EP1419224B1 - Highly desulfurised fuel oils, containing lubricity-enhancing additives with reduced emulsification susceptibility - Google Patents

Abstract

The invention relates to an additive for improving the lubrication capacity of fuel oils with a maximum sulphur content of 0.035 wt. %. Said additive contains at least one ester of a bivalent or polyvalent alcohol and a mixture of unsaturated and optionally saturated fatty acids, whose carbon chain lengths are between 8 and 30 carbon atoms, the aforementioned esters having an OH value less than 200 mg KOH/g ester and an iodine value greater than 100 g I/100 g ester. The invention also relates to fuel oils with a maximum sulphur content of 0.035 wt. %, which contain the inventive additives. The novel additives exhibit less tendency to emulsify than the additives in prior art.

Description

The present invention relates to additives of esters between polyols and fatty acid mixtures, as well as their use for improving the lubricity of highly desulfurized fuel oils with reduced emulsification tendency.

Mineral oils and mineral oil distillates used as fuel oils generally contain 0.5% by weight and more sulfur which causes the formation of sulfur dioxide upon combustion. In order to reduce the resulting environmental impact, the sulfur content of fuel oils is lowered further and further. The standard EN 590 relating to diesel fuels currently prescribes a maximum sulfur content of 350 ppm in Germany. In Scandinavia fuel oils of less than 50 ppm and in exceptional cases less than 10 ppm of sulfur are used. These fuel oils are usually prepared by hydrogenating the fractions obtained from the petroleum by distillation. In the desulfurization but other substances are removed, which give the fuel oils a natural lubricating effect. These substances include polyaromatic and polar compounds.

However, it has now been shown that the friction and wear-reducing properties of fuel oils deteriorate with increasing degree of desulfurization. Often, these properties are so poor that on the lubricated by the fuel materials, such as the distributor injection pumps of diesel engines after a short time must be expected with feeding phenomena. The maximum value set for the 95% distillation point of maximum 360 ° C according to EN 590 since the year 2000 and which has since been published in Scandinavia further lowered the 95% distillation point to below 350 ° C and partly below 330 ° C further aggravates this problem. The prior art therefore describes approaches which are intended to provide a solution to this problem (so-called lubricity additives).

EP-A-0 680 506 discloses that esters of fatty acids impart improved lubricity to highly desulfurized fuel oils. In particular, glycerol monooleate and diisodecyl adipate are mentioned.

EP-A-0 739 970 discloses the suitability of fatty acid mixtures for improving the lubricity of low sulfur fuel oils. Compositions of different degrees of esterification and different degrees of saturation of the fatty acids are disclosed.

EP-A-0 839 174 discloses in its lubricity improved fuel oils which are low in sulfur and comprise a mixture of polyol esters with unsaturated fatty acids.

DE-A-196 14 722 discloses lubricant and fuel additives, which consist essentially of fatty acid monoesters or mono- and diester mixtures of unsaturated fatty acids having 16 to 22 carbon atoms with at least two different polyols, have a more favorable low-temperature behavior than corresponding monoesters or mono- and diesters of uniform polyols. The polyol is preferably a mixture of glycerol and another polyol from the group trimethylolpropane, pentaerythritol and dipentaerythritol in a molar ratio of 1: 1 to 3: 1.

However, the fatty acid esters of the prior art based on commercial fatty acid mixtures show a pronounced tendency to emulsify in the fuel oils that are additized with them. This means that when such a fuel oil comes in contact with water, emulsification of the water in the fuel oil takes place. These emulsions, which can be found in particular at the oil / water interface, can not be separated or can be separated only with great effort. Since these emulsions can not be used as such as fuel oils, they reduce the value of the products. This problem is particularly pronounced when esters based on natural fatty acid mixtures are used.

The object of the present invention was therefore to find lubricant-improving additives for desulfurized fuel oils, which have a reduced emulsifier tendency compared with the prior art.

Surprisingly, it has been found that esters of fatty acid mixtures, which show a certain combination of hydroxyl number and iodine number, do not have the emulsifying ability of the esters of the prior art, and have an excellent lubricating effect in desulfurized fuel oils. Presumably, the reduced tendency for emulsification is brought about by two effects. On the one hand, the polarity range of the additives, which is determined by the OH number, causes a reduced affinity of the amphiphilic active substances for water. On the other hand, at the same time the formation of micellar, surface-active structures is disturbed by the number of double bonds in the alkyl radicals determined by iodine number.

