Two-phase lubricant

Abstract

The invention provides a lubricating oil composition comprising (a) 45 to 75 mass% of a low viscosity first base oil component which is a Fischer-Tropsch derived base oil having a kinematic viscosity at 100°C in the range of 3.5 to 7.0 mm2 / s; (b) 3 to 35 mass% of a high viscosity second base oil component which is a polyalkylene glycol; (c) an antifoam additive which is a non-ionic surfactant, wherein mass% is based on the total mass of the lubricating composition. The invention also provides a method for lubricating an axle, the method comprising supplying to the axle a lubricating oil composition comprising: (a) 45 to 75 mass% of a low viscosity first base oil component which is a Fischer-Tropsch derived base oil having a kinematic viscosity at 100°C in the range of 3.5 to 7.0 mm2 / s; (b) 3 to 35 mass% of a high viscosity second base oil component which is a polyalkylene glycol; (c) an antifoam additive which is a non-ionic surfactant, wherein mass% is based on the total mass of the lubricating composition.

Description

Technical Field

[0001] The present invention relates to a method for lubricating axles and a lubricating oil composition for use in the method. Background Technology

[0002] Fuel economy is a major challenge in the automotive industry. A key way to improve fuel efficiency is to use lubricants with lower viscosity. However, maintaining the appropriate lubricant viscosity across the entire temperature range of equipment operation is also important. In particular, maintaining the necessary level of protection under high load and high temperature conditions demonstrates the challenge of using low-viscosity lubricant formulations.

[0003] Two-phase lubricants consist of a low-viscosity component and a high-viscosity component. Typically, mineral base oils or poly-α-olefins (PAOs) are used as the low-viscosity component, and polyalkylene glycols are selected for the high-viscosity component. In two-phase lubricants, the polyalkylene glycol is in a phase separated from the low-viscosity component at room temperature and below, but begins to dissolve in the low-viscosity component as the temperature increases. This phenomenon then reverses as the temperature decreases. Therefore, at low temperatures, lubrication comes from the low-viscosity component and effectively reduces friction, while at high temperatures, the higher-viscosity component plays a crucial role in providing better wear protection.

[0004] WO9611244 discloses a lubricating oil that functions at both high and low temperatures by combining a low-viscosity lubricating oil and a high-viscosity lubricating oil. It utilizes only the properties of the low-viscosity lubricating oil at low temperatures, while simultaneously utilizing the property of the oil to increase viscosity by mixing the high-viscosity lubricating oil with the low-viscosity lubricating oil at high temperatures.

[0005] WO2014207172 teaches a drive system transmission oil composition having a kinematic viscosity of 3.5 mm at 100°C. 2 / s to 7.0mm 2 / s is produced by mixing the following substances: (i) a low-viscosity lubricant base oil component selected from mineral oils, synthetic oils and GTLs; (ii) a high-viscosity component based on polyalkylene glycols; and (iii) a control component.

[0006] Further research on the use of duplex lubricants is described in Kamata et al., Tribology Online, 11, 1 (2016), 24-33.

[0007] Blending two-phase lubricants presents numerous challenges. Any additive must be completely soluble and active at low temperatures when the lubricant is in a two-phase state, maintain its solubility and activity when the two phases are thoroughly mixed, and continue to maintain its solubility and activity when the temperature is lowered again. This activity must be maintained through repeated heating and cooling cycles. Of particular interest is providing defoaming additives that function in two-phase lubricants and provide significant defoaming protection over a wide temperature range. Attached Figure Description

[0008] Figure 1 a, Figure 1 b and Figure 1 c is a schematic diagram of a two-phase fluid in use. Summary of the Invention

[0009] This invention provides a lubricating oil composition comprising:

[0010] (a) 45% to 75% by mass of a low-viscosity first base oil component, wherein the low-viscosity first base oil component has a kinematic viscosity of 3.5 mm at 100°C. 2 / s to 7.0mm 2 Fischer-Tropsch derivative base oils in the range of / s;

[0011] (b) 3% to 35% by mass of a high-viscosity second base oil component, wherein the high-viscosity second base oil component is a polyalkylene glycol;

[0012] (c) An antifoaming additive, which is a nonionic surfactant, wherein the mass % is based on the total mass of the lubricating composition.

