophilic polymer is present on the membrane surface even when the membrane surface is scraped and the low fouling property can be maintained.

However, in general, when a hydrophilic polymer is blended with a polyvinylidene fluoride resin as in Patent Document 2, when forming a film by blending as it is, the film forming property is poor due to poor compatibility with the polyvinylidene fluoride resin. Even when the film could be formed, there was a problem that the hydrophilic polymer eluted out of the film during use in water and the low fouling property could not be maintained.
JP-A-61-161103 JP 60-216804 A Hisao Morisaki, Atsuko Hattori, Interface and Microorganisms, Society Publishing Center, 1986, P57-60

  The object of the present invention is to solve the above-mentioned problems of the prior art and to provide a polyvinylidene fluoride resin porous membrane excellent in low fouling properties.

In order to solve the above problems, the present invention has the following features. Sunawa Chi

(1) A porous film characterized in that a polymer having the following molecular unit A, a polymer having the molecular unit B, and a polymer having the molecular unit C are compatible and dispersed in the film. .

  (2) The porous film according to (1), comprising a polyvinylidene fluoride resin, a polyacrylate resin and / or a polymethacrylate resin, and a polyvinylpyrrolidone resin.

(3) The porous film according to (1), wherein the polymer having the molecular unit B is a polymer having the molecular unit C.

(4) The porous film according to any one of (1) to (3), comprising a porous substrate made of organic fibers.

(5) A method for producing a porous membrane, in which a film-forming stock solution obtained by mixing and dissolving the polymer having the molecular unit A, the polymer having the molecular unit B, and the polymer having the molecular unit C is phase-separated.

(6) The porous membrane according to (5), comprising a polyvinylidene fluoride resin, a polyacrylate resin and / or a polymethacrylate resin, and a polyvinylpyrrolidone resin Production method.

(7) The method for producing a porous film according to (5), wherein the polymer having the molecular unit B is a polymer having the molecular unit C.

(8) A solid-liquid separator provided with the porous membrane according to any one of (1) to (4).

(9) The solid-liquid separator according to (8), wherein the porous membrane is immersed in an activated sludge tank.

  Provided is a low fouling polyvinylidene fluoride resin porous membrane having no chemical elution of hydrophilic components and having chemical durability and physical durability.

  Details of the porous membrane of the present invention will be described below.

  In the present invention, the porous film is characterized in that the film structure contains A, B, and C molecular units of A vinylidene fluoride, B acrylic ester or methacrylic ester, and C vinyl pyrrolidone.

  A, B, and C may be contained in the film structure, and are preferably present as a part of the polymer, that is, the resin in the film. A, B, and C may be contained in different resins, and two or more of A, B, and C may be contained as a copolymer.

  Among them, the porous film is preferably a porous film containing a polyvinylidene fluoride resin, a polyacrylic acid ester resin and / or a polymethacrylic acid ester resin, and a polyvinylpyrrolidone resin.

  That is, by using a polyvinylidene fluoride resin as a film material, a film excellent in physical durability and chemical durability of the film can be obtained. Hydrophilic methacrylic acid ester resin and hydrophilic polyvinyl pyrrolidone By including a resin, the membrane can be made hydrophilic and low fouling can be imparted. In general, hydrophilic polymers such as polyvinylpyrrolidone resins are not compatible with hydrophobic polymers such as polyvinylidene fluoride resins, and even when mixed to form a film, only polyvinylpyrrolidone resins are used when used in water. Elutes in water and cannot maintain hydrophilicity. On the other hand, for example, polymethacrylate resins are hydrophilic and are known to be compatible with polyvinylidene fluoride resins at the molecular level (SP Nunes, KV Peinemann, Journal of Membrane Science 1992). 73 P25), and also has an affinity for polyvinylpyrrolidone resins. Therefore, the presence of the polyvinylidene fluoride resin together with the polyacrylic acid ester resin and the polymethacrylic acid ester resin serves as a compatibilizing agent, and the polyvinylpyrrolidone resin can be compatible and dispersed in the film. . At this time, it is considered that the polyvinylpyrrolidone-based resin forms microdomains and is finely dispersed.

