LUBRICANT COMPOSITION CONTAINING AN IONIC LIQUID

Abstract

A lubricant composition, including 20 to 99.5 wt. %, based on a total weight of the lubricant composition, of a base oil, the base oil having a solubility for ionic liquid methyltrioctylammonium-bis(fluorosulfonyl)imide of at least 3 wt. % at a room temperature of 20 C. The base oil contains a base stock A in a proportion of at least 50 wt. %, based on a total weight of the base oil, the base stock A having a solubility for the ionic liquid methyltrioctylammonium-bis(fluorosulfonyl)imide of at least 3 wt. % at a room temperature of 20 C. The lubricant composition further includes 0.5 to 80% wt. %, based on the total weight of the lubricant composition, of an ionic liquid whose anion is bis(fluorosulfonyl)imide.

Claims

1: A lubricant composition, comprising: 20 to 99.5 wt. %, based on a total weight of the lubricant composition, of a base oil, the base oil having a solubility for ionic liquid methyltrioctylammonium-bis(fluorosulfonyl)imide of at least 3 wt. % at a room temperature of 20 C., and the base oil containing a base stock A in a proportion of at least 50 wt. %, based on a total weight of the base oil, the base stock A having a solubility for the ionic liquid methyltrioctylammonium-bis(fluorosulfonyl)imide of at least 3 wt. % at a room temperature of 20 C.; and 0.5 to 80% wt. %, based on the total weight of the lubricant composition, of an ionic liquid whose anion is bis(fluorosulfonyl)imide.

2: The lubricant composition as recited in claim 1, wherein the base stock A is present in a proportion of 50 to 100 wt %.

3: The lubricant composition as recited in claim 1, wherein a proportion of the base oil, based on the total weight of the lubricant composition, is 40 wt. % to 95 wt. %.

4: The lubricant composition as recited claim 1, wherein the proportion of the base stock A, based on the total weight of the lubricant composition, is 10 wt. % to 99.5 wt. %.

5: The lubricant composition as recited in claim 1, wherein the base stock A is an ester and/or a polyglycol containing unsubstituted ethylene units as a carbon group in a repeating unit.

6: The lubricant composition as recited in claim 5, wherein the ester has an oxygen/carbon weight ratio of more than 0.1, and/or the polyglycol has an oxygen/carbon weight ratio of more than 0.44.

7: The lubricant composition as recited in claim 5, wherein the polyglycol is selected from homopolymers of ethylene oxide as a sole monomer and/or copolymers with unsubstituted ethyl groups and 1-methylethyl groups as carbon groups in a repeating unit.

8: The lubricant composition as recited in claim 5, wherein the ester is selected from carboxylic acid esters and mixtures thereof.

9: The lubricant composition as recited in claim 5, wherein the ester is selected from the group consisting of aliphatic ester of aliphatic monocarboxylic acids with a carbon number of C 5 to C 22 with an aliphatic tri-, tetra-, hexa-alcohol with a carbon number of C 3 to C 10, present singly or in mixtures, in particular trimethylolpropane, pentaerythritol, and/or dipentaerythritol, and/or aliphatic ester of aliphatic dicarboxylic acids with a carbon number of C6 to C20, with an aliphatic mono-alcohol and/or di-alcohol with a carbon number of C6 to C22, present singly or in mixtures, estolides, aromatic ester of aromatic tri- and tetra-carboxylic acids with one or a mixture of aliphatic C7 to C22 alcohols, and mixtures thereof.

10: The lubricant composition as recited claim 1, wherein the base oil contains the base stock A in a mixture with a base stock B, the base stock B having a solubility for the ionic liquid methyltrioctylammonium-bis(fluorosulfonyl)imide of less than 3 wt. % at a room temperature of 20 C.

11: The lubricant composition as recited in claim 10, wherein the base stock B is a base stock B1 having an oxygen/carbon weight ratio of at most 0.1 and/or the base stock B is a base stock B2 having a halogen content and/or silicon content of more than 5 wt. %, based on the total weight of the base stock B2.

12: The lubricant composition as recited in claim 10, wherein the base stock B is selected from a group consisting of group I, II, II+, III, IV base stocks and group V base stocks according to the classification of the American Petroleum Institute (API) [NLGI Spokesman, N. Samman, Volume 70, Number 11, pp. 14ff], polyalkylene glycols having ethylene units substituted with aliphatic or aromatic alkyl groups, a percentage by weight of unsubstituted ethylene units in the polyalkylene glycols being less than 20 wt. %, based on a total weight of the polyalkylene glycol, and aliphatic esters of aliphatic dicarboxylic acids with a carbon number of C 22 to C40, with an aliphatic mono-alcohol and/or di-alcohol with a carbon number of 6 to 22, present singly or in mixtures, aliphatic esters of aliphatic tricarboxylic acids with a carbon number of C33 to C60, with an aliphatic mono-alcohol and/or di-alcohol with a carbon number of 6 to 22, present singly or in mixtures, and mixtures thereof.

13: The lubricant composition as recited in claim 10, wherein a proportion of the base stock B is at most 48 wt. % based on the total weight of the lubricant composition, and/or a weight ratio between the base stock A and the base stock B is at least 50:50.

14: The lubricant composition as recited in claim 10, wherein a weight ratio between the base stock A and the base stock B is from 50:50 to 60:40, and a proportion of the ionic liquid whose anion is bis(fluorosulfonyl)imide is 0.5 to 10 wt. %, based on the total weight of the lubricant composition, and/or the weight ratio between the base stock A and the base stock B is from 60:40 to 70:30, and the proportion of the ionic liquid whose anion is bis(fluorosulfonyl)imide is 0.5% to 15 wt. %, based on the total weight of the lubricant composition, and/or the weight ratio between the base stock A and the base stock B is from 70:30 to 90:10, and the proportion of the ionic liquid whose anion is bis(fluorosulfonyl)imide is 0.5% to 40 wt. %, based on the total weight of the lubricant composition, and/or at the weight ratio between the base stock A and the base stock B is from 80:20 to 90:10, and the proportion of the ionic liquid whose anion is bis(fluorosulfonyl)imide is 0.5% to 80 wt. %, based on the total weight of the lubricant composition.

15: The lubricant composition as recited in claim 1, wherein the lubricant composition has a kinematic viscosity at 40 C. of from 20 mm.sup.2/sec to 1500 mm.sup.2/sec.

16: The lubricant composition as recited in claim 1, wherein the ionic liquid has a cation selected from a group consisting of symmetrical ammonium ions, unsymmetrical ammonium ions, NR1R2R3R4+, and phosphonium ions PR1R2R3R4+, wherein the substituents R1 to R4 are independently branched or unbranched, substituted or unsubstituted C1 to C24.

17: The lubricant composition as recited in claim 1, wherein the lubricant composition contains no ionic liquid whose anion is not bis(fluorosulfonyl)imide, or ionic liquids whose anion is not bis(fluorosulfonyl)imide in a proportion of no more than 0.5 wt %, based on the total weight of the lubricant composition.

18: The lubricant composition as recited in claim 1, wherein the lubricant composition contains no ionic liquid containing perfluoroalkyl groups or ionic liquids containing perfluoroalkyl groups in a proportion of no more than 0.5% wt %, based on the total weight of the lubricant composition.

19: The lubricant composition as recited in claim 1, wherein the ionic liquid whose anion is bis(fluorosulfonyl)imide is selected from a group consisting of: ##STR00004## ##STR00005## and mixtures thereof.

20: The lubricant composition as recited in claim 1, the lubricant composition contains a thickening agent in a proportion of from 3 to 35 wt. %, based on the total weight of the lubricant composition, the thickening agent being selected from urea, aluminum complex soaps, simple metal soaps of the elements of the 1st and 2nd main groups of the periodic table, simple lithium soaps, complex metal soaps of the elements of the 1st and 2nd main groups of the periodic table, lithium complex soaps, bentonite, sulfonate, silicate, polyimide, and mixtures thereof.

21: The lubricant composition as recited in claim 20, wherein the thickening agent is a urea with an amine or diamine of a general formula (H2N)xR, where x=1 or 2, and R is an aryl, alkyl, cycloalkyl or alkylene radical having 2 to 22 carbon atoms.

22: The lubricant composition as recited in claim 20, wherein the thickening agent is a diurea containing aliphatic, cycloaliphatic/aliphatic and/or cycloaliphatic ureas, and the diurea is represented by the formula A, ##STR00006## where R2 is a divalent aromatic C6-15 hydrocarbon radical; and R 1 and R3 are independently a C6-20 cycloalkyl radical, cyclohexyl radical, or a straight-chain or branched C8-20 alkyl radical.

23: The lubricant composition as recited in claim 20, wherein the thickening agent is a lithium complex soap, prepared starting from C4-C36 dicarboxylic acids and/or starting from higher functional carboxylic acids with 3 or more, wherein a number of carbon groups is 6 to 60, and/or starting from ester compounds, in each case combined with one or more monocarboxylic acids and/or combined with sebacic acid monostearylamide and/or terephthalic acid monostearylamide.

24: The lubricant composition as recited in claim 1, the lubricant composition contains, as an additive, an aromatic amine in a proportion of 0.5 to 23 wt. % based on the total weight of the lubricant composition.

25: The lubricant composition as recited in claim 1, wherein the lubricant composition has a lower service temperature of no greater than 30 C. according to IP 186, Edition 2015, and/or an upper service temperature of at least +160 C. according to DIN 51821 1+2, Edition 2016-07.

26: A method for lubricating drive elements, comprising, comprising: providing the lubricant composition according to claim 1; and applying the lubricant composition to the drive elements.

