KR102255814B1 - Transfer sheet for layer transfer and sheet with electrode catalyst layer - Google Patents

Abstract

The present disclosure provides a transfer sheet including a thermoplastic resin layer and a pair of porous fluororesin layers that are bonded to the thermoplastic resin layer and hold the thermoplastic resin layer therebetween. This transfer sheet is a transfer sheet capable of satisfactorily forming a transfer layer on the supporting surface, particularly, a transfer sheet capable of forming the transfer layer satisfactorily on the supporting surface even when heating is required to form the transfer layer. The layer transferred by this transfer sheet is, for example, an electrode catalyst layer used for an electrochemical device such as a fuel cell.

Description

A transfer sheet for transferring layers and a sheet with an electrode catalyst layer attached thereto {TRANSFER SHEET FOR LAYER TRANSFER AND SHEET WITH ELECTRODE CATALYST LAYER}

The present invention relates to a transfer sheet for transferring a layer, and more particularly, to a transfer sheet that can be used for carrying and transferring an electrode catalyst layer of an electrochemical device such as a fuel cell. Further, the present invention relates to a sheet to which an electrode catalyst layer is attached.

In a polymer electrolyte fuel cell (PEFC), a membrane electrode assembly (MEA) is used as its main component. MEA usually has an electrolyte membrane and an electrode catalyst layer, and a pair of electrode catalyst layers of an electrode catalyst layer for a fuel electrode and an electrode catalyst layer for a cathode are stacked on each main surface of the electrolyte membrane, respectively. A configuration of an MEA in which a diffusion layer is further formed on the surface of the electrode catalyst layer is also employed.

One of the methods of laminating the electrode catalyst layer on the electrolyte membrane is a transfer method. In the transfer method, a sheet having an electrode catalyst layer supported on the surface is prepared, and the electrode catalyst layer is transferred to an electrolyte membrane using the sheet as a transfer sheet. In Patent Document 1, a band-shaped electrolyte membrane and a band-shaped sheet carrying an electrode catalyst layer were stacked, the laminate was passed between a pair of heated thermal transfer rolls, and then the sheet was peeled off, and the electrode catalyst layer was formed as an electrolyte membrane. A method of continuous thermal transfer is disclosed. Patent Document 2 discloses a method of bonding an electrode catalyst layer formed on a substrate to a polymer electrolyte membrane by hot pressing, then peeling the substrate and transferring the electrode catalyst layer to the electrolyte membrane.

Japanese Patent Publication No. 2008-103251 Japanese Patent Application Publication No. 2013-073892

Along with the demand for miniaturization of fuel cells, there is a demand for thinning of the electrode catalyst layer. In the transfer method, it is attempted to form a thin electrode catalyst layer by using a low-viscosity paste. On the other hand, the main surface (support surface) of the sheet for supporting the transferred layer (transfer layer) needs to have a high releasability with respect to the transfer layer formed thereon. In consideration of this, as a transfer sheet, for example, a fluororesin sheet may be employed. However, when the viscosity of the paste is low, the paste applied onto the fluororesin sheet is repelled from the sheet, and a transfer layer cannot be formed satisfactorily on the transfer sheet in some cases.

In addition, the transfer sheet may be heated when forming an electrode catalyst layer or the like from a coating layer of a paste applied on the sheet.

One of the objects of the present invention is to provide a transfer sheet capable of satisfactorily forming a transfer layer on the supported surface, especially when heating is required to form a transfer layer. It is an offer.

The transfer sheet of the present invention is a transfer sheet for transferring a layer comprising a thermoplastic resin layer and a pair of porous fluororesin layers that are bonded to the thermoplastic resin layer and hold the thermoplastic resin layer therebetween.

The sheet to which the electrode catalyst layer of the present invention is attached includes a sheet including a thermoplastic resin layer and a pair of porous fluororesin layers that are bonded to the thermoplastic resin layer and hold the thermoplastic resin layer therebetween; It has an electrode catalyst layer. The electrode catalyst layer is disposed on at least one of the porous fluororesin layers of the sheet.

According to the present invention, a transfer sheet capable of satisfactorily forming a transfer layer on the supporting surface, in particular, a transfer sheet capable of forming the transfer layer satisfactorily on the supporting surface even when heating is required to form the transfer layer is achieved. .

1 is a cross-sectional view schematically showing an example of the transfer sheet of the present invention.
It is a schematic diagram for demonstrating the method of evaluating the curl height of a sheet.
It is a schematic diagram for demonstrating the method of evaluating the curl height of a sheet.
4 is a cross-sectional view schematically showing an example of a sheet with an electrode catalyst layer of the present invention.
5 is a cross-sectional view schematically showing an example of an MEA that can be manufactured using the transfer sheet of the present invention.
6 is a diagram schematically showing an example of a method of manufacturing an MEA using the transfer sheet of the present invention.

The transfer sheet of the first aspect of the present disclosure includes a thermoplastic resin layer and a pair of porous fluororesin layers that are bonded to the thermoplastic resin layer and hold the thermoplastic resin layer therebetween. to be.

In the second aspect of the present disclosure, in the transfer sheet of the first aspect, the layer transferred by the transfer sheet is an electrode catalyst layer.

