CN113557290A

CN113557290A - Lubricating composition for preventing pre-ignition

Info

Publication number: CN113557290A
Application number: CN202080020166.3A
Authority: CN
Inventors: S·法尤莱; G·帕品
Original assignee: Total Marketing Services SA
Current assignee: TotalEnergies Marketing Services SA
Priority date: 2019-02-04
Filing date: 2020-01-31
Publication date: 2021-10-26
Also published as: US20220119729A1; KR20210134906A; WO2020161007A1; FR3092337B1; JP2022519612A; FR3092337A1; EP3921396A1

Abstract

The present invention relates to the use of a lubricating composition comprising (i) at least one dithiocarbamate compound; and (ii) at least one base oil, said composition being used during at least one oil change interval without the addition of fresh lubricating composition, the dithiocarbamate compound being present in an amount of less than or equal to 1% by weight relative to the total weight of the lubricating composition.

Description

Lubricating composition for preventing pre-ignition

Technical Field

The present invention relates to the field of lubricants, particularly useful in vehicle engines, in particular lubricating compositions which make it possible to prevent or reduce pre-ignition (pre-ignition) in the engine.

Background

Under ideal conditions, when a fuel mixture (particularly a fuel mixture of fuel and air) is ignited in a combustion chamber inside a cylinder by a spark generated by a spark plug, normal combustion in the engine by spark ignition occurs. Such normal combustion is generally characterized by a flame front that expands through the combustion chamber in an orderly and controlled manner.

However, in some cases, the air/fuel mixture may be ignited prematurely via a flame source before ignition by a spark from a spark plug, which results in a phenomenon known as pre-ignition.

And it is preferable to reduce or even eliminate pre-ignition, as pre-ignition typically results in significant increases in temperature and pressure in the combustion chamber, with significant negative effects on the efficiency and overall performance of the engine. In addition, pre-ignition can cause significant damage to cylinders, pistons, spark plugs, and valves in the engine, and in some cases can even lead to engine failure, even engine damage.

Recently, Low-speed pre-Ignition (in the english "Low-speed pre-Ignition" or LSPI) has been identified by car manufacturers as a potential problem for engines of reduced size (so-called "downsize"). LSPI typically occurs at low speeds and high loads and can cause severe damage to the piston and/or cylinder.

Furthermore, the prevention and/or reduction of pre-ignition (in particular LSPI) must be maintained over time, i.e. during long-term use of the lubricating composition, e.g. between two oil changes or after a certain number of kilometres of driving.

Prior Art

Several theories have been proposed in an attempt to explain this complex phenomenon. In particular, it has been observed that the presence of small amounts of lubricant mixed with the fuel in the combustion chamber can exacerbate pre-ignition. Furthermore, a link may also be established between the presence of deposits in the combustion chamber and the occurrence of the LSPI phenomenon. Finally, the design of the engine itself may affect pre-ignition.

Thus, this phenomenon has proven to be very complex and difficult to predict. As mentioned above, the properties of the lubricant contribute greatly to this; lubricating compositions have therefore been proposed which make it possible to prevent or reduce the risk of pre-ignition (in particular LSPI).

Thus, application WO2015/023559 describes a method for reducing pre-ignition by adding to the lubricating composition an additive capable of retarding ignition, selected from organic compounds comprising at least one aromatic ring.

However, these light organic compounds tend to result in an excessive increase in the volatility of the lubricant.

It is thus also proposed to add polyalkylene glycols to the lubricating composition in order to prevent or reduce pre-ignition in the engine, as described in application WO2017/021521, or to add an organomolybdenum compound selected from molybdenum dithiophosphates and sulfur-free molybdenum complexes according to WO 2017/021523.

It is also known that the level of calcium-based detergent has a strong influence on triggering the LSPI. It has therefore been proposed to replace calcium-based detergents with magnesium-based detergents in lubricating compositions intended to reduce LSPI in vehicle engines.

The inventors have observed that the phenomenon of pre-ignition is exacerbated during long-term use of the lubricating composition. Thus, in the case of so-called "used" lubricating compositions, the pre-ignition is particularly exacerbated.

In particular, lubricating compositions have been shown to exhibit a reduction in LSPI when they are fresh and a deterioration in their performance when they are worn, as is demonstrated in particular in the following documents: low-speed prediction, Engine Technology International, 2018, month 9.

Finally, the solutions proposed in the prior art for fresh lubricating compositions have proved to be insufficient in the case of worn compositions.

Furthermore, a combination of at least one metal molybdenum dithiocarbamate compound and at least one methylene bis (dibutyldithiocarbamate) has been described in application WO 2013/182581, with the aim of maintaining the fuel economy performance of the lubricating composition.

However, this document does not suggest in any way the possible effect of one of the additives used in combination or alone on the pre-ignition phenomena that may occur in the engine.

The document by Hong Liu et al (SAE International Journal of Fuels and Lubricants,10(3),2017) relates to the development of low viscosity gasoline engine oils aimed at improving gasoline economy while preventing LSPI pre-ignition. However, this document does not mention at all the specific content of dithiocarbamate compounds nor its specific benefit for preventing the pre-ignition phenomena occurring in the engine.

In the meaning of the present invention, the term "used lubricating composition" is understood to mean a lubricating composition used during at least one oil change interval, i.e. during a vehicle travel distance of 10000-.

The expression "long-term" or "long-term" as used according to the present invention means that the use of the lubricating composition extends to worn lubricating compositions.

In the meaning of the present invention, the term "fresh lubricating composition" is understood to mean a lubricating composition that has never been used in an engine.

