JP2003321694A - Grease composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a grease composition which is used for lubricating mechanical parts performing rolling movements and having steel portions to be lubricated, can prevent the peeling of the steel portions due to metal fatigues caused by the thinning of oil films without thickening the oil films, and can thereby elongate the peeling-resistant lives of the steel portions. <P>SOLUTION: This grease composition used for lubricating the mechanical parts performing rolling movements and having steel portions to be lubricated is characterized by comprising a base oil, a thickener, and an organic sulfonate. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grease composition used for lubrication of a machine part having a steel lubricated portion that performs rolling motion, and particularly to a grease composition capable of prolonging the peeling life of the lubricated portion. Regarding things.

[0002]

2. Description of the Related Art Rolling bearings, ball screws, linear motion guide bearings, etc. are typical mechanical parts having a lubricated portion made of steel for rolling motion. On the other hand, opposite to the rolling motion, there is a sliding motion. The life here is not abrasion but mainly wear and seizure. As typical examples of mechanical parts for sliding motion, journal bearings (sliding bearings),
Examples include pistons, screws, ropes and chains.
The peeling life of the steel lubricated part that performs rolling motion is the life due to metal fatigue, and thickening the lubricating oil film has long been the only means to complete this life. Therefore, the grease used to lubricate the lubricated portion has conventionally been required only to have a sufficiently thick oil film, that is, to use a base oil having a sufficiently high viscosity.

On the other hand, recently, as described in Japanese Patent No. 2878749 (JP-A-3-210394),
The bearing for an automobile alternator was found to be a problem due to the peculiar peeling that causes an early life without the usual metal fatigue as described above. This is considered to be peeling due to hydrogen embrittlement,
The publication proposes an attempt to eliminate or reduce this specific peeling by using a grease to which a passivating oxidant is added. As a specific example, an example of adding sodium nitrite is disclosed. . However, in the general metal fatigue peeling, when the oil film becomes thin, the fine protrusions on the surface come into contact with each other, and peeling from the surface is likely to occur, resulting in a shorter life. The oil film thickness approaches zero infinitely when the speed of mechanical parts is zero. This state of zero speed is a state frequently seen in actual mechanical parts due to repeated start / stop and reciprocating rocking motion. No grease composition is known that extends the peeling life when the oil film becomes thin.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a grease composition used for lubricating a machine part having a lubricated portion made of steel which performs rolling motion. Another object of the present invention is to provide a grease composition capable of preventing peeling due to metal fatigue caused by thinning of the oil film, regardless of thickening of the oil film, and extending the peeling life. .

[0005]

SUMMARY OF THE INVENTION The present invention is a grease composition used for lubrication of a machine part having a lubricated portion made of steel which is in rolling motion, which comprises a base oil, a thickener, and an organic sulfone. The present invention provides a grease composition containing an acid salt. As described above, the peeling life due to metal fatigue has been conventionally fulfilled by increasing the oil film of grease, but the present invention does not require thickening of the oil film by adding a specific compound. A grease composition that can achieve the above object.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The organic sulfonate used in the present invention is a salt of sulfonic acid having an organic group which is a lipophilic group. Such organic sulfonates include petroleum sulfonic acids obtained by sulfonation of aromatic hydrocarbon components in lubricating oil distillates and synthetic sulfonic acids such as dinonylnaphthalene sulfonic acid and heavy alkylbenzene sulfonic acid. Can be mentioned. Organic sulfonates include metal salts, basic metal salts, and highly basic metal salts (base number 50 to 500 mg KOH
/ G), ammonium salts, amine salts and the like. Specific examples thereof include alkaline earth metal salts such as Ca, Mg and Ba, alkali metal salts such as Na, K and Li, Zn salt and Pb.
Examples thereof include salts, highly basic Ca salts, ammonium salts, and amine salts such as ethylenediamine. The basic or highly basic sulfonate is one in which fine particles of calcium carbonate, calcium hydroxide or the like are dispersed in the sulfonate in order to have an acid neutralizing action. Organic sulfonates can also be used.

