RU2501846C2 - Lubricating oil composition - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: described is lubricating oil composition which contains lubricating base oil which contains (A) a partial ester of a polyatomic alcohol and carboxylic acid in amount of 5-75 wt % per total weight of the base oil, and having kinematic viscosity at temperature of 100°C of 1-15 mm²/s. The composition has kinematic viscosity at temperature of 100°C of 1-20 mm²/s, the polyatomic alcohol is an alcohol from a diatomic alcohol to a hexatomic alcohol and the carboxylic acid is selected from a group comprising monobasic acids, polybasic acids and mixtures thereof.

EFFECT: reduced friction between components, which enables to save energy, high efficiency of the lubricating oil composition.

10 cl, 1 tbl

Description

FIELD OF THE INVENTION

The present invention relates to a lubricating oil composition, and more particularly, to a lubricating oil composition that has a low coefficient of adhesion, excellent energy saving characteristics and high efficiency, which is suitable for use in mechanical, automatic or continuously variable transmissions of automobiles, or in industrial gear transmission systems.

State of the art

Recently, energy savings in automobiles and construction or agricultural machinery, that is, fuel economy, have become an urgent need to solve environmental problems, such as reducing carbon dioxide emissions, and to components such as engines, transmissions, and lower gears stages, compressors or pumping stations began to impose more stringent requirements for energy savings. Therefore, it is necessary that the lubricating oils used in these systems provide a decrease in resistance to movement and friction resistance to a greater extent than before.

As an effective means of saving energy for the transmission and transmission of the last lowering stage, a decrease in the viscosity of the lubricating oil can be noted. For example, an automobile automatic transmission or continuously variable transmission has a torque converter, an oil-bath clutch, a gear bearing system, an oil pump and a hydraulic drive control system, while a manual manual transmission or a final reduction gear has a gear bearing system . Reducing the viscosity of the lubricating oil used in such transmissions can reduce the driving and frictional drags of the torque converter operating in the clutch oil bath, the gear bearing system and the oil pump, and thereby increase the efficiency of the power train, thereby improving performance fuel economy in the car.

However, a decrease in the viscosity of the lubricating oil used in these transmissions can result in a significant reduction in the fatigue life of the above-described units and their mechanisms, and can create seizure leading to malfunctions in the transmissions. In particular, when a low viscosity lubricating oil is mixed with an extreme pressure additive containing phosphorus compounds to enhance extreme pressure characteristics, fatigue life will be drastically reduced. Therefore, as a rule, reducing the viscosity of lubricating oil is problematic. Although fatigue life can be increased by using an anti-seize additive based on sulfur compounds, the oxidation resistance of the lubricating oil is impaired, and a large amount of antioxidant must be mixed in.

As described above, viscosity reduction has some limitations. Alternatively or in addition to lowering viscosity, energy savings or high energy efficiency can be successfully achieved by reducing friction of parts, such as tooth surfaces of gears operating under conditions of elastic hydrodynamic lubrication. In general, the contact pressure acting on the surface of the gear teeth can be 1 GPa or more, which is known for elastic hydrodynamic lubrication conditions. Under these conditions, it is known to use a lubricant oil having a low coefficient of adhesion to reduce friction and thereby contribute to energy savings.

List of references

Patent documents

Patent Document 1: Publication of Japanese Patent Application Laid-Open No. 10-213552

Patent Document 2: Publication of Japanese Patent Application Laid-Open No. 9-68161

SUMMARY OF THE INVENTION

Technical problem

The present invention has been made in the light of these circumstances and is aimed at creating a lubricating oil composition having a low coefficient of adhesion, which can reduce friction between parts, such as the surfaces of gear teeth operating under conditions of elastic hydrodynamic lubrication, to provide energy saving and high efficiency characteristics, suitable for use in mechanical, automatic and continuously variable transmissions of automobiles or industrial gear systems.

Solution

As a result of an in-depth study and research, the present invention was made based on the fact that the above problems could be solved using a lubricating oil composition comprising a base oil containing (A) a partial ester of polyhydric alcohol and a carboxylic acid.

That is, the present invention relates to a lubricating oil composition having a low coefficient of adhesion, including a lubricating base oil containing (A) a partial ester of polyhydric alcohol and a carboxylic acid in an amount of from 0.1 to 80 wt.%, Calculated on the total weight base oil, and having a kinematic viscosity at a temperature of 100 ° C from 1 to 15 mm ² / sec, and the composition has a kinematic viscosity at a temperature of 100 ° C from 1 to 20 mm ² / sec.

The present invention also relates to the aforementioned lubricating oil composition in which (A) a partial ester of a polyhydric alcohol and a carboxylic acid is a partial ester of a trimethylolpropane and a monobasic carboxylic acid.

The present invention also relates to the above lubricating oil composition, further comprising (B) a poly (meth) acrylate compound made up of a repeating structural unit represented by formula (I) below, in an amount of from 0.01 to 20% by weight:

in which R ¹ represents hydrogen or methyl, and R ² represents a hydrocarbon group having from 1 to 30 carbon atoms.

The present invention also relates to the above lubricating oil composition, the composition having an adhesion coefficient of 0.013 or less.

