Heat dissipating silicone composition and method for producing same

Abstract

The present invention provides a paste-like heat dissipating silicone composition in which a crosslinked structure is formed, and which contains an addition reaction product of a component (A) and a component (B), and components (C), (D), and (E): (A) an organopolysiloxane which has an alkenyl group bonded to a silicon atom, but does not have an alkoxy group bonded to a silicon atom at a molecular chain terminal; (B) an organohydrogenpolysiloxane which has a hydrogen atom bonded to a silicon atom; (C) a thermally conductive filler; (D) an electromagnetic wave absorbing filler; and (E) a hydrosilylation reaction catalyst. As a result, the present invention provides: a silicone composition which exhibits excellent mountability and reliability, and has both heat dissipation properties and electromagnetic wave absorption properties; and a method for producing the silicone composition.

Description

Heat-dissipating silicone composition and method for producing same

[0001] The present invention relates to a heat-dissipating silicone composition and a method for producing the same.

[0002] Conventionally, heat-dissipating silicone greases based on silicone oil and containing various heat-dissipating fillers have been known (see, for example, Patent Document 1).

[0003] These heat-dissipating silicone greases are easy to work with, such as for dispensing and screen printing, and they flexibly follow heat sources such as elements, demonstrating high heat dissipation performance. However, when used over long periods of time, problems such as pump-out and displacement from the element can occur, making it impossible to maintain heat dissipation performance.

[0004] As a means for solving these problems, a method has been proposed in which a thermally conductive filler is blended into partially cross-linked silicone (Patent Documents 2 and 3), but since partially cross-linked silicone is difficult to mix with the filler, it is difficult to obtain a paste-like composition, and there are also problems such as difficulty in adjusting the viscosity to a desired level.

[0005] Many curable materials have been proposed as materials that maintain heat dissipation performance over a long period of time (e.g., Patent Documents 4 and 5). These materials have excellent ejection properties and, because they are in a liquid state during the mounting process, they flexibly conform to the elements and exhibit high heat dissipation performance. In addition, because they harden, they have excellent long-term reliability.

[0006] However, these materials require several steps before they can be mounted. For example, one-component curing materials often require refrigeration or freezing, and require a thawing process to reach room temperature and a heat curing process before mounting. On the other hand, two-component curing materials can be stored and cured at room temperature, but require the accurate measurement and mixing of two liquid components.

[0007] In order to overcome the above-mentioned problems, heat-dissipating silicone compositions that are excellent in mountability, storage stability, and reliability have been proposed (for example, Patent Document 6).

[0008] Next, we will discuss electromagnetic wave absorption performance. With the development of information technology, electronic devices that utilize electromagnetic waves have become widespread in society. Examples include wireless LANs, mobile phones, portable information terminals, road information systems, and driving assistance systems, and the electromagnetic waves used are shifting to the high-frequency range.

[0009] On the other hand, as these electronic devices and technologies become more widespread, problems have arisen in that the electromagnetic waves they emit affect other electronic devices, causing them to malfunction. Therefore, electronic devices are required to minimize the unwanted emission of electromagnetic waves, or to prevent malfunctions even when exposed to electromagnetic waves, and technologies are being developed to give devices electromagnetic wave absorption and electromagnetic wave blocking capabilities.

[0010] Conventional blocking technologies that utilize electromagnetic wave reflection, such as metal alloy thin films and plates, are effective in blocking external electromagnetic noise and preventing leakage, but can cause reflection and scattering inside devices, resulting in adverse effects due to the proliferation of electromagnetic noise.

[0011] On the other hand, electromagnetic wave absorbing materials using soft magnetic metal fillers or ferrite fillers are highly effective in suppressing and preventing leakage of electromagnetic noise, and their development is being actively promoted (Patent Documents 7 and 8). However, most of the electromagnetic wave absorbing materials are designed to be molded into sheets.

[0012] Molded sheets have poor conformability to equipment, which can prevent them from fully demonstrating their electromagnetic wave absorption performance. Furthermore, while they are easy to handle, they are poorly suited to automated mounting on devices using equipment. While pick-and-place type equipment is available, they are generally large, presenting a high barrier to entry and also posing problems with the accuracy of sheet placement. Furthermore, if unexpected electromagnetic noise occurs, it is necessary to start over from scratch, including the design of the sheet shape, which limits the design flexibility of the equipment.

[0013] Japanese Patent Application Laid-Open No. 3-162493 Japanese Patent Application Laid-Open No. 04-268376 Japanese Patent Application Laid-Open No. 2002-294269 Japanese Patent Application Laid-Open No. 6791672 Japanese Patent Application Laid-Open No. 2022-029985 Japanese Patent Application Laid-Open No. 6705426 Japanese Patent Application Laid-Open No. 4699388 Japanese Patent Application Laid-Open No. 2021-174889

[0014] Therefore, an object of the present invention is to provide a silicone composition that has excellent mountability and reliability, as well as heat dissipation and electromagnetic wave absorption properties, and a method for producing the same.

[0015] The present invention provides a heat-dissipating silicone composition in the form of a paste having a crosslinked structure, the heat-dissipating silicone composition comprising an addition reaction product of the following components (A) and (B), and the following components (C), (D), and (E): (A) an organopolysiloxane having alkenyl groups bonded to silicon atoms and no alkoxy groups bonded to silicon atoms at the molecular chain terminals, (B) an organohydrogenpolysiloxane having hydrogen atoms bonded to silicon atoms, (C) a thermally conductive filler, (D) an electromagnetic wave absorbing filler, and (E) a hydrosilylation reaction catalyst.

[0016] The heat-dissipating silicone composition of the present invention has excellent mounting performance such as ejection properties, high reliability in terms of misalignment resistance, conforms to the device, exhibits high heat dissipation performance, and suppresses electromagnetic noise emitted by the device.

