JPH07108128A - Humidity control method of gas - Google Patents

Abstract

PURPOSE:To efficiently and stably control the humidity of gas for a long period by forming a film of a double-layered film composed of a hydrophobic porous film and a hydrophilic non-porous film in a method for controlling the humidity of gas by moving moisture between gas and a water-based humidity conditioning liquid through the film. CONSTITUTION:The film intermediately provided between gas and the water- based humidity conditioning liquid and for controlling the humidity of gas by moving the moisture is formed of the double-layered film composed of the hydrophobic porous film and the hydrophilic non-porous film, and the hydrophobic porous film is arranged to face to the water-based humidity conditioning liquid. As the water-based humidity conditioning liquid, 10-50wt.% high concentration aq. solution of lithium chloride, lithium bromide or the like is used. The hydrophobic porous film is >=0.01kg/cm<2> in water block pressure and <=600sec/100cc in air permeability and an ion exchange membrane of a dried resin 10-200wt.% in water absorption, 0.5-6mequiv./gH2O in fixed ion conc. and 0.6-5.0 equiv./g in ion exchange capacity is used as the hydrophilic non-porous film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting the humidity of various gases such as indoor air using an aqueous solution.

[0002]

2. Description of the Related Art In the conventional humidity control of gas, the transfer of water from a hydrogen control solution such as an aqueous salt solution to a gas, or the transfer of a gas containing water to a control solution is performed on the free surface of the control solution. It was often done through. With this method, there is a limit to the volumetric efficiency of the permeation area because it is a free surface, and it is difficult to prevent the trouble that the mist of the humidity control liquid mixes into the gas because the humidity control liquid and the gas are in direct contact. It was
On the other hand, it has been proposed to use a hydrophobic porous film as a moisture permeable film to allow moisture to move (JP-A-61-161).
186739). By using this technique, the above-mentioned problems can be initially solved.

However, in this case, the leakage of the humidity control liquid is basically prevented through the hydrophobicity of the porous film, and in the long-term use, salts in the humidity control liquid are deposited on the film surface. Since the membrane surface gradually becomes hydrophilic, it often led to a leak. Further, it has been proposed to use a hydrophilic film made of a polymer having a hydrophilic group as a molecule, such as cellulose acetate, as a water permeable membrane (Japanese Patent Laid-Open No. 2-293551).

This hydrophilic film is non-porous, yet has water permeability, and unlike the porous film, does not rely on hydrophobicity to prevent the transfer of the humidity-controlling liquid, and thus even when used for a long period of time. There are no leaks. However, such a hydrophilic film can move water in these films as expected when the concentration of the humidity controlling liquid is low, but when the concentration of the humidity controlling liquid is high, the moving speed of the moisture can be increased. Was found to be extremely small.

The cause of this is not always clear, but when a non-porous film is used as a water permeable membrane, the solute also penetrates into the membrane and the concentration in the membrane increases, so the mobility of water in the membrane decreases. It is considered to be a thing.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art.

[0007]

The present invention has been made to solve the above-mentioned problems, and controls the humidity of a gas by moving water between a water-based humidity control liquid and a gas through a membrane. In the method, the membrane is composed of a multilayer film of a hydrophobic porous film and a hydrophilic non-porous film, a gas characterized in that the hydrophobic porous film is arranged to face the water-based humidity control liquid A humidity control method is provided.

The present invention will be described in more detail below. As the gas to be conditioned by the present invention, various gases such as commercial or residential air, oxygen, nitrogen, hydrogen, helium and other inert gases whose humidity is desired to be controlled are targeted. Furthermore, the gas used for various equipments, such as a refrigerating room, a dryer, and a refrigerator, is also targeted. According to the present invention, these gases are humidified or dehumidified to have a humidity of 10 to 10 depending on the purpose.
The humidity is adjusted to an appropriate level of 90%.

On the other hand, as the water-based humidity control liquid used in the present invention for controlling the humidity of the gas, a concentrated aqueous solution of 10 to 50% by weight is usually used, although it varies depending on the desired humidity level. The solute of the concentrated aqueous solution preferably has a large water absorption property, and examples thereof include aqueous solutions of salts such as alkali metal halides, sulfates, nitrates or carboxylates. Of these, use of lithium chloride, lithium bromide or the like is preferable.

The membrane used in the present invention comprises a multi-layer membrane comprising a hydrophobic porous film and a hydrophilic nonporous film,
Here, the hydrophobic porous film preferably has a water blocking resistance of 0.01 kg / cm ² or more, particularly 0.1 kg / cm.
² or more and air permeability is preferably 600 seconds / 10
It has 0 cc or less, preferably 200 seconds / 100 cc or less. Here, the water blocking pressure is defined as the pressure at which water seeps to the opposite surface when water pressure is applied. The air permeability is
It is defined as the time for 100 cm ³ of air to pass through an area of 1 square inch with a pressure differential of 4.88 inch H ₂ O.

