JP4437933B2 - Cartridge filter for microfiltration - Google Patents

Description

  The present invention relates to a microfiltration cartridge filter used for removing fine particles in a liquid by filtration, and more particularly to a microfiltration cartridge filter used in the semiconductor industry.

  The cartridge filter is compact and has a long filtration life, so it can produce ultrapure water for cleaning semiconductor substrates, remove impurities from the etchant during semiconductor substrate production, soft drinks, mineral water, and alcoholic beverages. It is used in various fields, such as removal of impurities and bacteria from water, and filtration of fine particles in city water used in vending machines and water purifiers. Particularly in recent years, with the increase in the size of glass substrates for thin film displays, it has become necessary to use a large amount of cleaning pure water and chemicals. It is desired to make the length even longer.

  As these cartridge filters, in order to increase the filtration area, the filtration membrane is folded into a pleated shape, which is combined into a chrysanthemum-like cylindrical shape and sealed at both ends of the cylinder, and the donut-shaped filtration membrane is a disc shape. A unit-stacked type that is affixed to both sides of a filtration membrane support structure and laminated in a large number is used as a typical one, but especially in applications that require a cartridge filter with a long filtration life, the filtration membrane area is Many pleated cartridge filters are used.

  There are materials such as cellulose acetate, polysulfone, polyamide, and polytetrafluoroethylene as the microfiltration membranes that make up the cartridge filter. In the semiconductor industry, membranes made of polytetrafluoroethylene with excellent chemical resistance are used frequently. .

  However, these microfiltration membranes are weak in the strength of the membrane itself, so that when the membrane is melt-molded with the end cap, the membrane itself is easily buckled by molding pressure, and molding failure is likely to occur. Since it is difficult for the strength of itself to withstand the filtration pressure, the microfiltration membrane is supported from both sides by a mesh-like support such as a nonwoven fabric or a net. In order to extend the filtration life of such a microfiltration membrane Increasing the membrane area is difficult because it is supported by the mesh support.

  For this reason, the outer diameter of the cartridge filter is increased to φ83 mm, which is larger than the conventional φ70 mm, thereby increasing the filter filtration area and extending the filter life. However, the cartridge filter is not compatible with the existing housing, There is a problem in that it is an obstacle to downsizing, and a new housing has to be installed, which is also an obstacle to the economy.

  Therefore, as a cartridge filter having an outer diameter of 70 mm that is compatible with existing housings, a thin knitted fabric having a wire diameter of 50 to 150 μm and a thickness of 100 to 300 μm is used as a support to reduce the filtration area. Some increase the life of filtration by increasing it (Patent Document 1).

  In addition, by increasing the pitch of the pleats and setting a laid over state, the gap between adjacent pleats is reduced, the filtration area is increased, and the filtration life is extended (Patent Document 2).

Japanese Patent No. 2814599 Japanese National Patent Publication No. 8-50312

  However, the support made of a thin knitted fabric with a thickness of 100 to 300 μm as in Patent Document 1 is a knitted fabric made of warp and weft itself, and is rigid in itself, so that it melts with the end cap. Buckling due to molding pressure at the time of molding can be prevented, but on the contrary, since it is rigid, when the filter medium is folded into a pleat shape, the filter medium cannot be adhered and folded, and the filter medium spreads, and the conventional cartridge Only about 1.1 times the filtration area of the filter can be increased.

  Also, in the cartridge filter in which the pitch between the pleats is increased and the gap between adjacent pleats is reduced by increasing the pleat pitch as in Patent Document 2, the filtration area is about 1.1 times that of the conventional cartridge filter. However, it is not possible to increase the filtration life sufficiently.

  Accordingly, an object of the present invention is to provide a cartridge filter for microfiltration having a long filtration life while maintaining a filtration accuracy, which is a cartridge filter having an outer diameter of 70 mm that is compatible with an existing housing. .

  In order to achieve the above object, the present invention comprises a tubular core having a large number of liquid passage holes on the peripheral surface, a microfiltration membrane and a pair of supports disposed on both sides of the tubular core. A filter medium provided on the peripheral surface and pleated in a state where the microfiltration membrane and a pair of supports are overlapped, a cylindrical protector provided so as to cover the periphery of the filter medium, and these tubular core and filter medium And an end cap provided at both ends in the axial direction of the protector and sealing the microfiltration membrane in a liquid-tight manner by heat fusion with the microfiltration membrane, and the support for the microfiltration cartridge filter having an outer diameter of 70 mm The body is constituted by a net made of biaxially stretched resin, the height of the pleats constituting the filter medium is 14 to 16 mm, and the number of pleats is 200 to 330. .

