Lubricant composition for a screw compressor, on a re-refined oil basis

Abstract

The present invention relates to the use of a lubricant composition for lubricating moving parts in a screw compressor, said lubricant composition comprising an oil which is at least partially re-refined and has a reduced environmental impact.

Description

DESCRIPTION LUBRICANT COMPOSITION FOR SCREW COMPRESSORS BASED ON RE-REFINED OIL Technical field

[0001] The present disclosure relates to the field of lubricating compositions for screw compressors. More specifically, the present invention relates to the use of re-refined oils for the formulation of lubricating compositions for screw compressors. Prior art

[0002] A lubricating composition, also called "a lubricant", is commonly used in the various components of mechanical systems such as, for example, hydraulic systems, industrial machines or motor vehicles. The lubricating composition is mainly used to reduce the friction forces between the various moving metal parts in these mechanical systems. It is also effective in preventing premature wear or even damage to these parts, and in particular damage to their surface. A lubricating composition is conventionally composed of a base oil to which one or more dedicated additives are generally associated to adapt the lubricating performance of the base oil depending on the use of the lubricating composition.

[0003] A screw compressor is an industrial machine used in industries such as automotive, brewing, food packaging, aerospace, and construction, and requires the use of a lubricating compound for proper operation. A screw compressor compresses air using two rotors located in a chamber. Since the two rotors are in constant close contact, the lubricating compound reduces mechanical wear on both rotors.

[0004] During operation of the screw compressor, the lubricating composition used may oxidize in the presence of oxygen and degrade. This oxidation can be explained by various factors such as, for example, the high temperature and / or pressure conditions present in the screw compressor, the contact of the lubricating composition with impurities and the dissolution of metal particles likely to catalyze the degradation by oxidation of the lubricating composition.

[0005] A lubricating composition can also be polluted during use by contact with impurities.

[0006] The degradation and pollution of the lubricating composition are characterized by the formation of deposits and / or varnish, blackening of the lubricating composition or even an increase in the viscosity of the lubricating composition.

[0007] These various phenomena of degradation and pollution thus lead to a reduction in the cleanliness of the lubricating composition and of the mechanical parts in contact with the lubricating composition, lead to a loss of the initial performance of the lubricating composition and are therefore likely to impact the proper functioning of the screw compressor. Early replacement of the lubricating composition therefore proves necessary before the 2000 operating hours interval required by screw compressor manufacturers.

[0008] Additionally, the base oil for screw compressor lubricating compositions is currently a conventional base oil obtained by refining crude oil. A large amount of crude oil is generally required to obtain conventional base oil. Typically, to extract 1 liter of conventional base oil, 37 liters of crude oil are required. In addition, oil refining processes are very energy-intensive and generate large amounts of carbon dioxide.

[0009] The carbon footprint of currently used screw compressor lubricating compositions therefore does not correspond to current environmental concerns and resource conservation issues.

[0010] There is therefore a need to provide a lubricating composition for a screw compressor allowing the proper operation of a screw compressor for at least 2000 hours and a reduced carbon footprint compared to a lubricating composition comprising a conventional base oil obtained by refining crude oil. Summary

[0011] There is provided a use of a lubricating composition for lubricating moving parts in a screw compressor, said lubricating composition comprising: a base oil comprising: - more than 5% by weight, relative to the total weight of the lubricating composition, of at least one at least partly re-refined oil, and - less than 95% by weight, relative to the total weight of the lubricating composition, of at least one conventional base oil, and at least one additive chosen from an anti-corrosion agent, a metal passivation agent, a demulsifying agent, an antioxidant agent, an anti-wear agent, a calcium-based agent, an anti-foaming agent, a pour point depressant (PPD), an extreme pressure resistance agent, a detergent agent, a cleaning agent, a solvent, an anti-rust agent and mixtures thereof.

[0012] The use of an at least partly re-refined oil to formulate a lubricating composition for the lubrication of moving parts in a screw compressor has never been suggested in the prior art. And yet, the replacement of a conventional base oil with an at least partly re-refined oil in the lubricating composition used according to the invention proves to be surprisingly advantageous from an ecological and technical point of view.

[0013] Indeed, thanks to this replacement, the lubricating composition used according to the invention has a carbon footprint significantly lower than the carbon footprint of a lubricating composition comprising a base oil consisting of a conventional base oil obtained from the refining of crude oil.

[0014] In addition, the replacement of the conventional base oil with the at least partly re-refined oil combined with the additive surprisingly improves the resistance to degradation of the lubricating composition used according to the invention. This improvement in resistance to degradation is characterized by an improvement in the cleaning properties of the lubricating composition used according to the invention and a reduction in the variation in the viscosity of the lubricating composition used according to the invention.

[0015] These technical improvements can also lead to additional environmental improvements.

[0016] For example, improving the resistance to degradation of the lubricating composition used according to the invention allows: - to better protect the moving parts of the screw compressor, - to increase the service life of said lubricating composition to exceed 2000 hours, in particular 4000 hours, more particularly 8000 hours of operation in a screw compressor, while maintaining the lubrication performance targeted for this type of compressor. This advantageously makes it possible to increase the time between two consecutive oil changes of a screw compressor, and therefore - to operate the screw compressor in its optimum performance range for a longer period without the need for maintenance operations, i.e. to optimize the performance of said screw compressor.

[0017] Thus, a screw compressor using the lubricating composition implemented according to the invention advantageously has: - an improved lifespan because its moving parts are better protected, - a reduced carbon footprint because: - the quantities of lubricating composition and moving parts required for its proper functioning are reduced, and - its energy needs are reduced because its performance is optimized.

