Thermally conductive silicone composition

Abstract

The thermally conductive silicone composition comprises (A) an organopolysiloxane having at least one alkenyl group having 2 to 12 carbon atoms per molecule and having a viscosity of 10 to 10,000 mPa·s at 25°C, (B) hydrophobic fumed silica, (C) at least one thermally conductive filler, and (D) at least one polyether selected from the group consisting of (D1) polytetramethylene ether glycol, (D2) alcohol-initiated ethylene oxide and propylene oxide copolymers, and (D3) polyether-modified organopolysiloxanes. The composition exhibits good shape retention and high thermal conductivity despite its easy handling and dispensability.

Description

[Technical Field]

[0001] The present invention relates to a thermally conductive silicone composition that exhibits good shape retention properties and high thermal conductivity while still being easy to handle and dispense. [Background technology]

[0002] Thermally conductive silicone compositions are widely used in various industries due to their unique properties, including excellent electrical insulation and thermal stability. Therefore, they are used as thermally conductive silicone greases, thermally conductive silicone gel compositions, thermally conductive silicone rubber compositions, and the like, in various applications, such as encapsulants or potting materials in electrical / electronic devices where higher temperatures may be required. In certain applications, thixotropy is required for the thermally conductive silicone composition to retain its shape after dispensing. It is well known that thixotropy in silicone compositions is generally achieved by adding fine fillers such as hydrophobic fumed silica or some types of organic liquid compounds having polar groups such as silanol groups, epoxy groups, amine groups, or polyether groups.

[0003] For example, Patent Document 1 discloses a silicone composition for curing silicone products, which comprises an organopolysiloxane having an average of at least two alkenyl groups per molecule, an organopolysiloxane having an average of at least two silicon-bonded hydrogen atoms per molecule, an alumina filler, a polyether, and a hydrosilylation reaction catalyst.

[0004] Patent Document 2 discloses a thermally conductive silicone composition comprising an organopolysiloxane having a viscosity of at least 500 mPa·s at 25°C, a thermally conductive filler, fine silica powder, an organopolysiloxane represented by a specific general formula and having a viscosity of less than 500 mPa·s at 25°C, and a silane compound of the specific general formula.

[0005] Patent Document 3 discloses a thermosetting thermally conductive silicone grease composition containing an organopolysiloxane having a viscosity of 100 to 100,000 mPa·s at 25°C and containing at least one alkenyl group per molecule, an organopolysiloxane having a specific general formula, an organopolysiloxane having at least two silicon-bonded hydrogen atoms per molecule, a catalyst selected from the group consisting of platinum and platinum compounds, a thermally conductive filler having a thermal conductivity of at least 10 W / m·°C, and finely divided silica.

[0006] Patent Document 4 discloses a one-component, addition-type, heat-curable, thermally conductive silicone grease composition that can be stored at room temperature and contains: an organopolysiloxane having a viscosity of 50 to 100,000 mPa·s at 25°C and at least one alkenyl group per molecule; a liquid organopolysiloxane having a viscosity of 100 mPa·s or less at 25°C and having 2 to 10 Si-H groups per molecule, and having at least one alkoxy group and / or epoxy group bonded to the silicon atom via an alkylene group; a polysiloxane having a degree of polymerization of 15 or less and a cyclic structure-containing skeleton; a photoactive platinum complex curing catalyst; a thermally conductive filler having a thermal conductivity of at least 10 W / m·°C; an organopolysiloxane having a specific general formula; and fine silica.

[0007] Patent Document 5 discloses a thermally conductive organopolysiloxane composition comprising a thermally conductive filler, a siloxane compound represented by a specific general formula, an alkoxysilane compound represented by a specific general formula, an organopolysiloxane having one or more aliphatic unsaturated groups per molecule, an organopolysiloxane having two or more silicon-bonded hydrogen atoms per molecule, a platinum-based catalyst, and, optionally, fumed silica chemically treated with a silazane compound.

[0008] However, when the viscosity of such thermally conductive silicone compositions is reduced to improve their handling and dispensing properties, the coating begins to slide off after the surface to which it is applied is considered to be in a vertical position.

[0009] Prior art documents Patent documents Patent Document 1: U.S. Patent No. 6,448,329(A) Patent Document 2: U.S. Patent Application Publication No. 2011 / 0188213(A1) Patent Document 3: U.S. Patent Application Publication No. 2015 / 0148273(A1) Patent Document 4: U.S. Patent Application Publication No. 2019 / 0085167(A1) Patent Document 5: U.S. Patent Application Publication No. 2020 / 0140736(A1) Summary of the Invention [Problem to be solved by the invention]

[0010] An object of the present invention is to provide a thermally conductive silicone composition that has excellent handleability and dispensability at a low viscosity, and that, after being applied to a surface, does not drip over time or slide off even when the surface is considered to be in a vertical position. [Means for solving the problem]

[0011] The thermally conductive silicone composition of the present invention comprises: (A) an organopolysiloxane having at least one alkenyl group having 2 to 12 carbon atoms per molecule and a viscosity at 25°C of 10 to 10,000 mPa s; (B) hydrophobic fumed silica; (C) at least one thermally conductive filler; (D) at least one polyether selected from the group consisting of (D1) polytetramethylene ether glycol, (D2) alcohol-initiated ethylene oxide and propylene oxide copolymers, and (D3) polyether-modified organopolysiloxanes; Including, The content of component (A) is in the range of 0.5 to 5 mass %, the content of component (B) is in the range of 0.01 to 0.5 mass %, the content of component (C) is at least 90 mass %, and the content of component (D) is in the range of 0.05 to 5 mass %, relative to the total amount of each composition.

[0012] In various embodiments, component (D1) is typically a polytetramethylene ether glycol represented by the following general formula: H-(OCH2CH2CH2CH2) m -OH In the formula, m is a number appropriate for giving the polytetramethylene ether glycol a number average molecular weight (Mn) of 300 to 3,000 as measured by gel permeation chromatography.

[0013] In various embodiments, component (D2) is typically an alcohol-initiated ethylene oxide and propylene oxide copolymer containing 50% to 99% by weight of propylene oxide units in the copolymer.

[0014] In various embodiments, component (D3) is a polyether-modified organopolysiloxane typically selected from polyether-grafted organopolysiloxanes or block copolymers of polyethers and organopolysiloxanes.

