Two-phase lubricant

Abstract

The present 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; and (c) an antifoam additive which is a nonionic surfactant, the mass % being based on the total mass of the lubricating composition. The present invention also provides a method for lubricating an axle, the method comprising supplying the lubricating oil composition to the axle, the ... 2 (b) 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 1 / s; (b) 3 to 35 mass % of a high viscosity second base oil component which is a polyalkylene glycol; and (c) an antifoam additive which is a nonionic surfactant, the mass % being based on the total mass of the lubricating composition.

Description

[Technical Field]

[0001] This invention relates to a method for lubricating an axle and a lubricating oil composition used therefor. [Background technology]

[0002] Fuel economy is a major challenge in the automotive industry. A key method for improving fuel efficiency is the use of lubricants with lower viscosity. However, maintaining appropriate lubricant viscosity across the entire operating temperature range is also crucial. Maintaining the required level of protection under high-load and high-temperature conditions can prove difficult with low-viscosity lubricant formulations.

[0003] Two-phase lubricants consist of a low-viscosity component and a high-viscosity component. Typically, mineral base oil or poly-α-olefin (PAO) is used as the low-viscosity component, and polyalkylene glycol is selected as the high-viscosity component. In two-phase lubricants, polyalkylene glycol is in a phase separated from the low-viscosity component below room temperature, but begins to dissolve in the low-viscosity component as the temperature rises. Then, this phenomenon reverses as the temperature decreases. Therefore, at low temperatures, lubrication comes from the low-viscosity component, effectively reducing friction, while at high temperatures, the high-viscosity component plays a major role, providing greater wear protection.

[0004] International Publication No. 9611244 discloses a lubricant that functions at both high and low temperatures by combining a low-viscosity lubricant and a high-viscosity lubricant. At low temperatures, it utilizes only the properties of the low-viscosity lubricant, while at high temperatures, it utilizes the property of the oil whose viscosity increases by mixing the high-viscosity and low-viscosity lubricants.

[0005] International Publication No. 2014207172 describes a lubricant produced by mixing (i) a low viscosity lubricant base oil component selected from mineral oil, synthetic oil, and GTL, (ii) a high viscosity component of polyalkylene glycol, and (iii) a modifying component, with a kinematic viscosity of 3.5 to 7.0 mm at 100°C. 2 This describes a drive system power transmission oil composition with a value of / second.

[0006] Further research on the use of two-phase 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 fully soluble and active at low temperatures when the lubricant is two-phase, maintain both solubility and activity when the two phases are fully mixed, and continue to maintain both solubility and activity as the temperature drops again. Such activity must be maintained over repeated heating and cooling cycles. Of particular importance is the provision of antifoaming additives that act in two-phase lubricants and can provide substantial antifoaming protection over a wide temperature range. [Brief explanation of the drawing]

[0008] [Figure 1] Figures 1a, 1b, and 1c are schematic diagrams of a two-phase fluid in use. [Overview of the Initiative]

[0009] The present invention relates to a lubricating oil composition, (a) 3.5~7.0mm 2 A Fischer-Tropsch derivative base oil having a kinematic viscosity at 100°C in the range of / seconds, comprising a first base oil component with low viscosity of 45-75% by mass, (b) A second base oil component having a high viscosity of 3 to 35% by mass, which is polyalkylene glycol, (c) A lubricating oil composition is provided which comprises a nonionic surfactant as an antifoaming additive, and whose mass % is based on the total mass of the lubricating composition.

[0010] 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 is (a) 3.5~7.0mm 2 A Fischer-Tropsch derivative base oil having a kinematic viscosity at 100°C in the range of / seconds, comprising a first base oil component with low viscosity of 45-75% by mass, (b) A second base oil component having a high viscosity of 3 to 35% by mass, which is polyalkylene glycol, (c) A nonionic surfactant antifoaming additive, wherein the antifoaming additive is present in a mass % based on the total mass of the lubricating composition. [Modes for carrying out the invention]

[0011] Surprisingly, it has been found that nonionic surfactant-based defoamers provide excellent defoaming properties in a two-phase lubricating oil composition containing a Fischer-Tropsch base oil as a low-viscosity component and polyalkylene glycol as a high-viscosity component.

