EP0485773B1 - Petroleum middle distillate with improved cold flow characteristics - Google Patents

Abstract

Petroleum distillates with improved properties contain minor amts. of a conventional ethylene-based flow improver (I) and a copolymer (II) comprising 10-95 mol.% of one or more 1-26C alkyl (meth)acrylates and 5-90 mol.% of one or more ethylenically unsatd. dicarboxylic acids or anhydrides, post-reacted with one or more primary or sec. amines to form the corresp. monoamide or amide/ammonium salt. (I):(II) wt. ratio is 40-95:60-5. - Pref. (I) is a copolymer of ethylene with vinyl acetate, vinyl propionate or ethylhexyl acrylate. (II) is a copolymer of 40-95% lauryl acrylate or 8-18C alkyl acrylate and 5-60% maleic anhydride, post-reacted with di(hydrogenated tallow) amine (DHTA), behenylamine or n-octadecylamine. (II) is opt. grafted onto (I). The distillates contain 50-5,000 ppm (I)+(II).

Description

The present invention relates to petroleum middle distillates which contain small amounts of a conventional flow improver based on ethylene and copolymers of ethylenically unsaturated carboxylic acid esters of long-chain n-alkanols and ethylenically unsaturated dicarboxylic acid derivatives and which are characterized by improved flow properties in the cold.

Middle distillates such as gas oils, diesel oils or heating oils, which are obtained from petroleum by distillation, have different paraffin contents depending on the origin of the crude oil and the processing method in the refinery. The proportion of long-chain n-paraffins in particular determines the cold flow behavior of such distillates. Upon cooling, the n-paraffins separate out as platelet-shaped, interlocking crystals that build up a three-dimensional network (house of cards structure), in which large quantities of still liquid distillate are enclosed and immobilized. The crystallization of the n-paraffins is parallel to a decrease in fluidity and an increase in viscosity. This makes it difficult to supply middle distillates to the combustion units, the failed paraffins clog upstream filters, so that in extreme cases the supply can completely stop.

It has long been known that by adding so-called flow improvers, the clogging of the filters can be counteracted at low temperatures. The additives nucleate the formation of many small instead of less large paraffin crystals. At the same time they change their crystal modification so that the platelets described above do not form. The paraffin crystals formed in the presence of flow improvers are so small that they can pass through the filters or they build up a filter cake which is permeable to the still liquid portion of the middle distillate, so that trouble-free operation is ensured even at low temperatures.

Middle distillate cuts are increasingly appearing in refineries where the standard flow improvers are insufficient or even fail completely. This applies particularly to so-called high-cut oils, i.e. fractions with a high boiling point (S.E.> 370 ° C). However, boiling behavior is not the only criterion. So it happens that in two fractions with a similar boiling curve but different provinces of the base crude the standard flow improver responds well in one oil, but not in the other oil. The effectiveness of the flow improver is expressed indirectly according to DIN 51 428 by measuring the "Cold Filter Plugging Point" (CFPP).

Known per se as standard cold flow improvers are ethylene copolymers, especially copolymers of ethylene and unsaturated esters, such as those e.g. are described in DE-A 21 02 469 or EP-A 84 148.

In the art, however, new flow improvers or combinations are required which also show good effectiveness with the critical oils described above.

DE-A 16 45 785 discloses the use of polymers with unbranched, saturated side chains with at least 18 carbon atoms to lower the pour point of heating oil containing wax. Among others, "Reaction products of copolymers of acid anhydrides of unsaturated dicarboxylic acids and monoolefins or other olefinically unsaturated compounds with an aliphatic amine containing a long hydrocarbon chain". Copolymers with monoolefins are preferred.

DE-A 25 31 234 recommends the addition of alternating copolymers containing maleic acid diamide or maleimide structures as stabilizers in mineral oils, i.e. the carboxyl groups are completely reacted with amines to give the diamides or imides.

According to US Pat. No. 3,506,625, reaction products of monoamines with maleic anhydride polymers to the corresponding imides are also described, wherein when using less than one mole of amine per mole of maleic anhydride unit, remaining carboxyl groups are converted into metal salts by neutralization. For the copolymerization with maleic anhydride, alkyl vinyl ether and monovinyl hydrocarbons are preferably used.

