Thermal Conductive Composition and Cured Product Thereof

Abstract

To provide a thermally conductive composition which has fluidity even in the case of containing no solvent, has excellent thermal conductivity and develops sufficient strength after curing and to provide a cured product of thereof.SOLUTION: There is provided a thermally conductive composition which comprises (A) 100 pts.mass of an organopolysiloxane represented by the following formula (1) which is liquid at 23°C (wherein, R is a hydrogen atom, an alkyl group, an aryl group or an alkenyl group, X is a hydrogen atom or an alkyl group, a, b, c and d are a number satisfying 0≤a≤0.8, 0≤b≤0.8, 0.2≤c≤1, 0≤d≤0.8 and a+b+c+d=1 and e is a number satisfying 0≤e≤0.1) and (B) 2,000 to 7,000 pts.mass of a thermally conductive filler and has a viscosity at 25°C of 1,000 Pa s or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a thermally conductive composition and a cured product thereof. More specifically, the present invention relates to a thermally conductive composition used as a heat transfer material interposed at a thermal interface between an electronic component and a heat dissipation component such as a heat sink or a metal housing for cooling a heat-generating electronic component, and a cured product thereof.

Background Art

[0002] LSI chips such as CPUs, driver ICs, and memories used in electronic devices such as personal computers, digital video disks, and mobile phones have become capable of generating a large amount of heat themselves with the improvement in performance, speed, miniaturization, and high integration. The temperature rise of the chip due to this heat causes malfunction and destruction of the chip. Therefore, many heat dissipation methods for suppressing the temperature rise of the chip during operation and heat dissipation members used therefor have been proposed.

[0003] Furthermore, in recent years, in consideration of the global environment, the development of hybrid cars that combine an engine and a motor for driving automobiles and electric cars that do not use gasoline has been actively promoted. At the same time, the increase in the output of motors has been promoted. The miniaturization and high output of motors have been rapidly progressing. Along with this, the resin for sealing the coil parts is required to have not only the property of quickly dissipating the heat generated in the coil part but also toughness corresponding to the heat cycle accompanying the ON / OFF of operation.

[0004] As a resin for impregnating and sealing coils, an epoxy resin is preferably used because it has good heat and chemical resistance and excellent mechanical properties. Furthermore, since an epoxy resin can be formulated according to the purpose by combining a curing agent and various additives, it is widely used for sealing and molding of electrical components (Patent Documents 1 and 2). However, with respect to the increase in the amount of heat generated due to the high output of the motor as described above, it is difficult to say that the epoxy resin has sufficient heat resistance, and a more reliable resin design is desired.

[0005] On the other hand, in electronic devices and the like, conventionally, in order to suppress the temperature rise of the chip during operation, a heat sink using a metal plate having a high thermal conductivity such as aluminum or copper has been used. This heat sink conducts the heat generated by the chip and releases the heat from the surface due to the temperature difference with the outside air. In order to efficiently transfer the heat generated from the chip to the heat sink, it is necessary to closely attach the heat sink to the chip. However, due to the difference in height of each chip and the tolerance due to the assembly process, a flexible sheet or grease is interposed between the chip and the heat sink, and heat conduction from the chip to the heat sink is realized through this sheet or grease.

[0006] As a composition used for such a sheet or grease, a silicone composition filled with a thermally conductive filler is generally known (Patent Documents 3 to 12). These thermally conductive silicone compositions are mainly composed of a polymer having a linear silicone skeleton, and the cured product thereof is characterized by flexibility and has strong rubber properties and does not have the hardness of an epoxy resin cured product.

[0007] As a candidate for a crosslinked binder excellent in heat resistance and hardness, a silicone resin having a three-dimensional crosslinked structure can be mentioned. As a thermally conductive silicone composition using such a silicone resin, an insulating material composition obtained by compression molding a powder containing a silsesquioxane compound or a silsesquioxane derivative and a thermally conductive filler such as boron nitride is known (Patent Documents 13 and 14). These insulating material compositions are dispersed in an organic solvent or do not have fluidity in the absence of a solvent. Therefore, there is a demand for a thermally conductive composition that has fluidity and provides a cured product having sufficient strength.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Patent Document 9

Patent Document 10

Patent Document 11

Patent Document 12

Patent Document 13

Patent Document 14

Summary of the Invention

Problems to be Solved by the Invention

[0009] The present invention has been made in view of the above circumstances, and an object thereof is to provide a thermally conductive composition that has fluidity even when not containing a solvent, is excellent in thermal conductivity, and exhibits sufficient strength after curing, and a cured product thereof.

Means for Solving the Problems

[0010] As a result of intensive studies to achieve the above object, the present inventors have found that a thermally conductive composition containing a liquid polysiloxane having a three-dimensional crosslinked structure and a specific amount of a thermally conductive filler and having a specific viscosity has excellent thermal conductivity characteristics and can also provide a cured product having high strength, and thus completed the present invention.

