JP2019077843A - Thermally conductive silicone potting composition and cured product thereof - Google Patents

Abstract

To provide a thermally conductive silicone potting composition that has high fluidity, has good physical properties after curing and has a small change in physical properties after heat aging.SOLUTION: The composition includes: (A) an organopolysiloxane having two or more alkenyl groups in one molecule and having a viscosity at 25°C of 0.01 to 100 Pa s; (B) an organopolysiloxane represented by the average formula (1); (C) an organopolysiloxane having a siloxy group at one terminal; (D) a thermally conductive filler; (E) an organohydrogensiloxane; and (F) a hydrosilylation reaction catalyst. (R's are each independently a monovalent aliphatic saturated hydrocarbon group; Ris a monovalent aliphatic unsaturated monovalent hydrocarbon group; z is O or a divalent hydrocarbon group; a is 0.1 to 1.9; and b is an integer of 100 or more.)SELECTED DRAWING: None

Description

  The present invention relates to a thermally conductive silicone potting composition and a cured product thereof, and more specifically, it is possible to pour even an electronic component having a high fluidity even if containing a large amount of thermally conductive filler and having a fine structure. The present invention relates to a thermally conductive silicone potting composition and its cured product, which can be cured, have good physical properties after curing, and show little change in elongation at break even after heat aging.

With the rising awareness of global warming, the automotive industry has been developing environmentally friendly vehicles such as hybrid vehicles, plug-in hybrid vehicles, and electric vehicles for the purpose of reducing greenhouse gases, and aims to improve their fuel efficiency performance. Therefore, the inverter mounted on the vehicle has been enhanced and miniaturized.
Along with this, parts such as IC and reactor in the inverter are also miniaturized, and the amount of heat generation is also increasing. For such heat-generating parts, conventionally, a heat-conductive silicone composition such as a heat-conductive silicone grease, a heat-conductive silicone gel composition, a heat-conductive silicone potting composition and the like between the heat-generating part and the cooler By interposing objects, the cooling efficiency of the parts is improved to protect the parts.

For example, Patent Document 1 proposes a thermally conductive silicone composition comprising an organopolysiloxane, a hydrolyzable group-containing methylpolysiloxane, a thermally conductive filler, and a curing agent. Is difficult to adhere to parts having a microstructure.
Therefore, in Patent Document 2, a method in which the cooler and the heat generating component are assembled in advance, the highly conductive heat conductive silicone potting composition is poured therein, and the heat generating component and the cooler are thermally connected. It is disclosed.
However, as the miniaturization of parts has progressed with the recent miniaturization, the calorific value is increased, and a further improvement in thermal conductivity is also required for the thermally conductive silicone potting composition, however, Patent Document 2 When practical fluidity was maintained by the method of (1), the thermal conductivity of about 1.0 W / m · K was the limit.

As a technique for solving this problem, Patent Document 3 proposes a silicone potting composition in which a large amount of a thermally conductive filler is contained to achieve a high thermal conductivity while achieving high flowability. However, this composition has a large change in physical properties after heat aging, and in particular, the decrease in elongation at break is remarkable, and the silicone potting composition interposed between the heat generating component and the cooler peels off after heat aging. It has the problem that it is not possible to cool the part.
In addition, Patent Document 4 discloses a thermally conductive silicone potting composition in which the change in physical properties after thermal aging is small. However, in the method of Patent Document 4, in order to keep the change in physical properties after thermal aging small, the thermal conductivity of about 1.6 W / m · K is the limit.

  A thermally conductive silicone potting composition is desired which is not limited to a high thermal conductivity and high fluidity of 2.0 W / m · K or more and a small change in physical properties after thermal aging due to further high power and miniaturization of the inverter. However, no composition is known which meets these properties.

Patent No. 3543663 gazette Patent No. 5304623 gazette JP, 2016-84378, A Patent No. 585 3 989

  The present invention has been made in view of the above circumstances, and although it contains a large amount of thermally conductive filler, it has high fluidity, good physical properties after curing, and changes in physical properties after heat aging. It is an object to provide a small thermally conductive silicone potting composition and a cured product thereof.

  As a result of intensive studies to achieve the above object, the present inventors have found that a composition comprising predetermined three organopolysiloxanes, a thermally conductive filler, an organohydrogenpolysiloxane and a hydrosilylation reaction catalyst is It has been found that although it contains a large amount of thermally conductive filler, it has high flowability, good physical properties, and gives a cured product with a small change in physical properties after heat aging, thus completing the present invention. did.

