KR20060004442A - Method for preparing polymer electrolyte membrane and membrane thereof - Google Patents

Abstract

The present invention relates to a method for preparing a polymer electrolyte membrane and a polymer electrolyte membrane, and in particular, having a conductivity of equal to or higher than that of a known Nafion solid electrolyte polymer, minimizing swelling according to moisture, and having low methanol permeability. The present invention relates to a method for preparing a polymer electrolyte membrane capable of easily producing a polymer electrolyte membrane capable of improving methanol crossover and a polymer electrolyte membrane prepared by the method, and to preparing a hydrophobic porous polymer membrane and a supercritical fluid. And a polymerization step of inserting a monomer of an ion conductive polymer into pores of the hydrophobic porous polymer membrane and superposingly polymerizing the ion conductive polymer in the pores under supercritical conditions of the supercritical fluid. Method for producing electrolyte membrane The polymer electrolyte membrane is related.

Polymer, electrolyte membrane, supercritical

Description

Manufacturing Method of Polymer Electrolyte Membrane and Its Polymer Electrolyte Membrane {METHOD FOR PREPARING POLYMER ELECTROLYTE MEMBRANE AND MEMBRANE THEREOF}

1 is a schematic temperature-pressure diagram showing the three and supercritical states of carbon dioxide, one of the supercritical fluids of the present invention.

2 is a system schematic diagram of one embodiment of a supercritical reactor for carrying out the method of preparing a polymer electrolyte membrane of the present invention.

<Description of the symbols for the main parts of the drawings>

1: gas cylinder 2: pressure gauge

3: compressor 4: booster

5: autoclave 6: heating furnace

The present invention relates to a method for preparing a polymer electrolyte membrane and a polymer electrolyte membrane, and in particular, having a conductivity of equal to or higher than that of a known Nafion solid electrolyte polymer, minimizing swelling according to moisture, and having low methanol permeability. The present invention relates to a method for preparing a polymer electrolyte membrane which can easily produce a polymer electrolyte membrane capable of improving methanol crossover, and a polymer electrolyte membrane prepared by the method.

In general, a fuel cell is a device in which a hydrocarbon-based or hydrogen is used as a fuel, and carbon or hydrogen and oxygen contained in the air are directly converted into electrical energy through an electrochemical reaction. It is a clean by-product and has been proposed as the next generation fuel energy technology because of its high efficiency.

These fuel cells are classified into alkali type, phosphoric acid type, molten carbonate type, solid oxide type, solid polymer electrolyte type, and direct methanol type. Among them, there is no risk of corrosion or evaporation by electrolyte and high current density can be obtained. In addition, due to the advantages of operating at a relatively low temperature, much attention has been paid to the solid polymer electrolyte type and direct methanol type fuel cell.

The electrolyte membrane used in the solid polymer electrolyte type and direct methanol type fuel cell may include Nafion, and the Nafion membrane may have the highest conductivity as a hydrogen ion conductive membrane developed to date. It is known to have the most common use, but the price is high, and it is difficult to make it thin to reduce the resistance. In particular, since it has structural conductivity in the wet environment, the efficiency is drastically reduced by swelling for a long time, and it is a direct methanol fuel cell. In the case of Methanol crossover occurs, there is a problem in reducing the efficiency of the fuel cell.                         

Therefore, in order to improve these problems, metal nanoparticles are coated on the surface of Nafion, inorganic / organic hybrid membranes are developed, surface treatment for methanol penetration prevention on the surface of Nafion, or Nafion and other polymers are dissolved in a suitable solvent. Methods for producing a composite film have been proposed.

Among them, a technique for preparing a hydrogen ion electrolyte membrane that fills the pores of a porous polymer membrane with a hydrogen ion conductive polymer was introduced in Japanese Patent JP 2003-263998A, but the method is chemically applied to a polymer thin film based on one or several kinds of hydrogen ion conductive polymers. Since the hydrogenation conductivity is made through the polymerization reaction to bond, there is a problem that the manufacturing method is difficult and the economical efficiency is inferior.

