Polysiloxane composition

Abstract

The present invention relates to a lightweight silicone composition with high thermal conductivity. It comprises vinyl silicone oil, (C-1) aluminum hydroxide having an average particle size of 0.1 μm to 4 μm, (C-2) aluminum hydroxide having an average particle size of 4 μm to 20 μm, and (C-3) aluminum hydroxide having an average particle size of 80 μm to 100 μm. This composition can be used in the technical field of thermally conductive materials.

Description

[Technical Field]

[0001] The present invention relates to the technical field of thermally conductive silicone compositions. [Background technology]

[0002] Example 1 of CN104718254b discloses a polyurethane system containing various thermally conductive fillers (the thermally conductive filler loading ratio is 0.75). This composition contains aluminum hydroxide with average particle sizes of 125 μm, 40 μm, 2 μm, and 2.7 μm, and the amount of ultra-large 125 μm aluminum hydroxide is about 50% by weight, and the total weight of the thermally conductive filler is 100% by weight.

[0003] CN112778768a, Example 5, discloses a silicone gel system containing thermally conductive fillers, which contains vinyl silicone oil, hydrogen-containing silicone oil, catalyst, inhibitor, coupling agent octyltrimethoxysilane and aluminum hydroxide with different particle sizes.In this composition, the dosage ratio of aluminum hydroxide with different average particle sizes is 1 μm:10 μm:60 μm=1.5:2.5:6.

[0004] Example 4 of JP5304588B2 discloses a thermally conductive silicone composition containing vinyl silicone oil, hydrogen-containing silicone oil, alkoxy-modified silicone oil, and aluminum hydroxide with different particle sizes, in a ratio of 1 μm:10 μm:50 μm=2:4:4. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Chinese Patent No. 104718254 [Patent Document 2] Chinese Patent Application Publication No. 112778768 [Patent Document 3] Patent No. 5304588 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to obtain a highly thermally conductive composition that is highly filled, lightweight, and has a low viscosity. [Means for solving the problem]

[0007] The present invention provides Component (A) is an organopolysiloxane, preferably component (A-1) is an organopolysiloxane having two or more alkenyl groups per molecule; an optional component (B) which is an organohydrogenpolysiloxane having two or more hydrogen atoms directly bonded to silicon atoms, and which is contained in an amount such that the number of moles of hydrogen atoms directly bonded to silicon atoms in component (B) is 0.1 to 5.0 times the number of moles of alkenyl groups derived from component (A-1); Component (C) is a thermally conductive filler, 10 to 25% by weight of (C-1) aluminum hydroxide having an average particle size of 0.1 μm or more and 4 μm or less, For example, (C-1) having an average particle size of 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, or 2.8 μm and a content of 14% by weight, 16% by weight, 18% by weight, 20% by weight, 22% by weight, or 24% by weight; 18 to 37% by weight of (C-2) aluminum hydroxide having an average particle size of 4 μm or more and 20 μm or less, For example, (C-2) having an average particle size of 6, 8, 10, 12, 14, 16, or 18 μm and a content of 20% by weight, 22% by weight, 24% by weight, 26% by weight, 28% by weight, 30% by weight, 32% by weight, 34% by weight, or 36% by weight; (C-3) 48 to 65% by weight of aluminum hydroxide having an average particle size of 80 μm or more and 100 μm or less, For example, the average particle size of the (C-3) is 82, 84, 86, 88, 90, 92, 94, 96, or 98 μm, and the content is 50 wt%, 52 wt%, 54 wt%, 56 wt%, 58 wt%, 60 wt%, 62 wt%, or 64 wt%, In (C-1), (C-2), and (C-3), component (C) in the composition is calculated as 100% by weight, and optional component (D) which is a platinum group metal curing catalyst having a platinum group metal content of 0.1 to 1,000 ppm by weight relative to component (A-1), The composition is provided in which the loading of the thermally conductive filler is 0.88 or more, preferably 0.89 or more, preferably 0.90 or more. DETAILED DESCRIPTION OF THE INVENTION

[0008] In the present invention, the loading ratio is the total amount of thermally conductive filler / total weight of the composition. Generally, a loading ratio of 0.88 or more is considered to be a high loading ratio.

[0009] In the above compositions, the total amount of total aluminum hydroxide is greater than 95% by weight, preferably greater than 99% by weight, more preferably greater than 99.9% by weight, calculated based on the total amount of thermally conductive filler being 100% by weight.

[0010] In the above compositions, the total amount of total aluminum hydroxide is greater than 95% by weight, preferably greater than 99% by weight, more preferably greater than 99.9% by weight, calculated with the total amount of filler being 100% by weight.

[0011] In the above composition, the density of the composition is 2.4 g / cm 3 or less, preferably 2.2 g / cm 3 or less, more preferably 2.1 g / cm 3 The following is the result.

[0012] In the above composition, the thermal conductivity of the composition is 3.1 W / mK or more, preferably 3.2 W / mK or more, and more preferably 3.3 W / mK or more.

[0013] In the above compositions, (C-1), (C-2) and (C-3) aluminum hydroxides are all in amorphous form.

[0014] In the above composition, the amount of spherical filler is less than 10% by weight, preferably less than 1% by weight, calculated on the weight of the composition being 100% by weight.

[0015] In the above composition, the amount of spherical alumina is less than 10% by weight, preferably less than 1% by weight, based on 100% by weight of the composition.

[0016] In the above compositions, the content of Al(OH)3 in the aluminum hydroxides (C-1), (C-2) and (C-3) is 99.1% or more, preferably 99.5% or more.

[0017] In the above compositions, the content of Na2O in aluminum hydroxide (C-1), (C-2) and (C-3) is 0.1% or less, and preferably the total content of water-soluble Na2O and lattice-state Na2O is 0.1% or less.

[0018] In the above composition, at least one of the aluminum hydroxides (C-1), (C-2) and (C-3) is surface-treated, preferably with component (E-1).

