EP2791298B1 - Grease composition - Google Patents

Description

Field of the invention

The present invention relates to grease compositions, in particular to grease compositions having a reduced impact on the environment and which have good extreme pressure and corrosion properties, in particular with respect to metals or metal alloys. .

Technological background of the invention

The recent period has seen the rise of environmental problems on a planetary scale and the imposition of the protection of the terrestrial biosphere as a major problem in all sectors of industry. The field of fats is no exception to the rule, and the risk of pollution of water and soil represented in particular by the release into nature of base oils, the main ingredients of these products, justifies that we now expect to the latter that they are making progress in the field, particularly in terms of biodegradability for uses that involve risks of external leakage of grease. At the same time, machines, ever more powerful, are called upon under increasingly severe conditions and require from their lubricating products, in addition for example to biodegradability, significant performance gains in terms of properties. extreme pressure and corrosion.

The present invention relates to a grease composition that can be used in devices with risks of external leaks of grease such as automobiles, construction machinery or agricultural equipment, and which has both a reduced impact on the environment, good performance in extreme pressure and low corrosion vis-à-vis metals or metal alloys.

Surprisingly, the Applicant has found that a fat composition exhibiting a combination of at least one sulfur fatty acid ester, said ester providing a certain amount of active sulfur at 150 ° C. according to standard ASTM D1662 and at least one dimercaptothiadiazole derivative, in a base oil of polyol ester type, exhibits very good extreme pressure properties, is not corrosive in particular with respect to metals or metal alloys, in particular copper, while having reduced impact on the environment.

Requirement US 2006/025314 relates to fluid lubricating compositions, for applications as transmission fluids, formed predominantly of a base oil and comprising, as additives, at least one fatty sulfur oil in an amount sufficient to provide at least 1000 ppm of sulfur to the fluid composition and a compound of dialkyl thiadiazole type in an amount sufficient to provide at least 500 ppm of sulfur to the composition.

Requirement US 2003/139302 discloses a grease composition containing, in a lubricating base oil, relative to the total weight of the composition: 0.01 to 10% by weight of a fatty acid salt; 0.01 to 10% by mass of carbonate; 2 to 30% by mass of a thickener and 0.1 to 20% by mass of a sulfur-containing extreme pressure agent.

Brief description of the invention

The present text describes a fat composition comprising at least one base oil of polyol ester type, at least one fatty acid metallic soap, at least one dimercaptothiadiazole derivative and at least one sulfur fatty acid ester, the amount of sulfur active at 150 ° C. according to standard ASTM D1662 by mass provided by the sulfur fatty acid ester, relative to the total mass of the fat composition, being greater than or equal to 0.18%.

The invention relates to a fat composition comprising at least one base oil of polyol ester type, at least one fatty acid metallic soap, from 0.1 to 5% by mass, based on the total mass of the composition of fat, of at least one dimercaptothiadiazole derivative chosen from 2,5-dimercapto-1,3,4-thiadiazole derivatives of general formula (I) or (II), taken alone or as a mixture; and at least one sulfur fatty acid ester, the amount of sulfur active at 150 ° C according to ASTM D1662 by mass provided by the sulfur fatty acid ester, relative to the total mass of the fat composition, being greater than or equal to 0.18%.

Preferably, the polyol ester is chosen from neopentylglycol esters, trimethylolethane esters, trimethylolpropane esters, pentaerythritol esters and / or dipentaerythritol esters taken alone or as a mixture.

Preferably, the composition comprises from 50 to 95% by mass, relative to the total mass of the fat composition, of a base oil of the polyol ester type, preferably from 60 to 90%, more preferably from 70 to 80%.

Preferably, the composition comprises from 0.2 to 2%, by weight of the derivative of dimercaptothiadiazole, relative to the total weight of the fat composition, more preferably from 0.5 to 1%.

Preferably, the sulfur-containing fatty acid ester is a fatty acid triglyceride and / or a fatty acid methyl ester, taken alone or as a mixture.

Preferably, the composition comprises from 0.5 to 5% by weight of sulfur fatty acid ester, relative to the total weight of the fat composition, preferably from 1 to 4%, more preferably from 2 to 3% .

Preferably, the fatty acid metallic soap is a simple fatty acid metallic soap, preferably lithium or calcium.

Preferably, the fatty acid metallic soap is lithium 12-hydroxystearate.

Preferably, the composition comprises from 1 to 20% by mass, relative to the total mass of the fat composition, of fatty acid metallic soap, preferably from 2 to 15%, preferably from 4 to 12%.

Preferably, the polyol ester, or the mixture of polyol esters, has a kinematic viscosity at 40 ° C, measured according to the standard ASTM D 445, between 3 and 2000 cSt, preferably between 10 and 1500 cSt, more preferably between 40 and 500 cSt, even more preferably between 50 and 200 cSt.

Preferably, the composition has a consistency according to the ASTM D217 standard of between 220 and 430 tenths of a millimeter, preferably between 265 and 295 tenth of a millimeter.

Preferably, the quantity of active sulfur at 150 ° C. according to standard ASTM D1662 by weight provided by the sulfur fatty acid ester, relative to the total weight of the fat composition, greater than or equal to 0.19%, preferably greater than or equal to 0.20%, more preferably greater than or equal to 0.21%.

