Heat transfer fluids based on lubricating oils that are at least partially re-refined

Abstract

Title: Heat transfer fluids based on at least partially re-refined lubricating oils. This application relates to the use of a composition based on at least one partially re-refined lubricating oil as a heat transfer fluid. It also relates to a method for transferring heat in a mobile or stationary mechanical system, comprising at least one step of circulating, within said mechanical system, a composition based on at least one partially re-refined lubricating oil as a heat transfer fluid, as well as a heat transfer or thermal management device, in which a composition based on at least one partially re-refined lubricating oil is used as a heat transfer fluid.

Description

Title of the invention: Heat transfer fluids based on lubricating oils at least partially re-refined 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 oils for the formulation of heat transfer fluids. Previous technique

[0002] Heat transfer fluids find application in many systems, in which they allow heat to be transported between different temperature sources.

[0003] These fluids are classically involved in heat exchangers, for example in the cooling systems of thermal or electric motors, such as vehicle engines, refrigerators, boilers, air conditioners, solar thermal collectors, radiators of electrical circuits, particularly in the case of high power electrical transformers, or electronics, thermal power plants using coal, fuel oil, gas or nuclear power, wastewater heat exchangers.

[0004] A large number of heat transfer fluids have been documented and commercialized, employing a wide variety of base fluids and performance additives.

[0005] In general, heat transfer fluids must satisfy two requirements: on the one hand, they must allow for the efficient transfer of thermal energy and, on the other hand, it is essential that the heat transfer fluid does not degrade the system in which it is used, or does not degrade itself during its use.

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

[0007] Water is commonly used as the base liquid for heat transfer fluids due to its natural availability and the lack of environmental impact of its use. In fact, water is an excellent thermal energy carrier because of its high specific heat capacity, high thermal conductivity, and low viscosity. A significant limitation of the use of water as a fluid The main drawback of water-based heat transfer fluids is that they freeze at a relatively high temperature of 0°C, making them unsuitable for use in many systems requiring operating temperatures below 0°C. Furthermore, water-based heat transfer fluids are naturally corrosive and can cause significant damage to the systems in which they operate. To overcome these limitations, many heat transfer fluids have been developed in which freezing point depressants are added to the water to lower its freezing temperature, along with various additives to control corrosion.

[0008] Mineral oils from petroleum refining have also been proposed as base liquids for heat transfer fluids, particularly for applications in systems where the fluid is likely to be brought to high temperatures.

[0009] One can cite for example US document 7,972,999 which proposes to implement a base oil prepared from a paraffin wax to form a heat exchange liquid, and having in particular an auto-ignition temperature greater than 329°C and a high viscosity index.

[0010] However, a large quantity of crude oil is generally required to obtain refined oils. Typically, 37 liters of crude oil are needed to extract 1 liter of refined oil. Furthermore, oil refining processes are very energy-intensive. Current environmental protection and resource conservation concerns are driving manufacturers to offer more eco-friendly alternatives to conventional oils.

[0011] There therefore remains a need for heat transfer fluids that are more environmentally friendly, while exhibiting excellent physicochemical properties, or even improved properties compared to known heat transfer fluids. Description of the invention

[0012] The present invention aims to provide new heat transfer fluids that meet these expectations.

[0013] In particular, the inventors discovered that recycled lubricating base oils are particularly suitable for use as heat transfer fluids.

[0014] Thus, the invention relates, according to a first of its aspects, to the use of a composition based on at least one lubricating oil at least partly re-refined as a heat transfer fluid.

[0015] In the context of the present invention, the expression "at least partially re-refined lubricating oil," also referred to more simply in the following text as "re-refined oil," "regenerated oil," or "recycled oil," designates an oil derived at least in part from a used lubricating composition that has been subjected to a or several processing steps known as re-refining treatment.

[0016] According to the invention, the term "used lubricating composition" (or more simply "used lubricant" or "used lubricating oil") means any lubricating composition that has been used for the lubrication of moving parts, in particular metal parts, of a mechanical system, such as, but not limited to, bearings, gears or motors.

[0017] Used lubricating oil can come from various sources. In particular, as detailed later in the text, it can be a lubricant that has been used to lubricate a motorization system, in particular a "mobile" one, or to lubricate an industrial system, in particular a "stationary" one.

[0018] Due to their origin, used lubricating oils, particularly engine lubricating oils, contain a number of degradation products derived from the oil itself or the additives it contains, as well as metal particles, metal oxides, and other elements, originating, for example, from the engine. Used oil may, in particular, contain a high level of undesirable elements, for example, calcium (Ca), iron (Fe), magnesium (Mg), sodium (Na), nickel (Ni), phosphorus (P), silicon (Si), chlorine (Cl), zinc (Zn), etc.

[0019] Methods for re-refining or reconditioning used lubricating oils have been developed in order to regenerate these oils and allow their subsequent reuse.

[0020] A re-refined lubricating oil is thus an oil obtained after one or more processing steps of a used lubricant, aimed at eliminating, at least in part, a number of contaminating elements present therein, such as dust, water, fuel fractions, metallic elements and other residues resulting from the degradation of additives present in the lubricant.

[0021] To the inventors' knowledge, it has never been proposed to use recycled lubricating oil to formulate a heat transfer fluid.

[0022] The implementation according to the invention of a re-refined lubricating oil as a heat transfer fluid proves advantageous in several respects.

[0023] On the one hand, as illustrated in the examples that follow, the inventors have shown that re-refined lubricating oils have particularly advantageous thermo-physical properties, especially in terms of volatility, density, viscosity index, flash point and thermal conductivity, which make them particularly suitable as heat transfer fluids.