[0019] In the above composition, (C-1) aluminum hydroxide is surface-treated with component (E-1).

[0020] In the above composition, the component (C) is 10 to 20% by weight of (C-1) aluminum hydroxide having an average particle size of 0.5 μm or more and 3 μm or less; 20 to 35% by weight of (C-2) aluminum hydroxide having an average particle size of 7 μm or more and 15 μm or more; Contains 50 to 60% by weight of (C-3) aluminum hydroxide having an average particle size of 85 μm or more and 95 μm or more, In (C-1), (C-2) and (C-3), the component (C) in the composition is calculated as 100% by weight.

[0021] In the above composition, the weight ratio of surface-treated aluminum hydroxide to non-surface-treated aluminum hydroxide is less than 0.3, preferably less than 0.2, more preferably less than 0.15.

[0022] In the above composition, the weight ratio of (C-1) / (C-3) is between 0.2 and 0.4, preferably between 0.22 and 0.38, for example, 0.25, 0.27, 0.29, 0.31, 0.33, or 0.35.

[0023] In the above composition, the weight ratio of (C-2) / (C-3) is between 0.2 and 0.8, preferably between 0.25 and 0.75, for example, 0.3, 0.4, 0.5, 0.6, or 0.7.

[0024] In the above composition, the ratio of average particle size (C-1) / (C-2) is between 8 and 12, preferably between 9 and 11, more preferably between 9.5 and 10.5, for example, 9.6, 9.8, 10.0, 10.2, or 10.4.

[0025] In the above composition, the ratio of average particle size (C-1) / (C-3) is between 70 and 120, preferably between 75 and 100, more preferably between 80 and 99, for example, 82, 84, 86, 88, 90, 92, 94, 96, and 98.

[0026] In the above composition, (C- 3 ) / (C- 2 ) is between 7.0 and 12.0, preferably between 7.5 and 10, more preferably between 8.0 and 9.9, for example, 8.2, 8.4, 8.6, 8.8, 9.0, 9.2, 9.4, 9.6, or 9.8.

[0027] The definition of the average particle size refers to the cumulative average particle size (D50 median diameter) measured on a volume basis using a particle size analyzer LS 13 320 manufactured by Beckman Coulter.

[0028] (C-1) Aluminum hydroxide sample is prepared by the solution method. 0.1 g of (C-1) sample is placed in 10 ml of absolute ethanol, dispersed by ultrasonication (100 watts), and stirred for 2 minutes to completely disperse the aluminum hydroxide. Two to three drops of the sample solution are taken and placed in the sample cell of the particle size analyzer.

[0029] (C-2) and (C-3) Prepare aluminum hydroxide samples (or other thermally conductive fillers with an average particle size of 7 μm or more) using the dry powder method. Place an appropriate amount of the sample, dried at room temperature, into the filling cylinder of the particle size analyzer. Insert the filling cylinder into the detection slot of the analyzer.

[0030] In the present invention, the particle size distribution of the aluminum hydroxides (C-1), (C-2) and (C-3) is unimodal, or their particle sizes satisfy a unimodal or nearly unimodal particle size distribution.

[0031] In the present invention, an almost unimodal particle size distribution means that, although two or more peaks may be present in the volume integral map of the measurement sample, the volume integral area of ​​the main peak accounts for more than 80%, preferably more than 85%, more preferably more than 90%, and more preferably more than 95% of the total volume integral area.

[0032] Spherical fillers, which are generally spherical in shape, are filler materials obtained from amorphous fillers that have been treated by chemical and / or physical (including heat treatment) processes.

[0033] Spherical alumina is a product obtained after heat treatment of amorphous alumina, and is generally spherical in shape.

[0034] Preferably, the thermally conductive silicone composition contains 1 to 100 parts by mass, and preferably 1 to 50 parts by mass, of component (E) per 100 parts by mass of component (A), and component (E) is one or more selected from (E-1): E-1) is an alkoxysilane compound represented by the following formula (1). R 1 a R 2 b Si(OR 3 ) 4-a-b (1) [In the formula, each R 1 each independently represents an alkyl group having 1 to 24 carbon atoms, preferably 6 to 24 carbon atoms, and more preferably 12 to 18 carbon atoms; 2 each independently represents an unsubstituted or substituted hydrocarbon group having 1 to 10 carbon atoms, preferably methyl or ethyl; 3 independently represent an alkyl group having 1 to 6 carbon atoms, preferably methyl or ethyl; a represents an integer of 1 to 3, and b represents an integer of 0 to 2, with the proviso that a+b is an integer of 1 to 3.

[0035] In the present invention, the weight ratio of the component (C) to the component (E-1) is between 100 and 800, preferably between 200 and 500, and more preferably between 200 and 400.

[0036] Furthermore, the thermally conductive silicone composition preferably has an absolute viscosity at 25°C of 250,000 mPa·s or less, preferably 200,000 mPa·s or less, and more preferably 170,000 mPa·s or less.

[0037] Such a thermally conductive silicone composition has excellent moldability.

[0038] The present invention further provides a thermally conductive silicone cured product comprising the cured product of the thermally conductive silicone composition.

[0039] Such thermally conductive silicone cured products are excellent in both thermal conductivity and light weight.

[0040] As described above, the thermally conductive silicone composition of the present invention is made by carefully adjusting and blending a silicone composition containing a specific organopolysiloxane, hydrogenpolysiloxane, and thermally conductive filler, thereby allowing the substrate to be densely filled with the thermally conductive filler. This allows for a lightweight composition with high thermal conductivity, i.e., a thermal conductivity of 3.1 W / m K or more and a density of 2.4 g / cm. 3 It is possible to provide a thermally conductive silicone composition that yields the following thermally conductive silicone cured product: Such a thermally conductive silicone cured product is useful as a thermally conductive material to be interposed at the interface between the hot surface of a heat-generating electronic component and a heat dissipation member such as a heat sink or circuit board, and is particularly useful for cooling electronic components by thermal conduction.

