KR101855388B1 - Manufacturing method of filter media available at medium and high temperature and filter media manufactured thereby - Google Patents

Abstract

According to various embodiments of the present invention, a method for producing a filter medium for high/medium temperature flue gas treatment comprises: preparing a coating solution composed of a polytetrafluoroethylene (PTFE) dispersion solution and a thickener; and applying the coating solution to an inorganic fiber support and then treating the same with heat. According to various embodiments of the present invention, the filter medium for high/medium temperature flue gas treatment comprises: the inorganic fiber support composed of a weft yarn and a warp yarn, and dip-coated with PTFE; and a multilayer porous coating layer formed on an upper surface of the inorganic fiber support and having grooves formed by the weft yarns and the warp yarns.

Description

Technical Field [0001] The present invention relates to a method for producing a filter medium for medium to high-temperature flue gas treatment,

TECHNICAL FIELD The present invention relates to a method for producing a filter medium for treating medium- and high-temperature flue gas and a filter body produced thereby.

A filtration and dust collecting apparatus is most commonly used to remove dust in the exhaust gas discharged from a combustion process of an industrial company. The performance of the filtering and dust collecting device depends on the filter body mounted therein. In addition, the type of filter used varies depending on the temperature range of the exhaust gas. For medium to high temperature of 150 to 280, woven glass fiber is used. However, the glass fiber is very weak in strong acid and strong alkali, and the structure is destroyed by the strong acid and strong alkali component contained in the exhaust gas, so that the life of the filter body can be devastated.

In order to solve this problem, polytetrafluoroethylene (PTFE) resistant to strong acid or strong alkali is immersed and coated on glass fiber. However, since it is not possible to uniformly coat all the glass fibers by immersion coating alone, a method of complementing the surface of glass fiber immersed with PTFE by foam coating is also being developed. However, since the pores of the foam coated surface are about 15 - 30 탆 in size, fine dust or gaseous strong acid and strong alkali passes through the pores and can not be a perfect solution. A technique has been developed to minimize the effect of fine dust / ultrafine dust and gaseous strong acid and strong alkali by laminating a PTFE membrane having a pore size of 1 - 2 탆 on a foam coated surface. However, And the price of the product increases.

According to various embodiments of the present invention, there is provided a method for manufacturing a filter medium for medium to high temperature exhaust gas treatment which is excellent in the function of collecting fine dust / ultrafine dust harmful to human body and having excellent process efficiency and economical efficiency, To obtain a filter body.

The method for producing a filter medium for treating medium to high temperature exhaust gas according to various embodiments of the present invention comprises the steps of preparing a coating solution in which a polytetrafluoroethylene (PTFE) dispersion solution and a thickener are mixed ; And

Applying the coating solution to an inorganic fiber support, and heat treating the coating solution.

The filter medium for treating medium- and high-temperature exhaust gas according to various embodiments of the present invention comprises an inorganic fiber support composed of weft and slope and immersed in PTFE; And a multi-layered porous coating layer formed on the upper surface of the inorganic fiber support and the grooves formed by the weft yarns and the warp yarns.

The method for producing a filter medium for treating medium to high temperature flue gas according to various embodiments of the present invention can simultaneously perform immersion coating and multi-layer porous coating that can replace the conventional foam coating layer in a single process, And is excellent in process efficiency.

The filter medium for treating medium to high temperature flue gas according to various embodiments of the present invention is excellent in the function of collecting fine dust harmful to the human body and economical efficiency.

