KR20160052182A - Porous hollow fiber and manufacturing method same - Google Patents

Abstract

Disclosed are a porous hollow fiber membrane and a method for manufacturing the porous hollow fiber membrane, which can implement both excellent mechanical strength and excellent water permeability through deformation of a support layer structure of the porous hollow fiber membrane. The present invention provides a porous hollow fiber membrane which is manufactured in a dual-layer structure by simultaneously discharging a support layer and a coating layer using a triple spinning nozzle including a triple tube, wherein the support layer is formed by a thermal-induced phase separation method; the coating layer is formed by a non-solvent induced phase separation method; spherical crystal grains having diameters ranging from 2 to 20 μm, formed by a solid-liquid phase separation method, are present in the support layer; and micro-zones having diameters ranging from 0.1 to 2 μm are formed in the spherical crystal grains.

Description

TECHNICAL FIELD [0001] The present invention relates to a porous hollow fiber membrane and a method of manufacturing the porous hollow fiber membrane.

The present invention relates to a porous hollow fiber membrane and a method for producing the porous hollow fiber membrane, and more particularly, to a porous hollow fiber membrane excellent in mechanical strength and water permeability and a method for producing the same.

With the development of the industry and population growth, interest in efficient water use and treatment technologies is increasing. Recently, separation membrane technology has been increasingly applied to ensure the stability of water quality in water treatment and sewage treatment. There are hollow membrane separators and flat membranes in the separation membrane applied to the water treatment process. In the case of hollow membrane separators, many hollow membrane separators are being studied because the volume per unit area is large and the module manufacture and cost are relatively easy.

As a general water treatment membrane material, polysulfone, polyethylene (PE), polypropylene (PP), cellulose acetate (CA) and polyvinylidene fluoride (PVDF) are used. The PVDF (Polyvinylidene fluoride) hollow fiber membrane, which is superior in strength and chemical resistance in recent years, has been used as a water treatment agent for water purification and water treatment since it has been undergoing physical and chemical treatment to control membrane contamination in a water treatment process using a membrane. And is widely used as an industrial separator.

Initially, the hollow fiber membrane was prepared by applying the heat - induced phase transfer method to increase the strength of the hollow fiber membrane. However, such a membrane has a high strength but a low permeation flux. Thereafter, in order to simultaneously increase the strength and the permeation flux of the hollow fiber membrane, a porous membrane was prepared by coating a polymer solution on the membrane membrane. However, such separation membrane may peel off the coating layer. Recently, a dual-layer hollow fiber membrane is produced by simultaneously discharging a support layer and a coating layer of a hollow fiber membrane using a triple nozzle to increase the hollow fiber membrane strength and increase the permeation flux. These hollow fiber membranes are applied simultaneously with the thermal induction phase transfer method and the non-coalesced transfer method, and provide an asymmetric separator. Asymmetric separators have the advantage of increasing the selectivity in the coating layer while ensuring physical strength in the support layer structure.

In order to increase the strength and water permeability of the hollow fiber membrane, the hydrophilic or non-porous additive may be used to change the internal structure of the hollow fiber membrane to improve its physical properties.

[Prior Patent Literature]

- Korean Unexamined Patent Publication No. 10-2013-0111052 (Published Oct. 10, 2013)

- Korean Unexamined Patent Publication No. 10-2012-0001970 (2012.01.05. Disclosed)

- Korean Unexamined Patent Application Publication No. 10-2013-0122454 (Published Nov. 31, 2013)

- Korean Unexamined Patent Publication No. 10-2013-0122454 (Published Oct. 18, 2007)

The present invention relates to a porous hollow fiber membrane which is produced in a dual-layer structure by simultaneously discharging a support layer and a coating layer using a triple-layered spinning nozzle, and has excellent mechanical strength and water permeability And a method for producing the porous hollow fiber membrane.

