EP3918042A1

EP3918042A1 - Lubricating base oil synthesized from polyol esters and biosourced fatty acids

Info

Publication number: EP3918042A1
Application number: EP20707712.4A
Authority: EP
Inventors: Stéphanie LEBRUN; Salomé GRAVELAT; Guillaume Le
Original assignee: Arkema France SA
Current assignee: Arkema France SA
Priority date: 2019-01-29
Filing date: 2020-01-29
Publication date: 2021-12-08
Also published as: WO2020157433A1; JP2022518941A; CN113366095A; SG11202108270XA; US20220089964A1; FR3092112A1; KR20210121101A; US11453833B2; FR3092112B1

Abstract

The present invention relates to esters of at least one polyol and of a fatty acid mixture comprising at least one saturated C₅-C₁₂ fatty acid and at least one unsaturated C₁₀-C₁₂ fatty acid.

Description

DESCRIPTION

TITLE: LUBRICANT BASE OIL SYNTHETIZED FROM POLYOL ESTERS AND

BIOSOURCE FATTY ACIDS

Field of the invention

The present invention relates to esters of polyols and a mixture of fatty acids, their use as a lubricating base and their manufacturing process.

Currently, the lubricating base market is dominated by mineral oils of petroleum origin. In 2008, European production of lubricants amounted to 4.5 million tonnes per year. These lubricating bases are used in various industries such as motor oil, cutting oil for chainsaw chains, oil for offshore petroleum drilling, hydraulic oil for construction machinery and agricultural machinery, etc.

These mineral oils, once used, are not always recycled and cause environmental pollution due to discharge on the ground, in sewers, in lakes and rivers. In view of the potential impact of these lubricating oils on the environment, the development of environmentally friendly and biodegradable lubricating bases is essential, particularly for applications where the lubricant is likely to escape into the environment.

The use of vegetable and animal oils has been known for several years. These oils have the advantage of being environmentally friendly. However, they have low thermal stability, low resistance to oxidation compared to mineral oils and are susceptible to hydrolysis in the presence of water.

Biodegradable lubricating compositions comprising products derived from palm oil and polyols such as neopentylglycol or trimethylolpropane are described in patent application EPI 533360. However, such compositions are only suitable for temperatures ranging from 15 to 40 ° C.

In this context, it therefore remains necessary to develop esters of polyols whose structure can be derived from ingredients preferably of renewable origins, possessing excellent lubricating properties as well as safety with respect to man and the environment. Summary of the invention

In the context of the invention, it has been observed that esters of at least one polyol and of a mixture of fatty acids comprising at least one saturated C5-C12 fatty acid and at least one unsaturated C10 fatty acid -C12 exhibit excellent properties for lubricant applications.

The present invention results from the unexpected demonstration, by the inventors, that esters of at least one polyol and of a mixture of fatty acids in which the acids are a mixture of 10-undecylenic acid and of n-heptanoic acid from renewable resources exhibit excellent properties for applications in lubricants.

Thus, the present invention relates to esters of at least one polyol and a mixture of fatty acids comprising at least one saturated C5-C12 fatty acid and at least one unsaturated C10-C12 fatty acid.

The present invention also relates to the use of esters of at least one polyol and of a mixture of linear fatty acids comprising at least one saturated C5-C12 fatty acid and at least one unsaturated C10-C12 fatty acid such as as defined above as a lubricating base.

The present invention also relates to a lubricating base composition comprising esters of at least one polyol and of a mixture of linear fatty acids comprising at least one saturated C5-C12 fatty acid and at least one unsaturated C10- fatty acid. C12 as defined above.

The present invention also relates to a process for the preparation of esters comprising the esterification of a mixture of linear fatty acids comprising at least one saturated C5-C12 fatty acid and at least one unsaturated C10-C12 fatty acid with at least a polyol, optionally in the presence of a catalyst.

The present invention also relates to esters of at least one polyol and of a mixture of linear fatty acids comprising at least one saturated C5-C12 fatty acid and at least one unsaturated C10-C12 fatty acid obtained by the defined process. above.

