JP2002066268A - Chemical-resistant filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a filter cartridge which has resistance to high temperature filtration at 60-80 deg.C of isopropanol frequently used in a semiconductor manufacturing process and in which incineration disposal of used filter is easily performed. SOLUTION: A precision filtration filter cartridge characterized by a constitution wherein, in a pleat type filter cartridge prepared by a constitution wherein the whole of microporous filter membranes, membrane supports, a core, an outer peripheral cover and end plates constituting the filter cartridge is made of a polysulfone based polymer and the filter membranes with the membrane supports are pleat-processed under a condition that the microporous filter membranes are placed among a plurality of membrane supports and the mating surfaces of sheets rounded into a cylindrical shape are liquid-tightly sealed, and in addition, both ends of this cylinder are liquid-tightly sealed with the end plates and only both end parts of the cylindrical pleat filtration membranes are laminated with a polysulfone based polymer film with a thickness of at most 30 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cartridge filter using a microporous filtration membrane. The present invention particularly relates to a cartridge filter using a microporous microfiltration membrane having excellent chemical resistance and hydrophilicity, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, in the manufacture of semiconductors, there has been a demand for a filter for filtration which has high resistance to chemicals such as organic solvents, acids, alkalis and oxidizing agents and has a small amount of eluted substances. At present, a microporous microfiltration membrane made of polytetrafluoroethylene (PTFE) is used for filtering such a chemical solution, and a filtration filter using a fluoropolymer is used for other filter components. ing. However, the PTFE filtration membrane has a very strong hydrophobicity, and even if it is wetted with isopropanol at the beginning of the filtration, a slight amount of air bubbles causes air lock to prevent filtration. Further, in the disposal of used fluorine-based polymer filters, there is a problem that toxic gas is generated by incineration.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an acid, an alkali, an oxidizing agent or an alcohol frequently used in a semiconductor manufacturing process. To provide a filter cartridge that is resistant to high-temperature filtration of a mixed solution of (1) and isopropanol at 60 ° C to 80 ° C and that can easily incinerate a used filter.

A microfiltration filter cartridge characterized in that the microporous filtration membrane, the membrane support, the core, the outer peripheral cover and the end plate which constitute the filter cartridge are all made of a polysulfone-based polymer. A problem arises in that a seal failure occurs at both end seal portions of the filter cartridge, and it has been difficult to put it into practical use. As the filter cartridge, a pleated cartridge having a structure in which a filtration membrane and a membrane support for protecting the filtration membrane are folded in a pleated shape, and a flat plate laminated cartridge formed by laminating a plurality of flat plate filtration units are known. The invention is useful for pleated cartridge type filters. Examples of the structure of the pleated cartridge are disclosed in, for example, JP-A-4-235722 and JP-A-10-66842. The structure of the flat sheet laminated cartridge is disclosed in, for example, JP-A-63-80815, JP-A-56-129016, and JP-A-58-98111.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a microfiltration filter cartridge in which all of a microporous filtration membrane, a membrane support, a core, an outer peripheral cover, and an end plate constituting a filter cartridge are made of a polysulfone-based polymer. The problem was solved by a pleated-type microfiltration filter cartridge characterized by laminating a polysulfone-based polymer film on both ends of a filtration membrane. Hereinafter, the present invention will be described in detail.

[0006]

FIG. 1 is an exploded view showing the general structure of a general pleated microfiltration cartridge filter. The microfiltration membrane 3 is folded while being sandwiched by two membrane supports 2 and 4 and wound around a core 5 having many liquid collecting ports. An outer peripheral cover 1 is provided on the outside to protect the microfiltration membrane.
Microfiltration membranes are sealed at both ends of the cylinder by end plates 6a and 6b. The end plate is in contact with a seal portion of a filter housing (not shown) via a gasket 7. There is also a type in which an O-ring is provided on one end plate portion and is in contact with the filter housing via the O-ring. It is not essential that the gasket or O-ring be made of a polysulfone-based material because it can be easily attached and detached when it is disposed of. The filtered liquid is collected from a liquid collecting port of the core, and is discharged from a fluid outlet 8 provided at an end of the cylinder through a hollow portion of the core. Fluid outlets are provided at both ends of the cylinder, and fluid outlets are provided at only one end and one end is closed. FIG.
FIG. 1 is a diagram schematically showing a cross-sectional structure near an end plate, showing an embodiment of the present invention. 12, 14 in the figure
Is a membrane support, 13 is a filtration membrane, 17 is an end plate,
Reference numerals 15a and 15b denote polysulfone-based polymer films laminated on the end plates of the filtration membrane 13.

