KR101230842B1 - Manufacturing method of porous asymmetric membrane with various pore size and its product manufactured thereby - Google Patents

Abstract

The present invention relates to a method for preparing a porous asymmetric membrane that can be controlled in various pore sizes, and to a porous asymmetric membrane prepared therefrom.
In the method of preparing a porous asymmetric membrane of the present invention, the hydrophilicity of the membrane is improved by using a sulfonated polysulfone polymer-containing polymer solution, and an atmosphere containing volatile organic solvent vapor on the surface cast by the polymer solution is used by a casting process. By optimizing the exposure conditions upon exposure to the substrate, the porous asymmetric membrane increases in average pore size and can be controlled in a variety of pore sizes, reducing the time and cost of adjusting the desired asymmetric structural design, high permeability, and various pore sizes. Can be.

Description

Method for manufacturing porous asymmetric membrane and porous asymmetric membrane prepared therefrom {MANUFACTURING METHOD OF POROUS ASYMMETRIC MEMBRANE WITH VARIOUS PORE SIZE AND ITS PRODUCT MANUFACTURED THEREBY}

The present invention relates to a method for preparing a porous asymmetric membrane and a porous asymmetric membrane prepared therefrom, and more particularly, to improve hydrophilicity of a membrane by using a sulfonated polysulfone polymer-containing polymer solution, and using the casting process. The present invention relates to a method for preparing a porous asymmetric membrane that can be controlled to various pore sizes by increasing an average pore size on a surface cast from a solution, and a porous asymmetric membrane prepared therefrom.

Polymer membranes have been applied to a variety of applications, including medicine, food, semiconductor, water treatment. In particular, since the polyether sulfone resin has high thermal, oxidative stability, temperature stability, and hydrophilic polymer, it is very widely used because it is advantageous for water treatment.

In general, membranes can be divided into symmetrical and asymmetrical membranes in cross-sectional structure. The symmetric membrane has a problem that membrane surface contamination is easily induced by particles in raw water, so that the permeate flow rate is reduced and the service life is reduced.

On the other hand, the asymmetric membrane is composed of a very dense selective layer (0.1 to 10 μm) and a porous layer (100 to 200 μm) positioned outside the layer at a predetermined position in the cross section of the membrane, thereby allowing particles of a predetermined size or more to be formed by the selective layer. It has a high selectivity to remove the, due to the porous layer, it is possible to implement the mechanical strength maintenance and excellent selective transmission flow rate. Thus, research on asymmetric membranes is relatively active.

As an example of the research, US Patent No. 5,886,059 discloses a method for producing a membrane having an asymmetric structure having a pore size difference of 50: 1 on the surface and the back of the membrane. According to the above method, a polyethersulfone and a solvent are mixed, and then a non-solvent is added to uniformly prepare a polymer solution, and the solution is cast on a support under conditions exposed to air and precipitated in a coagulation bath to prepare a membrane having an asymmetric structure. It was.

In addition, U.S. Patent No. 5,906,742 is prepared by mixing a sulfonic polymer such as polyether sulfone, polysulfone, and polyaryl sulfone with a hydrophilic polymer such as polyvinylpyrrolidone, and then exposing it to a certain range of humidity within a certain time. Disclosed is a membrane of an asymmetric structure having a fine porosity. In other words, the cast film is exposed to air at a relative humidity of 50 to 80% for 2 to 20 seconds, and then coagulated in a coagulating liquid having a temperature range of 20 to 70 ° C. Branches are described for membranes.

The method for preparing the membrane described in US Pat. No. 4,933,081 is based on a dry-wet method, which is mixed with a polysulfone polymer and N-methyl-2-pyrrolidone, followed by a hydrophilic polymer polyvinylpyrrolidone and a nonsolvent. Add water and mix uniformly. The cast film is exposed to air for 2-30 seconds step by step under conditions of a temperature of 40 ° C. and a relative humidity of 60%. Then, it is described that after coagulation at 20 ° C., a membrane of microporous asymmetric structure can be obtained by drying.

The membrane prepared from the prior art has introduced hydrophilicity into a hydrophobic polysulfone-based membrane, and can provide a polysulfone-based fouling-resistant membrane that maintains the hydrophilicity of the membrane and has a low flow rate reduction rate due to a pollutant. However, while the polysulfone-based fouling resistant membrane has improved hydrophilicity and increased fouling resistance, the optimum conditions for controlling the average pore size of the membrane are not clear, and thus the desired asymmetric structure, high flow rate, and various pore sizes are controlled. Economical as it takes a lot of time and money to do this. Therefore, there is a problem in that it is practically difficult to apply to various process water.

