JP2018097916A - Back sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a back sheet made of a polyphenylene sulfide resin, which has adhesiveness to an electrolyte membrane.SOLUTION: A back sheet laminated on an electrolyte membrane of a reinforced electrolyte membrane that is obtained by reinforcing an electrolyte film with a porous film is a back sheet of a two-layer sheet comprising a first layer sheet on an electrolyte membrane side and a second layer sheet overlapping the first layer sheet. Both of the first layer sheet and the second layer sheet are sheets in which a polyphenylene sulfide resin is used. The first layer sheet has a lower melting point than the second layer sheet, and is melted and softened by being subjected to heat treatment performed during a manufacturing process of the reinforced electrolyte membrane.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a backsheet used for a reinforced electrolyte membrane.

  A reinforced electrolyte membrane is known in which a porous membrane, which is a reinforcing membrane, is reinforced by melting and impregnating an electrolyte membrane. Such a reinforced electrolyte membrane contributes to improving the durability of a fuel cell in which the reinforced electrolyte membrane is incorporated. In the manufacturing process of the reinforced electrolyte membrane, the electrolyte membrane and the backsheet are laminated on both surfaces of the porous membrane, and the electrolyte membrane is subjected to heat treatment and hydrolysis treatment in this laminated state (for example, Patent Document 1). ).

  From the viewpoint of handling such as winding the sheet, it is desirable that the back sheet has adhesiveness to the electrolyte membrane that does not cause natural peeling even after being subjected to a hydrolysis treatment, which is a subsequent process of the heat treatment. In view of such a demand for adhesion, a fluorine-based resin sheet, for example, a Teflon sheet (Teflon is a registered trademark) is often used as a backsheet.

Japanese Patent Application Laid-Open No. 2006-149284

  By the way, since the fluorine-based resin sheet has adhesion to the electrolyte membrane, there is also a demand to reduce the specification of fluorine, so that a back sheet of another material is required. The polyphenylene sulfide resin sheet is an inexpensive resin sheet and is known to have heat resistance against heat treatment of the electrolyte membrane, but it has the same degree of adhesion to the electrolyte membrane as the Teflon sheet. There is room for improvement. For these reasons, a back sheet made of polyphenylene sulfide resin having adhesion to the electrolyte membrane has been requested.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms.

(1) According to one aspect of the present invention, a backsheet is provided. The backsheet is a backsheet laminated on the electrolyte membrane of a reinforced electrolyte membrane in which the electrolyte membrane is reinforced with a porous membrane, the first layer sheet on the electrolyte membrane side, and the first layer sheet And the first layer sheet and the second layer sheet are both sheets using polyphenylene sulfide resin, and the melting point of the first layer sheet is the melting point of the second layer sheet. It has a lower melting point.

  In this form of the backsheet, the first layer sheet on the electrolyte membrane side has a lower melting point than the second layer sheet that overlaps the first layer sheet, so that the melting point of the first layer sheet is heated during the manufacturing process of the reinforced electrolyte membrane. If it is set as the heating temperature of a process, it will become possible to melt and soften a 1st layer sheet | seat in the case of this heat processing. The first layer sheet thus melted and softened spreads over the membrane surface of the electrolyte membrane following the membrane surface of the electrolyte membrane, and thus adheres to the membrane surface of the electrolyte membrane with high adhesion. Therefore, according to this form of the back sheet, the desired adhesion is maintained even after the hydrolysis process, which is a subsequent process of the heat treatment, while suppressing the cost by using an inexpensive sheet made of polyphenylene sulfide resin. it can.

  Note that the present invention can be realized in various modes. For example, it can be realized in the form of a manufacturing apparatus or manufacturing method of a reinforced electrolyte membrane.

