JP2017001029A - Multilayer separation film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer separation film that is high in the ability to remove underwater suspended components and the ability to adsorb and remove metal ions and has high strength.SOLUTION: A multilayer separation film at least has a porous adsorption layer comprising a fine particle having a chelating functional group, and a porous support layer.SELECTED DRAWING: None

Description

  The present invention is a multilayer having both turbidity removal ability suitable for various water treatment such as drinking water production, industrial water production, water purification treatment, wastewater treatment, seawater desalination, industrial water production and the removal of specific compounds such as metal ions. It relates to a separation membrane.

  In recent years, separation membranes have been used in various fields such as water treatment fields such as water purification treatment and wastewater treatment, medical applications such as blood purification, food industry fields, battery separators, charged membranes, fuel cell electrolyte membranes and the like.

  Especially in the field of drinking water production and industrial water production, i.e. water treatment such as water purification treatment, wastewater treatment, seawater desalination, etc., it is possible to replace conventional sand filtration, coagulation sedimentation, evaporation methods, and improve treatment water quality. Therefore, a separation membrane is used. Since the amount of treated water is large in these fields, if the water permeability of the separation membrane is excellent, it is possible to reduce the membrane area, and the equipment can be reduced because the equipment is compact, and the membrane replacement cost and installation area are reduced. Will also be advantageous.

  As the separation membrane for water treatment, one according to the size of the separation target substance contained in the water to be treated is used. Usually, since natural water contains many turbid components, microfiltration membranes and ultrafiltration membranes for removing turbid components in water are generally used. Here, depending on the water to be treated, harmful metal ions may be contained, but the ions are too small to be removed by a microfiltration membrane or an ultrafiltration membrane. For this reason, in addition to the turbidity removal process for removing turbid components, a process for removing metal ions in water is required.

  On the other hand, for removal of metal ions in water, adsorption removal using an ion exchange resin, adsorption removal using a chelate resin, and adsorption removal using an inorganic adsorbent such as a cerium compound (Patent Document 1) are known. However, there are practical problems such as clogging of water channels due to adsorption of turbid components in water to the adsorbent as well as economic problems such as equipment costs such as adsorption tower, initial investment of resin, resin regeneration cost, etc. . For this reason, in addition to the adsorption process for removing metal ions, a process for removing turbid components in water is necessary.

  In addition to this, a membrane provided with an adsorption layer having a chelating functional group by graft polymerization only on the surface or surface layer (Patent Document 2), and after introducing glycidyl methacrylate by graft polymerization on the surface of the porous membrane or the surface in the pores A film (Patent Document 3) in which a chelating functional group is chemically introduced is known. In these cases, operations such as graft polymerization and modification are required after obtaining the porous membrane, which complicates the production process and causes problems such as adsorption by turbid components in water and blockage of water channels. A cloth-like base material provided with a chelating functional group (Patent Document 4) and a chelating functional group-containing fiber (Patent Document 5) are also known. In addition to the adsorption process for removing metal ions, a process for removing turbid components in water was necessary.

  Here, a composite separation membrane (Patent Document 6) for simultaneously performing turbidity removal and adsorption removal is disclosed. By filtration through a composite separation membrane having a layer with a three-dimensional network structure and a porous layer containing an adsorbent, it is possible to obtain excellent fouling resistance, remove turbidity from seawater, and metal ions ( Boron) can be removed.

JP 2007-160271 A JP 58-205543 A Japanese Patent Laid-Open No. 7-24314 JP 2005-74378 A JP-A-4-83532 JP 2010-227757 A

  However, the conventional membrane has a low adsorption efficiency, and there is a problem that the strength of the membrane decreases when the amount of adsorbent is increased in order to increase the adsorption efficiency.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a film that can achieve both the strength of the film and the adsorption efficiency.

In order to achieve the above object, the present invention includes the following configurations.
(1) a porous adsorption layer containing fine particles having a chelating functional group and a base polymer;
A multilayer separation membrane comprising a porous support layer.
(2) The multilayer separation membrane according to (1), wherein the fine particles having a chelating functional group have a particle size of 0.15 μm to 3 μm.
(3) The porous adsorption layer has at least one of a three-dimensional network structure or a spherical structure,
The multilayer separation membrane according to (1) or (2).
(4) The multilayer separation membrane according to any one of (1) to (3), wherein the porous adsorption layer has a surface responsible for turbidity.
(5) The average value X of the number of atoms (%) of the chelating functional group-derived atoms and the standard deviation Y satisfy X ≧ 3Y when the cross section of the porous adsorption layer is subjected to elemental analysis by energy dispersive X-ray analysis.
The multilayer separation membrane according to any one of (1) to (4).
(6) The multilayer separation membrane according to (5), wherein the chelating functional group-derived atom is at least one selected from the group consisting of N, O, P, S, Na, K, Cu, Fe, and B.
(7) The multilayer separation membrane according to any one of (1) to (6), wherein the porous adsorption layer has a thickness of 10 μm or more and 500 μm or less.
(8) The multilayer separation membrane according to any one of (1) to (7), which is a hollow fiber membrane having an outer diameter of 800 μm or more and 2000 μm or less.
(9) The pure water permeation performance at 50 kPa and 25 ° C. is 0.01 m ³ / m ² · hr or more and 10 m ³ / m ² · hr or less, the breaking strength is 6 MPa or more, and the breaking elongation is 10% or more, The multilayer separation membrane according to any one of 1) to (8).
(10) The multilayer separation membrane according to any one of (1) to (9), wherein the porous adsorption layer is a layer obtained by a thermally induced phase separation method and / or a non-solvent induced phase separation method.
(11) The multilayer separation membrane according to any one of (1) to (10), wherein the porous support layer is a layer obtained by a thermally induced phase separation method and / or a non-solvent induced phase separation method.

  The multilayer separation membrane of the present invention includes a porous adsorption layer having fine particles having a chelating functional group and a support layer. As a result, the multilayer separation membrane can exhibit extremely high adsorption efficiency for metal ions and high membrane strength.

[1. Multilayer separation membrane]
The multilayer separation membrane of the present invention includes a porous adsorption layer (hereinafter sometimes simply referred to as “adsorption layer”) and a porous support layer (hereinafter sometimes simply referred to as “support layer”). Features.

(1-1) Porous adsorption layer The porous adsorption layer includes at least a base polymer having a porous structure and fine particles having a chelating functional group (hereinafter sometimes simply referred to as “chelate fine particles”).

  A known polymer can be contained as the base polymer. Examples of known various polymers include polyethylene, polypropylene, acrylic resin, polyacrylonitrile, acrylonitrile-butadiene-styrene (ABS) resin, polystyrene, acrylonitrile-styrene (AS) resin, vinyl chloride resin, cellulose ester, polyethylene terephthalate, Polyamide, polyacetal, polycarbonate, modified polyphenylene ether, polyphenylene sulfide, fluororesin-based polymer, polyamideimide, polyetherimide, polysulfone, polyethersulfone, and mixtures and copolymers thereof can be mentioned. Other resins miscible with these may be mixed.

  The fluororesin-based polymer in the present invention 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 vinyl fluoride, tetrafluoroethylene, propylene hexafluoride, and ethylene trifluoride chloride.

  The weight average molecular weight of the fluororesin-based polymer may be appropriately selected depending on the required strength and water permeability of the polymer separation membrane, but as the weight average molecular weight increases, the water permeability performance decreases and the weight average molecular weight decreases. As a result, the strength decreases. For this reason, the weight average molecular weight is preferably from 50,000 to 1,000,000. In the case of a water treatment application where the polymer separation membrane is exposed to chemical cleaning, the weight average molecular weight is preferably from 100,000 to 700,000, more preferably from 150,000 to 600,000.

