Lubricant composition for gas engines

Abstract

The invention relates to the use of a lubricant composition for lubricating a gas engine, said lubricant composition comprising at least one mineral base oil and at least one ester selected from polyol esters.

Description

[0001] This application is a divisional application of an invention application with an application date of July 6, 2017, application number 201780042080.9 (international application number PCT / EP2017 / 066886), and invention name “Lubricant composition for gas engines”. [Technical field]

[0002] The present invention relates to the field of lubricants for gas engines, preferably stationary gas engines. The invention more particularly relates to the use of a lubricant composition comprising at least one mineral base oil and at least one ester selected from polyol esters for lubricating a gas engine, preferably a stationary gas engine.

[0003] The invention also relates to a method of lubricating a gas engine, preferably a stationary gas engine. [Background technology]

[0004] Lubricants developed for gas engines, preferably stationary gas engines, have been known for many years. The first lubricants dedicated to such applications contain base oils of group I according to the API classification. These lubricants provide very good results at high temperatures, in particular they do not form any or only very little precipitates, but have limited resistance to oxidation, in particular to nitridation. Nitriding is oxidation by contact with nitrogen oxides (NOx).

[0005] Lubricants then contain API Group II base oils to improve the oxidation resistance. However, and especially in the case of very high power gas engines, the use of these lubricants can lead to the formation of high temperature deposits (or varnish). The same is true for lubricants based on Group III and Group IV base oils according to the API classification.

[0006] There is therefore a need for lubricant compositions for gas engines, preferably stationary gas engines, which have good detergency and thus form no or only little deposits, especially at high temperatures, while exhibiting satisfactory or even improved resistance to oxidation, especially nitridation.

[0007] It has now been found that the combination of at least one mineral base oil and at least one ester selected from polyol esters makes it possible to provide a lubricant composition specifically for lubricating gas engines, preferably stationary gas engines, providing antioxidant properties, in particular satisfactory or improved anti-nitridation properties, especially causing little or no deposits, especially at high temperatures.

[0008] The present invention thus provides a lubricant composition making it possible to solve all or part of the problems of lubricant compositions intended for lubricating gas engines, preferably stationary gas engines. [Summary of the invention]

[0009] The present invention therefore relates to the use of a lubricant composition comprising at least one mineral base oil and at least one ester selected from polyol esters for lubricating a gas engine.

[0010] Surprisingly, the Applicant has found that combining at least one mineral base oil and at least one ester chosen from polyol esters in a lubricant composition for gas engines, preferably stationary gas engines, makes it possible to improve the antioxidative properties, in particular the antinitridation properties, of the lubricant composition.

[0011] Advantageously, the lubricant composition according to the present invention provides very good resistance to oxidation, especially nitridation, while reducing or even eliminating the formation of deposits, especially at high temperatures.

[0012] Advantageously, the lubricant composition according to the invention provides very good resistance to oxidation, especially nitridation, and very good detergency when implemented in a gas engine, and the formulation of the lubricant composition is easy to implement.

[0013] Advantageously, the lubricant composition according to the invention provides very good resistance to oxidation, especially nitridation, and very good detergency when implemented in a gas engine, while being stable over a long period of time, especially when stored.

[0014] In one embodiment of the invention, the gas engine is a stationary gas engine.

[0015] In one embodiment of the present invention, the mineral base oil is selected from Group II base oil or Group III base oil according to API classification, preferably, selected from Group II base oil according to API classification.

[0016] In another embodiment of the present invention, the lubricant composition comprises at least 50 wt %, preferably 50 to 90 wt %, of mineral base oil, based on the total weight of the lubricant composition.

[0017] In another embodiment of the present invention, the ester is selected from esters of saturated or unsaturated linear or branched carboxylic acids comprising at least 8 carbon atoms and polyols.

[0018] In another embodiment of the present invention, the carboxylic acid is a saturated or unsaturated linear or branched monocarboxylic acid.

[0019] In another embodiment of the present invention, the carboxylic acid comprises 8 to 20 carbon atoms, preferably, 8 to 18 carbon atoms.

