JP2018040099A - Method for producing carbon fiber sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon fiber sheet with less through holes continuously.SOLUTION: The method for producing a carbon fiber sheet includes continuously travelling and heat treating a carbon fiber sheet precursor comprising at least a carbon fiber or an organic fiber capable of being turned into a carbon fiber inside a high-temperature furnace at a maximum temperature of 1500-3000°C and winding up a carbon fiber sheet. The method for producing a carbon fiber sheet is characterized by including cleaning at least one side of the carbon fiber sheet after it is passed through the high-temperature furnace.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for producing a carbon fiber sheet. The carbon fiber sheet of the present invention is preferably used as a heat-insulating material for gas diffusers of solid polymer fuel cells (PEFC), methanol fuel cells (DMFC) and phosphoric acid fuel cells (PAFC), and high-temperature equipment in an inert atmosphere. Can be used.

  A polymer electrolyte fuel cell generates electricity by supplying hydrogen and oxygen. As the material of the gas diffuser constituting the membrane-electrode assembly in which a power generation reaction occurs in a fuel cell, carbon paper in which carbon fibers are bound with resin carbide, carbon fiber nonwoven fabric or carbon fiber woven fabric in which carbon fibers are entangled are included. Generally used. Here, if a through hole having a major axis of 0.5 mm or more exists in carbon paper or carbon fiber nonwoven fabric, when it is incorporated into a polymer electrolyte fuel cell, oxygen and hydrogen permeation and discharge of water generated by the reaction are in-plane. It becomes non-uniform and causes the power generation performance of the fuel cell to deteriorate. Therefore, in order to avoid using the location where a through-hole exists as a porous carbon electrode base material for fuel cells, if a manufactured carbon fiber sheet has a large number of through-holes, the yield decreases.

  For such a problem, in Patent Document 1, the silicon content of the resin cured sheet is reduced to suppress the adhesion and dropping of the silicon compound adhering to the firing furnace wall, or the width of the resin cured sheet relative to the firing furnace width is reduced. By reducing the concentration to 90% or less, the concentration of impurities staying in the furnace is reduced and concentration is prevented, or a cover sheet made of a carbon material is placed above the sheet running path in the firing furnace, and the lower part is cured with resin The sheet travels continuously, and the resin cured sheet is covered with a cover sheet, so that the adhesion of silicon compounds can be prevented, the formation of through-holes can be suppressed, and the exhaust of the firing furnace should be the lower exhaust. Thus, there is described a method for preventing a through-hole from being formed by solids and organic substances adhering to the exhaust gas duct and falling on the cured resin sheet. Moreover, in patent document 2, the carbon fiber sheet precursor is covered with a heat-resistant sheet and fired to prevent accumulation of pyrolyzed carbides on the hearth and breakage of the carbon fiber sheet. In Patent Documents 3 and 4, the exhaust port of the firing furnace is provided on the lower surface and the side surface, so that precipitates around the exhaust port are prevented from dropping on the porous carbon fiber sheet, and appearance defects such as through holes are improved. It has been shown. Furthermore, Patent Documents 5 and 6 disclose a method of folding carbon fibers whose ends are not bound on the surface of the carbon fiber sheet, and a method of removing short carbon fibers that are detached from the resin carbide. .

JP2011-65926A JP 2009-191406 A JP 2010-196200 A JP 2010-196201 A JP 2008-34295 A JP 2010-70433 A

  However, in the method described in Patent Document 1, the silicon compound particles adhere to the porous carbon electrode substrate due to the removal of the silicon compound from the furnace wall or the silicon compound attached to the cover sheet. Has problems such as contact with the roll and opening of a through-hole when winding.

  Moreover, in patent document 2, the adhesion to the carbon fiber sheet of the granular carbide | carbonized_material dropped on the hearth, the fall of the carbide | carbonized_material from the furnace ceiling and the furnace wall in the location which cannot be covered with a heat-resistant sheet, and the adhesion to a carbon fiber sheet are the same. There is a problem that a through hole is opened.

  In the inventions described in Patent Documents 3 and 4, there is a problem that it is impossible to prevent the deposits accumulated on the furnace ceiling and the wall of the furnace away from the exhaust port.

  Further, in the inventions described in Patent Documents 5 and 6, in the method in which the carbon fiber sheet precursor is heat-treated inside the high-temperature furnace and once wound up and cleaned, the particles generated inside the high-temperature furnace are on or on the carbon fiber sheet. When the take-up device on the downstream side of the high-temperature furnace is continuously fed while being attached underneath, the particles are sandwiched between the roll and the carbon fiber sheet, or when the particles are taken up by the core bobbin, the carbon fiber sheet Between the two layers, causing a through hole in the carbon fiber sheet.

