Patent Application
20230024398
The present application relates to new lubricant compositions, in particular for reducing friction between mechanical parts, preferably between two parts of an engine, such as a vehicle engine. For example, the lubricant compositions according to the invention can be used to lubricate an internal combustion engine, in particular a vehicle engine, in particular a motor vehicle engine.
The purpose of lubricants is to reduce friction and wear of mechanical parts, especially in vehicle engines, and more particularly in motor vehicles.
To reduce these friction phenomena, it is known to incorporate friction modifiers in lubricants.
Among friction modifiers, organomolybdenum compounds represent a family of compounds whose friction-reducing properties have been widely described. However, it is known to the person skilled in the art that the use of organomolybdenum compounds, in particular organomolybdenum compounds comprising a dithiocarbamate group, can worsen the wearing of mechanical parts. Other solutions were then proposed to reduce friction between two mechanical parts.
Among these alternatives, polymeric organic friction modifiers are currently sometimes used.
For example, WO2011/116049 describes one type of polymeric organic friction modifier of interest.
This type of polymeric friction modifier makes it possible to achieve coefficients of friction between mechanical parts that are sometimes too high for the applications envisaged.
There is therefore a particular interest in the provision of lubricant compositions to reduce friction between mechanical parts.
One objective of the present application is to provide lubricant compositions for reducing friction between mechanical parts.
Further objectives will become apparent from the following description of the invention.
These objectives are fulfilled by the present invention which provides a lubricant composition comprising, based on the total weight of the lubricant composition:
R1.[(AO)n.-AO—R2]m (I)
More particularly, the inventors have surprisingly discovered that the combination of a polymeric organic friction modifier of the above type and an ester preferably selected from glycerol esters, citric acid esters, tartaric acid esters and mixtures thereof significantly improves the friction coefficient between mechanical parts.
Indeed, it has been discovered by the inventors that the ester chosen more particularly among glycerol esters, citric acid esters, tartaric acid esters and their mixture allows to boost surprisingly the effect of the polymeric organic friction modifier.
According to another preferred alternative, the polymeric organic friction modifier has a weight average molecular weight of from 3,000 to 8,000 Daltons. The weight average molecular weight can be measured by steric exclusion chromatography.
Application WO2011/116049 describes, for example, polymeric organic friction modifiers.
The polymeric organic friction modifier is built around a central group R1.
The central group R1 is the residue of a compound containing at least m hydrogen atoms, obtained after removal of said m hydrogen atoms.
Preferably, the m hydrogen atoms are hydrogen atoms of groups selected from amino groups and hydroxyl groups, and are advantageously hydrogen atoms of hydroxyl groups.
Preferably, the central group R1 is the residue of a substituted hydrocarbyl group, in particular a C3 to C30 substituted hydrocarbyl compound.
Preferably, the central group R1 is a residue of a compound containing at least m hydrogen atoms, obtained after removal of m hydrogen atoms, said compound being selected from:
Preferably, the central group R1 is a residue of a compound containing at least m hydrogen atoms, obtained after removal of m hydrogen atoms, said compound having at least 3, preferably 4 to 10, in particular 5 to 8, advantageously 6 groups selected from amino groups and hydroxyl groups.
Preferably, the central group R1 is a residue of a compound comprising at least 3, preferably 4 to 10, in particular 5 to 8, advantageously 6 hydroxyl groups.
Even more preferably, the central group R1 comprises a C4 to C7 linear chain, more preferably C6.
The hydroxyl or amino groups are preferably directly linked to the carbon atoms of the linear chain of the central group R1.
Advantageously, the central group R1 is a residue of a compound selected from open chain tetratol, open chain pentitol, open chain hexitol and open chain heptitol, or an anhydro compound derived from a compound selected from tetratol, pentitol, hexitol and heptitol, for example an anhydro cycloether group derived from a compound selected from tetratol, pentitol, hexitol and heptitol.
In a particularly preferred embodiment, the central group R1 is a residue of a sugar, more preferably of a monosaccharide, preferably selected from glucose, fructose and sorbitol, of a disaccharide, preferably selected from maltose, palitose, lactitol and lactose, or of an oligosaccharide with a degree of polymerisation higher than 2.
Advantageously, the central group R1 is the residue of a monosaccharide, preferably selected from glucose, fructose and sorbitol, and in particular a sorbitol residue.
The central group R1 is preferably in open chain form. However, the central group R1 may also comprise an internal cyclic ether function when the central group R1 synthesis pathway exposes it to relatively high temperatures or other conditions that favour such cyclisation.
