Use of a lubricant composition comprising at least one base oil and at least one fatty alcohol

Abstract

The present invention relates to the use of a lubricant composition comprising at least one base oil and at least one linear or branched, saturated or unsaturated fatty alcohol containing from 8 to 20 carbon atoms, for the lubrication of moving parts in a screw compressor.

Description

[0001] Description

[0002] Title: Use of a lubricating composition comprising at least one base oil and at least one fatty alcohol

[0003] Technical field

[0004] The present invention relates to the field of lubricating compositions. These compositions can be used for various applications, in particular for the lubrication of various mechanical systems, in particular as screw compressor oil.

[0005] It relates more particularly to the use of at least one specific fatty alcohol as an additive to improve the properties of a lubricant such as dispersant properties, in other words maintaining cleanliness (“keep clean” in English).

[0006] Prior art

[0007] Lubricating compositions, also called "lubricants", are commonly used in mechanical systems to reduce friction between parts and thus protect them against wear. In addition to wear phenomena, friction can oppose the relative movement of the parts in contact and induce energy losses that are detrimental to optimal operation of the mechanical system. To achieve this, a lubricating composition is conventionally composed of a base oil to which are generally associated several additives dedicated to boosting the lubricating performance of the base oil, but also to providing additional performance.

[0008] Lubricants are used for multiple applications, especially for screw compressors, used in particular in fields such as automotive, brewing, food packaging, aerospace or construction, etc.

[0009] During use, lubricants may be subjected to high temperature conditions. They can then oxidize and degrade in the presence of oxygen. This degradation can result in the formation of deposits, varnishes and sludge, an increase in the viscosity of the lubricant, an increase in the acidity of the lubricant, or even a blackening of the lubricant.

[0010] The oxidation stability of lubricating oils can be further reduced due to the dissolution of metals in these oils, as dissolved metals can catalyze the oxidative degradation of lubricants. Such degradation results in a loss of the lubricant's initial performance, which can impact the proper functioning of the mechanical system. A lubricant can also become contaminated during use by coming into contact with impurities.

[0011] These various degradation and pollution phenomena thus lead to a reduction in the cleanliness of the lubricant and the mechanical parts in contact with the lubricant. A replacement of the lubricant therefore becomes necessary after a certain period of use.

[0012] Improving the dispersant properties of lubricants during their use in mechanical systems, and in particular reducing the formation of deposits and varnish, therefore constitutes an important lever for extending the service life of lubricants, oil change intervals and maintenance intervals.

[0013] Thus, limiting or even avoiding the degradation of lubricating compositions also makes it possible to reduce their carbon impact due to the use of a smaller quantity of lubricating composition.

[0014] To limit the degradation of lubricants during lubrication, and in particular to reduce the formation of deposits and varnish, lubricants generally use high-quality base oils, for example polyalphaolefins (PAO), or oils with high solvency, for example esters, alkylated naphthalenes, naphthenic oils or alkylbenzenes.

[0015] However, these lubricants, especially PAOs and esters, are expensive, which is a barrier to their use, especially as oils with a 4000-hour lifespan. Furthermore, lubricants with high solvency are not always effective in maintaining dispersant properties.

[0016] The search for additive systems to increase the performance of lubricants in terms of dispersant properties, in particular to reduce the formation and / or presence of deposits and varnish, remains a constant concern to optimize the service life of lubricants, and extend oil change and maintenance intervals.

[0017] Lubricating compositions containing fatty alcohols to improve the cleanliness of a 4-stroke vehicle engine have been described in FR 3 066 200 AL. However, these compositions are not suitable for use in screw compressors, in particular with regard to the differences in the environment specific to each (for example, mixture of fuel or not with oil or difference in temperatures), or even the desired function.

[0018] Indeed, for an engine, the composition must lubricate and cool the engine parts, and the kinetic energy is recovered. In the case of screw air compressors, it is the compressed air that is recovered, and which must remain clean and uncontaminated. As a result, the lubricating composition used must have distinct properties, otherwise it risks clogging the entire system.

[0019] For example, lubricating compositions intended for engines contain very high quantities of detergents which are not suitable for lubricants intended for screw compressors, because this blocks the entire device and contaminates it.

[0020] Statement of the invention

[0021] The present invention aims precisely to propose a new additive system for the lubrication of moving parts in a screw compressor.

[0022] More specifically, it aims at a new additive system to improve cleanliness during lubrication in a screw compressor, and in particular to improve the maintenance of the dispersant properties of a composition for the lubrication of moving parts in a screw compressor.

[0023] Thus, the present invention relates, according to a first of its aspects, to the use of a lubricating composition comprising at least one base oil and at least one fatty alcohol, linear or branched, saturated or unsaturated, containing from 8 to 20 carbon atoms, for the lubrication of moving parts in a screw compressor.

