JPS5827822B2 - Grease composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a grease composition that has excellent heat dissipation properties, paintability, and heat resistance.

Conventionally, in order to obtain a grease composition with excellent heat dissipation,
Polyorganosiloxane must be filled with a large amount of inorganic substances such as east lead oxide, aluminum oxide, aluminum oxide, etc., which increases the hardness of the grease composition and worsens workability. However, it also had the disadvantage of being prone to separation.

As shown in U.S. Pat. No. 3,885,984, when a polyorganosiloxane with a long-chain alkyl group attached to the side chain is used, the amount of inorganic substances added can be reduced compared to the case of polydimethylsiloxane. Even if it is increased, the hardness will be lower, so it can compensate for the shortcomings mentioned in -H.

In addition, polyorganosiloxanes having such long-chain alkyl groups or aralkyl groups have excellent paintability and can be easily coated or plated on contaminated substrates compared to the case of polydimethylsiloxane. It has a number of advantages, including its lubricity and the fact that it does not adversely affect room temperature vulcanizable silicone rubber.

However, polyorganosiloxanes having such long-chain alkyl groups are easily degraded by heat.

Therefore, a grease composition using this as a base oil has lower heat resistance than one using only polydimethylsiloxane as a base oil, and discolors when heated.

By using an anti-aging agent and an organic acid or a metal salt thereof together as an additive, the present inventors further discovered that at least one of a specifically selected range of anti-aging agents can be used as an additive.
By using species, preferably two or more species in combination, it is possible to prevent deterioration of polyorganosiloxanes containing organic groups with low heat resistance such as long-chain alkyl groups and aralkyl groups. By using silica fine powder in combination, we have found that a larger amount of inorganic substances can be uniformly and stably dispersed in polyorcassiloxane, resulting in improved workability, resistance to separation, and heat resistance. The inventors discovered that it is possible to obtain a grease composition with heat dissipation properties, leading to the present invention.

That is, the present invention provides the following: (4) General formula (wherein R1 is a monovalent hydrocarbon group having 2 to 20 carbon atoms, R
2 represents a monovalent hydrocarbon group having fewer carbon atoms than R1, a + b is 19 to 27, the ratio of b to a + b is at least 0.05, and n is such that the polyorganosiloxane has the following viscosity: polyorganosiloxane having a viscosity at 25° C. of 10 to 1,000 cp, 10 to 50% by weight, based on the total amount with (B).

CB) Inorganic fine powder selected from the group consisting of Group 2 or Group 3 metals and their oxides, 50 to 90% by weight based on the total amount with (4).

0 Fatty acid having 8 or more carbon atoms or its metal salt, 0.01 to 10% by weight based on the total amount of (4) and [F]).

0 anti-aging agent, 0.0 for the total amount of (4) and (B).
1 to 10% by weight, and (8) hydrophobized fine silica powder;

The polyorganosiloxane (4) used in the present invention is represented by the general formula g', Rb5t04 a-b, and is generally linear, but may contain some branching.

The viscosity at 25°C is 10-10,0OOcp,
When used for heat dissipation, it is preferably 5OOcp or more.

If the viscosity is less than 10 cp, the grease composition tends to separate, and if it exceeds 10,000 cpr, workability deteriorates.

R1 in the formula is a monovalent hydrocarbon group having 2 to 20 carbon atoms, such as ethyl group, propyl group, butyl group, pentyl group, hexyl group, octyl group, decyl group, dodecyl group, tetradecyl group, octadecyl group, etc. Alkyl groups such as benzyl groups, α-phenethyl groups, β-phenethyl groups, β-phenylpropyl groups, alkenyl groups such as vinyl groups, propenyl groups, hexenyl groups, propynyl groups, butyl groups, hexynyl groups Examples include alkynyl groups such as , aryl groups such as phenyl groups, etc., but examples include alkynyl groups such as , and aryl groups such as phenyl groups. -14 alkyl or aralkyl groups are preferred.

In the general formula (4), a + b is 1.9 to 2.7, and the ratio of a to a + b is required to be at least 0.05, but the preferred range of the ratio of a to a + b is is 0.2 to 0.5.

In order to fill the composition with a large amount of inorganic material, R1 needs to be 5 moles or more of all the organic groups, and preferably 20 moles or more.

