KR102693118B1 - Water separation membrane, filter for water treatment including same, and method for manufacturing the same - Google Patents

Abstract

The present invention provides a water separation membrane including a first porous layer and a second porous layer, and provides a water separation membrane having excellent asymmetry using different phase separation inducing methods and a method for manufacturing the same, wherein the water separation membrane implements excellent tensile strength and nanoparticle removal rate, and can implement pure water permeability that can shorten the time for semiconductor purification treatment and water treatment.

Description

Water separation membrane, filter for water treatment including same, and method for manufacturing the same

The present invention relates to a water-soluble membrane having excellent asymmetry and a method for manufacturing the same.

The separation of substances using membranes has a relatively simple principle and process and a wide range of applications, so it is actively used in gas or liquid purification processes.

Membranes are actively being used in various fields of application, mainly for energy conservation and environmental protection, and membrane separation processes using them are being actively developed. In particular, membranes such as ultrafiltration membranes and precision filtration membranes have pores ranging from hundreds of nanometers to tens of micrometers in size, and are therefore applied in various fields including wastewater treatment, water production, food and medical industries, and recently, as interest in drinking water increases, their use is gradually increasing, and membranes are also being utilized in various ways in virus removal and special bio-processes.

As the usability of membranes has increased, the demand for membranes with various pore sizes has also increased, and technology development to provide various membranes is still being carried out.

Conventional separation membranes must be thickened in order to increase their mechanical properties, but when this thickness is increased, pressure or permeation decreases, making it difficult to achieve the efficiency of the separation membrane economically. In addition, in order to increase the separation amount, the thickness must be thinned, but in this case, there is a disadvantage in that long-term use is difficult due to the inferior mechanical properties of the separation membrane.

Therefore, satisfying the mass separation efficiency and mechanical properties by controlling the thickness, pore size, etc. still remains a challenge to be solved.

Republic of Korea Publication Patent No. 2016-0123426 A

The purpose of the present invention is to solve the above problems, and to provide a separation membrane, particularly a water separation membrane, which has a plurality of porous layers but has different pore sizes to simultaneously achieve mechanical properties and separation efficiency.

In addition, in one embodiment, it is intended to achieve uniformity of separation efficiency by using the same material as the material of multiple porous layers having different pore sizes.

As an example of implementation, the purpose is to provide a water separation membrane having excellent separation efficiency and excellent mechanical properties that can be used for a long period of time by making the pore sizes and porosities of the first porous layer and the second porous layer have different asymmetry.

As an embodiment, the purpose is to provide a water separation membrane capable of implementing the same permeation selectivity by having the first porous layer and the second porous layer coating film including the same thermoplastic resin.

In addition, as an example of implementation, a water separation membrane having excellent durability against solvents, excellent mechanical properties, and hydrophilicity can be provided, and thus can be used in the bio field, semiconductor purification, or wastewater treatment field.

The present invention is a water separation membrane including a second porous layer formed on one or both sides of a first porous layer,

A water separation membrane is provided in which the pore sizes of the first porous layer and the second porous layer are different, and the average pore size of one porous layer in the first porous layer or the second porous layer is 30 to 200 nm, and the average pore size of the other porous layer is 5 to 70 nm.

As an embodiment, the first porous layer and the second porous layer may include the same hydrophilic thermoplastic resin.

The present invention provides a water treatment filter including the water separation membrane described above.

The present invention provides a water treatment device including a water treatment filter.

The present invention comprises the steps of forming a first porous layer by applying a first porous layer composition comprising a thermoplastic resin, a pore-forming agent, a poor solvent, and a solvent on a substrate layer; and

A step of forming a second porous layer by applying a second porous layer composition including a thermoplastic resin, a poor solvent, and a solvent on the first porous layer;

A method for manufacturing a water-soluble membrane, comprising:

The present invention provides a method for producing a water-soluble membrane, wherein the second porous layer composition comprises 10 to 40 wt% of a solvent based on the total amount of the second porous layer composition.

As an embodiment, the step of forming the first porous layer may be a steam-induced phase separation method.

As an embodiment, the step of forming the second porous layer may be a non-solvent-induced phase separation method.

As an embodiment, the first porous layer composition may include 10 to 30 wt% of the thermoplastic resin, based on the total amount.

As an embodiment, the second porous layer composition may include 10 to 40 wt% of a thermoplastic resin.

