Biodegradable lubricating grease

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 base oil having a biodegradability after 28 days of at least 60% as measured according to standard OECD 301B; b) from 1% to 20% by weight of one or more thickening agents selected from fatty acid metal salts, each thickening agent having a biodegradability after 28 days of at least 60% as measured according to standard OECD 301B; c) 0.5% to 10% by weight of calcium carbonate having a D50 particle size greater than or equal to 3 [mu] m and a D90 particle size greater than or equal to 10 [mu] m.

Description

[0001] The present disclosure relates to the field of lubricating greases, particularly lubricating greases for off-highway, agricultural and wind energy markets, having improved anti-wear and extreme pressure properties and high biodegradability. Technical Field

[0002] Liquid lubricants are not suitable for many applications because they tend to "drift" from the lubrication point. These applications concern in particular bearings (ball, roller, needle), rolling and plain bearings, open gears, metal cable and chain drives, and more generally applications that do not include sealing systems.

[0003] For these applications, greases are used, which are solid or semifluid substances resulting from the dispersion of a thickener in a liquid lubricant, optionally integrating additives that give it special properties.

[0004] Currently used greases generally include mineral oils of fossil origin, which are not highly biodegradable. Document US2018 / 0030367 discloses a grease composition.

[0005] Industrialists are increasingly seeking to formulate biodegradable grease compositions, in particular greases that require regular renewal, for example for applications involving a high risk of leakage.

[0006] Document US2021 / 0277323 discloses a grease with little impact on the environment.

[0007] In some applications, especially for the off-highway market (construction equipment or agricultural machinery type) and the wind energy market (wind turbines), the need for more powerful machines in increasingly harsh conditions means that their lubricants must offer a significant performance increase in terms of extreme pressure properties in addition to biodegradability.

[0008] It is therefore an object of the present invention to provide a grease composition comprising a base oil and a thickener, both of which are biodegradable, and which also has excellent antiwear and extreme pressure properties and good adhesion. Summary of the invention

[0009] More specifically, the present invention relates to a grease composition comprising, relative to the total weight of the grease composition:

[0010] a) 70% to 95% by weight of one or more base oils, each having a 28-day biodegradability of at least 60% measured according to standard OECD 301B;

[0011] b) 1% to 20% by weight, preferably 2% to 20% by weight, of one or more thickeners chosen from metal salts of fatty acids, each thickener having a 28-day biodegradability of at least 60% measured according to standard OECD 301B;

[0012] 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.

[0013] In one embodiment, the grease composition of the present invention is characterized in that the composition has a 28-day biodegradability of at least 60%, calculated on the basis of the 28-day biodegradability of the one or more base oils and the one or more thickeners, the 28-day biodegradability of the one or more base oils and the one or more thickeners being measured according to standard OECD 301B.

[0014] Preferably, the thickener is selected from optionally hydroxylated fatty acid lithium salts, optionally hydroxylated fatty acid calcium salts and mixtures thereof, preferably selected from optionally hydroxylated fatty acid lithium salts, preferably lithium 12-hydroxystearate.

[0015] Preferably, the base oil is selected from ester oils.

[0016] Preferably, the D50 particle size of calcium carbonate is 3 μm to 20 μm, and the D90 particle size is 10 μm to 50 μm.

[0017] Preferably, the grease composition of the invention additionally 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.

[0018] Preferably, the grease composition of the present invention does not contain anti-wear additives of the amine phosphate type, zinc di(N,N-dipentyldithiocarbamate) type and zinc dialkyldithiophosphate type.

[0019] Preferably, the grease composition of the invention comprises at least 40% by weight of carbon of biogenic origin, preferably at least 45% by weight of carbon of biogenic origin, relative to the total weight of carbon atoms of the composition.

[0020] The present invention also relates to the use of the grease composition of the present invention in off-highway, agricultural or wind energy installations.

[0021] Preferably, the off-highway, agricultural or wind energy device is selected from the group consisting of construction equipment, agricultural machinery and wind energy turbines.

[0022] The grease composition of the present invention has excellent antiwear and extreme pressure properties and good adhesion even in the absence of antiwear additives.

