JP2009057261A - Method for producing carbon molding material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a carbon molding material having low anisotropy in physical properties, which suppresses the anisotropy and strain caused by shrinkage upon firing in a molded body accompanying the flow of the molding material upon injection molding. <P>SOLUTION: The method for producing a carbon molding material is characterized in that, to 100 pts.wt. of carbon powder having the average particle diameter of 100 to 2,000 μm, pitch powder having the average particle diameter of ≤100 μm and whose softening point is higher by 30 to 250°C than the temperature of a die upon injection molding is mixed in a ratio of 3 to 30 pts.wt., a resin solution obtained by dissolving a molding assistant composed of a thermosetting resin having an actual carbon ratio of ≥40% and an organic substance whose melting point is 40 to 150°C into an organic solvent is added to the mixed powder, kneading is performed at quantitative ratios in which, to 100 pts.wt. of the carbon powder, the resin solid content in the thermosetting resin is controlled to 10 to 40 pts.wt. and the content of the molding assistant is controlled to 0.1 to 5 pts.wt., subsequently, the kneaded matter is dried and pulverized, so as to produce molding powder, the molding powder is molded by injection molding, injection compression molding or transfer molding, and the obtained molded body is subjected to setting treatment at 180 to 280°C, and is next subjected to firing treatment at ≥800°C in a nonoxidizing atmosphere. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a carbon molding material for firing a molded article obtained by injection molding, injection compression molding or transfer molding, and in particular, shrinkage anisotropy during firing is small, and anisotropy of physical properties of the carbon material is reduced. The present invention relates to a method for producing a carbon molding material.

  In addition, it is possible to produce a carbon molding material that approximates the target final product shape, for example, when producing a deformed, complex shape carbon molding material, it is possible to minimize the part to be machined in post-processing, Furthermore, it is related with the manufacturing method of the carbon molding material which can suppress phenomena, such as a swelling and a crack which generate | occur | produce at the time of baking.

Carbon materials have excellent heat resistance and high temperature strength in a non-oxidizing atmosphere, and also have high electrical conductivity, thermal conductivity and chemical stability. Electricity, electronics, machinery, metallurgy, Widely used in a wide range of fields such as chemistry. Conventionally, this carbon material is made of carbonaceous powder such as coke powder, blended with a binder such as pitch or tar, heated and kneaded, then pulverized to produce the raw material powder, and the raw material powder is extruded. It is manufactured by molding, cold isostatic pressing or the like, firing the molded body, repeating pitch impregnation and refiring, and graphitizing as necessary.

  In this manufacturing process, particularly in the firing process, a large amount of volatile gas mainly derived from the binder is generated, and deformation and cracking such as swelling are likely to occur unless the generated gas is smoothly volatilized and discharged from the molded body. For this reason, it is necessary to heat the heating rate very slowly in the firing process, and the firing cycle usually requires a long period of one month or more. Further, in order to obtain a final product having a three-dimensional shape, machining is performed from a block-shaped carbon material to a desired shape, and thus there is a difficulty in that it becomes expensive.

  On the other hand, carbon powder such as graphite and a thermosetting resin with a relatively high carbonization rate are mixed and kneaded as a binder, then dried and pulverized to form a molded powder, and a molded body obtained by molding the molded powder into a desired shape is fired. There is a method to carbonize.

  And, as a molding method, there are molding methods such as injection molding, injection compression molding, transfer molding, etc. that can produce a relatively complex shaped molded body, in particular, a complex shaped molded body can be produced, An injection molding method having a short molding cycle time is useful. For example, Patent Document 1 discloses a paste-like composition in which a resin is highly bonded to the particle surface of carbon fine powder due to a mechanochemical phenomenon by adding high mechanical energy when carbon fine powder and a thermosetting resin are mixed. A manufacturing method is disclosed in which the composition is cast or injection molded and fired.

  However, the fluidity of the paste-like composition is important at the time of molding, and the amount of thermosetting resin is inevitably increased because it is necessary to maintain high fluidity particularly in injection molding. For example, in Patent Document 1, the carbon powder has an average particle size of 100 μm or less, and the amount of thermosetting resin as a binder increases. Swelling and cracking are likely to occur, and it is difficult to produce a thick carbon product.

