JP5687167B2 - Heat-resistant thermal grease - Google Patents

Description

  The present invention relates to a heat resistance improver for a heat conductive grease having a high heat conductivity and a heat resistant heat conductive grease containing the heat resistance improver and having a low rate of change in consistency at high temperatures.

Among semiconductor components used in electronic devices, there are components that generate heat during use, such as power semiconductors for power control such as computer CPUs, Peltier elements, LEDs, and inverters.
In order to protect these semiconductor components from heat and to function normally, there is a method of conducting the generated heat to heat dissipation components such as a heat spreader and a heat sink to dissipate heat. The thermally conductive grease is applied between the semiconductor component and the heat radiating component so that the semiconductor component and the heat radiating component are in close contact with each other, and is used to efficiently conduct the heat of the semiconductor component to the heat radiating component.
In recent years, the performance improvement of electronic devices using these semiconductor components and the implementation of compact and high-density mounting are rapidly progressing, and the amount of heat generated by semiconductors is increasing. Is required to have high thermal conductivity and the heat resistance of the grease itself.

Thermally conductive greases are based on liquid hydrocarbons, base oils such as silicone oil and fluorine oil, metal oxides such as zinc oxide and aluminum oxide, inorganic nitrides such as boron nitride, silicon nitride and aluminum nitride, aluminum and A grease-like composition in which a filler having a high thermal conductivity such as a metal powder such as copper is dispersed in a large amount.
The inventor has already formulated a metal soap composed of a divalent or higher metal ion and an organic acid as a surface modifier for improving the dispersibility of the inorganic powder filler, and further specified an amine-based antioxidant. We have found a heat-conducting grease that has a high consistency and excellent heat resistance. (See Patent Document 1)

JP 2009-046639 A

Thermally conductive grease is used at a thermal contact interface in a cooling device such as a CPU of a computer or a cooling device such as a power semiconductor used in a high-power inverter mounted on a hybrid vehicle or an electric vehicle. In recent years, semiconductor elements in these electronic devices have increased in heat generation density and heat generation along with downsizing and higher performance, and heat conductive grease is in an environment where it is exposed to higher temperatures than ever before.
When a heat conductive grease is used for a long time in such a high temperature environment, the consistency may be greatly lowered depending on the type of the heat conductive grease. As described above, when the consistency is greatly reduced or cured as a heat dissipation material, cracks or voids may be generated, and the heat dissipation performance may be deteriorated.

Therefore, in the case where the heat generation temperature of the semiconductor unit and the ambient environment temperature are high and used for a long period of time, the performance of the thermal conductive grease has a low rate of change in consistency at high temperatures. It is required to have excellent properties.
An object of the present invention is to provide a thermally conductive grease having a low rate of change in consistency at high temperatures.

Therefore, as a result of intensive studies to achieve the above-mentioned problems, the present inventor formulated a specific amount of a specific metal soap for improving the dispersibility of the inorganic powder filler, and a specific amount of a specific antioxidant. Furthermore, by adding a specific amount of a compound having a specific structure, it was found that the heat resistance can be remarkably improved while highly filling the inorganic powder filler to increase the thermal conductivity, and the present invention was completed. It came to.

That is, the present invention provides a heat resistance improver for thermally conductive grease filled with one or more inorganic powder fillers selected from compounds having a structure represented by general formulas (1) to (5). is there.

（一般式（１）において、Ｒ^１、Ｒ^２は、炭素数４〜１０の１価の炭化水素基であり、Ｒ^３は炭素数１〜１０の２価の炭化水素基である。）

(In General Formula (1), R ¹ and R ² are monovalent hydrocarbon groups having 4 to 10 carbon atoms, and R ³ is a divalent hydrocarbon group having 1 to 10 carbon atoms.)

（一般式（２）において、Ｒ^４、Ｒ^５は炭素数４〜１０のターシャリータイプの炭化水素基であり、Ｒ^６、Ｒ^７は水素原子または炭素数１〜１０の１価の炭化水素基であり、Ｒ^８は炭素数１〜１０の２価の炭化水素基である。）

(In General Formula (2), R ⁴ and R ⁵ are tertiary type hydrocarbon groups having 4 to 10 carbon atoms, and R ⁶ and R ⁷ are hydrogen atoms or monovalent hydrocarbons having 1 to 10 carbon atoms. And R ⁸ is a divalent hydrocarbon group having 1 to 10 carbon atoms.)

（一般式（３）において、Ｒ^９、Ｒ^１０、Ｒ^１１、Ｒ^１２、Ｒ^１３は水素原子または炭素数４〜１０のターシャリータイプの炭化水素基であり、かつ少なくとも一つは炭素数４〜１０のターシャリータイプの炭化水素基であり、Ｒ^１４、Ｒ^１５、Ｒ^１６、Ｒ^１７、Ｒ^１８は水素原子、水酸基または炭素数４〜１０のターシャリータイプの炭化水素基であり、かつ少なくとも一つは水酸基である。）

(In General Formula (3), R ⁹ , R ¹⁰ , R ¹¹ , R ¹² , and R ¹³ are a hydrogen atom or a tertiary type hydrocarbon group having 4 to 10 carbon atoms, and at least one of them has 4 carbon atoms. 10 is a tertiary type hydrocarbon group, R ¹⁴ , R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁸ are a hydrogen atom, a hydroxyl group or a tertiary type hydrocarbon group having 4 to 10 carbon atoms, and At least one is a hydroxyl group.)