（式中、Ｒは、互いに独立して脂肪族不飽和結合を有しない一価炭化水素基を表し、Ｒ¹は、脂肪族不飽和結合を有する一価炭化水素基を表し、ｚは、酸素原子または二価炭化水素基を表し、ａは、０．１〜１．９であり、ｂは、１００以上の整数である。）
（Ｃ）下記一般式（２）で示されるオルガノポリシロキサン、

（式中、Ｒ²は、互いに独立して非置換または置換の一価炭化水素基を表し、Ｒ³は、互いに独立して、アルキル基、アルコキシアルキル基、アルケニル基またはアシル基を表し、ｎは、２〜１００の整数であり、ｃは、１〜３の整数である。）
（Ｄ）熱伝導性充填材、
（Ｅ）オルガノハイドロジェンシロキサン、および
（Ｆ）ヒドロシリル化反応触媒
を含むことを特徴とする熱伝導性シリコーンポッティング組成物、
２． 前記ｚが、二価炭化水素基である１の熱伝導性シリコーンポッティング組成物、
３． 前記Ｒが、メチル基である１または２の熱伝導性シリコーンポッティング組成物、
４． 前記ｂが、１００〜３００である１〜３のいずれかの熱伝導性シリコーンポッティング組成物、
５． 前記ａが、０．３〜１．７である１〜４のいずれかの熱伝導性シリコーンポッティング組成物、
６． １〜５のいずれかの熱伝導性シリコーンポッティング組成物を硬化してなる硬化物
を提供する。 That is, the present invention
1. (A) an organopolysiloxane having a viscosity of 0.01 to 100 Pa · s at 25 ° C. and having at least two alkenyl groups in one molecule;
(B) an organopolysiloxane represented by the following average formula (1),

(Wherein, R independently represents a monovalent hydrocarbon group having no aliphatic unsaturated bond, R ¹ represents a monovalent hydrocarbon group having an aliphatic unsaturated bond, and z is oxygen Represents an atom or a divalent hydrocarbon group, a is 0.1 to 1.9, and b is an integer of 100 or more.)
(C) an organopolysiloxane represented by the following general formula (2),

(Wherein R ² independently represents an unsubstituted or substituted monovalent hydrocarbon group, R ³ independently represents an alkyl group, an alkoxyalkyl group, an alkenyl group or an acyl group, n Is an integer of 2 to 100, and c is an integer of 1 to 3.)
(D) thermally conductive filler,
A thermally conductive silicone potting composition comprising (E) an organohydrogensiloxane and (F) a hydrosilylation reaction catalyst,
2. The thermally conductive silicone potting composition according to 1, wherein z is a divalent hydrocarbon group.
3. 1 or 2 thermally conductive silicone potting compositions, wherein R is a methyl group,
4. The thermally conductive silicone potting composition according to any one of 1 to 3, wherein b is 100 to 300.
5. The thermally conductive silicone potting composition according to any one of 1 to 4, wherein a is 0.3 to 1.7.
6. A cured product obtained by curing any one of the heat conductive silicone potting compositions of 1 to 5 is provided.

The heat conductive silicone potting composition of the present invention has high fluidity before curing, can flow into fine spaces, good physical properties can be obtained after curing, and elongation reduction at break after heat aging. As a result, the parts can be protected without peeling from the heat-generating parts.
For this reason, the composition of the present invention is effective for potting, for example, when a component having a fine structure such as a transformer is fixed to a cooler, and such a member has high thermal conductivity after curing. While being able to transfer the heat of components to a cooler efficiently at a rate, it can cool efficiently also after thermal aging.

Hereinafter, the present invention will be described in more detail.
The thermally conductive silicone potting composition according to the present invention cures at room temperature or under heating and has adhesion to metals, organic resins, etc., and (A) at least two alkenyl groups in one molecule. Organopolysiloxane having (B) a trimethoxysilyl group and an alkenyl group simultaneously in one molecule, (C) an organopolysiloxane blocked at one end with an alkoxysilyl group or the like, (D) heat conduction And (E) organohydrogensiloxane and (F) hydrosilylation reaction catalyst.

(1) Component (A) Component (A) has a viscosity of 0.01 to 100 Pa · s, preferably 0.06 to 10 Pa · s at 25 ° C., and bonds to at least 2 silicon atoms in one molecule Organopolysiloxanes having alkenyl groups. If the viscosity at 25 ° C. is less than 0.01 Pa · s, the storage stability of the composition deteriorates, and if it exceeds 100 Pa · s, high flowability can not be ensured. In addition, the said viscosity is a measured value (it makes the same hereafter) by a rotational viscometer.
Such organopolysiloxane is not particularly limited as long as it satisfies the above viscosity and alkenyl group content, and a known organopolysiloxane can be used, and the structure is also linear or branched. Or mixtures of two or more organopolysiloxanes having different viscosities.

Although the alkenyl group couple | bonded with a silicon atom is not specifically limited, A C2-C10 alkenyl group is preferable and a C2-C8 alkenyl group is more preferable.
Specific examples thereof include vinyl, allyl, 1-butenyl, 1-hexenyl group and the like. Among these, vinyl groups are preferable in terms of easiness of synthesis and cost.
The alkenyl group may be present at either end or in the middle of the molecular chain of the organopolysiloxane, but from the viewpoint of flexibility, it is preferred to be present only at both ends.

