U.S. patent application number 14/768271 was filed with the patent office on 2015-12-17 for filter medium, manufacturing method therefor, and filter equipment using same.
The applicant listed for this patent is AMOGREENTECH CO., LTD.. Invention is credited to Jun Sik HWANG, Kyung Su KIM.
Application Number | 20150360157 14/768271 |
Document ID | / |
Family ID | 51748013 |
Filed Date | 2015-12-17 |
United States Patent
Application |
20150360157 |
Kind Code |
A1 |
HWANG; Jun Sik ; et
al. |
December 17, 2015 |
FILTER MEDIUM, MANUFACTURING METHOD THEREFOR, AND FILTER EQUIPMENT
USING SAME
Abstract
Provided are a filter medium, a manufacturing method thereof,
and a filter apparatus using the filter medium. The filter medium
includes: a porous substrate; a nanofiber web that is laminated on
both sides of the porous substrate, and that has a number of fine
pores formed by electrospinning a polymer material; and an adhesive
unit for adhering the porous substrate and the nanofiber web
integrally, wherein the adhesive unit is achieved by applying heat
whose temperature is lower than the melting point of the porous
substrate and higher than the melting point of the nanofiber
web.
Inventors: |
HWANG; Jun Sik; (Incheon,
KR) ; KIM; Kyung Su; (Bucheon-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AMOGREENTECH CO., LTD. |
Gimpo-si Gyeonggi-do |
|
KR |
|
|
Family ID: |
51748013 |
Appl. No.: |
14/768271 |
Filed: |
February 18, 2014 |
PCT Filed: |
February 18, 2014 |
PCT NO: |
PCT/KR2014/001295 |
371 Date: |
August 17, 2015 |
Current U.S.
Class: |
210/333.01 ;
156/243; 210/335; 210/490 |
Current CPC
Class: |
B32B 2305/20 20130101;
B01D 2239/025 20130101; B01D 2239/10 20130101; B32B 5/022 20130101;
B32B 37/24 20130101; B32B 2327/12 20130101; B32B 37/1207 20130101;
B29C 66/71 20130101; B29K 2001/00 20130101; B29K 2027/16 20130101;
B29K 2067/00 20130101; B29K 2033/20 20130101; B29K 2077/00
20130101; B29K 2023/00 20130101; B29C 66/71 20130101; B29C 66/71
20130101; B29C 66/71 20130101; B29C 66/71 20130101; B32B 5/08
20130101; B82Y 40/00 20130101; B01D 2239/0631 20130101; B32B
2037/1215 20130101; B01D 39/18 20130101; B01D 39/1623 20130101;
B01D 2323/39 20130101; B29C 66/71 20130101; B32B 2307/724 20130101;
B29C 66/71 20130101; B32B 2379/00 20130101; B01D 2239/0654
20130101; B01D 29/0093 20130101; D01D 5/0084 20130101; B01D
2239/0681 20130101; B32B 2262/0238 20130101 |
International
Class: |
B01D 39/16 20060101
B01D039/16; B01D 29/56 20060101 B01D029/56; B32B 38/00 20060101
B32B038/00; D01D 5/00 20060101 D01D005/00; B32B 37/12 20060101
B32B037/12; B01D 29/00 20060101 B01D029/00; B01D 29/68 20060101
B01D029/68 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 18, 2013 |
KR |
10-2013-0016680 |
Feb 18, 2014 |
KR |
10-2014-0018237 |
Claims
1. A filter medium comprising: a porous substrate; a nanofiber web
that is laminated on both sides of the porous substrate, and that
has a number of fine pores formed by electro spinning a polymer
material; and an adhesive unit for adhering the porous substrate
and the nano fiber web integrally, wherein the adhesive unit has a
thermally fusing structure that is achieved by applying heat whose
temperature is lower than the melting point of the porous substrate
and higher than the melting point of the nanofiber web.
2. The filter medium according to claim 1, wherein the porous
substrate is a nonwoven fabric of any one of a polyester-based,
nylon-based, polyolefin-based and cellulose-based nonwoven fabric,
and the polymer material forming the nanofiber web comprises a
polyvinylidene fluoride (PVdF).
3. The filter medium according to claim 2, wherein the polymer
material is a mixture of PVdF and polyacrylonitrile (PAN) at a
ratio of 5:5 or 6:4.
4. The filter medium according to claim 2, wherein the thermally
fusing structure is a structure that 1/5 to 1/2 the thickness of
the nano fiber web is melted and penetrated and bonded to the
nonwoven fabric.
5. The filter medium according to claim 2, wherein the nanofiber
web has a structure that the nanofiber web is laminated on the
entire surface except for the upper surface of the nonwoven
fabric.
6. The filter medium according to claim 1, wherein the nanofiber
web comprises a first nanofiber web layer that is formed by
electrospinning a low-concentration polymer material mixture
solution and a second nanofiber web layer that is formed by
electrospinning a high-concentration polymer material mixture
solution; and wherein the low-concentration polymer material
mixture solution contains a polymer material of 8.about.10 wt %,
and the high-concentration polymer material mixture solution
contains a polymer material of 15.about.17 wt %.
7. (canceled)
8. (canceled)
9. (canceled)
10. (canceled)
11. A filter medium comprising: a porous substrate; a nanofiber web
that is laminated on both sides of the porous substrate, and that
has a number of fine pores formed by electro spinning a polymer
material; and an adhesive unit for adhering the porous substrate
and the nano fiber web integrally, wherein the adhesive unit is a
hot-melt powder or hot-melt web.
