Lubricating grease

Abstract

A grease comprising: 30% to 60% by weight of a silicone oil; 10% to 35% by weight of a mineral oil; -10% to 45% by weight of an overbased calcium sulfonate thickener, wherein the amounts are described respectively based on the total weight of the grease.

Description

TECHNICAL FIELD

[0001] The present invention relates to a lubricating grease comprising a silicone oil and a mineral oil as base oil. Furthermore, the present invention relates to the use of the lubricating oil for lubricating a friction system, in particular for lubricating a friction system which has high requirements with regard to energy efficiency, even at low or high temperatures. The lubricating grease is able to achieve a good energy efficiency and a good coefficient of friction at low or high temperatures, even without the inclusion of PTFE. BACKGROUND

[0002] In order to lubricate a friction system which has high requirements with regard to energy efficiency, even at low or high temperatures, for example in the automotive sector, PTFE micro powder is often used in practice, since with the aid of the PTFE micro powder a very low friction level can be achieved.

[0003] Since PTFE micro powder also has a very high temperature resistance, the PTFE micro powder is furthermore often used as a thickener or additive in lubricating a friction system in the case of high use temperatures, for example at operating temperatures of more than 160°C and without continuous re-lubrication feasibility. It is likewise common to use perfluorinated or polyfluorinated products, such as polyfluorinated polyethers or fluorinated silicone oils, as base oils.

[0004] In use, PTFE powder can be used not only as a thickener but also as an additive in a dense lubricant.

[0005] PTFE is known to have an excellent lubricating effect with a very low and constant coefficient of friction, even at high loads, to be able to effectively prevent stick slip and to exhibit good stability even when used at high shear stresses. Furthermore, PTFE has a high chemical inertness with respect to oxygen. By this, deposits of oxidation which often occur in lubricating greases as a result of the reaction of the thickener with atmospheric oxygen can be prevented and a uniform and lasting lubricating effect is achieved.

[0006] A disadvantage of the use of perfluorinated or polyfluorinated products is that they are problematic for environmental reasons. SUMMARY

[0007] It is an object of the present invention to provide a lubricating grease which has a low coefficient of friction, in particular good anti-wear (AW) and extreme pressure (EP) properties, can be used for lubricating a friction system which has high requirements with regard to energy efficiency, for example in the automotive sector, in a wide temperature range. Furthermore, in the lubricating grease it should be possible to dispense with the use of PTFE as a thickener or additive.

[0008] This object is achieved by a lubricating grease comprising

[0009] - 30 to 60% by weight of a silicone oil,

[0010] - 10 to 35 wt.-% of a mineral oil,

[0011] - 10 to 45 wt.-% of a highly basic calcium sulfonate thickener,

[0012] The amounts stated are each based on the total weight of the grease.

[0013] Surprisingly, it was found that with the aid of the grease according to the invention it is possible to dispense with the use of PTFE as a thickener or additive, and the grease still has a very low coefficient of friction combined with good anti-wear (AW) and high-pressure (extreme pressure, EP) properties. The grease can therefore also be used for lubricating friction systems with high requirements with regard to energy efficiency, for example in the automotive sector and over a wide temperature range.

[0014] It is furthermore surprising that, despite the relatively high proportion of silicone oil in the grease according to the invention, it still has very good anti-wear (AW) and high-pressure (EP) properties, since silicone oil is known not to have these properties. For this reason, in practice silicone oil is usually supplemented with or thickened with a dedicated solid lubricant such as PTFE, which improves the friction properties of the silicone oil. In contrast, the grease according to the invention can dispense with the use of PTFE as a thickener or additive.

[0015] It is furthermore known and confirmed in practical tests that typical liquid anti-wear (AW) and high-pressure (EP) additives, such as sulfur carriers, aminophosphates, neutral phosphates, (organic) carbamates, thiophosphates, cannot replace PTFE.

[0016] It has furthermore been found that even typical solid lubricants such as calcium carbonate cannot sufficiently improve the anti-wear (AW) and high-pressure (EP) properties of silicone oil.

[0017] Surprisingly, however, the anti-wear (AW) and high-pressure (EP) properties are successfully improved by the use of a highly basic calcium sulfonate thickener. Without wishing to rely on any mechanism, it is assumed that, unlike conventional calcium carbonate, the calcium carbonate contained in the highly basic calcium sulfonate thickener is able to take on the role of separating friction partners - possibly because it is present in the form of micellar structures and thus in a very finely distributed manner.

[0018] It was found in practical tests that the use of a highly basic calcium sulfonate thickener in the grease according to the invention achieves a permanent and uniform mixing of the base oils, i.e. silicone oil and mineral oil, which cannot be mixed uniformly on their own.

[0019] In particular, it was found in practical tests that the highly basic calcium sulfonate thickener in the grease according to the invention exhibits almost equivalent properties to PTFE.

[0020] Thus, in a preferred embodiment of the present application, the grease does not comprise polytetrafluoroethylene and / or comprises polytetrafluoroethylene in a share of less than 4 wt.-%, more preferably less than 2 wt.-%, more preferably less than 1 wt.-%, more preferably less than 0.5 wt.-%, more preferably less than 0.1 wt.-%, each based on the total weight of the grease. However, in a more particularly preferred embodiment of the present application, the grease does not comprise polytetrafluoroethylene.