The organic group other than the alkenyl group bonded to the silicon atom is not particularly limited, but is preferably a monovalent hydrocarbon group having 1 to 20 carbon atoms, and more preferably a monovalent hydrocarbon group having 1 to 10 carbon atoms .
Specific examples thereof include alkyl groups such as methyl, ethyl, n-propyl, n-butyl, n-hexyl and n-dodecyl; aryl groups such as phenyl; and 2-phenylethyl and 2-phenylpropyl Aralkyl groups and the like can be mentioned.
In addition, part or all of the hydrogen atoms of these hydrocarbon groups may be substituted with a halogen atom such as chlorine, fluorine or bromine, and as a specific example thereof, a fluoromethyl group, a bromoethyl group, a chloromethyl group . Examples thereof include halogen-substituted monovalent hydrocarbon groups such as 3,3,3-trifluoropropyl group.
Among these, in view of easiness of synthesis and cost, it is preferable that 90 mol% or more is a methyl group.
Accordingly, the component (A) is particularly preferably dimethylpolysiloxane which is capped at both ends with a dimethylvinylsilyl group. The component (A) may be used alone or in combination of two or more.

(2) Component (B) The component (B) is an organopolysiloxane represented by the following average formula (1), and has the role of imparting fluidity and durability to the composition of the present invention.

（式中、Ｒは、互いに独立して脂肪族不飽和結合を有しない一価炭化水素基を表し、Ｒ¹は、脂肪族不飽和結合を有する一価炭化水素基を表し、ｚは、酸素原子または二価炭化水素基を表し、ａは、０．１〜１．９であり、ｂは、１００以上の整数である。）

(Wherein, R independently represents a monovalent hydrocarbon group having no aliphatic unsaturated bond, R ¹ represents a monovalent hydrocarbon group having an aliphatic unsaturated bond, and z is oxygen Represents an atom or a divalent hydrocarbon group, a is 0.1 to 1.9, and b is an integer of 100 or more.)

The monovalent hydrocarbon group having no aliphatic unsaturated bond of R is not particularly limited, but is preferably a monovalent hydrocarbon group having 1 to 10 carbon atoms, and has 1 to 6 carbon atoms. The hydrocarbon group is more preferable, and the monovalent hydrocarbon group having 1 to 3 carbon atoms is even more preferable.
Specific examples of the monovalent hydrocarbon group include an alkyl group, an aryl group, an aralkyl group, a halogenated alkyl group and the like.
The alkyl group may be linear, branched or cyclic, and specific examples thereof include linear alkyl groups such as methyl, ethyl, n-propyl, n-hexyl and n-octyl groups; isopropyl, Examples thereof include branched alkyl groups such as isobutyl, tert-butyl and 2-ethylhexyl groups; and cyclic alkyl groups such as cyclopentyl and cyclohexyl groups.
Specific examples of the aryl group include phenyl group and tolyl group.
Specific examples of the aralkyl group include 2-phenylethyl group, 2-methyl-2-phenylethyl group and the like.
Specific examples of the halogenated alkyl group include 3,3,3-trifluoropropyl group, 2- (nonafluorobutyl) ethyl group, 2- (heptadecafluorooctyl) ethyl group and the like.
Among these, as R, a methyl group and a phenyl group are preferable.

The monovalent hydrocarbon group having an aliphatic unsaturated bond of R ¹ is not particularly limited, but is preferably a monovalent hydrocarbon group having 2 to 10 carbon atoms, and is preferably a monovalent hydrocarbon group having 2 to 8 carbon atoms. Hydrocarbon groups are more preferred.
Specific examples of the monovalent hydrocarbon group include alkenyl groups such as vinyl, allyl, 1-butenyl and 1-hexenyl group.
Among these, vinyl groups are preferable in terms of easiness of synthesis and cost.
The divalent hydrocarbon group for z is not particularly limited, but is preferably a divalent hydrocarbon group having 2 to 10 carbon atoms, and more preferably a divalent hydrocarbon group having 2 to 8 carbon atoms.
The divalent hydrocarbon group may be linear, branched or cyclic, and specific examples thereof include ethylene, trimethylene, propylene and tetramethylene groups.
Among these, ^one having the same carbon number as R ¹ is preferable, and an ethylene group is more preferable, from the easiness of synthesis.

Although said b is an integer greater than or equal to 100, Preferably it is 100-300, More preferably, it is 100-200 from a heat resistant and fluid viewpoint. If b is less than 100, sufficient heat resistance can not be provided.
Although said a is 0.1-1.9, Preferably it is 0.2-1.8, More preferably, it is 0.3-1.7. If a is less than 0.1, heat resistance and fluidity can not be sufficiently imparted, and if it exceeds 1.9, the adhesiveness is lowered.
Specific examples of the component (B) include, but are not limited to, those shown below. The component (B) may be used alone or in combination of two or more.

