EP2346970B1 - Lubricating compositions for transmissions - Google Patents

Description

Technical area

The present invention relates to lubricating compositions for transmissions, in particular for gearboxes, and to their use for limiting the fuel consumption of motor vehicles. The compositions according to the invention are suitable for all types of vehicles, especially light vehicles, and are particularly suitable for vehicles with hybrid engines.

Current environmental concerns, particularly with a view to reducing carbon dioxide emissions, lead to an urgent need to reduce the fuel consumption of light-duty motor vehicles or heavy goods vehicles, as well as construction machinery and agricultural machinery. In particular, there is a growing demand for components such as the engine, transmissions, gearboxes, compressors and hydraulic systems to help reduce energy consumption.

As a result, the lubricants used in these bodies must be able to reduce frictional and bubbling losses to the lowest possible level. It is known to those skilled in the art that lowering the viscosity of the lubricating oil is a means of improving the fuel economy achieved in the transmissions.

Tests on a GMP (Powertrain) bench with a motor and gearbox assembly have shown that the fuel savings achieved are directly proportional to the viscosity of the transmission lubricant at the service temperature, which is generally between 20 and 40 ° C for use of vehicles on short journeys. The best performances are obtained with kinematic viscosity oils, measured according to the ASTM D445 standard, being around 20 mm ² / s at the operating temperature.

In addition, the specifications of the manufacturers systematically impose for the transmission oils of private vehicles, a viscosity at 100 ° C (or KV 100) measured according to the ASTM D445 standard between 5 and 15 mm ² / s, most often between 6 and 9 mm ² / s, preferentially targeted around 6.5 mm ² / s.

This limitation is related to mechanical considerations of design of gearboxes, bearings, gears. Indeed, below a limiting viscosity of about 5 mm ² / s, the sizing of the parts would have to be modified to reduce the load per unit area, since the lubricant would no longer participate sufficiently in the support of said load.

The viscosity behavior of the oils strongly depends on the bases used in their formulation to at least 50% by weight in general.

Thus, the formulation of transmission oils with a strong effect on fuel savings, or strong fuel-saving properties or so-called "fuel eco" properties, will preferentially use lubricating bases having a viscosity index or VI very high. The viscosity index or VI of a base measured according to ASTM D2270, quantifies its ability to limit its viscosity variations as a function of temperature, from the measurement of its kinematic viscosity at 40 ° C. (KV40) and 100 ° C. ° C (KV100) measured according to ASTM D445.

The VI of known conventional mineral bases is at most of the order of 200. Some synthetic oils make it possible to reach very high VI's, of the order of 400, but this high VI is accompanied by either a high viscosity, or solubility constraints additives, which do not provide the lubricant gear protection properties, friction control, ..., expected by the manufacturer. It is therefore difficult to formulate a transmission oil with fuel eco properties mainly from these bases. Their cost and availability are also problematic for the large-scale industrialization of lubricants incorporating them in a majority way.

Some naturally occurring fatty acid esters inherently have a very high VI, of the order of 250 or even 300 and above, combined with low viscosity. However, those skilled in the art are not encouraged to use these esters for automotive lubricants, in particular engine and transmissions, since the esters of this type which are liquid at ambient temperature have at least one double bond on their acid chain, which gives them a very low resistance to oxidation, resulting in a risk of degradation in service.

These esters, used as bases, do not particularly satisfy the high temperature oxidation tests, catalysed or not, which are part of the specifications of the car manufacturers for these applications.

The document EP 1 785 476 discloses a lubricating composition comprising an ester, a viscosity index improver, such as a polyalphaolefin, and at least one sulfur or phospho-sulfur compound.

Surprisingly, the applicant has found that it is possible to formulate transmissions oils of very high VI, greater than 250 or even 280, preferably greater than 300, or even of the order of 320 and beyond, from natural origin bases of fatty acid methyl ester types, and having a service life comparable to that of existing commercial products. Gearbox oils in particular must be designed for conditions of " full for life ", that is, they are never flushed throughout the life of the vehicle.

Without wishing to be bound by any theory, it seems that these esters, which form on the surface of the parts in friction of the films making it possible to maintain a hydrodynamic regime under heavy load, limit the heating in service of oils. Thus, despite poor results on standard oxidation tests, the results in service are quite satisfactory.

Brief description of the invention

• un ou plusieurs additifs antiusure et/ou extrême pression phosphorés, soufrés ou phospho soufrés,
• au moins 30 % en poids d'au moins un ester méthylique d'acide gras de formule RCOOCH3, où R est un groupement paraffinique ou oléfinique contenant de 11 à 23, préférentiellement de 13 à 19 atomes de carbone,
  et
• soit au moins un composé choisi dans le groupe des poly alpha oléfines lourdes de viscosité cinématique à 100 °C mesurée selon la norme ASTM D445 comprise entre 90 et 3000 mm²/s et de masse moléculaire en poids supérieure à 2500 daltons,
• soit au moins un composé choisi dans le groupe des poly alpha oléfines légères de viscosité cinématique à 100 °C mesurée selon la norme ASTM D445 comprise entre 1.5 et 6 mm²/s, de viscosité cinématique à 40 °C mesurée selon la norme ASTM D445, comprise entre 4 et 30 mm²/s, et une masse moléculaire en poids inférieure à 500 daltons, en combinaison avec un ou plusieurs composés de type polyméthacrylates, de masse moléculaire en poids inférieure à 30 000 daltons.

The present invention relates to lubricating compositions for gearboxes, of kinematic viscosity at 100 ° C., measured according to the ASTM D445 standard of between 5.5 and 7 mm ² / s, comprising

• one or more phosphorus, sulfur or phosphorus-sulfur antiwear and / or extreme pressure additives,
• at least 30% by weight of at least one fatty acid methyl ester of formula RCOOCH3, where R is a paraffinic or olefinic group containing from 11 to 23, preferably from 13 to 19 carbon atoms,
  and
• or at least one compound chosen from the group of heavy poly alpha olefins with a kinematic viscosity at 100 ° C., measured according to ASTM D445 standard of between 90 and 3000 mm ² / s and with a weight-average molecular weight greater than 2500 daltons,
• or at least one compound chosen from the group of light polyolefines having a kinematic viscosity at 100 ° C., measured according to the ASTM D445 standard of between 1.5 and 6 mm ² / s, with a kinematic viscosity at 40 ° C. measured according to the ASTM D445 standard , between 4 and 30 mm ² / s, and a weight-average molecular weight of less than 500 daltons, in combination with one or more polymethacrylate-type compounds, having a weight-average molecular weight of less than 30,000 daltons.

According to one embodiment, the lubricating composition comprises at least 20% by weight of at least one fatty acid methyl ester of formula R 1 COOCH 3, where R 1 is a mono, di or tri unsaturated olefinic group containing from 11 to 23, preferably from 15 to 19 atoms, preferably 17 carbon atoms.

According to one embodiment, the lubricating composition comprises at least 20% by weight of at least one fatty acid methyl ester of formula R 2 COOCH 3, where R 2 is a monounsaturated olefinic group containing from 11 to 23, preferably from 15 to 19 atoms, preferably 17 carbon atoms.

Preferably, the unsaturations of the olefinic groups R 1 and / or R 2 are in the cis configuration

Preferably in the lubricating composition the weight percentage of polyalphaolefin (s) heavy is at least 10% and the mass percentage of fatty acid methyl ester (s) is at least 60%

According to one embodiment, the lubricating composition comprises at least 50% by weight, preferably at least 55% by weight, of at least one ester. fatty acid methyl of formula R1COOCH3, wherein R1 is a mono, di or tri unsaturated olefinic group containing from 11 to 23, preferably from 15 to 19 atoms, preferably 17 carbon atoms.

