JP2010115842A - Method of manufacturing resin film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a resin film suppressing alignment anisotropy of a rolled resin film even when rolling the resin film with a pair of rolling rollers and further suppressing local wall-thinning, neck-in, or the like of the resin film when rolled. <P>SOLUTION: The method of manufacturing the resin film 22 is carried out by holding a columnar resin 21 between width direction center parts 11a, 12a of the pair of juxtaposed rolling rollers 11, 12 and rolling the columnar resin 21. As the pair of rolling rollers 11, 12, rolling rollers reduced in diameter toward at least one ends 11b, 12b from the center parts 11a, 12a are used to roll the columnar resin 21 so that the thickness of both ends 22b is thicker than that of the center part 22a of the resin film 22. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a resin film by rolling a columnar resin formed from granular primary particles such as polytetrafluoroethylene (hereinafter referred to as PTFE), and in particular, as a raw material for an electrolyte membrane for a fuel cell. The present invention relates to a method for producing a resin film suitable for a quality reinforcing material.

  A solid polymer fuel cell is known as one form of the fuel cell. As shown in FIG. 7, the polymer electrolyte fuel cell includes a membrane electrode assembly (MEA) 75 as a main component, and a separator 76 including a fuel (hydrogen) gas flow path and an air gas flow path. One fuel cell 70 called a single cell is formed by being sandwiched by 76. The membrane electrode assembly 75 has a structure in which an anode side electrode (anode catalyst layer) 73a is laminated on one side of an electrolyte membrane 71 which is an ion exchange membrane, and a cathode side electrode (cathode catalyst layer) 73b is laminated on the other side. The anode catalyst layer 73a and the cathode catalyst layer 73b are provided with diffusion layers 74a and 74b, respectively.

  As the electrolyte membrane 75, a thin film of perfluorosulfonic acid polymer (US, DuPont, Nafion membrane), which is an electrolyte resin (ion exchange resin), is mainly used, but sufficient strength cannot be obtained by itself. Therefore, for example, a porous film (film) obtained by making a thin film of polytetrafluoroethylene, high molecular weight polyethylene resin or the like porous by stretching it in one or two width directions is used as a porous reinforcing material. The electrolyte resin solution is impregnated into a reinforced electrolyte membrane.

  By the way, a resin film such as PTFE used as a raw material of a porous reinforcing material first generates a paste-like resin by kneading a lubricating oil into fine powder which is a solid particle of resin. Then, the paste-like resin is extruded and formed into a string shape (or a column shape), and this columnar resin is sandwiched and rolled between the center portions in the width direction of the pair of rolling rolls 81 and 82 as shown in FIG. Thus, a resin film is produced. Thereafter, as shown in FIGS. 6A and 6B, the end portion of the rolled resin film 92 is held with a clip 50, and the resin film is stretched at least uniaxially to produce a porous resin film. (See, for example, Patent Document 1).

JP 2007-287553 A

However, in such a manufacturing method, as shown in FIG. 4A, when the columnar resin 91 is rolled with a pair of rolling rolls 81 and 82, the resin in the central portion 92a of the resin film 92 in the width direction is Since it is less likely to flow in the flow direction MD and the width direction TD than the resin at the end (high flow resistance), it is rolled while causing an increase in density. As a result, the spring back due to processing becomes large (the spring back at the center of the film increases as the density increases), and the central portion 92a becomes thicker from the end over the width l ₂ in the width direction TD ( (Refer to FIG. 4 (c) and FIG. 5 (a)). Further, as shown in FIG. 5 (b), the extensibility in the width direction TD during rolling is lowered, the molecular orientation in the width direction TD is not sufficiently promoted, and as shown in FIG. 4 (b), Since the fluidity in the width direction TD is low, the orientation of molecules in the flow direction MD is high (orientation anisotropy is high), and further, a resin film in which the central portion 92a is uneven is formed. As a result, when a resin film is produced by stretching, the strength anisotropy is increased due to the high orientation anisotropy, and the stress applied during stretching is not uniform. As shown in FIG. 5, the resin film may be broken along the processing direction (flow direction MD) during stretching.

  Further, as shown in FIG. 4C, due to the film thickness of the central portion 92a during rolling, both end portions 92b are thin relative to the central portion 92a. In some cases, the resin in the portion gripped by the clip 50 is positively stretched, the resin gripping portion is thinned, and the necking-in phenomenon of the neck-in is promoted more than usual.

  The present invention has been made in view of the above circumstances, and even when the resin film is rolled with a pair of rolling rolls, the orientation anisotropy of the rolled resin film is suppressed, and The object of the present invention is to provide a method for producing a resin film capable of suppressing local thinning and neck-in of the resin film during stretching.

