EP2449063B2 - Ethylene/vinyl acetate/unsaturated esters terpolymer as an additive for improving the resistance to cold of liquid hydrocarbons such as middle distillates and fuels - Google Patents

Description

Technical area.

The invention relates to the use of copolymers of ethylene, vinyl acetate and ethyl-2-hexyl acrylate as additives improving the cold behavior of fuels and lubricants as well as fuel oils and packages containing these copolymers.

Prior art.

At reduced temperature, the hydrocarbon compositions, in particular based on middle distillate type containing paraffin waxes, such as, for example, diesel fuels and heating oils exhibit a significant reduction in their flow properties. It is well known that the crystallization of paraffins is a limiting factor in the use of middle distillates. Also, it is important to prepare diesel fuels adapted to the temperatures at which they will be used in motor vehicles, that is to say to the surrounding climate. Generally, cold operability of fuels at -10 ° C is sufficient in many warm or temperate countries. But in countries with cold climates, such as the Scandinavian countries, Canada and the countries of North Asia, one can reach temperatures of use of fuels well below -20 ° C. The same is true for domestic fuel oils stored outside buildings (houses, buildings, etc.). This suitability of the cold operability of fuels of the middle distillate type is important, in particular at cold starting of engines. If the paraffins are crystallized at the bottom of the tank, they can be entrained on start-up in the fuel circuit and in particular clog the filters and prefilters placed upstream of the injection systems (pump and injectors). Likewise for the storage of domestic fuel oils, paraffins precipitate at the bottom of the tank and can be entrained and obstruct the pipes upstream of the pump and the boiler supply system (nozzle and filter). It is evident that the presence of solids, such as paraffin crystals, prevents the normal circulation of the middle distillate.

To improve their circulation either in the engine or to the boilers, several types of additives have emerged.

Initially, the oil industry focused on the development of so-called cold flow improvers (CFI) additives, which promote the dispersion of paraffin crystals and thus prevent them from being organized into large networks. , responsible for clogging the filter pores. These additives essentially act on the limit filterability temperature (TLF) and the pour point, but do not modify the cloud point.

The prior art has described numerous CFI additives (see for example US 3,048,479 , US 3,627,838 , US 3,790,359 , US 3,961,961 , EP 261 957 ) which are in general copolymers of ethylene and unsaturated ester, such as ethylene / vinyl acetate (EVA), ethylene / vinyl propionate (EVP), ethylene / vinyl ethanoate (EVE), ethylene / vinyl methacrylate copolymers methyl (EMMA), and ethylene / alkyl fumarate.

To improve the properties of conventional CFIs, the prior art also provides mixtures of conventional CFI additives of ethylene / unsaturated ester type with lubricating agents (esters of mono- or polycarboxylic acid and of mono- or polyalcohols (see for example EP 721 492 ), with anti-sedimentation agents (see for example FR 2 490 669 ), with ethers (see for example US 3,999,960 , EP187 488 ).

Improved CFI additives are also found which are terpolymers or copolymers derived from more than 3 distinct monomers.

For example, US 6,509,424 describes a process for preparing ethylene terpolymers and at least two compounds containing ethylenic unsaturations, such as vinyl esters, (meth) acrylic esters, alkyl vinyl ethers in a tubular reactor. These terpolymers can be used as additives to improve the cold flow of oils and petroleum distillates.

US 3,642,459 describes terpolymers comprising 40 to 89% by weight of ethylene, 10 to 40% by weight of vinyl ester derived from short chain carboxylic acid (C2-C4), such as vinyl acetate, and unsaturated monoesters having a C10-C22 alkyl chain); these terpolymers are used as additives to lower the pour point of petroleum distillates and as anti-wax agents and to improve their filterability.

US 4,156,434 describes terpolymers of ethylene, vinyl acetate and acrylic ester derived from C12-C24 alcohol which lower the pour point of the fuels in which they are incorporated but nothing is said about the improvement of the cold filterability of these additives.

WO 2005/054314 discloses useful alpha olefin, vinyl ester and alpha-beta unsaturated monocarboxylic acid ester terpolymers. Exemplified are terpolymers, particularly preferred by Applicant, which contain more than 80 mole% ethylene and less than 9 mole% vinyl acetate. However, these terpolymers containing less than 9% by moles of vinyl acetate, although having an effect on the reduction of the TLF for middle distillates containing more than 18% of n-paraffins, are not satisfactory as far as concerns on the one hand solubility and on the other apart from the tendency to clogging (or filterability at room temperature): damaging filter clogging is observed.

