JP6296301B2 - Electrolyte membrane structure - Google Patents

Description

  The present invention relates to an electrolyte membrane structure.

  The thickness of an electrolyte membrane for a fuel cell is about several μm to several tens of μm and is relatively thin. Therefore, when manufacturing such an electrolyte membrane, an electrolyte membrane is formed on a carrier film. The technique of manufacturing is used.

The manufacturing method of such an electrolyte membrane includes (1) a method in which a solution obtained by dissolving a perfluorosulfonic acid polymer, which is a fluorine-based electrolyte resin, in an organic medium is coated on a carrier film; The electrolyte resin precursor (the end group of the polymer chain is -SO ₂ F) before imparting the ionic conductivity of the fluorosulfonic acid polymer is melt-extruded into a film, and then bonded onto the carrier film, and the aqueous alkaline solution And a production method in which the terminal group of the polymer chain is modified to a sulfone type (—SO ₃ H) with an acid aqueous solution. The fuel membrane electrolyte membrane, which is a relatively thin electrolyte membrane, is a reinforced electrolyte membrane having a porous membrane typified by a polytetrafluoroethylene stretched porous body in the electrolyte membrane. ) And the latter (2) are each added with a step of impregnating the porous membrane.

  In addition, as the carrier film in the method (2) manufactured by melt extrusion, it can withstand the heating temperature (220 to 250 ° C.) in the step of impregnating the porous membrane and can withstand alkali treatment and acid treatment. Until now, fluorine films such as PTFE (polytetrafluoroethylene) and PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) have been used (for example, see Patent Document 1). ).

JP 2013-171821 A

  However, (1) Fluorine-based films represented by PTFE and PFA are expensive and may be expensive. In addition, (2) the fluorine-based film is difficult to process, and the film itself is often distorted, so that wrinkles may occur during the transportation of the electrolyte membrane. Furthermore, (3) Fluorine-based films represented by PTFE and PFA have a high affinity with electrolyte membranes, and after winding the laminated product with the electrolyte membrane bonded to the fluorine-based film into a roll shape, The back surface of the film and the surface of the electrolyte membrane increase in adhesion in a short time, adhere to the same degree as the bonding strength of the bonded state, and when unrolled thereafter, the electrolyte membrane may peel off from the surface of the fluorine-based film (Refer to FIG. 15. In this specification, the difficulty of peeling off the electrolyte membrane from the carrier film is referred to as “blocking property”. If it is difficult to peel off, the blocking property is excellent, and if it is easy to peel off, the blocking property is poor.) Express).

  Here, considering the cost, it is considered that the fluororesin film is reusable because it is expensive. However, since the heat deformation occurs during the impregnation, it is actually difficult to recycle.

  Also, considering reusable films, according to the conventional method using a metal sheet coated with a fluororesin or laminated with a fluororesin sheet, thermal deformation is suppressed. It is conceivable to reduce the cost by doing so. However, as an adverse effect of productivity due to the use of a metal sheet, the coating of the fluororesin on the metal sheet may be difficult to manage, such as concern about metal corrosion due to pinholes. In addition, when using a metal sheet, it is difficult to align the end face by web handling because a slit cannot be provided, which may result in a meandering product. Furthermore, since the metal sheet is opaque, it is difficult to inspect the foreign matter, and the weight of the sheet is heavy, and it is necessary to make the equipment sturdy.

  Furthermore, conventionally, a sheet in which glass fiber is impregnated with PTFE has been proposed, but glass fiber cannot withstand alkali treatment.

  Therefore, the present invention suppresses cost, suppresses generation of wrinkles, and suppresses separation of the electrolyte membrane from the sheet when the sheet with the electrolyte membrane is wound up after being rolled up (blocking property). It is an object of the present invention to provide an electrolyte membrane structure that can improve the above.

In order to solve this problem, the present invention is an electrolyte membrane structure comprising a support substrate and an electrolyte membrane attached to the surface of the support substrate,
The support substrate is composed of a sheet of SPS (syndiotactic polystyrene),
The surface of the SPS sheet has higher adhesion than the back surface of the SPS sheet.

  Since the SPS sheet is cheaper than a fluorine-based film represented by PTFE or PFA, the cost can be suppressed as compared with a conventional electrolyte membrane transport sheet. In addition, since the SPS sheet itself has a small amount of distortion, wrinkles are unlikely to occur when the electrolyte membrane is conveyed. In addition, the surface of the SPS sheet on which the electrolyte membrane is bonded is subjected to a surface treatment for high adhesion, improving the wettability (reducing the surface free energy difference), and improving the adhesion. Since the high adhesion treatment is not carried out, the SPS sheet with the electrolyte membrane is wound into a roll shape, and the electrolyte membrane is prevented from peeling from the surface of the SPS sheet when unwinding thereafter (the blocking property is improved). .