[0024] The present invention also relates to the use of at least one fatty alcohol, linear or branched, saturated or unsaturated, containing from 8 to 20 carbon atoms in a lubricating composition comprising at least one base oil, to improve the performance of said composition used in a screw compressor, and in particular to improve the properties of maintaining the dispersant properties ("keep clean") of said composition used in a screw compressor.

[0025] In the remainder of the text, a fatty alcohol as defined above will be referred to more simply as "fatty alcohol" according to the invention. Surprisingly, the inventors have discovered that the addition of at least one fatty alcohol according to the invention to a lubricating composition makes it possible to significantly improve the performance of the composition in terms of dispersant properties.

[0026] In particular, as illustrated in the examples which follow, the inventors have shown that the presence of at least one fatty alcohol according to the invention in a lubricating composition makes it possible to reduce, or even prevent, the formation of deposits and varnish.

[0027] Consequently, it is possible to increase the service life of a lubricating composition by adding at least one fatty alcohol according to the invention, in particular up to durations of at least 2000 h, in particular at least 4000 h, in particular at least 8000 h of operation, or even at least 12000 h of operation in a screw compressor, while maintaining the lubrication performance targeted for these compressors.

[0028] It is thus possible to increase the intervals between two consecutive oil changes of a screw compressor.

[0029] Furthermore, it has been surprisingly and advantageously discovered that the present invention makes it possible to dispense with the ester compounds conventionally used in lubricating compositions containing high-quality base oils, for example polyalphaolefins (PAO), thanks to the use of at least one fatty alcohol, linear or branched, saturated or unsaturated, containing from 8 to 20 carbon atoms.

[0030] The invention further relates, according to another aspect, to a method for reducing the formation of deposits or varnish when lubricating a screw compressor with a lubricating composition comprising at least one base oil, the method comprising adding to said lubricating composition at least one fatty alcohol, linear or branched, saturated or unsaturated, containing from 8 to 20 carbon atoms.

[0031] It also relates to a method for lubricating a screw compressor, comprising a step of bringing at least one part of said screw compressor into contact with a lubricating composition comprising at least one base oil and at least one fatty alcohol, linear or branched, saturated or unsaturated, containing from 8 to 20 carbon atoms.

[0032] Other characteristics, variants and advantages of the use of at least one fatty alcohol according to the invention will become more apparent upon reading the description and examples which follow, given by way of illustration and not limitation of the invention.

[0033] The expressions "between ... and ...", "ranging from ... to ...", "formed from ... to ...", and "varying from ... to ...", must be understood inclusively, unless otherwise stated. Detailed description

[0034] Fatty alcohol

[0035] As previously indicated, the fatty alcohol used is a linear or branched, saturated or unsaturated fatty alcohol, containing 8 to 20 carbon atoms.

[0036] A composition may therefore comprise a single fatty alcohol according to the invention or several distinct fatty alcohols. If several distinct fatty alcohols are present, these may be added separately during the preparation of the lubricating composition and their mixture may then be formed in situ. They may also be implemented in the form of a mixture already commercially available.

[0037] Preferably, the fatty alcohol(s) have a flash point of at least 80°C, or even at least 100°C.

[0038] In particular, the fatty alcohol(s) have a melting temperature less than or equal to 15°C.

[0039] Preferably, the fatty alcohol(s) are liquid.

[0040] The fatty alcohol(s) may be chosen from linear or branched, saturated or unsaturated fatty alcohols, containing from 8 to 20 carbon atoms, preferably from 12 to 20 carbon atoms.

[0041] The fatty alcohol(s) are in particular chosen from linear or branched saturated fatty alcohols containing from 8 to 20 carbon atoms, preferably from 12 to 20 carbon atoms. In particular, the fatty alcohol(s) are chosen from linear and saturated fatty alcohols containing from 8 to 20 carbon atoms, preferably from 12 to 18 carbon atoms, or even from 12 to 14 carbon atoms, or from branched and saturated fatty alcohols containing from 14 to 20 carbon atoms, preferably from 16 to 20 carbon atoms, in particular branched only in the beta position relative to the alcohol function.

[0042] In particular, the fatty alcohol(s) are chosen from capric alcohol (also called octan-l-ol, CAS number 111-87-5), lauryl alcohol (also called dodecan-l-ol, CAS number 112-53-8), palmitic alcohol (also called hexadecan-l-ol), myristyl alcohol (also called tetradecan-l-ol, CAS number 112-72-1), stearyl alcohol (also called octadecan-l-ol, CAS number 112-92-5), 2-hexyldecanol (also called 2-hexyl-l-decanol, CAS number 2425-77-6), 2-octyldodecanol (also called 2-octyl-l-dodecanol, CAS number 5333-42-6), and mixtures thereof, preferably from lauryl alcohol, 2-hexyldecanol, 2-octyldodecanol, and mixtures thereof.