[0012] Furthermore, this lubricating oil composition can be widely and effectively used as an industrial lubricant such as power transmission oils, hydraulic fluids, and compressor oils for automobiles, including gear oils, automatic transmission oils, manual transmission oils, and continuously variable transmission oils. In a preferred embodiment, it is used as an axle fluid.

[0013] Fischer-Tropsch derivative base oils are prepared using the Fischer-Tropsch process to convert carbon monoxide and hydrogen into various liquid fuels and oils. The sources of carbon monoxide and hydrogen can be diverse. For example, gas-to-liquid (GTL) base oils are synthesized by the Fischer-Tropsch process using natural gas as a starting material. Various other XTL processes are known, where X represents the source of carbon and hydrogen atoms, such as coal-to-liquid (CTL), biomass-to-liquid (BTL), and power-to-liquid (PTL). GTL base oils or blends thereof are ideal for use as Fischer-Tropsch derivative base oils in this invention because, compared to mineral base oils produced from crude oil, they have extremely low sulfur and aromatic content, a very high paraffin component ratio, excellent oxidation stability, and extremely low evaporation losses.

[0014] Fischer-Tropsch derivative base oils have a wide range of kinematic viscosities (KV100) at 100°C, ranging from 3.5 to 7.0 mm. 2 In this invention, a Fischer-Tropsch derivative base oil having a KV100 in the range of / second is used. The Fischer-Tropsch derivative base oil is 3.5-7.0 mm 2 It may be a single Fischer-Tropsch derivative base oil having a KV100 in the range of / second, or a blend with a KV100 of 3.5-7.0 mm 2 It may also be a blend of two or more Fischer-Tropsch derivative base oils in the range of / second. More preferably, the first base oil component, which is a low viscosity Fischer-Tropsch derivative base oil, has a viscosity of 4.0 to 6.0 mm at 100°C. 2 It has a kinematic viscosity in the range of / second.

[0015] The amount of the first low-viscosity base oil component, which is a Fischer-Tropsch derivative base oil, is 45 to 75% by mass, preferably 45 to 65% by mass, based on the total mass of the lubricating oil composition.

[0016] The second base oil constituent with high viscosity is present in the range of 3 to 35% by mass based on the total mass of the lubricating oil composition. The second base oil constituent with high viscosity is a polyalkylene glycol. Preferred polyalkylene glycols include poly(oxypropylene)-based products. Preferably, the second base oil constituent with high viscosity is present in an amount in the range of 13 to 28% by mass based on the total mass of the lubricating oil composition.

[0017] A suitable second base oil constituent with high viscosity has a KV100 in the range of 90 to 120 mm 2 / sec, preferably 95 to 105 mm 2 / sec.

[0018] The lubricating oil composition also contains a nonionic surfactant as an antifoaming additive. Such nonionic surfactants tend to be polyalkoxylated alcohols, amines, and mixtures thereof.

[0019] In some embodiments of the present invention, it may be preferable to add an adjustment constituent containing one or more ester base oils to the lubricating oil composition. Such an ester base oil acts as an adjustment constituent for the two-phase oil separation temperature. Above this temperature, both phases become miscible, and below this temperature, both phases become immiscible. As described in Tribology Online, 11, 1 (2016), 24 - 33 by Kamata et al., the difference in polarity between the high-viscosity constituent and the low-viscosity constituent changes with the addition of this adjustment constituent.

[0020] Suitable esters have both a hydrophobic group and a hydrophilic group, dissolve in both the high-viscosity constituent and the low-viscosity constituent, change their polarities, and thus can control the temperature at which the two-phase oil separates. It is also possible to use a combination of two or more different ester base oils as the adjustment constituent.