In the meaning of the present invention, the term "aged lubricating composition" is understood to mean a lubricating composition that has undergone artificial aging by simulating the conditions of use of the lubricating composition in an engine. This artificial ageing makes it possible to reproduce in an accelerated manner the ageing of the oil when it is used in the engine during the oil change interval. In particular, this relates to a lubricating composition which has undergone iron-catalysed oxidation at a temperature above 150 ℃, preferably between 150 ℃ and 170 ℃ for a duration of at least 110 hours, preferably between 120 hours and 150 hours, according to the GFC Lu-43A-11 method.

All embodiments defined according to the present invention for the used lubricating composition are applicable to the aged lubricating composition.

As mentioned above, the pre-ignition phenomenon tends to be exacerbated during use of the lubricating composition and is therefore only truly effective when the lubricating composition is fresh. For obvious reasons, there is a need to propose a solution that prevents pre-ignition that is long-lasting over time.

There is therefore still a need to propose such a lubricating composition: the lubricating composition has the ability to prevent and/or reduce pre-ignition (particularly LSPI) of an engine (particularly a motor vehicle engine) in a prolonged manner during its use, more precisely from the age of the lubricating composition.

Prior solutions in the prior art recommend the selection of specific additives that can contribute to the reduction of the pre-ignition phenomena occurring in the engine. However, while lubricating compositions may incorporate a wide variety of different additives to impart particularly beneficial properties, it is unpredictable which additives will have a beneficial effect on preventing pre-ignition, not to mention long-term beneficial effects.

There is therefore still a need to propose the following additives: the additive enables the prevention and/or reduction of pre-ignition phenomena that may occur during long-term use thereof in an engine, once used in a lubricating composition.

Finally, there is a need for a solution to prevent pre-ignition that does not require the addition of fresh lubricating composition to the engine during long-term use of the engine, particularly between oil change intervals of the engine.

There is therefore still a need to propose such a lubricating composition: the lubricating composition enables the prevention and/or reduction of pre-ignition during its use in an engine without the need to add the lubricating composition between each engine oil change interval.

For obvious reasons, there is also a need to propose lubricating compositions which exhibit good stability, in particular good storage stability.

The present invention is intended to respond particularly to this need.

Disclosure of Invention

Summary of The Invention

Thus, the present invention relates according to a first aspect thereof to the use of a lubricating composition comprising a lubricating composition for preventing and/or reducing pre-ignition, in particular low speed pre-ignition, in a vehicle engine, preferably a motor vehicle engine

(i) At least one dithiocarbamate (dithiocarbamate) compound; and

(ii) at least one base oil, at least one oil,

said composition is used during at least one oil change interval, preferably during a distance travelled by the vehicle of 10000km to 30000km, without the addition of fresh lubricating composition,

the dithiocarbamate compound is present in an amount less than or equal to 1 wt.%, relative to the total weight of the lubricating composition.

In the meaning of the present invention, the term "motor vehicle" is understood to mean a vehicle comprising at least one wheel, preferably at least two wheels, driven by an engine, in particular a spark-ignited internal combustion engine, in particular a diesel or spark-ignited, rotary or reciprocating-piston internal combustion engine. Such engines may be, for example, two-stroke or four-stroke gasoline or diesel engines.

According to the present invention, the prevention and/or reduction of pre-ignition of used lubricating compositions relative to fresh lubricating compositions is preferentially measured.

Contrary to all expectations and as appears from the examples given below, the inventors have demonstrated that the addition of at least one dithiocarbamate compound in an aged lubricating composition enables a significant improvement in the ignition temperature of said composition (measured in particular by high pressure differential scanning calorimetry) and thus a retardation of the pre-ignition phenomena, in particular LSPI, that may occur during its use in engines. The ignition temperature here represents the starting temperature of the exothermic peak during warming, measured by High Pressure Differential Scanning Calorimetry, known as HPDSC (High-Pressure Differential Scanning Calorimetry).

This result is particularly surprising in view of the teaching of the document Low-speed pre-ignition (Engine technology international, 9 months 2018), according to which an oil comprising molybdenum dialkyldithiocarbamate is found to have a reduced performance in terms of LSPI when it is worn out.

The dithiocarbamate compound present in the lubricating composition according to the invention thus advantageously makes it possible to prevent the phenomenon of pre-ignition, in particular LSPI, when it is used during at least one oil change interval, preferably during a distance travelled by the vehicle of 10000km to 30000 km.

Thus, the lubricating composition does not have to be renewed during its use, for example between two oil changes of the engine, in order to effectively keep preventing and/or reducing the pre-ignition phenomenon, in particular the low speed pre-ignition phenomenon.

Furthermore, the inventors have surprisingly found that the use of a dithiocarbamate compound in the lubricating composition used according to the invention in a content of less than or equal to 1% by weight also enables satisfactory stability, in particular storage stability, of the composition to be maintained.

The storage stability is assessed visually by rating the deposits formed during storage of the composition, generally for a period of 1 day to 3 months and at different temperatures, typically at 0 ℃, ambient temperature and 60 ℃, and the appearance of the lubricating composition.

According to another of its aspects, the subject of the present invention is also the use of at least one dithiocarbamate compound, in particular a dithiocarbamate compound as defined below, in a lubricating composition comprising at least one base oil, for preventing and/or reducing pre-ignition, in particular low-speed pre-ignition, in a vehicle engine, preferably a motor vehicle engine, said lubricating composition being used during at least one oil change interval, preferably during a vehicle driving distance of 10000km to 30000km, without the addition of fresh lubricating composition.

According to another of its aspects, the subject of the present invention is also the use of at least one dithiocarbamate compound, in particular a dithiocarbamate compound as defined below, in a lubricating composition comprising at least one base oil for limiting the deterioration of the performance of said composition in terms of preventing and/or reducing pre-ignition, in particular low-speed pre-ignition, in a vehicle engine, preferably in a motor vehicle engine, after its use during at least one oil change interval, preferably during a distance travelled by a vehicle of 10000km to 30000km, without the addition of fresh lubricating composition.