Detailed description of the invention

The lubricating base compositions according to the invention synthesized from esters of at least one polyol and a mixture of fatty acids of renewable origin, such as for example erythritol and the mixture of fatty acids in which acids its † a mixture of n-heptanoic acid e † of 10-undecylenic acid (eg a mixture of OIeris® C7 e † Cl 1: 1 from Arkema), make it possible to achieve properties in terms of thermal stability, oxidation stability, as well as a viscosity index, higher than the usual esters don † the alcohol is non-biobased, such as, for example, trimethylolpropane, as detailed in the examples below.

Thus, the present invention provides a particular lubricating base composition which offers good thermal stability, improved oxidation stability and very good lubricating properties. The term “biodegradable” is used here to denote a compound formed from molecules which can be transformed into smaller molecules which pollute less, for example by microorganisms living in the natural environment, such as bacteria, fungi and algae. The end result of this degradation is usually water, carbon dioxide or methane.

By materials, compounds or ingredients "from renewable resources" or "biobased" are meant renewable natural materials, compounds or ingredients whose stock can be reconstituted over a short period on a human scale. These are in particular raw materials of animal or plant origin. By raw materials of renewable origin or bio-resourced raw materials is meant materials which include bio-resourced carbon or carbon of renewable origin. In fact, unlike materials made from fossil fuels, materials made from renewable raw materials contain carbon 14 ( ^{. 4} C). The “carbon content of renewable origin” or “bio-resourced carbon content” is determined in application of the standards ASTM D 6866 (ASTM D 6866-06) and ASTM D 7026 (ASTM D 7026-04).

The viscosity of a fluid refers to the resistance it opposes to the internal sliding of its molecules during its flow. The viscosity is given for a reference temperature. The expressed kinematic viscosity is m / s ² , is calculated using the following formula: o = h / r, where

h is the dynamic viscosity in Pa.s; and

p is the density of the fluid in kg / m ³

Kinematic viscosity is also expressed in Stockes (St) or in centistokes (cSt).

Kinematic viscosity is measured according to ISO 3104 standard. Oxidative stability can be determined via two measurements: oxygen induction time and oxygen induction temperature. The oxygen induction time and the oxygen induction temperature can be measured in a differential scanning calorimeter (DSC - Differential scanning calorimetry) according to ISO 1 1357-6: 2018.

The pour point of a product is the minimum temperature at which the product will still flow. The pour point is measured according to ISO 3016.

The viscosity index (VI) (unitless) indicates the rate of change in the viscosity of an oil over a given temperature range, usually between 40 ° C and † 100 ° C. The viscosity index can be defined as the kinematic viscosity gradient of a material, between 40 and 100 ° C. When the viscosity index is low (less than 100), the fluid shows a relatively large variation in viscosity with temperature. When the viscosity index is high (greater than 150), the fluid exhibits relatively little change in viscosity with temperature. In a variety of applications, a high or very high viscosity index is preferred. The viscosity index is measured according to the test method described in ASTM D 2270.

Esters

The esters according to the invention are formed from at least one polyol e † of a mixture of fatty acids comprising at least one saturated C5-C12 fatty acid e † at least one unsaturated C10-C12 fatty acid.

According to one embodiment, the esters according to the present invention can be mono-, di-, tri-, e † tetraesters.

The fatty acid mixture according to the invention is preferably derived from renewable resources. The fatty acid mixture according to the invention is preferably of plant or animal origin, linear or branched.

The mixture of fatty acids according to the invention is preferably composed mainly of linear fatty acids. Preferably, the mixture of fatty acids according to the invention consists of at least 50% by weight, more preferably from 50% to 70% by weight, still more preferably at least 70% by weight of acids. linear fats relative to the mass of the mixture of fatty acids. More preferably, the fatty acid mixture consists of 100% linear fatty acids. Preferably, linear fatty acids make it possible to increase the viscosity index of the lubricating bases synthesized, to improve their thermal stability and are more easily biodegradable than branched acids, mainly obtained from the petroleum industry.

