CA2391932A1

CA2391932A1 - Lubricity improver and a fuel and lubricant compositions containing said agent

Info

Publication number: CA2391932A1
Application number: CA002391932A
Authority: CA
Inventors: Siegbert Brand; Dietmar Posselt
Original assignee: Individual
Current assignee: BASF SE
Priority date: 1999-11-17
Filing date: 2000-11-16
Publication date: 2001-05-25
Also published as: PT1230328E; JP2003514953A; EP1230328A1; WO2001036568A1; DE19955354A1; DE50008267D1; ES2228644T3; EP1230328B1; DK1230328T3; NO20022357D0; ATE279497T1; KR20020052212A; NO20022357L

Abstract

The invention relates to additive mixtures comprising a) the reaction product formed after reaction of a dicarboxylic acid or a derivative thereof with a long-chain, aliphatic amine; and b) a natural fatty acid ester; c) the use of said additive mixture for improving the lubricity of fuels and for improving engine resistance to wear, in addition to fuel and lubricant compositions containing said additive mixtures.

Description

/I
s Lubricity improver and a fuel and lubricant compositions containing said agent The present invention relates to additive mixtures, their use for improving the lubricity of fuels and for improving the wear resistance of engines and to fuel compositions and additive packages containing them and their use as lubricant additives.
Carburetors and intake systems of gasoline engines as well as injection systems for fuel metering are increasingly becoming contaminated with impurities which are caused by dust particles from the air, uncombusted hydrocarbon residues from the combustion chamber and the crankcase vent gases passed into the carburetor.
These residues shift the air/fuel ration during idling and in the lower part-load range so that the mixture becomes leaner, the combustion more incomplete and hence the amounts of uncombusted or partially combusted hydrocarbons in the exhaust gas become larger, resulting in increased gasoline consumption.
It is known that these disadvantages are avoided by using fuel additives for keeping valves and carburetors or injection systems of gasoline engines clean (cf. for example: M. Rossenbeck in Katalysatoren, Tenside, Mineraloladditive, Editors J. Falbe and U. Hasserodt, page 223, G. Thieme Verlag, Stuttgart 1978).
Depending on the mode of action, but also the preferred site of action of such detergent additives, a distinction is now made between two generations.
The first generation of additive could only prevent the formation of deposits in the intake system but were unable to remove existing deposits, whereas the modern additives of the second generation can do both (keep-clean and clean-up effect) and, owing to their excellent thermal stability, can do so in particular in zones of high temperature, i.e. at the intake valves.
Such detergents which may originate from a large number of classes of chemical substances, for example polyalkenylamines, polyetheramines, polybutene Mannich bases or polybutenylsuccinamides, are used in general in combination with carrier oils and, if required, further additive components, for example corrosion inhibitors and demulsifiers. Gasoline fuels with and without such gasoline fuel additives exhibit different ~i behavior with respect to their lubricity and wear properties in gasoline engines, which however is unsatisfactory and should therefore be improved.
5 In contrast to fuel additives for diesel fuels, in which components for improving the lubricity of diesel fuels are part of the prior art, in the case of gasoline fuels there are only a few technical solutions for significantly increasing and hence improving the lubricity of gasoline fuels by adding suitable 10 additives to them. For example, it is known that fatty acids and derivatives thereof, (EP-A-780 460, EP-A- 829 527), alkenylsuccinic esters (WO 97/45507), bis(hydroxyalkyl)-fatty amines (EP-A-869 163) or hydroxyacetamides (WO-98/30658, US-A-5,756,435) when used as additives for gasoline fuels and/or 15 gasoline fuel additives, can improve the lubricity of the gasoline fuels. In the case of castor oil, too, it is known that its addition to diesel fuels (EP-A-605 857) and/or gasoline fuels (US-A-5,505,867) can increase the lubricity.
It is an object of the present invention to provide novel fuel additives which improve the lubricity, in particular of gasoline fuels, or the wear resistance, in particular of gasoline engines.
We have found that this object is achieved, surprisingly, by providing additive mixtures, in particular gasoline fuel additive mixtures, containing, as a lubricity additive, a mixture of a) at least one reaction product of a dicarboxylic acid or of a dicarboxylic acid derivative with a long-chain, aliphatic amine of, for example, up to 30 carbon atoms, the reaction product comprising a compound of the following formula I:
O

