AQUEOUS COMPOSITION FOR LUBRICATING MECHANICAL SYSTEMS

The present invention relates to an aqueous lubricant composition for lubricating moving parts in a mechanical system, comprising at least water, glycerol; and hypericin. It also relates to the use of this aqueous lubricant composition for lubricating moving parts in a mechanical system, in particular in a vehicle propulsion system.

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Description
TECHNICAL FIELD

The present invention relates to the field of lubricant compositions for the lubrication of mechanical systems, such as rolling bearings, gears, bearings or engines. The invention is more particularly directed toward proposing new aqueous lubricants.

PRIOR ART

Lubricant compositions, also called “lubricants”, are commonly used in mechanical systems for reducing friction between parts and thus protecting the parts against wear. In addition to wear phenomena, friction can oppose the relative movement of parts that are in contact and induce energy losses that are detrimental to the optimum functioning of the mechanical system.

Lubricants are used in many applications, for example in metalworking, notably for metal deforming operations, for gas or steam turbines in the aeronautical, naval, railway and power generation fields, for motor vehicle propulsion systems, for example for lubricating rolling bearings, gears, engines, etc.

The most common lubricants are hydrocarbon-based lubricants. These hydrocarbon-based lubricants are conventionally composed of one or more base oils which are generally combined with additives intended for stimulating the lubricant performance of the base oils, for instance friction-modifying additives.

Moreover, friction between the moving parts generates heat, and it may be necessary to simultaneously provide for cooling of the mechanical systems. This cooling is typically provided by a cooling fluid, different from the hydrocarbon-based lubricant, for instance air, an aqueous fluid, such as water, or a mixture of water and a glycol.

Nowadays, the development of new lubricants must take into consideration new constraints directed toward dispensing with the use of toxic or potentially toxic solvents, or toward reducing their impact on the environment and carbon dioxide emissions. In this respect, water-based formulations are of growing interest.

Although water is an excellent cooling fluid, it does not have the tribological properties required for a lubricant, particularly in terms of reducing friction and protecting parts against wear.

Water-based lubricant compositions, supplemented with various additives, have already been studied. For example, US 2012/0149616 proposes an aqueous lubricant comprising, in addition to water, water-soluble polyalkylene glycols, emulsifiers, antifreeze additives of alkylene glycol or glycerol type, anticorrosion additives, antifoaming additives and friction-reducing additives.

DISCLOSURE OF THE INVENTION

The present invention is directed toward proposing a novel water-based composition having tribological properties that are suitable for use its for the lubrication of mechanical systems. More particularly, the present invention relates, according to a first of its aspects, to an aqueous lubricant composition for lubricating moving parts in a mechanical system, comprising at least:

    • water, preferably deionized water;
    • glycerol; and
    • hypericin.

For the purposes of the present invention, the term “aqueous composition” is intended to denote a composition comprising water as the base fluid, in other words as the majority solvent. In particular, water, preferably deionized water, preferably represents more than 35% by mass of the total mass of the lubricant composition.

In the continuation of the text, the term “aqueous lubricant composition” or “aqueous lubricant” will be used to denote a lubricant composition according to the invention, intended for lubricating moving parts in a mechanical system.

For the purposes of the present invention, the term “osmosed water” is intended to denote water which has undergone a purification, notably via a reverse osmosis process, so as to reduce the content of organic and/or mineral compounds, for example to a content of less than 5.0% by weight, preferably less than 1.0% by weight. In the continuation of the text, the terms “demineralized water” or “ultrapure water” will be considered to be equivalent to or synonymous with the term “osmosed water”. In particular, osmosed water may be “deionized water”, in other words water which has undergone a purification so as to reduce the content of ions such as the Ca2+ and HCO3− ions generally present in water. Preferably, a deionized water does not comprise any ions.

Hypericin is a natural pigment found in certain species of insects and certain plants of the genus Hypericum, the common plant being St. John's wort. Hypericin is an aromatic polycyclic dione compound with numerous biological activities.

Hypericin has long been known for its use in traditional medicine, for example in the treatment of depression and the healing of wounds. In addition, hypericin is also known as an antiviral, antibacterial and antitumoral agent, or as a photosensitizer in the diagnosis and therapy of tumors.

However, to the inventors' knowledge, hypericin has never been proposed for use in lubricants intended for lubricating mechanical systems.

Contrary to all expectation, the inventors have discovered that it is possible, by supplementing a mixture of water and glycerol with hypericin, to obtain an aqueous formulation which has excellent tribological properties.

In particular, an aqueous composition according to the invention has good properties in terms of wear resistance and reduction of friction between moving parts in a mechanical system. Thus, the present invention also relates to the use of hypericin as an additive for improving the tribological properties, in particular in terms of friction reduction and wear resistance, of an aqueous composition moreover comprising at least water and glycerol, in particular comprising at least 35% by mass of water and at least 20% by mass of glycerol, relative to the total mass of the composition.

The aqueous compositions according to the invention thus prove to be suitable for use as lubricants for lubricating moving parts in a mechanical system. They can thus be used in all systems and for all applications, as a substitute for conventional hydrocarbon-based lubricants. Application examples are given in the continuation of the text.