The present invention also relates to the aforementioned lubricating oil composition, the composition having a ratio of adhesion coefficient to kinematic viscosity (mm ² / s) at a temperature of 100 ° C., which is 1.2 × 10 ⁻³ or less.

The present invention also relates to the aforementioned lubricating oil composition, the composition having a Brookfield dynamic viscosity at a temperature of −40 ° C. at a level of 40,000 mPa · s or less.

Advantageous Results of the Invention

The lubricating oil composition according to the present invention provides a low coefficient of adhesion and thus can maintain the characteristics required for gear oil and achieve energy saving and high efficiency parameters when used in mechanical, automatic or continuously variable transmissions of automobiles, or in industrial gear transmission systems.

Description of embodiment

Below will be described the composition of the lubricating oil according to the present invention.

The lubricating oil composition according to the present invention includes an ester-based base oil comprising (A) a partial ester of a polyhydric alcohol and a carboxylic acid.

The alcohol constituting the ester-based base oil is a polyol. The carboxylic acid constituting the ester base oil may be a monobasic or polybasic acid. However, the ester-based base oil is necessarily an incomplete ester, where at least a portion of the hydroxyl groups of the polyhydric alcohol remains unesterified.

Polyhydric alcohols can be ordinary alcohols from diatomic to decatomic, preferably diatomic to hexatomic. Specific examples of polyhydric alcohols from dihydric to tenhydric alcohols include dihydric alcohols, such as ethylene glycol, diethylene glycol, polyethylene glycol (trimeric to pentadecameric ethylene glycol), propylene glycol, dipropylene glycol, polypropylene glycol (trimeric to pentadecameric propylene glycol, 1,3-propylene 1,3-propylene glycol) propanediol, 1,3-butanediol, 1,4-butanediol, 2-methyl-1,2-propanediol, 2-methyl-1,3-propanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4- pentanediol, 1,5-pentanediol and neopentyl glycol; polyhydric alcohols, such as glycerol, polyglycerol (from its dimer to octamer, such as diglycerin, triglycerin and tetraglycerol), trimethylolalkanes (trimethylol ethane, trimethylol propane, trimethylolbutane) and their derivatives from its dimers to octameters and 1 octameters to octameters; , 2,4-butanetriol, 1,3,5-pentantriol, 1,2,6-hexanetriol, 1,2,3,4-butantetraol, sorbitol, sorbitan, condensation product of sorbitol and glycerol, adonite, arabitol, xylitol and mannitol ; saccharides such as xylose, arabinose, ribose, ramnose, glucose, fructose, galactose, mannose, sorbose, cellobiose, maltose, isomaltose, trehalose and sucrose; and mixtures thereof.

Among these polyhydric alcohols, preferred examples include dihydric to hexahydric alcohols such as ethylene glycol, diethylene glycol, polyethylene glycol (trimeric to decameric ethylene glycol), propylene glycol, dipropylene glycol, polypropylene glycol (trimeric to decameric propylene glycol), 1,3-propane -1,2-propanediol, 2-methyl-1,3-propanediol, neopentyl glycol, glycerol, diglycerin, triglycerin, trimethylol alkanes (trimethylol ethane, trimethylol propane, trimethylolbutane) and their derivatives from dimers to tetramers, entaerythritol, dipentaerythritol, 1,2,4-butanetriol, 1,3,5-pentantriol, 1,2,6-hexanetriol, 1,2,3,4-butanetetraol, sorbitol, sorbitan, condensation product of sorbitol and glycerol, adonite, Arabite, xylitol and mannitol, and mixtures thereof. More preferred examples include ethylene glycol, propylene glycol, neopentyl glycol, glycerin, trimethylol ethane, trimethylol propane, pentaerythritol and sorbitan, and mixtures thereof. Particularly preferred examples include neopentyl glycol, trimethylol ethane, trimethylol propane and pentaerythritol and mixtures thereof, for reasons of achieving higher thermal stability and oxidation stability, and trimethylol propane is the most preferred example.

Among the acids that make up the ester base oil used in the present invention, examples of monobasic acids include aliphatic acids, typically from 2 to 24 carbon atoms, which may be linear or branched, and are saturated or unsaturated. Specific examples include saturated aliphatic acids, such as acetic acid, propionic acid, linear chain or branched butanoic acid, linear or branched pentanoic acid, linear or branched hexanoic acid, linear or branched chain, or straight chain or branched acid , linear or branched decanoic acid, linear or branched undecanoic acid, linear or branched dodecanoic acid, linear or branched tridecanoic acid, linear or branched tetradecanoic acid, linear or branched pentadecanoic acid, linear or branched hexadecanoic acid or linear acid, linear or unless detecting eicosanoic acid, straight-chain or branched heneicosanoic acid, straight-chain or branched docosanoic acid, straight-chain or branched tricosylic acid, and straight-chain or branched tetracosanoic acid; unsaturated aliphatic acids, such as acrylic acid, linear chain or branched butenic acid, linear chain or branched pentenoic acid, linear chain or branched hexenoic acid, linear chain or branched heptenic acid, linear chain or branched octenoic acid, linear or chain branched linear chain or branched undecenoic acid, linear chain and whether branched dodecenoic acid, linear chained or branched tridecenoic acid, linear chained or branched tetradecenoic acid, linear chained or branched pentadecenoic acid, linear chained or branched hexadecenoic acid, linear chained or branched heptadecenoic acid or linear chained eicosenoic acid, linear chain I geneykozenovaya or branched acid, straight-chain or branched docosenoic acid, straight-chain or branched trikozenovaya acid and straight-chain or branched tetrakozenovaya acid; and mixtures thereof. Among these aliphatic acids, for reasons of further enhanced lubricity and processability, saturated aliphatic acids having 3 to 20 carbon atoms, unsaturated aliphatic acids having 3 to 22 carbon atoms, and mixtures thereof are preferred. More preferred are saturated aliphatic acids having 4 to 18 carbon atoms, unsaturated aliphatic acids having 4 to 18 carbon atoms, and mixtures thereof. From the standpoint of oxidation stability, saturated aliphatic acids having from 4 to 18 carbon atoms are most preferred.