[0023] In particular, the grease compositions of the present invention generally have the following properties:

[0024] According to standard ASTM D2596, 500kgf extreme pressure characteristics under 4-ball test;

[0025] Low wear of about 0.5 mm according to standard ASTM D2266;

[0026] Water spray resistance test result according to standard ASTM D4049, less than 30% loss.

[0027] The grease compositions of the present invention are generally highly biodegradable.

[0028] In the rest of this document, unless otherwise stated, expressions such as “between… and…”, “from… to…” and “ranging from… to…” are equivalent and are intended to include these limitations.

[0029] Unless otherwise stated, quantities in the product are expressed by weight relative to the total weight of the product. DETAILED DESCRIPTION

[0030] The present invention relates to a grease composition, which comprises, relative to the total weight of the grease composition:

[0031] a) 70% to 95% by weight of one or more base oils, each of which has a 28-day biodegradability of at least 60% measured according to standard OECD 301B,

[0032] b) 2% to 20% by weight of one or more thickeners chosen from metal salts of fatty acids, each thickener having a 28-day biodegradability of at least 60% measured according to standard OECD 301B,

[0033] 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,

[0034] Optionally 1 to 15% by weight of one or more additives different from the base oil a), different from the thickener b) and different from calcium carbonate c).

[0035] Preferably, the grease composition of the present invention is biodegradable.

[0036] In the sense of the present invention, a "compound" is said to be "biodegradable" if its biodegradability after 28 days, measured according to standard OECD 301B, is at least 60%.

[0037] In the sense of the present invention, a "grease composition" is termed "biodegradable" if the biodegradability of the grease composition, calculated on the basis of the biodegradability of the base oil(s) and the thickener(s), weighted by the proportions of the base oil(s) and the thickener(s) in the grease composition, is at least 60% at 28 days.

[0038] For example, if the grease composition comprises:

[0039] - v% by weight of a base oil, whose 28-day biodegradability measured according to standard OECD 301B is Bv%;

[0040] - y wt% of a base oil having a 28 day biodegradability measured according to OECD 301B of By %;

[0041] - z % by weight of thickener, whose 28-day biodegradability measured according to standard OECD 301B is Bz %;

[0042] - q% by weight of calcium carbonate;

[0043] —t weight % of additives,

[0044] The 28-day biodegradability Bc of the grease composition expressed as a percentage will then be calculated as follows: Bc = v% x Bv + y% x By + z% x Bz.

[0045] One or more base oils

[0046] The grease composition used in the present invention comprises one or more biodegradable base oils.

[0047] Preferably, the grease composition comprises at least one base oil of renewable origin, for example of vegetable or animal origin.

[0048] Preferably, the base oil of renewable origin represents at least 75% by weight of the total weight of the base oil.

[0049] In one embodiment, all base oils of the grease composition of the invention have a 28 day biodegradability of at least 60% measured according to standard OECD 301B.

[0050] Mixtures of several base oils may be used, for example mixtures of two, three or four base oils.

[0051] In one embodiment, the grease composition includes at least one ester-type base oil.

[0052] Preferably, the ester type base oil accounts for at least 50% by weight, preferably at least 70% by weight, of the total weight of the base oil.

[0053] Among those esters that can be used as base oils, mention may be made of polyol esters.

[0054] The polyol ester that can be used as the base oil is, for example, a diester, a triester, a tetraester, or a complex ester having four or more ester functional groups.

[0055] Acids useful for forming esters are monocarboxylic acids or dicarboxylic acids.

[0056] Preferably, the monocarboxylic acid has 3 to 22 carbon atoms, preferably 4 to 20, more preferably 6 to 18, further preferably 8 to 16, still further preferably 10 to 12 carbon atoms.

[0057] For example, hexanoic acid, octanoic acid, 2-ethylhexanoic acid, isooctanoic acid, nonanoic acid, decanoic acid, isodecanoic acid, oleic acid, stearic acid may be mentioned. Saturated acids which do not contain any unsaturation are preferred.