（一般式（４）において、Ｒ^１９、Ｒ^２０、Ｒ^２１、Ｒ^２２、Ｒ^２３、Ｒ^２４、Ｒ^２５、Ｒ^２６は炭素数１〜１０の１価の炭化水素基であり、Ｒ^２７、Ｒ^２８は水素原子または炭素数１〜１０の１価の炭化水素基であり、かつ少なくとも一つは水素原子であり、Ｒ^２９は炭素数１〜１２の２価の炭化水素基である。）

(In General formula (4), R <^19> , R <^20> , R <^21> , R <^22> , R <^23> , R < ²⁴ >, R < ²⁵ >, R < ²⁶ > is a C1-C10 monovalent hydrocarbon group, R <^27> , R ²⁸ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms, and at least one is a hydrogen atom, and R ²⁹ is a divalent hydrocarbon group having 1 to 12 carbon atoms.)

（一般式（５）において、Ｒ^３０、Ｒ^３１、Ｒ^３２、Ｒ^３３、Ｒ^３４は炭素数１〜１０の１価の炭化水素基であり、Ｒ^３５、Ｒ^３６は炭素数１〜１２の２価の炭化水素基であり、ｎは１〜２０である。）

(In the general formula ^{(5), R 30, R} 31, R 32, R 33, R 34 is a monovalent hydrocarbon group having 1 to 10 carbon ^{atoms, R 35,} R ³⁶ is from 1 to 12 carbon atoms (It is a divalent hydrocarbon group, and n is 1-20.)

In the present invention, the term “tertiary type hydrocarbon group having 4 to 10 carbon atoms” means that the substituent binding site of the hydrocarbon group having 4 to 10 carbon atoms as a substituent is a tertiary carbon atom. In the case of a saturated aliphatic hydrocarbon group having 4 carbon atoms, it means a tert-butyl group, and in the case of a saturated aliphatic hydrocarbon group having 5 carbon atoms, it means a tert-pentyl group.

The present invention also provides (A) 70 to 97% by mass of an inorganic powder filler, (B) 2 to 28 % by mass of a base oil, and (C) a metal soap comprising a divalent or higher metal ion and an organic acid. 0.001 to 3% by mass, and (D) 0.03 to 0.75% by mass of the amine-based antioxidant, and (E) a compound having a structure represented by the general formulas (1) to (5). One or more heat resistance improvers contained in a proportion of 0.001 to 1.0% by mass are provided.
The present invention also provides a thermally conductive grease in which the proportion of the polyalphaolefin contained in the base oil of component (B) is 5 to 100% by mass in the above thermally conductive grease.

The heat conductive grease of the present invention contains a specific amount of a specific metal soap for improving the dispersibility of the inorganic powder filler, a specific amount of a specific antioxidant, and a general formula (1)-( A particularly excellent heat resistance is realized by blending a specific amount of one or more selected from compounds having the structure represented by 5). By using the thermally conductive grease of the present invention, the heat dissipation of an electronic component that emits high heat can be improved, and it is particularly suitable as a heat dissipation material for automotive power semiconductors and LEDs that are exposed to high temperature environments.

  The inorganic powder filler (A) used in the present invention is not particularly limited as long as it has a higher thermal conductivity than the base oil, but powders such as metal oxides, inorganic nitrides, metals, silicon compounds, and carbon materials. Are preferably used. One kind of the inorganic powder filler of the present invention may be used, or two or more kinds may be used in combination.

  In the case where the above-mentioned inorganic powder filler is required for electrical insulation, non-conductive substances such as semiconductors and ceramics such as zinc oxide, aluminum oxide, titanium oxide, aluminum nitride, boron nitride, silicon carbide, silica, and diamond are used. Are preferably used, more preferably zinc oxide, aluminum oxide, aluminum nitride, boron nitride, and silicon carbide powder, and particularly preferably zinc oxide and aluminum oxide powder. These inorganic powder fillers may be used alone or in combination of two or more. In addition, when seeking higher thermal conductivity without requiring electrical insulation, metal powders such as aluminum, gold, silver, and copper, and carbon material powders such as graphite, fullerene, carbon nanotubes, and carbon nanohorns are suitable. Metal powder is more preferable, and aluminum powder is particularly preferable. Further, a metal powder or a carbon material powder can be used in combination with the above-mentioned non-conductive substance powder.