In order to solve the above-described problems, the present invention provides a porous hollow fiber membrane having a dual-layer structure by simultaneously discharging a support layer and a coating layer using a triple spinning nozzle, Wherein the coating layer is formed by a non-solvent induced phase separation, and the support layer is formed by a solid-liquid phase transition having a diameter of 2 to 20 占 퐉 Wherein the spherical crystal grains have spherical crystal grains and the spherical crystal grains have microzones of 0.1 to 2 mu m in diameter.

In order to solve the above-mentioned problem, the present invention provides a method for producing a coating solution for a coating layer, comprising the steps of: using an inner coagulant solution on the innermost side of the spinning nozzle, a coating layer polymer spinning solution on the outermost side, A porous hollow fiber membrane having a dual-layer structure, wherein the support layer is formed by thermal-induced phase separation, and the coating layer is formed by a non-volatile transition method solvent-induced phase separation, and the support layer polymer solution contains a polymer resin, a non-solvent, a good solvent, a poor solvent, a pore-forming agent, and an inorganic additive, wherein the non-solvent- Lithium is used and the temperature of the coagulation bath is maintained so that the supporting layer polymer spinning solution is quenched at a temperature difference of 100 to 160 DEG C during discharge, (Solid-liquid) by a phase change, and the spherical grains having a diameter of 2 ~ 20㎛ present, the spherical grains provides a method to ensure that the micro-zones having a diameter of 0.1 ~ 2㎛ formed.

The polymeric resin may also be selected from the group consisting of polyethersulfone (PES), polysulfone (PSf), polyethercetone (PEK), polyetherketone (PEEK), sulfonated polymer, polyvinylidene fluoride , Polytetrafluoroethylene (PTFE), polyvinylidene chloride (PVDC), chlorinate polyvinyl chloride (CPVC), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) and ethylene chlorotrifluoroethylene ECTFE). ≪ / RTI >

Also, the above-mentioned two kinds of solvents are at least one selected from the group consisting of NMP (N-mentyl-2-pyrrolidone), DMF (dimethylformamide), DMAc (N, N'- dimethyl acetamide), DMSO (dimethyl sulfoxide) and HMPA The method comprising the steps of:

Also, the poor solvent may be at least one selected from the group consisting of dibutyl phthalate (DBP), dimethyl phthalate (DMP), dioctyl sebacate (DO), dioctyl adipate (DOA), gum-butylolactone (GBL), and propylene carbonate The method comprising the steps of:

Also, the pore-forming agent is at least one selected from the group consisting of polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), and glycerol.

The solvent may be used in an amount of 1 to 20 parts by weight based on 100 parts by weight of the polymer resin, 10 to 60 parts by weight of the solvent, 5 to 200 parts by weight of the poor solvent, 1 to 50 parts by weight of the pore- And 0.1 to 10 parts by weight of an inorganic additive.

According to the present invention, in a porous hollow fiber membrane produced in a dual-layer structure by simultaneously discharging a support layer and a coating layer using a triple spinning nozzle including a triple pipe, It is possible to provide a porous hollow fiber membrane capable of simultaneously realizing excellent mechanical strength and water permeability by forming a supporting layer having a spherical crystal structure in which micro zones are formed as small spherical pores.

Also, it is possible to provide a method of easily fabricating a support layer having a spherical crystal structure in which a micro zone formed of small pores is formed by controlling the quenching temperature difference with the coagulation bath by using a support layer polymer spinning solution having a specific composition.

FIG. 1 and FIG. 2 are photographs showing the result of observing the cross-section of the support layer of the porous hollow fiber membrane produced according to Example 1 and Comparative Example 1 using a scanning electron microscope (SEM).

Hereinafter, preferred embodiments of the present invention will be described in detail. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. Throughout the specification, when an element is referred to as "including " an element, it means that it can include other elements, not excluding other elements, unless specifically stated otherwise.