[0020] In another embodiment of the present invention, the polyol comprises at least 3 -OH groups, preferably, 3 to 8 -OH groups.

[0021] In another embodiment of the present invention, the polyol comprises 3 to 10 carbon atoms.

[0022] In another embodiment of the present invention, the polyol ester comprises a mixture of at least one first ester of a polyol and a monocarboxylic acid as defined above and at least one second ester of a polyol and a monocarboxylic acid as defined above, the second ester being different from the first ester.

[0023] In another embodiment of the present invention, the ester is obtained by an esterification reaction between a polyol as defined above, at least one first monocarboxylic acid as defined above, and at least one second carboxylic acid chosen from linear or branched saturated or unsaturated dicarboxylic acids comprising at least 16 carbon atoms.

[0024] In another embodiment of the present invention, the lubricant composition comprises at least 2% by weight, preferably at least 5% by weight, of the polyol ester, based on the total weight of the lubricant composition.

[0025] In another embodiment of the present invention, the lubricant composition further includes polyisobutylene.

[0026] The invention also relates to the use of at least one mineral base oil as defined above and at least one ester chosen from polyol esters as defined above in a lubricant composition for lubricating a gas engine.

[0027] The invention also relates to a method of lubricating a gas engine, comprising contacting at least one mechanical part of said engine with a lubricant composition as defined above. [Specific implementation method]

[0028] The percentages given below correspond to the weight percentages of the active ingredients.

[0029] The lubricant composition according to the invention comprises at least one mineral base oil.

[0030] The mineral base oil used in the lubricant composition according to the invention may be an oil of mineral origin belonging to group I, II or III according to the categories defined in the API classification (or their equivalents according to the ATIEL classification) (Table A), or a mixture thereof.

[0031]

[0032] Table A

[0033] In a preferred embodiment of the present invention, the base oil is a Group II base oil or a Group III base oil according to the API classification.

[0034] In a more preferred embodiment of the present invention, the base oil is a Group II base oil according to API classification.

[0035] In another preferred embodiment of the present invention, the lubricant composition comprises at least 50% by weight, preferably 50 to 90% by weight, more preferably 60 to 90% by weight, even more preferably 65 to 90% by weight, advantageously 65 to 85% by weight of a mineral base oil, based on the total weight of the lubricant composition.

[0036] In another more preferred embodiment of the present invention, the lubricant composition comprises at least 70% by weight, preferably 70% to 90% by weight, more preferably 75% to 90% by weight, advantageously 75% to 85% by weight of mineral base oil, based on the total weight of the lubricant composition.

[0037] The lubricant composition according to the invention further comprises at least one ester selected from polyol esters.

[0038] A polyol ester according to the invention is understood to be any ester which is obtained by esterification of at least one carboxylic acid with at least one polyol.

[0039] Carboxylic acids according to the invention are understood to mean both monocarboxylic acids and polycarboxylic acids.

[0040] In one embodiment of the present invention, the ester is selected from esters of saturated or unsaturated linear or branched carboxylic acids or polyols comprising at least 8 carbon atoms.

[0041] In a preferred embodiment of the present invention, the carboxylic acid is a saturated or unsaturated linear or branched monocarboxylic acid.

[0042] Thus, the carboxylic acid may be selected from:

[0043] - saturated linear monocarboxylic acids;

[0044] - unsaturated linear monocarboxylic acids;

[0045] - saturated branched monocarboxylic acids;

[0046] - Unsaturated branched monocarboxylic acids.

[0047] In another preferred embodiment of the present invention, the carboxylic acid comprises 8 to 20 carbon atoms, preferably, 8 to 18 carbon atoms.

[0048] In a particular embodiment of the present invention, the carboxylic acid comprises 14 to 18 carbon atoms, preferably, 16 to 18 carbon atoms.

[0049] In another particular embodiment of the present invention, the carboxylic acid comprises 8 to 12 carbon atoms, preferably, 8 to 10 carbon atoms.

