Improved lubricating fluids and novel sulfur-containing functional additives.

Abstract

Invention details;

Description

[0001] Description

[0002] Title: IMPROVED LUBRICATING FLUIDS AND NEW FUNCTIONAL SULFUR ADDITIVES

[0003] FIELD OF THE INVENTION

[0004] The present invention relates to a lubricating fluid, in particular a semi-synthetic fluid, comprising a novel sulfur additive having extreme pressure and / or anti-wear and / or anti-biofilm properties. The present invention also relates to the use of this novel sulfur additive in a lubricating fluid, in particular in a semi-synthetic fluid. Finally, the present invention relates to a method for lubricating a metal or a composite comprising bringing said metal or said composite into contact with a lubricating fluid comprising said sulfur additive.

[0005] TECHNICAL BACKGROUND

[0006] For many industrial processes, it is known to use fluids or greases to lubricate mechanical systems. These lubricating compositions help limit corrosion and wear of mechanical systems, in order to keep them in good condition for as long as possible. Thus, lubricating fluids are used in various fields such as the metallurgical, mining, aeronautical, and automotive industries.

[0007] They are particularly used in the metalworking industry to cool and lubricate metal parts during the production and / or machining of these parts. Used in this context, they are commonly called metalworking fluids. Indeed, they reduce heat and friction between the tool and the metal part while preventing surface burning and the release of smoke. These "metalworking fluids" correspond to all fluids used for the production, removal, shaping, quenching or even protection of metals. The use of these fluids also improves the quality of metal parts by continuously removing both the tool used and the surface of the parts from the fine particles, chips and metal filings that accumulate there.They are therefore essential in this field and are categorized into four main classes: oils, emulsifiable oils, semi-synthetic fluids and synthetic fluids. These classes are notably defined in the ASTM D2881-19 standard, Standard Classification for Metalworking Fluids and Related Materials.

[0008] Straight oils typically comprise mineral oils and do not contain water. They may contain functional additives and are not emulsifiable in the presence of water. Emulsifiable oils (also called soluble oils) typically comprise at least 30% by weight of mineral oils. They also contain emulsifiers and other types of functional additives and are then diluted in water to form a macroemulsion (with an average particle size greater than 1 pm).

[0009] Semi-synthetic fluids generally comprise less than 50% by weight of mineral oils and at least 20% by weight of water. They include emulsifiers and other functional additives. When diluted in water, they generally form microemulsions (with an average particle size of less than 1 pm).

[0010] Finally, synthetic fluids do not contain mineral oil. They are divided into synthetic solution fluid, synthetic emulsion fluid, and synthetic oil.

[0011] All these lubricating fluids, regardless of their end use, must meet numerous criteria. In addition to their tribological properties, their composition must be stable, particularly during storage. This is particularly the case for fluids containing both water and oil(s) so as to form an emulsion.

[0012] Indeed, these types of fluids are easily contaminated by microorganisms, such as bacteria or fungi, due to the presence of water in these formulations. In addition, residual oils such as hydraulic oil or gear oil can represent another form of contamination. These oils leak and mix with the fluids. They can then contribute to the proliferation of microorganisms by providing them with nutrients and creating various conditions conducive to anaerobic growth.

[0013] Also, avoiding microbial proliferation is a major issue in the field of lubricating fluids comprising both water and oil(s) and in particular for metalworking fluids (see for example “Metalworking fluid basics, in Tribology & Lubrication technology” by STLE MWF Education & Training Committee, March 2023, 54-62.). These contaminants can cause destabilization of the emulsion and / or modify the properties of the fluids. These microbial populations are also responsible for corrosive phenomena on metals. They can also form a biofilm on surfaces that prevents or hinders production or machining work and requires significant maintenance.

[0014] To combat all these phenomena, biocides are generally added to lubricating fluids. However, biocides can be harmful to users and increasingly restrictive health regulations are being put in place. In addition, their systematic use can lead to the development of strains that are resistant to them. It is therefore desirable to limit the use of biocides as much as possible and to find new compounds that are just as effective, less harmful, and more environmentally friendly. Also, there is a need for new functional additives for lubricating fluids containing both water and oil(s). In particular, there is a need for lubricating fluids containing both water and oil(s) that are effective while exhibiting good stability, including good biological stability.

[0015] An objective of the present invention is to provide novel functional, preferably multifunctional, additives for lubricating fluids comprising both water and oil(s).

[0016] Another object of the present invention is to provide improved lubricating fluids comprising both water and oil(s) that are both effective and stable.

[0017] Another objective of the present invention is to provide lubricating fluids having a stable emulsion, with limited and / or inhibited biofilm formation.

[0018] SUMMARY OF THE INVENTION

[0019] The present invention meets all or part of the above objectives.

[0020] The present inventors have surprisingly discovered that homocysteine ​​and its derivatives (i.e. the sulfur compounds of general formula (I) below) have a triple effect. These compounds combine anti-wear, extreme pressure and anti-biofilm properties in lubricating fluids, in particular in lubricating fluids comprising both water and oil(s). They can also have an anti-corrosion effect and therefore possibly be tetrafunctional.

[0021] In order to determine such anti-wear and extreme-pressure properties, the person skilled in the art may refer to: the ASTM D2783-21 standard which describes a test method for measuring the extreme-pressure (EP) properties of a lubricating fluid (Standard Test Method for Measurement of Extreme-Pressure Properties of Lubricating Fluids (Four-Ball Method)); and the IP239 (2014) standard which describes a test method for measuring the extreme-pressure and anti-wear properties of a fluid or grease (Determination of extreme pressure and anti-wear properties of lubricating fluids and greases - Four ball method European conditions).