The fatty acid mixture according to the invention is preferably obtained from castor oil, coconut oil, cottonseed oil, dehydrated castor oil, soybean oil, tall oil, rapeseed oil, sunflower oil, linseed oil, palm oil, tung oil, oiticica oil, oil safflower, olive oil, wood, corn, squash, grape seed, jojoba oil, sesame, walnut, hazelnut, almond, shea, macadamia, alfalfa, rye, peanut, copra, or argan oil.

The term “fatty acid or the mixture of fatty acids“ derived from oil ”means a fatty acid present in the oil and / or fatty acids which can be obtained at the end of a transformation. chemical. For example, heptanoic acid and / or 10-undecylenic acid can be obtained from castor oil, typically, by the thermal cracking step of methyl ricinoleate which results from the transesterification of the oil. of castor.

Preferably, the saturated C5-C 12 fatty acid according to the invention is selected from the group consisting of pentanoic acid, isovaleric acid, caproic acid, heptanoic acid, n-heptanoic acid , caprylic acid, pelargonic acid, capric acid, citric acid, tetrahydrofuran 2,5 dicarboxylic acid, tetrahydrofuran 3,5 dicarboxylic acid, azelaic acid, undecanedioic acid, and dodecanedioic acid

Preferably, the saturated C5-C 12 fatty acid according to the invention is n-heptanoic acid, more preferably Oleris® n-Heptanoic acid (ARKEMA).

Preferably, the n-heptanoic acid is derived from castor oil.

Preferably, the unsaturated C10-C12 fatty acid according to the invention is selected from the group consisting of 10-undecylenic acid, and dodec-2-enedioic acid.

Preferably, the unsaturated C10-C12 fatty acid according to the invention is 10-undecylenic, more preferably Oleris® undecylenic acid (ARKEMA).

Preferably, the 10-undecylenic acid is obtained from castor oil. The mass ratio of saturated C5-C12 fatty acid to unsaturated C10-C12 fatty acid according to the invention is 1: 10 to 10: 1, preferably 8: 2 to 2: 8, more preferably of 7: 3.

The polyol according to the invention can be chosen from any polyol well known to those skilled in the art. The polyol according to the invention can be of petrochemical origin or from renewable resources.

Preferably, the polyol according to the invention is an organic compound containing several hydroxyl groups.

According to one embodiment, the polyols do not refer to compounds which contain functional groups other than hydroxyls.

The polyol according to the invention is preferably selected from the group consisting of frimethylolpropane, frimethylolethane, pentaerythritol, dipentaerythritol, tripentaerythritol, tetra pentaerythritol and neopenfyl glycol, or mixtures thereof.

The polyol obtained from renewable resources according to the invention is preferably biodegradable. The polyol obtained from renewable resources according to the invention can be a sugar polyol. Typically, the sugar polyol is a compound having the general chemical formula C _n H2n ₊ 20n and having at least two hydroxyl groups.

Preferably, the sugar polyol is selected from the group consisting of monosaccharides, disaccharides and frisaccharides.

Preferably, the monosaccharide according to the invention is selected from the group consisting of erythritol, xylose, arabinose, ribose, sorbitol, sorbitan, glucose, sorbose, fructose, xylifol and mannitol, more preferably from the group consisting of xylose, arabinose, ribose, glucose, sorbose and fructose.

Preferably, the disaccharide according to the invention is selected from the group consisting of malfose, lactose, and sucrose.

The frisaccharide according to the invention is preferably selected from the group consisting of raffinose, malfotriose, and hydrogenated hydrolysates of starch.

More preferably, the sugar polyol according to the invention is erythritol.

The polyol according to the invention is preferably selected from the group consisting of erythritol, xylifol, mannitol, frimethylolpropane, frimethylolethane, pentaerythritol, dipentaerythritol, tripentaerythritol, tetrapentaerythritol, malfose, lactose , sucrose, raffinose, maltotriose e † of neopentyl glycol or mixtures thereof, more preferably from the group consisting of erythritol, xylitol, mannitol, trimethylolpropane, trimethylolethane, pentaerythritol, dipentaerythritol, tripentaerythritol, tetrapentaerythoprityl, and glycol or mixtures thereof.

According to one embodiment, the sugar polyol according to the invention is obtained by hydrogenation of a sugar.

