Grease composition

Abstract

The present invention provides a grease composition comprising (a) a base oil, (b) a thickener comprising a urea compound, (c) an amine antioxidant at 0.5 to 5% by mass based on a total mass of the composition, and (d) a quinoline antioxidant at 0.5 to 5% by mass based on the total mass of the composition.

Claims

1. A grease composition comprising: (a) a base oil at 70 to 90% by mass based on a total mass of the composition; (b) a thickener comprising a urea compound at 5 to 25% by mass based on the total mass of the composition; (c) an amine antioxidant at 0.5 to 5% by mass based on the total mass of the composition; and (d) a quinoline antioxidant at 0.5 to 5% by mass based on the total mass of the composition, wherein the base oil comprises 10 to 20% by mass of a highly refined mineral oil having a pour point of −35° C. or lower based on a total mass of the base oil, wherein the urea compound is a diurea compound represented by the following formula (1): ##STR00004## where R.sup.2 is a divalent aromatic hydrocarbon group having 6 to 15 carbon atoms, and one of R.sup.1 and R.sup.3 is a saturated or unsaturated alkyl group having 6 to 30 carbon atoms, and the other is a cyclohexyl group, wherein the (c) amine antioxidant is alkyldiphenyl amine or phenyl-α-naphthyl amine, and wherein the (d) quinoline antioxidant is at least one quinoline antioxidant selected from the group consisting of 2,2,4-trimethyl-1,2-dihydroquinoline, 2-methyl-2,4-diethyl-1,2-dihydroquinoline, 2,2,4,6-tetramethyl-1,2-dihydroquinoline, 2,2,4,7-tetramethyl-1,2-dihydroquinoline, 6,6′-bis(2,2,4-trimethyl-1,2-dihydroquinoline), and homopolymers thereof.

2. The grease composition according to claim 1, wherein in the diurea compound, a molar ratio between the cyclohexyl group and the alkyl group is 10:90 to 50:50.

3. The grease composition according to claim 1, wherein the (a) base oil has a kinematic viscosity of 50 to 150 mm.sup.2/s at 40° C.

4. The grease composition according to claim 1, wherein a mass ratio between the (c) amine antioxidant and the (d) quinoline antioxidant is 1:3 to 3:1.

5. The grease composition according to claim 1, further comprising (e) a zinc rust inhibitor, wherein a content of the zinc rust inhibitor is 0.5 to 10% by mass based on the total mass of the grease composition.

6. The grease composition according to claim 1, which is for use for a rolling bearing for a motor which supports a rotor of the motor.

7. The grease composition according to claim 1, wherein the (c) amine antioxidant is alkyl diphenyl amine.

8. The grease composition according to claim 1, wherein the (d) quinoline antioxidant is a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline.

9. The grease composition according to claim 1, wherein the thickener is an alicyclic aliphatic diurea which is a reaction product of a cyclohexyl amine, an aliphatic amine and a diisocyanate.

10. The grease composition according to claim 1, wherein the content of the (c) amine antioxidant is 0.5 to 2.5% by mass based on the total mass of the composition.

11. The grease composition according to claim 1, wherein the content of the (d) quinolone antioxidant is 0.5 to 2.5% by mass based on the total mass of the composition.

Description

EXAMPLES

(1) A grease composition containing an aromatic diurea as a thickener (Example 6) was prepared by: allowing a predetermined amount of 4,4′-diphenyl methane diisocyanate and a raw material amine (p-toluidine) at a molar ratio of 1:2 to react with each other in the base oil specified in Table presented below; adding predetermined amounts of an amine antioxidant, a quinoline antioxidant, and a zinc rust inhibitor thereto; and adjusting the mixture to have a specified cone penetration with a three roll mill.

