KR20180069350A - Filter media, method for manufacturing thereof and Filter unit comprising the same - Google Patents

Abstract

Provided is a filter medium. According to an embodiment of the present invention, the filter medium includes: a first porous supporter; nanofiber webs placed in the upper and lower parts of the first supporter, respectively, and having a three-dimensional network structure including a plurality of pores formed by stacking nanofibers including graphene oxides; and a second porous supporter interposed between the first supporter and the nanofiber webs. Accordingly, the filter medium is capable of regulating pollution and having excellent water permeability with an improved hydrophilic property, and having an extended duty cycle by minimizing damage and structural and shape deformation even when a backwash process with high pressure is conducted. Moreover, since passage is smoothly secured even at the high pressure applied for filtration and/or backwashing, filtered water is quickly discharged out of the filter medium or the efficiency of backwashing is excellent, the filter medium is able to be applied to various water treatment fields.

Description

TECHNICAL FIELD The present invention relates to a filter medium, a method of manufacturing the filter medium, and a filter unit including the filter medium.

More specifically, the present invention relates to a filter medium having improved mechanical properties such as water permeability and chemical resistance by improving the hydrophilic property, easy control of contamination, excellent durability, and mechanical resistance To a method for manufacturing the same, and to a filter unit including the same.

The separation membrane can be classified into a microfiltration membrane (MF), an ultrafiltration membrane (UF), a nanofiltration membrane (NF), or a reverse osmosis membrane (RO) depending on the pore size.

Although the separation membranes have different usages and pore size differences, they have a common feature in that they are in the form of a filtration medium or a porous polymer filtration medium formed from fibers or a composite membrane thereof.

The porous polymer filter medium may be formed by forming pores formed in a polymer membrane or a polymer hollow fiber by sintering the pore former through a separate pore former contained in the tank solution or by dissolving the pore former in an external coagulating solution It is common. On the contrary, 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 applying heat / pressure or the like simultaneously with the spinning.

Typical examples of the filtration media formed from the fibers are nonwoven fabric. In general, the pores of the nonwoven fabric are controlled by the diameter of the short fibers, the basis weight of the medium, and the like. However, since the diameter of the short fibers included in the general nonwoven fabric is in the unit of microns, there is a limitation in realizing a separation membrane having a fine and uniform pore structure only by controlling the diameter and basis weight of the fibers. Accordingly, It is difficult to realize a separation membrane such as an ultrafiltration membrane or a nano separation membrane for filtration.

A method designed to solve this problem is a separation membrane produced through microfibers having a fiber diameter of nanometer. However, the microfine fiber having a diameter of nanometer unit is difficult to be manufactured by only one spinning process by a fiber spinning process such as a general wet spinning process, and it is necessary to elute the sea component separately after radiating to sea chart yarn, There is a problem that it is troublesome to work, the cost is increased, and the production time is extended. Recently, there has been a tendency to manufacture a large number of filter media formed from fibers by directly spinning fibers having a diameter of nanometer unit through electrospinning.

In the pore of the filtration media in which the water treatment process is repeatedly performed, some of various foreign substances contained in the for-treatment water may remain or an adherent layer may be formed on the surface of the filtration medium. there is a problem. In order to solve this problem, it is conceivable to prevent the occurrence of the fouling phenomenon itself by the pretreatment or to clean the filtration medium already having the fouling phenomenon. In the filtration medium, It is common to apply a high pressure to the filtration medium to remove the foreign matter remaining in the filtration medium so as to be in the opposite direction to the flow path through which the filtrate flows. However, the high pressure applied to the filtration media during washing may cause damage to the filtration media, and in the case of the filtration media formed in a multi-layer structure, the problem of interlayer separation may occur.

Graphene, on the other hand, refers to a two-dimensional single sheet made of sp ² hybrid carbon atoms arranged in a honeycomb hexagonal shape as a carbon isotope. Graphene Oxide (GO) is prepared using a method of oxidizing the graphene with a strong acid and an oxidizing agent, and includes various hydrophilic groups such as hydroxy, epoxy, and carbonyl groups, Ion exchange ability, and can easily interact with the polymer matrix. In addition, graphene oxide can be manufactured easily from raw materials as compared to carbon nanotubes, funrenes, and the like, and the manufacturing cost is relatively low, attracting attention recently.

In general, the filtration medium used for water treatment may contaminate the contaminants by adsorbing contaminants on the surface of the filter medium while filtering the contaminated raw water. If the contamination of the filtration media is excessive, the water permeation pressure, which acts upon filtration, Which may ultimately lower the filtration function of the filter medium. In order to control the contamination of such a filter medium, there is a method of cleaning using chlorine, acid, alkali or the like. However, since there is a problem of shortening the life of the filter medium, recently, Studies are underway to use a vinylidene resin or to make the filtration medium hydrophilic.

However, since conventional hydrophobic filtration media exhibit excellent chemical, thermal, and biological stability, it is desirable to combine hydrophilic properties capable of controlling contaminants with hydrophobic properties in the field of water treatment filtration media.

In general, a polyvinylidene fluoride (PVDF) filter medium has characteristics of being susceptible to contamination because its surface characteristics are hydrophobic. To prevent this, a method of chemical surface modification or coating in a post-treatment process Is widely used. However, in this case, there may be a problem of uniformity and durability of the surface, and the additional post-treatment process must be carried out, resulting in a low productivity and a long manufacturing process. Furthermore, in the case of a filtration medium whose surface is chemically modified, there may be disadvantages in terms of mechanical strength and chemical stability.

Accordingly, even in the backwash process performed at a high pressure, the shape, the structural deformation and the damage of the filter medium are minimized and the flow path is smoothly secured. Therefore, the flow rate and the speed of the treated water are increased, It is urgent to develop a filter medium having improved chemical resistance.