Preferably, the composition has a solder load according to ASTM D2596 greater than 315 kg, preferably greater than or equal to 400 kg.

Preferably, the composition has a welding load according to standard DIN 51350/4 greater than 300 daN, preferably greater than or equal to 320 daN, more preferably greater than or equal to 340 daN, even more preferably greater than or equal to 360 daN.

Preferably, the composition has a copper corrosion rating according to ASTM D4048 of 1 or 2.

The invention also relates to the use, in a fat composition comprising at least one base oil of polyol ester type and at least one fatty acid metallic soap, of at least one derivative of dimercaptothiadiazole and at least one sulfur fatty acid ester, the amount of active sulfur at 150 ° C according to ASTM D1662 by mass provided by the sulfur fatty acid ester being greater than or equal to 0.18%, relative to the total mass of fat composition, to improve extreme pressure performance according to ASTM D2596 and / or DIN 51350/4 standards for the grease composition.

The present text also describes a lubricating composition comprising at least one base oil of polyol ester type, at least one derivative of dimercaptothiadiazole and at least one sulfur-containing fatty acid ester, the amount of active sulfur at 150 ° C. according to the standard. ASTM D1662 by mass provided by the sulfur-containing fatty acid ester, relative to the total mass of lubricating composition, being greater than or equal to 0.18%.

The invention also relates to a lubricating composition comprising at least one base oil of polyol ester type, from 0.1 to 5% by mass, relative to the total mass of the grease composition, of at least one derivative of dimercaptothiadiazole. chosen from 2,5-dimercapto-1,3,4-thiadiazole derivatives of general formula (I) or (II), taken alone or as a mixture; and at least one sulfur fatty acid ester, the amount of sulfur active at 150 ° C according to ASTM D1662 by mass provided by the sulfur fatty acid ester, relative to the total mass of lubricating composition, being greater or equal to 0.18%.

detailed description Sulfur fatty acid ester

The fat according to the invention comprises at least one sulfur fatty acid ester.

The sulfur-containing fatty acid esters are obtained by sulfurizing fatty acid esters. Said fatty acid esters are obtained by reaction between one or more fatty acids and alcohols of all kinds or by transesterification between one or more fatty acid esters and alcohols of all kinds. The term “sulfur-containing fatty acid ester” is understood to mean an ester of at least one sulfur-containing fatty acid, it being understood that it is most of the time an ester of a mixture of sulfur-containing fatty acids.

The fatty acids which can be used to form the sulfur-containing fatty acid esters are all fatty acids comprising from 6 to 24 carbon atoms, preferably from 14 to 22 carbon atoms, more preferably from 16 to 20 carbon atoms. The fatty acids comprising 18 carbon atoms are the majority fatty acids, that is to say they are present at a concentration by mass of at least 50% relative to the total mass of sulfur fatty acid ester .

The sulfur-containing fatty acid esters may be sulfur-containing fatty acid monoesters, sulfur-containing fatty acid diesters, sulfur-containing fatty acid triesters or sulfur-containing fatty acid polyesters taken alone or as a mixture.

Preferred sulfur-containing fatty acid monoesters are C ₁ -C ₄ alkyl monoesters, such as methyl monoesters, ethyl monoesters, n -propyl monoesters, i -propyl monoesters, monoesters n -butyl, s -butyl monoesters, t -butyl monoesters. Preferably, the monoester is a methyl monoester. Preferably the sulfur fatty acid ester is a sulfur fatty acid methyl ester.

As example of sulfur-containing fatty acid triesters, mention may be made of sulfur-containing fatty acid triglycerides which will be completely or partially esterified and will therefore optionally comprise, in addition to triesters, diesters and / or monoesters.

As an example of sulfur-containing fatty acid polyesters, mention may be made of the pentaerythritol esters of sulfur-containing fatty acids.

An advantage of the invention is to provide a fat composition free from sulfur olefins and / or polysulphides. In fact, sulfur-containing fatty acid esters have a reduced impact on the environment, since they are compounds derived from renewable resources (fatty substances and fatty acids) and contain a high level of renewable carbon. This is not the case with sulfur-containing olefins which are obtained by sulphurization of olefins, products of hydrocarbon origin and polysulphides which are also obtained by sulphurization of hydrocarbon starting materials. It is remarkable to note that good extreme pressure performances have been obtained by using sulfur-containing fatty acid esters rather than sulfur-containing olefins or polysulfides, which are known to have better extreme-pressure properties, this being notably possible thanks to the presence in addition of a derivative of dimercapthotiadiazole in the fat composition.

For the purposes of the present invention, the term “active sulfur” is understood to mean the sulfur that a chemical compound is capable of yielding or of liberating when this compound is placed under the conditions of standard ASTM D1662. The ASTM D-1662 standard defines an active sulfur content of a compound at a given temperature as a difference expressed as a weight percentage of sulfur content before and after reacting a sample of this sulfur compounds with a given quantity of copper for a fixed time.

