Lubricant compositions for industrial applications

Abstract

The present invention relates to a lubricant composition comprising: - from 5 to 95% by weight of at least one polyalkylene glycol (PAG1) having a kinematic viscosity at 40°C of less than or equal to 100 cSt, - from 5 to 95% by weight of at least one polyalkylene glycol (PAG2) having a kinematic viscosity at 40°C of at least 5000 cSt, based on the total weight of the lubricant composition. The present invention is also directed to the use of the lubricant composition as an industrial oil, preferably as gear oil or compression oil, more preferably as worm gear oil.

Description

[0001] LUBRICANT COMPOSITIONS FOR INDUSTRIAL APPLICATIONS

[0002] FIELD OF THE INVENTION

[0003] The present invention concerns lubricant compositions for their use in the lubrification in industrial field, in particular in industrial gears or compressors such as worm gears. The present invention concerns in particular compositions having improved energy efficiency and in particular improved performances to lubricate gears, such as worm gears.

[0004] TECHNICAL BACKGROUND OF THE INVENTION

[0005] Lubricating compositions for gears, in particular industrial gears, must satisfy numerous requirements, in particular related to driving comfort (perfect gear shifting, silent running, operation without incident, high reliability), to the lifetime of the assembly (reduction of wear during cold shifting, no deposits and high thermal stability, high temperature lubrication safety, stable viscosity situation and absence of shear loss, long life) as well as taking into account environmental aspects (lower fuel consumption, reduction in lubricant consumption, low noise release, easy evacuation).

[0006] Poly (alkylmethacrylate)s (PAMA) are conventionally used in industrial oils for their very good addition of viscosity index, but nevertheless have low shear stability. In addition, PAMAS are expensive.

[0007] Polyalpha-olefins (PAOs) are also used in industrial oils because they have good shear stability, but their viscosity index contribution is low.

[0008] It is also known from US2015119303, polyalkylene glycol (PAGs) obtained by polymerization or copolymerization of alkylene oxide containing from 3 to 8 carbon atoms, including at least one butylene oxide.

[0009] Document US2019 / 225907 discloses a gear oil based on polyalkylene oxide. The gear oils disclosed in this document have a limited energy efficiency.

[0010] It is therefore an object of the present invention to improve the energy efficiency of these conventional gear oil.

[0011] There is a need in providing lubricant compositions for industrial applications such as gears or compressors, allowing high energy efficiency, in particular a higher energy efficiency than conventional industrial oils.

[0012] SUMMARY OF THE INVENTION

[0013] The invention concerns a lubricant composition comprising: from 5 to 95% by weight of at least one polyalkylene glycol (PAG1) having a kinematic viscosity at 40°C of less than or equal to 100 cSt, from 5 to 95% by weight of at least one polyalkylene glycol (PAG2) having a kinematic viscosity at 40°C of at least 5000 cSt, based on the total weight of the lubricant composition.

[0014] According to an embodiment, the lubricant composition of the invention comprises: from 5 to 95% by weight, preferably from 25 to 90% by weight, more preferably from 50 to 80% by weight, of at least one PAG1 having a kinematic viscosity at 40°C of less than or equal to 100 cSt, from 4 to 94% by weight, preferably from 9 to 74% by weight, more preferably from 19 to 49% by weight, of at least one PAG2 having a kinematic viscosity at 40°C of at least 5000 cSt,

[0015] 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight, of one or more functional additive(s), preferably selected from anti-wear and / or extreme-pressure additives, metal deactivators, corrosion inhibitors, antifoam agents, anti-oxidation agents, and mixtures thereof, based on the total weight of the lubricant composition.

[0016] According to an embodiment, the lubricant composition of the invention comprises: from 5 to 94% by weight, preferably from 25 to 90% by weight, more preferably from 50 to 80% by weight, of at least one PAG1 having a kinematic viscosity at 40°C of less than or equal to 100 cSt, from 5 to 94% by weight, preferably from 9 to 74% by weight, more preferably from 19 to 49% by weight, of at least one PAG2 having a kinematic viscosity at 40°C of at least 5000 cSt,

[0017] 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight, of one or more functional additive(s), preferably selected from anti-wear and / or extreme-pressure additives, metal deactivators, corrosion inhibitors, antifoam agents, anti-oxidation agents, and mixtures thereof, based on the total weight of the lubricant composition.

[0018] Preferably, the lubricant composition of the invention has one or several of the following features:

[0019] PAG1 has a kinematic viscosity at 40°C of less than or equal to 90 cSt, preferably less than or equal to 80 cSt, more preferably less than or equal to 60 cSt or a kinematic viscosity at 40°C ranging from 2 to 90 cSt, preferably from 5 to 80 cSt, more preferably from 10 to 60 cSt;

[0020] PAG2 has a kinematic viscosity at 40°C of at least 10000 cSt, preferably at least 12000 cSt, more preferably at least 15000 cSt or a kinematic viscosity at 40°C ranging from 10000 to 80000 cSt, preferably from 12000 to 70000 cSt, more preferably from 15000 to 60000 cSt; PAG1 and PAG2 represent at least 75% by weight, preferably at least 80% by weight, more preferably at least 90% by weight, of the total weight of the lubricant composition; the lubricant composition comprises at least one further functional additive, preferably selected from anti-wear and / or extreme-pressure additives, metal deactivators, corrosion inhibitors, anti-foam agents, anti-oxidation agents, and mixtures thereof; the lubricant composition has a kinematic viscosity at 40°C ranging from 50 to 1000 cSt;

[0021] PAG1 and PAG2 are selected from polyalkylene glycol comprising alkylene oxide units having from 2 to 8 carbon atoms, preferably from 2 to 4 carbon atoms, PAG1 and PAG2 can optionally have one or two terminal hydroxyl groups;

[0022] PAG1 and PAG2 are selected from poly(ethylene glycol) (PEG), polypropylene glycol) (PPG), copolymers comprising ethylene oxide units and propylene oxide units, and mixtures thereof, preferably from random copolymers comprising ethylene oxide units and propylene oxide units, preferably in a weight ratio ethylene oxide units / propylene oxide units ranging from 80 / 20 to 20 / 80;

[0023] PAG1 is a random copolymer of ethylene oxide and propylene oxide having a unique terminal hydroxyl group and PAG2 is a random copolymer of ethylene oxide and propylene oxide having two terminal hydroxyl groups;

[0024] The polyalkylene glycol, including PAG1 and PAG2, are selected from water- soluble polyalkylene glycol.