In one embodiment, the pore-forming agent is included in an amount of 1 to 20 wt% based on the total amount of the first porous layer composition, and the pore-forming agent may be one or more selected from polyvinylpyrrolidone, polyethylene glycol, polypropylene glycol, ethylene glycol, and glycerin.

The above solvent may be one or more selected from N-methyl-2-pyrrolidone (NMP), ε-caprolactam, methyl ethyl ketone, γ-butyrolactone, dimethylformamide (DMF), dimethyl sulfoxide, and dimethylacetamide (DMAc).

As an embodiment, the solvent may be one or more selected from isopropyl alcohol, ethylene glycol, butylene glycol, m-cresol, and nujol.

The water separation membrane of the present invention has excellent asymmetry by including a porous layer using different phase separation methods, and thus can realize high permeation flux and mechanical strength.

In addition, since the water separation membrane of the present invention has a laminated structure of porous layers containing the same thermoplastic resin, it can have excellent permeation selectivity.

In addition, the water-removing membrane of the present invention can have excellent chemical resistance and hydrophilicity by being manufactured using a hydrophilic thermoplastic resin.

In addition, the method for manufacturing a water-soluble film of the present invention can apply the second porous layer composition without damaging the first porous layer, and can control the thickness of each porous layer.

Figure 1 is an electron microscope photograph of the front and back surfaces of the first porous layer and the second porous layer of Example 1.
Specifically, (a) is a photograph of the front surface of the first porous layer of Example 1, (b) is a photograph of the back surface of the first porous layer of Example 1, (c) is a photograph of the front surface of the second porous layer, and (d) is a photograph of the back surface of the second porous layer of Example 2.

Unless otherwise defined, technical and scientific terms used in this specification have the meaning commonly understood by a person of ordinary skill in the art to which this invention belongs, and descriptions of well-known functions and configurations that may unnecessarily obscure the gist of the present invention are omitted in the following description and accompanying drawings.

Additionally, the singular forms used herein are intended to include the plural forms as well, unless the context specifically indicates otherwise.

Additionally, units used in this specification without special mention are based on weight, for example, % weight%.

Additionally, the numerical ranges used herein include lower and upper limits and all values within that range, increments logically derived from the shape and width of the defined range, all doubly defined values, and all possible combinations of upper and lower limits of numerical ranges defined in different shapes.

The term "comprises," as used herein, is an open-ended description equivalent to expressions such as "comprises," "contains," "has," or "characterized by," and does not exclude additional elements, materials, or processes not listed herein.

Additionally, the term ‘layer’ in this specification may refer to a film, a coating, a semi-film, a membrane or a sheet.

Additionally, the term “pore” in this specification may mean the average pore size or pores of the first porous layer, the second porous layer, or the separator.

In order to solve the problem of the above water separation membrane as an embodiment, a water separation membrane having a laminated structure including a first porous layer and a second porous layer having different pores is provided.

As an example of implementation, the first porous layer and the second porous layer may be made of the same thermoplastic polymer, thereby providing a water separation membrane having the same separation selectivity, etc.

In addition, as an implementation example, other water separation membranes can achieve excellent nanoparticle rejection rates and pure water permeability.

Below, the water separation membrane of the present invention is described.

As an embodiment, a water separation membrane having a laminated structure including a first porous layer and a second porous layer formed on one or both sides of the first porous layer, wherein the first porous layer and the second porous layer may be water separation membranes having different pores.

In one embodiment, a water separation membrane can be provided in which the pores of one porous layer in the first porous layer or the second porous layer can be 30 to 200 nm, and the average pores of the other porous layer can be 5 to 70 nm.

As an example embodiment, the pores of the first porous layer may be 30 to 200 nm, 50 to 150 nm, or 50 to 100 um, and the pores of the second porous layer may be 5 to 70 nm, 5 to 50 nm, or specifically 10 to 50 nm, but are not limited thereto.

By controlling the pores of each of the above porous layers, the mechanical strength is secured, thereby securing the life of the separation membrane. In addition, the permeation flow rate is increased, thereby accelerating the separation speed of the water separation membrane, so that the purpose of the present invention can be well achieved.

As an embodiment, the above 1 porous layer can be manufactured using a steam-induced phase separation method, or can be manufactured using a steam-induced phase separation method followed by a non-solvent phase separation method.

In addition, as an embodiment, the above two porous layers can be manufactured using only a non-solvent-induced phase separation method.

