WO2002038255A1

WO2002038255A1 - Antistatic membrane module

Info

Publication number: WO2002038255A1
Application number: PCT/JP2001/009922
Authority: WO
Inventors: Shinsuke Takegami; Takushi Yokota
Original assignee: Japan Gore-Tex Inc.
Priority date: 2000-11-13
Filing date: 2001-11-13
Publication date: 2002-05-16
Also published as: JP5025041B2; AU2002212766A1; JP2002143649A

Abstract

An antistatic membrane module comprising a housing made of a fluororesin and a porous fluororesin membrane disposed in the housing, wherein static buildup is less apt to occur and the separation membrane can be prevented from being damaged by electrical discharge. The antistatic membrane module, which comprises a housing made of a fluororesin and a porous fluororesin membrane disposed therein, is characterized in that all or part of the outer surface of the housing is coated with an antistatic material having a conductive layer.

Description

Specification

Antistatic membrane module Technical field

The present invention relates to a fluororesin membrane module in which a fluororesin porous membrane is housed in a fluororesin housing, and a method for transporting the membrane module. Background art

In recent years, ultrapure water has been found to have the function of removing impurities such as fine particles and metal elements on the surface of silicon wafers by adding a small amount of gas components, such as hydrogen, ozone, carbon dioxide, and chemicals. Was. It has gradually been found that cleaning with this functional cleaning water has a cleaning effect equal to or better than conventional cleaning using high-concentration chemicals. For example, ultrapure water to which a trace amount of ozone is added acts as an oxidizing agent, and decomposes and removes residual organic substances such as surfactants on the surface of the silicon wafer to form a uniform and flat oxide film. In the liquid crystal display manufacturing process, it is also used for cleaning glass substrates, cleaning after etching, and cleaning after rubbing.

However, it is very difficult to efficiently dissolve gas such as ozone in a liquid such as ultrapure water while controlling the amount of dissolution. Conventionally, as a method of dissolving a gas in a liquid, there are a method of publishing a gas in a liquid and a method of mechanically mixing after publishing, but the gas dissolution efficiency is poor and the amount of gas dissolved is controlled. Is also difficult. Also, in this method, fine bubbles are generated in the liquid and adhere to the surface of a silicon wafer or the like, and it is difficult to perform uniform cleaning. In addition, gases that were not dissolved during bubbling are likely to be released out of the system, which is unsuitable for dissolving harmful gases such as ozone.

On the other hand, a method in which a gas such as ozone is efficiently dissolved in a liquid such as ultrapure water using a porous membrane that allows gas to permeate without permeating the liquid has replaced the above-described coupling method. It is becoming mainstream. In this method, gas flows into one side of the separation membrane and liquid flows into the other side, so that the gas dissolves in the liquid through the membrane. Concentration control is also easy. In addition, fine bubbles are not generated in the liquid, and uniform cleaning of the substrate is possible. Such porous membranes for dissolving gas have been proposed in Japanese Patent Application Laid-Open Nos. 7-213880, 11-1227087, and the like. Each of these separation membranes uses a tubular porous polytetrafluoroethylene (porous PTFE) membrane. Japanese Patent Application Laid-Open No. 11-179167 discloses a spiral porous PT FE membrane. Some have also been proposed.

The ozone gas dissolving module generally uses a porous PTFE membrane as the separation membrane and polyvinylidene fluoride (PVDF) as the housing material. The reason is that ozone is a very strong oxidizing agent, and organic materials having insufficient ozone resistance, such as butyl chloride and polypropylene, are easily deteriorated and cannot be used.

However, it has been found that the ozone gas dissolution module using a PVDF housing has insufficient ozone gas durability. For this reason, PTF E materials with better ozone resistance have been used as housing materials instead of PVDF housings.

However, the present inventors have found that the ozone gas dissolving module using PTFE as a housing material tends to charge static electricity more easily than a conventional PVDF housing.If the housing is excessively charged, a discharge phenomenon occurs, It was found that when the discharge amount was large, a pinhole was formed in the separation membrane, and there was a risk that the liquid to be treated leaked to the gas side.