The index m is a measure of the functionality of the central group R1.
The index m is preferably greater than 3, preferably greater than or equal to 4 and less than or equal to 10, in particular greater than or equal to 5 and less than or equal to 8, advantageously greater than or equal to 5 and less than or equal to 6.
The index m can be a whole number or a decimal.
The R2 groups are the terminal groups of the (poly)alkylene oxide chains of the polymeric organic friction modifier of formula (I).
R2 is a hydrogen atom or a C—(O)—R3 group with R3 being a residue of a polyhydroxyalkyl carboxylic acid, a residue of a polyhydroxyalkenyl carboxylic acid, a residue of a hydroxyalkyl carboxylic acid, a residue of a hydroxyalkenyl carboxylic acid, a residue of an oligomer of a hydroxyalkyl carboxylic acid and/or a residue of an oligomer of a polyhydroxyalkenyl carboxylic acid.
Hydroxyalkyl carboxylic acid and hydroxyalkenyl carboxylic acid have the formula HO—X—COOH, wherein X is a divalent saturated or unsaturated, preferably saturated, aliphatic radical containing at least 8 and at most 20 carbon atoms, typically from 11 to 17 carbon atoms, and in which there are at least 4 carbon atoms between the hydroxyl group and the carboxylic acid group.
Preferably, the hydroxyalkyl carboxylic acid is 12-hydroxystearic acid.
In practice, hydroxyalkyl carboxylic acids are commercially available as mixtures of the hydroxylic acid and the corresponding unsubstituted fatty acid. For example, 12-hydroxystearic acid is typically made by hydrogenating castor oil fatty acids comprising the unsaturated C18 hydroxyl acid and the unsubstituted fatty acids (oleic and linoleic acids) which, on hydrogenation, give a mixture of 12-hydroxystearic acid and stearic acid.
Commercially available 12-hydroxystearic acid typically contains about 5-8% unsubstituted stearic acid.
Polyhydroxyalkyl carboxylic acid and polyhydroxyalkenyl carboxylic acid are manufactured by polymerisation of hydroxyalkyl carboxylic acid or hydroxyalkenyl carboxylic acid, respectively. Hydroxyalkyl carboxylic acid and hydroxyalkenyl carboxylic acid are as defined above.
The presence of the corresponding unsubstituted fatty acid in commercially available hydroxyalkyl carboxylic acids acts as a terminating agent and thus limits the chain length of the polymer. Preferably, the number of monomer units in the polyhydroxyalkyl carboxylic acid and in the polyhydroxyalkenyl carboxylic acid is on average from 2 to 10, preferably from 4 to 8 and advantageously about 7.
The molecular weight of the polyhydroxyalkyl carboxylic acid and polyhydroxyalkenyl carboxylic acid is typically 600 to 3000 g/mol, in particular 900 to 2700 g/mol, more particularly 1500 to 2400 g/mol and advantageously about 2100 g/mol.
Polyhydroxyalkyl carboxylic acid and polyhydroxyalkenyl carboxylic acid are characterised by a residual acid number of less than 50 mg KOH/g, preferably between 30 and 35 mg KOH/g.
Preferably, the hydroxyl value of the polyhydroxyalkyl carboxylic acid and the polyhydroxyalkenyl carboxylic acid is less than or equal to 40 mg KOH/g, advantageously between 20 and 30 mg KOH/g.
The hydroxyalkyl carboxylic acid oligomer and polyhydroxyalkenyl carboxylic acid oligomer differ from polyhydroxyalkyl carboxylic acid and polyhydroxyalkenyl carboxylic acid in that the terminus is not the corresponding unsubstituted fatty acid. Desirably, the hydroxyalkyl carboxylic acid oligomer and the polyhydroxyalkenyl carboxylic acid oligomer are dimers of hydroxylalkyl carboxylic acid and hydroxyalkenyl carboxylic acid, respectively.
The alkylene oxide residue AO is a group of the formula —(CrH2rO), where r is 2, 3 or 4, preferably 2 or 3, i.e. an ethylene oxide residue (—C2H4O—) or a propylene oxide residue (—C3H6O—). AO can represent different groups along the alkylene oxide chain (AO)n.
Preferably, (AO)n is a homopolymeric chain of the formula (—C2H4O—)n, n being between 1 and 100.