[0015] In various embodiments, the thermally conductive silicone composition may further comprise (E) an organopolysiloxane having at least two silicon-bonded hydrogen atoms per molecule, in an amount such that there are 0.1 to 5 moles of silicon-bonded hydrogen atoms in component (E) per mole of alkenyl groups in component (A), and (F) a hydrosilylation reaction catalyst in an amount sufficient to promote cure of the composition.

[0016] In various embodiments, the thermally conductive silicone composition may further comprise (G) a hydrosilylation reaction inhibitor in an amount sufficient to control the cure rate of the composition.

[0017] In various embodiments, the thermally conductive silicone composition may further comprise (H) a filler treating agent in an amount sufficient to treat component (C).

[0018] In various embodiments, the thermally conductive silicone composition may further comprise (I) a pigment in an amount sufficient for the composition to retain desired physical properties. [Effects of the Invention]

[0019] The thermally conductive silicone composition of the present invention exhibits good shape retention and high thermal conductivity while being easy to handle and dispense. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a schematic photograph of a long tailing observation test. [Figure 2] FIG. 1 is a schematic diagram for determining the aspect ratio (AR) at the initial stage and after standing for 24 hours. [Figure 3] 1 is a schematic photograph of a slumping resistance test. [Figure 4] 1 is a schematic photograph of a vertical holding test.

[0021] definition The terms "comprising" or "comprise" are used herein in their broadest sense to refer to and encompass the concepts of "including," "include," "consist(ing) essentially of," and "consist(ing) of." The use of "for example," "eg," "such as," and "including" to list examples does not limit the examples listed. Thus, "for example" or "such as" means "for example, but not limited to" or "such as, but not limited to," and encompasses other similar or equivalent examples. As used herein, the term "about" serves to reasonably encompass or describe slight variations in a numerical value determined by instrumental analysis or resulting from handling of a sample. Such slight variations may be as little as ±0-25, ±0-10, ±0-5, or ±0-2.5% of the numerical value. Furthermore, the term "about" applies to both numerical values ​​when relating to a range of values. Furthermore, the term "about" may be applied to numerical values ​​even when not explicitly stated.

[0022] It is understood that the appended claims are not limited to the explicit and specific compounds, compositions, or methods described in the detailed description, which may vary among specific embodiments falling within the scope of the appended claims. With respect to any Markush group relied upon herein to describe specific features or aspects of various embodiments, it should be understood that different, extraordinary, and / or unexpected results can be obtained from each element of the respective Markush group, independently of all other Markush elements. Each element of a Markush group may be relied upon individually and / or in combination to provide sufficient support for specific embodiments within the scope of the appended claims.

[0023] Any ranges and subranges relied upon in describing various embodiments of the present invention should also be understood to be within the scope of the appended claims, both individually and inclusively, and all ranges, including integer and / or fractional values, are understood to be described and contemplated therein, even if not expressly written herein. Those skilled in the art will readily recognize that the recited ranges and subranges fully describe and enable various embodiments of the present invention, and that such ranges and subranges may be further delineated into related halves, thirds, fourths, fifths, etc. As merely an example, a range "from 0.1 to 0.9" may be further delineated into a lower third, i.e., 0.1 to 0.3, a middle third, i.e., 0.4 to 0.6, and an upper third, i.e., 0.7 to 0.9, which are individually and inclusively within the scope of the appended claims and within which specific embodiments may be relied upon and provide sufficient support, individually and / or inclusively. Additionally, with respect to terms defining or modifying a range, such as "at least," "greater than," "less than," "less than or equal to," etc., such terms should be understood to include subranges and / or upper or lower limits. As another example, the range "at least 10" inherently includes subranges of at least 10 to 35, at least 10 to 25, 25 to 35, etc., each of which may be relied upon individually and / or collectively to provide sufficient support for specific embodiments within the appended claims. Finally, individual numbers within disclosed ranges may be relied upon to provide sufficient support for specific embodiments within the appended claims. For example, the range "from 1 to 9" includes various individual integers, such as 3, as well as individual numbers including decimal points (or fractions), such as 4.1, which may be relied upon to provide sufficient support for specific embodiments within the appended claims. DETAILED DESCRIPTION OF THE INVENTION

[0024] The thermally conductive silicone composition of the present invention will now be described in detail.

[0025] Component (A) is the main component of the composition and is an organopolysiloxane having at least one alkenyl group having 2 to 12 carbon atoms per molecule. Examples of the alkenyl group include vinyl, allyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, and dodecenyl groups, with vinyl being preferred. Examples of groups bonded to silicon atoms other than alkenyl groups in component (A) include alkyl groups having 1 to 12 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, heptyl, octyl, nonyl, decyl, undecyl, and dodecyl; aryl groups having 6 to 12 carbon atoms, such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups having 7 to 12 carbon atoms, such as benzyl, phenethyl, and phenylpropyl; and groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms, such as fluorine, chlorine, or bromine. Furthermore, the silicon atoms in component (A) may contain small amounts of hydroxyl or alkoxy groups, such as methoxy or ethoxy groups, as long as the objectives of the present invention are not impaired. However, the organopolysiloxane of component (A) does not have a polyether group in the molecule.

[0026] Examples of the molecular structure of component (A) include a linear structure, a linear structure with some branching, a branched structure, a cyclic structure, and a three-dimensional network structure. Component (A) may be one of organopolysiloxanes having these molecular structures, or a mixture of two or more organopolysiloxanes having these molecular structures.

[0027] Examples of component (A) include dimethylpolysiloxanes both ends of which are capped with dimethylvinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers both ends of which are capped with trimethylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers both ends of which are capped with dimethylvinylsiloxy groups, dimethylsiloxane-methylphenylsiloxane-methylvinylsiloxane copolymers both ends of which are capped with trimethylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers both ends of which are capped with silanol groups, and compounds of the formula (CH3)3SiO 1 / 2 Siloxane units represented by the formula (CH3)2(CH2=CH)SiO 1 / 2 Siloxane units represented by the formula CH3SiO 3 / 2 and siloxane units represented by the formula (CH)SiO 2 / 2 and combinations of two or more thereof.

[0028] Additionally, the viscosity of component (A) at 25°C is in the range of 10 to 10,000 mPa·s, preferably 10 to 5,000 mPa·s, alternatively 10 to 3,000 mPa·s, or alternatively 50 to 2,000 mPa·s. This is because, when the viscosity is at or above the lower limit of the aforementioned range, the mechanical properties of the cured product of the composition are improved, and when the viscosity is at or below the upper limit of the aforementioned range, the handling of the composition is improved. Note that, in this specification, the viscosity at 25°C is a value measured using a rheometer in accordance with ASTM D 1084.

