NO145725B - MEDIUM OIL OIL CONDITIONS, WITH IMPROVED FILTERABILITY AND FLOW CONDITIONS. - Google Patents

Description

The subject of the present invention is a middle distillate of petroleum that is suitable as diesel fuel or light heating oil, with improved filterability and improved flowability. These properties apply at temperatures above and below the flash point. In addition to known copolymers, monomers are added as solubilizers.

So-called middle distillates, for example gas oil, diesel oil or heating oil, as these are extracted by distilling crude oil, have a different content of paraffins depending on the origin of the crude oil. At low temperatures, paraffin wax separates in the form of plate-shaped crystals, which partly also contain inclusions of oil. This influences the flowability of the petroleum distillate - burning

respectively the fuels - to a considerable extent. This leads, for example, in the case of diesel fuel to clogging of filters and thus to interruptions. respective uneven supply of fuel oil to the combustion units such as engines or jet engines. Likewise, disturbances can occur with heating oils in winter if this kind of secretions, conditioned by low temperatures, occur. However, transport of middle distillates through pipelines over long distances can also be influenced in winter by paraffin crystals falling out.

It is well known to use various additives as modifiers for crystal growth for fuel and fuels from petroleum distillates, in particular the middle distillates.

Such additions change size and shape

on the wax crystals, so that the oil is also able to

flow at low temperatures. Such additives are known under the term "stock point improvers" or "flow improvers" or "flow point improvers". For this purpose, for example, according to US patent 2,189,924, condensation products of

chlorinated paraffins and naphthalene. In order to have sufficient success with this, however, such condensation products must be used in relatively large quantities. In addition to this strive

in recent times, as much as possible, chlorinated hydrocarbons have been discarded for this purpose in order to avoid corrosive gases that occur during combustion.

Also the use of oil-soluble or crude oil distillate dispersible copolymers as stock-point

and/or flow-improving agents are well known, see, for example, US patent 3,832,150.

The polymers proposed so far as stock-point and flow-improving agents are now showing practical application

at low temperatures, i.e. temperatures below the flash point, although the described properties as modifiers resp. growth inhibitors for paraffin crystals, but in many cases they show at temperatures above the flash point and up to approx. +30° significant disadvantages. This applies in particular, for example, to copolymers of ethylene and fatty acid vinyl esters or ethylene and acrylic acid esters, which are produced by solvent-free polymerization according to known high-tech processes.

Especially the diesel engines used in practice are, everything

depending on the purpose of application, equipped with filter materials of different pore sizes. An unhindered fuel-

supply must also be able to be provided under extreme conditions at all times. Especially in the military area, diesel engines increase over very narrow pore fuel filters with pore diameters of 2-40 µm. Multi-layer filters made of materials with very different pore widths for coarse and fine filtration are also frequently used.

Extensive tests have shown that copolymers of, for example, ethylene and fatty acid vinyl esters as well as ethylene and acrylic acid esters, which are produced according to the known high-tech processes, always also contain small proportions of higher-molecular polymerization products that are partially insoluble in petroleum distillate fuel - and fuels.

These higher-molecular polymerization products occur as by-products of radical polymerization of ethylene and, for example, fatty acid vinyl esters or acrylic acid esters. Depending on the nature and quantity of the higher-molecular polymerization products, insoluble deposits can therefore also occur in the petroleum distillate fuels and fuels already at temperatures above the actual flash point (i.e. the beginning of the separation of paraffin wax), as with the narrow-pored filter materials can already lead to blockages.

One was therefore faced with the task of changing the known production methods for copolymers or to propose suitable precautions to reduce filter clogging by means of small proportions of higher-molecular polymerization products, resp. completely tossing these out.

By the known production methods for copolymers

of ethylene and, for example, fatty acid vinyl esters or acrylic acid esters, for example, you work according to the principle of solution or suspension polymerization under pressure at elevated temperatures. With these methods, after the reaction is finished, the solvent and the unreacted monomers are separated by distillation, as described for example in BRD patent 25 15 805.

