JP2001089239A - High heat conductivity amorphous carbon composite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high heat conductivity amorphous carbon composite having good formability, excellent in heat conductivity and dimensional accuracy and also having high strength. SOLUTION: A molding material obtained by adding 20-80 wt.% high heat conductivity material to a modified novolak resin obtained by suspension polymerization is molded and the resulting molding is carbonized and fired to obtain the objective high heat conductivity amorphous carbon composite.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly thermally conductive amorphous carbon composite.

[0002]

2. Description of the Related Art Metallic materials and thermally conductive ceramic materials have been mainly used for products which have a small coefficient of thermal expansion and require thermal conductivity and dimensional accuracy. However, in recent years, the level of dimensional accuracy has increased, and lightweight materials have been required. However, metal materials have a large specific gravity, and have problems in chemical stability such as corrosion resistance and chemical resistance.
Ceramic materials also have a large specific gravity and could only satisfy a certain degree of dimensional accuracy.

On the other hand, a thermosetting resin forming a three-dimensional network structure, such as a phenol resin, a furan resin, and a polyimide resin, is molded and fired in a vacuum or in an inert gas atmosphere. The resulting amorphous carbon material is a material having excellent characteristics such as light weight, high strength, a small coefficient of thermal expansion, and a small coefficient of friction. However, since the thermal conductivity was as low as 5 to 6 W / m · K, it was not used as a member requiring thermal conductivity.

In addition, the thermosetting resin can be obtained only by a compression molding method or an extrusion molding method due to the properties of the resin, and lacks mass productivity and only obtains a flat plate-shaped molded body. I could not do it.

[0005]

SUMMARY OF THE INVENTION In view of such circumstances, an object of the present invention is to provide a highly thermally conductive amorphous carbon composite having good moldability, excellent thermal conductivity and dimensional accuracy, and high strength. .

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems. As a result, when the structure described below is adopted, the moldability is excellent, the thermal conductivity and the dimensional accuracy are excellent. The present inventors have found that a highly thermally conductive amorphous carbon composite having high strength can be obtained, and have reached the present invention.

That is, the gist of the present invention is to form a molding material obtained by adding 20 to 80% by weight of a high thermal conductive material to a modified novolak resin obtained by a suspension polymerization method. A highly thermally conductive amorphous carbon composite characterized by being carbonized and fired.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The molding material as a raw material of the high thermal conductive amorphous carbon composite of the present invention is obtained by adding a high thermal conductive material to a modified novolak resin obtained by a suspension polymerization method, and the modified novolak resin is For example, it can be manufactured as follows. That is, Japanese Unexamined Patent Publication No.
No. 9320, a method in which a novolak resin is subjected to suspension polymerization in an aqueous medium in the presence of an alkali catalyst and a methylene crosslinking agent such as hexamethylenetetramine and a suspension stabilizer (self-curing type modification). Novolak resin method)
Can be suitably adopted.
According to this method, spherical particles having a very high purity and a shape close to a true sphere can be obtained. In order to obtain a resin material having a large particle size, a method of granulating the fine particles to prepare a material having a predetermined particle size is effective.

In particular, the modified novolak resin has a heat fluidity of 60 to 180 mm, preferably 90 to 160 mm, measured by a disc cure method (JIS-K-6911).
It is preferable to use a phenol resin having a diameter of mm. Thermofluidity refers to the property of being solid at room temperature, but exhibiting fluidity when a load is applied in a heated state. However, since the modified novolak resin has a self-curing property different from the case of a normal thermoplastic resin, if heating is continued at a temperature showing fluidity for a certain period of time or more, intramolecular and intermolecular condensation starts. It has the property of curing by crosslinking. Therefore, as a scale representing thermal fluidity, the flow (elongation of diameter; mm) of a sample resin disk under a predetermined load at 160 ° C. measured by JIS standard (disc cure method) described later.

A resin having a heat fluidity of less than 60 mm has poor moldability, while a resin having a heat fluidity of more than 180 mm requires a long time for a curing reaction, resulting in poor productivity. Since it is trapped in the molded body, there is a possibility that the product will be defective.