Examples of polybasic acids include dibasic acids having from 2 to 16 carbon atoms, and trimellitic acid. Dibasic acids having from 2 to 16 carbon atoms can be linear chain or branched, or saturated or unsaturated. Specific examples include ethanedioic (oxalic) acid, propanedioic (malonic) acid, linear chain or branched pentanedioic acid, linear chain or branched hexanedioic acid, linear or branched chain or branched chain or branched chain linear chain or branched decanedic acid, linear chain or branched w undekandiovuyu acid, straight-chain or branched dodecanedioic acid, straight-chain or branched tridekandiovuyu acid, straight-chain or branched tetradekandiovuyu acid, straight-chain or branched geptadekandiovuyu acid and straight-chain or branched geksadekandiovuyu acid, straight-chain or branched or branched geksendiovuyu acid, straight-chain or branched geptendiovuyu acid, straight- or branched octendioic acid, line ynotsepochechnuyu or branched nonendiovuyu acid, straight-chain or branched detsendiovuyu acid, straight-chain or branched undetsendiovuyu acid, straight-chain or branched dodetsendiovuyu acid, straight-chain or branched tridetsendiovuyu acid, straight-chain or branched tetradetsendiovuyu acid, straight-chain or branched geptadetsendiovuyu acid, straight-chain or branched geksadetsendiovuyu acid, and their mixtures.

No particular restrictions are imposed on the combination of alcohol and acid constituting the ester. For example, the following esters can be used in the present invention. These esters can be used individually or in combination:

(a) an incomplete ester of a polyhydric alcohol and a monobasic acid

(b) an incomplete ester of a polyhydric alcohol and a polybasic acid

(c) a mixed partial ester of a polyhydric alcohol and a mixture of a monobasic acid and a polybasic acid

The percentage of hydroxyl groups remaining unesterified from all hydroxyl groups in the polyol is preferably from 3 to 80 percent, more preferably from 5 to 70 percent, more preferably from 10 to 60 percent, most preferably from 15 to 50 percent. When the percentage of the remaining hydroxyl groups is less than 3 percent, the resulting lubricating oil composition does not sufficiently reduce the adhesion coefficient. When this percentage exceeds 80 percent, the resulting lubricating oil composition would enhance friction due to increased viscosity and would have poor oxidation stability.

Among these esters, (a) a partial ester of a polyhydric alcohol and a monobasic acid is preferred due to its excellent cohesion coefficient, a dimer of trimethylolpropane and a monobasic acid having from 12 to 18 carbon atoms is more preferable, and a diester of trimethylolpropane and oleic acid is most preferred.

The lubricating oil composition according to the present invention contains a partial ester of polyhydric alcohol and a carboxylic acid in an amount of from 0.1 to 80 wt.%, Preferably from 5 to 75 wt.%, More preferably from 10 to 70 wt.%, More preferably from 15 up to 65 wt.%, and most preferably from 20 to 60 wt.%, calculated on the total weight of the base oil. An ester content of less than 0.1 wt.% May lead to a composition that may not meet the adhesion coefficient requirements, while an ester content of more than 80 wt.% May lead to a composition that enhances friction due to increased viscosity and has a deteriorated oxidation resistance.

The base oil of the lubricating oil composition according to the present invention may contain base oil components other than a partial ester of polyhydric alcohol and carboxylic acid, to the extent that the resulting mixed base oil has a kinematic viscosity at a temperature of 100 ° C from 1 to 15 mm ² / sec Such base oil components may be any one or more types of mineral base oils, any one or more types of synthetic base oils, or mixtures thereof.

Specific examples of the mineral oil include oils that can be obtained by subjecting a fraction of the lubricating oil obtained by vacuum distillation of the bottom residue after distillation at atmospheric pressure resulting from the distillation of crude oil at atmospheric pressure, to any one or more of the processing selected from solvent deasphalting, extraction solvents, hydrocracking, hydroisomerization, solvent dewaxing, catalytic dewaxing and hydrotreating; mineral oils with isomerized paraffins; and oils obtained by GTL WAX isomerization (gas-in-liquid paraffin).

