Patent Application
20250043209
The present invention relates to the field of greases, more particularly for electric motors, and more specifically for electric or hybrid vehicles.
There are many applications where liquid lubricants are not suitable because same “drift” from the lubrication point. The above involves in particular rolling and sliding bearings, open gears, steel cables and chain drives, and more generally applications without any sealing system.
For such applications, lubricating greases are used, which are solid or semi-fluid substances resulting from the dispersion of a thickener in a liquid lubricant, incorporating, possibly, additives which impart particular properties to the additives.
The thickeners may be organic or inorganic compounds.
Organic thickeners used in the manufacture of greases include in particular metal salts of fatty acids and polycarbamides (polyureas).
In addition to the lubrication function thereof, grease also serves as a sealing agent which prevents the entry of contaminants or external pollutants, which may cause a premature failure of grease and of the lubricated equipment.
Within the framework of certain applications, in particular electric motors, and more particularly in electric motors, greases are subjected to high temperatures and high speeds and should thus be apt to withstand these such stresses for as long as possible in order to prevent a failure.
Prior art greases comprising a base oil and a thickener, more particularly a polyurea thickener, sometimes have insufficient conductivity for certain applications.
It is thus a subject matter of the present invention to provide a grease composition having a higher conductivity, in particular for electric motor applications, and more particularly for electric or hybrid vehicles.
More specifically, the present invention relates to the use of a sulfonate additive to increase the electrical conductivity of a grease composition comprising at least one base oil and at least one thickener.
Preferably, the thickener is chosen from fatty acid metal salts and polyureas, preferably from polyureas, more preferably from diureas.
Preferably, the sulfonate additive is chosen from metal sulfonate salts. Preferably, the metal salt of the sulfonate salt is chosen from calcium salts, sodium salts, lithium salts, barium salts, magnesium salts, zinc salts, preferably from calcium salts, sodium salts, lithium salts, magnesium salts and zinc salts, or even preferably from calcium salts, sodium salts and advantageously from calcium salts.
Preferably, the sulfonate additive is chosen from sulfonates comprising at least one aromatic group optionally substituted by one or a plurality of aliphatic moieties.
Preferably, the sulfonate additive is chosen from sulfonates comprising at least one naphthalene moiety optionally substituted by one or a plurality of aliphatic moieties.
Preferably, the sulfonate additive is chosen from alkylnaphthalene sulfonate, dialkylnaphthalene sulfonate, alkylnaphthalene sulfonate/carboxylate and dialkylnaphthalene sulfonate/carboxylate, the alkyl moieties preferably being chosen from alkyl moieties containing from 1 to 24 carbon atoms, preferably from 3 to 18 carbon atoms, or even preferably from 5 to 12 carbon atoms.
According to one embodiment, the sulfonate additive is added in a concentration ranging from 0.1 to 10% by weight, preferably from 0.5 to 5% by weight, relative to the total weight of the grease composition after addition of the sulfonate additive.
The invention also relates to a grease composition comprising, relative to the total weight of the grease composition:
Preferably, sulfonate additive used in the grease composition according to the invention has one or more of the following features:
Hereinafter in the text, the expressions “comprised between . . . and . . . ”, “ranging from . . . to . . . ” and “varying from . . . to . . . ” are equivalent and mean that the limits are included, unless otherwise stated.
Unless otherwise indicated, the quantities in a product are expressed by weight, with respect to the total weight of the product.
The present invention relates to the use of a sulfonate additive for increasing the conductivity of a grease composition comprising at least one base oil and at least one thickener.
The sulfonate additive, as defined by the present invention, refers to a compound comprising at least one sulfonate moiety.
The sulfonate additive according to the invention may possibly be in the form of sulfonate/carboxylate complex, more particularly a sulfonate/salicylate complex.
The sulfonate additive used within the framework of the present invention is preferably chosen from sulfonate metal salts.
Preferably, the metal salt of the sulfonate salt is chosen from calcium salts, sodium salts, lithium salts, barium salts, magnesium salts, zinc salts, preferably from calcium salts, sodium salts, lithium salts, magnesium salts and zinc salts, or even preferably from calcium salts, sodium salts and advantageously from calcium salts.
According to one embodiment, the concentration of metal of the sulfonate additive ranges from 0.1 to 10% by weight, preferably from 0.5 to 8% by weight, or even preferably from 1 to 5% by weight, relative to the total weight of the sulfonate additive.
According to one embodiment, the sulfonate salt chosen from sulfonates comprising at least one aromatic moiety substituted, if appropriate, by one or a plurality of aliphatic moieties.
