JPH11256184A - Grease composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a grease composition having a high dropping point, a long oxidation life, capable of maintaining excellent lubricating characteristics for a long period of time, useful for a bearing and a motor of general purposes, by mixing a base oil with a thickening agent, an antioxidant and an aromatic dibasic acid (metal salt). SOLUTION: This grease composition is obtained by mixing (A) a base oil (e.g. a purified mineral oil or a synthetic oil having % CA of <=1% and <=20 ppm sulfur content and 5-500 cst viscosity at 40 deg.C) with (B) a thickening agent [e.g. a metallic soap obtained by saponifying a 12-24C fatty acid with an alkaline (earth) metal], (C) an antioxidant (e.g. a dithiocarbamate-based antioxidant, an amine-based antioxidant or a phenol-based antioxidant) and (D) an aromatic dibasic acid (metal salt) except lithium terephthalate. Preferably, the composition comprises 2-40 wt.% of the component B, 0.1-10 wt.% of the component C and 0.3-21 wt.% of the component D.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a grease composition, and more particularly to a grease composition having a high dropping point and a long oxidation life.

[0002]

2. Description of the Related Art Grease is widely used in various machines such as automobiles, electric equipment, construction machines, machine tools, etc., but the miniaturization, high output, light weight, and easy maintenance of machines are required year by year. Grease lubrication conditions are becoming increasingly severe. The downsizing of the machine and the increase in output mean that the dimensions and shape become smaller even with the same output. In addition, a material that does not conduct heat, such as a non-metal, is used to reduce the weight, which results in an increase in temperature. Further, the simplification of the maintenance means the extension of the service life, and therefore, the extension of the oxidation life and the extension of the lubrication characteristics are required. For these reasons, greases having a high dropping point, a long oxidation life, and long-lasting lubricating properties have been demanded.

Hitherto, various high drop point greases have been proposed. For example, Japanese Patent Publication No. 63-19560 discloses a grease in which a lithium salt of a hydroxy fatty acid, a lithium salt of an aliphatic dicarboxylic acid and a metal detergent are mixed and dispersed, but it is still insufficient to meet recent severe conditions. It is. On the other hand, improvement of the life extension of lubrication properties has also been proposed. For example, JP-A-54-6002 discloses a grease composition in which a lithium soap of a fatty acid and a lithium aromatic carboxylate are mixed. However, as the lithium aromatic carboxylate soap, specifically, lithium benzoate, the grease obtained from this is still insufficient in dropping point, and the life of lubrication properties is not satisfactory. .

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and has as its object to provide a grease composition having a high dropping point, a long oxidation life and a long-term lubricating property.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a base oil comprising a thickener, an antioxidant such as a dithiocarbamate, an amine or a phenol, and an aromatic dibasic acid or a metal salt of an aromatic dibasic acid. However, it is a grease composition containing (excluding lithium terephthalate) a base oil.
6% by weight, thickener 2-40% by weight, antioxidant 0.
1 to 10% by weight, aromatic dibasic acid or metal salt of aromatic dibasic acid (excluding lithium terephthalate) 0.3 to
Consists of 21% by weight.

[0006]

Embodiments of the present invention will be described below. The present invention relates to a base oil comprising a thickener, an antioxidant and an aromatic dibasic acid or a metal salt of an aromatic dibasic acid (however,
(Excluding lithium terephthalate).

Here, the base oil used in the present invention is not particularly limited, and any of conventionally known mineral oils and synthetic oils can be used. For example, mineral oils such as paraffinic, intermediate or naphthenic oils and the like can be used. Refined mineral oil obtained by solvent refining or hydrotreating these mineral oils, hydrocarbon-based synthetic oils such as α-olefins, oils and fats, synthetic esters, synthetic ethers, and the like can be used. Among these, refined mineral oil and synthetic oil are preferred. More specifically, the% C of the base oil
It is desirable that A is 1% or less, preferably 0.5% or less. Further, it is desirable that the sulfur content in the base oil is 20 ppm or less, preferably 10 ppm or less.
The viscosity of the base oil is not particularly limited, but may be appropriately selected from the range of usually 5 to 500 cst at 40 ° C., preferably 20 to 400 cst.

Next, the thickener is not particularly limited, and either a soap type or a non-soap type can be used. Examples of the soap system include metal soaps in which a fatty acid is saponified with a metal hydroxide such as an alkali metal or an alkaline earth metal. Examples of the metal include sodium, calcium, lithium, aluminum and the like, and examples of the fatty acid include oils and fats, crude fatty acids obtained by hydrolyzing the oil and removing glycerin, monocarboxylic acids such as stearic acid, and 12-hydroxystearic acid. And dibasic acids such as azelaic acid. Among them, those having 12 to 2 carbon atoms
4 fatty acids can be suitably used. These may be used alone or in combination.

