JP2021020145A - Separation membrane and method of manufacturing the same - Google Patents

Abstract

To provide a separation membrane capable of achieving high membrane strength and permeation performance in addition to excellent separation performance.SOLUTION: A separation membrane of the present invention is composed predominantly of polyarylene sulfide, and includes a hydrophilic macromolecule as an accessory component. The mass ratio of the hydrophilic macromolecule to the polyarylene sulfide, which is obtained by IR measurement, is in the range of 0.01-0.20.SELECTED DRAWING: None

Description

The present invention relates to a separation membrane and a method for producing the separation membrane.

Separation membranes are used in a wide range of fields, including water treatment applications for producing industrial water and drinking water by removing turbidity and ions from seawater and sewage wastewater, but with recent technological advances. , Heat resistance, pressure resistance and chemical resistance are required to be further improved in film strength.

As a separation membrane having extremely excellent membrane strength while maintaining moldability, a separation membrane containing polyarylene sulfide as a component thereof is known (Patent Documents 1 to 6). For example, Patent Document 6 describes a method of stretching an ultrafiltration membrane of polyarylene sulfide produced by heat-induced phase separation to improve the membrane strength.

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

However, although the conventional separation membrane containing polyarylene sulfide as a component can achieve the necessary and sufficient film strength, the pore size cannot be miniaturized and the separation performance at the nanofiltration membrane level cannot be obtained. .. Therefore, a separation film having excellent separation performance, high permeation performance, and high film strength has not been obtained. In the method described in Patent Document 6, the polyarylene sulfide and the solvent are already in a non-uniform state of phase separation, and stretching that enhances the orientation of the polyarylene sulfide cannot be performed. In addition, although it is mentioned that there is no significant change in permeation performance due to stretching, the relationship between stretching and separation performance and polymer orientation is not shown.

Therefore, an object of the present invention is to provide a separation membrane and a method for producing the same, which have excellent separation performance at the nanofiltration membrane level, exhibit high membrane strength, and also have remarkable permeation performance.

Provided is a separation membrane containing polyarylene sulfide as a main component and a hydrophilic polymer as an auxiliary component, and the ratio of the hydrophilic polymer to the polyarylene sulfide is in the range of 0.01 to 0.20. ..

According to the present invention, it is possible to provide a separation film capable of achieving high film strength and permeation performance in addition to excellent separation performance.

(Composition of separation membrane)
The separation membrane of the present invention needs to contain polyphenylene sulfide (hereinafter, "PAS") and other polyarylene sulfides (hereinafter, "PAS") as main components.

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

The weight average molecular weight (Mw) of PAS contained in the separation membrane of the present invention is preferably 10,000 to 200,000 in order to enhance mechanical properties such as film strength while considering moldability, and is preferably 30,000 to 20. It is more preferably 10,000, and even more preferably 80,000 to 200,000. The weight average molecular weight (Mw) of PAS can be calculated in terms of polystyrene by gel permeation chromatography (hereinafter, “GPC”), which is a 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 90 to 100% by mass in order to enhance heat resistance, pressure resistance, chemical resistance, and the like. Is even more preferable.

The separation membrane of the present invention contains a hydrophilic polymer as a subcomponent. Here, the "hydrophilic polymer" refers to a polymer having a hydrophilic group, and the contact angle between the film made of the polymer and water is 60 ° or less. Here, the "hydrophilic group" refers to a hydroxyl group, a carboxyl group, a carbonyl group, an amino group, a pyrrolidone group or an amide group. Examples of the hydrophilic polymer include polyester, polyamide, methyl polyacrylate, vinyl polyfatty acid acid, polyvinylpyrrolidone, cellulose ester, cellulose ether, polyethylene oxide or polypropylene oxide, or a copolymer thereof. Polyamide , Polyvinylpyrrolidone, polyethylene oxide, cellulose ester, cellulose ether or a copolymer of fatty acid vinyl and vinylpyrrolidone is preferred. Examples of the polyamide include nylon 6 and nylon 11. Examples of the cellulose ester include cellulose esters such as cellulose acetate, cellulose propionate or cellulose butyrate, cellulose acetate propionate or cellulose acetate butyrate.

The weight average molecular weight (Mw) of the subcomponent calculated by GPC measurement is preferably 5000 to 80,000. When the weight average molecular weight (Mw) is 5000 or more, elution in the dipping step described later is suppressed, and the membrane strength of the separation membrane becomes sufficient. On the other hand, when the weight average molecular weight (Mw) is 80,000 or less, the melt viscosity does not become excessively high, and stable melt film formation becomes possible.

In the separation membrane of the present invention, in order to achieve both high membrane strength and high water permeability, the mass ratio of the hydrophilic polymer as a sub-component to the main component polyarylene sulfide is in the range of 0.01 to 0.20. Is inside. The ratio of the sub-component to the main component can be determined by IR measurement. The ratio of the sub-component to the main component is preferably 0.03 to 0.15, more preferably 0.05 to 0.15.