[0043] Fatty alcohol can be a mixture of several different fatty alcohols, for example a mixture of lauryl alcohol and myristyl alcohol.

[0044] The lubricating composition may have a content of said fatty alcohol(s) less than or equal to 10% by mass, in particular varying from 0.01% to 10% by mass, more particularly varying from 0.02% to 8% by mass, preferably varying from 0.05% to 5% by mass, more preferably from 0.1% to 1% by mass, relative to the total mass of the lubricating composition.

[0045] In particular, the lubricating composition may have a content of said fatty alcohol(s) of 0.1% by mass, 0.2% by mass, 0.3% by mass, 0.4% by mass, 0.5% by mass, 0.6% by mass, 0.7% by mass, 0.8% by mass, or 0.9% by mass, relative to the total mass of the lubricating composition.

[0046] LUBRICATING COMPOSITION

[0047] Base oil

[0048] A lubricating composition implemented according to the invention comprises at least one base oil.

[0049] The base oils may be chosen from base oils conventionally used in the field of lubricating compositions, such as mineral, synthetic or natural, animal or vegetable oils, at least partly re-refined oils or mixtures thereof.

[0050] H can be a mixture of several base oils, for example a mixture of two, three or four base oils.

[0051] In the context of the present invention, the expression "at least partly re-refined oil", also referred to more simply in the remainder of the text as "re-refined oil", "regenerated oil" or even "recycled oil", designates an oil originating at least in part from a used lubricating composition having been subjected to one or more treatment steps known as re-refining treatment.

[0052] According to the invention, the term "used lubricating composition" (or more simply "used lubricant" or "used lubricating oil") is intended to denote any lubricating composition that has been used for the lubrication of moving parts, in particular metal parts, of a mechanical system, such as, but not limited to, bearings, gears or motors.

[0053] Used lubricating oil can come from different sources. In particular, as detailed in the rest of the text, it can be a lubricant used for the lubrication of a motorization system, in particular "mobile", or for the lubrication of a so-called industrial system, in particular "stationary".

[0054] Due to their origin, used lubricating oils, particularly engine lubricating oils, contain a number of degradation products derived from the oil itself or from the additives it contains, as well as metal particles, metal oxides and other elements, for example from the engine. Used oil may contain, in particular, a high content of undesirable elements, for example calcium (Ca), iron (Fe), magnesium (Mg), sodium (Na), nickel (Ni), phosphorus (P), silicon (Si), chlorine (Cl), zinc (Zn) etc.

[0055] Methods for re-refining or reconditioning used lubricating oils have been developed to regenerate these oils and enable their subsequent reuse.

[0056] A re-refined lubricating oil is thus an oil obtained at the end of one or more stages of treatment of a used lubricant, aimed at eliminating, at least in part, a certain number of contaminating elements present therein, such as dust, water, fuel fractions, metallic elements and other residues resulting from the degradation of the additives present in the lubricant.

[0057] The base oils of the lubricating compositions considered according to the invention may in particular be oils of mineral or synthetic origin belonging to groups I to V according to the classes defined in the API classification (or their equivalents according to the ATIEL classification) and presented in table 1 below or their mixtures.

[0058]

[0059] Table 1

[0060] Mineral base oils include all types of base oils obtained by atmospheric and vacuum distillation of crude oil, followed by refining operations such as solvent extraction, de-alphatting, solvent dewaxing, hydrotreating, hydrocracking, hydroisomerization and hydrofinishing.

[0061] Synthetic base oils may be esters of carboxylic acids and alcohols, polyalphaolefins or polyalkylene glycols (PAGs) obtained by polymerization or copolymerization of alkylene oxides comprising 2 to 8 carbon atoms, in particular 2 to 4 carbon atoms. The polyalphaolefins used as base oils are, for example, obtained from monomers comprising 4 to 32 carbon atoms, for example from decene, octene or dodecene, and whose viscosity at 100 °C is between 1.5 and 150 mm 2 .s -1according to ASTM D445. Their average molecular weight is generally between 250 and 3000 according to ASTM D5296.

[0062] In particular, the lubricating composition may comprise at least one base oil chosen from polyalphaolefins, carboxylic acid and alcohol esters, and mixtures thereof.

[0063] Blends of synthetic and mineral oils, which can be bio-sourced, can also be used.

[0064] There are generally no limitations on the use of different base oils in the lubricating composition, except that they must have properties, for example viscosity, viscosity index, sulfur content, suitable for the intended use, in particular for a screw compressor.

[0065] In particular, the base oil is chosen from group I, group II, group III, group IV and group V oils of the API classification, more particularly from group II and group III oils of the API classification, and mixtures thereof, and more preferably from group II oils.

