Thermally conductive silicone composition

Abstract

The present invention relates to a thermally conductive silicone composition comprising: (A) an organopolysiloxane having at least two silicon-bonded alkenyl groups, each having 2 to 12 carbon atoms, per molecule; (B) an organopolysiloxane having at least three silicon-bonded hydrogen atoms per molecule; (C) an organopolysiloxane having at most two silicon-bonded hydrogen atoms per molecule; (D) an aluminum hydroxide powder, specifically a mixture of an aluminum hydroxide powder having an average particle size of at least 0.1 μm and less than 5 μm, and an aluminum hydroxide powder having an average particle size of 5 μm to 50 μm; and (E) a hydrosilylation reaction catalyst. The composition cures to form a thermally conductive, soft material that exhibits minimal change in hardness, even when the composition is cured after prolonged storage.

Description

[Technical field]

[0001] The present invention relates to a thermally conductive silicone composition. [Background technology]

[0002] Thermally conductive silicone compositions that can be cured by a hydrosilylation reaction form thermally conductive materials that have excellent heat resistance and therefore find use in a variety of applications.

[0003] For example, as such a thermally conductive silicone composition, Patent Document 1 describes a silicone elastomer composition that includes an organopolysiloxane having an average of at least 0.1 alkenyl group per molecule, an organopolysiloxane having an average of at least two silicon-bonded hydrogen atoms per molecule, a platinum group metal catalyst, a thermally conductive filler such as aluminum hydroxide powder, an organosiloxane having an alkenyl group and a silicon-bonded alkoxy group per molecule, and an alkoxysilane compound, and the composition is suitable for producing an elastomer characterized by reduced hardness change even after thermal aging.

[0004] Patent Document 2 describes a thermally conductive silicone composition comprising an organopolysiloxane having at least two alkenyl groups in one molecule, an organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms, a thermally conductive filler comprising 15 to 25 mass% aluminum hydroxide having an average particle size of ≧0.1 μm and <5 μm, 35 to 45 mass% aluminum hydroxide having an average particle size of ≧5 μm and <40 μm, and 35 to 45 mass% aluminum hydroxide having an average particle size of ≧40 μm and <100 μm, and a platinum group metal-based curing catalyst.

[0005] Patent Document 3 describes a polysiloxane composition comprising an organoalkylpolysiloxane having an average of at least 0.1 alkenyl group per molecule, a polyorganosiloxane having an average of at least two silicon-bonded hydrogen atoms per molecule, a hydrosilylation reaction catalyst, a thermally conductive filler such as aluminum hydroxide powder, and an additive selected from the group consisting of metal-free phthalocyanine compounds and metal-containing phthalocyanine compounds.

[0006] Patent Document 4 describes a curable polymer composition for use as an encapsulant for power converters, comprising an organopolysiloxane having an average of at least 0.5 alkenyl groups per molecule, an organopolysiloxane curing agent having at least two silicon-bonded hydrogen atoms per molecule, a hydrosilylation catalyst, and a thermally conductive filler such as aluminum hydroxide powder, and optionally further comprising a filler treating agent and a hydrosilylation stabilizer.

[0007] Recently, thermally conductive soft materials with a Shore OO hardness of 10 to 70 have been evaluated for applications in the automotive and electronic / electrical fields.

[0008] However, a problem with these thermally conductive silicone compositions is that upon curing of the compositions after extended storage, they form soft thermally conductive materials of varying hardness.

[0009] Prior art documents Patent Literature Patent Document 1: U.S. Patent Application Publication No. 2010 / 0140538(A1) Patent Document 2: JP 2011-089079(A) Patent Document 3: U.S. Patent Application Publication No. 2013 / 0248163(A1) Patent Document 4: U.S. Patent Application Publication No. 2016 / 0009954(A1) Summary of the Invention

[0010] technical issues It is an object of the present invention to provide a thermally conductive silicone composition which forms a thermally conductive, soft material that exhibits little change in hardness even when the composition is cured after extended storage.