(Performance and structure of separation membrane)
The separation membrane of the present invention preferably has a divalent ion blocking rate of 5% or more, but in order to enhance separation performance, the divalent ion blocking rate is more preferably 10% or more, and it is 20% or more. Is even more preferable, and 35% or more is even more preferable.

Here, the "divalent ion blocking rate" refers to a separation membrane that has been hydrophilized by immersing it in a 10 mass% isopropyl alcohol aqueous solution for 1 hour, using a magnesium sulfate aqueous solution having a concentration of 2,000 ppm as feed water at a temperature of 25 ° C. and an operating pressure. It refers to the magnesium sulfate inhibition rate when supplied at 0.75 MPa and filtered.
As for the film thickness of the separation membrane, the cross section Z of the separation membrane obtained by cutting the separation membrane frozen in liquid nitrogen with a razor or a microtome was photographed with a scanning electron microscope, and the film thickness at 10 randomly selected locations was measured. Then, it can be calculated as the average value. The film thickness of the separation film is preferably 2 to 70 μm, more preferably 10 to 60 μm, and further preferably 15 to 50 μm in order to achieve both film strength and permeation performance.

The separation membrane of the present invention preferably has a porosity of 5 to 45%, more preferably 10 to 40%, and more preferably 15% to 30%, in order to achieve both membrane strength and separation performance and permeation performance. It is more preferably%.

For the porosity ε, the density of the separation membrane was ρ ₁ (g / cm ³ ) and the density of the resin contained in the separation membrane was ρ ₂ (g / cm ³ ) after vacuum drying for 8 hours under the condition of 25 ° C. Then, it can be calculated by the following formula (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, the separation membrane is a hollow fiber membrane, the density ρ ₁ of the hollow fiber membrane is determined after measuring the length L (m) of the hollow fiber membrane. When the mass M (g) of the hollow fiber membrane dried in vacuum for 8 hours under the condition of 25 ° C. was measured, and the outer diameter of the hollow fiber membrane was D ₁ (μm) and the inner diameter was D ₂ (μm). 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] × 10 6 ··· formula (3)

The outer diameter D ₁ and inner diameter D ₂ of the hollow fiber membrane are calculated by photographing the cross section Z with a scanning electron microscope, measuring the outer diameter and inner diameter of 10 randomly selected points, and calculating the average value of each. can do. The hollow ratio can be calculated by the following formula (4) from the calculated values of the outer diameter D ₁ (μm) and the inner diameter D ₂ (μm) 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 flat membrane (hereinafter, “flat membrane”) is preferably adopted. Among these, the hollow fiber membrane is more preferable because it can be efficiently filled in the module and the effective film area per unit volume of the module can be increased.

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

In the separation membrane of the present invention, the mass ratio of the hydrophilic polymer to the polyarylene sulfide in the central portion in the thickness direction is C, which is obtained by measuring the cross section in the thickness direction by micro IR, and the mass ratio of the hydrophilic polymer is C, and one surface portion of the cross section. When the mass ratio of the hydrophilic polymer to the polyarylene sulfide is S ₁ , and the mass ratio of the hydrophilic polymer to the polyarylene sulfide on the other surface portion of the cross section is S ₂ , C / S ₁ or The value of C / S ₂ is in the range of 0.80 to 1.20. Here, it is preferable that both C / S ₁ and C / S ₂ are 0.8 to 1.2. Further, the values of C / S ₁ and C / S ₂ are more preferably in the range of 0.85 to 1.15, and further preferably in the range of 0.99 to 1.10.

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

The curvature ratio of the separation membrane is calculated by the following formula (5), where D is the porosity (m) of the pores of the separation membrane, ε is the porosity (%), and k is the transmission coefficient (m ² ). Can be done.

Curve rate (-) = (D / 4) x √ (ε/100 / 2k) ・ ・ ・ Equation (5)
When the shape of the separation membrane is a flat membrane, k can be calculated by the following formula (6). Further, k can be calculated by the following formula (7) when the separation membrane is a hollow fiber membrane.

k (m ² ) = Q × μ × x / (P × A) ・ ・ ・ Equation (6)
k (m ² ) = (Q × μ × ln (D ₁ / D ₂ )) / (2π × L × P) ・ ・ ・ Equation (7)
Here, Q is the membrane permeation flow rate of water (m ³ / s), μ is the viscosity of water (Pa · s), x is the film thickness (m), P (Pa) is the applied pressure, and A is the membrane area (m). ² ), 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).

The separation membrane of the present invention preferably has an orientation degree of 1.04 or more, more preferably 1.10 or more, and more preferably 1.50 or more in order to enhance breaking strength and ion blocking performance. It is preferably 2.00 or more, more preferably 3.00 or more, and particularly preferably 3.00 or more. It is presumed that in the separation membrane of the present invention, a fine structure at the molecular level was formed by adopting a dense structure in which polyarylene sulfide chains were oriented, and high separation performance capable of blocking ions was exhibited. The degree of orientation can be calculated based on the measurement result of laser Raman.