The subject matter of the invention also relates to a method for preventing and/or reducing pre-ignition, in particular low-speed pre-ignition, in a vehicle engine, preferably a motor vehicle engine, preferably for a long period of time, comprising at least the following steps:

a) contacting the engine with a lubricating composition comprising at least one base oil and at least one dithiocarbamate compound, said dithiocarbamate compound being present in an amount less than or equal to 1% by weight relative to the total weight of the lubricating composition;

b) the engine is operated during at least one oil change interval, preferably during a distance travelled by the vehicle of 10000km to 30000km, without adding fresh lubricating composition.

The present invention also relates to the use of a lubricating composition comprising (i) at least one dithiocarbamate compound; and

(ii) at least one base oil, at least one oil,

said composition being subjected to iron-catalysed oxidation according to the GFC Lu-43A-11 method at a temperature higher than 150 ℃, preferably between 150 ℃ and 170 ℃, for a duration of at least 110 hours, preferably between 120 hours and 150 hours,

the dithiocarbamate compound is preferably present in an amount less than or equal to 1% by weight relative to the total weight of the lubricating composition.

Detailed Description

Composition comprising a metal oxide and a metal oxide

Dithiocarbamate compounds

As mentioned above, the lubricating composition used according to the present invention comprises (i) at least one dithiocarbamate compound.

The dithiocarbamate compound may be selected from the group consisting of metal dithiocarbamates, bisdithiocarbamates, and mixtures thereof, among others.

The metal dithiocarbamate can be more particularly defined according to the following general formula (I):

wherein the radical R₁And R₂Independently of one another, represent an optionally substituted hydrocarbon-based radical comprising from 1 to 30 carbon atoms, preferably from 4 to 18 carbon atoms, M represents a metal cation and n is the valence of the metal cation.

Preferably, M is molybdenum.

The metal dithiocarbamates which can be used according to the invention are compounds which are well known to the person skilled in the art and can be obtained by any method which is also known to the person skilled in the art. Examples of processes for preparing these compounds are described in particular in patent US 2492314.

The metal dithiocarbamates are known for their use as friction modifying additives in lubricating compositions.

The MoDTC compounds used according to the present invention may be selected from compounds wherein the core comprises two molybdenum atoms (dimeric MoDTC) and compounds wherein the core comprises three molybdenum atoms (trimeric MoDTC).

Trimeric MoDTC compounds generally have the formula Mo₃S_kL_mWherein:

k represents an integer at least equal to 4, preferably ranging from 4 to 10, advantageously from 4 to 7;

m represents an integer of 1 to 4; and

l represents an alkyldithiocarbamate radical comprising from 1 to 100 carbon atoms, preferably from 1 to 40 carbon atoms, advantageously from 3 to 20 carbon atoms.

As examples of trimeric MoDTC compounds, mention may be made of the compounds described in patent application WO-98-26030 and the preparation thereof.

An example of a trimeric MoDTC compound is known by the name Infineum International Ltd

A compound sold by C9455B.

Preferably, the MoDTC compound used in the lubricating composition used according to the present invention is a dimeric MoDTC compound. As examples of dimeric MoDTC compounds, mention may be made of the compounds described in patent EP-0757093 and the process for their preparation.

According to a particular embodiment of the invention, the metal dithiocarbamate compound is molybdenum dithiocarbamate (MoDTC) of formula (Ia) below:

wherein the radical R₁And R₂Independently of each other as defined above, are,

X¹、X²、X³and X⁴Are the same or different and independently represent an oxygen atom or a sulfur atom.

Advantageously, X¹And X²Can represent an oxygen atom and X³And X⁴May represent a sulfur atom.

Advantageously, the MoDTC compound is selected from compounds of formula (Ia) wherein:

X¹and X²Represents a hydrogen atom, and is represented by,

X³and X⁴Represents a sulfur atom, and represents a sulfur atom,

R₁represents an alkyl group containing 8 carbon atoms or an alkyl group containing 13 carbon atoms,

R₂represents an alkyl group containing 8 carbon atoms or an alkyl group containing 13 carbon atoms.

Thus, advantageously, the MoDTC compound can be selected from compounds of formula (Ia'):

wherein R is₁And R₂As defined for formula (I) above.

As a specific example of the MoDTC compound, mention may be made of the product Molyvan sold by the company r.t. vanderbilt company

Molyvan

Or Molyvan

Or the product Sakuralube sold by Adeka corporation

Sakuralube

Sakuralube

Or Sakuralube

The lubricating composition used according to the invention can also be used with an organomolybdenum compound selected from the MoDTC compounds described in patent application WO-2012-141855.

The bisdithiocarbamates can be more particularly defined according to the following general formula (II):

wherein:

-a group R₃And R₄Independently of one another, represent an optionally substituted hydrocarbon-based radical comprising from 1 to 30 carbon atoms, preferably from 2 to 24 carbon atomsAnd more preferably from 3 to 8 carbon atoms; and is

-a group R₅Represents a hydrocarbon-based group containing 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms.

The bisdithiocarbamate compounds which can be used according to the invention are compounds which are well known to the person skilled in the art and can be obtained by any method which is also known to the person skilled in the art.

The bisdithiocarbamates are known for their use as antioxidant additives in lubricating compositions.

It may advantageously involve methylenebis (dibutyldithiocarbamate).

As examples of commercial products, mention may be made of those sold by Vanderbilt

7723 or sold by Rhein Chemie

RC 6340。

According to one embodiment, the lubricating composition used according to the invention comprises a mixture of at least one metal dithiocarbamate and at least one bisdithiocarbamate, in particular as defined above.