[0018] According to another aspect, there is provided a lubricating composition for a screw compressor comprising: a base oil comprising: - more than 5% by weight, relative to the total weight of the lubricating composition, of at least one at least partly re-refined oil, and - less than 95% by weight, relative to the total weight of the lubricating composition, of at least one conventional base oil, and at least one additive chosen from an anti-corrosion agent, a metal passivation agent, a demulsifying agent, an antioxidant agent, an anti-wear agent, a calcium-based agent, an anti-foaming agent, a pour point depressant (PPD), and mixtures thereof.

[0019] According to another aspect, there is provided a method of lubricating a screw compressor comprising the following step: a) bringing into contact the moving parts in the screw compressor requiring lubrication lubricated with a lubricating composition, said lubricating composition comprising: a base oil comprising: - more than 5% by weight, relative to the total weight of the lubricating composition, of at least one at least partly re-refined oil (RBO), and - less than 95% by weight, relative to the total weight of the lubricating composition, of at least one conventional base oil (CBO), and at least one additive chosen from an anti-corrosion agent, a metal passivation agent, a demulsifying agent, an antioxidant agent, an anti-wear agent, a calcium-based agent, an anti-foaming agent, a pour point depressant (PPD), and mixtures thereof. Figures

[0020] [Figure 1]

[0021] Figure 1 shows a two-dimensional chromatogram as a function of the retention times of columns A and B obtained from the GC-2D method described in the patent application filed under number FR 24 0623 illustrating the presence of PAO in the re-refined oil RBO1 used in the examples.

[0022] [Figure 2]

[0023] Figure 2 shows a two-dimensional chromatogram as a function of the retention times of columns A and B obtained from the GC-2D method described in the patent application filed under number FR 24 0623 illustrating the presence of PAO in the re-refined oil RBO2 used in the examples. Description of the embodiments

[0024] According to a first aspect, there is provided a use of a lubricating composition for the lubrication of moving parts in a screw compressor, said lubricating composition comprising: a base oil comprising: - more than 5% by weight, relative to the total weight of the lubricating composition, of at least one oil which is at least partly re-refined and - less than 95% by weight, relative to the total weight of the lubricating composition, of at least one conventional base oil, and at least one additive chosen from an anti-corrosion agent, a metal passivation agent, a demulsifying agent, an antioxidant agent, an anti-wear agent, a calcium-based agent, an anti-foaming agent, a pour point depressant (PPD), an extreme pressure resistance agent, a detergent agent, a cleaning agent, a solvent, an anti-rust agent and mixtures thereof.

[0025] For the purposes of the present application, the expression "at least partly re-refined oil" {"Refined Base Oil" or "RBO" according to English terminology), also referred to more simply in the continuation of the text "re-refined oil" means an oil derived from a used lubricating composition which has been subjected to one or more re-refining treatment stages.

[0026] For the purposes of the present application, the expression "conventional base oil" ("Conventional Base Oil" or "CBO" according to English terminology) designates an oil which, as opposed to a re-refined oil, is conventionally used in the field of lubricating compositions, is directly obtained by refining a crude oil and which has not yet been used.

[0027] 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.

[0028] 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.

[0029] [Table 1]

[0030] For the purposes of this application, the expression “used lubricating composition” designates 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.

[0031] The lubricating composition used in the invention may have a kinematic viscosity at 40°C, measured according to standard ISO 3014-2020, greater than or equal to 40 mm 2 / s, especially 40 mm 2 / s at 49 mm 2 / s, more specifically 42 mm 2 / s at 47 mm 2 / s.

[0032] Advantageously, a lubricating composition having such a kinematic viscosity at 40°C is particularly suitable for use in a screw compressor. In addition, the inventors have noted that the viscosity of a lubricating composition having a viscosity at 40°C in these ranges, in particular 42 mm 2 / s at 47 mm 2 / s is particularly stable.

[0033] The base oil of the lubricating composition used according to the invention may comprise from 50% by weight to 75% by weight, relative to the total weight of the lubricating composition, of re-refined oil, in particular from 60% to 71% by weight.

[0034] The base oil of the lubricating composition used according to the invention may comprise from 20% by weight to 40% by weight, relative to the total weight of the lubricating composition, of the conventional base oil, in particular from 27% to 35% by weight.

[0035] The inventors noted that the lubricating composition used according to the invention comprising a base oil whose contents of re-refined oil and / or conventional base oil are in the ranges described is suitable for use in a screw compressor. In particular, such a lubricating composition can exhibit cleanliness performances making it possible to reduce, or even prevent, the formation of deposits and varnish on the moving parts of the screw compressor, which is characteristic of improved resistance to degradation.

[0036] The kinematic viscosity at 40°C of the re-refined oil can be 3.0 mm 2 / s at 10.0 mm 2 / s, especially 4.0 mm 2 / s at 7.5 mm 2 / s, more specifically 5.5 mm 2 / s at 6.0 mm 2 / s.

[0037] The kinematic viscosity at 100°C of the re-refined oil can be 4.0 to 40 mm 2 / s, especially 25 mm2 / s at 40 mm 2 / s, more particularly 30 mm 2 / s at 35 mm 2 / s, more particularly 31.5 mm 2 / s at 33.0 mm 2 / s.

[0038] According to one embodiment, the kinematic viscosity measured at 100°C of the re-refined oil may be greater than or equal to 3.0 mm 2 / s, in particular greater than or equal to 4.0 mm 2 / s, in particular between 4.0 and 12 mm 2 / s, in particular greater than or equal to 4.3 mm 2 / s and more particularly between 4.4 and 10 mm 2 / s, especially between 4.5 and 6 mm 2 / s

[0039] The viscosity index of the re-refined oil may be from 110 to 150, particularly from 115 to 130, more particularly from 120 to 125.

[0040] Alternatively, the viscosity index of the re-refined oil may be greater than or equal to 1 10, in particular between 1 10 and 130, preferably between 1 12 and 125, and more particularly between 1 18 and 124.