The inorganic powder filler is preferably an inorganic powder having an average particle size of 0.15 μm or more and less than 3 μm when only fine particles are used. By setting the average particle size to 0.15 μm or more, the balance between the amount of metal soap and the amount of liquid component that makes the surface of the inorganic powder filler oleophilic is good, and a higher consistency is achieved when the amount is high. Can be obtained. On the other hand, when the average particle size is less than 3 μm, it becomes easy to perform close packing, higher thermal conductivity can be obtained, and oil separation is difficult. In addition, by combining two or more kinds of fine particles having different average particle diameters, it becomes easy to perform close-packing and oil separation is difficult. Also in this case, from the viewpoint of thermal conductivity and mounting, the average particle size of each fine particle is preferably 0.15 μm or more and less than 3 μm. When using a combination of fine particles having different average particle sizes, the average particle size of the fine particles having a small average particle size is an average particle size of 60 to 10% with respect to the average particle size of the fine particles having a large average particle size. Preferably, the average particle size is 55 to 20%. The mixing ratio of the fine particles having a small average particle diameter and the fine particles having a large average particle diameter is preferably in the range of 5:95 to 85:15 in terms of mass ratio.

Furthermore, when combining a fine grain and a coarse grain, said fine grain and a coarse inorganic powder with an average particle diameter of 3-50 micrometers can be combined. In this case, it is easy to obtain higher thermal conductivity by setting the average particle size of the coarse particles to 3 μm or more, and the coating film is thinned by setting the average particle size of the coarse particles to 50 μm or less. The heat dissipation performance can be further enhanced.
When the inorganic powder filler is a combination of fine particles and coarse particles, the coarse particles can be a combination of two or more kinds of powders having different average particle sizes. Also in this case, it is preferable that the average particle diameter of each coarse grain is 3-50 micrometers from a viewpoint of heat conductivity and the thermal radiation performance at the time of mounting.
In the present invention, the average particle size of the inorganic powder filler can be calculated as a volume average particle size distribution measured by a laser diffraction scattering method (based on JIS R 1629).

Moreover, it is preferable to mix in the range of 20: 80-85: 15 mass ratio in the case of combining a fine grain and coarse grain inorganic powder filler. When two or more kinds of coarse particles are combined, the mass ratio between the coarse particles is not particularly limited. In this case, the mass ratio of the fine particles is preferably in the range of 20% to 85% of the inorganic powder filler. . By setting the blending ratio of the fine particles and the coarse particles in the above range, a high consistency can be obtained from the balance between the amount of the metal soap that makes the surface of the inorganic powder filler lipophilic and the amount of the liquid component. In addition, the balance between coarse and fine particles is suitable for closest packing, and oil separation is difficult.

  Although the content rate of an inorganic powder filler is 70-97 mass%, it is excellent in thermal conductivity, so that the content rate is high, Preferably it is 75-96 mass%. If it is less than 70% by mass, the thermal conductivity may be lowered or the oil may be easily removed. On the other hand, if it exceeds 97% by mass, the consistency will be low and sufficient coatability will not be maintained, or a thermally conductive grease will not be prepared.

As the base oil (B), various base oils can be used. For example, hydrocarbon base oils such as mineral oil and synthetic hydrocarbon oil, ester base oils, ether base oils, phosphate esters, silicone oils and fluorine Examples thereof include hydrocarbon base oils, ester base oils, and ether base oils. In terms of preventing oil separation, silicone oil and fluorine oil having a low surface tension are not preferred. A base oil may be used individually by 1 type, or may be used in combination of 2 or more type.
As mineral oil, for example, a mineral oil-based lubricating oil fraction is refined by appropriately combining purification methods such as solvent extraction, solvent dewaxing, hydrorefining, hydrocracking, wax isomerization, 150 neutral oil, 500 neutral Oil, bright stock, and high viscosity index base oil. The mineral oil is preferably a highly hydrorefined high viscosity index base oil.

Examples of the synthetic hydrocarbon oil include those obtained by polymerizing alpha olefins produced using ethylene, propylene, butene, and derivatives thereof as a raw material alone or in combination of two or more. As an alpha olefin, a C6-C14 thing is mentioned preferably.
Specific examples include polyalphaolefin (PAO) which is an oligomer of 1-decene and 1-dodecene, polybutene which is an oligomer of 1-butene and isobutylene, and a co-oligomer of ethylene, propylene and alphaolefin. Moreover, alkylbenzene, alkylnaphthalene, etc. can also be used.

Examples of ester base oils include diesters and polyol esters.
Examples of the diester include esters of dibasic acids such as adipic acid, azelaic acid, sebacic acid, and dodecanedioic acid. As the dibasic acid, an aliphatic dibasic acid having 4 to 36 carbon atoms is preferable. The alcohol residue constituting the ester portion is preferably a monohydric alcohol residue having 4 to 26 carbon atoms.
The polyol ester is an ester of neopentyl polyol in which a hydrogen atom does not exist on the β-position carbon, and specifically includes carboxylic acid esters such as neopentyl glycol, trimethylolpropane, and pentaerythritol. The carboxylic acid residue constituting the ester part is preferably a monocarboxylic acid residue having 4 to 26 carbon atoms.