[0066] Preferably, the lubricating composition comprises from 80% to 99.5% by mass, in particular from 90% to 99% by mass, preferably from 95% to 99% by mass, of one or more base oils, preferably chosen from group II base oils, group III base oils, group IV base oils, group V base oils and mixtures thereof, preferably chosen from group II base oils, relative to the total mass of said lubricating composition.

[0067] For example, the lubricating composition comprises from 80% to 99.5% by mass, in particular from 90% to 99% by mass, preferably from 95% to 99% by mass, of one or more base oils selected from group II base oils, mixtures of group II base oil and group III base oil, and group IV base oils, preferably selected from group II base oils.

[0068] Advantageously, the presence of at least one fatty alcohol according to the invention makes it possible to reduce or even eliminate the use of high-quality oils such as PAO oils while maintaining excellent performance for the composition containing it or them, particularly in terms of dispersant properties.

[0069] Preferably, the lubricating composition comprises from 80% to 99.5% by mass, in particular from 90% to 99% by mass, preferably from 95% to 99% by mass, of one or more base oils chosen from group II base oils and / or group III base oils, preferably group II base oils, relative to the total mass of said lubricating composition.

[0070] The inventors have shown that the addition of at least one fatty alcohol according to the invention to a group II base oil advantageously allows the composition containing them to achieve performances, particularly in terms of maintaining dispersant properties, as good as a mixture of group II and group III base oils.

[0071] It has also been shown that the presence of fatty alcohol in a lubricating composition comprising a group IV or group V base oil, i.e. a high quality oil, also makes it possible to improve the maintenance of the dispersant properties of the lubricating composition.

[0072] According to a particular embodiment, the lubricating composition may comprise a base oil from group IV or group V, in particular from group IV, in particular at a content of 80% to 99.5% by mass, in particular 90% to 99% by mass, preferably 95% to 99% by mass, relative to the total mass of said lubricating composition.

[0073] The inventors have shown that the addition of at least one fatty alcohol according to the invention to a group IV base oil advantageously allows the composition containing them to achieve performances, in particular in terms of maintaining dispersant properties, at least as good as a mixture of group IV and group V base oils.

[0074] In particular, base oils suitable for the invention may have a kinematic viscosity measured at 40°C according to ASTM D445 (KV40) ranging from 11 mm 2 / s at 1600 mm 2 / s.

[0075] The base oil(s), in particular as described above, may be present in a lubricating composition according to the invention in a content of at least 80% by mass, relative to the total mass of said composition, in particular at least 90% by mass, more particularly ranging from 80% to 99.5% by mass, in particular from 90% to 99% by mass, and preferably from 95% to 99% by mass.

[0076] Additives

[0077] A lubricating composition according to the invention may further comprise all types of additives suitable for the intended use of the lubricant.

[0078] All of the additional additives can be introduced in the form of a mixture or “package” of additives, or can be introduced individually when formulating the composition.

[0079] The fatty alcohol used according to the invention can be added in combination with one or more additives, in particular mixed with the additive package, or individually.

[0080] In a particular embodiment, the additional additives may represent from 0.1% to 30% by weight relative to the total weight of the composition, in particular from 0.5% to 20% by weight, in particular from 1% to 15% by weight, more particularly from 2% to 10% by weight, preferably from 2% to 5% by weight, even more preferably from 2% to 3% by weight. It is understood that the contents of additional additives do not include the content of fatty alcohol(s) according to the invention.

[0081] In particular, a lubricating composition implemented according to the invention comprises one or more additional additives chosen from additives chosen from anionic compounds comprising a long lipophilic hydrocarbon chain and a hydrophilic head, friction modifiers, anti-wear additives, extreme pressure additives, antioxidants, viscosity index (VI) improvers, pour point depressant (PPD) additives, dispersing agents, anti-foaming agents, demulsifying agents, thickeners, corrosion inhibitors, metal passivation agents, naphthenic solvents, and mixtures thereof.

[0082] It is understood that the nature and quantity of additional additives used are chosen so as not to affect the properties of the lubricating composition, in particular the performance conferred by the fatty alcohol used according to the invention.

[0083] In particular, a lubricating composition implemented according to the invention comprises one or more additional additives chosen from anionic compounds comprising a long lipophilic hydrocarbon chain and a hydrophilic head, anti-wear additives, extreme pressure additives, antioxidants, pour point depressant (PPD) additives, anti-foaming agents, demulsifying agents, corrosion inhibitors, metal passivation agents, naphthenic solvents, and mixtures thereof.

[0084] Preferably, a lubricating composition used according to the invention comprises one or more additional additives chosen from anti-wear additives, extreme pressure additives, antioxidants, pour point depressant (PPD) additives, anti-foaming agents, demulsifying agents, corrosion inhibitors and metal passivation agents.

[0085] Preferably, a lubricating composition used according to the invention does not comprise a friction modifying additive.

[0086] According to the invention, the fatty alcohol(s) used are not friction modifying additives.

