Field of the Invention

The present invention relates to low viscosity dispersants for use in a lubricant composition. In particular, the present invention relates to low viscosity polyester and polycarbonate dispersants. The dispersants are particularly suitable for use in a lubricant composition for internal combustion engines.

Background of the Invention

Lubricant compositions generally comprise a base oil of lubricating viscosity together with one or more additives. Lubricant additives are used to deliver certain properties to the lubricant, such as improved viscosity index, detergency and resistance of oxidation and corrosion.

Lubricant compositions are used to lubricate the crankcase of internal combustion engines. However, during operation of an engine, the crankcase lubricant can become diluted with fuel, water and/or coolant. The lubricant can also become contaminated with chemical species which can accelerate lubricant oil oxidation. Examples of these chemical species include wear metals and oxidative non-metallic substances which can enter the crankcase through blow-by. The lubricant is also subject to high temperatures. As a result of these chemical and physical conditions, oxidation, polymerisation and agglomeration of the lubricant base oil may occur, creating a highly viscous tar-like material known as sludge from the degraded oil. The sludge may also incorporate species derived from fuel, water, coolant, soot and wear metals.

Deposits, such as sludge, can build up on many components of the engine, including the rocker cover(s), the camshaft baffle, the timing chain cover, the oil pan and its baffle, the oil screen and the valve deck area. The presence of deposits on these engine components can reduce the overall performance of the engine. For instance, engine deposits can be a factor in compromised oil pathways and engine lubrication and, if left untreated, can cause engine failure.

The formation of deposits is controlled by using additives which disperse and prevent the agglomeration of insoluble particles such as soot, sludge and other precursors to engine deposits in a lubricant. Dispersant additives typically comprise hydrophilic head groups and hydrophobic tails. The hydrophilic head groups interact with low solubility / low miscibility components that may be found in the lubricant, whilst the hydrophobic tails have an affinity for the lubricant base oil, thereby keeping the insoluble particles suspended in the lubricant.

Dispersants commonly used in engine lubricants are amine appended polyf/.v - butene)succinimide (PIBSA) type dispersant. An example of this type of dispersant is a poly(/.v -butcnc)succinimidc-polyaminc detergent (PIBSA-PAM) having the following structure:

where n is typically greater than 10, e.g. from 20 to 75. However, dispersants such as PIBSA type dispersants are known to increase the viscosity of lubricant compositions to which they are added.

In recent years, regulations relating to the emission of CO2 from engines have become increasingly stringent. In order to meet the regulations, the fuel efficiency of engines has to rise. One way to achieve this is to use a thinner lubricant, thereby reducing viscous drag. However, reducing the viscosity of the lubricant base oil can lead to increased volatility and therefore enhanced loss of base oil during use. Low viscosity base oils are also believed to give lubricants with worse lubricity and wear-protection performance. Thus, it is common to include additives in lubricant compositions to address problems associated with lubricity and wear-protection. However, the more additives that are used in a lubricant composition, the higher the likelihood of incompatibilities between different additives or solubility issues.

Accordingly, there is a need for additives which provide a dispersant effect without the typical increase in viscosity that is observed with known dispersant additives.

US 2012/0264665 relates to lubricant blends comprising a base stock and a dispersant selected from the group consisting of a polyalphaolefin succinimide, a polyalphaolefin succinamide, a polyalphaolefin acid ester, a poly alphaolefin oxazoline, a polyalphaolefin imidazoline, a polyalphaolefin succinamide imidazoline, and combinations thereof. The dispersant is purported to provide effective protection against the effects of dirt and sludge accumulation without increasing the viscosity of the lubricant composition. US 2014/0087983 is directed to lubricant additives which comprise an amination product of a vinyl terminated macromonomer (VTM) and an amino compound containing at least one NH-group. The additive is disclosed as having improved dispersion characteristics and as increasing the viscosity of the lubricant less than conventional dispersants.

There remains a need for lubricant additives which are effective as dispersants, but which do not increase the viscosity of a lubricant composition as much as conventional dispersants.

Summary of the Invention

The present invention is based on the surprising discovery that compounds which comprise a polyester or polycarbonate group which is linked - either directly or via a linking group - to an amine group are highly effective as dispersants in a lubricant composition, yet provide a lower increase in viscosity than conventional dispersant compounds.

Accordingly, the present invention provides a lubricant additive of formula (I):

where: R ¹ is hydrocarbyl optionally substituted with one or more hydroxyl groups;

R ² is H or alkyl;

R ³ is H or alkyl;

A and B are alkylene;

L is a linker group or is absent;

X is O or is absent;

m is from 2 to 30; and

n is from 0 to 10.

Also provided is a lubricant composition comprising a lubricant additive of formula

(I)·

The present invention further provides a method for preparing a lubricant composition, said method comprising blending:

an oil of lubricating viscosity; and

a lubricant additive of formula (I).

The use of a lubricant additive of formula (I), e.g. as a dispersant and preferably as a low viscosity dispersant, in a lubricant composition is also provided, as is the use of a lubricant additive of formula (I) in a lubricant composition for preventing deposits on a surface to which the lubricant composition has been applied.

Further provided is a method for increasing the dispersion properties, and preferably also maintaining the viscometric properties, of a lubricant composition, said method comprising introducing an additive of formula (I) to the lubricant composition, as well as a method for preventing deposits on a surface in which a lubricant composition comprising an additive of formula (I) is applied to the surface and a method for prevent the build-up of non-deposited contaminants in a lubricant composition in which an additive of formula (I) is introduced into the lubricant composition.