[0021] Preferably, the ester base oil or a mixture thereof used as the adjustment constituent has a range of 3.5 to 10 mm 2 / sec, more preferably 3.5 mm2 It has a kinematic viscosity at 100°C of 100°C or more. Preferably, KV100 is 8 mm 2 Less than / second, more preferably 6mm 2 The kinematic viscosity of the first base oil component with low viscosity is less than or equal to 1 mm². Preferably, the ester base oil or mixture thereof used as the adjusting component has a kinematic viscosity of 1 mm². 2 Less than / second, more preferably 0.5mm 2 It has a kinematic viscosity at 100°C that is greater than or less than / second.

[0022] Suitable ester base oils for use as adjusting components are described in International Publication No. 2014207172, and these ester base oils (or mixtures thereof) are required to have an oxygen / carbon weight ratio of 0.080 to 0.350, preferably 0.080 to 0.300, and more preferably 0.080 to 0.250.

[0023] The ester base oil may be any of the following: a monoester, diester, partial ester, or full ester of a polyhydric alcohol.

[0024] The alcohol constituting the ester base oil may be a monohydric alcohol or a polyhydric alcohol, and the acid may be a monobasic acid or a polybasic acid.

[0025] The monohydric alcohol may have 1 to 24 carbon atoms, preferably 1 to 12, and more preferably 1 to 8 carbon atoms, and may be linear or branched in structure. They may also be saturated or unsaturated.

[0026] The polyhydric alcohol may be a dihydric to decahydric alcohol, but is preferably a dihydric to hexahydric alcohol. Dihydric alcohols are an example of dihydric to decahydric polyhydric alcohols. The alcohol constituting the ester base oil may be a monohydric alcohol or any of the polyhydric alcohols, and the acid may be a monobasic acid or a polybasic acid.

[0027] Examples of monobasic acids that form ester base oils include fatty acids with 2 to 24 carbon atoms, which may be linear or branched, saturated or unsaturated. Of the saturated and unsaturated fatty acids mentioned above, 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. Saturated fatty acids with 4 to 18 carbon atoms are most preferred when considering improved lubricity, ease of handling, and oxidation stability.

[0028] If present, the amount of the adjusting component containing one or more ester base oils is 1 to 20% by mass, preferably 2 to 10% by mass, based on the total mass of the lubricating oil composition.

[0029] The lubricating oil composition of the present invention may contain, individually or in combination with several other additives well known in the art, such as extreme pressure additives, dispersants, metallic detergents, friction modifiers, antioxidants, corrosion inhibitors, rust inhibitors, anti-emulsifiers, metal deactivators, pour point depressants, sealing swelling agents, defoaming agents, and colorants. Typically, some or all of these additives may be provided as an additive package.

[0030] Detailed description of the drawing Figures 1a, 1b, and 1c provide schematic diagrams of the use of a two-phase lubricating oil composition.

[0031] Figure 1a shows one embodiment of the lubricating oil composition of the present invention, illustrating a two-phase state 1, which is the state of the lubricating oil composition at low temperatures. The low-viscosity first base oil component 2 forms the upper phase, and the high-viscosity second base oil component 3 forms the lower phase. Figure 1b shows the state in which the lubricated machine 4 is in use and immersed in the upper phase of the lubricating oil composition. At startup (low temperature), the low-viscosity first base oil component 2, which forms the upper phase, mainly contributes 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 exhibits sufficient lubrication performance at low temperatures, the presence of only the low-viscosity component does not impair lubrication performance. Figure 1c shows a single-phase state 5 that is generated following a temperature rise resulting from continuous use of the machine 4.

[0032] Here, as a result of the temperature rise, the low-viscosity first base oil component 2 and the high-viscosity second base oil component 3 mix to produce a homogeneous lubricating oil composition. The decrease in viscosity of the low-viscosity first base oil component 2 due to the temperature rise is compensated for by the high-viscosity second base oil component 3, so even if the temperature rises, problems such as the breakdown of the oil film do not occur.

[0033] The present invention will now be demonstrated by the following non-limiting embodiments.

