JP4380380B2 - Method for producing liquid separation membrane - Google Patents

Description

The present invention relates to a method for producing drinking water production, water treatment, water treatment, such as wastewater treatment, pharmaceutical manufacturing field, a suitable liquid separation membrane in the food industry and the like.

  In recent years, separation 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 water treatment field such as drinking water production, water purification treatment, wastewater treatment, etc., separation membranes have been used to remove impurities in water as an alternative to conventional sand filtration and coagulation sedimentation processes. In the food industry field, separation membranes are used for the purpose of separating and removing yeasts used for fermentation and concentrating liquids.

  As described above, separation 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. 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, 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 separation membrane is also required to have 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 that have been mixed into the treated water have become apparent since the 1990s. Therefore, in order to prevent such an accident, the separation membrane is required to have sufficient separation characteristics and high physical strength so that the raw water is not mixed into the treated water.

  Thus, the separation membrane is required to have excellent separation characteristics, chemical strength (chemical resistance), physical strength, stain resistance, and permeation performance. Therefore, a separation membrane using a polyvinylidene fluoride resin having both chemical strength (chemical resistance) and physical strength has been used.

  However, the polyvinylidene fluoride resin film has a drawback that the film surface is easily contaminated by hydrophobic interaction. In particular, when used for separation / purification of physiologically active substances such as proteins in the pharmaceutical manufacturing process, adsorption / denaturation on the membrane surface leads to a decrease in the recovery rate, and a rapid decrease in the filtration rate due to the blocking of the membrane pores. Caused a serious problem.

  Therefore, it is conceivable to hydrophilize the hydrophobic resin film. For example, in the technique described in Patent Document 1, a sulfonic acid group is introduced, and in the technique described in Patent Document 2, polyethyleneimine polymers are introduced into the main chain, respectively. The hydrophobic resin film is hydrophilized by grafting. In the technique described in Patent Document 3, hydrophilicity is imparted by blending polyvinyl pyrrolidone), which is a hydrophilic polymer, with a hydrophobic resin film. However, the hydrophilic groups and hydrophilic polymers described in these documents have a strong polarity, and are rather counterproductive to charged substances, especially solutions containing amphoteric electrolytes such as proteins and humic acids present in surface water. there were. It is also conceivable to use a polyvinyl alcohol polymer having excellent hydrophilicity and a polarity similar to that of water molecules. However, it has been generally difficult to uniformly blend such a highly hydrophilic polymer with a polymer having high molecular cohesion such as a polyvinylidene fluoride resin.

  A method focusing on polyvinyl acetate mixed with a polyvinylidene fluoride resin is also disclosed. That is, in Patent Document 4, a film is first prepared by blending polyvinyl acetate and a polyvinylidene fluoride resin, and the polyvinyl acetate group in the film is saponified under alkaline conditions to obtain polyvinyl alcohol. The thus obtained blend film of polyvinyl alcohol and polyvinylidene fluoride resin exhibits excellent hydrophilicity and excellent stain resistance against proteins and the like. However, when the film thus obtained is washed with acid, alkali, chlorine, or the like as described above, the polyvinyl alcohol is attacked by chemicals, and there is a possibility that the performance is deteriorated. Moreover, since polyvinyl alcohol is strongly hydrophilic and water-soluble, it gradually dissolves when used in an aqueous system. Therefore, the use of the above-mentioned blend film of polyvinyl alcohol and polyvinylidene fluoride resin exhibiting excellent stain resistance is not preferred in applications that dislike contamination of permeated water, particularly in drinking water and purified water applications. Furthermore, since the solubility of polyvinyl alcohol increases as the water temperature rises, it is not suitable for the treatment of high-temperature water such as for boiler cooling water recovery. In addition to these, when the saponification treatment is performed under alkaline conditions, the polyvinylidene fluoride resin is also treated with alkali, which may lead to coloring and a decrease in strength.

As a method of hydrophilizing the hydrophobic resin film, there is a method of coating the film surface with a polymer having excellent hydrophilicity. Patent Document 5 discloses a method of coating a polyvinylidene fluoride resin film surface with polyethylene vinyl alcohol which is excellent in stain resistance and heat resistance and is insoluble in water. However, this method has a problem that the hydrophilicity is lost when the coating part is peeled off. In addition, if the coating thickness is not controlled skillfully, there is also a problem that the amount of water permeability is remarkably reduced.
JP 59-196322 A JP-A-57-174104 Japanese Patent Laid-Open No. 62-125802 Japanese Patent No. 3200095 Japanese Patent Application Laid-Open No. 2002-233739

The present invention provides a method for producing a liquid separation membrane having excellent dirt resistance as well as separation characteristics, water permeability, chemical strength (chemical resistance) and physical strength in view of the above-mentioned problems of the prior art. For the purpose.

The present invention for solving the above problems is achieved by the following configurations (1) to (5) .
(1 ) After forming a film from a polymer solution obtained by mixing and dissolving a polyvinylidene fluoride resin and a polyethylene vinyl acetate resin containing vinyl acetate in the range of 60 to 95 mol%, the polyethylene vinyl acetate resin in the film A method for producing a liquid separation membrane, which comprises hydrolyzing water.
(2) The method for producing a liquid separation membrane according to (1), wherein the polymer solution used for membrane formation further contains a surfactant.
(3) The method for producing a liquid separation membrane according to (1) or (2), wherein the polyethylene vinyl acetate resin is hydrolyzed under acidic conditions.
(4) Hydrolysis of 10 to 100 mol% of acetyl groups contained in the polyethylene vinyl acetate resin in the formed film is as described in any one of (1) to (3) above A method for producing a liquid separation membrane.
(5) concentration before Symbol polyvinylidene fluoride resin in the polymer solution is 10 to 50 wt%, and the concentration of polyethylene vinyl acetate-based resin, characterized in that 0.5 to 15 wt% The manufacturing method of the liquid separation membrane in any one of said (1)- (4) .

