JP2016044213A - Heat-conductive silicone composition and heat-conductive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-conductive silicone composition and a heat-conductive sheet which exhibit excellent heat radiation effect.SOLUTION: The heat-conductive silicone composition is provided that comprises a liquid silicone (A), a heat-conductive filler (B), and a hydrophobic spherical silica fine particle (C). The hydrophobic spherical silica fine particle, the constituent (C), is obtained by introducing a RSiOunit (Ris a substituted or unsubstituted 1-20C monovalent hydrocarbon group.) to the surface of a hydrophilic spherical fine particle substantially composed of a SiOunit obtained by hydrolyzing a tetra-functional silane compound, a partially hydrolyzed condensation product thereof, or a mixture thereof and subjecting the resultant hydrolyzed substance to condensation, and further introducing a RSiOunit (each Ris same or different, substituted or unsubstituted 1-6C monovalent hydrocarbon.) to the surface of the hydrophilic spherical fine particle, the hydrophobic spherical silica fine particle has a particle size of 0.005-1 μm, has a value of a particle size distribution D/Dof not greater than 3, and has an average circularity of 0.8-1.SELECTED DRAWING: None

Description

  The present invention relates to a heat conductive silicone composition and a heat conductive sheet.

Since many electronic components generate heat during use, it is necessary to remove the heat from the electronic components in order for the electronic components to function properly. In particular, an integrated circuit element such as a CPU used in a personal computer has an increased amount of heat generated due to an increase in operating frequency, and countermeasures against heat are an important issue.
Many methods have been proposed as means for removing this heat. In particular, for electronic components that generate a large amount of heat, a method for releasing heat by interposing a heat conductive grease or a heat conductive material such as a heat conductive sheet between the electronic component and a member such as a heat sink has been proposed (Japanese Unexamined Patent Application Publication No. Sho-sho). No. 56-28264: Patent Document 1, Japanese Patent Laid-Open No. 61-157487: Patent Document 2).
Further, as this heat conductive material, there is known a heat dissipating grease based on silicone oil and blended with zinc oxide or alumina powder (Japanese Patent Publication No. 52-33272: Patent Document 3, Japanese Patent Publication No. 59-52195). Publication: see Patent Document 4).

  Furthermore, in order to improve thermal conductivity, as the one using aluminum nitride powder, the above-mentioned Japanese Patent Application Laid-Open No. 56-28264 (Patent Document 1) includes a liquid organosilicone carrier and silica fiber, and dendritic zinc oxide, A thixotropic heat conductive material comprising at least one selected from flaky aluminum nitride and flaky boron nitride is disclosed. Japanese Patent Laid-Open No. 2-153955 (Patent Document 5) discloses a silicone grease composition prepared by blending a specific organopolysiloxane with a spherical hexagonal aluminum nitride powder having a certain particle size range. Japanese Laid-Open Patent Publication No. 10-110179 (Patent Document 7) discloses a thermally conductive silicone grease in which an aluminum nitride powder having a small particle diameter and an aluminum nitride powder having a coarse particle diameter are combined. Japanese Patent Application Laid-Open No. 2000-63872 (Patent Document 8) discloses a heat conductive grease composition using an aluminum nitride powder surface-treated with an organosilane. It is disclosed.

Aluminum nitride has a thermal conductivity of 70 to 270 W / mK, and diamond having a thermal conductivity of 900 to 2,000 W / mK is a material having a higher thermal conductivity. Japanese Patent Laid-Open No. 2002-30217 (Patent Document 9) discloses a thermally conductive silicone composition using diamond, zinc oxide, and a dispersant as a silicone resin.
Japanese Patent Application Laid-Open No. 2000-63873 (Patent Document 10) and Japanese Patent Application Laid-Open No. 2008-2222776 (Patent Document 11) disclose a thermally conductive grease composition in which metal aluminum powder is mixed with a base oil such as silicone oil. It is disclosed.
However, any heat conductive material or heat conductive grease has become insufficient for the amount of heat generated by integrated circuit elements such as recent CPUs.

JP-A-56-28264 JP-A 61-157487 Japanese Patent Publication No.52-33272 Japanese Patent Publication No.59-52195 Japanese Patent Laid-Open No. 2-153955 Japanese Patent Laid-Open No. 3-14873 JP-A-10-110179 JP 2000-63872 A JP 2002-30217 A JP 2000-63873 A JP 2008-222776 A

  This invention is made | formed in view of the said situation, and it aims at providing the heat conductive silicone composition and heat conductive sheet which show a favorable heat dissipation effect.

  As a result of intensive studies to achieve the above object, the inventors of the present invention dramatically reduce the viscosity of the composition by containing a specific amount of specific hydrophobic silica fine particles in the thermally conductive silicone composition. I found. Therefore, since the filling rate of the heat conductive filler can be increased, it has been found that the heat conductivity is improved as a result, and the present invention has been made.

Accordingly, the present invention provides a thermally conductive silicone composition comprising (A) liquid silicone, (B) thermally conductive filler, and (C) hydrophobic spherical silica fine particles, wherein the hydrophobic sphere of component (C) silica particles, tetrafunctional silane compound, its partial hydrolysis condensation product, or the surface of the hydrophilic spherical silica microparticles composed essentially of SiO ₂ units obtained by mixtures thereof to hydrolysis and condensation R ¹ SiO _3/2 units (R ¹ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms) are introduced, and R ² ₃ SiO _1/2 units (each R ² is the same or different). Is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms), and the particle size distribution is in the range of 0.005 to 1 μm, and the value of the particle size distribution D ₉₀ / D ₁₀ Is 3 or less and the average circularity is 0.8 to 1 Provided is a thermally conductive silicone composition characterized by being aqueous spherical silica particles.

In this case, the hydrophobic spherical silica fine particles of the component (C) are
(C1) General formula (I):
Si (OR ³ ) ₄ (I)
(In the formula, each R ³ is the same or different monovalent hydrocarbon group having 1 to 6 carbon atoms.)
By substantially hydrolyzing and condensing a tetrafunctional silane compound represented by the formula, a partial hydrolysis product thereof, or a mixture thereof in a mixture of a hydrophilic organic solvent and water in the presence of a basic substance, SiO 2 Obtain a mixed solvent dispersion of hydrophilic spherical silica fine particles consisting of ₂ units,
(C2) In the mixed solvent dispersion of the obtained hydrophilic spherical silica fine particles, the general formula (II):
R ¹ Si (OR ⁴ ) ₃ (II)
(In the formula, R ¹ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, and each R ⁴ is the same or different monovalent hydrocarbon group having 1 to 6 carbon atoms.)
The surface of the hydrophilic spherical silica fine particles is treated with R ¹ SiO on the surface of the hydrophilic spherical silica fine particles by adding a trifunctional silane compound represented by the formula, a partial hydrolysis product thereof, or a mixture thereof. _3/2 units (R ¹ is as described above) were introduced to obtain a mixed solvent dispersion of the first hydrophobic spherical silica fine particles,
(C3) In the mixed solvent dispersion of the obtained first hydrophobic spherical silica fine particles, the general formula (III):
R ² ₃ SiNHSiR ² ₃ (III)
(In the formula, each R ² is the same or different substituted or unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms.)
A silazane compound represented by the general formula (IV):
R ² ₃ SiX (IV)
(In the formula, R ² is as defined in the general formula (III), and X is an OH group or a hydrolyzable group.)
Is added to the surface of the first hydrophobic spherical silica fine particles, and the surface of the first hydrophobic spherical silica fine particles is treated with R ^2. It is preferable to obtain the second hydrophobic silica fine particles by introducing ₃ SiO _1/2 units (R ² is as defined in the general formula (III)).

（式中、Ｒ⁸は互いに独立に、炭素原子数１〜１８の、飽和又は不飽和の、非置換又は置換の一価炭化水素基であり、ｍは該オルガノポリシロキサンの２５℃での動粘度を１０〜５００，０００ｍｍ²／ｓとする数である。）

（式中、Ｒ⁹は炭素原子数８〜１８の置換又は非置換のアルキル基であり、Ｒ¹⁰は互いに独立に、炭素原子数１〜１８の、飽和又は不飽和の、非置換又は置換の一価炭化水素基である。ｍ¹は１〜２００、ｍ²は１〜１００の整数である。） Moreover, the liquid silicone of the said component (A) is the following average composition formula (V).
R ⁵ _a SiO _{(4-a) / 2} (V)
(In the formula, R ⁵ independently of each other is a saturated or unsaturated, unsubstituted or substituted monovalent hydrocarbon group having 1 to 18 carbon atoms, and 1.8 ≦ a ≦ 2.2. )
It is preferable that the composition contains an organopolysiloxane having a kinematic viscosity at 25 ° C. of 10 to 500,000 mm ² / s. In particular, the organopolysiloxane represented by the average composition formula (V) is represented by the following formula: It is preferable that it is a linear organopolysiloxane represented by (i) and / or the following formula (ii).

