JP5002195B2 - Grease composition - Google Patents

Description

  The present invention relates to a grease composition containing squalene. Specifically, the present invention relates to a grease composition that is suitably used for a lubrication part of a clutch or a torque limiter mechanism and has a high friction coefficient and excellent wear resistance.

Cars have been made lighter in consideration of environmental problems on the earth, and as a result, clutches and torque limiter mechanisms have been applied to various locations, and the number of operations has increased. . On the other hand, idling STOP that stops the engine when the signal is stopped, a hybrid vehicle, and the like have been put into practical use as countermeasures for exhaust gas from automobiles, which is one of the causes of global warming. In this case, in the case of idling STOP, the engine is started by the starter every time a signal is retransmitted from the stop of the signal, and the frequency is predicted to be 10 times or more the current level.
Of the clutch or torque limiter mechanism in which the grease composition is used, the place where the torque is the largest and the usage conditions are severe is the clutch of the engine starter of the automobile. The grease composition used in this part is (1) high coefficient of friction, (2) low temperature dependence of kinematic viscosity, etc. Silicone oil (dimethylsilicone or phenyl 5% methylsilicone) A grease composition based on a base oil is mainly used (see, for example, Patent Documents 1, 2, and 3). This is because the friction coefficient of silicone oil is high, but the surface tension of silicone oil is 20 to 25 dyn / cm ² , which is small compared to other oils. There are features. Currently, engine starter clutches that use commercially available silicone grease have a durability of about 3 to 50,000 times in the market. However, when idling STOP is incorporated, the high use frequency makes it a short period ( In several years), the clutch wears out and no torque is transmitted. As a result, the motor runs idle and the engine does not start.

It has also been proposed to use squalane grease using squalane saturated by hydrogenation of the squalene double bond as a watch oil (see, for example, Patent Document 4). However, there is a problem when grease based on squalane is used for the engine starter clutch. That is, squalane has a higher kinematic viscosity than squalene, and the influence of kinematic viscosity on the temperature is large, so the lubricating film becomes thicker and does not come into metal contact particularly under low temperature conditions (−40 ° C.), and the clutch is idle. Torque cannot be transmitted.
In addition, low-viscosity ester oil, naphthenic mineral oil, or the like is used in places where the absolute value of torque to be transmitted is small (see, for example, Patent Documents 5, 6, and 7). In addition to the metal contact (boundary lubrication state) described above, there is a traction drive that utilizes the traction force of the lubricant between metals as a torque transmission method.
However, as the clutch and torque limiter mechanisms become smaller and lighter and the usage conditions become more severe, the grease composition used in these mechanical components does not use silicone oil, has a high friction coefficient, and wear resistance. Development of a grease composition with excellent thermal stability and low temperature dependence of kinematic viscosity and excellent thermal stability over a wide temperature range from low temperature (-40 ° C) to high temperature (120 to 130 ° C) It is rare.

7-35824 JP-A-5-230486 JP-A-6-279777 JP 52-124577 JP 2000-234638 A JP 2000-253620 A JP2002-340146

  The objective of this invention is providing the grease composition used suitably for the lubrication part of a clutch or a torque limiter mechanism.

  As a result of diligent research to achieve the above object, the present inventors have found that by using squalene in the base oil component, it has equivalent low temperature torque transmission and wear resistance compared to silicone grease. As a result, it was found that a grease composition excellent in property improvement was obtained, and the present invention was completed.

  The present invention provides the following grease composition.

1. A grease composition comprising a thickener and a base oil, wherein the base oil contains squalene.
2. 2. The grease composition according to 1 above, wherein the content of squalene in the base oil is 10% by mass or more based on the entire base oil containing squalene.
3. 3. The grease composition according to 1 or 2 above, wherein the base oil has a friction coefficient at −40 ° C. of 0.14 or more.
4). 4. The grease composition according to any one of 1 to 3 above, wherein the thickener is silica or a urea compound.
5. The grease composition according to any one of the above 1 to 4, wherein the traction coefficient of the grease composition is 0.030 or more at 25 ° C.
6). A mechanical member in which the grease composition according to any one of 1 to 5 is encapsulated.
7). 7. The mechanical member as described in 6 above, which is a clutch or torque limiter mechanism.