[0024] Surprisingly, recycled lubricating oils even exhibit thermo-physical properties for their use as a heat transfer fluid, superior to those of refined base oils, in other words virgin or new base oils.

[0025] A refined base oil, also called a "virgin" or "new" base oil, unlike re-refined lubricating oils, is an oil directly from petroleum refining and not yet used.

[0026] Furthermore, the advantageous use of recycled lubricating oils as heat transfer fluids meets current expectations for reducing environmental impact and conserving resources. Thus, the use of heat transfer fluids based on regenerated lubricating oils advantageously reduces the carbon footprint of products compared to the use of virgin base oils.

[0027] As detailed later in the text, the re-refined lubricating oil(s) can be used as such, that is, alone, in other words without additives, as a heat transfer fluid. In a particular embodiment, the invention thus relates to the use of at least one lubricating oil, at least partially re-refined, as a heat transfer fluid.

[0028] The said re-refined lubricating oil(s) may also be used in combination with one or more other ingredients. In particular, they may be enhanced with one or more additives, for example intended to promote the compatibility of the heat transfer fluid with the materials of the system for which it is intended, such as, for example and without limitation, anti-corrosion additives, antioxidant additives, etc.

[0029] In this embodiment, the heat transfer fluid according to the invention is advantageously composed mainly of the re-refined lubricating oil(s). In particular, the re-refined lubricating oil(s) may represent more than 80% by mass of the total mass of the heat transfer fluid, in particular more than 90% by mass and more particularly more than 95% by mass of the total mass of the heat transfer fluid.

[0030] The said re-refined lubricating oil(s) can also be used in combination with at least one new base oil.

[0031] The present invention further relates to the use of at least one lubricating oil, at least partially re-refined, to formulate or prepare a heat transfer fluid.

[0032] It also relates to a process or method for preparing a heat transfer fluid comprising at least one step of obtaining a lubricating oil at least partly re-refined from a used lubricant.

[0033] The process for preparing a heat transfer fluid according to the invention may more particularly include the steps of: (i) prepare a lubricating oil at least partly re-refined from a used lubricant; (ii) optionally, mix said lubricating oil at least partially re-refined with one or more new base oil(s), separate from re-refined lubricating oils, for example one or more mineral oils; and (iii) optionally, supplement said lubricating oil at least partially re-refined from step (i), or the lubricating oil mixture from step (ii), with at least one additive, in particular selected from anti-corrosion additives, friction modifier additives, extreme-pressure additives, anti-wear additives, detergents, antioxidants, viscosity index (VI) improvers, pour point (PPD) lowering agents, dispersants, anti-foaming agents, and mixtures thereof.

[0034] The heat transfer fluid formulated according to the invention based on at least one re-refined lubricating oil can be used for multiple applications, in particular as a coolant for a vehicle engine, as a heat transfer fluid in an air conditioning or heating circuit of a building, etc.

[0035] Examples of applications of fluids formulated according to the invention are described in more detail later in the text.

[0036] In particular, the invention also relates, according to another of its aspects, to the use of a heat transfer fluid according to the invention, based on at least one lubricating oil at least partly re-refined, as a coolant in a mobile or stationary motorization system, in particular as a coolant for a vehicle engine, for example an electric or hybrid vehicle.

[0037] Other features, variations and advantages of using lubricating oils at least partially re-refined for the formulation of a heat transfer fluid according to the invention will become clearer from the description and examples that follow, given by way of illustration and not limitation of the invention.

[0038] The expressions "between ... and ...", "ranging from ... to ...", "made up of ... to ...", and "varying from ... to ...", must be understood inclusive of limits, unless otherwise stated.

[0039] In the description and examples, unless otherwise indicated, percentages are mass percentages. Percentages are therefore expressed in terms of mass relative to the total mass of the composition. Detailed description Lubricating oil, at least partially re-refined

[0040] As previously stated, the oil used to formulate a heat transfer fluid according to the invention is a lubricating oil that is at least partly re-refined, also called "regenerated oil" or "recycled oil", in other words, a lubricating oil derived from a used lubricating composition that has been subjected to one or more re-refining treatment steps can be used according to the invention.

[0041] It is understood that a used lubricating composition may be a mixture of several used lubricating compositions, from the same source or from several different sources.

[0042] Used lubricating compositions and, consequently, regenerated lubricating oils, comprise, in majority quantity, one or more base oils conventionally used in the field of lubricants, such as mineral, synthetic or natural, animal or vegetable oils or mixtures thereof.

[0043] It may be a mixture of several base oils, for example a mixture of two, three, or four base oils.

[0044] These base oils may be of natural origin, for example from plants or animals, such as vegetable, animal, fish 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, animal fats, and mixtures thereof.

[0045] Advantageously, these base oils are oils of mineral or synthetic origin belonging to groups I to V according to the classes defined in the API classification (or their equivalents according to the ATIEL classification) and presented in the following table, or their mixtures.

[0046] [Tables 1] Saturates content Sulfur content Viscosity index (VI) Group I Mineral oils < 90% > 0.03% 80 <VI < 120 Groupement II Huiles hydrocraquées >90% <0.03% 80 <VI < 120 Groupement III Huiles hydrocraquées ou hydro-isomérisées >90% <0.03% >120 Group IV Polyalphaolephs (PAOs) Group V Esters and other bases not included in groups I to IV

[0047] In particular, the used lubricating composition, from which the regenerated lubricating oil implemented according to the invention is derived, may comprise at least 50% by weight of base oil(s) relative to its total weight, in particular at least 60% by weight of base oil(s), and more particularly between 60 and 99% by weight of base oil(s).

