US20240343988A1 - Use of hemimellitic acid ester as a base oil for lubricant compositions

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US20240343988A1

Publication number: US20240343988A1
Application number: US18/682,523
Authority: US
Inventors: Stefan Seemeyer; Thomas Kilthau; Ling Ma; Nataliya Panagiotidou
Original assignee: Klueber Lubrication Muenchen SE and Co KG
Current assignee: Klueber Lubrication Muenchen GmbH and Co KG
Priority date: 2021-08-12
Filing date: 2022-08-04
Publication date: 2024-10-17
Also published as: CA3227839A1; AU2022327545A1; EP4384589A1; JP2024529150A; KR20240038052A; WO2023016908A1; CN117940537A; JP7771359B2

A use of a hemimellitic acid ester of formula I as a base oil a lubricant composition for lubricating tribological systems. In some embodiments, R1, R2 and R3, are independently of one another: a C5 to C20 aromatic group, a C5 to C20 cycloalkyl group, an unsubstituted, branched or unbranched C1 to C20 alkyl group, and/or a C1 to C5 alkyl group comprising at least one substituent selected from the group consisting of cycloalkyl groups and aromatic groups. In some embodiments, the hemimellitic acid ester of formula I is provided as a mixture of different compounds of formula I and/or the hemimellitic acid ester of formula I comprises groups R1, R2 and R3 at least partially differing from one another.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Phase application under 35 U.S.C. § 371 of International Application No. PCT/EP2022/071929, filed on Aug. 4, 2022, and claims benefit to German Patent Application No. DE 10 2021 121 037.2, filed on Aug. 12, 2021. The International Application was published in German on Feb. 16, 2023 as WO 2023/016908 A1 under PCT Article 21(2).

FIELD

The invention relates to the use of a hemimellitic acid ester as a base oil for lubricant compositions, and to lubricant compositions on the basis of hemimellitic acid ester as a base oil.

BACKGROUND

Lubricants are essential components of many industrial processes, in which two or more surfaces move in close contact. The application spectrum of lubricant oils is very wide and, among others, comprises automotive lubricants, lubricants for two-stroke and four-stroke gasoline engines, lubricants for diesel engines, gas engine oils, gas turbine oils, automatic transmission fluids, transmission oils etc.
Lubricants can be formed as lubricant oils and lubricant greases. Industrial lubricant oils comprise, among others, industrial transmission oils, pneumatic tool lubricants, high-temperature oils, air and gas compressor oils for all types of compressors, machine tool oils, textile oils, steam turbine oils, hydraulic fluids, paper machine oils, food machine oils, steam cylinder oils, metal processing fluids for cutting, rolling, drawing, forging and die-stamping of metals. Lubricant greases, in addition to lubricant oil, comprise one or more thickening agents.
In view of the sustainability of lubricants, it is desirable to have them contain at least a portion of bio-based base oils. Furthermore, it is advantageous in practical applications, for a lubricant to contain a base oil which can be extracted (at least in part) from both biological and petrochemical sources. This helps to combine high flexibility in lubricant production with the possibility of providing an environment-friendly and sustainable lubricant. However, many bio-based oils are not suitable for lubricant applications since they do not have the desired property profile, such as in relation to the oxidation stability and low-temperature performance.
The use of trimellitic acid ester as a base oil for lubricants is known and is used in practical applications. However, this ester is not extracted from biological raw materials on an industrial scale.
A high-temperature oil for the lubrication of chains, chain sprockets and belts of continuous presses is known from WO2012159738 A1, comprising 50 to 91.9 wt. % of a composition of the general formula II
wherein R is a linear or branched alkyl group having a chain length of 8 to 16 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 has very good performance in view of its thermal stability and the residue formation or the residue performance. However, this ester is not extracted from biological raw materials on an industrial scale at present.

SUMMARY

In an embodiment, the present disclosure provides a use of a hemimellitic acid ester of the following general formula I

- wherein R₁, R₂and R₃, are independently of one another
  a) an unsubstituted, branched or unbranched C₁to C₂₀alkyl residue, or
  b) a C₁to C₅alkyl residue comprising at least one substituent selected from the residue consisting of cycloalkyl residues and aromatic residues, or
  c) a C₅to C₂₀aromatic residue or a C₅to C₂₀cycloalkyl residue,
- wherein the hemimellitic acid ester of formula I is provided as a mixture of different compounds of formula I and/or the hemimellitic acid ester of formula I comprises residues R₁, R₂and R₃at least partially differing from one another,
- as a base oil of a lubricant composition for lubricating tribological systems.

In another embodiment, the use is characterized in that the hemimellitic acid ester of formula I is at least partially bio-based.
In some embodiments, the use is characterized in that the lubricant composition includes 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, in relation to the overall weight of organic carbon in the lubricant composition.
In some embodiments, the use is characterized in that the hemimellitic acid ester of formula I includes 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, in relation to the overall weight of the hemimellitic acid ester of formula I in the lubricant composition.
In some embodiments, the use is characterized in that the acid component of the hemimellitic acid ester of formula I includes 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, in relation to the overall weight of the acid components of the hemimellitic acid ester of formula I in the lubricant composition.
In some embodiments, at least one residue R₁, R₂and/or R₃is an unsubstituted, branched or unbranched C₅to C₂₀alkyl residue, more preferably a C₆to C₁₈alkyl residue and, in particular, a C₈to C₁₈alkyl residue.
In some embodiments, the use is characterized in that at least one residue R₁, R₂and/or R₃is a C₁to C₃alkyl residue and, in particular, a C₁to C₂alkyl residue, wherein the alkyl residue includes at least one substituent selected from the residue consisting of C₅to C₁₅cycloalkyl residues and C₅to C₁₅aromatic residues.
In some embodiments, the use is characterized in that at least one residue R₁, R₂and/or R₃is a methyl residue, ethyl residue or a propyl residue substituted with at least one C₅to C₁₅cycloalkyl residue or with a C₅to C₁₅aromatic residue.
In some embodiments, the use is characterized in that at least one residue R₁, R₂and/or R₃is selected from the residue consisting of octanyl, ethylhexanyl, nonanyl, decanyl, undecanyl, dodecanyl, isotridecyl, tricyclodecanmethyl, furfuryl.
In some embodiments, the use is characterized in that the residues R₁, R₂and R₃independently of one another include no other atoms but carbon and hydrogen.
In some embodiments, the use is characterized in that the lubricant composition includes the hemimellitic acid ester of formula I in an amount of 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. %, each in relation to the overall weight of the lubricant composition.
In some embodiments, the use is characterized in that the hemimellitic acid ester of formula I has a kinematic viscosity at 40° C. in the range from 30 mm²/s to 150 mm²/s.
In some embodiments, the use is characterized in that the lubricant composition includes 5 to 50 wt. %, more preferably, from 15 to 35 wt. % and, in particular, from 15 to 30 wt. % polyisobutylene, each in relation to the overall weight of the lubricant composition.
In some embodiments, the use is characterized in that the lubricant composition is provided in the form of an oil formulation and includes at least one further base oil in a proportion of 10 wt. % to 50 wt. %, more preferably from 10 wt. % to 40 wt. %, each in relation to the overall weight of the lubricant composition, or in that the lubricant composition is provided as a grease formulation and includes at least one further base oil in a proportion of 10 wt. % to 50 wt. %, more preferably from 25 wt. % to 50 wt. % and, in particular, from 30 wt. % to 50 wt. %, each in relation to the overall weight of the lubricant composition.
In some embodiments, the use is 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 C₇to C₂₂alcohols, or present in a mixture, esters of trimethylolpropane, pentaerythrite or dipentaerythrite with aliphatic C₇to C₂₂carboxylic acid, esters of C₁₈dimer acids with C₇to C₂₂alcohols, complex esters, as individual components or in any desired mixture, and triglycerides and/or estolides, polyalphaolefins, polyethers and/or mineral oils.
In another embodiment, the present disclosure provides a lubricant composition, formed 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, R₂and R₃, are independently of one another
  a) an unsubstituted, branched or unbranched C₁to C₂₀alkyl residue, or
  b) a C₁to C₅alkyl residue comprising at least one substituent selected from the residue consisting of cycloalkyl residues and aromatic residues, or
  c) a C₅to C₂₀aromatic residue or a C₅to C₂₀cycloalkyl residue,
- wherein the hemimellitic acid ester of formula I is provided as a mixture of different compounds of formula I and/or the hemimellitic acid ester of formula I comprises residues R₁, R₂and R₃at least partially differing from one another, as a base oil,
  - 5 wt. % to 50 wt. %, preferably 10 wt. % to 50 wt. % polyisobutylene,
  - 0.1 wt. % to 8 wt. % additives.