As the microfiltration membrane 3 or 13, a hydrophilic membrane made of aromatic polyallyl ether sulfone (hereinafter referred to as polysulfone-based polymer) is preferable because of its excellent heat resistance and chemical resistance. . Formulas 1 to 3 show typical chemical structures of the polysulfone-based polymer. The polymer shown in Chemical Formula 1 is sold by Amoco under the trade name Udel Polysulfone. On the other hand, a polyether sulfone represented by Chemical Formula 2 is sold by Sumitomo Chemical under the trade name of Sumika Excel PES. In the present invention, use of polyethersulfone is particularly preferred because of its particularly excellent chemical resistance. The method for producing a hydrophilic microporous microfiltration membrane using a polysulfone-based polymer as a material is described in JP-A-56-154051,
JP-A-56-86941, JP-A-56-12640, JP-A-62-27006
And JP-A Nos. 62-258707 and 63-141610.

[0008]

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[0009]

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[0010]

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The pore size of the filtration membrane is usually from 0.02 μm to 5 μm, but a pore size of 0.02 μm to 0.45 μm is preferably used in semiconductor manufacturing applications. preferable. The properties of such a membrane can be expressed as a water bubble point value of 0.3 MPa or more as measured by the method of ASTM F316, and can be expressed as 0.1 to 1 MPa at an ethanol bubble point. Particularly preferably, the ethanol bubble point is 0.3 to 0.7 MPa. The larger the ratio of pores to the apparent volume of the membrane is, the smaller the filtration resistance is. On the other hand, if there are too many holes, the film strength is reduced and the film is easily broken. Therefore, a preferable porosity of the filtration membrane is 40%.
From 90%. Particularly preferred is 57% to 85%
It is. The film thickness is usually 30 μm to 220 μm. If the thickness is too large, the film area that can be incorporated into the cartridge decreases, while if it is too thin, the film strength decreases. Therefore, a particularly preferable film thickness is from 60 μm to 160 μm. A more preferred thickness is from 90 μm to 140 μm. The material to be laminated on the filtration membrane is also a polysulfone-based polymer. It is particularly preferable to use the same material as the filtration membrane because the range of chemical resistance can be widened. Lamination can be performed, for example, by stacking a thin film of an adhesive in advance on the end of the filtration membrane. When laminating using an adhesive, the selection of a solvent is important. Usually, a solvent that does not dissolve the filtration membrane or has low solubility in the filtration membrane and is soluble in the end plate is selected. The solvent may be a single chemical species or a mixed solvent. When two or more solvents are mixed, at least the solvent having the higher boiling point does not have solubility in the filtration membrane. More preferably, the polymer is dissolved in the solvent adhesive in an amount of about 1% to 7%. The polymer to be dissolved is preferably of the same material as the laminated film. The thickness of the film to be laminated is preferably from 8 μm to 30 μm. If it is too thin, the ability to reinforce the membrane is insufficient, and if it is too thick, the pleating process becomes difficult, and the membrane area that can be incorporated in the filter cartridge decreases. The most preferred range is 15
To 25 μm. The width of the film to be laminated can be 2 mm to 30 mm. If the width is too narrow, lamination becomes difficult. If the width is too wide, the effective membrane area for filtration is reduced. Therefore, the preferred laminate film width is from 6 mm to 20 mm, particularly preferably from 9 mm to 16 mm. Lamination may be performed on only one side of the filtration membrane or on both sides. When it is performed on only one side, it may be performed on either the primary side or the secondary side of the filtration membrane.

The microfiltration membrane 3 is sandwiched between the membrane supports 2 and 4 and is usually pleated using a reciprocating pleating machine. In the conventional pleat cartridge,
As the primary side membrane support 2 and the secondary side membrane support 4, a non-woven fabric, a woven fabric, a net or the like is used. The role of the membrane support is to reinforce the filtration membrane against fluctuations in filtration pressure, to permeate the liquid from the liquid supply side to the filtration side, and to introduce liquid into the back of the pleated pleats in a direction parallel to the filtration membrane. I also carry. Therefore, it is necessary to have appropriate liquid permeability and physical strength enough to protect the filtration membrane. Any sheet material having such a function can be used, but in the past, in most cases, a nonwoven fabric of polyester or polypropylene has been used because of its low cost and excellent performance. The membrane support that can be used in the present invention needs to be a material that has both heat resistance and chemical resistance in addition to the above general functions, and that can be incinerated. Therefore, a material having the same heat resistance and chemical resistance as or higher than that of the filtration membrane 3 is preferable. Therefore, a polysulfone-based polymer is preferable because it has both heat resistance and chemical resistance. However, it is difficult to obtain a non-woven fabric of a polysulfone-based polymer.

