JP2005193192A - Polysulfone-based porous membrane and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polysulfone-based porous membrane excellent in a pure water a permeation performance, a fractioning performance, strength, heat resistance, a low water absorption property, chemical resistance, a process controlling property, a cost efficiency and a pore formation property using a heat induction phase separation method, and to provide its production method. <P>SOLUTION: The polysulfone-based porous membrane is formed by heat induction phase separation of a polysulfone-based polymer and a solvent. The porous membrane has fine pores having an average pore diameter of 3 μm or more on a membrane surface and has a pure water permeation speed of 30,000 L/m<SP>2</SP>/hr/98kPa or more and a fraction particle diameter of 1 μm or more. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is excellent in pure water permeation performance, fractionation performance, strength, heat resistance, chemical resistance, low water absorption, and process controllability, cost performance, and pore formation using a thermally induced phase separation method. The present invention relates to a polysulfone-based porous membrane and a method for producing the same.

  In recent years, the technology of separation means using a separation membrane having selective permeability has been remarkably advanced. Such separation operation technology has been put into practical use as a series of purification systems including separation means, washing means, sterilization means, etc., for example in the manufacturing process of drinking water, ultrapure water and pharmaceuticals, and sterilization and finishing of brewed products. ing. In these application fields, water refinement (advanced treatment), safety improvement, and accuracy improvement are required at a high level, and the use of separation membranes is progressing.

  The characteristics required of the separation membrane include not only permeation performance and fractionation performance, but also excellent strength, heat resistance, chemical resistance, and low water absorption. In view of these, these required characteristics are becoming more sophisticated. The balance between the transmission performance and the fractionation performance is important, and it is desirable that smaller particles can be removed at a higher transmission speed. With respect to strength, it is necessary to have strength that can withstand washing by bubbling as well as during filtration. In addition, a separation membrane having excellent heat resistance has a wide range of applications, such as being usable for removing foreign substances in hot water, and it is also necessary to have excellent chemical resistance when performing chemical cleaning. Furthermore, the low water-absorbing separation membrane is excellent in dimensional stability during filtration, and can realize a more advanced filtration treatment.

  Under such circumstances, separation membranes made of various polymers have been manufactured. The performance of the separation membrane, such as strength, heat resistance, chemical resistance, and water absorption, largely depends on the characteristics of the membrane material, but the permeation performance and fractionation performance of the separation membrane depend greatly on the membrane production method. Phase separation is often used as a method for producing a separation membrane having excellent permeation performance and fractionation performance. Production methods using such phase separation can be broadly divided into non-solvent induced phase separation methods and thermally induced phase separation methods.

  In the non-solvent induced phase separation method, a uniform polymer solution composed of a polymer and a solvent causes phase separation due to the concentration change due to the ingress of the non-solvent or evaporation of the solvent to the outside atmosphere. Polysulfone, which is excellent in strength, heat resistance, chemical resistance, and low water absorption, is often used as a material for separation membranes using such a non-solvent-induced phase separation method. It is known that a separation membrane is produced by developing non-solvent induced phase separation in a coagulation bath after being dissolved in a solvent such as N, N-dimethylacetamide (see, for example, Patent Document 1). However, in general, the non-solvent induced phase separation method is difficult to control the phase separation in the non-solvent, and the non-solvent is indispensable. Therefore, the manufacturing cost is high, and macro-voids (coarse pores) are easily generated. There are problems in terms of controllability and cost.

  On the other hand, the thermally induced phase separation method usually comprises the following steps. (1) A mixture of a polymer and a solvent having a high boiling point is melted at a high temperature. (2) After molding, the polymer is cooled by cooling at an appropriate rate to induce phase separation. (3) Extract the used solvent.