It is explanatory drawing which shows an example of the laminated film manufacturing apparatus used for formation of the laminated film containing the back sheet of this embodiment. It is explanatory drawing which shows roughly an example of the reinforcement membrane-izing apparatus which performs sequentially the melt impregnation of the electrolyte membrane to a porous membrane, and the hydrolysis process of an electrolyte membrane. FIG. 3 is a schematic cross-sectional view of a laminated film taken along line 3-3 in FIG. It is a schematic sectional drawing of the laminated film along line 4-4 in FIG. It is explanatory drawing which shows the evaluation result regarding the adhesiveness of an electrolyte membrane and a back sheet about embodiment goods and a comparative example goods.

FIG. 1 is an explanatory view showing an example of a laminated film manufacturing apparatus 10 used for forming a laminated film 200 including a back sheet 220 of the present embodiment. As shown in the figure, the laminated film 200 includes a porous film 231 in the central region, and an electrolyte film 210 and a back sheet 220 are laminated in this order on both film surfaces of the porous film 231. The electrolyte membrane 210 is impregnated in the porous membrane 231 in the reinforcing membrane forming device 30 described later, and is reinforced by the porous membrane 231. The electrolyte membrane 210 is a polymer membrane, has a sulfonic acid group (—SO ₃ H) in the side chain, and has proton conductivity. The porous membrane 231 is a porous polymer membrane and functions as a reinforcing membrane for the electrolyte membrane 210. The laminated film 200 becomes a reinforced electrolyte membrane in which the electrolyte membrane 210 is reinforced with the porous membrane 231 by peeling the backsheets 220 on both membrane surfaces after heat treatment and hydrolysis described below.

The laminated film manufacturing apparatus 10 includes an electrolyte membrane manufacturing unit 100, a back sheet bonding unit 110, and a reinforcing membrane / electrolyte film stacking unit 120. The electrolyte membrane manufacturing unit 100 forms the electrolyte membrane 210. As the electrolyte, a precursor of a perfluorosulfonic acid polymer having a sulfuryl fluoride group (—SO ₂ F) at the end of the side chain, such as a precursor of Nafion (registered trademark), can be used. In this embodiment, the electrolyte membrane manufacturing unit 100 uses the electrolyte precursor having an IEC (ion exchange equivalent) of 1.3 to 1.8 meg / g to form the electrolyte membrane 210 having a thickness of 2 to 30 μm. In the present embodiment, an electrolyte precursor having a sulfuryl fluoride group at the end of the side chain is used, but instead, an electrolyte precursor having a sulfuryl chloride group (—SO ₂ Cl) at the end of the side chain, or the side An electrolyte having a sulfonic acid group (—SO ₃ H) group at the chain end may be used. In addition, the halogenated sulfuryl group (sulfuryl fluoride group, sulfuryl chloride group) of the precursor of the electrolyte is easily converted to a sulfonic acid group (—SO ₃ H) group by hydrolysis treatment in a hydrolysis treatment tank 350 described later. Convert.

The back sheet bonding unit 110 includes a pair of bonding rolls 112 and a back sheet feeding roll 114. The back sheet feeding roll 114 feeds the back sheet 220. The fed back sheet 220 is a two-layer sheet, and the first layer sheet 221 is disposed on the electrolyte membrane 210 side, and the second layer sheet 222 is overlapped on the first layer sheet 221. Both the first layer sheet 221 and the second layer sheet 222 are sheets using polyphenylene sulfide resin (hereinafter abbreviated as PPS), and the back sheet 220 is a back sheet in a state in which both the layer sheets are laminated in advance. It is wound around the supply roll 114. PPS is a crystalline heat-resistant product produced by polycondensation reaction of paradichlorobenzene (p-DCB) and sodium sulfide (Na ₂ S) or sodium hydrosulfide (NaSH) in a polar solvent under high temperature and pressure. It is a polymer and usually has a high melting point of about 280 ° C. The melting point can be changed by changing the degree of polycondensation or changing the composition during the polycondensation reaction, and the first layer sheet 221 has a melting point of 240 to 250 ° C. Since the second layer sheet 222 has a melting point of 280 ° C., the first layer sheet 221 has a lower melting point than the second layer sheet 222 and is subjected to the heat treatment described later in the manufacturing process of the reinforced electrolyte membrane. Melts and softens.