(2) Grease compositions each containing an alicyclic aliphatic diurea as a thickener (Examples 1 to 5 and 7 to 13, and Comparative Examples 4 to 9) were prepared in the same method as the grease composition in Example 6 except that a cyclohexyl amine and a stearyl amine are used as raw material amines in place of the p-toluidine.

(3) Grease compositions each containing a lithium complex soap as a thickener (Comparative Examples 1 to 3) were prepared by: heating a mixture of the base oil with azelaic acid and 12-hydroxystearic acid; then adding an aqueous solution of lithium hydroxide to the mixture; followed by re-heating and then rapid cooling; adding predetermined amounts of the amine antioxidant, the quinoline antioxidant, and the zinc rust inhibitor thereto; and adjusting the mixture to have the specified cone penetration with the three roll mill.

(4) Here, in all the grease compositions, the cone penetration (worked penetration after 60 strokes) was adjusted to 260 (JIS K2220).

(5) (a) Base Oil

(6) Mineral oil A: viscosity index: 95 or higher, a kinematic viscosity of 10.8 mm.sup.2/s at 100° C. and a kinematic viscosity of 96.6 mm.sup.2/s at 40° C.

(7) Mineral oil B: viscosity index: 95 or higher, a kinematic viscosity of 11.2 mm.sup.2/s at 100° C. and a kinematic viscosity of 95.0 mm.sup.2/s at 40° C.

(8) Mineral oil C: viscosity index: 95 or higher, a kinematic viscosity of 6.0 mm.sup.2/s at 100° C. and a kinematic viscosity of 37.0 mm.sup.2/s at 40° C.

(9) Mineral oil D: viscosity index: 95 or higher, a kinematic viscosity of 31.6 mm.sup.2/s at 100° C. and a kinematic viscosity of 436 mm.sup.2/s at 40° C.

(10) Highly refined mineral oil A: viscosity index: 120 or higher, a kinematic viscosity of 7.80 mm.sup.2/s at 100° C. and a kinematic viscosity of 46.0 mm.sup.2/s at 40° C.

(11) (c) Amine Antioxidant

(12) Alkyldiphenyl amine Phenyl-α-naphthyl amine
(d) Quinoline Antioxidant Polymer of 2,2,4-trimethyl-1,2-dihydroquinoline (poly(2,2,4-trimethyl-1,2-dihydroquinoline) represented by the above formula (2)) [a specific gravity of 1.08 to 1.11, a softening point of 80 to 110° C., an ash content of 0.5% or less, and a loss on heating of 0.7% or less]) 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline [equivalent to an antidegradant ETMDQ specified in the above JIS K6211 “Rubber Antidegradants”]
(e) Zinc Rust Inhibitor Zinc naphthenate
(f) Phenolic Antioxidant Octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate
<Text Methods and Evaluation>
[Durability (Heat Resistance and Bearing Lubrication Life)]
Evaluation Method

(13) The test was carried out using a bearing lubrication life test machine in conformity with ASTM D3336.

(14) The test conditions are presented below. Here, a time period until the motor generated an overcurrent (4 amperes or more) or a time period until the temperature of the bearing outer ring increased to a test temperature +15° C., whichever was shorter, was taken as the seizure life.

(15) Bearing type: 6204 Metal seal

(16) Test temperature: 160° C.

(17) Rotation speed: 10000 rpm

(18) Grease amount: 1.8 g

(19) Test load: axial load of 66.7 N and radial load of 66.7 N

(20) Evaluation

(21) Bearing lubrication life 1000 hours or more . . . ∘ (Passed) Less than 1000 hours . . . x (Failed)
[Low Temperature Properties (Low Torque Properties)]
<Test Method>

(22) The test of the low torque properties was carried out in conformity with the low-temperature torque test specified at the section 18. in JIS K2220.

(23) Bearing type: 6204

(24) Test temperature: −30° C.

