JP2001019546A - Amorphous carbon composite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composite having low incidences of breakage and crack and excellent dimensional accuracy by adding a carbon material in a specific ratio range to a phenol resin synthesized by a suspension polymerization method, molding the mixture and carbonizing and firing the molding product in vacuum or in an inert gas. SOLUTION: A phenol resin is mixed with 5-60 wt.% of a carbon material. A novolak resin obtained by a suspension polymerization in an aqueous medium in the presence of an alkali catalyst also used as a methylene crosslinking agent such as hexamethylenetetramine or the like is used as a phenol resin raw material. Graphite powder having <=50 μm central sphere diameter or a carbon fiber having <=5 μm diameter and <=150 aspect ratio is preferable as the carbon material. A molding product is preferably mixed with 0.1-5 wt.% of a low surface tension substance such as lauric acid, etc. The phenol raw material is kneaded with the carbon material, molded and carbonized and fired in an inert gas at 800-1,600 deg.C to give an amorphous carbon composite.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an amorphous carbon composite.

[0002]

2. Description of the Related Art A thermosetting resin forming a three-dimensional network structure such as a phenolic resin, a furan resin, and a polyimide resin is molded and processed, and the molded body is fired in a vacuum or in an inert gas atmosphere to form an amorphous carbon. Can be obtained. Such amorphous carbon is a material having excellent properties such as light weight and high strength, a small coefficient of friction, excellent chemical resistance and gas impermeability, and a small coefficient of thermal expansion.

[0003] Amorphous carbon as described above exhibits low electric resistance in addition to gas impermeability and chemical resistance, and is therefore used for separating a reaction gas in a phosphoric acid type fuel cell or a polymer electrolyte fuel cell. Is attracting attention as a material for the separator. In addition, amorphous carbon has a small coefficient of thermal expansion and excellent dimensional stability, so its application to various small parts is being studied. Applications for various sliding parts such as the above are also being studied.

[0004] Due to the characteristics of the resin, the above-mentioned thermosetting resin, which is a raw material of amorphous carbon, can only be molded by a compression molding method or an extrusion molding method and has a simple shape such as a flat plate. Of the molded product of Example 1. Therefore, it was necessary to perform machining after carbonization and firing to finish to a desired size and shape. As described above, since amorphous carbon is much more difficult to mechanically process than a metal material, it has problems such as lack of mass productivity and considerable increase in cost.

When a thermosetting resin is molded and carbonized and baked, the hydrogen, nitrogen, carbon, and the like in the resin are generated as decomposition gases, resulting in a volume of about 50% and a weight of about 3%.
Reduce by 0%. Therefore, carbonized and fired amorphous carbon has large dimensional variations and is used for parts that do not require much dimensional accuracy. When used for products that require dimensional accuracy, post-processing such as cutting has to be performed.
In addition, when a resin molded product having a large thickness is fired, the rate of occurrence of cracks and cracks due to the generated gas increases, and it has been extremely difficult to obtain amorphous carbon having a large thickness.

[0006]

SUMMARY OF THE INVENTION In view of such circumstances, an object of the present invention is to reduce the occurrence of cracks and cracks, increase the thickness, and improve the dimensional accuracy without impairing the excellent properties of amorphous carbon. An object is to provide an amorphous carbon composite having good productivity.

[0007]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, formed a material obtained by adding a carbon material to a phenol resin synthesized by a suspension polymerization method, and formed a vacuum or vacuum. When carbonized and fired in an inert gas atmosphere,
An amorphous carbon composite can be obtained, and the amorphous carbon composite has been found to solve the above problems, and has reached the present invention.

That is, the gist of the present invention is to form a molding material in which a carbon material is added to a phenol resin synthesized by a suspension polymerization method in an amount of 5 to 60% by weight, and the obtained molded product is placed in a vacuum or an inert gas atmosphere. An amorphous carbon composite characterized by being carbonized and calcined. Further, as the carbon material, a graphite powder having a central sphere diameter of 50 μm or less,
Or an amorphous carbon composite using a carbon fiber having a diameter of 5 μm or less and an aspect ratio of 150 or less, in addition to the properties of the above-described amorphous carbon composite, strength,
It is excellent in gas impermeability and surface roughness. Furthermore, when a material containing 0.1 to 5% by weight of a low surface tension substance is used as the molding material, an amorphous carbon composite having better dimensional accuracy and higher productivity can be obtained.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The amorphous carbon composite of the present invention is obtained by molding a molding material obtained by adding a carbon material to a phenol resin synthesized by a suspension polymerization method, and calcining and firing the obtained molded product in a vacuum or an inert gas atmosphere. .