According to one embodiment, the lubricating composition comprises at least 45% by weight, preferably at least 50% by weight, of at least one fatty acid methyl ester of formula R 2 COOCH 3, where R 2 is a monounsaturated olefinic group containing from 11 to 23, preferably from 15 to 19 atoms, preferably 17 carbon atoms.

Preferably in the lubricating composition, the weight percentage of light polyalphaolefin (s) is at least 10% and the weight percentage of the mixture of polymethacrylate (s) and methyl ester (s) of acid (s) fat is at least 60%

Preferably in the lubricating composition, the ratio between the weight percentage of polymethacrylate (s) and the mass percentage of ester (s) of fatty acid (s) is between 0.8 and 1.2.

According to one embodiment, the lubricating composition comprises at least 85% by weight, preferably at least 90% by weight, even more preferably at least 95% by weight, of one or more fatty acid methyl esters of formula RCOOCH 3, where R is a paraffinic or olefinic group containing from 11 to 23, preferably from 13 to 19 carbon atoms, relative to the total weight of fatty acid esters present in said lubricating composition

According to one embodiment, the lubricating composition comprises at least 75% by weight, preferably at least 80% by weight, of at least one fatty acid methyl ester of formula R1COOCH3, where R1 is a mono, di or tri unsaturated olefinic group. containing from 11 to 23, preferably from 15 to 19 atoms, preferably 17 carbon atoms, relative to the total weight of fatty acid esters present in said lubricating composition

According to one embodiment, the lubricating composition comprises at least 65% by weight, preferably at least 70% by weight, of at least one fatty acid methyl ester of formula R 2 COOCH 3, where R 2 is a monounsaturated olefinic group containing from 11 to 23 preferably from 15 to 19 atoms, preferably 17 carbon atoms, relative to the total weight of fatty acid esters present in said lubricating composition.

Preferably, the unsaturations of the olefinic groups R 1 and / or R 2 are in the cis configuration.

According to one embodiment, the lubricating composition comprises at most 15% by weight, preferably at most 10% by weight, of saturated fatty acid esters, relative to the total weight of fatty acid esters present in said lubricating composition.

According to one embodiment in the lubricating composition, the S / P ratio between the sulfur element mass content measured according to the ASTM D2622 standard and the phosphorus element content measured according to the ASTM D5185 standard in said lubricating compositions is between 3 and 60, preferably less than 30, preferably less than 20, even more preferably less than 10, or even between 5 and 10.

According to one embodiment, the lubricating composition has a VI, measured according to the ASTM D2270 standard, greater than 250, preferably greater than 280, and even more preferably greater than 300.

Another aspect of the invention relates to the use of lubricant compositions for gearboxes described above, to generate fuel savings greater than 1%, preferably greater than 2.5%, measured under the standard conditions of the test. NEDC according to Directive EEC 90 / C81 / 01 on national emission ceilings for certain atmospheric pollutants ("test emission cycles for the certification of light duty vehicles in Europe", Brussels, 2001), on motor vehicles, equipped with boxes manual or automatic gears, or automated manual gearboxes.

Preferably, the fuel savings are generated on light-duty vehicle engines, preferably hybrid vehicles.

A preferred use is for vehicles equipped with manual gearboxes or automated manual gearboxes.

Finally, the present invention relates to the use of fatty acid methyl ester bases containing at least 85% by weight, preferably at least 90%, even more preferably at least 90% of fatty acid methyl esters, of formula RCOOCH3 where R is a paraffinic or olefinic group containing from 11 to 23, preferably from 13 to 19 carbon atoms, VI greater than 250, and kinematic viscosity at 100 ° C of less than 7 mm ² / s, as a lubricating base for formulating gearbox oils generating fuel savings greater than 1%, preferably greater than 2.5%, measured under the standard conditions of the NEDC test according to EEC Directive 90 / C81 / 01 01 setting emission ceilings for certain atmospheric pollutants ("test emission cycles for the certification of light duty vehicles in Europe", Brussels, 2001).

Compositions which comprise at least 75% by weight, preferably at least 80% by weight of at least one methyl ester, are preferably used. fatty acid of formula R1COOCH3, wherein R1 is a mono, di or tri unsaturated olefinic group containing from 11 to 23, preferably from 15 to 19 atoms, preferably 17 carbon atoms.

Compositions which comprise at least 65% by weight, preferably at least 70% by weight, of at least one fatty acid methyl ester of formula R 2 COOCH 3, where R 2 is a monounsaturated olefinic group containing from 11 to 23, preferably from 15 to 19 atoms, preferably 17 carbon atoms.

Preferably, compositions are used in which the unsaturations of the olefinic groups R 1 and / or R 2 are in the cis configuration.

Detailed description of the invention

The lubricant compositions according to the invention are compositions for transmissions, more particularly for gearboxes, making it possible to significantly save fuel on vehicles, in particular light vehicles, especially hybrid vehicles.

These fuel savings are measured by subjecting a power train to a test bench or an actual vehicle to the NEDC model cycle (also referred to as ECE / EUDC) according to EEC Directive 90 / C81 / 01 01 setting national emission ceilings for certain atmospheric pollutants ("emission test cycles for the certification of light duty vehicles in Europe", Brussels, 2001).

These performances are strongly correlated with their low kinematic viscosity, in particular their kinematic viscosity at 40 ° C. (representative of the temperature in service on short paths), which is of the order of 20 to 25 mm ² / s, measured according to the standard ASTM D445

For considerations of protection of mechanical parts, the oils according to the invention have a kinematic viscosity at 100 ° C imposed by the manufacturers between 5.5 and 7 mm ² / s, preferably between 6 and 7 mm ² / s, still more preferably between 6 and 6.7 mm ² / s, measured according to ASTM D445.

Thus, the oils according to the invention must, to ensure their role of protecting the mechanical parts while generating fuel savings, have VI (ASTM 2270) high, greater than 250, preferably greater than 280, even more preferably greater than 300, or of the order of 320 and beyond.

For this purpose, these oils according to the invention are formulated from lubricating bases of the fatty acid methyl ester type, high VI (greater than 250), and kinematic viscosity at 100 ° C. of less than 7 mm ² / s. , such as those described below, combined with heavy PAOs, or light PAOs in combination with PMAs, and / or possibly certain other compounds known to those skilled in the art as thickening additives.

In particular, the oils according to the invention contain at least 30% by weight of at least one fatty acid methyl ester of formula RCOOCH3, where R is a paraffinic or olefinic group containing from 11 to 23, preferably from 13 to 19 carbon atoms. This minimum content achieves high VI and low viscosity in service generating the fuel economy effect.

The oils according to the invention may contain at least 35, at least 50, or at least 60, 70, or 80% of such fatty acid methyl esters. It should be noted that very high levels of such esters, above 70% by weight, or above 80% by weight, may have an adverse effect on the level of insolubles formed during the aging of the oils. .

That is why their content will generally be between 30 and 80%, or between 30 and 70%. In the variants containing light PAO in combination with PMA, their content will generally be between 30 and 50%, or between 30 and 40%.

Preferably, the predominant fatty acid methyl esters have the formula R 1 COOCH 3, where R 1 is a mono, di or tri unsaturated olefinic group containing from 11 to 23, preferably from 15 to 19 atoms, preferably 17 carbon atoms. The lubricant compositions for gearboxes according to the invention preferentially contain at least 20% by weight, preferably at least 25% by weight of such esters.

Even more preferentially, the methyl esters of predominant fatty acids are of formula R 2 COOCH 3, where R 2 is a monounsaturated olefinic group containing from 11 to 23, preferably from 15 to 19 atoms, preferably 17 carbon atoms. The lubricant compositions for gearboxes according to the invention preferably contain at least 20% by weight of such esters.