[0058] Preferably, the dicarboxylic acid has 3 to 22 carbon atoms, preferably 4 to 20, more preferably 6 to 18, further preferably 8 to 16, and further preferably 10 to 12. For example, succinic acid, adipic acid, azelaic acid, and sebacic acid may be mentioned.

[0059] The alcohols that can be used to form esters are monohydric alcohols (forming diesters with dicarboxylic acids), dihydric alcohols, triols or tetraols. Preferred alcohols are polyhydric alcohols, such as neopentyl glycol, trimethylolpropane, pentaerythritol.

[0060] The base oil or base oil mixture preferably has a viscosity at 40° C. higher than or equal to 100 cSt, preferably higher than or equal to 200 cSt, more preferably higher than or equal to 300 cSt, further preferably higher than or equal to 400 cSt, still further preferably higher than or equal to 500 cSt.

[0061] The viscosity is preferably measured according to standard ASTM D445.

[0062] The one or more base oils preferably represent 70% to 95% by weight, preferably 75% to 90% by weight, based on the total weight of the grease composition.

[0063] The base oil which can be used in the present invention is a commercially available product.

[0064] Thickener

[0065] The grease composition of the present invention comprises at least one thickener selected from fatty acid metal salts.

[0066] Preferably, the grease composition of the present invention does not contain polyurea type thickeners.

[0067] The fatty acid metal salt may be selected from metal salts of fatty monoacids or metal salts of fatty diacids, the monoacid or the diacid preferably having 8 to 28 carbon atoms.

[0068] Preference is given to using long-chain fatty acids which generally comprise 10 to 28 carbon atoms, which are saturated or unsaturated and optionally hydroxylated.

[0069] Long chain fatty acids (generally having 10 to 28 carbon atoms) are for example capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, oleic acid, linoleic acid, erucic acid and hydroxylated derivatives thereof. A preferred derivative is 12-hydroxystearic acid.

[0070] Lithium 12-hydroxystearate is the preferred thickener for the grease compositions of the present invention.

[0071] These long-chain fatty acids usually come from vegetable oils such as palm oil, castor oil, rapeseed oil, sunflower oil... or from animal fats (beef tallow, whale oil...).

[0072] So-called simple soaps can be formed from one or more long-chain fatty acids, usually monoacids.

[0073] It is also possible to use one or more long chain fatty acids in combination with one or more dicarboxylic acids comprising a short hydrocarbon chain having up to 10 carbon atoms to form so-called complex soaps. In one embodiment, the carboxylic acid comprising a short hydrocarbon chain is selected from monocarboxylic acids and dicarboxylic acids, preferably having 3 to 10 carbon atoms.

[0074] The saponifying agent used to produce soap can be a lithium, sodium, calcium, aluminum metal compound, preferably lithium and calcium, preferably the hydroxides, oxides or carbonates of these metals.

[0075] One or more metal compounds may be used in the grease of the invention, whether or not they have the same metal cation. Thus, lithium soaps may be combined with calcium soaps in smaller proportions.

[0076] The one or more thickeners preferably constitute 3 to 20 wt. %, preferably 4 to 15 wt. %, more preferably 5 to 12 wt. % based on the total weight of the grease composition.

[0077] Thickeners that can be used in the present invention are commercially available products.

[0078] Calcium carbonate

[0079] The grease composition of the present 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.

[0080] In the sense of the present invention, particles with a D50 particle size of X μm mean that 50% by volume of the particles have a particle size smaller than X μm and 50% by volume of the particles have a particle size larger than X μm.

[0081] In the sense of the present invention, particles with a D90 particle size of X μm mean that 90% by volume of the particles have a particle size smaller than X μm and 10% by volume of the particles have a particle size larger than X μm.

[0082] The D50 and D90 particle sizes can be measured by laser diffraction using any method known to those skilled in the art. An example of one method is detailed in the Experimental Section.

[0083] In one embodiment, the calcium carbonate has a D50 particle size of 3 to 20 μm, a D90 particle size of 10 to 50 μm, preferably a D50 particle size of 4 to 15 μm, and a D90 particle size of 10 to 40 μm.

[0084] In one embodiment, the calcium carbonate has a D50 particle size of 5 μm to 10 μm and a D90 particle size of 10 μm to 30 μm.