A method for preventing static charge of a fluororesin is disclosed in JP-A-5-166594, JP-A-7-24898 and the like. Japanese Patent Application Laid-Open No. 5-166594 proposes a method for removing static electricity by bringing a fluorinated resin having a roughened surface into contact with a polar solvent such as alcohol, but an ozone gas dissolving module is used. Since the semiconductor manufacturing process is located in a clean clean room and extremely small amounts of impurities are not allowed, this method cannot be used.

Japanese Patent Application Laid-Open No. 7-24898 proposes an antistatic resin tube in which a belt made of a thermoplastic fluororesin mixed with carbon powder is integrally attached to an inner surface of a tube made of a thermoplastic fluororesin. However, when extremely oxidizing gas such as ozone is used, or when extremely corrosive liquid is processed, it is durable. Not available for gender. Also, in the semiconductor manufacturing process, ultrapure water is used in various cleaning processes, and a very small amount of impurities is not allowed. Therefore, there is a problem that this method cannot be adopted.

The present invention relates to a membrane module in which a fluororesin porous membrane is housed in a fluororesin housing, in which static electricity is unlikely to be charged, and an antistatic membrane module capable of preventing damage to a separation membrane due to a discharge phenomenon. An object of the present invention is to provide a method for transporting the membrane module. Disclosure of the invention

The present inventors have conducted intensive studies to solve the above problems, and as a result, completed the present invention.

That is, according to the present invention, there is provided a membrane module having a structure in which a fluororesin porous membrane is housed in a fluororesin housing, which has a conductive layer on the entire outer surface or a part of the outer surface of the housing. An antistatic membrane module characterized by being coated with a material is provided.

Further, according to the present invention, there is provided a method for transporting a membrane module in which a fluororesin porous membrane is housed in a fluororesin housing, wherein a polar solvent is stored in a liquid passage to be treated of the membrane module. There is provided a method for transporting a membrane module, which comprises transporting the membrane module. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram showing an antistatic membrane module of the present invention.

FIG. 2 is an explanatory sectional view of the antistatic membrane module of the present invention.

FIG. 3 is an explanatory sectional view showing a section of the antistatic material of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

As shown in FIG. 1, in the antistatic membrane module of the present invention, the entire surface or a part of the outer surface of the fluororesin housing 1 is coated with the antistatic material 2. Some antistatic materials may be provided with tabs 3 for attaching a ground wire and grounding. FIG. 2 is an explanatory sectional view of the antistatic membrane module shown in FIG.

Inside the fluororesin housing 1, a tube bundle 8 in which a plurality of fluororesin porous tubes are bundled is housed. The tube bundle 8 is connected to the housing cap 10 by a tube bundle connection member 9. This membrane module is applied as a gas dissolving module for dissolving gas components in a liquid to be treated or as a degassing module for removing gas components contained in a liquid to be treated.

To dissolve gas components in the liquid to be treated using the antistatic membrane module shown in Fig. 1, the liquid to be treated is supplied to the antistatic membrane module from the liquid inlet 4 and the tube connecting member 9a Through the inside of the fluororesin porous tube forming the tube bundle 8, and through the tube connecting member 9 b to be discharged from the liquid outlet 5.

On the other hand, a supply gas such as ozone gas is introduced from the gas supply port 6 into the chamber 11. The gas introduced into the chamber is discharged from the gas discharge port 7 after coming into contact with the outer surface of the fluororesin porous tube. When the supply gas comes into contact with the outer surface of the fluororesin porous tube in the chamber, the supply gas permeates the tube wall of the fluororesin porous tube and enters the untreated liquid flowing through the fluororesin porous tube. On the other hand, in order to apply the antistatic membrane module shown in Figs. 1 and 2 as a degassing module, a liquid to be treated in which gas components are dissolved is supplied to the membrane module from the liquid inlet 4 to form a tube bundle 8 Flow through the inside of the fluororesin porous tube to be discharged from the liquid outlet 5. A carrier gas, for example, nitrogen gas or air is supplied from the gas supply port 6 and discharged from the gas discharge port 7.