FR-A2 592 658 describes mixtures of an ethylene polymer and a reaction product of a primary amine with a copolymer of e.g. Acrylic acid alkyl esters, diisobutene and maleic anhydride and their use as an additive to middle distillates.

EP-A 283 293 discloses the use of polymers with at least one amide group from a secondary amine and a carboxyl group as an additive to middle distillates. The polymers can include by copolymerization of unsaturated esters with maleic anhydride and subsequent reaction with the secondary amine. The unsaturated ester monomers include Dialkyl fumarates and vinyl acetate are described.

However, these polymers leave something to be desired in terms of their effectiveness as a cold flow improver in middle distillation.

It was therefore the task to find additives to middle distillation that are more effective than Have cold flow improvers.

Accordingly, it has now been found that petroleum middle distillates containing small amounts of A known flow improvers based on ethylene and B copolymers consisting of 10 to 95 mol% of one or more alkyl acrylates or alkyl methacrylates with C ₁ - to C ₂₆ -alkyl chains and from 5 to 90 mol -1% of one or more ethylenically unsaturated dicarboxylic acids or their anhydrides, the copolymer having been largely reacted with one or more primary or secondary amines to form the monoamide or amide / ammonium salt of dicarboxylic acid, meet this requirement.

The copolymers B consist of 10 to 95 mol%, preferably 40 to 95 mol% and particularly preferably 60 to 90 mol-1% of alkyl (meth) acrylates and 5 to 90 mol%, preferably 5 to 60 mol% and particularly preferably 10 to 40 mol% from the olefinically unsaturated dicarboxylic acid derivatives.

The weight ratio of flow improver A to copolymer B is between 40:60 and 95: 5, preferably between 60:40 and 95: 5 and particularly preferably between 70:30 and 90:10.

The alkyl groups of the alkyl (meth) acrylates consist of 1 to 26, preferably 4 to 22 and particularly preferably 8 to 18 carbon atoms. They are preferably straight-chain and unbranched. However, up to 20% by weight of cyclic and / or branched portions can also be present.

Examples of particularly preferred alkyl (meth) acrylates are n-octyl (meth) acrylate, n-decyl (meth) arylate, n-dodecyl (meth) acrylate, n-tetradecyl (meth) acrylate, n-hexadecyl (meth) acrylate and n-octadecyl (meth) acrylate and mixtures thereof.

Examples of ethylenically unsaturated dicarboxylic acids are maleic acid, tetrahydrophthalic acid, citraconic acid and itaconic acid or their anhydrides and fumaric acid. Maleic anhydride is preferred.

in Betracht, in der R¹ einen geradkettigen oder verzweigten Alkylrest mit 1 bis 30, bevorzugt 8 bis 26 und besonders bevorzugt 16 bis 24 Kohlenstoffatomen und R¹ Wasserstoff oder C₁- bis Cao-Alkyl, bevorzugt Wasserstoff oder C₈- bis C₂₆-Alkyl und besonders bevorzugt Wasserstoff oder C₁₆- bis C₂₄-Alkyl bedeuten, wobei R¹ und R² zusammen auch einen 5 bis 6-gliedrigen Ring bilden können, der gegebenenfalls ein Heteroatom aus der Gruppe Sauerstoff, Stickstoff und Schwefel enthält. Im einzelnen seien Morpholin, Piperidin, 2-Ethylhexylamin, n-Octadecylamin, Oleylamin, Talgfettamin, N-Methyloctadecylamin und vorzugsweise Behenylamin, Dibehenylamin und hydriertes Ditalgfettamin genannt.Compounds of the formula come as amines

into consideration, in which R ^{1 is} a straight-chain or branched alkyl radical having 1 to 30, preferably 8 to 26 and particularly preferably 16 to 24 carbon atoms and R ^{1 is} hydrogen or C ₁ - to Cao-alkyl, preferably hydrogen or C ₈ - to C ₂₆ Alkyl and particularly preferably hydrogen or C ₁₆ to C ₂₄ alkyl, where R ¹ and R ² together can also form a 5 to 6-membered ring which optionally contains a heteroatom from the group consisting of oxygen, nitrogen and sulfur. In particular, morpholine, piperidine, 2-ethylhexylamine, n-octadecylamine, oleylamine, tallow fatty amine, N-methyloctadecylamine and preferably behenylamine, dibehenylamine and hydrogenated ditallow fatty amine may be mentioned.