The invention therefore relates to fuel oils with a maximum of 0.035 wt .-% sulfur content, containing at least one ester of a dihydric or polyhydric alcohol and a mixture of unsaturated and optionally saturated fatty acids whose carbon chain lengths are between 8 and 30 carbon atoms, said esters a OH number of between 110 and 195 mg KOH / g ester and an iodine value of more than 100 gl / 100 g ester, in amounts of 0.001 to 0.5 wt .-% based on the fuel oil.

Another object of the invention is the use of the additives of the invention in amounts of 0.001 to 0.5 wt .-% based on the fuel oil, to improve the lubricity of fuel oils with at most 0.035 wt .-% sulfur content.

Preferred fatty acids which are part of the fatty acid mixture are those having 10 to 26 C atoms, in particular 12 to 22 C atoms. The alkyl radicals of the fatty acids consist essentially of carbon and hydrogen. However, you can choose other substituents such as hydroxy, halogen, amino or

Wear nitro groups, provided that they do not affect the predominantly hydrocarbon character. The fatty acids contained in the fatty acid mixture preferably contain at least one double bond. They may contain multiple double bonds, for example 2 or 3 double bonds, and be of natural or synthetic origin. In the case of polyunsaturated carboxylic acids, their double bonds may be isolated or else conjugated. In preferred fatty acid mixtures contain at least 50 wt .-%, in particular at least 75 wt .-%, especially at least 90 wt .-% of the fatty acids one or more double bonds. The iodine numbers of the fatty acids on which the esters according to the invention are based are preferably between 105 and 190, in particular 110 to 180 and especially 120 to 180 g l / 100 g of ester.

Suitable fatty acid mixtures contain at least two unsaturated fatty acids having 10 to 26 carbon atoms. Suitable unsaturated fatty acids are, for example, oleic acid, erucic acid, palmitoleic, myristoleic, linoleic, linolenic, elaeosterolic, arachidonic acid, and / or ricinoleic acid. Preference is given to fatty acid mixtures or fractions obtained according to the invention from natural fats and oils, e.g. Peanut oil, fish, linseed oil, palm oil, rapeseed oil, ricinoleic, castor oil, rapeseed oil, soybean oil, sunflower oil and tall oil fatty acid having corresponding iodine numbers.

In addition, the fatty acid mixtures may contain minor amounts, i. up to 10 wt .-%, preferably less than 5%, especially less than 2% of saturated fatty acids such as lauric, tridecane, myristic, pentadecane, palmitic, margarine, stearic, isostearic, arachin and Contain behenic acid.

Also suitable as constituent of the fatty acid mixtures are dicarboxylic acids, such as dimer fatty acids and alkyl- and alkenylsuccinic acids with C ₈ -C ₅₀ -alk (en) yl radicals, preferably with C ₈ -C ₄₀ -, in particular with C ₁₂ -C ₂₂ -alkyl radicals. The alkyl radicals can be linear or branched (oligomerized alkenes, PIB). Preferred are proportions of up to 10 wt .-%, in particular less than 5 wt .-%. The fatty acids may further contain 1-40, especially 1-25 wt .-%, in particular 1-5 wt .-% resin acids.

Suitable alcohols preferably contain 2 to 6, in particular 3 to 4 carbon atoms, and 2 to 5, in particular 3 to 4 hydroxyl groups, but at most one hydroxyl group per carbon atom. Particularly suitable alcohols are ethylene glycol, diethylene glycol, propylene glycol, glycerol and pentaerythritol.

The esters can be prepared from alcohols and fatty acids in a known manner by esterification. Alternatively, the partial saponification of naturally occurring fats and oils is possible. Esters of the invention are those which can be prepared from a dihydric or polyhydric alcohol and a mixture of fatty acids. Both mixtures of, for example, monoesters of an alcohol with various fatty acids, of monoesters of different alcohols with different fatty acids, and of mixtures of mono-, di- and / or triesters, or optionally higher esters, of one or more alcohols with different fatty acids are included , According to the invention, the esters are if they can be prepared from a fatty acid mixture.

The iodine numbers of the esters according to the invention are preferably between 100 and 180, in particular 110 to 150 g l / 100 g ester. The iodine numbers result from the iodine value of the basic fatty acid mixture and the alcohol used for the esterification in a stoichiometric manner.