[0048] The re-refined lubricating oils implemented according to the invention advantageously have characteristics in terms of saturated compound content, sulfur content and viscosity index, satisfying the criteria defined by the API classification for group I, II, III, IV and / or V oils, in particular for group I, II, III and / or IV oils.

[0049] The invention thus relates to the use as a heat transfer fluid of a composition formed in whole or in part from at least one lubricating oil, at least partially re-refined, obtained after one or more processing steps of a used lubricant based on one or more oils of groups I to V according to the APL classification

[0050] According to a particular embodiment, the re-refined lubricating oil implemented according to the invention can be obtained from the treatment of a used lubricating composition that has been used for the lubrication of a motorization system, in particular "mobile", i.e. including light vehicles, heavy goods vehicles, mobile machines known as "off road", or marine vehicles.

[0051] According to another particular embodiment, the re-refined lubricating oil implemented according to the invention can be obtained from the treatment of a used lubricating composition that has been used for the lubrication of an industrial system, in particular a "stationary" one, i.e. including, but not limited to, turbines, compressors, hydraulic systems, gears, or even forming or cutting machines.

[0052] A used lubricating composition, from which the regenerated lubricating oil used according to the invention is derived, may contain various conventional additives in the field of lubricants, such as friction modifiers, extreme pressure additives, anti-wear additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressants (PPD) additives, dispersants, anti-foaming agents, thickeners, and mixtures thereof.

[0053] As already mentioned previously, the properties of the used lubricating composition are degraded due to its use, for a more or less long period, for the lubrication and / or cooling of a mechanical system, in particular a motorization system, such as a combustion engine.

[0054] Due to their origin, used lubricating compositions may thus contain one or more of the additives described above and impurities resulting from the degradation of additives originally present in the lubricant, or resulting from the wear of moving mechanical parts.

[0055] The composition of the used lubricant can of course be different depending on the origin of the lubricant, its initial formulation and the fact that it may have been contaminated differently depending on its use.

[0056] The regenerated lubricating oil implemented according to the invention comes more particularly from a used lubricating composition having been subjected to one or more prior pre-treatment steps known in the field of re-refining used lubricants.

[0057] In particular, these treatment steps aim to eliminate, at least partially, water, solid particles, fuel and / or other contaminants, such as polycyclic aromatic hydrocarbons (PAHs), which are undesirable in the context of lubricant formulation.

[0058] According to a particular embodiment, the regenerated lubricating oil implemented according to the invention comes from a used lubricant that has been subjected to one or more prior steps of dehydration, distillation, filtration, hydrogenation, liquid / liquid extraction, decantation and / or passing of the used lubricant over an adsorbent material, preferably as detailed below.

[0059] Thus, the invention relates to the use, as a heat transfer fluid, of a composition based on at least one lubricating oil at least partly re-refined, in particular formed of at least one lubricating oil at least partly re-refined, preferably as described above, said lubricating oil at least partly re-refined being obtained from a used lubricating composition having been subjected to at least one or more steps of dehydration, distillation, filtration, hydrogenation, liquid / liquid extraction, decantation and / or passing of said used lubricating composition over an adsorbent material, preferably carried out under the conditions detailed below.

[0060] Preferably, the regenerated lubricating oil implemented according to the invention is obtained by subjecting a used lubricating composition to at least one dehydration step. This dehydration step makes it possible to remove any water that may be present in the used lubricant.

[0061] Advantageously, the regenerated lubricating oil implemented according to the invention thus comprises a water content less than or equal to 10% by mass, in particular less than or equal to 5% by mass, in particular less than or equal to 2% by mass and more particularly less than or equal to 1% by mass, relative to the total mass of said regenerated lubricating oil.

[0062] This dehydration can be carried out by any method known to those skilled in the art, for example by distillation, evaporation, decantation, heating or passing a stream of hot air over the used lubricating composition.

[0063] According to one embodiment, the dehydration step can be carried out at a temperature temperature between 50 °C and 250 °C, preferably between 100 °C and 200 °C. In particular, it can be operated at a pressure between 50,000 and 150,000 Pa, preferably at atmospheric pressure.

[0064] Preferably, the regenerated lubricating oil implemented according to the invention is obtained by subjecting a 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 be a particulate or non-particulate filtration step. For example, it can be carried out by diatomaceous earth systems.

[0065] Preferably, the regenerated lubricating oil produced according to the invention is obtained by subjecting a used lubricating composition to at least one distillation step, preferably following a prior dehydration step. This distillation step(s) can be carried out using any technique known to those skilled in the art. For example, it could be atmospheric distillation or distillation under reduced pressure. The distillations can, for example, be carried out at a temperature between 100 °C and 500 °C, preferably between 200 °C and 400 °C, and more preferably between 300 °C and 380 °C. In particular, they can be carried out at a pressure between 25 and 2,000 Pa, preferably between 50 and 1,000 Pa, and more particularly between 50 and 250 Pa.

[0066] Advantageously, the regenerated lubricating oil implemented according to the invention is obtained by subjecting a used lubricating composition to at least one prior step of passing said used lubricating composition over an adsorbent material.

[0067] The adsorbent material advantageously allows for the selective adsorption of aromatic compounds, in particular PAHs.

[0068] In particular, passing over an adsorbent material, preferably activated carbon, advantageously reduces the content of polycyclic aromatic hydrocarbons (PAHs), notably chosen 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, of the used lubricant composition.

[0069] The term "passage of the used lubricating composition over an adsorbent material" means the flow of the used lubricating composition over the adsorbent support.

[0070] The adsorbent materials can be, for example, activated carbon, zeolites, clays or functionalized porous compounds. Preferably, they are activated carbon.

