Heat transfer fluid based on at least partially rerefined lubricating oil

Abstract

The present application relates to the use of a composition based on at least one at least partially rerefined lubricating oil as a heat transfer fluid. The invention also relates to a method for heat transfer in a mobile or stationary mechanical system, comprising at least one step of circulation of a composition as a heat transfer fluid at said mechanical system, said composition being based on at least one at least partially rerefined lubricating oil; the invention also relates to a heat transfer or heat management device in which a composition based on at least one at least partially rerefined lubricating oil is used as a heat transfer fluid.

Description

Technical Field

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

[0002] Heat transfer fluids have applications in a wide variety of systems where they enable heat to be transferred between sources of different temperatures.

[0003] These fluids are typically used in heat exchangers, for example in cooling systems of heat or electrical machines such as vehicle engines, refrigerators, boilers, air conditioners, solar collectors, radiators of electrical circuits, in particular in the following cases: high power electrical transformers, electronic transformers, coal, oil, gas or nuclear thermal power plants, waste water heat exchangers.

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

[0005] Generally, heat transfer fluids have to meet two requirements: on the one hand, they must be able to transfer thermal energy efficiently and, on the other hand, it must not harm the system in which they are used, or themselves degrade during use.

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

[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 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, which makes it unsuitable for use in many systems that require 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. In order to overcome these limitations, a large number of heat transfer fluids have been developed in which freezing point depressants are added to water to reduce its freezing point temperature, and various additives that can control corrosion are added.

[0008] Mineral oils derived from petroleum refining have also been proposed as base liquids for heat transfer fluids, particularly for applications in systems where the fluid may be heated to elevated temperatures.

[0009] One may cite, for example, document US Pat. No. 7,972,999, which proposes the use of base oils prepared from paraffin waxes to form heat exchange liquids and which have in particular an autoignition temperature greater than 329° C. and a high viscosity index.

[0010] However, in order to obtain refined oil, a large amount of crude oil is usually required. Typically, 37 liters of crude oil are required to extract 1 liter of refined oil. In addition, the oil refining process is also very energy-intensive. Current issues of environmental protection and resource conservation are driving manufacturers to provide more eco-friendly alternative solutions to conventional oils.

[0011] There is therefore still a need to provide heat transfer fluids which are more environmentally friendly and at the same time have excellent physicochemical properties, or even improved properties compared to known heat transfer fluids. Summary of the invention

[0012] Disclosure of the Invention

[0013] The present invention aims to propose new heat transfer fluids that meet these expectations.

[0014] More particularly, the present inventors have discovered that recycled lubricating base oil is particularly suitable for use as a heat transfer fluid.

[0015] The present invention therefore relates, according to its first aspect, to the use of a composition based on at least one at least partially rerefined lubricating oil as a heat-transfer fluid.

[0016] In the context of the present invention, the expression "at least partially rerefined lubricating oil", also referred to more simply as "rerefined oil", "regenerated oil" or "recycled oil" in the remainder of the text, refers to an oil which is at least partially obtained from a used lubricating composition which has undergone one or more treatment steps known as rerefining treatments.

[0017] According to the present invention, the term "used lubricating composition" (or more simply "used lubricant" or "used lubricating oil") is understood to mean any lubricating composition that has been used to lubricate moving parts, in particular metal parts, of a mechanical system, such as but not limited to bearings, gear mechanisms (engrenages) or engines.

[0018] The used lubricating oil may come from various sources. In particular, as described in detail below, it may be a lubricant that has been used to lubricate motorized systems, in particular "mobile" motorized systems, or that has been used to lubricate so-called industrial systems, in particular "stationary" industrial systems.

[0019] Considering its origin, used lubricating oils, in particular engine lubricating oils, contain a certain amount of degradation products derived from the oil itself or the additives contained therein, as well as particles of metals, metal oxides and other elements, for example from the engine. Used oils may contain high levels of undesirable elements, such as calcium (Ca), iron (Fe), magnesium (Mg), sodium (Na), nickel (Ni), phosphorus (P), silicon (Si), chlorine (Cl), zinc (Zn), etc.

[0020] Processes have been developed for refining or reconditioning used lubricating oils in order to regenerate these oils and permit their subsequent reuse.

[0021] A rerefined lubricating oil is thus an oil obtained from one or more treatment steps of used lubricants aimed at removing at least partially a certain number of contaminating components present therein, such as dust, water, fuel fractions, metallic elements and other residues resulting from the degradation of additives present in the lubricant.

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

[0023] The use of the rerefined lubricating oil according to the invention as a heat transfer liquid proves to be advantageous in several respects.

[0024] On the one hand, as shown in the following examples, the inventors have shown that rerefined lubricating oils have particularly advantageous thermophysical properties, particularly in terms of volatility, density, viscosity index, flash point and thermal conductivity, which make them particularly suitable as heat transfer fluids.

[0025] Surprisingly, the recycled lubricating oil has thermophysical properties superior even to those of refined base oil (in other words, virgin or new base oil) due to its use as a heat transfer fluid.

[0026] Unlike re-refined lubricating oils, refined base oils, also known as "virgin" or "new" base oils, are oils that result directly from petroleum refining and have not yet been used.

