JP5124333B2 - Resin molding material - Google Patents

Description

  The present invention relates to a resin alumina composite material in which alumina is contained in a resin. In particular, the present invention relates to a resin-alumina composite material suitable as a heat radiating material for efficiently radiating heat generated from heat generating components of various electric and electronic devices.

  In recent years, with the miniaturization and high performance of electronic devices, how to take heat dissipation measures has become an important issue. Therefore, in order to increase the thermal conductivity of the resin, a method is generally used in which fine particles having high thermal conductivity are added to the resin as fillers. As an electrically insulating filler added to form a highly heat-conductive insulating resin, alumina or alumina nitride having higher heat conductivity is often used. The effect of adding filler with a high thermal conductivity of the resin appears prominently when the filler filling amount is increased. However, if the filler filling amount is increased, the moldability and adhesiveness of the resin are deteriorated. At most, it is about 50-60 vol%.

  There is a need for a method that can provide a larger filler addition effect with a smaller filler addition amount. As one of the methods, a method using a filler having a fibrous structure can be considered. By using a filler having a fibrous shape as an additive, a continuous structure with a high thermal conductivity filler can be easily formed compared to the case of using a conventional spherical filler as an additive. Greater thermal conductivity can be expected. Fibrous high thermal conductive fillers such as alumina are hard and brittle and difficult to process into a desired shape. As described in JP-A-59-379658 (Patent Document 1), It is necessary to devise measures such as reducing purity and mixing with other fibers. JP-A-63-132045 (Patent Document 2) describes workability without lowering the purity of alumina or mixing with other fibers in order to avoid the result of lowering thermal conductivity. A method of forming fibrous alumina by processing an excellent alumina precursor into a desired shape and then firing it is known.

JP 59-39765 A JP-A-63-132045

  As described above, lowering the purity of alumina or mixing with other fibers is not preferable for maintaining thermal conductivity. In addition, the processing and firing of the alumina precursor is limited to the filling amount of the fibrous filler when the alumina / resin composite is formed because the precursor is fibrous and the alumina precursor undergoes volume shrinkage upon firing. There is. Further, the contact between the filled fibers is insufficient, the heat conduction is hindered, and there is a limit to improving the heat conductivity even with the resin alumina composite material. Accordingly, an object of the present invention is to provide a resin-alumina composite material that increases the filling amount of alumina and further improves the thermal conductivity.

  The features of the present invention that solve the above-described problems are as described in the claims.

  Alumina crystal precursor is impregnated into an alumina porous body precursor such as a sheet material made of fibrous alumina and fired to form alumina microcrystals having a crystallite diameter of 300 nm or less between the fibrous alumina surface and the fibrous alumina. Let me. As a result, an alumina porous body having a network structure in which alumina crystals grow between fibers made of α-alumina crystals having an average crystallite diameter of 300 nm or less and the alumina fibers are fixed by alumina crystals can be obtained. With the alumina porous body having such an alumina network structure, the alumina filling amount in the resin molding is increased and the thermal conduction is improved.

  The resin-alumina composite material of the present invention has an alumina porous body and a resin composition impregnated in the alumina porous body. The porous alumina body is preferably made of alumina microcrystals having a crystallite diameter of 300 nm or less. Fibrous alumina is easy to mold. In addition, the alumina microcrystals adhere to the surface of the fibrous alumina, increase the alumina density per volume of the porous alumina body, and increase the alumina filling amount in the resin alumina composite material. By joining the fibers to form a network structure, high thermal conductivity is achieved when a resin-alumina composite material is used.

  The alumina porous body is prepared by impregnating a fibrous alumina sheet made of an aggregate of fibrous α-alumina with an alumina precursor solution, drying the fibrous alumina sheet, and then firing. In addition, the fibrous alumina sheet can be produced by forming alumina precursor fibers such as a fiber-shaped aluminum compound into a sheet shape and firing it to form α-alumina. The resin-alumina composite material is prepared by impregnating an alumina porous body with a resin composition, molding and curing.

  ADVANTAGE OF THE INVENTION According to this invention, while increasing the filling rate of an alumina, the network structure is formed between the filled fibers, thermal conductivity is improved, and the resin alumina composite material which can be shape | molded in a desired shape is provided. it can.