In the third aspect of the present disclosure, in the transfer sheet of the first or second aspect, the curl height of the end portion when allowed to stand in an atmosphere of 120° C. for 5 minutes is 10 mm or less.

In the fourth aspect of the present disclosure, in the transfer sheet of any one of the first to third aspects, the thermoplastic resin layer and the pair of porous fluororesin layers are joined by fusion bonding.

In the fifth aspect of the present disclosure, in the transfer sheet of any one of the first to fourth aspects, the melting point of the thermoplastic resin constituting the thermoplastic resin layer is 280°C or less.

In the sixth aspect of the present disclosure, in the transfer sheet of any one of the first to fifth aspects, the thermoplastic resin constituting the thermoplastic resin layer is a group consisting of polyester, polyacetal, polyethylene, ultra-high molecular weight polyethylene, and polypropylene. It is at least one kind selected from.

In a seventh aspect of the present disclosure, in the transfer sheet of any one of the first to sixth aspects, the fluororesin constituting the porous fluororesin layer is polytetrafluoroethylene.

In an eighth aspect of the present disclosure, in the transfer sheet of any one of the first to seventh aspects, the average pore diameter of the fluororesin porous layer is 0.1 µm to 20 µm.

In the ninth aspect of the present disclosure, in the transfer sheet of any of the first to eighth aspects, the thickness of the fluororesin porous layer is 3 µm to 200 µm.

In a tenth aspect of the present disclosure, in the transfer sheet of any of the first to ninth aspects, the thickness of the transfer sheet is 15 µm to 400 µm.

An eleventh aspect of the present disclosure is a sheet including a thermoplastic resin layer and a pair of porous fluororesin layers that are bonded to the thermoplastic resin layer and hold the thermoplastic resin layer therebetween;

Having an electrode catalyst layer,

There is provided a sheet with an electrode catalyst layer, wherein the electrode catalyst layer is disposed on at least one of the fluororesin porous layer of the sheet.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following is a description of an example of the present invention, and the present invention is not limited to the range indicated by this example.

(Transfer sheet)

1 shows a transfer sheet 10 of this embodiment. The sheet 10 includes a thermoplastic resin layer (hereinafter simply referred to as "resin layer") 1 and a pair of fluororesin porous layers (hereinafter simply referred to as "porous layer") (2) It is equipped with. The sheet 10 is a transfer sheet for transferring a layer formed and supported thereon to another member. The supporting surface of the sheet 10 carrying the transferred layer (transfer layer) is at least one main surface of the porous layer 2 (the main surface 22 on the opposite side to the main surface 21 on the side in contact with the resin layer 1). )]to be. That is, the supported surface of the sheet 10 is made of a fluororesin, and high releasability for the transfer layer formed thereon is ensured. In order to support the transfer layer, the main surface 22 of the at least one porous layer 2 is exposed. As shown in Fig. 1, when the main surfaces 22 of both porous layers 2 are exposed on the surface of the sheet 10, both sides of the main surface 22 may be supported, and only one may be supported. do.

The supported surface of the sheet 10 is porous, for example, a material applied to the supported surface, as a more specific example, even when the viscosity and/or solid content concentration of the paste serving as the electrode catalyst layer after drying is low, a simple fluororesin sheet, In particular, compared to the transfer sheet, which is a non-porous fluororesin sheet, the material is less likely to repel.

In addition to this, the sheet 10 includes not only the porous layer 2 but also the resin layer 1 bonded thereto. In the case of the porous layer 2 alone, it is easy to extend as a sheet substrate, and the extension of the sheet causes damage such as deformation or cracking of the transfer layer formed on the supported surface. However, in the sheet 10, the resin layer 1 is a reinforcing layer. Thus, the occurrence of such deformation and damage of the transfer layer is suppressed. This property is particularly advantageous in the formation of the transfer layer by use of the strip-shaped sheet 10, so-called Roll to Roll.

Further, the sheet 10 has a configuration in which the resin layer 1 is sandwiched by a pair of porous layers 2. In this configuration, deformation of the sheet 10 is suppressed even when the sheet 10 is heated for, for example, formation of a transfer layer or the like. The deformation of the sheet 10 due to heating is the occurrence of curls due to a difference in the linear thermal expansion coefficient between the resin layer 1 and the porous layer 2, for example. Since the deformation of the transfer sheet 10 causes deformation and/or damage of the transfer layer due to, for example, contact with the wall of the heating furnace, the occurrence of such deformation and damage of the transfer layer is suppressed in the sheet 10. do.

In these respects, in the sheet 10, the transfer layer can be favorably formed on the supported surface. In particular, when a material that is easily repelled by a sheet substrate having high releasability is used for formation of the transfer layer, and when heating of the sheet substrate is required to form the transfer layer, the transfer layer should be well formed on the supported surface. I can. Being able to use a repellent material contributes to the stable formation of, for example, a thin transfer layer or a transfer layer having a uniform thickness.

The transfer layer transferred by the sheet 10 is not limited, for example, an electrode catalyst layer used in an electrochemical device such as a fuel cell, and as a more specific example, an electrode catalyst layer provided by the MEA. In general, since an electrode catalyst layer is formed through a heat drying process, and a thin electrode catalyst layer is required for a small electrochemical device, the sheet 10 is used as a transfer sheet for the electrode catalyst layer (a transfer sheet for an electrode catalyst layer). It has a high advantage. In addition, the precursor layer thereof is also included in the electrode catalyst layer.

