JP5593672B2 - Manufacturing method of long carbon fiber sheet, long carbon fiber sheet precursor and long carbon fiber sheet - Google Patents

Description

  The present invention relates to a method for producing a long carbon fiber sheet in which a plurality of carbon fiber sheet precursors or carbon fiber sheets are joined together, and the long carbon fiber sheet precursor or the long carbon fiber sheet.

  Since carbon fiber is excellent in heat resistance, it is used as a heat insulating material and heat-resistant protective material, and because it has electrical conductivity, it is applied and developed as an electrode material and current-carrying material for fuel cells. Is also underway.

  Carbon fiber is generally used in a state of being processed into a carbon fiber sheet such as a woven fabric, a nonwoven fabric, or a paper. A carbon fiber sheet is manufactured by carbonizing a carbon fiber sheet precursor. In using this carbon fiber sheet for the above-mentioned uses, heat treatment at about 150 to 400 ° C. may be performed again. In order to continuously perform the heat treatment again, there is a desire to lengthen the carbon fiber sheet. For example, Japanese Patent Application Laid-Open No. 2004-176233 (Patent Document 1) discloses a technique in which end portions of a plurality of carbon fiber sheets are overlapped and end with a spun yarn or filament bundle made of polyacrylonitrile-based oxidized fiber having predetermined properties. The method of lengthening a carbon fiber sheet by connecting the part sides together is described. Specifically, a method is described in which the ends of a woven carbon fiber sheet are sewn together using a needle. The stitching direction is different between the front side and the back side of the overlapped portion. From the front side, the length direction of the carbon fiber sheet from the back side is once at a predetermined angle α in an oblique direction with respect to the length direction of the carbon fiber sheet. Is sewn once at a predetermined length in parallel with this, and this is taken as one set.

  There are also demands for manufacturing large-scale carbonaceous materials depending on the industrial field. For example, Japanese Patent Application Laid-Open No. 61-155260 (Patent Document 2) includes a carbon aggregate (including carbon fiber) and a binder such as a phenol resin, and the ends of the formed carbonaceous material are bonded together. Thus, there is described a large-sized carbonaceous material and a production method in which, after bonding through an adhesive composed of a phenol resin and carbon particles and a graphite sheet, the whole is integrated as carbon by firing.

  Further, JP-A-5-301781 (Patent Document 3) discloses a carbon material obtained by impregnating a carbonaceous material such as a carbon fiber sheet or a carbonizable base material with a carbonizable thermosetting resin such as a phenol resin. Sheet-like adhesive, or carbon-like sheet-like adhesive made of carbonaceous filler and carbonizable thermosetting resin, and then bonding the carbonaceous materials together, followed by firing to carbonize the whole A material bonding method is described. Here, as a carbonaceous material, a carbonaceous molding material (precursor) before firing in which a sheet material such as a woven fabric or a nonwoven fabric made of carbon fiber is impregnated with a phenol resin as a binder, and this is compression-heat-molded is exemplified. ing.

JP 2004-176233 A JP-A-61-155260 JP-A-5-301781

  However, non-woven fabric and paper-like carbon fiber sheets are more fragile than woven fabrics, and when stitched with a needle, there is a high possibility that the needle will puncture and the crack will progress. There is a risk that the connecting portion will be broken.

  On the other hand, when producing a carbon fiber sheet, the carbon fiber sheet precursor is carbonized by running in a heat treatment furnace set at a predetermined temperature. However, since the carbon fiber sheet precursor is not endless, the temperature of the heat treatment furnace is temporarily lowered for each carbon fiber sheet precursor, and after placing a new carbon fiber sheet precursor on the traveling line, the temperature of the heat treatment furnace is again set. It is necessary to raise. Since the temperature of the heat treatment furnace is very high, these processes take a long time, and as a result, the operation efficiency of the heat treatment furnace is greatly reduced. Therefore, there are many demands for lengthening the carbon fiber sheet precursor.

  As a method of lengthening the carbon fiber sheet precursor, according to the method described in Patent Document 1, when the ends of the carbon fiber sheet precursor are stitched together using a needle, a nonwoven fabric or paper shape is used. As in the case of the carbon fiber sheet, there is a high possibility that a crack will occur at the location where the needle is stabbed, and there is a possibility that the joining portion will be broken by the progress of the crack.

  Further, as another method for lengthening the carbon fiber sheet precursor, in accordance with the method described in Patent Document 2, the end faces of the carbon fiber sheet precursor are abutted with each other through a flexible graphite sheet. When the method of joining with an adhesive is employed, the carbon fiber sheet precursor needs to have a thickness of at least about 20 mm, and may not be suitable for connecting a thin sheet of 10 mm or less, and the graphite sheet is joined. Since it is interposed on the surface, it may lead to high costs.

  Furthermore, as another bonding method, Patent Document 3 discloses a sheet-like adhesive material in which a carbonized thermosetting resin is impregnated on a substrate such as paper, sheet, and nonwoven fabric made of various organic fibers between carbon fiber sheet precursors. A method is described in which, after being cured by heating, the carbonization is performed by baking and carbonization at a high temperature. However, in any case, the carbon fiber sheet precursor having a predetermined shape is bonded to the entire surface via a sheet-like adhesive having the same shape and then calcined by firing, and batch-type carbonized bonding is disclosed. The carbon fiber sheet precursor and the sheet-like adhesive having the same shape and the same size interposed therebetween are difficult to handle and extremely inferior in production efficiency. In other words, not only has not paid attention to the point of efficiently producing a long carbon fiber sheet by joining the ends of the short carbon fiber sheet, but it naturally also describes the cost reduction by continuous firing. There is no.

