ES2127022T5 - FUELOLEO ADDITIVES AND COMPOSITIONS. - Google Patents

Abstract

Fuel oil compositions containing specific mixtures of esters of unsaturated monocarboxylic acids show improved lubricity properties.

Description

Additives and fuel oil compositions.

This invention relates to additives for improve the lubrication capacity of fuel oils such as fuel oil for diesel engines. Fuel oil compositions for Diesel engines that include additives exhibit a capacity of Improved lubrication and reduced engine wear.

Concern for the environment has given place for performances to significantly reduce components harmful in emissions when fuel oils are burned, particularly in engines such as diesel engines. They have made attempts, for example, to minimize dioxide emissions Sulfur As a result attempts have been made to minimize the Sulfur content of fuel oils. For example, although Fuel oils for typical diesel engines have contained in the past 1% by weight or more of sulfur (expressed as elemental sulfur) is considers it now desirable to reduce the level, preferably to 0.05% by weight and, advantageously, less than 0.01% by weight, particularly less than 0.001% by weight.

Additional refining of fuel oils, necessary To achieve these low levels of sulfur, it often results in reductions in the level of polar components. In addition, the Refinery procedures can reduce the level of polynuclear aromatic compounds present in said fuel oils.

The reduction of the level of one or more of the sulfur, polynuclear or polar aromatic components of diesel engine fuel oil can reduce oil capacity to lubricate the engine injection system in such a way that, for example, the engine fuel injection pump is breaks relatively soon in the life of an engine. Breakage can take place in fuel injection systems such as high pressure rotary distributors, pumps and injectors serially. The problem of poor lubrication capacity in fuel oils for diesel engines is likely to be exacerbated for the developments of the engines of the future aimed at reducing in addition the emissions, which will have more rigorous requirements of lubrication capacity than current engines. For example, it fits anticipate that the introduction of pressure block injectors elevated will increase the requirement of the lubrication capacity of the fuel oil

Similarly, poor lubrication capacity may lead to wear problems in other devices dependent mechanics for lubrication of the ability to Natural lubrication of fuel oil.

Additives with lubrication capacity for Fuel oils have been described in the art. Document WO 94/17160 describes an additive comprising an ester of a carboxylic acid and an alcohol in which the acid has from 2 to 50 carbon atoms and Alcohol has one or more carbon atoms. He glycerol mono-oleate is specifically described as an example Although mixtures are generally contemplated, they are not describes no specific mixture of esters.

The document US-A-3,273,981 describes an additive with lubrication capacity which is a mixture of A + B in which A it is a polybasic acid, or a prepared polybasic acid ester by reaction of the acid with monohydric alcohols C1-C5; while B is a partial ester of a polyhydric alcohol and a fatty acid, for example glyceryl mono-oleate, sorbitan mono-oleate or pentaerythritol mono-oleate. The mix finds its application in turbojet fuels.

However, in certain circumstances said esters of the prior art have unexpectedly found that promote the blocking of fuel filters, particularly the fine mesh filters typically present in the tubes of the diesel vehicle fuel. This problem of blocking the filter can lead to insufficient fuel flow and to engine performance deteriorated, and is especially evident at low temperatures.

In addition, it has been unexpectedly found that fuels containing the preferred ester (Additive D) described in WO 94/17160 show a loss of performance of its lubrication capacity after a storage period and cold filtration. Loss of performance may be evident. even in the absence of severe filter blockage problems. This loss in performance itself represents a problem significant, since under fuel conditions a fuel oil stored is typically subjected to temperature cycles and must to still be able to impart effective lubrication to mechanical devices downstream of the tube filters fuel. In a diesel vehicle fuel system, for For example, diesel engine fuel must first flow to through a fine grade filter before reaching the system fuel injection, including the injection pump. He decreased lubrication capacity performance after this filtration point therefore exposes the injection system to increased wear

There is thus a need for additives of enhanced lubrication capacity that show better capacity filtration and that, in fuel oils, do not show a loss in the yield after filtration after periods of cold storage

These problems have been resolved surprisingly now by additives comprising mixtures specific to certain esters.

The document GB-A-1,505,302 describes combinations of esters including, for example, monoesters of glycerol and glycerol diesters as fuel additives for diesel engines, describing the combinations as giving rise to advantages that include less wear of the injection equipment of the fuel, piston rings and sleeves cylinder interiors. The document GB-A-1,505,302 refers, without However, to overcome the operational disadvantages of the corrosion and wear through acidic combustion products, residues in the combustion chamber and in the exhaust system. He document states that these disadvantages are due to the Incomplete combustion under certain operating conditions. Typical diesel engine fuels on the date of The document contained, for example, from 0.5 to 1% by weight of sulfur, as elemental sulfur, based on the weight of the fuel.

The document US-A-3,287,273 describes additives with lubrication capacity that are reaction products of an acid dicarboxylic and an oil insoluble glycol. The acid is typical and predominantly a dimer of unsaturated fatty acids such as linoleic or oleic acid, although they may also be present minor proportions of the monomer acid. Alone alkane diols u oxa-alkane-diols are suggested specifically as the glycol reactant.

In a first aspect therefore, the invention provides a fuel oil composition comprising a proportion most important of a medium distillate fuel oil that has a sulfur content of 0.2% by weight or less, and a higher proportion small of an additive with lubrication capacity that understands:

(to)

 a ester of a monounsaturated monocarboxylic acid and an alcohol polyhydroxylated, and

(b)

 a ester of a polyunsaturated monocarboxylic acid and an alcohol polyhydroxylated having at least three hydroxy groups,

the esters (a) and (b) being different and being both partial esters, and being the relative proportions of (a) and (b) by weight in the range of 1:10 to 2: 1.

In a second aspect, the invention provides the use of the additive defined in the first aspect, to improve the Lubrication capacity of a medium distillate fuel oil.

In a third aspect, the invention provides the use of the fuel composition of the first aspect in a combustion apparatus to reduce the wear rate in the fuel supply system of said apparatus.

The mixture of esters (a) and (b) can unexpectedly provide a capacity performance of Improved lubrication when compared to individual performance of component (a) or (b). In addition, the mixture of (a) and (b) shows a improved filtration capacity and maintains good performance of lubrication capacity after cold storage followed by filtration

The invention will now be described with more detail.

The fuel oil composition (first aspect of the invention) (i) The additive

The expression "polyhydric alcohol" is use to describe a compound that has more than one hydroxy group. It is preferred that (a) be the ester of a polyhydric alcohol which It has at least three hydroxy groups.