12. (canceled)
13. (canceled)
14. A method of manufacturing a filter medium comprising the steps
of: preparing a nonwoven fabric; electrospinning a polymer material
on a release paper, to thus form a nanofiber web; and laminating
and thermally fusing the nanofiber web via a hot-melt powder or
hot-melt web on both surfaces of the nonwoven fabric.
15. (canceled)
16. A filter apparatus comprising: a housing having an inlet and an
outlet for sewage or waste water; a plurality of filter media that
are arranged at a predetermined interval in the housing, and for
filtering the waste water stored in the housing according to claim
1; and a pump that is connected to the outlet for pumping the water
of the housing, or supplying wash water into the housing.
17. The filter apparatus according to claim 16, further comprising
a nozzle for generating bubbles, which is provided at one side of
the housing and washes a filter medium.
Description
TECHNICAL FIELD
[0001] The present invention relates to a water treatment filter,
and more specifically, to a filter medium employing nanofiber webs
produced by using an electrospinning method, a method of
manufacturing the filter medium, and a filter apparatus using the
same.
BACKGROUND ART
[0002] Recent industrial advancement has required high purity and
high quality of products, and thus a separator (or a membrane)
technology has been recognized as a very important field. In the
environmental sector, especially as the need for clean water and
the awareness of a lack of water increases, a technology of using a
membrane has largely attracted much attention as one of ways to
solve these problems.
[0003] Processes such as water purification, sewage, waste water,
and desalination using a membrane, are already spreading. In
addition, the membrane technology has been developed for
applications away from the membrane itself, and has expanded into
surrounding technology development as well as has enhanced membrane
performance improvement according to applications.
[0004] The membrane is a substance having a selection capability
that is present between two different materials. In other words,
the membrane means a substance which serves to selectively pass
through or to exclude a material. Structures and substances of the
membrane, and conditions and principles of the movement of the
materials passing through the membrane, have no limitations. When a
substance is located between only two materials to isolate the two
materials each other, and the selective movement of the materials
through the substance between the two materials occurs, the
substance may be called a membrane.
[0005] The membranes are of a very variety of types and are
classified into several criteria.
[0006] First, a classification by a separation operation is a
classification method depending upon the state of a target material
to be separated, and is classified into a liquid separation method,
a gas-liquid separation method, a gas separation method, and so on.
The liquid separation method is classified into micro filtration,
ultra filtration, nano filtration, reverse osmosis filtration,
etc., in accordance with the size of an object for filtration.
[0007] The gas separation method is classified in detail in
accordance with the type of gas to be separated. The gas separation
membrane is classified into an oxygen-enriched membrane for
separating the oxygen gas, a nitrogen-enriched membrane for
separating the nitrogen gas, a hydrogen-enriched membrane for
separating the hydrogen gas, a dehumidifying film for removing
humidity, etc.
[0008] The membrane is classified according to a film-like shape,
and is classified into a flat membrane, a hollow fiber membrane, a
tubular membrane, etc. In addition, the membrane is also classified
into a plate-shaped type, a spiral wound type, a cartridge type, a
flat membrane cell type, an immersion type, a tubular type, and so
on, depending on the form of a filter module.
[0009] The membrane is classified according to a material and is
classified into an inorganic film and an organic film using a
polymer film. In recent years, however the inorganic films expand
their use based on the advantages of heat resistance, durability,
etc., most currently commercialized products are occupied by the
polymer membranes.
[0010] In general, filtration means to remove two or more
components from a fluid, that is, it means to separate undissolved
particles (solid) from the fluid. Filtering mechanisms in the
separation of the solid materials may be described as sieving,
adsorption, dissolution, diffusion mechanisms. Except for some
membranes such as gas separation membranes, reverse osmosis
membranes, etc., it can be said that most of the filtering
mechanisms depend entirely on the sieving mechanism.
[0011] Therefore, it is possible to use any materials with pores as
filter media. Nonwoven fabrics (nonwovens), woven fabrics (wovens),
meshes, porous membranes and the like are typical filter media.
[0012] It difficult to make pores not more than 1 .mu.m in the case
of nonwovens, wovens, meshes, etc. Thus, the nonwovens, wovens,
meshes, etc., are used as a pretreatment filter concept with a
limitation to a particle filtration area. Meanwhile, porous
membranes can make precise and small pores and have been used for a
process requiring a wide range of filtration areas and the highest
precision such as micro filtration, ultra filtration, nano
filtration, reverse osmosis filtration, etc.
[0013] Since the nonwovens, wovens, or meshes are made of fibers
having a thickness from several micrometers to several hundreds of
micrometers, it difficult to make fine pores not more than 1 .mu.m.
In particular, it is not possible actually to create uniform pores
since webs are formed by random arrangement of fibers in the case
of the nonwoven fabrics. The melt-blown nonwoven fabric may be
called a nonwoven fabric made of a very fine fiber having a
diameter of 1.about.5 .mu.m. The pore size before heat calendaring
is not less than six micrometers and the pore size after heat
calendaring is only three micrometers approximately. The deviation
in the average pore size occurs more than .+-.20% around a
reference point, and the melt-blown nonwoven fabric has a structure
in which very large pores coexist.