In the case of US Patents US Pat. No. 5,547,551 and 6425993 B1, a method of impregnating hydrogen ion transport materials into fine pores by introducing a thin porous polymer thin film into a solution in which a hydrogen ion transport polymer such as Nafion is dissolved is proposed. Even if impregnated in the hole of the ionic portion of the Nafion molecules are separated from the hydrophobic hydrocarbon portion in a partial separation, the methanol component infiltrated into the hydrated ionic portion can not prevent the phenomenon of permeation. There is a problem that it is not easy to impregnate the hydrogen ion transfer polymer evenly in the fine pores.

In order to solve the problems of the prior art as described above, the present invention has a conductivity equal to or higher than that of a known Nafion solid electrolyte polymer, while minimizing swelling according to moisture, and having low methanol permeability, thereby improving methanol crossover. It is an object of the present invention to provide a method for producing a polymer electrolyte membrane and a polymer electrolyte membrane produced thereby.

In addition, an object of the present invention is to provide a method for producing an electrolyte membrane which can be easily produced with high efficiency while satisfying the above conditions and a polymer electrolyte membrane produced thereby.

In addition, the present invention provides a method for preparing an electrolyte membrane and a polymer prepared thereby allowing the hydrophilic or hydrophobic ion conductive polymer to uniformly fill pores of the hydrophobic porous polymer membrane, and evenly disposed within the pores without bias of the ionic portion of the ion conductive polymer. It is an object to provide an electrolyte membrane.

The present invention to achieve the above object

Preparing a hydrophobic porous polymer membrane; And

Polymerization step of using a supercritical fluid as a solvent, in the supercritical conditions of the supercritical fluid, the monomer of the ion conductive polymer is inserted into the pores of the hydrophobic porous polymer membrane and polymerized and filled with the ion conductive polymer in the pores

It provides a method for producing a polymer electrolyte membrane comprising a.

In addition, the present invention

It provides a polymer electrolyte membrane, which is prepared by the production method.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.                     

The present invention relates to a method for preparing a polymer electrolyte membrane, comprising preparing a hydrophobic porous polymer membrane and using a supercritical fluid as a solvent, under supercritical conditions of the supercritical fluid, monomers of the ion conductive polymer in the pores of the hydrophobic porous polymer membrane. And a polymerization step of inserting and polymerizing and filling an ion conductive polymer in the pores.

That is, the polymer electrolyte membrane of the present invention is based on a hydrophobic porous polymer membrane in order to suppress the reaction with methanol and thereby prevent swelling and methanol crossover. Therefore, a hydrophobic porous polymer membrane for preparing an ion conductive polymer is prepared. As the hydrophobic porous polymer membrane, various known hydrophobic polymer membranes may be used, and in particular, a fluorine-based polymer, a hydrocarbon-based polymer, or a copolymer thereof may be used. The fluorine-based polymer may be poly (tetrafluoroethylene), poly (vinylidene fluoride), poly (trichlorofluoroethylene), poly (vinylfluoride) and the like are available, and hydrocarbon-based polymers may be used such as polyolefin, polysilane, polyester, polyamide, polyacrylate, polyvinyl chloride, polycarbonate, polyimide, etc. Various known methods may be applied to have a porous structure, and examples thereof may include a solvent and a plasticizer mixed with the polymer to prepare a film, and then obtain a porous structure by extracting a plasticizer through a solvent extraction method. have. Commercially available PP, Kapton (Dupont), Teflon (Dupont), U-Pore (Ubesa), Bayfol (Bayer Dormagon), and UPILEX (Ubesa) can also be used.                     

In addition, the hydrophobic porous polymer membrane has a thickness of 1 μm to 1 mm, a pore size of 1 nm to 10 μm, and a pore area of 10 to 90% of the total area, in terms of conductivity and reduction of resistance of the membrane. More preferably, the thickness is 5 μm to 300 μm, the average pore diameter is 10 nm to 1 μm, and the pore area is 20 to 80% of the total area to maintain proper membrane strength and to secure conductivity. (membrane) Good for reducing resistance.