[0071] For example, the regenerated lubricating oil used in the process of the invention can be obtained from the treatment of a used lubricating composition according to the process described in document WO 2018 / 109208.

[0072] In the case of passing the used lubricating composition over activated carbon, the quantity of activated carbon used is preferably between 0.5 and 60 g of activated carbon per litre of used lubricating composition, preferably between 0.5 and 50 g / L, preferably from 1 to 50 g / L, preferably between 1 and 30 g / L, for example between 5 and 60 g / L, preferably between 5 and 50 g / L.

[0073] The flow rate of the used lubricant composition can be between 1m3 / h and 15 m3 / h, for example between 5 and 10 m3 / h.

[0074] Preferably, the activated carbon is characterized by a density between 200 and 500 kg / m3, for example measured according to the ASTDM D2854 standard.

[0075] Preferably, the activated carbon is coal coal, preferably comprising 70 to 95%, advantageously 80 to 90% by weight of carbon.

[0076] The step of passing the used lubricating composition over an adsorbent support, preferably activated carbon, is advantageously preceded by the following preliminary steps: - one or more distillation stages; and - a filtration step, in particular as defined previously.

[0077] Advantageously, the regenerated lubricating oil implemented according to the invention can be obtained by subjecting a used lubricating composition to at least one preliminary hydrogenation (or hydrotreating) step, preferably following a preliminary dehydration and / or distillation step. This hydrogenation step(s) can be carried out by any technique known to those skilled in the art and generally consist of treating the lubricating oil with hydrogen, usually in the presence of a hydrotreating catalyst. Such a catalyst may contain, for example, at least one oxide or sulfide of at least one Group VI metal and / or at least one Group VIII metal, such as molybdenum, tungsten, nickel, or cobalt, and a carrier, for example, alumina, silica-alumina, or a zeolite.

[0078] Advantageously, the regenerated lubricating oil implemented according to the invention can be obtained by subjecting a used lubricating composition to at least one preliminary liquid / liquid extraction step with a solvent, preferably following a preliminary dehydration and / or distillation step. In particular, liquid / liquid extraction with a solvent advantageously makes it possible to lighten a dark-colored used oil, to at least partially eliminate unpleasant odors or aromatic compounds, in particular PAHs. The said extraction step(s) can be carried out by any technique known to those skilled in the art. The extraction is generally performed in a mixer-settler or in an extraction column, using a suitable extraction solvent.

[0079] Advantageously, the regenerated lubricating oil implemented according to the invention can be obtained by subjecting a used lubricating composition to at least one preliminary settling step. This settling step or steps can be carried out by any technique known to those skilled in the art.

[0080] It is understood that the invention is in no way limited to the use of regenerated oils obtained according to the treatment methods described above. Other lubricating oils, at least partially re-refined, for example Group I and / or II, obtained from treatment steps other than those described above, may be suitable for the invention.

[0081] In any event, a re-refined lubricating oil implemented according to the invention differs from a used lubricating oil, in particular due to the reduced content of certain undesirable contaminants, for example water, fuel, metallic elements or certain heteroatoms.

[0082] A regenerated lubricating oil implemented according to the invention is characterized in particular by a silicon content of between 0 ppm and 300 ppm, in particular between 1 and 300 ppm.

[0083] A regenerated lubricating oil implemented according to the invention is characterized in particular by a phosphorus content less than or equal to 100 ppm, in particular between 0 ppm and 100 ppm, for example 0 ppm.

[0084] A regenerated lubricating oil implemented according to the invention can also be characterized by its content of one or more other elements selected from chlorine, oxygen, and nitrogen. For example, it may have a chlorine content between 0 ppm and 50 ppm, for example, 0 ppm.

[0085] The content of these elements can be evaluated by any method known to a person skilled in the art, for example by X-ray fluorescence (XRF), or by Infrared or Ultraviolet spectroscopy.

[0086] On the other hand, a regenerated lubricating oil implemented according to the invention is distinguished, due to its formation from a used lubricant, from a virgin or new base oil, oil directly from petroleum refining, or even from native base oils, for example of natural origin, both in terms of its composition and its physico-chemical properties.

[0087] In particular, as previously stated, surprisingly, a regenerated lubricating oil exhibits excellent thermo-physical and hydraulic properties, particularly in terms of viscosity index, density, Noack volatility, flash point and / or thermal conductivity, and advantageously thermo-physical and hydraulic properties superior to those of a virgin base oil.

[0088] Preferably, the regenerated lubricating oil implemented according to the invention has a kinematic viscosity measured at 100 °C according to ASTM D445 between 2 and 12 mm2 / s', in particular between 3 and 10 mm2 / s'.

[0089] Preferably, the kinematic viscosity measured at 100 °C according to ASTM D445 of the lubricating oil, at least partially re-refined, is greater than or equal to 5 mm2 / s, for example between 5 and 12 mm2 / s, more particularly between 5 and 10 mm2 / s.

[0090] Advantageously, the regenerated lubricating oil implemented according to the invention has a kinematic viscosity measured at 40 °C according to ASTM D445 of between 20 and 40 mm2 / s, in particular between 25 and 35 mm2 / s.

[0091] Preferably, a regenerated lubricating oil implemented according to the invention has a viscosity index greater than or equal to 110. The viscosity index of the lubricating oil, at least partly re-refined, can thus be between 110 and 130, in particular between 112 and 125.

[0092] The viscosity index can in particular be determined according to standard NF ISO 2909.

[0093] Preferably, a regenerated lubricating oil implemented according to the invention has a Noack volatility of less than or equal to 15%. The Noack volatility of the lubricating oil, at least partially re-refined, can thus be between 8% and 15%.