In the sheet 10 of the present embodiment, the resin layer 1 and the porous layer 2 are fused (bonded by fusion). Bonding by fusion bonding of both layers is suitable for forming the sheet 10 having a uniform thickness and reducing the manufacturing cost of the sheet 10.

The fusion bonding of the porous layer 2 and the resin layer 1 can be performed, for example, by thermal lamination or hot pressing. In thermal lamination, the porous layer 2 and the resin layer 1 are fused by maintaining the temperature of the thermal roll at, for example, 130 to 290°C, and pressing this at a linear pressure of, for example, 10 to 40 N/m. The line speed at this time varies depending on the diameter of the heat roll and the heating temperature, but is preferably 3.0 to 20.0 m/min, for example. The thickness of the sheet 10 is, for example, in the range of 15 µm to 400 µm, and preferably in the range of 50 µm to 300 µm.

The form of bonding of the resin layer 1 and the porous layer 2 is not limited. The resin layer 1 and the porous layer 2 may be bonded together by, for example, an adhesive or an adhesive.

The melting point of the thermoplastic resin constituting the resin layer 1 is preferably 280°C or less. The thermoplastic resin constituting the resin layer 1 is preferably at least one selected from the group consisting of polyester, polyacetal (POM), polyethylene (PE), ultra high molecular weight polyethylene (UHMWPE) and polypropylene (PP). Polyester is, for example, polyethylene terephthalate (PET), polybutylene terephthalate, and the like. With respect to polyethylene terephthalate, a resin having a low softening temperature is preferable, and particularly, a resin whose softening starts at a temperature lower than 233°C is preferable. POM and PET are preferred thermoplastic resins from the viewpoints of difficulty in deterioration during heating, heat resistance and chemical resistance. The resin layer 1 made of a thermoplastic resin having a melting point of 280° C. or less can be fused with the porous layer 2 in good condition. With the sheet 10 in which the porous layer 2 and the resin layer 1 are satisfactorily fused, and both layers are difficult to peel from each other, a transfer layer can be better formed on the supported surface. In addition, the fluororesin porous layer 2 is excluded from the resin layer 1.

The thickness of the resin layer 1 is, for example, in the range of 12.5 µm to 200 µm, and preferably in the range of 25 to 175 µm. When the thickness of the resin layer 1 is excessively small, the handleability of the sheet 10 may be deteriorated. When the thickness of the resin layer 1 is excessively large, the weight of the roll may be excessive when the sheet 10 is formed in a roll shape. have.

The shape of the resin layer 1 is not limited, and may be, for example, a woven fabric, a nonwoven fabric, a net, a stretched porous film, a microparticle fusion porous film, or the like, but is preferably a non-porous film. If the resin layer 1 is a non-porous membrane, the surface roughness of the main surface 11 facing the porous layer 2 of the resin layer 1 decreases, so that the support surface of the sheet 10 through the porous layer 2 The value of the surface roughness Rz can be reduced. In addition, it is possible to more stably hold the transfer layer together with the porous layer 2.

The fluororesin constituting the porous layer 2 is, for example, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and tetrafluoroethylene-hexafluoropropylene. It is a copolymer (FEP). A preferred fluororesin is PTFE. The porous layer 2 does not have to contain components other than a fluororesin, and does not have to substantially contain components other than a fluororesin. In the present specification, "substantially not included" means that the content is less than 0.1% by weight, preferably less than 0.01% by weight.

The thickness of the porous layer 2 is, for example, in the range of 3 to 200 µm, preferably in the range of 4 to 150 µm, more preferably in the range of 5 to 90 µm, and even more preferably It is in the range of 7 to 80 μm. In these ranges, partial dropout of the porous membrane 2 due to cohesive failure or the like is unlikely to occur, and the handling property of the sheet 10 becomes better.

The average pore diameter of the porous layer 2 is, for example, in the range of 0.1 to 20 µm, preferably in the range of 0.2 to 15 µm, more preferably in the range of 0.2 to 10 µm, and further preferably Specifically, it is in the range of 1.5 to 7.0 μm. With the porous layer 2 having these appropriate average pore diameters, the above-described bounce of the material forming the transfer layer based on the high releasability of the sheet substrate can be suppressed more reliably. When the average pore diameter of the porous layer 2 becomes excessive, for example, after transferring the electrode catalyst layer, which is the transfer layer, carbon particles or catalyst components contained in the electrode catalyst layer may remain in the pores of the porous layer 2. have.

The contact angle with water on the supported surface of the sheet 10 is preferably 100 degrees or more, 120 degrees or more, and further 130 degrees or more. The supporting surface exhibiting a high contact angle with water has excellent releasability with the transfer layer. In this specification, the contact angle with water is a value evaluated by the static method specified in JIS R3257. In addition, although JIS R3257 is a standard regarding a method of evaluating the contact angle of the surface of the substrate glass, the contact angle of the supported surface of the sheet 10 with water can be evaluated under the test conditions determined in the standard.

