JPH07125137A - Heat-radiating electrically insulating sheet and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a heat radiating sheet of polyolefin synthetic rubber improved in electrical insulation, chemical resistance, and plasma gas resistance. CONSTITUTION:The heat radiation insulating sheet is made such that a glass fiber cloth layer is subjected to a filler treatment by a cured substance of an addition reactive polysiloxane-containing ethylene propylene diene rubber composite containing 60-90wt.% inorganic filler, and a polysiloxane--containing ethylene- propylene-diene rubber sheet containing a 60-90wt.% inorganic filler is laminated on at least one surface of the filler treated glass cloth layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulating heat dissipation sheet using a polyolefin synthetic rubber excellent in chemical resistance, insulation and plasma gas resistance, and a method for producing the same.

[0002]

2. Description of the Related Art Silicone rubber-based insulating heat-dissipating sheets have hitherto been used as the insulating heat-dissipating sheets, but their main applications are heat-generating electronic parts such as power transistors and thyristors. It was heat dissipation.

However, the silicone rubber type heat dissipation sheet which has been conventionally used has a moisture permeability coefficient of 1 for the silicone rubber.
Since it was as high as 00 gmm / m ² · 24 hr, the volume resistivity was lowered in a high temperature and high humidity atmosphere, and there was concern about the insulating property. Further, the silicone rubber-based heat radiation sheet is anxious about chemical resistance such as hydrochloric acid resistance and alkali resistance, and its application range is limited. Further, the silicone rubber-based heat-dissipating sheet has relatively high durability against plasma gas, but has a drawback that it deteriorates when exposed to plasma gas for a long time.

On the other hand, an insulating heat-dissipating sheet made of polyolefin rubber is proposed in Japanese Patent Publication No. 57-42921. This one uses a roll as a method of highly filling the synthetic rubber with boron nitride, but in this method it is said that if the shear stress is not applied to the boron nitride, it will be difficult for the boron nitride to collapse or orient. In addition, roll compounding under such conditions lacks mass productivity,
Not only the cost increases, but also the thermal resistance of the manufactured heat dissipation sheet increases.

Further, a method of producing a rubber by crosslinking a polyolefin synthetic rubber by peroxide vulcanization has been conventionally used, but this method causes foaming by hot air vulcanization and is excellent in mass productivity. The tunnel hot air drying oven could not be used.

The present invention has been made in view of the above circumstances, and is an insulating material capable of producing a polyolefin-based synthetic rubber insulating heat-dissipating sheet excellent in chemical resistance, insulation and plasma gas resistance with good mass productivity. A heat dissipation sheet and a method for manufacturing the same are provided.

[0007]

Means for Solving the Problems and Actions The inventors of the present invention have conducted extensive studies to achieve the above-mentioned object, and as a result, have a glass fiber cloth layer in the middle portion and are excellent in electrical insulation and thermal conductivity. Inorganic filler 60-90% (wt%, same below)
Insulating heat dissipation sheet made of filled siloxane-containing ethylene propylene diene rubber sheet is effective, and inorganic filler is used in an amount of 60 to 9 in producing such sheet.
A glass fiber cloth is sealed with an addition reaction-curable siloxane-containing ethylene propylene diene rubber composition blended with 0%, and after curing, a peroxide-curable and / or addition with 60 to 90% of an inorganic filler is blended. It is effective to apply the reaction-curable siloxane-containing ethylene propylene diene rubber composition to the glass fiber cloth and cure it, and the glass fiber cloth is previously stopped and cured with the addition reaction-curable siloxane-containing ethylene propylene diene composition. As a result, in the subsequent coating process, pinholes due to back penetration of the coating liquid and variations in sheet thickness due to coating unevenness are eliminated, and insulation (voltage resistance) is improved and thermal resistance is reduced. Based on this finding, the present invention has been completed.

Therefore, in the present invention, the glass fiber cloth layer is sealed with a cured product of an addition reaction curable siloxane-containing ethylene propylene diene rubber composition containing 60 to 90% of an inorganic filler, and An insulating heat dissipation sheet in which a siloxane-containing ethylene propylene diene rubber sheet containing 60 to 90% of an inorganic filler is laminated on at least one surface of the glass fiber cloth layer subjected to the sealing treatment, and the glass fiber cloth is provided with the inorganic filler. 60-90
% Of the addition reaction-curable siloxane-containing ethylene propylene diene rubber composition, the glass fiber cloth was pre-sealed, and the composition was heat-cured, and then the glass fiber cloth was applied to at least one side of the glass fiber cloth. Provided is a method for producing an insulating heat dissipation sheet, which comprises applying an addition reaction-curable and / or peroxide-curable siloxane-containing ethylene propylene diene rubber composition containing 60 to 90% of an inorganic filler and curing the composition.