The alumina porous body for the resin-alumina composite material of the present invention is produced by the following steps.
(1) A step of forming a precursor of an α-alumina porous body such as a fibrous alumina sheet by forming and firing the alumina precursor fiber into a sheet shape (2) Alumina porous body precursor such as a fibrous alumina sheet Step of forming alumina porous body by impregnating body with alumina precursor solution, drying and firing (3) Process of forming resin alumina composite by impregnating alumina porous body with resin

  The resin-alumina composite material thus formed easily achieves a desired shape and has a high thermal conductivity.

  As an alumina precursor fiber for producing a fibrous alumina sheet, a fibrous alumina precursor compound capable of forming an alumina fiber by firing is used. Alumina precursor fibers are formed into a sheet shape or other shapes and fired to obtain a fibrous alumina aggregate having a free shape such as a fibrous alumina sheet made of α-alumina fibers.

  Various methods for forming the alumina precursor fiber into a sheet shape are conceivable. For example, the dispersion liquid of the alumina precursor fiber is processed by suction filtration or the like, and is compressed into a sheet shape. In addition, the dispersion of organic fibers such as cellulose fibers, which are burned off by firing, is processed by suction filtration, etc., compressed, formed into a sheet, and then the alumina precursor fibers are adhered to the surface to form a sheet of alumina precursor fibers. Can be formed. The formed alumina precursor sheet is baked at a temperature for converting to α, to obtain an alumina sheet made of α-alumina fibers. The alumina fiber diameter of the fibrous alumina sheet is preferably smaller than the original alumina precursor fiber and 300 nm or less. This is because the alumina precursor solution enters the inside of the fibrous alumina sheet by sufficiently separating the fibers of the fibrous alumina sheet.

  As the alumina precursor fiber, for example, fibrous boehmite, basic aluminum chloride, basic aluminum sulfate, basic aluminum carbonate, or the like can be used. Fibrous boehmite, basic aluminum chloride, basic aluminum sulfate, basic aluminum carbonate, and other compounds have a fibrous structure, and have a crystallite diameter of 300 nm or less by firing at 1000 ° C. to 1500 ° C. Α-alumina can be formed.

  As described above, the fibrous alumina aggregate is not limited to a sheet shape. The alumina precursor fiber can be used in a desired shape according to the shape of the target resin alumina composite material.

  When alumina is attached to the surface of the alumina fiber of the fibrous alumina sheet and the alumina is bonded between the fibers to form an alumina porous body, an alumina precursor solution is used. The alumina precursor may be a compound that can form α-alumina by firing. For example, an aluminum salt, aluminum alkoxide, or aluminum chelate can be used. These can be used alone or as a mixture of two or more.

  Examples of aluminum salts include aluminum inorganic salts such as aluminum nitrate, ammonium nitrate aluminum, aluminum chloride, aluminum sulfate, ammonium alum, and ammonium aluminum carbonate, and aluminum such as aluminum oxalate, aluminum acetate, aluminum stearate, aluminum lactate, and aluminum laurate. Organic salts can be used.

  As the aluminum alkoxide, for example, aluminum isopropoxide, aluminum ethoxide, aluminum sec-butoxide, aluminum tert-butoxide and the like can be used.

  Examples of the aluminum chelate compound include ethyl acetoacetate aluminum diisopropylate, aluminum tris (ethyl acetoacetate), alkyl acetoacetate aluminum diisopropylate, aluminum monoacetylacetonate bis (ethyl acetoacetate), aluminum tris (acetylacetate), Tris (salicylaldehyde) aluminum or the like can be used.

  A fibrous alumina sheet is impregnated with an alumina precursor solution and fired at a temperature that produces α-alumina crystals. It is desirable to bake at about 1000 ° C to 1500 ° C. The α-alumina crystal constituting the fibrous alumina sheet becomes a seed crystal, and a crystal of the same size can be formed from the alumina precursor solution. However, if the firing temperature is too high or the time is too long, α-alumina is produced. Crystal grows. When the average crystallite diameter is 300 nm or more, the fibrous form of the alumina porous body cannot be maintained, and the porous body is easily broken. As a result, the fibrous heat conduction path by the alumina crystal is cut, causing a reduction in heat conductivity. The average crystallite diameter means the average value of the crystallite diameter, and is calculated by the Scherrer equation from the half width at the peak of alumina (2θ = 25.5 °) in the diffraction pattern obtained by the powder X-ray diffraction method. From the calculated crystallite diameter or transmission electron micrograph, the lengths of the major axis and minor axis of each of the 50 crystals are obtained and determined by the arithmetic average thereof.