The amount of active sulfur at 150 ° C. (ASTM D1662) in the grease composition is one of the important parameters for obtaining good performance, in particular under extreme pressure. This amount of active sulfur at 150 ° C (ASTM D1662) in the grease composition should not be too low, otherwise satisfactory extreme pressure behavior cannot be obtained. It should not be too high, otherwise it is the corrosion of the grease, in particular with respect to copper, which poses a problem and, moreover, a quantity of active sulfur at 150 ° C (ASTM D1662) that is too high without the presence of the derivative of dimercaptothiadiazole will not give either good performance especially in extreme pressure.

Preferably, the amount of active sulfur at 150 ° C according to ASTM D 1662 provided by the sulfur fatty acid ester in the fat composition is greater than or equal to 0.18% by mass, relative to the mass total fat composition, preferably greater than or equal to 0.19%, more preferably greater than or equal to 0.20%, even more preferably greater than or equal to 0.21%.

Preferably, the amount of active sulfur at 150 ° C according to ASTM D 1662 provided by the sulfur fatty acid ester in the fat composition is less than or equal to 5% by mass, relative to the total mass of fat composition, preferably less than or equal to 4%, more preferably less than or equal to 2%, even more preferably less than or equal to 1%.

Preferably, the amount of sulfur according to standard D2622 provided by the sulfur fatty acid ester in the fat composition is greater than or equal to 0.35% by mass, relative to the total mass of the fat composition, of preferably greater than or equal to 0.40%, more preferably greater than or equal to 0.45%.

Preferably, the fat composition comprises from 0.5 to 5% by weight, relative to the total weight of the fat composition, of sulfur fatty acid ester, preferably from 1 to 4%, more preferably from 2 at 3%.

Preferably, the fat composition according to the invention comprises at least two different sulfur fatty acid esters, to improve the extreme pressure performance, preferably at least one sulfur fatty acid methyl ester and at least one acid triglyceride. sulphurous fat. At a given quantity of active sulfur at 150 ° C, the combination of two different sulfur-containing fatty acid esters, in particular of a methyl ester of sulfur-containing fatty acid and of a triglyceride of sulfur-containing fatty acid, makes it possible to improve extreme pressure performance because sulfur is not released in the same way. The less crowded ester, such as sulfur fatty acid methyl ester, will release active sulfur faster, then the more crowded ester, such as sulfur fatty acid triglyceride will take over.

The sulfur-containing fatty acid esters used in the present invention are products available commercially, for example from the suppliers PCAS, King Industries, Dover, Magna, Arkema, Rhein Chemie.

Dimercaptothiadiazole derivative

The grease compositions according to the invention comprise at least one derivative of dimercaptiothiadiazole as defined in claim 1, an essential element of the invention for obtaining good extreme pressure performance.

Thiadiazoles are heterocyclic compounds comprising two nitrogen atoms, one sulfur atom, two carbon atoms and two double bonds, of general formula C ₂ N ₂ SH ₂ , which can exist in the following forms, respectively: 1,2, 3-thiadiazole; 1,2,4-thiadiazole; 1,2,5-thiadiazole; 1,3,4-thiadiazole:

Dimercaptothiadiazole derivatives are chemical compounds derived from the following four dimercaptothiadiazole molecules, below: 4,5-dimercapto-1,2,3-thiadiazole, 3,5-dimercapto-1,2,4-thiadiazole, 3,4 -dimercapto-1,2,5-thiadiazole, 2,5-dimercapto-1,3,4-thiadiazole, taken alone or as a mixture:

dans lesquelles, R₁ et R₂ sont indépendamment l'un de l'autre, des atomes d'hydrogène, des groupes alkyles linéaires ou ramifiés, saturés ou insaturés, comprenant de 1 à 24 atomes de carbone, de préférence de 2 à 18, plus préférentiellement de 4 à 16, encore plus préférentiellement de 8 à 12 ou des substituants aromatiques, n et m étant indépendamment l'un de l'autre des entiers égaux à 1, 2, 3 ou 4.According to the invention, the dimercaptothiadiazole derivative is chosen from 2,5-dimercapto-1,3,4-thiadiazole derivatives of general formula (I) or (II) taken alone or as a mixture:

in which, R ₁ and R ₂ are, independently of one another, hydrogen atoms, linear or branched alkyl groups, saturated or unsaturated, comprising from 1 to 24 carbon atoms, preferably from 2 to 18 , more preferably from 4 to 16, even more preferably from 8 to 12 or aromatic substituents, n and m being, independently of one another, integers equal to 1, 2, 3 or 4.

The aforementioned derivatives of dimercaptothiadiazole are compounds which include sulfur like the sulfur-containing fatty acid esters, but this sulfur is stabilized in the cycle and will not be released like the sulfur present in the sulfur-containing fatty acid esters. Thus, the dimercaptothiadiazole derivatives do not contain active sulfur at 150 ° C. unlike the sulfur-containing fatty acid esters. The sulfur which is active at 150 ° C. is therefore supplied only by the sulfur fatty acid ester.

Preferably, the amount of sulfur according to standard D2622 provided by the derivative of dimercaptothiadiazole in the fat composition is between 0.05 and 0.50% by mass, relative to the total mass of the fat composition, preferably between 0.10 and 0.30%, more preferably between 0.15 and 0.20%.

Preferably, the grease compositions according to the invention comprise from 0.1 to 5% by mass of dimercaptothiadiazole derivative, relative to the total mass of the lubricating composition, preferably from 0.2 to 4%, more preferably of 0.3 to 2%, even more preferably from 0.5 to 1%.

