Polyalkylene glycol-based lubricant composition

Abstract

The present application relates to a lubricant composition comprising: - an oil selected from among polyalkylene glycols (PAG); and - a wear-resistant additive selected from among the compounds of formula (I) where R1 and R2 are identical or different and independently represent a linear or branched secondary alkyl group containing 2 to 7 carbon atoms, preferably 3 to 6 carbon atoms. Said lubricant composition is particularly useful for lubricating a vehicle engine, preferably a motor vehicle engine.

Description

[0001] This application concerns the field of lubricating compositions, in particular lubricating compositions for vehicle engines, especially for motor vehicle engines. Specifically, this application concerns lubricating compositions based on polyalkylene glycols (PAGs) for the lubrication of vehicle engines, particularly motor vehicle engines.

[0002] Energy efficiency and reduced fuel consumption in automotive engines are growing concerns. It is well known that engine lubricants used in these vehicles play a significant role in this regard.

[0003] To formulate "Fuel-Eco" or fuel-saving lubricants, it is known to manipulate the viscosity of the base lubricants used. It is also known to use viscosity index (VI) improvers or friction modifiers (MF). However, viscosity index improvers have the drawback of degrading the engine cleanliness of the lubricant compositions in which they are used. Modern engines are subject to high thermal stresses, leading to significant deposit formation. These deposits are linked to the chemical transformation of the lubricant in the areas closest to the combustion chamber, and therefore the hottest.

[0004] Document WO 2016 / 016362 relates to a lubricating composition comprising PAGs and the use of this lubricating composition to reduce the fuel consumption of a vehicle.

[0005] US patent 6,004,910 relates to a lubricating composition comprising zinc dithiophosphates with secondary alkyl groups. Additives based on zinc dithiophosphates with secondary alkyl groups improve the anti-wear performance of the lubricating composition.

[0006] Fuel-Eco lubricant compositions based on PAG were described in document WO 2013 / 164449, these compositions also exhibiting good engine properties.

[0007] The document JP H06 80981 relates to lubricating compositions comprising, among other things, up to 80% by weight of PAG as well as an anti-wear additive selected from zinc dithiophosphates having primary or secondary alkyl groups.

[0008] However, the use of these PAGs can sometimes lead to increased wear on the engine's mechanical parts, and therefore a degradation of the engine's durability.

[0009] There is therefore an interest in providing a lubricating composition, in particular a lubricating composition for motor vehicle engines, which addresses all or part of the disadvantages of the prior art.

[0010] An objective of the present invention is to provide a PAG-based lubricating composition, in particular a PAG-based lubricating composition for motor vehicle engines, exhibiting improved anti-wear properties.

[0011] Another objective of the present invention is to provide a PAG-based lubricating composition, in particular a PAG-based lubricating composition for motor vehicle engines, exhibiting both improved anti-wear properties and satisfactory "Fuel-Eco" properties.

[0012] Another objective of the present invention is to provide a PAG-based lubricating composition, in particular a PAG-based lubricating composition for motor vehicle engines, exhibiting both improved anti-wear properties and not degrading engine cleanliness.

[0013] Another objective of the present invention is to provide a PAG-based lubricating composition, in particular a PAG-based lubricating composition for motor vehicle engines, exhibiting improved anti-wear properties, satisfactory "Fuel-Eco" properties and not degrading engine cleanliness.

[0014] Another objective of the invention is to provide a PAG-based lubricating composition, in particular a PAG-based lubricating composition for motor vehicle engines, exhibiting improved anti-wear properties and easy to formulate.

[0015] To meet the above objectives and address the drawbacks mentioned in the prior art, the present invention proposes a lubricating composition comprising: an oil chosen from polyalkylated glycols (PAG or polyalkylene glycols), and an anti-wear additive chosen from compounds of formula (I) in which R1 and R2, identical or different, independently represent a linear or branched secondary alkyl group comprising from 2 to 7 carbon atoms, preferably from 3 to 6 carbon atoms.