[0017] Furthermore, the heat-dissipating silicone composition of the present invention preferably contains an alkoxy group-containing organopolysiloxane (F) represented by the following general formula (5) as a wettability improver. (In the formula, R ６ are independently unsubstituted or substituted monovalent hydrocarbon groups, R ７ are independently an alkyl group, and x is a positive number from 5 to 120.

[0018] In such a heat-dissipating silicone composition, the wettability improver is a component that improves the wettability of the components (C) and (D) with the components (A) and (B), and this improved wettability also improves the thermal conductivity of the heat-dissipating silicone composition.

[0019] In this case, the heat-dissipating silicone composition of the present invention preferably contains: 100 parts by mass of the component (A); the component (B) in an amount such that the number of hydrogen atoms bonded to silicon atoms is 0.2 to 2.0 moles per mole of alkenyl groups bonded to silicon atoms in the component (A); the total of the components (C) and (D) is 30 to 90 volume % relative to 100 volume % of the total of the components (A) to (F), and of this, the component (D) is in an amount such that 20 volume % or more; the component (E) in an amount such that the platinum atom content is 0.1 to 1,000 ppm by mass relative to the component (A); and the component (F) in an amount such that 0.1 to 1,000 parts by mass relative to 100 parts by mass of the total of the components (A) and (B).

[0020] The heat-dissipating silicone composition of the present invention can have such a blending ratio, for example.

[0021] The heat-dissipating silicone composition of the present invention provides a method for producing a heat-dissipating silicone composition, comprising the following steps (1) to (3): (1) a step of uniformly mixing the components (A) to (E) to obtain a paste-like composition, (2) a step of heating and mixing the paste-like composition to promote a hydrosilylation reaction and cause maturation, thereby obtaining a paste-like composition in which a crosslinked structure has been formed, and (3) a step of cooling the matured paste-like composition to a temperature of 50°C or less, followed by shear mixing, to obtain the heat-dissipating silicone composition.

[0022] In addition, the present invention can be produced in this manner.

[0023] The heat-dissipating silicone composition of the present invention can be produced by a method for producing the heat-dissipating silicone composition, comprising the following steps (1) to (3): (1) uniformly mixing the components (A) to (F) to obtain a paste-like composition, (2) heating and mixing the paste-like composition to promote a hydrosilylation reaction and allow it to mature, thereby obtaining a paste-like composition in which a crosslinked structure has been formed, and (3) cooling the matured paste-like composition to a temperature of 50°C or less, followed by shear mixing, to obtain the heat-dissipating silicone composition.

[0024] When the heat-dissipating silicone composition of the present invention contains a wettability enhancer, it can be produced in this manner.

[0025] The heat-dissipating silicone composition produced by the production method of the present invention has excellent mounting performance such as ejection properties, high reliability in terms of misalignment resistance, conforms to the device, exhibits high heat dissipation performance, and suppresses electromagnetic noise emitted by the device.

[0026] As described above, there has been a need for the development of a silicone composition that has excellent mountability and reliability, as well as heat dissipation and electromagnetic wave absorption properties, and a method for producing the same.

[0027] As a result of extensive research into the above-mentioned problems, the present inventors have found that a composition obtained by a specific blending composition and production method can solve the above-mentioned problems, and have thus completed the present invention.

[0028] Specifically, the present invention provides a heat-dissipating silicone composition in the form of a paste having a crosslinked structure, the heat-dissipating silicone composition comprising an addition reaction product of the following components (A) and (B), and the following components (C), (D), and (E): (A) an organopolysiloxane having alkenyl groups bonded to silicon atoms and no alkoxy groups bonded to silicon atoms at the molecular chain terminals, (B) an organohydrogenpolysiloxane having hydrogen atoms bonded to silicon atoms, (C) a thermally conductive filler, (D) an electromagnetic wave absorbing filler, and (E) a hydrosilylation reaction catalyst.

[0029] The present invention is described in detail below, but is not limited thereto. First, the components contained in the heat-dissipating silicone composition (hereinafter also referred to as the heat-dissipating silicone grease composition) are described.

[0030] <Heat-dissipating silicone grease composition> The heat-dissipating silicone composition of the present invention is a paste-like heat-dissipating silicone composition in which a crosslinked structure has been formed, and contains an addition reaction product of the following components (A) and (B), and the following components (C), (D), and (E):

[0031] -(A) Organopolysiloxane- The organopolysiloxane of component (A) is an organopolysiloxane that has alkenyl groups bonded to silicon atoms but does not have alkoxy groups bonded to silicon atoms at the molecular chain terminals, and the number of silicon-bonded alkenyl groups per molecule is on average more than one, preferably 0.01 to 5 mol %, and more preferably 0.012 to 3 mol % of the total organic groups. These silicon-bonded alkenyl groups may be present at either the molecular chain terminals or non-terminal positions, or both, within the organopolysiloxane molecule, but it is preferred that they be present only at both molecular chain terminals, as this improves flexibility.

[0032] There are no particular restrictions on the molecular structure of the organopolysiloxane of this component, and examples include linear and branched chain structures.

[0033] The kinematic viscosity of the organopolysiloxane of this component at 25°C is not particularly limited, but is typically 100 to 1,000,000 mm ２ / s, which improves the stability of the silicone grease composition and facilitates mixing with components (B), (C), and (D), which will be described later. Therefore, it is preferable that the viscosity is 500 to 100,000 mm ２ The kinematic viscosity is a value measured by an Ostwald meter at 25°C.

[0034] The alkenyl group bonded to the silicon atom typically has 2 to 10 carbon atoms, and preferably 2 to 6. Specific examples include vinyl, allyl, 1-butenyl, and 1-hexenyl groups, with vinyl being preferred from the standpoints of ease of synthesis and economy.