According to the present invention, by separating polyethylene vinyl alcohol in a polyvinylidene fluoride resin, a liquid separation membrane having excellent separation resistance, water permeability, chemical strength (chemical resistance), physical strength, and soil resistance. It can be. As a result, the cleaning interval of the membrane becomes longer and the filtration life becomes longer, so that the water production cost can be reduced.

The method of the present invention comprises forming a film from a polymer solution in which a polyvinylidene fluoride resin and a polyethylene vinyl acetate resin containing vinyl acetate in the range of 60 to 95 mol% are mixed and dissolved, and then polyethylene polyethylene acetate in the film A liquid separation membrane having a structure in which polyethylene vinyl alcohol is dispersed in a thermoplastic resin is formed by hydrolyzing the resin to form polyvinyl alcohol.

  It is usually difficult to blend a polyethylene vinyl acetate resin and a thermoplastic resin having a large molecular cohesion represented by a polyvinylidene fluoride resin, but in the present invention, a high vinyl acetate content type polyethylene vinyl acetate resin is used. A uniform polymer solution can be obtained by adding a surfactant and improving the dispersibility of the molecules, and the above-described film can be formed.

  The polyvinylidene fluoride resin in the present invention is a resin containing a polyvinylidene fluoride homopolymer and / or a polyvinylidene fluoride copolymer. A plurality of types of polyvinylidene fluoride copolymers may be contained. Examples of the polyvinylidene fluoride copolymer include a copolymer of vinylidene fluoride and one or more selected from tetrafluoroethylene, propylene hexafluoride, and ethylene trifluoride chloride. Further, the weight average molecular weight of the polyvinylidene fluoride resin may be appropriately selected depending on the required strength and water permeability of the separation membrane, but the strength is low when the weight average molecular weight is low, and the water permeability is high when the weight average molecular weight is high. Since it tends to be low, in order to obtain a separation membrane having both high strength and high water permeability, 50,000 to 1,000,000 is preferable. And when the workability to a separation membrane is considered, 100,000 or more and 700,000 or less are preferable, and 150,000 or more and 600,000 or less are more preferable.

  Further, the polyvinylidene fluoride resin may contain up to 50% by weight of a miscible resin. For example, it is in a state containing a maximum of 50% by weight of an acrylic resin or a cellulose ester resin. The acrylic resin refers to a polymer compound mainly including a polymer such as acrylic acid, methacrylic acid and derivatives thereof such as acrylamide and acrylonitrile. In particular, an acrylic ester resin or a methacrylic ester resin is a polyvinylidene fluoride type. It is preferably used because of its high miscibility with the resin. The cellulose ester resin refers to a polymer compound containing an esterified cellulose such as cellulose acetate, cellulose propionate, and cellulose butyrate. The degree of esterification of the cellulose ester resin is a solvent together with the polyvinylidene fluoride resin. If it is a grade melt | dissolved in this, it will not specifically limit.

The polyethylene vinyl acetate resin in the present invention is a resin containing a polyethylene vinyl acetate copolymer. A plurality of types of polyethylene vinyl acetate copolymers may be contained. The polyethylene vinyl acetate copolymer is a copolymer of ethylene and vinyl acetate, but chlorinated ethylene, vinyl chloride, vinylidene fluoride, etc. may be copolymerized. When the vinyl acetate content of the polyethylene vinyl acetate resin is lowered, the solubility in an organic solvent is lowered and handling becomes difficult. On the other hand, when the ethylene content of the polyethylene vinyl acetate resin is lowered, the chemical durability and the heat resistance are lowered and the resin is easily swollen in water. Therefore, in order to prepare a uniform polymer solution while maintaining excellent heat resistance and water insolubility, a resin containing vinyl acetate in the range of 60 to 95 mol% is used as the polyethylene vinyl acetate resin. Furthermore, it is preferable that the polyethylene vinyl acetate resin contains vinyl acetate within a range of 65 to 90 mol%. In addition, although the vinyl acetate part of the polyethylene vinyl acetate resin has an acetyl group, a part of the acetyl group may be hydrolyzed into a hydroxyl group within a range where the polymer solution described above can be prepared.

As the solvent used in the film-forming solution in the present invention, the polyvinylidene fluoride resin及 beauty polyvinyl acetate-based resin at a temperature below the melting point of the above-mentioned polyvinylidene fluoride resin及 beauty polyvinyl acetate-based resin 5 to 60 It is not particularly limited as long as it can be dissolved within the range of wt%, preferably 10 to 50 wt%. Such solvents include cyclohexanone, isophorone, γ-butyrolactone, methyl isoamyl ketone, dimethyl phthalate, propylene glycol methyl ether, propylene carbonate, diacetone alcohol, glycerol triacetate, and other medium chain length alkyl ketones, esters, glycol esters. Organic carbonates, N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, methyl ethyl ketone, acetone, tetrahydrofuran, tetramethylurea, lower alkyl ketones such as trimethyl phosphate, esters, amides, and the like are preferably used. These solvents may be used alone or as a mixture of two or more.

Concentration composition put that polyvinylidene fluoride resin to these film-forming stock solution, considering the film forming property and film strength may in the range of 10 to 50 wt%. When producing a highly water-permeable film, the concentration of the polyvinylidene fluoride resin should be low, and preferably in the range of 10 to 25% by weight. The concentration composition of the vinyl acetate resin may be in a range where sufficient hydrophilicity can be obtained after the hydrolysis treatment, and the hydrophilicity can be arbitrarily set depending on the copolymer composition ratio and the degree of the hydrolysis treatment. In the range of 0.5 to 15% by weight.

  In addition to the above-described thermoplastic resin, vinyl acetate resin, and solvent, the film-forming stock solution of the present invention may contain a substance such as a pore-opening agent or a non-solvent as necessary.

