JP2022152151A - Method for winding carbon paper and method for producing carbon paper wound body using the same - Google Patents

Abstract

To provide a winding method capable of sufficiently reducing miswinding even when a carbon paper is formed into a large diameter wound body.SOLUTION: A carbon paper winding method for winding a continuously conveyed long carbon paper on a core bobbin is configured such that: a winding is performed at a constant tension of 40 N/m or more to a predetermined tension turning point at which the winding diameter increases by 40 mm or more as compared with that at the start of winding; after the tension turning point, the winding is performed while reducing the tension; and the tension at the end of winding is set to 20 N/m or more.SELECTED DRAWING: Figure 4

Description

The present invention relates to a method for winding carbon paper. Carbon paper is mainly used as a gas diffusion electrode base material for fuel cells such as polymer electrolyte fuel cells and methanol fuel cells, and as an electrode base material for batteries using gases such as oxygen and hydrogen as active materials.

Porous carbon paper, in which short carbon fibers are bonded with resin carbide, is generally used as a material for the gas diffusion electrode base material constituting the membrane-electrode assembly in which the power generation reaction occurs in the fuel cell. When conveying long carbon paper, it is necessary to wind the carbon paper and handle it as a roll. However, when winding carbon paper that has a small friction coefficient on the surface and is highly brittle, winding misalignment occurs if the winding tension is low, and winding misalignment does not occur if the winding tension is high. There is a problem that it is easy to break due to minute scratches on the part, and there is a unique difficulty in controlling the winding conditions.

As a method for winding carbon paper, Patent Document 1 proposes a method in which the initial winding tension is 30 N/m or more, the final winding tension is 20 N/m or more, and the winding tension is gradually decreased from the start to the end of winding. It is However, since carbon paper is porous and easily deformed in thickness, even if it is wound while gradually reducing the winding tension, the effect of gradual tension reduction decreases due to the relaxation of the pressure between the carbon papers, especially when trying to increase the diameter. still had the problem of occurrence of winding misalignment.

Further, Patent Document 2 proposes setting the final winding tension T2 to be equal to or greater than the initial winding tension T1, and further setting T2 to be equal to or less than the value calculated using the winding diameter. However, since the tightening force accumulated from the outer carbon paper is applied to the inner carbon paper, there is a problem that especially with low-density carbon paper, the winding is tightened on the inner circumference and misalignment due to the reduction in the thickness of the carbon paper tends to occur. there were.

Japanese Patent Application Laid-Open No. 2002-302557 Japanese Patent Application Laid-Open No. 2008-247610

An object of the present invention is to provide a winding that can sufficiently reduce winding misalignment even when carbon paper is used as a large-diameter winding body (typically, when the winding diameter is 500 mm or more at the end of winding). It is to provide a method.

The present invention for solving the above problems is as follows.
(1) A carbon paper winding method for winding a continuously conveyed long carbon paper around a core bobbin, wherein the tension is 40 N until a predetermined tension turning point at which the winding diameter increases by 40 mm or more compared to the start of winding. A method of winding carbon paper by winding with a constant tension of 1/m or more, winding while reducing the tension after passing the tension turning point, and setting the tension at the end of winding to 20 N/m or more.
(2) The carbon paper winding method according to (1), wherein the change rate of the winding diameter of the carbon paper from the start of winding to the tension turning point is 20 to 160%.
(3) The carbon paper winding method according to (1) or (2), wherein the change rate of the winding diameter of the carbon paper after the tension turning point has passed is 10 to 250%.
(4) The carbon paper winding method according to any one of (1) to (3), wherein the change rate of the winding torque after the tension turning point has passed is -100 to +160%.
(5) The carbon paper winding method according to any one of (1) to (4), wherein the winding diameter at the end of winding is 500 mm or more.
(6) The carbon paper winding method according to any one of (1) to (5), wherein the outer diameter of the core bobbin is 76 mm or more.
(7) Any one of (1) to (6) used for winding carbon paper having a flexural modulus of 2 to 50 GPa, a static friction coefficient of 0.1 to 0.7, and a tensile strength of 1 to 10 kN/m. The method for winding the carbon paper described above.
(8) An end position detection means is provided to detect the end position of the carbon paper before winding, and the detection signal of the end position detection means is controlled to prevent winding misalignment. (1) to (7) ).
(9) A method for producing a carbon paper roll, including the carbon paper winding method according to any one of (1) to (8).