[0041] As described above, there has been a need for the development of a lightweight, highly thermally conductive silicone cured product (thermally conductive resin molded article) and a thermally conductive silicone composition for forming such a cured product.

[0042] As a result of extensive research into achieving the above object, the inventors of the present invention have developed a silicone composition containing a specific organopolysiloxane, a hydrogenpolysiloxane, and a thermally conductive filler, which is precisely adjusted and blended, and by densely filling the base material with the thermally conductive filler, a silicone composition having a thermal conductivity of 3.1 W / m K or more and a density of 2.4 g / cm 3 We have found that it is possible to obtain a lightweight, thermally conductive silicone cured product with high thermal conductivity, as described below. This discovery led to the completion of the present invention.

[0043] Specifically, the thermally conductive silicone composition is characterized by comprising:

[0044] Component (A): organopolysiloxane, preferably component (A-1): alkenyl group-containing organopolysiloxane

[0045] Component (A) is an organopolysiloxane. Component (A) is the main component of the composition of the present invention. In general, the main chain portion is usually composed of basic diorganosiloxane repeating units, but this molecular structure may contain a partially branched structure or may be a cyclic structure. However, from the perspective of physical properties such as the mechanical strength of the cured product, it is preferable that the main chain be a linear diorganopolysiloxane.

[0046] Component (A-1) is an alkenyl-containing organopolysiloxane containing at least two silicon-bonded alkenyl groups per molecule. Component (A-1) functions as the main component of the composition of the present invention. Generally, the main chain is typically composed of basic diorganosiloxane repeating units, but this molecular structure may contain a partially branched structure or a cyclic structure. However, from the perspective of physical properties such as the mechanical strength of the cured product, it is preferred that the main chain be a linear diorganopolysiloxane.

[0047] The functional group bonded to silicon atom can include unsubstituted or substituted monovalent hydrocarbon group.For example, alkyl group, for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group and dodecyl group, cycloalkyl group, for example, cyclopentyl group, cyclohexyl group and cycloheptyl group, aryl group, for example, phenyl group, tolyl group, xylyl group, naphthyl group and biphenylyl group, aralkyl group, for example, benzyl group, phenylethyl group, phenylpropyl group and methylbenzyl group, and the group in which part or all of the hydrogen atoms bonded to carbon atoms of these groups are replaced with cyano group, halogen atom such as fluorine, chlorine and bromine. Examples of such substituted groups include chloromethyl, 2-bromoethyl, 3-chloropropyl, 3,3,3-trifluoropropyl, chlorophenyl, fluorophenyl, cyanoethyl, and 3,3,4,4,5,5,6,6,6-nonafluorohexyl. Typical examples of functional groups include those having 1 to 10 carbon atoms, and particularly those having 1 to 6 carbon atoms. Preferred examples of functional groups include unsubstituted or substituted alkyl groups having 1 to 3 carbon atoms, such as methyl, ethyl, propyl, chloromethyl, bromoethyl, 3,3,3-trifluoropropyl, and cyanoethyl, as well as unsubstituted or substituted phenyl groups, such as phenyl, chlorophenyl, and fluorophenyl. Furthermore, the functional groups bonded to the silicon atom do not all need to be the same.

[0048] Furthermore, the alkenyl group typically has about 2 to 8 carbon atoms. Examples include vinyl, allyl, propenyl, isopropenyl, butenyl, hexenyl, and cyclohexenyl groups. Among these, lower alkenyl groups such as vinyl and allyl are preferred, with vinyl being particularly preferred. Note that two or more alkenyl groups are required per molecule, and in order to improve the flexibility of the resulting cured product, it is preferred that each alkenyl group be bonded only to a silicon atom at the molecular chain terminal.

[0049] The organopolysiloxane of component (A) preferably has a viscosity at 25° C. in the range of 10 to 100,000 mPa·s, particularly preferably 50 to 50,000 mPa·s, more preferably 50 to 20,000 mPa·s, and even more preferably 50 to 2,000 mPa·s. The organopolysiloxane of component (A) is preferably polydimethylsiloxane.

[0050] Component (A-1): The alkenyl group-containing organopolysiloxane preferably has a viscosity at 25°C of 10 to 100,000 mPa·s, particularly preferably 50 to 10,000 mPa·s, more preferably 50 to 1,000 mPa·s, and even more preferably 50 to 200 mPa·s. A viscosity of 10 mPa·s or higher results in good storage stability of the resulting composition. On the other hand, a viscosity of 100,000 mPa·s or lower results in good stretchability of the resulting composition. Component (A-1) alkenyl group-containing organopolysiloxane is preferably a vinyl-terminated polydimethylsiloxane.

[0051] The organopolysiloxane of component (A) may be used alone or in combination of two or more different types with different viscosities and the like.

[0052] The alkenyl group-containing organopolysiloxane of component (A-1) may be used alone, or two or more different types with different viscosities may be used in combination.

[0053] Optional ingredient (B): organohydrogenpolysiloxane Component (B) is an organohydrogenpolysiloxane having at least two, and preferably 2 to 100, hydrogen atoms directly bonded to silicon atoms (Si-H groups) per molecule. This component acts as a crosslinker for component (A-1). Specifically, the Si-H groups of component (B) are added to the alkenyl groups of component (A-1) through a hydrosilylation reaction promoted by a platinum group metal curing catalyst (component (D)) described below, forming a three-dimensional network structure with a crosslinked structure. Note that component (B) will not cure if it has fewer than two Si-H groups per molecule.

[0054] The organohydrogenpolysiloxane used can be represented by the following average structural formula (4), but is not limited thereto.

[0055] [ka]

[0056] In the formula, each R' independently represents a hydrogen atom or an unsubstituted or substituted monovalent hydrocarbon group containing no aliphatic unsaturated bonds, at least two R' are hydrogen atoms, and e represents an integer of 1 or greater.

