CA3227839A1 - Use of hemimellitic acid ester as a base oil for lubricant compositions - Google Patents

Abstract

The invention relates to the use of hemimellitic ester of the following general formula I, wherein R1, R2 and R3 are independently of one another a) an unsubstituted, branched or unbranched C1 to C20 alkyl group or b) a C1 to C5 alkyl group containing at least one substituent selected from the group consisting of cycloalkyl groups and aromatic groups or C) a C5 to C20 aromatic group or a C5 to C20 cycloalkyl group, wherein the hemimellitic ester of formula I may be in the form of a mixture of different compounds of formula I, as a base oil of a lubricant composition for lubricating tribological systems.

Description

USE OF HEMIMELLITIC ACID ESTER AS BASE OIL FOR LUBRICANT
COMPOSITIONS
DESCRIPTION
[0001] The invention relates to the use of hemimellitic acid ester as base oil for lubricant compositions, and also to lubricant compositions based on hemimellitic acid ester as base oil.

[0002] Lubricants are substantial components of many industrial processes in which two or more surfaces move in close contact. The range of application for lubricating oils is very broad and comprises, inter alia, motor vehicle lubricants, lubricants for two-stroke and four-stroke gasoline engines, lubricants for diesel engines, gas engine oils, gas turbine oils, automatic transmission liquids, transmission oils, etc.

[0003] Lubricants can be designed as lubricating oils and lubricating greases.

Industrial lubricating oils comprise, inter alia, industrial transmission oils, pneumatic tool lubricants, high-temperature oils, air and gas compressor oils for all types of compressors, tool machine oils, textile oils, steam turbine oils, hydraulic fluids, paper machinery oils, food processing machinery oils, steam cylinder oils, metal-working fluids for metal cutting, metal rolling, metal drawing, metal forging, and metal stamping. Lubricating greases additionally comprise one or more thickeners in addition to the lubricating oil.

[0004] With regard to the sustainability of lubricants, it is desirable if these contain, at least in proportion, bio-based base oils. In addition, it is advantageous for use in practice if a lubricant contains a base oil which can be obtained both from (at least partially) biological and petrochemical sources.
As a result, a high flexibility in lubricant production can be agreed with the possibility of providing environmentally friendly, sustainable lubricant.
However, many bio-based oils are not suitable for lubricant applications, since they do not have the desired property profile, for example with respect to oxidation stability and low-temperature behavior.

[0005] The use of trimellitic acid ester as base oil for lubricants is known and 5 is used in practice. However, this ester is not currently obtained on an industrial scale from biological raw materials.

[0006] WO 2012159738 Al discloses a high-temperature oil for lubricating chains, chain rollers, and belts of continuous presses, comprising 40 to 10 91.9 wt.% of a compound of general formula (II), JL

wherein R is a linear or branched alkyl group having a chain length of 8 to 16 15 carbon atoms and 5 to 50 wt.% of a hydrogenated polyisobutylene, a fully hydrogenated polyisobutylene or a mixture of a fully hydrogenated and a hydrogenated polyisobutylene. The described two-component system performs very well with regard to thermal stability and residue formation or residue behavior. However, this ester is not currently obtained on an industrial 20 scale from biological raw materials.

[0007] The object of the present invention is to provide a base oil for a lubricant composition, which base oil can be obtained both from biological and petrochemical sources. Furthermore, the resulting lubricant composition 25 should have good oxidation stability, a good lubricating effect, and good low-temperature behavior. Furthermore, it should exhibit a good lubricating effect even at a constant high temperature over a long period. Furthermore, depending on the desired application, the lubricant composition should be able to be provided in different viscosities.

[0008]This object is achieved according to the invention by the use of hemimellitic acid ester of the following general formula I
o oRi o OR
oR3 5 o wherein R1, R2 and R3, independently of one another, are a) an unsubstituted, branched or unbranched Cl to C20 alkyl group, or b) a Cl to C5 alkyl group having at least one substituent selected from the 10 group consisting of cycloalkyl groups and aromatic groups, or c) a C5 to C20 aromatic group or a C5 to C20 cycloalkyl group, wherein the hemimellitic acid ester can be present as a mixture of different compounds of formula I, as base oil of a lubricant composition for lubricating tribolog ica I systems.

[0009] Surprisingly, it has been found that the use of hemimellitic acid ester of the above formula I as base oil allows a lubricant composition with good oxidation stability, lubricating effect, and good low-temperature behavior to be obtained. Furthermore, it also exhibits good lubrication properties over a long 20 period of time even at a constant high temperature. Furthermore, depending on the desired application, the lubricant composition can be provided in different viscosities. This was surprising because hemimellitic acid ester can be obtained from biological sources, and bio-based lubricants, as explained above, usually do not have the desired range of properties in relation to 25 oxidation stability, lubricating effect, and low-temperature behavior.

[0010]The preparation of hemimellitic acid ester starting from biomass is known and described, for example, in U51056287562. Depending on the raw materials used, the hemimellitic acid ester obtained can have a high proportion of bio-based carbon or may be completely bio-based. However, hemimellitic acid ester can also be obtained in a simple manner starting from petroleum or petrochemical sources, which increases the flexibility in lubricant production.

[0011] In a preferred embodiment, the hemimellitic acid ester is at least partially bio-based. This is to be understood as meaning that the hemimellitic acid ester is produced at least in part from raw materials originating from biological sources and/or renewable agricultural materials (including plant, animal and marine materials) and not from petroleum or petrochemical sources. Exemplary biological sources are agriculture, forestry, plant cultivation, or animal raw materials. Preferred biological sources are straw, animal waste products, waste from agriculture and forestry.

[0012] In the lubricant composition, hemimellitic acid ester can be present as the only base oil or mixed with further base oils.

[0013] A tribological system is to be understood to mean technical constructions whose function is realized by means of structural elements that are mechanically moved and thus sensitive to friction and subject to wear.
Tribological systems have the task of converting and transporting movements, energy, and material and of making them technically usable. Preferred tribological systems are tribological systems which comprise metallic and/or non-metallic materials, such as rolling and sliding bearings, in particular rolling and sliding bearings in vehicle technology, conveying technology, mechanical engineering and/or office technology, transmissions, chains, sliding guides and joints, in particular wheel bearings of motor vehicles, bearings in wind turbines, in particular rotor bearing, in wind turbines and/or rotating sliding bearings, for example fan bearings, or linearly guided sliding bearings and/or by ball joints, in particular by ball joints for use in the automotive sector. Possible tribological systems further comprise sliding partners in industrial plants and machines, but also in the fields of domestic machines, consumer electronics, in particular in oil-lubricated systems, lubrication of chains, chain rollers, and steel belts of continuous wood presses.

[0014] In a preferred embodiment, the tribological systems comprise surfaces containing metallic and/or non-metallic materials, preferably composite materials, aluminum, aluminum alloys, steel, stainless steel, and cast materials, non-ferrous metals, plastics, fiber-reinforced plastics and/or polymers.