According to the present invention, when the carbon paper is continuously wound, it is possible to form a wound body with small winding deviation even if it has a large diameter, prevent winding collapse during packing, transportation, etc., and the carbon paper can be wound. The handleability of the rotating body can be improved.

FIG. 10 is a side view showing an example of a state in which winding misalignment has occurred in the carbon paper roll; Schematic side view showing one embodiment of a winding device for carrying out the winding method of the present invention. FIG. 2 is a front view showing one embodiment of the carbon paper end position detection means; Graph showing changes in winding tension from the start of winding in Examples and Comparative Examples

Hereinafter, in this specification, "-" is used as a symbol indicating a range including numerical values at both ends thereof.

Carbon paper is a structure formed by binding a paper product containing short carbon fibers with a carbonized organic substance such as phenol resin. Carbon paper has a high flexural modulus, a low coefficient of static friction, is easily reduced in thickness by pressure, and is brittle, so the winding method of the present invention can be preferably applied to the carbon paper. Carbon paper is preferably used as a gas diffusion electrode base material for fuel cells such as polymer electrolyte fuel cells and methanol fuel cells, and as an electrode base material for batteries using gases such as oxygen and hydrogen as active materials.

Any of PAN-based, pitch-based, rayon-based carbon fibers, and the like can be used as carbon fibers constituting the carbon paper, but PAN-based carbon fibers are preferable because they are less likely to break during manufacture and use. Phenolic resin, furan resin, pitch, tar, and the like are examples of the organic matter that serves as a precursor of the carbide that binds the carbon fibers. Phenolic resins with high . are more preferred.

The fiber length of short carbon fibers constituting carbon paper is preferably 3 to 20 mm, more preferably 5 to 15 mm. By setting the fiber length of the short carbon fibers within the above range, it is possible to improve the dispersibility of the short carbon fibers during papermaking, and to suppress variations in basis weight.

The carbon paper may be water-repellent treated with a fluororesin such as polytetrafluoroethylene (PTFE). In addition, for winding carbon paper as a gas diffusion electrode base material provided on the surface with a mixture layer of carbon particles such as carbon black or graphite powder and a water-repellent resin such as PTFE (microporous layer of gas diffusion electrode base material) Also, the winding method of the present invention is effective. That is, in the present specification, the term "carbon paper" is used as a term including those provided with such additional elements.

The flexural modulus of carbon paper is preferably 2 to 50 GPa, more preferably 2 to 30 GPa, still more preferably 2 to 20 GPa. If the flexural modulus of the carbon paper is less than 2 GPa, for example, when it is used as a gas diffusion electrode base material for a fuel cell, the handling property is poor and it may fall into the grooves of the separator. If the flexural modulus of the carbon paper is greater than 50 GPa, when the carbon paper is wound around the core bobbin in a roll shape, the stiffness makes it difficult for the carbon paper to follow the core bobbin, reducing the ease of winding and causing winding misalignment. There is The flexural modulus of carbon paper can be determined according to the method specified in JIS K 6911 (1995). At this time, the width of the test piece is 15 mm, the length is 40 mm, and the distance between fulcrums is 15 mm. Also, the radius of curvature of the fulcrum and the indenter is 3 mm, and the loading speed is 2 mm/min. The flexural modulus is an index indicating the ease of winding into a roll and the quality of handling.

The static friction coefficient of the carbon paper is preferably 0.1 to 0.7, more preferably 0.2 to 0.6, still more preferably 0.2 to 0.5. If the static friction coefficient of the carbon paper is less than 0.1, the frictional force between the layers of the carbon paper in the wound body is small, so that the edges are likely to shift after winding. When the coefficient of static friction of the carbon paper is greater than 0.7, it is possible to obtain a roll of carbon paper with uniform winding end faces by conventional techniques. The static friction coefficient of carbon paper can be measured using a static friction coefficient measuring machine "Portable Friction Meter Muse Type: 94i" manufactured by Sintokagaku Co., Ltd., or the like. One sample cut to a diameter of 25 mm is attached to the weight on the bottom surface of the measuring device, the measuring device is placed on the other sample, and when measurement starts, a load is automatically applied to move the weight horizontally. The static friction coefficient μ is measured with the maximum static friction force F (N) as the load at the moment when the slide starts, and the vertical force G (N) as the weight of the weight. The coefficient of static friction μ can be obtained from the following formula. The number of measurements is 10, and the static friction coefficient is calculated from the 10 average values.

