JPH0322916B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a thermosetting heat-resistant adhesive having excellent thermal conductivity, electrical insulation, and heat resistance. [Technical background of the invention and its problems] Conventionally, when bonding a ceramic heater to a pressure cooker or a heat-retaining cooker that repeats cycles of heating and cooling to room temperature, thermal conductivity, electrical insulation, and heat resistance are required. An adhesive with both properties is required. Conventionally, heat-resistant adhesives containing SiO ₂ , FeO ₃ , Al ₂ O _3, etc. in silicone rubber are known, but while they have excellent electrical insulation properties, they have a thermal conductivity of 0.86. It has the disadvantage of low Kcal/mhr℃. Adhesive grease containing 95% ZnO in silicone oil is also known, but like the above, it has the disadvantage of a low thermal conductivity of 0.54 kcal/mhr°C.
Furthermore, heat-resistant adhesives with excellent thermal conductivity of 8 to 10 kcal/mhr°C are also known, but because they contain metal powder, they have a specific resistance of 8.4 Ω/cm and have poor electrical insulation properties. By the way, to improve only the thermal conductivity, it is sufficient to add metal powder such as Cu, Al, Ag, or silicon carbide (SiC) powder.For example, the thermal conductivity of synthetic resin is generally 0.1 to 0.2 kcal/mhr℃. , Cu
is 338kcal/mhr℃, Al is 194kcal/mhr℃, Fe
is 61.2kcal/mhr℃, and SiC is 450kcal/mhr. Therefore, if metal powder is added to the synthetic resin, the thermal conductivity will be improved, but the electrical insulation properties will be reduced, making it unusable. In addition, when flame-retardant inorganic adhesives are mixed with substances with excellent electrical insulation and thermal conductivity, they are susceptible to moisture, allowing moisture to pass through easily, impairing electrical insulation properties, and causing long-term effects. There are some drawbacks that make it unusable. [Purpose of the Invention] This invention has been made to eliminate the various drawbacks mentioned above, and it has been made to withstand repeated cycles of heating and cooling, has excellent thermal conductivity, electrical insulation, and heat resistance, and can be used for a long period of time. The aim is to provide an adhesive that can withstand [Summary of the Invention] This invention provides a heat-resistant adhesive comprising composite SiC particles 2 whose surfaces are coated with a ceramic layer 1 having excellent corrosion resistance and electrical insulation properties as shown in FIG. 1 in a thermosetting synthetic resin. It is a drug. Here, as a thermosetting synthetic resin, diamino diphenyl methane (DDM) is used as a trifunctional epoxy resin.

A mixture of [Formula] (for example, product name: Sumiepoxy
ELM-120 Sumitomo Chemical KK), silicone varnish (for example, product name: TSR-117 Toshiba Silicone KK),
Phenol resins (for example, Cemedine-120), polyurethanes (for example, Cemedine-700), acrylic adhesives (for example, trade name: Hardrock C Electrochemical KK), urea resins, melamine resins, polyimide resins, etc. are applicable. The thermal conductivity of SiC is theoretically approximately 450kcal/mhr℃
Although it has extremely high heat resistance and corrosion resistance, it is inconvenient for the purpose of the present application because semiconductivity usually exhibits electrical conductivity. Therefore, the present inventors
A composite whose grain surface is coated with stable and highly electrically insulating ceramics such as Si ₃ N ₄ , Al ₂ O ₃ , BN, etc.
When SiC particles were synthesized and used, the effects of the present application were obtained. Note that the proportion of the surface layer material is preferably 1 to 50%, preferably 5 to 20%, of the particles by weight from the viewpoint of thermal conductivity and electrical insulation. [Embodiments of the Invention] Examples of the invention will be described below. A solvent such as methyl ethyl ketone (MEK) is added to a thermosetting synthetic resin liquid such as epoxy resin, silicone varnish, phenolic resin, polyurethane, or acrylic resin to adjust the viscosity to an appropriate level, and then Si ₃ N ₄ or Al ₂ O ₃ is applied to the surface. The coated SiC particles were added and mixed thoroughly to obtain various heat-resistant adhesives. Each of the adhesives thus obtained was degassed in vacuum to remove the solvent, and then heated and cured to form a 1 cm ² cube, and the thermal conductivity was measured. Examples of the measurement results are shown in Tables 1 and 2. Table 1 shows epoxy resin (ELM)
Table 2 shows the relationship between the mixing ratio of the composite SiC grains in (-120) and the thermal conductivity, and Table 2 shows the relationship with silicon varnish (TSR-117). In addition, the weight in the table is shown in g, the mixing ratio is shown in weight%, and the thermal conductivity is shown in Kcal/mhr°C.

【table】

[Table] Similar favorable results were obtained with other resin examples, phenolic resin, and polyurethane. It was also possible to obtain an adhesive by adding, for example, Si ₃ N ₄ -coated SiC particles directly to the resin without using a solvent and stirring thoroughly. Generally, in order to increase thermal conductivity, it is better to reduce the resin content as much as possible, but if it is too small, it will become unusable, so it is necessary to have a content of 20% or more. [Effects of the Invention] As described above, the heat-resistant adhesive of the present invention has (1) superior thermal conductivity than conventionally commercially available heat-resistant adhesives, and (2) can maintain heat resistance at 150°C or higher at all times. 3. It can withstand heating and cooling cycles from room temperature to 150-200℃, 4. It has no electrical conductivity because no metal powder is added, 5. It is water resistant and can withstand long-term use, and 6. It has extremely good adhesion. play. Note that composite particles can be obtained relatively easily using a reaction involving a gas phase such as CDD.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing silicon carbide grains whose surfaces are coated with highly insulating ceramics used in the present invention. 1...Highly insulating ceramics, 2...Silicon carbide grains.

Claims (1)

[Claims] 1. A heat-resistant adhesive characterized by being made of a thermosetting synthetic resin containing silicon carbide particles whose surface is coated with highly insulating ceramic.