The present inventors have tried to solve the problems of the prior art, by adding a sulfonated polysulfone-based polymer to the polymer solution, by creating an optimum condition for obtaining a membrane of the desired asymmetric structure, increasing the average pore size to various pore sizes The present invention was completed by manufacturing a porous asymmetric membrane with improved permeability and service life from the method of manufacturing a controllable porous asymmetric membrane.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a porous asymmetric membrane, by using a polymer solution containing a sulfonated polysulfone polymer, which has improved hydrophilicity and can be controlled in various pore sizes.

Another object of the present invention is to provide a porous asymmetric membrane prepared from the above production method.

The present invention provides a method for producing a sulfonated polysulfone polymer containing polymer solution on a support;

2) controlling the average pore size by exposing the surface on which the polymer solution is cast to an air temperature of 20 to 50 ° C. in an atmosphere containing volatile organic solvent vapors,

3) It provides a method for producing a porous asymmetric membrane which is carried out by immersing in a coagulation bath to solidify and peeling from the support.

The sulfonated polysulfone polymer in step 1) is preferably contained 1 to 20% by weight based on the total polymer solution.

In addition, the support in step 1) is a metal material that satisfies 0 to 12 ℃, the polymer solution to be cast is maintained at a temperature of 25 to 70 ℃ to induce pore formation by the temperature difference between the support and the polymer solution.

The volatile organic solvent used in step 2) is at least one selected from the group consisting of acetone, methanol, isopropyl alcohol and tetrahydrofuran, wherein the volatile organic solvent vapor is supplied at a flow rate of 0.2 to 1.0 m / sec.

Step 2) is a process of exposing the cast surface for 5 to 60 seconds at the air temperature of 20 to 50 ℃.

The average pore size of the cast surface controlled through the step 2) process is formed to 0.1 to 10㎛.

The present invention provides a porous asymmetric membrane prepared by the above method, the micropores are formed on the surface of the membrane with pores formed by the temperature difference between the support and the polymer solution to satisfy the average pore size of 0.1 to 10㎛.

The present invention is to improve the hydrophilicity of the membrane by using a sulfonated polysulfone polymer solution, and by using a casting process of the air temperature and exposure time of the atmosphere containing the volatile organic solvent vapor on the surface of the polymer solution By exposing to optimum conditions, it is possible to provide a method for producing a porous asymmetric membrane that can be controlled in various pore sizes.

In addition, the present invention can provide a porous asymmetric membrane having improved hydrophilicity of the membrane by using a sulfonated polysulfone polymer-containing polymer solution. Accordingly, the porous asymmetric membrane of the present invention can increase the fouling resistance, increase the permeability and service life of the membrane, and can also reduce the economic cost.

1 is a surface scanning electron microscope (SEM) photograph measured at 5,000 magnification with respect to the surface of the porous asymmetric membrane prepared in Example 1 of the present invention,
2 is a scanning electron microscope (SEM) photograph measured at 5,000 magnification with respect to the surface of the porous asymmetric membrane prepared in Example 2 of the present invention,
3 is a scanning electron microscope (SEM) photograph measured at 5,000 magnification with respect to the surface of the porous asymmetric membrane prepared in Example 3 of the present invention,
4 is a scanning electron microscope (SEM) photograph measured at 5,000 magnification with respect to the surface of the porous asymmetric membrane prepared in Example 4 of the present invention.
5 is a scanning electron microscope (SEM) photograph measured at 5,000 magnification with respect to the surface of the porous asymmetric membrane prepared in Example 5 of the present invention.
6 is a scanning electron microscope (SEM) photograph measured at 5,000 magnification with respect to the surface of the porous asymmetric membrane prepared in Comparative Example 1 of the present invention.

Hereinafter, the present invention will be described in detail.

The present invention provides a method for preparing a porous asymmetric membrane having improved hydrophilicity using a polymer solution containing sulfonated polysulfone polymer. More specifically,

1) casting a sulfonated polysulfone polymer containing polymer solution onto a support;

2) controlling the average pore size by exposing the surface on which the polymer solution is cast to an air temperature of 20 to 50 ° C. in an atmosphere containing volatile organic solvent vapors,

3) It provides a method for producing a porous asymmetric membrane which is carried out by immersing in a coagulation bath to solidify and peeling from the support.

In the production method of the present invention, the support of step 1) by using a metal material of the surface temperature of 0 to 12 ℃, so that the pores are instantaneously formed by the temperature difference between the polymer solution cast on the support.