Patent No. 10-0871440

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a filter material having improved water permeability and water permeability and chemical resistance, and easy to control contamination, and a method for manufacturing the same.

Further, it is an object of the present invention to provide an easy filter material having excellent mechanical properties such as tensile strength and elongation, and a method for producing the filter material.

Also, it is an object of the present invention to provide a filter medium having a large flow rate and a high processing speed as the flow path is smoothly secured while minimizing the shape, structure, and damage of the filter medium during the water treatment operation, and a method for manufacturing the filter medium.

It is another object of the present invention to provide a filter material having excellent durability and a method of manufacturing the same, which can secure a flow path even under high pressure applied in a backwashing process and minimize delamination, damage to the membrane and the like.

It is another object of the present invention to provide a flat filter unit and a filter module that can be applied in various fields in the field of water treatment through a filter material having excellent water permeability and durability.

According to an aspect of the present invention, there is provided a three-dimensional network structure having a plurality of pores formed by stacking nanofibers each having a porous first support, A porous second support interposed between the nanofiber web and the first and nanofiber webs, respectively; And a filter medium.

The thickness of the first support may be 90% or more of the total thickness of the filter media.

In addition, the thickness of the first support may be 95% or more, more preferably 98 to 99.9% of the total thickness of the filter media.

The basis weight of the first support may be 250 to 800 g / m 2, and more preferably 350 to 600 g / m 2.

In addition, the thickness of the first support may be 2 to 8 mm, more preferably 2 to 5 mm, and still more preferably 3 to 5 mm.

The first support and the second support may be any one of a nonwoven fabric, a woven fabric, and a knitted fabric. More preferably, the first and second supports may be nonwoven fabrics.

The second support includes a second composite fiber including a support component and a low melting point component such that at least a part of the low melting point component is exposed to the outer surface, and the low melting point component of the second composite fiber is May be fused to the nanofiber web.

The first support of the filter media includes a first composite fiber including a support component and a low melting point component such that at least a part of the low melting point component is exposed on the outer surface, Component and the low melting point component of the second composite fiber, the first support and the second support may be bonded together.

The nanofiber web may have an average pore size of 0.1 to 3 占 퐉 and a porosity of 60 to 90%.

In addition, the nanofibers forming the nanofiber web may have an average diameter of 50 to 450 nm.

The basis weight of the second support may be 35 to 80 g / m 2, and the thickness may be 150 to 250 탆.

The present invention also provides a method of manufacturing a nanofiber web comprising the steps of (1) preparing a nanofiber web having nanofibers containing graphene oxide, (2) joining the nanofiber web and the second support, and (3) 1 is a perspective view showing a method for manufacturing a filter medium according to a first embodiment of the present invention;

The present invention also provides a flat filter unit comprising the above-described filter medium and a support frame for supporting the edge of the filter medium, and a flow path for allowing the filtrate filtered out from the filter medium to flow out.

In addition, the present invention provides a water treatment filter module in which several flat plate filter units are spaced apart from each other by a predetermined distance.

According to the present invention, the filter material is minimized in shape, structure, and damage of the filter material during the water treatment operation, and the flow path can be smoothly secured, so that it can have a high flow rate. In addition, due to the excellent durability of the filter media, even at high pressure applied during backwashing, it has a prolonged service life and improved hydrophilic properties, and thus can be applied in various water treatment fields due to its excellent water permeability.

1 is a sectional view of a filter medium according to an embodiment of the present invention,
FIG. 2 is a photograph of the swollen filter material after the washing liquid is trapped inside the filter material after being separated from the filter material by the backwashing process,
Fig. 3 is a schematic view showing direct lapping of the first support and the nanofiber web,
FIG. 4A is a schematic view illustrating a method for assembling a filter media according to an embodiment of the present invention, FIG. 4A is a view showing the nanofiber web and a second support joined together, FIG. 4B is a cross- Are arranged on both surfaces of the first support body and joined together,
5A and 5B are diagrams of nanofiber webs included in one embodiment of the present invention. FIG. 5A is a photograph of a surface electron microscope of the nanofiber web, FIG. 5B is a cross-sectional electron micrograph of the nanofiber web, 5c is a graph of the fineness distribution of the nanofibers provided in the nanofiber web, and FIG. 5d is a graph of the pore size distribution of the nanofiber web.
FIG. 6 is a cross-sectional electron micrograph of the filter media according to an embodiment of the present invention,
FIG. 7 is a plan view of a flat filter unit according to an embodiment of the present invention. FIG. 7A is a perspective view of a filter unit, and FIG. 7B is a schematic diagram showing a filtration flow based on a sectional view of a boundary line XX 'in FIG. 7A.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art to which the present invention pertains. The present invention may be embodied in many different forms and is not limited to the embodiments described herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and the same reference numerals are assigned to the same or similar components throughout the specification. The term "nano" as used herein also refers to nanoscale, and may include microunits. In the present invention, a nanofiber web in which a plurality of nanofibers are spun through electrospinning in a spinning solution to form a structure is defined as a void space between the nanofiber webs constituting the nanofiber separation membrane. The pore size, thickness, and porosity of the water-treating nanofiber-graphene membrane of the present invention are defined as pore size, thickness, and porosity after the nanofiber web is laminated and heat-treated.

As shown in FIG. 1, the filter media 1000 according to an embodiment of the present invention includes second supports 121 and 122 sequentially stacked on top and bottom of a first support 130, and nanofibrous webs 111 and 112 And a filtration flow in which the filtrate filtered through the nanofiber webs 111 and 112 flows in the direction of the first support body 130.

The nanofiber webs 111 and 112 are stacked on each of the surfaces of the second supports 121 and 122 which are in contact with the first support 130 and the nanofibrous webs 111 and 112, Dimensional network structure in which nanofibers of nanofibers are randomly and three-dimensionally stacked (see FIG. 5).