  The chelating functional group is a functional group that can selectively adsorb by interacting with a specific metal ion. Electron donating atoms such as nitrogen, oxygen, sulfur, and phosphorus contained in the chelating functional group coordinate to the metal ion to form a stable chelate such as a 5-membered ring or 6-membered ring. Adsorb selectively. The chelating functional group and the metal ion to be removed are exemplified in this section, but the present invention is not limited to the combination thereof, and may be appropriately selected and used based on the compatibility with the metal ion to be removed. it can. For example, an iminodiacetic acid group of a chelating functional group containing a nitrogen atom and an oxygen atom is suitable for selectively adsorbing metal ions such as iron, copper, manganese, lead, cadmium, mercury, and chromium. The amidoxime group is suitable for selectively adsorbing metal ions such as iron, manganese, lead, cadmium, cobalt, nickel, vanadium, titanium, copper, and chromium. Further, the N-methyl-glucamine group is suitable for selectively adsorbing boron. As a chelating functional group containing a sulfur atom, for example, a mercapto group is suitable for selectively adsorbing arsenic, and a dithiocarbamic acid group or a thiourea group. An aminophosphate group is a chelating functional group containing a phosphorus atom, and is suitable for selectively adsorbing metal ions such as iron, copper, lead, zinc, aluminum, nickel, manganese, titanium, cobalt, and cadmium. . In the case of chelating functional groups having a carboxy group or a phosphate group, such as an iminodiacetic acid group or an aminophosphate group, not only the H type but also a salt type such as a sodium salt or a potassium salt can be used with an alkali or acid as necessary. Can be converted.

  The polymer having a chelating functional group is a polymer having the above-described chelating functional group in the main chain and / or side chain. The polymer having a chelating functional group may have a crosslinked structure, and in this case, it is preferable in that an effect of suppressing elution and swelling of the polymer having a chelating functional group is obtained.

  As a method for introducing a chelating functional group into a polymer, a known method may be used, for example, a method of introducing a chelating functional group into a polymer by a chemical reaction, after introducing a chelating functional group into a monomer through a chemical reaction, Examples thereof include a method of polymerizing the monomer to make a homopolymer, and a method of copolymerizing with another monomer to make a copolymer. The chelating functional group to be introduced may be one kind or a plurality of different chelating functional groups.

  The chelate fine particles are fine particles containing at least a polymer having a chelating functional group, and those having a chelating functional group on the surface or a porous body having a chelating functional group exposed in the pores are preferable. Used.

  As a method for obtaining chelate fine particles, a known nanoparticle preparation method or the like may be used. In addition to dispersion polymerization, emulsion polymerization, suspension polymerization, seed polymerization, solvent evaporation method, etc., chelating properties obtained as described above. Examples thereof include a polymer having a functional group, a method of crushing a commercially available chelate polymer, surface modification of a chelating functional group to inorganic particles or polymer fine particles, and the like. Specific examples of the method for crushing the chelate polymer include a ball mill, a planetary ball mill, a bead mill, a jet mill, a roller mill, and freeze pulverization.

  Examples of the particle shape of the chelate fine particles include a spherical shape, an elliptical shape, an irregular shape having protrusions, and a porous shape. Any shape can be used, and a plurality of shapes of particles can be mixed and used.

The particle diameter of the chelate fine particles used in the present invention is preferably in the range of an average particle diameter of 0.15 to 3 μm. When the particle size is 0.15 μm or more, the generation of macrovoids due to the high hydrophilicity of the chelating functional group can be reduced, and since the uniform surface pore diameter is provided, the adsorption layer becomes the outermost layer High fouling resistance can be obtained. When the upper limit is 3 μm or less, the chelating functional group can be uniformly dispersed in the adsorption layer, and good metal ion removal performance can be obtained. Preferably it is 0.2-1.5 micrometers, More preferably, it is 0.3-1.0 micrometer. A narrow particle size distribution is preferable because heteroaggregation hardly occurs and the dispersion stability in the solution is improved. The particle diameter is obtained by taking a photograph of the chelate fine particles in the film using SEM or the like, measuring the particle diameter of 20 or more, preferably 30 or more, and averaging the number. When the shape is other than a circle, if the diameter of the circle inscribed in the shape is a and the diameter of the circumscribed circle is b, (a × b) ^0.5 is obtained as the equivalent circle diameter.

  In the porous adsorption layer, the chelate functional groups can be uniformly dispersed in the porous adsorption layer by dispersing the chelate fine particles having the above-mentioned average particle diameter in the film.

  Whether chelate fine particles are uniformly dispersed in the porous adsorption layer is determined by, for example, elemental analysis using energy dispersive X-ray analysis attached to a scanning electron microscope, and there is no significant bias in the distribution of the chelating functional group-derived atoms. You can confirm. In this case, using energy dispersive X-ray analysis, elemental analysis is performed at a magnification of 5000 times at 20 or more, preferably 50 or more different porous adsorption layers, and the number of atoms of chelating functional group-derived atoms ( %) And check the degree of bias. A standard deviation is preferably used as a guide for bias. The porous adsorption layer of the present invention is preferably a layer in which fine particles having a chelating functional group are uniformly dispersed, and the chelating functionality when the cross section of the porous adsorption layer is subjected to elemental analysis by energy dispersive X-ray analysis. The average value X and the standard deviation Y of the number of atoms (%) of the group-derived atoms are preferably uniform dispersion satisfying X ≧ 3Y, and X ≧ 5Y is more preferable.

  The atom derived from the chelating functional group may be any atom that can identify the chelating functional group, and includes atoms constituting the chelating functional group and atoms capable of forming a salt with the chelating functional group. In the case of a functional group, at least one selected from the group consisting of N, O, P, S, Na and K is preferably used. As another means for specifying the chelating functional group, the functional group selectively adsorbs with a specific metal ion, and after adsorbing a specific metal ion such as Cu, Fe, B, etc. Measurement of the number of atoms (%) of the ions is also preferably used.

  As the thickness of the porous adsorption layer increases, the chance of contact between the metal ions and the chelating functional group increases and the adsorption efficiency increases, and the adsorption capacity also increases. Performance decreases. For this reason, the thickness of the porous adsorption layer is preferably 10 μm or more and 500 μm or less, more preferably 20 μm or more and 400 μm or less, and further preferably 30 μm or more and 300 μm or less.

  The porous adsorption layer contains other components, for example, organic substances, inorganic substances, polymers, etc., within a range that does not depart from the spirit of the present invention, that is, within a range that does not impede extremely high adsorption efficiency for metal ions and high film strength. It may be.

  In order to prevent contamination by turbidity in the porous adsorption layer, at least one outermost layer or surface is provided with a turbidity-removable layer (responsible for turbidity) or a turbidity-removable (responsible for turbidity) It is preferable to have. In addition, the "surface which bears turbidity" here refers to the surface which an adsorption layer has, when not providing a turbidity layer separately. It is a preferred embodiment that a layer capable of turbidity is disposed on the raw water side of the porous adsorption layer, or a surface responsible for turbidity is disposed on the raw water side in the porous adsorption layer. In other words, after the turbidity in the raw water is turbidized by the layer or surface responsible for turbidity, the metal ions in the raw water are adsorbed in the porous adsorption layer.

  Since the turbidity layer or the surface responsible for turbidity is arranged closer to the raw water side than the porous adsorption layer, the multi-layer separation membrane is porous after removing the turbidity in water by the turbidity layer or the surface responsible for turbidity. Metal ion removal can be performed by the material adsorption layer. Therefore, contamination of the porous adsorption layer due to turbidity can be suppressed. Further, the turbid layer and the surface responsible for turbidity also have the effect of imparting excellent fouling resistance. As a result, in the water treatment field where a large amount of water to be treated must be treated in a short time, turbid component removal and metal ion adsorption removal in water can be performed sufficiently and stably.

  In addition, when it has the surface which bears turbidity, a film thickness can be made small compared with the case where a turbidity layer is provided separately, and it is preferable at the point which can make water permeability high.