    The advantages of the thermally induced phase separation method compared to the non-solvent induced phase separation method are as follows. (A) Macrovoids that cause a decrease in film strength are not generated. (B) In the non-solvent induced phase separation method, a non-solvent is required in addition to the solvent, so that control in the production process is difficult and reproducibility is low. On the other hand, the heat-induced phase separation method does not require a non-solvent, so it has excellent controllability and cost, and has high reproducibility. (C) The pore diameter control is relatively easy, the pore diameter distribution is sharp, and the hole forming property for forming good holes is excellent.

Thermally induced phase separation has a solid-liquid type and a liquid-liquid type, and which one is developed depends on the compatibility between the polymer and the solvent. When the compatibility of both is very high, solid-liquid type thermally induced phase separation is developed, but when compatibility is low, liquid-liquid type thermally induced phase separation is developed, and finally both become incompatible. . In general, in liquid-liquid type thermally induced phase separation, since phase separation proceeds by spinodal decomposition, it has a feature that a co-continuous structure is easily developed compared to solid-liquid type thermally induced phase separation. A separation membrane having excellent pore forming properties such as communication and uniformity can be produced. That is, in order to produce a separation membrane excellent in permeation performance and fractionation performance, it is preferable to select an appropriate polymer and solvent combination that exhibits liquid-liquid type thermally induced phase separation. In general, since the region where a polymer and a solvent exhibit liquid-liquid type thermally induced phase separation is small, it is known that it is extremely important to select an appropriate combination of a polymer and a solvent when producing a separation membrane by this method. (For example, Non-Patent Document 1).
Japanese Patent Laid-Open No. 11-104235 “Chemical Engineering” Chemical Industry Co., Ltd. June 1998, pages 453-464

  The object of the present invention is to provide pure water permeation performance, fractionation performance, strength, heat resistance, chemical resistance, and low water absorption using a heat-induced phase separation method. It is an object of the present invention to provide a polysulfone-based porous membrane excellent in the above and a method for producing the same.

  The polysulfone-based porous membrane of the present invention that solves the above problems is a porous membrane formed by thermally induced phase separation of a polysulfone-based polymer and a solvent.

  The polysulfone-based porous membrane of the present invention described above comprises a polysulfone-based polymer and a solvent that is compatible with the polysulfone-based polymer in a specific temperature region to be in a one-phase state and that can cause phase separation due to a temperature change. After preparing a mixed liquid kneaded at a temperature at which the polysulfone polymer and the solvent are compatible as a stock solution, cooling causes heat-induced phase separation and precipitation of the polysulfone polymer, and then the solvent is extracted. Can be manufactured.

  The polysulfone polymer in the present invention is a general term for polymer compounds having a sulfone bond, and is not particularly specified. However, for example, a polysulfone polymer represented by the following formula (1) is widely available on the market. It is preferable because it is easily available. The polysulfone-based polymer having the chemical structure represented by the formula (1) is marketed under the trade name “Udel” by Solvay Advanced Polymers Co., Ltd., and there are several types depending on the molecular weight and the like. It is necessary to be compatible with the solvent in the region to be in a single phase and to be able to cause thermally induced phase separation due to temperature changes. Furthermore, the higher the molecular weight, the better the strength of the resulting porous membrane, which is preferable. However, it should be noted that the phase separation form changes depending on the molecular weight. For example, as the molecular weight increases, the compatibility with the solvent generally decreases, so that the liquid-liquid type thermally induced phase separation goes through the liquid-liquid type thermally induced phase separation and finally becomes incompatible.

  As the solvent used in the present invention, a solvent that is compatible with the polysulfone-based polymer in a specific temperature region and causes heat-induced phase separation from the polysulfone-based polymer due to a temperature change is used. The phase separation includes solid-liquid type thermally induced phase separation and liquid-liquid type thermally induced phase separation. In the case of the polysulfone polymer represented by the formula (1), 2- (benzyloxy) ethanol, butyl salicylate, Dimethyl sulfoxide, sulfolane, trimethyl trimellitic acid, furfuryl alcohol, N-methylbenzenesulfonic acid amide, benzyl alcohol and the like are particularly preferable because they exhibit liquid-liquid type thermally induced phase separation. Furthermore, it is more preferable to use a solvent having a weight loss rate of 10% or less at (thermally induced phase separation temperature + 30) ° C. for 30 seconds because the pore opening property (opening rate) on the membrane surface becomes good. . The weight loss rate of the solvent is measured using, for example, a differential thermal / thermogravimetric measuring device (hereinafter sometimes abbreviated as TG (thermogravimetric) -DTA (differential heat)). Examples of such a solvent include 2- (benzyloxy) ethanol, dimethyl sulfoxide, trimethyl trimellitic acid, N-methylbenzenesulfonic acid amide, and benzyl alcohol.