  As a result of intensive studies, the inventors have made the thickness of both end portions of the resin film thicker than the thickness of the central portion, and rolling the columnar resin so that the resin can actively flow in the width direction. The orientation anisotropy of the resin film can be suppressed by only one rolling process, and the thickness of the porous reinforcing material processed by stretching (clip gripping) from the rolled resin film is made uniform. I got new knowledge that I can do it.

  The present invention is based on the inventors' new knowledge, and the resin film production method according to the present invention sandwiches a columnar resin between the center portions in the width direction of a pair of rolling rolls arranged side by side. A method for producing a resin film by rolling, wherein as the pair of rolling rolls, a rolling roll having a small diameter from the central portion toward at least one end portion, the center of the resin film is obtained. The columnar resin is rolled such that the thickness of both end portions thereof is greater than the thickness of the portion.

  According to the present invention, the rolling rolls arranged side by side have a resin sandwiched between the rolls by reducing the roll diameter from the central part in the width direction of the rolling rolls toward the end in the width direction. When it is not rare, the gap between the rolling rolls becomes larger as it comes into contact with the central portion and goes toward the end portion. Thereby, the flow resistance in the width direction of the columnar resin is reduced, the flow of the resin is promoted in the width direction during rolling (from the center of the rolling roll toward the end in the width direction), and the flow direction (rolling) The orientation of the molecules does not deviate in the conveying direction or processing direction of the columnar resin and the resin film by the roll. That is, since the obtained resin film has low molecular orientation anisotropy, stretching unevenness during stretching is reduced.

  At the same time, since the film thickness at both ends is thicker than the central portion in the width direction of the resin film, it is possible to suppress the thinning of the portion gripped by the resin film by the clip during stretching, and the gripped portion Neck-in can be reduced. In this way, the resin film can be prevented from tearing or perforating (due to stress concentration during stretching) in the gripped portion, and a uniform porous reinforcing material can be obtained.

  In addition, rolling the columnar resin so that the thickness of the both end portions is thicker than the thickness of the central portion in the width direction of the resin film means that the shape of the rolling roll, the rolling speed, the rolling load, the composition of the resin and This can be achieved by appropriately setting the temperature and the like, and the roll-shaped rolling roll described above is suitable for rolling a resin film in such a shape.

  Moreover, it is more preferable that the said rolling roll used in the manufacturing method of the resin film which concerns on this invention becomes a small diameter toward the both ends from the said center part. According to the present invention, since at least one rolling roll of the pair of rolling rolls has a small diameter from the central portion in the width direction toward both end portions, during rolling, the columnar resin is between the rolling rolls and the resin is the roll. It becomes easy to flow from the central part to both side parts, and a more uniform resin film can be obtained.

  Further, as another aspect, one of the pair of rolling rolls used in the method for producing a resin film according to the present invention has a smaller diameter from the central portion toward one end, and the other More preferably, the rolling roll has a smaller diameter from the central portion toward the other end portion.

  According to the present invention, one of the rolling rolls has a small diameter from the central portion toward the end on one side, whereby the columnar resin easily flows in the width direction on one side between the rolling rolls during rolling. . Further, the other rolling roll has a small diameter from the central portion toward the other end, so that the columnar resin easily flows in the width direction on the other side during rolling. Thereby, at the time of rolling, columnar resin becomes easy to flow toward the both ends from the center part of a rolling roll between rolling rolls, and can obtain a more uniform resin film.

  In the method for producing a resin film in the present invention, the columnar resin is more preferably made of polytetrafluoroethylene (PTFE). According to the present invention, a porous reinforcing material suitable for a polymer electrolyte membrane of a fuel cell can be obtained by using polytetrafluoroethylene (PTFE) as the columnar resin and stretching the rolled resin film. .

  According to the present invention, even when the resin film is rolled with a pair of rolling rolls, the orientation anisotropy of the rolled resin film is suppressed, and further, the resin film is locally thinned during stretching. Neck-in etc. can be suppressed.

Below, with reference to drawings, the manufacturing method of the resin film concerning the present invention is explained based on some embodiments.
Drawing 1 is a figure for explaining the manufacturing method of the resin film concerning a first embodiment, (a) is a figure for explaining the manufacturing method of a resin film, and (b) is a resin film. It is an image figure of the orientation of the molecule | numerator seen from the upper surface, (c) is sectional drawing of a resin film. 2 is a diagram for explaining a stretching process of the resin film manufactured in FIG. 1, (a) is a diagram showing the resin film before stretching, and (b) is a resin film. It is the figure which showed after extending | stretching.

