Heat transfer fluid based on at least partially re-refined lubricating oil

Abstract

This application relates to the use of a composition based on at least one at least partially re-refined lubricating oil as a heat transfer fluid. The application also relates to a method of transferring heat to a mobile or stationary mechanical system, the method comprising at least one step of circulating a composition based on at least one at least partially re-refined lubricating oil as a heat transfer fluid through the mechanical system. The application also relates to an apparatus for transferring heat or for heat management that uses a composition based on at least one at least partially re-refined lubricating oil as a heat transfer fluid.

Description

Technical Field

[0001] The present invention relates to the field of heat-transfer fluids. More specifically, the present invention relates to the use of re-refined lubricating oil for formulating heat-transfer fluids.

Background Art

[0002] Heat-transfer fluids are used in a wide range of systems that enable the transfer of heat between different temperature sources.

[0003] These fluids are typically used in heat exchangers, such as radiators in thermal or electric engines, such as automotive engines, refrigerators, boilers, air conditioners, thermal solar collectors, in particular in the case of high-power transformers of electric circuits, electronic transformers, cooling systems for coal-fired, oil-fired, gas-fired power plants or nuclear power plants, and waste heat exchangers.

[0004] A very large number of heat-transfer fluids using a wide variety of base fluids and performance additives have been described in the literature and marketed.

[0005] Generally, heat-transfer fluids must meet two requirements: first, they must be able to transfer heat energy efficiently, and second, it is essential that the heat-transfer fluid does not degrade the system in which it is used or itself during use.

[0006] The efficiency of heat transfer essentially depends on the thermophysical properties of the base fluid, in particular the specific heat capacity, thermal conductivity, density, and viscosity of the fluid, but also on the hydraulic performance of the heat-transfer fluid. Thus, the heat-transfer fluid must remain pumpable over the temperature range over which it must circulate within a given system. Thus, the viscosity of the heat-transfer fluid and its viscosity distribution with temperature determine its hydraulic performance.

[0007] Due to its natural availability and lack of impact on the environment in which it is used, water is commonly used as the base liquid for heat transfer fluids. In fact, water is an excellent medium for transferring thermal energy due to its high specific heat capacity, high thermal conductivity, and low viscosity. A significant limitation regarding the use of water as a heat transfer fluid is that it freezes at a relatively high temperature of 0°C, making it unsuitable for use in many systems that require operating temperatures below 0°C. Additionally, water-based heat transfer fluids are inherently corrosive and can cause significant damage to the systems in which they operate. To overcome these limitations, a large number of heat transfer fluids have been developed that add freezing point depressants to water to lower its freezing temperature and various additives to control corrosion.

[0008] Mineral oils derived from petroleum refining have also been proposed as the base liquid for heat transfer fluids, particularly for applications in systems where the heat transfer fluid is prone to being heated to high temperatures.

[0009] One example is U.S. Patent No. 7,972,999, which proposes using a base oil prepared from paraffin wax to form a heat exchange liquid and having a flash point of particularly higher than 329°C and a high viscosity index.

[0010] However, generally a large amount of crude oil is required to obtain refined oil. Typically, 37 liters of crude oil are required to extract 1 liter of refined oil. Also, the petroleum refining process is very energy-intensive. However, current environmental protection and resource conservation issues are driving manufacturers to propose more environmentally friendly alternatives to conventional oils.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0012] Thus, there still remains a need to provide a heat transfer fluid that is more environmentally friendly and at the same time has improved physical and chemical properties or properties even improved compared to known heat transfer fluids.

[0013] It is an object of the present invention to propose a novel heat transfer fluid that meets these demands.

Means for Solving the Problems

[0014] More specifically, the inventors have discovered that recycled lubricating base oils are particularly suitable for use as heat transfer fluids.

[0015] Thus, according to a first aspect thereof, the present invention relates to the use of a composition based on at least one at least partially re-refined lubricating oil as a heat transfer fluid.

[0016] In the context of the present invention, the expression "at least partially re-refined lubricating oil", which is also more simply referred to hereinafter as "re-refined oil", "recycled oil" or "recycled oil", means an oil derived from a used lubricating composition that has been subjected to one or more treatment steps known as re-refining processes, at least in part.

[0017] According to the present invention, a "used lubricating composition" (or more simply a "used lubricant" or "used lubricating oil") is understood to mean any lubricating composition used, but not limited to, in the lubricating moving parts of a mechanical system such as a rolling bearing, a gear or an engine, particularly a metal part.

[0018] Used lubricating oils can be derived from various sources. In particular, as detailed below, they can be lubricants used for the lubrication of drive systems, particularly "moving" systems, or industrial systems, particularly "stationary" systems.

[0019] As a result of its origin, used lubricating oils, particularly engine lubricating oils, contain many decomposition products derived from the oil itself or additives contained therein, as well as particles of metal and metal oxides and other components, such as those derived from the engine. Used oils may contain particularly high levels of undesirable elements such as calcium (Ca), iron (Fe), magnesium (Mg), sodium (Na), nickel (Ni), phosphorus (P), silicon (Si), chlorine (Cl), zinc (Zn), etc.

[0020] In order to regenerate these oils and enable their subsequent reuse, methods for re-refining or reconditioning used lubricating oils have been developed.

[0021] Thus, the re-refined lubricating oil is an oil obtained from one or more processes of treating used lubricants for the purpose of at least partially removing many contaminants such as dust, water, fuel fractions, metal elements, and residues resulting from the degradation of additives present in other lubricants that are present therein.