[0011] That is, the present invention relates to 1. (A) An organopolysiloxane represented by the following formula (1) and being liquid at 23°C: 100 parts by mass,

Chemical formula

Chemical formula

Chemical formula

Chemical formula

Advantages of the Invention

[0012] According to the present invention, it is possible to provide a thermally conductive composition that has fluidity and a high thermal conductivity and gives a cured product having sufficient strength.

Modes for Carrying Out the Invention

[0013] Hereinafter, the present invention will be specifically described. The thermally conductive composition of the present invention contains the following components (A) and (B). (A) An organopolysiloxane represented by the following formula (1) and being liquid at 23°C

Chemical formula

[0014] [Component (A)] Component (A) is an organopolysiloxane represented by the following formula (1) and being liquid at 23°C (under atmospheric pressure).

[0015]

Chemical formula

[0016] In the formula, each R is independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aralkyl group having 7 to 10 carbon atoms, or an alkenyl group having 2 to 8 carbon atoms. The alkyl group of R may be linear, branched, or cyclic, preferably having 1 to 8 carbon atoms, more preferably 1 to 6 carbon atoms. Specific examples thereof include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, neopentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, n-nonyl, n-decyl groups, etc. The aryl group preferably has 6 to 8 carbon atoms, and specific examples thereof include phenyl, tolyl, naphthyl groups, etc. The aralkyl group preferably has 7 to 9 carbon atoms, and specific examples thereof include benzyl, phenylethyl, phenylpropyl, methylbenzyl groups, etc. The alkenyl group may be linear, branched, or cyclic, preferably having 2 to 6 carbon atoms, more preferably 2 to 4 carbon atoms, and specific examples thereof include vinyl, allyl, methallyl, butenyl, hexenyl, cyclohexenyl, octenyl groups, etc. Also, in the C-H bond of these substituents, some or all of the hydrogen atoms may be substituted with halogen atoms such as chlorine, fluorine, bromine, etc. As an example, a 1,1,1-trifluoropropyl group (trifluoromethylethyl group) in which the 1-position of the propyl group is substituted with a fluorine atom, etc. can be mentioned. Among these, as R, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, phenyl, benzyl, vinyl groups are preferred, and methyl, ethyl, phenyl, vinyl groups are more preferred. Each X is independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. Specific examples of the alkyl group include the same groups as those having 1 to 3 carbon atoms among those exemplified for R, but among them, a hydrogen atom, a methyl group, and an ethyl group are preferred.

[0017] a, b, c, and d each represent the abundance ratio of 1- to 4-functional siloxane units (a 1-functional group is denoted as an M unit, a 2-functional group as a D unit, a 3-functional group as a T unit, and a 4-functional group as a Q unit hereinafter), and are numbers satisfying 0 ≦ a ≦ 0.8, 0 ≦ b ≦ 0.8, 0.2 ≦ c ≦ 1, 0 ≦ d ≦ 0.8, and a + b + c + d = 1. e is the abundance ratio of OX groups directly bonded to silicon atoms, and is a number satisfying 0 ≦ e ≦ 0.1.

[0018] Preferably, a is a number satisfying 0 ≦ a ≦ 0.6, more preferably 0.1 ≦ a ≦ 0.6. When a exceeds 0.8, the hardness of the cured product is inferior. Preferably, b is a number satisfying 0 < b ≦ 0.6, more preferably 0.2 ≦ b ≦ 0.6. When b exceeds 0.8, the ratio of D units increases, resulting in stronger elastomeric properties and inferior hardness of the cured product. Preferably, c is a number satisfying 0.4 ≦ c < 1, more preferably 0.4 ≦ c ≦ 0.7, and even more preferably 0.4 ≦ c ≦ 0.6. When c is less than 0.2, it becomes difficult to balance the fluidity of the composition and the hardness of the resulting cured product. Preferably, d is a number satisfying 0 ≦ d ≦ 0.6, more preferably 0 ≦ d ≦ 0.1. When d exceeds 0.8, the ratio of Q units increases, significantly impairing the fluidity of component (A). Also, preferably, e is a number satisfying 0 ≦ e ≦ 0.05. When e exceeds 0.1, the stability of the organopolysiloxane in component (A) deteriorates, and viscosity increase and gelation are likely to occur.

[0019] As component (A), an alkenyl group-containing organopolysiloxane represented by the following formula (2) can be used. With such an organopolysiloxane, in the presence of component (E) described later, a crosslink is formed by a hydrosilylation reaction with component (D), and a cured product can be obtained.