[0025] According to particular embodiment, the lubricant composition of the invention comprises: from 5 to 95% by weight, preferably from 25 to 90% by weight, more preferably from 50 to 80% by weight, of at least one PAG1 having a kinematic viscosity at 40°C of less than or equal to 80 cSt, from 4 to 94% by weight, preferably from 9 to 74% by weight, more preferably from 19 to 49% by weight, of at least one PAG2 having a kinematic viscosity at 40°C of at least 12000 cSt,

[0026] 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight, of at least one anti-wear and / or extreme-pressure additive, based on the total weight of the lubricant composition.

[0027] According to particular embodiment, the lubricant composition of the invention comprises: from 5 to 94% by weight, preferably from 25 to 90% by weight, more preferably from 50 to 80% by weight, of at least one PAG1 having a kinematic viscosity at 40°C of less than or equal to 80 cSt, from 5 to 94% by weight, preferably from 9 to 74% by weight, more preferably from 19 to 49% by weight, of at least one PAG2 having a kinematic viscosity at 40°C of at least 12000 cSt,

[0028] 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight, of at least one anti-wear and / or extreme-pressure additive, based on the total weight of the lubricant composition.

[0029] According to particular embodiment, the lubricant composition of the invention comprises: from 5 to 95% by weight, preferably from 25 to 90% by weight, more preferably from 50 to 80% by weight, of at least one copolymer comprising ethylene oxide units and propylene oxide units having a kinematic viscosity at 40°C of less than or equal to 80 cSt, from 4 to 94% by weight, preferably from 9 to 74% by weight, more preferably from 19 to 49% by weight, of at least one copolymer comprising ethylene oxide units and propylene oxide units having a kinematic viscosity at 40°C of at least 12000 cSt,

[0030] 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight, of one or more functional additive(s) selected from anti-wear and / or extreme-pressure additives, metal deactivators, corrosion inhibitors, anti-foam agents, anti-oxidation agents, and mixtures thereof, based on the total weight of the lubricant composition.

[0031] According to particular embodiment, the lubricant composition of the invention comprises: from 5 to 94% by weight, preferably from 25 to 90% by weight, more preferably from 50 to 80% by weight, of at least one copolymer comprising ethylene oxide units and propylene oxide units having a kinematic viscosity at 40°C of less than or equal to 80 cSt, from 5 to 94% by weight, preferably from 9 to 74% by weight, more preferably from 19 to 49% by weight, of at least one copolymer comprising ethylene oxide units and propylene oxide units having a kinematic viscosity at 40°C of at least 12000 cSt,

[0032] 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight, of one or more functional additive(s) selected from anti-wear and / or extreme-pressure additives, metal deactivators, corrosion inhibitors, anti-foam agents, anti-oxidation agents, and mixtures thereof, based on the total weight of the lubricant composition.

[0033] The invention is also directed to the use of the lubricant composition of the invention, as an industrial oil, preferably as gear oil or compression oil, more preferably as worm gear oil.

[0034] The invention is also directed to a gear coated with the lubricant composition of the invention.

[0035] Preferably, the gearbox is selected from worm gear.

[0036] The lubricant compositions of the invention allow to improve the energy efficiency.

[0037] The lubricant compositions of the invention allow to significantly reduce the energy consumption in industrial elements, in particular of gears or compressors.

[0038] The lubricant compositions of the invention are based on PAGs and are typically substantially free of conventional base oils, such as fossil origin base oils.

[0039] BRIEF DESCRIPTION OF THE FIGURES

[0040] Fig. 1 shows the coefficient of traction of lubricant compositions.

[0041] Fig. 2 shows the coefficient of friction of lubricant compositions with a SRR of 5%.

[0042] Fig. 3 shows the coefficient of friction of lubricant compositions with a SRR of 20%.

[0043] Fig. 4 shows the coefficient of friction of lubricant compositions with a SRR of 50%.

[0044] Fig. 5 shows the coefficient of friction of lubricant compositions with a SRR of 100%.

[0045] Fig. 6 shows the coefficient of traction of lubricant compositions.

[0046] Fig. 7 shows the coefficient of friction of lubricant compositions with a SRR of 20%.

[0047] Fig. 8 shows the coefficient of friction of lubricant compositions with a SRR of 50%.

[0048] Fig. 9 shows the coefficient of friction of lubricant compositions with a SRR of 100%.

[0049] DETAILED DESCRIPTION OF THE INVENTION

[0050] The invention is directed to a lubricant composition comprising, based on the total weight of the lubricant composition:

[0051] - from 5 to 95% by weight of at least one polyalkylene glycol (PAG1) having a kinematic viscosity at 40°C of less than or equal to 100 cSt,

[0052] - from 5 to 95% by weight of at least one polyalkylene glycol (PAG2) having a kinematic viscosity at 40°C of at least 5000 cSt, preferably wherein PAG1 and PAG2 represent at least 75% by weight, preferably at least 80% by weight, more preferably at least 90% by weight, of the total weight of the lubricant composition. The invention is also directed to the use of the lubricant composition defined in the invention to lubricate industrial machines, such as compressors or gears, in particular gears and more particularly worm gear.

[0053] The invention is also directed to a gearbox coated with the lubricant composition defined in the invention.

[0054] The invention is also directed to the use of a very low viscosity polyalkylene glycol and a very high viscosity polyalkylene glycol in a lubricant composition, in particular in an industrial lubricant composition, such as in a gear oil, to reduce energy consumption when the lubricant composition is lubricating an industrial machine, preferably an industrial gear, such as a worm gear.

[0055] The invention is also directed to a method of lubricating gears, the method comprising contacting at least one mechanical part of a gear such as at least a part of a worm gear, with the lubricant composition defined in the invention.

[0056] Within the context of the present invention, unless stated otherwise, the kinematic viscosity is measured according to ASTM D445.

[0057] PAG1

[0058] The lubricant composition of the invention comprises at least one first polyalkylene glycol, hereinafter named PAG1.

[0059] PAG1 is a very low kinematic viscosity polyalkylene glycol, i.e. a polyalkylene glycol having a kinematic viscosity at 40°C of less than or equal to 100 cSt. Preferably, PAG1 has a kinematic viscosity at 40°C of less than or equal to 90 cSt, preferably less than or equal to 80 cSt, more preferably less than or equal to 60 cSt.

