WO2023249482A1

WO2023249482A1 - Composition comprising base oil and ashless ionic liquid

Info

Publication number: WO2023249482A1
Application number: PCT/MY2023/050049
Authority: WO
Inventors: Farah Fazlina M YASIN; Andrea DOLFI; Geetha Srinivasan; Carlo PEROTTO; Maria Teresa SATERIALE; Małgorzata SWADŹBA-KWAŚNY
Original assignee: Petroliam Nasional Berhad (Petronas)
Priority date: 2022-06-21
Filing date: 2023-06-19
Publication date: 2023-12-28

Abstract

Provided herein is a composition comprising a base oil, and an ionic liquid having an anionic portion comprising two carboxylate groups and two ester or amide groups.

Description

COMPOSITION COMPRISING BASE OIL AND ASHLESS IONIC LIQUID

FIELD OF THE INVENTION

The invention relates to a composition comprising a base oil and an ashless ionic liquid, and to uses and methods involving the composition.

BACKGROUND

Ionic liquids have been investigated as lubricants and lubricant additives over two decades due to intrinsic properties such as high polarity, low vapor pressure, high thermal stability and tunability. These desirable properties render ionic liquids (ILs) as a possible new generation of friction modifiers, potentially as an alternative to conventional friction modifier/anti-wear additives that typically contain environmentally harmful metal, sulfur and phosphorous species to achieve friction reduction and anti-wear properties. While ILs are effective in reducing friction, they are generally too expensive for large scale use. In addition, many ILs contain halides that cause severe corrosion, rendering them unsuitable for many applications. Other ILs contain metallate-based cations that are toxic and environmentally harmful.

While carboxylic acids have been investigated as starting materials for ionic liquids, they are typically too polar for use in highly non-polar base oils. There is therefore a need for nontoxic and environmentally friendly friction modifiers suitable for use in base oils.

SUMMARY OF THE INVENTION

The inventors have developed a class of ionic liquids derived from dicarboxylic acids and diols/diamines that have highly tunable polarity and are suitable for use as friction modifiers in base oils.

The invention therefore provides the following numbered clauses.

A composition comprising: a base oil; and an ionic liquid having an anionic portion having formula la:

la; and a cationic portion having formula lb:

(X)«⁺ lb where: each Ri is independently selected from a linear or branched C1-C20 aliphatic hydrocarbyl group that is saturated or unsaturated, a C₆.Cio aryl group, and a 5-10 membered heteroaromatic ring system, where the C1-C20 aliphatic hydrocarbyl group is not interrupted or is interrupted by one or more groups selected from an aromatic or non-aromatic ring system having from 5 to 14 atoms, an ester group, an amide group, and a carbamate group, and where the C1-C20 aliphatic hydrocarbyl group is unsubstituted or substituted by one or more groups selected from the group consisting of hydroxyl, primary amino, secondary amino and tertiary amino, where the secondary and tertiary amino groups are substituted by one or two C1-10 hydrocarbyl groups, respectively;

R2 is selected from the group consisting of a linear, branched or cyclic C1-C40 aliphatic hydrocarbyl group that is saturated or unsaturated, a linear or branched C2-C40 polyalkyleneglycol group, a C₆-C₂2 aryl group, a moiety formed by removing two hydroxyl groups from a sugar alcohol, and a moiety formed by removing two hydroxyl groups from a dehydrated sugar alcohol or isosorbide, where the linear or branched C1-C40 aliphatic hydrocarbyl group and the linear or branched C2-C40 polyalkyleneglycol are saturated or unsaturated, where the linear or branched C1-C40 aliphatic hydrocarbyl group and the linear or branched C2-C40 polyalkyleneglycol is not interrupted or is interrupted by one or more groups selected from an aromatic or non-aromatic ring system having from 5 to 14 atoms, an ester group, an amide group, and a carbamate group, where the linear or branched C1-C40 aliphatic hydrocarbyl group and the linear or branched C2-C40 polyalkyleneglycol are unsubstituted or substituted by one or more groups selected from the group consisting of hydroxyl, primary amino, secondary amino and tertiary amino, where the secondary and tertiary amino groups are substituted by one or two C1-10 hydrocarbyl groups, respectively;

X represents a cationic species, where a is 1 or 2 and n is 1 or 2, provided that: when a is 1 then n is 2, and when a is 2 then n is 1 ; and each J independently represents O or NRN, where RN represents H or a Ci-Cis alkyl or alkenyl group.

2. The composition according to Clause 1 , wherein: each Ri is independently selected from a phenyl group, a furan group or, more particularly, a linear or branched C₄-Ci₈ (e.g. C4-C12) aliphatic hydrocarbyl group that is saturated or unsaturated, optionally wherein each R1 is independently selected from a 1 ,4-valent phenyl group, a 2,5-valent furan group, or more particularly, a linear or branched Ce-Cw aliphatic hydrocarbyl group that is saturated or unsaturated.

3. The composition according to Clause 2, wherein each R1 independently represents a moiety formed by removing both carboxylic acid groups from a compound selected from the list consisting of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1 ,12-dodecanedioic acid, 1 ,18-octadecanedioic acid, terephthalic acid, isophthalic acid, phthalic acid, and 2,5-furandicarboxylic acid.

4. The composition according to any one of the preceding clauses, wherein one or more of the following applies:

(a) the linear or branched C1-C20 aliphatic hydrocarbyl group or C1-C40 aliphatic hydrocarbyl group (e.g. C1-C40 aliphatic hydrocarbyl group) is substituted by one or more (e.g. one, two or three) hydroxyl groups and one or more (e.g. one, two or three) groups selected from the group consisting of primary amino, secondary amino and tertiary amino;

(b) the C2-C40 polyalkyleneglycol is derived from a homopolymer (e.g. is derived from polyethyleneglycol, polypropyleneglycol or polybutyleneglycol);

(c) the C2-C40 polyalkyleneglycol is derived from a block copolymer (e.g. is derived from a poly(ethoxylated)(propoxylated)glycol, a poly(propoxylated)(butoxylated)glycol) or a poly(ethoxylated)(butoxylated)glycol;

(d) the linear or branched C1-C20 aliphatic hydrocarbyl group or C1-C40 aliphatic hydrocarbyl group (e.g. C1-C40 aliphatic hydrocarbyl group) is interrupted by one or more (e.g. one, two or three) ester groups and/or is substituted by one or more (e.g. one, two or three) hydroxyl groups; and

(e) each J represents O.

5. The composition according to any one of the preceding clauses, wherein R2 is selected from the group consisting of a moiety formed by removing both hydroxyl groups from isosorbide, or more particularly, a linear or branched C2-C20 aliphatic hydrocarbyl group and a linear or branched C2-C20 polyalkyleneglycol, where the linear or branched C2-C20 aliphatic hydrocarbyl group and the linear or branched C2-C20 polyalkyleneglycol are saturated or unsaturated, where the linear or branched C2-C20 aliphatic hydrocarbyl group and the linear or branched C2-C20 polyalkyleneglycol are not interrupted or is interrupted by one or more groups selected from an aromatic or non-aromatic ring system having 5 or 6 atoms, an amide group, and a carbamate group.

6. The composition according to Clause 4, wherein R₂ represents a moiety formed by removing both hydroxyl groups from isosorbide, or more particularly, a linear or branched C3-C16 aliphatic hydrocarbyl group that is saturated or unsaturated, which hydrocarbyl group is not interrupted or is interrupted by one or more groups selected from an aromatic or nonaromatic ring system having 5 or 6 atoms, optionally wherein R₂ represents a moiety formed by removing both hydroxyl groups from isosorbide, or more particularly, a linear or branched C3-10 aliphatic hydrocarbyl group.

7. The composition according to any one of the preceding clauses, wherein:

(a) each J represents O and R₂ represents a moiety formed by removing both hydroxyl groups from a compound selected from the following: neopentyl glycol, 1 ,5-pentanediol, 1 ,9-nonanediol, 1 ,6-hexanediol, 2-methyl-1 ,3-propanediol, 2,5-hexanediol, 2,7-octanediol, a saturated straight chain C28 1 ,14-diol, an unsaturated

where each Z independently represents a Ci to C12 aliphatic hydrocarbyl group; or (b) one of the following applies:

R2 represents a C4-16 alkylene group and each J represents NH; or

R₂ represents propylene, one J represents NH and the other J represents NR_N where RN represents oleyl.