[0021] The content of polytetrafluoroethylene in the grease is preferably determined using the standard DIN EN ISO 1 1357-1 (04 / 2008 version) according to the melting enthalpy of PTFE. The measurement is suitably performed as follows: The oil phase of the grease (including the soluble share of additives) is separated from the solid, insoluble constituents (e.g. thickeners, insoluble additives and / or solid lubricants) by extraction with a suitable solvent, as this improves the measurement accuracy. The polytetrafluoroethylene is part of the insoluble constituents. Depending on the base oil used, special gasoline 80 / 1 10, ethanol and / or methyl perfluorobutyl ether are particularly suitable as solvents. Special gasoline 80 / 1 10 is particularly suitable for greases whose base oil comprises mineral oil, PAO, alkylated aromatics, phenyl ethers, esters, silicone oil and polyethylene glycols without or with a small amount of ethylene oxide and mixtures thereof. Ethanol is particularly suitable for greases comprising a base oil consisting of polyethylene glycols with a high content of ethylene oxide. Methyl perfluorobutyl ether is particularly suitable for greases comprising perfluoropolyethers as base oil. Greases comprising two non-miscible oils are preferably subjected to two extractions. Such greases are often referred to as mixed greases. For example, such mixed greases can not only comprise perfluoropolyethers but preferably also esters. Therefore, such mixed greases are preferably extracted not only with special gasoline 80 / 1 10 but also with methyl perfluorobutyl ether in order to separate the two oils and the additives dissolved therein. The solvent residues are removed from the obtained residues. The thus obtained dried residues are related to the amount of grease used. The share of the residues in wt.-% is obtained. 20 mg are weighed from the dried residues into a DSC crucible consisting of aluminium with a filling volume of 25 μl and heated to 600 °C with a heating rate of 10 K / min. The endothermic signal between 300 °C and 450 °C is integrated, the area of the peak (sample enthalpy) being proportional to the amount of PTFE in the residue. For calibration, a pure PTFE micro powder (particle size D50 according to ASTM D4894 standard = 5 μm; melt flow index according to ASTM D1238 at 372 °C / 2.16 kg / 2.095 mm = 0.5 g / 10 min) (reference enthalpy) is similarly measured. The content of PTFE in the grease is derived according to the following formula:

[0022] (sample enthalpy) / (reference enthalpy) * residue fraction in wt% = PTFE content in wt%

[0023] According to the present application, the term "grease" is to be understood in the usual sense. A grease is thus understood to be a solid to semi-liquid substance which can be produced by dispersing a thickener into a liquid lubricant. A grease can comprise, in addition to the thickener, further additives which impart special properties to the grease. Greases are described in the standard ASTM D217-21, 07th edition.

[0024] Mineral oil is a base oil which can be produced by distilling petroleum. Mineral oil comprises paraffin (saturated chain hydrocarbons), naphthene (saturated ring hydrocarbons) and / or aromatic (ring hydrocarbons with aromatic double bond systems) components. Typically, mineral oil comprises a mixture of the aforementioned components. In addition, mineral oil can also comprise olefins (alkenes) and, depending on the source, small amounts of fluctuating organic compounds containing sulphur and nitrogen. According to the classification of the American Petroleum Institute (API) [NLGI Spokesman, N. Samman, Vol. 70, No. 11, p. 14 ff.], mineral oil is assigned to group I, group II, group II+ and group III.

[0025] Preferably, the mineral oil is a solvent refined paraffinic mineral oil. Also preferably, the mineral oil comprises a combination of hydrocarbons obtained as a refinery product by a solvent extraction process. Also preferably, the mineral oil comprises at least 50 wt% of C20 to C50 saturated hydrocarbons, based on the total weight of the mineral oil.

[0026] Preferably, the mineral oil has a kinematic viscosity at 40°C measured according to DIN EN 16896-2017-02 of 12 mm 2 / s to 400 mm 2 / s, more preferably 16 mm 2 / s to 100 mm 2 / s, especially 18 mm 2 / s to 65 mm 2 / s.

[0027] In another preferred embodiment of the present application, the grease does not comprise boric acid and boron acid compounds selected from the group consisting of metal borates and borate esters, and / or comprises only a fraction of less than 2 wt%, more preferably less than 1 wt%, based on the total weight of the grease, of boric acid and boron acid compounds selected from the group consisting of boric acid, metal borates and borate esters. Here, the "fraction of boric acid and boron acid compounds" means the total amount of boric acid and boron acid compounds which can be contained in the grease. Said embodiment is advantageous because these compounds are undesired in toxicology. In a particularly preferred embodiment of the present application, the grease thus does not comprise boric acid and boron acid compounds selected from the group consisting of boric acid, metal borates and borate esters.

[0028] Metallic borates are boron compounds which can be obtained by chemical reaction of boric acid with inorganic bases. Borates are boron compounds which can be obtained by chemical reaction of boric acid with organic alcohols.

[0029] According to the present application, the grease comprises 30 to 60 wt.-%, preferably 33 to 57 wt.-%, more preferably 35 to 55 wt.-%, especially 40 to 50 wt.-% of a silicone oil, each based on the total weight of the grease. The silicone oil is used as base oil. Preferably, the silicone oil is a fluorine-free silicone oil, i.e. does not have a fluorine atom in its structural formula. Preferably, the silicone oil comprises an alkylated silicone oil, an arylated silicone oil and / or an alkylaryl silicone oil. Particularly preferably, the silicone oil comprises an alkylated silicone oil, preferably a C1-5 alkylated silicone oil, such as a methylated silicone oil, especially a dimethyl silicone oil and / or a phenylmethyl silicone oil. Particularly preferably, the grease comprises 30 to 60 wt.-%, preferably 33 to 57 wt.-%, more preferably 35 to 55 wt.-%, especially 40 to 50 wt.-% of a dimethyl silicone oil, each based on the total weight of the grease.