In another embodiment, the present disclosure provides a lubricant composition, formed as a grease formulation, comprising:

- 20 wt. % to 90 wt. % hemimellitic acid ester of the following general formula I

- wherein R₁, R₂and R₃, are independently of one another
  a) an unsubstituted, branched or unbranched C₁to C₂₀alkyl residue, or
  b) a C₁to C₅alkyl residue comprising at least one substituent selected from the residue consisting of cycloalkyl residues and aromatic residues, or
  c) a C₅to C₂₀aromatic residue or a C₅to C₂₀cycloalkyl residue,
- wherein the hemimellitic acid ester of formula I is provided as a mixture of different compounds of formula I and/or the hemimellitic acid ester of formula I comprises residues R₁, R₂and R₃at least partially differing from one another, as a base oil,
- 3 to 30 wt. % thickening agent,
- 0.1 to 8 wt. % additives.

- 20 wt. % to 70 wt. % hemimellitic acid ester of the following general formula I

- wherein R₁, R₂and R₃, are independently of one another
  a) an unsubstituted, branched or unbranched C₁to C₂₀alkyl residue, or
  b) a C₁to C₅alkyl residue comprising at least one substituent selected from the residue consisting of cycloalkyl residues and aromatic residues, or
  c) a C₅to C₂₀aromatic residue or a C₅to C₂₀cycloalkyl residue,
- wherein the hemimellitic acid ester of formula I is provided as a mixture of different compounds of formula I and/or the hemimellitic acid ester of formula I comprises residues R₁, R₂and R₃at least partially differing from one another, as a base oil,
- 3 to 30 wt. % thickening agent,
- 10 wt. % to 50 wt. % at least one further base oil,
- 0.1 to 8 wt. % additives.

In some embodiments, the lubricant composition is characterized in that the lubricant composition, formed as a grease formulation, includes 10 wt. % to 40 wt. % polyisobutylene.

BRIEF DESCRIPTION OF THE DRAWINGS

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:

FIG. 1 shows the dynamic viscosity of hemimellitic acid ester of formula I in comparison to trimellitic acid ester as a function of temperature; and

FIG. 2 shows the mean friction determined by means of SRV of a plurality of lubricant compositions containing hemimellitic acid ester of formula I in comparison to lubricant compositions containing trimellitic acid ester as a function of temperature.

DETAILED DESCRIPTION

The object of the present invention is to provide a base oil for a lubricant composition which can be extracted both from biological and from petrochemical sources. Furthermore, the resulting lubricant composition is to have good oxidation resistance, lubricant action and good low-temperature performance. In addition, it is to provide good lubricant action at constant high temperatures over a long period of time. Furthermore, the lubricant composition is to be provided in different grades of viscosity depending on the intended application.
The object is achieved according to the invention by the use of a hemimellitic acid ester of the following general formula I

- wherein R₁, R₂and R₃, are independently of one another
  a) an unsubstituted, branched or unbranched C₁to C₂₀alkyl group, or
  b) a C₁to C₅alkyl group comprising at least one substituent selected from the group consisting of cycloalkyl groups and aromatic groups, or
  c) a C₅to C₂₀aromatic group or a C₅to C₂₀cycloalkyl group,
- wherein the hemimellitic acid ester can be provided as a mixture of different compounds of formula I as a base oil of a lubricant composition for the lubrication of tribological systems.