R (I) \C - Rz 4o II

where R is a saturated or unsaturated Cz-C4-bridging group which is unsubstituted or mono- or polysubstituted, ~i R1 is NR3R4, where R3 and R4 are identical or different and are each a straight-chain or branched aliphatic radical selected from C8-C2o-alkyl, mono- or polyunsaturated Ce-C2o-alkenyl, C8-CZO-alkyloxy, and mono- or polyunsaturated C8-C2o-alkenyloxy, or one of the radicals R3 and R4 is H and the other radical is an aliphatic radical according to the above definition, and R2 is OH or O-NR5R6 + where R5 and R6, independently of one another and independently of R3 and R4, have the meanings stated for R3 and R4, and b) at least one fatty ester or one fatty ester-containing component.
The two components are present in a volume ratio of from about 1:10 to 10:1, in particular from about 1:5 to 5:1.
In a first preferred embodiment, additive mixtures according to the above definition are provided, where R is CZ-C4-alkylene or ethenylene. Suitable substituents on R are, for example, hydroxyl, C1-C4-alkyl, such as methyl and ethyl, and hydroxy-C1-C4-alkyl, such as hydroxymethyl and hydroxyethyl.
Examples of suitable dicarboxylic acid derivatives which can be used for the preparation of compounds of the formula I are in.
particular the cyclic dicarboxylic anhydrides. Preferred anhydrides are malefic anhydride and succinic anhydride and the corresponding substituted analogs thereof. Further preferred dicarboxylic acid derivatives are dicarboxylic esters, in particular esters of C1-Clo-monools, C1-Clo-monools being defined as stated below for the fatty esters.
Preferred meanings of R3, R4, R5 and R6 in compounds of the formula I are C8-C2o-alkyl, e.g. n-octyl, n-nonyl, n-decyl, n-undecyl, n-tridecyl, n-tetradecyl, n-pentadecyl and n-hexadecyl, and the singly and multiply branched analogs thereof .
Examples of suitable Ce-C2o-alkenyl radicals are the mono- or polyunsaturated, preferably monounsaturated analogs of the abovementioned alkyl radicals, it being possible for the double bond to be in any desired position of the carbon chain. Examples of suitable C$-CZO-alkyloxy and C$-C2o-alkenyloxy radicals are the ~i oxygen-terminated analogs of the abovementioned alkyl and alkenyl radicals.
Preferred long-chain aliphatic amines which are used for the reaction with the dicarboxylic acid or the dicarboxylic acid derivative are primary or secondary amines having one or two identical or different CB-C2o-alkyl or alkenyl radicals, in particular decylamine, undecylamine, dodecylamine, tridecylamine, tetradecylamine, pentadecylamine and hexadecylamine, and the corresponding secondary amines having two identical aliphatic radicals. Further examples are fatty amines and fatty amine mixtures, for example those of 16 to 18 carbon atoms.
Suitable fatty esters are synthesized from straight-chain or branched, mono- or polyunsaturated, unsubstituted or substituted C6-C3a-monocarboxylic acids and a monohydric or polyhydric, preferably monohydric to trihydric, alcohol. Polyhydric alcohols may be partially or completely esterified with the same or another fatty acid. Examples of saturated straight-chain fatty acids are caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, margaric acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid and melissic acid. Examples of monounsaturated fatty acids are palmitoleic acid, oleic acid and erucic acid. Examples of diunsaturated fatty acids are sorbic acid and linoleic acid. Examples of triunsaturated fatty acids are linolenic and eleostearic acid. Examples of fatty acids which are tetraunsaturated or have a higher degree of unsaturation are arachidonic acid, clupanodonic acid and docosahexaenoic acid. An example of a substituted fatty acid is ricinoleic acid ((R)-12-hydroxy-(Z)-9-octadecenoic acid). Further suitable fatty acids are naturally occurring fatty acids, such as gondoic acid and neronic acid. If the fatty acids contain double bonds, they may be present both in the cis and in the trans form. The substituents are preferably selected from hydroxyl and lower alkyl groups, e.g. methyl and ethyl. Furthermore, keto or epoxy groups, as in vernolic acid, may be present in the hydrocarbon radical. Further functional groups are cyclopropane, cyclopropene and cyclopentene rings, which may be formed by bridging two neighboring carbon atoms in the hydrocarbon radical of the fatty acid (cf. malvalic acid and chaulmoogric acid).
Examples of suitable alcohols are C1-Clo-monools, in particular methanol, ethanol, n-propanol, n-butanol, n-pentanol and the corresponding branched analogs thereof. Examples of suitable diols are CZ-C6-diols, such as ethane-1,2-diol, propane-1,3-diol, ai butane-1,2-diol and pentane-1,2-diol and the corresponding positional isomers of these diols. Examples of suitable alcohols having a higher functionality are in particular glycerol and sugar alcohols, e.g. sorbitol and inositol, pentaerythritol and 5 trimethylol propane. A preferred polyhydric alcohol is glycerol.
A preferred group of fatty esters comprises triglycerides of identical or different fatty acids according to the above definition or mixtures of such triglycerides and mixtures of such triglycerides with the corresponding mono- and/or diglycerides.
Natural triglycerides as are to be found, for example, in vegetable oils are particularly preferably used. Examples of particularly suitable vegetable oils are rapeseed oil, coconut oil, palm kernel oil, corn oil, olive oil, soybean oil, sunflower oil, linseed oil, peanut oil and castor oil. The triglycerides which can be used according to the invention can be isolated from these oils. If permitted by the triglyceride content of such oils, they can also be added directly to the novel additive compositions. For example, industrial castor oil can be used without further fractionation in the novel additive mixtures.
The present invention furthermore relates to the use of the novel additive mixtures for improving the lubricity of gasoline fuels and/or for improving the wear resistance of gasoline engines. The present invention also relates to fuel compositions, in particular for gasoline engines, containing a lubricity-improving amount of at least one additive mixture according to the present invention, if required in combination with further conventional fuel additives, in addition to a main amount of a hydrocarbon fuel. The present invention furthermore relates to additive concentrates containing a novel additive mixture in combination -- with further conventional additive components in solid or, if desired, dissolved or dispersed forms.
Surprisingly, it has been found that the wear of gasoline engines can be substantially reduced using fuels to which the novel fuel additives have been added. It has been possible to show that a synergistic effect is obtained by the novel combination of the reaction products of dicarboxylic acids or their derivatives of long-chain, aliphatic amines and natural fatty esters.
The reaction product of dicarboxylic acids or their derivatives with long-chain, aliphatic amines according to the formula defined above, as a component of the novel fuel additives, is obtained directly with the use of known processes (cf.