[0014] Accordingly, the nonwovens, wovens, or meshes have the
difficulty in preventing the leakage of contaminated materials
through relatively large pores and thus have low filter efficiency.
Therefore, the filter media are used in an inaccurate filtration
process or used as a pre-treatment concept of an accurate
filtration process.
[0015] Meanwhile, the porous membrane is prepared by a method such
as a non-solvent induced phase separation (NIPS) process, a
thermally induced phase separation (TIPS) process, a stretching
process, a track etching process, a sol-gel process, etc. The
materials of most of the porous membranes are made of
representative organic polymers, such as polytetrafluoroethylene
(PTFE), polyvinylidene fluoride (PVdF), nylon (Nylon6 or Nylon66),
polysulfone (PS), polyethersulfone (PES), polypropylene (PP),
polyethylene (PE), nitrocellulose (NC) or the like. While the
conventional porous membranes may create pores of precise and small
size, closed pores or blinded pores may be created inevitably in
the manufacturing process. As a result, the conventional porous
membranes have problems such as a small flow amount of filtration,
a high driving pressure, and a short filtration lift cycle, to thus
cause high operating costs and frequent filter replacement.
[0016] Korean Patent Application Publication No. 2013-0011192
discloses a method of producing a composite nonwoven fabric of
alumina including a first step of performing a plasma treatment of
a thermoplastic polymer fiber nonwoven fabric modify the surface of
the nonwoven fabric, and a second step of depositing the alumina on
the surface-treated fabric. However, the filter media using the
alumina composite nonwoven fabric has no damage caused by cutting
of the fiber, and is also excellent in the virus removal
performance, but has a low filtering efficiency disadvantage due to
the large pore size of the nonwoven fabric.
DISCLOSURE
Technical Problem
[0017] To solve the above problems or defects, it is an object of
the present invention to provide a filter medium using a nanofiber
web formed by an electrospinning method, to thereby improve
endurance and freely control the pore size, to thus make a variety
of products in accordance with an intended use, a method of
manufacturing the filter medium, and a filter apparatus using the
filter medium.
[0018] It is another object of the present invention to provide a
filter medium using a nanofiber web formed by an electrospinning
method, to thereby enable thickness of the filter medium to be made
thin and thus thickness of a filter plate to be made thin, to
accordingly laminate a large number of filter plates in a small
space to thus reduce size of a filtration system, a method of
manufacturing the filter medium, and a filter apparatus using the
filter medium.
[0019] It is still another object of the present invention to
provide a filter medium that is prepared by laminating a nanofiber
web having three-dimensional fine pores and a nonwoven fabric, to
thereby achieve excellent handling and strength, and improve filter
efficiency, a method of manufacturing the filter medium, and a
filter apparatus using the filter medium.
Technical Solution
[0020] To accomplish the above and other objects of the present
invention, according to an aspect of the present invention, there
is provided a filter medium comprising: a porous substrate; a
nanofiber web that is laminated on both sides of the porous
substrate, and that has a number of fine pores formed by
electrospinning a polymer material; and an adhesive unit for
adhering the porous substrate and the nanofiber web integrally,
wherein the adhesive unit has a thermally fusing structure that is
achieved by applying heat whose temperature is lower than the
melting point of the porous substrate and higher than the melting
point of the nanofiber web.
[0021] Alternatively, the adhesive unit has a thermally fusing
structure that is achieved by applying heat whose temperature is
higher than the melting point of the porous substrate and lower
than the melting point of the nanofiber web.
[0022] In addition, the adhesive unit may be a hot-melt powder or a
hot-melt web. The hot-melt powder is placed in a dot array pattern
to thus obtain an air-permeability after adhesion, and the hot-melt
web has a plurality of fine pores, is possible to ensure the
air-permeability after adhesion.
[0023] In addition, the porous substrate is a nonwoven fabric of
any one of a polyester-based, nylon-based, polyolefin-based and
cellulose-based nonwoven fabric, and the polymer material forming
the nanofiber web comprises a polyvinylidene fluoride (PVdF).
[0024] In addition, the polymer material is a mixture of PVdF and
polyacrylonitrile (PAN) at a ratio of 5:5 or 6:4.
[0025] In addition, the thermally fusing structure is a structure
that 1/5 to 1/2 the thickness of the nanofiber web is penetrated
and bonded to the nonwoven fabric, or 1/5 to 1/2 the thickness of
the nonwoven fabric is penetrated and bonded to the nonwoven
fabric.
[0026] In addition, the nanofiber web has a structure that the
nanofiber web is laminated on the entire surface except for the
upper surface of the nonwoven fabric.
[0027] According to another aspect of the present invention, there
is provided a filter medium comprising: a porous substrate; and a
nanofiber web that is laminated on both sides of the porous
substrate, and that has a number of fine pores formed by
electrospinning a polymer material, wherein the nanofiber web
comprises a first nanofiber web layer that is formed by
electrospinning a low-concentration polymer material mixture
solution and a second nanofiber web layer that is formed by
electrospinning a high-concentration polymer material mixture
solution.
[0028] In addition, the low-concentration polymer material mixture
solution contains a polymer material of 8.about.10 wt %, and the
high-concentration polymer material mixture solution contains a
polymer material of 15.about.17 wt %.