  Therefore, the present invention is excellent in productivity capable of efficiently producing a long carbon fiber sheet precursor or carbon fiber sheet in a nonwoven fabric or paper shape, and the carbon fiber sheet precursor or carbon fiber sheet at low cost. It aims to provide a manufacturing method.

Such a problem is solved by a method for producing a long carbon fiber sheet having the following configuration of the present invention, a long carbon fiber sheet precursor, and a carbon fiber sheet.
The basic structure of the manufacturing method of the long carbon fiber sheet of the present invention is that a phenol resin is added to the terminal end of the first carbon fiber sheet precursor or the start end of the second carbon fiber sheet precursor to be joined. A step of temporarily fixing two or more sheet-like adhesives composed of impregnated carbon fiber precursors, and a terminal portion of the first carbon fiber sheet precursor and a starting end portion of the second carbon fiber sheet precursor. It includes a step of overlapping, a step of adhering and joining the overlapped portions with a hot press device, and a step of continuously carbonizing the joined long carbon fiber sheet precursor. . According to a preferred embodiment, the starting end of the second carbon fiber sheet precursor, in the step of sequentially temporarily fixed to the two or more sheet-like adhesive comprising a carbon fiber precursor obtained by impregnating a phenolic resin, another Two or more sheet-like adhesives are temporarily fixed in advance in a discontinuous manner in the longitudinal direction of the second carbon fiber sheet precursor in a line. This temporary fixing is preferably performed in a part of each sheet-like adhesive.

  More preferably, it is good to perform the process from the process of superimposing the terminal part of said 1st carbon fiber sheet precursor, and the start part of said 2nd carbon fiber sheet precursor to carbonization on the same line. Further, in the continuous carbonization step, without stopping the running of the long carbon fiber sheet precursor, the terminal portion of the first carbon fiber sheet precursor and the second carbon fiber sheet precursor It is preferable that the first end portion of the two layers are sequentially stacked and bonded.

  The basic configuration of the long carbon fiber sheet precursor according to the present invention is such that the terminal portion of the first carbon fiber sheet precursor and the starting end portion of the second carbon fiber sheet precursor are overlapped, and the overlapping portion. Is a long carbon fiber sheet precursor formed by joining a carbon fiber precursor via a sheet-like adhesive layer impregnated with a phenol resin, and the adhesive layer is disposed discontinuously in the sheet longitudinal direction. It is characterized by having.

  In addition, the basic configuration of the long carbon fiber sheet according to the present invention is that the first carbon fiber sheet precursor is carbonized with the terminal portion of the first carbon fiber sheet, and the second carbon fiber sheet precursor is The carbonized second carbon fiber sheet overlaps with the start end portion, and the overlapping portion is a long carbon fiber sheet joined together via a carbide adhesive layer formed by carbonizing the sheet-like adhesive. The carbide adhesive layer is discontinuously disposed in the longitudinal direction of the sheet.

  According to the production method of the present invention, a high-quality long carbon fiber sheet can be efficiently and continuously produced with stable processability even if it is a non-woven fabric or paper-like thin material.

It is a top view which shows an example of the connection part of the elongate carbon fiber sheet precursor obtained by this invention, or a carbon fiber sheet. It is a top view which shows the other example of the connection part of the elongate carbon fiber sheet precursor obtained by this invention, or a carbon fiber sheet. It is a top view which shows the further another example of the connection part of the elongate carbon fiber sheet precursor obtained by this invention, or a carbon fiber sheet. It is a top view which shows the further another example of the connection part of the elongate carbon fiber sheet precursor obtained by this invention, or a carbon fiber sheet. It is a top view which shows the further another example of the connection part of the elongate carbon fiber sheet precursor obtained by this invention, or a carbon fiber sheet. It is a top view which shows the connection process of the following 2nd carbon fiber sheet precursor with respect to the preceding carbon fiber sheet precursor. It is a manufacturing process figure before the connection of the sheet | seat edge part in the continuous manufacturing method of the elongate carbon fiber sheet which concerns on this invention. It is explanatory drawing which shows the example of the hot press apparatus in the overlapping part of the sheet | seat edge part of the elongate carbon fiber sheet which concerns on this invention. It is a manufacturing process figure after the connection of the sheet | seat edge part in the continuous manufacturing method of the elongate carbon fiber sheet which concerns on this invention.

Hereinafter, a carbon fiber sheet precursor / carbon fiber sheet, which is a typical embodiment of the present invention, and a production method thereof will be specifically described with reference to the drawings.
First, the long carbon fiber sheet precursor and the long carbon fiber sheet of the present invention will be described.