[0034] Examples A series of lubricating oils were blended as listed in Tables 1 and 2. The compositions used are as follows: Low viscosity base oil: 5.5mm 2 Blend of GTL base oil with KV100 / second High viscosity base oil: Synalox 100-D450, e.g., Dow, a water-insoluble homopolymer of propylene oxide (KV40 at 713 cSt, KV100 at 110 cSt). Ester base oils: For example, Croda's Priolubé 1936, diester base oils (KV40 at 26 cSt, KV100 at 5.3 cSt) Adpack 1 - A commercially available multi-functional automotive gear package. Antifoaming agent 1-Viscoplex14-520, an organically modified siloxane antifoaming agent manufactured by Evonik. Antifoaming agent 2-DCF200-12500cSt(3%), for example, a polydimethylsiloxane-based antifoaming agent manufactured by Dow Corning. Antifoaming agent 3-Synative AC AMH-2 - Nonionic surfactant-based antifoaming agent, e.g., manufactured by Cognis. Friction modifier - Commercially available amine-based friction modifier.

[0035] The formulations shown in Tables 1 and 2 were blended using standard methods and tested using the standard test ASTM D892. As the tests demonstrate, a tendency for oil to foam can be a serious problem in systems such as high-speed gears, high-volume pumping, and splash lubrication. Insufficient lubrication, cavitation, and lubricant overflow losses can lead to mechanical failure. This test method is used in evaluating oils under such operating conditions. This test method encompasses the determination of the foaming properties of lubricating oils at 24°C and 93.5°C. It consists of three steps.

[0036] In procedure I, a portion of the sample, maintained at a constant temperature of 24°C ± 0.5°C, is foamed with air at a constant rate (94 mL / min ± 5 mL / min) for 5 minutes, and then allowed to stand for 10 minutes. The volume of the foam is measured at the end of both periods.

[0037] In step II, a second portion of the sample, maintained at a constant temperature of 93.5°C ± 0.5°C, is analyzed using the same airflow rate, foaming, and standing time as indicated in the previous step.

[0038] Finally, in Action Sequence III, the sample portion used in Action Sequence II is reused, but here any remaining foam is collapsed, and the temperature of the sample portion is cooled to below 43.5°C by leaving the test cylinder in air at room temperature before placing the cylinder in a bath maintained at 24°C ± 0.5°C. The same airflow, foaming, and standing time as in Action Sequence I are followed.

[0039] The results of the tested examples are shown in Table 1. SAE J2360 sets standards 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. Here, the maximum allowable volume of foam at the end of the 5-minute foaming period for action sequences I, II, and III are 20, 50, and 20 mL, respectively.

[0040] [Table 1]

[0041] [Table 2]

[0042] An antifoaming agent is required in lubricating oil compositions containing only low-viscosity base oils (see Examples 2-5, compared to Example 1). Organically modified siloxanes (antifoaming agent 1) did not provide the desired results, and polydimethylsiloxane-based defoaming agents (antifoaming agent 2) were required to provide the necessary reduction in foaming (see Examples 3-5).