[0057] Examples of the unsubstituted or substituted monovalent hydrocarbon group not containing an aliphatic unsaturated bond as R' other than hydrogen in formula (4) include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, heptyl, octyl, nonyl, decyl, and dodecyl groups; cycloalkyl groups such as cyclopentyl, cyclohexyl, and cycloheptyl groups; aryl groups such as phenyl, tolyl, xylyl, naphthyl, and biphenylyl groups; aralkyl groups such as benzyl, phenylethyl, phenylpropyl, and methylbenzyl groups; and groups in which some or all of the hydrogen atoms bonded to carbon atoms of these groups have been substituted with cyano groups or halogen atoms such as fluorine, chlorine, and bromine. Examples of such substituted groups include chloromethyl, 2-bromoethyl, 3-chloropropyl, 3,3,3-trifluoropropyl, chlorophenyl, fluorophenyl, cyanoethyl, and 3,3,4,4,5,5,6,6,6-nonafluorohexyl. Typical examples of monovalent hydrocarbon groups include those having 1 to 10 carbon atoms, with those having 1 to 6 carbon atoms being particularly typical. Preferred monovalent hydrocarbon groups include unsubstituted or substituted alkyl groups having 1 to 3 carbon atoms, such as methyl, ethyl, propyl, chloromethyl, bromoethyl, 3,3,3-trifluoropropyl, and cyanoethyl, as well as unsubstituted or substituted phenyl groups, such as phenyl, chlorophenyl, and fluorophenyl. Furthermore, all R groups do not have to be the same.

[0058] The amount of component (B) added is such that the amount of Si-H groups derived from component (B) is 0.1 to 5.0 moles (the number of moles of hydrogen atoms directly bonded to silicon atoms is 0.1 to 5.0 times the number of moles of alkenyl groups derived from component (A-1)) per mole of alkenyl groups derived from component (A-1), preferably 0.3 to 2.0 moles, and more preferably 0.5 to 1.0 mole. If the amount of Si-H groups derived from component (B) is less than 0.1 mole per mole of alkenyl groups derived from component (A-1), curing may not occur or the strength of the cured product may be insufficient, causing the molded article to be unable to maintain its shape and making it difficult to handle. On the other hand, if the amount exceeds 5.0 moles, the cured product may be inflexible and brittle.

[0059] The organopolysiloxane of component (B) may be used alone or in combination of two or more different types with different viscosities and the like.

[0060] In the above composition, component (B) can include (B-1) and (B-2).

[0061] Component (B-1) organic hydrogen-containing polysiloxane is an organic hydrogen-containing polysiloxane having at least three, preferably 3 to 100, hydrogen atoms (Si-H groups) directly bonded to silicon atoms in one molecule, and the hydrogen content is 0.5 to 4 mmol / g, preferably 0.8 to 3 mmol / g, more preferably 1.1 to 2.7 mmol / g, and more preferably 1.5 to 2.3 mmol / g.

[0062] The organic hydrogen-containing polysiloxane, component (B-2), is an organic hydrogen-containing polysiloxane having two hydrogen atoms directly bonded to silicon atoms (Si-H groups) per molecule, and has a hydrogen content of 0.01 to 1.5 mmol / g, preferably 0.1 to 1.2 mmol / g, more preferably 0.3 to 1.0 mmol / g, and more preferably 0.4 to 0.8 mmol / g.

[0063] In the above composition, component (B) contains (B-1) and (B-2), and the amount of component (B-1) is 0.5 to 3% by weight, preferably 1.5 to 2.5% by weight, based on component (A-1) calculated as 100% by weight.

[0064] In the above composition, component (B) contains (B-1) and (B-2), and the amount of component (B-2) is 10 to 50% by weight, preferably 20 to 40% by weight, based on component (A-1) calculated as 100% by weight.

[0065] Component (C): Thermally conductive filler

[0066] Aluminum hydroxide is inexpensive and has a yield of 2.42 g / cm 3 Its density is significantly lower than that of alumina. Aluminum hydroxide also inhibits the precipitation of thermally conductive fillers in silicone compositions, contributing to the weight reduction of equipment. Furthermore, aluminum hydroxide has a Mohs hardness of 3, making it much softer than alumina. It is useful as a thermally conductive filler that reduces wear on reactors and agitator blades and has flame-retardant and insulating properties. However, aluminum hydroxide has a lower thermal conductivity than alumina. Therefore, when using aluminum hydroxide to enhance the thermal conductivity of silicone thermally conductive compositions and their cured products, it is necessary to pack the aluminum hydroxide densely. However, such high-density packing is extremely difficult. For this reason, it has been difficult to produce thermally conductive silicone cured products with a thermal conductivity of 3.1 W / m·K or higher when aluminum hydroxide accounts for 0.9 or more parts by mass of the total thermally conductive filler. The present invention overcomes this problem of the prior art by carefully adjusting and formulating a silicone composition containing a specific organopolysiloxane, a hydrogenpolysiloxane, and a thermally conductive filler, thereby densely loading the base material with the thermally conductive filler. The present invention provides a thermally conductive silicone composition that can yield a lightweight thermally conductive silicone cured product with high thermal conductivity.

[0067] Preferably, component (C) is For example, 10 to 25% by weight of (C-1) aluminum hydroxide having an average particle size of 0.1 μm or more and less than 4 μm, and having an average particle size of 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, or 2.8 μm; 18 to 37% by weight of (C-2) aluminum hydroxide having an average particle size of 4 μm or more and 20 μm or less, for example, an average particle size of 6, 8, 10, 12, 14, 16, or 18 μm; For example, 48 to 65% by weight of (C-3) aluminum hydroxide having an average particle size of 80 μm or more and 100 μm or less, including those having average particle sizes of 82, 84, 86, 88, 90, 92, 94, 96, and 98 μm, The amounts of (C-1), (C-2) and (C-3) above are calculated based on 100% by weight of component (C) in the composition.