The present invention will be described in more detail below. The insulating heat dissipation sheet of the present invention is an addition reaction-curable siloxane-containing ethylene propylene diene rubber composition in which the glass fiber cloth layer contains 60 to 90% of an inorganic filler. And a siloxane-containing ethylene propylene diene rubber sheet containing 60 to 90% of an inorganic filler is laminated on at least one surface of the glass fiber cloth layer subjected to the sealing treatment. Heat dissipation sheet.

The glass fiber cloth used in the present invention may be a commercially available one, and the thickness thereof is 0.0
Those having a lattice spacing of 3 to 0.15 mm and a lattice spacing of 50 to 5,000 μm are preferable from the viewpoint of thermal conductivity and strength.

If the glass fiber cloth is treated with a commercially available silane coupling agent, the adhesion with the rubber material is improved. As the silane coupling agent, vinyl methoxy silane, vinyl ethoxy silane, γ-glycid is used. Examples include xypropyltrimethoxysilane and the like.

The addition reaction-curable siloxane-containing ethylene propylene diene rubber composition used for sealing the glass fiber cloth is not particularly limited, but (1) ethylene-propylene-diene copolymer A mixture of 60% or more of a polymer and 40% or less of an organopolysiloxane containing no silicon-bonded hydrogen atom, (2) an organohydrogenpolysiloxane having at least two hydrogen atoms bonded to a silicon atom in one molecule. , (3) platinum or a platinum compound, and (4) those containing an inorganic filler are preferably used.

Here, the ethylene-propylene-diene copolymer as the first essential component has a propylene content of 4
0 to 70%, especially 40 to 60% is preferable, and the diene monomer is generally ethylidene norbornene, dicyclopentadiene, 1,4-hexadiene and the like. Further, this copolymer has an iodine value of 1 to
It is preferably 40, especially 5 to 30.

As such a copolymer, a commercially available polyolefin synthetic rubber component can be used, and specifically, EP22 (manufactured by Nippon Synthetic Rubber Co., Ltd.) and Esplen 5 can be used.
67 (manufactured by Sumitomo Chemical Co., Ltd.), EPT3045 (manufactured by Mitsui Petrochemical Industry Co., Ltd.), EP33 (manufactured by Nippon Synthetic Rubber Co., Ltd.) and the like.

In the present invention, the above ethylene-propylene-
It is preferable to mix and use a diene copolymer with an organopolysiloxane having no hydrogen atom bonded to a silicon atom.

The organopolysiloxane is represented by the following general formula (1) R ¹ _a SiO 2 _{(4-a) / 2} (1) (wherein R ¹ is the same or different and is unsubstituted or substituted monovalent carbon). A hydrogen group, particularly a monovalent hydrocarbon group having 1 to 10 carbon atoms, such as an alkyl group such as a methyl group, an ethyl group, a propyl group or a butyl group, an alkenyl group such as a vinyl group, an allyl group or a butenyl group, a phenyl group, An aryl group such as a tolyl group,
Aralkyl groups such as benzyl group and β-phenylethyl group, and chloromethyl groups in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms, cyano groups, 2-cyanoethyl groups, 3,3,3 A trifluoropropyl group or the like, and a is a positive number of 1.99 to 2.02. ) And having at least two or more alkenyl groups such as vinyl group, allyl group and butenyl group in one molecule are preferably used. In this case, the group other than the alkenyl group is preferably one having a methyl group content of 50 mol% or more. When the methyl group is less than 50 mol%, it is difficult to manufacture and it is not economical.

The organopolysiloxane of the above formula (1) preferably has an average degree of polymerization of 500 to 10,000, particularly 3,000 to 10,000.

Specific examples of such an organopolysiloxane include methylvinylpolysiloxane, methylvinylphenylpolysiloxane, and methyl (3,3,3-trifluoropropyl) polysiloxane.

The mixing ratio of the ethylene-propylene-diene copolymer and the organopolysiloxane is 100 to 60%, preferably 100 to 70% of the above copolymer.
Further, the organopolysiloxane content is 0 to 40%, preferably 0 to 30%. If the mixing ratio is outside the above range, the strength of the cured rubber will be reduced.

