JP2000254456A - Micro filter formed from fiber sheet laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a micro filter which is formed from a fiber-sheet laminate and used for filtering a liquid and also has both sufficient metal-ion capturing capability and sufficient fine-particle capturing capability for the application to semiconductor manufacture and also to provide such a micro filter having excellent chemical resistance. SOLUTION: This micro filter has within it, a laminate formed by laminating at least one fiber sheet layer having metal-ion capturing capability and at least one microporous filtration film layer to each other, wherein the microporous filtration film preferably has 0.02-0.2 μm pore size, the cation exchange capacity of the fiber sheet is preferably >=0.2 meq/g, and each of the microporous filtration film and the base material of the fiber sheet preferably consists of any one of polysulfone, polyethersulfone and polyphenylenesulfone.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a microfiltration filter using a microporous filtration membrane used for filtering a liquid. More specifically, the present invention relates to a microfiltration filter having a metal ion capturing function in addition to a fine particle capturing function used for liquid filtration.

[0002]

2. Description of the Related Art Microporous membranes are used for filtration and sterilization of liquids such as washing water for the electronics industry, chemical liquids for semiconductor manufacturing, medical water, water for the pharmaceutical manufacturing process, food water, and the like. In particular, a microporous filtration membrane having high reliability from the viewpoint of capturing particles has attracted attention and has been widely used. JP-A-62-4991
No. 2 describes a polysulfone microporous membrane into which sulfonated polysulfone is kneaded. JP-A-1-188
No. 538 discloses a fluorinated resin-based cation exchange hollow fiber membrane. Japanese Patent Application Laid-Open No. 2-187136 discloses a method for introducing a chelating group into a polyolefin microporous membrane.

[0003]

In recent years, in the production of semiconductors, in order to obtain ultra-pure water or the like having a very high purity which can be used for the production of semiconductors, metal ions present at a concentration of less than ppm at the same time as capturing fine particles are also removed. The appearance of a filter that can be captured simultaneously is desired. There is a particular need for a microfiltration filter that also has a metal ion-capturing ability, has high resistance to chemicals such as acids, alkalis and oxidizing agents and has a small amount of eluted substances. Conventionally for such purpose,
Attempts have been made to impart an ion exchange function to the microporous membrane itself. However, an attempt to add a metal ion trapping function to such a microporous filtration membrane is difficult to achieve both with the fine particle trapping performance required by the semiconductor manufacturing process, which is becoming more stringent year by year. In addition, there is a limit in providing a sufficient ion exchange capacity, and only the ion exchange capacity is saturated before the filter is clogged, so that ions cannot be removed. An object of the present invention is to provide a microfiltration filter satisfying the above functions at the same time. Specifically, a first object of the present invention is to provide a microfiltration filter for filtering a liquid, which has a sufficient metal ion capturing ability and a fine particle capturing ability for semiconductor manufacturing applications. A second object of the present invention is to provide a microfiltration filter having excellent chemical resistance for filtering a liquid.

[0004]

The present invention has solved the above-mentioned problems by the following means. (1) A microfiltration filter wherein at least one layer of a fiber sheet having a metal ion capturing function and at least one layer of a microporous filtration membrane are laminated and incorporated.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The microporous filtration membrane used in the microfiltration filter of the present invention preferably has an average pore size in the range of 0.01 μm to 10 μm. Preferably,
It is 0.45 μm or more and 3 μm or less, preferably 0.45 μm or less. Alternatively, the thickness is preferably 0.02 μm or more and 0.2 μm or less, most preferably 0.02 μm
It is not less than 0.1 μm. For food filtration applications, 0.4
Those having a size of 5 μm or more and 3 μm or less are often used, and the microporous filtration membrane used in the semiconductor manufacturing process often has a pore size of 0.45 μm or less. In semiconductor applications, those having a thickness of 0.02 μm or more and 0.2 μm or less are particularly suitable.
As the degree of integration of the semiconductor increases, the pore size of the film used preferably decreases, and most preferably 0.0
It is 2 μm or more and 0.1 μm or less. The material of the membrane is polytetrafluoroethylene, which is a heat-resistant high-chemical-resistance, low-elution membrane material, depending on the type of chemical solution used.
There are fluororesins such as polyvinylidene fluoride, and polysulfone-based polymers such as polysulfone, polyethersulfone and polyphenylenesulfone. As a film material having excellent chemical resistance, there is a polyolefin film such as polyethylene or polypropylene.