[0094] More preferably, a regenerated lubricating oil implemented according to the invention has a Noack volatility strictly less than 12%. The Noack volatility of the lubricating oil, at least partially re-refined, can thus be between 8% and 11.9%.

[0095] Noack volatility can in particular be determined according to the CEC L-40-93 standard.

[0096] Preferably, a regenerated lubricating oil implemented according to the invention presents a sulfur content of between 0.02% and 0.2% by mass, relative to the total mass of said regenerated lubricating oil.

[0097] Preferably, a regenerated lubricating oil implemented according to the invention has an aromatic compound(s) content greater than or equal to 0.5% by mass, and in particular greater than or equal to 1% by mass, relative to the total mass of said regenerated lubricating oil. The aromatic compound(s) content in the regenerated lubricating oil can thus be between 1% and 25% by mass, and in particular between 2.5% and 20% by mass, relative to the total mass of said regenerated lubricating oil.

[0098] The contents of these different elements can be determined by any method known to a person skilled in the art, for example by X-ray fluorescence (XRF) or by Infrared or Ultraviolet spectroscopy.

[0099] The re-refined lubricating oil implemented according to the invention advantageously has at least one, at least two, at least three, or even all of the following characteristics: - a kinematic viscosity measured at 100 °C according to ASTM D445 greater than or equal to 5 mm2 / s, for example between 5 and 12 mm2 / s, more particularly between 5 and 10 mm2 / s; - a viscosity index greater than or equal to 110, in particular between 110 and 130, especially between 112 and 125; - a Noack volatility of less than or equal to 15%, in particular between 8% and 15%, preferably strictly less than 12%, more particularly between 8% and 11.9%; - a sulfur content of between 0.01% and 0.3% by mass, in particular between 0.02% and 0.2% by mass, relative to the total mass of said regenerated lubricating oil; - an aromatic compound(s) content greater than or equal to 0.5% by mass, in particular greater than or equal to 1% by mass, in particular between 1% and 25% by mass, more particularly between 2.5% and 20% by mass, relative to the total mass of said regenerated lubricating oil.

[0100] Advantageously, a regenerated lubricating oil implemented according to the invention has a density less than or equal to 870 kg / m3, in particular less than or equal to 860 kg / m3. The density of the lubricating oil, at least partially re-refined, can thus be between 830 and 870 kg / m3, in particular between 840 and 860 kg / m3.

[0101] The density can in particular be determined according to the standard NF EN ISO 12185.

[0102] Advantageously, a regenerated lubricating oil implemented according to the invention has a flash point greater than or equal to 225 °C, in particular greater than or equal to 228 °C. The flash point of the lubricating oil, at least partially re-refined, can thus be between 225 °C and 245 °C.

[0103] The flash point can in particular be determined according to the standard NF EN ISO 2592.

[0104] Advantageously, a regenerated lubricating oil implemented according to the invention has a thermal conductivity, measured at 100 °C and atmospheric pressure, greater than or equal to 125 mW / mK, in particular greater than or equal to 128 mW / mK. The thermal conductivity of the lubricating oil, at least partially re-refined, can thus be between 125 and 145 mW / mK, in particular between 128 and 140 mW / mK.

[0105] Thermal conductivity can in particular be determined according to ASTM D7896-19.

[0106] Due to these properties in terms of viscosity index, density, thermal conductivity, flash point, Noack volatility and density, the re-refined lubricating oils implemented according to the invention exhibit excellent performance in terms of both heat transfer efficiency and hydraulic performance, and advantageously increased performance compared to virgin base oils.

[0107] A high viscosity index makes it possible, in particular, to have a heat transfer fluid whose viscosity varies little with temperature, thus ensuring good hydraulic properties of the heat transfer fluid. Therefore, the heat transfer fluid according to the invention can be used in systems that may be subjected to large temperature variations, for example as coolant in vehicles, and remains pumpable over the temperature range in which it must circulate in said system.

[0108] In particular, re-refined lubricating oils advantageously have a low density, in particular lower than that of virgin base oils, and a high viscosity index, in particular higher than that of virgin base oils, which makes it possible to reduce pumping costs, while having better thermal properties. Heat transfer fluid

[0109] As mentioned previously, the re-refined lubricating oil(s) implemented according to the invention, in particular as 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.

[0110] The composition used as a heat transfer fluid may thus include one or more base oils distinct from the lubricating oil, at least partly re-refined, and / or one or more additives.

[0111] In a particular embodiment, the re-refined lubricating oil(s) may be formulated in combination with one or more separate base oils, in particular one or more new base oils.

[0112] In particular, they are chosen from among the base oils conventionally used in the field of lubricants, such as mineral, synthetic or natural, animal or vegetable oils or mixtures thereof.

[0113] Advantageously, these base oils are oils of mineral or synthetic origin belonging to groups I to V according to the classes defined in the API classification (or their equivalents according to the ATIEL classification) and presented in Table 1 above, or mixtures thereof.

[0114] A composition implemented according to the invention can thus comprise, or even be formed, of a mixture of one or more lubricating oils at least partly re-refined and one or more new base oils, for example at least one mineral oil.

[0115] In particular, a composition implemented according to the invention may comprise between 0% and 80% by mass, in particular between 5% and 75% by mass of new base oil(s), separate from re-refined lubricating oils required according to the invention and defined above, in relation to the total weight of the composition.

[0116] According to a particular embodiment, a composition used as a heat transfer fluid according to the invention comprises less than 50% by mass of new base oil(s), separate from re-refined lubricating oils.