[0020]

Chemical formula

[0021] In the formula, R 1 is, independently of each other, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms or an aralkyl group having 7 to 10 carbon atoms, and R 2 is, independently of each other, an alkenyl group having 2 to 8 carbon atoms, and a1, a2, a3, b1, b2, b3, c1, c2, c3 are numbers from 0 to 1, provided that 0 ≦ (a1 + a2 + a3) ≦ 0.8, 0 ≦ (b1 + b2 + b3) ≦ 0.8, 0.2 ≦ (c1 + c2 + c3) ≦ 1, 0 < (a2 + b2 + c2), and a1 + a2 + a3 + b1 + b2 + b3 + c1 + c2 + c3 + d = 1. d, e and X are as defined above.

[0022] R 1 Examples of the alkyl group having 1 to 10 carbon atoms, the aryl group having 6 to 10 carbon atoms and the aralkyl group having 7 to 10 carbon atoms of, and the alkenyl group having 2 to 8 carbon atoms of R 2 are the same groups as those exemplified above for R, respectively. Among them, as R 1 a methyl group and a phenyl group are preferable, and as R 2 a vinyl group is preferable.

[0023] a1, a2, a3, b1, b2, b3, c1, c2, c3 are preferably numbers from 0 to 0.8, and more preferably numbers from 0 to 0.6. a1, a2, a3 are numbers satisfying 0 ≦ (a1 + a2 + a3) ≦ 0.8, preferably 0 ≦ (a1 + a2 + a3) ≦ 0.6, and more preferably 0.1 ≦ (a1 + a2 + a3) ≦ 0.6. When a1 + a2 + a3 exceeds 0.8, the hardness of the cured product is inferior. b1, b2, b3 are numbers satisfying 0 ≦ (b1 + b2 + b3) ≦ 0.8, preferably 0 < (b1 + b2 + b3) ≦ 0.6, and more preferably 0.2 ≦ (b1 + b2 + b3) ≦ 0.6. When b1 + b2 + b3 exceeds 0.8, the ratio of the D unit becomes high, so that the properties as an elastomer become strong and the hardness of the cured product is inferior. c1, c2, and c3 are numbers that satisfy 0.2 ≦ (c1 + c2 + c3) ≦ 1, preferably 0.4 ≦ (c1 + c2 + c3) < 1, more preferably 0.4 ≦ (c1 + c2 + c3) ≦ 0.7, and even more preferably 0.4 ≦ (c1 + c2 + c3) ≦ 0.6. When c1 + c2 + c3 is less than 0.2, it becomes difficult to balance the fluidity of the composition and the hardness of the resulting cured product.

[0024] (a2 + b2 + c2), which represents the total ratio of the structural units having an alkenyl group directly bonded to a silicon atom, is a number that satisfies 0 < (a2 + b2 + c2), and preferably 0.1 ≦ (a2 + b2 + c2) ≦ 0.3. Also, (a3 + b3 + c3), which represents the total ratio of the structural units having a hydrogen atom directly bonded to a silicon atom, is preferably a number that satisfies 0 ≦ (a3 + b3 + c3) ≦ 0.2, and more preferably a3 = b3 = c3 = 0.

[0025] (Component A) can be produced according to a general method for producing organopolysiloxanes. For example, it can be obtained by hydrolytic condensation of a silane compound having a hydrolyzable group. The silane compound having a hydrolyzable group contains 1 to 4 chloro or alkoxy groups, which are hydrolyzable groups, on the silicon atom, and is not particularly limited as long as it is a silane compound having an organic substituent that satisfies the above conditions. Specific examples thereof include tetrachlorosilane, tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, methyltrichlorosilane, methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, methyltributoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldiisopropoxysilane, trimethylchlorosilane, trimethylmethoxysilane, trimethylethoxysilane, trimethylisopropoxysilane, ethyltrichlorosilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltrichlorosilane, propyltrimethoxysilane, propyltriethoxysilane, butyltrichlorosilane, butyltrimethoxysilane, butyltriethoxysilane, hexyltrichlorosilane, hexyltrimethoxysilane, hexyltriethoxysilane, phenyltrichlorosilane, phenyltrimethoxysilane, phenyltriethoxysilane, cyclohexyltrichlorosilane, cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, propylmethyldichlorosilane, propylmethyldimethoxysilane, propylmethyldiethoxysilane, hexylmethyldichlorosilane, hexylmethyldimethoxysilane, hexylmethyldiethoxysilane, phenylmethyldichlorosilane, phenylmethyldimethoxysilane, phenylmethyldiethoxysilane, diphenyldichlorosilane, diphenyldimethoxysilane, diphenyldiethoxysilane, dimethylphenylchlorosilane, dimethylphenylmethoxysilane, dimethylphenylethoxysilane, and partial hydrolyzates thereof. However, from the viewpoints of operability, ease of distilling by-products, and ease of obtaining raw materials, methoxysilane and ethoxysilane are preferred. Note that the above silane compound(s) may be used alone or in combination of two or more.

