Biodegradable lubricating greases

Abstract

The present invention relates to a grease composition comprising, relative to the total weight of the grease composition: a) from 70 to 95% by weight of one or more base oils each having a biodegradability after 28 days of at least 60%, as measured by the standard OECD 301B; b) from 1 to 20% by weight of one or more thickeners chosen from among metal salts of fatty acids, each thickener having a biodegradability after 28 days of at least 60%, as measured by the standard OECD 301B; c) from 0.5 to 10% by weight of calcium carbonate having a D50 particle size greater than or equal to 3 µm and a D90 particle size greater than or equal to 10 µm.

Description

[0001] Description

[0002] Title: Biodegradable lubricating greases.

[0003] The present invention relates to the field of greases, in particular for the off-road, agricultural and wind markets, having improved anti-wear and extreme pressure properties and high biodegradability.

[0004] Technical field

[0005] There are many applications where liquid lubricants are unsuitable because they "drift" from the greasing point. These include rolling bearings (ball, roller, needle), antifriction and sliding bearings, open gears, wire rope and chain drives, and more generally applications that do not have a sealing system.

[0006] For these applications, lubricating greases are used, which are solid or semi-fluid substances resulting from the dispersion of a thickener in a liquid lubricant, possibly incorporating additives which give them particular properties.

[0007] Currently used greases generally include fossil-based mineral oils that do not exhibit high biodegradability. US 2018 / 0030367 discloses a grease composition.

[0008] Manufacturers are increasingly seeking to formulate biodegradable grease compositions, particularly for greases that need to be renewed regularly, for example for applications involving a high risk of leakage.

[0009] Document US 2021 / 0277323 discloses a lubricating grease with low environmental impact.

[0010] In certain applications, particularly for off-road markets (such as construction or agricultural machinery) and wind power markets (wind turbines), the increasingly powerful machines are used in increasingly severe conditions and require their lubrication products, in addition to biodegradability, for example, to provide significant performance gains in terms of extreme-pressure properties.

[0011] It is therefore an object of the present invention to provide a grease composition comprising a base oil and a thickener which are both biodegradable, a grease which further exhibits excellent anti-wear and extreme pressure properties and good tackiness.

[0012] Summary of the invention

[0013] More specifically, the present invention relates to a grease composition comprising, relative to the total weight of the grease composition: a) from 70 to 95% by weight of base oil(s) each having a 28-day biodegradability of at least 60%, as measured according to OECD 301B, b) from 1 to 20% by weight, preferably from 2 to 20% by weight, of thickener(s) chosen from fatty acid metal salts, each thickener having a 28-day biodegradability of at least 60%, as measured according to OECD 301B, c) from 0.5 to 10% by weight of calcium carbonate having a D50 particle size greater than or equal to 3 μm and a D90 particle size greater than or equal to 10 μm.

[0014] According to one embodiment, the grease composition according to the invention is characterized in that it has a 28-day biodegradability of at least 60%, calculated from the 28-day biodegradability of the base oil(s) and thickener(s), the 28-day biodegradability of the base oil(s) and thickener(s) being measured according to the OECD 301B method.

[0015] Preferably, the thickener is chosen from lithium and optionally hydroxylated fatty acid salts, calcium and optionally hydroxylated fatty acid salts and mixtures thereof, preferably from lithium and optionally hydroxylated fatty acid salts, preferably from lithium 12-hydroxy stearate.

[0016] Preferably, the base oils are chosen from ester oils.

[0017] Preferably, the calcium carbonate has a D50 particle size ranging from 3 to 20 μm and a D90 particle size ranging from 10 to 50 μm.

[0018] Preferably, the grease composition according to the invention further comprises at least one extreme pressure additive, preferably in an amount ranging from 1 to 15% by weight, relative to the total weight of the composition.

[0019] Preferably, the grease composition according to the invention is free of anti-wear additive of amine phosphate type, and of zinc diamyl dithiocarbamate type and of zinc dialkyl dithiophosphate type. Preferably, the grease composition according to the invention comprises at least 40% by weight of carbon of biological origin, preferably at least 45% by weight of carbon of biological origin, relative to the total weight of carbon atoms in the composition.