Surprisingly, it has been found that the use of hemimellitic acid ester of the above formula as a base oil makes it possible to obtain a lubricant composition having good oxidation stability, lubricant action and good low-temperature performance. Moreover, it shows good lubrication properties even at constantly high temperatures over a long period of time. Furthermore, the lubricant composition can be provided with different grades of viscosity depending on the desired application. This was surprising because hemimellitic acid ester can be extracted from biological sources, and because bio-based lubricants, as explained above, mostly do not have the desired spectrum of properties in view of their oxidation stability, lubricant action and low-temperature performance.
The production of hemimellitic acid ester from biomass is well-known and described, for example, in U.S. Pat. No. 10,562,875B2. The thus obtained hemimellitic acid ester, depending on the raw materials used, can have a high proportion of bio-based carbon, or be completely bio-based. Hemimellitic acid ester can also be extracted, however, in a simple manner from petroleum or petrochemical sources, which increases flexibility during lubricant production.
In a preferred embodiment, the hemimellitic acid ester is at least partly bio-based. This means that the hemimellitic acid ester is at least partly made of raw materials derived from biological sources and/or renewable agricultural materials (including plant, animal and marine materials) rather than petroleum or petrochemical sources. Examples of biological sources are agriculture, forestry, horticulture or animal raw materials. Preferred biological sources are straw, animal waste, waste materials from agriculture and forestry.
In the lubricant composition, hemimellitic acid ester can be provided as a single base oil or in mixtures with further base oils.
A tribological system is a technical structure having a function implemented by structural elements, which are mechanically moved-and thus subject to friction and wear. Tribological systems have the function of converting movements, energy and material, as well as transporting them and making them technically useful. Preferred tribological systems are tribological systems including metallic and/or non-metallic materials, such as antifriction and plain bearings, in particular, antifriction and plain bearings in the automotive industry, conveying industry, mechanical engineering and/or office technology, transmissions, chains, sliding guides and joints, in particular wheel bearings of automotive vehicles, bearings in wind turbines, in particular rotor bearings, in wind turbines and/or rotating plain bearings, such as fan bearings, or linearly guided sliding-contact bearings and/or ball joints, in particular of ball joints for use in the automotive industry. Possible tribological systems further comprise sliding partners in industrial plants and machinery, but also in the fields of household machinery, consumer electronics, in particular, in oil-lubricated systems, lubrication of chains, chain sprockets and steel belts of continuous wood presses.
In a preferred embodiment, the tribological systems include surfaces containing metallic and/or non-metallic materials, preferably composite materials, aluminum, aluminum alloys, steel, stainless steel and cast materials, non-ferrous metals, plastic materials, fiber-reinforced plastics and/or polymers.
In a preferred embodiment of the invention, the lubricant composition includes 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, in relation to the overall weight of organic carbon in the lubricant composition. Herein, the percentage of bio-based carbon can be determined by means of the ASTM International Radioisotope Standard D 6866 method. The newest version of the standard applies as valid on the application day. This method determines the bio-based percentage of a material on the basis of the amount of bio-based carbon in the material as a percentage of the weight of the overall organic carbon in the material tested. The method is based on the fact that bio-based products have carbon isotope ratios of 13 C/12 C and 14 C/12 C which differ from those which are found in materials derived from petroleum.
In a further preferred embodiment of the invention, the hemimellitic acid ester of formula I includes 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, in relation to the overall weight of the hemimellitic acid ester of formula I in the lubricant composition, each measured in accordance with the ASTM International Radioisotope Standard D 6866 method. The newest version of the standard applies as valid on the application day.
In a further preferred embodiment of the invention, the acid component of the hemimellitic acid ester of formula I includes 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, in relation to the overall weight of the acid components of the hemimellitic acid ester of formula I in the lubricant composition, each measured in accordance with the ASTM International Radioisotope Standard D 6866 method. The newest version of the standard applies as valid on the application day.
In a preferred embodiment of the invention, at least one residue R₁, R₂and/or R₃is an unsubstituted, branched or unbranched C₁to C₂₀alkyl group, more preferably a C₅to C₂₀alkyl group, more preferably a C₆to C₁₈alkyl group and, in particular, a C₅to C₁₈alkyl group.
In a further particularly preferred embodiment of the invention, at least one residue R₁, R₂and/or R₃is selected from the group consisting of octanyl, ethylhexanyl, nonanyl, decanyl, undecanyl, dodecanyl.
In a further particularly preferred embodiment of the invention, at least one residue R₁, R₂and/or R₃is selected from the group consisting of octanyl, 2-ethylhexan-1-yl, 1-nonanyl, decanyl, 1-undecanyl, 1-dodecanyl.
In a further preferred embodiment of the invention, at least one residue R₁, R₂and/or R₃is a C₁to C₅alkyl group and, preferably a C₁to C₃alkyl group, more preferably a C₁to C₂alkyl group and, in particular, a C₁alkyl group, which includes at least one substituent selected from the group consisting of cycloalkyl groups and aromatic groups. In the present embodiment, the above-mentioned 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 comprise both monocyclic and polycyclic compounds.
Preferably, the substituents include independently of one another 5 to 19 carbon atoms, more preferably 5 to 17 carbon atoms and, in particular, 5 to 15 carbon atoms. Further preferably, the substituents are selected independently of one another from C5 to C19 cycloalkyl groups, or C5 to C19 aromatic groups, 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.
In a further preferred embodiment of the invention, at least one residue R₁, R₂and/or R₃is a methyl group, ethyl group or a propyl group 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, R₂and R₃are independently of one another a methyl group 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.
In a further embodiment of the invention, at least one residue R₁, R₂and/or R₃is a C5 to C20 aromatic group or a C5 to C20 cycloalkyl group. Preferably, at least one residue R₁, R₂and/or R₃is selected from phenyl, cyclopentyl, cyclohexyl, naphthyl, isotridecyl, tricyclodecanmethyl, furfuryl.
In a particularly preferred embodiment of the invention, at least one residue R₁, R₂and/or R₃, preferably at least two residues R₁, R₂and/or R₃and, in particular, all of the residues R₁, R₂and/or R₃are selected from the group consisting of octanyl, ethylhexanyl, nonanyl, decanyl, undecanyl, dodecanyl, isotridecyl, tricyclodecanmethyl, furfuryl.
In a further particularly preferred embodiment of the invention, at least one residue R₁, R₂and/or R₃, preferably at least two residues R₁, R₂and/or R₃and, in particular, all of the residues R₁, R₂and/or R₃are selected from the group consisting of octanyl, 2-ethylhexan-1-yl, 1-nonanyl, decanyl, 1-undecanyl, 1-dodecanyl, isotridecyl, tricyclodecanmethyl, furfuryl.
The residues R₁, R₂and R₃can be the same or different. In a further preferred embodiment, the hemimellitic acid ester of formula I includes residues R₁, R₂and R₃, which are at least partially different from one another. It is also preferred for the hemimellitic acid ester of formula I to be a mixture of different compounds of formula I.
Also preferably the residues R₁, R₂and R₃independently of one another include no other atoms but carbon and hydrogen.
In a preferred embodiment of the invention, the lubricant composition includes the hemimellitic acid ester of formula I in an amount of 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. %, each in relation to the overall weight of the lubricant composition.
In a further preferred embodiment of the invention, the hemimellitic acid ester of formula I has a kinematic viscosity at 40° C. [mm²/s] in the range from 30 mm²/s to 150 mm²/s, preferably from 30 mm²/s to 100 mm²/s, more preferably from 50 mm²/s to 150 mm²/s and, in particular, from 50 mm²/s to 90 mm²/s.
In a further preferred embodiment of the invention, the lubricant composition is provided as an oil formulation and has a kinematic viscosity at 40° C. [mm²/s] in the range from 100 mm²/s to 460 mm²/s, preferably from 150 mm²/s to 320 mm²/s.
In a further preferred embodiment of the invention, the lubricant composition is provided 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/s] in the range from 80 mm²/s to 460 mm²/s, preferably from 100 mm²/s to 320 mm²/s.