[0068] In this way, particles containing aluminum hydroxide as the main component with different particle sizes are carefully combined. Specifically, components (C-1) small particles, (C-2) medium particles, and (C-3) large particles are combined in a carefully examined blend ratio. This allows the base material to be densely packed so that the small to medium particles fill the gaps between the large particles.

[0069] On the other hand, if the average particle size of the aluminum hydroxide for components (C-1), (C-2), and (C-3) is outside the range, or if the composition ratio of components (C-1), (C-2), and (C-3) is outside the range, it will be difficult to prepare a thermally conductive silicone composition that will yield a thermally conductive silicone cured product that has a high thermal conductivity of 3.1 W / m K or more, is lightweight, and has a relatively low viscosity.

[0070] Each average particle size is a volume-based cumulative average particle size (D50 median diameter) measured using a particle size analyzer LS 13 320 manufactured by Beckman Coulter.

[0071] The small-diameter aluminum hydroxide (filler) of component (C-1), in combination with the medium- to large-diameter aluminum hydroxides of components (C-2) and (C-3), improves the thermal conductivity and fluidity of the composition and prevents filler precipitation. The average particle size of the small-diameter aluminum hydroxide is 0.1 μm or more and less than 4 μm, preferably 1 to 2 μm. If the average particle size is outside the above range, the effects of improving the thermal conductivity and fluidity of the composition and preventing filler precipitation in combination with components (C-2) and (C-3) cannot be obtained. One or more aluminum hydroxides of component (C-1) may be used as a composite.

[0072] Component (C-1) is blended in an amount of 10 to 25% by weight, preferably 19 to 21% by weight, of the aluminum hydroxide contained in component (C). If the mass ratio is outside this range, the effects of improving the thermal conductivity and fluidity of the composition and preventing precipitation of the filler, which are achieved by combining it with components (C-2) and (C-3), cannot be obtained.

[0073] The large-diameter aluminum hydroxide (filler) of component (C-3) enables a significant improvement in thermal conductivity. The average particle size of the large-diameter aluminum hydroxide is 80 μm or more and 100 μm or less, preferably 85 to 95 μm. If the average particle size is outside the above range, the effect of improving thermal conductivity decreases, the viscosity of the composition increases, and processability decreases. One or more types of aluminum hydroxide of component (C-3) may be used as a composite.

[0074] Component (C-3) is blended in an amount of 50 to 65% by weight, preferably 58 to 63% by weight, of the aluminum hydroxide contained in component (C). If the mass ratio is outside the above range, the thermal conductivity improving effect decreases, the viscosity of the composition increases, and processability decreases.

[0075] The amounts of (C-1), (C-2) and (C-3) above are calculated based on 100% by weight of component (C) in the composition.

[0076] Thermally conductive fillers generally do not contain fumed or precipitated silica.

[0077] In the compositions of the present invention, the content of fumed silica and / or precipitated silica is less than 1% by weight, preferably less than 0.1% by weight, calculated on 100% by weight of the total composition.

[0078] The different thermally conductive fillers are not particularly limited. Materials generally considered to be thermally conductive fillers can be used, such as non-magnetic metals such as copper or aluminum, metal oxides such as alumina, silica, magnesia, bengal, beryllia, titania, or zirconia, metal nitrides such as aluminum nitride, silicon nitride, or boron nitride, metal hydroxides such as magnesium hydroxide, artificial diamond, and silicon carbide. Also, particles with a particle size of 0.1 to 200 μm can be used. One or more of these may be used as a composite.

[0079] Component (C) should be blended in an amount of 800 to 4,000 parts by mass, preferably 900 to 2,000 parts by mass, and more preferably 900 to 1,500 parts by mass per 100 parts by mass of component (A). If the blending amount is less than 800 parts by mass, the thermal conductivity of the resulting composition will be poor. If the blending amount exceeds 2,000 parts by mass, kneading workability will be impaired and the cured product will become significantly brittle. To obtain a product with higher thermal conductivity and lighter weight, the filling factor of the composition is usually 0.88 or higher.

[0080] Optional component (D): Platinum group metal curing catalyst Component (D) is a platinum group metal-based curing catalyst, and is not particularly limited as long as it promotes the addition reaction between the alkenyl group derived from component (A-1) and the Si-H group derived from component (B). Examples of catalysts include known catalysts used in hydrosilylation reactions. Specific examples include platinum group metals such as platinum (including platinum black), rhodium, and palladium; platinum chloride; chloroplatinic acid; and chloroplatinic acid salts such as HPtCl·nH0, HPtCl·nH0, NaHPtCl·nH0, KHPtCl·nH0, NaPtCl·nH0, KPtCl·nH0, PtCl·nH0, PtCl, and NaHPtCl·nH0 (where n is an integer from 0 to 6, preferably 0 or 6); alcohol-modified chloroplatinic acid (U.S. Pat. No. 3,220,999); No. 72), complexes of chloroplatinic acid with olefins (see U.S. Pat. Nos. 3,159,601, 3,159,662, and 3,775,452), platinum black and platinum group metals such as palladium supported on a support such as alumina, silica, or carbon, rhodium-olefin complexes, chlorotris(triphenylphosphine)rhodium (Wilkinson's catalyst), complexes of platinum chloride, chloroplatinic acid, or chloroplatinate with vinyl group-containing siloxanes, particularly cyclic siloxanes containing no groups other than vinyl groups, and the like.

[0081] Component (D) is used in an amount that results in a platinum group metal content of 0.1 to 1,000 ppm by mass relative to component (A-1). If the content is less than 0.1 ppm, sufficient catalytic activity cannot be obtained. If the content exceeds 1,000 ppm, costs will increase without improving the effect of accelerating the addition reaction, and any catalyst remaining in the cured product may also reduce the insulating properties.