27: The method as recited in claim 26, wherein the drive elements are selected from a group of elements consisting of pulley bearings, fan bearings, vacuum pump bearings, rolling-element bearings of electric motors of hybrid and electric vehicles, generators of electric vehicles and rail vehicles, wind turbines, industrial motors, auxiliary units in vehicles, and joints of vehicles.

28: The method as recited in claim 26, wherein the lubricant composition is lubricates drive elements which require a lower service temperature of the lubricant composition of no greater than 30 C. according to IP 186, Edition 2015, and/or an upper service temperature of at least +160 C. determined according DIN 51821 1+2, Edition 2016-07.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Subject matter of the present disclosure will be described in even greater detail below based on the exemplary figures. All features described and/or illustrated herein can be used alone or combined in different combinations. The features and advantages of various embodiments will become apparent by reading the following detailed description with reference to the attached drawings, which illustrate the following:

[0014] FIG. 1 shows results of DSC measurements under O2 atmosphere; and

[0015] FIG. 2 shows results of DSC measurements under N2 atmosphere and shows that P666(14) fsi exhibits an appreciable exothermic reaction around 270 C., whereas P666(14) bta does not. Both tests confirm the lower thermal stability of the ionic liquid with the fsi anion in pure form.

DETAILED DESCRIPTION

[0016] In an embodiment, the present disclosure provides a lubricant composition that does not require the use of bta-containing ionic liquids, and yet has good tribologically relevant properties in terms of friction, wear, and electrical conductivity. In addition, the lubricant composition should have sufficient thermal stability, preferably to at least 180 C., and be able to contain a high proportion of polar base stocks.

[0017] The foregoing is achieved by a lubricant composition including: [0018] a) 20 to 99.5 wt. %, based on the total weight of the lubricant composition, of a base oil, the base oil having a solubility for the ionic liquid methyltrioctylammonium-bis(fluorosulfonyl)imide of at least 3 wt. % at a room temperature of 20 C., and the base oil containing a base stock A in a proportion of at least 50 wt. %, based on the total weight of the base oil, the base stock A having a solubility for the ionic liquid methyltrioctylammonium-bis(fluorosulfonyl)imide of at least 3 wt. % at a room temperature of 20 C. [0019] b) 0.5 to 80% wt. %, based on the total weight of the lubricant composition, of an ionic liquid whose anion is bis(fluorosulfonyl)imide.

[0020] In accordance with the present disclosure, it was found that the lubricant composition makes it possible to eliminate the use of bta-containing ionic liquids, and yet obtain good tribologically relevant properties in terms of friction, wear, and electrical conductivity. In addition, the lubricant composition can contain a high proportion of polar base stocks and also has sufficient temperature stability, preferably to at least 180 C. The high thermal stability of the lubricant composition according to the present disclosure was surprising, since ionic liquids based on bis(fluorosulfonyl)imide as an anion are known to have low thermal stability. Without being bound to any mechanism, it is believed that the surprisingly high thermal stability of bis(fluorosulfonyl)imide as an anion in the lubricant according to the present disclosure is due to a solubilization by the base oil, which has a stabilizing effect. Stabilization by preventing or delaying autocatalytic effects by the base oil is also provided.

[0021] According to the present disclosure, the lubricant composition includes a base oil having a solubility for the ionic liquid methyltrioctylammonium-bis(fluorosulfonyl)imide of at least 3 wt. % at a room temperature of 20 C. This dissolving capacity reveals the high polarity of the base oil. The base oil further contains a base stock A which also has a solubility for the ionic liquid methyltrioctylammonium-bis(fluorosulfonyl)imide of at least 3 wt. % at a room temperature of 20 C. The solubility for the ionic liquid methyltrioctylammonium-bis(fluorosulfonyl)imide is preferably determined as described in the Test Methods section.

[0022] The base oil can contain one or more base stocks A and, optionally, base stocks different from base stock A. However, according to the present disclosure, the lubricant composition does not include any additional base oils other than the base oil.

[0023] In an embodiment of the present disclosure, the base oil has a solubility for the ionic liquid methyltrioctylammonium-bis(fluorosulfonyl)imide of at least 3 wt. %, preferably at least 5 wt. %, more preferably at least 10 wt. %, at a room temperature of 20 C.

[0024] In an embodiment of the present disclosure, the base oil has a solubility for the ionic liquid methyltrioctylammonium-bis(fluorosulfonyl)imide at least in the range of 3 wt % to 30 wt %, and/or at least in the range of 5 wt % to 30 wt %, and/or at least in the range of 10 wt % to 30 wt %, and/or at least in the range of 3 wt % to 20 wt %, and/or at least in the range of 5 wt % to 20 wt %, and/or at least in the range of 10 wt % to 20 wt %, and/or at least in the range of 3 wt % to 15 wt %, and/or at least in the range of 5 wt % to 15 wt %, and/or at least in the range of 10 wt % to 15 wt % at a room temperature of 20 C.

[0025] In an embodiment of the present disclosure, the base oil does not contain an ionic liquid with a melting temperature of less than 100 C., the melting temperature being measured according to DIN EN 61074:1994-07.

[0026] In an embodiment of the present disclosure, the base oil is not an ionic liquid with a melting temperature of less than 100 C., the melting temperature being measured according to DIN EN 61074:1994-07.

[0027] In an embodiment of the present disclosure, the base oil does not contain ions. Preferably, the base oil is composed of organic compounds.

[0028] In an embodiment of the present disclosure, base stock A has a solubility for the ionic liquid methyltrioctylammonium-bis(fluorosulfonyl)imide of at least 3 wt. %, preferably at least 5 wt. %, more preferably at least 10 wt. %, at a room temperature of 20 C.

[0029] In an embodiment of the present disclosure, base stock A has a solubility for the ionic liquid methyltrioctylammonium-bis(fluorosulfonyl)imide at least in the range of 3 wt % to 99 wt %, and/or at least in the range of 5 wt % to 99 wt %, and/or at least in the range of 10 wt % to 99 wt %, and/or at least in the range of 3 wt % to 80 wt %, and/or at least in the range of 5 wt % to 80 wt %, and/or at least in the range of 10 wt % to 80 wt %, and/or at least in the range of 3 wt % to 15 wt %, and/or at least in the range of 5 wt % to 15 wt %, and/or at least in the range of 10 wt % to 15 wt % at a room temperature of 20 C.

[0030] In an embodiment, base stock A is present in a proportion of 50 to 100 wt %, and/or in a proportion of more than 55 wt %, for example of 55 to 100 wt %, and/or in a proportion of more than 60 wt %, for example of 60 to 100 wt %, more preferably in a proportion of more than 70 wt %, for example of 70 to 100 wt %, in each case based on the total weight of the base oil.

[0031] The proportion of the base oil based on the total weight of the lubricant composition is 20 wt. % to 99.5 wt. %, preferably 40 wt. % to 95%, more preferably 60 wt. % to 90%, more preferably 70 wt. % to 95%, and in particular 75 wt. % to 85 wt. %.

[0032] The proportion of base stock A based on the total weight of the lubricant composition is preferably 10 wt. % to 99.5 wt. %, more preferably 35 wt. % to 95%, more preferably 40 wt. % to 90%, in particular 35 wt. % to 85 wt. %.

[0033] In an embodiment, base stock A is an ester and/or a polyglycol, the polyglycol preferably being a polyglycol containing unsubstituted ethylene units as a carbon group in the repeating unit. A preferred polyglycol is a polyalkylene glycol containing unsubstituted ethylene units as a carbon group in the repeating unit, preferably a polyalkylene glycol containing unsubstituted ethylene units and methyl-substituted ethylene units as a carbon group in the repeating unit. Another preferred polyglycol is a polyalkylene glycol containing unsubstituted ethylene units as a carbon group in the repeating unit, the percentage by weight of the unsubstituted ethylene units preferably being at least 20 wt. %, based on the total weight of the polyglycol, for example 20 wt. % to 100 wt. %, preferably at least 30 wt. %, based on the total weight of the polyglycol, for example 30 wt. % to 100 wt. %.

[0034] In a preferred embodiment, the ester has an oxygen/carbon weight ratio of more than 0.1, for example of 0.1 to 0.35, preferably of more than 0.15, for example of 0.15 to 0.30, and/or the polyglycol has an oxygen/carbon weight ratio of more than 0.44, for example of 0.44 to 0.70, preferably of more than 0.50, for example of 0.50 to 0.68.

[0035] A preferred polyglycol is selected from homopolymers of ethylene oxide as the sole monomer and/or copolymers with unsubstituted ethyl groups and 1-methylethyl groups as carbon groups in the repeating unit, the percentage by weight of the unsubstituted ethylene units in the copolymers preferably being at least 20 wt. % based on the total weight of the polyglycol, for example 20 wt. % to 90 wt. %, preferably at least 30 wt. %, based on the total weight of the polyglycol, for example 30 wt. % to 90 wt. %. The end groups of the preferred polyglycol are independently preferably hydroxide groups and/or C1-C20 alkoxide groups, preferably C1-C6 alkoxide groups. The alkoxide end groups can, in addition, be substituted. The end groups can be introduced during the preparation of the polyglycol by reacting the monomeric ethylene oxides with a monofunctional starter. Monofunctional starters are preferably water and alcohols, in particular butanol. It can also be provided that two or more chains of the polyglycol are linked through an end group. The linking end groups are preferably alkyl groups. This can be accomplished during the preparation of the polyglycol from ethylene oxides with a nucleophilic di- or higher functional starter. Examples of difunctional starters are diols, in particular 1,2-ethanediol.

