JPH0812775A - Composite ion-exchange membrane and its production - Google Patents

Abstract

PURPOSE:To obtain a composite ion-exchange membrane excellent in ion exchange performance, permeability, electrical resistance, the ability to prevent mixing of electrolytes, strengths, etc., and used in the electrolysis, separation and modification of various liquids and gases by giving a specified membrane structure thereto. CONSTITUTION:The composite ion exchange membrane composed of a porous synthetic resin material one side of which is reinforced with synthetic resin fabric and the other side of which is covered with a nonporous dense layer made of an ion exchange resin. This membrane desirably satisfies the following requirements: the porosity of the porous synthetic resin material is 50-95%, the thickness is 5-50mum, and the ion-exchange resin is packed into 5-100% of the volume of the porous synthetic resin material to form the nonporous dense layer. A desirable example of the ion-exchange resin is a fluoropolymer having sulfo groups and an ion exchange capacity of 0.65-2.5meq./g resin. A desirable example of the synthetic resin fabric is a synthetic resin mesh which has a fiber diameter of 0.05-1mm and an opening of 40-95% and in which the fiber members are bonded together by melting at their crossing points.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite membrane used for electrolysis, separation or modification of various liquids and gases, and more particularly to a composite ion exchange membrane.

[0002]

2. Description of the Related Art Ion exchange membranes widely used in separation and reforming operations of various liquids and gases using electrolysis and other chemical methods are often formed by forming ion exchange resin into a membrane shape. Moreover, in order to improve characteristics such as electric resistance, the film is thinned within a range where strength can be secured,
The strength of ion exchange resins is usually not very high.

Therefore, a method of embedding a woven fabric in an ion exchange membrane for reinforcement and a method of laminating a synthetic resin porous body and an ion exchange resin film have been proposed.

[0004]

However, in the method of embedding a woven fabric in an ion exchange membrane for reinforcement, a woven fabric having a large area and strength has a large thickness, and the thickness of the ion exchange membrane is, for example, 100 μm or less. It was difficult to do.

Further, in a method of laminating a synthetic resin porous body and an ion exchange resin film to form a composite ion exchange membrane,
The thickness of the ion-exchange resin layer can be made small, but in order to secure sufficient membrane strength, the thickness of the synthetic resin porous body, which mainly receives the strength, becomes large, and in combination with the hydrophobicity of the synthetic resin, the expected solution is obtained. In many cases, it was not possible to obtain the transparency.

In addition, the ion exchange membrane used as a membrane for electrolysis is required to prevent mixing of the positive and negative electrode liquids and to have a low electric resistance, but a porous membrane is excellent in terms of electric resistance. Non-porous membranes are preferred because they do not have sufficient mixing prevention properties for the bipolar liquids. However, the non-porous film has a drawback that its electric resistance is several tens to several hundred times higher than that of the porous film.

It is an object of the present invention to provide a composite ion exchange membrane having excellent ion exchange characteristics and excellent permeability, electric resistance, polar liquid mixing prevention characteristics, strength and the like, and a method for producing the same.

[0008]

In the composite ion exchange membrane of the present invention, one side is reinforced with a synthetic resin fabric and a non-porous dense layer made of an ion exchange resin is formed on the other side. It is composed of a resin porous body.

The material of the synthetic resin porous body (hereinafter referred to as porous body) is, for example, polypropylene, polyethylene, P
TFE (polytetrafluoroethylene), polysulfone, or the like can be used, and synthetic resins made of these materials are formed into a porous body by a stretching method, an extraction method, or the like. Alternatively, after being formed into a nonwoven fabric, it may be pressed into a predetermined thickness and formed into a porous body. The pore diameter of the porous body is 0.1 μm to 20 μm.
m is preferable, and the pore diameter of the porous body is usually the value obtained from the bubble point.

The porosity and thickness of the porous body are
From the viewpoint of permeability and strength, porosity is 50% to 95%, respectively.
%, The thickness is preferably 5 μm to 50 μm, more preferably the porosity is 70% to 90%, and the thickness is 10 μm to 30 μm.

