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

Abstract

The present 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 for transferring heat into a mobile or stationary mechanical system, comprising at least one step of circulating, in said mechanical system, 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 device for transferring heat or for thermal management, wherein a composition based on at least one at least partially re-refined lubricating oil is implemented as a heat-transfer fluid.

Description

[0001] Description

[0002] Title: Heat transfer fluids based on at least partly re-refined lubricating oils

[0003] Technical field

[0004] 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.

[0005] Prior art

[0006] Heat transfer fluids find application in many systems, in which they allow heat to be transported between different temperature sources.

[0007] These fluids are typically used in heat exchangers, for example, cooling systems for thermal or electric engines, such as vehicle engines, refrigerators, boilers, air conditioners, thermal solar collectors, radiators in electrical circuits, particularly in the case of high-power electrical or electronic transformers, thermal power plants using coal, fuel oil, gas or nuclear power, and wastewater heat exchangers.

[0008] A large number of heat transfer fluids have been documented and marketed, implementing a wide variety of base fluids and performance additives.

[0009] Generally speaking, heat transfer fluids must meet two requirements: firstly, they must be able to transfer thermal energy efficiently and, secondly, 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.

[0010] Heat transfer efficiency depends primarily on the thermophysical properties of the base fluid, including specific heat capacity, thermal conductivity, density, and viscosity, as well as the hydraulic performance of the heat transfer fluid. A heat transfer fluid must remain pumpable over the temperature range in which it must circulate in a given system. The viscosity and viscosity-temperature profile of the heat transfer fluid thus determine its hydraulic performance. Water is commonly used as the base fluid 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 due to its high specific heat capacity, high thermal conductivity, and low viscosity.A significant limitation of using 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 requiring operating temperatures below 0°C. In addition, water-based heat transfer fluids are naturally 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 in which freezing point depressants are added to the water to lower its freezing temperature, along with various additives to control corrosion.

[0011] 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 heated to high temperatures.

[0012] For example, we can cite document US 7,972,999 which proposes using a base oil prepared from a paraffin wax to form a heat exchange liquid, and in particular having a self-ignition temperature greater than 329°C and a high viscosity index.

[0013] However, a large amount of crude oil is generally required to obtain refined oils. Typically, to extract 1 liter of refined oil, 37 liters of crude oil are required. Furthermore, oil refining processes are very energy-intensive. However, current environmental protection and resource conservation issues are pushing manufacturers to offer more eco-friendly alternatives to conventional oils.

[0014] There remains a need for more environmentally friendly heat transfer fluids, while having excellent physicochemical properties, or even improved properties compared to known heat transfer fluids.

[0015] Statement of the invention

[0016] The present invention aims to propose new heat transfer fluids meeting these expectations. More particularly, the inventors have discovered that recycled lubricating base oils are particularly suitable for use as heat transfer fluids.

[0017] 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.

[0018] In the context of the present invention, the expression "at least partly re-refined lubricating oil", also referred to more simply in the remainder of the text as "re-refined oil", "regenerated oil" or even "recycled oil", designates an oil originating at least in part from a used lubricating composition having been subjected to one or more treatment steps known as re-refining treatment.

[0019] According to the invention, the term "used lubricating composition" (or more simply "used lubricant" or "used lubricating oil") is intended to denote 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.

[0020] Used lubricating oil can come from different sources. In particular, as detailed in the rest of the text, it can be a lubricant used for the lubrication of a motorization system, in particular "mobile", or for the lubrication of a so-called industrial system, in particular "stationary".

[0021] Due to their origin, used lubricating oils, particularly engine lubricating oils, contain a number of degradation products derived from the oil itself or from the additives it contains, as well as metal particles, metal oxides and other elements, for example from the engine. Used oil may contain, in particular, a high content of undesirable elements, for example calcium (Ca), iron (Fe), magnesium (Mg), sodium (Na), nickel (Ni), phosphorus (P), silicon (Si), chlorine (Cl), zinc (Zn) etc.

[0022] Methods for re-refining or reconditioning used lubricating oils have been developed to regenerate these oils and enable their subsequent reuse.

[0023] A re-refined lubricating oil is thus an oil obtained at the end of one or more stages of treatment of a used lubricant, aimed at eliminating, at least in part, a certain number of contaminating elements present therein, such as dust, water, fuel fractions, metallic elements and other residues resulting from the degradation of the additives present in the lubricant.