In addition to the above, aliphatic dihydric alcohols such as ethylene glycol, propylene glycol, butylene glycol, 2-butyl-2-ethylpropanediol, and 2,4-diethyl-pentanediol, and linear or branched chain saturation Esters with fatty acids can also be used. As the linear or branched saturated fatty acid, a monovalent linear or branched saturated fatty acid having 4 to 30 carbon atoms is preferable.
Examples of the ether base oil include polyglycol and (poly) phenyl ether.
Examples of the polyglycol include polyethylene glycol, polypropylene glycol, and derivatives thereof.
Examples of (poly) phenyl ether include alkylated diphenyl ether, monoalkylated tetraphenyl ether, dialkylated tetraphenyl ether, and pentaphenyl ether.

  Examples of phosphate esters include triethyl phosphate, tributyl phosphate, triphenyl phosphate, tricresyl phosphate, and trixylenyl phosphate.

  Since the heat conductive grease is applied to the heat generating part, it is exposed to high temperature for a long time. For this reason, it is desirable that the base oil has excellent thermal oxidation stability. Among the above base oils, synthetic base oils are preferable, and synthetic hydrocarbon oils, ester base oils, and ether base oils are preferable. Among these base oils, those having particularly excellent thermal oxidation stability include polyalphaolefins for synthetic hydrocarbon oils, polyol esters for ester base oils, and (poly) phenyl ethers for ether base oils. Used as Furthermore, among these base oils, polyalphaolefins and polyol esters that can prepare greases having a relatively high viscosity index and high consistency when the grease is prepared and excellent coating properties are used as preferred base oils.

The content of the polyalphaolefin contained in the base oil is 5% by mass to 100% by mass, preferably 10% by mass to 100% by mass. By blending the polyalphaolefin in the base oil within the above range, a grease having excellent coatability can be prepared. In addition, when a particularly excellent coating property is not required, (poly) phenyl ether having a high viscosity can be used.
The kinematic viscosity of the base oil is preferably 10mm ² / s~1200mm ² / s at 40 ° C.. It is preferable to set the kinematic viscosity at 40 ° C. to 10 mm ² / s or more because evaporation of base oil and oil separation at high temperatures tend to be suppressed. Moreover, since kinematic viscosity in 40 degreeC shall be 1200 mm < ² > / s or less, since it becomes easy to obtain a high consistency, it is preferable.

The content of the base oil is 2 to 28 % by mass, preferably 3 to 28 % by mass, and particularly preferably 3 to 25% by mass. When the content exceeds 30% by mass, the consistency becomes too high, and the thermally conductive grease may flow out when placed in a high temperature environment. In addition, oil separation may occur and thermal conductivity may decrease.

The metal soap (C) used in the present invention is adsorbed on the surface of the inorganic powder filler, has a function as a surface modifier that improves the affinity with the base oil, and has high heat resistance. By using C) as a surface modifier, the heat resistance of the thermally conductive grease can be improved.

The metal soap (C) used in the present invention is a metal soap composed of a divalent or higher valent metal ion and an organic acid. Specific examples of the metal soap (C) include, for example, calcium soap, magnesium soap, aluminum soap, zinc soap and the like as single metal soap. Magnesium soap, aluminum soap and zinc soap are preferable, and zinc soap is particularly preferable. preferable. Examples of complex-type metal soaps include calcium complex soaps, barium complex soaps, and aluminum complex soaps.

Of these metal soaps, single metal soaps that can be added to grease by a pre-soap mixing method without using a saponification reaction are preferred. The organic acid portion of the metal soap is preferably a straight chain or a fatty acid having a hydroxy group, and more preferably a straight chain saturated fatty acid. In this case, the carbon number of the fatty acid is preferably 12 to 28, and 14 to 24 is particularly preferable when the heat resistance is further improved. Such fatty acid metal soaps include calcium stearate, magnesium stearate, zinc stearate, aluminum stearate, zinc laurate and the like, with magnesium stearate, zinc stearate and aluminum stearate being particularly preferred.

Although the metal soap (C) used for this invention contains 0.001 mass%-3 mass%, Preferably it is 0.005 mass%-2 mass%, More preferably, it is 0.01 mass%-1 mass. %, And most preferably 0.1% by mass to 1% by mass. When the content is less than 0.001% by mass, the content of the inorganic powder filler is insufficient to make the surface oleophilic, so a high consistency cannot be obtained and the filling rate tends to be difficult. In addition, when it is placed in an environment of high temperature and high humidity, the consistency decreases, or it tends to aggregate and harden easily. In addition, when the content is more than 3% by mass, the metal soap has a function as a thickener in the base oil. Therefore, when the grease is hardened or the filling rate of the inorganic powder filler is increased. It tends to be impossible to grease.