[0022] The term "biofilm" is understood to mean in particular a multicellular cluster of microorganisms (such as bacteria, microfungi, microalgae and / or protozoa) adhering to each other and to a surface, and characterized by the secretion of a polymeric matrix. In particular, said biofilm is formed by sulfurogenic microorganisms such as sulfate-reducing bacteria (SRB) and thiosulfate-reducing bacteria (TRB). The term "anti-biofilm" is understood to mean in particular that said sulfur compounds of general formula (I) make it possible to prevent and / or limit the formation of said biofilm. It is thus understood that the fluid comprising the sulfur compound of general formula (I) is biologically stable.

[0023] Such trifunctional additives offer numerous advantages. First, they reduce the number of components and therefore the cost of fluids while improving their recyclability. In particular, their anti-biofilm activity makes it possible to reduce the number and / or quantity of biocide(s) normally required and also to reduce cleaning and maintenance operations.

[0024] In addition, sulfur compounds of general formula (I), and in particular homocysteine, are biodegradable, and possibly biosourced, which makes it possible to obtain lubricating fluids improved in terms of respect for the environment and sustainability.

[0025] Sulfur compounds of general formula (I) are particularly compatible with fluid formulations comprising both water and oil(s): the emulsions are stable and do not release H2S during storage for at least two months.

[0026] Thus, the present invention relates to a lubricating fluid comprising: a) a sulfur compound of the following general formula (I), or one of its salts: R3-X-CH(NRiR2)-(CH2)n-(S) P -Z (I) in which:

[0027] Z is a hydrogen atom or a -(CH2) group n -CH(NRiR2)-X-R3 ;

[0028] Ri and R2, identical or different, are chosen from: a hydrogen atom or a hydrocarbon chain, saturated or unsaturated, linear, branched or cyclic, aromatic or not, of 1 to 20 carbon atom(s) and which may comprise one or more heteroatom(s);

[0029] - X is chosen from -C(=O)-, -CH2- or -CN;

[0030] - R3 is:

[0031] (i) is zero when X represents -CN,

[0032] (ii) either a hydrogen atom,

[0033] (iii) either - OR a , R abeing a hydrogen atom or a hydrocarbon chain, saturated or unsaturated, linear, branched or cyclic, aromatic or not, of 1 to 20 carbon atom(s) and possibly comprising one or more heteroatom(s);

[0034] (iv) either -NRbRc, Rb and R c , identical or different, being chosen from: a hydrogen atom or a hydrocarbon chain, saturated or unsaturated, linear, branched or cyclic, aromatic or not, of 1 to 20 carbon atoms and which may comprise one or more heteroatoms; n is an integer equal to 2; and p is an integer between 1 and 8, preferably p is equal to 1 or 2, with the condition that if Z is a hydrogen atom, then p is equal to 1; b) water; c) one or more oil(s); d) one or more emulsifier(s); and e) optionally one or more functional additive(s).

[0035] The present invention also relates to the use of a lubricating fluid such as according to the invention, for the lubrication and / or cleaning of mechanical devices, for metalworking, as a hydraulic fluid, or even as a fluid for mining.

[0036] The present invention relates to the use of a sulfur compound of general formula (I) or one of its salts, as an anti-wear and / or extreme pressure and / or anti-biofilm additive, preferably in a lubricating fluid, more preferably in a lubricating fluid such as according to the invention.

[0037] The present invention also relates to a method for lubricating a metal or a composite comprising a step of bringing said metal or said composite into contact with a lubricating fluid such as according to the invention.

[0038] DETAILED DESCRIPTION

[0039] The fluid according to the invention is a lubricating fluid comprising both water and oil(s), preferably for industrial use. It can be used for the lubrication of metals or composites. More particularly, it can be used for the lubrication and / or cleaning of mechanical devices, for metalworking, as a hydraulic fluid, or as a fluid for mining, for example in turbines. The fluid according to the invention can thus be used in many industrial fields, in particular the metallurgical and mining industries.

[0040] Preferably, said fluid is a metalworking fluid and especially a semi-synthetic fluid (for example as defined in ASTM D2881-19, Standard Classification for Metalworking Fluids and Related Materials). It can be used for metal removal processes such as boring, grinding, milling or cutting; metal shaping processes such as stamping, forming or forging; or metal hardening processes.

[0041] The metals concerned are particularly iron and ferrous metals such as steel (for example stainless steel, carbon steel or low-alloy carbon steel) or cast iron; non-ferrous metals such as copper, zinc, nickel, aluminum, magnesium, zirconium, cobalt, titanium and their alloys such as brass. Among the composites, mention may be made of nickel-cemented tungsten carbide. The fluid according to the invention is preferably in the form of an emulsion, in particular an oil-in-water type emulsion.

[0042] Said fluid can be used as is, serve as a basis for a more complex formulation or be diluted in water before use (it can be called "concentrated" before dilution). Preferably, the fluid is diluted in water before use. For such dilution, 1 to 20% by weight and preferably 5 to 10% by weight of said fluid (concentrated) can be diluted in water, relative to the total weight of the diluted fluid.

[0043] When diluted in water, the fluid can form a microemulsion, preferably of the oil-in-water type. A microemulsion is understood to mean an emulsion having an average particle size less than or equal to 1 pm, for example between 0.01 and 1 pm.

[0044] In particular, said fluid is basic, i.e. with a pH strictly greater than 7, preferably between 8 and 12.

