JP2006081984A - Method of manufacturing filter for dust precipitator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a filter for dust precipitator consisting of a porous membrane of polytetrafluoroethylene (PTFE) and a felt of of a thermoplastic resin fiber, laminated and integrated, which method does not damage the PTFE membrane nor impair the texture of the filter when the membrane and the felt are bonded to each other. <P>SOLUTION: The method comprises the steps of preparing a felt 1 of a thermoplastic resin fiber with fibers on the surface heated to form pills, as shown in Fig. (A), making the pill 2 flat by hot pressing, as shown in Fig. (B), and adhering the porous membrane 3 of PTFE onto the surface of the felt 1 through pressurization and heating, as shown in Fig. (C). The method permits manufacture of a filter for dust precipitator without damaging the membrane 3 and impairing the texture of the filter in bonding the membrane 3 to the felt 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a filter for a dust collector.

  Conventionally, a bag filter type dust collector has been used for recovering valuable powders in the food field represented by wheat flour and for recovering chemical compounds, cements, metal powders and the like in various fields. In addition, the dust filter from the flue gas generated in blast furnaces, iron making furnaces, incinerators, etc. is a bug filter type that has excellent collection performance instead of an electric dust collector from the viewpoint of pollution prevention, which has recently been particularly problematic. Dust collectors are increasingly used.

  In recent years, in these filters for dust collectors, polytetrafluoroethylene (PTFE) porous membranes have been used as filter materials to satisfy various physical properties such as high collection performance, heat resistance, chemical resistance and low energy detergency. It is used. When this PTFE porous membrane is used as a filter material, it is generally laminated with a breathable support such as felt, woven fabric or canvas. As a result, high collection performance and dust releasability can be realized by the PTFE porous membrane, and sufficient strength can be secured by the breathable support, so that the filter life can be greatly extended.

  Various materials are used for the air-permeable support depending on the operating conditions of the dust collector. For example, when operating at high temperatures, heat-resistant felts and woven fabrics are often used, such as glass fabrics, fluororesin felts, Conex and Nomex felts and fabrics, and polyphenylene sulfide (PPS). ), Various new materials such as P84 have been studied. On the other hand, in fields where the dust collection temperature is not so high, a relatively inexpensive polyester felt or the like is often used instead of an expensive heat-resistant material.

  In these dust collector filters, adhesion between the PTFE porous membrane and the air-permeable support is an important point. As the bonding method, when a felt made of thermoplastic resin fiber is used for the breathable support, there are many methods in which the surface of the felt is melted by heat and bonded to the PTFE porous membrane by thermal welding. . In the case of bonding with heat, a method has also been used in which the fibers on the felt surface are heated (burned) to form pills and are easily bonded to the PTFE porous membrane (see Patent Document 1). According to this method, a phenomenon that the melting point of the pill formed by heating is lowered is observed, so that the PTFE porous film and the felt can be bonded at a temperature lower than the melting point of the thermoplastic resin.

However, it is difficult to control the heat treatment of the fibers on the felt surface. If the heating is insufficient, the PTFE porous membrane and the felt may not adhere to each other by heat. In some cases, the PTFE porous membrane is damaged during bonding, or the surface of the filter after bonding becomes hard and the texture is impaired.
Japanese Patent Publication No. 4-17685

  Accordingly, an object of the present invention is to provide a PTFE porous membrane when adhering the PTFE porous membrane and the felt in a method for manufacturing a filter for a dust collector in which a PTFE porous membrane and a felt made of thermoplastic resin fibers are laminated and integrated. It is an object of the present invention to provide a production method that does not damage the filter and does not impair the texture of the filter.

  In order to achieve the above object, the production method of the present invention is a method of producing a filter for a dust collector in which a PTFE porous membrane and a felt made of thermoplastic resin fiber are laminated and integrated. This is a manufacturing method in which a felt in which pills are formed by heating fibers is prepared, the pills are flattened by hot pressing, and then the PTFE porous film is adhered to the surface of the felt by pressure heating.

  According to the present invention, a felt in which pills are formed by heating the fibers on the surface is prepared, and the pills are flattened by hot pressing to reduce irregularities on the felt surface and then bonded to the porous PTFE membrane. Therefore, the PTFE porous membrane is not damaged and the texture of the filter is not impaired. As a result, for example, when dust adhering to the filter is removed by reverse cleaning or the like, cracks are less likely to occur, and the durability of the filter can be improved. Further, by making the pills flat, the adhesion area between the felt and the PTFE porous membrane is increased, and the effect of improving the adhesiveness is also obtained.

