JP2011089079A - Heat conductive silicone composition and cured product of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat conductive silicone composition and a cured product of the same achieving heat conductivity of 1.5 W/mK or more and reducing wear of a reactor and a stirring blade in production and sedimentation of a heat conductive filler, preferably by skillfully combining aluminum hydroxides varying in particle size. <P>SOLUTION: The heat conductive silicone composition comprises: (A) 100 pts.mass of an organopolysiloxane having at least two alkenyl groups in the molecule; (B) an organohydrogen polysiloxane having at least two hydrogen atoms directly bonded to a silicon atom; (C) 200-2,500 pts.mass of a heat conductive filler wherein 70 mass% or more is occupied by an aluminum hydroxide; and (D) a platinum group metal curing catalyst. The content of the component (B) is set so that the number of moles of the hydrogen atoms directly bonded to the silicon atom is 0.1-5.0 times that of the alkenyl groups originated from the component (A). The content of the component (D) is 0.1-1,000 ppm in the mass terms of platinum group metal elements with respect to the component (A). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a heat conductive silicone composition useful as a heat transfer material interposed at the interface between a heat boundary surface of a heat generating electronic component and a heat radiating member such as a heat sink or a circuit board, particularly for cooling the electronic component by heat conduction. Product and its cured product.

  LSI chips such as CPUs, driver ICs, and memories used in electronic devices such as personal computers, digital video disks, and mobile phones are becoming more and more themselves as performance, speed, size, and integration increase. Heat is generated, and the temperature rise of the chip due to the heat causes malfunction and destruction of the chip. Therefore, many heat dissipating methods for suppressing the temperature rise of the chip during operation and heat dissipating members used therefor have been proposed.

Conventionally, in an electronic device or the like, a heat sink using a metal plate having a high thermal conductivity such as aluminum or copper is used in order to suppress a temperature rise of a chip during operation. The heat sink conducts heat generated by the chip and releases the heat from the surface due to a temperature difference from the outside air.
In order to efficiently transfer the heat generated from the chip to the heat sink, it is necessary to closely attach the heat sink to the chip.However, because there is a difference in the height of each chip and tolerance due to assembly processing, a flexible sheet or grease is used. It is interposed between the chip and the heat sink, and heat conduction from the chip to the heat sink is realized through this sheet or grease.
Sheets are superior in handling properties compared to grease, and heat conductive sheets (heat conductive silicone rubber sheets) formed of heat conductive silicone rubber or the like are used in various fields.

In JP-A-47-32400 (Patent Document 1), at least one selected from beryllium oxide, aluminum oxide, hydrated aluminum oxide, magnesium oxide, and zinc oxide is added to 100 parts by mass of a synthetic rubber such as silicone rubber. An insulating composition containing 100 to 800 parts by mass of a metal oxide is disclosed.
Japanese Patent Application Laid-Open No. 56-1009009 (Patent Document 2) discloses a heat-dissipating material used in a place that does not require insulation, and includes addition-curable silicone rubber compositions such as silica, silver, gold, and silicon. A composition containing 60 to 500 parts by mass of conductive powder is disclosed.

  However, all of these thermally conductive materials have low thermal conductivity, and when a large amount of thermally conductive filler is filled to improve thermal conductivity, liquid silicone rubber compositions have fluidity. In the case of a millable type silicone rubber composition, the plasticity increased, and there was a problem that all of the moldability became very poor.

  Therefore, as a method for solving this, Japanese Patent Laid-Open No. 1-66961 (Patent Document 3) discloses that 10 to 30% by mass of alumina particles having an average particle size of 5 μm or less and the average particle size of 10 μm or more of the remaining single particles. And a highly thermally conductive rubber / plastic composition filled with alumina composed of spherical corundum particles having a shape having no cutting edge. JP-A-4-328163 (Patent Document 4) discloses a gum-like organopolysiloxane having an average degree of polymerization of 6,000 to 12,000 and an oil-like organopolysiloxane having an average degree of polymerization of 200 to 2,000. A thermally conductive silicone rubber composition comprising a base combined with 500 and 1,200 parts by mass of spherical aluminum oxide powder is disclosed.

  However, even when these methods are used, for example, when aluminum oxide powder is highly filled with 1,000 parts by mass or more (aluminum oxide is 70% by volume or more), molding processability can be achieved only by combining particles and adjusting the viscosity of the silicone base. There was a limit to improvement.

  On the other hand, as electronic devices such as personal computers, word processors, and CD-ROM drives have become highly integrated, the amount of heat generated by integrated circuit elements such as LSIs and CPUs in the apparatus has increased, so conventional cooling methods may not be sufficient. is there. In particular, in the case of a portable laptop personal computer, a large heat sink or cooling fan cannot be attached because the space inside the device is narrow. Furthermore, in these devices, an integrated circuit element is mounted on a printed circuit board, and glass reinforced epoxy resin or polyimide resin having poor thermal conductivity is used as the material of the circuit board. Heat cannot escape to the substrate.