Generally, filter media formed only with nanofibers with small hydrophobicity have excellent chemical resistance. However, when such a filter medium is applied to the water treatment filter field, there is a problem that the water permeability is lowered due to the affinity to water due to the small number of characteristics of the filter medium. At this time, the water permeability of the hydrophobic filter material can be improved by using sufficient pressure, but since the required pressure is very high (150 to 300 psi), the filter material may be damaged. In addition, there is a problem in that it is weak against contaminants having a small number of properties, and research on hydrophilized or wet out treatment which gives a hydrophilic property to filter media is required.

As an example of such a method, there has been disclosed a method of filling a filter medium with a preparation such as glycerol to impart a hydrophilic property. However, since water molecules can serve as a plasticizer, a filter having a mechanical strength and thermal stability is required There is an unsuitable side.

In addition, a filter made of a compound having minority properties such as polytetrafluoroethylene (PTFE), polyethylene (PE), polypropylene (PP) and polyvinylidene fluoride (PVDF) There is a problem of uniformity and durability of the surface, and the additional post-treatment process must be performed, resulting in a low productivity and a long time. Furthermore, chemically modified filter media may have disadvantages in terms of mechanical strength and chemical stability.

On the other hand, nanofibers produced by electrospinning exhibit various physical properties that can not be obtained from conventional fibers, and have been applied to various fields as materials for filter media having porous properties. However, a filter material composed of only nanofibers is difficult to maintain proper strength, and there are many problems to be solved from the viewpoint of handleability.

Accordingly, the present invention realizes a nanofiber web containing nanoparticles containing oxide graphene (Graphene Oxide), which is excellent in mechanical properties, such as tensile strength and elongation, to ensure the stability of the filter media, The hydrophilic property of the fin provides a filter medium which is easy to handle water permeability and contamination control.

The oxidized graphene may be included on the inner and outer surfaces of the nanofibers constituting the nanofiber web. Typical oxidized graphene is a specific effect, in which the carbon particles of the oxidized graphene form a covalent bond, and the bonded carbon particles are formed into a sheet or layer, so that the specific surface area can be increased. According to one example, when the graphene oxide is provided on the surface of the nanofibers, more pollutants can be filtered due to the effect of increasing the specific surface area of the graphene oxide, thereby improving the filtration efficiency.

In addition, the graphene oxide exhibits excellent hydrophilic properties due to hydrophilic functional groups including oxygen. According to one example, when the nanofiber is produced from polyvinylidene fluoride (PVDF) as a fiber-forming component, the graphene oxide having excellent hydrophilic properties is included in the inner and outer surfaces of the nanofiber, Can be improved. That is, a nanofiber web including both a hydrophobic and a hydrophilic property, thereby enabling more efficient control of contaminants.

In addition, the graphene oxide exhibits excellent tensile strength. Generally, a nanofiber web composed of only nanofibers is excessively pressurized during backwashing, so that the nanofibers are broken or warped, resulting in mechanical deformation of the nanofiber web composed of the nanofibers. Therefore, since the graphene oxide is included in the inner and outer surfaces of the nanofiber, the tensile strength of the nanofiber increases, and the stability of the filter media can be restored.

Since the nanofiber web of filter media according to the present invention is formed of nanofibers containing graphene oxide, the hydrophilic property can be improved, and deterioration of filtration efficiency and mechanical strength of the filter filter material can be prevented have. In addition, since it has hydrophilic / hydrophobic properties, it can secure the chemical stability of the filter media, has excellent water permeability, and is easily applicable to various filter fields because of easy control of the pollutants.

Next, the nanofibers forming the nanofiber webs 111 and 112 may be formed of a known fiber-forming component. However, in order to exhibit excellent chemical resistance and heat resistance, a fluorine-based compound may be contained as a fiber-forming component, so that even if the water to be treated is a strong acid / strong base solution or a solution having a high temperature, And it has an advantage of securing the filtration efficiency / flow rate and having a long use period. The fluorine-based compound may be used without limitation in the case of a known fluorine-based compound that can be prepared as a nanofiber. Examples of the fluorine-based compound include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkylvinylether copolymer Tetrafluoroethylene-hexafluoropropylene copolymer (PEP), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer (EPE) (ETFE), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), and polyvinylidene fluoride (PVDF) More preferably, the production cost is low and mass production of nanofibers through electrospinning is easy, and the mechanical strength and chemical resistance are excellent In one aspect may be a polyvinylidene fluoride (PVDF). When the nanofiber includes PVDF as a fiber forming component, the PVDF may have a weight average molecular weight of 10,000 to 1,000,000, preferably 300,000 to 600,000, but is not limited thereto.

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

The thickness of the nanofibrous webs 111 and 112 may be 0.5 to 200 mu m, for example, 20 mu m. The porosity of the nanofiber webs 111 and 112 may be 40 to 90%, and more preferably 60 to 90%. In addition, the average pore diameter may be 0.1 to 5 占 퐉, more preferably 0.1 to 3 占 퐉, and may be 0.25 占 퐉, for example. The basis weight of the nanofiber webs 111 and 112 may be 0.05 to 20 g / m 2, and may be 10 g / m 2, for example, 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 more than one layer in the filter material 1000, and the pore size, pore size, basis weight, and / or thickness of each nanofiber web may be different.