~i Houben-Weyl, VIII, page 656, X/2, page 747; or J. March, Advanced Organic Chemistry, 3rd edition, 1985, page 371).
Preferred synergistic combinations comprise reaction products of carboxylic anhydrides with primary or secondary alkyl- or alkenylamines mixed with triglycerides. Mixtures of reaction products of malefic anhydride with primary or secondary alkylamines having a chain length of C8-C18, e.g. tridecylamine or ditridecylamine, and castor oil are particularly preferred.
The novel additive mixture can be used alone or in combination with further fuel additives, for example the abovementioned detergent additives described in more detail below.
Examples of further gasoline fuel additives (having a detergent action) which are used in addition to the novel fuel additives are those which have at least one hydrophobic hydrocarbon radical having a number average molecular weight (Mn) of from 85 to 20,000 and at least one polar group which is selected from (a) mono- or polyamino groups having up to 6 nitrogen atoms, at least one nitrogen atom having basic properties, (b) nitro groups, if required in combination with hydroxyl groups, (c) hydroxyl groups in combination with mono- or polyamino groups, at least one nitrogen atom having basic properties, (d) carboxyl groups or their alkali metal or alkaline earth metal salts, (e) sulfo groups or their alkali metal or alkaline earth metal salts, (f) polyoxy-C2-C4-alkylene groups which are terminated by hydroxyl groups or by mono- or polyamino groups, at least one nitrogen atom having basic properties, or by carbamate groups, (g) carboxylic ester groups, (h) groups derived from succinic anhydride and having hydroxyl and/or amino and/or amido and/or imido groups and (i) groups produced by Mannich reaction of phenolic hydroxyl groups with aldehydes and mono- or polyamines.