Specific examples of synthetic base oils include polybutenes and their hydrogenated derivatives; poly-α-olefins, such as 1-octene oligomer and 1-decene oligomer, and their hydrogenated derivatives; esters, including full esters of the aforementioned polyhydric alcohols and carboxylic acids, monoesters such as 2-ethylhexyl oleate, diesters such as ditridecylglutarate, di-2-ethylhexyl adipate, diisodecyl adipate, dithidecyl adipate, and di-2-ethyl di-ethyl di-ethyl rather than (A) partial esters of polyhydric alcohols and carboxylic acids; aromatic synthetic oils such as alkylnaphthalenes, alkylbenzenes and aromatic esters; and mixtures of the above derivatives.

The lubricating base oil used in the present invention has a kinematic viscosity at a temperature of 100 ° C necessarily from 1 to 15 mm ² / s, preferably from 2 to 14 mm ² / s, more preferably from 3 to 13 mm ² / s, more preferably from 4 to 12 mm ² / s, particularly preferably from 5 to 11 mm ² / s. When the kinematic viscosity at a temperature of 100 ° C of the lubricating base oil is more than 15 mm ² / s, the resulting lubricating oil composition would be poor in terms of low temperature viscosity characteristics. Meanwhile, when the kinematic viscosity at a temperature of 100 ° C of the lubricating base oil is less than 1 mm ² / sec, the resulting lubricating oil composition would have poor lubricity due to insufficient formation of an oil film at the lubrication points and would show large losses on the evaporation of the lubricating base oil.

The viscosity index of the lubricating base oil used in the present invention is not specifically limited. However, the viscosity index is preferably 80 or more, more preferably 90 or more, particularly preferably 110 or more. A viscosity index of 80 or more provides a composition exhibiting excellent viscosity characteristics at low to high temperatures.

The lubricating oil composition according to the present invention preferably contains (B) a poly (meth) acrylate compound having repeating structural units represented by formula (I) below.

This poly (meth) acrylate compound serves as a viscosity index modifier and / or depressant additive to lower the pour point. As used herein, the term “poly (meth) acrylate compound” generically refers to polyacrylate compounds and polymethacrylate compounds.

(In formula (I), R ₁ represents hydrogen or methyl, and R ₂ represents a hydrocarbon group having from 1 to 30 carbon atoms).

(B) a poly (meth) acrylate compound is a polymer from a monomer to produce a polymer containing a (meth) acrylate monomer (hereinafter referred to as “Monomer M-1”) represented by the formula (1) below.

In the above formula (1), R ¹ represents hydrogen or methyl, and R ² represents a linear or branched hydrocarbon group having from 1 to 30 carbon atoms.

Specific examples of a linear or branched hydrocarbon group having from 1 to 30 carbon atoms for the radical R ² include alkyl groups which may be linear chain or branched, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, hexadecyl and octadecyl groups; and alkenyl groups, which may be linear or branched, and the position of the double bond in which can vary, such as butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tetradecenyl, hexadecenyl and octadecenyl groups.

Typical examples of poly (meth) acrylate compounds include poly (meth) acrylates of the so-called non-dispersive type, obtained by homopolymerization of Monomer M-1 or copolymerization of two or more types of Monomers M-1.

The poly (meth) acrylate compound may be a poly (meth) acrylate of the so-called dispersing type, obtained by copolymerization of Monomer M-1 with one or more monomers selected from the group consisting of (meth) acrylate monomers represented by the following formula (2) ( hereinafter referred to as “M-2 Monomer”), and monomers represented by the formula (3) below (hereinafter referred to as “M-3 Monomer”).

In the above formula (2), R ³ represents hydrogen or methyl, R ⁴ represents an alkylene group having from 1 to 18 carbon atoms, E ¹ represents an amine residue or a heterocyclic residue having 1 or 2 nitrogen atoms and from 0 to 2 oxygen atoms, and “a” represents an integer equal to 0 or 1.

Specific examples of alkylene groups having from 1 to 18 carbon atoms for the R ⁴ radical include ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylen, dodecylene, hededecylene, pentodecylene, pentadecylene, pentene and octadecylene groups, all of which may be linear chain or branched.

Specific examples of the amine residue or heterocyclic residue represented by E ¹ include dimethylamino, diethylamino, dipropylamino, dibutylamino, aniline, toluidine, ksilidinovy fragments, acetylamino, benzoylamino, morpholino moiety, pyrrolyl, pyrroline, pyridyl, metilpiridilnuyu, pyrrolidinyl, piperidinyl, quinolyl, pyrrolidonyl, pyrrolidone, imidazoline and pyrazine groups.

In the formula (3), R ⁵ represents hydrogen or methyl, and E ² represents an amine residue or a heterocyclic residue having 1 or 2 nitrogen atoms and from 0 to 2 oxygen atoms.

Specific examples of the amine residue or heterocyclic residue represented by E ² include dimethylamino, diethylamino, dipropylamino, dibutylamino, aniline, toluidine, ksilidinovy fragments, acetylamino, benzoylamino, morpholino moiety, pyrrolyl, pyrroline, pyridyl, metilpiridilnuyu, pyrrolidinyl, piperidinyl, quinolyl, pyrrolidonyl, pyrrolidone, imidazoline and pyrazine groups.