[0085] The inventors have found that calcium carbonate having a particle size defined in the present invention can achieve good antiwear properties and good extreme pressure properties.

[0086] In the prior art, calcium carbonate, which is generally used as an anti-wear agent, has a smaller particle size (nanoscale).

[0087] Calcium carbonate accounts for 0.5 to 10 wt %, preferably 1 to 5 wt %, more preferably 2 to 4 wt % of the total weight of the grease composition of the present invention.

[0088] The calcium carbonate particles that can be used in the present invention are commercially available products.

[0089] One or more additives

[0090] As defined previously, the grease composition of the invention optionally comprises one or more further additives other than the base oil a), other than the thickener b) and other than calcium carbonate c).

[0091] In one embodiment, the other additives are selected from extreme pressure additives, antioxidant additives, anti-corrosion additives, metal passivation additives, and mixtures thereof.

[0092] These additives may be added alone and / or in the form of a mixture.

[0093] The grease composition of the present invention may include at least one antioxidant additive. The antioxidant additive may be selected from phenolic or aminic antioxidants.

[0094] The antioxidant additive may in particular be chosen from sterically hindered phenols, sterically hindered phenol esters and sterically hindered phenols comprising thioether bridges and mixtures thereof.

[0095] Amine compounds are another class of antioxidant additives that can be used optionally in combination with phenolic antioxidant additives. Examples of amine compounds are aromatic amines, such as those of the formula NR 10 R 11 R 12 Aromatic amines, where R 10 is an optionally substituted aliphatic or aromatic group, R 11 is an optionally substituted aromatic group, R 12 is a hydrogen atom, an alkyl group, an aryl group or a group of formula R 13 S(O) z R 14 A group in which R 13 is an alkylene or alkenylene group, R 14 is an alkyl, alkenyl or aryl group, and z is 0, 1 or 2. Among the aminic antioxidants, mention may be made of diphenylamine, 12 Alkyl-substituted diphenylamines, N,N'-dialkylaryl diamines and mixtures thereof.

[0096] The grease composition of the present invention may comprise 0.05% to 5% by weight, preferably 0.1% to 4% by weight, or 0.2% to 2% by weight of antioxidant relative to the total weight of the composition.

[0097] In one embodiment, the grease composition includes at least one extreme pressure additive.

[0098] In 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.

[0099] Preferably, the extreme pressure additive is selected from sulfur-containing olefins, sulfurized fatty acid esters and mixtures thereof.

[0100] The sulfurized fatty acid esters can be obtained by sulfurizing fatty acid esters obtained by reaction between one or more fatty acids and any kind of alcohol, or by transesterification between one or more fatty acid esters and any kind of alcohol.

[0101] Sulfurized fatty acid esters are understood to mean esters of at least one sulfurized fatty acid, with the proviso that in most cases the esters are esters of a mixture of sulfurized fatty acids.

[0102] The fatty acids that can be used to form the sulfurized fatty acid esters are all fatty acids having 6 to 24 carbon atoms, preferably 14 to 22 carbon atoms, more preferably 16 to 20 carbon atoms. Fatty acids having 18 carbon atoms are the majority of fatty acids, i.e., their weight concentration relative to the total weight of the sulfurized fatty acid esters is at least 50%.

[0103] The sulfurized fatty acid ester may be a sulfurized fatty acid monoester, a sulfurized fatty acid diester, a sulfurized fatty acid triester or a sulfurized fatty acid polyester, and may be used alone or in combination.

[0104] Preferred sulfurized fatty acid monoesters are C1-C4 alkyl monoesters, such as methyl monoesters, ethyl monoesters, n-propyl monoesters, isopropyl monoesters, n-butyl monoesters, sec-butyl monoesters, tert-butyl monoesters. Preferably, the monoesters are methyl monoesters. Preferably, the sulfurized fatty acid esters are sulfurized fatty acid methyl esters.

[0105] As examples of sulphurized fatty acid triesters, mention may be made of completely or partially esterified triglycerides of sulphurized fatty acids, which may thus optionally include diesters and / or monoesters in addition to the triesters.