[0013] The present invention also provides a method for lubricating an axle, the method comprising supplying a lubricating oil composition to the axle, the lubricating oil composition comprising

[0014] (a) 45% to 75% by mass of a low-viscosity first base oil component, wherein the low-viscosity first base oil component has a kinematic viscosity of 3.5 mm at 100°C. 2 / s to 7.0mm 2 Fischer-Tropsch derivative base oils in the range of / s;

[0015] (b) 3% to 35% by mass of a high-viscosity second base oil component, wherein the high-viscosity second base oil component is a polyalkylene glycol;

[0016] (c) An antifoaming additive, which is a nonionic surfactant, wherein the mass % is based on the total mass of the lubricating composition. Detailed Implementation

[0017] It has been surprisingly found that nonionic surfactant-based defoamers provide excellent defoaming properties in dual-phase lubricant compositions containing Fischer-Torque base oil as a low-viscosity component and polyalkylene glycol as a high-viscosity component.

[0018] This lubricating oil composition is also effective in a wide range of industrial lubricants, such as automotive gear oils, transmission oils (such as AT oils, MT oils, and CVT oils), hydraulic oils, and compressor oils. In a preferred embodiment, it is used as an axle fluid.

[0019] Fischer-Tropsch derived base oils are those produced using the Fischer-Tropsch process to convert carbon monoxide and hydrogen into a range of liquid fuels and oils. The sources of carbon monoxide and hydrogen can be diverse. For example, natural gas is used as a starting material to synthesize gas-to-liquid (GTL) base oils via the Fischer-Tropsch process. Various other XTL processes, where X represents the source of carbon and hydrogen atoms, are known, such as coal-to-liquid (CTL), biomass-to-liquid (BTL), and power-to-liquid (PTL). GTL base oils or blends thereof are ideally used as Fischer-Tropsch derived base oils in this invention because, relative to mineral oil base oils produced from crude oil, they have extremely low sulfur and aromatic content and a very high alkane composition, meaning they exhibit excellent oxidative stability and minimal evaporation loss.

[0020] Fischer-Tropsch derivative base oils exhibit a wide range of kinematic viscosities (KV100) at 100°C, but in this invention, a KV100 of 3.5 mm is used. 2 / s to 7.0mm 2 Those within the range of / s. The Fischer-Tropsch derivative base oil can be KV100 at 3.5mm. 2 / s to 7.0mm 2 A blend of a single Fischer-Tropsch derivative base oil or more than one Fischer-Tropsch derivative base oil within the range of / s, wherein the KV100 of the blend is within 3.5mm. 2 / s to 7.0mm 2 Within the range of / s. More preferably, the low-viscosity first base oil component, as a Fischer-Tropsch derived base oil, has a kinematic viscosity of 4.0 mm at 100°C. 2 / s to 6.0mm 2 Within the range of / s.

[0021] Based on the total mass of the lubricating oil composition, the amount of the low-viscosity first base oil component, which is a Fischer-Tropsch-derived base oil, is 45% to 75% by mass, preferably 45% to 65% by mass.

[0022] Based on the total mass of the lubricating oil composition, the high-viscosity second base oil component is present in an amount ranging from 3% to 35% by mass. The high-viscosity second base oil component is a polyalkylene glycol. Preferred polyalkylene glycols include products based on poly(propylene oxide). Preferably, based on the total mass of the lubricating oil composition, the high-viscosity second base oil component is present in an amount ranging from 13% to 28% by mass.

[0023] The appropriate KV100 for the high viscosity second base oil component is at 90 mm. 2 / s to 120mm 2 / s, preferably 95mm 2 / s to 105mm 2 Within the range of / s.

[0024] The lubricating oil composition also contains nonionic surfactants as defoaming additives. Such nonionic surfactants tend to be polyalkoxylated alcohols, amines, and mixtures thereof.

[0025] In some embodiments of the invention, it is preferable to add a control component comprising one or more ester base oils to the lubricating oil composition. Such one or more ester base oils serve as a control component for the two-phase oil separation temperature, above which both phases become miscible, and below which both phases become immiscible. As explained by Kamata et al., Tribology Online, 11, 1 (2016), 24-33, the polarity difference between the high-viscosity and low-viscosity components is altered by the addition of this control component.

