JP2022115689A - thermal grease - Google Patents

Abstract

The present invention provides a thermally conductive grease that achieves both malleability and thermal conductivity. A thermally conductive grease containing an inorganic powder filler and a base oil composition, wherein the inorganic powder filler is a first inorganic powder filler having an average particle size in the range of 10 μm or more and 100 μm or less. a second inorganic powder filler having an average particle size different from that of the first inorganic powder filler; and a third inorganic powder filler having an average particle size different from that of the first inorganic powder filler and the second inorganic powder filler. and the average particle size of the inorganic powder filler satisfies a predetermined relationship, and the base oil composition comprises a base oil, an amine-based additive, a phenol-based additive, and a thioether-based additive. Thermally conductive grease containing [Selection figure] None

Description

The present invention relates to thermally conductive greases.

Semiconductor parts used in electronic devices include heat-generating parts that generate heat during use, such as computer CPUs, Peltier devices, LEDs, and power semiconductors for power supply control such as inverters.

In order to protect these semiconductor parts from heat and to function normally, there is a method of transferring the heat generated from the heat-generating parts (semiconductor parts) to a heat-dissipating part such as a heat sink to dissipate the heat. Thermally conductive grease is applied between the heat-generating component and the heat-radiating component so as to bring them into close contact with each other, and is used to efficiently conduct heat from the heat-generating component to the heat-radiating component. In recent years, the performance of electronic devices using these semiconductor components has been improved, and the devices have become smaller and more densely mounted, so thermally conductive greases used for heat dissipation are required to have higher thermal conductivity.

Thermally conductive greases are composed of base oils such as liquid hydrocarbons, silicone oils, and fluorine oils, metal oxides such as zinc oxide and aluminum oxide, inorganic nitrides such as boron nitride, silicon nitride, and aluminum nitride, aluminum and It is a grease-like composition in which a large amount of filler with high thermal conductivity such as metal powder such as copper is dispersed. For example, a product containing a specific surface modifier (see Patent Documents 1 and 2, etc.) is disclosed.

Patent No. 59443064 JP 2008-280516 A

Thermally conductive grease is used for thermal contact interfaces between heat-generating parts such as computer CPUs and heat-radiating parts such as heat sinks, heat-generating parts such as high-output inverters mounted on hybrid and electric vehicles, and heat spreaders. It is used by applying it to the thermal contact interface with the heat radiating part. In recent years, semiconductor elements in these electronic devices have increased in heat density and heat generation due to miniaturization and high performance, and are often installed in close proximity to heat-generating parts that are other semiconductor parts. , thermally conductive greases are required to have higher heat dissipation properties.

In general, the heat dissipation of thermally conductive grease applied to the thermal contact interface is inversely proportional to the interfacial thermal resistance value at the thermal contact interface between the heat generating component and the heat radiating component. By reducing the interfacial thermal resistance value at the thermal contact interface, the heat generated from the heat-generating component can be effectively conducted to the heat-dissipating component and radiated.

In order to reduce the interfacial thermal resistance value at such a thermal contact interface, it is effective to apply thermally conductive grease so as to shorten the distance between the heat generating component and the heat radiating component. However, it is not always easy to apply thermally conductive grease uniformly and thinly to heat-generating parts such as recent miniaturized electronic devices without voids.

In order to apply the thermally conductive grease evenly and thinly, for example, after applying the thermally conductive grease to the heat-generating part to a certain thickness, the applied thermally conductive grease is pressurized to spread the thermally conductive grease. A method of spreading thinly is mentioned. In order to spread the thermally conductive grease thinly, the thermally conductive grease is required to have high malleability.

In order to increase the malleability of the thermally conductive grease, for example, the content of the inorganic powder filler contained in the thermally conductive grease is decreased and the content of the base oil contained in the thermally conductive grease is increased. Therefore, a method of reducing the friction between the particles of the inorganic powder filler, which is a factor that hinders the malleability of the thermally conductive grease, can be considered. However, when the content of the inorganic powder filler contained in the thermally conductive grease becomes low, the thermal conductivity of the thermally conductive grease itself also decreases. Therefore, it has been difficult to impart malleability to the thermally conductive grease when the content of the inorganic powder filler is increased.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thermally conductive grease which is excellent in malleability even when the content of an inorganic powder filler is increased.

As a result of intensive studies to achieve the above object, the inventors of the present invention have found that a thermally conductive grease containing a base oil composition containing a plurality of inorganic powder fillers with different average particle diameters and containing predetermined additives. If there is, it discovers that the above-mentioned subject can be solved, and came to complete the present invention.

(1) A first aspect of the present invention is a thermally conductive grease containing an inorganic powder filler and a base oil composition, wherein the inorganic powder filler has an average particle size in the range of 10 μm or more and 100 μm or less. A certain first inorganic powder filler, a second inorganic powder filler having a different average particle size from the first inorganic powder filler, and the first inorganic powder filler and the second inorganic powder filler having an average particle size and a third inorganic powder filler having a different diameter, wherein the average particle size of the inorganic powder filler satisfies the following relational expressions (1) and (2), and the base oil composition comprises a base oil, A thermally conductive grease containing an amine-based additive, a phenol-based additive, and a thioether-based additive.
D2 _/ D1<0.70 ( ₁ )
D ₃ /D ₂ <0.60 (2)
[In the formula: D1 represents the average particle size of the _first inorganic powder filler, D2 represents the average particle size of the _second inorganic powder filler, and D3 represents the average particle size of the _third inorganic powder filler. show. ]

(2) In the second aspect of the present invention, in the first aspect, the average particle size of the second inorganic powder filler is in the range of 1 μm or more and 50 μm or less, and the average particle size of the third inorganic powder filler is 0. .1 μm or more and 5 μm or less of thermally conductive grease.