[0106] As examples of sulfurized fatty acid polyesters, mention may be made of pentaerythritol esters of sulfurized fatty acids.

[0107] Sulfur-containing olefins are preferably sulfided olefins, and can be obtained, for example, by the sulfurization reaction of olefins with sulfur, hydrogen sulfide or hydrated alkali metal sulfide (such as sodium sulfide). For example, an example of the preparation method of the sulfur-containing olefins is described in patents US 4344854 and US 5135670. Very wide range of olefins can be sulfurized. Preferably, the sulfur-containing olefins are produced by isobutylene, diisobutylene, triisobutylene, tripropylene or tetrapropylene.

[0108] In a preferred embodiment, the sulfur-containing olefin is selected from sulfurized isobutylene (SIB).

[0109] In one embodiment, the grease composition of the present invention does not include a polymer.

[0110] The inventors have found that the grease composition of the present invention has good adhesion without adding polymer additives.

[0111] In one embodiment, the grease composition of the present invention is substantially free of antiwear agents of the amine phosphate type, zinc bis(N,N-dipentyldithiocarbamate) type, and zinc dialkyldithiophosphate type.

[0112] "Substantially free" means that the proportion is less than 0.01% by weight.

[0113] In one embodiment, the grease composition of the present invention is free of amine phosphate type antiwear agents, zinc bis(N,N-dipentyldithiocarbamate) type antiwear agents, and zinc dialkyldithiophosphate type antiwear agents.

[0114] In one embodiment, the grease composition is substantially free of anti-wear additives, preferably completely free of anti-wear additives.

[0115] The inventors have found that the grease composition of the present invention has good anti-wear properties without adding anti-wear additives (especially amine phosphate type, zinc di(N,N-dipentyldithiocarbamate) type and / or zinc dialkyldithiophosphate type).

[0116] In one embodiment, the grease composition of the present invention comprises, relative to the total weight of the grease composition:

[0117] - 70% to 95% by weight, preferably 75% to 90% by weight, of one or more base oils;

[0118] - 3 to 20% by weight, preferably 4 to 15% by weight, of one or more thickeners chosen from optionally hydroxylated lithium salts of fatty acids having 10 to 28 carbon atoms;

[0119] 0.5 to 10% by weight, preferably 1 to 5% by weight, of calcium carbonate having a D50 particle size of 3 to 20 μm and a D90 particle size of 10 to 50 μm.

[0120] In one embodiment, the grease composition comprises, relative to the total weight of the grease composition:

[0121] - 70% to 95% by weight, preferably 75% to 90% by weight, of one or more base oils;

[0122] - 3 to 20% by weight, preferably 4 to 15% by weight, of one or more thickeners chosen from optionally hydroxylated lithium salts of fatty acids having 10 to 28 carbon atoms;

[0123] 0.5 to 10% by weight, preferably 1 to 5% by weight, of calcium carbonate having a D50 particle size of 4 to 15 μm and a D90 particle size of 10 to 40 μm.

[0124] In one embodiment, the grease composition comprises, relative to the total weight of the grease composition:

[0125] 70% to 95% by weight, preferably 75% to 90% by weight, of one or more base oils including at least one ester oil;

[0126] - 3% to 20% by weight, preferably 4% to 15% by weight, of one or more thickeners comprising at least one optionally hydroxylated lithium salt of a fatty acid having 10 to 28 carbon atoms;

[0127] - 0.5 to 10% by weight, preferably 1 to 5% by weight, of calcium carbonate.

[0128] In one embodiment, the grease composition of the present invention comprises, relative to the total weight of the grease composition:

[0129] 70% to 95% by weight, preferably 75% to 90% by weight, of one or more base oils including at least one ester oil;

[0130] - 3% to 20% by weight, preferably 4% to 15% by weight, of one or more thickeners including lithium 12-hydroxystearate;

[0131] 0.5 to 10% by weight, preferably 1 to 5% by weight, of calcium carbonate having a D50 particle size of 3 to 20 μm and a D90 particle size of 10 to 50 μm.