The separation membrane of the present invention preferably has a tensile strength of 20 MPa or more in order to exhibit good membrane strength. The tensile strength is more preferably 30 MPa or more, and even more preferably 60 MPa or more. Higher tensile strength is preferable, but the practical upper limit is 500 MPa. When the separation film is a hollow thread film, the breaking strength is obtained by performing a tensile test in the long axis direction of the separation film 5 times under the conditions of a temperature of 20 ° C. and a humidity of 65% under the conditions of a sample length of 50 mm and a tensile speed of 100 mm / min. Repeatedly, the average value of tensile strength can be calculated as breaking strength (tensile strength) (MPa). When the separation membrane is a flat membrane, the tensile test in the length direction of the separation membrane is repeated 5 times under the conditions of a temperature of 20 ° C. and a humidity of 65% under the conditions of a sample length of 50 mm, a sample width of 10 mm, and a tensile speed of 100 mm / min. , The average value of tensile strength can be calculated as breaking strength (MPa). Examples of the tensile tester used for the tensile test include Tencilon UCT-100 (manufactured by Orientec).

The separation membrane of the present invention preferably has a membrane permeation flux of 1.0 × 10 ^-3 m ³ / m ² / day / MPa or more at 50 kPa and 25 ° C., preferably 1.3 × 10 ^-3 m ³ / ^{m 2} / day, more preferably at / MPa or more, further preferably ^{1.5 × 10 -3 m 3 / m} 2 / day / MPa or more. The calculation method will be described in detail in Examples.

(Manufacturing method of separation membrane)
The method for producing a separation film of the present invention comprises (1) a resin composition preparation step of melt-kneading PAS, a plasticizer, and a hydrophilic polymer to prepare a resin composition, and (2) the resin. A molding step of discharging the composition from a discharge port to form a resin molded product at a draft ratio of 20 or more, and (3) a dipping step of immersing the resin molded product in a solvent to obtain a separation film. To be equipped.
The method for producing the separation membrane preferably includes a stretching step of stretching the resin molded product after the step (2) in order to increase the degree of orientation of the resin molded product.

Another method for producing the separation film of the present invention is (1) a resin composition preparation step of melt-kneading PAS, a plastic agent, and a hydrophilic polymer to prepare a resin composition, and (1) 2) A molding step of discharging the resin composition from a discharge port to form a resin molded product, (3) a stretching step of stretching the resin molded product, and (4) using the resin molded product as a solvent. It is provided with a dipping step of obtaining a separation film by dipping in.

In the resin composition preparation step provided by the method for producing a separation membrane of the present invention, as a method for melt-kneading PAS, a plasticizer, and a hydrophilic polymer, for example, a kneader, a roll mill, a Banbury mixer, or a single shaft or two. A method using a mixer such as a shaft extruder can be mentioned, but a twin-screw extruder is preferable in order to improve the dispersibility of the plasticizer, the hydrophilic polymer, etc., and the two with vent holes can remove volatile substances. A shaft extruder is more preferred.

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

The proportion of the plasticizer in the resin composition prepared in the resin composition preparation step is preferably 5 to 40% by mass in order to achieve both the membrane strength and separation performance of the obtained separation membrane and the permeation performance. More preferably, it is 20 to 40% by mass.
The proportion of the hydrophilic polymer in the resin composition prepared in the resin composition preparation step is preferably 5 to 30% by mass in order to achieve both the membrane strength and separation performance of the obtained separation membrane and the permeation performance. More preferably, 10 to 20% by mass.

The "plasticizer" used in the resin composition preparation step refers to a compound that thermally plasticizes PAS, preferably a PAS having a Hansen solubility parameter in the range of 15.0 to 48.0 MPa ^1/2. A compound that is thermoplastic. In order to obtain a uniform resin composition with PAS, the plasticizer preferably has a Hansen solubility parameter in the range of 18.0 to 38.0 MPa ^1/2 . For the Hansen solubility parameter, the value contained 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 which is not described in the above software can be calculated by the Hansen sphere method using the above software.

Examples of the plasticizer include cyclic PPS oligomers, linear PPS oligomers, aromatic polyesters, aromatic polyester oligomers, vinylidene fluoride, polyphenyl ethers, polysulfones, benzophenones, diphenyl ethers, diphenyl sulfone, diphenyl sulfides, 4,4'-. Dibromobiphenyl, 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, pentachlorophenyl, 1-benzyl-2-pyrrolidione, 9-fluorenone, 2-benzoylnaphthalene, 1-bromonaphthalene, 1,3-diphenoxybenzene, fluorene, 1-Phenyl-2-pyrrolidinone, 1-methoxynaphthalene, 1-ethoxynaphthalene, 1,3-diphenylacetone, 1,4-dibenzoylptan, phenanthrene, 4-benzoylbiphenyl, 1,1-diphenylacetone, 0,0 '-Biphenol, 2,6-diphenylphenol, triphenylene, 2-phenylphenol, thiantrene, 3-phenoxybenzyl alcohol, 4-phenylphenol, 9,10-dichloroanthracene, triphenylmethane, 4,4'-dimethoxybenzophenone, 4,4'-difluorobenzophenone, 4,4'-dichlorobenzophenone, 4,4'-dibromobenzophenone, 9,10-diphenylanthracene, fluorantene, diphenylphthalate, diphenylcarbonate, 2,6-dimethoxynaphthalene, 2,7 -Dimethoxynaphthalene, 4-bromodiphenyl ether, pyrene, 9,9'-bi-fluorene, 4,4'-isopropyllidene-diphenol, epsilon-caprolactam, N-cyclohexyl-2-pyrrolidone, diphenylisophthalate, diphenylutater Phthalate, 1-chloronaphthalene or N-methyl-2-pyrrolidone (hereinafter, "NMP") can be mentioned, but cyclic PPS oligomers, linear PPS oligomers, benzophenones, because of their low molecular weight and easy subsequent dissolution. Preferably diphenylisophthalate, diphenyl-terphthalate, diphenylsulphon or diphenylsulfide, unaffected by terminal functional groups Cyclic PPS oligomers are more preferred. By using a cyclic PPS oligomer having the same basic structure as PAS as a plasticizer, the resin composition and the resin molded product are in a uniformly compatible state, and winding and stretching are performed under high draft ratio conditions. Can be done.