  The polyvinylidene fluoride resin is a resin containing a vinylidene fluoride homopolymer and / or a vinylidene fluoride copolymer. A plurality of types of vinylidene fluoride copolymers may be contained. Examples of the vinylidene fluoride copolymer include a copolymer of vinylidene fluoride and at least one selected from the group consisting of vinyl fluoride, tetrafluoroethylene, hexafluoropropylene, and ethylene trifluoride chloride. . Among these, vinylidene fluoride homopolymer is more preferably used from the viewpoint of film forming property, chemical durability, and cost.

  Although it does not specifically limit with polyacrylic ester resin, for example, methyl acrylate, ethyl acrylate, n-butyl acrylate, iso-butyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, glycidyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, etc. A homopolymer of an acrylate ester monomer, a copolymer thereof, and a copolymer with another copolymerizable vinyl monomer are shown.

  Although it does not specifically limit with polymethacrylate resin, for example, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, glycidyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate A homopolymer of a methacrylic acid ester monomer, a copolymer thereof, and a copolymer with another copolymerizable vinyl monomer. Among these polyacrylic acid ester resins and polymethacrylic acid ester resins, polymethyl methacrylate is more preferably used from the viewpoint of compatibility with polyvinylidene fluoride resin, film forming property, and cost.

  The polyvinylpyrrolidone resin refers to a vinylpyrrolidone homopolymer and a copolymer with other copolymerizable vinyl monomers.

  The weight average molecular weight of these resins may be appropriately selected depending on the required strength and water permeability of the membrane, but considering the processability to a porous membrane, it is 5,000 to 2,000,000, and further 10,000 to 100 It is preferably within the range of 10,000. When the weight average molecular weight is larger than this range, the viscosity of the resin solution becomes too high. When the weight average molecular weight is smaller than this range, the viscosity of the resin solution becomes too low, and it becomes difficult to form a porous film. In addition, there is a risk of elution during use.

  The porous film of the present invention may contain or adhere other resins, surfactants, inorganic fine particles and the like other than those described above without departing from the object of the present invention. Although not particularly limited, for example, resins such as polyvinyl acetate, surfactants such as polyvinyl alcohol, polyethylene glycol, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene fatty acid ester, and inorganic fine particles such as silica fine particles and activated carbon fine particles.

  Further, the present invention is characterized by comprising a polyvinylidene fluoride resin, and a copolymer mainly composed of vinyl pyrrolidone and either an acrylate ester monomer and / or a methacrylate ester monomer. A porous membrane is also a particularly preferred embodiment.

  In a polyvinylidene fluoride resin by using a copolymer of vinyl pyrrolidone and a monomer compatible with a polyvinylidene fluoride resin comprising an acrylic ester monomer and / or a methacrylate ester monomer Vinyl pyrrolidone can be fixed to and dispersed in. By fixing by copolymerization, polyvinylpyrrolidone can be easily introduced into the film during film formation, and by improving dispersibility, film formation stability and low fouling can be improved. The copolymer may be in any form such as a random copolymer, a block copolymer, an alternating copolymer, and a graft copolymer. The body may be contained. Although not particularly limited, for example, monomers capable of vinyl polymerization such as ethylene, propylene, isobutylene, vinyl chloride, acrylonitrile, vinyl acetate and vinyl alcohol are preferably contained.

  The weight-average molecular weight of polyvinylidene fluoride resin, acrylate monomer and / or methacrylic acid ester monomer and vinylpyrrolidone copolymer as main components is processability and durability to porous film Is preferably in the range of 5,000 to 2,000,000, more preferably 10,000 to 1,000,000.

Furthermore, the porous membrane of the present invention preferably has a pure water permeability coefficient of 1 × 10 ⁻⁹ m ³ / m ² · Pa · s or more. When this pure water permeability coefficient is less than 1 × 10 ⁻⁹ m ³ / m ² · Pa · s, it is necessary to operate at a high pressure because the permeability of the membrane is poor, and the operating cost may increase. .
Furthermore, the porous membrane of the present invention preferably has a rejection rate of fine particles having an average particle size of about 0.10 μm or less of 90% or more. When the blocking rate is less than 90%, clogging due to bacterial cells or sludge may occur, or the filtration differential pressure may increase and the life may be shortened.

