Background Art Electrolysis is a chemical action for separating bonded elements and compounds of ion conductive materials such as electrolyte solution or molten salt by passing an electric current through them. Namly, when a pair of electrodes made of metal or graphite, shaped as a rod or a plate, are put in ion condutive material and connected with direct current, positinve ions (catons) and negative ions (anions) in the ion conductive material are moved to the cathode electrode and the anode electrode, respectively.

More specifically, the electrolysis occurs as the followings : The anode electrode with a high electrical potential discharges negative ions (anions) thereon, which produces varous materials. For example, when electrolyzing in NaCI solution, the anode produces chlorine molecules and outputs chlorine gas as formula Cl---). Cl + e, 2Cf- CI2. Here, some of chlorine gas is melted in the water such that it occurs various chemical reaction. In

another chemical reaction, the anode may be melted in the electrolytic solution to produce positive ions thereof. For example, when zinc plate is used for an anode in a watery sulfuric acid, zinc is melted the zinc plate, as formula Zn Zn2+ + 2e.

The cathode electrode with a low electrical potential discharges positive ions (cations). For example, when electrolyzing sulfuric acid, the cathode produces hydrogen molecures and outputs hydrogen gas as formula H++e < H, 2H < H2. Also, metal may be produced from the cathode electrode. For example, when copper sulfate solution is electrolyzed, copper is produced on the cathode surface.

The process of the electrolysis is applied to various fields such as analysis, electrometallurgy, machining, electroplating, and capacitor, etc. Also the process is used for producing chlorine and NaOH by electrolyzing saline solution.

Also, when electrolyzing water, hydrogen and oxygen gases are obtained, which is called as"water electrolysis". Hydrogen is mainly obtained by water electrolysis. The water electrolyzer for the wlater electrolysis is combined with a pluralty of unit cells, as shown in FIGS. 1 and 2.

FIG. 1 is a schematic view of electrolyzer for explaining water electrolysis according to the prior art, and FIG. 2 is a partially enlarged view of the electrolyzer.

The electrolyzer employs iron for the cathode electrode, and nicle or iron plate plating nicle for the anode electrode. Here, iron has characteristics that hydrogen overvoltage is relatively small and corrosion resistance is relatively

large. Also, it uses KOH solution or NaOH solution as electrolytic solution, in which its conductivity is relatively large.

Meanwhile, to prevent the gases produced from the anode and cathode electrodes from mixing, the electrolyzer has a sepration membrane between them. Here, the separing membrane is preferbly implemented by asbestos sheet. Therefore, the electrolyzer can prouce hydrogen having a purity of more than 99. 5-99. 7% and oxygen haing a purity of more than 99. 0-99. 5%. Also, when electrolyzing in KOH or NaOH solution at a temperature of 60°C, theoretical decomposition voltage is adjusted to 1. 125V considering water evaporation together with electrolyte gas, but peferably may be adjusted to a cell voltage of 1. 4-2. 4V.

Meanwhile, there are two gas discharging holes formed on a upper part of the electrode plate, each of which passes hydrogen and oxygen gases therethrough. Also, the electrode plate has another holes at a lower part thereof, each of which supplys electrolytic solution therethrough.

Also, the electrolyzer is constructed with a plurality of unit cells which are stackedly combined. The cathode and anode electrodes are fixed to the unit cells. The unit cell as a sing cell includes a gasket, a membrane fixing ring, a cell frame, etc. together with a membrane and electrode plates.

The upper part of each membrane 20 forms an oxygen gas flowing hole and an hydrogen flowing hole, respectively. The lower part forms electrolytic solution flowing hole. Each space between the anode electrode and electrode 50, between the electrodes 50 charging another polarity, and between the electrode 50 and the cathode electrode has a disc type membrane 20 having a smaller diameter than that of the electrode 50.

Therefore, if the membrane 20 is tightly fixed to one side of the frame 10, while the membrane fixng ring 30 and each ring of the membrane 20 are positioned to communicate each other, each extension part of the membrane fixing rings 30 is tightly connected to the surfaces around a hole of the membrane 20. Here the membrane 20 is positioned between each electrode 50 of one unit cell and each electrode of the other unit cell.

By the membrane 20 above, hydrogen gas (or oxygen gas) produced by one surface of the electrode 50 of one unit cell does not mix with oxygen gas (or hydrogen gas) produced by corresponding surface of the electrode of the other unit cell.

At this time, the electrolytic solution flowing in the electrolytic flowing hole from the outside flows in a membrane front space via a first cleaved part of third cylindrical part formed around the electrolytic flowing hole of the cell frame 10 and a second cleaved part formed an extension part of the membrane fixing ring 30.

The steps of flowing the electrolytic solution and discharging hydrogen and oxygen gases are performed at all the unit cells in the electrolyzer. Here the electrolysis occurs at spaces between the electrodes in the electrolytic solution at each unit cell.