The organic sulfonate used in the present invention is
It is often used as a main additive of so-called rust preventive oil for the purpose of temporarily preventing rust in the storage, transportation, and maintenance of metal products. For grease that requires rust prevention,
It is commonly used as well as other rust inhibitors. However, the organic sulfonate itself does not have effects such as extreme pressure property and friction reduction, and is not an additive used for the purpose of improving lubricity. As far as the present inventor knows, there is no report or disclosure that the organic sulfonate itself prolongs the peeling life of steel due to metal fatigue.

In the grease composition of the present invention, the organic sulfonates may be used alone or in combination of two or more kinds. In the grease composition of the present invention, the content of the organic sulfonate is preferably 0.1 to
It is 10% by mass, more preferably 0.5 to 5% by mass. If the amount is less than 0.1% by mass, the effect is insufficient, and even if 10% by mass or more is added, the effect is saturated.

The thickener used in the grease composition of the present invention is not particularly limited. As a preferable example, L
Soap thickeners represented by i soap and complex Li soap, urea thickeners represented by diurea, inorganic thickeners represented by organic clay and silica, PT
Examples include organic thickeners represented by FE. Particularly preferred are urea thickeners. Recently,
A grease composition containing a urea thickener is often used for applications requiring peel resistance. this is,
It is presumed that this is due to the rolling surface protection of the urea compound, and when a urea-based thickener is used in the present invention,
The effect of improving the peeling life is more remarkable. Further, the urea-based thickener has few defects as compared with other thickeners, is relatively inexpensive, and is highly practical. The content of the thickener in the grease composition of the present invention varies depending on the type of the thickener. The consistency of the grease composition of the present invention is
200 to 400 is preferable, and the content of the thickener is the amount necessary to obtain this consistency. The content of the thickener in the grease composition of the present invention is usually 3 to 30% by mass, preferably 5 to 25% by mass.

The base oil used in the grease composition of the present invention is also not particularly limited. For example, all base oils including mineral oils can be used. In addition to mineral oils, ester-based synthetic oils such as diesters and polyol esters, poly-α-olefins, synthetic hydrocarbon oils such as polybutene, alkyl diphenyl ethers, ether-based synthetic oils such as polypropylene glycol, silicone oils, and fluorinated oils. Various synthetic oils such as oil can be used.

If desired, various additives can be added to the grease composition of the present invention. Examples of such additives include antioxidants, rust inhibitors, metal corrosion inhibitors, oiliness agents, antiwear agents, extreme pressure agents, solid lubricants, and the like.

In the grease composition of the present invention, there are still many unclear points regarding the mechanism by which the organic sulfonate improves the metal fatigue life, but at the present stage, the following reasoning can be considered. The main function of the rust preventive agent is to form a dense adsorption film on the metal surface and prevent the metal from coming into contact with water or oxygen and rusting. In particular organic sulfonate rust resistant strongly polar group (-SO ₃ ^-) has a, other rust inhibitors,
For example, it seems that a strong adsorption film is formed even when compared with an ester (alcohol) or amine type. Therefore, it is considered that a film is formed on the iron oxide layer in the lubricated portion to protect the hard and dense iron oxide layer, so that peeling can be effectively prevented even when the oil film is thin. As mentioned above,
The organic sulfonate of the present invention forms a coating on the iron oxide layer in the lubricated portion and protects the hard and dense iron oxide layer, thereby extending the peeling life without increasing the oil film thickness. It is considered possible.

