KR20100108905A - Grease composition having heat resistance and low friction force for constant velocity joints - Google Patents

Abstract

PURPOSE: A grease composition with a superior heat resistance feature and a superior low friction force for constant velocity joints are provided to simultaneously obtain heat resistance and low friction force features required for a grease composition. CONSTITUTION: A grease composition with a superior heat resistance feature and a superior low friction force for constant velocity joints includes a urea type grease thickener 5 to 25 wt%, diphenylamine 0.1 to 10 wt%, calcium salt 0.1 to 10.0 wt%, molybdenum dithiocarbamate 1.0 to 10.0 wt%, molybdenum dithiophosphate 0.5 to 5.0 wt%, zinc dialkyldithiophosphate 0.5 to 5 wt%, calcium sulfonate 1.0 to 10.0 wt%, molybden sulfide 0.1 to 5.0 wt%, graphite 0.1 to 5.0 wt%, and oil.

Description

Grease Composition having heat resistance and low friction force for constant velocity joints}

The present invention relates to a grease composition for constant velocity joints, and more particularly, to provide a grease composition for constant velocity joints having excellent heat resistance and lubricity and having low friction.

In the constant velocity joint drive shaft, the fixed type mainly focuses on durability, and the sliding type focuses on NVH characteristics and grease considering heat resistance. Since the amount of grease enclosed in the constant velocity joint is larger than that of the bearing, the grease used for the constant velocity joint is a low cost mineral oil grease in consideration of cost. The viscosity and type of mineral oil, for example paraffinic mineral oil or naphthenic mineral oil, are appropriately selected depending on the properties required in the apparatus to be used.

In general, constant velocity joint grease has been developed with extreme pressure resistance and wear resistance as important properties, and it is a cause of shortening the lifespan without considering heat resistance and low friction characteristics. As described above, however, the grease for automobile constant velocity joints must be excellent in heat resistance and low friction as well as extreme pressure and wear resistance.

In the sliding type constant velocity joint, grease having a low friction coefficient is used to improve NVH characteristics. In recent years, additives represented by an organic molybdenum compound and zinc dialkyldithiophosphate have been used, and these additives often exhibit synergistic effects with sulfur- or phosphorus-based additives. For this reason, the optimization of additive characteristics is tried by combining several types of additives.

Therefore, in order to simultaneously obtain the heat resistance and low friction properties required for the grease composition used in automobile constant velocity joints, it is required to develop a grease composition that exhibits the optimal properties combining appropriate grease thickeners and additives.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a grease composition for a constant velocity joint having excellent heat resistance and lubricity and improved low friction.

Grease composition for a constant velocity joint according to an aspect of the present invention for achieving the above object is 5 to 25 wt% of a urea grease thickener represented by the following formula, based on the weight of the total grease composition, 0.1% diphenylamine To 3.0 wt%, calcium salt 0.1 to 10 wt%, molybdenum dithiocarbamate 1.0 to 10.0 wt%, molybdenum dithiophosphate 0.5 to 5.0 wt%, zinc dialkyldithiophosphate 0.5 to 5 wt%, calcium sulfonate 1.0 To 10.0 wt%, molybdenum sulfide 0.1 to 5.0 wt%, and graphite 0.1 to 5.0 wt% and the balance includes base oil.

In the formula, R ₁ and R ₂ are each independently or simultaneously an aromatic hydrocarbon having 6 or 7 carbon atoms, a cyclohexyl group having 6 or 7 carbon atoms, or an aliphatic hydrocarbon having 6 to 20 carbon atoms.

The base oil may be any one selected from purified paraffinic mineral oil, naphthenic mineral oil, and mixtures thereof, and the base oil may have a kinematic viscosity of 8 to 15 cSt at 100 ° C.

The grease composition for constant velocity joints according to the present invention preferably has a dropping point of 250 ° C. or higher, and an SRV friction coefficient of 0.04 to 0.10.

As described above, according to the present invention, using a urea thickener having excellent heat resistance and low friction, it is possible to improve not only the extreme pressure and abrasion resistance of the constant velocity joint but also have excellent heat resistance and low friction resistance that can be used for a long time under high temperature conditions. It is effective to obtain a composition.