[0011] Solutions to the problem The thermally conductive silicone composition of the present invention comprises: (A) 100 parts by mass of an organopolysiloxane having at least two silicon-bonded alkenyl groups having 2 to 12 carbon atoms per molecule; (B) an organopolysiloxane having at least three silicon-bonded hydrogen atoms per molecule and represented by the general formula:

[0012] [ka] In the formula, each R 1 are independently a monovalent hydrocarbon group having 1 to 12 carbon atoms and no aliphatic unsaturated bonds, and each R 2 are independently a hydrogen atom or the above R 1 wherein "m1" is an integer from 10 to 200 and "m2" is an integer from 1 to 50, in an amount such that the number of silicon-bonded hydrogen atoms in this component is 0.01 to 0.5 moles per mole of total alkenyl groups in component (A); (C) an organopolysiloxane having up to two silicon-bonded hydrogen atoms per molecule and represented by the general formula:

[0013] [ka] In the formula, R 1 is as above, and each R 3 are independently a hydrogen atom or the above R 1wherein "n1" is an integer from 5 to 50 and "n2" is an integer from 0 to 2, in an amount such that the number of silicon-bonded hydrogen atoms in this component is 0.1 to 5 moles per mole of total alkenyl groups in component (A); (D) 200 to 2,500 parts by mass of aluminum hydroxide powder; (E) a catalytic amount of a hydrosilylation reaction catalyst.

[0014] In various embodiments, component (D) comprises (D-1) an aluminum hydroxide powder having an average particle size of at least 0.1 μm and less than 5 μm, and (D-2) an aluminum hydroxide powder having an average particle size of 5 μm to 50 μm, wherein the amount of component (D-1) is up to 50% by weight of component (D) and the amount of component (D-2) is greater than 50% by weight of component (D).

[0015] In various embodiments, the thermally conductive silicone composition further comprises (F) an alkoxysilane compound represented by the general formula: R 4 a R 5 b Si(OR 6 ) (4-a-b) In the formula, each R 4 are independently an alkyl group having 6 to 15 carbon atoms, and each R 5 are independently an alkyl group having 1 to 5 carbon atoms or an alkenyl group having 2 to 6 carbon atoms, and each R 6 are independently an alkyl group having 1 to 4 carbon atoms, "a" is an integer from 1 to 3, and "b" is an integer from 0 to 2, with the proviso that "a+b" is an integer from 1 to 3 in an amount of 0.01 to 50 parts by mass per 100 parts by mass of component (A).

[0016] In various embodiments, the thermally conductive silicone composition further comprises (G) a hydrosilylation reaction inhibitor in an amount of 0.001 to 5 parts by weight per 100 parts by weight of component (A).

[0017] In various embodiments, the thermally conductive silicone composition further comprises (H) a pigment in an amount of 0.01 to 5 parts by weight per 100 parts by weight of component (A).

[0018] The thermally conductive material of the present invention is obtained by curing the above-mentioned thermally conductive silicone composition.

[0019] Effect of the Invention The thermally conductive silicone composition of the present invention cures to form a thermally conductive soft material that exhibits a small change in hardness even when the composition is cured after long-term storage, yet exhibits the desired flexibility.

[0020] definition The term "comprising" is used broadly herein to mean and encompass the concepts of "including" or "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 account for slight variations in numerical values ​​as determined by instrumental analysis or as a result of handling samples. Such slight variations may be on the order of ±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 apply to numerical values ​​even if not expressly stated.

[0021] It is to be understood that the appended claims are not limited to the specific compounds, compositions, or methods described therein to describe the "detailed description," and may vary among specific embodiments within the scope of the appended claims. With respect to any Markush groups relied upon herein to describe particular features or aspects of various embodiments, it should be understood that different, special, and / or unexpected results may be obtained from each element of the respective Markush group independently of all other Markush elements. Each element of the Markush group may be relied upon individually and / or in combination to provide appropriate support for specific embodiments within the scope of the appended claims.

[0022] 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 ​​therein are understood to be described and contemplated, even if such values ​​are 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 relevant halves, thirds, fourths, fifths, etc. As merely an example, the range "0.1-0.9" may be further delineated into a lower third, i.e., 0.1-0.3, a middle third, i.e., 0.4-0.6, and an upper third, i.e., 0.7-0.9, which are individually and inclusively within the scope of the appended claims, and may be relied upon and provide sufficient support for specific embodiments within the scope of the appended claims, individually and / or inclusively. Furthermore, with respect to words defining or modifying a range, such as "at least," "greater than," "less than," "less than," etc., such words should be understood to include subranges and / or upper or lower limits. As another example, the range "at least 10" essentially includes subranges of at least 10 to 35, at least 10 to 25, 25 to 35, etc., and each subrange may be relied upon and fully supported by specific embodiments within the appended claims, individually and / or collectively. Finally, each individual number within a disclosed range may be relied upon and fully supported by specific embodiments within the appended claims. For example, the range "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 and fully supported by specific embodiments within the appended claims. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] First, the thermally conductive silicone composition of the present invention will be described in detail.