All these esters are preferably derived from fatty acid methyl ester bases as described below.

The basic system of the lubricants according to the present invention can also be completed by other bases, insofar as the VI of said lubricating compositions is greater than 250, preferably greater than 280, still more preferably greater than 300 or of the order 320 and beyond, and the kinematic viscosity at 100 ° C of said lubricant compositions is between 5.5 and 7 mm ² / s, preferably between 6 and 6.5 mm ² / s.

These other bases can be bases of mineral origin, synthetic or natural. However, preferentially, no database containing esters of fatty acids other than the bases of the fatty acid methyl esters described below.

Bases methyl esters of fatty acids

The so-called fatty acid ester bases used in the formulation of lubricants according to the invention, referred to herein as "fatty acid methyl ester bases", are in fact mixtures of fatty acid esters, comprising at least 85% by weight, preferably at least 90% or at least 92%, preferably at least 95%, still more preferably at least 98% or at least 99% by weight of fatty acid methyl esters of formula RCOOCH 3, where R is a paraffinic or olefinic group containing from 11 to 23, preferably from 13 to 19 carbon atoms.

The fatty acid methyl ester bases used in the lubricants according to the invention are also preferably substantially free of impurities of the ethyl ester type or, more generally, esters of alcohols containing 2 or more carbon atoms.

They are also practically free of mono, di or triglycerides, or of sterol (vitamin E) type compounds, or tocophenols.

Such impurities can indeed have an impact on the viscosity level and the VI of the ester bases, leading in particular to values of VI lower than desired (VI less than 250).

Thus, the total contents of such impurities will be less than 15% by weight, preferably less than 10%, or 8% or 5% by weight in the ester bases used to formulate the lubricants according to the invention. more preferably less than 2% or less than 1% by weight.

These fatty acid methyl ester bases preferably contain at least 70% by weight, preferably at least 75%, even more preferably at least 80% by weight of at least one fatty acid methyl ester of formula R 1 COOCH 3, where R 1 is a mono, di or tri unsaturated olefinic group containing from 11 to 23, preferentially from 15 to 19 atoms, preferably 17 carbon atoms,

Preferably, these fatty acid methyl ester bases contain at least 65% by weight, preferably at least 70% by weight of at least one fatty acid methyl ester of formula R 2 COOCH 3, where R 2 is a mono-unsaturated olefinic group containing 11 to 23, preferably from 15 to 19 atoms, preferably 17 carbon atoms

Preferably, the average chain length of the fatty acids composing the esters of said base is between 17 and 19.

In these bases, fatty acid methyl esters, the unsaturations of the groups R 1 and / or R 2 are preferably in the cis form.

The "cis" configuration refers to the "boat" form, where the two hydrogens are on the same side of the C = C double bond, the "trans" configuration refers to the chair form.

The cis or trans configuration of said monounsaturated fatty acid methyl esters affects their technical characteristics. A cis double bond creates a bend in the carbon chain while the trans double bond has an extended structure.

Unsaturated fatty acids are predominantly present in their "cis" form in their natural state. The "trans" form is present in the natural state at about 2 to 8% by weight in the milk fats, at about 4.5% by weight in the fats of beef and beef. sheep. However, it is mainly obtained during industrial processes for the hydrogenation of polyunsaturated fatty chains present in certain oils.

Preferably, these fatty acid methyl ester bases contain less than 5% by weight of unsaturated fatty acid methyl esters having at least one unsaturation of their olefinic chain in trans form (hereinafter "unsaturated fatty acid methyl esters"). trans ").

The fatty acid esters may be obtained from fatty acids themselves derived from natural resources or from synthetic fatty acids, obtained for example from petroleum fractions.

The term "fatty acids" denotes linear hydrocarbon-based monoacids containing from 8 to 24 carbon atoms. They can be saturated, monounsaturated, or polyunsaturated. The fatty acids from natural resources have an even number of carbon atoms.

These are, for example, the methyl esters of palmitoleic (16-1), oleic (18-1), linoleic (18-2), linolenic (18-3), eicosenoic (20-1) and erucic (22-1) acids. or nervonic (24-1). The methyl ester of oleic acid is particularly preferred (18-1).

Of the methyl esters of the above fatty acids, the predominant compound is those of palmitoleic (16-1), oleic (18-1) and linoleic (18-2) acids. The methyl ester of oleic acid is particularly preferred.

They are present, for example, in vegetable oils in the form of triglycerides, or triesters of glycerol. The hydrolysis of triglycerides leads to the corresponding fatty acids and glycerol. Methyl esters are obtained by esterification of fatty acids or directly by transesterification of the oils with methanol.

As a natural oil, mention may be made of conventional or genetically modified copra, palm, olive, peanut, rapeseed and sunflower oils so as to enrich their oleic acid content (rapeseed and oleic sunflower), soybean, cotton, beef tallow ...

Preferably, the fatty acid methyl ester bases used in the invention are of natural origin, especially vegetable, obtained for example from palm oil, olive, peanut, or rapeseed oils or classic or oleic sunflowers.

The bases of the fatty acid methyl ester type used in the invention typically have a kinematic viscosity at 100 ° C., measured by ASTM D445, of between 1.5 and 10 mm ² / s, preferably between 1.5 and 7. mm ² / s, and a VI (ASTM 2270) of the order of 250 to 400.

The VI of these bases is typically greater than 250, preferably greater than 280, or greater than 300, or of the order of 320 and beyond.

They are used as a lubricating base in the compositions according to the present invention, and represent at least 30% by weight of the finished lubricant, preferably at least 35% by weight. They may be present up to levels of the order of at least 50%, or 60%, or 70%, or even at least 80% by weight relative to the total weight of lubricant.

The lubricants according to the invention, formulated with the high-VI fatty acid methyl ester bases described above, show excellent results in fuel economy when they are used for example as gearbox oil.

They also have a very good thermal stability, as measured during tests of GFCT-021-A-90 type, when the bubbling of air is replaced by nitrogen bubbling.

In order to avoid any ambiguity, it is specified that the minimum amount of 30% of fatty acid methyl esters present in the compositions according to the invention, and the minimum quantity of 85% of fatty acid methyl esters present in the Fatty acid methyl ester type bases described above do not take into account any esters in the form of sulfur, phosphorus or phosphorus-sulfur compounds which are known as anti-wear and extreme pressure agents.

These quantities also do not take into account any borated esters known as friction modifying additives.

Polyalphaolefins and PMA: Heavy polyalphaolefins:

The polyalphaolefins employed in the lubricating compositions according to the present invention are called heavy polyalphaolefins or viscosity. They allow, in mixture with the esters, and optionally PMA, described above, to achieve in the lubricant compositions according to the invention the target of desired viscosity (between 5.5 and 7 mm ² / s, preferably between 6 and 7 mm ² / s, even more preferably between 6 and 6.7 mm ² / s at 100 ° C), without degrading the VI, which remains greater than 250.

The "heavy" polyalphaolefin ("PAO") or polyalphaolefin "viscosity" type compounds used in the composition according to the invention are chosen from PAOs with a kinematic viscosity at 100 ° C. measured according to ASTM D445 of between 40 and 3000 mm ² / s. preferably between 150 and 1500, preferably between 300 and 1200 mm ² / s.

Their molecular weight in weight Mw is greater than 2500 daltons, typically of the order of 4000 to 50000 approximately.

Their number-average molecular weight, Mn is greater than 2500 daltons, typically between 3000 and 20000, preferably between 3000 and 10000, preferably between 3000 and 7000.