Therefore, the above water separation membrane is a laminated water separation membrane including porous layers manufactured by different phase separation methods rather than a single phase separation method, and thus is more preferable because it can provide a water separation membrane having superior asymmetry than a water separation membrane manufactured using only a conventional water vapor-induced phase separation method.

The excellent asymmetry of the above water separation membrane may mean that the pore sizes and porosities of each porous layer are different, and therefore, each porous layer may act in combination with a porous layer manufactured by a steam-induced phase separation method and a porous layer manufactured by a non-solvent-induced phase separation method, so that the separation membrane may implement excellent mechanical strength and permeation flux, and specifically, the permeation flux may be 150 L/m ² ·hr or more.

The detailed phase separation method is explained in the water separation membrane manufacturing method described later.

As an example of implementation, as described above, the water separation membrane may have a structure in which porous layers having different porosities and pores are laminated.

As an embodiment, the first porous layer may have a thickness of 10 to 500 nm, may be 50 to 400 nm, and specifically may be 100 to 300 nm.

Additionally, in one embodiment, the second porous layer may have a thickness of 10 to 400 nm, specifically 50 to 300 nm, and specifically 100 to 200 nm.

The thickness of the above moisture separation membrane is not limited and may vary depending on the filter and device including the moisture separation membrane.

In one embodiment, the water barrier membrane may have a structure in which porous layers including the same thermoplastic polymer are laminated.

The above thermoplastic resin may be any hydrophilic thermoplastic polymer, but a polyethersulfone polymer may be preferred.

Polyethersulfone polymers are thermoplastic polymers with excellent hydrophilicity, and are preferred because they can have a better permeation rate than water separation membranes including polyacrylonitrile, polyvinylidene fluoride, and polytetrafluoroethylene, which are used in conventional water separation membranes.

The above polyethersulfone polymer may preferably contain a phenyl group, and specifically, a polyethersulfone of the following chemical formula 1 may be preferable because it has excellent chemical resistance and hydrophilicity.

[Chemical Formula 1]

The above polyethersulfone polymer may be preferred because it has excellent heat resistance, a wide applicable pH range, excellent solubility in solvents, and easy preparation of a dope. In addition, the above polyethersulfone may be preferred because it has high usability as a water separation membrane included in a bioprocess, water treatment filter, or semiconductor purification treatment device.

As an example embodiment, the polyethersulfone may have a weight average molecular weight of 10,000 to 1,000,000, but is not limited thereto.

Polyethersulfone having a weight average molecular weight within the above range can be dissolved in an organic solvent to provide a viscosity with good workability to the first porous layer composition and the second porous layer composition (dope solution), and a water separation membrane including the same can provide excellent mechanical strength and density.

As an embodiment, the water separation membrane may have a porosity of 20 to 70 vol%, specifically 30 to 70 vol%, and more specifically 40 to 70 vol%. A water separation membrane having a porosity in the above range may have productable mechanical strength and pure water permeability, and may realize an excellent nanoparticle removal rate, and is thus more preferred.

The present invention can provide a water treatment filter including the water separation membrane described above.

The above water treatment filter can be used without restriction in the form of a depth filter, wound filter, pleated filter or capsule filter. However, a pleated filter may be preferable because it may have better efficiency as an asymmetric separation membrane, but is not limited thereto.

In one embodiment, a water treatment device including the water treatment filter described above can be provided.

The above water treatment device may be a wastewater treatment device, a semiconductor purification device, a water purifier, a seawater desalination device, a food purification device, a blood purification device, a bio-impurity purification device, etc.

Hereinafter, the method for manufacturing a water-soluble membrane of the present invention will be described.

In one embodiment, a step of forming a first porous layer by applying a first porous layer composition comprising polyethersulfone, a pore-forming agent, a solvent, and a solvent on a substrate; and

A step of forming a second porous layer by applying a second porous layer composition containing polyethersulfone, a poor solvent, and a solvent onto the first porous layer;

A method for manufacturing a water-soluble membrane including the same can be provided.

As an embodiment, the second porous layer composition may contain 10 to 40 wt% of the solvent, 10 to 30 wt% of the solvent, or preferably 15 to 25 wt% of the solvent, based on the total amount of the second porous layer composition.

The second porous layer composition containing the solvent in the above range is more preferred because it dissolves the matrix resin of the first porous layer so as to prevent or minimize changes in the pore size or void ratio of the first porous layer, thereby not causing changes in separation ability, mechanical strength, etc.