<Carbon fiber sheet precursor / carbon fiber sheet>
1-5 is a top view which shows one Embodiment of the elongate carbon fiber sheet precursor 16 or the carbon fiber sheet 17 which concerns on this invention. In addition, in the code | symbol in drawing attached to this-application specification, the code | symbol which attached | subjected the parenthesis () has shown the structural material after carbonization.
The long carbon fiber sheet precursor 16 or the carbon fiber sheet 17 includes a terminal portion of the short first carbon fiber sheet precursor 11 or the first carbon fiber sheet 14 to be joined, and a second carbon. The fiber sheet precursor 12 or the start end portion of the second carbon fiber sheet 15 is overlapped with each other, and both sheet end portions are straightly connected in the length direction. Here, in this specification, the carbon fiber sheet precursor is a sheet-shaped material made of a binder resin or matrix resin before carbonization or before carbonization, which is a constituent material of the sheet. The carbon fiber sheet refers to a sheet after all of the sheet constituent materials are carbonized. Moreover, although the fiber material in a carbon fiber sheet precursor says the fiber before being carbonized normally, in this invention, the case where fiber itself is previously carbonized is included. In addition, the precursor resin in the present invention is a resin for binding between fibers, and refers to a resin before being carbonized.

  The overlapping portion 20 between the sheet end portions is a terminal portion of the short first carbon fiber sheet precursor 11 or the first carbon fiber sheet 14 and the second carbon fiber sheet 12 or the second carbon fiber sheet 15. Are connected to each other via a sheet-like adhesive 13 obtained by impregnating a carbon fiber precursor with a phenol resin, or a carbide adhesive layer 13a obtained by carbonizing the sheet-like adhesive 13. The carbon fiber sheet precursor 16 or the long carbon fiber sheet 17 is configured. Here, in the illustrated example, it is preferable that the sheet-like adhesive 13 or the carbide adhesive layer 13a is discontinuously arranged with respect to the sheet longitudinal direction.

The short first or second carbon fiber sheet precursors 11 and 12 are sheets containing carbon fibers before being carbonized, and the sheets may be woven, non-woven or paper. The length, thickness, and basis weight of the sheet can be appropriately set according to the purpose of use. For example, the length is preferably 50 to 1500 m, the thickness is 0.1 to 10 mm, and the basis weight is preferably 10 to ²⁰⁰ g / m ² .

  Carbonized fiber or carbonized fiber (hereinafter simply referred to as carbonized fiber or carbonized fiber contained in the short first and second carbon fiber sheet precursors 11 and 12, or the long carbon fiber sheet precursor 16 and the carbon fiber sheet 17). Examples of the type of carbon fiber include polyacrylonitrile (PAN) -based carbon fiber, pitch-based carbon fiber, rayon-based carbon fiber, and phenol-based carbon fiber. Since the bending strength and tensile strength of the obtained carbon fiber sheet 17 are increased, it is preferable to use a PAN-based carbon fiber or a pitch-based carbon fiber, and it is more preferable to use a PAN-based carbon fiber. The carbon fiber is preferably a short fiber having an average diameter of 4 to 10 μm.

  The long carbon fiber sheet 17 is a carbon fiber sheet in which carbon fibers are bound by carbon. Such a carbon fiber sheet 17 is obtained by continuously carbonizing the joined first and second carbon fiber sheet precursors 11 and 12 including a carbon fiber material and a carbon precursor resin. Can do.

  The length L of the overlapping portion 20 in which the end portion of the first carbon fiber sheet precursor 11 or the carbon fiber sheet 14 and the start end portion of the second carbon fiber sheet precursor 12 or the carbon fiber sheet 15 overlap each other is shown in FIG. As shown in FIG. 1, a range in which the short first and second carbon fiber sheet precursors 11 and 12 or the first and second carbon fiber sheets 14 and 15 can be connected by the sheet adhesive 13. However, 100 to 1500 mm is preferable, and 200 to 1000 mm is more preferable.

  The overlapping portion 20 between the terminal portion of the first carbon fiber sheet precursor 11 or the carbon fiber sheet 14 to be joined and the starting end portion of the second carbon fiber sheet precursor 12 or the carbon fiber sheet 15 is a sheet. By continuously disposing the sheet-like adhesive 13 in the longitudinal direction, it is difficult to peel off the connection part even if it is bent with a roll or the like, and continuously producing a long carbon fiber sheet with good quality. Is possible.

The sheet-like adhesive 13 can be appropriately selected in consideration of subsequent steps. For example, a resol type, a novolak type, or a blend of a resol and a novolak can be used. In addition, in this invention, the overlapping part 20 of the terminal part of the 1st carbon fiber sheet precursor 11 and the start part of the 2nd carbon fiber sheet precursor 12 should just pass safely without removing a carbonization process. Therefore, a thermosetting resin having a high residual carbon ratio is preferable, and a phenol resin is particularly preferable.
Further, the sheet material of the sheet-like adhesive 13 can be selected as appropriate. For example, a woven fabric shape, a nonwoven fabric shape, or a paper shape can be used, and the thickness is preferably 0.1 to 5 mm, and the basis weight is preferably 10 to 100 g / m ² .

  Furthermore, in this embodiment, when the overlapping part 20 which connected the 1st and 2nd carbon fiber sheet precursors 11 and 12 with the said sheet-like adhesive material 13 is continuously baked in a carbonization process, a roll For example, as shown in FIGS. 1 to 2, the sheet-like adhesive is discontinuous with respect to the longitudinal direction of the sheet in order to suppress the occurrence of peeling at the overlapping portion 20 and to be flexible when bent by, for example, 13 or a carbide adhesive layer 13a may be formed.