[0026] Suitable esters possess both hydrophobic and hydrophilic groups and can dissolve in both high-viscosity and low-viscosity components, thereby altering their polarity and controlling the temperature during two-phase oil separation. It should be noted that two or more different ester base oils can also be used in combination as control components.

[0027] Preferably, the kinematic viscosity of the ester base oil or its mixture used as the control component is 3.5 mm at 100°C. 2 / s to 10mm 2 Within the range of / s, more preferably not less than 3.5mm 2 / s. Preferably, KV100 is no greater than 8mm. 2 / s, and more preferably no more than 6mm 2 / s. More preferably, the kinematic viscosity of the ester base oil or its mixture used as the control component is at 100°C not more than 1 mm higher or lower than the kinematic viscosity of the low-viscosity first base oil component. 2 / s, more preferably not greater than 0.5mm 2 / s.

[0028] Suitable ester base oils for use as control components are described in WO2014207172, wherein the oxygen / carbon weight ratio of the ester base oil (or mixtures thereof) is required to be from 0.080 to 0.350, preferably from 0.080 to 0.300, and more preferably from 0.080 to 0.250.

[0029] Ester base oils can be any of the monoesters, diesters, and partial or complete esters of polyols.

[0030] The alcohol that forms the ester base oil can be a monohydric alcohol or any polyhydric alcohol, and the acid can be a monohydric acid or a polyhydric acid.

[0031] Monohydric alcohols can be alcohols with 1 to 24 carbon atoms, but preferably 1 to 12 and more preferably 1 to 8, and can be straight-chain or branched. They can also be saturated or unsaturated.

[0032] The polyol can be a dihydric to decahydric alcohol, but preferably a dihydric to hexahydric alcohol. Examples of dihydric to decahydric polyols include dihydric alcohols. The alcohol forming the ester base oil can be a monohydric alcohol, or any polyhydric alcohol, and the acid can be a monohydric acid or a polyhydric acid.

[0033] For the acids forming ester base oils, monocarboxylic acids comprise fatty acids with 2 to 24 carbon atoms, and these can be straight-chain or branched, and saturated or unsaturated. Among the aforementioned saturated and unsaturated fatty acids, saturated fatty acids with 3 to 20 carbon atoms, unsaturated fatty acids with 3 to 22 carbon atoms, and mixtures thereof are preferred, but saturated fatty acids with 4 to 18 carbon atoms, unsaturated fatty acids with 4 to 18 carbon atoms, and mixtures thereof are more preferred. Lubricity and handling qualities are improved, and saturated fatty acids with 4 to 18 carbon atoms are most preferred, taking oxidative stability into account.

[0034] If present, the amount of the controlled component comprising one or more ester base oils is from 1% to 20% by mass, preferably from 2% to 10% by mass, based on the total mass of the lubricating oil composition.

[0035] Various additives known in the art can be blended with the lubricating oil compositions of the present invention, either alone or in combinations of several types. These additives include, for example, extreme pressure additives, dispersants, metal detergents, friction modifiers, antioxidants, corrosion inhibitors, rust inhibitors, demulsifiers, metal passivators, pour point depressants, sealing swelling agents, defoamers, and colorants. Typically, some or all of these additives are available as additive packages.

[0036] Detailed description of the attached figures

[0037] Figure 1 a, Figure 1 b and Figure 1 c provides a schematic diagram of the use of the dual-phase lubricating oil composition.

[0038] Figure 1 'a' represents one aspect of the lubricating oil composition of the present invention and shows a two-phase state 1, which is the state of the lubricating oil composition at low temperature. A low-viscosity first base oil component 2 forms the upper phase, while a high-viscosity second base oil component 3 forms the lower phase. Figure 1 Figure b illustrates a state in which machine 4, which is being lubricated, is immersed in the upper phase of the lubricating oil composition. During startup (cold temperature), the low-viscosity first base oil component 2, which forms the upper phase, is the major contributor to lubrication, while the high-viscosity second base oil component 3 contributes almost nothing to lubrication. Since the low-viscosity first base oil component 2 provides sufficient lubrication performance at low temperatures, lubrication performance is not hindered even when only the low-viscosity component is present. Figure 1 c shows single-phase state 5, which occurs after the temperature rises due to continued use of machine 4.