  In addition, when the fiber diameter of the α-alumina crystal fiber is 300 nm or more, voids that are difficult to impregnate the resin are generated between the alumina fibers, and when the composite is formed by resin impregnation, the resin is not impregnated and becomes voids. This will cause a reduction in thermal conductivity.

  The resin content of the alumina porous body and the resin alumina composite formed from the resin is desirably 80 vol% or less. When it is 80 vol% or more, the network formation between the fibers of the alumina porous body is insufficient, and the anisotropy of the thermal conductivity is increased.

  The process of forming the alumina precursor fiber into a sheet and firing it to form the fibrous alumina sheet and the process of impregnating and drying the alumina precursor solution into the fibrous alumina sheet may be performed once, but repeatedly. By doing so, it is possible to increase the alumina content and increase the thermal conductivity of the resin-alumina composite material.

  The resin used in the process of forming the resin-alumina composite by impregnating the resin into the alumina porous body is not particularly limited, and is a thermosetting resin such as unsaturated polyester, epoxy, polyimide, phenol, polyamide, polycarbonate. , Thermoplastic resins such as polyacetal and polysulfone can be used. Silicone grease or the like can also be used.

  The resin alumina composite material can also be used as a prepreg. A prepreg refers to a sheet obtained by impregnating a base material such as a fiber material with a resin and reacting a part of the resin. A plurality of prepregs can be laminated and completely cured, and used as a laminate. A thermosetting resin is used as the resin for the prepreg. Among these, it is desirable to use an epoxy resin. Curing agents for epoxy resins should be amine compounds and their derivatives, alicyclic acid anhydrides, aliphatic acid anhydrides, aromatic acid anhydrides, imidazoles and their derivatives, phenols or their compounds and polymers. Can do. Two or more of these may be used in combination.

  In Example 1, fibrous basic aluminum sulfate crystals were used as alumina precursor fibers.

  A basic aluminum sulfate sheet is formed by suction filtration and compression of a dispersion of fibrous basic aluminum sulfate crystals. After the formed basic aluminum sulfate sheet was dried, it was calcined at 1200 ° C. for 4 hours to obtain a fibrous pregelatinized alumina sheet.

  Water was added to alumina nitrate to form a saturated aqueous solution to obtain an alumina precursor solution. The fibrous pregelatinized alumina sheet was immersed in an alumina precursor solution, impregnated with the alumina precursor between the fibers of the fibrous alumina sheet, and then dried at 100 ° C. Furthermore, the alumina precursor solution was impregnated again and dried at 100 ° C. Then, it was baked at 1200 ° C. for 4 hours, and the alumina precursor was converted to α. As a result, an α-alumina porous body is obtained. The obtained porous alumina was α-alumina having a crystallite diameter of 85 nm.

  An α-alumina porous body formed on a resin composition comprising an epoxy resin (manufactured by Japan Epoxy Resin: Epicoat 828), a curing agent (manufactured by Hitachi Chemical Co., Ltd .: MHAC-P), and a catalyst (manufactured by Shikoku Kasei: 2E4MZ-CN) The resin was impregnated in the pores of the alumina porous body by immersing and reducing the pressure. The epoxy resin was cured by heating the porous alumina body impregnated with the resin at 120 ° C./1 hour, 140 ° C./1 hour, 180 ° C./1 hour to obtain a resin alumina composite material. The resin content of the obtained resin alumina composite material was 70 vol%.

  When the thermal conductivity of the resin-alumina composite material was measured by the Xe flash method, the thermal conductivity in the in-plane direction was 5.3 W / m · K, and the thermal conductivity in the film thickness direction was 4.3 W / m.・ It was K.

  In the same manner as in Example 1, an α-alumina porous body was formed. An alumina porous body is immersed in a resin composition comprising an epoxy resin (manufactured by Japan Epoxy Resin: Epicoat 828), a curing agent (manufactured by Hitachi Chemical Co., Ltd .: MHAC-P), and a catalyst (manufactured by Shikoku Kasei Co., Ltd .: 2E4MZ-CN). By doing so, the resin was impregnated in the pores of the alumina porous body. The alumina porous body impregnated with the resin was semi-cured at 120 ° C./1 hour to prepare a prepreg.

