KR20140113115A - Positive charged poly(vinylidene fluoride) porous membranes and manufacturing method thereof - Google Patents

Abstract

The present invention relates to positive charged polyvinylidene fluoride-based porous membranes and a manufacturing method thereof, and more specifically, to positive charged polyvinylidene fluoride-based porous membranes which have low elution characteristics because of being formed through strong electrostatic interaction between a negative charge and cationic polymer electrolyte through oxidation, have excellent water permeability without an decrease of pores caused by crosslinking coating, and are expected to have low absorption rate of proteins and high recovery rate of proteins by having surface positive charge under various concentration ranges of hydrogen ion, thereby being useful for a filter process for a medicine and a biosimilar.

Description

TECHNICAL FIELD [0001] The present invention relates to a positively charged polyvinylidene fluoride porous separator,

The present invention relates to a positively charged polyvinylidene fluoride porous membrane and a method for producing the same. More particularly, the present invention relates to a positively charged polyvinylidene fluoride membrane having a low permeability to a specific protein, And to a method for producing the same.

The separation, purification and recovery of specific proteins from protein culture media, etc., in the fields of general pharmaceuticals, medicine, and especially biosimilars, are known as important technical fields with great commercial value. In order to separate, purify, and recover a specific protein, it is essential to remove intracellular toxic substances such as viruses and endotoxins existing in a mixed solution such as a culture solution under a condition of a specific hydrogen ion concentration (pH) The method is to use a porous filter material that is positively charged.

For example, conventional U.S. Patent Nos. 4673504 and 4906374 disclose a filter material having a positive charge by using a nylon-based polymer, an acrylic-based monomer and an amine-based monomer, and a manufacturing method thereof. However, the above method has a problem that the cation concentration is low due to the bonding with the monomer, and thus the protein adsorption ratio is high and the hydrophobic filter media is not used.

Meanwhile, as another research and development, there has been disclosed a production example of a positively charged porous separator by mixing a polyethersulfone polymer with a hydrophilic additive such as polyvinylpyrrolidone or polyethyleneglycol, cross-linking with polyethyleneimine-epichlorohydrin, and post- . However, the above-mentioned method also has a problem in that the hydrophilic additives PVP and PEG can not be dissolved elsewhere over a long period of time after the preparation of the membrane, and even if there is no problem with the elution property, the permeability decreases due to the reduction of pores due to crosslinking of the polymer.

On the other hand, an example has been disclosed in which a PES polymer and polyglycidylether and polyamine, which are additives, are mixed to prepare a membrane, followed by cross-linking heat treatment to produce a cationic membrane. However, this method also has the disadvantage of decomposing polyamine by heat treatment and also low cation concentration.

On the other hand, a method of preparing a membrane having a positive charge through polymerization or coating of a monomer adsorbed on a surface of a polyvinylidene fluoride polymer membrane after irradiating gamma rays or an electron beam onto the surface of the membrane, Lt; / RTI > However, the above method has a disadvantage in that the manufacturing process is complicated and the manufacturing cost is increased.

As described above, when the porous separator is manufactured through the coating or crosslinking method, the porosity decreases due to the hydrophilic coating and the pore size decreases due to the swelling of the hydrophilic polymer. It is disadvantageous in that the permeability is lowered or the crosslinking efficiency is low and the protein recovery rate is decreased. If the positively charged porous membrane is prepared by pretreatment of the polymer before the membrane production using the gamma ray or electron beam, And there arises a problem that the manufacturing cost is also increased.

Disclosure of the Invention The present invention has been conceived to solve the above-mentioned problems, and it is an object of the present invention to provide a biosimilar process which has a low protein adsorption rate and a high protein recovery rate, It is an object of the present invention to provide a positive charge polyvinylidene fluoride porous separator which can be used but is simple in manufacturing process and low in manufacturing cost.

In order to solve the above-described problems,

(1) oxidizing a polyvinylidene fluoride polymer; (2) preparing a polymer solution by mixing the oxidized polyvinylidene fluoride polymer, a cationic polymer electrolyte and a solvent; And (3) casting the polymer solution on a support, or spinning the solution through a spinning nozzle to produce a porous separator. The present invention also provides a method for manufacturing a positive electrode polyvinylidene fluoride separator.