  Here, the pure water permeability coefficient Flux is a raw water obtained by filtering drinking water through a dialysis membrane (manufactured by Toray Industries, Ltd., Filtizer B2-1.5H), and has a diameter of 25 ° C. under a head pressure of 1 m. Filtered through a 4 cm porous membrane,

Sought by. In the evaluation, the porous membrane was immersed in ethanol for 15 minutes and then immersed in water for 2 hours or more and used for evaluation. The pure water permeability coefficient may be obtained by converting a value obtained by applying pressure or suction with a pump or the like. The water temperature may also be converted by the viscosity of the evaluation liquid.

  The fine particle rejection rate was set on a stirring cell (VHP-43K manufactured by Advantech Co., Ltd.) with a membrane (diameter 4.3 cm), an evaluation pressure of 9.8 kPa, a stirring speed of 600 rpm, and a reverse osmosis membrane (Toray Industries, Inc.) An evaluation stock solution in which polystyrene latex fine particles having an average particle size of 0.10 μm or less (Celadin Co., Ltd. nominal particle size: 0.083 μm) are dispersed in filtered water by SUL-G10 manufactured to a concentration of 25 ppm is filtered. From the absorbance of ultraviolet light having a wavelength of 220 nm of the evaluation stock solution and the permeate,

Sought by. A spectrophotometer (U-3200) (manufactured by Hitachi, Ltd.) was used for the absorbance measurement.

  The shape of the porous membrane of the present invention may be a hollow fiber membrane or a flat membrane, and is selected according to its use.

  In the case of a flat membrane, the thickness is preferably in the range of 10 μm to 1 mm, more preferably 30 μm to 500 μm. The membrane may be a single membrane or a composite membrane with a porous substrate. In the case of a composite membrane, the surface of the porous substrate may be simply coated with the polymer layer, but there may be a layer in which the porous substrate and the polymer layer overlap. Further, the porous substrate and the polymer layer may completely overlap. When a porous substrate is used, it is preferable that the thickness including the planar support material be within the above-described range. Porous substrates include polyester fibers, nylon fibers, polyurethane fibers, acrylic fibers, rayon fibers, woven fabrics made of organic fibers such as cotton and silk, knitted fabrics, non-woven fabrics, and other inorganic fibers such as glass fibers and metal fibers. Porous base materials such as woven fabrics and knitted fabrics can be used. Among these, a porous substrate made of organic fibers is particularly preferable from the viewpoint of stretchability and cost. The pore diameter of the surface can be freely selected depending on the use, but is preferably in the range of 0.005 μm (5 nm) to 1.0 μm, more preferably 0.008 μm (8 nm) to 0.5 μm. The internal structure of the flat film is arbitrary, and so-called macro voids may be present or a homogeneous structure having holes of the same size in the film thickness direction may be used.

  In the case of a hollow fiber membrane, the inner diameter is 100 μm to 10 mm, further 150 μm to 8 mm, the outer diameter is 120 μm to 15 mm, further 200 μm to 12 mm, and the film thickness is 20 μm to 3 mm, further 50 μm to 1 mm. It is preferable to do. The pore diameter of the inner and outer surfaces of the hollow fiber membrane can be freely selected depending on the application, but is designed to be in the range of 0.005 μm (5 nm) to 1.0 μm, and further 0.008 μm (8 nm) to 0.5 μm. It is preferable to do. The internal structure of the hollow fiber membrane is arbitrary, and so-called macrovoids may exist or a homogeneous structure having pores of the same size in the film thickness direction may be used. Further, one side or the inner and outer surface sides may have a skin structure, and the other side surface and / or the inner structure may have a sponge structure or a spherulite structure.