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

Such additives include, for example, resins such as polyacrylonitrile, polyolefins, polyvinyl compounds, polycarbonates, poly (meth) acrylates or polyether sulfones, antioxidants, organic lubricants, crystal nucleating agents, organic particles, inorganic particles, etc. End-blocking agents, chain extenders, UV absorbers, infrared absorbers, color inhibitors, matting agents, antibacterial agents, antistatic agents, deodorants, flame retardants, weatherproofing agents, antistatic agents, antioxidants, ions Examples include exchanges, defoaming agents, color pigments, optical brighteners or dyes.

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

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

The resin molded product may be wound by a winding device. In this case, the value of the draft ratio indicated by the winding speed by the winding device / the discharge speed from the discharge port must be 20 or more in order to increase the degree of orientation of the obtained separation membrane, but without thread breakage. It is preferably 1,000 or less, and more preferably 50 to 900 for spinning. From the viewpoint of increasing the degree of orientation of the obtained separation membrane, the proportion of PAS in the resin composition prepared in the resin composition preparation step is preferably 55 to 90% by mass, more preferably 60 to 80% by mass.

The method for producing the separation membrane of the present invention preferably includes a stretching step of stretching the resin molded product after the resin composition preparation step. By stretching the resin molded product formed in the molding step, the degree of orientation of the obtained separation membrane can be increased. The resin molded product may be wound once by a winding device, unwound again, and then subjected to a stretching step, or may be directly subjected to a stretching step.

As a method of stretching in the stretching step, which may be provided in the method for producing a separation membrane of the present invention, for example, a resin molded product is heated while being conveyed on a heating roll, and stretched using the difference in peripheral speed between the heating rolls. Or a method of transporting and heating in a dry heat oven or a warm solvent, and stretching using the difference in peripheral speed between the heating rolls. Stretching may be performed in one 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., further preferably 80 to 110 ° C., and particularly preferably 85 to 95 ° C. in order to increase the degree of orientation of the resin molded product. 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 1.6 to 4. 0 times is more preferable. Further, in order to increase the degree of orientation of the resin molded product, 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 solvent used in the dipping step included in the method for producing a separation film of the present invention is not particularly limited as long as it is a solvent that dissolves the plastic agent, but it is difficult to dissolve PAS and easily dissolves the plastic agent (hereinafter, referred to as solvent X). May be preferable), and NMP, tetrahydrofuran, 1-chloronaphthalene, chloroform, paraxylene, benzene, dimethylformamide or dimethylacetamide are more preferable. The dipping step is a step of immersing the resin molded product in the solvent X. In the dipping step, it is preferable that the solvent X contains 1% by mass or more of the subcomponent. When the solvent X contains 1% by mass or more of the sub-component, the elution of the sub-component in the dipping step is suppressed, and the sub-component can be appropriately left in the resin molded product. If the solvent X contains an excessive amount of the sub-component, the film strength of the resin molded product that has undergone the dipping step decreases. Therefore, the content ratio of the sub-component is preferably less than 10% by mass. The content of the sub-component in the solvent X is more preferably 5 to 8% by mass.

The present invention will be described in more detail with reference to Examples below, but the present invention is not limited thereto.