[0020] The invention also relates to the use of the grease composition according to the invention, in a non-road, agricultural or wind device.

[0021] Preferably, the non-road, agricultural or wind device is chosen from construction machinery, agricultural machinery and wind turbines.

[0022] The grease composition according to the invention has excellent anti-wear and extreme pressure properties and good adhesive power, even in the absence of an anti-wear additive.

[0023] In particular, the grease composition according to the invention will typically have the following properties: extreme pressure properties in the 4-ball test according to standard ASTM D2596 of 500 kgf. low wear of the order of 0.5 mm according to standard ASTM D2266.

[0024] - a water spray off result of less than 30% loss according to ASTM D4049.

[0025] The grease composition according to the invention will typically exhibit high biodegradability.

[0026] In the rest of the text, the expressions "between ... and . . .", "ranging from . . . to ..." and "varying from ... to ..." are equivalent and are intended to mean that the limits are included, unless otherwise stated.

[0027] Unless otherwise indicated, quantities in a product are expressed by weight, relative to the total weight of the product.

[0028] Detailed Description The present invention relates to a grease composition comprising, relative to the total weight of the grease composition: a) from 70 to 95% by weight of base oil(s) each having a 28-day biodegradability of at least 60%, as measured according to OECD 301B, b) from 2 to 20% by weight of thickener(s) chosen from fatty acid metal salts, each thickener having a 28-day biodegradability of at least 60%, as measured according to OECD 301B, c) from 0.5 to 10% by weight of calcium carbonate having a D50 particle size greater than or equal to 3 μm and a D90 particle size greater than or equal to 10 μm, optionally from 1 to 15% by weight of additive(s), said additives being different from the base oils a), different from the thickeners b) and different from calcium carbonate c).

[0029] Preferably, the grease composition according to the invention is biodegradable.

[0030] For the purposes of the present invention, a “compound” will be said to be “biodegradable” if it exhibits a biodegradability at 28 days of at least 60%, as measured according to the OECD 301B standard.

[0031] For the purposes of the present invention, the "grease composition" will be said to be "biodegradable" if the biodegradability calculated from the biodegradability of the base oil(s) and thickener(s) weighted by the proportions of said base oil(s) and thickener(s) in said grease composition is at least 60% at 28 days.

[0032] For example, if the fat composition includes:

[0033] - v% by weight of a base oil having a biodegradability Bv% at 28 days, measured according to OECD 301B,

[0034] -y% by weight of a base oil having a biodegradability By% at 28 days, measured according to OECD 301B,

[0035] - z% by weight of a thickener having a biodegradability Bz% at 28 days measured according to OECD 301B,

[0036] - q% by weight of calcium carbonate,

[0037] - 1% by weight of additive(s), then the 28-day biodegradability of the grease composition, Bc expressed as a percentage, will be calculated as follows: Be = v% x Bv + y% x By + z% x Bz.

[0038] The grease composition used according to the invention comprises one or more biodegradable base oils.

[0039] Preferably, the grease composition comprises at least one base oil of renewable origin, for example of plant or animal origin.

[0040] Preferably, the base oils of renewable origin represent at least 75% by weight of the total weight of the base oils.

[0041] According to one embodiment, all the base oils of the grease composition according to the invention have a 28-day biodegradability of at least 60%, as measured according to the OECD 301B standard.

[0042] It can be a mixture of several base oils, for example a mixture of two, three, or four base oils.

[0043] According to one embodiment, the grease composition comprises at least one ester type base oil.

[0044] Preferably, the ester base oil(s) represent at least 50% by weight, preferably at least 70% by weight, of the total weight of the base oils.

[0045] Among the esters that can be used as base oil, we can cite polyol esters.

[0046] Polyol esters that can be used as base oils are, for example, diesters, triesters, tetraesters or complex esters comprising more than four ester functions.

[0047] The acids that can be used to form esters are monocarboxylic acids or dicarboxylic acids.

[0048] 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.

[0049] Examples include hexanoic, octanoic, 2-ethylhexanoic, isooctanoic, nonanoic, decanoic, isodecanoic, oleic, and stearic acids. Saturated acids that do not contain unsaturations are preferably used.