(Wherein R ⁸ independently of each other is a saturated or unsaturated, unsubstituted or substituted monovalent hydrocarbon group having 1 to 18 carbon atoms, and m represents the behavior of the organopolysiloxane at 25 ° C. (It is a number that makes the viscosity 10 to 500,000 mm ² / s.)

Wherein R ⁹ is a substituted or unsubstituted alkyl group having 8 to 18 carbon atoms, and R ¹⁰ is independently of each other a saturated or unsaturated, unsubstituted or substituted group having 1 to 18 carbon atoms. (It is a monovalent hydrocarbon group. M ¹ is an integer of ¹ to 200 and m ² is an integer of 1 to 100.)

  Furthermore, as the organopolysiloxane represented by the above average composition formula (V), one containing an organopolysiloxane having at least two alkenyl groups in one molecule can be used. The composition may further be an addition reaction curable composition containing an organohydrogenpolysiloxane having an average of 2 or more silicon-bonded hydrogen atoms in one molecule and a platinum-based catalyst. As the organopolysiloxane represented by the formula (V), those having molecular chain ends blocked with hydroxyl groups or alkoxy groups can be used. In this case, at least three thermally conductive silicone compositions are contained in one molecule. It is possible to obtain a condensation reaction curable composition containing a silane or siloxane having a silicon atom-bonded hydrolyzable group. .

（式中、Ｒ⁶は炭素原子数１〜６のアルキル基であり、Ｒ⁷は互いに独立に、炭素原子数１〜１８の、飽和又は不飽和の、非置換又は置換の一価炭化水素基であり、ｂは５〜１２０の整数である。）
で表される加水分解性基含有オルガノポリシロキサンを、成分（Ａ）の合計質量に対して１０〜９０質量％の量で更に含むことが好ましい。 In addition, the component (A) is represented by the following general formula (VI)

(Wherein R ⁶ is an alkyl group having 1 to 6 carbon atoms, and R ⁷ is independently of each other a saturated or unsaturated, unsubstituted or substituted monovalent hydrocarbon group having 1 to 18 carbon atoms. And b is an integer of 5 to 120.)
It is preferable to further contain the hydrolysable group-containing organopolysiloxane represented by the formula (A) in an amount of 10 to 90% by mass relative to the total mass of the component (A).

  In addition, the compounding quantity of a component (B) is 500-3,000 mass parts with respect to 100 mass parts of components (A), and the compounding quantity of a component (C) is 0.01-10 with respect to a component (B). It is preferable that it is mass%.

  The present invention further provides a heat conductive sheet obtained by molding the above heat conductive silicone composition.

  The heat conductive silicone composition of this invention exhibits a favorable heat dissipation effect.

The thermally conductive silicone composition of the present invention is
(A) liquid silicone,
(B) a thermally conductive filler,
(C) Contains hydrophobic spherical silica fine particles. Hereinafter, these components will be described in detail.

Ingredient (A)
The liquid silicone of component (A) is an organopolysiloxane having a kinematic viscosity at 25 ° C. of 10 to 500,000 mm ² / s, preferably 30 to 10,000 mm ² / s. If the kinematic viscosity of the organopolysiloxane is lower than the lower limit, oil bleed tends to occur when grease is used. Moreover, when larger than the said upper limit, there exists a possibility that the extensibility of a silicone composition may become scarce. In the present invention, the kinematic viscosity of the organopolysiloxane is a value of 25 ° C. measured with an Ostwald viscometer.

  In the present invention, the organopolysiloxane has only to have the above kinematic viscosity, and a conventionally known organopolysiloxane can be used. The molecular structure of the organopolysiloxane is not particularly limited, and may be any of linear, branched, and cyclic. In particular, the main chain is preferably composed of a repeating diorganosiloxane unit and has a linear structure in which both ends of the molecular chain are blocked with a triorganosiloxy group. The organopolysiloxane may be used alone or in combination of two or more.

The organopolysiloxane can be represented by the following average composition formula (V).
R ⁵ _a SiO _{(4-a) / 2} (V)
In the above formula (V), R ^{5 s} , independently of each other, are saturated or unsaturated, unsubstituted or substituted monovalent hydrocarbon groups having 1 to 18 carbon atoms, preferably 1 to 14 carbon atoms. Examples of the monovalent hydrocarbon group include methyl groups, ethyl groups, propyl groups, hexyl groups, octyl groups, decyl groups, dodecyl groups, tetradecyl groups, hexadecyl groups, octadecyl groups and other alkyl groups, cyclopentyl groups, cyclohexyl groups, and the like. Cycloalkyl groups such as groups, alkenyl groups such as vinyl groups and allyl groups, aryl groups such as phenyl groups and tolyl groups, aralkyl groups such as 2-phenylethyl groups and 2-methyl-2-phenylethyl groups, Or, a part or all of hydrogen atoms of these groups are substituted with halogen atoms such as fluorine, bromine, chlorine, cyano groups, etc., for example, 3,3,3-trifluoropropyl group, 2- (perfluoro Butyl) ethyl group, 2- (perfluorooctyl) ethyl group, p-chlorophenyl group and the like.

  In the above formula (V), a is a number in the range of 1.8 to 2.2, particularly in the range of 1.9 to 2.1. When a is in the above range, the resulting silicone composition can have a good viscosity required as a grease.

上記式において、Ｒ⁸は、互いに独立に、炭素原子数１〜１８、好ましくは１〜１４の、飽和又は不飽和の、非置換又は置換の一価炭化水素基である。該一価炭化水素基としては、上述した基が挙げられる。中でも、両末端のＲ⁸は全てメチル基であることが好ましい。ｍは該オルガノポリシロキサンの２５℃での動粘度が１０〜５００，０００ｍｍ²／ｓ、好ましくは３０〜１０，０００ｍｍ²／ｓ、更に好ましくは１００〜８，０００ｍｍ²／ｓとなる数である。また、好ましくは、主鎖のケイ素原子に結合しているＲ⁸のうち少なくとも１つは、炭素原子数８〜１８、好ましくは炭素原子数１０〜１４のアルキル基であるのがよい。該アルキル基は分岐を有していてもよい。 The organopolysiloxane represented by the average composition formula (V) is preferably a linear organopolysiloxane represented by the following formula (i).

In the above formula, R ⁸ is independently of each other a saturated or unsaturated, unsubstituted or substituted monovalent hydrocarbon group having 1 to 18 carbon atoms, preferably 1 to 14 carbon atoms. Examples of the monovalent hydrocarbon group include the groups described above. Especially, it is preferable that all R < ⁸ > of both ends is a methyl group. m is a number at which the kinematic viscosity of the organopolysiloxane at 25 ° C. is 10 to 500,000 mm ² / s, preferably 30 to 10,000 mm ² / s, more preferably 100 to 8,000 mm ² / s. . Preferably, at least one of R ⁸ bonded to the silicon atom of the main chain is an alkyl group having 8 to 18 carbon atoms, preferably 10 to 14 carbon atoms. The alkyl group may have a branch.

上記式（ｉｉ）において、Ｒ⁹は炭素原子数８〜１８、好ましくは炭素原子数１０〜１４の、置換又は非置換のアルキル基である。該アルキル基は分岐を有していてもよい。Ｒ¹⁰は炭素原子数１〜１８の、飽和又は不飽和の、非置換又は置換の一価炭化水素基であり、好ましくは炭素原子数１〜７の置換又は非置換のアルキル基又は上述した一価炭化水素基のうちアルキル基以外のものである。特に好ましくは、Ｒ¹⁰はメチル基である。ｍ¹は１〜２００、好ましくは５〜１００、更に好ましくは５〜５０の整数であり、ｍ²は１〜１００、好ましくは５〜５０の整数である。 Particularly preferred is a linear organopolysiloxane represented by the following formula (ii).

In the above formula (ii), R ⁹ is a substituted or unsubstituted alkyl group having 8 to 18 carbon atoms, preferably 10 to 14 carbon atoms. The alkyl group may have a branch. R ¹⁰ is a saturated or unsaturated, unsubstituted or substituted monovalent hydrocarbon group having 1 to 18 carbon atoms, preferably a substituted or unsubstituted alkyl group having 1 to 7 carbon atoms or the above-mentioned one. Among valent hydrocarbon groups, those other than alkyl groups. Particularly preferably, R ¹⁰ is a methyl group. m ¹ is an integer of ¹ to 200, preferably 5 to 100, more preferably 5 to 50, and m ² is an integer of 1 to 100, preferably 5 to 50.

（式（ＶＩ）中、Ｒ⁶は炭素原子数１〜６のアルキル基であり、Ｒ⁷は、互いに独立に、炭素原子数１〜１８の、飽和又は不飽和の、非置換又は置換の一価炭化水素基であり、ｂは５〜１２０の整数である。） In addition, the component (A) may contain an organopolysiloxane having a hydrolyzable group represented by the following general formula (VI) in combination with the organopolysiloxane represented by the average composition formula (V). Good. The content of the hydrolyzable organopolysiloxane (VI) in the component (A) is preferably 10 to 90% by mass, more preferably 20 to 80% by mass with respect to the total mass of the component (A). More preferably, the amount is 30 to 70% by mass.