Examples of polyhydric alcohols that they have at least three hydroxy groups are those that have 3 to 10, preferably 3 to 6, more preferably 3 to 4 hydroxy groups and having 2 to 90, preferably 2 to 30, more preferably 2 to 12 and most preferably 3 to 4 carbon atoms in the molecule. Such alcohols may be aliphatic, saturated or unsaturated, and linear or branched chain, or cyclic derivatives thereof. Linear, aliphatic and linear chain alcohols are preferred. saturated.

Advantageously, both (a) and (b) are esters of trihydric alcohols, especially glycerol or trimethylol propane Other polyhydric alcohols Suitable include pentaerythritol, sorbitol, mannitol, inositol, glucose and fructose

Unsaturated monocarboxylic acids from from which esters are obtained may have a group alkenyl, cyclo-alkenyl or aromatic hydrocarbyl bound to the carboxylic acid group. The term "hydrocarbyl" means a group that contains carbon and hydrogen that can be of linear or branched chain and that is attached to the acid group carboxylic by a carbon-carbon bond. The group hydrocarbyl may be interrupted by one or more heteroatoms such as O, S, N or P.

It is preferred that (a) and (b) be both esters of alkenyl monocarboxylic acids, having preferably 10 to 36 alkenyl groups, for example 10 to 22, more preferably 18-22, especially 18 to 20 carbon atoms The alkenyl group can be mono- or polyunsaturated. It is particularly preferred that (a) be an ester of a mono-unsaturated alkenyl acid monocarboxylic, and that (b) is an ester of an acid alkenyl polyunsaturated monocarboxylic. Acid polyunsaturated is preferably di- or tri-unsaturated Such acids can be obtained at from natural materials, for example plant extracts or animals.

Mono-unsaturated acids Especially preferred are oleic and elaidic acid. Acids Especially preferred polyunsaturates are the linoleic and linolenic acid.

It has been found that mixtures in which (a) it is an ester of a mono-unsaturated acid and (b) is a ester of a polyunsaturated acid have especially good performance of lubrication capacity and exhibit particularly good filtration capacity and resistance to cold storage.

Esters are partial esters, that is, some of the hydroxy groups of each polyhydric alcohol are esterified It is preferred that at least one of (a) or (b) be a mono-ester An especially good performance is obtained when (a) and (b) are both mono-esters.

The esters can be prepared by methods well known in the art, for example by reactions of condensation. If desired, the alcohols can be reacted with acid derivatives such as anhydrides or acyl chloride with in order to facilitate the reaction and improve yields.

Esters (a) and (b) can be prepared by separated and then mixed together, the mixing taking place either before adding to the fuel, or as a consequence of the separate addition of (a) and (b) to the fuel thereto or Different times. Alternatively, the ester mixture can be prepare directly from a mixture of materials adequate heading. It has been found that the latest products (is say ester blends formed directly from the reaction of a mixture of starting materials) have particularly good filtration capacity and show Especially good performance of lubrication capacity. In in particular, commercially available acid samples suitable can be reacted with a selected alcohol such as glycerol to form a mixed ester product according to the invention. Commercial acid mixtures particularly Preferred are those comprising oleic and linoleic acids. In said mixtures, a smaller proportion of other acids, or acid polymerization products, but this proportion should preferably not exceed 15%, more preferably not more than 10%, and most preferably not more than 5% by weight of the total acid mixture.

Similarly, mixtures of esters by reacting a single acid with a mixture of alcohols

A highly preferred mixture of esters is the obtained by reacting a mixture of oleic acids and linoleic cone glycerol, comprising predominantly the mixture (a) glycerol mono-oleate and (b) glycerol mono-linoleate, preferably in approximately equal proportions by weight.

In addition to esters (a) and (b), the additive with lubrication capacity can also comprise a further proportion small of other esters formed, for example, during esterification of the acid mixtures described previously.

(ii) Fuel oil

The fuel oil can be a base fuel oil of oil, suitably a medium distillate fuel oil, that is a fuel oil obtained in the refining of crude oil such as fraction between the fraction of kerosene and fuels for Lighter turbojet and heavy fuel oil fraction. Sayings distillate fuel oils have boiling points usually by above about 100 ° C. The fuel oil can comprise atmospheric distillate or vacuum distillate, or cracking diesel or a mixture in any proportion of distillate distillates direct and thermal cracking and / or catalytic. The base fuel oils of petroleum the most common are kerosene, fuels for turboreactors and preferably fuel oils for engines diesel.

The sulfur content of fuel oils is 0.2% by weight or less, preferably 0.05% by weight or less, more preferably 0.01% by weight or less, and most preferably 0.001% by weight or less based on the weight of the fuel oil The technique describes methods to reduce the content in sulfur from hydrocarbon medium distillate fuels, said methods including solvent extraction, treatment with sulfuric acid, and hydro-desulfurization.

Preferred fuel oils have an index of cetane of at least 40, preferably above 45 and most preferably above 50. The fuel oil may have said cetane indices prior to the addition of any cetane index improver or cetane fuel index can be raised by adding an index improver cetane

More preferably, the cetane number of Fuel oil is at least 52.

(iii) Treatment speeds

The concentration of the additive in the fuel oil it can be for example in the range of 10 to 5,000 ppm by weight of additive (active ingredient) by weight of fuel oil, for example 20 a 5,000 ppm such as 50 to 2,000 ppm by weight (active ingredient) per fuel weight, preferably 75 to 300 ppm, more preferably 100 to 200 ppm.

The relative proportions of (a) and (b) by weight inside the fuel oil they are in the range of 1:10 to 2: 1, preferably 1: 4 to 2: 1 and more preferably 1: 2 to 2: 1. The 1: 1 ratio is the most preferred.

The use of the additive (second aspect of the invention) and method (fourth aspect of the invention).

Preferred additives for the second and fourth aspect of the invention are those described hereinabove in relationship with the first aspect.

The fuel oil of the second and fourth aspect of the invention is preferably that described here previously in relation to the first aspect.

The use of the fuel oil composition (third aspect of the invention).

When fuel oil is fuel oil for engines diesel, the fuel oil composition of the first aspect of the invention finds application in diesel engines (compression-ignition) as a fuel that, In addition to providing good combustion properties, it reduces the wear rate in the fuel supply system, and particularly in the fuel injection pump. The use of fuel thus prolongs the life of the equipment and reduces the Need for replacement of expensive mechanical parts.

The fuel oil composition of the first aspect of the invention similarly finds application in other systems of fuel oil in which the mechanical devices in the system fuel supply rely on fuel oil for your lubrication, and are therefore subject to wear.