According to yet another of its aspects, the present invention relates to the use of an aqueous lubricant composition according to the invention for lubricating moving parts in a mechanical system, in particular in a vehicle propulsion system, and more particularly in the transmission section of a vehicle propulsion system.

According to another of its aspects, the invention also relates to a process for lubricating a mechanical system (or parts in a mechanical system), comprising at least one step of placing at least one part of said mechanical system in contact with an aqueous lubricant composition according to the invention.

The invention also relates to the use of an aqueous lubricant composition according to the invention for reducing friction between moving parts in a mechanical system, and also to the use of an aqueous lubricant composition according to the invention for reducing the wear of parts in a mechanical system.

Advantageously, a composition according to the invention thus combines good cooling properties linked to the presence of water, and good tribological properties, in particular friction reduction and wear resistance. Thus, an aqueous composition according to the invention can advantageously perform the dual function of lubrication and cooling.

Thus, the present invention also relates to the use of an aqueous lubricant composition according to the invention, for lubricating and cooling moving parts in a mechanical system, in particular in a vehicle propulsion system.

It is thus possible to take advantage of an aqueous composition according to the invention to dispense with the use of two separate fluids, on the one hand a cooling fluid and on the other hand a lubricant fluid.

Also, a composition according to the invention has the advantage of being easy to formulate. In addition to the combined cooling and lubricating properties, it has good stability. Advantageously, it also has good anticorrosion properties.

Other features, variants and advantages of an aqueous lubricant composition according to the invention will emerge more clearly on reading the description and the examples that follow, which are given as nonlimiting illustrations of the invention.

The terms “between . . . and . . . ”, “ranging from . . . to . . . ”, “formed from . . . to . . . ” and “varying from . . . to . . . ” should be understood as being limits inclusive, unless otherwise mentioned. In the description and the examples, unless otherwise indicated, the percentages are weight percentages. The percentages are thus expressed on a mass basis relative to the total mass of the composition. The temperature is expressed in degrees Celsius unless otherwise indicated, and the pressure is atmospheric pressure, unless otherwise indicated.

DETAILED DESCRIPTION Aqueous Lubricant Composition

As mentioned previously, an aqueous lubricant composition according to the invention, also called an aqueous lubricant, is a formulation comprising water as the majority solvent.

For the purposes of the invention, the term “majority solvent” means that water is present in greater amount than any other solvent that may be present in the composition.

Preferably, an aqueous lubricant composition according to the invention comprises at least 35% by mass of water, preferably between 35% and 90% by mass, more preferentially between 40% and 75% by mass, relative to the total mass of the composition.

Advantageously, in addition to its role as a solvent, water affords access to a lubricant composition with good cooling properties, which can be used as a cooling fluid for moving parts in a mechanical system.

According to a particular embodiment, the water used in an aqueous lubricant composition according to the invention is deionized water, also known as demineralized water.

Deionized water does not comprise any ions, such as the Ca2+ and HCO3− ions generally present in water, which are responsible for the conduction of electricity in water.

The use of deionized water is thus particularly advantageous in the context of the use of the aqueous lubricant according to the invention for applications requiring a fluid which conducts little or no electricity, for instance for the use of the aqueous lubricant for the lubrication and cooling of mechanical systems comprising an electrical circuit, for example electric or hybrid motors, in particular in electric or hybrid vehicles.

An aqueous lubricant composition according to the invention thus differs from lubricants conventionally used in mechanical systems, which comprise a majority proportion of one or more water-insoluble oils.

The term “water-insoluble oil” notably means an oil which does not substantially dissolve in water at room temperature (at about 25° C.). In particular, a water-insoluble oil has a solubility in water of less than 0.2 g/L at room temperature.

This notably concerns lubricant base oils belonging to groups I to V according to the classes defined in the API classification (or their equivalents according to the ATIEL classification) and mixtures thereof.

Preferably, an aqueous lubricant composition according to the present invention comprises less than 5% by mass, preferably less than 2% by mass, more preferentially less than 1% by mass of water-insoluble oil(s), relative to the total mass of the composition.

Advantageously, an aqueous lubricant composition according to the invention is totally free of water-insoluble oil.

Hypericin

As mentioned previously, an aqueous lubricant composition according to the invention uses hypericin.

Hypericin, also known as 1,3,4,6,8,13-hexahydroxy-10,11-dimethylphenanthro[1,10,9,8-opqra]perylene-7,14-dione or 4,5,7,4′,5′,7′-hexahydroxy-2,2′-dimethylnaphthodianthrone, is a compound formed of eight conjugated rings containing six hydroxyl groups, two carbonyl groups and two methyl groups, having the following chemical structure:

Hypericin may be obtained via any process known to those skilled in the art.

In particular, it may be obtained from fresh or dried plants of the Hypericum genus. Hypericum perforatum, also known as St John's wort, is a rich source of hypericin.

Hypericum extracts can be readily prepared by extraction with an organic solvent, such as acetone, acetonitrile, dichloromethane, ethyl acetate, ethanol, hexane, isopropanol or methanol, or by extraction with a supercritical fluid, such as carbon dioxide in the supercritical state. An example of such a process is notably described in U.S. Pat. No. 7,195,783.