Their polydispersity index Mw / Mn of the order of 1.1 to 5 and more.

These polyalphaolefins are for example obtained from monomers such as octene, decene, dodecene, tetradecene, hexadecene, etc., alone or mixed with other olefins.

They can be used alone or as a mixture in the compositions according to the invention, and represent at least 10% by weight of said compositions. Their mass percentage is preferably less than 30% by weight in said compositions, so as to avoid additive solubility constraints or excessively high viscosity. In other words, the mass percentage of heavy polyalphaolefins will be sufficiently high to give the compositions the required viscosity, but will have to remain within certain limits to avoid leading to too viscous compositions or to generate problems of solubility of the additives.

It is typically between 10 and 25%, or 10 and 20% by weight, or between 15 and 25% by weight, or between 10 and 18% by weight, preferably between 15 and 18% by weight of lubricants for gearbox according to the invention.

Preferably, when the lubricant compositions for gearboxes according to the invention contain heavy PAOs as described above, the percentage of fatty acid methyl esters of formula RCOOCH 3, where R is a paraffinic or olefinic group containing 11 to 23, preferably 13 to 19 carbon atoms, in said compositions, is greater than 60%.

Preferably, they then contain at least 50% by weight, preferably at least 55% by weight of at least one fatty acid methyl ester of formula R1COOCH3, where R1 is a mono, di or tri unsaturated olefinic group containing from 11 to 23, preferably from 15 to 19 atoms, preferably 17 carbon atoms.

Even more preferably, they then contain at least 45% by weight, preferably at least 50% by weight of at least one fatty acid methyl ester of formula R 2 COOCH 3, where R 2 is a mono-unsaturated olefinic group containing from 11 to 23, preferably from 15 to 19 atoms, preferably 17 carbon atoms.

PMA and light polyalphaolefins:

The compositions according to the invention can be formulated with high levels of unsaturated fatty acid methyl base (50% by weight of base, or even 60, 70% and beyond, which respectively corresponds to methyl ester percentages. unsaturated fatty acids C12-C24, preferably C16-C24, preferably C18, of the order of 35%, 45%, or 50% and more relative to the total weight of lubricant).

This being so, these compositions have the disadvantage of not being compatible with all the qualities of elastomeric seals, in particular those of the acrylate and fluoroelastomeric type.

For this purpose, in one variant of the invention, a portion of the amount of ester base used is substituted for one or more polymethacrylate (PMA) compounds, which are compounds that are well known to the person skilled in the art. profession, intervening in particular as thickening polymers in the lubricating formulation.

The PMAs of the present invention have a kinematic viscosity at 100 ° C., measured according to ASTM D445, preferably less than 500 mm ² / s, or even less than 250 mm ² / s, or about 200 mm ² / s.

Preferably, the weight percentage of PMA will be chosen so that the mixture of fatty acid methyl ester and PMA represents at least 60% by weight in the lubricants according to the invention.

Preferably, the mass percentage of PMA will be substantially equivalent to that of the fatty acid methyl esters, that is to say that the ratio between the mass percentage of polymethacrylate (s) and the mass percentage of ester (s) of fatty acid (s) is between 0.8 and 1.2.

The addition of these PMAs does not significantly degrade the VI of the compositions according to the invention.

To facilitate their mixing in a lubricating composition, the commercial polymethacrylates are in the form of polymer compounds in a predilution base oil. Said polymethacrylate compounds thus consist of 30 to 60% by weight, typically 50% by weight, of polymer (active ingredient), in the predilution oil.

The mass percentages of PMA mentioned in the present description refer to the percentage of compound consisting of the polymer mixture (active ingredient) plus predilution oil.

The PMAs employed in the compositions according to the invention have a relatively low molecular weight by weight of less than 30,000 daltons. Their incorporation however requires the incorporation of a co-solvent, which will also make it possible to respect the kinematic viscosity target at 100 ° C. of between 5.5 and 7 mm ² / s and to improve the compatibility with the elastomers for the coatings. lubricants according to the invention.

This co-solvent must not degrade the VI of the compositions.

Thus, in the embodiments of the invention comprising PMAs, light polyolefinolefins PAO are incorporated as cosolvent of said PMAs.

The PMAs as described above are thickening additives well known to those skilled in the art, whose role is to increase the viscosity when hot or cold.

In one variant of the invention, one alternative to these PMAs is one or more other thickening additives also known to those skilled in the art, in combination with the light polyalphaolefins described hereinafter as co-solvent. These other thickening additives can be used alone or as a mixture, and optionally in admixture with the LDCs, exactly under the same conditions as the LDCs.

These other thickeners will be selected for their high VI (greater than 200, preferably 250, or 280, or 300, preferably of the order of 320 or above), and for their shear strength adapted to use in lubricants for gearboxes.

Can thus be used to substitute a portion of the quantity of basic ester used in the compositions according to the invention, copolymers of polyalphaolefin (PAO) / Ethylene, such as for example marketed by Mitsui Lucant ^®, or ethylene-propylene dimer (EPDM), such as for example TRILENE CP 80 marketed by LYON Copolymers, or styrene-Acrylate copolymers or derivatives or copolymers of PMA. Polyisubutenes (PIBs) do not provide sufficient VI, and OCP or Starpolymers are not shear stable.

Some of these compounds, such as EPDMs, are in the form of liquid compounds almost exclusively made of polymeric active material (that is, for example, Trilene consists almost exclusively of EPDM)

Others are in the form of compounds consisting of polymer (active material) in a predilution base oil. This is the case, for example, of PAO / ethylene copolymers, which consist of 30 to 60% by weight, typically 50% by weight, of polymer (active material), in the predilution oil.

When this is the case, the mass percentages of thickeners mentioned in the present description refer to the percentage of compound consisting of the polymer mixture (active ingredient) plus predilution oil.

Preferably, the mass percentage of these thickeners, alone or in admixture, or in eventual mixing with the PMAs described above, will be chosen so that the mixture of fatty acid methyl ester, thickener (s), and optionally PMA, represents at least 60% by weight in the lubricants according to the invention.

Preferably, the weight percentage of the thickener or thickener mixture and PMA, will be substantially equivalent to that of the fatty acid methyl esters.

That is to say that the ratio between the mass percentage of the thickener (s), or thickener mixture and PMA, and the mass percentage of ester (s) of fatty acid (s) is between 0.8 and 1.2.

Light PAO:

As with the heavy polyalphaolefins, light polyalphaolefins are for example obtained from monomers such as octene, decene, dodecene, tetradecene, hexadecene, etc., alone or mixed with other olefins. They can also be used alone or as a mixture in the compositions according to the invention.

The so-called light PAOs have a kinematic viscosity at 100 ° C. measured according to the ASTM D445 standard of between 1.5 and 6 mm ² / s, preferentially less than 3 mm ² / s, of the order of 2 mm ² / s, a viscosity kinematic at 40 ° C measured according to ASTM D445 of between 4 and 32 mm ² / s, preferably less than 6 mm ² / s, of the order of 5 mm ² / s, and a weight-average molecular weight (obtained by gas chromatography), less than 500, preferably less than 300, typically of the order of 290 or 285 daltons.

They preferably represent at least 10% by weight of lubricants for gearboxes according to the invention. Their weight percentage is preferably less than 30% by weight in said lubricants, so as to avoid solubility of the additives. In other words, the weight percentage of light polyalphaolefins will be sufficiently high to solubilize the amount of PMA (and / or other thickeners as described above) necessary to give the compositions the required viscosity, but must remain within certain limits to avoid solubility problems of additives. Typically, their weight percentage is between 10 and 25%, preferably between 15 and 25% by weight, or between compositions according to the invention.

