JP2008198555A - Catalyst layer transfer sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transfer sheet with which a catalyst layer can be transferred superbly on an electrolyte membrane and which has no evil effect on performance of a fuel cell. <P>SOLUTION: The catalyst layer transfer sheet is the transfer film in which the catalyst layer is formed on one face of a base material sheet. The base material sheet is composed of a laminate of a biaxially-stretched polypropylene film and a metal foil, the biaxially-stretched polypropylene film has 2% or more of a heat shrinkage factor in the MD direction and/or the TD direction at 150°C, and the catalyst layer is formed on the biaxially-stretched polypropylene film side of the laminate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a catalyst layer transfer sheet.

  Various methods have been proposed to date for producing catalyst layers for fuel cells and the like. Among these, the transfer method of transferring the catalyst layer once produced using another base material to the electrolyte membrane is easy to form the catalyst layer, and since there is little adverse effect on the electrolyte membrane and the gas diffusion layer, It is advantageous.

  However, the transfer method has a problem that a part of the catalyst layer cannot be transferred when the catalyst layer is transferred to the electrolyte membrane.

  In order to solve such problems, a transfer film in which a fluorine-based release component is laminated between a base film and a catalyst layer has been proposed (Patent Document 1).

When the transfer film described in Patent Document 1 is used, the catalyst layer can be satisfactorily transferred to the electrolyte membrane. However, in the transfer film of Patent Document 1, it is inevitable that a part of the fluorine-based release component is transferred to the solid electrolyte membrane together with the catalyst layer, which has a problem that adversely affects the performance of the fuel cell. ing.
JP 2003-285396 A

  An object of the present invention is to provide a transfer sheet that can satisfactorily transfer the catalyst layer to the electrolyte membrane and that does not adversely affect the performance of the fuel cell.

  The present inventor has intensively studied in order to solve the above problems. As a result, it has been found that when a specific laminate is used as the base sheet of the transfer sheet, a desired transfer sheet can be obtained and the above problems can be solved. The present invention has been completed based on such findings.

The present invention provides the catalyst layer transfer sheet shown in the following items 1 to 3.
Item 1. A transfer sheet having a catalyst layer formed on one side of a base sheet, wherein the base sheet is a laminate of a biaxially stretched polypropylene film and a metal foil, and the biaxially stretched polypropylene film is 150 The thermal contraction rate of MD direction and / or TD direction in ° C is 2% or more, and the catalyst layer is a catalyst layer transfer sheet formed on the biaxially stretched polypropylene film side of the laminate.
Item 2. Item 2. The catalyst layer transfer sheet according to Item 1, wherein the thickness of the laminate is 20 to 150 µm.
Item 3. Item 3. The catalyst layer transfer sheet according to Item 1 or 2, wherein the thickness ratio of the biaxially stretched polypropylene film in the laminate is 10 to 50% of the entire laminate.

Catalyst layer transfer film The catalyst layer transfer sheet of the present invention is a transfer sheet in which a catalyst layer is formed on one surface of a base sheet. A sectional view showing an example of the catalyst layer transfer sheet of the present invention is shown in FIG.

Base Material Sheet The base material sheet of the present invention is composed of a laminate of a biaxially stretched polypropylene film and a metal foil.

  As the biaxially stretched polypropylene film, known films can be widely used as long as the thermal shrinkage in the MD direction and / or TD direction at 150 ° C. is 2% or more. The heat shrinkage rate in the MD direction and / or TD direction at 150 ° C. of the biaxially stretched polypropylene film is preferably 2 to 10%, more preferably 2 to 6%.

  The thickness of the biaxially stretched polypropylene film is usually 5 to 100 μm, preferably 10 to 40 μm, from the viewpoints of economy and handleability.

  As the metal foil, known materials can be widely used, and examples thereof include an aluminum foil, a copper foil, and a nickel foil. Among these, aluminum foil and copper foil are preferable.

  The thickness of the metal foil is usually 10 to 100 μm, preferably 20 to 50 μm, from the viewpoints of workability, economy, and the like.

  The total thickness of the laminate is preferably 20 to 150 μm, preferably 30 to 100 μm, from the viewpoints of workability and economics for forming the catalyst layer on the base film.

  The ratio of the thickness of the biaxially stretched polypropylene film in the laminate of the biaxially stretched polypropylene film and the metal foil is 10 to 50%, preferably 20 to 40% of the entire laminate.