[0026] When carrying out hydrolysis, a hydrolysis catalyst may be used. As the hydrolysis catalyst, conventionally known catalysts can be used, and those whose aqueous solutions exhibit acidity with a pH of 1 to 7 are preferred. In particular, acidic hydrogen halides, sulfonic acids, carboxylic acids, acidic or weakly acidic inorganic salts, solid acids such as ion exchange resins, etc. are preferred. Specific examples of the acidic catalyst include hydrogen fluoride, hydrochloric acid, nitric acid, sulfuric acid, methanesulfonic acid, p-toluenesulfonic acid, formic acid, acetic acid, maleic acid, benzoic acid, lactic acid, phosphoric acid, cation exchange resins having a sulfonic acid or carboxylic acid group on the surface, etc. The amount of the hydrolysis catalyst used is not particularly limited, but considering the rapid progress of the reaction and the ease of removing the catalyst after the reaction, a range of 0.0002 to 0.5 mol per 1 mol of the hydrolyzable silane is preferred.

[0027] The mass ratio of the hydrolyzable silane to the water required for the hydrolysis condensation reaction is not particularly limited, but considering preventing the deactivation of the catalyst and allowing the reaction to proceed sufficiently, and the ease of removing the water after the reaction, a ratio of 0.1 to 10 mol of water per 1 mol of the hydrolyzable silane is preferred. The reaction temperature during hydrolysis condensation is not particularly limited, but considering improving the reaction rate and preventing the decomposition of the organic functional groups of the hydrolyzable silane, -10 to 150 °C is preferred.

[0028] In addition, an organic solvent may be used during hydrolysis condensation. Specific examples of the organic solvent that can be used include methanol, ethanol, propanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, tetrahydrofuran, toluene, xylene, etc.

[0029] Also, the non-volatile content of the component (A) excluding solvents, etc. is preferably 85% by mass or more, and more preferably 90% by mass or more. When the volatile content increases, it may cause deterioration of the appearance due to void generation when the composition is cured and a decrease in mechanical properties.

[0030] The viscosity of component (A) at 23°C is preferably from 100 to 50,000 mPa·s, more preferably from 500 to 10,000 mPa·s, and particularly preferably from 1,000 to 5,000 mPa·s. If it is within such a range, the fluidity of the thermal conductive composition and the strength of the cured product will be better. The above viscosity is the measured value at 23°C using a B-type rotational viscometer (rotation speed: 30 to 60 rpm).

[0031] Specific examples of component (A) include, but are not limited to, those represented by the following formula. Among these, those having an alkenyl group directly bonded to a silicon atom are preferred, and those having at least two alkenyl groups directly bonded to a silicon atom in one molecule are more preferred. [Chemical formula] (In the formula, a1, b1, b2, b3, c1, d and e are the same as above. c10 and c11 are numbers satisfying c10≥0, c11≥0, and c10 + c11 = c1. Me represents a methyl group, Ph represents a phenyl group, and Vi represents a vinyl group.)

[0032] The organopolysiloxane of component (A) may be a single composition or a mixture of a plurality of compounds having different compositions. In particular, it can be preferably produced by mixing a plurality of compounds having different average compositions.

[0033] [Component (B)] Component (B) is a thermal conductive filler. Examples of the thermal conductive filler of component (B) include metals such as copper, silver, nickel, zinc, and stainless steel; metal oxides such as alumina, silica, magnesia, red iron oxide, beryllia, titania, and zirconia; metal nitrides such as aluminum nitride, silicon nitride, and boron nitride; artificial diamond; silicon carbide; and inorganic powders such as carbon. Known thermal conductive fillers can be used, and preferably, it is at least one selected from the group consisting of metal oxides and metal nitrides. Also, the shape of the thermal conductive filler is not particularly limited, such as spherical, irregular, needle-like, plate-like, etc.

[0034] The thermally conductive filler may be surface-treated as long as the effects of the present invention are not impaired. Specific examples of the surface treatment include treatment with a coupling agent such as a silane-based or titanate-based coupling agent, plasma treatment, and the like.

[0035] The average particle diameter of the thermally conductive filler is preferably 0.1 to 100 μm, more preferably 0.5 to 90 μm, and even more preferably 1 to 80 μm. In the present invention, the average particle diameter is the volume average particle diameter and is the measured value by a microtrack particle size distribution measuring device MT3300EX (Nikkiso Co., Ltd.).

[0036] The blending amount of the thermally conductive filler is 2,000 to 7,000 parts by mass, preferably 2,300 to 5,000 parts by mass, based on 100 parts by mass of the component (A). If the blending amount of the thermally conductive filler is too large, the cured product when used as the curable composition becomes brittle. On the other hand, if the blending amount is too small, the desired thermal conductivity cannot be obtained.

[0037] The component (B) may be used alone or in combination of two or more.