[0036] Preferred esters are carboxylic acid esters, preferably monoesters, diesters, triesters, tetraesters, pentaesters, polyesters, preferably estolides. Preferred are diesters, triesters, tetraesters, pentaesters, polyesters, estolides, and mixtures thereof. Other preferred carboxylic acid esters are aromatic esters, preferably of aromatic C8 to C20, preferably C8 to C10 di-, tri-, or tetra-carboxylic acids with one or a mixture of aliphatic C7-C22 alcohols, and aliphatic esters, preferably of aliphatic C4 to C22 monocarboxylic acids and/or dicarboxylic acids with an aliphatic mono-, di-, tri-, tetra-, penta-, hexa-alcohol with a carbon number of 3 to 22, present singly or in mixtures, preferably polyesters, such as preferably complex esters, estolides, and mixtures thereof. The acid and/or alcohol component and/or the hydroxycarboxylic acid component of the carboxylic acid esters independently preferably have a number of carbon atoms from C3 to C54. Preferred acid components have a number of carbon atoms from C4 to C22, preferred alcohol components have a number of carbon atoms from C3 to C22, and/or preferred hydroxycarboxylic acid components have a number of carbon atoms from C14 to C22. Preferred diesters are diesters whose acid component contains less than 36 carbon atoms, preferably 6 carbon atoms to 20 carbon atoms, more preferably 6 carbon atoms to 12 carbon atoms. The advantage of these esters is their good solvent power for the ionic liquid methyltrioctylammonium-bis(fluorosulfonyl)imide.

[0037] Estolides are oligomeric aliphatic hydroxycarboxylic acids, preferably 12-hydroxystearic acid or oligomers of unsaturated carboxylic acids, preferably oleic acid, where the terminal carboxylic acid group is esterified with a mono-alcohol, di-alcohol, tri-alcohol and/or tetra-alcohol, preferably branched mono-alcohols, preferably Guerbet alcohols, and where any free hydroxide groups can be esterified by reaction with monocarboxylic acids or dicarboxylic acids. Preferred are aliphatic esters of monocarboxylic acids and/or dicarboxylic acids with a carbon number from C3 to C20, preferably C6 to C20, with a mono-, di-, tri-, tetra, penta and/or hexa-alcohol with a carbon number of 3 to 22, present singly or in mixtures.

[0038] In an embodiment, the ester is selected from the group consisting of aliphatic ester of aliphatic monocarboxylic acids with a carbon number of C 5 to C 22 with an aliphatic tri-, tetra-, hexa-alcohol with a carbon number of C 3 to C 10, present singly or in mixtures, in particular trimethylolpropane, pentaerythritol and/or dipentaerythritol, and/or aliphatic ester of aliphatic dicarboxylic acids with a carbon number of C 6 to C 20, with an aliphatic mono-alcohol and/or di-alcohol with a carbon number of 6 to 22, present singly or in mixtures, estolides and aromatic ester of aromatic tri- and tetra-carboxylic acids with one or a mixture of aliphatic C7 to C22 alcohols, and mixtures thereof.

[0039] In an embodiment of the present disclosure, base stock A does not contain an ionic liquid with a melting temperature of less than 100 C., the melting temperature being measured according to DIN EN 61074:1994-07.

[0040] In an embodiment of the present disclosure, base stock A is not an ionic liquid with a melting temperature of less than 100 C., the melting temperature being measured according to DIN EN 61074:1994-07.

[0041] In an embodiment of the present disclosure, base stock A does not contain ions. Preferably, base stock A is composed of organic compounds.

[0042] Other suitable base oils according to the present disclosure contain base stock A in a mixture with a base stock B, base stock B having a solubility for the ionic liquid methyltrioctylammonium-bis(fluorosulfonyl)imide of less than 3 wt. %, for example of 0.01 wt. % to 3 wt. %, preferably of less than 2.5 wt. %, for example of 0.01 wt. % to 2.5 wt. %, more preferably of less than 2 wt. %, for example of 0.01 wt. % to 2 wt. %, more preferably of less than 1 wt. %, for example of 0.01 wt. % to 1 wt. %, at a room temperature of 20 C.

[0043] In an embodiment, base stock B is a base stock B1 having an oxygen/carbon weight ratio of at most 0.1, for example of 0 to 0.1, and/or a base stock B2 having a halogen content and/or silicon content of more than 5 wt. %, for example of 5 wt. % to 30 wt. %, preferably of 10 wt. % to 25 wt. %, based on the total weight of base stock B2.

[0044] If the base oil contains base stock A in a mixture with a base stock B, the proportion of base stock A is more than 50 wt. %, for example from 50 to 90 wt. %, more preferably more than 60 wt. %, for example from 60 to 85 wt. %, in particular more than 70 wt. %, for example from 70 to 85 wt. %, based on the total weight of the base oil.

[0045] Preferred base stocks B are selected from the group consisting of group I, II, II+, III, IV base stocks and group V base stocks according to the classification of the American Petroleum Institute (API) [NLGI Spokesman, N. Samman, Volume 70, Number 11, pp. 14ff], preferably diphenyl ethers, alkylated naphthalenes, polyisobutylenes, silicone oils, polytetrahydrofurans, and oxetane polymers, polyalkylene glycols having, preferably only, ethylene units substituted with aliphatic or aromatic alkyl groups, the percentage by weight of unsubstituted ethylene units in the polyalkylene glycols being less than 20 wt. %, based on the total weight of the polyalkylene glycol, and esters, preferably aliphatic esters of aliphatic dicarboxylic acids with a carbon number of C22 to C40, preferably C34 to C38, with an aliphatic mono-alcohol and/or di-alcohol with a carbon number of 6 to 22, present singly or in mixtures, aliphatic esters of aliphatic tricarboxylic acids with a carbon number of C33 to C60, preferably C50 to C58, with an aliphatic mono-alcohol and/or di-alcohol with a carbon number of 6 to 22, present singly or in mixtures, and mixtures thereof. Preferred base stocks are alkylated diphenyl ethers, polyisobutylenes, polyalfaolefins, and mixtures thereof. The base stocks can also be composed of mixtures of the foregoing base stocks.

[0046] The proportion of base stock B, if present, is preferably less than 50 wt. %, for example 10 to 49 wt. %, more preferably at most 40 wt. %, for example 10 wt. % to 40 wt. %, in particular at most 30 wt. %, for example 10 to 30 wt. %, based on the total weight of the base oil.

[0047] The proportion of base stock B, if present, is preferably at most 48 wt. %, for example 5 to 48 wt. %, more preferably at most 40 wt. %, for example 10 wt. % to 40 wt. %, in particular at most 30 wt. %, for example 10 to 30 wt. %, based on the total weight of the lubricant composition.

[0048] In an embodiment of the present disclosure, base stock B does not contain an ionic liquid with a melting temperature of less than 100 C., the melting temperature being measured according to DIN EN 61074:1994-07.

[0049] In an embodiment of the present disclosure, base stock B is not an ionic liquid with a melting temperature of less than 100 C., the melting temperature being measured according to DIN EN 61074:1994-07.

[0050] In an embodiment of the present disclosure, base stock B does not contain ions. Preferably, base stock B is composed of organic compounds.

[0051] The lubricant composition according to the present disclosure preferably has a kinematic viscosity at 40 C. from 20 mm.sup.2/sec to 1500 mm.sup.2/sec, preferably from 20 mm.sup.2/sec to 320 mm.sup.2/sec, more preferably from 25 mm.sup.2/sec to 220 mm.sup.2/sec, more preferably from 30 mm.sup.2/sec to 150 mm.sup.2/sec. The kinematic viscosity is determined according to ASTM D 7042, Edition 2021-01.

[0052] According to the present disclosure, the proportion of the ionic liquid whose anion is bis(fluorosulfonyl)imide is 0.5 wt. % to 80 wt. %, more preferably 2 wt. % to 40 wt. %, more preferably 2 wt. % to 20 wt. %, more preferably 3 wt. % to 15 wt. %, and in particular from 5 wt. % to 10 wt. %, based on the total weight of the lubricant composition.

[0053] In an embodiment, the base oil contains base stock A and base stock B in a weight ratio between base stock A and base stock B of at least 50:50, for example from 50:50 to 60:40, particularly preferably of at least 60:40, for example from 60:40 to 70:30, more preferably of at least 70:30, for example from 70:30 to 90:10, in particular of at least 80:20, for example from 80:20 to 90:10.

[0054] In an embodiment, the base oil contains base stock A and base stock B in a weight ratio between base stock A and base stock B of from 50:50 to 60:40, and the proportion of the ionic liquid whose anion is bis(fluorosulfonyl)imide (fsi) is 0.5 to 10 wt. %, preferably 3 to 10 wt. %, based on the total weight of the lubricant composition, and/or in a weight ratio between base stock A and base stock B of from 60:40 to 70:30, and the proportion of the ionic liquid whose anion is bis(fluorosulfonyl)imide (fsi) is 0.5% to 15 wt. %, preferably 3 wt. % to 15 wt. %, based on the total weight of the lubricant composition, and/or in a weight ratio between base stock A and base stock B of from 70:30 to 90:10, and the proportion of the ionic liquid whose anion is bis(fluorosulfonyl)imide (fsi) is 0.5% to 40 wt. %, preferably 3 wt. % to 20 wt. %, based on the total weight of the lubricant composition, and/or in a weight ratio between base stock A and base stock B of from 80:20 to 90:10, and the proportion of the ionic liquid whose anion is bis(fluorosulfonyl)imide (fsi) is 0.5% to 80 wt. %, based on the total weight of the lubricant composition.