Meanwhile, the nanofibers forming the nanofiber webs 111 and 112 may be modified to increase the hydrophilicity. For example, the hydrophilic coating layer may be further provided on at least a part of the outer surface of the nanofibers. If the nanofibers include a fluorine-based compound as described above, the fluorine-based compound has a very high hydrophobicity, and thus the flow rate is poor when the supernatant is a hydrophilic solution. For example, the hydrophilic coating layer may be formed on the surface of the hydrophobic nanofibers. The hydrophilic coating layer may be formed of a known hydrophilic polymer having a hydroxyl group, or the hydrophilic polymer may be crosslinked through a crosslinking agent . For example, the hydrophilic polymer may be a polyvinyl alcohol (PVA), an ethylenevinyl alcohol (EVOH), a sodium alginate, or the like, and most preferably a polyvinyl alcohol (PVA). The crosslinking agent may be used without limitation in the case of a known crosslinking agent having a functional group capable of crosslinking through a condensation reaction with a hydroxyl group of the hydrophilic polymer. For example, the functional group may be a hydroxyl group, a carboxyl group, or the like.

The hydrophilic coating layer may be formed by cross-linking a polyvinyl alcohol (PVA) and a cross-linking agent containing a carboxyl group to exhibit improved physical properties. The polyvinyl alcohol may have a degree of polymerization of 500 to 2000 and a degree of saponification of 85 to 90%. If the degree of polymerization of polyvinyl alcohol is excessively low, there is a problem that the formation of the hydrophilic coating layer is not smooth or even if it is formed easily, there is a problem that the hydrophilic coating layer may not be improved to the desired level. In addition, if the degree of polymerization is too high, 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. Further, when the saponification degree is too low, there is a problem that it is difficult to improve hydrophilicity.

The crosslinking agent may be a component containing a carboxyl group so as to be crosslinked with the polyvinyl alcohol described above. 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, in order to coat the surface of the nanofibers with improved hydrophobicity so that coating / adhesion to the surface of the nanofibers and the pore structure of the nanofibrous webs 111 and 112 are not changed, the cross-linking agent is coated with at least three carboxyl groups Based crosslinking agent. If the crosslinking agent has less than 3 carboxyl groups, it is difficult to form a coating layer on the surface of the hydrophobic nanofibers, and even if the crosslinking agent is formed, the adhesion force 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 per 100 parts by weight of the polyvinyl alcohol. If the amount of the crosslinking agent is less than 2 parts by weight, the formation of the hydrophilic coating layer may be deteriorated and the chemical resistance and mechanical strength may be deteriorated. If the cross-linking agent is present in an amount exceeding 20 parts by weight, the pore may be reduced due to the coating layer.

On the other hand, the hydrophilic coating layer may be formed on part or all of the outer surface of the nanofiber. At this time, the hydrophilic coating layer may be coated with nanofibers such that the hydrophilic coating layer contains 0.1 to 2 g per unit area (m2) of the nanofiber web.

As described above, the wetting angle of the surface of the nanofibrous web 111, 112 modified to have the hydrophilic coating layer may be 30 degrees or less, more preferably 20 degrees or less, still more preferably 12 degrees or less, 5 ° or less, thereby providing an advantage of securing an improved flow rate despite the fact that the fiber web is embodied as a nanofiber that is hydrophobic in terms of material.

Hereinafter, another configuration of the filter media 1000 will be described in detail.

First, the first support 130 supports the filter material 1000 and forms a large flow path to perform the filtration process or the backwash process more smoothly. Specifically, when a pressure gradient is formed so as to have a lower internal pressure than that of the filter media in the filtration process, the filter media can be squeezed. In this case, since the flow path through which the filtrate flows in the filter media is significantly reduced or blocked There is a problem that a larger differential pressure is applied to the filter filter material and the flow rate is remarkably lowered. In addition, during backwashing, an external force may be applied to expand the filter media toward the outside in both directions. However, the filter media may be damaged due to an external force applied when the mechanical strength is low.

The first support 130 is provided to prevent the above-mentioned problems occurring in the filtration process and / or the backwashing process. The first support 130 may be a known porous material that is used in the water treatment field and has mechanical strength. For example, The first support may be a nonwoven, fabric or fabric.

The fabric means that the fibers included in the fabric have longitudinal and lateral directions, and the specific structure may be plain weave, twill weave, etc., and the density of warp and weft yarn is not particularly limited. Further, the knitted fabric may be a known knit structure, a weft knitted fabric, a knitted fabric, or the like, and may be, for example, a tricot knitted yarn. 1, the first support body 130 may be a nonwoven fabric having no longitudinal and transverse directional properties on the fibers 130a, and may be a dry nonwoven fabric such as a chemical bonding nonwoven fabric, a thermal bonding nonwoven fabric, an airray nonwoven fabric, a wet nonwoven fabric, , Needle punching nonwoven fabric or melt blown nonwoven fabric may be used.

The first support 130 may occupy a thickness of 90% or more of the total thickness of the filter media as described above in order to exhibit sufficient mechanical strength. For example, the first support 130 may have a thickness of 2 to 8 mm, more preferably 2 to 5 mm, and still more preferably 3 to 5 mm. If the thickness is less than 2 mm, it may not exhibit sufficient mechanical strength to withstand frequent backwashing. Also, when the thickness exceeds 8 mm, the degree of integration of the filter material per unit volume of the module may be reduced when the filter material is implemented as a filter unit described below and a plurality of filter units are implemented by a limited space filter module.

 Preferably, the first support 130 may have a basis weight of 250 to 800 g / m 2, more preferably 350 to 600 g / m 2, while satisfying the thickness condition as described above. If the basis weight is less than 250 g / m < 2 >, it may be difficult to exhibit sufficient mechanical strength, and adhesion with the second support may decrease. If the basis weight exceeds 800 g / And there is a problem that smooth backwashing is difficult due to an increase in differential pressure.

When the first support 130 is formed of fibers such as nonwoven fabric, the fibers may have an average diameter of 5 to 50 mu m, preferably 20 to 50 mu m. In addition, the first support 130 may have an average pore size of 20 to 200 μm and a porosity of 50 to 90%, but the present invention is not limited thereto. In the filtration process and / or the backwash process, There is no restriction as to the degree of porosity and pore size so as to support the webs 111 and 112 to exhibit a desired level of mechanical strength and to smoothly form a flow path at high pressure.

