Dual Phase Lubricants

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] The present invention relates to a method of lubricating an axle and to a lubricating oil composition for use therein. [Background technology]

[0002] Fuel economy is a major issue in the automotive industry. An important method for improving fuel efficiency is the use of lubricants with lower viscosity. However, it is also important to maintain the proper lubricant viscosity over the full range of temperatures at which the equipment operates. In particular, maintaining the necessary protection levels at high load and high temperature conditions can prove difficult with low viscosity lubricant formulations.

[0003] A dual-phase lubricant consists of a low-viscosity component and a high-viscosity component. Typically, a mineral base oil or poly-α-olefin (PAO) is used as the low-viscosity component, and a polyalkylene glycol is selected as the high-viscosity component. In dual-phase lubricants, the polyalkylene glycol is in a separate phase from the low-viscosity component below room temperature, but begins to dissolve in the low-viscosity component as the temperature increases. This phenomenon is then reversed as the temperature decreases. Thus, 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 and provides greater wear protection.

[0004] WO 9611244 discloses a lubricating oil that functions at both high and low temperatures by combining a low-viscosity lubricating oil with a high-viscosity lubricating oil, utilizing only the properties of the low-viscosity lubricating oil at low temperatures, while utilizing the properties of an oil whose viscosity is increased by mixing a high-viscosity lubricating oil with a low-viscosity lubricating oil at high temperatures.

[0005] WO 2014207172 describes a lubricant having a kinetic viscosity of 3.5 to 7.0 mm at 100° C., which is produced by mixing (i) a low-viscosity lubricant base oil component selected from mineral oil, synthetic oil, and GTL, (ii) a high-viscosity component based on a polyalkylene glycol, and (iii) an adjusting component. 2 / sec.

[0006] Further research on the use of dual-phase lubricants is provided by Kamata et al., Tribology Online, 11, 1 (2016), 24-33.

[0007] Blending two-phase lubricants poses many challenges. Any additive must be fully soluble and active at low temperatures when the lubricant is two-phase, remain both soluble and active when the two phases are fully mixed, and continue to remain both soluble and active when the temperature is reduced again. Such activity must be maintained over repeated cycles of heating and cooling. Of particular importance is the provision of an antifoam additive that can function in two-phase lubricants and provide substantial antifoam protection over a wide range of temperatures. [Brief description of the drawings]

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

[0009] The present invention relates to a lubricating oil composition comprising: (a) 3.5 to 7.0 mm 2 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 wt. % of a high viscosity second base oil component which is a polyalkylene glycol; and (c) an antifoam additive that is a nonionic surfactant, wherein the weight percent is based on the total weight of the lubricating composition.

[0010] The present invention also provides a method for lubricating an axle, the method comprising supplying to the axle a lubricating oil composition comprising: (a) 3.5 to 7.0 mm 2 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 wt. % of a high viscosity second base oil component which is a polyalkylene glycol; and (c) an antifoam additive that is a nonionic surfactant, the weight percent being based on the total weight of the lubricating composition. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Surprisingly, it has been found that nonionic surfactant-based antifoam agents provide excellent antifoam properties in dual-phase lubricant compositions comprising a Fischer-Tropsch-based base oil as the low viscosity component and a polyalkylene glycol as the high viscosity component.

[0012] This lubricating oil composition can also be widely and effectively used as an industrial lubricating oil such as a power transmission oil, hydraulic oil, compressor oil, etc., such as automotive gear oil, AT oil, MT oil, and CVT oil. In a preferred embodiment, it is used as an axle fluid.

[0013] Fischer-Tropsch derived 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 the starting material. Various other XTL processes are known, such as Coal To Liquid (CTL), Biomass To Liquid (BTL) and Power To Liquid (PTL), where X represents the origin of carbon and hydrogen atoms. GTL base oils or blends thereof have extremely low sulfur and aromatic content and very high paraffin component ratio compared to mineral oil base oils produced from crude oil, and therefore are ideal for use as the Fischer-Tropsch derived base oil in the present invention, due to their excellent oxidation stability and extremely low evaporation loss.

[0014] For Fischer-Tropsch derived base oils, there is a wide range of kinematic viscosities at 100°C (KV100), from 3.5 to 7.0 mmHg. 2 The Fischer-Tropsch derived base oil has a KV100 in the range of 3.5-7.0 mm / s. 2 It may be a single Fischer-Tropsch derived base oil having a KV100 in the range of 3.5 to 7.0 mm / s, or the KV100 of the blend may be in the range of 3.5 to 7.0 mm / s. 2 More preferably, the low viscosity first base oil component which is a Fischer-Tropsch derived base oil may be a blend of two or more Fischer-Tropsch derived base oils having a viscosity in the range of 4.0 to 6.0 mm / s at 100°C. 2 / sec range of kinematic viscosity.

