US20200392421A1

US20200392421A1 - Use of a particular copolymer for preventing deposits on the valves of indirect injection petrol engines

Info

Publication number: US20200392421A1
Application number: US16/770,436
Authority: US
Inventors: Jerome Obiols
Original assignee: Total Marketing Services SA
Current assignee: TotalEnergies Marketing Services SA
Priority date: 2017-12-06
Filing date: 2018-12-06
Publication date: 2020-12-17
Also published as: FR3074499B1; FR3074499A1; WO2019110937A1; EP3720931A1

Abstract

The copolymers according to the invention are very particularly effective in preventing and/or cleaning the deposits on the valves while preventing the latter from sticking at low temperature.

Description

A subject matter of the present invention is the use of a specific copolymer to prevent the deposits which form at low temperature on the fuel intake valves in indirect injection spark ignition engines.

PRIOR ART

Liquid fuels for internal combustion engines contain components which can decompose during the operation of the engine. The problem of deposits in combustion engines is well known to auto mechanics. It has been shown that the formation of these deposits has consequences on the performance qualities of the engine and in particular has a negative impact on consumption and emissions of particles. Progress in the technology of fuel additives has made it possible to confront this problem. “Detergent” additives used in fuels have already been proposed to keep the engine clean by limiting deposits (“keep-clean” effect) or by reducing the deposits already present (“clean-up” effect). Mention may be made, by way of example, of U.S. Pat. No. 4,171,959, which describes a detergent additive for gasoline fuel containing a quaternary ammonium functional group. WO 2006/135881 describes a detergent additive containing a quaternary ammonium salt used for reducing or cleaning deposits, in particular on the intake valves.
In the case of indirect injection spark ignition engines (or gasoline engines), a specific problem is posed, related to the formation of deposits on the external parts of the engine and in particular on the stems of the intake valves for the mixture of air and fuel upstream of the combustion chamber, which results in a phenomenon of valve sticking.
This phenomenon, well known to specialists under the term “valve sticking”, is described in a reference publication by Seppo Mikkonen, Reino Karlsson and Jouni Kivi entitled “Intake Valve Sticking in Some Carburetor Engines”, SAE Technical Paper Series No. 881643, International Fuels and Lubricants Meeting and Exposition, Portland, Oreg., Oct. 10-13, 1988.
This phenomenon is caused, during operation of the engine at low temperature (in cold weather, for example), by an accumulation of deposits having a high viscosity at the interface between the intake valve stem and the valve guide, in the indirect injection spark ignition engines. The accumulation of such deposits on the valve stems hinders the movements of the latter, the stems stick to the valve guides, which causes poor closing of the valves, causes sealing problems in the combustion chamber, and can significantly affect the operation of the engine, and in particular can prevent it from starting in cold weather. This phenomenon of valve sticking is thus the cause of sealing problems in the combustion chamber, responsible for a reduction in the compression force and thus in the efficiency of the engines. In some extreme cases, the intake valve, which has remained open due to the accumulation of the deposits, can collide with the piston. This collision can then lead to deformation of the valve and/or of the valve stem and thus to the breakdown of the engine.
In a way known per se, a distinction is made between different types of deposits on the intake valves of indirect injection spark ignition engines. These types of deposits are well known to auto mechanics, and the appearance of some is dependent on the solutions for the treatment of the others.
On the one hand, a first type of deposit consists of those which form at high temperature on the intake valves of indirect injection spark ignition engines during the use of a fuel not containing a detergent additive. These deposits are in particular made up of carbon-based residues related to the phenomenon of coking and can also comprise deposits of soap and/or lacquering type. These deposits are generally treated by the use of detergent additive added to the fuel (additive-treated fuel).
On the other hand, a second type of deposit consists of viscous deposits, mentioned above, which form at low temperature, typically at a temperature of less than or equal to 5° C., and which appear on the stems of the intake valves of indirect injection spark ignition engines during the use of additive-treated fuels, thus causing the phenomenon of valve sticking described above. Low-temperature deposits are very particularly formed during certain operating conditions of the engine, such as, for example, short trips in cold weather. Under these conditions, the engine does not have the time to reach its normal operating temperature. This operating mode can be characterized by the fact that the temperature of the coolant rarely reaches more than 60° C., indeed even does not exceed 30° C.
Thus, the additivation of the fuel for the treatment and the prevention of the deposits which form at high temperature can cause the appearance of viscous deposits at low temperature.
As set out in the abovementioned publication (SAE Technical Paper Series No. 881643), the composition of the gasoline and of the additives which it contains have a very major influence on the phenomena of valve sticking. In particular, the detergent additives conventionally incorporated in gasolines in order to keep the valves clean at high temperature have paradoxically proved to promote phenomena of valve sticking at low temperature. In a way known per se, the problem of valve sticking does not occur or occurs very slightly when a fuel devoid of detergent additives is used. Furthermore, the abovementioned publication shows that polymeric additives, capable of being employed in gasolines and/or motor oils, are known to be agents which promote valve sticking.
In order to reduce the deposits on the intake valves and to prevent these sticking phenomena, the application 0 870 819 proposes to add, to the gasoline composition, additives obtained by a Mannich condensation reaction starting from a hydroxyaromatic compound substituted by a group derived from a polyolefin having a number-average molecular weight ranging from 500 to 3000 and by a C1 to C4 alkyl group; from an aliphatic polyamine having a single primary or secondary amino group; and from an aldehyde; with a molar ratio of the aldehyde to the amine of less than or equal to 1.2. This document additionally recommends incorporating the additive within a carrier oil, in particular of poly(oxyalkylene) type, which is described as reinforcing the effectiveness of the additive in minimizing or reducing deposits on the intake valves and/or the sticking of said valves.
This is because it is known to use a carrier oil containing detergents in order to limit or reduce the formation of deposits formed at high temperatures on the intake valves, while limiting the phenomenon of valve sticking. However, this solution proves to be expensive, and the aim is as far as possible to avoid the use of such an oil, or to reduce the amount thereof as much as possible.
The application U.S. Pat. No. 7,291,681 proposes the use, as detergent additive for gasolines of polyisobuteneamines having a number-average molecular weight Mn ranging from 500 to 1500 and a polydispersity index Mw/Mn of less than 1.4.
Example 2 of this document presents the results of comparative tests relating to the evaluation of the performance qualities of several fuels with or without additives, in terms of deposits on the valves, on the one hand, and valve sticking, on the other hand. These results confirm that an additive-free fuel does not cause valve sticking but generates significant deposits on the valves. These results also show that the specific polyisobuteneneamines according to this document make it possible to very significantly reduce the deposits on the valves while preventing the latter from sticking, provided, however, that they are introduced in combination with a carrier oil (poly(l-butene oxide)). In the absence of such an oil, a phenomenon of valve sticking occurs.
The solutions proposed in the prior art are therefore not entirely satisfactory.
Thus, there exists a need to propose a solution for additivation of the fuel which makes it possible to effectively prevent deposits which can appear on the intake valves and to thus avoid phenomena of sticking of these at low temperature.
In particular, there remains a need to propose fuel additives which can be used in the engines of indirect injection spark ignition engines which make it possible both to prevent (“keep-clean” effect) and to reduce (“clean-up” effect) in an effective way the deposits on the valves at low temperature.
These solutions should, if possible, also make it possible to avoid the use of a carrier oil, such as, for example, a poly(oxyalkylene) oil.

SUBJECT MATTER OF THE INVENTION

The applicant company has discovered that copolymers formed from specific units as described below have noteworthy properties when they are used as additive in fuels for indirect injection spark ignition engines. Used in these fuels, the copolymers according to the invention make it possible to keep the intake valves clean, preventing the phenomena of sticking of the latter at low temperature.
“Low temperature” denotes, in the present patent application, a temperature of less than or equal to 5° C., preferably of less than or equal to 0° C. and more preferentially still of less than or equal to −5° C.
These copolymers exhibit the additional advantage of being able to be used without a carrier oil.
These properties are all the more unexpected as the prior art teaches, on the contrary, that fuel additives and a fortiori polymeric compounds promote the phenomena of valve sticking.
The additional advantages associated with the use in fuels for spark ignition engines of the copolymers according to the invention are:

- optimum operation of the engine, in particular at low temperature,
- reduction in the fuel consumption,
- better handling of the vehicle,
- reduced emissions of pollutants, and
- savings due to less maintenance of the engine.

A subject matter of the present invention is the use, in order to prevent deposits at low temperature on the fuel intake valves in indirect injection spark ignition engines, of one or more copolymer(s) comprising:

- at least one unit of following formula (I):

- in which:
- u=0 or 1,
- R₁′ represents a hydrogen atom or a methyl group,
- E represents —O— or —N(Z)— or —O—CO— or —CO—O— or —NH—CO— or —CO—NH—, with Z representing H or a C₁to C₆alkyl group,
- G represents a group chosen from a C₁to C₃₄alkyl group, an aromatic nucleus, an aralkyl group comprising at least one aromatic nucleus and at least one C₁to C₃₄alkyl group, and
- at least one unit of following formula (II):

- in which:
- v=0 or 1,
- R₁″ is chosen from the hydrogen atom and the methyl group,
- Q is chosen from the oxygen atom and an —NR′— group with R′ being chosen from a hydrogen atom and C₁to C₁₂hydrocarbon chains,
- R represents a C₁to C₃₄hydrocarbon chain which can also contain one or more nitrogen and/or oxygen atoms and/or carbonyl groups, which is substituted by at least one amino group comprising a primary, secondary or tertiary amine or quaternary ammonium functional group, and optionally one or more hydroxyl groups.

By “preventing the deposits on the fuel intake valves” is understood to mean that the use according to the invention makes it possible to avoid the formation of deposits on said valves (“keep-clean” effect), but also to reduce the amount of deposits when such deposits are already present (“clean-up” effect).
As indicated above, the deposits treated in the context of the present invention are those which form at low temperature, that is to say at a temperature of less than or equal to 5° C., preferably of less than or equal to 0° C. and more preferentially still of less than or equal to −5° C. These are viscous deposits located at the stems of the valves and which are capable of causing phenomena of valve sticking.
Preferentially, the group G of the formula (I) is chosen from a C4 to C34 alkyl group, an aromatic nucleus, an aralkyl group comprising at least one aromatic nucleus and at least one C1 to C34 alkyl group, preferably a C4 to C34 alkyl group.
According to a first alternative form, the group G of the formula (I) is an aralkyl group comprising at least one aromatic nucleus and at least one C4 to C30 alkyl group.
According to a second preferred alternative form, the group G of the formula (I) is a C4 to C34 alkyl group.
According to a first embodiment, the group E of the formula (I) is chosen from: —O— and —N(Z)—, with Z representing H or a C1 to C6 alkyl group.
According to a second embodiment, the group E of the formula (I) is chosen from: —O—CO— and —NH—CO—; preferably the group E is the —O—CO— group, it being understood that the group E=—O—CO— is connected to the vinyl carbon by the oxygen atom and that the group E=—NH—CO— is connected to the vinyl carbon by the nitrogen atom.
According to a third embodiment, the group E of the formula (I) is chosen from: —CO—O— and —CO—NH—; preferably the group E is the —CO—O— group, it being understood that the group E is connected to the vinyl carbon by the carbon atom.
According to a first alternative form, the amino group present in the group R of the formula (II) is chosen from the groups having at least one amine, imine, amidine, guanidine, aminoguanidine or biguanidine functional group, such as alkylamines, polyalkylenepolyamines, polyalkylenimines, alkylimines, alkylamidines, alkylguanidines and alkylbiguanidines, it being possible for the alkyl substituent to be linear or branched, cyclic or acyclic, and preferably having from 1 to 34 carbon atoms, more preferentially from 1 to 12 carbon atoms, and the quaternized forms of these groups.
According to a second alternative form, said amino group present in the group R of the formula (II) is chosen from monocyclic or polycyclic heterocyclic groups, having from 3 to 34 atoms, preferably from 5 to 12 atoms, more preferentially from 6 to 10 atoms, and at least one nitrogen atom, it being understood that the polycyclic heterocyclic groups have, optionally, fused rings. The number of atoms includes the heteroatoms. Fused rings is understood to mean rings having at least two atoms in common. The heterocyclic groups can additionally comprise an oxygen atom and/or a carbonyl group and/or one or more unsaturations.
Mention may be made, as example of a heterocyclic amino group, of the following radicals: triazole, aminotriazole, pyrrolidone, piperidine, imidazole, morpholine, isoxazole, oxazole, indole and the quaternized forms of these radicals, said radical preferably being connected to the hydrocarbon chain by a nitrogen atom.
According to a preferred embodiment, the group R of the formula (II) is represented:

- when v has the value 1, by the formula (V):

L-R′₂ (V)

- when v has the value 0, by the formula (V) or the formula (V):

L-R′₂ (V)
L- (V)

- in which formulae (V) and (V′):
- R₂′ is chosen from C₁to C₃₄hydrocarbon chains, optionally substituted by at least one hydroxyl group, and
- L is chosen from the group consisting of:
  - the following groups:
    - amine: —NH₂; —NHR_a, —NR_aR_b;
    - imine: —HC═NH; —HC═NR_a; —N═CH₂, —N═CR_aH; —N═CR_aR_b; amidine: —(C═NH)—NH₂; —(C═NH)—NR_aH; —(C═NH)—NR_aR_b; —(C═NR_a)—NH₂; —(C═NR_a)—NR_bH; —(C═NR_a)—NR_bR_c; —N═CH(NH₂); —N═CR_a(NH₂); —N═CH(NR_aH); —N═CR_a(NR_aH); —N═CH(NR_aR_b); —N═CR_a(NR_bR_c);
    - guanidine: —NH—(C═NH)—NH₂; —NH—(C═NH)—NHR_a; —N═C(NH₂)₂; —N═C(NR_aH)₂; —N═C(NR_aR_b)₂; —N═C(NR_aH)(NR_bH);
    - aminoguanidine: —NH—(C═NH)—NH—NH₂; —NH—(C═NH)—NH—NHR_a; —N═C(NH₂)(NH—NH₂); —N═C(NR_aH)(NH—NH₂); —N═C(NR_aH)(NR_a—NH₂); —N═C(NR_aR_b)(NH—NH₂); —N═C(NR_aR_b)(NR_a—NH₂);
    - biguanidine: —NH—(C═NH)—NH—(C═NH)—NH₂; —NH—(C═NH)—NH—(C═NH)—NHR_a; —N═C(NH₂)—NH—(C═NH)—NH₂; —N═C(NH₂)—NH—(C═NR_a)—NH₂; —N═C(NH₂)—NH—(C═NH)—NR_aH; —N═C(NH₂)—NH—(C═NR_a)—NR_bH; —N═C(NH₂)—NH—(C═NH)—NR_aR_b; —N═C(NH₂)—NH—(C═NR_a)—NR_bR_c; —N═C(NR_aH)—NH—(C═NH)—NH₂; —N═C(NR_aH)—NH—(C═NR_b)—NH₂; —N═C(NR_aH)—NH—(C═NH)—NR_bH; —N═C(NR_aH)—NH—(C═NR_b)—NR_cH; —N═C(NR_aH)—NH—(C═NH)—NR_bR_c; —N═C(NR_aH)—NH—(C═NR_b)—NR_cR_d; —N═C(NR_aR_b)—NH—(C═NH)—NH₂; —N═C(NR_aR_b)—NH—(C═NR_c)—NH₂; —N═C(NR_aR_b)—NH—(C═NH)—NR_cH; —N═C(NR_aR_b)—NH—(C═NR_c)—NR_dH; —N═C(NR_aR_b)—NH—(C═NH)—NR_cR_d; —N═C(NR_aR_b)—NH—(C═NR_c)—NR_dR_e;
    - the quaternized forms of the above groups, when these contain at least one quaternizable nitrogen atom; and
  - polyamine and polyalkylenepolyamine groups, in particular those of formulae —NH—(R_f—NH)_k—H; —NH—(R_f—NH)_k—R_a;
  - with R_a, R_b, R_c, R_dand R_erepresenting, independently of one another, a C₁-C₃₄, preferably C₁-C₁₂, alkyl group, optionally comprising one or more NH₂functional groups and one or more —NH— bridges;
  - R_frepresents a C₁-C₆, preferably C₂-C₄, alkyl group; k represents an integer ranging from 1 to 20, preferably from 2 to 12.

Mention may be made, as example of polyamine and polyalkylenepolyamine groups, of: ethylenediamine, diethylenetriamine, triethylenetetramine or tetraethylenepentamine.
The quaternary ammonium functional group(s) optionally present in the group R of the units of formula (II) can be chosen in particular from pyrrolinium, pyridinium, imidazolium, triazolium, triazinium, oxazolium and isoxazolium quaternary ammoniums.
According to an alternative form, the quaternary ammonium functional group(s) is (are) chosen from trialkylammonium, iminium, amidinium, formamidinium, guanidinium and biguanidinium quaternary ammoniums, and preferably trialkylammonium quaternary ammonium.
According to a preferred embodiment, the quaternary ammonium functional group(s) optionally present in the group R of the units of formula (II) is (are) represented by one of the following formulae (III) and (IV):
in which:

- X⁻ is chosen from hydroxide or halide ions and organic anions, preferably organic anions, R₂is chosen from C₁to C₃₄hydrocarbon chains, optionally substituted by at least one hydroxyl group,
- R₃, R₄and R₅are identical or different and are chosen independently from C₁to C₁₈hydrocarbon chains, it being understood that the R₃, R₄and R₅groups can contain one or more groups chosen from: a nitrogen atom, an oxygen atom and a carbonyl group and that the R₃, R₄and R₅groups can be connected together in pairs to form one or more rings,
- R₆and R₇are identical or different and are chosen independently from C₁to C₁₈hydrocarbon chains, it being understood that the R₆and R₇groups can contain one or more groups chosen from: a nitrogen atom, an oxygen atom and a carbonyl group and that the R₆and R₇groups can be connected together to form a ring.
- According to a particularly preferred embodiment, the quaternary ammonium functional group(s) optionally present in the group R of the units of formula (II) is (are) represented by the above formula (III), in which:
- X⁻ is chosen from organic anions, preferably conjugate bases of carboxylic acids,
- R₂is chosen from C₁to C₃₄hydrocarbon chains, preferably C₁to C₁₈alkyl groups,
- R₃, R₄and R₅are identical or different and are chosen independently from C₁to C₁₈hydrocarbon chains, optionally substituted by at least one hydroxyl group, it being understood that at least one of the R₃, R₄and R₅groups contains one or more hydroxyl group(s).

According to a preferred embodiment, the copolymer employed in the present invention contains units of formula (II) comprising a group R containing at least one quaternary ammonium functional group.
According to a particularly preferred embodiment, from 5 mol % to 95 mol % of the units of formula (II) of the copolymer comprise, in the group R, at least one quaternary ammonium functional group.
In this embodiment, the units of formula (II) in which the group R does not comprise a quaternary ammonium functional group comprise, in the group R, at least one amino group comprising a primary, secondary or tertiary amine functional group. These units represent from 5 mol % to 95 mol % of the units of formula (II) of the copolymer according to the invention.
According to an advantageous alternative form of this embodiment, the copolymer comprises a first type of units of formula (II) in which the groups R comprise at least one quaternizable nitrogen atom and a second type of units of formula (II) obtained by quaternization of the units of the first type.
The copolymer employed in the present invention can be obtained by copolymerization of at least:

- a nonpolar monomer (m_a) corresponding to the following formula (VII):

- in which:
- R₁′, u, E and G are as defined above, and
- one or more polar monomers (m_b) corresponding to the following formula (VIII):

- in which:
- R₁″, v, Q and R are as defined above.

According to a preferred embodiment, from 5 mol % to 95 mol % of the polar monomers (mb) comprise a group R containing at least one quaternary ammonium functional group.
According to another embodiment, the copolymer employed in the invention is obtained by copolymerization of at least:

- a nonpolar monomer (m_a) corresponding to the following formula (VII):

in which:

- R₁′, u, E and G are as defined above, and
- a polar monomer (m_b) corresponding to the following formula (VIII):

- in which:
- R₁″, v and Q and are as defined above,
- and R represents a C₁to C₃₄hydrocarbon chain which can also contain one or more nitrogen and/or oxygen atoms and/or carbonyl groups, which is substituted by at least one amino group comprising a primary, secondary or tertiary amine functional group, and optionally one or more hydroxyl groups,
- the copolymerization being followed by a partial quaternization of the amino groups of the units resulting from the monomer (m_b).

“Partial quaternization” is understood to mean a quaternization of 5 mol % to 95 mol % of the amino groups of the units resulting from the monomer (mb). This quaternization of said amino groups implies that they comprise at least one quaternizable nitrogen atom.
According to a preferred embodiment, the monomer (ma) is chosen from C1 to C34 alkyl acrylates and C1 to C34 alkyl methacrylates.
According to a preferred embodiment, the copolymer according to the invention is chosen from block copolymers and random copolymers, and preferably the copolymer according to the invention is a block copolymer.
Preferably, the copolymer according to the invention is a block copolymer comprising:

- a block A corresponding to the following formula (XI):

- in which:
- p is an integer ranging from 2 to 100, preferably ranging from 5 to 80, preferably ranging from 10 to 70, more preferentially ranging from 20 to 60,
- R₁′, u, E and G are as defined above, and
- a block B corresponding to the following formula (XII):

- in which:
- n is an integer ranging from 2 to 50, preferably from 3 to 40, more preferentially from 4 to 20, more preferentially still from 5 to 10,
- R₁″, v, Q and R are as defined above.

According to a preferred embodiment, from 5 mol % to 95 mol % of the units of the block B comprise a group R containing at least one quaternary ammonium functional group.
Preferably, the block copolymer comprises at least:

- a block A consisting of a chain of structural units derived from one or more nonpolar monomers chosen from nonpolar monomers (m_a) of formula (VII), and
- a block B consisting of a chain of structural units derived from one or more polar monomers chosen from polar monomers (m_b) of formula (VIII).

According to a first embodiment, the block copolymer comprises at least:

- the block A consisting of a chain of structural units derived from a single nonpolar monomer chosen from nonpolar monomers (m_a) of formula (VII), and
- the block B consisting of a chain of structural units derived from a single polar monomer chosen from polar monomers (mb) of formula (VIII).

In this first embodiment, according to an advantageous alternative form, the block copolymer comprises at least:

- the block A consisting of a chain of structural units derived from a C1-C34 alkyl (meth)acrylate monomer (ma), and
- the block B consisting of a chain of structural units derived from an alkyl (meth)acrylate or alkyl(meth)acrylamide monomer (mb), the alkyl radical of which consists of a C1 to C34 hydrocarbon chain substituted by at least one amino group chosen from primary, secondary or tertiary amines and quaternary ammoniums, and optionally one or more hydroxyl groups.

According to a second embodiment, the block copolymer comprises at least:

- the block A consisting of a chain of structural units derived from a single nonpolar monomer chosen from nonpolar monomers (ma) of formula (VII), and
- the block B consisting of a chain of structural units, 5 mol % to 95 mol % of which are derived from a single polar monomer chosen from polar monomers (mb) of formula (VIII) in which the group R contains at least one quaternary ammonium functional group, and 5 mol % to 95 mol % of which are derived from a single polar monomer chosen from polar monomers (mb) of formula (VIII) in which the group R does not contain a quaternary ammonium functional group and comprises at least one amino group comprising a primary, secondary or tertiary amine functional group.

In this second embodiment, according to an advantageous alternative form, the block copolymer comprises at least:

- the block A consisting of a chain of structural units derived from a C1-C34 alkyl (meth)acrylate monomer (ma), and
- the block B consisting of a chain of structural units derived from alkyl (meth)acrylate or alkyl(meth)acrylamide monomers (mb), 5 mol % to 95 mol % of which have an alkyl radical consisting of a C1 to C34 hydrocarbon chain substituted by a quaternary ammonium group and optionally one or more hydroxyl groups, and 5 mol % to 95 mol % of which have an alkyl radical consisting of a C1 to C34 hydrocarbon chain substituted by a group chosen from primary, secondary or tertiary amines, preferably tertiary amines, and optionally one or more hydroxyl groups.