The material of the cell frame 10 is Fiber Reinforced Polymer having characteristics that a chemical-resistance and heat-reistance are relatively large and mechanical strength is also large such that it can be continuously used at a temperature of 90°C. Peferably, th material of the cell frame 10 is implementec by polysulfone, poly imide, polyphenylene sulfide, polypropylene, etc. The gasket 40 is made of material having characteristics that a chemical-resistance,

heat-reistance, and mechanical strength are large, and elasticity is high as well.

Perfeably, the mateial of the gasket 40 is implemented by ethylene propylene diene monomer (EPDM) and polytetra fluoroethylene (Teflon), etc.

The membrane 20 is manufactured as the followings : First of all, organic synthetic fiber of polyphenylene sulfide with a thickness of 0. 5-2. Omm is proceeded in thick sulfuric acid at a temperature of 70~80°C for about two hours, and then washed by water. After that, it is dried at a temperatue of 150°C for three hours, thereby improving heat resistance/ electrical conductivity/ion mobility.

However, the prior art separation membrane of the elecrolyzer has disadvantages that its heat resistance and electrical conductivity go down in an electrolyzer employing an electrolytic solution of KOH of 25weight % and in an electrolyzer emplyoing an electrolytic solution of NaOH of 30weight %, thereby the ion mobility goes down. Therfore, the prior art electrolyzer can not efficiently separate hydrogen and oxygen.

Brief Description of the Drawings FIG. 1 is a schematic view of an electrolyzer for water electrolysis according to the prior art; and FIG. 2 is a partially enlarged view of FIG. 1.

Problems to Solution The present invention is to solve the prior art problems that a heat resistance characteristic and an electrical conductive characteristic of an electrolyzer decrease, thereby decreasing an ion mobility, in which the

electrolyer employs an electrolytic solution of KOH of 25weight % or NaOH of 30weight%, and to provide a membrane for separating hydrogen and oxygen gases in an electrolyzer which capable of maximizing a separation efficiency of hydrogen and oxygen gases and an operation efficiency of the electrolzer by removing efficiency decreasment factors from the reduction of the effective area of the electrode, which is caused by generation of a large amount of bubles in the elctrolyzer due to a penetration of dye and chemical in a basic step of fiber machining method for producing the membrane, and factor of disturbing water level regulation due to pseudo water level phenomena.

Also the present invention is to provide a manufacturing method of a membrane for separating hydrogen and oxygen gases in an electrolyzer which capable of maximizing a separation efficiency of hydrogen and oxygen gases and an operation efficiency of the electrolzer.

Technical Solutions In one aspect of the present invention, a membrane for separating hydrogen and oxygen gases in an electrolyzer, which is combined with a plurality of unit cells together with a gasket, a electrode, a member fixing ring and a cell frame, so that different gases can be obtained as an electrolytic solution supplied into the electrolyzer is electrolyzed, wherein the membrane is manufactured by weaving polypropylene thread, and wherein the polypropylene thread is refined and curtailed for 2-5miniutes in 70-80C in mixed alkaline bath of caustic soda (NaOH)/soda ash/non-ion surfactant/Sodium Tripoly Phosphate (Na5P3010), so that it may have a thickness of 0. 2-3. 5mm and a specific gravity of 0. 84-0. 95.

In another aspect of the present invention, A method for manufacturing a membrane for separating hydrogen and oxygen gases in an electrolyzer, which is combined with a plurality of unit cells together with a gasket, a electrode, a member fixing ring and a cell frame, so that different gases can be obtained as an electrolytic solution supplied into the electrolyzer is electrolyzed, wherein the method comprising the steps of: preparing a polypropylene thread obtained by coating with an electrolytic solution having a thickness of 0. 2-3. 5mm, a specific weight of 0. 85-0. 96 and hardness of R85-110 ; hydrolyzing the polypropylene thread using NaOH solution and firstly processing the surface of the polypropylene thread; coating the polypropylene thread with the first surface process with KOH solution and secondly processing the polypropylene thread with the first surface process; heating and drying the polypropylene thread with the first and second surface processes by a method using thermoplasticity of synthetic fiber in a furnace with a temperature of 190-200C for 30-90seconds so as to adjust its width and concentration, thereby a 500-150 mesh having a shape stability ; and weaving the 500-150 mesh.

Preferbley, the first surface processing is used NaOH solution of which consentration is 30-45weight %.

Pereferably, the second surface processing is used KOH solution of which consentration is 25weight %.

In yet another aspect, a method for manufacturing a membrane for separating hydrogen and oxygen gases in an electrolyzer, which is combined with a plurality of unit cells together with a gasket, a electrode, a member fixing ring and a cell frame, so that different gases can be obtained as an electrolytic

solution supplied into the electrolyzer is electrolyzed, wherein the method comprising the steps of: preparing a polypropylene thread obtained by coating with an electrolytic solution having a thickness of 0. 2-3. 5mm, a specific weight of 0. 85-0. 96 and hardness of R85~110 ; hydrolyzing the polypropylene thread using NaOH solution and firstly processing the surface of the polypropylene thread; coating the polypropylene thread with the first surface process with KOH solution and secondly processing the polypropylene thread with the first surface process; hydrolyzing the polypropylene thread with the first and second surface processes in mixing alkaline bath of caustic soda/soda ash (NaOH)/nonion surfactant/Sodium Tripoly Phosphate (Na5P301o) ; at the same time, refining and reducing the polypropylene thread at a temperature of 70~98°C for 2-5 minutes; heat-processing using a thermoplasticity ; heating and drying the polypropylene thread in a furnace with a temperature of 190~200°C for 30-90seconds so as to adjust its width and concentration, thereby a 500-150 mesh having a shape stability; and weaving the 500-150 mesh.

