JP2009078967A - High thermal conductivity graphite material, and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a graphite material having a low thermal expansion coefficient while having excellent thermal conductivity, and to provide a method for producing the same. <P>SOLUTION: The method for producing the high thermal conductivity graphite material comprises: a kneading stage where a binder is added to the one obtained by pulverizing coal pitch-based mosaic coke in which spherical crystals composing the structure are large and whose needle ratio is low, so as to be the average grain size of 13 to 20 μm, and kneading is performed; a repulverizing stage; a molding stage; a firing stage; an impregnating stage; a refiring stage; a graphitizing stage; and a stage where, after the graphitizing stage, an impregnating stage, a firing stage and a graphitizing stage are repeated. Further, the high thermal conductivity graphite material is obtained by the above production method, and in which bulk density is ≥1.85 g/cm<SP>3</SP>, thermal conductivity in the respective directions of X, Y, Z directions is ≥170 W/m K and a thermal expansion coefficient is ≤5.5×10<SP>-6</SP>/K, and which is isotropic. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an isotropic graphite material and a method for producing the same. Specifically, for example, a material used for a heat sink, a heat exchanger, an electrode for arc discharge, a component for an ion implantation apparatus, a continuous casting member, and the like. The present invention relates to a graphite material having excellent thermal conductivity and a low thermal expansion coefficient, and a method for producing the same.

Conventionally, graphite materials are known, and for example, there are those disclosed in Patent Document 1 below. In Patent Document 1, in a carbon graphite material composed of an aggregate and a binder, the aggregate is bonded via a carbon / graphite layer derived from at least two kinds of binders having different graphitization properties. It is a carbon / graphite material characterized by
JP-A-1-160864

  However, since the thing of patent document 1 is a thing with a low thermal expansion coefficient but a low thermal conductivity, it is difficult to use it for materials that require high thermal conductivity, such as heat sink materials and continuous cast members. .

  Therefore, an object of the present invention is to provide a graphite material having a low thermal expansion coefficient while having excellent thermal conductivity, and a method for producing the graphite material.

In the method for producing a high thermal conductivity graphite material of the present invention, a binder is added to a pulverized coal pitch mosaic coke having a large spherulite structure and a low needle ratio to an average particle size of 13 to 20 μm. A kneading step for kneading at a temperature, a regrinding step for regrinding the kneaded material in the kneading step, a molding step for molding the reground material in the regrinding step at a predetermined pressure, and the molding step A firing step of firing the molded product at a predetermined temperature, an impregnation step of impregnating pitch into the product fired in the firing step, and a re-firing step of refiring the one impregnated with pitch in the impregnation step And a graphitization step of graphitizing the re-baked product in the re-baking step, and a step of repeating the impregnation step, the firing step, and the graphitization step after the graphitization step. Features A method for producing a highly heat-conductive graphite material. In particular, the coal pitch-based mosaic coke is preferably a coal pitch-based mosaic coke whose main component constituting the coke structure is bulk mesophase in which spherulites are grown and coalesced.
The high thermal conductive graphite material of the present invention has a bulk density of 1.85 g / cm ³ or more obtained by the above-described production method, and a thermal conductivity of 170 W / in each direction in the X, Y, and Z axis directions. It is an isotropic high thermal conductive graphite material having a (m · K) or more and a thermal expansion coefficient of 3.5 × 10 ^{−6 to} 5.5 × 10 ⁻⁶ / K.

  According to the present invention, it is possible to provide a high thermal conductive graphite material having a low thermal expansion coefficient while having excellent thermal conductivity.

The high thermal conductive graphite material according to the present invention uses a graphite material called mosaic coke as a raw material. This mosaic coke is a coke in which the optically anisotropic structure constituting the structure is not greatly grown like needle coke but is finely dispersed in a matrix.
Among the mosaic cokes, coal pitch-based mosaic coke is particularly suitable as a raw material for the high thermal conductive graphite material according to the present invention because it has good graphitization properties. Further, this mosaic coke is preferably one having a large spherulite constituting the structure and a low needle ratio, and more preferably just before growing into needle coke.

The coal pitch-based mosaic coke used for the high thermal conductive graphite material according to the present invention has a true density of 1.95 to 2.05 g / cm ³ and an average thermal expansion coefficient from room temperature to 130 ° C. of 1.5 ×. used as a ^{10 -6 ~3.5 × 10 -6 / K} .