Supercritical fluid as a solvent in the prepared porous hydrophobic polymer membrane, under supercritical conditions of the supercritical fluid, the monomer of the ion conductive polymer is inserted into the pores of the hydrophobic porous polymer membrane and polymerized by filling the ion conductive polymer in the pores The polymerization step is carried out. In other words, the method for producing a polymer electrolyte membrane of the present invention is characterized in that the polymerization is not performed inside the pores after the impregnation of the ion conductive polymer in the polymer state, but is performed in the supercritical solvent as well as the polymerization is carried out in the pores. Since the impregnation of the polymer state is not easy to impregnate the fine pores according to the size of the impregnated particles, the ion conductive polymer is formed through the polymerization reaction after the monomer is put into the pores to improve this. In particular, by conducting the environment in the supercritical fluid during the impregnation and polymerization, it is possible to obtain the effect of facilitating the inflow of the monomer into the pores by using the excellent diffusion force and low viscosity of the supercritical fluid. In particular, when the supercritical fluid flows into the polymer, its plasticizing action is active and the glass transition temperature of the polymer is lowered. Through this, the impregnated amount of the monomer can be increased to improve conductivity, and hydrophilic or hydrophobic. The ion conductive polymer of may evenly fill the pores of the hydrophobic porous polymer membrane, and evenly disposed within the pores without biasing the ionic portion of the ion conductive polymer.

The supercritical fluid refers to a fluid under a bilateral state that is controlled to have a density similar to that of the liquid phase with a transfer property such as diffusion coefficient and viscosity similar to that of the gas phase at a pressure and temperature above an intrinsic critical point (triple point). Various fluids available for known polymer polymerization reactions such as ethylene, propane, propylene, cyclohexane, isopropanol, benzene, toluene, ammonia, water, and nitric oxide can be applied, and in terms of being easily obtained from the surroundings, Water, methanol or carbon dioxide is preferred, and carbon dioxide or nitric oxide (N ₂ O) may be used when considering the ease of manufacture of the device for maintaining the supercritical conditions. Therefore, it is more preferable to use carbon dioxide that satisfies all these conditions. In other words, distilled water is easy to obtain from the surroundings, but the triple point (intrinsic critical point) condition has a temperature of 374.2 ° C. and a pressure of 217.6 atm. , The triple point condition of carbon dioxide is 31.1 ° C. and 73.8 atm, respectively, as shown in FIG. 1, and in the case of nitrogen oxide, the same condition is similar, so supercritical reactors can be formed at low temperatures and pressures. There is an advantage that can be configured. One embodiment thereof is as shown in FIG. 2. In addition, carbon dioxide is present in an infinite amount in nature, a large amount is generated as a waste in the steelmaking or petrochemical industry, it is colorless, odorless and chemically safe and has a favorable condition for use as a solvent.

In addition, the monomer of the ion conductive polymer corresponds to a hydrophilic monomer used in the synthesis of various known ion conductive polymers, and this includes the case where the ion conductive polymer is a hydrogen ion. Examples of the monomer of the ion conductive polymer include sulfonic acid and derivatives of phosphorous acid. Specific examples thereof include sodium acrylate sulfonate, sodium methacrylate sulfonate, sodium styrene sulfonate, acrylic acid, allylamine, allylsulfonic acid, allyl phosphoric acid, Strong acids such as vinyl groups, sulfonic acids, phosphorous acids, carboxyl groups, etc. in the structures of methacrylic sulfonic acid, methacrylic hose mixed acid, vinyl sulfonic acid, vinyl phosphoric acid, styrene sulfonic acid, styrene phosphoric acid, sulfonic acid of acrylamide, ethyleneimine, methacrylic acid, etc. Derivatives such as weak acid groups, strong bases such as primary to quaternary amines, monomers having weak bases, and esters thereof may be included.

