LUBRICANT COMPOSITION

Abstract

Disclosed is a lubricating oil composition containing a base oil, a viscosity index improver, a molybdenum-based friction modifier, a boron-containing dispersant, and at least two extreme-pressure additives selected from a sulfur-based extreme-pressure additive, a phosphorous-based extreme-pressure additive and a sulfur/phosphorus-based extreme-pressure additive, or a sulfur/phosphorus-based extreme-pressure additive. The base oil is a synthetic oil having a kinematic viscosity at 100 C. of 3 mm.sup.2/s or more and 10 mm.sup.2/s or less, the viscosity index improver is a resin having a number average molecular weight (Mn) of 1,000 or more and 10,000 or less, the mass ratio of boron atoms (B) contained in the boron-containing dispersant to molybdenum atoms (Mo) contained in the molybdenum-based friction modifier, [(B)/(Mo)] is 1 or more and 5 or less, and the mass ratio of sulfur atoms (S) to phosphorus atoms (P) contained in the extreme-pressure additive(s), [(S)/(P)] is 10 or more and 20 or less.

Claims

1. A lubricating oil composition, comprising: a base oil; a viscosity index improver; a molybdenum-based friction modifier; a boron-containing dispersant; and at least two extreme-pressure additives selected from the group consisting of a sulfur-based extreme-pressure additive, a phosphorous-based extreme-pressure additive and a sulfur/phosphorus-based extreme-pressure additive, or a sulfur/phosphorus-based extreme-pressure additive, wherein: the base oil is formed of only a synthetic oil; a kinematic viscosity of the base oil at 100 C. is 3 mm.sup.2/s or more and 10 mm.sup.2/s or less; the viscosity index improver is a resin having a number average molecular weight (Mn) of 1,000 or more and 10,000 or less; a mass ratio of boron atoms (B) contained in the boron-containing dispersant to molybdenum atoms (Mo) contained in the molybdenum-based friction modifier, [(B)/(Mo)] is 1 or more and 5 or less; and a mass ratio of sulfur atoms (S) to phosphorus atoms (P) contained in the extreme-pressure additive(s), [(S)/(P)] is 10 or more and 20 or less.

2. The lubricating oil composition according to claim 1, which has a kinematic viscosity at 100 C. of 6 mm.sup.2/s or more and 15 mm.sup.2/s or less.

3. The lubricating oil composition according to claim 1, wherein a boron atom-equivalent content of the boron-containing dispersant based on a total amount of the composition is 0.01% by mass or more and 0.1% by mass or less.

4. The lubricating oil composition according to claim 1, wherein a molybdenum atom-equivalent content of the molybdenum-based friction modifier based on a total amount of the composition is 0.005% by mass or more and 0.1% by mass or less.

5. The lubricating oil composition according to claim 1, wherein a sulfur atom content based on a total amount of the composition is 1.5% by mass or more and 5% by mass or less.

6. The lubricating oil composition according to claim 1, wherein a phosphorus atom content based on a total amount of the composition is 0.1% by mass or more and 0.5% by mass or less.

7. The lubricating oil composition according to claim 1, wherein the viscosity index improver is an olefinic copolymer.

8. The lubricating oil composition according to claim 1, wherein the molybdenum-based friction modifier is at least one selected from the group consisting of molybdenum dithiocarbamate, molybdenum dithiophosphate and an amine salt of molybdic acid.

9. The lubricating oil composition according to claim 1, wherein the boron-containing dispersant is a boron-containing succinimi de

10. The lubricating oil composition according to claim 1, which is adapted to function as a lubricating oil composition for gear oil.

Description

EXAMPLES

[0079] Next, the present invention is described in more detail with reference to Examples, but the present invention is not whatsoever restricted by these Examples.