[0050] 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. Examples that may be mentioned are succinic, adipic, azelaic and sebacic acids.

[0051] The alcohols that can be used to form esters are monoalcohols (formation of diesters with dicarboxylic acids), dialcohols, trialcohols or tetraalcohols. The preferred alcohols are polyols such as neopentyl glycol, trimethylolpropane, pentaerythritol.

[0052] The base oil or mixture of base oils preferably has a viscosity at 40°C greater than or equal to 100 cSt, preferably greater than or equal to 200 cSt, more preferably greater than or equal to 300 cSt, more preferably greater than or equal to 400 cSt, more preferably greater than or equal to 500 cSt.

[0053] Viscosity is preferably measured according to ASTM D445.

[0054] The base oil(s) preferably represent from 70 to 95% by weight, preferably from 75 to 90% by weight, of the total weight of the grease composition.

[0055] The base oils that can be used in the present invention are commercially available products.

[0056] The grease composition according to the invention comprises at least one thickener chosen from fatty acid metal salts.

[0057] Preferably, the grease composition according to the invention is free from polyurea-type thickeners.

[0058] The fatty acid metal salts may be chosen from metal salts of fatty monoacids or metal salts of fatty diacids, said monoacids or diacids preferably comprising from 8 to 28 carbon atoms.

[0059] Long-chain fatty acids are preferably used, typically comprising 10 to 28 carbon atoms, saturated or unsaturated, possibly hydroxylated.

[0060] Long-chain fatty acids (typically containing 10 to 28 carbon atoms) include, for example, capric, lauric, myristic, palmitic, stearic, arachidic, behenic, oleic, linoleic, erucic acids, and their hydroxylated derivatives. 12-Hydroxystearic acid is the preferred derivative.

[0061] Lithium 12-hydroxy stearate is the preferred thickener for the grease composition according to the invention.

[0062] These long-chain fatty acids generally come from vegetable oils, for example palm oil, castor oil, rapeseed oil, sunflower oil, etc. or animal fats (tallow, whale oil, etc.).

[0063] So-called simple soaps can be formed using one or more long-chain fatty acids, typically monobasic acids.

[0064] So-called complex soaps can also be formed by using one or more long-chain fatty acids in combination with one or more short-chain hydrocarbon dicarboxylic acids comprising a maximum of 10 carbon atoms. According to one embodiment, the short-chain hydrocarbon carboxylic acids are chosen from monocarboxylic acids and dicarboxylic acids preferably comprising from 3 to 10 carbon atoms.

[0065] The saponifying agent used to make soap may be a metallic compound of lithium, sodium, calcium, aluminum, preferably lithium and calcium, and preferably a hydroxide, oxide or carbonate of these metals.

[0066] One or more metallic compounds, whether or not having the same metallic cation, may be used in the greases according to the invention. Lithium soaps may thus be combined with calcium soaps in a lesser proportion.

[0067] The thickener(s) preferably represent from 3 to 20% by weight, preferably from 4 to 15% by weight, more preferably from 5 to 12% by weight, of the total weight of the grease composition.

[0068] The thickeners that can be used in the present invention are commercially available products.

[0069] Calcium carbonate The grease composition according to the invention comprises calcium carbonate having a D50 particle size greater than or equal to 3 μm and a D90 particle size greater than or equal to 10 μm.

[0070] For the purposes of the present invention, particles having a particle size D50 of X pm means that 50% by volume of the particles have a size less than X pm and that 50% by volume of the particles have a size greater than X pm.

[0071] For the purposes of the present invention, particles having a particle size D90 of X pm means that 90% by volume of the particles have a size less than X pm and that 10% by volume of the particles have a size greater than X pm.

[0072] The D50 and D90 particle size can be measured by laser diffraction, using any method well known to those skilled in the art. An example of a method is detailed in the experimental section.

[0073] According to one embodiment, the calcium carbonate has a D50 particle size ranging from 3 to 20 pm and a D90 particle size ranging from 10 to 50 pm, preferably a D50 particle size ranging from 4 to 15 pm and a D90 particle size ranging from 10 to 40 pm.

[0074] According to one embodiment, the calcium carbonate has a D50 particle size ranging from 5 to 10 μm and a D90 particle size ranging from 10 to 30 μm.