The dimercaptothiadiazole derivatives used in the present invention are products available commercially, for example from the suppliers Vanderbilt, Rhein Chemie, Afton.

Polyol ester base oil

The fat composition according to the invention comprises at least one base oil of renewable origin based on a polyol ester.

The esters of polyols which can be used as base oil are diesters, triesters, tetraesters or complex esters comprising more than four ester functions.

The acids which can be used to form the esters are monocarboxylic acids or dicarboxylic acids.

Preferably, the monocarboxylic acids have from 3 to 22 carbon atoms, more preferably from 4 to 20, even more preferably from 6 to 18, even more preferably from 8 to 16, even more preferably from 10 to 12.

Mention may be made, for example, of hexanoic, octanoic, 2-ethylhexanoic, isooctanoic, nonanoic, decanoic, isodecanoic, oleic and stearic acids. Preferably, saturated acids containing no unsaturations are used.

Preferably, the dicarboxylic acids have from 3 to 22 carbon atoms, more preferably from 4 to 20, even more preferably from 6 to 18, even more preferably from 8 to 16, even more preferably from 10 to 12. Mention may be made by example succinic, adipic, azelaic, sebacic acids.

The alcohols which can be used to form the esters are monoalcohols (formation of diesters with dicarboxylic acids), dialcohols, trialcohols or tetraalcohols. Preferred alcohols are polyols such as neopentylglycol, trimethylolpropane, pentaerythritol.

To obtain sufficient biodegradability, the fat composition according to the invention comprises from 50 to 95% by weight, relative to the total weight of the fat composition, of polyol ester, preferably from 60 to 90%, more preferably. from 70 to 80%.

These ester-type base oils are chosen for their negligible impact on the environment, unlike the base oils derived from petroleum conventionally used. However, the use of such base oils of the polyol ester type has a negative impact on the extreme pressure properties, since these base oils of the polyol ester type also tend to go to the surface of the lubricated parts and are in competition with other additives, hence the use of the specific combination of the derivative of dimercaptothiadiazole and the sulfur fatty acid ester.

The base oil of the polyol ester type or the mixture of base oils of the polyol ester type, has a kinematic viscosity at 40 ° C of between 3 and 2000 cSt (measured according to ASTM D445), preferably between 10 and 1500 cSt, more preferably between 20 and 1000 cSt, even more preferably between 40 and 500 cSt, even more preferably between 50 and 200 cSt. These viscosity ranges, in particular from 50 to 200 cSt, make it possible to obtain a good compromise between extreme pressure performance and biodegradability.

The base oils used in the present invention are products available commercially, for example from the suppliers Uniqema, Croda, Oleon, Akzo, Nyco.

Soaps

The fat compositions according to the invention are thickened with fatty acid metallic soaps, which can be prepared separately, or in situ during the manufacture of the fat (in the latter case, the fatty acid is dissolved in the fat. base oil, then the appropriate metal hydroxide is added).

These thickeners are products commonly used in the field of greases, readily available and inexpensive. Greases thickened with fatty acid metallic soaps exhibit very good mechanical stability, compared, for example, to greases comprising polyurea-based thickeners, which allows easy use in applications where the grease is in an enclosure. unconfined. In addition, polyureas are prepared from isocyanate, an extremely toxic compound, so it is not desirable to use polyurea-based thickeners to obtain a biodegradable, non-toxic grease free from products classified according to the regulation. CLP (CE n ° 1272/2008). The grease according to the invention is therefore free from polyurea-based thickeners and therefore only comprises thickeners of the fatty acid metal soap type.

Long chain fatty acids are preferably used, typically comprising from 10 to 28 carbon atoms, saturated or unsaturated, optionally hydroxylated.

Long chain fatty acids (typically comprising from 10 to 28 carbon atoms), are for example capric, lauric, myristic, palmitic, stearic, arachidic, behenic, oleic, linoleic, erucic acids, and their derivatives. hydroxylated. The most well-known derivative of this category is 12-hydroxystearic acid and is preferred. Lithium 12-hydoxystearate is the preferred thickener.

These long-chain fatty acids generally come from vegetable oils, for example palm, castor, rapeseed, sunflower oil, etc. or animal fats (tallow, whale oil, etc.).

So-called simple soaps can be formed by using one or more long-chain fatty acids. Simple soaps are preferred over complex soaps because they are more easily biodegradable and not bioaccumulative.

So-called complex soaps can also be formed using one or more long-chain fatty acids in combination with one or more short-chain hydrocarbon-based carboxylic acids comprising at most 8 carbon atoms.

The saponifying agent used to make the soap can be a metallic compound of lithium, sodium, calcium, aluminum, preferably lithium and calcium, and preferably a hydroxide, oxide or carbonate of these metals.

One or more metal compounds, having or not having the same metal cation, can be used in the greases according to the invention. It is thus possible to combine lithium soaps, combined with calcium soaps in a lesser proportion.

The metallic soaps are used at contents of the order of 1 to 20% by mass, relative to the total mass of the fat composition, preferably from 2 to 15%, preferably from 4 to 10%.

