JP5838944B2 - Method for producing reinforcing membrane used for electrolyte membrane for fuel cell - Google Patents

Description

  The present invention relates to a method for producing a reinforcing membrane used for an electrolyte membrane for fuel cells.

  In order to compensate for the decrease in strength caused by the thinning of the electrolyte membrane used in fuel cells, an electrolyte membrane reinforced by laminating a porous reinforcing membrane on the electrolyte membrane (also called “reinforcing electrolyte membrane”) is used. ing. The formation of a porous film used as a reinforcing film is performed by, for example, stretching and baking a sheet-like film material.

  Patent Document 1 discloses a technique for extending a film in the width direction by conveying a film material in one direction while being gripped by a gripping means in order to suppress the occurrence of stretching unevenness and neck-in. Has been. In Patent Document 2, the electrolyte membrane coated with the electrode paste is fixed to a fixing member and dried so that the electrolyte membrane is not deformed, and the electrolyte membrane absorbs moisture while fixing the dried electrolyte membrane to the fixing member. A technique for suppressing wrinkles from being generated in the membrane electrode assembly is disclosed.

JP 2010-99889 A JP 2012-164422 A

  Here, as the reinforcing membrane of the electrolyte membrane, it is desirable that the in-plane strength is high in order to improve fatigue durability, and the porous structure is good in order to improve power generation characteristics, for example, high porosity or high air permeability. It is desirable that On the other hand, when a porous reinforcing film using PTFE is formed by stretching or firing the film material as described above, neck-in during stretching, heat shrinkage during firing, etc. As a result, the porosity and the strength are reduced, and there is a problem that the pores are clogged by hot pressing during firing. For example, the porosity and the strength are reduced as follows. That is, in order to improve the porosity and strength of the film by PTFE, it is generally necessary to stretch in at least one direction, but the film gripping performed for stretching is released before firing after stretching. Alternatively, if unfired when fired, the film may shrink due to the elastic recovery force of the film material or relaxation of orientation heat, and the porosity and strength may be reduced. Further, the clogging of the pores occurs as follows, for example. That is, the stretched film material is fired, for example, by bringing the film material into contact with a heating roll (also referred to as a “baking roll”), but for heating and fixing, the heating temperature is higher than the melting point of PTFE. It is necessary to increase the amorphous part by breaking the crystal structure of PTFE. On the other hand, in order to improve the heating efficiency, if the heating roll is pressed against the film material at a predetermined pressure to ensure that the heating roll comes into contact with the film material, As a result, stress is applied from the heating roll, and deformation in the film thickness direction is caused by this stress, resulting in pore clogging (also referred to as “film collapse”). These problems are not limited to the formation of a reinforcing film using PTFE, and the same problem applies to the formation of other reinforcing films.

  In the film stretching technique of Patent Document 1, the suppression of neck-in in the width direction of the film is considered, but no consideration is given to thermal contraction of the film or deformation in the film thickness direction (film collapse). Absent. Moreover, in the manufacturing technique of the membrane electrode assembly of Patent Document 2, there is no description about the reinforcing membrane of the electrolyte membrane, and no consideration is given to the neck-in of the reinforcing membrane, thermal contraction of the membrane, and membrane collapse.

  As described above, in the production of a porous film used as a reinforcing film, it is desired to suppress thermal shrinkage and deformation in the film thickness direction when the film material is fired, which is a cause of destruction of the porous structure and a decrease in mechanical strength. It was.

  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 method for producing a porous reinforcing membrane used for an electrolyte membrane for fuel cells is provided. In this reinforcing film manufacturing method, a firing roll for firing the film material is disposed in a transport path of the film material at the time of manufacturing the reinforcing film, and guides are provided upstream and downstream along the firing roll. A roll is disposed; the film material is brought into contact with the calcining roll through the guide rolls on both sides, and the film material is fed out from the calcining roll, whereby the downstream guide roll is disposed from the upstream guide roll. In the meantime, the film material is fired by bringing it into contact with the firing roll. According to the manufacturing method of the reinforcing film in this form, the upstream and downstream guide rolls are fired by bringing the film material into contact with the firing roll without applying stress to the film material as in the past. Therefore, the deformation of the film material in the film thickness direction during firing can be suppressed, and the destruction of the porous structure such as the blocking of the pores can be suppressed. As a result, it is possible to manufacture a reinforcing membrane for an electrolyte membrane for a fuel cell while suppressing deformation in the thickness direction during firing of the membrane material, which is a cause of destruction of the porous structure.

