EP1857530A1 - Composition of fuel oils - Google Patents

Abstract

Fuel oil additive (I) comprises a copolymer of ethylene and 13-17 mol% of at least an acryl- or vinyl ester with 1-18C-alkyl residue and a melting viscosity V140 of at most 80 mPas; and comb polymer containing structural units of at least a olefin as monomer 1, which carries at least 8-18C alkyl residue at the olefinic double bond and at least an ethylenically unsaturated dicarboxylic acid as monomer 2, which carries at least 8-16C alkyl residue that is bound over an ester group, where the parameter Q, calculated using the formula as given in the specification, exhibits a value of 23-27. An independent claim is included for a fuel oil composition containing a vegetable or animal fuel oil and a fuel oil additive.

Description

The present invention relates to an additive, its use as a cold flow improver for vegetable or animal fuel oils and correspondingly fueled fuel oils.

With decreasing world oil reserves and the environmental impact of fossil and mineral fuel consumption, there is a growing interest in alternative energy sources based on renewable raw materials. These include, in particular, natural oils and fats of plant or animal origin. These are usually triglycerides of fatty acids with 10 to 24 carbon atoms, which have a comparable calorific value to conventional fuels, but at the same time are considered to be less harmful to the environment. Biofuels, ie fuels derived from animal or plant material, are obtained from renewable sources and thus produce only as much CO ₂ as was previously converted into biomass. It has been reported that combustion produces less carbon dioxide than equivalent amount of petroleum distillate fuel, eg, diesel fuel, and that very little sulfur dioxide is produced. In addition, they are biodegradable.

entsprechen, in der R ein aliphatischer Rest mit 10 bis 25 Kohlenstoffatomen ist, der gesättigt oder ungesättigt sein kann.Oils obtained from animal or vegetable material are mainly metabolites comprising triglycerides of monocarboxylic acids and generally of the formula

in which R is an aliphatic radical of 10 to 25 carbon atoms, which may be saturated or unsaturated.

Generally, such oils contain glycerides of a variety of acids, the number and variety of which varies with the source of the oil, and may additionally contain phosphoglycerides. Such oils can be obtained by methods known in the art.

Due to the sometimes unsatisfactory physical properties of the triglycerides, the art has shifted to converting the naturally occurring triglycerides into fatty acid esters of lower alcohols such as methanol or ethanol.

As an obstacle in the use of triglycerides as well as fatty acid esters of lower monohydric alcohols as a diesel fuel substitute alone or mixed with diesel fuel, their flow behavior at low temperatures has been proven. The reason for this is the high uniformity of these oils compared to mineral oil distillates. Thus, e.g. Rapeseed Acid Methyl Ester (RME) has a Cold Filter Plugging Point (CFPP) of -14 ° C. With the additives of the prior art, it has hitherto not been possible to reliably set a CFPP value of -20 ° C. required for use as winter diesel in Central Europe and for special applications of -22 ° C. and below. This problem is exacerbated by the use of oils containing larger amounts of saturated fatty acid esters, as contained in, for example, sunflower oil methyl ester, waste fat methyl ester (AME) or soya oil methyl ester.

EP-A-0 665 873 discloses a fuel oil composition comprising a biofuel, a petroleum-based fuel oil and an additive which comprises (a) an oil-soluble ethylene copolymer or (b) a comb polymer or (c) a polar nitrogen compound or (d) a compound in which at least one substantially linear alkyl group having 10 to 30 carbon atoms is bonded to a non-polymeric organic group to provide at least one linear chain of atoms including the carbon atoms of the alkyl groups and one or more non-terminal oxygen atoms, or (e) one or more of Components (a), (b), (c) and (d).

1. (I) Kammpolymer, das Copolymer von Maleinsäureanhydrid oder Fumarsäure und einem anderen ethylenisch ungesättigten Monomer, wobei das Copolymer verestert sein kann, oder Polymer oder Copolymer von α-Olefin, oder Fumarat- oder Itaconatpolymer oder -copolymer ist,
2. (II) Polyoxyalkylen-ester, -ester/ether oder eine Mischung derselben,
3. (III) Ethylen/ungesättigter Ester-Copolymer,
4. (IV) polarer, organischer, stickstoffhaltiger Paraffinkristallwachstumshemmstoff,
5. (V) Kohlenwasserstoffpolymer,
6. (VI) Schwefelcarboxyverbindungen und
7. (VII) mit Kohlenwasserstoffresten versehenes aromatisches Stockpunktsenkungsmittel

umfasst, mit der Maßgabe, dass die Zusammensetzung keine Mischungen von polymeren Estern oder Copolymeren von Estern von Acryl- und/oder Methacrylsäure umfasst, die von Alkoholen mit 1 bis 22 Kohlenstoffatomen abgeleitet sind. EP-A-0 629 231 discloses a composition comprising a major portion of oil consisting essentially of alkyl esters of fatty acids derived from vegetable or animal oils or both mixed with a minor proportion of mineral oil flow improver comprising one or more of the following:

1. (I) comb polymer, the copolymer of maleic anhydride or fumaric acid and another ethylenically unsaturated monomer, which copolymer may be esterified, or polymer or copolymer of α-olefin, or fumarate or itaconate polymer or copolymer,
2. (II) polyoxyalkylene ester, ester / ether or a mixture thereof,
3. (III) ethylene / unsaturated ester copolymer,
4. (IV) polar, organic, nitrogen-containing wax crystal growth inhibitor,
5. (V) hydrocarbon polymer,
6. (VI) sulfur carboxy compounds and
7. (VII) hydrocarbon residue-containing aromatic pour point depressant

with the proviso that the composition does not comprise mixtures of polymeric esters or copolymers of esters of acrylic and / or methacrylic acid derived from alcohols having from 1 to 22 carbon atoms.

1. a) an sich bekannte, zur Verbesserung des Tieftemperaturverhaltens von Mineralölen verwendete Additive PPD ("Pour Point Depressant") in Mengen von 0,0001 bis 10 Gew.-% bezogen auf die langkettigen Fettsäureester FAE zusetzt und
2. b) auf eine Temperatur unterhalb des Cold Filter Plugging Point der nichtadditivierten, langkettigen Fettsäureester FAE abkühlt und
3. c) die entstehenden Niederschläge (FAN) abtrennt.