[0060] According to an embodiment, PAG1 has a kinematic viscosity at 40°C ranging from 2 to 90 cSt, preferably from 5 to 80 cSt, more preferably from 10 to 60 cSt.

[0061] According to an embodiment, PAG1 has a kinematic viscosity at 100°C ranging from 0.5 to 30 cSt, preferably from 1 to 25 cSt, more preferably from 2 to 15 cSt.

[0062] According to an embodiment, PAG1 has a viscosity index ranging from 100 to 350, preferably from 120 to 300, more preferably from 150 to 250.

[0063] The viscosity index can be measured according to ASTM D2270.

[0064] PAG2

[0065] The lubricant composition of the invention comprises at least one second polyalkylene glycol, hereinafter named PAG2.

[0066] PAG2 is a very high kinematic viscosity polyalkylene glycol, i.e. a polyalkylene glycol having a kinematic viscosity at 40°C of at least 5000 cSt. Preferably, PAG2 has a kinematic viscosity at 40°C of at least 10000 cSt, preferably at least 12000 cSt, more preferably at least 15000 cSt.

[0067] According to an embodiment, PAG2 has a kinematic viscosity at 40°C ranging from 10000 to 80000 cSt, preferably from 12000 to 70000 cSt, more preferably from 15000 to 60000 cSt.

[0068] According to an embodiment, PAG2 has a kinematic viscosity at 100°C ranging from 500 to 12000 cSt, preferably from 1000 to 10000 cSt, more preferably from 1500 to 9000 cSt.

[0069] According to an embodiment, PAG2 has a viscosity index ranging from 200 to 800, preferably from 250 to 700, more preferably from 300 to 600.

[0070] PAG1 and PAG2

[0071] PAG1 and PAG2 are selected from polyalkylene glycol comprising alkylene oxide units having from 2 to 8 carbon atoms, preferably from 2 to 4 carbon atoms.

[0072] PAG1 and PAG2 are typically water-soluble polymers.

[0073] Within the context of the present invention, "water soluble polymers", refers to polymers that form a homogenous clear mixture when observed with the naked eye at ambient temperature and when mixed at concentrations ranging from 5% to 25wt % by weight of polymers in deionized water.

[0074] According to an embodiment, PAG1 and PAG2 are selected from poly(ethylene glycol) (PEG), polypropylene glycol) (PPG), copolymers comprising ethylene oxide units and propylene oxide units, and mixtures thereof.

[0075] Preferably, PAG1 and PAG2 are selected from copolymers comprising ethylene oxide units and propylene oxide units.

[0076] By "copolymers comprising ethylene oxide units and propylene oxide units" or “copolymers of ethylene oxide and propylene oxide” within the meaning of the present invention is meant copolymers comprising at least units derived from the polymerisation of ethylene glycol and at least units derived from the polymerisation of propylene glycol. These polymers may be, for example, block copolymers or random copolymers.

[0077] Preferably, PAG1 and PAG2 are selected from random copolymers comprising ethylene oxide units and propylene oxide units.

[0078] According to an embodiment, PAG1 and PAG2 have a weight ratio of ethylene oxide units / propylene oxide units ranging from 80 / 20 to 20 / 80, preferably from 75 / 25 to 25 / 75, more preferably from 75 / 25 to 50 / 50.

[0079] According to a particularly preferred embodiment, PAG1 has a weight ratio ethylene oxide units / propylene oxide units of 50 / 50 and PAG2 has a weight ratio ethylene oxide units / propylene oxide units of 75 / 25. PAG1 and / or PAG2 can optionally have one or two terminal hydroxyl groups. Indeed, PAG1 and / or PAG2 may optionally comprise alkyl end group(s), for example chosen from linear or branched alkyls containing from 1 to 8 carbon atoms, preferably from 1 to 4 carbon atoms.

[0080] According to a particularly preferred embodiment, PAG1 is a random copolymer of ethylene oxide and propylene oxide having a unique terminal hydroxyl group and PAG2 is a random copolymer of ethylene oxide and propylene oxide having two terminal hydroxyl groups.

[0081] According to a particularly preferred embodiment, PAG1 and PAG2 represent at least 75% by weight, preferably at least 80% by weight, more preferably at least 90% by weight, of the total weight of the lubricant composition.

[0082] Indeed, preferably, the lubricant composition of the invention comprises less than 10% by weight, preferably less than 5% by weight, more preferably less than 2% by weight of base oils (other than PAG, in particular other than PAG1 and PAG2), based on the total weight of the lubricant composition. Ideally, the lubricant composition is free of base oils (other than PAGs).

[0083] Also, the lubricant composition of the invention preferably comprises less than 10% by weight, preferably less than 5% by weight, more preferably less than 2% by weight of water.

[0084] Preferably, the lubricant composition has a kinematic viscosity at 40°C ranging from 50 to 1000 cSt, preferably from 60 to 700 cSt.

[0085] The skilled person will adjust the proportion of PAG1 and of PAG2 in order to reach the target kinematic viscosity of the lubricant composition.

[0086] According to an embodiment, the lubricant composition has a viscosity index ranging from 200 to 300. The viscosity index can be measured according to ASTM D2270.

[0087] According to an embodiment, the lubricant composition of the invention comprises:

[0088] - from 5 to 95% by weight of at least one polyalkylene glycol (PAG1) having a kinematic viscosity at 40°C of less than or equal to 100 cSt,

[0089] - from 5 to 95 % by weight of at least one polyalkylene glycol (PAG2) having a kinematic viscosity of 40°C of at least 5,000 cSt, based on the total weight of the lubricant composition, wherein PAG1 and PAG2 are selected from copolymers comprising ethylene oxide units and propylene oxide units, and wherein PAG1 and PAG2 represent at least 75% by weight of the total weight of the lubricant composition.

[0090] Functional additive(s)

[0091] According to an embodiment, the lubricant composition of the invention comprises one or more functional additives.

[0092] Within the meaning of the present invention “functional additives” are additives different from polyalkylene glycol and base oils.

[0093] According to an embodiment, the lubricant composition further comprises at least one functional additive selected from anti-wear and / or extreme-pressure additives, metal deactivators, corrosion inhibitors, anti-foam agents, anti-oxidation agents, and mixtures thereof.