[0024] To the inventors' knowledge, it has never been proposed to use recycled lubricating oil to formulate a heat transfer fluid.

[0025] The use according to the invention of a re-refined lubricating oil as a heat transfer liquid proves to be advantageous in several respects.

[0026] On the one hand, as illustrated in the examples which follow, the inventors have shown that the re-refined lubricating oils have particularly advantageous thermo-physical properties, in particular in terms of volatility, density, viscosity index, flash point and thermal conductivity, which make them particularly suitable as heat transfer fluids.

[0027] Surprisingly, recycled lubricating oils even exhibit thermo-physical properties for their use as heat transfer fluid, superior to those of refined base oils, in other words virgin or new base oils.

[0028] A refined base oil, also called "virgin" or "new" base oil, unlike re-refined lubricating oils, is an oil directly derived from petroleum refining and which has not yet been used.

[0029] On the other hand, the use of recycled lubricating oils as heat transfer fluids advantageously 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.

[0030] As detailed in the remainder of the text, said re-refined lubricating oil(s) may be used as such, i.e. 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 at least partly re-refined lubricating oil as a heat transfer fluid. Said re-refined lubricating oil(s) may also be used in combination with one or more other ingredients. They may in particular be supplemented 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 in a non-limiting manner, anti-corrosion additives, antioxidant additives, etc.

[0031] In the context of this embodiment variant, the heat transfer fluid according to the invention is advantageously formed mainly from said re-refined lubricating oil(s). In particular, said 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.

[0032] Said re-refined lubricating oil(s) may also be used in combination with at least one new base oil.

[0033] The present invention also relates to the use of at least one at least partially re-refined lubricating oil for formulating or preparing a heat transfer fluid.

[0034] It 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 partly re-refined from a used lubricant.

[0035] The process for preparing a heat transfer fluid according to the invention may more particularly comprise the steps consisting of:

[0036] (i) preparing an at least partly re-refined lubricating oil from a used lubricant;

[0037] (ii) optionally, mixing said at least partly re-refined lubricating oil with one or more new base oils, distinct from re-refined lubricating oils, for example one or more mineral oils; and

[0038] (iii) optionally, supplementing said at least partly re-refined lubricating oil from step (i), or the mixture of lubricating oils from step (ii), with at least one additive, in particular chosen from anti-corrosion additives, 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. 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.

[0039] Examples of applications of the fluids formulated according to the invention are described more particularly in the rest of the text.

[0040] 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 at least partly re-refined lubricating oil, 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.

[0041] Other characteristics, variants and advantages of the use of at least partly re-refined lubricating oils for the formulation of a heat transfer fluid according to the invention will become more apparent upon reading the description and examples which follow, given by way of illustration and not limitation of the invention.

[0042] The expressions "between ... and ...", "ranging from ... to ...", "formed from . . . to ...", and "varying from ... to ...", must be understood inclusively, unless otherwise stated.

[0043] In the description and examples, unless otherwise indicated, percentages are percentages by mass. The percentages are therefore expressed by mass relative to the total mass of the composition.

[0044] Detailed description

[0045] Lubricating oil at least partly re-refined

[0046] As previously specified, 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 from a used lubricating composition that has been subjected to one or more re-refining treatment steps can be used according to the invention. It is understood that a used lubricating composition can be a mixture of several used lubricating compositions, coming from the same source or from several different sources.

[0047] Used lubricating compositions and, consequently, regenerated lubricating oils, comprise, in the 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 their mixtures.

[0048] It can be a mixture of several base oils, for example a mixture of two, three, or four base oils.

[0049] 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.

[0050] 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.

[0051] [Table 1]

[0052]

[0053] In particular, the used lubricating composition, from which the regenerated lubricating oil used 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).

[0054] The re-refined lubricating oils used according to the invention advantageously have characteristics in terms of content of saturated compounds, sulfur content and viscosity index, satisfying the criteria defined by the API classification for oils of groups I, II, III, IV and / or V, in particular for oils of groups I, II, III and / or IV.

[0055] The invention thus aims at the use as heat transfer fluid of a composition formed in whole or in part from at least one lubricating oil at least partly re-refined, obtained at the end of one or more stages of treatment of a used lubricant based on one or more oils from groups I to V according to the API classification.