  While pressing for 60 minutes at a surface pressure of 10 MPa and 180 ° C., a laminated board in which two prepregs were integrated was prepared, and the resin composition was completely cured. Using NETZSCH (Bruker), nanoflash LFA447, the thermal conductivity was measured by the Xe flash method. The thermal conductivity in the in-plane direction was 5.0 W / m · K, and the thermal conductivity in the film thickness direction was It was 4.1 W / m · K. By laminating the prepreg, a thin resin layer was formed between the porous alumina bodies, and the thermal conductivity was lowered as compared with the case of a single layer, but a high thermal conductivity was achieved as a laminate.

  Example 3 is an example in which the crystallite diameter of the alumina porous body was grown larger than that of Example 1.

  A fibrous alumina sheet was obtained in the same manner as in Example 1. Water was added to alumina nitrate to form a saturated aqueous solution to obtain an alumina precursor solution. The fibrous alumina sheet was immersed in an alumina precursor solution, impregnated with an alumina precursor between the fibers, and then dried at 100 ° C. Further, the alumina precursor solution was impregnated twice and dried at 100 ° C., and then calcined at 1200 ° C. for 4 hours. The obtained porous alumina was α-alumina having a crystallite diameter of 96 nm.

  The formed alumina porous body was impregnated and cured in the same manner as in Example 1. The resin content of the obtained resin alumina composite material was 63 vol%. When the thermal conductivity was measured by the Xe flash method, the thermal conductivity in the in-plane direction was 8.2 W / m · K, and the thermal conductivity in the film thickness direction was 6.5 W / m · K. Thus, the thermal conductivity was able to be improved by enlarging the crystal | crystallization of an alumina porous body.

  The alumina porous body formed in the same manner as in Example 3 was impregnated with resin in the same manner as in Example 2 to form a laminate. When the thermal conductivity was measured by Xe flash method using NETZSCH (Bruker), nanoflash LFA447, the thermal conductivity in the in-plane direction was 7.7 W / m · K, and the thermal conductivity in the film thickness direction was 6 0.1 W / m · K.

[Comparative Example 1]
A fibrous alumina sheet was formed in the same manner as in Example 1, impregnated with an alumina precursor solution, dried at 100 ° C., and then calcined at 1500 ° C. for 4 hours. The obtained porous alumina was α-alumina having a crystallite diameter of 425 nm, and the fiber shape was not maintained. Since it was fired for a long time at a high temperature, it became an aggregate of large particles, and the porous body was partially broken.

  The formed alumina porous body was impregnated with an epoxy resin in the same manner as in Example 1 to obtain a resin alumina composite material. The obtained resin-alumina composite material has a resin content of 70 vol%, and the thermal conductivity measured by the Xe flash method using NETZSCH (Bruker), nanoflash LFA447, the thermal conductivity in the in-plane direction is 3. 1 W / m · K, the thermal conductivity in the film thickness direction was 2.2 W / m · K, which was a smaller value than the resin alumina composite material formed in Example 1 having the same alumina content. . Since the network between the alumina crystals of the porous alumina body is not maintained, the thermal conductivity is lowered.

[Comparative Example 2]
A fibrous pregelatinized alumina sheet was obtained in the same manner as in Example 1. The obtained fibrous alumina sheet was α-alumina having a crystallite diameter of 73 nm. The fibrous alumina sheet was immersed in an epoxy resin, and the resin was impregnated by reducing the pressure. The epoxy resin was cured by heating the resin-impregnated alumina at 120 ° C./1 hour, 140 ° C./1 hour, and 180 ° C./1 hour. The resin content of the obtained resin-alumina composite was 90 vol%, and the thermal conductivity was measured by Xe flash method using NETZSCH (Bruker), nanoflash LFA447, and the thermal conductivity in the in-plane direction was 1. 3 W / m · K, thermal conductivity in the film thickness direction is 0.7 W / m · K, lower thermal conductivity than Examples 1 and 3, and anisotropic thermal conductivity compared to Examples 1 and 3. It has become a material with great properties.

