KR20230127420A - Asymmetric microfiltaration membrane easy to manufacture in large-area and method for preparation thereof - Google Patents

Abstract

The present invention relates to an asymmetric microfiltration membrane that is easy to manufacture in a large area and a method for manufacturing the same, and more particularly, it is possible to manufacture a large area due to its excellent tensile strength even with a thin thickness, and it is possible to increase the insertion amount of a separator when manufacturing a cartridge. It relates to a large-area asymmetric microfiltration membrane that has excellent water permeability and can minimize changes in physical properties after high-temperature and high-pressure tests and a manufacturing method thereof.

Description

Asymmetric microfiltration membrane that is easy to manufacture in large area and method for manufacturing the same

The present invention relates to an asymmetric microfiltration membrane that is easy to manufacture in a large area and a method for manufacturing the same, and more particularly, it has excellent tensile strength even when it is thin, so that it is easy to manufacture a large area and can increase the insertion amount of a separator when manufacturing a cartridge. It relates to an asymmetric microfiltration membrane that has excellent pure permeability and can be easily manufactured in a large area and can minimize changes in physical properties after high temperature and high pressure tests, and a method for manufacturing the same.

Separation membrane technology is a high-level separation technology for almost completely separating and removing substances to be treated in treated water according to the pore size, pore distribution, and membrane surface charge of the membrane. Its application range is expanding, such as sewage/wastewater treatment and reuse, and clean production processes related to the development of non-discharge systems, and it is established as one of the core technologies that will attract attention in the 21st century.

Microfiltration membranes are widely applied in various processes such as semiconductors, medicines, food and beverages, as well as water treatment fields. In this field, microfiltration membranes are used to remove particulate matter or colloidal matter based on pore size.

Process separation membranes can generally be divided into symmetric and asymmetric polymer membranes in terms of the cross-sectional structure of the membrane. An asymmetric separation membrane is composed of a selective layer with a relatively dense pore size and a porous layer with a large pore size located on the other side, so it has high selectivity capable of removing particles and contaminants of a certain size or more by the selective layer, and the porous layer Due to this, it is designed to implement excellent water permeability.

General characteristics required for process separation membranes include appropriate porosity (number of pores) for the purpose of separation efficiency, uniform pore distribution for the purpose of improving fractionation accuracy, and optimal pore size for effectively separating separation targets. It is required to have In addition, as material characteristics, chemical resistance to post-treatment, heat resistance, and the like are required. In addition, excellent mechanical strength for extending service life and water permeability related to operating cost are required as characteristics that affect driving ability.

Polymer materials used in the water treatment process using membrane technology include sulfone-based polymers such as polysulfone and polyethersulfone, polyacrylonitrile, polyethylene, polypropylene, There is a material such as cellulose acetate (Cellulose actate). In particular, recently, a sulfone-based polymer material having heat resistance and chemical resistance has been spotlighted as a separator material for a process.

Nonsolvent Induced Phase Separation (NIPS), which is a phase conversion method using a non-solvent among the manufacturing methods of separation membranes for processes, can form various structures of the separation membrane, especially asymmetric structures, by changing various membrane forming conditions, , It is easy to control the pore size by adding various additives, and it has the advantage of obtaining high water permeability by imparting hydrophilization to the membrane, but finger-like macrovoids are formed, resulting in mechanical The downside is that it is weak. In addition, according to the existing process of forming a separator on a substrate and then peeling it off, it is difficult to maintain high uniformity when manufacturing a large area, and it is difficult to manufacture a large area due to weak tensile strength. There was a problem with less.

Therefore, there is a need to develop a microfiltration membrane that has high mechanical strength even when it is manufactured as a thin film, has high water permeability, and minimizes deterioration in physical properties even after high-temperature and high-pressure tests.

Korean Registered Patent Publication No. 10-1292398 (2013.07.26.)

The first problem to be solved by the present invention is that it has excellent tensile strength even with a thin thickness, so it is easy to manufacture a large area, it is possible to increase the insertion amount of a separator when manufacturing a cartridge, it has excellent water permeability, and it has physical properties after high temperature and high pressure tests. It is to provide a large-area asymmetric microfiltration membrane capable of minimizing the change.

In addition, the second problem to be solved by the present invention is excellent in tensile strength even with a thin thickness, it is possible to increase the insertion amount of the separator when manufacturing a cartridge, it is excellent in water permeability, and it is possible to minimize changes in physical properties even after high temperature and high pressure tests. It is to provide a method capable of manufacturing a large area as a method for manufacturing an asymmetric microfiltration membrane with

In order to solve the above-mentioned first problem, the present invention is a porous support layer in which the polysulfone-based resin is penetrated into the pores; A first polymer layer formed on one surface of the porous support and containing a polysulfone-based resin; And a second polymer layer formed on the other surface of the porous support and containing a polysulfone-based resin, wherein the porous support, the first polymer layer and the polysulfone-based resin of the second polymer layer are integrated and cured, It provides an asymmetric microfiltration membrane that is easy to manufacture in a large area, characterized in that the average pore size of the first polymer layer is smaller than the average pore size of the second polymer layer.

An asymmetric microfiltration membrane that can be easily manufactured in a large area according to a preferred embodiment of the present invention may satisfy both conditions 1) and 2) below.

1) 0.01 μm ≤ d ₂ - d ₁ ≤ 0.05 μm

2) d ₁ < d ₃ < d ₂

Here, d ₁ , d ₂ and d ₃ are the average pore size of the first polymer layer, the average pore size of the second polymer layer, and the average pore size of the polysulfone-based resin that has penetrated into the pores of the porous support layer, respectively. means

According to another preferred embodiment of the present invention, the thickness of the first polymer layer may be greater than the thickness of the second polymer layer.

An asymmetric microfiltration membrane that can be easily manufactured in a large area according to another preferred embodiment of the present invention may satisfy the following condition 3).