  Therefore, in Patent Document 2, 10 to 50 parts by weight of a benzylic ether type phenol resin is added to and kneaded with 100 parts by weight of carbon powder, and this kneaded product is injection molded or extruded to form a molded body, which is made into a non-oxidizing atmosphere. A method for producing a carbon molded body that is heat-treated at a temperature of 600 ° C. or higher has been proposed.

  Patent Document 2 uses a benzylic ether type phenolic resin that can obtain a kneaded material having good fluidity even if the amount of resin added is small, and it is said that a molded body having a complicated shape can be efficiently produced by injection molding. However, benzylic ether type phenolic resin has poor releasability, so it is necessary to add a mold release agent, and there are also more difficult volatile gases generated during calcination carbonization than phenolic resin. It becomes difficult to manufacture a molded body.

  Patent Document 3 discloses a method for producing a mesocarbon powder molded body in which a uniform mixture of mesocarbon powder and an organic binder is heated and injection molded. However, since the mesocarbon powder used has a small particle size of 1 to 80 μm and a plasticizer is added to improve the fluidity during molding, the amount of gas generated during the firing process increases, and the density of the carbon sintered body There is a drawback that the strength is lowered.

Patent Document 4 injects a resin composition mainly composed of 50 to 95% by mass of a novolac phenol resin having an ortho-position bond / para-position bond abundance ratio of 3 or more and a carbonaceous material of 50 to 5% by mass. An amorphous carbon molded body obtained by carbonizing and firing a molded body is disclosed, but since the fine particle having a carbonaceous material particle size of 100 μm or less is used, the resin amount ratio of the resin composition is high, and the amount of gas generated during firing There are many difficulties.
JP 59-195515 A Japanese Patent Laid-Open No. 01-115869 Japanese Patent Laid-Open No. 08-113668 JP 2004-131527 A

  Therefore, the inventors have studied the resin composition that is an injection molding material from various aspects to solve the above problems, and injection molded a resin composition in which carbon powder and a thermosetting resin that is a binder are mixed. In the molded body, a layer rich in resin is formed on the surface layer, and this resin-rich layer becomes a dense carbon layer during firing carbonization, and the discharge of gas generated during decomposition carbonization of the resin component is hindered. I found out.

  This tendency becomes prominent when the average particle size of the carbon powder is small, the mixing ratio of the thermosetting resin is high, and the thickness of the molded body is large, and the tendency of volatile decomposition gas generated from the thermosetting resin. The discharge does not proceed smoothly and blisters and cracks occur during firing carbonization. Furthermore, since the bonding force between the carbon powder and the thermosetting resin is reduced when the molded body is fired, it cannot withstand the pressure of the decomposition gas, and the occurrence of swelling and cracking is promoted.

  In addition, in injection molding, injection compression molding, transfer molding, etc., when the molding material enters the mold cavity, the molding material spreads and is filled with air, and then the air entrained by the molding material that is filled later Since it is filled so as to be crushed, anisotropy of physical properties tends to occur in the injection direction in the molded body and the fired carbon molded body.

  For example, the physical properties of the carbon molded body after firing have low strength in the flow direction (X direction) of the molding powder to be injected, high electrical resistance, and conversely, the physical properties in the direction perpendicular to the flow direction (Y direction) are strong. Anisotropy of physical properties such as high and low electrical resistance appears.

  In addition, since a large residual stress remains in the injection-molded product, the residual stress is released in the process of curing and firing, and it expands greatly in the injection direction due to the springback, causing distortion during curing and firing, resulting in damage. There is also.

  In order to solve these problems, the inventors have intensively studied the injection molding material mainly on the particle size of the carbon powder as the raw material and the particle size of the pitch powder and its softening point. It was found that the relationship between the temperature of the mold during molding and the softening point of the pitch powder is important.

  That is, the present invention reduces the anisotropy of the molded body due to the flow of the molding material at the time of injection molding and the like, and suppresses the distortion due to the shrinkage at the time of firing, thereby reducing the shrinkage anisotropy at the time of firing. It aims at providing the manufacturing method of the carbon molding material which reduced the anisotropy of the physical property of this.

  The present invention also provides a method for producing a carbon material that approximates the shape of the final product, and the blisters that occur during firing, even when producing irregularly shaped and complex shaped carbon materials. It aims at providing the manufacturing method of the carbon molding material which can reduce phenomena, such as a crack.