Preferably, the mass ratio of the polyol to the mixture of fatty acids is in the range of 1: 4 to 1: 10. More preferably, the weight ratio of polyol to fatty acid mixture is about 1: 5.

Preferably, the ester according to the invention has an oxygen induction time measured in a differential scanning calorimeter at 150 ° C of greater than 2 hours.

Preferably, the ester according to the invention has an oxygen induction temperature measured in a differential scanning calorimeter of greater than 200 ° C.

Preferably, the ester according to the invention has a kinematic viscosity of 14 to 30 mm ² / s at 40 ° C, and / or less than 6 mm ² / s at 100 ° C, which is measured according to the ISO 3104 standard. .

Preferably, the ester according to the invention has a pour point of less than -

20 ° C.

Process

Preferably, the esterification process according to the invention comprises a step of esterifying at least one polyol according to the invention in the presence of a mixture of excess fatty acids comprising at least one saturated fatty acid in Cs- C12 and at least one C10-C12 unsaturated fatty acid according to the invention, with or without catalyst.

The esterification step according to the invention is preferably carried out at a temperature between 140 ° C and 250 ° C for a period of 0.5 to 12 hours, preferably 1 to 10 hours, more preferably 2 at 8 o'clock.

The esterification step according to the invention is preferably carried out under an inert atmosphere.

The esterification step according to the invention is preferably carried out in a pressure range ranging from 30 mm Hg to 760 mm Hg. The esterification process according to the invention may comprise a step of adding an absorbent such as alumina, silica gel, zeolites, activated carbon, and clay.

The process according to the invention can further comprise a step of adding basic water to simultaneously neutralize the residual organic and mineral acids and / or to hydrolyze the catalyst. In this case, the method according to the invention may include a step of removing the water used by heating and placing under vacuum.

The process according to the invention can also include a step of filtering the solids of the ester mixture containing the major part of the excess acid mixture used in the esterification reaction.

The process according to the invention may include a step of removing excess acids by steam extraction or by any other method of distillation and recycling of the polyol in the reaction vessel. Preferably, the compound obtained by the process according to the invention is purified by distillation at reduced pressure of the unreacted acid. The distillation is preferably carried out under vacuum for 15 to 60 minutes. The distillation is further preferably carried out at a temperature between 140 ° C and 180 ° C. The amount of free acid remaining after the distillation step can be reduced by treatment with epoxy esters, by neutralization with any suitable alkali material such as lime, alkali metal hydroxides, metal carbonates alkaline or basic alumina. When treatment with epoxy esters is carried out, a second distillation under reduced pressure can be carried out to remove excess epoxy ester. When alkaline treatment is performed washing with water can be performed to remove excess unreacted alkaline material.

The process according to the invention may include a step of removing any residual solid matter from the ester extracted during a final filtration.

Preferably, the fatty acid mixture according to the invention is present in the reaction to form the ester according to the invention in an excess of about 10 to 50% by moles, preferably about 10 to 30%. in moles, relative to the amount of polyol used.

The process according to the invention can be carried out in the presence of a catalyst. The catalyst can be any catalyst well known to those skilled in the art for esterification reactions. Preferably, the catalyst is selected from the group consisting of tin chloride, sulfuric acid, p-toluene acid sulfonic acid, methane sulfonic acid, sulfosuccinic acid, hydrochloric acid, phosphoric acid, catalysts based on zinc, copper, tin, titanium, zirconium or tungsten; alkali metal salts such as sodium or potassium hydroxide, sodium or potassium carbonate, sodium or potassium ethoxide, sodium or potassium methoxide, zeolites and acidic ion exchangers , or mixtures thereof.

use

The esters according to the invention are preferably used as such as a lubricating base or lubricating base oil.

The esters according to the invention can also be used as a mixture with other base oils, such as mineral oils, highly refined mineral oils, polyalphaolefins (PAO), polyalkylene glycols (PAG), phosphate esters, silicone oils, diesfers, polyisobufylenes and polyol esters.

