Thermal Conductive Silicone Composition and Its Cured Product

Abstract

To provide a thermally conductive silicone composition having excellent insulating properties, thermal conductivity, processability, and heat resistance, and to provide a cured product thereof.SOLUTION: A thermally conductive silicone composition comprises: (A) an organopolysiloxane having two or more alkenyl groups per molecule; (B) an organohydrogenpolysiloxane having two or more hydrosilyl groups per molecule; (C) four alumina fillers with different average particle diameters; (D) a platinum group metal based curing catalyst; (E) an addition reaction control agent; (F) cerium oxide; and (G) a surfactant selected from one or more of the following (G-1) and (G-2), (G-1) an alkoxysilane compound represented by the following general formula (1), and (G-2) a dimethylpolysiloxane with one end of the molecular chain sealed with a trialkoxysilyl group, represented by the following general formula (2). R1aR2bSi(OR3)4-a-b (1).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a thermally conductive silicone composition and a cured product thereof.

Background Art

[0002] With the recent high functionality of electronic devices and the miniaturization and high integration of electronic components, the heat generation amount of electronic devices and electronic components has increased, and the heat generation density tends to be high. As a countermeasure, it is necessary to design devices with excellent heat dissipation or use materials with excellent thermal conductivity. In addition, in order to quickly transfer the heat generated from heat-generating components to cooling components such as heat sinks, heat dissipation greases and heat dissipation sheets are used, but high thermal conductivity is also required for heat dissipation materials. In order to increase the thermal conductivity of heat dissipation materials, for example, there are methods of using highly thermally conductive fillers such as aluminum nitride and boron nitride, or methods of increasing the filling amount of thermally conductive fillers. However, fillers with high thermal conductivity are costly, and problems such as an increase in the viscosity of the composition occur when the filling amount of the filler is increased.

[0003] In order to solve this problem, there is also a method of using only spherical alumina powder. However, in order to achieve high thermal conductivity, it is necessary to fill a large amount compared to amorphous alumina, which increases the viscosity of the composition and deteriorates the processability. In addition, there is also a method of using spherical alumina powder with a large particle diameter for high thermal conductivity. However, if the particle diameter is too large, there are problems such as wear of the reaction kettle and stirring blades during stirring of the material, deterioration of the processability during sheet molding, and brittleness of the molded sheet. In addition, when the filling amount of alumina powder in the silicone cured product increases, the hardness of the cured product tends to decrease significantly when used at high temperature for a long time. Depending on the application, such as a module with strong vibration, insufficient resilience causes poor adhesion, and there is a problem of an increase in thermal resistance over time.

[0004] Patent Document 1 describes a heat-resistant thermally conductive silicone composition containing spherical molten and solidified alumina. Patent Document 2 describes a heat-resistant silicone resin composition containing an organic polycyclic aromatic compound having one or more secondary amino groups and one or more ketone groups in a cyclic structure. Patent Document 3 describes a heat-conductive silicone composition containing spherical alumina and amorphous alumina having different particle sizes.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a heat-conductive silicone composition and a cured product thereof that are excellent in insulation, heat conductivity, processability, and heat resistance. In particular, an object is to provide a heat-conductive silicone composition and a cured product thereof whose hardness does not decrease even when used at a high temperature for a long time.

Means for Solving the Problems

[0007] In order to solve the above problems, the present invention provides a heat-conductive silicone composition comprising: (A) Organopolysiloxane having two or more alkenyl groups in one molecule: 100 parts by mass, (B) Organohydrogenpolysiloxane having two or more hydrosilyl groups in one molecule: an amount such that the number of moles of hydrosilyl groups is 0.1 to 5.0 times the number of moles of alkenyl groups derived from the component (A), (C) A heat-conductive filler composed of the following (C-1) to (C-4): 4,300 to 5,800 parts by mass, (C-1) Spherical alumina filler with an average particle size exceeding 70 μm and not exceeding 135 μm: 1,750 to 3,000 parts by mass, (C-2) Spherical alumina filler with an average particle size exceeding 8 μm and not exceeding 40 μm: 750 to 2,000 parts by mass, (C-3) Amorphous alumina filler with an average particle size exceeding 0.4 μm and not exceeding 4 μm: 750 to 1,500 parts by mass, (C-4) Spherical alumina filler with an average particle size exceeding 0.7 μm and not exceeding 4 μm: 125 to 750 parts by mass, (D) Platinum group metal-based hardening catalyst: 0.1 to 2,000 ppm in terms of the mass of platinum group metal elements relative to the component (A), (E) Addition reaction control agent: 0.01 to 2.0 parts by mass, (F) Cerium oxide: 7.5 to 25 parts by mass, and (G) One or more surface treatment agents selected from the following (G-1) and (G-2): 0.01 to 300 parts by mass, (G-1) Alkoxysilane compound represented by the following general formula (1), R 1 a R 2 b Si(OR 3 ) 4-a-b (1) (In the formula, R 1 is independently an alkyl group having 6 to 15 carbon atoms, R 2 is independently a group selected from an alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 12 carbon atoms, and an aralkyl group having 7 to 12 carbon atoms, R 3 is independently an alkyl group having 1 to 6 carbon atoms, a is an integer of 1 to 3, b is an integer of 0 to 2, provided that a + b is an integer of 1 to 3.) (G-2) Dimethylpolysiloxane having a trialkoxysilyl group-blocked molecular chain end represented by the following general formula (2),

Chemical formula

[0008] For such a thermally conductive silicone composition, the cured product thereof is excellent in insulation, thermal conductivity, processability, and heat resistance. In particular, it is a thermally conductive silicone composition that provides a cured product whose hardness does not decrease even when used at a high temperature for a long time. Such a thermally conductive silicone composition is suitably used, for example, as a thermally conductive resin molded body installed between a heat-generating component and a heat-radiating component in an electronic device.

[0009] Further, in the present invention, as the component (H), an organopolysiloxane having a kinematic viscosity at 23 °C represented by the following general formula (3) of 10 to 100,000 mm 2 / s is preferably contained in an amount of 0.1 to 100 parts by mass with respect to 100 parts by mass of the component (A).