[(CH ₃ O) ₃ SiOSi (CH ₃ ) ₂ O _1/2 ] _1.2 [(CH ₃ ) ₂ SiO] ₁₅₀ [Si (CH ₃ ) ₂ CH = CH ₂ O _1/2 ] _0.8
[(CH ₃ O) ₃ SiCH ₂ CH ₂ Si (CH ₃ ) ₂ O _1/2 ] _1.2 [(CH ₃ ) ₂ SiO] ₁₅₀ [Si (CH ₃ ) ₂ CH = CH ₂ O _1/2 ] _0.8
[(CH ₃ O) ₃ SiCH ₂ CH ₂ Si (CH ₃ ) ₂ O _1/2 ] _0.8 [(CH ₃ ) ₂ SiO] ₁₅₀ [Si (CH ₃ ) ₂ CH = CH ₂ O _1/2 ] _1.2
[(CH ₃ O) ₃ SiCH ₂ CH ₂ Si (CH ₃ ) ₂ O _1/2 ] _1.2 [(CH ₃ ) ₂ SiO] ₁₈₀ [Si (CH ₃ ) ₂ CH = CH ₂ O _1/2 ] _0.8
[(CH ₃ O) ₃ SiCH ₂ CH ₂ Si (CH ₃ ) ₂ O _1/2 ] _0.8 [(CH ₃ ) ₂ SiO] ₁₈₀ [Si (CH ₃ ) ₂ CH = CH ₂ O _1/2 ] _1.2
[(CH ₃ O) ₃ SiOSi (CH ₃ ) ₂ O _1/2 ] _1.2 [(CH ₃ ) ₂ SiO] ₁₅₀ [Si (CH ₃ ) ₂ CH ₂ CH = CH ₂ O _1/2 ] _0.8
[(CH ₃ O) ₃ SiCH ₂ CH ₂ CH ₂ Si (CH ₃ ) ₂ O _1/2 ] _1.2 [(CH ₃ ) ₂ SiO] ₁₅₀ [Si (CH ₃ ) ₂ CH ₂ CH = CH ₂ O _{1 / 2} ] _0.8
[(CH ₃ O) ₃ SiCH ₂ CH ₂ Si (CH ₃ ) ₂ O _1/2 ] _1.2 [(CH ₃ ) ₂ SiO] ₁₀₀ [CH ₃ C ₆ H ₅ SiO] ₅₀ [Si (CH ₃ ) ₂ CH = CH ₂ O _1/2 ] _0.8
[(CH ₃ O) ₃ SiCH ₂ CH ₂ Si (CH ₃ ) ₂ O _1/2 ] _1.2 [(CH ₃ ) ₂ SiO] ₁₉₈ [(C ₆ H ₅ ) ₂ SiO] ₂₂ [Si (CH ₃ ) ₂ CH = CH ₂ O _1/2 ] _0.8

  The compounding amount of the component (B) is not particularly limited, but from the viewpoint of flowability and durability, preferably 1 to 200 parts by mass, more preferably 100 parts by mass of the component (A). The amount is 5 to 180 parts by mass, and more preferably 10 to 170 parts by mass.

(3) Component (C) The component (C) is an organopolysiloxane represented by the following general formula (2) and has the role of imparting fluidity by reducing the viscosity of the composition.

（式中、Ｒ²は、互いに独立して非置換または置換の一価炭化水素基を表し、Ｒ³は、互いに独立して、アルキル基、アルコキシアルキル基、アルケニル基またはアシル基を表し、ｎは、２〜１００の整数であり、ｃは、１〜３の整数である。）

(Wherein R ² independently represents an unsubstituted or substituted monovalent hydrocarbon group, R ³ independently represents an alkyl group, an alkoxyalkyl group, an alkenyl group or an acyl group, n Is an integer of 2 to 100, and c is an integer of 1 to 3.)

The monovalent hydrocarbon group for R ² is not particularly limited, but is preferably a monovalent hydrocarbon group having 1 to 10 carbon atoms, and more preferably a monovalent hydrocarbon group having 1 to 6 carbon atoms, A C1-C3 monovalent hydrocarbon group is more preferable.
Specific examples of the monovalent hydrocarbon group include the groups exemplified as the monovalent hydrocarbon group having no aliphatic unsaturated bond of R and the monovalent hydrocarbon group having an aliphatic unsaturated bond of R ¹ described above and Although the same thing is mentioned, a methyl group, a phenyl group, and a vinyl group are especially preferable.
Examples of the alkyl group and alkenyl group for R ³ include the same groups as those exemplified for R and R ¹ above, and examples of the alkoxyalkyl group include methoxyethyl and methoxypropyl groups, and the like, and an acyl group As, for example, acetyl, octanoyl and the like can be mentioned.
Among these, R ³ is preferably an alkyl group, more preferably a methyl group or an ethyl group.
Although said n is an integer of 2-100, Preferably it is an integer of 5-80.
Although said c is an integer of 1-3, Preferably it is 3.