In a microporous filtration membrane, the larger the ratio of voids to the apparent volume (porosity), the lower the filtration resistance. However, if the porosity increases, the mechanical strength of the film decreases, so the porosity is preferably 50% or more and 88% or less, particularly preferably 57% or more and 85% or less, depending on the film material and the film thickness. Above all, 57% for polyolefin film and polyvinylidene fluoride film
It is preferably at least 70% and at most 75% for a polysulfone-based membrane.
% Or more and 85% or less. As the film thickness increases, the mechanical strength increases, and for the same pore size, the filtration accuracy increases as the film thickness increases. However, on the other hand, processing into a pleated cartridge has the disadvantage that the film area that can be incorporated is reduced.
In the case of a polyolefin or polytetrafluoroethylene film, there is also a problem that it is difficult to control the pore size in the entire thickness direction. Therefore, the thickness is usually 50 μm or more and 200 μm or less, and preferably 60 μm or more and 160 μm or less.
The thickness of the polyolefin film is preferably 65 μm or more and 90 μm or less. 100 μm for polyvinylidene fluoride film
More preferably, it is 135 μm or less. In the case of a polysulfone-based membrane, the thickness is particularly preferably 110 μm or more and 145 μm or less.

[0007] The microporous filtration membrane is stacked together with a fiber sheet having a metal ion capturing function, assembled into a compact cartridge, and subjected to filtration. As the filter cartridge, a pleated cartridge having a structure in which a fiber sheet and a 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. An example of the structure of a pleated cartridge is disclosed in
-235722. An example of the structure of the flat plate laminated cartridge is described in JP-A-63-80815. In the pleated cartridge, the filtration membrane is pleated on both sides of the primary side and the secondary side with a fiber sheet having a role of protecting the filtration membrane and guiding the filtrate, and is stored in the cartridge. On the other hand, in the case of a flat plate laminated cartridge, it is generally unnecessary to overlap the fiber sheet with the filtration membrane. Usually there is nothing on the primary side of the filtration membrane, and on the secondary side of the filtration membrane an injection molded plastic network is often installed to support the membrane. As described above, the fiber sheet is not usually used in the flat sheet laminated cartridge.

However, in the present invention, it is necessary to stack a fiber sheet having a metal ion capturing function on a microporous filtration membrane and to incorporate it into a cartridge. Fiber sheet with metal ion capturing function, even if installed on both sides of the filtration membrane,
Also, it may be installed on only one side. When a fiber sheet containing ion-exchange resin particles is used, a fiber sheet having a metal ion capturing function is preferably used only on the primary side of the filtration membrane in order to prevent the particles from falling off the fiber sheet. In the pleated cartridge as well, the primary fiber sheet that is thicker than the secondary side can be used.Thus, a fiber sheet that is thicker on the primary side and therefore has a larger metal ion capturing capacity is installed, and the secondary side has a metal ion capturing function. By installing a fiber sheet that does not have such a structure, a relatively inexpensive and highly effective configuration can be obtained.

[0009] The metal sheet has a metal ion capturing function,
A non-woven fabric or woven fabric is made using the fiber into which the ion-exchange group is introduced, and is made into a fiber sheet. This can be achieved by forming a woven fabric into a fiber sheet. The method of introducing ion exchange groups into the fiber sheet is as follows:
For example, Japanese Patent Application Laid-Open No. 6-207321 discloses a method in which a fiber having a core component of polypropylene and a sheath component of polyethylene is treated with concentrated sulfuric acid to introduce a sulfonic acid group. A method of grafting a monomer having the compound is described in JP-B-5-67325 and the like. A method of sulfonating a polyolefin nonwoven fabric with a diluted sulfur trioxide gas is disclosed in
No. 2042. Fibers having ion exchange groups can also be obtained by spinning a sulfonated polysulfone resin, or by immersing the fibers in a solution of the sulfonated polysulfone in a polar solvent and drying. A method of converting the ion exchange fiber into a nonwoven fabric is described in, for example, JP-A-9-75646.
A method for holding the ion-exchange resin particles on the nonwoven fabric is described in, for example, Japanese Patent Application Laid-Open No. 1-132043.

