Thermally conductive grease composition

Abstract

A thermally conductive grease composition containing a base oil (A), thermally conductive particles (B), and one or more compounds (C) selected from the group consisting of phosphite esters and phosphite ester salts.

Description

Thermally conductive grease composition

[0001] This invention relates to a thermally conductive grease composition. This application claims priority under Japanese Patent Application No. 2024-185264, filed in Japan on October 21, 2024, the contents of which are incorporated herein by reference.

[0002] In electronic devices such as computers, automotive parts, and mobile phones, cooling components such as heat sinks are commonly used to dissipate heat generated from heat-generating elements such as semiconductor elements and mechanical parts, and thermally conductive grease is used to improve the heat transfer efficiency to the cooling components.

[0003] For example, Patent Document 1 discloses a thermal conductive grease for transferring heat from a heating element to a cooling component, comprising a base oil consisting of at least one selected from a copolymer of an unsaturated dialkyl dicarboxylic acid ester and an α-olefin, and a poly-α-olefin, a dispersant consisting of a phosphate-based anionic surfactant, and a thermal conductive filler. This thermal conductive grease is disclosed to have the characteristic of having a lower viscosity than conventional greases when the type and amount of thermal conductive filler are the same, i.e., it has excellent thermal conductivity.

[0004] International Publication No. 2021 / 186875

[0005] Generally, the heat dissipation characteristics of a thermally conductive grease composition improve with decreasing viscosity, provided that the type and content of the thermally conductive filler are the same. This is because lower viscosity greases tend to be thinner when pressed under the same load, thus reducing thermal resistance. With the recent miniaturization and increased performance of electronic devices, there is a demand for thermally conductive grease compositions with even lower viscosity than conventional thermally conductive grease compositions, such as those described in Patent Document 1.

[0006] The present invention has been made in view of the above circumstances, and aims to provide a low-viscosity thermally conductive grease composition.

[0007] In order to solve the above problems, the present invention adopts the following configuration. [1] A thermally conductive grease composition containing a base oil (A), thermally conductive particles (B), and one or more compounds (C) selected from the group consisting of phosphites and salts of phosphites. [2] The thermally conductive grease composition according to [1], wherein the phosphite is a compound represented by the following general formula (C-1).

[0008] [In the formula, Rc １ and Rc ２ are each independently a hydrogen atom or an aliphatic hydrocarbon group having 16 or more carbon atoms. However, Rc １ and Rc ２ will not both be hydrogen atoms. ]

[0009] According to the present invention, a thermally conductive grease composition having a low viscosity can be provided.[[ID= sixteen]]

[0010] (Thermally conductive grease composition) The thermally conductive grease composition of the present embodiment contains a base oil (A), thermally conductive particles (B), and one or more compounds (C) selected from the group consisting of phosphites and salts of phosphites.

[0011] A thermally conductive grease is a grease used to coat between a heat generating body and a cooling part and fill the gap to increase the thermal conductivity.

[0012] <Base oil (A)> The thermally conductive grease composition of the present embodiment contains a base oil (A). The kinematic viscosity of the base oil (A) at 40°C is preferably 10 mm ２ / s or more, more preferably 20 mm ２ / s or more, and even more preferably 40 mm ２ / s or more. The kinematic viscosity of the base oil (A) at 40°C is preferably 700 mm ２ / s or less, more preferably 650 mm ２ / s or less, and even more preferably 450 mm ２ / s or less.

[0013] If the kinematic viscosity of the base oil (A) of the thermal conductive grease composition of this embodiment is within the above preferred range at 40°C, the base oil (A) and the thermal conductive particles will be less likely to separate.

[0014] For example, the kinematic viscosity of base oil (A) at 40°C is 10 mm². ２ / s or more 700mm ２ Preferably less than / s, and 20 mm ２ / s or more 650mm ２ / s or less is more preferable, and 40 mm ２ / s or more 450mm ２ A value of / s or less is even more preferable.