  In order to achieve the above object, the method for producing a carbon molding material according to the present invention is based on 100 parts by weight of carbon powder having an average particle size of 100 to 2000 μm, the average particle size is 100 μm or less, and the softening point is at the time of injection molding. Pitch powder 30 to 250 ° C. higher than the mold temperature is mixed in a proportion of 3 to 30 parts by weight, and the mixed powder is formed of a thermosetting resin having a residual carbon ratio of 40% or more and an organic material having a melting point of 40 to 150 ° C. A resin solution in which an auxiliary agent is dissolved in an organic solvent is added, and the amount ratio of the resin solid content of the thermosetting resin to 10 to 40 parts by weight and the molding auxiliary to 0.1 to 5 parts by weight with respect to 100 parts by weight of the carbon powder. After kneading, the kneaded product is dried and pulverized to produce a molding powder. The molding powder is molded by injection molding, injection compression molding or transfer molding, and the resulting molded body is cured at a temperature of 180 to 280 ° C. And then non-oxidizing atmosphere A structural feature is that the baking treatment is performed at a temperature of 800 ° C. or higher.

  As the molding aid, stearic acid, stearate, oleic acid, polyethylene wax, carnauba wax, organic phosphate ester, crosslinked polyolefin and the like, or a mixture of two or more of these are preferably exemplified, and carbon It is preferable to add 0 to 10 parts by weight of a baking aid such as cellulose fiber, rayon fiber, acrylic resin, polystyrene resin, corn starch or walnut powder with respect to 100 parts by weight of the powder.

  The method for producing a carbon molding material of the present invention uses carbon powder and pitch powder of a specific particle size as raw materials, sets the softening point of the pitch powder to a specific range in relation to the temperature of the molding die during injection molding, The weight ratio between the carbon powder and the pitch powder, and the weight ratio between the thermosetting resin and the molding aid as a binder with respect to the carbon powder were set in specific ranges and kneaded, and the kneaded product was dried and pulverized. By molding the molding powder by injection molding, injection compression molding, transfer molding, etc., the anisotropy of the molded body is small, and the strain anisotropy at the time of firing is small by suppressing distortion due to the shrinkage at the time of firing, It is possible to reduce the anisotropy of physical properties and to manufacture a carbon molding material that approximates the final shape of the target product.

  According to the present invention, for example, a carbon molding material that is useful as an antistatic material, an electromagnetic shielding material, a sliding member, a heat dissipation base, a far-infrared radiator, a heating element, a heating element such as electromagnetic induction, and the like is efficiently produced. can do.

  Various carbon powders are used as the raw material carbon powder, such as carbonized resin and pulverized carbon obtained by calcining coke. Graphite powder with a high degree of graphitization has high fluidity during injection and has high moldability. Artificial graphite powder and natural graphite powder are preferred from the viewpoint of moldability because they are good and have less nozzle clogging and short shots.

  The carbon powder is pulverized with a suitable pulverizer and the average particle size is adjusted to a particle size of 100 to 2000 μm, and carbon powder having an average particle size of 400 to 2000 μm is preferably used. If the average particle diameter of the carbon powder is less than 100 μm, the fluidity of the kneaded product is deteriorated and the moldability is deteriorated. If the average particle diameter is more than 2000 μm, the strength of the carbon molding material is reduced. Clogging is likely to occur near the mold gate.

  Petroleum pitch, coal pitch, synthetic pitch, etc. can be used for the pitch powder mixed with the carbon powder, but the average particle size is 100 μm or less and the softening point is 30 to 30 ° C. higher than the mold temperature at the time of injection molding. It is necessary to use pitch powder that is 250 ° C higher.

  The pitch powder is required to have a particle size smaller than that of the carbon powder, and pitch powder having an average particle size of 100 μm or less is used, and preferably 10 to 70 μm is used. When the average particle size of the pitch powder is larger than 100 μm, the pitch powder does not cling well to the surface of the carbon powder, and anisotropy occurs in the physical properties of the resulting molded body because air entrainment cannot be suppressed during injection molding. easy. Further, since the effect of baking tightening is not sufficiently exhibited during firing, shrinkage anisotropy may increase and breakage may occur.