[0016] In the context of the present invention, "linear or branched secondary alkyl comprising 2 to 7 carbon atoms" means an alkyl chosen to form a secondary alcohol with the O to which it is attached.

[0017] Most advantageously, the lubricating composition of the present invention is a lubricating composition for an engine, preferably for a vehicle, more preferably for a motor vehicle.

[0018] According to the invention, the PAG of the lubricating composition according to the invention can be a block polymer or a statistical polymer.

[0019] The PAG according to the invention comprises alkyl groups whose hydrocarbon chain lengths can vary. According to the invention, the hydrocarbon chain length is defined by an average value of the number of carbon atoms.

[0020] The PAG according to the invention is a block polymer of formula (VI) or a statistical polymer of formula (VI) in which ▪ R12 represents a linear or branched C1-C30-alkyl group, preferably a linear or branched C8-C15-alkyl group; ▪ s and t independently represent an average number from 1 to 5.

[0021] For a preferred PAG according to the invention, R12 represents a group selected from a linear C8-alkyl group; a branched C8-alkyl group; a linear C9-alkyl group; a branched C9-alkyl group; a linear C10-alkyl group; a branched C10-alkyl group; a linear C11-alkyl group; a branched C11-alkyl group; a linear C12-alkyl group; a branched C12-alkyl group; a linear C13-alkyl group; a branched C13-alkyl group; a linear C14-alkyl group; a branched C14-alkyl group; a linear C15-alkyl group; a branched C15-alkyl group.

[0022] For a preferred PAG according to the invention: ▪ s is greater than or equal to t; or ▪ s represents an average number from 2 to 4.5; or ▪ t represents an average number from 1.5 to 4.

[0023] For a preferred PAG according to the invention: ▪ s represents an average number ranging from 2.5 to 3.5; or ▪ t represents an average number ranging from 2 to 3.

[0024] For a preferred PAG according to the invention: ▪ s represents an average number equal to 2.5 and t represents an average number equal to 2; or ▪ s represents an average number equal to 3.5 and t represents an average number equal to 2.8.

[0025] For a preferred PAG according to the invention: ▪ its kinematic viscosity at 100 °C, measured according to ASTM D445, ranges from 2.5 to 4.5 mm 2< .s -1< ; or whose ▪ its viscosity index is greater than 160 or is between 160 and 210 ; or whose ▪ its pour point is less than -40 °C ; or whose ▪ its dynamic viscosity (CCS) at -35 °C, measured according to ASTM D5293 is less than 1200 mPa.s.

[0026] Methods for preparing PAG of formula (VI) are described in application WO-2016 / 016362. The PAG according to the invention comprises at least one butylene oxide motif.

[0027] The lubricating composition according to the invention comprises from 80 to 99.5% by weight of PAG. In addition to a PAG, the lubricating composition according to the invention comprises an anti-wear additive selected from compounds of formula (I) in which R1 and R2, identical or different, independently represent a linear or branched secondary alkyl group comprising from 2 to 7 carbon atoms, preferably from 3 to 6 carbon atoms.

[0028] Preferably, in which way the anti-wear additive is chosen from the compounds of formula (I) in which R1 and R2, identical or different, represent a secondary C3-alkyl group or a secondary C6-alkyl group.

[0029] Preferably, groups R1 and R2, identical or different, represent a dimethyl butyl group or an isopropyl group.

[0030] Even more preferably, the identical groups R1 and R2 represent a dimethyl butyl group or an isopropyl group.

[0031] In an even more preferred form, the anti-wear additive comprises a mixture: of at least one compound of formula (I) in which R1 represents a secondary C3-alkyl group and R2 represents a secondary C6-alkyl group, of at least one compound of formula (I) in which R1 and R2, identical, represent a secondary C6-alkyl group.