3) 0μm < D ₁ - D ₂ < 40μm

Here, D ₁ and D ₂ mean the average thickness of the first polymer layer and the average thickness of the second polymer layer, respectively.

According to another preferred embodiment of the present invention, the pore size in the first polymer layer gradually decreases from a region adjacent to the porous support layer to a region adjacent to the outer surface of the first polymer layer, and in the second polymer layer The pore size may gradually increase from a region adjacent to the porous support layer to a region adjacent to the outer surface of the second polymer layer.

According to another preferred embodiment of the present invention, the polysulfone-based resin may be a polyethersulfone resin (PES).

According to another preferred embodiment of the present invention, the porous support layer may be a woven or non-woven fabric.

According to another preferred embodiment of the present invention, an asymmetric microfiltration membrane that is easy to manufacture in a large area, characterized in that a hydrophilic additive is further included by mixing with the polysulfone-based resin.

An asymmetric microfiltration membrane that can be easily manufactured in a large area according to another preferred embodiment of the present invention may have average tensile strengths of 80 MPa or more in both the machine direction (MD) and the vertical direction (TD).

An asymmetric microfiltration membrane that can be easily manufactured in a large area according to another preferred embodiment of the present invention may have a net permeability of 15,000 to 30,000LMH.

In order to solve the above-described second problem, the present invention provides (1) applying and permeating a polymer crude liquid containing a polysulfone-based resin on one surface of a porous support layer; And (2) immersing the porous support layer coated with the crude polymer solution in an external coagulation solution in a coagulation tank to cure the crude polymer solution, thereby curing the first polymer layer and the second polymer layer containing pores on one side and the other side of the porous support layer, respectively. Forming two polymer layers; wherein the average pore size of the second polymer layer is larger than the average pore size of the first polymer layer. to provide.

According to a preferred embodiment of the present invention, step (1) may be to apply the polymer crude liquid only to one side of the porous support layer.

An asymmetric microfiltration membrane that can be easily manufactured in a large area according to another preferred embodiment of the present invention may satisfy both conditions 1) and 2) below.

1) 0.01 μm ≤ d ₂ - d ₁ ≤ 0.05 μm

2) d ₁ < d ₃ < d ₂

Here, d ₁ , d ₂ and d ₃ are the average pore size of the first polymer layer, the average pore size of the second polymer layer, and the polysulfone cured polymer crude liquid penetrating into the pores of the porous support layer, respectively. Means the average pore size of the phone-based resin.

According to another preferred embodiment of the present invention, in step (1), the crude polymer solution further includes a solvent and a non-solvent, and may be prepared by mixing at 40 ° C to 100 ° C.

According to another preferred embodiment of the present invention, the solvent and the non-solvent may be included in the polymer crude liquid at a weight ratio of 1:0.1 to 1:2.

According to another preferred embodiment of the present invention, in step (1), the crude polymer solution may further include a pore-forming agent and a hydrophilic additive.

According to another preferred embodiment of the present invention, the external coagulating liquid in step (2) includes at least one selected from water, polyethylene glycol, ethylene glycol, propylene glycol, diethylene glycol, isopropyl alcohol, methanol and ethanol it may be

Hereinafter, definitions of terms used in the present invention will be described.

The term "solvent" used in the present invention refers to a liquid substance capable of dissolving 5% by weight or more of a polymer resin even at a low temperature of 40 ° C or less, and "non-solvent" refers to a liquid material capable of dissolving 5% by weight or more of a polymer resin even when the temperature is raised to the melting point of the polymer resin. A liquid substance that does not dissolve or swell the resin.

The large-area asymmetric microfiltration membrane according to the present invention is easy to manufacture in a large area, has excellent water permeability even with a thin thickness, increases the insertion amount during cartridge manufacturing, and has the advantage of little change in physical properties even after high-temperature and high-pressure tests. , it can be widely used as a separator for pharmaceutical, semiconductor, and CMP (Chemical Mechanical Planarization) processes.

In addition, the large-area asymmetric microfiltration membrane according to the present invention has excellent water permeability, excellent tensile strength even with a thin thickness, an increased insertion amount during cartridge manufacturing, and a microfiltration membrane with little change in physical properties even after high-temperature and high-pressure tests can be provided. And, it is possible to provide a microfiltration membrane having the excellent physical properties over a large area.

1 is a view schematically showing a cross section of an asymmetric microfiltration membrane that can be easily manufactured in a large area according to a preferred embodiment of the present invention.
2 is a perspective view showing an approximate appearance of an asymmetric microfiltration membrane that can be easily manufactured in a large area according to a preferred embodiment of the present invention.
3 is a SEM image (x200 magnification) of a cross section of an asymmetric microfiltration membrane that can be easily manufactured in a large area according to Example 1 of the present invention.
4 is a SEM image (x200 magnification) of a cross section of a microfiltration membrane manufactured by the conventional NIPS method.

As described above, it is difficult to secure the uniformity of the microfiltration membrane when manufacturing the conventional microfiltration membrane in a large area, and it is difficult to manufacture the microfiltration membrane in a large area because the tensile strength is weak, and the manufactured microfiltration membrane is also difficult to insert when manufacturing the cartridge. The problem was that it wasn't enough.

Therefore, in order to solve this problem, the present inventors have a porous support layer in which the polysulfone-based resin is penetrated into the pores; A first polymer layer formed on one surface of the porous support layer and containing a polysulfone-based resin; And a second polymer layer formed on the other side of the porous support layer and containing a polysulfone-based resin, wherein the porous support layer, the first polymer layer and the polysulfone-based resin of the second polymer layer are integrated and cured , The average pore size of the first polymer layer is smaller than the average pore size of the second polymer layer, and the development of an asymmetric microfiltration membrane that is easy to manufacture in a large area was sought to solve the problem of difficulty in manufacturing a large area.

By providing a microfiltration membrane having an asymmetrical cross-sectional structure and having a structure of an integrated first polymer layer-porous support layer-second polymer layer, even when manufactured as a thin film, it has excellent tensile strength, making it easy to manufacture in a large area and at the same time It had excellent pure permeability and minimized changes in physical properties even after high-temperature and high-pressure tests.