  When the turbidity layer is not provided in the composite membrane and the porous adsorption layer is on the outermost layer on the separation target side, when the surface of the outermost layer is observed from directly above, the surface having pores is observed. Since the surface having the pores becomes the surface responsible for turbidity, the average pore diameter of the surface pores may be changed according to the application.

  The preferred value of the average pore size of the surface responsible for turbidity varies depending on the substance to be separated, but in order to achieve both high removal performance and high water permeation performance, it is preferably 1 nm or more and 1 μm or less, more preferably 5 nm or more and 0.5 μm or less. More preferably, it is 10 nm or more and 0.1 μm or less. In particular, in water treatment applications, the average surface pore diameter is preferably in the range of 5 nm to 0.5 μm, and more preferably in the range of 10 nm to 0.1 μm. When the average pore diameter on the surface is within this range, dirt in the water is less likely to clog the pores, and the water permeation performance is unlikely to deteriorate, so the separation membrane can be used continuously for a longer period. Moreover, even when clogged, dirt can be removed by so-called backwashing or air washing.

  Here, although it differs depending on the water source, for example, in rivers and lakes, inorganic substances and colloids derived from soil and mud, microorganisms and dead bodies thereof, humic substances derived from plants, and the like can be mentioned. Backwashing is the operation of passing permeate in the opposite direction to normal filtration. In the case of hollow fiber membranes, air washing is used to shake the hollow fiber membranes to remove dirt accumulated on the membrane surface. It is an operation to do.

  The average pore diameter of the surface of the porous adsorption layer is photographed at a magnification of 60000 using a scanning electron microscope on the surface of the porous adsorption layer, and the diameter of any pore of 10 or more, preferably 20 or more is measured. And number average. When the pores are not circular, a circle having an area equal to the area of the pores (equivalent circle) is obtained by an image processing device or the like, and the equivalent circle diameter is obtained by the method of setting the diameter of the pores. When the pores are not circular, a circle having an area equal to the area of the pores (equivalent circle) is obtained by an image processing device or the like, and the equivalent circle diameter is obtained by the method of setting the diameter of the pores.

(1-2) Porous support layer The porous support layer includes at least a thermoplastic resin having a porous structure. By providing the multilayer separation membrane with the porous support layer, the mechanical strength can be enhanced without impairing the permeation performance of the separation membrane. The relationship between the average pore diameter A of the surface pores of the porous adsorption layer or the average pore diameter B of the pores of the turbidity layer and the average pore diameter C of the internal pores of the porous support layer is A <C or B <C It is preferable that

  As the polymer for forming the porous support layer, the resin described in (1-1) can be used. Among the above-mentioned polymers, fluororesin-based polymers are preferably used because they have high resistance to various chemicals used in water treatment applications and high mechanical strength.

  The weight average molecular weight of the fluororesin-based polymer may be appropriately selected depending on the required strength and water permeability of the polymer separation membrane, but as the weight average molecular weight increases, the water permeability performance decreases and the weight average molecular weight decreases. As a result, the strength decreases. For this reason, the weight average molecular weight is preferably from 50,000 to 1,000,000. In the case of a water treatment application where the polymer separation membrane is exposed to chemical cleaning, the weight average molecular weight is preferably from 100,000 to 700,000, more preferably from 150,000 to 600,000.

  The thickness of the porous support layer is preferably 30 μm or more and 500 μm or less. Practical strength is obtained when the thickness is 30 μm or more, and good transmission performance is obtained when the thickness is 500 μm or less. 50 μm or more and 400 μm or less is more preferable, and 70 μm or more and 300 μm or less is more preferable.

  The average diameter of the spherical structure is 0.1 μm or more and 5 μm or less, more preferably 0.5 μm or more and 3 μm or less. When the average diameter is less than 0.1 μm, the gap formed in a spherical shape is narrowed and the mechanical strength is increased, but the transmission performance may be lowered. On the other hand, when the average diameter exceeds 5 μm, the gap formed by the spherical structure becomes wide and the water permeability increases, but the mechanical strength may tend to decrease. The average diameter of the spherical structure is obtained by taking a photograph of a cross section of the composite hollow fiber membrane at a magnification of 10,000 using a scanning electron microscope, measuring the diameters of 20 arbitrarily selected spherical structures, and calculating the number average. be able to. Here, the “spherical structure” means a structure in which a large number of spherical or substantially spherical solid components are connected directly or in a streak shape through the solid components.

(1-3) Other layers It is preferable to provide a porous turbidity layer as a layer other than the porous adsorption layer and the porous support layer because higher fouling resistance can be obtained. Examples of such a porous turbidity layer include a layer produced using a thermally induced phase separation method or a non-solvent induced phase separation method.

(1-4) Configuration of Multilayer Separation Membrane The multilayer separation membrane of the present invention includes at least an adsorption layer and a support layer, and may further include other layers. By disposing the turbidity layer or the surface responsible for turbidity at least one of the outermost layers and setting it as the raw water side, contamination inside the membrane due to turbidity can be prevented.

  The outer diameter of the multilayer separation membrane is preferably 800 μm or more and 2000 μm or less. When the outer diameter is 800 μm or more, the above-mentioned support layer thickness is sufficient to easily handle the membrane, and when the outer diameter is 2000 μm or less, the membrane area per unit volume is preferable. . 900 μm or more and 1900 μm or less are more preferable, and 1000 μm or more and 1800 μm or less are more preferable.

(1-5) Characteristics The membrane of the present invention can achieve both adsorption efficiency and strength by including a porous adsorption layer and a support layer.

The multilayer separation membrane of the present invention has a pure water permeation performance at 50 kPa and 25 ° C. of 0.01 m ³ / m ² · hr or more and 10 m ³ / m ² · hr or less, a breaking strength of 6 MPa or more, and a breaking elongation of 10 % Or more is preferable. The removal rate of 0.309 μm diameter particles is preferably 90% or more. The pure water permeation performance is more preferably 0.03 m ³ / m ² · hr to 8 m ³ / m ² · hr, more preferably 0.05 m ³ / m ² · hr to 6 m ³ / m ² · hr or less. is there. The breaking strength is more preferably 7 MPa or more, and further preferably 8 MPa or more. The breaking elongation is more preferably 20% or more. The removal rate of 0.309 μm diameter particles is more preferably 95% or more. By satisfying the above conditions, a separation membrane having sufficient strength and water permeability can be obtained for applications such as water treatment, medical treatment, food industry, battery separator, charged membrane, fuel cell electrolyte membrane and the like.

  The method for measuring the breaking strength and breaking elongation is not particularly limited. For example, using a tensile tester, test a sample with a measurement length of 50 mm at a pulling speed of 50 mm / min and changing the sample at least five times. And it can measure by calculating | requiring the average value of breaking strength, and the average value of breaking elongation.

  Here, the metal ion adsorption removal performance, that is, the metal ion removal performance is preferably 80% or more, more preferably 90% or more, still more preferably 95% or more, and particularly preferably 99% or more. The metal ion removal performance can be evaluated by quantitatively analyzing the metal ion concentration before and after filtration with an ICP emission spectrometer. In the present invention, a small module having an effective length of 200 mm composed of four hollow fiber membranes is manufactured, and an aqueous solution containing a predetermined metal ion at a predetermined concentration under the conditions of a temperature of 25 ° C. and a filtration differential pressure of 16 kPa Perform filtration for 30 minutes, analyze the metal ion concentration present in the feed water and permeated water with an ICP emission analyzer (P-4010, manufactured by Hitachi, Ltd.), and obtain the metal ion removal performance (%) using the following formula. Can do.

Metal ion removal performance (%) = [1-2 × (metal ion concentration in permeated water) / {(metal ion concentration in supplied water at the start of measurement) + (metal ion concentration in supplied water at the end of measurement)}] × 100
The turbid component removal performance can be evaluated by quantitatively analyzing the turbid component concentration before and after filtration using, for example, a spectrophotometer, preferably 90% or more, more preferably 95% or more, and 99% or more. Is more preferable. The measuring method will be described in detail in Examples.