[0117] Preferably, a composition used as a heat transfer fluid according to the invention is formed mainly of said re-refined lubricating oil(s). In particular, said re-refined lubricating oil(s) advantageously represent more than 80% by mass of the total mass of the heat transfer fluid, in particular more than 90% by mass and more particularly more than 95% by mass, of the total mass of the heat transfer fluid.

[0118] Thus, a composition implemented as a heat transfer fluid according to the invention advantageously comprises more than 80% by mass, in particular between 90% and 100% by mass, more particularly between 95% and 100% by mass of at least one lubricating oil at least partly re-refined, relative to the total mass of the composition.

[0119] In a particular embodiment, a composition implemented as a heat transfer fluid according to the invention is completely free of base oil distinct from re-refined lubricating oils.

[0120] In a particular embodiment, a composition implemented as a heat transfer fluid according to the invention may include, in addition to said re-refined lubricating oil(s), one or more additives, in particular intended to promote the compatibility of the heat transfer fluid with the materials of the system for which it is intended.

[0121] These additives may in particular be selected from among anti-corrosion additives, friction modifier additives, extreme-pressure additives, anti-wear additives, detergents, antioxidants, viscosity index (VI) improvers, pour point lowering (PPD) agents, dispersants, anti-foaming agents, and mixtures thereof.

[0122] These additives may be added to the regenerated base oil(s) used according to the invention or to a mixture of the regenerated base oil(s) and at least one new base oil in an appropriate quantity, determined by those skilled in the art. It is understood that the nature and quantity of the additives used are chosen in such a way that the advantageous properties, as a heat exchange fluid, of the composition based on the re-refined lubricating oil(s) are not, or are not substantially, altered by the intended addition.

[0123] A composition implemented as a heat transfer fluid according to the invention may comprise between 0% and 20% by mass, in particular between 0.01% and 10% by mass, of additives, in particular as described above, relative to the total weight of the composition.

[0124] The invention thus relates, according to another of its aspects, to a process or method for preparing a heat transfer fluid, comprising at least one step consisting of obtaining a lubricating oil at least partly re-refined from a used lubricant.

[0125] Advantageously, such a process or method comprises at least the steps of: (i) have at least partially re-refined lubricating oil obtained from a used lubricant, in particular formed by subjecting a used lubricant to at least one or more steps of dehydration, distillation, filtration, hydrogenation, liquid / liquid extraction, decantation and / or passing the used lubricant over an adsorbent material, preferably as detailed above; (ii) optionally, mix said lubricating oil, at least partially re-refined, with one or more new base oils, separate from re-refined lubricating oils, for example one or more mineral oils; and (iii) optionally, supplement said lubricating oil at least in part re-refined from step (i) or the mixture of lubricating oils from step (ii), with at least one additive, in particular as described above. Applications

[0126] As mentioned above, a lubricating oil that is at least partly re-refined is particularly suitable for use as a heat transfer fluid, due to its thermo-physical properties.

[0127] In particular, a fluid based on at least one re-refined lubricating oil according to the invention can be used for various systems and applications, in particular at the level of the heat transfer fluid circuit(s), as a substitute for conventional heat transfer fluids.

[0128] Heat transfer fluid circuits classically include means for forced or free circulation of the heat transfer fluid, for example a pump, or any other equivalent means, and means for evacuation, such as for example exchangers or any other equivalent means allowing the diffusion of heat.

[0129] The invention is therefore not limited to a particular application of fluids formulated according to the invention, the following development being given solely by way of illustration and not limitation.

[0130] In particular, the present invention relates to the use of a composition based on at least one lubricating oil, at least partly re-refined, as a heat transfer fluid, also called a heat exchange fluid, in a mobile or stationary mechanical system, in other words, to transfer heat in a mobile or stationary mechanical system.

[0131] A fluid according to the invention can for example be used to ensure heat exchange in "stationary" mechanical systems, such as boilers, air conditioners, in particular in data centers ("Data Centers" in English), solar thermal collectors, photovoltaic solar collectors, radiators of electrical circuits, in particular of electrical transformers, thermal power plants using coal, fuel oil, gas or nuclear power, wastewater heat exchangers, turbines, compressors, hydraulic systems, gears or even forming or cutting machines.

[0132] A fluid according to the invention can, for example, also be used to ensure heat exchange in "mobile" mechanical systems, including the components of light vehicles, heavy goods vehicles, so-called "off-road" mobile machines, or marine vehicles, in particular their engine systems.

[0133] The invention relates in particular to a process or method for transferring heat in a mobile or stationary mechanical system, in particular as described above, comprising at least one step of circulating at the level of said mechanical system, as a heat transfer fluid, a composition based on at least one lubricating oil at least partly re-refined, in particular as described previously.

[0134] Such a process or method includes, in particular, the steps of: a) have a composition comprising, or even being formed from, at least one lubricating oil that is at least partly re-refined, in particular as defined above; b) implement said composition of step a) at the level of a mechanical system, in particular as described above, more particularly at the level of one or more heat transfer fluid circuits; and c) to circulate said composition to ensure heat exchange during the operation of said mechanical system.

[0135] 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 coolant.

[0136] By way of illustration of a possible application, the fluid formulated according to the invention can be used as a coolant for moving parts in a mechanical system, and more particularly in a mobile or stationary motorization system.

[0137] A heat transfer fluid based on at least one re-refined lubricating oil according to The invention can thus be implemented as a coolant for cooling gears, bearings, bushings, such as rolling or sliding bearings, or even motors.

[0138] For the purposes of this invention, "motorization system" means a system comprising all the mechanical parts necessary for the intended mobile or stationary application and including at least one motor. This may be a combustion, gas (in particular hydrogen), ammonia, electric, or hybrid motorization system, depending on the nature of the motor(s) included in the motorization system: combustion, gas (in particular hydrogen), ammonia, and / or electric.