Alternatively, hypericin can be synthesized in the laboratory, according to synthetic methods known to those skilled in the art, as described, for example, in WO 2017/151111, U.S. Pat. No. 5,120,412 and EP 0 432 496.

Hypericin may also be commercially available, for example from the company Sigma-Aldrich.

The hypericin used according to the invention is generally in the form of a powder.

Preferably, hypericin is used in an aqueous lubricant composition according to the invention in an amount of from 0.01% to 5.0% by mass, preferably from 0.05% to 3.5% by mass and more preferentially from 0.1% to 1.5% by mass, relative to the total mass of the composition. In particular, a lubricant composition according to the invention may comprise water and hypericin in a water/hypericin mass ratio ranging from 100/1 to 200/1, in particular from 120/1 to 150/1.

According to an embodiment variant, it is possible to use, alternatively to or in conjunction with hypericin, one or more other polycyclic dianthraquinone compounds, and more generally one or more anthraquinone-based compounds.

Thus, more generally, an aqueous lubricant composition according to the invention may comprise one or more compounds chosen from polycyclic dianthraquinones, preferably from hypericin and derivatives thereof.

The polycyclic dianthraquinone compounds may correspond more particularly to formula (I) below:

in which:

    • R1, R6, R7 and R12 are chosen, independently of each other, from —H, —OH, —OR and —O(CO)R;
    • R3, R4, R9 and R10 are chosen, independently of each other, from —H, —R, —OH, —OR, —O(CO)R, —CH2—OH, —CH2—OR, —CH2—O(CO)R, —COOH and —COOR, preferably from —H, —OH, —OR, —O(CO)R, —CH2—OH, —CH2—OR and CH2—O(CO)R;
    • R2, R5, R8 and R11 are chosen, independently of each other, from —H, —R, —F, —Cl, —Br, —I and —SO3H, preferably from —H and —R;
    • R is an alkyl group, in particular comprising from 1 to 10 carbon atoms.

Such compounds may be obtained via any process known to those skilled in the art, such as the process described in U.S. Pat. No. 7,195,783.

Thus, according to an embodiment variant, an aqueous lubricant composition according to the invention may comprise at least water, glycerol and at least one polycyclic dianthraquinone compound, in particular chosen from hypericin and derivatives thereof, and more particularly of formula (I) as defined above.

In particular, said compound(s) of polycyclic dianthraquinone type, in particular chosen from hypericin and derivatives thereof, may be used in an amount of from 0.01% to 5.0% by mass, preferably from 0.05% to 3.5% by mass and more preferentially from 0.1% to 1.5% by mass, relative to the total mass of the composition.

Glycerol

As indicated previously, an aqueous lubricant composition according to the invention comprises at least glycerol.

Glycerol is an organic molecule containing three free hydroxyl groups, of the following formula:

Preferably, an aqueous lubricant composition according to the invention may comprise at least 20% by mass of glycerol, preferably between 20% and 75% by mass, more preferentially between 30% and 50% by mass, relative to the total mass of the composition. In particular, a lubricant composition according to the invention may comprise water and glycerol in a water/glycerol mass ratio ranging from 0.5/1 to 2/1.

In particular, a lubricant composition according to the invention may comprise glycerol and hypericin in a glycerol/hypericin mass ratio ranging from 50/1 to 300/1, in particular from 100/1 to 200/1.

According to an embodiment variant, it is possible to use, as an alternative to glycerol or in combination therewith, one or more other compounds of polyol type, in particular chosen from glycols and polyalkylene glycols.

Thus, more generally, an aqueous lubricant composition according to the invention may comprise one or more polyols, in particular chosen from glycerol, glycols, polyalkylene glycols and mixtures thereof.

The glycols are diols in which the two hydroxyl groups are borne by different carbon atoms, preferably by vicinal carbon atoms.

Preferably, the glycols are alkylene glycols, in particular containing from 2 to 10 carbon atoms, in particular from 2 to 6 carbon atoms. Examples that may be mentioned include monoethylene glycol, diethylene glycol and propylene glycol.

The polyalkylene glycols (noted “PAG”) are chosen from water-soluble polyalkylene glycols.

The term “water soluble” denotes a polyalkylene glycol having a solubility in water of at least 10 g/L, preferably at least 500 g/L, in water at room temperature (about 25° C.). The polyalkylene glycols may be more particularly formed of C1-C4, preferably C1-C3, more particularly C2-C3 alkylene oxide units.

Advantageously, a polyalkylene glycol used in an aqueous lubricant composition according to the invention comprises at least 50% by mass, in particular at least 80% by mass, more preferentially at least 90% by mass of propylene oxide and/or ethylene oxide units. It may be an ethylene oxide/propylene oxide statistical copolymer.

Preferably, a polyalkylene glycol used in an aqueous lubricant composition according to the invention has a kinematic viscosity measured at 100° C. (KV100), according to the standard ASTM D445, of between 100 and 5000 mm2/s, in particular between 150 and 3000 mm2/s. Preferably, a polyalkylene glycol used in an aqueous lubricant composition according to the invention has a kinematic viscosity measured at 40° C. (KV40), according to the standard ASTM D445, of between 500 and 30 000 mm2/s, more particularly between 1000 and 25 000 mm2/s.