Fat preparation process

The greases according to the invention are made by forming the metallic soap in situ or by using a preformed soap.

The method of preparing the fat by forming the metallic soap in situ is as follows.

One or more fatty acids, long chain or short chain, are dissolved in a fraction of the base oil or the base oil mixture at a temperature between 80 ° C and 90 ° C. This fraction is generally of the order of 40% to 60% by mass of the total quantity of oil contained in the final fat.

Metal compounds, preferably of metal oxide, hydroxide or carbonate type, are then added at the same temperature.

It is thus possible to add a single type of metal or to combine several metals. The preferred metal of the compositions according to the invention is lithium, optionally combined, in a lesser proportion, with calcium.

The saponification reaction of long chain or short chain fatty acids by the metal compound (s) is allowed to proceed at a temperature between 80 ° C and 90 ° C.

The water formed is then evaporated by cooking the mixture at a temperature of about 100 ° C to 200 ° C.

The fat is then cooled by the remaining fraction of the base oil.

The derivative of dimercaptothiadazole and the sulfur fatty acid ester, and any other additives, are then incorporated at approximately 80 ° C..

Then kneaded for a sufficient time to obtain a fat composition, which is then ground to make it more homogeneous.

The process for preparing the fat with the preformed metallic soap is identical, except that there is no saponification reaction since the soap is already formed. These preparation processes are well known to those skilled in the art.

Fat consistency

The consistency of a grease measures its hardness or fluidity at rest. It is quantified by the penetration depth of a cone of given dimensions and mass. The fat is first subjected to mixing. The conditions for measuring the consistency of a grease are defined by standard ASTM D 217.

Depending on their consistency, greases are divided into 9 classes or 9 NLGI (National Lubricating Grease Institute) grades commonly used in the field of greases. These grades are shown in the table below. NLGI grade Consistency according to ASTM D 217 (tenth of a millimeter) 000 445 - 475 00 400 - 430 0 355 - 385 1 310 - 340 2 265 - 295 3 220 - 250 4 175 - 205 5 130 - 160 6 85 - 115

Preferably, the greases according to the invention have a consistency of between 220 and 430 tenths of a millimeter according to the ASTM D217 standard, to cover grades 00, 0, 1, 2 and 3.

Preferably, the greases according to the invention have a consistency of between 265 and 295 tenths of a millimeter according to the ASTM D217 standard, to cover grade 2.

Other additives

The grease compositions according to the invention may also contain anti-oxidant additives, for example anti-oxidants of the phenolic type, anti-rust additives, such as for example oxidized waxes or amine phosphates, anti-rust additives. corrosion such as tolyltriazoles.

Technical performance of greases

The grease compositions according to the invention have good extreme pressure performance. In particular, the grease compositions according to the invention have a welding load measured according to standard ASTM D2596 greater than 315 kg, preferably greater than or equal to 400 kg. In particular, the grease compositions according to the invention have a welding load measured according to standard DIN 51350/4 greater than 300 daN, preferably greater than or equal to 320 daN, more preferably greater than or equal to 340 daN.

The grease compositions according to the invention are also very slightly corrosive, in particular towards metals or metal alloys, and more particularly towards copper. In particular, the grease compositions according to the invention only slightly tarnish the copper strips (classification 1 according to the ASTM D4048 standard) or only moderately tarnish the copper strips (classification 2 according to the ASTM D4048 standard).

The grease compositions according to the invention, in addition to having good extreme-pressure properties and not being corrosive towards metals and metal alloys, and more particularly towards copper, have an impact reduced on the environment. In particular, the fats according to the invention are biodegradable, non-bioaccumulative, non-toxic to aquatic environments and are renewable.

Preferably, the fat compositions according to the invention contain additives which do not present a danger to the environment and to human health.

Preferably, the grease compositions according to the invention are free from halogenated organic compounds, from compounds of nitrite type, from metals or from metal compounds other than sodium, potassium, magnesium, calcium, lithium and / or l 'aluminum.

Preferably, the fat compositions according to the invention are not toxic to the aquatic environment.

In particular, the fat compositions according to the invention have an aquatic toxicity of at least 1000 mg / l on algae, daphnia and fish according to OECD standards 201, 202 and 203.

Likewise, the main constituents of fat, that is to say those present at more than 5% by mass, relative to the total mass of the fat composition, such as base oil, and soap , have an aquatic toxicity of at least 100 mg / l on algae and daphnia according to OECD 201 and 202 standards.

Likewise, when a constituent has an aquatic toxicity of at least 100 mg / l on algae and daphnia according to OECD standards 201 and 202 (category D), said constituent may be present in the fat at any concentration. The grease compositions according to the invention have a mass concentration of constituents having an aquatic toxicity of between 10 mg / l and 100 mg / l on algae and daphnia according to OECD standards 201 and 202 (category E), less than or equal at 25%. The grease compositions according to the invention have a mass concentration of constituents having an aquatic toxicity of between 1 mg / l and 10 mg / l on algae and daphnia according to OECD standards 201 and 202 (category F), less than or equal at 2%, preferably less than or equal to 1%. This only concerns the constituents of the fat whose mass concentration in the fat is greater than or equal to 0.1%.

