Thermally conductive resin composition

Abstract

This thermally conductive resin composition has an organo-polysiloxane blended therein in an amount in a range of 0.1-10.0 parts by mass with respect to 100 parts by mass of a filler. A polysiloxane compound having, at one terminal of a main chain, an ester functional group having a terminal modified by a hydroxyl group is blended in an amount in a range of 0.4-5.0 parts by mass with respect to 100 parts by mass of the filler. With respect to 100 parts by mass of the filler, an alkoxy silane compound is blended in an amount in a range of 1.2X to 10.0X parts by mass, where X represents a value obtained by dividing, by the minimum coated area (m2 / g) of the alkoxy silane compound, a value obtained by multiplying the specific surface area (m2 / g) of the filler with 100 parts by mass indicating the amount of the filler.

Description

Thermally conductive resin composition

[0001] This invention relates to a thermally conductive resin composition comprising a resin and a thermally conductive filler. This application claims priority to Japanese Patent Application No. 2024-055594 filed on March 29, 2024, and Japanese Patent Application No. 2024-056768 filed on March 29, 2024, the contents of which are incorporated herein by reference.

[0002] In recent years, the amount of heat generated by electrical components has been increasing along with the advances in the performance of personal computers and smartphones and the development of electric vehicles and fuel cell vehicles. For example, lithium-ion batteries for automobiles generate a large amount of heat because they output a large amount of power continuously for a long period of time, and this large amount of generated heat must be efficiently dissipated to the outside. For this reason, thermally conductive resin materials with excellent thermal conductivity are sometimes used as heat dissipation materials for electrical components such as lithium-ion batteries and IC chips.

[0003] The thermally conductive resin composition for forming such a thermally conductive resin material contains a resin component and a thermally conductive filler, and by increasing the filling rate of the filler relative to the resin component, the thermal conductivity of the resulting thermally conductive resin material can be increased.

[0004] However, increasing the filler content relative to the resin component increases the hardness of the cured thermally conductive resin material and reduces its tackiness. The increased hardness reduces its conformability, making it difficult to position the thermally conductive resin material along a desired shape. Furthermore, the reduced tackiness makes the thermally conductive resin material more likely to flow, making it difficult to position it in a desired location.

[0005] For this reason, for example, Patent Document 1 discloses a silicone resin composition containing an organopolysiloxane and a thermally conductive filler. It is said that such a silicone resin composition can maintain fluidity even when filled with a thermally conductive filler at a high filling rate.

[0006] Furthermore, for example, Patent Document 2 discloses a thermally conductive composition containing a liquid silicone resin, a polysiloxane compound, and a thermally conductive filler in a predetermined mass ratio. This silicone resin composition is said to have high thermal conductivity, a low viscosity after curing, and a cured product with appropriate hardness.

[0007] JP 2023-012918 A JP 2023-148623 A

[0008] However, even with the thermally conductive resin compositions disclosed in Patent Documents 1 and 2, the reduction in hardness when the filling rate of the filler relative to the resin component is increased is limited, and there has been a demand for a thermally conductive resin composition that can form a thermally conductive resin material with even lower hardness and higher thermal conductivity.

[0009] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a thermally conductive resin composition that can suppress an increase in hardness of the cured thermally conductive resin material and a decrease in tackiness, even when the filling rate of the thermally conductive filler in the resin component is increased.

[0010] The present inventors have newly discovered that by adding an alkoxysilane compound, which is a crosslinking agent, in an amount that exceeds the amount required to completely cover the surface of the filler constituting the thermally conductive resin composition, for example, with a thickness equivalent to a monomolecular film, it is possible to increase the loading amount of the filler relative to the resin component and thereby improve the thermal conductivity, while keeping the hardness of the cured thermally conductive resin material low and preventing a decrease in tackiness.