[0022] To the best of the inventors' knowledge, it has never been proposed to use recycled lubricating oil for formulating heat transfer fluids.

[0023] The use of the re-refined lubricating oil according to the present invention as a heat transfer liquid has been proven to be advantageous in many respects.

[0024] First, as shown in the following examples, the inventors have shown that the re-refined lubricating oil has particularly advantageous thermophysical properties, particularly volatility, density, viscosity index, flash point, and thermal conductivity, and for this reason, the re-refined lubricating oil is particularly suitable as a heat transfer fluid.

[0025] Surprisingly, the recycled lubricating oil even has excellent thermophysical properties for use as a heat transfer fluid compared to refined base oils, i.e., virgin or new base oils.

[0026] Unlike a refined lubricant, a refined base oil, also referred to as "virgin" or "new" base oil, is an oil that is directly derived from petroleum refining and has not yet been used.

[0027] Second, the use of recycled lubricants as heat transfer fluids advantageously meets the current desire to reduce environmental impact and conserve resources. Thus, the use of heat transfer fluids based on recycled lubricants makes it possible to advantageously reduce the carbon footprint of the product compared to the use of virgin base oils.

[0028] As detailed below, the aforementioned refined lubricant can be used as the heat transfer fluid itself, i.e., alone, or in other words, without additivation. Thus, in one particular embodiment, the present invention relates to the use of at least one lubricant that is at least partially refined as a heat transfer fluid.

[0029] The aforementioned refined lubricant can further be used in combination with one or more other components. The aforementioned refined lubricant can in particular be additized with one or more additives, such as, for example, but not limited to, corrosion inhibitors, antioxidants, etc., which are intended to enhance the compatibility of the intended system materials with the heat transfer fluid.

[0030] In this alternative embodiment, it is advantageous for the heat transfer fluid according to the present invention to be mainly formed from the aforementioned refined lubricant. In particular, the aforementioned refined lubricant can represent more than 80% by mass, particularly more than 90% by mass, and more particularly more than 95% by mass of the total mass of the heat transfer fluid.

[0031] The aforementioned refined lubricant can also be used in combination with at least one new base oil.

[0032] The present invention also relates to the use of at least one lubricant that is at least partially refined for formulating or preparing a heat transfer fluid.

[0033] The present invention also relates to a process or method for preparing a heat transfer fluid, comprising at least one step consisting of obtaining a lubricating oil at least partially re-refined from a used lubricant.

[0034] The method for preparing a heat transfer fluid according to the present invention more specifically consists of: (i) preparing a lubricating oil at least partially re-refined from a used lubricant; (ii) optionally, mixing the aforementioned at least partially re-refined lubricating oil with one or more new base oils different from the re-refined lubricating oil, such as one or more mineral oils; and (iii) optionally, supplementing the aforementioned at least partially re-refined lubricating oil from step (i), or the mixture of lubricating oils from step (ii), with at least one additive selected in particular from corrosion inhibitors, friction modifier additives, extreme pressure additives, anti-wear additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressants (PPD), dispersants, anti-foaming agents, and mixtures thereof. It may include steps consisting of the above.

[0035] A heat transfer fluid formulated according to the present invention, based on at least one re-refined lubricating oil, can be used in numerous applications, in particular as a liquid coolant for automotive engines, as a heat transfer liquid in air conditioning or heating circuits of buildings, etc.

[0036] Examples of the uses of the fluid formulated according to the present invention are described more specifically below.

[0037] In particular, the present invention, according to one of its other aspects, further relates to the use of a heat transfer fluid according to the present invention, based on at least one at least partially re-refined lubricating oil, as a liquid coolant for mobile or stationary drive systems, in particular as a liquid coolant for automotive engines, such as electric or hybrid vehicles.

[0038] Other features, variations, and advantages of the use of at least partially re-refined lubricating oil according to the present invention for the formulation of heat transfer fluids will become more apparent upon reading the following description and examples set forth for purposes of illustration without limiting the present invention.

[0039] The expressions "between... and...", "in the range of... to...", "formed by... to...", and "vary from... to..." should be understood to include the boundaries unless otherwise specified.

[0040] In the description and examples, percentages are by mass unless otherwise indicated. That is, the percentage is expressed by mass relative to the total mass of the composition.

Mode for Carrying Out the Invention

[0041] At least partially re-refined lubricating oil As already mentioned, the oil used in the formulation of the heat transfer fluid according to the present invention is at least partially re-refined lubricating oil, also known as "reclaimed oil" or "recycled oil"; in other words, lubricating oil derived from a used lubricating composition and subjected to one or more re-refining treatment steps can be used according to the present invention.

[0042] It is understood that the used lubricating composition may be a mixture of one or more used lubricating compositions derived from the same origin or from more than one different origin.

[0043] The used lubricating composition and the resulting reclaimed lubricating oil contain, in a major amount, one or more base oils commonly used in the field of lubricants such as mineral, synthetic or natural, animal or vegetable oils or mixtures thereof.

[0044] This can be a mixture of more than one base oil, for example a mixture of two, three or four base oils.

[0045] These base oils can be of natural origin, such as oils derived from plants, animals or fish, such as vegetable or animal oils and mixtures thereof. Examples of such oils are rapeseed oil, canola oil, tall oil, sunflower oil, soybean oil, hemp oil, olive oil, linseed oil, mustard oil, palm oil, peanut oil, castor oil, coconut oil, tallow, and mixtures thereof.

[0046] These base oils are preferably oils of mineral or synthetic origin, or mixtures thereof, defined by the API classification (or its equivalent according to the ATIEL classification) and belonging to Groups I - V according to the classes shown in the following table.

