Grease composition and bearing

Abstract

A grease is provided which has an improved inflow property of the grease into a lubrication unit and has a long life when used for bearings even under a high temperature environment. A grease composition comprising a base oil and a thickener, characterized in that the base oil contains an ester synthetic oil, the content of the ester synthetic oil is not less than 20% by mass of the total mass of the base oil and the thickener contains a diurea compound represented by the Formula (I):
R.sup.1NHCONHR.sup.2NHCONHR.sup.3,(I) wherein R.sup.2 is a C.sub.6-15 divalent aromatic hydrocarbon group, R.sup.1 and R.sup.3 are the same or different, and represent cyclohexyl or C.sub.8-22 linear or branched alkyl, and the molar ratio of cyclohexyl to the total of cyclohexyl and C.sub.8-22 linear or branched alkyl is 60 to 95%.

Claims

1. A grease composition comprising a base oil and a thickener in the amount of 10.0 wt % to 18.0 wt % based on the total weight of the grease composition, characterized in that the base oil contains an ester synthetic oil and oil other than the ester synthetic oil, the ester synthetic oil is selected from the group consisting of complex ester oils, the complex ester oil is synthesized from pentaerythritol with mixtures of C.sub.7-C.sub.10 monovalent fatty acids and adipic acid, the content of the ester synthetic oil is 25-95% by mass of total base oil, the content of the ester synthetic oil is 20.5-77.9% by mass of total grease composition, the oil other than the ester synthetic oil is selected from the group consisting of mineral oils, synthetic hydrocarbon oils, ether synthetic oils, and combinations thereof, and the thickener contains a diurea compound represented by the Formula (I):
R.sup.1NHCONHR.sup.2NHCONHR.sup.3,(I) wherein R.sup.2 is a diphenylmethylene group, R.sup.1 and R.sup.3 are the same or different, and represent cyclohexyl or C.sub.18 linear alkyl and the molar ratio of cyclohexyl to the total of cyclohexyl and C.sub.18 linear alkyl is 70 to 90%.

2. The grease composition according to claim 1, which is for bearings.

3. The grease composition according to claim 1, wherein the bearings are rolling bearings for automobile electrical equipment or auxiliaries.

4. The grease composition according to claim 1, wherein the rolling bearings for automobile electrical equipment or auxiliaries are outer race rotation type bearings.

5. A bearing in which the grease composition according to claim 1 is filled.

6. The grease composition according to claim 1, wherein the amount of the thickener is about 14 wt %.

7. The grease composition according to claim 1, wherein the grease composition is configured to have more than 500 hours of the bearing life measured by the outer race rotating test and more than 500 hours of the bearing life measured by the bearing lubrication life test.

Description

EXAMPLES

(1) Preparation of Grease for Testing

(2) A base grease was prepared by reacting an aromatic diisocyanate (diphenylmethane diisocyante) with a predermined amount of amines (cyclohexylamine, stearylamine, p-toluidine) in a base oil and diluted the resultant with a base oil to attain the worked penetration of 280. Additives are added to this grease to prepare grease compositions of Examples 1 to 4 and Comparative Examples 1 to 4.
Content of cyclohexyl group(CH)(%)=[{(the number of moles of cyclohexyl group)/(the number of moles of cyclohexyl group+the number of moles of alkyl groups)}100]
Thickeners A1 to A5: cycloaliphatic/aliphatic diurea (cyclohexylamine and/or stearylamine were used)
Thickener B: aromatic diurea (p-toluidine was used)
Thickener C: Li soap (lithium 12-hydroxystearate)

(3) Base Oil

(4) Ester oil A: trimethylolpropane ester oil (kinematic viscosity at 40 C.: 24.5 mm.sup.2/s)

(5) Ester oil B: pentaerythritol ester oil (kinematic viscosity at 40 C.: 30.8 mm.sup.2/s)

(6) Ester oil C: dipentaerythritol ester oil (kinematic viscosity at 40 C.: 209 mm.sup.2/s)

(7) Ester oil D: complex ester oils (kinematic viscosity at 40 C.: 102 mm.sup.2/s)