  In the electrolyte membrane structure, high adhesion treatment may be performed on one side of the SPS sheet.

  As the high adhesion treatment, a fluororesin coat may be applied. For example, as a fluororesin coat, a coating method in which a fluororesin is dissolved and applied, or a coat layer added with a component copolymerizable with a fluororesin such as polyester in addition to the fluororesin may be used. The fluororesin layer ensures the adhesion between the electrolyte membrane being transported and the SPS sheet, and the back surface of the SPS sheet is laminated on the surface of the electrolyte membrane even when the SPS sheet with the electrolyte membrane is rolled up. Therefore, it can suppress that an electrolyte membrane peels from a back sheet when unwinding after that.

  When the electrolyte membrane is thinner than a predetermined value, the electrolyte membrane is preferably a reinforced electrolyte membrane having a porous membrane.

  The electrolyte membrane structure in this case may be one in which the SPS sheet is produced through the step of impregnating the porous membrane.

  Moreover, it is preferable that the thickness of the SPS sheet is thicker than the thickness of the fluororesin coat. As a structure excellent in impregnation property and handling property, from the viewpoint of heat resistance strength and thermal conductivity, an example of a preferable range of the thickness of the SPS sheet is 25 μm or more and less than 200 μm, and an example of a preferable range of the thickness of the fluororesin coat is 0.5 μm to 10 μm.

  According to the present invention, the cost is suppressed, the generation of wrinkles is suppressed, and the electrolyte membrane is prevented from peeling off from the sheet when the sheet with the electrolyte membrane is wound up in a roll shape (blocking property). Can be improved).

It is a figure which shows the structural example of the carrier film (electrolyte membrane conveyance sheet | seat) in one Embodiment of this invention. It is a perspective view of the electrolyte membrane preparation apparatus at the time of bonding an electrolyte resin precursor on a carrier film. It is a figure which shows the lamination | stacking state of the laminated body L1 by which an electrolyte resin precursor is bonded together on a carrier film. FIG. 3 is a perspective view of an electrolyte membrane creation apparatus when a porous body as a reinforcing material is bonded to the electrolyte resin precursor side of a laminate L1 obtained in Step 1. Furthermore, it is a figure which shows the lamination | stacking state of the laminated body L2 in which the reinforcing material was bonded together. It is a figure which shows the lamination | stacking state of the new laminated body L3 formed by bonding the electrolyte resin precursor side of the laminated body L1 to the reinforcement material side of the laminated body L2. It is a figure which shows the laminated body L4 which the electrolyte resin precursor melt | dissolved and impregnated the inside of the porous body which is a reinforcing material. It is a figure which shows the laminated body L5 after peeling the carrier film of the one side of the laminated body L4. It is a perspective view of the electrolyte membrane preparation apparatus which peels the carrier film of one side from the laminated body L4, and winds up in roll shape. It is a perspective view of the electrolyte membrane preparation apparatus which hydrolyzes the laminated body L5 and winds up in roll shape. It is a figure which shows the laminated body L6 after a hydrolysis process was performed. It is a table | surface which shows the result of the evaluation test of a carrier film. It is a figure which shows the SPS sheet which conveys an electrolyte membrane and this electrolyte membrane. It is a figure shown about an electrolyte membrane structure provided with a support base material and the electrolyte membrane affixed on the surface of the support base material. It is a figure shown about the conventional electrolyte membrane structure.

  Hereinafter, the configuration of the present invention will be described in detail based on an example of an embodiment shown in the drawings.

<Configuration of carrier film and electrolyte membrane>
The carrier film (electrolyte membrane transport sheet) 1 of this embodiment is a sheet used when transporting the electrolyte membrane 6 and is composed of a sheet (support base material) of SPS (syndiotactic polystyrene) (FIG. 1). reference). Further, one surface of the SPS sheet 2 is subjected to a high adhesion process. The high adhesion treatment is a surface treatment that increases the degree of adhesion between the SPS sheet 2 and the electrolyte membrane 6.