[0015] In a preferred embodiment of the invention, the lubricant composition comprises at least 10 wt.%, for example from 10 to 100 wt.% and/or 10 to 95 wt.%, preferably at least 15 wt.%, for example from 15 wt.% to 95 wt.%, in particular at least 20 wt.%, for example from 20 wt.% to 95 wt.%, bio-based carbon, based on the total weight of organic carbon in the lubricant composition. The content of bio-based carbon can thereby be determined by means of the ASTM International Radioisotope Standard Method D 6866. The latest version of the standard on the filing date applies. This method determines the bio-based content of a material based on the amount of bio-based carbon in the material as a percent of the weight of the total organic carbon in the material studied. The method is based on bio-based products having carbon isotope ratios of 13C/12C and 14C/12C, which differ from those found in materials obtained from mineral oil.

[0016] In a further preferred embodiment of the invention, the hemimellitic acid ester of formula I comprises at least 30 wt.%, for example from 30 to 100 wt.%, preferably at least 40 wt.%, for example from 40 wt.% to 100 wt.%, in particular at least 50 wt.%, for example from 50 wt.% to 100 wt.%, bio-based carbon, based on the total weight of the hemimellitic acid ester of formula I, in the lubricant composition, in each case measured by means of the ASTM
International Radioisotope Standard Method D 6866. The latest version of the standard on the filing date applies.

[0017] In a further preferred embodiment of the invention, the acid component of the hemimellitic acid ester of formula I comprises at least 30 wt.%, for example from 30 to 100 wt.%, preferably at least 40 wt.%, for example from 40 wt.% to 100 wt.%, in particular at least 50 wt.%, for example from 50 wt.%
5 to 100 wt.%, bio-based carbon based on the total weight of the acid component of the hemimellitic acid ester of formula I, in the lubricant composition, in each case measured by means of the ASTM International Radioisotope Standard Method D 6866. The latest version of the standard on the filing date applies.
10 [0018] In a preferred embodiment of the invention, at least one radical R1, R2 and/or R3 is an unsubstituted, branched or unbranched Cl to C20 alkyl group, even more preferably a C5 to C20 alkyl group, more preferably a C6 to C18 alkyl group, and in particular a C8 to C18 alkyl group.
15 [0019] In a further particularly preferred embodiment of the invention, at least one radical R1, R2 and/or R3 is selected from the group consisting of octanyl, ethylhexanyl, nonanyl, decanyl, undecanyl, dodecanyl.
[0020] In a further particularly preferred embodiment of the invention, at least 20 one radical R1, R2 and/or R3 is selected from the group consisting of octanyl, 2-ethylhexan-1-yl, 1-nonanyl, decanyl, 1-undecanyl, 1-dodecanyl.
[0021] In a further preferred embodiment of the invention, at least one radical R1, R2 and/or R3 is a Cl to C5 alkyl group, preferably a Cl to C3 alkyl group, 25 more preferably a Cl to C2 alkyl group and, in particular, a Cl alkyl group, each having at least one substituent selected from the group consisting of cycloalkyl groups and aromatic groups. In this embodiment, the stated number of carbon atoms of the alkyl group does not comprise the number of carbon atoms of the substituents. According to the invention, cycloalkyl groups 30 comprise both monocyclic and polycyclic compounds.

[0022] Preferably, the substituents independently of one another have 5 to 19 carbon atoms, more preferably 5 to 17 carbon atoms and in particular 5 to 15 carbon atoms. More preferably, the substituents independently of one another are selected from C5 to C19 cycloalkyl groups, or C5 to C19 aromatic groups, 5 more preferably from C5 to C17 cycloalkyl groups or C5 to C17 aromatic groups, and in particular from C5 to C15 cycloalkyl groups or C5 to C15 aromatic groups.
[0023] In a further preferred embodiment of the invention, at least one radical 10 R1, R2 and/or R3 is a methyl group, ethyl group or a propyl group, which is substituted with at least one cycloalkyl group having 5 to 15 carbon atoms or with at least one aromatic group having 5 to 15 carbon atoms, in particular 5 to 10 carbon atoms. Particularly preferably R1, R2 and R3 are, independently of one another, a methyl group which is substituted with at least one cycloalkyl 15 group having 5 to 15 carbon atoms or with at least one aromatic group having to 15 carbon atoms, in particular 5 to 10 carbon atoms.
[0024] In a further embodiment of the invention, at least one radical R1, R2 and/or R3 is a C5 to C20 aromatic group or a C5 to C20 cycloalkyl group.
20 Preferably at least one radical R1, R2 and/or R3 is selected from phenyl, cyclopentyl, cyclohexyl, naphthyl, isotridecyl, tricyclodecane methyl, furfuryl.
[0025] In a particularly preferred embodiment of the invention, at least one radical R1, R2 and/or R3, preferably at least two radicals R1, R2 and/or R3, 25 and in particular all radicals R1, R2 and R3 are selected from the group consisting of octanyl, ethylhexanyl, nonanyl, decanyl, undecanyl, dodecanyl, isotridecyl, tricyclodecane methyl, furfuryl.
[0026] In a further particularly preferred embodiment of the invention, at least 30 one radical R1, R2 and/or R3, preferably at least two radicals R1, R2 and/or R3, and in particular all radicals R1, R2 and R3 are selected from the group consisting of octanyl, 2-ethylhexan-1-yl, 1-nonanyl, decanyl, 1-undecanyl, 1-dodecanyl, isotridecyl, tricyclodecane methyl, furfuryl.
[0027] The radicals R1, R2 and R3 can be the same or different.
[0028] In a further preferred embodiment, the hemimellitic acid ester of formula I comprises radicals R1, R2 and R3 which are at least partially different from one another. Likewise preferably, the hemimellitic acid ester of formula I
is a mixture of different compounds of formula I.
[0029] Likewise preferably, the radicals R1, R2 and R3, independently of one another, do not have any atoms other than carbon and hydrogen.
[0030] In a preferred embodiment of the invention, the lubricant composition contains the hemimellitic acid ester of formula I in an amount of from 20 wt.%

to 90 wt.%, more preferably from 25 wt.% to 70 wt.%, even more preferably from 25 wt.% to 60 wt.%, and in particular from 30 wt.% to 50 wt.%, in each case based on the total weight of the lubricant composition.
[0031] In a further preferred embodiment of the invention, the hemimellitic acid ester of formula I has a kinematic viscosity at 40 C [mm2/sec] in the range of mm2/s to 150 mm2/s, preferably of 30 mm2/s to 100 mm2/s, more preferably 50 mm2/s to 150 mm2/s and in particular 50 mm2/s to 90 mm2/s.
25 [0032] In a further preferred embodiment of the invention, the lubricant composition is present as an oil formulation and has a kinematic viscosity at C [mm2/sec] in the range of 100 mm2/s to 460 mm2/s, preferably 150 mm2/s to 320 mm2/s.
30 [0033] In a further preferred embodiment of the invention, the lubricant composition is present as a grease formulation and the hemimellitic acid ester of formula I and/or a mixture of hemimellitic acid ester of formula I and further base oils has a kinematic viscosity at 40 C [mm2/sec] in the range of 80 mm2/s to 460 mm2/s, preferably 100 mm2/s to 320 mm2/s.
[0034] In a further preferred embodiment of the invention, the lubricant 5 composition comprises 5 to 50 wt.%, more preferably 15 to 35 wt.%, and in particular 15 to 30 wt.% polyisobutylene, in each case based on the total weight of the lubricant composition. An advantage of the use of polyisobutylene is that the viscosity of the lubricant composition can be set particularly easily with it. In addition, after complete evaporation a particularly good residue 10 behavior can be achieved in combination with the hemimellitic acid ester of formula I. According to a preferred embodiment, the polyisobutylene has a number average molecular weight of 115 to 15,000 g/mol, preferably of 160 to 5,000 g/mol, measured according to DIN 55672-1:2016-03 (Gel Permeation Chromatography (GPC) - Part 1: Tetrahydrofuran (THF) as eluent).
[0035] As already explained above, the lubricant composition can be present both as a grease formulation and as an oil formulation.
[0036] If the lubricant composition is present as a grease formulation, it then 20 contains a thickener. In a preferred embodiment of the invention, the lubricant composition therefore contains from 3 to 30 wt.% thickener.
[0037] The thickener is preferably a reaction product of a diisocyanate, preferably 2,4-diisocya natotoluene, 2,6-diisocyanatotoluene, 25 4,4'-diisocyanatod iphenylmethane, 2,4'-diisocyanatophenyl methane, 4,4'-diisocyanatod iphenyl, 4,4'-diisocya nato-3-3'-d imethylphenyl, 4,4'-diisocyanato-3,3'-dimethylphenyl methane, which can be used individually or in combination, with an amine of the general formula R'2-N-R, or a diamine of the general formula R'2N-R-N1112, wherein R is an aryl, alkyl or alkylene 30 radical having 2 to 22 carbon atoms and R' is identical to or different from a hydrogen, an alkyl, alkylene, or aryl radical, or identical to or different from mixtures of amines and diamines.

