KR20210035192A - Membrane and method of manufacturing the separation membrane - Google Patents

Abstract

In the present invention, a separation membrane containing polyarylene sulfide as a main component and having a divalent ion blocking rate of 5% or more, and (1) a resin composition preparation step of melt-kneading polyarylene sulfide and a plasticizer to prepare a resin composition, and (2) ) Providing a method for producing a separation membrane comprising a molding step of discharging the resin composition from a discharge orifice to mold a resin molded product at a draft ratio of 20 or more, and (3) an immersion step of obtaining a separator by immersing the resin molded product in a solvent. do.

Description

Separation Membrane and Method of Manufacturing Membrane

The present invention relates to a separation membrane and a method of manufacturing the separation membrane.

Separation membranes are used in a wide range of fields, including water treatment applications for manufacturing industrial water or drinking water by removing turbidity or ions from seawater or sewage water. However, there is a situation in which further improvement of the film strength is required.

As a separation membrane having excellent chemical durability while maintaining moldability, a separation membrane containing polyarylene sulfide as its component is known (Patent Documents 1 to 6). For example, in Patent Document 6, a method of improving the membrane strength by stretching an ultrafiltration membrane of polyarylene sulfide produced by thermal organic phase separation is described.

Japanese Patent Laid-Open Publication No. 60-248202 Japanese Patent Publication No. 2014-189747 Japanese Patent Laid-Open Publication No. 58-67733 Japanese Patent Publication No. 2010-254943 International Publication No. 2015/141540 Japanese Patent Laid-Open No. Hei 7-500527

However, in the conventional separation membrane containing polyarylene sulfide as a component, although it is possible to achieve necessary and sufficient chemical durability, it is not possible to realize the miniaturization of the pore diameter, and a problem is that the separation performance at the level of the nanofiltration membrane cannot be obtained. Had been. In the method described in Patent Document 6, the polyarylene sulfide and the solvent are already phase-separated in a heterogeneous state, and stretching to increase the orientation of the polyarylene sulfide cannot be performed. In addition, although it is mentioned that there is no significant change in the permeation performance due to stretching, the relationship between stretching and separation performance and orientation of the polymer is not shown.

Accordingly, an object of the present invention is to provide a separation membrane and a method of manufacturing the same, which has excellent membrane strength and exhibits high separation performance at the level of a nanofiltration membrane, and further has remarkable permeation performance.

The present invention provides a separation membrane containing polyarylene sulfide as a main component and having a divalent ion blocking rate of 5% or more.

In addition, the present invention is a resin composition preparation step of (1) melt-kneading polyarylene sulfide and a plasticizer to prepare a resin composition,

(2) a molding step of discharging the resin composition from a discharge orifice to mold a resin molded article with a draft ratio of 20 or more;

(3) There is provided a method for producing a separation membrane, comprising an immersion step of immersing the resin molded product in a solvent to obtain a separation membrane.

In addition, the present invention is a resin composition preparation step of (1) melt-kneading polyarylene sulfide and a plasticizer to prepare a resin composition,

(2) a molding step of discharging the resin composition from a discharge orifice to form a resin molded article,

(3) a stretching step of stretching the resin molded article and

(4) There is provided a method for producing a separation membrane including an immersion step of immersing the resin molded product in a solvent to obtain a separation membrane.

According to the present invention, in addition to excellent membrane strength, it is possible to provide a separation membrane and a method for producing the same, capable of realizing high separation performance and permeation performance.

(Composition of the separator)

The separation membrane of the present invention needs to contain polyarylene sulfide (hereinafter, "PAS") including polyphenylene sulfide (hereinafter, "PPS") as a main component.

Here, "having PAS as a main component" means that PAS is the component contained most by mass among all the components of the separation membrane.

The weight average molecular weight (Mw) of the PAS contained in the separation membrane of the present invention is preferably 10,000 to 200,000, more preferably 30,000 to 200,000, in order to increase mechanical properties such as membrane strength while considering moldability. , More preferably 80,000 to 200,000. In addition, the weight average molecular weight (Mw) of PAS can be calculated in terms of polystyrene by gel permeation chromatography (hereinafter "GPC"), which is one type of size exclusion chromatography.

The ratio of PAS to the entire resin contained in the separation membrane is preferably 70 to 100% by mass, more preferably 80 to 100% by mass, and more preferably 90 to 100% by mass in order to increase the film strength such as heat resistance, pressure resistance, and chemical resistance. % Is more preferable.

(Performance and structure of the separator)

The separation membrane of the present invention needs to have a divalent ion blocking rate of 5% or more, but in order to increase the separation performance, the divalent ion blocking rate is preferably 10% or more, more preferably 20% or more, and still more preferably 35% or more. Do.

Here, "divalent ion blocking rate" is supplied to a separation membrane made hydrophilic by immersing in a 10% by mass isopropyl alcohol aqueous solution for 1 hour, using a magnesium sulfate aqueous solution having a concentration of 2,000 ppm as feed water, and supplying it at a temperature of 25°C and an operating pressure of 0.75 MPa. It refers to the magnesium sulfate blocking rate at the time of filtering treatment.

The separation membrane of the present invention preferably has an average pore diameter D of 1 to 10 nm, and more preferably 5 to 10 nm, in order to achieve both separation performance and transmission performance. In the separation membrane of the present invention, it is assumed that the average pore diameter of the pores plays a role of reducing the effective film thickness of the membrane and improving the permeation performance. If the average pore diameter of the pores is too large, the permeated liquid flows only into the pores, and there is a fear that the separation performance may be deteriorated. If the pores are too small, there is a concern that the water permeability performance may be deteriorated. The pores here mean pores having a pore diameter of 1 nm or more as observed by a scanning electron microscope, a transmission electron microscope, or an atomic force microscope.

The average pore diameter D of the pores of the separation membrane can be determined as follows. First, the separator frozen with liquid nitrogen is cut with a razor or a microtome. The section Z of the cut separation membrane was observed with a scanning electron microscope, a transmission electron microscope, or an atomic force microscope, and from one surface of the separation membrane, in order, in the direction of the thickness of the separation membrane, each region 1 to 5 divided at equal intervals. Set 5. In each of the regions 1 to 5, the pore diameter d of all the pores included in the square microscope image in which the center of each region is observed is calculated, and _{the arithmetic mean of the n values d 1} to d n is calculated as the pores of the separation membrane. It can be set as the void D Further, the microscopic image is made to be a square in which 5 to 100 times the average pore diameter D of the pores is a length of one side.

Here, the pore diameter d of each pore can be calculated by the following equation (1) by measuring the area S of the pore in the microscope image by image processing, assuming a true circular hole of the same area.

d(m)=(4×S/π) ^0.5 … Equation (1)

In addition, the film thickness of the separation membrane can be calculated as the average value of the cross-section Z being photographed with a scanning electron microscope, measuring the thickness of 10 randomly selected films. The membrane thickness of the separation membrane is preferably 2 to 50 µm, more preferably 3 to 40 µm, and still more preferably 4 to 30 µm in order to achieve both membrane strength and permeation performance.