The present inventors have found that, in a porous hollow fiber membrane produced in a dual-layer structure by simultaneously discharging a supporting layer and a coating layer using a triple-layered spinning nozzle, a support layer spinning solution having a specific composition is used, It has been found that the water permeability can be significantly improved while having high mechanical strength of the hollow fiber membrane by preparing a support layer having a spherical crystal structure in which microns having small pores are formed by controlling the difference in quenching temperature.

Accordingly, the present invention provides a porous hollow fiber membrane having a dual-layer structure by simultaneously discharging a support layer and a coating layer using a triple-layered spinning nozzle, wherein the support layer is thermally-induced phase separation, wherein the coating layer is formed by a non-solvent induced phase separation, and the support layer has spherical crystal grains of 2 to 20 占 퐉 in diameter due to a solid-liquid phase transition, Wherein the spherical crystal grains have microzones of 0.1 to 2 mu m in diameter. Also, the porous hollow fiber membrane according to the present invention is characterized in that an inner coagulant solution is disposed at the innermost side of the spinning nozzle, a coating layer polymer spinning solution at the outermost side, and a spinning solution for supporting layer polymer at the middle Layer structure, and the support layer is formed by thermal-induced phase separation, and the coating layer is formed by a non-solvent induced phase separation method. Wherein the supporting layer polymer spinning solution comprises a polymer resin, a non-solvent, a poor solvent, a poor solvent, a pore-forming agent and an inorganic additive, wherein the non-solvent glycerol and lithium chloride are used as the inorganic additive, Maintaining the temperature of the coagulation bath so that the supporting layer polymer spinning solution is quenched to a temperature difference of 100 to 160 DEG C, whereby the support layer is subjected to a solid-liquid phase transition The spherical grains with a diameter of 2 ~ 20㎛ present, and the spherical grains may be such that the micro-zones having a diameter of 0.1 ~ 2㎛ formed. Hereinafter, the porous hollow fiber membrane according to the present invention will be described in detail.

The porous hollow fiber membrane according to the present invention is produced by simultaneously spinning a support layer and a coating layer using a triple nozzle. Specifically, a support layer is formed using a thermal-induced phase separation, and a coating layer is formed through a non-solvent induced phase separation.

Thermally induced phase transfer methods are widely used to produce crystalline polymers as separators. (S-L, Solid-Liquid) phase separation or Liquid-Liquid (Liquid-Liquid) phase separation can be performed according to the dilution agent and the spinning conditions of the spinning solution. The larger the difference in the quenching temperature between the spinning solution and the coagulation bath, the smaller the spherical crystals and the smaller the quenching temperature, the larger the size of the spherical crystals. The hollow fiber membrane produced by this method has no macrovoids and has uniform pore size and excellent mechanical strength. Here, a macropore is a pore having a diameter of 50 μm or more.

On the other hand, in the case of a hollow fiber membrane having an internal structure of spherical crystals, the hollow fiber membrane has a low water permeability because of its compactness between spherical crystals. A dense layer is formed on the surface of the hollow fiber membrane by diluting the solvent on the surface of the hollow fiber membrane during evaporation and coagulation of the solvent, which occurs in an air gap during spinning. Due to these causes, the hollow fiber membrane manufactured by the thermal induction phase transfer method has a disadvantage of low water permeability.

The non-volatile transition method is a method of manufacturing a hollow fiber membrane by mutual exchange by diffusion between a solvent of a polymer solution and a solvent of a coagulation tank, and the space occupied by the solvent and the non-solvent becomes pores. And can be classified into a finger-like structure and a sponge-like structure depending on the phase transition and pore shape. The hollow fiber membrane manufactured by this method has an advantage that the water permeability is superior to that of the hollow fiber membrane manufactured by the thermal induction phase transfer method, but the mechanical strength is low and the membrane is easily broken.