  The carrier film 1 of the electrolyte membrane 6 is required to have various properties such as heat resistance, chemical resistance (acid resistance, alkali resistance), transparency, durability during hydrolysis, and low cost. Other than the film, the resin having a melting point of about 250 ° C. may be PI (polyimide), PPS (polyphenylene sulfite), PMP (polymethylpentene), etc., but there is no alkali resistance, no acid resistance, and no heat resistance. Including problems such as lack of transparency. In this regard, the SPS sheet 2 found by the present inventor is suitable not only for heat resistance but also as a material for a carrier film in that it has characteristics satisfying the various requirements described above, such as being able to withstand a hydrolysis process. It is. However, since the adhesion between the SPS sheet 2 and the electrolyte membrane 6 is poor at the time of hydrolysis, it is important that a surface treatment (high adhesion treatment) that can improve the adhesion is performed while satisfying the above requirements. (See FIG. 13).

  Specific examples of such surface treatment include treatment such as surface treatment by physical unevenness and surface functional group modification by plasma treatment. For example, it is considered that surface treatment using physical unevenness can improve adhesion by a so-called anchor effect, but in practice, it is not appropriate because unevenness may not be achieved by applying unevenness. Moreover, although it is thought that there exists a tendency of the adhesive improvement by a hydrogen bond according to a plasma process, in reality, it is difficult to implement | achieve the adhesiveness which can endure a hydrolysis process.

  In this regard, in the present embodiment, high adhesion is realized by performing a high adhesion treatment that increases the adhesion between the SPS sheet 2 and the electrolyte membrane 6. A suitable example of the high adhesion treatment is to form a fluororesin layer 3 by applying a fluororesin coat on the surface of the SPS sheet 2 (see FIG. 1). According to the surface treatment by the fluorine treatment, the adhesion can be improved while satisfying the various properties required as described above.

<Method for creating reinforced electrolyte membrane>
An example of a method for creating an electrolyte membrane using an electrolyte membrane creation apparatus will be described below (see FIG. 2 and the like). In the figure, each part of the electrolyte membrane forming apparatus is denoted by reference numeral 101 in FIG. 2, reference numeral 102 in FIG. 4, reference numeral 103 in FIG. 9, reference numeral 104 in FIG.

(Step 1)
First, a belt-like electrolyte resin precursor (the end group of the polymer chain is —SO ₂ F) 4 is bonded onto the carrier film 1 (see FIG. 3) and wound up in a roll (see FIG. 2). The electrolyte resin precursor 4 is a fluorine-based ion exchange resin before imparting proton conductivity, and is, for example, a perfluorosulfonic acid polymer such as Naflon (registered trademark). The thickness of the strip-shaped electrolyte resin precursor 4 is about 4 to 15 μm, and if it is within the range of these thicknesses, a favorable power generation environment is easily obtained when applied to a fuel cell.

(Step 2)
Next, in order to make the reinforced electrolyte membrane 6, the porous body as the reinforcing material 5 is bonded to the electrolyte resin precursor 4 side of the laminate L1 obtained in Step 1 (see FIG. 5), and rolled. Wind up (see FIG. 4). The porous body used here is a porous film represented by a polytetrafluoroethylene stretched porous body.

(Step 3)
In order to arrange the reinforcing material 5 inside the reinforced electrolyte membrane 6, the electrolyte resin precursor 4 side of the laminated body L1 obtained in step 1 is attached to the reinforcing material 5 side of the laminated body L2 obtained in step 2. (Alternatively, the reinforcing material 5 side of the laminated body L2 obtained in step 2 may be bonded to the reinforcing material 5 side of the laminated body L2 obtained in step 2) to form a sandwich structure laminated body L3 (see FIG. 6), and then heated and roll pressed. As a result, the electrolyte resin precursor 4 is dissolved, and an impregnation state in which the inside of the porous body as the reinforcing material 5 is impregnated is obtained (see FIG. 7). A reinforcing material dissolved and impregnated with the electrolyte resin precursor 4 is denoted by reference numeral 5 'in the drawing. Through this process, the reinforcing material 5 and the electrolyte resin precursor 4 are integrated.

  The carrier film 1 is placed on both sides of the laminate L4 in which the reinforcing material 5 is impregnated with the electrolyte resin precursor 4 by heating and roll pressing (see FIG. 7). In the present embodiment, one of the carrier films 1 on both outer sides is peeled off (see FIG. 8) and wound into a roll (see FIG. 9).

(Step 4)
The laminate L5 obtained in the above step 3 is immersed in an alkaline solution, washed with water to remove the alkaline solution, further immersed in an acid solution, and washed with water to remove the acid. (See FIG. 10), the end group -SO ₂ F of the polymer chain of the electrolyte resin precursor 4 is modified to -SO ₃ H. When the terminal group is -SO ₃ H, proton conductivity necessary for the fuel cell can be imparted. The laminated body L6 after the hydrolysis treatment is in a state where the reinforced electrolyte membrane 6 is laminated on the carrier film 1 (see FIG. 11). After drying, the laminate L6 is wound into a roll (see FIG. 10).