The amine residue or heterocyclic residue in formulas (2) and (3) refers to the monovalent group formed by the removal of the hydrogen atom from the amine amino group, and the monovalent group formed by the removal of the hydrogen atom bound to the carbon in the heterocycle from the molecule having heterocyclic structure, respectively.

Specific preferred examples of Monomer-M-2 and Monomer M-3 include

dimethylaminomethylmethacrylate,

diethylaminomethyl methacrylate,

dimethylaminoethyl methacrylate,

diethylaminoethyl methacrylate,

2-methyl-5-vinylpyridine,

morpholinomethyl methacrylate,

morpholinoethyl methacrylate,

N-vinylpyrrolidone and mixtures thereof.

There are no specific restrictions on the molar ratio of Monomer M-1 and Monomers M-2 and M-3 in the copolymer. However, the ratio “M-1: M-2 and M-3” is preferably from 99: 1 to 80:20, more preferably from 98: 2 to 85:15, more preferably from 95: 5 to 90:10.

No specific restrictions are imposed on the method for producing the (B) poly (meth) acrylate compound, which, for example, is generally readily prepared by radical polymerization in a solution of an individual Monomer M-1 or a mixture of Monomer M-1 and Monomers M-2 and M- 3 in the presence of a polymerization initiator such as benzoyl peroxide.

The weight average molecular weight (Mw) (B) of the poly (meth) acrylate compound is preferably 5,000 or more, more preferably 10,000 or more, more preferably 20,000 or more, particularly preferably 30,000 or more, and most preferably 40,000 or more. The weight average molecular weight (Mw) is preferably 400,000 or less, more preferably 300,000 or less, more preferably 200,000 or less, and particularly preferably 100,000 or less.

A weight average molecular weight of less than 5000 leads to an insufficient improvement in the viscosity index and would increase the production cost of the composition. A weight average molecular weight of more than 400,000 would impair shear resistance or storage stability of the resulting composition.

The PSSI (constant shear resistance index) value of the poly (meth) acrylate compound is preferably 40 or less, more preferably 5 to 40, more preferably 10 to 35, particularly preferably 15 to 30, and most preferably 20 to 25 When the PSSI is more than 40, the resulting composition would exhibit poor shear resistance, whereas if the PSSI is less than 5, a sufficient improvement in the viscosity index would not be achieved, and this would lead to an increase in the cost of production of the composition.

As used herein, the term “PSSI” refers to the polymer constant shear resistance index calculated based on data measured according to ASTM D 6278-02 (Shear resistance test method for a polymer containing fluids using a European diesel injection system), in accordance with ASTM D 6022-01 (Standard Method for Calculating the Index of Resistance to Constant Shear Load).

The lubricating oil composition according to the present invention contains (B) a poly (meth) acrylate compound in an amount of preferably from 0.01 to 20 wt.%, More preferably from 0.03 to 10 wt.%, More preferably from 0.06 to 5 wt. %, particularly preferably from 0.1 to 3 wt.%, calculated on the total weight of the composition. A content of less than 0.01 percent by weight would lead to failure to obtain a predetermined effect of improving the viscosity index, while a content of more than 20 wt.% Would lead to a composition having poor shear resistance.

The lubricating oil composition of the present invention can be mixed with a variety of additives, such as extreme pressure additives, ashless dispersants, metal detergents, friction modifiers, antioxidants, corrosion inhibitors, viscosity index modifiers other than Component (B) described above, anti-corrosion additives, demulsifiers , metal deactivators, depressants to lower the pour point, sealants, antifoam additives and dyes, individually or in combination, to further improve the properties of the composition or to impart to the composition the properties required for various lubricating oils.

The lubricating oil composition according to the present invention can be mixed with at least one type of phosphoric extreme pressure additive selected from phosphorous acid, phosphoric acid monoesters, phosphoric acid diesters, phosphoric acid esters and their salts; with at least one type of sulfur extreme pressure additive selected from sulfonated fats and oils, sulfonated olefins, polysulfides with two hydrocarbon substituents, dithiocarbamates, thiadiazoles and benzthiazoles; and / or at least one type of phosphorus-sulfur extreme pressure additive selected from thiophosphoric acids, thiophosphoric acid monoesters, thiophosphoric acid diesters, thiophosphoric acid esters, dithiophosphoric acid esters, dithiophosphoric acid monoesters, dithiophosphoric esters, diesters acid, tritiophosphoric acid, tertiophosphoric acid monoesters, tritiophosphoric acid diesters, tritiophosphoric triesters, and salts.

Examples of ashless dispersants include ashless dispersants such as succinimides, benzylamines and polyamines, each of which has a hydrocarbon group having from 40 to 400 carbon atoms and / or derivatives thereof with boron compounds. The content of ashless dispersants is usually from 0.01 to 15 wt.%, Calculated on the total weight of the composition.

Examples of metal detergent additives include additives such as alkaline earth metal sulfonates, alkaline earth metal phenates, alkaline earth metal salicylates. The content of metal detergent additives is usually from 0.01 to 10 wt.%, Preferably from 0.1 to 5 wt.%.