Within the framework of the present invention, the term “aromatic” refers to a moiety or compound comprising at least one aromatic ring. Aromatic moieties include phenyl moieties and naphthalene moieties.
Within the framework of the present invention, the term “aliphatic” refers to a group or compound not including any aromatic ring. The aliphatic moiety may be linear, branched or cyclic, saturated or unsaturated, and may comprise one or a plurality of heteroatoms. The aliphatic moieties include alkyl, alkenyl and cycloalkyl moieties, said groups moieties including possibly one or a plurality of heteroatoms, such as one or a plurality of oxygen and/or nitrogen atoms.
According to one embodiment, the sulfonate additive chosen from sulfonates comprising at least one aromatic moiety including 6 to 12 carbon atoms, substituted by one or a plurality of alkyl moieties including 1 to 24 carbon atoms.
According to a particularly preferred embodiment, the sulfonate additive is chosen from metal alkylnaphthalene sulfonate, dialkylnaphthalene sulfonate, alkylnaphthalene sulfonate/carboxylate, dialkylnaphthalene sulfonate/carboxylate, the alkyl moieties including from 1 to 24 carbon atoms and the metal content ranging from 0.1 to 10% by weight relative to the total weight of the sulfonate additive.
According to embodiment, the sulfonate additive is chosen from alkylnaphthalene sulfonate and dialkylnaphthalene sulfonate, the alkyl moieties preferably being chosen from alkyl moieties including from 1 to 24 carbon atoms, preferably from 3 to 18 carbon atoms, or even preferably from 5 to 12 carbon atoms.
According to one embodiment, the sulfonate additive is chosen from calcium dialkylnaphthalene sulfonate, the alkyl moieties preferably including from 5 to 12 carbon atoms and the calcium concentration ranging from 1 to 5% by weight relative to the total weight of the sulfonate additive.
The grease composition used according to the invention comprises one or a plurality of base oils, preferably in a concentration of at least 70% by weight, preferably ranging from 70 to 99% by weight, or even preferably from 75 to 98% by weight, preferentially from 80 to 95% by weight, with respect to the of the grease composition.
Such base oils can be chosen from base oils conventionally used in the field of lubricating oils, such as mineral oils, either synthetic or natural, animal or plant oils or mixtures thereof.
There can be a mixture of a plurality of base oils, e.g. a mixture of two, three, or four base oils.
The base oils used in grease compositions according to the invention can be, in particular, mineral or synthetic oils belonging to groups I to V as per the classes defined by the API classification (or the equivalents thereof as per the ATIEL classification) and shown in Table 1 hereinafter, or mixtures thereof.
The mineral base oils include any type of base oil obtained by atmospheric distillation and vacuum distillation of crude oil, followed by refining operations such as solvent extraction, deasphalting, solvent dewaxing, hydrotreatment, hydrocracking, hydroisomerization and hydrofinishing.
Mixtures of synthetic and mineral oils which can be biosourced, can be further used.
There is generally no limitation with regard to the use of different base oils for producing the compositions used according to the invention, except that the compositions have to have properties, in particular in terms of viscosity, viscosity index or resistance to oxidation, suitable for use in propulsion systems of an either electric or hybrid vehicle.
The base oils of the compositions used according to the invention can be further chosen from synthetic oils, such as certain carboxylic acid esters and alcohol esters, polyalphaolefins (PAO), and polyalkylene glycol (PAG) obtained by polymerization or copolymerization of alkylene oxides comprising from 2 to 8 carbon atoms, in particular from 2 to 4 carbon atoms.
The PAOs used as base oils are e.g. obtained from monomers comprising from 4 to 32 carbon atoms, e.g. from octene or decene. The weight-average molecular weight of the PAO can vary quite significantly. Preferentially, the weight-average molecular weight of the PAO is less than 600 Da. The weight-average molecular weight of the PAO can further range from 100 to 600 Da, from 150 to 600 Da, or further from 200 to 600 Da. Advantageously, the base oil or oils of the composition used according to the invention can be chosen from the base oils of group II or III.
According to an alternative embodiment, the base oil or oils of the composition used according to the invention are chosen from polyalphaolefins (PAO), polyalkylene glycols (PAG) and carboxylic acid esters and alcohols ether.
The base oil or oils preferably represent from 70 to 90% by weight, preferably from 75 to 85% by weight, of the total weight of the grease composition.
The additive-containing grease composition according to the invention comprises at least one thickener, preferably chosen from metals salts of fatty acids and polyureas.
“Polyureas”, as defined by the present invention, refer to diureas, tetraureas, hexauras, octaureas, and combinations thereof.
