KR102400732B1 - Filter media, method for manufacturing thereof and Filter unit comprising the same - Google Patents

Abstract

A filter medium is provided. A filter medium according to an embodiment of the present invention includes a porous first support; a porous second support laminated on top and bottom of the first support; and a nanofiber web laminated on one surface of the second support to filter the water to be treated, and a pressure drop of 3 to 20 psi at a flow rate of 1 L/min; It is implemented so that a flow path flowing in the direction of the first support is formed. According to this, the shape, structural deformation, and damage of the filter medium are minimized during the water treatment operation, and the flow path is smoothly secured, so that it has a large flow rate and a high processing speed, and the backwashing efficiency can also be remarkably improved. In addition, the present invention can be variously applied in various water treatment fields because the flow path can be secured even at high pressure applied in the backwashing process, and at the same time, interlayer separation and membrane damage can be minimized.

Description

Filter media and a filter unit including the same

The present invention relates to a filter medium, and more particularly, to a filter medium having mechanical strength to withstand high pressure due to backwashing, excellent water permeability and significantly improved backwashing efficiency, and a filter unit comprising the same it's about

Separation membranes can be classified into microfiltration membranes (MF), ultrafiltration membranes (UF), nano membranes (NF), or reverse osmosis membranes (RO) according to pore sizes.

Although the separation membranes exemplified above have differences in use and pore size, they have in common that they are either a filter medium formed from fibers or a porous polymer filter medium, or have the form of a complex membrane.

The porous polymer filter media is formed through a method such as sintering the pore-forming agent through a separate pore-forming agent contained in the crude solution or dissolving the pores formed inside the polymer membrane or the polymer hollow fiber in an external coagulating solution. it is common In contrast, the filter medium formed from the fibers is generally manufactured by accumulating the manufactured short fibers and then applying heat/pressure or the like or by applying heat/pressure at the same time as spinning.

A representative example of the filter media formed from the fibers is a nonwoven fabric, and in general, the pores of the nonwoven fabric are controlled by the diameter of the short fibers, the basis weight of the media, and the like. However, since the diameter of the short fibers included in the general nonwoven fabric is in micro units, there was a limit to realizing a separator having a fine and uniform pore structure only by adjusting the diameter and basis weight of the fiber. Only a separation membrane comparable to a filtration membrane could be implemented, and it was difficult to implement a separation membrane such as an ultrafiltration membrane or a nano separation membrane for filtering finer particles.

A method devised to solve this problem is a separation membrane manufactured through microfibers with a diameter of nanoscale fibers. However, it is difficult to manufacture microfine fibers with a nano-unit diameter with only one spinning process with a fiber spinning process such as general wet spinning. There are problems of inconvenience, cost increase, and extension of production time. Accordingly, in recent years, there is a trend to manufacture a filter medium formed from fibers by directly spinning fibers having a diameter of nano units through electrospinning.

On the other hand, some of the various foreign substances contained in the water to be treated remain in the pores of the filtration medium that has been repeatedly subjected to the water treatment process, or an adhesion layer may be formed on the surface of the filtration medium. there is a problem.

In order to solve this problem, a method of preventing the occurrence of the above fouling phenomenon itself through pretreatment or a method of washing the filter medium in which the fouling phenomenon has already occurred can be considered. It is common to remove foreign substances remaining in the filtration medium by applying a high pressure to the filtration medium so as to be in the opposite direction to the inflow, filtration and outflow path.

However, high pressure applied during washing of the filter medium may cause damage to the filter medium, and in the case of a filter medium having a multi-layered structure, a problem of separation between layers may occur.

On the other hand, high pressure may be applied to the filtration medium even in the filtration process. In this case, the filtration medium is compressed depending on the direction in which the pressure is applied, and the flow rate is significantly reduced as the flow path is not smoothly secured.

Registered Patent Publication No. 10-0871440

The present invention was devised in consideration of the above points, and the shape, structural deformation, and damage of the filter medium during water treatment operation are minimized and the flow path is smoothly secured at the same time, so it has a large flow rate, a fast processing speed, and the backwashing efficiency is also significantly An object of the present invention is to provide an improved filter medium.

Another object of the present invention is to provide a filter medium having excellent durability in which a flow path can be secured even at high pressure applied in the backwashing process, and separation between layers and damage to the membrane can be minimized.

In addition, another object of the present invention is to provide a plate-type filter unit and filter module that can be variously applied in the water treatment field by having the filter medium as described above having excellent water permeability and durability.

In order to solve the above problems, the present invention provides a porous first support; a nanofiber web disposed on both sides of the porous first support to filter the water to be treated, and having a pressure drop of 3 to 20 psi at a flow rate of 1L/min; and a porous second support interposed between the first support and the nanofiber web.

According to an embodiment of the present invention, the total pressure drop of the filter medium having a flow path through which the filtrate filtered from the nanofiber web flows in the direction of the first support may be 2 to 10 psi at a flow rate of 1,000 L/hr. .

In addition, the first support and the second support may each independently be any one or more of a nonwoven fabric, a woven fabric, and a knitted fabric, and preferably, the first support and the second support may be a nonwoven fabric.

In addition, the basis weight of the first support may be 250 ~ 800 g / m 2 , and the thickness may be 2 ~ 8 mm.

In addition, the second support may include a second composite fiber disposed so that at least a portion of the low melting point component is exposed on the outer surface, including the support component and the low melting point component, and the low melting point of the second composite fiber The component may be fused to the nanofiber web.

In addition, the first support may include a first composite fiber disposed such that at least a portion of the low melting point component is exposed on the outer surface, including the support component and the low melting point component, and the low melting point component of the first composite fiber And the first support and the second support may be joined by fusion between the low-melting-point components of the second composite fiber.

In addition, the nanofiber web may include a fluorine-based compound as a fiber-forming component, and the fluorine-based compound is polytetrafluoroethylene (PTFE)-based, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA)-based , Tetrafluoroethylene-hexafluoropropylene copolymer (FEP)-based, tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer (EPE)-based, tetrafluoroethylene-ethylene copolymer (ETFE) )-based, polychlorotrifluoroethylene (PCTFE)-based, chlorotrifluoroethylene-ethylene copolymer (ECTFE)-based, and polyvinylidene fluoride (PVDF)-based compound may include any one or more compounds selected from the group consisting of .