Alternatively, (AO)n is a homopolymeric chain of porpylene oxide group of the formula (—C3H6O—)n, where n is between 1 and 100.
Alternatively, (AO)n is a block or random copolymer chain containing both ethylene oxide (—C2H4O—) and propylene oxide (—C3H6O—) residues. According to this embodiment, the molar proportion of ethylene oxide units (—C2H4O—) in the copolymer chain is at least 50%, preferably at least 70%.
The parameter n represents the number of alkylene oxide residues in the (poly)alkylene oxide (AO)nchains. Preferably, n is between 2 and 50, preferably between 3 and 20, advantageously between 5 and 10. The total of the indices n (i.e. n x m) is preferably between 10 and 300, preferably between 20 and 100, in particular between 5 and 70, advantageously between 30 and 50. The value of the index n is an average value, which includes the statistical variation of the length of the chain.
When the number of acyl residues —C—(O)—R3 in the polymeric organic friction modifier of formula (I) is significantly less than m, the distribution of these groups depends on the nature of the central group R1.
When the central group R1 is derived from pentaerythritol, the alkoxylation of pentaerythritol is evenly distributed over the four available sites to remove one hydrogen, and the distribution of acyl groups is close to the expected random distribution.
When the central group R1 is derived from compounds where the m hydrogen atoms are not equivalent, e.g. sorbitol, the alkoxylation will give unequal lengths of (poly)alkylene oxide chains. The introduction by esterification of —C—(O)—R3 residues onto the shorter (poly)alkylene oxide chains can be relatively difficult due to the strong steric effects exerted by the longer (poly)alkylene oxide chains. The introduction by esterification of —C—(O)—R3 acyl residues in this case takes place preferentially in the longer (poly)alkylene oxide chains.
The polymeric organic friction modifier of formula (I) is prepared from the compound containing at least m hydrogen atoms.
The first step in the preparation of the polymeric organic friction modifier of formula (I) is an alkoxylation of the groups containing the at least m hydrogen atoms. Alkoxylation is carried out by techniques well known to the skilled person, for example by reacting the compound containing at least m hydrogen atoms with the required amounts of alkylene oxide, for example ethylene oxide and/or propylene oxide.
The second step in the preparation of the polymeric organic friction modifier of formula (I) is to react the alkoxylated species obtained from the first step with a polyhydroxyalkyl carboxylic acid and/or a polyhydroxyalkenyl carboxylic acid and/or a hydroxyalkyl carboxylic acid and/or a hydroxyalkenyl carboxylic acid under standard catalysed esterification conditions at temperatures up to 250° C.
The lubricant composition according to the invention comprises from 0.005 to 10 wt %, preferably from 0.05 to 5 wt %, more preferably from 0.1 to 3 wt %, more preferably from 0.2 to 2 wt %, of polymeric organic friction modifier(s) as defined above, based on the total weight of the lubricant composition
The lubricant composition according to the invention comprises from 0.005 to 10% by weight, preferably from 0.05 to 5% by weight, preferably from 0.1 to 3% by weight, more preferably from 0.2 to 2% by weight, of at least one ester selected from glycerol esters, citric acid esters, tartaric acid esters, and mixtures thereof, based on the total weight of the lubricant composition.
The ester used according to the invention may be a mono-, di- or tri-ester. It can be a mixture of mono-, di- and/or tri-esters. Preferably, the ester used according to the invention comprises at least one triester.
Preferably, the ester is selected from glycerol esters, citric acid esters and mixtures thereof.
According to one embodiment of the invention, the glycerol ester is an ester of glycerol and a carboxylic acid having from 1 to 10 carbon atoms, preferably from 2 to 8 carbon atoms. Preferably, the carboxylic acid is a monocarboxylic acid. In one embodiment of the invention, the glycerol ester is selected from glycerol heptanoates and mixtures thereof.
The carboxylic acids used to prepare the glycerol ester are saturated or unsaturated, linear, cyclic or branched carboxylic acids, optionally substituted with hydroxyl and/or epoxy groups.
Preferably, the carboxylic acid used to prepare the glycerol ester is linear and saturated and has a hydrocarbon chain consisting of carbon and hydrogen atoms. In other words, according to a particular embodiment, the carboxylic acid used to prepare the glycerol ester does not comprise any heteroatoms other than those of the acid function.
