Use of Specific Base Oil for Reducing Particulate Emissions

The present application is a U.S. National Phase Application under 35 U.S.C. § 371 of International Patent Application No. PCT/EP2023/062442 filed May 10, 2023, which claims priority of French Patent Application No. 22 10488, filed Oct. 12, 2022 and French Patent Application No. FR 22 04459, filed May 11, 2022. The entire contents of which are hereby incorporated by reference.

The present invention relates to the use of a specific base for reducing particle emissions from motor vehicles.

In 1993, the first European standard on emissions from vehicles with combustion engines was introduced. The standard Euro VI anti-pollution (standard EC 595/2009) relating to heavy goods vehicle engines came into force on 1 Sep. 2014 for newly approved vehicles and applicable to all new vehicles as of 1 Jan. 2014. The above standard concerns four pollutants in particular: carbon monoxide (CO), unburned hydrocarbons (HC), nitrogen oxides (NOx), particle mass (PM) and number (PN), amongst which soot, the last two remaining the most problematic for the pollution control system of modern engines.

Going after COprompted manufacturers to increase the efficiency thereof so as to lower the consumptions. To this end, a for lean-burn operation (air in excess compared to the mass of fuel) was often chosen. Unfortunately, such a process generates a significant increase in the emissions of nitrogen oxide and particles.

In the past, manufacturers have also chosen to introduce particle filter systems for reducing the number and mass of particles emitted into the atmosphere. In most cases, the operation of such systems is based on the combustion of soot due to the temperature rise of the exhaust gases at the inlet of the filter. Such operation requires the presence of catalysis.

To comply with current and future standards, strict regulations on particle size and more particularly on the concentration in number of particles emitted (PN) have been introduced. Several studies have shown that, although particulate mass formation is low, the PN of particulates emitted by compressed natural gas (CNG) engines are not negligible compared to same of diesel engines, especially under high engine load conditions.

For the above reason, the new Euro VI emission standards prescribe a limit of 6×10particles per kWh, for diesel and CNG heavy vehicles.

The use of lubricant composition is considered to make a significant contribution to the emission of small particles (greater than 10 nm or 23 nm) emitted by the above type of engine.

There is an interest in providing lubricating compositions specifically suitable for reducing the number of particles emitted at the exhaust of a vehicle, in particular of a vehicle comprising at least one controlled ignition engine, preferably a combustion engine, in particular heavy or light vehicles, e.g. vehicles such as heavy goods vehicles.

A goal of the present invention is to provide a suitable lubricating composition having a direct impact on particle emissions.

Another goal of the present invention is to provide a specific base oil making the lubricating composition have a direct impact on particle emissions.

Further goals will emerge upon reading the following description of the invention.

Such goals are fulfilled by the present application which relates to the use of a lubricating composition comprising a base oil or a mixture of base oils having a viscosity (BOV or Base Oil Viscosity) of less than or equal to 4.5 mm/s, in particular less than or equal to 4 mm/s, for reducing the particulate emissions from an engine.

The present invention also relates to the use of a lubricating composition comprising a base oil or a mixture of base oils, for reducing particulate emissions from an engine, wherein said base oil or said mixture of base oils has a kinematic viscosity (BOV or base oil viscosity) measured at 100° C., as per the standard ASTM D445, of less than or equal to 4.5 mm/s, and wherein the lubricating composition has a viscosity at 150° C. and under constant shear of greater than or equal to 2.4 mPa.s.

In the context of the present invention, the term “particles” refers to the particles emitted by the exhaust of motor vehicles. It means a group of microscopic particles (about μm or less in size). Such substances are varied and are comprised in the vehicle exhaust gases coming from the combustion of fuel. Such substances can be either solid or liquid. The term particles comprises the term soots, which are formed, are oxidized and contain unburned hydrocarbons, oxygenated derivatives (ketones, esters, aldehydes, lactones, ethers, organic acids) and polycyclic aromatic hydrocarbons (the famous PAHs) along with the nitrated, oxygenated derivatives thereof, etc. There are further mineral (SO2, sulphates, etc.) and metal derivatives.

In a particularly advantageous manner, the present invention can be used for reducing the emissions of particles with a size greater than or equal to 10 nm, e.g. greater than 23 nm, or in particular equal to 10 nm.