1 shows a plan view of a filter medium for treating medium and high temperature flue gas according to various embodiments of the present invention.
2 is a cross-sectional view taken along line A-A 'in Fig.
Fig. 3 shows a cross-sectional view of a filtration element for treating medium- and high-temperature flue gas according to another embodiment.
FIG. 4 is a flow chart showing a manufacturing process of a filter medium for treating medium to high temperature flue gas according to various embodiments of the present invention.
5 is a view schematically showing a configuration of a lamination apparatus which can be used in the step of laminating.
Fig. 6 is a photograph of the surface of the filtrate produced according to Example 1. Fig.
Fig. 7 is a photograph of the surface of the filter body produced according to Example 2. Fig.
8 is a cross-sectional photograph of the filtrate produced according to Example 2. Fig.
Fig. 9 is a photograph of the surface of the filter body manufactured according to the comparative example.
10 is a photograph of the PTFE film laminated in Example 1. Fig.
Fig. 11 is a photograph of a filter body laminated with a PTFE membrane in Example 1 subjected to a friction test 100 times. Fig.
12 is a photograph of a PTFE membrane laminated in Example 2. Fig.
Fig. 13 is a photograph of a filter body obtained by laminating a PTFE membrane in Example 2 and subjected to a friction test 100 times. Fig.

Hereinafter, various embodiments of the present document will be described with reference to the accompanying drawings. It is to be understood that the embodiments and terminologies used herein are not intended to limit the invention to the particular embodiments described, but to include various modifications, equivalents, and / or alternatives of the embodiments.

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

Figure 1 shows a plan view of a filter body according to various embodiments of the present invention. 2 is a cross-sectional view taken along line A-A 'in Fig. Fig. 3 shows a cross-sectional view of a filtration body for treating medium- and high-temperature flue gas according to another embodiment.

1 and 2, the filter medium 10 for treating medium to high temperature flue gas according to various embodiments of the present invention includes an inorganic fiber support 100 and a multi-porous coating layer 200 .

The inorganic fiber support 100 may comprise a weft yarn 110 and a warp yarn 120. The inorganic fiber support 100 may include a lattice shape by the weft yarns 110 and the warp yarns 120. A groove 130 may be formed in the inorganic fiber support 100 by the weft yarns 110 and the warp yarns 120.

The inorganic fiber support 100 may be glass fiber. The filtration body 10 according to the present invention can be used for medium to high temperature of 150 to 280 through the inorganic fiber support 100. The inorganic fiber support 100 is immersed in a coating solution in which a PTFE dispersion solution and a thickener are mixed, and the multi-layer porous coating layer 100, which can replace the existing foam coating layer, (multi-porous coating) 200 may be simultaneously formed.

Further, according to another embodiment, the coating liquid may further include an additive. In other words, according to another embodiment, the inorganic fiber support 100 is formed by a multi-layer porous coating layer 200 capable of being immersed and capable of replacing a foam coating layer through a coating liquid in which a PTFE dispersion stock solution, a thickener and an additive are mixed . By including the additive in the coating liquid, the pore size of the multi-layer porous coating layer 200 can be controlled, and the permeability of the filter body can be adjusted according to industrial applications. This will be described in detail later.

The multi-layer porous coating layer 200 may be formed not only inside the inorganic fiber support 100 but also on the grooves 130 of the surface. The multi-layer porous coating layer 200 may also be formed on the upper surface of the inorganic fiber support 100. The multi-layer porous coating layer 200 may be formed to fill the grooves 130 of the inorganic fiber support 100. The multi-layer porous coating layer 200 may be formed by a coating liquid in which a PTFE dispersion stock solution and a thickener are mixed. Alternatively, the multi-layer porous coating layer 200 may be formed by a coating liquid in which a PTFE dispersion stock solution, a thickener, and an additive are mixed.

The inorganic fiber support 100 grooves 130 and the multi-layer porous coating layer 200 formed on the surface may include a first pore of 5 mu m to 15 mu m. The first pores of the multilayer porous coating layer 200 may be formed by evaporation of water, a thickener, and / or an additive contained in the PTFE dispersion stock solution. In addition, it may be formed by fine droplets formed according to the mixing amount of the thickener and the additive. The fine pores can be collected by the surface filtration through the first pores and the air permeability can be improved.