Examples 1 to 5 and Comparative Examples 1 to 10

[0080] Lubricating oil compositions were prepared in the blending formulation (% by mass) shown in Table 1 and Table 2. The properties thereof are shown in Table 1 and Table 2. The details of the components are as follows. [0081] Base Oil A: poly--olefin (PAO), 100 C. kinematic viscosity: 2 mm.sup.2/s, viscosity index: 117 [0082] Base Oil B: poly--olefin (PAO), 100 C. kinematic viscosity: 4 mm.sup.2/s, viscosity index: 117 [0083] Base Oil C: poly--olefin (PAO), 100 C. kinematic viscosity: 100 mm.sup.2/s, viscosity index: 117 [0084] Base Oil D: poly--olefin (PAO), 100 C. kinematic viscosity: 150 mm.sup.2/s, viscosity index: 117 [0085] Base Oil E: ester base oil, 100 C. kinematic viscosity: 4 mm.sup.2/s, viscosity index: 139 [0086] Base Oil F: mineral oil categorized as Group III of API base oil category, 100 C. kinematic viscosity: 2 mm.sup.2/s, viscosity index: 116 [0087] Base Oil G: mineral oil categorized as Group III of API base oil category, 100 C. kinematic viscosity: 10 mm.sup.2/s, viscosity index: 107 [0088] Viscosity Index Improver A: OCP (olefin copolymer): copolymer of ethylene and propylene, number average molecular weight: 2,600 [0089] Viscosity Index Improver B: OCP (olefin copolymer): copolymer of ethylene and propylene, number average molecular weight: 3,700 [0090] Viscosity Index Improver C: polymethacrylate, number average molecular weight: 50,000 [0091] Extreme-Pressure Additive A: mixture of sulfurized olefin and polysulfide (di-tert-butyl disulfide and di-tert-butyl trisulfide) [0092] Extreme-Pressure Additive B: mixture of phosphite and thiophosphate [0093] Extreme-Pressure Additive C: tricresyl phosphate [0094] Dispersant A: boron-containing succinimide (boron-containing polybutenylsuccinic bisimide), number average molecular weight of polybutenyl group: 2,300, nitrogen content: 1.76% by mass, boron content: 1.45% by mass [0095] Dispersant B: boron-containing succinimide (boron-containing polybutenylsuccinic bisimide), number average molecular weight of polybutenyl group: 2,000, nitrogen content: 1.45% by mass, boron content: 1.3% by mass [0096] Friction Modifier A: ash-free modifier (oleic amide) [0097] Friction Modifier B: molybdenum dithiocarbamate (MoDTC) [0098] Other Additives: pour point depressant, antioxidant, defoaming agent, etc.

[0099] The properties of the synthetic oil, the mineral oil and the lubricating oil composition were measured according to the following methods.

(1) Kinematic Viscosity

[0100] According to JIS K 2283:2000, the kinematic viscosity at 40 C. and 100 C. was measured.

(2) Viscosity Index (VI)

[0101] The viscosity index was measured according to JIS K 2283:2000. [0102] (3) Content of Boron Atom, Molybdenum Atom, Sulfur Atom and Phosphorus Atom

[0103] The contents of boron atom, molybdenum atom, sulfur atom and phosphorus atom were measured according to JIS-5S-38-92. [0104] (4) Content of Nitrogen Atom

[0105] The content of nitrogen atom was meeasured according to JIS K2609:1998.

[0106] A base oil and various additives of the type shown in Table 1 and Table 2 were blended in the blending ratio also shown therein, thereby preparing lubricating oil compositions of Examples and Comparative Examples. The resultant lubricating oil compositions were tested according to the methods mentioned below to evaluate the physical properties thereof. The evaluation results are shown in Table 1 and Table 2.

[Shear Stability Test]

[0107] The decreasing rate (%) of the kinematic viscosity at 100 C. after shearing was measured according to JPI-5S-29-88 (ultrasonic wave, Method A, 60 minutes, 30 mL). A lower decreasing rate (%) indicates more excellent shear stability.

[Traction Coefficient]

[0108] The traction coefficient was measured with MTM Traction Measuring Equipment. A smaller traction coefficient indicates more excellent fuel saving properties.

[0109] The measurement conditions are as follows. (Applied load: 45 N, oil temperature: 20 C., slide/roll ratio: 50%, mean rotational speed: 1 m/s)

[Intermetallic Friction Coefficient]

[0110] Using a block-on-ring tester (LFW-1) and according to JASO M358:2005, the intermetallic friction coefficient was measured. The data measured under the following test condition were compared. A smaller friction coefficient indicates more excellent fuel saving properties.