[0035] The silicon-bonded organic groups other than the silicon-bonded alkenyl groups are unsubstituted or substituted monovalent hydrocarbon groups typically having 1 to 20 carbon atoms, preferably 1 to 6 carbon atoms. Specific examples include alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, and dodecyl; aryl groups such as phenyl; aralkyl groups such as 2-phenylethyl and 2-phenylpropyl; and groups in which some or all of the hydrogen atoms in these groups have been substituted with halogen atoms such as chlorine or fluorine, such as chloromethyl and 3,3,3-trifluoropropyl. Of these, from the standpoints of ease of synthesis and economy, methyl and phenyl groups are preferred, and in particular, methyl groups account for 80 mol % or more, and especially 90 mol % or more, of all organic groups other than silicon-bonded alkenyl groups.

[0036] The organopolysiloxane of this component is, for example, an organopolysiloxane represented by the following average composition formula (1): ａ R １ ｂ SiO （４－ａ－ｂ）／２ (1) (wherein R is independently an unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond, R １ are independently an alkenyl group, a is a number that satisfies 0≦a<2.2, and b is a number that satisfies 0<b≦2.2, with the proviso that a+b is a number from 1.8 to 2.2.

[0037] In the above average composition formula (1), the unsubstituted or substituted monovalent hydrocarbon group represented by R typically has 1 to 20 carbon atoms, and preferably 1 to 6. Specific examples thereof include those exemplified as the unsubstituted or substituted monovalent hydrocarbon group in the organic group bonded to a silicon atom.

[0038] R １ The alkenyl group represented by the formula (I) has the number of carbon atoms of usually 2 to 10, preferably 2 to 6. Specific examples thereof include those exemplified above as the alkenyl group bonded to a silicon atom.

[0039] The organopolysiloxane of this component is preferably, for example, an organopolysiloxane represented by the following general formula (2):

[0040] (In the formula, R２ are independently unsubstituted or substituted monovalent hydrocarbon groups having no aliphatic unsaturated bonds, and R ３ are independently unsubstituted or substituted monovalent hydrocarbon groups, provided that R ３ at least one of the groups is an alkenyl group, and m is a positive number of 50 to 3,000.

[0041] In the above general formula (2), R ２ The unsubstituted or substituted monovalent hydrocarbon group represented by the formula (I) typically has 1 to 20 carbon atoms, and preferably 1 to 6 carbon atoms. Specific examples thereof include those exemplified as the unsubstituted or substituted monovalent hydrocarbon group in the silicon-bonded organic group other than the silicon-bonded alkenyl group.

[0042] R ３ The unsubstituted or substituted monovalent hydrocarbon group represented by the formula (I) typically has 1 to 20 carbon atoms, and preferably 1 to 6 carbon atoms. Specific examples thereof include those exemplified as the unsubstituted or substituted monovalent hydrocarbon group in the silicon-bonded organic group other than the silicon-bonded alkenyl group, and those exemplified as the silicon-bonded alkenyl group.

[0043] m is preferably a positive number of 100 to 2,000, more preferably 150 to 1,500.

[0044] Specific examples of the organopolysiloxane of this component include the following (I) to (III):

[0045] (wherein m is the same as above)

[0046] (In the formula, m １ and m ２ is m = m １ +m ２ is a positive number that satisfies

[0047] (In the formula, m １ and m ３ is m = m １ +m ３and the like, and preferably the organopolysiloxanes represented by formula (I) or formula (II) are used.

[0048] The organopolysiloxane of component (A) may use either a single compound, or a combination of two or more different compounds.

[0049] —(B) Organohydrogenpolysiloxane— The organohydrogenpolysiloxane of component (B) has hydrogen atoms bonded to silicon atoms in the molecule, and preferably has at least two, and more preferably 2 to 30, hydrogen atoms bonded to silicon atoms in each molecule. These silicon-bonded hydrogen atoms may be located at either the molecular chain terminals or non-terminal positions within the organohydrogenpolysiloxane molecule, or may be located at both the molecular chain terminals and non-terminal positions.

[0050] There are no particular limitations on the molecular structure of the organohydrogenpolysiloxane of this component, and examples include linear and branched chain structures.

[0051] The kinematic viscosity of the organohydrogenpolysiloxane of this component at 25°C is not particularly limited, but is usually 10 to 300 mm ２ / s, preferably 20 to 200 mm ２ / s.

[0052] The organic group bonded to the silicon atom other than the silicon-bonded hydrogen atom is typically an unsubstituted or substituted monovalent hydrocarbon group having a molecular weight of 1 to 20, preferably 1 to 6. Specific examples include alkyl groups such as methyl, ethyl, propyl, hexyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl, and octadecyl; cycloalkyl groups such as cyclopentyl and cyclohexyl; alkenyl groups such as vinyl and allyl; aryl groups such as phenyl and tolyl; aralkyl groups such as 2-phenylethyl and 2-methyl-2-phenylethyl; and halogenated hydrocarbon groups in which some or all of the hydrogen atoms in these groups have been substituted with halogen atoms such as chlorine or fluorine atoms, such as 3,3,3-trifluoropropyl, 3-(perfluorobutyl)ethyl, 2-(perfluorooctyl)ethyl, and p-chlorophenyl. Among these, from the viewpoints of ease of synthesis and economy, it is preferred that 90 mol % or more of all organic groups other than hydrogen atoms bonded to silicon atoms are methyl groups.

[0053] The organohydrogenpolysiloxane of this component is, for example, an organohydrogenpolysiloxane represented by the following average composition formula (3): ４ ｃ H ｄ SiO （４－ｃ－ｄ）／２ (3) (wherein, R ４ are independently an unsubstituted or substituted monovalent hydrocarbon group, c is a number that satisfies 0≦c<3, and d is a number that satisfies 0<d≦3, with the proviso that c+d satisfies 0<c+d≦3).