Preferably, the number of monomer equivalents (ma) of the block A is from 2 to 100 moles.
Preferably, the number of monomer equivalents (mb) of the block B is from 2 to 50 moles.
Preferably, the copolymer comprises at least one sequence of blocks AB, ABA or BAB, where said blocks A and B are linked together without the presence of an intermediate block of different chemical nature.
Preferentially, the block copolymer is obtained by block polymerization, optionally followed by one or more post-functionalizations.
The copolymer according to the invention is used by incorporating it in a fuel composition, to which it can be added alone or in the form of a fuel concentrate comprising one or more copolymer(s) according to the invention as defined above, as a mixture with an organic liquid, said organic liquid being inert with regard to said copolymer(s) and miscible with said fuel.
The fuel compositions, in which the copolymer according to the invention can be used, can result from one or more sources chosen from the group consisting of mineral, animal, vegetable and synthetic sources.
Preferably, the fuel is chosen from hydrocarbon fuels, fuels which are not essentially hydrocarbon fuels, and their mixtures.
Advantageously, the hydrocarbon fuel is chosen from gasolines.
Preferably, the copolymer according to the invention is used in the fuel composition at a minimum content of 5 ppm.
According to a preferred embodiment, said copolymer is used to prevent the formation of deposits at low temperature on the stems of the intake valves, and more particularly to prevent said valves from sticking at low temperature.
The invention additionally relates to a process for keeping clean, at low temperature, the fuel intake valves in an indirect injection spark ignition engine comprising at least the following stages:

- the preparation of a fuel composition by additivation of a fuel with a copolymer as described above, then
- the injection of said fuel composition into the spark ignition engine.

DETAILED DESCRIPTION

Other advantages and characteristics will emerge more clearly from the description which will follow. The specific embodiments of the invention are given as nonlimiting examples.
For reasons of simplicity, the following terms are employed in the present description:

- alkyl (meth)acrylate to denote an alkyl acrylate or an alkyl methacrylate;
- alkyl(meth)acrylamide to denote an alkylacrylamide or an alkylmethacrylamide;

and

- quaternary ammonium to denote a quaternary ammonium salt.

The copolymer:
The copolymer used in the present invention comprises:

- at least one unit of following formula (I):

- in which:
- v=0 or 1,

R₁″ is chosen from the hydrogen atom and the methyl group,

- Q is chosen from the oxygen atom and an —NR′— group with R′ being chosen from a hydrogen atom and C₁to C₁₂hydrocarbon chains,
- R represents a C₁to C₃₄hydrocarbon chain which can also contain one or more nitrogen and/or oxygen atoms and/or carbonyl groups, which is substituted by at least one amino group comprising a primary, secondary or tertiary amine or quaternary ammonium functional group, and optionally one or more hydroxyl groups.

According to a specific embodiment, the copolymer comprises only units of formula (I) and units of formula (II).
According to a specific embodiment, the copolymer is chosen from block copolymers and random copolymers.
According to a particularly preferred embodiment, the copolymer is a block copolymer.
According to a first alternative form, the unit of formula (I) is chosen from those satisfying u=0.
Preferentially, and according to this first alternative form, the copolymer is a block copolymer.
According to another alternative form, the unit of formula (I) is chosen from those satisfying u=1.
The group E of formula (I) is chosen from:

- E=—O—,
- E=—N(Z)—, with Z represents H or a linear or branched, cyclic or acyclic, preferably acyclic, C₁to C₆alkyl group,
- E=—O—CO—, it being understood that E is then connected to the vinyl carbon by the oxygen atom,
- E=—CO—O—, it being understood that E is then connected to the vinyl carbon by the carbon atom,
- E=—NH—CO—, and
- E=—CO—NH—.

According to a first embodiment, the group E of the formula (I) is chosen from: —O— and —N(Z)—, with Z representing H or a C1 to C6 alkyl group.
According to a second embodiment, the group E of the formula (I) is chosen from: —O—CO— and —NH—CO—, it being understood that the group E=—O—CO— is connected to the vinyl carbon by the oxygen atom and that the group E=—NH—CO— is connected to the vinyl carbon by the nitrogen atom.
According to this same embodiment, the group E of the formula (I) is preferably the —O—CO— group, it being understood that the —O—CO— group is connected to the vinyl carbon by the oxygen atom.
According to a third embodiment, the group E of the formula (I) is chosen from: —CO—O— and —CO—NH—, it being understood that the group E is connected to the vinyl carbon by the carbon atom.
According to this same implementational third, the group E of the formula (I) is preferably the —CO—O— group, it being understood that the —CO—O— group is connected to the vinyl carbon by the carbon atom.
According to a preferred embodiment, the unit of formula (I) is such that u=1, and the group E is a —CO—O— group, E being connected to the vinyl carbon by the carbon atom.
The group (G) of the formula (I) can be a C1 to C34 alkyl group, preferably a C4 to C34, preferably C4 to C30, more preferentially C6 to C24, more preferentially still C8 to C18 alkyl radical. The alkyl radical is a linear or branched, cyclic or acyclic, preferably acyclic, radical. This alkyl radical can comprise a linear or branched part and a cyclic part.
The group (G) of the formula (I) is advantageously an acyclic C1 to C34 alkyl, preferably a linear or branched, preferably branched, C4 to C34, preferably C4 to C30, more preferentially C6 to C24, more preferentially still C8 to C18 alkyl radical.
Mention may be made, without limitation, of alkyl groups, such as butyl, octyl, decyl, dodecyl, 2-ethylhexyl, isooctyl, isodecyl and isododecyl.
The group (G) of the formula (I) can also be an aromatic nucleus, preferably a phenyl or aryl group. Mention may be made, among aromatic groups, without limitation, of the phenyl or naphthyl group, preferably the phenyl group.
The group (G) of the formula (I) can, according to another preferred alternative form, be an aralkyl comprising at least one aromatic nucleus and at least one C1 to C34 alkyl group. Preferably, according to this alternative form, the group (G) is an aralkyl comprising at least one aromatic nucleus and one or more C4 to C34, preferably C4 to C30, more preferentially C6 to C24, more preferentially still C8 to C18 alkyl groups.
The aromatic nucleus can be monosubstituted or be substituted on several of its carbon atoms. Preferably, the aromatic nucleus is monosubstituted.
The C1 to C34 alkyl group can be in the ortho, meta or para position on the aromatic nucleus, preferably in the para position.
The alkyl radical is a linear or branched, cyclic or acyclic, preferably acyclic, radical.
The alkyl radical is preferably a linear or branched, preferably branched, acyclic radical.
The aromatic nucleus can be directly connected to the group E or to the vinyl carbon but it can also be connected to it via an alkyl substituent.
Mention may be made, by way of example of group G, of a benzyl group substituted in the para position by a C4 to C34, preferably C4 to C30, alkyl group.
Preferably, according to this alternative form, the group (G) of the formula (I) is an aralkyl comprising at least one aromatic nucleus and at least one C4 to C34, preferably C4 to C 30, more preferentially C6 to C24, more preferentially still C8 to C18 alkyl group.
According to a specific embodiment, the group Q of the formula (II) is the oxygen atom.
According to a first alternative form, the amino group present in the group R of the formula (II) is chosen from the groups having at least one amine, imine, amidine, guanidine, aminoguanidine or biguanidine functional group, such as alkylamines, polyalkylenepolyamines, polyalkylenimines, alkylimines, alkylamidines, alkylguanidines and alkylbiguanidines, it being possible for the alkyl substituent to be linear or branched, cyclic or acyclic, and preferably having from 1 to 34 carbon atoms, more preferentially from 1 to 12 carbon atoms, and the quaternized forms of these groups.
According to a second alternative form, the amino group present in the group R of the formula (II) is chosen from monocyclic or polycyclic heterocyclic groups, having from 3 to 34 atoms, preferably from 5 to 12 atoms, more preferentially from 6 to 10 atoms, and at least one nitrogen atom, it being understood that the polycyclic heterocyclic groups have, optionally, fused rings. The number of atoms includes the heteroatoms. Fused rings is understood to mean rings having at least two atoms in common. The heterocyclic groups can additionally comprise an oxygen atom and/or a carbonyl group and/or one or more unsaturations.
Mention may be made, as example of a heterocyclic amino group, of the following radicals: triazole, aminotriazole, pyrrolidone, piperidine, imidazole, morpholine, isoxazole, oxazole, indole and the quaternized forms of these radicals, said radical preferably being connected to the hydrocarbon chain by a nitrogen atom.
According to a preferred embodiment, the group R of the formula (II) is represented:

- when v has the value 1, by the following formula (V):

L-R′₂ (V)

- when v has the value 0, by one of the following formulae (V) and (V):

L-R′₂ (V)
L- (V)

- in which formulae (V) and (V′):
- R₂′ is chosen from cyclic or acyclic, linear or branched, C₁to C₃₄, preferably C₁to C₁₈, more preferentially C₁to C₈, more preferentially still C₂to C₄hydrocarbon chains, optionally substituted by at least one hydroxyl group; preferably, R₂′ is chosen from alkyl groups, optionally substituted by at least one hydroxyl group, and
- L is chosen from the group consisting of:
  - the following groups:
    - amine: —NH2; —NHR_a, —NR_aR_b;
    - imine: —HC═NH; —HC═NR_a; —N═CH₂, —N═CR_aH; —N═CR_aR_b;
    - amidine: —(C═NH)—NH₂; —(C═NH)—NR_aH; —(C═NH)—NR_aR_b; —(C═NR_a)—NH₂; —(C═NR_a)—NR_bH; —(C═NR_a)—NR_bR_c; —N═CH(NH₂); —N═CR_a(NH₂); —N═CH(NR_aH); —N═CR_a(NR_aH); —N═CH(NR_aR_b); —N═CR_a(NR_bR_c);
    - guanidine: —NH—(C═NH)—NH₂; —NH—(C═NH)—NHR_a; —N═C(NH₂)₂; —N═C(NR_aH)₂; —N═C(NR_aR_b)₂; —N═C(NR_aH)(NR_bH);
    - aminoguanidine: —NH—(C═NH)—NH—NH₂; —NH—(C═NH)—NH—NHR_a; —N═C(NH₂)(NH—NH₂); —N═C(NR_aH)(NH—NH₂); —N═C(NR_aH)(NR—NH₂); —N═C(NR_aR_b)(NH—NH₂); —N═C(NR_aR_b)(NR_a—NH₂);
    - biguanidine: —NH—(C═NH)—NH—(C═NH)—NH₂; —NH—(C═NH)—NH—(C═NH)—NHR_a; —N═C(NH₂)—NH—(C═NH)—NH₂; —N═C(NH₂)—NH—(C═NR_a)—NH₂; —N═C(NH₂)—NH—(C═NH)—NR_aH; —N═C(NH₂)—NH—(C═NR_a)—NR_bH; —N═C(NH₂)—NH—(C═NH)—NR_aR_b; —N═C(NH₂)—NH—(C═NR_a)—NR_bR_c; —N═C(NR_aH)—NH—(C═NH)—NH₂; —N═C(NR_aH)—NH—(C═NR_b)—NH₂; —N═C(NR_aH)—NH—(C═NH)—NR_bH; —N═C(NR_aH)—NH—(C═NR_b)—NR_cH; —N═C(NR_aH)—NH—(C═NH)—NR_bR_c; —N═C(NR_aH)—NH—(C═NR_b)—NR_cR_d; —N═C(NR_aR_b)—NH—(C═NH)—NH₂; —N═C(NR_aR_b)—NH—(C═NR_c)—NH₂; —N═C(NR_aR_b)—NH—(C═NH)—NR_cH; —N═C(NR_aR_b)—NH—(C═NR_c)—NR_dH; —N═C(NR_aR_b)—NH—(C═NH)—NR_cR_d; —N═C(NR_aR_b)—NH—(C═NR_c)—NR_dR_e;
    - the quaternized forms of the above groups, when these contain at least one quaternizable nitrogen atom; and
  - polyamine and polyalkylenepolyamine groups, in particular those of formulae —NH—(R_f—NH)_k—H; —NH—(R_f—NH)_k—R_a;
  - with R_a, R_b, R_c, R_dand R_erepresenting, independently of one another, a C₁-C₃₄, preferably C₁-C₁₂, alkyl group, optionally comprising one or more NH₂functional groups and one or more —NH— bridges;
  - R_frepresenting a C₁-C₆, preferably C₂-C₄, alkyl group; k represents an integer ranging from 1 to 20, preferably from 2 to 12.