[0075] The inventors have discovered that calcium carbonate having a particle size as defined in the present invention makes it possible to obtain both good anti-wear properties and good extreme pressure properties.

[0076] In the state of the art, it is a calcium carbonate with a much smaller particle size (nanometric) which is generally used as anti-wear.

[0077] Calcium carbonate represents from 0.5 to 10% by weight, preferably from 1 to 5% by weight, more preferably from 2 to 4% by weight of the total weight of the grease composition according to the invention.

[0078] The calcium carbonate particles that can be used in the present invention are commercially available products.

[0079] Additive(s) The grease composition according to the invention optionally comprises one or more additional additives different from the base oils a), different from the thickeners b) and different from the calcium carbonate c), defined previously.

[0080] According to one embodiment, the additional additive(s) are chosen from extreme pressure additives, antioxidant additives, anti-corrosion additives, metal passivator additives, and mixtures thereof.

[0081] These additives can be introduced individually and / or in the form of a mixture.

[0082] The grease composition according to the invention may comprise at least one antioxidant additive. The antioxidant additive may be chosen from phenolic or amine type antioxidants.

[0083] The antioxidant additives may in particular be chosen from sterically hindered phenols, sterically hindered phenol esters and sterically hindered phenols comprising a thioether bridge, and mixtures thereof.

[0084] Amino compounds are another class of antioxidant additives that can be used, possibly in combination with phenolic antioxidant additives. Examples of amino compounds are aromatic amines, for example aromatic amines of the formula NR 10 R n R 12 in which R 10 represents an aliphatic group or an aromatic group, optionally substituted, R 11 represents an aromatic group, optionally substituted, R 12 represents a hydrogen atom, an alkyl group, an aryl group or a group of formula R 13 S(O) Z R 14 in which R 13represents an alkylene group or an alkenylene group, R 14 represents an alkyl group, an alkenyl group or an aryl group and z represents 0, 1 or 2. Among the amine-type antioxidants, mention may be made of diphenylamines, diphenylamines substituted by at least one C1-C12 alkyl group, N,N'-dialkyl-aryl-diamines and mixtures thereof.

[0085] The grease composition according to the invention may comprise from 0.05 to 5% by weight, preferably from 0.1 to 4% by weight or from 0.2 to 2% by weight of antioxidant agent, relative to the total weight of the composition. According to one embodiment, the grease composition comprises at least one extreme pressure additive.

[0086] According to one embodiment, the grease composition comprises from 2 to 10% by weight of at least one extreme pressure additive, relative to the total weight of the grease composition.

[0087] Preferably, the extreme pressure additive is chosen from sulfur-containing olefins, sulfur-containing fatty acid esters, and mixtures thereof.

[0088] Sulfur-containing fatty acid esters can be 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.

[0089] By sulfur-containing fatty acid ester is meant an ester of at least one sulfur-containing fatty acid, it being understood that it is most often an ester of a mixture of sulfur-containing fatty acids.

[0090] The fatty acids that 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 mass concentration of at least 50% relative to the total mass of sulfur-containing fatty acid ester.

[0091] The sulfur fatty acid esters may be sulfur fatty acid monoesters, sulfur fatty acid diesters, sulfur fatty acid triesters or sulfur fatty acid polyesters taken alone or in mixtures.

[0092] Preferred sulfur-containing fatty acid monoesters are C1-C4 alkyl monoesters, such as methyl monoesters, ethyl monoesters, n-propyl monoesters, z-propyl monoesters, rz-butyl monoesters, s-butyl monoesters, z-butyl monoesters. Preferably, the monoester is a methyl monoester. Preferably, the sulfur-containing fatty acid ester is a sulfur-containing fatty acid methyl ester.

[0093] Examples of sulfur-containing fatty acid triesters include sulfur-containing fatty acid triglycerides that are fully or partially esterified and thus may include, in addition to triesters, diesters and / or monoesters. Examples of sulfur-containing fatty acid polyesters include sulfur-containing fatty acid pentaerythritol esters.