[0029] According to another aspect of the present invention, there
is provided a method of manufacturing a filter medium comprising
the steps of: preparing a nonwoven fabric; electrospinning a
polymer material on a release paper, to thus form a nanofiber web;
and laminating the nanofiber web on both surfaces of the nonwoven
fabric, and heating the laminated result at a temperature lower
than the melting point of the nonwoven fabric and higher than the
melting point of the nanofiber web, thus thermally fusing the
nonwoven fabric and the nanofiber web.
[0030] Alternatively, the thermally fusing is achieved by applying
heat whose temperature is higher than the melting point of the
porous substrate and lower than the melting point of the nanofiber
web.
[0031] According to another aspect of the present invention, there
is provided a method of manufacturing a filter medium comprising
the steps of: preparing a nonwoven fabric; electrospinning a
low-concentration polymer material mixture solution containing a
polymer material of 8.about.10 wt %, and a high-concentration
polymer material mixture solution containing a polymer material of
15.about.17 wt % in sequence, on one surface of the nonwoven
fabric, to thus form a nanofiber web; and electrospinning the
low-concentration polymer material mixture solution containing the
polymer material of 8.about.10 wt %, and the high-concentration
polymer material mixture solution containing the polymer material
of 15.about.17 wt % in sequence, on the other surface of the
nonwoven fabric, to thus form a nanofiber web.
[0032] According to another aspect of the present invention, there
is provided a method of manufacturing a filter medium comprising
the steps of: preparing a nonwoven fabric; electrospinning a
polymer material on a release paper, to thus form a nanofiber web;
and laminating and thermally fusing the nanofiber web via a
hot-melt powder or hot-melt web on both surfaces of the nonwoven
fabric.
[0033] According to another aspect of the present invention, there
is provided a filter apparatus comprising: a housing having an
inlet and an outlet for sewage or waste water; a plurality of
filter media that are arranged at a predetermined interval in the
housing, and for filtering the waste water stored in the housing;
and a pump that is connected to the outlet for pumping the water of
the housing, or supplying wash water into the housing.
[0034] The filter apparatus further comprises a nozzle for
generating bubbles, which is provided at one side of the housing
and washes a filter medium.
Advantageous Effects
[0035] As described above, the present invention provides a filter
medium that is formed by bonding a nanofiber web formed by an
electrospinning method on both sides of a nonwoven fabric by using
a thermally fusing structure or a hot melt adhesive, to thereby
improve endurance and freely control the pore size, to thus make a
variety of products in accordance with an intended use.
[0036] In addition, the present invention provides a filter medium
using a nanofiber web formed by an electrospinning method, to
thereby enable thickness of the filter medium to be made thin and
thus thickness of a filter plate to be made thin, to accordingly
laminate a large number of filter plates in a small space to thus
reduce size of a filtration system.
[0037] Further, the present invention provides a filter medium that
is prepared by laminating a nanofiber web having three-dimensional
fine pores and a nonwoven fabric, to thereby provide a filter
apparatus capable of achieving excellent handling and strength, and
improving filter efficiency.
DESCRIPTION OF DRAWINGS
[0038] FIG. 1 is a cross-sectional view of a filter apparatus
according to an embodiment of the present invention.
[0039] FIG. 2 is a plan view of a filter medium according to one
embodiment of the present invention.
[0040] FIG. 3 is a cross-sectional view of a filter medium
according to one embodiment of the present invention.
[0041] FIG. 4 is a close-up photograph of nanofiber webs in
accordance with one embodiment of the present invention.
[0042] FIG. 5 is a schematic diagram of an electrospinning
apparatus for forming a nanofiber web of a filter medium in
accordance with an embodiment of the present invention.
[0043] FIG. 6 is a partial sectional view illustrating a filter
medium according to an embodiment of the present invention.
[0044] FIG. 7 is an enlarged cross-sectional view of a nanofiber
web that is applied to a filter medium in accordance with an
embodiment of the present invention.
BEST MODE
[0045] Hereinafter, embodiments of the present invention will be
described with reference to the accompanying drawings. In the
process, the sizes and shapes of components illustrated in the
drawings may be shown exaggerated for convenience and clarity of
explanation. Further, by considering the configuration and
operation of the present invention the specifically defined terms
may be changed according to user's or operator's intention, or the
custom. Definitions of these terms herein need to be made based on
the contents across the whole application.
[0046] FIG. 1 is a cross-sectional view of a filter apparatus
according to an embodiment of the present invention.
[0047] Referring to FIG. 1, a filter apparatus according to an
embodiment of the present invention includes: a housing 10 in which
sewage or waste water is externally introduced and stored; a
plurality of filter media 20 that are arranged at a predetermined
interval in the housing 10, and for filtering the sewage or waste
water stored in the housing 10; and a plurality of bubble
generating nozzles 30 that are arranged at the lower side of the
housing 10 to thus function to flush the filter media 20.
[0048] The housing 10 is provided with an inlet 12 through which
water to be purified, for example, polluted water such as sewage
water or waste water is introduced, and an outlet 14 that is formed
at the upper side of the housing 10 and through which water
purified in the housing 10 is externally discharged.
[0049] As shown in FIGS. 2 and 3, each of the filter media 20
includes: a nonwoven fabric 22 having a plurality of pores through
which water can pass; a first nanofiber web 24 that is laminated on
one surface of the nonwoven fabric 22 and having fine pores capable
of filtering the water; and a second nanofiber web 26 that is
laminated on the other surface of the nonwoven fabric 22 and having
fine pores capable of filtering the water.