EP-A-0 543 356 discloses a process for the preparation of compositions having improved low-temperature behavior for use as fuels or lubricants, starting from the esters of long-chain fatty acids obtained from natural sources with monohydric C ₁ -C ₆ -alcohols (FAE), characterized in that

1. a) known per se used to improve the low-temperature behavior of mineral oils additives PPD ("pour point depressant") in amounts of 0.0001 to 10 wt .-% based on the long-chain fatty acid esters FAE added and
2. b) to a temperature below the cold filter plugging point of the non-additive, long-chain fatty acid ester FAE cools and
3. c) the resulting precipitation (FAN) is separated.

1. a) 58 bis 95 Gew.-% mindestens eines Esters im lodzahlbereich 50 bis 150, der sich von Fettsäuren mit 12 bis 22 Kohlenstoffatomen und niederen aliphatischen Alkoholen mit 1 bis 4 Kohlenstoffatomen ableitet,
2. b) 4 bis 40 Gew.-% mindestens eines Esters von Fettsäuren mit 6 bis 14 Kohlenstoffatomen und niederen aliphatischen Alkoholen mit 1 bis 4 Kohlenstoffatomen und
3. c) 0,1 bis 2 Gew.-% mindestens eines polymeren Esters.

DE-A-40 40 317 discloses mixtures of fatty acid lower alkyl esters having improved low temperature stability

1. a) 58 to 95% by weight of at least one ester in the iodine value range 50 to 150, which is derived from fatty acids having 12 to 22 carbon atoms and lower aliphatic alcohols having 1 to 4 carbon atoms,
2. b) 4 to 40 wt .-% of at least one ester of fatty acids having 6 to 14 carbon atoms and lower aliphatic alcohols having 1 to 4 carbon atoms and
3. c) 0.1 to 2 wt .-% of at least one polymeric ester.

EP-A-0 153 176 discloses the use of polymers based on unsaturated C ₄ -C ₈ dicarboxylic acid di-alkyl esters having average alkyl chain lengths of 12 to 14 as cold flow improvers for certain petroleum distillate fuel oils. Suitable comonomers are unsaturated esters, in particular vinyl acetate, but also α-olefins.

1. I) einem Copolymer mit mindestens 25 Gew.-% eines n-Alkylesters einer monoethylenisch ungesättigten C₄-C₈-Mono- oder Dicarbonsäure, wobei die durchschnittliche Zahl der Kohlenstoffatome in den n-Alkylresten 12 - 14 ist und einem anderen ungesättigten Ester oder einem Olefin enthält, mit
2. II) einem anderen NiedertemperaturFließverbesserer für Destillatbrennstofföle umfasst.

EP-A-0 153 177 discloses an additive concentrate which is a combination of

1. I) a copolymer having at least 25% by weight of an n-alkyl ester of a monoethylenically unsaturated C ₄ -C ₈ mono- or dicarboxylic acid, wherein the average number of carbon atoms in the n-alkyl radicals is 12-14 and another unsaturated ester or an olefin, with
2. II) another low temperature flow improver for distillate fuel oils.

EP-A-1 491 614 discloses oils of vegetable or animal origin and blends thereof with petroleum distillate fuel oils containing an ethylene vinyl ester copolymer containing at least 17 mole% vinyl ester to improve their low temperature properties and having a degree of branching of 5 or more alkyl branches per 100 methyl groups.

With the known additives, it is often not possible fatty acid esters, especially those containing in total more than 7 wt .-% of palmitic and stearic acid methyl ester, to a required for use as winter diesel in southern Central Europe CFPP of -10 ° C and in northern Central Europe of -20 ° C, as well as for special applications of -22 ° C and below safely set. A problem with the known additives is also a lack of resistance to cold oxidation of the additized oils, that is, the set CFPP value of the oils gradually increases when the oil is stored for a long time at changing temperatures in the range of its cloud point or below. In addition, especially oils with a high content of palmitic and stearic acid methyl ester show a strong tendency to sedimentation when stored at low temperatures. It is known from practice that sedimentation of the additized fatty acid esters in the cold occurring in laboratory tests despite CFPP can lead to filter blockages in the engine and thus the marketability of the fuel is not given.

It was therefore the object to provide additives for improving the cold flow behavior of fatty acid esters, which are derived, for example, from rapeseed, waste-oil, sunflower and / or soybean oil and which contain at least 7% by weight of palmitic and stearic acid methyl esters. whereby CFPP values of -10 ° C and -20 ° C and below are to be set and the set CFPP value remains constant even after prolonged storage of the oil in the region of its cloud point or below. In addition, these additives should help to prevent the sedimentation of these oils, so that even after storage for several days of the fatty acid esters, they remain homogeneous and flowable and their CFPP does not change.

Surprisingly, it has now been found that an additive containing ethylene copolymers and comb polymers is an excellent flow improver for such fatty acid esters.

1. A) ein Copolymer aus Ethylen und 13 bis 17 Mol-% mindestens eines Acryl- oder Vinylesters mit einem C₁-C₁₈-Alkylrest und einer Schmelzviskosität V₁₄₀ von höchstens 80 mPas, und
2. B) ein Kammpolymer, enthaltend Struktureinheiten aus
   1. B1) mindestens einem Olefin als Monomer 1, welches an der olefinischen Doppelbindung wenigstens einen C₈-C₁₈-Alkylrest trägt, und
   2. B2) mindestens einer ethylenisch ungesättigten Dicarbonsäure als Monomer 2, welche mindestens einen über eine Estergruppe gebundenen C₈-C₁₆-Alkylrest trägt,
   worin der Parameter Q $$\mathrm{Q}\mathrm{=}{\displaystyle \mathrm{\sum }_{\mathrm{i}}}{\mathrm{w}}_{\mathrm{1}\mathrm{i}}\mathrm{\cdot }{\mathrm{n}}_{\mathrm{1}\mathrm{i}}\mathrm{+}{\displaystyle \mathrm{\sum }_{\mathrm{i}}}{\mathrm{w}}_{\mathrm{2}\mathrm{j}}\mathrm{\cdot }{\mathrm{n}}_{\mathrm{2}\mathrm{j}}$$
   
   
   worin

   w₁

   der molare Anteil der einzelnen Kettenlängen n₁ in den Alkylresten von Monomer 1,

   w₂

   der molare Anteil der einzelnen Kettenlängen n₂ in den Alkylresten der Estergruppen von Monomer 2,

   n₁

   die einzelnen Kettenlängen in den Alkylresten von Monomer 1,

   n₂

   die einzelnen Kettenlängen in den Alkylresten der Estergruppen von Monomer 2,

   i

   die Laufvariable für die Kettenlängen in den Alkylresten von Monomer 1, und

   j

   die Laufvariable für die Kettenlängen in den Alkylresten der Estergruppen von Monomer 2 sind,