[0139] For the purposes of this invention, "propulsion system" means a system comprising the mechanical parts necessary for propelling a vehicle. More specifically, the propulsion system includes a motor, for example an electric motor comprising the rotor-stator assembly and power electronics (dedicated to speed regulation), a transmission, and optionally a battery. The battery itself generally consists of a set of electrical accumulators, called cells.

[0140] Also, a heat transfer fluid based on at least one re-refined lubricating oil according to the invention can be used as a coolant to cool the battery present in an electric or hybrid vehicle.

[0141] By way of application example, a heat transfer fluid according to the invention based on at least one re-refined lubricating oil can be used for cooling a propulsion system of an electric or hybrid vehicle, and more particularly the motor, power electronics, transmission and / or battery.

[0142] In another application variant, a fluid according to the invention based on at least one re-refined lubricating oil can be used as a coolant in metalworking, such as aluminum, steel, stainless steel, galvanized steel, yellow metals, in particular in any metalworking operation, for example in forming, cutting, joining or any other metal transformation processes such as forming, stamping, rolling, etc.

[0143] Such compositions used in metalworking processes are also commonly referred to as "metalworking compositions or fluids", "machining fluids" or "cutting fluids".

[0144] In another application variant, a fluid according to the invention based on at least one re-refined lubricating oil can be used, in particular as a coolant in a hydraulic system. It thus ensures heat transfer between the various components of a hydraulic system, particularly in hydraulic actuators (cylinders / motors) or machine assemblies on request.

[0145] Finally, in view of the rheological properties of the re-refined lubricating oils implemented according to the invention, a composition according to the invention based on at least one re-refined lubricating oil can be used jointly as a heat transfer fluid, in particular as a coolant, and as a lubricant, for all the mechanical systems described above, for example in a propulsion system of an electric or hybrid vehicle and / or in a hydraulic system.

[0146] Indeed, a composition according to the invention based on at least one re-refined lubricating oil makes it possible to jointly achieve good properties in terms of cooling and lubrication of the parts of such mechanical systems, in particular in a propulsion system of an electric or hybrid vehicle, such as an electric motor of an electric or hybrid vehicle.

[0147] The present invention also relates, according to another of its aspects, to a heat transfer or thermal management device, in which a composition based on at least one lubricating oil, at least partly re-refined, is used as a heat transfer fluid.

[0148] In particular, the device implements at least one heat transfer or thermal management circuit in which the composition based on at least one lubricating oil, at least partially re-refined, is implemented.

[0149] According to the invention, the particular, advantageous or preferred characteristics of these oils and compositions make it possible to define uses according to the invention which are also particular, advantageous or preferred.

[0150] The invention will now be described by means of the following examples, given by way of illustration and not limitation of the invention. Examples

[0151] Method for measuring kinematic viscosity

[0152] The kinematic viscosity of the oils is measured at 40 °C (KV40) and at 100 °C (KV100) using a viscometer, according to standard NF EN ISO 3104. This standard is technically equivalent to ASTM D445. The results are expressed in mm2 / s (equivalent to centistoke, denoted cSt).

[0153] Method for measuring volatility

[0154] Volatility allows the determination of the evaporation loss of oils at high temperatures. It is determined by the NOACK volatility test, carried out according to CEC L-40-93. During the test, the oil sample is subjected to a constant airflow, heated to approximately 250 °C, for about 60 minutes. The result is expressed as a fraction of weight loss, as a mass percentage.

[0155] Method for measuring density

[0156] The density of the oils is measured at 15°C using a U-tube densimeter, according to standard NF EN ISO 12185. It is expressed in kg / m3.

[0157] Method for measuring the viscosity index

[0158] The viscosity index is a dimensionless ratio that indicates how the viscosity of oils varies with temperature. It is calculated from the kinematic viscosity values ​​at 40°C and 100°C, according to standard NF ISO 2909. The higher this index, the less the viscosity of the oils is influenced by temperature variations.

[0159] Method for measuring thermal conductivity

[0160] Thermal conductivity, often denoted X, characterizes the oil's ability to diffuse heat into surrounding media. It is measured by a transient hot-wire liquid thermal conductivity method, according to ASTM D7896-19. It is expressed in mW / mK.

[0161] Method for measuring the flash point

[0162] The flash point indicates a product's ability to form a flammable mixture with air under controlled conditions. It is determined using an open-cup Cleveland apparatus, according to standard NF EN ISO 2592. The flash point at ambient atmospheric pressure is the lowest temperature at which passing a flame over the test cup containing the oil causes the vapors above the liquid's surface to ignite. It is expressed in degrees Celsius.

[0163] Method for measuring the content of sulfur and aromatic compounds

[0164] The sulfur and aromatic compound contents in the oil are determined by infrared or ultraviolet spectroscopy. Example 1

[0165] The properties of six re-refined lubricating oils II to 16, according to the invention and commercially available, were evaluated.

[0166] These oils are obtained from used base oils and have undergone at least one step of dehydration, distillation, filtration, hydrogenation, liquid / liquid extraction, decantation and / or passing of the used lubricant over an adsorbent material, in particular at least one step of dehydration, distillation, liquid / liquid extraction and / or hydrogenation.

[0167] Three new lubricating oils Cl to C3, not conforming to the invention because they have not undergone any recycling or re-refining steps, were also evaluated.

[0168] These oils are commercially available Group I or II base oils according to the API classification.

[0169] In particular, the kinematic viscosities at 40 °C and 100 °C, the viscosity index, The density, volatility, flash point and thermal conductivity of these oils were measured according to the protocols detailed above.