[0029] The content of component (A) is in the range of 0.5 to 5 mass % based on the total amount of the composition, because when the content of component (A) is equal to or greater than the lower limit of the above range, the handleability of the composition is improved, and when the content of component (A) is equal to or less than the upper limit of the above range, the thermal conductivity of the composition is improved.

[0030] Component (B) is hydrophobic fumed silica, preferably 100 to 400 m 2 / g, or 150-400m 2 / g, or 200-400m 2 / g, because the thixotropy of the composition is improved when the BET specific surface area of ​​the fumed silica is within the above range.

[0031] The content of component (B) is 0.01 to 0.5 mass % and preferably 0.01 to 0.1 mass % based on the total weight of the composition, because when the content is equal to or greater than the lower limit of the aforementioned range, the thixotropy of the composition is improved, and when the content is equal to or less than the upper limit of the aforementioned range, the handleability and dispensability of the composition are improved.

[0032] Component (C) is at least one thermally conductive filler. For example, component (C) can be any one or any combination of more than one thermally conductive filler selected from metals, alloys, nonmetals, metal oxides, metal hydrates, or ceramics. Exemplary metals include, but are not limited to, aluminum, copper, silver, zinc, nickel, tin, indium, and lead. Exemplary nonmetals include, but are not limited to, carbon, graphite, diamond, carbon nanotubes, carbon fiber, graphene, silicon carbide, and silicon nitride. Exemplary metal oxides, metal hydroxides, and ceramics include, but are not limited to, alumina, aluminum hydroxide, aluminum nitride, boron nitride, zinc oxide, beryllium oxide, magnesium oxide, and tin oxide. Desirably, component (C) is any one or any combination of two or more selected from the group consisting of alumina, aluminum, zinc oxide, boron nitride, aluminum nitride, and aluminum oxide trihydrate.

[0033] Component (C) is preferably a thermally conductive filler having an average particle size of 0.1 μm to 50 μm. Even more preferably, component (C) is any one or combination of two or more fillers selected from aluminum oxide particles having an average size of less than 5 μm, aluminum oxide particles having an average particle size of 5 μm or more, aluminum hydroxide particles having an average size of less than 5 μm, and aluminum hydroxide particles having an average particle size of 5 μm or more. The average particle size of the filler particles is determined as the median particle size (D50) using a laser diffraction particle size analyzer (CILAS 920 Particle Size Distribution Analyzer or Beckman Coulter LS 13 320 SW) according to the operating software.

[0034] The content of component (C) is at least 90% by mass, or in the range of 90 to 95% by mass, based on the total amount of the composition, because the thermal conductivity of the composition is improved when the content is equal to or greater than the lower limit of the above range.

[0035] Component (D) is a polyether that provides a composition with excellent slumping resistance and vertical retention performance. Component (C) is at least one polyether selected from the group consisting of (D1) polytetramethylene ether glycol (hereinafter "PTMEG"), (D2) alcohol-initiated ethylene oxide and propylene oxide copolymer (hereinafter "alcohol-initiated EO / PO copolymer"), and (D3) polyether-modified organopolysiloxane that does not have an alkenyl group.

[0036] Component (D1) is typically a polytetramethylene ether glycol represented by the following general formula: H-(OCH2CH2CH2CH2) m -OH.

[0037] In the formula, m is a number appropriate for giving PTMEG the following molecular weight: Specifically, m is preferably an integer satisfying 5≦m≦50, or 5≦m≦30, or 5≦m≦20.

[0038] Although there are no limitations on the molecular weight of such PTMEG, the number average molecular weight (Mn) measured by gel permeation chromatography is preferably within the range of 300 to 3,000 or 300 to 2,500. This is because, if the molecular weight exceeds the lower limit of the above range, the dynamic physical properties of the resulting cured product will be good, while, on the other hand, if the molecular weight is below the upper limit of the above range, the coatability of the composition will be improved.

[0039] Ingredient (D1) is commercially available from Aladdin as PTMEG 1000, PTMEG 1400, and PTMEG 2000.

[0040] Component (D2) is typically an alcohol-initiated EO / PO copolymer represented by the general formula: (A) z B (Wherein A is HO—(C3H6—O) x -(C2H4-O) y - (wherein x is 8 to 40, y is 1 to 20, and z is 1 to 12), and B is hydrogen or a monovalent, divalent, or polyvalent hydrocarbon group having 3 to 18 carbon atoms).

[0041] The arrangement of the ethylene oxide units (-C2H4-O-) and propylene oxide units (-C3H6-O-) in segment A may be random or oriented in any kind of block configuration, such as a single block of ethylene oxide units and a single block of propylene oxide units.

[0042] In the above formula, x and y are the average numbers of propylene oxide units and ethylene oxide units, respectively. The value of x can be 8 to 40, 10 to 35, 15 to 30, or 20 to 28. The value of y can be 1 to 20, 1 to 18, or 1 to 16.

[0043] In the above formula, z can be 1-12, 2-10, 3-8, or 4-6.

[0044] In the above formula, the value of (x+y+z) is sufficient to give the alcohol-initiated EO / PO copolymer the following molecular weight:

[0045] In the above formula, B may have 3 to 18 carbon atoms, 3 or 12 carbon atoms, 3 to 10 carbon atoms, 3 to 8 carbon atoms, or 4 to 6 carbon atoms. When B is a monovalent or divalent hydrocarbon group, the alcohol-initiated EO / PO copolymer has a linear structure. When B is a polyvalent (e.g., trivalent or higher) hydrocarbon group, the alcohol-initiated EO / PO copolymer exhibits a branched structure. B can be a sorbitol-derived group or a glycerol-derived group.

[0046] Alcohol-initiated EO / PO copolymers can be prepared from alcohol initiators having 3 or more carbon atoms, 4 or more carbon atoms, 5 or more carbon atoms, or even 6 or more carbon atoms, but typically 18 or fewer carbon atoms, 12 or fewer carbon atoms, 10 or fewer carbon atoms, 8 or fewer carbon atoms, or even 6 or fewer carbon atoms. The alcohol initiator can be a linear or branched alcohol, preferably a branched alcohol. The alcohol initiator can be a mono-, diol-, triol-, tetrol-, pentol-, or hexol. Preferably, the alcohol initiator is a hexol. Preferably, the alcohol initiator for preparing the EO / PO copolymer is sorbitol, glycerol, or a mixture thereof. The methods and conditions used to prepare the alcohol-initiated EO / PO copolymer are well known to those skilled in the art, such as temperatures ranging from 20 to 180°C or 100 to 160°C. The preparation of alcohol-initiated EO / PO copolymers can be found, for example, in J. Herzberger et al., "Polymerization of ethylene oxide, propylene oxide, and other alkylene oxides: synthesis, novel polymer architectures, and bioconjugation," Chemical Reviews, Volume 116, Issue No. 4, pages 2170-2243 (2016).