Chemical formula

[0010] For such a thermally conductive silicone composition, it is excellent in flexibility, and oil bleeding of the obtained cured product is less likely to occur.

[0011] Further, in the present invention, it is preferable that the viscosity of the thermally conductive silicone composition measured with a flow tester viscometer at 23 °C is 4,000 Pa·s or less.

[0012] For such a thermally conductive silicone composition, it is excellent in moldability (processability).

[0013] Further, in the present invention, a thermally conductive silicone cured product which is a cured product of the thermally conductive silicone composition described above is provided.

[0014] Such a thermally conductive silicone cured product has excellent insulation properties, thermal conductivity, processability, and heat resistance, and is preferably used, for example, as a thermally conductive resin molded body installed between a heat-generating component and a heat-radiating component in an electronic device.

[0015] In the present invention, it is preferable that the shape of the thermally conductive silicone cured product is sheet-like.

[0016] Such a thermally conductive silicone cured product has excellent handleability.

[0017] In the present invention, it is preferable that in the hardness of the thermally conductive silicone cured product measured by an Asker C hardness meter, the hardness after aging at 150 °C for 500 hours is -5 points or more and 40 points or less with respect to the hardness before aging.

[0018] Such a cured product of a thermally conductive silicone composition has a small decrease in hardness even when used at a high temperature for a long time.

[0019] In the present invention, it is preferable that the thermal conductivity of the thermally conductive silicone cured product at 23 °C measured by the hot disk method is 7.5 W / m·K or more.

[0020] Such a thermally conductive silicone cured product has excellent thermal conductivity.

[0021] In the present invention, it is preferable that the dielectric breakdown voltage of the thermally conductive silicone cured product at a thickness of 1 mm is 10 kV / mm or more.

[0022] Such a thermally conductive silicone cured product can stably ensure insulation during use.

Advantages of the Invention

[0023] As described above, the thermally conductive silicone composition of the present invention can provide a thermally conductive silicone composition and a cured product thereof that are excellent in insulation, thermal conductivity, and processability. Further, a decrease in hardness during high-temperature storage can be suppressed, and a thermally conductive silicone cured product having a thermal conductivity of 7.5 W / m·K or more and formed into a sheet shape can be provided.

Embodiments for Carrying Out the Invention

[0024] As described above, there has been a demand for the development of a thermally conductive silicone composition and a cured product thereof that are excellent in insulation, thermal conductivity, processability, and heat resistance.

[0025] As a result of intensive studies to achieve the above object, the present inventors have found that by mixing spherical alumina fillers having an average particle size exceeding 8 μm and not exceeding 40 μm, amorphous alumina fillers having an average particle size exceeding 0.4 μm and not exceeding 4 μm, spherical alumina fillers having an average particle size exceeding 0.7 μm and not exceeding 4 μm, and spherical alumina fillers having an average particle size exceeding 70 μm and not exceeding 135 μm at a specific ratio and using cerium oxide in combination, the above problems can be solved. That is, by blending a large amount of spherical alumina fillers having an average particle size exceeding 70 μm and not exceeding 135 μm and having a small specific surface area, it is possible to effectively improve the thermal conductivity, and a thermally conductive silicone composition and a cured product thereof having low viscosity and excellent processability have been found. In addition, by using spherical alumina fillers and amorphous alumina fillers having an average particle size of 40 μm or less in combination, and particularly by using amorphous alumina fillers and spherical alumina fillers in combination at a particle size of 4 μm or less, the fluidity of the thermally conductive silicone composition is improved and the processability is improved. Furthermore, since spherical alumina fillers are used for particles of 5 μm or more, it has been found that abrasion of the reaction kettle and stirring blades is suppressed and the insulation is improved. That is, it has been found that a thermally conductive silicone composition and a cured product capable of achieving the above object can be provided by compensating for the respective disadvantages of spherical alumina fillers with small particle sizes and spherical alumina fillers with large particle sizes. Furthermore, the inventors have found that by adding cerium oxide to the above-mentioned thermally conductive silicone composition, it is possible to suppress a decrease in the hardness of the cured product during high-temperature storage, and thus have completed the present invention.

[0026] That is, the present invention relates to a thermally conductive silicone composition comprising: (A) Organopolysiloxane having two or more alkenyl groups in one molecule: 100 parts by mass, (B) Organohydrogenpolysiloxane having two or more hydrosilyl groups in one molecule: an amount such that the number of moles of hydrosilyl groups is 0.1 to 5.0 times the number of moles of alkenyl groups derived from the component (A), (C) Thermally conductive filler composed of the following (C-1) to (C-4): 4,300 to 5,800 parts by mass, (C-1) Spherical alumina filler having an average particle diameter exceeding 70 μm and not exceeding 135 μm: 1,750 to 3,000 parts by mass, (C-2) Spherical alumina filler having an average particle diameter exceeding 8 μm and not exceeding 40 μm: 750 to 2,000 parts by mass, (C-3) Amorphous alumina filler having an average particle diameter exceeding 0.4 μm and not exceeding 4 μm: 750 to 1,500 parts by mass, (C-4) Spherical alumina filler having an average particle diameter exceeding 0.7 μm and not exceeding 4 μm: 125 to 750 parts by mass, (D) Platinum group metal-based curing catalyst: 0.1 to 2,000 ppm in terms of the mass of platinum group metal element with respect to the component (A), (E) Addition reaction control agent: 0.01 to 2.0 parts by mass, (F) Cerium oxide: 7.5 to 25 parts by mass, and (G) One or more surface treatment agents selected from the following (G-1) and (G-2): 0.01 to 300 parts by mass, (G-1) An alkoxysilane compound represented by the following general formula (1), R 1 a R 2 b Si(OR 3 ) 4-a-b (1) (In the formula, R 1is independently an alkyl group having 6 to 15 carbon atoms, R 2 is independently a group selected from an alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 12 carbon atoms, and an aralkyl group having 7 to 12 carbon atoms, R 3 is independently an alkyl group having 1 to 6 carbon atoms, a is an integer of 1 to 3, b is an integer of 0 to 2, provided that a + b is an integer of 1 to 3.) (G-2) A dimethylpolysiloxane having a molecular chain end blocked with a trialkoxysilyl group represented by the following general formula (2), [Chemical formula] (In the formula, R 4 is independently an alkyl group having 1 to 6 carbon atoms, and c is an integer of 5 to 100.) It is a thermally conductive silicone composition containing