[0132] In one embodiment, the grease composition of the present invention comprises, relative to the total weight of the grease composition:

[0133] 70% to 95% by weight, preferably 75% to 90% by weight, of one or more base oils including at least one ester oil;

[0134] - 3% to 20% by weight, preferably 4% to 15% by weight, of one or more thickeners including lithium 12-hydroxystearate;

[0135] 0.5 to 10% by weight, preferably 1 to 5% by weight, of calcium carbonate having a D50 particle size of 4 to 15 μm and a D90 particle size of 10 to 40 μm.

[0136] In one embodiment, the grease composition of the present invention comprises, relative to the total weight of the grease composition:

[0137] 70% to 95% by weight, preferably 75% to 90% by weight, of one or more base oils including at least one ester oil;

[0138] - 3 to 20% by weight, preferably 4 to 15% by weight, of one or more thickeners chosen from optionally hydroxylated lithium salts of fatty acids having 10 to 28 carbon atoms;

[0139] 0.5 to 10% by weight, preferably 1 to 5% by weight, of calcium carbonate;

[0140] - 1 to 15% by weight, preferably 2 to 10% by weight, of at least one additive chosen from extreme pressure additives.

[0141] In one embodiment, the grease composition of the present invention comprises, relative to the total weight of the grease composition:

[0142] 70% to 95% by weight, preferably 75% to 90% by weight, of one or more base oils including at least one ester oil;

[0143] - 3 to 20% by weight, preferably 4 to 15% by weight, of one or more thickeners chosen from optionally hydroxylated lithium salts of fatty acids having 10 to 28 carbon atoms;

[0144] 0.5 to 10% by weight, preferably 1 to 5% by weight, of calcium carbonate;

[0145] - 1 to 15% by weight, preferably 2 to 10% by weight, of at least one additive selected from extreme pressure additives selected from sulfurized fatty acid esters, sulfur-containing olefins and mixtures thereof.

[0146] In one embodiment, the grease composition of the present invention comprises, relative to the total weight of the grease composition:

[0147] 70% to 95% by weight, preferably 75% to 90% by weight, of one or more base oils including at least one ester oil;

[0148] - 3 to 20% by weight, preferably 4 to 15% by weight, of one or more thickeners chosen from optionally hydroxylated lithium salts of fatty acids having 10 to 28 carbon atoms;

[0149] 0.5 to 10% by weight, preferably 1 to 5% by weight, of calcium carbonate having a D50 particle size of 5 to 10 μm and a D90 particle size of 10 to 30 μm;

[0150] - 1 to 15% by weight, preferably 2 to 10% by weight, of at least one additive chosen from extreme pressure additives.

[0151] In one embodiment, the grease composition of the present invention comprises, relative to the total weight of the grease composition:

[0152] 70% to 95% by weight, preferably 75% to 90% by weight, of one or more base oils including at least one ester oil;

[0153] - 3 to 20% by weight, preferably 4 to 15% by weight, of a thickener of lithium 12-hydroxystearate;

[0154] 0.5 to 10% by weight, preferably 1 to 5% by weight, of calcium carbonate having a D50 particle size of 3 to 20 μm and a D90 particle size of 10 to 50 μm;

[0155] - 1 to 15% by weight, preferably 2 to 10% by weight, of at least one additive chosen from extreme pressure additives.

[0156] In one embodiment, the grease composition of the present invention comprises, relative to the total weight of the grease composition:

[0157] 70% to 95% by weight, preferably 75% to 90% by weight, of one or more base oils including at least one ester oil;

[0158] - 3 to 20% by weight, preferably 4 to 15% by weight, of a thickener of lithium 12-hydroxystearate;

[0159] 0.5 to 10% by weight, preferably 1 to 5% by weight, of calcium carbonate having a D50 particle size of 4 to 15 μm and a D90 particle size of 10 to 40 μm;

[0160] - 1 to 15% by weight, preferably 2 to 10% by weight, of at least one additive chosen from extreme pressure additives.