EP 1,391,498 describes additives improving the low temperature fluidity of middle distillates which are vinyl polymers (A), preferably ethylene-vinyl ester copolymers, in which the amount of material insoluble in hexane exceeds 60% by weight at -20 ° C and is less than 30% by weight at 10 ° C; the examples of EP 1,391,498 clearly show that the filterability temperature (CFPP) is lowered for copolymers and terpolymers in which the amount of material insoluble in hexane exceeds 60% by weight at -20 ° C and is less than 30% by weight at 10 ° C by compared to copolymers and terpolymers having the same repeating units present in the same proportions but in which the amount of material insoluble in hexane is outside the claimed range; the exemplified copolymers are EVA copolymers and ethylene-vinyl acetate-neodecanoate or 2-ethylhexanoate vinyl terpolymers.

There is an unresolved need for additives to improve the cold behavior of fuels (TLF and pour point) while reducing or even eliminating the risk of clogging, so as to avoid clogging the filters of fuel supply systems. engines or boilers (injection system and tanks).

Description of the invention

The present invention relates to the use of copolymers as additives improving the cold resistance of fuels (CFI additives); these copolymers are terpolymers of ethylene, vinyl acetate and 2-ethylhexyl acrylate.

• ▪ de 81 à 87 % en moles d'éthylène,
• ▪ de 10,5 à moins de 12 % en moles d'acétate de vinyle,
• ▪ de 1 à 8,5 % en moles d'acrylate d'éthyl-2-hexyle.

The copolymers according to the invention which can be used as CFI additives include:

• ▪ from 81 to 87% by moles of ethylene,
• ▪ from 10.5 to less than 12% by moles of vinyl acetate,
• ▪ from 1 to 8.5 mol% of ethyl-2-hexyl acrylate.

• A₁: 12 ; 2
• B: 12 ; 6
• C₁: 10,5 ; 5
• D: 10,5 ; 8,5.

Said terpolymers are inscribed in a quadrilateral A ₁ BC ₁ D in which A ₁ , B, C ₁ and D represent the vertices of said quadrilateral and correspond to the molar percentages of vinyl acetate and of 2-ethylhexyl acrylate:

• A _1: 12; 2
• B: 12; 6
• C ₁ : 10.5; 5
• D: 10.5; 8.5.

The copolymers according to the invention which are random copolymers have a number molecular mass (Mw) measured by GPC generally between 3,000 and 30,000, and a number average molecular mass (Mn) measured by GPC generally between 1,000 and 15,000.

These copolymers can be prepared in a known manner by any polymerization process, (see for example, Ullmann's Encyclopedia of Industrial Chemistry, 5th Edition, "Waxes", Vol. A 28, p.146 ; US 3,627,838 ; EP 7,590 ) in particular by radical polymerization, preferably under high pressure, typically of the order of 1000 to 3000 bars (100 to 300 MPa), preferably from 1500 to 2000 bars (150 to 200 MPa), the temperatures of reaction generally ranging from 160 to 320 ° C, preferably from 200 to 280 ° C, and in the presence of at least one radical initiator generally chosen from organic peroxides and / or oxygen or nitrogen compounds, and a molecular weight regulator (ketone or aliphatic aldehyde, ...). The copolymers can for example be prepared in a tubular reactor according to the process described in US 6,509,424 .

Hydrocarbon-based compositions in which the copolymers according to the invention are incorporated, are chosen from all types of fuel oils or fuels, such as diesel fuels, domestic fuel oils for heating installations (FOD), kerosene, aviation fuel oils, heavy fuel oils, etc.

In general, the sulfur content of the hydrocarbon compositions is less than 5000 ppm, preferably less than 500 ppm, and more preferably less than 50 ppm, or even less than 10 ppm and advantageously without sulfur.

The hydrocarbon-based compositions comprise middle distillates with a boiling point of between 100 and 500 ° C; their starting crystallization temperature Tcc is often greater than or equal to -20 ° C, generally between -15 ° C and + 10 ° C. These distillates can for example be chosen from the distillates obtained by direct distillation of crude hydrocarbons, the vacuum distillates, the hydrotreated distillates, the distillates resulting from the catalytic cracking and / or the hydrocracking of vacuum distillates, the distillates resulting from ARDS-type conversion processes (by desulfurization of atmospheric residue) and / or visbreaking, distillates resulting from the upgrading of Fischer Tropsch cuts, distillates resulting from the BTL (biomass to liquid) conversion of plant and / or animal biomass, taken alone or in combination and / or the esters of vegetable and animal oils or their mixtures.