[0041] The molar mass of the re-refined oil may be from 350 g / mol to 600 g / mol, in particular from 400 g / mol to 500 g / mol, more particularly from 430 g / mol to 450 g / mol. According to one embodiment, the molar mass of the re-refined oil may be from 425 g / mol to 440 g / mol.

[0042] The pour point of re-refined oil can be -40°C to 0°C, particularly -35°C to -10°C, more particularly -30°C to -15°C.

[0043] The pour point of re-refined oil may be -35°C to -5°C, more particularly -20°C to -9°C, for example -9°C, -12°C, or -15°C.

[0044] Preferably, the re-refined oils used according to the invention have, compared to conventional base oils of equivalent group according to the API classification, reduced volatility.

[0045] Volatility properties can be more specifically assessed by determining Noack volatility according to CEC L-40-93 standard.

[0046] Advantageously, a regenerated lubricating oil used according to the invention has a Noack volatility of less than or equal to 15%, in particular less than or equal to 14%.

[0047] More preferably, a regenerated lubricating oil used according to the invention may have a Noack volatility strictly less than 12%, in particular between 6% and 11%, more particularly 7% and 11%.

[0048] The inventors noted that a lubricating composition comprising a re-refined oil having at least one of the characteristics presented above, in particular at least two, more particularly at least three, very particularly at least four, very particularly five characteristics presented above and even more particularly all six characteristics presented above is suitable for use in a screw compressor.

[0049] Re-refining treatments for used lubricating compositions have therefore been developed in order to regenerate these compositions and allow their subsequent reuse as re-refined oil. A re-refined oil is thus an oil obtained at the end of one or more re-refining treatment stages of a used lubricating composition, aimed at eliminating, at least in part, a certain number of contaminating elements present therein, such as dust, water, fuel fractions, metallic elements, polycyclic aromatic hydrocarbons and other residues resulting from the degradation of the additives present in the used lubricating compositions.

[0050] Thus, the composition of a re-refined oil differs from the composition of a used lubricating composition at least by a reduced content of contaminating elements present therein.

[0051] The sulfur content of the re-refined oil can be from 5 ppm to 1500 ppm, particularly from 10 ppm to 1100 ppm, more particularly from 1000 ppm to 1050 ppm or from 20 ppm to 40 ppm.

[0052] The nitrogen content of the re-refined oil may be less than or equal to 100 ppm, in particular from 0 ppm to 75 ppm, more particularly from 1 ppm to 60 ppm.

[0053] The silicon content of re-refined oil may be less than or equal to 300 ppm, particularly from 1 ppm to 200 ppm.

[0054] The phosphorus content of the re-refined oil may be less than or equal to 100 ppm, in particular from 0 ppm to 50 ppm, for example 0 ppm.

[0055] The chlorine content of the re-refined oil may be less than or equal to 50 ppm, in particular from 0 ppm to 25 ppm, for example 0 ppm.

[0056] The sulfur, nitrogen, silicon, phosphorus and chlorine contents can be determined by any techniques known to those skilled in the art, for example by X-ray fluorescence (XRF), by infrared spectroscopy or by UV spectroscopy.

[0057] The inventors noted that a lubricating composition comprising a re-refined oil having at least one of the five contents presented above, in particular at least two, more particularly at least three, most particularly at least four, most particularly the five contents presented above is suitable for use in a screw compressor.

[0058] According to one embodiment, the at least partly re-refined base oil or oils have 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 at least partly re-refined base oil or oils.

[0059] Preferably, in the lubricating composition of the invention, the at least partly re-refined base oil or oils have a content of aromatic compound(s) of between 4% and 15% by mass, in particular of between 5% and 10% by mass, relative to the total mass of said at least partly re-refined base oil or oils.

[0060] 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.

[0061] A re-refined oil according to the present invention may comprise one or more alkylphenol(s). By "alkylphenol" is meant a phenolic compound with an alkyl group R1 in the para position, and therefore of formula R1 -C6H4-OH. The presence of alkylphenol is characteristic of re-refined oils, since conventional (unused) base oils do not comprise alkylphenol.

[0062] Preferably, the content of alkylphenol(s) in the re-refined oil according to the present invention is from 5 to 3,200 ppm, preferably from 10 to 2,000 ppm, preferably from 15 to 1,500 ppm, of alkylphenol(s).

[0063] According to one embodiment, a re-refined oil according to the present invention comprises from 10 to 300 ppm, preferably from 15 to 250 ppm, of alkylphenol(s).

[0064] According to one embodiment, a re-refined oil according to the present invention comprises from 150 to 2,000 ppm, preferably from 200 to 1,500 ppm, of alkylphenol(s), preferably 1,160 (+ / - 1,16) ppm or from 1,044 ppm to 1,276 ppm.

[0065] According to one embodiment, a re-refined oil according to the present invention comprises from 100 to 300 ppm, preferably from 145 to 180 ppm, of alkylphenol(s), preferably from 165(+ / -16) ppm or from 149 to 181 ppm.

[0066] The alkylphenol(s) content in the re-refined oil is measured according to the method described in the patent application filed under number FR 23 15133.

[0067] This method is based on the implementation of liquid chromatography and mass spectrometry steps, using a standard compound which is 4-hexadecylphenol.

[0068] For the liquid chromatography steps, a particle-filled column composed of C8-bonded silica is used. Measurements are carried out at 40°C with a flow rate of 0.4 mL / min.

[0069] Here, a so-called reversed-phase column is used to separate the different components of the sample (here, the re-refined oil to be analyzed) according to their polarity. The composition of the mobile phase is used to modify these interactions over time and thus gradually elute the different molecules of the sample analyzed (here, the re-refined oil).

[0070] The mobile phase is used in the form of a gradient as shown in the table below, from a solution A comprising 50% water and 50% acetonitrile and a solution B comprising 100% methanol.

