JPS6314725B2 - - 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 having 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, etc., which 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 with the aim of eliminating the drawbacks of the various thermally conductive materials mentioned above, and obtaining 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 consists of a hydrogenated polyhydroxybutadiene polymer having a melting point of 30 to 130°C and a molecular weight of 1,000 to 4,000 that is solid at room temperature, a prepolymer made of an isocyanate compound and having a terminal hydroxyl group, and a compound of the following formula ( ) The gist is a variable heat dissipating material composition characterized by comprising 100 parts by weight of a thermosetting resin consisting of a 2,4-toluene diisocyanate dimer represented by: and 50 to 1500 parts by weight of a thermally conductive filler. be. 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 a characteristic as shown in the curvature B in FIG. 2 with respect to the change in elastic modulus with respect to temperature of silicone rubber, etc., shown by the line A in FIG. 2. Therefore, when the thermosetting resin of the present invention is attached to a heating element, etc., it can adhere 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 the thermosetting resin used in this invention is a hydrogenated polyhydroxybutadiene polymer having a molecular weight of 1000 to 4000, and a terminal hydroxyl group made of a polyfunctional isocyanate compound having 1.5 or more isocyanate groups in the molecule. A thermosetting resin composed of a prepolymer having the following formula and a 2,4-toluene diisocyanate dimer represented by the above formula () is suitable. This molecular weight is 1000-4000
The hydrogenated polyhydroxybutadiene polymer has an average of 1.5 or more hydroxyl groups per molecule, preferably 1.7 to 5.0. Hydrogenated materials for this polyhydroxybutadiene polymer with a molecular weight of 1,000 to 4,000 include butadiene homopolymers or vinyl monomers such as styrene, acrylonitrile, methacrylic acid, vinyltoluene, and vinyl acetate in an amount of up to 50% by weight of butadiene. Some existing copolymers are hydrogenated by conventional methods. As the polyfunctional isocyanate compound to be reacted with the hydrogenated product of the polyhydroxybutadiene polymer, any isocyanate compound having 1.5 or more isocyanate groups in the molecule can be used, such as ethylene diisocyanate, propylene diisocyanate, Tetramethylene diisocyanate, pentamethylene diisocyanate, octamethylene 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'-
Triisocyanates and the like can be used alone or in combination of two or more. The prepolymer having a terminal hydroxyl group used in the present invention can be easily produced by reacting 2 moles of a hydrogenated polyhydroxybutadiene polymer with 1 mole of the polyfunctional isocyanate compound in a conventional manner. . As the curing agent for the prepolymer, a 2,4-toluene diisocyanate dimer represented by the formula () is used in a molar ratio of 0.6 to 1.1 with respect to the hydroxyl groups of the prepolymer.
By using 2,4-toluene diisocyanate dimer, the curing time at room temperature becomes extremely long, resulting in good workability. In other words, the curing reaction of the curing agent does not proceed at room temperature and at 150°C.
If the temperature is higher than that, the curing reaction will proceed rapidly, and triethylenediamine, dibutyltin dilaurylate,
When a urethanization catalyst such as tin octylate or copper acetate is used, the curing reaction can be completed by heating at 80 to 100°C. The blending ratio of the curing agent is preferably within the above range; when the molar ratio is 0.6 or less, the cured product becomes sticky, when the temperature is 100°C or higher, it flows even under small pressure, and when the molar ratio is 1.1 or higher, the cured product becomes hard. The elastic modulus of the object becomes high, and the change in elastic modulus upon heating becomes small, and the adhesion to the heating element, which is the object of this invention, decreases. The above blending ratio is selected within the above range depending on the amount of the thermally conductive filler added, which will be described below.If the amount of the thermally conductive filler is small, the molar ratio should be adjusted to prevent stickiness of the cured product. It is preferable to select a region with a high molar ratio and to select a region with a low molar ratio because if a large amount of thermally conductive filler is added, the elastic modulus of the cured product will be lowered. The thermally conductive filler used in this 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 shape dissipating material composition with high thermal conductivity, remarkable effects 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 1,500 parts by weight per 100 parts by weight of the thermosetting resin.
The parts by weight 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 is small. Moreover, if it exceeds 1500 parts by weight, the above range becomes the limit because it is not uniformly dispersed in the thermosetting resin and the cured product becomes very brittle. In practicing this 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:
In addition to catalysts for accelerating the curing reaction and pigments for coloring, glass cloth, glass mat, nonwoven fabric, metal plate, carbon cloth, carbon mat, etc. can be used as reinforcing materials. Next, a method for manufacturing the variable heat dissipating material composition of the present invention will be explained. First, a predetermined amount of a prepolymer prepared by reacting 2 moles of a hydrogenated polyhydroxybutadiene polymer with 1 mole of an isocyanate compound is heated at a temperature of 80 to 150°C to liquefy it. Then, the thermally conductive filler is added and mixed for 2 to 3 hours using a kneader or vacuum heated stirrer to uniformly disperse the thermally conductive filler. After dispersion, the mixture is cooled to room temperature, and 2,4-toluene diisocyanate dimer as a hardening agent is uniformly dispersed using two rolls. The compound obtained by the above method is sandwiched between release paper or plastic film and molded into a desired shape. It is preferable to use a calendar roll or a molding press for molding. Molding temperature is 70~
Perform at a temperature of 150℃. Furthermore, reinforcing materials such as the glass cloth and metal plate mentioned above can be simultaneously sanded during molding. The variable heat dissipating material composition 11 of the present invention obtained by the method described above has the following characteristics as shown in FIG. 3a:
When heated at temperatures between 50°C and 130°C or lower, 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. . Further, the variable heat dissipating material composition 11 of the present invention
When removed from the heating element 12 at room temperature, the shape of the heating element 12 is directly transferred as shown in FIG. 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., and has the advantage of being easy to wear and not flowing even at high temperatures. ,
Can be used for a wide range of heating elements. In order to explain this invention more specifically, examples will be described. Example 1 Hydrogenated polyhydroxybutadiene polymer (manufactured by Mitsubishi Kasei Corporation, Polyether H, hydroxyl value 45)
2492 parts (parts by weight, same hereinafter) was placed in a four-necked flask (No. 3) and heated to 90°C while flowing nitrogen gas. Stirring was started at 90°C, and 144 parts of 4,4-diphenylmethane diisocyanate (Isonate 143L, manufactured by Kasei Upjiyon Co., Ltd.) was gradually added through a dropping funnel attached to a four-necked flask. After completing the dropwise addition in about 40 minutes, the reaction was further carried out at 90°C for 1 hour to obtain a prepolymer having terminal hydroxyl groups.
The prepolymer had a melting point of about 80°C and a hydroxyl value of 21. Next, 100 parts of the prepolymer was placed in a vacuum heating stirrer, melted at 120°C, 460 parts of aluminum oxide was added, and the prepolymer was vacuum stirred at the same temperature (1 mm
Hg) was carried out for about 1 hour. The resulting mixture was cooled to room temperature and kneaded using two rolls. During kneading, 2.9 parts of 2,4-toluene diisocyanate dimer used as a curing agent was uniformly dispersed to obtain a variable heat dissipation compound. This compound was cured by heating at 150° C. for 20 minutes using a heating press into which a 2 mm spacer was inserted. The thermal conductivity of the cured sheet is 1.32Kcal/m・hr・℃
The temperature characteristics of hardness had a deformation temperature that rapidly decreased around 80°C. The cured sheet is 80
When heated to ℃ and pressed against a mounted printed circuit board, it adhered uniformly to all surfaces of ICs and resistors of different sizes. When the cured sheet was removed once it had cooled to room temperature, the shapes of the IC and resistor had been transferred to the cured sheet. In addition, the cured sheet was heated to 270
Does not flow even after heating at ℃ for 20 minutes, volatile content is 0.3%
It was below. Examples 2 to 6 A prepolymer having the composition shown in Table 1 below was synthesized in the same manner as in Example 1, and a thermally conductive filler and 2,4-toluene diisocyanate dimer were added to 100 parts of the obtained prepolymer. Variable heat dissipation compounds of Examples 2 to 6 were obtained by uniformly dispersing the mixture in the same manner as in Example 1. These compounds are molded into a 2mm thick molding press at a temperature of 150℃.
The cured sheet molded into the sheet has the properties shown in Table 2. In addition, all of the cured sheets in Table 2 are
The cured sheet easily adhered to the surface of the heating element, which had a complicated shape as shown in FIG.

【table】

【table】

【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. Fig. 2 is a diagram showing the elastic modulus-temperature dependence curve of the variable heat dissipation material composition of the present invention and a commercially available thermally conductive rubber sheet, and Fig. 3 is a, b, c, d. 2A and 2B are cross-sectional views of different states for explaining the use of the variable heat dissipation 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 of 30 to 130°C and a molecular weight of 1000 to 4000 that is solid at room temperature, a prepolymer made of an isocyanate compound and having a terminal hydroxyl group, and the following formula: () 1. A variable heat dissipating material composition comprising 100 parts by weight of a thermosetting resin comprising a 2,4-toluene diisocyanate dimer represented by: and 50 to 1500 parts by weight of a thermally conductive filler. 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 a mixture of alumina or magnesium oxide powder with an average particle size of 50 microns or less and hard mica fine powder is used as the thermally conductive filler.