[0032] In an even more preferred form, the anti-wear additive comprises a mixture: of at least one compound of formula (I) in which R1 represents a secondary C6-alkyl group and R2 represents a secondary C3-alkyl group, of at least one compound of formula (I) in which R1 and R2, identical, represent a secondary C6-alkyl group.

[0033] Examples of compounds with formula (I) include the product Lubrizol 1371 ®< marketed by the Lubrizol company.

[0034] Preferably, the lubricating composition according to the invention comprises from 0.1 to 3%, preferably from 0.1 to 2%, more preferably from 0.1 to 1% by weight of compound of formula (I).

[0035] In addition to a PAG and a compound of formula (I), the lubricating composition according to the invention may include a base oil.

[0036] In general, the lubricating composition according to the invention can include any type of lubricating base oil, mineral, synthetic or natural, animal or vegetable, suitable for its use.

[0037] The base oils used in the lubricating compositions according to the invention can therefore be oils of mineral or synthetic origin belonging to groups I to V according to the classes defined in the API classification (or their equivalents according to the ATIEL classification) (Table A) or mixtures thereof.

[0038] Preferably, the base oil is different from the PAG. Table A Saturated fat content Sulfur content Viscosity index (VI) Group I < 90 % > 0,03 % 80 ≤ VI < 120 Mineral oils Group II ≥ 90 % ≤ 0,03 % 80 ≤ VI < 120 Hydrocracked oils Group III ≥ 90 % ≤ 0,03 % ≥ 120 Hydrocracked or hydro-isomerized oils Group IV Polyalphaolefins (PAO) Group V Esters and other bases not included in groups I to IV

[0039] Mineral base oils that can be used for the lubricating composition according to the invention include any type of base oils obtained by atmospheric and vacuum distillation of crude oil, followed by refining operations such as solvent extraction, desalpha removal, solvent dewaxing, hydrotreating, hydrocracking, hydroisomerization, and hydrofinishing. Blends of synthetic and mineral oils can also be used.

[0040] There are generally no limitations on the use of different lubricating bases to produce the lubricating compositions according to the invention, except that they must have properties, in particular of viscosity, viscosity index, sulfur content and resistance to oxidation, suitable in particular for use in engines or vehicle transmissions.

[0041] The base oils for the lubricating compositions according to the invention can also be selected from synthetic oils, such as certain esters of carboxylic acids and alcohols, as well as from polyalphaolefins. Polyalphaolefins used as base oils are, for example, obtained from monomers comprising 4 to 32 carbon atoms, for example from octene or decene, and whose viscosity at 100 °C is between 1.5 and 15 mm².s⁻¹ according to ASTM D445. Their average molecular weight is generally between 250 and 3,000 according to ASTM D5296.

[0042] Advantageously according to the invention, the base oil can be chosen from group III oils, group IV oils and group V oils.

[0043] Advantageously, the lubricating composition according to the invention may comprise at least 50% by mass of base oils relative to the total mass of the composition. More advantageously, the lubricating composition according to the invention may comprise at least 60% by mass, or even at least 70% by mass, of base oils relative to the total mass of the composition. In a particularly advantageous manner, the lubricating composition according to the invention may comprise from 50, 60, or 70 to 99.9% by mass, or from 50, 60, or 70 to 90% by mass, of one or more base oils relative to the total mass of the composition.

[0044] The lubricating composition according to the invention may also include at least one additional additive. Numerous additional additives can be used for the lubricating composition according to the invention. Preferred additional additives for the lubricating composition according to the invention are selected from detergent additives, anti-wear additives other than compounds of formula (I), friction modifier additives, extreme pressure additives, dispersants, pour point enhancers, antifoaming agents, thickeners, and mixtures thereof.