(3) The third aspect of the present invention is the first or second aspect, wherein the first inorganic powder filler is contained in a ratio of 40 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the inorganic powder filler. , the second inorganic powder filler in a proportion of 10 to 50 parts by mass, and the third inorganic powder filler in a proportion of 10 to 40 parts by mass. .

(4) The fourth aspect of the present invention is the heat according to any one of the first to third aspects, wherein the base oil contains a polyol ester and/or an aromatic ester. conductive grease.

(5) In the fifth aspect of the present invention, in any one of the first to fourth aspects, the content of the amine additive is 0.1 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the base oil. The content of the phenol additive is 0.1 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the base oil, and the content of the thioether additive is 0 parts by mass per 100 parts by mass of the base oil. .1 parts by mass or more and 5 parts by mass or less of thermally conductive grease.

(6) The sixth aspect of the present invention is any one of the first to fifth aspects, further comprising an inorganic layered compound, wherein the inorganic layered compound is bentonite, mica, kaolin, sepiolite, saponite, and hectorite. A thermally conductive grease containing at least one selected.

(7) In a seventh aspect of the present invention, in any one of the first to sixth aspects, the inorganic powder filler is selected from copper, aluminum, zinc oxide, magnesium oxide, aluminum oxide, aluminum nitride and silicon carbide. A thermally conductive grease containing at least one or more.

The thermally conductive grease of the present invention has excellent malleability even when the inorganic powder filler content is increased.

Specific embodiments of the present invention (hereinafter referred to as "present embodiments") will be described in detail below. It should be noted that the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the purpose of the present invention. Further, in this specification, the notation "~" means "more than" and "less than", and the notation "X: Y to A: B" means "X: Y" and "A: B" themselves. and means a range between "X:Y" and "A:B".

≪Thermal conductive grease≫
The thermally conductive grease according to this embodiment contains a base oil composition and an inorganic powder filler. The inorganic powder filler contains a plurality of inorganic powder fillers having different average particle diameters, and the ratio of the average particle diameters of the inorganic powder fillers is within a predetermined range. It is characterized by containing an oil, an amine-based additive, a phenol-based additive, and a thioether-based additive.

The inventor's studies have revealed the following. That is, by containing the first, second, and third inorganic powder fillers having a predetermined average particle size, it is possible to reduce the amount of base oil that enters the interstices between the particles of the inorganic powder filler. Therefore, even when the content of the inorganic powder filler contained in the thermally conductive grease is increased, the thermally conductive grease can be imparted with malleability.

Furthermore, by using a base oil composition containing an amine-based additive, a phenol-based additive, and a thioether-based additive, these additives are adsorbed on the surface of the inorganic powder filler, and the inorganic powder It becomes possible to effectively reduce the frictional resistance between particles of the filler. This makes it possible to maintain sufficient malleability even when the content of the inorganic powder filler contained in the thermally conductive grease is further increased.

The inorganic powder filler and the base oil composition contained in the thermally conductive grease are described below.

<1. Inorganic powder filler>
The inorganic powder filler imparts high thermal conductivity to the thermally conductive grease. The inorganic powder filler used in the thermally conductive grease according to the present embodiment has an average particle diameter of 10 μm or more and 100 μm or less, and the first inorganic powder filler has an average particle diameter of A different second inorganic powdery filler and a third inorganic powdery filler having an average particle size different from that of the first inorganic powdery filler and the second inorganic powdery filler are contained.

The average particle diameter of the inorganic powder filler satisfies the following relational expressions (1) and (2).
D2 _/ D1<0.70 ( ₁ )
D ₃ /D ₂ <0.60 (2)
[In the formula: D1 represents the average particle size of the _first inorganic powder filler, D2 represents the average particle size of the _second inorganic powder filler, and D3 represents the average particle size of the _third inorganic powder filler. show. ]

By including three inorganic powder fillers having a predetermined average particle size relationship, it is possible to reduce the amount of base oil that enters the interstices between the particles of the inorganic powder filler. Therefore, even when the content of the inorganic powder filler is increased, it is possible to spread the thermally conductive grease uniformly.

The average particle size of the second inorganic powder filler is not particularly limited as long as it satisfies the above relational expression, but is preferably in the range of 1 μm or more and 50 μm or less. It is possible to spread the thermally conductive grease more evenly with an increased content of inorganic powder filler.

The average particle size of the third inorganic powder filler is not particularly limited as long as it satisfies the above relational expression, but is preferably in the range of 0.1 μm or more and 5 μm or less. This allows the thermally conductive grease to spread more evenly with an increased content of inorganic powder filler.

