EP3921396A1

EP3921396A1 - Lubricant composition for preventing pre-ignition

Info

Publication number: EP3921396A1
Application number: EP20701806.0A
Authority: EP
Inventors: Steve FAURE; Géraldine PAPIN
Original assignee: Total Marketing Services SA
Current assignee: TotalEnergies Onetech SAS
Priority date: 2019-02-04
Filing date: 2020-01-31
Publication date: 2021-12-15
Also published as: JP2022519612A; KR20210134906A; CN113557290A; FR3092337B1; FR3092337A1; WO2020161007A1; US20220119729A1

Abstract

The present invention relates to the use of a lubricant composition comprising (i) at least one dithiocarbamate compound; and (ii) at least one base oil, for preventing and/or reducing pre-ignition, in particular at low speed, in a vehicle engine, wherein said composition is applied during at least one change interval without the addition of a new lubricant composition, the content of dithiocarbamate compound being less than or equal to 1% by weight relative to the total weight of the lubricant composition.

Description

LUBRICANT COMPOSITION TO PREVENT PRE-IGNITION

Technical area

The present invention relates to the field of lubricants, in particular usable in vehicle engines, in particular lubricating compositions making it possible to prevent or reduce pre-ignition in an engine.

Under ideal conditions, normal combustion in a spark-ignition engine occurs when a mixture of fuel, especially fuel and air is ignited in the combustion chamber inside the cylinder by the production of a spark from a spark plug. Such normal combustion is generally characterized by the expansion of the flame front through the combustion chamber in an orderly and controlled manner.

However, in some cases, the air / fuel mixture can be prematurely ignited by an ignition source before ignition by the spark from the spark plug, leading to a phenomenon known as pre-ignition.

However, it is preferable to reduce, or even eliminate, the pre-ignition because this generally results in the presence of a strong increase in temperatures and pressures in the combustion chamber, and thus have a significant negative impact on the combustion chamber. efficiency and overall performance of an engine. Additionally, pre-ignition can cause significant damage to the cylinders, pistons, spark plugs and valves in the engine and in some cases can even result in engine failure or even engine breakage.

More recently, low speed pre-ignition (Low Speed Pre-Ignition in English or "LSPI") has been identified, in particular by car manufacturers, as a potential problem for small, so-called "downsized" engines. LSPI typically occurs at low speeds and high loads, and can cause severe damage to pistons and / or cylinders.

In addition, the prevention and / or reduction of pre-ignition, in particular of LSPI, must be maintained over time, that is to say during prolonged use of the lubricating composition, for example between two oil changes or after a certain number of kilometers traveled. Prior art

Several theories have been put forward in an attempt to explain this complex phenomenon. In particular, it has been observed that the presence of small amounts of lubricant in the combustion chamber coming to mix with the fuel can worsen pre-ignition. Also, a link between the presence of deposit in the combustion chamber and the occurrence of LSPI phenomena has been established. Finally, the design of the engine itself can influence pre-ignition.

Thus, this phenomenon is very complex and difficult to predict. As specified above, the nature of the lubricant contributes strongly to this and lubricating compositions making it possible to prevent or reduce the risk of pre-ignition, in particular LSPI, have therefore already been proposed.

Thus, application WO 2015/023559 describes a method for reducing pre-ignition by adding, in a lubricating composition, an additive making it possible to delay ignition, said additive being chosen from organic compounds comprising at least one aromatic nucleus.

However, these light organic compounds could cause an excessive increase in lubricant volatility.

It has therefore also been proposed to add polyalkylene glycol, as described in application WO 2017/021521, or else to integrate an organomolybdenum compound chosen from molybdenum dithiophosphates and sulfur-free molybdenum complexes, according to document WO 2017/021523, in a lubricating composition in order to prevent or reduce pre-ignition in an engine.

It is also known that the content of calcium-based detergent is a strong lever for triggering LSPI. Thus, it has been suggested to substitute detergents based on calcium with detergents based on magnesium in lubricating compositions intended to reduce LSPI in vehicle engines.

The inventors have been able to observe that the phenomenon of pre-ignition intensifies during the prolonged use of the lubricating composition. Thus, pre-ignition is particularly exacerbated in the case of so-called “used” lubricating compositions. In particular, it has already been demonstrated that lubricating compositions exhibiting a reduction in LSPI phenomena when they are new, see their properties deteriorate when they are used, in particular in the document “Low-speed pre-ignition”, Engine technology international, September 2018.

Finally, the solutions recommended in the prior art for new lubricating compositions prove insufficient in the case of used compositions.

Furthermore, the combination of at least one metal molybdenum dithiocarbamate compound, and at least one methylene bis (dibutyldithiocarbamate) has already been described in application WO 2013/182581 for the purpose of retaining the fuel economy properties of a lubricating composition.

However, this document in no way suggests a possible effect of this combination, or of any of the additives taken in isolation, on the pre-ignition phenomena that may occur in the engine.

Hong Liu et al., SAE International Journal of Fuels and Lubricants, 10 (3), 2017 relates to the development of low viscosity gasoline engine oils that aim to improve fuel economy. gasoline but also prevent LSPI pre-ignition. However, this document does not make any mention of a particular content of dithiocarbamate compound or of its specific interest for the prevention of pre-ignition phenomena occurring in engines.