  The pore-opening agent is not particularly limited as long as it promotes the porosity of the membrane produced using the membrane-forming stock solution. For example, polyethylene glycol, polypropylene glycol, polyvinyl alcohol, polyvinyl acetate, polyvinyl pyrrolidone, glycerin, etc. Polyhydric alcohols, inorganic salts such as lithium chloride, magnesium chloride, calcium chloride, ester bodies of polyhydric alcohols such as sorbitan fatty acid esters, ethylene oxide low mol adducts of sorbitan fatty acid esters, ethylene oxide low mol adducts of nonylphenol In addition, surfactants such as ethylene oxide low-mole adducts such as pluronic ethylene oxide low-mole adducts, polyoxyethylene alkyl esters, alkylamine salts, and polyacrylic acid soda are preferably used. Of these, surfactants are particularly preferably used because they not only act as pore-opening agents but also promote the dissolution of solutes such as polymers in solvents and disperse the solutes.

Also, the non-solvent, a solvent not dissolving the above-mentioned polyvinylidene fluoride resin及 beauty polyvinyl acetate-based resin, and is not particularly limited as long as it is a solvent which is miscible with the solvent for dissolving the polyvinylidene fluoride resin . Control of phase separation by adding a non-solvent is generally performed. However, if a large amount of non-solvent is added, gelation occurs or molding becomes difficult. Therefore, the composition of the polyvinylidene fluoride resin and the solvent to be used is reduced. It is necessary to adjust the addition amount accordingly. As the non-solvent, water is particularly preferred because it is inexpensive.

In the present invention, the hydrolysis treatment is a treatment for hydrolyzing the acetyl group of the polyethylene vinyl acetate resin under alkaline conditions or acidic conditions. Hydrolysis of the acetyl group to form a hydroxyl group increases the hydrophilicity of the membrane, reduces contamination due to hydrophobic interactions, and improves the stain resistance of the membrane. The degree of the hydrolysis treatment can be appropriately selected depending on the composition ratio of the polyethylene vinyl acetate resin and the polyvinylidene fluoride resin film and the vinyl acetate content in the polyethylene vinyl acetate resin. to improve the not preferable to hydrolyze to 100 mol% 10 mol% or more acetyl groups.

  When hydrolyzing (saponifying) under alkaline conditions, if the treatment is carried out under medium to strong alkaline conditions of pH 11 or higher, the polyvinylidene fluoride resin is also treated with alkali at the same time, and coloring and strength decrease occur. When the treatment is carried out under weak to medium alkaline conditions of pH 8 to 11, this problem is suppressed as the pH is lowered, but the hydrolysis rate of the polyethylene vinyl acetate resin is slowed down. Therefore, in order to achieve a practical hydrolysis rate while suppressing coloring and strength reduction of the polyvinylidene fluoride resin under alkaline conditions, it is preferable to perform the treatment at about pH 10-11.

  On the other hand, when hydrolyzing under acidic conditions, the polyvinylidene fluoride resin is stable even if treated under medium to strong acidic conditions. Accordingly, the hydrolysis treatment of the polyethylene vinyl acetate resin is preferably carried out under a medium to strongly acidic condition at pH 1 to 5, but is particularly preferably carried out at pH 1 to 4 in consideration of the treatment efficiency.

  In the present invention, chemical resistance of polyethylene vinyl alcohol can be further improved by performing a crosslinking treatment together with a hydrolysis treatment. At this time, the hydrolysis treatment and the crosslinking treatment may be performed after the hydrolysis treatment is performed first, or both treatments may be performed simultaneously. Here, in consideration of cost and ease of handling, it is preferable to simultaneously perform the hydrolysis treatment and the crosslinking treatment.

  The cross-linking treatment in the present invention may be any treatment that cross-links between polyethylene vinyl alcohol polymer chains using a hydroxyl group possessed by polyethylene vinyl alcohol, and the method will be described below with examples.

  That is, under acidic conditions, polyethylene vinyl alcohol is preferably reacted with a polyfunctional aldehyde to form an acetal bond. Since this method is simple and the reaction proceeds rapidly, it can be used particularly preferably in the present invention. As the aldehyde, glyoxal and glutaraldehyde are particularly preferably used because they can undergo a crosslinking reaction in a relatively wide pH range (pH 1 to 5). Moreover, the crosslinking treatment with the polyfunctional aldehyde may be performed subsequent to the hydrolysis treatment described above or may be performed simultaneously with the hydrolysis treatment.

  On the other hand, under alkaline conditions of pH 10-11, for example, polyethylene vinyl alcohol may be reacted with epichlorohydrin to produce glycidyl ether. After hydrolysis at pH 10-11, crosslinking treatment with epichlorohydrin is performed. The hydrolysis treatment and the crosslinking treatment may be carried out simultaneously at pH 10-11.

The liquid separation membrane of the present invention produced as described above may be a hollow fiber membrane or a flat membrane, and is selected according to its use. The film-forming stock solution of the present invention contains a polyvinylidene fluoride-based resin, a polyvinyl acetate-based resin, a solvent, a pore-opening agent, etc., and the viscosity of the film-forming stock solution varies greatly depending on the concentration and combination thereof. If the viscosity of the film-forming stock solution is too low, a film is not formed and a defect is caused or the strength of the film is lowered. If the viscosity is too high, thickness unevenness occurs or the water permeability of the film is lowered, which is not economical. Therefore, in the case of a hollow fiber membrane, the viscosity of the membrane forming stock solution is in the range of 1 Pa · s to 300 Pa · s, and in the case of a flat membrane, the viscosity of the membrane forming stock solution is in the range of 0.1 Pa · s to 10 Pa · s. It is preferable to do. More preferably, in the case of a hollow fiber membrane, it is in the range of 10 Pa · s to 200 Pa · s, and in the case of a flat membrane, it is in the range of 0.3 Pa · s to 1 Pa · s. By using a film-forming stock solution having such a viscosity, a film having high water permeability and strength can be easily obtained with a film having dimensions as described later. Further, when a polymer is coated on a support material to be described later, the support material supplements the strength, and thus the membrane is designed with emphasis on water permeability rather than strength. In this case, the viscosity of the membrane forming stock solution is preferably within the range of 0.01 Pa · s to 5 Pa · s in order to develop high water permeability in both the case of a flat membrane and the case of a hollow fiber membrane. Preferably, it is in the range of 0.05 Pa · s to 3 Pa · s.