With respect to the sheet 10, the curl height of the edge when the sheet is allowed to stand in an atmosphere of 120° C. for 5 minutes is, for example, 10 mm or less, preferably 7 mm or less, and more preferably 5 mm or less. The curl height at the end can be evaluated as follows. First, a sheet as an evaluation object is cut out to a width of 490 mm x 500 mm length to obtain a test piece 31 (Fig. 2(a) and Fig. 3(a)). 3 shows a cross section obtained by cutting the test piece 31 and the plane 32 shown in FIG. 2 into a cross-section of the test piece 31 in the width direction. In addition, the horizontal direction of the paper in FIG. 2 is the width direction of the test piece 31]. "Width" is, for example, the TD direction of the sheet (in the case of a belt-shaped sheet, the width direction). "Length" is, for example, the MD direction of the sheet (in the case of a belt-shaped sheet, the longitudinal direction). Next, the test piece 31 is accommodated in a dryer maintained at 120°C and left standing for 5 minutes. At that time, the test piece 31 is allowed to stand on a flat surface 32 that does not generate deformation at 120° C. that affects the evaluation of the curl height. The plane 32 is, for example, a surface of a metal plate. After standing for 5 minutes, the test piece 31 is taken out of the dryer for each of the flat surfaces 32 and cooled to room temperature. After cooling, for each of the short sides (left and right ends) 33a, 33b on both sides of the width direction of the test piece 31, the ends 33a, 33b floating from the plane 32 by standing for 5 minutes at 120°C. The maximum values (maximum values) of the heights h1 and h2 of are measured (Fig. 2(b) and Fig. 3(b)), and the average can be taken as the curl height of the edge of the sheet 10.

When the size of the sheet to be evaluated does not satisfy the size of the test piece 31 (490 mm width x 500 mm length), a sheet cut into a smaller size is used as the test piece, and the curl height of the end can be obtained by the above method. I can. However, as the size of the test piece decreases, the curl height actually measured even with the same sheet decreases. For this reason, the coefficient according to the size of the test piece used for measurement is multiplied by the measured value, and it is converted into a value when a test piece of 490 mm width x 500 mm length is used for measurement, and this conversion value is used as the curl height of the edge of the sheet. can do. The coefficient was measured by the above method while changing the size of the test piece on the sheet 10 available for obtaining a test piece of 490 mm width × 500 mm length, and the obtained measurement value (for a test piece of 490 mm width × 500 mm length) Can be calculated from measurements and measurements for smaller sized specimens). For example, when a test piece having a width of 300 mm x 300 mm in length is used, the measured value becomes 3% smaller than that of a test piece having a width of 490 mm x 500 mm in length. For this reason, the converted value obtained by multiplying the measured value by a coefficient of 1.03 (=1/0.97) can be used as the curl height of the edge of the sheet. In addition, when a test piece of 50 mm width x 100 mm length is used, the measured value becomes 10% smaller than the case where a test piece of 490 mm width x 500 mm length is used. For this reason, the converted value obtained by multiplying the measured value by a coefficient of 1.11 (=1/0.90) can be used as the curl height of the edge of the sheet.

(Sheet with electrode catalyst layer attached)

4 shows the sheet 15 of this embodiment. The sheet 15 includes a sheet 10 which is a laminate comprising a resin layer 1 and a pair of porous layers 2 for sandwiching the resin layer 1, and one main surface of the sheet 10 (porous It is a laminated sheet provided with the transfer layer 3 disposed on the main surface 22 of the layer 2]. In the form shown in Fig. 4, the transfer layer 3 is an electrode catalyst layer, and the sheet 15 is a sheet to which an electrode catalyst layer is attached. The sheet 15 is constituted by stacking a porous layer 2, a resin layer 1, a porous layer 2, and a transfer layer 3 in this order.

The sheet 10 includes a preferred example thereof, and is the same as the description of the transfer sheet 10 of the present invention described above. The transfer layer 3 is a layer having a thin and/or uniform thickness in which the occurrence of deformation and damage at the time of formation thereof is suppressed, for example, so that it can be understood from the description of the transfer sheet 10 so far. to be.

Using the sheet 15, the electrode catalyst layer can be transferred to the electrolyte membrane to form the MEA. As shown in FIG. 5, in the MEA 20, the transfer layer 3 transferred onto the electrolyte membrane 5 becomes the electrode catalyst layer 6. The configuration of the transfer layer 3, which is an electrode catalyst layer, is as described for the electrode catalyst layer 6 below.

(MEA)

An example of a product that can be manufactured using the sheet 10 or the sheet 15 is MEA for electrochemical devices such as PEFC.

As shown in FIG. 5, for example, the MEA 20 is formed by an electrolyte membrane 5, which is typically a polymer electrolyte membrane, and a pair of electrode catalyst layers 6 sandwiching and supporting the electrolyte membrane 5. It is composed. The electrode catalyst layer 6 is, for example, a porous thin film having pores having a diameter of 1 μm or less, and mainly contains catalyst material-carrying particles and a polymer electrolyte. As the polymer electrolyte constituting the electrolyte membrane 5 and the polymer electrolyte included in the electrode catalyst layer 6, a known polymer electrolyte such as a fluorine-based polymer electrolyte and a hydrocarbon-based polymer electrolyte may be used.