[Measurement method and evaluation method]
(1) Measurement of weight average molecular weight (Mw) of PAS The measurement conditions of GPC were as follows.
Equipment: SSC-7100 (manufactured by Senshu Kagaku)
Column name: GPC3506 (manufactured by Senshu Kagaku)
Eluent: 1-Chloronaphthalene detector: Differential refractive index detector Column temperature: 210 ° C
Pre-constant temperature bath temperature: 250 ° C
Pump constant temperature bath temperature: 50 ° C
Detector temperature: 210 ° C
Flow rate: 1.0 mL / min Sample injection amount: 300 μL (sample concentration: about 0.2% by mass)
Standard substance: Polystyrene (manufactured by PSS; ps8124, ps12034, ps18074, ps23025)
(2) Average pore size of voids The separation membrane frozen in liquid nitrogen is cut with a razor. The cross section Z of the split separation membrane was observed with an atomic force microscope (Dimenceion FastScan manufactured by Bruker AXS). In the case of a hollow fiber membrane, each region 1 to 5 divided into five at equal intervals is set in order from three locations on the outer surface of the separation membrane in the film thickness direction of the separation membrane. In the case of a flat film, each region 1 to 5 divided into five at equal intervals is set in order from three locations on one surface in the film thickness direction of the separation film. In each of the regions 1 to 5, a square region having a side of 200 nm was observed at the center of each region. The pore diameters d of all the voids contained in this microscopic image were calculated, and the arithmetic mean of the _n values d _{1 to} d _{n was taken} as the average pore diameter D of the voids of the separation membrane.
(3) Separation Membrane, Degree of Orientation of Resin Molded Body Using a separation membrane that has been vacuum-dried for 8 hours under the condition of 25 ° C. as a sample, the longitudinal direction (MD) and longitudinal direction of the sample are used using a near-infrared Raman spectrometer. With respect to the direction perpendicular to (the width direction of the flat membrane or the radial direction of the hollow fiber membrane) (TD), the band near 1,080 cm ^-1 of the Raman spectrum (sulfide bond (-Ph-S-Ph-)). , And the intensity of the band (phenyl ring surface extra-angle vibration) near 745 cm ^-1 was measured.

Regarding the degree of orientation DO of the separation membrane, the intensities of the bands near 1,080 cm ^-1 are IP _-MD and IP _-TD , respectively, and the intensities of the bands around 745 cm ^-1 are _IE-MD and _IE-TD , respectively. Then, it can be calculated by the following formula (8).

DO (-) = ( _IP-MD / _IE-MD ) / ( _IP-TD / _IE-TD ) ... Equation (8)
The specific measurement conditions are as follows.

Equipment: Near-infrared Raman spectrometer (Photoon Design)
Conditions: Measurement mode; Microscopic Raman objective lens; × 20
Beam diameter; 5 μm
Cross slit: 500 μm
Light source: YAG laser / 1,064 nm
Laser power; 1W
Diffraction grating; Single 300gr / mm
Slit; 100 μm
Detector; InGaAs (manufactured by Nippon Roper)
(4) Membrane Permeation Flow of Separation Membrane The separation membrane was hydrophilized by immersing it in a 10% by mass isopropyl alcohol aqueous solution for 1 hour, and the temperature was 25 ° C. and the operating pressure was 0. The membrane was supplied at 75 MPa and filtered, and the membrane permeation flux was calculated by the following formula (9) based on the area of the separation membrane and the amount of permeated water obtained.

Membrane permeation flux (m ³ / m ² / day / MPa) = permeated water volume per day / membrane area / 0.75 ... Equation (9)
When the separation membrane was a hollow fiber membrane, a small module filled with the hollow fiber membrane was prepared and subjected to the above filtration treatment.

More specifically, the hollow fiber membranes are bundled and inserted into a plastic pipe so that the membrane area based on the outer diameter is 0.1 m ² , and the gap between the end of the hollow fiber membrane bundle and the pipe is thermosetting. After sealing with resin, both ends were cut to obtain a small module.

(5) Divalent ion blocking rate of separation membrane The electrical conductivity of supplied water and permeated water in the evaluation of membrane permeation flux is measured with an electric conductivity meter, and the divalent ion blocking rate is calculated by the following formula (10). did.

Divalent ion blocking rate (%) = 100 × {1- (electrical conductivity of permeated water / electrical conductivity of supplied water)} ・ ・ ・ Equation (10)
(6) Mass ratio of hydrophilic polymer to polyarylene sulfide We prepared several types of standard samples in which polyarylene sulfide, which is the main component, and hydrophilic polymer, which is a sub-component, were mixed at different mixing ratios. IR measurement was performed, and a calibration line was prepared for the peak intensity ratio representing each of the polyarylene sulfide and the hydrophilic polymer in the obtained spectrum. After that, IR measurement was also performed on the separation membrane, and the ratio of the sub-component to the main component of the separation membrane was determined based on the prepared calibration curve.

(7) Mass ratio of hydrophilic polymer to polyarylene sulfide by micro IR After freezing the separation membrane with liquid nitrogen, stress is applied so that the cross section of the separation membrane in the thickness direction is exposed (as appropriate, razor or microtome). And so on). The cross section of the exposed separation membrane is measured by micro IR in the range of 2 μm to 5 μm from both surfaces and in the range of 3 μm centered on the position where the distances from both surfaces are equal, and the polyarylene sulfide in the central portion in the thickness direction. Mass ratio of hydrophilic polymer to C, mass ratio of hydrophilic polymer to polyarylene sulfide on one surface S ₁ , mass ratio of hydrophilic polymer to polyarylene sulfide on the other surface is S ₂ and The value was obtained based on the calibration line prepared in (6).