The hydrophobic porous film preferably has a thickness of 5 to 200 μm, particularly 10 to 100 μm. As its material, a fluorinated hydrocarbon polymer or a hydrocarbon polymer is used. Among them, polytetrafluoroethylene is used. It is preferable to use polyethylene, polypropylene, polysulfone, or the like.

The hydrophilic non-porous film has a leak pressure resistance of preferably 0.1 kg / cm ² or more, particularly 0.5 kg / cm ² or more as a measure of non-porous property, and has a hydrophilic group in the molecule. The thickness of the polymer formed is preferably 0.1 to 100 μm, particularly 1 to 20 μm. Examples thereof include cellulose acetate, moisture permeable urethane, vinyl acetate, ion exchange membrane, polyimide and the like.

Among them, the ion exchange membrane is preferable because it has a high water permeability. Although various types of ion exchange membranes can be used, the water absorption rate when immersed in pure water at 25 ° C is preferably 10 to 200% by weight, particularly 20 to 100%.
% By weight, ion exchange capacity preferably 0.6-5.0 meq / g dry resin, especially 0.8-3.0 meq / g
g dry resin, and when immersed in pure water at 25 ° C., the fixed ion concentration is preferably 0.5 to 6 meq / g H _2.
O, particularly 1-5 meq / gH ₂ O is preferred.

As the ion exchange membrane used in the present invention, either a cation exchange membrane or an anion exchange membrane can be used, but preferably a strongly acidic cation exchange membrane or a strongly basic cation exchange membrane is used. It is suitable. As a material for the ion exchange membrane, a styrene resin, an ethylene resin, a polysulfone resin, a fluorine-containing hydrocarbon resin, or the like can be used.
Among them, a sulfonic acid cation exchange membrane made of a fluorine-containing hydrocarbon resin, particularly the following chemical formula 1 from the viewpoints of heat resistance, chemical resistance, molding processability and mechanical properties, especially small damage due to swelling and shrinking. An ion exchange membrane made of a fluoropolymer having the general formula of is preferred.

[0015]

[Chemical 1]

In the above general formula, p and q are positive integers, q / p is 2 to 16, m is 0 or 1, and n is an integer of 1 to 5.

The multilayer film of the hydrophobic porous film and the hydrophilic non-porous film used in the present invention can be produced by various means. For example, a polymer forming an ion exchange membrane or a precursor thereof. Method of casting a solution on a hydrophobic porous film, a polymer or a precursor solution thereof is once cast on another polymer film,
A lamination method in which an adhesive material is applied to the cast film and a hydrophobic porous film is attached to the film and then the polymer film is peeled off, and further, a polymer or film for forming an ion exchange film is formed. A method is used in which the hydrophobic porous film is heated and pressed.

The multi-layer membrane produced as described above has a hollow fiber shape, a tubular shape or a flat membrane shape, and the total thickness is preferably 5 to 300 μm, particularly 10 to 120 μm. The thickness ratio between the hydrophobic porous film and the hydrophilic non-porous film can be appropriately selected, but the former / latter is preferably 1 to 1000, particularly 10 to 100.

In the present invention, when the water-based humidity control liquid is brought into contact with a gas to control the humidity of the gas through the multilayer film, the gas is applied to the multilayer film or the hydrophilic non-porous film constituting the film. The water-based humidity control liquid is supplied to the hydrophobic porous film side.
When a hollow fiber or tubular membrane is used as the multilayer membrane,
It is preferable to dispose the hydrophilic non-porous film on the outside and supply the gas to be conditioned to the outside of the hollow fiber-shaped or tubular membrane because the pressure loss during gas flow can be reduced.

The water-based humidity control liquid and the gas are brought into contact with each other in a cocurrent or countercurrent system, and the supply rate of the water-based humidity control liquid is preferably 1 to 100 cm / sec, and the gas is preferably 0.5 to.
It is supplied at 20 m / sec. Thus, due to the relationship between the concentration of the water-based humidity control liquid and the humidity of the gas, the moisture moves through the multilayer film to control the humidity of the gas.

[0021]

[Function] When a low-humidity gas having a vapor partial pressure lower than that of the water-based humidity control liquid and the water-based humidity control liquid are present through the multilayer film, the water-based humidity control liquid has a hydrophobic property of the porous body. Although it is blocked and does not reach the non-porous film, water vapor evaporates from the free surface of the aqueous solution on the porous body side to reach the non-porous film, and further permeates the film and diffuses into the gas.