In particular, the esters according to the invention are useful for the preparation of a lubricating base composition. The lubricating base composition according to the invention can be used in all types of industries, in particular as automotive lubricants, as metalworking oils, as hydraulic oils, as turbine oils, or even as oils for airplanes.

Preferably, the composition according to the invention may contain a level of tetraesters greater than or equal to 80% by weight relative to the total amount of ester. More preferably, the composition may contain a level of tetraesters greater than or equal to 93% by weight relative to the total amount of ester.

The composition according to the invention may contain, in addition to the esters according to the invention, one or more additives. Preferably, the additives are selected from the group consisting of antioxidants, thermal stability improvers, corrosion inhibitors, metal deactivators, lubricant additives, viscosity index improvers, pour point depressants, detergents, dispersing agents, defoamers, antiwear agents, and additives resistant to extreme pressures.

Preferably, the amount of additives in the composition according to the invention does not exceed 10% by weight, preferably 8% by weight, more preferably 5% by weight relative to the total weight of the lubricating base composition. Preferably, the amount of antioxidants used is between 0.01% and 5% relative to the total weight of the lubricating base composition.

Preferably, the amount of corrosion inhibitors is between 0.01% and 5% by weight relative to the total weight of the lubricating base composition.

Preferably, the amount of metal deactivators is between

0.001% and 0.5% by weight relative to the total weight of the lubricating base composition.

Preferably, the amount of lubricating additives is between 0.5% and 5% by weight relative to the total weight of the lubricating base composition.

Preferably, the amount of agents improving the viscosity index is between 0.01% and 2% by weight relative to the total weight of the lubricating base composition.

Preferably, the amount of pour point depressants is between 0.01% and 2% by weight relative to the total weight of the lubricating base composition.

Preferably, the amount of detergents is between 0.1% and 5% by weight relative to the total weight of the lubricating base composition.

Preferably, the amount of dispersing agents is between 0.1% and 5% by weight relative to the total weight of the lubricating base composition.

Preferably, the amount of anti-foaming agents is between 0.01% and

2% by weight relative to the total weight of the lubricating base composition.

Preferably, the amount of anti-wear agents is between 0.01% and 2% by weight relative to the total weight of the lubricating base composition.

Preferably, the amount of additives resistant to extreme pressures is between 0.1% and 2% by weight relative to the total weight of the lubricating base composition.

Antioxidants and thermal stability improvers can be selected from any of the antioxidants and thermal stability improvers well known to those skilled in the art. For example, the antioxidant and the thermal stability improving agent can be selected from the group consisting of:

diphenyl-amine, dinaphthyl-amine, phenylnaphthylamine, in which the phenyl group or the naphthyl group may be substituted, for example by the groups N, N'-diphenyl phenylenediamine, p-octyldiphenylamine, p, p-diocfyldiphenylamine, N-phenyll-naphthyl amine, N-phenyl-2-naphthyl amine, N- (p-dodecyl) phenyl-2-naphthyl amine, di-1-naphthyl amine, e † di-2-naphthyl amine;

phenofhazines, such as N-alkylphenothiazines;

imino (bisbenzyl); and

hindered phenols such as 6- (t-butyl) phenol, 2, ô-di- (t-butyl) phenol, 4-methyl-2, 6- di- (t-butyl) phenol, 4,4'- methylenebis (-2,6-di- (t-butyl) phenol).

Metal deactivators can be selected from any metal deactivators well known to those skilled in the art. By way of example, the metal deactivators can be selected from the group consisting of imidazole, benzamidazole, 2-mercaptobenzthiazole, 2,5-di-mercaptothiadiazole, salicylidin-propylenediamine, pyrazole, benzotriazole, tolutriazole, 2-methylbenzamidazole, 3,5-dimethyl pyrazole, and methylene bis-benzotriazole. Other examples of metal deactivators or corrosion inhibitors include:

- organic acids and their esters, metal salts and anhydrides, such as N-oleyl-sarcosine, sorbitan monooleate, lead naphthenate, dodecenyl-succinic acid and its partial esters and amides, and 4-nonylphenoxyacetic acid;

primary, secondary and tertiary aline and cycloaliphatic amines and amine salts of organic and inorganic acids, such as oil-soluble alkylammonium carboxylates;

- heterocyclic compounds containing nitrogen, such as thiadiazoles, substituted imidazolines and oxazolines;

quinolines, quinones and anthraquinones;

- propyl gallate:

barium dinonylnaphthalenesulfonate;

ester and amide derivatives of anhydrides or alkenylsuccinic acids, dithiocarbamates, dithiophosphates; amine salts of alkyl acid phosphates and their derivatives.