(2) In the method for manufacturing a reinforcing film according to the above aspect, gripping means for gripping both ends in the width direction perpendicular to the conveying direction of the film material for manufacturing the reinforcing film is disposed; the film material is gripped A firing roll for firing the film material is disposed in the conveyance path, and guide rolls are disposed on the upstream side and the downstream side along the firing roll; both sides of the film material are gripped by the gripping means. The film material is brought into contact with the calcining roll through the guide roll, and the film material is sent out from the calcining roll, so that between the upstream guide roll and the downstream guide roll, The film material may be fired by bringing it into contact with the firing roll. According to the manufacturing method of the reinforcing film of this embodiment, since the film material is held by the holding means in the firing process, deformation in the film thickness direction of the film material at the time of firing is suppressed, and pores are blocked. In addition to suppressing the destruction of the porous structure, neck-in and film shrinkage can be suppressed. As a result, it becomes possible to manufacture a reinforcing membrane for an electrolyte membrane for a fuel cell while suppressing thermal shrinkage and deformation in the thickness direction during firing of the membrane material, which is a cause of destruction of the porous structure and lowering of mechanical strength. .

  In addition, this invention can be implement | achieved with various forms, for example, can be implement | achieved with various forms, such as a manufacturing method and manufacturing apparatus of a reinforcement film | membrane.

It is a schematic explanatory drawing which shows the part of the baking apparatus contained in the manufacturing apparatus of a reinforcement film | membrane as one Embodiment to which this invention is applied. It is the table | surface shown about "film crushing", "heat shrinkage | contraction", and "baking time" as evaluation of the reinforcement film | membrane of the Example manufactured by the said embodiment. It is a graph which shows the porosity of the reinforcement film | membrane of the Example manufactured by the said embodiment. It is a graph which shows the elasticity modulus of the reinforcement film | membrane of the Example manufactured by the said embodiment.

  FIG. 1 is a schematic explanatory view showing a part of a firing apparatus included in a reinforcing film manufacturing apparatus as an embodiment to which the present invention is applied. 1A is a schematic diagram showing the firing apparatus 10 from the upper side, FIG. 1B is a schematic diagram showing a cross section AA of FIG. 1A, and FIG. It is a schematic diagram which expands and shows the part of the frame B of B). The baking apparatus 10 holds the film material PF drawn in a strip shape from a supply roll (not shown) in the conveyance path while holding the both ends in the width direction perpendicular to the conveyance direction (indicated by arrows) by the grasping means 20. Baking is performed by the arranged baking means 30. The fired film material PF is wound up on a winding roll (not shown). In addition, as a film | membrane material, what was comprised with resin members, such as PTFE, is used, for example.

  The gripping means 20 includes a gripping roll 22 and a gripping wire 24. An annular groove 22d is formed on the outer circumferential surface of the gripping roll 22, and the annular groove 22d is placed in the annular groove 22d over an appropriate rotation angle range with the end portion in the width direction of the film material PF interposed therebetween. The gripping wire 24 is inserted in an arc shape. The gripping means 20 holds the film material PF along the outer peripheral surface of the gripping roll 22 as the gripping roll 22 rotates and the gripping wire 24 moves while the film material PF is gripped and gripped by the gripping roll 22 and the gripping wire 24. Transport. The gripping wire 24 is fitted in an arc shape over an appropriate rotation angle range of the annular groove 22d of the gripping roll 22 by the wire rolls 26f and 26b arranged on the upstream side and the downstream side along the gripping roll 22. Inserted.

  The baking means 30 includes a baking roll 32 for baking the film material PF and guide rolls 34f and 34b for guiding the conveyance of the film material PF. The firing roll 32 is disposed on the lower surface side of the film material PF in the transport path in which the film material PF is gripped by the gripping means 20 and transported along the gripping roll 22. The guide rolls 34f and 34b are arranged on the upstream side and the downstream side along the arcuate outer peripheral surface of the firing roll 32 on the upper surface side of the film material PF opposite to the firing roll 32 with respect to the film material PF. The firing means 30 causes the film material PF to extend along the arcuate upper surface side of the outer circumferential surface of the firing roll 32 through the arcuate lower surface side of the outer circumferential surfaces of the both-side guide rolls 34f and 34b and from the firing roll 32 to the film. The material PF is sent out toward the take-up roll. Thereby, the film material PF is conveyed according to the rotation of the firing roll 32 while being in contact with the arcuate upper surface side of the outer peripheral surface of the firing roll 32 between the upstream guide roll 34f and the downstream guide roll 34b. Then, the film is fired by heat applied from a firing roll 32 heated to a temperature equal to or higher than the melting point of the film material (also referred to as “firing temperature”).