[0027] Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

[0028] [Thermally Conductive Silicone Composition] The thermally conductive silicone composition of the present invention is (A) An organopolysiloxane having two or more alkenyl groups in one molecule, (B) An organohydrogenpolysiloxane having two or more hydrosilyl groups in one molecule, (C) A thermally conductive filler composed of the following (C-1) to (C-4), (C-1) A spherical alumina filler having an average particle diameter exceeding 70 μm and not exceeding 135 μm, (C-2) A spherical alumina filler having an average particle diameter exceeding 8 μm and not exceeding 40 μm, (C-3) An amorphous alumina filler having an average particle diameter exceeding 0.4 μm and not exceeding 4 μm, (C-4) A spherical alumina filler having an average particle diameter exceeding 0.7 μm and not exceeding 4 μm, (D) A platinum group metal-based curing catalyst, (E) An addition reaction control agent, (F) Cerium oxide, (G) Surface treatment agent contains it as an essential component. Hereinafter, each component will be described in detail.

[0029] [(A) Alkenyl group-containing organopolysiloxane] The alkenyl group-containing organopolysiloxane as the component (A) is an organopolysiloxane having two or more alkenyl groups bonded to silicon atoms in one molecule, that is, an organopolysiloxane having two or more alkenyl groups in one molecule, and is the main component of the thermally conductive silicone composition of the present invention. Usually, the main chain portion is basically composed of a repetition of diorganosiloxane units, but this may include a branched structure in a part of the molecular structure, or may be a cyclic body. However, from the viewpoint of physical properties such as the mechanical strength of the obtained thermally conductive silicone cured product, a linear diorganopolysiloxane is preferable.

[0030] Examples of the above alkenyl group include those having 2 to 8 carbon atoms such as vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, hexenyl group, cyclohexenyl group, etc. Among them, lower alkenyl groups such as vinyl group and allyl group are preferable, and vinyl group is particularly preferable. In addition, the alkenyl group is characterized by being present in two or more in one molecule, preferably 2 to 6, more preferably 2 to 3. Further, in order to obtain a thermally conductive silicone cured product with good flexibility, it is most preferable to be bonded only to the silicon atom at the molecular chain end.

[0031] Examples of the functional group other than the alkenyl group bonded to the silicon atom include monovalent hydrocarbon groups having 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms. For example, alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, dodecyl group, etc., cycloalkyl groups such as cyclopentyl group, cyclohexyl group, cycloheptyl group, etc., aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group, biphenylyl group, etc., aralkyl groups such as benzyl group, phenylethyl group, phenylpropyl group, methylbenzyl group, etc. Among them, methyl group, ethyl group, propyl group, and phenyl group are preferably used. Further, the functional groups other than the alkenyl group bonded to the silicon atom may all be the same or different.

[0032] The kinematic viscosity of this organopolysiloxane at 23°C is usually in the range of 10 to 100,000 mm 2 / s, particularly preferably in the range of 500 to 50,000 mm 2 / s. If the kinematic viscosity is 10 mm 2 / s or more, the storage stability of the resulting thermally conductive silicone composition is improved, and if it is 100,000 mm 2 / s or less, the stretchability of the resulting thermally conductive silicone composition is improved. In this specification, the kinematic viscosity is the value measured at 23°C using a Cannon-Fenske viscometer by the method described in JIS Z 8803:2011.

[0033] This organopolysiloxane of component (A) may be used alone or in combination of two or more having different kinematic viscosities.

[0034] [(B) Organohydrogenpolysiloxane] (B) component of the organohydrogenpolysiloxane has two or more, preferably 2 to 100 hydrosilyl groups (hydrogen atoms directly bonded to silicon atoms) in one molecule, and is a component that acts as a crosslinking agent for the (A) component. That is, the hydrosilyl group in the (B) component and the alkenyl group in the (A) component are added by a hydrosilylation reaction promoted by the platinum group metal-based curing catalyst of the (D) component described later, giving a three-dimensional network structure having a crosslinked structure. Note that when the number of hydrosilyl groups is less than 2 in one molecule, it does not cure.

[0035] As the (B) component of the organohydrogenpolysiloxane, those represented by the following average structural formula (4) are used, but it is not limited thereto. [Chemical formula] (In the formula, R 6 is independently a monovalent hydrocarbon group selected from a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, and an aralkyl group having 7 to 12 carbon atoms. However, two or more, preferably 2 to 10 R 6 in one molecule are hydrogen atoms. Also, e is an integer of 1 or more, preferably an integer of 10 to 200.)

[0036] In formula (4), R 6 is independently a monovalent hydrocarbon group selected from a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, and an aralkyl group having 7 to 12 carbon atoms. However, two or more, preferably 2 to 10 R 6 in one molecule are hydrogen atoms. R 6Examples of the monovalent hydrocarbon group other than the hydrogen atom include alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, dodecyl group, etc., cycloalkyl groups such as cyclopentyl group, cyclohexyl group, cycloheptyl group, etc., aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group, biphenylyl group, etc., and aralkyl groups such as benzyl group, phenylethyl group, phenylpropyl group, methylbenzyl group, etc. Among these monovalent hydrocarbon groups, those having 1 to 10 carbon atoms are preferred, and those having 1 to 6 carbon atoms are particularly preferred. Among them, alkyl groups having 1 to 3 carbon atoms such as methyl group, ethyl group, propyl group, etc., and phenyl group are preferably used. Also, e is an integer of 1 or more, preferably an integer of 10 to 200.