[0038] [Component (C)] The thermally conductive composition of the present invention may further contain at least one selected from the group consisting of the following components (C-1) and (C-2) as the component (C). These interact with the surface of the thermally conductive filler and have the effect of improving the dispersibility in siloxane. (C-1) An alkoxysilane compound represented by the following general formula (3) (C-2) A dimethylpolysiloxane having a trialkoxysilyl group at the end of the molecular chain represented by the following general formula (4)

[0039] [Chemical formula]

[0040] In the formula, R 3 is an alkyl group having 6 to 18 carbon atoms, and R 4is, independently of each other, an alkyl group having 1 to 12 carbon atoms, and R 5 is, independently of each other, an alkyl group having 1 to 3 carbon atoms, m is an integer of 0 to 2, and n is an integer of 5 to 100.

[0041] R 3 As the alkyl group having 6 to 18 carbon atoms of R, any of linear, branched, and cyclic forms may be used, those having 8 to 12 carbon atoms are preferred, and those having 8 to 10 carbon atoms are more preferred. Specific examples thereof include n-hexyl, cyclohexyl, n-octyl, n-decyl, n-dodecyl, n-tetradecyl, n-hexadecyl, n-octadecyl groups and the like. R 4 As the alkyl group having 1 to 12 carbon atoms of R, any of linear, branched, and cyclic forms may be used, those having 1 to 10 carbon atoms are preferred, and those having 1 to 8 carbon atoms are more preferred. Specific examples thereof include the same groups as those exemplified for R, and further include n-undecyl, n-dodecyl groups and the like, among which a methyl group is preferred. R 5 As the alkyl group having 1 to 3 carbon atoms of R, any of linear and branched forms may be used, and specific examples thereof include the same groups as those having 1 to 3 carbon atoms among the groups exemplified for R. Among them, a methyl group and an ethyl group are preferred.

[0042] m is an integer of 0 to 2, and preferably 0. n is an integer of 5 to 100, preferably an integer of 10 to 80, more preferably an integer of 20 to 50.

[0043] Specific examples of the component (C-1) include, but are not limited to, hexyltrimethoxysilane, hexylmethyldimethoxysilane, hexyltriethoxysilane, hexylmethyldiethoxysilane, cyclohexyltrimethoxysilane, cyclohexylmethyldimethoxysilane, cyclohexyltriethoxysilane, cyclohexylmethyldiethoxysilane, octyltrimethoxysilane, octylmethyldimethoxysilane, octyltriethoxysilane, octylmethyldiethoxysilane, decyltrimethoxysilane, decylmethyldimethoxysilane, decyltriethoxysilane, decylmethyldiethoxysilane, dodecyltrimethoxysilane, dodecylmethyldimethoxysilane, dodecyltriethoxysilane, dodecylmethyldiethoxysilane, hexadecyltrimethoxysilane, hexadecylmethyldimethoxysilane, hexadecyltriethoxysilane, hexadecylmethyldiethoxysilane, octadecyltrimethoxysilane, octadecylmethyldimethoxysilane, octadecyltriethoxysilane, octadecylmethyldiethoxysilane, etc. Among these, octyltrimethoxysilane, decyltrimethoxysilane, and dodecyltrimethoxysilane are preferred, and decyltrimethoxysilane is more preferred.

[0044] Specific examples of the component (C-2) include, but are not limited to, dimethylpolysiloxane blocked with a trimethoxysilyl group at one end of the molecular chain and dimethylpolysiloxane blocked with a triethoxysilyl group at one end of the molecular chain.

[0045] When using the component (C), the blending amount is preferably 1 to 300 parts by mass, more preferably 10 to 200 parts by mass, based on 100 parts by mass of the component (A). Within such a range, the effect of improving the dispersibility of the thermal conductivity filler can be obtained more efficiently. The component (C) may be used alone or in combination of two or more.

[0046] When the component (A) of the thermally conductive composition of the present invention has at least two alkenyl groups having 2 to 8 carbon atoms directly bonded to a silicon atom in one molecule, the composition can be made into a thermosetting composition by further containing (D) a compound having at least two hydrogen atoms directly bonded to a silicon atom in one molecule and not having a three-dimensional crosslinked structure, and (E) a platinum group metal-based catalyst.

[0047] [Component (D)] Component (D) is a compound having at least two hydrogen atoms directly bonded to a silicon atom (Si-H group) in one molecule and not having a three-dimensional crosslinked structure, and is a component that cures the composition by forming a crosslink by a hydrosilylation reaction with the alkenyl group in component (A) in the presence of component (E). Note that this component is distinguished from component (A) in that it does not have a T unit (three-dimensional crosslinked structure).