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

1 is a view schematically showing a cross section of a microfiltration membrane according to a preferred embodiment of the present invention. Referring to FIG. 1, the microfiltration membrane 100 of the present invention includes a porous support layer 130 and a first polymer layer 110 formed on one side of the porous support layer 130 and a second polymer layer 120 formed on the other side. ), It can be seen that the porous support layer 130 and the first and second polymer layers 110 and 120 each include a polysulfone-based resin, and the polysulfone-based resin is integrated and cured.

As such, since the polysulfone-based resin included in the porous support layer 130 and the first and second polymer layers 110 and 120 are integrated and cured, the microfiltration membrane 100 according to the present invention has tensile strength It is excellent, and even if it is manufactured in a thin film or thin thickness, there is an advantage in that it is easy to manufacture in a large area because breakage does not occur easily.

First, the porous support layer 130 will be described.

In the microfiltration membrane of the present invention, the porous support layer is formed on both sides of the porous support layer when the microfiltration membrane is prepared by allowing the polymer layer forming component including the polysulfone-based resin to penetrate between the pores of the porous structure, and It functions to make it possible to integrate the second polymer layer and the porous support layer.

In addition, by supporting the polysulfone-based resin that has penetrated into the pores, when a tensile load is applied, the porous support layer has better strength against the tensile load than when the load is applied to the polysulfone-based resin itself by distributing the load. It has the effect of making it possible.

Such an effect can be confirmed through the experimental results of examples to be described later. In the microfiltration membrane according to Example 1, first and second porous support layers in which polyethersulfone resin (PES), a polysulfone-based resin, penetrated into pores, and first and second porous support layers integrated with the PES in the pores were formed on both sides of the porous support layer, respectively. As a microfiltration membrane including a polymer layer, it exhibits an average tensile strength of 110 MPa and a total average thickness of 114 μm. On the other hand, it can be seen that the microfiltration membrane according to Comparative Example 1 is a single-layer microfiltration membrane made of only PES, and has an average thickness of 110 μm and an average tensile strength of 3 MPa, which is significantly lower than that of Example 1.

The porous support layer may be a woven fabric or a non-woven fabric, and in addition, if it is a porous structure in which a polysulfone-based resin penetrates to form a polymer layer on both sides, it is selected without limitation from those generally known by those skilled in the filtration membrane manufacturing industry. and can be used. The fabric or non-woven fabric has high filterability, so that the polysulfone-based resin can easily penetrate, and has good strength, so that the tensile strength of the microfiltration membrane can be effectively improved. In addition, by infiltrating the polysulfone-based resin into the pores of the woven or non-woven fabric, uniformity of the thickness of the microfiltration membrane can be sufficiently secured even when manufactured in a large area, so that the microfiltration membrane according to the present invention has a large area compared to the conventional microfiltration membrane. It has the advantage of being easy to manufacture.

In addition, the porous support layer may be polypropylene (PP) or polyethylene terephthalate (PET), but is not limited thereto. Strong tensile strength can be obtained by using the porous support layer as the material described above.

In addition, the porous support layer may have a thickness of 50 to 150 μm. By having a thickness within the above range, the microfiltration membrane of the present invention can adequately secure tensile strength even if it is manufactured with a sufficiently thin thickness, and thus it is possible to manufacture it in a large area, and the input amount of the filtration membrane can be increased when manufacturing a cartridge. . This also means that the filtration performance can be improved.

Next, the first and second polymer layers 110 and 120 will be described.

In the microfiltration membrane of the present invention, the first and second polymer layers include a polysulfone-based resin, and the first and second polymer layers may be made of the same material.

The polysulfone-based resin is included in the first polymer layer, the porous support layer, and the second polymer layer, and serves to integrate the interlayer structure of the microfiltration membrane of the present invention. Therefore, the microfiltration membrane of the present invention can have strong tensile strength and has the effect of being easy to manufacture in a large area.

Since the filtration membrane (or separation membrane) containing the polysulfone-based resin has a very stable feature due to the electrostatic attraction by resonance electrons between the aromatic groups around the -SO ₂ functional group in the molecular structure of the polysulfone-based resin, the polysulfone-based resin In the case of including a filtration membrane, there is an effect of providing a microfiltration membrane having excellent stability and chemical resistance.

The polysulfone-based resin may include one or a combination of two or more selected from the group consisting of polysulfone, polyethersulfone (PES), and polyallylethersulfone polymers, and in addition to the above-mentioned -SO ₂ functional group by the same A person skilled in the art can easily select and use among polysulfone-based resins commonly used in the art, as long as they are effective, and their effects will also be easily understood by those skilled in the art.

More preferably, the polyethersulfone resin may be used as the polysulfone-based resin. In case of using polyethersulfone resin, as polyethersulfone resin is an amorphous resin, it has particularly high thermal and oxidative stability and stability against temperature, has excellent processability and is a hydrophilic polymer, so it can be widely used because it is advantageous for water treatment. There are advantages to being

The polysulfone-based resin may have a weight average molecular weight of 40,000 to 100,000. More preferably, a weight average molecular weight of 50,000 to 100,000 may be used, and most preferably, a weight average molecular weight of 50,000 to 90,000 may be used. If a polysulfone-based resin having a weight average molecular weight of less than 50,000 is used, there is a problem in that it may be difficult to form a filtration membrane due to its low viscosity, and when a polysulfone resin having a weight average molecular weight of more than 100,000 is used, the viscosity is too high to form pores. Since there may be a problem of not being formed well, it is advantageous to use a polysulfone-based resin having a weight average molecular weight within the above range.

In addition, in the microfiltration membrane according to another preferred embodiment of the present invention, a hydrophilic additive as well as a polysulfone-based resin may be added to the first polymer layer, the second polymer layer, and the porous support layer.