[0030] The silicone oil can also comprise a mixture of silicone oils having different chemical structures and / or different kinematic viscosities.

[0031] The silicone oil, preferably the dimethyl silicone oil and / or the phenylmethyl silicone oil, preferably has a dynamic viscosity of 550 mm 2 / s to 15000 mm 2 / s, more preferably 700 mm 2 / s to 10000 mm 2 / s, still more preferably 800 mm 2 / s to 8000 mm 2 / s. The silicone oil preferably also has a kinematic viscosity of 500 mm 2 / s to 10000 mm 2 / s, more preferably 1000 mm 2 / s to 6000 mm 2 / s.

[0032] In another preferred embodiment, the silicone oil has a dynamic viscosity of 10 mm 2 / s to 1000000 mm 2 / s, more preferably 50 mm 2 / s to 100000 mm 2 / s, more preferably 100 mm 2 / s to 25000 mm 2mm2 / s. The silicone oil preferably also has a kinematic viscosity of 500 mm2 / s to 10000 mm2 / s at 40°C, measured according to DIN EN 16896-2017-02. 2 mm2 / s to 10000 mm2 / s 2 mm2 / s, more preferably 1000 mm2 / s 2 mm2 / s to 6000 mm2 / s 2 mm2 / s. These viscosities are particularly well suited for lubricating joints and actuators in automobiles.

[0033] In a preferred embodiment, the lubricating grease comprises a share of 12% to 32%, in particular 15% to 30%, by weight of the total weight of the lubricating grease, of a mineral oil.

[0034] In addition to the mineral oil and the silicone oil, the lubricant composition can comprise further base oils. By base oil is understood a base liquid which is conventionally used for the production of lubricants, which can be attributed in particular to Group I, Group II, Group II+, Group III, Group IV or Group V according to the classification of the American Petroleum Institute (API) [NLGI Spokesman, N. Samman, Vol. 70, No. 11, p. 14 ff.]. Particularly preferred further base oils are selected from Group IV or Group V. Particularly preferred further base oils are selected from the group consisting of esters; ethers, in particular polyethers, diphenyl ethers, perfluoropolyethers; synthetic hydrocarbons, in particular polyalphaolefins; synthetic hydrocarbons which do not belong to the polyalphaolefins, in particular alkylated naphthalenes; mixed polymers of unsaturated hydrocarbons, such as polymers of ethylene and alpha-olefins (e.g. Lucant HC-600®); natural hydrocarbons; natural oils and derivatives of natural oils and mixtures thereof.

[0035] Particularly preferred further base oils according to the application here are: esters; ethers, preferably polyethers, diphenyl ethers, polyphenyl ethers; synthetic hydrocarbons, in particular polyalphaolefins; alkylated naphthalenes; mixed polymers of unsaturated hydrocarbons and / or mixtures thereof. More particularly preferred are ethers, preferably polyalkylene glycols, in particular polypropylene glycol homopolymers, and / or copolymers having ethyl groups and 1-methylethyl groups as carbon radicals in the repeating units.

[0036] In a more particularly preferred embodiment of the application, the further base oil is selected from the group consisting of: esters; ethers, preferably polyethers; synthetic hydrocarbons, in particular polyalphaolefins; perfluoropolyethers; alkylated naphthalenes and mixtures thereof.

[0037] Preferred further base oils are polyethers. By polyether is understood a polymer whose organic repeat units are formed from ether functions (C-O-C). In the subgroup of polyalkylene ethers, the carbon share of the repeat units is composed of phenyl groups. In the subgroup of polyalkylene glycols, the carbon share of the repeat units is composed of substituted or unsubstituted ethyl groups (O-C-C-O), such as ethyl, 1-methyl-ethyl groups, 1-ethyl-ethyl groups. Such polyalkylene glycols homo- polymers are also commonly referred to as polyethylene glycols, polypropylene glycols and polybutylene glycols. Also referred to as polyalkylene glycols are polymers which have a mixture of different substituted ethyl groups, such as ethyl groups, 1-methyl-ethyl groups, 1-ethyl-ethyl groups, as the carbon share of the repeat units. These polyalkylene glycols can exist not only as block polymers, but also as polymers with a statistical distribution of the carbon groups. Further preferred polyethers are polytetrahydrofuran and oxetane polymers, which have four carbons (O-C-C-C-O) or three carbons (O-C-C-O) in the carbon share of the repeat units.

[0038] Preferred polyethers are polyalkylene glycols. Particularly preferred polyalkylene glycols are polypropylene glycol homo- polymers and / or copolymers which have ethyl groups and 1-methyl-ethyl groups as carbon groups in the repeat units.

[0039] The end groups of the polyalkylene glycols, polytetrahydrofuran and oxetane polymers are independently of one another preferably hydroxyl groups and / or alkoxyl groups, wherein the alkyl share of the alkoxyl groups can be composed of Ci to C20 alkyl groups. The end groups of the polyalkylene groups can additionally be substituted. The end groups can be introduced when preparing the polyalkylene glycols, polytetrahydrofuran and oxetane polymers by reacting the monomers ethylene oxide, tetrahydrofuran or oxetane with a monofunctional initiator. The monofunctional initiator is preferably an alcohol, in particular butanol. Two or more chains in the polyalkylene glycols, polytetrahydrofuran and oxetane polymers can also be linked via the end groups. Preferably, alkyl groups are the end groups which act as linkers. This can be carried out when preparing the polyalkylene glycols, polytetrahydrofuran and oxetane polymers from ethylene oxide, tetrahydrofuran or oxetane with the aid of a nucleophilic bifunctional or higher functional initiator. An example of a bifunctional initiator is a diol, in particular 1,2-ethanediol.