[0010] The fiber having an iminodiacetic acid group for forming a metal chelate and the fiber having a sulfonic acid group for exchanging metal ions are, for example, TIN-60 from Toray.
0 and TIN-100. As the metal ion exchange group, a carboxyl group can be used in addition to a sulfonic acid group. As a base material of a fiber sheet having high chemical resistance, polytetrafluoroethylene (PT
FE), perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), ethylene / chlorotrifluoroethylene copolymer (ECTFE) or a fluororesin such as polyvinylidene fluoride; Polysulfone resins and polyolefins are preferred. Further, the material of the fiber sheet base and the material of the microporous filtration membrane are preferably the same or similar materials.

As the fiber sheet, a woven fabric or a nonwoven fabric is used. In particular, a nonwoven fabric is preferable because it easily provides a metal ion capturing function and is inexpensive. A fiber sheet having a fiber diameter of 10 μm or more and 50 μm or less can be used. The thicker the fiber diameter, the stronger and stronger the sheet can be. However, on the other hand, if it is too thick, the sheet will be too coarse, making it difficult to process. Accordingly, fibers having a size of 14 μm or more and 35 μm or less are preferable, and those having a size of 17 μm or more and 25 μm or less are particularly preferable. When the basis weight of the fiber sheet is increased, the ion exchange (ion trapping) capacity is increased and the mechanical strength is increased, which is preferable. However, on the other hand, there is a large obstacle that the membrane area which can be incorporated into the cartridge is reduced. Therefore, the basis weight is 20 to 80 g / m ^2.
Is preferred, and particularly preferably 30 to 60 g / m ² . The larger the ion exchange capacity of the fiber sheet, the more preferable it is because the fiber sheet can be used for a long time without replacing the filter. For semiconductor chemical solution filtration, a fiber sheet having a cation exchange capacity of 0.2 meq / g or more is preferable. Especially 1 meq / g
The above are preferred.

Based on the embodiments of the present invention described above, the present invention and its embodiments are summarized as follows. (1) A microfiltration filter wherein at least one layer of a fiber sheet having a metal ion capturing function and at least one layer of a microporous filtration membrane are laminated and incorporated. (2) The pore size of the microporous filtration membrane is 0.02 μm or more and 0.2
The microfiltration filter according to the above (1), which is not more than μm. (3) The microfiltration filter according to (1) or (2), wherein the porosity of the microporous filtration membrane is from 57% to 85%. (4) The film thickness of the microporous filtration membrane is 60 μm or more and 160 μm.
The microfiltration filter according to any one of (1) to (3), wherein: (5) The fiber sheet according to any one of (1) to (4), wherein the fiber diameter of the fiber sheet is 14 μm or more and 35 μm or less, and the basis weight is 20 g / m ² or more and 80 g / m ² or less.
The microfiltration filter according to the item.

(6) The microfiltration filter according to the above (5), wherein the cation exchange capacity of the fiber sheet is 0.2 meq / g or more. (7) The precision according to any one of (1) to (6), wherein the base of the fiber sheet and the microporous filtration membrane are made of any of polysulfone, polyethersulfone, and polyphenylenesulfone. Filtration filter. (8) The above (1) to (6), wherein the base of the fiber sheet and the microporous filtration membrane are made of polyvinylidene fluoride.
The microfiltration filter according to any one of the above. (9) The microfiltration filter according to any one of (1) to (6), wherein the base of the fiber sheet and the microporous filtration membrane are made of polyolefin. (10) The base of the fiber sheet is made of any of polytetrafluoroethylene, a perfluoroalkylvinyl ether copolymer or a tetrafluoroethylene / hexafluoropropylene copolymer, and the microporous filtration membrane is made of polytetrafluoroethylene. The microfiltration filter according to any one of the above (1) to (6), wherein:

(11) Any one of the above (1) to (10), wherein the fiber sheet has an ion exchange group.
The microfiltration filter according to the item. (12) The microfiltration filter according to any one of (1) to (10), wherein the fiber sheet contains ion exchange resin particles. (13) The microfiltration filter according to any one of (1) to (10), wherein the fiber sheet is made of a fiber having a chelate group. (14) The microfiltration filter according to any one of (1) to (13), wherein the fiber sheet is a nonwoven fabric. (15) The microfiltration filter according to any one of (1) to (13), wherein the chelate group is an iminodiacetic acid group.

(16) The above (1), wherein the ion exchange group is a sulfonic acid group or a carboxyl group.
The microfiltration filter according to 1) or (12). (17) The microfiltration filter according to (11), wherein a fiber sheet containing at least 10% or more of sulfonated polysulfone fibers is used. (18) The microfiltration filter according to any one of (1) to (17), wherein the filtration filter is processed into a pleated cartridge. (19) The microfiltration filter according to any one of (1) to (17), wherein the filtration filter is processed into a flat membrane laminated type cartridge.