  As shown in FIG. 1, the resin film manufacturing method according to the present embodiment uses a columnar resin 21 as a central portion (central portion) in the width direction TD of a pair of rolling rolls (calendar rolls) 11, 12 arranged side by side. The resin film 22 is manufactured by being sandwiched between 11a and 12b and rolling.

  First, the columnar resin 21 for performing the rolling process is manufactured. Specifically, polytetrafluoroethylene fine powder (unfired) is kneaded with a lubricating aid to make a uniform paste, and a columnar resin (round bar-shaped bead) is produced by extrusion molding or the like.

  Next, as shown in FIG. 1 (a), the columnar resin 21 is sandwiched between the center portions 11 a and 12 a of a pair of rolling rolls 11 and 12 arranged in parallel to each other, and the columnar resin is formed by the rolling rolls 11 and 12. 21 is rotated while being pressurized. Thereby, the columnar resin 21 is sent in the flow direction MD (the conveyance direction (processing direction) of the columnar resin 21 and the resin film 22) while being rolled.

  At this time, as the pair of rolling rolls, rolling rolls having a smaller diameter from the central portion in the width direction of the rolling roll toward at least one end portion are used. In this embodiment, as shown to Fig.1 (a), the upper side rolling roll 11 becomes a small diameter toward the both ends 11b and 11b from the center part 11a, and the lower side rolling roll 12 is also an upper side roll. Similar to the rolling roll 11, the diameter decreases from the central portion 12a toward both end portions 12b and 12b. More preferably, the upper rolling roll 11 and the lower rolling roll 12 have the same shape, and each of the rolling rolls 11 and 12 has a symmetrical shape with respect to the central axis of the rolling roll along the flow direction MD. It has become.

  By using such rolling rolls 11 and 12, the pressing force and the conveyance speed (in such a manner that the thickness of the both end portions 22 b becomes thicker than the thickness of the central portion 22 a in the width direction of the resin film 22 during rolling ( The columnar resin 21 is rolled by adjusting the rotation speed of the rolling roll).

  In the present embodiment, the roll diameters of the rolling rolls 11 and 12 are monotonously decreased from the central portions 11a and 12a toward both end portions 11b and 12b along the width direction. , 12b, the gap between the rolling rolls 11, 12 increases. Thereby, the flow resistance in the width direction of the columnar resin 21 decreases, and the flow of the resin is promoted in the width direction TD during rolling (from the center portion of the rolling roll toward both end portions in the width direction). As a result, as shown in FIG. 1B, the molecular orientation does not deviate in the flow direction MD, and the obtained resin film 22 has low molecular orientation anisotropy.

  At the same time, as shown in FIG. 1 (c), compared to the central portion 22a of the resin film 22 in the width direction TD, rolling is performed so that the film thickness of both end portions 22b and 22b in the width direction TD is thick. As shown to Fig.2 (a), the thinning of the part hold | gripped with the clip 50 at the time of extending | stretching of the resin film 22 can be suppressed, and neck-in can be reduced. Further, since the orientation anisotropy of the resin film 22 before stretching is reduced, the resin film 22 is torn (tear along the flow direction (processing direction) MD) / hole due to stress concentration during stretching in the gripped portion. Opening can be suppressed. As a result, as shown in FIG. 2B, the resin film 22 is uniformly stretched, and a porous reinforcing material suitable for a polymer electrolyte membrane of a fuel cell can be obtained.

  FIG. 3 is a diagram for explaining a method for producing a resin film according to the second embodiment, (a) is a diagram for explaining a method for producing a resin film, and (b) is a resin film. It is an image figure of the orientation of the molecule | numerator seen from the upper surface, (c) is sectional drawing of a resin film. As shown to Fig.3 (a), the point from which the manufacturing method of the resin film which concerns on this embodiment differs from the manufacturing method of the resin film which concerns on 1st embodiment is the point which used the roll roll of a different shape. .

  Specifically, as shown in FIG. 3A, the upper rolling roll 31 of the pair of rolling rolls has a small diameter from the central portion 31a in the width direction toward the end portion 31b on the one side, The roll diameter from the center part 31a to the other end part 31c is the same. On the other hand, as shown in FIG. 3 (a), the lower rolling roll 32 of the pair of rolling rolls has a smaller diameter from the central portion 32a in the width direction toward the other end portion 32b. The roll diameter from 32a to the other end 31c is the same. More preferably, the lower rolling roll 32 is a rolling roll having the same shape as the upper rolling roll 31.