Hereinafter, embodiments of the present invention will be described. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art, and are not intended to limit the scope of the present invention.

Grease composition for a constant velocity joint according to an aspect of the present invention is 0.1 to 3.0 wt% diphenylamine, 0.1 to 10 wt% calcium salt, 1.0 to 10.0 wt% molybdenum dithiocarbamate, 0.5 to 5.0 wt% molybdenum dithiophosphate , Zinc dialkyldithiophosphate 0.5 to 5 wt%, calcium sulfonate 1.0 to 10.0 wt%, molybdenum sulfide 0.1 to 5.0 wt%, and graphite 0.1 to 5.0 wt% and the balance includes a base oil,

(Wherein R ₁ and R ₂ are each independently or simultaneously aromatic hydrocarbons having 6 or 7 carbon atoms, cyclohexyl groups having 6 or 7 carbon atoms or aliphatic hydrocarbons having 6 to 20 carbon atoms)

5 to 25 wt% of a urea grease thickener represented by the following.

Urea grease is excellent in heat resistance, not only improves brake resistance but also exhibits low frictional properties, thereby improving NVH characteristics. Therefore, the grease thickener according to the present invention uses a urea-based grease thickener. In particular, the urea-based grease thickener used in the present invention is a urea-based compound represented by the following formula (1).

In the formula, R ₁ and R ₂ are each independently or simultaneously an aromatic hydrocarbon having 6 or 7 carbon atoms, a cyclohexyl group having 6 or 7 carbon atoms, or an aliphatic hydrocarbon having 6 to 20 carbon atoms.

The urea-based grease thickener of Formula 1 may be prepared by reacting 1 equivalent of diisocyanate with 2 equivalents of alkyl, cyclo or arylamine in the presence of a lubricating base oil. At this time, the urea-based grease thickener can adjust the heat resistance by changing the type of amine used as a raw material, or in the case of using two or more amines, by adjusting the mixing ratio of the amine to be mixed. As the amine used in the present invention, aliphatic amines and cycloaliphatic amines, and mixtures thereof can be used.

Here, examples of the diisocyanate may be 4,4-methylenebis (phenylisocyanate), and examples of the amine include an aromatic amine or cyclohexylamine having 6 to 7 carbon atoms, or an aliphatic amine having 6 to 20 carbon atoms. Can be used.

The use amount of the urea-based grease thickener is preferably 5 to 25 wt% based on the total grease composition. If the content of the urea-based grease thickener is less than 5 wt%, the problem is that the led is thin and the durability is poor. If the content of the urea-based grease thickener is greater than 25 wt%, the lead is poor and the lubricity and low temperature are deteriorated.

In order to obtain the low friction property, the grease composition for constant velocity joint according to the present invention contains various kinds of additives. For example, additives that can be used in the present invention include diphenylamine, calcium salt, molybdenum dithiocarbamate, molybdenum dithiophosphate, zincdialkyldithiophosphate, calcium sulfonate, molybdenum sulfide, and graphite. have. In the present invention, to improve the properties of the grease composition for constant velocity joints by adjusting the content of the additive to make an additive mixture to achieve a synergistic effect. The grease composition for a constant velocity joint of the present invention may further include an anti-wear agent, a friction reducer, an extreme pressure agent, or the like.

In the present invention, the grease composition for the constant velocity joint includes 0.1 to 3.0 wt% of diphenylamine, 0.1 to 10 wt% of calcium salt, 1.0 to 10.0 wt% of molybdenum dithiocarbamate, and molybdenum dithiophosphate based on the weight of the total grease composition. 0.5 to 5.0 wt%, zinc dialkyldithiophosphate 0.5 to 5 wt%, calcium sulfonate 1.0 to 10.0 wt%, molybdenum sulfide 0.1 to 5.0 wt%, and graphite 0.1 to 5.0 wt%.