Mention may be made, as example of polyamine and polyalkylenepolyamine groups, of: ethylenediamine, diethylenetriamine, triethylenetetramine or tetraethylenepentamine.
According to a specific embodiment, the R2′ group is chosen from linear or branched acyclic C1 to C34, preferably C1 to C18, more preferentially C1 to C8, more preferentially still C2 to C4 alkyl groups, which can be substituted by at least one hydroxyl group.
According to a preferred embodiment, the group R of the formula (II) comprising at least one amino group comprising a primary, secondary or tertiary amine functional group is represented by the formula (V) in which L is chosen from the groups: —NH2, —NHRa, —NRaRb, with Ra and Rb as defined above, and more preferably from the tertiary amine groups —NRaRb.
According to a preferred embodiment, the group R comprising at least one quaternary ammonium functional group is represented by one of the following formulas (III) and (IV):

- in which:
- X⁻ is chosen from hydroxide or halide ions and organic anions, in particular the acetate ion,
- R₂is chosen from cyclic or acyclic, linear or branched, C₁to C₃₄, preferably C₁to C₁₈, more preferentially C₁to C₈, more preferentially still C₂to C₄hydrocarbon chains, optionally substituted by at least one hydroxyl group; preferably, R₂′ is chosen from alkyl groups, optionally substituted by at least one hydroxyl group,
- R₃, R₄and R₅are identical or different and are chosen independently from linear or branched, cyclic or acyclic, C₁to C₁₈, preferably C₁to C₁₂, hydrocarbon chains, it being understood that the R₃, R₄and R₅alkyl groups can contain one or more nitrogen and/or oxygen atoms and/or carbonyl groups and can be connected together in pairs to form one or more rings,
- R₆and R₇are identical or different and are chosen independently from linear or branched, cyclic or acyclic, C₁to C₁₈, preferably C₁to C₁₂, hydrocarbon chains, it being understood that the R₆and R₇groups can contain one or more nitrogen and/or oxygen atoms and/or carbonyl groups and can be connected together to form a ring.

The nitrogen and/or oxygen atom(s) can be present in the R₃, R₄and R₅groups in the form of ether bridges or amine bridges or in the form of an amine or hydroxyl substituent.
The organic anions of the X− group are advantageously conjugate bases of organic acids, preferably conjugate bases of carboxylic acids, in particular acids chosen from cyclic or acyclic monocarboxylic or polycarboxylic acids. Preferably, the organic anions of the X− group are chosen from conjugate bases of saturated acyclic or aromatic cyclic carboxylic acids. Mention will be made, by way of example, of methanoic acid, acetic acid, adipic acid, oxalic acid, malonic acid, succinic acid, citric acid, benzoic acid, phthalic acid, isophthalic acid and terephthalic acid.
According to a specific embodiment, the R2 group is chosen from linear or branched acyclic C1 to C34, preferably C1 to C18, more preferentially C1 to C8, more preferentially still C2 to C4 alkyl groups, substituted by at least one hydroxyl group.
Advantageously, the group R comprising at least one quaternary ammonium functional group is represented by the formula (III), in which:

- X− is chosen from organic anions, preferably conjugate bases of carboxylic acids,
- R2 is chosen from C1 to C34 hydrocarbon chains, preferably C1 to C18 alkyl groups,
- R3, R4 and R5 are identical or different and are chosen independently from 01 to C18 hydrocarbon chains, optionally substituted by at least one hydroxyl group, it being understood that at least one of the R3, R4 and R5 groups contains one or more hydroxyl group(s).

According to a preferred embodiment, the copolymer used in the present invention contains units of formula (II) in which the group R contains at least one quaternary ammonium functional group.
The preferred groups R containing a quaternary ammonium functional group are those described above.
According to a particularly preferred embodiment, from 5 mol % to 95 mol % of the units of formula (II) of the copolymer comprise, in the group R, at least one quaternary ammonium functional group.
In this embodiment, the proportion in moles of the units of formula (II) in which the group R comprises at least one quaternary ammonium functional group, also referred to below as degree of quaternization of the units of formula (II), advantageously represents from 10% to 90%, more preferentially from 20% to 80% and more preferentially still from 40% to 60%, with respect to the total molar amount of units of formula (II) in the copolymer.
According to a very particularly preferred embodiment, the degree of quaternization of the units of formula (II) ranges from 45% to 55%, with respect to the total molar amount of units of formula (II).
In this embodiment, the units of formula (II) in which the group R does not comprise a quaternary ammonium functional group comprise at least one amino group comprising a primary, secondary or tertiary amine functional group. The preferred groups R containing a primary, secondary or tertiary amine functional group are those described above.
These units represent from 5 mol % to 95 mol % of the total molar amount of the units of formula (II) of the copolymer according to the invention, preferably from 10 mol % to 90 mol %, more preferentially from 20 mol % to 80 mol %, more preferentially still from 40 mol % to 60 mol % and better still from 45 mol % to 55 mol %.
In this embodiment, the quaternary ammonium functional groups of the group R of the formula (II) can advantageously be obtained by partial quaternization of one of the groups of formulae (V) and (V′) above, these containing at least one quaternizable nitrogen atom.
The quaternary ammonium functional groups can in particular be obtained by partial quaternization of at least one amine, imine, amidine, guanidine, aminoguanidine or biguanidine functional group; or else of a heterocyclic group having from 3 to 34 atoms and at least one nitrogen atom.
Particularly preferably, the quaternary ammonium functional groups of the group R are obtained by partial quaternization of tertiary amine functional groups.
According to a specific embodiment, the unit of formula (I) of the copolymer employed in the invention is obtained from a nonpolar monomer (ma).
Preferably, the nonpolar monomer (ma) corresponds to the following formula (VII):

- in which:
- R₁′, E, G and u are as defined above; the preferred alternative forms of R₁′, E, G and u according to the formula (I) as are defined above are also preferred alternative forms of the formula (VII).

Advantageously, the R1′ group is a hydrogen atom.
When the group E of the nonpolar monomer (ma) is the —O—CO— group, it being understood that the —O—CO— group is connected to the vinyl carbon by the oxygen atom, the monomer (ma) is preferably chosen from vinyl C1 to C34, preferably C4 to C30, more preferentially C6 to C24, more preferentially C8 to C22 alkyl esters. The alkyl radical of the vinyl alkyl ester is linear or branched, cyclic or acyclic, preferably acyclic.
Mention may be made, among the vinyl alkyl ester monomers, for example, of vinyl octanoate, vinyl decanoate, vinyl dodecanoate, vinyl tetradecanoate, vinyl hexadecanoate, vinyl octadecanoate, vinyl docosanoate or vinyl 2-ethylhexanoate.
When the group E of the nonpolar monomer (ma) is the —CO—O— group, it being understood that the —CO—O— group is connected to the vinyl carbon by the carbon atom, the monomer (ma) is preferably chosen from C1 to C34, preferably C4 to C30, more preferentially C6 to C24, more preferentially C8 to C22 alkyl acrylates or methacrylates. The alkyl radical of the acrylate or methacrylate is linear or branched, cyclic or acyclic, preferably acyclic.
Mention may be made, among the alkyl (meth)acrylates capable of being used, without limitation, of: n-octyl acrylate, n-octyl methacrylate, n-decyl acrylate, n-decyl methacrylate, n-dodecyl acrylate, n-dodecyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isooctyl acrylate, isooctyl methacrylate, isodecyl acrylate or isodecyl methacrylate.
According to a specific embodiment, the unit of formula (II) of the copolymer employed in the present invention is obtained from polar monomers (mb) chosen from those of formula (VIII):

- in which:
- R₁″, v, Q and R are as defined above; the preferred alternative forms of R₁″, Q and R according to the formula (II) as are defined above are also preferred alternative forms of the formula (VIII).

According to a first alternative form of this embodiment, from 5 mol % to 95 mol % of the polar monomers (mb) comprise a group R containing at least one quaternary ammonium functional group.
In this alternative form, preferably from 5 mol % to 95 mol % of the polar monomers (mb) comprise a quaternary ammonium functional group and are represented by at least one of the following formulae (IX) and (IX′):

- and from 5 mol % to 95 mol % of the polar monomers (m_b) do not comprise a quaternary ammonium functional group and are represented by the following formula (X):

- in which formulae (IX), (IX′) and (X):
- R₁″, v and Q are as defined above; the preferred alternative forms of R₁″ and Q according to formula (II) as defined above are also preferred alternative forms of the formulae (IX), (IX′) and (X);
- X⁻, R₂, R₃, R₄, R₅, R₆and R₇are as defined above; the preferred alternative forms of X⁻,
- R₂, R₃, R₄, R₅, R₆and R₇according to the formulae (III) and (IV) as defined above are also preferred alternative forms of the formulae (IX) and (IX′).
- R′₂and L are as defined above; the preferred alternative forms of R′2 and L according to the formula (V) are also preferred alternative forms of the formula (X).

According to a specific embodiment, the unit of formula (II) of the copolymer employed in the present invention is obtained from polar monomers (m_b) chosen from those of formula (VIII):

- in which:
- R₁″, v and Q are as defined above, the preferred alternative forms of R₁″ and Q according to the formula (II) as are defined above are also preferred alternative forms of the formula (VIII), and
- R represents a C₁to C₃₄hydrocarbon chain which can also contain one or more nitrogen and/or oxygen atoms and/or carbonyl groups, which is substituted by at least one amino group comprising a primary, secondary or tertiary amine functional group, and optionally one or more hydroxyl groups,
- the copolymerization of the monomer (m_b) being followed by a partial quaternization of the quaternizable amino groups, for 5 mol % to 95 mol % of the units resulting from said monomer (m_b).

This embodiment is preferred.
According to a specific embodiment, the copolymer can be obtained by copolymerization of at least one nonpolar monomer (ma) and at least one polar monomer (mb) as are described above.
According to a specific preferred embodiment, the copolymer is obtained solely from nonpolar monomers (ma) and polar monomers (mb).
The copolymer can be prepared according to any known polymerization process. The various polymerization techniques and conditions are widely described in the literature and fall within the general knowledge of a person skilled in the art.
According to a specific embodiment, the copolymer is a block copolymer comprising at least one block A and at least one block B.
The block A corresponds to the following formula (XI):

- in which:
- p is an integer ranging from 2 to 100, preferably from 5 to 80, preferably from 10 to 70, more preferentially from 20 to 60,
- R₁′, E, G and u are as defined above; the preferred alternative forms of R₁′, E, G and u according to the formula (I) as are defined above are also preferred alternative forms of the formula (XI).

The block B corresponds to the following formula (XII):

- in which:
- v=0 or 1,
- n is an integer ranging from 2 to 50, preferably from 3 to 40, more preferentially from 4 to 20, more preferentially still from 5 to 10,
- R₁″, Q and R are as defined above; the preferred alternative forms of R₁″, Q and R according to the formula (II) as are defined above are also preferred alternative forms of the formula (XII).

According to a preferred embodiment, from 5 mol % to 95 mol % of the units of the block B comprise a group R containing at least one quaternary ammonium functional group.
In this embodiment, the block B preferably comprises:

- from 5 mol % to 95 mol % of units comprising a quaternary ammonium functional group and corresponding to at least one of the following formulae (XIII) and (XIII′):

- and from 5 mol % to 95 mol % of units not comprising a quaternary ammonium functional group and corresponding to the following formula (XIV):

- in which formulae (XIII), (XIII′) and (XIV):
- Q, R₁″, n and v are as described above; the preferred alternative forms of Q and R₁″ according to the formula (II) as defined above are also preferred alternative forms of the formulae (XIII), (XIII′) and (XIV),
- X⁻, R₂, R₃, R₄, R₅, R₆and R₇are as defined above; the preferred alternative forms of X⁻,
- R₂, R₃, R₄, R₅, R₆and R₇according to the formulae (III) and (IV) as defined above are also preferred alternative forms of the formulae (XIII) and (XIII′),
- R′₂and L are as defined above; the preferred alternative forms of R′₂and L according to the formula (V) are also preferred alternative forms of the formula (XIV).