[0024] Component (A) is the main component of the composition and is an organopolysiloxane having at least two silicon-bonded alkenyl groups each having 2 to 12 carbon atoms per molecule. Examples of the alkenyl groups 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 are substituted with halogen atoms, such as fluorine, chlorine, or bromine. Furthermore, the silicon atoms in component (A) may have a small amount of hydroxyl or alkoxy groups, such as methoxy or ethoxy groups, within the scope of the present invention.

[0025] Examples of the molecular structure of component (A) include a linear structure, a partially branched linear structure, 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.

[0026] Examples of component (A) include dimethylpolysiloxane having both molecular chain terminals blocked with trimethylsiloxy groups, dimethylpolysiloxane having both molecular chain terminals blocked with dimethylvinylsiloxy groups, dimethylpolysiloxane having both molecular chain terminals blocked with methylphenylvinylsiloxy groups, copolymers of dimethylsiloxane and methylphenylsiloxane having both molecular chain terminals blocked with trimethylsiloxy groups, copolymers of dimethylsiloxane and methylphenylsiloxane having both molecular chain terminals blocked with dimethylvinylsiloxy groups, dimethylsiloxane having both molecular chain terminals blocked with trimethylsiloxy groups, copolymers of dimethylsiloxane and methylvinylsiloxane, copolymers of dimethylsiloxane and methylvinylsiloxane terminated at both molecular chain ends with dimethylvinylsiloxy groups, methyl(3,3,3-trifluoropropyl)polysiloxane terminated at both molecular chain ends with dimethylvinylsiloxy groups, copolymers of dimethylsiloxane and methylvinylsiloxane terminated at both molecular chain ends with silanol groups, dimethylpolysiloxane terminated at both molecular chain ends with silanol groups, copolymers of dimethylsiloxane and methylphenylsiloxane terminated at both molecular chain ends with silanol groups, formula: CH3SiO 3 / 2 Siloxane units represented by the formula: (CH3)2SiO 2 / 2 Organopolysiloxanes consisting of siloxane units represented by the formula: C6H5SiO 3 / 2 Siloxane units represented by the formula: (CH3)2SiO 2 / 2 Organopolysiloxanes consisting of siloxane units represented by the formula: (CH3)3SiO 1 / 2 Siloxane units represented by the formula: CH3SiO 3 / 2 and siloxane units represented by the formula: (CH3)2SiO 2 / 2 Organopolysiloxanes consisting of siloxane units represented by 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: (CH3)2SiO 2 / 2and combinations of two or more thereof.

[0027] In addition, the viscosity of component (A) at 25°C is in the range of about 10 to about 100,000 mPa·s, preferably in the range of 10 to 50,000 mPa·s, alternatively in the range of 10 to 10,000 mPa·s, alternatively in the range of 50 to 10,000 mPa·s. This is because when the viscosity of component (A) is at or above the lower limit of the aforementioned range, the mechanical properties of the thermally conductive material obtained by curing the silicone composition are improved, whereas when the viscosity of component (A) is at or below the upper limit of the aforementioned range, the handleability of the composition is improved.

[0028] Component (B) is a crosslinker for component (A) in the composition and is an organopolysiloxane having at least three silicon-bonded hydrogen atoms per molecule. The organopolysiloxane of component (B) is represented by the following general formula:

[0029] [ka]

[0030] Each R in the formula 1are independently monovalent hydrocarbon groups having 1 to 12 carbon atoms and containing no aliphatic unsaturated bonds. Examples of monovalent hydrocarbon groups 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 are substituted with halogen atoms, such as fluorine, chlorine, or bromine. Furthermore, the silicon atoms in component (B) may have a small amount of hydroxyl groups or alkoxy groups, such as methoxy groups or ethoxy groups, as long as the object of the present invention is not impaired.

[0031] Each R in the formula 2 are independently a hydrogen atom or the above R 1 is selected from.