The flash point of a polyalkylene glycol used in an aqueous lubricant composition according to the invention is preferably greater than or equal to 160° C., in particular greater than or equal to 220° C. The flash point can be measured by means of the standard ISO 2592 or ASTM D92.

Preferably, a polyalkylene glycol used in an aqueous lubricant composition according to the invention has a viscosity index, measured according to the standard ASTM D2270, of between 100 and 800, preferably between 250 and 550.

Thus, according to an embodiment variant, an aqueous lubricant composition according to the invention may comprise at least water, at least one polyol compound chosen from glycerol, glycols, notably alkylene glycols, polyalkylene glycols and mixtures thereof, preferably chosen from glycerol and polyalkylene glycols as defined previously, and hypericin.

In particular, said polyol compound(s) may be used in an amount of at least 20% by mass, preferably between 20% and 75% by mass, more preferentially between 30% and 50% by mass, relative to the total mass of the composition.

Thus, according to an embodiment variant, an aqueous lubricant composition according to the invention comprises at least:

    • water,
    • at least one polyol compound chosen from glycerol, glycols, notably alkylene glycols, polyalkylene glycols and mixtures thereof, preferably chosen from glycerol and polyalkylene glycols as defined previously; preferably glycerol; and
    • at least one polycyclic dianthraquinone compound, in particular chosen from hypericin and derivatives thereof, and more particularly of formula (I) as defined above, preferably hypericin.

Additives

An aqueous lubricant composition according to the invention may also comprise various additives.

It is understood that said additive(s) are compatible with their use in an aqueous medium. Advantageously, the additives are used in a water-soluble or water-emulsifiable form, for example in the form of salts or ionic liquids.

Needless to say, said additive(s) are chosen with regard to the intended application of the aqueous lubricant.

Needless to say, a person skilled in the art will take care to choose any additives and/or the amount thereof such that the advantageous properties of the aqueous lubricant composition according to the invention, in particular the tribological properties, notably in terms of reducing friction and protecting parts against wear, and of cooling, are not adversely affected by the envisaged addition.

Such additives may be chosen more particularly from antifoaming agents, biocides, pH regulators, corrosion inhibitors, antiwear and/or extreme-pressure additives, sequestrants, metal passivating agents, dyes, dispersants, emulsifying agents, and mixtures thereof. Advantageously, an aqueous lubricant composition according to the invention may comprise one or more additives chosen from antifoaming agents, extreme-pressure agents, corrosion inhibitors, pH regulators, metal passivating agents, dyes, and mixtures thereof.

An aqueous lubricant composition according to the invention may more particularly comprise from 0.1% to 10% by mass of additives, in particular from 1.0% to 8.0% by mass of additives, relative to the total mass of the composition.

Corrosion Inhibitor

An aqueous lubricant composition according to the invention may comprise at least one corrosion inhibitor. Corrosion inhibitors advantageously make it possible to reduce or even prevent the corrosion of metal parts. The nature of the corrosion inhibitor(s) can be chosen with regard to the metal to be protected against corrosion, such as aluminum, steel, galvanized steel, or yellow metals, for example copper or brass.

Among the inorganic corrosion inhibitors that may be mentioned are sodium, potassium, calcium or magnesium nitrites, sulfites, silicates, borates or phosphates, alkali metal phosphates, and zinc, magnesium or nickel hydroxides, molybdates or sulfates.

Among the organic corrosion inhibitors, mention may be made of alkanolamines, such as triethanolamine, aliphatic monocarboxylic acids, in particular containing from 4 to 15 carbon atoms, for example octanoic acid, aliphatic dicarboxylic acids containing from 4 to 15 carbon atoms, for example decanedioic acid, undecanedioic acid, dodecanedioic acid or mixtures thereof, polycarboxylic acids optionally neutralized with triethanolamine, such as 1,3,5-triazine-2,4,6-tris(6-aminocaproic acid), alkanoylamidocarboxylic acids, in particular isononanoylamidocaproic acid, and mixtures thereof. Borate-based amides, produced by the reaction of amines or amino alcohols with boric acid, may also be used.

An aqueous lubricant composition according to the invention may notably comprise from 0.1% to 5.0% by mass of corrosion inhibitor(s), preferably from 0.5% to 4.0% by mass, more preferentially from 1.0% to 2.5% by mass, relative to the total mass of the composition.

Antiwear/Extreme-Pressure Additive

An aqueous lubricant composition according to the invention may comprise at least one antiwear and/or extreme-pressure additive. Their function is to reduce wear and the coefficient of friction, or to prevent metal-to-metal contact by forming a protective film adsorbed onto these surfaces.

A wide variety of antiwear additives exists, among which mention may be made of those chosen from phosphosulfur additives such as metal alkylthiophosphates or salts thereof. Amine phosphates are also antiwear additives that may be used in a composition according to the invention.

Additives which do not supply any phosphorus may also be suitable for use, for instance polysulfides, notably sulfur-containing olefins.

Among the extreme-pressure additives that are suitable for use in the present invention, mention may be made of water-soluble extreme-pressure additives, such as 2,5-dimercapto-1,3,4-thiadiazole (DMTD) or a salt thereof, in particular a disodium salt (NaDMTD).