μ=F/G
The carbon paper preferably has a tensile strength of 1 to 10 kN/m, more preferably 2 to 10 kN/m. If it is less than 1 kN/m, the handleability tends to deteriorate. The tensile strength of the carbon paper is measured from the tension when a test piece of 15 mm×100 mm in size is pulled at a tensile speed of 2 mm/min and broken. At this time, sampling is performed so that the longitudinal direction of the long carbon paper is 100 mm. The number of measurements is 5, and the tensile strength is calculated from the average value of the 5 measurements.

A long carbon paper that is continuously conveyed is wound around a core bobbin to form a wound body. In order to prevent cracking of the wound carbon paper, the outer diameter of the core bobbin is preferably 76 mm or more, more preferably 152 mm or more. On the other hand, if the outer diameter of the core bobbin is too large, even if the long carbon paper is wound, the change rate of the winding diameter is small, so there is a tendency that it is difficult to obtain the effect of suppressing winding misalignment. Moreover, the whole wound body becomes large, and the problem that handling property falls also arises. Therefore, the outer diameter of the core bobbin is preferably 400 mm or less, more preferably 250 mm or less.

In the winding method of the present invention, the carbon paper is wound with a constant tension up to a predetermined point where the winding diameter increases by a certain amount or more compared to the time when winding is started. ”, and is defined by the amount of increase (mm) in the winding diameter compared to the start of winding. In the present invention, the carbon paper is wound with a constant tension until the winding diameter increases by 40 mm or more compared to the start of winding. In this case, the tension turning point is expressed as 40 mm or more. In the present invention, the tension turning point is 40 mm or more, more preferably 60 mm or more. If the portion to be wound with a constant tension is small, it is likely that winding deviation will occur near the tension turning point. If the range of the constant tension becomes large, the winding misalignment on the inner circumference becomes worse, so the length is preferably 450 mm or less.

In the present invention, the constant winding tension up to the tension turning point is set to 40 N/m or more, more preferably 200 N/m or more, in order to suppress winding deviation. In order to suppress breakage of highly brittle carbon paper, the tension is preferably 10 kN/m or less.

The change rate (A) of the winding diameter from the start of winding to the tension turning point is preferably 20% to 160%, more preferably 20% to 100%. If the tension is less than 20%, the effect of preventing winding slippage due to constant tension is insufficient, and if it exceeds 160%, winding slippage may increase as in the case of constant tension winding in a comparative example described later. The change rate (A) of the winding diameter from the start of winding to the tension turning point is calculated by the following formula.

A=(D2-D1)/D1×100
A: Change rate of winding diameter from the start of winding to the tension turning point
D1: Winding diameter at the start of winding
D2: Winding diameter at tension change point The winding diameter D1 at the start of winding is the outer diameter of the core bobbin to be wound, and is measured with a vernier caliper or ruler. The winding diameter after the start of winding is calculated by detecting the outermost peripheral surface position of the wound carbon paper with an infrared sensor. Alternatively, it is calculated from the previously measured thickness of the carbon paper to be wound, the number of rotations of the winding shaft, and D1.

Winding tension is measured with a tension meter set to a free roll.

In the present invention, after passing the tension turning point, the tension is reduced while winding, and the tension at the end of winding is 20 N/m or more. More preferably, the tension at the end of winding is 50 N/m or more. If the final winding tension is less than 20 N/m, the winding tends to collapse during packaging, transportation, and unwinding.

