JPH06218251A - Humidifying membrane - Google Patents

Abstract

PURPOSE:To reinforce a thin film-like ion exchange membrane to give moisture with a synthetic resin-made porous net body having a specific physical property. CONSTITUTION:A humidifying membrane is made by laminating an ion exchange membrane, and the porous net body which is formed from a fiber having 1-50mum fiber diameter, is 40-90% in porosity and 10-1000mum in average distance between fibers, and 10-500mum in apparent membrane thickness.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a humidifying membrane for giving moisture used for air conditioning of buildings, semiconductor manufacturing, food production / storage, precision machinery, maintenance and management of computers and the like.

[0002]

2. Description of the Related Art Conventionally, as a humidifying membrane for giving moisture, an ion exchange membrane has been proposed in which physical properties such as water absorption, fixed ion concentration and film thickness are defined (Japanese Patent Laid-Open No. 2-29355).
(See Japanese Patent Publication No. 1).

This membrane has an advantage that it can increase water and water vapor transmission rates and can provide necessary moisture in a short time.

[0004]

However, this film has a thickness as thin as 0.1 to several hundreds of μm, and has a drawback that it is partially damaged by long-term use or shock at the start of operation. In order to deal with this, the hole diameter of 0.
It has been proposed to use a porous base material having a surface of 0.1 to 100 μm, a thickness of 10 to 500 μm and a hydrophilic inner surface and an inner wall of the above-mentioned JP-A-2-293551, page 5, right column, upper column, lines 11 to 15. .

However, this porous substrate is in the form of a film, and it is necessary to make the surface and the inner wall hydrophilic.
It has a drawback that the means is complicated and it is difficult to obtain stable hydrophilicity.

[0006]

DISCLOSURE OF THE INVENTION The present invention has conducted various studies and studies for the purpose of eliminating the above-mentioned drawbacks and finding means capable of giving sufficient moisture to an ion exchange membrane, and as a result, instead of a porous film. It has been found that the above object can be achieved by using a fiber having specific physical properties, using an exchanger having a specific porosity and a specific thickness, and laminating an ion exchange membrane thereon.

Thus, the present invention uses an ion exchange membrane and fibers having a fiber diameter of 1 to 50 μm, and has a porosity of 40 to 90%,
Provided is a humidifying film in which a porous network having an average distance between fibers of 10 to 1000 μm and an apparent film thickness of 10 to 500 μm is laminated.

By adopting such physical properties in the present invention, even if a hydrophobic porous reticulate body is used, sufficient moisture can be given to the ion exchange membrane, and moreover, stable and long-term moisture can be given. It will be possible.

The fibers constituting the porous reticulate material used in the present invention are, for example, polyolefins such as polyethylene and polypropylene, halogenated polyolefins such as polyvinyl chloride, nylons, etc., because fibers are easy to produce and inexpensive. Polyamide such as polyamide and polyethylene terephthalate is preferably used. The fiber diameter (diameter) of these fibers needs to be 1 to 50 μm.

When the fiber diameter is smaller than 1 μm, the rigidity of the obtained porous reticulated body is low and the reticulated body is easily deformed by an external stress, and when it exceeds 50 μm, the surface of the obtained reticulated reticulated body is reduced. Unevenness becomes too large, and the reticulate body and the ion exchange membrane become less compatible with each other, and both are unsuitable.

The porosity of the porous reticulate body is 40 to 90%.
is necessary. Here, the porosity is 1-membrane weight (measured) /
It is defined as (apparent film area × apparent film thickness × material density). If the porosity is less than 40%, it becomes difficult for water to enter, and if it exceeds 90%, the strength of the obtained porous reticulate body is remarkably reduced.

Further, it is necessary that the average distance between the fibers constituting the porous network is 10 to 1000 μm.
When the average distance between the fibers is less than 10 μm, it becomes difficult for water to enter, and when the average distance exceeds 1000 μm, the strength of the reticulate body is remarkably reduced, and thus both are not suitable.
Here, the average distance between fibers is defined as the average distance between adjacent fibers when a film surface made of fibers is observed from the surface.

The apparent film thickness of the porous reticulate body is 1
It is necessary to be 0 to 500 μm. Here, the apparent film thickness is defined as the average distance between the film front surface and the back surface of the fiber film.

When the apparent film thickness is less than 10 μm, the strength of the reticulate body is remarkably low, and when it exceeds 500 μm, it becomes difficult for water to enter, so that both are unsuitable. Among the physical properties of these porous reticulate bodies, the fiber diameter is 3 to 30.
Porosity 50 to 80% using fibers of μm, average distance between fibers 50 to 30 μm, apparent film thickness 100 to 300 μ
It is particularly preferable to employ a porous reticulated body of m because the strength is sufficient and the penetration of water is sufficient.