The content of each of the first, second and third inorganic powder fillers is not particularly limited, but 40 parts by mass of the first inorganic powder filler is 80 parts by mass or less, the second inorganic powder filler is contained in a proportion of 10 parts by mass or more and 50 parts by mass or less, and the third inorganic powder filler is contained in a proportion of 10 parts by mass or more and 40 parts by mass or less. It is preferable to contain. When the content of each of the first, second and third inorganic powder fillers is in such a range, the thermal conductivity is maintained even if the content of the inorganic powder filler contained in the thermally conductive grease is increased. Malleability can be imparted to the grease.

The type of inorganic powder filler used in the thermally conductive grease according to the present embodiment is not particularly limited as long as it has a higher thermal conductivity than the base oil. (Alloys are also included.), powders such as silicon compounds are preferably used. In the present embodiment, one type of inorganic powder filler may be used, or two or more types may be used in combination.

Powders of non-conductive materials such as semiconductors and ceramics, such as zinc oxide, magnesium oxide, aluminum oxide, silicon oxide, aluminum nitride, boron nitride, silicon carbide, silica, and diamond, are suitable for electrical insulation. Powders of zinc oxide, magnesium oxide, aluminum oxide, silicon oxide, aluminum nitride, boron nitride, silicon carbide and silica are more preferred, and powders of zinc oxide, aluminum oxide and aluminum nitride are particularly preferred. If electrical insulation is not required and metal powder is used, it is preferable to use copper or aluminum powder. These inorganic powder fillers may be used alone or in combination of two or more.

The first, second and third inorganic powder fillers mean inorganic powder fillers having a predetermined average particle size. Further, for example, the first inorganic powder filler may be an inorganic powder filler made of one material as long as the average particle size is the same, or an inorganic powder filler made of two or more materials. good too. The same is true for the second and third inorganic powder fillers.

Moreover, the thermally conductive grease according to the present embodiment may contain inorganic powder fillers having different average particle sizes other than the first, second and third inorganic powder fillers. Among them, the content of the first, second and third inorganic powder fillers contained in the thermally conductive grease according to the present embodiment is 80 parts by mass or more with respect to 100 parts by mass of the inorganic powder filler. is preferably 90 parts by mass or more, more preferably 95 parts by mass or more, even more preferably 99 parts by mass or more, and 100 parts by mass (that is, the first , containing no inorganic powdery fillers having different average particle sizes other than the second and third inorganic powdery fillers).

In the thermally conductive grease according to this embodiment, the average particle diameter of the inorganic powder filler can be calculated as the volume average diameter of the particle size distribution measured by the laser diffraction scattering method (according to JIS R 1629:1997).

The thermally conductive grease according to the present embodiment contains three types of inorganic powder fillers having a predetermined average particle size relationship as described above, and includes an amine-based additive, a phenol-based additive, and a thioether-based additive. Since the base oil composition containing the agent is used, it has excellent spreadability even when the content of the inorganic powder filler is increased. The content of the inorganic powder filler is not particularly limited, and even if the content of the inorganic powder filler is low, the thermal conductive grease has excellent malleability. By containing the inorganic powder filler at a ratio of 50% by mass or more and 95% by mass or less based on the total amount of the powder, it is possible to achieve both high thermal conductivity and excellent malleability. The lower limit of the content of the inorganic powder filler is preferably 60% by mass or more, more preferably 70% by mass or more, and 80% by mass or more with respect to 100% by mass of the thermally conductive grease. is more preferred. The upper limit of the content of the inorganic powder filler is preferably 93% by mass or less.

<2. Base oil composition>
The base oil composition includes at least a base oil, an amine additive, a phenolic additive, and a thioether additive. By using such a base oil composition, the amine-based additive, phenol-based additive, and thioether-based additive are adsorbed on the surface of the inorganic powder filler to effectively reduce frictional resistance between particles. In this state, the base oil can enter the gaps between the particles of the inorganic powder filler, resulting in a thermally conductive grease with excellent malleability. Each component contained in the base oil composition will be described.

(1) Base oil As the base oil, various base oils can be used. For example, hydrocarbon base oils such as mineral oils and synthetic hydrocarbon oils, ester base oils, ether base oils, phosphate esters, silicon oils and fluorine oil. Among them, it is preferable to use one containing a polyol ester and an aromatic ester. By using a grease containing a polyol ester and an aromatic ester, a thermally conductive grease that is hard to harden, has a small evaporation loss, and is excellent in high-temperature stability can be obtained.

As the polyol ester, those conventionally used as base oils for high-temperature lubricating oils can be used. In particular, those in which the alcohol component constituting the polyol ester is dipentaerythritol, pentaerythritol, trimethylolpropane or neopentyl glycol are preferably used.

The acid component of the polyol ester is not particularly limited, but can be appropriately selected so that the viscosity of the lubricating oil is within the desired range. As the acid component, linear or branched saturated or unsaturated fatty acids having 7 to 10 carbon atoms can be used, and branched fatty acids are more preferably used. Specifically, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, 2-ethylpentanoic acid, 2,2-dimethylpentanoic acid, 2-ethyl-2-methylbutanoic acid, 2-methylheptanoic acid, 2-ethylhexane acid, 2-propylpentanoic acid, 2,2-dimethylhexanoic acid, 2-ethyl-2-methylheptanoic acid, 2-methyloctanoic acid, 2,2-dimethylheptanoic acid, 3,5,5-trimethylhexanoic acid , 2,2-dimethyloctanoic acid and the like. In particular, 3,5,5-trimethylhexanoic acid is preferred because of its excellent heat resistance.