Preferably, the weight percentage of light PAO is at least 10% and the mass percentage of PMA (s) (and / or other thickeners described above) will be chosen so that the mixture of fatty acid methyl ester with the PMA (s) and / or with the other thickeners as described above, represents at least 60% by weight in the lubricating compositions for gearboxes according to the invention.

Even more preferably, the weight percentage of PMA (s) and / or other thickener (s) as described above, will be substantially equivalent to that of the fatty acid methyl esters, that is to say that the ratio between the weight percentage of polymethacrylate (s) and the mass percentage of ester (s) of fatty acid (s) is between 0.8 and 1.2.

The compositions according to the invention thus formulated with fatty acid methyl ester bases, PMA and light PAO, have less aggressiveness than the variants containing only the methyl ester and the heavy PAO, during dynamic tests carried out on joints of various qualities. In particular, there is less variation in volume and deterioration of mechanical properties on fluoroelastomer seals.

Furthermore, there was a virtual absence of insolubles for the oils according to the invention containing PMA and light PAO, after GFCT-021-A-90 oxidation tests at 160 ° C, which constitutes a significant improvement over the other variant.

When carrying out thermal aging tests, under the conditions of GFCT-021-A-90, at 160 ° C, and replacing the bubbling of air by bubbling nitrogen, there is an initial thickening, probably due to to a transesterification phenomenon between the PMA and the methyl ester, then a subsequent stability of the product.

Other base oils:

The lubricating compositions according to the invention may contain, as lubricating bases, in addition to the fatty acid methyl esters described above, in combination with heavy PAOs, or light PAOs and PMAs, all types of lubricating bases known to those skilled in the art, insofar as the VI of said lubricating compositions is greater than 250, preferably greater than 280, still more preferably greater than 300 or of the order of 320 and beyond, and the kinematic viscosity at 100 ° C said lubricating compositions is between 5.5 and 7 mm ² / s. These base oils can be of mineral, synthetic or natural origin.

Mineral base oils may include any type of base obtained by atmospheric and vacuum distillation of crude oil, followed by refining operations such as solvent extraction, desalting, solvent dewaxing, hydrotreating, hydrocracking and hydroisomerization, hydrofinishing,. ..

Synthetic base oils may include oils belonging to groups IV, V and VI of the API classification, including polyalphaolefins, polyinternal olefins, alkyl aromatics, alkyl benzene, alkylnaphthalenes, esters, diesters, polyol esters such as as pentaerythritol esters, oligomers of aplhaolefins and esters, polyalkylene glycols.

Preferentially, no base containing esters of fatty acids other than the bases of the fatty acid methyl ester type described above will be used.

Viscosity and VI of the oils according to the invention.

The oils according to the invention are characterized by a very high VI. Their VI, measured according to the ASTM 2270 standard, is greater than 250, preferably greater than 280 or even greater than 300, or of the order of 320 and beyond.

They are also characterized by a low viscosity at operating temperatures (visco values at the temperature of use, value of the operating temperatures), and a kinematic viscosity at 100 ° C, KV100, measured according to ASTM D445, included between 5.5 and 7 mm ² / s, preferably between 6 and 6.5 mm ² / s.

The viscosity behavior of the lubricants is determined by the bases and the thickeners and VI modifiers used in their formulation.

In particular, it is important, in order to achieve the very high VI values of the oils according to the invention, that the monounsaturated fatty acid methyl ester (s) employed themselves have a very high VI.

However, the VI of these unsaturated fatty acid methyl esters is strongly affected by the presence of impurities, in particular by the presence of unsaturated fatty acid esters and alcohols other than methanol, for example ethanol. The methyl esters of commercial fatty acids thus have VIs which can vary in a very broad range, as shown by the VI values of commercial oleates below, extracted from the Unichema catalog. Methyl oleate KV 100 = 1.8 VI = 320 Isopropyl oleate KV 100 = 2.0 VI = 221 Isobutyl oleate KV 100 = 2.3 VI = 229 2-Ethylhexyl oleates KV 100 = 2.7- 2.8 VI = 159

Antiwear and / or extreme pressure additives .

The lubricating compositions according to the present invention contain at least one anti-wear agent and / or extreme phospho sulfur, sulfur or phosphorus pressure, preferably present at contents of between 0.01% and 12%, preferably between 0.01% and 5%, by weight. relative to the total weight of lubricant.

The compositions according to the invention preferentially contain both the sulfur element and the phosphorus element. Preferably, it contains either at least one phosphorus additive and at least one sulfur additive, or at least one phospho-sulfur additive.

The sulfur element mass contents are typically of the order of 1 to 3% by weight (depending on the formulations and the objectives) and the phosphorus contents of the order of 500 to 3000 ppm (according to the formulations and the objectives).

Phospho-sulfur anti-wear and extreme pressure additives.

The phospho-sulfur antiwear and extreme pressure additives used in the present invention are, for example and not exclusively, thiophosphoric acid, thiophosphorous acid, esters of these acids, their salts, and dithiophosphates, particularly zinc dithiophosphates.

Examples which may be mentioned as examples of phospho-sulfur-containing anti-wear and extreme pressure additives are those containing from 1 to 3 sulfur atoms, such as monobutylthiophosphate, monooctylthiophosphate, monolaurylthiophosphate, dibutylthiophosphate, dilaurylthiophosphate, tributylthiophosphate, trioctylthiophosphate, triphenylthiophosphate, trilaurylthiophosphate, monobutylthiophosphite, monooctylthiophosphite, monolaurylthiophosphite, dibutylthiophosphite, dilaurylthiophosphite, tributylthiophosphite, trioctylthiophosphite, triphenylthiophosphite, trilaurylthiophosphite and their salts.

Examples of salts of thiophosphoric acid esters and thiophosphorous acid are those obtained by reaction with a nitrogen compound such as ammonia or an amine or zinc oxide or zinc chloride.

Phosphorus antiwear and extreme pressure additives.

The lubricating compositions according to the present invention may also contain phosphorus anti-wear and extreme pressure additives, such as, for example, alkyl phosphates or alkyl phosphonates, phosphoric acid, phopsphorous acid, mono, di and triesters of phosphorous acid and phosphoric acid, and their salts.

Sulfur antiwear and extreme pressure additives.

Examples of sulfur anti-wear and extreme pressure additives include dithiocarbamates, thiadiazoles and benzothiazoles, sulfur-containing olefins.

The most common sulfur-containing olefins are also called SIBs for "sulfurized isobutylenes". These sulfur-containing olefins are generally obtained by a reaction of sulfurization of olefins with sulfur, hydrogen sulphide or alkali metal sulphides hydrate, example sodium sulphide.

Certain particular sulfurized olefins can be obtained by catalytic processes, for example by reacting hydrogen sulfide with isobutylene in the presence of catalyst. These processes lead to purer products, of better defined structure, having a higher sulfur content (ASTM D2622) and an active sulfur content (ASTM D-1662) generally lower than the commonly used SIBs.

S / P ratio.

In the lubricating compositions for transmissions, the sulfur content of the base oil or of the base oil mixture, as well as the respective amounts of phospho sulfur, phosphorus and sulfur-containing extreme pressure additives, in particular sulfur-containing olefins, are generally chosen so that said compositions have a ratio between their sulfur element content, measured by the ASTM D2622 standard and their phosphorus element content, measured by the ASTM D5185 standard, namely S / P, of between 3 and 60.

Transmission lubricants having a S / P ratio greater than 30 are generally "economical" type products with a very low rate of additive treatment and reduced phosphorus contents.

The mixed gearbox and bridge products generally have an S / P value of between 20 and 30, preferably close to 20, which corresponds to minimizing the amount of sulfur to improve compatibility with the synchros;

Products with a ratio of less than 20 are intended for gearboxes rather than bridges.