[0032] In the formula, "m1" is an integer of 10 to 200, optionally an integer of 50 to 200, or optionally an integer of 50 to 150. This is because when "m1" is equal to or greater than the lower limit of the above range, the molecular weight of the organosilicon compound can be increased and the volatility of the organosilicon compound can be reduced. On the other hand, when "m1" is equal to or less than the upper limit of the above range, the handling properties of the thermally conductive silicone composition can be improved.

[0033] In the formula, "m2" is an integer of 1 to 50, optionally an integer of 3 to 30, or optionally an integer of 5 to 20. This is because when "m2" is equal to or greater than the lower limit of the above range, the molecular weight of the organosilicon compound can be increased and the volatility of the organosilicon compound can be reduced. On the other hand, when "m2" is equal to or less than the upper limit of the above range, the curability of the thermally conductive silicone composition can be improved. When "m2" is 1, both R2 is a hydrogen atom, and when "m2" is 2, at least one R 2 is a hydrogen atom.

[0034] The content of component (B) is such that the number of silicon-bonded hydrogen atoms in this component is 0.01 to 0.5 moles, optionally 0.01 to 0.3 moles, or optionally 0.01 to 0.2 moles per mole of total alkenyl groups in component (A). This is because when the content of component (B) is equal to or greater than the lower limit of the above range, the resulting composition is sufficiently cured. On the other hand, when the content of component (B) is equal to or less than the upper limit of the above range, the heat resistance of the resulting thermally conductive material is improved.

[0035] Component (C) is a chain extender for component (A) in the composition and is an organopolysiloxane having up to two silicon-bonded hydrogen atoms per molecule. Organopolysiloxane component (C) is represented by the following general formula:

[0036] [ka]

[0037] Each R in the formula 1 is as stated above.

[0038] Each R in the formula 3 are independently a hydrogen atom or the above R 1 is selected from.

[0039] In the formula, "n1" is an integer of 5 to 50, optionally an integer of 5 to 30, or optionally an integer of 10 to 30. This is because when "n1" is equal to or greater than the lower limit of the above range, the molecular weight of the organosilicon compound can be increased and the volatility of the organosilicon compound can be reduced. On the other hand, when "n1" is equal to or less than the upper limit of the above range, the handling properties of the thermally conductive silicone composition can be improved.

[0040] In the formula, [n2] is an integer of 0 to 2. This is because when "n2" is equal to or greater than the lower limit of the above range, the molecular weight of the organosilicon compound can be increased and the volatility of the organosilicon compound can be reduced. On the other hand, when "n2" is equal to or less than the upper limit of the above range, the elasticity of the thermally conductive material obtained by curing the thermally conductive silicone composition can be improved. When "n2" is 0, both R 2 is a hydrogen atom, and when "n2" is 2, one R 2 is a hydrogen atom.

[0041] The content of component (C) is such that the number of silicon-bonded hydrogen atoms in this component is 0.1 to 5 moles, optionally 0.1 to 3 moles, or optionally 0.1 to 2 moles per mole of total alkenyl groups in component (A). This is because when the content of component (C) is equal to or greater than the lower limit of the above range, the resulting composition is sufficiently cured. On the other hand, when the content of component (C) is equal to or less than the upper limit of the above range, the heat resistance of the resulting thermally conductive material is improved.

[0042] Component (D) is aluminum hydroxide powder as a thermally conductive filler for providing thixotropic properties to the composition. Component (D) preferably includes (D-1) aluminum hydroxide powder having an average particle size of at least 0.1 μm and less than 5 μm, and (D-2) aluminum hydroxide powder having an average particle size of 5 μm to 50 μm.

[0043] The content of component (D-1) is not limited, but is preferably a maximum of 50% by mass, or a maximum of 40% by mass, of component (D). On the other hand, the content of component (D-2) is not limited, but is preferably more than 50% by mass, or more than 60% by mass, of component (D). This is because, when the content of component (D-1) is equal to or less than the upper limit of the above range, the thermal conductive properties of the resulting thermally conductive material are improved. On the other hand, when the content of component (D-2) is equal to or more than the lower limit of the above range, the thixotropic properties of the composition are improved.