  In the above configuration, the film material PF is not subjected to conventional heat press stress between the upstream side guide roll 34f and the downstream side guide roll 34b, and is moved in the direction of gravity due to gravity and tension in the conveyance direction of the film material. The film material PF is brought into contact with the firing roll 32 so as to cover the firing roll 32 along the outer peripheral surface of the firing roll 32 with the force of the above, and the film material PF is heated to be fired. For this reason, it can suppress that a big stress is added to a film | membrane material like the past, and it deform | transforms into a film thickness direction, and the destruction of the porous structure by blockade of a pore, etc. can be suppressed. In the above configuration, since the film material PF is gripped by the gripping means 20 in the firing process, neck-in, film shrinkage, and the like can be suppressed. As a result, it is possible to manufacture a reinforcing membrane for an electrolyte membrane for a fuel cell while suppressing thermal shrinkage during film material firing, deformation in the film thickness direction, and the like, which are factors that cause destruction of the porous structure and mechanical strength. According to the electrolyte membrane reinforced using the reinforcing membrane thus manufactured, it is possible to ensure a desired porous structure and strength, and obtain an electrolyte membrane with improved power generation characteristics and durability. It is possible.

  The roll clearance dc (FIG. 1C) between the firing roll 32 and the guide rolls 34f and 34b can transport the film material PF according to the rotation of the guide rolls 34f and 34b and the firing roll 32. The degree of force is set to be applied to the film material PF.

  The guide rolls 34f and 34b are preferably provided with an adjusting mechanism for adjusting the position with respect to the firing roll 32 in three dimensions (x, Y, and z axes), although illustration and description are omitted. Various general three-dimensional adjustment position adjustment mechanisms can be used as the adjustment mechanism. Thereby, it is possible to change the wrap angle θr (FIG. 1C) corresponding to the length in which the film material PF is brought into contact with the firing roll 32 between the upstream guide roll 34f and the downstream guide roll 34b. The firing time of the film material PF can be adjusted. Moreover, the roll clearance dc can be changed, and the difference in the thickness of the film material PF to be fired can be dealt with.

  Furthermore, although illustration and description are omitted, the guide rolls 34f and 34b are preferably provided with a rotation drive mechanism such as a motor in order to control the rotation of at least one guide roll. Thereby, conveyance resistance (inertia, sliding, etc.) to the film material can be reduced, and damage to the film material (blockage of pores, etc.) caused by the conveyance resistance can be suppressed. Further, the difference in the conveyance speed of the film material derived from the process upstream of the upstream guide roll 34f and the process downstream of the downstream guide roll 34b is determined by the rotation of the upstream guide roll 34f and the downstream guide roll 34b. It can be adjusted by making a difference in rotation.

  FIG. 2 is a table showing “film collapse”, “heat shrinkage”, and “firing time” as evaluation of the reinforcing film of the example manufactured according to the above embodiment. FIG. 3 is a graph showing the porosity of the reinforcing membrane of the example manufactured according to the above embodiment. FIG. 4 is a graph showing the elastic modulus of the reinforcing film of the example manufactured according to the above embodiment. In addition, the example of baking by a nip baking system, a belt baking system, and a clip holding | grip baking system was shown as a comparative example.

  The nip firing method is a method in which a nip roll is applied to a firing roll at a constant pressure, and a film material (porous film) is sandwiched between the rolls for firing and transporting. Note that both ends of the film material are gripped and conveyed at both ends in the width direction in the same manner as in this embodiment to suppress thermal shrinkage. In the belt firing method, the surface pressure between the firing assist belt and the firing roll is adjusted by adjusting the belt tension by placing the firing assist belt on the guide roll and applying the firing assist belt to the firing roll. In this method, the film material is sandwiched and fired and conveyed. The clip holding firing method is a method in which both ends of the film material in the width direction are held and transported by clips, and firing is performed by setting the ambient temperature to be equal to or higher than the firing temperature.

The “film collapse” is defined as the ratio of the porosity (film collapse amount) that changes after firing with respect to the porosity before firing.
[Film collapse amount] = (([Porosity before firing] − [Porosity after firing]) / [Porosity before firing]) × 100
“Heat shrinkage” is defined as the amount of change in width after firing relative to the width before firing (“heat shrinkage”), and “neck-in” is the ratio of heat shrinkage to the width before firing (“neck-in”). Amount ").
[Heat shrinkage] = [Width before firing]-[Width after firing]
[Neck-in amount] = ([Heat shrinkage amount] / [Width before firing]) × 100

  As shown in FIG. 3, the porosity after baking is about 87.4% in the baking method of the example (hereinafter also referred to as “lapping method”) with respect to the film material having a porosity of 93% before baking. In the comparative nip firing method, belt firing method, and clip gripping firing method, they were about 87.8%, 75.3%, and 44.6%, respectively. From these results, as shown in FIG. 2, each “film collapse” is about 6% in the lap firing method of the example, and in the nip firing method, belt firing method, and clip grip firing method of the comparative example, 52%, 19% and 11%.

