JP2015018829A - Polymer structure material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal conductive film or structure containing, for example, a heat conductive pigment powder, which is superior in heat conduction and less brittle, to obtain physical properties of pigment by mixing a large amount of pigment powders or particles with a polymer, in which hard and brittle physical properties of the pigment powder are also strongly reflected on the film or structure.SOLUTION: The heat conductor is a structure material which filled with graphite etc. as a heat conductive material by 70 wt.% or more; and a fiber material by 5-15 wt.% of entire structure material. With this, a thermal conductive structure with high heat conductivity and less brittle, which is filled with a large amount thermally conductive fillers such as graphite is obtained.

Description

  The present invention relates to a member used for a casing, a heat sink, a reflector, etc. of an electronic device that emits heat inside, a household electrical appliance, and the like, and more specifically, excellent in heat dissipation, insulation, workability, and corrosion resistance. It relates to a highly functional member.

  Furthermore, the present invention relates to a casing and sheet for electronic devices or household electrical appliances using the above-described members, and an electronic device or household electrical appliance using the casing and sheets, automobile parts, and decorations of the parts.

With the downsizing and high performance of electronic devices, heat emitted from these electronic components is often accumulated in a narrow space, and exhaust heat from the space is a problem. That is, since the high temperature inside the device due to heat generation in the electronic device may impair the performance of the precise electronic device body, it is an important issue to efficiently discharge the heat to the outside.
As materials having excellent thermal conductivity, carbon materials such as diamond, graphite, and carbon nanotubes, boron nitride, and alumina are known, but all of them are granular or powdery substances, and structural materials using these materials are used. However, there is a problem that the price is high and the structural material becomes brittle.

  In order to solve such a problem, Patent Document 1 discloses that heat is efficiently transferred to the outside by installing a sheet made of graphite inside or outside the device in order to prevent the temperature inside the device from being increased due to heat generation. Although it is disclosed to discharge, sheets made of graphite are expensive due to material and manufacturing costs.

  Patent Document 2 discloses a heat-radiating material made of a resin film excellent in bending workability, which contains a metal, a metal oxide, or the like as a pigment as a low-cost material with good workability and heat dissipation. . Here, the thermal diffusivity (several hundred [W / (mK)]) of the metal or metal oxide as the pigment is less than that of graphite (several thousand [W / (mK)]), and the thermal diffusivity of the resin is Nearly zero. Therefore, when using a metal or metal oxide as a pigment, it is necessary to increase the pigment / resin ratio, whereas when using graphite as a pigment, the desired thermal diffusivity is improved even if the ratio is relatively small. it can.

  Patent Document 3 discloses that heat transfer of a film is improved by blending a filler such as micron-sized graphite, diamond, and quartz powder, and nanoparticles of metal or graphite into a polymer.

  Patent Document 4 discloses that heat conduction and electrical resistance are improved by blending an electrically insulating and thermally conductive aluminum oxide filler and a thermally and electrically conductive graphite filler into nylon, polyamide and polyester. Has been.

  Patent Document 5 discloses that a blend composition of a curable polymer and a thermally conductive filler such as silica, diamond, and graphite having a maximum particle size of less than 25 microns is present between a thermally conductive material and a corresponding mating surface. Reducing thermal resistance is disclosed.

    Patent Document 6 discloses that glass fiber is filled at 15% by weight or less in order to improve the strength of the structural material.

JP 2010-171030 A JP 2008-155392 A JP 2007-504663 A JP 2010-535876 A JP 2007-503506 A JP 2005-239794 A

  A problem with Patent Document 2 is that it is difficult to improve the thermal diffusivity of the pigment-dispersed resin film because special carbon materials such as graphite and carbon nanotubes have low dispersibility in the resin. Furthermore, graphite and carbon anotube are anisotropic materials, and the thermal diffusion characteristics of graphite are 1000 [W / (mK)] or more in the high direction, but the low direction is about several tens [W / (mK)]. Therefore, when graphite is kneaded into a resin, good thermal diffusion characteristics cannot be obtained unless the graphite is oriented during film formation.