  When the hollow fiber membrane is used for filtering clear raw water such as groundwater, the inner diameter of the hollow fiber membrane is preferably in the range of 500 μm to 2000 μm because the pressure loss is high and inefficient at a small inner diameter. More preferably, it exists in the range of 600 micrometers-1500 micrometers. The film thickness is designed based on the inner diameter so as not to cause thread crushing or thread breakage during the filtration operation, but water permeability decreases as the film thickness increases. In the external pressure filtration, it is necessary to increase the film thickness as compared with the internal pressure filtration, and it is preferably in the range of 150 μm to 750 μm, more preferably in the range of 250 μm to 600 μm. In the internal pressure type filtration, the film thickness may be thinner than in the external pressure type filtration, and the film thickness in the range of 100 μm to 500 μm is preferably used. The outer diameter is automatically determined when the inner diameter and the film thickness are determined, and the outer diameter is preferably in the range of 800 μm to 3500 μm, more preferably in the range of 1000 μm to 2500 μm. The pore diameter of the inner and outer surfaces of the hollow fiber membrane can be freely selected depending on the substance to be separated, but if it is too small, the water permeability is lowered. For example, when removing Cryptosporidium having a diameter of about 4 μm, the pore diameter is preferably in the range of 0.01 μm to 2.0 μm, and considering water permeability and safety, it is 0.05 μm to 1.0 μm. Within the range is even better. On the other hand, in the case of filtering raw water with high turbidity such as surface water, turbidity deposits on the membrane surface are significant, and there are large regional and seasonal differences in turbid mass. In general, the inner diameter, the film thickness, and the outer diameter are designed according to the filtration of clear raw water, but particular attention is paid to the pore diameter. This is because if the pore size is larger than the turbidity, the turbidity enters the film, contaminates the film, and deteriorates the film performance. For high water permeability and high contamination resistance against turbid components, the pore diameter is preferably in the range of 0.01 μm to 0.5 μm, more preferably in the range of 0.05 to 0.3 μm.

  Further, the internal structure of the hollow fiber membrane is arbitrary, and a so-called macrovoid may exist or a homogeneous structure having pores of the same size in the film thickness direction may be used. In addition, hollow fiber fibers such as polyester, nylon, polysulfone, polyacrylonitrile, polyvinylidene fluoride, glass fibers, metal fibers, and the like are knitted into a cylindrical shape, and the liquid separation membrane according to the present invention is coated thereon. Alternatively, the liquid separation membrane according to the present invention may be combined with a part of the support material.

  On the other hand, in the case of a flat membrane, the film thickness is designed so as not to be broken during the filtration operation. However, when the film thickness increases, the water permeability decreases. For this reason, it is preferable that it exists in the range of 10 micrometers-1 mm of film thickness, and also in the range of 30 micrometers-500 micrometers. In the case of a flat membrane, the liquid separation membrane according to the present invention is coated on a sheet-like support material such as woven fabric, knitted fabric, or non-woven fabric, or a part of the support material is combined with the liquid separation membrane according to the present invention. Also good. In these cases, it is preferable that the thickness including the planar support material be within the above-described range. Further, the surface pore diameter can be freely selected depending on the separation target, but if it is too small, the water permeability is lowered. For example, when used for the filtration of clear raw water, and when Cryptosporidium having a diameter of about 4 μm is a substance to be removed, the pore diameter is preferably within a range of 0.01 μm to 2.0 μm, and water permeability and safety In consideration of the property, the range of 0.05 μm to 1.0 μm is more preferable. Moreover, if raw water with much turbidity such as surface water is filtered, the pore diameter is preferably in the range of 0.01 μm to 1.0 μm, more preferably in the range of 0.05 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.

The method for producing a liquid separation membrane of the present invention will be described in more detail. First , a polyvinylidene fluoride resin, a polyvinyl acetate resin, a solvent, a pore-opening agent, etc. are dissolved or heated and dissolved at room temperature, To do. Next, after the film forming solution is extruded from the die at a temperature considerably lower than the melting point of the resin, coated on a hollow fiber or cylindrical or planar support, or cast on a glass plate, A separation membrane is produced by contact with a liquid containing a non-solvent of the resin by non-solvent-induced phase separation. In addition, when a solvent that does not dissolve polyvinylidene fluoride resin at room temperature is used as a solvent for dissolving the resin , polyvinylidene fluoride resin, polyvinyl acetate resin, solvent, pore-opening agent, etc. are dissolved at high temperature. A membrane-forming solution is manufactured, and after the membrane-forming solution is discharged from the die, a separation membrane is manufactured by a heat-induced phase separation method in which the membrane is cooled and phase-separated and solidified. Thereafter, the polyethylene vinyl acetate resin is hydrolyzed to obtain polyethylene vinyl alcohol by immersing the liquid separation membrane in a water-alcohol mixed solution made acidic or alkaline by adding acid or alkali.

  The liquid separation membrane of the present invention that has been hydrophilized through the hydrolysis treatment is housed in a casing having a raw solution inlet, a permeate outlet, and the like and used as a membrane module. When the membrane module is a hollow fiber membrane, bundle a plurality of hollow fiber membranes and store them in a cylindrical container, and fix both ends or one end with polyurethane or epoxy resin so that the permeate can be collected. Alternatively, both ends of the hollow fiber membrane are fixed in a flat plate shape so that the permeate can be collected. When the liquid separation membrane is a flat membrane, the flat membrane is wound in an envelope shape around the liquid collection tube, wound in a spiral shape, and stored in a cylindrical container to allow permeate to flow, or a liquid collection plate Flat membranes are arranged on both sides of the plate to fix the periphery in a watertight manner so that the permeate can be collected.