  Further, as shown in FIG. 2, “heat shrinkage” and “neck-in” are 0 mm and 0% in the lap firing method of the example, and the nip firing method, belt firing method, clip of the comparative example of the comparative example. In the gripping firing method, they were 0 mm and 0%, 45 mm and 9%, 63 mm, and 12.6%, respectively. In addition, the width | variety of the film | membrane material before baking is 500 mm.

  In addition, as shown in FIG. 2, the “baking time” is 1 second at a baking temperature of 360 ° C. in the lap baking method of the example, and in the nip baking method, belt baking method, and clip gripping baking method of the comparative example, The firing temperature was 360 ° C., 0.6 seconds, 3 seconds, and 600 seconds.

  In the comparative nip firing method, fixing by holding both ends and firing by a firing roll, heat shrinkage and neck-in do not occur, and the firing time is as short as 0.6 seconds, but pressure is applied to the film material by the nip roll. Therefore, the film collapse increased to 52%. Further, in the clip gripping and firing method of the comparative example, since it is fixed by the gripping clip, there is shrinkage in the unfixed portion, so that the heat shrinkage is 63 mm and the neck-in is as large as 12.6%. Because of this, the firing time was also very long, 600 seconds. However, the film collapse was as small as 11% due to the atmospheric temperature firing. Further, in the belt firing method of the comparative example, the firing time is as short as 3 seconds because the firing is performed by the firing roll as in the nip firing method. In addition, the film collapse is relatively small as compared with the nip firing method because the film material is sandwiched between the firing auxiliary belt and the firing roll, but is slightly larger as 19% due to the pressure by the firing assist belt. became. In addition, heat shrinkage and neck-in are relatively small compared to the clip-grip firing method, but because the ends are not fixed as in the nip firing method, the heat shrinkage is 45 mm and the neck-in is slightly larger at 9%. It was.

  In contrast to the comparative example, the lap firing method of the example is fixed at both ends similarly to the nip firing method, and thus heat shrinkage and neck-in do not occur. Moreover, since it is baking by a baking roll, baking time is also as short as 1 second. In addition, since no external pressure was applied to the film material such as a pressure by a nip roll or a pressure from a firing auxiliary belt, the film collapse was as small as 6%.

  Further, as shown in FIG. 4, the elastic modulus of the film in the processing direction (conveyance direction) is not much different between the example and the comparative example, but the elastic modulus in the width direction is compared with the comparative example in the example. I found out that it was improving.

  As described above, the reinforcing membrane of the example manufactured according to the embodiment has improved properties such as elastic modulus, porosity, film collapse, and heat shrinkage, and is superior to the reinforcing membrane manufactured by any of the comparative examples. It was found that characteristics can be obtained.

  In the description of the above embodiment, only the configuration necessary for showing the features of the present invention has been shown and described. However, the present invention is not limited to these components, and the transport roller, the transport tension adjusting mechanism, the transport It is possible to apply various components desirable for the actual apparatus configuration such as a speed adjusting mechanism.

  The present invention is not limited to the above-described embodiments, reference forms, 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.

DESCRIPTION OF SYMBOLS 10 ... Baking apparatus 20 ... Holding means 22 ... Holding roll 22d ... Annular groove 24 ... Holding wire 26f ... Wire roll (upstream side wire roll)
26b ... Wire roll (downstream wire roll)
30 ... Firing means 32 ... Firing roll 34f ... Guide roll (upstream guide roll)
34b ... guide roll (downstream guide roll)
PF ... Membrane material

Claims (1)

A method for producing a porous reinforcing membrane used in an electrolyte membrane for fuel cells,
In the conveying path of the film material for manufacturing the reinforcing film, a firing roll for firing the film material is disposed, and a guide roll is disposed on the upstream side and the downstream side along the firing roll,
While bringing the film material into contact with the firing roll via the guide rolls on both sides, by sending the film material from the firing roll, between the upstream guide roll and the downstream guide roll, The film material is brought into contact with the firing roll and fired. A method for producing a reinforcing film.

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