The high thermal conductive material used in the present invention has a thermal conductivity of 20 W / 100 ° C.
Those having mK or more are preferable, and those having 30 W / mK or more are more preferable. If the thermal conductivity is less than 20 W / m · K, sufficient thermal conductivity cannot be obtained. As a specific example of the high heat conductive material, a ceramic high heat conductive material is preferable, for example, silicon carbide, magnesia, beryllium oxide,
Examples thereof include boron carbide, and these may be used alone or in combination of two or more. Among them, silicon carbide is preferable.

The proportion of the high thermal conductive material added to the modified novolak resin is 20 to 80% by weight, preferably 30 to 60% by weight.
% By weight. If the amount is less than 20% by weight, sufficient thermal conductivity cannot be obtained, while if it is more than 80% by weight, molding becomes difficult.

As described above, a high thermal conductive material is added to the modified novolak resin to form a molding material. In the present invention, a low surface tension substance may be further added to this molding material. A molding material to which a low surface tension substance is added has advantages in that productivity is improved and dimensional accuracy is improved. The low surface tension substance has a melting point of 30 ° C. to 160 ° C., preferably 40 ° C. to 80 ° C., is a low melting point compound which is solid at ordinary temperature, and has low surface tension such as lubricity, releasability and non-adhesion. A compound having characteristics specific to a substance (for example, a substance having a critical surface tension of about 35 dynes / cm or less at room temperature [25 ° C.]) is used. 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 include higher fatty acids such as lauric acid, palmitic acid and stearic acid; higher fatty acid esters such as lauric acid monoglyceride, ethyl stearate, stearic acid monoglyceride, sorbitan monopalmitate and sorbitan monostearate; Solid fats and oils such as trilaurin, tristearin, hardened castor oil;
Higher fatty acid amides such as stearic acid amide and ethylenebisstearic acid amide; higher aliphatic alcohols such as cetyl alcohol and stearyl alcohol; higher aliphatic (meth) acrylates such as stearyl methacrylate and stearyl acrylate; waxy hydrocarbons such as paraffin wax Polyvalent fluorine-containing higher fatty acids such as perfluorooctanoic acid and 9H-hexadecafluorononanoic acid; polyvalent fluorine-containing higher aliphatic sulfonamides such as N-ethylperfluorooctylsulfonamide; 2- (perfluorooctyl) Polyvalent fluorine-containing higher aliphatic iodides such as ethyl iodide and 2- (perfluorodecyl) ethyl iodide;
1H, 1H, 9H-hexadecafluorononanol, 2
Poly (fluorinated higher aliphatic alcohols such as-(perfluorooctyl) ethanol, 2- (perfluorodecyl) ethanol); 2- (perfluorodecyl) methyl methacrylate, 1H, 1H, 11H-icosafluoroundecyl acrylate, etc. Poly (fluorine-containing higher aliphatic (meth) acrylates); polyvalent fluorine-containing higher aliphatic hydrocarbons such as perfluorododecane; poly (methyl-oxybenzoate / hexafluoropropene trimer adduct) Polyvalent fluorine-containing aromatic hydrocarbons such as fluorinated aliphatic aromatic compounds and pentafluorobenzamide; polyvalent fluorine-containing oligomer compounds such as TFE wax (tetrafluoroethylene telomer) and CTFE telomer (chlorotrifluoroethylene telomer); Or derivatives thereof,
A low surface tension substance such as a mixture of one or more of these substances and a composition in which additives such as a polymerization catalyst are blended with these are exemplified.

The low surface tension substance is preferably contained in the molding material in an amount of 0.1 to 5% by weight. More preferably 0.2
-3% by weight. The content of the low surface tension substance is 0.
If the amount is less than 1% by weight, the molding may be blocked in the cylinder of the molding machine at the time of molding and it may be difficult to continuously perform molding. Becomes

The kneading of the molding material composed of the modified novolak resin raw material and the high thermal conductive material (and, if necessary, simultaneously with the addition of a low surface tension substance) may be carried out by any method as long as it is a method of uniformly mixing. It can be performed using a high-speed mixer or a twin-screw extruder.

The kneaded molding material preferably has a water content controlled to at most 1% by weight at least at the time of molding. Usually, the modified novolak resin as a raw material after polymerization contains water of several weight% or more. Therefore, prior to use, it is preferable to dry the water so that the water content is reduced within the above-mentioned limits and to perform the kneading. It is valid. As a drying method at this time, a method in which the granular modified novolak resin is heated to a temperature of 60 to 120 ° C. in a vacuum or under a circulation of dry air is recommended.