For the purposes of the present invention, the term “used lubricating composition” is intended to denote a lubricating composition used during at least one oil change interval, that is to say over a distance traveled by the vehicle of between 10 000 and 30,000 km, preferably between 15,000 and 30,000 km.

The expressions "in the long term" or "in the long term" used according to the invention mean that the application of the lubricant composition extends to a used lubricant composition.

For the purposes of the present invention, the term “new lubricating composition” is intended to denote a lubricating composition that has never been used in an engine. For the purposes of the present invention, the term “aged lubricating composition” is intended to denote a lubricating composition which has undergone artificial aging, by simulation of the conditions of use of the lubricating composition in an engine. This artificial aging makes it possible to reproduce in an accelerated manner the aging of the oil when it is used in an engine during an oil change interval. In particular, it is a lubricating composition having undergone an iron-catalyzed oxidation at a temperature above 150 ° C, preferably between 150 ° C and 170 ° C and for a period of at least 110 h, preferably between 120 h and 150 h, according to the GFC Lu-43 Al 1 method.

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

As stated above, pre-ignition phenomena tend to worsen during the implementation of a lubricating composition which is therefore only really effective when it is new. For obvious reasons, it is necessary to offer a solution for preventing pre-ignition that is sustainable over time,

There therefore remains a need for lubricating compositions having the capacity to prevent and / or reduce the pre-ignition, in particular LSPI, of an engine, in particular of a motor vehicle engine, for a prolonged period of time. of its use, more precisely when the lubricating composition is used.

The solutions favored in the prior art recommend selecting particular additives, making it possible to play a role in reducing the pre-ignition phenomena taking place within the engine. However, the lubricating compositions can integrate a large number of different additives, allowing them to be given particularly advantageous properties, without it being possible to predict which additives will have a beneficial impact on the prevention of pre-ignition, a fortiori on the long term.

There therefore remains a need to provide additives which make it possible, once implemented in a lubricating composition, to prevent and / or reduce the pre-ignition phenomena which may occur during its prolonged use in an engine. Finally, it is necessary to provide a pre-ignition prevention solution that does not require the addition of new lubricating composition to the engine during its prolonged use, in particular between the engine oil change intervals.

Thus, there still remains a need to provide a lubricating composition making it possible to prevent and / or reduce pre-ignition during its implementation in an engine, not requiring the addition of lubricating composition between each engine oil change interval. .

For obvious reasons, there is also a need to provide such lubricating compositions which have good stability, in particular on storage.

The present invention aims precisely to meet this need.

Summary of the invention

Thus, the present invention relates, according to a first of its aspects, to the use of a lubricating composition comprising:

(i) at least one dithiocarbamate compound; and

(ii) at least one base oil,

to prevent and / or reduce pre-ignition, in particular at low speed, in a vehicle engine, preferably a motor vehicle,

said composition being used during at least one oil change interval, preferably over a distance traveled by the vehicle of between 10,000 km and 30,000 km, without adding new lubricating composition,

the content of dithiocarbamate compound being less than or equal to 1% by weight, relative to the total weight of the lubricating composition.

The term “motor vehicle” within the meaning of the present invention is understood to denote a vehicle comprising at least one wheel, preferably at least two wheels, propelled by an engine, in particular a combustion and explosion engine, in particular an internal combustion engine. reciprocating or rotary pistons, Diesel or spark ignition. Such engines can for example be four-stroke or two-stroke gasoline or diesel engines. According to the invention, the prevention and / or reduction of pre-ignition is preferably measured for the used lubricating composition compared to the new lubricating composition.

Against all expectations, and as emerges from the examples appearing below, the inventors have demonstrated that the addition of at least one dithiocarbamate compound in an aged lubricating composition makes it possible to significantly improve the ignition temperature, in particular measured by high pressure differential calorimetric analysis of said composition and consequently delay the pre-ignition phenomena, in particular LSPI, liable to occur during its use in an engine. The ignition temperature here refers to the initiation temperature of the exothermic peak during a rise in temperature, measured by high pressure differential scanning calorimetry, known as "HPDSC" (High Pressure Differential Scanning Calorimetry).

This result is all the more surprising in view of the teaching of the document “Low-speed pre-ignition”, Engine technology international, September 2018, according to which an oil comprising a molybdenum dialkyldithiocarbamate sees its properties in terms of LSPI decrease when the latter is used.

The dithiocarbamate compounds present in a lubricating composition according to the invention therefore advantageously make it possible to prevent pre-ignition phenomena, in particular LSPI, when it is used during at least one drain interval, preferably over a period of distance traveled by the vehicle between 10,000 km and 30,000 km.

As a result, it is not necessary to renew the lubricating composition during its use, for example between two engine oil changes, in order to keep prevention and / or reduction of pre-ignition phenomena, in particular at low speed, effective. .