8. The composition according to any one of the preceding clauses, wherein a is 1 .

9. The composition according to any one of the preceding clauses, wherein the cationic portion is selected from one or more of the group consisting of a quaternary phosphonium cation, a quaternary sulphonium cation, a quaternary ammonium cation comprising at least one amide group, a quaternary ammonium cation comprising at least one ester group, a substituted quaternary imidazolium cation comprising at least one ester group, a substituted quaternary imidazolium cation comprising at least one alkyleneglycol group, a substituted quaternary imidazolium cation comprising at least one amide group, azaannulenium, azathiazolium, benzimidazolium, benzofuranium, benzothiophenium, benzotriazolium, borolium, cinnolinium, diazabicyclodecenium, diazabicyclononenium, 1 ,4- diazabicyclo[2.2.2]octanium, diazabicyclo-undecenium, dibenzofuranium, dibenzothiophenium, dithiazolium, dithiazolium, furanium, guanidinium, imidazolium, indazolium, indolinium, indolium, morpholinium, oxaborolium, oxaphospholium, oxazinium, oxazolium, /so-oxazolium, oxazolinium, pentazolium oxothiazolium, phospholium, phosphonium, phthalazinium, piperazinium, piperidinium, pyranium, pyrazinium, pyrazolium, pyridazinium, pyridinium, pyrimidinium, pyrrolidinium, pyrrolium, quinazolinium, quinolinium, /soquinolinium, quinoxalinium, quinuclidinium, selenazolium, sulfonium, tetrazolium, thiadiazolium, /so-thiadiazolium, thiazinium, thiazolium, /so-thiazolium, thiophenium, thiuronium, triazadecenium, triazinium, triazolium, /so-triazolium, combinations thereof, and cationic molecules comprising more than one of the foregoing.

10. The composition according to any one of the preceding clauses, wherein the cationic portion has the formula [YR₃R4R5R6]⁺, wherein:

Y represents N, P or S (e.g. N or P); and

(a) each of R3 to Re are independently selected from Ci to C30 straight chain or branched alkyl and alkenyl groups; C₃ to C₆ cycloalkyl groups; Ci to C30 arylalkyl groups; Ci to C30 alkylaryl groups; aryl groups; or any two of R₃ to R₆ combine to form an alkylene chain -(CH2)q- wherein q is from 3 to 6; wherein any one or more of said straight or branched chain alkyl and alkenyl groups, cycloalkyl groups, arylalkyl groups, alkylaryl groups; aryl groups or alkylene chains are optionally substituted by one to three groups selected from: Ci to C4 alkoxy, C2 to C₈ alkoxyalkoxy, C3 to C₈ cycloalkyl, -OH, -NH₂, -SH, -CO₂(Ci to C₆)alkyl, and -OC(O)(Ci to C₆)alkyl; or

(b) at least one of R₃ to R₆ have the formula -R₇O(C=O)R₈ or -R₇(C=O)-O-R₈, wherein R₇ is a Ci to Cw straight chain or branched alkyl or alkenyl group, or a C₃ to C₆ cycloalkyl or cycloalkenyl group; and R₈ is a Ci to C30 straight chain or branched alkyl or alkenyl group; a C₃ to C₆ cycloalkyl group; a Ci to C₃₀ arylalkyl group; a Ci to C₃₀ alkylaryl group; an aryl group; or any two respective R₈ groups combine to form an alkylene chain -(CH₂)_q- wherein q is from 3 to 6; wherein R₇ and/or R₈ are optionally substituted by one to three groups selected from: Ci to C₄ alkoxy, C₂ to C₈ alkoxyalkoxy, C₃ to C₈ cycloalkyl, -OH, -NH₂, -SH, -CO₂(Ci to C₈)alkyl, and -OC(O)(Ci to C₆)alkyl; and wherein the other of R₃ to R₆ that are not as defined above are independently selected from Ci to C₃₀ straight chain or branched alkyl and alkenyl groups such as Ci to Cw alkyl or alkenyl groups; C₃ to C₆ cycloalkyl groups; Ci to C₃₀ arylalkyl groups; Ci to C₃₀ alkylaryl groups; aryl groups; or any two of R_3] R₄, Rs and Re combine to form an alkylene chain -(CH₂)_q- wherein q is from 3 to 6; wherein any one or more of said straight or branched chain alkyl and alkenyl groups, cycloalkyl groups, arylalkyl groups, alkylaryl groups; aryl groups or alkylene chains is optionally substituted by one to three groups selected from: Ci to C₄ alkoxy, C₂ to C₈ alkoxyalkoxy, C₃ to C₈ cycloalkyl, -OH, -NH₂, -SH, -CO₂(Ci to Ce)alkyl, and -OC(O)(Ci to C₆)alkyl.

11 . The composition according to Clause 10, wherein option (a) applies.

12. The composition according to Clause 10 or 11 , wherein each of R₃ to R₆ independently represent Ci to C₃₀ straight chain or branched alkyl and alkenyl groups, optionally Ci to C₃₀ straight chain or branched alkyl groups, more optionally C₄ to Cis straight chain or branched alkyl groups, such as C₄ to Cw straight chain alkyl groups.

13. The composition according to any one of Clauses 10 to 12, wherein R₃ to R₅ are the same and R₈ is different to R₃ to Rs, optionally wherein R₆ represents methyl, and each of R₃ to R₅ represent octyl.

14. The composition according to any one of Clauses 10 to 12, wherein each of R₃ to R₈ are the same, optionally wherein each of R₃ to R₆ represents butyl. 15. The composition according to any one of Clauses 10 to 14, wherein Y represents P.

16. The composition according to any one of Clauses 1 to 7, wherein the cationic portion is selected from the group consisting of: trioctyl methyl ammonium; tetrabutylphosphonium; trioctylmethyl phosphonium; tetraoctyl ammonium; dioctadecyldiammonium; and

optionally wherein the cationic portion is tetrabutylphosphonium.

17. The composition according to any one of the preceding clauses, wherein the base oil comprises a base stock selected from the group consisting of a Group I base stock, a Group II base stock, a Group III base stock, a Group IV base stock, a Group V base stock, and combinations thereof.

18. The composition according to any one of the preceding clauses, wherein the composition comprises from 0.01 to 10 wt. % (e.g. 0.1 to 5 wt. %) ionic liquid.

19. Use of an ionic liquid as a friction modifier additive in a base oil (e.g. a base oil comprising a base stock selected from the group consisting of a Group I base stock, a Group II base stock, a Group III base stock, a Group IV base stock, a Group V base stock, and combinations thereof), wherein the ionic liquid is as defined in any one of Clauses 1 to 16.

20. A method of reducing the friction of a base oil, said method comprising the steps:

(i) providing a base oil; and (ii) mixing the base oil with an appropriate amount of an ionic liquid, which ionic liquid is as defined in any one of Clauses 1 to 16, optionally wherein the base oil comprises a base stock selected from the group consisting of a Group I base stock, a Group II base stock, a Group III base stock, a Group IV base stock, a Group V base stock, and combinations thereof.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 shows friction coefficient behaviour for a composition according to the invention, which comprises an ionic liquid in a commercial polyol ester (Pentaerythritol tetra- (octanoate/decanoate)).

Figure 2 shows friction coefficient average and measured scar wear diameter average for a composition according to the invention, which comprises an ionic liquid in a commercial polyol ester (Pentaerythritol tetra-(octanoate/decanoate)).

Figure 3 shows friction coefficient behaviour for a composition according to the invention, which comprises an ionic liquid in a commercial polylakylene glycol (alkoxylated decanol, 32 cSt @ 40°C).

Figure 4 shows friction coefficient average and measured scar wear diameter average for a composition according to the invention, which comprises an ionic liquid in a commercial polylakylene glycol (alkoxylated decanol, 32 cSt @ 40°C).

