JP7087528B2 - Cutting method of porous carbon base material - Google Patents

Description

The present invention relates to a method for cutting a porous carbon substrate.

A porous carbon substrate in which carbon fibers having a short fiber length are dispersed and bonded with a resin carbide is widely used as an electrode of a battery such as a lithium ion battery, a fuel cell, or a redox flow battery.
The porous carbon base material is usually manufactured as a long sheet and wound around a paper tube or the like to form a roll (Patent Document 1). Further, for example, when a porous carbon substrate is used as a gas diffusion layer (GDL) for a fuel cell, when water repellent treatment or coating treatment (MPL treatment) is performed, those treatments are roll-to-roll steps. It will be carried out at.

When using a porous carbon base material, a general cutting machine equipped with a Thomson blade or the like cuts the porous carbon base material drawn from a roll into a shape suitable for the intended use, and then cuts the porous carbon base material into a shape suitable for the intended use. And. However, in the conventional cutting machine, the porous carbon base material is easily cracked at the time of cutting, and chips of carbon fibers and resin carbides (crushed carbon) are likely to be generated. If chips remain on the porous carbon substrate after cutting, for example, when the porous carbon substrate is used as the electrode substrate, problems such as damage to the film at the time of joining with the electrolyte membrane occur.

Japanese Unexamined Patent Publication No. 2010-285194

An object of the present invention is to provide a method for cutting a porous carbon substrate, which can cut a sheet-shaped porous carbon substrate while suppressing residual chips.

The present invention has the following configurations.
[1] A method of cutting a sheet-shaped porous carbon substrate to which carbon fibers are bound by a resin carbide on a cutting table.
The cutting table has an air suction mechanism that sucks air from the surface in contact with the porous carbon substrate.
A method for cutting a porous carbon base material, which cuts a porous carbon base material on the cutting table while sucking air by the air suction mechanism.
[2] The porous carbon substrate according to [1], wherein the air suction surface of the cutting table is inclined, and the porous carbon substrate cut on the cutting table is slid down and sent to the downstream side. Cutting method.
[3] The porous carbon substrate according to [1], wherein the air suction surface of the cutting table is horizontal, and the porous carbon substrate cut on the cutting table is pulled and sent to the downstream side. Cutting method.
[4] Described in any one of [1] to [3], wherein the porous carbon base material is unwound from a roll-shaped material obtained by winding the porous carbon base material into a roll shape and cut on the cutting table. How to cut a porous carbon substrate.

According to the method for cutting a porous carbon substrate of the present invention, a sheet-shaped porous carbon substrate can be cut while suppressing residual chips.

It is a schematic diagram which showed an example of the cutting apparatus used for the cutting method of the porous carbon base material of this invention. It is a schematic diagram which showed the mode that the 1st conveyor was rotated in the cutting apparatus of FIG. 1, and the porous carbon base material of a single leaf was recovered. It is a top view which showed the state of cutting a sheet-shaped porous carbon base material. It is a schematic diagram which showed the other example of the cutting apparatus used for the cutting method of the porous carbon base material of this invention. It is a schematic diagram which showed the other example of the cutting apparatus used for the cutting method of the porous carbon base material of this invention.

The method for cutting a porous carbon substrate of the present invention comprises an air suction mechanism for sucking air from a sheet-like porous carbon substrate in which carbon fibers are bound by a resin carbide from a surface in contact with the porous carbon substrate. It is a method of cutting on a cutting table. In the present invention, the porous carbon substrate is cut on the cutting table while sucking air by the air suction mechanism.

(Porous carbon base material)
The porous carbon base material is a sheet-like porous base material in which carbon fibers are bound by resin carbides. In the porous carbon substrate, a plurality of carbon fibers are bonded by the resin carbide in a state of being dispersed in the sheet so that the fiber directions are oriented in random directions.

Examples of the carbon fiber include polyacrylonitrile (PAN) -based carbon fiber, pitch-based carbon fiber, and rayon-based carbon fiber. Of these, PAN-based carbon fibers are preferable. As the carbon fiber, one type may be used alone, or two or more types may be used in combination.