The support of the metal material satisfying the 0 to 12 ℃ can be used stainless steel, aluminum, copper alloy and the like, in the embodiment of the present invention has been described using a stainless steel support, induce a temperature difference between the support and the polymer solution It is not limited as long as the material is enough. At this time, when the temperature of the support is less than 0 ° C., the temperature difference between the polymer solutions to contact becomes large, and uniform coating is difficult, affecting the formation of the membrane. When it exceeds 12 ° C., the temperature difference between the polymer solutions decreases and the thermal induction phase transition method is performed. It is disadvantageous to control the structure of the pores.

The temperature of the polymer solution in contact with the support in step 1) of the present invention is maintained higher than the support temperature, preferably maintained at room temperature (25 ° C.) to 70 ° C. to form porosity due to the temperature difference between the supports. Induce. At this time, if the temperature of the polymer solution is less than 25 ℃, permeation flow rate decreases due to the increase in viscosity, when it exceeds 70 ℃ is rather disadvantageous due to the low viscosity.

The polymer solution used in the present invention is composed of 3 to 20% by weight of the polymer resin, 1 to 20% by weight of the sulfonated polysulfone polymer, 1 to 5% by weight of the pore regulator and 55 to 95% by weight of the solvent, and a hydrophobic polymer By containing the sulfonated polysulfone polymer in the resin, the hydrophilicity of the membrane is imparted and the rate of phase separation is controlled.

In this case, the composition ratio of each component in the polymer solution preferably includes 5 to 45% by weight of solid content except for the solvent and 55 to 95% by weight of the solvent. In this case, the ratio of the polymer to the additive is preferably 0.5 to 3 or less. If the ratio of the polymer / additive is less than 0.5, a symmetrical structure is formed and does not meet the object of the present invention. Is formed which is detrimental to the mechanical performance of the membrane.

Looking at the polymer solution of the present invention by composition, the polymer resin uses a weight average molecular weight range of 500,000 to 700,000 in order to consider the mechanical strength. Accordingly, preferred examples thereof include polysulfone polymer resins selected from polyether sulfone or polysulfone; Or polyvinylidene fluoride or polyacrylonitrile.

The polymer solution of the present invention contains a sulfonated polysulfone polymer in a hydrophobic polymer resin, thereby improving the hydrophilicity of the membrane. In this case, the sulfonated polysulfone polymer preferably contains 1 to 20% by weight based on the total polymer solution, and when the sulfonated polysulfone polymer is less than 1% by weight, the expected hydrophilicity improvement of the membrane is insufficient, and 20% by weight. If it is exceeded, since the viscosity of a polymer solution becomes low and film formation is difficult, it is not preferable.

The pore control agent used in the polymer solution of the present invention is not particularly limited as long as it is a hydrophilic substance having affinity for water in humidified air, more preferably glycols such as ethylene glycol and glycerol; Alcohols such as ethanol and methanol; Ketones such as acetone; Polyvinylpyrrolidone, a polyethylene glycol polymer or the like, or a mixture of two or more thereof can also be used.

The preferred content of the pore control agent is 1 to 5% by weight based on the total polymer solution.

The solvent used in the polymer solution of the present invention is any one selected from the group consisting of N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and dimethylacetamide (DMAc) One or two or more kinds may be used, and it corresponds to 55 to 95% by weight based on the total polymer solution.

In the manufacturing method of the present invention, step 2) is to expose the surface cast with the polymer solution in step 1) to the atmosphere containing the volatile organic solvent vapor, in this case, the exposure time 5 at an air temperature of 20 to 50 ℃ It is carried out for 60 seconds to control the average pore size of the membrane.

At this time, the volatile organic solvent vapor is one or more vapor selected from the group consisting of acetone, methanol, isopropyl alcohol and tetrahydrofuran, wherein the volatile organic solvent vapor is preferably supplied at a flow rate of 0.2 to 1.0m / sec. If supplied below 0.2m / sec, there is a problem that pore formation is difficult to implement, and if it exceeds 1.0m / sec, the appearance of the membrane is poor, which is not preferable as a membrane.

By exposing the surface cast in step 2) of the present invention to an atmosphere containing volatile organic solvent vapors, it is possible to form pores quickly at relatively mild conditions, ie at low temperatures.

More specifically, in step 2), the air temperature of the atmosphere containing the volatile organic solvent vapor is exposed at 20 to 50 ° C. for 5 to 60 seconds to control the average pore size on the cast surface. That is, the porous membrane of the present invention is exposed to a predetermined time in the atmosphere containing the volatile organic solvent vapor for a predetermined time at the same time or immediately after casting the formed polymer solution, so that the components of the cast polymer solution is dissolved and extracted in the solvent and moisture in the atmosphere Induces the formation of microporous pores, and can easily control the size of the pores by adjusting the air temperature of the atmosphere within a certain range.