Concentrates

The concentrates comprising the additive in mixing with a carrier liquid (for example as a solution or a dispersion) are convenient as a means to incorporate the additive in mass fuel oil, the incorporation of which can be carried out by methods known in the art. The concentrates can also contain other additives as required and preferably they contain from 3 to 75% by weight, more preferably 3 to 60% in weight, most preferably 10 to 50% by weight of the additives preferably in solution in the oil. The examples of liquids vehicle are organic solvents that include solvents hydrocarbons, for example petroleum fractions such as naphtha, kerosene, diesel oils and heating oils; aromatic hydrocarbons such as aromatic fractions, by example those sold under the trade name of "SOLVESSO"; paraffinic hydrocarbons such as hexane and pentane e isoparaffins; and oxygenated solvents such as alcohols. He liquid vehicle must of course be selected taking Be careful with its compatibility with the additive and with the fuel. The concentrates are added to the fuel oil in bulk in quantities sufficient to provide the speed of additive treatment indicated here above.

The additives of the invention can be incorporate into mass fuel oil by other methods such as those known in the art. If required co-additives, they can be incorporated into the mass fuel oil at the same time as the additives of the invention or At a different time.

Co-additives

The combustible composition of the first aspect of the invention may additionally comprise other compounds known to improve lubrication capacity such as co-additives, for example mono- or acidic acids polycarboxylic acids, such as acids di-carboxylic. These acids are preferably mixtures of polymerized unsaturated fatty acids, comprising mainly dimer and some acid trimer, with small proportions of monomer and / or higher polymers. Typical examples are the dimer acids of oleic acid, linoleic acid or mixtures of the same. Esters of these acids with alcohols monohydroxylated or dihydroxylated can also be used in combination with the mixture of esters (a) and (b), to provide additives further improved.

Similarly, they can be used co-additives with lubrication capacity of the type of ethoxylated amine.

The fuel oil of the first aspect of the invention may advantageously also comprise one or more improvers of the cold flow of fuel oil, as co-additives, such as one or more of:

(i)

ethylene-unsaturated ester copolymers,

(ii)

hydrocarbon polymers,

(iii)

sulfur-carboxy compound,

(iv)

polar compounds,

(v)

aromatic compounds substituted with hydrocarbyl,

(saw)

linear compounds, and

(vii)

comb polymers

as defined here more ahead.

(i) Ethylene-unsaturated ester copolymer

The copolymer flow improvers of ethylene for example copolymer flow improvers of ethylene-unsaturated ester, have a main structure of segment-divided polymethylene by side chains of hydrocarbyl interrupted by one or more oxygen atoms and / or carbonyl groups.

More especially, the copolymer can comprise an ethylene copolymer that has, in addition to the units obtained from ethylene, units of formula:

- CR 5 R 6 - CHR 7 -

in which R 6 represents hydrogen or a methyl group; R 5 represents a group -OOCR 8 or -COOR 8 in which R 8 represents hydrogen or a group C 1 to C 9 straight or branched chain alkyl, preferably C 1 to C 6, more preferably C 1 to C 3; and R 7 represents hydrogen or a group -COOR 8 or -OOCR 8.

These may comprise an ethylene copolymer with an ethylenically unsaturated ester, or derivatives thereof. An example is an ethylene copolymer with an ester of an acid unsaturated carboxylic acid such as ethylene acrylates (for example ethylene acrylate 2-ethylhexyl), but the ester is preferably one of an unsaturated alcohol with a saturated carboxylic acid such as It is described in the Document GB-A-1,263,152. A copolymer of ethylene-vinyl ester is advantageous. A copolymer of ethylene vinyl acetate, ethylene vinyl propionate, ethylene vinyl hexanoate, ethylene-2-ethylhexanoate, or ethylene vinyl octanoate. Preferably, the copolymers contain from 1 to 25 such as less than 25, for example 1 to 20 mol% of the vinyl ester, more preferably from 3 to 15 mol% vinyl ester. They can also be fit of mixtures of two copolymers such as those described in the Documents US-A-3,961,916 and EP-A-113,581. Preferably, the number average molecular weight, as measured by osmometry in vapor phase of the copolymer is 1,000 to 10,000, more preferably 1,000 to 5,000. If desired, the copolymers can be obtained at starting from additional comonomers, for example they can be terpolymers or tetrapolymers or higher polymers, for example when the additional comonomer is isobutylene or diisobutylene or other ester gives rise to different units of the above formula and in the that the mole% ester mentioned above refers to the ester total.

Also, the copolymers can include small proportions of chain transfer agents and / or modifiers of the molecular weight (for example acetaldehyde or propionaldehyde) that can be used in the polymerization process to prepare the copolymer

The copolymers can be prepared by direct polymerization of the comonomers. These copolymers are they can also prepare by trans-esterification, or by hydrolysis and re-esterification of an ethylene ester copolymer unsaturated to give an unsaturated ethylene ester copolymer different. For example, the copolymers of ethylene vinyl hexanoate and ethylene vinyl octanoate can be prepared from this way, for example from a copolymer of ethylene vinyl acetate.

The copolymers can have, for example, 15 or less, preferably 10 or less, more preferably 6 or less, what more preferably 2 to 5, lateral ramifications that end with methyl per 100 methylene groups, as measured by resonance nuclear magnetic, other than methyl groups on an ester comonomer and other than terminal methyl groups.

The copolymers can have a polydispersity from 1 to 6 preferably 2 to 4, the polydispersity being the ratio of the weight average molecular weight to the average molecular weight numerical as both are measured by chromatography of gel permeabilization using patterns polystyrene.

(ii) Hydrocarbon polymers Linear hydrocarbon polymers

These have one or more main structures of polymethylene, optionally divided into segments by short chain length hydrocarbyl groups, that is 5 or less carbon atoms

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The examples are those represented by the following general formula:

100

in the that

T represents H or R1;

U represents H, T or substituted aryl or without replace; Y

R 1 represents a hydrocarbyl group that It has up to 5 carbon atoms

and v and w represent relationships in moles, being v within the range of 1.0 to 0.0, and being w within the range of 0.0 to 1.0. Preferably, R1 is a linear chain alkyl group or branched.

These polymers can be prepared directly from ethylenically unsaturated monomers or indirectly by hydrogenation of the polymer prepared from monomers such as isoprene and butadiene.

Preferred hydrocarbon polymers are copolymers of ethylene and at least one α-olefin. Examples of such olefins are propylene, 1-butene, isobutene, and 2,4,4-trimethyl-2-pentene. The copolymer can also comprise small amounts, by example up to 10% by weight of other copolymerizable monomers, by example olefins other than α-olefins, and unconjugated dienes. The preferred copolymer is a copolymer of ethylene-propylene. It is within the scope of the invention include two or more copolymers of different ethylene-? -olefin of this type.