0.005-10 Pa.s is preferable and, as for the viscosity at 25 degrees C of (C) component, 0.005-1 Pa.s is more preferable. If the viscosity is in this range, oil bleeding from the composition does not easily occur, the possibility that the adhesive strength declines with time is reduced, and a composition having excellent fluidity is easily obtained.
Although the following compounds are mentioned as a specific example of the organopolysiloxane represented by Formula (2), It is not limited to these. The component (C) may be used alone or in combination of two or more.

  The compounding amount of the component (C) is not particularly limited, but preferably 1 to 200 parts by mass, more preferably 100 parts by mass of the component (A) from the viewpoint of viscosity and physical properties after curing. It is 10 to 180 parts by mass.

(4) Component (D) The component (D) is a thermally conductive filler, has a role of imparting thermal conductivity to the composition, and any conventionally known thermally conductive filler can be used.
Specific examples thereof include aluminum powder, copper powder, silver powder, nickel powder, gold powder, alumina powder, zinc oxide powder, magnesium oxide powder, aluminum nitride powder, boron nitride powder, silicon nitride powder, diamond powder, carbon powder, Indium, gallium, etc. may be mentioned, and these may be used alone or in combination of two or more.
The average particle size of the thermally conductive filler is not particularly limited, but is preferably 0.1 to 100 μm, and more preferably 0.5 to 90 μm. Within such a range, aggregation of the particles is less likely to occur, and the flowability of the particles themselves is excellent, so that a composition having excellent flowability is easily obtained. The shape of the filler is arbitrary and may be irregular or spherical. The average particle diameter shall be measured as the volume-based median diameter in the particle size distribution measurement by laser diffraction method (D _50).
The heat conductive filler used in the present invention is preferably one having a thermal conductivity of 10 W / m · K or more, in consideration of providing a sufficient thermal conductivity to the composition.

  Although the compounding quantity of (D) component is not specifically limited, It is preferably 400 parts with respect to 100 mass parts of (A) components from a viewpoint of the flowability of a composition, and the thermal conductivity of the hardened | cured material obtained. The amount is about 4,000 parts by mass, more preferably 500 to 3,500 parts by mass.

(5) Component (E) The molecular structure of the organohydrogensiloxane of component (E) may be linear, branched or network.
Also, the viscosity at 25 ° C., but are not limited to, preferably ^{1~10,000mm 2 / s, 1~1,000mm 2 /} s is more preferable. In addition, you may use several (E) components from which a viscosity differs.
Examples of the organic group other than a hydrogen atom bonded to the silicon atom of component (E) include monovalent hydrocarbon groups having 1 to 10 carbon atoms excluding alkenyl groups, and specific examples thereof include methyl, ethyl, propyl, Alkyl groups such as butyl group; aryl groups such as phenyl and tolyl groups; aralkyl groups such as phenylethyl and phenylpropyl groups; halogenated alkyl groups such as γ-chloropropyl and 3,3,3-trifluoropropyl groups It can be mentioned.

  Further, as component (E), a cyclic organohydrogensiloxane represented by the following general formula (3) may be used. This compound has a role to crosslink with the (A) component and the (B) component and a role to impart adhesiveness.

（式（３）中、Ｒ⁴は、互いに独立して炭素数１〜６のアルキル基を表し、Ｒ⁵は、互いに独立して、水素原子、それぞれ炭素原子もしくは炭素原子と酸素原子を介して珪素原子に結合しているエポキシ基、アクリロイル基、メタクリロイル基もしくはトリアルコキシシリル基、エーテル含有一価有機基、またはフェニル基含有一価有機基を表すが、Ｒ⁵で示される基のうち３つ以上は水素原子である。ｍは、２〜１０の正の整数である。）

(In the formula (3), R ⁴ independently represents an alkyl group having 1 to 6 carbon atoms, and R ⁵ independently of each other is a hydrogen atom, respectively via a carbon atom or a carbon atom and an oxygen atom An epoxy group bonded to a silicon atom, an acryloyl group, a methacryloyl group or a trialkoxysilyl group, an ether-containing monovalent organic group, or a phenyl group-containing monovalent organic group is represented, but three of the groups represented by R ⁵ The above is a hydrogen atom, and m is a positive integer of 2 to 10.)

Examples of the alkyl group having 1 to 6 carbon atoms of R ⁴ include methyl, ethyl, n-propyl, n-butyl, n-pentyl and n-hexyl groups. Among them, in view of easiness of synthesis and cost, it is preferable that 90 mol% or more is a methyl group.
As described above, three or more of the groups represented by R ⁵ are hydrogen atoms, but when three or more are not hydrogen atoms, react with an alkenyl group such as component (A) to form a crosslinked structure Can not
Moreover, as a specific example of groups other than a hydrogen atom in R ⁵ , epoxy group-containing compounds such as 3-glycidoxypropyl, 3-glycidoxypropylmethyl, 3-glycidoxyethyl, 3,4-epoxycyclohexylethyl and the like Organic groups; (meth) acryloyl group-containing organic groups such as methacryloxypropyl, methacryloxypropylmethyl, methacryloxyethyl, acryloxypropyl, acryloxypropyl methyl, acryloxyethyl groups; methoxysilylpropyl, methoxysilylpropylmethyl, methoxy Trialkoxysilyl group-containing organic groups such as silylethyl, triethoxysilylpropyl, triethoxysilylpropylmethyl and triethoxysilylethyl groups; oxyalkyl groups, alkyloxyalkyl groups, perfluorooxyalkyl groups, perfluoro groups Ether-containing organic group such as an alkyloxyalkyl; phenyl, diphenyl, phenyl-containing organic group such as bisphenol A residues.
Although m is a positive integer of 2 to 10, it is preferably a positive integer of 2 to 6, more preferably a positive integer of 2 to 4, and still more preferably 2.
Among the component (E) represented by the formula (3), organohydrogensiloxanes of the following formula (4) are particularly preferable.