[0027] On the other hand, the use of recycled lubricating oil as heat transfer fluid advantageously meets the current desire to reduce environmental impact and save resources. Therefore, the use of heat transfer fluid based on recycled lubricating oil advantageously enables to reduce the carbon footprint of the product compared to the use of virgin base oil.

[0028] As described in detail in the remainder of this document, the one or more re-refined lubricating oils can be used as such, that is, alone (in other words without additives) as a heat transfer fluid. In a particular embodiment, the present invention therefore relates to the use of at least one at least partially re-refined lubricating oil as a heat transfer fluid.

[0029] The one or more re-refined lubricating oils may be further used in combination with one or more other ingredients. They may be particularly enriched 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, but not limited to, anti-corrosion additives, anti-oxidation additives, etc.

[0030] Within the scope of this embodiment variant, the heat transfer fluid according to the invention is advantageously formed mainly by the one or more re-refined lubricating oils. In particular, the one or more re-refined lubricating oils may account for more than 80% by mass of the total mass of the heat transfer fluid, in particular more than 90% by mass of the total mass of the heat transfer fluid, more particularly more than 95% by mass of the total mass of the heat transfer fluid.

[0031] The one or more rerefined lubricating oils may also be used in combination with at least one new base oil.

[0032] The invention also relates to the use of at least one at least partially rerefined lubricating oil for formulating or preparing a heat transfer fluid.

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

[0034] The method for preparing a heat transfer fluid according to the invention may more particularly comprise the following steps, which consist in:

[0035] (i) preparing at least partially re-refined lubricating oil from used lubricants;

[0036] (ii) optionally, blending the at least partially re-refined lubricating oil with one or more new base oils, such as one or more mineral oils, different from the re-refined lubricating oil; and

[0037] (iii) optionally, supplementing the at least partly rerefined lubricating oil from step (i) or the mixture of lubricating oils from step (ii) with at least one additive, in particular selected from anti-corrosion additives, friction improving additives, extreme pressure additives, anti-wear additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressants (PPD), dispersants, defoamers and mixtures thereof.

[0038] The heat-transfer fluids formulated according to the invention based on at least one rerefined lubricating oil can be used in a variety of applications, in particular as coolants for vehicle engines, as heat-transfer liquids in air-conditioning or heating circuits in buildings, and the like.

[0039] Examples of applications of fluids formulated according to the invention are more particularly described in the remainder of this document.

[0040] In particular, the present invention, according to another aspect thereof, also relates to the use of a heat transfer fluid according to the invention based on at least one at least partially rerefined lubricating oil as a coolant in mobile or stationary motorization systems, in particular as a coolant for the engine of a vehicle, such as an electric or hybrid vehicle.

[0041] Other characteristics, variants and advantages of the use of the at least partially rerefined lubricating oil according to the invention for formulating heat-transfer fluids will emerge more clearly on reading the description and the subsequent examples given as non-limiting illustrations of the invention.

[0042] Unless otherwise stated, the expressions “between ... and ...”, “from ... to ...”, “formed from ... to ...” and “variant from ... to ...” are to be interpreted as including the limit values.

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

[0044] Detailed instructions

[0045] At least partially re-refined lubricating oils

[0046] As mentioned above, according to the present invention, the oil used to formulate the heat transfer fluid is an at least partially rerefined lubricating oil, also known as "reclaimed oil" or "recycled oil"; in other words, according to the present invention, a lubricating oil obtained from a used lubricating composition that has undergone one or more rerefining treatment steps can be used.

[0047] It is to be understood that the used lubricating composition may be a mixture of multiple used lubricating compositions from the same source or multiple different sources.

[0048] The used lubricating composition and the regenerated lubricating oil produced therefrom contain as main components one or more base oils conventionally used in the lubricant field, such as synthetic or natural mineral oils, animal oils or vegetable oils or mixtures thereof.

[0049] It may be a mixture of a plurality of base oils, for example a mixture of two, three or four base oils.

[0050] These base oils may be of natural origin, such as oils from plants or animals, such as vegetable oils, animal oils, fish oils and mixtures thereof. Examples of such oils are rapeseed oil, canola oil, tall oil, sunflower oil, soybean oil, Chanvre oil, olive oil, linseed oil, mustard oil, palm oil, peanut oil, castor oil, coconut oil, animal fats and mixtures thereof.

[0051] Advantageously, these base oils are oils of mineral or synthetic origin belonging to groups I to V according to the categories defined in the API classification (as shown in the table below) (or their equivalents according to the ATIEL classification), or mixtures thereof.

[0052] [Table 1]

[0053]

[0054] 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, in particular at least 60% by weight of base oil, more particularly 60% to 99% by weight of base oil relative to its total weight.

[0055] The rerefined lubricating oils used according to the invention advantageously have properties with respect to saturate content, sulfur content and viscosity index that meet the standards 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.

[0056] The present invention therefore relates to the use as a heat-transfer fluid of a composition formed wholly or partly from at least one at least partially rerefined lubricating oil obtained by one or more treatment steps of used lubricants based on one or more oils of groups I to V according to the API classification.

[0057] According to a particular embodiment, the rerefined lubricating oil used according to the invention may be produced by treating a used lubricating composition which has been used to lubricate motorized systems, in particular "mobile" motorized systems, i.e. light vehicles, heavy vehicles, so-called "off-road" mobile machines or marine vehicles.