[0082] Component (E): Surface treatment agent The composition of the present invention can be blended with a surface treatment agent, component (E), to hydrophobize the thermally conductive filler, component (C), during the preparation of the composition, thereby improving its wettability with the organopolysiloxane, component (A), thereby dispersing the thermally conductive filler, component (C), uniformly throughout the matrix of component (A). As component (E), the following components (E-1) and (E-2) are particularly preferred.

[0083] Component (E-1): an alkoxysilane compound represented by the following formula (1): R 1 a R 2 b Si(OR 3 ) 4-a-b (1) In the formula, each R 1 each independently represents an alkyl group having 1 to 24 carbon atoms, preferably 6 to 24 carbon atoms, and more preferably 12 to 18 carbon atoms; 2 independently represent an unsubstituted or substituted hydrocarbon group having 1 to 10 carbon atoms, preferably methyl or ethyl, and each R 3 each independently represents an alkyl group having 1 to 6 carbon atoms, a represents an integer of 1 to 3, and b represents an integer of 0 to 2, with the proviso that a+b is an integer of 1 to 3.

[0084] R in formula (1) 1 Examples of the alkyl group represented by R include a hexyl group, an octyl group, a nonyl group, a decyl group, a dodecyl group, and a tetradecyl group. 1 When the number of carbon atoms in the alkyl group represented by the formula (I) is in the range of 6 to 15, the wettability of component (A) is sufficiently improved, resulting in excellent handleability, and the composition also has good low-temperature properties.

[0085] R 2Examples of the unsubstituted or substituted hydrocarbon group represented by the formula (I) include alkyl groups such as methyl, ethyl, vinyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, heptyl, octyl, nonyl, decyl, and dodecyl groups; cycloalkyl groups such as cyclopentyl, cyclohexyl, and cycloheptyl groups; aryl groups such as phenyl, tolyl, xylyl, naphthyl, and biphenylyl groups; aralkyl groups such as benzyl, phenylethyl, phenylpropyl, and methylbenzyl groups; and groups in which some or all of the hydrogen atoms bonded to carbon atoms of these groups have been substituted with cyano groups or halogen atoms such as fluorine, chlorine, and bromine. Examples of such substituted groups include a chloromethyl group, a 2-bromoethyl group, a 3-chloropropyl group, a 3,3,3-trifluoropropyl group, a chlorophenyl group, a fluorophenyl group, a cyanoethyl group, and a 3,3,4,4,5,5,6,6,6-nonafluorohexyl group. Typical examples of monovalent hydrocarbon groups include those having 1 to 10 carbon atoms, and particularly typical examples include those having 1 to 6 carbon atoms. Preferred examples of monovalent hydrocarbon groups include unsubstituted or substituted alkyl groups having 1 to 3 carbon atoms, such as a methyl group, an ethyl group, a propyl group, a chloromethyl group, a bromoethyl group, a 3,3,3-trifluoropropyl group, and a cyanoethyl group, as well as unsubstituted or substituted phenyl groups, such as a phenyl group, a chlorophenyl group, and a fluorophenyl group.

[0086] R 3 Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, and a hexyl group. Furthermore, a and b are not particularly limited as long as a is an integer of 1 to 3, b is an integer of 0 to 2, and a+b is an integer of 1 to 3. Preferably, a is 1 and b is 0.

[0087] Component (E-1) is preferably an alkoxysilane containing a C6-18 long-chain alkyl group, more preferably a trialkoxysilane containing a C6-18 long-chain alkyl group, and more preferably hexadecyltrimethoxysilane, hexadecyltriethoxysilane, tetradecyltrimethoxysilane, tetradecyltriethoxysilane, dodecyltrimethoxysilane, or dodecyltriethoxysilane.

[0088] As the surface treatment agent for component (E), either or both of components (E-1) may be blended alone or in combination. The amount of component (E) is preferably 1 to 100 parts by mass, particularly preferably 1 to 50 parts by mass, and even more preferably 1 to 10 parts by mass per 100 parts by mass of component (A).

[0089] Component (F): Characterization agent

[0090] As component (F), an organopolysiloxane having a viscosity at 25° C. of 10 to 100,000 mPa·s and represented by the following formula (3) can be added.

[0091] [ka] [In the formula, each R 5 each independently represents a monovalent hydrocarbon group having 1 to 10 carbon atoms and no aliphatic unsaturated bonds, and d represents an integer of 5 to 2,000.

[0092] Component (F) is used as needed to impart properties such as viscosity modifier and plasticizer to the thermally conductive silicone composition, but is not limited to these. These may be used alone, or two or more may be used in combination.

[0093] Each R 5 R independently represents an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms. 5Examples of the alkyl group include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, heptyl, octyl, nonyl, decyl, and dodecyl groups; cycloalkyl groups such as cyclopentyl, cyclohexyl, and cycloheptyl groups; aryl groups such as phenyl, tolyl, xylyl, naphthyl, and biphenylyl groups; aralkyl groups such as benzyl, phenylethyl, phenylpropyl, and methylbenzyl groups; and groups in which some or all of the hydrogen atoms bonded to carbon atoms of these groups have been substituted with cyano groups or halogen atoms such as fluorine, chlorine, and bromine. Examples of such substituted groups include chloromethyl, 2-bromoethyl, 3-chloropropyl, 3,3,3-trifluoropropyl, chlorophenyl, fluorophenyl, cyanoethyl, and 3,3,4,4,5,5,6,6,6-nonafluorohexyl. Typical examples of monovalent hydrocarbon groups include those having 1 to 10 carbon atoms, and particularly typical examples include those having 1 to 6 carbon atoms. Preferred monovalent hydrocarbon groups include unsubstituted or substituted alkyl groups having 1 to 3 carbon atoms, such as methyl, ethyl, propyl, chloromethyl, bromoethyl, 3,3,3-trifluoropropyl, and cyanoethyl, as well as unsubstituted or substituted phenyl groups, such as phenyl, chlorophenyl, and fluorophenyl. Methyl and phenyl groups are particularly preferred.