Further, from the viewpoint of ease of synthesis, it is preferable that the amount does not exceed 50 mol.

Furthermore, (4) is most preferable because of the nature of the grease composition in which each silicon atom except the terminal silicon atom has one R1 attached thereto, and from the ease of synthesis of the polyorganosiloxane.

R2 is a monovalent hydrocarbon group having fewer carbon atoms than R1, and is preferably a methyl group from the viewpoint of heat resistance and ease of synthesis.

(J3) is a group 2 or 3 metal or its oxide, and examples include zinc, aluminum, lead oxide, magnesium oxide, aluminum oxide, aluminum oxide, calcium oxide, etc. Zinc oxide or aluminum oxide is preferable because it is free from carbon dioxide and is easy to handle.

The blending ratio of (4) and (B) is selected from a range such that (B) weighs 50 to 90% by weight relative to the total amount of (4) and (B), and in particular, 70% It is preferable to be upwind by weight.

If the weight is less than 50%, heat resistance and heat dissipation will be poor.
Moreover, if the amount exceeds 90% by weight, the hardness of the composition increases and workability deteriorates.

(C) The fatty acid or its metal salt, when used in combination with the anti-aging agent (0), synergistically enhances the effect of improving the heat resistance of polyorganosiloxane and prevents its thermal deterioration, and also improves the grease composition. It is a component that allows polyorganosiloxane to be filled with a large amount of inorganic material without increasing hardness.

As fatty acids, those having 8 or more carbon atoms are effective, such as fatty acids such as lauric acid, myristic acid, palmitic acid, and stearic acid, as well as their lithium salts, magnesium salts, calcium salts, aluminum salts, and lead acid. Examples include salt.

The blending amount of (C) is based on the total amount of (4) and [F]),
The weight φ is 0.01 to 10.

If it is less than this range, the effect of filling the polyorganosiloxane with inorganic substances without increasing the hardness of the grease composition and the effect of improving heat resistance cannot be achieved. This is because there is a tendency.

0 anti-aging agents include 1,2-dihydro-2,2,4-trimethylquinoline, 4,4'-thio-bis-(6-tert-butyl- 3-methylphenol), 2-mercaptobenzimidazole, and the zinc salt of 2-mercaptobenzimidazole.

These anti-aging agents may be used alone or in combination of two or more types, but when used in combination, the effect can be dramatically enhanced by carefully selecting the types and proportions.

For example, a combination of 4,4'-thio-bis-(6-cushary-butyl-3-methylphenol) and 2-mercaptobenzimidazole, particularly in a weight ratio of 1:1 to 1:
The combination used in the proportion of 4,4,4'-thio-bis-(6
-tert-butyl-3-methylphenol) and 2-
A combination of zinc salts of mercaptobenzimidazole, especially a combination of both in a weight ratio of 1:1 to 1:5;
,2-dihydro-2,2゜4-trimethylquinoline and 2
The heat resistance of the grease composition can be further improved by using a combination of -mercaptobenzimidazole, particularly a combination in which both are used in a weight ratio of 1:1 to 1:3.

The blending amount of the anti-aging agent is 0.1 to 10 weight, preferably 0.1 to 2 weight more than the total amount of (4) and (B).

If it is less than 0.1% by weight, it will not be effective as an antioxidant, and if it exceeds 10% by weight, it will discolor at high temperatures or have an adverse effect on members with which the grease composition comes into contact.

The fine silica powder [F] used in the present invention is surface-treated with linear or cyclic polyorganosiloxanes, organosilazanes, silane compounds, organic acids, etc. It may be made by.

By adding this (Eiff1 minute), the stability of the grease composition is significantly improved.

That is, if a silicone composition containing a large amount of metal oxide is left for a long time, it will cause layer separation due to separation, but this can be prevented by adding a small amount of treated silica powder.

The effect becomes especially clear when used at high temperatures.

The amount to be mixed is 0.1 to 10% of the total amount of (4) and 2).
It's heavy.

If it is less than 0.1%, there is no effect, and if it exceeds 10%,
This is because it is difficult to mix the silica powder itself, and the grease composition becomes hard, reducing workability.