  In the lamination of the biaxially stretched polypropylene film and the metal foil, an adhesive may be used or an adhesive resin may be used.

  In the present invention, it is essential to use a laminate of a biaxially stretched polypropylene film and a metal foil. When the biaxially stretched polypropylene film and the metal foil are each used alone for the base sheet, the effects of the present invention cannot be expressed.

Catalyst layer In the present invention, the catalyst layer is formed on the biaxially oriented polypropylene film side of the laminate.

  The catalyst layer is known and generally contains carbon particles supporting catalyst particles and a hydrogen ion conductive polymer electrolyte.

  Here, as a catalyst particle, platinum, a platinum compound, etc. are mentioned, for example. Examples of the platinum compound include an alloy of platinum and at least one metal selected from the group consisting of ruthenium, palladium, nickel, molybdenum, iridium, iron and the like.

  Examples of the hydrogen ion conductive polymer electrolyte include perfluorosulfonic acid-based fluorine ion exchange resins.

  In forming the catalyst layer on the base sheet, the carbon particles supporting the catalyst particles and the hydrogen ion conductive polymer electrolyte are mixed and dispersed in a suitable solvent and formed into a paste form. This paste is preferably applied on the biaxially oriented polypropylene film of the base sheet according to a known method so that the catalyst layer has a desired layer thickness.

  Examples of the solvent used include various alcohols, various ethers, various dialkyl sulfoxides, water, or a mixture thereof.

  The method of applying the paste is not particularly limited, and for example, general methods such as knife coater, bar coater, spray, dip coater, spin coater, roll coater, die coater, curtain coater, screen printing, etc. are applied. it can.

  After applying such paste, the catalyst layer is formed by drying. A drying temperature is about 40-100 degreeC normally, Preferably it is about 60-80 degreeC. Although depending on the drying temperature, the drying time is usually about 5 minutes to 2 hours, preferably about 30 minutes to 1 hour.

  The thickness of the catalyst layer is usually about 10 to 50 μm, preferably about 15 to 30 μm.

Catalyst Layer-Electrolyte Membrane Laminate The catalyst layer-electrolyte membrane laminate of the present invention is obtained by forming catalyst layers on both sides of the electrolyte membrane. An example of a cross-sectional view of the catalyst layer-electrolyte membrane laminate of the present invention is shown in FIG.

  The electrolyte membrane (catalyst layer-electrolyte membrane laminate) on which the catalyst layer of the present invention is laminated is, for example, after the transfer sheet is arranged and pressurized so that the catalyst layer surface of the transfer sheet of the present invention faces the electrolyte membrane surface The transfer sheet is manufactured by peeling the base sheet. By repeating this operation twice, a catalyst layer-electrolyte membrane laminate in which the catalyst layer surface is laminated on both surfaces of the electrolyte membrane is produced.

  In consideration of workability, the catalyst layer surface is preferably laminated on both surfaces of the electrolyte membrane at the same time. In this case, for example, the transfer sheet may be disposed such that the catalyst layer surface of the transfer sheet of the present invention faces both surfaces of the electrolyte membrane, and after pressing, the substrate sheet of the transfer sheet may be peeled off.

  The electrolyte membrane used is a known one. The thickness of the electrolyte membrane is usually about 20 to 250 μm, preferably about 20 to 80 μm. Specific examples of the electrolyte membrane include “Nafion” (registered trademark) membrane manufactured by DuPont, “Flemion” (registered trademark) membrane manufactured by Asahi Glass Co., Ltd., and “Aciplex” (registered trademark) membrane manufactured by Asahi Kasei Corporation. And “Gore Select” (registered trademark) membrane manufactured by Gore.

  The pressure level is usually about 0.5 to 10 Mpa, preferably about 1 to 10 Mpa in order to avoid transfer defects. Further, it is preferable to heat the pressure surface during this pressure operation in order to avoid transfer failure. The heating temperature is usually about 80 to 200 ° C., preferably about 135 to 150 ° C., in order to avoid breakage, modification and the like of the electrolyte membrane.

Electrode-electrolyte membrane assembly The electrode-electrolyte membrane assembly of the present invention is produced by placing electrode substrates on both sides of a catalyst layer-electrolyte membrane laminate and applying pressure.

  The electrode base material is well known, and various electrode base materials constituting a fuel electrode and an air electrode can be used.

  The pressure level is usually about 0.1 to 100 Mpa, preferably about 5 to 15 Mpa. It is preferable to heat at the time of this pressurization operation, and heating temperature may be about 120-150 degreeC normally.