  In actual water treatment, in addition to the turbid component removal performance, it is important to have excellent resistance to turbid components, that is, fouling resistance. In general, since a separation membrane for water treatment is used for 5 to 10 years, even if raw water containing a turbid component is filtered, filterability is restored by backwashing and it is required that it can be used repeatedly.

Fouling resistance can be evaluated by comparing the permeation performance of pure water before and after filtration of an aqueous solution containing a turbid component. In the present invention, a small module having an effective length of 200 mm composed of four hollow fiber membranes was manufactured, and the amount of permeated water (m) obtained by feeding distilled water over 1 hour under conditions of a temperature of 25 ° C. and a filtration differential pressure of 16 kPa. ³ ) is measured, converted into a numerical value per unit time (h) and unit membrane area (m ² ), and further converted into pressure (50 kPa), and the permeation performance of pure water (Q0, unit = m ³ / m ² / h). The unit membrane area is calculated from the average outer diameter and the effective length of the hollow fiber membrane. Next, typical contaminants humic acid (reagent, manufactured by Wako Pure Chemical Industries, Ltd.) is a component of 20ppm containing that solution filtered differential pressure 16 kPa, with external pressure all filtration under conditions of a temperature 25 ° C. ^2m 3 / Filter to m ² . Further, permeate is supplied for 1 minute at a backwash pressure of 150 kPa, and the permeation performance (Q1) of pure water immediately after that is measured. If A = Q1 / Q0 is used as an index of fouling resistance, the greater the value of A, the better the fouling resistance. From the viewpoint of long-term use, the value of A is preferably as high as possible. The lower limit is preferably 0.8 or more, more preferably 0.85 or more, and even more preferably 0.90 or more.

[2. Production method]
The multilayer separation membrane including the porous adsorption layer and the porous support layer of the present invention can be produced by various methods. For example, a method of forming a single layer of a porous support layer or a plurality of layers including a porous support layer and then laminating a porous adsorption layer on these layers can be mentioned. In this case, a single porous support layer or multiple layers including a porous support layer are prepared in advance using a thermally induced phase separation method or a non-solvent induced phase separation method, and porous adsorption is performed on these layers. After applying the polymer solution for layer formation, a porous adsorption layer can be obtained by using a thermally induced phase separation method or a non-solvent induced phase separation method. Furthermore, layers other than the porous adsorption layer and the porous support layer can be provided on the porous adsorption layer by using a thermally induced phase separation method or a non-solvent induced phase separation method.

  As another method for producing a multilayer separation membrane including a porous adsorption layer and a porous support layer, a porous adsorption layer and a porous support layer can be simultaneously formed using a die capable of discharging two or more kinds of polymer solutions. The method of forming is mentioned.

  The die for discharging the porous adsorption layer polymer solution and the porous turbidity layer forming polymer solution at the same time is not particularly limited, but when the shape of the separation membrane is a flat membrane, for example, two slits are provided. A double slit shape in which the sheets are arranged is preferably used. Further, when the shape of the separation membrane is a hollow fiber, for example, a triple tube type die is preferably used. The polymer solution for forming the porous adsorption layer and the polymer solution for the porous support layer are discharged from the outer tube and the intermediate tube of the triple tube type die, and solidified in the coagulation bath while discharging the hollow portion forming fluid from the inner tube. Thus, a hollow fiber membrane can be obtained. A hollow fiber membrane having a porous adsorption layer on the outside and a porous support layer on the inside by discharging the polymer solution for forming the porous adsorption layer from the outer tube and the polymer solution for the porous adsorption layer from the intermediate tube Conversely, by discharging the polymer solution for forming the porous adsorption layer from the intermediate tube and the polymer solution for the porous support layer from the outer tube, the porous adsorption layer is placed inside and the porous support layer is produced. A hollow fiber membrane having a layer on the outside can be obtained. Here, a layer other than the porous adsorption layer and the porous support layer can be provided using a multi-slit shape in the case of a flat membrane shape and a multi-tube type die in the case of a hollow fiber shape.

  A specific method for forming the porous adsorption layer and the porous support layer will be described below. In the following, each layer is described separately, but using a die capable of discharging two or more types of polymer solutions, it is possible to simultaneously form the porous adsorption layer, the porous support layer, and other layers, As described above.

<Method for forming porous adsorption layer>
The porous adsorption layer can be produced by using the above-described chelate fine particles and various known polymers by a phase transition method such as a thermally induced phase separation method or a non-solvent induced phase separation method. The method for introducing the chelating functional group into the polymer is as described above. These methods are preferable in that thermal decomposition of the chelating functional group can be suppressed because the film can be formed at a lower temperature than the melt film forming method. Among these, the non-solvent induced phase separation method is particularly preferable because it can form a film at a lower temperature.

  Here, the heat-induced phase separation is a method in which phase separation is induced by cooling a polymer solution dissolved at a high temperature to a temperature below the binodal line that is the boundary between the one-phase region and the two-phase region, This is a method of fixing the structure by glass transition. Non-solvent induced phase separation is a method in which phase separation is induced by concentration change due to penetration of a non-solvent into a uniform polymer solution or evaporation of the solvent into an external atmosphere. In the present application, a solution in which fine particles having an average particle size of 3 μm or less are dispersed is regarded as a uniform solution.

  In the thermally induced phase separation method, the thermoplastic resin solution is prepared by dissolving the thermoplastic resin in a poor solvent or a good solvent of the thermoplastic resin at a relatively high concentration of about 10 wt% to 60 wt% or less, The thermoplastic resin solution can be cooled and solidified to cause phase separation to form a porous structure. Here, the poor solvent cannot dissolve the thermoplastic resin by 5% by weight or more at a low temperature of 60 ° C. or lower, but dissolves by 5% by weight or more in a high temperature region exceeding 60 ° C. and below the melting point of the polymer. It is a solvent that can be made to occur. A solvent capable of dissolving 5% by weight or more of a thermoplastic resin in a low temperature region of 60 ° C. or less with respect to a poor solvent, a solvent that does not dissolve or swell the polymer up to the melting point of the thermoplastic resin or the boiling point of the solvent. Is defined as a non-solvent. Even a mixed solvent of a non-solvent and a poor solvent is defined as a poor solvent if it satisfies the definition of the poor solvent.

  Further, if the viscosity of the polymer solution is not within an appropriate range, handling is difficult and film formation cannot be performed. Therefore, the thermoplastic resin concentration is more preferably in the range of 30 wt% to 50 wt%. In cooling and solidifying the polymer solution, a method of discharging the polymer solution from a die into a cooling bath is preferable. At this time, the cooling liquid used in the cooling bath is preferably solidified using a liquid containing a poor solvent or a good solvent having a temperature of 5 to 50 ° C. and a concentration of 60 to 100% by weight. The cooling liquid may contain a non-solvent in addition to the poor solvent and the good solvent. However, when a liquid mainly composed of a non-solvent is used as the cooling liquid, the non-solvent intrusion is less than the phase separation by cooling solidification. Solvent induced phase separation tends to be preferred.

  In the non-solvent induced phase separation method, the thermoplastic resin is usually dissolved in a good solvent in the range of 5 to 30% by weight, more preferably in the range of 10 to 25% by weight to prepare the thermoplastic resin solution and immersed in a coagulation bath. Thus, the porous structure can be formed by causing the non-solvent to enter and phase separation. If it is less than 5% by weight, the physical strength is lowered, and if it exceeds 30% by weight, the permeation performance is lowered. Here, the melting temperature varies depending on the type and concentration of the thermoplastic resin and the type of solvent. In order to prepare the thermoplastic resin solution which is stable with good reproducibility, it is preferable that the solution is heated for several hours while stirring at a temperature not higher than the boiling point of the solvent so that a transparent solution is obtained.