  Therefore, it has been difficult to provide a carbon fiber sheet that is long and has few through holes.

  Therefore, the present invention has been made in view of the above-described problems in the prior art, and when a carbon fiber sheet precursor is fired to obtain a carbon fiber sheet, the carbon fiber sheet to which particles are attached in a firing furnace. It is an object of the present invention to provide a long carbon fiber sheet with few through-holes by winding the wire outside the furnace or pressing it on a roll.

  In order to solve the above-mentioned problems, the present invention is a heat treatment by continuously running a carbon fiber sheet precursor made of at least carbon fiber or carbon fiber- convertible organic fiber in a high-temperature furnace having a maximum temperature of 1500 to 3000 ° C. A method for producing a carbon fiber sheet that winds up the carbon fiber sheet, wherein the carbon fiber sheet is wound after cleaning at least one side of the carbon fiber sheet after passing through the high-temperature furnace. It is a manufacturing method of a sheet.

  According to the present invention, it is possible to provide a high-quality long carbon fiber sheet with few through holes.

It is the schematic which shows the example of the heat processing method of the carbon fiber sheet precursor in this invention. It is a side view which shows the example of the method of cleaning the carbon fiber sheet in this invention with a suction device and a spraying apparatus. It is a side view which shows the example of the method of cleaning the carbon fiber sheet in this invention with a suction device and a brush. It is a side view which shows the example of the positional relationship with the roll which contacts the cleaning location of the carbon fiber sheet in this invention. It is a front view which shows the example of the method of cleaning the carbon fiber sheet in this invention with a suction device and a spraying apparatus. It is a front view which shows the example of the method of cleaning the carbon fiber sheet in this invention with a suction device and a brush.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments of the invention will be described with reference to the drawings.
<Description of the device>
FIG. 1 is a schematic view showing a heat treatment method of a carbon fiber sheet precursor.

  The apparatus shown in FIG. 1 continuously runs inside the high-temperature furnace having a maximum temperature of 1500 to 3000 ° C. and heat-treats the carbon fiber sheet precursor 50 so that the inside of the high-temperature furnace 100 is continuously run. The carbon fiber sheet precursor 50 is heat-treated to make the carbon fiber sheet precursor 50 a carbon fiber sheet 10.

  The high temperature furnace 100 is provided with a furnace space 101 through which the carbon fiber sheet precursor 50 can pass. The furnace space 101 has two openings, one being an inlet (hereinafter referred to as the furnace inlet) 105 of the high temperature furnace and the other being an outlet (hereinafter referred to as the furnace outlet) 106 of the high temperature furnace. The carbon fiber sheet precursor 50 is inserted from the furnace inlet 105 and continuously moves in the furnace space 101 maintained at a high temperature toward the furnace outlet 106 so as to slide on the hearth 104. At that time, a heat-resistant sheet 110 is inserted on the furnace inlet 105 side so as to cover the upper surface of the carbon fiber sheet precursor 50.

  First, the high temperature furnace 100 will be described.

  The high-temperature furnace 100 used in the present invention can continuously run the carbon fiber sheet precursor 50 in the high-temperature furnace 100, and can heat-treat the carbon fiber sheet precursor 50 at a maximum temperature of 1500 ° C to 3000 ° C. .

  In particular, a high temperature furnace that can convey the carbon fiber sheet precursor in the horizontal direction inside the high temperature furnace, that is, a horizontal furnace shown in FIG. 1, is preferable from the viewpoint of handling the base material during heat treatment and preventing breakage.

  In order to maintain suitable electrical conductivity of the carbon fiber sheet 10, the maximum temperature (heat treatment temperature) of the high-temperature furnace is required to be 1500 ° C. or higher. When the maximum temperature (heat treatment temperature) of the high-temperature furnace is lower than 1500 ° C., the degree of graphitization of the carbon fiber sheet 10 is lowered, and the electrical conductivity and thermal conductivity are lowered. If the carbon fiber sheet 10 having low electrical conductivity or thermal conductivity is used as an electrode of a fuel cell, the performance as a battery is reduced. If the maximum temperature (heat treatment temperature) of the high-temperature furnace is higher than 3000 ° C., enormous energy is required for heating and the carbon members used in the furnace are significantly consumed, so the maximum temperature of the high-temperature furnace (heat treatment temperature) It is important that the temperature is 3000 ° C. or lower. The maximum temperature of the high temperature furnace is more preferably 1800 to 2800 ° C., and 1900 to 2600 ° C. is more preferable in order to maintain suitable electrical conductivity and thermal conductivity and to reduce the running cost of the apparatus.