(In the formula (VI), R ⁶ is an alkyl group having 1 to 6 carbon atoms, and R ⁷ is independently of one another saturated or unsaturated, unsubstituted or substituted, having 1 to 18 carbon atoms. And b is an integer of 5 to 120.)

  The organopolysiloxane represented by the above formula (VI) assists in highly filling the powder [component (C)] in the silicone composition. Furthermore, when the silicone composition contains the organopolysiloxane, the surface of the powder is covered with the organopolysiloxane, and the powder is less likely to aggregate. Since this effect lasts even at high temperatures, the heat resistance of the silicone composition is improved. Further, the surface of the powder can be hydrophobized with the organopolysiloxane.

In the formula (VI), R ⁶ is an alkyl group having 1 to 6 carbon atoms. Examples thereof include alkyl groups having 1 to 6 carbon atoms such as a methyl group, an ethyl group, and a propyl group, and a methyl group and an ethyl group are particularly preferable. R ⁷ independently of one another is a saturated or unsaturated, unsubstituted or substituted monovalent hydrocarbon group having 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms. Examples of the monovalent hydrocarbon group include alkyl groups such as methyl group, ethyl group, propyl group, hexyl group, octyl group, decyl group, dodecyl group, tetradecyl group, hexadecyl group, and octadecyl group, cyclopentyl group, and the like. Aralkyl groups such as cycloalkyl groups such as cyclohexyl groups, alkenyl groups such as vinyl groups and allyl groups, aryl groups such as phenyl groups and tolyl groups, 2-phenylethyl groups, and 2-methyl-2-phenylethyl groups Or a group in which some or all of the hydrogen atoms in these groups are substituted with a halogen atom such as fluorine, bromine or chlorine, a cyano group, for example, 3,3,3-trifluoropropyl group, 2- (par A fluorobutyl) ethyl group, a 2- (perfluorooctyl) ethyl group, a p-chlorophenyl group, and the like. A methyl group is particularly preferable. In said formula (VI), b is an integer of 5-120, Preferably it is an integer of 10-90.

Further, when the composition of the present invention is cured and used, a curable organopolysiloxane can be used as the component (A). For example, in the case of a composition addition reaction curable type, an organopolysiloxane having at least two alkenyl groups in one molecule can be used as the component (A). As the organopolysiloxane, a linear organopolysiloxane in which R ⁵ is selected so as to have at least two alkenyl groups in one molecule in the average composition formula (V), particularly in the above formula (i). , At least two of R ⁸ , particularly at least one of R ⁸ at both ends is an alkenyl group.

  When the composition is a condensation reaction curable type, a linear organopolysiloxane having a molecular chain terminal that is a hydroxyl group or an alkoxy group in the average composition formula (V) can be used.

Ingredient (B)
It is preferable that the heat conductive filler which is a component (B) is 10 W / mK or more in heat conductivity. If the thermal conductivity is less than 10 W / mK, the thermal conductivity itself of the thermally conductive silicone composition may be small. The upper limit of the thermal conductivity varies depending on the material used for the thermally conductive filler, but there is no particular upper limit. Examples of the thermally conductive filler 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, Examples thereof include powders and granular materials such as carbon powder, and these may be used alone or in combination.

  When powder or granular material is used as the thermally conductive filler, its shape may be indefinite, spherical, or any shape, but those having an average particle diameter of 0.1 to 100 μm may be used, preferably 0 It is 5-50 micrometers, More preferably, it is 0.5-30 micrometers. When the average particle diameter is less than 0.1 μm, the composition does not become grease-like and poor in extensibility, and when it exceeds 100 μm, the uniformity of the composition becomes poor. In addition, the average particle diameter in this case is a measured value by a method described later.

  As for the compounding quantity of the said heat conductive filler, 500-3,000 mass parts is preferable with respect to 100 mass parts of organopolysiloxane of a component (A). When the blending amount is less than 500 parts by mass, the necessary thermal conductivity cannot be obtained, and when it exceeds 3,000 parts by mass, the composition does not become a grease and the extensibility becomes poor. 800 to 2,500 parts by mass is preferable.

Ingredient (C)
The hydrophobic spherical silica fine particles which are the component (C) used in the present invention are substantially obtained by hydrolyzing and condensing a tetrafunctional silane compound, a partially hydrolyzed condensation product thereof, or a mixture thereof. R ¹ SiO _3/2 unit (R ¹ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms) is introduced on the surface of hydrophilic spherical silica fine particles composed of SiO ₂ units, and further R ² ₃ SiO _1/2 unit (each R ² is the same or different and is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms) and has a particle size of 0.005 Hydrophobic spherical silica particles having a particle size distribution D ₉₀ / D ₁₀ of 3 or less and an average circularity of 0.8 to 1 in a range of ˜1 μm.

  The hydrophobic spherical silica fine particles have a particle size of 0.005 to 1 μm, preferably 0.01 to 0.3 μm, particularly preferably 0.03 to 0.25 μm. If the particle size is smaller than 0.005 μm, the aggregation becomes violent, and if it is larger than 1 μm, the effect of reducing the viscosity of the grease composition becomes poor.

The value of D ₉₀ / D ₁₀ which is an index of the particle size distribution of the hydrophobic spherical silica fine particles is 3 or less. Here, D ₁₀ and D ₉₀ are values obtained by measuring the particle size distribution. When the particle size distribution of the powder is measured, the particle size that becomes 10% cumulative from the smaller side is called D ₁₀ , and the particle size that becomes 90% cumulative from the smaller side is called D ₉₀ . Since this D ₉₀ / D ₁₀ is 3 or less, the particle size distribution of the hydrophobic spherical silica fine particles in the present invention is sharp. Thus, it is preferable that the particles have a sharp particle size distribution from the viewpoint of reducing the viscosity of the grease composition. The D ₉₀ / D ₁₀ is more preferably 2.9 or less.

  In the present invention, the particle size distribution of the fine particles is measured by a dynamic light scattering method / laser Doppler nanotrack particle size distribution measuring apparatus (trade name: UPA-EX150, manufactured by Nikkiso Co., Ltd.), and the volume-based median diameter is determined. The particle diameter was taken. The median diameter is a particle diameter corresponding to 50% cumulative when the particle size distribution is expressed as a cumulative distribution.

  Further, the average circularity of the hydrophobic spherical silica fine particles is preferably 0.8 to 1. Here, “spherical” includes not only a true sphere but also a slightly distorted sphere. Such a “spherical” shape refers to a particle having a circularity in the range of 0.8 to 1 when evaluated by the circularity when the particles are projected two-dimensionally. Here, the circularity is (peripheral length of a circle equal to the particle area) / (peripheral length of particle). The average circularity is an average value obtained by measuring the circularity of 10 silica fine particles. This circularity can be measured by image analysis of a particle image obtained with an electron microscope or the like.

In the above, the hydrophilic spherical silica fine particles “consisting essentially of SiO ₂ units” means that the fine particles are basically composed of SiO ₂ units, but are not composed only of the units, It means having a large number of silanol groups at least on the surface as is generally known. In some cases, some of the hydrolyzable groups (hydrocarbyloxy groups) derived from the tetrafunctional silane compound and / or its partial hydrolysis-condensation product, which are raw materials, are not converted into silanol groups in a slight amount. It means that it may remain on the surface or inside.

  As described above, in the present invention, a small particle size sol-gel method silica obtained by hydrolysis of tetraalkoxysilane is used as a silica base (silica before hydrophobization treatment), and by performing a specific surface treatment thereto, When obtained as a powder, the particle size after the hydrophobization treatment maintains the primary particle size of the silica raw material, and aggregation of these can be prevented.

  Use of tetraalkoxysilane having a small number of carbon atoms in the alkoxy group as a silica particle having a small particle diameter, use of an alcohol having a small number of carbon atoms as a solvent, increasing the hydrolysis temperature, during hydrolysis of tetraalkoxysilane By changing the reaction conditions such as lowering the concentration of the catalyst and lowering the concentration of the hydrolysis catalyst, a silica raw material having an arbitrary particle size can be obtained.

  As described above and as will be described in more detail below, the silica particle having a small particle diameter is subjected to a specific surface treatment to obtain desired hydrophobic silica fine particles.

Next, one method for producing the hydrophobic spherical silica fine particles will be described in detail below.
<Method for Producing Hydrophobic Spherical Silica Fine Particles as Component (C)>
The hydrophobic spherical silica fine particles of the present invention are
Step (C1): Step of synthesizing hydrophilic spherical silica fine particles,
Step (C2): surface treatment step with a trifunctional silane compound,
Step (C3): Obtained by a surface treatment step with a functional silane compound. Hereinafter, each process is demonstrated one by one.