In a further preferred embodiment of the invention, the lubricant composition includes 5 to 50 wt. %, more preferably, from 15 to 35 wt. % and, in particular, from 15 to 30 wt. % polyisobutylene, each in relation to the overall weight of the lubricant composition. What is advantageous with the use of polyisobutylene is that, with it, the viscosity of the lubricant composition can be particularly easily adjusted. Moreover, in combination with the hemimellitic acid ester of formula I, a particularly good residue performance after complete evaporation can be achieved. According to a preferred embodiment, the polyisobutylene has an average (in numbers) molecular weight of 115 to 15,000 g/mol, preferably of 160 to 5,000 g/mol, measured in accordance with DIN 55672-1:2016-03 (gel permeation chromatography (GPC)—part 1: tetrahydrofuran (THF) as an eluent).
As explained above, the lubricant composition can be provided both as a grease and as an oil formulation.
If the lubricant composition is provided as a grease formulation, it contains a thickening agent. In a preferred embodiment of the invention, the lubricant composition thus contains 3 to 30 wt. % thickening agent.
The thickening agent is preferably a reaction product of a diisocyanate, preferably 2,4-diisocyanate toluene, 2,6-diisocyanate toluene, 4,4′-diisocyanato diphenylmethane, 2,4′-diisocyanato phenyl methane, 4,4′-diisocyanato diphenyl, 4,4′-diisocyanato-3-3′-dimethylphenyl, 4,4′-diisocyanato-3,3′-dimethylphenylmethane, 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′₂—N—R—NR′₂, wherein R is an aryl, alkyl or alkylene residue with 2 to 22 carbon atoms and R′ is identical or different, a hydrogen, an alkyl, alkylene or arylene residue, or with mixtures of amines and diamines.
In a further preferred embodiment, the thickening agent is selected from Al complex soaps, metal simple soaps of the elements of the first and second main group of the periodic table, metal complex soaps of the elements of the first and second main group of the periodic table, bentonites, sulfonates, silicates, Aerosil, polyimides or PTFE or a mixture of the aforementioned thickening agents.
In addition to the hemimellitic acid ester of formula I the lubricant composition can contain at least one further base oil.
If the lubricant composition is provided as an oil formulation and contains at least one further base oil, the proportion of the further base oil is preferably from 10 wt. % to 50 wt. %, more preferably from 10 wt. % to 40 wt. %, even more preferably from 20 wt. % to 40 wt. % and, in particular, from 25 wt. % to 40 wt. %, each in relation to the overall weight of the lubricant composition.
If the lubricant composition is provided as a grease formulation and contains at least one further base oil, the proportion of the further base oil 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. %, each in relation to the overall weight of the lubricant composition.
If the lubricant composition contains at least one further base oil, the lubricant composition preferably contains the hemimellitic acid ester of formula I in an amount of 20 wt. % to 70 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. %, each in relation to the overall weight of the lubricant composition.
Suitable further base oils are usually lubrication oils liquid at room temperature (20° C.). The further base oil preferably has a kinematic viscosity of 18 mm²/s to 20000 mm²/s, in particular from 30 mm²/s to 400 mm²/s at 40° C. Base oils are differentiated between mineral and synthetic oils. Base oils are understood to be the usual base fluids used for the production of lubricants, oils, in particular, which can be categorized into groups I, II, II+, III, IV or V in accordance with the classification of the American Petroleum Institute (API) [NLGI Spokesman, N. Samman, Volume 70, Number 11, p. 14 and the following]. Mineral oils are classified in accordance with the API group. API group I are mineral oils consisting, for example, of naphthene basic or paraffin basic oils. When these mineral oils are chemically modified in comparison to the API group I oils, are low-aromatic, low-sulfur and have a low proportion of saturated compounds and thus improved viscosity/temperature performance, the oils are classified in API groups II and III. So-called gas-to-liquid oils also belong in group III, which are not produced from the refining of crude oil, but by the chemical conversion of natural gas. Furthermore, re-raffinates can also be used.
Examples of synthesis oils include polyethers, esters, polyesters, preferably polyalphaolefins, in particular, metallocene polyalphaolefins, perfluoropolyalkylethers (PFPAE), alkylated naphthalenes, silicone oils and alkylaromatics and mixtures thereof. The polyether compound can have free hydroxyl groups, but can also be completely etherized or end groups thereof esterized and/or produced of a starter compound with one or more hydroxy and/or carboxyl groups (—COOH). Polyphenyl ethers, alkylated as the case may be, are also possible as sole components or, even better, as mixed components.
Esters of an aromatic and/or aliphatic di-, tri-, or tetracarboxylic acid with one C7 to C22 alcohol, or provided in a mixture thereof, esters of trimethylolpropane, pentaerythritol or dipentaerythritol with aliphatic C7 to C22 carboxylic acid, esters of C18 dimer acids with C7 to C22 alcohols, complex esters, as individual components or in any mixture can also be suitably used. Triglycerides and/or estolides are also preferred esters.
Silicone oils, native oils and derivatives of native oils are also suitable.
Further base oils particularly preferred according to the invention are esters, in particular, esters of an aromatic and/or aliphatic di-, tri-or tetracarboxylic acid, with tetracarboxylic acid with one C7 to C22 alcohol, or provided in a mixture thereof, esters of trimethylolpropane, pentaerythrite or dipentaerythrite with aliphatic C7 to C20 carboxylic acids, esters of C18 dimer acids with C7 to C22 alcohols, complex esters, as individual components or in any mixture, and triglycerides and/or estolides, polyalphaolefins, polyethers and/or mineral oils.
Furthermore, the lubricant composition can contain inorganic or organic solid lubricants, preferably in a proportion of 0.1 wt. % to 5 wt. %, preferably 0.1 wt. % to 3 wt. % in relation to the overall weight of the lubricant composition. Solid lubricants are preferred which are 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, graphites, graphene, nano-tubes, SiO2 modifications or a mixture thereof.
Further preferably, the lubricant composition contains 0.1 to 8 wt. % additives, selected from the group consisting of corrosion protection additives, antioxidants, wear protection additives, metal deactivators, ion complex formers and/or UV stabilizers.
The following compounds are particularly suitable antioxidants according to the invention: styrolized diphenylamines, diaromatic amines, phenolic resins, thiophenolic resins, phosphites, butylated hydroxytoluene, butylated hydroxyanisole, phenyl-alpha-naphthylamine, phenyl-beta-naphthylamine, octylated/butylated diphenylamine, di-alpha-tocopherol, di-tert-butyl-phenyl, benzolpropionic acid, sulfur-containing phenol compounds and mixtures of these components.
Suitable antioxidants are also compounds, which contain sulfur, nitrogen and/or phosphorus in the molecule. Preferred compounds, which contain sulfur, nitrogen and/or phosphorus in the molecule are selected from the group consisting of aromatic aminic antioxidants, such as alkylated phenyl-alpha-naphthylamine, dialkyldiphenylamine, sterically hindered phenols, such as butylhydroxytoluene (BHT), phenolic antioxidants with thio ether groups, Zn or Mo or W dialkyldithiophosphates and phosphites.
Preferred corrosion protection additives, metal deactivators and/or ion complex formers are triazols, imidazolines, N-methylglycine (Sarcosine), benzotriazole derivatives, N,N-bis(2-ethylhexyl)-ar-methyl-1 H benzotriazol-1-methanamine; n-methyl-N(1-oxo-9-octadecenyl) glycine, a mixture of phosphoric acid and mono-and diisooctyl ester converted with (C11-C14) alkyl amines, a mixture of phosphoric acid and mono-and diisooctyl ester, converted with tert-alkylamine and primary (C12-C14) amines, dodecanoic acid, triphenyl phosphorothionate and amine phosphates and mixtures thereof. Commercially available additives are the following: IRGAMET® 39, IRGACOR® DSS G, Amin O; SARKOSYL® O (Ciba), COBRATEC® 122, CUVAN® 303, VANLUBE® 9123, Cl-426, Cl-426EP, Cl-429 and Cl-498.
Preferred wear protection additives include amines, amine phosphates, phosphates, thiophosphates, phosphorothioates and mixtures of these components. Preferred wear protection additives are selected from the group consisting of anti-wear additives on the basis of diphenylkresylphosphate, amine neutralized phosphates, alkylated and non-alkylated triaryl phosphates, alkylated and non-alkylated triaryl thiophosphates, Zn- or Mo or W-dialkyl dithio phosphates, carbamates, thiocarbamates, Zn- or Mo- or W-dithio carbamates, dimercapto thiadiazol, calcium sulfonates and benzotriazole derivatives. The commercially available wear protection additives include IRGALUBE® TPPT, IRGALUBE® 232, IRGALUBE® 349, IRGALUBE® 211 and ADDITIN® RC3760 Liq 3960, FIRC-SHUN® FG 1505 and FG 1506, NA-LUBER KR-015FG, LUBEBOND®, FLUORO® FG, SYNALOX® 40-D, ACHESON® FGA 1820 and ACHESON® FGA 1810.
A further subject matter of the invention is a lubricant composition, formed 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, R₂and R₃, are independently of one another
  a) a branched or unbranched C₁to C₂₀alkyl group, or
  b) a C₁to C₅alkyl group comprising at least one substituent selected from the group consisting of cycloalkyl groups and aromatic groups, or
  c) a C₅to C₂₀aromatic group or a C₅to C₂₀cycloalkyl group,
- wherein the hemimellitic acid ester of formula I is provided as a mixture of different compounds of formula I, as a base oil,
- 5 wt. % to 50 wt. %, preferably 10 wt. % to 50 wt. % polyisobutylene,
- 0.1 wt. % to 8 wt. % additives.