[0056] According to a particular embodiment, the re-refined lubricating oil used according to the invention may come from the treatment of a used lubricating composition having been used for the lubrication of a motorization system, in particular “mobile”, that is to say including light vehicles, heavy goods vehicles, so-called “off-road” mobile machines, or even marine vehicles.

[0057] According to another particular embodiment, the re-refined lubricating oil used according to the invention may come from the treatment of a used lubricating composition having been used for the lubrication of a so-called industrial system, in particular “stationary”, that is to say including, in a non-limiting manner, turbines, compressors, hydraulic systems, gears, or even forming or cutting machines.

[0058] A used lubricating composition, from which the reclaimed lubricating oil used according to the invention is derived, may contain various conventional additives in the field of lubricants, such as friction modifier additives, extreme pressure additives, anti-wear additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressant (PPD) additives, dispersing agents, anti-foaming agents, thickeners, and mixtures thereof.

[0059] As already mentioned above, 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.

[0060] Due to their origin, used lubricating compositions may thus contain one or more 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.

[0061] The composition of used lubricant can of course vary depending on the origin of the lubricant, its initial formulation and the fact that it may have been contaminated differently depending on its use.

[0062] The regenerated lubricating oil used 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.

[0063] In particular, these treatment steps aim to remove, at least partially, water, solid particles, fuel and / or other contaminants, such as polycyclic aromatic hydrocarbons (PAHs), which are undesirable in the formulation of lubricants.

[0064] According to a particular embodiment, the regenerated lubricating oil used according to the invention comes from a used lubricant having been subjected to one or more prior steps of dehydration, distillation, filtration, hydrogenation, liquid / liquid extraction, decantation and / or passage of the used lubricant over an adsorbent material, preferably as detailed below.

[0065] Thus, the invention relates to the use, as a heat transfer fluid, of a composition based on at least one at least partly re-refined lubricating oil, in particular formed from at least one at least partly re-refined lubricating oil, preferably as described above, said at least partly re-refined lubricating oil 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 passage of said used lubricating composition over an adsorbent material, preferably carried out under the conditions detailed below.

[0066] Preferably, the regenerated lubricating oil used 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 eliminate any water possibly present in the used lubricant.

[0067] Advantageously, the regenerated lubricating oil used according to the invention thus comprises a water content of 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.

[0068] 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 flow of hot air through the used lubricating composition.

[0069] According to one embodiment, the dehydration step can be carried out at a temperature between 50°C and 250°C, preferably between 100°C and 200°C. In particular, it can be carried out at a pressure between 50,000 and 150,000 Pa, preferably at atmospheric pressure.

[0070] Preferably, the regenerated lubricating oil used according to the invention is obtained by subjecting a used lubricating composition to at least one prior filtration step. This filtration can be carried out by any method known to those skilled in the art. This filtration step can be a particulate or non-particulate filtration step. It can, for example, be carried out by diatomaceous earth type systems.

[0071] Preferably, the regenerated lubricating oil used according to the invention is obtained by subjecting a used lubricating composition to at least one distillation step, preferably following a prior dehydration step. Said distillation step(s) may be carried out by any technique known to those skilled in the art. It may be, for example, atmospheric distillation or distillation under reduced pressure. The distillations may, for example, be carried out at a temperature of between 100°C and 500°C, preferably between 200°C and 400°C, more preferably between 300°C and 380°C. In particular, they may be carried out at a pressure of between 25 and 2000 Pa, preferably between 50 and 1000 Pa, more particularly between 50 and 250 Pa.

[0072] Advantageously, the regenerated lubricating oil used 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.

[0073] The adsorbent material advantageously allows the selective adsorption of aromatic compounds, in particular PAHs.

[0074] In particular, passing over an adsorbent material, preferably over activated carbon, advantageously makes it possible to reduce 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 lubricating composition.

[0075] The term "passage of the used lubricating composition over an adsorbent material" means the flow of the used lubricating composition over the adsorbent support. The adsorbent materials may be, for example, activated carbon, zeolites, clays or functionalized porous compounds. Preferably, it is activated carbon.

[0076] For example, the regenerated lubricating oil used in the method of the invention can be obtained from the treatment of a used lubricating composition according to the method described in document WO 2018 / 109208.

[0077] 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 liter 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.

[0078] The flow rate of the used lubricating composition can be between lm 3 / h and 15 m 3 / h, for example between 5 and 10 m 3 / h.

[0079] Preferably, the activated carbon is characterized by a density between 200 and 500 kg / m 3 , for example measured according to ASTDM D2854.