  By using the transfer sheet of the present invention, a uniform catalyst layer can be formed on the electrolyte membrane.

  According to the present invention, it is possible to provide a transfer film for producing a catalyst layer-electrolyte membrane laminate that can transfer the catalyst layer to the electrolyte membrane satisfactorily and that does not adversely affect the performance of the fuel cell.

  Therefore, if the catalyst layer-electrolyte membrane laminate of the present invention is used, a high-quality fuel cell with excellent battery performance can be produced.

  The present invention will be further clarified by the following examples.

Reference example (creation of base sheet)
Aluminum foil having a thickness of 40 μm (Vespa 8021 manufactured by Sumisho Aluminum Foil Co., Ltd.) or copper foil having a thickness of 35 μm or 45 μm (NC-WS manufactured by Furukawa Circuit Foil Co., Ltd.) and a thickness of 5 μm, 10 μm, Adhesion of 20 μm or 40 μm biaxially stretched polypropylene (OPP, Treffan 2500 manufactured by Toray Industries, Ltd., thermal shrinkage in MD direction at 150 ° C.> 3%, thermal shrinkage in TD direction> 3%) Various base material sheets were manufactured by pasting together using an agent (AD-502 manufactured by Toyo Morton Co., Ltd.). The details of the base sheet are shown in Table 1 below.

  About the produced various base material sheets, the presence or absence of curling was evaluated according to the following criteria.

Presence or absence of curling (1) Each substrate sheet was allowed to stand for 10 minutes while being heated to 100 ° C. in an oven, and it was visually determined whether or not the substrate sheet was curled. The case where it did not curl was marked with ◎, and the case where it was curled was marked with ×.
(2) Using a hot press machine, various substrate sheets were hot-pressed at 150 ° C. and a pressure of 50 kg / cm ² for 5 minutes, and it was visually determined whether or not the substrate sheet was curled. The case where it did not curl was marked as ◎, and the case where it could not be curled and retained its shape was marked as x.

  These test results are also shown in Table 1.

Example 1
Platinum ruthenium-supported carbon (Pt: 27.2% by weight, Ru: 28.7% by weight) (Tanaka Kikinzoku Co., Ltd., TEC62E58) 10 parts by weight and 5% by weight electrolyte solution (manufactured by DuPont, DE-520, solvent) : 1-propanol / water = 1/1 (weight ratio)) was added to 100 parts by weight of isopropyl alcohol and 2 parts by weight of propylene glycol, and mixed and dispersed to prepare a catalyst layer forming paste.

  The catalyst layer forming paste is applied to one side of the base sheet A using a blade coater so that the thickness after drying is 20 μm and dried at 85 ° C. did.

Examples 2-6
A catalyst layer transfer sheet of the present invention was produced in the same manner as in Example 1 except that the base sheet B to the base sheet F were used instead of the base sheet A.

Evaluation test of transferability The catalyst layer transfer sheet produced in Examples 1 to 6 was cut into 2.5 cm x 2.5 cm and cut into 3.0 cm x 3.0 cm (Nafion 112, manufactured by DuPont). A transfer sheet was arranged on both sides of the transfer film so that the catalyst layer surface of the transfer film faced both surfaces of the electrolyte membrane, and transfer was performed at a temperature of 150 ° C. and a pressure of 6.5 MPa to produce a catalyst layer-electrolyte membrane laminate.

  The transfer properties of the transfer sheets obtained in Examples 1 to 6 were all good, and the catalyst layer could be easily transferred to the electrolyte membrane.

FIG. 1 is a cross-sectional view of the catalyst layer transfer sheet of the present invention. FIG. 2 is a cross-sectional view of the catalyst layer-electrolyte membrane laminate.

Claims (3)

A transfer sheet having a catalyst layer formed on one side of a base sheet,
The base sheet is composed of a laminate of a biaxially stretched polypropylene film and a metal foil,
The biaxially stretched polypropylene film has a thermal shrinkage of 2% or more in the MD direction and / or TD direction at 150 ° C.,
The catalyst layer is formed on the biaxially oriented polypropylene film side of the laminate,
Catalyst layer transfer sheet.   The catalyst layer transfer sheet according to claim 1, wherein the laminate has a thickness of 20 to 150 μm.   The catalyst layer transfer sheet according to claim 1 or 2, wherein the ratio of the thickness of the biaxially stretched polypropylene film in the laminate is 10 to 50% of the entire laminate.

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