[0055] In an embodiment of the present disclosure, the ionic liquid has a cation selected from the group consisting of symmetrical and unsymmetrical ammonium ions, NR.sub.1R.sub.2R.sub.3R.sub.4+ and phosphonium ions PR.sub.1R.sub.2R.sub.3R.sub.4+. The substituents R.sub.1 to R.sub.4 can independently be branched or unbranched, substituted or unsubstituted C.sub.1 to C.sub.24, preferably C.sub.1 to C.sub.18, particularly preferably C.sub.6 to C.sub.18 alkyl groups or C.sub.6 to C.sub.30 aryl groups. Preferred substituents are alkoxy, carboxy, amido, amino, thiocarboxy, carbamoyl, oxo, thioxo, and/or hydroxy.

[0056] Preferably, the substituents R.sub.1 to R.sub.4 are selected to have at least 10 carbon atoms in total, preferably at least 20 carbon atoms, more preferably at least 25 carbon atoms.

[0057] In an embodiment of the present disclosure, the ionic liquid has one or more cations selected from the group consisting of: trihexyltetradecylphosphonium, tributyltetradecylphosphonium, tetraoctylphosphonium, trioctylmethylammonium, tributylmethylphosphonium, tributylphosphonium. Preferred are trihexyltetradecylphosphonium, tributyltetradecylphosphonium, tetraoctylphosphonium, and trioctylmethylammonium.

[0058] The lubricant composition according to the present disclosure can also contain mixtures of different ionic liquids in which the anions are bis(fluorosulfonyl)imide, but the cations are different. The lubricant composition according to the present disclosure can also contain further ionic liquids whose anion is not bis(fluorosulfonyl)imide. In this case, the proportion of the further ionic liquid is preferably 0.5 wt. % to 5 wt. %, based on the total weight of the lubricant composition.

[0059] However, in an embodiment of the present disclosure, the lubricant composition contains no ionic liquids whose anion is not bis(fluorosulfonyl)imide. This is advantageous since the use of multiple ionic liquids increases the complexity of the production process and the associated production costs. Also preferably, the lubricant composition contains no ionic liquid containing bis(trifluormethylsulfonyl)imide (bta) as an anion. This is advantageous for toxicological reasons. In an of the present disclosure, the lubricant composition contains no ionic liquids whose anion is not bis(fluorosulfonyl)imide, or contains them in a proportion of no more than 0.5 wt %, based on the total weight of the lubricant composition. Further preferably, the lubricant composition contains no ionic liquid containing perfluoroalkyl groups or contains ionic liquids containing perfluoroalkyl groups in a proportion of no more than 0.5% wt %, based on the total weight of the lubricant composition. This is advantageous for toxicological reasons.

[0060] In an embodiment of the present disclosure, the ionic liquid whose anion is bis(fluorosulfonyl)imide is selected from the group consisting of:

##STR00001##

and mixtures thereof.

[0061] In an embodiment of the present disclosure, the lubricant composition contains a thickening agent. Thus, in a preferred embodiment, the lubricant composition is in the form of a lubricating grease.

[0062] Lubricating greases constitute a preferred embodiment of the lubricant composition, because the positive effects on the service life, which are due to the ionic liquid fsi, are particularly noticeable in lubricating greases, since lubricating greases are usually present in smaller quantities than lubricating oils at the lubrication point.

[0063] Preferably, the lubricant composition contains the thickening agent in a proportion of from 3 to 35 wt. %, more preferably from 4 to 30 wt. %, in particular from 6 to 20 wt. %, in each case based on the total weight of the lubricant composition.

[0064] Preferably, the worked penetration (in 1/10 mm) of the lubricant composition in the form of a lubricating grease is between 400 and 200, more preferably between 330 and 220, more preferably between 300 and 250. The worked penetration is determined according to DIN ISO 2137, Edition 2016-12.

[0065] Preferably, the thickening agent is selected from urea, aluminum complex soaps, simple metal soaps of the elements of the 1.sup.st and 2.sup.nd main groups of the periodic table, in particular simple lithium soaps, complex metal soaps of the elements of the 1.sup.st and 2.sup.nd main groups of the periodic table, in particular lithium complex soaps, bentonite, sulfonate, silicate, polyimide, and mixtures thereof. The term urea refers to reaction products of organic mono-, di-, tri- and higher functional isocyanates and/or mixtures thereof with aliphatic and/or aromatic mono-, di-, tri- or higher functional organic amines.

[0066] In an embodiment, the thickening agent is a urea. The advantage of ureas is that they can be used at high temperatures, and thus, the combination with the ionic liquid containing fsi as an anion results in lubricating greases with a particularly long service life. A preferred urea is a reaction product of a diisocyanate, preferably 2,4-diisocyanatotoluene, 2,6-diisocyanatotoluene, 4,4-diisocyanatodiphenylmethane, 2,4-diisocyanatodiphenylmethane, 4,4-diisocyanatodiphenyl, 4,4-diisocyanato-3,3-dimethyldiphenyl, 4,4-diisocyanato-3,3-dimethylphenylmethane, which can be used individually or in combination, with an amine or diamine of the general formula (H.sub.2N)xR, where x=1 or 2, and R is an aryl, alkyl, cycloalkyl or alkylene radical having 2 to 22 carbon atoms, present singly or in combination.

[0067] In an embodiment, the thickening agent is a diurea containing aliphatic, cycloaliphatic/aliphatic and/or cycloaliphatic ureas.

[0068] In an embodiment, the thickening agent is a diurea represented by formula A

##STR00002##

[0069] where R2 is a divalent aromatic C6-15 hydrocarbon radical; and R 1 and R3 are independently a C6-20 cycloalkyl radical, in particular cyclohexyl radical, or a straight-chain or branched C8-20 alkyl radical.

[0070] Diurea compounds which can be preferably used according to the present disclosure are described in DE112012001102A1.

[0071] Preferred thickening agents contain diurea compounds selected from:

##STR00003##

and mixtures thereof.

[0072] In the case of the ureas of formulas A-E, the alkyl groups are unbranched.

[0073] In an embodiment, the thickening agent is a lithium complex soap. The advantage of lithium complex soaps is that they can be used at high temperatures, and thus, the combination with the ionic liquid containing fsi as an anion results in lubricating greases with a particularly long service life. Preferred lithium complex soaps are prepared starting from C4-C36 dicarboxylic acids, preferably azelaic acid, sebacic acid, suberic acid, terephthalic acid, dodecanedioic acid, and/or starting from higher functional carboxylic acids with 3 or more, preferably 3 to 4 carboxylic acid groups, where the number of carbon groups can be 6 to 60, such as preferably citric acid and trimeric acids, and/or starting from ester compounds, in particular methyl esters and/or triglycerides of one or more of the aforementioned acids, in each case combined with one or more monocarboxylic acids, preferably combined with one or more C4-C24 monocarboxylic acids, preferably stearic acid, hydroxystearic acid, in particular 12-hydroxystearic acid, palmitic acid, oleic acid, salicylic acid, ester compounds, in particular methyl esters and/or triglycerides of one or more of the aforementioned acids, and/or combined with sebacic acid monostearylamide and/or terephthalic acid monostearylamide. Trimeric acids are understood to be tricarboxylic acids obtained by trimerization of unsaturated fatty acids having preferably 54 carbon atoms containing alkyl side chains, double bonds, and cyclic ring systems.

[0074] The lubricant composition can also contain inorganic and/or organic solid lubricants. Preferred solid lubricants are selected from the group consisting of polytetrafluoroethylene (PTFE), molybdenum disulfide, graphite, graphene, boron nitride (hexagonal), tin(IV) sulfide, zinc(II) sulfide, tungsten disulfide, metal sulfide, phosphate, preferably calcium phosphate, carbonate, preferably calcium carbonate, metal oxide, preferably amorphous silicon dioxide, silicate and layered silicate, talc, mica, and mixtures thereof. Preferred solid lubricants are selected from the group consisting of molybdenum disulfide, graphite, graphene, boron nitride (hexagonal), tin(IV) sulfide, zinc(II) sulfide, tungsten disulfide, metal sulfide, phosphate, preferably calcium phosphate, carbonate, preferably calcium carbonate, metal oxide, preferably amorphous silicon dioxide, silicate and layered silicate, talc, mica and mixtures thereof.

[0075] If present, the proportion of solid lubricant in the lubricant composition according to the present disclosure is preferably 0.5 wt. % to 23 wt. %, more preferably 0.5 wt. % to 20 wt. %, and in particular 0.5 wt. % to 18 wt. %, in each case based on the total weight of the lubricant composition.

[0076] In addition, the lubricant composition can contain additives, for example against corrosion, oxidation (antioxidants), and for protection against metal influences, such as chelate compounds, radical scavengers, UV stabilizers, reaction layer formers, viscosity improvers, pour-point depressants, adhesion improvers and/or additives for reducing oil separation in greases.

[0077] Preferably, the proportion of additives in the lubricant composition according to the present disclosure is 0.5 wt. % to 23 wt. %, more preferably 0.5 wt. % to 20 wt. %, more preferably 1 wt. % to 18 wt. %, and in particular 1.5 wt. % to 12 wt. %, based on the total weight of the lubricant composition. Preferably used are additives in the form of phosphorus-containing, sulfur-containing, nitrogen-containing and/or oxygen-containing compounds, polymers, and/or mixtures thereof. Additives which are preferred are aromatic amines, phenols, in particular alkylated phenols, triazoles such as benzotriazoles, tolyltriazoles, esters, in particular sulfurized fatty acid esters, glycerol mono- or di-esters, sorbitan esters, thiadiazoles, dithiocarbamates, in particular molybdenum dithiocarbamates, phosphates, in particular thiophosphates, oligomeric phosphates, oligomeric thiophosphates, dithiophosphates, zinc dialkyldithiophosphates, molybdenum dithiophosphates, amine phosphates, trialkyl phosphates, triaryl phosphates, posphites, metal salts, carboxylic acids, polymers, in particular polymethacrylates, olefin copolymers, and/or mixtures thereof.