The invention relates to an additive containing

1. A) a copolymer of ethylene and 13 to 17 mol% of at least one acrylic or vinyl ester having a C ₁ -C ₁₈ alkyl radical and a melt viscosity V ₁₄₀ of at most 80 mPas, and
2. B) a comb polymer comprising structural units
   1. B1) at least one olefin as monomer 1, which carries at least one C ₈ -C ₁₈ -alkyl radical on the olefinic double bond, and
   2. B2) at least one ethylenically unsaturated dicarboxylic acid as monomer 2 which carries at least one C ₈ -C ₁₆ -alkyl radical bonded via an ester group,
   wherein the parameter Q $$\mathrm{Q}\mathrm{=}{\displaystyle \underset{\mathrm{i}}{\mathrm{\Sigma }}}{\mathrm{w}}_{\mathrm{1}\mathrm{i}}\mathrm{\cdot }{\mathrm{n}}_{\mathrm{1}\mathrm{i}}\mathrm{+}{\displaystyle \underset{\mathrm{i}}{\mathrm{\Sigma }}}{\mathrm{w}}_{\mathrm{2}\mathrm{j}}\mathrm{\cdot }{\mathrm{n}}_{\mathrm{2}\mathrm{j}}$$
   
   
   wherein

   w ₁

   the molar fraction of the individual chain lengths n ₁ in the alkyl radicals of monomer 1,

   w ₂

   the molar fraction of the individual chain lengths n ₂ in the alkyl radicals of the ester groups of monomer 2,

   n ₁

   the individual chain lengths in the alkyl radicals of monomer 1,

   n ₂

   the individual chain lengths in the alkyl radicals of the ester groups of monomer 2,

   i

   the run variable for the chain lengths in the alkyl radicals of monomer 1, and

   j

   the run variables are the chain lengths in the alkyl radicals of the ester groups of monomer 2,

Values from 23 to 27.

Another object of the invention is a fuel oil composition containing a fuel oil of animal or vegetable origin and the additive defined above.

Another object of the invention is the use of the additive defined above to improve the cold flow properties of animal fuel oils or of vegetable origin.

Another object of the invention is a method for improving the cold flow properties of fuel oils of animal or vegetable origin by adding to fuel oils of animal or vegetable origin, the additive defined above.

In a preferred embodiment of the invention Q assumes values of 24 to 26.

Chain length of olefins is understood here as the chain length of the monomeric olefin minus the two olefinically bonded C atoms. For olefins having non-terminal double bonds, e.g. Olefins with vinylidene grouping, the chain length is equal to the total chain length of the olefin minus the two olefinically bonded carbon atoms.

If one does not consider the monomeric olefins but the polymers formed from the olefins B1) and the dicarboxylic acid esters B2), the chain length is the length of the alkyl radicals which, introduced into the polymer by the olefin, depart from the polymer backbone.

Preferred ethylene copolymers A) are those which contain from 13 to 17 mol% of one or more vinyl and / or (meth) acrylic esters and from 83 to 87% by weight of ethylene. Particularly preferred are ethylene copolymers with 15 to 17 mol% of at least one vinyl ester. Suitable vinyl esters are derived from fatty acids with linear or branched alkyl groups having 1 to 30 carbon atoms. Preferred ethylene copolymers have a melt viscosity V ₁₄₀ of at least 5, preferably 10 to 80, in particular 20 to 60 mPas.

Examples of suitable vinyl esters are vinyl acetate, vinyl propionate, vinyl butyrate, vinyl hexanoate, vinyl heptanoate, vinyl octanoate, vinyl laurate and vinyl stearate and branched fatty acid based esters of vinyl alcohol such as vinyl isobutyrate, vinyl pivalate, vinyl 2-ethylhexanoate, iso-nonanoic acid vinyl ester, vinyl neononanoate, vinyl neodecanoate and Neoundecansäurevinylester. Also suitable as comonomers are esters of acrylic and methacrylic acid having 1 to 20 C atoms in the alkyl radical, such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n- and isobutyl (meth) acrylate, hexyl , Octyl, 2-ethylhexyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl (meth) acrylate. Also suitable are mixtures of two, three, four or more of these comonomers.

Other preferred copolymers contain, in addition to ethylene and 13 to 17 mol% of vinyl esters, 0.5 to 10 mol% of olefins having 3 to 10 carbon atoms, such as propene, butene, isobutylene, hexene, 4-methylpentene, octene, diisobutylene and / or norbornene.

The copolymers A preferably have weight-average molecular weights M w, measured by gel permeation chromatography (GPC) against polystyrene standards in THF of from 1000 to 10 000, in particular from 1500 to 5000 g / mol. Their means of ¹ H NMR spectroscopy (400 MHz with CDCl ₃ as solvent) degrees of branching determined are preferably smaller than 6, especially less than 5 CH _3/100 CH ₂ groups. The methyl groups are derived from the short and long chain branches, and not from copolymerized comonomers.

The copolymers (A) can be prepared by the usual copolymerization methods such as suspension polymerization, solvent polymerization, gas phase polymerization or high-pressure bulk polymerization. The high-pressure mass polymerization is preferably carried out at pressures of from 50 to 400 MPa, preferably from 100 to 300 MPa, and at temperatures of from 100 to 300 ° C., preferably from 150 to 250 ° C. In a particularly preferred preparation variant, the polymerization takes place in a multi-zone reactor, wherein the temperature difference between the peroxide dosages along the tubular reactor is kept as low as possible, i. <50 ° C, preferably <30 ° C, in particular <15 ° C. The temperature maxima in the individual reaction zones preferably differ by less than 30 ° C., more preferably by less than 20 ° C. and especially by less than 10 ° C.