DETAILED DESCRIPTION OF THE INVENTION

In embodiments herein, the word “comprising” may be interpreted as requiring the features mentioned, but not limiting the presence of other features. Alternatively, the word “comprising” may also relate to the situation where only the components/features listed are intended to be present (e.g. the word “comprising” may be replaced by the phrases “consists of’ or “consists essentially of’). It is explicitly contemplated that both the broader and narrower interpretations can be applied to all aspects and embodiments of the present invention. In other words, the word “comprising” and synonyms thereof may be replaced by the phrase “consisting of” or the phrase “consists essentially of’ or synonyms thereof and vice versa.

The phrase “consists essentially of’ and its pseudonyms may be interpreted herein to refer to a material where minor impurities may be present. For example, the material may be greater than or equal to 90% pure, such as greater than 95% pure, such as greater than 97% pure, such as greater than 99% pure, such as greater than 99.9% pure, such as greater than 99.99% pure, such as greater than 99.999% pure, such as 100% pure.

The invention provides a composition comprising: a base oil; and an ionic liquid having an anionic portion having formula la:

(la); and a cationic portion having formula lb:

(X)“⁺ lb where: each Ri is independently selected from a linear or branched C1-C20 aliphatic hydrocarbyl group that is saturated or unsaturated, a C₆.Cio aryl group, and a 5-10 membered heteroaromatic ring system, where the C1-C20 aliphatic hydrocarbyl group is not interrupted or is interrupted by one or more groups selected from an aromatic or non-aromatic ring system having from 5 to 14 atoms, an ester group, an amide group, and a carbamate group, and where the C1-C20 aliphatic hydrocarbyl group is unsubstituted or substituted by one or more groups selected from the group consisting of hydroxyl, primary amino, secondary amino and tertiary amino, where the secondary and tertiary amino groups are substituted by one or two C1-10 hydrocarbyl groups, respectively;

R₂ is selected from the group consisting of a linear or branched C1-C40 aliphatic hydrocarbyl group, a linear or branched C2-C40 polyalkyleneglycol and a moiety formed by removing both hydroxyl groups from isosorbide, where the linear or branched C1-C40 aliphatic hydrocarbyl group and the linear or branched C2-C40 polyalkyleneglycol are saturated or unsaturated, where the linear or branched C1-C40 aliphatic hydrocarbyl group and the linear or branched C2-C40 polyalkyleneglycol is not interrupted or is interrupted by one or more groups selected from an aromatic or non-aromatic ring system having from 5 to 14 atoms, an ester group, an amide group, and a carbamate group, where the linear or branched C1-C40 aliphatic hydrocarbyl group and the linear or branched C2-C40 polyalkyleneglycol are unsubstituted or substituted by one or more groups selected from the group consisting of hydroxyl, primary amino, secondary amino and tertiary amino, where the secondary and tertiary amino groups are substituted by one or two C1-10 hydrocarbyl groups, respectively;

X represents a cationic species, where a is 1 or 2 and n is 1 or 2, provided that: when a is 1 then n is 2, and when a is 2 then n is 1 ; and each J independently represents O or NRN, where RN represents H or a C1-C18 alkyl or alkenyl group.

The composition comprises a base oil. As used herein a “base oil” refers to an oil comprising one or more base stocks. As used herein, a “base stock” is as defined according to API standard 1509, Appendix E. Typical lubricant base stocks that can be used in this invention may include natural base oils, including mineral oils, petroleum oils, paraffinic oils and vegetable oils, as well as oils derived from synthetic sources. In particular, lubricant base stocks that can be used in this invention may be petroleum-based or synthetic stocks including any fluid that falls into the API base stock classification as Group I, Group II, Group III, Group IV, and Group V. The hydrocarbon base oil may be selected from naphthenic, aromatic, and paraffinic mineral oils.

In some embodiments of the invention, the base oil comprises one or more base stocks selected from Group I base stocks, Group II base stocks, Group III base stocks, Group IV base stocks and Group V base stocks.

In some embodiments of the invention, the base oil comprises one or more synthetic oils selected from polyalpha-olefins, synthetic esters, polyalkylene glycols, phosphate esters, alkylated naphthalenes, silicate esters, ionic fluids, or multiply alkylated cyclopentanes.

The composition comprises an ionic liquid. As used herein, the term “ionic liquid” refers to a liquid that is capable of being produced by melting a salt, and when so produced consists solely of ions. An ionic liquid may be formed from a homogeneous substance comprising one species of cation and one species of anion, or it can be composed of more than one species of cation and/or more than one species of anion. Thus, an ionic liquid may be composed of more than one species of cation and one species of anion. An ionic liquid may further be composed of one species of cation, and one or more species of anion. Still further, an ionic liquid may be composed of more than one species of cation and more than one species of anion. The composition may comprise any suitable amount of ionic liquid, for example an amount that is sufficient to provide lubrication to the base oil. In some embodiments of the invention that may be mentioned herein, the composition may comprise from 0.01 to 10 wt. % (e.g. 0.1 to 5 wt. %) ionic liquid.

The term “ionic liquid” includes compounds having both high melting points and compounds having low melting points, e.g. at or below room temperature. Thus, many ionic liquids have melting points below 200°C, preferably below 150°C, particularly below 100°C, around room temperature (15 to 30°C), or even below 0°C. Ionic liquids having melting points below around 30°C are commonly referred to as “room temperature ionic liquids”. In room temperature ionic liquids, the structures of the cation and anion prevent the formation of an ordered crystalline structure and therefore the salt is liquid at room temperature. In some embodiments of the invention, the ionic liquid is liquid at a temperature of below 100°C.

Ionic liquids are most widely known as solvents, because of their negligible vapour pressure, temperature stability, low flammability and recyclability make them environmentally friendly. Due to the vast number of anion/cation combinations that are available it is possible to finetune the physical properties of the ionic liquid (e.g. melting point, density, viscosity, and miscibility with water or organic solvents) to suit the requirements of a particular application.

The ionic liquid useful in the present invention utilises a dual carboxylate and ester/amide functionality. This advantageously provides an anionic portion that has multiple organic chains, the length of which may be adjusted to fine tune the polarity of the ionic liquid for the desired application, as discussed above. The use of ester/amide linkages also enables the ionic liquids to be advantageously biodegradable and environmentally friendly, as well as being easy to synthesise using green processes.

The ionic liquid comprises an ionic liquid having an anionic portion having formula la:

la; and a cationic portion having formula lb:

(X)“⁺ lb where: each Ri is independently selected from a linear or branched C1-C20 aliphatic hydrocarbyl group that is saturated or unsaturated, a CB-CW aryl group, and a 5-10 membered heteroaromatic ring system, where the C1-C20 aliphatic hydrocarbyl group is not interrupted or is interrupted by one or more groups selected from an aromatic or non-aromatic ring system having from 5 to 14 atoms, an ester group, an amide group, and a carbamate group, and where the C1-C20 aliphatic hydrocarbyl group is unsubstituted or substituted by one or more groups selected from the group consisting of hydroxyl, primary amino, secondary amino and tertiary amino, where the secondary and tertiary amino groups are substituted by one or two C1-10 hydrocarbyl groups, respectively;

X represents a cationic species, where a is 1 or 2 and n is 1 or 2, provided that: when a is 1 then n is 2, and when a is 2 then n is 1 ; and each J independently represents O or NR_N, where R_N represents H or a C1-C18 alkyl or alkenyl group.

As used herein, the term “hydrocarbyl” refers to a radical hydrocarbon group, which radical has the valency that will be obvious to a person skilled in the art from the general formula in which the radical is present. In some embodiments of the invention that may be mentioned herein, a hydrocarbyl group may be an aliphatic hydrocarbyl group, such as alkyl/alkylene, alkenyl/alkenylene, and alkynyl/alkynylene, and equivalent groups having a valency of three or more. In a particular embodiment of the invention that may be mentioned herein, a hydrocarbyl group may be a saturated aliphatic group, e.g. an alkyl/alkylene group.

Moieties defined and referred to herein have a valency that will be obvious to a person skilled in the art from the context used. For example, a radical present in a general formula having a single covalent bond from the radical to another moiety will have a valency of one, while a radical present in a general formula having two covalent bonds from the radical to other moieties will have a valency of two. This can be defined generally as a radical present in a general formula having x covalent bonds from the radical to other moieties in the general formula will have a valency of x. By way of example, if the term “alkyl” is used herein in a context that requires two covalent bonds to be formed from the “alkyl” moiety, then the term alkyl in said context is intended to refer to a bivalent radical.