[0050] The filter media 20 are arranged at a predetermined interval
in the housing 10, and filter the sewage or waste water stored in
the housing 10.
[0051] Here, the nonwoven fabric that can be used in the present
invention is any one of, for example, a melt-blown nonwoven fabric,
a spun bond nonwoven fabric, a thermal bond nonwoven fabric, a
chemical bond nonwoven fabric, and a wet-raid nonwoven fabric. The
nonwoven fabric may include fibers having diameters of about 30
.mu.m to about 60 .mu.m, and pores of diameters of about 50 .mu.m
to about 200 .mu.m.
[0052] The nonwoven fabric 22 includes a large number of pores and
thus plays a role of a path through which water can pass, as well
as a support layer for supporting the first nanofiber web 24 and
the second nanofiber web 26 to maintain a flat type.
[0053] In the present invention, the filter medium may be
implemented by laminating a nanofiber web on both sides of a
nonwoven fabric as a porous substrate having a number of pores, in
which the nanofiber web has a number of fine pores formed by
electrospinning a polymer material. In this case, the filter medium
may include an adhesive unit for adhering the nonwoven fabric and
the nanofiber web integrally.
[0054] The adhesive unit may have a thermally fusing structure that
is achieved by applying heat whose temperature is lower than the
melting point of the porous substrate and higher than the melting
point of the nanofiber web.
[0055] The porous substrate may be a nonwoven fabric of any one of
a polyester-based, nylon-based, polyolefin-based and
cellulose-based nonwoven fabric, and the polymer material forming
the nanofiber web may include a polyvinylidene fluoride (PVdF).
[0056] Further, the polymer material that is electrospun in order
to form the nanofiber web is a mixture of PVdF and
polyacrylonitrile (PAN) at a ratio of 5:5 or 6:4, and the thermally
fusing structure is a structure that 1/5 to 1/2 the thickness of
the nanofiber web is penetrated and bonded to the nonwoven
fabric.
[0057] As described above, when thermal compression is performed by
applying heat whose temperature is lower than the melting point of
the porous substrate and higher than the melting point of the
nanofiber web, a portion of the nanofiber web, that is, 1/5 to 1/2
the thickness of the nanofiber web is melted and penetrated and
strongly adhered to the porous substrate, for example, the nonwoven
fabric.
[0058] Alternatively, the thermally fusing structure is achieved by
thermally compressing and bonding two members, that is, the porous
substrate and the nanofiber web, by applying heat whose temperature
is higher than the melting point of the porous substrate and lower
than the melting point of the nanofiber web. In this case, 1/5 to
1/2 the thickness of the porous substrate is melted and penetrated
and strongly adhered to the porous substrate, for example, the
nonwoven fabric.
[0059] In the filter medium having a thermally fusing structure as
described above, the nanofiber web may have a structure that the
nanofiber web is laminated on the entire surface except for the
upper surface of the porous substrate, that is, the nonwoven
fabric.
[0060] Meanwhile, according to another aspect of the invention, a
filter medium may also be configured by directly electrospinning a
first nanofiber web 24 and a second nanofiber web 26 on a porous
substrate, that is, a nonwoven fabric so as to be strongly adhered
thereto.
[0061] That is, as shown in FIG. 4, the first nanofiber web 24 and
the second nanofiber web 26 are formed by using a process having
the steps of: preparing a spinning solution by mixing a polymer
material and a solvent at a constant mixture ratio in which the
polymer material can be electrospun; forming nanofibers 112 and 114
by electrospinning the spinning solution; and accumulating the
nanofibers 112 and 114 on the surface of the nonwoven fabric 22 to
thus have fine pores 110 through which water may be filtered.
[0062] Here, diameters of the nanofibers 112 and 114 are preferably
in the range of 0.1 .mu.m to 3.0 .mu.m.
[0063] The thicknesses of the first nanofiber web 24 and the second
nanofiber web 26 are freely adjusted according to electrospinning
time from the electrospinning apparatus, and the sizes of the pores
110 are determined by the thicknesses of the nanofiber webs.
[0064] Therefore, since the sizes of the pores 110 of the first
nanofiber web 24 and the second nanofiber web 26 may be freely
adjusted in the present embodiment, the sizes of the pores 110 may
be produced in various ways according to type of a filter.
[0065] Thus, the filter medium that is configured by forming a
nanofiber web by directly electrospinning a polymer material on
both sides of a nonwoven fabric as described above, includes: a
porous substrate; and a nanofiber web that is formed by directly
electrospinning a polymer material on both sides of the porous
substrate in which the nanofiber web has fine pores.
[0066] In this case, the nanofiber web includes a first nanofiber
web layer that is formed by electrospinning a low-concentration
polymer material mixture solution and a second nanofiber web layer
that is formed by electrospinning a high-concentration polymer
material mixture solution. Here, the first nanofiber web layer may
be formed by a coating or spraying method as well as
electrospinning.
[0067] In addition, the low-concentration polymer material mixture
solution contains a polymer material of 8.about.10 wt %, and the
high-concentration polymer material mixture solution contains a
polymer material of 15.about.17 wt %.
[0068] The polymer material used for the embodiments of the present
invention may include, for example, hydrophilic polymers or/and
hydrophobic polymers that can be electrospun, or may include one
kind of the polymers or a mixture of two or more kinds of the
polymers.
