KR102306426B1 - Composite porous membrane of acetylated alkyl cellulose and polyolefinketone - Google Patents

Abstract

The present invention is composed of a support layer, and a coating layer provided concentrically on the outer circumferential surface of the support layer to surround the support layer, the support layer comprising an acetylated alkyl cellulose polymer, and the coating layer comprising a polyolefin ketone polymer The composite hollow fiber membrane according to the present invention has high water permeability and high removal rate while maintaining high strength. It can be applied to the next-generation high-efficiency separation process, such as a module for mixture separation and a pretreatment membrane module for seawater desalination.

Description

Composite hollow fiber membrane of acetylated alkyl cellulose and polyolefin ketone

The present invention relates to a composite hollow fiber membrane, and more particularly, by using an acetylated alkyl cellulose polymer to make a hollow fiber membrane having a porous surface and cross section, and coating the surface of the hollow fiber membrane with a polyolefin ketone polymer again to form a surface layer and a cross section It relates to a composite hollow fiber membrane that can be applied to a membrane distillation process because it has excellent water vapor permeability and excellent salt removal rate by densely changing the surface.

The membrane distillation process is operated at a lower pressure than ultrafiltration and reverse osmosis while using a porous membrane, and separation is achieved by a difference in vapor pressure. In addition, when the membrane distillation separation method is used, there is no entrainment of the traditional distillation method and there is no need to use a filter or a separation membrane operated at a high pressure in separating and removing nonvolatile substances such as salts. Due to the advantages of the membrane distillation separation process, the desalination (desalination) treatment process using the membrane distillation method is emerging as one of the competitive methods in the production of drinking water worldwide.

The membrane distillation method uses a hydrophobic polymer separation membrane, and the surface tension of the solvent or solute (hydrophilic material) is greater than the surface tension of the separation membrane, so it cannot pass through the membrane pores in a liquid state, and is repelled by the membrane surface, and the surface of the membrane At the pore inlet, the material to be separated is phase-transformed into a vapor phase, diffused and permeated into the pore, and finally condensed and separated at the permeation side. This membrane distillation method is performed through a separation membrane module composed of a supply side through which a feed solution passes through a separation membrane and a permeation side on which a material to be separated is condensed and separated. At this time, many studies have been conducted on the water permeation rate according to the supply temperature, the supply flow rate, and the material of the separator.

Korean Patent No. 10-1453803 discloses a step of melt-extruding a PTFE hollow fiber as a support layer with an ultra-high molecular weight polyethylene of 120° C. to 130° C., which has a lower melting point than the support layer; The ultra-high molecular weight polyethylene has a weight average molecular weight of 5 million to 7 million, and during melt extrusion in the melt extrusion step, the melt extrusion temperature is 130 ° C. to 150 ° C. Multilayer PTFE hollow membrane distillation, characterized in that Disclosed is a method for manufacturing a separation membrane.

However, in the case of conventional membrane distillation membranes, hydrophobic membrane materials are used to solve the problem of a decrease in the removal rate due to wetting of the membrane pores. Therefore, the material to be removed, such as sodium chloride, not only passes through the separation membrane, but also the feed solution stays in the pores serving as a diffusion path for water vapor, thereby reducing the diffusion rate.

The present invention is to solve the problems of the prior art described above, and one object of the present invention is to solve the problem of pore wetting of the hollow fiber membrane applied to the conventional membrane distillation method, so that the water vapor permeability is excellent and the salt removal rate is high To provide a composite hollow fiber membrane applicable to a membrane distillation method.

One aspect of the present invention for achieving the above object is,

A support layer and a coating layer provided concentrically on the outer circumferential surface of the support layer to surround the support layer, the support layer includes an acetylated alkyl cellulose polymer, and the coating layer includes a polyolefin ketone polymer. It's about the desert.

The polyolefin ketone polymer is represented by the following Chemical Formula 1 or Chemical Formula 2, wherein the polyolefin ketone resin of Chemical Formula 1 has an intrinsic viscosity of 4 to 7, and the polyolefin ketone resin of Chemical Formula 2 has an intrinsic viscosity of 1 to 3 and the content of propylene is 3 to 10 mol%.

[Formula 1]

where n is a real number from 4,000 to 13,000;

[Formula 2]

In the above formula, n is a real number from 500 to 2,000, and m is a real number from 15 to 200.