[0094] According to an embodiment, the further additive(s) represent from 0.01 to 10% by weight of the total weight of the lubricant composition, preferably from 0.05 to 5% by weight of the total weight of the lubricant composition, more preferably from 0.1 to 3% by weight of the total weight of the lubricant composition.

[0095] According to an embodiment, the further additive(s) comprise(s) at least one antiwear and / or extreme pressure additive. Anti-wear additives and extreme-pressure additives protect surfaces against friction through the forming of a protective film adsorbed on these surfaces. There is a large variety of anti-wear additives. Preferably, some additives are both anti-wear and extreme-pressure additives.

[0096] Preferably, for the lubricant composition of the invention, the anti-wear additives are selected from among ashless additives, such as sulfur- and phosphorus-containing antiwear and extreme-pressure additives.

[0097] The antiwear and extreme-pressure additives can represent from 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight of the total weight of the lubricant composition.

[0098] According to an embodiment, the further additive(s) comprise(s) at least one antioxidant additive.

[0099] The antioxidant additive generally allows delayed degradation of the composition in service. This degradation can particularly translate as the formation of deposits, the presence of sludge or an increase in the viscosity of the composition.

[0100] Antioxidant additives act in particular as radical scavengers or hydroperoxide decomposers. Among commonly employed antioxidant additives, mention can be made of antioxidant additives of phenolic type, antioxidant additives of amine type, sulfur- phosphorus antioxidant additives. Some of these antioxidant additives e.g. sulfurphosphorus antioxidant additives can generate ash. Phenolic antioxidant additives can be ash-free or in the form of neutral or basic metal salts. Antioxidant additives can particular be selected from among sterically hindered phenols, sterically hindered phenol esters, and sterically hindered phenols comprising a thioether bridge, diphenylamines, diphenylamines substituted by at least one C1-C12 alkyl group, N,N'-dialkyl-aryl-diamines and mixtures thereof.

[0101] Preferably, in the invention, the sterically hindered phenols are selected from among compounds comprising a phenol group in which at least one vicinal carbon of the carbon carrying the alcohol function is substituted by at least one C1- C10 alkyl group, preferably C1-C6 alkyl group, more preferably C4 alkyl group, further preferably by the tert-butyl group.

[0102] Amine compounds are another class of antioxidant additives able to be used, optionally in combination with phenolic antioxidant additives. Examples of amine compounds are aromatic amines e.g. aromatic amines of formula NR4R5R6 where R4 is an optionally substituted aliphatic group or aromatic group, R5 is an optionally substituted aromatic group, R6 is a hydrogen atom, alkyl group, aryl group or a group of formula R7S(O)zR8 where R7 is an alkylene group or alkenylene group, R8 is an alkyl group, alkenyl group or aryl group and z is 0, 1 or 2.

[0103] Sulfurized alkyl-phenols or the alkali or alkaline-earth metal salts thereof can also be used as antioxidant additives.

[0104] The antioxidant additives can represent from 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight of the total weight of the lubricant composition.

[0105] According to an embodiment, the further additive(s) comprise(s) at least one anticorrosion additive (also named corrosion inhibitor). Among anticorrosion additives that can be used in the lubricant composition of the invention, mention can be made of triazine- containing corrosion inhibitors, carboxylic acids and mixtures thereof.

[0106] Among carboxylic acids, mention may be made of hexanoic acid, octanoic acid or decanoic acid.

[0107] Among triazine-containing corrosion inhibitors, mention may be made of compounds comprising 1 ,3,5-triazine optionally substituted by one or more hydrocarbon groups optionally comprising heteroatoms, such as nitrogen and / or oxygen.

[0108] The corrosion inhibitor(s) can represent from 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight of the total weight of the lubricant composition. According to an embodiment, the further additive(s) comprise(s) at least one metal- deactivator. Among metal-deactivators, mention can be made of tolyltriazole, derivatives of tolyltriazole or dimercaptothiadiazoles. The metal-deactivator particularly allows neutralisation of the catalytic effect of metals such as copper and iron.

[0109] By « derivative of tolyltriazole » it is meant a tolyltriazole compound substituted preferably by one of more alkyl groups optionally comprising one or more heteroatoms.

[0110] The metal deactivator(s) can represent from 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight of the total weight of the lubricant composition.

[0111] According to an embodiment, the further additive(s) comprise(s) at least one antifoam agent. Among the anti-foam additives that can be used in the lubricant composition of the invention, mention can be made of silicone compounds and polyacrylate compounds.

[0112] The anti-foam agent(s) can represent from 0.001 to 2% by weight, preferably from 0.005 to 1 % by weight, more preferably from 0.01 to 0.5% by weight, of the total weight of the lubricant composition.

[0113] These additives can be added alone and / or in the form of a mixture. In particular, according to an embodiment, the additives are used in the form of an additive package. The additive package comprises several functional additives. The additive package can comprise all or part of the additives of the lubricant composition.

[0114] According to an embodiment, the lubricant composition of the invention comprises, preferably consists of:

[0115] - from 5 to 95% by weight, preferably from 25 to 90% by weight, more preferably from 50 to 80% by weight, of at least one PAG1 having a kinematic viscosity at 40°C of less than or equal to 100 cSt,

[0116] - from 4 to 95% by weight, preferably from 9 to 74% by weight, more preferably from 19 to 49% by weight, of at least one PAG2 having a kinematic viscosity at 40°C of at least 5000 cSt,

[0117] - 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight, of one or more functional additive(s), preferably selected from antiwear and / or extreme-pressure additives, metal deactivators, corrosion inhibitors, anti-foam agents, anti-oxidation agents, and mixtures thereof, based on the total weight of the lubricant composition,

[0118] PAG1 and PAG2 being preferably water-soluble polymers.

[0119] According to an embodiment, the lubricant composition of the invention comprises, preferably consists of: - from 5 to 94% by weight, preferably from 25 to 90% by weight, more preferably from 50 to 80% by weight, of at least one PAG1 having a kinematic viscosity at 40°C of less than or equal to 100 cSt,

[0120] - from 5 to 94% by weight, preferably from 9 to 74% by weight, more preferably from 19 to 49% by weight, of at least one PAG2 having a kinematic viscosity at 40°C of at least 5000 cSt,

[0121] - 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight, of one or more functional additive(s), preferably selected from antiwear and / or extreme-pressure additives, metal deactivators, corrosion inhibitors, anti-foam agents, anti-oxidation agents, and mixtures thereof, based on the total weight of the lubricant composition,

[0122] PAG1 and PAG2 being preferably water-soluble polymers.