The hydrocarbon compositions can also contain distillates resulting from more complex refining operations than those resulting from the direct distillation of hydrocarbons which can for example come from cracking, hydrocracking and / or catalytic cracking processes and visbreaking processes.

• les coupes les plus lourdes issues des procédés de craquage et de viscoréduction concentrées en paraffines lourdes, comprenant plus de 18 atomes de carbone,
• les distillats synthétiques issus de la transformation du gaz tels que ceux issus du procédé Fischer Tropsch,
• les distillats synthétiques résultant du traitement de la biomasse d'origine végétale et/ou animale, comme notamment le NexBTL,
• et les huiles et/ou esters d'huiles végétales et/ou animales,
• ou encore les biodiesel d'origine animale et/ou végétale.

They can also contain new sources of distillates, among which we can in particular quote:

• the heaviest cuts resulting from the cracking and visbreaking processes concentrated in heavy paraffins, comprising more than 18 carbon atoms,
• synthetic distillates resulting from the transformation of gas such as those resulting from the Fischer Tropsch process,
• synthetic distillates resulting from the treatment of biomass of plant and / or animal origin, such as in particular NexBTL,
• and oils and / or esters of vegetable and / or animal oils,
• or else biodiesel of animal and / or vegetable origin.

These new fuel bases can be used alone or as a mixture with conventional petroleum middle distillates as fuel base and / or domestic fuel oil base; they generally comprise long paraffinic chains greater than or equal to 10 carbon atoms and preferably from C14 to C30.

The copolymers as defined above with Mw between 5,000 and 27,000 and with Mn between 1,500 and 22,000, preferably with Mw between 5,000 and 25,000 and Mn between 1,500 and 20,000 are particularly effective. when they are incorporated into light middle distillates and / or low sulfur content (typically less than 50 ppm) and / or low starting crystallization temperature (typically up to -20 ° C). By light middle distillates is meant distillates in which the content of n-paraffins having 24 carbon atoms or more ranges from 0 to approximately less than 0.7% by weight of the total fuel composition; in which the C18-C23 n-paraffins represent approximately 3 to approximately 5% of the total weight of the fuel and in which the mass ratio of the C18-C23 n-paraffins relative to the C24 and more paraffins generally ranges from 10 to 35.

Copolymers of Mw between 5,000 and 10,000 and with Mn between 1,500 and 8,000, preferably with Mw between 5,000 and 8,000 and Mn between 1,500 and 5,000 are particularly effective when they are used. incorporated in heavy middle distillates and / or at a rather high starting crystallization temperature (typically ranging from 0 to 15 ° C). By heavy middle distillates is meant distillates in which the content of n-paraffins having 24 carbon atoms or more ranges from about 0.7 to about 2% by weight of the total fuel composition; in which the C18-C23 n-paraffins represent approximately 1 to approximately 10% of the total weight of the fuel and in which the mass ratio of C18-C23 n-paraffins to C24 + paraffins generally ranges from 1 to 10.

The copolymers can be added as such in the hydrocarbon compositions or preferably in the form of concentrated solutions, in particular solutions containing from 50 to 80%, preferably from 60 to 70% by weight of copolymer (s) in a solvent, such as aliphatic or aromatic hydrocarbons, alone or as a mixture (naphtha, kerosene, hydrocarbon fractions, such as Solvesso solvent, paraffinic hydrocarbons, such as pentane, hexane.

According to a preferred embodiment of the invention, the hydrocarbon compositions comprise from 10 to 5,000 ppm by weight of at least one copolymer described above optionally, preferably from 100 to 1,000 ppm, and advantageously from 150 to 500 ppm.

In addition to the CFI additives or cold resistance additives described above, the hydrocarbon compositions may also contain one or more other additives other than the copolymers according to the invention, chosen from detergents, anti-corrosion agents, dispersants, demulsifiers, anti-foam agents, biocides, reodorants, procetane additives, friction modifiers, lubricity additives or lubricity additives, combustion aids (catalytic combustion and soot promoters) , agents improving the cloud point, the pour point, the limit temperature of filterability, anti-sedimentation agents, anti-wear agents and / or agents modifying the conductivity.