The grease thickener according to the present invention contains the remaining amount of base oil except the urea-based grease thickener and additives. The base oil that can be used in the present invention may be paraffinic mineral oil, naphthenic mineral oil, or a mixture thereof. It is preferable to use refined mineral oil as a base oil. As the base oil, it is preferable to use purified paraffinic mineral oil or naphthenic mineral oil having a kinematic viscosity at 100 ° C. of 5 to 20 cSt and a kinematic viscosity at 40 ° C. of 50 to 200 cSt, more preferably 8 It is preferable to use the base oil whose kinematic viscosity in a range of -15 cSt and 40 degreeC is 80-150 cSt.

The grease composition for constant velocity joints according to the present invention preferably has a dropping point of 250 ° C. or higher, and an SRV friction coefficient of 0.04 to 0.10. The grease composition for constant velocity joints having excellent heat resistance and low friction can be used as a grease for constant velocity joints in automobiles.

Hereinafter, the present invention will be further described through examples. However, the present invention is not limited by these examples.

Example

In Examples 1 to 5 below, 4,4-methylenebis (phenylisocyanate) is used as the diisocyanate compound, and stearylamine or cycloamine is used as the amine, respectively or together, and reacted with a urea-based grease thickener. Reaction in base oil to prepare a grease composition for the constant velocity joint.

Example  One

1.0 mole of 4,4-methylenebis (phenylisocyanate) and 2.0 mole of stearylamine were reacted at 1400 g of a base oil having 8 to 15 cSt at 100 ° C. to uniformly disperse the grease.

Example  2

1.0 mole of 4,4-methylenebis (phenylisocyanate), 0.8 mole of cycloamine and 1.2 mole of stearylamine were reacted at 1400 g of base oil having 8 to 15 cSt at 100 ° C. to uniformly disperse the grease.

Example  3

1.0 mole of 4,4-methylenebis (phenylisocyanate), 1.0 mole of cycloamine, and 1.0 mole of stearylamine were reacted at 1400 g of base oil having 8 to 15 cSt at 100 ° C. to uniformly disperse the grease.

Example  4

1 mole of 4,4-methylenebis (phenylisocyanate), 1.2 mole of cycloamine, and 0.8 mole of stearylamine were reacted at 1400 g of base oil having 8 to 15 cSt at 100 ° C. to uniformly disperse the grease.

Example  5

1 mole of 4,4-methylenebis (phenylisocyanate) and 2.0 mole of cycloamine were reacted at 1400 g of base oil having 8 to 15 cSt at 100 ° C. to uniformly disperse the grease.

The properties of the greases Examples 1 to 5 prepared in the present invention are shown in Table 1 below.

division Example 1
(mole%) Example 2
(mole%) Example 3
(mole%) Example 4
(mole%) Example 5
(mole%) Thickener Aliphatic urea 100 60 50 40 - Cycloaliphatic urea - 40 50 60 100 Mixed race 300 310 305 302 315

Dropping was performed to compare the heat resistance of Examples 1 to 5. Dropping test was carried out according to the method of ASTM D 566. The method of ASTM D 566 is a test to determine the temperature at which the grease composition for constant velocity joints is separated into a thickener and base oil as it is continuously used at high temperatures. Fill a grease cup sample with the grease composition for the constant velocity joint using a dropping point tester, and measure the first falling temperature while raising the temperature according to a predetermined condition. The higher the dropping point, the better the heat resistance. In Table 2 below, the dropping points measured for Examples 1 to 5 are shown.

Example Example 1 Example 2 Example 3 Example 4 Example 5 Dropping point (℃) 210 235 245 260 280

Example  6 to 10

When a dropping point is 200 degreeC or more, it is excellent in heat resistance, More preferably, it is preferable that a dropping point is 250 degreeC or more. Therefore, Example 4 and Example 5 of the excellent heat resistance were selected, and the additive was further added, and the grease composition for the constant velocity joints of Examples 6-10 was prepared. The base oil used has a viscosity of 11 cSt at 100 ° C. The components of the grease compositions of Examples 6 to 10 are shown in Table 3 below.