[0050] Thus, the carboxylic acid may be selected from:

[0051] a saturated linear monocarboxylic acid comprising 8 to 20 carbon atoms, preferably 8 to 18 carbon atoms, more preferably 14 to 18 carbon atoms, advantageously 16 to 18 carbon atoms;

[0052] - an unsaturated linear monocarboxylic acid comprising 8 to 20 carbon atoms, preferably 8 to 18 carbon atoms, more preferably 14 to 18 carbon atoms, advantageously 16 to 18 carbon atoms;

[0053] - a saturated branched monocarboxylic acid comprising 8 to 20 carbon atoms, preferably 8 to 18 carbon atoms, more preferably 14 to 18 carbon atoms, advantageously 16 to 18 carbon atoms;

[0054] - an unsaturated branched monocarboxylic acid comprising from 8 to 20 carbon atoms, preferably from 8 to 18 carbon atoms, more preferably from 14 to 18 carbon atoms, advantageously from 16 to 18 carbon atoms.

[0055] The carboxylic acid may also be selected from:

[0056] - a saturated linear monocarboxylic acid comprising 8 to 12 carbon atoms, preferably 8 to 10 carbon atoms;

[0057] - an unsaturated linear monocarboxylic acid comprising 8 to 12 carbon atoms, preferably 8 to 10 carbon atoms;

[0058] - a saturated branched monocarboxylic acid comprising 8 to 12 carbon atoms, preferably 8 to 10 carbon atoms;

[0059] - unsaturated branched monocarboxylic acids comprising 8 to 12 carbon atoms, preferably 8 to 10 carbon atoms.

[0060] Examples of carboxylic acids according to the present invention include nonanoic acid, stearic acid, isostearic acid or oleic acid.

[0061] In another preferred embodiment of the present invention, the polyol comprises at least 3 -OH groups, preferably, 3 to 8 -OH groups, more preferably, 3 to 6 -OH groups.

[0062] In a more preferred embodiment of the present invention, the polyol comprises 3, 4 or 6 -OH groups.

[0063] In another preferred embodiment of the present invention, the polyol comprises 3 to 10 carbon atoms, preferably, 3 to 8 carbon atoms, more preferably, 3 to 6 carbon atoms.

[0064] Examples of the polyol according to the present invention include glycerin, trimethylolpropane, pentaerythritol, or dipentaerythritol.

[0065] In a particular embodiment of the invention, the polyol ester comprises a mixture of at least one first ester of a polyol and a monocarboxylic acid as defined above and at least one second ester of a polyol and a monocarboxylic acid as defined above, the second ester being different from the first ester.

[0066] In a more specific embodiment of the present invention, the ester comprises a mixture of:

[0067] - at least one triester of a polyol and a monocarboxylic acid,

[0068] - at least one diester of a polyol and a monocarboxylic acid,

[0069] Therein, the polyol and the monocarboxylic acid are as defined above.

[0070] In an even more specific embodiment of the invention, the ester comprises a mixture of:

[0071] at least one triester of trimethylpropane and a saturated or unsaturated monocarboxylic acid, preferably a saturated monocarboxylic acid comprising from 14 to 18 carbon atoms, advantageously from 16 to 18 carbon atoms,

[0072] at least one diester of trimethylpropane and a saturated or unsaturated monocarboxylic acid, preferably a saturated monocarboxylic acid comprising from 14 to 18 carbon atoms, advantageously from 16 to 18 carbon atoms.

[0073] As an example of a polyol ester according to the invention, mention may be made of Radialubes sold by the company Oleon.

[0074] In another particular embodiment of the invention, the ester is obtained by an esterification reaction between a polyol as defined above, at least one first monocarboxylic acid as defined above, and at least one second carboxylic acid chosen from linear or branched saturated or unsaturated dicarboxylic acids comprising at least 16 carbon atoms.