[0045] Sulfur compound of general formula (I):

[0046] In particular, the lubricating fluid according to the invention comprises a sulfur compound of the following general formula (I) or one of its salts:

[0047] R3-X-CH(NRiR2)-(CH2)n-(S) p -Z (I) in which:

[0048] - Z is a hydrogen atom when p is equal to 1, or a -(CH2) group n - CH(NRI R2)-X-R3(when p is between 2 and 8);

[0049] - R1 and R2, identical or different, are chosen from: a hydrogen atom or a hydrocarbon chain, saturated or unsaturated, linear, branched or cyclic, aromatic or not, of 1 to 20 carbon atom(s) and which may comprise one or more heteroatom(s);

[0050] - X is chosen from -C(=O)-, -CH2- or -CN;

[0051] - R3est:

[0052] (i) is zero when X represents -CN,

[0053] (ii) either a hydrogen atom,

[0054] (iii) either -ORa, R abeing a hydrogen atom or a hydrocarbon chain, saturated or unsaturated, linear, branched or cyclic, aromatic or not, of 1 to 20 carbon atom(s) and possibly comprising one or more heteroatom(s);

[0055] (iv) either -NRbRc, Rb and R c , identical or different, being chosen from: a hydrogen atom or a hydrocarbon chain, saturated or unsaturated, linear, branched or cyclic, aromatic or not, of 1 to 20 carbon atom(s) and possibly comprising one or more heteroatom(s);

[0056] - n is equal to 2; and

[0057] - p is an integer between 1 and 8, preferably p is equal to 1 or 2.

[0058] When Z is a group -(CH2)n-CH(NRiR2)-X-R3, it is understood that n and the different radicals X, Ri, R2 and R3 are respectively identical in the general formula (I): we obtain symmetrical sulfides, di- or polysulfides (see for example homocystine).

[0059] Preferably, said sulfur compound is of the following general formula (Ia):

[0060] R3-X-CH(NRiR2)-(CH2)n-SH (la) in which Ri, R2, R3, X and n are as defined above.

[0061] Heteroatoms include oxygen, nitrogen and sulfur.

[0062] In particular, Ri and R2 are hydrogen atoms.

[0063] In particular, p is an integer between 1 and 5, more preferably p is equal to 1 or 2 or 3.

[0064] Particularly preferred are compounds of general formula (I) or (Ia), for which X is -C(=O)- and R3 is -OR a , with R a as defined above. R a is preferentially H.

[0065] Preferred compounds include: homocysteine, of formula HS-(CH2)2-CH(NH2)-COOH (CAS 6027-13-0 for the L form and CAS 6027-14-1 for the D form); homocystine, of formula HOOC-CH(NH2)-(CH2)2-SS-(CH2)2-CH(NH2)-COOH (CAS 626-72-2 for the L form and CAS 870-93-9 for the D form); and dihomocysteine ​​trisulfide (HOOC-CH(NH2)-(CH2)2-SSS-(CH2)2-CH(NH2)-COOH), dihomocysteine ​​tetrasulfide, dihomocysteine ​​pentasulfide.

[0066] A very preferred sulfur compound is homocysteine.

[0067] When in the present description, reference is made to sulfur compounds of general formula (I), the salts of these compounds are included in this expression. When a salt of a compound of general formula (I) is used, it is preferably a basic salt. In particular, said salt is a metal salt or a quaternary ammonium salt. Preferably, said salt is chosen from alkali metal salts, alkaline earth metal salts and quaternary ammonium salts.

[0068] By "metals" for obtaining said metal salt, we mean in particular the metals of columns 1 to 5 (formerly IA to VA) of the periodic table of elements, as well as aluminum, tin and lead. In particular, said metal is chosen from the group consisting of: alkali metals, alkaline earth metals, scandium, titanium, zirconium, vanadium, niobium, aluminum, tin and lead. By "alkali metals" we mean the metals corresponding to group 1 (1 ère column) of the periodic table of elements. Particular mention may be made of lithium, sodium and potassium. By "alkaline earth metals" we mean the metals corresponding to group 2 (2 ème column) of the periodic table of elements. Particular mention may be made of magnesium, calcium, strontium and barium.

[0069] By "quaternary ammoniums" is meant in particular ammoniums of the following general formula (III):

[0070] + N(R5R6R7R8) (III) in which the radicals Rs, Re, R? and Rs, which may be identical or different, are chosen independently of one another from the group consisting of: the hydrogen atom, a (Ci-Cw)alkyl, a (Ce-Cio)aryl, a (Ci-Cw)alkoxy, a polyalkylalkoxy, a (Ci-Cw)alcohol and a polyol; preferably from the hydrogen atom, a (Ci-Cw)alkyl and a (Ci-Cio)alcohol. Mention may be made in particular of the ammonium of monoethanolamine ( + NH3(CH2CH2OH)), diethanolamine, triethanolamine and methyldiethanolamine.

[0071] In particular, said basic salt is chosen from monoalkali, dialkali, alkaline-earth or quaternary ammonium salts of homocysteine ​​or homocystine, preferably from dialkali or alkaline-earth salts of homocysteine ​​or homocystine.

[0072] Said basic salt is in particular chosen from the group consisting of: monosodium homocysteine, disodium homocysteine; disodium homocystine; monopotassium homocysteine, dipotassium homocysteine ​​and dipotassium homocystine. Disodium homocysteine ​​and disodium homocystine are particularly preferred.

[0073] The said sulfur compound can exist in any enantiomeric form, L-type, D-type or in racemic form. The L-form, which is found in nature, is particularly preferred.