The grease compositions according to the invention are biodegradable and not bioaccumulative. In particular, the grease compositions according to the invention have a mass concentration of constituents which are ultimately biodegradable in an aerobic environment (category A according to standards OCDE 301A-F, OCDE 306, OCDE 301) greater than 75%, a mass concentration of constituents intrinsically biodegradable in an aerobic environment (category B according to OECD 302B, OCDE 302C standards) or non-biodegradable and non-bio-accumulable constituents (category C) less than or equal to 25%, and a mass concentration of non-biodegradable and accumulable constituents (category X ) less than or equal to 0.1%. This only concerns the constituents of the fat whose mass concentration in the fat is greater than or equal to 0.1%.

The grease compositions according to the invention contain at least 45% by mass, relative to the total mass of the grease composition, of carbon originating from renewable raw materials.

The invention also relates to a method of lubrication using the grease compositions described above, said method comprising contacting the parts to be lubricated with the grease compositions described above.

The invention finally relates to a lubricating composition comprising at least one base oil of polyol ester type, at least one derivative of dimercaptothiadiazole and at least one sulfur-containing fatty acid ester, the amount of sulfur active at 150 ° C. according to the standard. ASTM D1662 by mass provided by the sulfur fatty acid ester, relative to the total mass of the fat composition, being greater than or equal to 0.17%. The polyol ester base oil has all of the characteristics given above. The same is true for the derivative of dimercaptothiadiazole and the fatty acid ester. The amounts used are those described in the present application and are expressed relative to the total mass of lubricating composition rather than of grease composition. The lubricating compositions therefore comprise the same additives as the grease compositions except the soap. The viscosity of the lubricating compositions is that of the base oils. The lubricating compositions also exhibit good extreme pressure and anti-corrosion properties, while having a reduced impact on the environment.

Examples

Different fat compositions are prepared from:
- Lithium 12-hydroxystearate (thickener). Its aquatic toxicity is greater than 100 mg / l on algae and daphnia according to OECD standards 201 and 202 (category D). Its biodegradability is equal to 83.8% according to the OECD 301B standard (category A).
- a derivative of dimercaptothiadiazole which is a mixture of the products of general formula (I) and (II), with R ₁ and R ₂ linear alkyl groups comprising an average carbon number of 12, n being equal to 1. Its aquatic toxicity is category E on algae and daphnia according to OECD 201 and 202 standards, its biodegradability is category C according to OECD 301B standard.
- methyl ester of sulfur fatty acid (sulfur ester 1), comprising 17% by mass, relative to the total mass of sulfur ester, of sulfur and 48% by mass of active sulfur at 150 ° C relative to the mass total sulfur ester. Its aquatic toxicity is between 10 mg / l and 100 mg / l on algae and daphnia according to OECD standards 201 and 202 (category E). Its biodegradability is category C according to the OECD 301B standard. It comprises 95% by mass of renewable carbon, relative to the total mass of sulfur ester.
- sulfur fatty acid triglycerides (sulfur ester 2), comprising 15% by mass, relative to the total mass of sulfur ester, of sulfur and 33% by mass of active sulfur at 150 ° C relative to the total mass of sulfur ester. 60% by mass of the sulfur ester, relative to the total mass of the sulfur ester, has an aquatic toxicity of between 10 mg / l and 100 mg / l on algae and daphnia according to OECD standards 201 and 202 ( category E) and 40% by mass of the sulfur ester has an aquatic toxicity of between 1 mg / l and 10 mg / l on algae and daphnia according to OECD standards 201 and 202 (category E). Its biodegradability is category C according to the OECD 301B standard. It comprises 95% by mass of renewable carbon, relative to the total mass of sulfur ester.
- ester of trimethylolpropane and saturated fatty acids (base oil 1). Its kinematic viscosity at 100 ° C (ASTM D445) is 4.4 cSt, its kinematic viscosity at 40 ° C (ASTM D445) is 19.6 cSt. Its aquatic toxicity is greater than 100 mg / l on algae and daphnia according to OECD standards 201 and 202 (category D). Its biodegradability is equal to 79% according to the OECD 301B standard (category A). It comprises 81% by mass of renewable carbon, relative to the total mass of sulfur ester.
- ester of trimethylolpropane and saturated fatty acids (base oil 2). Its kinematic viscosity at 100 ° C (ASTM D445) is 32.2 cSt and its kinematic viscosity at 40 ° C (ASTM D445) is 316 cSt. Its aquatic toxicity is greater than 100 mg / l on algae and daphnia according to OECD standards 201 and 202 (category D). Its biodegradability is equal to 67% according to the OECD 301B standard (category A). It comprises 55% by mass of renewable carbon, relative to the total mass of sulfur ester.
- 4,4'-methylene bis 2,6-di-tertio-butylphenol (antioxidant 1),
- Octadecyl 3- (3,5-ditertiobutyl-4-hydroxyphenyl) propanoate (antioxidant 2). Its aquatic toxicity is greater than 100 mg / l on algae and daphnia according to OECD standards 201 and 202 (category D). Its biodegradability is category B according to the OECD 301B standard.
- Oxidized hydrocarbon waxes (anti-corrosion 1). Its aquatic toxicity is between 10 mg / l and 100 mg / l on algae and daphnia according to OECD standards 201 and 202 (category E). Its biodegradability is equal to 55% according to the OECD 301B standard (category B).
- Tolyltriazole (anti-corrosion 2). Its aquatic toxicity is between 1 mg / l and 10 mg / l on algae and daphnia according to OECD standards 201 and 202 (category F). Its biodegradability is equal to 4% according to the OECD 301B standard (category C).
in the proportions (% by mass) of Table I below: Table I - Mass composition of fats GT ₁ GT ₂ GT ₃ GT ₄ Gl ₅ Gl ₆ GT ₇ GT ₈ Base oil 1 19.63 19.40 19.38 19.49 19.15 19.15 19.25 19.06 Base oil 2 65.72 64.95 64.97 65.26 64.20 64.20 64.60 63.79 Thickening 10.96 10.96 10.96 10.96 10.96 10.96 10.96 10.96 Anti-oxidant 1 0.09 0.09 0.09 0.09 0.09 0.09 0.09 0.09 Antioxidant 2 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 Anti-corrosion 1 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 Anti-corrosion 2 0.10 0.10 0.10 0.10 0.10 0.10 0.10 0.10 Dimercaptothiadiazole derivative 0.50 0.50 0.50 0.50 0.50 0.50 - - Sulfur ester 1 1.00 - 1.00 2.00 1.00 2.00 1.00 - Sulfur ester 2 - 2.00 1.00 - 2.00 1.00 2.00 4.00