In the present invention, polysulfone is used as a membrane support.
Can use microporous membranes made of base polymer
You. Its manufacturing method is basically the microporous microfiltration membrane referred to in the present invention.
Is the same as Water bubble in microporous membrane used for membrane support
The point is preferably between 20 and 150 kPa, from 40
100 kPa is more preferable. Hanging on membrane support surface
The water permeability in the direct direction is the water flow rate when a differential pressure of 0.1 MPa is applied
Is 150ml / cm per minute ^TwoMore preferably, 200ml / cm^Twothat's all
Is more preferable. Mullen rupture strength of membrane support
The degree is preferably 80 kPa or more, if it is 120 kPa or more
Still preferred. Add grooves and / or protrusions to the membrane support
The method is not particularly limited. Many projections formed on the surface
Between a metal roll and a backup roll with a flat surface
Embossed calender with continuous compression treatment with microporous membrane in between
-The purpose can be achieved by processing. Hard backup
When using Prowl, only grooves are formed in the membrane support
You. With soft backup rolls the opposite of the groove
Protrusions are simultaneously formed on the surface. The hole is crushed in the groove part
Since water permeability disappears, the groove formation area is the entire support film
Is preferably not more than half.

The grooves and / or projections provided on the membrane support may be provided on only one side of the support membrane or on both sides. Depth of unevenness given to membrane support is 5μm
From 0.25mm is available. Preferably from 20 μm to 0.1
It is 5 mm, particularly preferably 50 μm to 0.1 mm. The width of the grooves and peaks (hereinafter abbreviated as grooves) provided to the membrane support can be 5 μm to 1 mm. Preferably 20 μm
To 0.4 mm, particularly preferably 50 μm to 0.2 mm. The width and depth of the groove to be formed need not be constant everywhere. When grooves are formed, mutually independent circular or polygonal shapes are not preferable. A structure in which the grooves communicate and the liquid can flow in the plane direction is preferable. It is even more preferred if it is constituted by a number of longitudinal and transverse grooves which intersect each other. The distance between the grooves is preferably 4 mm or less even in a wide place, and 0.1 mm or less.
It is more preferable that the distance be 15 mm or more and 2 mm or less. The thickness of the microporous membrane used for the membrane support is preferably from 60 μm to 300 μm, particularly preferably from 100 μm to 220 μm. If it is too thin, the function of reinforcing the filtration membrane is inferior, and if it is too thick, the membrane area that can be incorporated into the cartridge is reduced, which is inconvenient.

In the present invention, it is also possible to use a membrane support in which holes are formed in the polysulfone-based polymer film and irregularities are formed on the front and back surfaces of the film by, for example, embossing. The method of making a hole in the film is not particularly limited. For example, there are a method using a punch, a method using a sharp needle, a method using a laser, and a method using a water jet. The size of the hole can be a diameter or a size corresponding to a circle, an ellipse or a rectangle having a diameter or a side of 10 μm to 5 mm. Preferred hole sizes are 30 μm to 1.5 mm, particularly preferably 60 μm.
μm to 0.5 mm. The ratio of the hole area to the membrane support area can be used in the range of 10 to 90%. If the hole area ratio is too small, the filtration resistance will be too large, while if the hole area ratio is too large, the mechanical strength will be reduced and the microporous filtration membrane will not be reinforced. When drilling a large hole, a large hole area ratio is required, and when drilling a small hole, a relatively small hole area ratio is sufficient.