The separation membrane of the present invention has a porosity of preferably 45% or less, more preferably 5 to 45%, further preferably 10 to 40%, and 15 in order to make the membrane strength and separation performance and permeation performance compatible. It is even more preferable that it is %-35%.

The porosity ε of the separation membrane can be calculated by the following equation (2) when the density of the separation membrane is vacuum-dried for 8 hours at 25°C and the density of the _{separation membrane is ρ 1} and the density of the resin contained in the separation membrane is ρ _2. .

ε(%)=(1-ρ ₁ /ρ ₂ )×100… Equation (2)

More specifically, for example, when the shape of the separation membrane is a hollow fiber, that is, when the separation membrane is a hollow fiber membrane, the density ρ ₁ of the hollow fiber membrane is, after measuring the length L of the hollow fiber membrane, vacuum drying for 8 hours under the condition of 25°C. When the mass M of the obtained hollow fiber membrane is measured, and the outer diameter of the hollow fiber membrane is D ₁ and the inner diameter is D ₂ , it can be calculated by the following formula (3).

ρ ₁ (g/cm 3 )=M/[π×{(D ₁ /2) ² -(D ₂ /2) ² }×L]… Equation (3)

In addition, the outer diameter D ₁ and the inner diameter D ₂ of the hollow fiber membrane can be calculated as the average value of each of the cross-section Z being photographed with a scanning electron microscope, measuring the outer diameters and the inner diameters of 10 randomly selected locations. In addition, the void ratio can be calculated by the following formula (4) from the calculated values _{of the outer diameter D 1} and the inner diameter D _{2 of the hollow fiber membrane.}

Hollow ratio (%) = (D ₂ ² /D ₁ ² )×100… Equation (4)

The shape of the separation membrane of the present invention is not particularly limited, but a hollow fiber-shaped separation membrane (hereinafter, "hollow fiber membrane") or a planar membrane (hereinafter, "flat membrane") is preferably employed. Among these, the hollow fiber membrane is more preferable because it can efficiently fill the module and the effective membrane area per unit volume of the module can be large.

The outer diameter D ₁ of the hollow fiber membrane is preferably 20 to 200 μm, and more preferably 40 to 150 μm, in order to increase the effective membrane area and membrane strength when the hollow fiber membrane is filled in the module. Moreover, it is preferable that it is 3 to 70%, and, as for the void ratio, it is more preferable that it is 10 to 70% from the relationship between the pressure loss of the fluid flowing through a hollow part and a buckling pressure.

The separation membrane of the present invention preferably has a curvature ratio of 5 to 500 in order to achieve both separation performance and permeation performance, more preferably 20 to 250 in order to further increase the separation performance while maintaining sufficient permeation performance, and 40 It is more preferable that it is -100, and it is especially preferable that it is 40-60. The curvature rate is a physical property value indicating the linearity of the flow path in the separation membrane. From the viewpoint of permeability, the smaller the value of the curvature rate is, the more preferable it is, but the theoretical lower limit is 1.0.

The curvature rate of the separation membrane can be calculated by the following equation (5) when the pore void (m) of the separation membrane is D, the porosity (%) is ε, and the transmission coefficient (m 2) is k.

Curvature rate (-)=(D/4)×√(ε/200k)… Equation (5)

k can be calculated by the following equation (6) when the shape of the separation membrane is a flat membrane. In addition, k can be calculated by the following formula (7) when the separation membrane is a hollow fiber membrane.

k(m²)=Q×μ×x/(P×A)… Equation (6)

k(㎡)=(Q×μ×ln(D ₁ /D ₂ ))/(2π×L×P)… Equation (7)

Where Q is the membrane permeation flow rate of water (㎥/s), μ is the viscosity of water (Pa·s), x is the film thickness (m), P(Pa) is the applied pressure, A is the membrane area (㎡), D ₁ Is the outer diameter of the hollow fiber membrane (µm), D ₂ is the inner diameter of the hollow fiber membrane (µm), and L is the length of the hollow fiber membrane (m).

In the separator of the present invention, in order to increase the breaking strength and ion blocking performance, the degree of orientation is preferably 1.04 or more, more preferably 1.10 or more, even more preferably 1.50 or more, even more preferably 1.55 or more, and particularly 2.00 or more. It is preferable, and it is most preferable that it is 3.00 or more. It is estimated that in the separation membrane of the present invention, by taking a dense structure in which polyarylene sulfide chains are oriented, a fine structure at the molecular level is formed, and a high separation performance capable of blocking ions is expressed.

The degree of orientation of the separation membrane can be calculated based on the measurement result of laser Raman.

In addition, the breaking strength, when the separation membrane is a hollow fiber membrane, under the conditions of a temperature of 20°C and a humidity of 65%, a sample length of 50 mm and a tensile speed of 100 mm/min, a tensile test in the long axis direction of the separation membrane was repeated 5 times, The average tensile strength value can be calculated as the breaking strength (tensile strength) (MPa). In addition, when the separation membrane is a flat membrane, the tensile test in the longitudinal direction of the separation membrane was repeated 5 times under conditions of a temperature of 20°C and a humidity of 65%, a sample length of 50 mm, a sample width of 10 mm, and a tensile speed of 100 mm/min The average tensile strength value can be calculated as the breaking strength (MPa). Moreover, as a tensile tester used for a tensile test, Tensilon UCT-100 (made by Orrientech) is mentioned, for example. In order to suppress membrane breakage during filtration, when the separation membrane is a hollow fiber membrane, 20 MPa or more is preferable, 30 MPa or more is more preferable, and 60 MPa or more is particularly preferable.

(Method of manufacturing a separator)

The manufacturing method of the separation membrane of the present invention includes (1) a process for preparing a resin composition in which PAS and a plasticizer are melt-kneaded to prepare a resin composition, and (2) the resin composition is discharged from a discharge orifice, and a resin molded product at a draft ratio of 20 or more. And (3) an immersion step of immersing the resin molded product in a solvent to obtain a separation membrane.

In order to increase the orientation degree of the resin molded product, the method for producing the separation membrane preferably includes a stretching step of stretching the resin molded product after the step (2).

Another aspect of the method for producing a separator of the present invention includes (1) a process for preparing a resin composition in which PAS and a plasticizer are melt-kneaded to prepare a resin composition, and (2) the resin composition is discharged from a discharge orifice, and a resin molded product And (3) a stretching step of stretching the resin molded product, and (4) an immersion step of immersing the resin molded product in a solvent to obtain a separation membrane.