(25) Rotation speed: 1 rpm

(26) Measured torques:

(27) Starting torque (the maximum torque at the start of measurement)

(28) Rotational torque (the average torque in the last 15 seconds for 10 minutes of rotation)

(29) Evaluation Criteria

(30) Starting torque (−30° C.) Less than 1000 mNm: Passed (∘) 1000 mNm or more: Failed (x)

(31) Rotational torque (−30° C.) Less than 100 mNm: Passed (∘) 100 mNm or more: Failed (x)
[Overall Evaluation]

(32) Passed in both the durability evaluation and the low torque property: ∘ (Passed)

(33) Failed in either one of the two evaluations: x (Failed)

(34) TABLE-US-00001 TABLE 1 Example 1 2 3 4 5 6 7 8 9 10 (A) Urea- Diphenylmethane Diisocyanate molar ratio 50 50 50 50 50 50 50 50 50 50 Thickener based Cyclohexylamine molar ratio 30 10 50 30 30 — 30 30 30 30 Stearyl Amine molar ratio 70 90 50 70 70 — 70 70 70 70 Para-toluidine molar ratio — — — — — 100 — — — — Soap- Lithium Complex Soap — — — — — — — — — — based Thickener Amount mass % 8.0 8.5 8.5 8.0 8.0 22.0 8.0 8.0 8.0 8.0 Base Oil Type Mineral Oil A 50 50 50 - 10 50 50 50 50 50 (mass ratio) Mineral Oil B 35 35 35 35 35 35 35 35 35 35 Mineral Oil C — — — 50 — — — — — — Mineral Oil D — — — — 40 — — — — — Highly Refined 15 15 15 15 15 15 15 15 15 15 Mineral Oil A kinematic viscosity mm.sup.2/s @40° C. 87.7 87.7 87.7 50.0 150.0 87.7 87.7 87.7 87.7 87.7 Additive (c) Amine-based Alkyldiphenyl Amine 1.5 1.5 1.5 1.5 1.5 1.5 0.5 5.0 0.5 1.5 (mass %) Antioxidant Phenyl α-naphthyl — — — — — — — — — — Amine (d) Quinoline- Polymerizate of 1.5 1.5 1.5 1.5 1.5 1.5 0.5 5.0 1.5 0.5 based 2,2,4-trimethyl- Antioxidant 1,2-dihydroquinoline 6-ethoxy-2,2,4- — — — — — — — — — — trimethyl-1,2- dihydroquinoline (f) Phenolic Octadecyl-3- — — — — — — — — — — Antioxidant (3,5-di-t-butyl-4- hydroxyphenyl) propionate (e) Zinc-based Zinc Naphthenate 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 4.5 Rust Inhibitor Worked Penetration 260 260 260 260 260 260 260 260 260 260 Durability Result Bearing Lubrication 1300 1220 1220 1150 1350 1010 1010 1390 1090 1100 Life, h 160° C. Evaluation ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ Low Torque Result Starting Torque 770 860 840 610 950 910 760 800 770 780 Properties mNm Rotational Torque 76 85 83 62 93 90 74 79 77 79 mNm Evaluation Starting Torque ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ Rotational Torque ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ Overall Evaluation ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ ∘ Example 11 12 13 14 15 16 (A) Urea- Diphenylmethane Diisocyanate molar ratio 50 50 50 50 50 50 Thickener based Cyclohexylamine molar ratio 30 30 30 30 30 30 Stearyl Amine molar ratio 70 70 70 70 70 70 Para-toluidine molar ratio — — — — — — Soap- Lithium Complex Soap — — — — — — based Thickener Amount mass % 8.0 8.0 8.0 8.0 8.0 8.0 Base Oil Type Mineral Oil A 50 50 50 50 50 50 (mass ratio) Mineral Oil B 35 35 35 35 35 35 Mineral Oil C 15 — 15 — — — Mineral Oil D — — — — — — Highly Refined — 15 — 15 15 15 Mineral Oil A kinematic viscosity mm.sup.2/s @40° C. 85.2 87.7 85.2 87.7 87.7 87.7 Additive (c) Amine-based Alkyldiphenyl Amine 1.5 1.5 1.5 — 1.5 — (mass %) Antioxidant Phenyl α-naphthyl — — — 1.5 — 1.5 Amine (d) Quinoline- Polymerizate of 1.5 1.5 1.5 1.5 — — based 2,2,4-trimethyl- Antioxidant 1,2-dihydroquinoline 6-ethoxy-2,2,4- — — — — 1.5 1.5 trimethyl-1,2- dihydroquinoline (f) Phenolic Octadecyl-3- — — — — — — Antioxidant (3,5-di-t-butyl-4- hydroxyphenyl) propionate (e) Zinc-based Zinc Naphthenate 4.5 — — 4.5 4.5 4.5 Rust Inhibitor Worked Penetration 260 260 260 260 260 260 Durability Result Bearing Lubrication 1210 1220 1200 1220 1210 1190 Life, h 160° C. Evaluation ∘ ∘ ∘ ∘ ∘ ∘ Low Torque Result Starting Torque 920 790 930 780 790 780 Properties mNm Rotational Torque 89 78 91 76 77 77 mNm Evaluation Starting Torque ∘ ∘ ∘ ∘ ∘ ∘ Rotational Torque ∘ ∘ ∘ ∘ ∘ ∘ Overall Evaluation ∘ ∘ ∘ ∘ ∘ ∘