Therefore, a system is used in which a natural cooling type or forced cooling type heat dissipating part is installed in the vicinity of the integrated circuit element and the heat generated in the element is transmitted to the heat dissipating part. If the element and the heat dissipation component are brought into direct contact with this method, the heat transfer will be worse due to the unevenness of the surface, and the heat dissipation insulation sheet will be slightly less flexible even if it is attached via a heat dissipation insulation sheet. There is a risk of stress being applied between the substrate and the substrate.
In addition, if a heat dissipation component is attached to each circuit element, an extra space is required, which makes it difficult to reduce the size of the device. Therefore, a cooling method may be adopted in which several elements are combined into one heat dissipation component. .
In particular, a BGA type CPU used in a notebook personal computer has a low height and a large amount of heat generation compared to other elements, and thus a cooling method must be sufficiently considered.

  Therefore, a low-hardness and high-heat conductive material that can fill various gaps caused by different heights for each element is required. There is a need for a thermal conductive sheet that is excellent in thermal conductivity, flexible, and can cope with various gaps. In addition, as the driving frequency is increased year by year, the CPU performance is improved and the amount of heat generation is increased. Therefore, a material having higher thermal conductivity is demanded.

  In this case, in Japanese Patent Laid-Open No. 2-196453 (Patent Document 5), a silicone sheet in which a heat conductive material such as a metal oxide is mixed with a silicone resin, which has a strength necessary for handling. A sheet in which a soft and easily deformable silicone layer is laminated on a resin layer is disclosed. Japanese Patent Application Laid-Open No. 7-266356 (Patent Document 6) discloses a porous material containing a heat conductive filler and having a silicone rubber layer having an Asker C hardness of 5 to 50 and pores having a diameter of 0.3 mm or more. A thermally conductive composite sheet combining a reinforcing material layer is disclosed. Japanese Patent Application Laid-Open No. 8-238707 (Patent Document 7) discloses a sheet in which a skeleton lattice surface of a flexible three-dimensional network or foam is coated with a heat conductive silicone rubber. Japanese Patent Application Laid-Open No. 9-1738 (Patent Document 8) has a thickness 0 in which a reinforcing sheet or cloth is incorporated, at least one surface is adhesive, and Asker C hardness is 5 to 50. A thermally conductive composite silicone sheet of 4 mm or less is disclosed. Japanese Patent Application Laid-Open No. 9-296114 (Patent Document 9) contains an addition reaction type liquid silicone rubber and a heat conductive insulating ceramic powder. The cured product has an Asker C hardness of 25 or less and a thermal resistance of 3.0. A heat dissipating spacer having a temperature of ℃ / W or less is disclosed.

  In these thermally conductive silicone cured products, when the thermal conductivity is in the range of 0.5 to 3 W / m · K, aluminum oxide (alumina) is often mainly used as the thermally conductive filler. However, alumina has a very high Mohs hardness of 9 as used in abrasives. For this reason, when a share is applied during the production of the thermally conductive silicone composition, there is a problem that the inner wall of the reaction kettle and the stirring blades are scraped off. Then, the components of the reaction kettle and the stirring blade are mixed into the thermally conductive silicone composition. In addition, the clearance between the reaction kettle and the stirring blade is widened, the stirring efficiency is lowered, and even if it is manufactured under the same conditions, a certain quality cannot be obtained. In addition, in order to prevent this, there is a problem that parts must be frequently replaced.

  Furthermore, since alumina has a very high specific gravity of 3.98, thermal conductivity is 1.5 W / m · K or more, and among the thermally conductive fillers, more than 70% by mass is occupied by alumina. If the silicone composition is allowed to stand, sedimentation of the thermally conductive filler occurs. If sedimentation occurs, the composition will have a different moldability and the product cannot be produced stably. If the stirring and mixing is performed again before using the thermally conductive silicone composition, the sedimentation can be eliminated, but the cost and time are also increased.

  In recent years, devices have been reduced in size and weight. In order to reduce the weight of the entire device, there is a demand for lighter weight while maintaining performance in units of grams or milligrams in terms of members. Thermally conductive silicone compositions having a thermal conductivity of 1.5 W / m · K or more and 70% by mass of the thermally conductive filler with alumina are disadvantageous from the viewpoint of weight reduction because of their large specific gravity. It is.

  Examples of thermally conductive fillers other than alumina include aluminum, copper, silver, boron nitride, and aluminum nitride, but they are very expensive compared to alumina and have a thermal conductivity of 0.5 to 3.0 W / m ·. It is difficult to use for K heat conductive resin compound from the viewpoint of cost. Furthermore, when aluminum, copper, silver, or the like is used, the insulating properties of the heat conductive silicone composition and the cured product are lowered.

  It is inexpensive and has a specific gravity of 2.42, which is considerably smaller than that of alumina, can suppress sedimentation of the thermally conductive filler of the silicone composition, contributes to weight reduction of the equipment, and has a Mohs hardness of 3 compared to alumina. Aluminum hydroxide is an example of a heat conductive filler that is very soft and that suppresses the wear of the reaction kettle and stirring blades and has a flame-retardant and insulating effect. However, since aluminum hydroxide has a lower thermal conductivity than alumina, in order to increase the thermal conductivity of the silicone thermal conductive composition and the cured product using aluminum hydroxide, it is necessary to fill aluminum hydroxide at a high level. Despite the fact that it does not become, the shape is only crushed and high filling is very difficult. Therefore, a thermal conductivity of 1.5 W / m · K or more is achieved with a thermally conductive silicone cured product in which 70% by mass or more of the total mass part of the thermally conductive filler has been occupied by aluminum hydroxide. Has been considered difficult.