[0094] The sulfur-containing olefins are preferably sulfurized olefins and can, for example, be obtained by a sulfurization reaction of olefins with sulfur, hydrogen sulfide or hydrated alkali metal sulfides, for example sodium sulfide. An example of processes for preparing such sulfur-containing olefins is, for example, described in US patents 4344854 and US 5135670. A very wide range of olefins can be sulfurized in this way. Preferably, sulfurized olefins are produced from isobutylene, diisobutylene, triisobutylene, tripropylene, or tetrapropylene.

[0095] According to a preferred embodiment, the sulfur-containing olefins are chosen from sulfur-containing isobutylenes (SIBs).

[0096] According to one embodiment, the grease composition according to the invention does not comprise a polymer.

[0097] The inventors have in fact discovered that the grease composition according to the invention has good adhesive power without the addition of a polymer-type additive.

[0098] According to one embodiment, the grease composition according to the invention is substantially free of anti-wear agents of the amine phosphate type, of the zinc diamyl dithiocarbamate type and of the zinc dialkyl dithiophosphate type.

[0099] “Substantially free” means a proportion of less than 0.01% by weight.

[0100] According to one embodiment, the grease composition according to the invention is free of amine phosphate type anti-wear, free of zinc diamyl dithiocarbamate type anti-wear and free of zinc dialkyl dithiophosphate type anti-wear.

[0101] According to one embodiment, the grease composition is substantially free of anti-wear additives, preferably completely free of anti-wear additives.

[0102] The inventors have in fact discovered that the grease composition according to the invention has good anti-wear properties without the addition of an anti-wear additive, in particular of the amine phosphate type, of the zinc diamyl dithiocarbamate type and / or of the zinc dialkyl dithiophosphate type.

[0103] According to one embodiment, the grease composition according to the invention comprises, relative to the total weight of the grease composition: from 70 to 95% by weight, preferably from 75 to 90% by weight, of base oil(s), from 3 to 20% by weight, preferably from 4 to 15% by weight of thickener(s) chosen from lithium salts and optionally hydroxylated fatty acid salts comprising from 10 to 28 carbon atoms, from 0.5 to 10% by weight, preferably from 1 to 5% by weight of calcium carbonate having a D50 particle size ranging from 3 to 20 μm and a D90 particle size ranging from 10 to 50 μm.

[0104] According to one embodiment, the grease composition according to the invention comprises, relative to the total weight of the grease composition: from 70 to 95% by weight, preferably from 75 to 90% by weight, of base oil(s), from 3 to 20% by weight, preferably from 4 to 15% by weight of thickener(s) chosen from lithium salts and optionally hydroxylated fatty acid salts comprising from 10 to 28 carbon atoms, from 0.5 to 10% by weight, preferably from 1 to 5% by weight of calcium carbonate having a D50 particle size ranging from 4 to 15 μm and a D90 particle size ranging from 10 to 40 μm.

[0105] According to one embodiment, the grease composition according to the invention comprises, relative to the total weight of the grease composition: from 70 to 95% by weight, preferably from 75 to 90% by weight, of base oil(s) comprising at least one ester oil, from 3 to 20% by weight, preferably from 4 to 15% by weight of thickener(s) comprising at least one lithium salt and optionally hydroxylated fatty acid comprising from 10 to 28 carbon atoms, from 0.5 to 10% by weight, preferably from 1 to 5% by weight of calcium carbonate.

[0106] According to one embodiment, the grease composition according to the invention comprises, relative to the total weight of the grease composition: from 70 to 95% by weight, preferably from 75 to 90% by weight, of base oil(s) comprising at least one ester oil, from 3 to 20% by weight, preferably from 4 to 15% by weight of thickener(s) comprising at least lithium 12-hydroxy stearate, from 0.5 to 10% by weight, preferably from 1 to 5% by weight of calcium carbonate having a D50 particle size ranging from 3 to 20 μm and a D90 particle size ranging from 10 to 50 μm.

[0107] According to one embodiment, the grease composition according to the invention comprises, relative to the total weight of the grease composition: from 70 to 95% by weight, preferably from 75 to 90% by weight, of base oil(s) comprising at least one ester oil, from 3 to 20% by weight, preferably from 4 to 15% by weight of thickener(s) comprising at least lithium 12-hydroxy stearate, from 0.5 to 10% by weight, preferably from 1 to 5% by weight of calcium carbonate having a D50 particle size ranging from 4 to 15 μm and a D90 particle size ranging from 10 to 40 μm.