[0037] (B) The amount of the component added is such that the hydrosilyl group derived from the component (B) is 0.1 to 5.0 moles per 1 mole of the alkenyl group derived from the component (A), that is, the number of moles of the hydrosilyl group is 0.1 to 5.0 times the number of moles of the alkenyl group derived from the component (A). Preferably, it is an amount of 0.3 to 2.0 moles, and more preferably an amount of 0.5 to 1.0 moles. When the amount of the hydrosilyl group derived from the component (B) is less than 0.1 mole per 1 mole of the alkenyl group derived from the component (A), it may not cure, or the strength of the thermally conductive silicone cured product may be insufficient and it may not be able to maintain the shape as a molded body and may not be handleable. Also, when it exceeds 5.0 moles, the flexibility of the thermally conductive silicone cured product is lost and the thermally conductive silicone cured product becomes brittle.

[0038] [(C) Thermally conductive filler] (C) The thermally conductive filler as the component is composed of the following components (C-1) to (C-4). (C-1) A spherical alumina filler having an average particle diameter exceeding 70 μm and not exceeding 135 μm, (C-2) A spherical alumina filler having an average particle diameter exceeding 8 μm and not exceeding 40 μm, (C-3) An amorphous alumina filler having an average particle size exceeding 0.4 μm and not exceeding 4 μm, (C-4) A spherical alumina filler having an average particle size exceeding 0.7 μm and not exceeding 4 μm. In the present invention, the average particle size is a value of the cumulative average particle size (median diameter) based on volume measured by the laser diffraction / scattering method using a Microtrac MT3300EX, a particle size analyzer manufactured by Nikkiso Co., Ltd.

[0039] (C-1) The spherical alumina filler of the component can significantly improve the thermal conductivity. The average particle size of the spherical alumina exceeds 70 μm and does not exceed 135 μm, preferably exceeds 70 μm and does not exceed 120 μm, and more preferably exceeds 70 μm and does not exceed 100 μm. When the average particle size is 70 μm or less, the effect of improving the thermal conductivity becomes low, and the viscosity of the thermally conductive silicone composition increases, resulting in poor processability. When the average particle size is larger than 135 μm, there is a concern that the wear of the reaction kettle and the stirring blades becomes remarkable and the insulation of the thermally conductive silicone composition decreases. Furthermore, there was a problem that separation between the spherical alumina filler and the resin occurred during press molding, and the sheet end became a filler-rich part and became brittle. In this case, the material yield in sheet molding is significantly reduced. As the spherical alumina filler of the component (C-1), one kind or a combination of two or more kinds may be used. When two or more kinds are used in combination, each may satisfy the above range of the average particle size.

[0040] (C-2) The spherical alumina filler of the component improves the thermal conductivity of the thermally conductive silicone composition and provides a barrier effect that suppresses the contact between the amorphous alumina filler described later in (C-3) and the reaction kettle and the stirring blades, thereby suppressing wear. The average particle size exceeds 8 μm and does not exceed 40 μm, preferably 10 to 40 μm. When the average particle size is 8 μm or less, the barrier effect decreases, and the wear of the reaction kettle and the stirring blades due to the amorphous alumina filler becomes remarkable.

[0041] (C-3) component's amorphous alumina filler also plays a role in improving the thermal conductivity of the thermally conductive silicone composition, but its main role is to adjust the viscosity of the thermally conductive silicone composition, improve smoothness, and improve fillability. The average particle size of the (C-3) component is more than 0.4 μm and 4 μm or less, and it is more preferable to be 0.6 - 3 μm for the expression of the above characteristics.

[0042] (C-4) component's spherical alumina filler also plays a role in improving the thermal conductivity of the thermally conductive silicone composition, but its main role is to adjust the viscosity of the thermally conductive silicone composition, improve smoothness, and improve fillability. The average particle size of the (C-4) component is more than 0.7 μm and 4 μm or less, and it is more preferable to be more than 0.7 μm and 3 μm or less for the expression of the above characteristics.

[0043] (C-1) component's blending amount is 1,750 - 3,000 parts by mass with respect to 100 parts by mass of the (A) component, preferably 1,875 - 2,500 parts by mass. If it is too little, it is difficult to improve the thermal conductivity. If it is too much, the abrasion of the reaction kettle and stirring blades becomes remarkable, and the insulation of the thermally conductive silicone composition decreases.

[0044] (C-2) component's blending amount is 750 - 2,000 parts by mass with respect to 100 parts by mass of the (A) component, preferably 1,000 - 1,600 parts by mass. If it is too little, it is difficult to improve the thermal conductivity. If it is too much, the fluidity of the thermally conductive silicone composition is lost and the moldability is impaired.

[0045] (C-3) component's blending amount is 750 - 1,500 parts by mass with respect to 100 parts by mass of the (A) component, preferably 900 - 1,250 parts by mass. If it is too little, it is difficult to improve the thermal conductivity. If it is too much, the fluidity of the thermally conductive silicone composition is lost and the moldability is impaired.

[0046] The blending amount of the (C) component is 125 to 750 parts by mass, preferably 125 to 375 parts by mass, with respect to 100 parts by mass of the (A) component. If it is too small, it is difficult to improve the thermal conductivity. If it is too large, the fluidity of the thermally conductive silicone composition is lost and the moldability is impaired.

[0047] Furthermore, the blending amount of the (C) component (that is, the total blending amount of the above (C-1) to (C-4) components) needs to be 4,300 to 5,800 parts by mass, preferably 4,500 to 5,200 parts by mass, with respect to 100 parts by mass of the (A) component. When this blending amount is less than 4,300 parts by mass, the thermal conductivity of the obtained thermally conductive silicone composition deteriorates. When it exceeds 5,800 parts by mass, the fluidity of the obtained thermally conductive silicone composition is lost and the moldability is impaired.

[0048] By using the (C) component in the above blending ratio, the effects of the present invention described above can be achieved more advantageously and surely.