[0094] From the viewpoint of the required viscosity, d is preferably an integer of 5 to 2,000, and particularly preferably an integer of 10 to 1,000.

[0095] Furthermore, the viscosity at 25°C is preferably 10 to 100,000 mPa·s, and particularly preferably 100 to 10,000 mPa·s. If the viscosity is 10 mPa·s or higher, the cured product of the resulting composition will be less prone to oil bleeding. If the viscosity is 100,000 mPa·s or lower, the resulting thermally conductive silicone composition will have adequate flexibility.

[0096] When component (F) is added to the thermally conductive silicone composition of the present invention, there are no particular restrictions on the amount added, and it can be 10 to 100 parts by mass per 100 parts by mass of component (A). When the amount added is within this range, it becomes easier to maintain good fluidity and operability of the thermally conductive silicone composition before curing, and it also becomes easier to fill the composition with the thermally conductive filler of component (C).

[0097] In the thermally conductive silicone composition of the present invention, the amount of component (F) is preferably less than 0.1 part by mass, and more preferably less than 0.01 part by mass, per 100 parts by mass of component (A), which prevents oil leakage and contamination of the substrate of the thermally conductive silicone composition.

[0098] Optional ingredient (G): Reaction inhibitor An addition reaction inhibitor can be used as component (G). Any of the known addition reaction inhibitors used in typical addition reaction curable silicone compositions can be used. Examples include acetylene compounds such as 1-ethynyl-1-hexanol and 3-butyn-1-ol, various nitrogen compounds, organic phosphorus compounds, oxime compounds, and organic chlorine compounds. When component (G) is blended, the amount used is preferably 0.01 to 1 part by mass, more preferably 0.1 to 0.8 parts by mass, per 100 parts by mass of component (A-1). This blend amount allows the curing reaction to proceed sufficiently, without impairing molding efficiency.

[0099] Other ingredients The thermally conductive silicone composition of the present invention may further contain other components as needed. Examples of optional components that can be blended include heat resistance improvers such as iron oxide and cerium oxide, viscosity modifiers such as silica, colorants, and release agents.

[0100] Embodiment Thermally conductive silicone cured product and method for producing same

[0101] The thermally conductive silicone cured product (thermally conductive resin molded article) of the present invention is a cured product of the above-mentioned thermally conductive silicone composition. The curing conditions for curing (molding) the thermally conductive silicone composition can be the same as those for known addition reaction curable silicone rubber compositions. For example, the composition will cure sufficiently at room temperature, but heating may be applied as necessary. Preferably, the thermally conductive silicone composition is addition cured at 100 to 120°C for 8 to 12 minutes. Such a cured product (molded article) of the present invention has excellent thermal conductivity.

[0102] Thermal conductivity of molded products The molded article of the present invention preferably has a thermal conductivity of 3.1 W / m·K or more. This is a measured value measured by the hot disc method at 25°C. Products with a thermal conductivity of 3.1 W / m·K or more are applicable to heat-generating components that generate large amounts of heat. This thermal conductivity can be adjusted by adjusting the type or particle size combination of the thermally conductive filler.

[0103] Hardness of molded product The molded article of the present invention is tested using a Zwick hardness tester. The hardness can be adjusted by changing the ratio of component (A-1) and component (B) to adjust the crosslink density.

[0104] The kinematic and static viscosity of the compositions of the present invention were tested according to DIN 53019 using an Anton Paar MCR302 instrument. [Example]

[0105] Components (A) to (G) used in the following examples and comparative examples are shown below.

[0106] Component (A): (A-1): An organopolysiloxane represented by the following formula (5), where X represents a vinyl group and n represents a number that gives a viscosity of 120 mPa·s.

[0107] [ka]

[0108] Ingredient (B): (B-1) A side chain hydrogen polysiloxane represented by the following formula (6), having a hydrogen content of 1.7 mmol / g.

[0109] [ka]

[0110] (B-2) A hydrogen-terminated polysiloxane represented by the following formula (5), where X represents hydrogen, and the hydrogen content is 0.53 mmol / g.

[0111] [ka]

[0112] Ingredients (C): (C-1-1) Aluminum hydroxide with an average particle size of 1.5 μm (C-1-2) Aluminum hydroxide having an average particle size of 1.5 μm, surface-treated with component (E-1) (C-2) Aluminum hydroxide with an average particle size of 10 μm (C-3) Aluminum hydroxide with an average particle size of 90 μm (C-4-1) Aluminum hydroxide with an average particle size of 50 μm (C-4-2) Aluminum hydroxide with an average particle size of 110 μm

[0113] Ingredients (D): 5% by mass solution of chloroplatinic acid in 2-ethylhexanol

[0114] Ingredients (E): Cetyltrimethoxysilane

[0115] Ingredients (G): Ethynylmethylidenecarbinol as an addition reaction inhibitor.

[0116] The above materials are provided by Wacker Chemie AG.

[0117] Components (A-1), (C) and (E) were added in the prescribed amounts described below in the Examples and Comparative Examples in Table 1 or Table 2, and the mixture was kneaded for 60 minutes with a planetary mixer.

[0118] To this mixture was added a predetermined amount of component (D) shown below in Table 2. The mixture was kneaded for 30 minutes.

[0119] To the obtained mixture, a predetermined amount of component (B) described later in Table 2 was added, and the mixture was kneaded for 30 minutes, thus obtaining compositions of Examples and Comparative Examples.

[0120] Molding method After mixing, the composition in Table 1 is obtained.

[0121] The resulting composition shown in Table 2 was poured into a mold measuring 60 mm x 60 mm x 6 mm and molded using a press molding machine at 100°C for 60 minutes.

[0122] Thermal conductivity evaluation method: The obtained compositions of Tables 1 and 2 were poured into a mold measuring 60 mm x 60 mm x 6 mm and used to measure thermal conductivity.