The OH number of the esters in the additive according to the invention is between 110 and 195, in particular between 130 and 190 mg KOH / g of ester. In general, these are mixtures of different esters, eg. As mixtures of mono-, di- and triglycerides, mixtures, such as those resulting from the esterification of polyols.

The additives according to the invention are added to oils in amounts of 0.001 to 0.5% by weight, preferably 0.005 to 0.3% by weight and especially 0.01 to 0.1% by weight. They can be used as such or dissolved in solvents, such as aliphatic and / or aromatic hydrocarbons or hydrocarbon mixtures such as toluene, xylene, ethylbenzene, decane, pentadecane, gasoline fractions, kerosene or commercial solvent mixtures such as Solvent Naphtha, ^® Shellsol AB, ^® Solvesso 150, ^® Solvesso 200, ^® Exxsol-, ^® Isopar- and ^® Shellsol D types are used. The additives according to the invention preferably contain 1 to 80%, especially 10 to 70%, in particular 25 to 60%, of solvent. The additives, which can be used without problems even at low temperatures of, for example, -30 ° C. and lower, improve the lubricity of the additized oils while at the same time reducing emulsification.

For the preparation of additive packages for specific problem solutions, the additives according to the invention can also be used together with one or more oil-soluble co-additives which in themselves improve the cold flow properties and / or lubricity of crude oils, lubricating oils or fuel oils. Examples of such co-additives are vinyl acetate-containing copolymers or terpolymers of ethylene, paraffin dispersants, comb polymers, alkylphenol-aldehyde resins and oil-soluble amphiphiles.

For example, mixtures of the additives according to the invention with copolymers which have 10 to 40% by weight of vinyl acetate and 60 to 90% by weight of ethylene have proven outstanding. According to a further embodiment of the invention, the additives according to the invention are used in admixture with ethylene / vinyl acetate / vinyl neononanoate terpolymers or ethylene / vinyl acetate / vinyl neodecanoate terpolymers to simultaneously improve the flowability and lubricity of mineral oils or mineral oil distillates. The terpolymers of vinyl neononanoate or vinyl neodecanoate contain, in addition to ethylene, 10 to 35% by weight of vinyl acetate and 1 to 25% by weight of the respective neo compound. Further preferred copolymers contain, in addition to ethylene and from 10 to 35% by weight of vinyl esters, from 0.5 to 20% by weight of olefin, such as diisobutylene, 4-methylpentene or norbornene. The mixing ratio of the additives according to the invention with the above described ethylene / vinyl acetate copolymers or the terpolymers of ethylene, vinyl acetate and the vinyl esters of neononan or neodecanoic acid is (in parts by weight) 20: 1 to 1:20, preferably 10: 1 to 1:10.

For use as flow improvers and / or lubricity additives, the reaction products according to the invention can also be used together with paraffin dispersants. Paraffin dispersants reduce the size of the paraffin crystals and cause the paraffin particles to not settle but remain colloidally dispersed with significantly reduced sedimentation effort. Furthermore, they increase the lubricity of the additives of the invention. Suitable paraffin dispersants are oil-soluble polar compounds having ionic or polar groups, eg amine salts and / or amides, which are prepared by reaction of aliphatic or aromatic amines, preferably long-chain aliphatic amines, with aliphatic or aromatic mono-, di-, tri- or tetracarboxylic acids or their Anhydrides are obtained (see. US 4 211 534 ). Other paraffin dispersants are copolymers of maleic anhydride and α , β-unsaturated compounds, which may optionally be reacted with primary monoalkylamines and / or aliphatic alcohols (cf. EP 0 154 177 ), the reaction products of Alkenylspirobislactonen with amines (see. EP 0 413 279 B1 ) and after EP 0 606 055 A2 Reaction products of terpolymers based on α , β-unsaturated dicarboxylic acid anhydrides, α , β-unsaturated compounds and polyoxyalkylene ethers of lower unsaturated alcohols. Alkylphenol-aldehyde resins are also suitable as paraffin dispersants.

Thus, the additives according to the invention can be used in mixture with alkylphenol-formaldehyde resins.