In other methods for producing the copolymers, one works, for example, completely without solvent at pressures of 500-2,000 bar and temperatures of, for example, 100-350°C, whereby the unreacted ethylene and the unreacted fatty acid vinyl esters resp. acrylic acid esters towards the end of the reaction are separated by pressure relief in the reactor. In solvent-free polymerization processes in particular, there may be formation of the insoluble in petroleum distillate fuel and fuels.

It has now been found that the solubility can be improved

to the copolymers of ethylene and fatty acid vinyl esters produced by processes known per se, resp. ethylene and acrylic acid esters in petroleum distillate fuels and fuels to a significant extent by means of small amounts of the corresponding monomers. The monomers that act as solubilizers generally cause a significant swelling of the waxy higher-molecular copolymers, whereby in the practical application, i.e. the addition of these copolymers to petroleum destiHat fuels and fuels, a strong improvement in the solubility of the copolymer is achieved and thus a considerable improvement in the filterability of the petroleum distillate at temperatures above the flash point.

Thus, the invention consists in middle distillates

of petroleum, which is suitable as diesel fuels or light fuel oil, with improved filterability and improved fluidity with a content of small amounts of modifiers

in the form of copolymers, selected from the group consisting of binary copolymers of ethylene and a vinyl ester of a Gj- or C^-alkanecarboxylic acid and binary copolymers of ethylene and a C^-Cg alkyl ester of a C^- or C^-alkene monocarboxylic acid , whereby the copolymers contain 60-95% by weight of ethylene and 5-40% by weight of the olefinically unsaturated ester polymerized and have a melt viscosity, measured according to DIN 51 562 (ASTM D 445) at 120°C, of 100-1000 mm<2>/sec., characterized

in that the middle distillates next to the copolymers contain 0.1-10 vol.%, calculated on the copolymer, of the monomeric vinyl esters of a C^-C^-alkane carboxylic acid or of monomeric_Ci-C8~ alkylesters of a C^- or C 1 -alkenecarboxylic acid.

The monomers are preferably present in amounts of 0.5-5 vol.%, calculated on the copolymer.

Middle distillates according to the invention preferably include such binary copolymers which are obtained by polymerization of ethylene and vinyl acetate resp. alkyl acrylates without solvent at pressures of 500-2,000 bar and temperatures of 100-350°C, preferably 200-300°C, and which have molecular weights of 500-10,000, preferably 1,000-5,000. Thereby, the radical copolymerization can quite easily started with air, but also with suitable peroxide initiators or is controlled by the addition of suitable regulating agents (for example aliphatic aldehydes).

After complete polymerization is preferably separated

the unreacted ethylene and vinyl acetate as well as lower-boiling oligomers from pressure relief in the reactor and the solubilizing monomers are also added to the ethylene-free copolymers.

Admittedly, the monomers are preferably added to the copolymer at the end. However, it is also possible to cool the polymerization mixture before pressure relief to temperatures below the boiling point of the monomers, so that, apart from ethylene, the unreacted monomers do not or only partially evaporate during the pressure relief. A combination of both of these precautions is also possible.

As monomers contained in the copolymers,

in particular vinyl esters of carboxylic acids with 1-4 carbon atoms are mentioned, preferably vinyl acetate with vinyl propionate as well as acrylic acid and methacrylic acid esters of C-^-Cg-alkanols, especially butyl, isobutyl, 2-ethylhexyl and lauryl acrylate.

As esters of maleic acid, maleic acid dimethyl ester or -dibutyl ester in particular come into consideration.

As already mentioned, the monomers that serve as solubility mediators, alone or in combination with each other, are usually added subsequently to the copolymers that have been prepared according to the known methods, as these copolymers are usually of a very tough consistency and have viscosities for example in range 100-1000 mm/s at 120°C.

For viscosity reduction and easier application, the copolymers are mostly dispersed in suitable solvents which have no, or only little, solubility-improving effect. For this purpose, for example, higher-boiling highly aromatic products are used, which for example contain polyalkylated benzenes, toluenes, xylenes, ethylbenzenes and possibly also higher alkylated naphthalenes. Another frequently used method is the dispersion of the copolymers grown in suitable petroleum distillates. Heavy petrol, petroleum, diesel oil or gas oil fractions.

