KR20110052244A - Novel polymer resin of polyvinylidenefluoride type hollow fiber membrane, pvdf hollow fiber membrane with resistant membrane-pollution and preparing method thereof - Google Patents

Abstract

PURPOSE: Polyvinylidenefluoride type hollow fiber membrane, a novel polymer resin of the polyvinylidenefluoride type hollow fiber membrane, and a preparing method of the same are provided to implement water purifying process with respect to waste water. CONSTITUTION: A polymer resin of the polyvinylidenefluoride type hollow fiber membrane includes polyvinylidene fluoride, a good solvent, a poor solvent, and a pore forming agent. 20 to 40 weight% of the polyvinylidene fluoride is included in the resin. The good solvent includes 15 to 60 weight% of one or more selected from dimethylformamide and dimethyl sulfuroxide. The poor solvent includes 10 to 50 weight% of ethylene carbonate. 1 to 5 weight% of the pore forming agent is included in the resin.

Description

Novel polymer resin of Polyvinylidenefluoride type hollow fiber membrane, PVDF hollow fiber membrane with resistant membrane-pollution and Preparing method

The present invention relates to a novel polymer resin for preparing PVDF hollow fiber membranes including polyvinylidene fluoride, a good solvent, a poor solvent, and a pore-forming agent, and a PVDF hollow fiber membrane having excellent membrane fouling resistance prepared by non-solvent induced phase transition. It is about.

In order to secure the stability of water quality in the water treatment process, interest in hollow fiber membranes is increasing. Among them, precision filtration membranes and ultrafiltration membranes are used for water treatment, sewage, and wastewater treatment as well as water treatment. Hollow fiber membrane module has a high area per unit volume and low membrane fouling, and is easy to clean the membrane. In addition, research is being conducted to improve the performance of hollow fiber membranes to increase permeate flow rate and to be effective in membrane fouling.

In general, chlorine, acid, and alkali are used to control the contamination of the separator, which has a problem of shortening the life of the separator. Recently, polyvinylidene fluoride resin, a material having high chemical resistance, has been used. There is.

In the method for producing a separator made of polyvinylidene fluoride resin, a polymer solution obtained by dissolving polyvinylidene fluoride resin in a good solvent is extruded from a nozzle at a temperature substantially lower than the melting point of polyvinylidene fluoride resin. Non-solvent induced phase separation method, which solidifies in a non-solvent and forms a porous structure, is generally used. However, the non-solvent induced phase separation has an advantage of freely adjusting the pore size.

Recently, Asahi Kasehi and Toray of Japan have developed a hollow fiber membrane having a high permeability for polyvinylidene fluoride resin by thermally induction phase separation. The thermally induced phase separation method uses a poor solvent without using a good solvent. Since the temperature is raised to the melting point of the polymer after spinning, it is less economical than the nonsolvent induced phase separation method.

In recent years, there is an increasing demand for a method of economically manufacturing a separator having excellent mechanical strength but small pore size, high permeability, and high membrane fouling resistance.

Accordingly, the present inventors have studied to compensate for the shortcomings of the hollow fiber membrane made by the conventional non-solvent induction phase separation method, it was to produce a polymer resin having the same specific composition and composition ratio by using a specific poor solvent mixed with a good solvent, When the hollow fiber membrane is manufactured using this, the porosity of the hollow fiber membrane is improved, so that the permeate flow rate is increased, thereby completing the present invention. In addition, when the hollow fiber membrane is manufactured, the polyvinylidene fluoride (PVDF) and the membrane fouling resistance enhancer are not coated on the hollow fiber membrane, but the hydrophilizing agent having excellent compatibility and compatibility with the PVDF is mixed with the polymer resin to be spun. It has been found that membrane fouling for hydrophobic materials has been reduced to complete the present invention.

Accordingly, an object of the present invention is to provide a polymer resin for preparing polyvinylidene fluoride (PVDF) -based hollow fiber membranes, a hydrophilized PVDF hollow fiber membrane having excellent membrane fouling resistance, and a method of manufacturing the same.

The present invention for solving the above problems 20 to 40% by weight of polyvinylidene fluoride (PVDF, Polyvinylidenefluoride); 15 to 60% by weight of a good solvent containing one or two or more selected from dimethylformamide, N-methyl-2-pyrrolidone, dimethylacetamide and dimethyl sulfoxide; 10 to 50% by weight of a poor solvent containing ethylene carbonate; And a pore-forming agent 1 to 5% by weight; to provide a polymer resin for producing PVDF hollow fiber membrane, characterized in that it comprises a.