The lubricant compositions according to the present invention have a S / P ratio as defined above of between 3 and 60, or between 5 and 60, more preferably less than 30, preferentially less than 20, even more preferably less than 15 or 10.

Other additives.

The lubricant compositions according to the invention may also contain any type of additive adapted to their use known to those skilled in the art for use in transmission oil formulations, for example one or more additives chosen from friction, antioxidant additives (eg antioxidants amines), corrosion inhibitors present at the usual levels required for the application.

Friction modifiers.

The friction modifying additives make it possible to limit friction in the limit or mixed lubrication regime by forming monolayers adsorbed on the surfaces of the metals; The methyl esters of fatty acids used as base in the lubricants according to the invention possess this property. However, when they are used as friction modifying additives in lubricating compositions, their mass percentage is less than 10%, generally between 0.01 and 5% by weight relative to the total weight of lubricating composition.

Said lubricants according to the invention may further contain, as friction modifiers, molecules such as fatty alcohols, ethoxylated fatty amines or not, fatty acids, amides obtained from fatty acids and amines, or succinimides formed by reaction of aliphatic succinic acids and primary amines, imidazoles, tertiary amines, aliphatic phosphonates, phosphates, thiophosphonates, aliphatic thiophosphates, organic Molybdenum derivatives.

The aliphatic chains of these compounds generally have a minimum of 8 carbon atoms.

Other friction modifying additives may contain combinations of N-substituted dihydroxyalkylamines substituted with an aliphatic group having about 14 to 20 carbon atoms, optionally in combination with trimethyl diamines having at least one N-aliphatic substituent, or with substituted N-imidazoles. by hydroxyalkyl aliphatic groups.

These compounds may be present, preferably, at contents of between 0.01% and 10% by weight in the lubricants according to the present invention.

Pour point depressants.

The compositions according to the invention may contain one or more additives of a pour point depressant additive. It may be, for example, poly-acrylates, Ethyl-Vinyl Acetates, ethylenic copolymers, condensation derivatives of naphthalene.

These additives may typically be present at from 0.1 to 2% by weight.

Anticorrosive agents and copper passivating agents.

These are, for example, compounds such as polyisobutene succinic anhydrides, sulfonates thiadiazoles, mercaptobenzothiazole. They are typically present in the lubricant compositions according to the invention at contents of between 0.01 and 1% by weight.

• des détergents tels que par exemple les sulfonates, phénates, salycilates de Calcium, Sodium, Magnésium, Barium, présents à des teneurs comprises entre entre 0 et 5% en poids
• des dispersants comme les dérivés de Poly Iso butylène succinic anhydride, entre 0 et 5%
• des antioxydants, qui peuvent être par exemple Antioxydants Aminés (Ocatadiphénylamines, Phényl-Alpha-Naphtyl Amines, ...), Phénoliques (BHT et dérivés), Soufrés (Phénates Sulfurisés).

The oils according to the invention may also contain all types of additives suitable for their use, and in particular:

• detergents such as, for example, sulphonates, phenates, calcium salycilates, sodium, magnesium and barium, present at contents of between 0 and 5% by weight
• dispersants such as polyisobutylene succinic anhydride derivatives, between 0 and 5%
• antioxidants, which may be for example Amino antioxidants (Ocatadiphenylamines, Phenyl-Alpha-Naphtyl Amines, ...), Phenolics (BHT and derivatives), Sulfurized (Phenates Sulfurized).

The present invention also relates to the use of the lubricant compositions for gearboxes described above to generate fuel savings greater than 1%, preferably greater than 2.5%, measured under the standard conditions of the NEDC test according to EEC Directive 90 / C81 / 01 establishing national emission ceilings for certain air pollutants ("emission test cycles for the certification of light duty vehicles in Europe", Brussels, 2001), on motor vehicles.

The compositions according to the invention are particularly suitable for generating fuel savings on gasoline or diesel light vehicles, or equipped with a hybrid electric motor.

Indeed, in a hybrid engine operation, the kinetic energy is recovered and accumulated during braking for subsequent restitution. The gearbox oil therefore has an even greater impact on the fuel savings generated in such a vehicle because the gearbox is also requested in these deceleration phases.

Another aspect of the invention also relates to the use of bases of the fatty acid methyl ester type as described above as a lubricating base for formulating gearbox oils which generate fuel savings of greater than 1%, preferably greater than 1%. at 2.5%, measured under the conditions NEDC standard according to EEC Directive 90 / C81 / 01 on national emission ceilings for certain air pollutants (Brussels, 2001). These bases are preferably used at levels of at least 30% by weight of the finished lubricant, preferably at least 35% by weight. They may be present up to levels of the order of at least 50%, or 60%, or 70%, or even at least 80% by weight relative to the total weight of lubricant.

Example 1 Preparation of Lubricating Compositions

Lubricating compositions according to the invention (oils A and B) comprising at least 35% by weight of a lubricating base consisting predominantly of unsaturated fatty acid methyl esters are prepared, the characteristics of which are given in table 1. Percentages are percentages by weight relative to the total weight of lubricant Table 1: Methyl ester base of unsaturated fatty acids. Methyl ester base of fatty acids Methyl esters of fatty acid (EN 14103) Content of fatty acid methyl esters, C12-C24 acids, (g / 100 g of base, according to standard EN 14103) 93.2 Saturated methyl ester content, (g / 100 g base, according to EN 14103) 9.2 Content of cis, mono, di, tri-unsaturated methyl esters, C16-C20 acids, (g / 100 g base, EN 14103) 80.6 Content of cis mono-unsaturated methyl esters, C16-C20 acids, (g / 100 g of base, according to standard EN 14103) 73.1 Methyl oleate content (g / 100 g base, according to standard EN 14103) 64.9 Free and total glycerol (EN 14105) Free glycerol (g / 100g base) <0.005 Monoglycerides (g / 100g base) <0.005 Diglycerides (g / 100g base) 0.01 Triglycerides (g / 100g base) 0.09 Total glycerol (g / 100g base) 0,011 Average chain length of fatty acids 17.7 KV 100 (ASTM D445), mm ² / s. 2.3 VI (ASTM D2270) 320

The heavy PAO used in oil A is available under the trade name ExxonMobil Chemicals, Spectracyn 1000, having a kinematic viscosity at 100 ° C of 1000 mm ² / s.

The light PAO used in oil B is marketed by Exxon Mobil Chemicals under the reference SHF-23, having a kinematic viscosity at 100 ° C. of 1.8 mm ² / s.

