FR3062387A1 - DILIPOATE OF DIMERE (S) DIOL AND USE THEREOF AS ADDITIVE - Google Patents

Abstract

The present invention relates to diol dimer dilipoate, its method of preparation, its use as an anti-wear additive, friction modifying additive and / or extreme pressure additive, as well as compositions comprising this additive.

Description

Holder (s):

OLEON NV.

O Extension request (s):

(® Agent (s): SANTARELLI.

(54) DIMER (S) DIOL DILIPOATE AND ITS USE AS AN ADDITIVE.

(57) The present invention relates to dimer (s) diol dilipoate, its preparation process, its use as an anti-wear additive, friction modifier additive and / or extreme pressure additive, as well as the compositions comprising this additive. .

FR 3 062 387 - A1

The present invention relates to a new type of diester, to a process for its preparation, to its uses as an anti-wear additive, friction modifier additive and / or extreme pressure additive, as well as to compositions comprising it, in particular lubricating compositions.

Anti-wear, friction modifier and extreme pressure additives are particularly used in the field of lubricants.

A lubricating composition generally comprises an oil, usually the majority constituent (ie the constituent whose content is the highest), and one or more additive (s).

An additive is used to reinforce one or more intrinsic property (s) of the oil and / or provide it with one or more additional property (s).

An anti-wear additive reduces wear on parts, such as metal parts, when brought into contact.

Among the anti-wear additives, mention may be made of polysulphides, dithiocarbamates, chlorinated paraffins, phosphates and thio-phosphates. Zinc dialkyl dithiophosphate (ZDDP) is one of the most used additives, because it is particularly effective as an anti-wear. However, this additive has a high toxicity. The decomposition of ZDDP releases various sulfur gases, such as hydrogen sulfide (H ₂ S) and mercaptans.

A friction modifier additive (or friction reducer) reduces friction between parts when they come into contact.

Among the most used friction modifying additives, there may be mentioned esters such as glycerol mono oleate (GMO), certain fatty acids and amides such as diethanolamide oleate (ODEA).

An extreme pressure additive prevents galling of metal parts by increasing the pressure and / or heat resistance of the oil present in the lubricating composition.

The most used extreme pressure additives today are compounds based on sulfur, phosphorus and / or chlorine. However, these types of compounds are not without impact on the environment because they contain significant amounts of phosphorus, sulfur and / or chlorine.

The US environmental protection agency has already banned the use of short-chain chlorinated paraffins and will gradually legislate on long chains of known toxicity. This change in legislation will lead to the gradual replacement of chlorinated paraffins by other less toxic extreme pressure additives such as sulfur and phosphorus derivatives.

Contacts and friction of metal surfaces take place in particular in applications such as metalworking (cutting, stamping, forming, ...), for which splashes of lubricants can be released into the environment.

It is therefore all the more advantageous for these applications to have the least toxic additive possible, such as a compound of renewable origin, with a reduced heteroatom content in order to limit the environmental impact.

The publication Lipoate ester multifunctional lubricant additives; Biresaw et al .; Industrial & Engineering Chemistry Research (2016), 55, 373-383, describes monoesters of renewable origin and their use as a multifunctional additive in vegetable oil. In particular, these are esters of lipoic acid and C4-C18 monoalcohols. The authors show that these purified esters are additives which improve the performance of an oleic sunflower oil, such as its viscosity index, its antioxidant properties and extreme pressure. On the other hand, these monoalcohol monolipoates bring no anti-wear and friction-modifying properties to this vegetable oil. In fact, oleic sunflower oil additivated to 5% by mass of monoalcohol monolipoate has friction coefficients and results in terms of wear equivalent or superior to those obtained with non-additive oleic sunflower oil (see Table 8 of this publication).

There is therefore always a need for high-performance and more environmentally friendly anti-wear, friction modifier and extreme pressure additives.

Surprisingly, it has been demonstrated that a particular diester makes it possible to obtain anti-wear, friction-modifying and extreme pressure properties comparable to those of products currently on the market and thus to confer on the oil with which it uses significantly improved performance, while being of renewable origin and having a lower impact on the environment.

The invention relates to a dilipoate of dimer (s) diol.

A dimer (s) diol dilipoate can also be called bis [5- (1,2-dithiolane3-yl) pentanoate] of dimer (s) diol, or bis [6,8-dithiooctanoate] of dimer (s) diol or thioctate of dimer (s) diol.