  The alumina precursor fiber becomes α-alumina when fired, and the thermal conductivity is increased, but the fiber diameter is reduced due to volume shrinkage due to firing, and the density is lowered. Therefore, when a composite material is used, the filling amount of alumina is about 10%, and high filling with alumina is difficult. Further, no alumina is precipitated between the fibers, and no network is formed. Therefore, the thermal conductivity in the vertical direction is lower than the thermal conductivity in the alumina fiber direction.

[Comparative Example 3]
A fibrous alumina sheet was obtained in the same manner as in Example 1. Water was added to alumina nitrate to form a saturated aqueous solution to obtain an alumina precursor. After diluting the alumina precursor solution to 1/5, the fibrous alumina sheet was immersed in the alumina precursor solution to impregnate the alumina precursor between the fibers, and then dried at 100 ° C. Further, it was impregnated with an alumina precursor solution, dried at 100 ° C., and then calcined at 1200 ° C. for 4 hours. The obtained alumina porous body was α-alumina having a crystallite diameter of 75 nm.

  The formed alumina porous body is immersed in a resin composed of an epoxy resin (manufactured by Japan Epoxy Resin: Epicoat 828), a curing agent (manufactured by Hitachi Chemical Co., Ltd .: MHAC-P), and a catalyst (manufactured by Shikoku Kasei: 2E4MZ-CN) and decompressed. Thus, the resin was impregnated in the pores of the alumina porous body. The epoxy resin was cured by heating the resin-impregnated alumina at 120 ° C./1 hour, 140 ° C./1 hour, and 180 ° C./1 hour. The resin content of the obtained resin-alumina composite material is 87 vol%, and when the thermal conductivity is measured by the Xe flash method, the thermal conductivity in the in-plane direction is 1.9 W / m · K, and the film thickness The thermal conductivity in the direction was 1.1 W / m · K. Compared with Examples 1 and 3, the thermal conductivity is low, and compared with Examples 1 and 3, the thermal conductivity anisotropy is large.

  Regarding the performance of the resin alumina composite, the resin content of the resin alumina composite, the crystallite diameter of alumina, and the thermal conductivity of the resin alumina composite are summarized in Table 1 below.

  The present invention can be applied to a technical field related to a high thermal conductive material.

It is a figure which shows the formation method of a resin alumina composite material

Explanation of symbols

1 Alumina precursor fiber 2 Firing (alpha)
3 Fibrous Alumina Sheet Consisting of α-Alumina Fibers 4 Impregnation of alumina precursor solution-Firing
5 Alumina porous body 6 Resin impregnation 7 Resin 8 Alumina composite material

Claims (8)

A resin alumina composite material comprising an alumina porous body and a resin composition impregnated in the alumina porous body, wherein a ratio of the resin composition in the resin alumina composite material is 63 vol% or more and 80 vol% or less. And the alumina porous body is made of α-alumina crystal, and the crystallite has an average crystallite diameter of 300 nm or less. The resin-alumina composite material according to claim 1,
The resin alumina composite material, wherein the resin composition is an epoxy resin composition containing an epoxy resin and a curing agent. The resin-alumina composite material according to claim 1,
The resin alumina composite material, wherein the resin composition is a semi-cured product. A laminate in which a plurality of composite materials composed of a base material and a resin composition are laminated,
A laminate comprising the resin alumina composite material according to claim 1 as at least one composite material. The resin-alumina composite material according to claim 1,
Resin alumina composite material characterized by having a network structure between fibers made of the alumina crystals bound with alumina crystal. A method for producing a resin-alumina composite material having a resin composition ratio of 63 vol% to 80 vol%,
An aggregate of fibers made of an alumina precursor is fired to produce a fibrous alumina sheet made of fibrous α-alumina, and the fibrous alumina sheet is impregnated with an alumina precursor solution and then fired to make an alumina porous material. A method for producing a resin-alumina composite material, comprising manufacturing a body and impregnating the alumina porous body with a resin composition. A method for producing a resin-alumina composite material according to claim 6,
The method for producing a resin-alumina composite material, wherein the alumina precursor solution contains at least one of an aluminum salt, an aluminum alkoxide, and an aluminum chelate. A method for producing a resin-alumina composite material according to claim 6,
Before SL fibrous alumina sheet alumina precursor solution is impregnated with a method for producing a resin-alumina composite and firing at 1000 ° C. to 1500 ° C. After drying.

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