Metal salts of fatty acids include lithium metal salts, such as lithium 12-hydroxystearate.
According to one embodiment of the invention, the grease composition comprises, relative to the total weight of the grease composition, less than 1% by weight of calcium 12-hydroxystearate and less than 1% by weight of calcium stearate, preferably less than 0.1% by weight of calcium 12-hydroxystearate and less than 0.1% by weight of calcium stearate, or even preferably the grease composition is free of calcium 12-hydroxystearate and free of calcium stearate. Preferably, the grease composition comprises, relative to the total weight of the grease composition, less than 1% by weight of metal salt of stearic or hydroxystearic acid, preferably less than 0.1% by weight of metal salt of stearic or hydroxystearic acid, or even preferably the grease composition is free of metal salt of stearic or hydroxystearic acid.
According to a preferred embodiment of the invention, the thickener used in the context of the use according to the invention is chosen from polyureas, preferably from diureas.
The polyureas may e.g. be obtained by reaction between one or a plurality of monoamines and one or a plurality of diisocyanates.
The diisocyanates which may be used include tolylene diisocyanate, diphenyl diisocyanate, phenylene diisocyanate, diphenyl methane diisocyanate, hexane diisocyanate, decane diisocyanate, octadecane diisocyanate.
Monoamines that can be used include oleylamine, aniline, p-toluidine, stearylamine, octylamine, dodecylamine, hexadecylamine, cyclohexylamine, dicyclohexylamine.
The additive or additives represent preferably from 5 to 20% by weight, preferably from 5 to 15% by weight, or even preferably from 8 to 12% by weight, of the total weight of the grease composition.
Preferably, the sulfonate additive is added to the grease composition comprising the base oil(s) and the thickener(s) in a concentration ranging from 0.1 to 10% by weight, preferably from 0.5 to 5% by weight, relative to the total weight of the grease composition (after addition of the sulfonate additive).
The addition of the additive according to the invention serves to improve the electrical conductivity of the grease composition.
Preferably, the resistivity at 100° C. of the grease composition is decreased by a factor greater than or equal to 10, preferably greater than or equal to 100, or even preferably greater than or equal to 500, when the sulfonate additive is added to a mixture comprising at least one base oil and at least one thickener.
Preferably, the resistivity at 100° C. of the grease composition is decreased by a factor greater than or equal to 10, preferably greater than or equal to 100, or even preferably greater than or equal to 500, when the sulfonate additive is added at a concentration on the order of 5% in a mixture comprising at least one base oil and at least one thickener.
The sulfonate additive defined in the invention further serves to reduce the breakdown voltage of a grease composition comprising at least one base oil and at least one thickener, more particularly a polyurea thickener.
The sulfonate additive defined in the invention further serves to improve the resistance to fatigue of the grease composition. More particularly, a grease composition comprising a sulfonate additive as defined in the invention can keep the performance thereof in terms of electrical conductivity over time.
The grease composition having improved conductivity is preferably used in electric motors, more particularly in electric motors of electric or hybrid vehicles.
An electric vehicle is a vehicle with an electric motor as the sole means of propulsion.
A hybrid vehicle is a vehicle including an electric motor and an internal combustion engine.
The invention further relates, according to another of the aspects thereof, to a method of increasing the electrical conductivity of a grease composition, said method comprising a step of mixing at least one sulfonate additive, with at least one base oil and a thickener, the thickener preferably being a polyurea.
According to one embodiment, the method includes a step wherein the conductivity is increased. Preferably, within the framework of the method of the invention, the resistivity at 100° C. of the grease composition is reduced by a factor greater than or equal to 10, preferably greater than or equal to 100, or even preferably greater than or equal to 500, when the sulfonate additive is added at a concentration on the order of 5%.
The grease composition obtained at the end of the use or of the method according to the invention preferably has a resistivity at 100° C. of less than or equal to 1.0×108 ohm·meters, preferably less than or equal to 5.0×107 ohm·meters.
All the features and preferences described for the use according to the invention also apply to the present method.
A further subject matter of the present invention is a grease composition comprising at least one base oil, at least one thickener chosen from polyureas and at least one sulfonate additive.
The composition according to the invention comprises, with respect to the total weight of the composition grease:
The composition according to the invention comprises, with respect to the total weight of the composition grease:
Preferably, the sulfonate additive of the grease composition according to the invention has one or a plurality of the features and the preferences hereinabove for the sulfonate additive.
Thereby, according to one embodiment, the grease composition according to the invention comprises, with respect to the total weight of the grease composition:
According to one preferred embodiment, the grease composition comprises, with respect to the total weight of the grease composition:
According to one embodiment, the grease composition comprises, with respect to the total weight of the grease composition:
Preferably, the base oil of the grease composition according to the invention has one or a plurality of the features and of the preferences described hereinabove for the base oil.