[0108] According to one embodiment, the grease composition according to the invention comprises, relative to the total weight of the grease composition: from 70 to 95% by weight, preferably from 75 to 90% by weight, of base oil(s) including at least one ester oil, from 3 to 20% by weight, preferably from 4 to 15% by weight of thickener(s) chosen from lithium salts and optionally hydroxylated fatty acid salts comprising from 10 to 28 carbon atoms, from 0.5 to 10% by weight, preferably from 1 to 5% by weight of calcium carbonate, from 1 to 15% by weight, preferably from 2 to 10% by weight, of at least one additive chosen from extreme pressure additives.

[0109] According to one embodiment, the grease composition according to the invention comprises, relative to the total weight of the grease composition: from 70 to 95% by weight, preferably from 75 to 90% by weight, of base oil(s) including at least one ester oil, from 3 to 20% by weight, preferably from 4 to 15% by weight of thickener(s) chosen from lithium salts and optionally hydroxylated fatty acid salts comprising from 10 to 28 carbon atoms, from 0.5 to 10% by weight, preferably from 1 to 5% by weight of calcium carbonate, from 1 to 15% by weight, preferably from 2 to 10% by weight, of at least one additive chosen from extreme pressure additives chosen from sulfur-containing fatty acid esters, sulfur-containing olefins and mixtures thereof.

[0110] According to one embodiment, the grease composition according to the invention comprises, relative to the total weight of the grease composition: from 70 to 95% by weight, preferably from 75 to 90% by weight, of base oil(s) including at least one ester oil, from 3 to 20% by weight, preferably from 4 to 15% by weight of thickener(s) chosen from lithium salts and optionally hydroxylated fatty acid salts comprising from 10 to 28 carbon atoms, from 0.5 to 10% by weight, preferably from 1 to 5% by weight of calcium carbonate having a D50 particle size ranging from 5 to 10 μm and a D90 particle size ranging from 10 to 30 μm, from 1 to 15% by weight, preferably from 2 to 10% by weight, of at least one additive chosen from extreme pressure additives.

[0111] According to one embodiment, the grease composition according to the invention comprises, relative to the total weight of the grease composition: from 70 to 95% by weight, preferably from 75 to 90% by weight, of base oil(s) including at least one ester oil, from 3 to 20% by weight, preferably from 4 to 15% by weight of lithium 12-hydroxystearate thickener, from 0.5 to 10% by weight, preferably from 1 to 5% by weight of calcium carbonate having a D50 particle size ranging from 3 to 20 μm and a D90 particle size ranging from 10 to 50 μm, from 1 to 15% by weight, preferably from 2 to 10% by weight, of at least one additive chosen from extreme pressure additives.

[0112] According to one embodiment, the grease composition according to the invention comprises, relative to the total weight of the grease composition: from 70 to 95% by weight, preferably from 75 to 90% by weight, of base oil(s) including at least one ester oil, from 3 to 20% by weight, preferably from 4 to 15% by weight of lithium 12-hydroxystearate thickener, from 0.5 to 10% by weight, preferably from 1 to 5% by weight of calcium carbonate having a D50 particle size ranging from 4 to 15 μm and a D90 particle size ranging from 10 to 40 μm, from 1 to 15% by weight, preferably from 2 to 10% by weight, of at least one additive chosen from extreme pressure additives.

[0113] According to one embodiment, the grease composition according to the invention comprises, relative to the total weight of the grease composition: from 70 to 95% by weight, preferably from 75 to 90% by weight, of base oil(s) including at least one ester oil, from 3 to 20% by weight, preferably from 4 to 15% by weight of lithium 12-hydroxystearate thickener, from 0.5 to 10% by weight, preferably from 1 to 5% by weight of calcium carbonate having a D50 particle size ranging from 4 to 15 μm and a D90 particle size ranging from 10 to 40 μm, from 1 to 15% by weight, preferably from 2 to 10% by weight, of at least one additive chosen from extreme pressure additives chosen from sulfur-containing fatty acid esters, sulfur-containing olefins and mixtures thereof.