  In contrast to Patent Document 3, non-polar particles are required to orient graphite used as a micron-size filler, and non-polar particles smaller than graphite to orient graphite used as nanoparticles. Particles are needed. In addition, even when using anisotropic materials, the polymer matrix is obtained by blending fillers or nanoparticles with no gaps in the polymer, since the desired properties must be covered by the filling rate because they are not oriented. The physical properties such as flexibility of the resin are remarkably changed.

  In contrast to Patent Document 4, the resin must have a chemical structure containing more pi electrons in the side chain than the main chain, and the particle size and shape of each filler must be in a specific range. If it changes, the thermophysical properties, mechanical properties, appearance, etc. required for the polymer structure cannot be satisfied.

  In contrast to Patent Document 5, if the thermosetting polymer is a polymer containing many pi electrons in the main chain, and the filler used is graphite, an anisotropic material, the particle size must be large and the aspect ratio should not be large. Due to the difficulty of orientation, etc., the heat conducting material of Patent Document 6 reduces the resin mechanical properties of the polymer structure in order to improve the thermal diffusion properties, and further increases the filler filling rate in order to improve the thermal diffusion properties. Then there is concern about becoming brittle.

  In Patent Document 6, the powder filling rate is controlled to 15% by weight or less. When reflecting the excellent thermal conductivity of the powder to the structural material, the filling rate of the powder needs to be at least 70% by weight, and if the powder is filled by 70% by weight or more, the structural material becomes brittle.

  In order to solve the above-mentioned problems, the thermal conductor of the present invention is a structural material in which 70% by weight or more of the entire structural material is filled with graphite or the like as the thermal conductive material, and the fiber material is 5 to 15% of the entire structural material. It is characterized by filling in weight%.

  Thereby, even if it is a structural material with high heat conductivity filled with many heat conductive fillers, such as graphite, the heat conductive structure which is not brittle can be provided.

  Even if it is a brittle structural material containing 70% by weight or more of powder or granular material having excellent thermal conductivity dispersed and mixed in the resin, a structure having high impact strength is provided by filling 5 to 15% by weight of the fiber material. be able to.

  Accordingly, by appropriate selection of resin or additive, a flexible sheet to a rigid and lighter structure than a metal, such as an electronic device such as a personal computer, a household appliance such as a refrigerator, an indoor unit of an air conditioner, or a radiator of an outdoor unit Although it is necessary to dissipate heat, etc., it is extremely useful as a part intended for a housing material.

  The present inventor has found a method for improving the impact strength of a structural material containing 70% by weight or more of powder or granular pigments.

In general, a material with a high pigment ratio reflects the physical properties of the pigment in the structure, and the structure obtained when the pigment is not flexible is brittle. Therefore, the pigment ratio is kept low and the impact strength is further improved. Then, rubber material is added as a connecting material.
When the above-mentioned powder or granular material contained in the above-mentioned structure is graphite having excellent thermal conductivity and the above-mentioned structure has a high thermal conductivity, the heat conduction of the structure depends on the content of graphite contained. Since the rate changes, even when rubber material is added for the purpose of improving the impact strength of the structure, if the graphite content is reduced, the thermal conductivity of the resulting structure will be reduced. The content of the resin, which is a material, must be reduced.
The structure of the present invention can provide a strong structure without reducing the characteristics of the powder or granular material by dispersing the fiber material without reducing the above-mentioned powder or granular material ratio.
The powder, the fiber material, and the connecting material may be dispersed evenly in the structure, or the fiber layer and the powder layer may be formed in layers via the connecting material.

[Powder or granular material]
The structure of the present invention is a structure excellent in thermal conductivity, and the powder or granular material used is graphite or boron nitride excellent in thermal conductivity, and in order to obtain a high thermal diffusivity, Although it is desirable that the aspect ratio is large, the particle size and shape are not particularly limited.