[0045] Preferably, the lubricating composition according to the invention comprises at least one organic friction modifier selected from esters, preferably from polyol monoesters, more preferably from glycerol monoesters. More preferably, the organic friction modifier is selected from glycerol monoesters obtained by esterification reaction between glycerol and a saturated or unsaturated carboxylic acid comprising at least 10 carbon atoms, preferably from 10 to 20 carbon atoms, more preferably from 15 to 20 carbon atoms, advantageously from 15 to 18 carbon atoms.

[0046] Glycerol mono-oleate can be cited as an example of organic friction modifiers according to the invention.

[0047] Preferably, the lubricating composition according to the invention comprises 0.1 to 2% by weight, preferably 0.1 to 1.5% by weight, more preferably 0.5 to 1.5% by weight of organic friction modifiers.

[0048] There is a wide variety of additional anti-wear additives different from formula compounds (I).

[0049] Amine phosphates are also anti-wear additives that can be used in the lubricant composition according to the invention. However, the phosphorus provided by these additives can act as a poison for the catalytic converters of automobiles because these additives generate ash. These effects can be minimized by partially substituting the amine phosphates with additives that do not provide phosphorus, such as, for example, polysulfides, particularly sulfur olefins.

[0050] Advantageously, the lubricating composition according to the invention may comprise from 0.01 to 6% by mass, preferably from 0.05 to 4% by mass, more preferably from 0.1 to 2% by mass relative to the total mass of lubricating composition, additional anti-wear additives.

[0051] The lubricating composition according to the invention may include at least one inorganic friction modifier. The inorganic friction modifier may be selected from a compound containing metallic elements and an ash-free compound. Examples of compounds containing metallic elements include transition metal complexes such as Mo, Sb, Sn, Fe, Cu, and Zn, the ligands of which may be hydrocarbon compounds comprising oxygen, nitrogen, sulfur, or phosphorus atoms.

[0052] Advantageously, the lubricating composition according to the invention may include at least one antioxidant additive. The antioxidant additive generally delays the degradation of the lubricating composition during service. This degradation can manifest itself, in particular, as the formation of deposits, the presence of sludge, or an increase in the viscosity of the lubricating composition.

[0053] Antioxidant additives act primarily as radical scavengers or hydroperoxide scavengers. Commonly used antioxidant additives include phenolic antioxidants, amine antioxidants, and phosphosulfur antioxidants. Some of these antioxidants, such as phosphosulfur antioxidants, can generate ash. Phenolic antioxidants may be ash-free or in the form of neutral or basic metal salts. Antioxidant additives may include sterically hindered phenols, sterically hindered phenol esters, sterically hindered phenols containing a thioether bridge, diphenylamines, diphenylamines substituted with at least one C1-C12 alkyl group, N,N'-dialkylaryl diamines, and mixtures thereof.

[0054] Preferably according to the invention, sterically hindered phenols are selected from compounds comprising a phenol group in which at least one vicinal carbon of the carbon bearing the alcohol function is substituted by at least one C1-C10 alkyl group, preferably a C1-C6 alkyl group, preferably a C4 alkyl group, preferably by the tert-butyl group.

[0055] Amino compounds are another class of antioxidant additives that can be used, possibly in combination with phenolic antioxidant additives. Examples of amine compounds are aromatic amines, for example aromatic amines of the formula NRa < Rb < Rc < where Ra represents an aliphatic or aromatic group, possibly substituted, Rb represents an aromatic group, possibly substituted, Rc represents a hydrogen atom, an alkyl group, an aryl group, or a group of the formula Rd < S(O)z < Re < where Rd < represents an alkylene or alkenylene group, Re < represents an alkyl, alkenyl, or aryl group, and z represents 0, 1, or 2.

[0056] Sulfurized alkyl phenols or their alkali and alkaline earth metal salts can also be used as antioxidant additives.

[0057] Another class of antioxidant additives consists of copper compounds, for example copper thio- or dithio-phosphates, copper salts of carboxylic acids, dithiocarbamates, sulfonates, phenates, and copper acetylacetonates. Copper I and II salts, succinic acid salts, and succinic anhydride salts can also be used.