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

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

[0017] A preferred high viscosity second base oil component is 90 to 120 mm 2 / sec, preferably 95-105mm 2 It has a KV of 100 / sec range.

[0018] The lubricating oil composition also contains a non-ionic surfactant as an anti-foam additive. Such non-ionic surfactants tend to be polyalkoxylated alcohols, amines, and mixtures thereof.

[0019] In some embodiments of the present invention, it may be preferable to add a modifying component comprising one or more ester base oils to the lubricating oil composition. Such ester base oils act as a modifying component of the two-phase oil separation temperature, above which both phases are miscible and below which both phases are immiscible. As explained in Kamata et al., Tribology Online, 11, 1 (2016), 24-33, the polarity difference between the high-viscosity component and the low-viscosity component is changed by the addition of this modifying component.

[0020] Suitable esters have both hydrophobic and hydrophilic groups and can dissolve in both high and low viscosity components to change their polarity and thus control the temperature at which the two-phase oil separates. It is also possible to use two or more different ester base oils in combination as the tailoring component.

[0021] Preferably, the ester base oil or mixtures thereof used as adjusting components have a viscosity of 3.5 to 10 mm. 2 / sec range, more preferably 3.5 mm2 The kinematic viscosity at 100°C is preferably 8 mm / s or more. 2 / sec or less, and more preferably 6 mm 2 Also preferably, the ester base oil or mixture thereof used as the adjusting component has a kinematic viscosity of 1 mm / s or less than that of the low viscosity first base oil component. 2 / sec or less, preferably 0.5 mm 2 100°C.

[0022] Suitable ester base oils for use as modifying components are described in WO2014207172 and require that the ester base oil (or mixtures thereof) have an oxygen / carbon weight ratio of 0.080 to 0.350, preferably 0.080 to 0.300, more preferably 0.080 to 0.250.

[0023] The ester base oil may be any of monoesters, diesters, partial esters, and full esters of polyhydric alcohols.

[0024] The alcohols that make up the ester base oil may be either monohydric or polyhydric alcohols, and the acids may be monobasic or polybasic acids.

[0025] The monohydric alcohol may be an alcohol having 1 to 24 carbon atoms, preferably 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, and may be linear or branched. 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. Examples of the dihydric to decahydric polyhydric alcohol include dihydric alcohols. The alcohol constituting the ester base oil may be either a monohydric alcohol or a polyhydric alcohol, and the acid may be either a monobasic acid or a polybasic acid.

[0027] The monobasic acid forming the ester base oil includes fatty acids having 2 to 24 carbon atoms, which may be linear or branched, and may be saturated or unsaturated. Among the above-mentioned saturated fatty acids and unsaturated fatty acids, saturated fatty acids having 3 to 20 carbon atoms, unsaturated fatty acids having 3 to 22 carbon atoms, and mixtures thereof are preferred, and saturated fatty acids having 4 to 18 carbon atoms, unsaturated fatty acids having 4 to 18 carbon atoms, and mixtures thereof are more preferred. In consideration of improved lubricity and ease of handling, and oxidation stability, saturated fatty acids having 4 to 18 carbon atoms are most preferred.

[0028] When present, the amount of modifying constituents comprising one or more ester base oils is from 1 to 20 mass %, preferably from 2 to 10 mass %, based on the total mass of the lubricating oil composition.

[0029] The lubricating oil composition of the present invention may contain various additives well known in the art, such as extreme pressure additives, dispersants, metal detergents, friction modifiers, antioxidants, corrosion inhibitors, rust inhibitors, demulsifiers, metal deactivators, pour point depressants, sealant swell agents, antifoaming agents, colorants, etc., either alone or in combination. Typically, some or all of these additives may be provided as an additive package.

[0030] Detailed Description of the Drawings Figures 1a, 1b, and 1c provide a schematic representation of the use of a dual phase lubricant composition.

[0031] FIG. 1a shows an embodiment of the lubricating oil composition of the present invention, showing a two-phase state 1, which is the state of the lubricating oil composition at low temperature. 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. FIG. 1b shows a state in which a lubricated machine 4 is used and the machine is immersed in the upper phase of the lubricating oil composition. At start-up (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 very little to lubrication. The low-viscosity first base oil component 2 provides sufficient lubricating performance at low temperatures, so that the lubricating performance is not hindered even when only the low-viscosity components are present. FIG. 1c shows a single-phase state 5, which is generated following an increase in temperature resulting from continuous use of the machine 4.