[0011] In order to solve the above problems, a thermally conductive resin composition according to one embodiment of the present invention proposes the following means. (1) A thermally conductive resin composition according to a first aspect of the present invention is a thermally conductive resin composition comprising a resin component including an organopolysiloxane, a polysiloxane compound, and an alkoxysilane compound, and a thermally conductive filler, wherein the organopolysiloxane is blended in an amount ranging from 0.1 parts by mass to 10.0 parts by mass when the filler is taken as 100 parts by mass, the polysiloxane compound has an ester functional group, the end of which is modified with a hydroxyl group, at one end of the polysiloxane main chain, the polysiloxane compound is blended in an amount ranging from 0.4 parts by mass to 5.0 parts by mass when the filler is taken as 100 parts by mass, and the specific surface area (m ２ / g) to obtain the minimum coverage area (m ２ / g) is defined as X, and the alkoxysilane compound is blended in an amount in the range of 1.2X to 10.0X parts by mass.

[0012] (2) Aspect 2 of the present invention is the thermally conductive resin composition of aspect 1, wherein the filler contains at least one of a metal oxide, a metal nitride, a metal carbide, a metal, and carbon.

[0013] (3) Aspect 3 of the present invention is the thermally conductive resin composition of aspect 2, wherein the filler is alumina particles.

[0014] (4) Aspect 1 of the present invention is the thermally conductive resin composition of any one of Aspects 1 to 3, wherein the organopolysiloxane is an alkenyl group-containing organopolysiloxane, and the resin component further contains a radical initiator.

[0015] (5) Aspect 5 of the present invention relates to the thermally conductive resin composition of Aspect 4, wherein the radical initiator comprises any one of an addition reaction type curing agent consisting of an organohydrogenpolysiloxane containing two or more silicon-bonded hydrogen atoms per molecule and a platinum group catalyst, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, and dicumyl peroxide.

[0016] (6) A sixth aspect of the present invention is the thermally conductive resin composition of any one of the first to fifth aspects, wherein the filler is contained in an amount of 1,000 parts by mass or more when the total mass of the resin components is 100 parts by mass.

[0017] According to an aspect of the present invention, it is possible to provide a thermally conductive resin composition that can suppress an increase in hardness of the cured thermally conductive resin material and a decrease in tackiness, even when the filling rate of the thermally conductive filler relative to the resin component is increased.

[0018] A thermally conductive resin material according to one embodiment of the present invention will be described below. Note that the following embodiment is specifically described to provide a better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

[0019] The thermally conductive resin composition of this embodiment forms a thermally conductive resin material by curing. The thermally conductive resin composition is composed of a resin component (R) mixed with a thermally conductive filler (F). The resin component (R) contains at least an organopolysiloxane (A), a polysiloxane compound (B), and an alkoxysilane compound (C).

[0020] [Organopolysiloxane (A)] Organopolysiloxane (A) is a liquid silicone-based base polymer, and has a structure in which an organic functional group is bonded to the Si—O of the main chain of polysiloxane. The general formula of such organopolysiloxane (A) is shown in the following formula (1). R Ｙ SiO （４－Ｙ）／２ ... (1) where R: organic group

[0021] In formula (1), the coefficients Y are each independently greater than 0 and represent the content of each component of the silicon-bonded organic group or the silicon-bonded oxygen-bonded organic group R. The organic group R is a functional group containing carbon atoms, hydrogen atoms, oxygen atoms, nitrogen atoms, phosphorus atoms, sulfur atoms, and halogen atoms, and is formed by any combination thereof.