In the present invention, in consideration of the disadvantages of the heat induction phase transfer method and the non-cost transfer method in manufacturing the hollow fiber membrane, a support layer is formed using a thermal induction phase transfer method using a triple nozzle, and a coating layer is formed using a non- Thereby producing a hollow-fiber membrane having a dual-layer structure. Therefore, hollow fiber membranes with high mechanical strength are produced by suppressing formation of dense layers, which is a disadvantage of the heat induced phase transfer method.

In the present invention, the support layer having spherical crystals can be realized by using a diluent (poor solvent), especially GBL (gama-butylolactone) and inducing S-L phase transition by raising the quenching temperature difference. Also, in order to maintain the mechanical properties of the hollow fiber membrane composed of spherical crystal grains and to form the porous structure, the solubility parameter difference with the polymer resin such as polyvinylidene fluoride is large and the hydrophilic organic The solvent, glycerol, is added to induce the LL phase transition. Thus, spherical crystal grains are formed by the S-L phase transition in the structure of the hollow fiber membrane support layer, and small pores having a predetermined diameter are formed in the spherical crystal grains. At this time, the content of the glycerol for the uniform pore size and the mechanical strength improvement without occurrence of the macropores can be 1 to 20 parts by weight, preferably 2 to 10 parts by weight, more preferably 2 to 10 parts by weight based on 100 parts by weight of the polymer resin May be 3 to 7 parts by weight.

The temperature of the support layer spinning solution and the coagulation bath should be set so that the quenching temperature difference is about 100 to 160 ° C, preferably 120 to 140 ° C. Specifically, the temperature of the quenching bath may be maintained at 150 to 170 ° C, preferably 155 to 165 ° C, and the coagulation bath temperature may be set to 1 to 10 ° C, preferably about 3 to 7 ° C.

On the other hand, in order to form small pores, it is difficult to precisely match the process conditions for formation of small pores such as the temperature of the support layer spinning solution, the temperature of the coagulation bath, the discharge speed, and the discharge distance. However, in the present invention, it is difficult to grasp clearly the reason yet, but it has been confirmed that small pores can be easily formed by adding lithium chloride in an appropriate amount as an inorganic additive. The content of lithium chloride for forming such small pores may be 0.1 to 10 parts by weight, preferably 0.2 to 5 parts by weight, more preferably 0.5 to 3 parts by weight, based on 100 parts by weight of the polymer resin, Preferably 1 to 2 parts by weight.

In the present invention, the spherical crystal grains may have an average diameter of 2 to 20 탆, preferably 2 to 10 탆, and more preferably 3 to 6 탆. The size of the small pores formed in the spherical crystal grains may be 0.1 to 2 탆, preferably 0.3 to 1 탆, and more preferably 0.5 to 0.7 탆 in average diameter. In the present invention, such small pores are referred to as " microzones ".

In the case of hollow fiber membranes with micron zones, the physical properties such that the mechanical strength is maintained and the water permeability is higher than that of the hollow fiber membrane produced by the same spinning conditions as the same polymer resin content can be confirmed by flux measurement. Previously, there was an example in which glycerol was used as a non-solvent additive, but no example of forming such a microzon by applying glycerol has been reported.

In the present invention, the polymer resin may be applied to the hollow fiber membrane of the present invention. The polymer resin may be selected from the group consisting of polyethersulfone (PES), polysulfone (PSf), polyethercetone (PEK) (PEEK), sulfonated polymer, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinylidene chloride (PVDC), chlorinate polyvinyl chloride Polyvinylidene fluoride (CPVC), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), ethylene chlorotrifluoroethylene (ECTFE) and the like can be applied, and polyvinylidene fluoride (PVDF) can be preferably applied. The polyvinylidene fluoride (PVDF) may have a weight average molecular weight of 50,000 to 2,000,000.