Advantage Effects The membrane for separating hydrogen and oxygen in an electrolyzer according to the present invention and the manufacturing method thereof can maximize the separating efficiency of hydrogen and oxygen gases as the heat- resistance and electrical conductivity of the electrolyzer are prevented from decreasing and ion mobility is prevented from decreasing, in which the electrolyzer uses an electrolytic solution of KOH of 25weigt % or NaOH of 95weight %.

Best Mode Carrying Out the Invention The preferred embodiment of the present invention will be explained in detail as the followings.

The embodiment of the present invention is related to a membrane for separating hydrogen and oxygen gases in an electrolyzer which is combined with a plurality of unit cells together with gasket, electrode, membrane fixing ring, cell frame.

Namely, the electrolyzer includes a plurality of unit cells stackedly combined and an anode and a cathode, which are fixed thereto. Here, the unit cell includes a gasket, a membrane fixing ring and cell frame, etc. together with a membrane and electrode plate. (Refer to FIGS. 1 and 2) The upper part of each membrane 20 forms an oxygen gas flowing hole and an hydrogen flowing hole, respectively. The lower part forms electrolytic solution flowing hole. Each space between the anode electrode and electrode 50, between the electrodes 50 charging another polarity, and between the electrode 50 and the cathode electrode has a disc type membrane 20 having a smaller diameter than that of the electrode 50.

The membrane 20 can be obtained by weaving polypropylene thread coated with electrolytic solution which is manufactured to have a specific weight of 085-0. 96 and a thickness of 0. 2-3. 5mm.

Also, the polypropylene thread manufactured as the above specification is refined and reduced in a mixing alkaline bath of caustic soda/soda ash (NaOH)/nonion surfactant/Sodium Tripoly Phosphate (Na5P301o) at a temperature of 70~98°C for 2-5minutes.

After that, the polypropylene thread coated with the electrolytic solution is dried in a furnace at a temperature of 190~200°C for 30-90seconds so as to adjust its width and concentration, thereby a 500-150 mesh having a shape stability can be obtained. Therefore the membrane 20 can be obtained by weaving the 500-150 mesh.

Now the manufacturing method of the membrane 20 will be explained in detail as the followings.

A polypropylene thread is obtained by coating with an electrolytic solution having a thickness of 0. 2-3. 5mm, a specific weight of 0. 85-0. 96 and hardness of R85-110.

The polypropylene thread coated by the above step is hydrolyzed using NaOH solution, which is called as first surface process.

The polypropylene thread with the first surface process is coated with KOH solution, which is called as second surface process. °C The polypropylene thread with the first and second surface processes is heat-processed by a method using thermoplasticity of synthetic fiber. Namely, it is heated and dried in a furnace with a temperature of 190~200°C for 30-90seconds so as to adjust its width and concentration, thereby a 500-150 mesh having a shape stability can be obtained. Therefore the membrane 20 can be obtained by weaving the 500-150 mesh.

Here, the concentration of the NaOH solution for the first surface process may be 30-45weight % and the concentration of the KOH solution for the second surface process may be 25weight %.

Preferred Embodiment of The Invention

As another embodiment of the present invention, the membrane 20 of the present invention is manufactured as a polypropylene thread is hydrolized in a mixing alkaline bath with a high consentration, at the same time, refined and reduced at a temperature of 70~98°C for 2-5 minutes, and heat-processed using a thermoplasticity.

Namely, a polypropylene thread is obtained by coating with an electrolytic solution having a thickness of 0. 2-3. 5mm, a specific weight of 0.85 - 0.96 and hardness of R85~110.

The polypropylene thread is hydrolyzed using NaOH solution, which is called as first surface process. The polypropylene thread with the first surface process is coated with KOH solution, which is called as a second surface process.

The polypropylene thread with the first and second surface processes is hydrolyzed in mixing alkaline bath of caustic soda/soda ash (NaOH)/nonion surfactant/Sodium Tripoly Phosphate (Na5P301o), at the same time, refined and reduced at a temperature of 70~98°C for 2-5 minutes, and heat-processed using a thermoplasticity.

After that, the polypropylene thread is heated and dried in a furnace at a temperature of 190~200°C for 30-90seconds so as to adjust its width and concentration, thereby a 500-150 mesh having a shape stability can be obtained. Therefore the membrane can be obtained by weaving the 500-150 mesh.

Having disclosed the embodiment of the present invention, many modifications thereto will become apparent to those skilled in the art to which it pertains, without deviation from the sprit of the invention, as defined by the scope of the appended claims.