[0032] Here, as a result of the temperature rise, the low-viscosity first base oil constituent 2 and the high-viscosity second base oil constituent 3 are mixed to produce a homogeneous lubricating oil composition. The viscosity reduction of the low-viscosity first base oil constituent 2 caused by the temperature rise is compensated for by the high-viscosity second base oil constituent 3, so that even if the temperature rise occurs, problems such as the collapse of the oil film do not occur.

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

[0034] Working Example A series of lubricating oils were blended as listed in Tables 1 and 2. The compositions used were as follows: Low viscosity base oil: 5.5mm 2 GTL base oil blend with KV100 / sec High viscosity base oil: Synalox 100-D450, e.g., Dow, water insoluble homopolymer of propylene oxide (KV40 of 713 cSt, KV100 of 110 cSt). Ester base oil: e.g. Croda's Priolube 1936, diester base oil (26cSt KV40, 5.3cSt KV100) Addpack 1 - Commercially available multi-function automotive gear package addpack. Defoamer 1 - Viscoplex 14-520, an organically modified siloxane defoamer manufactured by Evonik. Defoamer 2-DCF200-12500cSt (3%), e.g., a polydimethylsiloxane-based defoamer from Dow Corning. Defoamer 3-Synative AC AMH-2-Nonionic surfactant based defoamer, e.g., from Cognis. Friction Modifiers-Commercially available amine-based friction modifiers.

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

[0036] In Working Sequence I, a portion of the sample, maintained at a constant bath 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 rest for 10 minutes. The foam volume is measured at the end of both periods.

[0037] In Working Sequence II, a second portion of the sample maintained at a constant temperature of 93.5°C + / - 0.5°C is analyzed using the same air flow rates and foaming and resting times as indicated in the previous Working Sequence.

[0038] Finally, in Working Sequence III, the sample portion used in carrying out Working Sequence II is used again, but now 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 air flow rate, foaming, and resting times as indicated in Working 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 foam tendency characteristics of oils are determined by ASTM D892, where the maximum allowable foam volume at the end of the 5 minute foaming period for working sequences I, II and III are 20, 50 and 20 mL, respectively.

[0040] [Table 1]

[0041] [Table 2]

[0042] Antifoam agents are required in lubricating oil compositions containing only low viscosity base oils (see Examples 2-5, compared to Example 1). An organomodified siloxane (Antifoam Agent 1) does not provide the desired results, and a polydimethylsiloxane-based defoamer (Antifoam Agent 2) is required to provide the necessary reduction in foaming (see Examples 3-5).

[0043] However, use of this antifoam agent in a two-phase lubricant composition (Example 6) results in increased foaming compared to a single-phase composition. The nonionic surfactant-based antifoam agents used in Examples 7-10 provide excellent foaming results in two-phase lubricant compositions, whether used alone or in combination with other antifoam agents. Providing excellent foaming results over a range of temperatures (between two-phase and single-phase conditions) using a single antifoam agent in a two-phase fluid is a highly desirable result.

Claims

1. 1. A lubricating oil composition comprising: (a) 3.5-7.0mm ２ 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 / 200 / s; (b) 3 to 35 wt. % of a high viscosity second base oil component which is a polyalkylene glycol; and (c) an antifoam additive that is a nonionic surfactant, wherein the weight percent is based on the total weight of the lubricating composition.

2. The low viscosity first base oil component has a viscosity of 4.0 to 6.0 mm ２ 10. The lubricating oil composition of claim 1, having a kinematic viscosity at 100°C in the range of 1 / sec.

3. The high viscosity second base oil component is 90 to 120 mm ２ / sec, preferably 95 to 105 mm ２ 3. The lubricating oil composition of claim 1, having a kinematic viscosity at 100°C in the range of 1 / sec.

4. 3. The lubricating oil composition of claim 1 or 2, also comprising a conditioning component comprising one or more ester base oils.

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

300.

6. The ester base oil has a kinematic viscosity of the low viscosity first base oil component of 1 mm ２ / sec or less, more preferably 0.5 mm ２ 5. The lubricating oil composition of claim 4, having a kinematic viscosity at 100°C greater than or less than 1 / 2 second.

7. 5. The lubricating oil composition of claim 4, wherein the modifying component comprising one or more ester base oils is present in an amount of 2 to 10 wt. %, based on the total weight of the lubricating oil composition.

8. 3. The lubricating oil composition of claim 1, wherein the nonionic surfactant is selected from polyalkoxylated alcohols, polyalkoxylated amines, and mixtures thereof.

9. 1. A method for lubricating an axle, the method comprising supplying a lubricating oil composition to the axle, the lubricating oil composition comprising: (a) 3.5-7.0mm ２ 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 / 200 / s; (b) 3 to 35 wt. % of a high viscosity second base oil component which is a polyalkylene glycol; and (c) an antifoam additive that is a nonionic surfactant, wherein the weight percent is based on the total weight of the lubricating composition.

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