  In the case of hollow fibers, the membrane may be a single membrane or a composite membrane with a porous substrate. In the case of a composite membrane, the surface of the support material may be simply coated with the polymer layer, but there may be a layer in which the porous substrate and the polymer layer overlap. Further, the porous substrate and the polymer layer may completely overlap. As the porous substrate, a cylindrical porous substrate such as a woven fabric, a knitted fabric or a non-woven fabric made of the above organic fibers, or a cylindrical porous substrate such as a woven fabric or a knitted fabric made of inorganic fibers such as glass fibers or metal fibers. Can be used. Among these, a porous substrate made of organic fibers is particularly preferable from the viewpoint of stretchability and cost.

  The above-described porous membrane of the present invention can be produced, for example, by dissolving the resin in a membrane-forming solution and phase-separating it by any one or a combination of two or more of the following three methods.

  (1) A resin solution in which the resin is dissolved in a good solvent of polyvinylidene fluoride resin is molded by being extruded from a die at a temperature considerably lower than the melting point of the resin or cast on a support material. A wet solution method in which an asymmetric porous structure is formed by contact with a liquid containing a non-solvent of the resin by non-solvent-induced phase separation.

  (2) The resin is melt-kneaded with inorganic fine particles and an organic liquid, extruded from a die at a temperature equal to or higher than the melting point of the polyvinylidene fluoride resin, or pressed with a press, and then solidified by cooling, and then organically A melt extraction method that forms a porous structure by extracting liquid and inorganic fine particles.

  (3) The resin is dissolved at a high temperature in a solvent in which the polyvinylidene fluoride resin is difficult to dissolve at room temperature to produce a polyvinylidene fluoride resin solution. After the polyvinylidene fluoride resin solution is discharged from the base, it is cooled. Thermally induced phase separation method that causes phase separation and solidification.

  The porous membrane of the present invention produced as described above is configured as, for example, a plate-and-frame type membrane module in the case of a flat membrane shape, and a plurality of hollow fiber membranes in the case of a hollow fiber shape. The membrane module is bundled and stored in a cylindrical container, and both ends or ends thereof are fixed with polyurethane, epoxy resin, or the like. The membrane module is used as a solid-liquid separation device in which a plurality or a plurality of the membrane modules are arranged. The solid-liquid separation device is immersed in a processing tank containing a solid-liquid mixed liquid such as an activated sludge tank, and a pump is provided with pressure means on the processing stock solution side or suction means on the permeate side to perform filtration. . Of course, it is good also as filtration by a water level difference without providing a pump. In order to obtain the membrane cleaning effect, the solid-liquid separation device may be provided with means for flowing the solid-liquid mixed solution in parallel with the membrane surface, such as disposing an aeration device below the membrane. This porous membrane can be used for water purification, wastewater treatment, drinking water production, industrial water production, etc., and can treat river water, lake water, groundwater, seawater, sewage, drainage, activated sludge, food process water, etc. And can be used for removing suspended matters in the water to be treated.

  The pure water permeability coefficient and the blocking rate of the porous membrane in the examples were measured by the above methods.

  The fouling resistance of the membrane to sludge was compared based on the irreversible fouling ratio obtained by the following sludge basic filtration experiment.

<Measurement method of irreversible fouling ratio>
・ Experimental material [Distilled water for measuring pure water permeation resistance]
Wako Pure Chemical Industries, Ltd. distilled water was filtered through a dialysis membrane (Toray Industries, Ltd., Filtizer B2-1.5H).

[Sludge for sludge filtration resistance measurement]
Sludge collected from an agricultural settlement wastewater treatment plant was treated with dextrin medium (dextrin 12 g / L, polypeptone 24 g / L, ammonium sulfate 7.2 g / L, potassium phosphate 2.4 g / L, sodium chloride 0.9 g / L, magnesium sulfate. A sludge solution (MLSS 15) acclimatized with 0.3 g / L of heptahydrate and 0.4 g / L of calcium chloride dihydrate with a BOD volumetric load of 1 g-BOD / L · day and a water retention time of about 1 day. .17 g / L) was diluted with reverse osmosis membrane permeate so as to be MLSS 1 g / L. When a filter paper filtration test was performed on the diluted sludge, the permeation amount for 5 minutes of 1 μm pore size filter paper (Toyo Filter Paper No. 5C) with 50 mL of diluted sludge at 19.9 ° C. was 21.9 mL. The viscosity of the diluted sludge measured with a viscometer (VT-3E manufactured by Rion Co., Ltd., using rotor No. 4) was 1.2 mPa · s (19.9 ° C.).