[0058] According to another particular embodiment, the rerefined lubricating oil used according to the invention can be produced by treating used lubricating compositions that have been used to lubricate so-called industrial systems, in particular "stationary" industrial systems, i.e. including, in a non-limiting manner, turbines, compressors, hydraulic systems and gear mechanisms, as well as forming and cutting machines.

[0059] The used lubricating composition from which the regenerated lubricating oil to be used according to the present invention is derived may contain various additives commonly used in the lubricant art, such as friction modifier additives, extreme pressure additives, anti-wear additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressants (PPD), dispersants, defoamers, thickeners, and mixtures thereof.

[0060] As already mentioned above, the properties of the used lubricating composition are degraded due to its more or less long or short periods of use for lubricating and / or cooling mechanical systems, in particular motorized systems such as internal combustion engines.

[0061] Due to its origin, the used lubricating composition may therefore contain one or more additives as described above as well as impurities resulting from the degradation of the additives originally present in the lubricant or from the wear of moving mechanical parts.

[0062] The composition of the used lubricant may of course vary depending on the source of the lubricant, its initial formulation and the fact that it may have been differently contaminated depending on its use.

[0063] The regenerated lubricating oil used according to the invention comes more particularly from a used lubricating composition which has been subjected to one or more previous pre-treatment steps known in the art of re-refining used lubricants.

[0064] In particular, the purpose of these treatment steps is to at least partially remove water, solid particles, fuel and / or other contaminants such as polycyclic aromatic hydrocarbons (PAHs), which are undesirable in lubricant formulations.

[0065] According to a particular embodiment, the regenerated lubricating oil used according to the invention comes from a used lubricant that has been subjected to one or more of the following previous steps: dehydration, distillation, filtration, hydrogenation, liquid / liquid extraction, sedimentation separation and / or passing the used lubricant on an adsorption material, preferably as detailed below.

[0066] The present invention therefore relates to the use of a composition based on at least one at least partially rerefined lubricating oil, in particular a composition formed from at least one at least partially rerefined lubricating oil (preferably as described above), as a heat transfer fluid, said at least partially rerefined lubricating oil being obtained from a used lubricating composition that has been subjected to at least one or more of the following steps: dehydration, distillation, filtration, hydrogenation, liquid / liquid extraction, sedimentation separation and / or passing the used lubricant on an adsorption material, preferably under the conditions detailed below.

[0067] Preferably, the regenerated lubricating oil used according to the invention is obtained by subjecting a used lubricating composition to at least one dehydration step. The dehydration step removes any water that may be present in the used lubricant.

[0068] Advantageously, the regenerated lubricating oil used according to the invention therefore comprises a water content of less than or equal to 10% by mass, in particular less than or equal to 5% by mass, especially 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.

[0069] This dehydration may be carried out by any method known to those skilled in the art, such as by distillation, evaporation, separation by settling, heating or passing a stream of hot air through the used lubricating composition.

[0070] According to one embodiment, the dehydration step may be carried out at a temperature ranging from 50° C. to 250° C., preferably from 100° C. to 200° C. In particular, it may be carried out at a pressure ranging from 50 000 to 150 000 Pa, preferably at atmospheric pressure.

[0071] Preferably, the regenerated lubricating oil used according to the invention is obtained by subjecting the used lubricating composition to at least one preliminary filtration step. This filtration can be carried out by any method known to the person skilled in the art. This filtration step may or may not be a particle filtration step. It may be carried out, for example, using a diatomaceous earth type system.

[0072] Preferably, the regenerated lubricating oil used according to the present invention is obtained by subjecting the used lubricating composition to at least one distillation step, which step is preferably carried out after a preliminary dehydration step. The distillation step can be carried out by any technique known to those skilled in the art. For example, it can be an atmospheric distillation or a reduced pressure distillation. The distillation can be carried out, for example, at a temperature of 100°C-500°C, preferably 200°C-400°C, more preferably 300°C-380°C. In particular, they can be carried out at a pressure of 25-2000Pa, preferably 50-1000Pa, more particularly 50-250Pa.

[0073] Advantageously, the regenerated lubricating oil used according to the invention is obtained by subjecting a used lubricating composition to at least one previous step of passing said used lubricating composition over an adsorbent material.

[0074] The adsorption material advantageously allows the selective adsorption of aromatic compounds, in particular PAHs.

[0075] In particular, the content of polycyclic aromatic hydrocarbons (PAHs) of the used lubricating composition can be advantageously reduced by adsorbing on an adsorbent material, preferably on activated carbon, the PAHs being selected in particular from Benzo[b]fluoranthene, benzo[j]fluoranthene, benzo[k]fluoranthene, benzo[e]pyrene, benzo[a]pyrene, dibenzo[a,h]anthracene and / or benzo[a]anthracene.

[0076] “Passing the used lubricating composition over an adsorbent material” is understood to mean that the used lubricating composition flows over an adsorbent carrier.

[0077] The adsorbent material may for example be activated carbon, zeolite, clay or a functionalized porous compound. Preferably, it is activated carbon.

[0078] For example, the regenerated lubricating oil used in the method of the present invention can be obtained by treating a used lubricating composition according to the method described in document WO 2018 / 109208.