The control fats and according to the invention have the following biochemical characteristics (Table II): Table II - Biochemical characteristics of the fats GT ₁ GT ₂ GT ₃ GT ₄ GI ₅ GI ₆ GT ₇ GT ₈ Amount of sulfur fatty acid ester 0.17 0.30 0.32 0.34 0.47 0.49 0.47 0.60 Amount of dimercaptothiadiazole sulfur 0.15 0.15 0.15 0.15 0.15 0.15 0.00 0.00 Amount of active sulfur at 150 ° C fatty acid ester 0.082 0.010 0.131 0.163 0.181 0.213 0.181 0.199 Aquatic toxicity Category E (%) 2.5 2.7 3.1 3.5 3.7 4.1 3.2 3.4 Aquatic toxicity Category F (%) 0.1 0.9 0.5 0.2 0.9 0.5 0.9 1.7 Biodegradability Category A (%) 96 95 95 96 94 94 95 94 Biodegradability Category B + C (%) 3.6 4.6 4.6 4.6 5.6 5.6 5.1 6.1 Renewable carbon (%) 53 53 53 54 54 54 54 54

These grease compositions are subjected to extreme pressure and corrosion tests (Table III).

The control fats and according to the invention have the following performances (Table III): Table III - Extreme pressure performance and grease corrosion GT ₁ GT ₂ GT ₃ GT ₄ GI ₅ GI ₆ GT ₇ GT ₈ 4 Extreme Pressure balls Welding load (kg) ⁽¹⁾ 315 315 315 315 400 400 315 315 4 Extreme Pressure balls Last load before welding (daN) ⁽²⁾ 260 260 280 280 300 320 260 280 4 Extreme Pressure balls Welding load (daN) ⁽²⁾ 280 280 300 300 320 340 280 300 Copper corrosion ⁽³⁾ 1b 1b 1b 1b 1b 1b 1b 1b ⁽¹⁾ ASTM D2596
⁽²⁾ DIN 51350/4
⁽³⁾ ASTM D4048

The grease compositions GT ₁ to GT ₄ are control greases comprising both a derivative of dimercaptothadiazole and a sulfur fatty acid ester but with low active sulfur contents at 150 ° C. The grease compositions GT ₁ to GT ₄ have a low welding load of 315 kg (ASTM D2596) or 280 or even 300 daN (DIN 51350/4).

The GI ₅ and GI ₆ grease compositions are greases according to the invention comprising both a derivative of dimercaptothadiazole and a sulfur fatty acid ester but with higher active sulfur contents at 150 ° C. The GI ₅ and GI ₆ grease compositions exhibit an improved weld load of 400 kg (ASTM D2596) or of 320 or even 340 daN (DIN 51350/4).

The grease compositions GT ₇ and GT ₈ are control greases not comprising a derivative of dimercaptothadiazole, comprising only a sulfur fatty acid ester with high active sulfur contents at 150 ° C. The GT ₅ and GT ₆ grease compositions have a low weld load of 315 kg (ASTM D2596) or 280 or even 300 daN (DIN 51350/4). The presence of the sulfur fatty acid ester alone is not sufficient to obtain good extreme pressure performance.

These grease compositions are moreover very little corrosive towards copper.

These results demonstrate that obtaining high extreme pressure performance is due to the presence of the dimercaptothiadiazole derivative in combination with a sulfur fatty acid ester which provides the fat composition with a quantity of active sulfur at 150 ° C greater than or equal. at 0.18% by mass, based on the total mass of the fat composition. This extreme pressure performance goes hand in hand with low grease corrosion and a grease that is biodegradable, non-accumulative, non-toxic, and made from renewable raw materials.