[0080] Preferably, the activated carbon is a coal, preferably comprising from 70 to 95%, advantageously from 80 to 90% by weight of carbon.

[0081] The step of passing the used lubricating composition onto an adsorbent support, preferably onto activated carbon, is advantageously preceded by the following preliminary steps:

[0082] - one or more distillation stages; and

[0083] - a filtration step, in particular as defined previously.

[0084] Advantageously, the regenerated lubricating oil used according to the invention can be obtained by subjecting a used lubricating composition to at least one prior hydrogenation (or hydrotreatment) step, preferably which follows a prior dehydration and / or distillation step. Said 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, generally in the presence of a hydrotreatment catalyst. Such a catalyst can 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 support, for example alumina, silica-alumina or a zeolite.Advantageously, the regenerated lubricating oil used according to the invention can be obtained by subjecting a used lubricating composition to at least one prior step of liquid / liquid extraction by a solvent, preferably which follows a prior step of dehydration and / or distillation. In particular, the liquid / liquid extraction by a solvent advantageously makes it possible to lighten a dark-colored used oil, to eliminate at least in part the bad odor or the aromatic compounds, in particular the PAHs. Said extraction step(s) can be implemented by any technique known to those skilled in the art. The extraction is generally carried out in a mixer-settler or in an extraction column, using a suitable extraction solvent.

[0085] Advantageously, the regenerated lubricating oil used according to the invention can be obtained by subjecting a used lubricating composition to at least one prior decantation step. Said decantation step(s) can be carried out by any technique known to those skilled in the art.

[0086] 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 partly re-refined, for example group I and / or II, resulting from treatment steps different from those described above, may be suitable for the invention.

[0087] In any event, a re-refined lubricating oil used according to the invention is distinguished from a used lubricating oil, in particular due to the reduced content of certain undesirable contaminating elements, for example water, fuel, metallic elements or even certain heteroatoms.

[0088] A regenerated lubricating oil used according to the invention is notably characterized by a silicon content of between 0 ppm and 300 ppm, notably between 1 and 300 ppm.

[0089] A regenerated lubricating oil used according to the invention is in particular characterized by a phosphorus content of less than or equal to 100 ppm, in particular between 0 ppm and 100 ppm, for example 0 ppm. A regenerated lubricating oil used according to the invention may also be characterized by its content of one or more other elements chosen from chlorine, oxygen and nitrogen. It may, for example, have a chlorine content of between 0 ppm and 50 ppm, for example 0 ppm.

[0090] The content of these elements can be assessed by any method known to those skilled in the art, for example by X-ray fluorescence (XRF), or by infrared or ultraviolet spectroscopy.

[0091] On the other hand, a regenerated lubricating oil used according to the invention is distinguished, due to its formation from a used lubricant, from a virgin or new base oil, oil directly derived from petroleum refining, or even from native base oils, for example of natural origin, both in terms of its composition and its physicochemical properties.

[0092] In particular, as previously indicated, surprisingly, a reclaimed 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 superior thermo-physical and hydraulic properties to those of a virgin base oil.

[0093] Preferably, the regenerated lubricating oil used according to the invention has a kinematic viscosity measured at 100°C according to standard ASTM D445 of between 2 and 12 mm 2 / s -1 , especially between 3 and 10 min / s' 1 .

[0094] Preferably, the kinematic viscosity measured at 100°C according to ASTM D445 of the at least partly re-refined lubricating oil is greater than or equal to 5 mm 2 / s, for example between 5 and 12 mm 2 / s, more particularly between 5 and 10 mm 2 / s.

[0095] Advantageously, the regenerated lubricating oil used according to the invention has a kinematic viscosity measured at 40°C according to standard ASTM D445 of between 20 and 40 mm 2 / s, especially between 25 and 35 mm 2 / s.

[0096] Preferably, a regenerated lubricating oil used according to the invention has a viscosity index greater than or equal to 110. The viscosity index of the at least partly re-refined lubricating oil can thus be between 110 and 130, in particular between 112 and 125.

[0097] The viscosity index can in particular be determined according to standard NF ISO 2909.

[0098] Preferably, a regenerated lubricating oil used according to the invention has a Noack volatility of less than or equal to 15%. The Noack volatility of the at least partially re-refined lubricating oil can thus be between 8% and 15%.