The MEA manufacturing method using the sheet 10 includes, for example, an electrode catalyst layer lamination process, an electrolyte membrane lamination process, a heat compression bonding process, and a peeling process. The electrode catalyst layer lamination step is a step of forming the transfer layer 3 as an electrode catalyst layer on the sheet 10. The electrolyte membrane lamination process is a process of laminating the sheet 10 and the electrolyte membrane 5 so that the transfer layer 3 and the electrolyte membrane 5 contact each other. The heat-press bonding process is a process of heat-compressing the transfer layer 3 and the electrolyte membrane 5. The peeling process is a process of peeling the sheet 10 and leaving the transfer layer 3 as the electrode catalyst layer 6 on the electrolyte membrane 5.

An example of an electrode catalyst layer lamination process is shown. First, a coating film is formed by applying a catalyst solution (electrode catalyst layer paste) in which catalyst material-carrying particles and a polymer electrolyte are dispersed in a solvent on the main surface (supported surface) 22 of the sheet 10 on which the porous layer 2 is exposed. do. Subsequently, it is heated and dried at a temperature of about 30 to 180°C to obtain a laminate of the sheet 10 and the transfer layer 3 as an electrode catalyst layer (the sheet 15 to which the electrode catalyst layer is attached). Known methods, such as a doctor blade method, a screen printing method, a roll coating method, and a spray method, can be adopted as a method of applying the catalyst solution.

The heating and compression bonding process is performed by hot pressing the stack of the electrolyte membrane 5 and the sheet 15 in a state in which the electrolyte membrane 5 and the transfer layer 3 are in contact, or passing them through a pair of hot rolls. I can. The temperature of the heating and compression bonding at this time depends on the type of the electrolyte membrane 5 and the like, but is preferably about 80 to 150°C. Transfer layers 3 on both sides of the electrolyte membrane 5 by passing the stacked body supported by sandwiching both sides of the electrolyte membrane 5 with a sheet 15 on which two electrode catalyst layers are attached, through a pair of heat rolls, etc. ) May be pressed at the same time.

The peeling process can be performed by continuously peeling the sheet 10 from the compressed body of the electrolyte membrane 5 and the sheet 10 using, for example, a roll that winds up the sheet 10. The peeled sheet 10 can be reused.

Fig. 6 shows an example of an apparatus that performs a heat compression bonding process and a peeling process as a series of processes. The layer 3 of the sheet 15 with the electrode catalyst layer fed out from the feeding roll 52 is brought into contact with the electrolyte membrane 5 and passed between a pair of heating rolls 54 to make both of them in close contact. Thereafter, only the sheet 10 is peeled off and wound with the recovery roll 53, whereby the laminate 7 in which the electrode catalyst layer 6 is bonded to one side of the electrolyte membrane 5 can be continuously manufactured.

The catalyst material used for the catalyst material-carrying particles includes, for example, platinum group elements such as platinum, palladium, ruthenium, iridium, rhodium, and osmium; Metals such as iron, lead, copper, chromium, cobalt, nickel, manganese, vanadium, molybdenum, gallium, and aluminum; Alloys thereof; These are oxides and double oxides of metals. When the particle diameter of the catalyst is too large, the activity of the catalyst decreases, and when it is too small, the stability of the catalyst decreases. Therefore, 0.5 to 20 nm is preferable, and 1 to 5 nm is more preferable. The catalyst, which is a particle of one or two or more metals selected from the group consisting of platinum, gold, palladium, rhodium, ruthenium, and iridium, has excellent electrode reactivity, and the electrode reaction is efficiently and stably performed by the catalyst. A polymer electrolyte fuel cell having an electrode catalyst layer including such a catalyst exhibits high power generation characteristics.

As the particles carrying the catalyst material, carbon particles are suitable. The carbon particles are not particularly limited as long as they are particulate, have conductivity, and do not enter the catalyst, but examples thereof include carbon black, graphite, graphite, activated carbon, carbon fibers, carbon nanotubes, and fullerenes. If the particle diameter of the carbon particles is too small, it becomes difficult to form an electron conduction path, and if too large, the gas diffusibility of the electrode catalyst layer decreases, or the utilization rate of the catalyst decreases. It is preferably 10 to 100 nm.

For the polymer electrolyte, a known material can be used regardless of the difference in cation conductivity and anion conductivity. Cationic conductivity is, for example, proton conductivity. As the polymer electrolyte having proton conductivity, for example, a fluorine-based polymer electrolyte and a hydrocarbon-based polymer electrolyte can be used. The fluorine-based polymer electrolyte is, for example, Nafion (registered trademark) manufactured by DuPont. Hydrocarbon-based polymer electrolytes are, for example, sulfonated polyether ketone, sulfonated polyether sulfone, sulfonated polyether ether sulfone, sulfonated polysulfide, sulfonated polyphenylene, and the like. In consideration of the adhesion between the electrolyte membrane and the electrode catalyst layer, it is preferable that the electrolyte constituting the electrolyte membrane and the electrolyte constituting the electrode catalyst layer are the same.