As used herein, an “aliphatic” group is a group that does not comprise an aromatic ring.

An “aromatic” ring refers to a planar ring system comprising 4n+2 delocalised electrons in the pi system, where n is an integer.

Unless otherwise stated, the term “aryl” when used herein includes C₆-Ci₄ (such as C₆.Cio) aryl groups. Such groups may be monocyclic, bicyclic or tricyclic and have between 6 and 14 ring carbon atoms, in which at least one ring is aromatic. The point of attachment of aryl groups may be via any atom of the ring system. However, when aryl groups are bicyclic or tricyclic, they are linked to the rest of the molecule via an aromatic ring. C₆-14 aryl groups include phenyl, naphthyl and the like, such as 1 ,2,3,4-tetrahydronaphthyl, indanyl, indenyl and fluorenyl. Embodiments of the invention that may be mentioned include those in which aryl is phenyl.

As used herein, a “heteroaromatic” group or ring system refers to an aromatic group comprising at least one endocyclic atom that is not carbon. For example, an aromatic group comprising at least one endocyclic atom selected from the group consisting of N, O, and S.

As used herein, “interrupted” in the context of a group defined herein means that one or more covalent bonds in said group is replaced by a moiety as defined. When a group having a defined number of carbon atoms is interrupted by a carbon-containing group, the carbon atoms of said interrupting group do not count towards the number of carbon atoms of said interrupted group. For the avoidance of doubt, an aliphatic group as defined herein may be interrupted by an aromatic group. Moieties defined herein may be interrupted by one or more groups (e.g. from 1 to 5 groups, from 1 to 4 groups, from 1 to 3 groups, from 1 to 2 groups, or 1 group). For example, moieties defined herein may be interrupted by one or more groups selected from an aromatic or non-aromatic ring system having from 5 to 14 atoms, an ester group, an amide group, and a carbamate group. In some embodiments, the interrupting group may be an aromatic or non-aromatic ring system having from 5 to 14 atoms. In some embodiments, he interrupting group may be an ester group, an amide group, or a carbamate group.

Suitable interrupting aromatic or non-aromatic ring systems having from 5 to 14 atoms include cycloalkyl groups, cycloalkenyl groups, heterocycloalkyl groups, heterocycloalkenyl groups, aryl groups, and heteroaromatic groups having from 5 to 14 atoms in the ring system, such as from 5 to 10 atoms. In a specific embodiment of the invention that may be mentioned herein, the interrupting aromatic or non-aromatic ring system having from 5 to 14 atoms may be selected from aromatic and heteroaromatic groups having 5 or 6 atoms in the ring system, such as aryl and furan. Interrupting aromatic or non-aromatic ring systems may themselves be substituted as defined herein. In such cases, the number of atoms of the substituent does not count towards the number of atoms in the aromatic or non-aromatic ring system, which is from 5 to 14 atoms.

Moieties defined herein may also be interrupted by an ester group, said an amide group, or a carbamate group.

• In this context, an ester group means -O-C(=O)- or -C(=O)-O-

• In this context, an amide group means -NR_Na-C(=O)- or -C(=O)-NR_Na-, where R_Na is a C1-6 alkyl group.

• In this context, a carbamate group means -NRNa-C(=O)-O- or -O-C(=O)-NRNa-, where R_Na is a Ci-₆ alkyl group.

As used herein, “substituted” in the context of a group defined herein means that one or more hydrogen atoms in said group is replaced by a substituting moiety. When a group having a defined number of carbon atoms is substituted by a carbon-containing group, the carbon atoms of said substituting group do not count towards the number of carbon atoms of said substituted group. Moieties defined herein may be substituted by any appropriate number of groups as defined herein, for example from 1 to 5 groups, from 1 to 4 groups, from 1 to 3 groups, from 1 to 2 groups, or 1 group. Examples of suitable substituents include hydroxy, amino (whether primary, secondary or tertiary), hydrocarbyl groups (e.g. C1-20, such as C1-10 hydrocarbyl) As used herein “polyalkyleneglycol” refers to a moiety of the formula -[O-R]n-O, or where the context requires, H-[O-R]_n-O-H, where R represents an alkylene group (e.g. a C1-10 or C1-4 alkylene) and n represents an integer. A polyalkyleneglycol may comprise different R groups, or may comprise R groups that are all identical. A skilled person would easily understand from context when “polyalkyleneglycol” is intended to refer to a moiety -[O-R]_n-O-, e.g. when a bivalent moiety represents a polyalkyleneglycol group.

In some embodiments that may be mentioned herein, a polyalkyleneglycol chain in the ionic liquid may be derived from a homopolymer (e.g. is derived from polyethyleneglycol, polypropyleneglycol or polybutyleneglycol).

In some embodiments that may be mentioned herein, a polyalkyleneglycol chain in the ionic liquid may be derived from a block copolymer (e.g. is derived from a poly(ethoxylated)(propoxylated)glycol, a poly(propoxylated)(butoxylated)glycol) or a poly(ethoxylated)(butoxylated)glycol).

As used herein, “alkyl” refers to an unbranched or branched, cyclic, saturated hydrocarbyl radical, which may be substituted or unsubstituted.

As used herein, “alkenyl” refers to an unbranched or branched, cyclic, unsaturated hydrocarbyl radical, which may be substituted or unsubstituted. As used herein, an alkenyl group may comprise one, or more than one, carbon-carbon double bonds or carbon-carbon triple bonds. For the avoidance of doubt, the term “alkenyl” as used herein is intended to cover groups comprising C-C triple bonds (also known as alkynyl groups).

In general, each R1 is independently selected from a linear or branched C1-C20 aliphatic hydrocarbyl group that is saturated or unsaturated, a C₆.Cio aryl group, and a 5-10 membered heteroaromatic ring system, where the C1-C20 aliphatic hydrocarbyl group is not interrupted or is interrupted by one or more groups selected from an aromatic or non-aromatic ring system having from 5 to 14 atoms, an ester group, an amide group, and a carbamate group, and where the C1-C20 aliphatic hydrocarbyl group is unsubstituted or substituted by one or more groups selected from the group consisting of hydroxyl, primary amino, secondary amino and tertiary amino, where the secondary and tertiary amino groups are substituted by one or two C1-10 hydrocarbyl groups, respectively.

In some embodiments of the invention that may be mentioned herein, each R1 may be independently selected from a phenyl group, a furan group or, more particularly, a linear or branched C4-C18 (e.g. C4-C12) aliphatic hydrocarbyl group that is saturated or unsaturated. For example, a 1 ,4-valent phenyl group, a 2,5-valent furan group, or more particularly, a linear or branched CB-CW aliphatic hydrocarbyl group that is saturated or unsaturated (e.g. a linear or branched C₆-Ci₀ alkylene group that is saturated or unsaturated).

In some embodiments of the invention that may be mentioned herein, each R1 may independently represent a linear or branched C₄-Ci₈ (e.g. C4-C12) alkylene group.

In some embodiments of the invention that may be mentioned herein, each R1 may independently represent a moiety formed by removing both carboxylic acid groups from a compound selected from the list consisting of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1 ,12-dodecanedioic acid, 1 ,18-octadecanedioic acid, terephthalic acid, isophthalic acid, phthalic acid, and 2,5- furandicarboxylic acid.

In some embodiments of the invention that may be mentioned herein, R₂, or more particularly R1, may represent, or be derived from, an alkanolamino group. In other words, the linear or branched C1-C20 aliphatic hydrocarbyl group or C1-C40 aliphatic hydrocarbyl group (e.g. C1-C40 aliphatic hydrocarbyl group) is substituted by one or more (e.g. one, two or three) hydroxyl groups and one or more (e.g. one, two or three) groups selected from the group consisting of primary amino, secondary amino and tertiary amino.

In some embodiments of the invention that may be mentioned herein, R₂, or more particularly R1, may represent, or be derived from, an ester polyol. In other words, the linear or branched C1-C20 aliphatic hydrocarbyl group or C1-C40 aliphatic hydrocarbyl group (e.g. C1-C40 aliphatic hydrocarbyl group) is interrupted by one or more (e.g. one, two or three) ester groups and/or is substituted by one or more (e.g. one, two or three) hydroxyl groups.