The phenolic resin raw material used in the present invention is prepared by converting a novolak resin to an alkali catalyst and a methylene crosslinking agent such as hexamethylenetetramine and a suspension stabilizer as disclosed in, for example, JP-A-4-159320. In the presence of phenol and formaldehyde obtained by a method of performing suspension polymerization in an aqueous medium (self-curing modified novolak resin method) in an aqueous medium, phenol and formaldehyde are suspended in an aqueous medium in the presence of a basic catalyst and a suspension stabilizer. Those obtained by a polymerization method (solid resol resin method) such as a method of performing turbid polymerization can be suitably used. These phenolic resin raw materials are spherical phenolic resin raw materials having a shape close to a perfect sphere. In order to obtain a molding raw material having a large particle size, it is effective to prepare the raw material having a predetermined particle size by granulating the fine particles. .

Examples of the carbon material to be added to the phenol resin include graphite, carbon fiber, and a mixture thereof. Natural graphite powder and artificial graphite powder are preferable as graphite. The advantage of the carbon material as an additive is that it has many characteristics in common with amorphous carbon and has good bonding properties with amorphous carbon. Generally, carbon material is a material having heat resistance, chemical resistance, low electric resistance, low coefficient of friction, and high thermal conductivity, but is poor in bending strength and gas impermeability because it is porous. Known as material.

The proportion of the carbon material added is 5 to 60% by weight, preferably 20 to 55% by weight, more preferably 30 to 50% by weight.
% By weight. As the amount of addition increases, the bending strength of the composite becomes weaker, the bonding force between the amorphous carbon and the carbon material decreases, and the problem of powder falling occurs. If the addition ratio of the carbon material exceeds 60% by weight, the melt viscosity of the molding material increases, and the moldability becomes extremely poor. On the other hand, if it is less than 5% by weight, the effect of addition is difficult to appear.

In the present invention, when a powdered carbon material such as natural graphite powder or artificial graphite powder is added, the smaller the center particle size is, the better the dispersibility in the phenol resin is. If the center particle size exceeds 50 μm, The strength tends to decrease and the surface roughness tends to deteriorate. The practically used center particle size is 0.1 to 50 μm.

In the case of carbon fiber, it is preferable to use a carbon fiber having a diameter of 5 μm or less and an aspect ratio of 150 or less. When the diameter of the carbon fiber exceeds 5 μm, the strength tends to decrease and the surface roughness tends to deteriorate. In the present invention, the aspect ratio of carbon fiber (the ratio of length to diameter)
Is defined as above, when the aspect ratio exceeds 150, the fiber is likely to exist with a curvature instead of a straight line, the fiber itself is entangled, the resin does not enter well in between,
As a result, densification becomes difficult and strength is reduced.

Since the carbon material hardly undergoes dimensional shrinkage during firing, the larger the proportion of the carbon material added to the phenolic resin, the smaller the volume shrinkage and weight loss during firing and the smaller the dimensional variation. . Also, since carbon materials hardly release decomposition gas during firing, the greater the proportion of carbon material added to the phenolic resin, the lower the amount of gas generated from the resin molded product, and the lower the rate of cracking and cracking caused by firing. This is very effective when firing a molded article having a low thickness.

Further, it is preferable that a low surface tension substance is added to the molding material in an amount of 0.1 to 5% by weight based on the molding material. More preferably, the content is 0.2 to 3% by weight. If the compounding amount of the low surface tension substance is less than 0.1% by weight based on the molding material, blockage may occur in the cylinder of the molding machine during molding, and it may be difficult to continuously perform molding. ,
On the other hand, if it exceeds 5% by weight, the effect of improving moldability tends to level off. The low surface tension substance has a melting point of 30 ° C to 1 ° C.
It is a low melting point compound which is solid at room temperature of 60 ° C., preferably 40 ° C. to 80 ° C. and has a critical surface tension of about 35 dynes / cm or less at room temperature [25 ° C.], lubricity, mold release, non-adhesion It is a substance such as sex. If the melting point is less than 30 ° C., poor measurement tends to occur during molding, and if it exceeds 160 ° C., lubricity in the cylinder of the molding machine is poor, and stable moldability tends not to be obtained.