Conventionally, grease compositions that use polysiloxane containing long-chain alkyl groups or aralkyl groups as a base oil and add large amounts of inorganic fillers to improve heat dissipation have had poor heat resistance and stability. The invention improves this point and provides a heat dissipating grease composition with excellent heat resistance and stability.

In addition, compared to heat dissipating greases that use polydimethylsiloxane as a base oil and add large amounts of inorganic fillers, they are less hard, easier to work with, and have better paintability, and are used in applications that come into contact with room temperature vulcanizable silicone rubber It does not have an adverse effect on room temperature vulcanizable silicone rubber even when used in

The grease composition of the present invention is used as a heat dissipation grease for power transistors and power ICs, particularly those that use room temperature vulcanizable silicone rubber as a junction coating or thermally conductive rubber, and those that are used at high temperatures.

Examples of the present invention will be shown below.

All parts in the examples represent parts by weight.

Example 1 Composition 1 20 parts of polymethyldecylsiloxane (viscosity at 25° C. 1000 cp) whose terminal end is capped with a trimethylsilyl group and in which more than 50 moles of all the organic groups bonded to silicon atoms excluding the terminal group are decyl groups, oxidized 80 parts of zinc, 0.2 parts of 4,4'-thio-bis-(6-cushiary-butyl-3-methylphenol), 0.14 parts of 2-mercapto-benzimidazole, 0.5 parts of zinc stearate, and octamethyl Cyclotetrasiloxane treated dry silica fine powder 1.
A grease composition of 5 parts was prepared.

Composition 2 25 parts of polymethyldodecylsiloxane (viscosity 1500 cp at 25°C), terminals are capped with trimethylsilyl groups, and 40 moles φ of all organic groups bonded to silicon atoms excluding the terminal groups are dodecyl groups, 75 parts of zinc oxide Part, 4, 4
0.2 part of '-thio-bis-(6-tert-butyl-3-methylphenol), 0.6 part of zinc salt of 2-mercapto-benzimidazole, 0.5 part of magnesium stearate, and polydimethylsiloxane ( A grease composition was prepared from 2 parts of treated dry silica fine powder (viscosity 200 cp at 25°C).

Composition 3 Polymethyl β-phenethylsiloxane (2
25 parts (viscosity 4000 cp at 5°C), 75 parts aluminum oxide, 1 part 1,2-dihydro-2,2,4-1-limethylquinoline, 1 part stearic acid, hexamethyldisilazane treated fine dry silica powder 2 A grease composition was prepared consisting of:

Composition 4 Polymethylphenylsiloxane (25
20 parts (viscosity 3000 cp at °C), 80 parts aluminum oxide, 1 part 2-mercaptobenzimidazole,
A grease composition was prepared consisting of 1 part of lithium palmitate and 1.5 parts of octamethylcyclotetrasiloxane-treated wet silica fine powder.

Composition 5 30 parts of polymethyloctylsiloxane (viscosity at 25° C., 000 cp) in which the terminals are capped with trimethylsilyl groups and 50 moles of all organic molecules bonded to silicon atoms excluding the terminal groups are octyl groups, 70 parts of zinc oxide Part, 4, 4
'-thio-bis-(6-cushiary-butyl-3-methylphenol) 0.6 parts, magnesium myristate 1.
5 parts, hexamethyldisilazane-treated wet silica fine powder 1
A grease composition was prepared from the following parts.

Composition 6 The terminals are capped with trimethylsilyl groups, and 25 molar proportions of all the organic groups bonded to silicon atoms excluding the terminals are butyl groups, 2
Polymethylbutyl β in which 5 moles φ are β-phenethyl groups
- phenethylsiloxane (viscosity 6oo at 25°C)
cp) 30 parts, aluminum powder 50 parts, zinc oxide 20 parts
0.2 parts of 1,2-dihydro-2,2,4-trimethylquinoline, 0.4 parts of 2-mercaptobenzimidazole, 0.5 parts of zinc stearate, and 3 parts of octamethylcyclotetrasiloxane-treated fine dry silica powder. A grease composition was prepared consisting of:

Composition 7 (Comparative Example) Composition 7 was prepared by removing the aging agent from Composition 1 above.

Composition 8 (Comparative Example) Composition 8 was prepared by removing magnesium stearate from Composition 2 above.

Composition 9 (Comparative Example) Composition 9 was prepared from the above composition 5 by removing the hexamethyldisilazane treated ** wet silica powder.