  The chelate fine particles may be added in advance in a good solvent for the thermoplastic resin, or may be added after dissolving the thermoplastic resin. In order to improve the dispersibility of the chelate fine particles, it is preferably added in advance in a good solvent and dispersed with ultrasonic waves or the like, and after dissolving the thermoplastic resin in terms of inhibiting the decomposition of the chelating functional group It is preferable to add. Furthermore, by adding and mixing a solution in which a fine particle of chelate is added in advance in a good solvent and dispersed with ultrasonic waves, a thermoplastic resin solution having a decomposition temperature equal to or lower than the decomposition temperature of the chelating functional group is prepared separately. It is more preferable at the point which can acquire the effect of both dispersibility and decomposition | disassembly suppression of a chelating functional group. What is necessary is just to adjust the density | concentration of a chelate fine particle suitably in the range of 3 weight%-20 weight%. By adding 3% by weight or more, sufficient adsorption performance can be obtained, and by making it 30% by weight or less, a uniform three-dimensional network structure by phase separation of the thermoplastic resin can be obtained. Here, the three-dimensional network structure refers to a structure in which the solid content spreads in a three-dimensional network. In addition, the three-dimensional network structure has pores and voids partitioned by solid contents forming a network.

  The method for controlling the average pore size of the surface of the porous adsorption layer and the internal pores using the non-solvent induced phase separation method varies depending on the type and concentration of the polymer used, and can be performed by the following method, for example. An additive for controlling the pore size is put into the polymer solution to form a porous adsorption layer, or after the porous adsorption layer is formed, by eluting the additive, the surface and porous adsorption The average pore size of the internal pores of the layer can be controlled. Examples of the additive include organic compounds and inorganic compounds. As the organic compound, those that are soluble in both the solvent used in the polymer solution and the non-solvent that causes non-solvent-induced phase separation are preferably used. For example, water-soluble polymers such as polyvinylpyrrolidone, polyethylene glycol, polyethyleneimine, polyacrylic acid, and dextran, surfactants, glycerin, and saccharides can be used. As the inorganic compound, those that are soluble in both the solvent used in the polymer solution and the non-solvent that causes non-solvent-induced phase separation are preferable, and examples thereof include calcium chloride, magnesium chloride, lithium chloride, and barium sulfate. Moreover, it is also possible to control the average pore diameter of the internal pores of the surface and the porous adsorption layer by controlling the phase separation speed according to the kind, concentration and temperature of the non-solvent in the coagulation bath without using an additive. Generally, the average pore size is small when the phase separation rate is high, and it is large when the phase separation rate is low. Also, adding a non-solvent to the polymer solution is effective for controlling the phase separation rate.

  In particular, non-solvent induced phase separation is preferable because in the phase separation process, the chelate fine particles are easily arranged so as to be unevenly distributed on the channel side, and the chelating functional group can be used efficiently. Furthermore, in addition to being able to form a film at about room temperature, it is preferable because the average pore diameter of the surface and internal pores can be easily controlled by the method as described above.

<Method for forming porous support>
The porous support layer can be produced by the phase transition method such as the non-solvent induced layer separation method or the thermally induced phase separation method described above using the various known polymers described above. Use of the thermally induced phase separation method is preferable because high strength can be obtained.

  Hereinafter, the present invention will be described with reference to specific examples, but the present invention is not limited to these examples. In addition, the physical-property value regarding this invention can be measured with the following method.

(1) Average thickness and average pore diameter Using a scanning electron microscope, the cross section of the multilayer separation membrane was magnified 100 to 3000 times and photographed. In the image thus obtained, the thicknesses at arbitrary 10 positions of each layer were measured, and the number averaged from the obtained values was used as the average thickness of each layer.

  Regarding the average pore size of the turbid layer and the surface responsible for turbidity, the surface was photographed at 60000 times using a scanning electron microscope, and the diameter of 50 pores was measured in the obtained image, and the number average The average pore diameter of each surface was used.

  As for the average pore diameter of the internal pores of the porous adsorption layer, the diameter cross section of the multilayer separation membrane was photographed at 60000 times using a scanning electron microscope. In the image obtained in this manner, the diameters of 10 pores were measured in the range of the thickness within 1 μm close to the raw water side and the range within 1 μm from the interface with the support layer, and the number average pore size was measured. The internal pore average pore diameter of the adsorption layer was used.

(2) Inner diameter / outer diameter of hollow fiber membrane Using a scanning electron microscope, the cross section of the composite hollow fiber membrane was photographed at 50 times and 100 times, the major axis and minor axis were measured, and the number average was obtained. (3) Metal removal performance (copper removal performance)
A small module having an effective length of 200 mm composed of four hollow fiber membranes was produced. This module was subjected to external pressure total filtration for 30 minutes using a copper sulfate aqueous solution (copper concentration: 10 mg / L) under the conditions of a temperature of 25 ° C. and a filtration differential pressure of 16 kPa, and the copper concentration present in the supply water and permeated water was determined. It was measured. For the measurement of the copper concentration, an ICP emission analyzer (P-4010 manufactured by Hitachi, Ltd.) was used, and a sample diluted 10 times was measured. Copper removal performance (%) is defined by the following equation.

Copper removal performance (%) = [1-2 × (copper concentration in permeated water) / {(copper concentration in supply water at the start of measurement) + (copper concentration in supply water at the end of measurement)}] × 100
(4) Turbidity component removal performance A small module having an effective length of 200 mm made of four hollow fiber membranes was produced. This module was subjected to external pressure total filtration using an aqueous solution containing 20 ppm of polystyrene latex particles (reagent, manufactured by Magsphere) having an average particle size of 0.309 μm as a turbid component under the conditions of a temperature of 25 ° C. and a filtration differential pressure of 16 kPa. After 30 minutes, the concentration of turbid components present in the feed water and permeated water was calculated from the ultraviolet absorption coefficient at a wavelength of 234 nm, and the removal performance was determined from the concentration ratio. Here, a spectrophotometer (U-3200 manufactured by Hitachi, Ltd.) was used to measure the ultraviolet absorption coefficient at a wavelength of 234 nm. The turbidity component removal performance (%) is defined by the following equation.

(Turbidity component removal performance (%) = [1-2 × (turbidity component concentration in permeate)] / {(turbidity component concentration in feed water at the start of measurement) + (turbidity in feed water at the end of measurement) Ingredient concentration)}] × 100
(5) Permeation performance of pure water A small module having an effective length of 200 mm composed of four hollow fiber membranes was produced. The amount of permeated water (m ³ ) obtained by sending distilled water to this module over a period of 1 hour under the conditions of a temperature of 25 ° C. and a filtration differential pressure of 16 kPa was measured, and the unit time (h) and unit membrane area (m ² ) were measured. ), And further converted to pressure (50 kPa) to obtain the permeation performance of pure water (Q0, unit = m ³ / m ² / h). The unit membrane area was calculated from the average outer diameter and the effective length of the hollow fiber membrane. Next, a 20 ppm aqueous solution of humic acid (reagent, manufactured by Wako Pure Chemical Industries, Ltd.) was filtered to 2 m ³ / m ² by external pressure total filtration under the conditions of a filtration differential pressure of 16 kPa and a temperature of 25 ° C. Further, permeated water was supplied for 1 minute at a backwashing pressure of 150 kPa, and the permeation performance (Q1) of pure water immediately after that was measured.

(6) Fouling resistance A = Q1 / Q0 was used as an index of fouling resistance. It means that it is excellent in fouling resistance, so that the value of A is large.

(7) Breaking strength Using a tensile tester (TENSILON (registered trademark) / RTM-100, manufactured by Toyo Baldwin Co., Ltd.), test a sample with a measurement length of 50 mm at a pulling speed of 50 mm / min and changing the sample at least 5 times. And it calculated by calculating | requiring the average value of breaking strength.

(8) Polymer having a chelating functional group As a polymer having a chelating functional group, a chelate resin (Amberlite IRC748 (hereinafter referred to as polymer A)) commercially available from Organo Corporation was used. Polymer A has iminodiacetic acid Na groups as chelating functional groups. Polymer B was obtained by immersing 10 g of polymer A in 500 ml of aqueous HCl (0.01 mol / L) for 3 days and converting the functional group to iminodiacetic acid (H type).