Next, the manufacturing method of the high thermal conductivity graphite material according to the present invention will be described.
First, the above-described coal pitch mosaic coke is pulverized to an average particle size of 10 to 25 μm, a binder pitch is added to the pulverized product, and the mixture is kneaded at 150 to 250 ° C. to adjust the volatile content. In addition, although a coal tar pitch or petroleum pitch is used for a binder pitch, in order to improve wettability with an aggregate, what added the tar component may be used. Next, the kneaded product is reground to an average particle size of 20 to 60 μm, and the reground product is rubber molded at a pressure of 500 to 1000 kg / cm ² to obtain a molded body. And this molded object is baked at 800-1000 degreeC, and this baked molded object is pitch impregnated. Next, the pitch-impregnated shaped body is refired, and the refired shaped body is graphitized. Further, the graphitized shaped body is pitch impregnated, refired and graphitized.

  According to the manufacturing method, it is possible to provide a high thermal conductive graphite material having a low coefficient of thermal expansion while having excellent thermal conductivity.

  Next, for the following Examples 1 and 2 and Comparative Examples 1 to 3, thermal conductivity in the X, Y, and Z directions was measured by a laser flash method. Specifically, the sample was processed into a diameter of 10 mm and a thickness of 2 to 3 mm, the thermal diffusivity was determined with a laser flash thermal constant measuring device, and the thermal conductivity was calculated from the heat capacity and bulk density. The thermal expansion coefficient was measured by a so-called dilatometer method in which sample graphite was processed to 10 × 10 × 60 (mm) and the expansion length was detected.

Example 1
Coal pitch-based mosaic coke (true density 2.00 g / cm ³ ) was pulverized to an average particle size of 20 microns to obtain a filler. 58 parts of coal tar pitch as a binder was added to 100 parts of this filler, and the mixture was kneaded at 200 ° C., and volatile matter was adjusted and taken out. The kneaded material is pulverized to an average particle diameter of around 40 microns as usual, and then molded by rubber molding at 700 kg / cm ^{2 using} Cold Isostatic Pressing (hereinafter referred to as CIP). A graphite block (density 1.81 g / cm ³ ) was obtained through a firing step, a pitch impregnation firing step, and a graphitization step.
Further, the obtained graphite was pitch-impregnated and fired, and then graphitized.
The graphite material thus obtained was used as a sample of Example 1.

(Example 2)
Coal pitch-based mosaic coke (true density: 2.00 g / cm ³ ) was pulverized to an average particle size of 13 microns to obtain a filler. 62 parts of coal tar pitch as a binder was added to 100 parts of this filler, and the mixture was kneaded at 200 ° C., and volatile matter was adjusted and taken out. The kneaded material is pulverized to around 40 microns as usual, and then molded with CIP at 700 kg / cm ² to obtain a molded body. After the firing step, pitch impregnation firing step, and graphitization step, the graphite block (density 1.82 g / cm ³ ) was obtained.
Further, the obtained graphite was pitch-impregnated and fired, and then graphitized.
The graphite material thus obtained was used as a sample of Example 2.

(Comparative Example 1)
Coal pitch-based mosaic coke having a high needle ratio (true density 2.01 g / cm ³ ) was pulverized to an average particle size of 20 microns to obtain a filler. 58 parts of coal tar pitch was added to 100 parts of this filler, and the mixture was kneaded at 200 ° C., and volatile matter was adjusted and taken out. This was pulverized to about 40 microns as usual, and then rubber molded with CIP at 700 kg / cm ² to obtain a molded body. Further, a graphite block (density 1) was obtained through a firing step, a pitch impregnation firing step, and a graphitization step. .81 g / cm ³ ) was obtained.
Further, the obtained graphite was pitch-impregnated and fired, and then graphitized.
The graphite material thus obtained was used as a sample of Comparative Example 1.

(Comparative Example 2)
Coal pitch-based mosaic coke (true density 2.00 g / cm ³ ) having a smaller spherulite size than coal pitch-based mosaic coke used in Example 1 was pulverized to an average particle size of 20 microns to obtain a filler. 60 parts of coal tar pitch as a binder was added to 100 parts of this filler, and the mixture was kneaded at 200 ° C., and volatile matter was adjusted and taken out. The kneaded material is pulverized to about 40 microns as usual, and then rubber molded with CIP at 700 kg / cm ² to obtain a molded body. Further, a graphite block (density) is obtained through a firing step, a pitch impregnation firing step, and a graphitization step. 1.81 g / cm ³ ) was obtained.
The obtained graphite was pitch impregnated and fired, and then graphitized.
The graphite material thus obtained was used as a sample of Comparative Example 2.