[0074] The sulfur compound of general formula (I) is usually in solid form. It may be commercially available.

[0075] In the lubricating fluid according to the invention, the amount of said sulfur compound of general formula (I) may be between 0.1 and 30% by weight, preferably between 0.1 and 20% by weight, more preferably between 1 and 7% by weight, for example between 2 and 5% by weight relative to the total weight of the fluid. It is understood that said fluid may comprise several sulfur compounds as defined above. In this case, the total amount of these sulfur compounds may be between 0.1 and 30% by weight, preferably between 0.1 and 20% by weight, more preferably between 1 and 7% by weight, for example between 2 and 5% by weight relative to the total weight of said fluid. In the lubricating fluid according to the invention, said sulfur compound makes it possible in particular to obtain or improve the extreme pressure and / or anti-wear and / or anti-biofilm effect, preferably these three effects.

[0076] Water :

[0077] The water used can be more or less hard (hard water includes dissolved calcium and magnesium salts). Water with a hydrotimetric strength between 0 and greater than or equal to 40°f is preferably used. Demineralized water can be used in particular.

[0078] In particular, the amount of water in the fluid according to the invention is between 5 and 95% by weight, for example between 30 and 95% by weight, preferably between 55 and 90% by weight, more preferably between 55 and 80% by weight relative to the total weight of the fluid. In particular, the amount of water in said fluid is greater than or equal to, or even strictly greater than, 50% by weight, relative to the total weight of said fluid.

[0079] Oil(s):

[0080] The lubricating fluid according to the invention comprises one or more oil(s). The oil(s) may be of mineral, synthetic or bio-sourced origin (from plant or animal biomass), or mixtures thereof.

[0081] Mineral and synthetic oils can be specifically chosen from groups I to V of the API (American Petroleum Institute) classification. The API classification can be found on the NLGI (National Association of Lubricating Grease Manufacturers, Inc) website: https: / / www.nlai.org / arease-alossarv / api-aroups-iv / ). In particular, mineral oils belong to groups I to III while synthetic oils belong to groups IV and V. !

[0082] The mineral oils according to the invention include all types of oils obtained by atmospheric and vacuum distillation of crude oil, followed by refining operations such as solvent extraction, dealphating, solvent dewaxing, hydrotreatment, hydrocracking and hydroisomerization, or even hydrofinishing. Mention may in particular be made of paraffinic, naphthenic, aromatic mineral oils and their mixtures, preferably naphthenic.

[0083] The synthetic oils according to the invention can be chosen from carboxylic esters, phosphoric esters, silicones, glycols, polybutene, polyalphaolefins (PAO), alkylbenzenes, alkylnaphthalenes and their mixtures.

[0084] The oils may also be bio-sourced oils, for example esters of alcohol and carboxylic acids, which can be obtained from natural resources such as sunflower, rapeseed, palm, soybean, castor oil, etc. Preferably, said fluid comprises one or more mineral base oil(s), more preferably one or more naphthenic oil(s).

[0085] Preferably, the total quantity of oil(s) in the fluid according to the invention is between 1 and 50% by weight, more preferably between 5 and 30% by weight, for example between 5 and 20% by weight, relative to the total weight of the fluid.

[0086] The fluid according to the invention comprises one or more emulsifier(s). It may be one or more emulsifier(s) chosen from cationic, anionic, non-ionic, zwitterionic (or amphoteric) emulsifiers and their mixtures. The surfactants used may be bio-sourced. The non-ionic emulsifiers preferably have an HLB (Hydrophilic-Lipophilic Balance) of between 1 and 40.

[0087] For example, at least one emulsifier chosen from the following emulsifiers may be used.

[0088] ■ Soaps, especially alkaline soaps such as sodium or potassium soaps, ammonium soaps and amine soaps. In particular, the corresponding fatty acids in these soaps contain between 8 and 20 carbon atoms.

[0089] ■ Sulfonic acids or alkali sulfonates, preferably sodium sulfonates. Mention may be made of alkylsulfonic acids (in particular (C12-C17)alkylsulfonic acids) and alkylarylsulfonic acids such as alkylbenzenesulfonic acids and their alkali, ethanolamine or ammonium salts.

[0090] ■ Sulfonated fatty acids and sulfonated fatty acid esters, preferably comprising between 12 and 18 carbon atoms.

[0091] ■ Alkyl sulfates.

[0092] ■ Ether carboxylates, especially alkyl ether carboxylates such as glycolic acid ethoxylated oleyl ether.

[0093] ■ Alkoxylated alcohols, preferably ethoxylated or propoxylated. Said starting alcohols preferably comprise between 8 and 18 carbon atoms.

[0094] ■ Alkoxylated alkylphenols such as octyl- or nonylphenols.

[0095] ■ Primary, secondary or tertiary amines, their alkoxylated derivatives and their salts. The starting amine preferably comprises between 12 and 18 carbon atoms.

[0096] ■ Fatty amides, their polyethoxylated derivatives and their salts. The starting amides preferably comprise between 12 and 24 carbon atoms. Examples include mono- and diethanolamides of polyethoxylated fatty acids.

[0097] ■ Fatty acids and their polymeric derivatives. Said fatty acids preferably comprise from 14 to 24 carbon atoms. Particular mention may be made of tall oil fatty acid and poly(ricinoleic acids). ■ Esters of long-chain fatty acids, preferably comprising between 14 and 24 carbon atoms.

[0098] ■ Polyethylene glycol esters.

[0099] ■ Esters of polyhydric alcohols, for example pentaerythritol esters.

[0100] ■ Alkoxylated block copolymers.