[0058] The lubricating composition according to the invention may contain all types of antioxidant additives known to those skilled in the art.

[0059] Also advantageously, the lubricating composition according to the invention comprises from 0.5 to 2% by weight relative to the total mass of the composition, of at least one antioxidant additive.

[0060] The lubricating composition according to the invention may also include at least one detergent additive. Detergent additives generally reduce the formation of deposits on the surface of metal parts by dissolving oxidation and combustion byproducts.

[0061] The detergent additives usable in the lubricating composition according to the invention may be anionic compounds comprising a long lipophilic hydrocarbon chain and a hydrophilic head group. The associated cation may be a metallic cation of an alkali or alkaline earth metal. The detergent additives are preferably selected from alkali or alkaline earth metal salts of carboxylic acids, sulfonates, salicylates, naphthenates, and phenate salts. The alkali and alkaline earth metals are preferably calcium, magnesium, sodium, or barium. These metallic salts generally comprise the metal in stoichiometric amounts or in excess, i.e., in an amount greater than the stoichiometric amount.These are then over-based detergent additives; the excess metal giving the over-based character to the detergent additive is then generally in the form of a metallic salt insoluble in oil, for example a carbonate, a hydroxide, an oxalate, an acetate, a glutamate, preferably a carbonate.

[0062] Advantageously, the lubricating composition according to the invention may comprise 2 to 4% by weight of detergent additive relative to the total mass of the lubricating composition.

[0063] Also advantageously, the lubricating composition according to the invention may also include at least one pour point lowering additive.

[0064] By slowing down the formation of paraffin crystals, pour point lowering additives generally improve the cold behavior of the lubricating composition according to the invention.

[0065] Examples of pour point lowering additives include alkyl polymethacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalenes, and alkylated polystyrenes.

[0066] Advantageously, the lubricating composition according to the invention may also comprise at least one dispersing agent. The dispersing agent may be selected from Mannich bases, succinimides, and their derivatives.

[0067] Also advantageously, the lubricating composition according to the invention can comprise from 0.2 to 10% by mass of dispersing agent relative to the total mass of the lubricating composition.

[0068] Advantageously, the lubricating composition may also include at least one viscosity-enhancing polymer. Examples of viscosity-enhancing polymers include polymer esters, homopolymers or copolymers, hydrogenated or non-hydrogenated, of styrene, butadiene and isoprene, and polymethacrylates (PMA).

[0069] Also advantageously, the lubricating composition according to the invention may comprise from 1 to 15% by mass relative to the total mass of the lubricating composition of polymer improving the viscosity index.

[0070] Preferably, the lubricating composition according to the invention is used for the lubrication of an engine, preferably of a vehicle, more preferably of a motor vehicle.

[0071] Thus, the present invention also relates to the use of a lubricating composition according to the invention to lubricate an engine, preferably of a vehicle, more preferably of a motor vehicle.

[0072] More preferably, the present invention also relates to the use of a lubricating composition according to the invention to lubricate a vehicle engine, more preferably a motor vehicle engine.

[0073] The present invention also relates to a method of lubricating a vehicle engine, preferably a motor vehicle engine, comprising at least one step of bringing said engine into contact with the lubricating composition according to the invention.

[0074] The present invention also relates to the use of a compound of formula (I) to improve the anti-wear properties of a lubricating composition comprising an oil selected from PAGs.

[0075] All the characteristics and preferences relating to the compound of formula (I) and to PAG described above apply to this use.

[0076] The present invention will now be illustrated using non-limiting examples. Example 1: Lubricating compositions according to the invention

[0077] Lubricating compositions according to the invention are prepared in accordance with Table 1 below (the compositions are given by weight (g)).