[0047] [Table 1]

[0048] In particular, the used lubricating compositions induced to regenerated lubricating oils used according to the present invention can contain at least 50% by mass, particularly at least 60% by mass, more particularly 60% - 99% by mass of base oil based on their total mass.

[0049] The re-refined lubricating oils used according to the present invention preferably have properties that meet the criteria defined by the API classification for oils of Groups I, II, III, IV and / or V, particularly with respect to the content of saturated compounds, the content of sulfur, and the viscosity index.

[0050] Therefore, the object of the present invention is to use the resulting composition as a heat transfer fluid after one or more steps of treating a used lubricant formed, in whole or in part, at least in part from at least one re-refined lubricating oil and based on one or more oils of Groups I - V according to the API classification.

[0051] According to one particular embodiment, the re-refined lubricating oil used according to the present invention can be obtained from the treatment of a used lubricating composition that has been used to lubricate a drive system, particularly a "mobile" system, i.e., a drive system including passenger cars, large vehicles, mobile "off-road" vehicles or marine vessels.

[0052] According to another particular embodiment, the re-refined lubricating oil used according to the present invention can be obtained from the treatment of a used lubricating composition that has been used to lubricate an industrial system, particularly a "stationary" system, i.e., an industrial system including but not limited to turbines, compressors, hydraulic systems, gears or molding or cutting machines.

[0053] The used lubricating composition from which the regenerated lubricating oil used according to the present invention is derived can contain various additives common in the field of lubricants, such as friction modifier additives, extreme pressure additives, anti-wear additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressants (PPD), dispersants, defoamers, thickeners and mixtures thereof.

[0054] As previously mentioned, the properties of the used lubricating composition deteriorate as a result of being used over various lengths of time to lubricate and / or cool a mechanical system, particularly a drive system such as a combustion engine.

[0055] Thus, depending on its origin, the used lubricating composition can contain impurities resulting from the decomposition of one or more of the above additives and additives originally present in the lubricant, or resulting from the wear of moving mechanical parts.

[0056] The composition of the used lubricant can vary naturally depending on the origin of the lubricant, its initial formulation, and the changes in contaminants depending on what it has been used for.

[0057] More particularly, the regenerated lubricating oil used according to the present invention is derived from a used lubricating composition that has been subjected to one or more prior pretreatment steps known in the field of re-refining of used lubricants.

[0058] In particular, these processing steps are aimed at at least partially removing other contaminants such as water, solid particles, fuel and / or lubricant formulations of undesirable polycyclic aromatic hydrocarbons (PAHs).

[0059] According to one particular embodiment, the recycled lubricating oil used by the present invention is derived from a used lubricant that has been subjected to dehydration, distillation, filtration, hydrogenation, liquid-liquid extraction, sedimentation and / or passage over an adsorbent of the used lubricant, preferably one or more of the pre-treatment steps as detailed below.

[0060] Accordingly, the present invention relates to the use of a composition based on at least one lubricating oil that has been at least partially re-refined, in particular one formed from at least one lubricating oil that has been at least partially re-refined, preferably an oil as described above, i.e. dehydration, distillation, filtration, hydrogenation, liquid-liquid extraction, sedimentation and / or passage over an adsorbent of the used lubricant composition, preferably the aforementioned at least partially re-refined lubricating oil obtained from the aforementioned used lubricating composition that has been subjected to at least one or more steps carried out under the conditions detailed below, as a heat transfer fluid.

[0061] The recycled lubricating oil used by the present invention is preferably obtained by subjecting the used lubricating composition to at least one dehydration step. This dehydration step removes the water that may be present in the used lubricant.

[0062] Thus, the recycled lubricating oil used by the present invention advantageously has a water content of 10% by weight or less, particularly 5% by weight or less, especially 2% by weight or less, more particularly 1% by weight or less, based on the total mass of the aforementioned recycled lubricating oil.

[0063] This dehydration can be carried out by any method known to those skilled in the art, for example by distillation, evaporation, sedimentation, heating, or passing a stream of hot air through the used lubricating composition.

[0064] According to one embodiment, the dehydration step can be carried out at a temperature of 50°C to 250°C, preferably 100°C to 200°C. In particular, the dehydration step can be carried out at a pressure of 50,000 to 150,000 Pa, preferably at atmospheric pressure.

[0065] The regenerated lubricating oil used according to the present invention is preferably obtained by subjecting the used lubricating composition to at least one preliminary filtration step. This filtration can be carried out by any method known to those skilled in the art. This filtration step may or may not be a particle filtration step. It can be carried out, for example, in a diatomaceous earth type system.

[0066] The regenerated lubricating oil used according to the present invention is preferably obtained by subjecting the used lubricating composition to at least one distillation step, preferably following a preliminary dehydration step. The aforementioned distillation step can be carried out by any technique known to those skilled in the art. These include, for example, distillation at atmospheric pressure and distillation under reduced pressure. The distillation can be carried out, for example, at a temperature of 100°C to 500°C, preferably 200°C to 400°C, more preferably 300°C to 380°C. In particular, the upstream can be carried out at a pressure of 25 to 2000 Pa, preferably 50 to 1000 Pa, more particularly 50 to 250 Pa.

[0067] The regenerated lubricating oil used according to the present invention is advantageously obtained by subjecting the used lubricating composition to at least one preliminary step of passing the used lubricating composition over an adsorbent.

[0068] The adsorbent advantageously allows for the selective adsorption of aromatic compounds, particularly PAHs.

