Patent Application
20240052254
This invention relates to a method for lubricating an axle and a lubricant oil composition for use therein.
Fuel economy is a major challenge in the automotive industry. A key way to improve fuel efficiency is the use of lubricants with lower viscosities. However, it is also important to maintain an appropriate lubricant viscosity over the complete range of temperatures at which a piece of equipment operates. Particularly, maintaining the necessary level of protection at high load and high temperature conditions can prove challenging with a low viscosity lubricant formulation.
A dual phase lubricant consists of low and high viscosity components. Typically, mineral base oils or poly-α-olefins (PAOs) are used as the low viscosity component and polyalkylene glycols are chosen for the high viscosity component. In two phase lubricants, the polyalkylene glycols are in a separate phase from the low viscosity component at and below room temperature but begin to dissolve in the low viscosity component as the temperature rises. This phenomenon is then reversed as the temperature drops. Thus, at low temperatures, the lubrication comes from the low viscosity component and reduces friction effectively, while at high temperatures the higher viscosity component plays a large role providing greater wear protection.
WO9611244 discloses a lubricant oil which functions at both high and low temperatures, by combining a low viscosity lubricant oil as well as a high viscosity lubricant oil, which utilizes only the properties of the low viscosity lubricant oil at low temperatures while utilizing a property of the oil by which viscosity increases by mixing a high viscosity lubricant oil with a low viscosity lubricant oil at high temperatures.
WO2014207172 teaches a drive system transmission oil composition with a kinematic viscosity of from 3.5 to 7.0 mm2/s at 100° C., produced by mixing (i) a low viscosity lubricant base oil component selected from mineral oils, synthetic oils and GTL; with (ii) a polyalkylene glycol-based high viscosity component; and (iii) a control component.
Further studies on the use of dual phase lubricating oils are described in Kamata, et al. Tribology Online, 11, 1 (2016), 24-33.
Blending a dual phase lubricating oil has many challenges. Any additive needs to be fully dissolved and active at low temperatures when the lubricating oil is in two phases, remain both dissolved and active as the two phases mix thoroughly, and continue to remain both dissolved and active as the temperature is lowered again. Such activity must be maintained over repeated cycles of heating and cooling. Of particular concern is the provision of anti-foam additives that can work in dual phase lubricating oils and provide substantial anti-foam protection across a wide range of temperatures.
The present invention provides a lubricating oil composition comprising:
The present invention also provides a method for lubricating an axle said method comprising supplying to said axle a lubricating oil composition comprising
It has been surprisingly found that a non-ionic surfactant based anti-foam agent provides excellent anti-foaming properties in a dual-phase lubricating oil composition comprising a Fischer-Tropsch based base oil as the low viscosity component and a polyalkylene glycol as the high viscosity component.
This lubricating oil composition can also be used effectively over a wide range of industrial lubricating oils such as automotive gear oils, transmission oils such AT oils, MT oils and CVT oils, hydraulic oils and compressor oils. In a preferred embodiment it is used as an axle fluid.
Fischer-Tropsch derived base oils are those made using a Fischer-Tropsch process to convert carbon monoxide and hydrogen into a range of liquid fuels and oils. The source of the carbon monoxide and hydrogen can be diverse. For example, gas to liquid (GTL) base oils are synthesised by the Fischer-Tropsch process using natural gas as the starting material. Various other XTL processes, wherein X stands for the root source of carbon and hydrogen atoms, are known, for example coal to liquids (CTL), biomass to liquids (BTL) and power to liquids (PTL). GTL base oils, or blends thereof, are ideal for use as the Fischer-Tropsch derived base oil in this invention, being, relative to mineral oil base oils produced from crude oil, extremely low in sulfur content and aromatics content, and having a very high paraffin constituent ratio, which means that they have superior oxidative stability and extremely small evaporation losses.