Preferably, the polyurea thickener of the grease composition according to the invention has one or a plurality of the features described and of the preferences hereinabove.
The grease composition according to the invention preferably has a resistivity at 100° C. of less than or equal to 1.0×108 ohm·meters, preferably less than or equal to 5.0×107 ohm·meters.
According to one embodiment, the grease composition according to the invention further comprises at least one supplementary additive (i.e. different from the sulfonate additive), preferably chosen from antioxidant additives, anticorrosion additives, defoamer additives and mixtures thereof.
Typically, when present, the additional functional additives represent (in all) from 0.1 to 25% by weight, preferentially from 1 to 20% by weight, of the total weight of the grease composition.
The additives may be fed in individually and/or in the form of a mixture.
The lubricating composition according to the invention can comprise at least one antioxidant additive. The antioxidant additive may be chosen from phenolic or amine antioxidants.
The antioxidant additives can in particular be chosen from sterically hindered phenols, sterically hindered phenol esters and sterically hindered phenols comprising a thioether bridge, diphenylamines, diphenylamines substituted with at least one C1-C12 alkyl group, N,N′-dialkyl-aryl-diamines and mixtures thereof.
Amine compounds are another class of antioxidant additives which can be used, if appropriate, in combination with phenolic antioxidant additives. Examples of amine compounds are aromatic amines, e.g. aromatic amines with the formula NR10R11R12 wherein R10 represents an aliphatic group or a possibly substituted aromatic group, R11 represents a possibly substituted aromatic group, R12 represents a hydrogen atom, an alkyl group, an aryl group or a group with the formula R13S(O)zR14 wherein R13 represents an alkylene or an alkenylene group, R14 represents an alkyl group, an alkenyl group or an aryl group and z is 0, 1 or 2.
The grease composition according to the invention can further comprise at least one defoamer.
The defoamer can be chosen from silicones.
A grease composition according to the invention can comprise from 0.01 to 2% by weight or from 0.01 to 5% by weight, preferentially from 0.1 to 1.5% by weight or from 0.1 to 2% by weight of defoamer, with respect to the total weight of the composition.
The grease composition according to the invention can be prepared according to any method known to a person skilled in the art, for the preparation of grease. The sulfonate additive can be added to the mixture comprising at least one base oil and at least one thickener (so-called “base grease” mixture) by simple mixing and then the mixture thereby obtained can be homogenized by grinding.
The grease composition according to the invention can keep the performance thereof in terms of electrical conductivity over time.
The invention further relates to a method of lubricating at least one component of an electric motor, preferably of an electric or hybrid vehicle, said method comprising bringing the component into contact with a grease according to the invention.
All the features and preferences presented for the grease according to the invention apply to the method of lubricating the component of an electric motor according to the invention.
The invention will now be described by means of the following examples, given of course as an illustration of the invention, but not limited to.
The compositions described in Table 2 were prepared and tested.
The greases used in the examples were prepared as follows: a mixture of amines was reacted with a diisocyanate until a base grease comprising a mixture of diureas and base oil was obtained. The sulfonate additive was then added in different proportions and the grease composition was homogenized with a grinder.
The base grease (diureas and base oil) in Table 2 (CC1) had a resistivity at 100° C. of 1.19×109 ohm·meter.
The sulfonate additive is an neutral calcium dinonylnaphtalenesulfonate including approximately 2.1% by weight of calcium.
Table 2 shows the proportions of the ingredients in percentages by weight with respect to the total weight of composition.
The electrical conductivity was measured at 50° C., 100° C. and 150° C. according to the following protocol:
The results of the resistivity measurements with the ohmmeter are shown in Table 3.
3.63 × 1010
The results of Table 3 show that the addition of the sulfonate additive significantly decreases the resistivity, which is synonymous with an increase in electrical conductivity. The results also show that conductivity is improved even at low treatment rates.
The additives described in Table 4 were tested.
Grease compositions were prepared with the sulfonate additives of Table 4. Each grease composition comprises 2% by weight of sulfonate additive and 98% by weight of base grease described in example 1.
The measurements of the resistivity in ohm·meters were carried out according to the protocol described in example 1 at 100° C. and are shown in Table 5.
The results of Table 5 show that the resistivity is of the same order of magnitude as the different sulfonate additives tested.
| Number | Date | Country | Kind |
|---|---|---|---|
| FR2112986 | Dec 2021 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/084478 | 12/5/2022 | WO |