[0075] In another more specific embodiment of the present invention, the ester is obtained by an esterification reaction between:

[0076] - a polyol comprising 3 or 4 -OH groups and 3 to 6 carbon atoms,

[0077] at least one first saturated linear or branched monocarboxylic acid comprising 8 to 20 carbon atoms, preferably 8 to 18 carbon atoms, and

[0078] at least one second carboxylic acid chosen from saturated linear or branched dicarboxylic acids comprising at least 16 carbon atoms.

[0079] In another more specific embodiment of the present invention, the ester is obtained by the esterification reaction between:

[0080] - a polyol selected from pentaerythritol or trimethylolpropane,

[0081] - at least one first saturated or unsaturated linear or branched monocarboxylic acid comprising 8 to 18 carbon atoms, and

[0082] - at least one second carboxylic acid chosen from saturated linear or branched dicarboxylic acids comprising from 16 to 36 carbon atoms.

[0083] In another more specific embodiment of the present invention, the ester is obtained by an esterification reaction between:

[0084] - pentaerythritol,

[0085] - at least one first saturated or unsaturated linear or branched monocarboxylic acid comprising 18 carbon atoms, and

[0086] - at least one second carboxylic acid chosen from saturated linear or branched dicarboxylic acids comprising from 16 to 36 carbon atoms.

[0087] As an example of a polyol ester according to the invention, mention may be made of Priolube sold by the company Croda. or Nycobase sold by NYCO

[0088] In another particular embodiment of the invention, the ester is obtained by esterification reaction between a polyol as defined above and at least one saturated or unsaturated linear or branched monocarboxylic acid comprising 8 to 12 carbon atoms, preferably 8 to 10 carbon atoms.

[0089] In another more specific embodiment of the present invention, the ester is obtained by an esterification reaction between:

[0090] - dipentaerythritol, and

[0091] at least one saturated or unsaturated linear or branched monocarboxylic acid comprising 8 to 12 carbon atoms, preferably 8 to 10 carbon atoms.

[0092] In one embodiment of the present invention, the lubricant composition comprises at least 2%, preferably at least 5%, more preferably 5% to 30%, advantageously 5% to 25% or 5% to 15% polyol ester by weight, based on the total weight of the lubricant composition.

[0093] The lubricant composition according to the invention may also comprise, besides the polyol ester according to the invention, an additional base oil chosen from the group I, IV or V oils according to the API classification as defined above.

[0094] In particular, the additional base oil according to the invention may be chosen from synthetic oils such as polyalkylene glycols and from polyalphaolefins. The polyalphaolefins used as base oils are, for example, polyolefins comprising 4 to 32 carbon atoms (for example from octene or decene) and having a kinematic viscosity of 1.5 mm2 at 100° C. according to ASTM D445. 2 .s -1 With 15mm 2 .s -1 Their average molecular weight according to ASTM D5296 is generally between 250 and 3000.

[0095] A variety of additives may be used in the lubricant compositions used in accordance with the present invention.

[0096] In particular, the additives of the lubricant composition used according to the invention may be selected from friction modifiers, detergents, antiwear additives, extreme pressure additives, viscosity index improvers, dispersants, antioxidants, pour point improvers, defoamers, thickeners and mixtures thereof.

[0097] Antiwear additives and extreme pressure additives protect friction surfaces by forming a protective film that adsorbs onto these surfaces.

[0098] There are various anti-wear additives. In a preferred embodiment for the lubricant composition according to the invention, the anti-wear additive is selected from phosphorus-sulfur additives such as metal alkylthiophosphates, in particular zinc alkylthiophosphates, more particularly zinc dialkyldithiophosphates (ZnDTP). Preferred compounds have the formula Zn((SP(S)(OR 1 )(OR 2 ))2, where R may be the same or different 1 and R 2 Independently represents an alkyl group, preferably an alkyl group comprising 1 to 18 carbon atoms.

[0099] Phosphate amines are also anti-wear additives that can be used in the lubricant compositions according to the invention. However, the phosphorus provided by these additives may cause contamination of the automotive catalytic system because these additives generate ash. These effects can be minimized by partially replacing the phosphate amines with non-phosphorus additives, such as, for example, polysulfides, especially sulfur-containing olefins.