The reaction of the monomers is initiated by free radical initiators (free radical initiators). For example, oxygen, Hydroperoxides, peroxides and azo compounds such as cumene hydroperoxide, t-butyl hydroperoxide, dilauroyl peroxide, dibenzoyl peroxide, bis (2-ethylhexyl) peroxide carbonate, t-butyl perpivalate, t-butyl permalate, t-butyl perbenzoate, dicumyl peroxide, t-butylcumyl peroxide, di- (t-butyl ) peroxide, 2,2'-azobis (2-methylpropanonitrile), 2,2'-azobis (2-methylbutyronitrile). The initiators are used individually or as a mixture of two or more substances in amounts of 0.01 to 20 wt .-%, preferably 0.05 to 10 wt .-%, based on the monomer mixture. The high-pressure mass polymerization is carried out batchwise or continuously in known high-pressure reactors, for example autoclaves or tubular reactors, tube reactors have proven particularly useful. Solvents such as aliphatic and / or aromatic hydrocarbons or hydrocarbon mixtures, benzene or toluene may be present in the reaction mixture. Preferred is the substantially solvent-free operation. In a preferred embodiment of the polymerization, the mixture of the monomers, the initiator and, if used, the moderator, a tubular reactor via the reactor inlet and via one or more side branches supplied. Preferred moderators are, for example, hydrogen, saturated and unsaturated hydrocarbons such as propane or propene, aldehydes such as propionaldehyde, n-butyraldehyde or isobutyraldehyde, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and alcohols such as butanol. The comonomers as well as the moderators can be metered into the reactor both together with ethylene and separately via side streams. In this case, the monomer streams can be composed differently ( EP-A-0 271 738 and EP-A-0 922 716 ).

• Ethylen-Vinylacetat-Copolymere mit 10 - 40 Gew.-% Vinylacetat und 60 - 90 Gew.-% Ethylen;
• die aus DE-A-34 43 475 bekannten Ethylen-Vinylacetat-Hexen-Terpolymere;
• die in EP-A-0 203 554 beschriebenen Ethylen-Vinylacetat-Diisobutylen-Terpolymere;
• die aus EP-A-0 254 284 bekannte Mischung aus einem Ethylen-Vinylacetat-Diisobutylen-Terpolymerisat und einem Ethylen/Vinylacetat-Copolymer;
• die in EP-A-0 405 270 offenbarten Mischungen aus einem Ethylen-Vinylacetat-Copolymer und einem Ethylen-Vinylacetat-N-Vinylpyrrolidon-Terpolymerisat;
• die in EP-A-0 463 518 beschriebenen Ethylen/Vinylacetat/iso-Butylvinylether-Terpolymere;
  die aus EP-A-0 493 769 bekannten Ethylen/Vinylacetat/Neononansäurevinylester bzw. Neodecansäurevinylester-Terpolymere, die außer Ethylen 10 - 35 Gew.-% Vinylacetat und 1 - 25 Gew.-% der jeweiligen Neoverbindung enthalten;
• die in EP-A-0 778 875 beschriebenen Terpolymere aus Ethylen, einem ersten Vinylester mit bis zu 4 C-Atomen und einem zweiten Vinylester, der sich von einer verzweigten Carbonsäure mit bis zu 7 C-Atomen oder einer verzweigten, aber nicht tertiären Carbonsäure mit 8 bis 15 C-Atomen ableitet;
• die in DE-A-196 20 118 beschriebenen Terpolymere aus Ethylen, dem Vinylester einer oder mehrerer aliphatischer C₂- bis C₂₀-Monocarbonsäuren und 4-Methylpenten-1 ;
• die in DE-A-196 20 119 offenbarten Terpolymere aus Ethylen, dem Vinylester einer oder mehrerer aliphatischer C₂- bis C₂₀-Monocarbonsäuren und Bicyclo[2.2.1]hept-2-en;
• die in EP-A-0 926 168 beschriebenen Terpolymere aus Ethylen und wenigstens einem olefinisch ungesättigten Comonomer, das eine oder mehrere Hydroxylgruppen enthält.

Suitable copolymers or terpolymers include, for example:

• Ethylene-vinyl acetate copolymers with 10-40% by weight of vinyl acetate and 60-90% by weight of ethylene;
• from DE-A-34 43 475 known ethylene-vinyl acetate-hexene terpolymers;
• in the EP-A-0 203 554 described ethylene-vinyl acetate-diisobutylene terpolymers;
• from EP-A-0 254 284 known mixture of an ethylene-vinyl acetate-diisobutylene terpolymer and an ethylene / vinyl acetate copolymer;
• in the EP-A-0 405 270 disclosed blends of an ethylene-vinyl acetate copolymer and an ethylene-vinyl acetate-N-vinylpyrrolidone terpolymer;
• in the EP-A-0 463 518 described ethylene / vinyl acetate / iso-butyl vinyl ether terpolymers;
  from EP-A-0 493 769 known ethylene / vinyl acetate / vinyl neononanoate or vinyl neodecanoate terpolymers containing, in addition to ethylene, 10-35% by weight of vinyl acetate and 1-25% by weight of the respective neo compound;
• in the EP-A-0 778 875 described terpolymers of ethylene, a first vinyl ester having up to 4 carbon atoms and a second vinyl ester, which is derived from a branched carboxylic acid having up to 7 carbon atoms or a branched, but not tertiary carboxylic acid having 8 to 15 carbon atoms;
• in the DE-A-196 20 118 described terpolymers of ethylene, the vinyl ester of one or more aliphatic C ₂ - to C ₂₀ monocarboxylic acids and 4-methylpentene-1;
• in the DE-A-196 20 119 disclosed terpolymers of ethylene, the vinyl ester of one or more aliphatic C ₂ to C ₂₀ monocarboxylic acids and bicyclo [2.2.1] hept-2-ene;
• in the EP-A-0 926 168 described terpolymers of ethylene and at least one olefinically unsaturated comonomer containing one or more hydroxyl groups.

Preference is given to using mixtures of identical or different ethylene copolymers. Particularly preferably, the polymers underlying the mixtures differ in at least one characteristic. For example, they may contain different comonomers, have different comonomer contents, molecular weights and / or degrees of branching. The mixing ratio of the various ethylene copolymers is preferred between 20: 1 and 1:20, preferably 10: 1 to 1:10, in particular 5: 1 to 1: 5.