Finally, in a further embodiment of the invention, the additives according to the invention are used together with comb polymers. This term refers to polymers in which hydrocarbon radicals having at least 8, in particular at least 10, carbon atoms are bonded to a polymer backbone. Preferably, they are homopolymers whose alkyl side chains contain at least 8 and in particular at least 10 carbon atoms. In the case of copolymers, at least 20%, preferably at least 30% of the monomers have side chains (cf. Comblike Polymers-Structure and Properties; NA Platé and VP Shibaev, J. Polym. Sci. Macromolecular Revs. 1974, 8, 117 ff ). Examples of suitable comb polymers are, for example, fumarate / vinyl acetate copolymers (cf. EP 0 153 176 A1 ), Copolymers of a C ₆ -C ₂₄ α- olefin and a NC ₆ -C ₂₂ -alkylmaleimide (cf. EP 0 320 766 ), further esterified olefin / maleic anhydride copolymers, polymers and copolymers of α- olefins and esterified copolymers of styrene and maleic anhydride.

beschrieben werden. Darin bedeuten

A

R', COOR', OCOR', R"-COOR' oder OR';

D

H, CH₃, A oder R;

E

H oder A;

G

H, R", R"-COOR', einen Arylrest oder einen heterocyclischen Rest;

M

H, COOR", OCOR", OR" oder COOH;

N

H, R", COOR", OCOR, COOH oder einen Arylrest;

R'

eine Kohlenwasserstoffkette mit 8-150 Kohlenstoffatomen;

R"

eine Kohlenwasserstoffkette mit 1 bis 10 Kohlenstoffatomen;

m

eine Zahl zwischen 0,4 und 1,0; und

n

eine Zahl zwischen 0 und 0,6.

Comb polymers may, for example, be represented by the formula

to be discribed. Mean in it

A

R ', COOR', OCOR ', R "-COOR' or OR ';

D

H, CH _3, A or R;

e

H or A;

G

H, R ", R" -COOR ', an aryl radical or a heterocyclic radical;

M

H, COOR ", OCOR", OR "or COOH;

N

H, R ", COOR", OCOR, COOH or an aryl radical;

R '

a hydrocarbon chain of 8-150 carbon atoms;

R "

a hydrocarbon chain of 1 to 10 carbon atoms;

m

a number between 0.4 and 1.0; and

n

a number between 0 and 0.6.

The mixing ratio (in parts by weight) of the inventive additives with resins or comb polymers is 1:10 to 20: 1, preferably 1: 1 to 10: 1.

The additives of the invention are particularly well suited for use in middle distillates. As middle distillates are in particular those mineral oils which are obtained by distillation of crude oil and boil in the range of 120 to 450 ° C, for example kerosene, jet fuel, diesel and fuel oil. The oils may also contain or consist of alcohols such as methanol and / or ethanol. Preferably, the additives of the invention are used in such middle distillates containing less than 350 ppm of sulfur, especially less than 200 ppm of sulfur and in special cases less than 50 ppm of sulfur. These are generally those middle distillates that have been subjected to a hydrogenating refining, and therefore contain only small amounts of polyaromatic and polar compounds that give them a natural lubricating effect. The additives according to the invention are furthermore preferably used in middle distillates which have 95% distillation points below 370.degree. C., in particular 350.degree. C. and in special cases below 330.degree. They can also be used as components in lubricating oils.

The mixtures can be used alone or together with other additives can be used, for example, with pour point depressants or dewaxing aids, with corrosion inhibitors, antioxidants, sludge inhibitors, dehazers, conductivity improvers, lubricity additives, and additives for lowering the cloud point. Furthermore, they are successfully used together with additive packages containing, among others, known ashless dispersing additives, detergents, defoamers and corrosion inhibitors. Between the additives according to the invention and the other additives mentioned, the synergisms with regard to cold flow properties described in the prior art are used WO-95/03377 and Lubricity according to WO 96/18708 such as WO 96/23855 achieved.

The effectiveness of the additives according to the invention as lubricity additives is explained in more detail by the following examples.

Examples

Table 1: Characterization of the additives used (erf = according to the invention, V = comparison) additives OH number [mg KOH / g] Iodine number [g J / 100 g] chemical characterization A (required) 158 103 Partial esters of glycerine and soybean oil fatty acid B (V) 181 52 Partial esters of glycerol and tallow fatty acid C (V) 153 76 Partial esters of glycerin and olein D 88 116 Partial esters of glycerine and tall oil fatty acid E (erf) 193 122 Partial esters of glycerine and tall oil fatty acid F (V) 278 77 Partial esters of glycerin and olein

Determined amount of excess acetic anhydride and subsequent titration of the acetic acid formed.