As a method of melt-kneading PAS and a plasticizer in the process for preparing a resin composition provided by the method for producing a separator of the present invention, for example, a kneader, a roll mill, a Banbury mixer, or a mixer such as a single-screw or twin-screw extruder is used. Although it may be mentioned, in order to improve the dispersibility of a plasticizer, etc., a twin screw extruder is preferable, and a twin screw extruder with vent holes capable of removing volatile matter is more preferable.

The ratio of PAS to the resin composition prepared in the resin composition preparation step is preferably 55 to 90% by mass, more preferably 60 to 80% by mass, in order to make the membrane strength and separation performance and permeation performance of the obtained separation membrane compatible. desirable.

In addition, the ratio of the plasticizer to the resin composition prepared in the resin composition preparation step is preferably 10 to 45% by mass, and 20 to 40% by mass in order to achieve both the membrane strength and separation performance and permeation performance of the obtained separation membrane. It is more preferable.

The "plasticizer" provided in the resin composition preparation step refers to a compound that thermally plasticizes PAS, and preferably, a Hansen solubility parameter in the range of ^{15.0 to 48.0 MPa 1/2, refers to a compound that thermally plasticizes PAS.} In order to obtain a uniform resin composition with PAS, it is more preferable that the ^{plasticizer has a Hansen solubility parameter in the range of 18.0 to 38.0 MPa 1/2.} As for the Hansen solubility parameter, the value accepted in the software "Hansen Solubility Parameter in Practice" developed by Charles Hansen et al. was used. The three-dimensional Hansen solubility parameter of a plasticizer or polymer that is not described in the software can be calculated by the Hansen's old method using the software.

As a plasticizer, for example, cyclic PPS oligomer, linear PPS oligomer, polyethylene glycol, polyetherimide, polyetherimide oligomer, polyamide, polyamide oligomer, aromatic polyester, aromatic polyester oligomer, polyvinylidene fluoride, polyvinyl Pyrrolidone, copolymer of polyvinylpyrrolidone and vinyl acetate, cellulose ester, polyphenyl ether, polysulfone, benzophenone, diphenyl ether, diphenyl sulfone, diphenyl sulfide, 4,4'-dibromobi Phenyl, 1-phenylnaphthalene, 2,5-diphenyl-1,3,4-oxadiazole, 2,5-diphenyloxazole, triphenylmethanol, N,N-diphenylformamide, benzyl, anthracene, 4-benzoylbiphenyl, dibenzoylmethane, 2-biphenylcarboxylic acid, dibenzothiophene, pentachlorophenol, 1-benzyl-2-pyrrolidione, 9-fluorenone, 2-benzoylnaphthalene, 1-bro Monaphthalene, 1,3-diphenoxybenzene, fluorene, 1-phenyl-2-pyrrolidinone, 1-methoxynaphthalene, 1-ethoxynaphthalene, 1,3-diphenylacetone, 1,4-di Benzoylputane, phenanthrene, 4-benzoylbiphenyl, 1,1-diphenylacetone, 0,0'-biphenol, 2,6-diphenylphenol, triphenylene, 2-phenylphenol, thianthrene, 3- Phenoxybenzyl alcohol, 4-phenylphenol, 9,10-dichloroanthracene, triphenylmethane, 4,4'-dimethoxybenzophenone, 4,4'-difluorobenzophenone, 4,4'-dichlorobenzophenone , 4,4'-dibromobenzophenone, 9,10-diphenylanthracene, fluoranthene, diphenylphthalate, diphenylcarbonate, 2,6-dimethoxynaphthalene, 2,7-dimethoxynaphthalene, 4-bromodiphenyl ether, pyrene, 9,9'-bi-fluorene, 4,4'-isopropylidene-diphenol, epsilon-caprolactam, N-cyclohexyl-2-pyrrolidone, diphenyliso Phthalate, diphenylterphthalate, 1-chloronaphthalene, or N-methyl-2-pyrrolidone (hereinafter referred to as ``NMP''), but since the molecular weight is small and the dissolution is easy afterwards, cyclic PPS oligomer, linear PPS Oligomer, benzophenone, diphenyl isophthalate, diphenyl terphthalate, diphenyl sulfone or diphenyl sulfide are preferred, and cyclic PPS oligomers without the influence of terminal functional groups Is more preferable. By using the cyclic PPS oligomer having the same basic structure as the PAS as a plasticizer, the resin composition and the resin molded product are in a uniformly compatible state, and winding and stretching can be performed at a high draft ratio.

The resin composition prepared in the resin composition preparation step may contain additives other than PAS and a plasticizer.

Examples of such additives include resins such as cellulose ether, polyacrylonitrile, polyolefin, polyvinyl compound, polycarbonate, poly(meth)acrylate, polysulfone or polyethersulfone, antioxidants, organic lubricants, Crystal nucleating agent, organic particle, inorganic particle, terminal blocker, chain extender, ultraviolet absorber, infrared absorber, color inhibitor, matting agent, antibacterial agent, antistatic agent, deodorant, flame retardant, weathering agent, antistatic agent, antioxidant, ion exchange agent , An antifoaming agent, a colored pigment, an optical brightener, or a dye.

The resin composition prepared in the resin composition preparation step may be pelletized once, melted again, and then provided to the molding step, or may be directly provided to the molding step without pelletizing.

In the molding process provided by the method for producing a separation membrane of the present invention, for example, a hollow resin molded product that can become a hollow fiber membrane by using a double annular nozzle in which a gas flow path is arranged in the center as a discharge confinement, that is, a hollow You can mold the yarn. The resin composition may be discharged into the air from the discharge port, and the resin molded product may be molded by being cooled by a cooling device.

The resin molded product may be wound up by a winding device. In this case, the value of the draft ratio represented by the winding speed by the winding device/the discharge speed from the discharging cage needs to be 20 or more in order to increase the degree of orientation of the obtained separation membrane, but it is preferable to be 1,000 or less in order to perform spinning without breaking the thread. And, it is more preferable that it is 50-900, it is still more preferable that it is 70-850, and it is still more preferable that it is 100-800. In addition, from the viewpoint of increasing the degree of orientation of the obtained separation membrane, the ratio of PAS to the resin composition prepared in the resin composition preparation step is preferably 55 to 90% by mass, and more preferably 60 to 80% by mass.

Moreover, it is preferable that it is 1.05 or more, as for the orientation degree of a resin molded article, it is more preferable that it is 1.10 or more, and it is still more preferable that it is 1.25 or more.

The degree of orientation of the resin molded product can be calculated by a method similar to the degree of orientation of the separation membrane.

As a manufacturing method of the separation membrane of the present invention, it is preferable to include a stretching step of stretching a resin molded article after the resin composition preparation step. The degree of orientation of the separation membrane obtained by stretching the resin molded product formed in the molding step can be increased. The resin molded product may be wound up once by a winding device, and after unwinding it again, it may be provided to the stretching step, or may be directly provided to the stretching step.