  In order to prevent oxidation of the carbon fiber sheet 10 and the high temperature furnace 100 itself, it is preferable to keep the inside of the high temperature furnace 100 in an inert gas atmosphere such as nitrogen or argon. Carbon, graphite, metal, and ceramics can be used as the material constituting the high temperature furnace 100, but carbon, graphite, and metal are preferable because they are inexpensive, and the portion at 1000 ° C or higher is carbon due to chemical stability. Or graphite is more preferable.

  The high-temperature furnace 100 is a single furnace, and the carbon fiber sheet precursor 50 may be heat-treated at a maximum temperature of 1500 ° C. to 3000 ° C. to form the carbon fiber sheet 10, but in combination with a low-temperature furnace having a maximum temperature of 600 to 1000 ° C., The carbon fiber sheet precursor 50 may be heat treated by passing it through a low temperature furnace, and then heat treated in the high temperature furnace 100 to obtain the carbon fiber sheet 10. A method using both the low-temperature furnace and the high-temperature furnace 100 is preferable because it can prevent the cracked gas in the low-temperature furnace, in which the weight loss due to the heat treatment of the carbon fiber sheet precursor 50 is large, from flowing into the high-temperature part and solidifying and precipitated.

Next, the heat resistant sheet 110 will be described.

  The heat-resistant sheet 110 only needs to be a material that does not decompose in an inert gas atmosphere in the high-temperature furnace 100 in the range of 1500 to 3000 ° C., and has a porous structure with high durability and heat resistance inside the high-temperature furnace. It is preferable that it is a sheet | seat provided with. As the heat-resistant sheet 110, a nonwoven fabric or a woven fabric made of carbon fiber is preferably used.

  Non-woven fabric made of carbon fiber is made from non-woven fabric of PAN flame-resistant yarn obtained by heating polyacrylonitrile (PAN) fiber that can be made into carbon fiber in air at 200 to 300 ° C, and carbonized by heat treatment. Is obtained. As a woven fabric made of carbon fiber, a woven fabric obtained by carbonizing long woven fabric of PAN flame resistant yarn, a woven fabric obtained by carbonizing long woven fabric of PAN flame resistant yarn, and a spun yarn of PAN flame resistant yarn as a woven fabric, A woven fabric obtained by carbonization by heat treatment can be used.

  From the viewpoint of durability and handling properties, the heat-resistant sheet 110 is preferably a carbon fiber woven fabric, and more preferably a carbon fiber woven fabric obtained by carbonizing a spun yarn woven fabric of PAN flame resistant yarn from the viewpoint of wear resistance.

  In order to prevent falling of foreign particles such as precipitated particles (hereinafter abbreviated as precipitated particles) from the pyrolysis gas onto the carbon fiber sheet 10, the carbon fiber sheet precursor 50 and the muffle on the high temperature furnace 100 are configured. It is preferable to dispose a heat resistant sheet 110 wider than the carbon fiber sheet precursor 50 between the wall 102. Here, the width of the heat resistant sheet 110 is not particularly limited as long as it is wider than the width of the carbon fiber sheet precursor, but is preferably in the range of 1.0 to 1.5 times the width of the carbon fiber sheet precursor 50. If the width of the heat-resistant sheet 110 is larger than 1.5 times the width of the carbon fiber sheet 10, it is necessary to widen the width of the high-temperature furnace 100 by the width of the heat-resistant sheet 110. Since it leads to increase, it is not preferable. If the width of the heat-resistant sheet 110 is smaller than 1.0 times, the precipitated particles fall on the carbon fiber sheet precursor 50 not covered with the heat-resistant sheet 110, and the carbon fiber sheet 10 comes into contact with the roll, A through hole opens when removing. The width of the heat resistant sheet 110 is more preferably in the range of 1.1 to 1.3 times that of the carbon fiber sheet 10.

The basis weight of the heat resistant sheet 110 is preferably 50 to 800 g / m ² . When the basis weight is less than 50 g / m ^2, the strength of the heat-resistant sheet 110 is weak, and the heat-resistant sheet 110 is cut off when used for a long period of time. When the weight per unit area exceeds 800 g / m ² , when the heat-resistant sheet 110 is in contact with the carbon fiber sheet precursor 50, friction force is applied to the carbon fiber sheet precursor 50 due to its own weight, and the carbon fiber sheet precursor 50. This is not preferable because breaks and chips are likely to occur. The basis weight of the heat resistant sheet 110 is more preferably 200 to 600 g / m ² .

  The heat resistant sheet 110 is preferably made of a porous material so that the decomposition gas generated by the heat treatment of the carbon fiber sheet precursor 50 can be easily removed. In order to maintain suitable gas permeability, the heat-resistant sheet 110 preferably has a porosity of 50 to 90%, more preferably 60 to 80%. When the porosity exceeds 90%, the strength of the heat-resistant sheet 110 becomes too low and the durability becomes low.