Thus, the dithiocarbamate compound used in the composition according to the invention may more particularly be selected from molybdenum dithiocarbamate (MoDTC), methylene bis (dibutyldithiocarbamate) (mDTC) and mixtures thereof.

The dithiocarbamate compound is present in the lubricating composition used according to the invention in a content of less than or equal to 1% by weight relative to the total weight of the composition.

In particular, the dithiocarbamate compound may be present in the lubricating composition used according to the invention in a content strictly greater than 0.01% by weight, in particular from 0.02% to 1% by weight, preferably from 0.05% to 0.7% by weight, more preferably from 0.1% to 0.5% by weight, relative to the total weight of the composition.

When the dithiocarbamate compound is present in the lubricating composition used according to the invention in an amount of more than 0.01% by weight relative to the total weight of the composition, the ignition temperature, measured in particular by high pressure differential scanning calorimetry, is higher than that observed at contents below 0.01%.

Thus, a composition comprising a dithiocarbamate compound content of greater than 0.01% by weight relative to the total weight of the composition makes it possible to more significantly delay the phenomena of pre-ignition, in particular LSPI, that may occur when it is used in an engine.

Base oil

As mentioned above, the lubricating composition used according to the present invention comprises (ii) at least one base oil.

The one or more base oils may be mineral, synthetic or natural, animal or vegetable derived oils as known to those skilled in the art.

In particular, the mineral or synthetic oils commonly used in lubricating compositions belong to one of groups I to V according to the categories defined in the API classification (or their equivalents according to the ATIEL classification), as summarized in table 1 below.

The API classification is defined in the American Petroleum institute 1509 "Engine oil Licensing and verification System" (17 th edition, 9 months 2012).

The ATIEL classification is defined in "The ATIEL Code of Practice" (No. 18, 11/2012).

TABLE 1

There is generally no restriction on the use of the different base oils for producing the lubricating composition used according to the invention, except that they must have properties suitable for use in engines, especially vehicle engines, in particular viscosity, viscosity index, sulphur content, oxidation resistance.

Mineral base oils include all types of base oils obtained by: the crude oil is distilled at atmospheric pressure and vacuum, and then subjected to refining operations such as solvent extraction, deasphalting (deasphalting), solvent deparaffinization, hydrotreating, hydrocracking and hydroisomerization, and hydrofinishing.

The synthetic base oil may be selected from esters, silicones, glycols, polybutenes, Polyalphaolefins (PAO), alkylbenzenes or alkylnaphthalenes.

The base oil may also be an oil of natural origin, such as an ester of an alcohol and a carboxylic acid, which may be obtained from natural sources such as sunflower oil, rapeseed oil, palm oil, soybean oil, and the like.

The base oil may more particularly be selected from synthetic oils, mineral oils and mixtures thereof.

According to one embodiment, the lubricating composition used according to the invention comprises at least one base oil selected from: group III oils, group IV oils, and mixtures thereof.

Additive agent

The composition used according to the invention may also comprise one or more additives, as defined more precisely hereinafter, which are different from the dithiocarbamate compounds defined above.

Additives that may be incorporated into the composition according to the present invention may be selected from the group consisting of antioxidants other than the bisdithiocarbamate compound defined above, detergents, viscosity index improvers, friction modifiers other than the metal dithiocarbamate compound defined above, anti-wear additives, extreme pressure additives, dispersants, pour point improvers, anti-foaming agents, and mixtures thereof.

It will be appreciated that the nature and amount of the additives used are selected so as not to affect the performance of the lubricating composition, particularly with respect to preventing and/or reducing pre-ignition (especially LSPI) in the engine.

These additives may be introduced individually and/or in the form of mixtures, similar to those already provided on the market for commercial vehicle engine lubricant formulations, with performance levels as defined by ACEA (Association des structures Europ elemental ens' Automobiles) and/or API (American Petroleum institute), as is well known to those skilled in the art.

According to a particular embodiment, the composition used according to the invention may also comprise at least one antioxidant additive, more particularly different from the bisdithiocarbamate compound defined above.

The antioxidant additive typically enables the degradation of the composition in use to be delayed. This degradation may be manifested in particular by the formation of deposits, the presence of sludge or an increase in the viscosity of the composition. The antioxidant additive is particularly useful as a structure-breaking agent or free radical inhibitor for hydroperoxides.

Among the usual antioxidant additives, mention may be made of phenolic antioxidant additives, aminic antioxidant additives, phosphorus-sulfur antioxidant additives. Some of these antioxidant additives (e.g., phosphorus sulfur antioxidant additives) may be ash generators. The phenolic antioxidant additives may be ashless, or may be in the form of neutral or basic metal salts.

The antioxidant additive may in particular be chosen from sterically hindered phenols, sterically hindered phenol esters and sterically hindered phenols containing thioether bridges, diphenylamines, substituted by at least one C₁-C₁₂Alkyl group substituted diphenylamines, N, N' -dialkyl-aryl diamines, and mixtures thereof.

According to the invention, the sterically hindered phenol is preferably chosen from compounds comprising a phenol group whose carbon bearing an alcohol function is substituted by at least one C at least one carbon ortho to the carbon bearing the alcohol function₁-C₁₀Alkyl radical, preferably C₁-C₆Alkyl radical, preferably C₄Alkyl groups, preferably tert-butyl groups.

Aminated compounds are another class of antioxidant additives that can be used, optionally in combination with phenolic antioxidant additives.

Examples of aminating compounds are aromatic amines, e.g. of the formula NR⁴R⁵R⁶Wherein R is⁴Represents an optionally substituted aliphatic or aromatic radical, R⁵Represents an optionally substituted aromatic radical, R⁶Represents a hydrogen atomA proton, an alkyl group, an aryl group or of the formula R⁷S(O)_zR⁸Wherein R is⁷Represents an alkylene group or alkenylene group, R⁸Represents an alkyl group, an alkenyl group or an aryl group and z represents 0, 1 or 2.

