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Title:
LUBRICATING COMPOSITION COMPRISING A SULFUR-CONTAINING CARBOXYLIC ACID OR ESTER ADDITIVE
Document Type and Number:
WIPO Patent Application WO/2020/131603
Kind Code:
A1
Abstract:
The present invention relates to lubricating compositions comprising sulfur-containing additives as anti-wear and/or extreme pressure additives, methods of preparing the same and uses thereof. The sulfur-containing additive is free of disulfide and polysulfide bonds and/or comprises at least one sulfur-containing moiety, wherein the sulfur-containing moiety comprises vicinal dithioethers. In a particularly preferred embodiment, the sulfur-containing additive is compound of Formula 2 as defined herein.

Inventors:
YANG HONG (US)
KUSTEDJO KAREN (US)
PESCHEL HENDRIK (US)
Application Number:
PCT/US2019/066142
Publication Date:
June 25, 2020
Filing Date:
December 13, 2019
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
BP CORP NORTH AMERICA INC (US)
International Classes:
C10M135/26
Domestic Patent References:
WO1998002509A11998-01-22
WO1999021902A11999-05-06
WO2003099890A22003-12-04
WO2006099250A12006-09-21
Foreign References:
EP2703475A12014-03-05
EP0142078A11985-05-22
EP0713867A11996-05-29
EP3255129A12017-12-13
US4957651A1990-09-18
US4959168A1990-09-25
US5075020A1991-12-24
US7622431B22009-11-24
EP1533362A12005-05-25
US20050198894A12005-09-15
US20060090393A12006-05-04
Other References:
ENGINE OIL LICENSING AND CERTIFICATION SYSTEM, April 2007 (2007-04-01)
J. ORG. CHEM, vol. 50, no. 2, 1985, pages 4390 - 4393
TETRAHEDRON LETTERS, vol. 48, no. 3, 2007, pages 6312 - 631 7
BIOORGANIC & MEDICINAL CHEMISTRY LETTERS, vol. 17, no. 4, 2007, pages 6197 - 6201
J. AM. CHEM. SOC., vol. 121, no. 5, 1999, pages 482 - 483
CATALYSIS LETTERS, vol. 47, no. 6, 1997, pages 73 - 75
J. CHEM. SOC. PERKING TRANS, vol. 1, 1991
Attorney, Agent or Firm:
KOLMAN, Michael (US)
Download PDF:
Claims:
CLAIMS

1. A lubricating composition comprising a base fluid of lubricating vi scosity and a sulfur- containing additive, wherein the sulfur-containing additive comprises: i) at least one ester moiety and/or at least one carboxylic acid moiety; and ii) at least one sulfur-containing moiety, wherein the sulfur-containing moiety comprises a thioether; and wherein the sulfur- containing additive is free of disulfide and polysulfide bonds.

2 A lubricating composition according to Claim 1 , wherein the sulfur-containing additive comprises at least one sulfur-containing moiety according to Formula 1 :

wherein:

Ri and R2 are independently selected from monovalent hydrocarbyl groups;

M is ~(CH2)n~; and

n is 0 to 20.

3. A lubricating composition comprising a base fluid of lubricating viscosity and a sulfur- containing additive, wherein the sulfur-containing additive comprises: i) at least one ester moiety and/or at least one carboxylic acid moiety; and ii) at least one sulfur-containing moiety, wherein the sulfur-containing moiety comprises vicinal dithioethers.

4. A lubricating composition according to any one of the preceding claims, wherein the sulfur-containing moiety is of Formula la:

Formula la wherein:

Ri and R2 are independently selected from monovalent hydrocarbyl groups.

5. A lubricating composition according to any one of the preceding claims , wherein the sulfur-containing additive is of Formula 2:

Formula 2

wherein :

Ri, R2 and Rs are, at each occurrence, independently selected from monovalent hydrocarbyl groups;

R3 is a monovalent hydrocarbyl group or -C(=0)ORs;

Rr is a divalent hydrocarbyl group or -C(=0)OR6-.

R& is a divalent hydrocarbyl group;

Li and L2 are independently selected from a bond, a sulfur-containing moiety of Formula la, and a sulfur-containing moiety of Formula 3:

wherein p and q are integers independently selected from 0, 1 , 2, 3, 4 and 5, provided that p and q are not both 0.

6. A lubricating composition according to Claim 5, wherein:

Ri and R?. are, at each occurrence, independently selected from Ci to C12 alkyl, preferably Ci to Ce alkyl,

Rs is Ci to Ci8 alkyl, preferably Ci to C12 alkyl, or -C(=0)QRs; m is Ci to Ci2 alkylene, preferably Ci to Ce alkylene; C2 to C12 alkenylene, preferably Ci to Ce alkenylene; or -C(=0)0Re-;

Rs is Ci to Ci8 alkyl, preferably Ci to C12 alkyl;

Re is Ci to C12 alkylene, preferably Ci to Ce alkylene, or C2 to C12 alkenylene, preferably Ci to Ce alkenylene; and

p and q are integers independently selected from 0, 1 and 2

7. A lubricating composition according to Claim 5 or Claim 6, wherein:

Ri and R2 are, at each occurrence, independently selected from Ci to Ce alkyl, preferably Ci to C3 alkyl;

R3 is Ci to C 12 alkyl; preferably Cr to Cs alkyl;

Rr is Ci to C12 alkylene, preferably Ci to Ce alkylene; and

Rs is Ci to Ce alkyl, preferably Ci to C3 alkyl.

8. A lubricating composition according to any one of Claims 5 to 7, wherein at least one of Li and Li is a bond.

9. A lubricating composition according to Claim 8, wherein both Li and L2 are a bond.

10. A lubricating composition according to any one of Claims 5 to 7, wherein one of Li and L2, preferably Li, is a moiety of Formula 3.

1 1. A lubricating composition according to any one of the preceding claims, wherein the sulfur-containing additive is an adduct of the reaction of a dialkyl sulfide and an alkyl ester of a fatty acid.

12. A lubricating composition according to Claim 11, wherein the fatty acid is selected from crotonic acid, myristoleic acid, palmitoleic acid, sapienic acid, oleic acid, elaidic acid, vaccenic acid, gadoleic acid, eicosenoic acid, erucic acid, nervonie acid, linoleic acid, eicosadienoic acid, docosadienoic acid, or any combination thereof.

13. A lubricating composition according to any one of the preceding claims, wherein the the sulfur-containing additive is an adduct of the reaction of a dialkyl sulfide and an alkyl ester of a oleic acid or linoleic acid having the Formula 4 or Formula 5, respectively:

Formula 4

Formula 5 wherein;

Ri and R?. are, at each occurrence, independently selected from Ci to C3 alkyl, preferably wherein both Ri and R2 are methyl; and

R3 is selected from Ci to C& alkyl, preferably wherein R3 is methyl.

14. A lubricating composition according to any one of the preceding claims, wherein the total number of carbons atoms in the sulfur-containing additive is from 10 to 50, such as from 15 to 40, such as from 18 to 36, or from 20 to 30.

15. A lubricating composition according to any one of the preceding claims, wherein the sulfur-containing additive contains greater than 50 %, such as greater than 70 %, or greater than 90 % by weigh t of biobased carbon.

16. A lubricating composition according to any one of the preceding claims, wherein the lubricating composition is for use in an engine.

17. A lubricating composition according to Claim 16, wdierein the lubricating composition comprises one or more further lubricant additives selected from detergents, friction modifiers, dispersants, viscosity modifiers, dispersant viscosity modifiers, viscosity index improvers, pour point depressants, anti-wear additives, rust inhibitors, corrosion inhibitors, antioxidants, anti-foams, seal swell agents, extreme pressure additives, surfactants, demulsifiers, anti seizure agents, wax modifiers, lubricity agents, anti-staining agents, chromophoric agents, metal deactivators, and mixtures thereof.

18. A lubricating composition according to Claim 16 or Claim 17, wherein the base fluid is a base oil comprising a base stock selected from Group I, Group II, Group III, Group IV and Group V base stocks and mixtures thereof.

19. A lubricating composition according to Claim 18, wherein the lubricant composition comprises greater than 50 %, such as greater than 65 ¾, or greater than 80 % by weight of a base oil.