~i .<' 7 The hydrophobic hydrocarbon radical in these detergent additives, which ensures sufficient solubility in the fuel, has a number average molecular weight (Mn) of from 85 to 20,000, in particular from 113 to 10,000, especially from 300 to 5000. Suitable typical hydrophobic hydrocarbon radicals, in particular in combination with the polar groups (a), (c), (h) and (i), are the polypropenyl, polybutenyl and polyisobutenyl radicals, each having an Mn of from 150 to 5000, in particular from 500 to 2500, especially from 750 to 2250.
Examples of fuel additives having polar groups (a) are polyalkenyl monoamines or polyalkenyl polyamines or functional derivatives thereof, in particular poly-C2-C6-alkenylamines or functional derivatives thereof, for example based on polypropene, polybutene or polyisobutene. Additives containing mono- or polyamino groups (a) are preferably polyalkenyl monoamines or polyalkenylpolyamines based on polypropene or on highly reactive (i.e. having predominantly terminal double bonds, generally in the a- and ~- positions) or conventional (i.e. having predominantly central double bonds) polybutene or polyisobutene having an Mn of from 150 to 5000, preferably from about 500 to 2000, in particular from about 800 to 1500 g. Such additives based on highly reactive polyisobutene which can be prepared from polyisobutene, which may contain up to 20% by weight of n-butene units, by hydroformylation and reductive amination with ammonia, monoamines or polyamines, such.as dimethylaminopropylamine, ethylenediamine, diethylenetriamine, triethylenetetramine or tetraethylenepentamine, are disclosed in particular in EP-A-244 616 or EP-A-0 578 323. If polybutene or polyisobutene having predominantly central double bonds (generally in the ~- and y-positions) is used as a starting material in the preparation of the additives, a possible method of preparation is by chlorination and subsequent amination or by oxidation of the double bond with air or ozone to give the carbonyl or carboxyl compound and subsequent amination under reductive (hydrogenating) conditions. The same amines as those used above for the reductive amination of the hydroformylated highly reactive polyisobutene may be employed here for the amination. Corresponding additives based on polypropene are described in particular in WO-A 94/24231.
Further preferred additives containing monoamino groups (a) are the hydrogenation products of the reaction products of polyisobutenes having an average degree of polymerization P of from 5 to 100 with oxides of nitrogen or mixtures of oxides of nitrogen and oxygen, as described in particular in WO-A 97/03946.