  In order to obtain high thermal conductivity, a heat diffusible carbon material selected from at least one of carbon nanotubes, fullerenes, and diamonds may be mixed.

[Bonding material]
The material used for linking the structures used in the present invention is a polymer, and particularly the following polymers that are advantageous for dispersing a large amount of graphite. It is not particularly limited as long as it has an unsaturated bond in the unit chemical structure of the polymer material, and it may be selected by paying attention to strength, flexibility, heat resistance, etc. for each application. However, additives such as a curing agent and a release agent may be used as necessary.

[Fiber material]
The fiber material used in the present invention is not particularly limited as long as it is compatible with the material used for the heat conductive structure such as glass, carbon, aramid, polymers, metals, minerals, etc., as long as the material can be kneaded into the heat conductive structure. The surface of the material may be surface-treated as necessary for the purpose of improving affinity and the like.
A material having high strength of the fiber itself has a large effect of improving the strength of the heat conductive structure. For example, in glass, S glass having a strength higher than that of E glass has an effect of improving the strength of the heat conductive structure. Bigger than glass.
The fiber material may be cut for the purpose of facilitating handling, but since the effect expected when it is too short cannot be obtained sufficiently, the cut material is 1 mm or more in length rather than being powdery. If so, the effect of improving the strength of the heat conduction structure is greater. Further, the thinner the diameter of the material, the greater the effect, and it is desirable that the diameter is 100 μmφ or less.

[Mixing of heat conduction material and connecting material]
Each material was mixed using an IMC-1889 type 200 cc small mixer manufactured by Imoto Seisakusho. The blade of the agitation part is an Ellipse blade, and the blade or gear is rotated at a maximum of about 120 rpm by a Mitsubishi gear motor GM-S to agitate the powder or granular heat conduction material and the connecting material. When mixing only with a mixer, heat conduction material is added to the joining material little by little to the desired addition amount, and fiber material is added to fiber materials that are relatively hard fiber types such as glass fiber. What is necessary is just to produce the coating material used as the origin of a structure by low density | concentration or low rotation speed, or stirring for a short time so that it may not fracture.

[Dissolution of connecting material]
In order to make the resin finer when dispersing the material, it can also be heated during stirring, but if the temperature is near the thermal decomposition temperature of the resin or additive to be added, the resin or additive to be used, etc. However, by dissolving the resin in a solvent, the fluidity of the resin or additive can be secured at a low temperature.

  The resin is dissolved by mixing a solvent such as acetone with a ratio of the solvent 1 to the resin 1, for example, in a resin or pellets or powder that has a surface area as large as possible to allow the solvent to penetrate. Alternatively, a solvent may be added to such an extent that the resin swells and becomes a water tank state, and the mixture may be mixed with the heat conductive material.

  If an ultrasonic cleaner or a stirrer is used, it can be dissolved in a short time, and can be dissolved in a shorter time by heating. When the resin is not required to be dissolved, such as a resol type phenol resin, it is not necessary to use a solvent.

[Deposition of thermal conductive structure]
The resin mixture kneaded with the heat conductive material was formed into a film by the press method and the film was evaluated, but the film forming method is not particularly limited. The resin mixture of the present invention was formed by applying a press pressure under heating conditions so that the resin flowed easily when the film was deformed and the materials were easily connected.

  The heating conditions and the pressing pressure are not particularly limited, and may be set to the thermal decomposition temperature or lower of the resin or additive, or when using a thermosetting resin, the thermosetting temperature.

  The press pressure is not particularly limited as long as it can be molded to a desired thickness, and may be about 0.1 MPa or more per 100 mm 2 of the film-formed product.

  The molding thickness and area are not particularly limited, and may be formed to a desired thickness and area, but the thickness is 0.1 to 2 μm and the area is 5 to 40 mm in diameter as a sample for measuring thermal diffusion characteristics. The shape can be removed by cutting.