[0040] More particularly preferred polyethers are polyalkylene glycols, more preferably polypropylene glycol homo- polymers and / or copolymers which have ethyl groups and 1-methyl-ethyl groups as carbon groups in the repeat units. The above-mentioned polyalkylene glycols are likewise particularly preferred when butanol or 1,2-ethanediol is used as starter. They are likewise particularly preferred when the above-mentioned polyalkylene glycols have butyl groups as end groups and / or are linked via ethylene groups.

[0041] Preferred esters are carboxylic acid esters, preferably monoesters, diesters, triesters, tetraesters, pentaesters, polyesters; interesters and mixtures thereof. Especially preferred are diesters, triesters, tetraesters, pentaesters, polyesters, interesters and mixtures thereof. Herein more particularly preferred are interesters, since they can be particularly well suited for food grade lubricants.

[0042] Also preferred esters are aromatic esters, preferably aromatic esters formed from aromatic di-, tri- or tetracarboxylic acids with one or a mixture of C7 to C22 alcohols; and aliphatic esters, preferably aliphatic esters formed from mono- and / or di- carboxylic acids with one or a mixture of C3 to C22 mono-, di-, tri-, tetra-, penta- and hexaols; polyol esters, such as preferably complex esters; interesters; and mixtures thereof, wherein the esters preferably comply with NSF / H1. The acid component and / or the alcohol component of the carboxylic acid esters preferably independently of one another have a carbon number of C3 to C54.

[0043] Interesters are oligomers of aliphatic hydroxycarboxylic acids, preferably 12-hydroxystearic acid, or of unsaturated carboxylic acids, preferably oleic acid, wherein the terminal carboxylic acid groups are esterified with mono-, di-, tri- and / or tetraols, preferably branched mono-ols, more particularly preferred are Guerbet alcohols, and wherein the possibly free hydroxyl groups can be esterified by reaction with mono- or dicarboxylic acids.

[0044] Particularly preferred are aliphatic esters of mono- and / or di- carboxylic acids having a carbon number of C3 to C40 with one or a mixture of C3 to C22 mono-, di-, tri-, tetra-, penta- and hexaols.

[0045] More preferred are aliphatic esters of mono- and / or di- carboxylic acids having a carbon number of C3 to C40 with one or a mixture of C3 to C22 mono-, tri-, tetra- and hexaols.

[0046] More preferred are aliphatic esters of mono- carboxylic acids having a carbon number of C5 to C22 with one or a mixture of C3 to C10 tri-, tetra- and hexaols, especially trimethylolpropane, pentaerythritol and / or dipentaerythritol, and / or of di- carboxylic acids having a carbon number of C6 to C40, especially C18-dicarboxylic acid, with one or a mixture of C6 to C22 mono- and / or diols.

[0047] More particularly preferred are esters of trimethylolpropane, pentaerythritol and / or dipentaerythritol with aliphatic C7 to C22 carboxylic acids, and / or esters of C18 dimeric acids with C7 to C22 alcohols. More particularly preferred are esters for which a permission for occasional contact with foodstuffs can be obtained, inter alia according to EN ISO 21469 (February 2006), Appendix B. Here, the permission can preferably be carried out by the National Sanitation Foundation (NSF).

[0048] Preferably, if present, the share of the further base oil in the lubricant composition is 5 to 35% by weight, more preferably 10 to 25% by weight, in particular 12 to 20% by weight, each based on the total weight of the grease.

[0049] In a preferred embodiment of the application, the grease comprises 10 to 35% by weight, preferably 12 to 32% by weight, in particular 15 to 30% by weight of polyalphaolefin (PAO), each based on the total weight of the grease. The PAO can here be used as the further base oil. Polyalphaolefins (PAO) have the advantage that they show a good low-temperature behaviour.

[0050] The polyalphaolefin preferably also has a kinematic viscosity at 40°C of 14 mm 2 / s to 6000 mm 2 / s, more preferably 18 mm 2 / s to 1500 mm 2 / s, in particular 27 mm 2 / s to 400 mm 2 / s.

[0051] The polyalphaolefin can also be a mixture of polyalphaolefins having different chemical structures and / or different kinematic viscosities.

[0052] The polyalphaolefin can be an acid-catalytically produced polyalphaolefin or a metathesis-catalytically produced polyalphaolefin. The polyalphaolefin is preferably an acid-catalytically produced polyalphaolefin.

[0053] According to the application, the grease comprises 10 to 45% by weight, preferably 15 to 43% by weight, more preferably 15 to 41% by weight, more preferably 15 to 36% by weight, in particular 16 to 33% by weight of overbased calcium sulfonate thickener, based on the total weight of the grease.

[0054] Highly overbased calcium sulfonate thickeners are known thickeners. They are described, for example, in Lubricants and Lubrication, 2005, Wiley-VCH Verlage GmbH Co. KGaA, Weinheim, page 141, and disclosed, for example, in US Patent Nos. 3,242,079; 3,372,115; 3,376,222; 3,377,283; and 3,492,231.

[0055] It is assumed that the highly overbased calcium sulfonate thickener exists in a micellar structure when combined with a base oil, such as a silicone oil and / or a mineral oil. The core of the micelle is formed here from calcium carbonate with a certain proportion of crystalline calcium carbonate. At the surface of the calcium carbonate core, sulfonate anions and carboxylate anions accumulate. Therefore, according to the application, it is preferred that the highly overbased calcium sulfonate thickener exists in a micellar structure in the grease.