In a further preferred embodiment, the lubricant composition provided as an oil formulation additionally includes 10 wt. % to 45 wt. %, preferably 30 wt. % to 45 wt. % of at least one further base oil.
A further subject matter of the invention is a lubricant composition, formed 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

- wherein R₁, R₂and R₃, are independently of one another
  a) a branched or unbranched C₁to C₂₀alkyl group, or
  b) a C₁to C₅alkyl group comprising at least one substituent selected from the group consisting of cycloalkyl groups and aromatic groups, or
  c) a C₅to C₂₀aromatic group or a C₅to C₂₀cycloalkyl group, wherein the hemimellitic acid ester of formula I is provided as a mixture of different compounds of formula I, as a base oil,
- 3 to 30 wt. % thickening agent,
- 0.1 wt. % to 8 wt. % additives.

A further subject matter of the invention is a lubricant composition, formed 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

- wherein R₁, R₂and R₃, are independently of one another
  d) a branched or unbranched C₁to C₂₀alkyl group, or
  e) a C₁to C₅alkyl group comprising at least one substituent selected from the group consisting of cycloalkyl groups and aromatic groups, or
  f) a C₅to C₂₀aromatic group or a C₅to C₂₀cycloalkyl group, wherein the hemimellitic acid ester of formula I is provided as a mixture of different compounds of formula I, as a base oil,
- 3 to 30 wt. % thickening agent,
- 10 wt. % to 50 wt. % at least one further base oil,
- 0.1 to 8 wt. % additives.

In a preferred embodiment, the lubricant composition provided as a grease formulation includes 10 wt. % to 40 wt. % polyisobutylene.
In a further preferred embodiment, the lubricant composition provided as a grease formulation includes 0.1 wt. % to 5 wt. % inorganic or organic solid lubricants.
Preferred components of the lubricant composition according to the invention are those mentioned in the context of the use according to the invention.
In particular, particularly preferred thickening agents for the lubricant composition provided as a grease formulation are a reaction product of diisocyanate, preferably 2,4-diisocyanatotoluene, 2,6-diisocyanatotoluene, 4,4′-diisocyanatodiphenylmethane, 2,4′-diisocyanatophenyl-methane, 4,4′-diisocyanatodi-phenyl, 4,4′-diisocyanato-3-3′-dimethylphenyl, 4,4′-diisocyanato-3,3′-dimethylphenylmethane, 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′₂—N—R—NR′₂, wherein R is an aryl, alkyl or alkylene residue with 2 to 22 carbon atoms and R′ is identical or different from hydrogen, is an alkyl, alkylene or aryl residue, or with mixtures of amines and diamines.
In a further preferred embodiment, the thickening agent is selected from Al complex soaps, metal simple soaps of the elements of the first and second main group of the periodic table, metal complex soaps of the elements of the first and second main group of the periodic table, bentonites, sulfonates, silicates, Aerosil, polyimides or PTFE or a mixture of the aforementioned thickening agents.
Furthermore, particularly preferred further base oils for the lubricant composition according to the invention provided 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, with tetracarboxylic acid with one C7 to C22 alcohol, or provided in a mixture thereof, esters of trimethylolpropane, pentaerythritol or dipentaerythritol with aliphatic C7 to C22 carboxylic acid, esters of C18 dimer acids with C7 to C22 alcohols, complex esters, as individual components or in any mixture, and triglycerides and/or estolides, polyalphaolefins, polyethers and/or mineral oils.

Measuring Methods

Viscosity

Viscosity is measured in accordance with DIN 51562 (2018) using a Stabinger viscosimeter SVM 3000 (Anton Paar).

Bio-Based Carbon Content

The content of bio-based carbon is determined by means of the ASTM International Radioisotope Standard D 6866 method in the version valid on the day of application.
The invention will be described in more detail in the following with reference to examples not limiting the invention.

EXAMPLE 1: DETERMINATION OF THE DYNAMIC VISCOSITY OF HEMIMELLITIC ACID ESTER OF FORMULA I IN COMPARISON WITH TRIMELLITIC ACID ESTER

The hemimellitic acid ester 1 is produced by the following reaction:

Example 1-A

A mixture of 150 g bio-based hemimellitic acid, 369.6 g Nafol 810D and 60 ml xylol in a 1 l-three-necked flask, combined with a water separator, is refluxed at 1 atm. Within 4 h, the internal temperature rises from 126° C. to 200° C., and 0.52 g tetraisopropyl orthotitanate (0.1 wt. %) is added at an internal temperature of 160° C. Then, the clear reaction mixture is refluxed at 200° C. for 2 h and an overall amount of 38.8 g water is continuously distilled off. The xylol and the excess alcohol are distilled off at reduced pressure (T_int.=200° C., 10 mbar). After removal of the catalyst, the product (407.7 g) is obtained as a light-yellow oil.

Example 1-B

A mixture of 150 g bio-based hemimellitic acid, 369.6 g Nafol 810D and 45 ml xylol in a 1 l-three-necked flask, combined with a water separator, is refluxed at 1 atm. Within 2 h, the internal temperature rises from 139° C. to 210° C., and 0.026 g tetraisopropyl orthotitanate (0.005 wt. %) is added at an internal temperature of 150° C. Then, the clear reaction mixture is refluxed at 210° C. for 7.5 h and an overall amount of 39.6 g water is continuously distilled off. The xylol and the excess alcohol are distilled off at reduced pressure (T_int.=200° C., 8 mbar). The product (415 g) is obtained as a light-yellow oil.

Example 1-C

A mixture of 140 g bio-based hemimellitic acid, 375.1 g Nafol 810D and 40 ml xylol in a 1 l-three-necked flask, combined with a water separator, is refluxed at 1 atm. Within 5 h, the internal temperature rises from 130° C. to 215° C. Then, the clear reaction mixture is refluxed at 215° C. for 2 h and further at 220° C. for 6 h. An overall amount of 35.4 g water is continuously distilled off. The xylol and the excess alcohol are distilled off at reduced pressure (T_int.=210° C., 8 mbar). The product (388 g) is obtained as a light-yellow oil.
The dynamic viscosity of the hemimellitic acid ester 1-B is measured as a function of temperature and compared with the commercially available trimellitic acid ester 1′ which was esterized with the same alcohol mixture. The shearing rate is 1°/s, the temperature profile is 20 to −40° C., 0.2° C./min. The results of the rheological test are shown in FIG. 1 . It has been found that the hemimellitic acid ester 1 has a comparable dynamic viscosity at low temperatures that is as good as that of the trimellitic acid ester 1′.

EXAMPLE 2: DETERMINATION OF BASE DATA OF HEMIMELLITIC ACID ESTER 1 IN COMPARISON WITH TRIMELLITIC ACID ESTER 1′

The base data of the hemimellitic acid ester are measured and compared to the commercially available trimellitic acid ester 1′, which was esterized with the same alcohol mixture. The results are shown in the following table.


			TMA Ester 1′
Ex. 1-A	Ex. 1-B	Ex. 1-C	(commercial)

alcohols

n-C8 (45%), n-C10 (55%)

Kin. Visco. 40° C.	64.6	62.2	63.6	51.1
[mm²/sec]
Kin. Visco.	8.77	8.55	8.58	8.01
100° C.
[mm²/sec]
VI	+108.8	+109.0	+106.4	+126.3
SZ [mg KOH/g]	0.15	0.26	3.77	0.10

EXAMPLES 3-5

Production of further hemimellitic acid esters and one comparative ester (4′)

Example 3

A mixture of 140 g bio-based hemimellitic acid, 213 g 1-octanol, 142 g 1-dodecanol and 40 ml xylol in a 1 l-three-necked flask, combined with a water separator, is refluxed at 1 atm. Within 2 h, the internal temperature rises from 125° C. to 210° C., and 0.025 g tetraisopropyl orthotitanate (0.005 wt. %) is added at an internal temperature of 145° C. Then, the clear reaction mixture is refluxed at 210° C. for 4 h and further at 215° C. for 3.5 h. An overall amount of 37.7 g water is continuously distilled off. The xylol and the excess alcohol are distilled off at reduced pressure (T_int.=210° C., 10 mbar). The product (397.7 g) is obtained as a light-yellow oil.