In one embodiment, the glycerol ester is obtained from raw materials of renewable origin. The carboxylic acids that can be used to form the glycerol ester are, for example, carboxylic acids derived from vegetable oils, fats, of animal or vegetable origin, such as butyric acid, valeric acid, caproic acid, heptylic acid, caprylic acid, pelargonic acid, capric acid, crotonic acid, iso-crotonic acid, sorbic acid, isovaleric acid, taken alone or mixed. In another embodiment, the glycerol ester is obtained from raw materials of fossil origin. These are known as synthetic carboxylic acids. Synthetic carboxylic acids such as butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, taken alone or mixed, may also be used.
The glycerol esters used in the invention can be obtained by methods well known to the skilled person, for example by reacting carboxylic acids with glycerol. These chemical reactions, which are well known to the skilled person, can take place with or without a catalyst, with or without a solvent.
According to one embodiment, the glycerol ester used in the lubricant composition according to the invention is glycerol triheptanoate.
According to one embodiment, the tartaric acid ester is an ester of tartaric acid and an alcohol having from 1 to 10 carbon atoms, preferably from 2 to 8 carbon atoms. Preferably, the alcohol used to prepare the tartaric acid ester is a monoalcohol.
In one embodiment of the invention, the tartaric acid ester is selected from tartaric acid triesters.
According to one embodiment, the citric acid ester is an ester of citric acid and an alcohol having 1 to 10 carbon atoms, preferably 2 to 8 carbon atoms. Preferably, the alcohol used to prepare the citric acid ester is a monoalcohol.
In one embodiment of the invention, the citric acid ester is selected from citric acid triesters.
The alcohols used to prepare the citric acid ester or tartaric acid ester are saturated or unsaturated, linear, cyclic or branched alcohols, optionally substituted by acid and/or epoxy groups.
Preferably, the alcohol used to prepare the citric acid ester or tartaric acid ester is linear and saturated and has a hydrocarbon chain consisting of carbon and hydrogen atoms. In other words, according to a particular embodiment, the alcohol used to prepare the citric acid ester or tartaric acid ester does not comprise any heteroatoms other than those of the hydroxyl function.
The citric acid esters or tartaric acid esters used in the invention can be obtained by methods well known to the person skilled in the art, for example by reacting citric acid or tartaric acid with one or more alcohols. These chemical reactions, which are well known to the skilled person, can take place with or without a catalyst, with or without a solvent.
In one embodiment, the citric acid ester is selected from triethylcitrate, tributylcitrate and mixtures thereof.
According to an embodiment of the invention, the ester of the lubricant composition is selected from:
According to one embodiment of the invention, the ester of the lubricant composition is selected from glycerol triheptanoate, triethylcitrate, tributylcitrate and mixtures thereof.
The lubricant composition according to the invention comprises one or more base oils, preferably in an amount of at least 50% by weight, more preferably at least 60% by weight or even at least 70% by weight, based on the total weight of the lubricant composition.
The base oil(s) may be selected from the mineral, synthetic or natural, animal or vegetable lubricating base oils known to the skilled person.
The base oils used in the lubricant compositions according to the invention may be oils of mineral or synthetic origin belonging to groups I to V according to the classes defined in the API classification (or their equivalents according to the ATIEL classification) (table 1) or mixtures thereof.
Mineral base oils according to the invention include all types of base oils obtained by atmospheric and vacuum distillation of crude oil, followed by refining operations such as solvent extraction, de-alkalization, solvent dewaxing, hydrotreating, hydrocracking, hydroisomerization and hydrofining.
Mixtures of synthetic and mineral oils can also be used.
There is generally no limitation on the use of different lubricating bases to make the lubricant compositions according to the invention, except that they must have properties, in particular viscosity, viscosity index, sulphur content, resistance to oxidation, suitable for their use.
The base oils of the lubricant compositions according to the invention may also be chosen from synthetic oils, such as certain esters of carboxylic acids and alcohols, and from polyalphaolefins. Polyalphaolefins used as base oils are for example obtained from monomers with 4 to 32 carbon atoms, for example from octene or decene, and whose viscosity at 100° C. is between 1.5 and 15 mm2.s−1 according to ASTM D445. Their average molecular weight is generally between 250 and 3,000 according to ASTM D5296.
According to one particular embodiment, the lubricant composition according to the invention comprises from 60% to 99.5% by weight of base oils, preferably from 70% to 99.5 by weight of base oils, relative to the total weight of the composition.
Many additional additives can be used for this lubricant composition according to the invention.