[0069] In particular, the passage over the adsorbent, preferably activated carbon, advantageously allows for a reduction in the content of polycyclic aromatic hydrocarbons (PAHs) in the used lubricating composition, particularly selected from chrysene, benzo[b]fluoranthene, benzo[j]fluoranthene, benzo[k]fluoranthene, benzo[e]pyrene, benzo[a]pyrene, dibenz[a,h]anthracene and / or benz[a]anthracene.

[0070] The expression "passage of the used lubricant composition over the adsorbent" is understood to mean the flow of the used lubricating composition over the adsorbent support.

[0071] The adsorbent can be, for example, activated carbon, zeolite, clay or a functionalized porous compound, preferably activated carbon.

[0072] For example, the regenerated lubricating oil used in the process of the present invention can be obtained from the treatment of the used lubricating composition by the process described in International Publication No. WO 2018 / 109208.

[0073] When passing the used lubricating composition over activated carbon, the amount of activated carbon used is preferably 0.5 to 60 g, preferably 0.5 to 50 g / L, preferably 1 to 50 g / L, preferably 1 to 30 g / L, for example 5 to 60 g / L, preferably 5 to 50 g / L of activated carbon per liter of used lubricating composition.

[0074] The flow rate during the passage of the used lubricating composition is 1 m 3 / h to 15 m 3 / h, for example 5 to 10 m 3 / h.

[0075] The activated carbon is preferably characterized by a density of 200 to 500 kg / m 3 as measured according to, for example, ASTM D2854.

[0076] The activated carbon is preferably coal-based carbon and preferably contains 70 to 95%, advantageously 80 to 90% by mass of carbon.

[0077] The step of passing the used lubricating composition over the adsorbent support, preferably over activated carbon, advantageously comprises the following preliminary steps: - one or more distillation steps; and - a filtration step as particularly defined above preceding it.

[0078] The regenerated lubricating oil used according to the present invention can advantageously be obtained by subjecting a used lubricating composition to a process following at least one prior hydrogenation (or hydrotreating) step, preferably a prior dehydration and / or distillation step. The aforementioned hydrogenation step can be carried out by any technique known to those skilled in the art and generally consists of treating the lubricating oil with hydrogen, usually in the presence of a hydrotreating catalyst. Such a catalyst can contain, for example, at least one oxide or sulfide of molybdenum, tungsten, nickel or cobalt, and a support, such as at least one Group VI metal and / or at least one Group VIII metal of alumina, silica-alumina or zeolite, etc.

[0079] The regenerated lubricating oil used according to the present invention can advantageously be obtained by subjecting a used lubricating composition to a process following at least one prior step of liquid-liquid extraction with a solvent, preferably a prior dehydration and / or distillation step. In particular, liquid-liquid extraction with a solvent can advantageously lighten the dark used oil and at least partially remove the content of aromatic compounds, especially PAHs, or bad odors. The aforementioned extraction step can be carried out by any technique known to those skilled in the art. Extraction is usually carried out in a mixer-settler or an extraction column using a suitable extraction solvent.

[0080] The regenerated lubricating oil used according to the present invention can advantageously be obtained by subjecting a used lubricating composition to at least one prior sedimentation step. The aforementioned sedimentation step can be carried out by any technique known to those skilled in the art.

[0081] It is understood that the present invention is in no way limited to the use of the regenerated oil obtained by the above treatment method. Other at least partially re-refined lubricating oils obtained from treatment processes different from those described above, such as Group I and / or Group II oils, may be suitable for the present invention.

[0082] In any case, the re-refined lubricating oil used according to the present invention is different from the used lubricating oil, especially due to the reduced content of certain undesirable contaminating components such as water, fuel, metal elements or certain heteroatoms.

[0083] The regenerated lubricating oil used according to the present invention is characterized in particular by a silicon content of 0 ppm to 300 ppm, especially 1 to 300 ppm.

[0084] The regenerated lubricating oil used according to the present invention is characterized in particular by a phosphorus content of 100 ppm or less, especially 0 ppm to 100 ppm, for example 0 ppm.

[0085] The regenerated lubricating oil used according to the present invention may also be characterized by the content of one or more other elements selected from chlorine, oxygen, and nitrogen. It may have, for example, a chlorine content of 0 ppm to 50 ppm, for example 0 ppm.

[0086] The content of these elements can be evaluated by any method known to those skilled in the art, such as X-ray fluorescence (XRF), or infrared or ultraviolet spectroscopy.

[0087] On the other hand, due to its formation from the used lubricant, the regenerated lubricating oil used according to the present invention differs in both its composition and its physicochemical properties from virgin or new base oils, oils directly derived from petroleum refining, and natural base oils, such as oils of natural origin.

[0088] In particular, as previously shown, the regenerated lubricating oil surprisingly has excellent thermophysical and hydrodynamic properties, especially in terms of viscosity index, density, Noack volatility, flash point and / or thermal conductivity, and advantageously has better thermophysical and hydrodynamic properties than virgin base oils.