Examples of the amine antioxidant (D) used in the present invention include naphthylamines such as phenyl-α-naphthylamine and phenyl-β-naphthylamine, alkylated diphenylamines such as p, p′-dialkyldiphenylamine, and diphenyl-p-. Phenylenediamine, dipyridylamines, phenothiazines and the like are preferably used. Of these, naphthylamines and alkylated diphenylamines, which are highly oil-soluble and hardly generate sludge, are preferred, and alkylated diphenylamines are particularly preferred.
Naphthylamines preferably have a phenyl group, and those having a monovalent hydrocarbon group in the phenyl group are particularly preferred. 4-20 are preferable and, as for carbon number of a monovalent hydrocarbon group, 6-18 are more preferable. The monovalent hydrocarbon group is preferably an alkyl group.

Examples of the alkylated diphenylamines include monoalkylated diphenylamines, dialkylated diphenylamines, trialkylated diphenylamines, and tetraalkylated diphenylamines, with dialkylated diphenylamines being preferred.
The alkyl group in the alkylated diphenylamines is preferably an alkyl group having 1 to 20 carbon atoms, more preferably an alkyl group having 3 to 14 carbon atoms, and particularly preferably an alkyl group having 4 to 12 carbon atoms.
The amine-based antioxidant has an effect of preventing a radical chain reaction at a high temperature and has a low sublimation property. Therefore, the amine-based antioxidant has an effect of improving heat resistance as compared with the case of using another antioxidant.

These amine antioxidants may be used alone or in combination of two or more. Content of amine antioxidant is 0.03-0.75 mass%, and 0.1-0.6 mass% is preferable. If the content of the amine antioxidant is less than 0.03% by mass, the effect is small, and if it is greater than 0.75% by mass, the effect cannot be expected. The grease tends to be hardened due to the influence of the deteriorated product itself.

The heat resistance improver of the component (E) used in the present invention is remarkably improved in heat resistance of the heat conductive grease filled with the inorganic powder filler by using it together with the metal soap (C) and the amine-based antioxidant (D). Can be improved.
Examples of the heat resistance improver of the component (E) used in the present invention include compounds having a structure represented by the general formulas (1) to (5).

In the general formula (1), R ¹ and R ² are a tertiary type hydrocarbon group having 4 to 10 carbon atoms, and more preferably a tertiary type hydrocarbon group having 4 to 8 carbon atoms.
In the general formula (1), R ³ is a divalent hydrocarbon group having 1 to 10 carbon atoms, preferably a divalent hydrocarbon group having 1 to 8 carbon atoms, more preferably 1 to 5 carbon atoms. These are divalent hydrocarbon groups.
It limitation on the kind of the hydrocarbon group R ¹ to R ³ are not, but preferred are saturated hydrocarbon groups.

In the general formula (2), R ⁴ and R ⁵ are a tertiary type hydrocarbon group having 4 to 10 carbon atoms, preferably a tertiary type hydrocarbon group having 4 to 8 carbon atoms, more preferably It is a tertiary type hydrocarbon group having 4 to 6 carbon atoms. Moreover, although there is no restriction | limiting in the kind of hydrocarbon group, A saturated hydrocarbon group is preferable.
In the general formula (2), R ⁶ and R ⁷ are a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms, preferably a hydrogen atom or a tertiary type hydrocarbon group having 4 to 8 carbon atoms. More preferably a tertiary type hydrocarbon group having 4 to 6 carbon atoms. Moreover, in the case of a hydrocarbon group, there is no restriction | limiting in the kind, However, A saturated hydrocarbon group is preferable.
In the general formula (2), R ⁸ is a divalent hydrocarbon group having 1 to 10 carbon atoms, preferably a divalent hydrocarbon group having 1 to 8 carbon atoms, and more preferably 1 to 5 carbon atoms. The divalent hydrocarbon group is particularly preferably a divalent hydrocarbon group having 2 to 5 carbon atoms. Moreover, although there is no restriction | limiting in the kind of hydrocarbon group, A saturated hydrocarbon group is preferable.

In the general formula (3), R ⁹ , R ¹⁰ , R ¹¹ , R ¹² , R ¹³ are a hydrogen atom or a tertiary hydrocarbon group having 4 to 10 carbon atoms, and at least one of them has 4 to 10 is a tertiary type hydrocarbon group, and in the case of a tertiary type hydrocarbon group, it is preferably a tertiary type hydrocarbon group having 4 to 8 carbon atoms, more preferably 4 to 6 carbon atoms. This is a tertiary type hydrocarbon group. Moreover, in the case of a hydrocarbon group, there is no restriction | limiting in the kind, However, A saturated hydrocarbon group is preferable. In R ⁹ , R ¹⁰ , R ¹¹ , R ¹² , and R ¹³ , the number of hydrogen atoms is preferably 2 to 4, and more preferably 3 to 4.
In the general formula (3), R ¹⁴ , R ¹⁵ , R ¹⁶ , R ¹⁷ and R ¹⁸ are a hydrogen atom, a hydroxyl group or a tertiary hydrocarbon group having 4 to 10 carbon atoms, and at least one is a hydroxyl group. In the case of a tertiary type hydrocarbon group, it is preferably a tertiary type hydrocarbon group having 4 to 8 carbon atoms, and more preferably a tertiary type hydrocarbon group having 4 to 6 carbon atoms. Moreover, in the case of a hydrocarbon group, there is no restriction | limiting in the kind, However, A saturated hydrocarbon group is preferable. In R ¹⁴ , R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁸ , the number of hydrogen atoms is preferably 2 to 4.