Testing Tool

[0111] Ring: Falex S-10 Test Ring (SAE4620 Steel)

[0112] Block: Falex 11-60 Test Block (SAE01 Steel)

Test Condition:

[0113] Temperature: 110 C.

[0114] Load: 1112 N

[0115] Sliding Speed: 0.5 m/s

[ISOT Test]

[0116] According to JIS K 2514-1:2013, a copper/iron catalyst was made to exist in the lubricating oil composition of Examples and Comparative Examples, and the lubricating oil composition was thus degraded at a test temperature of 150 C. for a test period of time of 120 hours. The kinematic viscosity at 100 C. of the degraded oil was referred to as (kinematic viscosity)o, and the kinematic viscosity at 100 C. of undegraded oil was referred to as (kinematic viscosity)i. The viscosity reduction rate (=100((kinematic viscosity).sub.0, (kinematic viscosity).sub.1)100/(kinematic viscosity).sub.0) was calculated. A smaller value of viscosity reduction rate indicates a good lubricating oil composition hardly degradable and excellent in oxidation stability.

[Shell Four-Ball Test Load Bearing (EP) Test]

[0117] According to ASTM D2783-03 (2014), the test was carried out at a rotational number of 1800 rpm and at room temperature to measure the fusion load WL (N). A larger value of the measured data indicates more excellent load bearing properties (extreme-pressure properties).

[Shell Four-Ball Wear Test]

[0118] According to ASTM D4172-94 (2010), the test was carried out at 100 C., at 1800 rpm, at 392 N and for 60 minutes to measure the wear track diameter (mm). A smaller value of the measured data indicates more excellent wear resistance.

TABLE-US-00001 TABLE 1 Example 1 2 3 4 5 Composition Base Oil A mass % 50.00 55.70 61.55 64.00 Base Oil B mass % 69.75 Base Oil C mass % 28.30 8.00 Base Oil D mass % 28.10 25.00 20.00 Base Oil E mass % 5.00 5.00 Base Oil F mass % Base Oil G mass % Viscosity Index Improver A mass % 6.20 6.20 5.00 Viscosity Index Improver B mass % 3.00 3.00 Viscosity Index Improver G mass % Extreme-Pressure Additive A mass % 4.00 4.00 4.50 4.00 4.00 Extreme-Pressure Additive B mass % 1.20 1.20 1.35 1.20 1.20 Extreme-Pressure Additive C mass % 1.00 0.50 0.10 1.00 1.00 Dispersant A mass % 1.60 1.60 1.80 1.60 1.60 Dispersant B mass % 2.00 2.00 Friction Modifier A mass % 0.50 0.50 0.50 0.50 0.50 Friction Modifier B mass % 0.50 0.50 0.50 1.00 0.25 Other Additives mass % 1.70 1.70 1.70 1.70 1.70 Total mass % 100.00 100.00 100.00 100.00 100.00 Properties Base Oil Viscosity (40 C. Kinematic Viscosity) mm.sup.2/s 20.66 19.41 16.18 13.42 22.96 Base Oil Viscosity (100 C. Kinematic Viscosity) mm.sup.2/s 4.72 4.79 4.04 3.56 4.81 Base Oil Viscosity Index 154 181 157 155 134 Composition Viscosity (40 C. Kinematic Viscosity) mm.sup.2/s 48.8 40.7 31.9 26.9 49.8 Composition Viscosity (100 C. Kinematic Viscosity) mm.sup.2/s 9.90 8.85 7.33 6.41 10.00 Composition Viscosity Index 195 206 207 205 193 Boron (B) Content *.sup.1 mass % 0.023 0.023 0.026 0.049 0.049 Molybdenum (Mo) Content *.sup.2 mass % 0.020 0.020 0.020 0.040 0.010 Sulfur (S) Content *.sup.3 mass % 2.000 2.000 2.250 2.000 2.000 Phosphorus (P) Content *.sup.3 mass % 0.192 0.152 0.134 0.192 0.192 Nitrogen (N) Content *.sup.4 mass % 0.080 0.080 0.084 0.109 0.109 (B)/(Mo) 1.15 1.15 1.30 1.23 4.90 (S)/(P) 10.4 13.2 16.8 10.4 10.4 Evaluation Shear Stability % <3 <3 <3 <3 <3 Traction Coefficient 0.04 0.04 0.04 0.04 0.04 Intermetallic Friction Coefficient 0.07 0.07 0.05 0.04 0.06 Oxidation Stability (viscosity increase rate) % <5 <5 <5 <5 <5 Shell 4-Ball Test: EP (WL) N >3000 >3000 >3000 >3000 >3000 Shell 4-Ball Test: WEAR mm 0.40 0.41 0.44 0.43 0.42