[0123] According to an embodiment, the lubricant composition of the invention comprises, preferably consists of:

[0124] - from 5 to 95% by weight, preferably from 25 to 90% by weight, more preferably from 50 to 80% by weight, of at least one PAG1 having a kinematic viscosity at 40°C of less than or equal to 80 cSt,

[0125] - from 4 to 94% by weight, preferably from 9 to 74% by weight, more preferably from 19 to 49% by weight, of at least one PAG2 having a kinematic viscosity at 40°C of at least 12000 cSt,

[0126] - 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight, of one or more functional additive(s) selected from anti-wear and / or extreme-pressure additives, metal deactivators, corrosion inhibitors, anti-foam agents, antioxidation agents, and mixtures thereof, based on the total weight of the lubricant composition,

[0127] PAG1 and PAG2 being preferably water-soluble polymers.

[0128] According to an embodiment, the lubricant composition of the invention comprises, preferably consists of:

[0129] - from 5 to 95% by weight, preferably from 25 to 90% by weight, more preferably from 50 to 80% by weight, of at least one PAG1 having a kinematic viscosity at 40°C ranging from 5 to 80 cSt,

[0130] - from 4 to 94% by weight, preferably from 9 to 74% by weight, more preferably from 19 to 49% by weight, of at least one PAG2 having a kinematic viscosity at 40°C ranging from 12000 to 70000 cSt,

[0131] - 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight, of one or more functional additive(s) selected from anti-wear and / or extreme-pressure additives, metal deactivators, corrosion inhibitors, anti-foam agents, antioxidation agents, and mixtures thereof, based on the total weight of the lubricant composition,

[0132] PAG1 and PAG2 being preferably water-soluble polymers.

[0133] According to an embodiment, the lubricant composition of the invention comprises, preferably consists of:

[0134] - from 5 to 95% by weight, preferably from 25 to 90% by weight, more preferably from 50 to 80% by weight, of at least one copolymer comprising ethylene oxide units and propylene oxide units having a kinematic viscosity at 40°C of less than or equal to 80 cSt,

[0135] - from 4 to 94% by weight, preferably from 9 to 74% by weight, more preferably from 19 to 49% by weight, of at least one copolymer comprising ethylene oxide units and propylene oxide units having a kinematic viscosity at 40°C of at least 12000 cSt,

[0136] - 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight, of one or more functional additive(s) selected from anti-wear and / or extreme-pressure additives, metal deactivators, corrosion inhibitors, anti-foam agents, antioxidation agents, and mixtures thereof, based on the total weight of the lubricant composition,

[0137] PAG1 and PAG2 being preferably water-soluble polymers.

[0138] According to an embodiment, the lubricant composition of the invention comprises, preferably consists of:

[0139] - from 5 to 95% by weight, preferably from 25 to 90% by weight, more preferably from 50 to 80% by weight, of at least one copolymer comprising ethylene oxide units (EG) and propylene oxide units (PO) having a kinematic viscosity at 40°C of less than or equal to 80 cSt,

[0140] - from 4 to 94% by weight, preferably from 9 to 74% by weight, more preferably from 19 to 49% by weight, of at least one copolymer comprising ethylene oxide units and propylene oxide units having a kinematic viscosity at 40°C of at least 12000 cSt,

[0141] - 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight, of one or more functional additive(s) selected from anti-wear and / or extreme-pressure additives, metal deactivators, corrosion inhibitors, anti-foam agents, antioxidation agents, and mixtures thereof, based on the total weight of the lubricant composition,

[0142] PAG1 and PAG2 having a weight ratio EO / PO ranging from 80 / 20 to 20 / 80, preferably from 75 / 25 to 25 / 75, more preferably from 75 / 25 to 50 / 50. According to an embodiment, the lubricant composition of the invention comprises, preferably consists of:

[0143] - from 5 to 95% by weight, preferably from 25 to 90% by weight, more preferably from 50 to 80% by weight, of at least one copolymer comprising ethylene oxide units and propylene oxide units having a kinematic viscosity at 40°C ranging from 5 to 80 cSt,

[0144] - from 4 to 94% by weight, preferably from 9 to 74% by weight, more preferably from 19 to 49% by weight, of at least one copolymer comprising ethylene oxide units and propylene oxide units having a kinematic viscosity at 40°C ranging from 12000 to 70000 cSt,

[0145] - 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight, of one or more functional additive(s) selected from anti-wear and / or extreme-pressure additives, metal deactivators, corrosion inhibitors, anti-foam agents, antioxidation agents, and mixtures thereof, based on the total weight of the lubricant composition,

[0146] PAG1 and PAG2 being preferably water-soluble polymers.

[0147] According to an embodiment, the lubricant composition of the invention comprises, preferably consists of:

[0148] - from 5 to 95% by weight, preferably from 25 to 90% by weight, more preferably from 50 to 80% by weight, of at least one copolymer comprising ethylene oxide units (EG) and propylene oxide units (PO) having a kinematic viscosity at 40°C ranging from 5 to 80 cSt,

[0149] - from 4 to 94% by weight, preferably from 9 to 74% by weight, more preferably from 19 to 49% by weight, of at least one copolymer comprising ethylene oxide units and propylene oxide units having a kinematic viscosity at 40°C ranging from 12000 to 70000 cSt,

[0150] - 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight, of one or more functional additive(s) selected from anti-wear and / or extreme-pressure additives, metal deactivators, corrosion inhibitors, anti-foam agents, antioxidation agents, and mixtures thereof, based on the total weight of the lubricant composition,

[0151] PAG1 and PAG2 having a weight ratio EO / PO ranging from 80 / 20 to 20 / 80, preferably from 75 / 25 to 25 / 75, more preferably from 75 / 25 to 50 / 50.

[0152] According to an embodiment, the lubricant composition of the invention comprises:

[0153] - from 5 to 95% by weight, preferably from 25 to 90% by weight, more preferably from 50 to 80% by weight, of at least one PAG1 having a kinematic viscosity at 40°C of less than or equal to 100 cSt, - from 4 to 94% by weight, preferably from 9 to 74% by weight, more preferably from 19 to 49% by weight, of at least one PAG2 having a kinematic viscosity at 40°C of at least 5000 cSt,

[0154] - 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight, of at least one anti-wear and / or extreme-pressure additive, based on the total weight of the lubricant composition, PAG1 and PAG2 being preferably water-soluble polymers.