Step (C1): Synthesis step of hydrophilic spherical silica fine particles General formula (I):
Si (OR ³ ) ₄ (I)
(In the formula, each R ³ is the same or different monovalent hydrocarbon group having 1 to 6 carbon atoms.)
Hydrophilic spherical silica is obtained by hydrolyzing and condensing a tetrafunctional silane compound represented by the formula, a partial hydrolysis product thereof, or a mixture thereof in a mixture of a hydrophilic organic solvent containing a basic substance and water. A mixed solvent dispersion of fine particles can be obtained.

In the general formula (I), R ³ is a monovalent hydrocarbon group having 1 to 6 carbon atoms, preferably a monovalent hydrocarbon group having 1 to 4 carbon atoms, particularly preferably 1 to 2 carbon atoms. is there. Examples of the monovalent hydrocarbon group represented by R ³ include an alkyl group such as a methyl group, an ethyl group, a propyl group, and a butyl group; an aryl group such as a phenyl group, and preferably a methyl group, An ethyl group, a propyl group, or a butyl group, particularly preferably a methyl group or an ethyl group.

  Examples of the tetrafunctional silane compound represented by the general formula (I) include tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane; and tetraphenoxysilane, preferably , Tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane and tetrabutoxysilane, particularly preferably tetramethoxysilane and tetraethoxysilane. Examples of the partial hydrolysis-condensation product of the tetrafunctional silane compound represented by the general formula (I) include alkyl silicates such as methyl silicate and ethyl silicate.

The hydrophilic organic solvent is not particularly limited as long as it dissolves the tetrafunctional silane compound represented by the general formula (I), the partial hydrolysis-condensation product, and water. For example, alcohols Cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, cellosolve acetate; ketones such as acetone and methylethylketone; ethers such as dioxane and tetrahydrofuran, and the like, preferably alcohols and cellosolves. Examples include alcohols. The alcohols include the following general formula (VII):
R ¹¹ OH (VII)
(In the formula, R ¹¹ is a monovalent hydrocarbon group having 1 to 6 carbon atoms.)
The alcohol shown by is mentioned.

In the general formula (VII), R ¹¹ is preferably a monovalent hydrocarbon group having 1 to 4 carbon atoms, particularly preferably 1 to 2 carbon atoms. Examples of the monovalent hydrocarbon group represented by R ¹¹ include alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group and butyl group, preferably methyl group, ethyl group, propyl group and isopropyl group. Preferably a methyl group and an ethyl group are mentioned. Examples of the alcohol represented by the general formula (VII) include methanol, ethanol, propanol, isopropanol, butanol and the like, preferably methanol and ethanol. As the number of carbon atoms in the alcohol increases, the particle size of the spherical silica fine particles to be generated increases. Therefore, methanol is preferred in order to obtain the desired small particle size silica fine particles.

  Examples of the basic substance include ammonia, dimethylamine, diethylamine and the like, preferably ammonia, diethylamine, and particularly preferably ammonia. These basic substances may be dissolved in water in a required amount, and the obtained aqueous solution (basic) may be mixed with the hydrophilic organic solvent.

  The basic substance is used in an amount of 0.01 to 2 mol with respect to a total of 1 mol of the hydrocarbyloxy group of the tetrafunctional silane compound represented by the general formula (I) and / or its partial hydrolysis-condensation product. It is preferable that it is 0.02-0.5 mol, and it is especially preferable that it is 0.04-0.12 mol. At this time, the smaller the amount of the basic substance, the desired small particle size silica fine particles.

  The amount of water used in the hydrolysis and condensation is 0. 1 mol for the total of 1 mol of hydrocarbyloxy groups of the tetrafunctional silane compound represented by the general formula (I) and / or the partial hydrolysis condensation product thereof. It is preferably 5 to 5 mol, more preferably 0.6 to 2 mol, and particularly preferably 0.7 to 1 mol. The ratio of the hydrophilic organic solvent to water (hydrophilic organic solvent: water) is preferably 0.5 to 10 in terms of mass ratio, more preferably 3 to 9, and more preferably 5 to 8. Particularly preferred. As the amount of the hydrophilic organic solvent increases, silica particles having a desired small particle diameter can be obtained.

  Hydrolysis and condensation of the tetrafunctional silane compound represented by the general formula (I) can be carried out by a well-known method, that is, in a mixture of a hydrophilic organic solvent containing a basic substance and water in the general formula (I). It is performed by adding a tetrafunctional silane compound or the like shown.

  The concentration of silica fine particles in the mixed solvent dispersion of hydrophilic spherical silica fine particles obtained in this step (C1) is generally 3 to 15% by mass, preferably 5 to 10% by mass.

Step (C2): Surface treatment step with a trifunctional silane compound In the mixed solvent dispersion of the hydrophilic spherical silica fine particles obtained in the step (C1), the general formula (II):
R ¹ Si (OR ⁴ ) ₃ (II)
(In the formula, R ¹ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, and each R ⁴ is the same or different monovalent hydrocarbon group having 1 to 6 carbon atoms.)
To the surface of the hydrophilic spherical silica fine particles by adding a trifunctional silane compound represented by the formula (1), a partial hydrolysis product thereof, or a mixture thereof and treating the surface of the hydrophilic spherical silica fine particles thereby. R ¹ SiO _3/2 units (R ¹ is as described above) are introduced to obtain a mixed solvent dispersion of the first hydrophobic spherical silica fine particles.

  This step (C2) is indispensable for suppressing aggregation of silica fine particles in the subsequent concentration step. If the aggregation cannot be suppressed, the individual particles of the obtained silica-based powder cannot maintain the primary particle diameter, and the fluidity imparting ability is deteriorated.

In the general formula (II), R ¹ is preferably a monovalent hydrocarbon group having 1 to 3 carbon atoms, particularly preferably 1 to 2 carbon atoms. Examples of the monovalent hydrocarbon group represented by R ¹ include alkyl groups such as methyl group, ethyl group, n-propyl group, isopropyl group, butyl group, and hexyl group, preferably methyl group, ethyl group, n -A propyl group or an isopropyl group, particularly preferably a methyl group or an ethyl group. Further, some or all of the hydrogen atoms of these monovalent hydrocarbon groups may be substituted with halogen atoms such as fluorine atom, chlorine atom, bromine atom, preferably fluorine atom.

In the general formula (II), R ⁴ is preferably a monovalent hydrocarbon group having 1 to 3 carbon atoms, particularly preferably 1 to 2 carbon atoms. Examples of the monovalent hydrocarbon group represented by R ⁴ include alkyl groups such as a methyl group, an ethyl group, a propyl group, and a butyl group, preferably a methyl group, an ethyl group, or a propyl group, and particularly preferably a methyl group. Or an ethyl group is mentioned.

  Examples of the trifunctional silane compound represented by the general formula (II) include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, and n-propyltriethoxy. Unsubstituted or halogen-substituted trisilane such as silane, isopropyltrimethoxysilane, isopropyltriethoxysilane, butyltrimethoxysilane, butyltriethoxysilane, hexyltrimethoxysilane, trifluoropropyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane Alkoxysilane, etc., preferably methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane and ethyltriethoxysilane, more preferably methyltrimethoxysilane Emissions and methyltriethoxysilane, or their partially hydrolyzed condensation products thereof.

  The addition amount of the trifunctional silane compound represented by the general formula (II) is 0.001 to 1 mol, preferably 0.01 to 0.1 mol, per mol of Si atom in the used hydrophilic spherical silica fine particles. Most preferably, it is 0.01-0.05 mol. If the amount added is less than 0.001 mol, the dispersibility of the resulting hydrophobic spherical silica fine particles will deteriorate, so that the effect of imparting fluidity to boron nitride will not appear, and if it exceeds 1 mol, the silica fine particles will aggregate. There is a fear.

  The concentration of the silica fine particles in the mixed solvent dispersion of the first hydrophobic spherical silica fine particles obtained in this step (C2) is usually 3% by mass or more and less than 15% by mass, preferably 5 to 10% by mass. If the concentration is too low, there is an inconvenience that productivity is lowered, and if it is too high, there is an inconvenience that silica fine particles are aggregated.

-Concentration step The first hydrophobic spherical silica is obtained by removing a portion of the hydrophilic organic solvent and water from the mixed solvent dispersion of the first hydrophobic spherical silica fine particles thus obtained and concentrating. A mixed solvent concentrated dispersion of fine particles is obtained. At this time, the hydrophobic organic solvent may be added in advance (before the concentration step) or during the concentration step. In this case, the hydrophobic solvent used is preferably a hydrocarbon or ketone solvent. Specific examples of the solvent include toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone and the like, and methyl isobutyl ketone is preferable. Examples of the method for removing a part of the hydrophilic organic solvent and water include distillation and distillation under reduced pressure. The resulting concentrated dispersion preferably has a silica fine particle concentration of 15 to 40% by mass, more preferably 20 to 35% by mass, and particularly preferably 25 to 30% by mass. If the amount is less than 15% by mass, the surface treatment in the subsequent process may not proceed smoothly. If the amount is more than 40% by mass, the silica fine particles may be aggregated.