In some embodiments of the invention that may be mentioned herein, each J may represent O.

In general, R₂ is selected from the group consisting of a linear, branched or cyclic C1-C40 aliphatic hydrocarbyl group that is saturated or unsaturated, a linear or branched C2-C40 polyalkyleneglycol group, a C₆-C₂2 aryl group, a moiety formed by removing two hydroxyl groups from a sugar alcohol, and a moiety formed by removing two hydroxyl groups from a dehydrated sugar alcohol or isosorbide, where the linear or branched C1-C40 aliphatic hydrocarbyl group and the linear or branched C2-C40 polyalkyleneglycol are saturated or unsaturated, where the linear or branched C1-C40 aliphatic hydrocarbyl group and the linear or branched C2-C40 polyalkyleneglycol is not interrupted or is interrupted by one or more groups selected from an aromatic or non-aromatic ring system having from 5 to 14 atoms, an ester group, an amide group, and a carbamate group, where the linear or branched C1-C40 aliphatic hydrocarbyl group and the linear or branched C2-C40 polyalkyleneglycol are unsubstituted or substituted by one or more groups selected from the group consisting of hydroxyl, primary amino, secondary amino and tertiary amino, where the secondary and tertiary amino groups are substituted by one or two C1-10 hydrocarbyl groups, respectively;

In some embodiments of the invention that may be mentioned herein, R2 may be selected from the group consisting of a moiety formed by removing both hydroxyl groups from isosorbide, or more particularly, a linear or branched C2-C20 aliphatic hydrocarbyl group and a linear or branched C2-C20 polyalkyleneglycol, where the linear or branched C2-C20 aliphatic hydrocarbyl group and the linear or branched C2-C20 polyalkyleneglycol are saturated or unsaturated, where the linear or branched C2-C20 aliphatic hydrocarbyl group and the linear or branched C2-C20 polyalkyleneglycol are not interrupted or is interrupted by one or more groups selected from an aromatic or non-aromatic ring system having 5 or 6 atoms, an amide group, and a carbamate group.

In some embodiments of the invention that may be mentioned herein, R₂ may represent a moiety formed by removing both hydroxyl groups from isosorbide, or more particularly, a linear or branched C3-C16 aliphatic hydrocarbyl group that is saturated or unsaturated, which hydrocarbyl group is not interrupted or is interrupted by one or more groups selected from an aromatic or non-aromatic ring system having 5 or 6 atoms. For example, R₂ may represent a moiety formed by removing both hydroxyl groups from isosorbide, or more particularly, a linear or branched C3-10 aliphatic hydrocarbyl group.

In some embodiments of the invention that may be mentioned herein, each J may represent O and R₂ may represent a moiety formed by removing both hydroxyl groups from a compound selected from the following: neopentyl glycol, 1 ,5-pentanediol, 1 ,9-nonanediol, 1 ,6-hexanediol, 2-methyl-1 ,3- propanediol, 2,5-hexanediol, 2,7-octanediol, a saturated straight chain C₂s 1 ,14-diol, an unsaturated straight chain C₂₈ 1 ,14-diol,

where each Z independently represents a Ci to Ci₂ aliphatic hydrocarbyl group.

In some embodiments of the invention that may be mentioned herein, R₂ may represent a C4-16 alkylene group and each J represents NH.

In some embodiments of the invention that may be mentioned herein, R₂ may represent propylene, one J may represent NH and the other J may represent NR_N where R_N represents oleyl.

The ionic liquid comprises a cationic portion having formula lb:

(X)“⁺ lb

X represents a cationic species, where a is 1 or 2 and n is 1 or 2, provided that: when a is 1 then n is 2, and when a is 2 then n is 1 .

Thus, a and n are together selected to balance the charge of the anionic portion of the ionic liquid, which is 2-. In some embodiments of the invention that may be mentioned herein, a may represent 1. In other words, the cationic species X may have a charge of +1. In such embodiments, n may represent 2.

The cationic portion may be selected from any appropriate cationic portion that does not interfere with components in the base oil. In some embodiments of the invention that may be mentioned herein, the cationic portion may be selected from one or more of the group consisting of a quaternary phosphonium cation, a quaternary sulphonium cation, a quaternary ammonium cation comprising at least one amide group, a quaternary ammonium cation comprising at least one ester group, a substituted quaternary imidazolium cation comprising at least one ester group, a substituted quaternary imidazolium cation comprising at least one alkyleneglycol group, a substituted quaternary imidazolium cation comprising at least one amide group, azaannulenium, azathiazolium, benzimidazolium, benzofuranium, benzothiophenium, benzotriazolium, borolium, cinnolinium, diazabicyclodecenium, diazabicyclononenium, 1 ,4-diazabicyclo[2.2.2]octanium, diazabicyclo-undecenium, dibenzofuranium, dibenzothiophenium, dithiazolium, dithiazolium, furanium, guanidinium, imidazolium, indazolium, indolinium, indolium, morpholinium, oxaborolium, oxaphospholium, oxazinium, oxazolium, /so-oxazolium, oxazolinium, pentazolium oxothiazolium, phospholium, phosphonium, phthalazinium, piperazinium, piperidinium, pyranium, pyrazinium, pyrazolium, pyridazinium, pyridinium, pyrimidinium, pyrrolidinium, pyrrolium, quinazolinium, quinolinium, /soquinolinium, quinoxalinium, quinuclidinium, selenazolium, sulfonium, tetrazolium, thiadiazolium, /so-thiadiazolium, thiazinium, thiazolium, /so-thiazolium, thiophenium, thiuronium, triazadecenium, triazinium, triazolium, /so-triazolium, combinations thereof, and cationic molecules comprising more than one of the foregoing.

As mentioned above, the cationic portion may represent a species comprising more than one cationic group. For example, the cationic portion may represent a species comprising two cationic groups, each having a charge of 1+.

In some embodiments of the invention that may be mentioned herein, the cationic portion may have the formula [YRsF^RsRef, wherein:

Y represents N, P or S (e.g. N or P).

In such embodiments, each of R3 to Re may be independently selected from Ci to C30 straight chain or branched alkyl and alkenyl groups; C3 to Ce cycloalkyl groups; Ci to C30 arylalkyl groups; Ci to C30 alkylaryl groups; aryl groups; or any two of R₃ to R₆ combine to form an alkylene chain -(CH2)q- wherein q is from 3 to 6; wherein any one or more of said straight or branched chain alkyl and alkenyl groups, cycloalkyl groups, arylalkyl groups, alkylaryl groups; aryl groups or alkylene chains are optionally substituted by one to three groups selected from: Ci to C₄ alkoxy, C₂ to C₈ alkoxyalkoxy, C₃ to C₆ cycloalkyl, -OH, -NH₂, -SH, -CO₂(Ci to C₆)alkyl, and -OC(O)(Ci to C₆)alkyl; or

Alternatively, in such embodiments at least one of R₃ to R₆ may have the formula -R7O(C=O)R₈ or -R₇(C=O)-O-R₈, wherein R₇ is a Ci to Cw straight chain or branched alkyl or alkenyl group, or a C₃ to C₈ cycloalkyl or cycloalkenyl group; and R₈ is a Ci to C₃₀ straight chain or branched alkyl or alkenyl group; a C₃ to C₆ cycloalkyl group; a Ci to C₃o arylalkyl group; a Ci to C₃o alkylaryl group; an aryl group; or any two respective R₈ groups combine to form an alkylene chain -(CH₂)_q- wherein q is from 3 to 6; wherein R₇ and/or R₈ are optionally substituted by one to three groups selected from: Ci to C₄ alkoxy, C₂ to C₈ alkoxyalkoxy, C₃ to C₆ cycloalkyl, -OH, -NH₂, -SH, -CO₂(Ci to C₆)alkyl, and -OC(O)(Ci to C₆)alkyl; and the other of R₃ to R₆ that are not as defined above may be independently selected from Ci to C₃o straight chain or branched alkyl and alkenyl groups such as Ci to Cw alkyl or alkenyl groups; C₃ to C₆ cycloalkyl groups; Ci to C₃₀ arylalkyl groups; Ci to C₃₀ alkylaryl groups; aryl groups; or any two of R₃, R₄, Rs and R₈ combine to form an alkylene chain -(CH₂)_q- wherein q is from 3 to 6; wherein any one or more of said straight or branched chain alkyl and alkenyl groups, cycloalkyl groups, arylalkyl groups, alkylaryl groups; aryl groups or alkylene chains is optionally substituted by one to three groups selected from: Ci to C₄ alkoxy, C₂ to C₈ alkoxyalkoxy, C₃ to C₆ cycloalkyl, -OH, -NH₂, -SH, -CO₂(Ci to C₆)alkyl, and -OC(O)(Ci to C₆)alkyl.