  In the present invention, the thermally induced phase separation temperature is defined as follows. In a mixed liquid composed of a polysulfone-based polymer and a solvent, when the phase separation form is solid-liquid heat induced phase separation, in the process of cooling at a rate of 10 ° C./min from the temperature at which the mixed liquid is in a one-phase state, The glass transition temperature of the polymer is defined as the phase separation temperature. In the case of liquid-liquid heat induced phase separation, the temperature is defined as a temperature at which spinodal decomposition starts in the process of cooling at a rate of 10 ° C./min from the temperature at which the mixed solution is in a single phase.

  As a method for judging whether the phase separation state of a mixed liquid composed of a polysulfone-based polymer and a solvent is solid-liquid type thermally induced phase separation or liquid-liquid type thermally induced phase separation, observe under a microscope. In general, a method is used to compare the droplet structure forming temperature and the glass transition temperature observed by a differential scanning calorimeter (hereinafter sometimes abbreviated as DSC). First, a liquid mixture kneaded in advance is prepared on a preparation, placed on a hot plate, and cooled at a predetermined cooling rate from the high temperature side, and a droplet structure forming temperature is measured using a microscope. Further, the glass transition temperature is measured by cooling the mixture from the high temperature side at a predetermined cooling rate using DSC. If the droplet structure formation temperature and glass transition temperature obtained from both measurements are almost the same, solid-liquid type thermally induced phase separation is used. If the droplet structure formation temperature is higher, liquid-liquid type thermally induced phase separation is used. It can be judged that there is. From the viewpoint of structure control, the phase separation state is preferably liquid-liquid type thermally induced phase separation, and the temperature difference between the droplet structure forming temperature and the glass transition temperature is preferably 5 ° C. or more, more preferably It is 10 ° C or higher.

In addition, a mixture of a polysulfone-based polymer and a solvent that is compatible with the polysulfone-based polymer in a specific temperature region to be in a one-phase state and can undergo phase separation due to a temperature change, further, inorganic particles, and inorganic particles Add a flocculant having an affinity, prepare a mixed solution kneaded at a temperature at which the polysulfone polymer and solvent are compatible as a spinning stock solution, extrude, cool, and then heat-induced phase separation to cool the polysulfone system By precipitating the polymer and extracting the solvent, inorganic particles and flocculant which are components other than the polysulfone-based polymer, the membrane surface has fine pores with an average pore diameter of 3 μm or more, and a pure water permeation rate of 30000 L / m. ^A polysulfone-based porous membrane having a fractional particle diameter of 1 μm or more can be produced at ² / hr / 98 kPa or more.

  The inorganic particles used in the present invention are the core for the porous membrane to have a large pore size, and are desirably fine particles that can be easily extracted with chemicals and have a relatively narrow particle size distribution. Examples thereof include, for example, metal oxides or hydroxides such as silica, calcium silicate, aluminum silicate, magnesium silicate, calcium carbonate, magnesium carbonate, calcium phosphate, iron and zinc, and salts such as sodium, potassium and calcium. be able to. In particular, cohesive inorganic particles are usually added to a composition that causes phase separation between the polysulfone polymer and the solvent, so that the stability when the polysulfone polymer and the solvent are in a compatible state is improved. As a result, it becomes possible to produce a homogeneous porous film, and a porous film having a larger pore diameter can be produced. From such a cohesive point, silica is the best inorganic particle. In addition, inorganic particles having different agglomerated particle diameters can be mixed for the purpose of improving the pore diameter control of the porous membrane, in particular, improving the pore connectivity.