[0079] Where the used lubricating composition is passed over activated carbon, the amount of activated carbon used is preferably 0.5-60 g of activated carbon per litre of used lubricating composition, preferably 0.5-50 g / L, preferably 1-50 g / L, preferably 1-30 g / L, for example 5-60 g / L, preferably 5-50 g / L.

[0080] The flow rate of the used lubricating composition may be 1 m 3 / h-15m 3 / h, for example 5-10m 3 / h.

[0081] Preferably, the activated carbon is characterized by a density of 200-500 kg / m 3 , for example measured according to standard ASTDM D2854.

[0082] Preferably, the activated carbon is charcoal, preferably containing 70-95% by weight, advantageously 80-90% by weight, of carbon.

[0083] The step of passing the used lubricating composition over an adsorptive support, preferably activated carbon, is advantageously preceded by the following preliminary steps:

[0084] - one or more distillation steps; and

[0085] - A filtration step, in particular as described above.

[0086] Advantageously, the regenerated lubricating oil used according to the invention is obtained by subjecting the used lubricating composition to at least one preliminary hydrogenation (or hydrotreatment) step, preferably carried out after a preliminary dehydration and / or distillation step. The hydrogenation step can be carried out by any technique known to those skilled in the art and generally consists in treating the lubricating oil with hydrogen, generally in the presence of a hydrotreatment catalyst. Such a catalyst may comprise, 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 such as alumina, silica-alumina or a zeolite.

[0087] Advantageously, the regenerated lubricating oil used according to the invention is obtained by subjecting the used lubricating composition to at least one preliminary step of liquid / liquid extraction with a solvent, which step is preferably carried out after a preliminary dehydration and / or distillation step. In particular, the liquid / liquid extraction with a solvent advantageously lightens the dark-colored used oil and at least partially eliminates odorous or aromatic compounds, in particular PAHs. The extraction step can be carried out by any technique known to those skilled in the art. The extraction is generally carried out in a mixer-settler or an extraction column using a suitable extraction solvent.

[0088] Advantageously, the regenerated lubricating oil used according to the invention is obtained by subjecting a used lubricating composition to at least one preliminary sedimentation separation step. Said sedimentation separation step can be carried out by any technique known to a person skilled in the art.

[0089] It should be understood that the present invention is by no means limited to the use of regenerated oils obtained according to the above-described treatment method. Other at least partially re-refined lubricating oils, for example from Group I and / or II, obtained by treatment steps different from those described above may be suitable for the present invention.

[0090] In any case, the rerefined lubricating oil used according to the invention differs from the used lubricating oil in particular by virtue of having a reduced content of certain undesirable contaminating components such as water, fuel, metallic elements or certain heteroatoms.

[0091] The regenerated lubricating oil used according to the invention is characterized in particular by a silicon content of 0 ppm to 300 ppm, in particular 1-300 ppm.

[0092] The regenerated lubricating oil used according to the invention is characterized in particular by a phosphorus content of less than or equal to 100 ppm, in particular from 0 ppm to 100 ppm, for example 0 ppm.

[0093] The regenerated lubricating oil used according to the invention may also be characterized by its content of one or more other elements selected from chlorine, oxygen and nitrogen. It may, for example, have a chlorine content of 0 ppm to 50 ppm, for example 0 ppm.

[0094] The content of these elements can be estimated by any method known to those skilled in the art, for example by X-ray fluorescence (XRF) or by infrared or ultraviolet spectroscopy.

[0095] On the other hand, the regenerated lubricating oil used according to the invention differs from virgin or new base oils, oils obtained directly from petroleum refining or natural base oils (eg oils of natural origin) both in its composition and in its physicochemical properties because it is formed from used lubricants.

[0096] In particular, as described above, the regenerated lubricating oil surprisingly has excellent thermophysical and hydraulic properties, particularly in terms of viscosity index, density, Noack volatility, flash point and / or thermal conductivity, and advantageously has thermophysical and hydraulic properties that are superior to those of the original base oil.

[0097] Preferably, the regenerated lubricating oil used according to the invention has a kinematic viscosity measured at 100° C. according to standard ASTM D445 of 2 to 12 mm 2 / s -1 , especially 3-10mm 2 / s -1 .

[0098] Preferably, the at least partially re-refined lubricating oil has a kinematic viscosity, measured at 100° C. according to standard ASTM D445, of greater than or equal to 5 mm 2 / s, e.g. 5-12mm 2 / s, more particularly 5-10 mm 2 / s.

[0099] Advantageously, the regenerated lubricating oil used according to the invention has a kinematic viscosity measured at 40° C. according to standard ASTM D445 of 20-40 mm 2 / s, especially 25-35mm 2 / s.

[0100] Preferably, the 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 partially rerefined lubricating oil may thus be 110-130, in particular 112-125.

[0101] The viscosity index can be determined in particular according to the NF ISO 2909 standard.

[0102] Preferably, the regenerated lubricating oil used according to the invention has a Noack volatility less than or equal to 15%.The Noack volatility of the at least partially re-refined lubricating oil may thus be between 8% and 15%.

[0103] More preferably, the 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 may thus be between 8% and 11.9%.