The amino groups of the block B comprising quaternary ammonium functional groups are advantageously chosen from trialkylammonium, iminium, amidinium, formamidinium, guanidinium and biguanidinium quaternary ammoniums, preferably trialkylammonium quaternary ammoniums.
The amino groups of the block B comprising quaternary ammonium functional groups can also be chosen from heterocyclic compounds containing at least one nitrogen atom, in particular chosen from pyrrolinium, pyridinium, imidazolium, triazolium, triazinium, oxazolium and isoxazolium quaternary ammoniums.
The amino groups of the block B comprising quaternary ammonium functional groups are particularly preferably trialkylammonium quaternary groups.
According to a preferred alternative form, at least one of the alkyl groups of the quaternary ammonium of the block B is substituted by a hydroxyl group.
According to a particularly preferred embodiment, the block B comprises from 5 mol % to 95 mol % of units corresponding to the formula (XIII):

- in which:
- R₁″ is chosen from the hydrogen atom and the methyl group,
- Q is chosen from the oxygen atom and the —NR′— group, with R′ being chosen from a hydrogen atom and C₁to C₁₂hydrocarbon chains,
- X⁻ is chosen from organic anions, preferably conjugate bases of carboxylic acids,
- R₂is chosen from C₁to C₃₄hydrocarbon chains, preferably C₁to C₁₈alkyl groups,
- R₃, R₄and R₅are identical or different and are chosen independently from C₁to C₁₈hydrocarbon chains, optionally substituted by at least one hydroxyl group, it being understood that at least one of the R₃, R₄and R₅groups contains at least one hydroxyl group.

The distribution within the block B of the units, the group R of which comprises at least one quaternary ammonium functional group, with respect to the other units of the block B, can be of any type, and in particular random, statistical or block. Preferably, this distribution is of random type.
According to a specific embodiment, the block A consists of a chain of structural units derived from at least one monomer (ma) as described above.
According to a specific embodiment, the block B consists of a chain of structural units derived from monomers (mb) as described above.
According to a specific embodiment, the block A consists of a chain of structural units derived from an alkyl acrylate or alkyl methacrylate monomer (ma) and the block B corresponds to the formula (XII) described above.
According to a specific embodiment, the block copolymer is obtained by copolymerization of at least the alkyl (meth)acrylate monomer (ma) and at least the monomer(s) (mb) described above.
It is understood that it would not be departing from the invention if the copolymer (a) according to the invention were obtained from monomers other than (ma) and (mb), insofar as the final copolymer corresponds to that of the invention, that is to say comprises units of formula (I) and units of formula (II) as are described above. For example, it would not be departing from the invention if the copolymer were obtained by copolymerization of monomers other than (ma) and (mb), followed by a postfunctionalization.
For example, the blocks deriving from a nonpolar monomer (ma) can be obtained from vinyl alcohol or acrylic acid, respectively by transesterification or amidation reaction.
For example, the quaternary ammonium units of the block B can be obtained by postfunctionalization of the intermediate units (Mi) resulting from the polymerization of an intermediate (meth)acrylate or (meth)acrylamide monomer (m_i), of formulae:

- with
- Q and R₁″ are as described above,
- R₈is chosen from C₁to C₃₂hydrocarbon chains,
- R₉is chosen from hydrogen and C₁to C₆alkyl groups,
- said postfunctionalization corresponding to the reaction of said intermediate unit (M_i) with a tertiary amine NR₃R₄R₅or R₆N═R₇where R₃, R₄, R₅, R₆and R₇are as defined above in the formulae (Ill) and (IV).