The solvent used in the catalyst solution is not particularly limited as long as it does not corrode the catalyst material-carrying particles, and can dissolve or disperse the polymer electrolyte as a fine gel in a state of high fluidity. Examples of the solvent used in the catalyst solution include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol and pentanol; Ketone solvents such as acetone, methyl ethyl ketone, pentanone, methyl isobutyl ketone, heptanone, cyclohexanone, methyl cyclohexanone, acetonyl acetone, and diisobutyl ketone; Ether solvents such as tetrahydrofuran, dioxane, diethylene glycol dimethyl ether, anisole, methoxytoluene, and dibutyl ether; They are dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethylene glycol, diethylene glycol, diacetone alcohol, and 1-methoxy-2-propanol. The solvent used in the catalyst solution preferably contains a volatile organic solvent, and preferably contains a polar solvent. The solvent used in the catalyst solution may be a mixture of two or more of these solvents.

In order to disperse the catalyst substance-carrying particles satisfactorily, a dispersant may be contained in the catalyst solution. Dispersants are, for example, anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants. Among them, sulfonic acid type surfactants such as alkylbenzene sulfonic acid, oil-soluble alkylbenzene sulfonic acid, α-olefin sulfonic acid, sodium alkylbenzene sulfonate, oil-soluble alkylbenzene sulfonate, and α-olefin sulfonate are preferably used.

Example

Hereinafter, the present invention will be described in more detail by examples. The present invention is not limited to the following examples.

(Example 1)

With respect to 100 parts by weight of PTFE fine powder (manufactured by Daikin Kogyo Co., Ltd., Polyflon F-104), 20 parts by weight of a liquid lubricant (n-Dodecane, manufactured by Japan Energy Co., Ltd.) were uniformly mixed and compressed into a cylinder. Later, it extruded with a ram extruder to obtain a sheet-like molded body extending in the longitudinal direction. This sheet-shaped molded article was passed between metal rolling rolls in a state containing a liquid lubricant, and rolled so as to have a thickness of 0.2 mm. Then, the liquid lubricant was removed by heating the sheet-shaped molded body to 150°C, and the sheet-shaped molded body was dried. Thereafter, the sheet-shaped molded article was stretched at a magnification of 20 times in the longitudinal direction at 370°C. Subsequently, the obtained sheet-shaped molded article stretched in the longitudinal direction was stretched at 180° C. at a magnification of 5 times in the width direction to obtain a PTFE porous membrane having a thickness of 40 μm and an average pore diameter of 3.0 μm.

The obtained porous PTFE membrane was used as a porous layer, and a non-porous PET film (manufactured by Unitika Corporation, EMBLET SD-75, film thickness of 75 µm) was prepared as a resin layer. These layers were laminated by sandwiching the front and back sides of the PET film between a pair of porous PTFE membranes, and pressed with a high-temperature press at 280°C for 60 seconds at 20 kN, and the PET layer and a pair of sandwiching and supporting the PET film. A composite sheet to which a porous PTFE layer was fused was obtained.

(Example 2)

In the same manner as in Example 1, except that the membrane thickness of the PTFE porous membrane was changed to 80 µm and the average pore diameter was changed to 2.5 µm (manufactured by Nitto Denko Corporation, NTF1133), a PET layer and a pair of supporting it A composite sheet to which a porous PTFE layer was fused was obtained.

(Example 3)

In the same manner as in Example 1, except that the membrane thickness of the PTFE porous membrane was changed to 20 μm and the average pore diameter was changed to 0.4 μm (manufactured by Nitto Denko Corporation, NTF1026D), A composite sheet to which a porous PTFE layer was fused was obtained.

(Example 4)

In the same manner as in Example 1, except that a non-porous POM film (manufactured by Kurashiki Boseki Co., Ltd., PM-1500, film thickness of 100 µm) was used as the resin layer, and the temperature of the hot press machine was set to 200°C, A composite sheet was obtained in which a POM layer and a pair of porous PTFE layers supporting the POM layer were fused together.

(Example 5)

In the same manner as in Example 1, except that a non-porous PP film (manufactured by Toray Corporation, Toray Pan BO, film thickness of 100 μm) was used as the resin layer, and the temperature of the hot press machine was set to 180°C, Then, a composite sheet was obtained in which a pair of porous PTFE layers for sandwiching this were fused together.

(Example 6)

PP layer in the same manner as in Example 1, except that a non-porous UHMWPE film (manufactured by Nitto Denko Corporation, No.440, film thickness of 100 μm) was used as the resin layer, and the temperature of the hot press machine was set to 150°C. And, a composite sheet was obtained in which a pair of porous PTFE layers for sandwiching them were fused together.

(Example 7)

With respect to 100 parts by weight of PTFE fine powder (manufactured by Daikin Kogyo Co., Ltd., Polyflon F-104), 20 parts by weight of a liquid lubricant (n-Dodecane, manufactured by Japan Energy Co., Ltd.) were uniformly mixed and compressed into a cylinder. Later, it extruded with a ram extruder to obtain a sheet-like molded body extending in the longitudinal direction. This sheet-shaped molded article was passed between metal rolling rolls in a state containing a liquid lubricant, and rolled so as to have a thickness of 0.2 mm. Then, the liquid lubricant was removed by heating the sheet-shaped molded body to 150°C, and the sheet-shaped molded body was dried. Thereafter, the sheet-shaped molded body was stretched at a magnification of 20 times in the longitudinal direction at 370°C, and stretched again at 370°C at a magnification of 5 times. Subsequently, the obtained sheet-shaped molded article stretched in the longitudinal direction was stretched at 150°C at a magnification of 4 times the width direction to obtain a PTFE porous membrane having a film thickness of 10 µm and an average pore diameter of 10 µm.