20. A lubricating composition according to any one of Claims 16 to 19, wherein the sulfur- containing additive is present in the lubricant composition in an amount of from 0.01 % to 5 0 % by weight, preferably 0.01 % to 1.0% by weight.

21. A lubricating composition according to any one of Claims 16 to 20, wherein the lubricating composition has at least one of: a kinematic viscosity at 40 °C of less than 60 cSt, such as less than 55 cSt, or less than 50 cSt,

a kinematic viscosity at 100 °C of less than 12 cSt, such as less than 10 cSt, or less than 9.5 cSt;

a viscosity index of greater than 100, such as greater than 110, or greater than 120; a viscosity at 150 °C and a shear rate of 106 s 1 of no greater than 3 cP, such as no greater than 2.8 cP, and

a Noack volatility of less than 25 %, such as no more than 20%, less than 15 %, or less than 10 % by weight.

22. A lubricating composition according to any one of Claims 16 to 20, wherein the engine is an internal combustion engine, for instance in an automotive vehicle.

23. A lubricating composition according to any one of Claims 1 to 15, wherein the lubricating composition is for use as a metal working fluid.

24. A lubricating composition according to Claim 23, wherein the base fluid is oil based, aqueous based, a water-in-oil emulsion, or an oil-in-water emulsion.

25. A lubricating composition according to Claim 23 or Claim 24, wherein the lubricating composition comprises one or more further lubricant additives selected from corrosion inhibitors, pH modifying additives, biocides, surfactants and combinations thereof

26. A lubricating composition according to any one of Claims 23 to 25, wherein the sulfur- containing additive is present in the lubricant composition in an amount of from 0.1% to 30% by weight.

27. A method of preparing a lubricant composition according to any one of Claims 16 to 22, said method comprising providing a base oil and blending the base oil with a sulfur- containing additive as defined in any one of Claims 1 to 15 and one or more additional lubricant additives, for example as defined in Claim 17.

28. A method of preparing a lubricant composition according to any one of Claims 23 to 26, said method comprising providing a base fluid and blending the base fluid with the sulfur- containing additive as defined in any one of Claims 1 to 15 and one or more additional lubricant additives, for example as defined in Claim 25.

29. A method of lubricating a surface, said method comprising supplying a lubricant composition as defined in any one of Claims 1 to 26 to said surface.

30. A method according to Claim 29, wherein the surface is a surface in an engine and wherein the lubricating composition is as defined in any one of Claims 16 to 22.

31. A method according to Claim 29, wherein the surface is a metal surface and the wherein the lubricating composition is as defined in any one of Claims 23 to 26.

32. A use of a lubricant composition as defined in any of Claims 1 to 26 for lubricating a surface.

33. A use according to Claim 32, wherein the surface is a surface in an engine and wherein the lubricating composition is as defined in any one of Claims 16 to 22.

34. A use according to Claim 32, wherein the surface is a metal surface and the wherein the lubricating composition is as defined in any one of Claims 23 to 26.

35. A method of improving the fuel economy performance and/or piston cleanliness performance of an engine and/or a vehicle, such as an automotive vehicle associated with an internal combustion engine, comprising the step of providing to the engine and/or the vehicle a lubricating composition according to any one of Claims 16 to 22.

36. Use of a sulfur-containing additive as defined in any one of Claims 1 to 15, to improve the anti-wear performance and/or oxidative stability performance and/or extreme pressure performance of a lubricating composition.

37. Use of a lubricating composition according to any one of Claims 16 to 22 to improve the fuel economy performance and/or piston cleanliness performance of an engine and/or a vehicle, such as an automotive vehicle associated with an internal combustion engine.

38. A method of cutting, grinding, cleaning and/or cooling a metal surface comprising applying a metalworking fluid as defined in any one of Claims 23 to 26 to said metal surface.

39. Use of an additive as defined in any one of Claims 1 to 15 to improve the cutting, grinding, cleaning and/or cooling performance of a metal working fluid.

Description:
LUBRICATING COMPOSITION COMPRISING A SULFUR-CONTAINING

CARBOXYLIC ACID OR ESTER ADDITIVE

FIELD OF THE INVENTION

The present invention relates to lubricating compositions. In particular, the present invention relates to sulfur-containing additives for use in lubricating compositions as anti wear and/or extreme pressure additives, and to lubricating compositions containing said additives.

BACKGROUND OF THE INVENTION

Lubricating compositions have a variety of uses. A principal use of said compositions is in lubricating the moving parts of internal combustion engines in motor vehicles and powered equipment such as spark ignition engines and compression ignition engines. Said lubricant compositions generally comprise a variety of additives to aid the lubricating oils in performing their functions such as reduced friction and wear, improved viscosity index, detergency, and resistance to oxidation and corrosion. Said lubricant compositions generally comprise a base oil of lubricating viscosity together with the one or more additives. A lubricant base oil may comprise one or more sources of lubricating oil, referred to as base stocks. Typically, lubricants used in internal combustion engines contain about 90% by weight of base oil and around 10% by weight of additives. Lubricant base stocks may be derived from crude oil. Such base stocks are known as mineral oils. Such lubricant base stocks useful in automotive engine lubricants may be obtained as higher boiling fractions from the refining as crude oil or via synthetic routes, and are classified as Group I, II, III, IV and V base stocks according to API standard 1509,“ENGINE OIL LICENSING AND CERTIFICATION SYSTEM”, April 2007 version 16th edition Appendix E. Lubricant base stocks may also be obtained synthetically using synthetic hydrocarbons (that may themselves be derived from petroleum ). Such base stocks are known as synthetic base stocks and include polyalpha-olefins (PAO), synthetic esters, polyalkylene glycols (PAG), phosphate esters, alkylated naphthalenes (AN), silicate esters, ionic fluids and multiply alkylated cyclopentanes (MAC).

Metalworking fluids (MWFs) may also be considered to be lubricant compositions. Metalworking fluids are used in workshops worldwide for the cutting and forming of metals. Their main purposes are to cool and lubricate tools, work pieces and machines, inhibit corrosion, remove swarf, and assist in the cutting, grinding and cleaning of metals. There are a variety of different types of metalworking fluids. Metalworking fluids typically fall into one of the following categories: (1) non-water-miscible oils, (2) water-miscible oils, and (3) fully synthetic oil-free products. Non-water-miscible oils typically comprise a base oil (usually over 95%) This can be a mineral oil, ester oil (e.g. unrefined or chemically modified rapeseed oil) or synthetic oil (e.g. poly-alpha-olefm). Water-miscible oil based metalworking fluids are mixed with water before use, typically in water concentrations of 2 to 25% by weight of the metalworking fluid, depending on the product and type of machining. The same types of oils as used in non-water-miscible oil based metalworking fluids may be used. To combine the oil with water to yield an oil-in-water emulsion, an emulsifier is necessary. Fully synthetic oil-free metalworking fluids are water-miscible and free of oils. They do not require emulsifiers. They may comprise compounds such as water-miscible glycol compounds and water.

Lubricant compositions such as those discussed above may aid in achieving various forms of lubrication. Hydrodynamic lubrication occurs when a machine’s interacting surfaces are separated by a film of the lubricant composition. When the load on the moving parts of the machine is high, and they are moving at a slow speed, the hydrodynamic pressure of the lubricant film may not be sufficient to fully support the load. In this situation, asperities (surface defects) on the surfaces come into contact and undergo elastic deformation. The load is then supported by both the thin fluid film of lubricant and also the asperities. This form of lubrication is known as elastohydrodynamic lubrication (LI II .). When the pressure between the surfaces of two moving parts increases to an extent that the load can no longer be supported by elastohydrodynamic lubrication, the surface asperities deform and surface contact becomes a major component of supporting the load. This condition is known as boundary lubrication. Under these conditions, there is no separation of the interacting surfaces. Wear, abrasion, deformation and welding can ail occur due to dry sliding of the metal surfaces. Additives such as extreme pressure (EP) additives and anti-wear additives are added to the lubricant composition to prevent seizure and welding of the metal surfaces under these conditions. Extreme pressure additives typically contain sulfur and work by reacting with the iron surfaces at the high temperatures generated during boundary ' lubrication to produce an iron sulfide film between the surfaces. Typically, extreme pressure additives are added to lubricant compositions that are used in gearboxes and metalworking fluids used in the cutting and machining of metals.

