JP4896488B2 - Manufacturing method of conductive separator for fuel cell by cold pressing method - Google Patents

Description

  The present invention relates to a method for manufacturing a fuel cell conductive separator, and more particularly to a method for manufacturing a fuel cell conductive separator by a cold press method.

  Conventionally, as a conductive separator for a fuel cell, a metal separator plate in which the surface of a metal substrate is passivated, a composite material composed of conductive particles and a thermosetting resin is used in a molding machine such as compression, transfer and injection. A separator plate formed by molding, a separator plate obtained by cutting a composite material molded body formed into a block shape into a separator shape, and the like have been studied.

  Specifically, the metal base is used, for example, a surface of the metal base provided with a resin film having acid resistance and electrical conductivity (see, for example, Patent Document 1), or the surface of the metal base. A multilayer metal plate having a two-layer coating layer composed of a metal-based conductive coating layer and a graphite-based conductive coating layer (see, for example, Patent Document 2), and a multilayer metal plate having an outermost layer as a corrosion-resistant metal as a metal substrate. (For example, refer to Patent Document 3) and the like have been studied.

  On the other hand, as what molds the composite material which consists of electroconductive particle and a thermosetting resin with molding machines, such as compression, for example, the electroconductive particle which has a specific average particle diameter, and the phenol resin which has a specific average molecular weight , Which facilitates production by injection molding (see, for example, Patent Document 4), and uses a specific epoxy resin and phenol resin to improve moldability and mechanical strength (see, for example, Patent Document 5) )), An epoxy resin, an epoxy resin curing agent, a curing accelerator, and the like that do not require heat treatment such as firing (for example, see Patent Document 6) are being studied.

Further, regarding the groove forming process in the fuel cell conductive separator, it is a material for forming the fuel cell conductive separator using, for example, a molding die composed of a first mold and a second mold having projecting mold portions. A method of transferring the protrusions to the carbon-based material and forming grooves by strongly pressing the carbon-based material in the thickness direction (see, for example, Patent Document 7), and a material for forming a conductive separator for a fuel cell. After forming into a uniform sheet shape, the method (for example, refer patent document 8) etc. which transfer the shape of the groove shape to a sheet-like molded object using the rolling roller which has a predetermined groove | channel are examined.
JP 2003-249240 A JP 2004-111079 A JP 2005-5137 A JP 2000-331690 A JP 2001-261935 A JP 2002-83609 A JP-A-10-55809 JP 2002-198062 A

  However, the conductive separator for a fuel cell in which the surface of the metal substrate is passivated is difficult to prevent a sudden failure caused by a fine scratch or the like. Moreover, what cuts the composite-material molded object shape | molded in the block shape has the subject that work cost takes and manufacturing cost increases.

  On the other hand, molding a composite material composed of conductive particles and a thermosetting resin by compression molding, transfer molding, injection molding, or the like requires a complicated mold and increases manufacturing costs. In addition, in a conductive separator for a fuel cell, it is generally preferable to highly charge conductive particles in order to improve conductivity. However, a composite material highly filled with conductive particles has low fluidity at the time of molding and is compressed. It becomes difficult to perform molding, transfer molding, injection molding, and the like.

  For the decrease in fluidity at the time of molding, for example, improvement has been attempted by setting the average particle size of the conductive particles to a specific range, or setting the average molecular weight of the thermosetting resin to a specific range. It is hard to say that it has been solved sufficiently.

  Also, when producing a conductive separator for a fuel cell by compression molding, it is difficult to obtain a final shape by compression molding alone. There is a problem that the manufacturing cost increases. In addition, when manufacturing a fuel cell conductive separator by an injection molding method, there is a problem that the ratio of the content of the conductive particles and the thermosetting resin varies from part to part due to the difference in fluidity in the mold. .

  The present invention has been made to solve such a problem, and does not use a complicated mold used in compression molding, transfer molding, injection molding, etc., and has excellent conductivity. For the purpose of providing a method for producing a conductive separator for a fuel cell, which can be produced even when highly charged with conductive particles, and which is excellent in flatness and the like. Yes.