  Further, as shown in FIG. 6, when the length in the sheet longitudinal direction of each sheet-like adhesive 13 of the sheet-like adhesive 13 in the overlapping portion 20 having the length L in the sheet longitudinal direction is L1, L1 Is preferably 10 mm to 700 mm, more preferably 20 mm to 500 mm. It is preferable that the number of the sheet-like adhesives 13 arranged in the overlapping portion 20 is 2 to 30 places. Moreover, it is preferable that the space | interval L2 between each sheet-like adhesive material 13 in the overlap part 20 at this time is 5 mm-1000 mm, and 10 mm-500 mm are more preferable. Furthermore, it is good to provide a sheet-like adhesive absence area | region in the outermost edge where the sheet-like adhesive 13 of the 1st and 2nd carbon fiber sheet precursors 11 and 12 in the overlap part 20 at this time does not exist. At this time, the length L3 in the sheet longitudinal direction of the sheet-like adhesive absent region is preferably 0 mm to 50 mm.

  In addition, the sheet-like adhesives 13 in the overlapping portion 20 do not need to be continuous in one in the sheet width direction as shown in FIGS. 1 and 2, for example, as shown in FIGS. You may divide | segment into 2-5 places. Further, the length in the sheet width direction and the number of divisions at this time are not necessarily uniform.

  Further, as shown in FIG. 5, two of the terminal portions of the first carbon fiber sheet precursor 11 or the carbon fiber sheet 14 and at least one of the second carbon fiber sheet precursor 12 or the start end portion of the carbon fiber sheet 15 are used. The corners are preferably cut into a triangular shape having a length L4 in the sheet width direction and a length L5 in the sheet length direction. In particular, the warp of the side end portion in the carbon fiber sheet precursor is more likely to occur at the corner portion, so that the influence of the warp can be reduced by cutting off the corner portion. By cutting off the corner, it becomes difficult to catch the corner in the furnace or the like. Therefore, only the vicinity of the center of the overlapping portion 20 may be connected by a sheet-like adhesive 13 made of a phenol resin and a carbon material.

The carbon fiber sheet 17 of the present invention is suitable for various uses such as a heat insulating material, a heat-resistant protective material, an electrode material such as a fuel cell, and a current-carrying material.
Hereinafter, typical embodiments of the carbon fiber sheet precursor / carbon fiber sheet manufacturing method according to the present invention will be described in detail with reference to the drawings.

<Carbon fiber sheet precursor / carbon fiber sheet manufacturing method>
The carbon fiber sheet 17 of the present invention is prepared by, for example, manufacturing a short first and second carbon fiber sheet precursors 11 and 12 and then adding the phenol resin to the carbon fiber precursor so that they have the above-described configuration. Can be manufactured by carbonizing the joined carbon fiber sheet precursor 16. According to this method, the operating efficiency of the heat treatment furnace that performs carbonization can be increased.

  In addition, in this invention, in order to manufacture a long carbon fiber sheet, after manufacturing the 1st and 2nd carbon fiber sheet precursors 11 and 12 as mentioned above, they become the above-mentioned structure. As described above, the sheet-like adhesive 13 impregnated with a carbon fiber precursor is impregnated with a sheet-like adhesive 13, and the long carbon fiber sheet precursor 16 that is joined is carbonized to produce the sheet. The carbon material is previously carbonized, and after impregnating the carbon precursor resin to produce the first and second carbon fiber sheet precursors 11, 12, In addition, the carbon precursor resin and the sheet-like adhesive 13 can be continuously carbonized in a subsequent baking furnace by sequentially performing pre-heat treatment at a relatively low temperature.

Hereinafter, the former method will be described with reference to FIGS.
The first and second carbon fiber sheet precursors 11 and 12 become carbon fiber sheets by being carbonized at an extremely high temperature, and may be any of a woven shape, a nonwoven fabric shape, and a paper shape. The length, thickness, and basis weight of the first and second carbon fiber sheet precursors 11 and 12 can be appropriately set according to the purpose of use of the carbon fiber sheet 17 to be manufactured. For example, the length is 50 to 1500 m. The thickness is preferably 0.1 to 10 mm, and the basis weight is preferably 10 to ²⁰⁰ g / m ² .

  Examples of the first and second carbon fiber sheet precursors 11 and 12 include carbon fiber sheet precursors including fibers before carbonization and a carbon precursor resin. By carbonizing this carbon fiber sheet precursor, carbon fibers are bound by carbon to form a carbon fiber sheet.

  As a kind of carbon fiber material, polyacrylonitrile (PAN) -based carbon fiber, pitch-based carbon fiber, rayon-based carbon fiber, phenol-based carbon fiber, or the like can be used. Since the bending strength and tensile strength of the obtained carbon fiber sheet are increased, it is preferable to use a PAN-based carbon fiber or a pitch-based carbon fiber, and it is more preferable to use a PAN-based carbon fiber. The carbon fiber is preferably a short fiber having an average diameter of 4 to 10 μm.