Example 4

A mixture of 129.9 g bio-based hemimellitic acid, 91.5 g 1-nonanol, 165.5 g 1-undecanol, 81 g Exxal 9 (ExxonMobil), 41.1 g Exxal 10 (ExxonMobil) and 50 ml xylol in a 1 l-three-necked flask, combined with a water separator, is refluxed at 1 atm. Within 2 h, the internal temperature rises from 124° C. to 200° C., and 0.5 g tetraisopropyl orthotitanate (0.1 wt. %) is added at an internal temperature of 160° C. Then, the clear reaction mixture is refluxed at 200° C. for 2.5 h and an overall amount of 34.8 g water is continuously distilled off. The xylol and the excess alcohol are distilled off at reduced pressure (T_int.=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′, Reference Sample for Example 4)

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 xylol in a 1 l-three-necked flask, combined with a water separator, is refluxed at 1 atm and 0.35 g tetraisopropyl orthotitanate (0.1 wt. %) is added at the internal temperature of 145° C. Within 2 h, the internal temperature rises from 159° C. to 195° C. Then, the clear reaction mixture is refluxed at 195° C. for 4 h and an overall amount of 25.0 g water is continuously distilled off. The xylol and the excess alcohol are distilled off at reduced pressure (T_int.=200° C., 19 mbar). After removal of the catalyst, the product (295 g) is obtained as a light-yellow oil.

Example 5

A mixture of 150 g bio-based hemimellitic acid, 353.2 g 2-ethylhexane-1-ol and 40 ml xylol in a 1 l-three-necked flask, combined with a water separator, is refluxed at 1 atm. Within 8 h, the internal temperature rises from 124° C. to 210° C. and 0.025 g tetraisopropyl orthotitanate (0.005 wt. %) is added at an internal temperature of 145° C. Then, the clear reaction mixture is refluxed at 210° C. for 5.5 h. An overall amount of 39.1 g water is continuously distilled off. The xylol and the excess alcohol are distilled off at reduced pressure (T_int.=205° C., 16 mbar). The product (404.4 g) is obtained as a light-yellow oil.
Three different hemimellitic acid esters are produced by esterizing hemimellitic acid with different alcohols. The alcohols used and the obtained base data in comparison to corresponding trimellitic acid esters are shown in Table 6.

TABLE 6

	TMA Ester
	3′		TMA Ester 4′
Ex. 3	(commercial)	Ex. 4	(Ex. 4′)

alcohols

n-C8 (60%). n-C12 (40%)

n-C9 (25-27%). i-C9 (23%)

i-C10 (3-4%). n-C11 (47%)

Kin. Visco. 40° C.	64.1	51.4	81.0	65.6
[mm²/sec]
Kin. Visco.	8.89	8.17	10.0	9.46
100° C.
[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.	−54° C.

	TMA Ester 5′
Ex. 5	(commercial)	Ex. 6

alcohols

2-ethylhexane-1-ol

25 wt. %

			n-octanol
			40 wt. % 2EH-
			35 wt. %
			n-decanol
Kin. Visco. 40° C.	125.8	92.1	78.6
[mm²/sec]
Kin. Visco.	11.0	9.70	9.3
100° C.
[mm²/sec]
VI	+61.0	+79.0	93
SZ [mg KOH/g]	0.43	0.10	0.35
Pour point	−48° C.	−36° C.	−54° C.

EXAMPLE 6: PRODUCTION OF VARIOUS LUBRICANT COMPOSITIONS

Two lubricant compositions are produced with the composition described in Table 1:

	TABLE 1

	comparative	composition 2 acc.
	composition 1	to the invention

ester oil	41.985 wt. % trimellitic	41.985 wt. % hemimellitic
	acid ester 1′	acid ester
	(commercial)	Example 1-B

polyisobutylene	16.7	wt. %	16.7	wt. %
group III oil	37.61	wt. %	37.61	wt. %
foam inhibitor	0.02	wt. %	0.02	wt. %
additive package	3.685	wt. %	3.685	wt. %

The base data of the lubricant compositions are shown in Table 2.

TABLE 2

		composition 2
	comparative	acc. to the
requirement	composition	1	invention

appearance		clear, yellow	clear, light 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	1b - 150	1b - 150
(24 h/150° C.)

It turns out that the lubricant composition 2 according to the invention on the basis of hemimellitic acid ester shows base data comparable to those of the comparative composition 1 on the basis of trimellitic acid ester. The different viscosities that can be seen can be explained by the different initial viscosities of the base oils used.

EXAMPLE 7: DETERMINATION OF THE OXIDATION STABILITY OF THE LUBRICANT COMPOSITIONS OF EXAMPLE 6

The oxidation stability and the evaporation loss of the lubricant compositions of example 6 are determined by means of differential scanning calorimetry in accordance with DIN 51007 (04.2019) and thermogravimetric analysis in accordance with DIN 51006 (07.2005). The results are shown in Table 3.

	TABLE 3

	comparative	composition 2 acc.
	composition 1	to the invention

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.

It turns out that the lubricant compositions 2 according to the invention on the basis of hemimellitic acid ester shows high oxidation stability comparable to those of the comparative composition 1 on the basis of trimellitic acid ester.

EXAMPLE 8: THERMAL STABILITY TESTS

The lubricant compositions of Example 6 are tested in view of their evaporation behavior and the increase in their apparent dynamic viscosity under thermal stress.
To do this, the evaporation behavior and the change in the apparent dynamic viscosity (mPas) is determined as a criterion of progressive oxidation under thermal stress as a comparative measurement. Per test the specimen amount is 5 g (±0.1 g). The specimens are compared to one another after 72 h storage in an aluminum dish at 230° C. in an air-circulating oven.
In addition, the residue behavior after complete evaporation is determined with the Eisenmann test (250° C./72 h). To do this, the specimen to be tested is weighed at 5 g onto a steel sheet bent to shape and cleaned with solvent, and then evaporated off at 250° C. in an air-circulating cabinet for at least 72 h. The square metal sheet is manually bent on all four sides so that a dish shape is created. After cooling down, the results of the residual weight were documented. Key for this type of test is the determination of the partial solubility of the residue with fresh oil and the amount of the residue formed. For this purpose, a drop of the fresh oil is applied to the residue and gently rubbed in by means of a rounded glass bar in circular movements.
The results are illustrated in Table 4.

	TABLE 4

	comparative	composition 2 acc.
	composition 1	to the invention

evaporation loss with	27.0	wt. %	25.8	wt. %
closed dishes (72 h/230° C.).
dynamic viscosity^[1] of the	559	mPa · s	624	mPa · s
original formulation
dynamic viscosity ^[2] after	4617	mPa · s	3947	mPa · s
72 h at 230° C.

full evaporation acc. to	good solubility	good solubility
Eisenmann	category 4	category 4
(250° C./72 h)
solubility of the residues

full evaporation acc. to	6.2	wt. %	4.7	wt. %
Eisenmann
(250° C./72 h)
percentage of the residues

^[1]CP50, shearing rate 300 s⁻¹, 25° C.
^[2] CP25, shearing rate 300 s⁻¹, 25° C.

It turns out that all of the lubricant compositions have excellent performance. The lubricant compositions 2 according to the invention on the basis of hemimellitic acid ester show comparable evaporation behavior that is as good as, or even better than, that of the comparative composition 1 on the basis of trimellitic acid ester, and an even smaller increase of the dynamic viscosity after 72 h at 230° C. Moreover, the lubricant composition according to the invention forms a smaller amount of residue. All of the residues are excellently partially soluble with fresh oil.