(8) Porosity of the separation membrane The porosity ε of the separation membrane is when the density of the separation membrane is ρ ₁ and the density of the resin contained in the separation membrane is ρ ₂ after vacuum drying for 8 hours under the condition of 25 ° C. , Calculated by the following formula (2).

ε (%) = (1-ρ ₁ / ρ ₂ ) × 100 ・ ・ ・ Equation (2)
When the shape of the separation membrane is a hollow fiber, that is, the separation membrane is a hollow fiber membrane, the density ρ ₁ of the hollow fiber membrane is vacuumed for 8 hours under the condition of 25 ° C. after measuring the length L of the hollow fiber membrane. The mass M of the dried hollow fiber membrane was measured, and the outer diameter of the hollow fiber membrane was D ₁ and the inner diameter was D _2, and the calculation was performed by the following formula (3).

^{_{ρ 1 (g / cm 3)}} = M / [π × {(D 1/2) 2 - (D 2/2) 2} × L] ··· formula (3)
The outer diameter D ₁ and inner diameter D ₂ of the hollow fiber membrane are calculated by photographing the cross section Z with a scanning electron microscope, measuring the outer diameter and inner diameter of 10 randomly selected points, and calculating the average value of each. did. The hollow 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)
(9) Porosity of Separation Membrane The porosity of the separation membrane is calculated by the following formula, where D is the void (m) in the pores of the separation membrane, ε is the porosity (%), and k is the permeability coefficient (m ² ). Calculated according to (5).

Curve rate (-) = (D / 4) x √ (ε/100 / 2k) ・ ・ ・ Equation (5)
k was calculated by the following formula (6) when the shape of the separation membrane was a flat membrane. Further, k was calculated by the following formula (7) when the separation membrane was a hollow fiber membrane.

k (m ² ) = Q × μ × x / (P × A) ・ ・ ・ Equation (6)
k (m ² ) = (Q × μ × ln (D ₁ / D ₂ )) / (2π × L × P) ・ ・ ・ Equation (7)
Here, Q is the membrane permeation flow rate of water (m ³ / s), μ is the viscosity of water (Pa · s), x is the film thickness (m), P (Pa) is the applied pressure, and A is the membrane area (m). ² ), 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).

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

[Preparation of cyclic PPS oligomer mixture]
8.27 kg of 47.5 mass% sodium hydrosulfide aqueous solution (70.0 mol), 2.96 kg of 96 mass% sodium hydroxide aqueous solution (71.0 mol), 11.44 kg in a 70 L autoclave with a stirrer. NMP (116.0 mol), 1.72 kg of sodium acetate (21.0 mol), and 10.5 kg of ion-exchanged water were charged, and gradually heated to about 240 ° C. over about 3 hours while passing nitrogen gas at normal pressure. After distilling 14.8 kg of water and 280 g of NMP through the rectification tower, the autoclave was cooled to 160 ° C. During this liquid removal operation, 0.02 mol of hydrogen sulfide was scattered outside the system per 1 mol of the charged sulfur component.

Next, 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. The contents were heated to 270 ° C. at a rate of 0.6 ° C./min with stirring at 240 rpm and held at this temperature for 140 minutes. Then, 1.26 kg of water (70.0 mol) was press-fitted over 15 minutes to cool to 250 ° C. at a rate of 1.3 ° C./min, and further cooled to 220 ° C. at a rate of 0.4 ° C./min. Then, the mixture was rapidly cooled to near room temperature to obtain a slurry <1>. This slurry <1> was diluted with 20.0 kg of NMP to obtain a slurry <2>. A 10 kg slurry <2> heated to 80 ° C. was filtered off by a sieve (80 mesh, opening 0.175 mm) to obtain a granular PPS resin containing the 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 charged into a rotary evaporator, replaced with nitrogen gas, treated at 100 to 150 ° C. under reduced pressure for 1.5 hours, and then treated with a vacuum dryer at 150 ° C. for 1 hour. To obtain a solid substance. After adding 1,200 g (1.2 times the amount of slurry <3>) of ion-exchanged water to this solid, the mixture was stirred at 70 ° C. for 30 minutes to reslurry. This slurry was suction-filtered with a glass filter having an opening of 10 to 16 μm. To the obtained white cake, 1,200 g of ion-exchanged water was added, and the mixture was stirred at 70 ° C. for 30 minutes to reslurry. Similarly, suction filtration was performed, and then vacuum dried at 70 ° C. for 5 hours to obtain 11.0 g of a PPS mixture. <1> was obtained. As a result of 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. As a result of chromatogram analysis, the molecular weight was 5,000 or less. The mass fraction of the components of was 39%, and the mass fraction of the components having a molecular weight of 2,500 or less was 32%. 5 g of the PPS mixture <1> is taken, 120 g of chloroform is used as a solvent, and the PPS mixture <1> is brought into contact with the solvent for 3 hours at a bath temperature of about 80 ° C. by the Soxhlet extraction method to obtain an extract slurry. It was. The obtained extract slurry was in the form of a slurry containing some solid components at room temperature.