[0155] According to an embodiment, the lubricant composition of the invention comprises:

[0156] - from 5 to 95% by weight, preferably from 25 to 90% by weight, more preferably from 50 to 80% by weight, of at least one PAG1 having a kinematic viscosity at 40°C of less than or equal to 80 cSt,

[0157] - from 4 to 94% by weight, preferably from 9 to 74% by weight, more preferably from 19 to 49% by weight, of at least one PAG2 having a kinematic viscosity at 40°C of at least 12000 cSt,

[0158] - 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight, of at least one anti-wear and / or extreme-pressure additive, based on the total weight of the lubricant composition, PAG1 and PAG2 being preferably water-soluble polymers.

[0159] According to an embodiment, the lubricant composition of the invention comprises:

[0160] - from 5 to 95% by weight, preferably from 25 to 90% by weight, more preferably from 50 to 80% by weight, of at least one PAG1 having a kinematic viscosity at 40°C ranging from 5 to 80 cSt,

[0161] - from 4 to 94% by weight, preferably from 9 to 74% by weight, more preferably from 19 to 49% by weight, of at least one PAG2 having a kinematic viscosity at 40°C ranging from 12000 to 70000 cSt,

[0162] - 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight, of at least one anti-wear and / or extreme-pressure additive, based on the total weight of the lubricant composition, PAG1 and PAG2 being preferably water-soluble polymers.

[0163] According to an embodiment, the lubricant composition of the invention comprises:

[0164] - from 5 to 95% by weight, preferably from 25 to 90% by weight, more preferably from 50 to 80% by weight, of at least one copolymer comprising ethylene oxide units and propylene oxide units having a kinematic viscosity at 40°C of less than or equal to 80 cSt, - from 4 to 94% by weight, preferably from 9 to 74% by weight, more preferably from 19 to 49% by weight, of at least one copolymer comprising ethylene oxide units and propylene oxide units having a kinematic viscosity at 40°C of at least 12000 cSt,

[0165] - 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight, of at least one anti-wear and / or extreme-pressure additive, based on the total weight of the lubricant composition, PAG1 and PAG2 being preferably water-soluble polymers.

[0166] According to an embodiment, the lubricant composition of the invention comprises:

[0167] - from 5 to 95% by weight, preferably from 25 to 90% by weight, more preferably from 50 to 80% by weight, of at least one copolymer comprising ethylene oxide units (EG) and propylene oxide units (PO) having a kinematic viscosity at 40°C of less than or equal to 80 cSt,

[0168] - from 4 to 94% by weight, preferably from 9 to 74% by weight, more preferably from 19 to 49% by weight, of at least one copolymer comprising ethylene oxide units and propylene oxide units having a kinematic viscosity at 40°C of at least 12000 cSt,

[0169] - 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight, of at least one anti-wear and / or extreme-pressure additive, based on the total weight of the lubricant composition,

[0170] PAG1 and PAG2 having a weight ratio EO / PO ranging from 80 / 20 to 20 / 80, preferably from 75 / 25 to 25 / 75, more preferably from 75 / 25 to 50 / 50.

[0171] According to an embodiment, the lubricant composition of the invention comprises:

[0172] - from 5 to 95% by weight, preferably from 25 to 90% by weight, more preferably from 50 to 80% by weight, of at least one copolymer comprising ethylene oxide units and propylene oxide units having a kinematic viscosity at 40°C ranging from 5 to 80 cSt,

[0173] - from 4 to 94% by weight, preferably from 9 to 74% by weight, more preferably from 19 to 49% by weight, of at least one copolymer comprising ethylene oxide units and propylene oxide units having a kinematic viscosity at 40°C ranging from 12000 to 70000 cSt,

[0174] - 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight, of at least one anti-wear and / or extreme-pressure additive, based on the total weight of the lubricant composition,

[0175] PAG1 and PAG2 being preferably water-soluble polymers.

[0176] According to an embodiment, the lubricant composition of the invention comprises:

[0177] - from 5 to 95% by weight, preferably from 25 to 90% by weight, more preferably from 50 to 80% by weight, of at least one copolymer comprising ethylene oxide units (EO) and propylene oxide units (PO) having a kinematic viscosity at 40°C ranging from 5 to 80 cSt,

[0178] - from 4 to 94% by weight, preferably from 9 to 74% by weight, more preferably from 19 to 49% by weight, of at least one copolymer comprising ethylene oxide units and propylene oxide units having a kinematic viscosity at 40°C ranging from 12000 to 70000 cSt,

[0179] - 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight, of at least one anti-wear and / or extreme-pressure additive, based on the total weight of the lubricant composition,

[0180] PAG1 and PAG2 having a weight ratio EO / PO ranging from 80 / 20 to 20 / 80, preferably from 75 / 25 to 25 / 75, more preferably from 75 / 25 to 50 / 50.

[0181] The lubricant composition can be prepared according to processes well known by the skilled person to formulate lubricant compositions, for example by mixing ingredients at a temperature ranging from 20 to 50°C.

[0182] PAG1 and PAG2 are used in combination in a lubricant composition in order to improve the energy efficiency of industrial machines, such as compressors or gears.

[0183] In particular, the lubricant composition of the invention is used to lubricate industrial gears, in particular worm gears.

[0184] Within the meaning of the present invention, “industrial gears” means gears used in industries, working machines. In particular, the expression “industrial gears” exclude gearboxes of vehicles.

[0185] According to an embodiment, the combination of PAG1 and PAG2 in the lubricant composition is used to reduce energy consumption when the lubricant composition is lubricating an industrial machine, preferably a compressor or a gear, such as a worm gear.

[0186] The inventors surprisingly found that the combination of a very low viscosity polyalkylene glycol and a very high viscosity polyalkylene glycol, when added into a lubricant composition, allows to reduce energy consumption.

[0187] The invention is also directed to the use of the lubricant composition defined in the invention as an industrial oil, preferably as gear oil or compression oil, more preferably as worm gear oil.

[0188] In one embodiment of the invention, the lubricant composition is used in industrial gearing. According to an embodiment, the lubricant composition allows to reduce energy consumption when the lubricant composition is lubricating a gear, in particular a worm gear.