Examples of flow improvers A are the polymers already mentioned, described in DE-A 21 02 469 and EP-A 84 148, such as copolymers of ethylene with vinyl acetate, vinyl propionate, vinyl butyrate, vinyl pivalate or with esters of (meth) acrylic acid, which can be derived from alkanols with 1 to 12 carbon atoms. Mixtures of several copolymers of ethylene and vinyl acetate (EP-A 261 951, additive A), copolymers of ethylene with α-olefins (EP-A261 957, additive D) and the mixtures specified in DE-A 36 24 147 are also suitable Terpolymers of ethylene, vinyl acetate and diisobutene with oxidized polyethylene wax. Copolymers of ethylene with vinyl acetate or vinyl propionate or ethylhexyl acrylate are particularly preferred.

The alkyl (meth) acrylates are easily accessible. They can be obtained by the known esterification processes. For example, a solution of (meth) acrylic acid and an alkanol or a mixture of different alkanols is heated in an organic solvent with the addition of the usual polymerization inhibitors, e.g. Hydroquinone derivatives and esterification catalysts such as sulfuric acid, p-toluenesulfonic acid or acidic ion exchangers at the boil and remove the water of reaction formed by azeotropic distillation. The esterification products can usually be used unpurified for the polymerization. If a purer ester is required, this can be obtained by washing the ester solution with alkaline agents and water and by distillation.

Further possibilities for the production of the alkyl (meth) acrylates are the reaction of (meth) acrylic acid chloride or anhydride with the corresponding alkanols and the reaction of lower (meth) acrylic acid esters known as transesterification with the corresponding C ₈ to C _ls alkanols with addition acidic or basic catalysts and distillative removal of the lower alkanol.

As a rule, it is advantageous to use the dicarboxylic acids in the form of the anhydrides, if available, in the copolymerization, for example maleic anhydride, itaconic anhydride, citraconic anhydride and tetrahydrophthalic anhydride, since the anhydrides generally copolymerize better with the (meth) acrylates. The anhydride groups of the copolymers can then be reacted directly with the amines. 3rd

The reaction of the polymers with the amines takes place at temperatures of 50 to 200 ° C in the course of 0.3 to 30 hours. The amine is in amounts of about one to two moles per mole of polymerized dicarboxylic anhydride, i.e. about 0.9 to 2.1 mol / mol applied. The use of larger or smaller amounts is possible, but has no advantage. If more than two moles are used, free amine is present. If amounts less than one mole are used, there is no complete conversion to the monoamide and a correspondingly reduced effect is obtained.

In some cases it may be advantageous if the amide / ammonium salt structure is built up from two different amines. For example, a copolymer of lauryl acrylate and maleic anhydride can first be reacted with a secondary amine such as hydrogenated ditallow fatty amine to give the amide, after which the free carboxyl group derived from the anhydride can be reacted with another amine, e.g. 2-ethylhexylamine is neutralized to the ammonium salt. The reverse procedure is also conceivable: First the reaction with ethylhexylamine to form the monoamide, then with ditallow fatty amine to the ammonium salt. At least one amine is preferably used which has at least one straight-chain, unbranched alkyl group with more than 16 carbon atoms. It is immaterial whether this amine is present in the structure of the amide structure or as the ammonium salt of dicarboxylic acid.

Instead of the subsequent reaction of the carboxyl groups or the dicarboxylic acid anhydride with amines to give the corresponding amides or amide / ammonium salts, it can sometimes be advantageous to prepare the monoamides or amide / ammonium salts of the monomers and then to copolymerize them directly during the polymerization. In most cases, however, this is technically much more complex, since the amines can attach to the double bond of the monomeric dicarboxylic acid and then copolymerization is no longer possible.