The number average molecular weight of the copolymer of ethylene-? -olefin is less than 150,000, as measured by chromatography of gel permeabilization (CPG) with respect to patterns of polystyrene. For some applications, it is advantageously at least 60,000 and preferably at least 80,000. Functionally I don't know it presents no upper limit except for the difficulties of mixing that take place as a result of viscosity increased to molecular weights above approximately 150,000, and the preferred molecular weight ranges are from 60,000 and 80,000 to 120,000. For other applications, it is below of 30,000, preferably below 15,000 such as below 10,000 or below 6,000.

Advantageously, the copolymer has a content in moles in ethylene between 50 and 85 percent. More advantageously, the ethylene content is in the range from 55 to 80 per percent, and preferably is in the range from 55 to 75 per hundred; more preferably from 60 to 70 percent, and most preferably 65 to 70 percent.

Examples of copolymers of ethylene-? -olefin are ethylene-propylene copolymers with a content of moles of ethylene from 60 to 75 percent and an average molecular weight numerical in the range from 60,000 to 120,000, the copolymers Especially preferred are copolymers of ethylene-propylene with an ethylene content from 62 to 71% and a molecular weight from 80,000 to 100,000.

The copolymers can be prepared by any of the methods known in the art, for example using a Ziegler type catalyst. Advantageously, the polymers they are substantially amorphous, since highly polymers crystals are relatively insoluble in fuel oil to low temperatures.

(iii) Sulfur-carboxy compounds

The examples are those described in the Document EP-A-0.261.957 describing the use of compounds of the general formula:

one

in which -Y-R2 is SO 3 (-) (+) NR 3 3 R 2, -SO 3 (-) (+) HNR 3 2 R 2, -SO 3 (-) (+) H 2 NR 3 R 2, -SO 3 {(-) (+)} H 3 NR 2, -SO 2 NR 3 R 2 or -SO3 R2; and -X-R1 is -Y-R 2 or -CONR 3 R 1, -CO 2 (-) (+) NR 3 3 R 1, -CO 2 (-) (+) HNR 3 2 R 1, - R 4 -COOR 1, -NR 3 COR 1, -R 4 OR 1, -R 4 OCOR 1, -R 4, R 1, -N (COR 3) R 1 or -Z (-) (+) NR 3 3 R 1; -Z <(-)} is SO3 {(-)} or -CO2 {(-)};

R 1 and R 2 are alkyl, alkoxyalkyl or polyalkoxyalkyl containing at least 10 carbon atoms in the main chain;

R 3 is hydrocarbyl and each R 3 can be the same or different and R 4 is absent or is alkylene C_ {1} to C_ {5} and in

2

the link carbon-carbon (C-C) is fine a) ethylenically unsaturated when A and B can be alkyl groups, alkenyl or substituted hydrocarbyl or b) part of a structure cyclic that can be aromatic, polynuclear aromatic or aliphatic cycle, it is preferred that X-R 1 and Y-R 2 between them contain at least three alkyl, alkoxyalkyl or polyalkoxyalkyl.

Additive systems can be used Multicomponents and additive ratios to use will depend on the fuel to be treated

(iv) Polar compounds

Said compounds comprise a compound of oil soluble polar nitrogen carrying one or more, preferably two or more amino or imino substituents substituted with hydrocarbyl, the group (s) being hydrocarbyl monovalent and containing 8 to 40 carbon atoms, being optionally which substituent or one or more of which substituents

in the form of a cation obtained from them. The oil-soluble polar nitrogen compound is either ionic or non-ionic and is able to act as a growth modifier of paraffin crystals in fuels. Preferably, the hydrocarbyl group is linear or slightly linear, that is, may have a short length hydrocarbyl branch (1-4 carbon atoms). When the substituent is amino, can carry more than one of said hydrocarbyl group, the which can be the same or different.

The term "hydrocarbyl" refers to a group that has a carbon atom attached directly to the rest of the molecule and that has a hydrocarbon character or predominantly hydrocarbon. Examples include groups hydrocarbons, which include aliphatic groups (for example alkyl or alkenyl), alicyclic (for example cycloalkyl or cycloalkenyl), aromatic, and aromatic substituted with alicyclic, and aliphatic and alicyclic substituted with aromatic. These groups may contain non-hydrocarbon substituents with the condition that their presence does not alter the character predominantly hydrocarbon group. Examples include keto, halo, hydroxy, nitro, cyano, alkoxy and acyl. If the group hydrocarbyl is substituted, a single (mono) is preferred substituent

Examples of substituted hydrocarbyl groups include 2-hydroxyethyl, 3-hydroxypropyl, 4-hydroxybutyl, 2-ketopropyl, ethoxyethyl, and propoxypropyl. The groups may also or alternatively contain different atoms to carbon in a chain or ring otherwise composed of atoms carbon Suitable heteroatoms include, for example, nitrogen, sulfur, and, preferably, oxygen.

More especially, the or each amino substituent or imino is attached to a moiety via an intermediate link group such such as -CO-, -CO2 {(-)}, -SO3 {(-)} or hydrocarbylene. When the linkage group is anionic, the substituent is part of a cationic group, as in an amine salt group.

When the polar nitrogen compound carries more of an amino or imino substituent, the linkage groups for each Substituent may be the same or different.

Suitable amino substituents are primary, secondary, tertiary or quaternary amino substituents C 12 -C 40 long chain alkyl, preferably C 12 -C 24.

Preferably, the amino substituent is a dialkyl amino substituent, which, as indicated above, it may be in the form of an amine salt thereof; Tertiary and quaternary amines can only form salts of amine. Said alkyl groups may be the same or different.

Examples of amino substituents include dodecyl amino, tetradecyl amino, coco-amino, and tallow hydrogenated-amino. Examples of substituents of secondary amino include dioctadecyl amino and methyl behenyl amino. Can be present mixtures of amino substituents such as those obtained from amines that exist naturally. A substituent of preferred amino is the amino substituent secondary-hydrogenated tallow, the alkyl groups of which is obtained from hydrogenated tallow fat and are typically composed of 4% C14, 31% C16 and 59% in C 18 weight of n-alkyl groups.

Suitable imino substituents are long chain alkyl substituents C 12 -C 40, preferably C_ {12} -C_ {24}.

Said rest can be monomeric (cyclic or not cyclic) or polymeric. When it is non-cyclic, it can be obtained at starting from a cyclic precursor such as an anhydride or a spirobis-lactone.

