JPH0671147A - Dual film - Google Patents

Abstract

PURPOSE:To provide a dual film which makes prevention of frictional electrification possible without being influenced by the surrounding condition and can keep permeation characteristics as it is and can be manufactured by the conventional manufacturing facility and inexpensively. CONSTITUTION:A selective functional film is provided on another face of a porous substrate film wherein substrate fabric made of electrically conductive woven fabric or nonwoven fabric is embedded and at least part of the one face of the substrate fabric is exposed.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to composite membranes useful for the separation of gases or liquids, especially flammable gases and organic vapors.

[0002]

2. Description of the Related Art When a gas having a selective permeability to a specific molecule is used to separate a gas or a liquid of the specific molecule, one side of a porous support membrane in which a base cloth such as a woven cloth or a nonwoven cloth is embedded. A composite film having a selective functional film may be used. It has been proposed that the composite film is provided with a surfactant layer, a metal vapor deposition layer, or the like to prevent the above-mentioned triboelectric charging (JP-A-1-115406).

[0003]

However, the antistatic effect of the surfactant layer is temporary, is greatly affected by humidity, and its effect can hardly be expected under a dry condition. There is a problem when it is rewound and used after storage for a long time.

On the other hand, in the metal vapor deposition layer, the vapor-deposited metal particles are welded and integrated with each other and exhibit a considerable permeation resistance, so that the permeation performance of the composite membrane cannot be avoided.
Further, in order to continuously form a metal vapor deposition layer, a large apparatus with a high degree of vacuum is required at the film forming stage, which complicates the process and raises the cost. There is also the fear of contact wear.

An object of the present invention is to prevent frictional electrification without being affected by ambient conditions, to maintain the permeation performance as it is, and to manufacture it with existing manufacturing equipment at low cost. To provide a membrane.

[0006]

The composite membrane of the present invention is a porous support membrane in which a base fabric such as a conductive woven fabric or a non-woven fabric is embedded, and at least a part of one side of the base fabric is exposed. This is characterized in that a selective functional film is provided on the other surface of the porous support film, and the surface resistivity of one surface of the porous support film is 10 ⁹
It is preferably Ω / □ or less.

[0007]

The back surface of the porous support film has a low surface resistance because one surface of the conductive base cloth is exposed. Therefore, during winding or unwinding of the composite film, even if the back surface of the porous support film and the surface of the selective functional film make frictional contact, triboelectric charges are discharged through the back surface of the porous support film as a conductive path, preventing charging. To be done.

Further, the base cloth is made conductive by making the base cloth fibers conductive, and the conductivity of the base cloth is not affected at all by gas or liquid permeability. Permeability of the entire composite membrane is retained.

[0009]

EXAMPLES The composite membrane of the present invention comprises a porous support membrane and a selective functional membrane laminated, and in the porous support membrane,
A base cloth such as a conductive woven cloth or a non-woven cloth is embedded in the porous film, and one part or the whole of the base cloth is exposed from the back surface of the porous film. This conductive woven or non-woven fabric is made of carbon fiber or metal fiber such as stainless steel, aluminum, nickel, copper or alloy or non-conductive fiber coated with metal by vapor deposition. It can be obtained by weaving or paper-making one or more kinds of conductive fibers, or by blending or blending these conductive fibers with synthetic fibers or natural fibers.

For this porous support membrane, a solution of the material for the porous membrane is cast on one side of the base cloth to impregnate the base cloth with the solution and apply it to a predetermined thickness, and then dip-coagulate in a water bath. It can be used. This porous support membrane is an asymmetric membrane, and the conductive base fabric can be easily exposed from the back surface by adjusting the amount of solution impregnated into the base fabric. A porous support membrane having a symmetrical structure can also be used, in which case the conductive base fabric is exposed on at least a part of both surfaces of the porous support membrane.

As a material for the porous membrane, any material can be used as long as it does not swell by water vapor or vapor of an organic compound, but polyimide, polysulfone, polyamide, polyethersulfone, polyacrylonitrile, etc. are used. It is suitable.