[0071] [Table 2]

[0072] Using mass spectrometry detection, it is then possible to obtain the signal produced only by the molecules of interest, identified both by their mass and their retention time.

[0073] The ionization source used is preferably the electrospray ionization (ESI) source which allows the selective ionization of polar compounds. In the case of the method used here, the detection mode chosen is the negative detection mode because it allows the selective ionization of polar compounds with an acidic character. The range for masses (m / z) varies from 100 to 1200.

[0074] In particular, the method for measuring the alkylphenol content in the re-refined oil used according to the invention comprises a first step consisting of preparing the standard solution (4-hexadecylphenol) and the solution to be analyzed (re-refined oil): preparation of a standard solution at different concentrations to obtain a calibration line as explained later, by dilution in THF with the addition of 2% ammonium hydroxide; and preparation of a solution of said re-refined oil by dilution in THF with the addition of 3% ammonium hydroxide.

[0075] To establish the calibration curve, the intensity of the chromatographic peak associated with the 4-hexadecylphenol ion of the standard is recovered by plotting an "extracted ion chromatogram" which is more commonly called in English "extracted ion chromatogram (EIC)". This makes it possible to have an extracted chromatogram only for a given m / z, namely here 317.28 for the standard molecule, the deprotonated form corresponding to the [C22H37O]- ion. The intensity of the EIC is therefore recovered for each of the analyses at the different concentrations tested.

[0076] The data obtained allow the construction of the calibration line. This calibration line is obtained by injecting several standard solutions at different concentrations: the line is constructed by linear regression, and the calculation of the correlation coefficient (R 2 ) allows to check the linearity of the detector and the correct preparation of the standard solutions.

[0077] The associated equation then allows us to predict the concentration of an unknown sample by entering the value y obtained experimentally. Here, the equation is as follows: y = 1001.9x - 15309

[0078] To quantify the alkylphenols in the re-refined oil according to the invention, the analysis method comprises a step of identifying the m / z of the alkylphenol residues on the average mass spectrum by integrating the entire chromatogram. This average spectrum corresponds to an average of all the mass spectra obtained on the complete chromatographic run. This makes it possible to have all the compounds that were ionized during the analysis. From this average mass spectrum is extracted a mass list grouping together all the m / z ratios of the ions with the associated intensities.

[0079] The next step is to construct a Kendrick diagram with this mass list. This is a molecular map that allows us to identify series of compounds of the same type, but with different degrees of alkylation, by overcoming the mass defect of the hydrogens in the CH2 motif.

[0080] The Kendrick diagram can be made by calculating the following values: KM=mass (IUPAC or EXPER)x14.00000 / 14.01565 where KM corresponds to the Kendrick mass, IUPAC mass corresponds to the theoretical mass calculated from the sum of each element constituting the molecule of interest, here for the standard molecule hexadecylphenol of formula C22H37O-, the IUPAC mass = 317.284440 g.mol-1, and EXPER mass corresponds to an experimental mass measurement, measured during an experiment.

[0081] The Kendrick mass KM is calculated for each peak of the average mass spectrum, determined previously as explained above.

[0082] Then, the Kendrick MKD mass defect is typically calculated according to the following equation: KMD=NKM-KM where KMD corresponds to the Kendrick mass defect, KM corresponds to the Kendrick mass, and NKM is the nearest integer rounding of the Kendrick mass KM.

[0083] The Kendrick mass defect KMD is calculated for each peak (each peak corresponding for example to a compound present in the re-refined oil).

[0084] Kendrick diagrams are a 2D molecular map representing KMDs versus NKMs. Homologous compounds varying in their degree of alkylation appear as a horizontal line.

[0085] The set of m / z of the alkylphenols is obtained by applying a filter on the y-axis (KMD): this is the value KMD = 0.069. Once all the m / z at KMD = 0.069 are identified, they are used to construct “extracted ion chromatograms (EtC)” as described for the standard molecule. This allows to have a chromatogram dependent only on the requested m / z. The intensities of the EIC of each m / z corresponding to the alkylphenols are thus summed to have the total intensity (several alkylphenol type molecules are obtained on the spectra of re-refined oil according to the invention, these molecules varying by the length of their alkyl chain).

[0086] To obtain a quantification, the sum of the intensities of the EICs obtained is used as the value of y for the equation of the calibration line. For example, if the value obtained is 2.45E6, the quantification of alkylphenol residues in the re-refined oil used according to the invention is: y = 1001.9x - 15309 x= (y+15309) / 1001.9 and therefore x is equal to 2460.6 ppm.

[0087] In one embodiment, a re-refined oil according to the present invention comprises one or more polyalphaolefins (PAOs). The presence of polyalphaolefin(s) is characteristic of re-refined lubricating oils, since conventional (unused) base oils do not comprise polyalphaolefins (PAOs).

[0088] Reference is now made to Figures 1 and 2, each of which shows a two-dimensional chromatogram as a function of the retention times of columns A and B obtained from the GC-2D method described in the patent application filed under number FR 24 0623 illustrating the presence of PAO in the re-refined oils RBO1 and RBO 2 used in the examples. The arrow in each of the figures indicates the characteristic peak of PAO polyalphaolefins (at C30), a marker of re-refined oils.

[0089] According to one embodiment, a re-refined oil according to the present invention comprises one or more polyalphaolefins (PAOs) comprising less than 40 carbon atoms, and preferably comprising 30 carbon atoms.

[0090] The presence of PAOs in the re-refined oil is determined according to the method described in the patent application filed under number FR 24 0623

[0091] This method is based on the implementation of comprehensive two-dimensional gas chromatography (GCxGC) and classification steps.