By the above operation, the gas component dissolved in the liquid to be processed passes through the tube wall and moves into the carrier gas.

When degassing gas components dissolved in the liquid to be treated using the antistatic membrane module shown in Fig. 1 and Fig. 2, the gas supply port 6 is closed and the gas discharge port 7 is vacuum pumped. And make the inside of chamber 1 1 vacuum (reduced pressure).

By the above-mentioned operation, the gas component dissolved in the liquid to be treated is reduced to a vacuum chamber.

Degassed within 1 1

The fluororesin used as the housing material has a carbon-fluorine bond. Resins such as polytetrafluoroethylene (PTFE), copolymers of tetrafluoroethylene and ethylenically unsaturated monomers (eg, tetrafluoroethylene-hexafluoropropylene copolymer ( FEP), ethylene-tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene-perfluoroalkyl butyl ether copolymer (PFA), etc., polychlorinated trifluoroethylene (PCTFE), polyvinylidene fluoride ( PVDF) and polybutyl fluoride (PVF) can be used. Among them, PTFE and a copolymer of PTFE and an ethylenically unsaturated monomer are particularly preferably used because of their excellent ozone resistance. . In this case, PFA, FEP and the like are preferably used as the ethylenically unsaturated monomer copolymerizable with PTFE.

The housing 1 only needs to be able to store the fluororesin porous membrane in an airtight manner, and the shape is not particularly limited.If the chamber 11 for storing the fluororesin porous membrane is made cylindrical, various standardized pipes can be used. This is preferable because the cost can be reduced. For the joining between the housing cap and the chamber, a method such as welding, bonding, or screwing is appropriately used.

As the fluororesin porous membrane, porous membranes such as PTFE, FEP, ETFE, PFA, PCT FE, PVDF, and PVF can be used.In particular, expanded porous PTFE obtained by stretching a molded product of PTFE ( e PTFE) membrane is particularly preferably used because it has a small amount of eluted substances, has excellent chemical resistance, heat resistance, durability against ozone gas, and has high gas permeability. As these porous membranes, membranes formed into a tube shape or a flat film shape can be used.

Here, e PTFE refers to a paste that is obtained by mixing fine powder of PTFE with a molding aid, stretching it after or without removing the molding aid, and firing it if necessary. When formed by uniaxial stretching like a tube, the fibrils are oriented in the stretching direction and have a fibrous structure with voids between fibrils. In the case of biaxial stretching, as in the case of film, the fibrils spread radially and have a spider web-like fibrous structure with many holes defined by nodes and fibrils. The e-PTFE membrane having such a configuration allows gas to pass through pores. However, liquid cannot pass through. Therefore, for example, in the case of a tubular membrane, gas can enter the tube while the liquid is flowing through the ePTFE tube, and can be dissolved in the liquid.

As the tubular ePTFE membrane, for example, a tubular membrane proposed in JP-A-4-131443, JP-A-7-213880, and JP-A-11-227087 can be used. The ozone gas dissolving module cuts the tubular ePTFE membrane to an appropriate length, and bundles it into a bundle of many pieces, and ends the honeycomb with a heat-meltable fluororesin such as FEP, PFA, ETFE, etc. It is melt-formed into a shape. Attach both ends of the formed honeycomb shape to a fluororesin housing with connectors to manufacture a tube-type membrane module.

As the flat membrane-like ePTFE, for example, a flat membrane proposed in Japanese Patent Application Laid-Open No. 11-179167 can be used. The flat membrane is made into a bag shape, and both ends are bonded with the heat-fusible fluororesin to produce a spiral membrane module.

Various types of separation membrane modules have been proposed, such as pleated, hollow fiber, and flat and frame types, in addition to tube and spiral types, depending on the membrane storage method. The present invention can be applied to any of them.