Brief Description of the Figures

Figure 1 shows the results of experiments that were carried out to determine the elastic modulus (G’) of lubricant compositions containing polycarbonate additives of formula (I) at treat rates of 0.05 % (Fig. la) and 0.1 % (Fig. lb) by weight of baseline oil. For comparison, lubricant compositions containing commercially available PIBSA-PAM based dispersant additives Cl and C2 were also tested, as well as lubricant compositions containing additives A and B and the baseline oil.

Figure 2 shows the results of experiments that were carried out to determine the yield stress of the lubricant compositions. Specifically, the graphs show results obtained where the dispersant additives were added to the baseline oil in an amount of 0.1 % by weight of baseline oil (Fig. 2a). The areas under the curves in Figure 2a were calculated, and are also shown (Fig. 2b), together with the area under the curve where the dispersant additives were added in an amount of 0.05 % by weight of the baseline oil (Fig. 2c).

Figure 3 shows the results of experiments that were carried out to determine the effect of polycarbonate additives of formula (I) on the viscosity characteristics of a lubricant composition, specifically the kinematic viscosity (Fig. 3a) and the cold cranking viscosity (Fig. 3b) of a lubricant composition. For comparison, the effect of additives Cl, A and B was also tested. Figure 4 shows the results of experiments that were carried out to determine the yield stress of lubricant compositions to which polyester additives of formula (I) have been added in an amount of 0.05 % or 0.1 % by weight of baseline oil. Specifically, the graphs show the area under the curve that was obtained where m = 9 (Fig. 4a), m = 14 (Fig. 4b) and m = 19 (Fig. 4c). For comparison, results were also obtained using the baseline oil and additive C2.

Figure 5 shows the the results of experiments that were carried out to determine the effect of additives of formula (III) on the viscosity characteristics of a lubricant composition, specifically the kinematic viscosity (Fig. 5a) and the cold cranking viscosity of the lubricant composition (Fig. 5b). For comparison, the effect of additives Cl was also tested.

Detailed Description of the Invention

The present invention relates to additives which may be used as low viscosity dispersants in a lubricant composition.

The low viscosity dispersant additive

The lubricant additive

The lubricant additive of the present invention has the formula (I):

R ¹ is hydrocarbyl optionally substituted with one or more hydroxyl (i.e. -OH) groups.

R ¹ may contain at least 2, at least 4, at least 6, at least 8, at least 10, at least 12, at least 14, or at least 16 carbon atoms. R ¹ may contain up to 50, up to 48, up to 46, up to 44, up to 42, up to 40, up to 38, up to 36, up to 34, up to 32, up to 30, up to 28, or up to 26 carbon atoms.

Preferably, R ¹ is selected from optionally substituted C2-34 hydrocarbyl, more preferably from optionally substituted Cs so hydrocarbyl, still more preferably from optionally substituted C 12-28 hydrocarbyl, and still more preferably from optionally substituted C16-28 hydrocarbyl.

The hydrocarbyl group may be an alkyl group or an alkenyl group, but is preferably an alkyl group, e.g. having a chain length as described above.

R ¹ may be unsubstituted or substituted with one or more hydroxyl groups. Where R ¹ is substituted, it is preferably substituted with one hydroxyl group. R ¹ is preferably unsubstituted and, as such, is preferably an alkyl group.

R ¹ is preferably branched. R ¹ is preferably branched in the b- or g-position (i.e. relative to the oxygen to which R ¹ is attached), and more preferably in the b-position.

R ² is H or alkyl.

Where R2 is alkyl, R2 may contain up to 10, up to 8, up to 6, up to 4, or up to 2 carbon atoms.

Preferably, R ² is selected from H and Ci- ₆ alkyl, preferably from H and C alkyl, and still more preferably from H and C1-2 alkyl. R ² is most preferably H.

R ³ is H or alkyl.

Where R3 is alkyl, R3 may contain up to 20, up to 18, up to 16, up to 12, up to 10, up to 8, up to 6, up to 4, or up to 3 carbon atoms.

Preferably, R ³ is selected from H and Ci-12 alkyl, preferably from H and Ci- ₆ alkyl, more preferably from H and C1-3 alkyl, and still more preferably is H.

Where R4 is alkyl, R4 may contain up to 20, up to 18, up to 16, up to 12, up to 10, up to 8, up to 6, or up to 4 carbon atoms.

Preferably, R ⁴ is selected from H, Ci-12 alkyl and

. p y .

It will be appreciated that, where R ⁴ is ^{0 0} , then the compound of formula (I) is a dimer having the following structure:

Both sides of the dimer will typically be the same, i.e. both R ¹ groups are the same, both X groups are the same, both A groups are the same, both L groups are the same, and m is the same. However, in embodiments, each of the groups are independently selected from the lists given above, i.e. each R ¹ is independently selected, each X group is independently selected, each A group is independently selected, each L group is independently selected, and each m is independently selected from the options mentioned above.

A is alkylene.

A may contain at least 2, or at least 4 carbon atoms. A may contain up to 50, up to 48, up to 46, up to 44, up to 42, up to 40, up to 38, up to 36, up to 34, or up to 32 carbon atoms.

Preferably, A is selected from C2-40 alkylene, more preferably from C3-36 alkylene, and still more preferably from C4-32 alkylene.

A is preferably a branched alkylene group. For instance, A may have the structure:

where: R ⁵ is selected from H and alkyl;

R ⁶ is selected from alkyl; and

each q is independently from 1 to 4.