[0047] The alcohol-initiated EO / PO copolymer may comprise propylene oxide units (as propylene oxide chains) in an amount by weight of 50% or more, 52% or more, 55% or more, 58% or more, 60% or more, 62% or more, or even 65% or more, and at the same time 99% or less, 98% or less, 97% or less, 96% or less, or even 95% or less, based on the weight of the alcohol-initiated EO / PO copolymer.

[0048] The molecular weight of such component (D2) is not limited, but is preferably greater than 2,000 g / mol, for example, 2,100 g / mol or more, 2,200 g / mol or more, 2,300 g / mol or more, 2,500 g / mol or more, 2,600 g / mol or more, 2,700 g / mol or more, 2,800 g / mol or more, 2,900 g / mol or more, 3,000 g / mol or more, 3,200 g / mol or more, 3,500 g / mol or more, 3,800 g / mol or more, 4,000 g / mol or more, 4,500 g / mol or more. or more, 5,000 g / mol or more, 5,500 g / mol or more, 6,000 g / mol or more, 6,500 g / mol or more, 7,000 g / mol or more, 7,500 g / mol or more, 8,000 g / mol or more, or even 9,000 g / mol or more, while being 20,000 g / mol or less, 19,000 g / mol or less, 18,000 g / mol or less, 17,000 g / mol or less, 16,000 g / mol or less, 15,000 g / mol or less, or even 14,000 g / mol or less. As used herein, molecular weight refers to the number average molecular weight (Mn) as determined by gel permeation chromatography, calculated by (56100 x f) / OHV, where f represents the average number of hydroxyl groups per molecule of the alcohol-initiated EO / PO copolymer (also referred to as "OH functionality"), and OHV represents the hydroxyl number of the alcohol-initiated EO / PO copolymer in mg KOH / g as determined by ASTM D4274-2011. Molecular weights above the lower end of the range provide good dynamic properties for the resulting cured product, while molecular weights below the upper end of the range provide improved coatability for the composition.

[0049] The polyether-modified organopolysiloxane of component (D3) is not limited and may be any organopolysiloxane containing at least one polyether group. The polyether groups of the polyether-modified organopolysiloxane may be present at pendant positions, terminal positions, or both pendant and terminal positions. Component (D3) is typically a polyether-modified organopolysiloxane selected from polyether-grafted organopolysiloxanes or block copolymers of polyether and organopolysiloxane. For example, the polyether group may be part of the main chain of the polyether-modified organopolysiloxane. Alternatively or additionally, the main chain of the polyether-modified organopolysiloxane may contain only siloxane (Si—O—Si) bonds, or may contain other heteroatoms such as O, N, and / or S in addition to the divalent hydrocarbon linking group. The polyether-modified organopolysiloxane may contain any combination of M, D, T, and / or Q siloxy units, but typically the polyether-modified organopolysiloxane is linear and does not contain branching due to T and / or Q units.

[0050] Component (D3) is commercially available from Sigma-Aldrich.

[0051] The content of component (D) is in the range of 0.05 to 5 mass % based on the total amount of the composition, because when it is equal to or greater than the lower limit of the aforementioned range, the anti-slumping properties and vertical retention properties of the composition are improved, and when it is equal to or less than the upper limit of the aforementioned range, the stability of the composition is improved.

[0052] The addition of a curing agent renders the composition curable. When the composition is cured by a hydrosilylation reaction, such a curing agent is comprised of (E) an organopolysiloxane having at least two silicon-bonded hydrogen atoms per molecule and (F) a hydrosilylation reaction catalyst.

[0053] Component (E) is a crosslinker for component (A) in the composition and is an organopolysiloxane containing at least two silicon-bonded hydrogen atoms per molecule. Examples of silicon-bonded groups other than hydrogen groups in component (E) include alkyl groups having 1 to 12 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, heptyl, octyl, nonyl, decyl, undecyl, and dodecyl; aryl groups having 6 to 20 carbon atoms, such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups having 7 to 20 carbon atoms, such as benzyl, phenethyl, and phenylpropyl; and groups in which some or all of the hydrogen atoms in these groups have been substituted with halogen atoms, such as fluorine, chlorine, or bromine. Furthermore, the silicon atoms in component (E) may contain small amounts of hydroxyl groups or alkoxy groups, such as methoxy groups or ethoxy groups, as long as the objective of the present invention is not impaired, provided that the organopolysiloxane of component (E) contains no polyether groups or alkenyl groups in the molecule.

[0054] Examples of the molecular structure of component (E) include a linear, partially branched linear, branched, cyclic, and three-dimensional network structure, and the molecular structure is preferably a linear, partially branched linear, branched, or three-dimensional network structure.

[0055] Examples of such component (E) include methylhydrogenpolysiloxane capped at both ends of the molecule with trimethylsiloxy groups, copolymer of dimethylsiloxane and methylhydrogensiloxane capped at both ends of the molecule with trimethylsiloxy groups, dimethylpolysiloxane capped at both ends of the molecule with dimethylhydrogensiloxane groups, copolymer of dimethylsiloxane and methylhydrogensiloxane capped at both ends of the molecule with dimethylhydrogensiloxane groups, copolymer of methylhydrogensiloxane and diphenylsiloxane capped at both ends of the molecule with trimethylsiloxy groups, copolymer of methylhydrogensiloxane, diphenylsiloxane, and dimethylsiloxane capped at both ends of the molecule with trimethylsiloxy groups, (CH3)2HSiO 1 / 2 Units and SiO 4 / 2 Copolymer consisting of units, (CH3)2HSiO 1 / 2 Units, SiO 4 / 2 Units, and (C6H5)SiO 3 / 2 Included are copolymers of units, as well as mixtures of two or more of these.