[0044] The content of component (D) is in the range of about 200 to about 2,500 parts by mass, optionally about 300 to about 2,000 parts by mass, or optionally about 300 to about 1,500 parts by mass, relative to 100 parts by mass of component (A). This is because when the content of component (D) is equal to or higher than the lower limit of the above range, the heat conduction properties of the composition are improved, and when the content of component (D) is equal to or lower than the upper limit of the above range, the handleability of the composition is improved.

[0045] Component (E) is a hydrosilylation catalyst for promoting the curing of the composition. Examples of component (E) 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 them. In particular, platinum-based catalysts are preferred because they can dramatically promote 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 mixture of two or more of these.In particular, platinum-alkenylsiloxane complex is preferred because it can accelerate the curing of the present composition.

[0046] Examples of alkenylsiloxanes used in the platinum-alkenylsiloxane complex include 1,3-divinyl-1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, alkenylsiloxane oligomers in which a portion of the methyl groups of the alkenylsiloxane is substituted with an ethyl group, a phenyl group, etc., and alkenylsiloxane oligomers in which the vinyl groups of the alkenylsiloxane are substituted with an allyl group, a hexenyl group, etc. In particular, 1,3-divinyl-1,1,3,3-tetramethyldisiloxane is preferred in that the platinum-alkenylsiloxane complex produced has good stability.

[0047] In order 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.

[0048] The content of component (E) is a catalytic amount that promotes the curing of the composition, and is preferably about 0.01 to about 1,000 ppm of platinum group metal in this component in terms of mass units relative to the composition. Specifically, the content is preferably such that the content of platinum group metal in component (E) is in the range of about 0.01 to about 500 ppm, or in the range of about 0.1 to about 100 ppm, in terms of mass units relative to the composition. This is because when the content of component (E) is equal to or greater than the lower limit of the above range, the curability of the composition is good, whereas when the content of component (E) is equal to or less than the upper limit of the above range, coloring of the thermally conductive material is suppressed.

[0049] The composition may include (F) an alkoxysilane compound in order to utilize a large amount of component (C). Component (F) is an alkoxysilane represented by the following general formula: R 4 a R 5 b Si(OR 6 ) (4-a-b)

[0050] R in the formula 4 are independently an alkyl group having 6 to 15 carbon atoms. Examples of the alkyl group include a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, and a dodecyl group.

[0051] R in the formula 5 are independently an alkyl group having 1 to 5 carbon atoms or an alkenyl group having 2 to 6 carbon atoms. Examples of the alkyl group 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, and a neopentyl group. Examples of the alkenyl group include a vinyl group, an allyl group, a butenyl group, a pentenyl group, and a hexenyl group.

[0052] R in the formula 6 are independently an alkyl group having 1 to 4 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, and a tert-butyl group.

[0053] In the formula, "a" is an integer from 1 to 3, and "b" is an integer from 0 to 2, provided that "a+b" is an integer from 1 to 3, or "a" is 1 and "b" is an integer of 0 or 1, or "a" is 1 and "b" is 0.

[0054] Examples of alkoxysilanes of component (F) include hexyltrimethoxysilane, heptyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, dodecylmethyldimethoxysilane, dodecyltriethoxysilane, tetradecyltrimethoxysilane, octadecyltrimethoxysilane, octadecylmethyldimethoxysilane, octadecyltriethoxysilane, nonadecyltrimethoxysilane, or any combination of at least two thereof.

[0055] The content of component (F) is not limited, but is preferably 0.01 to 50 parts by mass, or about 0.01 to 20 parts by mass, or 0.1 to 10 parts by mass per 100 parts by mass of component (A). This is because when the content of component (F) is equal to or greater than the lower limit of the above range, the storage stability of the composition is good, whereas when the content of component (F) is equal to or less than the upper limit of the above range, the curability of the composition at low temperatures is good.

[0056] 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-ethynyl-cyclohexan-1-ol, 2-methyl-3-butyn-2-ol, 2-phenyl-3-butyn-2-ol, 2-ethynyl-isopropan-2-ol, 2-ethynyl-butan-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.

[0057] The content of component (G) is about 0.001 to 5 parts by mass, optionally about 0.001 to about 2 parts by mass, or optionally about 0.001 to about 1 part by mass per 100 parts by mass of component (A). This is because when the content of component (G) is equal to or greater than the lower limit of the above range, the handleability of the composition is good, whereas when the content of component (G) is equal to or less than the upper limit of the above range, the curability of the composition at low temperatures is good.