  In the concentration step, the silazane compound represented by the general formula (III) and the monofunctional silane compound represented by the general formula (IV) used as a surface treatment agent in the next step (C3) react with alcohol or water. In addition, the surface treatment becomes insufficient, and when the subsequent drying is performed, aggregation occurs, and the resulting silica powder cannot maintain the primary particle diameter, and has the significance of suppressing problems such as poor fluidity imparting ability. is there.

Step (C3): Surface treatment step with a functional silane compound In the mixed solvent dispersion of the first hydrophobic spherical silica fine particles obtained in Step (C2) or the concentrated dispersion, the general formula (III):
R ² ₃ SiNHSiR ² ₃ (III)
(In the formula, each R ² is the same or different substituted or unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms.)
Or a silazane compound represented by formula (IV):
R ² ₃ SiX (IV)
(In the formula, R ² is as defined in the general formula (III), and X is an OH group or a hydrolyzable group.)
Is added to treat the surface of the first hydrophobic spherical silica fine particles, and R ² ₃ SiO _1/2 units (provided that R 1 The second hydrophobic spherical silica fine particles are obtained by introducing ^{2 as} defined in the general formula (III). By the treatment in this step, R ² ₃ SiO _1/2 units are introduced to the surface in the form of triorganosilylation of silanol groups remaining on the surface of the first hydrophobic spherical silica fine particles.

In the above general formulas (III) and (IV), R ² is preferably a monovalent hydrocarbon group having 1 to 4 carbon atoms, particularly preferably 1 to 2 carbon atoms. Examples of the monovalent hydrocarbon group represented by R ² include alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, and a butyl group, preferably a methyl group, an ethyl group, or a propyl group, and particularly preferably , Methyl group or ethyl group. Further, some or all of the hydrogen atoms of these monovalent hydrocarbon groups may be substituted with halogen atoms such as fluorine atoms, chlorine atoms, bromine atoms, preferably fluorine atoms.

  Examples of the hydrolyzable group represented by X include a chlorine atom, an alkoxy group, an amino group, and an acyloxy group, preferably an alkoxy group or an amino group, and particularly preferably an alkoxy group.

  Examples of the silazane compound represented by the general formula (III) include hexamethyldisilazane and hexaethyldisilazane, preferably hexamethyldisilazane. Examples of the monofunctional silane compound represented by the general formula (IV) include monosilanol compounds such as trimethylsilanol and triethylsilanol; monochlorosilanes such as trimethylchlorosilane and triethylchlorosilane; monoalkoxy such as trimethylmethoxysilane and trimethylethoxysilane. Silane; monoaminosilane such as trimethylsilyldimethylamine and trimethylsilyldiethylamine; monoacyloxysilane such as trimethylacetoxysilane, preferably trimethylsilanol, trimethylmethoxysilane or trimethylsilyldiethylamine, particularly preferably trimethylsilanol or trimethylmethoxysilane It is done.

  The amount of the silazane compound and / or monofunctional silane compound used is 0.1 to 0.5 mol, preferably 0.2 to 0.4 mol, relative to 1 mol of Si atoms in the used hydrophilic spherical silica fine particles. Especially preferably, it is 0.25-0.35 mol. When the amount used is less than 0.1 mol, the dispersibility of the resulting hydrophobic silica fine particles is deteriorated, and when the amount used is more than 0.5 mol, it is economically disadvantageous.

  The hydrophobic spherical silica fine particles can be obtained as a powder by a conventional method such as atmospheric drying or reduced pressure drying.

  The amount of component (C) to component (B) is preferably 0.01 to 10% by mass, preferably 0.05 to 5% by mass, more preferably 0.1 to 3% by mass. It is. If it is less than 0.01% by mass, the effect of reducing the viscosity of the grease composition is lost, and if it exceeds 10% by mass, the viscosity of the grease composition may be increased, and the thermal conductivity may be deteriorated. But there is.

Other components In addition, the silicone composition of the present invention, if necessary, impairs the purpose of the present invention with a conventionally known antioxidant, dye, pigment, flame retardant, anti-settling agent, thixotropic agent, etc. It can mix | blend in the range which is not.

Furthermore, this composition can be made into a curable composition by mix | blending a hardening | curing agent.
In this case, when an alkenyl group-containing organopolysiloxane is used as the component (A) and the composition is cured by an addition reaction (hydrosilylation reaction), this curing agent has an average of 2 or more silicon atoms in one molecule. A composition comprising an organohydrogenpolysiloxane having a bonded hydrogen atom and a platinum-based catalyst is blended. Examples of the group bonded to the silicon atom bond in the organohydrogenpolysiloxane include the same linear alkyl group, branched alkyl group, cyclic alkyl group, aryl group, aralkyl group as in the formula (V), Examples include halogenated alkyl groups, preferably alkyl groups and aryl groups, and particularly preferably methyl groups and phenyl groups. Moreover, the viscosity is not limited at 25 ° C. The organohydrogenpolysiloxane, preferably in the range of 1~100,000mm ² / s, particularly preferably in the range of 1~5,000mm ² / s . The molecular structure of the organohydrogenpolysiloxane is not limited, and examples thereof include linear, branched, partially branched linear, cyclic, and dendritic (dendrimer). The organohydrogenpolysiloxane may be, for example, a single polymer having these molecular structures, a copolymer having these molecular structures, or a mixture thereof.

Examples of such organohydrogenpolysiloxane include dimethylhydrogensiloxy group-blocked dimethylpolysiloxane with molecular chain at both ends, trimethylsiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer with molecular chain at both ends, and dimethylhydrogen with molecular chain at both ends. Gensiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer, siloxane unit represented by formula: (CH ₃ ) ₃ SiO _1/2 and siloxane unit represented by formula: (CH ₃ ) ₂ HSiO _1/2 : Organosiloxane copolymers composed of siloxane units represented by SiO _4/2 and mixtures of two or more thereof.

  In the present composition, the content of the organohydrogenpolysiloxane is an amount necessary for the curing of the present composition. Specifically, with respect to 1 mol of the silicon-bonded alkenyl group in the component (A), The amount of silicon atom-bonded hydrogen atoms in this component is preferably in the range of 0.1 to 10 mol, more preferably in the range of 0.1 to 5 mol, The amount is preferably in the range of 0.1 to 3.0 mol. If the content of this component is less than the lower limit of the above range, the resulting silicone composition tends not to be cured sufficiently, while if the upper limit of the above range is exceeded, the resulting silicone cured product This is because objects tend to be very hard and have many cracks on the surface.

  The platinum catalyst is a catalyst for accelerating the curing of the composition, and examples thereof include chloroplatinic acid, chloroplatinic acid alcohol solution, platinum olefin complex, platinum alkenylsiloxane complex, and platinum carbonyl complex. It is done.

  In the present composition, the content of the platinum-based catalyst is an amount necessary for curing the present composition. Specifically, the platinum metal in this component with respect to the alkenyl group-containing organopolysiloxane of component (A). Is preferably in an amount in the range of 0.01 to 1,000 ppm, and particularly preferably in an amount in the range of 0.1 to 500 ppm. This is because when the content of this component is less than the lower limit of the above range, the resulting silicone composition tends not to be cured sufficiently, while on the other hand, the silicone obtained even if the amount exceeds the upper limit of the above range. This is because the curing rate of the composition tends not to be significantly improved.

  Moreover, in order to adjust the cure rate of this composition and to improve handling workability, 2-methyl-3-butyn-2-ol, 2-phenyl-3-butyn-2-ol, 1-ethynyl-1- Acetylene compounds such as cyclohexanol; ene-yne compounds such as 3-methyl-3-penten-1-yne and 3,5-dimethyl-3-hexen-1-yne; other hydrazine compounds, phosphine compounds, It is preferable to contain a curing reaction inhibitor such as a mercaptan compound. Although content of this hardening reaction inhibitor is not limited, It is preferable to exist in the range of 0.0001-1.0 mass part with respect to 100 mass parts of component (A).

  In addition, when an organopolysiloxane whose molecular chain end is blocked with a hydroxyl group or an alkoxy group is used as the component (A) and the composition is cured by a condensation reaction, the curing agent is at least 3 in one molecule. It is characterized by comprising a silane or siloxane oligomer having a silicon atom-bonded hydrolyzable group and, if necessary, a condensation reaction catalyst. Examples of the silicon atom-bonded hydrolyzable group in the silane include an alkoxy group, an alkoxyalkoxy group, an acyloxy group, a ketoxime group, an alkenoxy group, an amino group, an aminoxy group, and an amide group. In addition to the hydrolyzable group, the silicon atom of the silane includes, for example, a linear alkyl group, a branched alkyl group, a cyclic alkyl group, an alkenyl group, an aryl group, an aralkyl group, and a halogenated alkyl group. It may be bonded. Examples of such a silane or siloxane oligomer include tetraethoxysilane, methyltriethoxysilane, vinyltriethoxysilane, methyltris (methylethylketoxime) silane, vinyltriacetoxysilane, and ethyl orthosilicate.