[0104] The Noack volatility can be determined in particular according to the CEC L-40-93 standard.

[0105] Preferably, the regenerated lubricating oil used according to the present invention has a sulfur content of 0.02% to 0.2% by mass relative to the total mass of the regenerated lubricating oil.

[0106] Preferably, the regenerated lubricating oil used according to the invention has a content of aromatic compounds 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 the regenerated lubricating oil. The content of aromatic compounds in the regenerated lubricating oil can therefore be 1% to 25% by mass, in particular 2.5% to 20% by mass, relative to the total mass of the regenerated lubricating oil.

[0107] The amounts of these various components can be determined using any method known to those skilled in the art, such as by X-ray fluorescence (XRF) or by infrared or ultraviolet spectroscopy.

[0108] The rerefined lubricating oil used according to the invention advantageously has at least one, at least two, at least three or even all of the following properties:

[0109] - Kinematic viscosity measured at 100°C according to standard ASTM D445 is greater than or equal to 5 mm 2 / s, e.g. 5-12mm 2 / s, more particularly 5-10 mm 2 / s;

[0110] - a viscosity index greater than or equal to 110, in particular from 110 to 130, especially from 112 to 125;

[0111] - Noack volatility less than or equal to 15%, in particular from 8% to 15%, preferably strictly less than 12%, more particularly from 8% to 11.9%;

[0112] - a sulfur content of 0.01% to 0.3% by mass, in particular 0.02% to 0.2% by mass, relative to the total mass of the regenerated lubricating oil;

[0113] The content of aromatic compounds relative to the total mass of the regenerated lubricating oil is greater than or equal to 0.5 mass%, in particular greater than or equal to 1 mass%, especially 1-25 mass%, more especially 2.5-20 mass%.

[0114] Advantageously, the regenerated lubricating oil used according to the invention has a density less than or equal to 870 kg / m 3 , especially less than or equal to 860kg / m 3 The density of the at least partially re-refined lubricating oil may therefore be 830-870 kg / m 3 , especially 840-860kg / m 3 .

[0115] The density can be determined in particular according to the NF EN ISO 12185 standard.

[0116] Advantageously, the 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 partially rerefined lubricating oil may thus be between 225° C. and 245° C.

[0117] The flash point can be determined in particular according to the NF EN ISO 2592 standard.

[0118] Advantageously, the regenerated lubricating oil used according to the invention has a thermal conductivity measured at 100° C. and atmospheric pressure of 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 partially re-refined lubricating oil may thus be 125-145 mW / mK, in particular 128-140 mW / mK.

[0119] The thermal conductivity can be determined in particular according to the ASTM D7896-19 standard.

[0120] Due to these properties in terms of viscosity index, density, thermal conductivity, flash point, Noack volatility and density, the re-refined lubricating oil used according to the present invention has excellent properties in terms of heat transfer efficiency and hydraulic performance and advantageously has improved properties compared to the original base oil.

[0121] The high viscosity index makes it possible in particular to provide a heat transfer fluid whose viscosity varies little with temperature, thereby ensuring good hydraulic properties of the heat transfer fluid. Thus, the heat transfer fluid according to the invention can be used in systems that may be subject to strong temperature changes, for example as a coolant in a vehicle, and remains pumpable within the temperature range in which it must circulate in said system.

[0122] In particular, the re-refined lubricating oil advantageously has a low density (particularly lower than that of the original base oil) and a high viscosity index (particularly higher than that of the original base oil), which allows for reduced pumping costs while having better thermal properties.

[0123] Heat transfer fluid

[0124] As mentioned previously, the rerefined lubricating oil used according to the present invention, in particular the rerefined lubricating oil as defined and characterized above, can be used as a heat transfer fluid as such or can be formulated into a composition intended for use as a heat transfer fluid.

[0125] The composition for use as a heat-transfer fluid may therefore comprise one or more base oils different from the at least partially rerefined lubricating oil and / or one or more additives.

[0126] In one particular embodiment, the rerefined lubricating oil may be formulated in combination with one or more different base oils, particularly one or more new base oils.

[0127] They are chosen in particular from the base oils customary in the lubricant field, such as mineral, synthetic or natural, animal or vegetable oils or mixtures thereof.

[0128] Advantageously, these base oils are oils of mineral or synthetic origin belonging to groups I to V according to the categories defined in the API classification (as shown in table 1 above) (or their equivalents according to the ATIEL classification), or mixtures thereof.

[0129] The composition used according to the invention may therefore comprise or even be formed from a mixture of one or more at least partly rerefined lubricating oils with one or more new base oils, for example at least one mineral oil.

[0130] In particular, the composition used according to the invention may comprise 0% to 80% by mass, in particular 5% to 75% by mass, relative to the total weight of the composition, of one or more new base oils different from the rerefined lubricating oil required according to the invention and as defined above.

[0131] According to a particular embodiment, the composition used as heat-transfer fluid according to the invention comprises less than 50% by mass of one or more new base oils different from the rerefined lubricating oil.

[0132] Preferably, the composition used as the heat transfer fluid according to the present invention is mainly formed by the one or more re-refined lubricating oils. In particular, the one or more re-refined lubricating oils advantageously account for more than 80% by mass of the total mass of the heat transfer fluid, in particular more than 90% by mass of the total mass of the heat transfer fluid, more particularly more than 95% by mass of the total mass of the heat transfer fluid.