  The membrane module is used as a liquid separation device for forming water by providing at least a pressurizing means on the stock solution side or a suction means on the permeate side. A pump may be used as the pressurizing means, or a pressure due to a water level difference may be used. Moreover, what is necessary is just to utilize a pump and a siphon as a suction means.

  The water permeability of the membranes in the examples and comparative examples were measured as follows.

When the membrane is a hollow fiber membrane, a miniature module having a length of 200 mm consisting of four hollow fiber membranes is prepared, and the water permeation rate of pure water is measured under the conditions of a temperature of 25 ° C. and a filtration differential pressure of 16 kPa. 50 kPa) (Q0, unit = m ³ / m ² · h). Next, a 20 ppm aqueous solution of humic acid (reagent, manufactured by Wako Pure Chemical Industries, Ltd.) is filtered to 2 m ³ / m ² by total external pressure filtration under conditions of a filtration differential pressure of 16 kPa and a temperature of 25 ° C. Further, permeated water is supplied for 1 minute at a backwash pressure of 150 kPa, and the pure water permeation amount immediately after that is measured (Q1). Thereafter, the hollow fiber membrane was immersed in 5000 ppm of sodium hypochlorite aqueous solution at 80 ° C. for 24 hours, and then 20 ppm of humic acid aqueous solution was filtered at a pressure differential of 16 kPa and a temperature of 25 ° C. by external pressure total filtration at 2 m ³ / m. Filter to ² Finally, permeate is supplied for 1 minute at a backwash pressure of 150 kPa, and the pure water permeation amount immediately after that is measured (Q2). Sodium hypochlorite is a chemical that is generally used for cleaning hollow fiber membranes, and is used as an index for checking the chemical resistance of the membrane. In order to see the performance after long-term use, an accelerated test is conducted at high temperatures.

  A = Q1 / Q0 is used as an index of stain resistance. A film having a larger value of A is a film having superior stain resistance. On the other hand, B = Q2 / Q1 is used as an index of chemical resistance and high temperature water resistance. A film having a larger value of B is a film having excellent chemical resistance and high temperature water resistance.

  When the membrane is a flat membrane, it is cut into a circle with a diameter of 50 mm, set in a cylindrical filtration holder, and the other operations are the same as those for the hollow fiber membrane.

The number of surface pores of the separation membrane is obtained by taking a photograph using a scanning electron microscope and counting the number of observed pores. The photo of the scanning electron microscope is taken at a magnification of 50,000 times. The surface pore diameter of the separation membrane is determined by measuring the diameters of 20 arbitrary pores from the same scanning electron microscope photograph and calculating the average. When the pore is elliptical, the minor axis a and the major axis b are measured, and (a × b) ^0.5 is taken as the equivalent circular diameter. In this case, the surface pore diameter is the average of the equivalent circular diameters of 20 arbitrary pores.
<Example 1>
25% by weight of vinylidene fluoride homopolymer having a weight average molecular weight of 284,000, 3% by weight of polyethylene vinyl acetate copolymer (ethylene 30%, vinyl acetate 70%), 64% by weight of dimethylformamide, polyoxyethylene palm An oil fatty acid sorbitan (Sanyo Kasei Co., Ltd., trade name: IONET T-20C) was mixed and dissolved at a temperature of 95 ° C. at a rate of 5 wt% and water at 3 wt% to prepare a film forming stock solution. The membrane-forming stock solution was discharged from the die while accompanying a 50% by weight aqueous solution of dimethylformamide as a hollow portion forming liquid, and solidified in a coagulation bath comprising a 50% by weight aqueous solution of dimethylformamide at a temperature of 20 ° C. to produce a hollow fiber membrane. . 100 g of this hollow fiber membrane was immersed in 2000 ml of 0.5 mol / L sulfuric acid water-ethanol solution (water: ethanol = 1: 1) at 40 ° C. for 5 hours, subjected to hydrolysis treatment, and a polyethylene vinyl acetate copolymer Was converted to polyethylene vinyl alcohol.

The obtained hollow fiber membrane had an outer diameter of 1.4 mm, an inner diameter of 0.8 mm, and an average pore diameter of 0.02 μm. The pure water permeation amount at 50 kPa and 25 ° C. was 2.45 m ³ / m ² · h (Q0).

The aqueous humic acid solution was filtered to ² m ³ / m ² under the conditions of a temperature of 25 ° C. and a filtration differential pressure of 16 kPa, and backwashed. It was 2.30 m < ³ > / m < ² > * h when the pure water permeation amount was measured (Q1).

After immersing in 5000 ppm sodium hypochlorite aqueous solution 5000 ppm for 24 hours at 80 ° C., the humic acid aqueous solution was filtered to 2 m ³ / m ² at a temperature of 25 ° C. and a filtration differential pressure of 16 kPa, and backwashed. . It was 2.30 m < ³ > / m < ² > * h when the pure water permeation amount was measured (Q2).

The evaluation results are summarized in Table 1.
<Example 2>
Except that the hydrolysis treatment was changed to a 1 mol / L sodium hydroxide water-ethanol solution (water: ethanol = 1: 1) instead of the 0.5 mol / L sulfuric acid-ethanol solution, the same procedure as in Example 1 was performed. A hollow fiber membrane was prepared.

The obtained hollow fiber membrane had an outer diameter of 1.4 mm, an inner diameter of 0.8 mm, and an average pore diameter of 0.02 μm. The pure water permeability at 50 kPa and 25 ° C. was 2.55 m ³ / m ² · h (Q0).