The molding material prepared as described above is industrially preferably stored in a sealed container or sealed packaging until immediately before molding in view of quality control. Of course, even if the molding material is kneaded without drying the molding material as described above, if the molding is sufficiently dried immediately before molding and molded under conditions that do not absorb moisture, a molded product similar to the above can be obtained. Can be.

The molding material is molded to obtain a molded body.
Examples of the molding method include methods such as injection molding, transfer molding, and extrusion molding. In particular, when molding is performed by an injection molding method using a mold having a dimension and shape that allows for dimensional shrinkage during firing in advance, productivity is improved. This is particularly preferred in view of the above.
In order to carbonize and sinter the obtained molded body, the molded body is heated at 800 ° C. to 1600 ° C. in a vacuum, an inert gas or a reducing atmosphere.
Preferably, it is heated at 900 to 1500 ° C. If the carbonization firing temperature is lower than 800 ° C., the phenolic resin in the molded product does not completely turn into amorphous carbon. If the carbonization firing temperature exceeds 1600 ° C., excessive firing occurs and the graphitization tends to progress. Examples of the inert gas include gases such as nitrogen, helium, and argon, and nitrogen gas is preferable in terms of simplicity.

As described above, a highly thermally conductive amorphous carbon composite is obtained. The thus obtained high thermal conductive amorphous carbon composite has good moldability, excellent thermal conductivity and dimensional accuracy, and high strength.

[0021]

The present invention will be specifically described below with reference to examples. The present invention is not limited by 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 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 modified novolak resin raw material. Table 1 shows the characteristics of the modified novolak 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.

[0024]

[Table 1]

Examples 1 to 4 and Comparative Example 2 The components were blended at the ratios shown in Table 2 and uniformly mixed, followed by treatment at 110 ° C. in a twin-screw kneader to form pellets. It is pulverized using a pulverizer and has an average particle size of 2 mm (maximum 5 m
m) of a molding material for injection molding was obtained. Injection molding is performed using this molding material, and a bending test piece (width 12.5 mm
× length 126.0 mm × thickness 4.0 mm) and a disc-shaped shrinkage test specimen (outer diameter 90.0 mm × thickness 4.0 mm). In Comparative Example 1, injection molding was performed using only the modified novolak resin. Further, the compact was heated at 1600 ° C. in a nitrogen gas atmosphere.
Then, the temperature was raised and firing was performed. Bending strength of the obtained fired product,
The shrinkage rate and the thermal conductivity were measured in accordance with JIS K-6911. Table 2 shows the evaluation results.

[0026]

[Table 2]

As is clear from Table 2, the thermally conductive amorphous carbon composite of the example has a higher thermal conductivity than that of the comparative example 1 and has a low firing shrinkage and the same strength after firing. Was confirmed. In addition, stable continuous molding was also possible in injection moldability. In Comparative Example 2, injection molding could not be performed.

[0028]

The high thermal conductive amorphous carbon composite of the present invention has good moldability, excellent thermal conductivity and dimensional accuracy, and high strength. Therefore, it can be suitably used for electric parts and mechanical parts requiring such properties.

Continued on front page F term (reference) 4G001 BA22 BA78 BB22 BB60 BC26 BD03 4G032 AA14 AA33 BA00 4H012 MA01 4J002 AE032 BD122 BD152 CC071 DJ006 EB067 EC067 EF057 EH047 EH057 EH077 EP017 EV287 FD202 FD206 FD207

Claims (3)

[Claims] 1. A molding material obtained by adding a high thermal conductive material to a modified novolak resin obtained by a suspension polymerization method in an amount of 20 to 80% by weight, and the obtained molding is carbonized and fired. A highly thermally conductive amorphous carbon composite, characterized in that: 2. A highly thermally conductive amorphous carbon composite, wherein the highly thermally conductive material according to claim 1 is silicon carbide. 3. The high thermal conductive amorphous carbon composite according to claim 1, wherein the molding material contains a low surface tension substance in an amount of 0.1 to 5% by weight.