By “diol dimer (s)” is meant a diol dimer or a mixture of diol dimers capable of being obtained by intermolecular dimerization of one or more unsaturated carboxylic acid (s), followed by a reduction of acid functions into alcohol functions.

Each unsaturated carboxylic acid can have one or more unsaturations. Preferably, the unsaturation is a double bond.

Each unsaturated carboxylic acid preferably contains at least 16, more preferably at least 18 carbon atoms.

Advantageously, the unsaturated carboxylic acid is an unsaturated fatty acid derived from a renewable substance, such as vegetable oils, animal oils and animal fats. In particular, the unsaturated carboxylic acid is an unsaturated fatty acid containing from 16 to 24 carbon atoms, preferably from 18 to 22 carbon atoms.

It should be noted that, within the framework of the present request, and unless otherwise stipulated, the ranges of values indicated are understood to be bounds included.

According to a first embodiment, the dimer (s) diol is a dimer diol. It is capable of being obtained by intermolecular dimerization of an unsaturated carboxylic acid, in particular of an unsaturated fatty acid.

Thus, preferably, the dimer diol has from 32 to 48 carbon atoms, more preferably from 36 to 44 carbon atoms, even more preferably, the dimer diol has 36 carbon atoms.

In particular, the dimer diol is obtained from oleic acid or linoleic acid.

Generally, a diol dimer is a mixture of isomers, each of which may have an acyclic or cyclic structure.

Preferably, the dimer diol comprises more than 50% by mass, more preferably more than 70% by mass of acyclic isomer (s), the percentages by mass being given on the total mass of dimer diol.

According to a second embodiment, the diol dimer (s) is a mixture of diol dimers capable of being obtained by intermolecular dimerization of several (at least two, preferably at least three) unsaturated carboxylic acids, in particular, unsaturated fatty acids. Preferably, the diol dimer (s) is a mixture of diol dimers which may each and independently contain from 32 to 48 carbon atoms, preferably from 36 to 44 carbon atoms.

In particular, the mixture of diol dimers is obtained from fatty acids of a vegetable oil chosen from the group consisting of rapeseed oil, castor oil, sunflower oil, soybean oil , linseed oil and safflower oil.

As indicated previously, each diol dimer present in the mixture of diol dimers can be in the form of different isomers.

Preferably, the mixture of diol dimers comprises more than 50% by mass, more preferably more than 70% by mass, of acyclic isomer (s), the percentages by mass being given on the total mass of dimer diol.

Advantageously, at least 50%, preferably at least 60% by mass of dimer (s) diol of the total mass of dimer (s) diol has 36 carbon atoms and more than 50% by mass, preferably more than 70% by mass of diol dimer (s), out of the total mass of diol dimers, is acyclic.

By total mass of dimer (s) diol is meant the total mass of molecules of dimer diol.

The dilipoate of dimer (s) diol according to the invention is capable of being obtained by esterification of a dimer (s) diol, with lipoic acid.

The dimer (s) diol is as described above, including the advantageous and preferential modes.

Lipoic acid is also called 5- (1,2-dithiolane-3-yl) pentanoic acid, 6,8-dithiooctanoic acid or thioctic acid.

Preferably, the esterification is carried out at a temperature between 90 ° C and 170 ° C, more preferably between 100 ° C and 160 ° C, more preferably still, between 110 ° C and 150 ° C.

Advantageously, the esterification is carried out without a catalyst.

The absence of a catalyst has a notable economic advantage. Besides the saving on the cost of the catalyst itself, there is also a saving on the cost of the process for the preparation of the dimer (s) diol dilipoate, for which it is not necessary to add a recovery step. catalyst, neutralization and / or filtration type. Another advantage, the dimer (s) diol dilipoate is not contaminated by the presence, even in the form of a trace, of catalyst. In the absence of a catalyst, the reaction time generally lasts between 8 and 24 hours, preferably between 10 and 24 hours for a temperature between 110 ° C and 150 ° C.

Preferably, the lipoic acid represents between 0.8 and 1.5 equivalent, more preferably between 0.9 and 1.3 equivalent, even more preferably between 0.95 and 1.15 equivalent relative to the alcohol functions of the dimer ( s) diol.

More particularly, the dilipoate of dimer (s) diol is capable of being obtained by a process including the preparation of the dimer (s) diol, the process then comprising the following steps:

dimerization of at least one unsaturated carboxylic acid to form an acid dimer (s);

reduction of the acid functions into alcohol functions to form a dimer (s) diol;

esterification of the dimer (s) diol with lipoic acid to form dilipoate of dimer (s) diol.