  The reinforced electrolyte membrane 6 formed through the step of impregnating the reinforcing material 5 as described above is particularly suitable for a thin electrolyte membrane used for a fuel cell.

  As described so far, in this embodiment, the carrier film 1 used when forming the reinforced electrolyte membrane by melt extrusion is based on SPS (syndiotactic polystyrene) having heat resistance, chemical resistance, and the like. A film as a material is adopted, and the fluororesin layer 3 is formed on the carrier film 1. For example, conventional fluorinated carrier films are generally expensive, and may have streaks and distortions. In the web handling manufacturing process, wrinkles may occur during film conveyance or winding due to film distortion. The uneven film is transferred from the streaks to the electrolyte membrane, which is a factor that deteriorates the quality related to the durability of the electrolyte membrane. Instead of this, the carrier film of this embodiment adopting the SPS sheet 2 ( According to the electrolyte membrane conveyance sheet 1, such a problem can be solved. Therefore, it is inexpensive, makes it easy to perform wrinkles and visual inspection by web handling, and has both heat resistance and chemical resistance, has good adhesion in each process, and can enhance storage stability. A simple carrier film (electrolyte membrane transport sheet) 1 can be realized.

  In addition, when the fluororesin layer 3 secures the adhesion between the electrolyte membrane (reinforcing electrolyte membrane 6) being conveyed and the electrolyte membrane conveyance sheet 1, and when the conveyance sheet with the electrolyte membrane is wound into a roll shape In addition, since the back surface of the SPS sheet 2 is laminated on the surface of the electrolyte membrane 6, it is possible to prevent the electrolyte membrane 6 from being peeled off from the back sheet (the back surface of the SPS sheet 2) when unwinding thereafter, and to have blocking properties. Can be improved (see FIG. 14). In addition, the code | symbol 7 in FIG. 14 is the electrolyte membrane structure which consists of the SPS sheet (support base material) 2 and the electrolyte membrane 6 affixed on the surface of the SPS sheet 2. FIG.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention. For example, in this embodiment, although the example which coated the fluororesin on the single side | surface of the SPS sheet was shown, this is only a suitable example of a high contact | adherence process.

  In the above-described embodiment, the process of peeling one of the carrier films 1 on both sides on the outer side has been described (see FIG. 8 and the like). However, the carrier film 1 to be peeled does not require adhesion by the hydrolysis process. There is no need for high adhesion treatment.

  Each carrier film 1 was evaluated. The results are shown below as Example 1 (see FIG. 12).

  A reinforced electrolyte membrane 6 was formed using a film having the following configuration as the carrier film 1. Here, all the conditions were the same except that the carrier film 1 was changed.

  The SPS sheet 2 has five thicknesses of 25 μm, 50 μm, 100 μm, 150 μm, and 200 μm, and the fluororesin layer 3 has five thicknesses of none, 0.5 μm, 1 μm, 5 μm, and 10 μm. The following items were evaluated. The fluororesin layer 3 is a layer obtained by coating a liquid in which a fluororesin is dissolved.

<Blocking property>
About blocking property, evaluation was implemented by the laminated body L1 wound up in the roll shape after the process of step 1 in the formation method of the reinforced electrolyte membrane 6. FIG.

(Evaluation method)
The laminate L1 was wound up to 100 m in a roll shape and stored for 24 hours. The laminate L1 stored for 24 hours was unwound and evaluated by investigating whether or not the electrolyte resin precursor 4 on the carrier film 1 was peeled off from the carrier film 1.

(Evaluation criteria)
If it was not peeled, it was rated as ◯, if the peeled length was less than 10 m, Δ if it was 10 m or more. In addition, the meaning of a symbol is (circle): good, (triangle | delta): acceptable, x: improper (same in the following). If this example is applied, it will be ○ when the blocking property is excellent and × when it is inferior.

<Heat resistance>
About heat resistance, evaluation was implemented using the laminated body L3 wound up in the roll shape after the process of step 3 in the formation method of the reinforced electrolyte membrane 6. FIG.

(Evaluation method)
The difference between the width (TD direction width) a before carrying out heating and roll pressing and the width (TD direction width) b after carrying out heating and roll pressing was evaluated.