In the present invention, examples of suitable solvents for the spinning solution include N-mentyl-2-pyrrolidone, DMF, N, N'-dimethyl acetamide, DMSO and trimethyl phosphoramidite And it is particularly preferable to select a good solvent having a total solubility parameter of 21 to 27 MPa 1/2 and a boiling point of 130 to 230 ° C. The amount of both solvents can be controlled by adjusting the viscosity of the spinning solution, and it is necessary to completely dissolve the additives. The amount of the positive solvent to be added is preferably 10 to 60 parts by weight, more preferably 10 to 40 parts by weight, and most preferably 20 to 30 parts by weight based on 100 parts by weight of the polymer resin. When the amount of the positive solvent is less than 10 parts by weight, the flowability of the spinning solution is lowered and the kneading temperature must be raised to 150 ° C or more. When the amount of the solvent is more than 60 parts by weight, the phase transition speed of the spinning solution is increased, Or the strength of the hollow fiber membrane may be weakened.

Diputyl phthalate (DBP), dimethyl phthalate (DMP), dioctyl sebacate (DOS), dioctyl adipate (DOA), gum-butylolactone (GBL) and propylene carbonate have. The poor solvent has no solubility for the polymer at room temperature, and has the property of dissolving the polymer at high temperature. In the thermally induced phase transfer (TIPS) process, the poor solvent has the function of forming the pores of the polymer separator, improving the flowability of the spinning solution, and lowering the melting point of the polymer. From this viewpoint, GBL (gama-butylolactone) is preferably selected as the poor solvent. The amount of the poor solvent to be added is preferably 5 to 200 parts by weight, more preferably 10 to 150 parts by weight, and most preferably 90 to 130 parts by weight based on 100 parts by weight of the polymer resin. If the content of the poor solvent is less than 5 parts by weight, the porosity of the separation membrane is deteriorated and the permeation flow rate may be decreased. If the content of the poor solvent is more than 200 parts by weight, it may be difficult to expect the improvement of the permeation flow rate with respect to the content.

In the present invention, polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), glycerol and the like may be used in an amount of 1 to 50 parts by weight based on 100 parts by weight of the polymer resin. In order to form more uniform pores, And it is most preferably used in an amount of 5 to 10 parts by weight.

As the internal coagulant in the present invention, a good solvent for a polymer resin such as PVDF and a non-solvent may be mixed and used. In general, water, EG (ethylene glycol), alcohols, ketones, polyethylene glycol (PEG) and the like are used as the non-solvent for the internal coagulant, but preferably a mixed solution of the non-solvent DMAc and the non-solvent EG can be used. In general, the higher the ratio of the good solvent, the more the inner wall of the polymer membrane can be dissolved, and if the non-solvent ratio is high, the formation of pores in the inner wall of the hollow fiber membrane may be difficult. Therefore, it is preferable to control the amounts of both the solvent and the non-solvent according to the purpose of use.

The hollow fiber membrane is obtained through the coagulation bath and the washing bath in the wet system using the solvent and the additive, and the final hollow fiber membrane can be produced through the hydrothermal treatment and the chemical treatment bath. In the hydrothermal treatment and chemical treatment tank, the crystallization induction of residual microcrystalline part of the hollow fiber membrane, residual diluent extraction, and residual additive are extracted. For the hydrothermal treatment, water at 40 to 80 ° C may be used. In case of the chemical treatment tank, ethanol and glycerol may be used.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. However, the following examples are illustrative of the present invention, and the present invention is not limited to the examples described below.

Example  One

To prepare 100 parts by weight of PVDF (polyvinylidene fluoride), 111.25 parts by weight of a diluent GBL (Gamma-butyrolactone), 25 parts by weight of a positive solvent NMP (N-methyl-2-pyrrolidone) 7.5 parts by weight of polyvinylpyrrolidone, 1.25 parts by weight of lithium chloride, and 5 parts by weight of glycerol were heated and stirred at a high temperature of 160 ° C and a pressure of 1 bar for 3 hours to prepare a homogeneous polymer solution.