For aromatic esters, the aromatic carboxylic acid components include phthalic acid, 4-t-butylphthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, trimesic acid, pyromellitic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid, Examples include aromatic carboxylic acids such as 4,4'-thiobisbenzoic acid, anhydrides thereof, aromatic carboxylic acids and lower alcohol esters having 1 to 4 carbon atoms such as methanol and ethanol. Among these aromatic carboxylic acid components, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, and pyromellitic acid are particularly recommended. It is also desirable to use trimellitic acid, trimesic acid, or pyromellitic acid, which provide esters of high viscosity and low evaporation loss, when used as chain lubricating oils under extremely high temperature conditions.

As the alcohol component constituting the aromatic ester, an aliphatic monohydric alcohol having a linear or branched alkyl group with 4 to 18 carbon atoms is preferred. Specifically, 3,5,5-trimethylhexanol, n-butyl alcohol, isobutyl alcohol, n-amyl alcohol, isoamyl alcohol, n-hexanol, isohexanol, n-heptanol, isoheptanol, n-octanol, iso Octanol, 2-ethylhexanol, n-nonanol, isononanol, n-decanol, isodecanol, n-undecanol, isoundecanol, n-dodecanol, isododecanol, n-tridecanol, isotridecanol, n-tetradecanol , isotetradecanol, n-pentadecanol, isopentadecanol, n-dexadecanol, isohexadecanol, n-octadecanol, isooctadecanol and the like. Also, in place of these alcohols, it is possible to use their lower alkyl esters such as acetic esters. Among these monohydric alcohols, it is particularly desirable to use 2-ethylhexanol and 3,5,5-trimethylhexanol.

Examples of aromatic esters include di(3,5,5-trimethylhexyl) phthalate, di(3,5,5-trimethylhexyl) isophthalate, and tri(3,5,5-trimethylhexyl) trimellitate. ) ester, trimesic acid tri(3,5,5-trimethylhexyl) ester, pyromellitic acid tetra(3,5,5-trimethylhexyl) ester, phthalic acid di(2-ethylhexyl) ester, isophthalic acid di(2- ethylhexyl) ester, trimellitic acid tri(2-ethylhexyl) ester, trimesic acid tri(2-ethylhexyl) ester, pyromellitic acid tetra(2-ethylhexyl) ester, among which especially trimellitic acid tri(3,5, 5-trimethylhexyl) ester and trimellitic acid tri(2-ethylhexyl) ester.

When using one containing a polyol ester and an aromatic ester, the content of the polyol ester is preferably 69 parts by mass or more and 85 parts by mass or less with respect to 100 parts by mass of the base oil composition. If the content of the polyol ester is less than 69 parts by mass, the high temperature stability is lowered and the amount of sludge is increased. If the polyol ester content is more than 85 parts by mass, desirable initial evaporation resistance cannot be obtained. Moreover, the content of the aromatic ester is preferably 5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the base oil composition. If the content of the aromatic ester is less than 5 parts by mass, the desired initial evaporation resistance cannot be obtained. When the content of the aromatic ester is more than 20 parts by mass, the high-temperature stability is lowered and the amount of sludge is increased.

(2) Amine-Based Additive The amine-based additive is included together with the phenol-based additive and the thioether-based additive to reduce frictional resistance between particles of the inorganic powder filler. This allows the base oil to enter the gaps between the particles of the inorganic powder filler while effectively reducing the frictional resistance between the particles, resulting in a thermally conductive grease with excellent malleability. Amine additives include diphenylamines, phenyl-α-naphthylamines and phenylenediamines. Specific examples of diphenylamines include diphenylamine, p,p'-dibutyldiphenylamine, p,p'-dipentyldiphenylamine, p,p'-dihexyldiphenylamine, p,p'-diheptyldiphenylamine, p,p' -dioctyldiphenylamine, p,p'-dinonyldiphenylamine, mixed alkyldiphenylamine having 4 to 9 carbon atoms, and the like. Specific examples of phenyl-α-naphthylamines include N-phenyl-α-naphthylamine, N-butylphenyl-α-naphthylamine, N-pentylphenyl-α-naphthylamine, N-hexylphenyl-α-naphthylamine, N-heptyl phenyl-α-naphthylamine, N-octylphenyl-α-naphthylamine, N-nonylphenyl-α-naphthylamine and the like. Specific examples of phenylenediamines include p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylenediamine, and N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine. Amine-based additives that also function as antioxidants such as

The content of the amine additive is preferably 0.1 parts by mass or more and 10 parts by mass or less, more preferably 4 parts by mass or more and 8 parts by mass or less, relative to 100 parts by mass of the base oil. If the content of the amine additive is less than 0.1 parts by mass, the effect of reducing the frictional resistance between particles of the inorganic powder filler cannot be sufficiently obtained, and if it exceeds 10 parts by mass, the amount of sludge increases. I don't like it because