(9) Preparation of polymer fine particles Polymers A and B were washed with distilled water until neutral, and dried with a dryer at 40 ° C. for 2 days. Then, a ball mill (Planet Ball Mill P- manufactured by FRITSCH) was used. The resin was crushed using 5). The implemented crushing conditions are described for each example or comparative example. In addition, at the time of crushing, in order to suppress decomposition | disassembly of the chelate group by a heat | fever, the cooling time for 30 minutes was provided for every 1 hour of crushing. Hereinafter, the polymer A crushed may be referred to as chelate fine particles A, and the polymer B crushed may be referred to as chelate fine particles B.

(10) Particle size measurement Using a scanning electron microscope, the cross section of the multilayer separation membrane was magnified 3,000 times to 60,000 times and photographed. In the image thus obtained, the particle size of 50 arbitrary particles was measured, and the particle size was averaged from the obtained values.

(11) Number of atoms (%) of chelating functional group, average value X, standard deviation Y
The porous adsorption layer containing the chelate fine particles B is taken out after being immersed in a 0.1N sodium hydroxide aqueous solution for 1 hour, washed with distilled water until neutral, and the iminodiacetic acid group is converted into a Na salt. Measurements were made.

  Using the energy dispersive X-ray analysis (X-ray accelerating voltage 15 kV) attached to the scanning electron microscope (Hitachi High-Technologies Corporation SU1510), elemental analysis was performed at a magnification of 5000 times for 50 different porous adsorption layers. Then, the number (%) of Na atoms which are atoms derived from the chelating functional group was measured, and the average value X and the standard deviation Y were calculated.

<Example 1>
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. The polymer solution is 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 10 ° C., whereby a hollow fiber membrane-like support layer Was made. The obtained support layer had a structure in which spherical structures having an average diameter of 3.0 μm were accumulated, and the thickness of the support layer was 250 μm.

Next, the resin was crushed using a ball mill. Put 18 zirconia balls 18mm and 4g of polymer A in a 45ml agate container, crush them under conditions of 300rpm and 5H, and further change the zirconia balls to 1-2mm diameter and 50g, then crush 4H at 400rpm, Got.
The finely divided polymer A (5.5% by weight) and N-methyl-2-pyrrolidone (78.5% by weight) were mixed to uniformly disperse the fine particles, and then a vinylidene fluoride homopolymer having a weight average molecular weight of 284,000 was obtained. A polymer solution was prepared by mixing and dissolving 11.3% by weight and cellulose acetate (Eastman Chemical Co., CA435-75S, cellulose triacetate) 4.7% by weight at 95 ° C. This polymer solution was uniformly applied to the surface of the support layer and immediately solidified in a water bath to produce a hollow fiber membrane in which a porous adsorption layer was formed on the support layer. The obtained porous adsorption layer had a three-dimensional network structure, and the average pore diameter on the surface of the porous adsorption layer was 20 nm and the thickness was 50 μm.

  With respect to the porous adsorption layer of the obtained hollow fiber membrane, when the number of Na atoms (%) as an atom derived from the chelating functional group was measured, the average value X was 1.09 and the standard deviation Y was 0.19. The chelating functional group was uniformly dispersed in the porous adsorption layer. The shape and each physical property are as shown in Table 1, and were excellent in any of turbidity removal performance, adsorption performance, and mechanical strength.

<Example 2>
In the same manner as in Example 1, a hollow fiber membrane-shaped support layer was produced. The obtained support layer had a structure in which spherical structures having an average diameter of 3.0 μm were accumulated, and the thickness of the support layer was 250 μm.

  Next, in the same manner as in Example 1, the polymer A was atomized to produce a hollow fiber membrane in which a porous adsorption layer was formed on the support layer. The obtained porous adsorption layer had a three-dimensional network structure. The porous adsorption layer had an average pore diameter of 100 nm and a thickness of 20 μm, and the adsorption layer was thinner than Example 1.

  With respect to the porous adsorption layer of the obtained hollow fiber membrane, when the number of Na atoms (%) as an atom derived from the chelating functional group was measured, the average value X was 1.11 and the standard deviation Y was 0.18. The chelating functional group was uniformly dispersed in the porous adsorption layer. The shape and each physical property are as shown in Table 1, and were excellent in turbidity removal performance, adsorption performance, and mechanical strength. However, since the thickness of the porous adsorption layer was thinner than that in Example 1, adsorption was performed. The strip was narrow and the copper removal performance was slightly lower.

<Example 3>
In the same manner as in Example 1, a hollow fiber membrane-shaped support layer was produced. The obtained support layer had a structure in which spherical structures having an average diameter of 3.0 μm were accumulated, and the thickness of the support layer was 250 μm.

  Next, in the same manner as in Example 1, the polymer A was atomized to produce a hollow fiber membrane in which a porous adsorption layer was formed on the support layer. The obtained porous adsorption layer had a three-dimensional network structure. The porous adsorption layer had an average pore diameter of 50 nm and a thickness of 150 μm, and the porous adsorption layer was thicker than Example 1.

  With respect to the porous adsorption layer of the obtained hollow fiber membrane, when the number of Na atoms (%) as an atom derived from the chelating functional group was measured, the average value X was 1.06 and the standard deviation Y was 0.18. The chelating functional group was uniformly dispersed in the porous adsorption layer. The shape and physical properties were as shown in Table 1, and were excellent in turbidity removal performance, adsorption performance, and mechanical strength. However, since the thickness of the porous adsorption layer was thicker than that in Example 1, filtration was performed. As a result, the resistance to pure water decreased slightly.

<Example 4>
In the same manner as in Example 1, a hollow fiber membrane-shaped support layer was produced. The obtained support layer had a structure in which spherical structures having an average diameter of 3.0 μm were accumulated, and the thickness of the support layer was 250 μm.

  Next, in the same manner as in Example 1, the polymer A was atomized to produce a hollow fiber membrane in which a porous adsorption layer was formed on the support layer. The obtained porous adsorption layer had a three-dimensional network structure. The porous adsorption layer had an average pore diameter of 50 nm and a thickness of 300 μm, and the porous adsorption layer was thicker than Example 1.

  With respect to the porous adsorption layer of the obtained hollow fiber membrane, when the number of Na atoms (%) as an atom derived from the chelating functional group was measured, the average value X was 1.03, and the standard deviation Y was 0.20. The chelating functional group was uniformly dispersed in the porous adsorption layer. The shape and physical properties were as shown in Table 1, and were excellent in turbidity removal performance, adsorption performance, and mechanical strength. However, since the thickness of the porous adsorption layer was thicker than that in Example 1, filtration was performed. As a result, the resistance to pure water decreased slightly.

<Example 5>
In the same manner as in Example 1, a hollow fiber membrane-shaped support layer was produced. The obtained support layer had a structure in which spherical structures having an average diameter of 3.0 μm were accumulated, and the thickness of the support layer was 250 μm.

  Next, in the same manner as in Example 1, the polymer A was atomized to produce a hollow fiber membrane in which a porous adsorption layer was formed on the support layer. The obtained porous adsorption layer had a three-dimensional network structure, and the average pore diameter of the porous adsorption layer was 50 nm and the thickness was 50 μm.

  Finally, 15% by weight of vinylidene fluoride homopolymer having a weight average molecular weight of 284,000, 3% by weight of polyethylene glycol having a weight average molecular weight of 20,000, 80% by weight of N-methyl-2-pyrrolidone, and 2% by weight of water The polymer solution was prepared by mixing and dissolving at a temperature of 95 ° C. at a rate of%. This polymer solution was uniformly applied to the surface of the porous adsorption layer and immediately solidified in a water bath to produce a hollow fiber membrane in which a porous turbidity layer was formed on the porous adsorption layer. The obtained porous turbidity layer had a three-dimensional network structure, and the porous turbidity layer had an average pore diameter of 20 nm and a thickness of 50 μm.