The copolymers B are preferably derived from dicarboxylic acids B2 and their derivatives, such as esters and anhydrides. Preference is given to maleic acid, fumaric acid, itaconic acid and especially maleic anhydride.

Suitable comonomers are monoolefins B1 having from 10 to 20, in particular from 12 to 18, carbon atoms. These are preferably linear and the double bond is preferably terminal such as in dodecene, tridecene, tetradecene, pentadecene, hexadecene, heptadecene and octadecene.

The molar ratio of dicarboxylic acids / derivatives to olefin or olefins in the polymer is preferably in the range 1: 1.5 to 1.5: 1, in particular it is equimolar. In minor amounts of up to 20 mol%, preferably <10 mol%, especially <5 mol%, other comonomers besides B1 and B2 which are copolymerizable with dicarboxylic acids / derivatives and the stated olefins may also be present in the copolymers B. , Examples of such comonomers are olefins having 2 to 50 carbon atoms, allyl polyglycol ethers, C ₁ -C ₃₀ -alkyl (meth) acrylates, vinylaromatics or C ₁ -C ₂₀ -alkyl vinyl ethers. The same are preferably used in minor amounts poly (isobutylene) having molecular weights of up to 5,000 g / mol, with highly reactive variants with a high proportion of terminal vinylidene groups are preferred. These other comonomers are not taken into account in the calculation of the factor Q which is decisive for the effectiveness.

worin

R¹

Wasserstoff oder Methyl,

R²

Wasserstoff oder C₁-C₄-Alkyl,

m

eine Zahl von 1 bis 100,

R³

C₁-C₂₄-Alkyl, C₅-C₂₀-Cycloalkyl, C₆-C₁₈-Aryl oder -C(O)-R⁴,

R⁴

C₁-C₄₀-Alkyl, C₅-C₁₀-Cycloalkyl oder C₆-C₁₈-Aryl, bedeuten.

Allyl polyglycol ethers correspond to the general formula

wherein

R ¹

Hydrogen or methyl,

R ²

Hydrogen or C ₁ -C ₄ -alkyl,

m

a number from 1 to 100,

R ³

C ₁ -C ₂₄ -alkyl, C ₅ -C ₂₀ -cycloalkyl, C ₆ -C ₁₈ -aryl or -C (O) -R ⁴ ,

R ⁴

C ₁ -C ₄₀ alkyl, C ₅ -C ₁₀ cycloalkyl or C ₆ -C ₁₈ aryl.

The preparation of the copolymers B) according to the invention is preferably carried out at temperatures between 50 and 220 ° C, in particular 100 to 190 ° C. The preferred method of preparation is solvent-free bulk polymerization, but it is also possible to carry out the polymerization in the presence of aprotic solvents such as benzene, toluene, xylene or higher-boiling aromatic, aliphatic or isoaliphatic solvents or solvent mixtures such as kerosene or solvent naphtha. The polymerization is particularly preferably in less moderating, aliphatic or isoaliphatic solvents. The proportion of solvent in the polymerization mixture is generally between 10 and 90% by weight, preferably between 35 and 60% by weight. In the solution polymerization, the reaction temperature can be set particularly easily by the boiling point of the solvent or by working under reduced or elevated pressure.

The average molecular weight Mw of the copolymers B according to the invention is generally between 1,200 and 200,000 g / mol, in particular between 2,000 and 100,000 g / mol, measured by gel permeation chromatography (GPC) against polystyrene standards in THF. Copolymers of the invention must be oil-soluble in practice-relevant dosing quantities, ie they must dissolve in the oil to be additized at 50 ° C. without residue.

The reaction of the monomers is initiated by free radical initiators (free radical initiators). This class of substances includes, for example, oxygen, hydroperoxides and peroxides such as cumene hydroperoxide, t-butyl hydroperoxide, dilauroyl peroxide, dibenzoyl peroxide, bis (2-ethylhexyl) peroxide carbonate, t-butyl perpivalate, t-butyl permalonate, t-butyl perbenzoate, dicumyl peroxide, t-butylcumyl peroxide, Di (t-butyl) peroxide, and azo compounds such as 2,2'-azobis (2methylpropanonitrile) or 2,2'-azobis (2-methylbutyronitrile). The initiators are used individually or as a mixture of two or more substances in quantities of 0.01 to 20 wt .-%, preferably 0.05 to 10 wt .-%, based on the monomer mixture used.

The copolymers can be prepared either by reacting maleic, fumaric and / or itaconic acid or their anhydrides with the corresponding alcohol and subsequent copolymerization or by copolymerization of olefin or olefins with at least one unsaturated dicarboxylic acid or its derivative such as ltacon and / or Maleic anhydride and subsequent reaction with alcohols are produced. A copolymerization with anhydrides is preferably carried out and the resulting copolymer is converted after the preparation into an ester and / or a diester.

This esterification takes place in both cases, for example by reaction with 0.8 to 2.5 moles of alcohol per mole of anhydride, preferably with 1.0 to 2.0 moles of alcohol per mole of anhydride at 50 to 300 ° C. When using about 1 mole of alcohol per mole of anhydride half esters. Here, esterification temperatures of about 70 to 120 ° C are preferred. When using larger amounts of alcohol, preferably 2 moles of alcohol per mole of anhydride formed at 100 - 300 ° C, preferably 120 - 250 ° C diester. The water of reaction can be distilled off by means of an inert gas stream or discharged in the presence of an organic solvent by means of azeotropic distillation. Preference is given to 20-80, in particular 30-70, especially 35-55 wt .-% of at least one organic solvent used. As half esters, copolymers with acid numbers of 30-70 mg KOH / g, preferably 40-60 mg KOH / g, are considered here. Copolymers with acid numbers of less than 40, especially less than 30 mg KOH / g are considered as diesters. Particularly preferred are half esters.

Suitable alcohols are particularly linear, but they can also minor amounts, eg. B. up to 30 wt .-%, preferably up to 20 wt .-% and especially up to 10 wt .-% (in 1- or 2-position) branched alcohols. Particularly preferred are octanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, pentadecanol and hexadecanol. By using mixtures of different olefins in the polymerization and mixtures of different alcohols in the esterification, the effectiveness of special on Fatty acid ester compositions are adjusted.