  The carbon precursor resin is used for the purpose of binding between carbon fibers. For example, a thermoplastic resin such as polyvinyl alcohol (PVA), a thermosetting resin such as a phenol resin, pitch, starch, or the like is used. be able to. Among these, phenol resin and pitch become carbide by heat treatment for carbonization, and exhibit a function of binding between carbon fibers in the carbon fiber sheet. Moreover, starch and PVA exhibit the function which improves the passage property in obtaining a carbon fiber sheet precursor.

  In the case of a carbon fiber sheet precursor comprising carbon fiber and a carbon precursor resin, the content ratio of the carbon fiber is preferably 10 to 90% by mass, more preferably 20 to 60% by mass, and further 30 to 50% by mass. preferable. When the content ratio of the carbon fiber is less than 10% by mass, the tensile strength of the obtained carbon fiber sheet tends to be reduced or the carbon fiber sheet tends to be brittle and easily broken. On the other hand, if the carbon fiber content exceeds 90 wt%, the resulting carbon fiber sheet tends to be bulky, and the tensile strength and compressive strength tend to decrease. For example, it may not be suitable for use in fuel cell electrodes.

  The carbon fiber sheet precursor comprising carbon fiber and carbon precursor resin may contain carbon powder, metal powder, inorganic powder, metal fiber, inorganic fiber, etc. in addition to carbon fiber and carbon precursor resin. When the obtained carbon fiber sheet is used as a fuel cell electrode base material, it is preferable to contain carbon powder in order to improve conductivity and reduce impurities.

  As a method for producing the carbon fiber sheet precursor, a paper making method such as a wet method in which carbon fiber is dispersed in a liquid medium for paper making or a dry method in which carbon fiber is dispersed in air to be deposited can be applied. Of these, the wet method is preferred. In order to help the carbon fibers disperse into the single fibers and to prevent the dispersed single fibers from converging again, it is preferred to wet paper with an appropriate amount of carbon precursor resin.

As a method of mixing the carbon fiber and the carbon precursor resin, there are a method of stirring and dispersing in water and a method of directly mixing, but a method of stirring and dispersing in water is preferable for uniform dispersion. By mixing the carbon precursor resin with the carbon fiber in this way, the strength of the carbon fiber sheet precursor is maintained, and the carbon fiber is peeled off from the carbon fiber sheet precursor during the production, or the orientation of the carbon fiber is changed. Can be prevented.
The production of the carbon fiber sheet precursor is preferably performed continuously from the viewpoint of productivity and mechanical strength.

  As will be described later, when the first and second carbon fiber sheet precursors 11 and 12 are heat-treated at a plurality of stages of temperature, a sheet that has been heat-treated to an intermediate stage is also included in the carbon fiber sheet precursor of the present invention. Shall be.

The length L in the sheet longitudinal direction of the overlapping portion 20 formed by overlapping the terminal portion of the first carbon fiber sheet precursor 11 and the starting end portion of the second carbon fiber sheet precursor 12 is the first and second lengths. Although it can set suitably in the range which can connect the carbon fiber sheet precursor 11 and 12 with the said sheet-like adhesive material 13, 100-1500 mm is preferable and 200-1000 mm is more preferable.
At this time, from the viewpoint of preventing catching in the heat treatment furnace, the leading end portion of the preceding first carbon fiber sheet precursor 11 is on the lower side, and the starting end portion of the subsequent second carbon fiber sheet precursor 12 is on the upper side. It is preferable to overlap so as to become.

  Further, the sheet-like adhesive 13 is disposed on either the terminal end of the first carbon fiber sheet precursor 11 or the start end of the second carbon fiber sheet precursor 12, as shown in FIG. However, it is only necessary to temporarily fasten both ends of each strip-shaped adhesive sheet 13 so as to be discontinuous with respect to the longitudinal direction of the sheet so that it does not come off with a temporary fastening material 22 such as double-sided tape, bond, or glue. From the viewpoint of work efficiency, it is preferable to temporarily fasten to the starting end portion of the subsequent second carbon fiber sheet precursor 12 in advance.

  In addition, by making the sheet-like adhesive 13 discontinuously exist in the longitudinal direction of the sheet, the connection portion is hardly peeled off even when bent by a roll or the like in the heat treatment step (carbonization step), and the high quality long The carbon fiber sheet 17 can be continuously manufactured.

  In this embodiment, as shown in FIGS. 6-8, the terminal part of the 1st carbon fiber sheet precursor 11 and the start part of the 2nd carbon fiber sheet precursor 12 are piled up, and a heat press is carried out. The ends of the first and second carbon fiber sheet precursors 11 and 12 are connected using the device 35. At that time, the continuous firing step of the carbon fiber sheet precursor is temporarily stopped, and the terminal end portion of the first carbon fiber sheet precursor 11 and the start end portion of the second carbon fiber sheet precursor 12 are held with the sheet-like adhesive 13. Although connection may be made, it is preferable to perform the connection without stopping in order to improve the yield. From the viewpoint of workability, it is preferable to install a hot press device 35 comprising a continuous hot press device or a batch press device between the firing furnace 32 and the unwinding section 34.

  In addition, when performing a batch type press using a batch press apparatus etc., as shown in FIG. 7, the terminal part of the 1st carbon fiber sheet precursor 11 is loosened. Or it is preferable to install an accumulator, a dancer roll, etc., and to ensure the hardening time of the said sheet-like adhesive material 13 of the overlap part 20. FIG.