Thus, as a means for producing such a porous network, for example, fibers obtained by melt-spinning a polymer are randomly dispersed on a plate capable of being hot pressed, and then hot pressed to form fibers. It can be obtained by fusion bonding the overlapping points. The melt adhesion in this case is
For example, a method is preferred in which polypropylene fine fibers are used as a binder with respect to the polymer fiber, and this and the polymer fiber are heated and roll-pressed, and the polymer fiber is bonded with the melted polypropylene.

Next, the ion exchange membrane used in the present invention is not limited, but it has a water absorption of 20 to 150% by volume, a fixed ion concentration of 0.5 to 1.5 meq / gH ₂ O, and an ion exchange capacity. 0.65-3.5 meq / g resin, film thickness 1-10
A diameter of 0 μm is suitable. If the water absorption rate is less than 20% by volume, the water vapor transmission rate will be significantly reduced, and
When it exceeds 50% by volume, the film strength is remarkably lowered, which is not preferable.

The fixed ion concentration is 0.5 milliequivalent /
If it is less than gH ₂ O, the concentration of ion exchange groups will be low, resulting in a decrease in water vapor permeability. If it exceeds 15 meq / gH ₂ O, the concentration of ion exchange groups will be extremely high, and the water content in the membrane will be reduced. Of these, it is presumed that the amount of water interacting with the ion-exchange group increases and the amount of free water decreases, and the water vapor transmission rate decreases, which is not preferable.

When the ion exchange capacity is lower than 0.65 meq / g resin, it becomes difficult for water to permeate due to a decrease in ion exchange group concentration, and when it exceeds 3.5 meq / g resin. Is not preferable because the film strength decreases. Further, if the film thickness is less than 1 μm, defects tend to occur in the film, and if it exceeds 100 μm, the water vapor permeation rate decreases, which is not preferable.

Among the physical properties of the ion exchange membrane, the water absorption rate is 50 to
100% by volume, fixed ion concentration 1-10 meq / gH
_{The use of 2} O, an ion exchange capacity of 0.9 to 2.5 meq / g resin, and a film thickness of 3 to 20 μm is particularly preferable because an excellent film having a high water vapor transmission rate and a high film strength and no defects can be obtained.

The ion exchange group of the ion exchange membrane used in the present invention is a cation exchange group such as sulfonic acid, sulfonate, carboxylic acid, carboxylate, phosphoric acid, phosphate, acidic hydroxyl group and acidic hydroxide. 1 to 3 amino groups, 4
Anion-exchange groups such as a primary ammonium group can be exemplified, but among them, a sulfonic acid group has high water absorption, heat resistance in addition to little deterioration due to a chlorine component contained in water,
It is particularly preferable because it has excellent chemical resistance.

As the material of the ion exchange membrane, styrene-based resin, ethylene-based resin, polysulfone-based resin, fluorine-containing resin and the like can be used without any limitation, but heat resistance, chemical resistance, molding processability, and mechanical property A sulfonic acid cation exchange membrane made of a fluorine-containing resin, particularly the fluorine-containing polymer shown in Chemical formula 1, is preferable from the viewpoints of properties, in particular, membrane damage due to swelling / shrinkage.

[0022]

[Chemical 1] However, p and q are positive integers, and q / p is 2 to 16, m
Is 0 or 1, and n is an integer of 1 to 5. Alternatively, a sulfonated polysulfone polymer containing the structure shown in Chemical formula 2 is preferable.

[0023]

[Chemical 2] However, Ar is an allyl group selected from benzene, biphenyl, and bisphenol A, and n is a positive integer.

In the present invention, as a means for producing a laminate of such an ion exchange membrane and a porous reticulate body, for example, a predetermined porous reticulate body obtained in advance from a polymer to be an ion exchange membrane or a precursor solution thereof is used. A method of cast film formation on the above, or after the polymer or its precursor solution is once cast film formation on another polymer film, an adhesive solution is applied on the cast film formation film to form a porous reticulate body. There are various methods such as a laminating method in which the polymer film is peeled off after sticking and adhering, and a method in which a polymer to be an ion-exchange membrane is melt-extruded or cast on a polymer film to form a porous network and heat-pressed.

As a method of using the thus obtained laminated membrane, water is brought into contact with the porous reticulate body side and a humidifying gas is brought into contact with the ion exchange membrane side.

[0026]

According to the present invention, a porous reticulate body having relatively large pores and an ion-exchange membrane are laminated, and even if the fibers constituting the porous reticulate body are hydrophobic, they are water-permeable. Water is not easily affected and water can easily enter. Moreover, the porous reticulate body has a reinforcing effect on the ion exchange membrane, and it is possible to make the ion exchange membrane thin, and effective and practical humidification is exhibited. Next, the present invention will be described with reference to examples, but the present invention is not limited to the examples.

[0027]

【Example】

Example 1 Tetrafluoroethylene and CF ₂ ═CFO
CF ₂ CF (CF ₂ ) OCF ₂ SO ₂ F was copolymerized to obtain a copolymer A having an ion exchange capacity of 1.10 meq / g resin. The copolymer was treated with hydrolyzed after hydrochloric acid aqueous potassium hydroxide solution, to obtain a copolymer B replacing the ends -SO ₃ H. Copolymer B and ethanol were placed in an autoclave and stirred under heating to obtain a 10 wt% ethanol solution of copolymer B.