In some embodiments of the invention that may be mentioned herein, each of R₃ to R₆ may independently represent Ci to C₃₀ straight chain or branched alkyl and alkenyl groups, such as Ci to C₃₀ straight chain or branched alkyl groups, for example C₄ to C straight chain or branched alkyl groups. In a specific embodiment of the invention that may be mentioned herein, R₃ to R₆ may independently represent C₄ to Ci₈ straight chain alkyl groups.

In some embodiments of the invention that may be mentioned herein, R₃ to R₅ may be the same and R₈ may be different to R₃ to Rs. For example, R₈ may represent methyl, and each of R₃ to R₅ may represent octyl.

In other embodiments of the invention that may be mentioned herein, each of R₃ to R₈ may be the same. For example, each of R₃ to R₈ may represent butyl. In some embodiments of the invention that may be mentioned herein, Y may represent P.

In some embodiments of the invention that may be mentioned herein, the cationic portion may be selected from the group consisting of: trioctyl methyl ammonium; tetrabutylphosphonium; trioctylmethyl phosphonium; tetraoctyl ammonium; dioctadecyldiammonium; and

In some embodiments of the invention that may be mentioned herein, the cationic portion may be tetrabutylphosphonium.

The invention also provides the use of an ionic liquid as a friction modifier additive in a base oil (e.g. a base oil comprising a base stock selected from the group consisting of a Group I base stock, a Group II base stock, a Group III base stock, a Group IV base stock, a Group V base stock, and combinations thereof), wherein the ionic liquid is as defined herein.

The invention also provides a method of reducing the friction of a base oil, said method comprising the steps:

(i) providing a base oil; and

(ii) mixing the base oil with an appropriate amount of an ionic liquid, which ionic liquid is as defined herein.

As explained herein, the base oil may comprise a base stock selected from the group consisting of a Group I base stock, a Group II base stock, a Group III base stock, a Group IV base stock, a Group V base stock, and combinations thereof. The invention is illustrated by the below Examples, which are not to be construed as limitative.

EXAMPLES

Starting materials for ionic liquid synthesis were purchased from Sigma-Aldrich.

Example 1 : Synthesis of 5B-DC12 and 5B-DC10

5B-DC12:

110 g (0.4728 mol) of dodecanedioic acid (99% purity) and 24.87 g (0.2364 mol) of neopentyl glycol (99% purity) were mixed in a round bottom flask fitted with a gas inlet tube for nitrogen gas blanketing, with magnetic bar on a magnetic stirrer, a distillation column fitted with a cooled condenser and collection flask to collect distilled water by-product. The mixture was initially homogenized at 100°C using mechanical stirring, followed by gradual temperature increase to 180°C and subsequently to 210°C over 5 hours In order to drive the esterification to near completion, nitrogen gas was sparged into the reaction mixture at a rate of 0.5 SCFH. The reaction was deemed complete when no more water distilled water was collected. Upon cooling, a white waxy solid product was obtained (5B-DC12). The esters were characterised by ¹H NMR, ¹³C NMR and FTIR to confirm the formed structure.

5B-DC12 (neopentylglycol didodecanedioate), C29H52O8:

¹H NMR (CD3OD, 400 MHz) 6 (ppm) 3.87 (s, 4H), 2.32 (m, 4H, J = 8.0 Hz), 2.26 (m, 4H, J = 8.0 Hz), 1.58 (m, 8H, J = 8.0 Hz), 1.30 (m, 24H), 0.97 (s, 6H). ¹³C{¹H} NMR (CD3OD, 101 MHz): 6 (ppm) 176.33, 173.87, 68.66, 34.33, 33.57, 29.12, 28.97, 24.70, 20.68 FT-IR (cm ¹): 3031.97, 2918.77, 2850.82, 1735.73, 1694.62, 1466.89, 1431.89, 1383.90, 1279.85, 1221.84, 1167.75, 1002.92, 931.58, 723.69, 683.19.

5B-DC10:

108 g (0.529 mol) of sebacic acid (99% purity) and 27.55 g (0.2645 mol) of neopentyl glycol (99% purity) were mixed in a round bottom flask fitted with a gas inlet tube for nitrogen gas blanketing, with magnetic bar on a magnetic stirrer, a distillation column fitted with a cooled condenser and collection flask to collect distilled water by-product. The mixture was initially homogenized at 100°C using mechanical stirring, followed by gradual temperature increase to 180°C and subsequently to 210°C hours. In order to drive the esterification to near completion, nitrogen gas was sparged into the reaction mixture at a rate of 0.5 SCFH. The reaction was deemed complete when no more water distilled water was collected. Upon cooling, a white waxy solid product was obtained (5B-DC10). The esters were characterised by ¹H NMR, ¹³C NMR and FTIR to confirm the formed structure.

5B-DC10 (neopentylglycol disebacate), C25H44O8:

¹H NMR (CDCh, 400 MHz): 6 (ppm) 3.88 (s, 4H), 2.33 (m, 8H, J = 8.0 Hz), 1 .61 (m, 8H, J = 8.0 Hz), 1.31 (m, 16H), 0.96 (s, 6H).

¹³C{¹H} NMR (CDCh, 101 MHz): 6 (ppm) 179.78, 173.77, 69.05, 34.64, 34.26, 33.99, 29.09, 28.91 , 24.92, 21.76

FT-IR (cm ¹): 3031.97, 2933.65, 2852.76, 1738.44, 1701.48, 1470.79, 1303.77, 1242.73, 1178.69, 1005.87, 932.98, 724.39, 680.49.

Example 2: Formation of ionic liquids ILN18-5B-DC12 and ILP4-5B-DC10

ILN18-5B-DC12

In a round bottom flask, 4.1825 g (7.911 mmol) of synthesised 5B-DC12 (Example 1) was dissolved in 50 mL of ethanol. 4.1825 g (7.911 mmol) of trioctyl methyl ammonium methyl carbonate (50%) solution was charged into an addition funnel attached to the flask containing the ester solution, then the cation solution was slowly added at about 1 drop per second until completion. The mixture was stirred uninterrupted at room temperature overnight, followed by 2 h stirring at 50°C. The reaction formed methanol and CO₂ as byproducts, which were removed by rotary evaporation along with the ethanol solvent. The ionic liquid was further purified by high vacuum Schlenk-line drying overnight, resulting into an amber viscous liquid end product at 99% yield. The structure was confirmed by ¹H NMR, ¹³C NMR and FTIR spectroscopy.

ILN18-5B-DC12 (bis-(trioctyl methylammonium) didodecanedioate), C79H158N2O8:

¹H NMR (CD3OD, 400 MHz): 6 (ppm) 3.91 (s, 4H), 3.25 (m, 12H, J = 4.0 Hz), 3.00 (s, 6H), 2.33 (m, 4H, J = 4.0 Hz), 2.16 (m, 4H, J = 4.0 Hz), 1.71 (m, 12H), 1.59 (m, 8H), 1.35 (m, 84H), 0.98 (s, 6H), 0.91 (m, 18H).

¹³C{¹H} NMR (CD3OD, 101 MHz): 6 (ppm) 182.87, 175.89, 70.44, 63.10, 39.39, 36.11 , 35.42, 33.23, 30.55, 27.76, 26.50, 24.04, 23.51 , 22.41 , 14.76

FT-IR (cm ¹): 2923.64, 2854.74, 1735.82, 1578.55, 1466.80, 1376.72, 1251.89, 1175.86, 1073.89, 901.89, 732.88, 629.80, 586.40, 473.59.