[0058] The composition may contain a pigment (H) that has the effect of maintaining the desired physical characteristics of the thermally conductive silicone material, i.e., suitable flexibility and conformability. Examples of component (H) include red iron oxide, white titanium, carbon black, and phthalocyanine compounds. Among these, phthalocyanine compounds are preferred. Examples of phthalocyanine compounds include copper phthalocyanine and chlorinated copper phthalocyanine. Phthalocyanine compounds such as Stan-tone™ 40SP03 are commercially available from PolyOne Corporation, Avon Lake, Ohio, USA.

[0059] The content of component (H) is not limited, but is preferably such that, in terms of mass units, the pigment is present in an amount in the range of 0.01 to 5 parts by mass, alternatively in the range of 0.05 to 5 parts by mass, or alternatively in the range of 0.05 to 1 part by mass, per 100 parts by mass of component (A).

[0060] The composition may include reinforcing and / or non-reinforcing fillers. Examples of fillers include finely divided treated or untreated precipitated silica, or fumed silica, precipitated or ground calcium carbonate, zinc carbonate, clays such as finely divided kaolin, quartz powder, zirconium silicate, diatomaceous earth, wollastonite, pyrophylate, and one or more of metal oxides such as fumed or precipitated titanium dioxide, cerium oxide, magnesium oxide powder, zinc oxide, and iron oxide. They may also include glass fibers, talc, aluminite, calcium sulfate (anhydrite), gypsum, calcium sulfate, magnesium carbonate, magnesium hydroxide (brucite), graphite, barite, which is a form of barium sulfate, copper carbonate such as malachite, nickel carbonate such as zarachite, barium carbonate such as witherite, strontium carbonate such as strontianite, or similar inorganic fillers.

[0061] The thermally conductive silicone composition of the present invention can be prepared by combining all components at ambient temperature.Any of the mixing techniques and devices described in the prior art can be used for this purpose.The specific device used is determined by the viscosity of the components and the final composition.It may be desirable to cool the components during mixing to avoid premature curing.

[0062] Next, the thermally conductive material of the present invention will be described in detail.

[0063] The thermally conductive material of the present invention is characterized in that it is obtained by curing the above-mentioned thermally conductive silicone composition. The hardness of the thermally conductive material is not limited in Shore OO hardness, but is preferably in the range of 10 to 70, or 10 to 75. This is because when the thermally conductive material has a hardness within the above range, it has good flexibility with respect to the heat-generating material. In this specification, the Shore OO hardness is a value measured at 23±2°C using OO hardness according to ASTM D 2240. EXAMPLES

[0064] The thermally conductive silicone composition of the present invention will be described in detail below using examples and comparative examples, but the present invention is not limited to the explanations of the examples listed below.

[0065] <Viscosity> The viscosity at 23±2°C was measured in accordance with ASTM D 1084 "Standard Test Methods for Viscosity of Adhesive" using a Brookfield HA Type Rotational Viscometer at 1s. -1 and 10s -1 The measurements were performed using

[0066] <Thixotropy index> Thixotropy index is 10s -1 For viscosity measured at 25±2℃, 1s -1The viscosity was calculated as the ratio of the viscosity at 25±2°C measured at

[0067] <Shore OO hardness> The thermally conductive silicone composition was thermally cured in an air circulating oven at 120°C for 1 hour to obtain a thermally conductive material. For durometer measurement, the thermally conductive material was laminated to a thickness of at least 6 mm. The hardness of the thermally conductive material at 25°C was measured by type OO hardness according to the method specified by ASTM D 2240-00.

[0068] [Examples 1 to 3 and Comparative Examples 1 to 2] Using the components listed below, the thermally conductive silicone compositions shown in Table 1 were prepared. Additionally, in Table 1, "SiH / Vi(1)" represents the moles of silicon-bonded hydrogen atoms in component (B) per mole of vinyl groups in component (A), and "SiH / Vi(2)" represents the moles of silicon-bonded hydrogen atoms in component (C) per mole of vinyl groups in component (A).

[0069] The following components were used as component (A): Component (a-1): A dimethylpolysiloxane having a viscosity of approximately 450 mPa·s, with both ends of the molecular chain blocked with dimethylvinylsiloxy groups.