3, the filtration body 20 according to various embodiments may further include a PTFE membrane 300 on the multi-layer porous coating layer 200. The PTFE membrane 300 may be additionally formed depending on the use of the filtration body 20. The PTFE film 300 may be formed by a lamination process. The PTFE membrane 300 may include a second pore smaller than the first pore size of the multi-layer porous coating layer 200. For example, the second pore of the PTFE film 300 may be 0.5 탆 to 2.0 탆. Preferably, the second pore may be between 0.8 μm and 1.2 μm. Therefore, not only fine dust that is harmful to human body but also ultrafine dust can be collected through the filter 20.

Hereinafter, with reference to FIG. 4, a description will be given of a method for producing a filter medium for treating medium- and high-temperature exhaust gas according to various embodiments of the present invention.

As shown in FIG. 4, the method for producing a filter medium for treating medium to high temperature exhaust gas according to various embodiments of the present invention includes preparing a coating solution (S100), coating the coating solution on the inorganic fiber support, (Step S200). The method may further include a step (S300) of laminating the PTFE film on the heat-treated support after the additional heat treatment (S200).

In the step of preparing a coating liquid (S100), a coating liquid in which a PTFE dispersion stock solution and a thickening agent are mixed can be prepared. Alternatively, a coating liquid in which an additive is further mixed may be prepared to further control the pore size.

The PTFE dispersion stock solution to be prepared is a solution containing a fluorine-based heat-resistant water-soluble resin containing fluorine compound (- (CF ₂ CF ₂ ) n- and n is an integer of 10,000 to 100,000) Active agents. For example, the PTFE dispersion stock may comprise 60% PTFE solids, 35% water and 5% surfactant.

The thickener may be sodium alginate or an acrylic thickener. The thickener may be used for the purpose of controlling the viscosity of the coating liquid. Further, depending on the amount of the thickener to be mixed, the coating liquid is immersed in the inorganic fiber support 100 and the degree of coating on the groove 130 and the upper surface due to warp and weft of the inorganic fiber support 100 is determined, May serve as a key factor for determining whether the multilayer porous coating layer 200 is optimized. The thickener may be included in an amount of 0.5% to 3.0% based on the coating solution. When the thickener is contained in an amount of less than 0.5% based on the coating liquid, coating of the multilayer porous coating layer 200 on the upper surface of the inorganic fiber support 100 may not be performed well. In addition, when the thickener is contained in an amount of more than 3.0% based on the coating liquid, the size of the first pores of the multilayer porous coating layer 200 may be too small to reduce the air permeability. Further, the viscosity of the coating liquid can be adjusted to 1,500 mPas to 2,500 mPas by including 0.5% to 3.0% of the thickener relative to the coating liquid.

At this time, the coating liquid may further include an additive, and the additive may include a foam agent and a foam stabilizer. The foaming agent may be an anionic foaming agent including sodium laurate, sodium stearate, or a nonionic foaming agent including a polyethylene glycol type or a polyhydric alcohol type. The size of the foam may vary depending on the mixing amount of the foaming agent and the mixing speed of the coating liquid mixed with the foaming agent. Therefore, the foam formed by the foaming agent is not limited to the extent to which the coating liquid is immersed in the inorganic fiber support 100, the degree to which the inorganic fiber support 100 is coated on the groove 130 and the upper surface And contributes to formation of additional pores of the multi-layer porous coating layer 200. Therefore, the mixing ratio of the foam material can serve as another key factor for determining whether the multi-layer porous coating layer 200 is optimized. The foaming agent may be contained in an amount of 0.01% to 8.0% based on the coating liquid. If the foaming agent is contained in an amount of less than 0.01% based on the coating liquid, the formation of additional pores in the multilayer porous coating layer 200 may be insignificant. In addition, if the foaming agent is contained in excess of 8.0% with respect to the coating liquid, the size of the first pores formed in the multi-layer porous coating layer 200 becomes large, and the fine dust collecting efficiency may deteriorate.