According to a preferred embodiment of the present invention, the polyvinylidene fluoride-based polymer may include at least one selected from the group consisting of PVDF homopolymer, PVDF-HFP copolymer and PVDF-CTFE copolymer.

According to another preferred embodiment of the present invention, the step (1) may oxidize the polyvinylidene fluoride polymer by reacting in a mixture of an alkali solution and an alcohol.

According to another preferred embodiment of the present invention, the alkali solution may include at least one selected from the group consisting of potassium hydroxide (KOH), sodium hydroxide (NaOH), and potassium permanganate (KMnO ₄ ).

According to another preferred embodiment of the present invention, the polymer solution of the step (2) comprises 2 to 10 parts by weight of the cationic polymer electrolyte and 250 to 700 parts by weight of the solvent with respect to 100 parts by weight of the oxidized polyvinylidene fluoride polymer .

According to another preferred embodiment of the present invention, the cationic polymer electrolyte may be any one or more of polyarylamine or polyethyleneimine.

The present invention also relates to an oxidized polyvinylidene fluoride polymer; And a cationic polyelectrolyte crosslinked to the oxidized polyvinylidene fluoride polymer. The polyvinylidene fluoride porous separator according to the present invention comprises:

According to a preferred embodiment of the present invention, the polyvinylidene fluoride-based polymer may include at least one selected from the group consisting of PVDF homopolymer, PVDF-HFP copolymer and PVDF-CTFE copolymer.

According to another preferred embodiment of the present invention, the positively charged polyvinylidene fluoride porous film may include 2 to 10 parts by weight of the cationic polyelectrolyte relative to 100 parts by weight of the oxidized polyvinylidene fluoride polymer.

According to another preferred embodiment of the present invention, the positively charged polyvinylidene porous separator may have a zeta potential of 15 to 40 mV at pH 4.

According to another preferred embodiment of the present invention, the positively charged polyvinylidene porous separator may have a zeta potential of 0 to 30 mV at pH 7.

According to another preferred embodiment of the present invention, the positively charged polyvinylidene porous separator may have a zeta potential of 0 to 20 mV at a pH of 10.

According to another preferred embodiment of the present invention, the positively charged polyvinylidene porous separator has a permeability of 135 (L / m ² hr) or more and a BSA adsorption amount of 0 (μg / cm ² ) at a pH of 4.8 .

The positive electrode polyvinylidene fluoride porous separator of the present invention is formed through strong electrostatic interaction between a negative charge through oxidation and a cationic polyelectrolyte so that the elution property is remarkably low and there is no fear of reduction of porosity due to cross- Has excellent characteristics. Particularly, by having a surface positive charge under various hydrogen ion concentration ranges, a low protein adsorption rate and a high protein recovery rate can be expected, which are particularly useful for pharmaceutical, pharmaceutical and biosimilar filter processes.

In addition, the positively charged polyvinylidene porous separator of the present invention can remarkably improve the problem of membrane contamination such as biofouling represented by protein adsorption, and can be used as a secondary or tertiary solution in sewage treatment plants such as drinking water, Treatment and solid-liquid separation in a septic tank, it is possible to perform a long-term water treatment operation, and production cost can be reduced.

FIG. 1A is a micrograph showing the surface structure of a separation membrane made of non-oxidized PVDF. FIG.
FIG. 1B is a micrograph showing the surface structure of a separation membrane made of oxidized PVDF.
1C to 1E are micrographs of the surface structure of the separator prepared by adding the content of polyethyleneimine (PEI) to the oxidized PVDF, respectively.
FIG. 2 is a graph showing the zeta potential of a separator prepared by adding a different amount of polyethyleneimine (PEI) to a non-oxidized PVDF separator, a separator prepared from oxidized PVDF, and oxidized PVDF.

