JPS6314727B2 - - 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. In other words, this invention allows the heat distortion temperature to vary from room temperature to
A hydrogenated product of polyhydroxybutadiene polymer and a polyfunctional isocyanate having 1.5 or more isocyanate groups in the molecule were used as a thermosetting resin with a large thermal deformation in a narrow temperature range up to 130°C. The thermosetting resin is characterized by
The gist of the present invention is a variable heat dissipating material composition characterized by comprising 100 parts by weight of a heat-conductive filler and 50 to 1,500 parts by weight of a thermally conductive filler. 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, with respect to the change in elastic modulus of silicone rubber with respect to temperature shown by line A in FIG. 2, the thermosetting resin used in the present invention has characteristics as shown by curve B 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. The thermosetting resin used in this invention is based on a hydrogenated product of polyhydroxybutadiene polymer,
As the curing agent, a polyfunctional isocyanate compound having 1.5 or more isocyanate groups in the molecule can be obtained. 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 include styrene, acrylonitrile, methacrylic acid, vinyltoluene, butadiene homopolymer or butadiene.
There are copolymers containing 50% by weight or less of vinyl monomers such as vinyl acetate, which are hydrogenated using conventional methods. As the polyfunctional isocyanate compound used as a curing agent, 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-isocyanatomethyl-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,
Single or double 6,4'-triisocyanate etc.
Mixtures of more than one species can be used. The blending ratio of the hydrogenated product and polyfunctional isocyanate of the polyhydroxybutadiene polymer is based on the hydroxyl group of the polyhydroxybutadiene polymer.
It is preferable to use the polyfunctional isocyanate in a range of 0.6 to 11 (molar ratio). If it is less than 0.6 mole,
The molar ratio is preferably 0.6 or more because the cured product is sticky and may flow even under small pressure at a high temperature of 200° C. or higher. Also, the molar ratio is 1.1
In the above case, the elastic modulus of the cured product becomes high, the amount of change in the elastic modulus upon heating becomes small, and the adhesion to the heating element, which is the object of the present 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 in order to lower the elastic modulus of the cured product when a large amount of thermally conductive filler is added. The thermally conductive filler used in this invention is used to impart thermal conductivity, and includes powdered or fibrous silver, aluminum, copper, zinc,
Using pure metals or alloys such as tungsten, or metal oxides such as beryllium, aluminum, zinc, silicon, magnesium, titanium, etc., as well as carbon black, fluororesin powder, boron nitride, silicon carbide, silicon nitride, allyl urea, etc. Can be done. These thermally conductive fillers have an average particle size of 100
Preferably, it is in the form of a powder of microns or less or in the form of fibers with a fiber length of 5 mm or less. but,
In this invention, there is no need to particularly limit the particle size or fiber length of the thermally conductive filler, and this does not pose an essential problem in implementing the invention. 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. In other words, the amount of thermally conductive filler added is determined by the desired thermal conductivity of the variable heat dissipating material composition, and if it is less than 50 parts by weight, the thermal conductivity will be too low and the heat dissipating effect will be impaired. is small,
Further, if the amount exceeds 1500 parts by weight, the above range becomes the limit because it will not be uniformly dispersed in the thermosetting resin and the cured product will become very brittle. In carrying out this invention, the amount of the thermally conductive filler added is
A range of 150 to 800 parts by weight is most preferred. 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
Heat at a temperature of 150°C, and add a predetermined amount of thermally conductive filler and coloring agent in liquid state. Mix thoroughly with a kneader or vacuum heated stirrer so that the thermally conductive filler is evenly dispersed. 2~
After mixing for 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. This mixture is sandwiched between release paper or plastic film and molded into the desired shape.
It is preferable to use a calendar roll or a molding press for molding. The molding temperature is in the range of room temperature to 100°C. Furthermore, reinforcing materials such as the glass cloth and metal plate mentioned above can be simultaneously sanded during molding. The molded mixture is sandwiched between release paper and left for several days at room temperature or at a temperature below 100°C to fully harden the thermosetting resin used and form the product, the deformable heat dissipation material composition. get. 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. Become. Further, the variable heat dissipating material composition 11 of the present invention
If it detaches from the heating element 12 at room temperature,
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., and has excellent wearability and does not flow even at high temperatures. Moreover, for this reason, it can be used in a wide range of heating elements. In order to explain this invention more specifically, examples will be described. Example 1 100 parts (parts by weight, same hereinafter) of a hydrogenated polyhydroxy 1.4-butadiene polymer (manufactured by Sanhi Kasei Co., Ltd., product name Polytail H, hydroxyl value 45) was put into a container of a vacuum heating stirrer. Then, 498 parts of aluminum oxide with an average particle size of 20 microns was placed in the container,
The mixture was heated and stirred at 90°C. After stirring for 30 minutes at normal pressure, stirring was continued for about 1 hour under reduced pressure of 1 mmHg. Leak the container to normal pressure, 2,4
- 6.3 parts of toluene diisocyanate was added and mixed for 5 minutes under vacuum at the same temperature. Remove the mixture from the container, immediately cool to room temperature, and leave at room temperature for 3
This roll was passed through twice. This mixture was sandwiched between release paper inserting a 2 mm spacer and press-molded at 100° C. for 1 minute to obtain a sheet-shaped variable heat dissipation material composition. After this sheet-shaped variable heat dissipating material composition was left at room temperature for one week, its thermal conductivity, curing temperature characteristics, and fluidity at 250°C were examined. The results showed the properties shown in Table 1 below, and it was clear that the material had excellent thermal conductivity and deformability when heated.