Where R ⁵ is alkyl, R ⁵ may contain at least 2 carbon atoms. R ⁵ may contain up to 40, up to 38, up to 36, up to 34, up to 32, up to 30, up to 28, or up to 26 carbon atoms.

Preferably, R ⁵ is selected from H and Ci-30 alkyl, more preferably from H and C2-28 alkyl, and still more preferably from H and C2-26 alkyl.

R ⁶ may contain at least 2, or at least 3 carbon atoms. R ⁶ may contain up to 40, up to 38, up to 36, up to 34, up to 32, up to 30, up to 28, up to 26, up to 24, up to 22, up to 20, up to 18, up to 16, up to 14, up to 12, up to 10, or up to 8 carbon atoms.

Preferably, R ⁶ is selected from Ci -30, such as Ci -12 alkyl, more preferably from C2-10 alkyl, and still more preferably from C3-8 alkyl. q may be 1, 2, 3 or 4.

Preferably, each q is independently from 1 to 3, and more preferably is independently 1 or 2. Each q may take the same value or each q may take different values, though preferably each q is the same.

B is alkylene.

B may contain at least 2 carbon atoms. B may contain up to 20, up to 18, up to 16, up to 14, up to 12, up to 10, up to 8, up to 6, up to 4, or up to 3 carbon atoms.

Preferably, B is selected from Ci- ₈ alkylene, more preferably from C1-5 alkylene, and still more preferably from C2-3 alkylene.

L is a linker group or is absent. L may take a wide range of structures. Preferably L is selected from hydrocarbylene or is absent, more preferably L is selected from alkylene or is absent, and still more preferably L is selected from Ci-50 alkylene or is absent.

Where L is a linker group, it may contain at least 2 carbon atoms. L may contain up to up to 50, up to 48, up to 46, up to 44, up to 42, up to 40, up to 38, up to 36, up to 34, or up to 32 carbon atoms.

In some embodiments, L is selected from Ci-10 alkylene or is absent, more preferably from Ci - ₈ alkylene or is absent, and still more preferably from C2-6 alkylene or is absent.

In other embodiments, L has the structure A, where A is as defined above.

X is O or is absent. Where X is O, the additive is a polycarbonate additive. Where X is absent, the additive is a polyester additive. These embodiments are described in more detail below.

m is from 2 to 30.

m may be 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30.

Preferably, m is from 4 to 25, more preferably from 6 to 16, and still more preferably from 8 to 12.

n is from 0 to 10.

n may be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.

Preferably, n is from 1 to 8, more preferably from 2 to 7, and still more preferably from 3 to 6.

It will be appreciated that, as is standard in the art, the terms hydrocarbyl and hydrocarbylene refer to groups that consist only of carbon and hydrogen. The terms refer to groups which may be branched or unbranched and which may contain or consist of cyclic structures, though for the purposes of the present invention acyclic groups are preferred. The groups may be saturated or unsaturated groups. Unless otherwise specified, hydrocarbyl groups are unsubstituted.

Similarly, the terms alkyl and alkylene refer to saturated groups which may be branched or unbranched. The terms refer to groups which may contain or consist of cyclic structures, though for the purposes of the present invention acyclic groups are preferred. Unless otherwise specified, the terms alkyl and alkylene refer to groups that are unsubstituted and, as such, consist solely of carbon and hydrogen atoms.

Similarly, the terms alkenyl and alkenylene refer to alkyl groups but which comprise at least one carbon-carbon double bond. Thus, the terms refer to groups which may be branched or unbranched and which may contain or consist of cyclic structures, though for the purposes of the present invention acyclic groups are preferred. The groups are preferably, but not necessarily, bonded to the rest of the additive through a carbon which forms part of a double bond. Unless otherwise specified, the terms alkenyl and alkenylene refer to groups that are unsubstituted and, as such, consist solely of carbon and hydrogen atoms.

It will be appreciated that, as is standard in the art, the suffix “-yl” refers to monovalent groups, and the suffix“-ylene” refers to divalent groups.

As is also standard in the art, the term substituted, in connection with a hydrocarbon group in the lubricant additive of formula (I), means that one or more (e.g. 1, 2, 3, 4 or 5) of the hydrogen atoms in that group are replaced independently of each other by a corresponding number of non-hydrocarbon substituents. Thus, a branched alkyl group is considered to be an unsubstituted alkyl group, and not an alkyl group substituted with another alkyl group.

It will also be appreciated that m, n and q represent whole numbers.

Polycarbonate additives

Where X is O, then the present invention relates to lubricant additives of formula (II) which comprise a polycarbonate group: where: R ¹ , R ² , R ³ , R ⁴ , A, B, L, m and n are as described above.

The polycarbonate additives are effective as low viscosity dispersants in a lubricant composition.

Preferred R ¹ , R ² , R ³ , R ⁴ , A, B, L, m and n are as described above in connection with additives of formula (I).

However, in very specific embodiments, A represents:

where: R ⁵ is selected from alkyl.

Examples of polycarbonate additive of the present invention include:

Polyester additives

Where X is absent, then the present invention relates to lubricant additives of formula (III) which comprise a polyester group:

where: R ¹ , R ² , R ³ , R ⁴ , A, B, L, m and n are as described above.

Polyester additives are also effective as low viscosity dispersants in a lubricant composition.

Preferred R ¹ , R ² , R ³ , R ⁴ , A, B, L, m and n are as described above in connection with additives of formula (I).