The efficiency of sulfur-containing extreme pressure additives depends on the sulfur content and the sulfur activity of the additive. In general, the higher the sulfur content, the more effective the additive. The activity of the sulfur-containing additives is generally determined by the temperature at which the molecules react with the contact surface; active sulfur reacts at lower temperature than the inactive sulfur.

Suifurized sperm whale oil was used as an extreme pressure additive historically until it was banned in 1970. Suifurized Jojoba oil can be used as an expensive alternative. The other oldest sulfur-based additive still in use is suifurized lard oil, a suifurized animal triglyceride. Recently suifurized esters made from vegetable oil having unsaturated carbon- carbon bonds have found wide applications as anti-wear and extreme pressure additives.

These suifurized additives are normally prepared by either direct sulfurization with elemental sulfur, such as sulfur powder, or with hydrogen sulfide under high pressure.

Reaction using sulfur powder is difficult to control and yields a mixture of products with mono-sulfide (C-S) bonds, disulfide (C-S-S-C) bonds, and polysulfide (C-Sx-C) bonds. Disulfide or polysulfide bonds are more active than monosulfide bonds, and are known to be corrosive to yellow metals such as copper and alloys containing copper which are commonly found in vehicle engines and in industrial fluid piping. This is especially the case with polysulfide bonds. Inter-molecular sulfide bonds can also be formed by this method, which results in the production of heavy molecules. Furthermore, substantial amounts of hydrogen sulfide are also released in this process, which is very toxic and highly corrosive.

US 4,957,651 and US 4,959,168 disclose processes for producing sulfur-containing extreme pressure additives, which processes comprise reacting a partial fatty acid ester of a polyhydrie alcohol with a fatty acid and a sulfurising agent selected from elemental sulfur, hydrogen sulfide, sulfur halide, sodium sulfide, and a mixture of hydrogen sulfide and sulfur or sulfur dioxide US 5,075,020 discloses compounds for use as extreme pressure additives of the formula: R ! -S-X-S-S-R, wherein R l is either R-S or hydrogen, and R is independently either hydrocarby! or substituted hydrocarbyl, and x is a 1, 3- or 1, 4-diazine.

There is a continued need in the art for extreme pressure additives and anti -wear additives that do not have the problems discussed above associated with them, and that are improved extreme pressure additives when compared to those known in the art. In particular, there is a continued need for sulfur-containing extreme pressure additives that do not use or generate hydrogen sulfide in their process of manufacture and that are less corrosive to yellow metals.

SUMMARY OF THE INVENTION

The present invention is based, in part, on the surprising finding that certain sulfur- containing additives that comprise one or more thioether moieties and an ester or carboxylic acid moiety can be used in lubricant compositions as extreme pressure additives. Said additives have also been found to provide various advantages over sulfur-containing extreme pressure additives known in the art. Such advantages include there being no need to use hydrogen sulfide or elemental sulfur in their method of manufacture. Furthermore, no hydrogen sulfide is generated on manufacture of the additives. Said additives also do not contain any disulfide or polysulfide bonds and have found to be less corrosive to yellow metals than some existing extreme pressure additives that comprise sulfur. Said additives may also impart an improved extreme pressure additive function to lubricant compositions when compared to extreme pressure additives known in the art.

According to an aspect of the invention, there is provided a lubricating composition comprising a base fluid of lubricating viscosity and a sulfur-containing additive, wherein the sulfur-containing additive comprises: i) at least one ester moiety and/or at least one carboxylic acid moiety; and ii) at least one sulfur-containing moiety, wherein the sulfur- containing moiety comprises a thioether, and wherein the sulfur-containing additive is free of disulfide and polysulfide bonds. The sulfur-containing additive preferably comprises at least one ester moiety. The sulfur-containing additive preferably comprises at least one sulfur- containing moiety according to Formula 1 :

wherein;

Ri and R:> are independently selected from monovalent hydrocarbyl groups;

M is -(CHcln-, and

n is 0 to 20, for example 0 to 10 or 1 to 5.

More preferably, the at least one sulfur-containing moiety comprises vicinal dithioethers. For example, where n is 0 in Formula 1 above.

According to another aspect of the invention, there is provided a lubricating composition comprising a base fluid of lubricating viscosity and a sulfur-containing additive, wherein the sulfur-containing additive comprises: i) at least one ester moiety and/or at least one carboxylic acid moiety; and ii) at least one sulfur-containing moiety, wherein the sulfur- containing moiety comprises vicinal dithioethers. Preferably, the sulfur-containing additive is also free of disulfide and poly sulfide bonds.

In a preferred embodiment, the sulfur-containing moiety according to the above aspects is of Formula la:

Formula la

wherein:

Ri and R are independently selected from monovalent hydrocarbyl groups.

In another preferred embodiment, the sulfur-containing additive according to the above aspects is of Formula 2:

Formula 2

wherein:

Ri, R?. and R are, at each occurrence, independently selected from monovalent hydrocarbyl groups;

R3 is a monovalent hydrocarbyl group or -C(=0)0R5;

R4 is a divalent hydrocarbyl group or -C(=0)0R 6- Re is a divalent hydrocarbyl group;

Li and L2 are independently selected from a bond, a sulfur-containing moiety of Formula la, and a sulfur-containing moiety of Formul a 3:

wherein p and q are integers independently selected from 0, 1, 2, 3, 4 and 5, provided that p and q are not both 0.

According to yet another aspect of the invention, there is provided a method of preparing a lubricant composition of the invention as disclosed herein for use in an engine, said method comprising providing a base oil and blending the base oil with a sulfur- containing additive according to the present disclosure and one or more additional lubricant additives.

According to yet another aspect of the invention, there is provided a method of preparing a lubricant composition of the invention as disclosed herein for use as a metal working fluid, said method comprising providing a base fluid and blending the base fluid with a sulfur-containing additive according to the present disclosure and one or more additional lubricant additives.

According to yet another aspect of the invention, there is provided a method of lubricating a surface, said method comprising supplying a lubricant composition according to the present invention to said surface. In some embodiments, the surface is a surface in an engine and the lubricating composition is a lubricant composition as disclosed herein for use in lubricating an engine. In other embodiments, the surface is a metal surface and the lubricating composition is a lubricant composition as disclosed herein for use in a metal working fluid.

According to yet another aspect of the invention, there is provided the use of a lubricant composi tion of the invention for lubri cati ng a surface. In some embodiments, the surface is a surface in an engine and the lubricating composition is a lubricant composition as disclosed herein for use in lubricating an engine. In other embodiments, the surface is a metal surface and the lubricating composition is a lubricant composition as disclosed herein for use in a metal working fluid. According to yet another aspect of the invention, there is provided a method of improving the fuel economy performance and/or piston cleanliness performance of an engine and/or a vehicle, such as an automotive vehicle associated with an internal combustion engine, comprising the step of providing to the engine and/or the vehicle a lubricating composition of the invention as disclosed herein for use in an engine.

According to yet another aspect of the invention, there is provided the use of a sulfur- containing additive of the present disclosure, to improve the anti-wear performance and/or oxidative stability performance and/or extreme pressure performance of a lubricating composition.

According to yet another aspect of the invention, there is provided the use of a lubricating composition of the invention as disclosed herein for use in an engine to improve the fuel economy performance and/or piston cleanliness performance of an engine and/or a vehicle, such as an automotive vehicle associated with an internal combustion engine.

According to yet another aspect of the invention, there is provided a method of cutting, grinding, cleaning and/or cooling a metal surface comprising applying a

metalworking fluid as disclosed herein to said metal surface.

According to yet another aspect of the inventi on, there is provided the use of an sulfur-containing additive as disclosed herein to improve the cutting, grinding, cleaning and/or cooling performance of a metal working fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

The present inventions will now be described by way of example and with reference to the accompanying Figures in which;

Figure 1 illustrates an example of a reaction for producing sulfurized oleic acid and esters thereof by reacting said ester or acid with a dialkyl disulfide;

Figure 2 illustrates an example of a reaction for producing sulfurized linoleic acid and esters thereof by reacting said ester or acid with a dialkyl disulfi de,

Figure 3 sho 's a comparison between the colour of compound 1 (left) and the colour of two commercially available sulfurized esters known in the art and not according to the present disclosure;

Figure 4 compares the Thermal Gravimetric Analysis (TGA) of compound 1 in Example 1 with two commercial existing products;

Figure 5 A shows the Isothermal Thermogravimetric Measurements of compound 1 at different temperatures under oxygen flow; Figure 5 B shows the Isothermal Thermogravimetric Measurements of a commercial product Isofol 16 at different temperatures under oxygen flow,

Figure 6 compares the results of a copper strip storage test for a commercial automotive grade automatic transmission oil spiked with Compound 1 (left) in example 1 and an“inactive” sulfurized ester (right) after 48 h in 150°C.