[0133] Thus, the composition used as heat-transfer fluid according to the invention advantageously comprises more than 80% by mass, in particular 90% to 100% by mass, more particularly 95% to 100% by mass, of at least one at least partially rerefined lubricating oil, relative to the total mass of the composition.

[0134] In a particular embodiment, the composition used as a heat-transfer fluid according to the invention is completely free of base oils other than rerefined lubricating oils.

[0135] In a particular embodiment, the composition used as heat-transfer fluid according to the invention may comprise, in addition to the one or more rerefined lubricating oils, one or more additives intended in particular to promote the compatibility of the heat-transfer fluid with the materials of the system in which it is intended to be used.

[0136] These additives may be chosen in particular from anticorrosion additives, friction modifier additives, extreme pressure additives, antiwear additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressants (PPD), dispersants, defoamers and mixtures thereof.

[0137] These additives may be added to the one or more regenerated base oils used according to the invention or to a mixture of the one or more regenerated base oils and at least one new base oil in appropriate amounts determined by a person skilled in the art. It will be understood that the nature and amount of the additives used are selected so that the advantageous properties of the composition based on the one or more re-refined lubricating oils as a heat exchange fluid are not altered or substantially altered by the planned additions.

[0138] The composition used as heat-transfer fluid according to the invention may comprise from 0% to 20% by mass, in particular from 0.01% to 10% by mass, of additives, in particular as described above, relative to the total weight of the composition.

[0139] According to another of its aspects, the invention thus relates to a process or method for preparing a heat transfer fluid, comprising at least one step consisting in obtaining an at least partially re-refined lubricating oil from a used lubricant.

[0140] Advantageously, such a process or method comprises at least the following steps, which are:

[0141] (i) preparing an at least partially re-refined lubricating oil from a used lubricant, in particular by subjecting the used lubricant to at least one or more of the following steps: dehydration, distillation, filtration, hydrogenation, liquid / liquid extraction, sedimentation separation and / or passing the used lubricant over an adsorption material, preferably as detailed above;

[0142] (ii) optionally, blending the at least partially re-refined lubricating oil with one or more new base oils, such as one or more mineral oils, different from the re-refined lubricating oil; and

[0143] (iii) optionally, supplementing the 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 an additive as described above.

[0144] application

[0145] As noted above, at least partially rerefined lubricating oils are particularly suitable for use as heat transfer fluids due to their thermophysical properties.

[0146] In particular, fluids based on at least one rerefined lubricating oil according to the invention can be used in various systems and applications, in particular as a replacement for conventional heat transfer fluids at one or more heat transfer fluid circuits.

[0147] The heat transfer fluid circuit conventionally comprises means of forced or free circulation of the heat transfer fluid, such as a pump or any other equivalent means, and means of discharge, such as an exchanger or any other equivalent means making it possible to diffuse the heat.

[0148] The present invention is therefore not limited to the specific application of the fluid formulated according to the present invention, and the ensuing detailed discussion is given by way of illustration only and not limitation.

[0149] In particular, the invention relates to the use of a composition based on at least one at least partially rerefined lubricating oil as a heat transfer fluid (also known as heat exchange liquid) in mobile or stationary mechanical systems, in other words for transferring heat in mobile or stationary mechanical systems.

[0150] The fluid according to the invention can be used, for example, to ensure heat exchange in "stationary" mechanical systems, such as boilers, air conditioners (in particular in data processing centers ("Data Center" in English), solar thermal collectors, photovoltaic solar collectors, radiators of electrical circuits, in particular power transformers, coal-fired, oil-fired, gas-fired or nuclear thermal power plants, wastewater heat exchangers, turbines, compressors, hydraulic systems, gear mechanisms, or forming or cutting machines.

[0151] The fluid according to the invention can also be used, for example, to ensure heat exchange in "mobile" mechanical systems, including components of light vehicles, heavy vehicles, so-called "off-road" mobile machines or marine vehicles, in particular their motorization systems.

[0152] 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 as heat transfer fluid at said mechanical system a composition based on at least one at least partially rerefined lubricating oil, in particular as described above.

[0153] Such a process or method comprises in particular the following steps, which are:

[0154] a) providing a composition comprising or even consisting of at least one at least partially re-refined lubricating oil, in particular as defined above;

[0155] b) using the composition of step a) at a mechanical system, in particular as described above, more in particular at one or more heat transfer fluid circuits; and

[0156] c) circulating the composition to ensure heat exchange during operation of the mechanical system.

[0157] According to an advantageous embodiment, a fluid formulated according to the invention based on at least one rerefined lubricating oil is used as cooling liquid.

[0158] As an illustration of conceivable applications, the fluid formulated according to the invention can be used as a coolant for moving parts in mechanical systems, and more particularly at mobile or stationary motorized systems.

[0159] The heat transfer fluid according to the invention based on at least one rerefined lubricating oil can thus be used as a coolant for cooling gear mechanisms, rolling bearings, bearings (for example rolling bearings or sliding bearings) or engines.