  In the manufacturing method of the present invention, the adhesion by the pressure heating includes adhesion by lamination.

  In the production method of the present invention, the thermoplastic resin is preferably aromatic polyester, polyphenylene sulfide (PPS), or polypropylene. The aromatic polyester is not particularly limited, and examples thereof include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyarylate resin. The above thermoplastic resins are representative examples of those suitably used for dust collection, and as other thermoplastic resins, for example, polyethersulfone, polysulfone, polyethylene, polyvinyl chloride, polyurethane, styrene elastomer ( For example, styrene-butadiene, styrene-isoprene, etc.), polymethylpentene, polyetherimide, polyacetal, polyphenylene ether, polycarbonate, polymethacrylic ester resin, and the like can be used. These may be used alone, or may be used in combination of two or more kinds of typical thermoplastic resins that are suitably used.

In the production method of the present invention, the amount of air measured by the Frazier method based on the JIS L 1096 6.27.1 A method of the PTFE porous membrane is 4 cm ³ / It is preferably cm ² · sec or more. The upper limit is not particularly limited, but is, for example, 30 cm ³ / cm ² · sec. Accordingly, the amount of air measured by the Frazier method based on the JIS L 1096 6.27.1 A method of the PTFE porous membrane is, for example, in the range of 4 to ³⁰ cm ³ / cm ² · sec, preferably 8 to The range is 20 cm ³ / cm ² · sec. In the present invention, the amount of air measured by the Frazier method based on the JIS L 1096 6.27.1 A method of the PTFE porous membrane means the air permeability of the PTFE porous membrane.

  Below, an example of the process of the manufacturing method of this invention is demonstrated using FIG.

  First, as shown in FIG. 1 (A), a felt 1 made of thermoplastic resin fiber in which a fiber on the surface is heated to form a pill is prepared.

  The thermoplastic resin is as described above.

  As the felt 1, a commercially available one can be used, or it can be made in-house.

  In the case of using a commercially available felt for the felt 1, for example, Ambitic brand name FT0507D, which is an aromatic polyester fiber felt, Kyuha Tech brand name PSG50BP, which is a PPS fiber felt, and a polypropylene fiber felt. The product name FLT450EX manufactured by Nippon Felt Co., Ltd. can be used.

The felt 1 can be made in-house by, for example, baking fibers on the surface of the felt 1 with a flame such as a gas burner to form a hair ball. The conditions vary depending on the type of the thermoplastic resin. For example, the surface condition can be adjusted by changing the flame strength of the gas burner, the distance from the flame to the felt 1, the speed at which the felt 1 is moved, and the like. . The conditions are not particularly limited, but the diameter of the hair balls 2 is, for example, in the range of 0.2 to 0.8 mm, and the distribution density of the hair balls 2 on the surface of the felt 1 is, for example, 20 It is preferable to set it to ˜45 / cm ² .

  The thickness of the felt 1 is not particularly limited, but is, for example, in the range of 0.3 to 3.0 mm, preferably in the range of 0.5 to 2.5 mm, and more preferably in the range of 0.8 to The range is 2.0 mm.

  Next, as shown in FIG. 1 (B), the hair ball 2 is flattened by hot pressing to reduce irregularities on the surface of the felt 1.

  The method of the heat press is not particularly limited, and for example, it is possible to make the pill 2 flat with a flat plate press, but in consideration of workability, the felt 1 is passed between hot rolls. A pressing method is preferred. The pressure in the hot press is, for example, in the range of 0.1 to 10 MPa, preferably in the range of 0.2 to 2 MPa, and more preferably in the range of 0.3 to 1 MPa. Moreover, when performing the said hot press by letting a hot roll pass, the speed | rate is the range of 1-50 m / min, for example, Preferably, it is the range of 2-30 m / min, More preferably 5 to 20 m / min.