[0038] In a further preferred embodiment, the thickener is selected from complex aluminum soaps, single metal soaps of the elements of the first and second main groups of the periodic table, complex metal soaps of the elements 5 of the first and second main groups of the periodic table, bentonites, sulfonates, silicates, aerosil, polyimides, or PTFE, or a mixture of the aforementioned thickeners.
[0039] In addition to the hemimellitic acid ester of formula I, the lubricant 10 composition can also contain at least one further base oil.
[0040] If the lubricant composition is present as an oil formulation and contains at least one further base oil, then the proportion of the further base oil is preferably from 10 wt.% to 50 wt.%, more preferably from 10 wt.% to 40 wt.%, 15 even more preferably from 20 wt.% to 40 wt.%, and in particular from 25 wt.%
to 40 wt.%, based in each case on the total weight of the lubricant composition.
[0041] If the lubricant composition is present as a grease formulation and contains at least one further base oil, then the proportion of the further base oil 20 is preferably from 10 wt.% to 50 wt.%, more preferably from 25 wt.% to 50 wt.%
and in particular from 30 wt.% to 50 wt.%, based in each case on the total weight of the lubricant composition.
[0042] If the lubricant composition also contains at least one further base oil, 25 the lubricant composition preferably contains the hemimellitic acid ester of formula I in an amount of from 20 wt.% to 70 wt.%, more preferably from 25 wt.% to 70 wt.%, even more preferably from 25 wt.% to 60 wt.%, and in particular from 30 wt.% to 50 wt.%, based in each case on the total weight of the lubricant composition.
[0043] Other suitable base oils are typical lubricating oils at room temperature (20 C). The further base oil preferably has a kinematic viscosity of 18 mm2/s to 20,000 mm2/s, in particular of 30 mm2/s to 400 mm2/s at 40 C. In the case of base oils, a distinction is made between mineral oils and synthesis oils. A

base oil is understood to be the typical base liquids, in particular oils, which are used for the production of lubricants and which can be assigned to the 5 groups I, II, II+, III, IV or V according to the classification of the American Petroleum Institute (API) [NLGI Spokesman, N. Samman, Volume 70, Number 11, pp. 14]. Mineral oils are classified according to the API Group.
API Group I are mineral oils which consist, for example, of naphthenic or paraffinic oils. If, compared to API Group I oils, these mineral oils are 10 chemically modified, low aromatic, low sulfur, and have a low proportion of saturated compounds and thus an improved viscosity/temperature behavior, the oils are classified according to API Group II and III. The API Group III
also includes so-called gas-to-liquid oils which are not produced from the refining of crude oil but by the chemical conversion of natural gas. Furthermore, 15 reraffinates can also be used.
[0044] Polyethers, esters, polyesters, preferably polyalphaolefins, preferably metallocene polyalphaolefins, perfluoropolyalkyl ethers (PFPAE), alkylated naphthalenes, silicone oils, and alkylaromatics, and mixtures thereof are noted 20 as synthesis oils. The polyether compound can have free hydroxyl groups, but can also be completely etherified or end-group-esterified and/or can be prepared from a starter compound having one or more hydroxy and/or carboxyl groups (-COOH). Polyphenyl ethers are also possible, optionally alkylated, as the sole components or even better as mixed components.
[0045] Esters of an aromatic and/or aliphatic di-, tri- or tetracarboxylic acid with one C7 to C22 alcohol or C7 to C22 alcohols present in a mixture, esters of trimethylolpropane, pentaerythritol, or dipentaerythritol with aliphatic C7 to carboxylic acids, esters of C18 dimer acids with C7 to C22 alcohols, complex 30 esters, as individual components or in any desired mixture, are suitable.
Likewise preferred esters are triglycerides and/or estolides.

[0046] Silicone oils, native oils, and derivatives of native oils are likewise suitable.
[0047] Particularly preferred further base oils according to the invention are 5 esters, in particular esters of an aromatic and/or aliphatic di-, tri- or tetracarboxylic acid having one C7 to C22 alcohol or having C7 to C22 alcohols present in a mixture, esters of trimethylolpropane, pentaerythritol, or dipentaerythritol having aliphatic C7 to C22 carboxylic acids, esters of C18 dimer acids having C7 to C22 alcohols, complex esters, as individual 10 components or in any desired mixture, as well as triglycerides and/or estolides, polyalphaolefins, polyethers and/or mineral oils.
[0048] Furthermore, the lubricant composition can contain inorganic or organic solid lubricants, preferably in a proportion of 0.1 wt.% to 5 wt.%, preferably 15 0.1 wt.% to 3 wt.%, based on the total weight of the lubricant composition. Solid lubricants are preferably selected from PTFE, BN, pyrophosphate, Zn oxide, Mg oxide, pyrophosphates, thiosulfates, Mg carbonate, Ca carbonate, Ca stearate, Zn sulfide, Mo sulfide, W sulfide, Sn sulfide, gra phites, gra phene, nano tubes, 5i02 modifications or a mixture thereof.
[0049] Further preferably, the lubricant composition contains 0.1 to 8 wt.%
additives selected from the group consisting of anti-corrosion additives, antioxidants, anti-wear additives, metal deactivators, ion complexing agents, and/or UV stabilizers.
[0050] Particularly suitable antioxidants according to the invention are the following compounds: Styrolized diphenylamines, diaromatic amines, phenolic resins, thiophenol resins, phosphites, butylated hydroxytoluene, butylated hydroxyanisole, phenyl-a 1pha-naphthylamine, phenyl-beta-naphthylamine, octylated/butylated diphenylamine, di-alpha-tocopherol, di-tert-butylphenyl, benzenepropane acid, sulfur-containing phenol compounds, and mixtures of these components.