[0160] The term "motorization system" in the meaning of the present invention is understood to mean a system comprising all the mechanical components required for the intended mobile or stationary application and comprising at least one engine. It can be an internal combustion, gas (in particular hydrogen, ammonia), electric or hybrid motorization system, depending on the nature of the engine or engines included in the motorization system: internal combustion engine, gas (hydrogen, ammonia) engine and / or electric motor.

[0161] The term "propulsion system" in the sense of the present invention refers to a system comprising the mechanical components necessary for propelling the vehicle. The propulsion system thus comprises more particularly an engine, an electric motor such as a rotor-stator assembly including power electronics (specifically for speed regulation), a transmission and optionally a battery. The battery itself is generally composed of a group of accumulators (electrical storage cells), also called cells.

[0162] Furthermore, the heat transfer fluid based on at least one rerefined lubricating oil according to the invention can be used as a coolant for cooling batteries present in electric or hybrid vehicles.

[0163] As an example of application, the heat transfer fluid according to the invention based on at least one rerefined lubricating oil can be used to cool the propulsion system of an electric or hybrid vehicle, and more particularly to cool the engine, the power electronics, the transmission and / or the battery.

[0164] In another application variant, the heat transfer fluid according to the invention based on at least one rerefined lubricating oil can be used as a coolant in the processing of metals such as aluminum, steel, stainless steel, galvanized steel, yellow metals, in particular any metal machining operation, such as conformation, cutting, joining or any other metal transformation process such as forming, stamping, rolling, etc.

[0165] Such compositions used in metal machining processes are also often referred to as "metalworking compositions or fluids", "machining fluids" or "cutting fluids".

[0166] In another application variant, the 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 the hydraulic system, in particular in hydraulic actuators (cylinders / motors) or machine components as required.

[0167] Finally, with regard to the rheological properties of the rerefined lubricating oils used according to the invention, the composition according to the invention based on at least one rerefined lubricating oil can be used simultaneously as a heat transfer fluid, in particular as a coolant, and as a lubricant, for all the mechanical systems mentioned above, for example in the propulsion systems of electric or hybrid vehicles and / or in hydraulic systems.

[0168] Indeed, the composition according to the invention based on at least one rerefined lubricating oil makes it possible to simultaneously achieve good performance in cooling and lubrication of components of such mechanical systems, in particular in propulsion systems of electric or hybrid vehicles, for example electric motors of electric or hybrid vehicles.

[0169] According to another of its aspects, the invention also relates to a heat transfer or thermal management device in which a composition based on at least one at least partially rerefined lubricating oil is used as heat transfer fluid.

[0170] In particular, the device employs at least one heat transfer or heat management circuit in which the composition based on at least one at least partially rerefined lubricating oil is used.

[0171] According to the invention, the properties, advantages or preferred features of these oils and compositions make it possible also to define the properties, advantages and preferred features of the use according to the invention. DETAILED DESCRIPTION

[0172] The invention will now be described by means of the following examples, which are given as non-limiting illustrations of the invention.

[0173] Example

[0174] Measurement method of kinematic viscosity

[0175] According to the NF EN ISO 3104 standard, the kinematic viscosity of oil is measured at 40°C (KV40) and 100°C (KV100) using a viscometer. This standard is technically equivalent to the ASTM D445 standard. The results are given in mm 2 / s (equivalent to centistokes expressed in cSt).

[0176] Volatility Measurement Methods

[0177] Volatility is used to determine the evaporation loss of an oil at high temperatures. It is determined by the Noack volatility test performed according to the CEC L-40-93 standard. In the test, an oil sample is subjected to a constant stream of air, which is heated to about 250°C for about 60 minutes. The result is expressed as a fraction of weight loss, in mass percent.

[0178] Density measurement method

[0179] The density of oil is measured at 15°C using a U-tube densitometer according to NF EN ISO 12185. It is expressed in kg / m 3 express.

[0180] Viscosity Index Measurement Method

[0181] The viscosity index is a dimensionless ratio that gives an indication of how the viscosity of an oil changes with temperature. It is calculated according to the NF ISO 2909 standard from the kinematic viscosity values ​​at 40°C and 100°C. The higher the index, the less the viscosity of the oil is affected by temperature changes.

[0182] Thermal conductivity measurement method

[0183] Thermal conductivity, usually denoted as λ, characterizes the ability of the oil to diffuse heat in the medium. It is measured by the transient hot-wire liquid thermal conductivity method according to ASTM D7896-19 standard. It is expressed in mW / mK.

[0184] Flash point measurement method

[0185] The flash point gives an indication of the ability of a product to form a flammable mixture with air under controlled conditions. It is determined using the Cleveland open cup apparatus according to the NFEN ISO 2592 standard. The flash point at ambient atmospheric pressure is the lowest temperature at which a flame passing over a test cup containing the oil will cause the vapor above the surface of the liquid to ignite. It is expressed in degrees Celsius.

[0186] Method for determination of sulfur and aromatic compound content

[0187] Determination of sulfur and aromatic compound content in oil by infrared or ultraviolet spectroscopy.

[0188] Example 1

[0189] The properties of six re-refined lubricating oils I1-I6 according to the present invention and which are commercially available were evaluated.

[0190] These oils are obtained from used base oils that have been subjected to at least one of the following steps: dehydration, distillation, filtration, hydrogenation, liquid / liquid extraction, separation by sedimentation and / or passing the used lubricant on an adsorption material, in particular at least one step of dehydration, distillation, liquid / liquid extraction and / or hydrogenation.