[0039] Here, due to the increase in temperature, the low-viscosity first base oil component 2 and the high-viscosity second base oil component 3 mix, thereby producing a homogeneous lubricating oil composition. The viscosity decrease of the low-viscosity first base oil component 2 due to the increase in temperature is compensated by the high-viscosity second base oil component 3, so even when the temperature rise occurs, problems such as oil film rupture will not occur.

[0040] The invention will now be further illustrated by the following non-limiting embodiments.

[0041] Example

[0042] As shown in Tables 1 and 2, a series of lubricating oils were blended. The components used are as follows:

[0043] Low viscosity (vis) base oil: KV100 is 5.5mm. 2 / s of GTL base oil blends

[0044] High viscosity base oil: Synalox 100-D450, purchased from Dow; water-insoluble homopolymer of propylene oxide (KV40 is 713 cSt; KV100 is 110 cSt).

[0045] Ester base oil: Priolube 1936, purchased from Croda; diester base oil (KV40: 26 cSt; KV100: 5.3 cSt)

[0046] Additive Pack 1—Commercially available multi-functional automotive gear packaging additive pack.

[0047] Defoamer 1—Viscoplex 14-520, an organically modified siloxane defoamer from Evonik.

[0048] Defoamer 2—DCF 200—12500cSt (3%) is a polydimethylsiloxane-based defoamer, purchased from Dow Corning.

[0049] Defoamer 3—Synative AC AMH-2—a nonionic surfactant-based defoamer, purchased from Cognis.

[0050] Friction modifiers—commercially available amine-based friction modifiers.

[0051] The formulations shown in Tables 1 and 2 were blended using standard methods and tested using the standard test ASTM D892. As described in the test, the tendency of oil to foam can be a serious problem in systems such as high-speed transmissions, high-volume pumping, and splash lubrication. Inadequate lubrication, cavitation, and overflow losses of the lubricant can lead to mechanical failure. This test method is used to evaluate oils for such operating conditions. This test method covers the determination of the foaming properties of lubricating oils at 24°C and 93.5°C. It consists of three sequences.

[0052] In sequence I, a portion of the sample, maintained at a bath temperature of 24°C ± 0.5°C, was purged with air at a constant rate (94 mL / min ± 5 mL / min) for 5 min, and then allowed to settle for 10 min. The volume of foam was measured at the end of both cycles.

[0053] In Sequence II, the second portion of the sample maintained at a bath temperature of 93.5 °C ± 0.5 °C was analyzed using the same air flow rate and purging and settling durations as shown in the previous sequence.

[0054] Finally, in Sequence III, the sample portion used in Sequence II is used again, where any remaining foam is collapsed, and the sample portion is cooled to below 43.5°C by allowing the cylinder to stand in air at room temperature before placing it in a bath maintained at 24°C ± 0.5°C. The same airflow rate and purging and settling durations are followed as shown in Sequence I.

[0055] The results of the tested examples are shown in Table 1. SAE J2360 provides a standard for automotive gear lubricants for commercial and military applications. In the SAE J2360 standard, the foaming tendency characteristics of the oil are determined by ASTM D892. Specifically, for Sequence I, Sequence II, and Sequence III, the maximum permissible foam volumes at the end of a 5-minute purge period are 20 mL, 50 mL, and 20 mL, respectively.

[0056] Table 1 - Comparison example

[0057] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 low viscosity oil 85.70 85.63 85.64 84.78 84.75 49.27 High viscosity oil - - - - - 26.38 ester - - - - - 9.99 Additive Pack 1 14.30 14.30 14.29 14.15 14.14 14.29 Defoamer 1 - 0.07 - - - - Defoamer 2 - - 0.07 0.07 0.07 0.07 Friction modifier - - - 1.00 1.00 - Defoamer 3 - - - - 0.04 - Test I 170 / 0 130 / 0 0 / 0 0 / 0 0 / 0 20 / 0 Test II 30 / 0 10 / 0 30 / 0 20 / 0 30 / 0 80 / 0 Test III 150 / 0 70 / 0 0 / 0 0 / 0 0 / 0 20 / 0