  The temperature condition of the hot press varies depending on the type of the thermoplastic resin. For example, a PET fiber felt generally has a melting point of 250 to 260 ° C., depending on the degree of crystallization. As described in the aforementioned Patent Document 1, it is known that the pill 2 has a lower melting point. The inventor has found that in the PET fiber felt, the melting point of the pill 2 is lowered by about 20 to 50 ° C. Furthermore, it has also been found that the temperature at which the pill 2 is softened during hot pressing is 20 to 50 ° C. lower than the melting point of the pill 2. Therefore, in the PET fiber felt, the temperature of the hot press is, for example, 150 ° C., preferably 180 ° C. as the lower limit, and the upper limit is, for example, 220 ° C., preferably 210 ° C. Therefore, in the PET fiber felt, the temperature of the hot press is, for example, in the range of 150 to 220 ° C, and preferably in the range of 180 to 210 ° C. By setting the temperature within the above range, the temperature is too low to soften the pill 2 and it is difficult to reduce irregularities on the surface of the felt 1 even when pressure is applied. It can prevent that the surface of 1 melt | dissolves and a texture is impaired. For example, at 150 ° C., the pill 2 can be easily flattened by applying pressure. For example, at 220 ° C., the surface of the felt 1 is not melted and the texture is not impaired.

  Moreover, in the felt made from PPS fiber, unlike the said felt made from PET fiber, melting | fusing point exists in 270-280 degreeC, the fall of melting | fusing point of the said pill 2 is small, and is about 10-30 degreeC at most. Moreover, since the material is difficult to soften, the temperature at which the pill 2 is softened is not significantly different from the melting point of the pill 2. Therefore, in the felt made of PPS fiber, the temperature of the hot press is, for example, 240 ° C., preferably 250 ° C. as a lower limit, and the upper limit is, for example, 270 ° C. Therefore, in the PPS fiber felt, the temperature of the hot press is, for example, in the range of 240 to 270 ° C.

  And in the felt made from polypropylene fiber which is a material which is easy to soften, for example, the fuzz ball 2 can be sufficiently flattened in the range of 40 to 50 ° C. Therefore, in the felt made of polypropylene fiber, the temperature of the hot press is not particularly limited, but is, for example, in the range of 40 to 50 ° C.

  As described above, the temperature condition for making the pill 2 flat by hot pressing is completely different depending on the type of the thermoplastic resin. As described above, the thermoplastic resin is a representative example of those suitably used for dust collection, and the thermoplastic resin other than these is also pilled by hot press under a temperature condition where the pill 2 is softened. 2 can be flattened.

  The degree to which the pills 2 are flattened during the hot pressing is preferably, for example, such that the surface with irregularities due to the ball-like portion 2 is smooth by touch, and is not particularly limited. For example, it is preferable that the height of the pill 2 is about 10 to 20% before hot pressing.

  Next, as shown in FIG. 1C, a PTFE porous membrane 3 is bonded to the surface of the felt 1 by pressure heating.

  In the PTFE porous membrane 3 used in the present invention, the air permeability is as described above. In addition, the thickness is not particularly limited, but is, for example, in the range of 3 to 30 μm, and the average pore diameter is not particularly limited, but is, for example, in the range of 0.8 to 2.0 μm, and the porosity is Although not particularly limited, for example, it is in the range of 85 to 97%.

  The PTFE porous membrane 3 can be produced, for example, by making a non-fired PTFE sheet porous by stretching. Hereinafter, an example of this manufacturing method will be briefly described. The PTFE sheet is obtained by mixing unsintered PTFE powder (preferably PTFE fine powder) and a liquid lubricant, and molding the mixture into a sheet by at least one means selected from extrusion and rolling. The PTFE powder is not particularly limited, and a commercially available product can be used. The liquid lubricant is not particularly limited as long as it can wet the PTFE powder and can be removed later. Hydrocarbon oil such as liquid paraffin and naphtha, aromatic hydrocarbons such as toluene and xylene, alcohol Solvents of ketones, ketones and esters can be used. These may be used singly or in combination of two or more. The amount of the liquid lubricant added is, for example, in the range of 5 to 50 parts by weight with respect to 100 parts by weight of the PTFE powder. The thickness of the PTFE sheet is, for example, in the range of 0.1 to 0.7 mm.

  The liquid lubricant contained in the PTFE sheet is preferably removed by a heating method or an extraction method before the subsequent stretching step. The solvent used in the extraction method is not particularly limited, and examples thereof include normal decane, dodecane, naphtha, kerosene, and sumoyl.