[0092] In particular, it is implemented via a chromatography device, the chromatography device comprising a comprehensive two-dimensional gas chromatography module comprising a first column A and a second column B, and capable of separating different compounds of the product according to their volatility and their polarity, the chromatography device further comprising a flame ionization detector capable of measuring an intensity of electric ionization current generated for each compound included in the product, the chromatography device being calibrated with at least one calibration product, making it possible to correct the retention time of the different compounds present in the product.

[0093] The method is further implemented by an electronic classification device, comprising the following steps: a. determining a table describing the intensity of the electric ionization current generated for each compound included in the product as a function of the corrected retention times in columns A and B, from a measurement carried out by the chromatography device on the product; b. assigning a class to the product, from a plurality of classes, by applying a multivariate statistical algorithm to the table, said algorithm being trained on tables obtained from reference products.

[0094] The chromatography device comprises a comprehensive two-dimensional gas chromatography module comprising a first column A and a second column B. The comprehensive two-dimensional gas chromatography modules (2DGC or GCxGC) that can be used in the context of the present disclosure are those described in the literature.

[0095] These modules generally include an injection module, a vaporization module, a first column A, a modulator, and a second column B. They allow a two-dimensional separation of complex mixtures, because the product is subjected to two separations, we then obtain a two-dimensional chromatogram as a function of the retention times of columns A and B and a table describing the intensity of the electric ionization current generated for each compound included in the product as a function of the corrected retention times in columns A and B.

[0096] According to one embodiment, the first column A and the second column B are columns based on polydimethylsiloxane partially functionalized with phenyl groups. The percentage of phenyl group functionalization can be between 2% and 50%. According to a particular embodiment, the percentage of phenyl group functionalization of column A is greater than the percentage of phenyl group functionalization of column B. Advantageously, the length of column A is greater than that of column B. The diameter of the two columns A and B can be equivalent. The two columns can have a film thickness of 0.1 μm suitable for the separation of low-volatile samples. According to one embodiment, the temperature gradient applied to the oven is 2°C / min up to 400°C.

[0097] A quantity of product is injected into the first column A to obtain a first separation, then via the modulator, into the second column B to obtain a second separation. The product can be injected directly without pretreatment, particularly in the case of lubricating oil analysis.

[0098] The GCxGC device is coupled to a flame ionization detector, or FID. This is capable of measuring the intensity of the ionization electrical current generated for each compound included in the product. The flame ionization detector is located at the outlet of the second column.

[0099] Following analysis by the flame ionization detector, a table describing the intensity of the ionization electric current generated for each compound included in the product, as a function of the corrected retention times in columns A and B, is determined. The table is therefore derived from a two-dimensional chromatogram obtained from a measurement carried out by the chromatography device on the product.

[0100] In addition, during this initial step, an external calibration is performed to correct the retention time of the various compounds present in the product. This is performed by injecting at least one calibration product. In the case where the product to be classified is a lubricating oil, the calibration product may be a lubricating oil, preferably recycled. According to one embodiment, the calibration product comprises at least one marker, preferably at least two markers. The marker may be selected from n-paraffins, polyalphaolefins, and their mixture. The correction of the retention times may be performed by software.

[0101] At the end of this initial step, the classification device moves on to a next step, during which it assigns, via its product assignment module, a respective class from among the plurality of classes, by applying a multivariate statistical algorithm to the table, said algorithm being trained on tables obtained from reference products.

[0102] The multivariate statistical algorithm used in the allocation step may be a partial least squares regression multivariate statistical algorithm; the multivariate statistical algorithm preferably being selected from the group consisting of: a partial least squares regression algorithm, and a partial least squares regression algorithm with discriminant analysis. The algorithm is typically a partial least squares regression algorithm, such as the PLS algorithm or the PLS-DA algorithm.

[0103] The multivariate statistical algorithm used during the attribution step is trained on tables obtained from reference products.

[0104] In Partial Least Squares Discriminant Analysis (PLS-DA), the prediction coefficient on a scale of 0 to 1 represents the probability or confidence of a sample belonging to a particular class.

[0105] Here is how this coefficient is calculated and used:

[0106] 1. Creation of latent variables:

[0107] PLS-DA creates latent variables (components) that capture the maximum variance of the X data (the predictors) while maximizing the covariance with the Y classes (the categorical responses).

[0108] 2. Calculation of scores:

[0109] Samples are projected onto these latent variables, producing scores that are used to discriminate between classes.

[0110] 3. Modeling:

[0111] A linear model is fitted to these scores to predict the values ​​of Y. In the case of PLS-DA, Y is often binary encoded to represent classes (e.g., 0 for group A and 1 for group B).

[0112] 4. Prediction:

[0113] When predicting for new samples, the scores of these samples are calculated and passed through the linear model to obtain a continuous prediction. This continuous prediction is then transformed into a probability on a scale of 0 to 1.

[0114] 5. Interpretation of probabilities:

[0115] These probabilities are then interpreted to assign the samples to the different classes.

[0116] For example :

[0117] - If the probability is less than 0.4, the sample is classified in group A (here group of re-refined base oils); and

[0118] - If the probability is greater than or equal to 0.4, the sample is classified in group B (conventional base oil group).

[0119] The re-refined oil may have characteristics that meet the criteria defined by the API classification for Group I, Group II, Group III oils or combinations thereof, particularly Group I, Group II or combinations thereof, particularly Group I or Group II. These characteristics of the re-refined oil may be the saturates content, the sulfur content and / or the viscosity index.

[0120] The used lubricating composition may be a mixture of several used lubricating compositions, from the same source or from several different sources.

[0121] Used lubricating compositions comprise, in the majority quantity, one or more base oils conventionally used in the field of lubricants, such as mineral oils, synthetic oils, natural oils or their mixtures. Natural oils are of natural origin, for example they come 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. Mineral or synthetic oils that can be used as base oils conventionally used in the lubricant field can belong to Group I, Group II, Group III, Group IV and / or Group V according to the classes defined in the API classification.