At this time, in order to adjust the pore size of the membrane, the air temperature of the atmosphere is controlled to 20 to 50 ℃. If the air temperature of the atmosphere is less than 20 ℃, it is difficult to form pores according to the material transfer rate, if the air temperature of the atmosphere exceeds 50 ℃, the surface shrinkage of the membrane is so severe that it is difficult to apply as a membrane.

In addition, the exposure time for the microporous pore formation is carried out for 60 seconds or less, more preferably 2 to 60 seconds. If the exposure time is less than 2 seconds, the diffusion of the polymer in the polymer solution into the solvent in the air is weak, making it difficult to express the asymmetric structure. If the exposure time is over 60 seconds, the diffusion of the polymer in the polymer solution into the solvent in the air is excessive and the asymmetric structure is expressed. And productivity.

The average pore size of the cast surface controlled through the step 2) process is formed to 0.1 to 10㎛.

Thereafter, the membrane formed on the support is immersed in the coagulation bath as described above to perform coagulation through sufficient phase separation, and the membrane is peeled off from the support to obtain a porous asymmetric membrane. At this time, water is preferable as the coagulating solution.

In addition, a washing process may be further performed to remove the solvent remaining in the membrane membrane prepared above.

Water is preferably used as the washing liquid, and the washing time is not particularly limited, but is carried out for more than 12 hours to 1 day. The membrane of the present invention prepared as described above may be further carried out a process of drying in air after immersion in ethanol or methanol, wherein the immersion and drying time is not particularly limited, but is preferably 1 hour or less.

Furthermore, the present invention provides a porous asymmetric membrane prepared by the above method, wherein micropores having an average pore size of 0.1 to 10 μm are formed on the surface of the membrane with pores formed by the temperature difference between the support and the polymer solution. To FIG. 5].

In the present specification, the average pore diameter refers to a long diameter of 0.1 to 10 μm on the membrane surface of the present invention, based on the longest diameter, which is the longest diameter when the unit pores are spherical or elliptical in pores formed on the surface of the membrane. Includes a variety of pore sizes to meet the range.

The porous asymmetric membrane of the present invention contains a sulfonated polysulfone polymer in the polymer solution to be cast to impart a hydrophilic group to the membrane, so that the average pore size of the membrane is made of a polymer solution containing no sulfonated polysulfone polymer. And pitch is increased. Accordingly, the porous asymmetric membrane of the present invention has improved hydrophilicity from a sulfonated polysulfone polymer-containing polymer solution, thereby controlling the phase separation rate of the membrane, and manufacturing a porous membrane having various pore sizes [ FIGS. 1 to 5. ].

In addition, the porous asymmetric membrane of the present invention, when exposed to the atmosphere containing a volatile organic solvent on the surface on which the polymer solution is cast, the permeation amount and the average pore size increases as the air temperature and exposure time of the atmosphere is increased, Pore size can be controlled.

Hereinafter, the present invention will be described in more detail with reference to Examples.

This embodiment is intended to illustrate the present invention in more detail, and the scope of the present invention is not limited to these examples.

≪ Example 1 >

5% by weight sulfonated polysulfone polymer, 15% by weight polyethersulfone resin, 55% by weight N-methyl-2-pyrrolidone (NMP), 15% by weight polyethylene glycol (molecular weight 1000) and polyvinylpyrrolidone (PVP) A polymer solution consisting of 10% by weight was prepared and bubbles were removed while maintaining at 35 ° C. The polymer solution was coated at a rate of 2 m / min so that the thickness was uniform on a stainless steel support maintained at 0 ° C. At this time, the cast polymer solution was exposed to acetone vapor supplied at a flow rate of 0.2 m / sec for 30 seconds to induce phase separation on the support. At this time, the cast polymer solution was exposed to 25 ° C air temperature. Thereafter, the mixture was passed through a solidification tank maintained at room temperature, and solidified. In the subsequent process, the remaining solvent component contained in the membrane in the washing tank was extracted and dried under atmospheric conditions at room temperature to prepare a porous membrane.

<Example 2>

A membrane was prepared in the same manner as in Example 1 except that the polymer solution cast in Example 1 was exposed to an air temperature of 30 ° C. in the air.

<Example 3>

A membrane was prepared in the same manner as in Example 1, except that the polymer solution cast in Example 1 was exposed to an air temperature of 35 ° C. in the air.