  The columnar resin 41 is sandwiched between the center portions 31a and 32a in the width direction of the pair of rolling rolls 31 and 32, and the thickness of both end portions 42b with respect to the thickness of the center portion 42a in the width direction of the resin film 42. Roll to thicken. That is, when the upper rolling roll 31 has a smaller diameter from the central portion 31a toward the one end portion 31b, the gap also increases in the width direction between the one rolling rolls. 41 easily flows in the width direction on one side between the rolling rolls. Further, the lower rolling roll 32 has a smaller diameter from the central portion 32a toward the other end portion 32b, so that the gap also increases in the width direction between the other rolling rolls. The resin 41 easily flows in the width direction on the other side. Thereby, at the time of rolling, the columnar resin 41 easily flows between the rolling rolls from the center portions 31a and 32a of the rolling rolls toward both ends.

  In this way, as shown in FIG. 3B, the orientation of the molecules in the flow direction MD is not biased in the flow direction MD during rolling, and the orientation in the width direction TD is promoted. The orientation anisotropy of the resin molecules is lowered. At the same time, as shown in FIG. 3 (c), the rolling is performed so that the film thickness of both end portions 42b, 42b in the width direction TD is thicker than the central portion 42a of the resin film 42. Local thinning of the film 42 can be suppressed, and neck-in at the gripped portion can be reduced. In addition, since the orientation anisotropy of the resin film 42 before stretching is reduced, the resin film 42 can be prevented from tearing or opening. As a result, the resin film 22 is uniformly stretched, and a porous reinforcing material suitable for a polymer electrolyte membrane of a fuel cell can be obtained.

Hereinafter, the present invention will be described by way of examples.
[Example 1]
As a method for forming a resin film (resin tape), a polytetrafluoroethylene (PTFE) resin film was produced by a generally known particle fusion method. Specifically, first, 20% by mass of a liquid lubricant naphtha was uniformly dispersed in PTFE fine powder (unfired), and the mixture was compression-preformed. Next, this is extruded into a cylindrical shape (string-shaped bead), and the string-shaped bead is sandwiched between the center portions in the width direction of a pair of metal rolling rolls and rolled to obtain a resin having a thickness of about 300 μm. A film was made.

  Here, the pair of rolling rolls shown in the first embodiment were used as the metal rolling rolls. Specifically, the diameter of the central part is 300 mm, the diameters of both ends of the roll are 280 mm, and a rolling roll having a shape having a smaller diameter from the central part to the end part is used, with a rolling load of 20 t and a rolling speed of 2 m / min. Rolled.

  Here, for the purpose of evaluating the resin flowability in the width direction, the width and film thickness distribution in the width direction of the obtained resin film were measured. Furthermore, the in-plane dielectric constant of the resin film was measured, and the molecular anisotropy (MOR) was measured by comparing the magnitude of the dielectric constant. MOR is an index of orientation anisotropy and is determined by MOA-3012 manufactured by Oji Scientific Instruments. The larger the MOR value, the larger the anisotropy. When the MOR value is 1, the isotropic property is shown. These results are shown in Table 1. Here, the higher the dielectric constant, the higher the orientation anisotropy.

  Furthermore, in order to confirm stretchability, a plurality of resin films produced as described above were prepared, and as shown in FIG. 2, the gripping part was opened by biaxial stretching, and the appearance after stretching was evaluated. The results are shown in Table 1. In addition, as a criterion for use as a fuel cell electrolyte reinforcing material, ◎: very good, ○: good, ×: bad, thickness unevenness judgment… good ○, slightly bad △ The judgment results were also shown.

[Example 2]
In the same manner as in Example 1, a resin film was produced. The difference from Example 1 is that, as a pair of rolling rolls, the diameter of the central portion is 300 mm, the diameter of both ends of the roll is 250 mm, and the rolling roll has a shape that becomes smaller in diameter from the central portion to the end in the width direction. It is a point using. And it carried out similarly to Example 2, and evaluated the film width of the resin film, the molecular orientation anisotropy, the film thickness distribution, and the drawability. The results are shown in Table 1.

[Example 3]
In the same manner as in Example 1, a resin film was produced. The difference from Example 1 is that, as a pair of rolling rolls, the diameter in the center in the width direction is 300 mm, the diameter in the width on one side of the roll is 260 mm, and the diameter on one side is 300 mm on the other side. It is a point using a roll to be converted. And it carried out similarly to Example 1, and evaluated the film width of the resin film, the molecular orientation anisotropy, the film thickness distribution, and the drawability. The results are shown in Table 1.