[0049] [(D) Platinum group metal-based curing catalyst] The platinum group metal-based curing catalyst of the (D) component is a catalyst for promoting the addition reaction of the alkenyl group derived from the (A) component and the hydrosilyl group derived from the (B) component, and examples of the catalyst used in the hydrosilylation reaction include catalysts well-known as such. Specific examples thereof include, for example, simple substances of platinum group metals such as platinum (including platinum black), rhodium, and palladium, H 2 PtCl 4 ·nH 2 O, H 2 PtCl 6 ·nH 2 O, NaHPtCl 6 ·nH 2 O, KaHPtCl 6 ·nH 2 O, Na 2 PtCl 6 ·nH 2 O, K 2 PtCl 4 ·nH 2 O, PtCl 4 ·nH 2 O, PtCl 2 、Na 2HPtCl 4 ·nH 2 O (wherein, n is an integer of 0 to 6, preferably 0 or 6), platinum chloride, chloroplatinic acid and chloroplatinate such as these, alcohol-modified chloroplatinic acid (see U.S. Patent No. 3,220,972), complexes of chloroplatinic acid and olefins (see U.S. Patent Nos. 3,159,601, 3,159,662, 3,775,452), platinum black, platinum group metals such as palladium supported on carriers such as alumina, silica, carbon, etc., rhodium-olefin complexes, chlorotris(triphenylphosphine)rhodium (Wilkinson catalyst), complexes of platinum chloride, chloroplatinic acid or chloroplatinate and vinyl group-containing siloxanes, particularly vinyl group-containing cyclic siloxanes, etc. can be mentioned.

[0050] (D) The amount of use of the component is 0.1 to 2,000 ppm in terms of the mass of platinum group metal element with respect to the (A) component, preferably 50 to 1,000 ppm.

[0051] [(E) Reaction controller] (E) The addition reaction controller of the component is not particularly limited as long as it is a known addition reaction controller used in ordinary addition reaction curable silicone compositions. For example, acetylene compounds such as 1-ethynyl-1-hexanol, 3-butyn-1-ol, ethynylmethylidene carbinol, various nitrogen compounds, organic phosphorus compounds, oxime compounds, organic chloro compounds, etc. can be mentioned. As the amount of use when blending the (E) component, 0.01 to 2.0 parts by mass, particularly about 0.1 to 1.2 parts by mass, is desirable with respect to 100 parts by mass of the (A) component. If the blending amount of the (E) component is too small, the handleability of the thermally conductive silicone composition may be inferior due to the progress of the addition reaction, and if it is too large, the curing reaction may not proceed and the molding efficiency may be impaired.

[0052] [(F) Cerium oxide] (F) The cerium oxide of the component aims to improve heat resistance, particularly to suppress the softening deterioration of the cured product of the thermally conductive silicone composition. The addition amount of cerium oxide is 7.5 to 25 parts by mass, preferably 8.0 to 14 parts by mass, based on 100 parts by mass of the (A) component. If the addition amount is outside this range, there may be a risk of a decrease in hardness when stored at a high temperature of 150 °C.

[0053] By adding cerium oxide, the cured product of the thermally conductive silicone composition becomes excellent in heat resistance. Specifically, in terms of the hardness measured by the Asker C hardness meter of the cured product, the hardness after aging at 150 °C for 500 hours is preferably -5 points or more and +40 points or less, and more preferably -3 points or more and +20 points or less, relative to the hardness before aging.

[0054] [(G) Surface treatment agent] (G) The surface treatment agent of the component aims to hydrophobize the (C) component during the preparation of the thermally conductive silicone composition, improve the wettability with the (A) component, and uniformly disperse the (C) component in the matrix composed of the (A) component. As the (G) component, it is one or more surface treatment agents selected from the following (G-1) component and (G-2) component.

[0055] (G-1) The component is an alkoxysilane compound represented by the following general formula (1). R 1 a R 2 b Si(OR 3 ) 4-a-b (1) (In the formula, R 1 is independently an alkyl group having 6 to 15 carbon atoms, R 2 is independently a group selected from an alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 12 carbon atoms, and an aralkyl group having 7 to 12 carbon atoms, R 3 is independently an alkyl group having 1 to 6 carbon atoms, a is an integer of 1 to 3, b is an integer of 0 to 2, provided that a + b is an integer of 1 to 3.)

[0056] In the above general formula (1), R 1 Examples of the alkyl group having 6 to 15 carbon atoms represented by include, for example, hexyl group, octyl group, nonyl group, decyl group, dodecyl group, tetradecyl group and the like. This R 1 When the number of carbon atoms of the alkyl group represented by satisfies the range of 6 to 15, the wettability of the component (A) is sufficiently improved, the handleability is good, and the low-temperature characteristics of the composition are good.

[0057] R 2 Examples of the alkyl group having 1 to 5 carbon atoms represented by include, for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group. Examples of the aryl group having 6 to 12 carbon atoms include phenyl group, tolyl group, xylyl group, naphthyl group, biphenylyl group and the like. And examples of the group selected from the aralkyl group having 7 to 12 carbon atoms include benzyl group, phenylethyl group, phenylpropyl group, methylbenzyl group and the like. Among them, preferably, alkyl groups having 1 to 3 carbon atoms such as methyl group, ethyl group, propyl group, and phenyl group are mentioned. R 3 Examples of include methyl group, ethyl group, propyl group, butyl group, hexyl group and the like.

[0058] (Component (G-2) is a dimethylpolysiloxane in which the molecular chain fragment end represented by the following general formula (2) is blocked with a trialkoxysilyl group.)

Chemical formula

[0059] (As the surface treatment agent of component (G), either one of component (G-1) and component (G-2) or a combination of both can be blended without any problem.)

[0060] When compounded, the compounding amount of the (G) component is 0.01 to 300 parts by mass, preferably 0.1 to 200 parts by mass, based on 100 parts by mass of the (A) component. If the proportion of this component exceeds 300 parts by mass, it may induce oil separation.