The ionic liquid ILN18-5B-DC12 comprised:

as the anionic portion (1 equivalent); and trioctyl methyl ammonium (2 equivalents) as the cationic portion.

The ashless nature of the formed ionic liquid was confirmed by thermo-gravimetric analysis under nitrogen (0.4788 wt. % residue).

ILP4-5B-DC10

In a single neck round bottom flask equipped with a magnetic stirrer, 0.9963 g (2.02 mmol) of 5B-DC10 (Example 1) was dissolved in 10mL of ethanol. The mixture was stirred until solution was clear. In an addition funnel, 2.7973 g of tetrabutyl phosphonium hydroxide [P4444][OH] (4.04 mmol, 40% purity) was charged, and 10 mL of ethanol was added with stirring. The solution was then attached to the round bottom flask and the base was slowly dropped into the solution. Once done, the mixture was stirred for about 2 h before high vacuum distillation to dry off the solvent and water. The final product, which was a clear viscous liquid was collected with the product yield of 98%, characterised by ¹H NMR, ¹³C NMR, ³¹P NMR and FTIR spectroscopy.

ILP4-5B-DC10 (bis-(tetrabutyl phosphonium) disebacate), C57H114O8P2:

¹H NMR (CDCh, 400 MHz): 6 (ppm) 3.85 (s, 4H), 2.45 (m, 16H, J = 12.0 Hz), 2.27 (m, 4H, J = 4.0 Hz), 2.13 (m, 4H, J = 4.0 Hz), 1.58 (m, 8H), 1.49 (m, 32H), 1.26 (m, 16H), 0.94 (m, 30H).

¹³C{¹H} NMR (CDCh, 101 MHz): 6 (ppm) 178.41 , 172.82, 68.06, 38.91 , 33.67, 33.35, 29.49, 28.58, 28.25, 28.09, 24.06, 23.13, 22.97, 17.95, 17.48, 12.52.

³¹P NMR (CDCh, 162 MHz): 6 (ppm) 33.15.

FT-IR (cm ¹): 2928.81 , 2858.87, 1734.70, 1574.57, 1464.85, 1373.72, 1302.92, 1238.88, 1097.86, 1003.92, 908.69, 815.59, 723.88.

The ionic liquid ILP4-5B-DC10 comprised:

as the anionic portion (1 equivalent); and tetrabutyl phosphonium (2 equivalents) as the cationic portion.

Example 3: ILN18-5B-DC12 in lubricant base oils

ILN18-5B-DC12 was mixed in mineral base oil Group III+ (ETRO 4+), a commercial polyol ester of pentaerythritol derivative (PALMESTER 3971) and a commercial polyalkylene glycol (UCON OSP-32) at 1 wt. % concentration, respectively, to assess solubility and for tribology evaluation. Samples were prepared by mixing the solutions at 60°C for 1 h.

Experimental Solubility

Computer-modelled solubility

Liquid-liquid equilibrium (LLE) was calculated by COSMOtherm software in non-polar medium.

Calculated stable solubility of neutral and resultant IL compounds based on LLE point in non-polar model base oil (n-hexadecane), concentration by mass fraction (g/g), level of parameterization = TZVP-fine, at 2 different temperatures (25°C and 60°C). The LLE point in mass fraction (g/g) at 25°C was 2.5107 x 10^-19, while the LLE point in mass fraction (g/g) at 60°C was 3.157 x 10¹⁷.

ILN18-5B-DC12 was insoluble in non-polar base oils, soluble in commercial polyol esters of at least triester groups (by experiment) and soluble in commercial polyalkylene glycol (PAG) fluid (by experiment).

Tribology Evaluation

High Frequency Reciprocating Rig (HFRR): tribology test rubbing of ball to disc metal specimens, under pure sliding contact (boundary lubrication regime), load at 400 g, frequency at 20 Hz, temperature at 120°C for 60 mins. Only visually soluble solutions were evaluated, therefore, only Formulation 2 and Formulation 3 were tested. Reported values were the average of minimum 2 replicate runs.

Results for 1 wt% ILN18-5B-DC12 in commercial polyol ester 1 (Pentaerythritol tetra- (octanoate/decanoate), PALMESTER 3971):

• Friction coefficient behaviour over contact time is shown in Figure 1. The results show a significant friction reduction for polyol ester with 1 wt% ILN18-5B-DC12 compared to the baseline fluid.

• Friction coefficient average and measured wear scar diameter average from HFRR is shown in Figure 2. The results show a 56% friction reduction and 51% wear scar diameter reduction compared to the baseline fluid.

Results for 1 wt% ILN18-5B-DC12 in commercial polyalkylene glycol 1 (alkoxylated decanol, 32 cSt @ 40°C, UCON OSP-32)

• Friction coefficient behaviour over contact time is shown in Figure 3. The results also the reduction of friction, though to a lesser extent than for commercial polyol ester 1 . • Friction coefficient average and measured wear scar diameter average from HFRR is shown in Figure 4. The results show a 14% friction reduction and 41% wear scar diameter reduction compared to the baseline fluid.

The results demonstrate the efficacy of ionic liquids disclosed here in the reduction of friction in base fluids.

T1

Claims

1 . A composition comprising: a base oil; and an ionic liquid having an anionic portion having formula la:

la; and a cationic portion having formula lb:

R₂ is selected from the group consisting of a linear, branched or cyclic C1-C40 aliphatic hydrocarbyl group that is saturated or unsaturated, a linear or branched C2-C40 polyalkyleneglycol group, a C₆-C₂2 aryl group, a moiety formed by removing two hydroxyl groups from a sugar alcohol, and a moiety formed by removing two hydroxyl groups from a dehydrated sugar alcohol or isosorbide, where the linear or branched C1-C40 aliphatic hydrocarbyl group and the linear or branched C2-C40 polyalkyleneglycol are saturated or unsaturated, where the linear or branched C1-C40 aliphatic hydrocarbyl group and the linear or branched C2-C40 polyalkyleneglycol is not interrupted or is interrupted by one or more groups selected from an aromatic or non-aromatic ring system having from 5 to 14 atoms, an ester group, an amide group, and a carbamate group, where the linear or branched C1-C40 aliphatic hydrocarbyl group and the linear or branched C2-C40 polyalkyleneglycol are unsubstituted or substituted by one or more groups selected from the group consisting of hydroxyl, primary amino, secondary amino and tertiary amino, where the secondary and tertiary amino groups are substituted by one or two C1-10 hydrocarbyl groups, respectively;

2. The composition according to Claim 1 , wherein: each R1 is independently selected from a phenyl group, a furan group or, more particularly, a linear or branched C₄-Ci₈ (e.g. C4-C12) aliphatic hydrocarbyl group that is saturated or unsaturated, optionally wherein each R1 is independently selected from a 1 ,4-valent phenyl group, a 2,5-valent furan group, or more particularly, a linear or branched Ce-Cw aliphatic hydrocarbyl group that is saturated or unsaturated.

3. The composition according to Claim 2, wherein each R1 independently represents a moiety formed by removing both carboxylic acid groups from a compound selected from the list consisting of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1 ,12-dodecanedioic acid, 1 ,18-octadecanedioic acid, terephthalic acid, isophthalic acid, phthalic acid, and 2,5-furandicarboxylic acid.

4. The composition according to any one of the preceding claims, wherein one or more of the following applies:

(e) each J represents O.

5. The composition according to any one of the preceding claims, wherein R₂ is selected from the group consisting of a moiety formed by removing both hydroxyl groups from isosorbide, or more particularly, a linear or branched C₂-C₂o aliphatic hydrocarbyl group and a linear or branched C₂-C₂₀ polyalkyleneglycol, where the linear or branched C₂-C₂o aliphatic hydrocarbyl group and the linear or branched C₂-C₂₀ polyalkyleneglycol are saturated or unsaturated, where the linear or branched C₂-C₂o aliphatic hydrocarbyl group and the linear or branched C₂-C₂₀ polyalkyleneglycol are not interrupted or is interrupted by one or more groups selected from an aromatic or non-aromatic ring system having 5 or 6 atoms, an amide group, and a carbamate group.