The hydrophilic additive forms a porous structure by using low affinity with polysulfone-based resin, which is a hydrophobic material, and serves to increase water permeability by increasing hydrophilization.

The hydrophilic additive is polyvinylpyrrolidone-vinyl acetate (PVP-VA), ethylene vinyl alcohol (EVOH), polyvinyl alcohol (PVA), sulfonated polyethersulfone and sulfonated polysulfone It may include one or more selected from among.

More preferably, the hydrophilic additive may be at least one selected from sulfonated polyethersulfone (SPES) and sulfonated polysulfone. When SPES or sulfonated polysulfone is used as the hydrophilic additive, the hydrophilic additive, which is a hydrophilic material, has the same chemical structure as the polysulfone-based resin included in the first polymer layer, the porous support layer, and the second polymer layer. It has the advantage of minimizing the phenomenon of being washed away by water.

The first polymer layer and the second polymer layer include a polysulfone-based resin and include a plurality of pores therein, and the average pore size of the pores in the first polymer layer is the average of the pores in the second polymer layer. smaller than the pore size.

Referring to FIG. 1, the first polymer layer 110 and the second polymer layer 120 include a plurality of pores 140, and the number of pores 140 included in the first polymer layer 110 It can be seen that the average size is smaller than the average size of the pores 140 included in the second polymer layer 120 .

By having such an asymmetric structure, the first polymer layer 110 having a small average pore size has high selectivity and excellent filtering ability can be implemented, and the second polymer layer 120 has a relatively large average pore size, so that high It has the advantage of being able to implement a high flow rate and excellent anti-fouling performance, so that the use cycle becomes longer.

More preferably, the microfiltration membrane of the present invention may satisfy both conditions 1) and 2) below. Excellent filtration capacity and high flow rate can be realized by satisfying all of the following conditions, and if the following conditions are not satisfied, there may be problems such as poor filtration capacity or reduced use cycle.

1) 0.01 μm ≤ d ₂ - d ₁ ≤ 0.05 μm

2) d ₁ < d ₃ < d ₂

Here, d ₁ , d ₂ and d ₃ are the average pore size of the first polymer layer, the average pore size of the second polymer layer, and the average pore size of the polysulfone-based resin that has penetrated into the pores of the porous support layer, respectively. means

The porous support layer may also penetrate the polysulfone-based resin into the pores, and the polysulfone-based resin is included to integrate the first polymer layer, the porous support layer, and the second polymer layer, so that the porous support Pores are also included in the polysulfone-based resin that has penetrated into the pores of the layer. This fact can be confirmed in FIG. 1 .

Preferably, the average pore size may be the smallest in the first polymer layer as in condition 2), the next largest average pore size in the porous support layer, and the largest average pore size in the second polymer layer. there is.

Since the average pore size (d ₂ ) of the porous support layer has a value between d ₁ and d ₃ , the effect obtained by having the asymmetric cross-sectional structure as described above can be maximized. For example, the second polymer layer has an effect of realizing a high flow rate by having a large average pore size, and the porous support layer has an effect of realizing a high flow rate by having a medium average pore size and a particle filtration effect It implements, and the first polymer layer has a high particle selectivity due to the small average pore size, thereby improving the filtration capacity.

If d ₂ is greater than d ₃ , there is a problem in that the tensile strength of _the asymmetric microfiltration membrane is lowered, and it is meaningless because it is impossible to implement an effect beyond the effect of realizing a high flow rate due to the size of d ₃ . When d is less than ₁ , there is a problem in that the use cycle is reduced.

In addition, in the microfiltration membrane according to another preferred embodiment of the present invention, the average pore size of the first polymer layer may be 0.05 μm to 0.6 μm, and the average pore size of the second polymer layer may be 0.01 μm to 0.8 μm. can In the case of having an average pore size within the above range, it is possible to provide a microfiltration membrane having excellent filtration capacity, high flow rate and fouling resistance performance, and a long use cycle. If the average pore size is larger than the above range, there may be a problem of insufficient filtration performance, and if the average pore size is smaller than the above range, there may be a problem of lowering the net permeability and flow rate.

In the microfiltration membrane according to another preferred embodiment of the present invention, the pore size in the first polymer layer gradually decreases from a region adjacent to the porous support layer to a region adjacent to the outer surface of the first polymer layer, and the second polymer layer The size of pores in the layer may gradually increase from a region adjacent to the porous support layer to a region adjacent to the outer surface of the second polymer layer. That is, as shown in the above condition 1), while d1 < d3 < d2 is also satisfied, the average pore size in the region adjacent to the outer surface is the smallest and the average pore size in the region adjacent to the porous support layer is the largest even in the first polymer layer. . In the same way, in the second polymer layer, the average pore size of the region adjacent to the outer surface is the largest and the average pore size of the region adjacent to the porous support layer is the smallest. Accordingly, as shown in FIG. 1 , the size of the pores follows a distribution that gradually increases from the surface of the first polymer layer 110 to the surface of the second polymer layer 120 .

In addition, in the microfiltration membrane according to another preferred embodiment of the present invention, the thickness of the first polymer layer may be thicker than the thickness of the second polymer layer. Since the thickness of the first polymer layer is thicker than that of the second polymer layer, it is possible to improve the tensile strength of the microfiltration membrane and to realize excellent filtration performance.

In addition, the microfiltration membrane according to another preferred embodiment of the present invention may satisfy the following condition 3).

3) 0μm < D ₁ - D ₂ < 40μm

Here, D ₁ and D ₂ mean the average thickness of the first polymer layer and the average thickness of the second polymer layer, respectively.

By controlling the difference in thickness between the first polymer layer and the second polymer layer within the above range, it is possible to achieve high flow rate and long use cycle while maintaining the best tensile strength and performance of the filtration membrane.