Furthermore, the inventors have found, surprisingly, that the use of the dithiocarbamate compound in a content less than or equal to 1% by weight in a lubricating composition used according to the invention also made it possible to preserve satisfactory stability, in particular to the storage of said composition. Storage stability can be visually evaluated by rating the appearance of the lubricating composition and of the deposits formed during the storage of said composition, for a period generally ranging from 1 day to 3 months, and at different temperatures, typically 0 ° C, at room temperature and at 60 ° C.

Another subject of the invention, according to another of its aspects, is the use of at least one dithiocarbamate compound, in particular as defined below, in a lubricating composition comprising at least one base oil, to prevent and / or reduce the pre-ignition, in particular at low speed, in a vehicle engine, preferably of a motor vehicle, said lubricating composition being used during at least one oil change interval, preferably over a distance traveled by the vehicle between 10,000 km and 30,000 km, without adding new lubricating composition.

Another subject of the invention, according to another of its aspects, is the use of at least one dithiocarbamate compound, in particular as defined below, in a lubricating composition comprising at least one base oil, to limit the degradation of the performance of preventing and / or reducing pre-ignition, in particular at low speed, in a vehicle engine, preferably of a motor vehicle, of said composition, after its use during at least one interval of emptying, preferably over a distance traveled by the vehicle of between 10,000 km and 30,000 km, without adding new lubricating composition.

A further subject of the invention is a method for preventing and / or reducing pre-ignition, in particular at low speed, in a vehicle engine, preferably of a motor vehicle, preferably in the long term, comprising at least the following steps: a) bringing the engine into contact with a lubricating composition comprising at least one base oil and at least one dithiocarbamate compound, said dithiocarbamate compound being present in a content of less than or equal to 1% by weight, relative to the total weight of the composition lubricant;

b) use of the engine during at least one oil change interval, preferably over a distance traveled by the vehicle of between 10,000 km and 30,000 km, without adding new lubricating composition. The invention also relates to the use of a lubricating composition comprising:

(i) at least one dithiocarbamate compound; and

(ii) at least one base oil,

said composition having undergone an iron-catalyzed oxidation at a temperature above 150 ° C, preferably between 150 ° C and 170 ° C and for a period of at least 110 h, preferably between 120 h and 150 h, according to the GFC Lu-43A-11 method, the content of dithiocarbamate compound preferably being less than or equal to 1% by weight, relative to the total weight of the lubricating composition.

detailed description

COMPOSITION

Dithiocarbamate compound

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

The dithiocarbamate compound can in particular be chosen from metal dithiocarbamates, bisdithiocarbamates and mixtures thereof.

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

in which the groups R 1 and R 2 represent, independently of one another, hydrocarbon groups, optionally substituted, comprising from 1 to 30 atoms of carbon, preferably from 4 to 18 carbon atoms, M represents a metal cation and n is the valence of this metal cation.

Preferably M is molybdenum.

The metal dithiocarbamates which can be used according to the present invention are compounds that are well known to those skilled in the art and can be obtained by any process also known to those skilled in the art. An example of a process for preparing these compounds is described in particular in US Pat. No. 2,492,314.

Metal dithiocarbamates are especially known for their use in lubricating compositions as friction modifying additives.

The MoDTC compound used according to the invention can be chosen from compounds whose nucleus comprises two molybdenum atoms (dimeric MoDTC) and compounds whose nucleus comprises three molybdenum atoms (trimeric MoDTC).

The trimeric MoDTC compounds are generally of the formula Mo3S _k L _m in which:

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

m represents an integer ranging from 1 to 4; and

L represents an alkyl dithiocarbamate group 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 and their preparation processes described in patent application WO-98-26030.

An example of MoDTC trimeric compound is that marketed under the name C9455B Infmeum ^® by the company Infmeum International Ltd.

Preferably, the MoDTC compound used in the lubricating composition used according to the invention is a dimeric MoDTC compound. As examples of dimeric MoDTC compounds, mention may be made of the compounds and their preparation processes described in patent application EP-0757093. According to a particular embodiment of the invention, the metal dithiocarbamate compound is a molybdenum dithiocarbamate (MoDTC) of formula (la) below:

in which the groups R 1 and R 2 are, independently of one another, as defined above,

X ¹ , X ² , X ³ and X ⁴ , identical or different, independently represent an oxygen atom or a sulfur atom.

Advantageously, X ¹ and X ² can represent an oxygen atom and X ³ and X ⁴ can represent a sulfur atom.

Advantageously, the MoDTC compound is chosen from the compounds of formula (Ia) in which:

X ¹ and X ² represent an oxygen atom,

X ³ and X ⁴ represent a sulfur atom,

R 1 represents an alkyl group comprising 8 carbon atoms or an alkyl group comprising 13 carbon atoms,

R2 represents an alkyl group comprising 8 carbon atoms or an alkyl group comprising 13 carbon atoms.

Thus, advantageously, the MoDTC compound can be chosen from the compounds of formula (la ’):

in which R 1 and R 2 are as defined for formula (I) above.

As specific examples of MoDTC compounds, mention may be made of the products Molyvan L ^® , Molyvan 807 ^® or Molyvan 822 ^® sold by the company RT Vanderbilt. Compagny or the products Sakuralube 200 ^® , Sakuralube 165 ^® ,

Sakuralube 525 ^® or Sakuralube 600 ^® sold by the company Adeka.