2 and 3 are side views showing a carbon fiber sheet cleaning method in a winding device arranged on the downstream side of the high-temperature furnace.

  In FIG. 1, the carbon fiber sheet 10 that has been heat-treated in the high-temperature furnace 100 is continuously fed while being in contact with a plurality of rolls 300 in the middle, and is finally wound around the core bobbin 40. At this time, when the deposited particles and the like are fed to the surface of the carbon fiber sheet 10, carbon is deposited by the precipitated particles and the like at a position where the roll 300 and the wound body 20 of the carbon fiber sheet are in contact (marked X in the figure). There is a possibility that a through hole may be formed in the fiber sheet 10 or the roll 300 may be damaged. In particular, a carbon fiber sheet precursor formed by binding carbon fiber or carbon fiberable fiber with a carbonizable organic material is heat-treated, and a carbon fiber sheet obtained by binding carbon fiber with carbon or a nonwoven fabric in which carbon fibers are entangled. A certain carbon fiber sheet tends to generate a through hole. The carbon fiber sheet, which is a carbon fiber fabric, has a problem that foreign particles are pushed into the carbon fiber sheet, although the holes are relatively difficult to open. Therefore, a cleaning device such as a suction device 210 or a spraying device 220 for removing precipitated particles or the like is provided on the downstream side of the furnace outlet 106 of the high temperature furnace 100.

  First, the suction device 210 will be described.

  By providing a suction device on the downstream side of the high-temperature furnace, cleaning can be performed by a method of sucking at least one surface of the carbon fiber sheet after passing through the high-temperature furnace. By connecting a dust collector 211 to the suction device 210, it is possible to remove and collect the deposited particles and the like. From the viewpoint of destruction of the carbon fiber sheet 10 itself and prevention of redeposition of the deposited particles and the like removed from the carbon fiber sheet 10, the flow rate of the gas sucked from the carbon fiber sheet 10 depends on the suction capacity of the particles and the running of the substrate. From the viewpoint of stability, it is preferably 2 to 6 L / min / mm per suction width, more preferably 3 to 5 L / min / mm, still more preferably 4 to 5 L / min / mm with respect to the one-side surface. Further, as shown in FIGS. 5 and 6, the suction device 210 is preferably wider than the width Ws of the carbon fiber sheet 10 because the entire width of the carbon fiber sheet 10 can be reliably cleaned.

  Next, the spraying device 220 will be described.

  By providing a spraying device on the downstream side of the high temperature furnace, after passing through the high temperature furnace, cleaning can be performed by a method of spraying a gas on at least one surface of the carbon fiber sheet. As the gas to be blown, oxygen, nitrogen, air, or the like can be used, but it is preferable to blow air from the viewpoint of cost. By spraying the gas, the precipitated particles and the like can be removed without destroying the carbon fiber sheet 10 itself or destroying the surface of the carbon fiber sheet 10. The flow rate of the gas blown to the carbon fiber sheet 10 is 0 per spray width with respect to the surface on one side, from the effects of preventing the destruction of the carbon fiber sheet 10 and running stability, and removing the deposited particles adhering to the carbon fiber sheet 10. 0.1-3 L / min / mm is preferred, 0.3-1.5 L / min / mm is more preferred, and 0.5-1 L / min / mm is even more preferred.

  The angle of spraying is preferably 5 to 80 ° with respect to the running surface when the direction facing the traveling direction of the carbon fiber sheet 10 is 0 ° in order to blow off the deposited particles and the like on the carbon fiber sheet 10. 20-70 degrees is more preferable. Moreover, the method of using together with the suction device 210 is preferable so that the deposited particle etc. which were blown off may not adhere again. Further, as shown in FIG. 5, the width of the spraying device 220 is preferably wider than the width Ws of the carbon fiber sheet 10 because the entire width of the carbon fiber sheet 10 can be cleaned.

  The ratio of the suction flow rate to the spray flow rate is preferably 3-15, more preferably 4-10, and even more preferably 5-8. By increasing the suction flow rate more than the spray flow rate, the blown-off precipitated particles can be reliably sucked. Moreover, the carbon fiber sheet 10 is attracted and damaged by not making the ratio too high, and the running of the carbon fiber sheet 10 is prevented from becoming unstable.

  Next, the brush 230 will be described.

  By providing a brush on the downstream side of the high temperature furnace, after passing through the high temperature furnace, at least one surface of the carbon fiber sheet can be cleaned by a method of sweeping with the brush. The brush 230 is preferably made of a material equivalent to or softer than the carbon material constituting the carbon fiber sheet 10 so as not to destroy the carbon fiber sheet 10 itself or the surface of the carbon fiber sheet 10. For example, animal hair or synthetic fiber brush is suitable. Further, as shown in FIG. 6, the brush 230 is preferably wider than the width Ws of the carbon fiber sheet 10 because the entire width of the carbon fiber sheet 10 can be cleaned.