The cyclic ring system may include condensed homocyclic, heterocyclic or polycyclic assemblies, or a system in which two or more of said cyclic sets are joined to another and in which the cyclic sets can be the same or different. When there are two or more of these cyclic sets, the substituents may be on the same or different sets, preferably on the same set. Preferably, the or each cyclic set is aromatic, preferably a ring Benzene Most preferably, the cyclic ring system is a single benzene ring when it is preferred that the substituents are in ortho or goal positions, which benzene ring can be optionally further substituted.

The atoms of the ring in the set or sets cyclic are preferably carbon atoms but may include for example one or more atoms of N, S or O in the ring, in which case or cases the compound is a heterocyclic compound.

Examples of such polycyclic sets include:

(to)

condensed benzene structures such as naphthalene, anthracene, phenanthrene, and pyrene;

(b)

condensed ring structures when none of or not all Ring are benzene such as blue, indene, hydroindene, fluorene, and diphenylene oxides;

(C)

rings attached "at the end" such as diphenyl;

(d)

heterocyclic compounds such as quinoline, indole, 2: 3 dihydroindole, benzofuran, coumarin, isocumarin, benzothiophene, carbazole and thiodiphenyl amine;

(and)

non-aromatic or partially saturated ring systems such as decalin (i.e. decahydronaphthalene), α-pinene, cardinene, and bomylene; Y

(F)

structures three-dimensional such as norbornene, bicyclo-heptane (ie norbornano), bicyclo-octane, and bicyclo-octene.

Examples of polar nitrogen compounds are described below:

(I)

 a amine salt and / or amide of a mono- or acid polycarboxylic, for example having 1 to 4 groups of carboxylic acid. It can be prepared, for example, by doing react at least a molar ratio of a substituted amine with hydrocarbyl with a molar ratio of the acid or its anhydride.

When it forms an amide, the linking group is -CO-, and when a salt of amine, the linking group is -CO2 {(-)}.

The rest can Be cyclic or non-cyclic. Examples of cyclic remains are those in which the acid is acidic cyclohexane-1,2-dicarboxylic; acid cyclopentane-1,2-dicarboxylic; Y naphthalene dicarboxylic acid. Generally said Acids have 5 to 13 carbon atoms in the cyclic moiety. Sayings preferred cyclic acids are acids benzene dicarboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid, and acids benzene tetracarboxylic acids such as acid pyromellitic, with phthalic acid being particularly preferred. The Documents US-A-4,211,534 and EP-A-272,889 describe compounds of polar nitrogen containing said moieties.

Examples of non-cyclic residues are those in which the acid is an acid dicarboxylic substituted with long chain alkyl or alkylene such as succinic acid, as described for example in the Document US-A-4,147,520.

Other examples of non-cyclic residues are those in which the acid is an acid which contains nitrogen such as acid ethylenediaminetetraacetic.

Examples additional are the remains obtained when a dialkyl-spiro-bislactone is made React with an amine.

(II)

He Document EP-A-0.261.957 describes polar nitrogen compounds according to the present general formula description

3

in which -Y-R2 is SO 3 (-) (+) NR 3 3 R 2, -SO 3 (-) (+) HNR 3 2 R 2, -SO 3 (-) (+) H 2 NR 3 R 2, -SO 3 {(-) (+)} H 3 NR 2, -SO 2 NR 3 R 2 or -SO3 R2; and -X-R1 is -Y-R 2 or -CONR 3 R 1, -CO 2 (-) (+) NR 3 3 R 1, -CO 2 (-) (+) HNR 3 2 R 1, - R 4 -COOR 1, -NR 3 COR 1, -R 4 OR 1, -R 4 OCOR 1, -R 4, R 1, -N (COR 3) R 1 or -Z (-) (+) NR 3 3 R 1; -Z <(-)} is SO3 {(-)} or -CO2 {(-)};

R1 and R2 are alkyl, alkoxyalkyl or polyalkoxyalkyl containing at least 10 carbon atoms in the main chain;

R3 is hydrocarbyl and each R 3 may be the same or different and R 4 is absent or is C 1 to C 5 alkylene and in

4

the link carbon-carbon (C-C) is fine a) ethylenically unsaturated when A and B can be alkyl groups, alkenyl or substituted hydrocarbyl or b) part of a structure cyclic that can be aromatic, polynuclear aromatic or aliphatic cycle, it is preferred that X-R 1 and Y-R 2 between them contain at least three alkyl, alkoxyalkyl or polyalkoxyalkyl.

Can be used multi-component additive systems and additive ratios to use will depend on the fuel to be treated.

(III)

Document EP-A-0.316.108 describes an amine or diamine salt of (a) an acid sulfo-succinic, b) an ester or diester of an acid sulfo-succinic, c) an amide or a diamide of a sulfo-succinic acid, or d) a ester-amide of an acid sulfo-succinic.

(IV)

A chemical compound that comprises or includes a ring system cyclic, the compound carrying at least two substituents of the general formula (I) below on the system of ring

(I) - A - NR1 R2

in which A is an aliphatic hydrocarbyl group that is optionally interrupted by one or more heteroatoms and which is straight or branched chain, and R1 and R2 are the same or different and each is independently a hydrocarbyl group containing 9 to 40 atoms carbon optionally interrupted by one or more heteroatoms, the substituents being the same or different and the compound being optionally in the form of a salt thereof.

Preferably, A has from 1 to 20 carbon atoms and is preferably a group methylene or polymethylene.

Each group hydrocarbyl constituting R1 and R2 in the invention (Formula 1) can be for example an alkyl or alkylene group or a mono- or poly-alkoxyalkyl group. Preferably, Each hydrocarbyl group is a straight chain alkyl group. He number of carbon atoms in each hydrocarbyl group is preferably 16 to 40, more preferably 16 to 24.

I also know prefers the cyclic system to be substituted with only two substituents of general formula (I) and that A be a group methylene

Examples of salts of the chemical compounds are acetate and the hydrochloride

The compounds can be conveniently prepared by reducing the corresponding amide which can be prepared by reaction of a secondary amine with the appropriate chloride of acid.

(V)

 A primary or secondary long chain amine condensate with a polymer containing carboxylic acid.

Examples specific include polymers such as those described in the Documents GB-A-2,121,807, FR-A-2,592,387 and DE-A-3,941,561; and also esters of telomeric acid and alkanol amines such as described in the Document US-A-4,639,256; and the product of reaction of an amine containing a carboxylic acid ester branched, an epoxide and an acid polyester monocarboxylic such as described in the Document US-A-4,631,071.

The document EP-0.283.292 describes polymers containing amide and EP-0.343.981 describes polymers that They contain amine salt.

It should be noted that polar nitrogen compounds may contain another functionality such as ester functionality.