Preferred additional additives for the lubricant composition according to the invention are selected from detergent additives, anti-wear additives other than phospho-sulphur additives, friction modifying additives other than the polymeric organic friction modifiers defined above, extreme pressure additives, dispersants, pour point depressants, anti-foaming agents, thickeners and mixtures thereof.
Preferably, the lubricant composition according to the invention comprises, based on the total weight of lubricant composition:
Amine phosphates are anti-wear additives which can be used in the lubricant composition according to the invention. However, the phosphorus provided by these additives can act as a poison for automotive catalytic systems as these additives are ash generators. These effects can be minimised by partially substituting amine phosphates with non-phosphorous additives, such as polysulphides, especially sulphur-containing olefins.
Advantageously, the lubricant composition according to the invention may comprise from 0.01 to 6 wt. %, preferably from 0.05 to 4 wt. %, more preferably from 0.1 to 2 wt. % based on the total weight of lubricant composition, anti-wear additives and extreme pressure additives.
Advantageously, the lubricant composition according to the invention may comprise at least one additional friction modifier additive different from the polymeric organic friction modifiers defined above. The additional friction modifier additive may be selected from a compound providing metallic elements and an ash-free compound. Among the compounds providing metallic elements, we can mention transition metal complexes such as Sb, Sn, Fe, Cu, Zn, Mo whose ligands can be hydrocarbon compounds comprising oxygen, nitrogen, sulphur or phosphorus atoms.
Advantageously, the lubricant composition according to the invention may comprise at least one antioxidant additive.
The antioxidant additive generally delays the degradation of the lubricant composition in service. This degradation may result in the formation of deposits, the presence of sludge or an increase in the viscosity of the lubricant composition.
Antioxidant additives act as radical inhibitors or hydroperoxide destroyers. Commonly used antioxidant additives include phenolic antioxidant additives, amine antioxidant additives and phosphosulphur antioxidant additives. Some of these antioxidant additives, e.g. phosphosulphur antioxidant additives, can be ash-forming. Phenolic antioxidant additives can be ash-free or in the form of neutral or basic metal salts. The antioxidant additives may in particular be selected from sterically hindered phenols, sterically hindered phenol esters and sterically hindered phenols comprising a thioether bridge, diphenylamines, diphenylamines substituted by at least one C1-C12, alkyl group, N,N′-dialkyl-aryl-diamines and mixtures thereof.
Preferably according to the invention, the sterically hindered phenols are chosen from compounds comprising a phenol group in which at least one vicinal carbon of the carbon bearing the alcohol function is substituted by at least one C1-C10, alkyl group, preferably a C1-C6, alkyl group, preferably a C4, alkyl group, preferably by the ter-butyl group.
Amino compounds are another class of antioxidant additives that can be used, possibly in combination with phenolic antioxidant additives. Examples of amino compounds are aromatic amines, for example aromatic amines of the formula NR7R8R9 where R7 represents an aliphatic group or an aromatic group, optionally substituted, R8 represents an aromatic group, optionally substituted, R9 represents a hydrogen atom, an alkyl group, an aryl group or a group of formula R10S(O)zR11 in which R19 represents an alkylene group or an alkenylene group, R11 represents an alkyl group, an alkenyl group or an aryl group and z represents 0, 1 or 2.
Sulphurised alkyl phenols or their alkali and alkaline earth metal salts can also be used as antioxidant additives.
Another class of antioxidant additives are copper compounds, e.g. copper thio- or dithio-phosphates, copper salts of carboxylic acids, dithiocarbamates, sulphonates, phenates, copper acetylacetonates. Copper I and II salts, succinic acid or anhydride salts can also be used.
The lubricant composition according to the invention may contain any type of antioxidant additives known to the person skilled in the art.
Advantageously, the lubricant composition comprises at least one ash-free antioxidant additive.
Equally advantageously, the lubricant composition according to the invention comprises from 0.5 to 2% by weight, based on the total mass of the composition, of at least one antioxidant additive.
The lubricant composition according to the invention may also comprise at least one detergent additive.
Detergent additives generally reduce the formation of deposits on the surface of metal parts by dissolving oxidation and combustion by-products.
The detergent additives used in the lubricant composition according to the invention are generally known to the person skilled in the art. Detergent additives can be anionic compounds comprising a long lipophilic hydrocarbon chain and a hydrophilic head. The associated cation may be a metal cation of an alkali or alkaline earth metal.
The detergent additives are preferably selected from alkali or alkaline earth metals of carboxylic acids, sulphonates, salicylates, naphthenates, and phenate salts. The alkali and alkaline earth metals are preferably calcium, magnesium, sodium or barium.