In addition, by using only one type of such a monomer may form a homopolymer (Homopolymer) form, or by using two or more types may form a copolymer (Copolymer) form.

As a polymerization method of the monomer, various known polymerization methods may be applied thereto, and examples thereof include polymerization through an initiator addition.

In another aspect, the present invention provides a polymer electrolyte membrane in the form of a composite prepared by the above-described method. The polymer electrolyte membrane has a composite structure in which a hydrophobic matrix of a porous structure is filled with an ion conductive polymer.

The electrolyte membrane of the present invention can be applied to a variety of known fuel cells, and in particular, a form using the ion conductivity of the polymer solid electrolyte membrane and a polymer electrolyte capable of greatly improving the swelling problem of the hydrophilic ion conductive polymer membrane according to the present invention. It can be applied to fuel cells, and it can be applied to direct methanol fuel cell or reformed methanol fuel cell, because high efficiency fuel cell can be constructed through improvement of methanol crossover. It is more preferable to use it for the direct methanol fuel cell visualized.

According to the manufacturing method of the polymer electrolyte membrane of the present invention and the polymer electrolyte membrane, the polymerization is not only performed inside the pores after the impregnation of the ion conductive polymer in the polymer state, but also in the form of monomers, and such impregnation and polymerization is carried out in the supercritical solvent. By utilizing the excellent diffusion force and low viscosity of the supercritical fluid to facilitate the inflow of the monomer in the pores and to increase the amount of monomer impregnation to improve the conductivity, hydrophilic or hydrophobic ion conductive polymer is a hydrophobic porous polymer It has the advantage of evenly filling the pores of the membrane.

Therefore, it has a conductivity equal to or higher than that of known Nafion solid electrolyte polymers, and by applying a hydrophobic polymer, the base minimizes swelling according to the water required for ion conductivity, thereby securing durability of the polymer electrolyte membrane and fuel cell. There are advantages to it.

In addition, it has low methanol permeability through the hydrophobic nature of the matrix and evenly distributed arrangement of the ionic portion of the ion conductive polymer in the pores according to the supercritical polymerization conditions. A polymer electrolyte membrane for a fuel cell or a reformulated methanol fuel cell can be obtained, and an improved direct methanol fuel cell or a reformed methanol fuel cell can be obtained using the same.

In addition, the manufacturing method according to the present invention has the advantage of being able to easily prepare the electrolyte membrane with high efficiency while satisfying the above conditions.

The present invention described above is not limited to the above-described detailed description and drawings, and various modifications and changes made by those skilled in the art without departing from the spirit and scope of the present invention described in the claims below. Of course, it is also included within the scope of the present invention.

Claims (9)

Preparing a hydrophobic porous polymer membrane; And Polymerization step of using a supercritical fluid as a solvent, in the supercritical conditions of the supercritical fluid, the monomer of the ion conductive polymer is inserted into the pores of the hydrophobic porous polymer membrane and polymerized and filled with the ion conductive polymer in the pores Method for producing a polymer electrolyte membrane comprising a. The method of claim 1, The hydrophobic porous polymer membrane is a method for producing a polymer electrolyte membrane, characterized in that the fluorine-based, hydrocarbon-based or a copolymer thereof. The method of claim 1, The hydrophobic porous polymer membrane has a thickness of 1 μm to 1 mm, a pore size of 1 nm to 10 μm, and a pore area of 10 to 90% of the total area. The method of claim 1, The supercritical fluid is a method for producing a polymer electrolyte membrane, characterized in that carbon dioxide or nitrogen oxides. The method of claim 1, The monomer of the ion conductive polymer is a method for producing a polymer electrolyte membrane, characterized in that the derivative of sulfonic acid, phosphorous acid. A polymer electrolyte membrane, which is prepared by the method according to any one of claims 1 to 5. A fuel cell comprising the polymer electrolyte membrane of claim 6. A polymer electrolyte fuel cell comprising the polymer electrolyte membrane of claim 6. A direct methanol fuel cell comprising the polymer electrolyte membrane of claim 6.

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