[0069] The polymer materials used in the embodiments of the present
invention may be resins that may be dissolved in an organic solvent
for electrospinning, and that may be capable of forming nanofibers
by electrospinning, but are not specifically limited thereto. For
example, the polymer materials used in the present invention may
be: polyvinylidene fluoride (PVdF), poly(vinylidene
fluoride-co-hexafluoropropylene), perfluoropolymer, polyvinyl
chloride, polyvinylidene chloride, or copolymers thereof;
polyethylene glycol derivative containing polyethylene glycol
dialkylether and polyethylene glycol dialkylester;
poly(oxymethylene-oligo-oxyethylene); polyoxide containing
polyethylene oxide and polypropylene oxide; polyvinyl acetate,
poly(vinyl pyrrolidone-vinyl acetate), polystyrene, and a
polystyrene acrylonitrile copolymer; a polyacrylonitrile copolymer
containing polyacrylonitrile (PAN) and a polyacrylonitrile methyl
methacrylate copolymer; or polymethyl methacrylate, a poly methyl
methacrylate copolymer, or a mixture thereof.
[0070] Also, the polymer material used in the present invention may
be: aromatic polyester such as polyamide, polyimide,
polyamideimide, poly(meta-phenylene isophthal amide), polyester
sulfone (PES), polyether ketone, polyetherimide (PEI), polyethylene
terephthalate, polytrimethylene terephthalate, or polyethylene
naphthalate; polyphosphazene such as polytetrafluoroethylene,
polydifenoxiphosphazene, poly
{bis[2-(2-methoxyethoxy)phosphazene]}; polyurethane, and
polyurethane copolymer containing polyether urethane; or cellulose
acetate, cellulose acetate butyrate, cellulose acetate
propionate.
[0071] The polymer materials that may be particularly desirably
used as the filter material of the present invention may be
polyacrylonitrile (PAN), polyvinylidene fluoride (PVdF), polyester
sulfone (PES), and polystyrene (PS), alone or a mixture of
polyvinylidene fluoride (PVdF) and polyacrylonitrile (PAN), a
mixture of PVdF and PES, or a mixture of PVdF and thermoplastic
polyurethane (TPU).
[0072] Referring back to FIGS. 1 to 3, each of the filter media 20
is formed so that the first nanofiber web 24 and the second
nanofiber web 26 are respectively laminated on both surfaces of the
nonwoven fabric 22, the other three side edges except for the upper
surface of the nonwoven fabric 22 are compressed by a thermal
compression method so that the first nanofiber web 24 and the
second nanofiber web 26 are formed to surround the side portion of
the nonwoven fabric 22, the upper surface of the nonwoven fabric 22
protrudes with respect to the first nanofiber web 24 and the second
nanofiber web 26, the protruding portion 32 of the nonwoven fabric
22 is connected to a discharge pipe 50 through which water purified
via the nonwoven fabric 22 is discharged.
[0073] Here, the discharge pipe 50 includes: a fixing portion 52
that is fixed to wrap the protruding portion 32 of the nonwoven
fabric 22 so that only water that has passed through the nonwoven
fabric 22 can be discharged; and a connection tube 54 that is
connected to the fixing portion 52 and that is connected to an
outlet 14 formed in the housing 10.
[0074] Bubble generating nozzles 30 arranged at the lower side of
the housing 10 are connected to a compressor (not shown) or the
like by which air can be externally injected, and are arranged in
plurality on the bottom surface of the housing 10.
[0075] Here, the bubble generating nozzles 30 serve to discharge
air into the housing 10, to thus generate bubbles and water flows
and thus serve to remove an adhesion material adhered on the
surfaces of the filter media 20.
[0076] Any forms of nozzles capable of generating a flow of water
and air bubbles are applicable to the structures of the bubble
generating nozzles 30. In addition, a discharge passage (not shown)
is formed on the bottom of the housing 10, in which foreign
substances accumulated on the bottom of the housing 10 by washing
the filter media 20 are discharged through the discharge
passage.
[0077] A method of manufacturing filter media according to an
embodiment of the present invention will be described in detail in
the following.
[0078] FIG. 5 is a schematic diagram of an electrospinning
apparatus that manufactures a filter medium in accordance with an
embodiment of the present invention.
[0079] The electrospinning apparatus according to an embodiment of
the present invention includes: a first collector 110 along which a
nonwoven fabric 22 is transferred; first spinning nozzles 120
disposed on the upper surface of the first collector 110 and
connected to a high voltage generator (not shown) to thus form a
first nanofiber web 24 on one surface of the nonwoven fabric 22; a
second collector 130 along which the other surface of the nonwoven
fabric 22 on the one surface of which the first nanofiber web 24
has been formed is transferred to face upward; and second spinning
nozzles 140 disposed on the upper surface of the second collector
130 and connected to a high voltage generator (not shown) to thus
form a second nanofiber web 26 on the other surface of the nonwoven
fabric 22.
[0080] The first spinning nozzles 120 and the second spinning
nozzles 140 serve to produce ultrafine nanofiber yarns by
electrospinning a spinning solution that is formed by mixing a
polymer material and a solvent.
[0081] A nonwoven fabric roll 100 on which the nonwoven fabric 22
is wound is arranged in the front side of the first collector 110,
and a filter media roll 190 on which filter media 20 laminated with
the first nanofiber web 24 and the second nanofiber web 26 are
wound is arranged in the rear side of the second collector 130.