[0101] ■ Anhydrosorbitol esters such as sorbitan esters and their ethoxylated derivatives.

[0102] ■ Alkylpolyglucosides.

[0103] ■ Amine oxides.

[0104] ■ Salts of phosphoric acid esters.

[0105] ■ Quaternary ammoniums such as alkyltrimethylammonium, alkylbenzyldimethylammonium, ammonium salts of ethoxylated fatty amines and imidazolinium salts.

[0106] ■ Betaines and sulfobetaines.

[0107] ■ Imidazolium salts.

[0108] Preferably, the emulsifier(s) is(are) chosen from the group consisting of: alkoxylated alcohols, fatty acids such as tall oil fatty acid, sulfonic acids, alkali sulfonates, fatty amides, polyethylene glycol esters and mixtures thereof.

[0109] In particular, the total amount of emulsifier(s) in said fluid is between 1 and 40% by weight, preferably between 1 and 30% by weight, and preferentially between 1 and 20%, for example between 5 and 15% by weight, relative to the total weight of said fluid.

[0110] Other possible functional additives:

[0111] The lubricating fluid according to the invention may also comprise one or more other functional additive(s) known to those skilled in the art, in particular chosen from alkaline reserve agents, corrosion inhibitors, anti-wear additives, extreme pressure additives, biocides, antioxidants, metal deactivators, coupling agents, friction modifying additives, flame retardants, viscosity index improving additives and anti-foam additives. It is understood that these other functional additives are different from the sulfur compounds of general formula (I) according to the invention.

[0112] In particular, the total amount of the other functional additives is between 1 and 40%, preferably between 1 and 30%, more preferably between 1 and 20%, by weight relative to the total weight of the fluid.

[0113] The following functional additives can be mentioned in particular.

[0114] ■ Bases acting as alkaline reserve agents

[0115] Examples of alkaline buffering agents used are alkanolamines, aminomethylpropanol (AMP-95), diglycolamine (DGA), monoethanolamine (MEA), monoisopropanolamine (MIPA), butylethanolamine (NBEA), dicyclohexylamine (DOHA), diethanolamine (DEA), butyldiethanolamine (NBDEA), triethanolamine (TEA), alkali and alkaline earth metal hydroxides (such as lithium, sodium, potassium or magnesium hydroxides), metal carbonates and bicarbonates (such as sodium or potassium carbonate or bicarbonate) and mixtures thereof.

[0116] The total quantity of base(s) may be between 0.1 and 10%, preferably between 0.1 and 5%, by weight relative to the total weight of the fluid.

[0117] ■ Anti-wear additives

[0118] Among the anti-wear additives, organophosphorus compounds, and more specifically organophosphosulfur compounds, are generally used. Thus, we can cite: thiophosphoric acid, thiophosphorous acid, esters and salts of these acids, alkoxylated phosphoric esters, amine phosphates, dithiophosphates and their mixtures, preferably zinc dithiophosphates. We can cite more particularly zinc dialkyldithiophosphates and zinc diaryldithiophosphates. The total quantity of anti-wear additive(s) can be between 0.1 and 10%, preferably between 0.1 and 5%, by weight relative to the total weight of the fluid.

[0119] ■ Extreme pressure additives

[0120] Organosulfur compounds, organochlorine compounds and organophosphorus compounds and their mixtures are particularly used as extreme pressure additives.

[0121] For example, we can use:

[0122] - chlorinated paraffins;

[0123] - alkyl or alkylphenol polysulfides, sulfurized olefins, sulfur esters, metal dithiocarbamates, thiadiazoles and benzothioazoles;

[0124] - alkyl phosphates or alkyl phosphonates, phosphoric acid, phosphorous acid, mono-, di- and triesters of phosphorous acid and phosphoric acid and their salts.

[0125] Their total quantity can be between 0.1 and 10%, preferably between 0.1 and 5%, by weight relative to the total weight of the fluid.

[0126] ■ Biocides

[0127] Said fluid may also comprise one or more biocide(s), with fungicidal and / or bactericidal action. Such biocides may be chosen from parabens, aldehydes, reactive acetylacetone compounds, isothiazolinones, triazines, phenolic compounds, acid salts, halogenated compounds, quaternary ammoniums, alcohols and mixtures thereof.

[0128] For example, the biocide(s) may be selected from tetrakis Hydroxymethyl Phosphonium Sulfate (THPS), optionally substituted benzisothiazolinones (BIT), such as N-butyl-1,2-benzisothiazolin-3-one, methylisothiazolinones (MIT), mixtures of methylisothiazolinone and chloromethylisothiazolinone (MIT / CMIT), orthophenyl-phenol (OPP) or its sodium salt, 3-iodo-2-propynylbutylcarbamate (IPBC), chloro-cresol and N,N-methylene-bis-morpholine (MBM), sorbic acid and mixtures thereof. More particularly, the biocide(s) may be chosen from triazines, orthophenylphenol (OPP) or its sodium salt, 3-iodo-2-propynylbutylcarbamate, chlorocresol, benzisothiazolinones and N,N-methyleneisomorpholine, preferably from triazines.

[0129] For example, the total quantity of biocide(s) may be between 0.1 and 10%, preferably between 0.1 and 5% by weight, relative to the total weight of the fluid. The total quantity of biocide(s) is preferably less than the total quantity of biocides in a conventional fluid, due to the presence of a sulfur compound such as according to the invention in the fluid.