(3) Phenolic additive The phenolic additive reduces the frictional resistance between particles of the inorganic powder filler by being included together with the amine additive and the thioether additive. This allows the base oil to enter the gaps between the particles of the inorganic powder filler while effectively reducing the frictional resistance between the particles, resulting in a thermally conductive grease with excellent malleability. Phenolic additives include n-hexyl 3-methyl-5-tert-butyl-4-hydroxyphenyl)acetate, isohexyl (3-methyl-5-tert-butyl-4-hydroxyphenyl)acetate, (3-methyl -5-tert-butyl-4-hydroxyphenyl) n-heptyl acetate, (3-methyl-5-tert-butyl-4-hydroxyphenyl) isoheptyl acetate, (3-methyl-5-tert-butyl-4-hydroxy phenyl) n-octyl acetate, (3-methyl-5-tert-butyl-4-hydroxyphenyl) isooctyl acetate, (3-methyl-5-tert-butyl-4-hydroxyphenyl) acetate 2-ethylhexyl, (3- methyl-5-tert-butyl-4-hydroxyphenyl) n-nonyl acetate, (3-methyl-5-tert-butyl-4-hydroxyphenyl) isononyl acetate, (3-methyl-5-tert-butyl-4- hydroxyphenyl) n-decyl acetate, (3-methyl-5-tert-butyl-4-hydroxyphenyl) isodecyl acetate, (3-methyl-5-tert-butyl-4-hydroxyphenyl) n-undecyl acetate, (3 -methyl-5-tert-butyl-4-hydroxyphenyl)isoundecyl acetate, (3-methyl-5-tert-butyl-4-hydroxyphenyl)n-dodecyl acetate, (3-methyl-5-tert-butyl-4 -hydroxyphenyl) isododecyl acetate, (3-methyl-5-tert-butyl-4-hydroxyphenyl) n-hexyl propionate, (3-methyl-5-tert-butyl-4-hydroxyphenyl) isohexyl propionate, ( 3-methyl-5-tert-butyl-4-hydroxyphenyl) n-heptyl propionate, (3-methyl-5-tert-butyl-4-hydroxyphenyl) isoheptyl propionate, (3-methyl-5-tert- n-octyl butyl-4-hydroxyphenyl)propionate, isooctyl (3-methyl-5-tert-butyl-4-hydroxyphenyl)propionate, (3-methyl-5-tert-butyl-4-hydroxyphenyl)propionate acid 2-ethylhexyl, (3-methyl-5-tert-butyl-4-hydroxyphenyl) n-nonyl propionate, (3-methyl-5-tert-butyl-4-hydroxyphenyl) isononyl propionate, (3- methyl-5-tert -butyl-4-hydroxyphenyl) n-decyl propionate, (3-methyl-5-tert-butyl-4-hydroxyphenyl) isodecyl propionate, (3-methyl-5-tert-butyl-4-hydroxyphenyl) n-undecyl propionate, (3-methyl-5-tert-butyl-4-hydroxyphenyl)isoundecylpropionate, (3-methyl-5-tert-butyl-4-hydroxyphenyl)n-dodecylpropionate, (3 -methyl-5-tert-butyl-4-hydroxyphenyl)isododecyl propionate, (3,5-di-tert-butyl-4-hydroxyphenyl)n-hexyl acetate, (3,5-di-tert-butyl- 4-hydroxyphenyl)isohexyl acetate, (3,5-di-tert-butyl-4-hydroxyphenyl)n-heptyl acetate, (3,5-di-tert-butyl-4-hydroxyphenyl)isoheptyl acetate, (3 ,5-di-tert-butyl-4-hydroxyphenyl)n-octyl acetate, (3,5-di-tert-butyl-4-hydroxyphenyl)isooctyl acetate, (3,5-di-tert-butyl-4 -hydroxyphenyl) 2-ethylhexyl acetate, (3,5-di-tert-butyl-4-hydroxyphenyl) n-nonyl acetate, (3,5-di-tert-butyl-4-hydroxyphenyl) isononyl acetate, ( 3,5-di-tert-butyl-4-hydroxyphenyl) n-decyl acetate, (3,5-di-tert-butyl-4-hydroxyphenyl) isodecyl acetate, (3,5-di-tert-butyl- 4-hydroxyphenyl)n-undecyl acetate, (3,5-di-tert-butyl-4-hydroxyphenyl)isoundecyl acetate, (3,5-di-tert-butyl-4-hydroxyphenyl)n-dodecyl acetate, (3,5-di-tert-butyl-4-hydroxyphenyl) isododecyl acetate, (3,5-di-tert-butyl-4-hydroxyphenyl) n-hexyl propionate, (3,5-di-tert- Isohexyl butyl-4-hydroxyphenyl)propionate, n-heptyl (3,5-di-tert-butyl-4-hydroxyphenyl)propionate, (3,5-di-tert-butyl-4-hydroxyphenyl)propionate isoheptyl acid, (3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid n -octyl, (3,5-di-tert-butyl-4-hydroxyphenyl) isooctyl propionate, (3,5-di-tert-butyl-4-hydroxyphenyl) 2-ethylhexyl propionate, (3,5- Di-tert-butyl-4-hydroxyphenyl) n-nonyl propionate, (3,5-di-tert-butyl-4-hydroxyphenyl) isononyl propionate, (3,5-di-tert-butyl-4- hydroxyphenyl)n-decyl propionate, isodecyl (3,5-di-tert-butyl-4-hydroxyphenyl)propionate, n-undecyl (3,5-di-tert-butyl-4-hydroxyphenyl)propionate , (3,5-di-tert-butyl-4-hydroxyphenyl)isoundecylpropionate, (3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-dodecyl, (3,5-di- isodecyl tert-butyl-4-hydroxyphenyl)propionate, bis(3,5-di-tert-butyl-4-hydroxyphenyl), bis(3,5-di-tert-butyl-4-hydroxyphenyl)methane, 1,1-bis(3,5-di-tert-butyl-4-hydroxyphenyl)ethane, 1,2-bis(3,5-di-tert-butyl-4-hydroxyphenyl)ethane, 1,1- Bis(3,5-di-tert-butyl-4-hydroxyphenyl)propane, 1,2-bis(3,5-di-tert-butyl-4-hydroxyphenyl)propane, 1,3-bis(3, Phenolic additives that also function as antioxidants such as 5-di-tert-butyl-4-hydroxyphenyl)propane and 2,2-bis(3,5-di-tert-butyl-4-hydroxyphenyl)propane can be mentioned. Among these, n-heptyl 3,5-di-tert-butyl-4-hydroxyphenyl)propionate and n-nonyl (3,5-di-tert-butyl-4-hydroxyphenyl)propionate are particularly preferred.