[0016]

The present invention will be described in detail with reference to the following examples. However, the present invention is not limited to only this embodiment.

Example 1 A sulfonated polysulfone having about one sulfonic acid group per polysulfone repeating unit is dissolved in N-methylpyrrolidone. After immersing a 30 g / m ² basis weight polypropylene nonwoven fabric (fiber diameter 17 microns) in this solution,
Pulled up and dried. The basis weight of the nonwoven fabric thus formed was 50 g / m ² . The above nonwoven fabric was pleated on both sides of a polysulfone microfilter SE-10 (pore size 0.1 micron, film thickness 135 micron, porosity 78%) manufactured by Fuji Photo Film Co., Ltd., and assembled into a 10-inch size pleated cartridge. When 20 liters of an aqueous solution having a concentration of ferrous chloride of 1000 ppb was circulated through the filter at a flow rate of 10 liters per minute for 10 minutes, the concentration of iron chloride in the solution was reduced to less than 10 ppb. When this filter was installed in an ultrapure water line, a hydrofluoric acid system line, and a hydrochloric acid / hydrogen peroxide system line of a semiconductor manufacturing apparatus, the product yield was improved by 4% to 65% as compared with before the installation.

Example 2 35 parts of cation exchange fiber TIN-100 (fiber diameter 40 microns, ion exchange capacity 3 meq / g) manufactured by Toray Co., Ltd. Non-woven fabric consisting of
² ) on the primary side, then a polyethylene microporous membrane (Akzo Nobel, pore size 0.1 micron, thickness 75 micron, porosity 61%), and on the secondary side of the membrane a polypropylene non-woven fabric (Mitsui Petrochemical (Syntex PK-110) were stacked, pleated, and assembled into a 10-inch pleated cartridge. With this filter, ferrous chloride 1000
When 20 liters of an aqueous solution having a ppb concentration is circulated and filtered at a flow rate of 10 liters per minute for 10 minutes, the concentration of iron chloride in the solution becomes 1
It had fallen to less than 0 ppb.

[0019]

Since the microfiltration filter of the present invention has a high ability to trap metal ions and a high ability to trap fine particles, it can simultaneously remove fine particles and metal ions in ultrapure water or a chemical solution when used for liquid filtration. it can. Therefore, use of this filter makes it possible to easily obtain pure water or ultrapure water for washing water for the electronics industry, chemicals for semiconductor manufacturing, medical water, water for the pharmaceutical manufacturing process, water for food, and the like. In particular, when the present filter is used in a semiconductor manufacturing process, the product yield can be significantly improved.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01D 69/12 B01D 69/12 71/68 71/68 B32B 5/24 101 B32B 5/24 101 7/02 7/02 (72) Inventor Masato Nishimura 2-26-30, Nishiazabu, Minato-ku, Tokyo F-term in Fujisha Shin Film Co., Ltd. 4D006 GA07 HA42 HA71 MA03 MA06 MA22 MA24 MA31 MB11 MB15 MC22 MC23 MC29 MC30 MC61 MC62X MC63 NA01 NA64 PA01 PB02 PB70 PC02 PC11 PC42 4D019 AA03 BA13 BB02 BB03 BB08 BB10 BC04 BD01 CA02 CB03 DA03 4F100 AH04 AK07 AK54B AK55 AK55B AK55K AL07 AR00A AR00C BA02 BA03BA01 J01 DG01 DG01 DG01

Claims (5)

[Claims] 1. A microfiltration filter wherein at least one layer of a fiber sheet having a metal ion capturing function and at least one layer of a microporous filtration membrane are laminated and incorporated. 2. The microfiltration filter according to claim 1, wherein the pore size of the microporous filtration membrane is 0.02 μm or more and 0.2 μm or less. 3. The fiber sheet has a fiber diameter of 14 μm or more.
5 μm or less, with a basis weight of 20 g / m ^{2 to} 80 g / m ^2
The microfiltration filter according to claim 1 or ² , wherein the number is ² or less. 4. The fiber sheet substrate and the microporous filtration membrane,
The microfiltration filter according to any one of claims 1 to 3, comprising one of polysulfone, polyether sulfone, and polyphenylene sulfone. 5. The precision filtration filter according to claim 1, wherein the filtration filter is processed into a pleated cartridge.