JPS6314726B2 - - 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 comprises 100 parts by weight of a hydrogenated polyhydroxybutadiene polymer having a melting point in the range of -20 to 130°C and a molecular weight of 1000 to 4000, and a low molecular weight polyolefin compound having a molecular weight in the range of 500 to 5000. 50 to 1,500 parts by weight of thermally conductive filler per 100 parts by weight of a thermosetting resin using an isocyanate compound having 1.5 or more isocyanate groups in the molecule as a curing agent. The gist of the present invention is a variable heat dissipating material composition characterized by comprising: The thermosetting resin composition 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. In other words, the thermosetting resin composition used in the present invention has characteristics as shown in curve B in FIG. 2, with respect to the change in elastic modulus of silicone rubber due to temperature shown in curve A in FIG. 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 cured product of the thermosetting resin composition 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 specific thermosetting resin composition used in this invention includes 10 to 60 parts by weight of a low molecular weight polyolefin compound having a molecular weight in the range of 500 to 5000 per 100 parts by weight of a hydrogenated polyhydroxybutadiene polymer having a molecular weight of 1000 to 4000. It is composed of a mixture in which parts by weight are added, and an isocyanate compound having 1.5 or more isocyanate groups in the molecule as its curing agent. Further, as the low molecular weight polyolefin compound having a molecular weight in the range of 500 to 5000, low molecular weight polyethylene or polypropylene having a molecular weight in the above range is suitable. Furthermore, the polyfunctional isocyanate compound used as a curing agent for the mixture has 1.5
Any isocyanate compound having three or more isocyanate groups 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′-triisocyanate, etc. can be used alone or in a mixture of two or more. Hydrogenated product of polyhydroxybutadiene polymer and low molecular weight The blending ratio of the polyolefin compound and the isocyanate compound used as a curing agent is 100 parts by weight of hydrogenated polyhydroxybutadiene polymer and a low molecular weight polyolefin compound.
To a mixture to which 10 to 60 parts by weight is added, the molar ratio of the isocyanate compound to the hydroxyl group of the hydrogenated polyhydroxybutadiene polymer is adjusted in the range of 0.6 to 1.1. When the amount of low molecular weight polyolefin is smaller than the above-mentioned blending ratio, the change in physical properties upon heating will be very small, and the advantages of the specific thermosetting resin composition used in this invention will not be lost. If it is in excess, the strength of the cured product will drop significantly, and the low molecular weight polyolefin may flow during heating or adhere to the surface of the heating element and stain it, which is not preferable. Furthermore, if the molar ratio of the hydrogenated compound and the isocyanate compound in the polyhydroxybutadiene polymer is 0.6 mol or less, the cured product will become sticky and will flow even under small pressure at a high temperature of 200°C or higher. If the molar ratio is 1.1 or more, the elastic modulus of the cured product becomes high, which lowers the adhesion to the heating element, which is the object of the present invention, which is not preferable. The molar ratio of the hydrogenated compound and the isocyanate compound of the polyhydroxybutadiene polymer is selected within the above range depending on the amount of the thermally conductive filler added, which will be described below. In order to prevent stickiness of the cured product, it is preferable to select a region with a high molar ratio, and when a large amount of thermally conductive filler is added, it is preferable to select a region with a low molar ratio in order to lower the elastic modulus of the cured product. The thermally conductive filler used in this invention is used to impart thermal conductivity, and is made of pure metals or alloys such as powdered or fibrous silver, aluminum, copper, zinc, or tungsten, or beryllium or aluminum. , metal oxides such as zinc, silicon, magnesium, and titanium, as well as carbon black, fluororesin powder, boron nitride, silicon carbide, silicon nitride, and allyl urea. 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. However, 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:
In addition, glass cloth, glass mat, nonwoven fabric, metal plate (fin shape), carbon cloth, carbon mat, etc. can be used as a reinforcing material. Next, a method for manufacturing the variable heat dissipating material composition of the present invention will be explained. First, a predetermined amount of a hydrogenated polyhydroxybutadiene polymer and a low molecular weight polyolefin compound are heated at a temperature of 80 to 150°C, and then a predetermined amount of a thermally conductive filler, a colorant, etc. are added. Mix thoroughly with a kneader or vacuum heated stirrer so that the thermally conductive filler is evenly dispersed. After mixing for 2 to 3 hours, a predetermined amount of a curing agent consisting of an isocyanate compound is added,
Mix for a few minutes and immediately cool 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. Place the molded mixture between release paper, etc. at room temperature or
The thermosetting resin used is left to stand for several days at a temperature of 100° C. or lower to fully cure, and a variable heat dissipating material composition is obtained as a product. 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 between 50℃ and 130℃, the 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 A polyhydroxy compound with an average molecular weight of about 850 (manufactured by Daicel Chemical Co., Ltd., trade name Placcel 308, hydroxyl value
195) 100 parts (same below by weight) and 50 parts of low molecular weight polyolefin with a molecular weight of approximately 5000 (manufactured by Sanyo Kasei Co., Ltd., trade name Sanwax 161-P) were put into a container of a vacuum heating stirrer, and then the average particle size was 650 parts of 30 micron aluminum oxide was placed in the container and heated and stirred at 90°C. 120℃ under reduced pressure of approximately 1mmHg
Stirring was continued for about 1 hour. Return the container to normal pressure and 4,4'-diphenylmethane diisocyanate 39.2
After mixing for about 4 minutes under 1 mmHg,
The mixture was removed from the container and rapidly cooled to room temperature.