The average fiber length of the carbon fibers is preferably 2 to 30 mm, more preferably 2 to 12 mm. That is, the carbon fiber is preferably a carbon staple fiber. When the average fiber length of the carbon fibers is at least the lower limit of the above range, sufficient strength can be easily obtained. When the average fiber length of the carbon fiber is not more than the upper limit of the above range, the dispersibility of the carbon fiber is excellent.
The average fiber length of the carbon fibers was measured by observing the carbon fibers at a magnification of 50 times or more with a microscope such as a scanning electron microscope, and measuring the fiber lengths of 50 randomly selected short fibers. It is the average of the values.

The average fiber diameter of the carbon fibers is preferably 3 to 20 μm, more preferably 3 to 9 μm. When the average fiber diameter of the carbon fibers is at least the lower limit of the above range, the dispersibility of the carbon fibers is excellent, so that a carbon fiber sheet uniform in the plane direction can be obtained. When the average fiber diameter of the carbon fibers is not more than the upper limit of the above range, a carbon fiber sheet having high smoothness can be obtained.
The average fiber diameter of the carbon fibers was observed by magnifying the carbon fiber cross section by 50 times or more with a microscope such as a scanning electron microscope, and measuring the fiber diameters of 50 randomly selected single fibers. It is the average of the values of. In the case of a carbon fiber having a flat cross section, that is, when the cross section has a major axis and a minor axis, the major axis is defined as the fiber diameter of the fiber.

The tensile elastic modulus of the carbon fiber is preferably 200 to 600 GPa, more preferably 200 to 450 GPa.
The tensile modulus of carbon fiber is determined by a single fiber tensile test. In the single fiber tensile test, one single fiber is taken out from the carbon fiber, and the elastic modulus of the single fiber is measured using a universal testing machine under the test conditions of a test length of 5 mm and a tensile speed of 0.5 mm / min. Fifty single fibers are selected from the same carbon fibers, their elastic moduli are measured, and the average value is taken as the tensile elastic modulus of the carbon fibers.

The tensile strength of the carbon fiber is preferably 3000 to 7000 GPa, more preferably 3500 to 6500 GPa.
The tensile strength of carbon fiber is determined by a single fiber tensile test. In the single fiber tensile test, one single fiber is taken out from the carbon fiber, and the strength of the single fiber is measured using a universal testing machine under the test conditions of a test length of 5 mm and a tensile speed of 0.5 mm / min. Fifty single fibers are selected from the same carbon fibers, their strengths are measured, and the average value is taken as the tensile strength of the carbon fibers.

For carbon fibers, for example, a bundle of thousands to tens of thousands of carbon fiber filaments is impregnated with a sizing agent, and the dried and focused carbon fiber bundle is continuously or discontinuously used by a roving cutter, a guillotine cutter, or the like. It is obtained by cutting to a predetermined length.

The basis weight of the carbon fibers in the porous carbon substrate is preferably 10 to 140 g / m ² , more preferably 25 to 100 g / m ² . When the basis weight of the carbon fiber is at least the lower limit of the above range, sufficient strength can be easily obtained. When the basis weight of the carbon fibers is not more than the upper limit of the above range, the carbon fibers can be easily dispersed uniformly.

The content of carbon fibers in the porous carbon substrate is preferably 40 to 80% by mass, more preferably 50 to 70% by mass, based on the total mass of the porous carbon substrate. When the content of carbon fiber is at least the lower limit of the above range, sufficient strength can be easily obtained. When the content of the carbon fibers is not more than the upper limit of the above range, the content of the resin carbide can be relatively increased, so that the carbon fibers can be sufficiently bonded to each other.

The resin carbide is a carbonized resin. The binder resin used in the production of the porous carbon base material and the material obtained by carbonizing the binder fiber are included in the porous carbon base material as resin carbides.
The binder resin may be any resin as long as it has a binding force to carbon fibers and is carbonized, and thermosetting resins such as phenol resins and furan resins can be exemplified. As the binder resin, one type may be used alone, or two or more types may be used in combination.