An aqueous lubricant composition according to the invention may comprise between 0.01% and 10% by mass of antiwear and/or extreme-pressure additive(s) as defined above, preferably between 0.5% and 5.0% by mass, relative to the total mass of the composition.

Antifoaming Agent

An aqueous lubricant composition according to the invention may comprise at least one antifoaming additive. Antifoaming agents make it possible to prevent foaming of the lubricant fluid.

This may be, for example, an antifoaming agent based on polysiloxanes or acrylate polymers. Preferably, the antifoaming agent is chosen from three-dimensional siloxanes. Also, the antifoaming agents may be polar polymers such as polymethylsiloxanes or polyacrylates.

In particular, an aqueous lubricant composition according to the invention may comprise from 0.001% to 3.0% by mass of antifoaming additive(s), preferably from 0.005% to 1.5% by mass, more preferentially from 0.01% to 1.0% by mass, relative to the total mass of the lubricant composition.

pH Regulator

An aqueous lubricant composition according to the invention may comprise at least one pH-regulating additive, in particular an alkaline buffer. The pH regulator makes it possible to maintain the desired pH of the lubricant composition, in particular so as to preserve an alkaline pH, advantageously between 8 and 11, notably so as to prevent corrosion of metal surfaces.

The pH regulator may be chosen from the family of amines, in particular alkanolamines and amino alcohols.

It may notably be a pH-regulating additive chosen from ethanolamines, such as monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), diglycolamine (DGA), isopropanolamines, such as monoisopropanolamine (MIPA), diisopropanolamine (DIPA) and triisopropanolamine (TIPA), ethylene amines, such as ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA) and tetraethylenepentamine (TEPA), alkanolamines, such as methyldiethanolamine (MDEA), cyclamines, such as cyclohexylamine, 2-amino-2-ethyl-1,3-propanediol, 2-amino-2-methyl-1-propanol and mixtures thereof.

An aqueous lubricant composition according to the invention may notably comprise from 0.1% to 10% by mass of pH-regulating additive(s), preferably from 0.5% to 5.0% by mass, relative to the total mass of the composition.

Metal Passivating Agents

An aqueous lubricant composition according to the invention may comprise at least one metal passivating agent. Metal passivating agents make it possible to protect metal parts by promoting the formation of metal oxide on their surface.

The metal passivating agents may be chosen, for example, from triazole derivatives, such as tetrahydrobenzotriazole (THBTZ), tolyltriazole (TTZ), benzotriazole (BTZ), amines substituted with a triazole group, such as N,N-bis(2-ethylhexyl)-1,2,4-triazol-1-ylmethanamine, N′-bis(2-ethylhexyl)-4-methyl-1H-benzotriazol-1-methylamine, N,N-bis(heptyl)-ar-methyl-1H-benzotriazole-1-methanamine, N,N-bis(nonyl)-ar-methyl-1H-benzotriazole-1-methanamine, N,N-bis(decyl)-ar-methyl-1H-benzotriazole-1-methanamine, N,N-bis(undecyl)-ar-methyl-1H-benzotriazole-1-methanamine, N,N-bis(dodecyl)-ar-methyl-1H-benzotriazole-1-methanamine N,N-bis(2-ethylhexyl)-ar-methyl-1H-benzotriazole-1-methanamine, 1,2,4-triazoles, benzimidazoles, 2-alkyldithiobenzimidazoles, 2-alkyldithiobenzothiazoles, 2-(N,N-dialkyldithiocarbamoyl)benzothiazoles, 2,5-bis(alkyldithio)-1,3,4-thiadiazoles, such as 2,5-bis(tert-octyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-nonyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-decyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-undecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-dodecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-tridecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-tetradecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-pentadecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-hexadecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-heptadecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-octadecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-nonadecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-eicosyldithio)-1,3,4-thiadiazole, 2,5-bis(N,N-dialkyldithiocarbamoyl)-1,3,4-thiadiazoles, 2-alkyldithio-5-mercaptothiadiazoles, and mixtures thereof.

Preferably, the metal passivating agents are chosen from tetrahydrobenzotriazole (THBTZ), tolyltriazole (TTZ), benzotriazole (BTZ), and salts thereof, taken alone or as mixtures.

An aqueous lubricant composition according to the invention may notably comprise from 0.01% to 2.0% by mass of metal passivating agent(s), preferably from 0.1% to 1.0% by mass, relative to the total mass of the composition.

Dyes

An aqueous lubricant composition according to the invention may comprise one or more dyes. The dyes may be natural or synthetic, generally organic.

The dyes that may be used in an aqueous lubricant composition may be chosen more particularly from natural or synthetic water-soluble dyes, for example the dyes FDC Red 4, DC Red 6, DC Red 22, DC Red 28, DC Red 30, DC Red 33, DC Orange 4, DC Yellow 5, DC Yellow 6, DC Yellow 8, FDC Green 3, DC Green 5, FDC Blue 1, betanine (beetroot), carmine, a chlorophylline, methylene blue, anthocyans (enocianin, black carrot and hibiscus), caramel and riboflavin.