[Table] Example 2 70 parts of hydrogenated polyhydroxy 1,4-butadiene polymer used in Example 1 and polyhydroxy
1.2-Hydrogenated product of butadiene polymer (Santo Kasei Co., Ltd.)
After mixing 30 parts of Polytail HA manufactured by Co., Ltd. (product name: hydroxyl value 50) and 545 parts of magnesium oxide in the same manner as in Example 1, 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate was added. 9.2 parts were added and vacuum mixed for 5 minutes, cooled to room temperature and passed through three rolls twice. Place the mixture passed through the roll on a 1 mm thick aluminum plate, and
mm spacers and release paper were set and press molded at 50°C for 3 minutes. After pressing, it was left at room temperature for one week to completely cure. In this example, the thickness is 1 mm.
A composite was obtained in which a 2 mm thick deformable heat dissipating material composition was firmly adhered to an aluminum plate. When this composite was heated to 80°C and pressed against a mounted printed circuit board, the shapes of various ICs and resistors were transferred to the variable heat dissipation material. In addition, the thermal conductivity of the composite is 2.01Kcal/m.hr.℃,
It did not flow even after heating at 250°C for 30 minutes. Example 3 50 parts of the hydrogenated polyhydroxy 1.4-butadiene polymer of Example 2 and polyhydroxy 1.2-
50 parts of hydrogenated butadiene polymer and zinc oxide
After mixing 648 parts with the same method as in Example 1,
After cooling to room temperature, the resulting mixture was put into a kneader and kneaded. After kneading for about 10 minutes in a kneader, 4.4′-diphenylmethane diisocyanate
8.4 g was added and kneading was continued for an additional 10 minutes. After this kneading, a cured sheet with a thickness of 2 mm was obtained in the same manner as in Example 1. The thermal conductivity of the cured sheet is
It has a thermal conductivity of 2.8 Kcal/m.hr.°C, and its hardness at room temperature is 89, and when heated to 80°C, the hardness changes to 17, and it has excellent adhesion to the heating element. . Example 4 After heating and mixing 100 parts of the hydrogenated polyhydroxy 1,4-butadiene polymer used in Example 1 and 481 parts of aluminum oxide in the same manner as in Example 1, 3-isocyanate methyl-3, 5,5
-Trimethylcyclohexyl isocyanate 6.23
1 part and 1.4 parts of 2.4-toluene diisocyanate were added and mixed under vacuum for 5 minutes, and then cooled to room temperature. This mixture was formed into a 1 mm thick sheet using calender rolls. Next, the molded sheet and glass cloth were stacked in the order of molded sheet/glass cloth/formed sheet/glass cloth/formed sheet, and again passed through a calendar roll to obtain a variable heat dissipation sheet having a thickness of 3 mm and consisting of five layers. This sheet was heated at 50° C. for 4 days to completely cure it. As a result of measuring various properties of the cured sheet, the values shown in Table 2 below were shown, and it became clear that the sheet had excellent thermal conductivity, ease of attachment to a heating element, mechanical properties, and electrical insulation.

【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)

[Claims] 1. Hydrogenated polyhydroxybutadiene polymer with 1.5 molecules in the molecule as a thermosetting resin whose heat distortion temperature ranges from room temperature to 130°C and whose heat distortion amount is large in a narrow temperature range. A variable heat dissipating material composition characterized by using a polyfunctional isocyanate having the above isocyanate group and comprising 100 parts by weight of the thermosetting resin 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.