The polymethacrylate used in oil B is PAS 501 supplied by Sanyo Chemical

• un agent antiusure phosphoré,
• un agent extrême pression soufré,
• un inhibiteur de corrosion de type dimercaptanbenzothiadiazole
• un antioxydant aminé,

The additivation of the compositions according to the invention thus prepared is a conventional additivation of lubricants for gearboxes. These compositions comprise 9.5% by weight of the gear package marketed by Lubrizol under the reference OS 215497, and containing:

• a phosphorus antiwear agent,
• an extreme sulfur pressure agent,
• a dimercaptanbenzothiadiazole type corrosion inhibitor
• an amino antioxidant,

Table 2 groups together the characteristics of oils A and B according to the invention. The% indicated are% by weight relative to the total weight of lubricant. Table 2: Characteristics of the oils according to the invention AT B Trade name Chemical nature function OS 215497 Gear package 9.5% 9.5% Sturaco 7098S amine phosphate Friction modifier 0.5% 0.5% Methyl fatty acid ester base Methyl esters of fatty acids based 73.8% 35.45% PAS 501 LDCs based - 34.5% Spectracyn 100 PAO heavy KV 100 1000 mm ² / s VI Thickener & Enhancer 16 - PAO 2 PAOlight, KV100 1,8 mm ² / s VI Thickener & Enhancer - 20 SHF-23 SM31 Defoamers - % 0.05 Viscoplex 1-256 PPD (For Depressant Point or Pour Point Depressant) 0.2% - TOTAL: 100% 100% KV40, mm ² / s 19,98 21.49 (ASTM D445) KV 100, mm ² / s (ASTM D445) 6.53 6.51 VI 323 291 (ASTM D2270) KV-10 mm ² / s (ASTM D445) 119 S / P (respectively ASTM D2622 and ASTM D5185) 6.56 6.56

Example 2: NEDC Test

In-service and fuel consumption warm-up measurements are made by subjecting a test bench or actual vehicle engine to the NEDC model cycle (also referred to as ECE EUDC) according to EEC Directive 90 / C81 / 01 01 fixing national emission ceilings for certain atmospheric pollutants (Brussels, 2001). The characteristics of this engine cycle are grouped together figure 1 , which describes the speed (in km / hour) imposed as a function of time (in seconds), respectively in the cycles ECE 15 and EUDC.

The NEDC cycle corresponds to 4 ECE cycles and one EUDC cycle: NEDC = 4 x ECE 15 + EUDC

Table 3 below summarizes the overall characteristics of this cycle, representative of the average daily commute in Europe. <b> Table 3: ECE15 and EUDC cycles </ b> Characteristics units ECE 15 EUDC Distance km 4 × 1.013 = 4.052 6955 duration s 4 × 195 = 780 400 Average speed km / h 18.7, including stop 62.6 Maximum speed km / h 50 120

This NEDC cycle is carried out on an engine bench, which uses a 88 kW power gasoline engine, a manual gearbox and a Clemessy gearshift robot.

The reference oil (REF) is a commercial oil for manual gearbox used in passenger light vehicles, grade 75W80, kinematic viscosity 8 mm ² / s at 100 ° C and VI of the order of 150 , formulated with conventional Group I paraffinic bases (essentially of Solvent Neutral 150 type).

Example 3: Measurement of heating of oils in use

The initial temperature of the oils is 22 ° C. The final temperature of the gearbox oils tested at the end of the test are reported in Table 4 below.

It is observed that the oils according to the invention A and B, formulated with at least 35% by weight of base of the fatty acid methyl ester type, lead to heating up much lower than the commercial reference. It can also be seen that during tests simulating driving on fairly short paths, representative of the average of the daily journeys, the operating temperature of the gearbox oils is between 40 and 50 ° C. <b> Table 4: Temperature rise of oils in use </ b> AT B REF T initial (° C) 22 22 22 Final T (° C) 44.3 44.7 50 ΔT (° C) 22.3 22.7 28

Example 4: Measuring fuel economy

Fuel consumption is calculated according to EEC Directive 90 / C81 / 01 on National Emission Ceilings for Certain Air Pollutants (Brussels, 2001). We measure the amount of gas emitted to the exhaust, and we go back to the mass fuel consumption.

The results obtained are summarized in Table 5 below. Table 5: Measurement of fuel economy with oils according to the invention AT B REF Initial temperature ° C 22.0 22.0 22.0 Final temperature after NEDC, ° C 22.3 22.6 28.0 Fuel economy / REF, after NEDC (% of mass consumption) 3% 2.5% 0%

There are significant fuel savings with oils A and B according to the invention. The heating is also limited (5 to 6 degrees less than the reference).

In addition, during NEDC tests as described above, but performed on hybrid vehicles of higher power, equipped with automatic gearboxes, these oils have shown fuel savings of the order of 3%.

The hybrid vehicle used included an automated mechanical gearbox to apply a specific shift strategy to the optimization of a hybrid operation.

It should be noted that for automated gearboxes, the EEC 90 / C81 / 01 directive does not impose, as for manual gearboxes, the shift points. These are managed optimally by a calculator. It is therefore difficult to compare these last test results with the previous ones. speeds. These are managed optimally by a calculator. It is therefore difficult to compare these last test results with the previous ones.

However, in a hybrid engine operation, it slows down (with energy recovery) to brake. It is therefore reasonable to think that the gearbox oil has an impact all the more important on the fuel savings generated in such a vehicle.

Example 5: Correlation between Fuel Economy and Kinematic Viscosity at 40 ° C

Taking into account the temperature conditions in use, it was measured, for different gearbox oils, fuel savings in the conditions described above in Example 4, and correlated these savings to their kinematic viscosity at 40 ° C.

The results are summarized in Table 6 below: Table 6: correlation between fuel economy and kinematic viscosity at 40 ° C. Table 6 AT B H VS BOY WUT REF KV 40, mm2 / s 19.98 21.49 26,60 29.80 31,10 48,10 Fuel economy / REF, after NEDC cycle (% of mass consumption) 3% 2.5% 2% 0.8% 1.5% 0%

The oils A and B are the oils according to the invention whose characteristics are set out in Table 2, and REF the reference for the fuel consumption described above.

The oil C is a gearbox oil having the same additivation as the oils A and B, but formulated from mineral bases of group I and III with VI of 160

The oil G is an oil for gearboxes formulated from bases of group I, KV 100 = 8mm ² / s, VI of the order of 150.

Oil H is similar to oil C, with a VI of 200

It can be seen that the fuel savings achieved are all the higher as the kinematic viscosity at 40 ° C is low, with an almost linear correlation.

Example 6: Insoluble levels of the oils according to the invention.

An oxidation test according to the GFCT-021-A-90 standard, at 140 ° C., was carried out on oils according to the invention. Oils A and B are those whose characteristics are set out in Table 2. The results are summarized in Table 7 below. <b> Table 7: Oxidation Tests at 140 ° C, GFCT-021-A-90. </ b> Table 7 AT B New oil KV40, mm ² / s. 19.98 21.49 KV100, mm ² / s. 6.53 6.51 End of test KV40, mm ² / s. 64.95 KV100, mm ² / s. 14,02 165.4 Insoluble% mass 19.3 0.6

Unsurprisingly, the oils according to the invention are poorly resistant to high temperature oxidizing conditions, with a significant increase in their kinematic viscosity. However, their level of insoluble is low. In particular, oils B, formulated with fatty acid methyl esters combined with light PMA and PAO, have an exceptionally low level of insolubles.

Example 7 : Thermal Stability of oils according to the invention.

A thermal aging test was carried out on oils A and B according to the invention. This test is carried out under the conditions of the standardized test GFCT-021-A-90, at 160 ° C., but the bubbling of air is replaced by bubbling nitrogen so as to be placed under non-oxidizing conditions. This absence of oxygen in the air is representative of the confinement in which a gear box oil is placed in service. The evolution of the kinematic viscosity at 100 ° C. of the oils A and B according to the invention during the test is reported in Table 8 below: <b> Table 8: evolution of the kinematic viscosity at 100 ° C as a function of time, thermal aging test at 160 ° C. </ b> Table 8 Time (hour) Oil A Oil B Kinematic viscosity at 100 ° C (mm2 / s) 0 (new oil) 6.53 6.51 24 7.44 13.83 96 7.67 12.77 120 7.69 12.83 144 7.74 13,43 168 7.76 13.26 192 7.81 13.41

It is found that the oil A is very stable in temperature. For oil B, there is a significant initial increase in viscosity, and the product remains very stable over time. The level of insolubles measured for the two oils is very low, respectively 0.01 and 0.065 after 200 hours of testing. remains very stable over time. The level of insolubles measured for the two oils is very low, respectively 0.01 and 0.065 after 200 hours of testing.