[0061] [(H) Organopolysiloxane] In the thermally conductive silicone composition of the present invention, an organopolysiloxane as the (H) component may be compounded for the purpose of imparting characteristics such as viscosity adjustment of the thermally conductive silicone composition. As this (H) component, an organopolysiloxane having a kinematic viscosity at 23°C represented by the following general formula (3) of 10 to 100,000 mm 2 / s can be added. The (H) component may be used alone or in combination of two or more. [Chemical formula] (In the formula, R 5 is independently a group selected from an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, and an aralkyl group having 7 to 12 carbon atoms, and d is an integer of 5 to 2,000.)

[0062] In the above general formula (3), R 5 is independently a group selected from an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, and an aralkyl group having 7 to 12 carbon atoms. Specific examples of R 5 include, for example, alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, etc., cycloalkyl groups such as cyclopentyl group, cyclohexyl group, etc., aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group, biphenylyl group, etc., and aralkyl groups such as benzyl group, phenylethyl group, phenylpropyl group, methylbenzyl group, etc. Among them, preferably, alkyl groups having 1 to 3 carbon atoms such as methyl group, ethyl group, propyl group, etc., and phenyl group are mentioned, and particularly preferably, methyl group and phenyl group are preferred.

[0063] From the perspective of the required viscosity, d is preferably an integer of 5 to 2,000, particularly preferably an integer of 10 to 1,000.

[0064] Also, the kinematic viscosity of component (H) at 23°C is preferably 10 to 100,000 mm 2 / s, particularly preferably 100 to 10,000 mm 2 / s. If the kinematic viscosity is 10 mm 2 / s or more, the cured product of the resulting composition is less likely to generate oil bleed. If the kinematic viscosity is 100,000 mm 2 / s or less, the resulting thermally conductive silicone composition will have excellent flexibility.

[0065] When component (H) is added to the thermally conductive silicone composition of the present invention, its addition amount is not particularly limited and may be any amount that can achieve the desired effect. However, based on 100 parts by mass of component (A), it is preferably 0.1 to 100 parts by mass, more preferably 1 to 50 parts by mass. When the addition amount is within this range, it is easy to maintain good fluidity and workability in the thermally conductive silicone composition before curing, and it is also easy to fill the thermally conductive filler of component (C) into the composition.

[0066] [Other Components] For the thermally conductive silicone composition of the present invention, other components may be further blended according to the purpose of the present invention. For example, heat resistance improvers such as iron oxide; viscosity modifiers such as silica; colorants; optional components such as release agents can be blended.

[0067] [Thermally Conductive Silicone Cured Product] In the present invention, a thermally conductive silicone cured product, which is the cured product of the above thermally conductive silicone composition, is provided. The thermally conductive silicone cured product of the present invention is excellent in insulation, thermal conductivity, processability, and heat resistance, and is preferably used, for example, as a thermally conductive resin molded body installed between heat-generating components and heat-radiating components in electronic devices. Also, if the shape of the thermally conductive silicone cured product is sheet-like, it is preferable because of its excellent handleability.

[0068] [Preparation of Thermally Conductive Silicone Composition] The thermally conductive silicone composition of the present invention can be prepared by uniformly mixing the above-described components according to a conventional method.

[0069] [Viscosity of Thermally Conductive Silicone Composition] The viscosity of the thermally conductive silicone composition of the present invention is preferably 4,000 Pa·s or less, more preferably 3,000 Pa·s or less at 23°C. If the viscosity is 4,000 Pa·s or less, the moldability will not be impaired. In the present invention, this viscosity is based on the measurement by a flow tester viscometer.

[0070] [Method for Producing Thermally Conductive Silicone Cured Product] The curing conditions for molding the thermally conductive silicone composition may be the same as those for known addition reaction-curable silicone rubber compositions. For example, it can be sufficiently cured at room temperature, but heating may be carried out if necessary. Preferably, it is addition-cured at 100 to 120°C for 8 to 12 minutes. Such a thermally conductive silicone cured product of the present invention is excellent in thermal conductivity.

[0071] [Thermal Conductivity of Thermally Conductive Silicone Cured Product] In the present invention, the thermal conductivity of the thermally conductive silicone cured product is desirably such that the measured value at 23°C measured by the hot disk method is 7.5 W / m·K or more, particularly 8.0 W / m·K or more.

[0072] [Dielectric Breakdown Voltage of Thermally Conductive Silicone Cured Product] In the present invention, the dielectric breakdown voltage of the thermally conductive silicone cured product is preferably such that the measured value when the dielectric breakdown voltage at a thickness of 1 mm of the thermally conductive silicone cured product is measured in accordance with JIS K 6249:2003 is 10 kV / mm or more, more preferably 12 kV / mm or more. In the case of a cured product with a dielectric breakdown voltage of 10 kV / mm or more, stable insulation can be ensured during use. Such a dielectric breakdown voltage can be adjusted by adjusting the type and purity of the filler.

[0073] [Hardness of Thermally Conductive Silicone Cured Product] The hardness of the thermally conductive silicone cured product in the present invention preferably has a measured value at 23°C measured with an Asker C hardness meter of 60 or less, preferably 40 or less, more preferably 30 or less, and also preferably 5 or more. When the hardness is 60 or less, it deforms along the shape of the heat dissipation body and exhibits good heat dissipation characteristics without applying stress to the heat dissipation body. Such hardness can be adjusted by changing the ratio of component (A) and component (B) and adjusting the crosslinking density. Also, the hardness after aging at 150°C for 500 hours is preferably -5 points or more and 40 points or less with respect to the hardness before aging. For a cured product of such a thermally conductive silicone composition, the decrease in hardness is small even when used at a high temperature for a long time.

Examples

[0074] Hereinafter, examples and comparative examples will be shown to specifically explain the present invention, but the present invention is not limited to the following examples. The viscosity of the composition was measured with a flow tester viscometer at 23°C. As the measuring device, CFT-500EX manufactured by Shimadzu Corporation was used. The die hole diameter was 2 mm in diameter, the die length was 2 mm, the test load was 10 kg, and time and stroke were plotted, and the viscosity was calculated from the slope. Also, the average particle diameter is the value of the volume-based cumulative average particle diameter (median diameter) measured with a Microtrac MT3300EX, a particle size analyzer manufactured by Nikkiso Co., Ltd.