(35) TABLE-US-00002 TABLE 2 Comparative Example 1 2 3 4 5 6 7 8 9 (A) Urea- Diphenylmethane Diisocyanate molar ratio — — — 50 50 50 50 50 50 Thickener based Cyclohexylamine molar ratio — — — 30 30 30 30 30 30 Stearyl Amine molar ratio — — — 70 70 70 70 70 70 Para-toluidine molar ratio — — — — — — — — — Soap- Lithium Complex Soap 100 100 — — — — — — — based Thickener Amount mass % 10.0 10.0 10.0 8.0 8.0 8.0 8.0 8.0 8.0 Base Oil Type Mineral Oil A 50 50 50 50 50 50 50 50 50 (mass ratio) Mineral Oil B 35 35 35 35 35 35 35 35 35 Mineral Oil C — 15 — — — — — — — Mineral Oil D — — — — — — — — — Highly Refined 15 — 15 15 15 15 15 15 15 Mineral Oil A kinematic viscosity (40° C.) mm.sup.2/s 87.7 87.7 87.7 87.7 87.7 87.7 87.7 87.7 87.7 Additive (c) Amine-based Alkyldiphenyl Amine 1.5 1.5 1.5 — 1.5 — 3.0 — 1.5 (mass %) Antioxidant (d) Quinoline- Polymerizate of 1.5 1.5 1.5 1.5 — 3.0 — 1.5 — based 2,2,4-trimethyl- Antioxidant 1,2-dihydroquinoline (f) Phenolic Octadecyl-3- — — — — — — — 1.5 1.5 Antioxidant (3,5-di-t-butyl-4- hydroxyphenyl) propionate (e) Zinc-based Zinc Naphthenate 4.5 4.5 — 4.5 4.5 4.5 4.5 4.5 4.5 Rust Inhibitor Worked Penetration 260 260 260 260 260 260 260 260 260 Durability Result Bearing Lubrication 400 380 370 700 650 770 750 910 880 Life, h 160° C. Evaluation x x x x x x x x x Low Torque Result Starting Torque 790 1080 810 780 780 790 800 790 780 Properties mNm Rotational Torque 78 110 80 79 77 78 80 78 77 mNm Evaluation Starting Torque ∘ x ∘ ∘ ∘ ∘ ∘ ∘ ∘ Rotational Torque ∘ x ∘ ∘ ∘ ∘ ∘ ∘ ∘ Overall Evaluation x x x x x x x x x