The foam stabilizer may be at least one selected from the group consisting of hydroxyethyl cellulose, carboxyl methyl cellulose and ammonium stearate. Foam stabilizers are additives that determine the lifetime of the foam formed by the foaming agent in the coating fluid. Therefore, the degree to which the coating liquid is immersed in the inorganic fiber support 100 depending on the mixing ratio of the foam stabilizer, the extent to which the inorganic fiber support 100 is coated on the grooves and the upper surface due to weft and warpage, And thus it can serve as another key factor for determining whether to optimize the multilayer porous coating layer. Foam stabilizers may be included from 0.01% to 8% based on the coating solution. When the foam stabilizer is contained in an amount of less than 0.01% based on the coating liquid, additional pore formation may be insufficient in the multilayer porous coating layer 200. If the amount of the foam stabilizer is more than 8.0% with respect to the coating solution, the size of the first pores formed in the multi-layer porous coating layer 200 may be large and the fine dust collecting efficiency may be decreased.

Next, in the heat treatment step (S200), the coating liquid may be coated on the inorganic fiber support 100 and heat-treated. In the heat treatment step S200, the coating liquid is immersed and coated in the inorganic fiber support 100, and the coating liquid is coated on the grooves 130 and the upper surface by the weft 110 and the warp 120 to form a multilayer porous coating layer 200 ) Can be formed. That is, according to the present invention, the coating solution obtained by mixing the PTFE dispersion stock solution with the thickener and / or the additive is applied to the inorganic fiber support 100 and heat-treated to replace the existing foam coating layer A multi-layer porous coating layer 200 can be formed. Therefore, conventionally, the two processes of the dip coating and the foam coating for forming the foam coating layer can be achieved by a single process, so that the efficiency of the process is excellent, and the manufacturing cost and the product cost can be reduced.

In the heat-treating step (S200), the first pores of 5 mu m to 15 mu m may be formed in the multilayer porous coating layer (200). In the heat-treating step (S200), the water, the surfactant, the thickener and / or the additive contained in the PTFE dispersion stock solution are evaporated to form the first pores having a size of 5 mu m to 15 mu m. The heat-treating step (S200) may be carried out at 180 ° C to 330 ° C.

Step S300 of laminating may be performed as required. That is, if dust collecting of ultrafine dust is required according to the use of the filter body 20 as described above, the PTFE membrane may be laminated on the heat-treated support through the lamination step S300. The laminate can be carried out by heat welding or ultrasonic welding.

Hereinafter, with reference to FIG. 5, step S300 of laminating will be described in detail.

5 is a view schematically showing a configuration of a lamination apparatus which can be used in the step of laminating.

5, the PTFE membrane laminate apparatus 400 includes a multi-layer porous coating and a heat treated support feed member 410, a PTFE membrane feed member 415, a tension control member 430, a heating roller member 450, .

The PTFE film laminate apparatus 400 may include a guide roller member 420.

5, the frame to which the rotating shafts of the respective members such as the heat-treated supporting member supplying member 410 are connected is omitted. Such a frame may be suitably installed such that each rotation axis of the elements of the filter body is supported.

The heat treated support supply member 410 supplies a multi-layer porous coating and a heat-treated support 510, wherein the multi-layer porous coating and the heat-treated support 510 may be presented in the form of a wound roll.

The PTFE membrane supply member 415 supplies a PTFE membrane 520 to be coated on the heat-treated support 510 supplied by the heat-treated support member supply member 410, Can be presented in the form of a rolled roll.

The support 500, in which the heat-treated support 510 and the PTFE membrane 520 are combined and the finished PTFE membrane is laminated, is wound on the filter-sheath roller 460.

A plurality of feed rollers are provided between the heat treated support member feed member 410 and the filter member winder 460 and between the PTFE membrane feed member 415 and the filter member winder 460. A first conveying roller 401 for guiding the heat-treated support 510 and a second conveying roller 410 installed at a position where the heat-treated support 510 and the PTFE film 520 start to be joined together, And a third conveying roller 403 capable of pressing the heat treated support 510 and the PTFE film 520 at a lower position than the second conveying roller 402.