[0054] In the above average composition formula (3), R ４ The unsubstituted or substituted monovalent hydrocarbon group represented by the formula (I) typically has 1 to 20 carbon atoms, and preferably 1 to 6 carbon atoms. Specific examples include those exemplified as the unsubstituted or substituted monovalent hydrocarbon group in the organic group bonded to a silicon atom other than a hydrogen atom bonded to the silicon atom, and preferred are a methyl group, an ethyl group, a propyl group, and a phenyl group.

[0055] The organopolysiloxane of this component is preferably, for example, an organopolysiloxane represented by the following general formula (4):

[0056] (wherein n is a number from 5 to 200, and R ５ are independently a hydrogen atom or an unsubstituted or substituted monovalent hydrocarbon group, provided that at least two of them are hydrogen atoms.

[0057] In the above general formula (4), R ５ The unsubstituted or substituted monovalent hydrocarbon group represented by the formula (I) typically has 1 to 20 carbon atoms, and preferably 1 to 6. Specific examples thereof include the unsubstituted or substituted monovalent hydrocarbon groups exemplified in (A) in the organic groups bonded to silicon atoms other than hydrogen atoms bonded to silicon atoms.

[0058] n is preferably a number from 10 to 100, and more preferably from 15 to 90.

[0059] The amount of component (B) added is such that the number of hydrogen atoms bonded to silicon atoms in the organohydrogenpolysiloxane molecules of component (B) is preferably 0.2 to 2.0 moles, more preferably 0.5 to 1.5 moles, and particularly preferably 0.7 to 1.2 moles per mole of alkenyl groups bonded to silicon atoms in the organopolysiloxane molecules of component (A).

[0060] The organohydrogenpolysiloxane of component (B) may use either a single compound, or a combination of two or more different compounds.

[0061] -(C) Thermally conductive filler- The thermally conductive filler (component (C)) is a component that imparts thermal conductivity to the composition. This thermally conductive filler is not particularly limited, but is preferably one with good thermal conductivity. Specific examples include aluminum powder, zinc oxide powder, alumina powder, boron nitride powder, aluminum nitride powder, aluminum hydroxide powder, magnesium oxide powder, silicon nitride powder, copper powder, silver powder, diamond powder, nickel powder, zinc powder, stainless steel powder, and carbon powder.

[0062] The thermally conductive filler of this component is not particularly limited and may be, for example, spherical particles or a mixture of particles of various shapes without a particular defined shape. The average particle size of the thermally conductive filler is also not particularly limited, but is preferably 0.1 to 200 μm, more preferably 1 to 100 μm, as this provides a uniform composition with particularly excellent viscosity and extensibility.

[0063] - (D) Electromagnetic Wave Absorbing Filler - The electromagnetic wave absorbing filler of component (D) is a component for imparting electromagnetic wave absorbing properties to the composition. This electromagnetic wave absorbing filler is not particularly limited, and may be selected depending on the required absorption frequency band. Examples of soft magnetic metal powders include Fe-Ni, Fe-Co, Fe-Cr, Fe-Si, Fe-Al, Fe-Cr-Si, Fe-Cr-Al, and Fe-Al-Si alloys. Examples of ferrite fillers include MnFe, ２ O ４ , CoFe ２ O ４ , NiFe ２ O ４ , CuFe ２ O ４ , ZnFe ２ O ４ , MgFe ２ O ４ , Fe ３ O ４ Spinel ferrites such as Ba ２ Co ２ Fe １２ O ２２ , Ba ２ Ni ２ Fe １２ O ２２ , Ba ２ Zn ２ Fe １２ O ２２ , Ba ２ Mn ２ Fe １２ O ２２ , Ba ２ Mg ２ Fe １２ O ２２ , Ba ２ Cu ２ Fe １２ O ２２ , Ba ３ Co２ Fe ２４ O ４１ Examples of hexagonal ferrite include:

[0064] The electromagnetic wave absorbing filler of this component is not particularly limited and may be, for example, spherical particles, scaly particles, or a mixture of particles of various shapes with no particular defined shape. Furthermore, the average particle size of the electromagnetic wave absorbing filler is not particularly limited, but is preferably 0.1 to 100 μm, more preferably 1 to 30 μm, as this provides particularly excellent ejection and spreadability and allows for the production of a uniform composition.

[0065] The average particle size is usually determined by measuring the cumulative volume average diameter D ５０ Specifically, it can be determined as the cumulative 50% particle diameter (D) on a volume basis measured by a particle size distribution measuring device MT3000II manufactured by Microtrac Bell Co., Ltd. ５０ ) value.

[0066] The total amount of components (C) and (D) is preferably 30 to 90 volume %, more preferably 40 to 85 volume %, and even more preferably 70 to 80 volume %, based on 100 volume % of the total of components (A) to (D), component (E) described below, and, if included, component (F) described below, and of this, the amount of component (D) is 20 volume % or more, more preferably 30 volume % or more, and less than 90 volume %. When these ranges are satisfied, the composition will have excellent thermal conductivity and electromagnetic wave absorption performance.

[0067] The thermally conductive filler of component (C) may use either a single material or a combination of two or more different materials.

[0068] The electromagnetic wave absorbing filler of component (D) may be used alone or in combination of two or more.

[0069] -(E) Hydrosilylation Catalyst- The hydrosilylation catalyst, component (E), is a component that promotes the formation of a crosslinked structure by the addition reaction between components (A) and (B). As the hydrosilylation catalyst, any known catalyst can be used, including, for example, platinum alone or platinum compounds such as chloroplatinic acid, platinum-olefin complexes, and platinum-alcohol complexes.