JP 47-32400 A JP-A-56-100849 JP-A-1-69661 JP-A-4-328163 Japanese Patent Laid-Open No. 2-196453 JP-A-7-266356 JP-A-8-238707 Japanese Patent Laid-Open No. 9-1738 JP-A-9-296114

  The present invention has been made in view of the above circumstances, and 70% by mass or more of the total mass part of the heat conductive filler is occupied by aluminum hydroxide, and is installed, for example, between a heat generating component and a heat dissipation component in an electronic device. It is an object of the present invention to provide a thermally conductive silicone composition suitably used as a thermally conductive resin molding used for heat dissipation and a cured product thereof.

  As a result of intensive studies to achieve the above object, the present inventors have paid attention to various characteristics of aluminum hydroxide, and 70% by mass or more of the total mass part of the thermally conductive filler is occupied by aluminum hydroxide. Preferably used, a small particle size aluminum hydroxide having an average particle size of 0.1 μm or more and less than 5 μm, a medium particle size aluminum hydroxide of 5 μm or more and less than 40 μm, and a large particle size of 40 μm or more and 100 μm or less. It has been found that a heat conductive silicone cured product having a heat conductivity of 1.5 W / m · K or more can be obtained by skillfully combining the mixing ratio of aluminum hydroxide, and the present invention has been made.

（式中、Ｒ⁴は独立に炭素原子数１〜６のアルキル基であり、ｃは５〜１００の整数である。）
で表される分子鎖片末端がトリアルコキシシリル基で封鎖されたジメチルポリシロキサンからなる群から選ばれる少なくとも１種：０．０１〜５０質量部
を含有することを特徴とする請求項１又は２に記載の熱伝導性シリコーン組成物。
請求項４：
更に、（Ｇ）成分：下記一般式（３）

（式中、Ｒ⁵は独立に炭素原子数１〜１０の脂肪族不飽和結合を含まない１価炭化水素基、ｄは５〜２，０００の整数である。）
で表される２５℃における動粘度が１０〜１００，０００ｍｍ²／ｓのオルガノポリシロキサンを含有することを特徴とする請求項１〜３のいずれか１項に記載の熱伝導性シリコーン組成物。
請求項５：
絶対粘度が８００Ｐａ・ｓ以下である請求項１〜４のいずれか１項に記載の熱伝導性シリコーン組成物。
請求項６：
請求項１〜５のいずれか１項に記載の熱伝導性シリコーン組成物を硬化させてなる熱伝導性シリコーン硬化物。 Therefore, this invention provides the following heat conductive silicone composition and its hardened | cured material.
Claim 1:
(A) Organopolysiloxane having at least two alkenyl groups in the molecule: 100 parts by mass
(B) Organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to silicon atoms: The number of moles of hydrogen atoms directly bonded to silicon atoms is 0.1 to the number of moles of alkenyl groups derived from component (A). 5.0 times the amount,
(C) Thermally conductive filler in which 70% by mass or more is occupied by aluminum hydroxide: 200 to 2,500 parts by mass,
(D) Platinum group metal-based curing catalyst: 0.1 to 1,000 ppm in terms of mass of platinum group metal element with respect to component (A)
A thermally conductive silicone composition comprising:
Claim 2:
Aluminum hydroxide contained in the component (C)
(C-1) 15 to 25% by mass of aluminum hydroxide having an average particle size of 0.1 μm or more and less than 5 μm
(C-2) 35 to 45% by mass of aluminum hydroxide having an average particle size of 5 μm or more and less than 40 μm
(C-3) 35 to 45% by mass of aluminum hydroxide having an average particle size of 40 μm or more and 100 μm or less
A thermally conductive silicone composition characterized by being a mixture of
Claim 3:
Furthermore, as component (F),
(F-1) Component: The following general formula (1)
R ¹ _a R ² _b Si (OR ³ ) _4-ab (1)
Wherein R ¹ is independently an alkyl group having 6 to 15 carbon atoms, R ² is independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, and R ³ is independently And an alkyl group having 1 to 6 carbon atoms, a is an integer of 1 to 3, b is an integer of 0 to 2, provided that a + b is an integer of 1 to 3.)
And (F-2) component: the following general formula (2)

(In the formula, R ⁴ is independently an alkyl group having 1 to 6 carbon atoms, and c is an integer of 5 to 100.)
The molecular chain fragment terminal represented by the above formula contains at least one selected from the group consisting of dimethylpolysiloxane blocked with a trialkoxysilyl group: 0.01 to 50 parts by mass. The heat conductive silicone composition as described in 2. above.
Claim 4:
Furthermore, component (G): the following general formula (3)

(In the formula, R ⁵ is a monovalent hydrocarbon group that does not contain an aliphatic unsaturated bond having 1 to 10 carbon atoms, and d is an integer of 5 to 2,000.)
The heat conductive silicone composition according to any one of claims 1 to 3, further comprising an organopolysiloxane having a kinematic viscosity at 25 ° C represented by 10 to 100,000 mm ² / s.
Claim 5:
The heat conductive silicone composition according to any one of claims 1 to 4, wherein the absolute viscosity is 800 Pa · s or less.
Claim 6:
The heat conductive silicone hardened | cured material formed by hardening | curing the heat conductive silicone composition of any one of Claims 1-5.