  The aggregating agent used in the present invention refers to a compound that has an affinity for inorganic particles and has a function of improving the aggregating properties of the inorganic particles. In addition to such requirements, the flocculant must have a boiling point equal to or higher than the temperature at which the polysulfone polymer and the solvent are compatible. In addition, it is more preferable that the aggregating agent is a compound having a hydrophilic group from the viewpoint of improving the aggregation property of the inorganic particles. However, it is not necessary to add a new flocculant when the solvent also satisfies the requirements for the flocculant. Examples of flocculants include polyhydric alcohols such as ethylene glycol, propylene glycol, triethylene glycol, polyethylene glycol, and glycerin, polyglycerin fatty acid esters such as decaglyceryl monolaurate, and polyoxyethylene glyceryl monostearate. Polyoxyethylene glycerin fatty acid esters, polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene cetyl ether, polyoxyethylene polyoxypropylene alkyl ethers such as polyoxyethylene polyoxypropylene cetyl ether , Polyoxyethylene alkylphenyl ethers such as polyoxyethylene nonylphenyl ether, polyoxyethylene monopalmitate Polyoxyethylene sorbitan fatty acid esters such as Nsorubitan thereof. Furthermore, in order to control the aggregation state of the inorganic particles or to stabilize the molten state of the entire system, they can be mixed at an arbitrary ratio.

  The composition of the above-described polysulfone-based polymer and solvent, or a mixed liquid composed of the polysulfone-based polymer, the solvent, the inorganic particles, and the flocculant exhibits heat-induced phase separation, and more preferably exhibits liquid-liquid type heat-induced phase separation. It must be within the composition range. Furthermore, the manufactured porous membrane has a strength that can withstand practical use, and can be freely set within a range satisfying desired permeation performance and fractionation performance. The composition of the mixed solution varies depending on the chemical structure of each component described above, but in the case of a mixed solution composed of a polysulfone polymer and a solvent, it may be within the range of polysulfone polymer: solvent = 5-60: 95-40. More preferably, it exists in the range of 10-40: 90-60. Further, in the case of a mixed liquid composed of a polysulfone-based polymer and a solvent, and further inorganic particles and an aggregating agent, polysulfone-based polymer: solvent: inorganic particles: aggregating agent = 15-30: 25-80: 5-30: 5-40 It is desirable to be within. If the composition of the mixed solution is out of this range, the molding stability is lowered and it becomes difficult to produce a homogeneous porous membrane, and when the amount of the polysulfone polymer is larger than the above amount, the homogeneous porous membrane is Even if it can be produced, the porosity of the resulting porous membrane is low and the pore diameter is small, so that it tends to be difficult to obtain desired permeation performance.

  In the above-mentioned mixed liquid, various additives such as an antioxidant, an ultraviolet absorber, a hydrophilizing agent, a lubricant, an antiblocking agent, a dye, and a thickener are added as necessary within the range not impairing the object of the present invention. Can be added.

  The above-mentioned mixed solution is kneaded using a biaxial kneading equipment, a plast mill, a mixer, or the like. The kneading temperature is set in such a range that the polysulfone polymer and the solvent are compatible with each other and each component of the mixed solution is not decomposed. After the mixed solution is kneaded, bubbles are sufficiently removed, measured with a metering pump such as a gear pump, and then extruded through a sheet die or a nozzle having a double ring structure, and formed into a desired shape. When forming into a hollow fiber shape, it is necessary to simultaneously extrude a gas such as air, nitrogen, or a liquid having a boiling point equal to or higher than the extrusion temperature of the above mixed liquid from the center of the nozzle having a double ring structure. The liquid used for extruding from the center of the nozzle having the above-mentioned double ring structure is not particularly limited as long as the polysulfone polymer is not dissolved, and polyhydric alcohols such as tetraethylene glycol, propylene glycol, ethylene glycol, and glycerin. Or a solvent having the ability to cause heat-induced phase separation with a polysulfone polymer. Use of these is effective because it becomes easier to control the inner surface structure of the obtained hollow fiber.