In addition, the nanofiber web may have an average pore diameter of 0.1 to 5 μm, and a porosity of 40 to 90%.

In addition, the nanofibers forming the nanofiber web may have an average diameter of 0.05 to 1 μm.

In addition, the basis weight of the second support may be 10 ~ 200g / m 2 , and the thickness may be 100 ~ 400㎛.

On the other hand, the present invention is a filter medium according to the present invention as described above; and a support frame having a flow path through which the filtrate filtered from the filter medium flows out to the outside, and supporting the edge of the filter medium.

In addition, the present invention provides a filter module in which a plurality of the above-described plate-type filter units according to the present invention are spaced apart from each other at predetermined intervals.

Since the filter medium of the present invention includes a support having sufficient mechanical strength, the shape, structural deformation, and damage of the filter medium during water treatment operation are minimized and the flow path is smoothly secured at the same time, so that it has a large flow rate and a fast processing speed, Since the pressure applied to the formed layer is relatively large, the backwashing efficiency may also be significantly improved.

In addition, since the present invention includes a support having sufficient mechanical strength, a flow path can be secured even at a high pressure applied in the backwashing process, and at the same time, since it includes a support that increases the bonding force of each layer provided in the filter medium, separation between layers As it has durability that can minimize damage to , membranes, etc., it can be applied to various water treatment fields.

1 is a cross-sectional view of a filter medium according to an embodiment of the present invention;
2 is a photograph of a general filter medium in which the washing liquid is trapped inside the filter medium and swells after the layers are separated inside the filter medium by the backwashing process;
3 is a schematic diagram showing the direct lamination of the first support of the filter medium and the nanofiber web according to an embodiment of the present invention;
4 is a schematic view of laminating a filter medium according to an embodiment of the present invention, FIG. 4a is a view showing laminating a nanofiber web and a second support, FIG. 4b is a laminated nanofiber web and a second support A view showing the lamination by placing it on both sides of the first support,
5A to 5B are views of a nanofiber web constituting a filter medium according to an embodiment of the present invention. FIG. 5A is a surface electron micrograph of the nanofiber web, and FIG. 5B is a cross-sectional electron microscope of the nanofiber web. Picture,
6 is a cross-sectional electron micrograph of a filter medium according to an embodiment of the present invention, and
7 is a view of a plate-type filter unit according to an embodiment of the present invention. FIG. 7a is a perspective view of the filter unit, and FIG. 7b is a schematic view showing a filtration flow based on a cross-sectional view taken along the boundary line XX' of FIG. 7a.

Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those of ordinary skill in the art can easily carry out the present invention. The present invention may be embodied in many different forms and is not limited to the embodiments described herein. In order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and the same reference numerals are added to the same or similar elements throughout the specification.

1, the filter medium 1000 according to an embodiment of the present invention includes a porous first support 130; Nanofiber webs 111 and 112 that are disposed on both sides of the porous first support 130 to filter the water to be treated, and have a pressure drop of 3 to 20 psi at a flow rate of 1 L/min; and a porous second support (121, 122) interposed between the first support (130) and the nanofiber web (111, 112).

As shown in FIG. 1 , the filter medium 1000 according to the present invention has at least a five-layer structure and includes two types of supports 121 , 122/130 having different thicknesses. Before describing each layer constituting the filter media 1000 according to the present invention, the nanofiber webs 111 and 112 included in the filter media 1000 of the present invention have a pressure drop of 3 at a flow rate of 1 L/min. The reason why the ~ 20 psi must be satisfied will be explained first.

As the water treatment process using the filter media is repeated, foreign substances contained in the water to be treated adhere to the filter media to form an adhesion layer or become lodged inside the filter media to block the flow path and reduce the filtration function. Replacing it increases the cost of water treatment. Accordingly, in order to extend the use cycle of the filter medium, it is necessary to periodically apply a physical stimulus to the filter medium to perform a cleaning process to remove foreign substances adhering to or embedded in the filter medium, which is called backwashing. In general, backwashing removes foreign substances attached to or embedded in the filter media by strongly flowing washing water or blowing air in the direction opposite to the filtration direction of the filter media. It is necessary to supply washing water or air at a pressure higher than the pressure applied to the filter media in the filtration process in order to remove it.

Accordingly, the filter media 1000 according to the present invention includes nanofiber webs 111 and 112 having a pressure drop of 3 to 20 psi at a flow rate of 1 L/min in order to apply sufficient pressure to improve backwashing efficiency, The pressure drop of the nanofiber webs 111 and 112 may be preferably 3 to 18 psi, more preferably 5 to 13 psi at a flow rate of 1 L/min. As the pressure drop of the nanofiber webs 111 and 112 satisfies the above range, the backwashing efficiency can be remarkably improved through sufficient pressure. If the pressure drop of the nanofiber webs 111 and 112 is less than 3 psi at a flow rate of 1 L/min, the backwashing efficiency may not be good because the applied pressure is not sufficient. In addition, if the pressure drop exceeds 20 psi at a flow rate of 1 L/min, delamination may occur because the applied pressure is excessive.

Accordingly, it is important to have a mechanical strength enough to not deform or damage the filter media even with sufficient pressure applied to the filter media, and a support for supplementing the mechanical strength is usually provided in the filter media. Factors that can affect the mechanical strength of the support include the structure of the support, for example, when the support is a non-woven fabric, the diameter of the fibers forming the non-woven fabric, the length of the fibers, the bonding method between fibers, the thickness, the basis weight, and the thickness As the thickness or basis weight increases, the mechanical strength of the support may increase. Therefore, as an example for designing a filter medium resistant to backwashing, a thick nonwoven fabric may be used, or a nonwoven fabric having a very large basis weight may be used as a support even if the thickness is somewhat thin.

On the other hand, it is preferable that the support has a large pore diameter so as not to affect the flow of the filtrate of the filter medium. It is very undesirable for the flow rate to be lowered due to the support provided to supplement the mechanical strength, as it lowers the main physical properties of the filter medium. However, when a nonwoven fabric that exhibits sufficient mechanical strength despite its thin thickness is used as a support, the diameter and porosity of the pores in the nonwoven fabric are remarkably small as the basis weight of the nonwoven fabric is very large, and as it affects the filtrate flow of the filter media, The desired level of flow may not be achieved.