[0022] Specific examples of the organic group R include a vinyl group, an allyl group, a (meth)acrylic group, a carboxyl group, a nitrile group, a formyl group, a carbonyl group, a carbinol group, an amino group, an imino group, a nitro group, a cyano group, a sulfo group, a mercapto group, a thiol bond, an ether bond, an ester bond, an amide bond, an alkyl group having 1 to 20 carbon atoms, and a combination of functional groups including an aromatic functional group. Specific examples of the organic group R include a hydrogen atom, a methyl group, an ethyl group, a propyl group, a hexyl group, a decyl group, an octadecyl group, and the like. Examples thereof include a silyl group, a cyclopentyl group, a cyclohexyl group, an ethylene glycol monoethylene ether group, an acryloxypropyl group, an acryloxyoctyl group, a methacryloxypropyl group, a methacryloxyoctyl group, a glycidyl group, a glycidoxypropyl group, a glycidoxyoctyl group, a 1,2-epoxycyclohexyl-3-propyl group, a 1,2-epoxycyclohexyl-3-octyl group, a phenyl group, a phenethylene group, a styryl group, a vinyl group, and an allyl group.

[0023] The organopolysiloxane (A) of this embodiment may be any resin having an organopolysiloxane structure as the main chain, and specific examples of such resins include curable silicone resins and non-curable silicone resins. Examples of curable silicone resins include addition reaction curable silicone resins, condensation reaction curable silicone resins, and organic peroxide curable silicone resins.

[0024] When an addition reaction curable silicone resin is used as the organopolysiloxane (A), the reactive functional group contains an alkenyl group, which causes addition polymerization and cure. Examples of the alkenyl group include vinyl, allyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, and octenyl groups.

[0025] When the organopolysiloxane (A) contains an alkenyl group, it is preferable to include a radical initiator as a polymerization initiator for initiating addition polymerization. Examples of radical initiators include organic peroxides and azo compounds. The amount of the radical initiator is preferably 0.01% by mass or more and 0.1% by mass or less, relative to 100% by mass of the organopolysiloxane (A).

[0026] Specific examples of organic peroxides used as radical initiators include addition reaction type curing agents composed of organohydrogenpolysiloxanes containing two or more silicon-bonded hydrogen atoms per molecule and platinum group catalysts, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, dicumyl peroxide, etc. Furthermore, examples of azo compounds include azobisisobutyronitrile (AIBN).

[0027] The organopolysiloxane (A) of this embodiment as described above may be blended in an amount ranging from 0.1 to 10.0 parts by mass, based on 100 parts by mass of the thermally conductive filler (F) described below. The amount of organopolysiloxane (A) is preferably from 0.5 to 7.0 parts by mass, more preferably from 1.0 to 5.0 parts by mass, and even more preferably from 1.0 to 2.8 parts by mass.

[0028] [Polysiloxane Compound (B)] The polysiloxane compound (B) of this embodiment has an ester functional group, the end of which is modified with a hydroxyl group, bonded to one end of a polysiloxane main chain consisting of a siloxane bond (Si—O—Si…). The ester functional group may be any compound generated by dehydration condensation of an acid and an alcohol, and one example is a carboxylic acid ester (R—COO—R′).

[0029] An example of the polysiloxane compound (B) of this embodiment is a processed product in which a functional group in which the terminal R and R′ of such a carboxylic acid ester are modified with a hydroxyl group (—OH) is bonded to one end of a polysiloxane main chain.

[0030] The polysiloxane compound (B) of this embodiment as described above may be blended in an amount ranging from 0.4 to 5.0 parts by mass, when the filling ratio of the thermally conductive filler (F) described below is taken as 100 parts by mass. The amount of polysiloxane compound (B) is preferably from 0.4 to 4.0 parts by mass, more preferably from 0.5 to 3.5 parts by mass, and more preferably from 0.5 to 2.7 parts by mass.

[0031] [Alkoxysilane Compound (C)] The alkoxysilane compound (C) used in this embodiment is a silane coupling agent (crosslinking agent). When the organopolysiloxane (A) contains a condensation type silicone resin, the alkoxysilane compound can be, for example, a tetraalkoxysilane, trialkoxysilane, dialkoxysilane, trialkoxyalkene at both ends, alkyltriacetoxysilane, or alkenyltriacetoxysilane, each of which has a plurality of alkoxy groups. By using such an alkoxysilane compound (C), the hardness of the thermally conductive resin material obtained by curing the thermally conductive resin composition can be reduced, and shape conformability can be improved.

