KR101397798B1 - Manufacturing method of PVDF asymmetric porous hollow fiber membrane - Google Patents

Abstract

The present invention relates to a method for producing a polyvinylidene fluoride (PVDF) asymmetric porous hollow fiber membrane, and more particularly, to a method for producing a pore forming agent by using water without a separate extraction process using a chemical agent such as an aqueous alkaline solution The present invention relates to a method for producing a PVDF porous hollow fiber membrane that can facilitate the manufacturing process, lower the manufacturing cost, and does not affect the membrane structure in the process of removing the pore forming agent. The inside of the hollow fiber membrane has a spherical structure, and the asymmetric double structure of the bicontinuous structure is improved as it goes to the outer surface. Thus, the mechanical strength is excellent and the membrane cleaning process such as backwashing is effective. And more particularly, to a method for producing a PVDF asymmetric porous hollow fiber membrane excellent in filtration efficiency which simultaneously satisfies excellent rejection ratio while significantly improving water permeability.

Description

Technical Field [0001] The present invention relates to a method for producing asymmetric porous hollow fiber membranes,

TECHNICAL FIELD The present invention relates to a method for producing an asymmetric porous hollow fiber membrane of polyvinylidene fluoride (hereinafter abbreviated as "PVDF"), and more particularly, to a method for producing an asymmetric porous hollow fiber membrane using a fluorine-based material used for water treatment such as drainage, To a hollow fiber membrane using PVDF.

The separation membrane technology is a highly separation technology for almost completely separating and removing the materials to be treated present in the treatment water according to the pore size, the pore distribution and the membrane surface charge of the membrane. In the water treatment field, the production of high quality drinking water and industrial water, And clean production processes related to the development of waste water treatment and reuse, and free circulation systems are expanding and are becoming one of the key technologies to be noticed in the 21st century.

The membrane for water treatment may be a hollow fiber membrane. The hollow fiber membrane has a hollow-ring shape, which is advantageous in that it has a larger membrane area per module unit than a flat membrane. If the water treatment separator has a hollow fiber membrane structure, the membrane may be cleaned by backwashing to remove sediments by passing a clean liquid in a direction opposite to the filtration direction, air scrubbing for removing sediments by shaking the membrane by introducing air bubbles into the module Can be effectively used.

Typical properties required for water treatment hollow fiber membranes include adequate porosity (number of pores) for the purpose of separation efficiency, uniform pore distribution for the purpose of improving fractionation accuracy, It is required to have an optimum pore size. In addition, chemical resistance, chemical resistance, heat resistance, and the like for chemical treatment are required as material characteristics. In addition, properties that affect the operating capability are required to have good mechanical strength to extend service life, and water permeability associated with operating costs.

The membrane structure can be divided into a symmetric membrane having a uniform film as a whole and asymmetric membranes having different pore sizes formed in the thickness layer. The asymmetric membrane type has a lower permeation resistance from the viewpoint of mass permeability, It is possible to increase the selectivity of the selective separation layer while securing the physical film strength.

Polymeric materials used in the water treatment process using membrane technology include polysulfone, polyethersulfone, polyacrylonitrile, polyethylene, polypropylene, cellulose (cellulose) actate) and polyvinyldene fluoride (hereinafter referred to as " PVDF "). In particular, in recent years, a fluorine-based polymer material having a stain resistance from an organic pollution source has been attracting attention as a water treatment separator material due to a negative charge atmosphere.

The hollow fiber membrane can be divided into two types according to the manufacturing method. There are NIPS (Nonsolvent induced phase separation) method using a non-solvent and TIPS (Thermally inducedphase separation) method using heat.

The separation membrane prepared by the NIPS method can change various conditions of the spinning conditions to form various structures of the separation membrane, especially asymmetric structure, and it is easy to adjust the pore size by adding various additives, Which is advantageous in that high water permeability can be obtained, but it is disadvantageous in general that the strength is weak.