Figure 7 compares the colour of a commercial automotive grade automatic transmission oil containing no sulfurized ester extreme pressure additive ( top right) and the same commercial automotive grade automatic transmission oil containing Compound 1 (top left) after storage with copper strips for 7 days at 150 °C; and

Figures 8 to 12 show the results of a modified ASTM 5706, part 2 test performed upon various lubricant compositions.

DETAILED DESCRIPTION OF THE INVENTION

Definition of terms

For the purposes of the present invention, the following terms as used herein shall, unless otherwise indicated, be understood to have the following meanings. Other terms that are not as defined below are to be understood as their normal meaning in the art.

The term "hydrocarbyl" as used herein, refers to a monovalent or divalent group, preferably a monovalent group, comprising a major proportion of hydrogen and carbon atoms, preferably consisting exclusively of hydrogen and carbon atoms, which group may be aromatic or preferably saturated aliphatic or unsaturated aliphatic, and the hydrocarbyl group may be optionally substituted by one or more groups that are preferably selected from hydroxyl (-·( ) ! I) groups, carboxylic acid groups, Ci to Cr alkoxy, C 2 to Cg alkoxyalkoxy, C3 to Ce cycloalkyl, -C02(Ci to Cejalkyl, and -OC(0)(Ci to Cejalkyl. Additionally or alternatively, one or more of the carbon atoms, and any substituents attached thereto, of the hydrocarbyl group may be replaced with an oxygen atom (-0-), provided that the oxygen atom is not bonded to another heteroatom. The hydrocarbyl may contain from 1 to 40 carbon atoms.

The hydrocarbyl group may be entirely aliphatic or a combination of aliphatic and aromatic portions. In some examples, the hydrocarbyl group includes a branched aliphatic chain which is substituted by one or more aromatic groups. Examples of hydrocarbyl groups therefore include acyclic groups, as well as groups that combine one or more acyclic portions and one or more cyclic portions, which may be selected from carbocyclic and aryl groups. The hydrocarbyl group includes monovalent groups and polyvalent groups as specified and may, for example, include one or more groups selected from alkyl, alkenyl, alkynyl, carbocyclyl (e.g cycloalkyl or cycloalkenyl) and aryl.

The term "alkyl" as used herein refers to a monovalent straight- or branched-chain alkyl moiety containing from 1 to 40 carbon atoms. Examples of alkyl groups include alkyl groups containing from 1 to 30 carbon atoms, e.g. from 1 to 20 carbon atoms, e.g. from 1 to 18 carbon atoms. Particular examples include alkyl groups containing 4, 6, 8, 10, 12 or 14 carbon atoms. Unless specifically indicated otherwise, the term“alkyl” does not include optional substituents.

The term "cycloalkyl" as used herein refers to a monovalent saturated aliphatic hydrocarbyl moiety containing from 3 to 40 carbon atoms and containing at least one ring, wherein said ring has at least 3 ring carbon atoms. The cycloalkyl groups mentioned herein may optionally have alkyl groups attached thereto. Examples of cycloalkyl groups include cycloalkyl groups containing from 3 to 16 carbon atoms, e.g from 3 to 10 carbon atoms. Particular examples include cycloalkyl groups containing 3, 4, 5 or 6 ring carbon atoms. Examples of cycloalkyl groups include groups that are monocyclic, polycyclic (e.g bicyclic) or bridged ring system. Examples of cycloalkyl groups include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and the like.“Cycloalkenyl” groups correspond to non-aromatic cycloalkyl groups containing at least one carbon-carbon double bond.

The term "alkenyl" as used herein refers to a monovalent straight- or branched-chain alkyl group containing from 2 to 40 carbon atoms and containing, in addition, at least one carbon-carbon double bond, of either E or Z configuration unless specified. Examples of alkenyl groups include alkenyl groups containing from 2 to 28 carbon atoms, e.g. from 3 to 26 carbon atoms, e.g. from 4 to 24 carbon atoms. Examples of alkenyl groups include alkenyl groups containing from 2 to 20 carbon atoms, e.g. from 2 to 12 carbon atoms, e.g. from 2 to 10 carbon atoms. Particular examples include alkenyl groups containing 2, 3, 4, 5 or 6 carbon atoms. Examples of alkenyl groups include ethenyl, 2-propenyl, 1-butenyl, 2-butenyl, 3- butenyf, 1-pentenyl, 2-pentenyl, 3-pentenyl, 1-hexenyl, 2-hexenyl, 3-hexenyl and the like.

The term“alkylene” as used herein refers to a divalent straight- or branched-chain saturated hydrocarbyl group consisting of hydrogen and carbon atoms and containing from 1 to 30 carbon atoms. Examples of alkylene groups include alkylene groups that contain from 1 to 20 carbon atoms, e.g. from 1 to 12 carbon atoms, e.g. from 1 to 10 carbon atoms. Particular examples include alkylene groups that contain 1, 2, 3, 4, 5 or 6 carbon atoms.

The term "aryl" as used herein refers to an aromatic carbocyclic ring system containing from 6 to 14 ring carbon atoms. Examples of aryl groups include aryl groups containing from 6 to 10 ring carbon atoms, e.g. 6 ring carbon atoms. An example of an aryl group includes a group that is a monocyclic aromatic ring system or a polycyclic ring system containing two or more rings, at least one of which is aromatic. Examples of aryf groups include aryl groups that comprise from 1 to 6 exocyclic carbon atoms in addition to ring carbon atoms. Examples of aryl groups include aryl groups that are monovalent or polyvalent as appropriate. Examples of monovalent aryl groups include phenyl, benzyl naphthyl, fluorenyl, azulenyl, indenyl, anthryl and the like. An example of a divalent aryl group is 1 ,4- phenyl ene.

The term“vicinal dithioether” as used herein refers to a moiety comprising two thioether substituents on a hydrocarbyl chain, where the two thioether substituents are bonded to two different carbon atoms of the chain, where the two carbon atoms are bonded to each other. Thus, as will be appreciated, the dithioether moiety according to Formula 1 will be a vicinal dithioether where n is 0. As will also be appreciated, the dithioether moiety according to Formula la is a vicinal dithioether.

The term“disulfide bond” as used herein refers to two divalent sulfur atoms which are covalently bonded to each other by a single bond (-S-S-).

The term“polysulfide bond” as used herein refers to three or more divalent sulfur atoms, where at least one sulfur atom is covalently bonded to two other sulfur atoms by a single bond (-S-Sx-S-, where x is > 1).

The term“base fluid” as used herein refers to the continuous liquid phase of the lubricant composition in which the sulfur-containing additive is dissolved or dispersed. The base fluid may be oil-based, aqueous-based, or an emulsion depending on the intended use of the lubricating composition. The base fluids used in lubricating compositions of the present invention are of lubricating viscosity. The base fluids are typically liquid at room temperature and have a viscosity sufficient to cany out their intended lubricating function under the conditions found in engines.

Lubricant compositions typically require multiple additives in order to improve the overall performance of the lubricant composition. The class of compounds described herein when used as a single component additive or in combination with other lubricant additives impart improved extreme pressure and/or anti-wear properties over the base lubricant. Said additives may also impart improved oxidative stability to the lubricant relative to the base oil.

The sulfur-containing additives of the present disclosure comprise : i) at least one ester moiety and/or at least one carboxylic acid moiety; and ii) at least one sulfur-containing moiety, wherein the sulfur-containing moiety comprises a thioether, and wherein the sulfur- containing additive is free of disulfide and polysulfide bonds and the at least one sulfur- containing moiety preferably comprises vicinal dithioethers. Alternatively, or additionally, the sulfur-containing moiety comprises vicinal dithioethers and the sulfur-containing additive is preferably free of disulfide and polysulfide bonds. In either case, the sulfur-containing additives preferably comprise at least one ester containing moiety.

The sulfur-containing additives used in lubricant compositions of the invention may be any of the additives discussed above.