[0099] More preferably, a regenerated lubricating oil used according to the invention has a Noack volatility strictly less than 12%. The Noack volatility of the at least partially re-refined lubricating oil can thus be between 8% and 11.9%.

[0100] Noack volatility can be determined in particular according to the CEC L-40-93 standard.

[0101] Preferably, a regenerated lubricating oil used according to the invention has a sulfur content of between 0.02% and 0.2% by mass, relative to the total mass of said regenerated lubricating oil.

[0102] Preferably, a regenerated lubricating oil used according to the invention has a content of aromatic compound(s) greater than or equal to 0.5% by mass, in particular greater than or equal to 1% by mass, relative to the total mass of said regenerated lubricating oil. The content of aromatic compound(s) in the regenerated lubricating oil may thus be between 1% and 25% by mass, in particular between 2.5% and 20% by mass, relative to the total mass of said regenerated lubricating oil.

[0103] The contents of these different elements can be determined using any method known to those skilled in the art, for example by X-ray fluorescence (XRF) or by infrared or ultraviolet spectroscopy.

[0104] The re-refined lubricating oil used according to the invention advantageously has at least one, at least two, at least three, or even all of the following characteristics:

[0105] - a kinematic viscosity measured at 100°C according to ASTM D445 standard greater than or equal to 5 mm 2 / s, for example between 5 and 12 mm 2 / s, more particularly between 5 and 10 mm 2 / s; - a viscosity index greater than or equal to 110, in particular between 110 and 130, in particular between 112 and 125;

[0106] - a Noack volatility less than or equal to 15%, in particular between 8% and 15%, preferably strictly less than 12%, more particularly between 8% and 11.9%;

[0107] - 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;

[0108] - a content of aromatic compound(s) 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.

[0109] Advantageously, a regenerated lubricating oil used according to the invention has a density less than or equal to 870 kg / m 3 , in particular less than or equal to 860 kg / m 3 The density of the at least partly re-refined lubricating oil can thus be between 830 and 870 kg / m 3 , particularly between 840 and 860 kg / m 3 .

[0110] The density can in particular be determined according to standard NF EN ISO 12185.

[0111] Advantageously, a regenerated lubricating oil used 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 at least partly re-refined lubricating oil can thus be between 225°C and 245°C.

[0112] The flash point can in particular be determined according to standard NF EN ISO 2592.

[0113] Advantageously, a regenerated lubricating oil used according to the invention has a thermal conductivity, measured at 100°C and at 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 at least partly re-refined lubricating oil can thus be between 125 and 145 mW / mK, in particular between 128 and 140 mW / mK.

[0114] Thermal conductivity can in particular be determined according to the ASTM D7896-19 standard. Due to these properties in terms of viscosity index, density, thermal conductivity, flash point, Noack volatility and density, the re-refined lubricating oils used according to the invention have excellent performance both in terms of heat transfer efficiency and hydraulic performance, and advantageously increased performance compared to virgin base oils.

[0115] 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. Thus, the heat transfer fluid according to the invention can be used in systems which may be subject to large temperature variations, for example as a coolant in vehicles, and remains pumpable over the temperature range in which it must circulate in said system.

[0116] 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 allows for reduced pumping costs, while having better thermal properties.

[0117] Heat transfer fluid

[0118] As mentioned above, said re-refined lubricating oil(s) used according to the invention, in particular as defined and characterized above, can be used as such as a heat transfer fluid, or be formulated in a composition intended to be used as a heat transfer fluid.

[0119] The composition used as a heat transfer fluid may thus comprise one or more base oils distinct from the at least partly re-refined lubricating oil and / or one or more additives.

[0120] In a particular embodiment, said re-refined lubricating oil(s) may be formulated in combination with one or more distinct base oils, in particular one or more new base oils.

[0121] They are in particular chosen from base oils conventionally used in the field of lubricants, such as mineral, synthetic or natural, animal or vegetable oils or their mixtures. 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 their mixtures.

[0122] A composition implemented according to the invention may thus comprise, or even be formed from, a mixture of one or more at least partly re-refined lubricating oils and one or more new base oils, for example at least one mineral oil.

[0123] In particular, a composition used 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), distinct from re-refined lubricating oils required according to the invention and defined above, relative to the total weight of the composition.

[0124] 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), distinct from re-refined lubricating oils.

[0125] Preferably, a composition used as a heat transfer fluid according to the invention is formed mainly from 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.

[0126] Thus, a composition used 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.