In addition, the microfiltration membrane according to another preferred embodiment of the present invention may have average tensile strengths of 80 MPa or more in both machine direction (MD) and transeverse direction (TD). By having such tensile strength, even if the microfiltration membrane of the present invention is manufactured in a large area, the phenomenon of breakage during the manufacturing process is minimized, and it is significantly easier to manufacture in a large area compared to the conventional microfiltration membrane, which is a cartridge manufacturing It appears as an effect that can greatly increase the insertion amount of the time separation membrane.

In addition, the microfiltration membrane according to another preferred embodiment of the present invention may have a pure permeability of 15,000 to 30,000LMH. By having the pure permeability in the above range, durability and use cycle can be optimized, and at the same time, there is an advantage in that sufficient filtration performance can be obtained.

If the pure permeability is too high to exceed 30,000LMH, sufficient filtration performance cannot be obtained, and conversely, if the pure permeability is low to less than 15,000LMH, there is a problem that the use cycle is shortened.

According to the second aspect of the present invention, as a method for manufacturing a microfiltration membrane providing the above effect, (1) applying and infiltrating a crude polymer solution containing a polysulfone-based resin on one surface of a porous support layer; And (2) immersing the porous support layer coated with the crude polymer solution in an external coagulation solution in a coagulation tank to cure the crude polymer solution, thereby curing the first polymer layer and the second polymer layer containing pores on one side and the other side of the porous support layer, respectively. Forming two polymer layers; wherein the average pore size of the second polymer layer is larger than the average pore size of the first polymer layer. to provide.

By manufacturing the microfiltration membrane in this way, as a microfiltration membrane having an asymmetrical cross-sectional area, even when manufactured in a large area, the tensile strength and uniformity are excellent, making it easy to manufacture.

First, the step (1) will be described.

The present invention includes applying a crude polymer solution containing a polysulfone-based resin on one surface of a porous support layer to infiltrate the crude polymer solution into pores of the porous support layer and form a uniform film. Among them, the description of the porous support layer is omitted because it is the same as described above. Therefore, the crude polymer solution will be described below.

The crude polymer solution is then subjected to a curing process to form a polymer layer having a plurality of pores therein, which is the first polymer layer of the microfiltration membrane, the second polymer layer and the poly permeated into the pores of the porous support layer. It appears in the form of a sulfone-based resin.

The crude polymer solution includes a polysulfone-based resin, and since the details regarding the type, molecular weight, etc. of the polysulfone-based resin are the same as those described above, the following description is omitted.

In addition, the crude polymer solution may further include a solvent and a non-solvent in addition to the polysulfone-based resin.

The crude polymer solution may be prepared by mixing at 40 °C to 100 °C. If the temperature during mixing is lower than 40° C., the dissolution time of the polysulfone-based resin is consumed for a long time, which may have a disadvantage in that the physical properties inherent in the polysulfone-based resin are changed. Conversely, when the mixing temperature exceeds 100° C., the solvent and non-solvent evaporate and the desired composition cannot be properly adjusted.

According to a preferred embodiment of the present invention, the solvent may have a solubility of 18 to 35 MPa ^1/2 df. Preferably, the solvent may have a solubility of 20 to 28 MPa ^1/2 , and more preferably a solubility of 22 to 27 MPa ^1/2 . At this time, when the solubility of the solvent is less than 18 MPa ^1/2 , there may be a problem that the separation membrane is not formed, and when the solubility exceeds 35 MPa ^1/2 , there may be a problem that pores are not properly formed.

As a solvent having such solubility, among gamma butyrolactone (γ-butyrolactone), dimethylacetamide (DMAc), N-methyl-2-pyrrolidone, dimethylsulfoxide, dimethylformamide and glycerol triacetate (Glycerol triacetate) A selected one type or a mixture of two or more types may be used.

According to a preferred embodiment of the present invention, the solvent may be included in the polymer crude liquid in an amount of 100 to 600 parts by weight based on 100 parts by weight of the polysulfone-based resin. If the amount of the solvent used is less than 100 parts by weight, the viscosity is too high, which may make it difficult to form a film. If the amount of the solvent used exceeds 600 parts by weight, the concentration of the PES polymer is lowered, and a large number of macropores are formed, resulting in a large pore size. Since the control of may be difficult, it is preferable to use it within the above range.

In addition, according to a preferred embodiment of the present invention, the non-solvent may be one or a mixture of two or more selected from polyethylene glycol, ethylene glycol, propylene glycol, diethylene glycol and propylene glycol methyl ether, more preferably polyethylene One or a mixture of two or more selected from glycol, ethylene glycol, and diethylene glycol may be used.

The non-solvent is preferably used in an amount of 60 to 500 parts by weight, more preferably 100 to 400 parts by weight, and more preferably 120 to 350 parts by weight, based on 100 parts by weight of the polysulfone-based resin. At this time, if the amount of the non-solvent is less than 60 parts by weight, the phase transition rate increases and it may be difficult to form a separator, and if it exceeds 500 parts by weight, it may be difficult to form pores or the pore size may not be constant, and the pure permeability There may be problems with reduction.

According to another preferred embodiment of the present invention, the solvent and the non-solvent may be included in the polymer crude liquid at a weight ratio of 1:0.1 to 1:2. Inclusion in such a weight ratio is advantageous in terms of securing the pure permeability of the microfiltration membrane and the appropriate pore size, and when the non-solvent content is less than 0.1 with respect to 1 solvent weight, it is difficult to form an asymmetric structure. In this case, the fine structure collapses, making it difficult to form pores, and accordingly, a problem of reducing pure permeability may occur.

The crude polymer solution may further include a pore-forming agent and a hydrophilic additive. The pore-forming agent serves to generate pores in the crude polymer solution, and the amount of the pore-forming agent is preferably 25 to 300 parts by weight based on 100 parts by weight of the polysulfone-based resin. If the pore former is included in less than 25 parts by weight, there may be a problem in that the pore formation is not sufficiently formed and the permeability is significantly reduced. On the contrary, if it exceeds 300 parts by weight, the filtration performance as a microfiltration membrane is not sufficient There may be.

The pore forming agent may be appropriately selected and used among those generally used by those skilled in the art in the field of filters.