On the other hand, the separation membrane manufactured by the TIPS method generally has the same structure as the outer surface and the inside of the separation membrane, and has the advantage of obtaining high strength properties. However, it is difficult to easily control the pore size, And it is difficult to solve the additive.

Recently, research on PVDF hollow fiber membranes as a fluorine resin has been actively carried out. However, PVDF hollow fiber membranes prepared by the conventional NIPS method have weak mechanical strength and PVDF hollow fiber membranes prepared by the TIPS method are difficult to form asymmetric structures and control pores There was a problem. And there is a problem that the water permeability is significantly lowered due to the hydrophobicity of PVDF.

In the case of a conventional PVDF hollow fiber membrane produced by mixing an inorganic powder as a pore-forming agent, a mixed solution containing an inorganic powder is discharged through a nozzle to induce phase separation to form a hollow fiber membrane. Then, the hollow fiber membrane is immersed in an aqueous alkaline solution, There is a problem in that a separate step is required to remove the powder, which complicates the manufacturing process and increases the manufacturing cost. In addition, PVDF having a CH ₂ CF ₂ structure reacts with an aqueous alkali solution to remove HF and convert to a CHCF structure to form a carbon-carbon double structure in the course of removing the inorganic fine powder in the aqueous alkaline solution, The browning phenomenon occurs in which the color of the hollow fiber membrane becomes brown, the mechanical strength of the hollow fiber membrane is lowered, and the structure and pore size are severely affected.

Disclosure of the Invention The present invention has been made in order to overcome the above-mentioned problems, and it is an object of the present invention to provide a process for producing a pore- The present invention provides a method for manufacturing a PVDF asymmetric porous hollow fiber membrane which can be easily and easily produced and processed, has a low manufacturing cost, and has no effect on the membrane structure during the pore former removal process. It is another object of the present invention to provide a method for producing a PVDF asymmetric porous hollow fiber membrane excellent in mechanical strength, advantageous in a membrane cleaning process such as backwashing, satisfying high water permeability and rejection rate required for a water treatment membrane, There is a purpose.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems,

(1) melt mixing polyvinylidene fluoride (PVDF), a plasticizer and an organic fine powder at a temperature of 170 to 300 DEG C to prepare a crude liquid; (2) extruding the crude solution through a spinning nozzle to form a hollow fiber; And (3) dipping the formed hollow fiber in an external coagulating liquid.

According to a preferred embodiment of the present invention, the organic fine powder is prepared by (i) a bi-hydrophilic group containing at least one double bond and a hydrophilic group simultaneously containing a carboxyl group and (ii) at least one double bond And a micelle formed by mixing a hydrophilic group and a hydrophilic group containing both hydrophilic and hydrophilic groups at the same time.

According to another preferred embodiment of the present invention, the (i) hydrophobic group of the amphiphilic compound has 14 to 22 carbon atoms and may include at least one double bond.

According to another preferred embodiment of the present invention, the (ii) hydrophobic group of the amphiphilic compound has 8 to 41 carbon atoms and may include at least one double bond.

According to another preferred embodiment of the present invention, the organic fine powder may include a micelle formed by mixing oleic acid and oleylamine.

According to another preferred embodiment of the present invention, the mixing molar ratio of the (i), (ii) amphiphilic compound may be 4: 6 to 6: 4.

According to another preferred embodiment of the present invention, the plasticizer is selected from the group consisting of dibutyl phthalate, diethyl phthalate, dioctyl phthalate, dioctyl adipate, ethylene glycol Ethylene glycol, polyethylene glycol, dioctyl sebacate, glycerol triacetate, propylene glycol methyl ether, propylene carbonate, ethylene carbonate, ), Methyl phenylacetate, and the like.

According to another preferred embodiment of the present invention, the bath liquid of step (1) may include 60 to 230 parts by weight of a plasticizer and 25 to 75 parts by weight of an organic fine powder with respect to 100 parts by weight of PVDF.

According to another preferred embodiment of the present invention, the spinning nozzle of the step (2) may be maintained at a temperature of 占 폚 of the melting temperature of the step (1).

