JP2013136495A - Method for producing dense carbon thin plate, and carbon thin plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a carbon thin plate capable of producing a thicker carbon thin plate than hitherto without spoiling gas impermeability.SOLUTION: This method for producing a carbon thin plate includes: an impregnation step for impregnating a mixed solution containing a phenol resin mixed with a drying oil or a constituent fatty acid of a drying oil into a paper using cellulose fibers as a raw material, to thereby obtain an impregnated paper; a drying step for drying the impregnated paper, to thereby obtain a drying-treated impregnated paper; a laminating/press-bonding step for laminating and press-bonding a plurality of drying-treated impregnated papers, to thereby obtain a laminate; and a carbonizing step for calcining and carbonizing the laminate in a non-oxidizing atmosphere. The drying step is performed so that the proportion of the mass of a solid portion determined by removing the mass of a volatile portion and the paper from the mass of the drying-treated impregnated paper to the mass of the drying-treated impregnated paper is 25-55%, and the proportion of the mass of the volatile portion to the mass of the drying-treated impregnated paper is 2.5-5.5%.

Description

  The present invention relates to a method for producing a dense carbon thin plate, and a carbon thin plate produced by the production method.

  As a method for producing a dense carbon sheet with low gas permeability, conventionally, a paper is impregnated with a solution of a thermosetting resin such as a phenol resin, and a plurality of sheets of paper impregnated with a resin solution are laminated and pressed to form a laminate. A method of firing and carbonizing the laminate has been proposed (see, for example, Patent Document 1). The carbon thin plate thus obtained is made of amorphous carbon, and is used for applications that require gas impermeability and electrical conductivity, such as fuel cell separators. Patent Document 1 proposes that paper or a resin liquid contain graphite powder or carbon fiber in order to increase the electric conductivity of the obtained carbon thin plate.

  In the production method described above, gas is generated due to decomposition of the resin during firing, foaming occurs in the laminate, and many pores are formed in the resulting carbon thin plate, which may result in insufficient gas impermeability. Therefore, it has been proposed to mix a drying oil or a constituent fatty acid thereof with a thermosetting resin solution (see Patent Document 2). Thereby, it is considered that the resin is denatured, the thermal decomposition reaction becomes gentle, and the formation of pores is suppressed.

  In addition, for the purpose of increasing the gas impermeability of the carbon thin plate, a method for controlling the average porosity of the paper and the amount of the resin liquid carried on the paper is intended to sufficiently fill the pores of the paper with resin. Have been proposed (see Patent Document 3). Furthermore, it is considered that the occurrence of cracks during firing is caused by the magnitude of thermal shrinkage, and a method in which paper before impregnation with a resin liquid is preliminarily heated and contracted to some extent has been proposed (Patent Document 4). reference).

  However, in the above prior art, the thickness of the laminate before firing is only about 1.5 mm, and the thickness of the carbon thin plate obtained after firing (after carbonization) is less than 0.5 mm. For this reason, a carbon thin plate having a larger thickness has been demanded. In simple terms, it can be envisaged to increase the number of sheets of paper impregnated with resin liquid, but in that case, voids are formed between the layers, or separation between layers is likely to occur. May decrease.

  Therefore, in view of the above circumstances, the present invention provides a method for producing a dense carbon thin plate capable of producing a carbon thin plate having a thickness greater than that of the conventional one without impairing gas impermeability, and the production method. An object of the present invention is to provide a carbon thin plate manufactured by the above method.

  In order to solve the above-mentioned problems, a method for producing a dense carbon thin plate according to the present invention is described as follows: “A paper solution made of cellulose fiber is impregnated with a mixed solution containing a dry resin or a phenol resin in which a constituent fatty acid of a dry oil is mixed. An impregnation step for obtaining an impregnated paper, a drying step for drying the impregnated paper to obtain an impregnated paper after drying treatment, and a laminated crimping step for laminating a plurality of the impregnated paper after the drying treatment to obtain a laminate. And a carbonization step of firing and carbonizing the laminate in a non-oxidizing atmosphere, and the drying step is a mass of solid content excluding volatile matter and the mass of the paper from the mass of the impregnated paper after the drying treatment. So that the ratio of the mass of the impregnated paper after the drying treatment to 25% to 55% and the ratio of the volatile matter mass to the mass of the impregnated paper after the drying treatment is 2.5% to 5.5%. Is done.

  Examples of the “paper made from cellulose fibers” include paper made from natural fibers such as wood pulp, mulberry, Mitsumata, hemp, and cotton, and natural cellulose regenerated fibers (such as rayon).

  Examples of “drying oil” in “drying oil or constituent fatty acid of drying oil” include tung oil, linseed oil, poppy oil, perilla oil, sesame oil, safflower oil, and sunflower oil. Moreover, the "mixed solution" containing these and a phenol resin can use the solution which adjusted the density | concentration and the viscosity with the organic solvent, and toluene, acetone, ethanol etc. can be used as an organic solvent. Hereinafter, phenol resins and phenol resins modified by mixing with drying oil or fatty acids constituting drying oil may be collectively referred to simply as “resins”.