  The grease composition of the present invention has a high coefficient of friction and is excellent in improving the wear resistance of the lubrication part of the clutch or torque limiter mechanism.

  Mechanical parts are reflected in the difference in material thickness, that is, the weight, depending on how much the safety factor of strength is set when designing. Especially in the case of automobiles, considering the impact on the global environment such as exhaust gas regulations and global warming, it is essential to use lightweight materials, reduce the thickness by reducing the shaft diameter, etc. Conceivable. On the other hand, it is conceivable to buffer an excessive impact with a sliding mechanism, and the use of a clutch or a torque limiter mechanism is increasing.

  The lubrication grease used for the lubrication part of the clutch or torque limiter mechanism is required to have a high coefficient of friction and excellent wear resistance. In particular, in automotive applications such as for engine starters, it is necessary to cope with a wide temperature range from low temperature (−40 ° C.) to high temperature (120 to 130 ° C.). In addition, the coefficient of friction in the state where a lubricant is interposed between metal and metal depends on the thickness of the lubricant. Boundary lubrication state (metals are in direct contact), B. Elastohydrodynamic lubrication state, C.I. In this mechanism, when the torque is transmitted, the above-described A. When the boundary lubrication state occurs and torque is released, Elastic fluid lubrication state or C.I. It is desirable to be in a fluid lubrication state. The grease composition of the present invention is a hydrocarbon-based grease composition having torque transmission performance at a low temperature comparable to that of silicone grease and excellent in wear resistance in order to take this desirable lubricating state. This is an extremely useful invention.

Hereinafter, the grease composition of the present invention will be described in detail.
The base oil used in the grease composition of the present invention must contain squalene (SQUALENE). The chemical name of squalene is 2,6,10,15,19,23-hexamethyl-2,6,10,14,18,22-tetracosahexaene. This squalene is mainly collected from deep-sea shark liver oil, and the oil has a viscosity index of 211, which is characterized by low kinematic viscosity temperature dependence and high traction.
The base oil used in the grease composition of the present invention may be squalene alone, but may be used by mixing squalene and other base oils. The base oil that can be mixed with squalene is not particularly limited as long as it can be used in the lubricating oil and grease composition. Specific examples include at least one of the group of mineral oil and / or synthetic oil. Synthetic oils include ester, ester-based synthetic oil typified by polyol ester, poly-α-olefin, synthetic hydrocarbon oil typified by polybutene, alkyl diphenyl ether, ether-based synthetic oil typified by polypropylene glycol, silicone oil, Examples include fluorinated oils.
The amount of squalene in the base oil is preferably 10 to 100% by mass, more preferably 20 to 100% by mass, and most preferably 50 to 100% by mass with respect to the entire base oil containing squalene.

  The thickener used in the grease composition of the present invention is not particularly limited. Specifically, soap thickeners represented by lithium soap and composite lithium soap, urea thickeners represented by diurea, inorganic thickeners represented by organic clay and silica, polytetrafluoro Examples thereof include organic thickeners represented by ethylene and melamine cyanurate, and at least one selected from these groups can be used.

Preferably, it is selected from the group consisting of silica, lithium soap, composite lithium soap and urea compound. Particularly preferred are silica and urea compounds. Of the urea compounds, diurea thickeners are preferred, and those represented by the following general formula (1) are particularly preferred.
R ¹ —NHCONH—R ² —NHCONH—R ³ (1)
In the formula, R ¹ and R ³ represent the same or different monovalent hydrocarbon residues having 4 to 20 carbon atoms, such as an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group. R ² represents a divalent aromatic hydrocarbon group having 6 to 15 carbon atoms, and is represented by, for example, the following general formulas (2) to (4).