  The pitch powder used is one whose softening point is 30 to 250 ° C. higher than the mold temperature at the time of injection molding. When pitch powder with a softening point lower than the mold temperature is used, or when injection molding is performed at a temperature higher than the softening point of the pitch powder to be used, the softened pitch component forms a dense layer on the surface of the injection-molded product. The generated gas is not smoothly discharged, and hence the molded body is swollen by the gas. Further, since the curing rate of the thermosetting resin is delayed, the molded body is soft and easily deformed at the time of mold release.

  Therefore, a pitch powder whose softening point is 30 ° C. or higher than the mold temperature at the time of injection molding is used. However, as the softening point of the pitch powder increases, the carbonization temperature of the pitch and the thermal decomposition temperature of the thermosetting resin during the firing process become closer, and the amount of gas generated increases in this temperature range. It becomes difficult to volatilize, and the molded body tends to swell or break during firing. Therefore, pitch powder having a softening point of 250 ° C. or lower is selected and used.

  The softening point was measured in accordance with JIS K2207 “Testing Method for Softening Point (Ring and Ball Method)”, a sample was filled in a ring having a specified ring inner diameter of 15.9 mm and depth of 6.4 mm, and a glycerin bath. Support the inside horizontally, place a specified 0.5 g steel ball in the center of the sample, raise the bath temperature at a rate of 5 ° C. per minute, and the sample enclosing the steel ball touches the bottom plate of the ring base. The temperature at that time is read and used as the softening point.

  The above carbon powder and pitch powder are mixed with pitch powder in a ratio of 3 to 30 parts by weight with respect to 100 parts by weight of carbon powder to obtain mixed powder as a raw material. If the mixing ratio of the pitch powder is less than 3 parts by weight, air entrainment cannot be suppressed during injection molding, and anisotropy tends to occur in the molded body, and the effect of shrinkage during firing is not sufficiently exhibited, so that the anisotropic shrinkage The property becomes large and it becomes easy to break. On the other hand, when the mixing ratio of the pitch powder is more than 30 parts by weight, the fluidity of the molding powder is lowered, and short molding tends to occur.

  Carbon powder and pitch powder are mixed well with a suitable mixer such as a universal mixing stirrer, Henschel mixer, V-type blender and the like to prepare mixed powder.

The mixed powder is mixed with a resin solution obtained by dissolving a thermosetting resin having a residual carbon ratio of 40% or more and a molding aid made of an organic substance having a melting point of 40 to 150 ° C. in an organic solvent. The residual charcoal ratio is 30% at 1000 ° C. in a non-oxidizing atmosphere after putting the sample in a magnetic crucible, heating at 135 ° C. for 1 hour, further heating at 250 ° C. for 5 hours, then covering the magnetic crucible. It is measured by heating for 1 minute and dividing the weight of the sample after heating at 1000 ° C. for 30 minutes by the weight of the sample put in the porcelain crucible.
Residual carbon ratio (%) = (weight of sample after heating at 1000 ° C. for 30 minutes) / (weight of sample put in porcelain crucible) × 100

  The thermosetting resin used as the binder of the mixed powder is phenol resin, epoxy resin, polyimide resin, furan resin, unsaturated polyester resin, etc. with a residual carbon ratio of 40% or more, which is commonly used. Resins or epoxy resins are preferred.

  The molding aid functions to improve fluidity, moldability, and mold release during molding, and an organic substance having a melting point of 40 to 150 ° C. is used. When the melting point is lower than 40 ° C., only the molding aid flows to the cavity surface at the time of injection molding, so a thin film of the molding aid is formed on the surface of the injection molded product, and the molded product is cured in the mold. Since the discharge of the gas generated in this is hindered, the molded body is swollen. On the other hand, when the melting point is higher than 150 ° C., when the molding powder is injected, the molding aid is not sufficiently melted in the nozzle, so that the fluidity of the molding powder does not increase and short shots are likely to occur.

  These thermosetting resins and molding aids are dissolved in an appropriate organic solvent such as alcohol, ether, and acetone to prepare a resin solution, and the resin solution is added to a mixed powder of carbon powder and pitch powder to obtain carbon powder 100. The thermosetting resin is mixed and kneaded so that the resin solid content of the thermosetting resin is 10 to 40 parts by weight and the molding aid is 0.1 to 5 parts by weight.

  When the mixing ratio is less than 10 parts by weight with respect to 100 parts by weight of the carbon powder, the fluidity becomes low when injection molding the molding powder, and it is difficult to obtain a homogeneous molded body. On the other hand, when the resin solid content exceeds 40 parts by weight, the moldability is good, but gas cannot be smoothly released during injection molding, and the resin tends to swell and crack during firing.