(v) Hydrocarbon aromatic compounds

These materials are condensates that comprise aromatic and hydrocarbyl parts. The aromatic part is conveniently an aromatic hydrocarbon that can be without replace or substituted with, for example, substituents not hydrocarbons.

Said aromatic hydrocarbon contains preferably a maximum of these substituent groups and / or three condensed rings, and is preferably naphthalene. The part of hydrocarbyl is a part that contains hydrogen and carbon attached to the rest of the molecule through a carbon atom. Can be saturated or unsaturated, and linear or branched, and may contain one or more heteroatoms with the condition that they do not substantially affect to the hydrocarbyl nature of the part. Preferably the hydrocarbyl part is an alkyl part, which has conveniently more than 8 carbon atoms.

(vi) Linear compounds

Said compounds comprise a compound in the that at least one substantially linear alkyl group having 10 to 30 carbon atoms are attached via an optional bonding group that it may be branched to a non-polymeric moiety, such as a moiety organic, to provide at least one linear chain of atoms that includes the carbon atoms of said alkyl groups and one or more non-terminal oxygen, sulfur and / or nitrogen atoms. The group of Link can be polymeric.

By "substantially linear" you want mean that the alkyl group is preferably straight chain, but those straight chain alkyl groups having a small degree of branching such as in the form of a single methyl group branching.

Preferably, the compound has at least two of said alkyl groups when the linear chain may include the carbon atoms of more than one of said alkyl groups. When he compound has at least three of said alkyl groups, there may be more than one of said linear chains, which chains can be overlap The chain or linear chains can provide part of the linking group between any two of said alkyl groups in the compound

The oxygen atom or atoms, if they were present, are preferably interposed directly between carbon atoms in the chain and can, for example, be arranged in the liaison group, if present, in the form of a mono- or poly-oxyalkylene group, having said oxyalkylene group preferably 2 to 4 carbon atoms, being examples oxyethylene and oxypropylene.

As indicated the chain or chains include carbon, oxygen, sulfur and / or nitrogen atoms.

The compound may be an ester in which alkyl groups are attached to the rest of the compound as groups -O-CO- n alkyl, or -CO-O n alkyl, obtaining in the above the alkyl groups from an acid and obtaining the rest of the compound from an alcohol polyhydroxylated and in the latter obtaining alkyl groups a from an alcohol and obtaining the rest of the compound from of a polycarboxylic acid. Also, the compound may be an ether. in which the alkyl groups are attached to the rest of the compound as -O-n-alkyl groups. He compound can be both an ester and an ether or it can contain different ester groups.

Examples include esters of polyoxyalkylene, ethers, ester / ethers and mixtures thereof, particularly those containing at least one, preferably at least two, linear C 10 to C 30 alkyl groups and one group polyoxyalkylene glycol of molecular weight up to 5,000, preferably 200 to 5,000, containing the alkylene group in said polyoxyalkylene glycol from 1 to 4 atoms carbon, as described in the Document EP-A-61,895 and in the Patent of USA No. 4,491,455.

Preferred esters, ethers or esters / ethers that can be used may comprise compounds in which one or more groups (such as 2, 3 or 4 groups) of the formula -OR 25 are attached to a remainder E, in which E can for example represent A (alkylene) q, in which A represents C or N or is absent, q represents an integer from 1 to 4, and the group alkylene has from one to four carbon atoms, being A (alkylene) q for example N (CH 2 CH 2) 3; C (CH 2) 4; or (CH 2) 2; Y R 25 can be independently

(to)

n-alkyl-

(b)

n-alkyl-CO-

(C)

n-alkyl-OCO- (CH2) n -

(d)

n-alkyl-OCO- (CH2) nCO-

where n is, for example, 1 to 34, the linear alkyl group being and containing from 10 to 30 atoms carbon For example, they can be represented by the formula R 23 OBOR 24, each defining R 23 and R 24 as for R 25 above, and B representing the segment of polyalkylene of the glycol in which the alkylene group has from 1 at 4 carbon atoms, for example, polyoxymethylene moiety, polyoxyethylene or polyoxytrimethylene which is substantially linear; some degree of branching with side chains can be tolerated lower alkyl (as in the polyoxypropylene glycol) but it is preferred that the glycol must be substantially linear.

Suitable glycols are generally polyethylene glycols (PEG) and substantially linear polypropylene glycols (PPG) which have a molecular weight of approximately 100 to 5,000, preferably about 200 to 2,000. The ones are preferred esters and fatty acids containing from 10 to 30 atoms of carbon are useful for reacting with glycols to form the ester additives, with the use of C18 fatty acid being preferred C 24, especially behenic acid. Esters can be also prepare by esterifying fatty acids polyethoxylated or polyethoxylated alcohols.

The diesters, diesters, ether / esters of polyoxyalkylene and mixtures thereof are suitable as additives, diesters being preferred when the component based on oil is a distillate with a narrow boiling point, in the that smaller amounts of monoethers may also be present and mono-esters (which are often formed in the process of manufacturing). It is important for active behavior that is present a more important amount of the dialkyl compound. In in particular, diesters of stearic or behenic acid of polyethylene glycol, polypropylene glycol or mixtures of polyethylene / polypropylene glycol.

Examples of other compounds in this category general are those described in Japanese Patent Publications Nos. 2-51477 and 3-34790, and in Documents EP-A-117.108 and EP-A-326,356, and ethoxylates cyclic esterifiers such as those described in the Document EP-A-356,256.

(vii) Comb polymers

Comb polymers are treated in "Comb-Like Polymers. Structure and Properties", N.A. Platé and V.P. Shibaev, J. Poly. Sci. Macromolecular Revs., 8, pages 117 to 253 (1974).

Generally, comb polymers consist of in molecules in which the long chain branches such as hydrocarbyl branches, optionally interrupted with one or more oxygen atoms and / or carbonyl groups, which have from 6 to 30 such as 10 to 30, carbon atoms, are hanging of a basic polymer structure, said joints being joined ramifications directly or indirectly to the basic structure. The Examples of indirect binding include binding via atoms or groups interposed, which union may include covalent union and / or electrovalent as in a salt. Generally, type polymers Comb are distinguished by having a minimum molar ratio of units containing said long chain branches.

Advantageously, the comb polymer is a homopolymer having, or a copolymer of at least 25 and preferably at least 40, more preferably at least 50, for mole percent of the units of which they have, chains laterals containing at least 6 such as at least 8, and preferably at least 10 atoms, selected from for example carbon, nitrogen and oxygen, in a linear chain or a chain that contains a small amount of branching such as a single methyl branching.