An aqueous lubricant composition according to the invention may comprise between 0.01% and 2.0% by mass of dye(s), preferably between 0.01% and 1.5% by mass, more preferentially between 0.02% and 1.0% by mass, relative to the total mass of the composition.

Emulsifying Agents

An aqueous lubricant composition according to the invention may comprise one or more emulsifying agents, also called emulgators. Their function is to generate stable emulsions in water.

The emulsifying agents may more particularly be nonionic, for instance ethoxylated fatty alcohols, ethoxylated fatty acids, ethoxylated fatty amides; anionic, for example KOH or NaOH soaps; sulfonates; cationic, such as quaternary ammonium compounds; or water-soluble or water-emulsifiable carboxylic acid esters.

In particular, an aqueous lubricant composition according to the invention may comprise from 0.01% to 10% by mass of emulsifying agent(s), preferably from 0.1% to 5.0% by mass, relative to the total mass of the lubricant composition.

Sequestrants

An aqueous lubricant composition according to the invention may comprise at least one sequestrant. Sequestrants, also called chelating agents, make it possible to limit the incrustation of metal ions into the composition.

As examples of sequestrants, mention may be made of phosphonic acid and phosphonate derivatives, such as diethylenetriaminepentamethylphosphonic acid (DTPMPA), aminotri(methylenephosphonic acid) (ATMP), hydroxyethanediphosphonic acid (HEDP), 1-hydroxyethylidene 1,1-diphosphonate, 2-hydroxyethylaminedi(methylenephosphonic acid) (HEAMBP), diethylenetriaminepenta(methylenephosphonic acid) (DTMP), multifunctional organic acids and hydroxylated acids, such as ethylenediaminetetraacetic acid (EDTA), pteroyl-L-glutamic acid (PGLU), organic polyacids, such as maleic acid and polyaspartic acid, polysaccharides and carbohydrates, such as inulin, carboxymethylinulin and carboxymethylchitosan.

An aqueous lubricant composition according to the invention may comprise from 0.001% to 2.0% by mass of sequestrant(s), preferably from 0.01% to 1.0% by mass, relative to the total mass of the composition.

Biocides and Fungicides

An aqueous lubricant composition according to the invention may comprise at least one biocidal and/or fungicidal agent. The biocides and fungicides may be used to improve the biological stability of the composition by limiting the growth of bacteria, fungi and yeasts in the lubricant fluid.

Such biocides may be chosen from parabens, aldehydes, reactive acetylacetone compounds, isothiazolinones, phenolic compounds, acid salts, halogenated compounds, quaternary ammoniums, certain alcohols and mixtures thereof.

Preferably, the biocides may be chosen from optionally substituted benzisothiazolinones (BIT), such as N-butyl-1,2-benzisothiazolin-3-one, methylisothiazolinones (MIT), mixtures of methylisothiazolinone and chloromethylisothiazolinone (MIT/CMIT), ortho-phenylphenol (OPP) or its sodium salt, 3-iodo-2-propynylbutyl carbamate (IPBC), chlorocresol and N,N-methylenebismorpholine (MBM); sorbic acid; preferably from ortho-phenylphenol (OPP) or its sodium salt, 3-iodo-2-propynylbutyl carbamate, chlorocresol, benzisothiazolinones and N,N-methyleneisomorpholine.

An aqueous lubricant composition according to the invention may notably comprise between 0.01% and 10% by mass of biocide(s) and/or fungicide(s), preferably between 0.5% and 5.0% by mass, relative to the total mass of the composition.

Advantageously, a lubricant composition according to the invention has a kinematic viscosity, measured at 40° C. (KV40), according to the standard ASTM D445 (ISO 3104), ranging from 500 to 2000 mm2/s, in particular from 800 to 1200 mm2/s.

Advantageously, a lubricant composition according to the invention has a kinematic viscosity, measured at 100° C. (KV100), according to the standard ASTM D445 (ISO 3104), ranging from 30 to 70 mm2/s, in particular from 40 to 60 mm2/s.

According to one embodiment of the invention, an aqueous lubricant according to the invention comprises:

    • at least 35% by mass, preferably between 35% and 90% by mass, more preferentially between 40% and 75% by mass of water, in particular deionized water;
    • at least 20% by mass, preferably between 20% and 75% by mass, more preferentially between 30% and 50% by mass of glycerol;
    • from 0.01% to 5.0% by mass, preferably from 0.05% to 3.5% by mass and more preferentially from 0.1% to 1.5% by mass of hypericin,
      the contents being expressed relative to the total mass of the lubricant composition.

According to a particular embodiment, an aqueous lubricant composition according to the invention comprises:

    • at least 35% by mass of water, preferably deionized water;
    • at least 20% by mass of glycerol;
    • from 0.01% to 5.0% by mass of hypericin; and
    • optionally from 0.1% to 10% by mass of one or more additives chosen from antifoaming agents, extreme-pressure agents, corrosion inhibitors, pH regulators, metal passivating agents, dyes, emulsifying agents, sequestrants, and mixtures thereof, the contents being expressed relative to the total mass of the lubricant composition.