  The “non-oxidizing atmosphere” can be an inert gas such as argon gas, a nitrogen gas, a mixed gas atmosphere thereof, or a vacuum atmosphere.

  The “ratio of the mass of the solid content to the mass of the impregnated paper after the drying treatment” (hereinafter sometimes referred to as “solid content ratio”) is mainly influenced by the ratio of the resin solid content in the mixed solution. When the ratio of the resin solid content in the mixed solution is large, the viscosity of the mixed solution increases and the paper is not sufficiently impregnated (the mixed solution is not easily penetrated into the inside of the paper). The amount of gas generated by the thermal decomposition of the increases. On the other hand, when the ratio of the resin solid content in the mixed solution is small, the permeability of the mixed solution to paper increases, but the amount of resin carried on the paper decreases and the density of each layer in the laminate decreases. At the same time, the adhesion between the layers tends to be insufficient, and the resulting carbon thin plate has insufficient gas impermeability.

  The “ratio of the mass of the volatile matter relative to the mass of the impregnated paper after the drying treatment” (hereinafter sometimes referred to as “the volatile matter percentage”) is a ratio of the volatile matter remaining after the drying step, and is mainly dried. It is affected by temperature, drying time and the proportion of organic solvent in the mixed solution. When the drying temperature is high, penetration of the mixed solution into the paper proceeds at the start of drying, but the volatile component ratio tends to decrease, and when the drying temperature is low, the volatile component tends to remain. When the proportion of the organic solvent in the mixed solution is small, the viscosity of the mixed solution tends to increase and the paper impregnation tends to be insufficient. On the other hand, when the proportion of the organic solvent in the mixed solution is large, the permeability of the mixed solution into the paper is high, but pores are likely to remain in the impregnated paper after the drying treatment, and the resulting carbon thin plate has a gas impermeability. It tends to be insufficient.

  As a result of the study, the inventors have determined that the amount of resin impregnated in the paper is sufficient by setting both the solid content ratio and the volatile content ratio in the impregnated paper after the drying treatment within a predetermined range. The present inventors have found that it is possible to laminate a large number of impregnated papers with good interlayer adhesion, and to suppress foaming and swelling during firing. And according to this invention of the said structure, as it mentions later, manufacturing a carbon thin plate with a thickness larger than the conventional carbon thin plate while having a gas impermeability equivalent to or higher than that of the conventional carbon thin plate. Can do.

  The manufacturing method of the dense carbon thin plate concerning this invention shall be "the said lamination | stacking crimping | compression-bonding process is performed by the pressure of 1.5 MPa-5.0 MPa" in addition to the said structure.

  If the pressure in the lamination crimping process is high, the adhesion between the layers in the laminate can be increased, but the gas generated by the thermal decomposition of the resin during firing is less likely to be exhausted from the layers, causing swelling and delamination in the laminate. It will be easy. In the present invention, by adjusting the pressure in the lamination pressure bonding step to a range of 1.5 MPa to 5.0 MPa, the layers are bonded to each other to the extent that a path for discharging the gas generated by thermal decomposition remains. Thereby, the swelling and peeling at the time of baking are suppressed, and a carbon thin plate with high gas impermeability can be manufactured with a high yield (ratio in which a good product is obtained).

  In addition to the above-described structure, the method for producing a dense carbon thin plate according to the present invention can be “the carbonization step is performed at a temperature increase rate of 3.2 ° C./hr or more”.

  If the heating rate in the carbonization process is too high, the thermal decomposition of the resin proceeds rapidly, and foaming and swelling are likely to occur in the laminate, which may reduce the yield of carbon thin plates (ratio of the number of non-defective products in the number of production). There is. Therefore, conventionally, the carbonization process took several tens of days to several months. On the other hand, in the present invention having the above-described configuration, even when the temperature rising rate in the carbonization step is 3.2 ° C./hr or more, which is larger than the conventional temperature rising rate, foaming and swelling are suppressed and the yield is high. Carbon sheet can be manufactured and production efficiency is high. If the heating rate is in the range of 3.2 ° C./hr or more and 3.6 ° C./hr or less, the carbon thin plate can be produced with an extremely high yield while ensuring the production efficiency on the industrial production scale. This is more preferable.

  In addition to the above configuration, the method for producing a dense carbon thin plate according to the present invention may be “the carbonization step is performed in a state where the laminate is sandwiched between expanded graphite sheets”.

  An expanded graphite sheet is a graphite sheet obtained by rapidly heating graphite as an intercalation compound, gasifying an interlayer material to widen a layer interval, and then rolling, and has a thickness of 0.5 mm to 2.0 mm. Can be preferably used. In the above prior art, for the purpose of preventing warpage and the like, it is disclosed that the laminate is fired in a state of being sandwiched between “graphite plates”. It must be a plate material having a thickness of 5 mm or more, and is different from the expanded graphite sheet of the present invention.