・ Experimental method The sludge basic filtration experiment device pressurizes the reservoir tank with nitrogen gas as shown in FIG. 1, and per unit time permeating from a stirring cell (Amicon 8010 manufactured by Millipore, Inc., effective membrane area 4.1 cm ² ). It is the structure which monitors permeated water with an electronic balance. (Chia-Chi Ho, AL Zydney, Journal of Colloid and Interface Science, 2002. 232 P389). The electronic balance is connected to a computer and the membrane permeation resistance is calculated later from the change in weight over time. The membrane surface was given a membrane surface flux by the rotation of a magnetic stirrer attached to the stirring cell, the stirring speed of the stirring cell was always adjusted to 600 rpm, the evaluation temperature was 25 ° C., and the evaluation pressure was 20 kPa. An evaluation flow is shown in FIG. Evaluation was performed in the following order. Note that the membrane resistance may be calculated by converting the water temperature by the viscosity of the evaluation liquid.

1. 1. The porous membrane is immersed in ethanol for 15 minutes and then immersed in water for 2 hours or more. 2. Pure water permeation resistance (R1) measurement 3. Sludge filtration resistance (R2) measurement 4. Membrane cleaning Measurement of pure water permeation resistance (R3).

  Where each membrane resistance R is

I asked more.

  Here, fouling associated with sludge filtration of each membrane is (R2-R1), irreversible fouling is (R3-R1), and physical cleaning recovery (R2-R3) is related (FIG. 3). Here, irreversible fouling that has not been recovered by physical cleaning represents the ease of fouling of the film. Actually, fouling, irreversible fouling, and physical cleaning recovery amount are affected by the magnitude of the pure water permeation resistance R1 of the membrane, so the irreversible fouling ratio (R3-R1) normalized by R1 of each membrane is used for comparison between membranes / R1 was used.

  First, the membrane was immersed in ethanol and replaced with water, and then the pure water permeation resistance was measured for 5 minutes. At this time, the pure water permeation resistance (5-minute value) calculated from the permeated water amount for the last 20 seconds was defined as R1.

  After measuring the pure water permeation resistance, remove the reservoir tank, fill the cell with the sludge diluent (14.44 g) with the evaluated membrane set in the stirring evaluation cell, and add a fixed amount (7.5 g) of sludge diluent. Filtered. A certain amount of filtration was performed, and the sludge filtration resistance calculated from the amount of permeated water for the last 20 seconds during sludge filtration was defined as R2.

  After the sludge filtration was stopped, the residual sludge solution in the cell was taken out with the membrane set in the evaluation cell. Then, the inside of the evaluation cell was filled with distilled water, and the entire evaluation cell was vibrated for 1 minute at a speed of 1000 times / minute using an MS1 mini shaker (manufactured by IKA) and washed.

  Next, the cleaning liquid was taken out, a reservoir tank was attached, the pure water permeation resistance was measured again for 5 minutes, and the pure water permeation resistance calculated from the permeated water amount for the last 20 seconds was defined as R3.

<Molecular weight measurement>
The detection time of the polymer was measured with a GPC measuring apparatus (HLC-8220-GPC manufactured by Tosoh Corporation), and the molecular weight was calculated from a calibration curve obtained from polystyrenes having different molecular weights.

<Copolymerization ratio measurement>
The molar ratio was calculated by analyzing the ¹ H-NMR spectrum of the copolymer. ^{The 1} H-NMR spectrum was obtained by dissolving the copolymer in a deuterium solvent and using an NMR measurement apparatus (JNM-EX-270 manufactured by JEOL Ltd., 32 times of integration).