(Evaluation criteria)
The neck-in degree was calculated from the width a and the width b by the following formula.
Neck-in degree [%] = (a−b) / a × 100

  When the neck-in degree is less than 5%, it is evaluated as ◯ when it is 5% or more and less than 8%, and when it is 8% or more, it is evaluated as x. Here, shrinkage after heating is called neck-in, and a> b as described above. The shrinkage due to neck-in is small, that is, the film is pulled in the conveyance process while being heated, but the smaller shrinkage rate is superior to the tension.

<Impregnation>
(Evaluation method)
In step 3 of the method for forming the reinforced electrolyte membrane 6, the laminated body L3 in a bonded state before being heated and roll-pressed is cut into 10 cm × 10 cm and placed on a hot plate at 240 ° C. to prepare an electrolyte resin precursor The body 4 was evaluated by the time for impregnating the reinforcing material 5 made of a porous body.

(Evaluation criteria)
When the reinforcing material 5 (white) is impregnated with the electrolyte resin precursor (transparent) 4, the whole becomes transparent. The time until the object became transparent was measured. When the time was less than 100 seconds, it was evaluated as ◯, when 100 seconds or more but less than 120 seconds, Δ, and when it was 120 seconds or more, ×.

<Adhesion>
In the step 4 of the method for forming the reinforced electrolyte membrane 6, the adhesiveness of the laminate L <b> 6 in the hydrolysis treatment was evaluated.

When the terminal group of the polymer chain is modified to sulfone type (—SO ₃ H), the electrolyte polymer contains water and a force to swell acts. When the swelling force exceeds the adhesion between the carrier film 1 and the electrolyte membrane 6, the electrolyte membrane 6 is peeled off from the carrier film 1. If the electrolyte membrane 6 is peeled off from the carrier film 1, wrinkles are generated, which adversely affects durability.

(Evaluation method)
It was evaluated whether the electrolyte resin layer 6 and the carrier film 1 were peeled off by the hydrolysis treatment.

(Evaluation criteria)
If the electrolyte resin layer 6 and the carrier film 1 were not peeled off, it was rated as “◯”, and if it was peeled off, it was marked “x”.

<Result of evaluation>
In FIG. 12, the evaluation result in each carrier film (AJ) is shown. When only the fluororesin layer 3 was used, the blocking property was poor, and when only the SPS layer was used, the adhesion was poor. Moreover, it turned out that it becomes possible to satisfy blocking property and adhesiveness by setting it as 2 layer structure of a SPS layer and the fluororesin layer 3 (refer FIG. 12).

  On the other hand, when the SPS layer made of the SPS sheet 2 is 25 μm or less, the heat resistance is deteriorated, and when it is 200 μm or more, the impregnation property is deteriorated. From these, the desirable thickness range of the SPS layer is 25 μm or more and less than 200 μm. From the viewpoint of cost, the fluororesin layer 3 is preferably thin, and there is no problem if it is about 0.5 μm to 10 μm.

  The present invention is suitable for application to an electrolyte membrane transport sheet used when transporting an electrolyte membrane.

1 ... Carrier film (electrolyte membrane transport sheet)
2. SPS sheet (support base material)
3… Fluorine resin layer (Fluorine resin coat)
5. Reinforcing material (porous membrane)
6 ... (reinforced type) electrolyte membrane 7 ... electrolyte membrane structure

Claims (7)

A support substrate;
An electrolyte membrane attached to the surface of the support substrate;
An electrolyte membrane structure comprising:
The support substrate is composed of a sheet of SPS (syndiotactic polystyrene),
An electrolyte membrane structure in which one surface of the SPS sheet is subjected to high adhesion treatment, and the adhesion force of the surface of the support substrate to the electrolyte membrane is higher than that of the back surface of the support substrate. The electrolyte membrane structure according to claim 1 , wherein a fluororesin coat is applied as the high adhesion treatment. The electrolyte membrane structure according to claim 2 , wherein when the electrolyte membrane is thinner than a predetermined value, the electrolyte membrane is a reinforced electrolyte membrane having a porous membrane. The electrolyte membrane structure according to claim 3 , wherein the electrolyte membrane structure is created through a step of impregnating the porous membrane. The electrolyte membrane structure according to any one of claims 2 to 4 , wherein a thickness of the SPS sheet is thicker than a thickness of the fluororesin coat. The electrolyte membrane structure according to claim 5 , wherein the SPS sheet has a thickness of 25 μm or more and less than 200 μm. The electrolyte membrane structure according to claim 6 , wherein the fluororesin coat has a thickness of 0.5 μm to 10 μm.