The monomers that serve as solubility-improving agents can therefore be added to the copolymer waxes themselves, but also the dispersions of these waxes in suitable dispersants. Elevated temperatures of, for example, 30-90°C and good thorough mixing by stirring or re-pumping are appropriate.

When using polymerization-sensitive unsaturated esters, such as vinyl acetate or acrylic acid esters or unsaturated oligomers, it is recommended to stabilize these by adding technically common polymerization inhibitors, in order to avoid a subsequent polymerization of these components after they have been added as solvents. Common polymerization inhibitors are, for example, polyalkylated phenols, nitrogen-containing aromatic heterocycles or alkylated aromatic amino-phenols resp. substituted or unsubstituted phenylenediamines. The minimal discoloration of the petroleum distillates caused by the inhibitors is negligible.

Depending on the molecular weight of the copolymers used, the resp. the density and composition of the dispersants. as well as the proportion of the copolymer waxes to be dispersed, there may be deposits of the polymeric waxes in the dispersions. Above all when producing dispersions with a small proportion (for example 1-50% by weight) of copolymer ethylene/fatty acid vinyl esters resp. ethylene/acrylic acid esters, the obtained dispersions are not as stable as with larger proportions (for example over 50% by weight) of copolymer wax. It has now also been found that the above-described additions of monomers to copolymer waxes in the specified concentrations also have a thickening effect on the dispersions of the copolymer waxes.

By adding the monomers to the dispersions of the copolymer waxes, the stability of the dispersions is also significantly increased in many cases. A deposition of the copolymer waxes does not take place, or only to a small extent.

From US patent 3 627 838 it is known that a particularly good pour point improvement can be achieved if the polymerization is carried out so that free vinyl acetate is always present, even at the end of the reaction. From column 2, lines 29 and 30, however, it is stated that the monomers are removed during processing

("The product is stripped free of solvent and unreacted

vinyl acetate under vacuum"). After this, according to the patent, a product is used which has been freed from monomers, while the monomers, according to the present inventive Isis doctrine, remain in the products or are added to them.

In order to explain the invention, numerous filtration experiments are indicated in the following, whereby the viscosities of a number of dispersants are measured while the monomers are being added.

A suitable filtration test for petroleum distillate propellants containing copolymer flow improvers is carried out as follows:

Purpose of the provision

Clogging of the filterability of petroleum distillates

containing copolymeric flow improvers, at temperatures above the cloud point.

Brief description of the procedure

A certain amount of the petroleum distillate to be examined (for example kerosene, gas oil, diesel fuel, heating oil EL according to DIN 51 601) is filtered in water jet vacuum in portions of 100 ml over a membrane filter. The lead times are measured per 100 ml.

Vessels and chemicals

5,000 ml suction bottle

Water jet pump

Paper folding filter

Blue band filter no. 589<3> 0 15 cm

5,000 ml glass bottle

100 ml measuring cylinder

Sartorius membrane filter attachment type SM 16307 Sartorius membrane filter type SM 11301 pore sizer

8 µm, n-pentane

Execution of the filtering

The selected crude oil distillate is filtered before the experiment over a paper folding filter, to remove coarse suspended matter and dirt particles. For fine purification, the thus pre-cleaned sample is filtered in a water jet vacuum over a blue band filter.

Into 3,000 ml of the petroleum distillate pre-treated in this way, a certain amount of flow-improving medium 1 dispersion or cow's wax is mixed at room temperature. The filtration of the thus modified petroleum distillate over a membrane filter takes place in portions of 100 ml each. The flow time for 100 ml of liquid is measured each time and plotted graphically against the filtered volume. The time axis is logarithmic.

Assessment of the measurement

Method A: Comparison of the thus obtained filtration curves.

Method B: Quantitative determination of the higher-molecular proportions of copolymer wax that is insoluble in soil-oil path Hatet.

Before filtration, the membrane filter is washed with 100 ml of n-pentane, dried and weighed. After the filtration of the petroleum distillate to be examined, the membrane filter is washed again with 100 ml of oil-free n-pentane, dried and reweighed. The amount of higher-molecular residue which is insoluble in the crude oil fraction is given in % by weight calculated on the copolymer wax.