According to another preferred embodiment of the present invention, the extrusion of the step (2) may be performed at a speed of 40 to 90 rpm.

According to another preferred embodiment of the present invention, the external coagulating solution is selected from the group consisting of water, dibutyl phthalate, dimethyl phthalate, diethyl phthalate, dioctyl phthalate, (Dioctyl sebacate), glycerol triacetate, polyethylene glycol, ethylene glycol, propylene glycol, and diethylene glycol. In the present invention, It can be more than one.

According to another preferred embodiment of the present invention, the external coagulation liquid of step (3) may be -10 to 120 ° C.

According to another preferred embodiment of the present invention, in the step (3) of immersing the external coagulating solution, the organic fine particles may be extracted to form pores.

According to another preferred embodiment of the present invention, the step (4) of stretching the produced hollow fiber membrane may be further included.

According to another preferred embodiment of the present invention, the step (4) may be stretched at a stretching temperature of 15 to 150 ° C at a stretching ratio of 1.1 to 2.0 times.

The method of manufacturing the PVDF asymmetric porous hollow fiber membrane of the present invention can extract the pore forming agent by using water without any separate extraction process using a chemical agent such as an aqueous alkaline solution, And may not affect the membrane structure during the pore former removal process. The inside of the hollow fiber membrane has a spherical structure, and the asymmetric double structure of the bicontinuous structure is improved as it goes to the outer surface. Thus, the mechanical strength is excellent and the membrane cleaning process such as backwashing is effective. And it is possible to provide a PVDF asymmetric porous hollow fiber membrane excellent in filtration efficiency that simultaneously satisfies the excellent rejection ratio while significantly improving water permeability.

1 is a cross-sectional view of spherical micelles and reversed micellar organic fine powders formed according to a preferred embodiment of the present invention.
2 is a cross-sectional view of a double tubular nozzle for producing a PVDF asymmetric hollow fiber membrane according to the present invention.
3 is a photograph of a section of a PVDF hollow fiber membrane according to a preferred embodiment of the present invention.
4 is an enlarged photograph of the outer cross section of the PVDF hollow fiber membrane according to another preferred embodiment of the present invention at 1K.
5 is an enlarged photograph of the outer surface of the PVDF hollow fiber membrane according to another preferred embodiment of the present invention at 5K.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described in more detail with reference to the accompanying drawings.

In the case of the conventional PVDF hollow fiber membrane prepared by mixing the inorganic fine powder as the pore forming agent as described above, a step of removing the inorganic fine powder by dipping in an aqueous alkaline solution is separately required, so that the manufacturing process is complicated and the manufacturing cost is high In the process of removing the inorganic fine powder from the aqueous alkaline solution, the PVDF having the CH ₂ CF ₂ structure reacts with the aqueous alkaline solution to remove the HF and convert to the CHCF structure to form a carbon-carbon double structure. At this time, The color changes to browning, and the mechanical strength of the hollow fiber membrane is lowered and the structure and pore size are severely affected.

Accordingly, the present invention provides a method for producing a polyvinylidene fluoride resin composition, comprising the steps of: (1) melt mixing polyvinylidene fluoride (PVDF), a plasticizer and an organic fine powder at a temperature of 170 to 300 ° C to prepare a crude liquid; (2) extruding the crude solution through a spinning nozzle to form a hollow fiber; And (3) immersing the formed hollow fiber in an external coagulating solution. The present invention has been made to solve the above-mentioned problems by providing a method for producing a PVDF hollow fiber membrane. Accordingly, it is possible to extract the pore-forming agent using water without using a separate extraction process using a chemical agent such as an aqueous alkaline solution, so that the manufacturing process can be simplified, the manufacturing cost is lowered, It may not affect the structure. The inside of the hollow fiber membrane has a spherical structure, and the asymmetric double structure of the bicontinuous structure is improved as it goes to the outer surface. Thus, the mechanical strength is excellent and the membrane cleaning process such as backwashing is effective. And it is possible to simultaneously satisfy the excellent rejection rate while remarkably improving the water permeability.