Friction modifiers can be any compounds that are mainly used as friction modifiers for lubricating oils. Specific examples include amino compounds, imid compounds, aliphatic esters, aliphatic acid amides and metal salts of aliphatic acids, each of which has at least one alkyl or alkenyl group having 6 to 30 carbon atoms per molecule, especially a linear chain alkyl or alkenyl a group having from 6 to 30 carbon atoms. Alternatively, organic molybdenum compounds such as molybdenum dithiophosphate and molybdenum dithiocarbamate can also be used. The content of friction modifiers is usually from 0.01 to 5.0 wt.%, Based on the total weight of the composition.

Antioxidants can be any antioxidants that are commonly used in lubricating oils, such as phenolic or amine compounds. Specific examples of the antioxidant include alkyl phenols, such as 2,6-di-tert-butyl-4-methylphenol; bisphenols such as methylene-4,4-bisphenol (2,6-di-tert-butyl-4-methylphenol); naphthylamines such as phenyl-α-naphthylamine; dialkyl diphenylamines; zinc salts of dialkyldithiophosphoric acids such as di-2-ethylhexyl dithiophosphoric acid; and esters of (3,5-di-tert-butyl-4-hydroxyphenyl) aliphatic acid (propionic acid) or (3-methyl-5-tert-butyl-4-hydroxyphenyl) aliphatic acid (propionic acid) with a monohydric or polyhydric an alcohol such as methanol, octanol, octadecanol, 1,6-hexanediol, neopentyl glycol, thioethylene glycol, triethylene glycol and pentaerythritol. The antioxidant content is usually from 0.01 to 5% by weight, based on the total weight of the lubricating oil composition.

Examples of corrosion inhibitors include compounds such as benztriazole, tolyltriazole, thiadiazole and imidazole.

Examples of viscosity index modifiers other than Component (B) include non-dispersing or dispersing ethylene-α-olefin copolymers and their hydrogenated derivatives; polyisobutylene or their hydrogenated derivatives; hydrogenated styrene-diene copolymers; ester copolymers of styrene and maleic anhydride; and polyalkyl styrenes.

Examples of anti-corrosion additives include petroleum sulfonates, alkylbenzenesulfonates, dinonylnaphthalenesulfonates, alkenyl succinic acid esters and polyhydric alcohol esters.

Examples of demulsifiers include polyalkylene glycol nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers and polyoxyethylene alkyl naphthyl ethers.

Examples of metal deactivators include imidazolines, pyrimidine derivatives, alkylthiadiazoles, mercaptobenzthiazoles, benzotriazoles and their derivatives, 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazolyl-2,5-bis-dialkyl dithiocarbamate, 2- (alkyl dithio) benzimidazole ortho-carboxybenzylthio) propionitrile.

Depressor additives for lowering the pour point may be any of the known depressant additives for lowering the pour point, selected depending on the type of lubricating base oil, but are preferably polymethacrylates having a weight average molecular weight of from 80,000 to 200,000.

Anti-foam additives can be any compounds that are commonly used as anti-foam additives for lubricating oils. Examples of such antifoam additives include silicones such as dimethylsilicone and fluorosilicon.

Sealing agents may be any compounds that are commonly used as sealing agents for lubricating oils. Examples of such sealants include sealants based on esters, sulphurous and aromatic compounds.

Dyes can be any compounds that are commonly used and can be mixed in any quantity.

When these additives are mixed with the lubricating oil composition according to the present invention, the content of each additive is usually from 0.0005 to 5 wt.%, Based on the total weight of the composition, with the exception of additives, the amounts of which are specifically indicated above.

The kinematic viscosity of the lubricating oil composition at a temperature of 100 ° C according to the present invention is preferably adjusted to a mandatory level of from 1 to 20 mm ² / s, preferably from 2 to 15 mm ² / s, more preferably from 3 to 13 mm ² / s, more preferably from 4 to 12 mm ² / s, particularly preferably from 5 to 11 mm ² / s. When the kinematic viscosity at a temperature of 100 ° C of the lubricating oil composition is more than 20 mm ² / s, the composition would be poor in terms of low temperature viscosity characteristics. Meanwhile, when the kinematic viscosity at a temperature of 100 ° C. of a lubricating base oil is less than 1 mm ² / s, the resulting lubricating oil composition would have poor lubricity due to insufficient formation of an oil film at the lubrication points and would show large evaporation losses.

The lubricating oil composition of the present invention has an adhesion coefficient of preferably 0.013 or less, more preferably 0.010 or less, more preferably 0.008 or less, particularly preferably 0.006 or less. An adhesion coefficient of more than 0.013 would result in a composition that would not provide energy saving characteristics due to increased friction.

The lubricating oil composition according to the present invention has a ratio of adhesion to kinematic viscosity (mm ² / s) at a temperature of 100 ° C. at a level of preferably 1.2 × 10 ^-3 or less, more preferably 1.1 × 10 ^-3 or less, more preferably 1.0 x 10 ^-3 or less, particularly preferably 9.5 x 10 ^-4 or less. The ratio of the coefficient of adhesion to kinematic viscosity (mm ² / s) at a temperature of 100 ° C more than 1.2 × 10 ^-3 would lead to a composition that would not provide the characteristics of energy savings due to increased friction.