The B oil therefore has the advantage of an exceptionally low insoluble level after oxidation test, with one initial thickening found during the thermal aging tests.

Oil A, when it is very thermally stable, with insoluble levels very high during oxidation tests.

The acid number increases from 3.5 to 6.5 for the oil A, which shows a very low degradation of the fatty acid methyl ester base;

The acid number goes from 3.7 to 2.1 for the oil B, which is not surprising if we consider that the initial thickening phenomenon is due to a transesterification reaction of the methyl esters of fatty acids with the heavy alcohols of the PMA.

Example 8 : Measurement of service life of the oils according to the invention.

A real test was carried out on a Peugeot 307 wheeled vehicle, the manual transmission of which is lubricated with oil B.

The viscosity of the oil, representative of its aging, the contents of certain metallic elements, representative of the wear of the mechanical parts, as well as the content of certain elements (in particular Ca, Zn, P, Mg, Mo, Bo, Na), the presence of which makes it possible to check if the additives of the oil are not degraded.

The results are summarized in Table 9 below.

In particular, it can be seen that the viscosity at 100 and at 40 ° C., with measurement errors, has remained constant.

In fact, there is a slight decrease in KV 100: this is the effect of shearing in service.

In particular, no increase in viscosity due to a problem of oxidation of the oil is observed. The VI also stays in values to achieve an FE (Fuel Eco) effect.

These excellent results are a priori related to the moderate heating experienced by the oils in use, and the confinement of oils in the gearboxes, which limits the contact with oxygen in the air.

The element content present in the main gearbox additives (P, Ca, Zn,) measured by ICP also remains constant at measurement errors.

There is a slight "increase" in their content: it could be evaporation, but more likely the "natural" uncertainty of the measurement on

The levels of wear observed are low and can not detect any anomaly in the protection of the gearbox organs by the lubricant.

The low acid number measured on the oil after 30,000 km of vehicle test also leads to the conclusion that there is no degradation of the esters used as a lubricating base. <b> Table 9: Evolution of the physicochemical parameters and the element contents of the oil in service </ b> Table 9 B (initial) B (after 30000 km test vehicle) Oil KV 40 ° C (mm ² / s, ASTM D445) 21.49 22.5 KV 100 ° C (mm ² / s, ASTM D445) 6.51 6.3 VI (ASTM D2270) 291 258 additives Calcium ppm 3480 3579 Zinc ppm 1640 1686 Phosphorus ppm 2180 2296 Wear Fe ppm - 47 Pb ppm <0.6 4 Cu ppm - 18 Sn ppm - <1 Cr ppm - 1 Al ppm - 6 No ppm - <1 Acid value 2.6

Claims (14)

1. A lubricating composition for gearboxes, with a kinematic viscosity at 100°C measured according to the ASTM D445 standard, comprised between 5.5 and 7 mm²/s, comprising

   - one or more phosphorus-containing, sulfur-containing, or phosphorus-sulphur-containing antiwear and/or extreme pressure additives,

   - at least 30% by weight of at least one fatty acid methyl ester of formula RCOOCH₃, wherein R is a paraffinic or olefinic group containing from 11 to 23 carbon atoms,
   and

   - either at least one compound selected from the group of heavy polyalphaolefins with a kinematic viscosity at 100°C, measured according to the ASTM D445 standard, comprised between 90 and 3,000 mm²/s and with a molecular mass by weight greater than 2,500 daltons,

   - or at least one compound selected from the group of light polyalphaolefins with a kinematic viscosity at 100°C, measured according to the ASTM D445 standard, comprised between 1.5 and 6 mm²/s, with a kinematic viscosity at 40°C, measured according to the ASTM D445 standard, comprised between 4 and 30 mm²/s, and with a molecular mass by weight of less than 500 daltons in combination with one or more compounds of the polymethacrylate type, with a molecular mass by weight of less than 30,000 daltons.
2. The lubricating composition according to claim 1, comprising at least 20% by weight of at least one fatty acid methyl ester of formula R₁COOCH₃, wherein R₁ is a mono-, di- or tri-unsaturated olefinic group containing from 11 to 23 carbon atoms.
3. The lubricating composition according to claim 1 or 2, comprising at least 20% by weight of at least one fatty acid methyl ester of formula R₂COOCH₃, wherein R₂ is a mono-unsaturated olefinic group containing from 11 to 23 carbon atoms.
4. The lubricating composition according to claim 2 or 3, wherein the unsaturations of the olefinic groups R₁ and/or R₂ are in the cis configuration.
5. The lubricating composition according to one of claims 1 to 4, wherein the mass percentage of heavy polyalphaolefin(s) is at least 10%, and wherein the mass percentage of the fatty acid methyl ester(s) is at least 60%.
6. The lubricating composition according to claim 5, comprising at least 50% by weight of at least one fatty acid methyl ester of formula R₁COOCH₃, wherein R₁ is a mono-, di- or tri-unsaturated olefinic group containing from 11 to 23 carbon atoms.
7. The lubricating composition according to claim 5 or 6, comprising at least 45% by weight of at least one fatty acid methyl ester of formula R₂COOCH₃, wherein R₂ is a mono-unsaturated olefinic group containing from 11 to 23 carbon atoms.
8. The lubricating composition according to any of claims 1 to 7, comprising at least 85% by weight of one or more fatty acid methyl esters of formula RCOOCH₃, wherein R is a paraffinic or olefinic group containing from 11 to 23 carbon atoms, based on the total weight of fatty acid esters present in said lubricant composition.
9. The lubricating composition according to any of claims 1 to 8, characterized in that the ratio S/P between the mass content of the sulfur element measured according to the ASTM D2622 standard and the content of the phosphorus element measured according to the ASTM D5185 standard in said lubricating compositions is comprised between 3 and 60.
10. The use of lubricating compositions for gearboxes according to any of claims 1 to 9, for generating fuel savings of more than 1% measured under the standard conditions of the NDEC test according to the Directive EEC 90/C81/01 on motor vehicles compared to an oil for a manual gear box used in lightweight private vehicles, of grade 75W80, with a kinematic viscosity of 8mm²/s at 100°C and with a VI of the order of 150, formulated with standard paraffinic bases of Group I.
11. The use of the fatty acid methyl ester bases containing at least 85% by weight of fatty acid methyl esters of formula RCOOCH₃, wherein R is a paraffinic or olefinic group containing from 11 to 23 carbon atoms with a VI greater than 250, measured according to the ASTM D2270 standard, and with a kinematic viscosity at 100°C, measured according to the ASTM D445 standard, of less than 7 mm²/s, as a lubricating base for formulating oils for gearboxes generating fuel savings of more than 1% measured under the standard conditions of the NDEC test according to the Directive EEC 90/C81/01 compared to an oil for a manual gear box used in lightweight private vehicles, of grade 75W80, with a kinematic viscosity of 8mm²/s at 100°C and with a VI of the order of 150, formulated with standard paraffinic bases of Group I.
12. The use according to claim 11, wherein said fatty acid methyl ester bases comprise at least 75% by weight of at least one fatty acid methyl ester of formula R₁COOCH₃, wherein R₁ is a mono-, di- or tri-unsaturated olefinic group containing from 11 to 23 carbon atoms.
13. The use according to claim 11, wherein said fatty acid methyl ester bases comprise at least 65% by weight of at least one fatty acid methyl ester of formula R₂COOCH₃, wherein R₂ is a mono-unsaturated olefinic group containing from 11 to 23 carbon atoms.
14. The use according to claim 11 or 12, wherein the unsaturations of the olefinic groups R₁ and/or R₂ are in the cis configuration.

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