  The content of the silane or siloxane oligomer is an amount necessary for the curing of the present composition. Specifically, the content of the silane or siloxane oligomer is 0.1% with respect to 100 parts by mass of the hydroxy group or alkoxy group end-blocked organopolysiloxane of the component (A). It is preferably in the range of 01 to 20 parts by mass, and particularly preferably in the range of 0.1 to 10 parts by mass. This is because when the content of the silane or siloxane oligomer is less than the lower limit of the above range, the storage stability of the resulting composition tends to decrease or the adhesiveness tends to decrease. This is because if the amount exceeds the upper limit of the range, curing of the resulting composition tends to be remarkably slowed.

  The condensation reaction catalyst is an optional component, and is not essential when, for example, a silane having a hydrolyzable group such as an aminoxy group, amino group, or ketoxime group is used as a curing agent. Examples of such condensation reaction catalysts include organic titanates such as tetrabutyl titanate and tetraisopropyl titanate; organic titanium such as diisopropoxybis (acetylacetate) titanium and diisopropoxybis (ethylacetoacetate) titanium. Chelate compounds; organoaluminum compounds such as aluminum tris (acetylacetonate) and aluminum tris (ethylacetoacetate); organozirconium compounds such as zirconium tetra (acetylacetonate) and zirconium tetrabutyrate; dibutyltin dioctoate, dibutyltin dilaurate, Organic tin compounds such as butyltin-2-ethylhexoate; organic compounds such as tin naphthenate, tin oleate, tin butyrate, cobalt naphthenate, zinc stearate Rubonic acid metal salts; amine compounds such as hexylamine and dodecylamine phosphate and salts thereof; quaternary ammonium salts such as benzyltriethylammonium acetate; lower fatty acid salts of alkali metals such as potassium acetate; dimethylhydroxylamine and diethylhydroxylamine And dialkylhydroxylamines such as guanidyl group-containing organosilicon compounds.

  In the present composition, the content of the condensation reaction catalyst is an arbitrary amount, and may be an amount necessary for curing the present composition. Specifically, the hydroxy group or alkoxy group end-capping of component (A) is used. It is preferably within a range of 0.01 to 20 parts by mass, and particularly preferably within a range of 0.1 to 10 parts by mass with respect to 100 parts by mass of the organopolysiloxane. This is because, when this catalyst is essential, if the content of this catalyst is less than the lower limit of the above range, the resulting composition tends not to be sufficiently cured, while exceeding the upper limit of the above range. This is because the storage stability of the resulting composition tends to decrease.

  Moreover, when this composition hardens | cures by the free radical reaction by an organic peroxide, a hardening | curing agent is an organic peroxide. In this case, as the component (A), it is preferable to use the same alkenyl group-containing organopolysiloxane as that used in the addition reaction curable composition. Examples of the organic peroxide include benzoyl peroxide, di (p-methylbenzoyl) peroxide, di (o-methylbenzoyl) peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-bis. (T-Butylperoxy) hexane, di-t-butyl peroxide, and t-butylperoxybenzoate are mentioned. The content of the organic peroxide is an amount necessary for curing the present composition. Specifically, the content is 0.1 to 5 mass with respect to 100 parts by mass of the alkenyl group-containing organopolysiloxane of the component (A). The amount is preferably within the range of parts.

  Moreover, when this composition is a curable composition, the method of hardening it is not limited, For example, after shaping | molding this composition and leaving it to stand at room temperature, after shaping | molding this composition, 50-200 A method of heating to ° C is mentioned. In addition, the properties of the silicone cured product thus obtained are not limited, and examples thereof include gels, low-hardness rubbers, and high-hardness rubbers. It can be sufficiently adhered.

  The method for producing the silicone composition of the present invention is not particularly limited and may follow a conventionally known method for producing a silicone grease composition. For example, the above-mentioned components (A) to (C) and other components as necessary are mixed with Trimix, Twinwin, Planetary Mixer (all of which are mixers manufactured by Inoue Mfg. Co., Ltd., registered trademark), Ultramixer (Mizuho) It can be produced by mixing for 30 minutes to 4 hours in a mixer such as Kogyo Co., Ltd. (registered trademark), Hibis Disper Mix (special Kika Kogyo Co., Ltd., registered trademark). . Moreover, you may mix, heating as needed at the temperature of the range of 50-150 degreeC.

  The silicone composition of the present invention has an absolute viscosity measured at 25 ° C. of 10 to 600 Pa · s, preferably 50 to 500 Pa · s, more preferably 50 to 400 Pa · s, and particularly 50 to 350 Pa · s. Good. When the absolute viscosity is within the above range, a good grease can be provided and the workability is excellent. If the absolute viscosity is higher than the upper limit, workability may be deteriorated. If the absolute viscosity is smaller than the lower limit, the composition may flow out after being applied on various substrates, and the effect of misalignment resistance may not be exhibited. The absolute viscosity can be obtained by adjusting each component with the above-described blending amount. The absolute viscosity is measured using a model number PC-1TL (10 rpm) manufactured by Malcolm Corporation.

  The silicone composition of the present invention can have a high thermal conductivity at 25 ° C. of 1.0 W / mK or higher, preferably 2.0 W / mK or higher, more preferably 3.0 W / mK or higher. The upper limit of the thermal conductivity is not particularly limited, but is usually less than 10 W / mK, particularly less than 8 W / mK. The thermal conductivity can be measured using TPA-501 manufactured by Kyoto Electronics Industry Co., Ltd.

  The silicone composition of the present invention can be used as a grease. The embodiment in which the silicone composition of the present invention is used as a grease is not particularly limited, and may be used in the same manner as a conventional heat radiation (heat conductive) silicone grease. For example, in a mode in which the grease is sandwiched between an electric / electronic component such as LSI or other heat generating member and a cooling member or a heat radiating member, and heat from the heat generating member is transferred to the cooling member or heat radiating member to dissipate it. It can be used suitably. The silicone composition of the present invention has low viscosity, high thermal conductivity, and extremely excellent resistance to misalignment, so it is suitable for use as a heat dissipation (thermal conductivity) grease for high-quality semiconductor devices. can do.

  The silicone composition of the present invention can be molded and used as a heat conductive sheet. The aspect which uses the silicone composition of this invention as a heat conductive sheet is not restrict | limited in particular, What is necessary is just to use it by the method similar to the conventional heat conductive sheet. Moreover, as a use site | part, it can be used for the same use as the above-mentioned heat-release grease. Further, it may be used after being cured by a press or the like to form a sheet, or may be cured after being sandwiched between a heat generating portion and a heat radiating portion.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated in detail, this invention is not restrict | limited to the following Example. Each component used in the examples and comparative examples is described below.

（動粘度５，０００ｍｍ²／ｓ）
（Ａ−２）

（動粘度３９０ｍｍ²／ｓ）
（Ａ−３）

（動粘度３５ｍｍ²／ｓ） Component (A) Liquid silicone (A-1)

(Kinematic viscosity 5,000mm ² / s)
(A-2)

(Kinematic viscosity 390mm ² / s)
(A-3)

(Kinematic viscosity 35mm ² / s)

Component (B) Thermally conductive filler In the following, the average particle size of the thermally conductive filler of Component (B) is the cumulative volume based on the measurement using Microtrac MT3300EX, a particle size analyzer manufactured by Nikkiso Co., Ltd. Average diameter.
(B-1) Aluminum powder: average particle size 20 μm
(B-2) Zinc oxide powder: average particle size 1.0 μm
(B-3) Alumina powder: Average particle size 8.9 μm

Component (C) Hydrophobic spherical silica fine particle component (C) prepared hydrophobic fine particles (1) to (6) as described below (described in Table 1). Of these, (5) and (6) are for comparative examples.