As a method of stretching in the stretching step that the method for producing a separation membrane of the present invention may be equipped with, for example, a method of heating a resin molded product while conveying it on a heating roll, and stretching using a difference in circumferential speed between the heating rolls, or , A method of conveying and heating in a dry heat oven or a warm solvent, and stretching using the difference in circumferential speed between the heating rolls is mentioned. The stretching may be performed in a single stage, or in multiple stages of two or more stages.

The temperature at which the resin molded product is stretched is preferably 40 to 120°C, more preferably 60 to 110°C, even more preferably 80 to 110°C, and 85 to 95°C in order to increase the orientation degree of the resin molded product (after stretching). It is particularly preferred. Further, the draw ratio (when performing multi-stage stretching, the total draw ratio) is preferably 1.2 to 5.0 times, more preferably 1.4 to 4.5 times, and still more preferably 1.6 to 4.0 times. Further, in order to increase the degree of orientation of the resin molded product (after stretching), the stretching speed is preferably 20 cm/min or more, more preferably 200 cm/min or more, and particularly preferably 4000 cm/min or more.

The orientation degree of the resin molded article after stretching is preferably 1.20 or more, more preferably 1.60 or more, still more preferably 2.00 or more, and particularly preferably 3.00 or more.

The orientation degree of the resin molded article after stretching can be calculated by a method similar to the orientation degree of the separation membrane.

The solvent used in the immersion step provided in the method for producing the separation membrane of the present invention is not particularly limited as long as it dissolves the plasticizer, but a solvent that is difficult to dissolve PAS and easily dissolves the plasticizer is preferred, and NMP, tetrahydrofuran , 1-chloronaphthalene, chloroform, paraxylene, benzene, dimethylformamide, or dimethylacetamide is more preferable.

Example

The present invention will be described in more detail by showing examples below, but the present invention is not limited thereto.

[Measurement method and evaluation method]

(1) Measurement of the weight average molecular weight (Mw) of PAS

The measurement conditions of GPC were carried out in this way.

Device: SSC-7100 (manufactured by Senshu Chemical)

Column name: GPC3506 (Senshu Chemical Co., Ltd.)

Eluent: 1-chloronaphthalene

Detector: differential refractive index detector

Column temperature: 210 °C

Free bath temperature: 250℃

Pump bath temperature: 50℃

Detector temperature: 210℃

Flow: 1.0 mL/min

Sample injection volume: 300 μL (sample concentration: about 0.2% by mass)

Standard material: Polystyrene (made by PSS; ps8124, ps12034, ps18074, ps23025)

(2) the average pore diameter of the pores

The separator frozen in liquid nitrogen is cut with a razor. The cross section Z of the cut separation membrane was observed with an atomic force microscope (Dimension FastScan manufactured by Bruker AXS). In the case of a hollow fiber membrane, each of regions 1 to 5 divided into 5 at equal intervals in order from three outer surfaces of the separation membrane in the direction of the thickness of the separation membrane are set, respectively. In the case of a flat membrane, each region 1 to 5 divided into 5 at equal intervals in order from 3 places on one surface in the film thickness direction of the separation membrane is set, respectively. In each of the regions 1 to 5, a 200 nm square region was observed at the center of each region. The pore diameter d of all the pores contained in this microscopic image was calculated, and _{the arithmetic average of the n values d 1} to d _{n was taken} as the pore average pore diameter D of the separation membrane.

(3) Orientation of separation membrane and resin molding

Using a separation membrane vacuum-dried for 8 hours under the condition of 25°C as a sample, using a near-infrared Raman spectroscopy device, the longitudinal direction (MD) of the sample and the direction perpendicular to the longitudinal direction (the width direction of the flat membrane or the hollow fiber membrane For radial direction) (TD), ^{the band around 1,080 cm -1} of the Raman spectrum (sulfide bond (-Ph-S-Ph-)), and ^{the band around 745 cm -1} (phenyl ring out-of-plane variable angle vibration) The strength was measured respectively.

The degree of orientation of the membrane is DO, LA 1,080㎝ the intensity of each band in the vicinity _^-1-MD I _{P, I-P} and _TD, 745㎝ ^-1 strength, respectively in the vicinity of the _band-MD I _E, I _{E TD-la} When it did, it can calculate by following formula (8).

Moreover, about the orientation degree of a resin molded object and a resin molded object after extending|stretching, it measured and calculated similarly to the orientation degree of a separation membrane.

DO(-)=(I _P-MD /I _E-MD )/(I _P-TD /I _E-TD )… Equation (8)

Specific measurement conditions were carried out in this way.

Apparatus: Near-infrared Raman spectroscopy (Photon Design)

Condition: measurement mode; Brown rice raman

objective; ×20

Beam diameter; 5㎛

Cross slit: 500㎛

Light source; YAG laser/1,064nm

Laser power; 1W

Diffraction grating; Single 300gr/㎜

Slits; 100㎛

Detector; InGaAs (made by Nippon Roper)

(4) Membrane permeation flow rate of the membrane

The separation membrane was immersed in a 10% by mass isopropyl alcohol aqueous solution for 1 hour to make hydrophilic water, and was supplied with a 2,000 ppm magnesium sulfate aqueous solution as feed water at a temperature of 25°C and an operating pressure of 0.75 MPa, followed by filtration treatment, and the area of the separation membrane and Based on the obtained permeate amount, the membrane permeation flow rate was calculated by the following equation (9).

Membrane permeation flow rate (㎥/m²/day/MPa)=1 permeated water per day/membrane area/0.75… Equation (9)

In addition, when the separation membrane is a hollow fiber membrane, a small module filled with the hollow fiber membrane was prepared and the filtration treatment was performed.

More specifically, the hollow fiber membrane is tied so that the membrane area based on the outer diameter is 0.1 m 2, inserted into a plastic pipe, the end of the hollow fiber membrane bundle and the gap between the pipe are sealed with thermosetting resin, and then the small module is cut off at both ends. Got it.

(5) Divalent ion blocking rate of the separation membrane

The electrical conductivity in the feed water and permeate water in the evaluation of the membrane permeation flow rate was measured with an electric conductivity meter, and the divalent ion blocking rate was calculated by the following equation (10).

Divalent ion blocking rate (%) = 100×{1-(electrical conductivity of permeated water/electrical conductivity of supplied water)}… Equation (10)

(6) Porosity of the separator

The porosity ε of the separation membrane was calculated by the following equation (2) when the density of the separation membrane was vacuum-dried for 8 hours at 25°C and the density of the _{separation membrane was ρ 1} and the density of the resin contained in the separation membrane was ρ _2.