[0087] Preferably, a lubricating composition used according to the invention does not comprise any thickener(s).

[0088] According to a particular embodiment, a lubricating composition used according to the invention comprises less than 1%, in particular less than 0.1%, more particularly less than 0.01% by mass of detergent additive(s), distinct from the fatty alcohol(s) used, relative to the total weight of the composition, or even is devoid of detergent additive(s), distinct from the fatty alcohol(s) used.

[0089] Preferably, the compositions according to the invention do not comprise detergent additives, distinct from the fatty alcohol(s) used.

[0090] Preferably, a lubricating composition according to the invention comprises at least one anti-wear additive, an extreme pressure additive or their mixtures.

[0091] Anti-wear additives and extreme pressure additives are dedicated to protecting friction surfaces by forming a protective film adsorbed on these surfaces. There is a wide variety of anti-wear additives. Particularly suitable for the invention are anti-wear additives chosen from polysulfide additives, sulfur-containing olefin additives, phospho-sulfur additives, amine phosphates and mixtures thereof, and preferably amine phosphates.

[0092] According to a particular embodiment, a lubricating composition according to the invention may comprise from 0.01% to 6% by mass, in particular from 0.05% to 4% by mass, preferably from 0.1% to 2% by mass, and more preferably from 0.1% to 1% by mass, relative to the total weight of the composition, of anti-wear additives and extreme pressure additives.

[0093] According to a particular embodiment, a lubricating composition according to the invention may comprise at least one antioxidant additive.

[0094] The antioxidant additive helps to delay the degradation of the lubricating composition in service. They act in particular as radical inhibitors or hydroperoxide destroyers.

[0095] Commonly used antioxidant additives include phenolic antioxidants, amine antioxidant additives, and phosphosulfur antioxidant additives. Some of these antioxidant additives, for example phosphosulfur antioxidant additives, may be ash-generating. Phenolic antioxidant additives may be ash-free or in the form of neutral or basic metal salts. The antioxidant additives may in particular be chosen from sterically hindered phenols, sterically hindered phenol esters, and sterically hindered phenols comprising a thioether bridge, diphenylamines, diphenylamines substituted with at least one C1-C12 alkyl group, N,N'-dialkylaryldiamines, and mixtures thereof.

[0096] Preferably, the sterically hindered phenols are chosen from compounds comprising a phenol group in which at least one vicinal carbon of the carbon bearing the alcohol function is substituted by at least one C1-C10 alkyl group, preferably a C1-C6 alkyl group, preferably a C4 alkyl group, preferably by the tert-butyl group. Amino compounds are another class of antioxidant additives that can be used, optionally in combination with the phenolic antioxidant additives. Examples of amino compounds are aromatic amines, for example aromatic amines of formula NR 5 R 6 R 7 in which R 5 represents an aliphatic group or an aromatic group, optionally substituted, R 6 represents an aromatic group, optionally substituted, R 7represents a hydrogen atom, an alkyl group, an aryl group or a group of formula R 8 S(O) Z R 9 in which R 8 represents an alkylene group or an alkenylene group, R 9 represents an alkyl group, an alkenyl group or an aryl group and z represents 0, 1 or 2. Sulphurized alkyl phenols or their alkali and alkaline earth metal salts can also be used as antioxidant additives.

[0097] According to a particular embodiment, a lubricating composition according to the invention may comprise from 0.1% to 3% by mass, preferably from 0.5% to 2% by mass, relative to the total weight of the composition, of at least one antioxidant additive.

[0098] According to a particular embodiment, a lubricating composition used according to the invention comprises less than 1%, in particular less than 0.1%, more particularly less than 0.01% by mass of sulfur additive(s), relative to the total weight of the composition, or even is devoid of sulfur additive(s). A lubricating composition used according to the invention may also comprise at least one additive chosen from anionic compounds comprising a long lipophilic hydrocarbon chain and a hydrophilic head.

[0099] According to a particular embodiment, a lubricating composition implemented according to the invention may also comprise at least one pour point depressant additive (also called “PPD” agent for “Pour Point Depressant” in English).

[0100] By slowing the formation of paraffin crystals, pour point depressant additives generally improve the cold performance of the lubricating composition according to the invention. Examples of pour point depressants include polyalkyl methacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalenes and alkylated polystyrenes.

[0101] A lubricating composition according to the invention may comprise from 0.05% to 2%, preferably from 0.1% to 1% by mass of pour point lowering additive(s), relative to the total weight of the composition.

[0102] A lubricating composition used according to the invention may also comprise at least one dispersing agent.

[0103] They can be chosen from Mannich bases, succinimides and their derivatives, such as polyisobutylene succinic anhydride derivatives.

[0104] Preferably, a lubricating composition used according to the invention does not comprise any dispersing agent(s).