[Synthesis of hydrophobic spherical silica fine particles]
[Synthesis Example 1]
Step (C1): Step of synthesizing hydrophilic spherical silica fine particles 989.5 g of methanol, 135.5 g of water, and 28 mass in a 3 liter glass reactor equipped with a stirrer, a dropping funnel and a thermometer. % Aqueous ammonia (66.5 g) was added and mixed. The solution was adjusted to 35 ° C., and 436.5 g (2.87 mol) of tetramethoxysilane was added dropwise over 6 hours while stirring. Even after the completion of the dropwise addition, the suspension was further stirred for 0.5 hours for hydrolysis to obtain a suspension of hydrophilic spherical silica fine particles.
Step (C2): Surface treatment step with trifunctional silane compound 4.4 g (0.03 mol) of methyltrimethoxysilane was added dropwise to the suspension obtained above at room temperature over 0.5 hours. Thereafter, stirring was continued for 12 hours, and the surface of the silica fine particles was hydrophobized to obtain a dispersion of hydrophobic spherical silica fine particles.
Next, an ester adapter and a condenser tube are attached to a glass reactor, and the dispersion obtained in the previous step is heated to 60 to 70 ° C. to distill off a mixture of methanol and water, and 1021 g of hydrophobic spherical silica. A concentrated solvent dispersion of fine particles was obtained. At this time, the content of the hydrophobic spherical silica fine particles in the concentrated dispersion was 28% by mass.
Step (C3): Surface treatment step with a functional silane compound After adding 138.4 g (0.86 mol) of hexamethyldisilazane to the concentrated dispersion obtained in the previous step at room temperature, this dispersion The silica fine particles in the dispersion were trimethylsilylated by heating to 50-60 ° C. and reacting for 9 hours. Subsequently, the solvent in this dispersion was distilled off at 130 ° C. under reduced pressure (6,650 Pa) to obtain 186 g of hydrophobic spherical silica fine particles (1).
The hydrophilic spherical silica fine particles obtained in the step (C1) were measured according to the following measurement method 1. Moreover, it measured according to the following measuring methods 2-3 about the hydrophobic spherical silica fine particles obtained through each step of said process (C1)-(C3). The obtained results are shown in Table 1.

[Measurement methods 1 to 3]
1. Particle size measurement of the hydrophilic spherical silica fine particles obtained in the step (C1) By adding a silica fine particle suspension to methanol so that the silica fine particles are 0.5% by mass, and applying ultrasonic waves for 10 minutes, The fine particles were dispersed. The particle size distribution of the fine particles treated in this way is measured with a dynamic light scattering method / laser Doppler nanotrack particle size distribution measuring device (trade name: UPA-EX150, manufactured by Nikkiso Co., Ltd.), and the volume-based median diameter is measured as particles. The diameter. The median diameter is a particle diameter corresponding to 50% cumulative when the particle size distribution is expressed as a cumulative distribution.
2. Measurement of particle diameter and measurement of particle size distribution D ₉₀ / D ₁₀ of hydrophobic spherical silica fine particles obtained in step (C3) Silica fine particles were added to methanol so as to be 0.5% by mass, and subjected to ultrasonic waves for 10 minutes. The fine particles were dispersed by applying. The particle size distribution of the fine particles treated in this way is measured with a dynamic light scattering method / laser Doppler nanotrack particle size distribution measuring device (trade name: UPA-EX150, manufactured by Nikkiso Co., Ltd.), and the volume-based median diameter is measured as particles. The diameter. Measurement of particle size distribution D ₉₀ / D ₁₀ is the particle size of which cumulative from the smaller side in distribution when the above particle size measurement is 10% D _10, the particle size of which cumulative from the smaller side is 90% and D ₉₀ From the measured values, D ₉₀ / D ₁₀ was calculated.
3. Shape measurement of hydrophobic spherical silica fine particles The shape was confirmed by observation with an electron microscope (manufactured by Hitachi, Ltd., trade name: S-4700 type, magnification: 100,000 times). The term “spherical” includes not only a true sphere but also a slightly distorted sphere. Note that the shape of such particles is evaluated by the circularity when the particles are projected two-dimensionally, and the circularity is in the range of 0.8 to 1. Here, the circularity is (peripheral length of a circle equal to the particle area) / (peripheral length of particle). The circularity is an average value obtained by measuring 10 particles.

[Synthesis Example 2]
In Synthesis Example 1, except that the amounts of methanol, water, and 28% by mass ammonia water were changed to 10,045.7 g of methanol, 112.6 g of water, and 33.2 g of 28% by mass ammonia water in Step (C1). Similarly, 188 g of hydrophobic spherical silica fine particles (2) were obtained. Measurement was performed in the same manner as in Synthesis Example 1 using these hydrophobic spherical silica fine particles. The results are shown in Table 1.

[Synthesis Example 3]
-Process (C1):
In a 3 liter glass reactor equipped with a stirrer, a dropping funnel and a thermometer, 623.7 g of methanol, 41.4 g of water, and 49.8 g of 28% by mass ammonia water were added and mixed. This solution was adjusted to 35 ° C., and while stirring, 1,163.7 g of tetramethoxysilane and 418.1 g of 5.4% by mass ammonia water were simultaneously added, the former being 6 hours and the latter being 4 hours It was dripped over. Even after the tetramethoxysilane was added dropwise, the mixture was stirred for 0.5 hours for hydrolysis to obtain a silica fine particle suspension.
-Process (C2):
To the suspension thus obtained, 11.6 g of methyltrimethoxysilane (molar ratio of 0.01 equivalent to tetramethoxysilane) was added dropwise at room temperature over 0.5 hours and stirred for 12 hours after the addition. Then, the surface of the silica fine particles was treated.
An ester adapter and a cooling tube were attached to the glass reactor, and 1,440 g of methyl isobutyl ketone was added to the dispersion containing silica fine particles subjected to the above surface treatment, and then heated to 80 to 110 ° C. Was distilled off over 7 hours.
-Process (C3):
To the dispersion thus obtained, 357.6 g of hexamethyldisilazane was added at room temperature, heated to 120 ° C., and reacted for 3 hours to trimethylsilylate the silica fine particles. Thereafter, the solvent was distilled off under reduced pressure to obtain 472 g of spherical hydrophobic silica fine particles (3).
The silica fine particles (3) thus obtained were measured in the same manner as in Synthesis Example 1. The results are shown in Table 1.

[Synthesis Example 4]
Hydrophobic spherical silica fine particles (4) were obtained in the same manner as in Synthesis Example 3 except that the hydrolysis temperature of tetramethoxysilane was changed to 20 ° C. instead of 35 ° C. during the synthesis of the silica fine particles. 469 g was obtained. The same measurement as in Synthesis Example 1 was performed using this hydrophobic spherical silica fine particle (4). The results are shown in Table 1.

[Comparative Synthesis Example 1]
A 0.3 liter glass reactor equipped with a stirrer and a thermometer was charged with 100 g of deflagration silica (trade name: SOC1, manufactured by Admatechs), 1 g of pure water was added with stirring, and after sealing, Stir at 60 ° C. for 10 hours. Subsequently, after cooling to room temperature, 2 g of hexamethyldisilazane was added with stirring, and after sealing, the mixture was further stirred for 24 hours. The temperature was raised to 120 ° C., and the remaining raw material and the produced ammonia were removed while ventilating nitrogen gas to obtain 100 g of hydrophobic spherical silica fine particles (5).
The obtained silica fine particles (5) were measured in the same manner as in Synthesis Example 1. The results are shown in Table 1.

[Comparative Synthesis Example 2]
A 0.3 liter glass reactor equipped with a stirrer and a thermometer was charged with 100 g of deflagration silica (trade name: SOC1, manufactured by Admatechs), 1 g of pure water was added with stirring, and after sealing, Stir at 60 ° C. for 10 hours. Next, after cooling to room temperature, 1 g of methyltrimethoxysilane was added with stirring, and after sealing, the mixture was further stirred for 24 hours. Next, 2 g of hexamethyldisilazane was added with stirring. After sealing, the mixture was further stirred for 24 hours. The temperature was raised to 120 ° C., and the remaining raw material and generated ammonia were removed while ventilating nitrogen gas to obtain 101 g of hydrophobic spherical silica fine particles (6). The obtained silica fine particles (6) were measured in the same manner as in Synthesis Example 1. The results are shown in Table 1.

＜注＞
１）工程（Ｃ１）で得られた分散液の親水性球状シリカ微粒子の粒子径
２）最終的に得られた疎水性シリカ微粒子の粒子径

<Note>
1) Particle size of hydrophilic spherical silica fine particles of dispersion obtained in step (C1) 2) Particle size of finally obtained hydrophobic silica fine particles

[Examples 1 to 5 and Comparative Examples 1 to 3]
Preparation of Silicone Composition According to the composition and blending amount shown in Tables 2 and 3, the above components (A) to (C) were charged into a 5 liter planetary mixer (registered trademark, manufactured by Inoue Seisakusho Co., Ltd.) The mixture was stirred at 150 ° C. for 1 hour to produce a silicone composition.
About each silicone composition obtained by the said method, the viscosity and thermal conductivity were measured in accordance with the following method. The results are shown in Tables 2 and 3.

[Determination of viscosity / workability]
The absolute viscosity of each composition was measured at 25 ° C. using model number PC-1TL (10 rpm) manufactured by Malcolm.
When the viscosity exceeds 600 Pa · s, workability such as dispensing is extremely deteriorated. Therefore, when the viscosity is less than 600 Pa · s, it is determined as “◯”, and when it exceeds 600 Pa · s, it is determined as “x”.

[Thermal conductivity]
The thermal conductivity of each composition was measured at 25 ° C. using TPA-501 manufactured by Kyoto Electronics Industry Co., Ltd.

