JP2001079977A - Composite and method for producing the same - Google Patents

Abstract

(57) [Problem] To provide a light-weight composite having improved thermal conductivity and thermal responsiveness as compared with a material used for the purpose of rapid heat conduction, and light weight. The thickness is 0.01 mm to 0.3 mm, and the thermal conductivity in the plane direction is 500 W / m · K to 1000 W
/ M · K and a density of 0.5 g / cm ^{3 to} 1.5 g /
A composite having excellent thermal conductivity, comprising at least one sheet-like graphite material having a heat conduction anisotropy of at least ³ cm ³ and at least one other material composited therewith.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightweight composite (or composite material) having high thermal conductivity and a method for producing such a composite. Such a composite can be used, for example, for a molding pin of a mold, a structural material for aerospace, various cooling members, and the like.

[0002]

2. Description of the Related Art Materials having high thermal conductivity include, for example, carbon materials such as diamond and graphite, and metal materials such as silver and copper. Among such high heat conductive materials, diamond having the highest heat conductivity is diamond. The thermal conductivity of diamond is about 240
Although it is as large as 0 W / m · K, it cannot be obtained as a large crystal and is expensive, so it is not used as various structural materials, heat conductive materials and the like.

[0003] In the case of graphite, a single crystal has a thermal conductivity as large as 1000 W / m · K or more, but a crystal as large as diamond cannot be obtained. Therefore, a material obtained by solidifying graphite or carbon powder with a binder (also referred to as an expanded graphite sheet) is used. However, a material obtained by solidifying carbon powder with a binder has a thermal conductivity of at most 200 W / m · K, which is considerably smaller than that of a graphite single crystal. The carbon powder hardened with a binder has a problem that it breaks in 100 times or less even in a 90 ° bending test and lacks flexibility.

Although attention is not paid to the property of thermal conductivity, a carbon fiber reinforced composite in which carbon fibers are combined with a matrix of resin, metal, carbon, or the like is used from the viewpoint of strength. The thermal conductivity of such a carbon fiber reinforced composite is about 150 W / m · K or less.

[0005] Metals such as silver and copper have specific gravities of, for example, 10.50 for silver and 8.96 for copper, and therefore are not suitable for applications requiring weight reduction, such as structural materials for aerospace.
Further, since the metal has a large specific heat, in a portion where heating and cooling are repeated, such as a molding pin of a mold, the time required for heating and cooling becomes longer, and as a result, there is a problem that the molding tact becomes longer.

More specifically, for example, when considering a mold used for resin molding, the mold body can be formed to have a structure through which a heat medium can flow, and can be heated quickly by flowing a heating medium or a cooling medium.・ Cooling can be performed. However, a boss formed on the mold (for example, having a diameter of 8 m)
m or less) cannot have such a structure in which a heat medium flows. Therefore, a pin made of a material having high heat conductivity such as copper is used as a molding pin to cool the boss portion. . However, as compared with the mold body, it takes more time to heat and cool, resulting in a longer molding cycle.

[0007]

SUMMARY OF THE INVENTION The present invention provides a composite which has improved thermal conductivity and thermal responsiveness and is lighter in weight than materials currently used for rapid thermal conduction. The task is to provide.

[0008]

In view of the above problems, as a result of various studies, a thickness of 0.01 mm to 0.3 mm was obtained.
And the thermal conductivity in the plane direction is 500 W / m · K to 100
0 W / m · K and a density of 0.5 g / cm ^{3 to} 1.5
g / cm ³ , a composite obtained by compounding a sheet-like graphite material having a heat conduction anisotropy with another material, that is, a dissimilar material, is lightweight,
The inventors have found that the composite has excellent thermal conductivity and thermal responsiveness, and have completed the present invention.

Accordingly, the present invention provides, in a first aspect,
The thickness is 0.01 mm to 0.3 mm, the thermal conductivity in the plane direction is 500 W / m · K to 1000 W / m · K,
Heat conduction made that density is at least one other material at least one sheet-like graphite material and therewith has been complexed with a thermal conductivity anisotropy is 0.5g / cm ³ ~1.5g / cm ³ Provide a composite having excellent properties.