Chloroform was distilled off from this extract slurry using an evaporator, and then treated in a vacuum dryer at 70 ° C. for 3 hours to produce 2.1 g of a solid (yield 42% with respect to PPS mixture <1>). Got Infrared spectroscopic analysis (device: FTIR-8100A manufactured by Shimadzu Corporation) and high performance liquid chromatography (device: LC-10 manufactured by Shimadzu Corporation; column: C18; detector: photodiode) on the solid matter thus obtained. Based on mass spectrum analysis of the components divided by (diode array) (device: M-1200H manufactured by Hitachi) and molecular weight information by MALDI-TOF-MS, this solid substance is mainly composed of cyclic PPS oligomers having 4 to 12 repeating units. It turned out to be a mixture as an ingredient.

(Example 1)
Commercially available PPS (Toray's "Trelina (registered trademark) E1380"; ρ ₂ is 1.34 (g / cm ³ )) 60.0% by mass, cyclic PPS oligomer 30.0% by mass, and polyvinylpyrrolidone (weight average) A molecular weight of 9000) 10.0% by mass was melt-kneaded at 300 ° C. using a twin-screw extruder, homogenized and then pelletized to obtain a resin composition for melt spinning.

The dried resin composition is supplied to a twin-screw extruder, melt-kneaded at 300 ° C., introduced into a melt-spinning pack having a spinning temperature of 300 ° C., and has a mouthpiece hole (arc-shaped slit) under a discharge rate of 30 g / min. A type in which three parts are arranged to form 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) are discharged below the discharge port having 12 holes. .. The hollow thread formed by this discharge is guided to the cooling device (length 1 m) so that the distance L from the lower surface of the discharge port to the upper end of the cooling device (chimney) is 30 mm, and is 25 ° C. and the wind speed is 1.5 m / It was cooled by a second cooling air, oiled and converged, and then wound with a winder so that the draft ratio was 58.0. The hollow fiber was immersed in an NMP solution (25 ° C.) containing 8% by mass of polyvinylpyrrolidone for 12 hours to dissolve and remove the cyclic PPS oligomer. The physical characteristics of the obtained separation membrane are shown in Table 2.

(Examples 2 to 3)
A separation membrane was obtained in the same manner as in Example 1 except that the production conditions were changed as shown in Table 1. The physical characteristics of the obtained separation membrane are shown in Table 2.
(Example 4)
Commercially available PPS (Toray's "Trelina (registered trademark) E1380"; ρ ₂ is 1.34 (g / cm ³ )) 60.0% by mass, cyclic PPS oligomer 30.0% by mass, and polyvinylpyrrolidone (weight average) A molecular weight of 9000) 10.0% by mass was melt-kneaded at 300 ° C. using a twin-screw extruder, homogenized and then pelletized to obtain a resin composition for melt spinning.

The dried resin composition is supplied to a twin-screw extruder, melt-kneaded at 300 ° C., introduced into a melt-spinning pack having a spinning temperature of 300 ° C., and has a mouthpiece hole (arc-shaped slit) under a discharge rate of 30 g / min. A type in which three parts are arranged to form 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) are discharged below the discharge port having 12 holes. .. The hollow thread formed by this discharge is guided to the cooling device (length 1 m) so that the distance L from the lower surface of the discharge port to the upper end of the cooling device (chimney) is 30 mm, and is 25 ° C. and the wind speed is 1.5 m / It was cooled by a second cooling air, oiled and converged, and then wound with a winder so that the draft ratio was 58.0. The hollow yarn 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. The physical characteristics of the obtained separation membrane are shown in Table 2.
(Example 5)
A separation membrane was obtained in the same manner as in Example 4 except that the production conditions were changed as shown in Table 1. The physical characteristics of the obtained separation membrane are shown in Table 2.

(Comparative Example 1)
60.0% by mass of commercially available PPS (Toray's "Trelina (registered trademark) E1380") and 40.0% by mass of cyclic PPS oligomer are melt-kneaded at 300 ° C. using a twin-screw extruder, homogenized, and then pelletized. A resin composition for melt spinning was obtained.

The dried resin composition is supplied to a twin-screw extruder, melt-kneaded at 300 ° C., introduced into a melt-spinning pack having a spinning temperature of 300 ° C., and has a mouthpiece hole (arc-shaped slit) under a discharge rate of 30 g / min. A type in which three parts are arranged to form 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) are discharged below the discharge port having 12 holes. .. The hollow thread formed by this discharge is guided to a cooling device (length 1 m) so that the distance L from the lower surface of the discharge port to the upper end of the cooling device is 30 mm, and is cooled at 25 ° C. and a wind speed of 1.5 m / sec. After cooling by wind, applying an oil agent and converging, the film was wound with a winder so that the draft ratio was 14.0. The hollow fiber was immersed in NMP at 25 ° C. for 12 hours to dissolve and remove the cyclic PPS oligomer. The physical characteristics of the obtained separation membrane are shown in Table 4.