On the other hand, when the bonding force between the nanofiber webs 111 and 112 functioning as a filter material and the first support 130 is weak, the durability of the filter material according to backwashing may be reduced even though the mechanical strength is very excellent. That is, the high pressure applied during the backwashing process may accelerate the interfacial separation between the layers forming the filter medium, and in this case, as shown in FIG. As a separator, the function may be significantly reduced or completely lost.

Therefore, high adhesion between the first support 130 and the nanofiber webs 111 and 112 as a filter medium is very important in realizing the filter medium 1000 that exhibits sufficient durability even in frequent backwashing.

In general, in the method of attaching the support and the nanofiber web, the two layers can be joined by using a separate adhesive material or by fusing a low-melting component provided in the support to the nanofiber web. However, when the two layers are joined through a separate bonding material, there is a fear that the bonding material is dissolved by the water to be treated, and thus the contamination of the filtrate and/or water permeability may be reduced. If the filter media in which the bonding material is partially dissolved is backwashed, the filter media may become full or, in severe cases, the nanofiber web may be peeled off and completely lose its function as a filter media.

Accordingly, it is preferable to adopt a method in which the nanofiber web and the support are joined through fusion (A), and heat and / or They can be joined by applying pressure. However, the point to be considered when joining them by applying heat and/or pressure is to minimize the physical and chemical transformation of the nanofiber web 2 functioning as a filter material due to the applied heat and pressure, and if the thermal bonding process When the nanofiber web is physically and chemically deformed, the physical properties such as flow rate and filtration rate of the initially designed filter media may be changed.

The point to be considered when selecting heat and/or pressure conditions in the attachment process so that there is no physical/chemical deformation of the nanofiber web 2 may be the material properties of the nanofiber web and the support, for example, the melting point, thermal conductivity, heat capacity, etc. , usually by simultaneously applying a temperature above the melting point or a temperature and pressure above the melting point to fuse the low-melting component of the support to the nanofiber web, or apply a high pressure even if it is slightly lower than the melting point to fuse the low-melting component of the support to the nanofiber web. there is.

On the other hand, the material for forming the support or nanofiber web is a high molecular compound, and since such a high molecular compound has low thermal conductivity and a very large heat capacity, as shown in FIG. 3 , even when a predetermined heat (H ₁ , H ₂ ) is applied to both sides Heat (H ₁ , H ₂ ) reaches the interface between the nanofiber web 1 and the support 2 to increase the temperature of the low-melting-point component provided in the support 2 to the melting point. this should be applied Moreover, when the thickness of the support 1 is very thick as shown in FIG. 3 , the heat (H ₂ ) transmitted from the bottom is transferred to the vicinity of the interface between the nanofiber web 2 and the support 1, and the low provided in the support in the vicinity thereof. It may take a longer time to raise the temperature of the melting point component to the melting point, and it is necessary to apply more heat from the bottom to shorten the time. However, when too much heat is applied from below, the melting of the low-melting-point component may occur first in the lower portion of the first support, and the shape and structure of the support may be changed.

In another method, it is possible to solve the difficulties depending on the thickness of the support 1 by increasing the heat H1 applied from above, but in this case, physical/chemical deformation of the nanofiber web 2 may result, and It may not be able to fully express the physical properties of the filter media designed for

Accordingly, the filter media 1000 according to an embodiment of the present invention does not directly face the first support 130 and the nanofiber webs 111 and 112, but interposes the thinner second support 121 and 122. , through which the interlayer adhesion process can be performed more stably and easily, exhibit remarkably excellent bonding strength at the interface between each layer, and minimize interlayer separation and peeling problems even when a high external force is applied due to backwashing.

When this is explained through FIG. 4A , the second support 3 has a significantly smaller difference in thickness with the nanofiber web 2 compared to the thickness difference between the nanofiber web 2 and the first support 1, so the nanofiber The heat (H ₁ , H ₂ ) applied from above and below the laminate of the web (2)/second support body (3) reaches the interface between them and it is easier to form the fusion portion (B) compared to FIG. 3 . . In addition, as it is easier to control the amount and time of applied heat compared to FIG. 3 , it is advantageous to prevent physical/chemical deformation of the nanofiber web 2 , so the nanofiber web 2 on the second support 3 as shown in FIG. 4a . ) is combined, there is an advantage in that the nanofibers can be combined with excellent adhesion on the support without changing the physical properties of the nanofiber web 2 designed in the beginning.

Hereinafter, each configuration provided in the filter medium 1000 will be described in detail.

First, the first support 130 serves to support the filter medium 1000 and form a large flow path to more smoothly perform the filtering process or the backwashing process. Specifically, in the filtration process, if a pressure gradient is formed so that the pressure inside the filter medium is lower than that outside, the filter medium may be compressed. In this case, the flow path through which the filtrate can flow inside the filter medium is significantly reduced or blocked. At the same time a larger differential pressure is applied to the filter medium, the flow rate may be significantly reduced. In addition, in the backwashing process, an external force that expands the filter media in both directions from the inside to the outside may be applied. If the mechanical strength is low, the external force applied may damage the filter media.

The first support 130 is provided to prevent the above problems occurring in the filtration process and/or backwashing process, is used in the water treatment field, and may be a known porous member with mechanical strength guaranteed. The first support may be a nonwoven fabric, a woven fabric, or a fabric.

The fabric means that the fibers included in the fabric have a vertical and horizontal direction, and specific structures may be plain weave, twill, etc., and the density of warp and weft yarns is not particularly limited. In addition, the knitted fabric may be a known knitted structure, may be a weft knitted fabric, a warp knitted fabric, etc., for example, may be a tricot in which the yarn is warp knitted. In addition, as shown in FIG. 1 , the first support 130 may be a nonwoven fabric having no longitudinal and transverse direction to the first composite fiber 130a, and may include chemical bonding nonwoven fabric, thermal bonding nonwoven fabric, dry nonwoven fabric or wet nonwoven fabric such as airlay nonwoven fabric, A known nonwoven fabric manufactured by various methods such as spanless nonwoven fabric, needle punching nonwoven fabric or melt blown may be used.