The depth or height of the unevenness provided to the film can be from 5 μm to 1 mm. Preferably 20 μm
To 0.4 mm, particularly preferably 50 μm to 0.2 mm. The height and depth of the unevenness to be formed need not be constant everywhere. The recesses formed in the film are not preferably circular, polygonal or other shapes independent of each other. A structure is required in which the concave portions communicate with each other so that the liquid can flow in the surface direction in the formed groove. It is even more preferred if it is constituted by a number of longitudinal and transverse grooves which intersect each other. The width of the groove is preferably in the range of 5 to 1000 μm, more preferably in the range of 20 to 400 μm, and particularly preferably in the range of 50 to 200 μm. The distance between the grooves is preferably 4 mm or less even at a wide place, and more preferably 0.15 mm or more and 2 mm or less.
Ideally, all previously drilled holes have grooves. Originally, the pattern of the convex portions formed on the opposite surface of the groove as the groove is formed may be either continuous and continuous with each other or may be isolated from each other. However, when embossing is performed, the convex portion and the concave portion have a front-to-back relationship. Therefore, a convex portion isolated when viewed from one surface forms a discontinuous isolated concave portion when viewed from the opposite surface, which is not preferable for use in the present invention. The thickness of the film used for the membrane support is from 25 μm to 1
It is preferably 25 μm, particularly preferably 50 μm to 100 μm. If it is too thin, the function of reinforcing the filtration membrane is inferior, and if it is too thick, pleating becomes difficult. A third membrane support that can be used is a net. The net is formed by spinning a monofilament having a diameter of 50 μm to 300 μm and knitting it. The monofilament used for the net is thicker and stronger than the non-woven yarn, so that it can be spun relatively easily. The smaller the yarn diameter, the thinner the finished net and the easier it is to pleate. On the other hand, if it is thin, spinning becomes difficult, and the strength of the finished net also decreases. Therefore, the preferred filament shape is 80 to 160 μm. The microporous filtration membrane is sandwiched on both sides by a membrane support, and pleated in this state by a usual method. At least one, and in some cases, a plurality of membranes can be used. At least one membrane support can be used on one side, and in some cases more than one membrane support can be used.

The pleated body is obtained by inserting the core 5 inside the thus-formed cylindrical filter medium and covering it with the outer peripheral cover 1. In the end sealing step of bonding the both ends of the pleated body to the end plate 6 in a liquid-tight manner, a method based on heat melting is preferably used. In the hot melting method, only the sealing surface of the end plate is brought into contact with a hot plate, or only the surface is heated and melted by irradiating an infrared heater, and one end surface of the pleated body is pressed against the melting surface of the plate to perform adhesive sealing. At this time, if the film is not laminated, the weak filter membrane will not easily penetrate into the dissolved polymer on the plate, causing leakage due to poor sealing, or breaking the seal at low filtration pressure due to insufficient sealing strength. . Membrane support 2,
4. The materials used for the core 5, the outer peripheral cover 1 and the end plate 6 must also have heat resistance and chemical resistance and must be easily burnable. Therefore, a polysulfone-based polymer material is preferable, and polyethersulfone is particularly preferable because it is excellent in heat resistance and chemical resistance and relatively inexpensive. The materials of the members need not necessarily be the same as long as they can be bonded to each other, but the same materials are more preferable because they have good adhesiveness. When all the materials are unified with polyether sulfone, the range of chemical resistance is widened, and it is particularly preferable in terms of adhesive sealability.

[0018]

The microfiltration filter cartridge of the present invention is resistant to acids, alkali oxidizing agents, and high-temperature alcohols, has a sufficient seal strength for practical use, and easily burns out used filter cartridges. Can be processed.

[Brief description of the drawings]

FIG. 1 is a developed view showing a structure of a general pleated filter cartridge.

FIG. 2 is a diagram illustrating a structure near an end seal portion according to the embodiment of the present invention.

[Explanation of reference numerals] Peripheral cover 2. 2. Primary membrane support Microfiltration membrane 4. 4. Secondary membrane support Cores 6a, 6b. End plate 7. Gasket 8. Liquid outlet 12. 12. membrane support Microfiltration membrane 14. Membrane support 15a. Laminated film 15b. Laminated film 17. end plate

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D006 GA07 HA74 HA91 JA02A JA03A JA03B JA03C JA18C JA22Z JA27C JA30C JB07 MA03 MA06 MA22 MA24 MA31 MB09 MB11 MB12 MB13 MB15 MB16 MB20 MC62 MC63X NA45 PA01 PB12 PB13 PB20 PC01

Claims (1)

[Claims] 1. A microporous filtration membrane, a membrane support, a core, an outer peripheral cover and an end plate which constitute a filter cartridge are all made of a polysulfone-based polymer, and a microporous filtration membrane is provided between a plurality of membrane supports. The filter membrane is fold-folded together with the membrane support in a state where it is sandwiched, the seam of the sheet rolled into a cylindrical shape is sealed liquid-tight, and both ends of the cylinder are also sealed liquid-tight with end plates. A pleated filter cartridge, wherein a polysulfone-based polymer film having a thickness of 30 μm or less is laminated only on both ends of a cylindrical pleated filtration membrane.