In one embodiment, a phase separation method can be used as a method of forming pores and solidifying each porous layer composition. The pores are formed by removing the solvent and the poor solvent contained in each porous layer composition, and the pores can be formed by dissolving the solvent and the poor solvent contained in each porous layer composition in a non-solvent and removing them, and the solvent can be removed by volatilization through a drying process.

As an embodiment, the method for manufacturing the water separation membrane has the advantage of being able to continuously laminate each porous layer having a different phase separation method, and since each porous layer has a different phase separation method, the pores and porosity can be controlled. In addition, by controlling the thickness of each porous layer composition, the overall porosity and pores of the water separation membrane can be controlled, so that excellent asymmetry of the manufactured water separation membrane can be implemented, and the advantage of being able to control the asymmetry can be achieved.

As another embodiment, the method for manufacturing a water-repellent membrane can sequentially laminate each porous layer using a composition (dope solution) containing the same thermoplastic polymer, and can manufacture a water-repellent membrane in which multiple porous layers are laminated.

As an embodiment, each of the steps of forming the porous layer may include a drying step. Specifically, the step of forming the first porous layer may exclude the drying step.

The above drying step can use a method of drying in a natural environment for 24 hours or a method of drying with hot air at 20 to 60°C.

As an embodiment, the first porous layer composition can comprise 10 to 40 wt %, 10 to 30 wt %, specifically 10 to 20 wt % of polyethersulfone.

In addition, as an embodiment, the second porous layer composition may contain 10 to 50 wt%, 10 to 40 wt%, and specifically 10 to 30 wt% of polyethersulfone. The composition of each porous layer containing the polyethersulfone in the above range can be manufactured into a water separation membrane having a high porosity and can have a mechanical strength that is not too low, which is preferred.

The above solvent refers to a compound capable of dissolving 5 parts by weight or more of polyethersulfone at a temperature of about 60°C or less, and is not particularly limited as long as it dissolves polyethersulfone forming each porous layer.

In one embodiment, the solvent may be one or more selected from N-methyl-2-pyrrolidone (NMP), ε-caprolactam, methyl ethyl ketone, γ-butyrolactone, dimethylformamide (DMF), dimethyl sulfoxide, and dimethylacetamide (DMAc), and specifically, dimethylacetamide, N-methyl pyrrolidone, or a mixture thereof may be preferred because they have good solubility in polyethersulfone.

The above poor solvent may refer to a compound that cannot dissolve polyethersulfone at a low temperature of 60°C or lower, but can dissolve 5 wt% or more of polyethersulfone at a high temperature range of 60°C or higher or lower than the melting point of the polyethersulfone. In addition, in the phase separation method of each porous layer composition, it may refer to a compound that has excellent solubility with a non-solvent, so that pores can be easily formed through solvent exchange between the non-solvent and the poor solvent.

For example, the above-mentioned poor solvent may be one or more selected from isopropyl alcohol, ethylene glycol, butylene glycol, m-cresol, glycerol, nujol, polyethylene glycol and polybutylene glycol, specifically glycerol, polyethylene glycol and polybutylene glycol, and more specifically polyethylene glycol, polybutylene glycol or a mixture thereof.

In order to absorb the solidification heat of the polyethersulfone, polyethylene glycol may be preferable. However, polyethylene glycol having too high a weight average molecular weight may cause a problem of increasing the viscosity of the first porous layer composition and the second porous layer composition. Therefore, the polyethylene glycol having a weight average molecular weight of 100 to 1,000 g/mol is more preferable because it has good workability, viscosity, and can excellently absorb the solidification heat of the polyethersulfone.

Specifically, the polyethylene glycol may have a weight average molecular weight of 100 to 700 g/mol, and more specifically, may have a weight average molecular weight of 100 to 500 g/mol.

As an embodiment, the first porous composition may comprise 1 to 20 wt % of the pore-forming agent, specifically 1 to 10 wt %, and more specifically 5 to 10 wt %.

The above pore-forming agent is a polymer material commonly used in a phase separation method, and plays a role in helping to form pores when a composition containing the same undergoes phase transition. The pore-forming agent may be one or more selected from a nonionic surfactant and polyvinylpyrrolidone, but is not limited thereto as long as the purpose of the present invention is achieved.

Below, the phase separation method of each porous layer is explained.

As an example embodiment, the step of forming the first porous layer may use a steam-induced phase separation method and a non-solvent-induced phase separation method, and further, the step of forming the second porous layer may use a non-solvent phase separation method together with the applied second porous layer composition.