As the phenol resin, a resol type phenol resin obtained by the reaction of phenols and aldehydes in the presence of an alkaline catalyst can be exemplified. A novolak-type phenol resin having heat-fusion properties of a solid, which is produced by the reaction of phenols and aldehydes under an acidic catalyst, may be dissolved and mixed with a resol-type fluid phenol resin. In this case, it is preferable to use a self-crosslinking type containing, for example, hexamethylenediamine as a curing agent.
As the phenol resin, a commercially available product may be used.

Examples of the phenols include phenol, resorcin, cresol, and xylene. As the phenols, one type may be used alone, or two or more types may be used in combination.
Examples of aldehydes include formalin, paraformaldehyde, and furfural. As the aldehydes, one type may be used alone, or two or more types may be used in combination.

As the phenol resin, a water-dispersible phenol resin or a water-soluble phenol resin may be used.
Examples of the water-dispersible phenol resin include the resole-type phenol resin emulsion described in JP-A-2004-307815, JP-A-2006-56960, and the water-dispersible phenol resin also called an aqueous dispersion.
Examples of the water-soluble phenol resin include resol-type phenol resins having good water solubility described in JP-A-2009-84382.

The content of the resin carbide in the porous carbon substrate is preferably 20 to 60% by mass, more preferably 25 to 50% by mass, based on the total mass of the porous carbon substrate. When the content of the resin carbide is not less than the lower limit of the above range, the carbon fibers are easily sufficiently bonded to each other. When the content of the resin carbide is not more than the lower limit of the above range, the content of the carbon fiber can be relatively increased, so that sufficient strength can be easily obtained.

The porous carbon substrate may contain other components other than carbon fibers and resin carbides, if necessary. As another component, carbon powder can be exemplified. Since the porous carbon base material contains carbon powder, improvement in conductivity can be expected.
Examples of the carbon powder include graphite powder, carbon black, milled fiber, carbon nanotube, carbon nanofiber, coke, activated carbon, and amorphous carbon. As the carbon powder, one type may be used alone, or two or more types may be used in combination.

The graphite powder has a highly crystalline graphite structure, and the average particle size of the primary particles thereof is generally several μm to several hundred μm.
Examples of the graphite powder include pyrolysis graphite, spheroidal graphite, scaly graphite, lump graphite, earthy graphite, artificial graphite, and expanded graphite. From the viewpoint of exhibiting conductivity, pyrolysis graphite, spheroidal graphite, or scaly graphite can be used. preferable.

Carbon black generally exists as a structure (aggromate) in which primary particles having an average particle size of several tens of μm are fused to each other to form a structure, and the structures are further bonded to each other by a van der Waals force. Carbon black has a significantly larger number of particles per unit mass than graphite powder, and at a certain critical concentration or higher, agglomates are connected in a three-dimensional network to form a macroscopic conductive path.
Examples of carbon black include acetylene black, ketjen black, furnace black, channel black, lamp black, and thermal black.

The milled fiber may be a crushed virgin carbon fiber, or may be a crushed carbon fiber reinforced thermosetting resin molded product, a carbon fiber reinforced thermoplastic resin molded product, a prepreg or the like. The carbon fiber used as a raw material for the milled fiber may be a PAN-based carbon fiber, a pitch-based carbon fiber, or a rayon-based carbon fiber.

(Cutting device)
Hereinafter, an example of a cutting device used in the method for cutting a porous carbon substrate of the present invention will be described. It should be noted that the dimensions and the like of the figures exemplified in the following description are examples, and the present invention is not necessarily limited to them, and the present invention can be appropriately modified without changing the gist thereof. ..

As shown in FIG. 1, the cutting device 100 of the present embodiment includes a base material supply unit 110, a nip roll 112, a cutting table 114, a cutting machine 116, a first conveyor 118, a second conveyor 120, and a product. A collection unit 122 and a balance collection unit 124 are provided.
In the cutting device 100, a base material supply unit 110, a nip roll 112, a cutting table 114, a first conveyor 118, a second conveyor 120, and a balance collecting unit 124 are provided in this order. A cutting machine 116 is provided above the cutting table 114. A product recall unit 122 is provided below the downstream side of the first conveyor 118.