The composite hollow fiber membrane of the present invention may further include an intermediate support layer comprising a cellulosic polymer between the support layer and the coating layer. The support layer may have an average pore size of 0.08 μm to 0.2 μm, and the intermediate support layer may have an average pore size of 0.05 μm to 0.1 μm.

Another aspect of the present invention for achieving the above object is,

forming a support layer by forming a support layer dope solution containing an acetylated alkyl cellulose polymer and a poor solvent; and

It relates to a method for producing a composite hollow fiber membrane, comprising the step of preparing a coating layer dope solution containing a polyolefin ketone polymer and coating it around the acetylated alkyl cellulose support layer to form a coating layer.

The acetylated alkyl cellulose support layer may form a hollow fiber membrane by a heat-induced phase separation method, and the polyolefin ketone coating layer may form a coating layer by a non-solvent-induced phase separation method.

The method of the present invention may further include the step of forming an intermediate support layer composed of a cellulosic polymer between the step of preparing the acetylated alkyl cellulose support layer and the step of forming the polyolefin ketone coating layer. The intermediate support layer may be formed by a non-solvent induced phase separation method.

Since the composite hollow fiber membrane of acetylated alkyl cellulose and polyolefin ketone according to the present invention has a dense surface layer and a very small pore structure on the surface, water cannot pass through it directly, but only water molecules that are increased due to the characteristics of the polyolefin ketone material pass selectively and , the acetylated alkyl cellulose constituting the support layer has high hydrophilicity and a porous structure, so that water molecules that have passed through the surface layer can easily move to maintain high permeability.

The composite hollow fiber membrane according to the present invention has high water permeability and high salt removal rate while maintaining high strength. It can be applied to next-generation high-efficiency separation processes such as pretreatment membrane modules.

1 is a schematic diagram of a membrane distillation apparatus used in Examples.
2 is a photograph of a cross-section of the composite hollow fiber membrane prepared in Example 1 of the present invention observed with a scanning electron microscope.
3 is a photograph of a cross-section of the composite hollow fiber membrane prepared in Example 2 of the present invention observed with a scanning electron microscope.
4 is a photograph of a cross-section of the composite hollow fiber membrane prepared in Comparative Example 1 observed with a scanning electron microscope.
5 is a photograph of a cross-section of the composite hollow fiber membrane prepared in Comparative Example 2 observed with a scanning electron microscope.

Hereinafter, the present invention will be described in more detail. In describing the present invention, detailed descriptions of well-known functions or configurations may be omitted in order to clarify the gist of the present invention.

One aspect of the present invention is composed of a support layer, and a coating layer that is provided concentrically on the outer circumferential surface of the support layer to surround the support layer, the support layer includes an acetylated alkyl cellulose polymer, and the coating layer includes a polyolefin ketone polymer It relates to a composite hollow fiber membrane, characterized in that.

Since the acetylated alkyl cellulose polymer has high water permeability and has a porous structure, it has excellent water permeability and excellent stain resistance. As the support layer contains the acetylated alkyl cellulose polymer, water permeability and stain resistance of the support layer are improved can be On the other hand, since the polyolefin ketone layer has a dense and small pore structure, only vaporized water molecules pass selectively to solve the pore wetting problem of the hollow fiber membrane applied to the membrane distillation method, thereby providing a membrane with excellent water permeability and high salt removal rate can do.

The alkyl group of the acetylated alkyl cellulose may be a methyl group, an ethyl group, a propyl group, a hydroxy group, a hydroxypropyl group, and the like, and the support layer may include one or more kinds of the acetylated alkyl cellulose polymer.

The polyolefin ketone polymer is represented by the following Chemical Formula 1 or Chemical Formula 2, wherein the polyolefin ketone resin of Chemical Formula 1 has an intrinsic viscosity of 4 to 7, and the polyolefin ketone resin of Chemical Formula 2 has an intrinsic viscosity of 1 to 3 and the content of propylene is 3 to 10 mol%.

where n is a real number from 4,000 to 13,000;

In the above formula, n is a real number from 500 to 2,000, and m is a real number from 15 to 200.

In the composite hollow fiber membrane of the present invention, the support layer may be prepared by a heat-induced phase separation method, and the coating layer may be prepared by a non-solvent-induced phase separation method.

In another embodiment of the present invention, the composite hollow fiber membrane of the present invention may further include an intermediate support layer comprising a cellulosic polymer between the support layer and the coating layer. The intermediate support layer may be prepared by a non-solvent induced phase separation method. Since the support layer has a structure made by the heat-induced phase separation method, the surface pore size is larger and the smoothness is lower than that of the intermediate support layer made by the non-solvent-induced phase separation method. possible.