In addition, the present invention comprises the steps of preparing a spinning solution by heating the polymer resin for PVDF hollow fiber membrane production 50 ~ 120 ℃; And manufacturing the hollow fiber by spinning the spinning solution and the inner hole-forming agent in the same nozzle to phase change and solidify the spinning solution. The purpose is to provide a method.

In addition, an object of the present invention is to provide a PVDF hollow fiber membrane excellent in membrane fouling resistance prepared by the above production method.

The PVDF aerial desert of the present invention has a high porosity by using a specific poor solvent, and has the effect of improving the resistance to membrane fouling because of the addition of a hydrophilic polymer, and excellent water permeability and tensile strength, water treatment such as waste water and purified water Very suitable for In addition, the manufacturing method of the PVDF aerial desert of the present invention is excellent in economical efficiency because it is produced by spinning the raw material at a low temperature compared to the conventional thermal induction phase separation method.

The present invention described above will be described in more detail below.

Polymer resin for producing PVDF hollow fiber membrane of the present invention is polyvinylidene fluoride (PVDF, Polyvinylidenefluoride); Good solvent; Poor solvent; And a pore-forming agent. In addition, the present invention is characterized in that it may further include a hydrophilizing agent.

In the present invention, the PVDF is preferably used 20 to 40% by weight based on the total weight of the polymer resin, in this case, if the amount of PVDF is less than 20% by weight may have a weak strength of the hollow fiber, more than 40% by weight If the polymer solution phase transition proceeds too fast to increase the temperature of the polymer solution during spinning and the viscosity may be so high that spinning is not easy, it is preferable to use within the above range.

The good solvent is used to dissolve PVDF, and may be used one or two or more selected from dimethylformamide (DMF), N-methyl-2-pyrrolidone, dimethylacetamide and dimethyl sulfoxide, more preferably. Preferably, the use of dimethylformamide is advantageous in terms of economics. The good solvent may be used in an amount of 15 to 60% by weight, more preferably 40 to 55% by weight, based on the total weight of the polymer resin, wherein the amount of the good solvent is less than 15% by weight in preparing the polymer solution. There may be a problem that the temperature of the high-injection resin for spinning to 150 ℃ or more, and if it exceeds 60% by weight can not increase the PVDF content, the hollow fiber strength may be weakened, it is preferable to use within the above range Do.

When the poor solvent is mixed with a good solvent for a relatively high polymer material, the poor solvent lowers the dissolving power of the polymer solution, so that phase contact occurs easily when contacted with the non-solvent, thereby increasing the pore size and increasing the permeate flow rate. Ethylene carbonate (EC) can be used as the furnace. The poor solvent is preferably 10 to 50% by weight, more preferably 15 to 40% by weight based on the total weight of the polymer resin, wherein, if the amount of the poor solvent is less than 10% by weight, the porosity is worse, There may be a problem that the flow rate is not greatly improved, and if it exceeds 50% by weight, the temperature of the high-injection resin for spinning should be increased by 150 ° C. or more in the preparation of the polymer solution, and the phase transition may occur at a too fast rate so that spinning may Since it may not be easy, it is preferable to use within the said range.

The pore-forming agent increases the pore size and increases the flow rate of the pore-forming agent, polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), camphorsulfonic acid (CSA) and toluenesulfonic acid (TSA) It is advantageous to improve the performance by using one or two or more selected from among them, and more preferably using toluenesulfonic acid. In the present invention, it is preferable that the pore-forming agent is used in an amount of 1 to 5% by weight based on the total weight of the polymer resin. In this case, when the amount of the pore-forming agent is less than 1% by weight, the pore size does not increase and the permeate flow rate does not increase. There may be a problem that does not, and if it exceeds 5% by weight, there is a problem that the strength is weakened, it is preferable to use within the above range.

The hydrophilizing agent serves to improve the membrane fouling resistance of the PVDF hollow fiber membrane of the present invention, selected from polyacrylonitrile (PAN), cellulose acetate (CA), cellulose propionate (CP) and cellulose butyrate (CB) One kind or two or more kinds can be used, and more preferably, cellulose acetate is preferably used. And, the hydrophilizing agent is polyvinylidene fluoride; Good solvent; Poor solvent; And 0.1 to 5 parts by weight, more preferably 0.5 to 4 parts by weight, based on 100 parts by weight of the polymer resin including a pore-forming agent, wherein the amount of the hydrophilizing agent is less than 0.1 parts by weight. If it exceeds 5 parts by weight, there is a problem in that the compatibility with the PVDF is poor so that the dissolution is not good, it is preferable to use within the above range.