 In the step (1), polyvinylidene fluoride (PVDF), a plasticizer and an organic fine powder are melt mixed at a temperature of 170 to 300 ° C to prepare a crude liquid.

 The polyvinylidene fluoride (PVDF) used in the hollow fiber membrane of the present invention preferably has an average molecular weight of 200,000 to 1,000,000. If the PVDF average molecular weight is less than 200,000, it may be difficult to form a hollow fiber membrane due to a low viscosity. If the PVDF average molecular weight is more than 1,000,000, moldability may be deteriorated due to high viscosity during melting.

The plasticizer is not particularly limited as long as it can dilute polyvinylidene fluoride (PVDF) in a high temperature region, but it is more preferably selected from the group consisting of dibutyl phthalate, diethyl phthalate, dioctyl phthalate, Dioctyl adipate, Ethylene glycol, Polyethylene glycol, Dioctyl sebacate, Glycerol triacetate, Propylene glycol methyl ether, Propylene carbonate, ethylene carbonate or methyl phenylacetate, and most preferably, it may be dibutyl phthalate or dioctyl phthalate.

The present invention relates to a method of preparing a crude liquid containing an organic fine powder as a pore-forming agent by melt mixing. The organic fine powder may be contained in the form of a liquid and may be removed by immersion in external coagulating liquid during the film forming process without being subjected to a separate extraction process using a chemical agent such as an aqueous alkaline solution because it can be extracted by dissolving in water or the like. Therefore, PVDF having CH ₂ CF ₂ structure reacts with aqueous alkaline solution to remove HF and convert to CHCF structure, resulting in formation of a carbon-carbon double structure, resulting in lower mechanical strength, affecting the structure and pore size of the membrane, The occurrence of the phenomenon can be prevented.

 The organic fine powder is prepared by (i) a hydrophilic group having both a hydrophobic group containing at least one double bond and a hydrophilic group containing a carboxyl group and (ii) a hydrophobic group containing a hydrophobic group and an amine group containing at least one double bond, And a micelle that is formed by mixing both emulsifying compounds that are present at the same time.

As shown in FIG. 1, micelles formed by mixing both of the above-described (i) and (ii) amphophilic compounds may be in the form of spherical micelles. Depending on the surrounding environment, The hydrophilic group forms an outward micelle and the hydrophobic group forms an outer micelle when the surrounding environment is non-polar.

(I) and (ii) may be difficult to dissolve in water due to their small water-solubility when the hydrophobic group is long. However, when both hydrophilic groups of (i) and (ii) ), A hydrophilic group is formed outward in a polar environment such as water and can be easily dissolved in water. Therefore, it can be extracted and removed in a process of immersion in an external coagulating liquid during a film forming process without a separate extraction process.

The hydrophobic group containing at least one double bond of the (i) amphiphilic compound may more preferably have 14 to 22 carbon atoms, more preferably oleic acid, linoleic acid, For example, palmitic acid, eicosecic acid, erucic acid, or the like.

The hydrophobic group containing at least one double bond of the (ii) amphiphile compound may more preferably have 8 to 41 carbon atoms, more preferably oleylamine, bis (2-hydroxyethyl (N-bis (2-hydroxyethyl) laurylamine) or DSPE-PEG (1,2-Distearoyl-sn-glycero-3-phosphoethanolamine- N- Lt; / RTI >

The mixing molar ratio of the (i), (ii) amphiphilic compound may be 4: 6 to 6: 4, more preferably both amphiphilic compounds having a carboxyl group and amphiphilic compounds having an amine group are mixed in a ratio of 1: 1.

On the other hand, in the case of using an organic fine powder containing a micelle formed by mixing both of the hydrophilic compounds (i) and (ii) as compared with the case of using other organic fine powders, The organic fine powder can be more easily extracted and formed into pores (see Example 6).