  The expanded graphite sheet has a large thermal conductivity in the surface direction. Therefore, by performing carbonization with the laminate sandwiched between expanded graphite sheets, the temperature distribution in the laminate can be made closer to the uniform. Further, the expanded graphite sheet is excellent in slipperiness. Therefore, the laminate sandwiched between the expanded graphite sheets tends to contract smoothly along the expanded graphite sheet. Therefore, according to the present invention having the above-described configuration, it is possible to produce a carbon thin plate having no deformation while suppressing warpage or undulation of the laminate in the carbonization step.

  The method for producing a dense carbon thin plate according to the present invention includes, in addition to the above configuration, “the impregnation step uses paper containing 2% by mass to 12% by mass of carbonaceous filler as the paper, or the mixing It is carried out using the above-mentioned mixed solution containing a carbonaceous filler in which the ratio of the carbonaceous filler to the solid content obtained by removing volatile components from the solution is 1% by mass to 11% by mass.

  As the “carbonaceous filler”, graphite powder, carbon fiber, carbon black and the like can be used.

  The matrix of the carbon thin plate obtained through the carbonization step is amorphous carbon, and it cannot be said that the carbon material has high electrical conductivity. Then, the electrical conductivity of the carbon thin plate manufactured can be improved by containing a carbonaceous filler in paper or a mixed solution. However, when the amount of the carbonaceous filler to be contained increases, the gas impermeability of the produced carbon thin plate tends to decrease. According to the present invention, by impregnating paper with carbonaceous filler in a predetermined range or mixed solution containing carbonaceous filler in a predetermined range, the effect of increasing electrical conductivity is achieved. While being obtained, a carbon thin plate having practical gas impermeability can be produced.

  The method for producing a dense carbon thin plate according to the present invention includes, in addition to the above-described configuration, “a graphitization step in which, after the carbonization step, the carbonized laminate is fired at 1700 ° C. to 2300 ° C. in a non-oxidizing atmosphere and graphitized. It can be included.

  By firing the carbon thin plate made of amorphous carbon obtained through the carbonization step at 1700 ° C. to 2300 ° C., the amorphous carbon is graphitized, and a carbon thin plate having high electrical conductivity can be produced. However, when graphitized carbon crystals grow abnormally, gas impermeability is lowered and delamination tends to occur. In the present invention, by setting the graphitization temperature not to exceed 2300 ° C., it is possible to produce a carbon thin plate in which electrical conductivity is improved and delamination is suppressed without impairing gas impermeability.

Next, the carbon thin plate according to the present invention is “a carbon thin plate of amorphous carbon having a nitrogen gas permeability of 2 × 10 ⁻¹² cc / cm ² · sec to 4 × 10 ⁻⁷ cc / cm ^2. in seconds, the thickness is 0.5 mm to 2.4 mm ”.

  By the above-described impregnation step, drying step, lamination pressure bonding step, and method for producing a dense carbon thin plate comprising a carbonization step, as described later, while having a gas impermeability equivalent to or higher than that of a conventional carbon thin plate, It is possible to obtain a carbon thin plate having the present configuration that is thicker than a conventional carbon thin plate. That is, as described above, in the prior art, the thickness of the laminate before firing is limited to 1.5 mm at most, and the thickness of the carbon thin plate obtained through the carbonization step is less than 0.5 mm. On the other hand, according to the above-described method for producing a dense carbon thin plate, it is possible to produce a carbon thin plate (amorphous carbon) having a thickness of 0.5 mm or more which is larger than the conventional one, and has a thickness of at least 2.4 mm. It was confirmed that a thin carbon plate could be realized. In addition, a carbon thin plate (amorphous carbon) having the same thickness as that of the prior art is obtained by the method for manufacturing a dense carbon thin plate having the above-described impregnation step, drying step, lamination pressure bonding step, and carbonization step. Of course you can.

Further, the carbon thin plate according to the present invention, the "a graphitized carbon sheet, a nitrogen gas permeability ^{2 × 10 -11 cc / cm 2} · sec~8 × 10 -7 cc / cm 2 · sec, The thickness is 0.4 mm to 2.3 mm ”.