[0011] Such a porous body is liable to be curled when the area is large and may be difficult to handle (handling). Therefore, a synthetic resin fabric is heat-sealed or an appropriate adhesive is used. It is reinforced by being joined to the porous body. As the fabric, for example, a non-woven fabric or a woven fabric is used, and in particular, a synthetic resin mesh formed by arranging a plurality of linear members preferably intersecting at an angle of 10 to 90 ° and melting and joining the intersections is preferable. . When such a mesh is used, a large aperture ratio can be obtained, moreover, there is no displacement at the intersection, and deformation is less likely to occur. For the synthetic resin mesh, for example, polypropylene can be used, and it is preferable that the mesh has a linear shape of 0.05 mm to 1 mm and an opening ratio of 40% to 95%. The synthetic resin mesh is produced, for example, by a melt extrusion method or by hot pressing a plurality of woven cloths roughly woven with synthetic resin threads.

When used as a diaphragm for electrolysis, a spacer net is usually used to prevent direct contact between the electrode and the membrane, but if a mesh made of synthetic resin is used, it can also serve as a spacer net. Since it is not necessary to prepare a separate spacer net, the cost can be reduced, and the distance between the electrodes can be shortened, so that the cell voltage can be lowered. Especially in the electrolytic cell for producing ion-exchanged water,
From the viewpoint of safety, it is expected to lower the cell voltage, which is preferable.

The porous body made of the above-mentioned material is usually hydrophobic, and it is preferable to make the inside of the porous body hydrophilic so that the solution can enter the inside of the porous body having fine pores. Therefore, in the present invention, the inside of the porous body is coated by using an ion exchange resin and filling it.

As the ion exchange resin with which the porous material is filled, for example, styrene resin, ethylene resin, polysulfone resin, fluorine-containing resin, etc. can be used. You can use anything that can be converted. In particular, the fluoropolymer having a sulfonic acid group has good properties in terms of heat resistance, chemical resistance, moldability and mechanical properties, and is suitable as a diaphragm for electrolysis. For example, the fluoropolymer having a sulfonic acid group preferably has an ion exchange capacity of 0.65 to 2.5 meq / g resin.

The ion exchange resin which constitutes the dense layer is
It is not necessary to fill all the voids in the porous body, and it suffices if a substantially non-porous layer is formed in the porous body, so that continuous ions having a predetermined thickness over the length direction of the porous body. It is preferable to form a dense layer of the exchange resin, that is, an ion exchange resin layer.

When the amount of the ion exchange resin is too large, the thickness of the dense layer becomes unnecessarily large and the electric resistance increases. On the other hand, when the amount of the ion exchange resin is small, defects occur in the dense layer or the inside of the porous body is insufficiently hydrophilized to increase the electric resistance. Therefore, the amount of ion exchange resin to be filled is 5% to 100%, preferably 10% to 60% of the volume of the porous body void portion.
% Is good.

In the method of the present invention for producing such a composite ion exchange membrane, a liquefied ion exchange resin or its precursor liquid is cast on a substrate film,
One side is pressed against the other side of the synthetic resin porous body reinforced with a synthetic resin fabric, the synthetic resin porous body is impregnated with the above ion exchange resin solution, and then the solvent is evaporated or crosslinked and cured, and ion exchange is performed. A non-porous dense layer made of resin is formed on the other side of the synthetic resin porous body.

A non-porous dense layer made of an ion-exchange resin is formed on the other side of the synthetic resin porous body by impregnation as described above, and a synthetic resin fabric is pressed against one side of the porous body. You may manufacture by heat fusion etc.

As the substrate film, for example, a film made of polytetrafluoroethylene (PTFE) can be used.

As the liquid material of the above ion exchange resin or its precursor, a method of using a solvent, a method of heat melting, or a method of using the precursor (monomer or the like) as it is can be used. A method using a solvent whose viscosity can be easily adjusted is preferable.