In preferred embodiments, the sulfur-containing moiety is of Formula la:

wherein:

Ri and R2 are independently selected from monovalent hydrocarbyl groups.

In more preferred embodiments, the sulfur-containing additive is of Formula 2:

Formula 2

wherein:

Ri, R2 and R? are, at each occurrence, independently selected from monovalent hydrocarbyl groups;

R3 is a monovalent hydrocarbyl group or -C(=0)0R5;

R4 is a divalent hydrocarbyl group or -C(=0)0R6-.

Re is a divalent hydrocarbyl group; Li and Li are independently selected from a bond, a sulfur-containing moiety of Formula la, and a sulfur-containing moiety of Formula 3 :

wherein p and q are integers independently selected from 0, 1, 2, 3, 4 and 5, provided that p and q are not both 0

In still more preferred embodiments, Ri and Rz are, at each occurrence, independently selected from Ci to C12 alkyl, preferably Ci to Ce alkyl;

R3 is Ci to Cis alkyl, preferably Ci to C12 alkyl, or -C(=0)OR5;

R-s is Ci to C12 alkyl ene, preferably Ci to Ce alkylene; C2 to C12 alkenyl ene, preferably Ci to

C6 alkenylene; or -C(=0)OR6-;

R5 is Ci to Ci8 alkyl, preferably Ci to C12 alkyl;

Re is Ci to C12 alkylene, preferably Ci to Ce alkylene, or C2 to C12 alkenylene, preferably Ci to Ce alkenylene; and

p and q are integers independently selected from 0, 1 and 2.

In even more preferred embodiments:

Ri and R2 are, at each occurrence, independently selected from Ci to Ce. alkyl, preferably Ci to C3 alkyl;

R3 is Ci to C12 alkyl, preferably Cb to (b alkyl,

R4 is Ci to C ! 2 alkylene, preferably Ci to Ce alkylene; and

R5 is Ci to Ce alkyl, preferably Ci to C3 alkyl.

In some embodiments, at least one of Li and L2 is a bond. In a preferred embodiment instance, Li and L2 are a bond. In another preferred embodiment, one of Li and L2, more preferably Li, is a moiety of Formula 3.

The sulfur-containing additive may be an adduct of the reaction of a di alkyl disulfide with a compound having an alkene groups, such as an alkyl ester of an un saturated fatty acid. Preferably, the fatty acid is a mono or di-unsaturated fatty acid. Most preferably, the fatty acid is selected from crotonic acid, myristoleic acid, palmitoleic acid, sapienic acid, oleic acid, elaidic acid, vaccenic acid, gadoleic acid, eicosenoic acid, erucic acid, nervonic acid, linoleic acid, eicosadienoic acid, docosadienoic acid, or any combination thereof.

In preferred embodiments, the sulfur-containing additive is an adduct of the reaction of a dialkyl disulfide and an alkyl ester of a oleic acid or linoleic acid having the Formula 4 or Formula 5, respectively:

Formula 5

wherein:

Ri and R2, at each occurrence, are independently selected from Ci to Cs alkyl, preferably wherein both Ri and R2 are methyl, and

R3 is selected from Ci to Ce alkyl, preferably wherein R3 is methyl.

Accordingly, in particularly preferred embodiments, the sulfur-containing additives are compounds of formula 4 and formula 5 wherein Ri, R2 and R3 are all methyl.

The total number of carbons atoms in the sulfur-containing additive is typically from

10 to 50, preferably from 15 to 40, more preferably from 18 to 36, and most preferably from 20 to 30. The sulfur-containing additive may typically contain greater than 50 %, such as greater than 70 %, or greater than 90 % by weight of biobased carbon.

The sulfur-containing additives typically comprise from 10 to 50 carbon atoms, such as from 15 to 40 carbon atoms, such as from 18 to 36 carbon atoms or from 20 to 30 carbon atoms. In some embodiments, the sulfur-containing additives contain some amount biobased carbon. For example, the sulfur-containing additives may contain greater than 50%, greater than 70% or greater than 90% by weight of biobased carbon. The sulfur-containing additives of the present invention, comprising vicinal dithioethers, may be synthesised by any technique known in the art for synthesising said compounds. A common approach for the preparation of vicinal dithioethers is through disulfide addition to an alkene functional group, for example dialkyl sulfide or diary 1 sulfide addition to an alkene functional group. Such a transformation is, for instance, known as an analytical technique for assisting in the determination of the location of double bonds in unsaturated compounds. However, chemistry such as this has never been used before in the preparation of sulfur-containing additives for use in lubricant compositions. Typically, the reaction is conducted in the presence of a catalyst. In some embodiments, a homogeneous solution catalyst, such as iodine, dissolved in a suitable solvent is used. Examples of suitable solvents include paraffinic or naphthenic base oils. In other embodiments, the solvent is the reacting component itself.

In some embodiments, the sulfur-containing additives of the invention are synthesised by reacting a compound comprising an alkene group, such as an unsaturated fatty acid ester, with dialkyl disulfide (e.g. dimethyl disulfide) in the presence of a solution catalyst, such as iodine dissolved in a solvent, for example diethyl ether. Synthetic schemes showing the production of sulfur-containing additives of the present disclosure via reaction of dialkyl disulfides with fatty acid esters or fatty acids are shown in Figures 1 and 2.

Preferably, the sulfur-containing additives of the disclosure are adducts of the reaction of a dialkyl disulfide and an alkyl ester of a fatty acid. The fatty acid is an unsaturated fatty acid such as a mono-unsaturated, di-unsaturated, or poly-unsaturated fatty acid. Preferably, the fatty acid is a mono-unsaturated fatty acid. Examples of fatty acids that may be used include the following: crotonic acid, myristoleic acid, palmitoleic acid, sapienic acid, oleic acid, elaidic acid, vaccenic acid, gadoleic acid, eicosenoic acid, erucic acid, nervonic acid, linoleic acid, eicosadienoic acid, docosadienoic acid, or any combination thereof.

A number of other approaches suitable for the preparation of vicinal dithioethers are described in the following: 1) J. Org. Chem, 1985, 50 page 4390-4393; 2) Tetrahedron Letters, 48, 2007, 6312-6317; 3) Bioorganic & Medicinal Chemistry' Letters 17 (2007) 6197- 6201, 4) J. Am. Chem. Soc. 1999, 12 L 482-483, 5) Catalysis Letters 47 (1997) 73-75; and 6) J. Chem. Soc. Perking Trans. 1 1991.

Lubricating compositions for use in engines

The term lubricating composition or lubricant composition as used herein in the context of a lubricating composition for use in an engine is intended to refer to compositions suitable for lubricating the working parts of an engine. Preferably, the engine is an internal combustion engine. Suitable internal combustion engines include, for example, engines used in automotive applications, engines used in marine applications and engines used in land- based power generation plants and engines in wind turbine. The lubricating compositions are particularly suited to use in an automotive internal combustion engine.

The base fluids useful lubricant compositions intended for use in engines are oil-based and are therefore referred to hereinbelow as base oils. As will be appreciated, an oil of a particular viscosity may be suitable for one specific lubricating function within an engine, whereas a different oil with different viscosity may be suitable for a different lubricating function within said engine. The suitability of a particular oil for a particular lubricating function in an engine would be familiar to those of skill in the art.

The lubricating compositions of the present disclosure for use in engines may comprise a base oil formed of one or more base stocks. The base oils employed in said lubricating compositions are typically oils used in automotive and industrial applications such as, among others, turbine oils, hydraulic oils, gear oils, crankcase oils and diesel oils. In particular, said lubricating compositions find utility as gear oils due to the particular need for extreme pressure additives in said oils. 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, Group V, and combinations thereof. The hydrocarbon base oil may be selected from naphthenic, aromatic, and paraffinic mineral oils. Suitable synthetic oils may also be selected from, among others, ester-type oils (such as silicate esters, pentaerythritol esters and carboxylic acid esters), esters, diesters, polyol esters, polyalphaolefins (also known as PAOS or poly-alpha-oiefms), hydrogenated mineral oils, silicones, silanes, polysiloxanes, alkylene polymers, polyglycol ethers, polyols, bio-based lubricants and/or mixtures thereof.