[0048] As component (D), for example, an organohydrogenpolysiloxane having a linear or cyclic siloxane skeleton, a compound in which this organohydrogenpolysiloxane is linked by a hydrocarbon group, etc. can be used. Specific examples of the organohydrogenpolysiloxane include methylhydrogenpolysiloxane, methylhydrogenpolysiloxane·dimethylsiloxane cyclic copolymer, both ends trimethylsiloxy group-blocked methylhydrogenpolysiloxane, both ends trimethylsiloxy group-blocked dimethylsiloxane·methylhydrogenpolysiloxane copolymer, both ends dimethylhydrogenoxysilyl group-blocked dimethylpolysiloxane, both ends dimethylhydrogenoxysilyl group-blocked dimethylsiloxane·methylhydrogenpolysiloxane copolymer, etc. Examples of the compound in which the organohydrogenpolysiloxane is linked by a hydrocarbon group include an addition reaction product of methylhydrogenpolysiloxane and a diene compound such as vinylnorbornene. Further, those in which a part or all of the methyl groups in these exemplified compounds are substituted with other alkyl groups, etc. are included. Component (D) may be used alone or in combination of two or more.

[0049] Specific examples of component (D) include, but are not limited to, the following. [Chemical formula] (In the formula, R 6 and R 7 are each independently a single bond or an alkylene group having 1 to 3 carbon atoms (such as a methylene, ethylene, trimethylene group, etc.), p, q, and r are numbers from 1 to 50, and s is a number from 1 to 10. Me represents a methyl group.)

[0050] When using component (D), its blending amount is preferably such that the number of hydrogen atoms directly bonded to the silicon atom in component (D) is 0.1 to 5.0 times, more preferably 0.5 to 2.0 times, the number of alkenyl groups in component (A).

[0051] [Component (E)] The platinum group metal-based catalyst of component (E) is a catalyst for promoting the addition reaction of the alkenyl group derived from component (A) and the hydrosilyl group derived from component (D). Specific examples of component (E) include, for example, simple substances of platinum group metals such as platinum (including platinum black), rhodium, palladium; platinum chlorides, chloroplatinic acid, and chloroplatinates such as H2PtCl4·nH2O, H2PtCl6·nH2O, NaHPtCl6·nH2O, KHPtCl6·nH2O, Na2PtCl6·nH2O, K2PtCl4·nH2O, PtCl4·nH2O, PtCl2, Na2HPtCl4·nH2O; alcohol-modified chloroplatinic acid (see US Patent No. 3220972); complexes of chloroplatinic acid and olefins (see US Patent Nos. 3159601, 3159662, 3775452); platinum group metals such as platinum black and palladium supported on carriers such as alumina, silica, and carbon; rhodium-olefin complexes; chlorotris(triphenylphosphine)rhodium (Wilkinson's catalyst); complexes of platinum chloride, chloroplatinic acid, or chloroplatinate with vinyl group-containing siloxanes, particularly vinyl group-containing cyclic siloxanes, etc.

[0052] When using the component (E), the blending amount thereof is 0.1 to 2,000 ppm in terms of the mass of the platinum group metal element relative to the mass of the component (A), preferably 50 to 1,000 ppm.

[0053] [Other components] In addition to the above components (A) to (E), the thermally conductive composition of the present invention may be added with known additives within a range that does not impair the object of the present invention. For example, when the composition of the present invention is a thermosetting composition, an addition reaction control agent can be used as necessary. As the addition reaction control agent, all known addition reaction control agents used in ordinary addition reaction-curing type silicone compositions can be used. Examples thereof include acetylene compounds such as ethynylmethylidene carbinol, 1-ethynyl-1-hexanol, and 3-butyn-1-ol, various nitrogen compounds, organic phosphorus compounds, oxime compounds, and organic chloro compounds. When using the addition reaction control agent, the blending amount thereof is preferably 0.01 to 5 parts by mass, more preferably 0.1 to 2 parts by mass, relative to 100 parts by mass of the component (A).

[0054] The thermally conductive composition of the present invention preferably has a solvent-free form that substantially does not contain an organic solvent, but a solvent can also be added and used from the viewpoints of its use and workability. Here, "substantially" means that the solvent contained in the composition is 1% by mass or less, particularly 0.1% by mass or less. Specific examples of the usable solvent include the same ones as the reaction solvent used in the production of the (A) organopolysiloxane. The solvent also includes those that are not intentionally added components in the composition, such as the reaction solvent that could not be completely removed by distillation under reduced pressure.

[0055] [Production method] The thermally conductive composition of the present invention can be obtained by mixing the above components (A), (B), and other components in an arbitrary order at room temperature and stirring them.

[0056] The thermal conductive composition of the present invention has a viscosity at 25°C of 1,000 Pa·s or less, preferably 300 Pa·s or less. If the viscosity is too high, the moldability may be impaired. The lower limit of the viscosity is not particularly limited, but is usually about 0.1 Pa·s. The above viscosity was measured using a rheometer (HAAKE MARS 40 manufactured by Thermo Fisher Scientific), setting the gap value to 0.3 mm with a parallel plate rotor (diameter 20 mm), at 25°C and a rotation speed of 10 cycles per second.