The change rate (B) of the winding diameter after the tension turning point has passed is preferably 10 to 250%, more preferably 100% to 220%. If the rate of change is less than 10%, there is a tendency that the effect of reducing the tension to suppress winding deviation cannot be sufficiently obtained, and if it exceeds 250%, winding deviation is likely to occur, as in the case where the tension is gradually reduced from the start of winding. tend to become The change rate (B) of the winding diameter after the tension turning point is calculated by the following formula.

B=(D3-D2)/D2×100
B: Rate of change in winding diameter after passing the tension turning point
D2: Winding diameter at tension turning point
D3: Winding diameter at the end of winding The change rate (C) of the winding torque after the tension turning point is preferably -100% to +160%, more preferably -90% to 50%. If the rate of change is less than -100%, the winding tends to collapse during packing, transportation, or unwinding, and the handling of the wound body tends to deteriorate. Moreover, when the rate of change exceeds +160%, the winding misalignment tends to worsen. The change rate (C) of the winding torque after the tension turning point is calculated by the following formula.

C=(T3×D3−T2×D2)/(T2×D2)×100
C: Rate of change in winding torque after passing the tension turning point
T2: Tension at tension turning point
T3: Tension at end of winding
D2: Winding diameter at tension turning point
D3: Winding diameter at the end of winding As shown in Fig. 1, the amount of winding misalignment t is obtained by measuring the total width W including the winding misalignment of the wound body and the width _WS of the carbon paper using a scale or vernier caliper, and calculating the following formula: can ask for more.

t= _WWS
t: winding misalignment amount (mm)
W: Full width including winding misalignment of the winding body (mm)
W _S : Width of carbon paper (mm)
In order to prevent winding misalignment due to deviation of the winding position in a direction parallel to the central axis direction of the winding shaft due to meandering of the carbon paper or the like, when winding the carbon paper by the method of the present invention, the following steps are taken. Thus, it is preferable to provide an edge position detection means 6 for detecting the edge position of the carbon paper before winding, and to control the winding misalignment according to the detection signal of the edge position detection means. Specifically, based on the detection signal of the end position detection means 6, the winding shaft 3, the nip roll 5, the free roll 7, etc. arranged on the downstream side of the end position detection means are set as the central axis of the winding shaft. It is preferable to move the winding device in a parallel direction, that is, in a left-right direction perpendicular to the traveling direction of the carbon paper so that the winding device follows the meandering of the carbon paper, thereby reducing winding misalignment.

FIG. 3 is a front view showing one embodiment of the carbon paper edge position detecting means. As shown in FIG. 3, it is preferable that the edge position detection means 6 be installed so as to detect the position of one or both ends of the carbon paper 1 in the traveling direction. It is preferable to use a non-contact type carbon paper end position detection means such as EPC (registered trademark: Nireco Corporation) as the position detection means for the end of the carbon paper. The sensor portion of the means for detecting the position of the ends of the carbon paper may be a photoelectric sensor using an infrared light emitting diode as a light source, an ultrasonic sensor, or a detection method using air pressure, but there is no particular limitation.

Needless to say, the carbon paper manufacturing method including the winding method described above is also understood as one aspect of the present invention.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples.

[Example 1]
Polyacrylonitrile-based carbon fiber “Torayca” (registered trademark) T300-6K (average single fiber diameter: 7 μm, number of single fibers: 6000) manufactured by Toray Industries, Inc. was cut into lengths of 12 mm, and water was continuously used as a papermaking medium. , further immersed in a 10% by weight aqueous solution of polyvinyl alcohol and dried to obtain a long carbon fiber paper product having a carbon fiber basis weight of about 37 g/m ² and wound into a roll. The adhered amount of polyvinyl alcohol is equivalent to 20 parts by weight with respect to 100 parts by weight of the carbon fiber paper.

A dispersion was prepared by mixing flake graphite (average particle size: 5 μm), phenolic resin, and methanol. The above carbon fiber paper product was continuously impregnated with the dispersion so that 110 parts by weight of the phenolic resin was added to 100 parts by weight of the carbon fiber paper, dried, and wound into a roll. As the phenolic resin, a resin obtained by mixing a resol-type phenolic resin and a novolac-type phenolic resin in a solid weight ratio of 1:1 was used.