The material of the first support body 130 is not limited if it is used as a support for the separation membrane. By way of non-limiting example, synthetic polymer components selected from the group consisting of polyester based, polyurethane based, polyolefin based and polyamide based; Or a natural polymer component including a cellulose system may be used. However, if the first support has a brittle physical property, it may be difficult to expect a desired level of bonding force in the process of laminating the first support and the second support. This is because the first support has a smooth surface The surface may be macroscopically roughened while forming the porosity, and the surface formed by the fibers, such as nonwoven fabric, may not have a smooth surface depending on the arrangement of the fibers and the fineness of the fibers, to be. If the remaining portions are bonded while the portion not in contact with the interface between the two layers being bonded is present, delamination may be started due to the non-adhered portion. In order to solve this problem, it is necessary to carry out the lapping process while increasing the degree of close contact between the two layers by applying pressure in both layers. If the brittle physical property is strong, The supporting member may be damaged when applying a larger pressure, so that the material of the first supporting member may be flexible, the material of high elongation may be suitable, and preferably the second supporting member 121, The first support 130 may be a polyolefin-based material.

Meanwhile, the first support body 130 may include a low melting point component to bond with the second support bodies 121 and 122 without a separate adhesive or an adhesive layer. When the first support 130 is the same fabric as the nonwoven fabric, it may be made of the first composite fiber 130a having a low melting point component. The first composite fiber 130a may include a support component and a low melting point component so that at least a part of the low melting point component is exposed on the outer surface. For example, a cis-core type conjugate fiber in which a support component forms a core portion and a low melting point component forms a sheath portion surrounding the core portion, and a side-by-side composite fiber having a low- Lt; / RTI > The low-melting-point component and the support component may be polyolefin-based in view of the flexibility and elongation of the support, as described above. For example, the support component may be polypropylene and the low-melting component may be polyethylene. The melting point of the low melting point component may be 60 to 180 ° C.

Next, the second supporting bodies 121 and 122 arranged on both surfaces of the above-described first supporting body 130 will be described.

The second supports 121 and 122 support the nanofibrous webs 111 and 112 to be described later and function to increase the bonding force of the layers provided in the filter media.

The second support members 121 and 122 are not particularly limited as long as they generally serve as a support for the filter media, but they may preferably be woven, knitted or nonwoven fabric. The fabric means that the fibers included in the fabric have longitudinal and lateral directions, and the specific structure may be plain weave, twill weave, etc., and the density of warp and weft yarn is not particularly limited. The knitted fabric may be a known knitted fabric, and may be a knitted fabric, a knitted fabric, or the like, but is not particularly limited thereto. The nonwoven fabric means that the fibers are not oriented in the longitudinal and transverse directions. The nonwoven fabric may be a dry nonwoven fabric such as a chemical bonding nonwoven fabric, a thermal bonding nonwoven fabric, an airlay nonwoven fabric, a wet nonwoven fabric, a spunless nonwoven fabric, a needle punching nonwoven fabric or a meltblown A non-woven fabric manufactured by the above-mentioned method can be used.

The second supporting members 121 and 122 may be nonwoven fabric. The fibers forming the second supporting members 121 and 122 may have an average diameter of 5 to 30 μm. The thickness of the second support bodies 121 and 122 may be 100 to 400 탆, more preferably 150 to 400 탆, still more preferably 150 to 250 탆, for example, 200 탆 .

The second support bodies 121 and 122 may have an average pore size of 20 to 100 μm and a porosity of 50 to 90%. However, the present invention is not limited to this, and it may be possible to support the nanofiber webs 111 and 122 to be described later to develop a desired level of mechanical strength and to prevent the flow of the filtrate flowing through the nanofiber webs 111 and 122 Porosity, and pore size.

The basis weight of the second support bodies 121 and 122 may be 10 to 200 g / m 2, more preferably 35 to 200 g / m 2, and still more preferably 35 to 80 g / m 2. , And 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 described later may be small. It may not be possible to exhibit the desired level of bonding force due to a decrease in the bonding area. Further, the nanofibrous web may not exhibit sufficient mechanical strength to support the nanofiber web, and the adhesion with the first support may be reduced. If the basis weight exceeds 200 g / m < 2 >, it may be difficult to obtain the desired level of flow rate, and there may be a problem that smooth backwashing is difficult due to an increase in differential pressure.

The second support members 121 and 122 are not limited as far as they are used as a support for filter media. By way of non-limiting example, synthetic polymer components selected from the group consisting of polyester based, polyurethane based, polyolefin based and polyamide based; Or a natural polymer component including a cellulose system may be used.

However, the second supports 121 and 122 may be a polyolefin-based polymer component for enhancing adhesion between the nanofiber webs 111 and 112 described later and the first support 130 described above. If the second support members 121 and 122 are made of the same material as the nonwoven fabric, they may be made of the second composite fiber 121a having a low melting point component. The second composite fiber 121a may include a support component and a low melting point component so that at least a part of the low melting point component is exposed on the outer surface. For example, a cis-core type conjugate fiber in which a support component forms a core portion and a low melting point component forms a sheath portion surrounding the core portion, and a side-by-side composite fiber having a low- Lt; / RTI > The low-melting-point component and the support component may be polyolefin-based in view of the flexibility and elongation of the support, as described above. For example, the support component may be polypropylene and the low-melting component may be polyethylene. The melting point of the low melting point component may be 60 to 180 ° C.

If the first support 130 is embodied as a first composite fiber 130a having a low melting point component to exhibit a further improved bonding strength with the second supports 121 and 122, A more firmly fused portion due to fusion of the low melting point component of the first conjugated fiber 130a and the low melting point component of the second conjugated fiber 121a can be formed at the interface between the two supports 121. At this time, the first composite fiber 130a and the second composite fiber 121a may be made of the same material in terms of compatibility.