The unsaturated carboxylic acid is as described above.

The reduction step can be carried out under hydrogen pressure, optionally using a catalyst such as lithium tetrahydruroaluminate, sodium hydride or diisobutylaluminum hydride.

A step of esterification of the acid functions into ester functions, such as the formation of methyl esters, can precede the step of reduction to alcohols. In this case, the formation of the dimer (s) diol is carried out by reduction of the ester functions into alcohol functions.

Prior to the esterification step of the dimer (s) diol, the process can also comprise a purification step, such as distillation, in order to isolate the dimer (s) diol from the by-product (s) and / or residual fatty acid (s).

More particularly still, the dilipoate of dimer (s) diol is capable of being obtained by a process comprising the following steps:

dimerization of unsaturated fatty acids from vegetable oil to form a mixture of acid dimers;

optionally, esterification of the acid functions into methyl esters; reduction of the acid or ester functions into alcohol functions to form a mixture of diol dimers;

optionally, purification of the mixture of diol dimers;

esterification of the mixture of dimer diol with lipoic acid to form dilipoate of dimer diol.

The dimer (s) diol dilipoate preferably contains from 48 to 64 carbon atoms. More preferably, from 52 to 60 carbon atoms, even more preferably, the dimer (s) diol dilipoate has 52 carbon atoms.

Since the dimer (s) diol can be a mixture of dimer diol, then the dilipoate of dimer (s) diol can therefore be a mixture of dilipoate of dimer diol, preferably each comprising independently and independently of 48 to 64 carbon atoms, more preferably of 52 to 60 carbon atoms.

Each dimer diol dilipoate can also be a mixture of isomers, each of which may have an acyclic or cyclic structure. Preferably, the dilipoate of dimer (s) diol comprises more than 50% by mass, more preferentially more than 70% by mass, of isomer (s) acyclic (s), the percentages by mass being given on the total mass of dilipoate of diol dimer (s). In particular, the dimer (s) diol dilipoate is acyclic.

Advantageously, at least 50% by mass, preferably at least 60% by mass of dimer (s) diol dilipoate contains 52 carbon atoms and more than 50% by mass, preferably more than 70% by mass of dimer dilipoate (s ) diol is acyclic, the percentages by mass being given on the total mass of dilipoate of dimer (s) diol.

By total mass of dimer (s) diol dilipoate is meant the total mass of molecules of dimer diol dilipoate.

Preferably, the dimer (s) diol dilipoate is saturated.

The invention also relates to a process for preparing a dilipoate of dimer (s) diol by esterification between a dimer (s) diol and lipoic acid.

The lipoic acid, the dimer (s) diol and the esterification are as described above, including the advantageous and preferential modes.

More particularly, the process for the preparation of the dimer (s) diol dilipoate can include the preparation of the dimer (s) diol, the process then comprises the following steps:

dimerization of at least one unsaturated carboxylic acid to form an acid dimer (s);

reduction of the acid functions into alcohol functions to form a dimer (s) diol;

esterification of the dimer (s) diol with lipoic acid to form dilipoate of dimer (s) diol.

The unsaturated carboxylic acid is as described above.

The reduction step can be carried out under hydrogen pressure, optionally using a catalyst such as lithium tetrahydruroaluminate, sodium hydride or diisobutylaluminum hydride.

A step of esterification of the acid functions into ester functions, such as the formation of methyl esters, can precede the step of reduction to alcohols. In this case, the formation of the dimer (s) diol is carried out by reduction of the ester functions into alcohol functions.

Prior to the esterification step of the dimer diol, the process can also comprise a purification step, such as distillation, in order to isolate the dimer diol from the by-product (s) and / or the acid (s). (s) residual fat (s).

Advantageously, the process for the preparation of the dilipoate of dimer (s) diol comprises the following stages:

dimerization of unsaturated fatty acids from vegetable oil to form a mixture of acid dimers;

optionally, esterification of the acid functions into methyl esters; reduction of the acid or ester functions into alcohol functions to form a mixture of diol dimers;

optionally, purification of the mixture of diol dimers;

esterification of the mixture of dimer diol with lipoic acid to form dilipoate of dimer diol.

The invention also discloses the uses of the dimer (s) diol dilipoate according to the invention.