  The extruded product extruded from the sheet die or nozzle undergoes heat-induced phase separation between the polysulfone-based polymer and the solvent due to a change in temperature such as cooling, and then the polysulfone-based polymer is solidified. When the mixed solution is solidified by contact with the poor solvent of the polysulfone polymer, a portion corresponding to the interface between the mixed solution and the poor solvent forms a dense skin layer, and the resulting porous film has a non-uniform structure and is high. Separation accuracy may not be obtained. The cooling method includes a method of performing in air, a method of introducing into the liquid, a method of once passing through the air and then introducing into the liquid, and any method may be used. Therefore, it is desirable to control the ambient temperature with warm air so that the cooling rate can be controlled, or to control the temperature of the liquid used for cooling. As the liquid used for cooling, water is industrially preferable, but a solvent can also be used.

  Subsequently, a solvent etc. are extracted from the molding formed from the above, and a porous film is obtained. The extraction of these components can be carried out continuously in the process together with operations such as extrusion and solidification, or can be carried out after the molded product is once wound up on a frame or cassette, or the molded product can be formed into a predetermined shape. You may carry out after storing in a case and modularizing. The extraction agent used for extraction needs to be a non-solvent of the polysulfone polymer at the extraction temperature. For example, when the solvent is benzyl alcohol, acetone or methanol can be used. The porous film is dried after being subjected to these treatments, for example, in a state of being wound around a frame or a cassette.

  In the present invention, it is also possible to perform a stretching treatment in order to improve the strength of the porous membrane. As the stretching method, methods such as hot stretching, cold stretching, and heat setting can be appropriately combined according to the intended strength. However, if the degree of stretching is too high, the resulting porous membrane will be fibrillated and the pores will be slit-like, resulting in low separation accuracy and a decrease in strength in the direction perpendicular to the stretching direction. Therefore, it is not preferable. In membrane filtration, strength in all directions is important. Therefore, it is necessary to control the stretching ratio within a range in which the membrane surface does not become slit-like holes but retains a circular or elliptical shape. The stretching may be performed in a state where a solvent is present after molding, or may be performed after extracting the solvent. By performing such stretching, not only the strength is improved but also the porosity is increased.

Thus, the polysulfone porous membrane of the present invention obtained using the polysulfone polymer and the solvent as a stock solution has a pure water permeation rate of 100 L / m ² / hr / 98 kPa or more. Furthermore, by adding inorganic particles and an aggregating agent to the stock solution, the porous membrane has fine pores having an average pore diameter of 3 μm or more, a pure water permeation rate of 30000 L / m ² / hr / 98 kPa or more, and a fractional particle diameter of 1 μm or more. Can be manufactured. When the pore size is increased, a gas such as air can permeate at a low pressure of 100 kPa or less even in a wet state, so that cleaning by physical means such as gas backwashing is possible. The cross section of the film is preferably a net-like structure, but may have a symmetric structure, an asymmetric structure, a finger-like structure, or a void. The porosity, which is the volume ratio of the space in the porous membrane, is 40 to 95%, preferably 60 to 90%. When the porosity is lower than 40%, it is difficult to obtain a sufficient pure water permeation rate. When the porosity exceeds 95%, the strength of the membrane decreases, and the porous membrane breaks or breaks during membrane filtration. And lacks durability as a separation membrane.

  A membrane module is obtained by bundling a predetermined number of porous membranes after drying and storing them in a case having a predetermined shape, and then fixing the ends with urethane resin, epoxy resin, or the like. For example, in the case of a hollow fiber membrane, as a membrane module, a type in which both ends of the hollow fiber membrane are fixed open, a type in which one end of the hollow fiber membrane is open and the other end is sealed but not fixed The thing of various forms, such as a thing, is well-known.