Example Example 6
(wt%) Example 7
(wt%) Example 8
(wt%) Example 9
(wt%) Example 10
(wt%) Base oil 82.2 82.2 82.0 82.2 82.0 Thickener 10.7 10.7 10.4 9.7 10.5 Diphenylamine 0.5 0.5 0.5 0.5 0.5 Zinc Dialkyl Dithio Phosphate 1.5 1.0 1.5 1.5 1.0 Molybdenum dithiophosphate 1.0 1.5 1.5 1.5 1.5 Molybdenum dithiocarbamate 1.0 1.0 1.0 1.0 1.0 Calcium salt 0.5 0.5 0.5 0.5 0.5 Calcium Sulfonate 2.0 2.0 2.0 2.0 2.0 Molybdenum sulfide 0.3 0.3 0.3 0.3 - Graphite 0.3 0.3 0.3 0.3 1.0 Molybdenum Complex - - - 0.5 -

<Measurement of friction coefficient>

SRV test was performed to measure the coefficient of friction of Examples 6 to 10. The test method was conducted according to ASTM D 5707. The test conditions shall be 50 Hz of frequency, 1.0 mm of stroke, 200 N of load, temperature of 80 ° C., and time of 60 minutes. The coefficients of friction of the grease compositions for constant velocity joints of Examples 6 to 10 are shown in Table 4 below.

Example Example 6 Example 7 Example 8 Example 9 Example 10 Coefficient of friction 0.063 0.056 0.058 0.061 0.054

In Table 4, the friction coefficients of Examples 6 to 10 all have a value of 0.050 to 0.065. In general, when the friction coefficient of the constant velocity joint grease composition is 0.100 or less, it is evaluated to have a low frictional property, and thus, the grease composition for constant velocity joints of Examples 6 to 10 manufactured according to the present invention may have a low frictional property. .

Rotational durability evaluation

In order to evaluate the rotational durability of the grease composition for the constant velocity joints of Examples 6 to 10, the durability of the grease was evaluated using an Automax Four Square Test System. Test conditions are shown in Table 5 below. The test was performed 20 times each.

step Taming One 2 3 4 5 5-load torque 69 911 725 461 245 186 4 revolutions 780 230 300 480 880 1550 time 12h 10m9s 8m24s 49m12s 97m54s 6h2m46s Joint angle (deg)   7

The test was conducted according to the test conditions of Table 5 and then visually observed the surface to determine the durability. As a result, it was confirmed that the rotational durability is excellent when using the grease for the constant velocity joint manufactured in the present invention.

The invention is not to be limited by the foregoing embodiments and the accompanying drawings, but should be interpreted by the appended claims. In addition, it will be apparent to those skilled in the art that various forms of substitution, modification, and alteration are possible within the scope of the present invention without departing from the technical spirit of the present invention.

Claims (5)

5 to 25 wt% of urea grease thickener, 0.1 to 3.0 wt% of diphenylamine, 0.1 to 10 wt% of calcium salt, 1.0 to 10.0 molybdenum dithiocarbamate, based on the weight of the total grease composition. wt%, molybdenum dithiophosphate 0.5 to 5.0 wt%, zinc dialkyldithiophosphate 0.5 to 5 wt%, calcium sulfonate 1.0 to 10.0 wt%, molybdenum sulfide 0.1 to 5.0 wt%, and graphite 0.1 to 5.0 wt% and The remaining amount of the grease composition for the constant velocity joint comprises a base oil:

In the above formula, R ₁ and R ₂ are each independently or simultaneously an aromatic hydrocarbon having 6 or 7 carbon atoms, a cyclohexyl group having 6 or 7 carbon atoms, or an aliphatic hydrocarbon having 6 to 20 carbon atoms. The method of claim 1, The base oil is any one selected from purified paraffinic mineral oil, naphthenic mineral oil, and mixtures thereof. The method of claim 1, The base oil is a constant velocity joint grease composition, characterized in that the kinematic viscosity at 100 ℃ 8 to 15 cSt. The method of claim 1, Grease composition for a constant velocity joint, characterized in that the dropping point is 250 ℃ or more. The method of claim 1, Grease composition for a constant velocity joint, characterized in that the SRV friction coefficient is 0.04 to 0.10.