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

As described above, the conventional porous filter media having a positive charge has a problem in that a positively charged porous separator is produced by coating or cross-linking the surface of the porous separator, thereby reducing the porosity due to the hydrophilic coating and the porosity due to the swelling of the hydrophilic polymer In addition, there is a disadvantage in that the permeability is lowered due to decrease in size or the crosslinking efficiency is lowered, and the recovery rate of the protein is decreased. Also, if a positively charged porous membrane is prepared by pretreatment of the polymer before the membrane preparation using gamma rays or electron beams, There is a problem in the continuous production, and the manufacturing cost due to this is also increased.

Accordingly, the present invention provides a method for producing a polyvinylidene fluoride polymer, comprising: (1) oxidizing a polyvinylidene fluoride polymer; (2) preparing a polymer solution by mixing the oxidized polyvinylidene fluoride polymer, a cationic polymer electrolyte and a solvent; And (3) casting the polymer solution onto a support, or spinning the solution through a spinning nozzle to produce a porous separator. The present invention also provides a method for producing a positive electrode polyvinylidene fluoride separator, .

As a result, a positive charge polyvinylidene porous separator having a surface adsorption rate under various hydrogen ion concentration ranges, exhibiting a low protein adsorption rate and a high protein recovery rate, .

 Specifically, the step (1) oxidizes the polyvinylidene fluoride-based polymer.

The polyvinylidene fluoride polymer of the present invention used in the oxidation step may be a polyvinylidene fluoride (PVDF) homopolymer, a polyvinylidenefluoride-co-hexafluoropropylene (PVDF-HFP) vinylidenefluoride-co-chlorotrifluoroethylene), etc. In the case of the copolymer, the PVDF is preferably 50 mol% or more.

The polyvinylidene fluoride polymer to be used preferably has a weight average molecular weight of 200,000 to 1,000,000. If the molecular weight of the polyvinylidene fluoride polymer is lower than 200,000, the mechanical strength after the film formation is lowered. If the molecular weight is more than 1 million, the film formation may be difficult due to the viscosity increase.

The polyvinylidene fluoride polymer can be reacted with a mixture of an alcohol and an oxidizing agent in an alkali solution as a reaction medium to form an oxidized polyvinylidene fluoride polymer. The alcohol as the reaction medium used in the oxidation step may be in the form of methanol, ethanol or isopropyl alcohol, or the like, and most preferably methanol. The alkali solution used in the oxidation step may be an aqueous alkaline solution containing a single or mixed form of potassium hydroxide (KOH), sodium hydroxide (NaOH) or potassium permanganate (KMnO ₄ ), and most preferably potassium hydroxide (KOH) Aqueous solution.

 The concentration of the oxidizing agent (KOH or the like) in the alkali solution may be suitably considered in connection with the reaction time and the reaction temperature, preferably 1 to 30 wt%. When the oxidizing agent concentration is less than 1 wt%, formation of oxides is difficult. When the oxidizing agent concentration is more than 30 wt%, mechanical strength is weakened due to denaturation of the polymer after film formation.

The weight ratio of the alcohol to the alkali solution is preferably 3: 1 to 20: 1.

In addition, the concentration of the polyvinylidene fluoride polymer to be reacted in the alkali solution during the oxidation reaction need not be limited to a large extent, but is preferably 5 to 20% by weight in view of productivity and yield. The reaction time for the oxidation reaction of the polymer is not limited, but it is preferable to conduct the reaction for 2 to 6 hours in consideration of the productivity and the yield. In order to accelerate the oxidation reaction, It is preferable to carry out it.

Through these reaction conditions, the polyvinylidene fluoride polymer can gradually change to brown and precipitate in the initial white as the reaction time elapses. The oxidized polyvinylidene fluoride polymer formed after completion of the reaction may be filtered and washed with alcohol or the like, and then dried at 60 to 90 ° C for at least 24 hours.

 In the step (2), an oxidized polyvinylidene fluoride polymer, a cationic polymer electrolyte and a solvent are mixed to prepare a polymer solution.