In the composite hollow fiber membrane composed of a support layer, an intermediate support layer, and a coating layer, the support layer may have an average pore size of 0.1 μm to 5 μm, and the intermediate support layer may have an average pore size of 0.03 μm to 0.1 μm.

The cellulosic polymer constituting the intermediate support layer is acetylated alkyl cellulose, cellulose acetate, cellulose triacetate, cellulose proprianate, cellulose butyrate, cellulose acetylpropionate, cellulose diacetate, cellulose dibutyrate and cellulose tributyrate. It may include one or more selected from the group.

Another aspect of the present invention relates to a method for manufacturing a composite hollow fiber membrane.

In the method of the present invention, a support layer dope solution containing an acetylated alkyl cellulose polymer and a poor solvent is formed into a film to form a support layer, and then a coating layer dope solution containing a polyolefin ketone polymer is prepared and coated around the acetylated alkyl cellulose support layer. A polyolefin ketone coating layer is formed.

The polyolefin ketone polymer is represented by the following Chemical Formula 1 or Chemical Formula 2, wherein the polyolefin ketone resin of Chemical Formula 1 has an intrinsic viscosity of 4 to 7, the polyolefin ketone resin of Chemical Formula 2 has an intrinsic viscosity of 1 to 3, and propylene A content of 3 to 10 mol% may be used.

[Formula 1]

where n is a real number from 4,000 to 13,000;

[Formula 2]

In the above formula, n is a real number from 500 to 2,000, and m is a real number from 15 to 200.

In the present invention, the acetylated alkyl cellulose support layer is manufactured by a heat-induced phase separation method to prepare a hollow fiber membrane, and the polyolefin ketone coating layer forms a coating layer by a non-solvent-induced phase separation method.

The process of manufacturing a hollow fiber membrane by heat-induced phase separation (TIPS) using an acetylated alkyl cellulose polymer is to achieve a porous membrane by contacting a dope solution dissolved at a high temperature with a medium at a low temperature to cause liquid-solid phase separation and solidification. method, and the process of manufacturing a coating by non-solvent induced phase separation (NIPS) using polyolefin ketone polymer is by dissolving the polymer in a solvent capable of dissolving the polymer so that the solvent and the non-solvent are interchanged in the dope solution. A porous membrane is formed by inducing liquid-solid phase separation and solidification.

As described above, by phase separation using TIPS for the support layer and NIPS for the coating layer, a high-strength, high-permeability hollow fiber membrane with easy pore control can be formed.

In the method for manufacturing a composite hollow fiber membrane according to an embodiment of the present invention, the dope solution forming the support layer includes acetylated alkyl cellulose and a poor solvent. At this time, the content ratio of each component is preferably composed of 15 to 40 wt% of acetylated alkyl cellulose and 60 to 85 wt% of the poor solvent.

In the production method of the present invention, the poor solvent is a hydrophilic polymer or organic material easily soluble in water such as polyethylene glycol, polyvinyl alcohol, maleic anhydride, surfactant, etc., alone or as a mixture of two or more, added to the acetylated alkyl cellulose dope solution. It can be used, and it is preferable to use polyethylene glycol.

Before the dope solution is spun, degassing may be performed by a method such as reduced pressure to remove air bubbles remaining in the solution, and the degassed dope solution contains impurities in the solution, especially undissolved polymer or carbonized polymer It may be filtered using a metal mesh or the like to remove solid impurities, but the manufacturing method of the present invention is not limited thereto, and the degassing and filtering may be selectively performed by checking the state of the dope solution.

In the present invention, the dope solution for forming the support layer is preferably prepared at 130 to 200° C., and must be subjected to a defoaming process in order to remove bubbles present in the solution. Generally, it solidifies at a temperature of 130° C. or less to form a hollow fiber membrane, or when in contact with a non-solvent having a temperature of 130° C. or less, a hollow fiber separation membrane is formed by phase separation. Therefore, it is preferable to discharge the dope solution as a coagulating solution through a spinning nozzle maintaining a temperature of at least 130° C. or more, preferably 130 to 180° C. for the preparation of the acetylated alkyl cellulose support layer.