[0161] In one embodiment, the grease composition of the present invention comprises, relative to the total weight of the grease composition:

[0162] 70% to 95% by weight, preferably 75% to 90% by weight, of one or more base oils including at least one ester oil;

[0163] - 3 to 20% by weight, preferably 4 to 15% by weight, of a thickener of lithium 12-hydroxystearate;

[0164] 0.5 to 10% by weight, preferably 1 to 5% by weight, of calcium carbonate having a D50 particle size of 4 to 15 μm and a D90 particle size of 10 to 40 μm;

[0165] - 1 to 15% by weight, preferably 2 to 10% by weight, of at least one additive selected from extreme pressure additives selected from sulfurized fatty acid esters, sulfur-containing olefins and mixtures thereof.

[0166] The grease composition of the present invention preferably has a viscosity at 40° C. higher than or equal to 100 cSt, more preferably higher than or equal to 200 cSt, further preferably higher than or equal to 300 cSt, still further preferably higher than or equal to 400 cSt, most preferably higher than or equal to 500 cSt.

[0167] The viscosity is preferably measured according to standard ASTM D445.

[0168] The grease composition of the invention preferably has a carbon content of biogenic origin greater than or equal to 40% by weight, preferably at least 45% by weight, relative to the total weight of carbon atoms of the grease composition.

[0169] The carbon content of biological origin, also known as biogenic carbon content, can be measured according to the test method of ASTM D6866.

[0170] The grease composition of the present invention can be prepared by any method for preparing greases known to those skilled in the art. Preferably, a preformed thickener is used in the preparation method. Generally, the preparation method of the grease includes a step of contacting the thickener with the calcium carbonate in the base oil and a heating step of melting the soap (forming the grease). If additives are used, they can be added before or after cooling. After cooling, the grease composition is generally homogenized by grinding.

[0171] The present invention also relates to the use of the grease composition in off-highway, agricultural, wind energy machinery, such as off-road vehicles and construction equipment, agricultural machinery and wind energy turbines.

[0172] Typically, the grease composition of the present invention is used to lubricate at least one component of an off-highway, agricultural or wind energy machine, preferably selected from the group consisting of construction equipment, agricultural machinery and wind energy turbines.

[0173] The invention also relates to a method for lubricating at least one component of an off-highway, agricultural or wind energy machine, preferably selected from construction equipment, agricultural machinery and wind energy turbines, the method comprising contacting the component with the grease of the invention.

[0174] More specifically, the greases of the invention can be used in bearings (ball, roller, needle), roller and plain bearings, open gears, metal cables and chain drives, and more generally in applications that do not involve sealing systems.

[0175] All characteristics and preferences of the lubricating grease according to the invention are applicable to the method according to the invention for lubricating off-road vehicle components.

[0176] The invention will now be described by means of the following examples which are of course non-limiting illustrations of the invention.

[0177] Example

[0178] Example: Preparation of grease composition

[0179] Prepare the grease according to the following scheme:

[0180] The grease used in the examples was prepared as follows: thickener and calcium carbonate were placed in base oil and heated until the soap melted. After cooling, additives were added in different proportions and the grease composition was homogenized in a grinder.

[0181] Table 1 details the grease compositions prepared and tested, giving the proportions expressed by weight relative to the total weight of the grease composition.

[0182]

Table 1

[0183]

[0184]

[0185] The one or more base oils include a mixture of two ester type oils. The one or more base oils have a 28 day biodegradability of 70% and 75% measured according to standard OECD 301B.

[0186] The thickener is lithium 12-hydroxystearate. The 28-day biodegradability of the thickener is 97%.

[0187] CaCO3(1) is calcium carbonate having a D50 particle size of 2.14 μm and a D90 particle size of 8.04 μm.

[0188] CaCO3(2) is calcium carbonate having a D50 particle size of 7.08 μm and a D90 particle size of 14.9 μm.

[0189] The antiwear agent is an antiwear agent comprising a phosphate amine mixture.

[0190] The additive package includes a sulfurized ester type extreme pressure additive, an antioxidant and a metal passivation additive.

[0191] Calculated based on the biodegradability of the base oil and the thickener, the 28-day biodegradability of the composition CI4 of the present invention is 67.26%.

[0192] The particle size of the calcium carbonate used in the examples was measured using a laser diffraction method well known to those skilled in the art.