1. a) les additifs procétane, notamment (mais non limitativement) choisis parmi les nitrates d'alkyle, de préférence le nitrate de 2-éthyl hexyle, les peroxydes d'aroyle, de préférence le peroxyde de benzyle, et les peroxydes d'alkyle, de préférence le peroxyde de ter-butyle ;
2. b) les additifs anti-mousse, notamment (mais non limitativement) choisis parmi les polysiloxanes, les polysiloxanes oxyalkylés, et les amides d'acides gras issus d'huiles végétales ou animales. Des exemples de tels additifs sont donnés dans EP 861 882 , EP 663 000 , EP 736 590 ;
3. c) les additifs détergents et/ou anti-corrosion, notamment (mais non limitativement) choisis dans le groupe constitué par les amines, les succinimides, les alkénylsuccinimides, les polyalkylamines, les polyalkyles polyamines et les polyétheramines. Des exemples de tels additifs sont donnés dans EP 938 535 .
4. d) additif de lubrifiance ou agent anti-usure, notamment (mais non limitativement) choisi dans le groupe constitué par les acides gras et leurs dérivés ester ou amide, notamment le monooléate de glycérol, et les dérivés d'acides carboxyliques mono- et polycycliques. Des exemples de tels additifs sont donnés dans les documents suivants: EP 680 506 , EP 860 494 , WO 98/04656 , EP 915 944 , FR2 772 783 , FR 2 772 784 .
5. e) les additifs de point de trouble, notamment (mais non limitativement) choisis dans le groupe constitué par les terpolymères oléfine à chaîne longue/ester (méth)acrylique /maléimide, et les polymères d'esters d'acides fumarique /maléique. Des exemples de tels additifs sont donnés dans EP 71 513 , EP 100 248 , FR 2 528 051 , FR 2 528 051 , FR 2 528 423 , EP1 12 195 , EP 1 727 58 , EP 271 385 , EP 291367 ;
6. f) les additifs d'anti-sédimentation et/ou dispersants de paraffines notamment (mais non limitativement) choisis dans le groupe constitué par les copolymères acide (méth)acrylique/(méth)acrylate d'alkyle amidifié par une polyamine, les alkénylsuccinimides de polyamine, les dérivés d'acide phtalamique et d'amine grasse à double chaîne ; des résines alkyl phénol. Des exemples de tels additifs sont donnés dans EP 261 959 , EP593 331 , EP 674 689 , EP 327 423 , EP 512 889 , EP 832 172 ; US 2005/0223631 ; US 5 998 530 ; WO 93/14178 .
7. g) les additifs polyfonctionnels d'opérabilité à froid choisis dans le groupe constitué par les polymères à base d'oléfine et de nitrate d'alkényle tels que décrits dans EP 573 490 . ;
8. h) d'autres additifs CFI améliorant la tenue à froid et la filtrabilité, tels que les copolymères EVA et/ou EVP.

Among these additives, there may be mentioned in particular:

1. a) procetane additives, in particular (but not limited to) chosen from alkyl nitrates, preferably 2-ethylhexyl nitrate, aroyl peroxides, preferably benzyl peroxide, and alkyl peroxides, preferably tert-butyl peroxide;
2. b) anti-foam additives, in particular (but not limited to) chosen from polysiloxanes, oxyalkylated polysiloxanes, and fatty acid amides obtained from vegetable or animal oils. Examples of such additives are given in EP 861 882 , EP 663,000 , EP 736 590 ;
3. c) detergent and / or anti-corrosion additives, in particular (but not limited to) chosen from the group consisting of amines, succinimides, alkenylsuccinimides, polyalkylamines, polyalkyl polyamines and polyetheramines. Examples of such additives are given in EP 938 535 .
4. d) lubricity additive or anti-wear agent, in particular (but not limited to) chosen from the group consisting of fatty acids and their ester or amide derivatives, in particular glycerol monooleate, and mono- and polycyclic carboxylic acid derivatives . Examples of such additives are given in the following documents: EP 680 506 , EP 860 494 , WO 98/04656 , EP 915 944 , FR2 772 783 , FR 2 772 784 .
5. e) cloud point additives, in particular (but not limited to) chosen from the group consisting of long-chain olefin / (meth) acrylic ester / maleimide terpolymers, and polymers of esters of fumaric / maleic acids. Examples of such additives are given in EP 71 513 , EP 100 248 , FR 2 528 051 , FR 2 528 051 , FR 2 528 423 , EP1 12 195 , EP 1 727 58 , EP 271 385 , EP 291367 ;
6. f) anti-sedimentation additives and / or paraffin dispersants, in particular (but not limited to) chosen from the group consisting of (meth) acrylic acid / (meth) acrylate copolymers of alkyl amidated with a polyamine, alkenylsuccinimides of polyamine, phthalamic acid and double chain fatty amine derivatives; alkyl phenol resins. Examples of such additives are given in EP 261 959 , EP593 331 , EP 674 689 , EP 327 423 , EP 512 889 , EP 832 172 ; US 2005/0223631 ; US 5,998,530 ; WO 93/14178 .
7. g) polyfunctional cold operability additives chosen from the group consisting of olefin-based polymers and alkenyl nitrate as described in EP 573 490 . ;
8. h) other CFI additives improving cold resistance and filterability, such as EVA and / or EVP copolymers.