  The heat conductive silicone composition and the cured product of the present invention particularly preferably have a heat conductivity of 1.5 W / m · K or more by skillfully combining aluminum hydroxides having different particle sizes, It is possible to provide a thermally conductive silicone composition and a cured product that can suppress the abrasion of the reaction kettle and the stirring blades and settling of the thermally conductive filler, and further reduce the weight of the material per volume.

The thermally conductive silicone composition of the present invention is
(A) an alkenyl group-containing organopolysiloxane,
(B) organohydrogenpolysiloxane,
(C) a thermally conductive filler,
(D) A platinum group metal-based curing catalyst is contained as an essential component.

[Organopolysiloxane]
The alkenyl group-containing organopolysiloxane as component (A) is an organopolysiloxane having two or more alkenyl groups bonded to silicon atoms in one molecule, and serves as a main component of the cured product of the present invention. Usually, the main chain part is generally composed of repeating diorganosiloxane units, but this may be a part of the molecular structure containing a branched structure or cyclic. However, linear diorganopolysiloxane is preferred from the viewpoint of physical properties such as mechanical strength of the cured product.

  The functional group other than the alkenyl group bonded to the silicon atom is an unsubstituted or substituted monovalent hydrocarbon group, for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl. Group, pentyl group, neopentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, dodecyl group and other alkyl groups, cyclopentyl group, cyclohexyl group, cycloheptyl group and other cycloalkyl groups, phenyl group, tolyl group Aryl groups such as xylyl group, naphthyl group, biphenylyl group, aralkyl groups such as benzyl group, phenylethyl group, phenylpropyl group, methylbenzyl group, and part of hydrogen atoms having carbon atoms bonded to these groups Or a group in which all of them are substituted with a halogen atom such as fluorine, chlorine or bromine, a cyano group or the like For example, chloromethyl group, 2-bromoethyl group, 3-chloropropyl group, 3,3,3-trifluoropropyl group, chlorophenyl group, fluorophenyl group, cyanoethyl group, 3,3,4,4,5,5, 6,6,6-nonafluorohexyl group and the like are mentioned, typical ones having 1 to 10 carbon atoms, particularly typical ones having 1 to 6 carbon atoms, preferably methyl group An unsubstituted or substituted alkyl group having 1 to 3 carbon atoms such as ethyl group, propyl group, chloromethyl group, bromoethyl group, 3,3,3-trifluoropropyl group, cyanoethyl group, and phenyl group, chlorophenyl group, An unsubstituted or substituted phenyl group such as a fluorophenyl group. Moreover, it is not limited that all functional groups other than the alkenyl group bonded to the silicon atom are the same.

  Examples of the alkenyl group include those having usually about 2 to 8 carbon atoms such as vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, hexenyl group and cyclohexenyl group. And a lower alkenyl group such as an allyl group is preferable, and a vinyl group is particularly preferable. In addition, although it is preferable that two or more alkenyl groups exist in the molecule, it is preferable that the alkenyl group is bonded only to the silicon atom at the end of the molecular chain in order to make the obtained cured product flexible.

Kinematic viscosity at 25 ° C. This organopolysiloxane is usually, 10~100,000mm ² / s, particularly preferably from 500~50,000mm ² / s. If the viscosity is too low, the storage stability of the resulting composition will be poor, and if it is too high, the extensibility of the resulting composition may be poor. The kinematic viscosity is a value when using an Ostwald viscometer.

  This organopolysiloxane of component (A) may be used alone or in combination of two or more having different viscosities.

[Organohydrogenpolysiloxane]
The organohydrogenpolysiloxane of component (B) is an organohydrogenpolysiloxane having a hydrogen atom (Si-H group) directly bonded to 2 or more, preferably 2 to 100 silicon atoms on average in one molecule. It is a component that acts as a crosslinking agent for component (A). That is, the Si—H group in the component (B), the alkenyl group in the component (A) and the hydrosilylation reaction promoted by the platinum group metal-based curing catalyst of the component (D) described later are added to form a crosslinked structure. A three-dimensional network structure is provided. In addition, when the number of Si-H groups is less than one, there exists a possibility that it may not harden | cure.

（式中、Ｒ⁶は独立に脂肪族不飽和結合を含有しない非置換又は置換の１価炭化水素基あるいは水素原子であるが、少なくとも２個は水素原子であり、ｎは１以上の整数である。） As the organohydrogenpolysiloxane, one represented by the following average structural formula (4) is used, but is not limited thereto.

(In the formula, R ⁶ independently represents an unsubstituted or substituted monovalent hydrocarbon group or hydrogen atom that does not contain an aliphatic unsaturated bond, but at least two are hydrogen atoms, and n is an integer of 1 or more. is there.)

In the formula (4), examples of the unsubstituted or substituted monovalent hydrocarbon group not containing an aliphatic unsaturated bond other than hydrogen of R ⁶ include, for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl Group, tert-butyl group, pentyl group, neopentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, alkyl group such as dodecyl group, cycloalkyl group such as cyclopentyl group, cyclohexyl group, cycloheptyl group, Carbon groups are bonded to aryl groups such as phenyl, tolyl, xylyl, naphthyl, and biphenylyl, aralkyl groups such as benzyl, phenylethyl, phenylpropyl, and methylbenzyl, and these groups. Some or all of the hydrogen atoms are substituted with halogen atoms such as fluorine, chlorine and bromine, cyano groups, etc. For example, chloromethyl group, 2-bromoethyl group, 3-chloropropyl group, 3,3,3-trifluoropropyl group, chlorophenyl group, fluorophenyl group, cyanoethyl group, 3,3,4,4,5,5 , 6,6,6-nonafluorohexyl group, etc., typical ones having 1 to 10 carbon atoms, particularly typical ones having 1 to 6 carbon atoms, preferably methyl Groups, ethyl groups, propyl groups, chloromethyl groups, bromoethyl groups, 3,3,3-trifluoropropyl groups, cyanoethyl groups, etc., unsubstituted or substituted alkyl groups having 1 to 3 carbon atoms and phenyl groups, chlorophenyl groups , An unsubstituted or substituted phenyl group such as a fluorophenyl group. Further, R ⁶ is not limited to being all the same.