Further preferred additives containing monoamino groups (a) are the compounds obtainable from polyisobutene epoxides by reaction with amines and subsequent dehydration and reduction of the amino alcohols, as described in particular in DE-A 196 20 262.
Additives containing nitro groups, if desired in combination with hydroxyl groups, (b) are preferably reaction products of polyisobutenes having an average degree of polymerization P of from 5 to 100 or from 10 to 100 with oxides of nitrogen or mixtures of oxides of nitrogen and oxygen, as described in particular in WO-A 96/03367 and in WO-A 96/03479. These reaction products are as a rule mixtures of pure nitropolyisobutanes (e. g.
a,~-dinitropolyisobutane) and mixed hydroxynitropolyisobutanes (e. g. a-nitro-~-hydroxypolyisobutane).
Additives containing hydroxyl groups in combination with mono- or polyamino groups (c) are in particular reaction products of polyisobutene epoxides, obtainable from polyisobutene having preferably predominantly terminal double bonds and an Mn of from 150 to 5000, with ammonia, or mono- or polyamines, as described in particular in EP-A 476 485.
Additives containing carboxyl groups or their alkali metal or alkaline earth metal salts (d) are preferably copolymers of C2-CQO-olefins with malefic anhydride, having a total molar mass of from 500 to 20,000, some or all of whose carboxyl groups having been converted into the alkali metal or alkaline earth metal salts and the remainder of whose carboxyl groups having been reacted with alcohols or amines. Such additives are disclosed in particular in EP-A 307 815. Such additives serve mainly for preventing valve seat wear and, as described in WO-A 87/01126, can advantageously be used in combination with conventional fuel detergents, such as poly(iso)butenylamines or polyetheramines.
Additives containing sulfo groups or their alkali metal or alkaline earth metal salts (e) are preferably alkali metal or alkaline earth metal salts of an alkyl sulfosuccinate, as described in particular in EP-A-639 632. Such additives serve mainly for preventing valve seat wear and can advantageously be used in combination with conventional fuel detergents, such as poly(iso)butenylamines or polyetheramines.
Additives containing polyoxy-C2-C4-alkylene groups (f) are preferably polyethers or polyetheramines, which are obtainable by reacting C2-C6o-alkanols, C6-C3o-alkanediols, mono- or di-C2-C3o-alkylamines, C1-C3o-alkylcyclohexanols or C1-C3o-alkylphenols with from 1 to 30 mol of ethylene oxide and/or ~i propylene oxide and/or butylene oxide per hydroxyl group or amino group and, in the case of the polyetheramines, by subsequent reductive amination with ammonia, monoamines or polyamines. Such products are described in particular in EP-A-310 875, EP-A-356 725, EP-A-700 985 and US-A-4,877,416. For example poly-C2-C6-alkylene oxide amines or functional derivatives thereof can be used as polyetheramines. In the case of polyethers, such products also have carrier oil properties. Typical examples of these are tridecanol butoxylates, isotridecanol butoxylates, isononylphenol butoxylates and polyisobuteneol butoxylates and progoxylates and the corresponding reaction products with ammonia.
Additives containing carboxylic ester groups (g) are preferably esters of mono- di- or tricarboxylic acids with long-chain alkanols or polyols, in particular those having a minimum viscosity of 2 mm2/s at 100~C, as described in particular in DE-A-38 38 918. The mono-, di- or tricarboxylic acids used may be aliphatic or aromatic acids, and suitable ester alcohols and ester polyols are in particular long-chain members having, for example, 6 to 24 carbon atoms. Typical esters are adipates, phthalates, isophthalates, terephthalates and trimellitates of isooctanol, of isononanol, of isodecanol and of isotridecanol.
Such products also have carrier oil properties.
Additives containing groups which are derived from succinic anhydride and have hydroxyl and/or amino and/or amido and/or imido groups (h) are preferably corresponding derivatives of polyisobutenylsuccinic anhydride, which are obtainable by reacting conventional or highly reactive polyisobutene having an Mn of from 150 to 5000 with malefic anhydride by a thermal route or via the chlorinated polyisobutene. Of particular interest here are derivatives with aliphatic polyamines, such as ethylenediamine, diethylenetriamine, triethylenetetramine or tetraethylenepentamine. Such gasoline fuel additives are described in particular in US-A-4,849,572.
Additives containing groups (i) produced by Mannich reaction of substituted phenols with aldehydes and mono- or polyamines are preferably reaction products of polyisobutene-substituted phenols with formaldehyde and mono- or polyamines, such as ethylenediamine, diethyletriamine, triethylenetetramine, tetraethylenepentamine or dimethylaminopropylamine. The polyisobutene-substituted phenols may originate from conventional or highly reactive polyisobutene having an Mn of from 150 bis l 5000. Such polyisobutene Mannich bases are described in particular in EP-A 831 141.
Further detergent additives suitable according to the invention are described, for example in EP-A-0 277 345, EP-A-0 484 736, EP-A-0 539 821, EP-A-0 543 225, EP-A-0 548 617, EP-A-0 561 214, EP-A-0 567 810 and EP-A-0 568 873, and in DE-A-39 42 860, DE-A-43 09 074, DE-A-43 09 271, DE-A-43 13 088, DE-A-44 12 489, DE-A-044 25 834, DE-A-195 25 938, DE-A-196 06 845, DE-A-196 06 846, DE-A-196 15 404, DE-A-196 06 844, DE-A-196 16 569, DE-A-196 18 270 and DE-A-196 14 349. Particularly useful detergent additives are sold by BASF AG, Ludwigshafen, under the trade name Kerocom~ PIBA. These contain polyisobutenylamines dissolved in aliphatic Clo-C14-hydrocarbons.
For a more exact definition of the individual gasoline fuel additives mentioned, express reference is made here to the disclosures of the abovementioned prior art publications.
The. novel gasoline fuel additives or gasoline fuels to which additives have been added can moreover contain further conventional components and additives, for example carrier oils, corrosion inhibitors, demulsifiers and markers.
Examples of useful carrier oils or carrier oil liquids are mineral carrier oils, synthetic carrier oils and mixtures thereof which are compatible with the additive or additives used and with the gasoline fuel. Suitable mineral carrier oils are fractions obtained in mineral oil processing, such as kerosene or naphtha, Brightstock or base oils having viscosities of, for example, class SN 500-2000, as well as aromatic hydrocarbons, paraffinic -- hydrocarbons and alkoxyalkanols.
Examples of suitable synthetic carrier oils are polyolefins, (poly)esters, (poly)alkoxylates and in particular polyethers, aliphatic polyetheramines, alkylphenol-initiated polyethers and alkylphenol-initiated polyetheramines. Suitable carrier oil systems are described, for example, in DE-A-38 38 918, DE-A-38 26 608, DE-A-41 42 241, DE-A-43 09 074, US-A-4,877,416 and EP-A-0 452 328, which are hereby expressly incorporated by reference. Examples of particularly suitable synthetic carrier oils are alkanol-initiated polyethers having from about 10 to 35, for example from about 15 to 30, C3-C6-alkylene oxide units, which are selected, for example, from propylene oxide, n-butylene oxide and isobutylene oxide units or mixtures thereof.