Table 1 shows the results of one test of heat resistance, discoloration, oil separation, and layer separation using Compositions 1 to 6 and Comparative Example Compositions 7 to 9.

Example 2 Compositions 10 to 14 Composition 1 was prepared with the same composition except that 0.6 part of the following anti-aging agent was used in place of the two anti-aging agents in Composition 1.
0 to 13 were obtained.

Composition 1.04,4',-thio-bis-(6-cushary-butyl-3-methylphenol) Composition 112-mercapto-benzimidazole Composition 12 2,6-di-tert-butyl-4-
Methyl-phenol composition 13 dilaurylthiodipropionate and
In place of the two anti-aging agents in composition 6, 1,2-
Dihydro-2,2,4-trimethylquinoline only 0.6
Composition 14 was obtained.

The results of the same tests as in Example 1 performed on the above compositions 10 to 14 are shown together with the results of composition 1.6 and comparative sample 7, which were tested at the same time.

Example 3 The worked penetration and thermal conductivity according to JIS K2560 were measured for Compositions 1 to 6 used in Example 1 and Comparative Example Compositions 15 to 17 prepared from polydimethylsiloxane and zinc oxide. did.

However, Comparative Example Compositions 15 to 17 were adjusted according to the blending ratios shown in Table 3.

The measurement results are shown in Table 4.

The composition according to the invention has a much higher thermal conductivity at the same hardness than a comparative sample based on polydimethylsiloxane.

Example 4 Compositions 18 to 22 were prepared by varying the amounts of 1,2-dihydro-2,2°4-trimethylquinoline and 2-mercaptobenzimidazole in Composition 6 as shown in Table 5.

The same experiment as in Example 1 was conducted using these and Composition 6.

The results are shown in Table 6.

Claims (1)

[Scope of Claims] (In the formula, R1 is a monovalent hydrocarbon group having 2 to 20 carbon atoms, R
2 represents a monovalent hydrocarbon group with fewer carbon atoms than R1, a + b is 1.9 to 2.7, the ratio of a to a + b is at least 0.05, and n is the viscosity of the polyorganosiloxane as follows: Polyorganosiloxane having a viscosity at 25° C. of 10 to 10,000 ep, expressed as 10 to 50% by weight, based on the total amount of CB). (b) Inorganic fine powder selected from the group consisting of Group 2 or Group 3 metals and their oxides, 50 to 90% by weight based on the total amount with (4). (0 Fatty acid with 8 or more carbon atoms or its metal salt (4) and 0
0.01 to 10 weight φ with respect to the total amount of 3). 01.2-dihydro-2,2,4-trimethylquinoline, 4,4-thio-bis(6-tert-butyl-3-
methylphenol), 2-mercaptobenzimidazole, and one or more anti-aging agents selected from the group consisting of zinc salts of 2-mercaptobenzimidazole, based on the total amount of (4) and (3). 1 to 10% by weight [F] A grease composition consisting essentially of hydrophobized fine silica powder, 0.1 to 10% by weight based on the total amount of (4) and (B). 2. The composition according to claim 1, wherein R1 in 2(A) is an alkyl group or an aralkyl group having 4 to 14 carbon atoms. 3(A) a The ratio of a to ten is 0.2 to 0.5
The composition according to claim 1, which is Claim 1, wherein R2 in 4(A) is a methyl group
Compositions as described in Section. Claim 1, wherein 5(B) is a metal oxide selected from the group consisting of zinc oxide and aluminum oxide.
Compositions as described in Section. 6. The anti-aging agent is a blend of 4,4'-thio-bis-(6-cushary-phthyl-3-methylphenol) and 2-methicaptopenzimidazur in a weight ratio of 1:1 to 1:4. , the composition according to claim 1, wherein the anti-aging agent is a zinc salt of 4,4'-thio-bis-(6-tert-phthyl-3-methylphenol)to-2-mercaptobenzimidazur. Weight ratio of 1:1 to 1:5
A composition according to claim 1, which is a formulation of. 8 Anti-aging ■), cutting 1,2-dihydro-2,2,4-
The composition of claim 1, which is a blend of trimethylquinoline and 2-mercaptobenzimidazole in a weight ratio of 1:1 to 1:3.