Next, the roll 300 will be described.

  A plurality of rolls are preferably disposed on the downstream side of the high-temperature furnace 100 in order to balance the tension in the width direction of the carbon fiber sheet 10 and stabilize traveling. By arranging a plurality of rolls, it is possible to suppress tension from being concentrated on one side in the width direction, and the carbon fiber sheet 10 can be continuously wound without breaking during traveling.

  As shown in FIG. 4, the plurality of rolls include rolls 301 and 302 that are in contact with one surface 11 of the carbon fiber sheet 10 and a roll 303 that is in contact with the other surface 12. It is preferable that a suction device 210 and a spraying device 220 for removing the precipitated particles and the like are provided before contacting the roll 303 that contacts the first time. In addition, arrangement | positioning of a some roll is not limited to the structure of FIG. 4, According to the physical property of the carbon fiber sheet 10, it can set suitably.

  Next, as a method of winding the carbon fiber sheet 10 in a roll shape, the carbon fiber sheet 10 can be continuously wound around the core bobbin 40 disposed on the winding shaft 30. The outer diameter of the core bobbin is preferably 76 to 330 mm in diameter, and more preferably 152 to 330 mm. When the outer diameter of the core bobbin is smaller than 76 mm in diameter, the core bobbin is easily broken particularly when the thickness of the carbon fiber sheet is 0.2 mm or more. When the outer diameter of the core bobbin is larger than 330 mm, the outer diameter of the carbon fiber sheet winding body is increased, leading to an increase in cost during storage and transportation, which is not preferable.

  The core bobbin 40 can be made of any commonly used material such as paper, resin, or metal, but is preferably made of paper or resin in terms of weight and cost.

<Description of manufacturing method>
An example of a method for producing a carbon fiber sheet according to the present invention is a carbon fiber sheet precursor formed by binding carbon fiber or carbon fiber- convertible organic fiber with a carbonizable organic substance, having a maximum temperature of 1500 to 3000 ° C. The inside of the high-temperature furnace is continuously run and heat-treated, and the carbon fiber is wound as a carbon fiber sheet bound with an organic carbide, and at least one side of the carbon fiber sheet is cleaned after passing through the high-temperature furnace. Later, the carbon fiber sheet is wound up.

  The manufacturing method of the carbon fiber sheet precursor 50 heat-processed in this example is demonstrated.

  The carbon fiber sheet precursor 50 is composed of at least carbon fiber or organic fiber that can be carbonized. A more preferable carbon fiber sheet precursor 50 is configured by binding carbon fibers or organic fibers that can be carbonized with an organic material that can be carbonized.

  As the carbon fiber, any of polyacrylonitrile (PAN) -based carbon fiber, pitch-based carbon fiber, rayon-based carbon fiber, and phenol-based carbon fiber can be used. Among these, it is preferable to use a PAN-based carbon fiber or a pitch-based carbon fiber that can increase the bending strength and tensile strength of the obtained carbon fiber sheet 10, and it is more preferable to use a PAN-based carbon fiber.

  As the carbonizable organic substance, a thermoplastic resin such as polyvinyl alcohol, a thermosetting resin such as a phenol resin, or the like can be used for the purpose of binding the carbon fibers contained in the carbon fiber sheet precursor 50.

  When the carbon fiber sheet precursor 50 is obtained by impregnating a resin into a sheet made of short carbon fibers or carbon fibers capable of being carbonized, and then curing the resin, the length of the short fibers is 3 It is preferable to be within a range of ˜12 mm. It is more preferable that the length of the short fiber is in the range of 6 to 9 mm, because a good dispersibility can be obtained during papermaking of the short fiber, and a carbon fiber sheet having high tensile strength and not easily torn can be obtained. .

  In the paper making process, short fibers of carbon short fibers cut to a suitable length or carbon fibers capable of carbonization are uniformly dispersed in water, and the dispersed short fibers are made on a net and made into a paper. Is immersed in an aqueous dispersion of polyvinyl alcohol, and the immersed sheet is pulled up and dried. Polyvinyl alcohol serves as a binder that binds short fibers to each other, and in a state where the short fibers are dispersed, a sheet of short fibers in a state where they are bound by the binder is manufactured. In addition, styrene-butadiene rubber, epoxy resin, or the like can be used as the binder.

  In the resin impregnation step, the carbon fiber sheet precursor 50 is manufactured by immersing the short fiber sheet manufactured in the paper making step in a solution of the thermosetting resin, and lifting and drying the immersed sheet.