The method for producing a conductive separator for a fuel cell according to the present invention comprises a composite material preparation step for obtaining a composite material mainly comprising graphite powder having an average particle size of 0.5 to 25 μm and a thermosetting resin, and the composite material. A sheet preparation step for obtaining a semi-cured resin sheet by heat treatment at a temperature of 40 to 50 ° C. for 2 to 120 hours, and a gas flow path forming pattern is formed on the heated semi-cured resin sheet A fuel cell conductive by a cold pressing method comprising a cold pressing step of cold pressing at a temperature lower than the semi-cured resin sheet by a pair of opposed molds to obtain a conductive separator for a fuel cell The semi-cured resin sheet in the sheet preparation step is pressed on both sides in the graphite powder, and the graphite powder is adhered to the both surfaces. And it is characterized in that it is surface-treated by.

It is preferred before Symbol thermosetting resin as a main component phenolic resin or epoxy resin.

  In the present invention, the semi-cured resin sheet produced in the sheet preparation process is continuous, and the cold press process is continuously performed on such a continuous semi-cured resin sheet. Is preferred. In this cold pressing step, it is preferable that the semi-cured resin sheet is cold pressed and simultaneously cut into a predetermined size.

  According to the present invention, a complicated mold such as that used in conventional compression molding, transfer molding, injection molding or the like is used by performing cold pressing using a resin sheet that has been semi-cured in advance. There is no need, and even when the conductive particles are highly filled, it can be reliably molded, and a conductive separator for a fuel cell having excellent flatness can be produced.

  Hereinafter, the present invention will be described in detail. The method for producing a conductive separator for a fuel cell according to the present invention comprises a composite material preparation step for obtaining a composite material mainly comprising a conductive material and a thermosetting resin, and a sheet for obtaining a semi-cured resin sheet comprising the composite material A cold press is performed at a lower temperature than the semi-cured resin sheet by a pair of opposing molds on which a gas flow path forming pattern is formed on the preparation process and the heated semi-cured resin sheet. And a cold pressing step for obtaining a conductive separator for a fuel cell.

  As described above, the composite material used in the present invention mainly contains a conductive material and a thermosetting resin. The conductive material is not necessarily limited as long as it has conductivity, but materials other than metal powder and short metal fibers are preferable. That is, when metal powder or short metal fibers are used, the surface of the conductive separator for fuel cells is likely to corrode due to the influence of ion groups present in the fuel cell, high temperature, and electric field.

  Specifically, a carbonaceous material is preferably used as the conductive material. Although it does not specifically limit as a carbonaceous material, When it is finally set as the electrically conductive separator for fuel cells, it is preferable that it is a substance and a shape which become high electroconductivity.

  As such a carbonaceous material, for example, artificial or natural graphite powder is preferable. There are two types of artificial graphite derived from petroleum-based coke and coal-based coke, and natural graphite includes flaky graphite and soil graphite, and any of them may be used in the present invention.

  When graphite powder is used as the carbonaceous material, it is preferable to use one having an average particle diameter in the range of 0.5 μm to 100 μm, and an average particle diameter in the range of 0.5 μm to 25 μm. More preferably, it is used. By using a material having such an average particle size, the conductivity of the conductive separator for a fuel cell can be improved.

  When graphite powder is used as the conductive substrate, two or more types of graphite particles having different average particle diameters may be used. When two or more types of graphite powder having different average particle diameters are used, the average particle diameter of each graphite powder is preferably selected from the above-described range of the average particle diameter. By making the graphite powder consist of two or more kinds having such different average particle diameters, it becomes possible to fill the graphite powder with high density in the conductive separator for fuel cells, and the conductivity is good. Can be.

  As the carbonaceous material, materials other than graphite powder can be used. That is, carbon fiber, carbon black, fullerene such as cylindrical or spherical, and the like can be used. Moreover, as a carbonaceous material, two or more types of carbonaceous materials can also be used together. When a fibrous material is used as the carbonaceous material, a short fibrous material is preferable, and an aspect ratio of 3 to 300, which is a ratio of the fiber length to the fiber diameter, is preferable.

  As the thermosetting resin, a resin excellent in heat resistance, chemical resistance and mechanical strength is particularly preferably used. Specific examples of thermosetting resins include epoxy resins, unsaturated polyester resins, urea resins, melamine resins, silicone resins, fluorine resins, guanamine resins, phenol resins, polyamide resins, and polyimides. Resin, maleimide resin, and the like, and these may be used alone or in combination of two or more. Among these thermosetting resins, epoxy resins and phenol resins are particularly preferably used from the viewpoint of ease of handling and performance, and among these, phenol resins are preferably used from the viewpoint of price.

