JPS6314728B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a deformable heat dissipating material composition with excellent thermal conductivity, and more specifically, it has excellent compatibility with heat-generating devices and devices of all shapes, has low contact thermal resistance, and has excellent thermal conductivity. The present invention relates to a variable heat dissipating material composition. Thermoplastic resins and thermosetting resins, or resin liquids in which these resins are dissolved in organic solvents,
It is well known that thermally conductive materials, such as viscous silicone grease, mixed with a large amount of filler with excellent thermal conductivity are commercially available. These thermally conductive materials are used to guide excess heat generated during the operation of various mechanical devices, electrical/electronic devices, and parts to shafts, frames, or heat sinks for heat dissipation. However, the above-mentioned commercially available thermally conductive materials each have major drawbacks and cannot be applied to various heating elements, and the actual range of use is limited. For example, if a thermally conductive material made of a thermoplastic resin matrix is used in equipment or equipment that generates a calorific value higher than the melting point of the thermoplastic resin, the thermally conductive material will melt and flow, so there is a limit to the operating temperature. be. It also has poor chemical resistance and solvent resistance. Furthermore, when a thermally conductive filler is mixed into a thermoplastic resin, the amount of the thermally conductive filler mixed in is small due to the high melt viscosity of the thermoplastic resin, which has the disadvantage that only a material with low thermal conductivity can be obtained. are doing. On the other hand, thermally conductive materials using thermosetting resins are
It does not have the disadvantage of flowing at high temperatures, and since it contains a large amount of liquid resin before curing, a large amount of thermally conductive filler can be mixed in. However, if a resin with high hardness after curing is used (for example, epoxy resin or unsaturated polyester resin), it is impossible to apply it to equipment or parts that require flexibility. Furthermore, if the contact surface with the thermally conductive material is uneven, there is a method of casting or injecting a mixture of a thermosetting liquid resin and a thermally conductive filler to minimize the contact thermal resistance. In this case, since the mixture must be in a liquid state, the amount of the thermally conductive filler mixed becomes small, resulting in a disadvantage that the thermal conductivity decreases. In addition, mixtures of elastic thermosetting resins (e.g. silicone rubber, vulcanized rubber, etc.) and thermally conductive fillers are highly flexible and can be easily attached to various heating elements; When attaching to a heating element that is holding an object, a heating element with rough surface precision, or a heating element with a narrow gap on the surface of the heating element, the rebound resilience of the elastic resin creates parts that do not come into close contact with the heating element, and as a result, Contact thermal resistance increases, significantly reducing thermal conductivity. Each figure in Figure 1 is an application example using a commercially available thermally conductive rubber sheet. 3 indicates a cooling part such as a metal frame. In order to ensure that the thermally conductive rubber sheet 1 is brought into close contact with the heating elements 2a, 2b, 2c from the state shown in Fig. 1 a1, b1, c1 to the state shown in Fig. 1 a2, b2, c2, it is necessary to Pressure (tightening force) is required, and heating elements 2a, 2b, 2c
The larger the dimensional difference between the protrusions on the surface, the higher the pressure required. Then, when the difference in the dimensions of the protrusions is about 1 mm,
A sufficient pressure is required to destroy the matrix of thermally conductive sheets. In addition, in order to maintain close contact with the heating element at all times, consideration must be given to applying pressure P uniformly. In order to ensure that the thermally conductive rubber sheet shown in each figure in Figure 1 is in close contact with the surface of the heating element and to improve its thermal conductivity, it is necessary to tighten it with pressure that will destroy the matrix of the rubber sheet, or to tighten the parts that do not adhere properly. There are methods such as interposing a filler such as thermally conductive grease, but none of these methods can be said to be preferable. For example, application to precision equipment, equipment, electrical/electronic equipment, or parts that may malfunction due to external pressure must be avoided. Furthermore, when a filler such as grease is used, there are major drawbacks such as reduced workability and flow of the grease due to heat. In addition, with the thermally conductive material that can be coated using the organic solvent mentioned above, gaps and unevenness of about several tens of microns can be smoothed by coating, but when the gap is about 1 mm or more, it is necessary to coat the material repeatedly. Must. Furthermore, when an organic solvent is used, the working environment becomes a problem, so it cannot be said to be a preferable method. The inventors of this invention have conducted extensive research in order to eliminate the drawbacks of the various thermally conductive materials mentioned above, and to obtain a heat dissipating material that can be attached to any heating element and has an extremely low contact thermal resistance. As a result of repeated efforts, we succeeded in obtaining a variable heat dissipating material composition that can fully achieve the above objectives. That is, this invention provides a hydrogenated product of a polyhydroxybutadiene polymer having a melting point in the range of 40 to 130°C, having hydroxyl groups at both ends of the molecule, and a molecular weight in the range of 500 to 5,000, and a curing agent thereof. An isocyanate compound having 1.5 or more isocyanate groups in the molecule and is represented by the following formula (). (However, in formula (), R represents an aliphatic hydrocarbon residue having 8 to 20 carbon atoms) Thermosetting resin using both an isocyanate compound masked by a phenol compound
The gist of the present invention is a variable heat dissipating material composition characterized in that 50 to 1500 parts by weight of a thermally conductive filler is added to 100 parts by weight. The thermosetting resin used in this invention has high elasticity at room temperature, but its elastic modulus becomes extremely low when heated at a temperature of 130° C. or lower.