[0070] The amount of component (E) to be blended is preferably 0.1 to 1,000 ppm, and especially 1 to 500 ppm, based on the mass of platinum atoms, relative to the organopolysiloxane of component (A).

[0071] The hydrosilylation reaction catalyst of component (E) may use either a single compound, or a combination of two or more different compounds.

[0072] Other Components In addition to the components (A) to (E), the following other components may be blended as necessary. These other components may be used alone or in combination of two or more.

[0073] <Wettability Improver> The wettability improver is a component for improving the wettability of the components (C) and (D) with respect to the components (A) and (B), and the improvement in wettability also improves the thermal conductivity of the composition. Specific examples thereof include alkoxysilane and the component (F) represented by the following general formula (5):

[0074] (In the formula, R ６ are independently unsubstituted or substituted monovalent hydrocarbon groups, R ７ are independently an alkyl group, and x is a positive number from 5 to 120.

[0075] In the above general formula (5), R ６The unsubstituted or substituted monovalent hydrocarbon group represented by the formula (I) typically has 1 to 20 carbon atoms, preferably 1 to 18, and more preferably 1 to 6. Specific examples thereof include alkyl groups such as methyl, ethyl, propyl, hexyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl, and octadecyl; cyclohexyl groups such as cyclopentyl and cyclohexyl; alkenyl groups such as vinyl and allyl; aryl groups such as phenyl and tolyl; aralkyl groups such as 2-phenylethyl and 2-methyl-2-phenylethyl; and halogenated hydrocarbon groups in which some or all of the hydrogen atoms in these groups have been substituted with halogen atoms such as chlorine and fluorine, such as 3,3,3-trifluoropropyl, 2-(perfluorobutyl)ethyl, 2-(perfluorooctyl)ethyl, and p-chlorophenyl, with methyl and vinyl being preferred.

[0076] R ７ The number of carbon atoms in the alkyl group represented by the formula (I) is usually 1 to 6. Specific examples thereof include a methyl group, an ethyl group, and a propyl group, and preferred are a methyl group and an ethyl group.

[0077] x is preferably a positive number of 10 to 90, and more preferably 15 to 80.

[0078] Examples of the alkoxysilane include alkoxysilanes represented by the following general formula (6): ８ ｙ R ９ ｚ Si(OR １０ ) ４－ｙ－ｚ (6) (wherein, R ８ are independently unsubstituted or substituted monovalent hydrocarbon groups having no aliphatic unsaturated bonds, and R ９ are independently unsubstituted or substituted monovalent hydrocarbon groups, R １０ are independently an alkyl group, y is an integer of 0 to 2, preferably 1, and z is an integer of 0 to 2, preferably 0 or 1, with the proviso that y+z is 1 or 2.

[0079] In the above general formula (6), R ８The unsubstituted or substituted monovalent hydrocarbon group represented by the formula (I) is a linear alkyl group typically having 6 to 15 carbon atoms, preferably 8 to 12 carbon atoms. When this range is satisfied, the wettability of components (C) and (D) is improved, and the handleability of this component is also improved. Specific examples include alkyl groups such as hexyl, octyl, nonyl, decyl, dodecyl, and tetradecyl.

[0080] R ９ The monovalent hydrocarbon group represented by the formula (I) typically has 1 to 8 carbon atoms, preferably 1 to 6. Specific examples thereof include alkyl groups, cycloalkyl groups, and alkenyl groups, and more specific examples include alkyl groups such as methyl, ethyl, propyl, hexyl, and octyl groups; cycloalkyl groups such as cyclopentyl and cyclohexyl groups; alkenyl groups such as vinyl and allyl groups; aryl groups such as phenyl and tolyl groups; aralkyl groups such as 2-phenylethyl and 2-methyl-2-phenylethyl groups; and halogenated hydrocarbon groups in which some or all of the hydrogen atoms in these groups have been substituted with halogen atoms such as chlorine and fluorine atoms, such as 3,3,3-trifluoropropyl, 2-(nanofluorobutyl)ethyl, 2-(heptadecafluorooctyl)ethyl, and p-chlorophenyl groups, and the like, and are preferably methyl, ethyl, vinyl, or phenyl groups.

[0081] R １０ The number of carbon atoms in the alkyl group represented by the formula (I) is usually 1 to 6. Specific examples thereof include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group, and preferred are a methyl group and an ethyl group.

[0082] Specific examples of alkoxysilanes represented by the above formula (6) include C ６ H １３ Si(OCH ３ ) ３ , C １０ H ２１ Si(OCH ３ ) ３ , C １２ H ２５ Si(OCH ３ ) ３ , C １２H ２５ Si(OC ２ H ５ ) ３ , C １０ H ２１ Si(CH ３ )(OCH ３ ) ２ , C １０ H ２１ Si(C ６ H ５ )(OCH ３ ) ２ , C １０ H ２１ Si(CH ３ )(OC ２ H ５ ) ２ , C １０ H ２１ Si(CH=CH ２ )(OCH ３ ) ２ , C １０ H ２１ Si(CH ２ CH ２ CF ３ )(OCH ３ ) ２ etc.

[0083] The amount of the wettability improver to be added is preferably 0.1 to 1,000 parts by mass, more preferably 0.5 to 600 parts by mass, and even more preferably 100 to 550 parts by mass, per 100 parts by mass of the total of components (A) and (B). When this range is satisfied, the wettability of components (C) and (D) is improved.

[0084] <Reaction Retarder> The reaction retarder is a component that is suitably used to control or inhibit the rate of progress of the addition reaction between component (A) and component (B) and to obtain a uniform composition. Specific examples thereof include acetylene compounds, nitrogen compounds, organic phosphorus compounds, oxime compounds, organic chloro compounds, etc. These reaction retarders are preferably used after being dissolved in an organic solvent such as toluene, xylene, or isopropyl alcohol in order to improve dispersibility in the composition.