TABLE-US-00002 TABLE 2 Comparative Example 1 2 3 4 5 Composition Base Oil A mass % 28.30 61.30 64.30 78.30 Base Oil B mass % 14.00 Base Oil C mass % Base Oil D mass % 17.00 Base Oil E mass % 5.00 5.00 5.00 5.00 5.00 Base Oil F mass % 38.30 Base Oil G mass % 40.00 50.00 Viscosity Index Improver A mass % 6.20 6.20 6.20 6.20 Viscosity Index Improver B mass % Viscosity Index Improver C mass % 6.20 Extreme-Pressure Additive A mass % 4.00 4.00 4.00 4.00 4.00 Extreme-Pressure Additive B mass % 1.20 1.20 1.20 1.20 1.20 Extreme-Pressure Additive C mass % 1.00 1.00 1.00 1.00 1.00 Dispersant A mass % 1.60 1.60 1.60 1.60 1.60 Dispersant B mass % Friction Modifier A mass % 0.50 0.50 0.50 0.50 0.50 Friction Modifier B mass % 0.50 0.50 0.50 0.50 0.50 Other Additives mass % 1.70 1.70 1.70 1.70 1.70 Total mass % 100.00 100.00 100.00 100.00 100.00 Properties Base Oil Viscosity (40 C. Kinematic Viscosity) mm.sup.2/s 20.1 25.6 12.8 7.79 6.72 Base Oil Viscosity (100 C. Kinematic Viscosity) mm.sup.2/s 4.27 4.98 3.31 2.28 2.04 Base Oil Viscosity Index 119 122 133 104 93 Composition Viscosity (40 C. Kinematic Viscosity) mm.sup.2/s 39.3 43.4 39.6 23.8 20.8 Composition Viscosity (100 C. Kinematic Viscosity) mm.sup.2/s 7.34 7.82 9.02 5.74 5.20 Composition Viscosity Index 154 152 219 199 199 Boron (B) Content *.sup.1 mass % 0.023 0.023 0.023 0.023 0.023 Molybdenum (Mo) Content *.sup.2 mass % 0.020 0.020 0.020 0.020 0.020 Sulfur (S) Content *.sup.3 mass % 2.000 2.000 2.000 2.000 2.000 Phosphorus (P) Content *.sup.3 mass % 0.192 0.192 0.192 0.192 0.192 Nitrogen (N) Content *.sup.4 mass % 0.080 0.080 0.080 0.080 0.080 (B)/(Mo) 1.15 1.15 1.15 1.15 1.15 (S)/(P) 10.4 10.4 10.4 10.4 10.4 Evaluation Shear Stability % <3 <3 10 <3 <3 Traction Coefficient 0.08 0.07 0.04 0.04 0.04 Intermetallic Friction Coefficient 0.07 0.07 0.07 0.07 0.07 Oxidation Stability (viscosity increase rate) % <5 <5 <5 10 12 Shell 4-Ball Test: EP (WL) N >3000 >3000 >3000 >3000 >3000 Shell 4-Ball Test: WEAR mm 0.42 0.44 0.43 0.42 0.43 Comparative Example 6 7 8 9 10 Composition Base Oil A mass % 51.00 51.40 51.30 50.50 Base Oil B mass % 71.00 Base Oil C mass % 8.90 28.40 28.50 28.50 29.10 Base Oil D mass % Base Oil E mass % 5.00 5.00 5.00 5.00 5.00 Base Oil F mass % Base Oil G mass % Viscosity Index Improver A mass % 5.00 6.20 6.20 6.20 6.20 Viscosity Index Improver B mass % Viscosity Index Improver C mass % Extreme-Pressure Additive A mass % 4.00 4.00 4.00 2.50 4.00 Extreme-Pressure Additive B mass % 1.20 1.20 1.20 1.20 0.90 Extreme-Pressure Additive C mass % 1.00 1.00 1.00 1.00 0.00 Dispersant A mass % 1.60 1.60 1.60 Dispersant B mass % 0.50 0.50 Friction Modifier A mass % 0.50 0.50 0.50 0.50 0.50 Friction