<Example 1>
Polyvinylidene fluoride homopolymer (PVDF, weight average molecular weight 358,000) and poly (methyl methacrylate) / polyvinylpyrrolidone graft copolymer (PMMA-g-PVP, polymerization average molecular weight 195,000, copolymerization molar ratio 46: 54), N, N-dimethylacetamide (DMAc, manufactured by Wako Pure Chemical Industries, Ltd.), polyvinyl alcohol (PVA500 manufactured by Wako Pure Chemical Industries, Ltd., average polymerization degree 500, saponification degree 86-90%), These were sufficiently stirred and mixed and dissolved at a temperature of 90 ° C. with the following composition to obtain a film forming stock solution. Table 1 shows the charged composition of the film forming solution.

PVDF: 9.0% by weight
PMMA-g-PVP: 2.0% by weight
PVA500: 3.0% by weight
Water: 3.0% by weight
DMAc: 83.0% by weight.

Next, the film-forming stock solution is cooled to 40 ° C., applied to a nonwoven fabric made of polyester fiber having a density of 0.48 g / cm ³ and a thickness of 220 μm, and immediately immersed in a water coagulation bath at 25 ° C. for 5 minutes. A porous substrate on which a porous resin layer was formed was obtained.

  This porous substrate was immersed in hot water at 95 ° C. for 2 minutes to wash out DMAc and PVA500, thereby obtaining a separation membrane.

Next, the rejection of fine particles having an average particle size of 0.083 μm was measured for the separation membrane, and it was 98%. Moreover, the pure water permeability coefficient was 27 * 10 < ^-9 > m < ³ > / m < ² > * s * Pa. The irreversible fouling ratio in the sludge basic filtration experiment was 1.2. Table 2 shows the results of the sludge basic filtration experiment.

<Example 2>
PVDF, random copolymer of polyethyl acrylate and polyvinyl pyrrolidone (PEA-co-PVP, polymerization average molecular weight 66,000, copolymer molar ratio 52:48), polypropylene glycol (PPG3000, Wako Pure Chemical Industries, Ltd.) ), Average molecular weight 3000, diol type), polyoxyethylene monopalmitate (N = 20) sorbitan (Tween 40), dimethyl sulfoxide (DMSO, manufactured by Wako Pure Chemical Industries, Ltd.) The mixture was sufficiently stirred and dissolved at a temperature to obtain a film-forming stock solution. This was formed in the same manner as in Example 1 to obtain a separation membrane.

PVDF: 10.0% by weight
PEA-co-PVP: 3.0% by weight
PPG3000: 2.0% by weight
Tween 40: 3.0
Water: 3.0% by weight
DMSO: 79.0% by weight.

Next, the rejection of fine particles having an average particle size of 0.083 μm was measured for the separation membrane, and it was 97%. Moreover, the water permeability was 37 × 10 ⁻⁹ m ³ / m ² · s · Pa. The irreversible fouling ratio in the sludge basic filtration experiment was 1.3.

<Example 3>
PVDF, polymethyl methacrylate (PMMA, weight average molecular weight 1,400,000), polyvinylpyrrolidone (PVP K-90, manufactured by Wako Pure Chemical Industries, Ltd., average molecular weight 360000), polyoxyethylene (N = 20) sorbitan monopalmitate (Tween 40) and N, N-dimethylformamide (DMF, manufactured by Mitsubishi Rayon Co., Ltd.) were used, and these were sufficiently stirred and mixed and dissolved at a temperature of 90 ° C. to obtain a film forming stock solution. This was formed in the same manner as in Example 1 to obtain a separation membrane.

PVDF: 9.5% by weight
PMMA: 3.0% by weight
PVP K-90: 4.0% by weight
Water: 2.0% by weight
DMF: 81.5% by weight.