[0089] The regenerated lubricating oil used according to the present invention preferably has a kinematic viscosity measured at 100 °C according to ASTM D445 standard of 2 to 12 mm 2 / s -1 、especially 3 to 10 mm 2 / s -1 has a kinematic viscosity of

[0090] The kinematic viscosity of the at least partially re-refined lubricating oil, measured at 100 °C in accordance with ASTM D445, is 5 mm 2 / s or more, for example 5 to 12 mm 2 / s, more particularly 5 to 10 mm 2 / s is preferably

[0091] The recycled lubricating oil used according to the invention has a kinematic viscosity of 20 to 40 mm when measured at 40 °C in accordance with ASTM D445 2 / s, in particular 25 to 35 mm 2 / s, which is advantageous

[0092] The recycled lubricating oil used according to the invention preferably has a viscosity index of 110 or more. That is, the viscosity index of the at least partially re-refined lubricating oil can be 110 to 130, in particular 112 to 125

[0093] The viscosity index can in particular be determined in accordance with the NF ISO 2909 standard

[0094] The recycled lubricating oil used according to the invention preferably has a Noack volatility of 15% or less. Thus, the Noack volatility of the at least partially re-refined lubricating oil can be 8% to 15%

[0095] More preferably, the recycled lubricating oil used according to the invention has a Noack volatility of strictly less than 12%. Thus, the Noack volatility of the at least partially re-refined lubricating oil can be 8% to 11.9%

[0096] The Noack volatility can in particular be determined in accordance with the CEC L-40-93 standard

[0097] The recycled lubricating oil used according to the invention preferably has a sulfur content of 0.02% to 0.2% by weight relative to the total weight of the aforementioned recycled lubricating oil

[0098] The recycled lubricating oil used according to the present invention preferably has an aromatic compound content of 0.5% by mass or more, particularly 1% by mass or more, based on the total mass of the aforementioned recycled lubricating oil. Thus, the aromatic compound content in the recycled lubricating oil can be 1% to 25% by mass, particularly 2.5% to 20% by mass, based on the total mass of the aforementioned recycled lubricating oil.

[0099] The contents of these various components can be determined according to any method known to those skilled in the art, for example, by X-ray fluorescence (XRF), or by infrared or ultraviolet spectroscopy.

[0100] The re-refined lubricating oil used according to the present invention preferably has the following characteristics: - A kinematic viscosity of 5 mm 2 / s or more, for example 5 to 12 mm 2 / s, more particularly 5 to 10 mm 2 / s, measured at 100 °C according to ASTM D445 standard; - A viscosity index of 110 or more, particularly 110 to 130, especially 112 to 125; - A Noack volatility of 15% or less, particularly 8% to 15%, preferably strictly less than 12%, more particularly 8% to 11.9%; - A sulfur content of 0.01% to 0.3% by mass, particularly 0.02% to 0.2% by mass, based on the total mass of the aforementioned recycled lubricating oil; - An aromatic compound content of 0.5% by mass or more, particularly 1% by mass or more, especially 1% to 25% by mass, more particularly 2.5% to 20% by mass, based on the total mass of the aforementioned recycled lubricating oil having at least one, at least two, at least three, or even all of them.

[0101] The recycled lubricating oil used according to the present invention preferably has a density of 870 kg / m 3 or less, particularly 860 kg / m 3 or less. Thus, the density of the at least partially re-refined lubricating oil is 830 to 870 kg / m 3 , particularly 840 to 860 kg / m3 It may be.

[0102] The density can be determined in particular according to the NF EN ISO 12185 standard.

[0103] The recycled lubricating oil used according to the present invention advantageously has a flash point of 225 °C or higher, particularly 228 °C or higher. Thus, the flash point of the at least partially re-refined lubricating oil can be 225 °C to 245 °C.

[0104] The flash point can be determined in particular according to the NF EN ISO 2592 standard.

[0105] The recycled lubricating oil used according to the present invention advantageously has a thermal conductivity of 125 mW / mK or higher, particularly 128 mW / mK or higher, measured at 100 °C and atmospheric pressure. Thus, the thermal conductivity of the at least partially re-refined lubricating oil can be 125 to 145 mW / mK, particularly 128 to 140 mW / mK.

[0106] The thermal conductivity can be determined in particular according to the ASTM D7896-19 standard.

[0107] Due to these properties, with respect to viscosity index, density, thermal conductivity, flash point, Noack volatility, and density, the re-refined lubricating oil used according to the present invention has excellent performance in both heat transfer efficiency and hydraulic performance, and advantageously has enhanced performance compared to virgin base oil.

[0108] A high viscosity index particularly enables providing a heat transfer fluid whose viscosity hardly changes with temperature, thus ensuring good hydraulic characteristics in the heat transfer fluid. Thus, the heat transfer fluid according to the present invention can be used, for example, as an automotive liquid coolant in a system that can be exposed to large temperature variations, and can remain pumpable over the temperature range that has to be circulated in the aforementioned system.

[0109] In particular, the re-refined lubricating oil advantageously has a low density, in particular lower than that of the virgin base oil, and a high viscosity index, in particular higher than that of the virgin base oil, which makes it possible to reduce the pumping cost while having better thermal properties.

[0110] Heat transfer fluid As described above, the aforementioned re-refined lubricating oil used according to the present invention, in particular those defined and characterized above, can be used as such as a heat transfer fluid or formulated in a composition intended to be used as a heat transfer fluid.

[0111] Thus, the composition used as a heat transfer fluid may contain one or more base oils and / or one or more additives that are at least partially different from the re-refined lubricating oil.

[0112] In one particular embodiment, the aforementioned re-refined lubricating oil can be formulated in combination with one or more different base oils, in particular one or more new base oils.

[0113] The base oil is particularly selected from base oils commonly used in the field of lubricants such as mineral, synthetic or natural, animal or vegetable oils or mixtures thereof.

[0114] These base oils are advantageously oils of mineral or synthetic origin or mixtures thereof belonging to groups I to V according to the classes defined in the API classification and shown in Table 1 above (or their equivalents according to the ATIEL classification).