In the present invention, “excellent in thermal conductivity” means that
The composite of the present invention has a higher thermal conductivity than the other material (or dissimilar material) inherently, ie, conducts more heat (and thus transfers heat faster). ) Or means that the composite of the present invention is lighter in density than the other materials even with the same thermal conductivity. Such composites transfer heat from one heat source to another more quickly (eg, transfer heat,
To dissipate or dissipate heat).

Thus, in one aspect, the present invention provides:
Provided is a composite for heat conduction, wherein a sheet-like graphite material having heat conduction anisotropy is compounded in a different kind of material. That is, the present invention provides a composite in which heat from a heat source is quickly transferred to another place to suppress an increase in the temperature of the heat source or to lower the temperature of the heat source.

According to a second aspect of the present invention, there is provided a method for producing a composite having excellent thermal conductivity, the method comprising:
m to 0.3 mm, and the thermal conductivity in the plane direction is 500 W /
m · K to 1000 W / m · K and a density of 0.5 g /
Provided is a production method characterized in that at least one sheet-like graphite material having a heat conduction anisotropy of from cm ^{3 to} 1.5 g / cm ³ is combined with at least one other material.

In the present specification, “composite” means
A substantially single member or material that combines two or more different materials (sheet graphite material and other materials) so that they work together to perform one function (eg, heat conduction) Means that it can be treated as

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a sheet-like graphite material having specific properties as described above is a material that can be considered to have properties substantially equivalent to graphite, It has high thermal anisotropy in the plane direction. The thermal conductivity in the plane direction is preferably 50 to 500 times the thermal conductivity in the thickness direction, and 100 to 500 times.
More preferably, it is 300 times. Therefore, in the composite of the present invention, the direction of heat conduction is mainly along the surface of the sheet-like graphite material. The term “sheet-like” means that the dimension in the thickness direction is relatively smaller than the dimension in the plane direction.

[0015] Such a graphite material can be produced, for example, by the method described in JP-A-3-75211. For example, it can be obtained by heat-treating a polymer film of polyimide, polyoxadiazole, or the like at a temperature of 2400 ° C. or higher (for example, 2700 ° C.). This sheet-like graphite material has a large thermal conductivity in the plane direction of 500 to 1000 W / m · K, and the graphite material produced by this method was found to have only a graphite structure by Raman spectroscopy. Further, the content of impurities is 1% or less, and therefore, it has substantially the same properties as graphite. The sheet-like graphite material manufactured by this method can be used in a 90 ° bending test or a rubbing fatigue test (using a JIS P 8115 MIT type automatic bending tester (with a bending angle of 90 °)).
It has the flexibility not to break even if it is bent 0 times or more.

[0016] The thickness of the sheet-like graphite material is more preferably 0.05 mm to 0.15 mm. Further, the thermal conductivity in the plane direction is more preferably 500 W / m.
· K to 800 W / m · K. Furthermore, the density is more preferably ^{0.8g / cm 3 ~1.1g / cm 3} .

Of course, as long as it is available and has the specific properties described above, the sheet graphite material may be manufactured by other methods or may be naturally occurring.

In the composite of the present invention, a plurality of sheet-like graphite materials may be present, which is often preferred. For example, the sheet-like graphite material may be wound at least one time around the other material present as a core, and the other material (the same as the core) may be wound around the wound sheet-like graphite material. Or another type of material).

As described above, when a plurality of sheet-like graphite materials are present, even if the sheet-like graphite materials are adjacent to (or in contact with) each other, a space exists between the sheet-like graphite materials. Alternatively, the sheet-like graphite materials may be adjacent to each other via another material, or such various states may be mixed in any combination.

In the composite of the present invention, the other material or the different material to which the above-mentioned sheet-like graphite material is compounded is not particularly limited. For example, a metal material (eg, copper, nickel, aluminum) , Gold), plastic material (for example, phenolic resin, epoxy resin, furan resin, polyimide resin) or inorganic material (for example, carbon (graphitized carbon, vitrified carbon, pyrolytic carbon, and carbonized plastic material) ), Silicon, and boron), or may be a composite of these in advance.

The form of these other materials is not particularly limited, and may be, for example, a sheet,
It may be in the form of a film or a thin film. Of course, other materials may be in a commonly available form (for example, cylindrical, cylindrical, etc.).