EXAMPLE 9: MEASUREMENT OF FRICTIONAL WEAR OF THE LUBRICANT COMPOSITIONS OF EXAMPLE 6

The lubricant compositions of Example 6 are tested with a linear-oscillating friction and wear test (SRV) to measure frictional wear. The SRV can be used to test the coefficient of friction. The SRV is standardized in DIN 51 834.
The tested lubricant compositions are measured following DIN 51 834 at 250N load, 50 Hz, 165 min in a stepped-temperature cycle (50 to 250° C.). In this test, a steel ball is moved in oscillation against the end side of a fixedly mounted steel disc. By these means, the effect, load carrying capacity and useful life can be determined with oscillating movements under mixed friction conditions.
The results of the test are shown in FIG. 2 .
It turns out that the lubricant compositions according to the invention on the basis of hemimellitic acid ester have a comparable frictional value that is as good as that of the comparative composition 1 on the basis of trimellitic acid ester.

EXAMPLE 10: PRODUCTION AND TEST OF THE GREASE FORMULATION 3 ON THE BASIS OF HEMIMELLITIC ACID ESTER AND THE COMPARATIVE GREASE FORMULATION 4 ON THE BASIS OF TRIMELLITIC ACID ESTER

The grease formulation 3 according to the invention on the basis of hemimellitic acid ester and the comparative grease formulation 4 on the basis of trimellitic acid ester are formulated with the compositions shown in the following Table.

TABLE 5

	comparative grease
	formulation 4	grease formulation 3

ester base oil

82

wt. %

82

wt. %

	trimellitic acid ester	hemimellitic acid ester
	(Example 4′)	(Example 4)

urea thickening	15	wt. %	15	wt. %
agent
antioxidant	0.50	wt. %	0.50	wt. %
corrosion	2.5	wt. %	2.5	wt. %
protection

Example 4, Table 6a is used as the hemimellitic acid ester and TMA ester 4′ of Table 6a is used as the trimellitic acid ester.
The base data of the grease formulation 3 and the comparative grease formulation 4 are shown in the following Table.

TABLE 6

	comparative grease	grease
performance	formulation 4 TMA	formulation 3
profile	ester	bio. HMA ester

worked	250-280 [0.1 mm]	256 [0.1 mm]	265 [0.1 mm]
penetration, 60 dT
DIN ISO 2137
worked	max. 370	281 [0.1 mm]	287 [0.1 mm]
penetration, 10⁵dT	[0.1 mm]
DIN ISO 2137
Delta worked		+25 [0.1 mm]	+22 [0.1 mm]
penetration
DIN ISO 2137
penetration at rest	min. 220	243 [0.1 mm]	252 [0.1 mm]
DIN ISO 2137	[0.1 mm]
shear stability	max. +60	241 [0.1 mm]	253 [0.1 mm]
2 h @ 130° C.	[0.1 mm]	264 [0.1 mm]	271 [0.1 mm]
		+23 [0.1 mm]	+18 [0.1 mm]

shear viscosity @

2000-4000

2707

mPa · s

4271

mPa · s

25° C.	mPas
DIN 51810
water resistance	0	0	0
3 h @ 90° C.
DIN 51807-1

oil separation	max. 3.00%	1.99%	2.52%
7 d @ 40° C.
DIN 51817
oil separation	max. 5.00%	0.74%	0.81%
30 h @ 150° C.
ASTM D 6184
Emcor	max. 1	0	0
168 h, demi. water
following DIN
51802

R0F	appr. 700000	837500	mm/min	1005000	mm/min
speed factor	mm/min

Anderon	max. 2/3	Start: 1	Start: 1
		Damping: 2	Damping: 3
		Peak: 1	Peak: 1
SKF BQ + Noise	GN3	96, 100, 100, 100	97, 100, 100, 100
Class ÖNORM		GN4	GN4
M8127 p2
water content	max. 0.40%	0.051%	0.069%
Karl-Fischer

Both the grease formulation 3 and the comparative grease formulation 4 show comparative good working 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 COMPARATIVE GREASE FORMULATION 4

The high-temperature properties of the grease formulation 3 and the comparative grease formulation 4 are studied. The results are shown in the following table.

TABLE 7

High-temperature properties of the grease formulation
3 and the comparative grease formulation 4

	comparative
performance	grease	grease
profile	formulation 4	formulation 3

dropping point	min. 250° C.	299.0° C.	301.3° C.
DIN ISO 2176
copper corrosion	max. 2	1	1
24 h @ 160° C.
DIN 51811
copper corrosion	max. 1	1	1
24 h @ 150° C.
DIN 51811
FE9	L50: min. 100 h	L10: 224 h	L10: 253 h
B, 1500N, 6000		L50: 268 h	L50: 333 h
rpm, 180° C.		β: 10.6	β: 6.9
DIN 51821

It turns out that, in the high-temperature domain, both formations have a dropping point of about 300° C. In the copper corrosion test at 150° C. and 160° C., a comparatively good result is obtained for both formulations. Moreover, both laboratory specimens show very good thermal stability in the FE9 test.

EXAMPLE 11: PRODUCTION AND TEST OF THE GREASE FORMULATIONS 5 ON THE BASIS OF HEMIMELLITIC ACID ESTER AND THE COMPARATIVE GREASE FORMULATION 6 ON THE BASIS OF TRIMELLITIC ACID ESTER

The grease formulation 5 on the basis of hemimellitic acid ester and the comparative grease formulation 6 on the basis of trimellitic acid ester are formulated with the compositions shown in the following Table.

	TABLE 8

	comparative
	grease formulation	grease formulation 5
	6 TMA ester	bio. HMA ester

ester base oil	87 wt. %	87 wt. %
	trimellitic acid ester A	hemimellitic acid ester
		Example 6

urea thickening	10	wt. %	10	wt. %
agent
aminic antioxidant	0.50	wt. %	0.50	wt. %
corrosion protection	0.75	wt. %	0.75	wt. %
wear protection	1.75	wt. %	1.75	wt. %

The following alcohol mixture is used as an alcohol for the production of the hemimellitic acid ester of Example 6:

- 25 wt. % n-octanol
- 40 wt. % 2EH-ol
- 35 wt. % n-decanol


			comparative
			grease	grease
			formulation 6	formulation 5
Method	Parameter	Standard	(TMA ester)	(HMA ester)

composition			ester	ester
thickening agent			Urea	Urea
water content		Karl-	0.059%	0.072%
		Fischer

working	@ 25° C.,	DIN ISO	303	[0.1 mm]	303	[0.1 mm]
penetration	60 ds	2137
working	@ 25° C.,	DIN ISO	360	[0.1 mm]	343	[0.1 mm]
penetration	100,000 ds	2137

shear viscosity

@ 25° C.

DIN 51810

3195

4325

base oil viscosity

@ 40° C.

DIN 51562

71.1

mm²/s

80.5

mm²/s

base oil viscosity

@ 100° C.

DIN 51562

—

7.38

mm²/s

Cu corrosion	24 h @	DIN 51811	1	1
	160° C.
Emcor	168 h, dist	DIN 51802	0	0
	water
oil separation	7 d @ 40° C.	DIN 51817	2.49%	2.43%
oil separation	30 h @	ASTM D	1.27%	2.64%
	150° C.	6184

flow pressure	@ −40° C.	DIN 51805-2	475	mbar	475	mbar
flow pressure	@ −45° C.	DIN 51805-2	675	mbar	650	mbar
low-temperature	@−45° C.;	IP 186	234	Nmm	196	Nmm
torque	start/run		116	Nmm	89	Nmm
dropping point		DIN ISO	277.3°	C.	270.4°	C.
		2176

noise behavior		II	II
MoreQuiet
noise behavior		1	1
MoreQuiet
noise behavior	noise class	GN1	GN1
SKF BQ+

R0F

speed factor

837.500

mm/min

1.005.000

mm/min

FE9	B, 1500N,	DIN 51821	PK1 529 h	PK1 380 h
	6000 rpm,		PK2 395 h	PK2 >547 h
	180° C.		PK3 272 h	PK3 >547 h
			PK4 473 h	PK4 >547 h
			PK5 624 h	PK5 >547 h
water resistance	3 h @ 90° C.	DIN 51807-1	0-90	0-90

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.
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.