Most preferably, the organic fine powder of the present invention may include a micelle formed by mixing oleic acid and oleylamine. It was confirmed that when the organic fine powder formed by mixing oleic acid and oleylamine was used, the mechanical strength was excellent, and both the water permeability and the rejection rate were remarkably excellent. 1)

The conditioning liquid in the step (1) may include 60 to 230 parts by weight of a plasticizer and 25 to 75 parts by weight of an organic fine powder with respect to 100 parts by weight of PVDF. If the amount of the plasticizer is less than 60 parts by weight, the viscosity of the discharged liquid may be too high to form a film and water permeability may be lowered. If the plasticizer is more than 230 parts by weight, the PVDF polymer concentration may be lowered and the mechanical strength may be lowered. If the amount of the organic fine powder is less than 25 parts by weight, the pore size and porosity may be lowered and the water permeability may be lowered. If the amount of the organic fine powder is more than 75 parts by weight, the pores on the outer surface have a large pore size, There is a problem that the rejection rate is lowered and the tensile strength is lowered.

The melting temperature in step (1) is preferably 170 to 300 ° C. If the temperature is lower than 170 ° C, the melting temperature is lower than the melting point of the PVDF polymer. Therefore, the melt can not be uniformly melted and the shape of the hollow fiber membrane may become unstable. , The plasticizer or surfactant may be vaporized and water permeability may be lowered.

In the step (2), the crude solution is extruded through a spinning nozzle to form a hollow fiber.

The crude solution may be manufactured outside the spinning nozzle and flowed into the extruder, or may be formed inside the extruder. The spinning nozzle of the step (2) may be maintained at a temperature of ± 20 ° C above the melting temperature of the step (1). If the temperature of the spinning nozzle deviates from the melting temperature of the step (1) by ± 20 ° C, the degree of crystallization of the polymer may change, Porosity and strength.

If the screw speed is less than 40 rpm, the additive or the like may be vaporized in the extruder. If the extruder is operated at 90 rpm or more, mixing of the polymer and the plasticizer is not smoothly performed, It can be difficult.

 The spinning nozzle may be a double tubular spinning nozzle, and Fig. 2 is a sectional view of a double tubular spinning nozzle 5 for discharging the spinning solution. The spinning stock solution in the step (1) may be discharged to the outer tube 2 of the double tubular spinning nozzle 5 and the inner coagulant may be simultaneously discharged to the inner tube 1 of the double tubular spinning nozzle.

The internal coagulant is used for internal hollow formation and is not particularly limited as long as it is uniformly mixed with PVDF and can be mixed at the time of immersion in an external coagulating liquid. More preferred is dibutyl phthalate, dimethyl phthalate Dimethyl phthalate, diethyl phthalate, dioctyl phthalate, dioctyl sebacate, glycerol triacetate, polyethylene glycol, ethylene glycol, Propylene glycol, diethylene glycol, and the like.

 In the step (3), the formed hollow fiber is discharged or immersed in an external coagulating solution to produce a hollow fiber membrane.

The external coagulating solution in the step (3) is not particularly limited as long as it can be mixed with a plasticizer and an internal coagulant, and more preferably water, dibutyl phthalate, dimethyl phthalate, diethyl phthalate Diethyl phthalate, dioctyl phthalate, dioctyl sebacate, glycerol triacetate, polyethylene glycol, ethylene glycol, propylene glycol, Diethylene glycol, and the like.

The organic fine powder which has been mixed can be extracted and removed by the external coagulating liquid in the process of immersing in the external coagulating liquid to form pores. Conventional PVDF hollow fiber membranes prepared by mixing inorganic fine powders require a step of immersing in an aqueous alkaline solution in order to remove the inorganic fine powder to form pores, which complicates the manufacturing process, increases the manufacturing cost, The structure and pore size of the hollow fiber membrane change during the removal of the fine powder, and browning phenomenon occurs. Accordingly, the present invention does not require a separate step of immersing in an aqueous alkaline solution by mixing the organic fine powder that can be extracted with an external coagulating liquid such as water in the process of immersing the external coagulating liquid, and the structure and color of the hollow fiber membrane are changed It is possible to produce a PVDF hollow fiber membrane excellent in mechanical strength and excellent in filtration efficiency.