Examples 1 to 7 and Comparative Examples 1 to 5 As shown in Tables 1 and 2, a base grease was mixed with a predetermined amount of an additive and mixed well, and kneaded with a three-roll mill to prepare a grease composition. Was manufactured. Base grease A Thickener: Diurea base oil: P-based mineral oil, 230mm ² / s @ 40 ° C Consistency: No. 1 Grade B Thickener: Li soap base oil: P-based mineral oil, 230mm ² / s @ 40 ° C Consistency: No. 1 grade additive C Dinonylnaphthalene sulfonic acid calcium salt (KING
INDUSTIRES NASUL 729) D Dinonylnaphthalene sulfonic acid zinc salt (KING INDUS
TIRES NASUL ZS) E Dinonylnaphthalene sulfonic acid ammonium salt (KI
NG INDUSTRIES NASUL AS) F Highly basic organic sulfonic acid calcium salt (Witco Br
yton C-400C), G sorbitan monooleate (NOF OP made by NOF CORPORATION)
(80R)

Evaluation test method Rolling four-ball test Outline of test method Three steel balls for bearings each having a diameter of 15 mm were prepared, and an inner diameter of 36.
It is placed in a cylindrical container having an inner diameter of 0 mm, an inner diameter of 31.63 mm at the upper end and a depth of 10.95 mm, and 20 g of test grease is applied.
When one φ5 / 8 inch steel ball for bearing is brought into contact with these three steel balls and rotated at a predetermined rotation speed, the lower three steel balls revolve while revolving. This is continuously rotated until peeling occurs on the steel spherical surface. * Peeling occurs between balls with the highest surface pressure. * The service life is the total number of rotations when peeling occurs. Test condition Test steel ball: φ5 / 8in bearing steel ball (rotating ball), φ15mm
Steel ball for bearing (driven ball) Test load (W): 400kgf (6.5GPa) * Rotation speed (n): 1500rpm Number of test repetitions: 5 (average life: average of n = 5) * Maximum between balls Hertz pressure. The value of 6.5 GPa is a very high surface pressure and the oil film is in a considerably thin state. The composition of the grease and the test results are shown in Tables 1 and 2.

[0015]

[Table 1] <Example>

[0016]

[Table 2] <Comparative example>

Consideration Urea-based base grease A is used (Examples 1 to 1)
3, 5, 6 and Comparative Examples 1, 3) have a longer peel life than those using the Li soap base grease B (Example 4, Comparative Example 2) (Examples 3 and 3). Four
And the comparison between Comparative Example 1 and Comparative Example 2). Although some differences are recognized depending on the base grease, when the organic sulfonate of the present invention is added, the peel life is about 1.5-4.
It can be seen that the length is doubled (comparison between Examples 1 to 3 and Comparative Example 1, and comparison between Example 4 and Comparative Example 2).

Comparative Example 3 uses sorbitan monooleate and exhibits only a peel life equivalent to that of Comparative Example 1 without the additive. As described above, the effect of prolonging the peeling life of the organic sulfonate of the present invention is remarkable, and when the urea-based thickener is used (Examples 1-3, 5 and 6).
Turns out to be particularly good.

[0019]

The grease composition of the present invention can prolong the peeling life regardless of the thickening of the oil film.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) // C10N 10:04 C10N 10:04 50:10 50:10 (72) Inventor Shinya Kondo Fujisawa City, Kanagawa Prefecture Tsujido Kamidai 1-4-1, Kyodo Yushi Co., Ltd. in the Tsujido Factory (72) Inventor Junichi Imai 1-4-1, Tsujido Jindai, Fujisawa-shi, Kanagawa K-Dono Yushi Co., Ltd. F Term (reference) 4H104 AA17C BE13B BG06C DA02A DB07C DB02C07 EB02 EB06 FA02 QA18

Claims (3)

[Claims] 1. A grease composition used for lubrication of a machine part having a lubricated portion made of steel which performs rolling motion, comprising a base oil, a thickener, and an organic sulfonate. And a grease composition. 2. The grease composition according to claim 1, wherein the organic sulfonate is a calcium salt, a zinc salt, an ammonium salt, or a highly basic calcium salt. 3. The grease composition according to claim 1, wherein the thickener is a urea compound.