[0021]

EXAMPLES Tetrafluoroethylene and CF ₂ = CFOC
F ₂ CF (CF ₃ ) OCF ₂ CF ₂ SO ₂ F was copolymerized to obtain a copolymer A having an ion exchange capacity of 1.10 meq / g resin. After hydrolyzing the copolymer in an aqueous potassium hydroxide solution, to obtain a copolymer B replacing the ends were treated with hydrochloric acid to -SO ₃ H. Copolymer B and ethanol were placed in an autoclave, heated and stirred, and 10% by weight of copolymer B was added.
To obtain an ethanol solution. This solution was cast on a polytetrafluoroethylene (PTFE) film having a thickness of 50 μm, and cast to a total film thickness of 100 μm.

On the other hand, one side has a linear shape of 0.5 mm and an opening of 3.
PT having a pore size of 3 μm, a porosity of 90% and a thickness of 15 μm, which was reinforced by heat-sealing a polypropylene mesh of 5 mm × 6.0 mm, an opening ratio of 80% and a thickness of 20 μm.
The other side of the FE porous body was pressed against the above-mentioned copolymer B on the PTFE film and dried at 50 ° C. for 2 hours in a constant temperature bath to obtain a composite ion exchange membrane C. .

The obtained composite ion-exchange membrane C was treated with 0.1 K
A water leak test was conducted at a pressure of g / cm ² , and it was confirmed that there was no water leak and a dense layer was formed. This composite ion-exchange membrane was excellent in rigidity and dimensional stability, and was easy to handle. Further, this composite ion exchange membrane was used in a saline solution having a concentration of 0.5 N and a temperature of 22 ° C. for 0.1 to 0.
When a direct current of 5 A / cm ² was applied and the electric resistance of the film was measured, it was a very small value of 0.3 Ω · cm ² .

The use of the composite ion exchange membrane of the present invention is not limited to the diaphragm for electrolysis and the diaphragm for producing ionized water, but is suitable for other uses such as dialysis.

[0025]

The composite ion-exchange membrane of the present invention is made of a synthetic resin porous body, and one side is reinforced with a synthetic resin fabric so that it has excellent strength, and the other side is made of an ion-exchange resin. Since the ion-exchange resin layer, which is a non-porous dense layer, is formed, it has excellent permeability and electric resistance, and also has excellent ion-exchange properties and polar liquid mixing prevention properties.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location // B29K 27:12

Claims (5)

[Claims] 1. A composite ion exchange characterized by comprising a synthetic resin porous body having one side reinforced with a synthetic resin fabric and the other side having a non-porous dense layer made of an ion exchange resin formed thereon. film. 2. The synthetic resin porous body has a porosity of 50% to 95.
%, The thickness is 5 μm to 50 μm, and 5 to 100% of the volume of the void portion of the synthetic resin porous body is filled with an ion exchange resin to form a non-porous dense layer. 1. The composite ion exchange membrane according to 1. 3. The ion exchange resin has an ion exchange capacity of 0.6.
A fluoropolymer having a sulfonic acid group of 5 to 2.5 meq / g resin. 3.
The composite ion exchange membrane according to 1. 4. The synthetic resin fabric has a linear shape of 0.05.
The composite ion exchange according to any one of claims 1 to 3, wherein the mesh is a synthetic resin mesh in which the intersections of the linear members are melt-bonded to each other with an opening ratio of -1 mm and an opening ratio of 40% to 95%. film. 5. A liquid material of an ion exchange resin or its precursor is cast on a substrate film, and one side is pressed on the other side of a synthetic resin porous body reinforced with a synthetic resin fabric. After impregnating the ion-exchange resin into the synthetic resin porous body by applying, by evaporating or crosslinking curing the solvent,
A method for producing a composite ion exchange membrane, comprising forming a non-porous dense layer made of an ion exchange resin on the other side of the synthetic resin porous body.