  When a resin is used as the carbonizable organic substance contained in the carbon fiber sheet precursor 50, examples of such resins include thermosetting resins such as epoxy resins, unsaturated polyester resins, phenol resins, polyimide resins, and melamine resins. A thermoplastic resin such as an acrylic resin, a polyvinylidene chloride resin, or a polytetrafluoroethylene resin can be used, but a thermosetting resin having a high carbonization yield is preferably used, and a phenol resin is more preferably used. .

  The carbon fiber sheet precursor 50 may contain carbon powder, metal powder, inorganic powder, metal fiber, inorganic fiber, or the like depending on the performance required for the carbon fiber sheet 10 in addition to carbon fiber and organic matter. . When used as a fuel cell electrode substrate, it is preferable to include carbon powder in order to improve conductivity and reduce impurities. The ratio in the case of using carbon powder is preferably 1 to 50% by mass of the carbon fiber sheet in order to improve conductivity.

  Other examples of the method for producing the carbon fiber sheet precursor 50 include a method in which a PAN flame resistant yarn is made into a non-woven fabric in a dry process and calendered with a heating roll, but is not limited thereto.

Next, the manufacturing method of the carbon fiber sheet 10 in this invention is demonstrated.

  In the method for producing the carbon fiber sheet 10 of the present invention, the carbon fiber sheet precursor 50 described above is heat-treated in the high temperature furnace 100 described above, and the organic matter constituting the carbon fiber sheet precursor 50 is carbonized to carbonize the carbon fiber sheet 10. Is to be manufactured.

  The running method of the carbon fiber sheet precursor 50 is a furnace provided on the muffle lower wall 103 in which the carbon fiber sheet precursor 50 is introduced into the high temperature furnace 100 from the furnace inlet 105 of the high temperature furnace 100. A method in which the carbon fiber sheet 10 fed from the furnace outlet 106 is wound in a roll shape outside the furnace after being conveyed and heat-treated while dragging on the floor 104 horizontally is preferable. When this method is used, the carbon fiber sheet precursor 50 can be easily transported and traveled, which is preferable as a method for producing a long carbon fiber sheet 10.

  The carbon fiber sheet precursor 50 can be transported and heat-treated even if it is a single sheet or a plurality of sheets, but it is preferable to transport the sheets by stacking a plurality of sheets because the production efficiency of the carbon fiber sheet 10 can be increased. The number of sheets to be stacked is preferably 2 to 6 and more preferably 2 to 4 in order to perform uniform heat treatment. As described below, when a plurality of sheets are conveyed and heat treated, the precipitated particles and the like often adhere to the top surface of the plurality of stacked carbon fiber sheets 10, so at least the top sheet of the stacked carbon fiber sheets It is preferable to clean the upper surface. When transported while being dragged horizontally on the hearth, the deposited particles are likely to adhere to the lowermost surface of the stacked carbon fiber sheets, so the upper surface of the uppermost sheet of the stacked carbon fiber sheets and It is more preferable to clean the lower surface of the lowermost sheet. It is more preferable to clean both surfaces of all the sheets conveyed in a stacked manner because the deposited particles and the like adhering between the carbon fiber sheets can be removed when a plurality of sheets are conveyed and heat-treated.

  The high-temperature furnace 100 is an open type furnace having openings at the furnace inlet 105 and the furnace outlet 106 that can continuously run inside the high-temperature furnace 100 as described above. Temperature distribution can be achieved from the inlet 105 and the furnace outlet 106 to the maximum temperature region. Although the generation | occurrence | production location of precipitation particle | grains changes with structures and temperature distribution of the high temperature furnace 100, it is easy to generate | occur | produce in a 800-2500 degreeC temperature range. In particular, the organic pyrolysis gas generated in a higher temperature region becomes solid in the process of being cooled according to the temperature distribution in the furnace, and tends to accumulate in the form of icicles on the upper wall of the muffle.

  Therefore, in the case of the high-temperature furnace 100 that is heat-treated in the range of 1500 to 3000 ° C., as shown in FIG. 1, the heat-resistant sheet 110 is moved to a position corresponding to the range from the furnace inlet 105 of the high-temperature furnace 100 until the temperature reaches 2500 ° C. If it arrange | positions, it can prevent that the precipitation particle | grains etc. which generate | occur | produce from organic substance fall to a carbon fiber sheet. That is, in the present invention, it is preferable to heat-treat the carbon fiber sheet precursor while disposing a heat-resistant sheet wider than the carbon fiber sheet precursor on the upper side of the carbon sheet precursor in the high temperature furnace. Here, the heat-resistant sheet is not particularly limited as long as it is a material that does not decompose in the range of 1500 to 3000 ° C. in an inert gas atmosphere in the high-temperature furnace 100 as described above.