According to a first aspect of the invention, the invention discloses the use of the dimer (s) diol dilipoate according to the invention as an anti-wear additive.

The inventors have in fact found that the dilipoate of dimer (s) diol acts as an anti-wear additive. The dimer (s) diol dilipoate makes it possible to reduce wear during friction of parts when they come into contact. This effect is more fully described in Examples 2.2 and 2.4.

According to a second aspect of the invention, the invention discloses the use of the dimer (s) diol dilipoate according to the invention as a friction-modifying additive.

The inventors have found that the dimer (s) diol dilipoate acts as a friction-modifying additive. The dilipoate of dimer (s) diol in fact makes it possible to reduce the coefficient of friction during friction of parts when they are brought into contact. This effect is more fully described in Examples 2.3 and 2.4.

According to a third aspect of the invention, the invention discloses the use of the dimer (s) diol dilipoate according to the invention as an extreme pressure additive.

The inventors have found that the dimer (s) diol dilipoate acts as an extreme pressure additive. Indeed, the introduction of dimer (s) diol dilipoate in mineral oil makes it possible to reduce the time before rupture thereof when it is subjected to high pressures. This effect is more fully described in the Example

2.5.

Finally, according to a fourth aspect of the invention, the invention discloses the use of the dimer (s) diol dilipoate according to the invention as a multi-property additive.

The inventors have found that when dimer (s) diol dilipoate is added to a mineral oil, the latter has improved properties, in particular in terms of wear, reduction of friction and / or extreme pressure.

Advantageously, the dimer (s) diol dilipoate according to the invention is used as an anti-wear additive, friction-modifying additive and / or extreme pressure additive.

The present invention also relates to a composition comprising a dilipoate of dimer (s) diol according to the invention and an oil.

An oil is a hydrophobic substance which is present in the liquid state at room temperature and atmospheric pressure.

The oil can be chosen from among mineral oils, natural oils and synthetic oils.

Mineral oils are oils from petroleum refining. They are essentially made up of carbon and hydrogen atoms, such as paraffinic oils, hydrorefined oils, hydrocracked oils and hydroisomerized oils.

Natural oils are more particularly intended for vegetable, animal or algae oils.

Synthetic oils are obtained by chemical reaction between molecules of petrochemical origin and / or of renewable origin, with the exception of the usual chemical reactions making it possible to obtain mineral oils (such as hydrorefining, hydrocracking, l hydro-isomerization, etc.). Among the various chemical families of synthetic oil, mention may in particular be made of esters, polyalkylene glycols (PAG) and polyalphaolefins (PAO).

Advantageously, the composition according to the invention is a lubricating composition. Preferably, the lubricant composition is a metalworking oil, a motor oil, a transmission oil, a hydraulic oil, or a gear oil.

In the field of lubricants, the oil represents at least 50% by mass of the mass of the lubricating composition.

Advantageously, the oil of the composition according to the invention is chosen from among mineral oils and / or synthetic oils. Preferably, the oil of the composition according to the invention is a mineral oil.

Mineral oils are classified into three groups:

group I oils: these oils have a saturated hydrocarbon content of less than 90% by mass, an aromatic hydrocarbon content of more than 1.7% by mass, a sulfur content of more than 0.03% by mass, and a viscosity index of between 80 and 120;

group II oils: these oils have a saturated hydrocarbon content greater than 90% by mass, an aromatic hydrocarbon content less than 1.7% by mass, a sulfur content of less than 0.03% by mass, and a viscosity index of between 80 and 120;

group III oils: these oils have a saturated hydrocarbon content of more than 90% by mass, an aromatic hydrocarbon content of less than 1.7% by mass, a sulfur content of less than 0.03% by mass, and a viscosity index of more than 120;

the percentages by mass being given relative to the mass of the oil.

Group II mineral oils are widely used in the metalworking industry. Also, advantageously, the oil of the composition according to the invention is a group II mineral oil.

Preferably, the composition according to the invention comprises an amount of dimer (s) diol dilipoate of at least 2% by mass, more preferably at least 3% by mass, more preferably still at least 3.5% by mass per relative to the total mass of the composition.

Preferably, the composition according to the invention additionally comprises an additive other than a dilipoate of dimer (s) diol.