Claims (14)

1. Grease composition comprising at least one polyol ester base oil, at least one fatty acid metal soap, from 0.1% to 5% by weight, relative to the total weight of grease composition, of at least one dimercaptothiadiazole derivative and at least one sulfur-containing fatty acid ester, the amount of active sulfur at 150°C according to the standard ASTM D1662 by weight provided by the sulfur-containing fatty acid ester, relative to the total weight of grease composition, being greater than or equal to 0.18%,
   said dimercaptothiadiazole derivative being chosen from the 2,5-dimercapto-1,3,4-thiadiazole derivatives of general formula (I) or (II), taken alone or as a mixture

   

   

   in which, R₁ and R₂ are, independently of one another, hydrogen atoms, saturated or unsaturated, linear or branched, alkyl groups comprising from 1 to 24, preferably from 2 to 18, more preferentially from 4 to 16, more preferentially from 8 to 12 carbon atoms or aromatic substituents, n and m being, independently of one another, integers equal to 1, 2, 3 or 4.
2. Composition according to Claim 1, in which the polyol ester is chosen from neopentyl glycol esters, trimethylolethane esters, trimethylolpropane esters, pentaerythritol esters and/or dipentaerythritol esters, taken alone or as a mixture.
3. Composition according to Claim 1 or 2, comprising from 50% to 95% by weight, relative to the total weight of grease composition, of polyol ester base oil, preferably from 60% to 90%, more preferentially from 70% to 80%.
4. Composition according to any one of Claims 1 to 3, comprising from 0.2% to 2% by weight of dimercaptothiadiazole derivative, relative to the total weight of grease composition, more preferentially from 0.5% to 1%.
5. Composition according to any one of Claims 1 to 4, in which the sulfur-containing fatty acid ester is a fatty acid triglyceride and/or a fatty acid methyl ester, taken alone or as a mixture.
6. Composition according to any one of Claims 1 to 5, comprising from 0.5% to 5% by weight of sulfur-containing fatty acid ester, relative to the total weight of grease composition, preferably from 1% to 4%, more preferentially from 2% to 3%.
7. Composition according to any one of Claims 1 to 6, in which the fatty acid metal soap is a simple fatty acid metal soap, preferably a lithium or calcium soap.
8. Composition according to any one of Claims 1 to 7, in which the fatty acid metal soap is lithium 12-hydroxystearate.
9. Composition according to any one of Claims 1 to 8, comprising from 1% to 20% by weight, relative to the total weight of the grease composition, of fatty acid metal soap, preferably from 2% to 15%, preferentially from 4% to 12%.
10. Composition according to any one of Claims 1 to 9, in which the polyol ester, or the mixture of polyol esters, has a kinematic viscosity at 40°C, measured according to the standard ASTM D445, of between 3 and 2000 cSt, preferably between 10 and 1500 cSt, more preferentially between 40 and 500 cSt, more preferentially still between 50 and 200 cSt.
11. Composition according to any one of Claims 1 to 10, having a consistency according to the standard ASTM D217 of between 220 and 430 tenths of a millimetre, preferably between 265 and 295 tenths of a millimetre.
12. Composition according to any one of Claims 1 to 11, comprising an amount of active sulfur at 150°C according to the standard ASTM D1662 by weight provided by the sulfur-containing fatty acid ester, relative to the total weight of grease composition, of greater than or equal to 0.19%, preferentially greater than or equal to 0.20%, more preferentially greater than or equal to 0.21%.
13. Use, in a grease composition comprising at least one polyol ester base oil and at least one fatty acid metal soap, of at least one dimercaptothiadiazole derivative and of at least one sulfur-containing fatty acid ester, the amount of active sulfur at 150°C according to the standard ASTM D1662 by weight provided by the sulfur-containing fatty acid ester being greater than or equal to 0.18%, relative to the total weight of grease composition, in order to improve the extreme pressure performance according to the standards ASTM D2596 and/or DIN 51350/4 of the grease composition, said dimercaptothiadiazole derivative being chosen from the 2,5-dimercapto-1,3,4-thiadiazole derivatives of general formula (I) or (II), taken alone or as a mixture

    

    

    in which, R₁ and R₂ are, independently of one another, hydrogen atoms, saturated or unsaturated, linear or branched, alkyl groups comprising from 1 to 24, preferably from 2 to 18, more preferentially from 4 to 16, more preferentially from 8 to 12 carbon atoms or aromatic substituents, n and m being, independently of one another, integers equal to 1, 2, 3 or 4.
14. Lubricant composition comprising at least one polyol ester base oil, from 0.1% to 5% by weight, relative to the total weight of grease composition, of at least one dimercaptothiadiazole derivative and at least one sulfur-containing fatty acid ester, the amount of active sulfur at 150°C according to the standard ASTM D1662 by weight provided by the sulfur-containing fatty acid ester, relative to the total weight of lubricant composition, being greater than or equal to 0.18%,
    said dimercaptothiadiazole derivative being chosen from the 2,5-dimercapto-1,3,4-thiadiazole derivatives of general formula (I) or (II), taken alone or as a mixture

    

    

    in which, R₁ and R₂ are, independently of one another, hydrogen atoms, saturated or unsaturated, linear or branched, alkyl groups comprising from 1 to 24, preferably from 2 to 18, more preferentially from 4 to 16, more preferentially from 8 to 12 carbon atoms or aromatic substituents, n and m being, independently of one another, integers equal to 1, 2, 3 or 4.