[0082] When a high-voltage electrostatic force of 90 through 120 Kv
is applied between the first collector 110 and each of the first
spinning nozzles 120 and between the second collector 130 and each
of the second spinning nozzles 140, ultrafine fiber strands 112 and
114 are spun to thus form an ultrafine nanofiber web.
[0083] Air spraying devices 70 and 72 are provided on the first
spinning nozzles 120 and the second spinning nozzles 140,
respectively, and thus the fiber strands spun from the first
spinning nozzles 120 and the second spinning nozzles 140 are
prevented from blowing without being captured by the first and
second collectors 110 and 130.
[0084] The multi-hole spin pack nozzles used in the present
invention are made to set air pressure of air spraying to be in the
range of about 0.1 to about 0.6 MPa. In this case, air pressure
less than about 0.1 MPa, does not contribute to capture and
integrate the flying fibers. In the case that air pressure exceeds
about 0.6 MPa, the cone of each spinning nozzle is hardened to thus
cause a clogging phenomenon of the needle to occur and to thereby
cause a spinning trouble to occur.
[0085] In this way, a process of preparing the filter media by
using the electrospinning device as constructed above will be
described in the following.
[0086] First, when the first collector 110 is driven, the nonwoven
fabric 22 rolled on the nonwoven fabric roll 100 is moved along the
upper surface of the first collector 110.
[0087] In addition, when a high-voltage electrostatic force is
applied between the first collector 110 and each of the first
spinning nozzles 120, a spinning solution from the first spinning
nozzles 120 is made into ultrafine fiber strands 112 and spun on
one surface of the nonwoven fabric 22. Then, ultrafine fiber
strands are accumulated on one surface of the nonwoven fabric 22,
and thus the first nanofiber web 24 having ultrafine pores is
formed.
[0088] Then, when the first nanofiber web 24 is completely
produced, a process of laminating the second nanofiber web 26 on
the other side of the nonwoven fabric 22 is performed.
[0089] In other words, the nonwoven fabric 22 on one surface of
which the first nanofiber web 24 is laminated is moved to the
second collector 130. In this case, since the second collector 130
is disposed on the lower side of the first collector 110, the
nonwoven fabric 22 is moved to the second collector 130 in a
180.degree. reversed state. Then, the other surface of the nonwoven
fabric 22 faces upward.
[0090] In addition, when a high-voltage electrostatic force is
applied between the second collector 130 and each of the second
spinning nozzles 140, a spinning solution from the second spinning
nozzles 140 is made into ultrafine fiber strands 114 and spun on
the other surface of the nonwoven fabric 22. Then, ultrafine fiber
strands are accumulated on the other surface of the nonwoven fabric
22, and thus the first nanofiber web 26 having ultrafine pores is
formed.
[0091] The filter media 20 prepared via these processes are
pressurized to a predetermined thickness while passing through a
pressure roller 180, to then be wound on a filter medium roll
190.
[0092] Here, in some embodiments, there is provided a method of
manufacturing a filter medium comprising the steps of: preparing a
nonwoven fabric; electrospinning a low-concentration polymer
material mixture solution containing a polymer material of
8.about.10 wt %, and a high-concentration polymer material mixture
solution containing a polymer material of 15.about.17 wt % in
sequence, on one surface of the nonwoven fabric, to thus form a
nanofiber web; and electrospinning the low-concentration polymer
material mixture solution containing the polymer material of
8.about.10 wt %, and the high-concentration polymer material
mixture solution containing the polymer material of 15.about.17 wt
% in sequence, on the other surface of the nonwoven fabric, to thus
form a nanofiber web.
[0093] In addition, in some embodiments, there is also provided a
method of manufacturing a filter medium comprising the steps of:
preparing a nonwoven fabric; electrospinning a polymer material on
a release paper, to thus form a nanofiber web; and laminating the
nanofiber web on both surfaces of the nonwoven fabric, and heating
the laminated result at a temperature higher than the melting point
of the nonwoven fabric and lower than the melting point of the
nanofiber web, thus thermally fusing the nonwoven fabric and the
nanofiber web.
[0094] Further, according to another embodiment of the present
invention, the filter medium may be prepared by adhering a nonwoven
fiber and a nanofiber web by using a hot melt powder or a hot melt
web.
[0095] Hereinbelow, operation of a filter apparatus formed of the
filter media will be described.
[0096] When water flows into the housing 10 for filtering, a pump
16 connected to the outlet 14 is driven to make the water pass
through the filter media 20 to thus be filtered and then discharged
via the outlet 14.
[0097] Further, when a process of washing the filter media 20 is
performed to remove materials attached to the surfaces of the
filter media 20, the pump 16 is driven in the reverse direction to
thus make the wash water introduced into the housing 10 through the
outlet 14. The wash water may include chemicals needed to wash the
filter media.
[0098] Here, the pump 16 is connected to the outlet 14, thus
housing 10, performing the function of pumping the water through
the outlet 14 out of the housing 10 or supplying the wash water
into the housing 10 through the outlet 14.
[0099] When the wash water is introduced into the housing 10
through the outlet 14, the wash water introduced through the
nonwoven fabric 22 is discharged through the first nanofiber web 24
and the second nanofiber web 26, to thereby make materials attached
to the first nanofiber web 24 and the second nanofiber web 26
detached therefrom.