The method described above makes it possible to examine both unmodified petroleum distillates and petroleum distillates containing copolymer waxes or dispersions or solutions of these grow. In preliminary tests according to method A with filters with different pore widths, it is ensured that by using a membrane filter with a pore width of 8 µm, it is possible to distinguish between copolymer waxes with different contents of higher molecular proportions.

Method A also ensures that the filtration curves of petroleum distillate propellants, which do not contain any copolymer waxes, do not show an increase in filtration duration with increasing filtration volume. The filtration duration for 100 ml of filtered product only depends on the viscosity or the density of the petroleum destiHate. According to method A, the petroleum distillate that is not modified with wax copolymers gives no indication of filter clogging.

The following examples illustrate the invention using the above-described filtration test (method A

and B) .

In the case of copolymers grown with extremely high proportions of higher-molecular compounds, which can usually cause stronger filter clogging, the above filtration test can be varied, as smaller volume parts (e.g. portions of 20 ml) are filtered. In this way, it is possible to distinguish between very similar cow waxes which all give a very poor filtration curve according to method A.

In the case of copolymers grown with extremely small proportions of higher-molecular compounds, the membrane filter is only clogged by larger passages of modified petroleum distillate (e.g. 10-100 1). In this case, it is also recommendable with a larger sample volume, 500 or 1,000 ml, for the filtration test.

The effectiveness of the monomer addition is maintained at a constant temperature even after a long storage time for the dispersions of copolymers grow.

However, the temperature is essential for the filtration ratio of petroleum destiHater, which is here modified with flow-improving agents. It could be shown that the solubility of the small proportions of higher-molecular compounds contained in the copolymer waxes is a function of temperature.

Thus, in filtration tests according to method A with decreasing filtration temperatures for the modified petroleum distillate for the same copolymer wax, a steeper progression of the filtration curves is obtained and according to method B a correspondingly larger amount of higher-molecular compounds which under these conditions are insoluble in copolymer wax.

Nevertheless, it remains a strong solution mediator

effect of the monomers to be used according to the invention also existing at lower temperatures, possibly only the addition amounts of the solvent mediators to the copolymer wax need to be increased.

The solubilizing effect of the monomers extends to temperatures well above the natural flash point of the petroleum distillate (e.g. 30°C) to well below the flash point (e.g. -40°C). By resp. below the flash point, in petroleum distillates, paraffin crystals begin to separate with further decreasing temperature. By adding ethylene/fatty acid vinyl esters or ethylene/acrylic acid esters as flow-improving agents, these paraffin crystals are modified and disturbed in their weight, the oil is indeed cloudy due to secreted paraffins, but retains the ability to flow and be pumped. When using the copolymer flow-improving agents, which may also contain certain amounts of higher-molecular proportions, become considerably more insoluble with decreasing temperatures, so that either just above or first below the natural clouding point of the petroleum distillates together with the paraffins can precipitate out and lead to disturbances in the cold conditions of the petroleum distillates. Filter and valve clogging in these cases is not caused by the paraffin crystals modified in their crystal form below the flash point, but already above the flash point by insoluble higher-molecular components in the copolymer flow improver falling out. For the impeccable effectiveness of the copolymer flow improvers, it is therefore necessary that the proportions of the higher molecular compounds always present due to the polymerization process are kept in solution as well as possible. This takes place by adding the solvents according to the invention.

Example 1

In table 1, the physical data for various copolymer waxes based on ethylene/vinyl acetate are listed.

The table also shows those in the copolymer waxes still

proportions of monomeric vinyl acetate present.

The cow waxes listed in Table 1 were prepared in different dispersants as 50% dispersions,

and the filtration ratio for different gas oils after the addition of 500 vol.-ppm of the flow-improving effective dispersions investigated according to method A. The higher molecular proportions present in the 50% dispersions and according to method 3 obtained are compiled in table 2 .

Figs 1 and 2 show the filtration curves determined according to method A for the cow waxes from table 2, whereby here and in the following t means the filtration time in seconds and v the filtration volume in ml.