[0122] For example, the re-refined oil may be derived at least in part from a used lubricating composition that has been subjected to one or more re-refining processing steps, said used lubricating composition comprising a base oil belonging to Group I, Group II, Group III, Group IV, Group V or combinations thereof according to the API classification.

[0123] The used lubricating composition 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).

[0124] The used lubricating composition may comprise various conventional additives in the lubricant field, such as friction modifier additives, extreme pressure additives, anti-wear additives, detergents, antioxidants, viscosity index (VI) improvers, pour point depressants (PPD) additives, dispersing agents, anti-foaming agents, thickeners, and mixtures thereof.

[0125] Due to their origin, the used lubricating composition may include a number of degradation products derived from the composition itself or from the additives it contains and resulting from the use of the lubricating composition for a more or less long period. The used lubricating composition may also include metal particles, metal oxides and other elements, for example from a mechanical system. In particular, a used lubricating composition may contain 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.

[0126] The re-refined oil may more particularly come from a used lubricating composition having been subjected to one or more prior pre-treatment steps chosen from a dehydration step, a distillation step, a filtration step, a hydrogenation step, a liquid / liquid extraction step, a decantation step, a step of passing said used lubricating composition over an adsorbent material or combinations thereof, in particular a step of passing said used lubricating composition over an adsorbent material.

[0127] The dehydration step makes it possible to eliminate any water present in the used lubricating composition. The dehydration step can be carried out by any method known to those skilled in the art, for example by distillation, evaporation, decantation, heating or passing a stream of hot air over the used lubricating composition. The step dehydration 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.

[0128] Advantageously, the re-refined oil may comprise 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 re-refined oil.

[0129] The distillation step can be carried out after the dehydration step. The distillation step can be carried out by any technique known to those skilled in the art such as atmospheric distillation or distillation under reduced pressure. The distillation step can for example be carried out at a temperature between 100°C and 500°C, preferably between 200°C and 400°C, more preferably between 300°C and 380°C. In particular, it can be carried out at a pressure between 25 and 2,000 Pa, preferably between 50 and 1,000 Pa, more particularly between 50 and 250 Pa.

[0130] The filtration step can be carried out after the dehydration step. The filtration step 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.

[0131] The step of passing the used lubricating composition over an adsorbent material can be implemented by flowing the used lubricating composition over an adsorbent material. The adsorbent material advantageously makes it possible to selectively adsorb aromatic compounds, in particular polycyclic aromatic hydrocarbons. In particular, passing over an adsorbent material, preferably over activated carbon, advantageously makes it possible to reduce the content of polycyclic aromatic hydrocarbons, in particular 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.

[0132] The flow rate of the used lubricating composition can be between 1 m 3 / h and 15 m 3 / h, for example between 5 and 10 m 3 / h.

[0133] Absorbent materials may be, for example, activated carbon, zeolites, clays, or functionalized porous compounds. Preferably, it is activated carbon.

[0134] 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.

[0135] Preferably, the activated carbon is characterized by a density between 200 and 500 kg / m 3 , for example measured according to ASTDM D2854.

[0136] Preferably, the activated carbon is a coal, preferably comprising from 70 to 95%, advantageously from 80 to 90% by weight of carbon.

[0137] The step of passing the used lubricating composition over an adsorbent material, preferably over activated carbon, is advantageously preceded by the following steps: - one or more distillation stages; and - a filtration step, in particular as defined previously.

[0138] For example, re-refined oil may be obtained from the treatment of a used lubricating composition according to the method described in WO 2018 / 109208.

[0139] The hydrogenation step may be carried out by any technique known to those skilled in the art and generally consists of treating the lubricating oil with hydrogen, generally in the presence of a hydrogenation catalyst. Such a catalyst may contain, for example, at least one oxide or sulfide of at least one group VI metal and / or at least one group VIII metal, such as molybdenum, tungsten, nickel or cobalt, and a support, for example alumina, silica-alumina or a zeolite. The hydrogenation step may preferably follow a dehydration and / or distillation step.

[0140] The liquid / liquid extraction step using a solvent advantageously makes it possible to lighten a dark-colored used oil, to eliminate at least part of the bad odor or the aromatic compounds, in particular PAHs. The liquid / liquid extraction step can be carried out by any technique known to those skilled in the art. The liquid / liquid extraction step is generally carried out in a mixer-settler or in an extraction column, using a suitable extraction solvent. The liquid / liquid extraction step by a solvent may preferably follow a dehydration and / or distillation step.

[0141] The decantation step can be carried out by any technique known to those skilled in the art.

[0142] The conventional base oil of the lubricating composition used according to the invention may be an oil of mineral or synthetic origin belonging, according to the API classification, to group I, group II, group III or their combinations, in particular to group I, group II or their combinations, more particularly to group I or group II.

[0143] The lubricating composition used according to the invention comprises at least one additive chosen from an anti-corrosion agent, a metal passivation agent, a demulsifying agent, an antioxidant agent, an anti-wear agent, a calcium-based agent, an anti-foaming agent, a pour point depressant (PPD), an extreme pressure resistance agent, a detergent agent, a cleaning agent, a solvent, an anti-rust agent and mixtures thereof.

[0144] These additives are known to those skilled in the art and are therefore not described in more detail.

[0145] The lubricating composition used according to the invention may comprise from 0.5% by weight to 6% by weight, relative to the total weight of the lubricating composition, of said at least one additive, in particular from 0.9% to 1.10% by weight.

[0146] The implementation according to the invention may comprise at least two, at least three, at least four, at least five, at least six, at least seven, at least eight, at least nine, at least ten, at least eleven, at least twelve or the thirteen additives described above.