  Component (B) is added in an amount such that the Si-H group derived from component (B) is 0.1 to 5.0 moles per mole of alkenyl group derived from component (A), preferably 0.3. -2.0 mol, more preferably 0.5-1.0 mol. When the amount of the Si-H group derived from the component (B) is less than 0.1 mol relative to 1 mol of the alkenyl group derived from the component (A), the cured product does not have sufficient strength or the molded product has insufficient strength. The shape may not be retained and may not be handled. Moreover, when it exceeds 5 mol, the flexibility of the cured product is lost, and the cured product may become brittle.

[Thermal conductive filler]
(C) The heat conductive filler which is a component is aluminum hydroxide or aluminum hydroxide and another heat conductive filler. In this case, the aluminum hydroxide needs to occupy 70% by mass or more of the total amount of the thermally conductive filler, preferably 75% by mass or more, more preferably 80% by mass or more, and may be 100% by mass.

Aluminum hydroxide is
(C-1) 15 to 25% by mass of aluminum hydroxide having an average particle size of 0.1 μm or more and less than 5 μm
(C-2) 35 to 45% by mass of aluminum hydroxide having an average particle size of 5 μm or more and less than 40 μm
(C-3) 35 to 45% by mass of aluminum hydroxide having an average particle size of 40 μm or more and 100 μm or less
It is preferable that it is a mixture of the ratio.
The average particle diameter is a volume-based cumulative average particle diameter (median diameter) measured by Microtrac MT3300EX, a particle size analyzer manufactured by Nikkiso Co., Ltd.

  On the other hand, other heat conductive fillers include, for example, non-magnetic metals such as copper and aluminum, metal oxides such as alumina, silica, magnesia, bengara, beryllia, titania, zirconia, aluminum nitride, silicon nitride, and nitride. A material generally used as a heat conductive filler such as a metal nitride such as boron, a metal hydroxide such as magnesium hydroxide, artificial diamond, or silicon carbide can be used. Moreover, 0.1-200 micrometers can be used for a particle size, You may use 1 type or in combination of 2 or more types.

  (C) The compounding quantity of a component needs to be 200-2500 mass parts with respect to 100 mass parts of (A) component, Preferably it is 300-1,500 mass parts. When the blending amount is less than 200 parts by mass, the resulting composition has poor thermal conductivity and may have poor storage stability. When it exceeds 2,500 parts by mass, the composition The extensibility of the resin may be poor and the molded product may be weak.

[Platinum group metal curing catalyst]
The (D) component platinum group metal-based curing catalyst is a catalyst for accelerating the addition reaction of the (A) component-derived alkenyl group and the (B) component-derived Si—H group, and is used for the hydrosilylation reaction. Well-known catalysts are mentioned as the catalyst to be used. Specific examples thereof include platinum group metals such as platinum (including platinum black), rhodium and palladium, H ₂ PtCl ₄ · nH ₂ O, H ₂ PtCl ₆ · nH ₂ O, NaHPtCl ₆ · nH ₂ O. , KaHPtCl 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 (where, n is an integer of 0 to 6, preferably 0 or 6.) Chlorine chloroplatinic acid and chloroplatinic acid salt, alcohol-modified chloroplatinic acid (US Pat. No. 3,220,972) ), Complex of chloroplatinic acid and olefin (see US Pat. Nos. 3,159,601, 3,159,662, and 3,775,452), platinum black Platinum group gold such as palladium Genus supported on a support such as alumina, silica, carbon, rhodium-olefin complex, chlorotris (triphenylphosphine) rhodium (Wilkinson catalyst), platinum chloride, chloroplatinic acid or chloroplatinate and vinyl group-containing siloxane In particular, a complex with a vinyl group-containing cyclic siloxane may be mentioned.

  The amount of component (D) used may be a so-called catalytic amount, and usually about 0.1 to 1,000 ppm in terms of the mass of the platinum group metal element relative to component (A).

[Reaction control agent]
As the component (E), an addition reaction control agent can be used. As the addition reaction control agent, all known addition reaction control agents used in ordinary addition reaction curable silicone compositions can be used. Examples thereof include acetylene compounds such as 1-ethynyl-1-hexanol and 3-butyn-1-ol, various nitrogen compounds, organic phosphorus compounds, oxime compounds, and organic chloro compounds. As a usage-amount, about 0.01-1 mass part is desirable with respect to 100 mass parts of (A) component.

[Surface treatment agent]
In the composition of the present invention, the thermally conductive filler as component (C) is hydrophobized during preparation of the composition to improve the wettability with the organopolysiloxane as component (A). In order to uniformly disperse the thermally conductive filler as described above in the matrix composed of the component (A), a surface treating agent of the component (F) can be blended. As the component (F), the following components (F-1) and (F-2) are particularly preferable.