The above steam-induced phase separation method exposes the first porous layer composition coated on the substrate to air at 30 to 60°C containing 80% water vapor, thereby forming pores on the surface of the first porous layer composition coated on the substrate and penetrating into the interior of the first porous layer composition to form small pores.

As another example, by inducing the pore formation of the first porous layer in advance, when using the non-solvent phase separation method in the subsequent step, larger and more uniform pores can be achieved, which is more preferable. By adopting this method, the first porous layer can realize excellent mechanical strength, more uniform pores and porosity, and can form pores of 50 nm or more, which is even better.

As an example of implementation, the steam-induced phase separation method can partially separate polyethylene sulfone on the surface of the first porous layer, but cannot completely separate the polyethylene sulfone, so it may be desirable to use it in combination with a non-solvent-induced phase separation method.

The above non-solvent-induced phase separation method forms pores by removing the solvent and poor solvent included in each porous layer composition using a non-solvent, and further, the non-solvent phase separation method can coagulate the polyethylene sulfone included in each porous layer composition. The above non-solvent-induced phase separation method can form pores less than 50 nm, and has the advantages of a wide porosity and pore distribution.

As an example embodiment, the step of forming the second porous layer composition may preferably use the non-solvent induced phase separation method described above.

Therefore, the above method for manufacturing a water-separating membrane can manufacture a water-separating membrane with excellent asymmetry by using different phase separation methods for the first porous layer composition and the second porous layer composition.

In addition, as an embodiment, the method for manufacturing the water-separating membrane provides a method capable of laminating each porous layer using a different phase-separation method using the same resin, polyethersulfone, and can also provide a method for applying the composition of each porous layer without dissolving the matrix porous layer. Therefore, the method for manufacturing the water-separating membrane can solve the problem of difficulty in controlling the porosity and pore size of the water-separating membrane by using the water-separating membrane induced phase-separation method only for one porous layer.

In addition, the problem of significantly reducing the permeation rate of the water separation membrane due to the formation of pores of 10 um or less, which prevent water vapor from penetrating into the water separation membrane by increasing the thickness of the water separation membrane, can be solved.

As a result, the water separation membrane can control the porosity and pore size, and a water separation membrane with excellent permeation rate can be manufactured, thereby shortening the time of the purification process and, at the same time, manufacturing a water separation membrane with excellent nanoparticle removal rate.

Hereinafter, the present invention will be described by way of examples. That is, the present invention can be better understood by the following examples, and the following examples are for the purpose of illustrating the present invention. However, the examples of the present invention are not intended to limit the scope of protection defined by the appended claims.

[measurement method]

1. Measurement of permeate flow rate

The membranes manufactured in the following examples and comparative examples were installed so that the first porous layer surface faced the direction in which distilled water was sprayed. The pure water permeability measurement experiment was conducted by spraying distilled water under pressure of 1 bar and in an environment of 20°C, and measuring the water permeate after 30 minutes from the time of permeation through the membrane (18 cm ² ). The amount of water permeated for 1 hour was measured and calculated using the following calculation formula 1.

[Calculation formula 1]

Permeate flow rate (LMH, L/m ² ·hr) = Amount of water permeated (L) / Permeate time (1 hr) * Membrane area (0.0018 m ² )

2. Measurement of nanoparticle removal rate

For the measurement of the nanoparticle removal rate, a membrane was installed as in the above pure water permeation efficiency, and 50 mL of a suspension containing 20 nm polystyrene at a concentration of 5 ppm was filtered under a pressure of 1 bar. At this time, 10 mL of the supplied suspension and the filtered suspension were collected every hour, and the absorbance was measured using UV-vis (Analytik Jena, Specord 210 Plus) to calculate the removal rate.

3. Measurement of the average pore size of the membrane

The average pore size of the water separation membranes manufactured in the examples and comparative examples was measured using a permporometer (Alfa Wassermann, Promatix 1000).

[Example 1]

A first porous layer composition was prepared by mixing 14 wt% of polyethersulfone (weight average molecular weight: 35,000 g/mol), 30 wt% of dimethylacetamide, 50 wt% of polyethylene glycol (number average molecular weight: 200 g/mol), and 6 wt% of polyvinylpyrrolidone (weight average molecular weight: 40,000 g/mol, K30) at 60°C for 24 hours.