  As described later, the gas impermeability equivalent to or higher than that of a conventional carbon thin plate is obtained by the method for producing a dense carbon thin plate having the impregnation step, the drying step, the lamination pressure bonding step, the carbonization step, and the graphitization step. While having it, the carbon thin plate of this structure with a large thickness compared with the conventional carbon thin plate can be obtained. That is, in the prior art, the thickness of the carbon thin plate before firing is as small as about 1.5 mm, so the thickness of the carbon thin plate carbonized and graphitized is less than 0.4 mm. On the other hand, according to the method for producing a dense carbon thin plate having the above-described impregnation step, drying step, lamination pressure bonding step, carbonization step, and graphitization step, the thickness is 0.4 mm or more which is larger than the conventional one. It was confirmed that a carbon thin plate (graphitized) can be produced and a carbon thin plate having a thickness of at least 2.3 mm can be realized. In addition, a carbon thin plate (graphitization) having the same thickness as that of the prior art is produced by the method for producing a dense carbon thin plate having the above-described impregnation step, drying step, lamination pressure bonding step, carbonization step, and graphitization step. Of course you can get.

  As described above, as an effect of the present invention, a method for producing a dense carbon thin plate capable of producing a carbon thin plate having a larger thickness than the conventional one without impairing gas impermeability, and the production method. A manufactured carbon sheet can be provided.

  Hereinafter, specific embodiments of the present invention will be described. A method for producing a dense carbon thin plate according to the first embodiment (hereinafter simply referred to as “production method”) is a mixture comprising a phenol resin in which a dry fiber or a constituent fatty acid of a dry oil is mixed with paper using cellulose fibers as a raw material. An impregnation step for impregnating a solution to obtain an impregnated paper; a drying step for drying the impregnated paper to obtain an impregnated paper after drying treatment; And a carbonization step for firing and carbonizing the laminate in a non-oxidizing atmosphere, and the drying step is a drying treatment of the mass of the solid content excluding the volatile matter and the mass of the paper from the mass of the impregnated paper after the drying treatment. The ratio is 25% to 55% with respect to the mass of the post-impregnated paper, and the ratio of the mass of the volatile matter to the mass of the impregnated paper after the drying treatment is 2.5% to 5.5%. .

  More specifically, examples of the paper to be impregnated with the mixed solution in the impregnation step include commercially available kraft paper, linter paper, and kraft / linter mixed paper.

  In addition, as the paper to be impregnated with the mixed solution, a paper containing a carbonaceous filler obtained by blending a paper raw material with a carbonaceous filler and making paper can be used. As the carbonaceous filler, graphite powder, carbon fiber, carbon black, or the like can be used. In the case of graphite powder and carbon black, the particle diameter is desirably 20 μm or less. In the case of carbon fiber, it is desirable that the fiber diameter is 20 μm or less and the length is 3 mm or less. In addition, the mixing ratio of the carbonaceous filler to the paper is desirably 2% by mass to 12% by mass. If the size of the carbonaceous filler is large, or if the proportion of carbonaceous filler in the paper is large, the denseness and uniformity of the paper structure will be reduced, and the mixed solution carried on the paper will be insufficient or unsatisfactory. There is a possibility that the gas impermeability may be lowered due to uniformity. On the other hand, when the blending ratio of the carbonaceous filler to the paper is small, the effect of increasing the electrical conductivity of the produced carbon thin plate cannot be sufficiently exhibited.

  As the mixed solution to be impregnated into the paper in the impregnation step, a solution obtained by dissolving a dry oil or a phenol resin mixed with a constituent fatty acid of the dry oil in an organic solvent is used. As the organic solvent, toluene, acetone, ethanol or the like can be used.

  Moreover, it can replace with the case where a paper contains a carbonaceous filler, and can also contain a carbonaceous filler in a mixed solution. As the carbonaceous filler in this case, graphite powder, carbon fiber, carbon black and the like can be used as described above. The size of the graphite powder and carbon black is 20 μm or less in the case of graphite powder and carbon black. In this case, it is desirable that the fiber diameter is 20 μm or less and the length is 3 mm or less. Moreover, as a mixed solution containing a carbonaceous filler, the mixed solution from which the ratio of the carbonaceous filler with respect to solid content which removed the volatile matter from the mixed solution will be 1 mass%-11 mass% is desirable. When the size of the carbonaceous filler is large, the carbonaceous filler adhering to the surface of the paper increases, and it becomes easy to peel off during firing. Moreover, when the ratio of the carbonaceous filler in the mixed solution is large, the distribution of the carbonaceous filler and the resin component in the mixed solution supported on paper is likely to be non-uniform, and the gas impermeability may be reduced. On the other hand, when the ratio of the carbonaceous filler in the mixed solution is small, the effect of increasing the electrical conductivity of the produced carbon thin plate cannot be sufficiently exhibited.

  In the impregnation step, it is desirable to sufficiently remove moisture by heating and drying the paper prior to the operation of impregnating the paper with the mixed solution. Insufficient water removal from the paper makes it difficult for the organic solvent-based mixed solution to impregnate the paper. In addition, moisture is left behind in the mixed solution impregnated in the pores of the paper, and then the laminated crimping process is performed. In the carbonization process, foaming, swelling, delamination and the like are likely to occur. The heating for drying the paper is desirably performed at a temperature of 100 ° C. or more and not exceeding 230 ° C. If it is 100 ° C. or lower, moisture hardly evaporates, and if it exceeds 230 ° C., the cellulose fibers of the paper are deteriorated, and the mechanical strength of the finally produced carbon sheet may be lowered.