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

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

in which :

- the groups R3 and R4 represent, independently of one another, hydrocarbon groups, optionally substituted, comprising from 1 to 30 carbon atoms, preferably from 2 to 24 carbon atoms, more preferably from 3 to 8 carbon atoms; and

- The R5 groups represents a hydrocarbon group comprising from 1 to 8 carbon atoms, preferably from 1 to 4 carbon atoms.

The bisdithiocarbamate compounds which can be used according to the present invention are compounds which are well known to those skilled in the art and can be obtained by any process also known to those skilled in the art.

Bisdithiocarbamates are especially known for their use in lubricating compositions as antioxidant additives.

It can advantageously be methylene bis (dibutyldithiocarbamate). As examples of commercial products can be cited the

Vanlube ^® 7723 sold by the company Vanderbilt or Additin ^® RC 6340 sold by the company Rhein Chemie. According to one embodiment, a lubricating composition used according to the present invention comprises a mixture of at least one metal dithiocarbamate and of at least one bisdithiocarbamate, in particular as defined above.

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

The dithiocarbamate compound is present in a 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 can be present in a lubricating composition used according to the invention in a content strictly greater than 0.01% by weight, in particular in a content ranging 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 a lubricating composition used according to the invention in a content greater than 0.01% by weight, relative to the total weight of the composition, the ignition temperature, in particular measured by differential calorimetric analysis at high pressure, is higher than that observed for contents of less than 0.01% by weight.

Consequently, a composition comprising a content greater than 0.01% by weight of dithiocarbamate compound, relative to the total weight of the composition, makes it possible to further delay the pre-ignition phenomena, in particular of LSPI, liable to damage. 'intervene during its implementation in an engine.

Base oil

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

The base oil (s) may be oils of mineral, synthetic or natural, animal or plant origin, known to those skilled in the art. In particular, the mineral or synthetic oils generally used in the lubricating composition belong to one of groups I to V according to the classes defined in the API classification (or their equivalents according to the ATIEL classification) as summarized in Table 1 below. below.

API classification is defined in American Petroleum Institute 1509

"Engine oil Licensing and Certification System" 17th edition, September 2012.

The ATIEL classification is defined in "The ATIEL Code of Practice", issue 18, November 2012.

TABLE 1

There is generally no limitation as to the use of oils of different bases to produce a lubricating composition used according to the invention, except that they must have properties, in particular of viscosity, of viscosity, sulfur content, oxidation resistance, suitable for use in engines, especially vehicle engines.

Mineral base oils include all types of bases obtained by atmospheric and vacuum distillation of crude oil, followed by refining operations such as solvent extraction, deasphalting, solvent dewaxing, hydrotreatment, hydrocracking and hydroisomerization, hydrofinishing.

The synthetic base oils can be chosen from esters, silicones, glycols, polybutene, polyalphaolefins (PAO), alkylbenzene or alkylnaphthalene. The base oils can also be oils of natural origin, for example esters of alcohols and carboxylic acids, obtainable from natural resources such as sunflower oil, rapeseed oil, palm oil, soybeans etc.

The base oil can be more particularly chosen from synthetic oils, mineral oils and mixtures thereof.

According to one embodiment, a lubricating composition used according to the present invention comprises at least one base oil chosen from group III oils, group IV oils and their mixtures.

Additives

A composition used according to the present invention may further comprise one or more additives as defined more precisely in the remainder of the text, distinct from the dithiocarbamate compound defined above.

The additives which can be incorporated into a composition according to the invention can be chosen from antioxidants distinct from the bisdithiocarbamate compound defined above, detergents, viscosity index improvers, friction modifiers distinct from the metal dithiocarbamate compound defined above. above, antiwear additives, extreme pressure additives, dispersants, pour point improvers, antifoams and mixtures thereof.

It is understood that the nature and the amount of additives used are chosen so as not to affect the properties of the lubricating composition, in particular with regard to the prevention and / or reduction of pre-ignition, in particular of LSPI, in a motor.

These additives can be introduced individually and / or in the form of a mixture like those already available for sale for the formulations of commercial lubricants for vehicle engines, with a performance level as defined by G ACEA (Association European Automobile Manufacturers) and / or GARI (American Petroleum Institute), well known to those skilled in the art. According to a particular embodiment, a composition used according to the invention can also comprise at least one antioxidant additive, more particularly distinct from the bisdithiocarbamate compound defined above.

The antioxidant additive generally helps to delay the degradation of the composition in service. This degradation can be reflected in particular by the formation of deposits, by the presence of sludge or by an increase in the viscosity of the composition. Antioxidant additives act in particular as radical inhibitors or destroyers of hydroperoxides.

Among the antioxidant additives commonly used, mention may be made of antioxidant additives of phenolic type, antioxidant additives of amine type, phosphosulfurized antioxidant additives. Some of these antioxidant additives, for example phosphosulfurized antioxidant additives, can generate ash. The phenolic antioxidant additives can be free from ash or be in the form of neutral or basic metal salts.