Representative examples of low surface tension substances include higher fatty acids such as lauric acid, palmitic acid and stearic acid; lauric acid monoglyceride, ethyl stearate, stearic acid monoglyceride, sorbitan monopalmitate, sorbitan monostearate and the like. Higher fatty acid esters such as trilaurin, tristearin, and hardened castor oil; higher fatty acid amides such as stearic acid amide and ethylenebisstearic acid amide; higher fatty alcohols such as cetyl alcohol and stearyl alcohol; stearyl methacrylate and stearyl acrylate Higher aliphatic (meth) acrylates, etc .; waxy hydrocarbons, such as paraffin wax; polyvalent fluorine-containing higher fatty acids, such as perfluorooctanoic acid and 9H-hexadecafluorononanoic acid ; 含多 number fluorine higher aliphatic sulfonamides such as N- ethyl perfluorooctyl sulfonamide; 2- (perfluorooctyl) ethyl iodide,
Polyvalent fluorine-containing higher aliphatic iodides such as ethyl 2- (perfluorodecyl) iodide; 1H, 1H, 9H-hexadecafluorononanol, 2- (perfluorooctyl) ethanol, 2- (perfluorodecyl) Polyvalent fluorine-containing higher aliphatic alcohols such as ethanol; 2- (perfluorodecyl) methyl methacrylate, 1H, 1H, 11H-
Polyvalent fluorine-containing higher aliphatic (meth) acrylates such as eicosafluoroundecyl acrylate; polyvalent fluorine-containing higher aliphatic hydrocarbons such as perfluorododecane; 2- (P
A polyvalent fluorine-containing aromatic aromatic compound such as methyloxybenzoate / hexafluoropropene trimer adduct; a polyvalent fluorine-containing aromatic hydrocarbon such as pentafluorobenzamide; TFE wax (tetrafluoroethylene telomer); CTFE Low surface tension substances such as polyvalent fluorine-containing oligomer compounds such as telomers (chlorotrifluoroethylene telomer), or derivatives thereof, mixtures of one or more of these, and compositions in which additives such as polymerization catalysts are added thereto. Is mentioned.

The kneading of the phenolic resin raw material and the carbon material (and, if necessary, a low surface tension substance) can be performed by any method that can be uniformly mixed, for example, using a high speed mixer or a twin screw extruder. May be used.

Preferably, the water content of the kneaded molding material is controlled to 1% by weight or less at least at the time of molding. Usually, the phenolic resin raw material after polymerization contains water of several weight% or more. Therefore, it is effective to dry the phenolic resin raw material so as to reduce the water content within the above-mentioned limits and knead the material before use. is there. At this time, the granular phenol resin raw material is dried in a vacuum or under a circulation of dry air for 6 hours.
A method of heating to a temperature of 0 to 120 ° C. is recommended.
As described above, the molding material preferably has a water content of 1% by weight or less, more preferably 0.5% by weight or less. If the water content exceeds 1% by weight, pores remain in the molded product during molding, and depending on the molding conditions, degradation phenomena such as hydrolysis may occur.

A molding material in which a carbon material is added to the phenol resin in an amount of 5 to 60% by weight (and a low surface tension substance is added in an amount of 0.1 to 5% by weight, if necessary) is molded. The carbonization firing is performed in a vacuum or an inert gas atmosphere. As a molding method, it can be performed by a usual method. At this time, if molding is performed by an injection molding method using a mold in which dimensional shrinkage at the time of firing is anticipated, the dimensional accuracy is good and the required dimensional shape is obtained. This eliminates the need for costly post-processing such as cutting, and is excellent in mass productivity.

The carbonization firing temperature is usually 800 ° C. to 1600
C is preferable, and 900 C to 1500 C is more preferable.
If the carbonization firing temperature is less than 800 ° C., the phenolic resin in the resin molded product is not completely amorphous carbon,
If the temperature exceeds 1600 ° C., excessive firing occurs, and the graphitization tends to proceed. Examples of the inert gas include a nitrogen gas, a helium gas, and an argon gas.