The first support 130 may have a thickness capable of expressing sufficient mechanical strength, and for example, the thickness of the first support 130 may be 2 to 8 mm, preferably 2 to 5 mm, more Preferably, it may be 3 to 5 mm. If the thickness is less than 2 mm, it may not develop sufficient mechanical strength to withstand frequent backwashing. In addition, when the thickness exceeds 8 mm, when a plurality of filter units are implemented as a filter module of a limited space after the filter media is implemented as a filter unit to be described later, the degree of integration of the filter media per unit volume of the module may be reduced.

Preferably, the first support 130 may have a basis weight of 250 to 800 g/m 2 while satisfying the thickness, and more preferably 350 to 600 g/m 2 . If the basis weight is less than 250 g/m2, it may be difficult to express sufficient mechanical strength, and the adhesion to the second support may be reduced. decreased, and smooth backwashing may be difficult due to an increase in differential pressure.

In addition, when the first support 130 is formed of fibers such as a nonwoven fabric, the average diameter of the fibers may be 5 to 50 μm, preferably 20 to 50 μm. In addition, the first support 130 may have an average pore diameter of 20 to 200 μm, and a porosity of 50 to 90%, but is not limited thereto, and nanofibers to be described later in the filtering process and/or backwashing process. There is no limitation as long as the porosity and pore size are sufficient to support the webs 111 and 112 to express a desired level of mechanical strength and to smoothly form a flow path even at high pressure.

When the first support 130 is a material used as a support for the separation membrane, there is no limitation in the material thereof. Non-limiting examples thereof include a synthetic polymer component selected from the group consisting of polyester-based, polyurethane-based, polyolefin-based and polyamide-based; Alternatively, a natural polymer component including cellulose may be used. However, if the first support has strong brittle physical properties, it may be difficult to expect a desired level of binding force in the process of laminating the first support and the second support, which means that the first support has a smooth surface like a film. Rather, the surface may be macroscopically rough while forming porosity, and the surface formed of fibers, such as a nonwoven fabric, may not have a smooth surface depending on the arrangement of the fibers and the fineness of the fibers, and the degree may be different depending on the location. am. If the remaining parts are joined while the non-adherent part exists at the interface between the two layers to be laminated, interlayer separation may start due to the non-adherent part. In order to solve this problem, it is necessary to perform the lamination process in a state where the degree of adhesion between the two layers is increased by applying pressure from both sides of the two layers. There is a limit in heightening, and since the support may be damaged if a greater pressure is applied, the material of the first support may be suitable for a material having good flexibility and high elongation, and preferably has excellent adhesion to the second support 121 and 122 The first support 130 may be made of a polyolefin-based material.

Meanwhile, the first support 130 may include a low-melting component in order to be bound to the second supports 121 and 122 without a separate adhesive or adhesive layer. When the first support 130 is a fabric such as a nonwoven fabric, it may be made of the first composite fiber 130a including a low melting point component. The first composite fiber 130a may include a support component and a low-melting-point component, and may be arranged such that at least a portion of the low-melting-point component is exposed to the outer surface. For example, a sheath-core type composite fiber in which a support component forms a core portion and a low melting point component forms a sheath portion surrounding the core portion, or a side-by-side composite fiber in which a low melting point component is disposed on one side of the support component can be As described above, the low-melting component and the supporting component may be preferably polyolefin-based in terms of flexibility and elongation of the support, for example, the supporting component may be polypropylene, and the low-melting component may be polyethylene. The melting point of the low melting point component may be 60 ~ 180 ℃.

Next, the second supports 121 and 122 interposed between the above-described first support 130 and the nanofiber webs 111 and 112 described later will be described.

The second supports 121 and 122 support the nanofiber webs 111 and 112 to be described later, and serve to increase the bonding strength of each layer provided in the filter medium.

The second supports 121 and 122 are not particularly limited as long as they normally serve as support for the filter media, but may preferably be woven, knitted or non-woven in shape. The fabric means that the fibers included in the fabric have a vertical and horizontal direction, and specific structures may be plain weave, twill, etc., and the density of warp and weft yarns is not particularly limited. In addition, the knitted fabric may be a known knitted fabric, and may be a weft knitted fabric, a warp knitted fabric, or the like, but is not particularly limited thereto. In addition, the nonwoven fabric means that there is no longitudinal and lateral direction in the fibers contained therein, and known such as chemical bonding nonwoven fabric, thermal bonding nonwoven fabric, dry nonwoven fabric or wet nonwoven fabric such as airlay nonwoven fabric, spanless nonwoven fabric, needle punching nonwoven fabric or melt blown nonwoven fabric A nonwoven fabric manufactured by the method described above may be used.

The second supports 121 and 122 may be, for example, non-woven fabrics. In this case, the fibers forming the second supports 121 and 122 may have an average diameter of 5 to 30 μm. In addition, the second supports 121 and 122 may have a thickness of 100 to 400 μm, more preferably 150 to 400 μm, even more preferably 150 to 250 μm, for example 200 μm. can

Also, the second supports 121 and 122 may have an average pore diameter of 20 to 100 μm, and a porosity of 50 to 90%. However, it is not limited thereto, and it supports the nanofiber webs 111 and 112 to be described later to express a desired level of mechanical strength and at the same time not to inhibit the flow of the filtrate flowing through the nanofiber webs 111 and 112. There is no limitation as far as porosity and pore size are concerned.

In addition, the second supports 121 and 122 may have a basis weight of 10 to 200 g/m 2 , more preferably 35 to 200 g/m 2 , and even more preferably 35 to 80 g/m 2 , for example. , may be 40 g/m 2 . If the basis weight is less than 10 g/m 2 , the amount of fibers forming the second support distributed at the interface formed with the nanofiber webs 111 and 112 to be described later may be small, and accordingly, the effectiveness of the second support in contact with the nanofiber web It may not be possible to express a desired level of bonding strength due to a decrease in the adhesive area. In addition, it may not be able to express sufficient mechanical strength to support the nanofiber web, the adhesion to the first support may be reduced. In addition, if the basis weight exceeds 200 g/m 2 , it may be difficult to secure a desired level of flow rate, and smooth backwashing may be difficult.

When the second supports 121 and 122 are a material used as a support for the filter medium, there is no limitation in the material thereof. Non-limiting examples thereof include a synthetic polymer component selected from the group consisting of polyester-based, polyurethane-based, polyolefin-based and polyamide-based; Alternatively, a natural polymer component including cellulose may be used.