In the general formula (4), R ¹⁹ , R ²⁰ , R ²¹ , R ²² , R ²³ , R ²⁴ , R ²⁵ , R ²⁶ are monovalent hydrocarbon groups having 1 to 10 carbon atoms, preferably carbon atoms. A monovalent hydrocarbon group having 1 to 8 carbon atoms, more preferably a monovalent hydrocarbon group having 1 to 6 carbon atoms. Moreover, although there is no restriction | limiting in the kind of hydrocarbon group, A saturated hydrocarbon group is preferable.
In the general formula (4), R ²⁷ and R ²⁸ are a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms, and at least one is a hydrogen atom, preferably both are hydrogen atoms. When R ²⁷ and R ²⁸ are monovalent hydrocarbon groups, they are preferably monovalent hydrocarbon groups having 1 to 8 carbon atoms, more preferably monovalent hydrocarbon groups having 1 to 6 carbon atoms. . Moreover, in the case of a hydrocarbon group, there is no restriction | limiting in the kind, However, A saturated hydrocarbon group is preferable.
In the general formula (4), R ²⁹ is a divalent hydrocarbon group having 1 to 12 carbon atoms, preferably a divalent hydrocarbon group having 4 to 10 carbon atoms, and more preferably 6 to 10 carbon atoms. These are divalent hydrocarbon groups. Moreover, although there is no restriction | limiting in the kind of hydrocarbon group, A saturated hydrocarbon group is preferable.

In the general formula (5), R ³⁰ , R ³¹ , R ³² , R ³³ , and R ³⁴ are monovalent hydrocarbon groups having 1 to 10 carbon atoms, preferably monovalent hydrocarbons having 1 to 8 carbon atoms. Group, more preferably a monovalent hydrocarbon group having 1 to 6 carbon atoms. Moreover, although there is no restriction | limiting in the kind of hydrocarbon group, A saturated hydrocarbon group is preferable.
In the general formula (5), R ³⁵ and R ³⁶ are a divalent hydrocarbon group having 1 to 12 carbon atoms, preferably a divalent hydrocarbon group having 1 to 8 carbon atoms, and more preferably a carbon number. 1 to 5 divalent hydrocarbon groups. Moreover, although there is no restriction | limiting in the kind of hydrocarbon group, A saturated hydrocarbon group is preferable.
In General formula (5), it is n = 1-20, Preferably it is n = 5-18, More preferably, it is n = 8-16.

As the heat resistance improver of the component (E), those exhibiting a heat resistance effect having a consistency change rate of ± 10% or less in the high temperature standing test of the heat conductive grease described in the examples are preferable. The consistency change rate in the high temperature storage test is more preferably ± 9% or less, further preferably ± 8% or less, and particularly preferably ± 7% or less.
As the heat resistance improver for the component (E), any compound represented by the general formulas (1) to (5) may be used, but the compounds represented by the general formulas (2) to (5) are preferable, and more preferably. Compounds of general formula (2), general formula (3), and general formula (5), more preferably compounds of general formula (2) and general formula (5), most preferably general formula (5). It is a compound of this.

(E) Content of the heat resistance improver of a component is 0.001 mass%-1.0 mass%, Preferably it is 0.005 mass%-1.0 mass%, More preferably, it is 0.005. It is from mass% to 0.8 mass%, more preferably from 0.005 mass% to 0.5 mass%.
By making content of the heat resistance improver of (E) component into the said range, the heat resistance of heat conductive grease can be improved. Although the details are not known, it is conceivable that the component (E) supplements radicals generated by the thermal history of the thermally conductive grease.
(E) Content of the heat resistance improver of a component is a ratio of 0.01 mass%-5 mass% with respect to content of a liquid component, and 0.05 mass%-2 mass% are more preferable. When the content of the component (E) with respect to the liquid component is less than 0.01% by mass, it becomes difficult to obtain excellent heat resistance, and when the content of the component (E) with respect to the liquid component exceeds 5% by mass, The degree is low, and it is difficult to obtain good coating properties.

  Moreover, a well-known additive can be suitably mix | blended with the heat conductive grease of this invention as needed. These include, for example, secondary antioxidants such as sulfur antioxidants such as sulfide, disulfide, trisulfide, and thiobisphenol, and phosphorus antioxidants such as alkyl phosphite and ZnDTP. Is sulfonate, carboxylic acid, carboxylate, succinate, etc., corrosion inhibitor is benzotriazole and its derivatives, thiadiazole compounds, thickener is polybutene, polymethacrylate, olefin copolymer, high Examples of thickeners such as polyalphaolefin having a viscosity include urea compounds, sodium terephthalate, polytetrafluoroethylene, organic bentonite, silica gel, petroleum wax, polyethylene wax and the like. The amount of these additives may be a normal amount.