Next, the rejection of fine particles having an average particle size of 0.083 μm was measured for the separation membrane, and it was 98%. Moreover, the water permeation amount was 30 × 10 ⁻⁹ m ³ / m ² · s · Pa. The irreversible fouling ratio in the sludge basic filtration experiment was 1.5.
<Example 4>
PVDF, random copolymer of polymethyl methacrylate and polyvinylpyrrolidone (PMMA-co-PVP, weight average molecular weight 42,000, copolymerization molar ratio 55:45), polyethylene glycol (PEG400, manufactured by Wako Pure Chemical Industries, Ltd.) , Average molecular weight 400), PVA500, and DMAc, and these were sufficiently stirred and mixed and dissolved at a temperature of 90 ° C. with the following composition to obtain a film-forming stock solution. This was formed in the same manner as in Example 1 to obtain a separation membrane.

PVDF: 11.7% by weight
PMMA-co-PVP: 1.3% by weight
PEG400: 2.0% by weight
PVA500: 3.0% by weight
Water: 3.0% by weight
DMAc: 79.0% by weight.

Next, the rejection of fine particles having an average particle size of 0.083 μm was measured for the separation membrane, and it was 97%. Moreover, the water permeability was 51 × 10 ⁻⁹ m ³ / m ² · s · Pa. The irreversible fouling ratio in the sludge basic filtration experiment was 1.3.

<Example 5>
PVDF, PMMA-co-PVP, polyethylene glycol (PEG 20000 manufactured by Wako Pure Chemical Industries, Ltd., average molecular weight 20000), PVA500, DMF were sufficiently mixed and dissolved under the following composition at a temperature of 90 ° C. A film-forming stock solution was obtained. This was formed in the same manner as in Example 1 to obtain a separation membrane.

PVDF: 9.1% by weight
PMMA-co-PVP: 3.9% by weight
PEG 20000: 5.0% by weight
Water: 3.0% by weight
DMF: 79.0% by weight.

Next, the rejection of fine particles having an average particle size of 0.083 μm was measured for the separation membrane, and it was 98%. Moreover, the water permeability was 24 × 10 ⁻⁹ m ³ / m ² · s · Pa. The irreversible fouling ratio by the sludge basic filtration experiment was 1.0.

<Comparative Example 1>
Using PVDF, PEG 20000, and DMAc, these were sufficiently stirred and mixed and dissolved at a temperature of 90 ° C. with the following composition to obtain a film forming stock solution. This was formed in the same manner as in Example 1 to obtain a separation membrane.

PVDF: 13.0% by weight
PEG 20000: 5.0% by weight
Water: 3.0% by weight
DMAc: 79.0% by weight.

Next, the rejection of fine particles having an average particle size of 0.083 μm was measured for the separation membrane, and it was 98%. Moreover, the water permeability was 63 × 10 ⁻⁹ m ³ / m ² · s · Pa. The irreversible fouling ratio in the sludge basic filtration experiment was 1.9.

<Comparative Example 2>
PVDF, PMMA, PEG400, Tween40, and DMF were used, and these were sufficiently stirred and mixed and dissolved at a temperature of 90 ° C. with the following composition to obtain a film forming stock solution. This was formed in the same manner as in Example 1 to obtain a separation membrane.

PVDF: 11.7% by weight
PMMA: 1.3% by weight
PEG400: 2.0% by weight
Tween 40: 3.0% by weight
Water: 2.5% by weight
DMF: 79.5% by weight.

Next, the rejection of fine particles having an average particle size of 0.083 μm was measured for the separation membrane, and it was 98%. Moreover, the water permeability was 66 × 10 ⁻⁹ m ³ / m ² · s · Pa. The irreversible fouling ratio in the sludge basic filtration experiment was 2.2.

<Comparative Example 3>
Using PVDF, PMMA, PEG 20000, and DMAc, these were sufficiently stirred and mixed and dissolved at a temperature of 90 ° C. with the following composition to obtain a film forming stock solution. This was formed in the same manner as in Example 1 to obtain a separation membrane.

PVDF: 9.1% by weight
PMMA: 3.9% by weight
PEG 20000: 5.0% by weight
Water: 3.0% by weight
DMAc: 79.0% by weight.

Next, the rejection of fine particles having an average particle size of 0.083 μm was measured for the separation membrane, and it was 96%. Further, the water permeability was 34 × 10 ⁻⁹ m ³ / m ² · s · Pa. The irreversible fouling ratio in the sludge basic filtration experiment was 2.0.