As the water treatment process using the filter media is repeated, the foreign substances contained in the for-treatment water adhere to the filter media to form an adherent layer, or they are embedded in the filter media, thereby blocking the flow path and deteriorating the filtering function. There is a problem that the cost of water treatment increases when the filter media is replaced. Accordingly, in order to extend the service life of the filter media, it is necessary to perform a cleaning process of periodically applying physical stimulus to the filter media to adhere to the filter media or to remove impurities contained in the filter media. BACKGROUND OF THE INVENTION [0003] BACKGROUND OF THE INVENTION [0004] BACKGROUND OF THE INVENTION [0005] BACKGROUND OF THE INVENTION [0005] [Background Art] [0005] Backwashing typically involves washing water in a direction opposite to the filtration direction of 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.

Accordingly, in order for the filter media to have the backwashing ability, it is important that the filter media have such mechanical strength that the filter media is not deformed or damaged even under high applied pressure, and a support for compensating mechanical strength is usually provided in the filter media . Factors that may affect the mechanical strength of the support include the structure of the support, for example, the diameter of the fibers forming the nonwoven fabric when the support is nonwoven, the length of the fibers, the manner of interfiber bonding, thickness and basis weight, The thicker or larger the basis weight, the greater the mechanical strength of the support. Therefore, for example, a nonwoven fabric having a large thickness or a nonwoven fabric having a very large basis weight may be used as a support for designing a filter medium which is resistant to backwashing.

On the other hand, it is preferable that the support has a large pore size so as not to affect the flow of the filtrate of the filter media. The lowering of the flow rate due to the support provided for the purpose of compensating the mechanical strength is very undesirable because it deteriorates the main properties of the filter media. However, when a nonwoven fabric having sufficient mechanical strength is used as a support even though the thickness is thin, the basis weight of the nonwoven fabric is very large, and thus the diameter and porosity of the pores in the nonwoven fabric are inevitably small. As a result, There is a problem that the desired level of flow can not be secured.

Accordingly, the filter support 1000 according to the present invention may have a thickness of 90% or more of the entire filter support, which secures a sufficient flow passage while securing mechanical strength of the filter support, 130 may preferably be at least 95%, more preferably 98 to 99.9% of the total thickness of the filter media. If the first support is less than 90% of the total thickness of the filter media, the filter media may not have sufficient mechanical strength to perform backwashing, which may shorten the replacement period of the filter media. In addition, securing the mechanical strength of the first support to such an extent that it is less than 90% of the total thickness of the filter media and sufficient to withstand backwashing is highly desirable because there may be flow interruption and flow reduction of the filtrate due to the first support Can not do it.

However, if the binding force between the nanofiber webs 111 and 112 functioning as filter media and the first support 130 is weak, the durability of the filter media due to backwashing may be deteriorated even though the mechanical strength is excellent. That is, the high pressure applied during backwashing can accelerate the interfacial separation between the layers forming the filter media. In this case, as shown in FIG. 2, There is a problem that the function as the separation membrane can be remarkably reduced or completely lost.

Therefore, the high adhesion between the first support having a considerably increased thickness and the nanofiber web as a filter medium is very important in realizing a filter material exhibiting sufficient durability for frequent backwashing.

In general, a method of attaching the support and the nanofiber web may be performed by using a separate adhesive material or by fusing a low melting point component provided on the support to the nanofiber web to bond the two layers together. However, when the two layers are bonded to each other through a separate bonding material, there is a possibility that the bonding material is dissolved by the for-treatment water, thereby causing a problem of contamination of the filtrate and lowering of water permeability. If the binder material is partially backwashed, the backfill of the filter media or the nanofiber web may peel off and the filter media may be completely lost.

Accordingly, it is possible to employ a method in which the nanofiber web and the support are bonded to each other through fusion (A), and heat and / or heat may be applied to both the support 1 and the nanofiber web 2, Pressure can be applied to bond them. However, when applying heat and / or pressure, consideration must be given to minimizing the physical and chemical transformation of the nanofiber web 2, which acts as a filter media due to the applied heat and pressure, The physical properties such as the flow rate and the filtration rate of the filter material designed at the beginning can be changed when the nano web is physically and chemically deformed.

What should be considered when selecting the heat and / or pressure conditions in the attachment process so that there is no physical / chemical deformation of the nanofiber web 2 can be the material properties of the nanofiber web, the support, such as melting point, thermal conductivity, A low melting point component of the support may be fused to the nanofiber web or a high pressure may be applied even if the melting point is somewhat lower than the melting point so that the low melting point component of the support may be fused to the nanofiber web have.

On the other hand, the material forming the support or the nanofiber web is a polymer compound. Since such a polymer compound has a small thermal conductivity and a very large heat capacity, even if a predetermined heat (H ₁ , H ₂ ) is applied to both sides In order for the heat (H ₁ , H ₂ ) to reach the interface between the nanofiber web 1 and the support 2 to raise the temperature of the low melting point component provided in the support 2 to the melting point, Should be applied. 3, when the thickness of the support 1 is very large, heat (H ₂ ) transmitted from below is transmitted to the vicinity of the interface between the nanofiber web 2 and the support 1, 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 a larger amount of heat downward to shorten the time. However, when too large heat is applied from below, melting of the low melting point component may occur first in the lower part of the first support, and the shape and structure of the support may be changed.

In this case, the nanofibrous web 2 may be physically / chemically deformed. In this case, the heat (H1) applied to the nanofibrous web 2 may be increased, There is a problem in that the physical properties of the filter media designed in the present invention can not be fully manifested.