  However, since the carbon constituting the heat-resistant sheet 110 is depleted by reaction with oxygen, hydrogen, and nitrogen, which is an atmospheric gas, contained in the thermal decomposition product of the carbon fiber sheet precursor, the temperature is increased from the furnace inlet 105 of the high-temperature furnace 100. In some cases, the heat-resistant sheet 110 cannot be arranged in the entire range up to 2500 ° C. Therefore, it is preferable that the heat-resistant sheet 110 is inserted from the inlet side (referred to as the furnace inlet) of the high-temperature furnace, and 30 to 90% of the distance from the furnace inlet 105 to the furnace outlet 106 is covered with the heat-resistant sheet. Even when a guide member such as a bending member disclosed in Japanese Patent Laid-Open No. 2007-2394 is provided in the furnace, disposing the heat-resistant sheet 110 over the entire length of the furnace deteriorates workability. It is preferable that 30 to 90% of the distance from the furnace inlet to the furnace outlet is covered with a heat-resistant sheet while being inserted from the side called the inlet. Precipitate particles etc. are likely to adhere to the carbon fiber sheet during the heat treatment in the part not covered with the heat-resistant sheet, and the precipitate particles adhering to the guide member such as the bending member also easily fall off into the shape of the carbon fiber sheet during the heat treatment. The effect of the cleaning application of the invention is great.

  The heat-resistant sheet 110 does not need to run together with the carbon fiber sheet precursor 50, and may be fixed to the furnace inlet 105 and the furnace outlet 106 outside the high temperature furnace 100. The fixing method is not particularly limited, and it is sufficient that the heat resistant sheet 110 does not move greatly during the heat treatment of the carbon fiber sheet precursor 50. After the heat treatment of the carbon fiber sheet precursor 50 is finished, if the heat-resistant sheet 110 can be easily taken out from the high-temperature furnace 100, the deposits attached to the heat-resistant sheet 110 can be cleaned.

  The heat-resistant sheet 110 is more preferably disposed so as to be in contact with the carbon fiber sheet precursor 50. That is, it is more preferable to perform the heat treatment by dragging the carbon fiber sheet precursor 50 while bringing the heat resistant sheet into contact with the carbon sheet precursor. A plurality of heat-resistant sheets 110 may be used in a stacked manner.

  On the carbon fiber sheet 10 sent out from the furnace outlet 106, there are cases where deposited particles and the like generated in a portion that cannot be covered with the heat-resistant sheet 110 are attached. 10 and the carbon fiber sheet winding body 20 and the position where it contacts the roll 300 (X in the figure), the carbon fiber sheet 10 is made through-holes by the precipitated particles or the roll 300 is damaged. There is a risk of getting on.

  Since the precipitated particles and the like mainly accumulate on the muffle upper wall 102, the precipitated particles and the like often adhere to the upper surface of the carbon fiber sheet 10. For this reason, when cleaning at least one surface of the carbon fiber sheet after passing through the high temperature furnace, it is preferable to clean at least the upper surface of the sheet when transporting the inside of the high temperature furnace in the horizontal direction. More specifically, when transporting the carbon fiber sheet in the horizontal direction inside the high temperature furnace, it is preferable to clean at least the upper surface of the sheet when transporting the interior of the high temperature furnace in the horizontal direction. More preferably, since the deposited particles attached to the lower surface of the carbon fiber sheet 10 can be removed when the deposited particles attached to the hearth 104 are dragged with the carbon fiber sheet 10, it is more preferable to clean both surfaces of the sheet. . In the present invention, the horizontal direction means not only the completely horizontal 0 degree, but also the direction including a range changed ± 5 degrees therefrom.

  Examples of the cleaning method include a method of sucking at least one side of the carbon fiber sheet, a method of spraying gas on at least one side of the carbon fiber sheet, and a method of sweeping at least one side of the carbon fiber sheet with a brush. That is, as described above, the carbon fiber sheet cleaning method includes the suction device 210, the spray device 220, the brush 230, and the like, and any one or a combination thereof can be used for cleaning. In order to prevent the removed precipitated particles and the like from reattaching to the carbon fiber sheet, a cleaning method combining the spraying device 220, the brush 230, and the suction device 210 is more preferable from the balance of the effect of removing the precipitated particles and the like. In order to further reduce the damage to the surface of the sheet 10, a method of cleaning by combining the spraying device 220 and the suction device 210 that can be cleaned without contact is more preferable.

  As another method for cleaning the surface of the carbon fiber sheet 10, a method of removing the precipitated particles or the like by an adhesive roll or a method of removing the precipitated particles or the like while running the carbon fiber sheet vertically outside the high temperature furnace 100 and applying vibrations is used. Also good.