That is, the thermosetting resin used in the present invention has characteristics as shown by curve B in FIG. 2, with respect to the change in elastic modulus with respect to temperature of silicone rubber, etc., shown by line A in FIG. Therefore, when the thermosetting resin of the present invention is attached to a heating element, etc., it can be attached to the heating element with very small pressure by heating, and it can be attached to the heating element without any shape. It has an excellent property of adhering to all surfaces even when it is covered. moreover,
The thermosetting resin of the present invention has the excellent property that if it is cooled in a deformed state, it will maintain its deformed shape, and if it is heated again, it will return to its pre-deformed shape. A specific example of a thermosetting resin used in this invention is a hydrogenated polyhydroxybutadiene polymer as a main ingredient, and a hardening agent for the hydrogenated resin.
A thermosetting resin composed of a polyfunctional isocyanate compound having 1.5 or more isocyanate groups, an isocyanate compound masked by a phenol compound represented by the above formula (), and a curing catalyst is preferred. This hydrogenated polyhydroxybutadiene polymer has an average of 1.5 or more hydroxyl groups per molecule, preferably 1.7 to 1.
It has 5.0 pieces. Hydrogenated materials for this polyhydroxybutadiene polymer include butadiene homopolymer or vinyl monomers such as styrene, acrylonitrile, methacrylic acid, vinyltoluene, and vinyl acetate for butadiene.
Some copolymers present in an amount of 50% by weight or less are hydrogenated using conventional methods. As the polyfunctional isocyanate compound used as a curing agent, any compound having 1.5 or more isocyanate groups in the molecule can be used. For example, ethylene diisocyanate, propylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, octa Methylene diisocyanate, 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate, cyclohexylene 1,4-diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, xylylene-1,4-diisocyanate,
xylylene-1,3-diisocyanate, 4,
4′-diphenylmethane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-1,4-diisocyanate, p,p′,p″-triphenylmethane triisocyanate, diphenyl-4,6,4′ - triisocyanate etc. can be used alone or in a mixture of two or more. Furthermore, the isocyanate compound masked with a phenol compound used as a curing agent is a phenol compound of the following formula () with respect to the isocyanate group of the above-mentioned isocyanate compound. Obtained by reacting equivalent amounts of compounds. (However, in formula (), R represents an aliphatic hydrocarbon residue having 8 to 20 carbon atoms) Examples of the phenol compound include 4-octylphenol, 4-nonylphenol, 4-dodecylphenol, cardanol, etc. These can be used alone or in combination of two or more. The mixing ratio of the hydrogenated product of the polyhydroxybutadiene polymer and the isocyanate compound masked with an isocyanate compound and a phenol compound is (hydrogenated product of the polyhydroxybutadiene polymer)/(
Isocyanate compound) + (Isocyanate compound masked with a phenol compound) = (1 mol) / (0.2 mol) + (0.6 mol) ~ (1 mol)
The range of /(0.3 mol)+(0.7 mol) is preferable. If outside this range, there will be a shortage of curing agent and the cured product will become sticky, or there will be an excess of curing agent and the crosslinking density will increase.