[0032] Regarding the alkoxysilane compound (C) of the present embodiment as described above, when the filling ratio of the thermally conductive filler (F) described later is 100 parts by mass, the specific surface area (m ２ / g) is multiplied to obtain the minimum coverage area (m ２ / g) is defined as X, and the alkoxysilane compound (C) may be blended in an amount in the range of 1.2X to 10.0X parts by mass. The amount of the alkoxysilane compound (C) is preferably 1.2X to 8.0X, more preferably 1.2X to 7.0X, and more preferably 2.6X to 5.6X. The coating thickness of the alkoxysilane compound (C) in this minimum coating area is the thickness equivalent to a monomolecule. The minimum coating area (m ２ / g) is calculated by the following formula: ２ / g) = (6.02 × 10 ２３x13 x 10 －２０ ) / (molecular weight of alkoxysilane compound)

[0033] That is, the blending amount of the alkoxysilane compound (C) described above corresponds to the addition of an excessive blending amount of the alkoxysilane compound (C), which is 1.2 to 10.0 times the minimum required amount of the alkoxysilane compound (C) necessary to cover the surfaces of all the filled fillers (F) with a thickness equivalent to a monomolecular film of the alkoxysilane compound.

[0034] In this manner, in the present embodiment, by adding an excessive amount of the alkoxysilane compound (C), such as 1.2 to 10.0 times the amount required to completely cover the surface of the filler (F), the filling amount of the filler (F) relative to the resin component (R) is increased to improve the thermal conductivity, and the hardness, for example, the Asker hardness C, can be kept low, and a decrease in tackiness can be prevented.

[0035] [Filler (F)] The filler (F) is a material that imparts thermal conductivity by filling the resin component (R). It may be composed of a material containing at least one of metal oxide, metal nitride, metal carbide, metal, and carbon. More specifically, examples of the filler include alumina (aluminum oxide), silicon carbide, zinc oxide, aluminum nitride, and boron nitride. In this embodiment, a mixture of alumina with multiple particle sizes is used. The thermally conductive filler refers to a filler composed of a material with a higher thermal conductivity than the resin components, organopolysiloxane (A) and polysiloxane compound (B).

[0036] The filler (F) may be formed into particles having a particle size of approximately 0.1 μm to 100 μm. A mixture of filler (F) particles having different particle sizes may also be used. In this embodiment, alumina particles having an average particle size (D50) of approximately 22.1 μm are used as the filler (F). The average particle size of the filler (F) is the particle size (D50) at which the cumulative volume frequency of particles is 50% in a volume-based particle size distribution measured using a laser diffraction / scattering particle size distribution analyzer (MT3300, manufactured by Nikkiso Co., Ltd.).

[0037] The filler (F) of the present embodiment as described above may be contained in an amount of 1,000 parts by mass or more, preferably 1,000 parts by mass or more and 5,000 parts by mass or less, and more preferably 1,500 parts by mass or more and 1,800 parts by mass or less, when the total mass of the resin component (R) is 100 parts by mass.

[0038] According to the thermally conductive resin composition of this embodiment having the above-described configuration, the amount of the alkoxysilane compound (C) used as the crosslinking agent is in an excess amount, such as 1.2 to 10.0 times the minimum amount of alkoxysilane compound (C) required to cover the surfaces of all of the filled fillers (F) with a thickness equivalent to a monolayer of the alkoxysilane compound. This allows the hardness of the cured thermally conductive resin material, such as the Asker hardness C, to be maintained low even when the amount of filler (F) loaded relative to the resin component (R) is increased, for example, to 1,000 parts by mass or more per 100 parts by weight of the resin component. This allows a thermally conductive resin material to be obtained that has excellent thermal conductivity, low hardness, and excellent shape conformability due to the high loading of the filler. The thermally conductive resin material obtained by curing the thermally conductive resin composition of this embodiment preferably has a thermal conductivity of 4.5 W / mK or more, more preferably 5.0 W / mK or more. The Asker C hardness is preferably 85 or less, more preferably 65 or less. The tack strength is preferably 0.3 N / mm or more, and more preferably 1.0 N / mm or more.