However, the second supports 121 and 122 may be polyolefin-based polymer components to improve adhesion between the nanofiber webs 111 and 112 and the first support 130 to be described later. In addition, when the second supports 121 and 122 are fabrics such as nonwoven fabrics, they may be made of the second composite fibers 121a including a low melting point component. The second composite fiber 121a may include a support component and a low-melting-point component, and may be arranged such that at least a portion of the low-melting-point component is exposed to the outer surface. For example, a sheath-core type composite fiber in which a support component forms a core portion and a low melting point component forms a sheath portion surrounding the core portion, or a side-by-side composite fiber in which a low melting point component is disposed on one side of the support component can be As described above, the low-melting component and the supporting component may be preferably polyolefin-based in terms of flexibility and elongation of the support, for example, the supporting component may be polypropylene, and the low-melting component may be polyethylene. The melting point of the low melting point component may be 60 ~ 180 ℃.

If the above-described first support 130 is implemented as a first composite fiber 130a including a low-melting component in order to express a more improved bonding force with the second support 130, the first support 130 and the first A more robust fusion portion may be formed at the interface between the two supports 121 due to fusion of the low-melting-point component of the first composite fiber 130a and the low-melting-point component of the second composite fiber 121a. In this case, the first composite fiber 130a and the second composite fiber 121a may be made of the same material in terms of compatibility.

Next, the nanofiber webs 111 and 112 disposed on both sides of the above-described first support 130 will be described. The nanofiber webs 111 and 112 may have a three-dimensional network structure formed by randomly three-dimensionally stacking one or several nanofibers (see FIG. 5).

The nanofibers forming the nanofiber web may be formed of known fiber-forming components. However, preferably, in order to express excellent chemical resistance and heat resistance, a fluorine-based compound may be included as a fiber-forming component, and through this, even if the water to be treated is a solution of a strong acid/base or a solution with a high temperature, the desired level without changing the physical properties of the filter medium This has the advantage of securing filtration efficiency/flow rate and having a long use cycle. The fluorine-based compound may be used without limitation in the case of known fluorine-based compounds that can be prepared into nanofibers, for example, polytetrafluoroethylene (PTFE)-based, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer ( PFA) type, tetrafluoroethylene-hexafluoropropylene copolymer (FEP) type, tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer (EPE) type, tetrafluoroethylene-ethylene copolymer Containing any one or more compounds selected from the group consisting of copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), and polyvinylidene fluoride (PVDF) More preferably, it may be polyvinylidene fluoride (PVDF) in terms of low manufacturing cost, easy mass production of nanofibers through electrospinning, and excellent mechanical strength and chemical resistance. In this case, when the nanofiber includes PVDF as a fiber-forming component, the weight average molecular weight of the PVDF may be 10,000 to 1,000,000, preferably 300,000 to 600,000, but is not limited thereto.

In addition, the nanofiber may have an average diameter of 0.05 to 1 μm, and an aspect ratio of 1,000 to 100,000, but is not limited thereto. For example, the nanofibers provided in the nanofiber webs 111 and 112 include a first group of nanofibers having a diameter of 0.1 to 0.2 μm, a second group of nanofibers having a diameter of 0.2 to 0.3 μm, and a first group of nanofibers having a diameter of 0.3 to 0.4 μm. 3 nanofiber groups may include 35 wt%, 53 wt%, and 12 wt%, respectively, based on the total weight of the nanofiber web 111.

The above-described nanofiber webs 111 and 112 may have a thickness of 0.5 to 50 μm, for example, 20 μm. The porosity of the nanofiber webs 111 and 112 may be 40 to 90%, more preferably 60 to 90%. In addition, the average pore diameter may be 0.1 ~ 5㎛, more preferably 0.1 ~ 1㎛. For example, the average pore diameter of the nanofiber webs 111 and 112 may be 0.2 to 0.45 μm. If the average pore diameter of the nanofiber webs 111 and 112 is less than 0.1 μm, the pressure drop of the nanofiber webs 111 and 112 is excessive, the durability of the filter media may be poor, and the average pore diameter exceeds 5 μm Doing so may result in poor backwashing efficiency.

The nanofiber webs 111 and 112 may have a basis weight of 0.05 to 20 g/m 2 , but may be, for example, 10 g/m 2 , but is not limited thereto, and may be appropriately changed in consideration of the desired water permeability and filtration efficiency.

In addition, the nanofiber webs 111 and 112 may be provided in the filter medium 1000 in one or more layers, and in this case, the porosity, pore size, basis weight and/or thickness of each nanofiber web may be different.

On the other hand, the nanofibers forming the nanofiber webs 111 and 112 may be modified to increase hydrophilicity, and for example, a hydrophilic coating layer may be further provided on at least a portion of the outer surface of the nanofiber. If the nanofiber contains the fluorine-based compound as described above, the fluorine-based compound has very strong hydrophobicity, and thus the flow rate may be poor when the filtrate is a hydrophilic solution. To this end, a hydrophilic coating layer may be further provided on the surface of the hydrophobic nanofiber, and the hydrophilic coating layer may be a known one, and is formed including, for example, a hydrophilic polymer having a hydroxyl group, or the hydrophilic polymer is cross-linked through a cross-linking agent. can be formed. For example, the hydrophilic polymer may be in the form of a single or a mixture of polyvinyl alcohol (PVA), ethylenevinyl alcohol (EVOH), sodium alginate, etc., most preferably polyvinyl alcohol (PVA). In addition, the crosslinking agent may be used without limitation in the case of a known crosslinking agent having a functional group that can be crosslinked through a condensation reaction with a hydroxyl group of the hydrophilic polymer. For example, the functional group may be a hydroxyl group, a carboxy group, or the like.

The hydrophilicization coating layer may be formed by crosslinking polyvinyl alcohol (PVA) and a crosslinking agent including a carboxyl group in order to express more improved physical properties. The polyvinyl alcohol may have a polymerization degree of 500 to 2000 and a saponification degree of 85 to 90%. When the polymerization degree of polyvinyl alcohol is excessively low, the formation of the hydrophilic coating layer may not be smooth or may be easily peeled off even if formed, and the hydrophilicity may not be improved to a desired level. In addition, when the polymerization degree is too large, the formation of the hydrophilic coating layer may be excessive, and thus the pore structure of the nanofiber web may be changed or the pores may be closed. In addition, when the degree of saponification is too low, it may be difficult to improve hydrophilicity.