[0130] ■ Corrosion inhibitors

[0131] In particular, boric acids and their salts, tolyltriazole and its salts, benzotriazoles and their salts, imidazolines and their salts, alkanolamines and amides, sulfonates, alkali metal and alkanolamine salts of naphthenic acids, amine salts of phosphate esters, alkali metal nitrites, alkali metal carbonates, carboxylic acids and their derivatives, alkylsulfonamide carboxylic acids, arylsulfonamide carboxylic acids, phenoxy derivatives, sodium molybdate, alkoxylated amines, tertiary polyamines such as pentamethyldipropylenetriamine and their salts, alkyl polyalkylene glycol ether phosphate salts and mixtures thereof are used as corrosion inhibitors.

[0132] Their total quantity can be between 0.1 and 10%, preferably between 0.1 and 5%, by weight relative to the total weight of the fluid.

[0133] ■ Antioxidants

[0134] As antioxidants, phenolic derivatives, amines and their mixtures are generally used, the total quantity of which can be between 0.1 and 10%, preferably between 0.1 and 5%, by weight relative to the total weight of the fluid.

[0135] ■ Metal deactivators

[0136] Triazoles are generally used as metal deactivators. Their total quantity can be between 0.1 and 10%, preferably between 0.1 and 5%, by weight, relative to the total weight of the fluid.

[0137] ■ Coupling agents

[0138] Alcohols, Cs-Cis alkoxylated alcohols, such as phenoxypropanol and isopropanol, and mixtures thereof may be added as coupling agents. Their total amount may be between 0.1 and 10%, preferably between 0.1 and 5%, by weight, relative to the total weight of the fluid.

[0139] ■ Friction modifying additives Friction modifying additives are chosen in particular from fatty acid esters, alkoxylated (di)amines and their mixtures. Their total quantity can be between 0.1 and 10% by weight, relative to the total weight of the fluid.

[0140] The fluid may also include other functional additives such as flame retardants, viscosity modifiers, thickeners such as clays, barite or galena, or manufactured iron oxides.

[0141] In particular, the lubricating fluid according to the invention does not comprise or comprises little (for example less than 10% by weight, for example between 0.1 and 10% by weight) chlorinated paraffins. In particular, the lubricating fluid according to the invention does not comprise or comprises little (for example less than 10% by weight, for example between 0.1 and 10% by weight) chlorinated compounds or more generally halogenated compounds. In particular, the lubricating fluid according to the invention does not comprise chlorinated compounds or more generally halogenated compounds as extreme pressure and / or anti-wear additives.

[0142] More particularly, said fluid comprises only a sulfur compound of general formula (I) as defined above as an extreme pressure and / or anti-wear additive.

[0143] In particular, the fluid according to the invention does not comprise a long-chain aliphatic amine and / or does not comprise a tertiary cycloalkylamine. In particular, said fluid does not comprise a C8-C24 primary amine and / or does not comprise an ethoxylated tertiary cycloalkylamine.

[0144] A preferred fluid according to the invention comprises (or consists of): between 0.5 and 20% by weight of a sulfur compound of general formula (I), as defined above; between 55 and 80% by weight of water; between 10 and 30% by weight of oil(s) as defined above; between 1 and 20% by weight of emulsifier(s) as defined above; and between 5 and 30% by weight of other functional additives, preferably chosen from alkaline reserve agents, corrosion inhibitors, anti-wear additives, extreme pressure additives, biocides, antioxidants, metal deactivators, coupling agents, friction modifying additives, flame retardants, viscosity index improving additives and anti-foaming additives, relative to the total weight of the fluid.

[0145] The fluids according to the invention can be prepared by methods conventional to those skilled in the art, in particular by mixing the different components. For example, the additives can be added to the base oil(s), then the water added at the end. Description of the Figures

[0146] Figure 1

[0147] [Fig 1] represents the experimental setup used for the Reichert test.

[0148] Figure 2

[0149] [Fig 2] shows a photograph of carbon steel coupons, exposed to homocysteine ​​(left) or cysteine ​​(right), after 7 days.

[0150] Figure 3

[0151] [Fig 3] represents the logarithmic reduction of the average concentration obtained in BSR, BTR after 7 days of contact of the marine sulfurogenic microbial consortium with 250 ppm of L-Homocysteine ​​or L-Cysteine. The white bars with black dots correspond to the logarithmic reduction of BSR and the black bars with black squares correspond to the logarithmic reduction of BTR.

[0152] EXAMPLES

[0153] EXAMPLE 1: Study of the tribological properties of lubricating fluids

[0154] 1. Preparation of lubricating fluids

[0155] 1- A lubricating fluid was prepared as described below.

[0156] Composition of the concentrated fluid before addition of the sulfur additive: mixture of monoethanolamine and triethanolamine (alkaline reserve agents): 1-5% sodium sulfonate (emulsifier): 5-10% fatty amide (emulsifier): 5-10% PEG ester (emulsifier): 1-5% tall oil fatty acid (emulsifier): 5-10% ethoxylated alcohol (emulsifier): 1-3% triazine-based biocide: 1-3% coupling agents: 1-3% naphthenic mineral oil: 10-15% water: 55-60%, by weight relative to the total weight of the concentrated fluid.

[0157] 2- A sulfur additive was then added to the concentrated fluid according to Table 1 below. The fluid was homogenized using a magnetic stirrer at room temperature (20-25°C).

[0158] The sulfur additives added at a rate of 1% sulfur in the concentrated fluid are as follows: [Table 1]

[0159] * commercial extreme pressure and anti-wear additives

[0160] ** This is the percentage by weight relative to the weight of the concentrated fluid mentioned above (i.e. not added).