RapidOxy Test

1. A use of a hemimellitic acid ester of the following general formula I

wherein R₁, R₂and R₃, are independently of one another:

a C₅to C₂₀aromatic group, a C₅to C₂₀cycloalkyl group, an unsubstituted, branched or unbranched C₁to C₂₀alkyl group, and/or a C₁to C₅alkyl group comprising at least one substituent selected from the group consisting of cycloalkyl groups and aromatic groups

wherein the hemimellitic acid ester of formula I is provided as a mixture of different compounds of formula I and/or the hemimellitic acid ester of formula I comprises groups R₁, R₂and R₃at least partially differing from one another,

as a base oil of a lubricant composition for lubricating tribological systems.

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

3. The use according to claim 1, wherein the lubricant composition includes at least 10 wt. %, from 10 to 100 wt. % from 10 to 95 wt. %, at least 15 wt. %, from 15 wt. % to 95 wt. %, at least 20 wt. %, and/or from 20 wt. % to 95 wt. % bio-based carbon, in relation to the overall weight of organic carbon in the lubricant composition.

4. The use according to claim 1, wherein the hemimellitic acid ester of formula I includes at least 30 wt. %, from 30 to 100 wt. %, at least 40 wt. %, from 40 wt. % to 100 wt. %, at least 50 wt. %, and/or from 50 wt. % to 100 wt. % bio-based carbon, in relation to the overall weight of the hemimellitic acid ester of formula I in the lubricant composition.

5. The use according to claim 1, wherein the acid component of the hemimellitic acid ester of formula I includes at least 30 wt. %, at least 40 wt. %, from 40 wt. % to 100 wt. %, at least 50 wt. %, and/or from 50 wt. % to 100 wt. % bio-based carbon, in relation to the overall weight of the acid components of the hemimellitic acid ester of formula I in the lubricant composition.

6. The use according to claim 1, wherein at least one residue R₁, R₂and/or R₃is an unsubstituted, branched or unbranched C₅to C₂₀alkyl group, a C₆to C₁₈alkyl group and/or, a C₈to C₁₈alkyl group.

7. The use according to claim 1, wherein at least one residue R₁, R₂and/or R₃is a C₁to C₃alkyl group a C₁to C₂alkyl group, wherein the alkyl group includes at least one substituent selected from the group consisting of C₅to C₁₅cycloalkyl groups and C₅to C₁₅aromatic groups.

8. The use according to claim 1, wherein at least one group R₁, R₂and/or R₃is a methyl group, ethyl group or a propyl group substituted with at least one C₅to C₁₅cycloalkyl group or with at least one C₅to C₁₅aromatic group.

9. The use according to claim 1, wherein at least one residue R₁, R₂and/or R₃is selected from the group consisting of octanyl, ethy lhexanyl, nonanyl, decanyl, undecanyl, dodecanyl, isotridecyl, tricyclodecanmethyl, and furfuryl.

10-11. (canceled)

12. The use according to claim 1, wherein the residues R₁, R₂and R₃independently of one another include no other atoms but carbon and hydrogen.

13. The use according to claim 1, wherein the lubricant composition includes the hemimellitic acid ester of formula I in an amount of 20 wt. % to 90 wt. %, from 25 wt. % to 70 wt. %, from 25 wt. % to 60 wt. %, and/or from 30 wt. % to 50 wt. %, each in relation to the overall weight of the lubricant composition.

14. The use according to claim 1, wherein the hemimellitic acid ester of formula I has a kinematic viscosity at 40° C. in the range from 30 mm²/s to 150 mm²/s.

15. The use according to claim 1, wherein the lubricant composition includes 5 to 50 wt. %, from 15 to 35 wt. % and/or from 15 to 30 wt. % polyisobutylene in relation to the overall weight of the lubricant composition.

16. The use according to claim 1, wherein the lubricant composition is provided in the form of an oil formulation and includes at least one further base oil in a proportion of 10 wt. % to 50 wt. %, and/or from 10 wt. % to 40 wt. %, in relation to the overall weight of the lubricant composition, or

wherein the lubricant composition is provided as a grease formulation and includes at least one further base oil in a proportion of 10 wt. % to 50 wt. %, from 25 wt. % to 50 wt. % and/or from 30 wt. % to 50 wt. %, in relation to the overall weight of the lubricant composition.

17. The use according to claim 16, wherein the further base oil is selected from esters, esters of an aromatic and/or aliphatic di-, tri- or tetracarboxylic acid with one C₇to C₂₂alcohols, esters of trimethylolpropane, pentaerythrite or dipentaerythrite with aliphatic C₇to C₂₂carboxylic acid, esters of C₁₈dimer acids with C₇to C₂₂alcohols, complex esters, as individual components or in any desired mixture, and triglycerides and/or estolides, polyalphaolefins, polyethers and/or mineral oils.

18. A lubricant composition, formed as an oil formulation, the lubricant composition comprising:

20 wt. % to 90 wt. %, and/or 50 wt. % to 85 wt. % hemimellitic acid ester of the following general formula I

wherein R₁, R₂and R₃, are independently of one another:

an unsubstituted, branched or unbranched C₁to C₂₀alkyl group, a C₅to C₂₀aromatic group, a C₅to C₂₀cycloalkyl group, and/or a C₁to C₅alkyl group comprising at least one substituent selected from the group consisting of cycloalkyl groups and aromatic groups

wherein the hemimellitic acid ester of formula I is provided as a mixture of different compounds of formula I and/or the hemimellitic acid ester of formula I comprises residues R₁, R₂and R₃at least partially differing from on another, as a base oil;

5 wt. % to 50 wt. %, and/or 10 wt. % to 50 wt. % polyisobutylene; and

0.1 wt. % to 8 wt. % additives.

19. A lubricant composition, formed as a grease formulation, the lubricant composition comprising:

20 wt. % to 90 wt. % hemimellitic acid ester of the following general formula I

wherein R₁, R₂and R₃, are independently of one another:

an unsubstituted, branched or unbranched C₁to C₂₀alkyl group, a C₅to C₂₀aromatic group, a C₅to C₂₀cycloalkyl group, and/or a C₁to C₅alkyl group comprising at least one substituent selected from the group consisting of cycloalkyl groups and aromatic groups,

wherein the hemimellitic acid ester of formula I is provided as a mixture of different compounds of formula I and/or the hemimellitic acid ester of formula I comprises residues R₁, R₂and R₃at least partially differing from one another, as a base oil;;

3 to 30 wt. % thickening agent; and

0.1 to 8 wt. % additives.

20. A lubricant composition, formed as a grease formulation, the lubricant composition comprising:

20 wt. % to 70 wt. % hemimellitic acid ester of the following general formula I

wherein R₁, R₂and R₃, are independently of one another;

3 to 30 wt. % thickening agent;

10 wt. % to 50 wt. % at least one further base oil; and

0.1 to 8 wt. % additives.

21. The lubricant composition according to claim 17, wherein the lubricant composition, formed as a grease formulation, further comprises 10 wt. % to 40 wt. % polyisobutylene.

22. The lubricant composition according to claim 18, wherein the lubricant composition, formed as a grease formulation, further comprises 10 wt. % to 40 wt. % polyisobutylene.