Particularly preferred copolymers B contain half esters of primary alcohols as monomer B2.

By using mixtures of different olefins in the polymerization and mixtures of different alcohols in the esterification, the effectiveness can be further adapted to specific fatty acid ester compositions.

In a preferred embodiment, in addition to components A and B, the additives may also contain polymers and copolymers based on C ₁₀ -C ₂₄ -alkyl acrylates or methacrylates (component C). These poly (alkyl acrylates) and methacrylates have molecular weights Mw of 800 to 1,000,000 g / mol, and are preferably derived from caprylic, capric, undecyl, lauryl, myristyl, cetyl, palmitoleyl, stearyl alcohol or their mixtures such as coconut, palm tallow or behenyl from.

In a preferred embodiment, mixtures of different copolymers B are used, the average (weight average) of the parameters Q of the mixture components assuming values of 23 to 27 and preferably values of 24 to 26.

The mixing ratio of the additive components A and B according to the invention is (in parts by weight) 20: 1 to 1:20, preferably 10: 1 to 1:10, in particular 5: 1 to 1: 5. The proportion of component C in the formulations of A, B and C may be up to 40% by weight; it is preferably less than 20% by weight, in particular between 1 and 10% by weight, based on the total weight of A, B and C.

The additives of the invention are added to oils in amounts of 0.001 to 5 wt .-%, preferably 0.005 to 1 wt .-% and especially 0.01 to 0.6 wt .-%. They may be dissolved as such or dissolved or dispersed in solvents such as aliphatic and / or aromatic hydrocarbons or hydrocarbon mixtures such. Toluene, xylene, ethylbenzene, decane, Pentadecane, gasoline fractions, kerosene, naphtha, diesel, heating oil, isoparaffins or commercial solvent mixtures such as Solvent Naphtha, ^® Hydrolsol A 200N, ^® Shellsol A 150 ND, ^® Caromax 20 LN, ^® Shellsol AB, ^® Solvesso 150, ^® Solvesso 150 ND, ^® Solvesso 200, ^® Exxsol, ^® Isopar and ^® Shellsol D types. Preferably, they are dissolved in fuel oil of animal or vegetable origin based on fatty acid alkyl esters. The additives according to the invention preferably contain 1 to 80%, especially 10 to 70%, in particular 25 to 60%, of solvent.

In a preferred embodiment, the fuel oil, which is often referred to as "biodiesel" or "biofuel", is fatty acid alkyl esters of fatty acids having 12 to 24 carbon atoms and alcohols having 1 to 4 carbon atoms. Usually, a major part of the fatty acids contains one, two or three double bonds.

Examples of oils derived from animal or vegetable material and in which the additive according to the invention can be used are rapeseed oil, coriander oil, soybean oil, cottonseed oil, sunflower oil, castor oil, olive oil, peanut oil, corn oil, almond oil, palm kernel oil, coconut oil, mustard seed oil, Beef tallow, bone oil, fish oils and used edible oils. Other examples include oils derived from wheat, jute, sesame, shea nut, arachis oil and linseed oil. The fatty acid alkyl esters, also referred to as biodiesel, can be derived from these oils by methods known in the art. Rapeseed oil, which is a mixture of glycerol partially esterified fatty acids, is preferred because it is available in large quantities and is readily available by squeezing rapeseed. Furthermore, the also widespread oils of used fat, palm oil, sunflower and soybeans and their mixtures with rapeseed oil are preferred.

Particularly suitable as biofuels are lower alkyl esters of fatty acids. Here are, for example, commercially available mixtures of ethyl, propyl, butyl and especially methyl esters of fatty acids having 14 to 22 carbon atoms, for example of lauric, myristic, palmitic, palmitolic, stearic, oleic, elaidic, petroselinic, ricinoleic, elaeostearic, linoleic, linolenic , Eicosanoic acid, gadoleic acid, Docosanic acid or erucic acid, which preferably have an iodine value of 50 to 150, in particular 90 to 125. Mixtures with particularly advantageous properties are those which contain mainly, ie at least 50 wt .-%, methyl esters of fatty acids having 16 to 22 carbon atoms and 1, 2 or 3 double bonds. The preferred lower alkyl esters of fatty acids are the methyl esters of oleic, linoleic, linolenic and erucic acids.

Commercially available mixtures of the type mentioned are obtained, for example, by cleavage and esterification or by transesterification of animal and vegetable fats and oils with lower aliphatic alcohols. The same are also used edible oils as starting materials. For the preparation of lower alkyl esters of fatty acids, it is advantageous to start from fats and oils with high iodine, such as sunflower oil, rapeseed oil, coriander oil, castor oil (castor oil), soybean oil, cottonseed oil, peanut oil or beef tallow. Lower alkyl esters of fatty acids based on a new type of rapeseed oil whose fatty acid component is derived to greater than 80% by weight of unsaturated fatty acids containing 18 carbon atoms are preferred.

Thus, a biofuel is an oil obtained from plant or animal matter or both, or a derivative thereof, which can be used as a fuel and especially as a diesel or fuel oil. Although many of the above oils can be used as biofuels, vegetable oil derivatives are preferred, with particularly preferred biofuels being alkyl ester derivatives of rapeseed oil, cottonseed oil, soybean oil, sunflower oil, olive oil or palm oil, with methyl rapeseed oil, methyl sunflower oil, palm oil methyl ester and soybean oil methyl ester being most preferred. Due to the high demand for biofuels, more and more manufacturers of fatty acid methyl esters are switching to other raw material sources with higher availability. Particularly noteworthy here is waste oil, which is used as Altfettölmethylester as biodiesel alone or in admixture with other fatty acid methyl esters, such as rapeseed, methyl sunflower oil, palm oil and methyl soybean oil. Also, blends of rapeseed oil methyl ester with soybean oil methyl ester or rapeseed oil methyl ester with a blend from soybean oil methyl ester and palm oil methyl ester or a mixture of soybean oil methyl ester and palm oil methyl ester to mention especially.

The additive may be added to the oil to be treated according to methods known in the art. If more than one additive component or co-additive component is to be used, such components may be incorporated into the oil together or separately in any combination.