The crosslinking agent may be a component containing a carboxyl group to be crosslinked with the above-described polyvinyl alcohol. For example, the crosslinking agent may include at least one material selected from the group consisting of poly(acrylic acid-maleic acid), polyacrylic acid, and poly(styrenesulfonic acid-maleic acid). In addition, the crosslinking agent is at least three or more carboxyl groups to express a more improved flow rate while being coated very thinly so that there is no change in the pore structure of the nanofiber webs 111 and 112 and the coating/adhesiveness of the more hydrophobic nanofiber surface. It may be a multifunctional crosslinking agent comprising a. If the number of carboxyl groups included in the crosslinking agent is less than 3, it is difficult to form a coating layer on the surface of the hydrophobic nanofiber, and even if it is formed, the adhesion is very weak and can be easily peeled off. For example, the crosslinking agent having three or more carboxyl groups may be poly(acrylic acid-maleic acid).

The hydrophilic coating layer may be formed by crosslinking 2 to 20 parts by weight of a crosslinking agent containing a carboxyl group based on 100 parts by weight of the polyvinyl alcohol. If less than 2 parts by weight of the crosslinking agent is provided, the formability of the hydrophilic coating layer may be reduced, and chemical resistance and mechanical strength may be reduced. In addition, when the crosslinking agent is provided in excess of 20 parts by weight, pores may be reduced due to the coating layer, thereby reducing the flow rate.

On the other hand, the hydrophilic coating layer may be formed on some or all of the outer surface of the nanofiber. In this case, the hydrophilic coating layer may be coated with the nanofibers to contain 0.1 ~ 2g per unit area (m2) of the nanofiber web.

The wetting angle of the surface of the nanofiber webs 111 and 112 modified to have a hydrophilic coating layer as described above may be 30° or less, more preferably 20° or less, even more preferably 12° or less, even more preferably It may be 5° or less, and through this, there is an advantage of securing an improved flow rate despite the fibrous web implemented with nanofibers that are hydrophobic in terms of material.

On the other hand, the total pressure drop of the filter medium according to the present invention in which the flow path through which the filtrate filtered from the nanofiber web flows in the direction of the first support is formed may be 2 to 10 psi at a flow rate of 1,000 L/hr, preferably It may be 4 to 8 psi, for example, the total pressure drop of the filter medium may be 5.8 psi at a flow rate of 1,000 L/hr.

The above-described filter media 1000 may be manufactured by a manufacturing method described later, but is not limited thereto.

The filter medium 1000 according to the present invention comprises the steps of (1) laminating a nanofiber web and a second support; and (2) placing the laminated nanofiber web and the second support on both sides of the first support so that the second support is in contact with the first support, respectively, and laminating the support.

First, as step (1) according to the present invention, a step of laminating the nanofiber web and the second support is performed.

The nanofiber web may be used without limitation in the case of a method of forming a fiber web of a three-dimensional network shape by providing nanofibers. Preferably, the nanofiber web may be formed by electrospinning a spinning solution containing a fluorine-based compound on a second support to form a nanofiber web.

The spinning solution may include, for example, a fluorine-based compound and a solvent as a fiber-forming component. The fluorine-based compound is preferably included in the spinning solution in an amount of 5 to 30% by weight, preferably 8 to 20% by weight, and if the fluorine-based compound is less than 5% by weight, it is difficult to form into a fiber, and it is not spun into a fiber during spinning and is in a droplet state Even if it is sprayed to form a film or spinning, a lot of beads are formed and the solvent is not volatilized well, which may cause clogging of pores in the calendering process to be described later. In addition, if the fluorine-based compound exceeds 30% by weight, the viscosity rises and solidification occurs on the surface of the solution, making it difficult to spin for a long time, and the fiber diameter may increase so that it may not be possible to make a fibrous shape having a size of micrometers or less.

The solvent may be used without limitation in the case of a solvent that does not form a precipitate while dissolving the fluorine-based compound as a fiber-forming component and does not affect the radioactivity of nanofibers to be described later, but is preferably γ-butyrolactone, cyclohexanone, 3 -hexanone, 3-heptanone, 3-octanone, N-methylpyrrolidone, dimethylacetamide, acetone, dimethylsulfoxide, may include any one or more selected from the group consisting of dimethylformamide. For example, the solvent may be a mixed solvent of dimethylacetamide and acetone.

The prepared spinning solution may be prepared into nanofibers through a known electrospinning device and method. For example, the electrospinning apparatus uses an electrospinning device having a single spinning pack having one spinning nozzle, or an electrospinning device having a plurality of single spinning packs for mass production, or an electrospinning device having a spinning pack having multiple nozzles. it is free to use In addition, in the electrospinning method, dry spinning or wet spinning having an external coagulation bath can be used, and there is no limitation according to the method.

A nanofiber web formed of nanofibers can be obtained when the electrospinning solution is put into the electrospinning device and electrospun on a collector, for example, paper. The specific conditions for the electrospinning are as an example, and the air pressure of the air jet nozzle provided in the nozzle of the spinning pack may be set in the range of 0.01 to 0.2 MPa. If the air pressure is less than 0.01 MPa, it cannot contribute to collection and accumulation, and if it exceeds 0.2 MPa, the cone of the spinning nozzle hardens and blocks the needle, which may cause spinning trouble. In addition, when spinning the spinning solution, the injection rate of the spinning solution per nozzle may be 10 ~ 30㎛ / min. In addition, the distance between the tip of the nozzle and the collector may be 10 to 30 cm. However, it is not limited thereto and may be changed and implemented according to the purpose.

Alternatively, the nanofiber web may be formed directly on the second support by directly electrospinning the nanofibers on the above-described second support. The nanofibers accumulated/collected on the second support have a three-dimensional network structure, and heat and/or pressure are applied to maintain a porosity, pore size, basis weight, etc. suitable for expressing the desired water permeability and filtration efficiency of the separation membrane. By being further applied to the accumulated/collected nanofibers, it can be implemented as a nanofiber web having a three-dimensional network structure. As a specific method of applying the heat and/or pressure, a known method may be adopted, and a conventional calendering process may be used as a non-limiting example thereof, and the temperature of the applied heat may be 70 to 190°C. In addition, when performing the calendering process, it may be divided into several steps and performed multiple times. For example, after performing a drying process to remove some or all of the solvent and moisture remaining in the nanofiber through primary calendering, the pores Secondary calendering may be performed to improve control and strength. In this case, the degree of heat and/or pressure applied in each calendering process may be the same or different.