Thereafter, the first porous layer composition was applied to a glass plate (450 cm ² ) with a thickness of 200 ㎛, exposed to steam at 80% humidity for 1 minute, and then immersed in a 20° C. water bath to form the first porous layer.

A second porous layer composition was prepared by mixing 20 wt% of polyethersulfone (weight average molecular weight: 20,000 to 50,000 g/mol, Sigma-Aldrich), 20 wt% of dimethylacetamide, and 60 wt% of polyethylene glycol (number average molecular weight: 200 g/mol, Sigma-Aldrich), stirring the mixture at 60° C. for 24 hours, and removing air bubbles.

Thereafter, the second porous layer manufactured as described above was applied on the first porous layer with a thickness of 150 μm while maintaining the temperature at 20°C, immersed in a 20°C water tank to manufacture a water separation film, and the glass plate and the manufactured water separation film were peeled off.

The manufactured water separation membrane was measured and is shown in Table 1 below.

[Example 2]

A first porous layer composition was prepared and a first porous layer was formed on a glass plate in the same manner as in Example 1.

A second porous layer composition was prepared by mixing 15 wt% of polyethersulfone (weight average molecular weight: 20,000 to 50,000 g/mol, Sigma-Aldrich), 20 wt% of dimethylacetamide, and 65 wt% of polyethylene glycol (number average molecular weight: 200 g/mol, Sigma-Aldrich), stirring the mixture at 60° C. for 24 hours, and removing air bubbles.

Thereafter, the second porous layer manufactured as described above was applied on the first porous layer with a thickness of 150 μm while maintaining the temperature at 20°C, immersed in a 20°C water tank to manufacture a water separation film, and the glass plate and the manufactured water separation film were peeled off.

The manufactured water separation membrane was measured and is shown in Table 1 below.

[Example 3]

A first porous layer composition was prepared and a first porous layer was formed on a glass plate in the same manner as in Example 1.

A second porous layer composition was prepared by mixing 13 wt% of polyethersulfone (weight average molecular weight: 20,000 to 50,000 g/mol, Sigma-Aldrich), 22 wt% of dimethylacetamide, and 65 wt% of polyethylene glycol (number average molecular weight: 200 g/mol, Sigma-Aldrich), stirring the mixture at 60° C. for 24 hours, and removing air bubbles.

Thereafter, the second porous layer manufactured as described above was applied on the first porous layer with a thickness of 150 μm while maintaining the temperature at 20°C, immersed in a 20°C water tank to manufacture a water separation film, and the glass plate and the manufactured water separation film were peeled off.

The manufactured water separation membrane was measured and is shown in Table 1 below.

[Example 4]

A first porous layer composition was prepared by mixing 14 wt% of polyethersulfone (weight average molecular weight: 20,000 to 50,000 g/mol, Sigma-Aldrich), 30 wt% of dimethylacetamide, 50 wt% of polyethylene glycol (number average molecular weight: 200 g/mol, Sigma-Aldrich), and 6 wt% of polyvinylpyrrolidone (weight average molecular weight: 40,000 g/mol, K30) at 60°C for 24 hours.

After that, the mixture was applied to a thickness of 200 ㎛ on a glass plate and exposed to water vapor at 80% humidity for 1 minute.

A second porous layer composition was prepared by mixing 20 wt% of polyethersulfone (weight average molecular weight: 20,000 to 50,000 g/mol, Sigma-Aldrich), 20 wt% of dimethylacetamide, and 60 wt% of polyethylene glycol (number average molecular weight: 200 g/mol, Sigma-Aldrich), stirring the mixture at 60° C. for 24 hours, and removing air bubbles.

Thereafter, the second porous layer manufactured as described above was applied on the first porous layer with a thickness of 150 μm while maintaining the temperature at 20°C, immersed in a 20°C water tank to manufacture a water separation film, and the glass plate and the manufactured water separation film were peeled off.

The manufactured water separation membrane was measured and is shown in Table 1 below.

[Comparative Example 1]

A first porous layer composition was prepared by mixing 14 wt% of polyethersulfone (weight average molecular weight: 20,000 to 50,000 g/mol, Sigma-Aldrich), 30 wt% of dimethylacetamide, 50 wt% of polyethylene glycol (number average molecular weight: 200 g/mol, Sigma-Aldrich), and 6 wt% of polyvinylpyrrolidone (weight average molecular weight: 40,000 g/mol, K30) at 60°C for 24 hours.