With the additives according to the invention, the CFPP value of biodiesel can be adjusted to values of -10 ° C. and below -20 ° C. and in some cases to values below -25 ° C., as required for marketing, in particular in winter become. In the same way, the pour point of biodiesel is reduced by the addition of the additives according to the invention. The additives according to the invention are particularly advantageous in problematic oils which have a high proportion of esters of saturated fatty acids palmitic acid and stearic acid of more than 7% by weight, as contained, for example, in fatty acid methyl esters of used oil, sunflower and soya. It is thus possible with the additives of the invention also to adjust mixtures of rapeseed and / or Altfettölmethylester and / or sunflower and / or soybean oil fatty acid methyl ester to CFPP values of -10 ° C and -20 ° C and below. Thus, with the additives according to the invention, it is also possible to adjust waste oil methyl ester or sunflower oil or soya oil fatty acid methyl ester to CFPP values of -10 ° C. or -20 ° C. and below. In addition, the oils thus added have good cold-cycle stability, ie the CFPP value remains constant even when stored under winter conditions and does not tend to sediment at constant low temperatures (e.g. -10 ° C or -22 ° C).

For the preparation of additive packages for special 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 of crude oils, lubricating oils or fuel oils. Examples of such co-additives are polar compounds which cause a paraffin dispersion (paraffin dispersants) and oil-soluble amphiphiles.

The additives of the invention can be used in admixture 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. As paraffin dispersants, both low molecular weight and polymeric, oil-soluble compounds having ionic or polar groups such. As amine salts and / or amides proven. Particularly preferred paraffin dispersants contain reaction products of secondary fatty amines having 20 to 44 carbon atoms, in particular dicocoamine, ditallow fatty amine, distearylamine and dibehenylamine with carboxylic acids and derivatives thereof. Paraffin dispersants which have been obtained 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 have proven particularly suitable (cf. US 4 211 534 ). Likewise, amides and ammonium salts of aminoalkylene polycarboxylic acids such as nitrilotriacetic acid or ethylenediaminetetraacetic acid with secondary amines are suitable as paraffin dispersants (cf. EP 0 398 101 ). Other paraffin dispersants are copolymers of maleic anhydride and α, β-unsaturated compounds, which can optionally be reacted with primary monoalkylamines and / or aliphatic alcohols (cf. EP 0 154 177 ) and the reaction products of alkenyl spiro-bis-lactones with amines (cf. EP 0 413 279 B1 ) and after EP-A-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.

The mixing ratio (in parts by weight) of the additives according to the invention with paraffin dispersants is 1:10 to 20: 1, preferably 1: 1 to 10: 1.

The oils treated with the additive according to the invention can also be added to middle distillates obtained from petroleum. The resulting mixtures of biofuel and middle distillate can in turn be mixed with cold additives such as flow improvers or wax dispersants, and Performance Packages.

The mixing ratio between biofuel and middle distillates can be between 1:99 and 99: 1 lie. Particularly preferred are mixing ratios of biofuel: middle distillate = 3:97 to 30:70.

The middle distillate is 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. Preferably, such middle distillates are used which contain 0.05% by weight of sulfur and less, more preferably less than 350 ppm of sulfur, in particular less than 200 ppm of sulfur and in special cases less than 50 ppm of sulfur. These are generally those middle distillates which have been subjected to a hydrogenating refining, and therefore contain only small amounts of polyaromatic and polar compounds. These are preferably middle distillates which have 95% distillation points below 370.degree. C., in particular 350.degree. C. and in special cases below 330.degree. Synthetic fuels, such as those obtainable by the Fischer-Tropsch process, are also suitable as middle distillates.

The additives can be used alone or together with other additives, for example with other pour point depressants or dewaxing aids, with antioxidants, cetane number improvers, dehazers, demulsifiers, detergents, dispersants, defoamers, dyes, corrosion inhibitors, conductivity improvers, sludge inhibitors, odorants and / or additives for lowering the cloud point.

Examples

Table 1 Characterization of the ethylene copolymers used example Comonomer (s) V ₁₄₀ CH _3/100 CH ₂ Content of vinyl ester A1 (V) Ethylene / VAC / vinyl neodecanoate 110 mPas 4.2 13.3 mol% A2 Ethylene / VAC 35 mPas 3.9 16.6 mol% A3 (V) Ethylene / VAC 154 mPas 3.0 16.7 mol% A4 (V) Ethylene / VAC 125 mPas 3.0 13.8 mol% VAC = vinyl acetate The vinyl ester content was measured by pyrolysis and subsequent titration. The viscosity (V ₁₄₀ ) was measured with a Haake Reostress 600 viscometer. The degree of branching (CH ₃ / 100CH ₂ ) was measured on a ¹ H NMR instrument at 400 MHz in CDCl ₃ , and calculated by integration of the individual signals. example comonomers alcohol Q Acid number [mg KOH / g] B1 MSA-co-C _14/16 -α-olefin (1: 0.5: 0.5) C ₁₂ / C ₁₆ alcohol (85%: 15%) 25.6 49.9 B2 MSA-co-C _14/16 -α-olefin (1: 0.5: 0.5) C ₁₂ alcohol 25.0 48.2 B3 MSA-co-C _14/16 -α-olefin (1: 0.5: 0.5) C ₁₂ alcohol 23.0 51.1 C1 Poly (octadecyl acrylate), K value 32 C2 Poly (phenyl acrylate), K value 18 Oil No .: CFPP [° C] composition E1 -8th SoyaMe / RME 30:70 E2 -7 RME / PME 85:15 E3 -11 RME / AME 60:40 E4 -10 RME / AME 50:50 E5 -8th RME / AME 40:60 E6 -8th RME / AME 45:55 Soyme = soya methyl ester
RME = rapeseed oil methyl ester
PME = palm oil methyl ester
AM E = used fat methyl ester E1 E2 E3 E4 E5 E6 C16: 0 6.53 6.21 6.74 7.33 8.13 7.76 C18: 0 1.19 2.36 2.71 2.97 3.32 3.16 C18: 1 45.19 48.73 52.56 50.84 45.36 46.77 C18: 2 36,33 28.77 26.45 28.17 32.27 31.00 C18: 3 8.37 9.18 6.36 5.49 5.45 5.89 C20: 1/2/3 0.79 1.25 1.14 1.04 0.97 1.03 C20: 0 0.39 0.57 0.58 0.56 0.53 0.57 C22: 0 0.15 0.39 0.48 0.51 0.50 0.49