~i -i Further conventional additives are corrosion inhibitors, for example based on ammonium salts of organic carboxylic acids, which salts tend to form films, or on heterocyclic aromatics in the case of corrosion protection of nonferrous metals, antioxidants or stabilizers, for example based on amines, such as p-phenylenediamine, dicyclohexylamine or derivatives thereof or on phenols, such as 2,4-di-tert-butylphenol or 3,5-di-tert-butyl-4-hydroxyphenylpropionic acid, demulsifiers, antistatic agents, metallocenes, such as ferrocene or methylcyclopentadienylmanganesetricarbonyl, further lubricity additives, such as specific fatty acids, alkenylsuccinic esters, bis(hydroxyalkyl)-fatty amines or hydroxyacetarnides and markers.
If required, it is also possible to add amines for reducing the pH of the fuel.
The novel fuel additive combinations, if required in combination with one or more of the abovementioned further fuel additives having the polar groups (a) to (i) and the other components mentioned, are metered into the fuel and display their action there. The components or additives can be added to the fuel individually or as a previously prepared concentrate (additive packet).
Suitable solvents or diluents (in the preparation of additive packets) are aliphatic and aromatic hydrocarbons, e.g. solvent naphtha or kerosene.
The novel fuel additive mixtures are added to the fuel, for example, in an amount of from ~10 to 150, preferably from 20 to 100, ppm (mg/kg of fuel). The further fuel additives having the polar groups (a) to (i) are added to the gasoline fuel usually in an amount of from 10 to 5000 ppm, in particular from 50 to 1000 ppm, and the other components and additives mentioned are, if desired, added in customary amounts.
The gasoline fuel to which the novel fuel additive mixtures are added are not subject to any particular restrictions per se. They may be, for example, a fuel according EN 228. The fuel may be, for example, a gasoline fuel having an aromatics content of not more than 42, e.g. from 30 to 42, ~ by volume and a sulfur content of not more than 150 ppm, e.g. from 5 to 150 ppm.
The gasoline fuel can moreover have an olefin content of not more than 21, e.g. from 6 to 21, ~ by volume.