[0191] Three new lubricating oils C1-C3 which are not according to the invention were also evaluated, since they had not undergone any recycling or re-refining steps.

[0192] These oils are base oils of group I or II according to the API classification and are commercially available.

[0193] In particular, the kinematic viscosity 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.

[0194] Table 2 below shows the results for rerefined and virgin oils having the same properties as those defined by the API classification for Group I base oils, and Table 3 below shows the results for rerefined and virgin oils having the same properties as those defined by the API classification for Group II base oils.

[0195] [Table 2]

[0196] Oil I1 I2 I3 I4 I5 C1 <![CDATA[KV40[mm 2 / s]]]> 33.0 27.9 29.4 26.5 29.1 31.3 <![CDATA[KV100[mm 2 / s]]]> 5.9 5.2 5.4 5.0 5.4 5.3 Viscosity Index 122 118 118 114 119 102 <![CDATA[Density [kg / m 3 > 849.3 851 854.1 850.9 854.1 872.5 Noack volatility [%] 7.2 9.4 11.6 10.6 - 13.1 Flash point[℃] 236 228 230 230 228 224 Thermal conductivity [mW / mK] 131.3 129.3 - 131.4 128.4 124.3 Sulfur content [%] 0.11 0.16 0.06 0.06 0.15 0.26 Aromatic compound content [%] 7.2 - 12.5 17.5 9.8 15

[0197] [Table 3]

[0198] Oil I6 C2 C3 <![CDATA[KV40[mm 2 / s]]]> 28.2 30.1 - <![CDATA[KV100[mm 2 / s]]]> 5.6 5.4 5.0 Viscosity Index 120 115 - <![CDATA[Density [kg / m 3 > 849.5 852.8 - Noack volatility [%] 10.9 12 - Flash point[℃] 230 222 - Thermal conductivity [mW / mK] 133.2 126.7 127.6 Sulfur content [%] 0.02 <0.0003 <0.001 Aromatic compound content [%] 9 0.4 0.002

[0199] result

[0200] All at least partially rerefined oils required according to the invention have a higher viscosity index and thermal conductivity and a lower density than the original oils unsuitable for the invention and have otherwise comparable properties.

[0201] This at least partially rerefined oil therefore has particularly advantageous thermophysical properties, which make it possible to achieve performances as a heat transfer fluid that are superior to those of new lubricating oil which has not undergone any recirculation.

[0202] The lower density and high viscosity index also ensure good hydraulic properties, in particular reducing the costs associated with pumping these oils during use as heat transfer fluids. In addition, the at least partially re-refined oil has better performance than new lubricating oil in terms of energy saving, in particular in terms of fuel saving.

[0203] Moreover, the at least partially re-refined oil required according to the invention has a reduced volatility and a higher flash point compared to the volatility and flash point measured for an oil not suitable for the invention. Thus, the at least partially re-refined oil enables an increased safety to be achieved compared to new lubricating oils.

[0204] Overall, at least partly rerefined lubricating oils have particularly advantageous properties, in particular properties superior to those of new oils, making them useful as heat transfer fluids, in particular as coolants.

Claims

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

2. Use according to the preceding claim, wherein the at least partially re-refined lubricant oil comes from a used lubricant that has undergone one or more of the following previous steps: dehydration, distillation, filtration, hydrogenation, liquid / liquid extraction, sedimentation separation and / or passing the used lubricant over an adsorption material.

3. The use according to any one of the preceding claims, wherein the at least partially re-refined lubricating oil has a kinematic viscosity measured at 100° C. according to standard ASTM D445 of greater than or equal to 5 mm 2 / s, especially 5-12mm 2 / s, more particularly 5-10 mm 2 / s.

4. The method according to claim 1, wherein the at least partially re-refined lubricating oil has a viscosity index greater than or equal to 110, in particular from 110 to 130, in particular from 112 to 125.

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

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

7. The method according to claim 1 , wherein the at least partially re-refined lubricating oil has a content of aromatic compounds greater than or equal to 0.5% by mass, in particular greater than or equal to 1% by mass, in particular from 1% to 25% by mass, more particularly from 2.5% to 20% by mass, relative to the total mass of the regenerated lubricating oil.

8. The use according to any one of the preceding claims, wherein the at least partially re-refined lubricating oil has a viscosity less than or equal to 870 kg / m 3 , especially 830-870kg / m 3 , especially less than or equal to 860kg / m 3 , and more particularly 840-860 kg / m 3 density.

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

10. Use according to any of the preceding claims, wherein the composition comprises one or more base oils other than the at least partially rerefined lubricating oil 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 depressants (PPD), dispersants, defoamers and mixtures thereof.

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

12. Method for transferring heat in a mobile or stationary mechanical system, comprising at least one step of circulating as heat-transfer fluid at said mechanical system a composition based on at least one at least partially rerefined lubricating oil, in particular as defined in any one of claims 2 to 10.

13. Heat transfer or heat management device, wherein a composition is used as heat transfer fluid, said composition being based on at least one at least partially rerefined lubricating oil, in particular as defined in any one of claims 2 to 10.

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