The copolymer according to the invention can also be obtained by postfunctionalization of an intermediate block polymer, comprising at least one intermediate block containing units (Mi) and at least one block A as described above.
According to a particularly preferred embodiment, the block B of formula (XII) is obtained by quaternization, according to any known method, of from 5 mol % to 95 mol % of the units of an intermediate block Bi comprising a single unit of formula (XII) in which the groups R contain a tertiary amine group of formula NR3R4R5 or R6N═R7 in which R3, R4, R5, R6 and R7 are as defined above.
The quaternization stage can be carried out before the copolymerization reaction, on an intermediate monomer carrying the tertiary amine, for example by reaction with an alkyl halide or an epoxide (oxirane) according to any known process, optionally followed by a anion-exchange reaction.
The quaternization stage can also be carried out by postfunctionalization of an intermediate polymer carrying the tertiary amine, for example, by reaction with an alkyl halide, optionally followed by an anion-exchange reaction. Mention may be made, by way of example of quaternization, of a postfunctionalization reaction of an intermediate polymer carrying the tertiary amine, by reaction with an epoxide (oxirane) according to any known process.
It is preferred to copolymerize intermediate monomers carrying a tertiary amine functional group and then, in a second stage, to functionalize the intermediate copolymer obtained by quaternization of the tertiary amine present in the intermediate copolymer, rather than to copolymerize monomers which are already quaternized.
In addition, it will be preferable to carry out the quaternization involving an epoxide.
The block copolymer can be obtained by block polymerization, preferably by controlled block polymerization, optionally followed by one or more postfunctionalizations.
According to a specific embodiment, the block copolymer described above is obtained by controlled block polymerization. The polymerization is advantageously chosen from controlled radical polymerization; for example atom transfer radical polymerization (ATRP); nitroxide-mediated radical polymerization (NMP); degenerative transfer processes, such as degenerative iodine transfer polymerization (ITRP: iodine transfer radical polymerization) or reversible addition-fragmentation chain-transfer radical polymerization (RAFT: reversible addition-fragmentation chain transfer); polymerizations derived from ATRP, such as polymerizations using initiators for continuous activator regeneration (ICAR) or using activators regenerated by electron transfer (ARGET).
Mention will be made, by way of example, of the publication “Macromolecular engineering by atom transfer radical polymerization”, JACS, 136, 6513-6533 (2014), which describes a controlled block polymerization process for forming block copolymers.
Mention may be made, by way of example, for NMP, of the identification by C. J. Hawker of an alkoxyamine capable of acting as a unimolecular agent, providing both the reactive initiating radical and the intermediate nitroxide radical in stable form (C. J. Hawker, J. Am. Chem. Soc., 1994, 116, 11185). Hawker has also developed a universal NMP initiator (D. Benoit et al., J. Am. Chem. Soc., 1999, 121, 3904).
Reversible addition-fragmentation chain transfer (RAFT) radical polymerization is a living radical polymerization technique. The RAFT technique was discovered in 1998 par by the Australian scientific research organization CSIRO (J. Chiefari et al., Macromolecules, 1998, 31, 5559). The RAFT technique very rapidly became the subject of intensive research studies by the scientific community since it makes possible the synthesis of macromolecules exhibiting complex architectures, in particular block, grafted, comb or else star-branched structures, while making it possible to control the molecular weight of the macromolecules obtained (G. Moad et al., Aust. J. Chem., 2005, 58, 379). RAFT polymerization can be applied to a very wide range of vinyl monomers and under various experimental conditions, including in the preparation of water-soluble materials (C. L. McCormick et al., Acc. Chem. Res., 2004, 37, 312). The RAFT process includes the conventional radical polymerization of a substituted monomer in the presence of a suitable chain-transfer agent (CTA or RAFT agent). The RAFT agents commonly used comprise thiocarbonylthio compounds, such as dithioesters (J. Chiefari et al., Macromolecules, 1998, 31, 5559), dithiocarbamates (R. T. A. Mayadunne et al., Macromolecules, 1999, 32, 6977; M. Destarac et al., Macromol. Rapid. Commun., 2000, 21, 1035), trithiocarbonates (R. T. A. Mayadunne et al., Macromolecules, 2000, 33, 243) and xanthates (R. Francis et al., Macromolecules, 2000, 33, 4699), which perform the polymerization by a reversible chain-transfer process. The use of a suitable RAFT agent makes possible the synthesis of polymers exhibiting a high degree of functionality and exhibiting a narrow molecular weight distribution, that is to say a low polydispersity index (PDI).
Mention may be made, by way of example of description of RAFT radical polymerization, of the following documents: WO 1998/01478, WO 1999/31144, WO 2001/77198, WO 2005/00319 and WO 2005/000924.
The controlled block polymerization is typically carried out in a solvent, under an inert atmosphere, at a reaction temperature generally ranging from 0° C. to 200° C., preferably from 50° C. to 130° C. The solvent can be chosen from polar solvents, in particular ethers, such as anisole (methoxybenzene) or tetrahydrofuran, or nonpolar solvents, in particular paraffins, cycloparaffins, aromatics and alkylaromatics having from 1 to 19 carbon atoms, for example benzene, toluene, cyclohexane, methylcyclohexane, n-butene, n-hexane, n-heptane and the like.
For the atom transfer radical polymerization (ATRP), the reaction is generally carried out under vacuum in the presence of an initiator, of a ligand and of a catalyst. Mention may be made, by way of example of ligand, of N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA), 1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA), 2,2′-bipyridine (BPY) and tris(2-pyridylmethyl)amine (TPMA). Mention may be made, by way of example of catalyst, of: CuX, CuX2, with X=Cl or Br, and complexes based on ruthenium Ru2+/Ru3+.
The ATRP polymerization is preferably carried out in a solvent chosen from polar solvents.
According to the controlled block polymerization technique, it can also be envisaged to work under pressure.
The numbers of equivalents of nonpolar monomer (ma) of the block A and of polar monomer (mb) of the block B reacted during the polymerization reaction can be identical or different.
“Number of equivalents” is understood to mean the amounts (in moles) of material of the monomers (ma) of the block A and of the monomers (mb) of the block B employed during the polymerization reaction.
The number of equivalents of nonpolar monomer (ma) of the block A is preferably from 2 to 100 eq, preferably from 5 to 80 eq, preferably from 10 to 70 eq and more preferentially from 20 to 60 eq.
The number of equivalents of polar monomers (mb) of the block B is preferably from 2 to 50 eq, preferably from 3 to 40 eq, more preferentially from 4 to 20 eq and more preferentially still from 5 to 10 eq.
The number of equivalents of monomer (ma) of the block A is advantageously greater than or equal to that of the monomers (mb) of the block B.
Preferably, when the group E of the nonpolar monomer (ma) is a —CO—O— group, E being connected to the vinyl carbon by the carbon atom, the number of equivalents of monomer (ma) of the block A is between 20 and 60 moles, and G is chosen from C4 to C30 hydrocarbon chains.
More preferentially still, when the group E of the nonpolar monomer (ma) is a —CO—O— group, E being connected to the vinyl carbon by the carbon atom, the number of equivalents of monomer (ma) of the block A is between 20 and 60 moles, and G is chosen from C4 to C30 hydrocarbon chains, and the copolymer has a number-average molecular weight (Mn) ranging from 1000 and 10 000 g·mol-1.
In addition, the weight-average molar mass Mw of the block A or of the block B is preferably less than or equal to 15 000 g·mol.-1, more preferentially less than or equal to 10 000 g·mol.-1.
The block copolymer advantageously comprises at least one sequence of blocks AB, ABA or BAB where said blocks A and B are linked together without the presence of an intermediate block of different chemical nature.
Other blocks can optionally be present in the block copolymer described above insofar as these blocks do not fundamentally change the nature of the block copolymer. Nevertheless, block copolymers containing only blocks A and B will be preferred.
Advantageously, the blocks A and B represent at least 70% by weight, preferably at least 90% by weight, more preferentially at least 95% by weight, more preferentially still at least 99% by weight of the block copolymer.
According to a specific embodiment, the block copolymer is a diblock copolymer.
According to another specific embodiment, the block copolymer is a triblock copolymer having alternating blocks comprising two blocks A and one block B (ABA) or comprising two blocks B and one block A (BAB).
According to a specific embodiment, the block copolymer also comprises an end chain I consisting of a cyclic or acyclic, saturated or unsaturated, linear or branched, C1 to C32, preferably C4 to C24, more preferentially C10 to C24 hydrocarbon chain.
Cyclic hydrocarbon chain is understood to mean a hydrocarbon chain, at least a part of which is cyclic, in particular aromatic. This definition does not exclude hydrocarbon chains comprising both an acyclic part and a cyclic part.
The end chain I can comprise an aromatic hydrocarbon chain, for example a benzene chain, and/or a saturated and acyclic, linear or branched, hydrocarbon chain, in particular an alkyl chain.
The end chain I is preferably chosen from alkyl chains, preferably linear alkyl chains, more preferentially alkyl chains of at least 4 carbon atoms, more preferentially still of at least 12 carbon atoms.
For the ATRP polymerization, the end chain I is located in the end position of the block copolymer. It can be introduced into the block copolymer by virtue of the polymerization initiator. Thus, the end chain I can advantageously constitute at least a part of the polymerization initiator and is positioned within the polymerization initiator in order to make it possible to introduce, during the first stage of initiation of the polymerization, the end chain I in the end position of the block copolymer.
The polymerization initiator is, for example, chosen from the free-radical initiators employed in the ATRP polymerization process. These free-radical initiators well known to a person skilled in the art are in particular described in the paper “Atom transfer radical polymerization: current status and future perspectives”, Macromolecules, 45, 4015-4039, 2012.
The polymerization initiator is, for example, chosen from carboxylic acid alkyl esters substituted by a halide, preferably a bromine in the alpha position, for example ethyl 2-bromopropionate, ethyl α-bromoisobutyrate, benzyl chloride or bromide, ethyl α-bromophenylacetate and chloroethylbenzene. Thus, for example, ethyl 2-bromopropionate can make it possible to introduce into the copolymer the end chain I in the form of a C2 alkyl chain and benzyl bromide in the form of a benzyl group.
For the RAFT polymerization, the transfer agent can conventionally be removed from the copolymer at the end of polymerization according to any known process.
According to an alternative form, the end chain I can also be obtained in the copolymer by RAFT polymerization according to the methods described in the paper by Moad, G. et al., Australian Journal of Chemistry, 2012, 65, 985-1076. For example, the end chain I can, for example, be modified by aminolysis when a transfer agent is used in order to give a thiol functional group. Mention may be made, by way of example, of transfer agents of thiocarbonylthio, dithiocarbonate, xanthate, dithiocarbamate and trithiocarbonate type, for example S,S0-dibenzyl trithiocarbonate (DBTTC), S,S-bis(α,α′-dimethyl-α″-acetic acid) trithiocarbonate (BDMAT) or 2-cyano-2-propyl benzodithioate (CPD).
According to a known process, the transfer agent can be cleaved at the end of polymerization by reacting a cleaving agent, such as C2-C6 alkylamines; the end functional group of the copolymer can in this case be a thiol —SH group.
According to another process described in the patent EP 1 751 194, the sulfur of the copolymer obtained by RAFT polymerization introduced by the sulfur-based transfer agent, such as thiocarbonylthio, dithiocarbonate, xanthate, dithiocarbamate and trithiocarbonate, can be converted in order to remove the sulfur from the copolymer.
According to a specific embodiment, the block copolymer is a diblock copolymer. The block copolymer structure can be of the IAB or IBA type, advantageously IAB type. The end chain I can be directly connected to the block A or B according to the structure IAB or IBA respectively or can be connected via a bonding group, for example an ester, amide, amine or ether functional group. The bonding group then forms a bridge between the end chain I and the block A or B.
According to a specific embodiment, the block copolymer can also be functionalized at the chain end according to any known process, in particular by hydrolysis, aminolysis and/or nucleophilic substitution.
Aminolysis is understood to mean any chemical reaction in which a molecule is split into two parts by reaction of a molecule of ammonia or of an amine. A general example of aminolysis consists in replacing a halogen of an alkyl group by reaction with an amine, with elimination of hydrogen halide. Aminolysis can be used, for example, for an ATRP polymerization which produces a copolymer having a halide in the end position or for a RAFT polymerization in order to convert the thio, dithio or trithio bond introduced into the copolymer by the RAFT transfer agent into a thiol functional group.
An end chain I′ can thus be introduced by postfunctionalization of the block copolymer obtained by controlled block polymerization of the monomers ma and mb described above.
The end chain I′ advantageously comprises a linear or branched, cyclic or acyclic, C1 to C32, preferably C1 to C24, more preferentially C1 to C10 hydrocarbon chain, more preferentially still an alkyl group, optionally substituted by one or more groups containing at least one heteroatom chosen from N and O, preferably N.
For an ATRP polymerization using a metal halide as catalyst, this functionalization can, for example, be carried out by treating the copolymer IAB or IBA obtained by ATRP with a primary C1 to C32 alkylamine or a C1 to C32 alcohol under mild conditions in order not to modify the functional groups present on the blocks A, B and I.
Use
The present invention consists in using the copolymers described above in order to prevent the deposits which form at low temperature on the fuel intake valves in indirect injection spark ignition engines.
To this end, the copolymer is incorporated in a liquid fuel for a spark ignition engine and in particular a fuel chosen from gasolines.
The copolymer(s) according to the invention is (are) used in the fuel composition in a total content of at least 5 ppm by weight, preferably of at least 10 ppm, more preferentially at a content of 10 to 5000 ppm, more preferentially still of 20 to 2000 ppm and better still of 50 to 1000 ppm.
In particular, the use of the copolymers according to the invention is targeted at keeping the valves clean, by preventing the valves from sticking at low temperature.
The liquid fuel advantageously results from one or more sources chosen from the group consisting of mineral, animal, plant and synthetic sources. Oil will preferably be chosen as mineral source.
The liquid fuel is preferably chosen from hydrocarbon fuels and fuels which are not essentially hydrocarbon fuels, alone or as a mixture.
Hydrocarbon fuel is understood to mean a fuel formed of one or more compounds consisting solely of carbon and hydrogen.
Fuel which is not essentially hydrocarbon fuel is understood to mean a fuel formed of one or more compounds which are not essentially formed of carbon and hydrogen, that is to say which also contain other atoms, in particular oxygen atoms.
Hydrocarbon fuels comprise in particular light distillates having a boiling point in the range of the gasolines. These distillates can, for example, be chosen from the distillates obtained by direct distillation of crude hydrocarbons, vacuum distillates, hydrotreated distillates, distillates resulting from the catalytic cracking and/or from the hydrocracking of vacuum distillates, distillates resulting from conversion processes of ARDS (atmospheric residue desulfurization) and/or visbreaking type, or distillates resulting from the upgrading of Fischer-Tropsch fractions.
In other words, the hydrocarbon fuel is chosen from gasolines.
Gasolines in particular comprise any commercially available fuel composition for a spark ignition engine. Mention may be made, by way of representative example, of the gasolines corresponding to the standard NF EN 228. Gasolines generally have octane numbers which are sufficiently high to prevent the phenomenon of knocking. Typically, the fuels of gasoline type sold in Europe, in accordance with the standard NF EN 228, have a motor octane number (MON) of greater than 85 and a research octane number (RON) of a minimum of 95. Fuels of gasoline type generally have an RON ranging from 90 to 100 and an MON ranging from 80 to 90, the RON and MON values being measured according to the standard ASTM D 2699-86 or D 2700-86.
Fuels which are not essentially hydrocarbon fuels comprise in particular oxygen-based compounds, for example distillates resulting from the BTL (biomass to liquid) conversion of plant and/or animal biomass, taken alone or in combination; biofuels, for example plant and/or animal oils and/or ester oils; biodiesels of animal and/or plant origin and bioethanols.
The mixtures of hydrocarbon fuel and of fuel which is not essentially hydrocarbon fuel are typically gasolines of Ex type.
Gasoline of Ex type for a spark ignition engine is understood to mean a gasoline fuel which contains x % (v/v) of oxygen-based compounds, generally ethanol, bioethanol and/or ethyl tert-butyl ether (ETBE).
The sulfur content of the liquid fuel is preferably less than or equal to 50 ppm, indeed even less than 10 ppm and advantageously sulfur-free.
The use of the copolymer(s) as described above as additives in the liquid fuel exhibits the advantage of preventing the phenomena of valve sticking.
The level of valve sticking can be determined according to the standardized engine test method CEC F 16-T-96. This method consists in running a spark ignition gasoline engine according to operating points described in the method, in then halting it and gradually bringing the temperature from +90° C. down to +5° C. over 10 h (temperature of the coolant), then maintaining it at +5° C. for an additional 5 h. On conclusion of this, cylinder compression measurements are carried out, which reflect the quality of the sealing in the combustion chamber. If the reference compression pressure is not achieved for one or more cylinders, this reflects the presence of a phenomenon of valve sticking.
Thus, according to a particularly preferred embodiment, a subject matter of the invention is the use of the copolymer as described above for preventing deposits at low temperature on fuel intake valves and in particular for preventing the sticking of said valves, which is determined according to the standardized method CEC F 16-T-96.
In order to demonstrate and quantify the valve sticking, it is also possible to employ the method described in the abovementioned publication SAE Technical Paper Series No. 881643 (see method described on page 3 and in Appendix 1 of this publication).
According to a specific embodiment, the use of said copolymer additionally makes it possible to reduce the fuel consumption of the spark ignition engine.
The copolymer(s) as described above can be used alone or as a mixture with other additives, for example in the form of an additive concentrate.
The copolymers according to the invention can be added to the liquid fuel within a refinery and/or be incorporated downstream of the refinery and/or optionally as a mixture with other additives in the form of an additive concentrate, also known according to common use as “additive package”.
According to one embodiment, the copolymer according to the invention is used as a mixture with an organic liquid which is inert with regard to said copolymer and miscible with the fuel composition, intended to facilitate the incorporation of said copolymer in the composition.
According to a specific embodiment, a concentrate for fuel comprises one or more copolymers as described above, as a mixture with an organic liquid.
The organic liquid is inert with regard to the block copolymer(s) according to the invention and miscible in the liquid fuel described above. Miscible is understood to mean the fact that the copolymer and the organic liquid form a solution or a dispersion so as to facilitate the mixing of the copolymer according to the invention in the liquid fuels according to conventional processes for the additivation of fuels.
The organic liquid can, for example, be chosen from aromatic hydrocarbon solvents, such as the solvent sold under the name Solvesso, alcohols, ethers and other oxygen-based compounds, and paraffinic solvents, such as hexane, pentane or isoparaffins, alone or as a mixture.
The concentrate can advantageously comprise a total amount of copolymer(s) according to the invention ranging from 5% to 99% by weight, preferably from 10% to 80% by weight, more preferentially from 25% to 70% by weight.
The concentrate can typically comprise from 1% to 95% by weight, preferably from 20% to 90% by weight, more preferentially from 30% to 75% by weight of organic liquid, the remainder corresponding to the copolymer according to the invention, it being understood that the concentrate can comprise one or more copolymers as described above.
Generally, when the copolymer according to the invention is a block copolymer, its solubility in the organic liquids and the liquid fuels which are described above depends in particular on the weight-average and number-average molar masses, respectively Mw and Mn, of the copolymer. The average molar masses Mw and Mn of the copolymer according to the invention will be chosen so that the copolymer is soluble in the liquid fuel and/or the organic liquid of the concentrate for which it is intended.
The average molar masses Mw and Mn of the copolymer according to the invention can also have an influence on the effectiveness of the copolymer as additive in fuels. The average molar masses Mw and Mn will thus be chosen so as to optimize the effect of the copolymer according to the invention, in particular the effect of preventing valve sticking.
The average molar masses Mw and Mn can be optimized by routine tests open to a person skilled in the art.
According to a specific embodiment, the copolymer according to the invention advantageously exhibits a weight-average molar mass (Mw) ranging from 500 to 30 000 g·mol-1, preferably from 1000 to 10 000 g·mol-1, more preferentially less than or equal to 4000 g·mol-1, and/or a number-average molar mass (Mn) ranging from 500 to 15 000 g·mol-1, preferably from 1000 to 10 000 g·mol-1, more preferentially less than or equal to 4000 g·mol-1. The number-average and weight-average molar masses are measured by size exclusion chromatography (SEC). The operating conditions for the SEC, in particular the choice of the solvent, will be chosen as a function of the chemical functional groups present within the block copolymer.
The molar ratio and/or the ratio by weight between the polar monomer (mb) and the nonpolar monomer (ma) and/or between block A and B in the block copolymer described above will also be chosen so that the block copolymer is soluble in the fuel and/or the organic liquid of the concentrate for which it is intended. Likewise, this ratio can be optimized as a function of the fuel and/or of the organic liquid so as to obtain the best effect of prevention of the valve sticking.
The molar ratio and/or the ratio by weight can be optimized by routine tests open to a person skilled in the art.
According to a specific embodiment, the molar ratio of the nonpolar monomer (ma) to the polar monomer (mb), or of the block A to the block B as molar percentage of the nonpolar monomer (ma) of the block A to the polar monomer (mb) of the block B, is preferably between 95:5 and 50:50, more preferentially between 90:10 and 75:25, more preferentially still between 85:15 and 70:30.
According to a specific embodiment, the copolymer according to the invention is used in the form of an additive concentrate in combination with at least one other additive for internal combustion engine fuel other than the copolymers according to the invention described above.
The additive concentrate can typically comprise one or more other additives other than the copolymers according to the invention, chosen from detergent additives, corrosion inhibitors, antioxidants, dispersants, demulsifiers, biocides, reodorants, friction modifiers, lubricity additives, combustion aids (catalytic soot combustion promoters), antisettling agents, antiwear agents and conductivity modifiers.
Mention may in particular be made, among these additives, and without limitation, of:
a) lubricity additives or antiwear agents, in particular (but not limitingly) chosen from the group consisting of fatty acids and their ester or amide derivatives, in particular glyceryl monooleate, and mono- and polycyclic carboxylic acid derivatives. Examples of such additives are given in the following documents: EP 680 506, EP 860 494, WO98/04656, EP 915 944, FR 2 772 783, FR 2 772 784;
b) detergent additives, in particular (but not limitingly) chosen from the group consisting of succinimides, polyetheramines and quaternary ammonium salts; for example, those described in the documents U.S. Pat. No. 4,171,959 and WO2006135881.
These other additives are generally added in an amount ranging from 10 to 1000 ppm (each), preferably from 100 to 1000 ppm, by weight in the fuel composition.
The additive concentrate can also comprise an organic liquid as described above, inert with regard to the additives described above and miscible with the fuel composition, intended to facilitate the incorporation of the additives in the composition.
The invention additionally relates to a process for keeping clean, at low temperature, the fuel intake valves in an indirect injection spark ignition engine comprising at least the following stages:

The process for keeping clean (keep-clean) preferably comprises the successive stages of:

- 1) determination of the additivation most suitable for the fuel, said additivation corresponding to the selection of the block copolymer(s) described above to be incorporated in combination, optionally, with other fuel additives as described above, and the determination of the degree of treatment necessary in order to achieve a given specification relating to the cleanness of the valves; then
- 2) incorporation in the fuel of the selected copolymer(s) at the content determined in stage 1) and, optionally, of the other fuel additives.

Alternatively, the copolymer according to the invention and the other additives, if appropriate, can be used in the form of a concentrate or of an additive concentrate as described above.
Stage 1) is carried out according to any known process and comes within the common practice in the field of the additivation of fuels. This stage involves defining at least one characteristic representative of the properties of the fuel composition in terms of effect on the cleanness of the valves.
The characteristic representative of the properties of the fuel can in particular correspond to the appearance of phenomena of deposits on the valves and/or to the appearance of phenomena of valve sticking, measured in particular according to the standardized method CEC F-16-T96.
The amount of copolymer(s) according to the invention to be added to the fuel composition in order to achieve a given specification (stage 1) described above) will typically be determined by comparison with the fuel composition but without the copolymer(s) according to the invention.
The amount of copolymer(s) according to the invention can also vary as a function of the nature and of the origin of the fuel.
The process for keeping clean can also comprise an additional stage 3) after stage 2), of checking the target reached and/or of adjusting the degree of additivation with the copolymer(s) according to the invention.
The examples below are targeted at illustrating the invention and should not be interpreted as limiting the scope thereof.

Examples

1. Preparation of a Copolymer According to the Invention:
A quaternized EHMA/DAMEMA diblock copolymer in accordance with the present invention was synthesized by RAFT-type radical copolymerization, in accordance with the protocol described below.
EHMA Block A:
30.01 g (0.26 mmol) of 2-ethylhexyl methacrylate (EHMA), 2.89 g (13 mmol) of 2-cyano-2-propyl benzodithioate and 35 ml of toluene are introduced into a 250 ml round-bottomed flask. 210 mg (1.29 mmol) of azobisisobutyronitrile (AIBN) are weighed out in a 20 ml round-bottomed flask and then dissolved in 4 ml of toluene. The two solutions are degassed with nitrogen for 30 minutes. The solution containing the EHMA monomer is heated to 80° C. When the temperature is reached, the AIBN solution is added using a syringe purged with nitrogen beforehand. The reaction medium is stirred at 80° C. for 24 h under an inert atmosphere (N2).
A 250 μl sample is withdrawn at t0 (immediately after addition of AIBN) and at tf (final t) in order to measure the content of residual monomers by HPLC and thus to deduce the conversion thereof.
Result: the ratio of areas of the peaks of the EHMA monomer gives a conversion of 98% (98% of the EHMA monomer was converted into polymer).
HPLC method employed: HPLC UltiMate 300 from Thermo Fisher. The stationary phase of the device is a Symmetry Shield RP 18 column. The mobile phase is composed of two eluents, a first, the composition of which is water/methanol with CH2O2 at pH 5; the second is composed of methanol with methanoic acid, also at pH 5. This mobile phase has a flow rate of 1 ml/min. The temperature of the oven is set at 40° C. The injection volume is 5 μl. The products are detected via a diode array detector.
Addition of the DAMEMA Block B:
10.22 g (88.7 mmol) of 2-(dimethylamino)ethyl methacrylate (DAMEMA) are weighed out in a 50 ml round-bottomed flask. 11 ml of toluene are added. Furthermore, 221 mg (1.35 mmol) of AIBN are weighed out in a 20 ml round-bottomed flask and then dissolved via 3 ml of toluene. After degassing the two solutions with nitrogen for 30 minutes, the DAMEMA monomer is added, via a syringe purged beforehand with nitrogen, to a round-bottomed flask containing the EHMA block A heated to 80° C.; the AIBN solution is subsequently added. The reaction medium is stirred for 24 h under an inert atmosphere (N2).
A 250 μl sample is withdrawn at t0 (immediately after addition of AIBN) and at tf (final t) in order to measure the content of residual monomers by HPLC (as described for the block A above) and thus to deduce the conversion thereof.
A sample is also withdrawn in order to determine, by 1H and 13C NMR, the numbers of EHMA and DAMEMA units and the molar ratio of the two monomers.
Analytical Methods:
The 1H and 13C NMR spectroscopy analyses were carried out in deuterated chloroform CDCl3 with a Brüker Avance III 400 MHz NMR spectrometer (Larmor frequency of the 1H) operating under TopSpin 3.2: SEX 10 mm 13C probe with pulsed magnetic field z-gradient and 2H lock operating at 300K and BBI 5 mm 1H probe with pulsed magnetic field z-gradient and 2H lock operating at 300K. An external standard (1,2,4,5-tetrachloro-3-nitrobenzene) is used to carry out the measurements.
Finally, the number-average molar masses Mn and weight-average molar masses Mw, and also the dispersity index, which reflects the size dispersity, PI (PI=Mw/Mn), were determined by GPC.
The GPC analyses were carried out in THF. In a typical analysis, 100 μl of a 0.5% w/w sample, filtered beforehand through a 0.45 μm Millipore filter, are injected into Waters Styragel columns operating at 40° C. and 645 psi with a THF flow rate of 1 ml/min. The number-average molar masses (Mn) were determined by RI (refractive index) detection from calibration curves constructed for PMMA standards. The analyses were carried out within a column of Waters Styragel type with the refractive index as detector.
Results:

- Conversion by HPLC: the ratio of the areas of the peaks of the DAMEMA monomer gives a conversion of 97% (97% of the DAMEMA monomer was converted into polymer).
- Microstructure by ¹H et ¹³C NMR: based on the signals relating to the chain ends, 17 EHMA units and 6 DAMEMA units are determined. The molar relative composition: 71% EHMA, 29% DAMEMA.
- For the calculation of the number of units, by ¹³NMR, by setting the integral of the signal at 132.3 ppm (associated with 1 aromatic CH group of the benzodithioate) at 1, an integral for the broad unresolved peak of the OCH₂groups (1C) of the EHMA units (67.8-66.5 ppm) of 17 and an integral for the broad unresolved peak of the NCH₂groups (1C) of the DAMEMA units (57.4-56.8 ppm) of 6, respectively, are obtained. Thus, if it is assumed that all the polymer chains comprise the benzodithioate group as end group, then the copolymer comprises 17 EHMA units and 6 DAMEMA units.
- GPC: M_n=2800 g/mol; M_w=3400 g/mol; PI=1.28.

Partial Quaternization of the Block B of the EHMA/DAMEMA Diblock Copolymer:

- 28.5 g of the solution of diblock polymer in toluene prepared above are withdrawn and introduced into a 100 ml round-bottomed flask. 10.5 g of butanol, 912 mg (12.6 mmol) of epoxybutane and 735 mg (12.2 mmol) of acetic acid are introduced. The mixture is heated at 60° C. for 24 h, a Vigreux column on the round-bottomed flask. At the end of the reaction, the mixture is evaporated under reduced pressure.
- After drying, a sample of the polymer is analyzed by ¹H and ¹³C NMR.

Results:

- The degree of quaternization of the block B (DAMEMA block) is 40 mol %.
- The degree of quaternization is determined by ¹³C NMR. In ¹³C NMR, the broad unresolved peak at approximately 70 ppm is assigned to the CH₂of the CH₂CHOHCH₂CH₃group alpha to the quaternized nitrogen atom. Based on the EHMA/DAMEMA molar proportion (71/29), and by comparing the integral of the broad unresolved peak at 70 ppm and the integral of the signal at 11 ppm (associated with one of the two CH₃groups of the pendant EHMA chain), the degree of quaternization is deduced therefrom, which degree is 40%.

2. Comparative Tests:
2.1. Tests of Valve Sticking at Low Temperature:
The quaternized EHMA/DAMEMA copolymer obtained in example 1 (hereinafter additive A) was compared with a detergent additive sold under the name Kerocom PIBA by BASF (hereinafter additive B), and which consists of a polyisobuteneamine as described in example 2 of the patent U.S. Pat. No. 7,291,681.
The two additives were each incorporated in a gasoline of RON 98 lead-free premium grade gasoline type containing 15% v/v of ETBE (ethyl tert-butyl ether), with a degree of treatment of 300 mg of active material per kg, in the absence of any other additive.
Evaluation tests on the valve sticking were carried out at +5° C. according to the CEC F16-T-96 method on a VW Waterboxer engine.
The gasoline containing the comparative additive B resulted, in these tests, in the appearance of valve sticking. With the gasoline containing the additive A according to the invention, no valve sticking was observed.
2.2. Fouling Tests on the Valves at High Temperature (Coking):
The performance qualities of the two additives A and B as regards keeping the intake valves clean were also evaluated, in accordance with the standardized method M102E (CEC F-05-93).
These tests were carried out on a reference gasoline, in which one or other of the additives A and B was incorporated, at different degrees of treatment.
The results obtained are described in detail in the table below:


		Amount of deposits
	Degree of treatment	CEC F-05-93
Additive	(mg/kg)	(mg/valve)

None	—	321
A	200	1442
A	100	1277
A	50	1072
B	100	877
B	200	30

The two tests above show that the effects of one and the same additive on the deposits capable of forming on the fuel intake valves in spark ignition engines vary substantially, according to whether deposits which form at low temperature (valve sticking) or at high temperature (coking) are concerned.
Thus, the additive B, which is conventionally employed to prevent the fouling of the valves by coking during the operation of the engine at high temperature, results in deposits at low temperature, which bring about a phenomenon of valve sticking.
On the other hand, the additive A according to the invention makes it possible to effectively prevent valve sticking but does not automatically result in good performance qualities for preventing the coking at high temperature.