  On the other hand, when the mixing ratio of the molding aid is less than 0.1 parts by weight with respect to 100 parts by weight of the carbon powder, the fluidity of the mixed raw material is lowered and short shot is likely to occur, and the releasability is also deteriorated. However, if the mixing ratio exceeds 5 parts by weight, the amount of gas generated increases because of many decomposition components generated from the molding aid during firing, and blistering and cracking are likely to occur during firing.

  This molding aid needs to be volatilized and disappeared in the firing process before decomposition of the thermosetting resin. As the molding aid, stearic acid, stearate, oleic acid, polyethylene wax, carnauba wax, A compound such as an organic phosphate ester or a cross-linked polyolefin, or a mixture of two or more of these is preferably used.

  Furthermore, it is preferable to add a firing aid in these raw material systems, and the firing aid is decomposed and volatilized before the resin component is carbonized by firing the thermosetting resin. It functions to facilitate the volatilization and release of gas by forming the outflow path of the generated gas. Examples of the baking aid include cellulose fiber, rayon fiber, acrylic resin, polystyrene resin, corn starch, and walnut powder.

  The firing aid is added at a ratio of 0 to 10 parts by weight with respect to 100 parts by weight of the carbon powder. The baking aid does not need to be added if no blistering or cracking occurs during firing, but if the amount ratio exceeds 10 parts by weight, the physical properties of the carbon material become non-uniform and the strength also decreases.

  Carbon powder, pitch powder, thermosetting resin, molding aid and, if necessary, firing aid are mixed and kneaded at a predetermined weight ratio. After kneading with a kneader, a pressure kneader, or a suitable kneader such as a twin screw kneader, the kneaded product is dried by vacuum drying, air drying, etc. to remove organic solvents and volatile components that evaporate at a low temperature. After removing, it is pulverized to produce a molding powder.

  The firing aid can be mixed beforehand with a carbon powder, a thermosetting resin, a molding aid and a mixer or the like. However, when the resin solution is prepared and dispersed with a cutter mixer or the like, uniform mixing can be performed.

  The molding powder is preferably pulverized into particles of 5 mm or less, and molding methods such as injection molding, injection compression molding, transfer molding, etc. are applied as the molding method. Is preferred.

  In the molded body thus obtained, a resin-rich layer is easily formed on the surface. This resin-rich layer is converted into a carbon layer (glassy carbon layer) having a dense structure due to carbonization of the resin during the baking treatment. This carbon layer prevents the permeation of the resin decomposition gas generated by the carbonization of the resin component during the curing treatment and the firing treatment, and the gas emitted from the molding aid and firing aid, and the swelling of the carbon material. Cause cracks. Therefore, in order to smoothly volatilize these gases, it is preferable to remove a part of the surface layer of the molded body and remove the resin rich layer in advance.

  The removal amount of the resin-rich layer depends on conditions such as the production conditions of the molded body, the size of the molded body, the curing process, and the baking process, but usually the surface layer is removed by 10 μm or more, preferably about 40 to 50 μm. The removal of the resin-rich layer may be performed by polishing or grinding with sandpaper or sandblast, or by burning the surface resin layer with a burner or the like.

  After removing the resin-rich layer formed on the surface of the molded body, the resin component is cured by heating to a temperature of 180 to 280 ° C. by a conventional method, and then non-oxidizing such as inert gas or nitrogen gas A carbon molding material is produced by heating to 800 ° C. or higher in an atmosphere and baking the resin component to carbonize, and depending on the purpose of use, it is heat-treated to a temperature of about 3000 ° C. and graphitized. The

  Hereinafter, the present invention will be described in detail by comparing Examples and Comparative Examples.

Examples 1-6, Comparative Examples 1-12
Artificial graphite was pulverized as carbon powder, and the particle size was adjusted to use graphite powder having different average particle sizes. Also, as the pitch powder, synthetic pitches having different softening points are used, pulverized, and adjusted to a particle size to prepare pitch powders having different average particle diameters. Mixed powder was prepared by mixing.