On the other hand, when the second support is implemented as a low-melting composite fiber, binding through the thermal fusion of the nanofiber web and the second support can be simultaneously progressed through the calendering process.

In addition, a separate hot melt powder or hot melt web may be further interposed in order to bind the second support and the nanofiber web. At this time, the applied heat may be 60 ~ 190 ℃, the pressure may be applied at 0.1 ~ 10 kgf / ㎠, but is not limited thereto. However, components such as hot melt powder added separately for binding generate fumed or are melted in the laminating process between supports and between supports and nanofibers to close pores frequently. may not be able to In addition, it is preferable to bind the second support and the nanofiber web without including it because it can be dissolved in the water treatment process and cause negative environmental problems.

Next, before performing step (2) to be described later, the step of forming a hydrophilic coating layer by treating the composition for forming a hydrophilic coating layer on the nanofiber web may be further performed.

Specifically, this step comprises the steps of treating the composition for forming a hydrophilic coating layer on the nanofiber web; and heat-treating the hydrophilic coating layer-forming composition to form a hydrophilic coating layer.

First, the composition for forming a hydrophilic coating layer may include a hydrophilic component and a crosslinkable component, for example, polyvinyl alcohol, a crosslinking agent including a carboxyl group, and a solvent for dissolving them, for example, water. The composition for forming the hydrophilic coating layer may contain 2 to 20 parts by weight of a crosslinking agent and 1,000 to 100,000 parts by weight of a solvent based on 100 parts by weight of polyvinyl alcohol.

On the other hand, when the nanofiber forming the prepared nanofiber web contains a fluorine-based compound, since hydrophobicity is strong, the coating layer may not be properly formed on the surface even if the above-described hydrophilic coating layer-forming composition is treated. Accordingly, the hydrophilic coating layer-forming composition may further include a wettability improving agent in order to make the hydrophilic coating layer-forming composition well wet on the outer surface of the nanofiber.

The wettability improving agent may be used without limitation if it is a component capable of improving the wettability of the outer surface of the hydrophobic nanofiber with respect to the hydrophilic solution and soluble in the composition for forming a hydrophilic coating layer. For example, the wettability improving agent may be one or more components selected from the group consisting of isopropyl alcohol, ethyl alcohol and methyl alcohol. In addition, the wettability improving agent may be included in an amount of 1,000 to 100,000 parts by weight based on 100 parts by weight of polyvinyl alcohol included in the composition for forming a hydrophilic coating layer. If the wettability improving agent is provided in less than 1000 parts by weight, the wettability improvement of the nanofibers is weak, so the formation of the hydrophilic coating layer may not be smooth, and the peeling of the hydrophilic coating layer may be frequent. In addition, when the wettability improving material is included in excess of 100,000 parts by weight, the degree of wettability improvement may be insignificant, and the concentration of polyvinyl alcohol and crosslinking agent provided in the composition for forming the hydrophilic coating layer is lowered, so that the formation of the hydrophilic coating layer may not be smooth.

On the other hand, without a wettability improving agent in the composition for forming a hydrophilic coating layer, the nanofiber web is pretreated with a wettability improving agent and then the hydrophilic coating layer forming composition is treated to form a hydrophilic coating layer. However, when the nanofiber web in which the wettability improving agent is supported in the pores is immersed in the hydrophilic coating layer-forming composition, the wettability improving agent supported in the pores comes out of the nanofiber web, and at the same time, the time it takes for the hydrophilic coating layer-forming composition to penetrate the pores This length may extend the manufacturing time. In addition, since the degree of penetration of the composition for forming the hydrophilic coating layer is different depending on the thickness of the nanofiber web and the diameter of the pores, the hydrophilic coating layer may be non-uniformly formed for each position of the fibrous web. Furthermore, as the hydrophilic coating layer is formed non-uniformly, the pores in a part of the nanofiber web may be closed with the hydrophilic coating layer, and in this case, the desired flow rate may not be obtained as the pore structure of the initially designed nanofiber web is changed. It is advantageous to provide a wettability improving agent in the composition for forming the hydrophilic coating layer without changing the pore structure of the nanofiber web while simultaneously achieving shortening of the manufacturing time, simplification of the manufacturing process, and improvement of the formability of the hydrophilic coating layer.

The method for forming the above-described hydrophilic coating layer-forming composition on the nanofiber web may be employed without limitation in the case of a known coating method, for example, dipping, spraying, etc. may be used.

Thereafter, a step of heat-treating the hydrophilic coating layer-forming composition treated on the nanofiber web to form a hydrophilic coating layer; may be performed. Through the heat treatment, the drying process of the solvent in the composition for forming the hydrophilic coating layer may be simultaneously performed. The heat treatment may be performed in a dryer, and the heat applied at this time may be at a temperature of 80 to 160° C., and the treatment time may be 1 to 60 minutes, but is not limited thereto.

Next, as the step (2) according to the present invention, the nanofiber web and the second support laminated on both sides of the first support so that the second support comes into contact with the first support in the laminated second support and the nanofiber web, respectively. to perform the step of arranging and supporting lamination.

The step (2) is 2-1) laminating the second support and the nanofiber web laminated in step (1) above on both sides of the first support; and 2-2) applying any one or more of heat and pressure to fusion-bond the first support and the second support.

As a specific method of applying heat and/or pressure in step 2-2), a known method may be adopted, and a conventional calendering process may be used as a non-limiting example thereof, and the temperature of the applied heat is 70 It may be ~ 190 °C. In addition, when performing the calendering process, it may be divided into several divisions and performed a plurality of times, for example, the second calendering may be performed after the first calendering. In this case, the degree of heat and/or pressure applied in each calendering process may be the same or different. Through the step 2-2), bonding can occur between the second support and the first support through thermal fusion, and there is an advantage that a separate adhesive or adhesive layer can be omitted.

The present invention includes a filter unit implemented by including the filter media manufactured through the above-described manufacturing method.