The lubricant additives can be selected from any lubricant additives well known to those skilled in the art. As an example of lubricant additives, we can mention long-chain derivatives of fatty acids and natural oils, such as esters, amines, amides, imidazolines and borates.

The viscosity index improvers can be selected from any viscosity index improver well known to those skilled in the art. By way of example of agents which improve the viscosity index, mention may be made of polymethacrylates, vinylpyrrolidone copolymers and methacrylates, polybutenes and styrene-acrylate copolymers.

Pour point depressants can be selected from any pour point depressants well known to those skilled in the art. By way of example of pour point depressants, mention may be made of polymethacrylates such as ethylene methacrylate-vinyl acetate terpolymers; alkylated naphthalene derivatives; e † Friedel-Crafts condensation products catalyzed by urea with naphthalene or phenols.

Detergent and dispersant agents can be selected from any detergent and dispersant agents well known to those skilled in the art. By way of example of detergent and dispersant agents, mention may be made of polybutenylsuccinic acid amides; polybutenylphosphonic acid derivatives; long chain alkyl substituted aromatic sulfonic acids in their salts; e † metal salts of alkylsulphides, of alkylphenols e † of condensation products of alkylphenols e † of aldehydes.

Anti-foaming agents can be selected from any anti-foaming agents well known to those skilled in the art. As an example of an anti-foaming agent, we can mention silicone polymers and certain acrylates.

Antiwear agents and additives resistant to extreme pressure can be selected from any antiwear agents and additives resistant to extreme pressure. As an example of anti-wear agents and additives resistant to extreme pressures, we can mention:

- sulfurized fatty acids and fatty acid esters, such as sulfurized octyl fallafe;

- sulfurized ferpenes;

sulfurized olefins;

- organopolysulphides;

organo-phosphorus derivatives including amine phosphates, alkyl acid phosphates, dialkyl phosphates, aminedithiophosphates, trialkyl and triaryl phosphorothionates, trialkyl e † triaryl phosphines, e † dialkyl phosphites such as phosphoric acid monohexyl ester amine salts, dinonylnaphthalenesulfonate amine salts, triphenyl phosphate, trinaphthyl phosphate, diphenylcresyl and phenylphenyl phosphates, naphthyldiphenyl phosphate, triphenylphosphorothionate;

dithiocarbamates, such as antimony dialkyldithiocarbamate; chlorinated and / or fluorinated hydrocarbons and xanthafes.

The invention will be further explained with the aid of the following nonlimiting Examples.

Examples

The inventors have studied the properties of an ester according to the present invention for application in lubricants.

1. Preparation of the ester

5 samples are tested:

erythritol ester e † of a mixture of n-hepfanoic acid e † of 10-undecylenic acid (ester according to the invention);

n-hepfanoic acid trimefhylolpropane ester (Comparative Example 1);

10-undecylenic acid trimefhylolpropane ester (Comparative Example 2);

trimefhylolpropane ester of unsafe fatty acids (comparative example commercial 3-product PRIOLUBE 2044 ^® from CRODA);

pentaerythritol e † ester of linear fatty acids (comparative example 4-commercial product NYCOBASE ^® 8410 from NYCO);

pentaerythritol e † ester of branched fatty acids (comparative example 5- commercial product NYCOBASE ^® 1060X from NYCO).

Ester according to the invention: Synthesis of an erythritol e † tefraesfer of a mixture of hepfanoiaue and undecyléniaue acids with a molar excess of acid

Erythritol (16.4g, 0.13mol), n-hepfanoic acid (64.3g, 0.49mol) e † 10-undecylenic acid (27.8g, 0.15 mol) with a mass ratio of 70 / 30 are loaded in a 250ml three-necked flask equipped with a stirrer, a thermometer, a condenser and an inlet for nitrogen.