  Phenol resin (residue PG-2411 manufactured by Gunei Chemical Industry Co., Ltd.) with a residual carbon ratio of 50% is used as the thermosetting resin, stearic acid with a melting point of 80 ° C. is used as the molding aid, and acetone is organic. Using a solvent, a phenol resin and stearic acid were dissolved in acetone at different concentrations and completely dissolved to prepare a resin solution. In addition, when preparing a resin solution, the hexamine which is a hardening | curing agent of a phenol resin was added.

  This resin solution is added to the mixed powder of graphite powder and pitch powder, and mixed so that the resin solid content of the phenol resin and the weight part of stearic acid are different from each other in 100 parts by weight of the graphite powder. The kneader kneaded for 60 minutes. The kneaded product was air-dried at room temperature to remove acetone and volatile components and then pulverized to produce a molding powder having a particle size of 3 mm or less. In Example 6, cellulose microfibers were added as a baking aid.

  These molding powders were injection-molded by taking a single plate with a 150 × 150 × 5 tmm mold using a 150-t general-purpose injection molding machine. The injection molding conditions were a cylinder temperature of 90 ° C., a mold temperature of 150, 170, 200 ° C., and the injection pressure and speed were selected in accordance with the raw material composition of the molding powder. The surface layer surface of the molded body was ground with a # 1000 paper file, and the resin-rich layer formed on the surface layer surface was removed by 30 μm.

  Next, after curing by heating at a temperature of 250 ° C. for 5 hours, the temperature was once returned to room temperature, and then heated at a temperature of 1000 ° C. for 5 hours in a nitrogen atmosphere to perform a baking treatment to produce a carbon molding material. However, in Comparative Examples 2, 5, 7, 11, and 12, which were swollen or deformed during molding, or were short-molded, firing was not performed. These production conditions and moldability are shown in Table 1.

  Next, these carbon molding materials were measured for bulk specific gravity, bending strength, specific resistance, thermal conductivity and the like by the following methods. In order to evaluate the anisotropy of physical properties, a test piece in the injection direction and a test piece in a direction perpendicular to the injection direction are cut out from one plane, and the injection direction (X direction) and the injection direction are The physical properties in the perpendicular direction (Y direction) were measured. However, physical properties were not measured for Comparative Examples 2, 5, 7, 11, and 12 that were not fired, and specific resistance was measured for Comparative Examples 6, 8, 9, and 10 that were swollen or cracked by firing. Measurement of thermal conductivity was not possible. The results are shown in Table 2.

Bulk specific gravity;
It was determined by measuring the dry weight of the sample and the weight in water (at room temperature of 25 ° C.) by the Archimedes method.

Bending strength (MPa);
A three-point bending test was performed according to JIS K7203 under the conditions of a test piece size of 90 × 10 × 5 t (mm), a fulcrum distance of 80 mm, and a crosshead speed of 0.5 mm / min.

Specific resistance (Ω.m);
Calculated by measuring the voltage drop at a terminal distance of 67 mm (room temperature 25 ° C.) by passing a direct current of 0.5 A in the longitudinal direction of the test piece size 90 × 10 × 5 t (mm) by the voltage drop method of JIS R7202. .

Thermal conductivity (Wm ⁻¹ K ⁻¹ );
Measured by laser flash method. TC-7000 type manufactured by Vacuum Riko Co., Ltd. is used as the measuring device. A laser beam with a predetermined energy is applied to a test piece size of 10φ × 2t (mm), and the temperature change of the test piece and the temperature change of the laser light and the back of the projection surface The specific heat capacity and the thermal diffusivity in the thickness direction were measured and calculated from thermal conductivity = specific heat capacity × thermal diffusivity × density.

Examples 1-6 are all good in moldability, and do not generate blisters or cracks even when fired.
It can be seen that a carbon molding material having a small anisotropy of physical properties of the carbon molding material, in particular, anisotropy of bending strength, can be produced.

  Since Comparative Example 1 did not contain pitch powder, it was not possible to reduce the entrainment air by suppressing the spread of the molding material at the time of injection molding, and the obtained carbon molding material had an injection direction (X direction) and an injection. Anisotropy of physical properties in the direction perpendicular to the direction (Y direction) was increased. Moreover, since there is no effect of attracting and baking the carbon powders when the pitch powder is baked and carbonized, the shrinkage anisotropy during the firing cannot be suppressed, and there are some which are cracked by strain.

  In Comparative Example 2, the average particle size of the graphite powder was as small as 50 μm, so the flowability of the molding material was poor and short molding was achieved.