  The impregnated paper obtained through the impregnation step is dried in a dryer maintained at a predetermined temperature in the range of 110 ° C. to 150 ° C. in the drying step. Depending on the concentration of the mixed solution (resin concentration) in the impregnation step and the amount of paper impregnation, the solid content ratio is adjusted to 25% to 55%, and the concentration of the mixed solution (organic solvent concentration) in the impregnation step and drying are adjusted. Adjustment is performed so that the volatile content ratio is 2.5% to 5.5% depending on the drying temperature and drying time in the process.

The solid content ratio and the volatile content ratio are calculated by the following equations, respectively. Here, the “volatile matter” includes the organic solvent content that is removed by further heat-treating the impregnated paper after the drying treatment, and the polymerization reaction of the unreacted resin in the liquid impregnated in the paper by further heat treatment. The amount of water that progresses further and vaporizes as a result of the polymerization reaction is included. Therefore, hereinafter, the impregnated paper after the process of removing the volatile matter from the impregnated paper after the drying treatment is referred to as “impregnated paper after the volatile matter removal”. The treatment for removing volatile components from the impregnated paper after drying treatment can be performed by heating the impregnated paper after drying treatment at 150 ° C. for 30 minutes.
Solid content ratio = ((mass of impregnated paper after removal of volatile matter) − (mass of paper)) × 100 / (mass of impregnated paper after drying treatment)
Volatile content ratio = ((mass of impregnated paper after drying treatment) − (mass of impregnated paper after removal of volatile matter)) × 100 / (mass of impregnated paper after drying treatment)

  The post-drying impregnated paper that has undergone the drying process is laminated in a laminating and crimping process, and heat-pressed to obtain a laminate. The heating temperature is preferably 130 to 150 ° C., which is the steam heating temperature, according to a conventional method. The pressure bonding pressure is 1.5 MPa to 5.0 MPa. If the pressure is too low, the adhesion between the laminated impregnated papers will be weak, while if the pressure is too high, the adhesion between the laminated impregnated papers will be too high, and the thermal decomposition of the resin will occur in the carbonization step performed later. This makes it difficult to smoothly discharge the gas generated.

  In the carbonization step, the laminate obtained through the laminate pressure bonding step is fired in a state of being sandwiched between expanded graphite sheets. At this time, the plurality of laminates can be stacked by sandwiching an expanded graphite sheet between each of the plurality of laminates, and further, the whole can be embedded in the packing powder and fired in a state of being sandwiched between the graphite plates from the outside. Thus, by sandwiching the laminate in the expanded graphite sheet having a high thermal conductivity, the temperature distribution in the laminate becomes uniform, and the laminate smoothly contracts along the expanded graphite sheet having a high slip property. Warpage and deformation of the laminate are suppressed. Furthermore, since the whole several laminated body is pinched | interposed into the graphite board and baked in the state embedded in the filling powder, the curvature and deformation | transformation of a laminated body are suppressed more effectively.

  Firing in the carbonization step is performed by raising the temperature from room temperature to 800 ° C. in an electric furnace maintained in a non-oxidizing atmosphere. The lower the temperature increase rate, the more the thermal decomposition of the resin becomes milder, and the incidence of defective products due to foaming and swelling decreases. On the other hand, if the temperature increase rate is too small, the time required for firing (days) is longer and the carbon thin plate The production efficiency is poor.

  The carbon thin plate made of amorphous carbon manufactured through the impregnation step to the carbonization step has a thickness of 1.7 mm to 2.4 mm, which is larger than that of the conventional carbon thin plate, as shown in Examples described later. Nevertheless, it has a gas impermeability equivalent to or higher than that of conventional carbon thin plates.

  Next, the manufacturing method of 2nd embodiment is demonstrated. The production method of the second embodiment is the same as the production method of the first embodiment until the carbonization step, and after the carbonization step, the carbonized laminate is calcined at 1700 ° C. to 2300 ° C. in a non-oxidizing atmosphere. The graphitization process is carried out.

  In the graphitization step, several to ten carbon thin plates made of amorphous carbon obtained through the carbonization step are stacked and sandwiched between expanded graphite sheets. With this as a unit, a plurality of units are laminated, and the whole is sandwiched between carbon plates, embedded in packing powder, and fired. The carbon thin plate that has become amorphous carbon has higher thermal conductivity than the laminate before carbonization, so it can be prevented from warping and deformation without having to be sandwiched between graphite sheets. Thus, a graphitized carbon sheet can be produced with high yield.

  Firing in the graphitization step is performed by raising the temperature to a predetermined temperature within a range of 1700 ° C. to 2300 ° C. over several hours to several tens of hours in an electric furnace such as an Atchison furnace held in a non-oxidizing atmosphere. If the firing temperature exceeds 2300 ° C., graphite crystals grow abnormally, the structure becomes porous, and gas impermeability may be reduced. Further, due to the anisotropy in the graphite crystals, delamination is likely to occur, and the yield may be reduced.