~ I

The benzene content may be not more than 1.0, e.g. from 0.5 to 1.0, $ by volume; the oxygen content may be, for example, from 1.0 to 2.7~ by weight.
The content of alcohols and ethers in the gasoline fuel is usually relatively low. Typical maximum contents are 3$ by volume for methanol, 5% by volume for ethanol, 10~ by volume for isopropanol, 7~ by volume for tert-butanol, 10$ by volume for isobutanol and 15~ by volume for ethers having 5 or more carbon atoms in the molecule.
The summer vapor pressure of the gasoline fuel is usually not more than 70, in particular 60, kPa, (in each case at 37~C).
The research octane number (RON) of the gasoline fuel is as a rule from 90 to 100. A customary range for the corresponding motor octane number (MON) is from 80 to 90.
The stated specifications are determined by conventional methods (DIN EN 228).
The non-restricting examples which follow illustrate the invention.
Examples:
An HFRR (High Frequency Reciprocating Rig; HFR2 from PCS
Instruments, London) and a tribometer as described, for example in EP-A-0 605 857, were used for testing the lubricity and the wear, respectively. Measuring conditions adapted to gasoline - fuels were chosen. The applicability of these test methods is -- demonstrated in D. Margaroni, Industrial Lubrication and Tribology, Vol. 50, No. 3, May/June 1998, 108-118 and W.D. Ping, S. Korcek, H. Spikes, SAE Techn. Paper 962010, 51-59 (1996).
The gasoline fuels used (typical gasoline fuels according to EN
228) were evaporated down to 50% by volume of the original volume by distillation under gentle conditions before the measurement.
This 50~ residue served as a blank test sample in the testing in the tribometer and was combined with the novel fuel additive mixtures or pure additive components in accordance with the.
examples shown below. The resulting frictional wear value is stated in micrometers. The lower this value, the less the resulting wear.

~i Example 1 (according to the invention):
The novel fuel additive mixture was prepared by mixing the components malefic anhydride (MA)/tridecylamine condensate (50~ by weight) and castor oil (technical-grade, 50$ by weight). The components were advantageously mixed at about 50°C. The condensate was initially taken, and castor oil was then added slowly with thorough stirring. Thorough stirring or circulation was carried out until a homogeneous mixture resulted. The condensate was prepared beforehand by initially taking MA (1.6 parts by weighty in a solvent (5 parts by weight of heavy solvent naphtha) and adding tridecylamine (3.4 parts by weight) in such a way that the reaction temperature did not exceed 90~C.
Example 2 (comparison):
The 50$ residue of a European premium-grade fuel according to EN
228 gave a blank value of 654 micrometers in the HFRR test. The addition of 50 mg/kg of castor oil according to Example 1 gave a fretting value of 667 micrometers and hence no improvement in the lubricity.
Example 3 (comparison):
The 50~ residue of a European premium-grade fuel according to EN
228 gave a blank value of 654 micrometers in the HFRR test. The addition of 50 mg/kg of MA/tridecylamine condensate, prepared according to Example 1, gave a fretting value of 669 micrometers and hence no improvement in the lubricity.
Example 4 (according to the invention):
The 50$ residue of a European premium-grade fuel according to EN
228 was tested by the abovementioned HFRR method and gave a fretting value of 732 micrometers. The addition of 50 mg/kg of the additive mixture comprising MA/tridecylamine condensate and castor oil according to Example 1 led to a substantial improvement in the fretting value to 688 micrometers and hence exhibited the synergistic effect in comparison with Examples 2 and 3.
Example 5 (according to the invention):
The 50~ residue of a European premium-grade fuel according to EN
228 gave a blank value of 728 micrometers in the HFRR test. The addition of 1250 mg/kg of a detergent additive packet (containing polyisobutenylamine, synthetic carrier oil, corrosion inhibitors ~i and kerosene) still led to a value of 710 micrometers. When the fuel additive according to Example 1 was added, according to the invention, to his packet, the fretting value was substantially improved. The further addition of 50 mg/kg of the fuel additive according to Example 1 to the packet (1250 mg/kg) gave 672 micrometers, while 100 mg/kg gave 655 micrometers.
Example 6 (according to the invention):
The 50~ residue of a European premium-grade fuel according to EN
228 gave a blank value of 872 micrometers in the HFRR test. The addition of 900 mg/kg of a detergent additive packet (containing polyisobutene, polyetheramine, corrosion inhibitors and kerosene), mixed with 50 mg/kg of the fuel additive according to Example 1, led to 782 micrometers and hence to a significant improvement in the lubricity.