In particular, an aqueous lubricant composition according to the invention may consist of:

    • at least 20% by mass of glycerol;
    • from 0.01% to 5.0% by mass of hypericin; and
    • optionally from 0.1% to 10% by mass of one or more additives chosen from antifoaming agents, extreme-pressure agents, corrosion inhibitors, pH regulators, metal passivating agents, dyes, emulsifying agents, sequestrants, and mixtures thereof,
    • the contents being expressed relative to the total mass of the lubricant composition;
    • the remainder being water, preferably deionized water.

According to an embodiment variant, an aqueous lubricant composition according to the invention may comprise:

    • at least 35% by mass of water, preferably deionized water;
    • at least 20% by mass of one or more polyol compounds chosen from glycerol, glycols, notably alkylene glycols, polyalkylene glycols and mixtures thereof, preferably chosen from glycerol and polyalkylene glycols as defined previously; preferably glycerol; and
    • from 0.01% to 5.0% by mass of one or more compounds of polycyclic dianthraquinone type, in particular chosen from hypericin and derivatives thereof, and more particularly of formula (I) as defined above, preferably hypericin;
    • the contents being expressed relative to the total mass of the lubricant composition.

More particularly, according to an embodiment variant, an aqueous lubricant composition according to the invention may consist of:

    • at least 20% by mass of one or more polyol compounds chosen from glycerol, glycols, notably alkylene glycols, polyalkylene glycols and mixtures thereof, preferably chosen from glycerol and polyalkylene glycols as defined previously; preferably glycerol; and
    • from 0.01% to 5.0% by mass of one or more polycyclic dianthraquinone compounds, in particular chosen from hypericin and derivatives thereof, and more particularly of formula (I) as defined above, preferably hypericin;
    • the contents being expressed relative to the total mass of the lubricant composition;
    • the remainder being water, preferably deionized water.

More generally, the present invention thus relates to the use of at least one polycyclic dianthraquinone compound, chosen from hypericin and derivatives thereof, and more particularly of formula (I) as defined above, preferably hypericin, as an additive for improving the tribological properties, in particular in terms of friction reduction and wear resistance, of an aqueous composition comprising at least water and at least one polyol compound chosen from glycerol, glycols, notably alkylene glycols, polyalkylene glycols and mixtures thereof, preferably chosen from glycerol and polyalkylene glycols as defined previously preferably glycerol.

Applications

As mentioned previously, an aqueous lubricant composition formulated according to the invention, in particular as described previously, has excellent tribological properties, notably in terms of friction reduction and wear resistance, which makes it particularly suitable for use as a lubricant fluid.

Aqueous lubricant compositions can be used in a variety of applications. In general, they can be used as lubricant fluids for systems and applications as a substitute for conventional hydrocarbon-based lubricants.

An aqueous lubricant composition according to the invention may thus be used for lubricating gears, rolling bearings, or bearings such as rolling or sliding bearings, or motors.

By way of example, an aqueous lubricant composition according to the invention may be used for lubricating an engine, notably an internal combustion engine, for example a vehicle engine. Advantageously, it makes it possible to reduce the wear of the engine parts.

In another application variant, an aqueous lubricant composition according to the invention may be used for metal working, for example for processing metals, for example aluminum, steel, galvanized steel or yellow metals.

Advantageously, a lubricant composition according to the invention, formed mainly of water, has little toxicological impact notably with respect to persons using this lubricant.

Advantageously, although water is the majority solvent of an aqueous lubricant according to the invention, the treated surface is correctly lubricated.

Furthermore, the presence of a large proportion of water makes it easier to clean the surface to be treated, notably by simply passing over or rinsing with water.

An aqueous lubricant composition according to the invention may also find an advantageous application for the lubrication of an electric or hybrid vehicle propulsion system, and more particularly of the motor, the power electrics, the transmission and/or the battery.

An aqueous composition according to the invention may thus be used both as a cooling fluid and as a lubricant, for example in a motorization system of an electric or hybrid vehicle.

Advantageously, a composition according to the invention simultaneously affords good properties in terms of cooling and lubrication of the parts of the motorization system of an electric or hybrid vehicle.

More particularly, a composition according to the invention makes it possible to cool and lubricate an electric motor of an electric or hybrid vehicle. It notably proves to be effective for cooling the power electronics and/or the rotor and/or the stator of an electric motor. It can also ensure lubrication of the rolling bearings located between the rotor and the stator of an electric motor of an electric or hybrid vehicle.

Advantageously, a composition according to the invention makes it possible to ensure lubrication of the transmission, when it is present, in particular the gearbox, of an electric or hybrid vehicle. Also, a composition according to the invention advantageously makes it possible to effectively cool the battery present in an electric or hybrid vehicle.

Thus, advantageously, it is possible, for example, by using a single composition according to the invention, to ensure both the cooling of the battery and the lubrication of the transmission, in particular the gearbox, in an electric or hybrid vehicle.

According to the invention, the particular, advantageous or preferred features of the composition according to the invention make it possible to define uses according to the invention that are also particular, advantageous or preferred.

The invention will now be described by means of the examples that follow, which are, needless to say, given as nonlimiting illustrations of the invention.