  Regarding the production of the high thermal conductivity grease of the present invention, the method is not limited as long as the components can be mixed uniformly. As a general production method, there is a method of kneading with a mortar, a planetary mixer, a twin-screw extruder, or the like to form a grease and then uniformly kneading with three rolls.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited at all by this.
It shows below about each component used for the Example and the comparative example.
(A-1) Zinc oxide 1 Average particle diameter: 0.29 μm (laser diffraction scattering method)
(A-2) Zinc oxide 2 Average particle diameter: 0.6 μm (laser diffraction scattering method)
(B-1) Poly-alpha-olefin (1-decene-oligomer) 40 ° C. kinematic viscosity: 47 mm ² / s
(B-2) Ester of pentaerythritol and monocarboxylic acid having 8 and 10 carbon atoms 40 ° C. kinematic viscosity: 32 mm ² / s
(C) Zinc stearate (D) amine-based antioxidant dioctyl diphenylamine

(E-1) 1,2-bis (3,5-di-tert-butyl-4-hydroxyhydrocinnamori) hydrazine (R ¹ and R ² in the general formula (1) are tert-butyl groups, and R ³ is Ethylene group.)
(E-2) 2- [1- (2-Hydroxy-3,5-di-tert-pentylphenyl) ethyl] -4,6-di-tert-pentylphenyl acrylate (R ⁴ in the general formula (2), R ⁵ , R ⁶ and R ⁷ are tert-pentyl groups, and R ⁸ is a methylmethylene group.)
(E-3) 2,4-di-tert-butylphenyl-3,5-di-tert-butyl-4-hydroxybenzoate (R ⁹ , R ¹¹ , R ¹⁵ , R ¹⁷ in the general formula (3) are tert -Butyl group, R ¹⁰ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁸ are hydrogen atoms, and R ¹⁶ is a hydroxyl group.)

(E-4) 4-tert-butylphenyl salicylate (R ¹¹ in the general formula (3) is a tert-butyl group, R ⁹ , R ¹⁰ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ , and R ¹⁷ is a hydrogen atom, and R ¹⁸ is a hydroxyl group.)
(E-5) bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate (R ^{19 to} R ²⁶ in the general formula (4) are all methyl groups, R ²⁷ and R ²⁸ are hydrogen atoms, R ²⁹ is a — (CH ₂ ) ₈ — group.
(E-6) Polycondensate of dimethyl succinate and 1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine (R ^{30 to} R ³³ in the general formula (5) (All are methyl groups, R ³⁵ and R ³⁶ are ethylene groups, R ³⁴ is a methyl group, and n = 14.)

(E-7) 2-tert-butyl-6- (3-tert-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate (R ⁴ and R ⁷ in the general formula (2) are tert- (Butyl group, R ⁵ and R ⁶ are methyl groups, and R ⁸ is a methylene group.)
(E-8) 2,2,4,4-tetrahydroxybenzophenone (E-9) bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate (R ^{19 to} R ¹⁹ in the general formula (4)) R ²⁸ is a methyl group, and R ²⁹ is a — (CH ₂ ) ₈ — group.) And methyl (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate. )
In addition, the mass% of the content of (E) in the liquid component in the table means that among the components constituting the composition, (A) the sum of the components excluding the inorganic powder filler is 100, of which The ratio of (E) is shown.

The heat conductive grease was prepared as follows.
The antioxidant was dissolved in the base oil and placed in a planetary mixer together with an inorganic powder filler, metal soap, and a compound having a structure represented by the general formulas (1) to (5). The mixture was kneaded while being heated to about 120 ° C. to 150 ° C. and mixed well to obtain a grease. Thereafter, kneading with three rolls was carried out once or twice to prepare a heat conductive grease.

The performance shown below was evaluated using the obtained heat conductive grease.
For the penetration, the immiscibility penetration was measured according to JIS-K2220. The greater the consistency value, the softer the heat conductive grease, and vice versa.
The thermal conductivity was measured at room temperature using a rapid thermal conductivity meter QTM-500 manufactured by Kyoto Electronics Industry Co., Ltd.
The high temperature storage test was performed by sandwiching 0.25 ml of heat conductive grease between iron plates, forming a thin film with a thickness of 200 μm, and heating at 180 ° C. for 240 hours. The consistency before and after the test was simply measured. Here, the consistency change rate in the high temperature standing test was calculated by the following equation.

ちょう度変化率の絶対値が小さい程、耐熱性が優れている。

The smaller the absolute value of the consistency change rate, the better the heat resistance.