As the above-mentioned selective functional membrane, one having a selective permeability to the organic substance or water vapor or liquid to be separated is used, and polydimethylsiloxane, chitosan or poly-4 is used depending on the vapor or liquid. Methylpentene or derivatives thereof are used. The selective functional film may be either a single layer or a heterogeneous multilayer. The thickness of the selective functional film is usually 0.03 μm to 50 μm.
The thickness is preferably 0.1 μm to 20 μm.

On the other hand, the thickness of the porous support membrane is usually 1 μm to 8000 μm, preferably 10 μm to 800.
μm.

In the production of the composite membrane of the present invention, a solution of the selective functional membrane material is applied to a predetermined thickness on the other surface of the porous support membrane having the conductive base cloth exposed on a part or all of one side. Then, a method of drying, or dropping the solution of the selective functional membrane material on the water surface, to form a thin film by the water surface development method, the conductive substrate is exposed on part or all of one side of the porous support membrane A method of bringing this thin film into close contact with the other surface can be used.

The composite membrane of the present invention is used by being incorporated into a plate-and-frame type module, a spiral type module or a tubular type module in the form of a flat membrane or a tubular membrane. .

In the composite membrane of the present invention, conductive fibers are used as the fibers of the base fabric of the porous support membrane, and the base fabric may be exposed on at least a part of the back surface of the porous support membrane.
The exposure of the base fabric can be easily performed by adjusting the amount of the porous membrane material solution impregnated into the base fabric, so that the base fabric can be easily manufactured at low cost with existing manufacturing equipment.

Further, the permeation resistance of the base fabric in the composite membrane can be neglected with respect to the permeation resistance of the porous membrane, the selective functional membrane and the like. Since the low permeation resistance is substantially retained, the permeation performance of the entire composite membrane can be retained as it is. Further, even if the fibers of the base cloth are made of conductive fibers such as metal fibers, the strength of the base cloth can be sufficiently ensured and the mechanical reinforcing effect of the porous support membrane can be well maintained.

Therefore, according to the present invention, it is possible to obtain a composite membrane in which the back surface, that is, the outer surface of the porous support membrane, is electrically conductive, while maintaining the permeation performance and the mechanical strength substantially in the existing manufacturing equipment. it can. If the conductivity of the outer surface of the porous support membrane is set to a value sufficient to prevent electrification (usually a surface resistivity of about 10 ⁹ Ω / □ or less), the selectivity when the composite membrane is wound or unwound is selected. Despite the contact friction between the outer surface of the functional film and the porous support film, the surface potential of the selective functional film can be remarkably lowered, and the film damage due to discharge on the surface can be avoided.

Even if the gas or the like that is selectively permeated is a flammable gas such as an organic solvent vapor, the charge generated by frictional contact between the membrane and the gas is discharged when passing through the conductive base cloth. Since it is possible to reliably prevent discharge in the transmission chamber,
Can be safely separated.

Thus, in the composite membrane of the present invention,
The outer surface of the porous support film can be made sufficiently conductive (surface resistivity of 10 ⁹ Ω / □ or less), and the surface potential of the selective functional film based on triboelectrification can be remarkably lowered. This is clear from the comparison between the following examples and comparative examples.

In the following, the surface resistivity is 24 ± 2 ° C. and 60 ± 5% using Hi resta manufactured by Mitsubishi Petrochemical Co., Ltd.
RH was measured with an applied voltage of 10 V, and the surface potential was measured with a current collector-type potential measuring device (KS-471 type manufactured by Kasuga Electric Co., Ltd.).

Example 1 One side of a non-woven fabric obtained by wet-fabrication of 75 parts by weight of polyester fiber and 25 parts by weight of carbon fiber was coated and impregnated with an N, N-dimethylformamide solution containing 18% by weight of polyimide to obtain a coating thickness. The thickness was set to 180 μm, and then immersed in a water bath to prepare a polyimide porous support film.

On one side of this polyimide porous support membrane,
Cross-linking silicone resin containing cross-linking agent 4% by weight of isooctane solution was applied to a thickness of 100 μm, and then heated at 120 ° C. for 5 minutes to evaporate isooctane and form a selective functional film made of the cross-linking silicone resin. To obtain a composite membrane.