Since the role and type of the hydrophilic additive are the same as those described above, description thereof will be omitted. It is preferably included in 5 to 45 parts by weight, and most preferably included in 5 to 40 parts by weight. If the amount of the hydrophilic additive used is less than 4 parts by weight, there may be a problem in that the amount of the hydrophilic additive is too small and the degree of hydrophilization of the separation membrane is low, so that the pure permeability is lowered. Since there may be a problem of lowering the physical properties of or a problem of lowering the pure permeability due to a small pore size, it is good to use it within the above range.

The crude polymer solution prepared by the above method may be applied to the porous support layer. The coating method may be selected without limitation within a range that does not change the chemical composition and physical properties of the polymer crude liquid if it is a method known in the art, but preferably a method of spraying onto the porous support layer using a slot die can be used.

At this time, according to a preferred embodiment of the present invention, in step (1), the crude polymer solution may be applied only to one side of the porous support layer. The thickness of the first polymer layer and the second polymer layer formed by applying the crude polymer solution only to one side of the porous support layer can be different, and thus the asymmetry of the microfiltration membrane becomes more pronounced, and the physical properties of the separation membrane can improve

Next, in step (2), pores are formed on one side and the other side of the porous support layer by immersing the porous support layer containing the crude polymer solution containing the polysulfone-based resin into the pores in an external solidifying solution to cure the crude polymer solution. By forming a first polymer layer and a second polymer layer containing, it is possible to manufacture an asymmetric microfiltration membrane that is easy to manufacture in a large area according to the present invention.

At this time, the external coagulation liquid is not particularly limited, but more preferably water, polyethylene glycol, ethylene glycol, propylene glycol, diethylene glycol, isopropyl alcohol, methanol, and ethanol, or a mixture of two or more selected from among them is used. It is desirable to do

As can be seen in FIG. 1, the prepared microfiltration membrane has an asymmetrical cross section rather than a symmetrical shape, which is a result of the composition of the crude polymer solution or the temperature difference between the crude polymer solution and the external coagulation solution. am.

Since the physical properties of the manufactured microfiltration membrane are the same as those described above, the following description is omitted.

Hereinafter, the present invention will be described in more detail through examples, but the following examples are not intended to limit the scope of the present invention, which should be interpreted to aid understanding of the present invention.

<Example 1>

에서 서서히 혼합하여 균일한 고분자 조액을 제조하였다.Based on 100 parts by weight of PES (Basf 6020) resin having a weight average molecular weight of 75,000, 366 parts by weight of DMF (Dimethylformamide, solubility: 24.9 MPa ^1/2 ) as a solvent, 120 parts by weight of polyethylene glycol as a non-solvent, and polyvinyl film as a pore former. Rolidone (ISP K30) 73 parts by weight and hydrophilic additive SPES 5 parts by weight 50 parts by weight

was slowly mixed to prepare a homogeneous crude polymer solution.

Next, after removing air bubbles contained in the crude polymer solution using a vacuum pump, the polymer solution was applied only on one side of the porous support layer using a casting knife. The crude polymer solution applied on the porous support layer was immersed in a coagulation tank containing a non-solvent composed of general industrial water to induce phase separation to prepare an asymmetric microfiltration membrane.

An SEM photograph of the prepared asymmetric microfiltration membrane is shown in FIG. 1, and it can be seen that it has an asymmetric structure (first polymer layer-porous support layer-second polymer layer). In addition, the average pore size of the entire asymmetric microfiltration membrane was 0.2 μm, and the average tensile strength was 110 MPa.

Meanwhile, the average pore size of the first polymer layer was 0.19 μm, and the average pore size of the second polymer layer was 0.23 μm.

In addition, the average thickness of the porous support layer was 64 μm, the average thickness of the first polymer layer was 30 μm, and the average thickness of the second polymer layer was 20 μm.

<Example 2>

An asymmetric microfiltration membrane was prepared in the same manner as in Example 1, but using a PES resin having a weight average molecular weight of 92,000.

The average pore size of the entire prepared asymmetric microfiltration membrane was 0.1 μm.

Meanwhile, the average pore size of the first polymer layer was 0.09 μm, and the average pore size of the second polymer layer was 0.11 μm.

In addition, the average thickness of the porous support layer was 64 μm, the average thickness of the first polymer layer was 45 μm, the average thickness of the second polymer layer was 10 μm, and the average tensile strength was 110 MPa.

<Example 3>

An asymmetric microfiltration membrane was prepared in the same manner as in Example 1, but using a PES resin having a weight average molecular weight of 58,000.

The average pore size of the entire prepared asymmetric microfiltration membrane was 0.4 μm.

Meanwhile, the average pore size of the first polymer layer was 0.37 μm, and the average pore size of the second polymer layer was 0.41 μm.

In addition, the average thickness of the porous support layer was 64 μm, the average thickness of the first polymer layer was 20 μm, the average thickness of the second polymer layer was 20 μm, and the average tensile strength was 110 MPa.

<Example 4>

An asymmetric microfiltration membrane was prepared in the same manner as in Example 1, except that the pore-forming agent was not polyvinylpyrrolidone but hydrolyzed PET.

The average pore size of the entire prepared asymmetric microfiltration membrane was 0.2 μm, the average pore size of the first polymer layer was 0.19 μm, and the average pore size of the second polymer layer was 0.22 μm.

In addition, the average thickness of the porous support layer was 64 μm, the average thickness of the first polymer layer was 30 μm, the average thickness of the second polymer layer was 20 μm, and the average tensile strength was 110 MPa.

<Example 5>

A PES separator was prepared in the same manner as in Example 1, except that polyvinylpyrrolidone (ISP K90) was used as the pore former instead of polyvinylpyrrolidone (ISP K30).

The total average pore diameter of the prepared PES separator was 0.1 μm, and the average tensile strength was 110 MPa.

Meanwhile, the average pore size of the first polymer layer was 0.08 μm, and the average pore size of the second polymer layer was 0.12 μm.