  The composite material in the present invention is mainly composed of the conductive material and the thermosetting resin as described above, but as long as it does not contradict the gist of the present invention, and if necessary, a curing agent, a curing catalyst, Various additives such as coupling agents such as epoxy silanes and other additives may be added.

  The composite material according to the present invention contains, for example, the conductive material and the thermosetting resin, which are essential components as described above, and after blending various additives as described above as necessary, the Henschel mixer, It can be obtained by mixing uniformly using a mixing device such as a universal mixer (composite material preparation step).

  Further, this composite material is made into a semi-cured resin sheet by forming into a sheet or curing reaction (sheet preparation step). The uncured state (A-stage) is a state in which the three-dimensional crosslinking of the thermosetting resin is not formed, and the completely cured state (C-stage) is the three-dimensional crosslinking of the thermosetting resin. Is a completed state, and the semi-cured state (B-stage) refers to a state that is neither an uncured state nor a completely cured state.

  When the resin sheet is in an uncured state, the resin sheet is too hard in the next cold pressing step as it is, so that the cold pressing cannot be performed, while on the other hand, in order to reduce the hardness, When heated in the pressing step, it liquefies and cannot be cold pressed. In addition, even when the resin sheet is in a completely cured state, the resin sheet is too hard in the next cold pressing process in the state as it is, so cold pressing cannot be performed, while in the cold pressing process Even when heated, the hardness is not reduced because it is already completely cured, and cold pressing cannot be performed.

  In the present invention, the resin sheet used in the cold pressing step is made into a semi-cured state, so that the hardness of the resin sheet is effectively increased by heating the resin sheet in the cold pressing step. Can be reduced. In addition, by setting the resin sheet used in the cold pressing process to a semi-cured state, it is possible to suppress liquefaction as in the uncured state due to heating in the cold pressing process, and to ensure cold pressing. To be able to do that.

  Preparation of a semi-cured resin sheet is, for example, by simply forming a composite material into a non-cured resin sheet and then subjecting it to a heat treatment to advance the curing reaction to a semi-cured resin sheet. Alternatively, it may be performed by proceeding with the curing reaction of the composite material to form a sheet that is a semi-cured resin sheet.

  After obtaining an uncured resin sheet, heat treatment is performed on the resin sheet to obtain a semi-cured resin sheet. For example, the composite material is kneaded without heating using a biaxial roll machine or the like to form a sheet. After obtaining an uncured resin sheet by this, a method of advancing a curing reaction by performing heat treatment on the uncured resin sheet using various heat treatment apparatuses to obtain a semi-cured resin sheet is mentioned. It is done.

  As a method for obtaining a resin sheet, in addition to the method using a biaxial roll machine as described above, for example, a method in which a composite material is filled in a predetermined mold and press-molded, the composite material is heated to the melting temperature or higher. And a method of pouring into a predetermined mold, and the like can be appropriately selected and used.

  The heat treatment for proceeding the curing reaction of the uncured resin sheet to obtain a semi-cured resin sheet is not necessarily limited, but it is easily liquid when heated in the next cold press process. Moreover, it is preferable to set it as the heat processing which can reduce hardness to the grade which can be cold-pressed by this heating.

  This heat treatment is preferably performed at a temperature of 40 ° C. to 50 ° C. for about 2 hours to 120 hours, for example. If it is less than 40 ° C. or less than 2 hours, the curing reaction is not sufficient, and the resin sheet may be liquified easily by heating in the cold pressing step. Moreover, when it exceeds 50 degreeC or exceeds 120 hours, hardening reaction will advance too much and there exists a possibility that the hardness of a resin sheet cannot be reduced to the grade which can be cold-pressed by the heating in a cold press process.

  On the other hand, as a method of forming a semi-cured resin sheet after proceeding with the curing reaction of the composite material, for example, the curing reaction was advanced by kneading the composite material while heating using a biaxial heating roll machine. Later, a method of extruding into a sheet form from this biaxial heating roll machine to obtain a semi-cured resin sheet can be mentioned. Even in such a case, the heat treatment as described above may be performed as necessary. According to such a method, since the curing reaction is advanced in advance, the heat treatment can be omitted, or the treatment time can be shortened even when the heat treatment is performed.