[0105] A lubricating composition implemented according to the invention may also comprise at least one additive improving the viscosity index (VI).

[0106] Preferably, a lubricating composition used according to the invention does not comprise an additive improving the viscosity index (VI).

[0107] A lubricating composition used according to the invention may also comprise at least one anti-foam additive, for example chosen from polar polymers such as polymethylsiloxanes or polyacrylates.

[0108] In particular, a lubricating composition according to the invention may comprise from 0.001% to 1% by mass of anti-foam additive(s), relative to the total weight of the lubricating composition.

[0109] It may also comprise at least one anti-corrosion agent or metal passivation agent, for example compounds such as polyisobutene succinic anhydrides, thiadiazole sulfonates, mercaptobenzothiazoles, alkyl phosphites, or alkyl amino acetic acids.

[0110] They are typically present in a lubricating composition according to the invention at contents of between 0.01% and 1% by mass, relative to the total weight of the composition. A lubricating composition used according to the invention may also comprise an aromatic or non-aromatic, alcoholic or non-alcoholic solvent, and in particular a naphthenic solvent. The naphthenic solvent makes it possible to use several additives in the form of a mixture or package of additives in the naphthenic solvent, which can then be introduced into the base oil during the formulation of the composition. In particular, a lubricating composition according to the invention may comprise from 0.01% to 5% by mass, preferably from 0.1% to 3% by mass, or even from 0.5% to 2% by mass of solvent(s), in particular naphthenic solvent(s), relative to the total weight of the composition.

[0111] According to a particular embodiment, a lubricating composition used according to the invention comprises less than 1%, in particular less than 0.1%, more particularly less than 0.01% by mass of solvent(s), in particular naphthenic solvent(s), relative to the total weight of the composition, or even is free of solvent(s), in particular naphthenic solvent(s).

[0112] In terms of formulation of a lubricating composition implemented according to the invention, said fatty alcohol(s) considered according to the invention can be added individually to a base oil or mixture of oils, then possibly other additional additives are added.

[0113] Supplementary additives may be added individually or as one or more supplementary additive blends.

[0114] Alternatively, said fatty alcohol(s) may be added to a pre-existing lubricant formulation, including in particular one or more base oils and additional additives.

[0115] Supplemental additives may have been added individually or as one or more supplemental additive blends to form the pre-existing lubricant formulation.

[0116] The pre-existing formulation may also be a lubricant formulation already commercially available.

[0117] Said fatty alcohol(s) may further be formulated in the form of an additive package, in combination with one or more complementary additives. The mixture of the additive package thus formed may then be introduced into a base oil or a mixture of base oils.

[0118] According to a particular embodiment, a lubricating composition implemented according to the invention may comprise, or even consist of:

[0119] - a base oil or a mixture of base oils, in particular as defined above;

[0120] - one or more fatty alcohols according to the invention, in particular as defined above;

[0121] - optionally one or more additives, distinct from said fatty alcohol(s), in particular chosen from anionic compounds comprising a long lipophilic hydrocarbon chain and a hydrophilic head, anti-wear additives, extreme pressure additives, antioxidants, pour point depressant (PPD) additives, anti-foaming agents, demulsifying agents, corrosion inhibitors, metal passivation agents, solvents, in particular naphthenic solvents, and mixtures thereof.

[0122] Preferably, a lubricating composition formulated according to the invention comprises, or even consists of:

[0123] - from 80% to 99.5% by mass, in particular from 90% to 99% by mass, preferably from 95% to 99% by mass, of one or more base oils, in particular chosen from base oils of group II, group III, group IV and their mixtures, in particular of group II, group III and their mixture, in particular of group II;

[0124] - from 0.01% to 10% by mass, preferably from 0.02% to 8% by mass, more particularly from 0.05% to 5% by mass, and more preferably from 0.1% to 1% by mass, of one or more fatty alcohols, in particular as defined above, notably chosen from capric alcohol, lauryl alcohol, 2-hexyldecanol, 2-octyldodecanol and their mixtures;

[0125] - from 0.1% to 30% by mass, preferably from 1% to 15% by mass, more preferably from 1% to 5% by mass, of one or more additive(s) chosen from anionic compounds comprising a long lipophilic hydrocarbon chain and a hydrophilic head, anti-wear additives, extreme pressure additives, antioxidants, pour point depressant (PPD) additives, anti-foaming agents, demulsifying agents, corrosion inhibitors, metal passivation agents, solvents, in particular naphthenic solvents, and mixtures thereof; the contents being expressed relative to the total mass of said lubricating composition. According to a particular embodiment, a lubricating composition according to the invention has a kinematic viscosity, measured at 40°C according to the ASTM D445 standard, of between 20 mm 2 / s and 800 mm 2 / s, preferably between 20 mm 2 / s and 200 mm 2 / s.