However, in very specific embodiments, A represents:

where: R ⁵ is H. Examples of polyester additives of the present invention include:

Lubricant compositions

The additives of formula (I) may be used as part of a lubricant composition. The lubricant composition will typically be a non-aqueous lubricant composition.

The lubricant composition may comprise greater than 50 %, preferably greater than 65 %, and more preferably greater than 70 %, or 75 %, of an oil of lubricating viscosity, such as a base oil. Base oils comprise at least one base stock. Base stocks which are suitable for use in the lubricant composition of the present invention include non-aqueous base stocks such as Group I, Group II, Group III, Group IV and Group V base stocks, as classified according to API standard 1509, "ENGINE OIL LICENSING AND CERTIFICATION SYSTEM", 17 ^th Edition, Annex E (October 2013 with Errata March 2015):

In addition to an oil of lubricating viscosity, the lubricant compositions of the present invention comprise an additive of formula (I). The additive may be present in the lubricant composition at a concentration of at least 0.01 %, preferably at least 0.05 %, and more preferably at least 0.1 % by weight of the lubricant composition. The additive may be present in the lubricant composition at a concentration of up to 15 %, preferably up to 10 %, more preferably up to 8 %, and still more preferably up to 5 % by weight of the lubricant composition. Thus, the additive may be present in the lubricant composition at a concentration of from 0.01 to 10 %, preferably from 0.05 to 8 %, and more preferably from 0.1 to 5 % by weight of the lubricant composition. It will be appreciated that, where more than one additive of formula (I) is used in the lubricant composition, these values refer to the total amount of additives of formula (I) that are present in the lubricant composition. It will also be appreciated that the concentrations are expressed by weight of active additive compounds, i.e. independent of any solvent or diluent.

The lubricant composition may also comprise one or more further lubricant additives.

The one or more further lubricant additives include detergents (including metallic and non- metallic detergents), friction modifiers, dispersants other than the additives of formula (I) (including metallic and non-metallic dispersants and dispersant viscosity modifiers), viscosity modifiers, viscosity index improvers, pour point depressants, anti wear additives, rust inhibitors, corrosion inhibitors, antioxidants (sometimes also called oxidation inhibitors), anti-foams (sometimes also called anti-foaming agents), seal swell agents (sometimes also called seal compatibility agents), extreme pressure additives (including metallic, non-metallic, phosphorus containing, non-phosphorus containing, sulfur containing and non-sulfur containing extreme pressure additives), surfactants, demulsifiers, anti-seizure agents, wax modifiers, lubricity agents, anti-staining agents, chromophoric agents, metal deactivators, and mixtures of two or more thereof.

Examples of suitable detergents include ashless detergents (that is, non-metal containing detergents) and metal-containing detergents. Suitable non-metallic detergents are described for example in US 7,622,431. Metal-containing detergents comprise at least one metal salt of at least one organic acid, which is called soap or surfactant. Suitable organic acids include for example, sulfonic acids, phenols (suitably sulfurised and including for example, phenols with more than one hydroxyl group, phenols with fused aromatic rings, phenols which have been modified for example, alkylene bridged phenols, and Mannich base-condensed phenols and saligenin-type phenols, produced for example by reaction of phenol and an aldehyde under basic conditions) and sulfurised derivatives thereof, and carboxylic acids including for example, aromatic carboxylic acids (for example hydrocarbyl-substituted salicylic acids and derivatives thereof, for example hydrocarbyl substituted salicylic acids and sulfurised derivatives thereof).

Examples of suitable friction modifiers include for example, ash-producing additives and ashless additives. Examples of suitable friction modifiers include fatty acid derivatives including for example amides, amines, and ethoxylated amines. Examples of suitable friction modifiers also include molybdenum compounds for example, organo molybdenum compounds, molybdenum dialkyldithiocarbamates, molybdenum dialkylthiophosphates, molybdenum disulfide, tri-molybdenum cluster dialkyldithiocarbamates, non-sulfur molybdenum compounds and the like. Suitable molybdenum-containing compounds are described for example, in EP 1533362 A1 for example in paragraphs [0101] to [0117]

Examples of suitable ashless dispersants (other than the additives of formula (I)) include oil soluble salts, esters, amino-esters, amides, imides and oxazolines of long chain hydrocarbon-substituted mono- and polycarboxylic acids or anhydrides thereof; thiocarboxylate derivatives of long chain hydrocarbons; long chain aliphatic hydrocarbons containing polyamine moieties attached directly thereto; Mannich condensation products formed by condensing a long chain substituted phenol with formaldehyde and polyalkylene polyamine; Koch reaction products and the like. Examples of suitable dispersant viscosity modifiers and methods of making them are described in WO 99/21902, WO 2003/099890 and WO 2006/099250.

Examples of suitable viscosity modifiers include high molecular weight hydrocarbon polymers (for example polyisobutylene, copolymers of ethylene and propylene and higher alpha-olefins); polyesters (for example polymethacrylates); hydrogenated poly( styrene-co- butadiene or isoprene) polymers and modifications (for example star polymers); and esterified poly(styrene-co-maleic anhydride) polymers. Oil- soluble viscosity modifying polymers generally exhibit number average molecular weights of at least 15000 to 1000000, preferably 20000 to 600000 as determined by gel permeation chromatography or light scattering methods.