<Comparative example 4>
Using PVDF, PVP K-90, PVA500 and DMAc, these were sufficiently stirred and mixed and dissolved at a temperature of 90 ° C. with the following composition to obtain a film forming stock solution. This was formed in the same manner as in Example 1 to obtain a separation membrane.

PVDF: 11.7% by weight
PVP K-90: 1.3% by weight
PVA500: 5.0% by weight
Water: 3.0% by weight
DMAc: 79.0% by weight.

Next, the rejection of fine particles having an average particle size of 0.083 μm was measured for the separation membrane, and it was 96%. Further, the water permeability was 66 × 10 ⁻⁹ m ³ / m ² · s · Pa. The irreversible fouling ratio in the sludge basic filtration experiment was 2.0.

<Comparative Example 5>
Using PVDF, PVP K-90, PPG3000, and DMF, these were sufficiently stirred and mixed and dissolved at a temperature of 90 ° C. with the following composition to obtain a film forming stock solution. This was formed in the same manner as in Example 1 to obtain a separation membrane.

PVDF: 11.7% by weight
PVP K-90: 1.3% by weight
PPG3000: 6.0% by weight
Water: 2.0% by weight
DMF: 79.0% by weight.

Next, the rejection of fine particles having an average particle size of 0.083 μm was measured for the separation membrane, and it was 97%. Moreover, the water permeability was 44 × 10 ⁻⁹ m ³ / m ² · s · Pa. The irreversible fouling ratio in the sludge basic filtration experiment was 2.1.

<Comparative Example 6>
PVDF, polyethyl acrylate (PEA, manufactured by Sigma Aldrich Co., Ltd., average molecular weight 95,000), polyoxyethylene monostearate (N = 20) sorbitan (Tween 60) and DMSO were used, and they were heated to 90 ° C. with the following composition. The mixture was sufficiently stirred and mixed and dissolved to obtain a stock solution. This was formed in the same manner as in Example 1 to obtain a separation membrane.

PVDF: 9.0% by weight
PEA: 3.0% by weight
Tween 60: 6.0% by weight
Water: 3.5% by weight
DMSO: 78.5% by weight.

Next, the rejection of fine particles having an average particle size of 0.083 μm was measured for the separation membrane, and it was 98%. The water permeability was 71 × 10 ⁻⁹ m ³ / m ² · s · Pa. The irreversible fouling ratio in the sludge basic filtration experiment was 3.3.

It is a figure explaining a membrane permeation resistance measuring device. It is a figure explaining the sludge basic filtration experiment flow. It is a figure explaining the relationship between film resistance and fouling.

Explanation of symbols

B ... Pressure regulator B ... Valve C ... Pressure gauge II ... Reservoir for water supply E ... Magnetic stirrer F ... Membrane filtration unit G ... Electronic balance

Claims (9)

A porous film characterized in that a polymer having the following molecular unit A, a polymer having a molecular unit B, and a polymer having a molecular unit C are mixed and dispersed in the film.
  2. The porous membrane according to claim 1, comprising a polyvinylidene fluoride resin, a polyacrylate resin and / or a polymethacrylate resin, and a polyvinylpyrrolidone resin. The porous membrane according to claim 1, wherein the polymer having the molecular unit B is a polymer having the molecular unit C.   The porous membrane according to any one of claims 1 to 3, comprising a porous substrate made of organic fibers. A method for producing a porous membrane, in which a film-forming stock solution obtained by mixing and dissolving the polymer having the molecular unit A, the polymer having the molecular unit B, and the polymer having the molecular unit C is phase-separated. 6. The method for producing a porous membrane according to claim 5, comprising a polyvinylidene fluoride resin, a polyacrylate resin and / or a polymethacrylate resin, and a polyvinylpyrrolidone resin. 6. The method for producing a porous film according to claim 5, wherein the polymer having the molecular unit B is a polymer having the molecular unit C. The solid-liquid separator provided with the porous membrane in any one of Claims 1-4 . The solid-liquid separator according to claim 8, wherein the porous membrane is immersed in an activated sludge tank.