[0078] Especially preferred additives are aromatic amines, alkylated phenols, thiadiazoles, dithiocarbamates, triaryl phosphates, amine phosphates, benzotriazoles, and/or mixtures thereof.

[0079] Preferred additives are aromatic amines, since it was surprisingly found that their use makes it possible to very significantly delay the start of oxidation by the ionic liquid.

[0080] Aromatic amines which are preferred in accordance with the present disclosure are styrenated diphenylamine, phenyl-alpha-naphthylamine, phenyl-beta-naphthylamine, octylated and/or butylated diphenylamine, in particular p,p-dioctyl diphenylamine, nonylated diphenylamine. Thus, in an embodiment of the present disclosure, the lubricant composition contains diphenylamine, in particular p,p-dioctyl diphenylamine, as antioxidants.

[0081] In an embodiment of the present disclosure, the lubricant composition contains the additives in a proportion of from 0.5 to 23 wt. %, more preferably from 0.5 to 20 wt. %, in particular from 0.5 to 10 wt. %, based on the total weight of the lubricant composition.

[0082] Preferably, the lubricant composition is characterized by a lower service temperature of no greater than 30 C., for example of 60 C. to 30 C., preferably of no greater than 40 C., for example of 60 C. to 40 C., determined according to IP 186, Edition 2015, and/or preferably an upper service temperature of at least +160 C., for example of 160 C. to 220 C., preferably of at least +180 C., for example of 180 C. bis 220 C., determined according DIN 51821 1+2, Edition 2016-07.

[0083] The present disclosure further provides a lubricant composition including: [0084] a) 20 to 99.5 wt. %, based on the total weight of the lubricant composition, of a base oil, the base oil containing a base stock A in a proportion of at least 50 wt. %, based on the total weight of the base oil, the base stock A containing an ester having an oxygen/carbon weight ratio of more than 0.1, for example of 0.1 to 0.35, preferably of more than 0.15, for example of 0.15 to 0.30, and/or a polyglycol, preferably a polyglycol, containing unsubstituted ethylene units as a carbon group in the repeating unit and having an oxygen/carbon weight ratio of more than 0.44, for example of 0.44 to 0.70, preferably of more than 0.50, for example of 0.50 to 0.68, [0085] b) 0.5 to 80% wt. %, based on the total weight of the lubricant composition, of an ionic liquid whose anion is bis(fluorosulfonyl)imide.

[0086] Embodiments of the aforementioned lubricant composition include embodiments described with respect to the lubricant composition according to the present disclosure mutatis mutandis. For example, embodiments of the aforementioned lubricant composition for base stock A include embodiments described with respect to the disclosed lubricant composition for base stock A.

[0087] A further subject matter of the present disclosure includes the use of the lubricant composition according to the present disclosure for lubricating drive elements, preferably rolling-element bearings, gears, plain bearings, actuators, and/or chains.

[0088] Preferred are drive elements, preferably rolling-element bearings, gears, plain bearings, actuators, and/or chains, at which electrical potentials are present.

[0089] Other preferred drive elements are rolling-element bearings, gears, plain bearings, actuators, and/or chains, which are disposed in systems and machines for producing and conveying foodstuffs, in wind turbines, in vehicles, preferably automobiles, in particular in hybrid and electric vehicles, in rail vehicles, industrial plants, industrial robots, and/or in ships.

[0090] Preferred are the drive elements selected from pulley bearings, fan bearings, vacuum pump bearings, rolling-element bearings of electric motors, in particular of hybrid and electric vehicles, generators, in particular of electric vehicles and rail vehicles, wind turbines, industrial motors, auxiliary units in vehicles, and/or joints of vehicles.

[0091] The lubricant composition is preferably used for lubricating rolling-element bearings of electric motors of hybrid and/or electric vehicles.

[0092] This has the advantage that the lubricant composition according to the present disclosure exhibits a particularly suitable combination of properties for these applications. The very good temperature stability combined with the capability of dissipating electrical potentials is particularly advantageous.

[0093] Another subject matter of the present disclosure includes the use of the lubricant composition according to the present disclosure for lubricating drive elements, preferably rolling-element bearings, which require a lower service temperature of no greater than 30 C., for example of 60 C. to 30 C., preferably of no greater than 40 C., for example of 60 C. bis 40 C. determined according to IP 186, Edition 2015, and/or preferably an upper service temperature of at least +160 C., for example of 160 C. to 220 C., preferably of at least +180 C., for example of 180 C. bis 220 C., determined according DIN 51821 1+2, Edition 2016-07.

[0094] Embodiments of the present disclosure will now be illustrated by several examples, which are non-limiting.

Example 1

[0095] The ionic liquids trihexyl(tetradecyl)phosphonium bis(fluorosulfonyl)imide (P666(14) fsi) and trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)imide (P666(14) bta) are subjected to TGA measurements and the obtained values are compared.

TABLE-US-00001 TABLE 2 Table 2: TGA evaporation losses under air and N2 P666(14) P666(14) P666(14) P666(14) Dynamic TGA based on DIN 51006 bta fsi bta fsi Heating rate 1 C./min. Purge gas Air Nitrogen Antioxidant None Crucible material Aluminum Evaporation loss 120 C. % (m) 0.6 0.6 0.1 Evaporation loss 140 C. % (m) 0.8 0.8 0.2 Evaporation loss 160 C. % (m) 0.9 1.0 0.3 Evaporation loss 180 C. % (m) 0.4 1.2 1.1 0.5 Evaporation loss 200 C. % (m) 0.5 2.4 1.2 1.0 Evaporation loss 220 C. % (m) 0.8 3.9 1.3 1.9 Evaporation loss 240 C. % (m) 1.4 6.7 1.5 3.6 Evaporation loss 260 C. % (m) 2.1 12.9 1.8 7.3

[0096] As expected, the TGA measurements show better temperature stability for the P666(14) bta compared to P666(14) fsi. The evaporation loss values are lower for the P666(14) bta, both when measured under air and under N.sub.2. The better temperature stability of the bta can be explained by the strong carbon-fluorine bond in the anion.

Example 2

[0097] The ionic liquids trihexyl(tetradecyl)phosphonium bis(fluorosulfonyl)imide (P666(14) fsi) and trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)imide (P666(14) bta) are subjected to DSC measurements.

[0098] In FIG. 1, it can be seen that the P666(14) fsi has an earlier onset and, thus, a lower stability than P666(14) bta.

Example 3

[0099] In order to determine the evaporation loss, trihexyl(tetradecyl)phosphonium bis(fluorosulfonyl)imide (P666(14) fsi) and trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)imide (P666(14) bta) are filled into cylindrical screw-cap vials (base area 1.5 cm.sup.2, height 5 cm). An accurately weighed amount of 200 mg of each of the two ILs is filled in. One vial without a ball and one vial with a ball (100Cr6 steel balls according to DIN 51350-1, Edition 2015-03) are used for each of two test temperatures. This is to check whether reactions occur between the metal of the ball and the ionic liquid in the vial.

TABLE-US-00002 TABLE 3 values at 150 C. P666(14) P666(14) bta fsi bta fsi without a ball with a ball Evaporation loss after 24 h [%] 1.15 0.30 14.28 0 Evaporation loss after 48 h [%] 1.45 0.15 15.94 14.44 Evaporation loss after 72 h [%] 1.45 0.70 16.42 13.40 Evaporation loss after 168 h [%] 1.80 1.90 17.40 12.03

TABLE-US-00003 TABLE 4 values at 180 C. P666(14) P666(14) bta fsi bta fsi without a ball with a ball Evaporation loss after 24 h [%] 1.50 0.50 2.00 0 Evaporation loss after 48 h [%] 2.00 2.64 2.59 1.85 Evaporation loss after 72 h [%] 2.25 5.33 4.59 4.13 Evaporation loss after 168 h [%] 2.99 13.04 4.60 14.04

[0100] At a test temperature of 150 C., the two ionic liquids in pure form exhibit differences in evaporation loss. For the samples without a ball, the evaporation loss of the P666(14) bta increases continuously over the measured time period. In comparison, an overall increase in weight can be observed in the values for the fsi sample. In the presence of the steel ball, P666(14) fsi exhibits a lower evaporation loss than P666(14) bta. With a ball, both substances have overall significantly higher evaporation loss values. However, for the P666(14) fsi, the value decreases after an initial increase toward the end.

[0101] At 180, the evaporation losses for both substances are naturally higher than at 150 C. The value curve for the P666(14) fsi is inconspicuous in contrast to the lower test temperature. Nevertheless, at the end of the period, the evaporation losses are higher than for the P666(14) bta. Overall, the observed values can be interpreted to mean that, in addition to decomposition with mass loss, phenomena such as absorption/release of water, corrosion of the steel ball, and catalyzed decomposition also play a role. At 180 C., the tests of the substances in pure form suggest that the stability of the fsi-containing ILs is lower than the stability of the bta-containing ILs.

Example 4

Preparation of Two Greases According to the Present Disclosure and a Reference Grease from a Base Grease A.