[0051] Likewise suitable antioxidants are compounds which contain sulfur, nitrogen and/or phosphorus in the molecule. Preferred compounds containing sulfur, nitrogen and/or phosphorus in the molecule are selected from the group 5 consisting of aromatic aminic antioxidants, such as alkylated phenyl-alpha-naphthylamine, dialkyldiphenylamine, sterically hindered phenols, such as butylhydroxytoluene (BHT), phenolic antioxidants with thioether groups, Zn or Mo or W dialkyldithiophosphates and phosphites.
10 [0052] Preferred anti-corrosion additives, metal deactivators and/or ion-complexing agents are triazoles, imidazolines, N-methylglycine (sarcosine), benzotriazole derivatives, N,N-bis(2-ethylhexyl)-methyl-1 H-benzotriazol-1-methanamine; n-methyl-N(1-oxo-9-octadecenyl)glycine, a mixture of phosphoric acid and mono and diisooctyl ester reacted with (C11-15 14)-alkylamines, a mixture of phosphoric acid and mono and diisooctyl ester reacted with tert-alkylamine and primary (C12-14)-amines, dodecanoic acid, triphenylphosphonate, and amine phosphates and mixtures thereof.
Commercially obtainable additives are the following: IRGAMET8 39, IRGACOR 8 DSS G, Amin 0; SARKOSYL8 0 (Ciba), COBRATEC 8 122, 20 CUVAN 8 303, VANLUBE 0 9123, CI-426, CI-426EP, CI-429 and CI-498.
[0053] Anti-wear additives preferred according to the invention are amines, amine phosphates, phosphates, thiophosphates, phosphate thionates, and mixtures of these components. Preferred anti-wear additives are selected from 25 the group consisting of anti-wear additives based on diphenylcresyl phosphate, amine-neutralized phosphates, alkylated and non-alkylated triaryl phosphates, alkylated and non-alkylated triarylthiophosphates, zinc or Mo or W-dialkyldithiophosphates, carbamates, thiocarbamates, zinc or Mo or W
dithiocarbamate, dimercapto-thiadiazole, calcium sulfonates and 30 benzotriazole derivatives. Commercially available anti-wear additives include IRGALUBE 8 TPPT, IRGALUBE 8 232, IRGALUBE 8 349, IRGALUBE 8 211 and ADDITIN 8 RC3760-Liq-3960, FIRC-SHUN FG 1505 and FG 1506, NA-LUBER KR-015FG, LUBEBONDO, FLUOROO FG, SYNALOX 40-D, ACHESON FGA 1820 and ACHESON FGA 1810.
[0054]A further subject matter of the invention is a lubricant composition 5 designed as an oil formulation comprising:
- 20 wt.% to 90 wt.%, preferably 50 wt.% to 85 wt.%, hemimellitic acid ester of the following general formula I, o oRi o OR
oR3 o wherein R1, R2 and R3, independently of one another, are a) a branched or unbranched Cl to C20 alkyl group, or b) a Cl to C5 alkyl group having at least one substituent selected from the group consisting of cycloalkyl groups and aromatic groups, or 15 c) a C5 to C20 aromatic group or a C5 to C20 cycloalkyl group, wherein the hemimellitic acid ester of formula I can be present as a mixture of different compounds of formula I, as base oil, - 5 wt.% to 50 wt.%, preferably 10 wt.% to 50 wt.%, polyisobutylene, - 0.1 wt.% to 8 wt.% additives.
[0055] In a further preferred embodiment, the lubricant composition designed as an oil formulation additionally comprises 10 wt.% to 45 wt.%, preferably wt.% to 45 wt.%, of at least one further base oil.
25 [0056]A further subject matter of the invention is a lubricant composition designed as a grease formulation comprising:
- 20 wt.% to 90 wt.%, preferably 30 wt.% to 90 wt.%, more preferably 40 wt.%
to 90 wt.%, hemimellitic acid ester of the following general formula I, o oRi o OR
oR3 o wherein R1, R2 and R3, independently of one another, are 5 a) a branched or unbranched Cl to C20 alkyl group, or b) a Cl to C5 alkyl group having at least one substituent selected from the group consisting of cycloalkyl groups and aromatic groups, or c) a C5 to C20 aromatic group or a C5 to C20 cycloalkyl group, wherein the hemimellitic acid ester of formula I can be present as a mixture of 10 different compounds of formula I, as base oil, - 3 to 30 wt.% thickener, - 0.1 to 8 wt.% additives.
[0057]A further subject matter of the invention is a lubricant composition 15 designed as a grease formulation comprising:
- 20 wt.% to 70 wt.%, preferably 30 wt.% to 70 wt.%, more preferably 40 wt.%
to 70 wt.%, hemimellitic acid ester of the following general formula I, o oRi o OR
oR3 o wherein R1, R2 and R3, independently of one another, are d) a branched or unbranched Cl to C20 alkyl group, or e) a Cl to C5 alkyl group having at least one substituent selected from the group consisting of cycloalkyl groups and aromatic groups, or f) a C5 to C20 aromatic group or a C5 to C20-cycloalkyl group, wherein the hemimellitic acid ester of formula I can be present as a mixture of different compounds of formula I, as base oil, 3 to 30 wt.% thickener, 5 - 10 wt.% to 50 wt.% of at least one further base oil, - 0.1 to 8 wt.% additives.
[0058] In a preferred embodiment, the lubricant composition designed as a grease formulation comprises 10 wt.% to 40 wt.% polyisobutylene.
[0059] In a further preferred embodiment, the lubricant composition designed as a grease formulation comprises 0.1 wt.% to 5 wt.% inorganic or organic solid lubricants.
15 [0060] Preferred components of the lubricant compositions according to the invention are those mentioned with respect to the use according to the invention.
[0061] Particularly preferred thickeners for the lubricant composition designed 20 as a grease formulation are a reaction product of a diisocyanate, preferably 2,4-diisocyanatotoluene, 2,6-d iisocyanatotoluene, 4,4'-diisocyanatod iphenylmethane, 2,4'-diisocyanatophenyl methane, 4,4'-diisocyanatod iphenyl, 4,4'-diisocya nato-3-3'-d imethylphenyl, 4,4'-diisocyanato-3,3'-dimethylphenyl methane, which can be used individually 25 or in combination, with an amine of the general formula R'2A-R, or a diamine of the general formula R'2N-R-N1112, wherein R is an aryl, alkyl or alkylene radical having 2 to 22 carbon atoms and R' is identical to or different from a hydrogen, an alkyl, alkylene, or aryl radical, or identical to or different from mixtures of amines and diamines.
[0062] In a further preferred embodiment, the thickener is selected from complex aluminum soaps, single metal soaps of the elements of the first and second main groups of the periodic table, complex metal soaps of the elements of the first and second main groups of the periodic table, bentonites, sulfonates, silicates, aerosil, polyimides, or PTFE, or a mixture of the aforementioned thickeners.
[0063] Furthermore, particularly preferred further base oils for the lubricant compositions according to the invention, which are designed as a grease formulation or as an oil formulation, are esters, in particular esters of an aromatic and/or aliphatic di-, tri- or tetracarboxylic acid having one C7 to alcohol or C7 to C22 alcohols present in a mixture, esters of trimethylolpropane, pentaerythritol, or dipentaerythritol having aliphatic C7 to C22 carboxylic acids, esters of C18 dimer acids with C7 to C22 alcohols, complex esters, as individual components or in any desired mixture, as well as triglycerides and/or estolides, polyalphaolefins, polyethers and/or mineral oils.
DESCRIPTION OF THE DRAWINGS
Fig. 1 shows the dynamic viscosity of hemimellitic acid ester of formula I
compared to trimellitic acid ester, as a function of the temperature.
Fig. 2 shows the average friction, determined by means of SRV, of a plurality of claimed lubricant compositions containing hemimellitic acid ester of formula I compared to lubricant compositions comprising trimellitic acid ester, as a function of the temperature.
Measuring methods [0064] Viscosity:
The viscosity measurement is carried out with DIN 51562 (2018) using a Stabinger viscosimeter SVM 3000 (Anton Paar).
[0065] Bio-based carbon content:

The content of bio-based carbon is determined by means of the ASTM
International Radioisotope Standard Method D 6866 with the version valid at the filing date.
5 [0066] The invention is explained in more detail below with reference to examples which do not limit the invention.
Example 1: Determination of the dynamic viscosity of hemimellitic acid ester of formula I compared to trimellitic acid ester [0067] The hemimellitic acid ester 1 is prepared through the following reaction:

0 [11], xylene, 0 Dean-Stark-app.
H H _____________ b.
OR
OH ¨H20 SR
Nafol 810D
(C8-/C10-alcohol) 15 Example 1-A:
[0068] A mixture of 150 g bio. hemimellitic acid, 369.6 g Nafol 810D and 60 mL

xylene in a 1L three-necked flask, combined using a water separator, is refluxed at 1 atm. Within 4 h, the internal temperature increases from 126 C
to 20 200 C and 0.52 g tetraisopropyl orthotitanate (0.1 wt.%) is added at an internal temperature of 160 C. The clear reaction mixture is then refluxed at 200 C for 2 h, and 38.8 g water is distilled off continuously. The xylene and the excess alcohol are distilled off under reduced pressure (Tinn. = 200 C, 10 mbar).
After removal of the catalyst, the product (407.7 g) is obtained as a light yellow oil.
Example 1-B:

18 [0069] A mixture of 150 g bio. hemimellitic acid, 369.6 g Nafol 810D and 45 mL

xylene in a 1L three-necked flask, combined using a water separator, is refluxed at 1 atm. Within 2 h, the internal temperature increases from 139 C
to 210 C and 0.026 g tetraisopropyl orthotitanate (0.005 wt.%) is added at an 5 internal temperature of 150 C. The clear reaction mixture is then refluxed at 210 C for 7.5 h, and 39.6 g water is distilled off continuously. The xylene and the excess alcohol are distilled off under reduced pressure (Trin. = 200 C, 8 mbar). The product (415 g) is obtained as a light yellow oil.
10 Example 1-C:
[0070] A mixture of 140 g bio. hemimellitic acid, 375.1 g Nafol 810D and 40 mL

xylene in a 1L three-necked flask, combined using a water separator, is refluxed at 1 atm. Within 5 h, the internal temperature increases from 130 C
to 15 215 C. The clear reaction mixture is then refluxed at 215 C for 2 h and further at 220 C for 6 h. In total, 35.4 g water is distilled off continuously. The xylene and the excess alcohol are distilled off under reduced pressure (Trin. = 210 C, 8 mbar). The product (388 g) is obtained as a light yellow oil.
20 [0071] The dynamic viscosity of the hemimellitic acid ester 1-B is measured as a function of the temperature and compared with the commercial trimellitic acid ester 1', which was esterified with the same alcohol mixture. The shear rate is 1/s, the temperature profile is 20 to -40 C, 0.2 C/min. The results of the rheological examination are indicated in Figure 1. It is apparent that the 25 hemimellitic acid ester 1 has a comparably good dynamic viscosity at low temperatures as the trimellitic acid ester 1'.
Example 2: Determination of base data of hemimellitic acid ester 1 compared to trimellitic acid ester 1'

19 [0072] The basic data of the hemimellitic acid ester 1 are measured and compared with the commercial trimellitic acid ester 1' which was esterified with the same alcohol mixture. The results are shown in the following table Ex. 1-A Ex. 1-B Ex. TMA
ester 1' (commercial) Alcohols n-C8 (45%), n-C10 (55%) Kin. Visco. 40 C [mm2/sec] 64.6 62.2 63.6 51.1 Kin. Visco. 100 C [mm2/sec] 8.77 8.55 8.58 8.01 VI +108.8 +109.0 +106.4 +126.3 SZ [mg KOH/g] 0.15 0.26 3.77 0.10 Example 3-5 [0073] Preparation of further hemimellitic acid esters and of a comparison ester (4') Example 3:
[0074] A mixture of 140 g bio. hemimellitic acid, 213 g 1-octanol, 142 g 1-dodecanol and 40 mL xylene in a 1L three-necked flask, combined using a water separator, is refluxed at 1 atm. Within 2 h, the internal temperature increases from 125 C to 210 C and 0.025 g tetraisopropyl orthotitanate (0.005 wt.%) is added at an internal temperature of 145 C. The clear reaction mixture is then refluxed at 210 C for 4 h and further at 215 C for 3.5 h. In total, 37.7 g water is distilled off continuously. The xylene and the excess alcohol are distilled off under reduced pressure (Tinn. = 210 C, 10 mbar). The product (397.7 g) is obtained as a light yellow oil.
Example 4:
[0075] A mixture of 129.9 g bio. hemimellitic acid, 91.5 g 1-nonanol, 165.5 g 1-undecanol, 81 g Exxal 9 (ExxonMobil), 14.1 g Exxal 10 (ExxonMobil) and 50 mL xylene in a 1L three-necked flask, combined using a water separator, is refluxed at 1 atm. Within 2 h, the internal temperature increases from 124 C
to 200 C and 0.5 g tetraisopropyl orthotitanate (0.1 wt.%) is added at an internal temperature of 160 C. The clear reaction mixture is then refluxed at 200 C for 2.5 h, and a total of 34.8 g of water is distilled off continuously. The xylene and 5 the excess alcohol are distilled off under reduced pressure (Tnn. = 195 C, 13 mbar). After removal of the catalyst, the product (377 g) is obtained as a light yellow oil.
Example 4' (TMA ester 4', comparison sample for Ex. 4):
[0076] A mixture of 90 g petrochemical trimellitic acid, 63.5 g 1-nonanol, 114.7 g 1-undecanol, 56.1 g Exxal 9 (ExxonMobil), 9.76 g Exxal 10 (ExxonMobil) and 35 mL xylene in a 1L three-necked flask, combined using a water separator, is refluxed at 1 atm. 0.35 g tetraisopropyl orthotitanate 15 (0.1 wt.%) is added at an internal temperature of 145 C. Within 2 h, the internal temperature increases from 159 C to 195 C. The clear reaction mixture is then refluxed at 195 C for 4 h and a total of 25.0 g of water is distilled off continuously. The xylene and the excess alcohol are distilled off under reduced pressure (Tnn. = 200 C, 19 mbar). After removal of the catalyst, the product

20 (295 g) is obtained as a light yellow oil.
Example 5 [0077] A mixture of 150 g bio. hemimellitic acid, 353.2 g 2-ethylhexane-1-ol 25 and 40 mL xylene in a 1L three-necked flask, combined using a water separator, is refluxed at 1 atm. Within 8 h, the internal temperature increases from 124 C to 210 C and 0.025 g tetraisopropyl orthotitanate (0.005 wt.%) is added at an internal temperature of 145 C. The clear reaction mixture is then refluxed at 210 C for 5.5 h. In total, 39.1 g water is distilled off continuously.
30 The xylene and the excess alcohol are distilled off under reduced pressure (Tnn. = 205 C, 16 mbar). The product (404.4 g) is obtained as a light yellow oil.