(Comparative Example 3)
Coal pitch-based mosaic coke was pulverized to an average particle size of 7 microns to obtain a filler. 75 parts of coal tar pitch as a binder was added to 100 parts of this filler, and the mixture was kneaded at 200 ° C., and the volatile matter was adjusted and taken out. The kneaded material is pulverized to around 40 microns as usual, and then rubber molded at 700 kg / cm ^{2 with} CIP to obtain a molded body. Further, the graphite block (density) is obtained through a firing step, a pitch impregnation firing step, and a graphitization step. 1.84 g / cm ³ ) was obtained.
Further, it was graphitized after pitch impregnation and firing.
The graphite material thus obtained was used as a sample of Comparative Example 3.

  Table 1 below shows the measurement results of the bulk density, thermal conductivity, and thermal expansion coefficient (for 623 to 723K) in the X, Y, and Z directions of the samples of Examples 1 and 2 and Comparative Examples 1 to 3.

When each step of Examples 1 and 2 is performed with the average particle diameter of the coal pitch mosaic coke being between 10 and 25 microns, the bulk density is 1.85 g / cm ³ or more, and each of the X, Y, and Z axis directions. It was confirmed that an isotropic high thermal conductive graphite material having a thermal conductivity in the direction of 170 W / m · K or more and a thermal expansion coefficient of 5.5 × 10 ⁻⁶ / K or less can be provided.
On the other hand, as in Comparative Example 1, the high thermal conductivity graphite material when coke having a high needle rate is used as a raw material is clearly inferior in thermal conductivity to the high thermal conductivity graphite material of Examples 1 and 2. Was confirmed.
Moreover, in the high thermal conductivity graphite material in which mosaic coke having a small spherulite size is used as a raw material as in Comparative Example 2, both the thermal conductivity and the thermal expansion coefficient are high thermal conductivities of Examples 1 and 2. It was confirmed that it was clearly inferior to the graphite material.
Further, as in Comparative Example 3, even in the originally proper mosaic coke, in the high thermal conductive graphite material when the fine particles are used as a raw material, compared to the high thermal conductive graphite material of Examples 1 and 2, It was found that the thermal conductivity was clearly inferior, and the thermal expansion coefficient was confirmed to be somewhat inferior.

  Therefore, the high thermal conductivity graphite materials of Examples 1 and 2 according to the present invention have a thermal conductivity superior to that of the conventional one (the high thermal conductivity graphite materials of Comparative Examples 1 to 3), and a low thermal expansion coefficient. It has also been confirmed that it also has.

  The present invention can be modified in design without departing from the scope of the claims, and is not limited to the above embodiment.

Claims (3)

A kneading process in which a binder is added to a pulverized coal pitch mosaic coke having a large spherulite structure and a low needle ratio to an average particle size of 13 to 20 μm and kneaded at a predetermined temperature;
A regrinding step for regrinding the kneaded material in the kneading step;
A molding step for molding the one re-pulverized in the re-pulverization step at a predetermined pressure;
A firing step of firing the product molded in the molding step at a predetermined temperature;
An impregnation step of impregnating pitch into the one fired in the firing step;
A refiring step of refiring the pitch impregnated in the impregnation step;
A graphitization step of graphitizing the refired step in the rebaking step;
A method for producing a high thermal conductivity graphite material, comprising the step of repeating the impregnation step, the firing step, and the graphitization step after the graphitization step.   The said coal pitch type mosaic coke is a coal pitch type mosaic coke whose main component which comprises a coke structure | tissue is the bulk mesophase (Coarse isotropic) in which the spherulite grew and united. A method for producing a high thermal conductive graphite material. Obtained by the production method of claim 1,
The bulk density is 1.85 g / cm ³ or more, the thermal conductivity in each of the X, Y, and Z axis directions is 170 W / (m · K) or more, and the thermal expansion coefficient is 5.5 × 10 ^−6. Isotropic high thermal conductive graphite material characterized by being / K or less.