[0102] Base grease A is composed of 85 wt. % of a trimellitic acid ester with C9-C11 alcohols having an oxygen/carbon ratio of 0.20 and a base oil viscosity at 40 C. of approx. 72 mm.sup.2/sec (TMSE-A), of 11% wt. % of a urea thickener composed of reaction products of aliphatic saturated amines, aliphatic unsaturated amines, and aromatic amines with a mixture of MDI (4,4-diisocyanatodiphenylmethane) and TDI (mixture of 2,4-diisocyanatotoluene and 2,6-diisocyanatotoluene in a molar ratio of approx. 4:1). The additives used are 0.5 wt. % p,p-dioctyl diphenylamine and 3.5 wt. % of other additives (corrosion protection, anti-wear).

[0103] To this base grease A, 5 wt. % of P666(14) fsi (grease 1 according to the present disclosure) and 5 wt. % of P666(14) bta (reference grease 2) are added and the mixtures are homogenized using a three-roll mill. For grease 3 according to the present disclosure, 5% by weight of N1888 FSI is used and incorporated in the same way.

[0104] Compared to base grease A, the specific electrical resistance is reduced by approx. 3 powers of ten. Surprisingly, the disclosed grease 1 shows an approximately 50% increased service life at 180 compared to reference grease 2, which contains an ionic liquid that is not in accordance with the present disclosure. The grease according to the present disclosure also meets the service life requirement of DIN 51821 1+2 at 200 C.

TABLE-US-00004 Grease 1 according to Grease 2 the present reference Method Standard Unit disclosure grease General data Appearance, color visual beige beige Worked penetration DIN ISO 1/10 mm 269 278 60 DT 2137 Dropping point DIN ISO C. 262 268 2176 Water content by % 0.05 0.06 Karl Fischer Behavior after working Prolonged worked DIN EN 1/10 mm +40 +53 penetration 2137 after 100,000 DT Low-temperature performance Flow pressure DIN mBar 675 650 at 45 C. 51805 Oil separation Oil separation after ASTM D wt % 3.7 2.8 30 h/150 C. 6184 Oil separation after DIN wt % 2.1 1.6 168 h/40 C. 51817 Upper service temperature FAG FE 9 DIN h L 10: 691 h L 10: 423 h 6000 rpm, 1,500N, 51821 L 50: 694 h L 50: 457 h 180 C., B, Edition 1 + 2 2016-07 FAG FE 9 DIN h L 10: 113 h 6000 rpm, 1,500N, 51821 L 50: 249 h 200 C., B, Edition 1 + 2 2016-07 Chemical resistance Water resistance, DIN 0 0 static, 3 h/90 C. 51807 SKF Emcor, dist. based on 0 0 water Water DIN 51802 Corrosion characteristics Copper corrosion DIN 1 1 24 h/160 C. 51811 Noise characteristics SKF BeQuiet+ based on GN3 GN3 Norm M8127 Electrical conductivity Specific electrical based on Ohm*cm 3.18 * 106 3.81 * 106 resistance DIN 53482 Grease 1 Grease 3 according to according to Base Require- the present the present grease Method ments disclosure disclosure A FAG FE 9 L 50 > L 10: 113 h L 10: 105 h L 10: 60 h 6000 rpm, 100 h L 50: 249 h L 50: 146 h L 50: 90 h 1,500N, 200 C., B, DIN 51821 1 + 2, Edition 2016-07

[0105] During endurance testing at 200 C., the grease 1 according to the present disclosure shows a significant increase in the achieved service life by more than a factor of 2.5, relative to the L 50 value. The grease 3 according to the present disclosure also shows an increase in service life by 50% compared to base grease A.

Example 5

[0106] Several greases (greases 4-8) according to the present disclosure and a reference grease are prepared from a base grease B.

[0107] Base grease B is composed of 85 wt. % of a trimellitic acid ester with linear C8 and C10 alkyl groups present in a (molar) ratio of 1:1 (TMSE-B) with an oxygen/carbon ratio of 0.22, 13.5 wt. % of a urea thickener prepared by reacting MDI (4,4-diisocyanatodiphenylmethane) with octylamine in a (molar) ratio of 1.2, 1 wt. % of p,p-dioctyl diphenylamine, 1 wt. % of calcium sulfonate anti-corrosion additive.

TABLE-US-00005 Proportion N1888 P666614 FAG FE 9 of base fsi fsi 6000 rpm, 1,500N, 200 C., B, DIN grease B (wt %) wt % 51821 1 + 2, Edition 2016-07 Base grease B 100 L 10 = 145 h L 50 = 187 h = 7.4 Grease 4 99 1 L 10 = 92 h L 50 = 219 h = 2.2 Grease 5 97 3 L 10 = 83 h L 50 = 141 h = 3.5 Grease 6 95 5 L 10 = 203 h L 50 = 261 h = 7.5 Grease 7 90 10 L 10 = 139 h L 50 = 229 h = 3.8 Grease 8 97 3

[0108] The grease 6 according to the present disclosure shows an increase in service life by approx. 50% compared to base grease B (reference grease) while maintaining the very steep failure curve (high 13 values). The grease 7 according to the present disclosure shows an increase in service life by approx. 40%.

[0109] All greases according to the present disclosure meet the requirements of DIN 51821 1+2 at 200 C., since the L 50 value is above 100 h. This makes it possible to decrease the electrical resistance (see table below) while maintaining the upper service temperature of 200 C.

TABLE-US-00006 Specific electrical Worked penetration resistance [ohm*cm], 60 double strokes 10 V DC voltage, [ 1/10 mm] DIN based on DIN 53482 ISO 2137 Base grease B 2.85E*10exp09 242 Grease 4 3.51*10exp07 249 Grease 5 5.98*10exp06 256 Grease 6 2.35*10exp06 263 Grease 7 7.49*10exp05 261 Grease 8 5.51*10exp06 254

[0110] By adding the IL P666(14) fsi, the specific electrical resistance is significantly reduced. In contrast, the worked penetration changes only to a small extent, which shows that the thickening effect is not disturbed by the ionic liquid.

Example 6

[0111] The specific electrical resistances of mixtures of P666(14) fsi and P666(14) bta in a polyglycol are measured.

[0112] The polyglycol A used is a polyglycol having a kinematic viscosity of 220 mm.sup.2/sec. It is a random copolymer of ethylene oxide and propylene oxide in a (molar) ratio of 1:1 with glycol as a starter. The oxygen/carbon ratio is 0.53.

TABLE-US-00007 Proportion of polyglycol A (wt %) 100 99 97 65 90 Proportion of 0 1 3 5 10 P666(14) fsi (wt %) Specific 7.10 0.41 0.13 0.079 0.031 resistance [Mohm*cm] Proportion of 0 1 3 5 10 P666(14) bta (wt. %) Specific 7.10 0.68 0.22 0.13 0.056 resistance [Mohm*cm based on DIN 53482]

[0113] The tables show that the lubricant compositions according to the present disclosure with P666(14) fsi lead to lower specific resistances compared to P666(14) bta.

[0114] This was surprising because, as shown in the following table, the viscosities of P666(14) fsi are higher than those of P666(14) bta.

TABLE-US-00008 P666(14) fsi P666(14) bta Viscosity at 40 C. 152.9 147.4 [mm.sup.2/s] Viscosity at 100 C. 19.87 18.33 [mm.sup.2/s] VI 150 139 Density at 20 C. 1.014 1.077 [g/cm.sup.3] Density at 100 C. 0.963 1.020 [g/cm.sup.3]

[0115] This suggests that in the case of fsi, the ion pair is actually more tightly bound, i.e., less mobile, and should therefore show lower conductivities. Surprisingly, however, this is not the case, as shown above.

Example 7

[0116] The influence of N1888 fsi on the thermal oxidative stability of an ester oil is investigated.

[0117] The base oil used is the trimellitic acid ester B (trimellitic acid ester with linear C8 and C10 alkyl groups present in a (molar) ratio of 1:1); p,p-dioctyl diphenylamine is used as an aminic antioxidant (Aminic AO).

TABLE-US-00009 Name Oil 1 Oil 2 Oil 3 Oil 4 Aminic AO 1 1 3 3 N1888(14) fsi 0 1 1 3 TMSE-B 99 98 96 94 TGA, air, 180 0.1 180 0.1 180 0.3 180 0.1 temperature 200 0.2 200 0.3 200 0.4 200 0.3 gradient 1 220 0.5 220 0.5 220 0.8 220 0.7 k/min 240 1.2 240 1.2 240 1.7 240 1.8 260 3.2 260 3.2 260 4.0 260 4.6 280 9.7 280 8.4 280 9.3 280 11.1 300 50.1 300 38.6 300 26.6 300 29.7 DSC, O2, Ox. start 204.5 Ox. start 256.7 Ox. start 240.2 Ox. start 239.5 temperature Onset 242.5 Onset 269.1 1st onset 261.2 Onset 283.2 gradient 1 2nd onset 276.5 k/min Open dish 43.24 29.64 22.38 23.02 test 230 C., 63.22 54.92 36.58 34.28 24/48/72 h 79.76 (lacquer) 69.63 (dense oil, 48.82 (oil, 53.03 (oil, Loss [%] slightly grainy) grainy) highly grainy) Shear viscosity 108 113 119 125 Start 1355 266 209 208 24 h 33800 1320 391 298 48 h 12150 647 72 h Specific 3.43*1012 3.26*1010 2.95*1010 2.60*1010 resistance [Ohm*cm] based on DIN 53482 Name Oil 5 Oil 6 Oil 7 Aminic AO 0 0 3 N1888 fsi 3 1 0 TMSE-B 97 99 97 TGA, air, 180 0.1 180 0.3 180 0.3 temperature 200 0.2 200 0.5 200 0.5 gradient 1 220 0.7 220 0.9 220 0.9 k/min 240 2.0 240 1.9 240 1.9 260 8.4 260 4.4 260 4.2 280 21.7 280 20.2 280 10.6 300 49.2 300 51.8 300 45.3 DSC, O2, Ox. start 223.7 Ox. start 224.7 Ox. start 205.7 temperature 1st onset 234.1 Onset 231.8 Onset 253.9 gradient 1 2nd onset 264.0 k/min Open dish 36.26 38.49 28.30 test 230 C., 56.86 59.95 53.14 24/48/72 h 73.04 (tar- 77.04 (rubber- 67.23 (tar- Loss [%] like) like) like) Shear viscosity 116 109 117 Start 577 920 405 24 h 3550 11950 7630 48 h 110500 42100 72 h Specific 3.08*1010 4.99*1010 1.38*1013 resistance [Ohm*cm] based on DIN 53482

[0118] The shear viscosity is determined at 25 C. at a shear rate of 300 l/s according to DIN 53019-1,3. The open dish test is performed using evaporation dishes made of aluminum, diameter 50 mm. An accurately weighed amount of 5 g+/0.1 g is filled in. The measurement is carried out in a circulating air oven. The measurement is conducted over 24/48/72 h. In each case, the evaporation loss is determined and the shear viscosity is measured.