  Hereinafter, the present invention will be described specifically by way of examples. In addition, this invention does not receive any limitation by this.

Example 1
Polysulfone (manufactured by Solvay Advanced Polymers Co., Ltd., Udel P-3500) and 2- (benzyloxy) ethanol (manufactured by Nippon Emulsifier Co., Ltd., benzyl glycol) as a solvent so that the weight ratio is 20:80. It added in the twin-screw kneading extruder. The composition of this mixed solution is shown in Table 1. 1. Outer diameter on the extrusion surface of the spinneret for forming a hollow fiber membrane, which is heated and kneaded (temperature: 230 ° C.) in a twin-screw kneading extruder and attached to the extrusion port in the head (temperature: 210 ° C.) at the tip of the extruder. Extrusion was performed from a double ring structure nozzle having a diameter of 0 mm and an inner diameter of 1.1 mm. At this time, tetraethylene glycol was injected into the hollow portion of the extrudate.

  In order to develop heat-induced phase separation in the extruded product extruded from the nozzle into the air, the air traveled 20 cm. Next, the mixture was placed in a water bath (temperature: 10 ° C.) and passed through an about 80 cm water bath to be cooled and solidified. The obtained hollow fiber was immersed twice in acetone at 40 ° C. for 60 minutes twice to extract and remove the solvent (2- (benzyloxy) ethanol) and the injection solution (tetraethylene glycol), and then washed with water and dried. A hollow fiber membrane was obtained. The manufactured hollow fiber membrane was tested according to the following method. The test results are shown in Table 2. The heat-induced phase separation temperature of a mixture of polysulfone (Udel P-3500) and the solvent 2- (benzyloxy) ethanol in a weight ratio of 20:80 was 22 ° C., and the solvent 2- (benzyloxy) ) The weight loss rate of ethanol at 52 ° C. for 30 seconds was less than 0.1% (<0.1%).

(Average pore diameter)
The hollow fiber membrane is photographed using a scanning electron microscope (S-3000N, manufactured by Hitachi, Ltd.), the inner radius of all the holes visible in the field of view of the photograph is measured, and the number of holes to be measured is 100 The above operation was performed until the above was reached. Then, the average value of the measured inner radius was calculated | required and this was made into the average hole diameter. When the inner radius cannot be measured because the hole diameter is smaller than 0.1 μm, it is expressed as <0.1 μm.

(Fractional particle size)
The rejection rate of at least two kinds of particles having different particle diameters is measured, and the value of S at which R is 90 is obtained in the following approximate formula (2) based on the measured values. It was.
R = 100 / (1−m × exp (−a × log (s))) (2)
In the formula (2), a and m are constants determined by the hollow fiber membrane, and are calculated based on measured values of two or more types of rejection. In addition, the fractional particle size when the blocking rate of particles having a diameter of 0.01 μm is 90% or more is expressed as <0.01 μm.

(Pure water transmission rate)
Using a hollow fiber membrane module with an open end of 3 cm in effective length, using pure water as raw water, filtering from the outside to the inside of the hollow fiber membrane under conditions of a filtration pressure of 50 kPa and a temperature of 25 ° C. (external pressure filtration) Then, the water permeation amount per hour was measured and calculated by a numerical value converted into the water permeation amount per unit membrane area, unit time and unit pressure.

(Strength, elongation)
Measurement was performed using a tensile tester (manufactured by Shimadzu Corporation, Autograph AGS-100G). The measurement was carried out in water at 20 ° C., the distance between chucks was 50 mm, the tensile speed was 100 mm / min, and the strength was determined by dividing the load at break by the membrane cross-sectional area. Further, the elongation was determined using the following formula (3).
Elongation (%) = (Distance between chucks at break-Distance between chucks at the start of measurement) / Distance between chucks at the start of measurement × 100 (3)