[0085] The amount of the reaction inhibitor added is preferably 0.01 to 1 part by weight, and more preferably 0.1 to 5 parts by weight, per 100 parts by weight of the organopolysiloxane of component (A).

[0086] <Non-reactive organopolysiloxane> A non-reactive organopolysiloxane is an organopolysiloxane that does not have a reactive group in the molecule and that can suitably adjust the viscosity and workability of the resulting composition. The molecular structure of this non-reactive organopolysiloxane is not particularly limited, and may be linear or branched.

[0087] Examples of the reactive group include a hydrogen atom bonded to a silicon atom, a hydroxy group bonded to a silicon atom (i.e., a silanol group), an alkoxy group bonded to a silicon atom, an amino group, a carboxyl group, an epoxy group, a vinyl group, a mercapto group, and a methacryloxy group.

[0088] The non-reactive organopolysiloxane is not particularly limited, but dimethylpolysiloxane, phenylmethylpolysiloxane, etc. are preferred from an economical viewpoint.

[0089] The non-reactive organopolysiloxane preferably has a viscosity at 25°C of 10 to 1,000,000 mm ２ / s, more preferably 100 to 100,000 mm ２ / s.

[0090] The amount of non-reactive organopolysiloxane added is preferably 0 to 50 parts by weight, and more preferably 0 to 30 parts by weight, per 100 parts by weight of the combined total of components (A) and (B).

[0091] The present invention preferably provides a heat-dissipating silicone composition containing, for example, 100 parts by mass of component (A); component (B) in an amount such that the number of silicon-bonded hydrogen atoms is 0.2 to 2.0 moles per mole of silicon-bonded alkenyl groups in component (A); components (C) and (D) in an amount such that the total of components (A) to (F) is 100 volume % and that component (D) accounts for 30 to 90 volume % of the total, with component (A) to (F) accounting for 20 volume % or more; component (E) in an amount such that the platinum atom content is 0.1 to 1,000 ppm by mass relative to component (A); and component (F) in an amount such that 0.1 to 1,000 parts by mass per 100 parts by mass of the total of components (A) and (B).

[0092] <Production Method> The heat-dissipating silicone composition of the present invention is produced by a method comprising the following steps: (1) uniformly mixing components (A) to (E) (or components (A) to (F)) to obtain a paste-like composition; (2) heating and mixing the paste-like composition to promote the hydrosilylation reaction and cause maturation, thereby obtaining a paste-like composition in which a crosslinked structure has been formed; and (3) cooling the matured paste-like composition to a temperature of 50°C or less, followed by shear mixing, to obtain the heat-dissipating silicone composition.

[0093] The mixing includes, for example, mixing by stirring and kneading using a mixer or the like described below.

[0094] Step (1) is a step of obtaining a paste-like composition in which the components (A) to (E) are uniformly mixed. This paste-like composition may be obtained in any manner, and may be obtained by mixing a premix of the components (A) to (D) with the component (E), or by mixing the components (A) to (E) all at once. Specifically, the paste-like composition may be obtained, for example, by the following method.

[0095] First, components (A) to (D) are mixed by stirring, optionally together with a wettability enhancer (e.g., component (F)), a non-reactive organopolysiloxane, etc., and stirring is continued until the mixture becomes a paste, thereby obtaining a paste-like composition. During the stirring process up to this point, the mixture may be heated to approximately 50 to 200°C if necessary; however, if heated, the mixture is cooled to room temperature before adding the next component (E). If a reaction inhibitor is to be incorporated into the composition, the reaction inhibitor is then added to the obtained paste-like composition and stirred until it is uniformly mixed in the composition. Then, component (E) is added to the obtained paste-like composition, and stirring is continued until component (E) is uniformly dispersed in the composition.

[0096] Step (2) is a step in which the paste-like composition is heated and mixed to accelerate the hydrosilylation reaction and ripen. This step promotes the reaction between components (A) and (B) and forms a crosslinked structure in the composition.

[0097] When the paste-like composition is heated and mixed at a temperature of 90°C or higher, the hydrosilylation reaction proceeds at an appropriate rate, and it does not take a long time for the reaction to be completed (to reach a matured state). The heating and mixing is preferably carried out at a temperature of 90 to 200°C, more preferably 120 to 180°C.

[0098] The heating and mixing time is until the aging of the paste composition is completed, and is not particularly limited, but is usually 30 minutes to 5 hours, and preferably 1 to 3 hours to ensure aging.

[0099] Step (3) Step (3) involves cooling the aged paste-like composition to a temperature of 50°C or less while standing, followed by mixing under shear. This step yields the heat-dissipating silicone composition. Cooling may be achieved by natural heat dissipation or by using a cooling device or the like. Mixing under shear may be achieved using, for example, a mixer such as a planetary mixer, a three-roll mill, a two-roll mill, a kneader, a Disper, a Shinagawa mixer, a Supermascolloider, a Trimix, or a Twinmix, or a combination of these. Here, no particular shear force needs to be applied in this step until the cooling temperature is reached.

[0100] When the cooling temperature is 50°C or lower, sufficient shear force can be applied to the paste-like composition. Moreover, excessive cooling does not increase the shear force and improves workability, so the cooling is preferably carried out to 0 to 50°C, more preferably to 10 to 40°C. By undergoing this step (3), the viscosity and dischargeability of the composition can be adjusted.

[0101] The viscosity of the resulting composition is not particularly limited, but is, for example, 100 to 1,000 Pa·s, and preferably 200 to 800 Pa·s, as measured at 25°C using a Malcolm viscometer.