The hydrophilic property of the porous body gradually progresses, but since the gas side of the porous body has a non-porous film, gas such as air is present in the pores from the beginning. Therefore, the infiltration of the water-based humidity control liquid into the pores is reduced as compared with the case where there is no non-porous film. Furthermore, if the porous body is made hydrophilic locally, it will lead to leakage if the porous body is used alone and cause a problem for the entire system, but in the case of a non-porous film / porous body configuration, there is no water-based humidity control liquid. The perforated film prevents it from leaking. Although the water permeation performance of the part where the water-based humidity control liquid contacts the non-porous film is lowered, it can be used as a system until the range occupies a considerable part, and the life is greatly extended.

[0023]

【Example】

Example 1 Tetrafluoroethylene and CF ₂ ═CFO
CF ₂ CF (CF ₃ ) OCF ₂ CF ₂ SO ₂ F was copolymerized to obtain a copolymer A having an ion exchange capacity of 1.1 meq / g resin. The terminal processes the copolymer A in an aqueous solution of potassium hydroxide in the hydrolysis after hydrochloric acid to obtain a copolymer B was replaced -SO ₃ H. Copolymer B and ethanol were placed in an autoclave and heated and stirred to obtain an ethanol solution of copolymer B.

This solution was reinforced with a nylon cloth to give a pore size of 0.
6 μm, porosity 85%, thickness 20 μm made of polytetrafluoroethylene (PTFE) porous body (trade name Microtex, manufactured by Nitto Denko Corporation) to form a film of 10 μm in thickness, made of PTFE hydrophobic Non-porous water permeable film of porous film and ion exchange membrane (water absorption 23% by weight,
A composite membrane with a fixed ion concentration of 4.8 mol / kg H ₂ O) was prepared.

The obtained composite membrane was constructed into a two-chamber cell, and the porous body side was filled with a 40% by weight LiCl aqueous solution at room temperature, and the non-porous porous body film side was conditioned at various flow rates of 1 m / sec. When the humidity of the air coming out of the cell was measured while introducing air to measure the state of water permeation, the results shown in Table 1 were obtained.

[0026]

[Table 1]

Comparative Example 1 Tetrafluoroethylene and C
F ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ SO
₂ F was copolymerized to obtain a copolymer A having an ion exchange capacity of 1.1 meq / g resin. This copolymer A is hydrolyzed with an aqueous solution of potassium hydroxide and then treated with hydrochloric acid to terminate the end with -SO.
Copolymer B exchanged with ₃ H was obtained.

Copolymer B and ethanol were placed in an autoclave and heated and stirred to obtain an ethanol solution of copolymer B. After coating this solution on PTEF film, 60
After evaporating the solvent in a constant temperature bath at ℃, it was peeled from the PTFE film to obtain a 40 (μm) thick ion exchange membrane.

The obtained ion-exchange membrane was sandwiched in the same cell as in Example 1, 40% by weight of LiCl aqueous solution was filled into the porous body side at room temperature, and the nonporous film side was conditioned at various flow rates at a flow rate of 1 m / sec. When the humidity of the air coming out of the cell was measured while introducing air to measure the state of water permeation, the results shown in Table 2 were obtained.

[0030]

[Table 2]

Comparative Example 2 PTFE reinforced with nylon cloth, having a pore size of 0.6 μm, porosity of 85% and thickness of 20 μm
A porous film (trade name: Microtex, manufactured by Nitto Denko Corporation) is sandwiched between cells, and 40% LiCl on one side at room temperature.
The conditions of water permeation were measured by measuring the humidity of the air coming out of the cell while introducing the conditioned air of various humidities into the other side at a flow rate of 1 m / sec on the other side, and the results of Table 3 were obtained. was gotten.

[0032]

[Table 3]

[0033]

EFFECTS OF THE INVENTION In the present invention, the use of the multi-layer membrane allows the moisture transfer rate to be high and stable over a long period of time, so that the humidity control of gas can be efficiently performed. Further, since the water movement speed can be controlled by changing the concentration of the water-based humidity control liquid and the type of salt, it can be applied to the humidity control of various gases.

Claims (4)

[Claims] 1. A method for controlling the humidity of a gas by moving water between the gas and an aqueous humidity control solution through the film, wherein the film comprises a hydrophobic porous film and a hydrophilic non-porous film. A method for controlling the humidity of a gas, comprising a multilayer porous film, and a hydrophobic porous film facing the water-based humidity control liquid. 2. The water blocking withstand pressure of the hydrophobic porous film is 0.
01 kg / cm ² or more and the air permeability is 600 seconds /
The humidity control method according to claim 1, which is 100 cc or less. 3. A hydrophilic nonporous film having a water absorption rate of 10 to 2
00% by weight, fixed ion concentration 0.5-6 meq / gH
The humidity control method according to claim 1 or 2, which is an ion exchange membrane of ₂ O and an ion exchange capacity of 0.6 to 5.0 meq / g dry resin. 4. A water-based humidity control solution comprising Li having a concentration of 10% by weight or more.
The humidity control method according to claim 1, 2 or 3, which is a Cl aqueous solution.