[0078] In the compositions below: PAG 1 (comparative): PAG comprising propylene oxide and butylene oxide motifs and a -OH termination. PAG 2: (according to the invention) PAG comprising propylene oxide and butylene oxide motifs and a -OCH 3 termination (corresponding to formula (VI) with s ≈ 3.5 and t ≈ 2.8) Anti-wear 1 (Lubrizol 1371®< marketed by LUBRIZOL): mixture of compound of formula (I) in which R1 and R2 represent a dimethyl butyl group and compound of formula (I) in which R1 and R2 represent an isopropyl group. Anti-wear 2 (RC3045®< marketed by RheinChemie): mixture of compound of formula (I) in which R1 and R2 represent a pentyl group and compound of formula (I) in which R1 and R2 represent a butyl group. Anti-wear 3 (KT2203®< marketed by Kangtai Lubricant Additives): compound of formula (I) in which R1 and R2 represent a primary C-8 alkyl group. Friction modifier 1: glycerol monooleate. Friction modifier 2 (Sakuralube 525®< marketed by Adeka): dithiocarbamate of molybdenum, Table 1 Composition Comparative 1 Comparison 2 Comparison 3 Comparison 4 1 2 PAGE 1 99,5 99,5 99,3 98,5 PAGE 2 98,5 99 Anti-wear 1 0,5 0,5 0,5 0,5 Anti-wear 2 0,5 Anti-wear 3 0,7 Friction modifier 1 1 1 Friction modifier 2 0,5 Example 2: Evaluation of anti-wear properties

[0079] This evaluation is based on a procedure based on the ASTM D2670 standard requiring the use of a FALEX tribometer and whose test conditions are described below. Test specimens: FALEX steel. Break-in time: 300 s. Test time: 180 min. Break-in load: 445 N. Test load: 1335 N. Speed: 290 rpm. Ambient temperature.

[0080] The results are presented in Table 2 and are expressed in µm; the lower the value obtained, the better the anti-wear properties of the evaluated composition. Table 2 Composition Comparative 1 Comparison 2 Comparison 3 Comparison 4 1 2 Total wear (µm) 63 102 136 26 5 11

[0081] The results show that the lubricating compositions according to the invention (compositions 1 and 2) exhibit improved anti-wear properties compared to the comparative lubricating compositions (comparative compositions 1, 2, 3 and 4).

Claims

1. Lubricant composition comprising 80 to 99.5% by weight of an oil selected from polyalkylated glycols (PAG or polyalkylene glycols) and an anti-wear additive selected from compounds of formula (I) in which R1 and R2, which may be identical or different, independently represent a secondary linear or branched alkyl group comprising from 2 to 7 carbon atoms, preferably from 3 to 6 carbon atoms, the PAG being a block polymer of formula (VI) or a random polymer of formula (VI) in which ▪ R12 represents a linear or branched C1-C30 alkyl group, preferably a linear or branched C8-C15alkyl group; ▪ s and t independently represent an average number from 1 to 5.

2. Composition according to claim 1 for which the anti-wear additive is selected from compounds of formula (I) in which R1 and R2, which may be identical or different, represent a secondary C3-alkyl group or a secondary C6-alkyl group.

3. Composition according to one of claims 1 to 2 comprising from 0.1 to 3%, preferably from 0.1 to 2%, more preferably from 0.1 to 1% by weight of the compound of formula (I).

4. Composition according to any of claims 1 to 3 comprising a lubricating base oil.

5. Composition according to any of claims 1 to 4 further comprising a friction modifier.

6. Composition according to any of claims 1 to 4 further comprising an organic friction modifier selected from esters, preferably from polyol monoesters, more preferably selected from glycerol monoesters.

7. Composition according to any of claims 1 to 4 further comprising an inorganic friction modifier.

8. Use of a lubricant composition according to any of claims 1 to 7 for lubricating a vehicle engine, preferably a motor vehicle engine.

9. Use of a lubricant composition according to any of claims 1 to 7 for reducing wear in a vehicle engine.

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