21 [0078] Three different hemimellitic acid esters are prepared by esterification of hemimellitic acid with different alcohols. The alcohols used and the base data obtained in comparison with the corresponding trimellitic acid esters are shown in Table 6.
TMA ester TMA ester 4' (Ex.
Ex. 3 3' (commercial) Ex. 4 4') n-C9 (25-27%), i-C9 (23%) Alcohols n-C8 (60%), n-C12 (40%) .
i-C10 (3-4%), n-Cll (47%) Kin. Visco. 40 C
64.1 51.4 81.0 65.6 [mm2/sec]
Kin. Visco. 100 C
8.89 8.17 10.0 9.46 [mm2/sec]
VI +113.1 +130.2 +104.1 +123.6 SZ [mg KOH/g] 0.55 0.20 0.30 0.27 Pour point -51 C -48 C

Table 6a TMA ester 5' Ex. 5 Ex. 6 (commercial) 25 wt.% n-octanol 40 wt.% 2EH
Alcohols 2-ethylhexan-1-ol 35 wt.%
n-decanol Kin. Visco. 40 C [mm2/sec] 125.8 92.1 78.6 Kin. Visco. 100 C [mm2/sec] 11.0 9.70 9.3 VI +61.0 +79.0 93 SZ [mg KOH/g] 0.43 0.10 0.35 Pour point -48 C -36 C -Table 6b Example 6: Preparation of different lubricant compositions [0079] Two lubricant compositions with the compositions described in Table 1 are prepared:
Comparison composition 1 Claimed composition 2

22 E 41.985 wt.% trimellitic acid 41.985 wt.% hemimellitic ster oil ester l' (commercial) acid ester Example 1-B
Polyisobutylene 16.7 wt.%
16.7 wt.%
Group III oil 37.61 wt.%
37.61 wt.%
Defoamer 0.02 wt.%
0.02 wt.%
Additive 3.685 wt.% 3.685 wt.%
package Table 1 [0080] The basic data of the lubricant compositions are shown in Table 2.
Comparison Claimed Requirement composition 1 composition 2 Appearance clear, yellow clear, bright orange Kinematic viscosity 260 268.5 290.9 40 C [mm2/sec]
Kinematic viscosity 27.4-30.6 30.1 30.6 100 C [mm2/sec]
Viscosity index at least 140 +150.5 +143.6 Density 20 C 0.9107 0.9120 Pour point max. -20 C < -30 C
<-30 C
Copper corrosion max. 2-150 lb - 150 lb - 150 (24h/150 C) Table 2 [0081] It is apparent that the lubricant composition 2 according to the invention based on hemimellitic acid esters exhibits comparable base data to the comparison composition 1 based on trimellitic acid esters. The different observed viscosities are to be explained by the different starting viscosities of the base oils used.
Example 7: Determination of the oxidation stability of the lubricant compositions from Example 6 [0082]The oxidation stability and the evaporation loss of the lubricant compositions from Example 6 are determined by means of differential

23 scanning calorimetry according to DIN 51007 (04/2019) and thermogravimetric analysis according to DIN 51006 (07/2005). The results are shown in Table 3.
Comparison composition 1 Claimed composition 2 180 C (wt.%) 0.3 0.2 200 C (wt.%) 0.8 0.7 220 C (wt.%) 1.9 1.7 240 C (wt.%) 4.2 4.0 260 C (wt.%) 8.8 8.5 280 C (wt.%) 17.5 17.0 300 C (wt.%) 45.2 43.1 Oxidation start 207 C 207 C
5 Table 3 [0083] It is apparent that the lubricant composition 2 according to the invention based on hemimellitic acid esters demonstrates oxidation stability that is as high comparably as the comparison composition 1 based on trimellitic acid 10 esters.
Example 8: Thermal resistance studies [0084] The lubricant compositions from Example 6 are examined with regard 15 to their evaporation behavior and the increase in their apparent dynamic viscosity under temperature stress.
[0085] For this purpose, the evaporation behavior and the change of the apparent dynamic viscosity [mPas] are determined as a criterion of 20 progressive oxidation under thermal load as a comparative measurement.
For each test, the sample amount is 5 g (+/-0.1 g). After 72 h storage, the samples are compared with one another in an aluminum dish at 230 C in a circulating air oven.

24 [0086] In addition, the residue behavior is determined after complete evaporation using the Eisenmann test (250 C/72h). For this purpose, 5 g of the sample to be tested is weighed out on a steel sheet, which has previously been bent into shape and cleaned with solvent, and then evaporated at 250 C
5 in a circulating air drying cabinet for at least 72 hours. The square metal sheet is bent manually on all four sides so that a shell shape is created. After cooling, the results of the backweighing are documented. The determination of the solubility of the residue with fresh oil and the amount of residue formed are material to this test. For this purpose, a drop of the fresh oil is applied to the 10 residue and rubbed gently in circular movements using a rounded glass rod.
[0087] The results are illustrated in Table 4.
Comparison Claimed composition 1 composition 2 Evaporation loss in the closed dish 27.0 wt. 25.8 wt.%
(72 h/230 C). %
Dynamic viscositym of the original 559 mPa=s 624 mPa=s formulation Dynamic viscosity[2] after 72 h at 230 C 4617 mPa=s 3947 mPa=s Full vaporization according to Eisenmann good solubility good solubility (250 C/72 h) Solubility of the residues category 4 category 4 Full vaporization according to Eisenmann 6.2 wt. 4.7 wt.%
(250 C/72 h) Proportion of the residues 15 Table 4 [1] CP50, shear rate 300 s-3-, 25 C
[2] CP25, shear rate 300 s-3-, 25 C
20 [0088] It is apparent that all lubricant compositions perform very well.
The lubricant compositions 2 according to the invention based on hemimellitic acid esters demonstrate a comparably good or better evaporation behavior and an even lower rise in the dynamic viscosity after 72 h at 230 C than the comparison composition 1 based on trimellitic acid esters. Furthermore, the lubricant composition according to the invention forms less residue. All residues can be dissolved very well with fresh oil.
Example 9: Measurement of the friction wear of the lubricant compositions 5 from Example 6 [0089] The lubricant compositions from Example 6 are examined to measure the friction wear using an oscillation friction wear test (SRV). The coefficient of friction can be examined using the SRV. The SRV is standardized in 10 DIN 51 834.
[0090] The lubricant compositions investigated are measured in accordance with DIN 51 834 at 250 N load, 50 HZ, 165 min in a temperature range (50 to 250 C). A steel ball is thereby moved in an oscillating manner against a fixedly 15 mounted steel disk on the end face. The effect, load capacity and service life of the lubricant compositions can thereby be determined in oscillating movements under mixed friction conditions.
[0091] The results of the test are shown in Fig. 2.
[0092] It is apparent that the lubricant compositions according to the invention based on hemimellitic acid esters exhibit a coefficient of friction that is as good comparably as the comparison composition 1 based on trimellitic acid esters.