750 parts by weight of DMAc (dimethylacetamide), 50 parts by weight of PVP (polyvinylpyrrolidone), 50 parts by weight of LiCl (lithium chloride) and 100 parts by weight of polyvinylpyrrolidone were added to 100 parts by weight of PVDF (polyvinylidene fluoride, solef 6010) And 50 parts by weight of EG (ethylene glycol) were heated and stirred at 100 占 폚 for 3 hours to prepare a homogeneous polymer solution.

For the preparation of the coagulant solution in the hollow fiber membrane, DMAc: EG was gradually mixed in a weight ratio of 60:40 to prepare a homogeneous solution.

Thereafter, the inner coagulant solution is discharged to the innermost side of the spinneret using a triple spinning nozzle including a triple pipe, the coating solution for polymer coating is discharged to the outermost side of the spinneret, The polymer solution was discharged. The support layer polymer solution was discharged to the coagulation bath through a spinneret at 140 캜 while keeping the temperature at 160 캜, the coating layer polymer solution at 25 캜 and the internal coagulant at 25 캜. The distance between the spinning nozzle and the coagulation bath was 7 cm.

The hollow fiber membrane radiated through the nozzle was immersed in a coagulation tank maintained at 5 ° C and immersed in a heat bath containing an ethanol / glycerol solution maintained at 40 ° C through a washing tank maintained at 20 ° C for 12 hours to have an outer diameter of 1,280 μm and an inner diameter A porous hollow fiber membrane having a size of 710 mu m was prepared.

Example  2

Porous hollow fiber membranes having an outer diameter of 1,270 mu m and an inner diameter of 700 mu m were prepared in the same manner as in Example 1 except that 27.5 parts by weight of NMP and 2.5 parts by weight of glycerol were used in the support layer polymer spinning solution of Example 1.

Example  3

A porous hollow fiber membrane having an outer diameter of 1,320 탆 and an inner diameter of 710 탆 was prepared in the same manner as in Example 1, except that 22.5 parts by weight of NMP and 7.5 parts by weight of glycerol were used in the support layer polymer spinning solution of Example 1.

Example  4

Porous hollow fiber membranes having an outer diameter of 1,420 탆 and an inner diameter of 500 탆 were prepared in the same manner as in Example 1, except that 20 parts by weight of NMP and 10 parts by weight of glycerol were used in the support layer polymer spinning solution of Example 1.

Comparative Example  One

Porous hollow fiber membranes having an outer diameter of 1,350 탆 and an inner diameter of 710 탆 were prepared in the same manner as in Example 1, except that glycerol in the support layer polymer solution for Example 1 was changed to glycerol by EG (ethylene glycol).

Comparative Example  2

Porous hollow fiber membranes having an outer diameter of 1,250 탆 and an inner diameter of 670 탆 were prepared in the same manner as in Example 1 except that LiCl was not used in the support layer polymer spinning solution of Example 1 and GBL was changed to 112.5 parts by weight.

Comparative Example  3

Porous hollow fiber membranes having an outer diameter of 1,310 탆 and an inner diameter of 710 탆 were prepared in the same manner as in Example 1 except that NMP and LiCl were not used in the support layer polymer spinning solution of Example 1 and GBL was changed to 137.5 parts by weight.

Test Example  One

The breaking strength and the water permeability of the porous hollow fiber membranes prepared according to the above Examples and Comparative Examples were measured in the following manner, and the results are shown in Table 1 below. In addition, the cross-section of the support layer of the porous hollow fiber membranes prepared according to Examples and Comparative Examples was observed using a scanning electron microscope (SEM). The results of the hollow fiber membranes of Example 1 and Comparative Example 1 are shown in FIGS. 1 and 2 Respectively.