Specifically, a lithium soap using 12-hydroxystearic acid and a lithium composite soap using 12-hydroxystearic acid and azelaic acid are preferred. When compounding this thickener, the fatty acid and the metal hydroxide may be added to the base oil and saponified in the base oil. This thickener is usually 2 to 40% by weight, preferably 3 to 20% by weight in the grease composition.
Mix. Thickener is intended to impart consistency, the desired consistency is not obtained if the amount is too small,
On the other hand, if the amount is too large, the lubricity of the grease is reduced.

In the present invention, an aromatic dibasic acid or a metal salt of an aromatic dibasic acid (excluding lithium terephthalate)
Is blended. Here, as the aromatic dibasic acid or the aromatic dibasic acid of the metal salt of the aromatic dibasic acid, those having 8 to 18 carbon atoms can be used. For example, terephthalic acid, phthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid can be mentioned, and terephthalic acid is preferable. The metal base of the metal salt of an aromatic dibasic acid contains a metal,
There is no particular limitation as long as it reacts with an aromatic dibasic acid to form a salt. Specific examples include hydroxides and carbonates of alkali metals such as lithium and sodium, alkaline earth metals such as magnesium and calcium, Group Ib metals such as copper, and Group IIb metals such as zinc. As the metal substrate, lithium hydroxide and its monohydrate, lithium carbonate, calcium hydroxide, zinc hydroxide and the like are preferable, and lithium hydroxide is particularly preferable.

Specific examples of the aromatic dibasic acid or the metal salt of the aromatic dibasic acid include sodium terephthalate, magnesium terephthalate, calcium terephthalate, zinc terephthalate, lithium isophthalate, sodium isophthalate, magnesium isophthalate, and the like. Calcium isophthalate, zinc isoterephthalate, lithium 2,6 naphthalenedicarboxylate, sodium 2,6 naphthalenedicarboxylate, magnesium 2,6 naphthalenedicarboxylate,
Examples thereof include calcium 2,6 naphthalenedicarboxylate and zinc 2,6 naphthalenedicarboxylate. Among these, calcium terephthalate, zinc terephthalate, lithium isophthalate, calcium isophthalate,
Zinc isoterephthalate, lithium 2,6 naphthalenedicarboxylate, calcium 2,6 naphthalenedicarboxylate,
Zinc 2,6 naphthalenedicarboxylate is preferred.

The aromatic dibasic acid or the metal salt of the aromatic dibasic acid is usually added to the metal base in an amount of 0.1 equivalent to 1 equivalent of the aromatic dibasic acid.
It is obtained by blending about 8 to 1.2 equivalents. For example, in the case of calcium terephthalate, the equivalent of terephthalic acid is usually equivalent to about 0.8 to 1.2 equivalents of calcium hydroxide,
Preferably, it is preferable to mix them in substantially the same equivalent. For example, it is preferable to use about 1.8 parts by weight of calcium hydroxide with respect to 4 parts by weight of terephthalic acid.

A high drop point grease can be obtained by blending the aromatic dibasic acid or the metal salt of the aromatic dibasic acid. The compounding amount of these aromatic dibasic acids or metal salts thereof is 0.3 to 21% by weight, preferably 3 to 9% by weight in the grease composition. If the amount is too small, the oxidation life may not be improved. If the amount is too large, the life of the bearing may be adversely affected.

In the present invention, an antioxidant is blended. The antioxidant is not particularly limited, and examples thereof include an amine antioxidant and a phenolic antioxidant. Examples of the amine antioxidant include monooctyldiphenylamine; monoalkyldiphenylamine such as monononyldiphenylamine; 4,4′-dibutyldiphenylamine; 4,4′-dipentyldiphenylamine;
4,4'-diheptyldiphenylamine;4,4'-dioctyldiphenylamine; dialkyldiphenylamines such as 4,4'-dinonyldiphenylamine;tetrabutyldiphenylamine;tetrahexyldiphenylamine;tetraoctyldiphenylamine; tetra Polyalkyldiphenylamines such as nonyldiphenylamine, α-naphthylamine; phenyl-α-naphthylamine; butylphenyl-α-naphthylamine; pentylphenyl-α-naphthylamine; hexylphenyl-α-naphthylamine; heptylphenyl-α-naphthylamine; octylphenyl- α-naphthylamine; nonylphenyl-α-
Examples include naphthylamines such as naphthylamine, and among these, monoalkyldiphenylamines, dialkyldiphenylamines, and naphthylamines are preferred.