The surface resistivity on the back surface side (polyimide porous support film surface side) of this example product was 10 ⁴ Ω / □ or less.

The rubber roller was rotated 10 times on the surface of the selective functional film of this example, and then wound and rewound to measure the surface potential of the selective functional film, which was 0.3 KV or less. It was

Comparative Example 1 The same as Example 1 except that a non-woven fabric made only of polyester fibers was used. When the surface resistivity was measured in the same manner as in Example product 1, it was 10 ¹² Ω / □ or more, and the surface potential was measured, it was 7 KV or more. From the comparison between this comparative example and Example 1 above, the excellent antistatic effect of the present invention is clear.

Example 2 The same as Example 1 except that as the non-woven fabric, a non-woven fabric obtained by wet papermaking of 75 parts by weight of polyester fiber and 25 parts by weight of stainless fiber was used. When the surface resistivity was measured in the same manner as in Example product 1, it was 10 ⁴ Ω / □ or less, and when the surface potential was measured, it was 0.2 KV or less.

Example 3 The same procedure as in Example 1 was carried out except that an N, N-dimethylformamide solution containing 18% by weight of polysulfone was used as the material solution for the porous membrane. When the surface resistivity was measured in the same manner as in Example product 1, it was 10 ⁴ Ω / □ or less, and the surface potential was measured, it was 0.3 KV or less.

Comparative Example 2 A 1% by weight ethanol solution of a quaternary ammonium salt cationic surfactant (trade name: Cationogen, manufactured by Daiichi Kogyo Co., Ltd.) was applied to the back side of the composite film of Comparative Example 1. Deferred, about 100
The surface resistivities of the surface-active agent layers of the ones coated at a thickness of μm and dried at room temperature (25 ° C., 64% RH) and those dried by heating (120 ° C., 10 min) were measured. 0.27 × 10 ⁹ Ω / □, and the latter was 1.48 × 10 ¹⁰ Ω / □.

The humidity is about 13 for each of these.
When the surface resistivity was measured in a dry environment of% RH (temperature 25 ° C.), the former was 1.54 × 10 ¹⁰ Ω / □, and the latter was 9.85 × 10 ¹⁰ Ω / □. . Further, when the surface resistivity was measured by leaving it in a dryer at 100 ° C. for 30 minutes, it was almost 7.
It was 00 × 10 ¹¹ Ω / □.

As described above, in the comparative example product, the surface resistance of the back surface of the composite film becomes extremely high in a dry state, and effective prevention of triboelectrification cannot be expected.

[0032] However, for the above Examples 1 to 3 was measured composite film backside surface resistivity of the slurry was allowed to stand for 30 minutes in a 100 ° C. oven, all 10 ⁴
It is Ω / □ or less, and it is clear that excellent triboelectrification prevention can be achieved regardless of the dry state. .

[0033]

In the composite membrane of the present invention, in order to make the back surface conductive for preventing static electricity, the fibers of the base fabric of the porous support membrane are made electrically conductive, and this base fabric is provided on at least the back surface of the porous support membrane. Since it is carried out by exposing it partially, it is possible to reliably ensure antistatic due to the stable conductivity of the conductive fiber.

Further, since the gap of the base cloth can be maintained as it is, there is no influence on the permeation characteristics, and furthermore, the exposure of the base cloth on the back surface of the porous support membrane depends on the amount of the porous membrane material solution impregnated into the base cloth. This can be easily carried out by adjustment, and it is possible to easily manufacture at low cost without requiring special equipment for making the back surface conductive for antistatic.

Claims (2)

[Claims] 1. A selective functional membrane is provided on the other surface of a porous support membrane in which a base cloth such as a conductive woven cloth or a non-woven cloth is embedded, and at least a part of one side of the base cloth is exposed. A composite membrane characterized in that 2. The surface resistivity of one side of the porous support membrane is 10 ⁹
The composite film according to claim 1, which has an Ω / □ or less.