The obtained porous PTFE membrane was used as a porous layer, and a non-porous PP film (manufactured by Toray Corporation, Toray Pan BO, film thickness of 100 µm) was prepared as a resin layer. These layers are laminated by sandwiching both the front and back sides of the PP film between a pair of porous PTFE membranes, and by pressing for 30 seconds at 4.5 kN with a 180°C high-temperature press, the PP layer and a pair of sandwiching and supporting the PP layer A composite sheet in which the porous PTFE layer of was fused was obtained.

(Example 8)

In the same manner as in Example 1, except that a PP net (film thickness of 100 μm) was used as the resin layer and the temperature of the high-temperature press was set to 180°C, a PP net and a pair of porous PTFE for sandwiching the net were used. A composite sheet to which the layers were fused was obtained.

(Example 9)

A PE-based nonwoven fabric (Herves, film thickness of 75 µm) was used as the resin layer, and the same was carried out as in Example 1, except that the temperature of the hot press machine was set to 180°C. A composite sheet to which a porous PTFE layer was fused was obtained.

(Comparative Example 1)

As the fluorine resin layer, a non-porous PTFE sheet (manufactured by Nitto Denko Corporation, No.900UL, film thickness of 100 µm) was used as the resin layer, and a non-porous PET film (manufactured by Unitika, EMBLET SD-75, thickness 75). Μm) was prepared. These layers are laminated so that the front and back sides of the PET film are sandwiched between a pair of PTFE sheets, and pressed at 4.5 kN for 30 seconds with a high-temperature press at 280°C, and the PET layer and a pair of PTFE sandwiching the PET film. A composite sheet to which a non-porous layer was fused was obtained.

(Comparative Example 2)

UHMWPE was carried out in the same manner as in Comparative Example 1 except that a non-porous UHMWPE film (manufactured by Nitto Denko Corporation, No.440, film thickness of 100 μm) was used as the resin layer, and the temperature of the hot press machine was set to 150°C. A composite sheet was obtained in which a layer and a pair of non-porous PTFE layers supporting the layer were fused together.

(Comparative Example 3)

A PP layer in the same manner as in Comparative Example 1 except that a non-porous PP film (manufactured by Toray Corporation, Toray Pan BO, film thickness of 100 μm) was used as the resin layer, and the temperature of the hot press machine was set to 180°C. And, a composite sheet was obtained in which a pair of non-porous PTFE layers for sandwiching this were fused together.

(Comparative Example 4)

As the fluorine resin layer, a porous PTFE membrane (manufactured by Nitto Denko Corporation, NTF1133, film thickness of 80 µm, average pore diameter of 2.5 µm) was used as a single film. In Comparative Example 4, the thermoplastic resin layer was not used.

(Comparative Example 5)

As the fluororesin layer, a non-porous PTFE membrane (manufactured by Nitto Denko Corporation, No. 900UL, film thickness of 100 μm) was used as a single membrane. In Comparative Example 5, the thermoplastic resin layer was not used.

(Comparative Example 6)

A PTFE porous film (manufactured by Nitto Denko Corporation, NTF1133, film thickness 80 µm, average pore diameter 2.5 µm) as a fluorine resin layer was used as a resin layer, and a non-porous PET film (manufactured by Unitika Corporation, EMBLET SD-75, A film thickness of 75 µm) was prepared. A porous PTFE membrane was laminated on only one side of the PET film, and pressed with a high-temperature press at 280°C for 60 seconds at 20 kN to obtain a composite sheet in which a porous PTFE layer of one layer and a PET layer of one layer were fused together.

The properties of the sheets produced in Examples and Comparative Examples were evaluated as follows.

(Film thickness)

The film thickness of the sheet was measured using a dial thickness measuring device (manufactured by Ozaki Seisakusho Co., Ltd., G-6C, 1/1000 mm, measuring diameter 5 mm).

(Contact angle)

The contact angle (unit: degree) between the main surface of the PTFE layer (porous layer or non-porous layer) and water is in accordance with JIS R3257 (wetability test method on the substrate glass surface, static method), and a contact angle measuring device (Contact Angle System OCA 30, Data Physics Instruments). GmbH product) was used.

(Fusibility)

The fusion properties of the PTFE layer (porous layer or non-porous layer) and the resin layer were determined based on the following criteria according to the fusion state of both layers. When trying to peel off each layer of the composite sheet by hand, the PTFE layer is not easily peeled off from the end of the composite sheet. × (impossible)".

(Preparation of a paste for forming an electrode catalyst layer)

With reference to the description of Japanese Patent Application Laid-Open No. 2008-269847, a paste for forming an electrode catalyst layer was prepared by the following method.

Nafion solution DE1020 (trade name; manufactured by DuPont) and carbon black were weighed and mixed so that the value obtained by dividing the weight of Nafion contained in the Nafion solution by the weight of carbon black became 0.8. Further, pure water was mixed so that the alcohol ratio contained was 25% by mass to obtain a mixed solution. In addition, Nafion Solution DE1020 contained alcohol. The mixture was centrifuged for 5 minutes with a mixer (manufactured by Sinki Co., Ltd., brand name ``Awatori Rentaro''), and then stirred with a homogenizer (HG-200, manufactured by HSIANGTAI) to form an electrode catalyst layer. I got a paste for it.