Iodine numbers are determined by Kaufmann. For this purpose, a sample of known composition is admixed with a defined, excess amount of a methanolic bromine solution, with an amount of bromine equivalent to the content of double bonds in the sample being added to the double bonds. The excess of bromine is back titrated with sodium thiosulfate. Table 2: Esters according to the prior art (comparative values) ester OH number [mg KOH / g] Iodine number [g J / 100 g] Glycerol monooleate (pure) 315 71 Glycerol dioleate (pure) 90 82 EP 0 839 174 , Eg A 181 78 EP 0 839 174 , Eg B 315 71 EP 0 839 174 , Eg C 317 143 EP 0 739 970 , Eg A 181 77 EP 0 739 970 , Eg G 284 120 EP 0 739 970 , Eg H 141 44 EP 0 739 970 , I 155 72 EP 0 739 970 , Eg J 111 74 EP 0 739 970 , Eg K 185 78 EP 0 739 970 , Eg L 122 81 EP 0 739 970 , Eg M 192 77 EP 0 739 970 , Eg N 8th 86 EP 0 739 970 , Eg O 84 75 EP 0 739 970 , Ex. P 227 76 EP 0 739 970 , Q. 184 73 EP 0 739 970 , Eg R 192 62

Emulsification in middle distillates

The testing of the emulsification of additives is carried out according to ASTM D 1094-85. 80 ml of a diesel fuel are mixed in a 100 ml cylinder with 250 ppm of the additive to be tested and tempered for 15 minutes at 60 ° C and shaken. After cooling to room temperature, 2 ml of buffer solution are added and shaken for 2 minutes. After 5 minutes, the sample is assessed visually according to the following criteria: Table 3: Emulsification of the additives Evaluation of the separation layer Evaluation of the phase separation 1 Clear and clean 1 Complete absence of all emulsions and / or precipitates in both phases or on top of the oil phase. 1 b small, clear bubbles that are estimated to cover no more than 50% of the release layer. No streaks, no film formation or other wetting on the release layer. 2 Like (1), but in addition small air bubbles or small water droplets in the oil phase. 2 Streaking, film formation or other wetting on the release layer 3 Emulsions and / or precipitates in both phases or on top of the oil phase, and / or drops in the water phase or on the wall adhering (except the wall over the oil phase). In parentheses: amount of water phase 3 Narrow hem or slight foaming, or both 4 Dense hem or heavy foaming, or both example additive Interface phase separation oil phase water phase 1 A 1b 2 (20 ml H ₂ O) slightly cloudy clear 2 (V) B 3 3 (8 ml H ₂ O) cloudy clear 3 (V) C 4 3 (10 ml H ₂ O) cloudy clear 4 D 2 2 (20 ml H ₂ O) slightly cloudy clear 5 e 2 2 (20 ml H ₂ O) slightly cloudy clear 6 (V) F 3 3 (6 ml H ₂ O) cloudy clear

Lubricating effect in middle distillates

The lubricating effect of the additives was carried out using an HFRR instrument from PCS Instruments on additized oils at 60 ° C. The High Frequency Reciprocating Rig Test (HFRR) is described in D. Wei, H. Spikes, Wear, Vol. 2, p. 217, 1986 , The results are given as coefficient of friction and Wear Scar (WS 1.4). A low coefficient of friction and a low Wear Scar show a good lubricating effect.

The test oil used was a Scandinavian winter diesel with the following characteristics: boiling range: 185 - 320 ° C Density: 0.820 g / cm ³ Cloud Point: - 29 ° C sulfur content: 3 ppm

The boiling characteristics are determined according to ASTM D-86 and the determination of the cloud point according to ISO 3015. Table 4: Wear Scar in test oil 2 example additive metering Wear Scar Friction 7 (V) Without - 679 μm 0.40 8 (V) Glycerol monooleate (99% pure) 100 ppm 230 μm 0.13 9 (V) dioleate 100 ppm 306 μm 0.16 10 A 100 ppm 210 μm 0.12 11 (V) B 100 ppm 263 μm 0.14 12 (V) C 100 ppm 284 μm 0.14 13 D 100 ppm 206 μm 0.12 14 e 100 ppm 301 μm 0.14 15 (V) F 100 ppm 291 μm 0.13