The form of the composite of the present invention is not particularly limited as long as the graphite material is present in the form of a sheet. , Cylindrical, columnar, plate-like or the like. In one preferred embodiment of the composite of the present invention, the sheet graphite material is present inside another material. Specifically, the sheet-like graphite material is, for example, embedded in, surrounded by, or covered by another material. Of course, the sheet-like graphite material may be exposed, but the sheet-like graphite material has mechanical strength,
In particular, since the abrasion strength is low, it is preferable that the material is protected from being exposed by other materials.

For example, using different materials as a core or a shaft,
A cylindrical composite around which a sheet-like graphite material is arranged in a cylindrical shape may be used. Alternatively, a cylindrical composite may be used with a hollow shaft (that is, an annular shape). In the latter case, the weight can be reduced. Further, another material (which may be the same material as another material inside or another material) may be arranged around the cylindrical sheet-like graphite material. For example, such other material may be coated or a sheet of such other material may be wrapped.

The method for producing the composite of the present invention is not particularly limited as long as it can be composited with the above-mentioned sheet-like graphite material. A specific method of compounding may be any method as long as the above-described “compositing” of different materials such as a sheet-like graphite material and another material can be achieved.

For example, the following methods can be used as a compounding method: (1) Attachment (a bonding of different materials by some physical and / or chemical force, for example a plastic material as another material or a precursor thereof) (Plastic material before curing) (which may be melted or dissolved or dispersed in a solvent, if necessary) is applied (or applied)); (2) Adhesion (adhesive is applied between different materials) (3) mechanical fastening (mechanical means (eg, staples,
(4) crimping (compressing different materials together and applying heat if necessary); (5) plating (plating metal material on graphite material) Do);

(6) vapor deposition (CVD, PVD, chemically or physically attaching molecules of another material to the graphite material); (7) welding (applying another material that has been melted to the graphite material, or graphite) (8) Modification (in a state where the graphite material and the other material are in contact with each other, for example, the graphite material is combined with the other material by the method described in (1) to (7) above). After that, the other material is chemically and / or thermally denatured and converted into another material, thereby being complexed with another material).

For example, a method of performing composite with a metal material by plating a metal material on a sheet-like graphite material, a method of performing composite with a plastic material by coating a plastic material on a sheet-like graphite material, It is also preferable to apply a plastic material to the sheet-like graphite material, and then heat-treat and carbonize the plastic material to form a composite with carbon.

In the composite of the present invention, if the thickness of the sheet-like graphite material to be used is less than 0.01 mm, the strength becomes weak, and it is generally difficult to produce the composite of the present invention. Become. Conversely, when the thickness is more than 0.3 mm, the flexibility is reduced, and it may not be possible to form a composite with another material in a free shape. Further, when the thermal conductivity in the plane direction is less than 500 W / m · K, when other materials are combined with a metal having good thermal conductivity such as copper, even when copper and sheet graphite material are combined. Thermal conductivity is not so improved (of course, there is an advantage of light weight). On the other hand, a sheet-like graphite material having a thermal conductivity of more than 1000 W / m · K is not currently available.

Further, when the density of the sheet-like graphite material is smaller than 0.5 g / cm ³ , the sheet-like graphite material has many voids and becomes very brittle in strength.
Not suitable for compounding. Conversely, if the density of the sheet-like graphite material is greater than 1.5 g / cm ³ , the sheet loses flexibility and is not suitable for compounding in this case. In some cases, the graphite material breaks and the desired heat conduction cannot be achieved.

Further, in a third aspect, the present invention provides a heat diffusion member, for example, a molding pin and a radiation fin, manufactured using the above-described composite. The longitudinal direction of this pin corresponds to the plane direction of the sheet-like graphite material.
In yet another aspect, the present invention provides a structural material formed by the above-described composite, for example, a partition wall of a fusion reactor, a structural material for a satellite.

[0031]

(Example 1) In order to improve the thermal conductivity and thermal responsiveness of a metal material and to further reduce the weight, a composite in which a sheet-like graphite material is compounded in a metal material is produced.
A composite is produced using copper having high thermal conductivity as a metal material, and the density and thermal conductivity are compared with copper alone.