Advantageously, the additive other than a dilipoate of dimer (s) diol is chosen from the additives used in the field of lubricants, such as antioxidant additives, antiwear additives, additives improving the viscosity index, friction modifying additives, extreme pressure additives, pour point lowering additives, anti-foam additives, demulsifying additives, corrosion inhibiting additives, thickening additives, detergent additives and dispersing additives.

A person skilled in the art knows how to choose the most suitable additive (s) according to the chosen application, such as a lubricant application.

The additive other than a dimer (s) diol dilipoate, can be chosen from:

- antioxidant additives, such as dialkyl-dithiophosphates, substituted phenols and / or aromatic amines;

- anti-wear additives, such as zinc dialkyl-dithiophosphates and / or phosphorus derivatives, these can be added in an amount less than that usually used;

- viscosity index improving additives, such as polymers of olefin copolymers (OCP), polyisobutenes, polymethacrylates, diene polymers, polyalkylstyrenes and / or molybdenum derivatives;

- friction modifying additives, such as glycerol monooleate (GMO), these being able to be added in a quantity lower than that usually used;

- extreme pressure additives, such as organometallic derivatives of molybdenum, compounds derived from fatty acids, phosphosulfur molecules and / or borates, these can be added in a quantity lower than that usually used;

- pour point lowering additives, such as metallic soaps, carboxylic acids, polymethacrylates, alkylphenols, dialkylaryl esters of phthalic acid, maleate-styrene copolymers, naphthalene paraffins and / or polyesters of vinyl fumarate acetate type;

- anti-foam additives, such as silicone oils, silicone polymers and / or alkyl acrylates;

- demulsifying additives, such as propylene oxide copolymers;

- anticorrosion (or anti-rust) additives such as alkali and / or alkaline earth metal sulfonates (Na, Mg, Ca salts), fatty acids, fatty amines, akenylsuccinic acids and / or their derivatives, benzotriazole, and / or tolyltriazole;

- thickening additives, such as fatty esters;

- detergent additives, such as calcium and / or magnesium salts of alkylaryl sulfonates, alkylphenates, alkylsalicylates and / or their derivatives;

- dispersing additives, such as alkenyl succinimides, succinic esters and / or their derivatives, and / or Mannich bases;

- metal deactivating additives, such as heterocyclic compounds containing nitrogen and / or sulfur, for example triazole, tolutriazole, and benzotriazole;

or their mixtures.

Note that an additive can have several properties, such as zinc dialkyldithiophosphate which is an antioxidant, anti-wear, anti-corrosion and slightly dispersing additive.

Due to the anti-wear, friction-modifying and extreme pressure properties of the dimer (s) diol dilipoate of the invention, the presence of the dimer (s) diol dilipoate in the composition makes it possible to reduce the quantity usually required of the other additive, in particular when it is an anti-wear additive, a friction modifier additive and / or an extreme pressure additive, thus making it possible to reduce the environmental impact of this other additive, in particular if it has a certain toxicity.

As indicated above, the compositions according to the invention are particularly suitable for use as a lubricating composition.

The present invention finally discloses a process for preparing a composition according to the invention, comprising a step of mixing an oil with a dilipoate of dimer (s) diol according to the invention.

Preferably, the process for the preparation of a composition according to the invention comprises a step of mixing a mineral oil and / or a synthetic oil, with a dilipoate of dimer (s) diol, more preferably, a step of mixing a mineral oil with a dilipoate of dimer (s) diol according to the invention.

The invention will be better understood in the light of the following examples, given by way of illustration, with reference to:

Figure 1, which is a graph representing Stribeck curves (i.e. curves representing the friction coefficient measurements as a function of the speed of rotation) obtained from a non-additive mineral oil and the same additive oil of 10% by mass of diol dimer dilipoate (1 test and 2 repetitions with each sample);

Figure 2, which is a graph representing the average improvement (on the test and the two repetitions of Fig. 1) of the coefficient of friction between a non-additive mineral oil and the same additive oil of 10% by mass of dilipoate of diol dimers;

Figure 3, which is a graph representing Stribeck curves obtained from three samples, a control and two samples containing dimer diol dilipoate and GMO respectively;

Figure 4, which is a graph showing Stribeck curves obtained from two samples containing dimer diol dilipoate and n-octyl lipoate respectively.

Example 1 Preparation of a dimer diol dilipoate according to the invention

100 g of lipoic acid (98% lipoic acid, CAS number: 1077-28-7) and 132.5 g of diol dimers (Radianol® 1990 sold by Oleon NV, composed of at least 98% of diol dimers including at least 95% of diol dimers containing 36 carbon atoms, and at least 75% of acyclic isomers).