The aqueous humic acid solution was filtered to ² m ³ / m ² under the conditions of a temperature of 25 ° C. and a filtration differential pressure of 16 kPa, and backwashed. The pure water permeability was measured to be 2.40 m ³ / m ² · h (Q1).

After immersing in 5000 ppm sodium hypochlorite aqueous solution 5000 ppm for 24 hours at 80 ° C., the humic acid aqueous solution was filtered to 2 m ³ / m ² at a temperature of 25 ° C. and a filtration differential pressure of 16 kPa, and backwashed. . It was 2.35 m < ³ > / m < ² > * h when the pure water permeation amount was measured (Q2).

The evaluation results are summarized in Table 1.
<Comparative Example 1>
A hollow fiber membrane was prepared in the same manner as in Example 1 except that the polyethylene vinyl acetate copolymer was not added to the membrane forming stock solution, and the weight percent thereof was changed to dimethylformamide. Further, the same hydrolysis treatment as in Example 1 was performed.

The obtained hollow fiber membrane had an outer diameter of 1.4 mm, an inner diameter of 0.8 mm, and an average pore diameter of 0.02 μm. The pure water permeation amount at 50 kPa and 25 ° C. was 2.50 m ³ / m ² · h (Q0).

The aqueous humic acid solution was filtered to ² m ³ / m ² under the conditions of a temperature of 25 ° C. and a filtration differential pressure of 16 kPa, and backwashed. The pure water permeation amount was 1.95 m ³ / m ² · h (Q1).

After immersing in 5000 ppm sodium hypochlorite aqueous solution 5000 ppm for 24 hours at 80 ° C., the humic acid aqueous solution was filtered to 2 m ³ / m ² at a temperature of 25 ° C. and a filtration differential pressure of 16 kPa, and backwashed. . The pure water permeation amount was 1.95 m ³ / m ² · h (Q2).

The evaluation results are summarized in Table 1.
<Comparative example 2>
A hollow fiber membrane was produced in the same manner as in Example 1. However, this membrane was not hydrolyzed.

The obtained hollow fiber membrane had an outer diameter of 1.4 mm, an inner diameter of 0.8 mm, and an average pore diameter of 0.02 μm. The pure water permeation amount at 50 kPa and 25 ° C. was 1.98 m ³ / m ² · h (Q0).

The aqueous humic acid solution was filtered to ² m ³ / m ² under the conditions of a temperature of 25 ° C. and a filtration differential pressure of 16 kPa, and backwashed. It was 1.60 m < ³ > / m < ² > * h when the pure water permeation amount was measured (Q1).

After immersing in 5000 ppm sodium hypochlorite aqueous solution 5000 ppm for 24 hours at 80 ° C., the humic acid aqueous solution was filtered to 2 m ³ / m ² at a temperature of 25 ° C. and a filtration differential pressure of 16 kPa, and backwashed. . It was 1.58 m < ³ > / m < ² > * h when the pure water permeation amount was measured (Q2).

The evaluation results are summarized in Table 1.
<Comparative Example 3>
A hollow fiber membrane was prepared in the same manner as in Example 2 except that polyvinyl acetate was used instead of the polyethylene vinyl acetate copolymer. It was immersed in a 1 mol / L sodium hydroxide water-ethanol solution (water: ethanol = 1: 1) for hydrolysis treatment to convert polyvinyl acetate into polyvinyl alcohol.

The obtained hollow fiber membrane was brown and had an outer diameter of 1.4 mm, an inner diameter of 0.8 mm, and an average pore diameter of 0.02 μm. The pure water permeation amount at 50 kPa and 25 ° C. was 2.65 m ³ / m ² · h (Q0).

The aqueous humic acid solution was filtered to ² m ³ / m ² under the conditions of a temperature of 25 ° C. and a filtration differential pressure of 16 kPa, and backwashed. It was 2.55 m < ³ > / m < ² > * h when the pure water permeation amount was measured (Q1).

After immersing in 5000 ppm sodium hypochlorite aqueous solution 5000 ppm for 24 hours at 80 ° C., the humic acid aqueous solution was filtered to 2 m ³ / m ² at a temperature of 25 ° C. and a filtration differential pressure of 16 kPa, and backwashed. . It was 2.35 m < ³ > / m < ² > * h when the pure water permeation amount was measured (Q2).

  The evaluation results are summarized in Table 1.

When polyvinyl acetate was used, chemical resistance and high temperature water resistance were worse than when polyethylene vinyl acetate copolymer was used.
<Example 3>
12% by weight of vinylidene fluoride homopolymer having a weight average molecular weight of 284,000, 1% by weight of polyethylene vinyl acetate copolymer (ethylene 30%, vinyl acetate 70%), 79% by weight of dimethylacetamide, and T-20C A film forming stock solution was prepared by mixing and dissolving 5% by weight and 3% by weight of water at a temperature of 95 ° C.

  Next, after the film-forming stock solution is cooled to 25 ° C., it is applied to a polyester cylindrical support having an outer diameter of 1730 μm and an inner diameter of 900 μm. Immediately after application, the film-forming stock solution is immersed in pure water at 25 ° C. for 5 minutes, and further 80 ° C. A hollow fiber membrane in which a porous membrane was formed on the surface of a polyester cylindrical support was prepared by immersing it in hot water three times and washing it. 100 g of this hollow fiber membrane was immersed in 2000 ml of 0.5 mol / L sulfuric acid water-ethanol solution (water: ethanol = 1: 1) at 40 ° C. for 5 hours to perform a hydrolysis treatment.

The obtained hollow fiber membrane had an outer diameter of 1.8 mm, an inner diameter of 0.9 mm, and an average pore diameter of 0.05 μm. The pure water permeation amount at 50 kPa and 25 ° C. was 1.12 m ³ / m ² · h (Q0).

The aqueous humic acid solution was filtered to ² m ³ / m ² under the conditions of a temperature of 25 ° C. and a filtration differential pressure of 16 kPa, and backwashed. It was 1.05 m < ³ > / m < ² > * h when the pure water permeation amount was measured (Q1).