  The back sheet 220 normally has a sheet thickness of 20 to 100 μm. In the present embodiment, the back sheet 220 is a two-layer sheet in which a first layer sheet 221 and a second layer sheet 222 are laminated. The sheet thicknesses of the first layer sheet 221 and the second layer sheet 222 can be variously adjusted. From the viewpoint of maintaining the sheet form and laminating thin sheets, the first layer sheet 221 will be described later. In this embodiment, the sheet thickness of the back sheet 220 is 50 μm, the sheet thickness of the first layer sheet 221 is 10 μm, and the sheet thickness of the second layer sheet 222 is 40 μm. If the sheet thickness of the second layer sheet 222 is larger than the sheet thickness of the first layer sheet 221, the sheet thickness of each layer sheet can be changed as appropriate. The back sheet 220 obtained in this way is wound around the back sheet feeding roll 114 in advance, and is fed from the back sheet feeding roll 114 to the pair of bonding rolls 112. At this time, the back sheet 220 is sent to the bonding roll 112 so that the first layer sheet 221 is positioned on the electrolyte membrane 210 side. The back sheet bonding unit 110 is passed through the sheet bonding surface 210f of the electrolyte membrane 210 by passing the electrolyte membrane 210 and the back sheet 220 between two rolls of the pair of bonding rolls 112. The electrolyte membrane 210 and the back sheet 220 are laminated while the first layer sheet 221 of 220 is in close contact.

  The reinforcing membrane / electrolyte membrane laminate 120 includes a pair of laminate rolls 122, a paste extruder 124, and a stretching machine 126. The paste extruder 124 mixes a fine powder of polytetrafluoroethylene (PTFE) and Isopar (Isopar is a registered trademark), and extrudes it into a band shape to form a band-shaped reinforcing film 230. The stretching machine 126 stretches the band-shaped reinforcing film 230 to a thickness of 1 to 5 μm and a porosity of about 40 to 60%, and bakes it at about 350 ° C. to form the porous film 231 and laminate the porous film 231. Send to roll 122. For example, the stretching machine 126 may stretch the reinforcing film 230 by using a pair of rolls and pressing while passing the reinforcing film 230 therebetween. In the present embodiment, the reinforcing film / electrolyte film stacking unit 120 includes the paste extruder 124 and manufactures the reinforcing film 230, but a separately prepared reinforcing film 230 may be used.

  In this embodiment, polytetrafluoroethylene is used as the reinforcing film 230 for obtaining the porous film 231. However, polytetrafluoroethylene containing 10 mol% of polyethylene, polypropylene, an ethylene-propylene copolymer, and a copolymer component is used. Polyolefin resins such as copolymers: polysiloxane; methacrylate resins such as polymethyl methacrylate (PMMA); polystyrene, acrylonitrile-styrene copolymer (AS resin), acrylonitrile-butadiene-styrene copolymer (ABS resin) Polystyrenes such as polyamide; polyimide (PI); polyetherimide (PEI); polyamideimide; polyesterimide; polycarbonate (PC); polyacetal; Polyphenylene sulfide (PPS); Polyarylate; Polyaryl; Polysulfone (polysulfone); Polyethersulfone (PES) (polyethersulfone); Polyurethanes; Polyester resins such as polyethylene terephthalate (PET); Polyether ketones such as PEEK) and polyether ketone ketone (PEKK); polyacrylates such as polybutyl acrylate and polyethyl acrylate; polyvinyl esters such as polybutoxymethylene; polysiloxanes; polysulfides Polyphosphazenes, polytriazines, polycarboranes, polynorbornene, epoxy resins, polyvinyl alcohol, polyvinyl pyrrolidone, polyisoprene and polybutane Polydienes such as ene; polyalkenes such as polyisobutylene; vinylidene fluoride resin, hexafluoropropylene resin, or may be used in the resin, such as hexafluoroacetone-based resin (such as a thermoplastic resin).