The mixture is heated to 140 ° C, with stirring. The progress of the reaction is followed by thin layer chromatography. After 24 hours of reaction, the alcohol conversion is complete.

The reaction mixture is purified on Combi-Flash by passage over a column of silica gel, with heptane as eluent with a gradient of 0 to 5% acetone.

After evaporation of the eluent, the dimer diol dilipoate is obtained in the form of a yellowish viscous oil.

The mixture of diol dimer dilipoate obtained contains 98.3% of diol dimer dilipoate containing 52 carbon atoms and 76% of acyclic isomers.

Example 2: Evaluation of the properties of the dimer diol dilipoate of Example 1

2.1-Preparation of samples

Five samples were prepared using:

Chevron Neutral oil 220R group II mineral oil (hereinafter referred to as “mineral oil”), and the dimer diol dilipoate of Example 1.

The composition of the samples numbered from A to E is indicated in Table 1 below:

Sample Content AT 100% Group II mineral oil Chevron Neutral oil 220R B Mineral oil + 5% * by mass of diol dimer dilipoate VS Mineral oil + 10% * by mass of diol dimer dilipoate D Mineral oil + 3.5% * by mass of diol dimer dilipoate E Mineral oil + 2% * by mass of diol dimer dilipoate

* on the total mass of the sample

Table 1: Contents of samples A to E tested

2.2- Evaluation of the anti-wear property of the dimer diol dilipoate of Example 1

The effect of dimer diol dilipoate was measured on the four-ball wear test according to standard ASTM D4172-94 (2016). The test consists in applying three balls disposed on the same plane and immersed in a sample, a weight of 40 kg with rotation at 1200 rpm for one hour at 75 ° C, via the 4 ^th ball placed at the intersection of the other three marbles.

During the test conducted with sample A, an average wear of the balls of 1.110 mm was observed.

The same test conducted with sample C, reduced wear to 0.625 mm, a decrease in wear by 43.7%.

A similar result, wear of 0.650 mm, was observed with sample E.

The addition of 2% by mass of diol dimer dilipoate in a group II mineral oil makes it possible to reduce the wear of the metal in contact with this composition by 41.4%.

2.3- Evaluation of the friction-modifying property of the dimer diol dilipoate of Example 1

To quantify the decrease in friction, the friction coefficient of samples A, C and E was measured on an MCR-502 rheometer equipped with an Anton-Paar MCR tribometer.

A 100Cr6 steel ball is brought into contact with 3 100Cr6 steel cylinders with a rotation ranging from 1000 mm / s to 0.01 mm / s at 25 ° C and applying a force of 10 Newtons. The three cylinders and the ball are immersed in 0.5 mL of the test sample. The coefficient of friction as a function of the speed of rotation is then measured to establish a Stribeck curve.

With sample A, it was observed that by repeating the test 2 times, the coefficient of friction at low speed (<0.25 mm / s), increases significantly each time (Fig. 1).

Conversely, with sample C, the coefficient of friction remains stable after 2 repetitions, at values much lower than those obtained with sample A (Fig. 1).

At low speeds and therefore maximum metal-to-metal contact, a reduction in the coefficient of friction is observed up to 53% (Fig. 2).

Similar results are obtained with sample E, by lowering the loading from 10% to 2% by mass of dimer diol dilipoate.

Adding 2% by weight of dimeric diol dilipoate to Group II mineral oil reduces friction by up to approximately 53% compared to using the same non-additive oil. Dimer diol dilipoate can therefore be used as a friction-modifying additive.

2.4- Evaluation of the anti-wear and friction-modifying property of the dimer diol dilipoate of Example 1

The anti-wear and friction-modifying properties of dimer diol dilipoate were also measured using the HFRR test (“High Frequency Reciprocating Rig”), a device with high frequency reciprocating motion, similar to what is described in the ASTM standard. D6079 - 11 (2016).

The test involves applying a weight to a moving ball on a disc to measure wear and the coefficient of friction at different temperatures.

Two samples were tested: sample A and C. A few milliliters of each sample are used to immerse the ball before each test.

A wear of the ball of 255.3 x 231.8 pm is observed with the use of sample A. The coefficient of friction is 0.166 at 70 ° C, 0.202 at 100 ° C and 0.241 at 130 ° C.