[0075] Components (A) to (H) used in the following examples and comparative examples are shown below. Component (A): The organopolysiloxane represented by the following formula (5).

Chemical formula

[0076] (Component (B-1)): An organohydrogenpolysiloxane represented by the following formula (6-1). [Chemical formula] (Component (B-2)): An organohydrogenpolysiloxane represented by the following formula (6-2). [Chemical formula]

[0077] (Component (C)): Spherical alumina filler and amorphous alumina filler with an average particle size as follows. (C-1) Spherical alumina filler with an average particle size of 98.8 μm. (C-2) Spherical alumina filler with an average particle size of 23.4 μm. (C-3) Amorphous alumina filler with an average particle size of 1.7 μm. (C-4) Spherical alumina filler with an average particle size of 2.3 μm.

[0078] (Component (D)): 5 mass% solution of chloroplatinic acid in 2-ethylhexanol

[0079] (Component (E)): Ethynylmethylidene carbinol

[0080] (Component (F)): Cerium oxide

[0081] (Component (G)): Component (G-2) Dimethylpolysiloxane with an average degree of polymerization of 30, one end of which is blocked with a trimethoxysilyl group, represented by the following formula (7). [Chemical formula]

[0082] (Component (H)) As a plasticizer, dimethylpolysiloxane having a kinematic viscosity at 23 °C of 100 mm 2 / s represented by the following formula (8). [Chemical formula]

[0083] [Examples 1 to 4, Comparative Examples 1 to 4] In Examples 1 to 4 and Comparative Examples 1 to 4, the heat-conductive silicone compositions were prepared as follows using the predetermined amounts of the above components (A) to (H) shown in Table 1 below, molded and cured, and the viscosity of the heat-conductive silicone compositions, the thermal conductivity, hardness, and dielectric breakdown voltage of their cured products were measured according to the following methods. The results are also shown in Table 1.

[0084] [Preparation of Heat-Conductive Silicone Composition] Components (A), (C), (F), (G), and (H) were added in the predetermined amounts shown in Examples 1 to 4 and Comparative Examples 1 to 4 of Table 1 below and kneaded with a planetary mixer for 60 minutes. Component (D) was added thereto in the predetermined amounts shown in Examples 1 to 4 and Comparative Examples 1 to 4 of Table 1 below, and an effective amount of KF-54, a phenyl-modified silicone oil manufactured by Shin-Etsu Chemical Co., Ltd., was added as an internal release agent to promote release from the separator, and kneaded for 30 minutes. Components (B) and (E) were further added thereto in the predetermined amounts shown in Examples 1 to 4 and Comparative Examples 1 to 4 of Table 1 below and kneaded for 30 minutes to obtain a heat-conductive silicone composition.

[0085] [Molding Method] The heat-conductive silicone compositions obtained in Examples 1 to 4 and Comparative Examples 1 to 4 were poured into molds having a length of 60 mm × width of 60 mm and a thickness of 6 mm or 1 mm, and molded at 120 °C for 10 minutes using a press molding machine.

[0086] [Evaluation Method] Viscosity of Heat-Conductive Silicone Composition:[[]] The viscosities of the heat-conductive silicone compositions obtained in Examples 1 to 4 and Comparative Examples 1 to 4 were measured at 23 °C using a flow tester viscometer.

[0087] Thermal conductivity: The thermally conductive silicone compositions obtained in Examples 1 to 4 and Comparative Examples 1 to 4 were cured into a 6-mm-thick sheet using a press molding machine under the conditions of 120°C for 10 minutes. Using two such sheets, the thermal conductivity of the sheet was measured with a thermal conductivity meter (trade name: TPS-2500S, manufactured by Kyoto Electronics Industry Co., Ltd.).

[0088] Dielectric breakdown voltage: The thermally conductive silicone compositions obtained in Examples 1 to 4 and Comparative Examples 1 to 4 were cured into a 1-mm-thick sheet using a press molding machine under the conditions of 120°C for 10 minutes, and the dielectric breakdown voltage was measured in accordance with JIS K 6249:2003.

[0089] Hardness: The thermally conductive silicone compositions obtained in Examples 1 to 4 and Comparative Examples 1 to 4 were cured into a 6-mm-thick sheet in the same manner as above, and two such sheets were stacked and measured with an Asker C hardness meter.

[0090] Hardness after storage at 150°C for 500 hours: The cured products obtained by curing the thermally conductive silicone compositions obtained in Examples 1 to 4 and Comparative Examples 1 to 4 into a 6-mm-thick sheet using a press molding machine under the conditions of 120°C for 10 minutes were stored in a high-temperature furnace at 150°C for 500 hours, and then two such sheets were stacked and measured with an Asker C hardness meter.

[0091]

Table 1

[0092] In Examples 1 to 4, good results were obtained for the viscosity of the thermally conductive silicone composition, the moldability, the thermal conductivity of the thermally conductive silicone cured product, the dielectric breakdown voltage, and the hardness. Further, due to the addition of (F) cerium oxide, even when stored at a high temperature of 150°C, no decrease in hardness due to softening and deterioration was observed.

[0093] When the (C-4) component (spherical alumina filler with an average particle size exceeding 0.7 μm and being 4 μm or less) was not contained as in Comparative Example 1, the viscosity of the thermally conductive silicone composition increased significantly. When the addition amount of cerium oxide (F) deviated from the scope of the present invention as in Comparative Example 2, the hardness after storage at 150 °C for 500 hours decreased. When the blending amount of the thermally conductive filler (C) was too large as in Comparative Example 3, the wettability of the thermally conductive filler was insufficient, and a grease-like uniform thermally conductive silicone composition could not be obtained. When the blending amount of the thermally conductive filler (C) was too small as in Comparative Example 4, the thermal conductivity of the thermally conductive silicone cured product decreased significantly.