The reaction mixture was heated at 210 ° C under a nitrogen atmosphere for a period of 5 hours, until the theoretical amount of water was stable. Zirconium tetrabutanolate (1.35 g, 80% in butanol, 1% by weight / total weight of the reactants) is then added in batch to the reactor. The assembly is gradually placed under maximum vacuum at 190 ° C for 2h30 to distill off the excess unreacted acid and yields 82.8g of product.

Downstream treatment with activated basic alumina is carried out on the reaction crude and results in an oil with an acid number of 0.02 mgKOH / g.

The kinematic viscosities, the viscosity index (VI.) And the pour point of the product are evaluated and reported in Table 2.

The chemical composition of the product was established by chromatography

gas as follows: 93.6% tetraesters, 4.8% anhydroesters and 0.1% triesters.

Comparative Example 1: Synthesis of an ester of trimethylolpropane and n-heptanoïaue acid with a molar excess of acid

Trimethylolpropane (53.8g, 0.4 mol) and n-heptanoic acid (181.5g, 1.38mol) are loaded into a 500ml three-necked flask equipped with an agitator, a thermometer, a condenser and 'an inlet for nitrogen. The reaction mixture was heated at 185 ° C under a nitrogen atmosphere for a period of 3 hours, until the theoretical amount of water was collected. Zirconium tetrabutanolate (1.5 g, 80% in butanol, 0.5% by weight / total weight of the reactants) is then added in batch to the reactor. The assembly is gradually placed under maximum vacuum at 185 ° C for 3 hours 30 minutes to distill off the excess unreacted acid and yields 187.4g of product. A downstream treatment with activated basic alumina is carried out on the reaction crude and results in an oil with an acid number of

0.1 mgKOH / g. The chemical composition of the product has been established by

gas chromatography as follows: 98.8% of trimethylol propane triheptanoate and 0.03% of trimethylol propane diheptanoate.

Comparative example 2: Synthesis of a trimethylolpropane ester of 10-undecylenic acid with a molar excess of acid Trimethylolpropane (40.4g, 0.30 mol) e † 10-undecylenic acid (218g, 1.17mol) are loaded into a 500ml three-necked flask equipped with a stirrer, a thermometer, a condenser and 'an inlet for nitrogen. The reaction mixture was heated at 185 ° C. under a nitrogen atmosphere for a period of 3 h, until the theoretical quantity of water was collected. Zirconium tetrabutanolate (3.2 g, at 80% in butanol, 1% by mass / total mass of the reactants) is then added in batch to the reactor. The assembly is gradually placed under maximum vacuum at 185 ° C. for 3 hours 30 minutes to distill off the excess unreacted acid and leads to 195.3 g of product.

Downstream treatment with activated basic alumina is carried out on the reaction crude and results in an oil with an acid number of 1.8 mgKOH / g. The chemical composition of the product was established by chromatography

gaseous as follows: 98.3% of trimethylol propane triundecylenate and 0.99% of trimethylol propane diundecylenate.

2. Measurement of oxidation resistance

Oxidative stability is determined by two measurements: the oxygen induction time and the oxygen induction temperature. The oxygen induction time and the oxygen induction temperature are measured in a Differential Scanning Calorimeter (DSC).

To measure the oxygen induction time, the sample is heated to 150 ° C and then kept at constant temperature. It is then exposed to an oxidizing atmosphere. The time between contact with oxygen and the onset of oxidation is the oxygen induction time.

For measurement of the oxygen induction temperature, the sample is heated with a constant heating rate under an oxidizing atmosphere until the reaction begins. The oxygen induction temperature is the temperature at which the oxidation reaction begins.

The results are presented in Table 1 below:

[Tables 1]

Table 1: measurement of the resistance to oxidation

The measurements show that the oxygen induction time at 150 ° C of the three samples are similar. The ester according to the invention has a higher oxygen induction temperature than Comparative Examples 1 e † 2. Consequently, the ester according to the invention has better oxidation resistance properties than usual ester synthesized from a non-biobased alcohol.