The change in elastic modulus during heating, which is the object of this invention, is reduced. In addition, the mixing ratio of the isocyanate compound and the isocyanate compound masked by the phenol compound is preferably within the above range, and if the isocyanate compound exceeds this range and becomes excessive, the curing reaction will be accelerated, resulting in a decrease in workability. Conversely, if the isocyanate compound masked by the phenol compound becomes excessive, the phenol compound liberated after curing will bleed onto the surface of the cured product. As a catalyst for accelerating the curing reaction of the thermosetting resin, a suitable amount of a urethanization reaction catalyst such as triethylene diamine, dibutyltin dilaurylate, tin octylate, copper acetate, or tributyltin acetate can be used. The thermally conductive filler used in the present invention is used to impart thermal conductivity, and metal oxides such as powdered beryllium, aluminum, zinc, silicon, magnesium, and titanium are suitable. In particular, in order to obtain a variable heat dissipating material composition with high thermal conductivity, a remarkable effect can be obtained by using aluminum oxide powder with an average particle size of 50 microns or less in combination with finely powdered hard mica. The amount of the thermally conductive filler used in this invention is 50 to 50 parts by weight per 100 parts by weight of the thermosetting resin.
The amount is 1500 parts by weight, but it can be changed depending on the type of thermally conductive filler and the viscosity of the thermosetting resin before curing. The amount of the thermally conductive filler added is determined by the desired thermal conductivity of the variable heat dissipating material composition; if it is less than 50 parts by weight, the thermal conductivity is too low and the heat dissipating effect will be poor. small.
Moreover, if it exceeds 1500 parts by weight, it will not be uniformly dispersed in the thermosetting resin and the cured product will become very brittle, so the above range becomes the limit. In the embodiment of the present invention, the amount of the thermally conductive filler added is most preferably in the range of 150 to 800 parts by weight. Further, the variable heat dissipating material composition of the present invention includes:
A catalyst for accelerating the curing reaction, a pigment for coloring, and a reinforcing material such as glass cloth, glass mat, nonwoven fabric, metal plate, carbon cloth, carbon mat, etc. can be used. Next, a method for manufacturing the variable heat dissipating material composition of the present invention will be explained. First, the hydrogenated product of polyhydroxybutadiene polymer, which is the main ingredient, is added to 80 to 150%
It is heated at a temperature of °C, and a predetermined amount of a thermally conductive filler and a coloring agent are added in a liquid state. Mix thoroughly with a kneader or vacuum heated stirrer so that the thermally conductive filler is evenly dispersed. After mixing for 2-3 hours, a predetermined amount of hardening agent consisting of an isocyanate compound is added, mixed for several minutes and immediately cooled to room temperature. The cooled mixture is passed through two or three rolls to uniformly disperse the thermally conductive filler. The compound obtained by the above method is sandwiched between release paper or plastic film,
Mold into desired shape. It is preferable to use a calendar roll or a molding press for molding. The molding temperature is in the range of 70 to 150°C. Furthermore, reinforcing materials such as the glass cloth and metal plate mentioned above can be simultaneously sanded during molding. As shown in FIG. 3, the variable heat dissipating material composition 11 of the present invention obtained by the above method has
When heated at temperatures between 130°C and below, its elastic modulus becomes extremely low, allowing it to deform freely under very small pressure. Therefore, if it is pressed against the heating element 12 in this state, it will come into close contact with the entire surface of the heating element 12, which has a complicated shape as shown in FIG. 3b, and the efficiency of heat dissipation will be extremely high. Become. Further, the variable heat dissipating material composition 11 of the present invention
If it is detached from the heating element 12 at room temperature, it will become as shown in Fig. 3c.
As shown in FIG. 2, the shape of the heating element 12 is transferred as is, and it can be seen that the adhesion to the heating element and the ease of mounting are excellent. Furthermore, the deformable heat dissipating material composition 11 of the present invention has the advantage that it returns to its original shape when reheated, as shown in FIG. 3d. In addition, in FIGS. 3a to 3d, 13 is a cooling part such as a metal frame. The variable heat dissipating material composition according to the present invention is extremely effective in cooling various mechanical devices, electrical equipment, electronic equipment, etc., has the advantage of being easy to wear, does not flow even at high temperatures, and has the advantage of being able to generate heat over a wide range of Can be used on the body. In order to explain this invention more specifically, reference examples and examples will be described. Reference example 1 440 parts of nonylphenol (parts by weight, same below)
Place in a four-necked flask and heat to 80°C while flowing nitrogen gas. Then, with stirring, 2.