[0094] This specification includes the following aspects. [1]: A thermally conductive silicone composition, (A) Organopolysiloxane having two or more alkenyl groups in one molecule: 100 parts by mass, (B) Organohydrogenpolysiloxane having two or more hydrosilyl groups in one molecule: an amount such that the number of moles of hydrosilyl groups is 0.1 to 5.0 times the number of moles of alkenyl groups derived from the component (A), (C) A thermally conductive filler composed of the following (C-1) to (C-4): 4,300 to 5,800 parts by mass, (C-1) Spherical alumina filler having an average particle size exceeding 70 μm and being 135 μm or less: 1,750 to 3,000 parts by mass, (C-2) Spherical alumina filler having an average particle size exceeding 8 μm and being 40 μm or less: 750 to 2,000 parts by mass, (C-3) Amorphous alumina filler having an average particle size exceeding 0.4 μm and being 4 μm or less: 750 to 1,500 parts by mass, (C-4) Spherical alumina filler having an average particle size exceeding 0.7 μm and being 4 μm or less: 125 to 750 parts by mass, (D) Platinum group metal-based curing catalyst: 0.1 to 2,000 ppm in terms of the mass of platinum group metal elements with respect to the component (A), (E) Addition reaction control agent: 0.01 to 2.0 parts by mass, (F) Cerium oxide: 7.5 to 25 parts by mass, and (G) One or more surface treatment agents selected from the following (G-1) and (G-2): 0.01 to 300 parts by mass, (G-1) An alkoxysilane compound represented by the following general formula (1), R 1 a R 2 b Si(OR 3 ) 4-a-b (1) (In the formula, R 1 is independently an alkyl group having 6 to 15 carbon atoms, and R 2 is independently a group selected from an alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 12 carbon atoms, and an aralkyl group having 7 to 12 carbon atoms, and R 3 is independently an alkyl group having 1 to 6 carbon atoms, a is an integer of 1 to 3, b is an integer of 0 to 2, provided that a + b is an integer of 1 to 3.) (G-2) A dimethylpolysiloxane having a trialkoxysilyl group-blocked molecular chain end represented by the following general formula (2),

Chemical formula

Chemical formula

[0095] Note that the present invention is not limited to the above embodiments. The above embodiments are examples, and any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits the same operational effects is included in the technical scope of the present invention.

Claims

1. A thermally conductive silicone composition comprising: (A) 100 parts by mass of an organopolysiloxane having two or more alkenyl groups in one molecule; (B) An organohydropolysiloxane having two or more hydrosilyl groups in one molecule, in an amount such that the number of moles of hydrosilyl groups is 0.1 to 5.0 times the number of moles of alkenyl groups derived from the component (A); (C) A thermally conductive filler composed of the following (C-1) to (C-4): 4,300 to 5,800 parts by mass; (C-1) Spherical alumina filler having an average particle diameter exceeding 70 μm and not exceeding 135 μm: 1,750 to 3,000 parts by mass; (C-2) Spherical alumina filler having an average particle diameter exceeding 8 μm and not exceeding 40 μm: 750 to 2,000 parts by mass; (C-3) Amorphous alumina filler having an average particle diameter exceeding 0.4 μm and not exceeding 4 μm: 750 to 1,500 parts by mass; (C-4) Spherical alumina filler having an average particle diameter exceeding 0.7 μm and not exceeding 4 μm: 125 to 750 parts by mass; (D) A platinum group metal-based curing catalyst: 0.1 to 2,000 ppm in terms of the mass of platinum group metal element with respect to the component (A); (E) An addition reaction control agent: 0.01 to 2.0 parts by mass; (F) Cerium oxide: 7.5 to 25 parts by mass, and (G) One or more surface treatment agents selected from the following (G-1) and (G-2): 0.01 to 300 parts by mass; (G-1) An alkoxysilane compound represented by the following general formula (1); R １ ａ R ２ ｂ Si(OR ３ ) ４－ａ－ｂ (1) (wherein, R １ is independently an alkyl group having 6 to 15 carbon atoms, and R ２ is independently a group selected from an alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 12 carbon atoms, and an aralkyl group having 7 to 12 carbon atoms, and R ３ is independently an alkyl group having 1 to 6 carbon atoms, a is an integer of 1 to 3, b is an integer of 0 to 2, provided that a + b is an integer of 1 to 3.) (G-2) A dimethylpolysiloxane having a trialkoxysilyl group at the end of the molecular chain segment represented by the following general formula (2), 【Chemical 1】 (wherein R ４ is independently an alkyl group having 1 to 6 carbon atoms, and c is an integer of 5 to 100.) A thermally conductive silicone composition characterized by containing the above components.

2. Furthermore, as the component (H), an organopolysiloxane having a kinematic viscosity at 23°C represented by the following general formula (3) of 10 to 100,000 mm ２ / s is contained in an amount of 0.1 to 100 parts by mass with respect to 100 parts by mass of the component (A). The thermally conductive silicone composition according to claim 1, characterized in that it is such a composition. [Chemical 2] (wherein, R ５ is independently a group selected from an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, and an aralkyl group having 7 to 12 carbon atoms, and d is an integer of 5 to 2,000.)

3. The thermally conductive silicone composition according to claim 1 or claim 2, wherein the viscosity of the thermally conductive silicone composition measured by a flow tester viscometer at 23°C is 4,000 Pa·s or less.

4. A thermally conductive silicone cured product, which is a cured product of the thermally conductive silicone composition according to claim 1.

5. The thermally conductive silicone cured product according to claim 4, wherein the shape of the thermally conductive silicone cured product is in the form of a sheet.

6. In the hardness measured by an Asker C hardness meter of the thermally conductive silicone cured product, the hardness after aging at 150 °C for 500 hours is -5 points or more and 40 points or less with respect to the hardness before aging. The thermally conductive silicone cured product according to claim 4 or claim 5, characterized in that.

7. The thermally conductive silicone cured product according to claim 4 or claim 5, characterized in that the thermal conductivity at 23 °C measured by the hot disk method of the thermally conductive silicone cured product is 7.5 W / m·K or more.

8. The thermally conductive silicone cured product according to claim 4 or claim 5, characterized in that the dielectric breakdown voltage at a thickness of 1 mm of the thermally conductive silicone cured product is 10 kV / mm or more.

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