A wide range of kinematic viscosities at 100° C. (KV100) exist for Fischer-Tropsch derived base oils, but those with a KV 100 in the range of from 3.5 to 7.0 mm2/s are to be used in the present invention. Said Fischer-Tropsch derived base oils may be a single Fischer-Tropsch derived base oil with a KV100 in the range of from 3.5 to 7.0 mm2/s or a blend of more than one Fischer-Tropsch derived base oil wherein the KV100 of the blend is in the range of from 3.5 to 7.0 mm2/s. More preferably, the low viscosity first base oil component which is a Fischer-Tropsch derived base oil has a kinematic viscosity at 100° C. in the range of from 4.0 to 6.0 mm2/s.
The amount of low viscosity first base oil component which is a Fischer-Tropsch derived base oil is 45 to 75 mass %, preferably, 45 to 65 mass %, based on the overall mass of the lubricating oil composition.
The high viscosity second base oil component is present in the range of from 3 to 35 mass %, based on the overall mass of the lubricating oil composition. Said high viscosity second base oil component is a polyalkylene glycol. Preferable polyalkylene glycols include poly(oxypropylene)-based products. Preferably said high viscosity second base oil component is present in an amount in the range of from 13 to 28 mass %, based on the overall mass of the lubricating oil composition.
Suitable high viscosity second base oil components have a KV100 in the range of from 90 to 120 mm2/s, preferably 95 to 105 mm2/s.
The lubricating oil composition also comprises a non-ionic surfactant as an anti-foam additive. Such non-ionic surfactants tend to be poly-alkoxylated alcohols, amines and mixtures thereof.
In some embodiments of the present invention, it may be preferable to add a control component, which comprises one or more ester base oils, to the lubricating oil composition. Such ester base oil or oils acts as a control component for the dual phase oil separation temperature above which both phases become miscible and below which both phases become immiscible. As explained in Kamata, et al. Tribology Online, 11, 1 (2016), 24-33, the difference in polarities of the high and low viscosity components are changed through the addition of this control component.
Suitable esters have both hydrophobic and hydrophilic groups and can dissolve in both the high and low viscosity components modifying their polarities and thus controlling temperature at which the dual phase oil separates. Note that it is also possible to combine and use two or more different ester base oils as control components.
Preferably, said ester base oils or mixtures thereof used as the control component have a kinematic viscosity at 100° C. in the range of from 3.5 to 10 mm2/s, more preferably not less than 3.5 mm2/s. Preferably the KV100 is not more than 8 mm2/s, and more preferably not more than 6 mm2/s. Also preferably, the ester base oils, or mixtures thereof, used as the control component have a kinematic viscosity at 100° C. of no more than 1 mm2/s, more preferably no more than 0.5 mm2/s above or below that of the low viscosity first base oil component.
Suitable ester base oils for use as the control component are described in WO2014207172, wherein said ester base oils (or mixtures thereof) are required to have an oxygen/carbon weight ratio of from 0.080 to 0.350, preferably from 0.080 to 0.300, more preferably from 0.080 to 0.250.
The ester base oils may be any of monoesters, diesters and partial or total esters of polyhydric alcohols.
The alcohols forming the ester base oils may be monohydric alcohols, or any of the polyhydric alcohols, and the acids may be monobasic acids or polybasic acids.
The monohydric alcohols may be alcohols of carbon number 1 to 24, but preferably 1 to 12 and more preferably 1 to 8, and may be straight-chain or branched. They may also be saturated or unsaturated.
The polyhydric alcohols may be dihydric to decahydric alcohols, but preferably dihydric to hexahydric. Examples of dihydric to decahydric polyhydric alcohols include dihydric alcohols. The alcohols forming the ester base oils may be monohydric alcohols, or any of the polyhydric alcohols, and the acids may be monobasic acids or polybasic acids.