  In the pair of laminated rolls 122, the electrolyte membrane 210 on which the backsheet 220 has been laminated is disposed on both membrane surfaces of the porous membrane 231, and "backsheet 220-electrolyte membrane 210-porous membrane 231-electrolyte membrane 210- A laminated film 200 having a five-layer structure of the “back sheet 220” is formed. Moreover, the lamination of the electrolyte membrane 210 and the back sheet 220 is in a state where the first layer sheet 221 is in close contact with the sheet attachment surface 210f of the electrolyte membrane 210. The laminated film 200 thus obtained is a laminated film in which the electrolyte membrane 210 and the back sheet 220 are laminated in this order on both membrane surfaces of the porous membrane 231, and the membrane width of each membrane is the same. In the present embodiment, in the laminated film manufacturing apparatus 10, a laminated film 200 having a film width of 100 to 500 mm is continuously formed with a length of 100 to 500 m, and the laminated film 200 is reinforced as described later in which the next step is executed. The film is transferred to the film forming apparatus 30. Conveyance of the laminated film 200 to the next step can be performed by roller conveyance using a conveyance roller, or can be performed by winding the laminated film 200 around a take-up roll and in units of take-up rolls.

  FIG. 2 is an explanatory diagram schematically showing an example of a reinforcing membrane forming apparatus 30 that sequentially executes the melt impregnation of the electrolyte membrane 210 into the porous membrane 231 and the hydrolysis treatment of the electrolyte membrane 210. The reinforcing membrane forming apparatus 30 includes an impregnating device group 31 that performs heating of the laminated film and impregnation with an electrolyte membrane and a hydrolysis device group 32 that performs hydrolysis, and conveys the laminated film 200 between the two device groups by rollers. Alternatively, the laminated film 200 that has been subjected to the laminated film heating and the electrolyte membrane impregnation in the impregnation device group 31 may be wound around a take-up roll, and the laminated film 200 may be sent out from the take-up roll to the hydrolysis device group 32.

  The impregnation device group 31 includes a conveyance roller 300, a first heat roll 310, a second heat roll 320, and a conveyance roller 330. The transport roller 300 transports the laminated film 200 to the first heat roll 310. The laminated film 200 is conveyed to the second heat roll 320 along the roll surface of the first heat roll 310. The 1st heat roll 310 and the 2nd heat roll 320 are heated by 240 to 260 degreeC, and heat the laminated film 200 which contacted each roll surface. This heating temperature is about the same as the melting point of the first layer sheet 221. Moreover, the 1st heat roll 310 and the 2nd heat roll 320 pinch | stack the laminated film 200 conveyed between rolls, and between these rolls, the laminated film 200 is a pressure (nip pressure) of 0.1-0.8 MPa. Pressurize with. The electrolyte membrane 210 of the laminated film 200 is melted and softened by the heating of the heat roller, and the porous electrolyte membrane 231 is impregnated with the melted electrolyte membrane 210. The impregnation of the melted / softened electrolyte membrane 210 into the porous membrane 231 occurs due to the pressurization between the rolls and also while being conveyed while being pressed against the surface of the heat roll by the tension applied during the conveyance.

  The electrolyte membrane 210 conveyed to the impregnation device group 31 impregnates the porous membrane 231 as follows. FIG. 3 is a schematic cross-sectional view of the laminated film 200 taken along line 3-3 in FIG. FIG. 4 is a schematic cross-sectional view of the laminated film 200 taken along line 4-4 in FIG.

  Prior to reaching the first heat roll 310, the laminated film 200 is in a state where the electrolyte membrane 210 and the back sheet 220 are simply laminated on both membrane surfaces of the porous membrane 231 as shown in FIG. Since it is not heated, the initial film thickness Ts remains unchanged. The laminated film 200 is in close contact with the roll surface of the first heat roll 310 by further conveyance, and is heated by the first heat roll 310. The laminated film 200 is conveyed while being heated from the roll surface, and reaches between the rolls of the first heat roll 310 and the second heat roll 320 shown in FIG. Until reaching between the rolls, the electrolyte film 210 of the laminated film 200 is melted and softened by heating from the roll surface of the first heat roll 310 and impregnated in the porous film 231. Further, after the laminated film 200 reaches between the rolls, the laminated film 200 is in close contact with the roll surface of the second heat roll 320 and is heated by the second heat roll 320. Soften and impregnate the porous membrane 231. Heating from the roll surfaces of the first heat roll 310 and the second heat roll 320 is also performed on the back sheet 220, and the first layer sheet 221 and the second layer sheet 222 of the back sheet 220 are heated. The second layer sheet 222 does not melt because its melting point is as high as 280 ° C. On the other hand, the first layer sheet 221 having a lower melting point than the second layer sheet 222 is melted and softened by being heated from the roll surface. The melting / softening of the first layer sheet 221 will be described later.