[0056] Therefore, the highly overbased calcium sulfonate thickener preferably comprises calcium sulfonate, calcium carbonate with a certain proportion of crystalline calcium carbonate, and calcium carboxylate. In addition to the crystalline calcium carbonate, the calcium carbonate can also comprise amorphous calcium carbonate.

[0057] In order to calculate the proportion of the highly overbased calcium sulfonate thickener in the grease, the sum of the amounts of the calcium sulfonate, the calcium carbonate with a certain proportion of crystalline calcium carbonate, and the calcium carboxylate is determined according to the application and is based on the total weight of the grease. Preferably, the proportion of the crystalline calcium carbonate is greater than 90% by weight, particularly preferably greater than 95% by weight, based on the total amount of the calcium carbonate.

[0058] Also preferably, the proportion of the crystalline calcium carbonate is 25% to 50% by weight, based on the total amount of the highly overbased calcium sulfonate thickener.

[0059] The preferred process according to the application for preparing the calcium sulfonate thickener is a two-stage process with the steps “promoting” and “converting”. In general, the first step (“promoting”) consists in reacting an alkylbenzenesulfonic acid, carbon dioxide (CO2) and other acids with an excess of calcium oxide (CaO) or calcium hydroxide (Ca(OH)2) as a base source, wherein an oil-soluble highly overbased calcium sulfonate with amorphous calcium carbonate dispersed therein is obtained. The reaction can be carried out in a suitable base oil, such as a silicone oil and / or a mineral oil. This highly overbased calcium sulfonate cannot yet be regarded as a calcium sulfonate thickener, but is a liquid, usually a Newtonian liquid. The highly overbased calcium sulfonate can be introduced into a suitable base oil, such as a silicone oil and / or a mineral oil.

[0060] The second step ("conversion") usually consists in adding, if necessary, one or more conversion agents, such as propylene glycol, isopropyl alcohol, water, fatty acids, formic acid and / or acetic acid, and suitable base oils, such as silicone oils and / or mineral oils, to the product of the promoting step, thereby not making the reaction mixture too hard, so that the amorphous calcium carbonate contained in the overbased calcium sulfonate is converted into a very finely distributed crystalline calcium carbonate (calcite) dispersion. When acetic acid or another acid is used as conversion agent, usually water and another non-aqueous conversion agent (third conversion agent, such as an alcohol) is used as well; alternatively, only water is added (without a third conversion agent), but the conversion is then usually carried out in a pressure vessel. Since an excess of calcium hydroxide or calcium oxide is used in order to achieve the overbase, small amounts of residual calcium oxide or calcium hydroxide can also be present as part of the oil-soluble overbased calcium sulfonate and dispersed in the initial lipid structure. The very finely distributed calcium carbonate (also called colloidal dispersion) produced by the conversion interacts with the calcium sulfonate and forms a lipid-like consistency. In this case, an overbased calcium sulfonate thickener is produced. Neutral conversion agents, such as water and alcohols, can act as swelling agents in the micellar core. Such overbased calcium sulfonate thickeners prepared by a two-stage process are disclosed, for example, in U.S. Pat. Nos. 3,242,079; 3,372,115; 3,376,222; 3,377,283; and 3,492,231.

[0061] It is also possible to combine the two steps into a single step. In the single-stage process, the overbased calcium sulfonate thickener is prepared by reacting a suitable sulfonic acid either with calcium hydroxide or with calcium oxide in the presence of carbon dioxide and a reagent system which simultaneously acts not only as a promoter (amorphous calcium carbonate overbase produced by the reaction of carbon dioxide with the excess calcium oxide or calcium hydroxide) but also as a conversion agent (conversion of the amorphous calcium carbonate into very finely distributed crystalline calcium carbonate). In this way, a lipid-like consistency is formed in a single step, in which the overbased oil-soluble calcium sulfonate (product of the first step of the two-stage process, which is not yet a thickener) is actually never formed and is not isolated as a separate product. Such single-stage processes are disclosed, for example, in U.S. Pat. Nos. 3,661,622; 3,671,012; 3,746,643; and 3,816,310.

[0062] In a preferred embodiment of the present application, the overbased calcium sulfonate thickener is manufactured by a method which comprises adding one or more conversion agents, preferably propylene glycol, isopropyl alcohol, water, fatty acids, formic acid and / or acetic acid, to the overbased calcium sulfonate, thereby obtaining the overbased calcium sulfonate thickener.

[0063] The overbased calcium sulfonate comprises an excess of calcium carbonate and / or calcium hydroxide. Preferred embodiments of the method include the embodiments described above and below.

[0064] Preferably, the calcium sulfonate thickener has a primary particle size of 100 nm to 250 nm, more preferably 120 nm to 200 nm, measured according to DIN Spec 52407:2015 DE.

[0065] The overbased calcium sulfonate thickener preferably comprises calcium sulfonate. It is assumed that in the grease, the calcium sulfonate of the overbased calcium sulfonate thickener is oriented such that the polar part is oriented towards the calcium carbonate particles and the non-polar part is oriented towards the oil phase. The term "calcium sulfonate" shall here include a single calcium sulfonate compound or a mixture of different calcium sulfonate compounds. Preferably, the calcium sulfonate comprises a mixture of different calcium sulfonate compounds. In the following, the term "calcium sulfonate" is used for simplicity in describing preferred embodiments, wherein the term "calcium sulfonate" shall also include a mixture of different calcium sulfonate compounds as set forth above.