The copolymers B are prepared by known batch or continuous polymerization processes such as bulk, suspension, precipitation or solution polymerization and initiation with customary radical donors such as acetylcyclohexanesulfonyl peroxide, diacetyl peroxidicarbonate, dicyclohexyl peroxidicarbonate, di-2-ethylhexyl peroxidicylate, 2,2'-dodecarboxylate, tert. -Azobis (4-methoxy-2,4-dimethylvaleronitrile), tert-butyl perpivalate, tert-butyl per-2-ethylhexanoate, tert-butyl permaleinate, 2,2'-azobis (isobutyronitrile), bis- ( tert-butyl peroxide) cyclohexane, tert-butyl peroxyisopropyl carbonate, tert-butyl peracetate, dicumyl peroxide, di-tert-amyl peroxide, di-tert-butyl peroxide, p-menthane hydroperoxide, cumene hydroperoxide or tert-butyl hydroperoxide and mixtures with one another. In general, these initiators are used in amounts of 0.1 to 20% by weight, preferably 0.2 to 15% by weight, based on the monomers.

The polymerization is generally carried out at temperatures of 40 to 400 ° C, preferably 70 to 300 ° C, with the use of solvents with boiling temperatures below the polymerization temperature is advantageously carried out under pressure. The polymerization is conveniently carried out in the absence of air, i.e. if it is not possible to work under boiling conditions, e.g. performed under nitrogen or carbon dioxide, since oxygen delays the polymerization. The reaction can be accelerated by using redox coinitiators such as benzoin, dimethylaniline, ascorbic acid and organically soluble complexes of heavy metals such as copper, cobalt, manganese, iron, nickel and chromium. The amounts usually used are 0.1 to 2000 ppm by weight, preferably 0.1 to 1000 ppm by weight. When choosing the initiator or initiator system, it is advisable to ensure at the chosen polymerization temperature that the half-life of the initiator or initiator system is less than 3 hours.

To achieve low molecular weight copolymers it is often advisable to work in the presence of regulators. Suitable regulators are, for example, allyl alcohols, such as but-1-en-3-ol, organic mercapto compounds, such as 2-mercaptoethanol, 2-mercaptopropanol, mercaptoacetic acid, mercaptopropionic acid, tert-butyl mercaptan, n-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan and tert-dodecyl mercaptan, which are generally used in amounts of 0.1 to 10 wt .-%.

Equipment suitable for the polymerization is e.g. Conventional stirred kettles with, for example, anchor, blade, impeller or multi-stage impulse countercurrent stirrers and for the continuous production of stirred kettle cascades, tubular reactors and static mixers.

The simplest method of polymerization is bulk polymerization. The monomers are polymerized in the presence of an initiator and in the absence of solvents. Advantageously, all monomers are mixed in the desired composition and a small part, e.g. about 5 to 10%, in the reactor before, heated to the desired polymerization temperature with stirring and metered in the remaining monomer mixture and the initiator and optionally coinitiator and regulator evenly within 1 to 10 hours, preferably 2 to 5 hours. It is expedient to meter in the initiator and the coinitiator separately in the form of solutions in a small amount of a suitable solvent. The copolymer can then be converted directly into the melt or after being taken up in a suitable solvent to the flow improver according to the invention.

A continuous high-pressure process which permits space-time yields of 1 to 50 kg of polymer per liter of reactor and hour is also suitable for producing the desired copolymers. As Polymerisa tion apparatus, for example, a pressure vessel, a pressure vessel cascade, a pressure tube or a pressure vessel with a downstream reaction tube, which is provided with a static mixer, can be used. The monomers of (meth) acrylic acid esters and unsaturated dicarboxylic acids or their anhydrides are preferably polymerized in at least two polymerization zones connected in series. One reaction zone can consist of a pressure-tight vessel, the other of a heatable static mixer. You get sales of more than 99%. A copolymer of (meth) acrylic acid esters and maleic anhydride can be prepared, for example, by continuously feeding the monomers and a suitable initiator to a reactor or two reaction zones connected in series, for example a reactor cascade, and the reaction product after a residence time of from 2 to 60, preferably from 5 to 30 minutes, continuously discharged from the reaction zone at temperatures between 200 and 400 ° C. The polymerization is expediently carried out at pressures of more than 1 bar, preferably between 1 and 200 bar. The copolymers obtained have solids contents of over 99% and can then be further converted to the corresponding amides or amide / ammonium salts.