The second component of the above composition is an organohydrogenpolysiloxane having at least two hydrogen atoms bonded to silicon atoms in one molecule.

In this case, the above-mentioned organohydrogenpolysiloxane acts as a cross-linking agent, and is represented by, for example, the following general formula (2) H _b R ¹ _c SiO 2 _{(4-bc) / 2} (1) R ² is an unsubstituted or substituted monovalent hydrocarbon group excluding the same or different aliphatic unsaturated group, particularly 1 to 1 carbon atoms.
0, such as methyl, ethyl, propyl,
Examples thereof include alkyl groups such as butyl group, aryl groups such as phenyl group and tolyl group, aralkyl groups such as benzyl group and β-phenylethyl group, cycloalkyl groups such as cyclohexyl group, and b is 0.002 to 1.0. Is a positive number, c is 1.99
A positive number of up to 2.02 and b + c is 1.992 to 3.0. ).

Specific examples of such an organohydrogenpolysiloxane include compounds represented by the following structural formulas.

[0023]

[Chemical 1] (K is an integer of 2 to 10, and m and n are integers of 0 to 10).

The amount of the second component added is 0.7 to 5, particularly 1 to 5, hydrogen atoms bonded to the silicon atom of the siloxane, per one diene and alkenyl group in the first component.
It is preferable that the amount is three. 0.7 hydrogen atoms
A sufficient amount of crosslinking effect may not be obtained if the amount is less than 5, and no improvement in properties may be observed even if the amount is more than 5.

Further, the third component platinum or platinum compound is
A catalyst for advancing the above-mentioned addition reaction between the first component and the second component, such as platinum, platinum black, chloroplatinic acid, a complex salt of chloroplatinic acid with an olefin or an aldehyde, and an alcohol-modified chloroplatinic acid. And so on.
The amount of platinum or platinum compound used may be a catalytic amount, but may be appropriately increased or decreased depending on the composition so that the curing rate due to the reaction between the first component and the second component is desirable. The amount of platinum is usually 1 ppm to 1% with respect to the amount of the first component used.

Further, examples of the inorganic filler of the fourth component include boron nitride, alumina, aluminum nitride, quartz powder, etc. One of these may be used alone or two or more thereof may be used in combination. Especially, boron nitride is preferable from the viewpoint of insulating property. The boron nitride is not particularly limited, but low-pressure hexagonal boron nitride (h-BN) having a layered structure similar to graphite is used. As such boron nitride, KBN (h)
-10, KBN (h) -SQ, KBN (h) -SP, K
Examples thereof include BN (h) -S (produced by Shin-Etsu Chemical Co., Ltd.) and VHP-EX (produced by Showa Denko KK).

The compounding amount of the above-mentioned filler is 60 to 90%, especially 60 to 80% of the total composition. If it is less than 60%, the heat resistance of the heat-dissipating sheet becomes high and the heat dissipation is poor.
If it exceeds 0%, the strength of the heat-dissipating sheet is lowered and the cost is increased.

The composition of the present invention contains, in addition to the above-mentioned essential components, optional components for adjusting the physical properties of the cured product, if necessary, such as fumed silica, precipitated silica, aluminum silicate, fused silica powder, silica. Fillers such as clay, calcium carbonate, titanium dioxide, carbon black,
An antiaging agent, an ultraviolet absorber, a coloring agent, etc. can be added.

Further, in the present invention, it is preferable to use the composition of the above components in the form of slurry, and various organic solvents are used as the solvent, for example, toluene, xylene, benzene, solvent naphtha, industrial use. gasoline,
Examples thereof include cyclohexanone and n-hexane. A slurry having a viscosity of 100 to 100,000 cp can be used, preferably 500 to 50,000 cp.

In the present invention, the method for sealing the glass fiber cloth using the above addition reaction-curable siloxane-containing ethylene propylene diene rubber composition is as follows:
It can be carried out by using a slurry of the composition and using a known impregnator as shown in FIGS.

Here, FIG. 1 shows a vertical type impregnating machine using a scraping tool, 1 is a glass fiber cloth, 2
Is a tank for containing the slurry 3 of the above composition, 4 is a dipping roll, 5 is a scraping tool, and 6 is an edging tool. Also,
FIG. 2 shows a horizontal type impregnator, which uses a squeeze roll 7. In addition, 8 is an overflow mechanism.