As examples of preferred comb polymers those containing units of formula may be mentioned general

101

in the that

D represents R 11, COOR 11, OCOR 11, R 12 COOR 11 or OR 11;

E represents H, D or R 12;

G represents H or D;

J represents H, R 12, R 12 COOR 11, or a substituted or unsubstituted heterocyclic or aryl group;

K represents H, COOR12, OCOR12, OR 12 or COOH;

L represents H, R 12, COOR 12, OCOR 12 or substituted or unsubstituted aryl;

R 11 representing a hydrocarbyl group that it has 10 or more carbon atoms, and

R 12 representing a hydrocarbyl group that it is divalent in the group R 12 COOR 11 and being otherwise monovalent,

and m and n represent relationships in moles, being its sum 1 and being m finite and being up to e including 1 and being n from zero to less than 1, m being preferably within the range from 1.0 to 0.4, being n in the range from 0 to 0.6. R 11 advantageously represents a hydrocarbyl group with from 10 to 30 carbon atoms, preferably 10 to 24, more preferably 10 to 18. Preferably, R 11 is a linear or slightly alkyl group branched and R 12 advantageously represents a group hydrocarbyl with from 1 to 30 carbon atoms when it is monovalent, preferably with 6 or higher, more preferably 10 or higher, preferably up to 24, more preferably up to 18 carbon atoms Preferably, R 12, when it is monovalent, is a linear or slightly branched alkyl group. When R 12 is divalent, it is preferably a methylene group or ethylene. By "slightly branched" it is meant that It has a single branch of methyl.

The comb polymer may contain units obtained from other monomers if desired or required, examples being CO, vinyl acetate and ethylene. It is inside the scope of the invention include two or more comb copolymers different.

Comb polymers can, for example, be copolymers of maleic anhydride or fumaric acid and other ethylenically unsaturated monomer, for example a α-olefin or an unsaturated ester, for example, vinyl acetate as described in the Document EP-A-214,786. It is preferred but it is not essential that equimolar amounts of comonomers be used although molar proportions in the range of 2 to 1 and 1 to 2 are adequate. Examples of olefins that can be copolymerized with by example maleic anhydride, include 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and styrene Other examples of comb polymer include methacrylates and acrylates.

The copolymer can be esterified by any suitable and although preferred technique is not essential that the maleic anhydride or fumaric acid are at least 50% esterified Examples of alcohols that can be used include 1-n-decanol, 1-n-dodecanol, 1-n-tetradecanol, 1-n-hexadecanol, and 1-n-octadecanol. Alcohols they can also include up to one methyl branching per chain, by example, 1-methyl-pentadecanol-1, 2-methyl-tridecanol-1 as described in the Document EP-A-213,879. Alcohol can be a mixture of normal and branched alcohols with a single methyl. It is preferred to use pure alcohols rather than mixtures of alcohols such as those that may be commercially available; whether mixtures are used the number of carbon atoms in the alkyl group is take the average number of carbon atoms in the groups alkyl of the mixture of alcohols; if the alcohols are used that they contain a branch in positions 1 or 2 the number of carbon atoms in the alkyl group are taken to be the number in the segment of the basic linear chain structure of the group alkyl of alcohol.

Comb polymers can be especially polymers and copolymers of fumarate or itaconate such such as those described in the Patent Applications European 153,176, 153,177, 156,577 and 225,688, and Document WO 91/16407.

Particularly preferred fumarate comb polymers are copolymers of alkyl and vinyl acetate fumarates, in which the alkyl groups have from 12 to 20 carbon atoms, more especially polymers in which the alkyl groups have 14 carbon atoms or in which the alkyl groups are a mixture of C 14 / C 16 alkyl groups, prepared, for example, by solution copolymerization of an equimolar mixture of fumaric acid and vinyl acetate and reacting the copolymer obtained with the alcohol or mixture of alcohols, which are preferably straight chain alcohols. When the mixture is used, it is advantageously a 1: 1 mixture by weight of normal C 14 and C 16 alcohols. In addition, mixtures of the C 14 ester with the mixed C 14 / C 16 ester can be advantageously used. In such mixtures, the ratio of C 14 to C 14 / C 16 is advantageously in the range from 1: 1 to 4: 1, preferably 2: 1 to 7: 2, and most preferably about 3 : 1, by weight. Particularly preferred fumarate comb polymers can have, for example, a number average molecular weight in the range of 1,000 to 100,000, preferably 1,000 to 50,000, as measured by vapor phase osmometry
(VPO)

Other suitable comb polymers are those α-olefin polymers and copolymers and the esterified copolymers of styrene and maleic anhydride, and esterified copolymers of styrene and fumaric acid as described in the Document EP-A-282,342; mixtures can be used of two or more comb polymers according to the invention and, as indicated above, such use may be advantageous.

Other examples of comb polymers are the hydrocarbon polymers such as ethylene copolymers and al minus an α-olefin, preferably having the α-olefin at most 20 carbon atoms, examples being 1-n-octene, 1-isooctene, 1-n-decene and 1-n-dodecene, 1-n-tetradecene and 1-n-hexadecene (for example, according to It is described in WO9319106).

Preferably, the average molecular weight numerical measured by permeabilization chromatography through gel versus the polystyrene standards of such a copolymer is for example, up to 30,000 or up to 40,000. Copolymers hydrocarbons can be prepared by methods known in the technique, for example using a Ziegler type catalyst. Sayings hydrocarbon polymers may for example have an isotacticity 75% or higher.

Some of the co-additives cold flow improvers described above may provide synergistic improvements to the capacity performance of lubrication when in combination with the ester mixture (a) and (b).

Additional co-additives that are they can use are those known in the art, for example detergents, antioxidants, corrosion inhibitors, agents turbidity eliminators, demulsifiers, deactivators metal, antifoaming agents, combustion enhancers such as cetane index improvers, co-solvents, compatibilizing agents of package, reodorants and additives based on metallic compounds such as metal combustion enhancers.

Evaluation of the benefits of the various aspects of the invention

It is believed that the mixture of esters (a) and (b) is capable of forming at least partial layers of a composition lubricant on certain metal surfaces. By this you it means that the layer formed is not necessarily Complete on the contact surface. The formation of said layers and the degree of its covering power of a contact surface it can be demonstrated by, for example, the measure of resistance to electrical contact or electrical capacitance.