Subsequently, the resin-impregnated carbon fiber papermaking body is set in a press molding machine so that the upper and lower plates are parallel to each other, and is intermittently transported at a platen temperature of 200 ° C. while repeating opening and closing of the press. The carbon paper before baking was subjected to heat and pressure treatment and wound into a roll.

The obtained carbon paper was baked by introducing it into a heating furnace maintained in a nitrogen gas atmosphere and having a maximum temperature of 2000° C., and the obtained carbon paper was wound into a roll. The obtained carbon paper had a thickness of 0.18 mm, a porosity of 80%, a flexural modulus of 10 GPa, a static friction coefficient of 0.3 and a tensile strength of 2.5 kN/m.

FIG. 2 shows how the carbon paper is wound. A winding shaft 3 for winding into a roll, a nip roll 5 for nipping the carbon paper 1 in front of the winding shaft 3, an edge position detection means 6 for the carbon paper provided upstream of the nip roll 5, and the position. Using a carbon paper winding device comprising a moving means for moving the winding shaft in a direction parallel to the center axis of the winding shaft according to a detection signal from the detection, and a control section for controlling the moving means , The carbon paper is wound on a core bobbin 4 with an outer diameter of 170 mm, and the carbon paper with a width of 300 mm and a length of 1600 m is wound with a winding tension T1 = 800 N / m at the start of unwinding to a winding diameter D2 = 240 mm. (Tension turning point = 70 mm), and then the tension was gradually decreased with a constant reduction amount per length, and the tension at the end of winding was T3 = 100 N/m. Stable winding was possible without causing problems such as large winding misalignment, breakage, and chipping. Table 1 shows the specifications and winding results. Also, FIG. 4 shows the transition of the winding tension.

[Example 2]
Winding was carried out in the same manner as in Example 1 except that T1 = 850 N/m and winding diameter D2 = 400 mm (tension turning point = 230 mm), and tension T3 at the end of winding was set to 600 N/m. Table 1 shows the specifications and winding results. Also, FIG. 4 shows the transition of the winding tension.

[Example 3]
A carbon paper with a length of 1100 m is wound at T1 = 780 N / m until the winding diameter D2 = 220 mm (tension turning point = 50 mm), and the tension T3 at the end of winding is set to 250 N / m. Winded in the same way as 1. Table 1 shows the specifications and winding results. Also, FIG. 4 shows the transition of the winding tension.

[Example 4]
Winding was carried out in the same manner as in Example 1 except that T1 = 751 N/m and winding diameter D2 = 244 mm (tension turning point = 74 mm), and tension T3 at the end of winding was set to 578 N/m. Table 1 shows the specifications and winding results. Also, FIG. 4 shows the transition of the winding tension.

[Comparative Example 1]
A carbon paper having a length of 1000 m was wound up in the same manner as in Example 1 except that T1 was 430 N/m and the tension was kept constant until the end of winding. When winding 1000m, the winding deviation became large. Table 1 shows the specifications and winding results. Also, FIG. 4 shows the transition of the winding tension.

[Comparative Example 2]
A carbon paper with a length of 1000 m is wound up until the winding diameter D2 = 200 mm at T1 = 30 N / m (tension turning point = 30 mm), and the tension at the end of winding T3 = 20 N / m Example except that Winded in the same way as 1. When winding 600m, winding deviation became large. Table 1 shows the specifications and winding results. Also, FIG. 4 shows the transition of the winding tension.

[Example 5]
In the same manner as in Example 1 except that the basis weight of the carbon fiber was 30.5 g / m Got carbon paper. The carbon paper with a length of 1800 m was wound up until the winding diameter D2 = 222 mm at T1 = 499 N / m (tension turning point = 52 mm), and the tension T3 at the end of winding was set to 333 N / m. It was wound up as in Example 1. Table 1 shows the specifications and winding results. Also, FIG. 4 shows the transition of the winding tension.

[Example 6]
Winding was carried out in the same manner as in Example 5 except that T1 = 521 N/m and winding diameter D2 = 232 mm (tension turning point = 62 mm), and tension T3 at the end of winding was set to 155 N/m. Table 1 shows the specifications and winding results. Also, FIG. 4 shows the transition of the winding tension.