The base material supply unit 110 is provided with a roll-shaped material 200 in which a long sheet-shaped porous carbon base material CS is wound around a paper tube or the like in a roll shape, and the porous carbon material 200 is used to obtain porous carbon. The base material CS can be unwound.

The cutting machine 116 cuts the sheet-shaped porous carbon base material CS on the cutting table 114. The cutting machine 116 may be any as long as it can cut the porous carbon base material CS into a desired shape on the cutting table 114, and examples thereof include a cutting machine provided with a Thomson blade, a laser irradiation means, and the like.
In the cutting machine 116 of this example, as shown in FIG. 3, the porous carbon substrate CS is spaced apart in the length direction of the sheet-shaped porous carbon substrate CS, and the four rectangular corners of the porous carbon substrate CS are rounded, respectively. Cut it so that it is punched into a tinged shape. As a result, the product 210, which is a porous carbon base material having four rectangular corners rounded, and the balance 212 of the ladder-shaped (frame-shaped) porous carbon base material are formed.

The cutting table 114 is a table for cutting the sheet-shaped porous carbon base material CS. In the cutting table 114, the porous carbon base material CS unwound and supplied from the base material supply unit 110 comes into contact with the upper surface 114a. The porous carbon base material CS is cut by the cutting machine 116 on the upper surface 114a of the cutting table 114.

The cutting table 114 is provided with an air suction mechanism for sucking air from the upper surface 114a in contact with the porous carbon base material CS. By operating the air suction mechanism, the upper surface 114a of the cutting table 114 becomes the air suction surface. With the supplied porous carbon base material CS in contact with the upper surface 114a of the cutting table 114, the porous carbon base material CS can be cut by the cutting machine 116 while sucking air.

By cutting using such a cutting table 114, even if chips are generated during cutting of the porous carbon base material CS, the chips are sucked from the product (porous carbon base material) 210 after cutting. Will be removed. Further, since the porous carbon base material CS at the time of cutting is attracted to the upper surface 114a by the suction of air, the unexpected movement of the porous carbon base material CS is suppressed, and the cutting can be performed more stably.

The air suction mechanism is not particularly limited, and examples thereof include a mechanism in which a plurality of air suction holes are formed on the upper surface 114a of the cutting table 114 and air is sucked from each air suction hole by a suction means such as a vacuum pump. Be done.

The air suction hole is formed in a portion of the upper surface 114a of the cutting table 114 corresponding to the cutting position (the position where the blade or the laser is applied) of the porous carbon base material CS from the viewpoint of easy suction removal of chips. It is preferable to have.
The plurality of air suction holes may be formed on the entire surface of the upper surface 114a of the cutting table 114, or may be partially formed. If the air suction holes are evenly formed on the entire surface of the upper surface 114a of the cutting table 114, the chips can be stably sucked and removed even if the cutting shape is changed, so that various cutting shapes can be supported.

The shape of the open end of the air suction hole is not particularly limited, and examples thereof include a circular shape.
The opening area per air suction hole can be appropriately set, and can be, for example, 1 to 200 mm ² .
The number of air suction holes is not particularly limited, and can be, for example, 25 to 20000 per 100 cm ² .
The arrangement pattern of the plurality of air suction holes is not particularly limited, and examples thereof include a staggered pattern and a grid pattern.

The cutting table 114 of this example is inclined so that the upper surface 114a, which is the air suction surface in contact with the porous carbon base material CS, becomes lower from the upstream side to the downstream side. As a result, in this example, by cutting the porous carbon base material CS on the cutting table 114 and then stopping the suction of air, the product 210 produced by the cutting slides down on the inclined upper surface 114a and is on the downstream side. It is supposed to be sent to.

The inclination angle of the upper surface 114a of the cutting table 114 with respect to the horizontal direction is preferably 5 to 45 °, more preferably 10 to 30 °. When the inclination angle is equal to or higher than the lower limit of the above range, the porous carbon substrate after cutting tends to slip off. When the inclination angle is not more than the upper limit of the above range, it is possible to prevent abrupt slipping after cutting and damage to the end portion of the porous carbon substrate.