[0161] 3- Finally, the obtained additive concentrated fluids were diluted to 10% by weight in demineralized water. The pH of the final dilution is measured for each formulation. A non-additive and diluted fluid serves as a control.

[0162] 2. Reichert Test

[0163] The Reichert test is a test used to determine the anti-wear properties of lubricating fluids. a) Principle of the test

[0164] A finely clamped test roll is pressed, by a double lever system, against a rough rotating slip ring ("grinding ring"), the lower third of which is immersed in the fluid whose load capacity is being tested.

[0165] The rotational speed of the drive motor and that of the slip ring which rotates directly with the motor are determined in such a way that a sufficient quantity of fluid can always penetrate into the contact point (friction wear point) between the test roller and the test ring.

[0166] As the slip ring rotates, abrasion zones (elliptical wear marks) are produced on the test roll - their size depends on the load capacity of the test roll.

[0167] The lower this wear mark after 100m of travel, the greater the load capacity (specific pressure). In addition, during the test operation, a grinding noise is audible. This noise index is also noted (the distance from which no noise is heard is determined).

[0168] This test is explained in Encyclopedia of Lubricants and Lubrication, 2014, p.2142-2144 and Figure 1 shows the experimental setup used. b) Test conditions:

[0169] The ring and the measuring roller are made of hardened steel of different hardnesses (ring: 60 H RC hardness and roller: 62 H RC hardness).

[0170] A mass equivalent to 1500 gf (gram-force) is placed on the lever on the left side of the device. The circular speed of the ring is 1.70 ms' 1 , so the test distance of 100m is reached after about 1 minute.

[0171] Fluid quantity: 30 g

[0172] Test mechanism: ring and roller, axes intersecting perpendicularly

[0173] Sliding speed: 1.7 m / sec

[0174] Duration of the test: 100m run (approximately 1 min.)

[0175] Ring and roller material: 100 CR6 steel

[0176] Normal load: 294.3 N

[0177] Type of friction: Sliding friction c) Results:

[0178] The results are reported in Table 2 below:

[0179] [Table 2]

[0180] A very significant reduction in noise index and a reduction in wear footprint are observed for fluids containing homocysteine. Homocysteine ​​therefore exhibits anti-wear properties in a lubricating fluid. These anti-wear properties are even improved compared to commercial and commonly used anti-wear additives.

[0181] 3. 4-ball test

[0182] The 4-ball test is a test used to determine the extreme pressure properties of lubricating fluids. a) Fluid preparation:

[0183] The fluid was prepared as described in paragraph 1.

[0184] The difference is that the sulfur additive is added at a rate of 3% sulfur in the concentrated fluid according to table 3 below.

[0185] [Table 3]

[0186] * commercial extreme pressure and anti-wear additives

[0187] ** This is the percentage by weight relative to the weight of the concentrated fluid mentioned above (i.e. not added).

[0188] The dilution of concentrated fluids with additives is also identical to paragraph 1.

[0189] A non-additive and diluted fluid serves as a control. b) Test conditions:

[0190] The 4-ball test was performed according to the standard method ASTM D2783-21.

[0191] In this test, the extreme pressure measurement is carried out by rotating a stainless steel ball over three stainless steel balls held stationary, the four balls being entirely covered with a lubricating fluid. A load is applied to the balls and gradually increased (every minute according to the parameters below) until the balls weld together. The balls are changed before each increase in load. The extreme pressure effect corresponds to the load value from which the four balls weld together, preventing the rotation of the top ball over the other three. The greater the load, the greater the extreme pressure effect.

[0192] The conditions are as follows:

[0193] Speed: 1450 + / - 50 rpm

[0194] 100 Cr6 steel balls c) Results:

[0195] The results are reported in Table 4 below.

[0196] [Table 4]

[0197] Free homocysteine ​​and its basic salt form are the most effective extreme pressure additives. The welding load is significantly higher when homocysteine ​​or its basic salt form are used as additives compared to other commercial products (at iso %S): homocysteine ​​and its salt form allow a welding load of up to 250 kgf, while the two commercial products do not exceed 160 kgf.

[0198] Homocysteine ​​therefore exhibits extreme pressure and anti-wear properties. These extreme pressure and anti-wear properties are even improved compared to commonly used commercial additives. EXAMPLE 2: Biological stability studies

[0199] The development of a microbial population and the formation of a biofilm were evaluated according to the presence of different sulfur additives (homocysteine ​​and cysteine) in synthetic water.

[0200] 1. Protocol:

[0201] The tests were carried out in synthetic water according to ASTM D1141-98 enriched with the additive studied and inoculated with a reference consortium, composed of microorganisms producing sulfides such as sulfate-reducing bacteria (SRB) and thiosulfate-reducing bacteria (TRB). The reference consortium therefore consists of sulfurogenic microorganisms with corrosive properties towards carbon steel.

[0202] Synthetic water is a standardized condition to accelerate microorganism-induced corrosion through biofilm formation.

[0203] Polished carbon steel coupons (Grade 600; Appendix 2) measuring 30 x 20 x 2 mm with no biofilm on their surface were immersed in synthetic water containing 5.10 6 microorganisms / mL (concentrations of microorganisms present in seawater) in the presence or absence of the different additives tested (250 ppm of each additive) for 7 days at 30°C.

[0204] The coupons are then removed from the synthetic medium and observed and analyzed using different methods.