  In Comparative Example 3, the graphite powder having a large average particle diameter of 2200 μm was used. Therefore, the flowability of the molding material was good, and the appearance of the molded body and the fired product was good, but the strength was significantly reduced.

  In Comparative Example 4 in which a pitch powder having a large average particle size of 200 μm was used, the flowability of the molding material was good and the moldability was good, but the pitch powder was not sufficiently clinging to the graphite powder, so Since the holding cannot be suppressed, the strength anisotropy of the carbon molded body is increased, the shrinkage effect during firing is not exhibited, and the shrinkage anisotropy is increased and the carbon molded body is cracked.

  In Comparative Example 5, since the softening point of the pitch powder was lower than the mold temperature at the time of injection molding, the pitch component softened at the time of injection molding formed a dense surface layer, and the molded body was swollen by the gas generated during the injection molding. In addition, the cured pitch of the phenol resin was slowed by the melted pitch, and the molded product was soft and deformed when released.

  In Comparative Example 6 using the pitch powder whose softening point is significantly higher than the mold temperature at the time of injection molding, the moldability was good, but the firing temperature of the phenol resin and the decomposition temperature of the pitch powder are close to each other. The amount of cracked gas in the temperature range increases, it is difficult to volatilize smoothly, swelling and cracks occur during firing, and the resulting carbon molded body has a low bulk specific gravity and low strength. became.

  In Comparative Example 7 where the blending amount of the pitch powder was as large as 35 parts by weight, the amount of fine powder in the mixed powder increased, and the fluidity of the molding material decreased, resulting in short molding.

  In Comparative Example 8 where the amount of phenol resin was as small as 8 parts by weight, the flowability of the molding material was poor, and a weld line was formed in the molded body.

  In Comparative Example 9, since the phenol resin amount was increased to 45 parts by weight, the fluidity was improved and the moldability was good, but the injection molded body became dense and the permeation and volatilization of the decomposition gas during firing was not sufficient. As a result, swelling occurred, the bulk density of the carbon molding material was small, and the strength was also lowered.

  In Comparative Example 10, since the molding aid was not blended, the fluidity of the molding material was lowered, and the molding material could not be filled into the mold, resulting in short molding. Therefore, the baked carbon molding material is easy to break along the weld line and has low strength.

  In Comparative Example 11, since 11 parts by weight of the molding aid was added, the flowability of the molding material was good, but the molding aid floated on the surface layer of the molded body to form a film, and the generated gas could not be discharged smoothly. The molded body swelled.

  In Comparative Example 12, 1 part by weight of a molding aid having a melting point of 30 ° C. was added and injection molding was performed. However, only the molding aid flowed first to the cavity surface during the injection molding, and the molding aid was formed on the surface of the molded body. A thin film was formed, and the gas generated during curing could not be discharged, and the molded body was swollen.

Claims (3)

  For 100 parts by weight of carbon powder having an average particle diameter of 100 to 2000 μm, pitch powder having an average particle diameter of 100 μm or less and a softening point of 30 to 250 ° C. higher than the mold temperature at the time of injection molding is 3 to 30 parts by weight. Mix and add a resin solution in which a molding aid made of a thermosetting resin having a residual carbon ratio of 40% or more and an organic substance having a melting point of 40 to 150 ° C. is dissolved in an organic solvent to the mixed powder, to 100 parts by weight of carbon powder. On the other hand, after the thermosetting resin is kneaded to a quantity ratio of 10 to 40 parts by weight of resin solids and 0.1 to 5 parts by weight of molding aid, the kneaded product is dried and pulverized to produce a molding powder and molded. The powder is molded by injection molding, injection compression molding or transfer molding, and the resulting molded body is cured at a temperature of 180 to 280 ° C, and then fired at a temperature of 800 ° C or higher in a non-oxidizing atmosphere. Characteristic carbon molding material Manufacturing method.   2. The carbon molding according to claim 1, wherein the molding aid is a compound such as stearic acid, stearate, oleic acid, polyethylene wax, carnauba wax, organophosphate ester, crosslinked polyolefin, or a mixture of two or more thereof. Material manufacturing method.   The method for producing a carbon molding material according to claim 1, wherein 0 to 10 parts by weight of a baking aid such as cellulose fiber, rayon fiber, acrylic resin, polystyrene resin, corn starch, and walnut powder is added to 100 parts by weight of the carbon powder. .