The heat-treated support 510 and the PTFE film 520 transferred to the third conveying roller 403 are heated and adhered via the heating roller member 450.

The heating roller member 450 is heated in such a manner that the PTFE layer 520 coated on the heat-treated support 510 adheres to the heat-treated support 510, .

The heating roller member 450 is provided at its lower end with the PTFE layer 520 coated on the heat-treated support member 510 so as to be adhered to the heat- A heat-treated support 510 and a support roller 455 for supporting the PTFE membrane 520 are installed.

The tension adjusting member 430 is capable of adjusting the tension of the heat-treated support 510 supplied by the heat-treated support member supplying member 410. The heat-treated support member supplying member 410 includes a heat- For example, between the first conveying roller 401 and the second conveying roller 402, before the joined support 510 is joined to the PTFE membrane 520.

The tension adjusting member 430 includes a pair of tension adjusting rollers 431 through which the heat treated support body 510 passes, a lifting member 432 for lifting the pair of tension adjusting rollers 431, . The elevating member 432 is provided with a hydraulic motor or the like, and can be raised and lowered with respect to the pedestal 433.

The pair of tension adjusting rollers 431 are elevated by the elevating member 432 so that the tension of the heat treated support body 510 can be adjusted so that it is connected to the heat treated support body 510 The tension of the support 500 laminated with the PTFE film can be adjusted as well and the phenomenon of sagging of the support 500 with the heat treated support 510 and the PTFE film can be prevented, Deterioration of the quality of the support 500 laminated with the PTFE membrane can be prevented.

The guide roller member 420 guides the movement of the heat-treated support body 510 supplied from the heat-treated support body feeding member 410 toward the tension adjusting member 430.

The guide roller member 420 may include a pair of guide rollers. One of the pair of guide rollers may be moved from the heat-treated support member supply member 410 to the first conveying roller 401, The heat-treated support body 510 is deflected in the direction of movement of the heat-treated support body 510 and the other of the pair of guide rollers is deflected again in the moving direction of the heat- (401).

As the guide roller member 420 is installed, the heat treated support body 510 is prevented from sagging, and the heat treated support body 510 and the PTFE film laminated support body 500 can be prevented from crying .

The temperature at which the heat-treated support 510 supplied from the heat-treated supporter supply member 410 laminates the PTFE membrane 520 by heating may be 300 ° C or higher

Hereinafter, preferred embodiments of the present invention will be described. However, the following examples are only a preferred embodiment of the present invention, and the present invention is not limited by the following examples.

Example 1

98% of the PTFE dispersion stock solution and 2% of the acrylic thickener were uniformly mixed to prepare a coating solution.

The prepared coating solution and air were introduced into a foam generator to prepare a foamed coating liquid by a rotating stirrer.

The prepared coating solution was coated on the surface of the inorganic fiber support at a rate of 3 to 6 m / min, followed by a primary heat treatment at a temperature of 180 for 5 minutes, followed by a secondary heat treatment at a temperature of 280 for 5 minutes, A filter body having a multilayer porous coating layer formed on a fibrous support was prepared.

Example 2

A coating liquid was prepared by uniformly mixing 90% of PTFE dispersion stock solution, 2% of acrylic thickener, 6% of ammonium stearate stabilizer, 2% of fatty acid amide foaming agent and the like.

The prepared coating solution and air were introduced into a foam generator to prepare a foamed coating liquid by a rotating stirrer.

The prepared coating solution was coated on the surface of the inorganic fiber support at a rate of 3 to 6 m / min, followed by a primary heat treatment at a temperature of 180 for 5 minutes, followed by a secondary heat treatment at a temperature of 280 for 5 minutes, A filter body having a multilayer porous coating layer formed on a fibrous support was prepared.

Comparative Example

The inorganic fiber support was dip-coated with a diluted solution of PTFE dispersion stock solution.