(Thermally induced phase separation temperature)
The thermally induced phase separation temperature was determined by measuring the temperature at which the droplet structure was formed and the glass transition temperature of a mixed solution composed of a polysulfone polymer and a solvent. The droplet structure formation temperature was measured using an optical microscope (Nikon Corporation, ECLIPSE E600POL) with a temperature controller (Limka, TH-600PM). The liquid mixture previously kneaded was dissolved by holding for 2 minutes at the temperature at the time of kneading, and then cooled at 10 ° C./min, and the temperature of droplet structure formation observed in the process was measured. On the other hand, the glass transition temperature was measured using DSC (manufactured by PERKIN ELMER, Pyris 1). After the pre-kneaded mixture was heated from room temperature to the kneading temperature at 90 ° C./min, held at the kneading temperature for 2 minutes, then cooled at 10 ° C./min, from the endothermic peak observed in the process The glass transition temperature was estimated. Both measurements were performed at least twice, and both temperatures were determined from the average value. If the difference between the droplet structure formation temperature and the glass transition temperature obtained from the above measurement was in the range of ± 5 ° C., it was judged as solid-liquid type thermally induced phase separation, and the glass transition temperature was defined as the thermally induced phase separation temperature. On the other hand, if the droplet structure forming temperature is higher by 5 ° C. or more than the glass transition temperature, it is determined that the liquid-liquid type thermally induced phase separation is used, and the droplet structure forming temperature is defined as the thermally induced phase separation temperature.

(Weight loss rate of solvent)
10 mg of solvent is set in TG-DTA (Rigaku Denki Co., Thermo Plus TG8120), heated to 500 ° C / min to (thermally induced phase separation temperature +30) ° C, and then (thermally induced phase separation temperature +30) ° C. Holding for 30 seconds, the weight loss rate of TG (thermal weight) of the solvent within this time was estimated.

Example 2
A hollow fiber membrane was obtained in the same manner as in Example 1 except that trimethyl trimellitic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) was used as the solvent. Table 1 shows the composition of the mixed solution used for the production of this hollow fiber membrane, and Table 2 shows the test results. The heat-induced phase separation temperature of a mixture of polysulfone (manufactured by Solvay Advanced Polymers Co., Ltd., Udel P-3500) and trimethyl trimellitic acid in a ratio of 20:80 by weight is 89 ° C. The weight loss rate of trimethyl meritate at 119 ° C. for 30 seconds was less than 0.1% (<0.1%).

Example 3
Polysulfone (manufactured by Solvay Advanced Polymers Co., Ltd., Udel P-3500), 2- (benzyloxy) ethanol (manufactured by Nippon Emulsifier Co., Ltd., benzyl glycol) as a solvent, and silica (manufactured by Tokuyama Co., Ltd., Fine Seal X) as inorganic particles -45, average agglomerated particle diameter 4.0 to 5.0 μm), and a hollow fiber membrane in the same manner as in Example 1 except that a mixed solution was prepared so as to have a weight ratio of 20:80:10. Got. Table 1 shows the composition of the mixed solution used for the production of this hollow fiber membrane, and Table 2 shows the test results. In addition, since the solvent 2- (benzyloxy) ethanol agglomerates silica of the inorganic particles, the aggregating agent is not added.

Example 4
Polysulfone (manufactured by Solvay Advanced Polymers Co., Ltd., Udel P-3500), trimethyl trimellitic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) as a solvent, and silica 1 (manufactured by Tokuyama Co., Ltd., Fine Seal X-45, average) as inorganic particles Agglomerated particle diameter of 4.0 to 5.0 μm) and silica 2 (Fukuseal Co., Ltd., Fine Seal X-30, average agglomerated particle diameter of 2.5 to 4.0 μm) and polyoxyethylene nonylphenyl ether (as an aggregating agent) A mixture with NP-10) manufactured by Nikko Chemicals Co., Ltd., and polysulfone: trimethyltrimellitic acid: silica 1: silica 2: polyoxyethylene nonylphenyl ether in a weight ratio of 20: 80: 2.5: 7 Extruded product was obtained in the same manner as in Example 1 except that the ratio was set to 5:10. Next, after extracting the solvent and the injection solution, the hollow was carried out in the same manner as in Example 1 except that it was stretched to a length of about 1.5 times the original length in the fiber direction at 300 ° C. by a dry heat stretching machine. A yarn membrane was obtained. Table 1 shows the composition of the mixed solution used for the production of this hollow fiber membrane, and Table 2 shows the test results.