These other additives are generally added in an amount ranging from 100 to 1000 ppm (each).

The improved cold resistance additives according to the invention can be added to the hydrocarbon compositions within the refinery, and / or be incorporated downstream of the refinery, optionally as a mixture with other additives, in the form of a package. or package of additives.

Examples

In a tubular reactor, are synthesized by radical polymerization under high pressure (1,400 to 2,500 bars (140 to 250 MPa) and at a polymerization temperature of 200 to 280 ° C terpolymers of ethylene, vinyl acetate and of ethyl-2, hexyl acrylate. The synthesis is carried out using an aliphatic aldehyde (propanal) to control the molecular masses and using peroxides as polymerization initiators. In Table 1 below, the Mn are indicated. and Mw of the terpolymers synthesized as well as their percentages of the monomers. Table 1: Characteristics of the polymers synthesized Copolymer [vinyl acetate] [2-ethylhexyl acrylate] Mn Mw % weight % moles % weight % moles 6 (comparative) 13.3 6.6 22.1 5.1 12 627 14,610 7 (comparative) 13.1 6.5 22.4 5.2 8,842 10,460 12 (comparative) 27.6 13.7 20.7 4.8 11180 13255 13 (comparative) 28.4 14.1 20.4 4.7 12100 14372 16 (comparative) 19.3 9.6 21.5 5 4,498 8,443 18 (comparative) 36.7 17 3.5 0.8 10,000 11000 17 19 10.4 30.8 7.9 12000 15000 19 (comparative) 28 11 0 0 3000 8000 20 (comparative) 30.5 12 0 0 4000 9000

The ability to improve the cold resistance of these terpolymers is evaluated by incorporating them into 2 distillates of motor diesel type called GOM 1 and GOM 2, the characteristics of which are given in Table 2 below. Table 2: Fuel characteristics ASTM D86 Distillation GOM 1 GOM 2 T90-T20 (° C) 129.6 100.4 PF-T90 (° C) 19.5 24.9 T95 (° C) 353.5 362.4 Cloud point (° C) NF EN 23015 -6 -4 TLF (° C) EN 116 -6 -7 Pour point (° C) NF T 60105 -15 -10 Paraffin content (% mass) Chromatography 14.72 14.68 TCC (° C) IP 389 -6.2 -6.3 Sulfur content (ppm) EN ISO 20846 18.6 38

400 ppm by weight of each copolymer below is incorporated into the distillate of motor diesel type called GOM 1 and then the FBT (Filter Blocking Tendency) clogging index is measured according to the IP 387 standard. GOM 1 without additives has an index. 1.01 FBT clogging. It is observed that the terpolymer 17 according to the invention makes it possible not to degrade the tendency for GOM 1 to clog, that is to say that the GOM 1 additive with 400 ppm of terpolymer has an FBT of less than 1.41. The results are shown in Table 3 below. Table 3 Tendency to clogging (IP387) of GOM 1 additivated to 400 ppm of the various terpolymers. Additive added FBT clogging index (IP 387) 6 (comparative) 6.08 7 (comparative) 6.08 12 (comparative) 1.01 13 (comparative) 1.03 16 (comparative) 5.1 17 1.0 18 (comparative) 1.24 19 (comparative) 5.1 20 (comparative) 1.9