The external coagulation liquid in the step (3) may be -10 to 120 캜. If the cooling rate in the external coagulation solution is low, the spherical size inside the hollow fiber membrane may become large, and the spherical size may become small at a high cooling rate. If the temperature of the external coagulating solution is less than -10 ° C, the cooling rate is too fast and the water permeability may be reduced due to too small spherical structure. If the temperature exceeds 120 ° C, the cooling rate becomes too slow. The density and the connection sites between the spherical structures are reduced, and the porosity and tensile strength may be lowered.

The hollow fiber membrane produced in the step (3) may further include (4) continuously feeding and stretching the hollow fiber membrane into a stretching machine including a stretching solution. In the above stretching step, the stretching solution may be ethylene glycol, glycerol, polyethylene glycol having a molecular weight of 400 or less, water, or the like, and may be stretched at a stretching ratio of 1.1 to 2.0 times at a stretching temperature of 15 to 150 캜.

When the stretching temperature is less than 15 ° C, partial stretching may occur and the hollow fiber membrane may not be uniformly stretched. When the stretching temperature is more than 150 ° C, film shrinkage and trimming are likely to occur. If the stretching ratio is less than 1.1 times the length of the hollow fiber, the effect of pore control and strength increase due to stretching is insufficient. If the stretching ratio is more than 2.0 times, the film thickness may decrease and the mechanical properties may become weak.

 The PVDF hollow fiber membranes prepared by the above-mentioned method are hollow; And a separation layer formed along the outer periphery of the hollow, wherein the separation layer includes a spherical structure and may include a Bicontinuous structure toward the outer surface of the separation layer.

 The PVDF asymmetric porous hollow fiber membrane as described above has an increased mechanical strength and improved water permeability as compared with a PVDF hollow fiber membrane forming a conventional sponge like structure. Compared with the symmetrical spherical structure, the hollow fiber membrane has a spherical structure, which enhances the selectivity by realizing a bicontinuous structure having a smaller pore size than the interior as it goes to the outer surface while securing the physical film strength. There is an advantage that can be made.

Bicontinuous structure means a double continuous structure, meaning that the polymer crystals are formed in a three-dimensional network structure by connecting the polymer crystals in the interior of the separation membrane. In the same sense as commonly used in the art, Respectively.

 The PVDF asymmetric porous hollow fiber membrane as described above has a tensile strength of 10 MPa or more and can secure the mechanical strength. In the actual process, the pore forming agent is extracted using water without a separate extraction process using a chemical agent such as an aqueous alkaline solution Which can facilitate the manufacturing process and may not affect the membrane structure in the process of removing the pore forming agent.

In addition, the PVDF asymmetric hollow fiber membrane has a water permeability of 1000 LMH or more and satisfies a BSA removal rate of 98% or more, thereby exhibiting excellent filtration efficiency.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples should not be construed as limiting the scope of the present invention, and should be construed to facilitate understanding of the present invention.

≪ Example 1 >

50 parts by weight of dibutylene phthalate, 75 parts by weight of dioctyl phthalate and 25 parts by weight of a mixture of oleic acid and oleylamine were mixed with 100 parts by weight of PVDF (Solef 6013, Solvay) having a weight average molecular weight of 4,400 (1: 1 ratio) were simultaneously injected into the twin-screw extruder (screw diameter: 30 mm). In the extruder at 220 DEG C, the molten mixture was transferred to a nozzle maintained at 200 DEG C using a gear pump. Then, the mixed solution was discharged using dibutyl phthalate as an internal coagulant, and the air gap of the nozzle and coagulation bath was maintained at 1 cm.

The resulting mixed solution was cooled through a coagulation bath maintained at 35 ° C. to induce phase separation, and then the PVDF hollow fiber membrane was prepared by winding at 80 ° C. in a water bath at a rate of 20 m / min.

≪ Example 2 >

The procedure of Example 1 was repeated except that linoleic acid was used instead of oleic acid.