Examples of suitable pour point depressants include C _H to Cis dialkyl fumarate/vinyl acetate copolymers, methacrylates, polyacrylates, polyarylamides, polymethacrylates, polyalkyl methacrylates, vinyl fumarates, styrene esters, condensation products of haloparaffin waxes and aromatic compounds, vinyl carboxylate polymers, terpolymers of dialkyfumarates, vinyl esters of fatty acids and allyl vinyl ethers, wax naphthalene and the like.

Examples of suitable anti-wear additives include non-phosphorus containing additives for example, sulfurised olefins. Examples of suitable anti-wear additives also include phosphorus-containing antiwear additives. Examples of suitable ashless phosphorus-containing anti-wear additives include trilauryl phosphite and triphenylphosphorothionate and those disclosed in paragraph [0036] of US 2005/0198894. Examples of suitable ash-forming, phosphorus-containing anti-wear additives include dihydrocarbyl dithiophosphate metal salts. Examples of suitable metals of the dihydrocarbyl dithiophosphate metal salts include alkali and alkaline earth metals, aluminium, lead, tin, molybdenum, manganese, nickel, copper and zinc. Particularly suitable dihydrocarbyl dithiophosphate metal salts are zinc dihydrocarbyl dithiophosphates (ZDDP).

Examples of suitable rust inhibitors include non-ionic polyoxyalkylene polyols and esters thereof, polyoxyalkylene phenols, polyoxyalkylene polyols, anionic alky sulfonic acids, zinc dithiophosphates, metal phenolates, basic metal sulfonates, fatty acids and amines. Examples of corrosion inhibitors include phosphosulfurised hydrocarbons and the products obtained by the reaction of phosphosulfurised hydrocarbon with an alkaline earth metal oxide or hydroxide, non-ionic polyoxyalkylene polyols and esters thereof, polyoxyalkylene phenols, thiadiazoles, triazoles and anionic alkyl sulfonic acids. Examples of suitable epoxidised ester corrosion inhibitors are described in US 2006/0090393.

Examples of suitable antioxidants include alkylated diphenylamines, N-alkylated phenylenediamines, phenyl-a-naphthylamine, alkylated phenyl-a-naphthylamines, dimethylquino lines, trimethyldihydroquino lines and oligomeric compositions derived therefrom, hindered phenolics (including ashless (metal-free) phenolic compounds and neutral and basic metal salts of certain phenolic compounds), aromatic amines (including alkylated and non-alkylated aromatic amines), sulfurised alkyl phenols and alkali and alkaline earth metal salts thereof, alkylated hydroquinones, hydroxylated thiodiphenyl ethers, alkylidenebisphenols, thiopropionates, metallic dithiocarbamates, 1,3,4- dimercaptothiadiazole and derivatives, oil soluble copper compounds (for example, copper dihydrocarbyl thio- or thio-phosphate, copper salts of a synthetic or natural carboxylic acids, for example a Csto Cis fatty acid, an unsaturated acid or a branched carboxylic acid, for example basic, neutral or acidic Cu(I) and/or Cu(II) salts derived from alkenyl succinic acids or anhydrides), alkaline earth metal salts of alkylphenolthioesters, suitably containing C5 to C12 alkyl side chains, calcium nonylphenol sulfide, barium t-octylphenyl sulfide, dioctylphenylamine, phosphosulfised or sulfurised hydrocarbons, oil soluble phenates, oil soluble sulfurised phenates, calcium dodecylphenol sulfide, phosphosulfurised hydrocarbons, sulfurised hydrocarbons, phosphorus esters, low sulfur peroxide decomposers and the like.

Examples of suitable anti-foam agents include silicones, organic polymers, siloxanes (including poly siloxanes and (poly) dimethyl siloxanes, phenyl methyl siloxanes), acrylates and the like.

Examples of suitable seal swell agents include long chain organic acids, organic phosphates, aromatic esters, aromatic hydrocarbons, esters (for example butylbenzyl phthalate) and polybutenyl succinic anhydride.

Other additives may also be present in the lubricant composition and these include, for example, extreme pressure additives (including metallic, non-metallic, phosphorus containing, non-phosphorus containing, sulfur containing and non-sulfur containing extreme pressure additives), surfactants, demulsifiers, anti-seizure agents, wax modifiers, lubricity agents, anti-staining agents, dispersant viscosity modifiers (polymers), chromophoric agents and metal deactivators.

In some embodiments, the lubricant composition may comprise solvent e.g. which has been used to ensure that the additives are in a form in which they can be stored or combined with the lubricant. Examples of suitable solvents include highly aromatic, low viscosity base stocks, for example 100N, 60N and 100SN base stocks.

Representative typical and more typical independent amounts of additives (if present) in the lubricant composition are given in the table below. For the additives, the concentrations are expressed by weight (of the lubricant composition) of active additive compounds, i.e. independent of any solvent or diluent. Where more than one additive of each type is present in the lubricant composition, the total amount of each type of additive is expressed in the table below.

Preferred lubricant compositions meet the requirements set out in SAE J300 (2015-

01).

The lubricant compositions of the present invention may be prepared by a method which comprises blending: an oil of lubricating viscosity; and an additive of formula (I). Suitable methods for blending lubricant compositions are known in the art.

The method may further comprise blending one of more of the above-mentioned lubricant additives into the lubricant composition. The additives may be used in the form of additive concentrates or as part of an additive pack which contains more than one additive, optionally comprising solvent or diluent.

Uses and methods

The additive of formula (I) may be used in a lubricant composition, e.g. a lubricant composition described above.