[0056] The content of component (E) is an amount that provides 0.5 to 5 moles, preferably 0.5 to 3 moles, or 0.5 to 2 moles of silicon-bonded hydrogen atoms per mole of alkenyl groups in component (A). This is because, when the content is above the lower limit of the above range, the composition is sufficiently cured. On the other hand, when the content is below the upper limit of the above range, the heat resistance of the cured product is improved.

[0057] Component (F) is a hydrosilylation catalyst for accelerating the curing of the composition. Examples of component (F) include platinum group element catalysts and platinum group element compound catalysts, and specific examples include platinum-based catalysts, rhodium-based catalysts, palladium-based catalysts, and combinations of at least two of these. Platinum-based catalysts are particularly preferred because they can dramatically accelerate the curing of the composition. Examples of these platinum catalysts include platinum fine powder; platinum black; chloroplatinic acid, alcohol-modified chloroplatinic acid; chloroplatinic acid / diolefin complex; platinum / olefin complex; platinum / carbonyl complex such as platinum bis(acetoacetate) and platinum bis(acetylacetonate); chloroplatinic acid / alkenylsiloxane complex such as chloroplatinic acid / divinyltetramethyldisiloxane complex and chloroplatinic acid / tetravinyltetramethylcyclotetrasiloxane complex; platinum / alkenylsiloxane complex such as platinum / divinyltetramethyldisiloxane complex and platinum / tetravinyltetramethylcyclotetrasiloxane complex; complex of chloroplatinic acid and acetylene alcohol; and mixtures of two or more of these.In particular, platinum-alkenylsiloxane complex is preferred because it can accelerate the curing of the composition.

[0058] Examples of alkenylsiloxanes used in platinum-alkenylsiloxane complexes include 1,3-divinyl-1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, alkenylsiloxane oligomers in which some of the methyl groups of alkenylsiloxanes have been substituted with ethyl groups, phenyl groups, etc., and alkenylsiloxane oligomers in which the vinyl groups of alkenylsiloxanes have been substituted with allyl groups, hexenyl groups, etc. In particular, 1,3-divinyl-1,1,3,3-tetramethyldisiloxane is preferred because the resulting platinum-alkenylsiloxane complexes have good stability.

[0059] To improve the stability of the platinum-alkenylsiloxane complexes, it is preferable to dissolve these platinum-alkenylsiloxane complexes in an organosiloxane oligomer such as an alkenylsiloxane oligomer, such as 1,3-divinyl-1,1,3,3-tetramethyldisiloxane, 1,3-diallyl-1,1,3,3-tetramethyldisiloxane, 1,3-divinyl-1,3-dimethyl-1,3-diphenyldisiloxane, 1,3-divinyl-1,1,3,3-tetraphenyldisiloxane, or 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, or a dimethylsiloxane oligomer, and it is particularly preferable to dissolve the complexes in an alkenylsiloxane oligomer.

[0060] The content of component (F) is a catalytic amount that accelerates the curing of the composition, preferably from about 0.01 to about 1,000 ppm of platinum group metal in this component, expressed in terms of mass units relative to the composition. Specifically, the content is preferably such that the platinum group metal content in component (F) is in the range of from about 0.01 to about 500 ppm, or from about 0.1 to about 100 ppm, expressed in terms of mass units relative to the composition. This is because, when the content is above the lower limit of the above range, the curability of the composition is improved, whereas when the content is below the upper limit of the above range, discoloration of the cured product is suppressed, the cost of the composition is reduced, and the curing rate of the composition can be controlled.

[0061] The composition may contain (G) a hydrosilylation reaction inhibitor to extend the working time at ambient temperature and improve storage stability. Examples of component (G) include acetylene alcohols such as 1-ethynylcyclohexane-1-ol, 2-methyl-3-butyn-2-ol, 2-phenyl-3-butyn-2-ol, 2-ethynylisopropan-2-ol, 2-ethynylbutan-2-ol, and 3,5-dimethyl-1-hexyn-3-ol; silylated acetylene alcohols such as trimethyl(3,5-dimethyl-1-hexyn-3-oxy)silane, dimethylbis(3-methyl-1-butyn-oxy)silane, methylvinylbis(3-methyl-1-butyn-3-oxy)silane, and ((1,1-dimethyl-2-propynyl)oxy)trimethylsilane; diallyl maleate, dimethyl maleate, diethyl fumarate, and the like. unsaturated carboxylic acid esters such as bis(2-methoxy-1-methylethyl)maleate, mono-octyl maleate, mono-isooctyl maleate, mono-allyl maleate, mono-methyl maleate, mono-ethyl fumarate, mono-allyl fumarate, and 2-methoxy-1-methylethyl maleate; ene-yne ​​compounds such as 2-isobutyl-1-buten-3-yne, 3,5-dimethyl-3-hexen-1-yne, 3-methyl-3-penten-1-yne, 3-methyl-3-hexen-1-yne, 1-ethynylcyclohexene, 3-ethyl-3-buten-1-yne, and 3-phenyl-3-buten-1-yne; and mixtures of two or more thereof.

[0062] The content of component (G) is not limited as long as it is an amount sufficient to control the curing rate of the composition. However, it is preferably about 0.001 to 5 parts by mass, about 0.001 to about 2 parts by mass, or about 0.001 to about 1 part by mass per 100 parts by mass of component (A). This is because, when the content is above the lower limit of the above range, the composition becomes easy to handle, whereas, when the content is below the upper limit of the above range, the composition becomes easy to cure at low temperatures.

[0063] Component (H) is at least one filler treating agent to aid in the dispersion of component (C) in component (A). Component (H) is preferably a filler treating agent selected from, but not limited to, the following: (H1) An organosiloxane represented by the following general formula (1): R 1 3SiO(SiR 1 2O) a SiR 1 b (OR 2 ) (4-b) (H2) Alkoxysilanes represented by the following general formula (2): R 3 c R 4 d Si(OR 5 ) (4-c-d) and mixtures of components (H1) and (H2).

[0064] In formula (1), each R 1 are independently an alkyl group having 1 to 3 carbon atoms or an alkenyl group having 2 to 6 carbon atoms. 1 Examples of the alkyl group of R include a methyl group, an ethyl group, and a propyl group, and among these, a methyl group is preferred. 1 Examples of the alkenyl group include a vinyl group, an allyl group, a butenyl group, a pentenyl group, and a hexenyl group, and among these, a vinyl group is preferred.

[0065] In formula (1), each R 2 are independently alkyl groups having 1 to 3 carbon atoms. 4 Examples of the alkyl group include a methyl group, an ethyl group, and a propyl group, with a methyl group being preferred.