  A nip pressure by the first heat roll 310 and the second heat roll 320 acts on the front and back surfaces of the laminated film 200, and a pressing force against the surface of the heat roll acts by a tension applied during conveyance. As shown in FIG. 3, the electrolyte membrane 210 melted and softened by the heat treatment under pressure is impregnated into the porous membrane 231 in the central region of the film thickness from both membrane surfaces. The laminated film 200 has an impregnation process film thickness Tm smaller than the initial film thickness Ts due to the impregnation of the electrolyte film 210 into the porous film 231 and the action of nip pressure and pressing force.

As shown in FIG. 4, the laminated film 200 that has passed through the second heat roll 320 has a final film thickness Te smaller than the impregnation process film thickness Tm, as shown in FIG. 4, upon completion of the impregnation of the electrolyte film 210 into the porous film 231. In the laminated film 200 in this state, the porous film 231 is present in the substantially central region of the thickness of the electrolyte membrane 210, and the electrolyte membrane 210 is impregnated throughout the porous membrane 231. As shown in FIG. 2, the laminated film 200 thus impregnated with the electrolyte membrane 210 is conveyed to the hydrolysis treatment tank 350 of the hydrolysis device group 32 via the conveyance roller 330, and is included in the laminated film 200. Is hydrolyzed. The hydrolysis treatment tank 350 includes a plurality of tanks such as an alkali treatment tank, a cleaning layer, and an oxidation treatment tank. While the laminated film 200 passes through each tank, the electrolyte membrane 210 is subjected to alkali treatment and oxidation treatment, The electrolyte membrane 210 is hydrolyzed. Thereby, the electrolyte membrane 210 becomes an electrolyte membrane having proton conductivity having a sulfonic acid group (—SO ₃ H) group. And the laminated film 200 after hydrolysis is sent out to the manufacturing apparatus of a membrane electrode assembly or the fuel cell manufacturing apparatus through the transport roller 360. The laminated film 200 may be wound around a take-up roll downstream of the transport roller 360, and the laminated film 200 may be sent from the take-up roll to a membrane electrode assembly manufacturing apparatus or a fuel cell manufacturing apparatus.

  In the back sheet 220 of the present embodiment constituting the laminated film 200 described above, the first layer sheet 221 on the side of the electrolyte film 210 has a lower melting point than the second layer sheet 222 overlapping therewith, and the manufacturing process of the reinforced electrolyte film The first layer sheet 221 is melted and softened during the heat treatment performed in (1). The first layer sheet 221 thus melted and softened follows the surface irregularities of the sheet application surface 210f of the electrolyte membrane 210, as shown in the enlarged illustrations of FIGS. 3 and 4, over the entire area of the sheet application surface 210f of the electrolyte membrane 210. Therefore, it adheres to the sheet pasting surface 210f of the electrolyte membrane 210 with high adhesion. Therefore, according to the back sheet 220 of the present embodiment that constitutes the laminated film 200, the cost is reduced by using an inexpensive PPS sheet instead of the fluorine-based resin sheet, and the water treatment that is a subsequent process of the heat treatment is performed. Even after undergoing the decomposition treatment, the desired adhesion can be maintained. Hereinafter, this adhesion maintenance is demonstrated.

  FIG. 5 is an explanatory diagram showing the evaluation results regarding the adhesion between the electrolyte membrane and the back sheet for the embodiment product and the comparative product. The embodiment product and the comparative product in this evaluation result used a back sheet 220 as follows.