The content of the phenolic additive is preferably 0.1 parts by mass or more and 5 parts by mass or less, more preferably 1 part by mass or more and 4 parts by mass or less, relative to 100 parts by mass of the base oil. If the content of the phenolic additive is less than 0.1 parts by mass, the effect of reducing the frictional resistance between particles of the inorganic powder filler cannot be sufficiently obtained, and if it exceeds 5 parts by mass, the amount of sludge increases. I don't like it because

(4) Thioether Additive A thioether additive is included together with an amine additive and a phenol additive to effectively reduce the frictional resistance between particles of the inorganic powder filler. This allows the base oil to enter the gaps between the particles of the inorganic powder filler while effectively reducing the frictional resistance between the particles, resulting in a thermally conductive grease with excellent malleability. Thioether additives include dilauryl 3,3-thiodipropionate, dimyristyl 3,3-thiodipropionate, distearyl 3,3-thiodipropionate, pentaerythrityl tetrakis(3-laurieuthiopropionate ), ditridecyl 3,3′-thiodipropionate, bis(2-methyl-4-(3-n-alkylthiopropionyloxy)-5-t-butylphenyl)sulfide thioether-based additions that also function as antioxidants agents. Among these, bis(2-methyl-4-(3-n-alkylthiopropionyloxy)-5-t-butylphenyl)sulfide is preferred, and its alkyl group is preferably C12 or C14.

The content of the thioether additive is preferably 0.1 parts by mass or more and 5 parts by mass or less, more preferably 0.5 parts by mass or more and 3 parts by mass or less, relative to 100 parts by mass of the base oil. If the content of the thioether-based additive is less than 0.1 parts by mass, the effect of reducing the frictional resistance between particles of the inorganic powder filler cannot be sufficiently obtained, and if it exceeds 5 parts by mass, the amount of sludge increases. I don't like it because

(5) Inorganic layered compound The thermally conductive grease may further contain an inorganic layered compound. Inorganic layered compounds are compounds in the form of platelets or platelets, which are mainly layered clay minerals. The inorganic stratiform compound increases the consistency of the thermally conductive grease and improves the spreadability of the thermally conductive grease.

Specific examples of inorganic layered compounds include layered clay minerals such as bentonite, mica, kaolin, sepiolite, saponite, and hectorite. Among these, it is particularly preferable to use bentonite. In particular, bentonite can act as a thickener that improves the consistency of the thermally conductive grease, thereby improving the applicability of the thermally conductive grease and further improving the thermal conductivity.

Further, since the layered inorganic compound is mixed and dispersed in the base oil, it is preferable that the surface thereof is organically treated. Compounds for organic modification include, for example, amine salts such as stearic acid and oleic acid.

Although the content of the inorganic stratiform compound is not particularly limited, it is preferably 1 part by mass or more and 20 parts by mass or less per 100 parts by mass of the base oil. When the content of the inorganic layered compound is 1 part by mass or more, the thermal conductivity can be increased, and the consistency can be appropriately adjusted, thereby improving the coatability.

Also, the content of the inorganic layered compound is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, relative to 100 parts by mass of the base oil. Also, the content of the inorganic layered compound is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, relative to 100 parts by mass of the base oil.

(6) Other additives One or more selected from dispersants, antifoaming agents, rust inhibitors, corrosion inhibitors, thickeners/thickeners, and extreme pressure agents in order to enhance various properties of thermally conductive grease. can be further contained.

Dispersants include compounds such as acid hydrocarbon polymers and higher fatty acid esters.

Rust inhibitors include compounds such as sulfonates, carboxylic acids, and carboxylates.

Corrosion inhibitors include compounds such as benzotriazole and its derivatives, and thiadiazole compounds.

Examples of thickeners and thickeners include compounds such as polybutene, polymethacrylate, fatty acid salts, urea compounds, petroleum wax and polyethylene wax.