[0119] The oils 2, 3, 4, 5 and 6 represent lubricant compositions according to the present disclosure.

[0120] A comparison of the samples containing only P666(14) fsi (oils 6 and 5) with the samples containing only aminic AO (oils 1 and 7) shows that the start of oxidation is delayed to a greater extent by the ionic liquid.

[0121] The samples in which the aminic antioxidant p,p-dioctyl diphenylamine is combined with P666(14) fsi show a significant positive influence on the evaporation losses in the TGA up to 300 C., on the start of oxidation and the onset in the DSC, and on the evaporation values in the open dish test (see, e.g., the evaporation values after 24 h.)

Example 8

[0122] Solubility tests are performed to determine the solubility of N1888fsi in base oils containing base stocks of different polarity. The results are shown in the following tables.

TABLE-US-00010 Base oil: PAO 8/trimellitic acid ester B with linear C8 and C10 alkyl groups (ratio of the two base stocks 60:40). PAO 8 has an oxygen/carbon ratio of 0. The trimellitic acid ester B has an oxygen/carbon ratio of 0.22. This results in an oxygen/carbon ratio of 0.088 for the base oil. Amount of N1888fsi 0 wt % 1 wt % 3 wt % 5 wt % 10 wt % Visual assessment (clear/2 phases) 2 2 2 clear clear phases phases phases V 40 [mm.sup.2/s] 44.789 46.035 V 100 [mm.sup.2/s] 7.58 7.73 V I 136 136 Density 40 C. 0.8675 0.8692 g/ml Density 100 C. 0.8286 0.8300 g/ml Specific 1.60E+11 1.73E+08 resistance [*cm]

[0123] The base stock mixture used here is not suitable for producing a lubricant composition according to the present disclosure, as the content of base stock A is too low and, therefore, the solubility of N1888fsi is too low.

TABLE-US-00011 Base oil: PAO 8/trimellitic acid ester B with linear C8 and C10 alkyl groups (ratio of the two base stocks 30:70). PAO 8 has an oxygen/carbon ratio of 0. The trimellitic acid ester B has an oxygen/carbon ratio of 0.22. This results in an oxygen/carbon ratio of 0.15 for the base oil. Amount of N1888fsi 0 wt % 1 wt % 3 wt % 5 wt % 10 wt % Visual assessment (clear/2 phases) clear clear clear clear clear V 40 46.608 47.900 50.759 53.966 63.845 [mm.sup.2/s] V 100 7.68 7.81 8.14 8.53 9.66 [mm.sup.2/s] V I 132 131 132 132 133 Density 0.9105 0.9118 0.9140 0.9163 0.9217 40 C. g/ml Density 0.8698 0.8710 0.8733 0.8754 0.8811 100 C. g/ml Specific 1.25E+11 4.84E+07 5.73E+06 1.48E+06 3.36E+05 resistance [*cm]

[0124] The base stock mixture used here is suitable for producing a lubricant composition according to the present disclosure, as the content of base stock A is sufficient and, therefore, the solubility of N1888fsi is sufficient.

TABLE-US-00012 Base oil: PAO 8/trimellitic acid ester B with linear C8 and C10 alkyl groups (ratio of the two base stocks 20:80). PAO 8 has an oxygen/carbon ratio of 0. The trimellitic acid ester B has an oxygen/carbon ratio of 0.22. This results in an oxygen/carbon ratio of 0.18 for the base oil. Amount of N1888fsi 0 wt % 1 wt % 3 wt % 5 wt % 10 wt % Visual assessment (clear/2 phases) clear clear clear clear clear V 40 47.839 49.129 51.802 54.932 63.716 [mm.sup.2/s] V 100 7.77 7.90 8.20 8.56 9.53 [mm.sup.2/s] V I 130 130 130 130 130 Density 40 C. 0.9259 0.9270 0.9289 0.9309 0.9358 g/ml Density 0.8846 0.8857 0.8877 0.8896 0.8947 100 C. g/ml Specific 9.55E+10 3.31E+07 3.89E+06 1.17E+06 3.05E+05 resistance [*cm]

[0125] The base stock mixture used here is suitable for producing a lubricant composition according to the present disclosure, as the content of base stock A is sufficient and, therefore, the solubility of N1888fsi is sufficient.

TABLE-US-00013 Base oil: trimellitic acid ester B with linear C8 and C10 alkyl groups. The trimellitic acid ester B has an oxygen/carbon ratio of 0.22. Amount of N1888fsi 0 wt % 1 wt % 3 wt % 5 wt % 10 wt % Visual assessment (clear/2 phases) clear clear clear clear clear V 40 51.173 56.315 55.093 58.045 66.018 [mm.sup.2/s] V 100 7.99 8.41 8.41 8.74 9.58 [mm.sup.2/s] V I 125 121 125 126 125 Density 40 C. 0.9587 0.9594 0.9612 0.9626 0.9663 g/ml Density 0.9162 0.9171 0.9186 0.9202 0.9241 100 C. g/ml Specific 9.54E+10 1.54E+07 1.85E+06 6.55E+05 1.92E+05 resistance [*cm] Base oil: trimellitic acid ester B with linear C8 and C10 alkyl groups Amount of N1888fsi 20 wt % 40 wt % 60 wt % 80 wt % Visual assessment (clear/2 phases) clear clear clear clear V 40 [mm.sup.2/s] 84.201 125.240 167.340 200.530 V 100 [mm.sup.2/s] 11.31 14.77 18.34 21.32 V I 123 120 122 126 Density 40 C. 0.9734 0.9883 0.9626 1.0173 g/ml Density 100 C. 0.9872 0.9472 1.0158 0.9780 g/ml Specific 6.98E+04 2.74E+04 2.35E+04 2.08E+04 resistance [*cm]

[0126] The examples show that the ionic liquid N1888fsi can be mixed with the trimellitic acid ester over a very wide concentration range.

[0127] The base stock used here is suitable for producing a lubricant composition according to the present disclosure, since only base stock A is present and, therefore, the solubility of N1888fsi is very good.

TABLE-US-00014 Base oil: polypropylene oxide homopolymer (non-polar), butanol-started, kinematic viscosity at 40 C. approx. 120 mm.sup.2/sec with an oxygen/carbon ratio of 0.44 Amount of N1888fsi 0 wt % 1 wt % 3 wt % 5 wt % 10 wt % Visual assessment (clear/2 phases) 2 2 2 2 clear phases phases phases phases V 40 [mm.sup.2/s] V 100 [mm.sup.2/s] V I Density 40 C. g/ml Density 100 C. g/ml Specific resistance [*cm]

[0128] The base stock used here is not suitable for producing a lubricant composition according to the present disclosure, since no base stock A is contained and, therefore, the solubility of N1888fsi is not sufficient.

TABLE-US-00015 Base oil: polypropylene oxide homopolymer (non-polar), butanol-started, kinematic viscosity at 40 C. approx. 120 mm.sup.2/sec/trimellitic acid ester B with linear C8 and C10 alkyl groups (polar), mixture ratio in wt % 50:50. The oxygen/carbon ratio of 0.22 of base oil is 0.33. Amount of N1888fsi 0 wt % 1 wt % 3 wt % 5 wt % 10 wt % Visual assessment (clear/2 phases) clear clear clear clear clear V 40 82.62 84.02 86.92 90.15 98.79 [mm.sup.2/s] V 100 13.85 13.97 14.20 14.64 15.51 [mm.sup.2/s] V I 173 172 170 170 167 Density 0.9675 0.9682 0.9693 0.9708 0.9741 40 C. g/ml Density 0.9241 0.9249 0.9263 0.9278 0.9312 100 C. g/ml Specific 1.32E+10 1.18E+07 2.02E+06 7.91E+05 2.13E+05 resistance [*cm]

[0129] The base stock mixture used here is suitable for producing a lubricant composition according to the present disclosure, as the content of base stock A is sufficient and, therefore, the solubility of N1888fsi is sufficient.

TABLE-US-00016 Base oil: hydrogenated dimer acid ester (non-polar), alcohol component: 2-ethylhexanol. The oxygen/carbon ratio is 0.10. Amount of N1888fsi 0 wt % 1 wt % 3 wt % 5 wt % 10 wt % Visual assessment (clear/2 phases) 2 2 2 clear clear phases phases phases V 40 [mm.sup.2/s] 102.61 103.93 V 100 [mm.sup.2/s] 14.33 14.40 V I 143 142 Density 0.8934 0.8947 40 C. g/ml Density 0.8548 0.8561 100 C. g/ml Specific 1.36E+11 2.75E+08 resistance [*cm]

[0130] The base stock used here is not suitable for producing a lubricant composition according to the present disclosure, since no base stock A is contained and, therefore, the solubility of N1888fsi is not sufficient.