[0205] 2. Analysis Methods and Results: a) Macroscopic Analysis:

[0206] Cysteine ​​stimulates biofilm formation on the carbon steel coupon, this phenomenon is visible macroscopically (see Figure 2). The coupon exposed to homocysteine ​​does not present this biofilm deposition. b) Quantification of viable and culturable Sulfate-Reducing Bacteria (SRB) producing corrosive sulfides for steels in liquid medium based on the NF T90-413 standard. c) Quantification of viable and culturable Thiosulfate-Reducing Bacteria (TRB) producing corrosive sulfides for steels in liquid medium based on the NF T90-413 standard.

[0207] The results of analyses b) and c) are given in Figure 3. Under the test conditions, a concentration of 250 ppm of homocysteine ​​reduces the amount of BSR by a factor of ~7 and the amount of BTR by a factor of ~10. These results highlight an anti-biofilm activity of homocysteine.

[0208] Conversely, the addition of 250 ppm cysteine ​​led to an increase of ~9 times the amount of BSR and a ~7 times the amount of BTR. These results highlight a biofilm-inducing property of cysteine.

[0209] Thus, unlike cysteine, homocysteine ​​has an anti-biofilm property.

[0210] EXAMPLE 3: Fluid stability study

[0211] A study of the stability of concentrated fluids having the same formulation as those of Example 1 (before dilution) and including different concentrations of cysteine ​​or homocysteine ​​after 83 days at room temperature was carried out.

[0212] It is observed that the emulsion comprising homocysteine ​​remains stable, unlike that comprising cysteine.

[0213] [Table 5]

[0214] These results show that the fluids according to the invention are stable and do not release H2S, which is a toxic and strongly odorous compound. These results are confirmed by the appearance of the lead acetate paper.

Claims

DEPCT6902 / 06 / 25691. Lubricating fluids which consist of: a) sulfur-containing compounds of the general formula (I) as follows or a salt of one of such compounds: R3-X-CH(NR1R2)-(CH2)n-(S)pZ(I) where:-Z is a hydrogen atom or the same or different groups of (CH2)n-CH(NR1R2)-X-R3-R1 and R2 chosen from: hydrogen atoms or saturated or unsaturated straight, branched or cyclic aromatic or non-aromatic hydrocarbon chains of 1 to 20 carbon atoms and which can be combined with heterogeneous One or more atoms -X are chosen from -C(=O)-,-CH2- or -CN-R3, i.e.:(i) none, where X represents -CN(ii) or hydrogen atoms(iii) or -ORa, where Ra is a hydrogen atom or a saturated or unsaturated straight-chain, branched or cyclic aromatic or non-aromatic hydrocarbon chain containing 1 to 20 carbon atoms and capable of incorporating one or more heteroatoms(iv) or -NRbRc,Rb and Rc, which are the same or different, chosen from: hydrogen atoms or a saturated or unsaturated straight-chain hydrocarbon chain,Branched chain or ring type aromatic or non-aromatic compounds containing 1 to 20 carbon atoms and capable of incorporating one or more heteroatoms, -n is an integer equal to 2 and -p is an integer between 1 and 8, provided that if Z is a hydrogen atom, then p is equal to 1; b) water; c) one or more oils; d) one or more emulsifying agents; and e) one or more functional additives, selectively; 2. Lubricating fluids according to claim 1, in which such sulfur-containing compounds have the general formula (Ia) as follows, or salts of sulfur. One such compound:R3-X-CH(NR1R2)-(CH2)n-SH(Ia), where R1, R2, R3, X and n are as specified in Reputation 13. A lubricating fluid according to Reputation 1 in which such compound of general formulation (I) is selected from a group consisting of: homocysteine, homocysteine, dihomocysteine ​​trisulfide, dihomocysteine ​​tetrasulfide, dihomocysteine ​​pentasulfide and one of these salts is desirablely homocysteine4. A lubricating fluid according to one of the preceding Reputations in which the amount of sulfur-containing compound of general formulation (I) is between 0.1% and 30% by weight,Desirable is between 0.1% and 20% by weight, and even more desirable is between 1% and 7% by weight when considering the total weight of the fluid.

5. Lubricating fluids under any of the preceding claims in which the water content is between 5% and 95% by weight, it is desirable to have between 55% and 80% by weight when considering the total weight of the fluid.

6. Lubricating fluids under any of the preceding claims in which the total oil content is between 1% and 50% by weight, it is desirable to have between 5% and 30% by weight when considering the total weight of the fluid.

7. Lubricating fluids under any of the preceding claims in which the emulsifying agent is selected from a group consisting of: alkoxymented alcohols, fatty acids, sulfonic acids, sulfonates of alkali metals, fatty amides,8. Esters of polyethylene glycol and mixtures of these substances.

9. Lubricating fluids according to any of the preceding claims in which the total amount of emulsifying agent is between 1% and 40% by weight, and desirable is between 1% and 30% by weight when considering the total weight of the fluid.

10. Use of any of the lubricating fluids specified in claims 1 to 8 for the lubrication and / or cleaning of mechanical equipment, for metal processing, as hydraulic fluid, or including as mining fluid.

11. Use of sulfur-containing compounds of general formulation (I) or salts of any of the compounds specified in claims 1 to 3 as additives for wear protection and / or high-pressure protection and / or prevention of biofilm formation in any of the lubricating fluids specified in claims 1 to 8.

12. Use according to claim 10 in which such sulfur-containing compounds are selected from the group consisting of: homocysteine, homocystine, dihomocysteine ​​trisulfide, dihomocysteine ​​tetrasulfide,Dihomocysteine ​​pentasulfide and one of their salts, preferably homocysteine12. A process for the lubrication of metals or composite materials which includes a step of bringing such metal or composite material into contact with a lubricating fluid as specified in any of Claims 1 to 8;