Examples of extreme pressure agents include compounds such as phosphorus-based extreme pressure agents and boron-containing extreme pressure agents.

The content of these additives can be about the same as the content used in ordinary thermally conductive greases, as long as the properties of the present invention are not impaired.

≪Method for producing thermally conductive grease≫
Regarding the production of the thermally conductive grease according to the present embodiment, the method is not particularly limited as long as the components can be uniformly mixed. As a general manufacturing method, there is a method of performing kneading with a planetary mixer, a rotation-revolution mixer, or the like, and then uniformly kneading with a triple roll.

EXAMPLES The present invention will be further described below based on examples and comparative examples of the present invention, but the present invention is not limited by the following examples.

1. Production of Thermally Conductive Composition Using the materials shown in (A) to (E) below, a thermally conductive composition having the composition shown in Table 1 below was produced.

[Structure and manufacturing method of thermally conductive composition]
(Structural component)
(A) Inorganic powder filler (A)-1: First inorganic powder filler Alumina 1: Average particle size = 40 μm
Alumina 2: average particle size = 30 μm
Alumina 3: average particle size = 50 μm
Alumina 4: average particle size = 70 μm
Alumina 5: average particle size = 110 μm
Alumina 6: average particle size = 5 µm

(A)-2: Second inorganic powder filler alumina 7: average particle size = 8 μm
Alumina 8: average particle size = 15 µm
Alumina 9: average particle size = 20 µm
Alumina 10: average particle size = 30 µm
Alumina 11: average particle size = 3.4 µm
Zinc oxide 1: average particle size = 10 μm

(A)-3: third inorganic powder filler alumina 12: average particle size = 0.53 μm
Alumina 13: average particle size = 0.83 µm
Alumina 14: average particle size = 0.18 µm
Alumina 15: average particle size = 5 μm
Zinc oxide 2: average particle size = 0.60 µm

The average particle size of each inorganic powder filler was measured by a laser diffraction scattering method using a particle size distribution analyzer (SALD-7000 manufactured by Shimadzu Corporation).

(B) Base oil (B)-1: dipentaerythritol isononanoic acid ester
(B)-2: trimellitic acid tri(2-ethylhexyl) ester
(B)-3: trimellitic acid tri(3,5,5-trimethylhexyl) ester

(C) Amine additive (C)-1: p,p'-dioctyldiphenylamine (C)-2: N-octylphenyl-α-naphthylamine

(D) Phenyl additive (D)-1: (3,5-di-tert-butyl-4-hydroxyphenyl) n-nonyl propionate (D)-2: (3,5-di-tert-butyl n-heptyl-4-hydroxyphenyl)propionate

(E) Thioether additive (E)-1: bis(2-methyl-4-(3-n-alkylthiopropionyloxy)-5-t-butylphenyl)sulfide

(F) Inorganic layered compound (F)-1: organically treated bentonite (F)-2: organically treated sepiolite

(G) Other Additives (G)-1: Extreme Pressure Agent: Phosphorus Additive (G)-2: Dispersant: Acid Hydrocarbon Polymer (G)-3: Dispersant: Higher Fatty Acid Ester

First, (B) base oil was added with (C) amine-based additive, (D) phenyl-based additive, (E) thioether-based additive, and (G) extreme pressure Additives were added and mixed in a mortar to prepare additive-containing base oils (listed as containing oils 1 to 18 in the table).

Preparation of Thermally Conductive Grease Next, after dissolving (F) a layered inorganic compound and (G) a dispersant in contained oils 1 to 18 so that the content ratios shown in Tables 2 and 3 are obtained, ( A) The thermally conductive greases of Examples and Comparative Examples were prepared by agitating with an inorganic powder filler in a rotation-revolution mixer. In Tables 2 and 3, the numerical value of the content of each inorganic powder filler in the "content of each component in the thermal conductive grease (% by mass)" is the "total content in the grease (% by mass) )” and the value of “content of each component in the inorganic powder filler (% by mass)” and displayed to one decimal place.

[evaluation]
The thermally conductive greases of Examples and Comparative Examples were evaluated for greasability, thermal conductivity, malleability, fluidity, and drip resistance according to the following procedures.

(Possibility of greasing)
The propriety of greasing was determined by visually confirming the samples produced as described above and judging whether or not they were in the form of grease. A case where it could be made into grease was rated as "acceptable", and a case where it could not be made into grease was rated as "impossible". Evaluation results are shown in Tables 4 and 5.
The following evaluation was not performed on samples that could not be made into grease.

(Thermal conductivity)
The thermal conductivity of the prepared thermally conductive grease was measured at room temperature using a transient thermal measurement device (according to ASTM D5470). Tables 4 and 5 show the measurement results.

(malleability)
A size of φ6 mm was applied to a thickness of 500 μm on a slide glass substrate, and the applied thermally conductive grease was covered with a slide glass and pressurized at a pressure of 0.1 MPa. After pressurization, the area was calculated from the diameter of the deformed thermally conductive grease, and the thickness of the thermally conductive grease was calculated. Tables 4 and 5 show the calculation results.

(Liquidity)
The prepared thermally conductive grease was applied on a glass substrate with an applicator to a thickness of 100 μm. It is checked whether printing is possible without problems during application, and if the specified shape can be printed without fading, it is judged to have fluidity, and it is judged to be "O". It was judged to be sufficient and was set to "x" (initial evaluation).