<+>^ Here and in the following:

Residue from the oxo-synthesis of n-butanol (essentially consisting of 2-ethylhexanol as the main component (approx.

35-60 %), 4-methyl-2-ethylpentanol (approx. 4-7 %), various butyl butyrates (3-6 %), di-n-butyl acetate (1-5 %), 2-ethy1-hexy1-n -butyrate (1-4 isomeric pentanols (2-3 isomeric butanols (1%)

As table 2 and fig. 1 and 2 show, all investigated waxes in the used dispersants show poor filterability (according to method A) and correspondingly large proportions of higher-molecular products according to method B. The following examples show the cultivation method of the solubilizers according to the invention.

Example 2

The one in table 1 and fig. 1 already mentioned cow wax no. 1 was added as a 50% dispersion in C 2 -oxo-alcohol residue as a dispersant with the solvents according to the invention. The thus improved dispersions were mixed with a diese1 fuel in an amount of 500 vol.-ppm and examined according to methods A and B.

Table 3 shows the effect of the solvents on the amount of the higher-molecular residue present in cow wax no. 1. The residues were determined according to method B. In fig. 3, the filtration curves belonging to table 3 are shown.

Example 3

The cow wax no. 3 mentioned in table 1 was set as

50% dispersion in C2-oxo-alcohol residue. As Table 2 shows, in the filtration test according to method B, an amount of 3.6% of higher-molecular fractions is found. Curve 5 in fig. 1 and A

in fig. 4 shows correspondingly poor filtration conditions (according to method A). By adding 1% by weight of vinyl acetate to the 50% dispersion of cow wax no. 3 in the C4-oxo-alcohol residue is found after the addition of 500 vol.-ppm of the thus improved dispersion to a fuel oil EL (according to DIN 51601) and the filter test according to method B only 0.34% higher molecular fractions. Curve B in fig. 4 shows the filtration curves according to method A.

Example 4

One by polymerization without solvent at 220°C

and 1,500 bar prepared copolymer wax of ethylene and vinyl acetate with a vinyl acetate content of 28.5% by weight, a viscosity (120°C) of 210 mm<2>/s; an average molecular weight of 1,880 and et

content of 0.75% by weight of monomeric vinyl acetate (calculated on the copolymer) was set as a 50% dispersion in a C₁-oxo-alcohol residue.

The filtration tests according to method A were carried out extra easily after adding 500 vol.-ppm of the 50% dispersion of the copolymer wax in C₁-oxo-alcohol residue to a commercial fuel oil (according to DIN 51 601). It was obtained in fig. 5 produced filtration curve No. 1.

The dependence of the solvent effect on the content of monomeric vinyl acetate was then likewise shown in the filtration test according to method A by increasing additions of further amounts of monomeric vinyl acetate.

Fig. 5 shows the dependence of the solvent effect on the content of monomeric vinyl acetate in the dispersion in the filtration test according to method A. In the filtration curves 2, 3, 4 and 5, the 50% dispersion of the copolymer wax was further added 0.25, 0.50 , 1.0 and 3.0% by weight of monomeric vinyl acetate.

Example 5

A copolymer wax produced by continuous polymerization without solvent at 220°C and 1,500 stretches of ethylene and vinyl acetate with a content of 27.2% by weight of vinyl acetate and a viscosity at 120°C of 365 mm/s and an average molecular weight of 2,230 and a residual content of monomeric vinyl acetate of 0.55% by weight

(based on copolymer) is set as a 40% dispersion in petroleum.

A filtration test according to methods A and B is carried out extra easily (according to DIN 51 601) by adding 800 vol.-ppm of the 40% dispersion to a commercial fuel oil. The filter test takes place immediately, as well as after 8

and 30 days shelf life for the additive fuel oil. The corresponding filtering curves 1, 2 and 3 in fig. 6 and according to method B a proportion of higher-molecular compounds of 9.5 (curve 1), 9.7 (curve 2) and 10.1% by weight (calculated on cow wax). Further filtration tests according to methods A and B are carried out, after a quantity of 0.5% by weight of monomeric vinyl acetate had been added to the dispersion in advance. Of this improved flow improver dispersion, the same fuel oil was likewise added at 800 vol.-ppm.