[0066] The calcium sulfonate can comprise natural sulfonates derived from petroleum fractions, synthetic sulfonates derived from alkylations of aromatic compounds or mixtures composed of natural or synthetic sulfonates. Synthetic sulfonates are especially alkyl sulfonates and alkylaryl sulfonates. Preferably, the calcium sulfonate comprises alkylaryl sulfonates, more preferably alkylbenzyl sulfonates and especially comprises dialkylbenzyl sulfonates, preferably dialkylbenzyl sulfonates in combination with monoalkylbenzyl sulfonates. In the alkylbenzyl sulfonates, the alkyl groups preferably constitute one or more side chains which are attached as substituents to the benzyl position of the benzyl ring. Also preferably, each side chain independently of the other has 1 to 25 carbon atoms, preferably 1 to 19 carbon atoms. The side chains can be linear or branched. Linear side chains are preferred. It is also particularly preferred that the calcium sulfonate comprises at least two structurally different alkylbenzyl sulfonates.

[0067] In a particularly preferred embodiment, the calcium sulfonate comprises a calcium salt of an alkylbenzyl sulfonate of the formula

[0068]

[0069] wherein the residues R1and R2are independently of each other selected from the group consisting of: hydrogen; C1-C 25 alkyl, preferably C1-C 19 alkyl, with the proviso that R1and R2are not hydrogen at the same time. Preferably, R1is selected from the group consisting of hydrogen, C1-C4alkyl, and R2is selected from the group consisting of C7-C 19 alkyl. More particularly preferably, R1is selected from the group consisting of hydrogen, C1-C4alkyl, and R2is selected from the group consisting of C 10 -C 19alkyl. Preferably, the residues R1and R2are unbranched. Preferably, the residue C(R1R2) is in para position relative to the sulfonic acid residue. The alkyl benzyl sulfonic acid preferably comprises a mixture of structurally different alkyl benzene sulfonic acids. The alkyl benzyl sulfonic acid preferably comprises a mixture of alkyl benzene sulfonic acids differing in chain length of the alkyl substituent.

[0070] In a particularly preferred embodiment, the calcium sulfonate comprises a calcium salt of an alkyl benzyl sulfonic acid of the formula

[0071]

[0072] wherein R1is selected from C1-C4alkyl, preferably C2-C4alkyl and especially C3alkyl, and R2is selected from C4-C 19 alkyl, preferably C5-C 19 alkyl, more preferably C7-C 19 alkyl, and especially C 19 alkyl. Preferably, the residues R1and R2are unbranched. Preferably, the residue C(R1R2) is in para position relative to the sulfonic acid residue. Also preferably, the residues R1and R2are unbranched.

[0073] Also preferably, the calcium sulfonate comprises a calcium salt of an alkyl benzyl sulfonic acid of the formula

[0074]

[0075] wherein R1is selected from hydrogen, and R2is selected from C3-C 25 alkyl, preferably C5-C 19 alkyl, more preferably C7-C 19 alkyl, and especially C 10 -C 19 alkyl. Preferably, the residues R1and R2are unbranched. The calcium salt is preferably a mixture obtainable from structurally different alkyl benzene sulfonic acids. Also preferably, the residue C(R1R2) is in para position relative to the sulfonic acid residue. Also preferably, the residues R1and R2are unbranched.

[0076] In a more particularly preferred embodiment, the calcium sulfonate comprises: a calcium salt of an alkyl benzyl sulfonic acid of the formula

[0077]

[0078] wherein R1is selected from C1-C4alkyl, preferably C2-C4alkyl and especially C3alkyl, and R2is selected from C4-C 19 alkyl, preferably C5-C 19 alkyl, more preferably C7-C 19 alkyl, and especially C 19 alkyl;

[0079] Calcium salts of alkylbenzylsulfonic acids of the formula

[0080]

[0081] wherein R1 is selected from hydrogen and R2 is selected from C3-C 25 alkyl, preferably C5-C 19 alkyl, more preferably C7-C 19 alkyl and especially C 10 -C 19 alkyl. Preferably, the residue C (R1R2) is in para position relative to the sulfonic acid residue. Also preferably, the residues R1 and R2 are unbranched. The calcium salt is preferably a mixture which can be obtained from structurally different alkylbenzenesulfonic acids. Also preferably, the alkyl substituents are in para position relative to the sulfonic acid residue.

[0082] In a more particularly preferred embodiment of the present application, the overbased calcium sulfonate thickener comprises calcium dodecylsulfonate. Also preferably, the overbased calcium sulfonate thickener comprises calcium octadecylsulfonate. More particularly preferably, the overbased calcium sulfonate thickener comprises calcium dodecylsulfonate in combination with calcium octadecylsulfonate.

[0083] Furthermore, preferably, the calcium sulfonate thickener comprises calcium carboxylate. The term "calcium carboxylate" shall here include a single calcium carboxylate compound or a mixture of different calcium carboxylate compounds. In the following, the term "calcium carboxylate" is used in the description of the preferred embodiments for the sake of simplicity, wherein the term "calcium carboxylate" shall also include a mixture of different calcium carboxylate compounds as set forth herein above.

[0084] In a preferred embodiment of the present application, the calcium carboxylate comprises C1-C 20 alkyl calcium carboxylate. Preferably, the calcium carboxylate comprises a combination consisting of calcium acetate and / or calcium propionate with calcium stearate. Particularly preferably, the calcium carboxylate comprises calcium acetate in combination with calcium stearate, preferably calcium acetate in combination with calcium hydroxystearate, especially calcium acetate in combination with calcium 12-hydroxystearate.

[0085] The calcium sulfonate thickener also preferably comprises calcium carbonate with a certain fraction of crystalline calcium carbonate.