[0114] The grease composition according to the invention preferably has a viscosity at 40°C greater than or equal to 100 cSt, more preferably greater than or equal to 200 cSt, more preferably greater than or equal to 300 cSt, more preferably greater than or equal to 400 cSt, more preferably greater than or equal to 500 cSt.

[0115] Viscosity is preferably measured according to ASTM D445.

[0116] The grease composition according to the invention preferably has a carbon content of biological origin greater than or equal to 40% by weight, preferably at least 45% by weight, relative to the total weight of carbon atoms in the grease composition.

[0117] The content of carbon of biological origin, also called biogenic carbon content, can be determined according to the ASTM D6866 method.

[0118] The grease composition according to the invention may be prepared according to any method known to those skilled in the art for the preparation of grease. Preferably, a preformed thickener is used during the preparation process. Typically, the grease preparation process comprises a step of contacting the calcium carbonate thickener in the base oil and a heating step until the soap melts (and the grease is formed). If additives are present, they may be added before or after cooling. After cooling, the grease composition is generally homogenized by grinding.

[0119] The invention also relates to the use of the grease composition in off-road, agricultural and wind machines, such as off-road vehicles, construction machinery, agricultural machinery and wind turbines.

[0120] Typically, the grease composition according to the invention is used to lubricate at least one component of an off-road, agricultural or wind machine, preferably chosen from construction machinery, agricultural machinery and wind turbines. The invention also relates to a method for lubricating at least one component of an off-road, agricultural or wind machine, preferably chosen from construction machinery, agricultural machinery and wind turbines, said method comprising bringing the component into contact with a grease according to the invention.

[0121] More particularly, the grease according to the invention can be used in bearings (ball roller needle), rolling and sliding bearings, open gears, metal cables and chain drives, and more generally applications not comprising a sealing system.

[0122] All of the characteristics and preferences presented for the grease according to the invention apply to the method of lubricating the component of an off-road vehicle according to the invention.

[0123] The invention will now be described by means of the following examples, given of course by way of illustration and not limitation of the invention.

[0124] Examples

[0125] Example 1: Preparation of grease compositions

[0126] Greases were prepared according to the following protocol: The greases used in the examples are prepared as follows: the thickener and calcium carbonate are placed in its base oil and heated until the soap melts. After cooling, the additives are then added in different proportions and the grease composition is homogenized with a grinder.

[0127] The prepared and tested grease compositions are detailed in Table 1 where the proportions are proportions expressed by weight, relative to the total weight of the grease composition.

[0128] [Table 1]

[0129] The base oil(s) comprises a blend of two ester oils. The base oil(s) have a biodegradability measured according to OECD 301B at 28 days of 70% and 75%. The thickener is lithium 12-hydroxy stearate. It has a biodegradability at 28 days of 97%.

[0130] CaCO3 (1) is a calcium carbonate with a D50 particle size of 2.14 pm and a D90 particle size of 8.04 pm.

[0131] CaCO3(2) is a calcium carbonate with a D50 particle size of 7.08 pm and a D90 particle size of 14.9 pm.

[0132] Anti-wear is an anti-wear comprising a mixture of phosphate amines.

[0133] The additive package includes a sulfur ester extreme pressure additive, an antioxidant additive and a metal passivator additive.

[0134] The CI4 composition according to the invention has a 28-day biodegradability of 67.26%, calculated from the biodegradabilities of the base oils and the thickener.

[0135] The particle size of the calcium carbonate used in the examples was measured by a laser diffraction method well known to those skilled in the art.

[0136] In this example, a Malvern Mastersizer Hydro R diffractometer was used.

[0137] If macroscopic agglomerates are present (e.g. sizes greater than 400 pm) then mechanical sieving can be implemented with two different sieves (400 pm and 800 pm) in order to reduce macroscopic agglomerates.

[0138] If macroscopic agglomerates still remain after mechanical sieving, drying the sample at 100°C can be implemented to further reduce the amount of macroscopic agglomerates.