Next, the thermally conductive grease-coated glass substrate was vertically placed in an electric furnace heated to 250° C. and held for 4 hours. After that, it was taken out and cooled, and then the thermally conductive grease was stirred with a spatula to determine the presence or absence of fluidity. A case where a grease-like state was maintained and could be stirred was judged to have flowability and was judged to be "O", and a case where it was solidified and could not be stirred was judged to have no fluidity and was judged to be "X". The evaluation results are shown in Tables 4 and 5.

(Drip resistance)
The prepared thermally conductive grease was applied on a glass substrate with an applicator to a thickness of 100 μm. Next, the thermally conductive grease-coated glass substrate was vertically placed in an electric furnace heated to 250° C., and the presence or absence of dripping was checked in that state (initial evaluation).

Then, after being kept in the electric furnace for 4 hours, it was taken out and cooled. When the thermally conductive grease remained in its original position and did not drip, it was evaluated as "◯", and when the thermally conductive grease was dripping down, it was evaluated as "X". The evaluation results are shown in Tables 4 and 5.

As can be seen from the results in Tables 4 and 5, the thermally conductive greases of Examples 1 to 36 within the scope of the present invention have a high thermal conductivity of 4.8 W/(m/K) or more. , the malleability is easily thinned to 92 μm or less, and the drip resistance is good while maintaining sufficient fluidity even after high temperature storage at 250° C. for 4 hours.

On the other hand, in the configuration of the present invention, Comparative Example 1 in which the particle size ratio D ₂ /D ₁ of the inorganic powder filler is 0.70 or more and the particle size ratio D ₃ /D ₂ of the inorganic powder filler is 0.70. In Comparative Example 2 in which the average particle diameter of the first inorganic powder filler having the largest particle diameter is 60 or more and in Comparative Example 3 in which the average particle diameter of the first inorganic powder filler exceeds 100 μm, the liquid component does not spread between the particles, and the malleability of the thermally conductive grease is reduced. However, the heat conductive grease does not exhibit the effects of the present invention.

In addition, Comparative Example 4 containing no amine additive, Comparative Example 5 containing no amine additive and thioether additive, Comparative Example 6 containing no amine additive and phenol additive, and phenol additive In Comparative Example 7, which does not contain a thioether-based additive, the frictional resistance between particles of the inorganic powder filler cannot be reduced, and the malleability of the thermally conductive grease is reduced. It is not conductive grease.

Moreover, these Comparative Examples 4 to 7 lost fluidity after high temperature storage and did not have sufficient heat resistance.

Claims (7)

A thermally conductive grease comprising an inorganic powder filler and a base oil composition,
The inorganic powder filler includes a first inorganic powder filler having an average particle size in the range of 10 μm or more and 100 μm or less, a second inorganic powder filler having an average particle size different from that of the first inorganic powder filler, and the a third inorganic powder filler having an average particle size different from that of the first inorganic powder filler and the second inorganic powder filler;
The average particle diameter of the inorganic powder filler satisfies the following relational expressions (1) and (2),
The base oil composition comprises a base oil, an amine additive, a phenolic additive, and a thioether additive,
Thermally conductive grease.
D2 _/ D1<0.70 ( ₁ )
D ₃ /D ₂ <0.60 (2)
[In the formula: D1 represents the average particle size of the _first inorganic powder filler, D2 represents the average particle size of the _second inorganic powder filler, and D3 represents the average particle size of the _third inorganic powder filler. show. ] The average particle size of the second inorganic powder filler is in the range of 1 μm or more and 50 μm or less,
The thermally conductive grease according to claim 1, wherein the average particle size of the third inorganic powder filler is in the range of 0.1 µm or more and 5 µm or less. For 100 parts by mass of the inorganic powder filler,
Containing the first inorganic powder filler at a ratio of 40 parts by mass or more and 80 parts by mass or less,
Containing the second inorganic powder filler at a ratio of 10 parts by mass or more and 50 parts by mass or less,
The thermally conductive grease according to claim 1 or 2, containing the third inorganic powder filler in a proportion of 10 parts by mass or more and 40 parts by mass or less. The thermally conductive grease according to any one of claims 1 to 3, wherein the base oil contains polyol ester and/or aromatic ester. The base oil composition, with respect to 100 parts by mass of the base oil,
Containing the amine-based additive at a ratio of 0.1 parts by mass or more and 10 parts by mass or less,
Containing the phenolic additive at a ratio of 0.1 parts by mass or more and 5 parts by mass or less,
The thermal conductive grease according to any one of claims 1 to 4, containing the thioether-based additive in a proportion of 0.1 parts by mass or more and 5 parts by mass or less. Further containing an inorganic layered compound,
The thermally conductive grease according to any one of claims 1 to 5, wherein the inorganic stratiform compound contains at least one selected from bentonite, mica, kaolin, sepiolite, saponite, and hectorite. The thermal conductive grease according to any one of claims 1 to 6, wherein the inorganic powder filler contains at least one selected from copper, aluminum, zinc oxide, magnesium oxide, aluminum oxide, aluminum nitride and silicon carbide. .