(F-1) Component: The following general formula (1)
R ¹ _a R ² _b Si (OR ³ ) _4-ab (1)
Wherein R ¹ is independently an alkyl group having 6 to 15 carbon atoms, R ² is independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, and R ³ is independently And an alkyl group having 1 to 6 carbon atoms, a is an integer of 1 to 3, b is an integer of 0 to 2, provided that a + b is an integer of 1 to 3.)
It is the alkoxysilane compound represented by these.

In the general formula (1), examples of the alkyl group represented by R ¹ include a hexyl group, an octyl group, a nonyl group, a decyl group, a dodecyl group, and a tetradecyl group. When the number of carbon atoms of the alkyl group represented by R ¹ satisfies the range of 6 to 15, the wettability of the component (A) is sufficiently improved, the handleability is good, and the low temperature characteristics of the composition are good. Become.
Examples of the unsubstituted or substituted monovalent hydrocarbon group represented by R ² include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a neopentyl group, Hexyl, heptyl, octyl, nonyl, decyl, dodecyl and other alkyl groups, cyclopentyl, cyclohexyl, cycloheptyl and other cycloalkyl groups, phenyl, tolyl, xylyl, naphthyl, biphenylyl An aryl group such as a group, an aralkyl group such as a benzyl group, a phenylethyl group, a phenylpropyl group, and a methylbenzyl group, and a part or all of the hydrogen atoms having a carbon atom bonded to these groups are fluorine, chlorine, Groups substituted with halogen atoms such as bromine, cyano groups, etc., such as chloromethyl group, 2-bromoe Group, 3-chloropropyl group, 3,3,3-trifluoropropyl group, chlorophenyl group, fluorophenyl group, cyanoethyl group, 3,3,4,4,5,5,6,6,6-nonafluoro A hexyl group, etc., typical ones having 1 to 10 carbon atoms, particularly typical ones having 1 to 6 carbon atoms, preferably methyl, ethyl, propyl, chloro Unsubstituted or substituted alkyl group having 1 to 3 carbon atoms such as methyl group, bromoethyl group, 3,3,3-trifluoropropyl group, and cyanoethyl group, and unsubstituted or substituted phenyl group, chlorophenyl group, fluorophenyl group, etc. A substituted phenyl group may be mentioned.

（式中、Ｒ⁴は独立に炭素原子数１〜６のアルキル基であり、ｃは５〜１００、好ましくは５〜７０、特に１０〜５０の整数である。）
で表される分子鎖片末端がトリアルコキシシリル基で封鎖されたジメチルポリシロキサンである。
上記一般式（２）において、Ｒ⁴で表されるアルキル基は、上記一般式（１）中のＲ³で表されるアルキル基と同種のものである。 (F-2) Component: The following general formula (2)

(In the formula, R ⁴ is independently an alkyl group having 1 to 6 carbon atoms, and c is an integer of 5 to 100, preferably 5 to 70, particularly 10 to 50.)
Is a dimethylpolysiloxane in which one end of a molecular chain represented by is blocked with a trialkoxysilyl group.
In the general formula (2), the alkyl group represented by R ⁴ is the same type as the alkyl group represented by R ³ in the general formula (1).

  As the surface treating agent for the component (A), any one of the component (F-1) and the component (F-2) may be combined. In this case, the component (F) is preferably 0.01 to 50 parts by mass, particularly 0.1 to 30 parts by mass with respect to 100 parts by mass of the component (A). Increasing the proportion of this component can induce oil separation.

（式中、Ｒ⁵は独立に炭素原子数１〜１０の脂肪族不飽和結合を含まない１価炭化水素基、ｄは５〜２，０００の整数である。）
で表される２５℃における動粘度が１０〜１００，０００ｍｍ²／ｓのオルガノポリシロキサンを添加することができる。（Ｇ）成分は、熱伝導性シリコーン組成物の粘度調整剤等の特性付与を目的として適宜用いられるが、限定されるものではない。１種単独で用いても、２種以上を併用してもよい。 [Organopolysiloxane]
As the component (G), the following general formula (3)

(In the formula, R ⁵ is a monovalent hydrocarbon group that does not contain an aliphatic unsaturated bond having 1 to 10 carbon atoms, and d is an integer of 5 to 2,000.)
An organopolysiloxane having a kinematic viscosity of 10 to 100,000 mm ² / s at 25 ° C. represented by The component (G) is appropriately used for the purpose of imparting properties such as a viscosity modifier of the heat conductive silicone composition, but is not limited thereto. One type may be used alone, or two or more types may be used in combination.