The polyolefin ketone coating layer may be prepared, for example, by a liquid coating method. In the liquid coating method, a coating solution is prepared by dissolving polyolefin ketone in an appropriate solvent. At this time, the concentration of the copolymer in the prepared coating solution is not particularly limited, and may be, for example, 0.5% (w/v) to 8% (w/v). In addition, as a solvent usable in preparing the coating solution, at least one metal salt solution selected from the group consisting of ZnCl2, CaCl2 and LiCl, m-cresol, hexafluoro-2-propanol (Hexafluoro-2- propanol, HFIP), but is not necessarily limited thereto.

In addition, a separate pore control agent may be additionally used to control the pore size of the prepared polyolefin ketone coat layer. These pore-controlling agents may be used by selecting a known pore-controlling agent suitable for a desired pore size and adding an appropriate amount. Poly(ethylene glycol), poly(vinylpyrrolidone), and poly(vinyl alcohol) of various molecular weights can be selectively used as a pore control agent for increasing the pore size, and 1,4 as a pore control agent for reducing the pore size -Dioxane, diethylene glycol dimethyl ether, etc. can be used selectively.

In the liquid coating method, after coating the coating solution prepared as above on a support, phase separation in a coagulation bath, washing and drying steps to prepare a separation membrane. As the coating method, a conventional method such as dip coating, spin coating or spray coating may be used.

In the phase separation of polyolefin ketone, a non-solvent induced phase separation method may be used, and the solvent used as the non-solvent may be selected from the group consisting of γ-butyrolactone, ethanol, and lithium chloride.

In another embodiment, the step of forming an intermediate support layer composed of a cellulosic polymer between the step of preparing the acetylated alkyl cellulose support layer and the step of forming the polyolefin ketone coating layer may be further included. In this case, the intermediate support layer may be formed by a non-solvent induced phase separation method.

When the support layer is formed in two layers, the support layer dope solution, the intermediate support layer dope solution and the hollow former constituting the intermediate support layer are simultaneously spun into the external coagulation tank through the triple nozzle to form the support layer hollow fiber membrane. . At this time, the hollow forming agent is discharged through the inner nozzle of the triple spinneret, the dope solution forming the intermediate support layer is discharged through the outer nozzle, and the dope solution forming the support layer is discharged through the nozzle between the inside and the outside. . As such, by simultaneously spinning the support layer and the intermediate support layer dope solution through the triple spinneret, it is possible to manufacture a composite hollow fiber membrane having a uniform thickness even after the hollow fiber membrane is formed and the coating layer is not peeled off.

The method of forming the polyolefin ketone coating layer is the same as described above.

In the present invention, a washing process may be further included to remove organic matter including solvent remaining inside and outside the membrane of the hollow fiber membrane transferred to the atmosphere from the coagulation solution. Water is preferably used as the washing liquid, and the washing time is not particularly limited, but preferably at least 1 day or more and 5 days or less.

Drying conditions performed after the above-described washing process are not particularly limited as long as the solvent contained in the coating solution is sufficiently removed, for example, after coating, the separator is placed in an oven or vacuum oven and about 20 to 80 It can be carried out by performing a drying process at ℃ for about 24 hours.

Hereinafter, the present invention will be described in more detail through examples. However, the following examples are only for illustrating the present invention, and the scope of the present invention is not limited by the following examples.

Example

Example One

A support layer hollow fiber membrane was prepared by a heat-induced phase separation method in which 25 wt% of acetylated methyl cellulose (AMC) and 75 wt% of triethylene glycol were dissolved at 160°C, discharged through a spinneret, and solidified in a coagulation bath composed of water at 25°C. . After coating the prepared hollow fiber membrane in a coating solution composed of 10 wt% of polyolefin ketone and 90 wt% of methacresol by dipping method, it was solidified in a coagulation bath composed of ethanol at 25 ° C. By forming, a composite hollow fiber membrane of acetylated methyl cellulose and polyolefin ketone was prepared.