  The graphitized carbon sheet produced through the impregnation step to the graphitization step has a large thickness as described above, and has a high electric conductivity and a practical gas impermeability as described later. ing.

  Next, the grounds for defining the conditions of the manufacturing method of the present embodiment as described above will be described with specific examination results. The examination was performed using the following 36 types of samples.

In Samples 1 to 20, Kraft / Linter mixed paper (made by Oji Paper Co., Ltd., 100 g / m ² ) was used as the paper. In Samples 21 to 36, after preparing a papermaking stock solution containing wood pulp, water, and graphite powder, a round net paper machine was used, and 100 g of rice basis weight was the same as the above Kraft / Linter mixed paper. Paper made of graphite powder mixed paper of / m ^{2 to} 120 g / m ² was made. As the graphite powder, pulverized artificial graphite for blast furnace bricks having an average particle diameter of 14 μm was used. The ratio of the graphite powder to the graphite powder mixed paper was 5 mass%, 5 mass%, 8 mass%, 12 mass%, and 14 mass%. Here, the ratio of graphite to the graphite powder mixed paper was calculated by the following formula.
(Mass of graphite powder) × 100 / ((mass of softwood kraft pulp (NKP)) + (mass of graphite powder) + (mass of acrylic flocculant))
The proportion of the acrylic flocculant was 3% by mass of the graphite powder mixed paper regardless of the proportion of the graphite powder.

  Both kraft / linter mixed paper and graphite powder mixed paper were cut into 300 mm × 300 mm. The cut paper was heated at 230 ° C. to sufficiently remove moisture.

  As a mixed solution to be impregnated into paper (drying oil or a mixed solution containing a phenolic resin mixed with constituent fatty acids of drying oil), tung oil modified with tung oil and phenol, then added with formalin to proceed with the reaction A phenolic resin was prepared by diluting with toluene. Samples 1 to 4 out of samples using Kraft / Linter mixed paper as paper and Samples 21 to 26 using graphite powder mixed paper as paper, the mixed solutions prepared as described above were used as they were. In the state of (impregnation step).

On the other hand, for Sample 5 to Sample 20, the mixed solution prepared as described above was impregnated with a mixed solution obtained by mixing graphite powder (impregnation step). As the graphite powder, the same powder as above (powder obtained by pulverizing artificial graphite for blast furnace bricks to an average particle diameter of 14 μm) was used. The ratio of the graphite powder in the mixed solution is 5 types in which the ratio of the graphite powder to the solid content obtained by removing the volatile component from the mixed solution is 1% by mass, 3% by mass, 8% by mass, 11% by mass, and 13% by mass. did. Here, the ratio (mass%) of the graphite powder with respect to solid content which removed the volatile matter from the mixed solution was computed by following Formula.
(Mass of graphite powder in 50 ml of mixed solution) × 100 / (Mass of residual after heating 50 ml of mixed solution at 150 ° C. for 1 hour)

  The impregnated paper impregnated with the mixed solution was dried in a dryer maintained at 130 ° C. (drying process). Samples with different solid content ratios and volatile content ratios were prepared by adjusting the concentration of the mixed solution, the drying time, and the like.

  After the drying treatment, 15 to 26 impregnated papers were laminated, pressed at a predetermined pressure for 30 minutes at a temperature of 150 ° C., and pressed to form a laminated body having a thickness of 2.6 mm to 3.7 mm (laminated pressure bonding). Process).

  For each sample, Table 1 summarizes the type of paper, the sample added with graphite, the ratio, the solid content ratio, the volatile content ratio, the number of stacked layers, the pressure of pressure bonding, and the thickness of the molded laminate.

About each sample, a laminated body and an expanded graphite sheet were piled up alternately, 10 laminated bodies were piled up, and also the whole was pinched | interposed with a pair of graphite plate of thickness 5mm, and was embed | buried in the stuffing powder. In this state, a load of about 5 g / cm ² was applied, left in an electric furnace, and heated from normal temperature to 800 ° C. in a non-oxidizing atmosphere (carbonization step). Regarding the rate of temperature increase, two types of 3.2 ° C./hr and 3.6 ° C./hr were used. Here, as the expanded graphite sheet, a TYK graphite sheet having a thickness of 0.8 mm was used.

  For comparison, a graphite plate having a thickness of 5 mm is used instead of the expanded graphite sheet, and the laminate and the graphite plate are alternately stacked to stack 10 laminates. A sample sandwiched between a pair of graphite plates and embedded in the stuffed powder in that state was also subjected to the same load, heated from room temperature to 800 ° C. at a temperature rising rate of 3.2 ° C./hr, and fired.