This solution was cast on a polytetrafluoroethylene (PTFE) sheet and dried at 90 ° C. to prepare a thin film of copolymer B having a thickness of about 20 μm. Similarly, a 10 wt% ethanol solution of copolymer B was applied on this thin film in a liquid film thickness of 20 μm. On the other hand, polypropylene having a fiber diameter of 7 μm and polyethylene terephthalate fiber having a fiber diameter of 7 μm were mixed at a ratio of 50:50 (weight ratio), and 35 g of both fibers were evenly dispersed per 1 m ² , and the mixture was heated and pressed to have a porosity of 63%, A porous reticulate body having an average distance between fibers of 200 μm and an apparent film thickness of 120 μm was obtained, which was immediately stuck to the polymer B and dried at 90 ° C.

The resulting multi-layer membrane is sandwiched between cells, water is flown to the porous reticulate body side and nitrogen is flown to the ion exchange membrane side, and the water vapor permeability is calculated from the relative humidity at the cell inlet and the cell outlet. The results are shown in Table 1.

[0030]

[Table 1]

Comparative Example 1 A polyethylene film-like porous membrane having a film thickness of 50 μm, an average pore diameter of 0.4 μm, and a porosity of 50% prepared by a stretch opening method was used as the porous reticulate body. A multilayer film was prepared in the same manner as in 1. When the humidification amount was measured by the same method as in Example 1, the N ₂ gas surface flux was 1.0 m / s, the inlet absolute humidity was 10 g / m ³ , and 2
The humidification amount at 5 ° C. was a small value of 0.15 kgH ₂ O / m ² · h.

Example 2 A film of copolymer B having a thickness of 20 μm was formed on a polyethylene terephthalate film in the same manner as in Example 1. As a porous network, a polyethylene terephthalate 14 μm fiber,
Polypropylene 10 μm fiber weight ratio 70:30
Mix evenly and scatter 30 g per 1 m ³ evenly.
Molding was performed at 0 ° C. to obtain a porous reticulate body having a porosity of 60%, an average distance between fibers on the membrane surface of 10 μm, and a film thickness of 50 μm.

The film of copolymer B and the porous network were laminated by a heating roll press to obtain a composite film. Example 1
A multilayer film was prepared in the same manner as in. When the humidification amount was measured by the same method as in Example 1, the N ₂ gas surface flux was 1.0.
The humidification amount was 0.55 kgH ₂ O / m ² · h at m / s, absolute humidity at the inlet of 10 g / m ³ , and 25 ° C.

[Example 3] A reaction was conducted with 4,4'-diphenol-2-dihalodiphenyl sulfone in the same manner as in the synthesis method described in JP-A-61-168629, and an aromatic polysulfone unit was formed. A precursor in which m was 10 was synthesized, and then the precursor was reacted with dihalodiphenyl sulfone and sodium sulfide to obtain an aromatic polysulfone-polythioether sulfone copolymer C represented by Chemical formula 3.

[0035]

[Chemical 3] However, x / y = 10/10, intrinsic viscosity 0.65

Next, the copolymer C was dissolved in 1,1,2-trichloroethane, and a solution of sulfuric acid / triethyl phosphate in a ratio of 2/1 (molar ratio) was added to the solution of trichloroethane and 1 of the copolymer C. The reaction was performed at 25 ° C. for 43 hours so that 2 equivalents of the complex per unit were brought into contact with each other to obtain a sulfonated copolymer D having an ion exchange capacity of 1.85 meq / g resin.

The copolymer D thus obtained was dissolved in N-methyl-2-pyrrolidone to prepare a sulfonated copolymer solution, and a multilayer film was prepared by the same method as in Example 1 using the solution. Then, the amount of humidification was evaluated. The amount of humidification of the multilayer film is N
₂ Gas surface flux 1.0 m / s, inlet absolute humidity 10 g / m
³ , 0.50 kgH ₂ O / m ² · h at 25 ° C.

[0038]

EFFECTS OF THE INVENTION The humidifying membrane of the present invention comprises a porous reticulate body having specific physical properties and an ion exchange membrane laminated together, and even if the ion exchange membrane is used as a thin film, a sufficient reinforcing effect and water absorption can be obtained. It can be applied to an ion exchange membrane.

Front page continuation (72) Inventor Haruhisa Miyake 1150 Hazawa-machi, Kanagawa-ku, Yokohama-shi, Kanagawa Asahi Glass Co., Ltd. Central Research Laboratory

Claims (1)

[Claims] 1. An ion exchange membrane and a fiber having a fiber diameter of 1 to 50 μm, a porosity of 40 to 90%, an average distance between fibers of 10 to 1000 μm, and an apparent film thickness of 10 to 500 μm.
A humidifying membrane in which a porous network of m is laminated.