  As described above, the embodiment product is the back sheet 220 of the two-layer sheet in which the first layer sheet 221 and the second layer sheet 222 are laminated, the sheet thickness of the back sheet 220 is 50 μm, and the first layer sheet 221 is formed. The sheet thickness of the second layer sheet 222 is 10 μm. The first layer sheet 221 and the second layer sheet 222 are both sheets using PPS, and the back sheet 220 is a back sheet in which both layer sheets are laminated in advance.

  Each of the back sheets of Comparative Example Product 1 to Comparative Example Product 4 is a single-layer back sheet using PPS, and the sheet thickness is 50 μm. As shown in FIG. 5, the back sheet of Comparative Example Product 1 is not subjected to any surface treatment. Therefore, the back sheet of Comparative Example Product 1 is referred to as an unprocessed back sheet for convenience. The comparative example product 2 is subjected to plasma treatment in which plasma irradiation is performed on the sheet surface of the electrolyte membrane 210 that is in close contact with the sheet attachment surface 210f. Therefore, the back sheet of the comparative example product 2 is referred to as a plasma-treated back sheet for convenience. The comparative product 3 is subjected to a flame treatment in which a flame is blown onto the surface of the electrolyte membrane 210 that is in close contact with the sheet application surface 210f. Therefore, the back sheet of the comparative example product 3 is referred to as a flame-treated back sheet for convenience. The comparative product 4 is subjected to a blasting process in which fine blasting is sprayed onto the sheet surface of the electrolyte membrane 210 that is in close contact with the sheet application surface 210f. Therefore, the back sheet of the comparative example product 4 is referred to as a blasted back sheet for convenience. Further, when the back sheet subjected to the above surface treatment is generically referred to, it is referred to as a surface treated back sheet.

  The water contact angle shown in FIG. 5 is the surface of the first layer sheet 221 in the back sheet 220 of the example product, the surface of the untreated back sheet of the comparative example product 1, the treated surface of the plasma treated back sheet of the comparative product 2. The treated surface of the flame-treated backsheet of Comparative Example Product 3 and the treated surface of the blasted backsheet of Comparative Example Product 4 were measured by an existing method such as a liquid suitability method or a diffusion / shrinkage method. The water contact angle of each back sheet of the embodiment product and each comparative product was 60 to 80 °.

  In obtaining the adhesion strength after impregnation and the adhesion strength after hydrolysis shown in FIG. 5, a laminated film 200 was manufactured for each of the back sheets of the embodiment product and each comparative product as follows. First, each back sheet of the embodiment product and each comparative product is sent to the laminated film manufacturing apparatus 10 in FIG. 1, and the unimpregnated / unhydrolyzed laminated film 200 is provided for each back sheet of the embodiment product and each comparative product. To manufacture. Thereafter, the non-impregnated / non-hydrolyzed laminated film 200 for each back sheet of the embodiment product and each comparative product is sequentially conveyed to the impregnation device group 31 and the hydrolysis device group 32 of the reinforcing membrane forming device 30, and the electrolyte membrane The laminated film 200 that has been subjected to the melting / impregnation and hydrolysis treatment is manufactured for each back sheet of the embodiment product and each comparative product. Then, the laminated film 200 that has just been melted and impregnated with the electrolyte film by the impregnation device group 31 is cut in the downstream region of the second heat roll 320 in FIG. Further, the back sheet 220 that has been subjected to the melting / impregnation of the electrolyte membrane by the impregnation device group 31 and the hydrolysis treatment by the hydrolysis device group 32 is cut in the downstream region of the transport roller 360 in FIG. Use a strength measurement sheet.