Claims

We claim:

1. A synergistic gasoline additive mixture consisting of a) at least one reaction product of a dicarboxylic acid or of a dicarboxylic acid derivative with a long-chain, aliphatic amine, the reaction product comprising a compound of the following formula I:

where R is a saturated or unsaturated C2-C4-bridging group which is unsubstituted or mono- or polysubstituted, R1 is NR3R4, where R3 and R4 are identical or different and are each a straight-chain or branched aliphatic radical selected from C8-C20-alkyl, mono- or polyunsaturated C8-C20-alkenyl, C8-C20-alkyloxy, and mono- or polyunsaturated C8-C20-alkenyloxy, or one of the radicals R3 and R4 is H and the other radical is an aliphatic radical according to the above definition, and R2 is OH or O-NH2R5R6 + where R5 and R6, independently of one another and independently of R3 and R4, have the meanings stated for R3 and R4, and b) at least one fatty ester or one fatty ester-containing component.

2. An additive mixture as claimed in claim 1, wherein R is -(CH2)n-, where n is 2-4 or,-CH=CH-.

3. An additive mixture as claimed in either of the preceding claims, wherein the dicarboxylic acid derivative is a dicarboxylic anhydride.

4. An additive mixture as claimed in any of the preceding claims, wherein the aliphatic amine is a primary or secondary C8-C18-alkylamine or C8-C18-alkenylamine.

5. An additive mixture as claimed in any of the preceding claims, wherein the fatty ester is a triglyceride, if required as a mixture with the corresponding mono- and/or diglyceride.

6. An additive mixture as claimed in any of the preceding claims, wherein the fatty ester-containing component is selected from vegetable oils.

7. An additive mixture as claimed in claim 6, wherein the vegetable oil is selected from rapeseed oil, coconut oil, palm kernel oil, corn oil, olive oil, soybean oil, sunflower oil, linseed oil, peanut oil and castor oil.

8. An additive mixture as claimed in any of the preceding claims, which contains a) the reaction product of maleic anhydride with tridecylamine or ditridecylamine and b) castor oil.

9. An additive mixture as claimed in any of the preceding claims, which contains a) and b) in a volume ratio of from about 1:5 to 5:1.

10. An additive mixture as claimed in any of the preceding claims, consisting of a synergistic combination of components a) and b) and additionally at least one detergent additive.

11. The use of an additive mixture as claimed in any of the preceding claims for improving the lubricity of gasoline fuels and/or for improving the wear resistance of gasoline engines.

12. A gasoline fuel composition containing a main amount of a hydrocarbon fuel and a lubricity-improving amount of at least one additive mixture as claimed in any of claims 1 to 10 and, if required, further conventional additives or components.

13. A fuel composition as claimed in claim 12, which contains the additive mixture as claimed in any of claims 1 to 10 in an amount of from 10 to 150 ppm.

14. A lubricant composition containing at least one additive mixture as claimed in any of claims 1 to 9 in addition to a main amount of conventional lubricants.

15. A gasoline fuel additive concentrate containing an additive mixture as claimed in any of claims 1 to 9, if required in combination with further conventional additive components.

16. An additive concentrate as claimed in claim 15, additionally containing at least one detergent additive.