Thereafter, a coating solution was prepared by uniformly mixing 90% of a diluted PTFE dispersion stock solution, 2% of an acrylic thickener, 6% of an ammonium stearate stabilizer, and 2% of a fatty acid amide foaming agent. The prepared coating solution and air were introduced into a foam generator to prepare a foamed coating liquid by a rotating stirrer.

The prepared coating solution was coated on the surface of the immersion coated inorganic fiber support at a speed of 3 to 6 m / min, followed by a first heat treatment at a temperature of 180 for 5 minutes and a second heat treatment at a temperature of 280 for 5 minutes. To prepare a filter body having a foam coating layer formed on an immersion coated inorganic fiber support.

The pore size, air permeability, filtration efficiency, pressure loss, and weight of the filtrate prepared according to Examples 1, 2, and Comparative Example are shown in Table 1 below. Here, the pore size of the multilayer porous coating layer was measured in Examples 1 and 2, and the pore size of the foam coating layer was compared with that of the multilayer porous coating layer in Comparative Example.

Example 1 Example 2 Comparative Example Pore size (탆) 3.8 8.5 18.8 Air permeability (125 Pa)
(Cm3 / cm2 / sec) 4.74 9.35 8.90 Filtration efficiency
(%) 65.8 45.89 37.38 Pressure loss
(mmAq) 28.5 9.0 9.98 Weight (g / ㎡) 783.08 763.08 797.25 Relative process cost (won) 60 60 100

Referring to Table 1, the pore size of the multi-layer porous coating layer of the filter produced according to Example 1 was 3.8 μm. In addition, the air permeability of the filter produced according to Example 1 was 4.74 cm 3 / cm 2 / sec. The filtration efficiency was 65.8%, which is much higher than that of the comparative example. That is, it can be seen that an adequate level of air permeability can be ensured through the filter body manufactured according to Example 1, and the fine dust can be filtered even without further forming a PTFE membrane. In addition, it can be seen that the process cost is lower by 40% than the comparative example, which is economically advantageous.

In addition, the pore size of the multi-layer porous coating layer of the filter prepared according to Example 2 was 8.5 탆 and the air permeability was 9.35 cm 2 / sec / sec. That is, in Example 2, it can be understood that the pore size is larger than that in Example 1 by controlling the pore size included in the multilayer porous coating layer through the coating solution containing the additive. As a result, the air permeability of the filter body was increased and a small pressure loss could be secured. In addition, the pore size of Example 2 was reduced by 50% or more, but the air permeability was increased and the pressure loss was lowered to show excellent performance as a filter body. In addition, it can be seen that the process cost is lower by 40% than the comparative example, which is economically advantageous.

Fig. 6 is a photograph of the surface of the filtrate produced according to Example 1. Fig. Fig. 7 is a photograph of the surface of the filter body produced according to Example 2. Fig. 8 is a cross-sectional photograph of the filtrate produced according to Example 2. Fig. Fig. 9 is a photograph of the surface of the filter body manufactured according to the comparative example.

Referring to FIG. 6, it can be seen that the size of the pores included in the filtrate prepared according to Example 1 is uniform and small. Referring to FIG. 7, it can be seen that air permeability increases and pressure loss decreases due to coating of porous foam having a large pore size compared to that of Example 1 in the groove formed by warp and weft of the inorganic fiber support. Referring to FIG. 8, it can be seen that the inside of the inorganic fiber support is coated and the immersion coating is well performed. In addition, referring to FIG. 9, it can be seen that, in the case of the comparative example in which a relatively large number of processes are required, the pore size is larger than that in Examples, even when it is visually confirmed.

Meanwhile, a PTFE membrane was further laminated on the multi-layer porous coating layer of the filter fabricated according to Examples 1 and 2, and the dust collection efficiency, pressure loss, and air permeability are shown in Table 2 below.

Air permeability (125 Pa)
(Cm3 / cm2 / sec) Filtration efficiency
(%) Pressure loss
(mmAq) A PTFE film was further formed in Example 1 2.1 99.64 51.0 A PTFE film was further formed in Example 2 2.81 99.775 35.3

The air permeability of the filter obtained by laminating the PTFE membrane to the filter prepared according to Example 1 was 2.1 cm 3 / cm 2 / sec. The filtration efficiency was 99.64% and the pressure loss was 51.0 mmAq. have.