[0015] The kinematic viscosity of base oil (A) at 100°C is 2 mm ２ Preferably 5 mm / s or more. ２ / s or more is more preferable, 7 mm ２ A value of 1 / s or higher is even more preferable. The kinematic viscosity of base oil (A) at 100°C is 70 mm². ２ Preferably less than / s, and 65 mm ２ / s or less is more preferable, and 60 mm ２ A value of / s or less is even more preferable.

[0016] If the kinematic viscosity of the base oil (A) of the thermal conductive grease composition of this embodiment is within the above preferred range at 100°C, the base oil (A) and the thermal conductive particles will be less likely to separate.

[0017] For example, the kinematic viscosity of base oil (A) at 100°C is 2 mm ２ / s or more 70mm ２ Preferably less than / s, and 5 mm ２ / s or more 65mm ２ / s or less is more preferable, and 7 mm ２ / s or more 60mm ２ A value of / s or less is even more preferable.

[0018] In this specification, the kinematic viscosity at 40°C and 100°C refers to the kinematic viscosity at 40°C measured in accordance with JIS K2283:2000.

[0019] Examples of the base oil (A) in the thermally conductive grease composition of this embodiment include synthetic oils and mineral oils.

[0020] <<Synthetic Oil>> As synthetic oils, for example, polyolefins such as poly-α-olefins, ester base oils such as diesters and polyol esters, polyalkylene glycols, alkylbenzenes, alkylnaphthalenes, ether base oils, silicone oils, and fluorine oils can be mentioned. Among these synthetic oils, from the viewpoints of availability, cost, viscosity characteristics, and oxidation stability, polyolefins are preferable, and poly-α-olefins (PAO) are more preferable. As the base oil (A) of the heat-conductive grease composition of the present embodiment, one kind of synthetic oil may be used alone, or a plurality of synthetic oils may be mixed and used.

[0021] <<Mineral Oil>> As the mineral oil, the distillate oil obtained by atmospheric distillation of crude oil can be used. Further, the distillate oil obtained by subjecting this distillate oil to vacuum distillation and purified by various purification processes can also be used as the lubricating oil fraction. As the purification processes, hydrorefining, solvent extraction, solvent dewaxing, hydrodewaxing, sulfuric acid washing, and clay treatment can be appropriately combined. By treating these purification processes in an appropriate order in combination, mineral oil can be obtained. Further, a mixture of a plurality of refined oils having different properties obtained by subjecting different crude oils or distillate oils to different combinations of purification processes may be used.

[0022] As the mineral oil, group I base oil (hereinafter referred to as "API group I base oil"), group II base oil (hereinafter referred to as "API group II base oil"), or group III base oil (hereinafter referred to as "API group III base oil") of the API base oil classification, or a mixed base oil thereof can be used. The API group I base oil is a mineral oil-based base oil having a sulfur content of more than 0.03% by mass and / or a saturation content of less than 90% by mass and a viscosity index of 80 or more and less than 120. The API group II base oil is a mineral oil-based base oil having a sulfur content of 0.03% by mass or less, a saturation content of 90% by mass or more, and a viscosity index of 80 or more and less than 120. The API group III base oil is a mineral oil-based base oil having a sulfur content of 0.03% by mass or less, a saturation content of 90% by mass or more, and a viscosity index of 120 or more.

[0023] As the base oil (A) of the heat-conductive grease composition of the present embodiment, a mineral oil may be used alone, or a plurality of mineral oils may be mixed and used. In the mixed mineral oil containing a plurality of mineral oils, their API classifications may be the same or different from each other.

[0024] As the base oil (A) of the heat-conductive grease composition of the present embodiment, either a mineral oil or a synthetic oil may be used, or a mineral oil and a synthetic oil may be mixed and used. As the base oil (A) of the heat-conductive grease composition of the present embodiment, it is preferable to contain a synthetic oil, and more preferably to contain poly-α-olefin.