25 Example 10: Preparation and testing of the grease formulation 3 based on hemimellitic acid esters and the comparison grease formulation 4 based on trimellitic acid esters [0093] The grease formulation 3 according to the invention based on 30 hemimellitic acid ester and the comparison grease formulation 4 based on trimellitic acid ester are formulated using the compositions shown in the following table.

26 Comparison grease Grease formulation 3 formulation 4 82 wt.% trimellitic acid 82 wt.% hemimellitic acid ester base oil ester (Example 4') ester (Example 4) urea thickener 15 wt.% 15 wt.%
antioxidant 0.50 wt.% 0.50 wt.%
corrosion 2.5 wt.% 2.5 wt.%
protection Table 5 [0094] Example 4, Table 6a is used as the hemimellitic acid ester and Example 4', Table 6a is used as trimellitic acid ester TMA ester.
[0095] The base data of the grease formulation 3 and the comparison grease formulation 4 are shown in the following table.
Comparison Grease Requirement grease formulation 3 profile formulation 4 bio. HMA ester TMA ester Walk penetration, 60dT 250-280 [0.1 256 [0.1 mm] 265 [0.1 mm]
DIN ISO 2137 mm]
Walk penetration, 105dT max. 370 [0.1 281 [0.1 mm] 287 [0.1 mm]
DIN ISO 2137 mm]
Delta walk penetration DIN
+25 [0.1 mm] +22 [0.1 mm]

Rest penetration DIN ISO min. 220 [0.1 243 [0.1 mm] 252 [0.1 mm]
2137 mm]
241 [0.1 mm] 253 [0.1 mm]
Shear stability 2 h @ max. +60 [0.1 264 [0.1 mm] 271 [0.1 mm] +
130 C mm]
+ 23 [0.1 mm] 18 [0.1 mm]
Shear viscosity @ 25 C 2000-4000 2707 mPa=s 4271 mPa=s DIN 51810 mPas Water resistance 3h @ 0 0 Oil separation 7 d @ 40 C max. 3.00% 1.99% 2.52%

Oil separation 30 h @
max. 5.00% 0.74%
0.81%

27 Emcor 168h, demi. water max. 1 0 in acc. with DIN 51802 ROF Speed Factor appr. 700,000 837,500 1,005,000 mm/min mm/min mm/min Start: 1 Start: 1 Anderon max. 2/3 Damping: 2 Damping: 3 Peak: 1 Peak: 1 SKF BQ+Noise Class 96, 100, 100, 97, 100, 100, ONORM M8127 p2 100 GN4 100 GN4 Karl-Fischer water content max. 0.40% 0.051%
0.069%
Table 6 [0096] Both the grease formulation 3 and the comparison grease formulation 4 5 exhibit comparably good walk stability and shear stability. The water resistance, oil separation, noise ratio and water content of all formulations are at the same level.
Example 11: High-temperature properties of the grease formulation 3 and the 10 comparison grease formulation 4 [0097] The high-temperature properties of the grease formulation 3 and the comparison grease formulation 4 are investigated. The results are shown in the following table.
Comparison Request Grease grease profile formulation 3 formulation 4 Drop point DIN ISO 2176 min. 250 C 299.0 C
301.3 C
Copper corrosion 24 h max. 2 1 1 @160 C DIN 51811 Copper corrosion 24 h max. 1 1 1 @150 C DIN 51811 L10: 224 h L10: 253 h FE9 B, 1500 N, 6000 L50: min.
L50: 268 h L50: 333 h rpm, 180 C DIN 51821 100 h 13: 10.6 13:
6.9

28 Table 7 High-temperature properties of grease formulation 3 and comparison grease formulation 4 [0098] It is found that both formulations have a drop point of about 300 C in 5 the high-temperature range. In the case of the copper corrosion test at and 160 C, a comparably good result is obtained for both formulations. In addition, both laboratory samples exhibit very good thermal stability in the Test.
10 Example 11: Preparation and testing of the grease formulations 5 based on hemimellitic acid ester and the comparison grease formulation 6 based on trimellitic acid ester [0099] The grease formulation 5 according to the invention based on 15 hemimellitic acid ester and the comparison grease formulation 6 based on trimellitic acid ester are formulated with the compositions shown in the following table.
Comparison grease Grease formulation 5 formulation 6 TMA ester bio. HMA
ester 87 wt.% trimellitic acid 87 wt.%
hemimellitic acid Ester base oil ester A ester Example 6 Urea thickener 10 wt.% 10 wt.%
Amine antioxidant 0.50 wt.% 0.50 wt.%
Corrosion 0.75 wt.% 0.75 wt.%
protection Anti-wear 1.75 wt.% 1.75 t.%

20 Table 8 [0100] The following alcohol mixture is used as alcohol for the preparation of the hemimellitic acid ester, Example 6:
25 wt.% n-octanol 25 40 wt.% 2-ethylhexanol

29 35 wt.% n-decanol Comparison Grease Method Parameter Standard grease formulation formulation 6 5 (HMA
(TMA ester) ester) Composition Ester Ester Thickener Urea Urea Water content Karl Fischer 0.059%
0.072%
Walk @ 25 C, DIN ISO
303 [0.1 mm] 303 [0.1 mm]
penetration 60 ds 2137 Walk @ 25 C, DIN ISO
360 [0.1 mm] 343 [0.1 mm]
penetration 100,000 ds 2137 Shear @ 25 C DIN 51810 3195 viscosity Base oil @ 40 C DIN 51562 71.1 mm2/s 80.5 mm2/s viscosity Base oil @ 100 C DIN 51562 - 7.38 mm2/s viscosity Cu corrosion 24 h @

168 h, dist.
Emcor DIN 51802 0 0 water 7 d @
Oil separation DIN 51817 2.49% 2.43%

Oil separation 30 h @ ASTM D
1.27% 2.64%

Flow @ -40 C DIN 51805-2 475 mbar 475 mbar pressure Flow @ -45 C DIN 51805-2 675 mbar 650 mbar pressure Low-temperature @ -45 C; 234 Nmm 116 196 Nmm 89 rotary Start! Run Nmm Nmm moment DIN ISO
Drop point 2176 277.3 C 270.4 C
Noise behavior ll ll More Quiet Noise behavior 1 1 More Quiet Noise Noise behavior SKF GN1 class BQ+
Speed 837,500 1,005,000 ROF
factor mm/min mm/min PK1 529 h PK1 380 h 13, 1500 N, PK2 395 h PK2 > 547 h FE9 6000 rpm, DIN 51821 PK3 272 h PK3 > 547 h 180 C PK4 473 h PK4 > 547 h PK5 624 h PK5 > 547 h Water 3 h @

resistance 90 C
160 C, RapidOxy 30%
16.6h 16h test pressure drop

Claims (19)

Claims

1. A use of hemimellitic acid ester of the following general formula l wherein R1, R2 and R3 independently of one another, are a) an unsubstituted, branched or unbranched Ci to C20 alkyl group, or b) a Ci to C5 alkyl group having at least one substituent selected from the group consisting of cycloalkyl groups and aromatic groups, or c) a C5 to C20 aromatic group or a C5 to C20 cycloalkyl group, wherein the hemimellitic acid ester of formula l is present as a mixture of different compounds of formula l and/or the hemimellitic acid ester of formula l comprises radicals Ri, R2 and R3, which are at least partially different from one another, as base oil of a lubricant composition for lubricating tribological systems.