Lubricating compositions of the present disclosure for use in engines may comprise any suitable amount of one or more base stocks and any suitable amount of one or more sulfur-containing additives as described herein. Typically, the composition comprises the one or more sulfur-containing additives in an amount of from 0 01 wt. % to 20 wt. %, preferably from 0.01 wt. % to 10 wt. %, and more preferably from 0.01 wt. % to 5 wt. %. Most preferably, the composition comprises the one or more sulfur-containing additives in an amount of from 0.01 wt. % to 1.0 wt. %. Typically, the base oil, including one or more base stocks, is present in the composition in an amount of from 60% to 95% by weight of the lubricating composition. Preferably, the base oil is present in the composition in an amount of from 70% to 90%, and more preferably from 80% to 90%.

The lubricating composition may also comprise additional lubricant additives. The lubricating composition may comprise a single lubricant additive, in addition to the sulfur- containing additive, though it will typically comprise a combination of additional lubricant additives. The combined amount of lubricant additives (including polymer additives) will typically be present in the lubricating composition in an amount of from about 5 % to about 40 % by weight, such as about 10 % to about 30 % by weight.

Suitable lubricant additives include detergents (including metallic and non- metallic detergents), friction modifiers, dispersants (including metallic and non-metallic dispersants), viscosity modifiers, dispersant 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 sw ? eli agents (sometimes also called seal compatibility agents), extreme pressure additives (including metallic, non-metallic, phosphorus containing, non-phosphorus containing, additional 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.

In some embodiments, the lubricating composition comprises a detergent. Examples of 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).

In some embodiments, the lubricating composition comprises a friction modifier. Suitable friction modifiers include for example, ash-producing additives and ashless additives. Examples of suitable friction modifiers include faty acid derivatives including for example, fatty acid esters, amides, amines, and ethoxyiated amines. Examples of suitable ester friction modifiers include esters of glycerol for example, mono-, di-, and tri-oleates, mono-palmitates and mono-rnyri states. A particularly suitable faty acid ester friction modifier is glycerol monooleate. Examples of suitable friction modifiers also include molybdenum compounds for example, organo molybdenum compounds, molybdenum dialkyl dithiocarbamates, 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 [01 17]

In some embodiments, the lubricating composition comprises a dispersant. Examples of suitable ashless dispersants 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 polya!kylene polyamine, Koch reaction products and the like.

In some embodiments, the lubricating composition comprises a dispersant viscosity modifier. Examples of suitable dispersant viscosity modifiers and methods of making them are described in WO 99/21902, WO 2003/099890 and WO 2006/099250.

In some embodiments, the lubricating composition comprises a viscosity index improver. Exampl es 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 about 15000 to about 1000000, such as about 20000 to about 600000 as determined by gel permeation chromatography or light scattering methods.

In some embodiments, the lubricating composition comprises a pour point depressant. Examples of suitable pour point depressants include Cs to Cis dialkyl fumarate/vinyl acetate copolymers, methacrylates, polyacrylates, polyarylamides, polymethacrylates, polyalkyl methacrylates, vinyl fumarates, styrene esters, condensation products of haloparaffm waxes and aromatic compounds, vinyl carboxylate polymers, terpolymers of di alky fumarates, vinyl esters of faty acids and ally! vinyl ethers, wax naphthalene and the like. In at least some examples, the at least one lubricant additive includes at least one anti-wear additive. Examples of suitable anti-wear additives include non-phosphorus containing additives for example, sulfurised olefins. Examples of sui table anti -wear additives also include phosphorus-containing anti-wear 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).

In some embodiments, the lubricating composition comprises a rust inhibitor. 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, faty acids and amines.

In some embodiments, the lubricating composition comprises a corrosion inhibitor. Examples of suitable 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 al yl sulfonic acids. Examples of suitable epoxidised ester corrosion inhibitors are described in US 2006/0090393.

In some embodiments, the lubricating composition comprises an antioxidant. Examples of suitable antioxidants include alkylated diphenylamines, N-alkylated phenylenediamines, phenyl -a-naphthyl amine, alkylated phenyl-a- naphthylamines, dimethyl quinolines, trimethyl dihydroquinolines 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 Cs to Cis fatty acid, an unsaturated acid or a branched carboxylic acid, for example basic, neutral or acidic Cu(I) and/or Cu(IT) salts derived from alkenyl succinic acids or anhydrides), alkaline earth metal salts of aikylphenolthioesters, suitably containing Cs to C12 alkyl side chains, calcium nonyl phenol sulfide, barium t-octylphenyl sulfide, di octyl phenyl amine, phosphosulfurised or sulfurised hydrocarbons, oil soluble phenates, oil soluble sulfurised phenates, calcium dodecylphenol sulide, phosphosulfurised hydrocarbons, sulfurised hydrocarbons, phosphorus esters, low sulfur peroxide decomposers and the like.

In some embodiments, the lubricating composition comprises an antifoam agent. 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.

In some embodiments, the lubricating composition comprises a seal swell agent.

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

The lubricating composition may comprise lubricant additives in the amounts shown in Table 1.

Table 1

The lubricating compositions may have a kinematic viscosity at 40 °C of less than about 60 cSt, such as less than about 55 cSt, or less than about 50 cSt. The lubricating compositions may have a kinematic viscosity at 100 °C of less than about 12 cSt, such as less than about 10 cSt, or less than about 9.5 cSt. The lubricating compositions may have a viscosity index of greater than about 100, such as greater than about 110, or greater than about 120. The kinematic viscosity at 40 °C and the kinematic viscosity at 100 °C may be measured according to ASTM D445. The viscosity index may be calculated according to ASTM D2270.

The lubricating compositions may have a Noack volatility of less than about 25 %, such as less than about 20 %, less than about 15 %, or less than about 10 % by weight. Noack volatility may be measured according to CEC-L-40-A-93.

The lubricating compositions may have a viscosity at 150 C 'C and a shear rate of 10 6 s 1 of no greater than 3 cP, such as no greater than 2.8 cP. This high temperature high shear viscosity may be measured according to CEC-L-30-A-90.

The lubricating composition may have at least one of:

an oxidative stability performance on a CEC-L-088-02 and/or CEC-L-11 1-16 test indicated by an absolute viscosity increase at 40 °C of no more than 45 cSt, such as no more than 35 cSt or no more than 25 cSt; a fuel economy performance on a CEC-L-054-96 test of at least 2.5 %, such as at least 3 %; and a piston cleanliness performance on a CEC-L-088-02 and/or CEC-L-1 11-16 test indicated by an overall piston merit of at least 8.5, such as 9.

The lubricating compositions may have a cold-crankcase simulator performance at -30 °C of less than about 3000, such as less than about 2800, or less than about 2750, for example as measured according to ASTM D5293.

Preferred lubricating compositions meet the requirements set out in SAE J300.

Preferably, the lubricating composition has at least one of:

a kinematic viscosity at 40 °C of less than 60 cSt, such as less than 55 cSt, or less than

50 cSt;

a kinematic viscosity at 100 °C of less than 12 cSt, such as less than 10 cSt, or less than 9.5 c St;

a viscosity index of greater than 100, such as greater than 1 10, or greater than 120; a viscosity at 150 °C and a shear rate of 10 6 s 1 of no greater than 3 cP, such as no greater than 2.8 cP; and

a Noack volatility of less than 25 %, such as no more than 20%, less than 15 %, or less than 10 % by weight.

Lubricant compositions for use as metal working fluids

Lubricant compositions of the invention may also be suitable for use as metalworking fluids. Accordingly, the invention provides metalworking fluids which may comprise or consist of lubricating compositions of the invention. The metal working fluids according to the invention may be any type of metalworking fluid known in the art such as: (1) non-water-miscible oils, (2) water-miscible oils, and (3) fully synthetic oil-free products. Accordingly, the metalworking fluids may be oil based, aqueous based, a water-in-oil emulsion, or an oil-in-water emulsion. If the metal working fluid is an oil-in-water or water-in-oil emulsion, the metalworking fluid may also comprise an emul sifier to aid in formation of the oil-in-water emulsion or water-in-oil emulsion.

The metalworking fluids of the invention may further comprise one or more additives such as those typically found in metal working fluids. Such additives will be known and familiar to the person skilled in the art. Typical additives for use in metalworking fluids include corrosion inhibitors, pH modifying additives, biocides, surfactants, antioxidants, yellow metal inhibitors, extreme pressure (EP) additives, anti -wear (AW) additives, boundary lubricating additives and combinations thereof.