 The oxidized polyvinylidene fluoride polymer is more negatively charged than the non - oxidized polyvinylidene fluoride polymer and can bind to the cationic polyelectrolyte through strong electrostatic interaction to significantly reduce the elution of the cationic material. If a cationic polyelectrolyte is added to a non-oxidized polyvinylidene fluoride polymer, the bonding strength is weakened, and the polymer electrolyte is eluted at the time of water permeation, thereby decreasing the positive charge intensity and causing protein adsorption.

In the prior art, the permeability is reduced due to the reduction of porosity by applying a positive charge through a method of cross-coating the surface of the separation membrane. In contrast, the present invention provides a separation membrane having a positive charge imparted to the polymer solution without coating the separation membrane surface, The permeability can be improved while lowering the adsorption rate.

The polymer solution composition in the step (2) may include 2 to 10 parts by weight of the cationic polyelectrolyte and 250 to 700 parts by weight of the solvent, based on 100 parts by weight of the oxidized polyvinylidene fluoride polymer.

If the amount of the cationic polymer electrolyte is less than 2 parts by weight, the concentration of the cation is low and the protein adsorption ratio is increased. If the amount is more than 10 parts by weight, the viscosity is increased due to the strong interaction between the oxidized polymer and the cationic polymer electrolyte. . The cationic polyelectrolyte has a characteristic of strongly binding to the oxidized polyvinylidene fluoride polymer through electrostatic interaction and may be any one or more of polyallylamine or polyethyleneimine, May be polyethyleneimine.

The added cationic polymer electrolyte binds to the oxidized polyvinylidene fluoride polymer so that the porous separator has a positive charge as a whole, and the protein adsorption rate can be remarkably lowered. If a separation membrane is prepared using only a polyvinylidene fluoride polymer without addition of a cationic polyelectrolyte to the oxidized polyvinylidene fluoride polymer, such a porous separation membrane becomes negatively charged, and intracellular toxic substances such as endotoxin It is not suitable for biosimilar process for recovering various proteins.

When the amount of the solvent constituting the polymer solution is less than 250 parts by weight, the water permeability may be decreased. When the amount of the solvent is more than 700 parts by weight, the content of the polymer is too small to form the film and the mechanical strength is low even after the film formation . The solvent is not particularly limited as long as it can dissolve the polyvinylidene fluoride polymer and the cationic polymer electrolyte uniformly. However, the solvent may be a single or a mixture of N-methylpyrrolidone, dimethylacetamide, dimethylsulfoxide or dimethylformamide More preferable.

 In the step (3), the polymer solution prepared in the step (2) is cast on a support or spun through a spinning nozzle to produce a porous separator.

The process for producing the porous separation membrane is not particularly limited, but preferably a separation membrane can be produced through a conventional non-solvent-derived phase separation process. The non-solvent induction phase separation process is widely used for manufacturing a separator, and is widely known through a patent application. In the present invention, an example of preparing a separator using the same will be described, but the present invention is not limited thereto and it is within the scope of the present invention to manufacture a porous separator using the polymer solution.

In the case of a flat membrane through casting, the polymer solution is cast on a non-porous substrate such as a glass substrate or a metal substrate or a porous substrate such as a nonwoven fabric, and then immersed in the coagulating solution in the non-solvent for coagulation, washing and drying A porous flat membrane can be formed. If the coagulating liquid temperature is below room temperature, there is a problem in productivity because the coagulating liquid is delayed when the coagulating liquid temperature is below room temperature. If the coagulating liquid temperature exceeds 60 ° C, There is a disadvantage in that the temperature decreases. Then, a positive charge porous film may be prepared by washing with water to remove residual solvent and unreacted polymer electrolyte, and drying under a room temperature atmosphere. The time for washing and drying is not particularly limited, but it is preferably 24 hours or more for washing and 12 hours or more for drying. In general, a process such as glycerin coating is not required to prevent shrinkage of membrane pores during drying There are advantages.

Meanwhile, when the hollow fiber membrane is coated on the porous hollow support, the polymer solution is discharged into an outer tube of a double nozzle maintained at a temperature of 60 to 60 ° C, and at the same time, 10 m / min. The hollow fiber membrane coated on the support is passed through an air gap having a length of 0 to 10 cm and then immersed in a coagulating solution composed of water at a temperature ranging from room temperature to 60 ° C or lower. Coated positive charge porous hollow fiber membrane can be produced.