  The post-impregnation adhesion strength shown in FIG. 5 was measured by a 180 ° peel strength measurement method for the post-impregnation adhesion strength measurement sheet obtained for each of the back sheets of the embodiment product and each comparative product. The adhesion strength after impregnation for each back sheet of the embodiment product and each comparative product was 35 to 60 N / m. The post-hydrolysis adhesion strength shown in FIG. 5 was measured by a 180 ° peel strength measurement method for the post-hydrolysis adhesion measurement sheet obtained for each of the back sheets of the embodiment product and each comparative product. The adhesion strength after hydrolysis for each of the back sheets of the embodiment product and each comparative product was 0 N / m or 1 N / m.

  The following analysis can be performed from the evaluation result shown in FIG. When the water contact angle is small, the surface roughness of the backsheet increases, and therefore, in the process of melting and impregnating the electrolyte membrane, the melted / softened electrolyte membrane 210 enters fine irregularities on the surface of the backsheet, and the adhesion strength increases. is assumed. The post-impregnation adhesion strength measurement sheet including the plasma-treated back sheet of Comparative Example Product 2 is in close contact with the electrolyte membrane 210 with high adhesion strength in a state where the electrolyte membrane is melted and impregnated. This increase in adhesion strength can be attributed to the small water contact angle. In the back sheet 220 of the embodiment product and the post-impregnation adhesion strength measurement sheets of the comparative product 1 and the comparative product 3 to 4, the water contact angle is larger than that of the comparative product 2, but it is determined whether the contact is good or bad. Since it is in close contact with the electrolyte membrane 210 with an adhesive strength exceeding the strength of 25 N / m, it is a good judgment.

  On the other hand, regarding the post-hydrolysis adhesion strength, only the post-hydrolysis adhesion strength measurement sheet including the back sheet 220 of the embodiment product can obtain a post-hydrolysis adhesion strength of 1 N / m exceeding zero N / m. It was. That is, in each of the post-impregnation adhesion strength measurement sheets of Comparative Examples 1 to 4, since the adhesion strength after hydrolysis was zero, the electrolyte membrane was subjected to melting / impregnation of the electrolyte membrane and subsequent hydrolysis treatment. Later, spontaneous peeling can occur. On the other hand, for the post-hydrolysis adhesion strength measurement sheet including the back sheet 220 of the embodiment product, that is, the laminated film 200, the back sheet 220 after being subjected to the melting / impregnation of the electrolyte film and the hydrolysis process in the subsequent step. It can be said that the natural peeling of can be suppressed. These results can be explained as follows.

  In the course of the hydrolysis treatment, a chemical reaction of the composition component occurs in the electrolyte membrane 210 by the alkali treatment and the acid treatment, and this chemical reaction penetrates into the micro unevenness of the surface of the surface-treated backsheet of Comparative Examples 1 to 4. It also occurs at the electrolyte membrane site. Therefore, as the chemical reaction progresses, the adhesion accompanying the entry into the micro unevenness of the backsheet surface decreases, and the post-hydrolysis adhesion strength measurement sheet of each of Comparative Examples 1 to 4 provides the post-hydrolysis adhesion strength. Absent. In the post-hydrolysis adhesion strength measurement sheet in which the back sheet 220 of the embodiment product is in close contact with the electrolyte membrane 210, since the water contact angle of the first layer sheet 221 is large, the adhesion due to entering into the micro unevenness is much obtained. In addition, the lowering of the adhesiveness due to entering into the fine irregularities does not have much influence. Nevertheless, as described above, the adhesion strength that can suppress natural peeling with the post-hydrolysis adhesion strength measurement sheet in which the back sheet 220 of the embodiment product is closely adhered to the electrolyte membrane 210 can be secured. The first layer sheet 221 in close contact with the sheet application surface 210f of the electrolyte membrane 210 is melted and softened during the heat treatment because of its low melting point, and as shown in the enlarged views of FIGS. 3 and 4, the electrolyte membrane 210 This is because the entire surface of the sheet sticking surface 210f of the electrolyte membrane 210 is distributed over the entire surface of the sheet sticking surface 210f. Secondly, the sheet adheres to the sheet application surface 210f of the electrolyte membrane 210 with high adhesion as it reaches the sheet application surface following the surface irregularities of the sheet application surface 210f. In addition, since the water contact angle is small, the adhesion due to penetration into the micro unevenness increases the adhesion strength after hydrolysis that can suppress natural peeling with the post-hydrolysis adhesion strength measurement sheet of Comparative Example Product 2. This is because the backsheet is not melted or softened on the side of the sheet attachment surface 210f of the electrolyte membrane 210 as in the embodiment. Specifically, since the back sheet does not melt or soften, the back sheet does not spread to the sheet attaching surface 210f following the surface irregularities of the sheet attaching surface 210f shown in the enlarged view of FIG. 3 or FIG. .