[0086] In a preferred embodiment, the crystalline calcium carbonate comprises calcium carbonate having a calcite crystal structure. The crystalline calcium carbonate can also comprise calcium carbonate having a röntgenite-type structure and / or calcium carbonate having a halurgite sub-type structure.

[0087] In a preferred embodiment, the overbased calcium sulfonate thickener is at least partially present in the form of micelles. Micelles are molecular complexes (aggregates) formed by the aggregation of amphiphilic molecules. It is advantageous in this regard that the thickener component is present in a very finely distributed form, so that it can assume the function of separating friction partners particularly well.

[0088] In a preferred embodiment of the present application, the grease comprises 1 to 20 wt.-%, preferably 3 to 15 wt.-%, more preferably 4 to 11 wt.-%, each based on the total weight of the grease, of a co-thickener. The co-thickener is preferably selected from the group consisting of bentonite; lithium soaps, in particular Li-12-hydroxystearate; boron nitride; talc; graphite; metal phosphates; polyether ether ketone (PEEK); polyphenylene sulfide; in particular calcium phosphates; molybdenum disulfide; polyimides; melamine cyanurate; tin sulfide; sodium pyrophosphate; sodium thiosulfate; zinc sulfide and / or fumed silica. Also preferably, the grease comprises 1 to 20 wt.-%, preferably 3 to 15 wt.-%, more preferably 4 to 11 wt.-%, each based on the total weight of the grease, of bentonite and / or fumed silica as co-thickener. The co-thickener preferably comprises bentonite and fumed silica, particularly preferably the ratio of bentonite to fumed silica is 30 wt.-%:70 wt.-% to 70 wt.-%:30 wt.-%. The preferred fumed silica is a fumed silica functionalized with organic groups. Preferably, the bentonite has a particle size of 2 to 15 pm, measured by means of laser diffraction method, evaluated by means of Mie theory (ISO 13320:2020-1).

[0089] Suitable fumed silicas are described, for example, in the technical journal “Technical Overview: Aerosil-Pyrogene Kieselsäure von Evonic Industries 03-2017”. In this journal, suitable fumed silicas functionalized with organic groups are also described.

[0090] In a particularly preferred embodiment, the fumed silica is a fumed silica functionalized with organic groups. Particularly preferably, the functionalized fumed silica has a specific surface area of 10 m 2 / g to 500 m 2 / g, more preferably 50 m 2 / g to 400 m 2 / g, in particular 50 m 2 / g to 200 m 2The functionalized fumed silica preferably has a BET surface of 50 to 400 m2 / g. It is also preferred that the functionalized fumed silica has a primary particle size of 5 nm to 50 nm, measured by means of transmission electron microscopy. It is also preferred that the functionalized fumed silica has a tap density of 50 g / l to 280 g / l, more preferably 50 g / l to 200 g / l, measured according to ISO 787 / 11 1995. It is also preferred that the functionalized fumed silica has a carbon content of 0.5 wt.% to 8.8 wt.%, preferably 0.5 wt.% to 6 wt.%, in particular 0.5 wt.% to 2 wt.%, measured according to ISO-3262-20 2021.

[0091] Here, preferred organic radicals are branched or unbranched aliphatic radicals and / or aromatic radicals having preferably 1 to 20 carbons. Preferred aromatic radicals have 6 to 10 carbons. Preferred aliphatic radicals have 1 to 10 carbons. Particularly preferred organic radicals are methyl, ethyl, propyl, ethenyl, butyl, pentyl, hexyl, heptyl, octyl and / or phenyl. More particularly preferred organic radicals are methyl radicals. The advantage of using these materials is likewise a friction level similar to PTFE, even at high frictional loads, and the realization of a lubrication concept with significantly reduced shear viscosity compared to PTFE products.

[0092] It is also preferred that the grease comprises 0.1 wt.% to 8 wt.% of an additive selected from the group consisting of corrosion protection additives, antioxidants, antiwear additives, metal deactivators, ion complexing agents and / or UV stabilizers.

[0093] Particularly suitable antioxidants according to the application are the following compounds: styrenated diphenylamine, bisaromatic amines, phenolic resins, thiophenolic resins, phosphites, butylated hydroxytoluene, butylated hydroxyanisole, phenyl-alpha-naphthylamine, phenyl-beta-naphthylamine, octylated / butylated diphenylamine, bis-alpha-tocopherol, di-tert-butylphenol, benzenepropanoic acid, sulfur-containing phenolic compounds and mixtures of these components.

[0094] Also suitable antioxidants are 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 amine antioxidants, such as alkylated phenyl-alpha-naphthylamines, dialkyldiphenylamines; sterically hindered phenols, such as butylated hydroxytoluene (BHT); phenolic antioxidants with sulfide groups; Zn or Mo or W-dialkyldithiophosphates and phosphites.

[0095] Preferred corrosion protection additives, metal deactivators and / or ion complexing agents are triazoles, imidazolines, N-methylglycine (sarcosine), n-methyl-N-(1-oxo-9- octadecenyl)glycine, mixtures of phosphoric acid and mono- and diisooctyl esters in reaction with (C11-14)alkylamines, mixtures of phosphoric acid and mono- and diisooctyl esters in reaction with tertiary alkylamines and (C12-14)primary amines, dodecanoic acid, triphenylphosphorothioate and amine phosphates and mixtures thereof. Commercially available additives include 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.