  With respect to the porous adsorption layer of the obtained hollow fiber membrane, when the number of Na atoms (%) as an atom derived from the chelating functional group was measured, the average value X was 1.13, and the standard deviation Y was 0.21. The chelating functional group was uniformly dispersed in the porous adsorption layer. The shape and physical properties are as shown in Table 1 and were excellent in turbidity performance, adsorption performance, and mechanical strength. However, since a turbidity layer was provided, the film thickness was compared with Example 1. Because of its thick thickness, the resistance to filtration increased, and the permeation performance of pure water decreased slightly.

<Example 6>
In the same manner as in Example 1, a hollow fiber membrane-shaped support layer was produced. The obtained support layer had a structure in which spherical structures having an average diameter of 3.0 μm were accumulated, and the thickness of the support layer was 250 μm.

  Next, a hollow fiber membrane having a porous adsorption layer formed on a support layer was produced in the same manner as in Example 1 except that the polymer B having an chelating functional group (containing iminodiacetic acid group) was used. The obtained porous adsorption layer had a three-dimensional network structure, and the average pore diameter of the porous adsorption layer was 20 nm and the thickness was 50 μm. Finally, it was immersed in NaOH to convert iminodiacetic acid to Na iminodiacetic acid.

  With respect to the porous adsorption layer of the obtained hollow fiber membrane, when the number of Na atoms (%) as an atom derived from the chelating functional group was measured, the average value X was 1.18 and the standard deviation Y was 0.19. The chelating functional group was uniformly dispersed in the porous adsorption layer. The shape and each physical property are as shown in Table 1, and were excellent in any of turbidity removal performance, adsorption performance, and mechanical strength.

<Example 7>
In the same manner as in Example 1, a hollow fiber membrane-shaped support layer was produced. The obtained support layer had a structure in which spherical structures having an average diameter of 3.0 μm were accumulated, and the thickness of the support layer was 250 μm.
Next, the resin was crushed using a ball mill. Put 18 zirconia balls 18 mm and 4 g of polymer A in a 45 ml agate container and crush them under the conditions of 400 rpm and 5 H. Furthermore, after replacing the zirconia balls with 1 to 2 mm diameter and 50 g, crush 10 H at 400 rpm to obtain particles. Got.

  Using this finely divided polymer A, a hollow fiber membrane in which a porous adsorption layer was formed on a support layer was produced in the same manner as in Example 1. The obtained porous adsorption layer had a three-dimensional network structure, and the average pore diameter of the porous adsorption layer was 60 nm and the thickness was 50 μm.

  With respect to the porous adsorption layer of the obtained hollow fiber membrane, when the number of Na atoms (%) as an atom derived from the chelating functional group was measured, the average value X was 0.94, and the standard deviation Y was 0.28. The chelating functional group was uniformly dispersed in the porous adsorption layer. The shape and each physical property were as shown in Table 1, and were excellent in turbidity removal performance, adsorption performance and mechanical strength, but the surface pore size was large and the fouling resistance was slightly lowered. Large pores due to macrovoids are generated on the membrane surface, and the fine dispersion of the chelate polymer particles further increases the uniform dispersibility. The ionic character of the chelate polymer affects the phase separation behavior. I think.

<Example 8>
In the same manner as in Example 1, a hollow fiber membrane-shaped support layer was produced. The obtained support layer had a structure in which spherical structures having an average diameter of 3.0 μm were accumulated, and the thickness of the support layer was 250 μm.
Next, the resin was crushed using a ball mill. Put 18 zirconia balls 18mm and 4g polymer A in a 45ml agate container, crush them under conditions of 300rpm and 5H, and further change the zirconia balls to 1-2mm diameter and 50g, then crush 8H at 400rpm, Got.

  Using this finely divided polymer A, a hollow fiber membrane in which a porous adsorption layer was formed on a support layer was produced in the same manner as in Example 1. The obtained porous adsorption layer had a three-dimensional network structure, and the average pore diameter of the porous adsorption layer was 40 nm and the thickness was 50 μm.

  With respect to the porous adsorption layer of the obtained hollow fiber membrane, when the number of Na atoms (%) as an atom derived from the chelating functional group was measured, the average value X was 1.05, and the standard deviation Y was 0.20. The chelating functional group was uniformly dispersed in the porous adsorption layer. The shape and each physical property were as shown in Table 1, and were excellent in turbidity removal performance, adsorption performance and mechanical strength, but the surface pore size was large and the fouling resistance was slightly lowered. Large pores due to macrovoids are generated on the membrane surface, and the fine dispersion of the chelate polymer particles further increases the uniform dispersibility. The ionic character of the chelate polymer affects the phase separation behavior. I think.

<Example 9>
In the same manner as in Example 1, a hollow fiber membrane-shaped support layer was produced. The obtained support layer had a structure in which spherical structures having an average diameter of 3.0 μm were accumulated, and the thickness of the support layer was 250 μm.
Next, the resin was crushed using a ball mill. In a 45 ml agate container, 18 10 mm diameter zirconia balls and 4 g of polymer A were placed and crushed under conditions of 300 rpm and 1 H to obtain particles.

  Using this finely divided polymer A, a hollow fiber membrane in which a porous adsorption layer was formed on a support layer was produced in the same manner as in Example 1. The obtained porous adsorption layer had a three-dimensional network structure, and the average pore diameter of the porous adsorption layer was 20 nm and the thickness was 50 μm.

  With respect to the porous adsorption layer of the obtained hollow fiber membrane, when the number of Na atoms (%) as an atom derived from the chelating functional group was measured, the average value X was 1.13 and the standard deviation Y was 0.19. The chelating functional group was uniformly dispersed in the porous adsorption layer. The shape and each physical property are as shown in Table 1, and were excellent in any of turbidity removal performance, adsorption performance, and mechanical strength.

<Example 10>
In the same manner as in Example 1, a hollow fiber membrane-shaped support layer was produced. The obtained support layer had a structure in which spherical structures having an average diameter of 3.0 μm were accumulated, and the thickness of the support layer was 250 μm.
Next, the resin was crushed using a ball mill. In a 45 ml agate container, 18 10 mm diameter zirconia balls and 4 g of polymer A were placed and crushed under the conditions of 100 rpm and 30 min to obtain particles.

  Using this finely divided polymer A, a hollow fiber membrane in which a porous adsorption layer was formed on a support layer was produced in the same manner as in Example 1. The obtained porous adsorption layer had a three-dimensional network structure, and the average pore diameter of the porous adsorption layer was 20 nm and the thickness was 50 μm.

  With respect to the porous adsorption layer of the obtained hollow fiber membrane, when the number of Na atoms (%) as an atom derived from the chelating functional group was measured, the average value X was 1.05 and the standard deviation Y was 0.33. It was. The shape and physical properties are as shown in Table 1 and were excellent in turbidity removal performance, adsorption performance, and mechanical strength, but the uniform dispersibility was slightly lowered and the adsorption performance was slightly lowered. It was.

<Example 11>
In the same manner as in Example 1, a hollow fiber membrane-shaped support layer was produced. The obtained support layer had a structure in which spherical structures having an average diameter of 3.0 μm were accumulated, and the thickness of the support layer was 250 μm.
Next, the resin was crushed using a ball mill. In a 45 ml agate container, 18 15 mm diameter zirconia balls and 4 g of polymer A were placed and crushed under the conditions of 100 rpm and 30 min to obtain particles.

  Using this finely divided polymer A, a hollow fiber membrane in which a porous adsorption layer was formed on a support layer was produced in the same manner as in Example 1. The obtained porous adsorption layer had a three-dimensional network structure, and the average pore diameter of the porous adsorption layer was 20 nm and the thickness was 50 μm.