ε(%)=(1-ρ ₁ /ρ ₂ ) ×100… Equation (2)

When the shape of the separation membrane is hollow fiber, that is, when the separation membrane is a hollow fiber membrane, the density ρ ₁ of the hollow fiber membrane is measured after measuring the length L of the hollow fiber membrane, and then the mass M of the hollow fiber membrane vacuum-dried for 8 hours at 25°C. Further, the outer diameter of the hollow fiber membrane was set to D ₁ , and the inner diameter was set to D ₂ , and was calculated by the following formula (3).

ρ ₁ (g/cm 3 )=M/[π×{(D ₁ /2) ² -(D ₂ /2) ² }×L]… Equation (3)

In addition, as for the outer diameter D ₁ and the inner diameter D ₂ of the hollow fiber membrane, the cross section Z was photographed with a scanning electron microscope, and the outer diameters and inner diameters of 10 randomly selected locations were measured, and each of them was calculated as an average value. In addition, the void ratio was calculated by the following formula (4) from the calculated values _{of the outer diameter D 1} and the inner diameter D _{2 of the hollow fiber membrane.}

Hollow ratio (%) = (D ₂ ² /D ₁ ² )×100… Equation (4)

(7) The curvature rate of the separator

The curvature rate of the separation membrane was calculated by the following equation (5), with the pore void (m) of the separation membrane as D, the porosity (%) as ε, and the transmission coefficient (m2) as k.

Curvature rate (-)=(D/4)×√(ε/200k)… Equation (5)

k was calculated by the following formula (6) when the shape of the separation membrane was a flat membrane. In addition, k was calculated by the following formula (7) when the separation membrane was a hollow fiber membrane.

k(m²)=Q×μ×x/(P×A)… Equation (6)

k(㎡)=(Q×μ×ln(D ₁ /D ₂ ))/(2π×L×P)… Equation (7)

Here, Q is the membrane permeation flow rate of water (㎥/s), μ is the viscosity of water (Pa·s), x is the film thickness (m), P(Pa) is the applied pressure, A is the membrane area (㎡), D ₁ Is the outer diameter of the hollow fiber membrane (µm), D ₂ is the inner diameter of the hollow fiber membrane (µm), and L is the length of the hollow fiber membrane (m).

(8) breaking strength

Breaking strength is, when the separation membrane is a hollow fiber membrane, under the conditions of a temperature of 20°C and a humidity of 65%, a tensile strength test in the long axis direction of the separation membrane is repeated 5 times under conditions of a sample length of 50 mm and a tensile speed of 100 mm/min. The average value was calculated as the breaking strength (tensile strength) (MPa). In addition, when the separation membrane is a flat membrane, the tensile test in the longitudinal direction of the separation membrane was repeated 5 times under conditions of a temperature of 20°C and a humidity of 65%, a sample length of 50 mm, a sample width of 10 mm, and a tensile speed of 100 mm/min. The average tensile strength was calculated as the breaking strength (MPa). Further, as a tensile tester used for the tensile test, Tensilon UCT-100 (manufactured by Orientech Co., Ltd.) was used.

[Preparation of cyclic PPS oligomer mixture]

In a 70 L autoclave equipped with a stirrer, 8.27 kg of 47.5 mass% aqueous sodium hydroxide solution (70.0 mol), 2.96 kg of 96 mass% aqueous sodium hydroxide solution (71.0 mol), 11.44 kg of NMP (116.0 mol), 1.72 kg of acetic acid Sodium (21.0 mol) and 10.5 kg of ion-exchanged water were added, and slowly heated to about 240° C. over about 3 hours while passing nitrogen gas at normal pressure, and 14.8 kg of water and 280 g of NMP were added through a rectification tower. After flowing out, the autoclave was cooled to 160°C. Further, during this liquid removal operation, 0.02 mol of hydrogen sulfide per mol of the added sulfur component was scattered out of the system.

Then, 10.3 kg of p-dichlorobenzene (70.3 mol) and 9.00 kg of NMP (91.0 mol) were added to the autoclave, and the autoclave was sealed under nitrogen gas. While stirring the content at 240 rpm, the temperature was raised to 270° C. at a rate of 0.6° C./min, and maintained at this temperature for 140 minutes. Thereafter, 1.26 kg of water (70.0 mol) was press-in over 15 minutes, cooling to 250°C at a rate of 1.3°C/min, further cooling to 220°C at a rate of 0.4°C/min, and then rapid cooling to near room temperature. Thus, a slurry <1> was obtained. This slurry <1> was diluted with 20.0 kg of NMP to obtain a slurry <2>. 10 kg of slurry <2> heated to 80° C. was filtered through a sieve (80 mesh, eye size 0.175 mm) to obtain a granular PPS resin containing a slurry as a mesh-on component. Moreover, 7.5 kg of slurry <3> was obtained as a filtrate component.

1,000 g of the obtained slurry <3> was put into a rotary evaporator, substituted with nitrogen gas, and then treated at 100 to 150°C for 1.5 hours under reduced pressure, and then treated at 150°C for 1 hour in a vacuum dryer to obtain a solid. To this solid, 1,200 g (1.2 times the amount of slurry <3>) of ion-exchanged water was added, followed by stirring at 70° C. for 30 minutes to re-slurry. This slurry was suction filtered through a glass filter having an eye size of 10 to 16 μm. 1,200 g of ion-exchanged water was added to the obtained white cake, stirred at 70° C. for 30 minutes to re-slurry, and similarly, after suction filtration, and vacuum dried at 70° C. for 5 hours, 11.0 g of a PPS mixture <1> was obtained. As a result of performing GPC measurement of this PPS mixture <1>, the number average molecular weight (Mn) was 5,200 and the weight average molecular weight (Mw) was 28,900, and as a result of analyzing the chromatogram, the mass fraction of the component having a molecular weight of 5,000 or less was 39%. , The mass fraction of the component having a molecular weight of 2,500 or less was 32%. 5 g of the PPS mixture <1> was aliquoted, and 120 g of chloroform was used as a solvent, and the PPS mixture <1> was brought into contact with the solvent for 3 hours by Soxhlet extraction at a bath temperature of about 80°C to obtain an extract slurry. The obtained extract slurry was in the form of a slurry containing some solid components at room temperature.

After distilling chloroform from the extract slurry using an evaporator, it was treated in a vacuum dryer at 70°C for 3 hours to obtain 2.1 g of a solid (a yield of 42% based on a PPS mixture <1>). Infrared spectroscopic analysis of the thus obtained solid (device: FTIR-8100A manufactured by Shimadzu Corporation), high-performance liquid chromatography (apparatus: LC-10 manufactured by Shimadzu Corporation; column: C18; detector: photodiode array) From the mass spectrum analysis of the components (equipment: M-1200H manufactured by Hitachi) and the molecular weight information by MALDI-TOF-MS, it was found that this solid was a mixture containing as a main component a cyclic PPS oligomer having 4 to 12 repeating units.