For the acids forming the ester base oils, the monobasic acids include fatty acids of 2 to 24 carbons, and they may be straight-chain or branched, and saturated or unsaturated. Of the aforementioned saturated fatty acids and unsaturated fatty acids, these preferred are saturated fatty acids of carbon number 3 to 20, unsaturated fatty acids of carbon number 3 to 22, and mixtures thereof, but saturated fatty acids of carbon number 4 to 18, unsaturated fatty acids of carbon number 4 to 18, and mixtures thereof, are more preferred. Lubricity and handling qualities are enhanced, and if consideration is also given to oxidative stability, saturated fatty acids of carbon number 4 to 18 are most preferred.
If present, the amount of the control component which comprises one or more ester base oils is 1 to 20 mass %, preferably 2 to 10 mass %, based on the overall mass of the lubricating oil composition.
Various additives known in the art may be blended singly or in combinations of several kinds with the lubricating oil compositions of the inventions for example extreme pressure additives, dispersants, metallic detergents, friction modifiers, anti-oxidants, corrosion inhibitors, rust preventatives, demulsifiers, metal deactivators, pour point depressants, seal swelling agents, defoamers and colourants. Typically some or all of these additives may be provided as an additive package.
Here, as a result of an increase in temperature, the low viscosity first base oil component 2 and the high viscosity second base oil component 3 mix, producing a homogeneous lubricating oil composition. The decrease in viscosity which accompanies an increase in the temperature of low viscosity first base oil component 2 is compensated for by the high viscosity second base oil component 3, so even when an increase in temperature occurs, issues such as collapse of the oil film do not occur.
The invention will now be demonstrated by the following, non-limiting examples.
A series of lubricating oils were blended as set out in Tables 1 and 2. The components used were as follows:
The formulations shown in Tables 1 and 2 were blended using standard methodology and were tested using the standard test ASTM D892. As described by the test, the tendency of oils to foam can be a serious problem in systems such as high-speed gearing, high-volume pumping, and splash lubrication. Inadequate 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 covers the determination of the foaming characteristics of lubricating oils at 24° C. and 93.5° C. It consists of three sequences.
In sequence I, a portion of sample, maintained at a bath temperature of 24° C.+/−0.5° C. is blown with air at a constant rate (94 mL/min+/−5 mL/min) for 5 min, then allowed to settle for 10 min. The volume of foam is measured at the end of both periods.
In sequence II, a second portion of sample, maintained at a bath temperature of 93.5° C.+/−0.5° C., is analysed using the same air flow rate and blowing and settling time duration as indicated in the previous sequence.
Finally, in sequence III, the sample portion used in conducting sequence II is used again, where any remaining foam is collapsed and the sample portion temperature cooled below 43.5° C. by allowing the test cylinder to stand in air at room temperature, before placing the cylinder in the bath maintained at 24° C.+/−0.5° C. The same air flow rate and blowing and settling time duration as indicated in sequence I is followed.
Results for the examples tested are shown in Table 1. The SAE J2360 provides the standard for automotive gear lubricants for commercial and military use. In the SAE J2360 standard, the foaming tendency characteristics of the oil are determined by ASTM D892. There, the maximum permissible volume of foam at the end of the 5-minute blowing period for sequences I, II and II are 20, 50 and 20 mL, respectively.
Anti-foam additives are required for lubricating oil compositions comprising just the low viscosity base oil (see Examples 2 to 5 in comparison with Example 1). The organo-modified siloxane (Anti-foam 1) does not provide desirable results and a polydimethylsiloxane based defoamant (Anti-foam 2) is required to provide the necessary reduction in foaming (see Examples 3 to 5). However, the use of this anti-foam in a dual phase lubricating oil composition (Example 6) leads to an increase in foaming compared to a single-phase composition. The non-ionic surfactant-based anti-foam used in Examples 7 to 10 provides excellent foaming results in the dual phase lubricating oil composition whether used alone or in combination with other anti-foams. The use of a single anti-foam in a dual phase fluid to produce excellent foaming results over a range of temperatures (during two phase and one phase states) is a highly desirable outcome.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/060540 | 4/21/2022 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63180261 | Apr 2021 | US |