[0025] The content of the base oil (A) of the heat-conductive grease composition of the present embodiment is preferably 3% by mass or more, more preferably 3.5% by mass or more, and still more preferably 4% by mass or more with respect to the total amount of the heat-conductive grease composition. The content of the base oil (A) of the heat-conductive grease composition of the present embodiment is preferably 21% by mass or less, more preferably 19% by mass or less, and still more preferably 17% by mass or less with respect to the total amount of the heat-conductive grease composition. For example, the content of the base oil (A) of the heat-conductive grease composition of the present embodiment is preferably 3% by mass or more and 21% by mass or less, more preferably 3.5% by mass or more and 19% by mass or less, and still more preferably 4% by mass or more and 17% by mass or less with respect to the total amount of the heat-conductive grease composition.

[0026] <Heat-conductive particles (B)> The heat-conductive grease composition of the present embodiment contains heat-conductive particles (B). Examples of the heat-conductive particles (B) include metals, metal oxides, metal nitrides, metal hydroxides, metal carbides, graphite, carbon fibers, and the like.

[0027] Examples of metals include aluminum, silver, copper, and nickel. Examples of metal oxides include aluminum oxide, magnesium oxide, and zinc oxide. Examples of metal nitrides include boron nitride and aluminum nitride. Examples of metal hydroxides include aluminum hydroxide. Examples of metal carbides include silicon carbide. Examples of carbon fibers include pitch-based carbon fibers, PAN-based carbon fibers, carbonized resin fibers, and graphitized resin fibers.

[0028] Among the above, metal nitrides are preferred as the thermally conductive particles (B), and aluminum nitride is more preferred.

[0029] The average particle diameter D50 of the thermally conductive particles (B) is preferably 0.1 μm or more, more preferably 0.3 μm or more, and even more preferably 0.5 μm or more. The average particle diameter D50 of the thermally conductive particles (B) is preferably 150 μm or less, more preferably 130 μm or less, and even more preferably 120 μm or less. For example, the average particle diameter D50 of the thermally conductive particles (B) is preferably 0.1 μm or more and 150 μm or less, more preferably 0.3 μm or more and 130 μm or less, and even more preferably 0.5 μm or more and 120 μm or less.

[0030] In this specification, the average particle diameter D50 is the particle diameter at which the cumulative volume proportion from the smallest particle side becomes 50% in the volume-based cumulative particle diameter distribution curve obtained by laser diffraction / scattering particle diameter distribution measurement. The average particle diameter D50 of thermally conductive particles (B) can be measured using a commercially available laser diffraction / scattering particle diameter distribution analyzer.

[0031] The thermal conductive grease composition of this embodiment preferably contains two or more thermal conductive particles (B) with different average particle diameters D50, and more preferably contains thermal conductive particles (B1) with an average particle diameter D50 of less than 30 μm and thermal conductive particles (B2) with an average particle diameter D50 of 30 μm or more.

[0032] The average particle diameter D50 of the thermal conductive particles (B1) is less than 30 μm, preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less. The average particle diameter D50 of the thermal conductive particles (B1) is preferably 0.1 μm or more, more preferably 0.3 μm or more, and even more preferably 0.5 μm or more. For example, the average particle diameter D50 of the thermal conductive particles (B1) is preferably 0.1 μm or more and less than 30 μm, more preferably 0.1 μm or more and 20 μm or less, even more preferably 0.3 μm or more and 15 μm or less, and particularly preferably 0.5 μm or more and 10 μm or less. The thermal conductive grease composition of this embodiment preferably contains two or more types of thermal conductive particles (B1).

[0033] The average particle diameter D50 of the thermally conductive particles (B2) is preferably 30 μm or more and 150 μm or less, more preferably 30 μm or more and 130 μm or less, and even more preferably 30 μm or more and 120 μm or less.

[0034] The thermal conductive particles (B) may be used alone or in a mixture of multiple types. The content of thermal conductive particles (B) in the thermal conductive grease composition of this embodiment is preferably 79% by mass or more, more preferably 81% by mass or more, and even more preferably 83% by mass or more, based on the total amount of the thermal conductive grease composition. The content of thermal conductive particles (B) in the thermal conductive grease composition of this embodiment is preferably 97% by mass or less, more preferably 96.5% by mass or less, and even more preferably 96% by mass or less, based on the total amount of the thermal conductive grease composition. For example, the content of thermal conductive particles (B) in the thermal conductive grease composition of this embodiment is preferably 79% by mass or more and 97% by mass or less, more preferably 81% by mass or more and 96.5% by mass or less, and even more preferably 83% by mass or more and 96% by mass or less, based on the total amount of the thermal conductive grease composition.