(Example 1)

Commercially available PPS ("Torrelina (registered trademark) E1380" manufactured by Toray; ρ ₂ is 1.34 (g/cm 3 )) 60.0 mass% and cyclic PPS oligomer 40.0 mass% are melt-kneaded at 300°C with a twin screw extruder. After homogenization, pelletization was carried out to obtain a resin composition for melt spinning.

The dried resin composition was supplied to a twin-screw extruder, melt-kneaded at 300°C, and then introduced into a melt spinning pack at a spinning temperature of 300°C, and under the condition of a discharge amount of 30 g/min, a detent hole (three arc-shaped slits were arranged. A type forming one discharge hole, a discharge hole radius of 0.86 mm, a slit pitch of 0.10 mm, and a slit width of 0.12 mm) were discharged downward from a discharge port having 12 holes. The hollow fiber molded by this discharge is guided to a cooling device (1m in length) so that the distance L from the lower surface of the discharge cap to the top of the cooling device (chimney) is 30 mm, and a cooling wind at 25°C and a wind speed of 1.5m/sec. After cooling by, and applying an oil agent to converge, it was wound up with a winder so that the draft ratio became 58.0, and a hollow fiber (resin molded product) was obtained. The hollow fiber was stretched under the conditions of a temperature of 90.0°C, a magnification of 3.3, and a stretching speed of 4000.0 cm/min, and then immersed in NMP at 25°C for 12 hours to dissolve and remove the cyclic PPS oligomer. Table 1 shows the physical properties of the obtained separation membrane.

(Example 2)

Commercially available PPS (Toray's "Torrelina (registered trademark) E1380") 60.0 mass% and cyclic PPS oligomer 40.0 mass% are melt-kneaded at 300°C with a twin screw extruder, homogenized, and pelletized, and then melted. The used resin composition was obtained.

The dried resin composition was supplied to a twin-screw extruder, melt-kneaded at 300°C, and then introduced into a melt spinning pack at a spinning temperature of 300°C, and under the condition of a discharge amount of 30 g/min, a detent hole (three arc-shaped slits were arranged. A type forming one discharge hole, a discharge hole radius of 0.86 mm, a slit pitch of 0.10 mm, and a slit width of 0.12 mm) were discharged downward from a discharge port having 12 holes. The hollow fiber molded by this discharge is guided to a cooling device (1m in length) so that the distance L from the lower surface of the discharge port to the top of the cooling device is 30mm, and cooled by a cooling wind at 25°C and a wind speed of 1.5m/sec. Then, after applying an oil agent and performing the procedure, it was wound up with a winder so that the draft ratio became 58.0, and a hollow fiber (resin molded product) was obtained. This hollow fiber was immersed in NMP at 25° C. for 12 hours to dissolve and remove the cyclic PPS oligomer. Table 1 shows the physical properties of the obtained separation membrane.

(Example 3)

Commercially available PPS (Toray's "Torrelina (registered trademark) E1380") 60.0 mass% and cyclic PPS oligomer 40.0 mass% are melt-kneaded at 300°C with a twin-screw extruder, homogenized, and pelletized. The used resin composition was obtained.

The dried resin composition was supplied to a twin-screw extruder and melt-kneaded at 300°C, and then introduced into a melt-spinning pack at a spinning temperature of 300°C. A type forming one discharge hole, a discharge hole radius of 0.86 mm, a slit pitch of 0.10 mm, and a slit width of 0.12 mm) were discharged downward from a discharge port having 12 holes. The hollow fiber molded by this discharge is guided to a cooling device (1m in length) so that the distance L from the lower surface of the discharge port to the top of the cooling device is 30mm, and cooled by a cooling wind at 25°C and a wind speed of 1.5m/sec. Then, after applying an oil agent to perform the procedure, it was wound up with a winder so that the draft ratio was 72.0 to obtain a hollow fiber (resin molded product). This hollow fiber was immersed in NMP at 25° C. for 12 hours to dissolve and remove the cyclic PPS oligomer. Table 1 shows the physical properties of the obtained separation membrane.

(Example 4)

Commercially available PPS ("Torrelina (registered trademark) E1380" manufactured by Toray; ρ ₂ is 1.34 (g/cm 3 )) 60.0 mass% and cyclic PPS oligomer 40.0 mass% are melt-kneaded at 300°C with a twin screw extruder. After homogenization, pelletization was carried out to obtain a resin composition for melt spinning.

The dried resin composition was supplied to a twin-screw extruder, melt-kneaded at 300°C, and then introduced into a melt spinning pack at a spinning temperature of 300°C, and under the condition of a discharge amount of 30 g/min, a detent hole (three arc-shaped slits were arranged. A type forming one discharge hole, a discharge hole radius of 0.86 mm, a slit pitch of 0.10 mm, and a slit width of 0.12 mm) were discharged downward from a discharge port having 12 holes. The hollow fiber molded by this discharge is guided to a cooling device (1m in length) so that the distance L from the lower surface of the discharge cap to the top of the cooling device (chimney) is 30 mm, and a cooling wind at 25°C and a wind speed of 1.5m/sec. After cooling by, and applying an oil agent to converge, it was wound up with a winder so that the draft ratio became 58.0, and a hollow fiber (resin molded product) was obtained. The hollow fiber was stretched under the conditions of a temperature of 85.0°C, a magnification of 2.0 times, and a stretching speed of 300.0 cm/min, and then immersed in NMP at 25°C for 12 hours to dissolve and remove the cyclic PPS oligomer. Table 1 shows the physical properties of the obtained separation membrane.

(Example 5)

Commercially available PPS ("Torrelina (registered trademark) E1380" manufactured by Toray; ρ ₂ is 1.34 (g/cm 3 )) 60.0 mass% and cyclic PPS oligomer 40.0 mass% are melt-kneaded at 300°C with a twin screw extruder. After homogenization, pelletization was carried out to obtain a resin composition for melt spinning.

The dried resin composition was supplied to a twin-screw extruder, melt-kneaded at 300°C, and then introduced into a melt spinning pack at a spinning temperature of 300°C, and under the condition of a discharge amount of 30 g/min, a detent hole (three arc-shaped slits were arranged. A type forming one discharge hole, a discharge hole radius of 0.86 mm, a slit pitch of 0.10 mm, and a slit width of 0.12 mm) were discharged downward from a discharge port having 12 holes. The hollow fiber molded by this discharge is guided to a cooling device (1m in length) so that the distance L from the lower surface of the discharge cap to the top of the cooling device (chimney) is 30 mm, and a cooling wind at 25°C and a wind speed of 1.5m/sec. After cooling by, and applying an oil agent to converge, it was wound up with a winder so that the draft ratio became 58.0, and a hollow fiber (resin molded product) was obtained. After stretching this hollow fiber under the conditions of a temperature of 85.0°C, a magnification of 2.0 times, and a stretching speed of 20.0 cm/min, it was immersed in NMP at 25°C for 12 hours to dissolve and remove the cyclic PPS oligomer. Table 1 shows the physical properties of the obtained separation membrane.