[0170] The results are presented in Table 2 for re-refined and virgin oils whose characteristics are equivalent to those defined by the API classification for Group I base oils and in Table 3 for re-refined and virgin oils whose characteristics are equivalent to those defined by the API classification for Group II base oils, below.

[0171] [Tables2] Oil II 12 13 14 15 Cl KV40 [mmVs] 33.0 27.9 29.4 26.5 29.1 31.3 KV100 [mmVs] 5.9 5.2 5.4 5.0 5.4 5.3 Viscosity Index 122 118 118 114 119 102 Density [kg .W] 849.3 851 854.1 850.9 854.1 872.5 Volatility Noack [%] 7 7- 9.4 11.6 10.6 13.1 Flash Point [°C] 236 77 R 230 230 228 224 Thermal Conductivity [mW / mK] 13 L 3 129.3 - 131.4 128.4 124.3 Sulfur content [%] 0.11 0.16 0.06 0.06 0.15 0.26 Aromatic content [%] 7 A 12.5 17.5 9.8 15

[0172] [Tables3] Oil 16 C2 C3 KV40 [mmVs] 28.2 30.1 - KV100 [inmVs] 5.6 5.4 5.0 Viscosity Index 120 115 Density [kg / mJ] 849.5 852s8 - Volatility Noack [%] 10.9 12 - Flash Point [°C] 230 77? - Thermal Conductivity [mW / mK] 133.2 126.7 127.6 Sulfur Content [%] 0.02 < 0.0003 <0.001 Aromatic Content [%] 9 0.4 0.002 Results

[0173] All oils at least partially re-refined required according to the invention have a higher viscosity index and thermal conductivity as well as a lower density, compared to virgin oils not suitable for the invention, and whose properties are otherwise equivalent.

[0174] Consequently, oils that are at least partially re-refined exhibit particularly advantageous thermo-physical properties, enabling performance as heat transfer fluids to be superior to that of new lubricating oils that have not undergone any recycling.

[0175] A lower density and a high viscosity index also ensure good hydraulic performance, in particular reducing the costs associated with pumping these oils during their use as a heat transfer fluid. Furthermore, oils that are at least partially re-refined exhibit better energy-saving properties, particularly in terms of fuel economy, than virgin lubricating oils.

[0176] Furthermore, the at least partially re-refined oils required according to the invention exhibit reduced volatility and a higher flash point compared to those measured for oils not suitable for the invention. Consequently, at least partially re-refined oils provide increased safety compared to virgin lubricating oils.

[0177] In conclusion, a lubricating oil that is at least partially re-refined has particularly advantageous properties, especially superior to those of a new oil, allowing its use as a heat transfer fluid, in particular as a coolant.

Claims

Demands

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

2. Use according to the preceding claim, wherein the lubricating oil, at least partly re-refined, is derived from a used lubricant that has been subjected to one or more prior steps of dehydration, distillation, filtration, hydrogenation, liquid / liquid extraction, decantation and / or passing the used lubricant over an adsorbent material.

3. Use according to any one of the preceding claims, wherein the lubricating oil, at least partially re-refined, has a kinematic viscosity, measured at 100 °C according to ASTM D445, greater than or equal to 5 mm2 / s, in particular between 5 and 12 mm2 / s, more particularly between 5 and 10 mm2 / s.

4. Use according to any one of the preceding claims, wherein the lubricating oil, at least partly re-refined, has a viscosity index greater than or equal to 110, in particular between 110 and 130, in particular between 112 and 125.

5. Use according to any one of the preceding claims, wherein the lubricating oil, at least partly re-refined, has a Noack volatility of less than or equal to 15%, in particular between 8% and 15%, preferably strictly less than 12%, and more particularly between 8% and 11.9%.

6. Use according to any one of the preceding claims, wherein the lubricating oil, at least partly re-refined, has a sulfur content of between 0.02% and 0.2% by mass, relative to the total mass of said regenerated lubricating oil.

7. Use according to any one of the preceding claims, wherein the lubricating oil, at least partly re-refined, has an aromatic compound(s) content greater than or equal to 0.5% by mass, in particular greater than or equal to 1% by mass, in particular between 1% and 25% by mass, more particularly between 2.5% and 20% by mass, relative to the total mass of said regenerated lubricating oil.

8. Use according to any one of the preceding claims, wherein the lubricating oil, at least partially re-refined, has a density less than or equal to 870 kg / m³, in particular including between 830 and 870 kg / m3, in particular less than or equal to 860 kg / m3, and more particularly between 840 and 860 kg / m3.

9. Use according to any one of the preceding claims, wherein the lubricating oil, at least partly re-refined, has a thermal conductivity, measured at 100 °C and atmospheric pressure, greater than or equal to 125 mW / mK, in particular between 125 and 145 mW / mK, in particular greater than or equal to 128 mW / mK and more particularly between 128 and 140 mW / mK.

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

11. Use according to any one of the preceding claims, wherein said composition comprises more than 80% by mass, in particular between 90% and 100% by mass and more particularly between 95% and 100% by mass of at least one lubricating oil, at least partially re-refined, relative to the total mass of said composition.

12. A method for transferring heat in a mobile or stationary mechanical system, comprising at least one step of circulating at the level of said mechanical system, as a heat transfer fluid, a composition based on at least one lubricating oil at least partly re-refined, in particular as defined in any one of claims 2 to 10.

13. Heat transfer or thermal management device, wherein a composition based on at least one lubricating oil, at least partially re-refined, in particular as defined in any one of claims 2 to 10, is implemented as a heat transfer fluid.