[Comparative Example 3]
Winding was performed in the same manner as in Example 5, except that T1 was 400 N/m and the tension was kept constant until the end of winding. At a winding length of 1,300 m, winding deviation became large and winding was stopped. Table 1 shows the specifications and winding results. Also, FIG. 4 shows the transition of the winding tension.

[Example 7]
After the carbon paper described in Example 5 was heat-treated at 2000°C, the carbon paper wound into a roll was unwound, immersed in a PTFE aqueous dispersion, pulled out, and dried in a tunnel dryer set at 110°C. The PTFE adhesion rate of the carbon paper was set to 2 wt%. Subsequently, after applying a microporous layer coating liquid containing PTFE and carbon black using a die coater, it is passed through a dryer at 110 ° C to dry the moisture, and further passed through a sintering furnace set at 350 ° C and baked. After knotting and slitting at both ends, a long sheet of paper with a thickness of 0.05 mm was piled up to prevent transfer of the microporous layer to the carbon paper, and was wound up with a winder. The resulting carbon paper having a microporous layer on one side had a thickness of 0.18 mm, a flexural modulus of 5 GPa, a static friction coefficient of 0.5 and a tensile strength of 5 kN/m. The carbon paper with a width of 280 mm and a length of 1600 m, which is provided with the above microporous layer on one side, is wound at T1 = 350 N / m until the winding diameter D2 = 350 mm (tension turning point = 180 mm), and then tension is applied. The film was wound while reducing the tension, and the tension at the end of winding was set to T3=130 N/m. Table 1 shows the specifications and winding results. Also, FIG. 4 shows the transition of the winding tension.

[Example 8]
The carbon paper with a length of 1,100 m was wound up at T1 = 514 N / m until the winding diameter D2 = 429 mm (tension turning point = 259 mm), and the tension at the end of winding was T3 = 201 N / m. It was wound up in the same manner as 7. Table 1 shows the specifications and winding results. Also, FIG. 4 shows the transition of the winding tension.

[Comparative Example 4]
Winding was performed in the same manner as in Example 8, except that T1 was 514 N/m and the tension was kept constant until the end of winding. Winding length 1100m Winding was stopped. Table 1 shows the specifications and winding results. Also, FIG. 4 shows the transition of the winding tension.

1: Carbon paper 2: Carbon paper roll 3: Winding shaft 4: Core bobbin 5: Nip roll 6: Carbon paper end position detection means 7: Free roll
W: Full width including winding misalignment of the carbon paper roll
W _S : Width of carbon paper

Claims (9)

A carbon paper winding method for winding a continuously conveyed long carbon paper around a core bobbin, comprising:
Winding with a constant tension of 40 N/m or more until a predetermined tension turning point where the winding diameter increases by 40 mm or more compared to the start of winding, winding while decreasing the tension after the tension turning point, and at the end of winding A method of winding carbon paper with a tension of 20 N/m or more. The carbon paper winding method according to claim 1, wherein a rate of change in the winding diameter of the carbon paper from the start of winding to the tension turning point is 20 to 160%. 3. The method of winding carbon paper according to claim 1, wherein the rate of change of the winding diameter of the carbon paper after the tension turning point has passed is 10 to 250%. The carbon paper winding method according to any one of claims 1 to 3, wherein the rate of change in winding torque after the tension turning point has passed is -100 to +160%. The carbon paper winding method according to any one of claims 1 to 4, wherein the winding diameter at the end of winding is 500 mm or more. The carbon paper winding method according to any one of claims 1 to 5, wherein the core bobbin has an outer diameter of 76 mm or more. The carbon according to any one of claims 1 to 6, which is used for winding carbon paper having a flexural modulus of 2 to 50 GPa, a static friction coefficient of 0.1 to 0.7, and a tensile strength of 1 to 10 kN/m. Paper winding method. 8. The carbon paper according to any one of claims 1 to 7, wherein edge position detection means for detecting the edge position of the carbon paper is provided before winding, and a detection signal from the edge position detection means is controlled to prevent winding misalignment. A winding method for the described carbon paper. A method for producing a carbon paper roll, comprising the carbon paper winding method according to any one of claims 1 to 8.

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