In the present invention, the glass fiber cloth is impregnated with the addition reaction-curable siloxane-containing ethylene propylene diene rubber composition as described above, and then the composition is heat-cured. The heat-curing can be performed by hot air. In this case, a tunnel type hot air drying oven can be used. In the peroxide-curable composition as the above composition, foaming occurs when heated with hot air, and it is difficult to use a hot air drying oven,
In the case of an addition reaction curing type composition, hot air heat curing can be performed without foaming.

The conditions for this heat curing are appropriately selected,
Conditions of 100 to 250 ° C. and 30 seconds to 60 minutes can be adopted.

Next, in the present invention, a siloxane-containing ethylene propylene diene sheet containing 60 to 90% of an inorganic filler is laminated on one side, preferably both sides, of the glass fiber cloth subjected to the sealing treatment. The siloxane-containing ethylene propylene diene rubber composition used for forming the rubber sheet may be an addition reaction curable type or a peroxide curable type.

In this case, the addition reaction-curable composition may be the same as the above-mentioned addition reaction-curable composition, while the peroxide-curable composition may be the above-mentioned composition. In the addition reaction-curable composition,
(2) An organohydrogenpolysiloxane having at least two hydrogen atoms bonded to silicon atoms in one molecule of the component, t-butylcumyl peroxide, benzoyl peroxide instead of the platinum or platinum compound of the (3) component. Dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, di-t-butylperoxide, or other organic peroxides may be used.

As a method of forming the rubber sheet on the glass fiber cloth, a glass fiber cloth subjected to sealing is coated with a slurry of an addition reaction-curable and / or peroxide-curable siloxane-containing ethylene propylene diene composition. The coating is performed to adjust the film thickness, and as a coating method, a known knife coater, blade coater, spray coater, inclined plate curtain coater or the like can be used. Next, in order to remove the solvent, it may be naturally dried, but a hot air drying furnace may be used in consideration of mass productivity. Then, the coated composition is cured to obtain an insulative heat dissipation sheet. In this case, the composition may be vulcanized by a known method such as hot press or pressure hot roll. From the standpoint of mass productivity, etc., a slurry of an addition reaction-curable and / or peroxide-curable siloxane-containing ethylene propylene diene composition is applied to one side of the sealing-treated glass fiber cloth, and the other side is then dried with hot air. To the surface of the composition, dried with hot air to produce a preform, the preform with a cutter into a predetermined shape,
It is recommended to vulcanize by hot pressing after cutting to size.

The vulcanization conditions are 100 to 25 ° C., especially 150.
The temperature can be set to ˜200 ° C., 30 seconds to 60 minutes, and especially 5 to 30 minutes. The thickness of the rubber sheet is 100 to
It is preferably 3,000 μm, and particularly preferably 200 to 800 μm.

[0038]

The present invention has the following effects. 1. When the glass fiber cloth is impregnated and coated with the slurry-like raw material, a continuous treatment device excellent in mass productivity can be used, which is advantageous in terms of cost. 2. Dispersion of boron nitride in synthetic rubber can be performed with a mixer for slurry dispersion without using high stress such as rolls, so almost no shear stress is applied, so that boron nitride does not collapse Therefore, a heat dissipation sheet that does not have high heat resistance and is advantageous in terms of performance can be manufactured. 3. When the glass fiber cloth is pre-filled with the slurry-like addition reaction-curable siloxane-containing ethylene propylene diene rubber composition, a hot air heating curing furnace can be used,
Since the cloth can be completely stopped, pinholes and coating unevenness in the next process do not occur, insulation is high, and there is no variation in thermal resistance due to variation in film thickness, and it is possible to manufacture a heat dissipation sheet with excellent quality. . 4. Since boron nitride can be highly filled in the synthetic rubber and the glass fiber cloth layer is provided in the middle, a heat dissipation sheet having excellent tear strength can be manufactured. 5. Since a cured product of a siloxane-containing ethylene propylene diene rubber composition is used as the synthetic rubber, hydrochloric acid resistance,
It has excellent resistance to alkalis and plasma gas, and has no decrease in volume resistivity even in a high temperature and high humidity atmosphere, and has excellent electrical insulation.

[0039]

EXAMPLES The present invention will be specifically described below by showing Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Examples 1 to 3, Comparative Examples 1 and 2] Polyolefin synthetic rubber EP22 (manufactured by Japan Synthetic Rubber Co., Ltd., iodine value 22), (CH ₂ = CH) (CH ₃ ) SiO unit 0.5 average polymerization degree both ends consisting of mole% (CH ₃₎ and ₂ SiO units 99.5 mol% was blocked with hydroxyl groups 8,0
00 methyl vinyl polysiloxane, specific surface area is 200
m ² / g of silica Aerosil 200 (manufactured by Nippon Aerosil Co., Ltd.) was blended in a ratio shown in Table 1 using a two-roll mill, and then dissolved in toluene to obtain a 20% rubber-toluene solution.