The antioxidant additives can in particular be chosen from sterically hindered phenols, sterically hindered phenol esters and sterically hindered phenols comprising a thioether bridge, diphenylamines, diphenylamines substituted with at least one C1-C12 alkyl group, N, N '- Dialkyl-aryl-diamines and mixtures thereof.

Preferably according to the invention, the sterically hindered phenols are chosen from compounds comprising a phenol group of which at least one carbon vicinal of the carbon carrying the alcohol function is substituted by at least one C 1 -Cio alkyl group, preferably an alkyl group. C _I -C _O, preferably a C4 alkyl group, preferably tert-butyl group.

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

Examples of amino compounds are aromatic amines, for example aromatic amines of formula NR ⁴ R ⁵ R ⁶ in which R ⁴ represents an aliphatic group or an aromatic group, optionally substituted, R ⁵ represents an aromatic group, optionally substituted, R ⁶ represents a hydrogen atom, an alkyl group, an aryl group or a group of formula R ⁷ S (0) _z R ⁸ in which R ⁷ represents an alkylene group or an alkenylene group, R ⁸ represents an alkyl group, an alkenyl group or an aryl group and z represents 0, 1 or 2.

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

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

A composition used according to the invention can contain all types of antioxidant additives known to those skilled in the art.

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

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

According to another embodiment, a composition used according to the invention may further comprise at least one detergent additive.

Detergent additives generally reduce the formation of deposits on the surface of metal parts by dissolving by-products of oxidation and combustion.

The detergent additives which can be used in a composition used according to the invention are generally known to those skilled in the art. The detergent additives can be anionic compounds comprising a long lipophilic hydrocarbon chain and a hydrophilic head. The associated cation can be a metal cation of an alkali or alkaline earth metal.

The detergent additives are preferably chosen from alkali metal or alkaline earth metal salts of carboxylic acids, sulphonates, salicylates, naphthenates, as well as salts of phenates. The alkali metals and alkaline earth metals are preferably calcium, magnesium, sodium or barium. These metal salts generally include the metal in a stoichiometric amount or else in excess, therefore in an amount greater than the stoichiometric amount. These are then overbased detergent additives; the excess metal providing the overbased character to the detergent additive is then generally in the form of a metal salt insoluble in oil, for example a carbonate, a hydroxide, an oxalate, an acetate, a glutamate, preferably a carbonate .

A composition used according to the invention can contain all types of detergent additives known to those skilled in the art.

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

In particular, when the detergent is chosen from alkaline earth metal salts, the detergent additive can be added to the composition so as to provide a metal element content ranging from 150 ppm to 2000 ppm, preferably from 250 ppm to 1500 ppm.

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

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

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

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

Antiwear additives and extreme pressure additives protect rubbing surfaces by forming a protective film adsorbed on these surfaces. There is a wide variety of antiwear additives. Preferably for the lubricating composition according to the invention, the anti-wear additives are chosen from phospho-sulfur additives such as metal alkylthiophosphates, in particular zinc alkylthiophosphates, and more specifically zinc dialkyldithiophosphates or ZnDTP. The preferred compounds are of formula Zn ((SP (S) (OR ² ) (OR ³ )) 2, in which R ² and R ³ , identical or different, independently represent an alkyl group, preferably an alkyl group comprising from 1 to 18 carbon atoms.

Amine phosphates are also antiwear additives which can be used in a composition according to the invention. However, the phosphorus provided by these additives can act as a poison in automobile catalytic systems because these additives generate ash. These effects can be minimized by partially substituting the amino phosphates with additives which do not provide phosphorus, such as, for example, polysulfides, in particular sulfur-containing olefins.

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

A composition used according to the invention is preferably free from antiwear additives and extreme pressure additives. In particular, a composition used according to the invention can be free from phosphate additives.

A composition used according to the invention may comprise at least one friction modifier additive, more particularly distinct from the metal dithiocarbamate compound defined above. The friction modifier additive can be chosen from a compound providing metallic elements and an ash-free compound. Among the compounds providing metallic elements, mention may be made of transition metal complexes such as Mo, Sb, Sn, Fe, Cu, Zn, the ligands of which may be hydrocarbon compounds comprising oxygen, nitrogen or carbon atoms. sulfur or phosphorus. The ash-free friction modifying additives are generally of organic origin and can be chosen from monoesters of fatty acids and polyols, alkoxylated amines, alkoxylated fatty amines, fatty epoxides, borate fatty epoxides; fatty amines or fatty acid glycerol esters. According to the invention, the fatty compounds comprise at least one hydrocarbon group comprising from 10 to 24 carbon atoms.

A composition used according to the invention can 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. weight of friction modifier additive, relative to the total weight of the composition.

Advantageously, a composition used according to the invention is free from a friction modifier additive distinct from the metal dithiocarbamate compound defined above.

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

By slowing the formation of paraffin crystals, pour point depressant additives generally improve the cold behavior of the composition.

Examples of pour point depressant additives include polymethacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalenes, alkylated polystyrenes.

Also, a composition used according to the invention can comprise at least one dispersing agent.

The dispersing agent can be chosen from Mannich bases, succinimides and their derivatives.