Sulfurized alkylphenols or their alkali and alkaline earth metal salts can also be used as antioxidant additives.

Another class of antioxidant additives are copper compounds, such as copper thiophosphates or dithiophosphates, salts of copper and carboxylic acids, dithiocarbamates, sulfonates, phenates, copper acetylacetonate. Salts, succinic anhydrides or acid salts of copper I and II may also be used.

The compositions used according to the invention may comprise all types of antioxidant additives known to the person skilled in the art.

Advantageously, the composition used according to the invention comprises at least one antioxidant additive chosen from diphenylamine, phenols, esters of phenols and mixtures thereof.

The composition used according to the invention comprises from 0.05 to 2% by weight, preferably from 0.5 to 1% by weight, relative to the total weight of the composition, of at least one antioxidant additive.

According to another embodiment, the composition used according to the invention may also comprise at least one detergent additive (additif tergent).

Detergent additives generally enable the formation of deposits on the surface of metal parts to be reduced by dissolving the byproducts of oxidation and combustion.

Detergent additives useful in the compositions used according to the present invention are generally known to those skilled in the art. Detergent additives may be anionic compounds comprising a lipophilic long hydrocarbon chain and a hydrophilic top end. The relevant cation may be a metal cation of an alkali metal or alkaline earth metal.

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

These metal salts generally contain a stoichiometric or excess (and thus an amount greater than stoichiometric) of the metal. This thus relates to overbased detergent additives; the excess metal to impart overbased character to the detergent additive is then typically in the form of an oil-insoluble metal salt, such as a carbonate, hydroxide, oxalate, acetate, glutamate, preferably a carbonate.

The compositions used according to the present invention may comprise any type of detergent additive known to those skilled in the art.

Advantageously, the composition used according to the invention comprises at least one detergent additive chosen from: alkaline earth metal salts, preferably selected from calcium salts, magnesium salts and mixtures thereof.

In particular, when the detergent is selected from alkaline earth metal salts, the detergent additive may be added to the composition to provide a metallic element content of 150ppm to 2000ppm, preferably 250ppm to 1500 ppm.

According to yet another embodiment, the composition used according to the invention may further comprise a viscosity index improving additive.

As examples of viscosity index improving additives, mention may be made of polymeric esters, hydrogenated or non-hydrogenated homopolymers or copolymers of styrene, butadiene and isoprene, polyacrylates, Polymethacrylates (PMA) or olefin copolymers, in particular ethylene/propylene copolymers.

Advantageously, the composition used according to the invention comprises at least one viscosity index improving additive chosen from: hydrogenated or non-hydrogenated homopolymers or copolymers of styrene, butadiene and isoprene. Preferably, it is a hydrogenated styrene/isoprene copolymer.

The composition used according to the invention may for example comprise from 2% to 15% by weight of viscosity index improving additive relative to the total weight of the composition.

Antiwear and extreme pressure additives are used to protect friction surfaces by forming a protective film that adsorbs onto these surfaces.

A wide variety of anti-wear additives exist. Preferably for the lubricating composition according to the invention, the antiwear additive is selected from the group consisting of phosphorus sulphur additives,such as metal alkylthiophosphates, especially zinc alkylthiophosphates, and more particularly zinc dialkyldithiophosphate or ZnDTP. Preferred compounds have the formula Zn ((SP (S)) (OR)²)(OR³))₂Wherein R is²And R³Identical or different, independently represent an alkyl group, preferably an alkyl group comprising from 1 to 18 carbon atoms.

Amine salts of phosphoric acid esters are also anti-wear additives, which may be used in the compositions according to the invention. However, the phosphorus provided by these additives may act as a poison to automotive catalytic systems because these additives are ash generators. These effects can be minimized by partial replacement of the amine phosphate salt with additives that do not provide phosphorus, such as polysulfides, especially sulfur-containing olefins.

The composition used according to the invention may comprise from 0.01 to 6% by weight, preferably from 0.05 to 4% by weight, more preferably from 0.1 to 2% by weight, of antiwear and extreme pressure additives, relative to the total weight of the composition.

The composition used according to the invention is preferably free of antiwear and extreme pressure additives. In particular, the composition used according to the invention may be free of phosphorus-containing additives.

The composition used according to the invention may comprise at least one friction-improving additive, which is more particularly different from the metal dithiocarbamate compound defined above. The friction modifying additive may be selected from the group consisting of metal element providing compounds and ash-free compounds. Among the compounds providing the metallic element, complexes of transition metals such as Mo, Sb, Sn, Fe, Cu, Zn, whose ligands may be hydrocarbon compounds containing oxygen, nitrogen, sulfur or phosphorus atoms, may be mentioned. The ash-free friction modifying additive is typically of organic origin and may be selected from monoesters of fatty acids and polyols, alkoxylated amines, alkoxylated fatty amines, fatty epoxides, borated fatty epoxides, fatty amines or fatty acid glycerides. According to the invention, the fatty compound comprises at least one hydrocarbon group comprising from 10 to 24 carbon atoms.

The composition used according to the invention may comprise from 0.01% to 2% by weight or from 0.01% to 5% by weight, preferably from 0.1% to 1.5% by weight or from 0.1% to 2% by weight, of friction-improving additive, relative to the total weight of the composition.

Advantageously, the composition used according to the invention is free of friction modifying additives other than the metal dithiocarbamate compounds defined above.

The composition used according to the invention may also comprise at least one pour point depressant additive.

Pour point depressant additives generally improve the cold behavior of the composition by slowing the formation of paraffin crystals.

Mention may be made, as examples of pour point depressant additives, of polyalkylmethacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalenes, alkylated polystyrenes.