≪ Example 3 >

Except that N, N-bis (2-hydroxyethyl) laurylamine was used instead of oleylamine in place of oleylamine. .

<Example 4>

PEG (1,2-Distearoyl-sn-glycero-3-phosphoethanolamine-N-methoxy (polyethyleneglycol) instead of palmitic acid and oleylamine instead of oleic acid. ]) Were mixed in the same manner as in Example 1. The results are shown in Table 1 below.

&Lt; Example 5 >

The procedure of Example 1 was repeated except that the mixing ratio of oleic acid and oleylamine was 2: 1.

&Lt; Example 6 >

The procedure of Example 1 was repeated except that 20 parts by weight of dioctyl phthalate and 5 parts by weight of dibutyl phthalate were mixed in place of the mixture of oleic acid and oleylamine.

&Lt; Comparative Example 1 &

The procedure of Example 1 was repeated except that hydrophobic silica was used instead of the mixture of oleic acid and oleylamine.

&Lt; Comparative Example 2 &

The hydrophobic silica was mixed in place of the mixture of oleic acid and oleylamine. The resultant hollow fiber membrane was immersed in a 50% by weight aqueous ethanol solution for 30 minutes, transferred to water and immersed for 30 minutes, The procedure of Example 1 was repeated except that the hydrophobic silica was immersed in a 5 wt% caustic soda aqueous solution for 1 hour and was washed 10 times with immersion in hot water at 40 캜 for 1 hour.

<Experimental Example>

The pure water permeability, tensile strength and rejection rate of the hollow fiber membranes prepared in Examples 1 to 6 and Comparative Examples 1 and 2 were measured by the following methods, and the results are shown in Table 1.

1. Measurement of pure water permeability

The hollow fiber membrane module thus prepared was supplied with pure water at a room temperature at a pressure of 1.0 atm on one side of the module by a DEAD-END method, and the amount of permeated water was measured

After which the permeation amount per unit time, unit membrane area, and unit pressure was calculated.

2. Measurement of rejection rate

BSA (bovine serum albumin, Aldrich, Mw 66,000) was added to pure water at room temperature

To prepare an aqueous solution having a concentration of 1,000 ppm. The aqueous solution was supplied to one side of the prepared hollow fiber membrane module at a pressure of 1.0 kg / cm ² , and the BSA concentration dissolved in the permeated aqueous solution and the raw water initially supplied was measured using an ultraviolet spectrophotometer (Cary-100) Respectively.

Thereafter, the relative ratio of the absorption peaks measured at a wavelength of 278 nm was calculated using the following equation

The BSA exclusion rate was determined as a percentage.

Excretion rate (%) = ((concentration of raw liquid - permeation concentration)) / concentration of raw liquid x 100

3. Measurement of tensile strength

The tensile strength and tensile elongation of the hollow fiber membranes prepared through the tensile tester were measured. The tensile test was carried out at room temperature at a gripping distance of 10 cm and a crosshead speed of 3 cm / min.

(Initial sample length: 100 mm, crosshead speed: 200 mm / min) at a temperature of 23 DEG C and a relative humidity of 50% using a tensile tester ("RTM-100" manufactured by Toyo Baldwin Co., Ltd.).

division Pure permeability
(L / m ² hr) BSA exclusion rate
(%) The tensile strength
(MPa) Browning Example 1 1000 98 10 X Example 2 860 97 7 X Example 3 800 97 7 X Example 4 710 97 6 X Example 5 920 97 9 X Example 6 640 98 8 X Comparative Example 1 520 97 8 X Comparative Example 2 900 96 5 O

As can be seen from Table 1, Examples 1 to 6, in which the organic fine powder according to the present invention was mixed, were superior in mechanical strength and filtration efficiency to Comparative Examples 1 and 2 in which the inorganic fine powder was mixed.