R ⁵ is independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms. Examples of R ⁵ include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group. Alkyl groups such as dodecyl group, cycloalkyl groups such as cyclopentyl group, cyclohexyl group and cycloheptyl group, aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group and biphenylyl group, benzyl group, phenylethyl group, phenylpropyl group Groups in which some or all of the hydrogen atoms bonded to carbon atoms are substituted with halogen atoms such as fluorine, chlorine or bromine, cyano groups, etc. For example, chloromethyl group, 2-bromoethyl group, 3-chloropropyl group, 3, 3, 3 Examples include trifluoropropyl group, chlorophenyl group, fluorophenyl group, cyanoethyl group, 3,3,4,4,5,5,6,6,6-nonafluorohexyl group, etc. 1-10, particularly typical ones having 1-6 carbon atoms, preferably methyl, ethyl, propyl, chloromethyl, bromoethyl, 3,3,3-trifluoropropyl Group, an unsubstituted or substituted alkyl group having 1 to 3 carbon atoms such as a cyanoethyl group, and an unsubstituted or substituted phenyl group such as a phenyl group, a chlorophenyl group, and a fluorophenyl group, particularly a methyl group and a phenyl group Is preferred.
From the viewpoint of the required viscosity, d is preferably an integer of 5 to 2,000, and particularly preferably an integer of 10 to 1,000.

Further, the kinematic viscosity at 25 ° C., preferably 10~100,000mm ² / s, it is preferable in particular 100~10,000mm ² / s. When the kinematic viscosity is lower than 10 mm ² / s, the cured product of the resulting composition tends to generate oil bleeding. If the kinematic viscosity is greater than 100,000 mm ² / s, the flexibility of the resulting heat conductive silicone composition tends to be poor.

  (G) When adding a component to the heat conductive silicone composition of this invention, the addition amount is not limited, What is necessary is just the quantity from which a desired effect is acquired, (A) With respect to 100 mass parts of component The amount is preferably 0.1 to 100 parts by mass, more preferably 1 to 50 parts by mass. When the addition amount is within this range, it is easy to maintain good fluidity and workability in the thermally conductive silicone composition before curing, and the composition is filled with the thermally conductive filler of component (C). Easy to do.

[Viscosity of composition]
The viscosity of the thermally conductive silicone composition at 25 ° C. is 800 Pa · s or less, preferably 400 Pa · s or less, more preferably 200 Pa · s or less, and particularly preferably 100 Pa · s or less. This viscosity is based on measurement with a B-type viscometer.

[Method for producing thermally conductive silicone cured product]
The curing conditions for molding the thermally conductive silicone composition may be the same as those of a known addition reaction curable silicone rubber composition. For example, it is sufficiently cured at room temperature, but may be heated as necessary. Preferably, the addition curing is performed at 100 to 120 ° C. for 8 to 12 minutes. Such a molded product of the present invention is excellent in thermal conductivity.

[Thermal conductivity of molded body]
As for the thermal conductivity of the molded product in the present invention, the measured value at 25 ° C. measured by the hot disk method is preferably 1.5 W / m · K or more. When the thermal conductivity is less than 1.5 W / m · K, application to a heating element having a large calorific value becomes impossible. Note that such thermal conductivity can be adjusted by adjusting the combination of the type and particle size of the thermally conductive filler.

[Hardness of molded body]
The hardness of the molded product in the present invention is preferably 60 or less, preferably 30 or less, more preferably 20 or less, and further 10 or less as measured at 25 ° C. measured with an Asker C hardness meter. When the hardness exceeds 60, it may be difficult to exhibit good heat dissipation characteristics without applying stress to the heat radiating body due to deformation along the shape of the heat radiating body. Such hardness can be adjusted by changing the ratio of the component (A) and the component (B) to adjust the crosslinking density.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example. The kinematic viscosity was measured with an Ostwald viscometer at 25 ° C. The average particle diameter is a volume-based cumulative average particle diameter (median diameter) measured by Microtrac MT3300EX, a particle size analyzer manufactured by Nikkiso Co., Ltd.

（Ｘはビニル基であり、ｎは下記粘度を与える数である。）
（Ａ−１）動粘度：６００ｍｍ²／ｓ
（Ａ−２）動粘度：３０，０００ｍｍ²／ｓ [Preparation of composition]
The components (A) to (F) used in the following examples and comparative examples are shown below.
(A) component:
Organopolysiloxane represented by the following formula (5).

(X is a vinyl group, and n is a number giving the following viscosity.)
(A-1) Kinematic viscosity: 600 mm ² / s
(A-2) Kinematic viscosity: 30,000 mm ² / s

（平均重合度：ｏ＝２８、ｐ＝２） (B) component:
Hydrogen polysiloxane in which both ends represented by the following formula (6) are blocked with hydrogen.

(Average polymerization degree: o = 28, p = 2)

Component (C):
Aluminum hydroxide and spherical alumina whose average particle size is as follows.
(C-1) Aluminum hydroxide having an average particle diameter of 1 μm (C-2) Aluminum hydroxide having an average particle diameter of 10 μm (C-3) Aluminum hydroxide having an average particle diameter of 50 μm (C-4) Average particle diameter Is a spherical alumina (D) component having a diameter of 70 μm:
5 mass% chloroplatinic acid 2-ethylhexanol solution (E) component:
Ethynylmethylidenecarbinol as an addition reaction control agent.

(F) component: (F-2) component The dimethylpolysiloxane by which the one terminal of the average polymerization degree 30 shown by following formula (7) was blocked with the trimethoxysilyl group.

(G) Component Dimethylpolysiloxane represented by the following formula (8) as a plasticizer.

（ｒ＝８０）

(R = 80)

Components (A), (C), (F), and (G) were added in predetermined amounts shown in Examples 1 to 7 and Comparative Examples 1 to 5 below, and kneaded for 60 minutes with a planetary mixer.
(D) component and (E) component are added in predetermined amounts shown in Examples 1 to 7 and Comparative Examples 1 to 5 below, and an effective amount of an internal release agent that further promotes release from the separator is added. Kneaded for 30 minutes.
The component (B) was further added in a predetermined amount shown in Examples 1 to 7 and Comparative Examples 1 to 5 below, and kneaded for 30 minutes to obtain a composition.