TABLE-US-00017 Polyethylene glycol, molecular weight 200 (polar). The oxygen/carbon ratio is 0.66. Amount of N1888fsi 0 wt % 1 wt % 3 wt % 5 wt % 10 wt % Visual assessment (clear/2 phases) clear clear clear clear clear V 40 22.33 22.46 22.80 23.14 24.17 [mm.sup.2/s] V 4.16 4.19 4.23 4.28 4.40 100 [mm.sup.2/s] V I 77 79 80 82 84 Density 1.1088 1.1081 1.1064 1.1048 1.1004 40 C. g/ml Density 1.0610 1.0603 1.0588 1.0573 1.0534 100 C. g/ml Specific 8.54E+03 1.86E+03 8.68E+02 5.95E+02 3.37E+02 resistance [*cm]

[0131] The base stock used here is suitable for producing a lubricant composition according to the present disclosure, since only base stock A is present and, therefore, the solubility of N1888fsi is very good.

[0132] It turns out that N1888fsi is readily soluble in base oils with a polar base stock content of more than 50 wt. %, even in larger quantities. The polar base stocks are selected from esters and polyalkylene glycols prepared with ethylene oxide as a component of the reaction mixture.

Example 9: A Base Grease C and, Based on this, a Grease 9 that is not in Accordance with the Present Disclosure are Produced

TABLE-US-00018 Propor- FAG FE 9 tion N1888 6000 rpm, 1,500N, 160 C., of base fsi A, DIN 51821 1 + 2, grease C (wt %) Edition 2016-07 Base grease 100 L 10 = 164 h L 50 = 236 h = 7.4 C Grease 9, 97 3 L 10 = 167 h L 50 = 207 h = 8.7 not in accordance with the present disclosure

[0133] Base grease C is considered to belong to NLGI class 1. The base oil has a kinematic viscosity of 130 mm.sup.2/sec at 40 C. and is a non-polar mixture of mineral oil/PAO. The oxygen/carbon ratio is close to zero. The thickener is a mixture of urea/calcium complex soap. Also contained are common additives for oxidative stabilization, for improving the load-carrying capacity, and for protection against corrosion. The addition of the ionic liquid does not increase the service life, the L 50 value is even reduced. It turns out that in greases whose base stock is non-polar (mineral oil and PAO), no improvement is achieved by using the ionic liquids.

Example 10

[0134] A lubricating grease D is prepared having the following composition: [0135] 41 wt. % of trimellitic acid ester A with C9-C11 V 40 approx. 72 mm.sup.2/sec (oxygen/carbon ratio of 0.20) [0136] 17 wt. % of PIB, Mn approx. 1300 g/mol determined with GPC (oxygen/carbon ratio of 0.0) [0137] 20 wt. % of alkylated diphenyl ether, V 40 approx. 100 mm.sup.2/sec (oxygen/carbon ratio of 0.04) [0138] 13 wt. % lithium complex thickener from azelaic acid/12-hydroxystearic acid [0139] 4% wt. % of aminic antioxidant [0140] 5 wt. % of a corrosion protection additive package, AW and EP

[0141] The percentage by weight of trimellitic acid ester A in the total base oil is 52.6%.

TABLE-US-00019 Example grease D + 3% N1888 Example fsi according grease D to the present reference Method Standard Unit disclosure grease General data Worked penetration DIN ISO 1/10 mm 283 273 60 DT 2137 Dropping point DIN ISO C. Greater than Greater than 2176 300 C. 300 C. Flow pressure DIN mBar 537 825 at 40 C. 51805 Oil separation after ASTM D wt % 7.3 5.8 30 h/150 C. 6184 Specific resistance based on [ohm*cm] 9.68E+07 3.88E+10 DIN 53482 Evaporation loss, DIN % 15.6 11.4 24 h/180 C. 58397 Shear viscosity at DIN mPas 5300 5800 25 C., shear rate 300 53019- 1/s, fresh 1, 3 Shear viscosity at DIN mPas 3660 5935 25 C., shear rate 300 53019- 1/s, after evaporation 1, 3 loss test 24 h/180 C. according to DIN 58397

[0142] The disclosed composition shows advantages in terms of reducing the specific resistance, the low-temperature performance (flow pressure), and avoiding hardening when stored at 180 C. (no increase in the dynamic viscosity).

Example 11: Solubility Test of N1888 Fsi in an Estolide Base Stock

TABLE-US-00020 Estolide base stock, homopolymer 12-hydroxystearic acid, esterified with 2-ethylhexanol, kinematic viscosity at 40 C. approx. 148 mm.sup.2/s; the oxygen/carbon ratio is 0.17) Amount of N1888fsi 0 wt % 1 wt % 3 wt % 5 wt % 10 wt % Visual assessment (clear/2 phases) clear clear clear clear clear V 40 148.35 149.84 153.81 159.24 184.61 [mm.sup.2/s] V 100 21.5 21.6 21.9 22.7 24.9 [mm.sup.2/s] V I 170 170 169 171 167 Density 0.8990 0.9004 0.9028 0.9051 0.9111 40 C. g/ml Density 0.8598 0.8610 0.8634 0.8658 0.8719 100 C. g/ml Specific 2.63E+10 8.83E+07 7.72E+06 2.35E+06 5.37E+05 resistance [*cm]

[0143] In the concentration range investigated, N1888 fsi is soluble in the estolide base stock. As the amount of IL, increases, the specific resistance decreases.

[0144] The base stock used here is suitable for producing a lubricant composition according to the present disclosure, since only base stock A is present and, therefore, the solubility of N1888fsi is sufficient.

Evaluation of the Test Results

[0145] Overall, it could be demonstrated that lubricant compositions and, in particular, greases containing ionic liquids based on fsi as an anion achieve performance levels in the range of those achieved with a product doped with bta-based ionic liquids as additives. Thus, fsi-based ionic liquids are a good alternative to bta-containing ionic liquids. In addition, fsi-based additives have the advantage over bta-containing additives that they do not contain persistent CFx groups.

[0146] In the tests in which the P666(14) fsi was investigated in pure form, the results show, as expected, a lower thermal stability compared to P666(14) bta. This can mainly be explained by the fact that the anion lacks strong carbon-fluorine bonds, which has an overall effect on the stability of the molecule.

[0147] Surprisingly, the difference in performance between the two ionic liquids is significantly lower when they are used as an additive in the grease. The values of the tested properties show that the performance effect of P666(14) fsi in the grease system under consideration is very similar to that of P666(14) bta. With the fsi material as an additive, the requirements for high and low temperature properties and for electrical conductivity can be met in the temperature ranges considered.

[0148] In addition, the corrosion stability requirements can also be met with the lubricant composition according to the present disclosure.

[0149] Overall, it could be shown that, in terms of performance, lubricant compositions containing fsi-based ionic liquids are a good alternative to lubricant compositions with bta-containing ionic liquids. In addition, the lubricant compositions according to the present disclosure do not contain persistent CFx groups and are therefore biodegradable.

Test Methods

[0150] In order to determine the solubility of the ionic liquid N1888 fsi in the base stocks or base oils, the base stock(s) that form(s) the base oil(s) is/are placed in a beaker and N1888 fsi is added in the respective concentration. The mixture is stirred at 60 C. for 10 min using a magnetic stirrer. After cooling to room temperature, the mixtures are visually inspected and the electrical resistance is determined. N1888 fsi is insoluble in base stock or base oil at a certain concentration if the turbidity value determined by a turbidity measurement according to DIN EN ISO 7027-1:2016-11 at 25 C. is more than 1 FNU higher than for pure base stock or base oil. Similarly, N1888 fsi is insoluble in base stock or base oil at a certain concentration when two or more phases are formed. N1888 fsi is soluble in base stock or base oil at a certain concentration if the turbidity value determined by a turbidity measurement according to DIN EN ISO 7027-1:2016-11 at 25 C. is no more than 1 FNU higher than for pure base stock or base oil. Preferably, a 2100 AN IS from Hach is used as a measuring device.

[0151] In order to determine the kinematic viscosity at 40 C., 100 C., the viscosity index, and the densities at 40 C. and 100 C., a Stabinger viscometer according to ASTM D 7042, Edition 2021-01, is used, unless otherwise specified.

[0152] Determination of the carbon content: The carbon content is determined using ASTM D 5291:2021.

[0153] The oxygen contents are determined using JPI-5S-68-11.

[0154] The oxygen/carbon weight ratio is obtained by dividing the mass fraction of oxygen (wt %), determined according to JPI-5S-68-11, by the mass fraction of carbon (wt %), determined according to ASTM D 5291:2021.

[0155] While subject matter of the present disclosure has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. Any statement made herein characterizing the invention is also to be considered illustrative or exemplary and not restrictive as the invention is defined by the claims. It will be understood that changes and modifications may be made, by those of ordinary skill in the art, within the scope of the following claims, which may include any combination of features from different embodiments described above.

[0156] The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article a or the in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of or should be interpreted as being inclusive, such that the recitation of A or B is not exclusive of A and B, unless it is clear from the context or the foregoing description that only one of A and B is intended. Further, the recitation of at least one of A, B and C should be interpreted as one or more of a group of elements consisting of A, B and C, and should not be interpreted as requiring at least one of each of the listed elements A, B and C, regardless of whether A, B and C are related as categories or otherwise. Moreover, the recitation of A, B and/or C or at least one of A, B or C should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B and C.