  When a batch press apparatus is used, the upper and lower press surfaces 35a and 35b may be flat plates. As shown in FIG. 7, one press surface 35a is a convex surface and the other press surface 35b is fitted to the convex surface. It is preferable to make the concave surface to be jammed, since it is easy to align the sheet end when connecting the carbon fiber sheet precursor.

  As a condition of the hot press device 35, although the heating temperature varies depending on the resin to be used, 200 to 300 ° C. is preferable, and regarding the molding pressure, it is sufficient that the sheet-like adhesive 13 is pressed to such an extent that it does not peel off. It is preferable to pressurize at a pressure of 5 MPa to 10 MPa. Moreover, it is preferable that it is 30 seconds-10 minutes about the time of heat-pressure molding.

  After joining the 1st and 2nd carbon fiber sheet precursors 11 and 12 as mentioned above, the long carbon fiber sheet precursor 16 joined together is carbonized. The carbonization at this time can be performed by running the joined long carbon fiber sheet precursor 16 in the heat treatment furnaces 31 and 32.

  Carbonization of the joined long carbon fiber sheet precursor 16 is preferably performed by heat treatment at different stages of temperature. Carbonization of the long carbon fiber sheet precursor 16 when the first and second carbon fiber sheet precursors 11 and 12 that have been heat-treated to an intermediate stage are connected may be performed by subsequent heat treatment.

As the carbonization treatment, the carbon fiber sheet precursor is carbonized at a temperature of 1000 ° C. or higher. By this carbonization treatment, the carbon precursor resin is carbonized, and a carbon fiber sheet can be obtained. The carbonization treatment temperature is preferably 1000 to 3000 ° C, and more preferably 1000 to 2200 ° C. The carbonization treatment is preferably performed in an inert atmosphere. The carbonization treatment time is preferably 10 minutes to 1 hour.
Prior to the carbonization treatment by the firing furnace 32, the carbon fiber sheet precursor can be pre-carbonized at a temperature of 300 to 800 ° C. in a pre-heat treatment furnace. The precarbonization treatment is preferably performed in an inert atmosphere.
Since it is preferable to perform heat treatment at a plurality of temperatures as described above for carbonization, the pre-heat treatment furnace 31 and the firing furnace 32 for performing carbonization may have a plurality of regions that can be set at different temperatures. preferable. The plurality of regions may be installed in one heat treatment furnace, or a plurality of heat treatment furnaces may be combined.

It is preferable that a bending member (not shown) for bending the long carbon fiber sheet precursor 16 that runs continuously is provided in the carbonization furnace and the pre-carbonization furnace. By doing so, wrinkles and irregularities are less likely to occur in the obtained long carbon fiber sheet 17.
The bending member can be provided, for example, in the hearth in the heat treatment furnace, the hearth ceiling, or between the hearth and the hearth ceiling. In order to bring the bending member into contact with the entire width of the long carbon fiber sheet precursor 16, it is preferably provided in a direction crossing the traveling direction of the carbon fiber sheet precursor 16. From this point of view, a rod-like bending member is preferable, but a plate-like bending member may be used. In addition, suppose that the ratio of the major axis and minor axis of a cross section is less than 4 times with rod shape. By setting it as a rod shape, the height of the bending member can be lowered, the contact length with the carbon fiber sheet precursor can be shortened, and wear of the carbon fiber sheet precursor can be prevented. As a material of the bending member, it is preferable to use a carbon material that is inexpensive and chemically stable even in an inert atmosphere.

  The carbon fiber sheet precursor before connection is preferably oxidized at a temperature of 200 ° C. or higher and lower than 300 ° C. By this oxidation treatment, the carbon fibers can be further fused with the carbon precursor resin, and the carbonization rate of the carbon precursor resin can be improved. The temperature of the oxidation treatment is more preferably 240 to 270 ° C. The oxidation treatment is preferably performed in an air atmosphere. The time for the oxidation treatment is preferably 10 minutes to 2 hours, more preferably 10 minutes to 90 minutes.

  Moreover, it is preferable to heat-press mold the carbon fiber sheet precursor before connection at a temperature of less than 300 ° C. By carrying out like this, carbon fiber can be fused with a carbon precursor resin, and the thickness nonuniformity of the carbon fiber sheet obtained can be reduced. The heat press molding may be any technique that can uniformly heat press mold the carbon fiber sheet precursor. For example, it may be a method of hot pressing with smooth rigid plates from both upper and lower surfaces, using a continuous belt press device. The method of performing may be used.

  In order to effectively smooth the surface, the heating temperature is preferably less than 300 ° C, more preferably 200 to 270 ° C. Regarding the molding pressure, when the ratio of the carbon precursor resin is large, it is easy to smooth the surface of the carbon fiber sheet precursor even if the molding pressure is low. If the press pressure is increased more than necessary at this time, there may be a problem that the carbon fiber is destroyed at the time of molding or the structure of the obtained carbon fiber sheet becomes too dense. Therefore, it is preferable to pressurize at a pressure of 0.02 MPa to 10 MPa. The heating and pressing time is preferably 30 seconds to 10 minutes.