[0147] For example, the additive may be a mixture of metal passivation agent, antioxidant agent, anti-wear agent, calcium-based agent, pour point depressant (PPD) and anti-foam agent.

[0148] Alternatively, the additive may be a mixture of metal passivating agent, antioxidant, solvent, extreme pressure resistance agent, anti-wear agent, anti-corrosion agent, pour point depressant (PPD), anti-foaming agent, detergent agent, cleaning agent and demulsifying agent.

[0149] Some agents can combine multiple functions. For example, an agent can be both detergent and cleaning. This is also the case, for example, with spiroboronate, which is known as a detergent agent and, unexpectedly, also acts as an antioxidant in the composition of the present invention.

[0150] Indeed, the inventors have found that the PAI of the lubricating composition used according to the invention comprising spiroboronate is low, which proves the unexpected antioxidant effect of spiroboronate.

[0151] Thus, spiroboronate can be at least one of the additives of the lubricating composition used according to the invention.

[0152] For example, the lubricating composition used according to the invention may comprise from 0.1% by weight to 1% by weight, relative to the total weight of the lubricating composition, of spiroboronate, in particular from 0.4% to 0.6% by weight.

[0153] The lubricating composition used according to the invention may comprise, relative to the total weight of the lubricating composition: from 0.50% to 1.5% by weight of a mixture of metal passivation agent, antioxidant agent, anti-wear agent, calcium-based agent, in particular from 0.80% to 1% by weight, from 0.05% to 0.25% by weight of pour point depressant (PPD), in particular from 0.10% to 0.20% by weight, and from 0.01% to 0.15% by weight of anti-foaming agent, in particular from 0.04% to 0.1% by weight.

[0154] Alternatively, the lubricating composition used according to the invention may comprise, relative to the total weight of the lubricating composition: from 0.01% to 0.15% by weight of metal passivation agent, in particular from 0.04% to 0.06% by weight, from 0.10% to 1% by weight of antioxidant agent, in particular from 0.4% to 0.5% by weight, from 0.50% to 1.5% by weight of solvent, in particular from 0.9% to 1% by weight, from 0.05% to 0.5% by weight of a mixture of extreme pressure resistance agent and anti-wear agent, in particular from 0.20% to 0.25%, from 0.01% to 0.10% by weight of anti-corrosion agent, in particular from 0.04% to 0.06%, from 0.05% to 0.5% by weight of pour point depressant (PPD), in particular from 0.1 to 0.3% by weight, from 1% to 3% by weight of a mixture of detergent agent and cleaning agent, in particular from 1.8% to 2.2% by weight, and from 0.05% to 1% by weight of demulsifying agent, in particular from 0.4% to 0.6% by weight.

[0155] For the purposes of the present application, the expression "eco-material content" designates the ratio, in percentage, between the weight of the re-refined oil of the lubricating composition used according to the invention and the total weight of said lubricating composition.

[0156] Thus, the lubricating composition used according to the invention may have an eco-material content of at least 5%, in particular 50% to 75%, more particularly 65% ​​to 71%.

[0157] According to another aspect, there is provided a use of a re-refined oil to increase the eco-material content of a lubricating composition for a screw compressor.

[0158] According to another aspect, there is provided a lubricating composition for a screw compressor comprising: a base oil comprising: - more than 5% by weight, relative to the total weight of the lubricating composition, of at least one at least partly re-refined oil, and - less than 95% by weight, relative to the total weight of the lubricating composition, of at least one conventional base oil, and at least one additive chosen from an anti-corrosion agent, a metal passivation agent, a demulsifying agent, an antioxidant agent, an anti-wear agent, a calcium-based agent, an anti-foaming agent, a pour point depressant (PPD), and mixtures thereof.

[0159] The base oil, the at least partly re-refined oil, the conventional base oil and the additive are as defined above in connection with the use of a lubricating composition for the lubrication of moving parts in a screw compressor.

[0160] According to another aspect, there is proposed a use of the lubricating composition for improving the eco-performance of a screw compressor.

[0161] The lubricating composition used in this use is as defined above in connection with the use of a lubricating composition for the lubrication of moving parts in a screw compressor.

[0162] For example, eco-performance is the increase in the life of the screw compressor, the decrease in the environmental impact of the screw compressor or both.

[0163] Indeed, as explained above, the lubricating composition used according to the invention has improved resistance to degradation which allows: - to better protect the moving parts of the screw compressor, and therefore to increase the service life of said screw compressor, and - to reduce the quantities of lubricating composition, moving parts and energy required for the proper operation of the screw compressor, and therefore to reduce the environmental impact of said screw compressor.

[0164] According to another aspect, there is provided a method of lubricating a screw compressor comprising the following step: a) contacting the moving parts in the screw compressor requiring lubrication with a lubricating composition

[0165] The lubricating composition used in this process is as defined above in connection with the use of a lubricating composition for the lubrication of moving parts in a screw compressor. Examples

[0166] Measurement of the properties of lubricating compositions

[0167] The cleanliness performance of various lubricant compositions was evaluated by a test according to ASTM 7873-2022 modified (“TOST”, acronym for “Thermal Oxidation Stability Test”), this test being modified as follows. The lubricating composition is heated to 140°C in the presence of copper and steel catalysts in a glass container placed in an oil bath. Oxygen is bubbled through the lubricating composition maintained at 140°C for a certain period of time. At the end of the test, the visual appearance of the container is observed. It is noted whether deposits and / or varnishes have formed on the surface of the glass, as well as their appearance. The appearance of the catalysts is also observed. A sample of the composition obtained at the end of the test is filtered through a filter capable of filtering out particles larger than 1 μm. The color of the filtered particles is noted.