Claims

1. The use, in order to prevent deposits at low temperature on the fuel intake valves in indirect injection spark ignition engines, of one or more copolymer(s) comprising:

at least one unit of following formula (I):

in which:

u=0 or 1,

R₁′ represents a hydrogen atom or a methyl group,

E represents —O— or —N(Z)— or —O—CO— or —CO—O— or —NH—CO— or —CO—NH—, with Z representing H or a C₁to C₆alkyl group,

G represents a group chosen from a C₁to C₃₄alkyl group, an aromatic nucleus, an aralkyl group comprising at least one aromatic nucleus and at least one C₁to C₃₄alkyl group, and

at least one unit of following formula (II):

in which:

v=0 or 1,

R₁″ is chosen from the hydrogen atom and the methyl group,

Q is chosen from the oxygen atom and an —NR′— group with R′ being chosen from a hydrogen atom and C₁to C₁₂hydrocarbon chains,

R represents a C₁to C₃₄hydrocarbon chain which can also contain one or more nitrogen and/or oxygen atoms and/or carbonyl groups, which is substituted by at least one amino group comprising a primary, secondary or tertiary amine or quaternary ammonium functional group, and optionally one or more hydroxyl groups.

2. The use of a copolymer as recited in claim 1, in which the amino group present in the group R of the formula (II) is chosen from:

the groups having at least one amine, imine, amidine, guanidine, aminoguanidine or biguanidine functional group, such as alkylamines, polyalkylenepolyamines, polyalkylenimines, alkylimines, alkylamidines, alkylguanidines and alkylbiguanidines, it being possible for the alkyl substituent to be linear or branched, cyclic or acyclic, and preferably having from 1 to 34 carbon atoms, more preferentially from 1 to 12 carbon atoms, and the quaternized forms of these groups; and

monocyclic or polycyclic heterocyclic groups, having from 3 to 34 atoms, preferably from 5 to 12 atoms, more preferentially from 6 to 10 atoms, and at least one nitrogen atom, it being understood that the polycyclic heterocyclic groups have, optionally, fused rings.

3. The use of a copolymer as recited in claim 1, in which the group R of the formula (II) is represented:

when v has the value 1, by the formula (V):

L-R′₂ (V)

when v has the value 0, by the formula (V) or the formula (V′):

L-R′₂ (V)

L- (V′)

in which formulae (V) and (V′):

R₂′ is chosen from C₁to C₃₄hydrocarbon chains, optionally substituted by at least one hydroxyl group, and

L is chosen from the group consisting of:

the following groups:

amine: —NH₂; —NHR_a, —NR_aR_b;

imine: —HC═NH; —HC═NR_a; —N═CH₂, —N═CR_aH; —N═CR_aR_b;

amidine: —(C═NH)—NH₂; —(C═NH)—NR_aH; —(C═NH)—NR_aR_b; —(C═NR_a)—NH₂; —(C═NR_a)—NR_bH; —(C═NR_a)—NR_bR_c; —N═CH(NH₂); —N═CR_a(NH₂); —N═CH(NR_aH); —N═CR_a(NR_aH); —N═CH(NR_aR_b); —N═CR_a(NR_bR_c);

guanidine: —NH—(C═NH)—NH₂; —NH—(C═NH)—NHR_a; —N═C(NH₂)₂; —N═C(NR_aH)₂; —N═C(NR_aR_b)₂; —N═C(NR_aH)(NR_bH);

aminoguanidine: —NH—(C═NH)—NH—NH₂; —NH—(C═NH)—NH—NHR_a; —N═C(NH₂)(NH—NH₂); —N═C(NR_aH)(NH—NH₂); —N═C(NR_aH)(NR′—NH₂); —N═C(NR_aR_b)(NH—NH₂); —N═C(NR_aR_b)(NR_a—NH₂);

biguanidine: —NH—(C═NH)—NH—(C═NH)—NH₂; —NH—(C═NH)—NH—(C═NH)—NHR_a; —N═C(NH₂)—NH—(C═NH)—NH₂; —N═C(NH₂)—NH—(C═NR_a)—NH₂; —N═C(NH₂)—NH—(C═NH)—NR_aH; —N═C(NH₂)—NH—(C═NR_a)—NR_bH; —N═C(NH₂)—NH—(C═NH)—NR_aR_b; —N═C(NH₂)—NH—(C═NR_a)—NR_bR_c; —N═C(NR_aH)—NH—(C═NH)—NH₂; —N═C(NR_aH)—NH—(C═NR_b)—NH₂; —N═C(NR_aH)—NH—(C═NH)—NR_bH; —N═C(NR_aH)—NH—(C═NR_b)—NR_cH; —N═C(NR_aH)—NH—(C═NH)—NR_bR_c; —N═C(NR_aH)—NH—(C═NR_b)—NR_cR_d; —N═C(NR_aR_b)—NH—(C═NH)—NH₂; —N═C(NR_aR_b)—NH—(C═NR_c)—NH₂; —N═C(NR_aR_b)—NH—(C═NH)—NR_cH; —N═C(NR_aR_b)—NH—(C═NR_c)—NR_dH; —N═C(NR_aR_b)—NH—(C═NH)—NR_cR_d; —N═C(NR_aR_b)—NH—(C═NR_c)—NR_dR_e;

the quaternized forms of the above groups, when these contain at least one quaternizable nitrogen atom; and

polyamine and polyalkylenepolyamine groups, in particular those of formulae —NH—(R_f—NH)_k—H; —NH—(R_f—NH)_k—R_a;

with R_a, R_b, R_c, R_dand R_erepresenting, independently of one another, a C₁-C₃₄, preferably C₁-C₁₂, alkyl group, optionally comprising one or more NH₂functional groups and one or more —NH— bridges;

R_frepresents a C₁-C₆, preferably C₂-C₄, alkyl group; k represents an integer ranging from 1 to 20, preferably from 2 to 12.

4. The use of a copolymer as recited in claim 1, in which the copolymer contains units of formula (II) comprising a group R containing at least one quaternary ammonium functional group.

5. The use of a copolymer as recited in claim 4, in which from 5 mol % to 95 mol % of the units of formula (II) of the copolymer comprise, in the group R, at least one quaternary ammonium functional group, preferably from 10% to 90%, more preferentially from 20% to 80% and more preferentially still from 40% to 60%, with respect to the total molar amount of units of formula (II) in the copolymer.

6. The use of a copolymer as recited in claim 1, in which the quaternary ammonium functional group(s) optionally present in the group R of the units of formula (II) is (are) represented by one of the following formulae (III) and (IV):

in which:

X⁻ is chosen from hydroxide or halide ions and organic anions, preferably organic anions,

R₂is chosen from C₁to C₃₄hydrocarbon chains, optionally substituted by at least one hydroxyl group,

R₃, R₄and R₅are identical or different and are chosen independently from C₁to C₁₈hydrocarbon chains, it being understood that the R₃, R₄and R₅groups can contain one or more groups chosen from: a nitrogen atom, an oxygen atom and a carbonyl group and that the R₃, R₄and R₅groups can be connected together in pairs to form one or more rings,

R₆and R₇are identical or different and are chosen independently from C₁to C₁₈hydrocarbon chains, it being understood that the R₆and R₇groups can contain one or more groups chosen from: a nitrogen atom, an oxygen atom and a carbonyl group and that the R₆and R₇groups can be connected together to form a ring.

7. The use of a copolymer as recited in claim 6, in which the quaternary ammonium functional group(s) present in the group R of the units of formula (II) is (are) represented by the formula (III), in which:

X⁻ is chosen from organic anions, preferably conjugate bases of carboxylic acids,

R₂is chosen from C₁to C₃₄hydrocarbon chains, preferably C₁to C₁₈alkyl groups,

R₃, R₄and R₅are identical or different and are chosen independently from C₁to C₁₈hydrocarbon chains, optionally substituted by at least one hydroxyl group, it being understood that at least one of the R₃, R₄and R₅groups contains one or more hydroxyl group(s).

8. The use of a copolymer as recited in claim 1, in which, in the formula (I), the group G is a C₄to C₃₄alkyl.

9. The use of a copolymer as recited in claim 1, in which, in the formula (I), R₁′ is a hydrogen atom.

10. The use of a copolymer as recited in claim 1, in which, in the formula (I), the group E is chosen from: —O— and —N(Z)—, with Z representing H or a C₁to C₆alkyl group.

11. The use of a copolymer as recited in claim 1, in which, in the formula (I), the group E is chosen from: —O—CO— and —NH—CO—; preferably, the group E is the —O—CO— group, it being understood that the group E=—O—CO— is connected to the vinyl carbon by the oxygen atom and that the group E=—NH—CO— is connected to the vinyl carbon by the nitrogen atom.

12. The use of a copolymer as recited in claim 1, in which, in the formula (I), the group E is chosen from: —CO—O— and —CO—NH—; preferably the group E is the —CO—O— group, it being understood that the group E is connected to the vinyl carbon by the carbon atom.

13. The use of a copolymer as recited in claim 1, in which the copolymer is chosen from block copolymers and random copolymers; preferably, the copolymer is a block copolymer.

14. The use of a copolymer as recited in claim 13, in which the copolymer is a block copolymer comprising at least:

a block A corresponding to the following formula (XI):

in which:

p is an integer ranging from 2 to 100, preferably ranging from 5 to 80, preferably ranging from 10 to 70, more preferentially ranging from 20 to 60, and

R₁′, u, E and G are as defined in claim 1, and

a block B corresponding to the following formula (XII):

in which:

n is an integer ranging from 2 to 50, preferably from 3 to 40, more preferentially from 4 to 20, more preferentially still from 5 to 10,

R₁″, v, Q and R are as defined in claim 1.

15. The use of a copolymer as recited in claim 14, in which, from 5 mol % to 95 mol % of the units of the block B comprise a group R containing at least one quaternary ammonium functional group.

16. The use of a copolymer as recited in claim 15, in which the block B comprises from 5 mol % to 95 mol % of units corresponding to the formula (XIII):

in which:

R₁″ is chosen from the hydrogen atom and the methyl group,

Q is chosen from the oxygen atom and the —NR′— group, with R′ being chosen from a hydrogen atom and C₁to C₁₂hydrocarbon chains,

R₃, R₄and R₅are identical or different and are chosen independently from C₁to C₁₈hydrocarbon chains, optionally substituted by at least one hydroxyl group, it being understood that at least one of the R₃, R₄and R₅groups contains at least one hydroxyl group.

17. The use of a copolymer as recited in claim 15, in which:

the block A consists of a chain of structural units derived from a C₁-C₃₄alkyl (meth)acrylate monomer, and

the block B consists of a chain of structural units derived from alkyl (meth)acrylate or alkyl(meth)acrylamide monomers, 5 mol % to 95 mol % of which have an alkyl radical consisting of a C₁to C₃₄hydrocarbon chain substituted by a quaternary ammonium group and optionally one or more hydroxyl groups, and 5 mol % to 95 mol % of which have an alkyl radical consisting of a C₁to C₃₄hydrocarbon chain substituted by a group chosen from primary, secondary or tertiary amines, preferably tertiary amines, and optionally one or more hydroxyl groups.

18. The use of a copolymer as recited in claim 1, in which the copolymer is incorporated in a liquid fuel in a total content of at least 5 ppm by weight, preferably of at least 10 ppm, more preferentially at a content of 10 to 5000 ppm, more preferentially still of 20 to 2000 ppm and better still of 50 to 1000 ppm.

19. The use of a copolymer as recited in claim 1, for preventing the sticking of said valves, which is determined according to the standardized method CEC F-16-T96.

20. A process for keeping clean, at low temperature, the fuel intake valves in an indirect injection spark ignition engine comprising at least the following stages:

the preparation of a fuel composition by additivation of a fuel with a copolymer as defined in claim 1, then

the injection of said fuel composition into the spark ignition engine.