[0115] Thus, the composition used according to the present invention may contain or consist precisely of a mixture of one or more re-refined lubricating oils and one or more new base oils, for example at least one mineral oil.

[0116] In particular, the composition used according to the present invention may contain, based on the total mass of the composition, from 0% to 80% by mass, in particular from 5% to 75% by mass, of a new base oil different from the re-refined lubricating oil required by the present invention and defined above.

[0117] According to one particular embodiment, the composition used as a heat transfer fluid according to the present invention contains a new base oil different from the re-refined lubricating oil of less than 50% by mass.

[0118] The composition used as a heat transfer fluid according to the present invention is preferably mainly formed from the above-mentioned re-refined lubricating oil. In particular, the above-mentioned re-refined lubricating oil advantageously represents more than 80% by mass, in particular more than 90% by mass, and more particularly more than 95% by mass of the total mass of the heat transfer fluid.

[0119] Thus, the composition used as a heat transfer fluid according to the present invention advantageously contains at least one lubricating oil that is at least partially re-refined and that is more than 80% by mass, in particular from 90% to 100% by mass, and more particularly from 95% to 100% by mass, based on the total mass of the composition.

[0120] In one particular embodiment, the composition used as a heat transfer fluid according to the present invention does not contain any base oil different from the re-refined lubricating oil.

[0121] In one particular embodiment, the composition used as a heat transfer fluid according to the present invention may contain, in addition to the above-mentioned re-refined lubricating oil, one or more additives, in particular additives intended to enhance the compatibility of the heat transfer fluid with the materials of the intended system.

[0122] These additives may be particularly selected from corrosion inhibitors, friction modifier additives, extreme pressure additives, anti-wear additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressants (PPD), dispersants, anti-foaming agents, and mixtures thereof.

[0123] These additives can be added in an appropriate amount determined by a person skilled in the art to the aforementioned regenerated base oil used according to the present invention, or a mixture of the aforementioned regenerated base oil and at least one new base oil. It is understood that the type and amount of additives used are selected so that the advantageous properties of the composition based on the aforementioned re-refined lubricating oil as a heat exchange fluid are not affected or are not significantly affected by the addition.

[0124] The composition used as a heat transfer fluid according to the present invention may contain 0% to 20% by mass, particularly 0.01% to 10% by mass of additives, particularly the additives described above, based on the total mass of the composition.

[0125] Thus, according to another aspect thereof, the present invention relates to a process or method for preparing a heat transfer fluid comprising at least one step of obtaining at least partially re-refined lubricating oil from used lubricant.

[0126] Such a process or method preferably comprises at least: (i) preparing at least partially re-refined lubricating oil obtained from used lubricant, particularly by subjecting the used lubricant to at least one or more steps such as dehydration, distillation, filtration, hydrogenation, liquid-liquid extraction, sedimentation and / or passage over an adsorbent of the used lubricant, preferably formed as detailed above; (ii) optionally, mixing the aforementioned at least partially re-refined lubricating oil with one or more new base oils different from the re-refined lubricating oil, such as one or more mineral oils; (iii) optionally, supplementing the aforementioned at least partially re-refined lubricating oil from step (i), or the mixture of lubricating oils from step (ii) with at least one additive, particularly those described above comprising the steps consisting of.

[0127] Use As described above, at least partially re-refined lubricating oil is particularly suitable for use as a heat transfer fluid due to its thermophysical properties.

[0128] In particular, at least one fluid based on a re-refined lubricating oil according to the invention can be used as a substitute for conventional heat transfer fluids in various systems and applications, and in particular in one or more heat transfer fluid circuits.

[0129] The heat transfer fluid circuit includes means for the forced or free circulation of the conventional heat transfer fluid, such as a pump or any other equivalent means, and dissipation means, such as an exchanger or any other equivalent means of heat diffusion.

[0130] Thus, the present invention is not limited to a specific use of the fluid formulated according to the invention, and the following developments are given by way of example only without limitation.

[0131] In particular, the present invention relates to the use of at least one composition based on at least partially re-refined lubricating oil as a heat transfer fluid (also referred to as a heat exchange liquid), i.e., for heat transfer in mobile or stationary mechanical systems.

[0132] The fluid according to the invention can be used, for example, to ensure heat exchange in "stationary" mechanical systems such as boilers, air conditioners, especially data centers, thermal solar collectors, photovoltaic solar collectors, radiators of electrical circuits, especially transformers, coal-fired, oil-fired, gas-fired or nuclear power plants, waste heat exchangers, turbines, compressors, hydraulic systems, gears, or molding or cutting machines.

[0133] The fluid according to the invention can also be used, for example, in "mobile" mechanical systems, including parts of light vehicles, large vehicles, mobile "off-road" vehicles or marine vessels, especially in their drive systems, to ensure heat exchange.

[0134] The present invention relates in particular to a process or method for heat transfer in mobile or stationary mechanical systems, in particular those described above, which comprises at least one step of circulating, as a heat transfer fluid, in the aforementioned mechanical system, at least one lubricating oil which has been at least partially re-refined, in particular a composition based on those described above.

[0135] Such a process or method in particular: a) preparing a composition comprising or consisting precisely of at least one lubricating oil which has been at least partially re-refined, in particular as defined above; b) using the aforementioned composition from step a) in a mechanical system, in particular those described above, and more particularly in one or more heat transfer fluid circuits; and c) circulating the aforementioned composition to ensure heat exchange during the operation of the aforementioned mechanical system comprises the steps consisting of.

[0136] According to an advantageous embodiment, the fluid formulated according to the invention, based on at least one re-refined lubricating oil, is used as a liquid coolant.