[0035] <Phosphite ester or salt thereof (C)> The thermal conductive grease composition of this embodiment contains one or more compounds (C) selected from the group consisting of phosphite esters and salts of phosphite esters. Examples of phosphite esters include dibutyl hydrogen phosphite, di(nonylphenyl) hydrogen phosphite, monolauryl hydrogen phosphite, dilauryl hydrogen phosphite, monomyristyl hydrogen phosphite, dimyristyl hydrogen phosphite, monopalmytyl hydrogen phosphite, dipalmytyl hydrogen phosphite, monostearyl hydrogen phosphite, distearyl hydrogen phosphite, monooleyl hydrogen phosphite, dioleyl hydrogen phosphite, ditetracosyl hydrogen phosphite, and the like.

[0036] Examples of phosphite ester salts include alkali metal salts of phosphite esters and amine salts of phosphite esters.

[0037] Examples of alkali metals used as raw materials for alkali metal salts of phosphite esters include sodium and potassium.

[0038] Examples of amines used as raw materials for amine salts of phosphite esters include monoamines, polyamines, and alkanolamines.

[0039] Examples of monoamines include primary, secondary, and tertiary monoamines. Specific examples of primary amines include ethylamine, n-propylamine, butylamine, 1-ethylbutylamine, 1,3-diaminopropane, and cyclohexylamine. Specific examples of secondary amines include diethylamine, di-n-propylamine, di-n-butylamine, 4,4'-diaminodiphenylamine, diethylenetriamine, tetraethylenepentamine, and N-(2-aminoethyl)ethanolamine. Specific examples of tertiary amines include dimethylethylamine, diethylmethylamine, triethylamine, and tributylamine.

[0040] Examples of alkanolamines include monoethanolamine, diethanolamine, triethanolamine, diethylethanolamine, and propanolamine.

[0041] Specifically, examples of polyamines include alkylene polyamines such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, propylenediamine, dipropylenetriamine, tripylenetetramine, tetrapropylenepentamine, pentapropylenehexamine, butylenediamine, dibutylentriamine, tripbutylenetetramine, tetrabutylenepentamine, and pentabutylenehexamine; N-alkylethylenediamines such as N-methylethylenediamine, N-ethylethylenediamine, and N-propylethylenediamine; N-alkenylethylenediamines such as N-vinylethylenediamine, N-propenylethylenediamine, and N-butenylethylenediamine; and N-alkyl or N-alkenylalkylene polyamines such as N-alkyldiethylenetriamine, N-alkenyldiethylenetriamine, and N-alkyltriethylenetetramine. In addition, the above polyamines also include polyamines derived from fats and oils (such as beef tallow polyamines).

[0042] The one or more compounds (C) selected from the group consisting of phosphite esters and salts of phosphite esters preferably include one or more compounds selected from the group consisting of compounds represented by the following general formula (C-1) and salts of compounds represented by the following general formula (C-1).

[0043] [In the formula, Rc １ and Rc ２ Each of these is independently a hydrogen atom or an aliphatic hydrocarbon group having 16 or more carbon atoms. However, Rc １ and Rc ２ None of these can become hydrogen atoms.

[0044] In the above general formula (C-1), Rc １ and Rc ２The aliphatic hydrocarbon group having 16 or more carbon atoms is preferably an aliphatic hydrocarbon group having 16 to 40 carbon atoms, more preferably an aliphatic hydrocarbon group having 16 to 30 carbon atoms, and even more preferably an aliphatic hydrocarbon group having 16 to 25 carbon atoms.

[0045] In the above general formula (C-1), Rc １ and Rc ２ The aliphatic hydrocarbon group having 16 or more carbon atoms in this compound may be linear or branched, and may be saturated or unsaturated aliphatic hydrocarbon.