(Applicability of electrode catalyst layer)

The paste for forming the electrode catalyst layer obtained as described above was applied to the main surface of the PTFE layer (porous layer or non-porous layer) of the sheets prepared in Examples and Comparative Examples using an applicator, and maintained at 120°C. It dried for 5 minutes using a dryer to obtain a sheet with an electrode catalyst layer attached thereto. At this time, with respect to the applicationability of the paste to the sheet, when the paste is not repelled on the sheet surface and the sheet is not deformed due to the application construction, ``○ (good)'', and the paste was not repelled on the sheet surface. , The case where the sheet was deformed due to application construction was evaluated as "Δ (possible)", and the case where the paste repelled on the surface of the sheet was evaluated as "x (impossible)".

(Evaluation of transfer of electrode catalyst layer)

The sheet with the electrode catalyst layer obtained as described above and the electrolyte membrane (manufactured by DuPont, Nafion 115, film thickness of 125 μm) were stacked so that the electrolyte membrane and the electrode catalyst layer were in contact, and the thickness was 5 kN using a 120°C hot press Heated for 60 seconds. Then, the sheet was peeled from the laminate, and the transferability of the electrode catalyst layer to the electrolyte membrane was evaluated. Transferability is "◎ (excellent)" when all areas of the electrode catalyst layer have been transferred, "○ (good)" when an area of 90% or more has been transferred, and "△ (possible)" when an area of 80% or more has been transferred. , The case where the transfer area was less than 80% was evaluated as "x (impossible)".

(Evaluation of curl properties)

The curl property of the sheet was evaluated as follows. The sheet as an evaluation object was cut out to a width of 490 mm × 500 mm in length to obtain a test piece. The width direction of the test piece was the TD direction of the PTFE layer, and the length direction was the MD direction of the PTFE layer. Next, the test piece was accommodated in a dryer maintained at 120° C. in a state mounted on a metal plate, and allowed to stand for 5 minutes. After that, take the test piece out of the dryer while it is loaded on the metal plate, cool it to room temperature, and then measure the height of both short sides (left and right ends) in the width direction of the test piece (height from the metal plate generated by curls). It measured, and the average of the maximum value of each height was made into the curl height of the edge part of the said sheet.

The evaluation results are shown in Tables 1A and 1B below.

[Table 1A]

[Table 1B]

The present invention can be applied to other embodiments as long as it does not deviate from its intention and essential characteristics. Embodiments disclosed in this specification are illustrative in all respects, and are not limited thereto. The scope of the present invention is indicated by the appended claims rather than the above description, and all changes in the meaning and scope equivalent to the claims are included therein.

The transfer sheet of the present invention can be used, for example, for production by a transfer method of an electrode catalyst layer provided in an electrochemical device such as a fuel cell.

Claims (14)

It is a transfer sheet for transferring the layer supported on the supported surface to another member,
A thermoplastic resin layer and a pair of porous fluororesin layers that are bonded to the thermoplastic resin layer and hold the thermoplastic resin layer therebetween,
At least one main surface of the porous fluororesin layer on a side opposite to the main surface on the side of the thermoplastic resin layer is the supported surface,
A transfer sheet having a thickness of 50 µm or more. The transfer sheet according to claim 1, wherein the layer transferred by the transfer sheet is an electrode catalyst layer. The transfer sheet according to claim 1, wherein the curl height at the end portion when allowed to stand in an atmosphere at 120° C. for 5 minutes is 10 mm or less. The transfer sheet according to claim 1, wherein the thermoplastic resin layer and the pair of porous fluororesin layers are joined by fusion bonding. The transfer sheet according to claim 1, wherein the melting point of the thermoplastic resin constituting the thermoplastic resin layer is 280°C or less. The transfer sheet according to claim 1, wherein the thermoplastic resin constituting the thermoplastic resin layer is at least one selected from the group consisting of polyester, polyacetal, polyethylene, ultra-high molecular weight polyethylene, and polypropylene. The transfer sheet according to claim 1, wherein the thermoplastic resin layer has a thickness of 12.5 µm or more. The fluororesin according to claim 1, wherein the fluororesin constituting the fluororesin porous layer is polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PFA), or tetrafluoroethylene- Transfer sheet which is a hexafluoropropylene copolymer (FEP). The transfer sheet according to claim 1, wherein the fluororesin constituting the porous fluororesin layer is polytetrafluoroethylene. The transfer sheet according to claim 1, wherein the fluororesin porous layer has an average pore diameter of 0.1 µm to 20 µm. The transfer sheet according to claim 1, wherein the fluororesin porous layer has a thickness of 3 µm to 200 µm. The transfer sheet according to claim 1, wherein the transfer sheet has a thickness of 50 µm to 400 µm. The transfer sheet according to claim 1, wherein the supported surface has a contact angle of 100 degrees or more with water. The transfer sheet according to claim 1, and
Having an electrode catalyst layer,
A sheet with an electrode catalyst layer, wherein the electrode catalyst layer is disposed on at least one of the porous fluororesin layers of the sheet.

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