LUBRICATING OIL COMPOSITION

Abstract

A lubricating oil composition comprising a base oil, a zinc dialkyldithiophosphate, and a sarcosine derivate is described. The lubricating oil composition may comprise the zinc dialkyldithiophosphate at a concentration of 0.10 to 10 mass % and the sarcosine derivate at a concentration of 0.01 to 5.0 mass %. The lubricating oil composition may have a kinematic viscosity at 100° C. of 6.5 mm.sup.2/s or less, and can be used for lubricating a speed reducer.

Claims

1. A lubricating oil composition, comprising: a base oil, a zinc dialkyldithiophosphate, and a sarcosine derivative.

2. The lubricating oil composition of claim 1, having a kinematic viscosity at 100° C. of 6.5 mm.sup.2/s or less.

3. The lubricating oil composition of claim 1, comprising the zinc dialkyldithiophosphate at a concentration of 0.10 to 10 mass % based on the total mass of the lubricating oil composition.

4. The lubricating oil composition of claim 1, comprising the sarcosine derivative at a concentration of 0.01 to 5.0 mass % based on the total mass of the lubricating oil composition.

5. The lubricating oil composition of claim 1, wherein a mass ratio of the zinc dialkyldithiophosphate to the sarcosine derivative is 1.0 to 10.0.

6. The lubricating oil composition of claim 1, wherein the zinc dialkyldithiophosphate is represented by the following general formula (b-1): ##STR00009## wherein R.sup.1 to R.sup.4 are each independently a hydrocarbon group.

7. The lubricating oil composition of claim 6, wherein at least one of R.sup.1 to R.sup.4 is a group represented by the following general formula (i) or (ii): ##STR00010## wherein R.sup.11 to R.sup.13 are each independently an alkyl group, and wherein * represents a bonding position to an oxygen atom in the formula (b-1)

8. The lubricating oil composition of claim 1, wherein the sarcosine derivative is represented by the following general formula (c-1): ##STR00011## wherein R is a hydrocarbon group having 6 to 30 carbon atoms.

9. The lubricating oil composition of claim 8, wherein R is either an alkyl group having 6 to 30 carbon atoms or an alkenyl group having 6 to 30 carbon atoms.

10. (canceled)

11. A method of lubricating a speed reducer, the method comprising: contacting a speed reducer with a lubricating oil composition, wherein the lubricating oil composition comprises a base oil, a zinc dialkyldithiophosphate, and a sarcosine derivate.

12. A method for producing a lubricating oil composition, the method comprising: adding a zinc dialkyldithiophosphate and a sarcosine derivative to a base oil.

Description

EXAMPLES

[0132] Next, the present invention will be described in much more detail with reference to Examples, but the present invention is in no way limited to these Examples. Measuring methods for various properties are as follows.

(1) Kinematic Viscosity, Viscosity Index

[0133] The kinematic viscosity and viscosity index were measured and calculated in accordance with JIS K2283:2000.

(2) Contents of Zinc Atoms, Phosphorus Atoms, Calcium Atoms, and Molybdenum Atoms

[0134] The contents were measured in accordance with JPI-5S-38-92.

(3) Content of Sulfur Atoms

[0135] The content was measured in accordance with JIS K2541-6:2013.

(4) Base Number (Perchloric Acid Method)

[0136] The base number was measured in accordance with JIS K2501:2003 (perchloric acid method).

(5) Weight-Average Molecular Weight (Mw)

[0137] Using a gel permeation chromatograph apparatus (manufactured by Agilent Technologies, Inc., “1260 model HPLC”), the weight-average molecular weight was measured under the following conditions, and a value measured in terms of standard polystyrene was used.

(Measurement Conditions)

[0138] Column: sequentially connected two of “Shodex LF404”.

[0139] Column temperature: 35° C.

[0140] Developing solvent: chloroform

[0141] Flow rate: 0.3 mL/min

(6) Base Number

[0142] The base number was measured by perchloric acid method in accordance with JIS K2501:2003 “Petroleum products and lubricants—Determination of neutralization number”, 7.

Examples 1 to 4, Comparative Examples 1 to 4

[0143] A base oil and various additives of types shown in Table 1 were added and mixed in amounts shown in Table 1, thereby preparing each lubricating oil composition.

[0144] Details of each component used in the preparation of the lubricating oil composition are as follows. In any of the lubricating oil compositions, the content of molybdenum atoms was less than 2 ppm by mass.

<Component (A): Base Oil>

[0145] “Mineral oil (1)”: hydrocracked mineral oil, 100° C. kinematic viscosity=2.7 mm.sup.2/s, viscosity index=111.

[0146] “Mineral oil (2)”: hydrocracked mineral oil, 100° C. kinematic viscosity=4.1 mm.sup.2/s, viscosity index=125.

[0147] “PAO (1)”: poly-α-olefin, 100° C. kinematic viscosity=1.8 mm.sup.2/s.

[0148] “PAO (2)”: poly-α-olefin, 100° C. kinematic viscosity=100 mm.sup.2/s, viscosity index=170.