[0058] Table 2 - Embodiments of the Invention

[0059] Example 7 Example 8 Example 9 Example 10 low viscosity oil 49.25 48.19 48.26 48.19 High viscosity oil 26.37 26.40 26.40 26.40 ester 9.99 10.00 10.00 10.00 Additive Pack 1 14.28 14.30 14.30 14.30 Defoamer 1 - - - 0.07 Defoamer 2 0.07 0.07 - - Friction modifier - 1.00 1.00 1.00 Defoamer 3 0.04 0.04 0.04 0.04 Test I 0 / 0 0 / 0 10 / 0 10 / 0 Test II 40 / 0 50 / 0 20 / 0 10 / 0 Test III 10 / 0 0 / 0 10 / 0 0 / 0

[0060] Lubricating oil compositions containing only low-viscosity base oils require defoaming additives (see Examples 2 through 5 for comparison with Example 1). Organically modified siloxanes (defoamer 1) did not provide the desired results, and defoamers based on polydimethylsiloxane (defoamer 2) are needed to provide the necessary foam reduction (see Examples 3 through 5).

[0061] However, compared to single-phase compositions, the use of this defoamer in a two-phase lubricating oil composition (Example 6) resulted in increased foaming. Whether used alone or in combination with other defoamers, the nonionic surfactant-based defoamers used in Examples 7 through 10 provided excellent foaming results in the two-phase lubricating oil compositions. Using a single defoamer in a two-phase fluid to produce excellent foaming results over a certain temperature range (during both two-phase and single-phase states) is a highly desirable outcome.

Claims

1. A lubricating oil composition, said lubricating oil composition comprising: (a) 45% to 75% by mass of a low-viscosity first base oil component, wherein the low-viscosity first base oil component has a kinematic viscosity of 3.5 mm at 100°C. 2 / s to 7.0mm 2 Fischer-Tropsch derivative base oils in the range of / s; (b) 3% to 35% by mass of a high-viscosity second base oil component, wherein the high-viscosity second base oil component has a kinematic viscosity of 90 mmHg at 100°C. 2 / s to 120mm 2 Within the range of / s, the high-viscosity second base oil component is a polyalkylene glycol; (c) An antifoaming additive, said antifoaming additive being a nonionic surfactant, wherein said nonionic surfactant is selected from polyalkoxylated alcohols, polyalkoxylated amines, and mixtures thereof; and (d) Controlled components, said controlled components comprising one or more ester base oils, The percentage by mass is based on the total mass of the lubricating oil composition.

2. The lubricating oil composition according to claim 1, wherein the low-viscosity first base oil component has a kinematic viscosity of 4.0 mm at 100°C. 2 / s to 6.0mm 2 Within the range of / s.

3. The lubricating oil composition according to claim 1 or 2, wherein the high-viscosity second base oil component has a kinematic viscosity of 95 mmHg at 100°C. 2 / s to 105mm 2 Within the range of / s.

4. The lubricating oil composition according to claim 1 or 2, wherein the oxygen / carbon weight ratio of the ester base oil is from 0.080 to 0.

350.

5. The lubricating oil composition according to claim 1 or 2, wherein the oxygen / carbon weight ratio of the ester base oil is from 0.080 to 0.

300.

6. The lubricating oil composition according to claim 1 or 2, wherein the kinematic viscosity of the ester base oil at 100°C is not more than 1 mm higher or lower than the kinematic viscosity of the low-viscosity first base oil component. 2 / s.

7. The lubricating oil composition according to claim 1 or 2, wherein the kinematic viscosity of the ester base oil at 100°C is not more than 0.5 mm higher or lower than the kinematic viscosity of the low-viscosity first base oil component. 2 / s.

8. The lubricating oil composition according to claim 1 or 2, wherein the controlled component comprising one or more ester base oils is present in an amount of 2% to 10% by mass based on the total mass of the lubricating oil composition.

9. A method for lubricating an axle, the method comprising supplying the axle with a lubricating oil composition according to any one of claims 1 to 8.

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