The amorphous carbon composite obtained by adding the carbon material in the above ratio impairs the excellent properties of amorphous carbon such as light weight, chemical resistance, low friction coefficient, gas impermeability and dimensional stability. In addition, the thermal conductivity can be increased, and the specific resistance can be reduced.

[0023]

EXAMPLES Next, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples.

Reference Example Novolak resin (# 600 manufactured by Mitsui Toatsu Chemicals, Inc.) 15
0 parts by weight were melted at 160 ° C. to dissolve 1 part by weight of completely saponified polyvinyl alcohol (degree of polymerization: about 2000).
The suspension was poured into hot water (220 parts by weight) at 0 ° C. while stirring to form a suspension, and then 24 parts by weight of hexamine was dissolved in 40 parts by weight of warm water and added. The suspension was stirred for 20 minutes to carry out suspension polymerization. After the reaction was completed, the suspension was subjected to solid-liquid separation and dried to obtain a phenol resin raw material. Table 1 shows the characteristics of the phenol resin raw material. However, these characteristics shown in Table 1 were measured by the following methods.

The thermal fluidity (HPF) is measured according to JIS-K-69.
11 (1979) 5.3.2 [Molding material (disc type)], 1 g of a sample at 1145k at 160 ° C for 1 minute
It was hot-pressed under a load of g and determined from the diameter (average value of the longest diameter and the shortest diameter) of the formed disk. The average particle size was obtained by developing a sample on a glass plate, taking a micrograph, measuring 100 randomly selected particle sizes, and indicating the average value. The moisture was measured using an infrared heater,
C. for 30 minutes and the weight loss was determined.

[0026]

[Table 1]

Examples 1 to 5 The phenolic resin raw material obtained in Reference Example had a center particle size of 0.5 to
30 μm of natural graphite powder was mixed at a ratio of 20 to 60% by weight to obtain a molding material. At that time, stearic acid and stearic acid monoglyceride, which are low surface tension substances, were each added in an amount of 0.5% by weight to the molding material. This molding material was injection-molded using a M150BL-TS molding machine manufactured by Meiki Seisakusho Co., Ltd. The size of the obtained molded product was 15 mm in width, 120 mm in length, and 6 mm in thickness. This molded product was carbonized and fired in a nitrogen gas atmosphere at a maximum temperature of 1500 ° C. using a high-performance firing furnace to obtain an amorphous carbon composite. The moldability during injection molding, the rate of occurrence of cracks and cracks in the amorphous carbon composite in 100 samples, and the range of dimensional variation by length measurement in the length direction were evaluated. The results are shown in Table 2.

[0028]

[Table 2]

Examples 6 to 10 In place of the natural graphite powder used in Examples 1 to 5, artificial graphite powder was used. Otherwise, an amorphous carbon composite was obtained in the same manner as in Examples 1 to 5. The evaluation of the moldability and the amorphous carbon composite at the time of injection molding was performed in Examples 1 to 5.
The results are shown in Table 3.

Example 11 An artificial graphite powder having a center particle diameter of 60 μm was added to a phenol resin raw material at 40% by weight and mixed. At that time, stearic acid and stearic acid monoglyceride, which are low surface tension substances, were each added in an amount of 0.5% by weight to the molding material. This molding material is injection-molded in the same manner as in Examples 1 to 5,
The firing was performed. The moldability during injection molding and the evaluation of the amorphous carbon composite were evaluated in the same manner as in Examples 1 to 5, and the results are shown in Table 3. Due to the large central particle size of the artificial graphite powder, the gas impermeability, which is an excellent property of amorphous carbon, was impaired, and the surface roughness deteriorated.

[0031]

[Table 3]

Examples 12 to 16 Carbon fibers were used in place of the natural graphite powder used in Examples 1 to 5. Otherwise, an amorphous carbon composite was obtained in the same manner as in Examples 1 to 5. The moldability during injection molding and the evaluation of the amorphous carbon composite were evaluated in the same manner as in Examples 1 to 5, and the results are shown in Table 4.

[0033]

[Table 4]

Examples 17 to 21 Carbon fiber of various shapes was added to a phenol resin raw material by 40% by weight, and stearic acid and stearic acid monoglyceride, which are low surface tension substances, were added to the molding material in amounts of 0.5% each. % By weight. This molding material was used in Example 1.
Injection molding was performed in the same manner as in Nos. 1 to 5, and firing was performed. The moldability at the time of injection molding and the evaluation of the amorphous carbon composite were evaluated in the same manner as in Examples 1 to 5, and the results are shown in Table 5. If the diameter of the carbon fiber is large or the aspect ratio is large, the carbon fiber does not disperse well in the phenolic resin, and the fired amorphous carbon composite does not densify as a result, has low flexural strength, and is impermeable to gas. Was bad.