[0126] APPLICATION

[0127] The lubricating composition used according to the invention can be useful for the lubrication of moving parts in all types of mechanical systems, in particular for gas or steam turbines in the fields of aeronautics, naval, rail transport and electricity production, for compressors, in particular screw compressors, used in particular in fields such as the automobile industry, brewing, food packaging, aerospace or construction, for wind power devices, in particular for the production of electrical energy, for hydraulic systems, etc.

[0128] According to the invention, the composition according to the invention is used for the lubrication of moving parts in a screw compressor, in particular for the production of compressed air.

[0129] Advantageously, thanks to the invention, the maintenance of the dispersant properties of the lubricating composition is improved.

[0130] Thus, the lubricating composition can more particularly be used to maintain the cleanliness of a screw compressor.

[0131] Maintaining the dispersant properties of the lubricating composition, and thus maintaining the cleanliness of the mechanical system, is generally referred to by the Anglo-Saxon terminology “keep clean”.

[0132] This means that the lubricating composition used generates few, if any, deposits, varnish or any other residue on the surface of the moving parts of the mechanical system or in the lubricating composition, in particular when lubricating the mechanical system with the lubricating composition.

[0133] The dispersant properties of a lubricating composition may be evaluated by visual observation following a test according to modified ASTM D7873, for example, following oxygen bubbling in a lubricating composition at 140°C in the presence of copper and steel catalysts, or a test according to JIS K2514 at 165°C, as described in the examples. For example, the lubricating composition of the invention may be added to a mechanical system after draining a used lubricating formulation, to maintain the cleanliness of the mechanical system.

[0134] In particular, the lubricating composition considered according to the invention can be used to reduce the formation of deposits and / or varnish in said screw compressor. The screw compressor can therefore remain clean for longer and its degradation can be slowed down. In particular, the lubricating composition considered according to the invention can be used to reduce the frequency of cleaning and replacement of parts of a screw compressor. In particular, the lubricating composition considered according to the invention can be used to extend the interval between two successive maintenances of the screw compressor.

[0135] The fatty alcohol(s) according to the invention may also be used in a lubricating composition comprising at least one base oil, to improve the performance of said composition used in a screw compressor.

[0136] In particular, the fatty alcohol(s) according to the invention can be used to improve the maintenance of the dispersant properties of said composition used in a screw compressor.

[0137] More particularly, the fatty alcohol(s) according to the invention may be used to slow down or even prevent the degradation of the lubricating composition during the lubrication of moving parts in the screw compressor, in particular to reduce the formation of deposits and / or varnish in the lubricating composition, in particular during the lubrication of moving parts in the screw compressor. The fatty alcohol(s) according to the invention may in particular be used to maintain the lubricating properties of the lubricating composition during its use. The fatty alcohol(s) according to the invention thus make it possible to increase the service life of a lubricating composition while retaining high lubricating properties.

[0138] In particular, the fatty alcohol(s) may be used to increase the service life of a lubricating composition as described above in said screw compressor. In particular, the use of the fatty alcohol(s) makes it possible to extend the interval between two consecutive oil changes of said screw compressor.

[0139] Preferably, the interval between two consecutive oil changes may be at least 2000 h, preferably at least 4000 h, more preferably at least 8000 h of operation, or even at least 12000 h of operation, of said screw compressor. A lubricating composition considered according to the invention may be used to lubricate the moving parts in a screw compressor, in particular to lubricate the rotating screw(s) of a screw compressor. In particular, the mechanical system is a screw compressor for the production of compressed air. The mechanical system may be an oil-injected screw compressor. The screw compressor may be intended for various applications, for example for the automotive, brewing, food packaging, aerospace or construction sectors.

[0140] All of the characteristics and particular modes relating to fatty alcohols and to the lubricating composition comprising them also apply to the uses and processes targeted according to the invention.

[0141] The invention will now be described by means of the following examples, given by way of illustration and not limitation of the invention.

[0142] Example

[0143] Measuring cleanliness performance

[0144] The cleanliness performance of the lubricating compositions was evaluated by a test according to ASTM 7873 modified (“TOST”, acronym for “Thermal Oxidation Stability Test”), this test being modified as follows.

[0145] 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 168 h. 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.

[0146] 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;

[0147] + The glass container is covered with a rather transparent black / dark brown deposit and / or varnish and the filtered particles are black / dark brown;

[0148] ++ The glass container is covered with a transparent black deposit and / or varnish and the filtered particles are black / dark brown;

[0149] +++ The glass container is covered with a light deposit and / or clear varnish and the filtered particles are black / dark brown;

[0150] ++++ No deposit is visible on the surface of the glass container and the filtered particles are yellow / light beige.