[0100] Then, bubbles generated from the bubble generating nozzles
30 are supplied to the surfaces of the first nanofiber web 24 and
the second nanofiber web 26, to thus play a role of making
materials attached to the first nanofiber web 24 and the second
nanofiber web 26 detached therefrom. In other words, the bubble
generating nozzles 30 are provided at one side of the housing 10
and serve to wash the filter media 20.
[0101] FIG. 6 is a partial sectional view illustrating a filter
medium according to an embodiment of the present invention. FIG. 7
is an enlarged cross-sectional view of a nanofiber in a nanofiber
web in accordance with an embodiment of the present invention.
[0102] The above-described filter medium has a structure in which a
nanofiber web is laminated on a nonwoven fabric. The nanofiber web
may be implemented in a structure of a first nanofiber web
laminated on one surface of a nonwoven fabric and a second
nanofiber web laminated on the other surface of the nonwoven
fabric, or in a structure in which a nanofiber web is laminated on
the entire surface except for the upper surface of the nonwoven
fabric.
[0103] In this case, the nonwoven fabric and the nanofiber web may
be fused by thermal compression. The melting point of the nanofiber
web is designed to be lower than the melting point of the nonwoven
fabric, so that the nanofiber web is preferably melted and fused to
the nonwoven fabric by heat applied during thermal compression. For
example, when the polymer material for forming a nanofiber web is
applied as PVdF, the melting point of PVdF is 155.degree. C., and
thus the nonwoven fabric includes a polyester-based, nylon-based,
or cellulose-based nonwoven fabric having a melting point higher
than 155.degree. C.
[0104] Therefore, during thermal compression, the nanofiber web
region contacting the nonwoven fabric is melted and fused on the
nonwoven fabric. Here, since the pore size of the nonwoven fabric
is much greater than the pore size of the nanofiber web, a portion
of the melted nanofiber web is penetrated into the pores of the
nonwoven fabric. That is, as shown in FIG. 6, based on a boundary
surface 29 between a nonwoven fabric 28b and a nanofiber web 28a
prior to thermal compression, the melted nanofiber web after
thermal compression is spread in distribution in the nanofiber web
direction (A) and the nonwoven fabric direction (B), from the
boundary surface 29. When an amount of the melted nanofiber web is
controlled based on this technical feature, the melted nanofiber
web enters the pores of the nonwoven fabric. Accordingly, the
melted nanofiber web having entered the pores of the nonwoven
fabric plays a role of a locking function to thus improve adhesion
between the nanofiber web and the nonwoven fabric.
[0105] In some embodiments, a polymer material forming the
nanofiber web includes a mixture of polyvinylidene fluoride (PVdF)
and polyacrylonitrile (PAN) at a ratio of 5:5 or 6:4. In this case,
as shown in FIG. 7, an electrospun nanofiber is formed to include a
core 27a, made of PAN and an outer skin 27b surrounding the outer
peripheral surface of the core 27a and made of PVdF. The nanofibers
of this structure are stacked to form a nanofiber web. When the
nanofiber web that is formed by laminating the nanofibers each
having the structure of the core 27a and the outer skin 27b, and
the nonwoven fabric are thermally compressed, the PVdF the outer
skin 27b is melted and penetrated to be fused into the nonwoven
fabric.
[0106] According to another embodiment of the present invention, a
fuse reinforcement material (not shown) is interposed between the
nanofiber web and the nonwoven fabric. The fuse reinforcement
material may have a good adhesion force respectively with a
nanofiber web and a nonwoven fabric. That is, since the nanofiber
web is fused on one surface of the fuse reinforcement material, and
the nonwoven fabric is fused on the other side of the fuse
reinforcement material, the nanofiber web and the nonwoven fabric
are fused by using the fuse reinforcement material. As a result, a
bonding strength between the nanofiber web and the nonwoven fabric
when using the fuse reinforcement material may be further increased
in comparison with the case that the nanofiber web and the nonwoven
fabric are fused by thermal compression. Therefore, this filter
medium structure may remarkably reduce a delamination phenomenon
between the nanofiber web and the nonwoven fabric that may occur
during iteratively performing a filter function and a washing
function in the filter apparatus. In this case, the fusion process
may be the process of respectively melting the nanofiber web and
the nonwoven fabric by thermal compression, and then fusing the
nanofiber web and the nonwoven fabric by using the fuse
reinforcement material.
[0107] Further, the fuse reinforcement material should include
openings through which water can passed. These openings connect
pores of the nanofiber web with pores of the nonwoven fabric, so
that water can pass smoothly between the nanofiber web and the
nonwoven fabric. In addition, the fuse reinforcement material may
be implemented with a material having the ability to enhance the
strength of the filter medium.
[0108] The fuse reinforcement material may include a hot melt
powder or a hot-melt web.
[0109] As described above, the present invention has been described
with respect to particularly preferred embodiments. However, the
present invention is not limited to the above embodiments, and it
is possible for one who has an ordinary skill in the art to make
various modifications and variations, without departing off the
spirit of the present invention. Thus, the protective scope of the
present invention is not defined within the detailed description
thereof but is defined by the claims to be described later and the
technical spirit of the present invention.
INDUSTRIAL APPLICABILITY
[0110] The present invention may be applied to a filter medium
employing a nanofiber web that is prepared by electrospinning.
* * * * *