As can be seen from Tables 1 to 3, Examples 1 to 13 have a very high consistency of 200 or more, and have very little change in consistency after a high-temperature standing test at 180 ° C. × 240 hours. Are better.
On the other hand, Comparative Examples 1 to 4, which do not contain the compounds having the structures represented by the general formulas (1) to (5), have a large change in consistency after a high-temperature standing test at 180 ° C. × 240 hours, and are inferior in heat resistance.
The heat-resistant thermal conductive grease of the present invention can improve the heat dissipation of electronic components that require heat countermeasures, and is particularly suitable as a heat dissipation material for CPUs, power semiconductors, and LEDs.

The heat-resistant thermal conductive grease of the present invention can improve the heat dissipation of electronic components that require heat countermeasures, and is particularly suitable as a heat dissipation material for CPUs, power semiconductors, and LEDs.

Claims (3)

A heat resistance improver for thermally conductive grease filled with one or more inorganic powder fillers selected from compounds having a structure represented by general formulas (1) to (5).

(In General Formula (1), R ¹ and R ² are monovalent hydrocarbon groups having 4 to 10 carbon atoms, and R ³ is a divalent hydrocarbon group having 1 to 10 carbon atoms.)

(In General Formula (2), R ⁴ and R ⁵ are tertiary type hydrocarbon groups having 4 to 10 carbon atoms, and R ⁶ and R ⁷ are hydrogen atoms or monovalent hydrocarbons having 1 to 10 carbon atoms. And R ⁸ is a divalent hydrocarbon group having 1 to 10 carbon atoms.)

(In General Formula (3), R ⁹ , R ¹⁰ , R ¹¹ , R ¹² , and R ¹³ are a hydrogen atom or a tertiary type hydrocarbon group having 4 to 10 carbon atoms, and at least one of them has 4 carbon atoms. 10 is a tertiary type hydrocarbon group, R ¹⁴ , R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁸ are a hydrogen atom, a hydroxyl group or a tertiary type hydrocarbon group having 4 to 10 carbon atoms, and At least one is a hydroxyl group.)

(In General formula (4), R <^19> , R <^20> , R <^21> , R <^22> , R <^23> , R < ²⁴ >, R < ²⁵ >, R < ²⁶ > is a C1-C10 monovalent hydrocarbon group, R <^27> , R ²⁸ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms, and at least one is a hydrogen atom, and R ²⁹ is a divalent hydrocarbon group having 1 to 12 carbon atoms.)

(In the general formula ^{(5), R 30, R} 31, R 32, R 33, R 34 is a monovalent hydrocarbon group having 1 to 10 carbon ^{atoms, R 35,} R ³⁶ is from 1 to 12 carbon atoms (It is a divalent hydrocarbon group, and n is 1-20.) (A) 70 to 97% by mass of inorganic powder filler,
(B) 2 to 28 % by mass of base oil,
(C) 0.001 to 3% by mass of metal soap composed of a divalent or higher metal ion and an organic acid,
(D) 0.03 to 0.75% by mass of an amine-based antioxidant,
(E) It contains one or more heat resistance improvers selected from compounds having the structures represented by the general formulas (1) to (5) in a proportion of 0.001 to 1.0% by mass. Heat conductive grease.

(In General Formula (1), R ¹ and R ² are monovalent hydrocarbon groups having 4 to 10 carbon atoms, and R ³ is a divalent hydrocarbon group having 1 to 10 carbon atoms.)

(In General Formula (2), R ⁴ and R ⁵ are tertiary type hydrocarbon groups having 4 to 10 carbon atoms, and R ⁶ and R ⁷ are hydrogen atoms or monovalent hydrocarbons having 1 to 10 carbon atoms. And R ⁸ is a divalent hydrocarbon group having 1 to 10 carbon atoms.)

(In General Formula (3), R ⁹ , R ¹⁰ , R ¹¹ , R ¹² , and R ¹³ are a hydrogen atom or a tertiary type hydrocarbon group having 4 to 10 carbon atoms, and at least one of them has 4 carbon atoms. 10 is a tertiary type hydrocarbon group, R ¹⁴ , R ¹⁵ , R ¹⁶ , R ¹⁷ , R ¹⁸ are a hydrogen atom, a hydroxyl group or a tertiary type hydrocarbon group having 4 to 10 carbon atoms, and At least one is a hydroxyl group.)

(In the general formula ^{(4), R 19, R} 20, R 21, R 22, R 23, R 24, R 25, R 26 is a monovalent hydrocarbon group having 1 to 10 carbon ^{atoms, R 27,} R ²⁸ is a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms, and at least one is a hydrogen atom, and R ²⁹ is a divalent hydrocarbon group having 1 to 12 carbon atoms.)

(In the general formula ^{(5), R 30, R} 31, R 32, R 33, R 34 is a monovalent hydrocarbon group having 1 to 10 carbon ^{atoms, R 35,} R ³⁶ is from 1 to 12 carbon atoms (It is a divalent hydrocarbon group, and n is 1-20.) The thermally conductive grease according to claim 2, wherein the proportion of the polyalphaolefin contained in the base oil of component (B) is 5 to 100% by mass.