An assay that can be used to demonstrate one or more of a reduction in wear, a reduction in friction or an increase in resistance to electrical contact in accordance with this invention is the alternative high frequency bench test (or "HFRR "), described in the standard test methods CEC PF 06-T-94 or ISO / TC22 / SC7 / WG6 /
N188

The degree to which an additive composition gives place to block the fuel oil tube filters can be measured using an assay of known filtration capacity. For example, a method to measure the filtration capacity of the compositions of fuel oils is described in the Institute of Petroleum's Standard designated "IP 387/190" and titled "Determination of filter blocking tendency of gas oils and distillate diesel fuels ". In summary, a sample of the fuel oil composition to be tested is made pass at a constant flow rate through a means of fiberglass filter; the pressure drop is observed through of the filter, and the volume of fuel oil that passes the medium of filter within a prescribed pressure drop. The tendency to filter lock of a fuel composition can be describe as the pressure drop through the filter medium to that 300 ml of fuel pass at a speed of 20 ml / min. Be refers to the Standard mentioned above for Additional Information. In the evaluation of the composition of additive of the present invention this method was adapted when performing the measurements at various temperatures lower than those specified in The Standard, to simulate cold storage conditions They take place in operation.

The invention is further illustrated as a reference to The following Examples.

Example 1

The following materials were used and procedures

Fuel oil

A fuel oil for diesel engines "Class I" Which has the features shown below:

Sulfur: 4.5 ppm weight / weight Index of cetane: 51.6 CFPP (Car): -36ºC

       \ vskip1.000000 \ baselineskip
    

Distillation : 50% of evaporation 237.1 ° C Point of final boil 294.1 ° C Residue (% by volume) 1.2

Additives

Additives A, B, C and D were added to the fuel oil for diesel engines in the quantities recorded in the Table 1, and the filtration capacity of each of the fuel compositions were evaluated according to the test IP 387/90 at the temperatures shown in Table 1. In each case, After complete mixing, the sample of the composition of fuel cooled to the required temperature in a unit of cooling and stored at that temperature during the period established time before being subjected to the test of filtration.

5

Additive A was prepared by esterification of a commercial mixture of oleic and linoleic acids with glycerol, to produce a mixed ester product prevailing in (a) glycerol mono-oleate and (b) glycerol mono-linoleate, in approximately equal proportions by weight, with smaller amounts of di- and glycerol tri-oleate and linoleate also present. In addition, the acid mixture contained a higher proportion. small of other acids, esters of which it is not believed that represent more than about 6% by weight of the ester product mixed.

Additive B was prepared by esterification of oleic acid with glycerol, to form a predominant product in glycerol mono-oleate (Document Additive D WO 94/17160).

Additive C was prepared by esterification of linoleic acid with glycerol, to form a product that predominates in glycerol mono-linoleate.

Additive D was a 1: 1 mole mixture of additive B and additive C.

In Table 1, the test results indicate the pressure drop on the filter at the end of each test, indicating the highest pressure drops a greater degree of partial blockage of the filter. When the pressure drop became greater than 103.4 kPa during the 15-minute test, the test time at which this pressure was reached (103.4 kPa, corresponds to the intense blockage of the filter and is considered for these purposes as an essay "failure").

It can be seen from the results in Table 1 that shows 2 (fuel composition of the invention) showed surprisingly improved filtration capacity over sample 3 (comparative fuel composition that contains additive D of WO 94/17160), both at 0 ° C and at -10 ° C. In addition, although both examples exceeded 103.4 kPa in the test after 1 week at -10 ° C, sample 2 showed a better behavior (exceeded just before the end of the trial of 15 minutes in contrast to sample 3 that exceeded this drop of pressure almost immediately).

In addition, the results at -5 ° C indicate that the samples 2 and 5 (fuel compositions of the invention) showed significantly improved filtration capacity over samples 3 and 4 (comparative), failing both of these two comparative examples the essay. Sample 2 containing the additive A (prepared by esterification of a mixture of starting acids) also surprisingly showed a improved behavior compared to sample 5 that contains additive D (prepared by mixing the esters together components).

Example 2

A small aliquot of each was separated of the samples of Example 1 stored at -5 ° C for 2 weeks immediately prior to the filtration stage described in Example 1, and the HFRR behavior at 60 ° C of each part was measured aliquot as an indication of the capacity performance of "pre-filtration" lubrication. Behavior HFRR at 60 ° C of each corresponding sample filtrate produced in Example 1 was also measured as an indication of the yield of the "post-filtration" lubrication capacity. The results are compared in Table 2 below.

TABLE 2

Sample Additive Concentration of additive HFRR Wear Mark HFRR Brand wear (ppm of ingredient before filtration after the filtration active, weight / weight) (\ mum) (\ mum) one None Zero 623 610 2 TO 200 309 330 3 B 200 249 396 4 C 200 343 411 5 D 200 292 274

The results in Table 2 indicate that the samples 3 and 4 (comparative) show capacity performance of significantly worse lubrication after filtration (i.e. a larger wear mark), in contrast to the samples 2 and 5 (fuel compositions of the invention) which they maintained their performance of lubrication capacity.

Untreated fuel (sample 1) did not show change, confirming that the differences in the results of other samples are due to the additives present in these compositions

Differences in the diameter of the brand of wear after filtration indicate a technical improvement significant and demonstrate the capacity properties of Enhanced lubrication provided by ester blends (a) and (b), on comparative additives.

Claims (11)

1. A fuel oil composition comprising a more important proportion of an average distillate fuel oil than it has a sulfur content of 0.2% by weight or less, and a smaller proportion of an additive with lubrication capacity that understands

(to)

 a ester of a monounsaturated monocarboxylic acid and an alcohol polyhydroxylated, and

(b)

 a ester of a polyunsaturated monocarboxylic acid and an alcohol polyhydroxylated having at least three hydroxy groups,

the esters (a) and (b) being different and being both partial esters, and being the relative proportions by weight of (a) and (b) in the range of 1:10 to 2: 1. 2. The composition of claim 1, in which the fuel oil has a sulfur content of 0.01% by weight or less. 3. The composition of claim 1 or the claim 2, wherein the fuel oil is a fuel for diesel engines 4. The composition of any of the preceding claims, wherein (a) is an ester of a polyhydric alcohol having at least three hydroxy groups. 5. The composition of any of the preceding claims, wherein (a) and (b) are esters of alkenyl monocarboxylic acids. 6. The composition of claim 5, in which both acids have alkenyl groups of 10 to 36 atoms of carbon. 7. The composition of any of the claims 4 to 6, wherein (a) and (b) are both esters of trihydric alcohols, especially glycerol. 8. The composition of claim 7, in which (a) and (b) are both mono-esters. 9. The composition of claim 8, in which (a) is a mono-ester of oleic acid and glycerol, and (b) is a mono-ester of linoleic acid and glycerol. 10. The use of the additive defined in any preceding claim to improve lubrication capacity of medium distillate fuel oil. 11. The use of the fuel oil composition of any one of claims 1 to 9, in an apparatus of combustion to reduce the wear rate in the system fuel supply of said apparatus.