Examples of the phenol antioxidant include 4,4'-methylenebis (2,6-di-t-butylphenol); 4,4'-bis (2,6-di-butylphenol); Bis (2-methyl-6-t-butylphenol); 2,2'-methylenebis (4-ethyl-
2,2'-methylenebis (4-methyl-6-t-butylphenol); 4,4 '
-Butylidenebis (3-methyl-6-t-butylphenol); 4,4'-isopropylidenebis (2,6-di-t-butylphenol); 2,2'-methylenebis (4-methyl-6-nonylphenol); 2,2′-isobutylidenebis (4,6-dimethylphenol);
Bisphenols such as 2,2'-methylenebis (4-methyl-6-cyclohexylphenol) and 2,6-di-
t-butyl-4-methylphenol; 2,6-di-t-
Butyl-4-ethylphenol; 2,4-dimethyl-6
-T-butylphenol; 2,6-di-t-amyl-p
-Alkyl phenols such as cresol, 2,6-di-t
-Butyl-4- (N, N'-dimethylaminomethylphenol);4,4'-thiobis (2-methyl-6-t-
4,4'-thiobis (3-methyl-6-t-butylphenol); 2,2'-thiobis (4-methyl-6-t-butylphenol); bis (3
-Methyl-4-hydroxy-5-t-butylbenzyl)
Sulfide; bis (3,5-di-t-butyl-4-hydroxybenzyl) sulfide; n-octadecyl-3-
(4-hydroxy-3,5-di-t-butylphenyl)
Propionate; 2,2'-thio [diethyl-bis-3
-(3,5-di-t-butyl-4-hydroxyphenyl) propionate]. Among these, bisphenols and alkylphenols are particularly preferred.

As the metal salt antioxidant, for example, the following formula (I)

Embedded image

Wherein M is a metal such as Ni or Zn;
x is the valence of the metal, and R ₁ and R ₂ each have 3 carbon atoms.
Represents up to 20 alkyl groups or alkenyl groups, and R ₁ and R ₂ may be the same or different. ),
More specifically, the following formula (II)

[0018]

Embedded image

(Wherein R ₁ and R ₂ each have 3 to 3 carbon atoms)
Represents 20 alkyl groups or alkenyl groups, and R ₁ and R ₂ may be the same or different. ), And more specifically, nickel dibutyldithiocarbamate,
Examples include carbamate antioxidants such as zinc dibutyldithiocarbamate and metal phosphate antioxidants such as zinc dialkyldithiophosphate and nickel dialkyldithiophosphate. Of these, amine antioxidants, phenolic antioxidants, and carbamate antioxidants are preferred.

These antioxidants can be used alone or as a mixture of two or more, but it is particularly preferred to use a mixture of two or more antioxidants. When two or more antioxidants are used in combination, the combination is not particularly limited, but an antioxidant selected from the respective amine antioxidants, phenolic antioxidants or carbamate antioxidants. Are preferably used in combination of two or more, and it is particularly preferable to use an antioxidant selected from each of an amine antioxidant and a carbamate antioxidant.

The amount of the antioxidant is usually about 0.1 to 10% by weight in the grease composition, preferably 0.2 to 10% by weight.
~ 5% by weight. If the amount is too small, the desired antioxidant effect cannot be obtained, and if it is too large, deterioration is accelerated. In the present invention, an aromatic dibasic acid or a metal salt of an aromatic dibasic acid (excluding lithium terephthalate) and the above-mentioned antioxidant, especially two or more kinds of antioxidants are used in combination to form a compound. It exhibits excellent antioxidant performance, prolongs oxidation life, and maintains lubrication properties for a long time.

The grease of the present invention can be manufactured, for example, as follows. First, a thickener is added to the base oil. When compounding the thickener, the base oil is mixed with a fatty acid as a raw material of the thickener, and a metal hydroxide such as lithium hydroxide / monohydrate is added at 80 ° C to 110 ° C to form the thickener. May be blended. After blending the thickener with the base oil, an aromatic dibasic acid such as terephthalic acid or an aromatic dibasic acid such as terephthalic acid and calcium hydroxide or lithium hydroxide monohydrate are added at a temperature of about 80 ° C. to 110 ° C. And then heated to 190 ° C. to 215 ° C., cooled, and then charged with an antioxidant. In addition, a dispersant can be added during the compounding process.