2 is an electron micrograph showing a cross section of the hollow fiber membrane obtained in Example 1. FIG. 4 is an electron micrograph showing a cross section of a hollow fiber membrane obtained in Example 4. FIG.

Claims (13)

  A polysulfone-based porous membrane formed by thermally induced phase separation of a polysulfone-based polymer and a solvent. 2. The membrane surface has fine pores having an average pore diameter of 3 μm or more, a pure water permeation rate of 30000 L / m ² / hr / 98 kPa or more, and a fractional particle diameter of 1 μm or more. Polysulfone porous membrane.   The polysulfone-based porous membrane according to claim 1 or 2, wherein the polysulfone-based porous membrane is stretched after thermally induced phase separation between the polysulfone-based polymer and the solvent.   The polysulfone-based porous membrane according to any one of claims 1 to 3, wherein the solvent has a weight loss rate of 10% or less in 30 seconds at (thermally induced phase separation temperature + 30) ° C. .   The polysulfone porous membrane according to any one of claims 1 to 4, wherein the porous membrane is a hollow fiber membrane.   Kneading a polysulfone-based polymer and a solvent that is compatible with the polysulfone-based polymer in a specific temperature range to become a one-phase state and can cause phase separation due to temperature change at a temperature at which the polysulfone-based polymer and the solvent are compatible. A method for producing a polysulfone-based porous membrane, comprising preparing a mixed liquid and then cooling to cause heat-induced phase separation and precipitation of the polysulfone-based polymer, and then extracting a solvent.   A polysulfone-based polymer, a solvent that is compatible with the polysulfone-based polymer in a specific temperature range, and that can undergo phase separation due to a temperature change, inorganic particles, and an aggregating agent having an affinity for the inorganic particles Is prepared at a temperature at which the polysulfone-based polymer and the solvent are compatible, and then cooled to cause thermally induced phase separation and precipitation of the polysulfone-based polymer, and then the solvent, inorganic particles and A method for producing a polysulfone-based porous membrane, wherein a flocculant is extracted.   A polysulfone-based polymer, inorganic particles, a solvent having compatibility with the inorganic particles, which is compatible with the polysulfone-based polymer in a specific temperature region to be in a one-phase state and can cause phase separation due to a temperature change. After preparing a mixed liquid kneaded at a temperature at which the polysulfone polymer and the solvent are compatible, cooling causes heat-induced phase separation and precipitation of the polysulfone polymer, and then the solvent and inorganic particles are extracted. A process for producing a polysulfone-based porous membrane.   The method for producing a polysulfone-based porous membrane according to any one of claims 6 to 8, wherein the heat-induced phase separation and the precipitation of the polysulfone-based polymer are performed, followed by stretching treatment.   The solvent is at least one solvent selected from the group consisting of 2- (benzyloxy) ethanol, butyl salicylate, dimethyl sulfoxide, sulfolane, trimethyl trimellitic acid, furfuryl alcohol, N-methylbenzenesulfonic acid amide, and benzyl alcohol. The method for producing a polysulfone-based porous membrane according to any one of claims 6 to 9, wherein:   The polysulfone-based porous membrane according to any one of claims 6 to 9, wherein the solvent has a weight loss rate of 10% or less in 30 seconds at (thermally induced phase separation temperature + 30) ° C. Manufacturing method.   The method for producing a polysulfone-based porous membrane according to claim 7, wherein the flocculant is a compound having a hydrophilic group.   The method for producing a polysulfone-based porous membrane according to any one of claims 6 to 12, wherein the porous membrane is a hollow fiber membrane.