[0168] The visual appearance of the glass container and the filtered particles created allows the performance in terms of maintaining the cleanliness of the lubricating composition evaluated to be classified: 0 The glass container is covered with a non-transparent black deposit and / or varnish and the filtered particles are very dark black / brown; + The glass container is covered with a rather transparent black / dark brown deposit and / or varnish and the filtered particles are black / dark brown; ++ The glass container is coated with a transparent black deposit and / or varnish and the filtered particles are black / dark brown; +++ The glass container is covered with a light deposit and / or clear varnish and the filtered particles are black / dark brown; ++++ No deposit is visible on the surface of the glass container and the filtered particles are yellow / light beige.

[0169] The duration of the thermal oxidation stability test is: 216 hours for compositions 11 and C1 presented below, 168 hours for compositions I2 and C2 presented below, and 336 hours for the I3 compositions and the ROTAIR commercial comparative lubricant composition presented below.

[0170] The kinematic viscosity at 40°C of the lubricating composition is measured according to ISO 3104-2020. At the end of the thermal oxidation stability test described above, the lubricating composition is recovered and its kinematic viscosity at 40°C is measured according to ISO 3104-2020 to calculate the viscosity variation at 40°C.

[0171] The PAI of the lubricating composition is measured according to DIN 51453-2004

[0172] Example 1: Preparation of lubricating compositions.

[0173] Lubricating compositions according to the invention (11 to 13) and comparative lubricating compositions (C1 and C2) were formulated.

[0174] Table 3 shows the properties of the two re-refined oils, denoted RBO 1 or RBO 2 in Table 3, included in the lubricating compositions according to the invention (11 to 13)

[0175] [Table 3]

[0176] Tables 3, 4 and 5 present the compositions and properties of the lubricating compositions according to the invention (11 to 13), of the comparative lubricating compositions (C1 and C2) and of a commercial comparative lubricating composition (ROTAIR) without re-refined oil. The percentages are percentages by weight relative to the total weight of the lubricating composition.

[0177] Conventional base oil (denoted CBO in Tables 4 to 6) is Group II.

[0178] Additive blend 1 includes a metal passivating agent, an antioxidant, an anti-wear agent and a calcium-based agent.

[0179] Additive Blend 2 includes a metal passivating agent, an antioxidant, a solvent, an extreme pressure resistance agent, an anti-wear agent, an anti-corrosion agent, a pour point depressant (PPD), an anti-foaming agent, a detergent agent, a cleaning agent, and a demulsifying agent.

[0180] Table 4 highlights that the substitution of conventional base oil with re-refined RBO 1 oil strongly stabilizes the kinematic viscosity at 40°C and improves the cleanliness performance of the lubricating composition.

[0181] Table 5 shows that the substitution of conventional base oil with re-refined RBO 2 oil does not alter the stability of the kinematic viscosity at 40°C. Indeed, the variations in kinematic viscosity at 40°C of compositions I2 and C2 are of the same order of magnitude. Table 5 also highlights that the substitution of conventional base oil with re-refined RBO 2 oil does not change the cleanliness performance of the lubricating composition.

[0182] Table 6 highlights that the substitution of conventional base oil with re-refined RBO 1 oil and the use of spiroboronate as an additive allows: to increase the oxidation resistance of the lubricating composition, because the PAI decreases significantly, and to improve the cleanliness performance of the lubricating composition.

[0183] [Table 4]

[0184] [Table 5]

[0185] [Table 6]

Claims

Claims

1. Use of a lubricating composition for lubricating moving parts in a screw compressor, said lubricating composition comprising: a base oil comprising: - more than 5% by weight, relative to the total weight of the lubricating composition, of at least one at least partly re-refined oil, and - less than 95% by weight, relative to the total weight of the lubricating composition, of at least one conventional base oil, and at least one additive chosen from an anti-corrosion agent, a metal passivation agent, a demulsifying agent, an antioxidant agent, an anti-wear agent, a calcium-based agent, an anti-foaming agent, a pour point depressant (PPD), an extreme pressure resistance agent, a detergent agent, a cleaning agent, a solvent, an anti-rust agent and mixtures thereof.

2. Use according to claim 1, wherein the base oil comprises from 50% by weight to 75% by weight, relative to the total weight of the lubricating composition, of said at least one at least partly re-refined oil.

3. Use according to claim 1 or claim 2, wherein the base oil comprises from 20% by weight to 40% by weight, relative to the total weight of the lubricating composition, of said at least one conventional base oil.

4. Use according to any one of claims 1 to 3, in which the lubricating composition has a kinematic viscosity at 40°C greater than or equal to 40 mm 2 / s.

5. Use according to any one of claims 1 to 4 wherein said at least one at least partly re-refined oil has characteristics satisfying the criteria defined by the API classification for oils of group I, group II, group III or their combinations.

6. Use according to any one of claims 1 to 5 wherein said at least one conventional base oil is an oil of mineral or synthetic origin belonging, according to the API classification, to group I, group II, group III or their combinations.

7. Use according to any one of claims 1 to 6 in which spiroboronate is at least one of the additives of the lubricating composition.

8. Use according to claim 7 in which the lubricating composition comprises from 0.1% by weight to 1% by weight, relative to the total weight of the lubricating composition, of spiroboronate.

9. Use according to any one of claims 1 to 8, in which the lubricating composition has an eco-material content of at least 5%, the eco-material content being defined as the ratio, in percentage, between the weight of said at at least one at least partially re-refined oil of said lubricating composition on the total weight of said lubricating composition.

10. Use of a lubricating composition for improving the eco-performance of a screw compressor, said lubricating composition being as defined in any one of claims 1 to 9.

11. Use according to claim 10, wherein the eco-performance is increasing the life of the screw compressor, decreasing the environmental impact of the screw compressor or both.

12. A method of lubricating a screw compressor comprising the following step: a) contacting the moving parts in the screw compressor requiring lubrication with a lubricating composition, said lubricating composition being as defined in any one of claims 1 to 9.

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