[0046] In the above general formula (C-1), Rc １ and Rc ２ Examples of aliphatic hydrocarbon groups in this context include alkyl groups, alkenyl groups, alkadienyl groups, and alkatrineyl groups.

[0047] Examples of alkyl groups having 16 or more carbon atoms include palmityl group (hexadecyl group), stearyl group (octadecyl group), nonadecyl group, eicosyl group, and henicosyl group. Examples of alkenyl groups having 16 or more carbon atoms include hexadecenyl group, octadecenyl group, nonadecenyl group, eicocenyl group, and henicosenyl group. The position of the double bond is arbitrary; for example, an oleyl group (9-octadecenyl group) is one example.

[0048] Examples of salts of the compound represented by the general formula (C-1) include alkali metal salts of the compound represented by the general formula (C-1), amine salts of the compound represented by the general formula (C-1), etc. Specifically, Rc of the compound represented by the general formula (C-1) １ and Rc ２ Compounds in which the Rc is an alkali metal or compound represented by the general formula (C-1) １ and Rc ２ This compound is a group obtained by removing one hydrogen atom from the amine mentioned above.

[0049] The phosphite ester or its salt (C) may be used alone or in a mixture of several types. The content of the phosphite ester or its salt (C) in the thermal conductive grease composition of this embodiment is preferably 0.1% by mass or more, more preferably 0.15% by mass or more, and even more preferably 0.2% by mass or more, based on the total amount of the thermal conductive grease composition. The content of the phosphite ester or its salt (C) in the thermal conductive grease composition of this embodiment is preferably 10% by mass or less, more preferably 9% by mass or less, and even more preferably 8% by mass or less, based on the total amount of the thermal conductive grease composition. For example, the content of the phosphite ester or its salt (C) in the thermal conductive grease composition of this embodiment is preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.15% by mass or more and 9% by mass or less, and even more preferably 0.2% by mass or more and 8% by mass or less, based on the total amount of the thermal conductive grease composition.

[0050] <Optional Components> The thermal conductive grease composition of this embodiment may contain optional components other than the base oil (A), thermal conductive particles (B), and phosphite ester or its salt (C) described above. Examples of such optional components include thickeners, anti-wear agents, antioxidants, rust inhibitors, and corrosion inhibitors.

[0051] Examples of thickeners include metal soap-based thickeners, urea-based thickeners, bentonite, and inorganic thickeners such as silica gel. When a thermal conductive grease composition contains a thickener, its content is, for example, 0.1 to 20% by mass of the total amount of the thermal conductive grease composition. The thickener may be used alone or as a mixture of multiple solid lubricants.

[0052] Examples of anti-wear agents include organozinc compounds such as zinc dialkyldithiophosphate and zinc dialkyldithiocarbamate; sulfur-containing compounds such as molybdenum dialkyldithiocarbamate, dihydrocarbyl polysulfide, sulfur esters, thiazole compounds, and thiadiazole compounds; and phosphorus-based extreme pressure agents such as phosphate esters, acidic phosphate esters, amine salts of acidic phosphate esters, and phosphite esters. When a thermal conductive grease composition contains an anti-wear agent, its content is preferably, for example, 0.1 to 10% by mass, and more preferably 0.5 to 1.5% by mass, relative to the total amount of the thermal conductive grease composition. The anti-wear agent may be used alone, or multiple anti-wear agents or extreme pressure agents may be mixed and used.

[0053] Examples of antioxidants include phenolic compounds such as 2,6-di-t-butylphenol and 2,6-di-t-butyl-p-cresol; and amine compounds such as diphenylamine, dialkyldiphenylamine, phenyl-α-naphthylamine, and p-alkylphenyl-α-naphthylamine. When the thermal conductive grease composition contains an antioxidant, its content is, for example, 0.5 to 10% by mass of the total amount of the thermal conductive grease composition. The antioxidant may be used alone or in a mixture of multiple antioxidants.