Furthermore, the composition used according to the invention may comprise at least one dispersant.

The dispersant may be selected from Mannich bases, succinimides and derivatives thereof.

The compositions used according to the invention may for example comprise from 0.2 to 10% by weight of dispersant, relative to the total weight of the composition.

Applications of

The lubricating composition according to the invention is more particularly intended for use in engines, in particular vehicle engines, especially gasoline vehicle engines.

It thus advantageously has properties suitable for use in engines, in particular vehicle engines, in particular viscosity, viscosity index, sulphur content and oxidation resistance.

Thus, preferably, the lubricating composition has a kinematic viscosity measured according to standard ISO 3104 at 100 ℃ of 5 to 20mm²S, preferably 5 to 15mm²S and more particularly 6 to 13mm²/s。

As indicated above, the composition as described above has the advantage that it makes it possible to prevent and/or reduce the pre-ignition that occurs in said engine for a long time, in particular after the use of a duration corresponding to at least one oil change interval, through its use in the engine.

The present invention therefore relates to the use of a composition as defined above, for preventing and/or reducing pre-ignition, in particular low-speed pre-ignition, in a vehicle engine, preferably in a motor vehicle engine, said composition being used during at least one oil change interval, preferably during a vehicle distance of from 10000km to 30000km, without the addition of fresh lubricating composition.

In particular, the pre-ignition phenomenon is observed at low engine speeds (LSPI) and is further exacerbated in direct injection engines, particularly in reduced size engines.

The present application therefore also relates to the use of a lubricating composition for preventing and/or reducing low speed pre-ignition (LSPI) in a vehicle engine, preferably a motor vehicle engine, the lubricating composition comprising:

(i) at least one dithiocarbamate compound; and

(ii) at least one base oil, at least one oil,

the composition is used during at least one oil change interval, preferably during a distance travelled by the vehicle of 10000km to 30000km, without the addition of fresh lubricating composition.

Particularly surprisingly, the present inventors have found that the presence of a dithiocarbamate compound in an aged lubricating composition enables the occurrence of pre-ignition phenomena in the engine to be significantly reduced.

The present invention therefore also relates to the use of at least one dithiocarbamate compound, in particular a dithiocarbamate compound as defined above, in a lubricating composition comprising at least one base oil for preventing and/or reducing pre-ignition, in particular low speed pre-ignition, in a vehicle engine, preferably a motor vehicle engine, said lubricating composition being used during at least one oil change interval, preferably during a vehicle distance of from 10000km to 30000km, without the addition of fresh lubricating composition.

As demonstrated in the examples below, the selection of a specific additive, namely a dithiocarbamate compound, makes it possible to propose a lubricating composition which makes it possible to prevent and/or reduce the phenomena of pre-ignition which can occur during its prolonged use in an engine, without the addition of fresh lubricating composition.

Thus, as is also demonstrated in the examples, the lubricating composition according to the present invention has an ignition temperature higher than that obtained for a lubricating composition that does not comprise any dithiocarbamate compound or comprises additional additives other than the dithiocarbamate compound required according to the present invention.

In other words, the properties of the dithiocarbamate compound cannot be clearly deduced from its previously possible known function.

The composition as defined above thus has the advantage of preventing and/or reducing pre-ignition in the engine by its prolonged use in the engine.

The invention thus also relates to a method for preventing and/or reducing pre-ignition, in particular low-speed pre-ignition, in a vehicle engine, preferably a motor vehicle engine, preferably for a long period of time, comprising at least the following steps:

As mentioned above, the used lubricating composition used according to the present invention has an ignition temperature which is higher than the ignition temperature of used lubricating compositions which do not meet this definition.

In particular, the increase in temperature, measured according to the procedure detailed in the examples, is at least 2%, preferably at least 4%, more preferably at least 5% relative to the ignition temperature of a lubricating composition comprising a base oil but no dithiocarbamate compound. This ignition temperature corresponds to the following temperatures: from this temperature, an exothermic reaction is initiated.

The present invention therefore also relates to the use of at least one dithiocarbamate compound, in particular a dithiocarbamate compound as defined above, for increasing the ignition temperature of a lubricating composition, measured by high pressure differential scanning calorimetry, especially by at least 2%, preferably by at least 4%, relative to a used lubricating composition which does not contain any dithiocarbamate compound, which is used during at least one oil change interval, preferably during a vehicle distance of from 10000km to 30000km, without adding fresh lubricating composition.

According to the invention, the particular, advantageous or preferred properties of the composition according to the invention enable the definition of the use according to the invention which is likewise particular, advantageous or preferred.

Throughout the specification including the claims, unless otherwise specified, the expression "comportant un (including or comprising …)" is to be understood as being synonymous with "comportant au moinsun (including or comprising at least one or at least one …)".

The expressions "between", "including or including.. to.", "formed from … to …", "from.. to." are to be inclusive of the stated values unless otherwise stated.

In the specification and examples, percentages are by weight unless otherwise indicated. The percentages are therefore expressed by weight relative to the total weight of the composition. Unless otherwise stated, temperatures are in degrees celsius and pressures are atmospheric pressure unless otherwise stated.

Detailed Description

The invention will now be described by way of the examples given below, which are of course given by way of non-limiting illustration of the invention.

Examples

Method

Method for aging lubricating oil

The oils used in the following examples were subjected to simulated aging. The simulation was carried out by catalytic oxidation of the oil with 100ppm iron at 170 ℃ for 144 hours according to method GFC-Lu-43A-11.

Laboratory measurement of pre-ignition propensity

In the examples detailed below, the tendency to pre-ignition is determined on the basis of the onset temperature of the exothermic reaction measured by High-Pressure Differential Scanning Calorimetry, so-called "HPDSC" (High-Pressure Differential Scanning Calorimetry).