<Example 4>

A membrane was prepared in the same manner as in Example 1 except that the polymer solution cast in Example 1 was exposed to the atmosphere for an exposure time of 40 seconds.

<Example 5>

A membrane was prepared in the same manner as in Example 1 except that the polymer solution cast in Example 1 was exposed to the atmosphere for an exposure time of 50 seconds.

&Lt; Comparative Example 1 &

A membrane was prepared in the same manner as in Example 1, except that the polymer solution prepared by removing the sulfonated polysulfone polymer from the polymer solution of Example 1 was used.

Comparative Example 2

A membrane was prepared in the same manner as in Example 2, except that the polymer solution prepared by removing the sulfonated polysulfone polymer from the polymer solution of Example 2 was used.

Experimental Example Evaluation of Membrane Properties

For the membranes prepared in Examples 1 to 4 and Comparative Example 1, the average pore size was measured by using a porosity evaluator, and the permeation amount was mounted on a sample holder having a diameter of 90 mm and permeated at a constant pressure (1 bar) for 60 seconds. One amount was measured and listed in Table 1 below.

As shown in Table 1, in the case of the membrane prepared in Examples 1 to 3, when the cast polymer solution is exposed to the atmosphere containing the solvent fixed at the same time conditions, permeability and average as the air temperature of the atmosphere increases The size of pore increased.

In addition, as the exposure time of the cast polymer solution increased under the same atmospheric air temperature, the permeation amount and the average pore size of the membrane also increased.

On the other hand, even if performed under the same film forming conditions as the membrane preparation process of Examples 1 and 2, it was confirmed that the membrane of Comparative Examples 1 and 2 prepared without containing sulfonated polysulfone polymer has a small average pore size.

Thus, the results of evaluation of the properties of the membranes prepared in Examples 1 and 2 compared to the membranes of Comparative Examples 1 and 2 show that the average pore size and the permeation increase are increased according to the sulfonated polysulfone polymer, that is, the hydrophilic group. I could confirm it. From these results, it is possible to control the phase separation rate of the membrane according to the hydrophilic group provision, and to prepare a porous membrane having various pore sizes.

As described above, the present invention improves the hydrophilicity of the membrane by using a sulfonated polysulfone polymer-containing polymer solution, and in the air containing volatile organic solvent vapor on the surface cast with the polymer solution using a casting process Exposure to optimum conditions provided a method for producing porous asymmetric membranes that could increase the average pore size and control the various pore sizes.

Thus, the production method of the present invention can reduce the time and cost consumed to adjust the desired asymmetrical structure design, high permeability, various pore sizes by devising the optimum conditions for adjusting the average pore size of the membrane.

In addition, the porous asymmetric membrane having improved hydrophilicity of the membrane by using the sulfonated polysulfone polymer-containing polymer solution of the present invention may increase fouling resistance and increase membrane permeability and service life.

While the invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (9)

1) Cast a polymer solution containing 3 to 20% by weight of hydrophobic polymer resin, 1 to 20% by weight of sulfonated polysulfone polymer, 1 to 5% by weight pore control agent and 55 to 95% by weight of solvent. ,
2) controlling the average pore size by exposing the surface on which the polymer solution is cast to an air temperature of 20 to 50 ° C. in an atmosphere containing volatile organic solvent vapors,
3) A method for producing a porous asymmetric membrane carried out by immersing in a coagulation bath to solidify and peeling from the support. delete The method of claim 1, wherein the support is a metal material satisfying a surface temperature of 0 to 12 ℃. The method of claim 1, wherein the polymer solution to be cast in step 1) is maintained at a temperature of 25 to 70 ℃ to form pores by the temperature difference between the supports. The method of claim 1, wherein the volatile organic solvent of step 2) is at least one selected from the group consisting of acetone, methanol, isopropyl alcohol and tetrahydrofuran. The method of claim 1, wherein the volatile organic solvent vapor of step 2) is supplied at a flow rate of 0.2 to 1.0 m / sec. The method of claim 1, wherein the cast surface of step 2) is exposed to the atmosphere for 5 to 60 seconds. The method of claim 1, wherein the average pore size of the cast surface controlled from the process of step 2) is 0.1 to 10㎛. Prepared by the manufacturing method of claim 1,
A porous asymmetric membrane, in which micropores having an average pore diameter of 0.1 to 10 µm are formed on the surface of a membrane in which pores are formed due to a temperature difference between a support and a polymer solution, and the flow rate of the membrane satisfies 60 ml / min · cm · bar or more.

Images