Another simple method for producing the copolymers B is solution polymerization. It is carried out in solvents in which the monomers and the copolymers formed are soluble. All solvents that meet this requirement and that do not react with the monomers are suitable for this. For example, these are toluene, xylene, ethylbenzene, cumene, high-boiling aromatic mixtures such as Solvesso® 100, 150 and 200, aliphatic and cycloaliphatic hydrocarbons such as e.g. n-Hexane, cyclohexane, methylcyclohexane, n-octane, iso-octane, paraffin oils, Shellsol® TD, T and Ksie as well as tetrahydrofuran and dioxane, tetrahydrofuran and dioxane being particularly suitable for achieving low molecular weight copolymers. When carrying out the solution polymerization, it is advisable to add solvent and part of the monomer mixture (e.g. about 5 to 20%) and to meter in the rest of the monomer mixture with the initiator and, if appropriate, coinitiator, regulator and solvent. The monomers can also be metered in individually at different rates. This is recommended for monomers with very different reactivities, as is the case with (meth) acrylates and unsaturated dicarboxylic acids (anhydrides) n and when a particularly uniform distribution of the less reactive monomer in the polymer is desired. The less reactive monomer is metered in faster and the more reactive monomer more slowly. It is also possible to present the entire amount of a monomer, preferably the less reactive anhydride, and to meter in only the (meth) acrylate. Finally, it is also possible to initially charge all of the monomers and the solvent and to meter in only the initiator and, if appropriate, coinitiator and regulator ("batch" procedure). When carrying out this procedure on a larger scale, problems with heat dissipation can occur, so that this procedure should only be used at low concentrations of the monomers to be polymerized. The concentrations of the monomers to be polymerized are between 10 and 80% by weight, preferably 30 and 70% by weight. The solid copolymer can easily be obtained by evaporating the solvent. However, it is advisable to choose a solvent for the polymerization in which the reaction with the amines can take place and which is compatible with the middle distillate, so that the polymer solution can be added directly to the middle distillate. Solution polymerization is the preferred form of preparation for the copolymers of (meth) acrylates and dicarboxylic acid (anhydrides).

There is a need in industry to provide the additives according to the invention, consisting of a flow improver A and a copolymer B, in an easily manageable form. For this purpose, polymers A and B should be present together in the form of a concentrate, since the use of 2 concentrates - one each for polymer A and polymer B - makes handling more difficult. Due to the possible incompatibility of the polymers A and B, phase separation can occur when the two polymers are mixed in a common solvent. This can optionally be suppressed by suitable solvents and / or additives. Suitable are e.g. Alkanols such as iso-butanol, n-hexanol, 2-ethylhexanol, iso-decanol and their adducts with ethylene oxide, propylene oxide and / or butylene oxide as well as half esters or diesters of dicarboxylic acids with alkanols or (oligo) alkylene oxide semi-ethers such as mono- or dibutyl phthalate, mono- or Di-2-ethylhexyl phthalate or di (2-methoxyethyl) phthalate.

Another method of avoiding possible phase separation is to graft copolymer B at least in part onto the flow improver. Bulk or solution polymerization is preferably used for the grafting. The polymerization can be carried out according to the "batch" or feed procedure. In the "batch" procedure, the total amount of flow improver A to be grafted is initially introduced together with the monomers and initiator and, if appropriate, coinitiator and regulator are metered in. In the feed procedure, the total amount of flow improver A to be grafted is optionally introduced together with some of the monomers and the rest of the monomers, initiator and, if appropriate, coinitiator and regulator are metered in. After the end of the polymerization, the reaction with the amines then takes place.

As already mentioned, it is not necessary to graft the copolymer B onto the entire proportion of the flow improver A. For example, at a ratio A: B of 90:10, for reasons of space-time yield, the copolymer B will only be grafted to a proportion of 2 to 20% by weight of the total amount of A. With an A: B ratio of 40:60, however, in a proportion of 30 to 100% by weight of the total amount of A.