The filter test for the thus additive fuel oil also takes place here immediately or after 8 days and 30 days.

You get the corresponding filtering curves 4, 5 and

6 in fig. 6 and according to method B proportions of higher-molecular compounds of 0.38% (curve 4) and 0.45%

(curves 5 and 6).

Example 6

a) One by continuous polymerization without solvent at a temperature of 245°C and a pressure of 1,500 bar of

ethylene and 2-ethylhexyl acrylate prepared copolymer wax with a content of 46.2% by weight 2-ethylhexyl acrylate, a viscosity (at 120°C) of 252 mm<2>/s and an average molecular weight of 2,440 was set as 58% dispersion in petroleum, heated with stirring for 1 hour at 80°C, cooled to

room temperature and subjected to a filtration test according to methods A and B. Thereby a commercial fuel oil (extra light) was added to 500 ppm of the 5% dispersion. The filtration test was repeated after 24, 48, 108 and 240 hours at room temperature. The amount of polymeric residues and the associated filtration curves are shown in table 4 and

fig. 7.

b) The 58% dispersion was now added with 1% by weight vinyl acetate (stabilized with 0.1% 2,6 di-tert-butyl-p-cresol), the mixture was heated to 80°C with stirring, cooled to room temperature and the filtration test A and B after the addition of 500 ppm of the dispersion provided with vinyl acetate carried out at room temperature after 24, 48, 108 and 240 hours. The quantities of polymeric residues and the associated filtration curves are contained in table 4 and fig. 7. Where t means filtration time in seconds, v filtration volume in ml, curves 1, 2, 3, 4 according to (a) after 24, 48, 108 and 240 hours, curves 5, 6, 7, 8 according to ( b) after 24, 48, 108 and 240 hours.

Example 7

To show the effect of the monomer addition when performing the filtration test near the flash point of the modified petroleum distillate, the copolymer wax no. 1 described in Table 1 is set as a 50% dispersion in an oxo-alcohol residue from the butanol synthesis. The dispersion is heated with stirring to 80°C, cooled to room temperature and used after a standing time of 36 days at room temperature for the filter tests A and B. For this purpose, a commercially available fuel oil (extra light) with a flash point of -2°C is added

500 ppm by weight of the dispersion and cooled in a cooling bath during 35 minutes at 0°C. The oil thus obtained is filtered according to method B. A polymer residue of 130 mg (= 26.2% calculated on the proportion of wax in the dispersion) is obtained.

If you carry out the same test after having previously added 1% by weight of vinyl acetate (precipitated on wax and stabilized with 0.1% 2,6-di-tert.-buty1-p-cresol) to the dispersion, then you get according to method B only a polymer residue of 44.2 mg (= 8.8%).

If one increases the amount of vinyl acetate to ialt

3% by weight and works in the same way, then you only get 5.5 mg (= 1.1%) of polymer residue.

Example 8

In a large-scale experiment, 30,000 kg of a copolymer wax of ethylene and vinyl acetate with a content of 29.2% vinyl acetate, a viscosity of (at 120°C) of 247 mrn^/s and an average molecular weight of 1,940.

a) An average sample of wax with a monomeric vinyl acetate content of 0.6% is set as 50%

dispersion in an oxo-oil residue from the butanol synthesis. A commercial diesel fuel with a cloud point of -2°C at room temperature is added with 500 ppm by weight of this dispersion, the mixture is cooled in a cooling bath to 0°C over 35 minutes and then a filtration test is carried out according to methods A and B. A polymer residue of 3 7.2 mg (= 7.4% by weight calculated on growing len in the dispersion) is obtained.

b) If 2% by weight of vinyl acetate (calculated on wax and stabilized with 0.1% 2,6-di-tert.-buty1-p-cresol) is added

50% dispersion and the filtration test described above repeated at 0°C, only 4.1 mg of polymer residue is obtained (= 0.83% by weight calculated on the wax portion in the dispersion). The filtration curves for both filtration tests show

fig. 8.