EXAMPLES Tribological Tests

The coefficient of friction of the lubricant compositions and the ball wear in μm3 in diameter of the ball footprint are measured using a reciprocating ball-on-flat tribometer. For each test, the ball and/or flat surface mechanical parts are changed. The properties of the parts used are shown in Table 1 below.

TABLE 1 Properties of the mechanical parts used in this study SiC AISI52100 SiC Si3N4 AISI52100 ball steel ball flat flat steel flat Diameter [mm] 10 12.7 — — — Surface roughness 31.5 19.7 8.3 6.7 4.0 (Ra) [nm]

The test conditions on the reciprocating ball-on-flat tribometer are:

    • Temperature: 25° C.;
    • Frequency: 0.75 Hz;
    • Maximum contact pressure: 580 MPa;
    • Track length: 2 mm;
    • Time: 1.1 h;
    • Volume of the lubricant composition: about 50 pt.

Example 1 Preparation of the Lubricant Compositions

A reference composition (I0), comprising only glycerol and water, and a composition in accordance with the invention (I1), corresponding to composition I0 supplemented with hypericin, were prepared by simply mixing, at room temperature, of the components indicated in Table 2. The percentages are expressed on a mass basis relative to the total mass of the composition.

TABLE 2 Composition I0 I1 Deionized water [%] 50 49.82 Glycerol [%] 50 49.82 Hypericin [%] 0 0.36

Evaluation of the Properties of the Lubricant Compositions

The tribological properties of the aqueous compositions thus prepared were evaluated in accordance with the measurement protocol detailed above.

The results are collated in Tables 3 and 4 below.

TABLE 3 Coefficient of friction measured for each ball- on-flat configuration and for each composition Composition I0 I1 SiC ball - Si3N4 flat 0.081 0.071 Steel ball - Steel flat 0.180 0.100 Steel ball - Si3N4 flat 0.020 0.010 Steel ball - SiC flat 0.100 0.010

TABLE 4 Ball footprint diameter (in μm3) measured for each ball-on-flat configuration and for each composition Composition I0 I1 SiC ball - Si3N4 flat 1.80 × 104 1.50 × 104 Steel ball - Steel flat 2.90 × 104 0.40 × 104 Steel ball - Si3N4 flat 1.35 × 104 0.80 × 104 Steel ball - SiC flat 0.30 × 104 0.20 × 104

It is clear from these examples that the composition in accordance with the invention (I1) has reduced wear and a reduced coefficient of friction compared to the reference composition (I0), which does not contain hypericin.

Claims

1. An aqueous lubricant composition for lubricating moving parts in a mechanical system, comprising at least:

water, preferably deionized water;
glycerol; and
hypericin.

2. The aqueous lubricant composition as claimed in claim 1, comprising at least 35% by mass, preferably between 35% and 90% by mass, more preferentially between 40% and 75% by mass of water, relative to the total mass of the composition.

3. The aqueous lubricant composition as claimed in claim 1 or 2, comprising at least 20% by mass, preferably between 20% and 75% by mass, more preferentially between 30% and 50% by mass of glycerol, relative to the total mass of the composition.

4. The aqueous lubricant composition as claimed in any one of the preceding claims, comprising from 0.01% to 5.0% by mass, preferably from 0.05% to 3.5% by mass, more preferentially from 0.1% to 1.5% by mass of hypericin, relative to the total mass of the composition.

5. The aqueous lubricant composition as claimed in any of the preceding claims, also comprising at least one additive chosen from antifoaming agents, biocides, pH regulators, corrosion inhibitors, antiwear and/or extreme-pressure additives, sequestrants, metal passivating agents, dyes, dispersants, emulsifying agents, and mixtures thereof, preferably chosen from antifoaming agents, extreme-pressure agents, corrosion inhibitors, pH regulators, metal passivating agents, dyes, and mixtures thereof.

6. The aqueous lubricant composition as claimed in any of the preceding claims, comprising less than 5% by mass, preferably less than 2% by mass, more preferentially less than 1% by mass of water-insoluble oil(s), relative to the total mass of said composition.

7. The aqueous lubricant composition as claimed in any of the preceding claims, said composition being free of water-insoluble oil.

8. The use of an aqueous lubricant composition as claimed in any of the preceding claims, for lubricating moving parts in a mechanical system, in particular in a vehicle propulsion system.

9. The use of an aqueous lubricant composition as defined in any one of claims 1 to 7, for lubricating and cooling moving parts in a mechanical system, in particular in a vehicle propulsion system.

10. The use of hypericin as an additive for improving the tribological properties, in particular in terms of friction reduction and wear resistance, of an aqueous composition moreover comprising at least water and glycerol.

11. The use as claimed in the preceding claim, said aqueous composition comprising at least 35% by mass of water and at least 20% by mass of glycerol, relative to the total mass of said composition.

Patent History
Publication number: 20240060001
Type: Application
Filed: Jun 21, 2021
Publication Date: Feb 22, 2024
Inventors: Maria Isabel DE BARROS BOUCHET (ECULLY), Yun LONG (LYON), Jean-Michel MARTIN (CHAZAY D'AZERGUES), Benoît THIEBAUT (SOLAIZE), Chantal BOYER (SOLAIZE)
Application Number: 18/012,394
Classifications
International Classification: C10M 173/02 (20060101);