[0100] Advantageously, the lubricant composition according to the invention may comprise 0.01 to 6% by weight, preferably 0.05 to 4% by weight, more preferably 0.1 to 2% by weight of antiwear additives and extreme pressure additives, based on the total weight of the lubricant composition.

[0101] Advantageously, the lubricant composition according to the invention may comprise at least one friction-modifying additive. The friction-modifying additive may be chosen from compounds providing metal elements and ashless compounds. Among the compounds providing metal elements, mention may be made of transition metal complexes such as Mo, Sb, Sn, Fe, Cu and Zn, whose ligands may be hydrocarbons comprising oxygen, nitrogen, sulfur or phosphorus. Ashless friction-modifying additives are generally of organic origin and may be chosen from alkylated amines, alkylated fatty amines, fatty epoxides, boric fatty epoxides or fatty amines. According to the invention, the fatty compound comprises at least one hydrocarbon group comprising 10 to 24 carbon atoms.

[0102] Advantageously, the lubricant composition according to the invention may comprise 0.01% to 2% or 0.01% to 5%, preferably 0.1% to 1.5% or 0.1% to 2% by weight of friction modifier additives, based on the total weight of the lubricant composition.

[0103] Advantageously, the lubricant composition according to the invention may comprise at least one antioxidant additive.

[0104] Antioxidant additives are generally used to delay the degradation of lubricant compositions during use. In particular, such degradation may lead to the formation of deposits, the presence of sludge or an increase in the viscosity of the lubricant composition.

[0105] In particular, the antioxidant additive acts as a free radical inhibitor or destroyer of hydroperoxides. Among the commonly used antioxidant additives, phenolic antioxidant additives, amine antioxidant additives, phosphorus-sulfur antioxidant additives can be mentioned. Some of these antioxidant additives, such as phosphorus-sulfur antioxidant additives, may be ash-producing. Phenolic antioxidant additives may be ashless or may be in the form of neutral or alkaline metal salts. In particular, the antioxidant additive may be selected from hindered phenols, hindered phenol esters and esters including thioether bridges, diphenylamine, with at least one C1-C 12 Alkyl-substituted diphenylamines and hindered phenols of N,N'-dihydrocarbyl-aryl diamines and mixtures thereof.

[0106] Preferably, according to the present invention, the sterically hindered phenol is selected from the group consisting of phenols in which at least one adjacent carbon of the carbon having the alcohol function is replaced by at least one C1-C 10 A compound having a phenolic group substituted by an alkyl group, preferably a C1-C6 alkyl group, preferably a C4 alkyl group, preferably a tributyl group.

[0107] Amino 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, for example, of the formula NR 3 R 4 R 5 Aromatic amines, where R 3represents an optionally substituted aliphatic or aromatic group, R 4 represents an optionally substituted aromatic group, R 5 represents a hydrogen atom, an alkyl group, an aryl group, or a chemical formula R 6 S(O) z R 7 A group, wherein R 6 represents an alkylene group or an alkenylene group, R 7 represents an alkyl group, an alkenyl group or an aryl group and z represents 0, 1 or 2.

[0108] Sulfurized alkylphenols or their alkali metal and alkaline earth metal salts may also be used as antioxidant additives.

[0109] Another class of antioxidant additives are copper compounds, for example copper thio- or dithiophosphates, copper and carboxylates, dithiocarbamates, sulfonates, phenates, copper acetylacetonate. Copper salts I and II, succinic acid or anhydride salts can also be used.

[0110] The lubricant composition according to the invention may contain all types of antioxidant additives known to the person skilled in the art.

[0111] Advantageously, the lubricant composition may include at least one ashless antioxidant additive.

[0112] Advantageously too, the lubricant composition according to the invention may comprise from 0.5% to 2% by weight of at least one antioxidant additive, relative to the total weight of the lubricant composition.

[0113] The lubricant composition according to the invention may also comprise at least one detergent additive.

[0114] Detergent additives generally make it possible to reduce the formation of deposits on the surfaces of metal parts by dissolving secondary oxidation and combustion products.