<Component (B): ZnDTP>

[0149] ZnDTP: secondary zinc dialkyldithiophosphate; compound represented by the aforementioned general formula (b-1) wherein all of R.sup.1 to R.sup.4 are groups represented by the aforementioned general formula (ii); zinc atom content=9.0 mass %, phosphorus atom content=8.2 mass %, sulfur atom content=17.1 mass %.

<Component (C): Sarcosine Derivative>

[0150] Oleoyl sarcosine: compound of the aforementioned general formula (c-1) wherein R is an oleyl group (C18).

<Oily Agent>

[0151] Oleyl alcohol

[0152] Oleylamine

<Various Additives>

[0153] Ashless dispersant: non-modified polybutenyl bis-succinimide having a butenyl group of Mw=950.

[0154] Ca-based detergent: overbased calcium sulfonate, base number (perchloric acid method)=405 mgKOH/g, calcium atom content=15.2 mass %.

[0155] Sulfur-based extreme pressure agent: thiadiazole, sulfur atom content=35 mass %.

[0156] Viscosity index improver: solution having a resin concentration of 42 mass % obtained by diluting polymethacrylate of Mw=30,000 with a diluent oil.

[0157] Amine-based antioxidant: alkylated diphenylamine.

[0158] Phenol-based antioxidant: hindered phenol.

[0159] Anti-foaming agent: silicone-based anti-foaming agent (solution having a resin concentration of 1.0 mass % obtained by dilution with a diluent oil)

[0160] Regarding the lubricating oil compositions prepared, the kinematic viscosity and viscosity index were measured or calculated, and the following test was carried out. The results of them are set forth in Table 1.

(1) FZG Scuffing Test (A10/16.6R/90)

[0161] A load was stepwise increased based on the regulations using an A10 type gear under the conditions of a sample oil temperature of 90° C., a rotational speed of 2880 rpm and an operating time of 15 minutes in accordance with ASTM D5182-97, and when scoring occurred, a stage of the load was determined. It can be said that the larger the value of the stage is, the better the seizure resistance of the lubricating oil composition becomes. In the present examples, when the stage was 8 or more, the seizure resistance was judged to be “pass”.

(2) Shell Wear Test

[0162] Shell wear test was carried out using a four-ball tester under the test conditions of a load of 490 N, a rotational speed of 1,800 rpm, an oil temperature of 120° C., and a testing time of 30 minutes in accordance with ASTM D2783. After the test, an average value of wear mark diameters of three ½-inch balls was calculated as “Shell wear volume”. It can be said that the smaller the value is, the better the wear resistance of the lubricating oil composition becomes. In the present examples, when the average value (Shell wear volume) of the wear mark diameters was 0.65 mm or less, the wear resistance was judged to be “pass”.

TABLE-US-00001 TABLE 1 Comp. Comp. Comp. Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Formulation of Component (A) Mineral oil (1) mass % 52.62 78.62 92.62 — 79.12 78.62 78.62 80.32 lubricating oil Mineral oil (2) mass % 30.00 — — — — — — — composition PAO(1) mass % — — — 92.62 — — — — PAO(2) mass % — 6.50 — — 6.50 6.50 6.50 6.50 Component (B) ZnDTP mass % 1.70 1.70 1.70 1.70 1.70 1.70 1.70 — Component (C) Oleoyl sarcosine mass % 0.50 0.50 0.50 0.50 — — — 0.50 Oily agent Oleyl alcohol mass % — — — — — 0.50 — — Oleylamine mass % — — — — — — 0.50 — Various Ashless dispersant mass % 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 additives Ca-based detergent mass % 2.60 2.60 2.60 2.60 2.60 2.60 2.60 2.60 Sulfur-based extreme mass % 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 pressure agent Viscosity index improver (*1) mass % 10.00 7.50 — — 7.50 7.50 7.50 7.50 Amine-based antioxidant mass % 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 Phenol-based antioxidant mass % 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 Anti-foaming agent (*2) mass % 0.30 0.30 0.30 0.30 0.30 0.30 0.30 0.30 Total mass % 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 Component (B)/Component (C) — 3.40 3.40 3.40 3.40 — — — — Various 40° C. kinematic viscosity mm.sup.2/s 18.0 18.0 10.8 6.3 17.8 17.9 17.9 17.6 properties 100° C. kinematic viscosity mm.sup.2/s 4.6 4.6 2.9 2.0 4.6 4.6 4.6 4.6 Viscosity index — 186 186 120 107 190 188 188 194 Various tests FZG scuffing test (A10/16.6R/90), Load stage — 11 11 10 10 10 10 10 6 Shell wear test, Wear mark diameter mm 0.34 0.34 0.37 0.39 0.68 0.73 0.69 0.42 (*1): This represents the amount of a solution added having a resin concentration of 42 mass % obtained by dilution with a diluent oil. (*2): This represents the amount of a solution added having a resin concentration of 1.0 mass % obtained by dilution with a diluent oil.

[0163] From Table 1, the seizure resistance and the wear resistance of the lubricating oil compositions of Examples 1 to 4 proved to be good despite the low viscosities. On the other hand, the results for the lubricating oil compositions of Comparative Examples 1 to 3 were inferior in wear resistance. The result for the lubricating oil composition of Comparative Example 4 was inferior in seizure resistance.