No specific restrictions are placed on the kinematic viscosity at 40 ° C. of the lubricating oil composition of the present invention, which, however, is preferably from 10 to 100 mm ² / s, more preferably from 15 to 90 mm ² / s, more preferably from 20 up to 80 mm ² / s, particularly preferably from 25 to 70 mm ² / s. When the kinematic viscosity at a temperature of 40 ° C of the lubricating oil composition is more than 100 mm ² / s, the resulting composition would be poor in terms of low temperature viscosity characteristics. Meanwhile, when the kinematic viscosity at a temperature of 40 ° C is less than 10 mm ² / s, the resulting lubricating oil composition would have poor lubricity due to insufficient oil film formation at the lubrication points and would show large evaporation losses.

No particular restrictions are imposed on Brookfield dynamic viscosity (BF viscosity) at a temperature of −40 ° C. of the lubricating oil composition of the present invention, which, however, is preferably 40,000 mPa · s or less, more preferably 35,000 mPa · s or less, more preferably 30,000 mPa · s or less, particularly preferably 25,000 mPa · s or less. When the BF viscosity at a temperature of -40 ° C of the lubricating oil composition is more than 40,000 mPa · s, the composition would be poor in terms of low temperature viscosity characteristics and thus would have degraded properties in terms of energy saving characteristics. Used in this description, the term "BF-viscosity" means the viscosity, measured in accordance with the "method for determining the low-temperature viscosity of gear oil" prescribed in the instruction JPI-5S-26-85.

No particular restrictions are placed on the viscosity index of the lubricating oil composition of the present invention, which, however, is preferably 120 or more, more preferably 140 or more, particularly preferably 160 or more. A viscosity index of 120 or greater enables a composition to exhibit excellent viscosity characteristics at low to high temperatures.

No specific limitations are imposed on the evaporation loss of the lubricating oil composition of the present invention. However, the evaporation loss according to the Noack test (NOACK) is preferably from 10 to 50 wt.%, More preferably from 20 to 40 wt.%, Particularly preferably from 22 to 35 wt.%. The use of a lubricating oil composition having a NOACK evaporation loss adjusted within the above ranges makes it possible to achieve both low temperature and antiwear properties. As used herein, the term “NOACK evaporation loss” means the evaporation loss measured in accordance with CEC instruction L-40-T-87.

The lubricating oil composition according to the present invention is excellent in terms of energy-saving properties and has high efficiency, and can contribute to improving the fuel consumption of a car and energy saving in enterprises, used in mechanical, automatic or continuously variable transmissions of automobiles, or in industrial gear transmission systems.

Examples

The present invention will now be described in more detail with reference to the following examples and comparative examples, which should not be construed as limiting the scope of the invention.

(Examples 1 and 2, Comparative Examples 1-5)

The lubricating oil compositions of the present invention (Examples 1 and 2) were prepared in accordance with the compositions set forth in Table 1. The adhesion coefficient of each composition was measured, and the results are also presented in Table 1.

Comparison lubricating oil compositions (Comparative Examples 1-5) were prepared in accordance with the compositions set forth below in Table 1. The adhesion coefficient of each composition was measured, and the results are also presented in Table 1.

[Cohesion coefficient measurement]

Cohesion coefficient was measured under the following conditions using a tester with an EHL film (elastic hydrodynamic lubricant) *.

(*) described in Tribology International (March 2007) by R. Kapadia et al.

(Test conditions)

Test sample: SUJ2 (bearing structural steel)

Oil temperature: 100 ° C

Surface pressure: 0.514 GPa

Slip coefficient: 100%

As set forth in Table 1, the compositions, each of which includes a partial ester of polyhydric alcohol and carboxylic acid (Examples 1 and 2), clearly have a lower coefficient of adhesion than the compositions, each of which includes a full ester of polyhydric alcohol (Comparative Examples 1-3), which includes a trimellitic acid ester (Comparative Example 4), and which includes PAO (poly-b-olefin) (Comparative Example 5).