(8) Mineral oil: kinematic viscosity at 40 C.: 102 mm.sup.2/s

(9) Synthetic hydrocarbon oil: kinematic viscosity at 40 C.: 63.3 mm.sup.2/s

(10) Phenyl ether oil: dialkyldiphenyl ether oil (kinematic viscosity at 40 C.: 100 mm.sup.2/s)

(11) Additive A: amine antioxidant (alkyl diphenylamine)

(12) Additive B: sulfonate rust inhibitor (zinc dinonylnaphthalene sulfonate)

(13) Test Method for Grease Composition

(14) Worked penetration (JIS K2220): all the consistencies were set at 280

(15) Outer Race Rotating Test

(16) Outer race rotating test which estimates the bearing life under a high temperature was conducted. The bearing was driven under the following conditions, and the bearing life was determined when the motor overcurrent or abnormal vibration was detected, or the temperature of the motor exceeded the prescribed temperature by +15 C.

(17) Bearing type: 6203 rubber seal

(18) Test temperature: 160 C.

(19) Rotation rate: 16000 rpm

(20) Test load: radial load 800 N

(21) Bearing Lubrication Life Test (based on ASTM D3336)

(22) Inner race rotating test which estimates the bearing life under a high temperature was conducted. The bearing was driven under the following conditions, and the bearing life was judged when the motor overcurrent was detected, or the temperature of the motor exceeded the prescribed temperature by +15 C.

(23) Bearing type: 6204 metal seal

(24) Test temperature: 180 C.

(25) Rotation rate: 10000 rpm

(26) Test load: axial load 66.7 N

(27) Radial load 66.7N

(28) Overall Judgment

(29) Outer Race Rotating Test qualified 500 hours or more disqualified less than 500 hours

(30) Bearing Lubrication Life qualified 500 hours or more disqualified less than 500 hours

(31) Qualified in Both the Test: , the Others: x

(32) The results are shown in Table 1.

(33) TABLE-US-00001 TABLE 1 Examples Comparative Examples Component 1 2 3 4 1 2 3 4 Thickener A1 14.0 Thickener A2 14.0 Thickener A3 14.0 Thickener A4 14.0 14.0 Thickener A5 14.0 Thickener B 23.0 Thickener C 9.0 Ester Oil A 20.5 Ester Oil B 45.1 45.1 87.0 Ester Oil C 73.8 36.9 36.9 Ester Oil D 49.2 8.2 73.0 Mineral Oil 8.2 Synthetic Hydrocarbon Oil 61.5 Phenyl Ether Oil 32.8 73.8 Additive A 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 Additive B 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Worked Penetration 280 280 280 280 280 280 280 280 CH Content in Thickener 70 75 87 90 50 90 0 0 Ester Oil Content in Base Oil 90 25 100 60 100 10 100 100 Outer Race Rotating Test (H) 520 550 1020 770 300 390 240 20 Bearing Lubrication Life Test (H) 600 610 1000 810 330 370 515 28 Overall Judgment x x x x

(34) All of the results of the outer race rotating test and the bearing lubrication life test of the grease compositions of the Examples 1 to 4 were more than 500 hours, in which compositions the content of the thickener represented by the general formula (I) in which thickener the content of cyclohexyl group (CH) was 60 to 95%, and the content of the ester synthetic oil in the base oil was not less than 20% by mass based on the total base oil. Therefore, the grease compositions are excellent in the heat-resistant property and the inflow property.

(35) In contrast, all of the results of the outer ring rotating test, the bearing lubrication life test or both of the tests of the grease composition of the Comparative Example 1 in which the thickener represented by the general formula (I) in which thickener the content of cyclohexyl group (CH) is 50%, the composition of the Comparative Example 2 in which the content of ester synthetic oil in the base oil is 10% by mass based on the total base oil and the composition of the Comparative Examples 3 and 4 in which the thickener represented by the general formula (I) in which thickener cyclohexyl group (CH) is not contained is used is less than 500 hours. Therefore, this shows that the object of the present invention is not attained.