[0151] Preparation and evaluation of compositions according to the invention and comparative compositions

[0152] Lubricating compositions according to the invention (II to 116) and comparative lubricating compositions (C1 to C5) were formulated either by adding an additive concentrate in a solvent, or by adding each additive individually, i.e. in the absence of solvent, in the mass percentages indicated in the following tables. The percentages are expressed by mass relative to the total mass of the composition.

[0153] Additives are a mixture of additives comprising one or more antioxidant, pour point depressant, extreme pressure, anti-wear, anti-corrosion additives, one or more metal passivating agents, one or more demulsifying agents and / or one or more anti-foam additives.

[0154] The compositions of the additive mixture are identical for compositions C1 and II to 17; compositions C2 and III; compositions 18 to 110; compositions C3, 112 and 113; and compositions C5, 115 and 116.

[0155] The cleanliness performance of the lubricating compositions was evaluated according to the TOST test described above. The classification of each composition is summarized in the tables below.

[0156]

[0157] Table 2

[0158] Table 3

[0159] Table 4

[0160] Table 5

[0161] Table 6

[0162] It is observed that the compositions according to the invention, comprising a fatty alcohol according to the invention, exhibit higher cleanliness at the end of the test than the compositions devoid of fatty alcohol.

[0163] Comparison of compositions 12 and 110 further shows that it is possible to obtain similar cleanliness performances for a composition comprising a group II base oil and a fatty alcohol according to the invention, but devoid of group III base oil, compared to a similar composition further comprising a group III base oil.

[0164] Comparison of compositions C5 and 116 further shows that it is possible to obtain higher cleanliness performances for a composition comprising a group IV base oil and a fatty alcohol according to the invention, but devoid of group V base oil, compared to a similar composition further comprising a group V base oil.

[0165] Two tests were also carried out according to the Japanese standard JIS K2514 (“1SOT test”, acronym for “Indiana Stirring Oxidation Test”) which confirm the results detailed above.

Claims

Claims 1. Use of a lubricating composition comprising at least one base oil and at least one linear or branched, saturated or unsaturated fatty alcohol, containing from 8 to 20 carbon atoms, for the lubrication of moving parts in a screw compressor.

2. Use according to claim 1, in which the fatty alcohol(s) are chosen from capric alcohol, lauryl alcohol, palmitic alcohol, myristyl alcohol, stearyl alcohol, 2-hexyldecanol, 2-octyldodecanol, and mixtures thereof, preferably from lauryl alcohol, 2-hexyldecanol, 2-octyldodecanol, and mixtures thereof.

3. Use according to any one of the preceding claims, in which the lubricating composition has a content of said fatty alcohol(s) less than or equal to 10% by mass, in particular varying from 0.01% to 10% by mass, more particularly varying from 0.02% to 8% by mass, preferably varying from 0.05% to 5% by mass, more preferably from 0.1% to 1% by mass, relative to the total mass of the lubricating composition.

4. Use according to any one of the preceding claims, wherein the lubricating composition comprises from 80% to 99.5% by mass, in particular from 90% to 99% by mass, preferably from 95% to 99% by mass, of one or more base oils, preferably chosen from group II base oils, group III base oils, group IV base oils, group V base oils and mixtures thereof, preferably from group II base oils and / or group III base oils, and more preferably from group II base oils, relative to the total mass of said lubricating composition.

5. Use according to any one of the preceding claims, said lubricating composition comprising at least one base oil chosen from polyalphaolefins, carboxylic acid and alcohol esters, and mixtures thereof.

6. Use according to any one of the preceding claims, said lubricating composition further comprising one or more additional additives chosen from anionic compounds comprising a long lipophilic hydrocarbon chain and a hydrophilic head, anti-wear additives, extreme pressure additives, antioxidants, pour point depressant (PPD) additives, anti-foaming agents, agents demulsifiers, corrosion inhibitors, metal passivating agents, naphthenic solvents, and mixtures thereof.

7. Use according to any one of the preceding claims, the screw compressor being a screw compressor for the production of compressed air.

8. Use according to any one of the preceding claims, for reducing the formation of deposit and / or varnish in said screw compressor.

9. Use of at least one fatty alcohol, linear or branched, saturated or unsaturated, containing from 8 to 20 carbon atoms in a lubricating composition comprising at least one base oil, to improve the performance of said composition used in a screw compressor.

10. Use according to the preceding claim, to improve the properties of maintaining the dispersing properties of said composition used in a screw compressor.

11. Use according to claim 9 or 10, for increasing the lifetime of said composition in said screw compressor, in particular for extending the interval between two consecutive oil changes of said screw compressor, more particularly so that the interval between two consecutive oil changes of said screw compressor is at least 2000 h, preferably at least 4000 h, more preferably at least 8000 h, or even at least 12000 h of operation, of said screw compressor.

12. Use according to one of claims 9 to 11, said fatty alcohol(s), said base oil(s), said screw compressor and / or said composition being as defined in any one of claims 1 to 7.

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