After immersing in 5000 ppm sodium hypochlorite aqueous solution 5000 ppm for 24 hours at 80 ° C., the humic acid aqueous solution was filtered to 2 m ³ / m ² at a temperature of 25 ° C. and a filtration differential pressure of 16 kPa, and backwashed. . It was 1.05 m < ³ > / m < ² > * h when the pure water permeation amount was measured (Q2).

The evaluation results are summarized in Table 1.
<Example 4>
After producing a hollow fiber membrane in the same manner as in Example 3, 100 g of this hollow fiber membrane was immersed in 2000 ml of 0.5 mol / L sulfuric acid-ethanol solution (water: ethanol = 1: 1) at 40 ° C. for 5 hours. Then, the hydrolysis treatment was performed. At this time, in order to perform not only hydrolysis treatment but also crosslinking treatment, glutaraldehyde was added to a sulfuric acid water-ethanol solution so as to be 1% by weight.

The obtained hollow fiber membrane had an outer diameter of 1.8 mm, an inner diameter of 0.9 mm, and an average pore diameter of 0.05 μm. The pure water permeability at 50 kPa and 25 ° C. was 1.05 m ³ / m ² · h (Q0).

The aqueous humic acid solution was filtered to ² m ³ / m ² under the conditions of a temperature of 25 ° C. and a filtration differential pressure of 16 kPa, and backwashed. The pure water permeability was measured to be 0.98 m ³ / m ² · h (Q1).

After immersing in 5000 ppm sodium hypochlorite aqueous solution 5000 ppm for 24 hours at 80 ° C., the humic acid aqueous solution was filtered to 2 m ³ / m ² at a temperature of 25 ° C. and a filtration differential pressure of 16 kPa, and backwashed. . It was 0.97 m < ³ > / m < ² > * h when the pure water permeation amount was measured (Q2).

The evaluation results are summarized in Table 1.
<Comparative example 4>
A hollow fiber membrane was prepared in the same manner as in Example 3 except that the polyethylene vinyl acetate copolymer was not added to the membrane forming stock solution, and dimethylacetamide was used in the weight percent. Further, the hydrolysis treatment was performed in the same manner as in Example 3.

The obtained hollow fiber membrane had an outer diameter of 1.4 mm, an inner diameter of 0.8 mm, and an average pore diameter of 0.02 μm. The pure water permeability at 50 kPa and 25 ° C. was 1.25 m ³ / m ² · h (Q0).

The aqueous humic acid solution was filtered to ² m ³ / m ² under the conditions of a temperature of 25 ° C. and a filtration differential pressure of 16 kPa, and backwashed. It was 1.06 m < ³ > / m < ² > * h when the pure water permeation amount was measured (Q1).

After immersing in 5000 ppm sodium hypochlorite aqueous solution 5000 ppm for 24 hours at 80 ° C., the humic acid aqueous solution was filtered to 2 m ³ / m ² at a temperature of 25 ° C. and a filtration differential pressure of 16 kPa, and backwashed. . It was 1.05 m < ³ > / m < ² > * h when the pure water permeation amount was measured (Q2).

The evaluation results are summarized in Table 1.
<Comparative Example 5>
25% by weight of vinylidene fluoride homopolymer having a weight average molecular weight of 284,000, 3% by weight of polyethylene vinyl acetate copolymer (ethylene 50%, vinyl acetate 50%), 64% by weight of dimethylformamide, polyoxyethylene palm Oil fatty acid sorbitan (Sanyo Kasei Co., Ltd., trade name Ionette T-20C) was mixed and dissolved at a temperature of 95 ° C. at a ratio of 5 wt% and water 3 wt%, but a polyethylene vinyl acetate copolymer (ethylene 50%, Vinyl acetate 50%) was not completely dissolved, and a uniform film-forming stock solution could not be obtained, so that film formation was not possible.
<Example 5>
A vinylidene fluoride homopolymer having a weight average molecular weight of 41,000 and γ-butyrolactone were dissolved at a temperature of 170 ° C. at a ratio of 38% by weight and 62% by weight, respectively. This resin solution was discharged from the die while accompanying γ-butyrolactone as a hollow portion forming liquid, and solidified in a cooling bath composed of an 80% by weight aqueous solution of γ-butyrolactone at a temperature of 20 ° C. to prepare a base hollow fiber.

  Next, 13% by weight of vinylidene fluoride homopolymer having a weight average molecular weight of 284,000, 3% by weight of polyethylene vinyl acetate copolymer (ethylene 30%, vinyl acetate 70%), and 76% of N-methyl-2-pyrrolidone. A film-forming stock solution was prepared by mixing and dissolving at a temperature of 95 ° C. in a proportion of 5% by weight, 5% by weight of T-20C, and 3% by weight of water. This membrane-forming stock solution was uniformly applied to the surface of the base hollow fiber and immediately solidified in a water bath to produce a hollow fiber membrane in which a porous membrane was formed on the surface of the base hollow fiber. 100 g of this hollow fiber membrane was immersed in 2000 ml of 0.5 mol / L sulfuric acid water-ethanol solution (water: ethanol = 1: 1) at 40 ° C. for 5 hours to perform a hydrolysis treatment.

The obtained hollow fiber membrane had an outer diameter of 1.4 mm, an inner diameter of 0.8 mm, and an average pore diameter of 0.05 μm. The pure water permeability at 50 kPa and 25 ° C. was 1.05 m ³ / m ² · h (Q0).

The aqueous humic acid solution was filtered to ² m ³ / m ² under the conditions of a temperature of 25 ° C. and a filtration differential pressure of 16 kPa, and backwashed. It was 1.00 m < ³ > / m < ² > * h when the pure water permeation amount was measured (Q1).