This measurement was carried out using the device Mettler Toledo LG3300 according to the procedure detailed below:

-weighing 2 ± 0.05mg of the sample to be analyzed in the cell;

-placing the open sample and the reference on the surface of the detector;

-closing the cell (cell) in a sealed and mechanical manner;

-applying a pressure of 1 to 20 bar to the cell;

-the temperature of the sample is equilibrated at a measurement starting temperature of 20-80 ℃, preferably 30-70 ℃, for 1-15 minutes, preferably 2-10 minutes;

-applying at least one temperature ramp to the sample between the starting temperature and a temperature of 100 ℃ to 400 ℃, preferably 150 ℃ to 350 ℃, more preferably 200 ℃ to 300 ℃.

Software such as STARe software enables visualization of the heat exchange differences between the sample and the reference.

The temperature at which the exotherm occurs on the curve thus obtained is compared to the phenomenon of pre-ignition, for example LSPI.

This temperature is time dependent. Thus, the higher it is, the more delayed the pre-ignition in the combustion chamber will be during use of the composition.

Measurement of stability

The stability of the compositions was evaluated by rating the change in appearance after storage at different temperatures.

After preparation of the lubricating composition, three samples were dispensed into test tubes and then they were closed.

The tubes were stored for 3 months under the following conditions:

one test tube is stored in a chamber maintained at a constant temperature of about 60 ℃,

-one test tube is stored at ambient temperature;

one test tube is stored in a refrigerated cabinet at about 0 ℃.

During the first month, ratings were performed on the first day, the third day, then once a week, and then once every two weeks. Samples that reached a rating of 5 were discarded even before the end of three months of storage.

The rating is done according to three criteria:

-clarity: the test tube was visually as received;

general evaluation of deposits: inverting the tube and evaluating the deposit; and

-the form of a deposit.

Depending on the form of the deposit, the diameter (D) and/or the thickness (E) (in mm) of the deposit can also be determined.

The composition is defined as stable or unstable according to the rating obtained for each of these three criteria.

Example 1: preparation of lubricating compositions

Lubricating compositions a0 to a4 were prepared.

Their kinematic viscosity at 100 ℃ is determined according to standard ISO 3104 and their properties in terms of flammability tendency are measured.

The details of the compositions are given in table 2 below, wherein the proportions of the various compounds are expressed in mass%.

TABLE 2

Additive package is a mixture of different additives commonly and commercially available in the lubricant field. It comprises an antiwear additive of the zinc dithiophosphate type, a detergent based on calcium and magnesium and a dispersant of the PIBSI type.

In each composition thus prepared, the amount of calcium was 1350ppm by weight and the amount of magnesium was 300ppm by weight.

The compositions were prepared by mixing the compounds detailed in table 2 at a temperature of about 30-40 ℃.

The lubricating compositions so prepared have kinematic viscosity values at 100 ℃ suitable for their use in engines, particularly vehicle engines.

The lubricating composition is then aged according to the procedure detailed above (aging method).

Example 2: evaluation of LSPI Performance of lubricating compositions

The starting temperature (ignition temperature) of the exothermic reaction of each of the lubricating compositions of example 1 was measured according to the measurement method defined above (laboratory method of pre-ignition tendency).

The results are given in table 3 below.

Composition comprising a metal oxide and a metal oxide	Ignition temperature [ deg.C]
		A0 (ref)	196
A1 (the invention)	210
		A2 (the invention)	211
A3 (the invention)	210
		A4 (the invention)	214

TABLE 3

Compositions a1 to a4 according to the invention comprising molybdenum dithiocarbamate or methylenebis (dibutyldithiocarbamate) have a higher ignition temperature than the same composition (reference composition a0) which does not comprise any dithiocarbamate required according to the invention.

These measurements may thus demonstrate that the addition of at least one dithiocarbamate in the aged lubricating composition enables a significant delay in pre-ignition, especially LSPI, during its use in an engine under conditions which simulate the aging of the lubricating composition.

In the following examples, lubricating compositions were prepared and tested in comparison to a reference lubricating composition that did not contain any dithiocarbamate.

For this reference composition, the kinematic viscosity at 100 ℃ is determined according to standard ISO 3104. The composition is then aged according to the catalytic aging procedure described above. Finally, the starting temperature (light-off temperature) of the exothermic reaction was measured according to the measurement method defined above (laboratory method of pre-ignition propensity).

The details (mass percentages) of the reference composition and the results obtained are listed in table 4 below.

TABLE 4

Example 3: preparation of lubricating compositions

Lubricating compositions B0 to B7 were prepared.

In particular, composition B0 is outside the present invention because it contains a dithiocarbamate compound content of greater than 1% by weight.

Compositions B1 to B7 are according to the invention.

Their kinematic viscosity at 100 ℃ is determined according to standard ISO 3104.

The details of the compositions are given in table 5 below, wherein the proportions of the various compounds are expressed in mass%.

TABLE 5

The compositions were prepared by mixing the compounds detailed in table 5 at a temperature of about 30-40 ℃.

Example 4: evaluation of the Properties of lubricating compositions

The starting temperature (ignition temperature) of the exothermic reaction of each of the lubricating compositions of example 3 was measured according to the measurement method defined above (laboratory method of pre-ignition tendency).

The stability of each lubricating composition was also evaluated according to the procedure defined above (measurement of stability).

The results are given in table 6 below.

Composition comprising a metal oxide and a metal oxide	Ignition temperature [ deg.C]	Stability of
			B0 (outside of the invention)	N/A	Poor stability
B1 (inventive)	208	Good stability
			B2 (inventive)	211	Good stability
B3 (inventive)	210	Good stability
			B4 (inventive)	208	Good stability
B5 (inventive)	210	Good stability
			B6 (inventive)	209	Good stability
B7 (inventive)	206	Good stability

TABLE 6

The compositions B1 to B7 according to the invention comprising a content of molybdenum dithiocarbamate of less than or equal to 1% by weight have good stability, in contrast to the composition B0 which has a poor stability rating with a cloudy appearance.