The appearance of the carbon thin plate taken out from the electric furnace cooled after firing was observed with the naked eye for each of the sandwiched state in the carbonization process and the case where the temperature increase rate conditions were different, and warped, swollen, separated, cracked. The number of non-defective products that did not occur was counted. That is, the comparison of the three conditions A, B, and C in the carbonization process. The comparison results are shown in Table 2.
Condition A: The laminate is sandwiched between expanded graphite sheets, and the temperature rise rate is 3.2 ° C./hr.
Condition B: Laminate is sandwiched between expanded graphite sheets, heating rate 3.6 ° C./hr
Condition C: The laminate is sandwiched between graphite plates, and the heating rate is 3.2 ° C./hr.

  Samples 1, 3, 5 to 8, 24, 26, 28, and 29 were all good in appearance in all cases. On the other hand, Samples 11, 14, 20, 31, and 36 warped in total, and defects such as swelling, peeling, and cracking occurred. For other samples with different numbers of non-defective products depending on the conditions, a comparison was made between the case where the laminate was sandwiched between the expanded graphite sheets and the same conditions and only the temperature increase rate was different (conditions A and B). ), The one with a lower temperature increase rate (Condition A) tends to have more non-defective products, the temperature increase rate conditions are the same, and the material between the laminates differs depending on whether it is an expanded graphite sheet or a graphite plate. When the cases were compared (contrast between conditions A and C), the number of non-defective products was larger when the material between the laminates was an expanded graphite sheet (condition A). From the above, it was considered that a carbon thin plate having a good appearance can be produced in a high yield by sandwiching the laminate between expanded graphite sheets and firing at a temperature rising rate of about 3.2 ° C./hr. Moreover, if the rate of temperature increase was in the range of 3.2 ° C./hr to 3.6 ° C./hr, it was considered that both the yield and production efficiency of the carbon thin plate were within a practical range.

  The carbon thin plate obtained through the carbonization process under the condition A with the highest percentage of good products was measured for thickness, gas permeability, electrical resistivity, and three-point bending strength by the following methods. Went. Here, the gas permeability was measured by using a soap film flow meter and measuring the nitrogen gas permeation amount per unit time under a differential pressure of 0.1 MPa. The electrical specific resistance was calculated from a voltage value when a strip-shaped test piece having a width of 20 mm was cut out from a carbon thin plate and the distance between the electrodes was 50 mm and the current was 1A. Further, the three-point bending strength was measured by cutting a strip-shaped test piece having a width of 20 mm from a carbon thin plate, and having a distance between supporting points of 20 mm and a crosshead speed of 1.5 mm / min. All tests were conducted in an environment maintained at 20 ° C. ± 3 ° C. In each test, three test pieces were measured and the average value was calculated. The measurement results are shown in Table 1.

  As is clear from Table 1, all samples except the samples 11, 14, 20, 31, and 36, which were defective in appearance, were thicker than the conventional carbon thin plate. Carbon thin plates of 0.7 mm to 2.4 mm were obtained.

However, the sample 26 had insufficient gas impermeability among the measured physical property values. In other samples 1 to 10, ¹² , 13, 15 to 19, 21 to 25, 27 to 30, and 32 to 35, the nitrogen gas permeability is 2 × 10 ⁻¹² cc / cm ² · sec to 4 × 10 ^{−. 7} cc / cm ² · sec, excellent gas impermeability comparable to that of conventional carbon thin plates, and electrical resistivity of 1.8 × 10 ⁻³ Ω · cm to 5.3 × 10 ⁻³ Ω · cm, which is similar to the electrical specific resistance of the conventional carbon thin plate. In addition, the three-point bending strength was also in a practical range of 99 MPa to 151 MPa.

From the above results, the samples 11, 14, 20, 31, and 36, all of which were defective in appearance, and the sample 26 that had insufficient physical properties were excluded, and the conditions under which only good products could be manufactured were examined. As a result, the following conditions were extracted.
When carbon is not included in the paper or mixed solution to be impregnated:
Solid content ratio = 25 mass% to 55 mass%, and volatile content ratio = 2.5 mass% to 5.5 mass%

In addition, when carbon is included in the paper or the mixed solution to be impregnated, only good products are produced. Therefore, the following conditions were extracted as conditions to be provided in addition to the solid content ratio and the volatile content ratio in the above ranges.
In the case of paper: ratio of graphite powder to paper = 2 mass% to 12 mass%
In the case of a mixed solution: ratio of graphite powder to solid content obtained by removing volatile components from the mixed solution = 1 mass% to 11 mass%

  Next, non-defective amorphous carbon thin plates (samples 1 to 10, 12, 13, 15 to 19, 21 to 25, 27 to 30, and 32 to 35) were graphitized. In this process, three non-defective carbon thin plates are stacked one by one between expanded graphite sheets, and the whole is further sandwiched between a pair of graphite plates having a thickness of 5 mm and heated in an Atchison-type graphitization furnace (graphitization). Process). There were two heating temperatures of 2300 ° C. and 2500 ° C., and the temperature was raised from normal temperature over 13 hours and 15 hours, respectively, and graphitized. The furnace temperature was measured with a radiation thermometer.