[0102] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the examples, the viscosity is measured at 25°C.

[0103] [Component (A)] (A-1) A linear copolymer having vinyl groups at both ends and a kinematic viscosity of 600 mm ２ (A-2) Dimethylpolysiloxane having a kinematic viscosity of 30,000 mm3 and a linear chain copolymer having vinyl groups at both ends (Vi value: 0.015 mol / 100 g, specific gravity: 1.0). ２ / s dimethylpolysiloxane (Vi value: 0.00375 mol / 100g, specific gravity: 1.0).

[0104] [Component (B)] (B-1) The following average composition formula (7): Organohydrogenpolysiloxane represented by the formula (H value: 0.005 mol / g, specific gravity: 1.0).

[0105] (B-2) The following average composition formula (8) Organohydrogenpolysiloxane represented by the formula (H value: 0.0013 mol / g, specific gravity: 1.0).

[0106] [Component (C)] (C-1) Aluminum oxide powder (average particle size: 75 μm, specific gravity: 3.98) (C-2) Aluminum oxide powder (average particle size: 2 μm, specific gravity: 3.98) (C-3) Zinc oxide powder (average particle size: 0.25 μm, specific gravity: 5.67) (C-4) Aluminum hydroxide powder (average particle size: 1 μm, specific gravity: 2.42) (C-5) Magnesium oxide powder (average particle size: 90 μm, specific gravity: 3.58)

[0107] [Component (D)] (D-1) Fe-Cr-Si soft magnetic powder (average particle size: 8 μm, specific gravity: 7.90)

[0108] [Component (E)] (E-1) A solution of platinum-divinyltetramethyldisiloxane complex dissolved in the same dimethylpolysiloxane as in (A-1) above (platinum atom content: 1 mass %, specific gravity: 1.0).

[0109] [Component (F)] (F-1) Formula (9) below An organopolysiloxane wettability improver represented by the formula (specific gravity: 1.0).

[0110] [Component (G)] (G-1) Ethynylcyclohexanol reaction retarder (specific gravity: 1.0)

[0111] [Viscosity of Composition] The viscosity of the composition was measured at 25°C using a rotational viscometer, and was measured at 25°C using a Malcom viscometer (Type PC-10AA) manufactured by Malcom Co., Ltd.

[0112] [Thermal Conductivity of Composition] The thermal conductivity of the composition was measured at 25°C using a TPS-2500S manufactured by Kyoto Electronics Manufacturing Co., Ltd. by the hot disc method in accordance with ISO 22007-2.

[0113] [Extrusion Properties of Composition] The ejection properties of the composition were evaluated by filling a 30 cc tipless syringe (Optimum, manufactured by Nordson Corporation) with the composition and ejecting it under a pressure of 0.4 MPa for 60 seconds.

[0114] [Composition Displacement Test] A 0.25 mm spacer was provided, and the composition was sandwiched between an aluminum plate (80 mm x 50 mm) and a glass plate (80 mm x 50 mm) to form a circle with a diameter of 1.6 cm. The test specimen was placed at a 90° angle with respect to the ground, and a 500-cycle test was performed using a thermal shock tester (model number: TSE-11-A) manufactured by Espec Corporation, set to alternate between -40°C and 125°C (30 minutes each). After 500 cycles, the amount of displacement of the composition from its original position was measured. <Criteria> If it is 2 mm or less, it can be said that the displacement resistance is excellent.

[0115] Appearance of Composition After Shear Test The state of the composition after 500 cycles was observed. A state in which there were no voids or cracks in the composition was marked as ◯, and a state in which there were voids or cracks was marked as ×.

[0116] [Measurement of Transmission Attenuation Rate of Composition] To evaluate the electromagnetic wave absorption performance of the composition, the transmission attenuation rate Rtp from 1 GHz to 30 GHz was measured at a thickness of 1 mm using a microstrip line method in accordance with IEC 62333. The higher the transmission attenuation rate Rtp value, the higher the electromagnetic wave absorption performance, and the unit is dB. 3 dB means 50% absorption, 10 dB means 90% absorption, and 20 dB means 99% absorption, and a value of 10 dB or higher is considered to be excellent.

[0117] Examples 1 to 8: Each component was charged as shown in Table 1, and compositions were prepared according to the following procedure. Step (1): Component (A), component (C), component (D), and, if necessary, component (F) were charged into a planetary mixer and stirred at room temperature until a paste was formed. Then, component (G) was added and stirred for 10 minutes, and then component (E) was added and stirred for 10 minutes. Finally, component (B) was added and stirred for 10 minutes, completing step (1). Step (2): The paste-like composition obtained in step (1) was heated to 160°C and heated and stirred for 2 hours to promote the hydrosilylation reaction, and then heated and stirred for an additional 1 hour to mature the composition, thereby obtaining a composition having a crosslinked structure. Step (3): The composition obtained in step (2) was cooled to room temperature and stirred at room temperature for 1 hour, completing the preparation of the composition.

[0118] The compositions thus obtained were subjected to the above-mentioned tests and measurements, and the results are shown in Table 1.

[0119] *For convenience, the number of silicon-bonded hydrogen atoms in component (B) per silicon-bonded alkenyl group in component (A) is represented as H / Vi.

[0120] In Examples 1 to 8, the components (A) and (B) formed a crosslinked structure in the composition, and the values ​​in the displacement test were 2 mm or less, demonstrating excellent displacement resistance. Furthermore, even at high viscosity, the discharge properties were maintained, resulting in excellent workability. The transmission attenuation rate (Rtp) was large, indicating high electromagnetic wave absorption performance.

[0121] Comparative Examples 1 and 2 Compositions were prepared by charging the components shown in Table 2. In Comparative Example 1, a composition was prepared in the same manner as in Examples, except that component (E) was not added. In Comparative Example 2, a composition was prepared in the same manner as in Examples, except that component (D) was not added.