Hereinafter, a method of manufacturing a PVDF hollow fiber membrane using the polymer resin for preparing the PVDF hollow fiber membrane will be described.

Method for producing a PVDF hollow fiber membrane having excellent membrane fouling resistance of the present invention comprises the steps of preparing a spinning solution by heating the polymer resin for producing PVDF hollow fiber membrane to 50 ~ 120 ℃; And spinning the spinning solution and the inner hole-forming agent in the same nozzle to prepare hollow fibers by phase shifting and solidifying the spinning solution.

The composition of the polymer resin for PVDF hollow fiber membrane production is PVDF as described above; Good solvent; Poor solvent; And a pore-forming agent, and may further include a hydrophilizing agent. The composition ratios and kinds thereof are the same as described above.

In order to prepare the spinning solution, the polymer resin for preparing the PVDF hollow fiber membrane in solution phase is heated to 50 to 120 ° C, more preferably to 80 to 100 ° C, and then transferred to the spinning nozzle. At this time, if the polymer solution is heated below 50 ° C., the solid solution of the polymer solution occurs and spinning is impossible. If the heating is over 120 ° C., the carbonization phenomenon of the polymer may occur and the spinning may be difficult, thus maintaining the temperature range. Good to do. When the polymer resin for PVDF hollow fiber membrane production is transferred, nitrogen gas is applied to a certain pressure, and then the quantity is transferred to the nozzle by a gear pump, and the transfer line and the nozzle are maintained to maintain a constant temperature from the spinning solution to the nozzle. It is good to heat up.

When the spinning solution is spun from the nozzle, an internal hole former is injected into the nozzle for spinning the spinning solution using a metering pump to form an intermediate hole. The inner hole former is non-solvent; And a good solvent; 1: 0.1 to 1.5 by weight ratio, more preferably 0.1 to 1 by weight, characterized in that, wherein the non-solvent and the good solvent is less than 1: 0.1 by weight, the pore formation of the inner hole of the hollow fiber membrane This is difficult, and if the ratio exceeds 1: 1.5, there may be a problem in that the formation of a constant hole is difficult due to the dissolution of the inner hole occurs. In addition, the temperature of the inner hole forming agent is 1 ~ 60 ℃, preferably 10 ~ 50 ℃ and if the temperature is less than 1 ℃ freezing occurs inside the hole formation is difficult, if the temperature exceeds 60 ℃ single yarn of the hollow yarn is continuous It can be a difficult problem for regular radiation.

As the non-solvent as the internal hole former component, water, ethylene glycol, alcohols or ketones may be used, and preferably water may be used. In addition, the good solvent as an internal hole former component may use one or two or more selected from dimethylformamide, N-methyl-2-pyrrolidone, dimethylacetamide and dimethyl sulfoxide.

PVDF hollow fiber membrane of the present invention prepared by the above manufacturing method, as shown in Figure 1, it was confirmed that the fingerless, the overall sponge-like shape of the spherical cells are connected. In addition, looking at the measurement of the surface of the hollow fiber membrane of the present invention with the PMI shown in Figure 2, it was confirmed that the spherical cells are connected. The PVDF hollow fiber membrane of the present invention has an average pore size of 0.01 to 0.4 μm, preferably 0.02 to 0.1 μm, and a pure permeate flow rate of 300 to 1,300 L / m 2 · hr (−500 mmHg), porosity of 60% or more, more preferably. Is characterized by having from 60 to 99.9%, in particular, excellent membrane fouling resistance.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the scope of the present invention is not limited by the following examples.

Example 1 Preparation of PVDF Hollow Fiber Membrane

30 wt% polyvinylidene fluoride (PVDF), 15 wt% dimethylformamide (DMF) as a good solvent, 50 wt% ethylene carbonate (EC) as a poor solvent, and 5 wt% toluenesulfonic acid (TSA) as a pore-forming agent Then, these were mixed to prepare a polymer resin, which was then heated to 120 ° C. As the internal hole former, the solution mixed in a water / DMF 1: 1 weight ratio was transferred to a nozzle at 10 ° C., and then the polymer resin was transferred to the nozzle. Then, the nozzle was spaced 5 cm from the coagulation bath water, and then spun in the coagulation bath water and wound at the rear end to produce a PVDF hollow fiber membrane. The film thickness, pore size, cross section and surface state of the prepared PVDF hollow fiber membranes were measured by scanning electron microscope (Scanning Electron Microscope, SEM, Hitachi S-2140), and are shown in FIGS. Sponge-shaped, spherical cells were connected to the shape was confirmed.