The sulfur-containing additives of the present disclosure may be present in the metalworking fluids of the present disclosure in any suitable amount. Typically, the sulfur- containing additives of the present disclosure are present in the lubricant composition in an amount of from 0.1% to 30% by weight when said lubricant composition is for use in a metalworking fluid. The exact amount that the sulfur-containing additive is included in the metalworking fluid will depend upon the intended use of the metal working fluid.

Metalworking fluids of the invention may be used in grinding and honing applications as a grinding oil. In such applications, the sulfur-containing additives would typically be present in the lubricant compositions in an amount of from 0.1 to 10 wt. % of the

composition. As discussed above, lubricant compositions of the invention have been found to be less corrosive to yellow metals in use when compared to lubricant compositions known in the art. When used as a grinding oil, metalworking fluids of the invention would typically encounter cobalt since the tools used in grinding typically comprise nickel or cobalt carbide. Cobalt may thus leach into the lubricant oil compositions when used in grinding oil applications. The lower corrosiveness of lubricant compositions of the invention causes less cobalt to leach into the lubricant composition in use.

Metalworking fluids of the disclosure may also be used as cutting oils or broaching oils. In this application, the sulfur-containing additive would typically be present in the lubricant compositions in an amount of from 1 to 20 wt. % of the composition.

Metalworking fluids of the disclosure may also be used as deformation metalworking applications, such as in evaporating stamping fluids. In such applications, typically, the sulfur-containing additives may be present in the lubricant composition in an amount of from 0 1 % to 10 wt. %.

Metalworking fluids of the disclosure may also be used as water-miscible

metalworking fluids. Typically, in such applications, the sulfur-containing additive is present in the metalworking fluid in an amount of from 0.1 wt % to 30 wt. %. At low concentrations such as from 0.1 wt. % to 3 wt. %, the sulfur-containing additives may act as yellow metal corrosion inhibitors. Examples of yellow metals that the sulfur-containing additives may inhibit corrosion of include coper, brass, bronze, and various white metals such as tin-based alloys. In such applications, said sulfur-containing additives may replace known yellow metal inhibitors such as benzotriazole or tolyitri azole. At higher concentrations of sulfur-containing additive such as up to 30 wt. %, the metalworking fluids of the disclosure may be particularly useful on harder metals such as stainless steel.

The invention also provides methods of preparing a lubricant composition according to the present disclosure for use as a metalworking fluid, said method comprising providing a base fluid and blending the base fluid with a sulfur-containing additive of the present disclosure. Said methods of blending would be known to those skilled in the art.

Methods and uses

The present invention also provides methods of lubricating a surface, said method comprising supplying a lubricant composition as described above to said surface. The invention also provides the use of lubricant compositions of the present invention for lubricating a surface. The surface can be a surface in an engine in the case where the lubricant composition is being used as an engine lubricant. Alternatively, wherein the lubricant composition is a metalworking fluid, the surface can be the metal surface of a machining apparatus or a metal substrate.

The invention also provides methods of improving the fuel economy performance and/or piston cleanliness performance of an engine and/or a vehicle, such as an automotive vehicle associated with an internal combustion engine, comprising the step of providing to the engine and/or the vehicle a lubricating composition according to the invention. The invention also provides the use of a lubricating composition of the invention to improve the fuel economy performance and/or piston cleanliness performance of an engine and/or a vehicle, such as an automotive vehicle associated with an internal combustion engine. In said applications, the lubricant composition is for use in lubricating an engine.

The invention also provides a method of cutting, grinding, cleaning and/or cooling a metal surface comprising applying a metalworking fluid of the present disclosure to said metal surface. The invention also provides the use of an additive of the present disclosure to improve the cutting, grinding, cleaning and/or cooling performance of a metal working fluid. In such applications, the lubricant composition is suitable for use as a metalworking fluid.

Methods of operating said engines using lubricants of the invention including the application of said lubricants to the engines are known to the skilled person, as are methods of using lubricant compositions of the invention as metalworking fluids in metalworking operations. The skilled person would also be aware of the necessary amounts of lubricating oil compositions of the invention to use in the methods and uses discussed above.

The present invention also provides the use of a sulfur-containing additive of the present disclosure to improve the anti-wear performance and/or oxidative stability

performance and/or extreme pressure performance of a lubricating composition. The additive may be used to improve any one or more of the above properties of lubricant compositions. Preferably, the additive is used to improve the extreme pressure performance of a lubricant composition, more preferably both the extreme pressure properties and antiwvear properties of a lubricant composi tion, and most preferably all of the extreme pressure, anti -wear and oxidative stability performance of the lubricant composition. .

The term“anti-wear” properties as used herein or“wear reducing properties” with respect to a lubricating oil composition are well known terms of art that the skilled person will be familiar with. The wear properties of a lubricating oil composition are a measure of the extent to which surfaces to which the lubricating oil composition is applied are worn down in use. Wear can be measured, for example, by wear scar which is a distance measurement. The greater the wear scar distance, the more a surface has been worn down in use of the lubricating oil composition. A lubricating oil composition with a lower wear scar distance measurement would be said to have improved anti-wear properties. Tests for measuring wear are known to the skilled person. For example, the w ? ear properties of a lubricating oil composition can be measured by ASTM D4172 - 94 (2016).

The ability of sulfur-containing additives of the present disclosure to impart extreme pressure properties to a lubricant composition can be measured by standard techniques known in the art for measuring said property. For example, extreme pressure properties of a lubricant composition can be measured using technique ASTM D7421-I6.

The oxidative stability performance of lubricant compositions of the present invention can be measured by standard techniques known in the art for measuring said property. For example, oxidative stability performance can be measured using technique ASTM D4742-17. The sulfur-containing additives of the present disclosure comprise similar weight percentages of sulfur to currently commercially available extreme pressure additives for lubricant compositions. In the synthetic schemes shown in Figures 1 and 2, if Ri, II2 and R3 are all methyl groups, then for su!furized methyl oleate, the additive will comprise 16. 4 wt.% sulfur. For sulfurized methyl linoleate, the additive will comprise 26.5 wt.% sulfur. These weight percentages of sulfur are within the sulfur weight percentage range of currently commercially available extreme pressure additives for lubricant compositions. Thus, the additives of the present disclosure are of similar efficiency to commercially available extreme pressure additives since they contain similar amounts of sulfur to react with the metal surfaces of a machine’s moving parts to form the iron sulfide lubricating film between said surfaces.

With regard to sulfur activity, the extreme pressure additives of the present disclosure contain only mono-sulfide bonds. They do not contain di-sulfide or poly-sulfide bonds. As discussed above compounds with di -sulfide and poly-sulfide bonds are more active than compounds that contain only mono-sulfide bonds. Accordingly, the compounds of the present disclosure have a lower sulfur activity than many existing commercially available sulfur- containing extreme pressure additives that comprise poly-sulfide and di-sulfide bonds. As such, additives of the present disclosure are less corrosive to yellow metals that existing compounds and have higher oxidative stability. Presence of the ester group or carboxylic acid group in the sulfur-containing additives of the present disclosure has been found to be beneficial to the lubricity of the compositions containing the additive.

The invention will now 7 be described with reference to the accompanying examples, which are not limiting in nature.

EXAMPLES

Example 1

The compound methyl 9, 10-bis(methylthio)octadecanoate (Compound 1) was prepared by the following method. To a solution of methyl oleate (50 ml, 0.15 mol) was added dimethyldisulfide (DMDS) (10 equivalents). A suspension of I2 (4 equivalents) in Et?.0 (500 mL) was added, after which the mixture turned dark. The resulting mixture was stirred overnight at room temperature. The mixture was washed with a saturated Nai^Ch solution until most colour had disappeared from the organic layer. The organic layer was dried over Na?.S04 and concentrated. Purification using silica gel column chromatography (2.5% EtOAc in heptane) provided the product (0.125 mmol) as light yellow' oil. The product was stirred with activated carbon to remove as much as DMDS, the final product had a purity >98% by

GC-MS.

Compound 1 obtained in Example 1 was added to a base oil containing 80% rapeseed oil and 20% methyl oleate and tested in 4-ball tribometer. The wear scar w'as 0.4 mm 2 for a 5 wt. % Compound 1 in a standard mixture matrix as compared to 0.3 mm 2 for the pure matrix, which indicated the formation of iron sulfide and that the compound could be used as an extreme pressure additive. The wear scar was determined according to ASTM 4172. In this case, a higher wear scar means a better performance since it means that the sulfur in the additive has reacted with the iron surface indicating a higher activity.