The first conveyor 118 and the second conveyor 120 may be any as long as they can convey the product 210 after cutting the porous carbon substrate CS and the remaining 212 of the porous carbon substrate to the downstream side.
As shown in FIG. 2, the first conveyor 118 of this example rotates downward about the rotation shaft 118a provided on the upstream side in the side view.

The product recall unit 122 is a portion for recalling the single-wafer product 210 cut into a desired shape. The mode of the product recall unit 122 is not particularly limited, and examples thereof include a mode in which a packing material is arranged.

The remaining portion collecting unit 124 is a portion for collecting the remaining portion 212 of the porous carbon base material. The balance recovery unit 124 of this example is a winder that winds up the balance 212 of the porous carbon substrate. The remaining portion collecting unit 124 is not limited to the winder, and may be, for example, a transfer type collecting the remaining portion 212 of the porous carbon base material.

(Cut method)
Hereinafter, a method using the cutting device 100 will be described as an example of the method for cutting the porous carbon substrate of the present invention.
As shown in FIG. 1, the sheet-shaped porous carbon base material CS is unwound from the roll-shaped material 200 installed in the base material supply unit 110 and sent to the upper surface 114a of the cutting table 114 via the nip roll 112. As shown in FIGS. 1 and 3, the porous carbon base material CS sent to the upper surface 114a of the cutting table 114 is sucked by the cutting machine 116 while sucking air from each air suction hole on the upper surface 114a by the air suction mechanism. It is cut intermittently to form a plurality of single-wafer products 210. Chips generated from the porous carbon base material CS at the time of cutting are sucked into each air suction hole by suction of air and removed, and thus are removed from each product 210.

The suction power of the upper surface 114a in contact with the porous carbon base material CS to be cut on the cutting table 114 is preferably 50 W to 400 W, more preferably 100 W to 350 W, still more preferably 150 W to 300 W. When the suction power is equal to or higher than the lower limit of the above range, chips generated inside the porous carbon substrate can be easily removed by suction, and it is easy to prevent chips from remaining in the product. When the suction power is not more than the upper limit of the above range, it is possible to prevent the porous carbon substrate from breaking due to strong suction.

In the cutting device 100, the upper surface 114a of the cutting table 114 is inclined. Therefore, by stopping the suction of air in the portion corresponding to the product 210 generated by cutting, the product 210 slides down the upper surface 114a of the cutting table 114 and is the second on the downstream side without pulling the product 210 to the downstream side. It reaches up to 118 on one conveyor.

After cutting, the product 210 and the remaining 212 of the porous carbon substrate are conveyed by the first conveyor 118 and the second conveyor 120. Further, as shown in FIG. 2, by intermittently rotating the first conveyor 118 during transportation, the product 210 is separated from the remaining 212 of the porous carbon substrate and slid off, and is recalled by the product recall unit 122. do. The balance 212 of the porous carbon base material is continuously conveyed by the second conveyor 120, and is wound up and recovered by the balance recovery unit 124.

As described above, in the method for cutting a porous carbon substrate of the present invention, air is sucked by an air suction mechanism using a cutting table having an air suction mechanism for sucking air from a surface in contact with the porous carbon substrate. While doing so, the porous carbon substrate is cut on the cutting table. As a result, even if chips are generated from the porous carbon substrate during cutting, the chips can be removed by suction, so that it is possible to prevent the chips from remaining in the product.

The method for cutting the porous carbon substrate of the present invention is not limited to the method using the cutting device 100 described above.
The method for cutting a porous carbon substrate of the present invention is a method of pulling a porous carbon substrate cut on a cutting table using a cutting table having a horizontal air suction surface and sending it to the downstream side. May be good. For example, a method using the cutting device 100A illustrated in FIG. 4 may be used. The same parts as those in FIG. 1 in FIG. 4 are designated by the same reference numerals, and the description thereof will be omitted.

The cutting device 100A is the same as the cutting device 100 except that the cutting table 114A is provided instead of the cutting table 114.
The cutting table 114A is the same as the cutting table 114 except that the upper surface 114a, which is an air suction surface, in contact with the sheet-shaped porous carbon base material CS is horizontal.