When performing the heat and pressure molding of the carbon fiber sheet precursor between the rigid plates or with the continuous belt device, apply a release agent in advance so that the carbon precursor resin or the like does not adhere to the rigid plate or belt, It is preferable that the release paper is sandwiched between the carbon fiber sheet precursor and the rigid plate or belt.
Hereinafter, the present invention will be described more specifically with reference to examples.

  As short carbon fibers, polyacrylonitrile (PAN) carbon fibers (manufactured by Mitsubishi Rayon Co., Ltd.) having an average fiber diameter of 7 μm and an average fiber length of 3 mm, and PAN carbon fibers having an average fiber diameter of 4 μm and an average fiber length of 3 mm Carbonized short fibers mixed with 70:30 (mass ratio) (Mitsubishi Rayon Co., Ltd.) were used. As binder fibers, 1.1 dtex, 5 mm cut vinylon short fibers (Unitika Ltd. Unitika Vinylon F) and polyvinyl alcohol (PVA) short fibers (Kuraray VBP105-1 cut length 3 mm) were prepared.

First, carbonized short fibers are uniformly dispersed in water in a slurry tank of a wet short net continuous paper making apparatus to be defibrated into single fibers, and when sufficiently dispersed, the PVA short fibers and vinylon short fibers are carbonized short fibers 100. relative to the weight parts, 18 weight parts, respectively, 32 parts by mass so as to uniformly disperse, which the basis weight 20 g / m ² using a conventional Fourdrinier papermaking method, length 500m at 40 g / m ² Two types of carbon fiber paper were obtained.

Next, the carbon fiber paper was uniformly contacted one side at a time on a roller to which a methanol solution containing 40% by mass of phenol resin (Phenolite J-325 manufactured by DIC Corporation) was adhered, and then dried by spraying hot air continuously. Two types of resin-attached carbon fiber papers having a basis weight of 32 g / m ² and 64 g / m ² were obtained. Two sheets of this resin-attached carbon fiber paper were bonded together so that the surface in contact with the long mesh faced outward, and then a continuous heating press device (double belt press device: DBP) equipped with a pair of endless belts was used. Then, two types of surface smoothed sheets having a sheet thickness of 0.17 mm and 0.30 mm, a width of 300 mm, and a length of 450 m were obtained. At this time, the resin-attached carbon fiber paper was sandwiched between two release papers so as not to stick to the belt.

  Thereafter, the obtained surface smoothing sheet was heated for 5 minutes in a continuous preheat treatment furnace at 500 ° C. in a nitrogen gas atmosphere to perform preheat treatment, thereby curing and precarbonizing the phenol resin. Subsequently, the obtained cured resin sheet was heated in a continuous baking furnace at 2000 ° C. for 5 minutes in a nitrogen gas atmosphere to be carbonized to continuously obtain a porous carbon fiber sheet 36 having a length of 400 m. It was wound up on an inch cylindrical paper tube. Although this porous carbon fiber sheet 36 is thinned, it is an electrode substrate that is smooth and easy to handle, and has excellent bending strength and gas permeability.

  In this embodiment, as shown in FIGS. 6 to 9, the pre-heat treatment furnace 31 immediately before the second carbon fiber sheet precursor 12 disappears from the rolled carbon fiber sheet precursor 33 in the unwinding portion 34. The preceding first carbon fiber sheet precursor 11 is nipped by the entry side nip roll 38, and all the terminal portions of the first carbon fiber sheet precursor 12 are unwound from the unwinding portion 34.

Next, a double-sided tape having a width of 5 mm is attached to both ends of the sheet-like adhesive 13 in advance so that the sheet-like adhesive 13 is discontinuous in the longitudinal direction of the starting end of the subsequent second carbon fiber sheet precursor 12. After attaching the temporarily fixed to the unwinding portion 34, the starting end portion is unwound from the unwinding portion 34, and the starting end portions of the first carbon fiber sheet precursor 11 and the second carbon fiber sheet precursor 12 are removed. The layers were connected using a hot press device 35 under the conditions of 250 ° C. × 2 minutes and 0.5 MPa.
After the connection of the sheets, the looseness of the sheet from the unwinding portion 34 to the entry side nip roll 38 of the pre-heat treatment furnace 31 was removed, and the nip roll 38 was opened.

  At the same time, the joined carbon fiber sheet precursor 16 is introduced into the pre-heat treatment furnace 31 and heated in a continuous pre-heat treatment furnace at 500 ° C. for 5 minutes in a nitrogen gas atmosphere to cure the thermosetting resin that can be carbonized. The sheet-like porous carbon fiber sheet that has been pre-carbonized and passed through the pre-heat treatment furnace 31 is subsequently introduced into a continuous firing furnace 32 at 2000 ° C. in a nitrogen gas atmosphere, and then carbonized, and then the winding unit 37. On a roll. Alternatively, the sheet is cut at the exit from the nip roll 39 on the exit side of the continuous firing furnace 32, the porous carbon fiber sheet 36 of the winding unit 37 is removed, and a new cylindrical paper tube having an outer diameter of 6 inches is used as the winding unit 37. After mounting, the porous carbon fiber sheet 36 was wound up.