[0066] In formula (1), a is an integer of 5 to 150, or an integer of 10 to 120.

[0067] In formula (1), b is 0 or 1, and is preferably 0.

[0068] Examples of component (H1) include organopolysiloxanes represented by the following formula: (CH3)3SiO[Si(CH3)2O] 20 Si(OCH3)3 (CH3)3SiO[Si(CH3)2O] 50 Si(OCH3)3 (CH3)3SiO[Si(CH3)2O] 110 Si(OCH3)3 (CH2=CH)(CH3)2SiO[Si(CH3)2O] 10 Si(OCH3)3 (CH2=CH)(CH3)2SiO[Si(CH3)2O] 20 Si(OCH3)3

[0069] In formula (2), each R 3 are independently alkyl groups having 1 to 3 carbon atoms. 3 Examples of the alkyl group include a methyl group, an ethyl group, and a propyl group, with a methyl group being preferred.

[0070] In formula (2), each R 4 are independently alkyl groups having 6 to 12 carbon atoms. 4 Examples of the alkyl group include a hexyl group, a cyclohexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, and a dodecyl group, and among these, an octyl group and a decyl group are preferred.

[0071] In formula (2), each R 5 are independently alkyl groups having 1 to 3 carbon atoms. 5 Examples of the alkyl group include a methyl group, an ethyl group, and a propyl group, with a methyl group being preferred.

[0072] In formula (2), if c+d is 1 or 2, then c is 0 or 1 and d is 0 or 1.

[0073] Examples of alkoxysilanes of component (H2) include methyltrimethoxysilane, hexyltrimethoxysilane, heptyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, dodecylmethyldimethoxysilane, dodecyltriethoxysilane, tetradecyltrimethoxysilane, octadecyltrimethoxysilane, octadecylmethyldimethoxysilane, octadecyltriethoxysilane, nonadecyltrimethoxysilane, or any combination of at least two thereof.

[0074] The content of component (H) is not limited as long as it is an amount sufficient to treat component (C). However, it is preferably in the range of 0.1 to 5 mass %, or 0.1 to 3 mass %, or 0.5 to 3 mass % of the composition. This is because, when the content is above the lower limit of the above range, component (C) is sufficiently surface-treated before being filled into the composition, whereas when the content is below the upper limit of the above range, the storage stability of the composition is improved.

[0075] The composition may further comprise (I) a pigment, which has the effect of maintaining the desired physical characteristics of the cured product of the composition, i.e., suitable flexibility and conformability. Examples of component (I) include red iron oxide, titanium white, carbon black, and phthalocyanine compounds. Among these, phthalocyanine compounds are preferred. Examples of phthalocyanine compounds include copper phthalocyanine and chlorinated copper phthalocyanine. Phthalocyanine compounds are commercially available from Alfa-Aesar.

[0076] The content of component (I) is not limited as long as it is an amount sufficient to maintain the desired physical properties, but is preferably an amount in terms of mass units such that the pigment is present in an amount in the range of 0.01 to 5 parts by mass, alternatively 0.05 to 5 parts by mass, or alternatively 0.05 to 1 part by mass, per 100 parts by mass of component (A).

[0077] Additionally, the addition of small amounts of auxiliary ingredients to the present compositions is permissible, such as various fillers other than thermally conductive fillers and fumed silica fillers, antioxidants, dyes, heat stabilizers, adhesion promoters, flame retardants, plasticizers, and the like.

[0078] The viscosity of the composition at 25°C is not particularly limited, but is preferably 10,000 Pa·s or less, in the range of 500 to 10,000 Pa·s, or in the range of 1,000 to 10,000 Pa·s. This is because, if the viscosity of the composition exceeds the lower limit of the above range, the mechanical properties of the resulting cured product will be good, whereas, if the viscosity is below the upper limit of the above range, the handleability of the resulting composition will be improved and the possibility of air being entrained in the cured product will be reduced.

[0079] The composition can be prepared by uniformly mixing components (A) to (D) and, if necessary, any other components. When preparing the composition, mixing can be performed at room temperature using various types of stirrers or kneaders, and, if necessary, mixing can be performed while heating. Furthermore, the order in which the various components are combined is not limited, and mixing can be performed in any order. Furthermore, the composition can be a one-component composition in which all components are blended in the same container, or a two-component composition in which the components are mixed during use in consideration of storage stability. [Example]

[0080] The thermally conductive silicone composition of the present invention will be described in detail below using examples and comparative examples. However, the present invention is not limited to the descriptions of the examples listed below. Viscosity was measured at 25°C. Furthermore, in the examples, measurements and evaluations were performed as follows.

[0081] <Thermal conductivity> Thermal conductivity (W / m·K) was measured using a Thermal Interface Material (TIM) Tester manufactured by LONGWIN Instrument in accordance with ASTM D 5470 "Standard Test Method for Thermal Transmission Properties of Thermally Conductive Electrical Insulation Materials."

[0082] <Distribution speed> The thermally conductive silicone composition is loaded into a 30 cc EFD plastic cartridge without a tip, and then dispensed under 90 psi (621 kPa), recording the weight of the composition dispensed in 1 minute. The test is repeated 5 times, and the average value is recorded.

[0083] <Long tailing observation> After dispensing five small sample dots of approximately 0.15 mL each, observe whether there is a long tail at the end and whether the tail does not break easily. Check whether the material forms a tail when lifting the dispensing syringe. The sample dots have a total height of approximately 10 mm. If the total height of the sample dot is higher than 1.2 mm and the tail height is higher than 5 mm, it is recorded as a failure.

[0084] <Slumping resistance test> Five small sample dots were dispensed onto an Al plate, and the height and base length of the dots were measured. The Al plate was placed horizontally for 24 hours. The dot shape was observed, and the height and base length of the dots were measured to calculate the aspect ratio of the dispensed dots. The slumping tendency (ST) value, which is the change in aspect ratio over 24 hours, was calculated. If ST≦1.05, it could be marked as "no slumping." If the value >1.05, it was marked as "slumping."

[0085] The aspect ratio (AR) of the dispensed sample dot can be defined as the (height / diameter) of the specimen. AR=h / d

[0086] The slumping tendency (ST) of a dispensed sample dot can be defined as the ratio of the initial AR of the specimen to the AR of the specimen after a specific time. ST=AR1 / AR2=(h1×d2) / (d1×h2) If ST>1, it indicates that the sample has a tendency towards horizontal slumping.

[0087] The higher the ST value, the stronger the tendency to slumping.