[0057] Considering the application to a heating element with a large calorific value, the thermal conductivity of the thermal conductive composition of the present invention preferably has a measured value at 25°C by the hot disk method of 3.0 W / mK or more, more preferably 4.0 W / mK or more. The upper limit of the thermal conductivity varies depending on the material used for the thermally conductive filler and is not particularly limited, but is usually about 500 W / mK. The thermal conductivity can be adjusted by the combination of the particle size, type, and addition amount of the thermally conductive filler.

[0058] [Cured product] The thermal conductive composition of the present invention can be cured by a known curing method under known curing conditions. Specifically, it can usually be cured at a heating temperature of 80 to 200°C, preferably 100 to 160°C, for a heating time of about 0.5 minutes to 3 hours, preferably about 1 minute to 1 hour.

[0059] The thermal conductive composition of the present invention contains polysiloxane as a main component as a binder component, and since this component has a silicone structure with an essential three-dimensional siloxane cross-linked structure, it has excellent heat transfer performance and gives a high reinforcing effect. The thermal conductive composition of the present invention can be suitably used, for example, as a thermal conductive material for impregnating and filling motor coil parts, etc., to dissipate heat while maintaining the strength of the housing. In addition, the thermally conductive composition of the present invention can be used, for example, as a thermally conductive grease. Furthermore, the thermally conductive cured product obtained by hydrosilylation can be used as a thermally conductive potting agent that fills and cures the gaps of heat dissipating molded bodies or heat generating members such as motor coils.

Examples

[0060] Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[0061] In the following Examples and Comparative Examples, the apparatuses used for property evaluation are as follows. (1) Viscosity The viscosity of component (A) was measured at 23°C using a B-type rotational viscometer (TVB-10 manufactured by Toki Sangyo Co., Ltd., rotor: TM3 or TM4, rotation speed: 30 rpm or 60 rpm). The viscosity of the thermally conductive composition was measured using a rheometer (HAAKE MARS 40 manufactured by Thermo Fisher Scientific), with a parallel plate rotor (diameter 20 mm), a gap value set to 0.3 mm, and under the conditions of 25°C and a rotation speed of 10 cycles per second. (2) Thermal conductivity The thermal conductivity of the composition at 25°C was measured in accordance with ISO 22007-2 using a hot disk method thermal property measuring device TPS 2500 S manufactured by Kyoto Electronics Industry Co., Ltd. (3) Durometer hardness A sheet obtained by curing the composition to a thickness of 6 mm was measured in accordance with JIS K7215 using a hardness tester type D indenter manufactured by TECLOCK Co., Ltd.

[0062] The components used in the following Examples and Comparative Examples are shown below. In the following formulas, Me represents a methyl group and Ph represents a phenyl group.

[0063] (A) component: Organopolysiloxane having a structural unit ratio represented by the following formula

Chemical formula

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

Chem.

[0064] Component (B): (B-1) Amorphous alumina with an average particle size of 3.6 μm (B-2) Spherical alumina with an average particle size of 17 μm (B-3) Spherical alumina with an average particle size of 45 μm (B-4) Spherical alumina with an average particle size of 70 μm (B-5) Granular aluminum nitride with an average particle size of 1.0 μm (B-6) Granular aluminum nitride with an average particle size of 20 μm

[0065] Component (C): A compound represented by the following formula

Chemical formula

[0066] Component (D): A compound represented by the following formula

Chemical formula

Chemical formula

Chemical formula

[0067] Component (E): 5 mass% solution of chloroplatinic acid in 2-ethylhexanol

[0068] Component (F): Ethynylmethylidene carbinol as an addition reaction control agent

[0069] [1] Production of the thermal conductivity composition [Examples 1-1 to 1-3, Comparative Examples 1-1 to 1-4] Components (A) to (C) in the proportions (parts by mass) shown in Table 1 were kneaded with a planetary mixer for 60 minutes, and then vacuum degassing was performed for 30 minutes to obtain a composition. The viscosity and thermal conductivity of the obtained composition are shown in Table 1.

[0070] [Table 1]

[0071] As shown in Table 1, the thermally conductive compositions of Examples 1-1 to 1-3 had low viscosity, excellent fluidity, and exhibited high thermal conductivity. On the other hand, Comparative Example 1-1 contained an excessive amount of thermally conductive filler, so the fluidity of the composition was poor. Comparative Example 1-2 had insufficient thermally conductive filler, so sufficient thermal conductivity was not exhibited. Comparative Example 1-3 had a low ratio of T units and a high ratio of D units in the organopolysiloxane. Although it had the same blending amount of thermally conductive filler as Example 1-1, its thermal conductivity was low. Also, Comparative Example 1-4 had a low ratio of T units and a high ratio of Q units in the organopolysiloxane, and its viscosity was very high. As a result, the fluidity of the thermally conductive composition was poor and it was not practical.