In this example, as the sheet-like adhesive 13, the resin-attached carbon fiber paper having a basis weight of 64 g / m ² and a width of 300 mm is used, and the length L1 in the sheet longitudinal direction is 4 types of 20 mm, 50 mm, 200 mm, and 300 mm. A strip-shaped adhesive material having a length L1 of 700 mm is obtained by cutting the strips into the first to fifth embodiments as shown in Table 1 using a predetermined number of sheets at predetermined intervals. Example 6 was arranged alone.
Table 1 shows an example in which two types of carbon fiber sheet precursors, a thin carbon fiber sheet (sheet thickness 0.17 mm) with a smooth surface and a thick carbon fiber sheet (sheet thickness 0.30 mm), were used. Each process permeability in the baking process of the connection part of 1-6 is shown.

  As can be understood from Table 1, the process passability in each of Examples 1 to 5 is good, and even a thick sheet does not cause any particular trouble. On the other hand, in Example 6 using one continuous sheet-like adhesive material without discontinuously arranging the sheet-like adhesive in the longitudinal direction, there was no particular problem in process passability in the thin sheet, but the thick sheet Then, it was confirmed that breakage of the sheet sometimes occurred.

As described above, the continuous production method of a porous long carbon fiber sheet according to the present invention includes the terminal portion of the preceding first carbon fiber sheet precursor 11 and the subsequent second carbon fiber sheet in the continuous carbonization heat treatment step. The steps from the step of overlapping the carbon fiber sheet precursor 12 of the carbon fiber sheet precursor 12 and adhering with the sheet-like adhesive to the carbonization are performed on the same line, the sheet-like adhesive in the longitudinal direction of the connecting portion By discontinuously arranging the sheet in the longitudinal direction of the sheet, the breakage of the connection part due to the rolls in the process, the guide roll (guide bar) in the furnace, etc. is suppressed, and the connection between the sheets can be performed without stopping the firing process. Thus, the productivity of the long carbon fiber sheet 17 (36) can be greatly expected.
In addition, it will be understood from the above description that the present invention is not limited to the above embodiment.

DESCRIPTION OF SYMBOLS 11 1st carbon fiber sheet precursor 12 2nd carbon fiber sheet precursor 13 Sheet-like adhesive material 13a Carbide adhesive layer 14 1st carbon fiber sheet 15 2nd carbon fiber sheet 16 The long carbon fiber joined together Sheet precursor 17 Joined long carbon fiber sheet 20 Overlapping portion 22 Temporary fastening material 31 Pre-heat treatment furnace 32 Firing furnace 33 Rolled carbon fiber sheet precursor 34 Unwinding portion 35 Hot press device 35a Upper press surface 35b Lower press Surface 36 (Long) porous carbon fiber sheet 37 Winding portion 38 Nip roll 39 on the entrance side of the preheating furnace 39 Nip roll on the exit side of the firing furnace

Claims (6)

Two consisting of the beginning of the end portion or the second carbon fiber sheet precursor of the first carbon fiber sheet precursor to be align tie (11) (12), the carbon fiber precursor obtained by impregnating the phenolic resin A step of temporarily fixing the above-mentioned sheet-like adhesive (13) sequentially;
Superimposing the end portion of the first carbon fiber sheet precursor (11) and the start portion of the second carbon fiber sheet precursor (12);
Bonding and joining the overlapping portion (20) with a hot press device (35);
A step of continuously carbonizing the joined long carbon fiber sheet precursor (16);
A method for producing a long carbon fiber sheet comprising: In the step of sequentially temporarily fixing the two or more sheet-like adhesives (13) made of a carbon fiber precursor impregnated with a phenol resin at the start end of the second carbon fiber sheet precursor (12), The two or more sheet-like adhesives (13) are temporarily fixed in a discontinuous manner in the longitudinal direction of the sheet at the starting end of the second carbon fiber sheet precursor (12) in advance in a line. A method for producing a long carbon fiber sheet. Two or more sheet-like adhesions composed of a carbon fiber precursor impregnated with a phenol resin at the end of the first carbon fiber sheet precursor (11) or the start of the second carbon fiber sheet precursor (12) The method for producing a long carbon fiber sheet according to claim 1 or 2 , wherein in the step of temporarily fastening the material (13), the temporary fastening is performed in a part of each of the two or more sheet-like adhesive materials (13).   The process from the step of overlapping the terminal end of the first carbon fiber sheet precursor (11) and the start end of the second carbon fiber sheet precursor (12) to carbonization on the same line. The manufacturing method of the elongate carbon fiber sheet in any one of 1-3. The end portion of the first carbon fiber sheet precursor (11) and the start end portion of the second carbon fiber sheet precursor (12) overlap, and the overlap portion (20) adds phenol resin to the carbon fiber precursor. A long carbon fiber sheet precursor (16) joined through two or more sheet-like adhesives (13) impregnated, wherein the two or more sheet-like adhesives (13) are in the sheet longitudinal direction. A long carbon fiber sheet precursor that is discontinuously disposed on the surface. A terminal portion of the first carbon fiber sheet (14) in which the first carbon fiber sheet precursor (11) is carbonized, and a second carbon in which the second carbon fiber sheet precursor (12) is carbonized. and it overlaps the leading end of the fiber sheet (15), the overlapping portion (20) of starvation over preparative type adhesive material (13) the elongated were joined together through the carbide adhesive layer obtained by carbonization (13a) A carbon fiber sheet (17), wherein the carbide adhesive layer (13a) is discontinuously arranged in the sheet longitudinal direction.

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