Example 9

In one as in fig. 9 shows continuously working equipment, diesel oils are pumped over a commercially available fuel filter. The equipment consists of an insulated storage vessel (B 1) with a volume of 110 1 for the diesel oil, in which there is a cooling hose driven by a cooling sole (s), a Bosch fuel pump (P-l) for 0-1.5 bar, a fuel filter (F), Bosch no. 1,457,434,052, with a differential pressure gauge (PI-2) and a continuous fuel flow measurement (Fl). Furthermore, pressure measuring points (TI-1, TI-2 and TI-3) have been installed, as well as temperature gauges TI-1, TI-2 and TI-3. The amount of diesel oil pumped over the filter F is collected in the collector vessel B-2 ( volume 110 1).Pump and filter are located in a dry ice-powered cooling box, in order to avoid temperature increases during heat conduction and pump work.

In this apparatus, gas oils previously purified over a paper filter were pumped at temperatures immediately above their flash point with a flow rate of

10 l/h above the filter F.

A criterion for the coating of the fuel filter

with higher-molecular proportions of the copolymer flow improvers, the pressure rise on the differential pressure monometer is PI-2.

The curves for the relevant pressure progression (mm WS) are plotted graphically against the duration of the experiment. The subsequent fig. 10 where P means pressure drop in mm water column and t the duration of the experiment in seconds, shows the results with different copolymer ethylene/vinyl acetate waxes as flow improvers with and without the addition of monomeric vinyl acetate.

Curve 1: Cow wax of ethylene/vinyl acetate with 28.1% by weight vinyl acetate, average molecular weight 2,160, melt viscosity (120°C) 230 mm<2>/s, content of monomeric vinyl acetate 0.07% by weight, as 50% ig dispersion in oxo-oil residue from the butanol synthesis.

Dosage of the dispersion in diesel oil: 500 vol.-ppm

- without further addition of solvents - Temperature: + 0°C.

Curve 2: as 1, but after addition of 0.5% by weight of monomer

vinyl acetate (stabilized), calculated on cow wax.

Curve 3: as 2, but with 1.0% by weight of monomeric vinyl acetate.

Curve 4: as 2, but with 3.0% by weight of monomeric vinyl acetate.

Example 10

The one in table 1 and fig. 1 said cow wax no. 1 was added as a 50% dispersion in C 2 -oxo-alcohol residue with solubilizers according to the invention as a dispersant. The thus improved dispersions were mixed with a diesel fuel in an amount of 500 vol.-ppm and examined according to methods A and B.

The effect of the solvents on the amount of the higher-molecular residue present in cow wax No. 1 is shown in the following table. The residues were determined according to method B.

In fig. 11, the filtration curves corresponding to table 5 are listed.

Claims (4)

1. Middle distillate of petroleum, for use as diesel fuel f or light heating oil, with improved filterability and improved fluidity, containing small amounts of modifiers in the form of copolymers, selected from the group consisting of binary copolymers of ethylene and a vinyl ester of a C 2 - or C 1 -alkanecarboxylic acid and binary copolymers of ethylene and a C 2 -C 8 -alkyl ester of a C 2 - or C 3 -alkene monocarboxylic acid, whereby the copolymers contain 60-95% by weight of ethylene and 5-40% by weight % of the olefinically unsaturated ester polymerized and has a melt viscosity, measured according to DIN 51 562 (ASTM D 445) at 120°C, of 100-1000 mm<2>/sec., characterized in that the middle distillate at side of the copolymers contains 0.1-10 vol.%, calculated on the copolymer, of the monomeric vinyl esters of a C^-C^-alkenecarboxylic acid or of monomeric C^-Cg-alkyl esters of a C^- or C^-alkenecarboxylic acid. 2. Middle distillate as stated in claim 1, characterized in that it contains monomeric vinyl acetate. 3. Middle distillate as stated in claim 1, characterized in that it contains monomeric acrylic acid ester of C₁-C₆ alkanols. 4. Middle distillate as stated in claim 1, characterized in that it contains monomeric C1-C0 alkyl esters of maleic acid.