  As described above, in the microfiltration cartridge filter according to the present invention, the support is constituted by a net made of biaxially stretched resin, and extends in the radial direction of the microfiltration cartridge filter, that is, the height of the pleats constituting the filter medium. While increasing the length to 14 to 16 mm and increasing the number of peaks to 200 to 330, which is about 1.5 to 2 times that of the prior art, it can be folded in close contact during pleating and has a sufficient filtration area. In addition, the buckling of the filter medium during melt molding with the end cap can be prevented, so that the filtration life of the microfiltration cartridge filter can be extended.

  As described above, according to the cartridge filter for microfiltration according to the present invention, although it is a cartridge filter having an outer diameter of 70 mm that can be attached to an existing housing, the microfiltration has an excellent filtration life of about 2 to 5 times the conventional one. A cartridge filter can be provided.

  Next, an embodiment of a cartridge filter for microfiltration according to the present invention will be described with reference to the drawings. FIG. 1 is a partially cut perspective view of a cartridge filter for microfiltration according to the present embodiment. The cartridge filter 1 for microfiltration according to the present embodiment is composed of a tubular core 2 having a large number of liquid passage holes on the peripheral surface, a microfiltration membrane 4 and a pair of supports 3 and 5 disposed on both sides thereof. The filter medium 8 is provided on the peripheral surface of the tubular core 2 and is pleated in a state where the microfiltration membrane 4 and the pair of supports 3 and 5 are overlapped with each other, and the filter medium 8 is provided so as to cover the periphery of the filter medium 8. A cylindrical protector 6, an end cap 7 that is provided at both axial ends of the tubular core 2, the filter medium 8, and the protector 6, and seals the microfiltration membrane 4 in a liquid-tight manner by thermal fusion with the microfiltration membrane 4; It has.

  The thickness of the microfiltration membrane 4 is preferably 15 to 60 μm, and more preferably 20 to 45 μm. In addition, when the thin microfiltration membrane 4 is used, a plurality of sheets can be used in a stacked manner, and the thickness of the plurality of stacked sheets is preferably 15 to 60 μm, and more preferably 20 to 45 μm. If the microfiltration membrane 4 is thinner than this range, the rigidity is insufficient and it becomes difficult to perform pleating and welding with the end cap, and even a slight damage makes it easy to open a large hole, resulting in low reliability in preventing fine particles. On the other hand, if it is thicker than this range, the resistance increases and a sufficient treatment flow rate cannot be obtained. The microfiltration membrane 4 is preferably composed of polytetrafluoroethylene having excellent chemical resistance.

  The support bodies 3 and 5 are high in terms of pleating workability, sealing performance of the terminal when the pleating is made into a cylindrical shape, melting adhesion to end caps at both ends of the cylinder, and elution into water / chemicals. It is preferable to use density polyethylene or polypropylene as a material. In the case of polypropylene, the thickness is preferably 70 to 150 μm, and in the case of high density polyethylene, the thickness is preferably 150 to 250 μm. If the supports 3 and 5 are too thin, the rigidity is insufficient when pleating, and stable pleats cannot be produced. Conversely, if the support is thicker than this range, the number of pleats that can be put into the protector 6 And the filtration area cannot be increased. It is preferable that the support bodies 3 and 5 are comprised from the net | network which consists of biaxially-stretched polypropylene or biaxially-stretched high-density polyethylene, and when comprised from a knitted fabric by comprising such biaxially-stretched resin. Compared to the above, the rigidity is small, and it can be bent in close contact during pleating, and the filter medium does not spread, so the filtration area can be increased sufficiently. A biaxially stretched resin refers to a resin obtained by a biaxially stretched construction method.

  Further, the hole area ratio of the supports 3 and 5 is preferably 30% or more. When the hole area ratio is less than 30%, the channel resistance increases, and even if the number of pleats is increased, the cartridge can be used as a cartridge. The processing flow rate does not increase.