  The appearance of the graphitized carbon thin plate taken out from the furnace cooled after firing was observed with the naked eye, and the presence or absence of warpage, blistering, peeling, cracking, etc. was observed. As a result, when the firing temperature was 2300 ° C., the total number was good in appearance. On the other hand, when the firing temperature was 2500 ° C., cracks or cracks occurred in the whole number.

  Next, the non-defective graphitized carbon sheet (fired at 2300 ° C.) was measured for nitrogen gas permeability, electrical resistivity, and three-point bending strength in the same manner as described above. Table 3 shows the measurement results and the thickness measurement results of the graphitized carbon sheet.

Table 3 As seen from the comparison between Table 1, the electrical resistivity is ^{1.2 × 10 -3 Ω · cm~3.6 ×} 10 -3 Ω · cm, in all graphitized samples, electrical The specific resistance was smaller than that of amorphous carbon (after the carbonization process and before the graphitization process). That is, the electrical conductivity increased by graphitization. On the other hand, the gas for the impermeable, as it tended to decrease by graphitization, but still had a gas impermeable comparable to conventional carbon thin (nitrogen gas permeability, 2 × 10 ^{- 11 cc / cm 2 · sec~8 ×} 10 -7 cc / cm 2 · sec). Further, the three-point bending strength tended to decrease slightly due to graphitization, but was still in a practical range of 92 MPa to 140 MPa.

  For samples 1, 3, 5-8, 24, 28, and 29, all of which were good in appearance after the carbonization step, three carbon thin plates (amorphous carbon) were sandwiched between the expanded graphite sheets. When they were stacked and fired at 2300 ° C., almost all of the samples were graphitized carbon thin plates with good appearance. From this, it was considered that the action of suppressing deformation such as warpage and swelling by sandwiching between the expanded graphite sheets during firing is more important in the carbonization process than in the graphitization process.

  Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited to the above-described embodiments, and various improvements and design changes can be made without departing from the scope of the present invention. It is.

Japanese Patent Laid-Open No. 60-161144 JP 60-231470 A Japanese Patent Publication No. 8-25817 JP-A-60-145952

Claims (8)

Impregnation step of impregnating paper made of cellulose fiber with a mixed solution containing a phenolic resin mixed with a dry oil or a constituent fatty acid of a dry oil to obtain an impregnated paper;
Drying the impregnated paper and making it impregnated paper after drying treatment;
A lamination pressure bonding step of laminating a plurality of impregnated papers after the drying treatment and pressing to obtain a laminate;
A carbonization step of firing and carbonizing the laminate in a non-oxidizing atmosphere,
In the drying step, the ratio of the mass of the solid content obtained by removing the volatile content and the mass of the paper from the mass of the impregnated paper after the drying treatment to the mass of the impregnated paper after the drying treatment is 25% to 55%, and the volatilization is performed. A method for producing a dense carbon thin plate, wherein the ratio of the mass of the minute to the mass of the impregnated paper after the drying treatment is 2.5% to 5.5%. The method for producing a dense carbon thin plate according to claim 1, wherein the lamination pressure bonding step is performed at a pressure of 1.5 MPa to 5.0 MPa. The method for producing a dense carbon thin plate according to claim 1, wherein the carbonization step is performed at a temperature rising rate of 3.2 ° C./hr or more. The method for producing a carbon thin plate according to any one of claims 1 to 3, wherein the carbonization step is performed in a state where the laminate is sandwiched between graphite sheets. In the impregnation step, a paper containing 2% by mass to 12% by mass of a carbonaceous filler is used as the paper, or the ratio of the carbonaceous filler to the solid content obtained by removing volatile components from the mixed solution is 1% by mass. It is performed using the said mixed solution containing a carbonaceous filler used as -11 mass%, The manufacturing method of the carbon thin plate as described in any one of Claim 1 thru | or 4 characterized by the above-mentioned. 6. The method according to claim 1, further comprising a graphitization step of baking and graphitizing the carbonized laminate at 1700 ° C. to 2300 ° C. in a non-oxidizing atmosphere after the carbonization step. The manufacturing method of the carbon thin plate as described in one. A carbon thin plate of amorphous carbon,
A carbon thin plate having a nitrogen gas permeability of 2 × 10 ⁻¹² cc / cm ² · sec to 4 × 10 ⁻⁷ cc / cm ² · sec and a thickness of 0.5 mm to 2.4 mm. A graphitized carbon sheet,
Nitrogen gas permeability at ^{2 × 10 -11 cc / cm 2} · sec~8 × 10 -7 cc / cm 2 · sec, the carbon sheet, wherein the thickness is 0.4Mm～2.3Mm.