It is also not necessary to graft the copolymer B completely onto part of the flow improver A. This is difficult anyway, since the grafting yield generally does not reach 100%, so that in addition to graft copolymers and unconverted or admixed flow improver A, copolymer B may also be present in the concentrates described.

The K values (according to H. Fikentscher, Celulosechemie Volume 13, pages 58 to 64 and 71 to 74 (1932)), determined in 2% (w / v) xylene solution of the copolymers B, are between 10 and 50, preferably between 10 to 40 and particularly preferably between 13 and 30. The particularly preferred range corresponds to molecular weights between approximately 5000 and 25,000 g / mol (number average values, determined by gel permeation chromatography against polystyrene standards).

The additives A and B according to the invention are added to the petroleum middle distillates in amounts of altogether 50 to 5000 ppm, preferably 100 to 2000 ppm.

The middle distillates according to the invention, containing small amounts of a flow improver A and a copolymer B, can, depending on the intended use, other additives or additives such as dispersants, anti-foam additives, corrosion inhibitors, antioxidants, dyes and others. contain.

The invention is illustrated by the following examples:

Preparation of the copolymers B according to the invention example 1

In a reactor which was provided with a stirrer, heating and feed device, 177.5 lauryl acrylate (n-alkyl acrylate mixture, produced from a commercially available fatty alcohol mixture consisting of max. 1.5% by weight n-decanol, 51 to 57 % By weight n-dodecanol, 41 to 47% by weight n-tetradecanol and max.1.5% by weight n-hexadecanol), 28.5 g maleic anhydride and 88.3 g Solvesso® 150 (high-boiling aromatic mixture of Esso) heated to 80 ° C. in a gentle stream of nitrogen with stirring and a solution of 0.6 g of azoisobutyronitrile in 38.3 g of Solvesso® 150 was metered in uniformly within 4 hours. A solution of 0.4 g of azoisobutyronitrile in 11.5 g of Solvesso® 150 was then added, the mixture was reheated at 80 ° C. for one hour and diluted with 69 g of Solvesso® 150. A clear, yellowish, approximately 50% by weight solution was obtained. The K value of the polymer was 22.9; the molar ratio of acrylate to maleic anhydride is about 70:30.

Example 2

In a reactor according to Example 1, 84.4 g of lauryl acrylate, 17.6 g of maleic anhydride and 102 g of Solvesso® 150 were heated to 100 ° C. in a slow stream of nitrogen with stirring and a solution of 0.6 g of tert-butyl per was added within 4 hours 2-ethylhexanoate in 17.6 g Solvesso® 150 and, within two hours, a solution of 97.8 g lauryl acrylate in 13.6 g Solvesso® 150 evenly metered in. A solution of 0.4 g of tert-butyl per-2-ethylhexanoate in 5 g of Solvesso® 150 was then added, the mixture was reheated at 100 ° C. for one hour and diluted with 61.6 g of Solvesso® 150. A clear, yellowish, approximately 50% by weight polymer solution was obtained. The K value of the polymer was 16.0; the molar ratio of acrylate to maleic anhydride is approximately 80:20.

Example 3

Like example 2, but instead of Solvesso® 150, a high-boiling n- and iso-paraffin mixture from Shell (Shellsol® K) was used as the solvent.

A clear, light yellow, viscous, approximately 50% by weight polymer solution was obtained. The K value of the polymer was 25.9; the molar ratio of acrylate to maleic anhydride approx. 80:20:

Example 4

As in Example 3, but instead of lauryl acrylate, an n-alkyl acrylate mixture, prepared from a commercially available fatty alcohol mixture of the following composition, was used.

5 to 8 wt% n-octanol, 5 to 7 wt% n-decanol, 44 to 50 wt% n-dodecanol, 14 to 20 wt% n-tetradecanol, 8 to 10% by weight n-hexadecanol and 8 to 12% by weight n-octadecanol.

A clear, light yellow, viscous, approximately 50% by weight polymer solution was obtained. The K value of the polymer was 23.8; the molar ratio of acrylate to maleic anhydride is approximately 80:20.