A composition used according to the invention may for example comprise from 0.2 to 10% by weight of dispersing agent, relative to the total weight of the composition.

APPLICATIONS

A lubricating composition according to the invention is intended more particularly to be used in an engine, in particular in a vehicle engine, in particular in a gasoline vehicle engine.

It therefore advantageously exhibits properties, in particular of viscosity, of viscosity index, of sulfur content, of resistance to oxidation, suitable for use in engines, in particular vehicle engines. Thus, preferably, a lubricating composition has a kinematic viscosity measured at 100 ° C according to the ISO 3104 standard of between 5 and 20 mm ² / s, preferably between 5 and 15 mm ² / s and more particularly between 6 and 13 mm ² / s.

As indicated above, a composition as described above is advantageous in that it allows, by its implementation in an engine, to prevent and / or reduce the pre-ignition phenomena occurring within said engine over the long term. term, in particular after use for a period corresponding to at least one oil change interval.

Thus, the invention relates to the use of a composition as defined above for preventing and / or reducing pre-ignition, in particular at low speed, in a vehicle engine, preferably a motor vehicle, said composition being used. implemented during at least one oil change interval, preferably over a distance traveled by the vehicle of between 10,000 km and 30,000 km, without adding new lubricant composition.

In particular, the pre-ignition phenomena have been observed at low speed in engines (LSPI) and are more exacerbated in direct injection engines, in particular downsized.

Thus, the present application also relates to the use of a lubricating composition comprising:

(i) at least one dithiocarbamate compound; and

(ii) at least one base oil,

for preventing and / or reducing low speed pre-ignition (LSPI) in a vehicle engine, preferably a motor vehicle, said composition being used during at least one oil change interval, preferably over a distance traveled by the vehicle between 10,000 km and 30,000 km, without adding new lubricating composition.

Particularly surprisingly, the inventors have observed that the presence of a dithiocarbamate compound in an aged lubricating composition makes it possible to significantly reduce the occurrence of pre-ignition phenomena in an engine. Thus, the present invention also relates to the use of at least one dithiocarbamate compound, in particular as defined above, in a lubricating composition comprising at least one base oil, said lubricating composition being used during at least an oil change interval, preferably over a distance traveled by the vehicle of between 10,000 km and 30,000 km, without the addition of new lubricant composition, to prevent and / or reduce pre-ignition, in particular at low speed, in a vehicle engine, preferably a motor vehicle.

As demonstrated in the examples below, the selection of a particular additive, namely a dithiocarbamate compound, made it possible to propose a lubricating composition making it possible to prevent and / or reduce the pre-ignition phenomena which may occur during its setting. prolonged use in an engine, without adding new lubricating composition.

Thus, still as demonstrated in the examples, a lubricating composition according to the invention has an ignition temperature greater than that obtained for a lubricating composition comprising no dithiocarbamate compound or comprising an additional additive, distinct from the dithiocarbamate required according to the invention.

In other words, the nature of the dithiocarbamate additive was not clearly deductible from its possibly previously known functions.

The composition defined above therefore has the advantage of preventing and / or reducing pre-ignition in an engine, due to its prolonged use in an engine.

Thus, the invention also relates to a method for preventing and / or reducing pre-ignition, in particular at low speed, in a vehicle engine, preferably of a motor vehicle, preferably in the long term, comprising at least the following steps a) bringing the engine into contact with a lubricating composition comprising at least one base oil and at least one dithiocarbamate compound, said dithiocarbamate compound being present in a content of less than or equal to 1% by weight, relative to the total weight of the composition lubricant;

b) operation of the engine during at least one oil change interval, preferably over a distance traveled by the vehicle of between 10,000 km and 30,000 km, without the addition of new lubricating composition.

As specified above, a used lubricating composition used according to the invention has an ignition temperature higher than that of a used lubricating composition that does not comply with this definition.

In particular, the temperature increase is at least 2%, preferably at least 4%, more preferably at least 5%, measured according to the protocol detailed in the examples, relative to the temperature of ignition of a lubricating composition comprising a base oil but being free of the dithiocarbamate compound. The ignition temperature corresponds to the temperature from which an exothermic reaction is initiated.

Thus, the invention also relates to the use of at least one dithiocarbamate compound, in particular as defined above, in order to increase the ignition temperature, measured by high pressure differential scanning calorimetry, of a lubricating composition, in particular at least 2%, preferably at least 4%, said composition being used during at least one oil change interval, preferably over a distance traveled by the vehicle of between 10 000 km and 30,000 km, without the addition of new lubricating composition, compared to a used lubricating composition free of any dithiocarbamate compound.

According to the invention, the particular, advantageous or preferred characteristics of the composition according to the invention make it possible to define uses according to the invention which are also particular, advantageous or preferred.

Throughout the description, including the claims, the expression "comprising a" should be understood as being synonymous with "comprising at least one", unless specified to the contrary.

The expressions "between ... and ...", "includes from ... to ...", "formed from ... to ...", and "ranging from ... to ..." , must be understood with limits included, unless otherwise specified.

In the description and the examples, unless otherwise indicated, the percentages are weight percentages. The percentages are therefore expressed by weight relative to to the total weight of the composition. Temperature is expressed in degrees Celsius unless otherwise specified, and pressure is atmospheric pressure, unless otherwise specified.