  With respect to the porous adsorption layer of the obtained hollow fiber membrane, when the number of Na atoms (%) as an atom derived from the chelating functional group was measured, the average value X was 0.97, and the standard deviation Y was 0.45. It was. The shape and physical properties are as shown in Table 1 and were excellent in turbidity removal performance, adsorption performance, and mechanical strength, but the uniform dispersibility was slightly lowered and the adsorptivity performance was slightly lowered. Was.

<Comparative example 1>
In the same manner as in Example 1, a hollow fiber membrane-shaped support layer was produced. The obtained support layer had a structure in which spherical structures having an average diameter of 3.0 μm were accumulated, and the thickness of the support layer was 250 μm.
Next, the resin was crushed using a ball mill. Put 18 zirconia balls 18mm and 4g of polymer A in a 45ml agate container, crush them under the conditions of 400rpm, 7H, and replace the zirconia balls with 1-2mm diameter, 50g, then crush 15H at 400rpm, Got.

  Using this finely divided polymer A, a hollow fiber membrane in which a porous adsorption layer was formed on a support layer was produced in the same manner as in Example 1. The obtained porous adsorption layer had a three-dimensional network structure, and the average pore diameter of the porous adsorption layer was 80 nm and the thickness was 50 μm.

  With respect to the porous adsorption layer of the obtained hollow fiber membrane, when the number of Na atoms (%) as an atom derived from the chelating functional group was measured, the average value X was 0.91 and the standard deviation Y was 0.27. The chelating functional group was uniformly dispersed in the porous adsorption layer. The shape and each physical property are as shown in Table 2, and were excellent in turbidity removal performance, adsorption performance, and mechanical strength, but the surface pore diameter was large and the fouling resistance was low. It is thought that large-diameter holes due to macrovoids were partially formed on the film surface, which deteriorated the fouling resistance. The reason for the formation of macrovoids is that the size of the chelate fine particles is reduced and more chelating functional groups are exposed, increasing the amount of ionic functional groups in the system and affecting the phase separation. I think it was given.

<Comparative example 2>
In the same manner as in Example 1, a hollow fiber membrane-shaped support layer was produced. The obtained support layer had a structure in which spherical structures having an average diameter of 3.0 μm were accumulated, and the thickness of the support layer was 250 μm.
Subsequently, the chelate polymer was crushed using an agate mortar to obtain particles.

  Using this finely divided polymer A, a hollow fiber membrane in which a porous adsorption layer was formed on a support layer was produced in the same manner as in Example 1. The obtained porous adsorption layer had a three-dimensional network structure, and the average pore diameter of the porous adsorption layer was 20 nm and the thickness was 50 μm.

The porous adsorption layer of the obtained hollow fiber membrane was measured for the number of Na atoms (%) as atoms derived from the chelating functional group. The average value X was 0.87, and the standard deviation Y was 0.49. It was. The shape and physical properties are as shown in Table 2, and it was excellent in turbidity removal performance, adsorption performance, and mechanical strength, but the uniform dispersibility of the chelating functional group was slightly lowered, and the adsorptivity The performance was slightly degraded.
<Comparative Example 3>
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 27% by weight and 58% by weight, respectively. To this polymer solution, 15% by weight of chelate fine particles prepared in the same manner as in Example 9 was added with further stirring, followed by stirring and mixing to obtain a dispersion solution. The dispersion solution is discharged from the base 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 10 ° C., whereby a hollow fiber membrane-like support layer Was made. The obtained support layer had a structure in which chelate fine particles were dispersed in a spherical structure having an average diameter of 3.0 μm, and the thickness of the support layer was 300 μm.

  Next, a hollow fiber membrane having a porous turbidity layer formed thereon was produced in the same manner as in Example 5. The obtained porous turbidity layer had a three-dimensional network structure, and the porous turbidity layer had an average pore diameter of 20 nm and a thickness of 50 μm.

The obtained hollow fiber membrane had a pure water permeation performance of 1.1 m ³ / m ² / hr, a turbid component removal performance of 99%, a fouling resistance of 0.98, a copper removal performance of 38%, and a breaking strength of 5. 5 MPa. The shape and physical properties are as shown in Table 2. This hollow fiber membrane was a composite separation membrane having a layer having a three-dimensional network structure and a porous structure layer containing chelate fine particles, but the adsorbent was placed in relatively large pores in the support layer. Since the adsorbent has a low uniform dispersibility and there are few opportunities for contact with metal ions, the adsorption efficiency of the porous layer containing the adsorbent with respect to metal ions was poor. Further, the film strength is also lowered, which is considered to be caused by an increase in the interface due to the addition of particles having a small diameter in the support layer. When the number of Na atoms (%) as an atom derived from the chelating functional group was measured for the porous structure layer containing the adsorbent of the hollow fiber membrane, the average value X was 0.81 and the standard deviation Y was 0. .90, and chelating functional groups were present in a biased manner. The evaluation results are summarized in Table 2.

<Comparative example 4>
In the same manner as in Example 1, a hollow fiber membrane-shaped support layer was produced. The obtained support layer had a structure in which spherical structures having an average diameter of 3.0 μm were accumulated, and the thickness of the support layer was 250 μm.

  Next, a hollow fiber membrane having a porous turbidity layer formed thereon was produced in the same manner as in Example 5. The obtained porous turbidity layer had a three-dimensional network structure, and the porous turbidity layer had an average pore diameter of 20 nm and a thickness of 50 μm.

The obtained hollow fiber membrane had a pure water permeability of 1.8 m ³ / m ² / hr, a turbid component removal performance of 99%, a fouling resistance of 0.98, a copper removal performance of 0%, and a breaking strength of 8. Since it was 8 MPa and there was no porous adsorption layer, adsorption performance was not shown. The evaluation results are summarized in Table 2.

  Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

According to the present invention, the multi-layer separation having high strength and high fouling resistance, including at least an adsorption layer and a support layer, capable of removing turbidity in water by a surface responsible for turbidity and removing metal ions by the adsorption layer. A membrane is provided. As a result, when applied to the water treatment field, turbid component removal in water and adsorption removal of metal ions can be sufficiently performed.

Claims (11)

A porous adsorption layer containing fine particles having a chelating functional group and a base polymer;
A multilayer separation membrane comprising a porous support layer. 2. The multilayer separation membrane according to claim 1, wherein the fine particles having a chelating functional group have a particle size of 0.15 μm to 3 μm. The porous adsorption layer has at least one of a three-dimensional network structure or a spherical structure;
The multilayer separation membrane according to claim 1 or 2.   The multilayer separation membrane according to any one of claims 1 to 3, wherein the porous adsorption layer has a surface responsible for turbidity. The average value X of the number of atoms (%) of the chelating functional group-derived atoms and the standard deviation Y satisfy X ≧ 3Y when the cross section of the porous adsorption layer is subjected to elemental analysis by energy dispersive X-ray analysis.
The multilayer separation membrane according to any one of claims 1 to 4. The multilayer separation membrane according to claim 5, wherein the chelate functional group-derived atom is at least one selected from the group consisting of N, O, P, S, Na, K, Cu, Fe and B.   The multilayer separation membrane of any one of Claims 1-6 whose thickness of the said porous adsorption layer is 10 micrometers or more and 500 micrometers or less. The multilayer separation membrane according to any one of claims 1 to 7, which is a hollow fiber membrane having an outer diameter of 800 µm or more and 2000 µm or less. The pure water permeation performance at 50 kPa and 25 ° C. is 0.01 m ³ / m ² · hr to 10 m ³ / m ² · hr, the breaking strength is 6 MPa or more, and the breaking elongation is 10% or more. Item 9. The multilayer separation membrane according to any one of Item 8.   The multilayer separation membrane according to any one of claims 1 to 9, wherein the porous adsorption layer is a layer obtained by a thermally induced phase separation method and / or a non-solvent induced phase separation method.   The multilayer separation membrane according to any one of claims 1 to 10, wherein the porous support layer is a layer obtained by a thermally induced phase separation method and / or a non-solvent induced phase separation method.