[0127] In a particular embodiment, a composition used as a heat transfer fluid according to the invention is completely free of base oil other than re-refined lubricating oils.

[0128] In a particular embodiment, a composition used as a heat transfer fluid according to the invention may comprise, 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. These additives may in particular be chosen from anti-corrosion additives, 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.

[0129] These additives may be added to the said regenerated base oil(s) used according to the invention or to the mixture of the said regenerated base oil(s) and at least one new base oil in an appropriate quantity, determined by a person 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 said re-refined lubricating oil(s), are not or are not substantially altered by the envisaged addition.

[0130] A composition used 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.

[0131] 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.

[0132] Advantageously, such a process or method comprises at least the steps consisting of:

[0133] (i) having an at least partly 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 passage of the used lubricant over an adsorbent material, preferably as detailed previously;

[0134] (ii) optionally, mixing said at least partly re-refined lubricating oil with one or more new base oils, distinct from re-refined lubricating oils, for example one or more mineral oils; and

[0135] (iii) optionally, supplementing said at least partly re-refined lubricating oil from step (i) or the mixture of lubricating oils from step (ii), with at least one additive, in particular as described above.

[0136] Applications

[0137] As mentioned above, an at least partially re-refined lubricating oil is particularly suitable for use as a heat transfer fluid due to its thermo-physical properties.

[0138] 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.

[0139] Heat transfer fluid circuits typically include means for forced or free circulation of the heat transfer fluid, for example a pump, or any other equivalent means, and evacuation means, such as for example exchangers or any other equivalent means allowing the diffusion of calories.

[0140] The invention is thus not limited to a particular application of the fluids formulated according to the invention, the following development being given solely for illustrative and non-limiting purposes.

[0141] In particular, the present invention relates to the use of a composition based on at least one at least partly re-refined lubricating oil as a heat transfer fluid, also called a heat exchange liquid, in a mobile or stationary mechanical system, in other words for transferring heat in a mobile or stationary mechanical system.

[0142] A fluid according to the invention can, for example, be used to ensure heat exchanges in “stationary” mechanical systems, such as boilers, air conditioners, in particular in data processing centers (“Data Centers” in English), thermal solar 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.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 even marine vehicles, in particular their motorization systems.

[0143] 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 said mechanical system, as heat transfer fluid, a composition based on at least one at least partly re-refined lubricating oil, in particular as described above.

[0144] Such a process or such a method comprises in particular the steps consisting of: a) having a composition comprising, or even being formed from, at least one at least partly re-refined lubricating oil, in particular as defined previously; b) implementing said composition of step a) at the level of a mechanical system, in particular as described previously, more particularly at the level of one or more heat transfer fluid circuits; and c) circulating said composition to ensure heat exchanges during the operation of said mechanical system.

[0145] 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.

[0146] As an 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.

[0147] A heat transfer fluid based on at least one re-refined lubricating oil according to the invention can thus be used as a coolant for cooling gears, bearings, bearings, such as rolling or sliding bearings or even motors.

[0148] By "motorization system" within the meaning of the present invention, is meant a system comprising all the mechanical parts necessary for the intended mobile or stationary application and including at least one engine. It may be a combustion, gas, in particular hydrogen, ammonia, electric or hybrid engine system, depending on the nature of the engine(s) included in the motorization system: combustion, gas, in particular hydrogen, ammonia and / or electric engine.

[0149] For the purposes of the present invention, the term "propulsion system" is understood to mean a system comprising the mechanical parts necessary for the propulsion of a vehicle. The propulsion system more particularly includes a motor, for example an electric motor comprising the rotor-stator assembly of the power electronics (dedicated to speed regulation), a transmission and possibly a battery. The battery itself is generally made up of a set of electrical accumulators, called cells. 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.

[0150] As an example of application, 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 engine, the power electronics, the transmission and / or the battery.

[0151] 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 the working of metals, such as aluminum, steel, stainless steel, galvanized steel, yellow metals, in particular in any metal machining operation, for example in shaping, cutting, joining processes or any other transformation of the metal such as forming, stamping, rolling, etc.

[0152] Such compositions used in metal machining processes are also commonly referred to as “metalworking compositions or fluids”, “machining fluids” or “cutting fluids”.