Antistatic material 2 is composed of a conductive layer alone, an adhesive layer or an adhesive layer laminated on a conductive layer, a plastic film laminated on a conductive layer surface, and a plastic film laminated on a conductive layer surface. A material that can transfer charged charges to the fluororesin housing, such as a material in which an adhesive layer or an adhesive layer is stacked on the conductive layer opposite to the plastic film, can be appropriately used.

The conductive layer includes, at least in part, a sheet or foil made of a conductive metal, a sheet into which a conductive powder such as a conductive metal or carbon is kneaded, a conductive plastic sheet, or a conductive fiber. Conductive materials such as woven fabrics, knits, meshes and nets can be used as appropriate, but aluminum foil is inexpensive and has excellent conductivity and durability, and is particularly preferably used.

An adhesive or a pressure-sensitive adhesive may be used to fix the conductive layer and the housing. In this case, the material and thickness of the adhesive layer or pressure-sensitive adhesive layer What is necessary is just to determine suitably within the range which does not prevent the charged electric charge from flowing into a conductive layer.

When using a metal sheet or foil for the conductive layer, a sheet into which conductive powder such as conductive metal or garbon is kneaded, or a woven fabric, knitted fabric, mesh, net, etc. containing at least a portion of conductive fibers In this case, it is preferable to provide a plastic film layer on the surface of the conductive layer. In the semiconductor manufacturing process, ozone water or various chemicals may adhere to the housing.If the conductive layer made of aluminum foil or the like that is easily corroded by such chemicals is used in a bare state, the surface corrodes due to the effects of these chemicals. This may be a source of dust.

As the plastic film provided on the surface of the conductive layer, a plastic material that can be laminated to the conductive layer by adhesion or fusion can be used as appropriate.Polyolefin such as polyethylene and polypropylene, fluororesin such as PFA and FEP, polyamide, polyester, and the like This film is preferably used because it is heat-fusible and generates less dust.

FIG. 3 shows an explanatory cross-sectional view of one embodiment of the antistatic material preferably used in the present invention. In this figure, 2b indicates a conductive layer, 2c indicates an adhesive layer laminated on the back surface (housing side) of the conductive layer, and 2a indicates a plastic film layer laminated on the surface of the conductive layer. The conductive layer and the plastic film layer may be bonded by a heat fusion method, or may be laminated via an adhesive layer or a pressure-sensitive adhesive layer. The thickness of the pressure-sensitive adhesive layer 2c is from 200 to ； μππι, preferably from 50 to 20 μm.

The antistatic material is attached to the entire or part of the outer surface of the fluororesin housing. The antistatic effect is the greatest when mounted on the entire surface of the fluororesin housing, but the cost is high, so it is preferable to mount it on a part of the outer surface of the fluororesin housing. The mounting location in this case is not particularly limited as long as a predetermined antistatic effect can be obtained, but is preferable because an antistatic material can be easily attached to a relatively large area of a part of the chamber. The area ratio of the installed antistatic material to the fluororesin housing surface area is determined as appropriate based on the charge amount of the fluororesin housing, the expected static elimination effect, and the temperature and humidity in the room where the module is grounded. Although good, it is preferably 15 to 1%, more preferably 30 to 80%. If it is less than 15%, a sufficient static elimination effect cannot be obtained. As a method of attaching the antistatic material to the fluororesin housing, any method may be used as long as the antistatic material is fixed in contact with a part or the whole surface of the fluororesin housing. Such methods include a bonding method, a fusion method, an adhesion method, and a physical method such as a snap ring, a clip, sewing, and the like.

It is preferable that the conductive layer be grounded via an earth wire because charges charged in the fluororesin housing can be rapidly eliminated through the earth wire.

Next, a method for transporting the membrane module of the present invention will be described.