[0189] The invention also concerns a gear lubricating method comprising applying the lubricant composition according to the invention onto gears, wherein gears are preferably industrial gears, such as worm gears.

[0190] The invention also concerns a gear coated with the lubricant composition according to the invention. In one embodiment, the gear is a worm gear.

[0191] EXAMPLES

[0192] In the remainder of the present description, examples are given for the purpose of illustrating the present invention which are in no way intended to limit the scope thereof.

[0193] Example 1 : Preparation of lubricant compositions

[0194] Lubricant compositions Cl 1 , CC1 and CC2 were prepared with the ingredients and amounts listed in Table 1.

[0195] Table 1 :

[0196] PAG1 is a water-soluble random copolymer of ethylene oxide (EO) and propylene oxide (PO) having a unique terminal hydroxyl group, and having a kinematic viscosity at 40°C of 20 cSt.

[0197] PAG2 is a water-soluble random copolymer of ethylene oxide and propylene oxide having two terminal hydroxyl groups, and having a kinematic viscosity at 40°C of 18000 cSt.

[0198] PAG3 is a water-soluble random copolymer of ethylene oxide and propylene oxide having a unique terminal hydroxyl group, and having a kinematic viscosity at 40°C of 460 cSt. PAG4 is a water-soluble random copolymer of ethylene oxide and propylene oxide having a unique terminal hydroxyl group, and having a kinematic viscosity at 40°C of 320 cSt.

[0199] PAG5 is a water-soluble random copolymer of ethylene oxide and propylene oxide having a kinematic viscosity at 40°C of around 320 cSt.

[0200] Additive package comprises additives suitable for industrial oil application, including notably sulfur-containing anti-wear additive(s), anti-corrosion additive(s) and anti-foam additive(s). KV40 is the kinematic viscosity at 40°C of the lubricant compositions.

[0201] Example 2: Coefficient of Traction

[0202] In this example, compositions CC1 , CC2 and CI1 detailed in Table 1 were tested and the Coefficient of traction at 80°C was measured.

[0203] The coefficient of traction (COT) was measured using the PCS instrument MTM tribometer. It is used to evaluate the performance of lubricants in terms of friction in the mixed / hydrodynamic regime. This test consists of putting a steel ball and a steel plane in relative motion at different speeds, making it possible to define the %SRR (Slide-to-Roll Ratio) which corresponds to the sliding speed / rolling speed.

[0204] The measurement conditions were 75 N load, at a rated temperature of 80°C for a SRR from 5% to 100%.

[0205] The lower the traction coefficient for a lubricant composition, the lower the friction between the metal parts, resulting in a reduced energy consumption.

[0206] The results are provided in Fig. 1.

[0207] It can be seen from Fig. 1 that the lubricant composition of the invention shows a reduced coefficient of traction and thus a reduced energy consumption compared with compositions CC1 and CC2.

[0208] Example 3: Coefficient of friction

[0209] In this example, compositions CC1 , CC2 and CI1 detailed in Table 1 were tested and the Coefficient of friction at 80°C was measured.

[0210] The tribological properties can be evaluated by a test on a rotating ball-disk tribometer (also called ball-plane) of the Linear reciprocating tribometer type. This test makes it possible to evaluate the performance of lubricants in terms of friction in mixed / limited regime according to the conditions of load, pressure or speed applied.

[0211] The coefficient of friction of the lubricant compositions tested is determined using a hardened steel ball of approximately 2 cm diameter, for example 1.905 cm diameter, on a hardened steel plane. The tribometer may be a device for relatively moving a steel ball and a steel plane to determine the friction / friction coefficients for a given lubricant composition, while varying various properties such as speed, load, and temperature. The hardened steel plane is AISI 52100 with a mirror finish and the ball is also AISI 52100 made of hardened steel.

[0212] The load applied is 75 N and the rolling speed varies from 5 mm / s to 2500 mm / s. In particular, the coefficient of friction is determined at a Rolling speed of 5 to 2500 mm / s, at 80°C. The coefficient is determined at a Slide-to-Roll Ratio (%SRR) of 5%, 20%, 50% and 100%.

[0213] Approximately 50 ml of the tested lubricant composition was introduced into the device. The ball is engaged face to face, with the ball and the plane independently actuated so as to create a mixed rolling / sliding contact.

[0214] The coefficient of friction (COF) is measured and recorded via a load cell.

[0215] The results are shown in Figs 2 to 5.

[0216] Fig. 2 corresponds to the results with a SRR of 5%.

[0217] Fig. 3 corresponds to the results with a SRR of 20%.

[0218] Fig. 4 corresponds to the results with a SRR of 50%.

[0219] Fig. 5 corresponds to the results with a SRR of 100%.

[0220] It can be seen from Fig. 2 to Fig. 5 that the lubricant composition of the invention shows a reduced coefficient of traction and thus a reduced energy consumption compared with comparative compositions CC1 and CC2.

[0221] Example 4: Comparative examplesLubricant compositions CC3, CC4 and CC5 were prepared with the ingredients and amounts listed in Table 2.

[0222] Table 2: PAG6 is a water-soluble random copolymer of ethylene oxide (EO) and propylene oxide (PO) having a kinematic viscosity at 40°C of 239 cSt and having a 50:50 EO:PO weight ratio.

[0223] PAG7 is a water-soluble random copolymer of ethylene oxide (EO) and propylene oxide (PO) having a kinematic viscosity at 40°C of 1000 cSt and having a 50:50 EO:PO weight ratio.

[0224] PAG8 is a water insoluble homopolymer of propylene oxide (PO) having a unique terminal hydroxyl group, and having a kinematic viscosity at 40°C of 330 cSt.

[0225] PAG9 is an oil-soluble PAG having a kinematic viscosity at 40°C of 46 cSt.

[0226] PAG10 is an oil-soluble PAG having a kinematic viscosity at 40°C of 680 cSt.

[0227] Additive package 2 comprises additives suitable for industrial oil application, including notably sulfur-containing anti-wear additive(s), anti-corrosion additive(s) and anti-foam additive(s).

[0228] Example 5: Coefficient of Traction

[0229] In this example, compositions CC3, CC4, and CC5 were compared to CI1 (detailed Table 1) in terms of traction properties. For this purpose, the coefficient of traction at 80°C was measured under the same experimental conditions as those used in Example 2.

[0230] The results are provided in Fig. 6.