Meanwhile, as another manufacturing example, the hollow fiber membrane without support is discharged from the outer tube of the double nozzle maintained at a room temperature to 60 ° C, and at the same time, the inner coagulant is injected into the inner tube of the double nozzle in an amount of 1.0 to 15 ml / min, and the discharged hollow fiber membrane is precipitated in an external coagulating liquid composed of water at a temperature ranging from room temperature to 60 ° C to form a hollow fiber membrane, and then a positively charged porous membrane can be manufactured through the same washing and drying processes as those described above .

 In addition, the positively charged polyvinylidene-based porous separator of the present invention produced as described above is characterized by comprising an oxidized polyvinylidene fluoride polymer; And a cationic polyelectrolyte crosslinked to the oxidized polyvinylidene fluoride polymer.

 The positive-acting polyvinylidene fluoride separator of the present invention crosslinks the oxidized polyvinylidene fluoride polymer which is more negatively charged than the non-oxidized polyvinylidene fluoride polymer through a strong electrostatic interaction with the polyvinylidene fluoride polymer The elution of the cationic substance can be remarkably lowered. If a cationic polyelectrolyte is added to a non-oxidized polyvinylidene fluoride polymer, the bonding strength between the non-oxidized polyvinylidene fluoride polymer and the cationic polymer electrolyte becomes weak, and the polymer electrolyte elutes upon permeation of water, A problem that adsorption occurs may occur. On the other hand, when the porous separator contains only a polyvinylidene fluoride polymer and does not contain a cationic polymer electrolyte, the porous separator has a negative charge, and it is difficult to remove intracellular toxic substances such as endotoxin generated during protein culture. And the like.

In the prior art, the permeability of the surface of the separation membrane was decreased due to the decrease of porosity due to the crosslinking of various polymers. On the other hand, the positively charged polyvinylidene porous separator of the present invention has a positive charge without coating the separation membrane surface, While the water permeability can be improved.

The positively charged polyvinylidene porous separator of the present invention may contain 2 to 10 parts by weight of the cationic polyelectrolyte relative to 100 parts by weight of the oxidized polyvinylidene fluoride polymer. If the amount of the cationic polymer electrolyte is less than 2 parts by weight, there is a disadvantage in that the positive charge is reduced and the protein adsorption ratio is increased. If the amount is more than 10 parts by weight, the membrane itself is difficult to form.

 The positively charged polyvinylidene porous separator of the present invention can exhibit a low protein adsorption rate and a high protein recovery rate by having a positive charge under various hydrogen ion concentration ranges. Specifically, the positively charged polyvinylidene fluoride separator may have a zeta potential of 15 to 40 mV at a pH of 4, a zeta potential of 0 to 30 mV at a pH of 7, and a zeta potential of 0 to 20 mV at a pH of 10 .

FIG. 2 is a graph showing the results of a comparison between a non-oxidized PVDF separator, a separator made of oxidized PVDF, and a polyimide oxide (PEI) added to the oxidized PVDF (3, 5 and 10 parts by weight, respectively, based on 100 parts by weight of oxidized PVDF) The zeta potential of the membrane is shown. In the case of the non-oxidized PVDF membrane, it can be seen that the membrane has a very narrow range of surface charge within the range of pH 4 to 10. On the other hand, in the case of the membrane made of PVDF polymer oxidized with potassium hydroxide (KOH) It is understood that the PVDF membrane has a very strong anion character in the range of 10 to 10 compared to the non-oxidized PVDF membrane. On the other hand, in the case of the membrane prepared by adding the cationic polymer electrolyte to the oxidized PVDF polymer, the membrane having a strong positive charge with an increase in the amount of addition, in particular, in the case of the membrane containing 7 parts by weight of polyethyleneimine, the zeta potential described above at pH 4, All are satisfied, and it can be confirmed that they all have a complete surface positive charge within a range of pH 4 to 10.