Within the framework of the present invention, the term “particle size” refers to particles, or agglomerate of particles the size of which is comprised between 10 and 100 nm, e.g. between 10 and 60 nm, and else preferably 10 to 40 nm, e.g. between 23 and 100 nm, preferably between 23 and 60 nm, and else preferably between 23 and 40 nm.

The particle size can be measured by spectrometry, e.g. using a spectrometer manufactured by Cambustion under the commercial reference DMS500. The number of particles according to the size (PN10 or PN23) thereof can be determined e.g. using particle counters such as APC 489 marketed by AVL or else MEXA-2000 SPCS marketed by HORIBA.

Reduction of particle emissions refers, in particular, to the reduction of the number of particles, in particular of particles having a size greater than or equal to 10 nm, e.g. greater or equal to 23 nm. It is in particular a question of reducing the number of particles emitted during a cycle on a WHTC regulatory cycle, e.g. during WLTC or RDE cycles. Thereof is measured according to the work supplied over the cycle (in #/kWh). The reduction is also measured as a function of the number of kilometers traveled.

Preferably, the present application relates to the reduction of soot emissions.

Preferably, the present invention relates to the reduction of emissions of particles, preferably of particles with a size greater than or equal to 10 nm, e.g. greater than or equal to 23 nm, preferably of soots, over the entire regulatory cycle for heavy goods vehicle WHTC (World Harmonized Transient Cycle) applications.

Preferably, the present invention relates to the reduction of the emission of particles, preferably particles of size less than or equal to 23 nm, preferably soots, during the urban (low speed), peri-urban (moderate speed) and road (high speed) cycles defined by the WLTC (or WLTP) (Worldwide Harmonized Light Vehicle Test Procedure) and across all WLTC, and also over the RDE (Real Drive Emissions) cycle.

In the context of the present invention, viscosity (also called BOV for Base Oil Viscosity) is a kinematic viscosity and is measured at 100° C., according to the standard ASTM D445. The viscosity of the base oil at 100° C. corresponds to the kinematic viscosity of the base oil mixture at 100° C. of the formulation before the addition viscosity modifier additives and of a pour point depressor.

In the case of a base oil mixture, it should be understood that the viscosity of the base oil mixture is less than or equal to 4.

Preferably, the base oil or base oil mixture has a viscosity comprised between 1.5 and 4.

In the case of a mixture of base oils, it should be understood that it is the viscosity of the mixture of base oils which is preferably less than or equal to 4.5 mm/s.

Preferably, the base oil or the mixture of base oils has a kinematic viscosity, measured at 100° C., of from 1.5 to 4.5 mm/s, in particular from 1.5 to 4 mm/s.

According to one embodiment, the kinematic viscosity, measured at 100° C., of the base oil or of the mixture of base oils is comprised between 3 and 4.5 mm/s, and preferentially between 4 and 4.5 mm/s.

Preferably, the viscosity index of the base oil or of the mixture of base oils is greater than or equal to 130, preferably greater than or equal to 150.

The viscosity index is calculated by measuring the kinematic viscosity at 40° C. and 100° C. The measurements are then compared with the results of two reference oils. The method of calculation thereof is described in the standard ASTM D2270.

The lubricating composition according to the invention has e.g. a grade according to the SAEJ300 classification of type XW-(Y) with X representing 0, 5 or 10 and Y representing an integer comprised between 6 and 50, or comprised between 8 and 40, preferably 12 or 30 or 40.

The base oils used in the lubricating compositions of the invention can be oils of mineral or synthetic origin belonging to groups I to V according to the classes defined by the API classification (or the equivalents thereof according to the ATIEL classification (Table 1) or the mixtures thereof.

The mineral base oils of the invention include any type of base oil obtained by atmospheric distillation and vacuum distillation of crude oil, followed by refining operations such as solvent extraction, deasphalting, solvent dewaxing, hydrotreatment, hydrocracking, hydroisomerization and hydrofinishing.

The base oils of the lubricating compositions used according to the invention can be further chosen from synthetic oils, such as certain esters of carboxylic acids and alcohols, and polyalphaolefins. The polyalphaolefins used as base oil are e.g. obtained from monomers comprising from 4 to 32 carbon atoms, e.g. from octene or decene, and for which the viscosity at 100° C. is comprised between 1.5 and 15 mm.sas per the standard ASTM D445.