  In such a semi-cured resin sheet, a shape holding material such as a carbon fiber woven fabric may be incorporated. By incorporating such a shape-retaining material into the inside, it can be prevented from being easily deformed during the heat transfer in the cold pressing process, which is the next process.

  Further, such a semi-cured resin sheet is preferably subjected to a surface treatment for attaching a conductive material to the surface thereof. By attaching a conductive material to the surface of a semi-cured resin sheet, when it is used as a conductive separator for a fuel cell, the contact resistance can be reduced and the power generation efficiency of the fuel cell is improved. It can be.

  As the conductive material to be attached, the same material as the conductive material used for manufacturing the composite material can be used, and for example, a carbonaceous material is preferable. The timing for performing the surface treatment is not necessarily limited. For example, when a non-cured resin sheet is heat-treated to form a semi-cured resin sheet, it is performed at the stage of the uncured resin sheet. Alternatively, a semi-cured resin sheet may be used. In addition, examples of the surface treatment method include a method of spraying a conductive material onto a resin sheet, a method of pressing a resin sheet against the conductive material, and the like. Further, after that, the conductive material is reliably adhered to the resin sheet. A method such as pressure treatment may be used, and can be appropriately selected and used.

  The semi-cured resin sheet thus prepared is heated and cooled at a temperature lower than that of the semi-cured resin sheet by a pair of opposed molds on which gas flow path forming patterns are formed. An intermediate press is performed to form a conductive separator for a fuel cell (cold pressing step). In the present invention, a semi-cured resin sheet in a heated state is cold-pressed with a pair of opposed dies, for example, in an injection molding method. Since the fluidity is different, it is possible to prevent the content of the conductive material and the thermosetting resin from being different in each portion of the conductive separator for the fuel cell or the flatness from being lowered.

  FIG. 1 shows an example of such a cold pressing process, and shows an example in the case where the cold pressing is continuously performed on a continuous semi-cured resin sheet 1. A cold press machine 2 that cold-presses the semi-cured resin sheet 1 mainly includes, for example, a heating unit 3 and a molding unit 4.

  The heating unit 3 is for heating the semi-cured resin sheet 1 before feeding the semi-cured resin sheet 1 to the molding unit 4, and includes, for example, a heater. The molding unit 4 includes an upper mold 5 and a lower mold 6 as a pair of opposed molds. Gas flow path forming patterns 7 and 8 for forming gas flow paths of the conductive separator for the fuel cell are formed on the opposing surfaces of the upper mold 5 and the lower mold 6, Cooling portions 9 and 10 for cooling are formed inside.

  In the example shown in the figure, the gas flow path forming patterns 7 and 8 of the upper mold 5 and the lower mold 6 are formed so as to be orthogonal to each other. Although not particularly shown in the example shown in the figure, the cold press 2 is provided with a pressurizing device for operating the upper mold 5 and the lower mold 6, for example.

  Such a cold press process by the cold press machine 2 is first performed by the rotational force of the carry-in rubber rolls 11, 12, 13, 14, etc. in which the semi-cured resin sheet 1 continuous from the left side in the figure is arranged above and below. It is sent to the heating unit 3 of the cold press machine 2. In the heating unit 3, the semi-cured resin sheet 1 is heated by a heater or the like.

  The temperature condition at the time of heating the semi-cured resin sheet 1 in the heating unit 3 is particularly important, and it is preferable that the following condition is satisfied. (1) When the semi-cured resin sheet 1 is cold-pressed by the molding part 4, the parts other than the cold press should not be deformed. (2) The semi-cured resin sheet 1 can be conveyed to the molding unit 4 and can be carried out of the molding unit 4. (3) The gas flow path can be reliably formed (transferred) in the semi-cured resin sheet 1 by cold pressing in the molding section 4.

  If the above conditions (1) to (3) are not satisfied, for example, it becomes difficult to carry the semi-cured resin sheet 1 into or out of the molded part 4, and continuously cold It may be difficult to press, and the resulting fuel cell conductive separator may be deformed, or the gas flow path may be insufficiently formed. The temperature that satisfies the conditions (1) to (3) is slightly different depending on the type of the thermosetting resin, but is generally preferably 60 ° C. or higher and 90 ° C. or lower.