As shown in FIG. 7A , the filter media 1000 may be implemented as a plate-type filter unit 2000 . Specifically, the plate-type filter unit 2000 includes a filter medium 1000 and a support frame 1100 for supporting the edge of the filter medium 1000, and a filter medium is provided in any one area of the support frame 1100. A suction port 1110 that can gradient the pressure difference between the outside and the inside of 1000 may be provided. In addition, in the support frame 1100, the filtrate filtered from the nanofiber webs 101 and 102 can flow out to the outside through the support 200 on which the second support/first support inside the filter medium 1000 is stacked. A flow path may be formed.

Specifically, in the filter unit 2000 as shown in FIG. 7A , when a high pressure suction force is applied through the suction port 1110, the filtrate P disposed outside the filter medium 1000 as shown in FIG. 7B is the filter medium 1000 ), and the filtrate (Q1) filtered through the nanofiber webs 101 and 102 flows along the flow path formed through the support 200 in which the second support / first support is stacked, and then the support frame 1100. It is introduced into the flow path E provided in the , and the introduced filtrate Q2 may be discharged to the outside through the suction port 1110 .

In addition, the plate-type filter unit 2000 as shown in FIG. 7A may implement a filter module in which a plurality of filter modules are provided in one outer case with a predetermined interval therebetween, and such filter modules are stacked/blocked in plurality to form a large size. It is also possible to constitute a water treatment device.

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

<Example>

First, in order to prepare a spinning solution, 12 g of polyvinylidene fluoride (Arkema, Kynar761) as a fiber-forming component was mixed in 88 g of a mixed solvent in which the weight ratio of dimethylacetamide and acetone was 70:30 at a temperature of 80° C. for 6 hours. During the dissolution using a magnetic bar to prepare a mixed solution. The spinning solution was put into the solution tank of the electrospinning device and discharged at a rate of 15 μl/min/hole. At this time, the temperature of the spinning section is maintained at 30°C, the humidity is 50%, the distance between the collector and the spinning nozzle tip is 20 cm, the second support is on the collector, the thickness is about 200 μm, and the melting point is about 120°C. After placing a nonwoven fabric (Namyang Nonwoven Fabric, CCP40) formed of low-melting composite fiber with polypropylene as the core and then applying a voltage of 40 kV or more to the Spin Nozzle Pack using a high voltage generator, At the same time, an air pressure of 0.03 MPa per nozzle of the spinning pack was applied to prepare a laminate having a nanofiber web formed of PVDF nanofibers on one surface of the second support. Next, the solvent and moisture remaining in the nanofiber web of the laminate were dried, and in order to heat-seal the second support and the nanofiber web, heat and pressure were applied at a temperature of 140° C. or higher and 1 kgf/cm 2 to perform a calendering process. . In the manufactured laminate, the second support and the nanofiber web were thermally fused and bound as shown in FIG. 6, and the nanofiber web had a three-dimensional network structure as shown in FIGS. 5a and 5b.

Thereafter, the prepared laminate was immersed in the hydrophilic coating layer-forming composition prepared in the following preparation example and dried at a temperature of 110° C. in a dryer for 5 minutes to provide a hydrophilic coating layer on the nanofiber surface of the nanofiber web.

Thereafter, the laminate was disposed on both sides of the first support so that the second support faced in the manufactured laminate. At this time, the first support has a thickness of about 5 mm, a nonwoven fabric (Namyang nonwoven fabric, NP450) formed of a low-melting composite fiber having polyethylene as a sheath part and polypropylene as a core part having a melting point of about 120°C was used. Thereafter, a filter medium was prepared by applying heat and a pressure of 1 kgf/cm 2 to a temperature of 140° C. or higher.

< preparation example > - Composition for forming a hydrophilic coating layer

After mixing 7142 parts by weight of ultrapure water with respect to 100 parts by weight of polyvinyl alcohol (Kuraray, PVA217) as a hydrophilic component, the PVA was dissolved using a magnetic bar at a temperature of 80° C. for 6 hours to prepare a mixed solution. After lowering the mixed solution to room temperature, as a crosslinking agent, polyacrylic acid commaleic acid (Aldrich, PAM) was mixed in the mixed solution so as to be 15 parts by weight based on 100 parts by weight of polyvinyl alcohol, and dissolved at room temperature for 12 hours. Thereafter, 7142 parts by weight of isopropyl alcohol (Duksan Chemical, IPA) was added to the mixed solution based on 100 parts by weight of polyvinyl alcohol and mixed for 2 hours to prepare a composition for forming a hydrophilic coating layer.

Although one embodiment of the present invention has been described above, the spirit of the present invention is not limited to the embodiments presented herein, and those skilled in the art who understand the spirit of the present invention can add components within the scope of the same spirit. , changes, deletions, additions, etc. may easily suggest other embodiments, but this will also fall within the scope of the present invention.

101,102,111,112: nanofiber web 121,122: second support
130: first support 1000: filter media
2000, 2000': filter unit

Claims (14)

a porous first support; a nanofiber web disposed on both sides of the porous first support to filter the water to be treated; and a porous second support interposed between the first support and the nanofiber web;
The first support is made of a first composite fiber having a thickness of 2 to 5 mm, a basis weight of 350 to 600 g/m2, and a low-melting component having a melting point of 60 to 180 ° C.
The nanofiber web has a pressure drop of 5 to 13 psi at a flow rate of 1 L/min, a thickness of 0.5 to 50 μm, an average pore diameter of 0.1 to 1 μm, and a basis weight of 0.05 to 20 g/m2,
The nanofiber web includes polyvinylidene fluoride (PVDF) nanofibers, and the surface of the nanofiber has a hydrophilic coating layer comprising 2 to 20 parts by weight of poly(acrylic acid-maleic acid) with respect to 100 parts by weight of polyvinyl alcohol. is formed,
The second support has a thickness of 150 ~ 400㎛, has a basis weight of 35 ~ 200g / ㎡, is made of a second composite fiber containing a low melting point component having a melting point of 60 ~ 180 ℃,
The total pressure drop of the filter media having a flow path through which the filtrate filtered from the nanofiber web flows in the direction of the first support is 4 to 8 psi at a flow rate of 1,000 L/hr. delete delete The filter medium according to claim 1; and
A flat plate filter unit comprising a; having a flow path through which the filtrate filtered from the filter medium flows out to the outside, and a support frame for supporting the edge of the filter medium. A filter module provided with a plurality of the plate-type filter units according to claim 4 spaced apart from each other at predetermined intervals. delete delete delete delete delete delete delete delete delete

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