In the first transport method of the present invention, the membrane module is transported in a state where the polar solvent is stored in the liquid passage to be processed of the membrane module. More specifically, after the quality inspection is completed, the polar module is injected from the liquid inlet or the liquid outlet after the quality inspection, and the liquid inlet and the liquid outlet are plugged while the liquid flow path to be processed is almost filled with the polar solvent. After the membrane module is cleaned, if necessary, the outer surface of the membrane module is packaged and transported. The work from quality inspection to packing is preferably performed in a clean room because it can prevent dust and dirt from adhering to the membrane module surface. The polar solvent is preferably injected at a rate of 20 to 100%, preferably 50 to 100%, based on the volume of the liquid channel to be processed of the membrane module.

As the polar solvent, a polar solvent having a dielectric constant of 10 or more is preferably used. Examples of such polar solvents include alcohols such as methanol, ethanol and isopropanol, water, acetonitrile, acetone, pyridine, dimethylformamide, dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone. And so on.

When the membrane module is transported while the polar solvent is stored in the liquid flow path of the membrane module to be treated, even if the membrane module is charged by friction or peeling action, the fluorine resin porous membrane is charged to the housing. Since the charged electric charge is neutralized by the polar solvent, the charged voltage of the membrane module can be reduced.

In the second transportation method of the present invention, the membrane module is sealed in a packaging bag made of a conductive film and transported. More specifically, the membrane module is sealed in a packing bag made of conductive film after the quality inspection, after cleaning the outer surface of the membrane module if necessary, and in a cardboard box if necessary. Boxed Transported. The work from quality inspection to packing is preferably performed in a clean room because it can prevent dust and dirt from adhering to the membrane module surface.

Examples of the conductive film include a film obtained by kneading a car pump rack or metal powder into a usual packaging film such as polyethylene, polypropylene, polyvinyl chloride, polyester, or polyamide, or a polyethylene dalicol or polyethylene oxide. Films having an antistatic agent kneaded or coated on the surface and having a surface resistance of 10 ¹² Ω or less are preferably used. Also, a sheet material containing a conductive layer of a metal foil such as an aluminum foil, a woven fabric, a nonwoven fabric, a mesh, a net, or the like in which conductive fibers such as a metal fiber and a carbon fiber are woven can be used. It is preferable to use a specification that does not allow greetings to pass through from the viewpoint of preventing dust from attaching to the surface of the membrane module. The conductive film is cut into a predetermined shape and then formed into a bag shape by fusion or adhesion. The method of inserting and sealing the membrane module is not particularly limited as long as dust can be prevented from entering the bag.However, it is preferable to use an ultrasonic fusion machine or a heat fusion machine to fuse the opening. preferable. At this time, it is preferable to evacuate the air in the bag and perform vacuum packing, since the membrane module does not move in the bag during transportation, and a frictional charge between the membrane module and the bag can be prevented.

The transport method of the present invention is applied to a membrane module in which a fluororesin porous membrane is housed in a fluororesin housing, but is preferably applied to an antistatic membrane module of the present invention. The antistatic membrane module of the present invention has excellent antistatic properties, and the conventional transport method can be applied. However, by adopting the transport method of the present invention, a higher level of control is achieved. Electricity effect can be achieved. Example

Next, the present invention will be described more specifically with reference to examples.

Comparative Example 1

A bundle of 60 e-PTFE tubes with an inner diameter of 1.7 mm, an outer diameter of 3.1 mm, and a length of 3 m is bundled and housed in a PTFE housing with a diameter of 140 mm and a length of 300 mm. A resin film module was produced. e The method for producing the PTFE tube is according to the method described in Example 1 in JP-A-7-218380. Example 1

A 70 μπι-thick aluminum adhesive sheet (S-Kesinema # 50) with a thickness of 70 μπι was cut to a size of 23.2 X 45 mm at approximately the center of a part of the housing chamber of the membrane module of Comparative Example 1, and the aluminum was cut. The foil was adhered with an adhesive provided on one side of the foil, and the antistatic membrane module shown in Figs. The coverage of the aluminum adhesive sheet (the ratio to the total surface area of the housing) was 63%.

The aluminum pressure-sensitive adhesive sheet has a three-layer structure, in which a pressure-sensitive adhesive layer is laminated on the back surface (adhesion surface with the housing) of the aluminum foil, and a polyester film layer is laminated on the surface.