[0035]

[Table 5]

Comparative Example 1 Stearic acid and stearic acid monoglyceride, which are low surface tension substances, were added to a phenol resin raw material without adding a carbon material at 0.5% by weight based on the phenol resin raw material.
Was added. This molding material was injection-molded in the same manner as in Examples 1 to 5 and fired. However, the size of the molded product was 15 mm in width, 120 mm in length, and 4 mm in thickness. The moldability during injection molding and the evaluation of the amorphous carbon composite were evaluated in the same manner as in Examples 1 to 5, and the results were shown in Table 6.
Shown in If the thickness of the molded product is 4 mm, firing can be performed without adding a carbon material, but the range of dimensional variation is large because the volume shrinkage during firing is large.

Comparative Example 2 Stearic acid and stearic acid monoglyceride, which are low surface tension substances, were added to a phenol resin raw material without adding a carbon material in an amount of 0.5% by weight based on the phenol resin raw material.
Was added. This molding material was injection-molded in the same manner as in Examples 1 to 5 and fired. The moldability during injection molding was evaluated in the same manner as in Examples 1 to 5, and the results were shown in Table 6.
Shown in In Comparative Example 2, since no carbon material was added, cracks and cracks occurred in the amorphous carbon due to the gas generated during firing, and a good product could not be obtained.
However, when a carbon material was added to the phenolic resin as in the example, it was possible to fire even a molded product having a thickness of 6 mm, and it was also possible to fire a thicker molded product.

Comparative Example 3 To a phenol resin raw material was added 65% by weight of a natural graphite powder having a center particle size of 10 μm and mixed. At that time, stearic acid and stearic acid monoglyceride, which are low surface tension substances, were each added in an amount of 0.5% by weight to the molding material. This molding material was injection molded in the same manner as in Examples 1 to 5. However, the addition ratio of natural graphite powder was large, and the melt viscosity of the molding material was high, so that injection molding could not be performed. Table 6 shows the results.

Comparative Example 4 An artificial graphite powder having a center particle diameter of 10 μm was added to a phenol resin raw material at 65% by weight and mixed. At that time, stearic acid and stearic acid monoglyceride, which are low surface tension substances, were each added in an amount of 0.5% by weight to the molding material. This molding material was injection molded in the same manner as in Examples 1 to 5. However, as in the case of natural graphite powder, the addition ratio of artificial graphite powder was large, and the melt viscosity of the molding material was high, so that injection molding was not possible. Table 6 shows the results.

[0040]

[Table 6]

[0041]

According to the present invention, a carbon material is added to a phenol resin material produced by a suspension polymerization method in an amount of 5 to 60% by weight.
By molding the added molding material and firing the molded product in a vacuum or inert gas atmosphere, it is possible to produce amorphous carbon composites with low crack and crack occurrence rates, large thickness and good dimensional accuracy. Can be provided well. The obtained amorphous carbon composite has strength and strength without impairing the excellent properties of amorphous carbon.
Since it has excellent thermal conductivity and electrical conductivity, it can be used for fuel cell separators, sliding parts, semiconductor parts, precision parts and the like. Further, by selecting the carbon material to be added, the gas impermeability and the surface roughness are improved.

Claims (4)

[Claims] 1. A molding material in which a carbon material is added to a phenol resin synthesized by a suspension polymerization method in an amount of 5 to 60% by weight, and the obtained molding is carbonized and fired in a vacuum or an inert gas atmosphere. An amorphous carbon composite, comprising: 2. The amorphous carbon composite according to claim 1, wherein the carbon material is a graphite powder having a central sphere diameter of 50 μm or less. 3. The amorphous carbon composite according to claim 1, wherein the carbon material is a carbon fiber having a diameter of 5 μm or less and an aspect ratio of 150 or less. 4. The molding material contains a low surface tension substance in an amount of from 0.1 to 0.1%.
2. The composition according to claim 1, wherein the content is 5% by weight.
The described amorphous carbon composite.