Example 5

In a reactor according to Example 1, 305 g of lauryl acrylate, 176.4 g of maleic anhydride and 120 g of toluene were heated to 100 ° C. in a gentle stream of nitrogen with stirring, and a solution of 2.4 g of tert-butyl per-2-ethylhexanoate was added within 3 hours evenly metered in 40 g of toluene. The mixture was then heated to boiling and a solution of 0.96 g of tert-butyl perbenzoate in 46 g of toluene was added, the mixture was reheated at 125 ° C. for two hours and diluted with 270 g of toluene. A clear, brown, approximately 50% by weight polymer solution was obtained. The K value of the polymer was 32.2; the molar ratio of acrylate to maleic anhydride is approximately 40:60.

Example 6

Grafting of lauryl acrylate and maleic anhydride onto a flow improver, consisting of 60% by weight of ethylene and 40% by weight of vinyl propionate with an average molecular weight of approx. 2500 (determined by vapor pressure osmometry) = FI (A).

In a reactor according to Example 1, 196.8 g of the flow improver FI (A), 34.5 g of maleic anhydride and 91.5 g of Solvesso® 150 were heated to 100 ° C. in a gentle stream of nitrogen while stirring. For this purpose, 77 g of a mixture of 358.7 g of lauryl acrylate and 40 g of Solvesso® 150 and the rest of the mixture were metered in uniformly in 2 hours. At the same time, 1.18 g of tert-butyl per-2-ethylhexanoate, dissolved in 65 g of Solvesso® 150, were metered in uniformly over the course of 4 hours. A solution of 0.38 g of tert-butyl per-2-ethylhexanoate in 14.8 g of Solvesso® 150 was then added, the mixture was heated for one hour and diluted with 379 g of Solvesso® 150. An approximately 50% by weight slightly cloudy polymer solution with a K value of 25.4 was obtained.

Examples 7 to 18 Reaction of the copolymers from Examples 1 to 4 with amines

The reaction was carried out by adding the appropriate amount of the amine to the above polymer solutions and stirring at 100 ° C. until the anhydride band had disappeared in the infrared spectrum.

Example 18

81.3 g of the polymer solution from Example 15 were mixed with 109.7 g of FI (A) and 109.7 g of Solvesso® 150 at 60 ° C. A mixture which was cloudy at room temperature and had a total of about 80 parts was obtained Flow improver FI (A) and 20 parts of copolymer B. The mixture is stable for more than 10 weeks at room temperature.

Example 19

As in Example 18, but with 76 g of the polymer solution from Example 16, 121.1 g of FI (A) and 121.1 g of Solvesso® 150.

Example 20

25 g of a 50% by weight polymer solution according to Example 7 were stirred with 0.99 g of 2-ethylhexylamine and 0.99 g of Solvesso® 150 at 40 ° C. for 30 minutes. The polymer is thereby converted into the amide / ammonium salt. In this example, the monoamide is formed by means of amine A, the ammonium salt with 2-ethylhexylamine.

Example 21

• Amin A: handelsübliche Aminmischung eines hydrierten Ditalgfettamins mit folgender durchschnittlicher Kettenlängenverteilung: 1 % n-C₁₂, 4 % n-C₁₄, 31 % n-C₁₆, 59 % n-C₁₈, Rest ungesättigt
• Amin B: handelsübliches Behenylamin mit folgender durchschnittlicher Kettenlängenverteilung: 1,3 % n-C₁₄, 4,7 % n-C₁₆, 42 % n-C₁₈, 12 % n-C₂₀ und 40 % n-C₂₂
• Amin O: n-Octadecylamin

100 g of a 50% by weight polymer solution according to Example 1 were mixed with 9.1 g (approx. 1 mol per mol maleic anhydride) of ethylhexylamine at room temperature with stirring, heated to 100 ° C. and stirred for 30 minutes, after which the formation of the monoamide was finished. Then 35.3 g of amine A (1 mol per mol of maleic anhydride) were added and the mixture was stirred for 30 minutes with slow cooling to room temperature. In this example, the monoamide is formed using ethylhexylamine and the ammonium salt with amine A.