[0043] However, the use of this defoamer in a two-phase lubricating oil composition (Example 6) results in increased foaming compared to a single-phase composition. The nonionic surfactant-based defoamers used in Examples 7 to 10 provide excellent foaming results in two-phase lubricating oil compositions, whether used alone or in combination with other defoamers. Obtaining excellent foaming results (between the two-phase and single-phase states) over a certain temperature range using a single defoamer in a two-phase fluid is a highly desirable outcome. The embodiments are described below. Appearance 1 A lubricating oil composition, (a) 3.5~7.0mm 2 A Fischer-Tropsch derivative base oil having a kinematic viscosity at 100°C in the range of / seconds, comprising a first base oil component with low viscosity of 45-75% by mass, (b) A second base oil component having a high viscosity of 3 to 35% by mass, which is polyalkylene glycol, (c) A lubricating oil composition comprising a nonionic surfactant as an antifoaming additive, wherein the mass % is based on the total mass of the lubricating composition. Appearance 2 The first base oil component with low viscosity is 4.0 to 6.0 mm 2 The lubricating oil composition according to embodiment 1, having a kinematic viscosity at 100°C in the range of / seconds. Appearance 3 The aforementioned high-viscosity second base oil component is 90-120 mm 2 / second, preferably 95-105mm 2 A lubricating oil composition according to embodiment 1 or 2, having a kinematic viscosity at 100°C in the range of / seconds. Pattern 4 A lubricating oil composition according to any one of embodiments 1 to 3, which also includes a conditioning component containing one or more ester base oils. Appearance 5 The lubricating oil composition according to embodiment 4, wherein the ester base oil has an oxygen / carbon weight ratio of 0.080 to 0.350, preferably 0.080 to 0.300. Appearance 6 The ester base oil reduces the kinematic viscosity of the low-viscosity first base oil component to 1 mm². 2 Less than / second, more preferably 0.5mm 2 A lubricating oil composition according to embodiment 4 or 5, having a kinematic viscosity at 100°C that is greater than or less than / second. Appearance 7 The lubricating oil composition according to any one of embodiments 4 to 6, wherein the adjusting component containing 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. Appearance 8 The lubricating oil composition according to any one of embodiments 1 to 7, wherein the nonionic surfactant is selected from polyalkoxylated alcohols, polyalkoxylated amines, and mixtures thereof. Appearance 9 A method for lubricating an axle, the method comprising supplying a lubricating oil composition to the axle, wherein the lubricating oil composition is (a) 3.5~7.0mm 2 A Fischer-Tropsch derivative base oil having a kinematic viscosity at 100°C in the range of / seconds, comprising a first base oil component with low viscosity of 45-75% by mass, (b) A second base oil component having a high viscosity of 3 to 35% by mass, which is polyalkylene glycol, (c) A method comprising a nonionic surfactant as an antifoaming additive, wherein the mass % is based on the total mass of the lubricating composition.

Claims

1. (a) 3.5-7.0mm ２ A Fischer-Tropsch derivative base oil having a kinematic viscosity at 100°C in the range of / seconds, comprising a first base oil component with low viscosity of 45-75% by mass, (b) A polyalkylene glycol having a kinematic viscosity at 100°C in the range of 90 to 120 mm² / second, comprising 3 to 35% by mass of a second high-viscosity base oil component, (c) an antifoaming additive which is a nonionic surfactant selected from polyalkoxylated alcohols, polyalkoxylated amines, and mixtures thereof, A lubricating oil composition comprising one or more ester base oils as a conditioning component, wherein the mass percentage is based on the total mass of the lubricating oil composition.

2. The first low-viscosity base oil component is 4.0 to 6.0 mm ２ The lubricating oil composition according to claim 1, having a kinematic viscosity at 100°C in the range of 1 / second.

3. The aforementioned high-viscosity second base oil component is 95-105 mm ２ A lubricating oil composition according to claim 1 or 2, having a kinematic viscosity at 100°C in the range of 1 / second.

4. The lubricating oil composition according to claim 1, wherein the ester base oil has an oxygen / carbon weight ratio of 0.080 to 0.350, preferably 0.080 to 0.

300.

5. The ester base oil reduces the kinematic viscosity of the first base oil component with low viscosity to 1 mm². ２ Less than 0.5 mm / second, more preferably 0.5 mm ２ The lubricating oil composition according to claim 1, having a kinematic viscosity at 100°C that is greater than or less than / second.

6. The lubricating oil composition according to claim 1, wherein the adjusting component containing 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.

7. A method for lubricating an axle, the method comprising supplying a lubricating oil composition to the axle, wherein the lubricating oil composition is (a) 3.5-7.0mm ２ A Fischer-Tropsch derivative base oil having a kinematic viscosity at 100°C in the range of / seconds, comprising a first base oil component with low viscosity of 45-75% by mass, (b) A polyalkylene glycol having a kinematic viscosity at 100°C in the range of 90 to 120 mm² / second, comprising 3 to 35% by mass of a second high-viscosity base oil component, (c) an antifoaming additive which is a nonionic surfactant selected from polyalkoxylated alcohols, polyalkoxylated amines, and mixtures thereof, A method comprising a modified component containing one or more ester base oils, wherein the mass percentage is based on the total mass of the lubricating oil composition.

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