Add 174 parts of 4'-toluene diisocyanate dropwise over 30 minutes. After completion of the dropwise addition, the reaction was continued for about 1 hour at the same temperature, and then taken out from the reaction vessel. In this way, 602 g of nonylphenol-masked 2,4-toluene diisocyanate with a melting point of about 50° C. was obtained. Reference example 2 777 parts of alkylphenol with a molecular weight of approximately 370 and 4,
250 parts of 4'-diphenylmethane diisocyanate was reacted in the same manner as in Reference Example 1, and the melting point was about 70°C.
975 g of alkylphenol masked 4,4'-diphenylmethane diisocyanate was obtained. Example 1 100 parts of a hydrogenated polyhydroxybutadiene polymer (manufactured by Mitsubishi Kasei Corporation, Polytail H, OH value 45), 14.8 parts of the isocyanate compound obtained in Reference Example 1, 0.1 part of tin octylate, aluminum oxide 356
Transfer a portion to a heated vacuum stirrer container and continue mixing at 90°C for about 2 hours. Next, 2.0 g of 4,4'-diphenylmethane diisocyanate was added and 5 g was added under the same conditions.
After stirring for a minute, the mixture was removed from the container. The resulting mixture was kneaded with two rolls to uniformly disperse the aluminum oxide to obtain a variable heat dissipation compound. This compound was press-molded at 150°C for 40 minutes to obtain a cured sheet with a thickness of 2 mm. The thermal conductivity of the cured sheet is 0.92Kcal/m・hr・℃,
The temperature characteristics of hardness are as shown in Table 1 below, and it was found that it changes rapidly around 80°C.
In addition, the cured sheet was heated to 80℃, and the surface shape was
When pressed against a heating element with unevenness of mm width and 0.5 mm thickness, it completely adhered to all surfaces of the concave and convex parts.
When the cured sheet was further cooled to room temperature and removed from the surface of the heating element, the surface shape of the heating element was transferred to the cured sheet.

[Table] Examples 2 to 7 Variable heat dissipation compounds having the compositions shown in Table 2 below were prepared in the same manner as in Example 1, and these compounds were molded to a thickness of 2 mm using a molding press at a temperature of 150°C. A cured sheet was prepared. The cured sheet exhibited thermal conductivity and electrical insulation properties shown in Table 3 below. Furthermore, all of the cured sheets in Table 3 exhibited deformability that allowed them to easily adhere to heating elements having complex shapes as shown in FIG.

【table】

[Table] 1) Polyhydroxybutadiene (Mitsubishi Kasei (
Co., Ltd.).

【table】 [Brief explanation of the drawing]

Fig. 1 a1, b1, c1 are cross-sectional views before attaching commercially available thermally conductive rubber sheets to different heating elements, Fig. 1 a2, b2, c2 are cross-sectional views after attaching the same to different heating elements. , c1 respectively; FIG. 2 is a diagram showing the elastic modulus-temperature dependence curves of the variable heat dissipating material composition of the present invention and a commercially available thermally conductive rubber sheet; FIG. 3 is a, b, c, d are cross-sectional views of different states for explaining the use of the variable heat dissipating material composition according to the present invention. 1... Heat conductive rubber sheet, 2a, 2b, 2c...
Heating element, 3... Cooling part, 11... Variable heat dissipation material composition, 12... Heating element, 13... Cooling part. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A hydrogenated product of a polyhydroxybutadiene polymer having a melting point in the range of 40 to 130°C, a hydroxyl group at both ends of the molecule, and a molecular weight in the range of 500 to 5,000, and a curing agent thereof. is an isocyanate compound having 1.5 or more isocyanate groups in the molecule and is represented by the following formula (). (However, in formula (), R represents an aliphatic hydrocarbon residue having 8 to 20 carbon atoms) Thermosetting resin using both an isocyanate compound masked by a phenol compound
1. A variable heat dissipating material composition, characterized in that 50 to 1500 parts by weight of a thermally conductive filler is added to 100 parts by weight. 2. The variable heat dissipating material composition according to claim 1, wherein the thermally conductive filler is a metal oxide. 3. The variable heat dissipating material composition according to claim 1, wherein the thermally conductive filler is a mixture of alumina oxide or magnesium oxide powder with an average particle size of 50 microns or less and hard mica fine powder.