[Molding method]
The obtained composition was poured into a 60 mm × 60 mm × 6 mm mold and molded using a press molding machine at 120 ° C. for 10 minutes.
[Evaluation methods]
Thermal conductivity:
The compositions obtained in Examples 1 to 7 and Comparative Examples 1 to 5 below were cured into a 6 mm thick sheet at 120 ° C. for 10 minutes, and two sheets were used to produce a thermal conductivity meter (product Name: TPA-501, manufactured by Kyoto Electronics Co., Ltd.), the thermal conductivity of the sheet was measured.
hardness:
The compositions obtained in the following Examples 1 to 7 and Comparative Examples 1 to 5 were cured into a 6 mm thick sheet in the same manner as described above, and the two sheets were stacked and measured with an Asker C hardness meter.
Specific gravity (density):
Measurements were made using the underwater displacement method.
Settling of thermally conductive filler:
At the stage of preparing the composition according to the above preparation method, when the components (A), (C), (F), (G), (D), and (E) were added, that is, components other than the component (B) were added. The composition at that time was allowed to stand in a container, and when it was allowed to stand at room temperature for 1 month, it was judged as “Yes” if sedimentation of the thermally conductive filler was observed, and “No” if not observed.

[Examples 1-7 and Comparative Examples 1-5]
As shown in Table 1, in Examples 1-7 and Comparative Examples 1-5, compositions (A) to (G) were prepared using predetermined amounts and cured, and the thermal conductivity according to the above method, The hardness, specific gravity (density), and sedimentation of the thermally conductive filler were measured or observed.

  When the total mass part of the thermally conductive filler was 100 parts by mass as in Comparative Examples 1 and 2, the density of the composition was low, and no precipitation of the thermally conductive filler was observed, but the thermal conductivity was 0. .6 W / m · K, which is very low. When a thermally conductive silicone composition was prepared using only alumina without using aluminum hydroxide as in Comparative Example 3, the density increased to 2.6, and sedimentation of the thermally conductive filler was observed. Moreover, when the mass% of aluminum hydroxide is less than 70 mass% in the total mass part of the thermally conductive filler as in Comparative Example 4, the thermal conductivity is increased, but the density is increased to 2.4, Sedimentation of the thermally conductive filler was observed. As in the examples, when aluminum hydroxide accounted for 70% by mass of the total mass part of the thermally conductive filler, no sedimentation was observed regardless of the total mass part of the thermally conductive filler.

Claims (6)

(A) Organopolysiloxane having at least two alkenyl groups in the molecule: 100 parts by mass
(B) Organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to silicon atoms: The number of moles of hydrogen atoms directly bonded to silicon atoms is 0.1 to the number of moles of alkenyl groups derived from component (A). 5.0 times the amount,
(C) Thermally conductive filler in which 70% by mass or more is occupied by aluminum hydroxide: 200 to 2,500 parts by mass,
(D) Platinum group metal-based curing catalyst: 0.1 to 1,000 ppm in terms of mass of platinum group metal element with respect to component (A)
A thermally conductive silicone composition comprising: Aluminum hydroxide contained in the component (C)
(C-1) 15 to 25% by mass of aluminum hydroxide having an average particle size of 0.1 μm or more and less than 5 μm
(C-2) 35 to 45% by mass of aluminum hydroxide having an average particle size of 5 μm or more and less than 40 μm
(C-3) 35 to 45% by mass of aluminum hydroxide having an average particle size of 40 μm or more and 100 μm or less
A thermally conductive silicone composition characterized by being a mixture of Furthermore, as component (F),
(F-1) Component: The following general formula (1)
R ¹ _a R ² _b Si (OR ³ ) _4-ab (1)
Wherein R ¹ is independently an alkyl group having 6 to 15 carbon atoms, R ² is independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, and R ³ is independently And an alkyl group having 1 to 6 carbon atoms, a is an integer of 1 to 3, b is an integer of 0 to 2, provided that a + b is an integer of 1 to 3.)
And (F-2) component: the following general formula (2)

(In the formula, R ⁴ is independently an alkyl group having 1 to 6 carbon atoms, and c is an integer of 5 to 100.)
The molecular chain fragment terminal represented by the above formula contains at least one selected from the group consisting of dimethylpolysiloxane blocked with a trialkoxysilyl group: 0.01 to 50 parts by mass. The heat conductive silicone composition as described in 2. above. Furthermore, component (G): the following general formula (3)

(In the formula, R ⁵ is a monovalent hydrocarbon group that does not contain an aliphatic unsaturated bond having 1 to 10 carbon atoms, and d is an integer of 5 to 2,000.)
The thermally conductive silicone composition according to any one of claims 1 to 3, kinematic viscosity, characterized in that it contains an organopolysiloxane 10~100,000mm ² / s in the represented 25 ° C..   The heat conductive silicone composition according to any one of claims 1 to 4, wherein the absolute viscosity is 800 Pa · s or less.   The heat conductive silicone hardened | cured material formed by hardening | curing the heat conductive silicone composition of any one of Claims 1-5.