Next, 2 parts of the organohydrogenpolysiloxane represented by the following formula (A), 0.1 part of a 5% isopropyl alcohol solution of chloroplatinic acid, and hexagonal boron nitride KB were added to the obtained 20% rubber-toluene solution.
N (h) -10 (manufactured by Shin-Etsu Chemical Co., Ltd., trade name) 2
00 parts and 0.1 parts of a 50% toluene solution of ethynylcyclohexanol were added and mixed to prepare a composition for sealing glass fiber cloth. Next, using the manufacturing apparatus shown in FIG. 3 in which the impregnator and the hot-air drying furnace are connected, a thickness of 0.0
A glass fiber cloth treated with vinyltrimethoxysilane was impregnated with a sealing composition at 6 mm, a lattice spacing of 50 μm, and a mass of 488 g / m ² to perform impregnation sealing. In addition,
Web speed is 1 m / min, hot air drying oven temperature is 150
It was ℃. For comparison, the same filling treatment was performed by adding 2 parts of dicumyl peroxide instead of the 5% isopropyl alcohol solution of organohydrogenpolysiloxane chloroplatinic acid and the 50% toluene solution of ethynylcyclohexanol. It was

[0042]

[Chemical 2]

Here, in FIG. 3, 9 is a hot air drying oven, 1
Reference numeral 0 is a winding roll, and other reference numerals are the same as those in FIG.

The obtained glass fiber cloths of Examples 1 to 3 which had been subjected to the sealing treatment were uniformly filled with rubber at the lattice intervals, and there were no problems such as eye-opening. However, Comparative Example 1
What was hardened by the above-mentioned peroxide foamed.

[0045]

[Table 1]

Next, the compositions of Examples 1 to 3 shown in Table 1 were prepared.
Connected knife coater and hot air drying oven shown in Fig. 4
Coated on one side of the glass fiber cloth that has been sealed with the manufacturing equipment.
Processed and dried (web speed 1 m / min, hot air drying oven 8
0 ° C). In addition, apply the same material to the other surface and dry.
did. The obtained preform is length x width = 300 x 300
Cut to mm and use a hot press to 120 ℃, 50
kg / cm²of Press for 10 minutes under the conditions, and insulate heat dissipation
I got a card. The obtained heat dissipation sheet and Comparative Example 2 were
Lath fiber cloth with a silicone rubber layer containing BN
Insulation heat dissipation sheet TC-45BG (Shin-Etsu Chemical Co., Ltd.
Table 2 shows the results of physical properties and chemical resistance of a product manufactured by Co., Ltd.
Shown in.

In FIG. 4, 11 is a glass fiber cloth having been sealed, 12 is a coating liquid, 13 is a knife, and 14 is a coating liquid.
Is a hot air drying furnace, and 15 is a winding roll.

[0048]

[Table 2]

The thermal resistance was measured by the following method. Punched sample of thermal resistance transistor TO-3 type is Transistor 2SD113 (Toshiba, trade name) and Fin F
It was attached to a torque inverter by sandwiching it between BA-150-PS (manufactured by OS Co., Ltd., trade name), and a transistor transient thermal resistance measuring device TH-156 (manufactured by Kuwano Electric Co., Ltd. name) DC10V. A power of 3 A was applied, and one minute later, it was calculated from ΔV _EB (mV) by the following equation.

[0050]

[Equation 1] ΔV _EBS … with sample sandwiched ΔV _EB ΔV _EBO … radiation grease G746 (Shin-Etsu Chemical Co., Ltd., trade name) Δ when applied to transistors
V _EB C ... Temperature coefficient of ΔV _EB of transistor (ΔV _EB / ΔT ≈
2.2 mV / ° C) α ... Correction term based on base current (α = 0.9 W)

[Examples 4 to 6 and Comparative Example 2] Polyolefin
-Based synthetic rubber Esplene 567 (Sumitomo Chemical Co., Ltd.)
Made, propylene content 46% by weight, iodine value 5), (C
H₂= CH) (CH₃) SiO unit 0.5 mol% and (C₆
H_Five) SiO unit 10 mol% and (CH₃)₂SiO unit 8
Methyl having an average degree of polymerization of 8,000 consisting of 9.5 mol%
Vinylphenyl polysiloxane and HAF carbon are shown in Table 3.
Dissolved in toluene after blending with 2 rolls at the ratio shown in
However, a 30% rubber-toluene solution was prepared. 30% obtained
Add 3 parts dicumyl peroxide to the rubber toluene solution
Then, a coating liquid was prepared.