The positively charged polyvinylidene porous separator of the present invention satisfies the above-described positive charge property and exhibits a BSA adsorption amount of 0 (μg / cm ² ) at a pH of 4.8, and at the same time an excellent permeability of more than 135 (L / m ² hr) Lt; / RTI >

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 >

To prepare the oxidized polyvinylidene fluoride resin, 1,000 g of methanol and 100 g of a 5% by weight aqueous solution of potassium hydroxide (KOH) were added to a flask, and 100 g of PVDF was added thereto under stirring conditions with an RPM of 150. After stirring at room temperature for 4 hours, precipitated brown PVDF powder was filtered and washed three times with methanol kept at 0 ° C. The PVDF powder was then dried in an oven at 80 ° C for 24 hours.

 Thereafter, a flask containing 400 g of NMP (N-methyl pyrrolidone, DAEJUNG) as a solvent was charged with 10 g of a 30 wt% polyethyleneimine (PEI) aqueous solution (Mn 70,000, Wako) Lt; / RTI > Then, 100 g of the oxidized PVDF polymer was added and stirred at rpm 200 for 2 hours to prepare a homogeneous polymer solution.

Then, a part of the solution was poured on a substrate of a normal temperature, and then the film was formed to a thickness of 200 μm by using a casting knife. Thereafter, the PVDF membrane was dried at room temperature for 12 hours to prepare a positive charge PVDF membrane.

≪ Example 2 >

A positive positive PVDF membrane was prepared in the same manner as in Example 1, except that 18 g of a 30 wt% polyethyleneimine (PEI) aqueous solution (Mn 70,000, Wako) was added.

≪ Example 3 >

A positive charge PVDF membrane was prepared in the same manner as in Example 1, except that 25 g of a 30 wt% polyethyleneimine (PEI) aqueous solution (Mn 70,000, Wako) was added.

<Example 4>

A positive charge PVDF membrane was prepared in the same manner as in Example 1, except that 37 g of a 30 wt% polyethyleneimine (PEI) aqueous solution (Mn 70,000, Wako) was added.

However, the viscosity of the prepared solution increased sharply and it was observed that the casting was not performed properly due to the high viscosity.

&Lt; Comparative Example 1 &

100 g of PVDF homopolymer (Solvay 1015, Mw: 570,000) was added to a flask containing 400 g of NMP (N-methyl pyrrolidone, DAEJUNG) as a solvent. Thereafter, the temperature of the solution was maintained at 65 ° C, and the solution was stirred at rpm 200 for 2 hours to prepare a homogeneous polymer solution. A part of the prepared solution was poured on a substrate of a normal temperature, and the film was formed to a thickness of 200 μm by using a casting knife, and then washed for 24 hours in flowing tap water at room temperature. After drying at room temperature for 12 hours, a non - oxidized PVDF membrane was prepared.

&Lt; Comparative Example 2 &

To oxidize the PVDF membrane, 1000 g of methanol and 100 g of a 5 wt% KOH aqueous solution were mixed and the PVDF membrane sample of Comparative Example 1 was immersed for 4 hours. Thereafter, the resultant was washed three times with methanol maintained at 0 占 폚 and dried in an oven at 80 占 폚 for 2 hours. Thereafter, 17 g of a 30 wt% polyethyleneimine (PEI) aqueous solution (Mn 70,000, Wako) and 83 g of distilled water were mixed to prepare a uniform aqueous solution of a cationic polymer electrolyte. Then, the surface-oxidized PVDF porous membrane was immersed in the aqueous solution for 2 hours, washed several times with methanol, and dried in an oven at 80 ° C for 2 hours to form a cationic coating layer.

<Experimental Example>

1. Measurement of permeability

For the permeability evaluation, the membrane specimens were pre-immersed in 30% ethanol solution for 10 minutes and then continuously immersed in distilled water for 30 minutes. The unit membrane area (m ² ), the unit time (hr), and the unit pressure (bar) were measured after the pure water at room temperature was pressurized under a constant pressure of 1 atm and the amount of water filtered for 60 minutes in the dead- And converted into the amount (L) of water to be filtered.

The results of permeability measurement of Examples 1 to 4 and Comparative Examples 1 and 2 are shown in Table 1.