[0054] Examples of rust inhibitors include amines, neutral or overbasic petroleum-based or synthetic oil-based metal sulfonates, carboxylate metal salts, esters, phosphoric acid, and phosphates. When a thermal conductive grease composition contains a rust inhibitor, its content is, for example, 0.005 to 5% by mass of the total amount of the thermal conductive grease composition. The rust inhibitor may be used alone or in a mixture of multiple rust inhibitors.

[0055] As corrosion inhibitors, known corrosion inhibitors such as benzotriazole compounds, tolyltriazole compounds, thiadiazole compounds, and imidazole compounds can be used. When the thermal conductive grease composition contains a corrosion inhibitor, its content is, for example, 0.01 to 10% by mass of the total amount of the thermal conductive grease composition. The corrosion inhibitor may be used alone or in a mixture of multiple corrosion inhibitors.

[0056] The thermal conductive grease composition of this embodiment contains a base oil (A), thermal conductive particles (B), and a phosphite ester or a salt thereof (C). The thermal conductive grease composition of this embodiment has a reduced viscosity (improved workability) and excellent thermal conductivity. The reason for this is not clear, but it is thought that compared to phosphate esters, phosphite esters or salts thereof do not contain unstable oxygen atoms that do not adsorb to the thermal conductive filler surface, so the phosphate portion adsorbs to the thermal conductive particles more stably, and the hydrophobic portion of the alkyl chain has excellent affinity with the base oil, resulting in a thermal conductive grease with low viscosity.

[0057] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0058] <Preparation of Thermally Conductive Grease Compositions> The thermally conductive grease compositions of Examples 1 to 3, and the thermally conductive grease compositions of Comparative Examples 1 and 2, were prepared in the proportions shown in Table 1. The values ​​in Table 1 represent the proportion (mass%) of each thermally conductive grease composition relative to the total amount of the thermally conductive grease composition.

[0059] (1) Base oil (A) ・(A)-1: Poly-α-olefin (40°C kinematic viscosity = 412 mm) ２ / s, density 0.846g / cm ３ )

[0060] (2) Thermally conductive particles (B) ・(B)-1: Aluminum nitride (spherical, average particle size D50 0.9 μm) ・(B)-2: Aluminum nitride (polyhedral, average particle size D50 8 μm) ・(B)-3: Aluminum nitride (spherical, average particle size D50 30 μm)

[0061] (3) One or more compounds selected from the group consisting of phosphite esters and salts of phosphite esters (C) ・(C)-1: A mixture containing phosphite esters (LUBRIZOL 6178, manufactured by Lubrizol Nippon Co., Ltd.)

[0062] (4) Additive X-1: Oleyl acid phosphate ester (JP-518-O, manufactured by Johoku Chemical Co., Ltd.)

[0063] [Measurement of rotational viscosity] The rotational viscosity of each example of the thermally conductive grease composition was measured under the following measurement conditions. The results are shown in Table 1. <Measurement conditions> Equipment used: HAAKE MARS3 Measurement temperature: 25℃ Sensor used: Parallel plate type 25 mm Sample thickness: 1 mm Shear rate: 10 s⁻¹

[0064]

[0065] As shown in Table 1, the thermal conductive grease composition of the example was found to have lower viscosity compared to the thermal conductive grease composition of the comparative example. Therefore, it can be seen that the thermal conductive grease composition of the example is easier to thin when pressed under the same load, reducing thermal resistance and thus exhibiting superior heat dissipation characteristics.

[0066] While preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments. Additions, omissions, substitutions, and other modifications are possible without departing from the spirit of the invention. The present invention is not limited by the foregoing description, but only by the scope of the appended claims.

Claims

1. A thermally conductive grease composition comprising a base oil (A), thermally conductive particles (B), and one or more compounds (C) selected from the group consisting of phosphite esters and salts of phosphite esters.

2. The thermally conductive grease composition according to claim 1, wherein the phosphite ester is a compound represented by the following general formula (C-1). [In the formula, Rc １ and Rc ２ Each of these is independently a hydrogen atom or an aliphatic hydrocarbon group having 16 or more carbon atoms. However, Rc １ and Rc ２ None of these can become hydrogen atoms.

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