2. The use according to claim 1, characterized in that the hemimellitic acid ester of formula I is at least partially bio-based.

3. The use according to either claim 1 or 2, characterized in that the lubricant composition comprises at least 10 wt.%, for example from 10 to 100 wt.% and/or 10 to 95 wt.%, preferably at least 15 wt.%, for example from 15 wt.% to 95 wt.%, in particular at least 20 wt.%, for example from 20 wt.%
to 95 wt.%, bio-based carbon, based on the total weight of organic carbon in the lubricant composition.

4. The use according to one or more of the preceding claims, characterized in that the hemimellitic acid ester of formula I comprises at least 30 wt.%, for example from 30 to 100 wt.%, preferably at least 40 wt.%, for example from 40 wt.% to 100 wt.%, in particular at least 50 wt.%, for example from 50 wt.% to 100 wt.%, bio-based carbon, based on the total weight of the hemimellitic acid ester of formula I, in the lubricant composition.

5. The use according to one or more of the preceding claims, characterized in that the acid component of the hemimellitic acid ester of formula I comprises at least 30 wt.%, preferably at least 40 wt.%, for example from 40 wt.% to 100 wt.%, in particular at least 50 wt.%, for example from 50 wt.% to 100 wt.%, bio-based carbon, based on the total weight of the acid component of the hemimellitic acid ester of formula I in the lubricant composition.

6. The use according to one or more of the preceding claims, wherein at least one radical R1, R2 and/or R3 is an unsubstituted, branched or unbranched C5 tO C20 alkyl group, more preferably a C6 tO C18 alkyl group and in particular a C8 tO C18 alkyl group.

7. The use according to one or more of the preceding claims, characterized in that at least one radical R1, R2 and/or R3 is a C]. to C3 alkyl group and in particular a C]. to C2 alkyl group, wherein the alkyl group comprises at least one substituent selected from the group consisting of C5 tO

C15 cycloalkyl groups and C5 tO C15 aromatic groups.

8. The use according to one or more of the preceding claims, characterized in that at least one group R1, R2 and/or R3 is a methyl group, ethyl group or a propyl group, which is substituted with at least one C5 tO

cycloalkyl group or with a C5 tO C15 aromatic group.

9. The use according to one or more of the preceding claims, characterized in that at least one radical R1, R2 and/or R3 is selected from the group consisting of octanyl, ethylhexanyl, nonanyl, decanyl, undecanyl, dodecanyl, isotridecyl, tricyclodecane methyl, furfuryl.

10. The use according to one or more of the preceding claims, characterized in that the radicals R1, R2 and R3, independently of one another, do not comprise any atoms other than carbon and hydrogen.

11. The use according to one or more of the preceding claims, characterized in that the lubricant composition contains the hemimellitic acid ester of formula I in an amount of from 20 wt.% to 90 wt.%, more preferably from 25 wt.% to 70 wt.%, and even more preferably from 25 wt.% to 60 wt.%, and in particular from 30 wt.% to 50 wt.%, in each case based on the total weight of the lubricant composition.

12. The use according to one or more of the preceding claims, characterized in that the hemimellitic acid ester of formula I has a kinematic viscosity at 40 C in the range of 30 mm2/5 to 150 mm2/s.

13. The use according to one or more of the preceding claims, characterized in that the lubricant composition comprises 5 to 50 wt.%, more preferably 15 to 35 wt.%, and in particular 15 to 30 wt.% polyisobutylene, in each case based on the total weight of the lubricant composition.

14. The use according to one or more of the preceding claims, characterized in that the lubricant composition is present as an oil formulation and contains at least one further base oil in a proportion of from 10 wt.% to 50 wt.%, more preferably from 10 wt.% to 40 wt.%, in each case based on the total weight of the lubricant composition, or in that the lubricant composition is present as a grease formulation and contains at least one further base oil in a proportion of from 10 wt.% to 50 wt.%, more preferably from 25 wt.% to 50 wt.%, and in particular from 30 wt.% to 50 wt.%, in each case relative to the total weight of the lubricant composition.

15. The use according to claim 14, characterized in that the further base oil is selected from esters, in particular esters of an aromatic and/or aliphatic di-, tri- or tetracarboxylic acid, with one C7 to C22 alcohol or C7 to C22 alcohols present in a mixture, esters of trimethylolpropane, pentaerythritol, or dipentaerythritol with aliphatic C7 to C22 carboxylic acids, esters of C18 dimer acids with C7 to C22 alcohols, complex esters, as individual components or in any desired mixture, and triglycerides and/or estolides, polyalphaolefins, polyethers and/or mineral oils.

16. A lubricant composition designed as an oil formulation comprising:
- 20 wt.% to 90 wt.%, preferably 50 wt.% to 85 wt.%, hemimellitic acid ester of the following general formula I, wherein R1, R2 and R3 independently of one another, are a) an unsubstituted, branched or unbranched Ci to C20 alkyl group, or b) a Ci to C5 alkyl group having at least one substituent selected from the group consisting of cycloalkyl groups and aromatic groups, or c) a C5 to C20 aromatic group or a C5 to C20 cycloalkyl group, wherein the hemimellitic acid ester of formula I is present as a mixture of different compounds of formula I and/or the hemimellitic acid ester of formula I comprises radicals R1, R2 and R3 which are at least partially different from one another, as base oil, - 5 wt.% to 50 wt.%, preferably 10 wt.% to 50 wt.%, polyisobutylene, - 0.1 wt.% to 8 wt.% additives.

17. The lubricant composition designed as a grease formulation comprising:
- 20 wt.% to 90 wt.% hemimellitic acid ester of the following general formula l wherein R1, R2 and R3 independently of one another, are a) an unsubstituted, branched or unbranched Ci to C20 alkyl group, or b) a Ci to C5 alkyl group having at least one substituent selected from the group consisting of cycloalkyl groups and aromatic groups, or c) a C5 to C20 aromatic group or a C5 to C20 cycloalkyl group, wherein the hemimellitic acid ester of formula l is present as a mixture of different compounds of formula l and/or the hemimellitic acid ester of formula l comprises radicals R1, R2and R3, which are at least partially different from one another, as base oil, - 3 to 30 wt.% thickener, - 0.1 to 8 wt.% additives.

18. The lubricant composition designed as a grease formulation comprising:
- 20 wt.% to 70 wt.% hemimellitic acid ester of the following general formula l wherein R1, R2 and R3 independently of one another, are a) an unsubstituted, branched or unbranched Ci to C20 alkyl group, or b) a Ci to C5 alkyl group having at least one substituent selected from the group consisting of cycloalkyl groups and aromatic groups, or c) a C5 to C20 aromatic group or a C5 to C20 cycloalkyl group, wherein the hemimellitic acid ester of formula I is present as a mixture of different compounds of formula I and/or the hemimellitic acid ester of formula I comprises radicals R1, R2and R3, which are at least partially different from one another, as base oil, - 3 to 30 wt.% thickener, - 10 wt.% to 50 wt.% of at least one further base oil 0.1 to 8 wt.% additives.

19. The lubricant composition according to claim 17 or 18, characterized in that the lubricant composition designed as a grease formulation comprises wt.% to 40 wt.% polyisobutylene.