[0115] Detergent additives that can be used in the lubricant composition according to the present invention are generally known to those skilled in the art. The detergent additive can be an anionic compound comprising a long lipophilic hydrocarbon chain and a hydrophilic head. The associated cation can be a metal cation of an alkali metal or an alkaline earth metal.

[0116] The detergent additive is preferably selected from alkali metal or alkaline earth metal salts of carboxylic acids, sulfonates, salicylates, naphthenates and phenates. The alkali metal and alkaline earth metal are preferably calcium, magnesium, sodium or barium.

[0117] These metal salts typically include a stoichiometric amount or an excess of the metal, so that the amount is greater than the stoichiometric amount. This is then associated with overbased detergent additives; wherein the excess metal that makes the detergent additive overbased is then typically in the form of an oil-insoluble metal salt, such as a carbonate, hydroxide, oxalate, acetate, glutamate, preferably a carbonate.

[0118] Advantageously, the lubricant composition according to the invention may comprise 0.5% to 4% by weight of detergent additive, relative to the total weight of the lubricant composition.

[0119] Likewise advantageously, the lubricant composition according to the invention may also comprise at least one pour point depressing additive.

[0120] Pour point depressing additives generally improve the cold performance of the lubricant compositions according to the present invention by slowing down the formation of paraffin crystals.

[0121] As examples of pour point depressing additives, mention may be made of alkyl polymethacrylates, polyacrylates, polyaromatic amides, octylphenols, polyalkylnaphthalenes and alkylated polystyrenes.

[0122] Advantageously, the lubricant composition according to the invention may also comprise at least one dispersant.

[0123] The dispersant may be selected from Mannich bases, succinimide and derivatives thereof.

[0124] Likewise advantageously, the lubricant composition according to the invention may comprise 0.2% to 10% by weight of dispersant, relative to the total weight of the lubricant composition.

[0125] The lubricant composition of the present invention may also include at least one thickener, such as, for example, polyisobutylene and its derivatives.

[0126] In a preferred embodiment of the present invention, the lubricant composition may include polyisobutylene as a thickener.

[0127] In particular, such an embodiment makes it possible to further improve the detergency properties of the lubricant composition, in particular at high temperatures.

[0128] Advantageously, the lubricant composition according to the invention may comprise 0.1% to 5% by weight of thickener, relative to the total weight of the lubricant composition.

[0129] The lubricant composition according to the invention may also include at least one viscosity index improving additive. Examples of viscosity index improving additives include polymeric esters, homopolymers or copolymers, hydrogenated or non-hydrogenated styrene, butadiene and isoprene, polyacrylates, polymethacrylates (PMA) or alternatively, olefin copolymers, especially ethylene / propylene copolymers.

[0130] The lubricant composition according to the present invention may be in various forms. In particular, the lubricant composition according to the present invention may be an anhydrous composition.

[0131] Preferably, the lubricant composition is not an emulsion.

[0132] Preferably, the lubricant composition according to the invention is characterized by a KV100 (measured according to ASTM D445) greater than or equal to 12 cSt, preferably between 12 cSt and 17 cSt.

[0133] The lubricant composition as defined above is used for lubricating a gas engine.

[0134] The lubricant composition as defined above is used for lubricating gas engines using any type of gas, in particular gas with a low methane number, preferably less than 80, more preferably less than 60.

[0135] It will be appreciated that the lower the methane number, the lower the combustion quality of the gas.

[0136] More particularly, the gas engine according to the present invention refers to:

[0137] - Stationary gas engines;

[0138] - Mobile gas engines, in particular: gas engines for vehicles, including heavy goods vehicles or public transport vehicles, such as buses, and also marine vehicles, such as boats.

[0140] In a preferred embodiment, the lubricant composition as defined above is used for lubricating a stationary gas engine.

[0141] The invention also relates to the use of at least one mineral base oil and at least one ester selected from polyol esters in a lubricant composition for lubricating a gas engine.