In addition, the average thickness of the porous support layer was 64 μm, the average thickness of the first polymer layer was 30 μm, and the average thickness of the second polymer layer was 20 μm.

<Example 6>

A microfiltration membrane was prepared in the same manner as in Example 1, except that diethylene glycol was used as a non-solvent instead of polyethylene glycol.

The total average pore diameter of the prepared PES separator was 0.3 μm, and the average tensile strength was 110 MPa.

Meanwhile, the average pore size of the first polymer layer was 27 μm, and the average pore size of the second polymer layer was 31 μm.

In addition, the average thickness of the porous support layer was 64 μm, the average thickness of the first polymer layer was 30 μm, and the average thickness of the second polymer layer was 20 μm.

<Example 7>

An asymmetric microfiltration membrane was prepared in the same manner as in Example 1, except that the solvent content was 80 parts by weight based on 100 parts by weight of PES. The prepared asymmetric microfiltration membrane had an overall average pore size of 0.1 μm and an average tensile strength of 110 MPa.

Meanwhile, the average pore size of the first polymer layer was 0.08 μm, and the average pore size of the second polymer layer was 0.15 μm.

<Example 8>

It was carried out in the same manner as in Example 1, except that a crude polymer solution containing 800 parts by weight of a non-solvent based on 100 parts by weight of the PES resin was used. The total average pore size of the prepared asymmetric microfiltration membrane was 0.2 μm, and the average tensile strength was about 110 MPa.

Meanwhile, the average pore size of the first polymer layer was 0.17 μm, and the average pore size of the second polymer layer was 0.21 μm.

<Comparative Example 1>

An asymmetric microfiltration membrane was prepared in the same manner as in Example 1, but during casting, it was applied on a glass plate without application on the porous support layer and then solidified to prepare a separation membrane containing only the PES polymer layer.

The prepared separator had only a polymer layer without a porous support layer, and it was confirmed that the polymer layer had an asymmetric structure. The average pore size of the entire prepared asymmetric microfiltration membrane was 0.2 μm, and the average tensile strength was 3 MPa.

And, the average thickness of the prepared asymmetric microfiltration membrane was 110㎛.

<Comparative Example 2>

A microfiltration membrane was prepared in the same manner as in Example 1, except that no non-solvent was added to the crude polymer solution. The prepared microfiltration membrane had an average pore size of about 0.2 μm, and there was no difference in average pore size between the first polymer layer and the second polymer layer. The average thickness of the first polymer layer and the second polymer layer were 30 μm and 20 μm, respectively, and the average thickness of the porous support layer was 64 μm.

Experimental Example: Measurement of Physical Properties of PES Separator

The pure permeability, tensile strength, and porosity of the PVDF hollow fiber membranes prepared in Examples and Comparative Examples were measured in the following manner, and the results are shown in Table 1 below.

(1) Measurement method of pure permeability

For the prepared membrane, pure water at room temperature is supplied to one side of the module in a dead-end method at 1.0 atmospheric pressure, and the amount of permeated water is measured, and then permeation per unit time, unit membrane area, and unit pressure. converted to

(2) Tensile strength measurement method

Tensile strength and tensile elongation of the manufactured separator were measured through a tensile tester. The tensile test was conducted at room temperature with a grip distance of 10 cm and a crosshead speed of 3 cm/min.

It was measured using a tensile tester (“RTM-100” manufactured by Toyo Baldwin) in an atmosphere of a temperature of 23° C. and a relative humidity of 50% under conditions of an initial sample length of 100 mm and a crosshead speed of 200 mm/min.

division d ₁
(μm) d ₂
(μm) _D1
(μm) _D2
(μm) pure permeability
(LMH) tensile strength
(MPa) Example 1 0.19 0.23 30 20 21,200 110 Example 2 0.09 0.11 45 10 14,100 110 Example 3 0.37 0.41 20 20 28,100 110 Example 4 0.19 0.22 30 20 16,000 110 Example 5 0.08 0.12 30 20 4,400 110 Example 6 0.27 0.31 30 20 5,100 110 Example 7 0.08 0.15 30 20 11,600 110 Example 8 0.17 0.21 60 15 12,100 110 Comparative Example 1 0.20 - 110 - 22,500 3 Comparative Example 2 0.20 0.20 30 20 8,100 110 * Here, d ₁ , d ₂ , D ₁ , and D ₂ mean the average pore size of the first polymer layer, the average pore size of the second polymer layer, the average thickness of the first polymer layer, and the average thickness of the second polymer layer, respectively. do. In the case of Comparative Example 1, since there was no distinction between layers, all layers were considered to be composed of the first polymer layer.

Referring to Table 1, it can be seen that all except for Comparative Example 1, which does not include a porous support layer, have excellent tensile strength of about 110 MPa. Accordingly, those skilled in the art will readily recognize that large-area manufacturing will be easy.

In addition, in the case of Comparative Example 2 in which an asymmetric structure was not formed because it did not contain a non-solvent at all, the water permeability was remarkably low and the flow rate was reduced, indicating that the physical properties of the microfiltration membrane were deteriorated.

However, in the case of Example 2 having a high PES molecular weight, the average pore size was smaller than that of Example 1, and the average pore size ratio was also low, and the water permeability was also reduced. In the case of Example 3 having a low PES molecular weight, the average pore size was larger than that of Example 1, the average pore size ratio was similar, and the net permeability increased.

In addition, Example 5 using a pore former having a high molecular weight compared to Example 1 showed a small pore size, and because of the high molecular weight, the pore former was not extracted into the coagulation tank during the phase transition of the separator, so the average pore size ratio was very low and the water permeability was also reduced. .