Here, as the dispersant, for example, a sulfonate, salicylate, phenate or phosphonate of an alkali metal or an alkaline earth metal can be used regardless of whether it is basic or neutral. Here, examples of the alkali metal include lithium, sodium, and potassium, and examples of the alkaline earth metal include calcium, magnesium, and barium. Of these, sodium, barium or calcium sulfonates are preferred. As other dispersants, sulfonic acid, succinimide, borated succinimide obtained by treating the succinimide with a boron compound, and the like can also be preferably used.
These may be used alone or in combination.

This dispersant is for dispersing the thickener uniformly in the oil or dispersing the oil and insolubles generated during use of the grease. If the dispersant is too small, the effect cannot be expected. If too much, there is a problem that water resistance is deteriorated. Therefore, the amount of the dispersant is usually 0.1 to 5% by weight in the grease composition. Other additives can be added to the grease composition of the present invention. For example,
As rust inhibitors, sorbitan esters, oxidized waxes and metal salts thereof, lanolinic acid soaps, and the like can be mentioned. As extreme pressure additives, sulfide oils, sulfide mineral oils, phosphites, acid phosphates, phosphates, dithiocarbamic acids and metal salts thereof , Dialkyldithiophosphate metal salts, and the like. Examples of the oleaginous agent include fatty acids and esters thereof. In addition, other additives may be blended according to the purpose. Examples thereof include dyes and fragrances. The amount of these components is usually 0.001 to 10% by weight in the grease composition. Some dispersants can be used as detergents and rust preventives. These additives that perform a plurality of functions may be used in appropriate combination.

[0025]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Various Performance Test Methods in Examples and Comparative Examples (1) Consistency Measured in accordance with JIS K-2220. (2) Dropping point Measured according to JIS K-2220. (3) Accelerated oxidation test Measured at a test temperature of 125 ° C. in accordance with JIS K-2220. That is, using a grease oxidation stability tester, 5% by weight of copper powder was added to the prepared grease, and oxygen was added to 0.1 g.
It was sealed at 755 MPa, and the time required for a sudden pressure drop at 125 ° C. was measured, and this was defined as the oxidation life. (4) Bearing life test (ASTM D1741) Specified load (thrust: 25 lb) using 6306 bearing
s), 125 ° C., 20-hour operation / 4-hour stop cycle,
When operating at 3500 rpm, the number of hours during which operation was impossible due to seizure was measured.

[Examples 1 to 7] A base oil, a thickener and a dispersant were charged into a reaction vessel at the compounding ratio shown in Table 1 and the mixture was heated at 90 ° C.
Then, the aromatic dibasic acid and the metal base material were added in the mixing ratio shown in Table 1 and treated at 190 ° C., and then the antioxidant shown in Table 1 was added. I got something. The above test was performed for each. The results are shown in Table 1. [Comparative Example 1] A test was conducted in the same manner as in Example 1, except that azelaic acid was used instead of terephthalic acid and lithium hydroxide monohydrate was used instead of calcium hydroxide as the metal base material. Was done. The results are shown in Table 2.

[0027]

[Table 1]

[0028]

As will be understood from the examples, comparative examples and reference examples, the grease composition of the present invention has a high dropping point, a long oxidation life, a long bearing life, and a long-lasting lubricating property. You. Therefore, it can be suitably used for bearings, general-purpose motor grease, and the like.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C10M 129: 52) C10N 10:16 30:06 30:10 40:02 50:10

Claims (7)

[Claims] 1. A grease composition comprising a base oil and a thickener, an antioxidant and an aromatic dibasic acid or a metal salt of an aromatic dibasic acid (excluding lithium terephthalate). 2. A thickener of 2 to 40% by weight, an antioxidant of 0.1 to 10% by weight, an aromatic dibasic acid or a metal salt of an aromatic dibasic acid (excluding lithium terephthalate).
2. The grease composition according to claim 1, wherein the grease composition comprises 3 to 21% by weight. 3. The grease composition according to claim 1, wherein the% CA of the base oil is 1% or less. 4. The base oil has a sulfur content of 20 ppm.
The grease composition according to any one of claims 1 to 3, which is as follows. 5. The antioxidant according to claim 1, wherein the antioxidant is at least one selected from the group consisting of a dithiocarbamate antioxidant, an amine antioxidant, and a phenol antioxidant. Grease composition. 6. The antioxidant is a combination of at least two antioxidants selected from at least two of dithiocarbamate antioxidants, amine antioxidants and phenolic antioxidants. The grease composition according to any one of claims 1 to 4. 7. The antioxidant according to claim 1, wherein the antioxidant is a combination of at least one selected from dithiocarbamate antioxidants and at least one selected from amine antioxidants. Grease composition.