As a result of observing the cross section of the support layer using a scanning electron microscope with respect to the porous hollow fiber membrane produced according to the embodiment of the present invention, it was confirmed that microzones were formed in all spherical crystal grains. According to Example 1 In the case of the porous hollow fiber membrane manufactured, it can be confirmed that the spherical crystal grains have a diameter of about 3 to 6 탆 and the spherical crystal grains have microzones having a diameter of about 0.6 탆. In contrast, when glycerol was not used as a non-solvent (Comparative Example 1), it was confirmed that no microzones were formed in the spherical crystal grains as in FIG. 2, and in the case where LiCl was not used (Comparative Examples 2 and 3) It was confirmed that no zone was formed.

Next, referring to Table 1, there is no problem in fracture strength in the case where glycerol is not used (Comparative Example 1) and when no LiCl is used (Comparative Examples 2 and 3), but the water permeability is at most 752 L / hr. < / RTI > In contrast, the porous hollow fiber membrane produced according to the present invention exhibited micro-zone formation, and the fracture strength was slightly lowered compared with the comparative example, but the water permeability was remarkably improved while maintaining excellent breaking strength of 3 MPa or more.

The preferred embodiments of the present invention have been described in detail above. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Accordingly, the scope of the present invention is defined by the appended claims rather than the foregoing detailed description, and all changes or modifications derived from the meaning, range, and equivalence of the claims are included in the scope of the present invention Should be interpreted.

Claims (7)

A porous hollow fiber membrane having a dual-layer structure by simultaneously discharging a support layer and a coating layer using a triple spinning nozzle including a triple pipe,
Wherein the support layer is formed by thermal-induced phase separation, the coating layer is formed by a non-solvent induced phase separation,
Wherein the support layer has spherical crystal grains of 2 to 20 mu m in diameter due to a solid-liquid phase transition, and the spherical crystal grains have microzones of 0.1 to 2 mu m in diameter. A three-layered spinning nozzle was used to discharge the inner coagulant solution on the innermost side of the spinning nozzle, the coating layer polymer spinning solution on the outermost side, and the spinning solution for supporting layer polymer solution on the outermost side, ) Structure of porous hollow fiber membranes,
Wherein the support layer is formed by thermal-induced phase separation, the coating layer is formed by a non-solvent induced phase separation,
Wherein the supporting layer polymer spinning solution comprises a polymer resin, a non-solvent, a poor solvent, a poor solvent, a pore-forming agent and an inorganic additive, wherein the non-solvent glycerol and the inorganic additive use lithium chloride, Wherein the support layer is maintained at a temperature of the coagulation bath so that the solution is quenched to a temperature difference of 100 to 160 占 폚 so that spherical crystal grains having a diameter of 2 to 20 占 퐉 are present due to a solid- Micrometer < / RTI > 3. The method of claim 2,
The polymer resin may be at least one selected from the group consisting of polyethersulfone (PES), polysulfone (PSf), polyethercetone (PEK), polyetherketone (PEEK), sulfonated polymer, polyvinylidene fluoride (PTFE), polyvinylidene chloride (PVDC), chlorinate polyvinyl chloride (CPVC), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) and ethylene chlorotrifluoroethylene (ECTFE ). ≪ / RTI > 3. The method of claim 2,
The above-mentioned two solvents are at least one selected from the group consisting of N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), N, N'-dimethyl acetamide (DMAc), dimethylsulfoxide (DMSO), and trimethyl phosphoramide Lt; / RTI > 3. The method of claim 2,
The poor solvent may be one or more selected from the group consisting of dibutyl phthalate (DBP), dimethyl phthalate (DMP), dioctyl sebacate (DOS), dioctyl adipate (DOA), gum- butylolactone (GBL) and propylene carbonate Lt; / RTI > 3. The method of claim 2,
Wherein the pore-forming agent is at least one selected from the group consisting of polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), and glycerol. 3. The method of claim 2,
Wherein the non-solvent is 1 to 20 parts by weight, the two solvents are 10 to 60 parts by weight, the poor solvent is 5 to 200 parts by weight, the pore-forming agent is 1 to 50 parts by weight, And 0.1 to 10 parts by weight of an additive.

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