  Next, the PTFE sheet is stretched. The PTFE sheet is made porous by stretching at a temperature not higher than the melting point (327 ° C.) of PTFE by uniaxial stretching or biaxial stretching. For example, in the longitudinal direction of the PTFE sheet, it is stretched at a temperature of 240 to 320 ° C. so that the length is in the range of 5 to 30 times, and then the length in the width direction of the sheet-like molded body. Is stretched at a temperature of 25 to 200 [deg.] C. so as to be in the range of 10 to 50 times. After the stretching, the stretched state is maintained and heated to a temperature equal to or higher than the melting point (327 ° C.) of PTFE and baked to improve the mechanical strength and increase the dimensional stability. In addition, this baking process is arbitrary. As described above, a PTFE porous membrane can be produced.

  In addition, the PTFE porous membrane in this invention is not restrict | limited to the above-mentioned manufacturing method, You may manufacture with another manufacturing method and may use a commercially available PTFE porous membrane.

  The PTFE porous membrane 3 is bonded to the surface of the felt 1 by pressure heating at a temperature not higher than the melting point of the felt 1 and not lower than the melting point of the pill 2. In the adhesion by the pressure heating, the pressure is, for example, in the range of 0.2 to 5 MPa, preferably in the range of 0.3 to 2 MPa, and more preferably in the range of 0.4 to 0.6 MPa. Further, when the adhesion by pressure heating is performed by lamination, the speed is, for example, in the range of 0.5 to 10 m / min, preferably in the range of 0.8 to 6 m / min, more preferably 1 to 1. The range is 4 m / min.

  Next, examples of the present invention will be described together with comparative examples. However, the present invention is not limited by the following examples and comparative examples. In addition, the measuring method of each characteristic in an Example and a comparative example is as showing below.

(1) Breathability The breathability of the PTFE porous membrane was measured in accordance with the Frazier method based on the 6.27.1 A method of JIS L 1096.

(2) Repeat Bending Test An MIT testing machine based on JIS R 3420 was used for this test. Cut a test piece 15 mm wide and about 110 mm long from the filter for the dust collector, attach it to the grip of the tester, and repeatedly fold the test piece 5000 times under the conditions of 1 kg load and 175 times / min. The occurrence of cracks was visually observed.

(3) Collection efficiency The collection efficiency of the dust collector filter was measured by the method specified in JIS K 0901 using dioctyl phthalate (DOP) particles specified in JIS Z 8901.

(4) Adhesiveness between PTFE porous membrane and felt Pressure of air until the PTFE porous membrane is destroyed by blowing air with an air gun having a 2 mmφ nozzle at a distance of 1 cm from the membrane surface of the dust collector filter. MPa).

A dust collector filter was manufactured by the process shown in FIG. For the felt 1 shown in FIG. 1 (A), an aromatic polyester fiber felt (trade name FT0507D, manufactured by Amvic Co., Ltd., thickness 1.8 mm) in which pills are formed by heating the fibers on the surface was used. The pill 2 on the surface of the felt 1 was in a state of softening around 210 ° C. The felt 1 was pressed with a hot roll under the conditions of a temperature of 220 ° C., a pressure of 0.4 MPa, and a speed of 10 m / min to obtain a felt 1 having a smooth surface with the hand shown in FIG. As shown in FIG. 1 (C), PTFE porous membrane 3 (trade name NTF5110 manufactured by Nitto Denko Corporation, thickness 10 μm, average pore diameter 1.5 μm, porosity 91%, air permeability 10 cm ³ / cm ² · sec. ) And 230 ° C., 0.5 MPa, 4 m / min.

  A dust collector filter was manufactured by the process shown in FIG. For the felt 1 shown in FIG. 1 (A), a polypropylene fiber felt (trade name FLT450EX manufactured by Nippon Felt Co., Ltd., thickness 2.0 mm) in which pills are formed by heating the surface fibers was used. The melting point of the felt 1 was 170 ° C., but the pill 2 on the surface was softened at a temperature 40 ° C. lower than that. This was pressed with a hot roll under conditions of a temperature of 130 ° C., a pressure of 0.6 MPa, and a speed of 5 m / min to obtain a felt 1 having a smooth surface with the hand shown in FIG. As shown in FIG. 1 (C), this was adhered to the same PTFE porous membrane 3 as used in Example 1 by lamination under the conditions of 150 ° C., 0.4 MPa, 3 m / min to obtain a filter for a dust collector. It was.