（２）

(2)

（３）

(3)

（４）

(4)

  The diurea thickener can be obtained, for example, by reacting a predetermined diisocyanate with a predetermined monoamine in a base oil. A preferred specific example of the diisocyanate is diphenylmethane-4,4'-diisocyanate. Monoamines include aliphatic amines, aromatic amines, alicyclic amines or mixtures thereof. Specific examples of the aliphatic amine include octylamine, dodecylamine, hexadecylamine, octadecylamine and oleylamine. Specific examples of the aromatic amine include aniline and p-toluidine. Specific examples of alicyclic amines include cyclohexylamine. Of the monoamines described above, diurea thickeners obtained using cyclohexylamine, octylamine, dodecylamine, hexadecylamine, octadecylamine or mixtures thereof are preferred.

  The content of the thickener is appropriately determined according to the desired consistency, but is usually 1.0 to 30.0% by mass, preferably 2.0 to 20.0% by mass, and more preferably Is 2.5 to 10.0% by mass.

  Other additives that may be added to the grease composition of the present invention include antioxidants, rust inhibitors, metal deactivators, detergent dispersants, extreme pressure additives, antifoaming agents, anti-emulsifiers, oiliness Additives commonly used in grease compositions, such as improvers. These can be used alone or in admixture of two or more. These additives are added as necessary, and the amount added is generally 0.01 to 10% by mass, but is not particularly limited as long as the object of the present invention is not impaired. Absent.

The penetration of the grease composition of the present invention is preferably 200 to 550, more preferably 230 to 520, and most preferably 280 to 500.
Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are not intended to limit the present invention, and all modifications that are made without departing from the spirit of the present invention are included in the technical scope of the present invention. The

1. Evaluation test 1.1 Measurement of friction coefficient by barbell plate test A barbell-shaped mating material is brought into contact with the plate surface, and the plate is rotated while applying a load in this state to slide the mating material surface and the plate surface. This is an experiment. The mating material is Fe—Cr alloy steel composed of two disks of φ13 mm × thickness 5 mm and a shaft connecting the central portions of these two disks. Of these, the peripheral portion of the disk is in sliding contact with the plate surface.
(1) Test piece material
Barbell type specimen: SCr415
Plate type test piece: SUJ2

(2) Test method By adopting the cylindrical wire contact form, a stable contact state with less per piece can be obtained even under relatively low surface pressure conditions. Table 1 shows the test conditions. The friction coefficient was measured by measuring the torque in the sliding direction with a load cell.

(3) Test condition table 1

1.2 Grease Traction Coefficient with Ball / Disk EHL Tester The steel disk rotates at a rotational speed Ud, and the ball is free at a rotational speed Ub. The ball rotation axis is offset from the center of the disk. The generation of the sliding motion Us (sliding speed relative to the ball rotation) detects the traction in the ball axis direction with the load cell, and the ratio of the maximum value to the load is set as the maximum traction coefficient.
(1) Test conditions Maximum Hertz pressure: 0.711Gpa
Speed: 0.5m / s
Temperature: 25 ° C

1.3 Overrunning clutch slip test A specified amount of grease was sealed in the overrunning clutch portion of the starter of an automobile, and it was examined whether it could be engaged without slipping by rotating it with a start switch under specified conditions (−40 ° C.). An R type (reduction type) starter was used.

2. Manufacture of grease In a base oil, a predetermined amount of diisocyanate and amine or amine mixture is heated under predetermined conditions, cooled, treated with a roll mill, and those containing additives add a predetermined amount of additives, A grease was produced.