  In order to manufacture a reinforced electrolyte membrane using the back sheet 220 of the present embodiment, the back sheet wound around the back sheet feeding roll 114 is composed of a low melting point first layer sheet 221 and a high melting point second layer sheet 222. It is only necessary to change to the back sheet 220 of the two-layer sheet laminated. Therefore, since it has the back sheet 220 of this embodiment, the laminated film 200 which can suppress natural peeling can be easily obtained by diverting the existing equipment configuration.

  The present invention is not limited to the above-described embodiments, examples, and modifications, and can be realized with various configurations without departing from the spirit thereof. For example, the technical features in the embodiments, examples, and modifications corresponding to the technical features in each embodiment described in the summary section of the invention are to solve some or all of the above-described problems, or In order to achieve part or all of the above-described effects, replacement or combination can be performed as appropriate. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.

  In the embodiment described above, the electrolyte membrane 210 is laminated on both membrane surfaces of the porous membrane 231, but the electrolyte membrane 210 is laminated on one membrane surface of the porous membrane 231, and the other membrane surface of the porous membrane 231 is obtained. The back sheet 220 may be laminated on the surface of the electrolyte membrane 210. In this case, the electrolyte membrane manufacturing unit 100 may be omitted from one back sheet bonding unit 110 in the laminated film manufacturing apparatus 10 shown in FIG. Then, an electrolyte membrane 210 having a large film thickness is laminated on one membrane surface of the porous membrane 231, and the first layer sheet 221 and the second layer 221 are laminated on the electrolyte membrane 210 laminated on one membrane surface of the porous membrane 231. At least the back sheet 220 laminated with the layer sheet 222 is laminated, and in this case, the back sheet 220 may be laminated with the first layer sheet 221 in close contact with the electrolyte membrane 210.

  In the above-described embodiment, the first heat roll 310 and the second heat roll 320 are used as means for heating the laminated film 200. However, the present invention is not limited to this. It is also possible to be justified by providing various heating means such as a heater facing the laminated film 200 on the roll surface.

DESCRIPTION OF SYMBOLS 10 ... Laminated film manufacturing apparatus 30 ... Reinforcement film forming apparatus 31 ... Impregnation apparatus group 32 ... Hydrolysis apparatus group 100 ... Electrolyte membrane manufacturing part 110 ... Back sheet bonding part 112 ... Bonding roll 114 ... Back sheet feeding roll 120 ... Reinforcement Membrane / electrolyte membrane laminating section 122 ... Laminated roll 124 ... Paste extruder 126 ... Stretching machine 200 ... Laminated film 210 ... Electrolyte membrane 210f ... Sheet application surface 220 ... Back sheet 221 ... First layer sheet 222 ... Second layer sheet 230 ... Reinforcing membrane 231 ... Porous membrane 300 ... Conveying roller 310 ... First heat roll 320 ... Second heat roll 330 ... Conveying roller 350 ... Hydrolysis tank 360 ... Conveying roller Te ... Final film thickness Tm ... Impregnation process film thickness Ts ... Initial film thickness

Claims (1)

A backsheet laminated on the electrolyte membrane of a reinforced electrolyte membrane in which the electrolyte membrane is reinforced with a porous membrane,
A first layer sheet on the electrolyte membrane side;
A second layer sheet overlapping the first layer sheet,
The first layer sheet and the second layer sheet are both sheets using polyphenylene sulfide resin,
The melting point of the first layer sheet is lower than the melting point of the second layer sheet,
Back sheet.

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