<Characteristics of carbon fiber sheet>
The carbon fiber sheet 10 obtained in the present invention preferably has an area, which is the product of the width and length of the carbon fiber sheet, of 50 m ² or more, more preferably 70 m ² or more, and a major axis of 0.5 mm or more. preferably the number of through holes having is 0 to 0.2 pieces / ^{m 2,} more preferably 0 to 0.18 pieces / ^{m 2,} more preferably at 0 to 0.15 pieces / ^{m 2.} The number of through holes having a major axis of 0.5 mm or more in the carbon fiber sheet can be detected by transmitting light from the back surface of the carbon fiber sheet 10 and observing it visually. In the case of a shape, the longest diameter portion is indicated, and the length of the long diameter can be measured by observing the through hole with a magnifying loupe. The larger the area of the carbon fiber sheet, the more efficient post-processing such as water repellent treatment. The smaller the number of through holes, the more efficiently the processing can be achieved by reducing the number of times of avoiding the through hole portion during post-processing and reducing the generation of debris.

  When the carbon fiber sheet 10 including the through holes is incorporated in, for example, a solid polymer fuel cell, non-uniform power generation occurs in the surface, and the deterioration of the electrolyte membrane is promoted, thereby deteriorating the durability of the fuel cell. Sometimes. Therefore, the carbon fiber sheet 10 including the through hole cannot be used as a fuel cell application, and it is better to mark the portion including the through hole and remove it after a post-processing step such as water repellent treatment.

DESCRIPTION OF SYMBOLS 10 Carbon fiber sheet 11 One surface 12 The other surface 20 Winding body 30 of carbon fiber sheet Winding shaft 40 Core bobbin 50 Carbon fiber sheet precursor 100 High temperature furnace 101 Furnace space 102 Muffle upper wall 103 Muffle lower wall 104 Hearth 105 High Temperature Furnace Inlet 106 High Temperature Furnace Outlet 107 Heat Source 110 Heat Resistant Sheet 210 Suction Device 211 Dust Collector 220 Spraying Device 221 Compressor 230 Brush 300 Roll 301 First Roll 302 in Contact with One Surface 302 Roll 303 in Contact with One Surface Other Surface The first roll to touch

Claims (11)

A carbon fiber sheet comprising a carbon fiber sheet precursor made of at least carbon fiber or carbon fiber-convertible organic fiber, continuously heat-treated in a high-temperature furnace having a maximum temperature of 1500 to 3000 ° C., and wound up the carbon fiber sheet A manufacturing method of
A method for producing a carbon fiber sheet, comprising: cleaning the at least one surface of the carbon fiber sheet after passing through the high temperature furnace, and then winding the carbon fiber sheet. The carbon fiber sheet is a method for producing a carbon fiber sheet for conveying the carbon fiber sheet in a horizontal direction inside the high temperature furnace,
The method for producing a carbon fiber sheet according to claim 1, wherein at least the upper surface of the sheet when being conveyed in the horizontal direction inside the high-temperature furnace is cleaned.   The method for producing a carbon fiber sheet according to claim 1 or 2, wherein the cleaning method is a method of sucking at least one surface of the sheet.   The method for producing a carbon fiber sheet according to any one of claims 1 to 3, wherein the cleaning method is a method of blowing a gas onto at least one surface of the sheet.   The method for producing a carbon fiber sheet according to any one of claims 1 to 4, wherein the cleaning method is a method of sweeping at least one surface of the sheet with a brush.   The method for producing a carbon fiber sheet according to any one of claims 1 to 5, wherein the carbon fiber sheet precursor is formed by binding carbon fibers or organic fibers that can be carbonized with an organic material that can be carbonized.   The method for producing a carbon fiber sheet according to any one of claims 1 to 6, wherein one or a plurality of the carbon fiber sheet precursors are stacked and heat-treated by continuously running inside the high-temperature furnace.   The carbon fiber sheet according to any one of claims 1 to 7, wherein a heat resistant sheet having a width wider than that of the carbon fiber sheet precursor is heat-treated inside the high temperature furnace while being disposed on the upper side of the carbon sheet precursor. Production method.   The manufacturing method of the carbon fiber sheet of Claim 8 which arrange | positions the said heat resistant sheet so that the said carbon sheet precursor may be contact | connected.   The heat-resistant sheet is inserted from the inlet (referred to as furnace inlet) side of the high-temperature furnace, and 30 to 90% of the distance from the furnace inlet to the outlet of the high-temperature furnace (referred to as furnace outlet) is the heat-resistant sheet. The manufacturing method of the carbon fiber sheet of Claim 8 or 9 covered. The area that is the product of the width and length of the carbon fiber sheet is 50 m ² or more,
11. The carbon fiber sheet according to claim 1, wherein the number of through-holes having a major axis of 0.5 mm or more is 0 to 0.2 / m ² in the carbon fiber sheet. Manufacturing method.

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