  Then, the semi-cured resin sheet 1 heated to a predetermined temperature is sent to the molding section 4 and both main surfaces are pressurized with the upper mold 5 and the lower mold 6 kept at a lower temperature. Thus, the gas flow path forming patterns 7 and 8 are transferred to both main surfaces of the semi-cured resin sheet 1 to form gas flow paths 15 and 16, respectively. Although the temperature of the upper mold 5 and the lower mold 6 is not particularly limited as long as it is lower than the temperature of the semi-cured resin sheet 1, it is generally preferably 20 ° C. or higher and 50 ° C. or lower.

  The gas flow paths 15 and 16 formed on both main surfaces may be used as they are as a conductive separator for a fuel cell. However, it is better to carry out the curing reaction completely by further heating or rapid cooling. For example, as shown in FIG. 1, a post-processing unit 17 for further heating and cooling may be provided after the forming unit 4 to perform heating and cooling. And what formed the gas flow paths 15 and 16 in both main surfaces is carried out of the cold press machine 2 by the carry-out rubber rolls 18 and 19.

  In such a cold press 2, the semi-cured resin sheet 1 may be cut into a predetermined size simultaneously with the cold press of the semi-cured resin sheet 1. For example, cutting teeth capable of cutting the semi-cured resin sheet 1 are provided around the upper mold 5 and the lower mold 6 of the molding unit 4, and a cold press of the semi-cured resin sheet 1 is performed. You may make it cut | disconnect simultaneously. By doing in this way, it becomes possible to obtain continuously the conductive separator for fuel cells cut into the predetermined shape.

  As described above, the cold pressing process in the present invention has been described with reference to FIG. 1, but the cold pressing process of the present invention is not necessarily limited to that shown in FIG. For example, since the composite material kneaded with a biaxial heating roll or the like and made into a sheet is in a semi-cured state and is heated, the cold press 2 as it is if the above temperature conditions are satisfied. Can be carried into the molding part 4 and heating in the heating part 3 can be omitted.

  Further, for example, in the cold pressing step shown in FIG. 1, the semi-cured resin sheet 1 is continuous, and the semi-cured resin sheet 1 is continuously heated and cold pressed. However, instead of this, for example, a semi-cured resin sheet is previously set to the size of one conductive separator for a fuel cell, and such semi-cured resin sheets are cold-pressed one by one. It may be carried into a machine and heated and cold pressed.

  Hereinafter, the present invention will be described in more detail with reference to examples.

( Reference Example 1)
First, a composite material used for manufacturing a semi-cured resin sheet was prepared. Graphite powder (average particle size 3 μm) as a conductive material for preparing a composite material, cresol novolac type epoxy resin (softening temperature 87 ° C.) as a thermosetting resin, novolak type phenol resin (softening temperature 85 ° C.) as a curing agent An imidazole catalyst (softening temperature 84 ° C.) was used as a curing catalyst, and a carnauba natural wax (softening temperature 85 ° C.) was used as a lubricant.

  The compounding ratio of each component is such that the graphite powder is 88% by weight and the carnauba natural wax is 0.2% by weight, with the remainder being cresol novolac type epoxy resin, novolac type phenol resin, imidazole catalyst. It was made to become. The cresol novolac type epoxy resin and the novolac type phenol resin were in an equivalent ratio, and the imidazole catalyst was 0.75% by weight in the total amount of the cresol novolac type epoxy resin, the novolac type phenol resin and the imidazole catalyst. . Then, a blend having such a blend ratio was put into a Henschel mixer and mixed uniformly to obtain a composite material.

  The composite material was heated and kneaded with a 90 ° C. biaxial roll machine, and then scraped into a sheet from the biaxial roll machine to obtain a resin sheet. The resin sheet is cut into the size of one conductive separator for a fuel cell, and then the cut resin sheet is placed in a 50 ° C. air circulation type heating and drying machine and heated for 24 hours to cure the resin. To obtain a semi-cured resin sheet.

  After heating the semi-cured resin sheet to 65 ° C., a gas flow path forming pattern is formed, and cold pressing is performed with the opposing upper and lower molds maintained at 30 ° C. A path was formed to provide a conductive separator for a fuel cell.