[0137] As an example of a possible use, the fluid formulated according to the invention can be used as a liquid coolant for the moving parts of a mechanical system, and more particularly a mobile or stationary drive system.

[0138] Thus, the heat transfer fluid according to the invention, based on at least one re-refined lubricating oil, can be used as a liquid coolant for cooling gears, rolling bearings, bearings such as roller or sliding bearings, or engines.

[0139] "Drive system" is understood to mean, for the purposes of the present invention, a system comprising all the mechanical parts necessary for a mobile or stationary application in which at least one engine is involved and which includes it. It can be a combustion engine, a gas engine, in particular a hydrogen engine, an ammonia engine and / or an electric engine, a combustion, gas, in particular hydrogen, ammonia, electric or hybrid drive system, depending on the type of engine comprised in the drive system.

[0140] The "propulsion system" is understood, for the purposes of the present invention, to mean the system including the mechanical parts necessary for the propulsion of the vehicle. The propulsion system more particularly includes an engine, for example a rotor-stator assembly (for speed regulation) in electrical engineering, a transmission and, optionally, an electric engine including a battery. The battery itself generally consists of an accumulator battery, known as a set of cells.

[0141] Similarly, the at least one lubricating oil-based heat transfer fluid according to the present invention can be used as a liquid coolant for cooling the battery included in an electric or hybrid vehicle.

[0142] As an example of an application, the heat transfer fluid according to the present invention based on at least one re-refined lubricating oil can be used to cool the propulsion system of an electric or hybrid vehicle, more particularly an engine, electrical engineering, a transmission and / or a battery.

[0143] In another variant of the application, the fluid according to the present invention based on at least one re-refined lubricating oil can be used as a liquid coolant in the processing using aluminum, steel, stainless steel, galvanized steel or gold, particularly in metal machining operations, such as shaping, cutting or joining processes or any other deformation processes of other metals, such as forming, punching, rolling, etc. in metalworking.

[0144] Such compositions used in metal machining processes are generally also referred to as "metalworking compositions or fluids", "machining fluids" or "cutting fluids".

[0145] In yet another variant of the application, the fluid according to the present invention based on at least one re-refined lubricating oil can be used particularly as a liquid coolant in a hydraulic system, thus ensuring heat transfer between various parts when necessary in a hydraulic system, particularly in a hydraulic actuator (cylinder / engine) or in machine assembly.

[0146] Finally, with regard to the rheological properties of the refined lubricating oil used according to the present invention, a composition according to the present invention based on at least one refined lubricating oil can be used simultaneously as a heat transfer fluid for all the mechanical systems described above, for example in the propulsion system and / or hydraulic system of an electric or hybrid vehicle, especially as a liquid coolant and lubricant.

[0147] In particular, a composition according to the present invention based on at least one refined lubricating oil enables good properties to be achieved simultaneously with respect to cooling and lubricating parts in such mechanical systems, especially in the propulsion system of an electric or hybrid vehicle, such as an electric engine of an electric or hybrid vehicle.

[0148] According to another aspect thereof, the present invention also relates to a heat transfer or thermal management device in which a composition based on at least one lubricating oil that is at least partially refined is used as a heat transfer fluid.

[0149] In particular, the device uses at least one heat transfer or thermal management circuit in which a composition based on at least one lubricating oil that is at least partially refined is used.

[0150] According to the present invention, the special, advantageous or preferred features of these oils or compositions make it possible to define a use according to the present invention that is likewise special, advantageous or preferred.

[0151] Here, by way of example and without limiting the present invention, the present invention will be described by the following examples given without limitation.

Examples

[0152] Method for Measuring Kinematic Viscosity The kinematic viscosity of the oil is measured at 40 °C (KV40) and 100 °C (KV100) using a viscometer in accordance with the NF EN ISO 3104 standard. This standard is technically equivalent to the ASTM D445 standard. The results are expressed in mm 2 / s (equivalent to centistokes denoted as cSt).

[0153] Method for measuring volatility Volatility is used to determine the loss due to evaporation of the oil at high temperature and is determined by the Noack volatility test conducted in accordance with the CEC L-40-93 standard. In the test, a sample of the oil is subjected to a constant air flow heated to approximately 250 °C for approximately 60 minutes. The result is expressed as a mass percentage as the ratio of the lost mass.

[0154] Method for measuring density The density of the oil is measured at 15 °C using a U-tube densitometer in accordance with the NF EN ISO 12185 standard and is expressed in kg / m 3 represented.

[0155] Method for measuring viscosity index The viscosity index is a dimensionless ratio that serves as an indicator of the temperature-dependent variation of the viscosity of the oil and is calculated from the kinematic viscosity values at 40 °C and 100 °C in accordance with the NF ISO 2909 standard. The higher this index, the less the viscosity of the oil is affected by changes in temperature.

[0156] Method for measuring thermal conductivity Thermal conductivity, often denoted by λ, characterizes the ability of the oil to diffuse heat into the medium and is measured by the transient hot-wire liquid thermal conductivity method in accordance with the ASTM D7896-19 standard and is expressed in mW / mK.

[0157] Method for measuring flash point The flash point serves as an indicator of the ability of the product to form a combustible mixture with air under controlled conditions and is determined using a Cleveland open cup apparatus in accordance with the NF EN ISO 2592 standard. The flash point at ambient atmospheric pressure is the lowest temperature at which the vapor on the surface of the liquid ignites when a flame passes over the test cup containing the oil and is expressed in degrees Celsius.