[0122] In Comparative Example 1, the components (A) and (B) were not crosslinked (not an addition reaction product) in the composition, so the viscosity was low and the ejection properties were high, but the slippage resistance was low and the reliability was low. Furthermore, the transmission attenuation rate could not be measured because a uniform thickness could not be maintained. In Comparative Example 2, the component (D) was not included, so a clear transmission attenuation rate could not be detected.

[0123]

[0124] The present invention includes the following inventions.

[0125] [1]: A heat-dissipating silicone composition in the form of a paste having a crosslinked structure, the heat-dissipating silicone composition comprising an addition reaction product of the following components (A) and (B), and the following components (C), (D), and (E): (A) an organopolysiloxane having alkenyl groups bonded to silicon atoms and no alkoxy groups bonded to silicon atoms at the molecular chain terminals, (B) an organohydrogenpolysiloxane having hydrogen atoms bonded to silicon atoms, (C) a thermally conductive filler, (D) an electromagnetic wave absorbing filler, and (E) a hydrosilylation reaction catalyst.

[0126] [2]: The heat-dissipating silicone composition according to the above item [1], further comprising, as a wettability improver, an alkoxy group-containing organopolysiloxane (F) represented by the following general formula (5): (In the formula, R ６ are independently unsubstituted or substituted monovalent hydrocarbon groups, R ７ are independently an alkyl group, and x is a positive number from 5 to 120.

[0127] [3]: The heat-dissipating silicone composition according to (2) above, comprising: 100 parts by mass of component (A); component (B) in an amount such that the number of silicon-bonded hydrogen atoms is 0.2 to 2.0 moles per mole of silicon-bonded alkenyl groups in component (A); the sum of components (C) and (D) is 30 to 90 volume%, assuming the total of components (A) to (F) to be 100 volume%, and of this, component (D) is 20 volume% or more; component (E) in an amount such that the platinum atom content is 0.1 to 1,000 ppm by mass relative to component (A); and component (F) in an amount of 0.1 to 1,000 parts by mass relative to 100 parts by mass of component (A) and component (B).

[0128] [4]: A method for producing a heat-dissipating silicone composition, comprising the following steps (1) to (3): (1) uniformly mixing the components (A) to (E) to obtain a paste-like composition; (2) heating and mixing the paste-like composition to promote a hydrosilylation reaction and allow it to mature, thereby obtaining a paste-like composition in which a crosslinked structure has been formed; and (3) cooling the matured paste-like composition to a temperature of 50°C or less, followed by shear mixing, to obtain the heat-dissipating silicone composition described in (1) above.

[0129] [5]: A method for producing a heat-dissipating silicone composition, comprising the following steps (1) to (3): (1) uniformly mixing the components (A) to (F) to obtain a paste-like composition; (2) heating and mixing the paste-like composition to promote a hydrosilylation reaction and allow it to mature, thereby obtaining a paste-like composition in which a crosslinked structure has been formed; and (3) cooling the matured paste-like composition to a temperature of 50°C or less, followed by shear mixing, to obtain the heat-dissipating silicone composition described in [2] or [3] above.

[0130] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention.

Claims

1. A paste-like heat-dissipating silicone composition having a crosslinked structure, comprising an addition reaction product of the following components (A) and (B), and the following components (C), (D), and (E): (A) an organopolysiloxane having alkenyl groups bonded to silicon atoms and no alkoxy groups bonded to silicon atoms at the molecular chain terminals, (B) an organohydrogenpolysiloxane having hydrogen atoms bonded to silicon atoms, (C) a thermally conductive filler, (D) an electromagnetic wave absorbing filler, and (E) a hydrosilylation reaction catalyst.

2. The heat-dissipating silicone composition according to claim 1, further comprising an alkoxy group-containing organopolysiloxane (F) represented by the following general formula (5) as a wettability improver: (In the formula, R ６ are independently unsubstituted or substituted monovalent hydrocarbon groups; R ７ are independently an alkyl group, and x is a positive number from 5 to 120.

3. The heat dissipating silicone composition according to claim 2, comprising: 100 parts by mass of said component (A); said component (B) in an amount such that hydrogen atoms bonded to silicon atoms are 0.2 to 2.0 moles per mole of alkenyl groups bonded to silicon atoms in component (A); the sum of said components (C) and (D) is 30 to 90 volume%, assuming that the total of said components (A) to (F) is 100 volume%, and of this, component (D) is 20 volume% or more; said component (E) in an amount such that the platinum atom amount is 0.1 to 1,000 ppm by mass relative to said component (A); and said component (F) in an amount of 0.1 to 1,000 parts by mass relative to 100 parts by mass of said components (A) and (B).

4. A method for producing a heat-dissipating silicone composition, comprising the following steps (1) to (3): (1) homogeneously mixing the components (A) to (E) to obtain a paste-like composition, (2) heating and mixing the paste-like composition to promote a hydrosilylation reaction and allow it to mature, thereby obtaining a paste-like composition in which a crosslinked structure has been formed, and (3) cooling the matured paste-like composition to a temperature of 50°C or less, followed by shear mixing, to obtain the heat-dissipating silicone composition according to claim 1.

5. A method for producing a heat-dissipating silicone composition, comprising the following steps (1) to (3): (1) homogeneously mixing the components (A) to (F) to obtain a paste-like composition, (2) heating and mixing the paste-like composition to promote a hydrosilylation reaction and allow it to mature, thereby obtaining a paste-like composition in which a crosslinked structure has been formed, and (3) cooling the matured paste-like composition to a temperature of 50°C or less, followed by shear mixing, to obtain the heat-dissipating silicone composition according to claim 2.

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