The lubricant composition may be used in an internal combustion engine, wheel bearings, gears, marine applications, robotics, turbines and other industrial application. The lubricant composition may be used as a functional fluid (e.g. a metalworking fluid which may be used to lubricate metals during machining, rolling and the like), or a transmission fluid (e.g. as an automatic transmission fluid, e.g. in a drive line, gear box, or clutch (e.g. a dual clutch)).

The lubricant composition is preferably used in an internal combustion engine, e.g. as a crankcase lubricant. Suitable internal combustion engines include spark-ignition engines (which typically run on gasoline fuels, e.g. direct injection and port fuel injection engine) and compression ignition engines (which typically run on diesel fuel). The internal combustion engine may be used to power an automotive vehicle (e.g. a motorcycle, car, truck or lorry), an aeroplane, or a marine vessel. Thus, the lubricant composition may be an automotive lubricant, an aviation lubricant or a marine lubricant, and is preferably an automotive lubricant.

The lubricant composition may be used to lubricate a surface at temperature which might typically be encountered in a lubricating environment, such as at a temperature such as may be encountered in an internal combustion engine, e.g. a temperature in the range of ambient to 250 °C, e.g. 90 °C to 120°C. Typical ambient temperature is 20 °C, but in at least some examples, is less than 20 °C, for example 0 °C or lower.

The additives of formula (I) may be used as a dispersant in a lubricant composition to which they are added. Thus, a method for improving the dispersancy characteristics of a lubricant composition may comprise introducing an additive of formula (I) to the lubricant composition.

The efficacy of the additives of formula (I) as a dispersant may be tested according to a deposit test e.g. compared to a lubricant composition which does not contain the additive. Suitable deposit tests include the hot liquid process simulator (HLPS) test, a hot-tube test in which oil compositions are subjected to heating stress for a period of time. The test may be conducted using the following conditions: tube temp = 250 °C; oil sump temp = 100 °C; oil flow rate = 10 ml/min; test time = 2.5 hours; tube material = stainless steel; and tube diameter = 3.212 mm. Deposits may be measured using white light interferometry. A reduction in maximum deposit thickness, and preferably also in total deposit volume, indicates effective dispersancy.

Since the additives of formula (I) are effective as dispersants, they may be used to prevent the build-up of deposits, such as sludge, on a surface. Thus, a method for preventing the build-up of deposits on a surface may comprise applying the lubricant composition of the present invention to the surface. The surface is preferably found in an internal combustion engine. For instance, the surface may form part of a piston, a piston crown, a piston ring, a cylinder liner (sleeve) or a turbocharger.

The additives of formula (I) may also be used to prevent the build-up of non- deposited contaminants, such as soot or sludge, in a lubricant composition. Thus, a method for preventing the build-up of non-deposited contaminants in a lubricant composition may comprise introducing an additive of formula (I) into the lubricant composition. The lubricant composition is preferably found in an internal combustion engine.

The additives of formula (I) are preferably used as low viscosity dispersants in a lubricant composition to which they are added. Thus, a method for improving the dispersion properties, and preferably also maintaining the viscosity properties, of a lubricant composition may comprise introducing an additive of formula (I) to the lubricant composition.

It will be appreciated that the term Tow viscosity’ is understood in the art to denote compounds which increase the viscosity of a lubricant composition to which they are added less than conventional lubricant dispersant additives, such as conventional PIBSA- PAM dispersants. The efficacy of the additives of formula (I) as low viscosity additives may be tested by measuring their kinematic viscosity at 100 °C (KV100) according to ASTM D7279-16. For instance, additives of formula (I) may be considered to be low viscosity additives if, when used in an otherwise dispersant-free base oil or lubricant composition in an amount of 4 % by weight of the additised base oil/lubricant, they increase KV100 by less than 1 cSt as compared to the un-additised base oil/lubricant. Suitable lubricant compositions for the test method may comprise detergent, anti-oxidant, anti-wear and anti- foam additives in a total amount of 4 to 5 % and a viscosity modifier in an amount of 7 to 8%, with the balance made up of base oil (e.g. 80 to 85 % Yubase 4 and 3 to 8 % Yubase 6).

Since the additives of formula (I) are effective as low viscosity dispersants in a lubricant for an internal combustion engine, they may be used for maintaining fuel economy, maintaining power, preventing wear and/or improving oil drain in an internal combustion engine in which the lubricant is used. Thus, a method for maintaining fuel economy, maintaining power, preventing wear, and/or improving oil drain in an internal combustion engine may comprise supplying a lubricant composition of the present invention to the engine. It will be appreciated that these effects may be achieved at the same time as the above-mentioned effects of enhanced dispersancy and/or prevention of the build-up of deposits.

Though it is generally preferred for a blended lubricant to be supplied to the engine, the additive of formula (I) may also be added into the lubricant within the engine in which the lubricant is used, e.g. by addition of the dispersant to the oil sump, or by addition of the dispersant directly into the combustion chamber. As discussed in more detail below, the additive of formula (I) may also be transferred to the lubricant from a fuel into which the dispersant has been combined.

It will also be appreciated that the additive of formula (I) may be added to the lubricant composition in the form of a precursor compound which, under the combustion conditions encountered in an engine, breaks down to form the additive of formula (I).

Fuel compositions

In some embodiments, the additive of formula (I) may be transferred to the lubricant from a fuel into which the additive has been combined during operation of an engine in which the fuel and lubricant are used, thereby providing dispersant and/or viscosity modifying benefits to the lubricant. The ingress of fuel and fuel additives into the crankcase lubricant of an internal combustion engine is known, for example from paragraph 2 of the abstract of SAE paper 2001-01-1962 by C. Y. Thiel et al.“The Fuel Additive/lubricant Interactions: ..