（式（４）中、Ｒ⁴およびＲ⁵は上記と同じ意味を表す。）

(In formula (4), R ⁴ and R ⁵ have the same meaning as described above.)

  Although the thing shown by a following formula is mentioned as a specific example of the organohydrogen siloxane shown by Formula (4), It is not limited to these. The component (E) may be used alone or in combination of two or more.

  Although the compounding quantity of (E) component is not specifically limited, When the alkenyl group of (A) component and (B) component and (C) component contain an alkenyl group, those alkenyl groups were also included. Ratio of the total number of Si-H groups of component (E) to the total number of alkenyl groups, ie, [total number of Si-H groups of component (E)] / [alkenyl groups of components (A) to (C)] The total amount of [] is preferably in the range of 0.6 to 1.5, and more preferably in the range of 0.7 to 1.4. If the ratio of the total number of Si-H groups to the total number of alkenyl groups is in this range, the hardness of the cured product may be insufficient or too high due to the network having a suitable network structure. Prevention can be expected.

(6) (F) Component The (F) component is a platinum group metal catalyst.
The platinum group metal catalyst comprises an alkenyl group of components (A) and (B) (including an alkenyl group if component (C) contains an alkenyl group) and a Si-H group of component (E) Any known catalyst may be used as long as it accelerates the addition reaction, and among them, catalysts selected from platinum and platinum compounds are preferred.
Specific examples of the catalyst include platinum (including platinum black), platinum group metals such as rhodium and palladium, H ₂ PtCl ₄ .nH ₂ O, H ₂ PtCl ₆ .H ₂ O, NaHPtCl ₆ .nH ₂ O , KHPtCl ₆ · nH ₂ O, Na ₂ PtCl ₆ · nH ₂ O, K ₂ PtCl ₄ · nH ₂ O, PtCl ₄ · nH ₂ O, PtCl ₂ , Na ₂ HPtCl ₄ · nH ₂ O (wherein the formula is n is an integer of 0 to 6, preferably 0 or 6.) platinum chloride such as chloroplatinic acid, chloroplatinic acid salt, alcohol-modified chloroplatinic acid, chloroplatinic acid-olefin complex, platinum black , Platinum group metals such as palladium supported on a carrier such as alumina, silica, carbon, etc., rhodium-olefin complex, chlorotris (triphenylphosphine) rhodium (Wilkinson catalyst), platinum chloride, white chloride Examples thereof include complexes of auric acid or chloroplatinic acid salt and a vinyl group-containing siloxane, and these may be used alone or in combination of two or more.

The compounding amount of the component (F) is an effective amount as a catalyst, and may be an amount capable of advancing the reaction between the components (A) and (B) and the component (E), depending on the desired curing rate. It may be adjusted appropriately.
From the viewpoint of catalytic action and economics, in particular, the amount of 0.1 to 7,000 ppm based on the mass converted to platinum group metal atoms relative to the mass of the component (A) is preferable, and 1 to 6,000 ppm Is more preferred.

Known additives may be added to the thermally conductive silicone potting composition of the present invention as optional components other than the above components (A) to (F) within the range that does not impair the object of the present invention.
For example, a reaction control agent may be blended in order to suppress the curing reaction of the composition at room temperature and extend shelf life and pot life.
Any reaction control agent may be used as long as it can suppress the catalytic activity of the component (F), and conventionally known reaction control agents can be used.
Specific examples thereof include acetylene alcohol compounds such as 1-ethynyl-1-cyclohexanol and 3-butyn-1-ol, various nitrogen compounds, organic phosphorus compounds, oxime compounds, organic chloro compounds and the like. The species may be used alone, or two or more species may be used in combination. Among these, acetylene alcohol compounds having no corrosiveness to metals are preferable.

The compounding amount of the reaction control agent is preferably 0.01 to 5 parts by mass with respect to 100 parts by mass of the component (A) in consideration of the shelf life and pot life of the composition and the curability of the composition. And more preferably 0.05 to 1 part by mass.
The reaction control agent may be used after diluting with an organic solvent such as toluene, xylene, isopropyl alcohol or the like in order to improve the dispersibility in the silicone resin.