The efficiency in cold strength TLF of the terpolymers incorporated in the GOM 1 and GOM 2 at a concentration of 210 ppm is measured; the results are collated in Table 4. Table 4: TLF efficiency tests on 2 low sulfur gas oils. Additive added TLF measurements (° C) EN 116 GOM 1 GOM 2 210 ppm 210 ppm Additives free -6 -5 6 -15 7 -16 -15 12 -7 -4 13 -7 -5 17 -19 - 18 -7 - 19 -15 - 20 -16 -

It is observed that the terpolymer 17 according to the invention is the most effective on gas oil GOM 1. Moreover, from the results of Table 3, it is noted that the terpolymer 17 added at a rate of 400 ppm in GOM 1 does not degrade. the tendency to clogging. This is not the case with the comparative terpolymers 6; 7; 16 and 18 according to WO 2005/054314 which strongly degrade the tendency to clogging measured according to IP 387 and are not as effective in TLF as additive 17 of the invention.

Claims (9)

1. Use, as additive which improves the resistance to cold and the filterability of fuels, of at least one terpolymer comprising units derived from ethylene, units derived from vinyl acetate and units derived from 2-ethylhexyl acrylate, comprising:

   - from 81 mol% to 87 mol% of ethylene,

   - from 10.5 mol% to less than 12 mol% of vinyl acetate,

   - from 1 mol% to 8.5 mol% of 2-ethylhexyl acrylate, the said terpolymer being included in a quadrilateral A₁BC₁D in which A₁, B, C₁ and D represent the apexes of the said quadrilateral and correspond to the molar percentages of vinyl acetate and 2-ethylhexyl acrylate:

   A₁: 12; 2

   B: 12; 6

   C₁: 10.5; 5

   D: 10.5; 8.5.
2. Use according to Claim 1 of at least one terpolymer with a number-average molecular weight (Mw), measured by GPC, of between 3000 and 30 000, preferably 3000 to 20 000, and a number-average molecular weight (Mn), measured by GPC, in general of between 1000 and 20 000, preferably ranging from 1500 to 15 000.
3. Use according to either one of Claims 1 and 2 of at least one terpolymer as additive which improves the resistance to cold and the filterability without damaging the tendency towards clogging of middle distillates, such as diesel fuels, domestic heating oils, kerosene, aviation fuels or heavy fuel oils.
4. Use according to any one of Claims 1 to 3 of at least one terpolymer as additive which improves the resistance to cold and the filterability of fuels, the sulfur content of which is less than 5000 ppm, preferably less than 500 ppm, more preferably less than 50 ppm, indeed even less than 10 ppm, and advantageously of fuels without sulfur.
5. Hydrocarbon composition comprising a major amount of a middle distillate with a boiling point ranging from 100 to 500°C and of 10 to 5000 ppm by weight of at least one terpolymer comprising units derived from ethylene, units derived from vinyl acetate and units derived from 2-ethylhexyl acrylate, comprising:

   - from 81 mol% to 87 mol% of ethylene,

   - from 10.5 mol% to less than 12 mol% of vinyl acetate,

   - from 1 mol% to 8.5 mol% of 2-ethylhexyl acrylate, the said terpolymer being included in a quadrilateral A₁BC₁D in which A₁, B, C₁ and D represent the apexes of the said quadrilateral and correspond to the molar percentages of vinyl acetate and 2-ethylhexyl acrylate:

   A₁: 12; 2

   B: 12; 6

   C₁: 10.5; 5

   D: 10.5; 8.5.
6. Composition according to Claim 5, characterized in that it contains biodiesel of animal and/or vegetable origin.
7. Composition according to Claim 5 or 6, characterized in that it is chosen from diesel fuels, domestic heating oils, kerosene, aviation fuels or heavy fuel oils.
8. Composition according to any one of Claims 5 to 7, characterized in that it comprises from 100 to 1000 ppm by weight of the said terpolymer, preferably from 150 to 500 ppm.
9. Composition according to any one of Claims 5 to 8, characterized in that it comprises one or more other additives, different from the terpolymers according to the invention, chosen from detergents, corrosion inhibitors, dispersants, demulsifiers, antifoam agents, biocides, reodorants, cetane number improvers, friction modifiers, slip agents or lubricity additives, combustion aids (catalytic promoters of combustion and of soot), agents which improve the cloud point, the pour point or the cold filter plugging point, antisettling agents, antiwear agents and/or conductivity modifiers.