Examples 2 to 13 and Comparative Examples 1 to 3

In the same manner as in Example 1, except that PVDF hollow fiber membrane was prepared in the composition, composition ratio and manufacturing conditions shown in Table 1.

As a pore-forming agent, Example 4 is polyvinylpyrrolidone (PVP, trade name: PVP 40,000, manufacturer: Wako), and Example 5 is polyethylene glycol (PEG, trade name: PEG 600, manufacturer: Wako), and Example 6 used camphorsulfonic acid (CSA, Aldrich), and Example 7 used toluenesulfonic acid (TSA).

And Examples 7 to 10 were carried out in the same manner as in Example 1, while changing the temperature of the polymer resin as shown in Table 1 below. Examples 11 to 13 were carried out while varying the composition of the internal hole former to produce PVDF hollow fiber membranes.

Examples 14-18

In the same manner as in Example 1, with respect to 100 parts by weight of the polymer resin containing PVDF, a good solvent, poor solvent, a pore-forming agent, using a hydrophilizing agent 2 parts by weight to 5 parts by weight as shown in Table 1 below. PVDF hollow fiber membranes were prepared. Examples 14 to 15 used cellulose acetate (CA), Example 16 was polyacrylonitrile (PAN), Example 17 was cellulose propionate (CP), and Example 18 was cellulose. Butyrate (CB) was used.

Comparative Example 4

15 wt% polyvinylidene fluoride, 55 wt% dimethylacetamide (good solvent), 20 wt% diethylene glycol monohexyl ether (poor solvent), 10 wt% polyvinylpyrrolidone (pore-forming agent) After preparing the mixed polymer resin, it was heated to 125 ℃ and left at 120 ℃ to prepare a stabilized polymer resin. Next, the stabilized polymer solution was filtered and then heated to 130 ° C. in a closed space to prepare a spinning solution. Next, the hollow fiber membrane was prepared by the phase shifting process of the spinning solution. At this time, the temperature of the polymer solution is 120 ℃, the phase transition bath temperature is 80 ℃, the temperature of the internal coagulation bath is 80 ℃, the nitrogen pressure is 0.5 kgf / ㎠, the metering pump speed of the internal coagulation bath is 4.0 ml / Minutes, the gap between the nozzle and the non-solvent of the phase transfer bath was 10 cm, the discharge air temperature was 20 ° C., and the humidity was 50%.

Comparative Example 5

15% by weight of polyvinylidene fluoride, 55% by weight of dimethylacetamide (good solvent), 20% by weight of gamma-butyrolactone (poor solvent) and 10% by weight of polyvinylpyrrolidone (pore-forming agent) are mixed. Using one polymer resin, the same procedure as in Comparative Example 4 was carried out to produce a hollow fiber membrane.

Experimental Example 1 Physical Property Measurement Experiment

The physical properties of the PVDF hollow fiber membranes prepared in Examples 1 to 18 and Comparative Examples 1 to 5 were measured by the following method, and the results are shown in Table 2 below.

In this experiment, the average pore size was measured using PMI. In addition, the net permeate flow rate was measured by inhaling the pure water in the tank (20 ℃) using a suction pump in the Out-In method by manufacturing a module having a constant length and the number of strands of the hollow fiber membrane. The porosity of the separator was measured using a mercury porometer.

Looking at the measurement results of the physical properties of Table 2, Comparative Examples 1 to 3 can be confirmed that the pure permeate flow rate is not good when only one type or poor use of the poor solvent and pore-forming agent. In addition, Comparative Example 4 has a problem that the net permeation flow rate is small despite the relatively large average pore size (0.35 μm), and compared with Example 7 having a similar average pore size (0.40 μm), the pure permeate flow rate It can be seen that this Example 7 is much larger. It can be seen that the difference in effect by the porosity, the porosity has a direct effect on the net permeate flow rate. In addition, the relationship between the porosity and the pure permeation flow rate can also be confirmed through experimental results of other comparative examples and examples. As a specific composition ratio and poor solvent between the composition of the hollow fiber membrane through the experiment, it was found that the use of ethylene carbonate selected to have a great influence on the porosity, thereby affecting the net permeate flow rate, through which the present invention You can check the excellence of