Pass the quenched mixture through three rolls twice at room temperature,
Aluminum oxide was uniformly dispersed. This mixture was sandwiched between release papers inserted with a 3 mm spacer and press-molded at 110° C. for 20 minutes to obtain a sheet-like variable heat dissipation material composition. The thermal conductivity of this sheet-shaped variable heat dissipation material composition is 1.35 Kcal/m・
hr・℃, and the hardness upon heating changed rapidly at 60℃. That is, it has been revealed that when the sheet is heated to 90° C. and pressed against the surface of the heating element, it can be firmly attached to the surface of the heating element with a small force. Example 2 Polyhydroxy compound with an average molecular weight of about 2000 (manufactured by Daicel Chemical Co., Ltd., trade name Placcel 220, hydroxyl value
56) 100 parts and a low molecular weight polyolefin with a molecular weight of approximately 2000 (manufactured by Sanyo Kasei Co., Ltd., trade name Sanwax 151)
-P) and 822 parts of zinc oxide were heated and stirred under vacuum in the same manner as in Example 1, and then 7.0 parts of 2,4-toluene diisocyanate as a curing agent was added and mixed under vacuum for 5 minutes. Thereafter, in the same manner as in Example 1, a 3 mm variable heat dissipating material composition was obtained.
The thermal conductivity of this sheet is 2.98Kal/m・hr・℃, and the curing temperature characteristics are 78 at room temperature and 90℃.
It suddenly changed to 16. Example 3 100 parts of a hydrogenated polyhydroxybutadiene polymer with an average molecular weight of about 3000 (manufactured by Mitsubishi Kasei Co., Ltd., trade name Polytail H, hydroxyl value 45) and 100 parts of a hydrogenated polyhydroxybutadiene polymer with an average molecular weight of about 1500.
10 parts of low molecular weight polyolefin (manufactured by Sanyo Kasei Co., Ltd., trade name Sanwax 171-P) and 638 parts of magnesium oxide were mixed in the same manner as in Example 1, and then 3-isocyanatomethyl- as a curing agent was mixed.
After adding 6.23 parts of 3,5,5-trimethylcyclohexyl isocyanate and vacuum mixing for 10 minutes, the mixture was removed from the container and rapidly cooled to room temperature.
The quenched mixture was passed through three rolls twice to uniformly disperse the magnesium oxide, and then, while being sandwiched between release paper, the mixture was passed through calender rolls and formed into a sheet with a thickness of 2 mm. The sheet was allowed to stand at room temperature for about one week to complete the curing reaction. The sheet-shaped variable heat dissipating material composition obtained by the above method had properties as shown in Table 1 below.

[Table] Example 4 Polyhydroxy compound with an average molecular weight of approximately 2000 (manufactured by Mitsubishi Kasei Corporation, trade name Polytail HA, hydroxyl value
50) 100 parts and a low molecular weight polyolefin with a molecular weight of approximately 3500 (manufactured by Sanyo Chemical Co., Ltd., trade name Sanwax 131)
-P) and 518 parts of aluminum powder with an average particle size of 60 microns were mixed in vacuum in the same manner as in Example 1, and then 8.5 parts of 2,4-toluene diisocyanate as a hardening agent was added and mixed in vacuum for 5 minutes. Next, in the same manner as in Example 3, it was passed through a calender roll and formed into a sheet with a thickness of 2 mm, and then a sheet with a thickness of 1 mm was formed.
A composite of the deformable heat dissipating material and the aluminum plate was obtained. The composite was left at room temperature for one week to fully cure.
The thermal conductivity of this composite is 69.9Kcal/m・
When this composite was heated to 80°C and pressed against the uneven surface of a heating element at intervals of 0.5 mm in height and 1 mm in width, it adhered to all surfaces of the heating element.

[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. A melting point in the range of -20 to 130°C and a molecular weight
The main ingredient is a mixture of 100 parts by weight of a hydrogenated polyhydroxybutadiene polymer with a molecular weight of 500 to 4000 and 10 to 60 parts by weight of a low molecular weight polyolefin compound with a molecular weight in the range of 500 to 5000. 1. A variable heat dissipating material composition characterized in that 50 to 1500 parts by weight of a thermally conductive filler is blended with 100 parts by weight of a thermosetting resin using an isocyanate compound having 1.5 or more isocyanate groups. 2. The variable heat dissipating material composition according to claim 1, wherein a low molecular weight polypropylene having a molecular weight of 800 to 5000 is used as the low molecular weight polyolefin compound. 3. The variable heat dissipating material composition according to claim 1, wherein low molecular weight polyethylene having a molecular weight of 1,000 to 5,000 is used as the low molecular weight polyolefin compound. 4. Claims 1, 2, or 3, wherein the thermally conductive filler is a powder or fibrous metal.
The variable shape heat dissipating material composition described in 1. 5. The variable heat dissipating material composition according to claim 1, 2 or 3, wherein the thermally conductive filler is a metal oxide.