Thus, the present invention provides a fuel composition which comprises an additive of formula (I). The low viscosity dispersant may be present in the fuel at a concentration of from 150 to 4000 ppm by weight. The present invention also provides the use of an additive of formula (I) in a fuel composition, e.g. as a dispersant and preferably as a low viscosity dispersant.

The fuel composition is preferably for use in an internal combustion engine, e.g. an internal combustion engine as described above.

Suitable liquid fuels, particularly for internal combustion engines, include hydrocarbon fuels, oxygenate fuels and combinations thereof. Hydrocarbon fuels may be derived from mineral sources and/or from renewable sources such as biomass (e.g. biomass-to-liquid sources) and/or from gas-to-liquid sources and/or from coal-to-liquid sources. Suitable sources of biomass include sugar (e.g. sugar to diesel fuel) and algae. Suitable oxygenate fuels include alcohols, for example straight and/or branched chain alkyl alcohols having from 1 to 6 carbon atoms, esters, for example fatty acid alkyl esters and ethers, for example methyl tert butyl ether. Suitable fuels may also include LPG-diesel fuels (LPG being liquefied petroleum gas).

One or more further fuel additives may be present in the fuel composition.

The fuel composition may be prepared by blending a fuel with an additive of formula

(I)· Further provided is the use of the fuel composition for:

preventing the build-up of deposits (e.g. sludge) on a surface, such as a surface in an internal combustion engine;

preventing the build-up of non-deposited contaminants (e.g. soot or sludge) in a lubricant composition; and/or

maintaining fuel economy, maintaining power, preventing wear, and/or improving oil drain in an internal combustion engine,

e.g. as a result of ingress of the dispersant into the lubricant that is used in the engine, e.g. the crankcase lubricant.

Also provided is a method for:

preventing the build-up of deposits (e.g. sludge) on a surface in an internal combustion engine,

preventing the build-up of non-deposited contaminants (e.g. soot or sludge) in a lubricant composition; and/or

maintaining fuel economy, maintaining power, preventing wear, and/or improving oil drain in an internal combustion engine,

said method comprising supplying the fuel composition to the engine.

The method may further comprise operating the engine, i.e. such that the additive of formula (I) ingresses from the fuel into the lubricant that is used in the engine, e.g. the crankcase lubricant.

Examples

The invention will now be described with reference to the following non-limiting examples.

Example 1 : Preparation of lubricant additives of the present invention

Lubricant additives of the present invention were prepared using procedures that are standard in the art. As an example, certain polycarbonate additives were prepared according to the following protocol:

A: Pyridine/dichloromethane; triphosgene; -70 °C to room temperature;

B: R'OH; dichloromethane; a thiourea-based organocatalyst having the structure:

-diazabicyclo[5.4.0]undec-7-ene; room temperature

C: Prop-2-enoyl chloride; dichloromethane, base

D: Acetonitrile, tetraethylenepentamine, room temperature

Certain polyester additives were prepared according to the following protocols:

A: 3-Chlorobenzene-l-carboperoxoic acid; dichloromethane; trifluoromethanesulfonic acid

B: R'OH; triethylaluminium; tetrahydrofuran

C: Tosyl chloride; triethylamine; 4-dimethylaminopyridine; dichloromethane

D: Acetonitrile, tetraethylenepentamine, 50 °C By following these or similar protocols, the following lubricant additives were prepared:

Example 2: Elastic modulus of lubricant compositions comprising polycarbonate

additives of formula (II)

Lubricant compositions were prepared by adding 0.05% by weight of additives 15, 17 and 18 to a baseline oil. The baseline oil was a drain oil from a Cummins ISB engine that was prepared in accordance with the first 100 hours of ASTM D7484-16 to give approximately 6 % soot loading. For comparison, lubricant compositions were also prepared comprising 0.05% by weight of commercially available PIBSA-PAM based dispersant additives, Cl and C2, as well as additives A and B having the following structures:

The resulting lubricants were tested to determine their elastic modulus (G’), a useful measure of the solid like behaviour of the system. Specifically, oscillatory rheometry was used to determine each lubricant’s response to a constantly changing shear stress. G’ values were determined according to the procedure given in Smith et al, SAE Technical Paper 2007, 01-4142. The results of the tests are shown in Figure la.

High performing dispersants should prevent soot agglomeration, and hence produce a lower G’, and in terms of usefulness for automotive applications move the peak G’ to outside the normal operating temperature of an engine e.g. to a higher temperature. This means that the lubricant will be less viscous, thereby preventing oil thickening leading to blocking of oil galleries and increased fuel consumption, and eventually seizure of the engine. It can be seen that each of the lubricant additives 15, 17 and 18 lowered G’ and moved peak G’ compared to the baseline oil. Particularly good results were observed with lubricant additives 18 and 15.

The experiments were repeated using 0.1 % by weight of the described additives within the baseline oil, and similar results were obtained. The results are shown in Figure lb. To ensure that the effects observed are due to dispersancy, rather than just dilution, 0.5 % by weight of Yubase 4, a base oil containing no dispersant, was added to the baseline oil. The elastic modulus (G’) was assessed. Yubase 4 exhibited no effect on G’. Example 3: Yield stress of lubricants comprising polycarbonate additives of formula (II)

The lubricant compositions of Example 2 were further analysed to determine their yield stress, a measure of how readily a lubricant composition will behave like a Newtonian fluid. Specifically, the yield stress was determined according to the procedure given in Smith et ai, SAE Technical Paper 2007, 01-4142. The results where the dispersant additives were used in an amount of 0.1 % by weight of the baseline oil are shown in Figure 2a. The areas under the curves in Figure 2a were calculated, and are also shown in Figure 2b. The areas under the curve where the dispersant additives were added in an amount of 0.05 % by weight of the baseline oil are shown in Figure 2c.