The invention will now be described by means of the following examples, given of course by way of illustration and not limiting the invention.

Examples

Methods

Lubricating Oil Aging Method

The oils used in the examples below were subjected to aging simulation. This simulation is performed by oxidation of oil catalyzed by 100 ppm iron at 170 ° C for 144 hours, according to the GFC-Lu-43A-11 method.

Laboratory measurement of the pre-ignition tendency

In the examples detailed below, the tendency to pre-ignition is determined in terms of the initiation temperature of the exothermic reaction, measured by high pressure differential calorimetric analysis, known as “HPDSC” (High Pressure Differential Scanning Calorimetry in English language).

This measurement is carried out on a Mettler Toledo LG3300 device according to the protocol detailed below:

- Weigh 2 ± 0.05 mg of sample to be analyzed in a cuvette;

- Place the open sample and the reference on the detector surface;

- The cell is closed hermetically and mechanically;

- A pressure between 1 and 20 bar is applied to the cell;

- The temperature of the sample is equilibrated at the starting temperature of the measurement, between 20 ° C and 80 ° C, preferably between 30 ° C and 70 ° C, maintained for 1 to 15 minutes, preferably for 2 at 10 minutes;

- At least one temperature ramp is applied to the sample, between the starting temperature and a temperature between 100 ° C and 400 ° C, preferably between 150 ° C and 350 ° C, more preferably between 200 ° C and 300 ° C.

Software, such as STARe software, can be used to visualize the differences in heat exchange between the sample and the reference.

The temperature of the appearance of an exotherm on the curve thus obtained is assimilated to the phenomenon of pre-ignition, such as LSPI, This temperature is correlated with time. Thus, the higher it is, the more the pre-ignition will be delayed in the combustion chamber during the implementation of the composition.

Stability measurement

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

After preparation of the lubricating composition, three samples are distributed in test tubes which are then closed.

The test tubes are stored for 3 months under the following conditions:

- 1 tube stored in an enclosure thermostatically controlled at around 60 ° C,

- 1 tube stored at room temperature;

- 1 tube stored in a refrigerated cabinet at around 0 ° C.

During the first month, quotes are carried out on the 1 ^st day, the 3 ^rd day then once a week, and then once every two weeks. Samples reaching a rating of 5 are discarded, even before the end of 3 months of storage.

The rating is carried out according to three criteria:

- clarity: the test tube is viewed as it is;

- general assessment of deposits: the test tube is turned upside down and the deposits are assessed; and

- the form of deposits.

Depending on the shape of the deposit, it is also possible to determine the diameter (D) and / or the thickness (E) of the deposit (in mm).

Depending on the rating results obtained for each of these three criteria, it is defined whether the composition is stable or not.

Example 1: Preparation of lubricating compositions

The lubricating compositions AO to A4 were prepared.

Their kinematic viscosity at 100 ° C. was determined according to the ISO 3104 standard and their properties in terms of predisposition to self-ignition were measured.

The details of the compositions are presented in Table 2 below, in which the proportions of different compounds are indicated in percentage by mass.

* The additive pack is a mixture of various additives common in the field of lubricants and available commercially. It includes zinc dithiophosphate type antiwear agents, calcium and magnesium based detergents and PIB SI type dispersants.

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

The compositions are prepared by mixing, at a temperature of the order of 30 to 40 ° C, the compounds detailed in Table 2.

The lubricating compositions thus prepared exhibit kinematic viscosity values at 100 ° C. suitable for their use in engines, in particular vehicle engines.

The lubricating compositions are then aged according to the protocol (aging method) detailed above.

Example 2: Evaluation of the LSPI performances of lubricating compositions

The initiation temperature of the exothermic reaction (ignition temperature) was measured for each of the lubricating compositions of Example 1, according to the measurement method (laboratory method of the tendency to pre-ignition) defined below. above.

The results are shown in Table 3 below.

TABLE 3

Compositions A1 to A4 according to the invention, comprising molybdenum dithiocarbamate or methylene bis (dibutyldithiocarbamate), exhibit higher ignition temperatures than for the same composition comprising no dithiocarbamate compound required according to the invention (composition AO of reference).

These measurements therefore make it possible to demonstrate that the addition of at least one dithiocarbamate compound in an aged lubricating composition makes it possible to significantly delay the pre-ignition phenomena, in particular of LSPI, during its use in an engine, in conditions simulating the aging of the lubricant composition.

In the examples which follow, the lubricating compositions are produced and tested in comparison with a reference lubricating composition, comprising no dithiocarbamate compound.

For this reference composition, the kinematic viscosity at 100 ° C. was determined according to the ISO 3104 standard. The composition was then aged according to the catalyzed aging protocol described above. Finally, the initiation temperature of the exothermic reaction (ignition temperature) was measured, according to the measurement method (laboratory method of the tendency to pre-ignition) defined above.

The detail of the reference composition (in percentage by mass) and the results obtained are presented in Table 4 below.

TABLE 4

Example 3: Preparation of lubricating compositions

The lubricating compositions B0 to B7 were prepared.