Accordingly, the filter media 1000 according to an embodiment of the present invention does not face the first support 130 and the nanofiber webs 111 and 112 directly but interposes the second supports 121 and 122 having a smaller thickness This makes it possible to carry out the interlayer adhesion process more stably and easily and to exhibit a remarkably excellent bonding force at the interface between the respective layers and to minimize delamination and peeling problems even when a high external force is applied due to backwashing or the like.

4a, the second support 3, which occupies less than 10% of the total thickness of the filter media, is different in thickness from the nanofiber web 2 in that the nanofiber web 2 and the first support 1 The heat (H ₁ , H ₂ ) applied above and below the laminated body of the nanofiber web 2 / the second support 3 reaches the interface therebetween, B) is easier than in Fig. In addition, since the amount and time of heat to be applied is more easily controlled than in FIG. 3, it is advantageous to prevent physical / chemical deformation of the nanofiber web 2, ), There is an advantage that the nanofibers can be bonded with excellent adhesive force on the support without changing the physical properties of the nanofiber web 2 designed at the beginning.

The filter material 1000 described above can be manufactured by a manufacturing method described later, but is not limited thereto.

The filter media 1000 according to the present invention includes the steps of (1) preparing a nanofiber web having nanofibers containing graphene oxide, (2) laminating the nanofiber web and the second support, and (3) And arranging and laminating the lapped nanofiber web and the second support on both sides of the first support so that the second support abuts the first support.

First, in step (1) according to the present invention, a step of producing a nanofiber web having nanofibers containing graphene oxide is performed.

The step (1) includes the steps of: (1-1) preparing a spinning solution containing oxidized graphene and a fiber forming component; and (1-2) spinning the spinning solution to produce a nanofiber web .

The step (1) includes the steps of (1-1) preparing a spinning solution containing a hydrophilic component and a fiber forming component, (1-2) spinning the spinning solution to prepare a nanofiber web, and -3) crosslinking the hydrophilic component of the nanofiber web and the fiber forming component.

The step (1-1) is a step of preparing a spinning liquid containing oxidized graphene and a fiber forming component. The spinning solution may include a graphene oxide dispersion in which graphene oxide is prepared and dispersed in a solvent.

 The oxidized graphene can be produced by a conventional method. For example, it may include the steps of (a) mixing graphite with a strong acid, (b) mixing the mixed graphite with a strong oxidizing agent, and (c) adjusting the pH of the mixed graphite to neutrality .

In one embodiment, the strong acid may use at least one strong acid in hydrochloric acid, sulfuric acid, and nitric acid, and potassium permanganate may be used as the strong oxidizing agent. As described above, the surface of each layer in the graphite is oxidized, and a part of the carbon bonds with oxygen to have a carbonyl group. The graphite may have a size of 0.1 mu m to 1.0 mu m, and the dispersibility in the solvent is excellent in the above range, and the graphite can be easily combined with a fiber forming component to be described later to improve the mechanical properties.

The graphene oxide thus prepared may be put into a solvent and dispersed to prepare the graphene oxide dispersion. At this time, examples of the solvent include cyclohexane, 1,2-dichloroethane, dichlorobenzene, dichloromethane, diethyl ether, dimethylether ), Dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and the like. These may be used singly or in combination of two or more. When the solvent of this kind is used, the graphene oxide can be easily dispersed. In one embodiment, the solvent and the graphene oxide may be mixed and dispersed by ultrasonication to form a dispersion.

In one embodiment, the oxidizing graphene in the spinning solution may be adjusted to be included in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the fiber forming component. Preferably 0.5 to 3.5 parts by weight. More preferably 0.5 to 2 parts by weight. In the above range, the water-treatment nano fiber-graphene separation membrane is excellent in hydrophilicity and excellent in mechanical strength and chemical resistance. When the amount of the graphene oxide is less than 0.1 part by weight, the hydrophilic property is deteriorated. When the amount of the graphene oxide is more than 10 parts by weight, dispersion of the graphene oxide in the spinning solution becomes difficult, There may be a disadvantage that the fins are not uniformly distributed.

The fiber-forming component may include, for example, a fluorine-based compound and a solvent. The fluorine-based compound may be contained in the spinning solution in an amount of 5 to 30 wt%, preferably 8 to 20 wt%. If the fluorine-based compound is less than 5 wt%, it is difficult to form fibers, Even if the film is formed or spun, a large amount of beads are formed and the volatilization of the solvent is not performed well, so that the pores may be clogged in the calendering process described later. If the amount of the fluorine-based compound exceeds 30% by weight, the viscosity increases and the surface of the solution becomes solidified, which makes it difficult to spin for a long period of time.

The solvent can be used without limitation in the case of a solvent which does not affect the radioactivity of the nanofiber described later without dissolving the fluorine-based compound as a fiber-forming component and does not produce a precipitate, but preferably is selected from the group consisting of г-butyrolactone, cyclohexanone, And at least one selected from the group consisting of hexanone, 3-heptanone, 3-octanone, N-methylpyrrolidone, dimethylacetamide, acetone dimethylsulfoxide and dimethylformamide. For example, the solvent may be a solvent for the mixing of dimethylacetamide and acetone.

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

Next, (1-2) spinning the spinning solution to produce a nanofiber web.

The prepared spinning solution can be produced by a known electrospinning apparatus and method. For example, the electrospinning device may be an electrospinning device having a single spinning pack with one spinning nozzle or an electrospinning device with a plurality of single spinning packs or a spinning pack with multiple nozzles for mass production Also, Also, in the electrospinning method, wet spinning with dry spinning or external coagulation can be used, and there is no limitation with respect to the method.