[0088] <Vertical hold> Dispense five sample dots of 0.4 g and 1 g each onto an Al plate. Place the Al plate vertically for 24 hours and observe whether the sample dots remain in place.

[0089] <Viscosity and thixotropy index> Viscosity at 25°C was measured using an ARES G2 rheometer under the following conditions: sawtooth parallel plates 25 mm in diameter; gap 1 mm; flow sweep mode; shear rates: 0.1 (1 / s) and 1 (1 / s) according to ASTM D 1084 "Standard Test Methods for Viscosity of Adhesives". The thixotropy index is given by the following formula: Thixotropy index = η(0.1) / η(1) In the formula, η(0.1) is the viscosity at a low shear rate of 0.1 (1 / s), and η(1) is the viscosity at a high shear rate of 1 (1 / s).

[0090] The following components were used to prepare thermally conductive silicone compositions in the examples and comparative examples.

[0091] The following components were used as component (A): V-P1:Following formula: (CH2=CH)(CH3)2SiO-[Si(CH3)2O] 75 -Si(CH3)2(CH=CH2) Dimethylpolysiloxane having a viscosity of 78 mPa·s and a vinyl group content of 1.25% by mass. V-P2: The following formula: (CH2=CH)(CH3)2SiO-[Si(CH3)2O] 380 -Si(CH3)2(CH=CH2) Dimethylpolysiloxane having a viscosity of 2000 mPa·s and a vinyl group content of 0.24% by mass.

[0092] The following components were used as component (B): Filler-1: 175~225m 2 Hydrophobic fumed silica (AEROSIL 200V from Evonik) with a BET specific surface area of ​​1000 nm / g

[0093] The following components were used as component (C): Filler-2: Spherical Al2O3 with an average particle size of 90 μm (available from Denka Co., Ltd. (Japan) under the name DAW-90) Filler-3: Roundish Al2O3 with an average particle size of 35 μm (available from Chialco under the name A-SF-60) Filler-4: amorphous Al2O3 with an average particle size of 2 μm (available from Nippon Steel Chemical & Material Co., Ltd. under the name AZ2-75) Filler-5: ZnO with irregular particle size and an average particle size of 0.11-0.13 μm (commercially available from Zochem as Zoco 102) Filler-6: Platelet-shaped boron nitride filler with an average particle size along the platelets of approximately 45 μm and a platelet thickness of 5-10 μm (commercially available as PolarTherm PT110 from Momentive Performance Materials). Filler-7: Spherical AlN with an average particle size of 80 μm (commercially available as ANF S-80 ST204 from Maruwa Co., Ltd., Japan) Filler 8: Spherical Al2O3 with an average particle size of 2 μm (available from Showa Denko K.K. under the name ALUNABEADS (trademark) CB-P02)

[0094] The following component was used as component (H): TA-1: n-decyltrimethoxysilane (available from Gelest as SID2670.0) TA-2: An organopolysiloxane represented by the following average formula: (CH3)3SiO[(CH3)2SiO] 110 Si(OCH3)3

[0095] The following components were used as component (I): Blue pigment: Copper phthalocyanine powder (CuPc) CAS 147-14-8 (40 wt%) was dispersed by a three-roll mill in trimethyl-terminated polydimethylsiloxane (200 Fluid) (60 wt%) Alfa-Aesar Catalogue No. 43650-09 having a viscosity of 350 mPa s and DOWSIL™ 200 Fluid 350 cSt.

[0096] The following component was used as component (G): Inhibitor: methyl(tris(1,1-dimethyl-2-propynyloxy))silane (commercially available as ACM83817714 from Alfa Chemistry, 2200 Smithtown Avenue, Ronkonkoma, NY)

[0097] The following component was used as component (D): Additive-1: PTMEG poly(tetramethylene ether glycol) with Mn = about 1000 to about 2000 (commercially available from Aladdin as PTMEG 2000) Additive-2: EO / PO copolymer polyalkoxylate containing ethylene oxide / propylene oxide block copolymer, sorbitol-initiated alcohol alkoxylate (propylene oxide = 94 wt%). The copolymer had an Mn of 9600 g / mol, a viscosity of 13,400 mPa·s at 25°C, and an OHV of 30-36 mg KOH / g, where OHV represents the hydroxyl number of the alcohol alkoxylate as determined by ASTM D4274-2011 (commercially available from Dow as DOWFAX™ DF-162 nonionic surfactant). Additive-3: Polyether-grafted organopolysiloxane (CAS 68037-64-9) obtained by hydrosilylation reaction of a copolymer of dimethylsiloxane and methylhydrogensiloxane with polyoxyethylene polyoxypropylene glycol monoacetate allyl ether (CAS 68037-64-9) (available from Sigma-Aldrich)

[0098] The following components were used as component (E): XL 1: A copolymer of dimethylsiloxane and methylhydrogensiloxane having 0.11 mol % SiH and a viscosity of 19 mPa·s, end-capped with trimethylsiloxy groups at both ends of the molecular chain, represented by the average formula: (CH3)3SiO[(CH3)2SiO] 25 [(CH3)HSiO]2Si(CH3)3 (Commercially available from Gelest as HMS-071)

[0099] The following component was used as component (F): Pt-1: Platinum-divinyltetramethyldisiloxane complex (CAS 68478-92-2), 1.0% Pt in vinyl-terminated PDMS (available from Gelest)

[0100] [Examples IE1 to IE5 and Comparative Examples CE1 and CE2] A 1 L Sigma blade kneader mixer was used to prepare the thermally conductive silicone compositions shown in Table 1.

[0101] The specified amounts of V-P1, V-P2, TA1, TA2, and pigment are placed in a mixer and mixed for 5 minutes at 20 revolutions per minute (RPM) under a nitrogen flow of 0.4 cubic meters per hour. While mixing, add Filler-1 and Filler-5 and continue mixing for 10 minutes at 45 RPM under a nitrogen purge. Add Filler-8 and mix for 10 minutes at 45 RPM under a nitrogen purge. Stop mixing and scrape material from the walls of the mixing vessel and cover. Add Filler-6 and Filler-7 and mix for 10 minutes at 30 RPM under a nitrogen purge. Stop mixing and scrape material from the walls of the mixing vessel. Continue mixing at 30 RPM under vacuum and heat to 130°C for 40 minutes. Cool to 40°C, stop mixing, and release the vacuum. Scrape material from the walls of the vessel and mixer blades. Add inhibitor, XL 1, and Additives 1-3 and mix for 15 minutes at 30 RPM under a nitrogen purge, then for 15 minutes. Cool to 25°C, add Pt 1 to the mixer and mix for 45 minutes at 30 RPM under a nitrogen purge. Continue mixing at 30 RPM with full vacuum for 20 minutes. Stop mixing and release the vacuum to obtain a thermally conductive silicone composition for CE or IE.