2. Observation of morphology

An electron scanning microscope (SNE-3000M, SEC) was used to observe the microstructure of the membrane surface. Membrane specimens were prepared by cutting in liquid nitrogen and the surface of the sample after Au deposition was measured.

1A to 1E, the amounts of polyethyleneimine (PEI) added to the non-oxidized PVDF separation membrane, the separation membrane made of oxidized PVDF, and the oxidized PVDF were separately added (3, 5, and 10 parts by weight ) Microscopic photographs showing the surface structure of the prepared membrane were shown. As can be seen from FIG. 1, no significant change was observed between the membrane surfaces of the non-oxidized PVDF membrane and the other modified PVDF membrane.

3. Measurement of contact angle

The contact angle (CAM DSA100S2, Germany) was attached to the holder and the droplet was dropped on the surface of the membrane to observe the drop of water drop for 20 seconds. Respectively. The contact angle was measured after three measurements with different surface positions and then averaged.

The contact angle measurement results of Examples 1 to 4 and Comparative Examples 1 to 2 are shown in Table 1.

4. Measurement of surface charge (zeta-potential)

For the measurement of Zeta potential (Anton Paar KG, Graz, Austria), a 1 cm x 2 cm membrane sample was inserted into a holder and the electrical conductivity was adjusted to 127.8 mS / m using a KCl solution at 20 ° C. After the pH was adjusted to 4.8 using 0.1 M HCl and 0.1 M NaOH aqueous solution, the Zeta potential of the membrane was measured.

FIG. 2 shows the results obtained by adding different amounts of polyethyleneimine (PEI) to the non-oxidized PVDF separation membrane, the PVDF separation membrane, and the oxidized PVDF (adding 3, 5 and 10 parts by weight, respectively, to 100 parts by weight of oxidized PVDF) The zeta potential of the membrane was shown. As can be seen from FIG. 2, the separation membrane to which the cationic polyelectrolyte is added to the oxidized PVDF polymer has a positive charge.

5. Measurement of adsorption amount of BSA (Bovine Serum Albumin) at pH 4.8

BSA was dissolved in pure water at room temperature at 0.1 wt% under hydrogen ion concentration of 4.8, which is the isoelectric point of BSA (Bovine Serum Albumin, Aldrich, MW 66,000). Then, 6 membrane samples of the same composition with a membrane area of 4 cm ² were prepared and the weight of the three membranes was measured and averaged. On the other hand, a certain amount of BSA solution was dropped on the surface of the remaining three membranes, followed by drying at 80 ° C for 2 hours. The dried membrane was washed three times with an aqueous solution of pH 4.8, dried at 80 ° C for 2 hours, and weighed. The average BSA adsorption amount was calculated using the following equation.

Average adsorption amount (μg / cm ² ) = (separation membrane weight after adsorption - separation membrane weight before adsorption) / membrane area

 Table 2 shows the BSA adsorption amount measurement results of Examples 1 to 4 and Comparative Examples 1 and 2.

division PVDF
( Weight portion ) NMP
( Weight portion ) PEI Pitcher
(L / m ²  h bar ) Contact angle (°) Comparative Example 1 100 400 0 129 83 Comparative Example 2 100 400 coating 36 74 division Oxidation PVDF
( Weight portion ) NMP
( Weight portion ) PEI
( Weight portion ) Pitcher
(L / m ²  h bar ) Contact angle (°) Example 1 100 400 3 173 75 Example 2 100 400 5.4 152 75 Example 3 100 400 7.5 138 74 Example 4 100 400 11.1 No forming

As can be seen from the results in Table 1, in Examples 1 to 4 in which polyethyleneimine (PEI) was added to the oxidized PVDF as compared with the non-oxidized PVDF membrane (Comparative Example 1), the water permeability was significantly improved, Respectively. These results can be attributed to the fact that the original hydrophobic PVDF was changed to hydrophilic PVDF. In the case of Comparative Example 2 in which the PVDF membrane was coated with PEI to provide a positive charge, the permeability was remarkably reduced due to the decrease of the contact angle due to the surface PEI coating. This is because the surface coating of the polymer reduces the average pore size of the membrane It is because. On the contrary, Examples 1 to 4 prepared by adding PEI of the present invention show improved water permeability.