Example 2

25 wt% of acetylated methyl cellulose and 75 wt% of triethylene glycol were dissolved at 160°C to prepare a dope solution for the support layer, and 10 wt% of acetylated methyl cellulose and 90 wt% of dimethylacetamide were dissolved at 60°C to prepare a dope solution for the intermediate support layer. made Then, a heat-induced phase separation method and a non-solvent-induced phase separation method in which the prepared support layer dope solution and the intermediate support layer dope solution containing the prepared acetylated methylcellulose polymer are discharged through a triple spinneret and solidified in a coagulation bath composed of 25°C water. A hollow fiber membrane was prepared. The prepared hollow fiber membrane was coated with a dipping method in a solution composed of 10 wt% of polyolefin ketone and 90 wt% of metacresol, and then solidified in a coagulation bath composed of ethanol at 25°C to form a polyolefin ketone coating layer by a non-solvent-induced phase separation method. Thus, a composite hollow fiber membrane of acetylated methyl cellulose and polyolefin ketone was prepared.

comparative example One

A hollow fiber membrane was prepared by a heat-induced phase separation method in which 25 wt% of acetylated methyl cellulose and 75 wt% of triethylene glycol were dissolved at 160°C, discharged through a spinneret, and solidified in a coagulation bath composed of water at 25°C.

comparative example 2

25 wt% of acetylated methyl cellulose and 75 wt% of triethylene glycol were dissolved at 160 °C to prepare a support layer dope solution, and 90 wt% of acetylated methyl cellulose (10 wt%, dimethylacetamide) was dissolved at 60 °C to dope coating solution. made A hollow fiber membrane combining a heat-induced phase separation method and a non-solvent-induced phase separation method in which the prepared dope solution for the support layer containing the acetylated methylcellulose polymer and the dope solution for the coating layer are discharged through a triple spinneret and simultaneously solidified in a coagulation bath composed of 25°C water. was prepared.

test example 1: Scanning electron microscope analysis

The composite hollow fiber membranes prepared in Examples 1 and 2 and Comparative Examples 1 and 2 were observed using a scanning electron microscope, and the results are shown in FIGS. 2 to 5 .

2-3, as a result of observing a part of the cross-section of the composite hollow fiber membrane prepared in Examples 1 and 2 with a scanning electron microscope, it was found that the polyolefin ketone coating layer was well formed on the outer peripheral surface of the acetylated alkyl cellulose support layer. can

test example 2: Permeability analysis

In order to compare the permeation performance of the composite hollow fiber membranes or composite hollow fiber membranes prepared in Examples and Comparative Examples of the present invention, the physical properties of the composite hollow fiber membranes prepared in Examples 1 and 2 and Comparative Examples 1 and 2 are shown in FIG. The permeation performance analysis experiment as follows was performed using the membrane distillation apparatus as shown, and the analysis results are shown in Table 1 below.

1) Test Example 1 - Permeation flow evaluation

Through the composite hollow fiber membrane of the membrane distillation apparatus of FIG. 1, the permeation flow rate of water vapor to a 3.5% NaCl aqueous solution at 60°C was measured. Specifically, the amount of water vapor contained in the air with a condenser after placing an aqueous solution at 60° C. and 3.5% on the outside of the hollow fiber membrane between the manufactured hollow fiber membranes, and passing air through the hollow part in the middle of the hollow fiber membrane at a flow rate of 1 l/min. was measured, and the amount of water vapor permeated per unit time and per unit area was evaluated to calculate the permeation flow.

2) test example 2 - salt removal rate evaluation

The salt removal rate was calculated by the following formula.

In the above formula, R is the salt removal rate, Cf is the concentration of the solute in the NaCl aqueous solution, and Cp is the concentration of the solute in the permeated water obtained by condensing the permeated water vapor.

hollow fiber membrane
water vapor transmission
(g/ft2,d) Salt removal rate (%) Comparative Example 1 7.49 75.432 Comparative Example 2 12.36 30.227 Example 1 4.18 99.999 Example 2 6.39 99.999

Looking at the results of Table 1, the composite hollow fiber membrane of acetylated alkyl cellulose and polyolefin ketone of the present invention prepared in Examples 1 and 2 had a salt removal rate higher than that of the acetylated alkyl cellulose separation membrane prepared in Comparative Examples 1 and 2 excellence can be seen.

The composite hollow fiber membrane according to the present invention is a coating layer comprising a polyolefin ketone polymer having excellent water permeability, excellent stain resistance, and an acetyl alkyl cellulose polymer having a high salt removal rate due to dense pores, and a polyolefin ketone polymer having high mechanical strength and chemical resistance. It is composed, and maintains high water permeability, and can exhibit excellent salt removal rate and mechanical properties. In addition, the hollow fiber membrane according to the present invention can be applied to a water treatment process such as seawater, brine, sewage and wastewater, in particular, has an effect that can be applied to a desalination process.

Although the present invention has been described in detail above, it will be understood that the present invention is not limited to the above-described embodiments, and that various modifications and variations are possible from these descriptions by those skilled in the art to which the present invention pertains. will be. Accordingly, the protection scope of the present invention should be defined not only in the claims described below, but also in the scope equivalent to the claims.