With sample C, the wear is reduced to 153.9 x 156.6, i.e. 40% x 32% decrease. The coefficient of friction is then 0.142 at 70 ° C, 0.114 at 100 ° C and 0.111 at 130 ° C, i.e. a reduction in the coefficient of friction of 14% at 70 ° C, 44% at 100 ° C and 54% at 130 ° C.

This HFRR test confirms the anti-wear and friction-modifying property of dimer diol dilipoate.

2.5- Evaluation of the extreme pressure property of the diol dimer dilipoate of Example 1

The extreme pressure property of dimer diol dilipoate was evaluated using the Twist Compression Test (TCT) from TribSys. For this test, a rotary annular module is brought into contact with a fixed and flat plate at a defined speed and pressure.

After stirring the samples, 0.3-0.5 milliliters of each sample was deposited on the plate using a pipette and the data collected at 50Hz.

The dynamic tests were carried out at 10 revolutions per minute and at a pressure of 69 MPa at the pressure interface on a metal plate made of steel 410 and with an annular steel module of type D2 (60-65 Rc), up to '' lubrication failure.

This rupture corresponds either to a clear variation in the coefficient of friction curve showing a change in behavior of the parts in friction and therefore of the lubrication, or to a coefficient of friction reaching a value of 0.2.

The friction force transmitted by the annular module to the metal plate changes when the lubricated interface changes following the rotation of the module under the applied weight.

The results are collated in Table 2 below:

Sample Sulfur content (% by mass) Time before rupture (s) AT 0 0.26 B 0.7 58

Table 2: Time before rupture at a pressure of 69 MPa

The addition of 5% by mass of dimer diol dilipoate in a group II mineral oil makes it possible to increase the time before rupture. Dimer diol dilipoate can therefore be used as an extreme pressure additive.

Another test was carried out at 10 revolutions per minute and at a pressure of 103 MPa; the result is given in Table 3 below:

Sample Sulfur content (% by mass) Time before rupture (s) D 0.5% by mass of sulfur 26

Table 3: Time before rupture at a pressure of 103 MPa

This test confirms that dimer diol dilipoate can be used as an extreme pressure additive. At 3.5% by mass in a group II mineral oil, and under a pressure of 103 MPa, the time before rupture is increased.

Example 3: Comparisons of the Properties of the Dipol Dimer Diol of Example 1

3.1-Preparation of samples

In addition to the samples already prepared in Example 2, six other samples were prepared using:

Chevron Neutral oil 220R Group II mineral oil (hereinafter referred to as "mineral oil");

n-octyl lipoate prepared according to the preparation process described in the publication Lipoate ester multifunctional lubricant additives; Biresaw et al .; Industrial & Engineering Chemistry Research (2016), 55, 373-383.

the zinc dialkyldithiophosphate anti-wear additive (hereinafter referred to as "ZDDP");

the additin® RC 2540 extreme pressure additive from RheinChemie (a dialkylpentasulfide containing 40% by mass of sulfur, hereinafter referred to as "Additin");

the extreme pressure additive Paroil® 140-LV from Dover Chemical Corporation (a chlorinated paraffin containing 42% by mass of chlorine, hereinafter referred to as “Paroil”), and the friction modifying additive glycerol monooleate Radiasurf® 7149 from OIeon (hereinafter referred to as "GMO").

The composition of the samples numbered from F to K is indicated in Table 4 below:

Sample Content F Mineral oil + 1% * by mass of ZDDP G Mineral oil + 3.5% * by mass of Additin RC 2540 H Mineral oil + 10% * by mass of Paroil 140-LV I Mineral oil + 7% * by mass of n-octyl lipoate J Mineral oil + 10% * by mass of GMO K Mineral oil + 10% * by mass of n-octyl lipoate

* on the total mass of the sample

Table 4: Contents of samples F to K tested

3.2-Four-ball wear test

The comparative tests were carried out under the same conditions as those described in Example 2.2.

3.2 a) -With the ZDDP anti-wear additive

The test carried out with sample F leads to a wear of 0.570 mm, ie a wear reduction of 48.6%.

Samples C and F each contain a sulfur content of 1.4% · The dimer diol dilipoate has an anti-wear property (reduction of 43.7%) comparable to ZDDP, an anti-wear additive among the most used today . This confirms that the dimer diol dilipoate can be used as an anti-wear additive.