  In addition, reinforcing agents such as hindered phenolic antioxidants, calcium carbonate and the like, non-reinforcing fillers such as calcium carbonate, and pigments such as pigments and dyes can also be added.

The method of producing the thermally conductive silicone potting composition of the present invention is not particularly limited, and may be in accordance with conventionally known methods, for example, components (A) to (F) and, if necessary, other components. The components may be mixed, and the form thereof may be one-pack type or two-pack type.
In addition, if it is 1 liquid type, it can be stored for a long period by refrigerated or frozen, and if it is 2 liquid type, it can be stored at normal temperature for a long time.

  For the composition of the one-pack type, for example, the components (A), (B), (C), and (D) are charged into a gate mixer (product name: Planetary mixer manufactured by Inoue Seisakusho Co., Ltd. The mixture is heated and mixed at 150 ° C. for 1 hour and then cooled. Thereafter, the (F) component and the reaction control agent are added and mixed for 30 minutes at room temperature. Further, it can be obtained by adding the component (E) and mixing for 30 minutes at room temperature to be uniform.

  On the other hand, the composition of the two-pack type can be composed of any combination as long as the combination of the (A) component, the (B) component, the (E) component and the (F) component does not coexist. For example, components (A), (B), (C), and (D) are charged into a gate mixer, mixed by heating at 150 ° C. for 1 hour, and then cooled. Thereafter, the component (F) is added and mixed at room temperature for 30 minutes to obtain a composition obtained as material A. Next, the component (A), the component (B), the component (C), and the component (D) are charged into a gate mixer, mixed by heating at 150 ° C. for 1 hour, and then cooled. Thereafter, a reaction control agent is added and mixed for 30 minutes at room temperature, and the component (E) is further added, and a composition obtained by mixing for 30 minutes at room temperature is used as a material B. Thereby, the composition of 2 liquid type of A material and B material can be obtained.

The heat conductive silicone potting composition preferably has a viscosity at 25 ° C. of 1 to 100 Pa · s, more preferably 5 to 50 Pa · s. Within such a range, settling of the thermally conductive filler is suppressed, and a composition having more excellent fluidity is obtained. The viscosity is measured with a B-type rotational viscometer.
The heat conductive silicone potting composition preferably has a flowability of 100 mm or more at 23 ° C. whose measurement method will be described in detail in the following examples. Where a component having a microstructure such as a transformer is attached to the cooler, it is preferably 120 mm or more when pouring the silicone potting composition. The upper limit of flowability is preferably as high as possible.

The curing conditions of the thermally conductive silicone potting composition of the present invention are not particularly limited, and may be the same as conventionally known silicone gels.
The heat conductive silicone potting composition may be cured by heat from the heat generating component after being poured in, or may be actively heat cured. The heat curing conditions are preferably 60 to 180 ° C., more preferably 80 to 150 ° C., preferably 0.1 to 3 hours, more preferably 0.5 to 2 hours.

When the heat conductive silicone potting composition of the present invention is used as a filler in a case containing a minute heat generating component, it has high fluidity and flows into every minute structure of the fine structure, and after curing, the heat generating component etc. Since it can be adhered well to have high thermal conductivity, the heat of the heat-generating component can be efficiently transmitted to the case, and the reliability thereof can be dramatically improved.
In addition, since the decrease in elongation at cutting is small even after thermal aging, it is possible to expect to follow the heat-generating component and to cool efficiently.

Hereinafter, the present invention will be more specifically described by way of examples and comparative examples, but the present invention is not limited to the following examples.
Each component used in the Example and the comparative example is shown below.

(A) Component A-1: Both ends capped with dimethylvinylsilyl group, dimethylpolysiloxane having a viscosity of 0.06 Pa · s at 25 ° C. A-2: Both ends capped with dimethylvinylsilyl group C., dimethylpolysiloxane having a viscosity of 0.4 Pa · s at 25 ° C .: A-3: dimethylpolysiloxane blocked at both ends with a dimethylvinylsilyl group and having a viscosity of 0.6 Pa · s at 25 ° C.

Component (B) Component B-1: an organopolysiloxane represented by the following formula [(CH ₃ O) ₃ Si-CH ₂ CH ₂ -Si (CH ₃ ) ₂ O _1/2 ] _1.2 [(CH ₃ ) ₂ SiO] ₁₄₀ [CH = CH ₂ (CH ₃ ) ₂ SiO _1/2 ] _0.8
B-2: an organopolysiloxane represented by the following formula

(C) Component C-1: an organopolysiloxane represented by the following formula

(D) Component D-1: Alumina powder having an average particle diameter of 80 μm D-2: Alumina powder having an average particle diameter of 40 μm D-3: Alumina powder having an average particle diameter of 10 μm D-4: Average particle diameter 1. 0 μm alumina powder

(E) Component E-1: Organohydrogensiloxane represented by the following formula

E-2: Organohydrogensiloxane represented by the following formula

E-3: Organohydrogensiloxane represented by the following formula

E-4: organohydrogensiloxane represented by the following formula

(F) Component F-1: Dimethylpolysiloxane solution of platinum-divinyl tetramethyldisiloxane complex (dissolved in the same dimethylpolysiloxane as A-3 above, containing 1% as a platinum atom)