Experimental Example 2 Membrane Contamination Resistance Measurement Experiment

After measuring the pure permeate flow rate, the permeate flow rate after 6 hours of operation under a pressure of -500 mmHg using a 100 ppm aqueous solution of bovine serum albumin (BSA) was measured and expressed as the rate of permeate flow reduction compared to the pure permeate flow rate. It is expressed as relative flux of. For example, if the initial permeate flow rate is 500 L / m ² hr and the permeate flow rate after 6 hours is 200 L / m ² hr, the relative flux is 200/500, that is, 0.4.

Using this method, the membrane fouling resistance measurement experiments were performed using the hollow fiber membranes prepared in Examples 14 to 18 and the hollow fiber membranes prepared in Comparative Examples 1 and 4 and 5, and the results are shown in Table 3 below. Shown in

division relative flux Example 14 0.52 Example 15 0.65 Example 16 0.51 Example 17 0.60 Example 18 0.58 Comparative Example 1 0.43 Comparative Example 4 0.37 Comparative Example 5 0.39

Through the above experimental example it can be confirmed that the membrane fouling resistance of the PVDF hollow fiber membrane of the present invention prepared using a hydrophilizing agent than the comparative example.

Through the examples and experimental examples confirmed the superiority of the PVDF hollow fiber membrane prepared by using the polymer resin for producing PVDF hollow fiber membrane of the present invention, the present invention is expected to be widely used in water treatment, such as wastewater treatment, purified water treatment .

1 is a photograph of the cross section of the PVDF hollow fiber membrane prepared in Example 1 with an electron microscope.

Figure 2 is a photograph of the surface of the PVDF hollow fiber membrane prepared in Example 1 observed with an electron microscope.

Claims (8)

20 to 40% by weight of polyvinylidene fluoride (PVDF); 15 to 60% by weight of a good solvent containing one or two or more selected from dimethylformamide, N-methyl-2-pyrrolidone, dimethylacetamide and dimethyl sulfoxide; 10 to 50% by weight of poor solvent containing ethylene carbonate; And Pore former 1 to 5% by weight; Polymer resin for manufacturing PVDF hollow fiber membrane, comprising a. The method of claim 1, wherein based on 100 parts by weight of the polymer resin, 0.1 to 5 parts by weight of one or two or more hydrophilizing agents selected from polyacrylonitrile, cellulose acetate, cellulose propionate and cellulose butyrate; Polymer resin for the production of PVDF hollow fiber membrane further comprising a. The polymer resin for producing PVDF hollow fiber membranes according to claim 1, wherein the pore-forming agent comprises one or two or more selected from polyvinylpyrrolidone, polyethylene glycol, camphorsulfonic acid and toluenesulfonic acid. Preparing a spinning solution by heating the polymer resin for preparing the PVDF hollow fiber membrane of claim 1 to 50 to 120 ° C .; And Manufacturing the hollow fiber by spinning the spinning solution and the inner hole-forming agent in the same nozzle, thereby phase shifting and solidifying the spinning solution; Method for producing a PVDF hollow fiber membrane having excellent membrane fouling resistance, comprising a. 5. The method of claim 4, wherein the inner hole former is non-solvent; And a good solvent or a poor solvent; 1 to 0.1 to 1.5 by weight ratio of the manufacturing method of PVDF hollow fiber membrane excellent membrane fouling resistance, characterized in that it comprises. The method of claim 5, wherein the non-solvent comprises water, ethylene glycol, alcohol or ketones, the good solvent is selected from dimethylformamide, N-methyl-2-pyrrolidone, dimethylacetamide and dimethyl sulfoxide A method for producing a PVDF hollow fiber membrane having excellent membrane fouling resistance, comprising two or more species, and the poor solvent is ethylene carbonate. The method of manufacturing a PVDF hollow fiber membrane having excellent membrane fouling resistance according to claim 5, wherein the inner hole former is 1 to 60 ° C. 7. A PVDF hollow fiber membrane prepared by the method of any one of claims 4 to 7, wherein the average pore size of 0.01 ~ 0.4 ㎛, pure water flux 300 ~ 1,300 L / ㎡ · hr (-500 mmHg) and porosity 60% PVDF hollow fiber membranes having excellent membrane fouling resistance, characterized in that ~ ~ 99.9%.

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