Example 2

A ground wire was attached to the aluminum adhesive sheet (tab portion) of the antistatic membrane module of Example 1 and grounded.

Example 3

The liquid passage to be treated of the membrane module of Comparative Example 1 was filled with ultrapure water, and plugs were screwed into the liquid inlet and the liquid outlet to plug.

Example 4

The membrane module of Comparative Example 1 was wrapped with an antistatic treatment film (Absostat HA-T, manufactured by Shikoku Kako Co., Ltd., thickness: 100 μπι, surface resistance: 109 to 1 ⁹ ^ Ω), and the opening was heated while reducing the pressure Sealed.

Comparative Example 2

The membrane module of Comparative Example 1 was packaged with a normal polyethylene film without antistatic treatment (Clean film: 100 / zm, manufactured by Towa Kako Co., Ltd.), and heat-sealed while decompressing the opening.

The surfaces of the samples obtained in the above Examples and Comparative Examples were rubbed 20 times with a cotton nonwoven fabric (B EMCOT 2 OmmX 2 Omm manufactured by Asahi Kasei Corporation) (Examples 1 to 3, Comparative Example 1 is a part of the chamber, and Example 4). In Comparative Example 2, a portion of the chamber was rubbed from above the packaging bag, and then the charged voltages on the surface of the chamber and the surface of the tube bundle were measured. In Example 4 and Comparative Example 2, the bag was opened after rubbing, and the membrane module was taken out of the bag and measured. The charging voltage is PFM-71 1A Electrostatic, manufactured by Prostat Corporation. It was measured using a quill meter. Table 1 shows the measurement results.

ADVANTAGE OF THE INVENTION According to this invention, the problem of the damage of the porous film by the electrostatic discharge which was seen in the film module of the structure which accommodated the fluororesin porous film in the housing by the fluororesin property can be solved.

Claims

The scope of the claims

I. A membrane module having a structure in which a fluororesin porous membrane is housed in a fluororesin housing, wherein the entire outer surface or a part of the outer surface of the housing is coated with an antistatic material having a conductive layer. An antistatic membrane module, characterized in that:

2. The antistatic membrane module according to claim 1, wherein the antistatic material is grounded.

3. The antistatic membrane module according to claim 1, wherein the antistatic material is a material in which a plastic film is laminated on the surface of the conductive layer.

4. The antistatic membrane module according to any one of claims 1 to 3, wherein the conductive layer is an aluminum film.

5. The antistatic membrane module according to any one of claims 1 to 4, wherein the fluororesin porous membrane is a porous polytetrafluoroethylene tube.

6. The method according to any one of claims 1 to 5, wherein the material of the fluororesin housing is polytetrafluoroethylene or a copolymer of polytetrafluoroethylene and an ethylenically unsaturated monomer. Conductive membrane module.

7. The antistatic membrane module according to any one of claims 1 to 6, wherein the membrane module is an ozone gas dissolving module for dissolving ozone gas in a liquid to be treated.

8. The antistatic membrane module according to any one of claims 1 to 6, wherein the membrane module is a degassing module for removing dissolved gas from a liquid to be treated.

9. A method for transporting a membrane module in which a fluororesin porous membrane is housed in a fluororesin housing, wherein the membrane module is transported in a state where a polar solvent is stored in a liquid passage to be processed of the membrane module. A method for transporting a membrane module, comprising:

10. A method for transporting a membrane module in which a fluororesin porous membrane is housed in a fluororesin housing, characterized in that the membrane module is transported in a packing bag made of a conductive film. Method of transporting membrane modules.

I I. The method for transporting a membrane module according to claim 9 or 1, wherein the fluororesin porous membrane is a porous polytetrafluoroethylene tube.

12. The material according to any one of claims 9 to 11, wherein the material of the fluororesin housing is polytetrafluoroethylene or a copolymer of polytetrafluoroethylene and an ethylenically unsaturated monomer. 3. The method for transporting a membrane module according to item 1.