6. The composition according to Claim 4, wherein R₂ represents a moiety formed by removing both hydroxyl groups from isosorbide, or more particularly, a linear or branched C3-C16 aliphatic hydrocarbyl group that is saturated or unsaturated, which hydrocarbyl group is not interrupted or is interrupted by one or more groups selected from an aromatic or non- aromatic ring system having 5 or 6 atoms, optionally wherein R₂ represents a moiety formed by removing both hydroxyl groups from isosorbide, or more particularly, a linear or branched C3-10 aliphatic hydrocarbyl group.

7. The composition according to any one of the preceding claims, wherein:

(a) each J represents O and R₂ represents a moiety formed by removing both hydroxyl groups from a compound selected from the following: neopentyl glycol, 1 ,5-pentanediol, 1 ,9-nonanediol, 1 ,6-hexanediol, 2-methyl-1 ,3-propanediol, 2,5-hexanediol, 2,7-octanediol, a saturated straight chain C₂₈ 1 ,14-diol, an unsaturated straight chain C₂₈ 1 ,14-diol,

R₂ represents a C4-16 alkylene group and each J represents NH; or

R₂ represents propylene, one J represents NH and the other J represents NRN where RN represents oleyl.

8. The composition according to any one of the preceding claims, wherein a is 1 .

9. The composition according to any one of the preceding claims, wherein the cationic portion is selected from one or more of the group consisting of a quaternary phosphonium cation, a quaternary sulphonium cation, a quaternary ammonium cation comprising at least one amide group, a quaternary ammonium cation comprising at least one ester group, a substituted quaternary imidazolium cation comprising at least one ester group, a substituted quaternary imidazolium cation comprising at least one alkyleneglycol group, a substituted quaternary imidazolium cation comprising at least one amide group, azaannulenium, azathiazolium, benzimidazolium, benzofuranium, benzothiophenium, benzotriazolium, borolium, cinnolinium, diazabicyclodecenium, diazabicyclononenium, 1 ,4- diazabicyclo[2.2.2]octanium, diazabicyclo-undecenium, dibenzofuranium, dibenzothiophenium, dithiazolium, dithiazolium, furanium, guanidinium, imidazolium, indazolium, indolinium, indolium, morpholinium, oxaborolium, oxaphospholium, oxazinium, oxazolium, /so-oxazolium, oxazolinium, pentazolium oxothiazolium, phospholium, phosphonium, phthalazinium, piperazinium, piperidinium, pyranium, pyrazinium, pyrazolium, pyridazinium, pyridinium, pyrimidinium, pyrrolidinium, pyrrolium, quinazolinium, quinolinium, /soquinolinium, quinoxalinium, quinuclidinium, selenazolium, sulfonium, tetrazolium, thiadiazolium, /so-thiadiazolium, thiazinium, thiazolium, /so-thiazolium, thiophenium, thiuronium, triazadecenium, triazinium, triazolium, /so-triazolium, combinations thereof, and cationic molecules comprising more than one of the foregoing.

10. The composition according to any one of the preceding claims, wherein the cationic portion has the formula [YR₃R₄RsR6]⁺, wherein:

Y represents N, P or S (e.g. N or P); and

(a) each of R₃ to R₆ are independently selected from Ci to C₃₀ straight chain or branched alkyl and alkenyl groups; C₃ to C₆ cycloalkyl groups; Ci to C₃₀ arylalkyl groups; Ci to C₃₀ alkylaryl groups; aryl groups; or any two of R₃ to R₆ combine to form an alkylene chain -(CH2)q- wherein q is from 3 to 6; wherein any one or more of said straight or branched chain alkyl and alkenyl groups, cycloalkyl groups, arylalkyl groups, alkylaryl groups; aryl groups or alkylene chains are optionally substituted by one to three groups selected from: Ci to C₄ alkoxy, C₂ to C₈ alkoxyalkoxy, C₃ to C₆ cycloalkyl, -OH, -NH₂, -SH, -CO₂(Ci to C₆)alkyl, and -OC(O)(Ci to C₆)alkyl; or

(b) at least one of R₃ to R₆ have the formula -R₇O(C=O)R₈ or -R₇(C=O)-O-R₈, wherein R₇ is a Ci to Cw straight chain or branched alkyl or alkenyl group, or a C₃ to C₈ cycloalkyl or cycloalkenyl group; and R₈ is a Ci to C₃o straight chain or branched alkyl or alkenyl group; a C₃ to C₆ cycloalkyl group; a Ci to C₃₀ arylalkyl group; a Ci to C₃o alkylaryl group; an aryl group; or any two respective R₈ groups combine to form an alkylene chain -(CH₂)_q- wherein q is from 3 to 6; wherein R₇ and/or R₈ are optionally substituted by one to three groups selected from: Ci to C₄ alkoxy, C₂ to C₈ alkoxyalkoxy, C₃ to C₆ cycloalkyl, -OH, -NH₂, -SH, -CO₂(Ci to C₆)alkyl, and -OC(O)(Ci to C₆)alkyl; and wherein the other of R₃ to R₆ that are not as defined above are independently selected from Ci to C₃o straight chain or branched alkyl and alkenyl groups such as Ci to Cw alkyl or alkenyl groups; C₃ to C₆ cycloalkyl groups; Ci to C₃₀ arylalkyl groups; Ci to C₃₀ alkylaryl groups; aryl groups; or any two of R_3] R₄, R₅ and R₆ combine to form an alkylene chain -(CH₂)_q- wherein q is from 3 to 6; wherein any one or more of said straight or branched chain alkyl and alkenyl groups, cycloalkyl groups, arylalkyl groups, alkylaryl groups; aryl groups or alkylene chains is optionally substituted by one to three groups selected from: Ci to C₄ alkoxy, C₂ to C₈ alkoxyalkoxy, C₃ to C₆ cycloalkyl, -OH, -NH₂, -SH, -CO₂(Ci to C₆)alkyl, and -OC(O)(Ci to Ce)alkyl.

11 . The composition according to Claim 10, wherein option (a) applies.

12. The composition according to Claim 10 or 11 , wherein each of R₃ to R₈ independently represent Ci to C₃₀ straight chain or branched alkyl and alkenyl groups, optionally Ci to C30 straight chain or branched alkyl groups, more optionally C₄ to Ci₈ straight chain or branched alkyl groups, such as C₄ to Cis straight chain alkyl groups.

13. The composition according to any one of Claims 10 to 12, wherein R₃ to R₅ are the same and R₆ is different to R₃ to R₅, optionally wherein R₆ represents methyl, and each of R₃ to R₅ represent octyl.

14. The composition according to any one of Claims 10 to 12, wherein each of R₃ to Re are the same, optionally wherein each of R₃ to Re represents butyl.

15. The composition according to any one of Claims 10 to 14, wherein Y represents P.

16. The composition according to any one of Claims 1 to 7, wherein the cationic portion is selected from the group consisting of: trioctyl methyl ammonium; tetrabutylphosphonium; trioctylmethyl phosphonium; tetraoctyl ammonium; dioctadecyldiammonium; and

optionally wherein the cationic portion is tetrabutylphosphonium.

17. The composition according to any one of the preceding claims, wherein the base oil comprises a base stock selected from the group consisting of a Group I base stock, a Group II base stock, a Group III base stock, a Group IV base stock, a Group V base stock, and combinations thereof.

18. The composition according to any one of the preceding claims, wherein the composition comprises from 0.01 to 10 wt. % (e.g. 0.1 to 5 wt. %) ionic liquid.

19. Use of an ionic liquid as a friction modifier additive in a base oil (e.g. a base oil comprising a base stock selected from the group consisting of a Group I base stock, a Group II base stock, a Group III base stock, a Group IV base stock, a Group V base stock, and combinations thereof), wherein the ionic liquid is as defined in any one of Claims 1 to 16.

(i) providing a base oil; and

(ii) mixing the base oil with an appropriate amount of an ionic liquid, which ionic liquid is as defined in any one of Claims 1 to 16, optionally wherein the base oil comprises a base stock selected from the group consisting of a Group I base stock, a Group II base stock, a Group III base stock, a Group IV base stock, a Group V base stock, and combinations thereof.