A polyimide film having a thickness of 75 μm is graphitized at 2700 ° C. based on a method described in Japanese Patent Application Laid-Open No. 3-75211 to form a polyimide film having a thickness of 10 μm.
0 μm, density 1.0 g / cm ³ , thermal conductivity in plane direction is 8
A sheet-like graphite material of 00 W / m · K was produced.

This sheet-like graphite material was supplied with φ2.0
5 mm, and wound around the copper as a core having a length of 50 mm five times, and fastened with a carbon-based adhesive to make the thickness of the sheet-like graphite material portion 0.5 mm, and then, the outer peripheral portion was made 1 mm using copper sulfate. A composite having a thickness of 5.0 mm and a length of 50 mm and having a high thermal conductivity was formed by plating copper with a thickness to form a composite.

When the overall density of the composite was measured, it was 6.8 g / cm ³ . This is a value that is at least 20% smaller than the copper density of 8.9 g / cm ³ . The thermal conductivity of this composite is 550 W / m · K, which is higher than the thermal conductivity of copper, about 400 W / m · K.
The thermal conductivity was measured by a laser flash method.

Next, in order to evaluate the thermal conductivity of the composite, a cylindrical copper core (B) having the same shape as the composite (A) was prepared, and one end was contacted with a heat source (100 ° C.). Let
The time change of the temperature at the other end was measured by a thermocouple (the time of contact was zero at the time of contact). After 130 seconds, the heat source was released. The result is shown in FIG. As can be seen from this figure, the composite of Example 1 has higher thermal conductivity and thus higher thermal conductivity than the copper core, and also has excellent thermal responsiveness because of its small heat capacity.

Further, the bending strength of the composite in the case of two-point support was measured. As a test condition, the distance between fulcrums was 40 m
m, the head speed was 10 mm / min. As a result, the strength of the composite was 74 kgf, and the bending strength of the copper core was 86 kgf. Although the composite of Example 1 is slightly weaker in strength than copper alone, it can be understood that the composite is generally preferable as a heat conductive material in consideration of its light weight and good thermal conductivity.

(Example 2) In order to improve the thermal conductivity and thermal responsiveness of the resin material and to further reduce the weight, a composite in which a sheet-like graphite material is compounded in the resin material is produced. First, the sheet-like graphite material prepared in Example 1 was used, and the sheet-like graphite material was changed to φ2.0.
After winding 5 times around a resin material (made of epoxy resin) as a core having a thickness of 5 mm and fastening with an epoxy resin to reduce the thickness of the sheet-like graphite material to 0.5 mm, the outer periphery was coated with an epoxy resin. After that, heat the resin,
The mixture was cured to produce a columnar composite having a diameter of 5.0 mm.

As a result of measuring the density of the obtained composite,
It was 1.6 g / cm ³ . This is equivalent to the density of the epoxy resin. However, when the thermal conductivity was measured, 20
W / m · K, and the thermal conductivity of the epoxy resin is from 0.5 to 1 W / m · K, filled with aluminum powder for casting. Therefore, this composite has high thermal conductivity. Understand. Therefore, this composite has a weight equivalent to that of the resin material and is suitable for applications in which higher thermal conductivity is required than that of the resin material.

In this embodiment, the other material is an epoxy resin, and the composite method of the epoxy resin and the sheet-like graphite material is performed by bonding with an epoxy resin which also functions as an adhesive.
Or it can be said that it is simply adhesion of the epoxy resin.

Example 3 In order to improve the thermal conductivity and thermal responsiveness of a carbon material, a composite in which a sheet-like graphite material is combined with a carbon material is prepared.

The sheet-like graphite material produced in Example 1 was wound around the carbon-based material (comprising carbon powder and binder) as a core having a diameter of 2.0 mm five times and fastened with a carbon-based adhesive. After the thickness of the portion was set to 0.5 mm, a phenol resin was applied to the outer peripheral portion. At this time, it may be mixed with a solvent such as methanol or xylene in order to lower the viscosity of the resin. Thereafter, the resin was carbonized by firing at a temperature of 1000 ° C. or higher in an inert atmosphere. Thereafter, application and carbonization of the resin were repeated (a total of three times) to finally obtain a composite having a diameter of 5.5 mm. In addition, since the resin is thermally decomposed by firing to form voids, it was necessary to repeat application and firing of the resin.