[0072] [Examples 1-4 to 1-10, Comparative Examples 1-5, 1-6] Components (A) to (C) and component (F) in the proportions (parts by mass) shown in Table 2 were kneaded with a planetary mixer for 60 minutes. Components (D) and (E) were added thereto and kneaded for 30 minutes, and then vacuum degassing was performed for 30 minutes to obtain a composition. The viscosity and thermal conductivity of the obtained composition are shown in Table 2.

[0073] [2] Production of cured sheet [Examples 2-1 to 2-7, Comparative Examples 2-1, 2-2] The compositions obtained in Examples 1-4 to 1-10 and Comparative Examples 1-5 and 1-6 were poured into a mold of 60 mm × 60 mm × 6 mm, and heat-cured using a press molding machine under the conditions of 120 °C for 10 minutes to obtain a cured sheet. The durometer hardness of the obtained cured sheet is shown in Table 3.

[0074] [Table 2]

[0075] [Table 3]

[0076] As shown in Tables 2 and 3, the thermal conductive compositions of Examples 1-4 to 1-10 were excellent in fluidity and thermal conductivity, and the hardness of the cured products obtained by curing these compositions was high. On the other hand, Comparative Example 1-5 using an organopolysiloxane with a low ratio of T units and a high ratio of D units had a low thermal conductivity and a low hardness of the obtained cured product, even though it had the same blending amount of the thermal conductive filler as Examples 1-4 and 1-5. In addition, Comparative Example 1-6 using an organopolysiloxane with a low ratio of T units and a high ratio of Q units had very high viscosity of the organopolysiloxane, resulting in poor fluidity of the thermal conductive composition and being impractical. Even though it had the same blending amount of the thermal conductive filler as Examples 1-4 and 1-5, its thermal conductivity was low.

Claims

1. (A) 100 parts by mass of an organopolysiloxane represented by the following formula (1) and being a liquid at 23°C: [Chemical Formula 1] (In the formula, each R is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, or an aralkyl group having 7 to 10 carbon atoms; each X is independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms; a, b, c, and d are numbers satisfying 0 ≦ a ≦ 0.8, 0 ≦ b ≦ 0.8, 0.2 ≦ c ≦ 1, 0 ≦ d ≦ 0.8, and a + b + c + d = 1; and e is a number satisfying 0 ≦ e ≦ 0.1), and (B) 2,000 to 7,000 parts by mass of a heat conductive filler A heat conductive composition containing the above and having a viscosity at 25°C of 1,000 Pa·s or less.

2. The heat conductive composition according to Claim 1, wherein the component (A) is an organopolysiloxane represented by the following formula (2). [Chemical Formula 2] (In the formula, R 1 is independently an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, or an aralkyl group having 7 to 10 carbon atoms; R 2 is independently an alkenyl group having 2 to 8 carbon atoms; a1, a2, a3, b1, b2, b3, c1, c2, c3 are numbers from 0 to 1, provided that 0 ≦ (a1 + a2 + a3) ≦ 0.8, 0 ≦ (b1 + b2 + b3) ≦ 0.8, 0.2 ≦ (c1 + c2 + c3) ≦ 1, 0 = (a2 + b2 + c2), 0 = (a3 + b3 + c3), and a1 + a2 + a3 + b1 + b2 + b3 + c1 + c2 + c3 + d = 1 are satisfied. d, e, and X have the same meanings as above.)

3. The heat conductive composition according to Claim 1 or 2, wherein the heat conductive filler (B) is at least one selected from the group consisting of metal oxides and metal nitrides.

4. Further, (C) at least one selected from the group consisting of the following components (C-1) and (C-2): 0.01 to 300 parts by mass with respect to 100 parts by mass of component (A) The thermally conductive composition according to any one of claims 1 to 3, which contains this. (C-1) An alkoxysilane compound represented by the following general formula (3) [Chemical 3] (In the formula, R 3 is an alkyl group having 6 to 18 carbon atoms, and R 4 are each independently an alkyl group having 1 to 12 carbon atoms, and R 5 are each independently an alkyl group having 1 to 3 carbon atoms, and m is an integer of 0 to 2.) (C-2) A dimethylpolysiloxane in which the molecular chain fragment ends are blocked with a trialkoxysilyl group and represented by the following general formula (4) [Chemical 4] (In the formula, R 5 has the same meaning as above, and n is an integer of 5 to 100.)

5. The thermally conductive composition according to any one of claims 1 to 4, wherein the content of the solvent is 1% by mass or less with respect to the whole composition.

6. The thermally conductive composition according to any one of claims 1 to 5, wherein the thermal conductivity is 3.0 W / mK or more.

7. A thermally conductive cured product obtained by curing the thermally conductive composition according to any one of claims 1 to 6.

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