[0039] Furthermore, according to the thermally conductive resin composition of this embodiment, it is possible to obtain a thermally conductive resin material with excellent workability, which can prevent a decrease in tackiness even when the filling amount of filler is increased.

[0040] Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit (requirements) of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims.

[0041] The thermally conductive resin composition samples were actually produced and their properties were investigated. The constituent materials used were as follows: (1) Organopolysiloxane (A): Addition reaction curing type silicone resin, Model No. KE-1051J-A / B, manufactured by Shin-Etsu Chemical Co., Ltd. (2) Polysiloxane compound (B): Hydroxyl-terminated polysiloxane, Model No. FM-DA21, manufactured by JNC Corporation (3) Alkoxysilane compound (C): Model No. KBM3103C, manufactured by Shin-Etsu Chemical Co., Ltd. (4) Filler (F): A mixture of (a) spherical alumina, DAM-45 (manufactured by Denka Co., Ltd., average particle size 46.1 μm), 49.2 wt%, (b) spherical alumina, DAM-05 (manufactured by Denka Co., Ltd., average particle size 6.4 μm), 32.8 wt%, and (c) low soda alumina, AES-11C (Sumitomo Chemical Co., Ltd., average particle size 0.39 μm), 18.0 wt%. The volume-based particle size distribution of the filler (F) was measured using a laser diffraction / scattering particle size distribution analyzer (MT3300, manufactured by Nikkiso), and the particle size (D50) at which the cumulative volume frequency of particles was 50% was calculated. D50 was defined as the average particle size of the filler (F).

[0042] The blending ratios of the materials in Examples 1 to 6 of the present invention and Comparative Examples 1 to 4 of the conventional invention when the filler was 1500 parts by weight are shown in Table 1 below. The blending ratios of the materials in Examples 7 to 13 of the present invention and Comparative Examples 5 to 7 of the conventional invention when the filler was 1800 parts by weight are shown in Table 2 below. The specific surface area of ​​the filler (F) used was 1.48 (m ２ / g), and the minimum coverage area of ​​the filler by the alkoxysilane compound (C) is 297 (m ２ / g).

[0043] Each of the thermally conductive resin compositions of the present invention and comparative examples was cured at 120°C for 24 hours to obtain a thermally conductive resin material. The thermal conductivity, Asker C hardness, and tackiness of each of the obtained thermally conductive resin materials were measured under the following conditions.

[0044] (a) Thermal conductivity: Measurement was performed using a thermal conductivity measuring device (IE-1237, manufactured by Iwasaki Tsushinki Co., Ltd.) by a steady-state method with the high-temperature side at 80°C and the low-temperature side at 15°C. The sample had a vertical length of 30 mm, a horizontal length of 30 mm, and a thickness of 3 mm. (b) Asker C hardness: Measurement was performed using a durometer (Asker Rubber Hardness Meter Type C, manufactured by Kobunshi Keiki Co., Ltd.) based on JIS K 7312. (c) Tack strength: Measurement was performed using a Texture Analyzer (Model No. FRTS-100N, manufactured by Imada Co., Ltd.) under the following conditions. A Teflon rod (Teflon: registered trademark) with a diameter of 15 mm was pressed into the sample at a downward speed of 1 mm / sec to a maximum pressure of 50 N. Next, the maximum pulling stress (tack strength) was measured when the sample was pulled up at a pulling speed of 1 mm / sec.

[0045] The results of measuring the thermal conductivity, Asker C hardness, and tack strength of each sample are shown in Tables 1 and 2, respectively.

[0046]

[0047]

[0048] As shown in the results in Table 1, when 1500 parts by mass of filler was filled with 100 parts by mass of resin component (R), in Examples 1 to 6 of the present invention, a thermal conductivity of approximately 4.56 to 5.54 (W / mK) was ensured, and the maximum Asker C hardness was 64 or less. In addition, the tack strength was in the range of 1.0 to 1.9 (N / mm).