(Example 6)

Commercially available PPS ("Torrelina (registered trademark) E1380" manufactured by Toray; ρ ₂ is 1.34 (g/cm 3 )) 60.0 mass% and cyclic PPS oligomer 40.0 mass% are melt-kneaded at 300°C with a twin screw extruder. After homogenization, pelletization was carried out to obtain a resin composition for melt spinning.

The dried resin composition was supplied to a twin-screw extruder, melt-kneaded at 300°C, and then introduced into a melt spinning pack at a spinning temperature of 300°C, and under the condition of a discharge amount of 30 g/min, a detent hole (three arc-shaped slits were arranged. A type forming one discharge hole, a discharge hole radius of 0.86 mm, a slit pitch of 0.10 mm, and a slit width of 0.12 mm) were discharged downward from a discharge port having 12 holes. The hollow fiber molded by this discharge is guided to a cooling device (1m in length) so that the distance L from the lower surface of the discharge cap to the top of the cooling device (chimney) is 30 mm, and a cooling wind at 25°C and a wind speed of 1.5m/sec. After cooling by, and applying an oil agent to converge, it was wound up with a winder so that the draft ratio became 58.0, and a hollow fiber (resin molded product) was obtained. The hollow fiber was stretched under the conditions of a temperature of 85.0°C, a magnification of 1.5 times, and a stretching speed of 200.0 cm/min, and then immersed in NMP at 25°C for 12 hours to dissolve and remove the cyclic PPS oligomer. Table 1 shows the physical properties of the obtained separation membrane.

(Example 7)

Commercially available PPS ("Torrelina (registered trademark) E1380" manufactured by Toray; ρ ₂ is 1.34 (g/cm 3 )) 60.0 mass% and cyclic PPS oligomer 40.0 mass% are melt-kneaded at 300°C with a twin screw extruder. After homogenization, pelletization was carried out to obtain a resin composition for melt spinning.

The dried resin composition was supplied to a twin-screw extruder, melt-kneaded at 300°C, and then introduced into a melt spinning pack at a spinning temperature of 300°C, and under the condition of a discharge amount of 30 g/min, a detent hole (three arc-shaped slits were arranged. A type forming one discharge hole, a discharge hole radius of 0.86 mm, a slit pitch of 0.10 mm, and a slit width of 0.12 mm) were discharged downward from a discharge port having 12 holes. The hollow fiber molded by this discharge is guided to a cooling device (1m in length) so that the distance L from the lower surface of the discharge cap to the top of the cooling device (chimney) is 30 mm, and a cooling wind at 25°C and a wind speed of 1.5m/sec. After cooling by, and applying an oil agent to converge, it was wound up with a winder so that the draft ratio became 58.0, and a hollow fiber (resin molded product) was obtained. The hollow fiber was stretched under the conditions of a temperature of 85.0°C, a magnification of 1.5 times, and a stretching speed of 20.0 cm/min, and then immersed in NMP at 25°C for 12 hours to dissolve and remove the cyclic PPS oligomer. Table 1 shows the physical properties of the obtained separation membrane.

(Example 8)

Commercially available PPS (Toray's "Torrelina (registered trademark) E1380") 60.0 mass% and cyclic PPS oligomer 40.0 mass% are melt-kneaded at 300°C with a twin screw extruder, homogenized, and pelletized, and then melted. The used resin composition was obtained.

The dried resin composition was supplied to a twin-screw extruder, melt-kneaded at 300°C, and then introduced into a melt spinning pack at a spinning temperature of 300°C, and under the condition of a discharge amount of 30 g/min, a detent hole (three arc-shaped slits were arranged. A type forming one discharge hole, a discharge hole radius of 0.86 mm, a slit pitch of 0.10 mm, and a slit width of 0.12 mm) were discharged downward from a discharge port having 12 holes. The hollow fiber molded by this discharge is guided to a cooling device (1m in length) so that the distance L from the lower surface of the discharge port to the top of the cooling device is 30mm, and cooled by a cooling wind at 25°C and a wind speed of 1.5m/sec. Then, after applying an oil agent and performing the procedure, it was wound up with a winder so that the draft ratio became 58.0, and a hollow fiber (resin molded product) was obtained. This hollow fiber was immersed in 1-chloronaphthalene at 50° C. for 12 hours to dissolve and remove the cyclic PPS oligomer. Table 1 shows the physical properties of the obtained separation membrane.

(Comparative Example 1)

Commercially available PPS (Toray's "Torrelina (registered trademark) E1380") 60.0 mass% and cyclic PPS oligomer 40.0 mass% are melt-kneaded at 300°C with a twin screw extruder, homogenized, and pelletized, and then melted. The used resin composition was obtained.

The dried resin composition was supplied to a twin-screw extruder, melt-kneaded at 300°C, and then introduced into a melt spinning pack at a spinning temperature of 300°C, and under the condition of a discharge amount of 30 g/min, a detent hole (three arc-shaped slits were arranged. A type forming one discharge hole, a discharge hole radius of 0.86 mm, a slit pitch of 0.10 mm, and a slit width of 0.12 mm) were discharged downward from a discharge port having 12 holes. The hollow fiber molded by this discharge is guided to a cooling device (1m in length) so that the distance L from the lower surface of the discharge port to the top of the cooling device is 30mm, and cooled by a cooling wind at 25°C and a wind speed of 1.5m/sec. Then, after applying an oil agent and performing the procedure, it was wound up with a winder so that the draft ratio became 14.0, and a hollow fiber (resin molded product) was obtained. This hollow fiber was immersed in NMP at 25° C. for 12 hours to dissolve and remove the cyclic PPS oligomer. Table 1 shows the physical properties of the obtained separation membrane.

(Comparative Example 2)

A commercially available PPS (Toray's "Torrelina (registered trademark) E1380") 100.0% by mass was supplied to a twin screw extruder, melt-kneaded at 310°C, and then introduced into a melt spinning pack having a spinning temperature of 310°C, and discharged Under the condition of 30g/min, a discharge confinement with 12 holes (a type in which three arc-shaped slits are arranged to form one discharge hole, a discharge hole radius of 0.86 mm, a pitch between slits of 0.10 mm, and a slit width of 0.12 mm) It was discharged downward from. The hollow fiber molded by this discharge is guided to a cooling device (1m in length) so that the distance L from the lower surface of the discharge port to the top of the cooling device is 30mm, and cooled by a cooling wind at 25°C and a wind speed of 1.5m/sec. Then, after applying an oil agent and performing the procedure, it was wound up with a winder so that the draft ratio became 58.0, and a hollow fiber (resin molded product) was obtained. Table 1 shows the physical properties of the obtained separation membrane. Water permeability was not exhibited at a pressure of 0.75 MPa.