[0139] For the exploitation of the results, it is possible to disregard the proportion of macroscopic agglomerates, with a cut for example at 100 pm, or at 50 pm or even at 25 pm (depending on the size of the agglomerates). The cut has no significant impact on the measurement of D50 or D90 particle size of the calcium carbonate used in the examples.

[0140] Example 2: Determination of anti-wear and extreme pressure properties

[0141] The anti-wear and extreme pressure (EP) properties of the grease compositions detailed in Table 1 were determined and the results are shown in Table 2.

[0142] [Table 2]

[0143] The results in Table 2 show that the grease composition according to the invention CI4 has better anti-wear and extreme pressure properties than the grease compositions CCI, CC2 and CC3.

[0144] While the CI4 grease composition does not include anti-wear, it has better anti-wear properties than the CCI and CC2 grease compositions including an anti-wear additive.

[0145] The CI4 grease composition comprising a calcium carbonate having the claimed particle size exhibits better anti-wear properties than the CC3 composition comprising a calcium carbonate having another particle size.

[0146] Example 3: Determination of stickiness

[0147] The CCI and CI4 compositions were tested for their adhesive power using a water spray off test.

[0148] The viscosity at 40°C of the compositions is 680 cSt, measured according to ASTM D445.

[0149] The stickiness is shown in Table 3. [Table 3]

[0150] The results in Table 3 show that the CI4 composition has very good adhesive power. The grease composition according to the invention is therefore particularly well suited to the components of off-road vehicles with low rotation speeds.

Claims

Demands 1. Fat composition comprising, in relation to the total weight of the fat composition: a) 70 to 95% by weight of base oil(s), each having a 28-day biodegradability of at least 60%, as measured according to OECD 301B standard, b) 1 to 20% by weight of thickener(s) selected from metallic salts of fatty acids, each thickener having a 28-day biodegradability of at least 60%, as measured according to OECD 301B standard, c) 0.5 to 10% by weight of calcium carbonate having a D50 particle size greater than or equal to 3 µm and a D90 particle size greater than or equal to 10 µm.

2. Composition according to claim 1, comprising, in relation to the total weight of the fat composition: a) 70 to 95% by weight of base oil(s), each having a 28-day biodegradability of at least 60%, as measured according to OECD 301B, b) 2 to 20% by weight of thickener(s) selected from fatty acid metal salts, each thickener having a 28-day biodegradability of at least 60%, as measured according to OECD 301B, c) 0.5 to 10% by weight of calcium carbonate having a D50 particle size greater than or equal to 3 µm and a D90 particle size greater than or equal to 10 µm.

3. Composition according to claim 1 or 2, characterized in that it has a 28-day biodegradability of at least 60%, calculated from the 28-day biodegradability of the base oil(s) and thickener(s), the 28-day biodegradability of the base oil(s) and thickener(s) being measured according to OECD method 301B.

4. Composition according to any one of claims 1 to 3, wherein the thickener is selected from lithium salts and optionally hydroxylated fatty acids, calcium salts and optionally hydroxylated fatty acids, and mixtures thereof, of preference among lithium salts and possibly hydroxylated fatty acids, preferably among lithium 12-hydroxy stearate.

5. Composition according to any one of claims 1 to 4, wherein the base oils are selected from ester oils.

6. Composition according to any one of claims 1 to 5, wherein the calcium carbonate has a D50 particle size ranging from 3 to 20 pm and a D90 particle size ranging from 10 to 50 pm.

7. Composition according to any one of claims 1 to 6, further comprising at least one extreme-pressure additive, preferably in an amount from 1 to 15% by weight, relative to the total weight of the composition.

8. Composition according to any one of claims 1 to 7, said composition being free from anti-wear additives of the amine phosphate type, and of the zinc diamyl dithiocarbamate type and of the zinc dialkyl dithiophosphate type.

9. Composition according to any one of claims 1 to 8, comprising at least 40% by weight of carbon of biological origin, preferably at least 45% by weight of carbon of biological origin, relative to the total weight of carbon atoms in the composition.

10. Use of the grease composition according to any one of claims 1 to 9, in a non-road, agricultural or wind power device.

11. Use according to claim 10, wherein the non-road, agricultural or wind-powered device is selected from construction equipment, agricultural machinery and wind turbines.

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