[0142] All characteristics and preferences described above for mineral base oils, polyol esters and gas engines also apply to this use.

[0143] The invention also relates to a method for lubricating a gas engine, comprising contacting at least one mechanical part of the engine with a lubricant composition comprising at least one mineral base oil and at least one ester chosen from polyol esters.

[0144] All characteristics and preferences described above with respect to the lubricant composition and the gas engine also apply to this method.

[0145] Various aspects of the invention can be illustrated by the following non-limiting examples:

[0146] Example 1: Preparation of a lubricant composition according to the present invention

[0147] The various components of the lubricant composition CL1 according to the invention are mixed according to the nature and quantities of the products presented in Table 1. The percentages indicated correspond to percentages by weight.

[0148]

[0149] Table 1

[0150] Example 2: Evaluation of the Oxidation Performance of CL1 Lubricant Compositions

[0151] The evaluation involved subjecting the lubricant composition to oxidation with nitrogen oxides at a temperature of 150° C. over a period of 48 hours.

[0152] The antioxidant performance was evaluated by measuring the difference in kinematic viscosity measured at 100° C. according to ASTM D445 before and after oxidation and expressed as a percentage of viscosity increase; the lower the percentage, the better the antioxidant performance.

[0153] A percentage increase in viscosity of less than or equal to 35% corresponds to acceptable antioxidant performance.

[0154] The results are described in Table 2.

[0155] CL1 Antioxidant properties 32

[0156] Table 2

[0157] The results show that the lubricant composition according to the present invention has acceptable antioxidant properties.

[0158] Example 3: Preparation of a lubricant composition according to the present invention

[0159] The various components of the lubricant compositions CL2, CL3 and CL4 according to the invention and of the comparative lubricant composition CC1 were mixed according to the properties and quantities of the products presented in Table 3.

[0160] The indicated percentages correspond to mass percentages.

[0161]

[0162]

[0163] Table 3

[0164] Example 4: Storage stability evaluation of CL2, CL3 and CL4 lubricant compositions

[0165] The visual assessment was performed at room temperature and was based on the turbidity that appeared in the composition.

[0166] The results are described in Table 4.

[0167] CL2 CL3 CL4 Storage stability Stablize Stablize Stablize

[0168] Table 4

[0169] The results show that the lubricant composition according to the present invention is stable over a long period of time.

[0170] Example 5: Evaluation of the Detergent Performance of Lubricant Compositions CL2 and CC1

[0171] The evaluation was performed by means of the PCT test according to GFC Lu29-A-15.

[0172] The higher the rated value, the better the detergency of the lubricant composition.

[0173] The results are described in Table 5.

[0174] CL2 CC1 Piston quality assessment 9.2 7.5

[0175] Table 5

[0176] The results show that the lubricant composition according to the present invention has improved detergency performance, especially at high temperatures.

[0177] Example 6: Preparation of a lubricant composition according to the present invention

[0178] The various components of the lubricant compositions CL5, CL6, CL7, CL8, CL9 and CL10 according to the invention and of the comparative lubricant composition CC2 were mixed according to the nature and quantities of the products presented in Table 6. The indicated percentages correspond to percentages by weight.

[0179]

[0180]

[0181] Table 6

[0182] Example 7: Storage Stability Evaluation of CL5, CL6, CL7, CL8, CL9 and CL10 Lubricant Compositions

[0183] The visual evaluation was the same as that of Example 4.

[0184] The results are described in Table 7.

[0185] CL5 CL6 CL7 CL8 CL9 CL10 Storage stability Stablize Stablize Stablize Stablize Stablize Stablize

[0186] Table 7

[0187] The results show that the lubricant composition according to the present invention is stable over a long period of time.

[0188] Example 8: Antioxidant properties of lubricant compositions CL5, CL6, CL8, CL9, CL10 and lubricant composition CC2 Evaluate

[0189] The evaluation is the same as described in Example 2.

[0190] The results are described in Table 8.

[0191] CL5 CL6 CL7 CL8 CL10 CC2 Antioxidant performance (%) 15 12 18 15 13 14

[0192] Table 8

[0193] The results show that the lubricant composition according to the present invention has good anti-oxidation performance.