division PVDF
( Weight portion ) NMP
( Weight portion ) PEI BSA
Adsorption amount ( mg / cm ² )
at pH  4.8 Comparative Example 1 100 400 0 2.5 Comparative Example 2 100 400 coating 0.13 division Oxidation PVDF
( Weight portion ) NMP
( Weight portion ) PEI
( Weight portion ) BSA
Adsorption amount ( mg / cm ² ) Example 1 100 400 3 0.0 Example 2 100 400 5.4 0.0 Example 3 100 400 7.5 0.0 Example 4 100 400 11.1 0.0

As can be seen from the results in Table 2, the BSA adsorption amount of the non-oxidized PVDF membrane (Comparative Example 1) was 2.5 (μg / cm ² ) while the adsorption amount of BSA in the membranes of Examples 1 to 4 having surface positive charge 0 (μg / cm ² ). On the other hand, in the case of Comparative Example 2 in which the PVDF membrane was coated with PEI, the BSA adsorption amount was 0.13 (μg / cm ² ), and in Examples 1 to 4, the water permeability was remarkably improved as compared with Comparative Example 2, The results are shown.

Claims (13)

(1) oxidizing a polyvinylidene fluoride polymer;
(2) preparing a polymer solution by mixing the oxidized polyvinylidene fluoride polymer, a cationic polymer electrolyte and a solvent;
(3) casting the polymer solution onto a support or spinning the solution through a spinning nozzle to produce a porous separator.
The method according to claim 1,
Wherein the polyvinylidene fluoride-based polymer comprises at least one selected from the group consisting of a PVDF homopolymer, a PVDF-HFP copolymer, and a PVDF-CTFE copolymer.
The method according to claim 1,
Wherein the step (1) comprises oxidizing the polyvinylidene fluoride polymer by reacting in a mixture of an alkali solution and an alcohol.
The method of claim 3,
Wherein the alkali solution comprises at least one selected from the group consisting of potassium hydroxide (KOH), sodium hydroxide (NaOH), and potassium permanganate (KMnO ₄ ).
The method according to claim 1,
Wherein the polymer solution of step (2) comprises 2 to 10 parts by weight of a cationic polyelectrolyte and 250 to 700 parts by weight of a solvent based on 100 parts by weight of the oxidized polyvinylidene fluoride polymer. (2).
The method according to claim 1,
Wherein the cationic polyelectrolyte is at least one of polyarylamine and polyethyleneimine. &Lt; RTI ID = 0.0 &gt; 11. &lt; / RTI &gt;
Oxidized polyvinylidene fluoride polymer; And
And a cationic polyelectrolyte crosslinked to the oxidized polyvinylidene fluoride polymer. The positive electrode polyvinylidene fluoride separator according to claim 1,
8. The method of claim 7,
Wherein the polyvinylidene fluoride-based polymer comprises at least one selected from the group consisting of PVDF homopolymer, PVDF-HFP copolymer, and PVDF-CTFE copolymer.
8. The method of claim 7,
Wherein the positively charged polyvinylidene fluoride porous film comprises 2 to 10 parts by weight of a cationic polyelectrolyte based on 100 parts by weight of the oxidized polyvinylidene fluoride polymer.
8. The method of claim 7,
Wherein the positively charged polyvinylidene fluoride porous separator has a zeta potential of 15 to 40 mV at pH 4.
8. The method of claim 7,
Wherein the positively charged polyvinylidene fluoride porous separator has a zeta potential of 0 to 30 mV at a pH of 7.
8. The method of claim 7,
Wherein the positively charged polyvinylidene fluoride porous separator has a zeta potential of 0 to 20 mV at a pH of 10.
8. The method of claim 7,
Wherein the positively charged polyvinylidene fluoride porous separator has a water permeability of 135 (L / m ² hr) or more and a BSA adsorption amount of 0 (μg / cm ² ) at a pH of 4.8. Membrane.

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