(Comparative Example 2)
100.0% by mass of commercially available PPS (Toray's "Trelina (registered trademark) E1380") was supplied to a twin-screw extruder, melt-kneaded at 310 ° C., and then introduced into a melt-spun pack having a spinning temperature of 310 ° C. Under the condition of a discharge rate of 30 g / min, a mouthpiece hole (a type in which three arc-shaped slits are arranged to form one discharge hole, a discharge hole radius of 0.86 mm, a slit-to-slit pitch of 0.10 mm, and a slit width of 0. 12 mm) was discharged below the discharge port having 12 holes. The hollow thread formed by this discharge is guided to a cooling device (length 1 m) so that the distance L from the lower surface of the discharge port to the upper end of the cooling device is 30 mm, and is cooled at 25 ° C. and a wind speed of 1.5 m / sec. After cooling by wind, applying an oil agent and converging, the film was wound with a winder so that the draft ratio was 58.0. The physical characteristics of the obtained separation membrane are shown in Table 4. At a pressure of 0.75 MPa, no water permeability was exhibited.

(Comparative Example 3)
50.0% by mass of commercially available PPS (manufactured by Toray Industries, Inc .; "Trelina (registered trademark) E2088") and 50.0% by mass of cyclic PPS oligomer were applied to a twin-screw melt kneader, and melt forming was performed at 300 ° C. did. By setting the drum temperature to 60 ° C. and adjusting the winding speed, a PPS polymer / cyclic PPS oligomer mixture film having a thickness of 30 μm was prepared. The obtained film was cut into a circular shape having 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 and then repeating washing with ion-exchanged water three times, vacuum drying was performed 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, film tear occurred and the separation performance could not be evaluated.

(Comparative Examples 4 to 5)
A separation membrane was obtained in the same manner as in Example 1 except that the composition and production conditions of the resin composition were changed as shown in Table 3. The physical characteristics of the obtained separation membrane are shown in Table 4.

The separation membranes of Examples 1 to 5 all showed a divalent ion blocking rate of 5% or more, a breaking strength of 20 MPa or more, and a membrane permeation flux of 1.0 × 10 ^-3 or more, and excellent separation. It had high performance, high film strength, and high permeation performance. The separation membranes of Examples 4 and 5 have improved removal performance than the separation membranes of Examples 1 to 3, and in the resin composition having the same PPS mass ratio, the higher the degree of orientation, the more divalent ions are blocked. The result was a high rate. Further, the degree of orientation increases as the stretching ratio and stretching speed increase. It is presumed that the high degree of orientation forms a dense structure in which the molecular chains in the separation membrane are lined up, thereby exhibiting high separation performance. Although the separation membrane of Comparative Example 1 showed high water permeability, the divalent ion blocking rate was less than 5%. The separation membrane of Comparative Example 2 did not exhibit water permeability, and the evaluation of the divalent ion inhibition rate itself could not be performed. In Comparative Example 3, the film was torn at a pressure of 0.75 MPa, and the divalent ion blocking rate itself could not be evaluated. Although Comparative Example 4 showed a high divalent ion blocking rate, the water permeability was less than 1.0 × 10 ^-3 . In Comparative Example 5, the breaking strength was less than 20 MPa.

The separation membrane of the present invention is used for selective separation of a liquid mixture containing an organic solvent, concentration / purification of an organic solvent or a strong acid or strong basic solution, production of industrial ultrapure water, wastewater treatment, recovery of valuable resources, etc. be able to.

Claims (10)

Mainly composed of polyarylene sulfide
Contains hydrophilic polymer as an accessory component
The mass ratio of the hydrophilic polymer to the polyarylene sulfide obtained by IR measurement is in the range of 0.01 to 0.20.
Separation membrane. The separation membrane according to claim 1, wherein the divalent ion blocking rate is 5% or more. The separation membrane according to claim 1 or 2, wherein the value of the porosity is in the range of 5 to 45%. Obtained by measuring the cross section of the separation membrane in the thickness direction with micro IR.
The mass ratio of the hydrophilic polymer to the polyarylene sulfide in the central portion in the thickness direction is C.
The mass ratio of the hydrophilic polymer to the polyarylene sulfide on one surface portion of the cross section is S ₁ , and the mass ratio of the hydrophilic polymer to the polyarylene sulfide on the other surface portion of the cross section is S ₂ . When you do
The separation membrane according to any one of claims 1 to 3, wherein the value of C / S ₁ or C / S ₂ is in the range of 0.80 to 1.20. The separation membrane according to any one of claims 1 to 4, wherein the bending ratio is 5 to 500. The separation membrane according to any one of claims 1 to 5, wherein the degree of orientation is 1.04 or more. The separation membrane according to any one of claims 1 to 6, wherein the degree of orientation is 1.55 or more. The separation membrane according to any one of claims 1 to 7, wherein the subcomponent is polyvinylpyrrolidone. (1) A resin composition preparation step of preparing a resin composition by melt-kneading a polyarylene sulfide, a hydrophilic polymer, and a plasticizer.
(2) A molding step in which the resin composition is discharged from a discharge port to mold a resin molded product at a draft ratio of 20 or more.
(3) A method for producing a separation membrane, comprising a dipping 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 9, further comprising a stretching step of stretching the resin molded product after the step (2).