  Furthermore, the tensile strength of the supports 3 and 5 is preferably 500 g / 15 mm or more, and more preferably 600 g / 15 mm or more in order to withstand pleating and actual use. Furthermore, it is preferable to use the supports 3 and 5 that do not contain various additives in order to reduce as much as possible the eluate caused by chemicals such as water, acid, and alkali organic solvents. The supports 3 and 5 are arranged on both sides of the microfiltration membrane 4, that is, the primary side and the secondary side. However, as long as the above specifications are satisfied, those having different properties such as thickness may be used.

The filter medium 8 composed of the microfiltration membrane 4 and the supports 3 and 5 is pleated, and then melted and bonded at the start and end to form a cylindrical shape. Then, the tubular core is disposed inside and inserted into the protector 6. . Further, the end cap 7 is melt-molded at both ends, but the rigidity of the filter medium 8 itself composed of the microfiltration membrane 4 and the supports 3 and 5 is weak, and the filter medium is easily buckled during melt molding. It is necessary to increase the buckling strength as an intimate pleated filter medium. Further, when the number of pleat peaks exceeds 330 , the degree of adhesion becomes too high, and a dead space is generated in the microfiltration membrane 4. In particular, when biaxially stretched polypropylene is used as the supports 3 and 5, the number of pleats is preferably 240 to 330, and when biaxially stretched high-density polyethylene is used, the number of pleats is 200 to 250. It is preferable that In addition, if the height of the pleats constituting the filter medium is 16 mm or more, insufficient pressure strength at the time of filtration due to insufficient axial strength or molding failure at the end molding occurs, and if it is 14 mm or less. The filtration area cannot be sufficiently secured, and the filtration life of the microfiltration cartridge filter cannot be extended. Therefore, the thickness is preferably 14 to 16 mm.

  The end cap 7 is preferably made of the same material as the supports 3 and 5, for example, polypropylene or high density polyethylene. As described above, the end cap 7 is made of the same material as the supports 3 and 5, so that the supports 3 and 5 are melted together with the end cap 7 when the end cap 7 is thermally fused to the microfiltration membrane 4. Then, even if the thickness of the microfiltration membrane 4 is as thin as 15 to 60 μm, for example, the end cap 7 has both ends of the microfiltration membrane 4 together with the supports 3 and 5. It can be tightly sealed.

  Next, Example 1 of a cartridge filter for microfiltration according to the present invention was produced. The cartridge filter for microfiltration according to Example 1 uses a microfiltration membrane 4 made of polytetrafluoroethylene having a thickness of 42 μm, an average pore diameter of 0.34 μm, and a nominal pore diameter of 0.20 μm. As a net, a net made of biaxially stretched polyethylene and having a thickness of 230 μm and an open area ratio of 34% was used. The microfiltration membrane 4 and the supports 3 and 5 are overlapped to form a three-layer structure, and the three-layer filter medium 8 is fold-folded to be 15 mm / mountain, so that the number of peaks is 230. A filter medium was prepared.

  The protector 6, the tubular core 2, and the end cap 7 are made of polyethylene. The tubular core 2 has an inner diameter of 27 mm, an outer diameter of 36 mm, and a height of 241 mm. The protector 6 has an inner diameter of 66 mm, an outer diameter of 70 mm, and a height of 237 mm. These members were used.

At the time of assembling, a cylindrical pleated filter medium was first obtained by fusing 230 pleated filter media with a heat at about 190 ° C. to form a cylindrical shape. The tubular core 2 was disposed inside the tubular pleated filter medium, incorporated into the protector 6, and the end surface of the pleated filter medium protruding from the protector 6 was cut to produce a cartridge filter processing intermediate. An end cap 7 heated and melted at a surface temperature of 230 to 300 ° C. is pressed and immersed at both ends of the processing intermediate with a pressing pressure of 0.4 MPa, so that the length is 10 inches (25.4 cm) and the outer diameter is 70 mm. A cartridge filter was obtained. The membrane area of the obtained cartridge filter was 1.6 m ² .