  A dust collector filter was manufactured by the process shown in FIG. For the felt 1 shown in FIG. 1 (A), a PPS fiber felt (trade name PSG50BP, thickness 1.7 mm, manufactured by Kureha Tech Co., Ltd.) in which a fiber on the surface was heated to form pills was used. The pill 2 on the surface of the felt 1 was in a state of softening around 255 ° C. This was pressed with a hot roll under the conditions of a temperature of 250 ° C., a pressure of 0.5 MPa, and a speed of 10 m / min to obtain a felt 1 having a smooth surface with the hand shown in FIG. As shown in FIG. 1 (C), this was adhered to the same PTFE porous membrane 3 used in Example 1 by lamination under the conditions of 265 ° C., 0.5 MPa, 4 m / min, and a filter for a dust collector was obtained. It was.

(Comparative Example 1)
As a felt, an aromatic polyester fiber felt (trade name FT0507D, manufactured by Amvic Co., Ltd., thickness 1.8 mm) in which a fiber on the surface described in Example 1 is heated to form a hairball is used. Using the same PTFE porous membrane as used in Example 1, it was adhered by lamination under the conditions of 230 ° C., 0.5 MPa, 4 m / min to obtain a dust collector filter.

(Comparative Example 2)
As a felt, a PPS fiber felt (product name: PSG50BP, thickness 1.7 mm, manufactured by Kureha Tech Co., Ltd.) in which a fiber on the surface described in Example 3 is heated to form a hairball is used. The sample was used as it was, and adhered to the same PTFE porous membrane as used in Example 1 by lamination under the conditions of 265 ° C., 0.5 MPa, and 4 m / min to obtain a filter for a dust collector.

  Table 1 below shows the measurement results of the characteristics of the dust collector filters obtained in Examples 1 to 3 and Comparative Examples 1 and 2.

(Table 1)
Repeated bending test Collection efficiency (%) Adhesiveness
Example 1 No crack 98.9 No break even at 0.6 MPa Example 2 No crack 97.5 No break even at 0.6 MPa Example 3 No crack 99.2 No break even at 0.6 MPa Comparative Example 1 With crack 89.4 Fracture comparison at 0.4 MPa 2 Crack present 88.7 Fracture at 0.4 MPa

  As shown in Table 1 above, the dust collector filters obtained in Examples 1 to 3 had higher collection efficiency than the dust collector filters obtained in Comparative Examples 1 and 2, and bonded the porous PTFE membrane and the felt. In doing so, it was found that the PTFE porous membrane was not damaged. Moreover, it was found that the dust collector filters obtained in Examples 1 to 3 were free from cracks due to repeated bending tests, and the durability was improved as compared with the dust collector filters obtained in Comparative Examples 1 and 2. . And in the filter for dust collectors obtained in Examples 1-3, it turned out that the adhesiveness of a PTFE porous film and a felt is improving rather than the filter for dust collectors obtained in Comparative Examples 1 and 2. FIG.

  According to the production method of the present invention, when the PTFE porous membrane and the felt are bonded, the filter for the dust collector can be produced without damaging the PTFE porous membrane and without damaging the texture of the filter. The dust collector filter manufactured by the manufacturing method of the present invention can be used for, for example, a bag filter type dust collector.

It is process drawing which shows an example of the process of the manufacturing method of this invention.

Explanation of symbols

1 Felt 2 Hairball 3 PTFE porous membrane

Claims (3)

A method of manufacturing a filter for a dust collector in which a polytetrafluoroethylene (PTFE) porous membrane and a felt made of thermoplastic resin fiber are laminated and integrated, and as the felt, surface fibers are heated to form pills. A manufacturing method in which the felt is prepared, the hair ball is flattened by hot pressing, and then the porous PTFE membrane is bonded to the surface of the felt by pressure heating. The method according to claim 1, wherein the thermoplastic resin is at least one selected from the group consisting of aromatic polyester, polyphenylene sulfide, and polypropylene. ^3. The production method according to claim 1, wherein the PTFE porous membrane has an air amount of 4 cm ³ / cm ² · sec or more measured by a fragile method based on JIS L 1096 6.27.1 A method.

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