(G) component (other components)
G-1: 1-ethynyl-1-cyclohexanol G-2: triallyl isocyanurate G-3: organopoly having a viscosity of 1 Pa · s at 25 ° C. blocked at both ends with a trimethoxysilyl group Siloxane G-4: iron oxide (Fe ₃ O ₄ ) powder G-5: acetylene black (manufactured by Denka Co., Ltd .: HS-100)
G-6: cerium oxide (Ce ₂ O ₃ ) powder

[Examples 1 and 2, Comparative Examples 1 to 4]
The components (A) to (G) were mixed as follows to obtain a silicone potting composition.
(A) component, (B) component, (C) component, (D) component, (D) component, G-3 in the amount shown in Table 1 in a 5 L gate mixer (Inoue Mfg. Co., Ltd. product name; 5 L planetary mixer) In addition, the mixture was heated and mixed at 150 ° C. for 2 hours. After cooling the mixture, the (F) component was added and mixed at room temperature for 30 minutes to be uniform. Next, reaction control agents G-1 and G-2 were added and mixed at room temperature for 30 minutes so as to be uniform. Finally, component (E) and G-4 to G-6 were added and mixed at room temperature for 30 minutes.
The following physical properties of the obtained composition were measured. The results are shown in 2.

[1] Thermal Conductivity The thermal conductivity of the cured product of the thermally conductive silicone potting composition at 25 ° C. was measured using a hot disk method thermal physical property measuring apparatus TPA-501 manufactured by Kyoto Electronics Industry Co., Ltd.
[2] Viscosity The viscosity at 25 ° C. of the thermally conductive silicone potting composition was measured at 20 rpm using a B-type viscometer.
[3] Hardness The thermally conductive silicone potting composition was press-cured at 120 ° C. for 10 minutes at a thickness of 2.0 mm and further heated in an oven at 120 ° C. for 50 minutes. Three sheets of the obtained silicone sheet were stacked, and the hardness was measured by a type A durometer specified in JIS K 6253.
[4] Elongation at break The thermally conductive silicone potting composition was press-cured at 120 ° C. for 10 minutes at a thickness of 2.0 mm and further heated in an oven at 120 ° C. for 50 minutes. The tensile strength and elongation at break of the obtained silicone sheet were measured according to JIS K 6251.
[5] Flowability 0.60 cc of the thermally conductive silicone potting composition was weighed and dropped onto an aluminum plate (JIS H 4000, thickness 0.5 × width 25 × length 400 mm). Immediately after dripping, the aluminum plate was inclined at 28 ° and left to stand under an atmosphere of 23 ° C. (± 2 ° C.) for 1 hour. The length of the heat conductive silicone potting composition after standing was measured from the end to the end which flowed.
[6] Thermal Aging The thermally conductive silicone potting composition was press cured at a thickness of 2.0 mm at 120 ° C. for 10 minutes and then heated in an oven at 120 ° C. for 50 minutes. The obtained silicone sheet was left in a thermostat at 170 ° C. for 2000 hours to carry out heat aging.

  As shown in Table 2, the thermally conductive silicone potting composition of the present invention has good fluidity before curing and good physical properties after curing, and also has a reduction in elongation at break after heat aging. I understand that there are few.

Claims (6)

(A) an organopolysiloxane having a viscosity of 0.01 to 100 Pa · s at 25 ° C. and having at least two alkenyl groups in one molecule;
(B) an organopolysiloxane represented by the following average formula (1),

(Wherein, R independently represents a monovalent hydrocarbon group having no aliphatic unsaturated bond, R ¹ represents a monovalent hydrocarbon group having an aliphatic unsaturated bond, and z is oxygen Represents an atom or a divalent hydrocarbon group, a is 0.1 to 1.9, and b is an integer of 100 or more.)
(C) an organopolysiloxane represented by the following general formula (2),

(Wherein R ² independently represents an unsubstituted or substituted monovalent hydrocarbon group, R ³ independently represents an alkyl group, an alkoxyalkyl group, an alkenyl group or an acyl group, n Is an integer of 2 to 100, and c is an integer of 1 to 3.)
(D) thermally conductive filler,
A thermally conductive silicone potting composition comprising (E) an organohydrogensiloxane and (F) a hydrosilylation reaction catalyst.   The thermally conductive silicone potting composition according to claim 1, wherein z is a divalent hydrocarbon group.   The heat conductive silicone potting composition according to claim 1 or 2, wherein R is a methyl group.   The thermally conductive silicone potting composition according to any one of claims 1 to 3, wherein b is 100 to 300.   The thermally conductive silicone potting composition according to any one of claims 1 to 4, wherein a is 0.3 to 1.7.   A cured product obtained by curing the thermally conductive silicone potting composition according to any one of claims 1 to 5.