Thereafter, the mixture was applied to a glass plate with a thickness of 200 ㎛, exposed to water vapor at 80% humidity for 1 minute, and then immersed in a tank containing water at 20° C. to produce a water separation film, and the glass plate and the produced water separation film were peeled off.

The manufactured water separation membrane was measured and is shown in Table 1 below.

[Comparative Example 2]

A second porous layer composition was prepared by mixing 20 wt% of polyethersulfone (weight average molecular weight: 20,000 to 50,000 g/mol, Sigma-Aldrich), 20 wt% of dimethylacetamide, and 60 wt% of polyethylene glycol (number average molecular weight: 200 g/mol, Sigma-Aldrich) on a glass plate, stirring the mixture at 60° C. for 24 hours, and removing air bubbles.

Thereafter, the second porous layer manufactured as described above was applied on the first porous layer with a thickness of 150 μm while maintaining the temperature at 20°C, immersed in a 20°C water tank to manufacture a water separation film, and the glass plate and the manufactured water separation film were peeled off.

The manufactured water separation membrane was measured and is shown in Table 1 below.

[Comparative Example 3]

A first porous layer composition was prepared by mixing 14 wt% of polyethersulfone (weight average molecular weight: 20,000 to 50,000 g/mol, Sigma-Aldrich), 30 wt% of dimethylacetamide, 50 wt% of polyethylene glycol (number average molecular weight: 200 g/mol, Sigma-Aldrich), and 6 wt% of polyvinylpyrrolidone (weight average molecular weight: 40,000 g/mol, K30) at 60°C for 24 hours.

Thereafter, the mixture was applied to a glass plate with a thickness of 200 ㎛, exposed to steam at 80% humidity for 1 minute, and then immersed in a 20°C water bath to form a first porous layer.

A second porous layer composition was prepared by mixing 13 wt% of polyethersulfone (weight average molecular weight: 20,000 to 50,000 g/mol, Sigma-Aldrich), 50 wt% of dimethylacetamide, and 38 wt% of polyethylene glycol (number average molecular weight: 200 g/mol, Sigma-Aldrich), stirring the mixture at 60° C. for 24 hours, and removing air bubbles.

Thereafter, the second porous layer manufactured as described above was applied on the first porous layer with a thickness of 150 μm while maintaining the temperature at 20°C, immersed in a 20°C water tank to manufacture a water separation film, and the glass plate and the manufactured water separation film were peeled off.

The manufactured water separation membrane was measured and is shown in Table 1 below.

Pure transmittance
(L/m2 ^· hr) Nanoparticle removal rate
(%) Average pore size
(nm) Example 1 220 95 21 Example 2 310 91 25 Example 3 420 88 31 Example 4 150 92 36 Comparative Example 1 15,000 0 300 Comparative Example 2 350 60 60 Comparative Example 3 2,500 0 80

Example 1 is a water separation membrane manufactured by including 20 wt% of polyethylene sulfone in the second porous layer composition, Example 2 is a water separation membrane manufactured by including 15 wt% of polyethylene sulfone in the second porous layer composition, and Example 3 is a water separation membrane manufactured by including 13 wt% of polyethylene sulfone in the second porous layer composition.

When the measured values of pure water permeability of Examples 1 to 4 are checked in Table 1 above, it can be confirmed that they have values of 500 L/m ² ·hr or less, and it can be confirmed that the measured value of pure water permeability of Example 1 is the smallest. This suggests that as the content of thermoplastic resin included in the second porous layer increases, the porosity and average pore size of the second porous layer decrease.

In the above Table 1, it can be confirmed that Example 4 has a pure permeability of 150 L/m ² hr, which is smaller than that of other examples. Example 4 is manufactured by partially permeating the second porous layer composition onto the first porous composition without forming the first porous layer, and although the average pore size is no different from that of other examples, it suggests that the pore size of the boundary between the first porous layer and the second porous layer of Example 4 is small.

In the above Table 1, it can be confirmed that the pure water permeability measurement value of Comparative Example 1 is significantly higher than that of Examples 1 to 4. Comparative Example 1 is a water separation membrane including only the first porous layer manufactured using a water vapor phase separation method and has a high porosity, but it can be confirmed that it has a disadvantage of a wide pore size distribution, as shown in the average pore size measurement value of Comparative Example 1 in the above Table 1. Therefore, looking at Comparative Example 1 in the above Table 1, it can be confirmed that the pure water permeability measurement value is significantly higher than that of Examples 1 to 4, and that the nanoparticle removal rate is not achieved.