The air permeability of the filter obtained by laminating the PTFE membrane to the filtrate prepared in Example 2 was 2.81 cm 3 / cm 2 / sec, the filtration efficiency was 99.775%, and the pressure loss was 35.3 mmAq. .

10 is a photograph of the PTFE film laminated in Example 1. Fig. Fig. 11 is a photograph of a filter body laminated with a PTFE membrane in Example 1 subjected to a friction test 100 times. Fig. 12 is a photograph of a PTFE membrane laminated in Example 2. Fig. Fig. 13 is a photograph of a filter body obtained by laminating a PTFE membrane in Example 2 and subjected to a friction test 100 times. Fig.

10 and 11, the durability performance of the PTFE membrane-laminated filter body was checked. As a result, no phenomenon was observed that the PTFE film laminated on the surface was peeled or peeled and the durability was degraded.

Similarly, referring to Figs. 12 and 13, as a result of checking the durability performance, there was found no phenomenon that the PTFE film laminated on the surface was peeled or peeled, and the durability was degraded.

The features, structures, effects and the like described in the foregoing embodiments are included in at least one embodiment of the present invention and are not necessarily limited to one embodiment. Further, the features, structures, effects and the like illustrated in the embodiments can be combined and modified by other persons skilled in the art to which the embodiments belong. Therefore, it should be understood that the present invention is not limited to these combinations and modifications.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be construed as limiting the scope of the present invention. It can be seen that various modifications and applications are possible. For example, each component specifically shown in the embodiments can be modified and implemented. It is to be understood that the present invention may be embodied in many other specific forms without departing from the spirit or essential characteristics thereof.

Claims (14)

Preparing a coating liquid in which a polytetrafluoroethylene (PTFE) dispersion solution, a thickener, a foaming agent and a foam stabilizer are mixed; And
Applying the coating liquid to an inorganic fiber support and subjecting the coating liquid to heat treatment,
The thickener is contained in an amount of 0.5% to 3.0% based on the total weight of the coating liquid,
The foaming agent is a fatty acid amide foaming agent and is contained in an amount of 0.01% to 8.0% based on the total weight of the coating liquid,
The foam stabilizer is an ammonium stearate stabilizer and is contained in an amount of 0.01% to 8.0% based on the total weight of the coating liquid,
The viscosity of the coating liquid is 1,500 mPas to 2,500 mPas,
The inorganic fiber support is composed of weft yarns and warp yarns,
In the heat treatment step,
The coating liquid is dip-coated in the inorganic fiber support,
Wherein the coating liquid is coated on the grooves and the upper surface by the weft yarns and the warp yarns to form a multilayer porous coating layer having a pore size of 3.8 μm to 8.5 μm.



delete delete delete delete The method according to claim 1,
After the heat treatment step,
Further comprising laminating a PTFE membrane on the heat-treated support. ≪ RTI ID = 0.0 > 11. < / RTI >
The method according to claim 6,
Wherein the PTFE membrane has pores of 0.8 占 퐉 to 1.2 占 퐉.

The method according to claim 1,
Wherein the thickening agent is an acrylic thickener.
The method according to claim 1,
Wherein the inorganic fiber support is glass fiber.
The method according to claim 1,
Wherein the dispersion stock solution comprises PTFE solids, water and a surfactant.
A filter medium for medium to high temperature flue gas treatment produced by the method according to claim 1,
An inorganic fiber support composed of weft and slope, PTFE dip-coated; And
And a multilayer porous coating layer formed on the upper surface of the inorganic fibrous support and having a pore size of 3.8 to 8.5 mu m.


delete 12. The method of claim 11,
And a PTFE membrane formed on the multi-layer porous coating layer.
12. The method of claim 11,
Wherein the inorganic fiber support is glass fiber.

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