[0102] [Table 1]

[0103] The results of Examples IE1 to IE5 confirmed the following. The total filler loading (AlN, BN, Al2O3, SiO2, and ZnO) was 95.83 wt%, resulting in these samples exhibiting a thermal conductivity of 9.2 W / m K. However, these samples also exhibit excellent slumping resistance and vertical retention.

[0104] The results of Comparative Examples CE1 and CE2 confirmed the following. The total filler loading (AlN, BN, Al2O3, SiO2, and ZnO) was 95.83 wt%, resulting in these samples exhibiting thermal conductivities of 9.2 W / m K or 9.3 W / m K. However, these samples exhibited poor slumping resistance and poor vertical retention.

[0105] [Example IE6 and Comparative Examples CE3 and CE4] A 4 L Sigma blade kneader mixer was used to prepare the thermally conductive silicone compositions shown in Table 2.

[0106] The specified amounts of V-P1, V-P2, TA1, TA2, and pigment are placed in a mixer and mixed for 5 minutes at 20 revolutions per minute (RPM) under a nitrogen flow of 0.4 cubic meters per hour. While mixing, add Filler-1 and Filler-5 and continue mixing for 10 minutes at 45 RPM under a nitrogen purge. Add Filler-4 and mix for 10 minutes at 45 RPM under a nitrogen purge. Stop mixing and scrape material from the walls of the mixing vessel and cover. Add Filler-3 and mix for 10 minutes at 30 RPM under a nitrogen purge. Add Filler-2 and mix for 10 minutes at 30 RPM under a nitrogen purge. Stop mixing and scrape material from the walls of the mixing vessel. Continue mixing at 30 RPM under vacuum and heat to 130°C for 40 minutes. Cool to 40°C, stop mixing, and release the vacuum. Scrape material from the walls of the vessel and mixer blades. Add inhibitor, XL 1, and Additive-1 and mix for 15 minutes at 30 RPM under a nitrogen purge, then for 15 minutes. Cool to 25°C, add Pt 1 to the mixer and mix for 45 minutes at 30 RPM under a nitrogen purge. Continue mixing at 30 RPM with full vacuum for 20 minutes. Stop mixing and release the vacuum to obtain a thermally conductive silicone composition for CE or IE.

[0107] [Table 2]

[0108] The results of Example IE6 confirmed the following: The total filler (Al2O3, SiO2, and ZnO) loading was 95.92 wt%, resulting in a thermal conductivity of 6.2 W / m K. However, the samples exhibited excellent slumping resistance and vertical retention.

[0109] The results of Comparative Examples CE3 and CE4 confirmed the following. The total filler (Al2O3, SiO2, and ZnO) loading for CE3 was 95.92 wt%, resulting in a thermal conductivity of 6.2 W / m K. However, this sample exhibited poor slumping resistance and poor vertical retention.

[0110] On the other hand, the total filler loading (Al2O3, SiO2, and ZnO) for CE4 was also 95.92% by mass, resulting in a thermal conductivity of 6.0 W / m·K. However, the dot tips were still prone to collapse but were able to maintain their original position during the vertical holding test. The high loading of nano-SiO2 also significantly increased the viscosity. The long tailing performance and poor distribution did not meet the requirements. [Industrial Applicability]

[0111] The thermally conductive curable silicone composition of the present invention exhibits good shape retention and high thermal conductivity while being easy to handle and dispense, making it useful as an encapsulant or potting material in electrical / electronic devices.

Claims

1. A thermally conductive silicone composition comprising: (A) an organopolysiloxane having at least one alkenyl group having 2 to 12 carbon atoms per molecule and a viscosity at 25°C of 10 to 10,000 mPa·s; (B) hydrophobic fumed silica; and (C) at least one thermally conductive filler; (D) (D １ ) polytetramethylene ether glycol, (D ２ ) alcohol-initiated ethylene oxide and propylene oxide copolymers, and (D ３ ) at least one polyether selected from the group consisting of polyether-modified organopolysiloxanes, A thermally conductive silicone composition, wherein the content of component (A) is in the range of 0.5 to 5 mass %, the content of component (B) is in the range of 0.01 to 0.5 mass %, the content of component (C) is at least 90 mass %, and the content of component (D) is in the range of 0.05 to 5 mass %, each of which is relative to the total amount of the composition.

2. Ingredients (D １ ) is a polytetramethylene ether glycol represented by the general formula: H-(OCH) ２ CH ２ CH ２ CH ２ ) ｍ -OH 2. The thermally conductive silicone composition of claim 1, wherein m is a number appropriate to give the polytetramethylene ether glycol a molecular weight, number average molecular weight (Mn), of 300 to 3,000 as measured by gel permeation chromatography.

3. Ingredients (D ２ 10. The thermally conductive silicone composition of claim 1, wherein ethylene oxide and propylene oxide copolymer (II) is an alcohol-initiated ethylene oxide and propylene oxide copolymer containing 50% to 99% by weight of propylene oxide units in the copolymer.

4. Ingredients (D ３ 2. The thermally conductive silicone composition according to claim 1, wherein said organopolysiloxane is a polyether-modified organopolysiloxane selected from polyether-grafted organopolysiloxanes and block copolymers of polyethers and organopolysiloxanes.

5. 2. The thermally conductive silicone composition of claim 1, further comprising: (E) an organopolysiloxane having at least two silicon-bonded hydrogen atoms per molecule, in an amount such that there are 0.1 to 5 moles of silicon-bonded hydrogen atoms in component (E) per mole of alkenyl groups in component (A); and (F) a hydrosilylation reaction catalyst in an amount sufficient to promote cure of the composition.

6. 6. The thermally conductive silicone composition according to claim 5, further comprising (G) a hydrosilylation reaction inhibitor in an amount sufficient to control the cure rate of the composition.

7. 10. The thermally conductive silicone composition of claim 1, further comprising (H) a filler treating agent in an amount sufficient to treat component (C).

8. 10. The thermally conductive silicone composition of claim 1, further comprising (I) a pigment in an amount sufficient for the composition to retain desired physical properties.

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