The density of the obtained composite was 1.4 g / cm.
^{Was 3} . This is equivalent to a carbon-based composite such as a carbon fiber / carbon composite. However, the thermal conductivity is 2
50 W / m · K, the conventional carbon fiber / carbon composite has a thermal conductivity of 100 W / m · K, and the high thermal conductive carbon fiber / boron carbide composite has a thermal conductivity of 150 W described in JP-A-8-81261. It can be seen that the thermal conductivity is higher than / m · K. Therefore, the composite obtained in this example is
It is suitable for applications where heat resistance is required and high thermal conductivity is required, for example, a reactor wall of a fusion reactor.

In this embodiment, the other material is a carbonized phenol resin, that is, carbon, and in this case, the composite method can be said to be modification.

[0044]

According to the present invention, a composite having excellent thermal conductivity and thermal responsiveness can be obtained by combining a sheet-like graphite material with a conventionally used metal, resin or carbon material.
Therefore, for example, when used for a molding pin of a mold, since heating and cooling are repeated, the thermal responsiveness of the molding pin is high,
The molding tact can be accelerated.

[Brief description of the drawings]

FIG. 1 is a graph comparing the heat transfer performance of the composite of Example 1 with copper.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yasushi Okada 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F term (reference) 4F100 AA00B AA37A AB01B AK01B AT00B BA02 BA10A BA10B CC00B DD31 EH71B GB90 JA13A JA20AJJ01A 4G032 AA04 AA12 AA41 BA00 4G046 EA05 EB06 EC01 EC05

Claims (14)

[Claims] 1. The thickness is 0.01 mm to 0.3 mm, and the thermal conductivity in the plane direction is 500 W / m · K to 1000 W.
/ M · K and a density of 0.5 g / cm ^{3 to} 1.5 g /
A composite comprising at least one sheet-like graphite material having a heat conduction anisotropy of cm ³ and at least one other material composited therewith. 2. A sheet made of a graphite material has a thickness of 0.05 mm to 0.15 mm, a thermal conductivity in a plane direction of 500 W / m · K to 800 W / m · K, and a density of 0.8 g. 2. The composite according to claim 1, wherein the weight ratio is in the range of 0.1 g / cm ^{3 to} 1.1 g / cm ³ . 3. The composite according to claim 1, wherein at least one round of the sheet-like graphite material is wound around the other columnar material. 4. The composite according to claim 1, wherein at least one round of the sheet-like graphite material is wound around the other cylindrical material. 5. The composite according to claim 3, wherein another material is further disposed around the sheet-like graphite material. 6. The composite according to claim 1, wherein the other material is a metal material, a plastic material, or an inorganic material. 7. A method for producing a composite, the method comprising:
01 mm to 0.3 mm, and the thermal conductivity in the surface direction is 50
0 W / m · K to 1000 W / m · K, and the density is 0.1 W / m · K.
Production wherein the at least complexed with one other material at least one sheet-like graphite material having a thermal conductivity anisotropy is ^{5g / cm 3 ~1.5g / cm 3} . 8. The method according to claim 7, wherein the composite is formed by plating a sheet-like graphite material with a metal material. 9. The method for producing a composite according to claim 7, wherein the composite is formed by applying a plastic material to the sheet-like graphite material. 10. The method for producing a composite according to claim 7, wherein the composite is formed by applying a plastic material to the sheet-like graphite material, and then heat-treating and carbonizing the plastic material. 11. A step of forming a composite by winding the sheet-like graphite material around at least one turn around another material present as a core, and the same as or different from the core around the wound sheet-like graphite material. The method for producing a composite according to claim 7, comprising a step of compounding the material. 12. A sheet-like graphite material used for producing a composite having excellent thermal conductivity by being composited with another material, having a thickness of 0.01 mm to 0.3 mm and a planar direction. Has a thermal conductivity of 500 W / m · K to 1000 W
/ M · K and a density of 0.5 g / cm ^{3 to} 1.5 g /
graphite material is cm ^3. 13. A heat diffusion member manufactured by using the composite according to claim 1. Description: 14. The heat diffusion member according to claim 13, which is a molded pin.