Figure 3 show's a comparison between the colour of Compound 1 and the colour of two commercially available sulfurized fatty acid methyl ester lubricant additives known in the art containing a high proportion of disulfide bonds and not according to the present disclosure. Compound 1 has a light yellow' colour and is shown in the bottle on the far left. The compounds in the middle and far right bottles are the commercially available sulfurized fatty acid methyl ester lubricant additives. Compound 1, and the two commercially available additives w'ere each mixed into a commercial automotive grade automatic transmission oil. The commercially available additives are noticeably darker which indicates that they have undergone oxidation to a greater extent than Compound 1. It is also generally preferable to provide fluids that are paler since they are generally perceived in the art to be of a higher quality.

Thermal Gravimetric Analysis (TGA) of Compound 1 from Example 1 and two existing commercial additives (based on fatty alcohols) was conducted, the results of which are shown in Figure 4. TGA measures the mass of a sample as the temperature changes with time. The measurement gives information such as phase transitions, evaporation, thermal decomposition, desorption/adsorption of a sample under the temperature change. The results show' that Compound 1 from Example 1 show's a similar evaporation behavior as existing commercial lubricant additives Isoloi 16 and Isold 20, which are Guerbert alcohols comprising 16 and 20 carbon atoms respectively Isold 16 and Isoloi 20 are used in metal working fluids. Moreover, Compound 1 has approximately 50°C wider application window towards higher temperatures (i.e. it evaporates at higher temperatures). The above properties of the sulfur-containing compound (Compound 1) used in accordance with the present invention are particularly useful in a lubricating composition, especially one for use as a metal working fluid. An increasing trend in tool development is to increase the speed of the moving parts of the tool so as to shorten the contact time of the workpiece and the tool to avoid heat transfer. When this technique is used, more heat remains in the workpiece which either needs more effective cooling or a chemistry that remains active at higher temperatures. Thus lubricating compositions of the invention have particular utility in this application as they may have a higher boiling point than certain existing commercially available lubricants for this application.

Isothermal Thermogravimetric Measurements of Compound land a commercial product (Isofol 16) were taken at different temperatures under standard oxygen flow, the results of which are shown in Figures 5A and Figure 5B, respectively. The results show that

Compound 1 is clearly advantageous over the commercial products for thermal stability under oxidation conditions as is shown by the longer time taken for Compound 1 to degrade.

The above property is useful for engine lubricant applications and also for formulated metalworking fluids, particularly those used in recirculating applications like neat oils or forming fluids. The thermal stability of Compound 1 is also particularly useful in lubricants for use in gear boxes in industrial, HPT (wind turbine) or automotive engines. The results also show that Compound 1 breaks down less when under thermal strain, which indicates that the sulfur-containing compound will be less reactive to copper and therefore stain/corrode it to a lesser extent.

A copper storage test was conducted for an automotive grade automatic transmission oil, the results of wTiich are shown in Figure 6. Storage tests were undertaken for 48 hours at 150°C. The strip on the left in Figure 6 is Compound 1 in the transmission oil, and the strip on the right a commercial copper inactive sulfurized fatty acid methyl ester extreme pressure additive containing a high proportion of disulfide bonds in the same transmission oil. The commercial extreme pressure additive in this case is normally used as an extreme pressure or mild anti-wear additive in industrial fluids, for example, those used in neat cutting applications. Remarkable differences are seen here between the oil containing Compound 1 and the oil containing the commercial extreme pressure additive. The test was stopped early as the copper strip with the commercial extreme pressure additive was completely covered in copper sulfide. This indicates that the commercial extreme pressure additive molecule has released some sulfur to react with the copper metal surface. The fluid w¾s also significantly darker than that containing Compound 1. Accordingly, this example demonstrates that Compound 1 w¾s far less corrosive to copper than the existing commercial sulfurized ester additive.

Example 7

ICP-MS combines a high-temperature ICP (Inductively Coupled Plasma) source with a mass spectrometer. The ICP source converts the atoms of the elements in the sample to ions. These ions are then separated and detected by the mass spectrometer. Metal leaching analysis using inductively coupled plasma (ICP-MS) was also conducted for samples having undergone the copper storage test described in Example 6, one of said samples having the copper strip placed in an automotive grade automatic transmission oil (alone and another strip of the same dimensions in the same transmission oil together with 5 wt.% Compound 1. The results of the metal leaching analysis are shown in Table 2 below. The results show that copper leaching w¾s lower with the sample containing Compound 1 compared to the transmission oil alone (98 ppm vs 116 ppm), despite there being more than 8 times of the sulfur content in the composition comprising Compound 1 (8583 ppm vs 1077). This data shows that the oil comprising

Compound 1 in fact leached copper to a lesser extent than the oil containing no sulfurized ester additive.

Table 2

Figure 7 compares the colour of the transmission oil containing no sulfurized ester extreme pressure additive (top right) and transmission oil containing Compound 1 (top left) after the storage with copper strips for 7 days at 150 °C. The fluid without Compound 1 was appreciably darker (as shown at the top of the figure). At the bottom of the figure, it can be seen that the colour of copper strips is only one sub note (2c vs 2b) less than with the transmission oil alone, despite having more than 8 times sulfur content. The colour was determined according to ASTM D-130.

To test the use of sulfur-containing additives of the invention, tests were carried out with a commercial lubricating fluid. The following samples w ? ere tested:

Sample 1 : Pure commercial lubricating fluid

Sample 2: Commercial lubricating fluid with 66 wt.% of the fluid replaced with a non-sulfurized fatty acid methyl ester.

Sample 3: Commercial lubricating fluid with 66 wt.% of the fluid replaced with Compound 1.

Sample 4: Commercial lubricating fluid with 66 wt.% of the fluid replaced with an copper inactive suifurized fatty acid methyl ester comprising a high proportion of disulfide bonds.

Sample 5: A repetition of Sample 3.

Accordingly, Samples 3 and 5 are lubricant compositions according to the present invention, whereas Samples 1, 2 and 4 are not according to the present invention. Each sample was tested by the method according to ASTM 5706, part 2, which is a standard test for determining the extreme pressure properties of lubricating greases using a high-frequency linear oscillation (SRV) Test machine. The ASTM test prescribes the use of a steel ball bearing in the test method whereas in the present test the method was modified by replacing the steel ball bearing with a steel material (DD13) that is very similar to the lamella used in automatic gear boxes and conforms with DIN --- EN 101 1 1. The results of the tests on Samples 1 to 5 are shown in Figures 8 to 12, respectively.

It can be seen form the results shown in Figures 8 to 12 that Samples 3 and 5 see a drop in the coefficient of friction to 0.36. Lubricating compositions containing Compound 1 thus offer better boundary lubrication at lower loads compared to the other samples tested.

At the end of each test, it is seen that the coefficient of friction rapidly rises. This indicates that all of the sulfur in each lubricating composition has been used up by reacting with the metal surfaces to form iron sulfide films.

The results show that Compound 1 provides very good performance as an additive for providing boundary lubrication under low loads. The performance is comparable to a copper inactive low sulfur content methyl ester (Sample 4). However, Compound 1 provides various advantages over inactive low sulfur content methyl esters such as lower copper corrosion, as shown in previous examples. The results further show that lubricants containing Compound 1 have superior performance to those comprising the non-sulfurized fatty acid methyl ester compound and the commercial copper inactive sulfurized fatty acid methyl ester (Samples 2 and 4, respectively). Neither the commercial sulfurized and non-sulfurized methyl esters offer sufficient boundary lubrication at the start of the tests and therefore do no provide the same extent of extreme pressure additive performance as Compound l and certainly not whilst avoiding copper corrosion to the extent observed with Compound 1.

The results demonstrate that the sulfur-containing compounds used in the present invention, which do not comprise disulfide or polysulfide bonds and/or comprise vicinal thioethers, are a new class of sulfur-containing compounds that could be very useful additives in lubricants for providing boundary lubrication. In particular, the results show that sulfur- containing compounds of the present disclosure could be very' good boundary' lubricants for sliding operations such as in the lamella of gearboxes.