Claims (17)

A support layer and a coating layer provided concentrically on the outer circumferential surface of the support layer to surround the support layer, the support layer includes an acetylated alkyl cellulose polymer, and the coating layer includes a polyolefin ketone polymer. desert.
According to claim 1, wherein the polyolefin ketone polymer is represented by Formula 1 or Formula 2, the polyolefin ketone resin of Formula 1 has an intrinsic viscosity of 4 to 7, and the polyolefin ketone resin of Formula 2 is Composite hollow fiber membrane, characterized in that the intrinsic viscosity is 1 to 3, and the content of propylene is 3 to 10 mol%.
[Formula 1]

where n is a real number from 4,000 to 13,000;
[Formula 2]

In the above formula, n is a real number from 500 to 2,000, and m is a real number from 15 to 200.
The composite hollow fiber membrane according to claim 1, wherein the support layer is manufactured by a heat-induced phase separation method, and the coating layer is a membrane manufactured by a non-solvent-induced phase separation method.
The composite hollow fiber membrane according to claim 1, wherein the composite hollow fiber membrane further comprises an intermediate support layer comprising a cellulosic polymer between the support layer and the coating layer.
The composite hollow fiber membrane according to claim 4, wherein the support layer has an average pore of 0.08 μm to 0.2 μm, and the intermediate support layer has an average pore of 0.05 μm to 0.1 μm.
According to claim 4, wherein the cellulosic polymer constituting the intermediate support layer is acetylated alkyl cellulose, cellulose acetate, cellulose triacetate, cellulose proprianate, cellulose butyrate, cellulose acetylpropionate, cellulose diacetate, cellulose dibutyrate and Composite hollow fiber membrane, characterized in that at least one polymer selected from the group containing cellulose tributyrate.
[Claim 5] The composite hollow fiber membrane according to claim 4, wherein the intermediate support layer is a membrane prepared by a non-solvent induced phase separation method.
forming a support layer by forming a support layer dope solution containing an acetylated alkyl cellulose polymer and a poor solvent; and
A method for producing a composite hollow fiber membrane, comprising the step of preparing a coating layer dope solution containing a polyolefin ketone polymer and coating it around the acetylated alkyl cellulose support layer to form a coating layer.
The method of claim 8, wherein the polyolefin ketone polymer is represented by the following Chemical Formula 1 or Chemical Formula 2, wherein the polyolefin ketone resin of Chemical Formula 1 has an intrinsic viscosity of 4 to 7, and the polyolefin ketone resin of Chemical Formula 2 is A method for producing a composite hollow fiber membrane, characterized in that the intrinsic viscosity is 1 to 3, and the content of propylene is 3 to 10 mol%.
[Formula 1]

where n is a real number from 4,000 to 13,000;
[Formula 2]

In the above formula, n is a real number from 500 to 2,000, and m is a real number from 15 to 200.
According to claim 8, wherein the acetylated alkyl cellulose support layer is a hollow fiber membrane by a heat-induced phase separation method, and the polyolefin ketone coating layer is a composite hollow fiber membrane, characterized in that the coating layer is formed by a non-solvent-induced phase separation method Way.
The method of claim 8, further comprising the step of forming an intermediate support layer composed of a cellulosic polymer between the step of preparing the acetylated alkyl cellulose support layer and the step of forming the polyolefin ketone coating layer. The method of claim 11, wherein the intermediate support layer is formed by a non-solvent induced phase separation method.
The composite hollow according to claim 11, wherein the method further comprises simultaneously spinning the support layer dope solution, the intermediate support layer dope solution constituting the intermediate support layer, and the hollow former into an external coagulation bath through a triple nozzle. Desert manufacturing method.
The method according to claim 8, wherein the poor solvent is at least one selected from the group consisting of polyethylene glycol, polyvinyl alcohol, and maleic anhydride.
The method according to claim 10, wherein the solvent used as a non-solvent in the non-solvent-induced phase separation method is selected from the group consisting of γ-butyrolactone, ethanol, and lithium chloride. Way.
The method according to claim 11, wherein the solvent used for the non-solvent-induced phase separation of the intermediate support layer is N,N-dimethylacetamide or 1-methyl-2-pyrrolidone. .
The method according to claim 8, wherein the temperature of the polymer dope solution forming the support layer is in a temperature range of 130 to 180°C.

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