Claims (15)

1. A fuel oil having a maximum sulfur content of 0.035% by weight, comprising at least one ester of a di- or polyhydric alcohol and a mixture of unsaturated and optionally saturated fatty acids whose carbon chain lengths are between 8 and 30 carbon atoms, the esters mentioned having an OH number of between 110 and 195 mg KOH/g of ester and an iodine number of more than 100 g of l/100 g of ester, in amounts of from 0.001 to 0.5% by weight based on the fuel oil.
2. A fuel oil as claimed in claim 1, wherein the iodine number is between 100 and 180 g of l/100 g of ester.
3. A fuel oil as claimed in claim 1 and/or 2, wherein the fatty acids which are a constituent of the fatty acid mixture contain from 10 to 26 carbon atoms.
4. A fuel oil as claimed in one or more of claims 1 to 3, wherein the fatty acid mixtures contain up to 10% by weight of saturated fatty acids.
5. A fuel oil as claimed in one or more of claims 1 to 4, wherein the alcohols contain from 2 to 6 carbon atoms.
6. A fuel oil as claimed in one or more of claims 1 to 5, wherein the alcohols contain from 2 to 5 hydroxyl groups, but a maximum of one hydroxyl group per carbon atom.
7. A fuel oil as claimed in one or more of claims 1 to 6, wherein a constituent of the fatty acids is dicarboxylic acid.
8. A fuel oil as claimed in one or more of claims 1 to 7, wherein an alkylphenol-formaldehyde resin is additionally present in an additive:resin ratio of from 1:10 to 20:1 by weight.
9. A fuel oil as claimed in one or more of claims 1 to 7, wherein copolymers which contain from 10 to 40% by weight of vinyl acetate and from 60 to 90% by weight of ethylene,
   ethylene/vinyl acetate/vinyl neononanoate terpolymers or ethylene/vinyl acetate/vinyl neodecanoate terpolymers which, apart from ethylene, contain from 10 to 35% by weight of vinyl acetate and from 1 to 25% by weight of the particular neo compound, or
   copolymers which, in addition to ethylene and from 10 to 35% by weight of vinyl esters, also contain from 0.5 to 20% by weight of olefin,
   are additionally present in a mixing ratio of additive to the above-described copolymers or terpolymers (in parts by weight) of from 20:1 to 1:20.
10. A fuel oil as claimed in one or more of claims 1 to 7, wherein oil-soluble polar compounds having ionic or polar groups which are obtained by reacting aliphatic or aromatic amines with aliphatic or aromatic mono-, di-, tri- or tetracarboxylic acids or anhydrides thereof are additionally present.
11. A fuel oil as claimed in one or more of claims 1 to 7, wherein comb polymers of the formula

    

    where

    A is R', COOR', OCOR', R"-COOR' or OR';

    D is H, CH₃, A or R;

    E is H or A;

    G is H, R", R"-COOR', an aryl radical or a heterocyclic radical;

    M is H, COOR", OCOR" , OR" or COOH;

    N is H, R", COOR", OCOR, COOH or an aryl radical;

    R' is a hydrocarbon chain having from 8-150 carbon atoms;

    R" is a hydrocarbon chain having from 1 to 10 carbon atoms;

    m is a number between 0.4 and 1.0; and

    n is a number between 0 and 0.6

    are additionally present in a mixing ratio (in parts by weight) of the additives with comb polymers of from 1:10 to 20:1.
12. A fuel oil as claimed in one or more of claims 1 to 7, wherein copolymers of maleic anhydride and α,β-unsaturated compounds which may optionally be reacted with primary monoalkylamines and/or aliphatic alcohols are additionally present.
13. A fuel oil as claimed in one or more of claims 1 to 7, wherein reaction products of alkenyl-spiro-bislactones with amines are additionally present.
14. A fuel oil as claimed in one or more of claims 1 to 7, wherein reaction products of terpolymers based on α,β-unsaturated dicarboxylic anhydrides, α,β-unsaturated compounds and polyoxyalkylene ethers of lower unsaturated alcohols are additionally present.
15. The use of an additive as defined in one or more of claims 1 to 7 in amounts of from 0.001 to 0.5% by weight based on the fuel oil for improving the lubricity of fuel oils having a sulfur content of at most 0.035% by weight.