3. Measurement of kinematic viscosity

The kinematic viscosity was measured at 40 ° C. e † at 100 ° C. according to the ISO 3104 standard. The results, expressed in mm ² / s, are presented in Table 2 below.

4. Measurement of the viscosity index

The viscosity index (unitless) is measured according to the test method described in ASTM D 2270. The results are presented in Table 2 below.

5. Measuring the pour point

The pour point, expressed in ° C, es † measured according to the ISO 3016 standard. The results are presented in Table 2 below. [Tables 2]

Table 2: Measurement of kinematic viscosity, viscosity index and pour point.

These examples show that the ester according to the invention, synthesized from substances of renewable origin, has the lowest kinematic viscosities at 40 ° C e † 100 ° C as well as the highest viscosity index, which means that the lubricating base according to the invention has a stable viscosity as a function of the temperature. The lubricating base of the invention has the lowest pour point, compared to those of the comparative examples synthesized from alcohols obtained from the petroleum industry and from unsaturated fatty acids, or linear or branched.

Claims

[Claim 1] Esters of at least one polyol and a mixture of fatty acids comprising at least one saturated C5-C12 fatty acid and at least one unsaturated C10-C12 fatty acid.

[Claim 2] Esters according to claim 1, in which the mixture consists predominantly of linear fatty acids.

[Claim 3] Esters according to claim 1 or 2, wherein the saturated C5-C12 fatty acid is n-heptanoic acid.

[Claim 4] Esters according to any of claims 1 to 3, wherein the unsaturated C10-C12 fatty acid is 10-undecylenic acid.

[Claim 5] Esters according to any one of claims 1 to 4, wherein the mass ratio of saturated C5-C12 fatty acid to unsaturated C10-C12 fatty acid is from 1: 10 to 10: 1 .

[Claim 6] Esters according to any one of claims 1 to 5, wherein the mass ratio of saturated C5-C12 fatty acid to unsaturated C10-C12 fatty acid is 8: 2 to 2: 8 .

[Claim 7] Esters according to any one of claims 1 to 6, wherein the mass ratio of saturated C5-C12 fatty acid to unsaturated C10-C12 fatty acid is 7: 3.

[Claim 8] Esters according to any one of claims 1 to 7, wherein the weight ratio of polyol to fatty acid mixture is at least 1: 5.

[Claim 9] Esters according to any one of claims 1 to 8, wherein the saturated C5-C12 fatty acid and the unsaturated C10-C12 fatty acid are obtained from renewable resources.

[Claim 10] Esters according to any one of claims 3 to 4, wherein the saturated C5-C12 fatty acid and the unsaturated C10-C12 fatty acid are derived from castor oil.

[Claim 1 1] Esters according to any one of claims 1 to 10, wherein the polyol is selected from the group consisting of sorbitol, erythritol, xylitol, mannitol, trimethylolpropane, trimethylolethane, pentaerythritol, dipentaerythritol, tripentaerythritol, tetrapentaerythritol, maltose, lactose, sucrose, raffinose, maltotriose, and neopentyl glycol or mixtures thereof.

[Claim 12] Esters according to any one of claims 1-1 1, wherein the polyol is derived from a renewable resource.

[Claim 13] Use of the ester of at least one polyol and of a mixture of fatty acids comprising at least one saturated C5-C12 fatty acid and at least one unsaturated C10-C12 fatty acid as defined in one of claims 1 to 12 as a lubricating base.

[Claim 14] Composition of a lubricating base comprising an ester of at least one polyol and of a mixture of fatty acids comprising at least one C5-C12 saturated fatty acid e † at least one C10- unsaturated fatty acid C12 as defined in one of claims 1 to 12.

[Claim 15] Process for preparing an ester comprising G esterification of a mixture of fatty acids comprising at least one saturated C5-C12 fatty acid e † at least one unsaturated C10-C12 fatty acid with at least one polyol , optionally in the presence of a catalyst.

[Claim 16] Esters of at least one polyol e † of a mixture of fatty acids comprising at least one saturated C5-C12 fatty acid e † at least one unsaturated C10-C12 fatty acid obtained by the process according to claim 15.