The lubricating composition used according to the invention can comprise at least 50% by weight of base oil with respect to the total weight of the composition. More advantageously, the lubricating composition according to the invention comprises at least 60% by weight, or even at least 70% by weight of base oils with respect to the total weight of the lubricating composition. In a more preferred way, the lubricating composition according to the invention comprises from 50% to 97% by weight of base oils, preferably from 50% to 85% by weight of base oils, or from 75% to 97% by weight of base oils with respect to the total weight of the composition.

According to one embodiment, the quantity of base oil or of the mixture of base oils is between 50% and 97% by weight with respect to the total weight of the lubricating composition as defined hereinabove.

As mentioned hereinabove, the lubricating composition used according to the invention preferably has a viscosity at 150° C. and under constant shear greater than or equal to 2.4 mPa.s. The viscosity is also referred to by the term HTHS 150.

HTHS (High Temperature, High Shear) viscosity is a measure of the viscosity of the residual oil film under high stress (shear under mechanical pressure) at high temperature. Herein, the HTHS 150 viscosity value is measured at 150° C. The values are measured as per the standards CEC L-036-90 or ASTM D4683.

According to one embodiment, the viscosity at 150° C., and under constant shear, of the lubricating composition (or HTHS 150) is comprised between 2.4 mPa.sand 5 mPa.s, preferably between 2.6 mPa.sand 5 mPa.s.

According to one embodiment, the lubricating composition used according to the invention has a grade according to the SAEJ300 classification of type XW-(Y) with X representing 0, 5 or 10 and Y representing an integer comprised from 6 to 50, preferably from 8 to 40, preferably 12, 20, 30 or 40, preferentially 20 or 30.

The lubricating composition used according to the invention may also comprise at least one viscosity index improving additive such as a butylene and hydrogenated styrene polymer, an ethylene propylene copolymer, or else a polymethacrylate polymer, preferably a butylene and hydrogenated styrene polymer. The lubricating composition according to the invention may thus also comprise at least one additive improving the viscosity index, chosen from the group consisting of hydrogenated butylene and styrene polymers, ethylene propylene copolymers and polymethacrylate polymers, said viscosity index improving additive preferably being a hydrogenated butylene and styrene polymer. The lubricating composition according to the invention can comprise from 0.1% to 15% by weight of additive improving the viscosity index, with respect to the total weight of lubricating composition.

The composition of the invention can further comprise at least one additive.

Many additives can be used in the lubricating compositions according to the invention.

The preferred additives for the lubricating composition according to the invention are chosen from detergent additives, friction modifying additives different from the molybdenum compounds defined above, extreme pressure additives, dispersants, pour point activators, antifoaming agents, thickeners and mixtures thereof.

Preferentially, the lubricating compositions according to the invention comprise at least one extreme pressure additive, or a mixture.

Anti-wear additives and extreme pressure additives protect surface friction by forming a protective film adsorbed on the surfaces.

There is a wide variety of anti-wear additives. Preferentially, for the lubricating compositions of the invention, the anti-wear additives are chosen from additives comprising phosphorus and sulfur, such as alkylthiophosphate metals, in particular zinc alkylthiophosphate, and more precisely zinc dialkyldithiophosphate or ZnDTP. Preferred compounds have the formula Zn((SP(S)(OR)(OR′))2, wherein R and R′—either identical or different—independently stands for an alkyl group, preferentially an alkyl group comprising from 1 to 18 carbon atoms.

Amine phosphates as well are anti-wear additives which can be used in the lubricating compositions of the invention. However, the phosphorus atoms provided by such additives can act as a poison in the catalytic systems of automobiles since same generate ash. Such effects can be minimized by substituting part of the amine phosphates with non-phosphorus additives, such as polysulfides, in particular sulfur-containing olefins.

Advantageously, the lubricating compositions according to the invention can comprise from 0.01% to 6% by weight, preferentially from 0.05% to 4% by weight, more preferentially from 0.1% to 2% by weight with respect to the total weight of lubricating composition of anti-wear additives and extreme pressure additives.