These measurements thus make it possible to demonstrate that the addition of at least one dithiocarbamate compound to an aged lubricating composition in a content of not more than 1% by weight makes it possible to obtain a lubricating composition which remains stable over time.

Moreover, the ignition temperatures of compositions B1 to B7 were all higher than those obtained with the above-mentioned reference composition, and thus enabled a significant delay of the pre-ignition phenomenon, in particular LSPI, during its use in engines, under conditions simulating the ageing of the lubricating composition.

The results in terms of ignition temperature are particularly better when the dithiocarbamate compound content of the composition is greater than 0.01% by weight.

Example 5: preparation of lubricating compositions

Lubricating compositions C1 and C2 according to the invention were prepared.

The details of the compositions are given in table 7 below, wherein the proportions of the various compounds are expressed in mass%.

TABLE 7

The compositions were prepared by mixing the compounds detailed in table 7 at a temperature of about 30-40 ℃.

Example 6: evaluation of lubricating composition

The results are given in table 8 below.

Composition comprising a metal oxide and a metal oxide	Ignition temperature [ deg.C]	Stability of
			C1 (inventive)	214	Good stability
C2 (inventive)	211	Good stability

TABLE 8

The compositions C1 and C2 according to the invention are stable and have an ignition temperature higher than that measured for the reference composition, thus enabling a significant delay in the pre-ignition phenomenon, in particular LSPI, during its use in engines, under conditions simulating the ageing of the lubricating composition.

Claims

1. Use of a lubricating composition comprising a lubricating composition for preventing and/or reducing pre-ignition, in particular low speed pre-ignition, in a vehicle engine, preferably a motor vehicle engine

(i) At least one dithiocarbamate compound; and

(ii) at least one base oil, at least one oil,

2. Use according to claim 1, wherein the dithiocarbamate compound is selected from the group consisting of metal dithiocarbamates, bisdithiocarbamates and mixtures thereof, preferably from the group consisting of molybdenum dithiocarbamates, methylenebis (dibutyldithiocarbamates) and mixtures thereof.

3. Use according to any one of claims 1 or 2, in which the dithiocarbamate compound is present in a content strictly greater than 0.01% by weight, in particular from 0.02% to 1% by weight, preferably from 0.05% to 0.7% by weight, more preferably from 0.1% to 0.5% by weight, relative to the total weight of the composition.

4. Use according to any one of the preceding claims, wherein the base oil is selected from the group consisting of group III oils, group IV oils and mixtures thereof.

5. Use according to any one of the preceding claims, wherein the lubricating composition further comprises at least one antioxidant additive different from the dithiocarbamate compound as defined in claim 1 or 2, in particular selected from diphenylamine, phenols, esters of phenols and mixtures thereof.

6. Use according to the preceding claim, wherein the lubricating composition comprises from 0.05% to 2% by weight, preferably from 0.5% to 1% by weight, of an antioxidant additive, relative to the total weight of the composition.

7. Use according to any of the preceding claims, wherein the lubricating composition further comprises at least one detergent additive selected from alkaline earth metal salts, preferably selected from calcium salts, magnesium salts and mixtures thereof.

8. Use according to any preceding claim, wherein the lubricating composition comprises at least one viscosity index improving additive selected from hydrogenated or non-hydrogenated homopolymers or copolymers of styrene, butadiene and isoprene, preferably it is a hydrogenated styrene/isoprene copolymer.

9. Use according to the preceding claim, in which the composition comprises from 2% to 15% by weight of viscosity index improving additive, relative to the total weight of the composition.

10. Use of at least one dithiocarbamate compound, in particular a dithiocarbamate compound as defined according to claim 2, in a lubricating composition comprising at least one base oil for preventing and/or reducing pre-ignition, in particular low speed pre-ignition, in a vehicle engine, preferably in a motor vehicle engine, which lubricating composition is used during at least one oil change interval, preferably during a vehicle distance of travel of 10000km to 30000km, without the addition of fresh lubricating composition.

11. Use of at least one dithiocarbamate compound, in particular a dithiocarbamate compound as defined according to claim 2, in a lubricating composition comprising at least one base oil for limiting the deterioration of the performance of said composition in terms of preventing and/or reducing pre-ignition, in particular low speed pre-ignition, in a vehicle engine, preferably in a motor vehicle engine, after its use during at least one oil change interval, preferably during a distance travelled by the vehicle of 10000km to 30000km, without the addition of fresh lubricating composition.

12. Use of at least one dithiocarbamate compound, in particular a dithiocarbamate compound as defined according to claim 2, for increasing the ignition temperature of a lubricating composition, measured by high pressure differential scanning calorimetry, by especially at least 2%, preferably at least 4%, relative to a used lubricating composition which does not contain any dithiocarbamate compound, said lubricating composition being used during at least one oil change interval, preferably during a vehicle distance of from 10000km to 30000km, without the addition of fresh lubricating composition.

13. Method for preventing and/or reducing pre-ignition, in particular low speed pre-ignition, in a vehicle engine, preferably a motor vehicle engine, comprising at least the steps of:

14. The method according to the preceding claim, wherein the lubricating composition is as defined according to any one of claims 2-9.

15. Use of a lubricating composition for preventing and/or reducing pre-ignition, in particular low speed pre-ignition, in a vehicle engine, preferably a motor vehicle engine, the lubricating composition comprising:

(i) at least one dithiocarbamate compound; and

(ii) at least one base oil, at least one oil,