It can be seen that each of the lubricant additives 15, 17 and 18 reduced the instantaneous viscosity of the lubricant with increasing shear stress as compared to the baseline oil. Particularly good results were observed with lubricant additive 18.

Example 4: Deposit control of lubricants comprising polycarbonate additives of formula

01)

Fubricant compositions were prepared by adding 0.25 % by weight of additives 13, 14 and 15 to a dispersant-free baseline formulation. The baseline formulation contained detergent, anti-oxidant, anti- wear and anti- foam additives in a total amount of 3.7 % and a viscosity modifier in an amount of 7.4 %.

For comparison, lubricant compositions were also prepared comprising 0.25% by weight of the commercially available PIBSA-PAM dispersant additive Cl and of additives A and B.

The ability of the resulting lubricant compositions to prevent deposits on a surface was tested using a hot liquid process simulator (HEPS) method. HEPS testing is used as a means for characterising the propensity of an oil to create deposits in a hot region of the engine by simulating pressurized oil lines. The test was conducted using the following conditions: tube temp = 250 °C; oil sump temp = 100 °C; oil flow rate = 10 ml/min; test time = 2.5 hours; tube material = stainless steel; and tube diameter = 3.212 mm. Deposits were measured using white light interferometry. The results of the HEPS analysis are provided in the table below:

It can be seen that each of the lubricant additives 13, 14 and 15 drastically reduced the formation of deposits as compared to the baseline formulation. Particularly good results were observed with lubricant additives 13 and 14.

Example 5: Viscometrics of lubricants comprising polycarbonate additives of formula (II) Lubricant compositions were prepared by combining conventional lubricant additives with 4 % by weight of additives 13 to 15, 17 and 18 in a base oil.

For comparison, a lubricant composition was also prepared comprising 4 % by weight of additives A and B, and the commercially available PIBSA-PAM dispersant additive Cl.

The viscosity of the resulting lubricant compositions was tested according to ASTM

D7279-16. The results of the experiments are shown in Figure 3a.

It can be seen that the increase in viscosity from using the additives of formula (II) is less than that associated with conventional dispersant additives at both 40 °C and 100 °C. Additive A was not soluble at the level 4 % by weight, and so viscosity could not be measured.

The lubricants were also tested to determine their cold cranking viscosity (CCS), according to ASTM D5293-17a. The results of the experiments are shown in Figure 3b.

It can be seen that the CCS performance of additives of formula (II) is far superior to that of conventional dispersant additives. Indeed, the lubricant composition comprising Cl falls outside the CCS limit of 6200 cP at -35 °C that is required for 0W lubricant grades, whereas the lubricant compositions comprising additives of formula (II) are comfortably within these limits.

The KV40 and KV100 experiments were repeated but with lubricants comprising the additive in an amount of 0.25 % by weight. Viscosity benefits were still observed at the lower treat rate.

Example 6: Yield stress of lubricants comprising polyester additives of formula (III) Lubricant compositions were prepared by as described in Example 2 but comprising 0.05 % or 0.1 % by weight of additives 1 to 12.

For comparison, lubricant compositions were also prepared comprising 0.05 % and 0.1 % by weight of the commercially available PIBSA-PAM dispersant additive C2.

The resulting lubricant compositions were analysed to determine their yield stress using the method described in Example 3. Figures 4a to 4c show the areas under the curve when the different dispersant additives were used at different concentrations.

Changes in the area under the curve demonstrate that the dispersant is interacting with the soot. It can be seen that excellent results were obtained with lubricant additive 1 , which reduced the area under the curve compared to both the baseline oil and dispersant additive C2. Superior results were obtained where R4 was H. Superior results were also generally obtained where m is lower than 19.

Example 7 : Deposit control of lubricants comprising polyester additives of formula (III)

Lubricant compositions were prepared by adding additives 1, 2 and 4 to 12 to a reference oil to give lubricant compositions having the same nitrogen content as that prepared using 0.5 % by weight of the commercially available dispersant additive Cl . The reference oil was as described in Example 4.

The ability of the resulting lubricant compositions to prevent deposits on a surface was tested using the hot liquid process simulator (HLPS) method described in Example 4. The results are provided in the table below:

It can be seen that most of the lubricant additives produce similar or lower amounts of deposits as compared to the dispersant additive Cl. Particularly good results were observed with the lubricant additives in which R ₄ was H. Lubricant additive 4 provided exceptional results, producing fewer deposits than the baseline.

Example 8: Viscometrics of lubricants comprising polyester additives of formula (III)

Lubricant compositions were prepared by combining conventional lubricant additives with 5 % by weight of additives 1 to 12 in a base oil.

For comparison, lubricant compositions were also prepared comprising 5 % by weight of the commercially available PIBSA-PAM dispersant additive Cl.

The viscosity of the resulting lubricant compositions was tested using the methods described in Example 5. The results of the experiments are shown in Figures 5a and 5b.

It can be seen that the increase in viscosity from using the additives of formula (III) is less than that associated with conventional dispersant additives, at 40 °C, 100 °C and in cold-crank conditions.