3. Judgment of effect Barbell plate test (-40 ° C friction coefficient)
Pass (○): 0.14 or more Fail (×): Less than 0.14 grease traction coefficient (25 ℃)
Pass (○): 0.035 to 0.100 Fail (×): Value outside the pass range
(3) Overrunning clutch slip test (test results at the mounting location)
Pass (○): No slip Fail (×): There is slip
(4) Comprehensive evaluation Pass (○): When all passes Passes fail (×): When there is one or more failures

4). Test results The formulas for grease (base oil, thickener, antioxidant), the base oil component ratio, and the chemical structure of the thickener are shown in the upper part of Tables 2 to 6. The lower part of Tables 2 to 6 shows the barbell plate test results, the grease traction coefficient, the overrunning clutch slip test and the evaluation results.

Table 2 Examples 1-5

Table 3 Examples 6-10

Table 4 Examples 11-15

Table 5 Example 16, Comparative Examples 1-4

Table 6 Comparative Examples 5-8

PAO (Poly α-olefin): 40 ° C Kinematic viscosity 30 mm ² / s
PET (pentaerythritol ester): Kinematic viscosity at 40 ° C 30 mm ² / s
ADE (alkyl diphenyl ether): Kinematic viscosity at 40 ° C 100 mm ² / s
P mineral oil: Kinematic viscosity at 40 ° C 100 mm ² / s
N-based mineral oil: Kinematic viscosity at 40 ° C 100 mm ² / s
* 1 Urea thickener:
R ¹ -NHCONH-R ² -NHCONH-R ³
* 2 DM:

*３ 酸化防止剤：フェノール系酸化防止剤（３，５−ジ−ｔ−ブチル−４−ヒドロキシフェニルプロパン酸プロピル）
*４ Ｌｉ石けん：１２−ヒドロキシステアリン酸リチウム

* 3 Antioxidant: Phenolic antioxidant (propyl 3,5,5-di-t-butyl-4-hydroxyphenylpropanoate)
* 4 Li soap: 12-hydroxylithium stearate

As described above, in Examples 1 to 16 in which the base oil component contains squalene in the grease composition composed of the thickener and the base oil, the barbell plate test (−40 ° C.) is 0.14 to 0.21. The traction coefficient of the grease was 0.035 to 0.080, and the overrunning clutch slip test showed no slip, and all passed the effect judgment.
On the other hand, in the case of Comparative Examples 1 to 8 not containing squalene, the barbell plate test (−40 ° C.) is 0.07 to 0.12, the traction coefficient of grease is 0.020 to 0.085, and the result of slipping in the overrunning clutch slip test is shown. It turns out that it is unacceptable in an effect determination and is clearly inferior compared with an Example.

Claims (7)

A grease composition comprising a thickener and a base oil, wherein the base oil contains squalene, and the thickener is any one of metal soap, silica or a urea compound, and a grease composition for a clutch or torque limiter mechanism object. The grease composition for a clutch or torque limiter mechanism according to claim 1, wherein the urea compound is represented by the following formula (1) .
R ¹ —NHCONH—R ² —NHCONH—R ³ ( 1 )
(In the formula, R ¹ and R ³ are the same or different monovalent aliphatic hydrocarbon group, alicyclic hydrocarbon group or aromatic hydrocarbon group having 4 to 20 carbon atoms. R ² is 6 to 6 carbon atoms. 15 represents a divalent aromatic hydrocarbon group of 15 ) The grease composition for a clutch or torque limiter mechanism according to claim 1 or 2 , wherein the content of squalene in the base oil is 10% by mass or more based on the entire base oil containing squalene. The grease composition for a clutch or torque limiter mechanism according to any one of claims 1 to 3, wherein the grease composition has a friction coefficient at -40 ° C of 0.14 or more. The grease composition for a clutch or torque limiter mechanism according to any one of claims 1 to 4 , wherein a traction coefficient of the grease composition is 0.030 or more at 25 ° C.   The mechanical member which enclosed the grease composition of any one of Claims 1-5.   The mechanical member according to claim 6, which is a clutch or torque limiter mechanism.