[0158] Method for measuring the sulfur and aromatic compound content The sulfur and aromatic compound content in the oil is determined by infrared or ultraviolet spectroscopy.

[0159] (Example 1) The properties of six commercially available re-refined lubricating oils I1 to I6 that comply with the present invention were evaluated.

[0160] These oils are obtained from used base oils that have undergone at least one process of dehydration, distillation, filtration, hydrogenation, liquid-liquid extraction, sedimentation, and / or passage over an adsorbent for used lubricants, particularly at least one process of dehydration, distillation, liquid-liquid extraction, and / or hydrogenation.

[0161] In addition, three new lubricating oils C1 to C3 that do not comply with the present invention because they have not undergone any recycling or re-refining process were also evaluated.

[0162] These oils are commercially available Group I or II base oils according to API classification.

[0163] In particular, the kinematic viscosities, viscosity indices, densities, volatilities, flash points, and thermal conductivities of these oils at 40°C and 100°C were measured according to the protocol detailed above.

[0164] The results are shown in Table 2 below for re-refined and virgin oils having properties equivalent to those defined as Group I base oils according to API classification, and in Table 3 below for re-refined and virgin oils having properties equivalent to those defined as Group II base oils according to API classification.

[0165] [Table 2]

[0166] [Table 3]

[0167] Results All of the at least partially re-refined oils required by the present invention have a higher viscosity index, higher thermal conductivity, and lower density compared to virgin oils that do not comply with the present invention but have equivalent properties in other respects.

[0168] The at least partially re-refined oil has particularly advantageous thermophysical properties as a result, and for this reason it is possible to achieve better performance than a new lubricating oil that has not undergone any recycling as a heat transfer fluid.

[0169] The lower density and higher viscosity index also make it possible to ensure good hydraulic performance, and in particular to reduce the costs associated with pumping these oils when used as heat transfer fluids. In addition, the at least partially re-refined oil has better properties than new lubricating oils, particularly in terms of energy and fuel savings.

[0170] Also, the at least partially re-refined oil required by the present invention has a lower volatility and a higher flash point compared to those measured for oils unsuitable for the present invention. The at least partially re-refined oil thus allows for increased safety compared to new lubricating oils.

[0171] In conclusion, the at least partially re-refined lubricating oil has particularly advantageous properties that allow for use as a heat transfer fluid, in particular as a liquid coolant, and in particular better properties than new oils.

Claims

1. Use as a heat transfer fluid of a composition based on at least one at least partially re-refined lubricating oil.

2. The use according to claim 1, wherein the at least partially re-refined lubricating oil is derived from a used lubricant, and the used lubricant has been subjected to one or more prior steps of dehydration, distillation, filtration, hydrogenation, liquid-liquid extraction, sedimentation and / or passage over an adsorbent of the used lubricant.

3. The at least partially re-refined lubricating oil has a kinematic viscosity of 5 mm 2 / s or more, particularly 5 to 12 mm 2 / s, more particularly 5 to 10 mm 2 / s, as measured at 100 °C in accordance with ASTM D445, for use according to claim 1 or 2.

4. The use according to any one of claims 1 to 3, wherein the at least partially re-refined lubricating oil has a viscosity index of 110 or more, in particular 110 to 130, especially 112 to 125.

5. The use according to any one of claims 1 to 4, wherein the at least partially re-refined lubricating oil has a Noack volatility of 15% or less, in particular 8% to 15%, preferably strictly less than 12%, more particularly 8% to 11.9%.

6. The use according to any one of claims 1 to 5, wherein the at least partially re-refined lubricating oil has a sulfur content of 0.02% to 0.2% by mass based on the total mass of the regenerated lubricating oil.

7. The use according to any one of claims 1 to 6, wherein the at least partially re-refined lubricating oil has an aromatic compound content of 0.5% by mass or more, in particular 1% by mass or more, especially 1% to 25% by mass, more particularly 2.5% to 20% by mass based on the total mass of the regenerated lubricating oil.

8. The at least partially re-refined lubricating oil has a density of 870 kg / m 3 Hereinafter, particularly 830 to 870 kg / m 3 , particularly 860 kg / m 3 Hereinafter, more particularly 840 to 860 kg / m 3 and is used according to any one of claims 1 to 7.

9. The use according to any one of claims 1 to 8, wherein the at least partially re-refined lubricating oil has a thermal conductivity of 125 mW / mK or more, in particular 125 to 145 mW / mK, especially 128 mW / mK or more, more particularly 128 to 140 mW / mK measured at 100 °C and atmospheric pressure.

10. The use according to any one of claims 1 to 9, wherein the composition comprises one or more base oils different from the at least partially re-refined lubricating oil and / or one or more additives selected in particular from corrosion inhibitors, friction modifier additives, extreme pressure additives, anti-wear additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressants (PPD), dispersants, anti-foaming agents, and mixtures thereof.

11. The use according to any one of claims 1 to 10, wherein the composition comprises more than 80% by mass, in particular 90% to 100% by mass, more particularly 95% to 100% by mass of at least one of the at least partially re-refined lubricating oils based on the total mass of the composition. **Claim 12** A method of transferring heat in a movable or stationary mechanical system, comprising at least one step of circulating through the mechanical system, as a heat transfer fluid, a composition based on at least one lubricating oil that has been at least partially re-refined, in particular a composition as defined in any one of claims 2 to 10. **Claim 13** A heat transfer or heat management device in which a composition based on at least one lubricating oil that has been at least partially re-refined, in particular a composition as defined in any one of claims 2 to 10, is used as a heat transfer fluid.

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