These metal salts generally contain the metal in a stoichiometric amount or in excess, i.e. in an amount greater than the stoichiometric amount. These are overbased detergent additives; the excess metal giving the overbased character to the detergent is generally in the form of oil-insoluble metal salts, e.g. carbonate, hydroxide, oxalate, acetate, glutamate, preferably carbonate.
Advantageously, the lubricant composition according to the invention may comprise from 2% to 4% by weight of detergent additive relative to the total weight of the lubricant composition.
Equally advantageously, the lubricant composition according to the invention may also comprise at least one pour point depressant additive.
By slowing down the formation of paraffin crystals, pour point depressant additives generally improve the cold behaviour of the lubricant composition according to the invention.
Examples of pour point depressant additives are alkyl polymethacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalenes, alkylated polystyrenes.
Advantageously, the lubricant composition according to the invention may also comprise at least one dispersing agent.
The dispersing agent may be selected from Mannich bases, succinimides and derivatives thereof.
Advantageously, the lubricant composition according to the invention may comprise from 0.2% to 10% by weight of dispersant(s) based on the total weight of the lubricant composition.
The lubricant composition of the present invention may also comprise at least one additional polymer that can improve the viscosity index. Examples of additional viscosity index improving polymers are polymeric esters, hydrogenated or non-hydrogenated homopolymers or copolymers of styrene, butadiene and isoprene, polymethacrylates (PMA).
The present invention also relates to the use of the lubricant composition as defined above for the lubrication of metal parts, in particular for the lubrication of engines, in particular internal combustion engines, for example vehicle engines.
Advantageously, the lubricant composition according to the invention makes it possible to reduce friction, in particular between two mechanical parts, for example two parts of an engine, in particular an internal combustion engine, for example a vehicle engine.
Thus, the invention relates to the use of the lubricant composition according to the invention to reduce the wear of mechanical parts, for example parts of an engine, in particular a vehicle engine.
The present application also relates to a method of lubricating mechanical parts, particularly in an engine, such as an internal combustion engine, comprising at least one step of bringing a part into contact with the lubricating composition according to the invention.
The present invention will now be described with the help of non-limiting examples.
The compositions in Table 2 (LC: lubricant composition according to the invention; CC: comparative composition) were prepared by mixing at 60° C. the ester and/or polymeric friction modifier in a composition comprising base oil, viscosity index improver and additive package, to give the proportions shown in Table 2. The percentages shown are based on 100% by weight of the lubricant composition including the ester and/or polymeric friction modifier.
The tribological tests were carried out under the following conditions:
The coefficient of friction of the lubricant compositions tested is determined at 100° C. using an MTM (Mini Traction Machine) device using a 2 cm diameter hardened steel ball on a hardened steel plane.
The MTM device can be a PCS Instruments device. This device allows a steel ball and a steel plane to be moved relative to each other in order to determine the coefficients of friction for a given lubricant composition while varying various properties such as speed, load, and temperature.
The hardened steel plane is AISI 52100 with a mirror finish (Ra less than 0.01 μm) and the ball is also AISI 52100 made of hardened steel.
The applied load is 30 N (0.96 Gpa) and the rotation speed varies from 0.007 m/s to 3 m/s.
Approximately 50 ml of the tested lubricant composition was introduced into the device. The ball is engaged face to face with the plane, said ball and plane being independently actuated so as to create a mixed rolling/sliding contact.
The coefficient of friction is measured and recorded by means of a force sensor.
The test is conducted for a duration of 121 minutes (alternating between slip-slip and Stribeck periods). The velocity is initially held constant at 0.1 m/s and at each interval defined in the table, the velocity is increased from 3 to 0.007 m/s for one minute before returning to a velocity of 0.1 m/s at the end of said defined period.
The coefficient of friction is thus measured as a function of the defined speed.
Table 4 gives the results for the compositions in Table 2, expressed in terms of coefficient of friction versus slip speed.
The results show that:
| Number | Date | Country | Kind |
|---|---|---|---|
| 19 14410 | Dec 2019 | FR | national |
The present application is a U.S. National Phase Application under 35 U.S.C. § 371 of International Patent Application No. PCT/EP2020/085748 filed Dec. 11, 2020, which claims priority of French Patent Application No. 19 14410 filed Dec. 13, 2019. The entire contents of which are hereby incorporated by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2020/085748 | 12/11/2020 | WO |