[Example 6]
<Creation of thermal conductive sheet>
60 parts by mass of the following component (A-4), 30 parts by mass of component (A-3), 1,000 parts by mass, 250 parts by mass of components (B-1) and (B-2), Furthermore, 0.5 part by mass of hydrophobic silica fine particles (1) was put into a planetary mixer (registered trademark, manufactured by Inoue Seisakusho Co., Ltd.) having a capacity of 5 liters and stirred at 150 ° C. for 1 hour to obtain a mixture Obtained. After cooling the mixture, 0.45 parts by mass of a 50% by weight toluene solution of 1-ethynyl-1-cyclohexanol and a platinum-divinyltetramethyldisiloxane complex were dissolved in the same dimethylpolysiloxane as the following component (A-4). 0.15 parts by mass of a solution (platinum content: 1% by mass) was sequentially added and stirred for 15 minutes each. Furthermore, 10 mass parts of component (A-5) was added, and the silicone composition was obtained. This silicone composition was formed into a sheet by press molding (150 ° C./60 minutes) using a mold to prepare a heat conductive sheet (thickness 2.0 mm).
(Evaluation)
About the said heat conductive sheet, the heat conductivity and the handleability of the heat conductive sheet were determined by finger touch. “○” indicates that there is no problem in handling, and “x” indicates that the sheet is fragile and difficult to handle. In addition, the heat conductivity was measured at 25 degreeC using the TPA-501 by the Kyoto Electronics Industry Co., Ltd. similarly, 5 sheets of 2 mm sheets were piled up.

[Comparative Example 4]
A thermally conductive sheet was prepared in the same manner as in Example 6 except that the hydrophobic silica fine particles (1) were not added, and evaluated in the same manner. The results are shown in Table 4.

（動粘度３５ｍｍ²／ｓ）
（Ａ−４）：両末端がジメチルビニルシリル基で封鎖され、２５℃における動粘度が６００ｍｍ²／ｓのジメチルポリシロキサン
（Ａ−５）：下記式に示される、２５℃における動粘度が、２７ｍｍ²／ｓのハイドロジェンポリシロキサン

成分（Ｂ）
（Ｂ−１） アルミニウム粉末：平均粒子径２０μｍ
（Ｂ−２） 酸化亜鉛粉末：平均粒子径１．０μｍ
成分（Ｃ）
表１の疎水性シリカ微粒子（１） Ingredient (A)
(A-3)

(Kinematic viscosity 35mm ² / s)
(A-4): Dimethylpolysiloxane having both ends blocked with dimethylvinylsilyl groups and a kinematic viscosity at 25 ° C. of 600 mm ² / s (A-5): The kinematic viscosity at 25 ° C. represented by the following formula: 27mm ² / s hydrogen polysiloxane

Ingredient (B)
(B-1) Aluminum powder: average particle size 20 μm
(B-2) Zinc oxide powder: average particle size 1.0 μm
Ingredient (C)
Hydrophobic silica fine particles of Table 1 (1)

Claims (11)

A thermally conductive silicone composition comprising (A) liquid silicone, (B) thermally conductive filler, and (C) hydrophobic spherical silica fine particles, wherein the hydrophobic spherical silica fine particles of component (C) are tetrafunctional. R ¹ SiO _3/2 units (on the surface of hydrophilic spherical silica fine particles substantially composed of SiO ₂ units obtained by hydrolyzing and condensing a functional silane compound, a partial hydrolysis-condensation product thereof or a mixture thereof) R ¹ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, and further R ² ₃ SiO _1/2 units (wherein each R ² is the same or different, substituted or unsubstituted Is a monovalent hydrocarbon group having 1 to 6 carbon atoms), the particle diameter is in the range of 0.005 to 1 μm, and the value of the particle size distribution D ₉₀ / D ₁₀ is 3 or less, Hydrophobic spherical silica particles having an average circularity of 0.8 to 1 A thermally conductive silicone composition characterized by the above. The hydrophobic spherical silica fine particles of component (C) are
(C1) General formula (I):
Si (OR ³ ) ₄ (I)
(In the formula, each R ³ is the same or different monovalent hydrocarbon group having 1 to 6 carbon atoms.)
By substantially hydrolyzing and condensing a tetrafunctional silane compound represented by the formula, a partial hydrolysis product thereof, or a mixture thereof in a mixture of a hydrophilic organic solvent and water in the presence of a basic substance, SiO 2 Obtain a mixed solvent dispersion of hydrophilic spherical silica fine particles consisting of ₂ units,
(C2) In the mixed solvent dispersion of the obtained hydrophilic spherical silica fine particles, the general formula (II):
R ¹ Si (OR ⁴ ) ₃ (II)
(In the formula, R ¹ is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, and each R ⁴ is the same or different monovalent hydrocarbon group having 1 to 6 carbon atoms.)
The surface of the hydrophilic spherical silica fine particles is treated with R ¹ SiO on the surface of the hydrophilic spherical silica fine particles by adding a trifunctional silane compound represented by the formula, a partial hydrolysis product thereof, or a mixture thereof. _3/2 units (R ¹ is as described above) were introduced to obtain a mixed solvent dispersion of the first hydrophobic spherical silica fine particles,
(C3) In the mixed solvent dispersion of the obtained first hydrophobic spherical silica fine particles, the general formula (III):
R ² ₃ SiNHSiR ² ₃ (III)
(In the formula, each R ² is the same or different substituted or unsubstituted monovalent hydrocarbon group having 1 to 6 carbon atoms.)
A silazane compound represented by the general formula (IV):
R ² ₃ SiX (IV)
(In the formula, R ² is as defined in the general formula (III), and X is an OH group or a hydrolyzable group.)
Is added to the surface of the first hydrophobic spherical silica fine particles, and the surface of the first hydrophobic spherical silica fine particles is treated with R ^2. The thermally conductive silicone according to claim 1, which is obtained as second hydrophobic silica fine particles by introducing ₃ SiO _1/2 units (R ² is as defined in formula (III)). Composition. The liquid silicone of the component (A) has the following average composition formula (V)
R ⁵ _a SiO _{(4-a) / 2} (V)
(In the formula, R ⁵ independently of each other is a saturated or unsaturated, unsubstituted or substituted monovalent hydrocarbon group having 1 to 18 carbon atoms, and 1.8 ≦ a ≦ 2.2. )
The thermally conductive silicone composition according to claim 1 or 2, which comprises an organopolysiloxane having a kinematic viscosity at 25 ° C of 10 to 500,000 mm ² / s. The thermally conductive silicone according to claim 3, wherein the organopolysiloxane represented by the average composition formula (V) is a linear organopolysiloxane represented by the following formula (i) and / or the following formula (ii). Composition.

(Wherein R ⁸ independently of each other is a saturated or unsaturated, unsubstituted or substituted monovalent hydrocarbon group having 1 to 18 carbon atoms, and m represents the behavior of the organopolysiloxane at 25 ° C. (It is a number that makes the viscosity 10 to 500,000 mm ² / s.)

Wherein R ⁹ is a substituted or unsubstituted alkyl group having 8 to 18 carbon atoms, and R ¹⁰ is independently of each other a saturated or unsaturated, unsubstituted or substituted group having 1 to 18 carbon atoms. (It is a monovalent hydrocarbon group. M ¹ is an integer of ¹ to 200 and m ² is an integer of 1 to 100.)   The heat conductive silicone composition of Claim 3 in which the organopolysiloxane represented by the said average compositional formula (V) contains the organopolysiloxane which has at least 2 alkenyl group in 1 molecule.   The thermally conductive silicone composition according to claim 5, further comprising an organohydrogenpolysiloxane having an average of 2 or more silicon-bonded hydrogen atoms in one molecule and a platinum catalyst.   The thermally conductive silicone composition according to claim 3, wherein the organopolysiloxane represented by the average composition formula (V) has a molecular chain terminal blocked with a hydroxyl group or an alkoxy group.   Furthermore, the heat conductive silicone composition of Claim 7 containing the silane or siloxane oligomer which has at least 3 silicon atom bond hydrolysable group in 1 molecule. The component (A) is represented by the following general formula (VI)

(Wherein R ⁶ is an alkyl group having 1 to 6 carbon atoms, and R ⁷ is independently of each other a saturated or unsaturated, unsubstituted or substituted monovalent hydrocarbon group having 1 to 18 carbon atoms. And b is an integer of 5 to 120.)
The thermal conductivity according to any one of claims 1 to 8, further comprising a hydrolyzable group-containing organopolysiloxane represented by the formula (A) in an amount of 10 to 90% by mass relative to the total mass of the component (A). Silicone composition.   The compounding quantity of a component (B) is 500-3,000 mass parts with respect to 100 mass parts of components (A), and the compounding quantity of a component (C) is 0.01-10 mass% with respect to a component (B). The thermally conductive silicone composition according to any one of claims 1 to 9.   The heat conductive sheet formed by shape | molding the heat conductive silicone composition of any one of Claims 1-10.