[0153] 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 makes it possible to ensure heat transfer between the various components of a hydraulic system, in particular in hydraulic actuators (cylinders / motors) or machine assemblies on request. Finally, in view of the rheological properties of the re-refined lubricating oils used 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 of the mechanical systems described above, for example in a propulsion system of an electric or hybrid vehicle and / or in a hydraulic system.

[0154] 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.

[0155] 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 at least partly re-refined lubricating oil is used as a heat transfer fluid.

[0156] In particular, the device implements at least one heat transfer or thermal management circuit in which the composition based on at least one at least partially re-refined lubricating oil is implemented.

[0157] 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.

[0158] The invention will now be described by means of the following examples, given by way of illustration and not limitation of the invention.

[0159] Example

[0160] Method for measuring kinematic viscosity

[0161] The kinematic viscosity of 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 standard ASTM D445. The results are expressed in mm 2 / s (equivalent to centistoke, noted cSt).

[0162] Volatility measurement method

[0163] Volatility is used to determine 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 flow of air, heated to approximately 250 °C, for approximately 60 minutes. The result is expressed as a fraction of weight loss, as a mass percentage.

[0164] Method of measuring density

[0165] The density of oils is measured at 15°C using a U-tube densimeter, according to standard NF EN ISO 12185. It is expressed in kg / m 3 .

[0166] Method of measuring viscosity index

[0167] The viscosity index is a dimensionless ratio that provides an indication of 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 oils is influenced by temperature variations.

[0168] Method of measuring thermal conductivity

[0169] Thermal conductivity, often denoted λ, characterizes the oil's ability to diffuse heat into the environment. It is measured by a transient hot-wire liquid thermal conductivity method, according to ASTM D7896-19. It is expressed in mW / mK.

[0170] Flash point measurement method

[0171] The flash point provides an indication of a product's ability to form a flammable mixture with air under controlled conditions. It is determined using a Cleveland open-cup apparatus, according to standard NF EN ISO 2592. The flash point at ambient atmospheric pressure is the lowest temperature at which the passage of a flame over the test vessel containing the oil causes the vapors above the surface of the liquid to ignite. It is expressed in degrees Celsius.

[0172] Method for measuring sulfur and aromatic compound content

[0173] The sulfur and aromatic compound contents in the oil are determined by infrared or ultraviolet spectroscopy.

[0174] Example 1

[0175] The properties of six re-refined lubricating oils II to 16, in accordance with the invention and commercially available, were evaluated.

[0176] These oils are obtained from used base oils and having undergone at least one step of dehydration, distillation, filtration, hydrogenation, liquid / liquid extraction, decantation and / or passage of the used lubricant over an adsorbent material, in particular at least one step of dehydration, distillation, liquid / liquid extraction and / or hydrogenation.

[0177] Three new lubricating oils Cl to C3, not in accordance with the invention because they had not undergone any recycling or re-refining step, were also evaluated.

[0178] These oils are commercially available API Group I or II base oils.

[0179] In particular, the kinematic viscosities at 40 °C and 100 °C, viscosity index, density, volatility, flash point and thermal conductivity of these oils were measured according to the protocols detailed above.

[0180] The results are presented in Table 2 for re-refined and virgin oils with characteristics equivalent to those defined by the API classification for Group I base oils and in Table 3 for re-refined and virgin oils with characteristics equivalent to those defined by the API classification for Group II base oils, below.

[0181] [Table 2]

[0182] [Table 3]

[0183] Results

[0184] All at least partly re-refined oils 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.

[0185] Consequently, at least partially re-refined oils have particularly advantageous thermophysical properties, enabling them to achieve performance as heat transfer fluids superior to that of new lubricating oils which have not undergone any recycling.

[0186] 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 heat transfer fluid. In addition, at least partially re-refined oils have better energy-saving properties, especially fuel-saving, than new lubricating oils.

[0187] Furthermore, the at least partly re-refined oils required according to the invention have reduced volatility and a higher flash point compared to those measured for oils not suitable for the invention. Consequently, the at least partly re-refined oils allow increased safety compared to new lubricating oils.

[0188] In conclusion, a lubricating oil that is at least partly re-refined has particularly advantageous properties, in particular 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 mm 2 / s, in particular between 5 and 12 mm 2 / s, particularly between 5 and 10 mm 2 / 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 3 , in particular between 830 and 870 kg / m 3 , in particular less than or equal to 860 kg / m 3 , and more specifically between 840 and 860 kg / m 3 .

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 partly 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 within said mechanical system, as a heat transfer fluid, 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.

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.

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