[0123] The compositions obtained in the Examples and Comparative Examples shown in Table 2 below were cured at 100°C for 60 minutes to form 6 mm thick sheets. Using two sheets of each composition, the thermal conductivity was measured using a thermal conductivity meter (product name: TC3000E, manufactured by Xi'an Xiatech Electronics Co., Ltd.).

[0124] hardness: The compositions obtained in the following Examples and Comparative Examples were cured into 6 mm thick sheets as described above. Two sheets from each composition were stacked on top of each other and measured with a Zwick hardness tester to obtain Shore 00 values.

[0125] Density: Measurements were performed using a METTLER TOLEDO ML204.

[0126] [Table 1]

[0127] In Table 1, when the proportions of small, medium, and large particle diameter aluminum hydroxides are the same, a comparison of Ex. 1 and C.Ex. 1 reveals that the silicone grease composition obtained in Ex. 1 (using aluminum hydroxide (C-3) having an average particle diameter of 90 μm) has a lower viscosity and higher thermal conductivity than the silicone grease composition obtained in C.Ex. 1 (using aluminum hydroxide (C-4-1) having an average particle diameter of 50 μm). A comparison of Ex. 3 and C.Ex. 3 reveals that the silicone grease composition obtained in Ex. 1 (using aluminum hydroxide (C-3) having an average particle diameter of 90 μm) has a lower viscosity and higher thermal conductivity than the silicone grease composition obtained in C.Ex. 3 (using aluminum hydroxide (C-4-2) having an average particle diameter of 110 μm). In other words, the present inventors have discovered that better performance can be achieved by using aluminum hydroxide with an average particle diameter of approximately 90 μm, rather than the previously considered large particle diameter of 40 to 150 μm.

[0128] Furthermore, when the ratio of (C-1):(C-2):(C-3) is 2:2:6, the product obtained in Ex.1 has the distinct effect of lower viscosity and higher thermal conductivity than the product in C.Ex.4.

[0129] [Table 2]

[0130] In Table 2, a comparison of Ex. 10 and C.Ex. 10 shows that the coking product obtained from Ex. 1 (using (C-3-1) aluminum hydroxide having an average particle size of 0 μm) has a lower viscosity and higher thermal conductivity than the coking product obtained from C.Ex. 10 (using (C-4-1) aluminum hydroxide having an average particle size of 50 μm).

Claims

1. Component (A) is an organopolysiloxane, preferably component (A-1) is an organopolysiloxane having two or more alkenyl groups per molecule; an optional component (B) which is an organohydrogenpolysiloxane having two or more hydrogen atoms directly bonded to silicon atoms, and which is contained in an amount such that the number of moles of hydrogen atoms directly bonded to silicon atoms in component (B) is 0.1 to 5.0 times the number of moles of alkenyl groups derived from component (A-1); Component (C) is a thermally conductive filler, 10 to 25% by weight of (C-1) aluminum hydroxide having an average particle size of 0.1 μm or more and less than 4 μm; 18 to 37% by weight of (C-2) aluminum hydroxide having an average particle size of 4 μm or more and 20 μm or less; (C-3) aluminum hydroxide having an average particle size of 80 μm or more and 100 μm or less, 48 ​​to 65% by weight; In (C-1), (C-2), and (C-3), component (C) in the composition is calculated as 100% by weight, and optional component (D) which is a platinum group metal curing catalyst having a platinum group metal element content of 0.1 to 1,000 ppm by weight relative to component (A-1), The filling rate of the thermally conductive filler is 0.88 or more, Filling rate = total amount of thermally conductive filler / total weight of composition; A composition wherein the total amount of all aluminum hydroxide is greater than 95% by weight, calculated based on the total amount of thermally conductive filler being 100% by weight.

2. 10. The composition of claim 1, wherein the total amount of total aluminum hydroxide is greater than 99% by weight, calculated based on the total amount of thermally conductive filler being 100% by weight.

3. The density of the composition is 2.4 g / cm ３ 3. The composition of claim 1 or 2, wherein:

4. The composition according to any one of claims 1 to 3, wherein the composition has a thermal conductivity of 3.1 W / mK or more.

5. Further comprising component (E-1), the weight ratio of the component (C) to the component (E-1) is between 100 and 800; The composition according to any one of claims 1 to 4, wherein component (E-1) is an alkoxysilane compound represented by the following formula (1): R １ ａ R ２ ｂ Si(OR ３ ) ４－ａ－ｂ (1) [In the formula, each R １ independently represent an alkyl group having 1 to 24 carbon atoms, and each R ２ independently represent an unsubstituted or substituted hydrocarbon group having 1 to 10 carbon atoms, and each R ３ independently represent an alkyl group having 1 to 6 carbon atoms; a represents an integer of 1 to 3, and b represents an integer of 0 to 2, with the proviso that a+b is an integer of 1 to 3.

6. The composition described in claim 5, wherein the amount of component (E-1) is 1 to 100 parts by mass per 100 parts by mass of component (A).

7. The component (C) is 10 to 20% by weight of (C-1) aluminum hydroxide having an average particle size of 0.5 μm or more and 3 μm or less; 20 to 35% by weight of (C-2) aluminum hydroxide having an average particle size of 7 μm or more and 15 μm or more; (C-3) aluminum hydroxide (50 to 60% by weight) having an average particle size of 85 μm or more and 95 μm or more; The composition according to any one of claims 1 to 6, wherein in (C-1), (C-2), and (C-3), the component (C) in the composition is calculated as 100% by weight.

8. 8. The composition according to claim 1, wherein the ratio of average particle sizes of (C-3) / (C-2) is between 7.0 and 12.

0.

9. 9. The composition according to claim 1, wherein the weight ratio of (C-1) / (C-3) is between 0.2 and 0.

4.

10. The composition according to any one of claims 1 to 9, wherein the weight ratio of (C-2) / (C-3) is between 0.2 and 0.8.

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