Next, Example 2 of the cartridge filter for microfiltration according to the present invention was produced. The cartridge filter for microfiltration according to Example 2 uses a microfiltration membrane 4 made of hydrophilic polytetrafluoroethylene having a thickness of 40 μm, an average pore diameter of 0.40 μm, and a nominal pore diameter of 0.20 μm. 5, a net made of biaxially oriented polypropylene and having a thickness of 110 μm and a porosity of 36% was used. By pleating the microfiltration membrane 4 and the supports 3 and 5 in a three-layered state, 300 pleated filter media were produced. A cartridge filter was produced in the same manner as in Example 1 except that the protector 6, the tubular core 2, and the end cap 7 were made of polypropylene. The membrane area of the produced cartridge filter was 2.1 m ² .

Comparative Example 1

Next, Comparative Example 1 was created. In the microfiltration cartridge filter according to Comparative Example 1, the microfiltration membrane 4 is the same membrane as in Example 1, and the supports 3 and 5 are made of polyethylene, with a monofilament wire diameter of 86 μm and an aperture ratio of 34%. A net of some knitted fabric was used. The microfiltration membrane and the support are stacked in three layers, and the three-layer filter medium is fold-folded to the same 15 mm / peak as in Example 1 to produce a pleated filter medium. A cartridge filter was produced by assembling in the same manner. The pleated filter medium was low in adhesion and could only incorporate 170 peaks, so the membrane area of the cartridge filter was 1.2 m ² .

Comparative Example 2

As Comparative Example 2, a cartridge filter was produced in the same manner as in Example 1 except that the height of the pleats was 11 mm. The pleated filter media could incorporate 240 piles and the membrane area of the cartridge filter was 1.24 m ² .

Comparative Example 3

As Comparative Example 3, a commercially available polytetrafluoroethylene membrane cartridge filter (manufactured by Company A) having a membrane area of 1.1 m ² and a nominal pore diameter of 0.20 μm was prepared.

Comparative Example 4

As Comparative Example 4, a commercially available hydrophilic polytetrafluoroethylene membrane cartridge filter (manufactured by B company) having a membrane area of 1.1 m ² , a nominal pore size of 0.20 μm, and an outer diameter of φ83 mm was prepared.

Experimental Examples Performance comparison tests were performed on the cartridge filters according to Examples 1 and 2 and Comparative Examples 1 to 4. In the performance comparison test, water at a flow rate of 10 L / min in the city water supply is filtered through each cartridge filter, and the difference between the inlet pressure and the outlet pressure at the time of the filtration is recorded. This was done by examining the amount. The performance comparison test was performed by combining the same type of membrane, that is, Example 1 and Comparative Examples 1 to 3, and Example 2 and Comparative Example 4. The test results are shown in Tables 1 and 2.

  From the results of the test, it was confirmed that the cartridge filter for microfiltration of the present invention has a filtration capacity that is equal to or greater than the filtration area ratio as compared with each comparative example.

1 is a partially cut perspective view showing an embodiment of a cartridge filter for microfiltration according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cartridge filter 2 Tubular core 3, 5 Support body 4 Microfiltration membrane 6 Protector 7 End cap 8 Filter material

Claims (3)

A tubular core having a large number of liquid passage holes on the peripheral surface;
A filter medium comprising a microfiltration membrane and a pair of supports disposed on both sides thereof, and provided on the peripheral surface of the tubular core, and pleated in a state where the microfiltration membrane and the pair of supports are overlapped When,
A cylindrical protector provided to cover the periphery of the filter medium;
End caps that are provided at both ends in the axial direction of the tubular core, the filter medium, and the protector, and seal the microfiltration membrane in a liquid-tight manner by thermal fusion with the microfiltration membrane;
In the cartridge filter for microfiltration with an outer diameter of φ70 mm equipped with
The microfiltration membrane has a thickness of 15 to 60 μm before pleating,
The support is constituted by a net made of biaxially stretched polypropylene having a thickness of 70 to 150 μm before pleating or biaxially stretched high-density polyethylene having a thickness of 150 to 250 μm before pleating.
A cartridge filter for microfiltration, wherein a height of pleats constituting the filter medium is 14 to 16 mm, and a number of pleats is 200 to 330. Before Symbol support, open porosity of 30% or more, a tensile microfiltration cartridge filter according to claim 1, wherein the intensity is equal to or is 500 gf / 15 mm or more. It said end cap and said support according to claim 1 or 2 Symbol placement microfiltration cartridge filter characterized by being composed of the same material.

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