Modifier B mass % 0.10 0.50 0.50 0.50 Other Additives mass % 1.70 1.70 1.70 1.70 1.70 Total mass % 100.00 100.00 100.00 100.00 100.00 Properties Base Oil Viscosity (40 C. Kinematic Viscosity) mm.sup.2/s 23.5 20.4 20.3 20.3 21.0 Base Oil Viscosity (100 C. Kinematic Viscosity) mm.sup.2/s 4.80 4.72 4.72 4.72 4.72 Base Oil Viscosity Index 128 159 160 160 150 Composition Viscosity (40 C. Kinematic Viscosity) mm.sup.2/s 49.8 48.7 48.7 48.7 48.7 Composition Viscosity (100 C. Kinematic Viscosity) mm.sup.2/s 10.00 9.89 9.89 9.89 9.89 Composition Viscosity Index 193 195 195 195 195 Boron (B) Content *.sup.1 mass % 0.023 0.007 0.007 0.023 0.023 Molybdenum (Mo) Content *.sup.2 mass % 0.004 0.020 0.000 0.020 0.020 Sulfur (S) Content *.sup.3 mass % 2.000 2.000 2.000 1.250 2.000 Phosphorus (P) Content *.sup.3 mass % 0.192 0.192 0.192 0.192 0.084 Nitrogen (N) Content *.sup.4 mass % 0.080 0.059 0.059 0.080 0.080 (B)/(Mo) 5.75 0.35 1.15 1.15 (S)/(P) 10.4 10.4 10.4 6.5 23.8 Evaluation Shear Stability % <3 <3 <3 <3 <3 Traction Coefficient 0.04 0.04 0.04 0.04 0.04 Intermetallic Friction Coefficient 0.09 0.10 0.11 0.07 0.07 Oxidation Stability (viscosity increase rate) % <5 <5 <5 <5 <5 Shell 4-Ball Test: EP (WL) N >3000 >3000 >3000 2452 >3000 Shell 4-Ball Test: WEAR mm 0.41 0.45 0.44 0.39 0.69
Notes) *1 to *4 in Table 1 and Table 2 are as follows. [0119] *1: The boron (B) content is a boron atom-equivalent content of the boron-containing dispersant (the boron atom content contained in the boron-containing dispersant) based on the total amount of the composition. [0120] *2: The molybdenum (Mo) content is a molybdenum atom-equivalent content of the molybdenum-based friction modifier (the molybdenum atom content contained in the molybdenum-based friction modifier) based on the total amount of the composition. [0121] *3: The sulfur (S) content and the phosphorus (P) content are the total content of the sulfur atoms and the total content of the phosphorus atoms contained in the extreme-pressure additive used. [0122] *4: The nitrogen (N) content is the total amount of the nitrogen content in the dispersant and the nitrogen (N) fraction (0.052% by mass) contained in the antioxidant in the other additive.

INDUSTRIAL APPLICABILITY

[0123] The lubricating oil composition of the present invention is a lubricating oil composition satisfying both fuel saving properties and extreme-pressure properties, and having shear stability, oxidation stability and wear resistance, and is, in particular, favorably used for gear systems, for example, for gear oil for automobiles, industrial gear oil, etc., and is especially favorably used for lubrication for differential gearing in automobiles.