In the following tables, the mixing ratio by weight of additives A, B and C is as A: B = 4: 1 or, if C is present in the mixtures, A: B: C = 4: 1: 0.2. The total amount of additive is shown in the table header. Table 6 CFPP Testing in Test Oil E1 Ex. comb polymer ethylene copolymer polyacrylate 2000ppm 3000ppm 4000ppm 1 (V) B2 A4 - -12 -13 -12 2 (V) B2 A3 - -16 -18 -10 3 B2 A2 - -17 -18 -18 4 B1 A2 - -14 -15 -17 5 (V) B1 A1 - -13 -13 -11 6 (V) B2 A1 - -11 -17 -11 7 B2 A2 C1 -18 -20 -20 8th B3 A2 - -18 -20 -20 Ex. comb polymer ethylene copolymer polyacrylate 2000ppm 3000ppm 4000ppm 9 B1 A2 - -7 -7 -11 10 (V) B2 A3 - -7 -10 -10 11 B1 A2 - -7 -9 -12 12 B1 A2 C2 -9 -10 -12 13 B3 A2 - -9 -9 -12 Ex. comb polymer ethylene copolymer polyacrylate 2000ppm 3000ppm 14 (V) B1 A1 - -18 -11 15 B1 A2 - -19 -20 16 B3 A2 - -18 -20 Ex. comb polymer ethylene copolymer polyacrylate 2000ppm 3000ppm 17 (V) B1 A1 - -17 -10 18 B1 A2 - -18 -20 19 (V) B1 A4 - -17 -10 Ex. comb polymer ethylene copolymer polyacrylate 2000ppm 3000ppm 20 (V) B2 A1 - -12 -9 21 (V) B1 A1 - -10 - 9 22 B1 A2 - -12 -19 23 B1 A2 C2 -13 -19 24 (V) B1 A3 - -10 -9 Ex. comb polymer ethylene copolymer polyacrylate 4000 ppm 25 (V) B2 A1 - - 8th 26 (V) B1 A1 - - 9 27 B2 A2 - -19 28 (V) B1 A4 - -8th

Claims (15)

Fuel oil additive containing A) a copolymer of ethylene and 13 to 17 mol% of at least one acrylic or vinyl ester having a C ₁ -C ₁₈ alkyl radical and a melt viscosity V ₁₄₀ of at most 80 mPas, and B) a comb polymer comprising structural units B1) at least one olefin as monomer 1, which carries at least one C ₈ -C ₁₈ -alkyl radical on the olefinic double bond, and B2) at least one ethylenically unsaturated dicarboxylic acid as monomer 2 which carries at least one C ₈ -C ₁₆ -alkyl radical bonded via an ester group, wherein the parameter Q $$\mathrm{Q}\mathrm{=}{\displaystyle \underset{\mathrm{i}}{\mathrm{\Sigma }}}{\mathrm{w}}_{\mathrm{1}\mathrm{i}}\mathrm{\cdot }{\mathrm{n}}_{\mathrm{1}\mathrm{i}}\mathrm{+}{\displaystyle \underset{\mathrm{i}}{\mathrm{\Sigma }}}{\mathrm{w}}_{\mathrm{2}\mathrm{j}}\mathrm{\cdot }{\mathrm{n}}_{\mathrm{2}\mathrm{j}}$$

wherein w _{1 is} the molar fraction of the individual chain lengths n ₁ in the alkyl radicals of monomer 1, w _{2 is} the molar fraction of the individual chain lengths n ₂ in the alkyl radicals of the ester groups of monomer 2, n _{1 is} the individual chain lengths in the alkyl radicals of monomer 1, n _{2 is} the individual chain lengths in the alkyl radicals of the ester groups of monomer 2, i is the running variable for the chain lengths in the alkyl radicals of monomer 1, and j are the running variables for the chain lengths in the alkyl radicals of the ester groups of monomer 2, Values from 23 to 27. A fuel oil additive according to claim 1, wherein Q assumes values of 24 to 26. A fuel oil additive according to claim 1 and / or 2, wherein component A) comprises 15 to 17 mol% of at least one vinyl ester. A fuel oil additive according to one or more of claims 1 to 3, wherein component A) comprises 0.5 to 10 mol% of olefins having 3 to 10 carbon atoms. Fuel oil additive according to one or more of claims 1 to 4, wherein the degree of branching of component A) is less than 6 CH _3/100 CH ₂ groups, determined by ¹ H NMR spectroscopy, is. A fuel oil additive according to one or more of claims 1 to 5, wherein the olefins which form component B1) are α-olefins. A fuel oil additive according to one or more of claims 1 to 6, wherein the molar ratio of the comonomers B1) to the comonomers B2) in the copolymer B) is between 1.5: 1 and 1: 1.5. Fuel oil additive according to one or more of claims 1 to 7, wherein the copolymer B in addition to the comonomers B1) and B2) still up to 20 mol% of further, different from B1) and B2) comonomers selected from olefins having less than 10 and more than 20 carbon atoms, Allylpolyglykolethern C ₁ -C ₃₀ alkyl (meth) acrylates, vinyl aromatic or C ₁ -C ₂₀ alkyl vinyl ethers, and polyisobutenes having molecular weights of up to 5,000 g / mol. A fuel oil additive according to one or more of claims 1 to 8, wherein the component A) has a melt viscosity V ₁₄₀ of 5 to 80 mPas. A fuel oil additive according to one or more of claims 1 to 9, wherein the component A) has a molecular weight Mw of from 1000 to 10000 g / mol. A fuel oil additive according to one or more of claims 1 to 10, wherein the component B) has a molecular weight of 1200 to 200,000 g / mol. A fuel oil composition containing a fuel oil of vegetable or animal origin and a fuel oil additive according to one or more of claims 1 to 11. A fuel oil composition according to claim 12, wherein the fuel oil comprises a mixture of fatty acid esters of C ₁ to C ₄ alcohols. A fuel oil composition according to claim 13, wherein the fatty acid esters comprise stearic acid methyl ester and palmitic acid methyl ester in a proportion of at least 7% by weight. Use of a fuel oil additive according to one or more of claims 1 to 11 for improving the low-temperature behavior of fuel oils of vegetable or animal origin.