(Comparative Example 3)

Commercially available PPS (Toray's "Torrelina (registered trademark) E2088"; ρ ₂ is 1.34 (g/cm 3 )) 60.0 mass% and cyclic PPS oligomer 40.0 mass% were supplied to a twin-screw melt kneader, and 300°C Melt film formation was performed at. By setting the drum temperature to 60°C and adjusting the winding speed, a PPS polymer/cyclic PPS oligomer mixture film (resin molded product) having a thickness of 30 μm was produced. The obtained film was cut out into a circle shape with a diameter of 5 cm, and immersed in 100 mL of NMP at 100° C. for 12 hours to dissolve and remove the cyclic PPS oligomer. After washing with 20 mL of NMP, washing with ion-exchanged water was repeated three times, followed by vacuum drying at 100° C. for 3 hours to prepare a PPS separation membrane. Table 1 shows the physical properties of the obtained separation membrane.

(Comparative Example 4)

Commercially available PPS (manufactured by Toray; "Torrelina (registered trademark) E2088") 50.0 mass% and cyclic PPS oligomer 50.0 mass% were supplied to a twin-screw melt kneader, and melt film formation was performed at 300°C. By setting the drum temperature to 60°C and adjusting the winding speed, a PPS polymer/cyclic PPS oligomer mixture film (resin molded product) having a thickness of 30 μm was produced. The obtained film was cut out into a circle shape with a diameter of 5 cm, and immersed in 100 mL of NMP at 100° C. for 12 hours to dissolve and remove the cyclic PPS oligomer. After washing with 20 mL of NMP, washing with ion-exchanged water was repeated three times, and then vacuum-dried at 100° C. for 3 hours to prepare a PPS separation membrane. The porosity was 50% and the breaking strength was 48 MPa. At a pressure of 0.75 MPa, membrane breakage occurred, and the separation performance could not be evaluated.

(Comparative Example 5)

Commercially available PPS (Toray's "Torrelina (registered trademark) E1380") 60.0 mass% and diphenyl sulfone (Tokyo Kasei) 40.0 mass% are melt-kneaded at 290°C with a twin screw extruder, homogenized, and then pelletized. It was transformed, and the resin composition for melt spinning was obtained.

The dried resin composition was supplied to a twin-screw extruder and melt-kneaded at 300°C, and then introduced into a melt-spinning pack at a spinning temperature of 290°C. A type forming one discharge hole, a discharge hole radius of 0.86 mm, a slit pitch of 0.10 mm, and a slit width of 0.12 mm) were discharged downward from a discharge port having 12 holes. The hollow fiber molded by this discharge is guided to a cooling device (1m in length) so that the distance L from the lower surface of the discharge port to the top of the cooling device is 30mm, and cooled by a cooling wind at 25°C and a wind speed of 1.5m/sec Then, after applying an oil agent to perform the procedure, it was wound up with a winder so that the draft ratio was 14.0 to obtain a hollow fiber (resin molded product). This hollow fiber was immersed in NMP at 25° C. for 12 hours to dissolve and remove diphenylsulfone. Table 1 shows the physical properties of the obtained separation membrane.

The separation membrane of Example 1 has improved removal performance than the separation membrane of Example 2. In the resin composition of the same PPS mass ratio, the higher the degree of orientation was, the higher the divalent ion blocking ratio was. In addition, the degree of orientation is larger as the draw ratio and draw speed are higher. It is presumed that the high degree of orientation forms a dense structure in which molecular chains in the separation membrane are arranged, thereby exhibiting high separation performance. The separator of Comparative Example 1 exhibited high water permeability, but the divalent ion blocking rate did not reach 5%. The separation membrane of Comparative Example 2 did not exhibit water permeability, and the evaluation of the divalent ion blocking rate itself was not possible. Although the separator of Comparative Example 3 exhibited high water permeability, the divalent ion blocking rate did not reach 5%. Since the separation membranes of Comparative Examples 1 and 3 had a low degree of orientation and a structure in which molecular chains in the separation membrane were small, it was estimated that the separation performance was lowered. In Comparative Example 4, film breakage occurred at a pressure of 0.75 MPa, and the evaluation of the divalent ion blocking rate itself was not possible. It is considered that the separation membrane of Comparative Example 4 has a high porosity of 50%, and a load on the membrane is greater than that of a membrane having a porosity of 40% or less. The separation membrane of Comparative Example 5 did not show a divalent ion blocking rate. It is estimated that the average pore diameter of the pores is large and the permeated liquid flows only in the pores, so that the separation performance at the molecular level is not obtained. In addition, in the resin composition produced under the same conditions as in Comparative Example 5, under the condition that the draft ratio was 20.0 or more, yarn breakage occurred and the hollow fiber could not be wound.

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

This application is based on the Japanese patent application (Japanese Patent Application No. 2018-142175) for which it applied on July 30, 2018, The content is taken in here as a reference.

The separation membrane of the present invention can be used for selective separation of liquid mixtures containing organic solvents, concentration and purification of organic solvents or strong acidic or strong basic solutions, production of industrial ultrapure water, wastewater treatment, or recovery of valuables.

Claims (9)

A separation membrane containing polyarylene sulfide as a main component and having a divalent ion blocking rate of 5% or more. The separation membrane according to claim 1, wherein the average pore diameter D of the pores is 1 to 10 nm. The separation membrane according to claim 1 or 2, wherein the porosity is 45% or less. The separation membrane according to any one of claims 1 to 3, wherein the curvature ratio is 5 to 500. The separation membrane according to any one of claims 1 to 4, wherein the degree of orientation is 1.04 or more. The separation membrane according to any one of claims 1 to 4, wherein the degree of orientation is 1.55 or higher. (1) a resin composition preparation step of melt-kneading polyarylene sulfide and a plasticizer to prepare a resin composition, and
(2) a molding step of discharging the resin composition from a discharge orifice to mold a resin molded article with a draft ratio of 20 or more;
(3) A method for producing a separation membrane, comprising an immersion step of immersing the resin molded product in a solvent to obtain a separation membrane. (1) a resin composition preparation step of melt-kneading polyarylene sulfide and a plasticizer to prepare a resin composition, and
(2) a molding step of discharging the resin composition from a discharge orifice to form a resin molded article,
(3) a stretching step of stretching the resin molded article and
(4) A method for producing a separation membrane, comprising an immersion step of immersing the resin molded product in a solvent to obtain a separation membrane. The method for producing a separation membrane according to claim 7, including a stretching step of stretching the resin molded article after the step (2).