  The specific gravity of the film varies depending on the mixing ratio of each material and the resin, but the following evaluation was performed after confirming that the specific gravity was a high filling specific gravity satisfying the theoretical specific gravity of 50% or more.

  Hereinafter, preferred embodiments of the present invention will be specifically described based on Examples and Comparative Examples, but the present invention is not limited to these Examples.

[Examples and Comparative Examples 1 to 3]
The thermal conductive structure of the example uses a resol resin (phenol resin HP3000A manufactured by Asahi Organic Chemicals) as a connecting material, a special grade reagent graphite manufactured by Wako Pure Chemicals as a thermal conductive material, and S glass (S manufactured by AGY). -2G 3 mm length) and the ratio of the material (5 to 15% by weight of the entire structure) and the material type were changed. The ratio of graphite in the above heat conductive structure was adjusted to be 70% by weight or more of the entire structure.
The thermal conductive structures of the examples tended to decrease the impact strength when the ratio of graphite was increased. However, when the ratio of graphite in the thermal conductive structure was 75% by weight of the entire structure, The impact strength was 10 kJ / m ² and the thermal conductivity of the structure was 35 W / mK.
The structure of Comparative Example 1 was the same as the example in the film forming method, except that the composition was only the connecting material.
The structure of Comparative Example 2 was a structure made only of Toray's high impact strength ABS resin (Toyolac 930), and the same film forming method and the like were used.
The ratio of the graphite of the heat conductive material structure of Comparative Example 3 was 70% by weight or more of the entire structure, and the film forming method was the same as in the examples except that the fiber was not included.
In the heat conductive material structure of Comparative Example 4, the ratio of graphite is 70% by weight or more of the entire structure, and the joining resin is Torayak high impact strength ABS resin (Toyolac 930), and it does not contain fibers. The film method was the same as in the examples.

Comparative Example 1 was a structure directly reflecting the impact strength ² kJ / m ² of the resole resin, and the thermal conductivity was 0.3 or less.
Comparative Example 2 is the impact strength 13 kJ / m ² directly reflects structure having a high impact strength ABS resin but the thermal conductivity was 0.3 or less.
The heat conductive structure of Comparative Example 3 contained 75% by weight of graphite having a high heat conductivity, so that the heat conductivity was as high as 35 W / mK, but the impact strength was less than 1 kJ / m ² .
The thermal conductivity structure of Comparative Example 4 contained 75% by weight of graphite having a high thermal conductivity, so that the thermal conductivity was as high as 35 W / mK. However, although the impact strength was high, the impact strength was It was less than 1 kJ / m ² .

[Evaluation of structure]
[Thermal conductivity test]
In the heat dissipation test, the sample was measured and confirmed with a thermal diffusivity measuring device LFA457 Microflash manufactured by NETZSCH. In the heat dissipation test, the film produced by the above heating press was cut into a sample shape of 10 mm × 10 mm × 1 mmt and a diameter of 25 mm × about 0.4 mmt, and the thermal characteristics in the thickness direction and in-plane direction were measured.
[Strength measurement]
The strength test was conducted using a D-type impact tester No. The Charpy impact strength of the sample was measured and confirmed using 258-D.
Results of Evaluation of Structures of Examples and Comparative Examples From Table 1, the thermally conductive structure of the present invention provides a thermally conductive structure with improved strength of the above-described structure without reducing thermal conductivity characteristics.

  The present invention relates to a housing and sheet for electronic devices or home appliances using the member, and a member used for an electronic device or home appliance using the housing and the sheet.

Claims (3)

A polymer structural material comprising 70% by weight or more of powder and 5 to 15% by weight of a fiber material with respect to the entire structural material. The polymer structural material according to claim 1, wherein the powder is any one of graphite, carbon, boron nitride, and alumina. The polymer structural material according to claim 1, wherein the powder is a mixture containing at least one kind of graphite, carbon, boron nitride, and alumina.