[0194] Example 9: Evaluation of the Detergent Performance of Lubricant Compositions CL5, CL7 and CL9

[0195] This evaluation is the same as that described in Example 5.

[0196] The results are described in Table 9.

[0197] CL5 CL7 CL9 Piston quality assessment 9.6 7.8 9.6

[0198] Table 9

[0199] The results show that the lubricant composition according to the present invention has improved detergency performance, especially at high temperatures.

[0200] Example 10: Evaluation of the Detergent Performance of Lubricant Compositions CL5, CL6, CL7, CL8, CL9 and CL10

[0201] The evaluation was performed by means of the MCT test according to GFC L-27-T-07.

[0202] The higher the rated value, the better the detergency of the lubricant composition.

[0203] The higher the temperature when the first paint appears, the better the cleaning performance at high temperatures.

[0204] The results are described in Table 10.

[0205]

[0206] Table 10

[0207] The results show that the lubricant composition according to the present invention has improved detergency performance, especially at high temperatures.

[0208] The results also show that the addition of polyisobutylene makes it possible to further improve the detergency performance, especially at high temperatures.

[0209] Example 11: Preparation of a lubricant composition according to the present invention

[0210] The various components of the lubricant composition CL11 according to the invention were mixed according to the properties and quantities of the products presented in Table 11.

[0211] The indicated percentages correspond to mass percentages.

[0212]

[0213]

[0214] Table 11

[0215] Example 12: Evaluation of the Antioxidant Performance of Lubricant Composition CL11

[0216] The evaluation is the same as described in Example 2.

[0217] The results are described in Table 12.

[0218] CL11 Antioxidant performance (%) 18

[0219] Table 12

[0220] The results show that the lubricant composition according to the present invention has good anti-oxidation performance.

[0221] Example 13: Evaluation of the Detergent Performance of Lubricant Composition CL11

[0222] The evaluation is the same as that described in Example 5 and Example 10.

[0223] The results are described in Table 13.

[0224]

[0225] Table 13

[0226] The results show that the lubricant composition according to the present invention has improved detergency performance, especially at high temperatures.

Claims

1. A method for improving the detergency of a lubricant composition for a gas engine, the lubricant composition comprising at least 50% by weight of at least one mineral base oil, the method comprising including in the lubricant composition an additive of 5 to 15% by weight of at least one ester selected from polyol esters, The polyol ester is obtained by esterification of at least one carboxylic acid with at least one polyol, the polyol comprising 6 -OH groups and comprising 6 to 10 carbon atoms, and the carboxylic acid is a saturated and branched monocarboxylic acid comprising 8 to 20 carbon atoms.

2. The method according to claim 1, wherein: The gas engine is a stationary gas engine.

3. The method according to claim 1 or 2, wherein: The mineral base oil is selected from Group II base oil or Group III base oil according to API classification, preferably, selected from Group II base oil according to API classification.

4. The method according to claim 1 or 2, wherein: The lubricant composition includes 50 to 90 weight percent of a mineral base oil based on the total weight of the lubricant composition.

5. The method according to claim 1 or 2, wherein: The carboxylic acid comprises 8 to 18 carbon atoms.

6. The method according to claim 1 or 2, wherein: The polyol esters comprise a mixture of at least one first ester of a polyol according to claim 1 and a monocarboxylic acid and at least one second ester of a polyol according to claim 1 and a monocarboxylic acid, the second ester being different from the first ester.

7. The method according to claim 1 or 2, wherein: The esters are obtained by an esterification reaction between a polyol according to claim 1, at least one first monocarboxylic acid according to claim 1, and at least one second carboxylic acid chosen from linear or branched saturated or unsaturated dicarboxylic acids comprising at least 16 carbon atoms.

8. The method according to claim 1 or 2, wherein: The lubricant composition further includes polyisobutylene.

9. The method according to claim 1 or 2, for reducing or even eliminating the formation of precipitates.

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