Table 1 Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 The composition of the base oil (calculated on the total weight of the base oil) Ester base oil 1 ¹⁾ Mass% 43 43 Ester base oil 2 ²⁾ Mass% 57 57 Ester base oil 3 ³⁾ Mass% one hundred one hundred Ester base oil 4 ⁴⁾ Mass% one hundred Ester base oil 5 ⁵⁾ Mass% one hundred Poly-b-olefin ⁶⁾ Mass% one hundred Additives (based on the total weight of the composition) Polymethacrylate ⁷⁾ Mass% 0.5 0.5 Transmission oil additive package ⁸⁾ Mass% 15.8 15.8 15.8 15.8 15.8 15.8 15.8 Kinematic viscosity at a temperature of 40 ° C mm ² / s 47.8 47.9 48.5 48.6 48.5 83.1 60 100 ° C mm ² / s 9.6 9.6 9,4 9.5 9.2 9.3 9,4 Viscosity index 190 190 183 183 176 86 138 Brookfield viscosity at -40 ° C MPa · sec 113,000 19,000 > 1,000,000 58,000 310,000 40 Adhesion coefficient 0.009 0.009 0.014 0.014 0.012 0,026 0,021 The ratio of the coefficient of adhesion / kinematic viscosity at a temperature of 100 ° C 9.4 × 10 ^-4 9.4 × 10 ^-4 1.5 × 10 ^-3 1.5 × 10 ^-3 1.3 × 10 ^-3 2.8 × 10 ^-3 2.2 × 10 ^-3 1) ester base oil 1: diester of trimethylolpropane and oleic acid (kinematic viscosity at 40 ° C: 541.7, kinematic viscosity at 100 ° C: 55.3, viscosity index: 168)
2) ester base oil 2: mono-ester of oleic acid and 2-ethylhexyl alcohol (kinematic viscosity at 40 ° C: 8.7, kinematic viscosity at 100 ° C: 2.7, viscosity index: 174)
3) Ester base oil 3: trimethylolpropane and oleic acid triester (kinematic viscosity at 40 ° C: 48.1, kinematic viscosity at 100 ° C: 9.5, viscosity index: 187)
4) ester base oil 4: trimethylolpropane and stearic acid triester (kinematic viscosity at 40 ° C: 47.2, kinematic viscosity at 100 ° C: 9.3, viscosity index: 183)
5) Ester base oil 5: trimellitic acid and 2-ethylhexyl alcohol complex ester (kinematic viscosity at 40 ° C: 89, kinematic viscosity at 100 ° C: 9.6, viscosity index: 79)
6) RAO: poly-α-olefin (mixture RAO1: RAO2 = 95: 5; RAO1 <kinematic viscosity at 40 ° C: 64.89, kinematic viscosity at 100 ° C: 9.912, viscosity index: 137>; RAO2 <kinematic viscosity at 40 ° C: 18.33, kinematic viscosity at 100 ° C: 4.081, viscosity index: 124>)
7) PMA: polymethacrylate (weight average molecular weight: 60,000, normal C12-, C14-, C16-, C18-alkyls)
8) Transmission oil additive package (containing phosphoric acid ester, thiophosphoric acid, olefin sulfide)
The unit of each kinematic viscosity is mm ² / s.

Industrial applicability

The lubricating oil composition according to the present invention is extremely useful because it has a low coefficient of adhesion and thus can retain the characteristics required for gear oil and provides energy-saving parameters and high efficiency when used in mechanical, automatic or continuously variable transmissions of automobiles, or in industrial systems gears.

Claims (10)

1. A lubricating oil composition comprising a lubricating base oil containing (A) an incomplete ester of polyhydric alcohol and carboxylic acid in an amount of 5 to 75% based on the total weight of the base oil and having a kinematic viscosity at a temperature of 100 ° C of 1 to 15 mm ² / s, the composition having a kinematic viscosity at 100 ° C from 1 to 20 mm ² / s, a polyhydric alcohol is an alcohol of dihydric to hexahydric, and the carboxylic acid is selected from the group consisting of monobasic acids, polybasic acids and with Thou. 2. The lubricating oil composition according to claim 1, wherein the polyhydric alcohol is selected from the group consisting of ethylene glycol, propylene glycol, neopentyl glycol, glycerin, trimethylol ethane, trimethylol propane, pentaerythritol, sorbitan, and mixtures thereof. 3. The lubricating oil composition according to claim 1, wherein the monobasic acid is a monobasic carboxylic acid having from 2 to 24 carbon atoms, and the polybasic acid is a dibasic acid having from 2 to 16 atoms, or trimellitic acid. 4. The lubricating oil composition according to claim 1, in which (A) a partial ester of a polyhydric alcohol and a carboxylic acid is an incomplete ester of trimethylolpropane and a monobasic carboxylic acid. 5. The lubricating oil composition according to claim 1, in which the lubricating base oil contains (A) a partial ester of polyhydric alcohol and carboxylic acid in an amount of from 10 to 70% based on the total weight of the base oil. 6. The lubricating oil composition according to claim 1, in which the lubricating base oil contains (A) a partial ester of polyhydric alcohol and a carboxylic acid in an amount of from 5 to 75 and a monoester comprising the rest, based on the total weight of the base oil. 7. The lubricating oil composition according to claim 1, further comprising (B) a poly (meth) acrylate compound made up of a repeating structural unit represented by formula (I) below, in an amount of from 0.01 to 20 wt.%:

in which R ¹ represents hydrogen or methyl and R ² represents a hydrocarbon group having from 1 to 30 carbon atoms. 8. The lubricating oil composition according to claim 1, wherein the composition has an adhesion coefficient of 0.013 or less. 9. The lubricating oil composition according to claim 1, wherein the composition has a coefficient of adhesion to kinematic viscosity (mm ² / s) at a temperature of 100 ° C, which is 1.2 × 10 ^-3 or less. 10. The lubricating oil composition according to claim 1, wherein the composition has a Brookfield dynamic viscosity at a temperature of −40 ° C. at a level of 40,000 mPa · s or less.