3.2 b) -With n-octyl lipoate

The tests carried out with samples I and K lead to wear of 0.775 mm and 0.783 mm respectively, ie a reduction in wear of 30.2% and 29.5%.

The diol dimer dilipoate has an anti-wear property superior to the anti-wear effect of n-octyl lipoate, and this as well with equal quantity (10%) of ester in oil (samples C and K), which 'with equal sulfur content (samples C and I). Samples C and I both contain a sulfur content of 1.4%.

3.3- Test on rheometer

The comparative tests were carried out under the same conditions as those described in Example 2.3.

3.3 a) -With the GMO friction modifier additive

The test carried out with sample J shows that the GMO lowers the coefficient of friction in a similar way to the dilipoate of dimers diol (Fig. 3).

This comparative test confirms that the dimer diol dilipoate can be used as a friction modifier additive.

3.3 b) -With n-octyl lipoate

The test carried out with sample K also makes it possible to observe a reduction in the coefficient of friction at low speeds. However, this reduction is less compared to dilipoate (Fig. 4).

Diol dimer dilipoate has a higher friction-modifying property than n-octyl lipoate.

3.4- HFRR test

The comparative test was carried out under the same conditions as those described in Example 2.4.

With sample K, wear of the ball of 213.6 x 176.5 pm is observed, ie a decrease of 16% x 24%. The coefficient of friction is 0.142 to 70 ° C, 0.125 to 100 ° C and 0.143 to 130 ° C, i.e. a decrease in the coefficient of friction of 14% at 70 ° C,

38% at 100 ° C and 41% at 130 ° C.

This HFRR test demonstrates the best anti-wear and friction-modifying property of dimer diol dilipoate compared to n-octyl lipoate.

3.5-Rotation compression test

The comparative tests were carried out under the same conditions as those described in Example 2.5.

The results are collated in Table 5 below:

Sample Sulfur content (% by mass) Time before rupture (s) AT 0 0.26 B 0.7 58 VS 1.4 83 G 1.4 51

Table 5: Comparison of time before rupture with a sulfur additive

For a similar time before rupture, the use of diol dimer dilipoate makes it possible to reduce the sulfur content. For example, for a rupture time of between 51 and 58 seconds, the sulfur content is divided by two, i.e. 0.7% in the composition comprising dimer diol dilipoate, against 1.4% in the composition comprising Additin.

Other tests were carried out at 10 revolutions per minute and at a pressure of 103 MPa; the results are collated in Table 6 below:

Sample Heteroatom content (S, Cl) (mass%) Time before rupture (s) D 0.5% by mass of sulfur 26 H 4.2% chlorine 22

Table 6: Comparison of time before rupture with a chlorine additive

Compared to the commercial extreme pressure additive, Paroil, the dimer diol dilipoate used in less quantity (3.5% against 10% by mass), containing a sulfur content of 0.5% by mass (against 4.2% in chlorine), has a longer time before rupture and therefore better.

Claims (11)

1. Dilipoate of dimer (s) diol. 2. Process for the preparation of a dimer (s) diol dilipoate by esterification between a dimer (s) diol and lipoic acid. 3. Use of the dimer (s) diol dilipoate according to claim 1, as an anti-wear additive. 4. Use of the dimer (s) diol dilipoate according to claim 1, as a friction modifier additive. 5. Use of the dimer (s) diol dilipoate according to claim 1, as an extreme pressure additive. 6. Use of the dimer (s) diol dilipoate according to claim 1, as a multi-property additive. 7. Composition comprising a dilipoate of dimer (s) diol according to claim 1, and an oil. 8. Composition according to claim 7, in which the oil is a mineral oil. 9. Composition according to claim 7 or 8, further comprising an additive other than a dilipoate of dimer (s) diol. 10. Use of a composition according to any one of claims 7 to 9, as a lubricating composition. 11. A method of preparing a composition according to any one of claims 7 to 9, comprising a step of mixing an oil with a dilipoate of dimer (s) diol. 1/2 CN 00 LO CN m LO t — 1 t — 1 O LH t — 1 m in m LO CD o CD CD O O o t — 1 m LO CN LD o O in 00 ^ r CN in in in 00 CD O O o o o o t — 1 CN LH CD in in in oo LO CD 00 τ — 1 τ — 1 O o o o o o where where where where t — 1 t — 1 in r < a t — 1 in LH t — 1 t — 1 o t — 1 m LO CN a CD CD t — 1 CN LD CD Speed mm / s