[Comparative Example 1]
In the same manner as in Example 1, a resin film was produced. The difference from Example 1 is that the diameter of the center part in the width direction is 300 mm and the diameter of both ends of the roll is 300 mm as a pair of rolling rolls, and the roll diameter does not change from the center part to the end part. This is a point using a rolling roll. And it carried out similarly to Example 1, and evaluated the film width of the resin film, the molecular orientation anisotropy, the film thickness distribution, and the drawability. The results are shown in Table 1.

[Results and discussion]
In Comparative Example 1, since the resin fluidity in the width direction is low, the orientation anisotropy is high, and the end of the resin film is thinned, and stress is easily concentrated in the vicinity of the portion gripped by the clip during stretching. In some cases, film perforation and thinning occurred.

  In Examples 1 to 3, by reducing the roll diameter from the center to the end, the resin fluidity in the width direction is promoted (the orientation of the resin molecules is promoted). The directionality was reduced. Further, as is clear from the results of Example 2, the rolling roll used in Example 2 has a larger reduction rate of the roll diameter from the central part to the end part than the other examples. It is considered that the molecular orientation of the resin in the width direction is further promoted, and the end portion of the resin film in the width direction is thicker than the central portion of the resin film.

  As a result of stretching of the resin films of Examples 1 to 3 and Comparative Example 1, porous resin films were obtained from these resin films. Further, in terms of stretchability, particularly in Examples 1 to 3, since the end portion was thickened, no hole was generated, and in particular, the resin film of Example 2 was a porous reinforcing material in the vicinity of the gripping portion. The thinning was also reduced.

It is a figure for demonstrating the manufacturing method of the resin film which concerns on 1st embodiment, (a) is a figure for demonstrating the manufacturing method of a resin film, (b) is from the upper surface of the resin film. It is the image figure of the orientation of the molecule | numerator seen, (c) is sectional drawing of a resin film. It is the figure for demonstrating the extending process of the resin film manufactured in FIG. 1, (a) is the figure which showed before extending | stretching of the resin film, (b) showed after extending | stretching of the resin film. Figure. It is a figure for demonstrating the manufacturing method of the resin film which concerns on 2nd embodiment, (a) is a figure for demonstrating the manufacturing method of a resin film, (b) is from the upper surface of the resin film. It is the image figure of the orientation of the molecule | numerator seen, (c) is sectional drawing of a resin film. It is a figure for demonstrating the manufacturing method of the conventional resin film, (a) is a figure for demonstrating the manufacturing method of a resin film, (b) is the molecule | numerator seen from the upper surface of the resin film. It is an image figure of orientation, (c) is sectional drawing of a resin film. It is a figure for demonstrating the rolling state of the resin film in the manufacturing method shown in FIG. 4, (a) is sectional drawing which showed the cross section of the rolling roll and resin film which become perpendicular | vertical with respect to a flow direction. (B) is a figure for demonstrating the resin flow seen from the cross section of the rolling roll and resin film which are perpendicular | vertical with respect to the width direction, and this corresponding to this. It is a figure for demonstrating damage of the resin film at the time of extending | stretching, (a) is a figure for demonstrating a film tear, (b) is thinning of a holding part, a hole opening, and neck-in. The figure for demonstrating. The schematic diagram explaining an example of a polymer electrolyte fuel cell (single cell).

Explanation of symbols

  11: Upper rolling roll, 11a: Central part, 11b: End part, 12: Lower rolling roll, 12a: Central part, 12b: End part, 21: Columnar resin, 22: Resin film, 22a: Central part, 22b: end, 31: upper rolling roll, 31a: center, 31b: end, 32: lower rolling roll, 32a: center, 32b: end, 41: columnar resin, 42: resin film, 42a: center portion, 42b: end portion

Claims (4)

A method for producing a resin film by sandwiching and rolling a columnar resin in the center in the width direction of a pair of rolling rolls arranged side by side,
As the pair of rolling rolls, using a rolling roll having a small diameter from the central portion toward at least one end, the thickness of both ends of the resin film is thicker than the thickness of the central portion of the resin film. Thus, the method for producing a resin film, comprising rolling the columnar resin.   The method for producing a resin film according to claim 1, wherein the rolling roll has a small diameter from the central portion toward both end portions.   Of the pair of rolling rolls, one rolling roll has a small diameter from the central portion toward one end, and the other rolling roll has a small diameter from the central portion toward the other end. The method for producing a resin film according to claim 1, wherein:   The said columnar resin consists of polytetrafluoroethylene, The manufacturing method of the resin film in any one of Claims 1-3 characterized by the above-mentioned.

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