The nanofiber web formed of nanofibers can be obtained when a spinning solution stirred in the electrospinning device is injected to electrospray on a collector, for example, paper. The specific conditions for the electrospinning are, for example, that the air pressure of the air injection 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 can not contribute to the collection and accumulation. If the air pressure exceeds 0.2 MPa, the cone of the spinneret is hardened and the needle may be clogged and radiation trouble may occur. In addition, when the spinning solution is spinned, the injection rate of the spinning solution per nozzle may be 10 to 30 μl / min. The distance between the tip of the nozzle and the collector may be 10 to 30 cm. However, it is not limited to this, and it can be changed according to purpose.

Next, (2) a step of laminating the nanofiber web and the second support is performed.

When the second support is formed of a low-melting-point compound fiber, the binding through the thermal fusion between the nanofiber web and the second support may be promoted simultaneously through the calendering process.

Further, another hot melt powder or hot melt web may be further interposed to bind the second support and the nanofiber web. In this case, the applied heat may be 60 to 190 ° C, and the pressure may be 0.1 to 10 kgf / cm 2, but is not limited thereto. However, components such as hot melt powder, which are separately added for binding, are frequently melted in the laminating process between the support and the support and between the support and the nanofiber to frequently open the pores, thereby achieving the initial designed filter media flow rate It can not be done. In addition, it may dissolve in the water treatment process, which may cause environmental negative problems, so that it is preferable to bond the second support and the nanofiber web without preferably including them.

The step (2) may be performed by applying at least one of (2-1) heat and pressure to fuse the first support and the second support.

As a specific method of applying heat and / or pressure in the step (2-1), a known method may be adopted, and as a non-limiting example, a conventional calendering process can be used, and the temperature of the applied heat is 70 to 190 < 0 > C. When the calendering process is carried out, it may be carried out a plurality of times, for example, a first calendering followed by a second calendering. At this time, the degree of heat and / or pressure applied in each calendering process may be the same or different. Through the step (2-1), bonding can be performed through thermal fusion between the second support and the first support, and an additional adhesive or adhesive layer can be omitted.

Next, in step (3) according to the present invention, the laminated nanofibrous web and the second support on both sides of the first support so that the second support in the laminated second support and the nanofiber web contact with the first support, Thereby performing a step of assembling.

The step (3) may be performed by applying at least one of (3-1) heat and pressure to fuse the first support and the second support.

As a specific method of applying heat and / or pressure in the step (3-1), a known method may be adopted. As a non-limiting example, a conventional calendering process can be used, and the temperature of the applied heat is 70 to 190 < 0 > C. When the calendering process is carried out, it may be carried out a plurality of times, for example, a first calendering followed by a second calendering. At this time, the degree of heat and / or pressure applied in each calendering process may be the same or different. Through the above step (3-1), bonding can be performed through thermal fusion between the second support and the first support, and an additional adhesive or adhesive layer can be omitted.

The present invention includes a filter unit implemented with a filter material manufactured through the above-described manufacturing method.

As shown in FIG. 7A, the filter filter material 1000 may be implemented as a flat filter unit 2000. More specifically, the flat filter unit 2000 includes a filter filter material 1000 and a support frame 1100 for supporting a rim of the filter filter material 1000. In one region of the support frame 1100, A suction port 1110 capable of slanting the pressure difference between the outside and the inside of the main body 1000 can be provided. The filtration liquid filtered through the nanofiber webs 101 and 102 is discharged to the outside through the support 200 on which the second support body and the first support body in the filter media 1000 are stacked, Can be formed.

7A, when a suction force of a high pressure is applied through the suction port 1110, the overflow liquid P, which is disposed outside the filter filter material 1000 as shown in FIG. 7B, And the filtrate Q1 filtered through the nanofiber webs 101 and 102 flows along the flow path formed through the support 200 on which the second support body and the first support body are stacked, And the inflow filtrate Q2 can be discharged to the outside through the inlet 1110. [

7A, a plurality of filter modules may be arranged in a single outer case at a predetermined interval, and the filter module may be stacked / A water treatment apparatus may be constituted.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

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

Claims (12)

A porous first support;
A nanofibrous web of a three-dimensional network structure having a plurality of micropores formed by nanofibers, each of which is disposed on upper and lower portions of the first support, and including graphene oxide; And
A porous second support interposed between the first support and the nanofiber web, respectively; / RTI > The method according to claim 1,
Wherein the thickness of the first support is at least 90% of the total thickness of the filter media. The method according to claim 1,
Wherein the first support and the second support are any one of a nonwoven fabric, a fabric, and a knitted fabric. The method according to claim 1,
Wherein the first support has a basis weight of 250 to 800 g / m 2 and a thickness of 2 to 8 mm. The method of claim 1, wherein the second support comprises:
And a second composite fiber including a support component and a low melting point component and arranged such that at least a part of the low melting point component is exposed to the outer surface, . 6. The method of claim 5,
Wherein the first support of the filter media comprises a first composite fiber including a support component and a low melting point component so that at least a part of the low melting point component is exposed on an outer surface, Wherein the first support and the second support are bonded by fusion bonding of the low melting point components of the second composite fiber. The method according to claim 1,
Wherein the nanofiber web has an average pore size of 0.1 to 3 占 퐉 and a porosity of 60 to 90%. The method according to claim 1,
Wherein the nanofibers forming the nanofiber web have an average diameter of 50 to 450 nm. The method according to claim 1,
The basis weight of the second support is 35 to 80 g / m 2, and the thickness is 150 to 250 탆. (1) preparing a nanofiber web comprising nanofibers containing graphene oxide;
(2) laminating the nanofiber web and the second support; And
(3) arranging and laminating the lapped nanofiber web and the second support on both sides of the first support so that the second support abuts the first support. 10. Filter media according to any one of claims 1 to 9; And
A support frame for supporting the rim of the filter media, the filter having a flow path for allowing the filtrate filtered out from the filter media to flow out to the outside; And a second filter unit. The filter module according to claim 13, wherein a plurality of flat plate filter units are spaced apart from each other at a predetermined interval.

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