Even when the cutting device 100A is used, the porous carbon base material CS sent to the upper surface 114a of the cutting table 114 is intermittently sucked by the cutting machine 116 while sucking air from each air suction hole on the upper surface 114a by the air suction mechanism. To form a plurality of single-wafered products 210. Chips generated from the porous carbon base material CS at the time of cutting are sucked into each air suction hole by suction of air and removed, and thus are removed from each product 210.

In the cutting device 100A, the remaining portion 212 of the porous carbon substrate after cutting is pulled by the remaining portion collecting portion 124 and wound up, so that the product 210 remains fitted in the cut portion on the upper surface 114a of the cutting table 114. It is pulled downstream together with the remainder 212 of the porous carbon substrate and reaches the first conveyor 118.
Then, while being conveyed by the first conveyor 118 and the second conveyor 120, the first conveyor 118 is intermittently rotated to collect the product 210 by the product recovery unit 122, and the balance 212 of the porous carbon substrate is recalled. Collect in part 124.

In the method using the cutting device 100 and the cutting device 100A, the product 210 was separated from the remaining 212 of the porous carbon substrate by rotating the first conveyor 118, but the remaining 212 of the porous carbon substrate 212. May be separated from the product 210 by pulling up.
For example, a method using the cutting device 100B illustrated in FIG. 5 may be used. The same parts as those in FIG. 1 in FIG. 5 are designated by the same reference numerals, and the description thereof will be omitted.

The cutting device 100B is the same as the cutting device 100 except for the following aspects.
Instead of the two first conveyors 118 and the second conveyor 120, one conveyor 126 is provided. A balance recovery unit 124 is provided so as to pull up the balance 212 of the porous carbon substrate after cutting from the conveyor 126 and wind it up. A product recall unit 122 is provided below the downstream side of the conveyor 126.

In the cutting device 100B, the product 210 after cutting and the remaining 212 of the porous carbon base material reach the conveyor 126, and the remaining portion 212 of the porous carbon base material moves upward at the portion of the guide roll 128 during transportation. It is pulled up, wound up by the balance collecting unit 124, and collected. As a result, the product 210 on the conveyor 126 is separated from the balance 212 of the porous carbon substrate and collected by the product recovery unit 122 on the downstream side of the conveyor 126.

The method for cutting the porous carbon base material of the present invention is not limited to the method for cutting a long sheet-shaped porous carbon base material unwound from a roll, and is not limited to the method for cutting a single-leaf sheet-shaped porous carbon. A method of cutting the base material into a desired shape on a cutting table may be used.

In the method for cutting a porous carbon substrate of the present invention, for example, long porous carbon substrates are spaced in the longitudinal direction and along the width direction so that no residue of the porous carbon substrate is generated after cutting. It may be a method of cutting intermittently. In this case, a cutting device that does not have a balance collecting unit can be used.

100 ... cutting device, 110 ... base material supply unit, 112 ... nip roll, 114 ... cutting table, 114a ... top surface, 116 ... cutting machine, 118 ... first conveyor, 120 ... second conveyor, 122 ... product recovery unit, 124 ... Remaining part recovery part, 200 ... Roll, 210 ... Product, 212 ... Remaining part of porous carbon base material, CS ... Porous carbon base material.

Claims (4)

It is a method of cutting a sheet-like porous carbon base material in which carbon fibers are bound by resin carbide on a cutting table.
The cutting table has a plurality of air suction holes, and has an air suction mechanism for sucking air from a surface in contact with the porous carbon substrate.
A method for cutting a porous carbon base material, which cuts a porous carbon base material on the cutting table while sucking air by the air suction mechanism. The method for cutting a porous carbon substrate according to claim 1, wherein the air suction surface of the cutting table is inclined, and the porous carbon substrate cut on the cutting table is slid down and sent to the downstream side. The method for cutting a porous carbon substrate according to claim 1, wherein the air suction surface of the cutting table is horizontal, and the porous carbon substrate cut on the cutting table is pulled and sent to the downstream side. The porous according to any one of claims 1 to 3, wherein the porous carbon base material is unwound from a roll-shaped material obtained by winding the porous carbon base material into a roll shape and cut on the cutting table. Cutting method of carbon base material.

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