[0231] It can be seen from Fig. 6 that the lubricant composition of the invention shows a reduced coefficient of traction and thus a reduced energy consumption compared with compositions CC3, CC4 and CC5.

[0232] Example 6: Coefficient of friction

[0233] In this example, compositions CC3, CC4, and CC5 were compared to CI 1 (detailed in Table

[0234] 1) in terms of friction properties. For this purpose, the coefficient of friction at 80°C was measured under the same experimental conditions as those used in Example 3.

[0235] The results are shown in Figs 7 to 9.

[0236] Fig. 7 corresponds to the results with a SRR of 20%.

[0237] Fig. 8 corresponds to the results with a SRR of 50%.

[0238] Fig. 9 corresponds to the results with a SRR of 100%.

[0239] It can be seen from Fig. 7 to Fig. 9 that the lubricant composition of the invention shows a reduced coefficient of traction and thus a reduced energy consumption compared with comparative compositions CC3, CC4 and CC5.

Claims

CLAIMS1. A lubricant composition comprising:- from 5 to 95% by weight of at least one polyalkylene glycol (PAG1) having a kinematic viscosity at 40°C of less than or equal to 100 cSt,- from 5 to 95% by weight of at least one polyalkylene glycol (PAG2) having a kinematic viscosity at 40°C of at least 5000 cSt, based on the total weight of the lubricant composition.

2. Lubricant composition according to claim 1 , comprising:- from 5 to 95% by weight, preferably from 25 to 90% by weight, more preferably from 50 to 80% by weight, of at least one PAG1 having a kinematic viscosity at 40°C of less than or equal to 100 cSt,- from 5 to 94% by weight, preferably from 9 to 74% by weight, more preferably from 19 to 49% by weight, of at least one PAG2 having a kinematic viscosity at 40°C of at least 5000 cSt,0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight, of one or more functional additive(s), preferably selected from anti-wear and / or extreme-pressure additives, metal deactivators, corrosion inhibitors, anti-foam agents, anti-oxidation agents, and mixtures thereof, based on the total weight of the lubricant composition.

3. Lubricant composition according to claim 1 or 2, wherein PAG1 has a kinematic viscosity at 40°C of less than or equal to 90 cSt, preferably less than or equal to 80 cSt, more preferably less than or equal to 60 cSt or a kinematic viscosity at 40°C ranging from 2 to 90 cSt, preferably from 5 to 80 cSt, more preferably from 10 to 60 cSt.

4. Lubricant composition according to any one of claims 1 to 3, wherein PAG2 has a kinematic viscosity at 40°C of at least 10000 cSt, preferably at least 12000 cSt, more preferably at least 15000 cSt or a kinematic viscosity at 40°C ranging from 10000 to 80000 cSt, preferably from 12000 to 70000 cSt, more preferably from 15000 to 60000 cSt.

5. Lubricant composition according to any one of claims 1 to 4, wherein PAG1 and PAG2 represent at least 75% by weight, preferably at least 80% by weight, more preferably at least 90% by weight, of the total weight of the lubricant composition.

6. Lubricant composition according to any one of claims 1 to 5, wherein the lubricant composition comprises at least one further functional additive, preferably selected from anti-wear and / or extreme-pressure additives, metal deactivators, corrosion inhibitors, anti-foam agents, anti-oxidation agents, and mixtures thereof.

7. Lubricant composition according to any one of claims 1 to 6, having a kinematic viscosity at 40°C ranging from 50 to 1000 cSt.

8. Lubricant composition according to any one of claims 1 to 7, wherein PAG1 and PAG2 are selected from polyalkylene glycol comprising alkylene oxide units having from 2 to 8 carbon atoms, preferably from 2 to 4 carbon atoms, PAG1 and PAG2 can optionally have one or two terminal hydroxyl groups.

9. Lubricant composition according to any one of claims 1 to 8, wherein PAG1 and PAG2 are selected from poly(ethylene glycol) (PEG), polypropylene glycol) (PPG), copolymers comprising ethylene oxide units and propylene oxide units, and mixtures thereof, preferably from random copolymers comprising ethylene oxide units and propylene oxide units, preferably in a weight ratio ethylene oxide units / propylene oxide units ranging from 80 / 20 to 20 / 80.

10. Lubricant composition according to any one of claims 1 to 9, wherein PAG1 is a random copolymer of ethylene oxide and propylene oxide having a unique terminal hydroxyl group and PAG2 is a random copolymer of ethylene oxide and propylene oxide having two terminal hydroxyl groups.

11. Lubricant composition according to any one of claims 1 to 10, comprising:- from 5 to 95% by weight, preferably from 25 to 90% by weight, more preferably from 50 to 80% by weight, of at least one PAG1 having a kinematic viscosity at 40°C of less than or equal to 80 cSt,- from 5 to 94% by weight, preferably from 9 to 74% by weight, more preferably from 19 to 49% by weight, of at least one PAG2 having a kinematic viscosity at 40°C of at least 12000 cSt,0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight, of at least one anti-wear and / or extreme-pressure additive,based on the total weight of the lubricant composition.

12. Lubricant composition according to any one of claims 1 to 11 , comprising:- from 5 to 95% by weight, preferably from 25 to 90% by weight, more preferably from 50 to 80% by weight, of at least one copolymer comprising ethylene oxide units and propylene oxide units having a kinematic viscosity at 40°C of less than or equal to 80 cSt,- from 5 to 94% by weight, preferably from 9 to 74% by weight, more preferably from 19 to 49% by weight, of at least one copolymer comprising ethylene oxide units and propylene oxide units having a kinematic viscosity at 40°C of at least 12000 cSt, 0.01 to 10% by weight, preferably from 0.05 to 5% by weight, more preferably from 0.1 to 3% by weight, of one or more functional additive(s) selected from anti-wear and / or extreme-pressure additives, metal deactivators, corrosion inhibitors, antifoam agents, anti-oxidation agents, and mixtures thereof, based on the total weight of the lubricant composition.

13. Lubricant composition according to any one of claims 1 to 12, wherein the polyalkylene glycol are water-soluble polyalkylene glycol.

14. Use of the lubricant composition according to any one of claims 1 to 13, as an industrial oil, preferably as gear oil or compression oil, more preferably as worm gear oil.

15. Gear coated with the lubricant composition according to any one of claims 1 to 13.

16. Gear according to claim 15, wherein the gearbox is selected from worm gear.

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