It can be confirmed that the measured values of pure water permeability of the above Comparative Example 2 are similar to those of Examples 1 to 4. Comparative Example 1 is a water separation membrane including only a second porous layer manufactured using a non-solvent phase separation method, and although the size and porosity of the pores can be controlled, it can be confirmed that it has a wide disadvantage in that large pores can be included, as shown in the measured values of the average pore size of Comparative Example 1 in Table 1. Therefore, looking at Comparative Example 2 in Table 1, it can be confirmed that the pure water permeability is equivalent to that of Examples 1 to 4, but the average pore size is larger than that of Examples 1 to 2, and the nanoparticle removal rate is not excellent at 60%.

Comparative Example 3 is a water separation membrane manufactured by including 50 wt% of a solvent in the second porous layer composition, and as a result, Comparative Example 3 is manufactured in which the first porous layer is partially dissolved due to the solvent of the second porous layer composition. Therefore, when checking Comparative Example 3 in Table 1 above, it can be confirmed that it is significantly higher than Examples 1 to 4 and that the nanoparticle removal rate is not implemented.

As a result of the example, the asymmetric separation membrane of the present invention can realize an excellent nanoparticle rejection rate and an appropriate pure water permeability by including a first porous layer and a second porous layer having different pore sizes.

Therefore, the separation membrane of the present invention can provide a separation membrane applicable to general water treatment and semiconductor processes.

Although the present invention has been described through specific matters and limited examples and comparative examples, these have been provided only to help a more general understanding of the present invention, and the present invention is not limited to the above examples, and those skilled in the art to which the present invention pertains can make various modifications and variations from this description.

Therefore, the idea of the present invention should not be limited to the described embodiments, and all things that are equivalent or equivalent to the claims described below as well as the claims are included in the scope of the idea of the present invention.

Claims (12)

A water separation membrane including a second porous layer formed on one or both sides of a first porous layer,
A water separation membrane in which the pore sizes of the first porous layer and the second porous layer are different, and the average pore size of one porous layer in the first porous layer or the second porous layer is 30 to 200 nm, and the average pore size of the other porous layer is 5 to 70 nm,
The first porous layer and the second porous layer contain the same polyether sulfone polymer,
The above water separation membrane has a permeation rate of 220 to 420 L/㎡·hr,
The above water separation membrane is a water separation membrane having a polystyrene removal rate of 88 to 95 wt% in a suspension containing 5 ppm of polystyrene having an average particle size of 20 nm. delete A water treatment filter comprising a water separation membrane according to claim 1. A water treatment device comprising a water treatment filter according to claim 3. A step of forming a first porous layer by applying a first porous layer composition including a thermoplastic resin, a pore-forming agent, a poor solvent, and a solvent on a substrate layer; and
A step of forming a second porous layer by applying a second porous layer composition including a thermoplastic resin, a poor solvent, and a solvent on the first porous layer;
A method for manufacturing a water-soluble membrane, comprising:
The above second porous layer composition is characterized in that it contains 10 to 40 wt% of a solvent with respect to the total amount of the second porous layer composition.
The step of forming the first porous layer uses a non-solvent phase separation method after a steam phase separation method,
A method for manufacturing a water separation membrane, wherein the step of forming the second porous layer uses a non-solvent-induced phase separation method. delete delete In paragraph 5,
A method for producing a water-removing membrane, wherein the first porous layer composition contains 10 to 30 wt% of a thermoplastic resin based on the total amount. In paragraph 5,
A method for producing a water-removing membrane, characterized in that the second porous layer composition comprises 10 to 40 wt% of a thermoplastic resin. In paragraph 5,
A method for producing a water separation membrane, wherein the pore-forming agent is included in an amount of 1 to 20 wt% based on the total amount of the first porous layer composition, and the pore-forming agent is one or more selected from polyvinylpyrrolidone, polyethylene glycol, polypropylene glycol, ethylene glycol, and glycerin. In paragraph 5,
A method for producing a water separation membrane, wherein the solvent is one or more selected from N-methyl-2-pyrrolidone (NMP), ε-caprolactam, methyl ethyl ketone, γ-butyrolactone, dimethylformamide (DMF), dimethyl sulfoxide, and dimethylacetamide (DMAc). In paragraph 5,
A method for producing a water-soluble membrane, wherein the above-mentioned solvent is one or more selected from isopropyl alcohol, ethylene glycol, butylene glycol, m-cresol, and nujol.