( Reference Example 2)
First, a composite material used for manufacturing a semi-cured resin sheet was prepared. Uses graphite powder (average particle size 3 μm) as the conductive material for preparing the composite material, cresol-type phenol resin (softening temperature 84 ° C) as the thermosetting resin, and carnauba natural wax (softening temperature 85 ° C) as the lubricant. It was. The compounding ratio of each component was such that the graphite powder was 88% by weight and the carnauba natural wax was 0.2% by weight, with the remainder being a cresol type phenolic resin based on the total composite material. Then, the blend having such a blend ratio was put into a universal mixer and mixed uniformly to obtain a composite material.

  This composite material was heated and kneaded with a biaxial roll machine at 85 ° C., and then scraped into a sheet form from the biaxial roll machine to obtain a resin sheet. The resin sheet is cut into a size equivalent to one conductive separator for a fuel cell, and then the cut resin sheet is placed in a 40 ° C. air circulation type heating and drying machine and heated for 12 hours to cure the resin. To obtain a semi-cured resin sheet.

  After heating the semi-cured resin sheet to 65 ° C., a gas flow path forming pattern is formed, and cold pressing is performed with the opposing upper and lower molds maintained at 30 ° C. A path was formed to provide a conductive separator for a fuel cell.

(Example 1 )
The composite material obtained in the same manner as in Reference Example 1 was heat-kneaded with a 90 ° C. biaxial roll machine, and then scraped into a sheet form from this biaxial roll machine to obtain a resin sheet. Both surfaces were pressed into the graphite powder in which the soft resin sheet just scraped off from this biaxial roll machine was put into the pad, and the graphite powder was made to adhere to both surfaces. Then, the resin sheet on which the graphite powder was adhered was placed in a metal plate shape, stretched with a metal rod, and pressure was applied from the upper surface to make the surface treatment by fixing the graphite powder on the surface.

After the surface-treated resin sheet is cut into the size of one fuel cell conductive separator, heat treatment is performed in the same manner as in Reference Example 1 to obtain a semi-cured resin sheet. It pressed and it was set as the electrically conductive separator for fuel cells.

With respect to the conductive separators for fuel cells of Example 1 and Reference Examples 1 and 2 thus produced, the appearance was visually observed to check for the presence of defects such as voids, and the surface resistivity was measured. The results are shown in Table 1.

  As apparent from the results shown in Table 1, according to the manufacturing method of the present invention, defects such as voids can be obtained without using complicated molds used in conventional compression molding, transfer molding, injection molding and the like. It was confirmed that a conductive separator for a fuel cell excellent in flatness could be produced. Moreover, it was recognized that the surface resistivity of the conductive separator for fuel cells can be reduced by treating the surface of the resin sheet with a conductive material.

Schematic which showed an example of the cold press process in this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Semi-cured resin sheet, 2 ... Cold press, 3 ... Heating part, 4 ... Molding part, 5 ... Upper metal mold, 6 ... Lower metal mold, 7 ... Gas flow path formation pattern (Upper metal mold) ), 8 ... Gas flow path forming pattern (lower mold), 9 ... Cooling section (mold), 10 ... Cooling section (lower mold), 11, 12, 13, 14 ... Incoming rubber roll, 15, 16 ... Gas flow path, 17 ... post-processing section, 18, 19 ... unloading rubber roll

Claims (2)

A composite material preparation step for obtaining a composite material mainly comprising graphite powder having an average particle size of 0.5 to 25 μm and a thermosetting resin;
A sheet preparation step of obtaining a semi-cured resin sheet made of the composite material by a heat treatment at a temperature of 40 to 50 ° C. for 2 to 120 hours ;
The heated semi-cured resin sheet is cold-pressed at a temperature lower than that of the semi-cured resin sheet by a pair of opposed molds on which gas flow path forming patterns are formed. Cold pressing process to obtain a conductive separator for
A method for producing a conductive separator for a fuel cell by a cold press method comprising:
The fuel by the cold press method, wherein the semi-cured resin sheet in the sheet preparation step is subjected to surface treatment by pressing both sides in graphite powder and attaching the graphite powder to both sides A method for producing a conductive separator for a battery. Method for producing a conductive separator for a fuel cell by cold pressing of claim 1 Symbol mounting, characterized in that before Symbol thermosetting resin as a main component phenolic resin or epoxy resin.

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