In particular, the BO composition is outside the invention since it comprises a content of dithiocarbamate compound greater than 1% by weight.

Compositions B1 to B7 are in accordance with the invention.

Their kinematic viscosity at 100 ° C was determined according to the ISO 3104 standard.

The details of the compositions are presented in Table 5 below, in which the proportions of different compounds are indicated in percentage by mass.

TABLE 5

The compositions are prepared by mixing, at a temperature of the order of 30 to 40 ° C, the compounds detailed in Table 5.

Example 4 Evaluation of the performances of the lubricating compositions The initiation temperature of the exotherm reaction (ignition temperature) was measured for each of the lubricating compositions of Example 3, according to the measurement method (laboratory method of the pre-ignition tendency) defined above.

The stability of each of the lubricating compositions was also evaluated according to the protocol (Measurement of stability) defined above.

The results are shown in Table 6 below.

TABLE 6

Compositions B1 to B7 according to the invention, comprising molybdenum dithiocarbamate in a content of less than or equal to 1% by weight, exhibit good stability, unlike composition B0 which has a poor rating for stability with the appearance of cloudiness.

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

Furthermore, the compositions B1 to B7 all exhibit higher ignition temperatures than that obtained with the reference composition indicated above, and therefore make it possible to significantly delay the pre-ignition phenomena, in particular of LSPI, during their use in an engine, under conditions simulating the aging of the lubricating compositions.

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

Example 5: Preparation of lubricating compositions

The lubricating compositions C1 and C2, in accordance with the invention, were prepared.

The details of the compositions are presented in Table 7 below, in which the proportions of different compounds are indicated in percentage by mass.

TABLE 7

The compositions are prepared by mixing, at a temperature of the order of 30 to 40 ° C, the compounds detailed in Table 7.

Example 6: Evaluation of the lubricating compositions

The initiation temperature of the exothermic reaction (ignition temperature) was measured for each of the lubricating compositions of Example 3, according to the measurement method (laboratory method of the tendency to pre-ignition) defined below. above.

The results are shown in Table 8 below.

TABLE 8 Compositions C1 and C2 according to the invention are stable and exhibit ignition temperatures higher than that measured for the reference composition, therefore making it possible to significantly delay the pre-ignition phenomena, in particular of LSPI, during their setting. used in an engine, under conditions simulating the aging of the lubricating compositions.

Claims

1. Use of a lubricating composition comprising:

(i) at least one dithiocarbamate compound; and

(ii) at least one base oil,

2. Use according to claim 1, in which the dithiocarbamate compound is chosen from metal dithiocarbamates, bisdithiocarbamates and their mixtures, preferably from molybdenum dithiocarbamate, methylene bis (dibutyldithiocarbamate) and mixtures thereof.

3. Use according to any one of claims 1 or 2, wherein the content of dithiocarbamate compound is strictly greater than 0.01% by weight, in particular varies from 0.02% to 1% by weight, preferably from 0 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, in which the base oil is chosen from group III oils, group IV oils and mixtures thereof.

5. Use according to any one of the preceding claims, in which the lubricating composition further comprises at least one antioxidant additive distinct from the dithiocarbamate compound defined in claim 1 or 2, in particular chosen from diphenylamine, phenols, phenol esters. and their mixtures.

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

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

8. Use according to any one of the preceding claims, in which the lubricating composition comprises at least one additive improving the viscosity index chosen from homopolymers or copolymers, hydrogenated or non-hydrogenated, styrene, butadiene and l. isoprene, preferably which 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 additive improving the viscosity index, relative to the total weight of the composition.

10. Use of at least one dithiocarbamate compound, in particular as defined according to claim 2, in a lubricating composition comprising at least one base oil, to prevent and / or reduce pre-ignition, in particular at low speed, in a vehicle engine, preferably of a motor vehicle, said lubricating composition being used during at least one oil change interval, preferably over a distance traveled by the vehicle of between 10,000 km and 30,000 km, without addition of new lubricating composition.

11. Use of at least one dithiocarbamate compound, in particular as defined according to claim 2, in a lubricating composition comprising at least one base oil, to limit the degradation of the performance of prevention and / or reduction of pre-ignition. , in particular at low speed, in a vehicle engine, preferably a motor vehicle, of said composition, after its implementation during at least one oil change interval, preferably over a distance traveled by the vehicle between 10,000 km and 30,000 km, without adding new lubricating composition.

12. Use of at least one dithiocarbamate compound, in particular as defined in claim 2, in order to increase the ignition temperature, measured by high pressure differential scanning calorimetry, of a lubricating composition, in particular d 'at least 2%, preferably at least 4%, said composition being used during at least one oil change interval, preferably over a distance traveled by the vehicle of between 10,000 km and 30,000 km , without addition of composition new lubricant, compared to a used lubricant composition free of any dithiocarbamate compound.

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

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

b) operation of the engine during at least one oil change interval, preferably over a distance traveled by the vehicle of between 10,000 km and 30,000 km, without adding new lubricant composition.

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

15. Use of a lubricating composition comprising:

(i) at least one dithiocarbamate compound; and

(ii) at least one base oil,