[0070] The following components were used as component (B): Component (b-1): An organopolysiloxane having a viscosity of 150 mPa·s and represented by the following formula:

[0071] [ka]

[0072] The following components were used as component (C): Component (c-1): An organopolysiloxane having a viscosity of 20 mPa·s and represented by the following formula:

[0073] [ka]

[0074] The following components were used as component (D): Component (d-1): Aluminum hydroxide powder having an average particle diameter of about 1 μm. Component (d-2): Aluminum hydroxide powder having an average particle diameter of about 25 μm.

[0075] The following components were used as component (E): Component (e-1): A catalyst master batch (platinum content=0.1% by mass) of 1,3-divinyl-1,1,3,3-tetramethyldisiloxane and a platinum complex with the above component (a-1).

[0076] The following components were used as component (F): Component (f-1): n-decyltrimethoxysilane

[0077] The following components were used as component (G): Component (g-1): A hydrosilylation reaction inhibitor master batch of 0.5 mass % of 2-phenyl-3-butyn-2-ol and 99.5 mass % of the above component (a-1).

[0078] The following components were used as component (H): Component (h-1): A pigment master batch of 40% by mass of copper phthalocyanine and 60% by mass of the above component (a-1).

[0079] [Table 1] [Industrial Applicability]

[0080] The thermally conductive silicone composition of the present invention exhibits excellent stability of thixotropic properties during long-term storage, and cures to form a thermally conductive soft material with small hardness change even when the composition is cured after long-term storage.Therefore, the thermally conductive silicone composition is useful in thermally conductive materials for electric / electronic devices.

Claims

1. A thermally conductive silicone composition comprising: (A) 100 parts by weight of an organopolysiloxane having at least two silicon-bonded alkenyl groups having from 2 to 12 carbon atoms per molecule; (B) an organopolysiloxane having at least three silicon-bonded hydrogen atoms per molecule and represented by the following general formula: 【Chemistry 1】 In the formula, each R １ are independently a monovalent hydrocarbon group having 1 to 12 carbon atoms and no aliphatic unsaturated bonds, and each R ２ are independently the above R １ wherein "m1" is an integer from 10 to 200 and "m2" is an integer from 3 to 50, in an amount such that the number of silicon-bonded hydrogen atoms in this component is 0.01 to 0.5 moles per mole of total alkenyl groups in component (A); (C) an organopolysiloxane having two silicon-bonded hydrogen atoms per molecule and represented by the following general formula: 【Chemistry 2】 In the formula, R １ is as described above, and each R ３ are independently the above R １ wherein "n1" is an integer from 5 to 50 and "n2" is an integer of 2, in an amount such that the number of silicon-bonded hydrogen atoms in this component is 0.1 to 5 moles per mole of total alkenyl groups in component (A); (D) 200 to 2,500 parts by mass of aluminum hydroxide powder; (E) a catalytic amount of a hydrosilylation reaction catalyst.

2. 2. The thermally conductive silicone composition according to claim 1, wherein component (D) comprises (D-1) an aluminum hydroxide powder having an average particle size of at least 0.1 μm and less than 5 μm, and (D-2) an aluminum hydroxide powder having an average particle size of 5 μm to 50 μm, the amount of component (D-1) being up to 50 mass% of component (D), and the amount of component (D-2) being more than 50 mass% of component (D).

3. The composition further comprises an alkoxysilane compound (F) represented by the following general formula in an amount of 0.01 to 50 parts by mass per 100 parts by mass of the component (A): R ４ ａ R ５ ｂ Si(OR ６ ) （４－ａ－ｂ） In the formula, each R ４ is independently an alkyl group having 6 to 15 carbon atoms; ５ is independently an alkyl group having 1 to 5 carbon atoms or an alkenyl group having 2 to 6 carbon atoms, and each R ６ are independently an alkyl group having 1 to 4 carbon atoms, "a" is an integer from 1 to 3, and "b" is an integer from 0 to 2, with the proviso that "a+b" is an integer from 1 to 3.

4. 3. The thermally conductive silicone composition according to claim 1, further comprising (G) a hydrosilylation reaction inhibitor in an amount of 0.001 to 5 parts by mass per 100 parts by mass of component (A).

5. 3. The thermally conductive silicone composition according to claim 1, further comprising (H) a pigment in an amount of 0.01 to 5 parts by weight per 100 parts by weight of component (A).

6. A thermally conductive material obtained by curing the thermally conductive silicone composition according to any one of claims 1 to 5.

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