Specifically, in Comparative Example 1 in which hydrophobic silica was mixed and no separate extraction step was performed, hydrophobic silica could not be extracted, pores could not be formed, and the pure water permeability was remarkably decreased. Further, hydrophobic silica was mixed and extracted with an aqueous alkaline solution The comparative example 2 in which the process was carried out is not only complicated in the production process but also shows that the mechanical strength is weakened and the browning phenomenon also occurs in the process of immersing in an aqueous alkaline solution and reacting. On the other hand, in Examples 1 to 5 in which the organic fine powder containing spherical micelles according to the present invention were mixed, the organic fine powders were easily extracted in the process of immersing in external coagulating solution without any additional extraction process, , Mechanical strength, water permeability and rejection ratio. It can be confirmed that the case of Example 1 using the organic fine powder which forms micelles by mixing oleic acid and oleylamine is most effective. On the other hand, in Example 6 using the organic fine powder of dioctyl phthalate and dibutyl phthalate, which is not the organic fine powder forming the spherical micelle according to the present invention, the water permeability was lowered because the extraction was somewhat less in the external flocculating liquid immersion process .

Claims (15)

delete (1) melt mixing of polyvinylidene fluoride (PVDF), a plasticizer and an organic fine powder at a temperature of 170 ° C to 300 ° C to prepare a crude liquid;
(2) extruding the crude solution through a spinning nozzle to form a hollow fiber; And
(3) immersing the formed hollow fiber in an external coagulating liquid,
The organic fine powder
(I) an amphiphilic compound having both a hydrophobic group containing at least one double bond and a hydrophilic group containing a carboxyl group and
(Ii) a micelle formed by mixing a hydrophilic group having at least one double bond and a hydrophilic group having an amine group at the same time.
3. The method of claim 2,
Wherein the hydrophobic group of the (i) amphiphilic compound has 14 to 22 carbon atoms and at least one double bond.
3. The method of claim 2,
Wherein the hydrophobic group of the (ii) amphiphilic compound has 8 to 41 carbon atoms and at least one double bond.
3. The method of claim 2,
Wherein the organic fine powder comprises micelle formed by mixing oleic acid and oleylamine. &Lt; RTI ID = 0.0 &gt; 21. &lt; / RTI &gt;
3. The method of claim 2,
Wherein the mixing molar ratio of the (i) and (ii) amphiphilic compound is from 4: 6 to 6: 4.
3. The method of claim 2,
The plasticizer may be selected from the group consisting of dibutyl phthalate, diethyl phthalate, dioctyl phthalate, dioctyl adipate, ethylene glycol, polyethylene glycol, Consisting of Dioctyl sebacate, Glycerol triacetate, Propylene glycol methyl ether, Propylene carbonate, Ethylene carbonate, Methyl phenylacetate, and the like. Wherein the PVDF hollow fiber membrane has a thickness of at least 100 μm.
3. The method of claim 2,
Wherein the crude solution of step (1) comprises 60 to 230 parts by weight of a plasticizer and 25 to 75 parts by weight of an organic fine powder with respect to 100 parts by weight of PVDF.
3. The method of claim 2,
Wherein the spinning nozzle of the step (2) is kept at a temperature of 占 0 占 폚 than the melting temperature of the step (1).
delete 3. The method of claim 2,
The external coagulating solution may be selected from the group consisting of water, dibutyl phthalate, dimethyl phthalate, diethyl phthalate, dioctyl phthalate, dioctyl sebacate, glycerol triacetate Wherein the PVDF hollow fiber membrane is at least one selected from the group consisting of glycerol triacetate, polyethylene glycol, ethylene glycol, propylene glycol, and diethylene glycol. Way.
3. The method of claim 2,
Wherein the external coagulation liquid in step (3) is -10 to 120 ° C.
3. The method of claim 2,
Wherein the organic fine particles are extracted in the step of immersing the external coagulating solution in step (3) to form pores.
3. The method of claim 2,
And (4) stretching the prepared hollow fiber membrane.
15. The method of claim 14,
Wherein the step (4) is carried out at a draw ratio of 1.1 to 2.0 at a draw temperature of 15 to 150 캜.

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