[0049] On the other hand, Comparative Example 1, in which no alkoxysilane compound (C) was added, had a low thermal conductivity of 4.36 W / mK. Furthermore, Comparative Examples 2 and 4, in which no polysiloxane compound (B) was added, had tack strengths of 0.5 (N / mm) and 0.7 (N / mm), respectively, which were lower than Invention Examples 1 to 6.

[0050] Furthermore, as shown in the results in Table 2, when 1,800 parts by mass of filler was filled with 100 parts by mass of resin component (R), in Examples 7 to 13 of the present invention, the thermal conductivity was approximately 5.49 to 6.99 (W / mK), and the maximum Asker C hardness was 84 or less. The tack strength was also in the range of 0.3 to 2.0 (N / mm).

[0051] On the other hand, in Comparative Example 5, in which the amount of alkoxysilane compound (C) added was small, the thermal conductivity was 4.71 (N / mm), which was lower than the thermal conductivity of Inventive Examples 7 to 13. In Comparative Example 6, in which no polysiloxane compound (B) was added, the Asker C hardness was high at 90, and the tack strength was extremely low at 0.1 (N / mm). Furthermore, in Comparative Example 7, in which no polysiloxane compound (B) was added, the tack strength was 0 (N / mm), posing a problem with shape retention.

[0052] As described above, it was confirmed that in Examples 1 to 12 of the present invention, a thermally conductive resin composition can be obtained that can form a thermally conductive resin material that has high thermal conductivity, low Asker C hardness and excellent processability, and maintains a certain level of tackiness and excellent shape retention performance.

[0053] If a thermally conductive resin material obtained by curing the thermally conductive resin composition of this embodiment is applied to, for example, an IC chip or a lithium ion battery, it can be arranged so as to easily adhere to the surface shape of each component, and the large amount of heat generated in the heat-generating portion can be efficiently conducted with high thermal conductivity toward a heat dissipation component, etc. Therefore, the thermally conductive resin composition of this embodiment is suitably applied as a heat dissipation component for electrical components such as IC chips and lithium ion batteries.

Claims

1. A thermally conductive resin composition comprising a resin component including an organopolysiloxane, a polysiloxane compound, and an alkoxysilane compound, and a thermally conductive filler, wherein the organopolysiloxane is blended in an amount ranging from 0.1 parts by mass to 10.0 parts by mass when the filler is taken as 100 parts by mass, the polysiloxane compound has an ester functional group, the end of which is modified with a hydroxyl group, at one end of the polysiloxane main chain, the polysiloxane compound is blended in an amount ranging from 0.4 parts by mass to 5.0 parts by mass when the filler is taken as 100 parts by mass, and the specific surface area (m ２ / g) to obtain the minimum coverage area (m ２ / g) is defined as X, and the alkoxysilane compound is blended in an amount in the range of 1.2X to 10.0X parts by mass.

2. The thermally conductive resin composition according to claim 1, wherein the filler contains at least one of a metal oxide, a metal nitride, a metal carbide, a metal, and carbon.

3. The thermally conductive resin composition according to claim 2, wherein the filler is alumina particles.

4. A thermally conductive resin composition according to any one of claims 1 to 3, wherein the organopolysiloxane is an alkenyl group-containing organopolysiloxane, and the resin component further contains a radical initiator.

5. The thermally conductive resin composition according to claim 4, wherein the radical initiator comprises one of an addition reaction type curing agent consisting of an organohydrogenpolysiloxane containing two or more silicon-bonded hydrogen atoms per molecule and a platinum group catalyst, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, and dicumyl peroxide.

6. A thermally conductive resin composition according to any one of claims 1 to 3, which contains 1,000 parts by mass or more of the filler when the total mass of the resin components is 100 parts by mass.

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