[0193] In this example, a Malvern Mastersizer Hydro R diffractometer was used.

[0194] If macroagglomerates are present (eg, larger than 400 μm in size), mechanical sieving can be performed using two different sieve sizes (400 μm and 800 μm) to reduce the macroagglomerates.

[0195] If macroaggregates are still present after mechanical sieving, the sample can be dried at 100 °C to further reduce the number of macroaggregates.

[0196] For the interpretation of the results, the proportion of macroagglomerates with a cut-off of, for example, 100 μm, 50 μm or 25 μm (depending on the agglomerate size) may not be taken into account. The cut-off has no significant effect on the measurement of the D50 or D90 particle size used in the examples.

[0197] Example 2: Determination of anti-wear and extreme pressure properties

[0198] The antiwear and extreme pressure (EP) properties of the grease compositions detailed in Table 1 were determined and the results are shown in Table 2.

[0199]

Table 2

[0200]

[0201] The results in Table 2 show that the grease composition CI4 of the present invention has better antiwear and extreme pressure properties than the grease compositions CC1, CC2 and CC3.

[0202] Although grease composition CI4 does not include an antiwear agent, it exhibits better antiwear properties than grease compositions CC1 and CC2 that include antiwear additives.

[0203] The grease composition CI4 comprising calcium carbonate of the desired particle size exhibits better anti-wear properties than the composition CC3 comprising calcium carbonate of other particle sizes.

[0204] Example 3: Determination of Adhesion

[0205] The adhesion of compositions CC1 and CI4 was tested using the water spray resistance test.

[0206] The viscosity of the composition at 40° C., measured according to standard ASTM D445, is 680 cSt.

[0207] Table 3 gives the adhesion properties.

[0208]

Table 3

[0209]

[0210] The results in Table 3 show that composition CI4 has very good adhesion. Therefore, the grease composition of the invention is particularly suitable for components of off-road vehicles with low rotation speeds.

Claims

1. A grease composition, comprising, relative to the total weight of the grease composition: a) 70% to 95% by weight of one or more base oils, each having a 28-day biodegradability of at least 60% measured according to standard OECD 301B; b) 1% to 20% by weight of one or more thickeners chosen from metal salts of fatty acids, each thickener having a 28-day biodegradability of at least 60% measured according to standard 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.

2. The composition according to claim 1, comprising, relative to the total weight of the grease composition: a) 70% to 95% by weight of one or more base oils, each having a 28-day biodegradability of at least 60% measured according to standard OECD 301B; b) 2% to 20% by weight of one or more thickeners chosen from metal salts of fatty acids, each thickener having a 28-day biodegradability of at least 60% measured according to standard 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. The composition according to claim 1 or 2, wherein The composition has a 28-day biodegradability of at least 60% calculated based on the 28-day biodegradability of the one or more base oils and the one or more thickeners, wherein the 28-day biodegradability of the one or more base oils and the one or more thickeners is measured according to the method of OECD 301B.

4. The composition according to any one of claims 1 to 3, wherein the thickener is selected from optionally hydroxylated fatty acid lithium salts, optionally hydroxylated fatty acid calcium salts and mixtures thereof, preferably selected from optionally hydroxylated fatty acid lithium salts, preferably lithium 12-hydroxystearate.

5. The composition according to any one of claims 1 to 4, wherein the base oil is selected from ester oils.

6. The composition according to any one of claims 1 to 5, wherein the calcium carbonate has a D50 particle size of 3 to 20 μm and a D90 particle size of 10 to 50 μm.

7. Composition according to any one of claims 1 to 6, further comprising 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.

8. The composition according to any one of claims 1 to 7, which is free of anti-wear additives of the amine phosphate type, zinc bis(N,N-dipentyldithiocarbamate) type and zinc dialkyldithiophosphate type.

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

10. Use of a grease composition according to any one of claims 1 to 9 in off-highway, agricultural or wind energy installations.

11. The use of claim 10, wherein the off-highway, agricultural or wind energy device is selected from the group consisting of construction equipment, agricultural machinery and wind turbines.

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