• Amine A: commercially available amine mixture of a hydrogenated ditallow fatty amine with the following average chain length distribution: 1% nC ₁₂ , 4% nC ₁₄ , 31% nC ₁₆ , 59% nC ₁₈ , the rest unsaturated
• Amine B: Commercial behenylamine with the following average chain length distribution: 1.3% nC ₁₄ , 4.7% nC ₁₆ , 42% nC ₁₈ , 12% nC ₂₀ and 40% nC ₂₂
• Amine O: n-octadecylamine

Examples of use

• FI= Fließverbesserer, im besonderen
• FI(A) Ethylen/Vinylpropionat (mit ca. 40 Gew.% Vinylpropionat) mit einem mittleren Molekulargewicht von ca. 2500 (bestimmt durch Dampfdruckosmometrie)
• FI(B) Ethylen/Vinylacetat (mit ca. 30 Gew.-% Vinylacetat) mit einem mittleren Molekulargewicht von ca. 2500

The following mean:

• FI = flow improver, in particular
• FI (A) ethylene / vinyl propionate (with approx. 40% by weight vinyl propionate) with an average molecular weight of approx. 2500 (determined by vapor pressure osmometry)
• FI (B) ethylene / vinyl acetate (with approx. 30% by weight vinyl acetate) with an average molecular weight of approx. 2500

The flow improvers FI (A) and FI (B) are commercially available products, e.g. the Keroflux® brands from BASF.

• Testmethode: geprüft wurde der "Cold Filter Plugging Point" (CFPP) nach DIN 51 428. Die Ergebnisse sind in der folgenden Tabelle zusammengefaßt
  
  
  

Heating oils and diesel fuels in commercial West German refinery quality were used as middle distillates. They are referred to as middle distillate I, II, III and IV.

• Test method: The "Cold Filter Plugging Point" (CFPP) was tested according to DIN 51 428. The results are summarized in the following table
  
  
  

As the above examples show, the conventional flow improvers FI (A) and FI (B) only work insufficiently in the middle distillates. The sole addition of the copolymers according to the invention rather worsens the CFPP of the middle distillates. The synergistic effect of flow improvers and copolymers according to the invention is illustrated by Examples 6 to 22.

Claims (8)

1. A process for preparing petroleum middle distillates having enhanced flow properties in the cold, which comprises adding to the petroleum distillations small amounts

A) of conventional flow enhancers based on ethylene and

B) copolymers, consisting of 10- 95 mol% of one or more alkyl acrylates or alkyl methacrylates having C_i- to C₂₆-alkyl chains and of 5 - 90 mol% of one or more ethylenically unsaturated dicarboxylic acids or their anhydrides, the copolymer being largely reacted with one or more primary or secondary amines to give the monoamide or amide/ammonium salt of the dicarboxylic acid, the weight ratio ofAto B being 40 to 60 - 95 to 5.

2. A process as claimed in claim 1, wherein copolymers B are added which consist to 40 - 95 mol% of alkyl (meth)acrylates and to 5 - 60 mol% of ethylenically unsaturated dicarboxylic acid derivatives.

3. A process as claimed in claim 1, wherein the alkyl (meth)acrylates carry straight-chain, unbranched C₄- to C₂₂-alkyls.

4. A process as claimed in claim 1, wherein the ethylenically unsaturated dicarboxylic acids or their derivatives in the copolymers B used are reacted with primary or secondary alkylamines having at least one unbranched hydrocarbon chain containing at least 16 carbons largely to give the monoamide.

5. A process as claimed in claim 1, wherein the ethylenically unsaturated dicarboxylic acids or their derivatives in the copolymers B used are reacted with primary or secondary alkylamines having at least one unbranched hydrocarbon chain containing at least 16 carbons largely to give the amide/ammonium salt.

6. A process as claimed in claim 1, wherein, as conventional flow enhancers, copolymers of ethylene with vinyl acetate, vinyl propionate or ethyl hexylacrylate are added.

7. A process as claimed in claim 1, wherein copolymers are added which are grafted to 0 - 100% onto the conventional flow enhancers.

8. A process as claimed in claim 1, wherein the flow enhancers A and the copolymers B are added together in amounts from 50 to 5000 ppm.