Next, using the manufacturing apparatus shown in FIG.
The glass fiber cloth with the sealing treatment obtained in Example 3 was treated as above.
The coating liquid was applied (web speed 1 m / min, hot air drying
Furnace 90 ° C). The obtained preform is length x width = 300 x
Cut to 300 mm and use heat press to 170
℃, 30kg / cm²of Insulate by pressing for 10 minutes under the conditions
The heat dissipation sheet was obtained. Physical properties and resistance of the obtained heat dissipation sheet
Table 4 shows the results of the chemical properties.

[0053]

[Table 3]

[0054]

[Table 4]

From the above results, the insulating heat dissipation sheets obtained in Examples 1 to 6 are superior in chlorine resistance and alkali resistance as compared with the conventional silicone rubber heat dissipation sheets, and are chlorine-based or fluorine-based. It is recognized that it has excellent durability against plasma gas. Also, 40 ℃, 90% RH
Table 5 shows the results of measuring the volume specific resistance immediately after standing for 5 hours in the atmosphere.

[0056]

[Table 5]

From the above results, it is recognized that the sheets of Examples 1 to 6 are excellent in dielectric breakdown strength, and at the same time, are not deteriorated in volume resistivity even in an atmosphere of high temperature and high humidity and are excellent in electric insulation. .

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of an impregnating machine.

FIG. 2 is a schematic cross-sectional view showing another example of an impregnating machine.

FIG. 3 is a schematic cross-sectional view showing an example of a sealing treatment device.

FIG. 4 is a schematic cross-sectional view showing an example of a rubber sheet forming apparatus.

[Explanation of reference numerals] 1 glass fiber cloth 3 slurry 9 hot air drying furnace 11 glass fiber cloth with sealing treatment 14 hot air drying furnace

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsutomu Yoneyama 1 Hitomi, Oita, Matsuida-cho, Usui-gun, Gunma 10 Shin-Etsu Chemical Co., Ltd. Silicone Electronic Materials Research Laboratory

Claims (5)

[Claims] 1. The glass fiber cloth layer comprises 60 inorganic fillers.
To 90% by weight of the addition-reaction-curable siloxane-containing ethylene propylene diene rubber composition, which has been subjected to a sealing treatment, and an inorganic filler is applied to at least one surface of the sealing-treated glass fiber cloth layer. ~ 90
An insulating heat-dissipating sheet obtained by laminating a siloxane-containing ethylene propylene diene rubber sheet, which is contained by weight. 2. An addition reaction curable siloxane-containing ethylene propylene diene rubber composition comprising (1) 60% by weight or more of an ethylene-propylene-diene copolymer and 40% by weight of organopolysiloxane containing no silicon atom-bonded hydrogen atom. A mixture of (2) an organohydrogenpolysiloxane having at least two hydrogen atoms bonded to silicon atoms in one molecule, (3) platinum or a platinum compound, and (4) containing boron nitride as an inorganic filler. The insulating heat dissipation sheet according to claim 1, wherein 3. A glass fiber cloth containing 60 to 60% of an inorganic filler.
At 90% by weight of the addition reaction-curable siloxane-containing ethylene propylene diene rubber composition, the glass fiber cloth was pre-sealed, and the composition was heat-cured. A method for producing an insulating heat-dissipating sheet, which comprises applying an addition reaction-curable and / or peroxide-curable siloxane-containing ethylene propylene diene rubber composition containing 60 to 90% by weight of an inorganic filler to one surface and curing the composition. . 4. The method according to claim 3, wherein the sealing treatment of the glass fiber cloth with the addition reaction-curable siloxane-containing ethylene propylene diene rubber composition is carried out by impregnating a slurry of the composition and then heating and curing with hot air. 5. A slurry of an addition reaction-curable and / or peroxide-curable siloxane-containing ethylene propylene diene composition is applied to one surface of a sealing-treated glass fiber cloth, dried on hot air, and then dried on the other surface. The production method according to claim 4, wherein a slurry of the composition is applied, dried with hot air to produce a preform, and the preform is cut with a cutter and then vulcanized by hot pressing.