After immersing in 5000 ppm sodium hypochlorite aqueous solution 5000 ppm for 24 hours at 80 ° C., the humic acid aqueous solution was filtered to 2 m ³ / m ² at a temperature of 25 ° C. and a filtration differential pressure of 16 kPa, and backwashed. . It was 1.00 m < ³ > / m < ² > * h when the pure water permeation amount was measured (Q2).

The evaluation results are summarized in Table 1.
<Comparative Example 6>
A hollow fiber membrane was produced in the same manner as in Example 5 except that the polyethylene vinyl acetate copolymer was not added to the membrane-forming stock solution, and its weight% was changed to N-methyl-2-pyrrolidone.

The obtained hollow fiber membrane had an outer diameter of 1.4 mm, an inner diameter of 0.8 mm, and an average pore diameter of 0.02 μm. The pure water permeation rate at 50 kPa and 25 ° C. was 1.33 m ³ / m ² · h (Q0).

The aqueous humic acid solution was filtered to ² m ³ / m ² under the conditions of a temperature of 25 ° C. and a filtration differential pressure of 16 kPa, and backwashed. It was 1.10 m < ³ > / m < ² > * h when the pure water permeation amount was measured (Q1).

After immersing in 5000 ppm sodium hypochlorite aqueous solution 5000 ppm for 24 hours at 80 ° C., the humic acid aqueous solution was filtered to 2 m ³ / m ² at a temperature of 25 ° C. and a filtration differential pressure of 16 kPa, and backwashed. . It was 1.08 m < ³ > / m < ² > * h when the pure water permeation amount was measured (Q2).

The evaluation results are summarized in Table 1.
<Example 6>
13% by weight of vinylidene fluoride homopolymer having a weight average molecular weight of 284,000, 3% by weight of polyethylene vinyl acetate copolymer (ethylene 30%, vinyl acetate 70%), 76% by weight of dimethylacetamide, and T-20C A film forming stock solution was prepared by mixing and dissolving 5% by weight and 3% by weight of water at a temperature of 95 ° C.

Next, after the film-forming stock solution is cooled to 25 ° C., it is applied to a non-woven fabric made of polyester fiber having a density of 0.48 g / cm ³ and a thickness of 220 μm. Immediately after application, it is immersed in pure water at 25 ° C. for 5 minutes. Further, it was washed by immersing it in hot water at 80 ° C. three times to obtain a flat film. 100 g of this flat membrane was immersed in 2000 ml of a 0.5 mol / L sulfuric acid aqueous solution-ethanol (water: ethanol = 1: 1) at 40 ° C. for 5 hours for hydrolysis treatment.

The surface pore diameter of the obtained flat membrane was 0.05 μm to 0.1 μm. The pure water permeation amount at 50 kPa and 25 ° C. was 6.48 m ³ / m ² · h (Q0).

The aqueous humic acid solution was filtered to ² m ³ / m ² under the conditions of a temperature of 25 ° C. and a filtration differential pressure of 16 kPa, and backwashed. It was 6.32m < ³ > / m < ² > * h when the pure water permeation amount was measured (Q1).

After immersing in 5000 ppm sodium hypochlorite aqueous solution 5000 ppm for 24 hours at 80 ° C., the humic acid aqueous solution was filtered to 2 m ³ / m ² at a temperature of 25 ° C. and a filtration differential pressure of 16 kPa, and backwashed. . It was 6.30 m < ³ > / m < ² > / h when the pure water permeation amount was measured (Q2).

The evaluation results are summarized in Table 1.
<Comparative Example 7>
A flat membrane was produced in the same manner as in Example 6 except that the polyethylene vinyl acetate copolymer was not added to the membrane-forming stock solution, and its weight% was changed to N-methyl-2-pyrrolidone.

The surface pore diameter of the obtained flat membrane was 0.05 μm to 0.1 μm. The pure water permeation amount at 50 kPa and 25 ° C. was 6.66 m ³ / m ² · h (Q0).

The aqueous humic acid solution was filtered to ² m ³ / m ² under the conditions of a temperature of 25 ° C. and a filtration differential pressure of 16 kPa, and backwashed. It was 6.10 m < ³ > / m < ² > * h when the pure water permeation amount was measured (Q1).

After immersing in 5000 ppm sodium hypochlorite aqueous solution 5000 ppm for 24 hours at 80 ° C., the humic acid aqueous solution was filtered to 2 m ³ / m ² at a temperature of 25 ° C. and a filtration differential pressure of 16 kPa, and backwashed. . It was 6.10 m < ³ > / m < ² > * h when the pure water permeation amount was measured (Q2).

  The evaluation results are summarized in Table 1.

Liquid separation membrane thus be produced in the present invention method, water treatment if the field of water treatment, drinking water treatment, waste water treatment, available in such industrial water production, river water, lake water, ground water, seawater, sewage, drainage It can utilize for the water treatment which uses as a treated water.

Claims (5)

After forming a film from a polymer solution in which a polyvinylidene fluoride resin and a polyethylene vinyl acetate resin containing vinyl acetate in the range of 60 to 95 mol% are mixed and dissolved, the polyethylene vinyl acetate resin in the film is hydrolyzed. A method for producing a liquid separation membrane. The method for producing a liquid separation membrane according to claim 1, wherein the polymer solution used for membrane formation further contains a surfactant. The method for producing a liquid separation membrane according to claim 1, wherein the polyethylene vinyl acetate resin is hydrolyzed under acidic conditions. The method for producing a liquid separation membrane according to any one of claims 1 to 3, wherein 10 to 100 mol% of acetyl groups contained in the polyethylene vinyl acetate resin in the membrane is hydrolyzed. . Claim 1 in which the concentration of pre-Symbol polyvinylidene fluoride resin in the polymer solution is 10 to 50 wt%, and the concentration of polyethylene vinyl acetate-based resin, characterized in that 0.5 to 15 wt% The manufacturing method of the liquid separation membrane in any one of -4 .