And, in the case of Example 6, in which diethylene glycol was used instead of polyethylene glycol as a non-solvent, the pore uniformity of the polymer structure layer was lowered, resulting in a large pore size and a very low average pore size ratio, even though the pore size was large. Water permeability was significantly reduced. That is, although the average pore size was large, the porosity was low and the water permeability was reduced. In Example 6, diethylene glycol was used instead of polyethylene glycol. Since diethylene glycol has a slower phase transition rate with water in the coagulation bath than polyethylene glycol, the porosity is lowered, and the above results were obtained.

In addition, in the case of Example 7, in which the average pore size of the first polymer layer and the second polymer layer differ greatly by 0.05 μm or more, the water permeability is significantly lower, and the physical properties of the microfiltration membrane are inferior to those of Example 1. It can be confirmed that .

In addition, in the case of Example 8, where the difference in thickness between the thickness of the first polymer layer and the second polymer layer was remarkably 45 μm due to the excessive addition of non-solvent to the crude polymer solution, the pure permeability was remarkably low, so the flow rate was low and the use cycle was short. it can be expected that

Through the above examples and experimental examples, it was confirmed that the asymmetric microfiltration membrane including the porous support layer of the present invention has appropriate net permeability and high average pore size, and can be easily manufactured in a large area due to high tensile strength.

100: microfiltration membrane
110: first polymer layer
120: second polymer layer
130: porous support layer
140: pore

Claims (17)

A porous support layer in which a polysulfone-based resin is penetrated into the pores;
A first polymer layer formed on one surface of the porous support layer and containing a polysulfone-based resin; and
A second polymer layer formed on the other side of the porous support and containing a polysulfone-based resin;
The porous support layer, the first polymer layer and the polysulfone-based resin of the second polymer layer are integrated and cured, and the average pore size of the first polymer layer is smaller than the average pore size of the second polymer layer. An asymmetric microfiltration membrane that is easy to manufacture. According to claim 1,
An asymmetric microfiltration membrane that is easy to manufacture in a large area, characterized in that it satisfies both the following conditions 1) and 2):
1) 0.01 μm ≤ d ₂ - d ₁ ≤ 0.05 μm
2) d ₁ < d ₃ < d ₂
Here, d ₁ , d ₂ and d ₃ are the average pore size of the first polymer layer, the average pore size of the second polymer layer, and the average pore size of the polysulfone-based resin that has penetrated into the pores of the porous support layer, respectively. means According to claim 1,
An asymmetric microfiltration membrane that is easy to manufacture in a large area, characterized in that the thickness of the first polymer layer is greater than the thickness of the second polymer layer. According to claim 3,
An asymmetric microfiltration membrane that is easy to manufacture in a large area, characterized in that it satisfies the following condition 3):
3) 0μm < D ₁ - D ₂ < 40μm
Here, D ₁ and D ₂ mean the average thickness of the first polymer layer and the average thickness of the second polymer layer, respectively. According to claim 2,
The pore size in the first polymer layer gradually decreases from the region adjacent to the porous support layer to the region adjacent to the outer surface of the first polymer layer, and the pore size in the second polymer layer increases in the region adjacent to the porous support layer. An asymmetric microfiltration membrane that is easy to manufacture in a large area, characterized in that it increases as it goes to the area adjacent to the outer surface of the second polymer layer. According to claim 1,
The polysulfone-based resin is an asymmetric microfiltration membrane that is easy to manufacture a large area, characterized in that the polyethersulfone resin (PES). According to claim 1,
The porous support layer is an asymmetric microfiltration membrane that is easy to manufacture in a large area, characterized in that woven or non-woven fabric. According to claim 7,
An asymmetric microfiltration membrane that is easy to manufacture in a large area, characterized in that a hydrophilic additive is further included by mixing with the polysulfone-based resin. According to claim 1,
An asymmetric microfiltration membrane that is easy to manufacture in a large area, characterized in that the average tensile strength in both the machine direction (MD) and the vertical direction (TD) is 80 MPa or more. According to claim 1,
An asymmetric microfiltration membrane that is easy to manufacture in a large area, characterized in that the pure permeability is 15,000 to 30,000LMH. (1) applying and infiltrating a crude polymer solution containing a polysulfone-based resin onto one surface of the porous support layer; and
(2) a first polymer layer and a second polymer layer containing pores on one side and the other side of the porous support layer, respectively, by immersing the porous support layer coated with the crude polymer solution in an external coagulation solution in a coagulation tank to cure the crude polymer solution; Forming a polymer layer; including,
The method of producing an asymmetric microfiltration membrane that is easy to manufacture a large area, characterized in that the average pore size of the second polymer layer is larger than the average pore size of the first polymer layer. According to claim 11
The step (1) is a method for producing an asymmetric microfiltration membrane that is easy to manufacture in a large area, characterized in that the polymer crude liquid is applied only to one side of the porous support layer. According to claim 11,
Method for producing an asymmetric microfiltration membrane that is easy to manufacture in a large area, characterized in that both conditions 1) and 2) are satisfied:
1) 0.01 μm ≤ d ₂ - d ₁ ≤ 0.05 μm
2) d ₁ < d ₃ < d ₂
Here, d ₁ , d ₂ and d ₃ are the average pore size of the first polymer layer, the average pore size of the second polymer layer, and the polysulfone cured polymer crude liquid penetrating into the pores of the porous support layer, respectively. Means the average pore size of the phone-based resin. According to claim 11,
In step (1), the crude polymer solution further includes a solvent and a non-solvent, and is prepared by mixing at 40 ° C to 100 ° C. According to claim 14,
The solvent and the non-solvent are 1: 0.1 to 1: 2, characterized in that contained in the crude polymer solution in a weight ratio of a large area manufacturing method of an asymmetric microfiltration membrane that is easy to manufacture. According to claim 14,
In step (1), the crude polymer solution further comprises a pore-forming agent and a hydrophilic additive. According to claim 11,
The external coagulating liquid in step (2) is easy to prepare a large area, characterized in that it contains at least one selected from water, polyethylene glycol, ethylene glycol, propylene glycol, diethylene glycol, isopropyl alcohol, methanol and ethanol. Manufacturing method of asymmetric microfiltration membrane.