[0096] Preferred anti-wear additives according to the application are amines, amine phosphates, phosphates, thiophosphates, phosphorothionates and mixtures of these components. Preferred anti-wear additives are selected from the group consisting of: anti-wear additives based on diphenylcresol phosphates, amine-neutralized phosphates, alkylated and unalkylated triarylphosphates, alkylated and unalkylated triarylthiophosphates, zinc or Mo or W-dialkyldithiophosphates, carbamates, thiocarbamates, zinc or Mo or W-dithiocarbamates, dimercaptothiadiazoles, neutral calcium sulfonates and benzotriazole derivatives. Commercially available anti-wear additives include: IRGALUBE® TPPT, IRGALUBE® 232, IRGALUBE® 349, IRGALUBE® 211 and ADDITIN® RC 3760 liquid 3960, FIRC-SHUN® FG 1505 and FG 1506, NA-LUBE® KR-015 FG, LUBEBOND®, FLUORO® FG, SYNALOX® 40-D, ACHESON® FGA 1820 and ACHESON® FGA 1810.

[0097] In a preferred embodiment of the application, the greases are used for lubricating joints and actuators in automobiles. Here, the greases are particularly suitable for lubricating ball joints, in particular for joints for commercial vehicles and / or for PA overmolded joints, for sliding sunroofs, spindle drives, in particular spindle drives with nuts (for example for rear axle steering and / or parking brakes), for actuators, in particular for actuators with a burner structure, for belt starters and / or planetary gear mechanisms.

[0098] In a particularly preferred embodiment of the application, the grease is used for lubricating ceramic friction partners. Here, the grease is particularly suitable for lubricating a friction system composed of ceramic friction partners. It has surprisingly been found that the grease exhibits almost equivalent properties to PTFE in these applications, making it possible to dispense with PTFE.

[0099] In the following examples, which are not examples of the application, attempts were made to improve the properties of silicone oils with conventional liquid additives.

[0100]

[0101]

[0102] It has been shown that the properties of silicone oils cannot be improved with selected liquid additives.

Claims

1. A lubricating grease, said lubricating grease comprising: - 30% to 60% by weight of silicone oil, - 10% to 35% by weight of mineral oil, - 10% to 45% by weight of highly alkaline calcium sulfonate thickener, The quantities are calculated based on the total weight of the grease.

2. The lubricating grease according to claim 1, characterized in that, The grease does not contain polytetrafluoroethylene and / or contains less than 1% by weight, more preferably less than 0.5% by weight, and more preferably less than 0.1% by weight of polytetrafluoroethylene, respectively, based on the total weight of the grease.

3. The lubricating grease according to claim 1 or 2, characterized in that, The grease does not contain boric acid and does not contain boric acid compounds selected from boric acid, metal borates and borate esters, and / or contains only less than 1% by weight of boric acid and boric acid compounds selected from metal borates and borate esters based on the total weight of the grease.

4. The lubricating grease according to one or more of the preceding claims, characterized in that, The grease comprises 33% to 57% by weight, more preferably 35% to 55% by weight, and especially 40% to 50% by weight of silicone oil based on the total weight of the grease.

5. The lubricating grease according to one or more of the preceding claims, characterized in that, The grease contains 30% to 60% by weight of dimethyl silicone oil based on the total weight of the grease.

6. The lubricating grease according to one or more of the preceding claims, characterized in that, The silicone oil has a thickness of 10 mm at 25°C, as measured according to DIN EN 16896-2017-02. 2 / s to 1,000,000 mm 2 / s, more preferably 50mm 2 / s to 100000mm 2 / s, more preferably 100mm 2 / s to 25000mm 2 kinematic viscosity / s.

7. The lubricating grease according to one or more of the preceding claims, characterized in that, The grease has a polyalphaolefin (PAO) comprising 10% to 35% by weight, preferably 12% to 32% by weight, and especially 15% to 30% by weight of the total weight of the grease.

8. The lubricating grease according to claim 7, characterized in that, The polyalphaolefin has a thickness of 14 mm at 40°C, as measured according to DIN EN 16896-2017-02. 2 / s to 6000 mm² / s, more preferably 18 mm 2 / s to 1500mm 2 / s, especially 27mm 2 / s to 400mm 2 kinematic viscosity / s.

9. The lubricating grease according to one or more of the preceding claims, characterized in that, The grease contains mineral oil in a proportion of 12% to 32% by weight, particularly 15% to 30% by weight, based on the total weight of the grease.

10. The lubricating grease according to one or more of the preceding claims, characterized in that, The grease contains 15% to 41% by weight, more preferably 15% to 36% by weight, and especially 16% to 33% by weight of a highly alkaline calcium sulfonate thickener based on the total weight of the grease.

11. The lubricating grease according to one or more of the preceding claims, characterized in that, The highly alkaline calcium sulfonate thickener comprises calcium sulfonate, calcium carbonate with a certain proportion of crystalline calcium carbonate, and calcium carboxylate.

12. The lubricating grease according to one or more of the preceding claims, characterized in that, The calcium sulfonate comprises: a calcium salt of an alkylbenzylsulfonic acid of the following formula. R1 is selected from C1-C4 alkyl, preferably C2-C4 alkyl, and especially C3 alkyl, and R2 is selected from C4-C 19 Alkyl, preferably C5-C 19 Alkyl, more preferably C8-C 19 Alkyl groups, especially C9-C 19 Alkyl groups, calcium salts of alkylbenzylsulfonic acids as follows, R1 is selected from hydrogen, and R2 is selected from C3-C. 25 Alkyl, preferably C5-C 19 Alkyl, more preferably C7-C 19 And especially C 10 -C 19 alkyl.

13. The lubricating grease according to one or more of the preceding claims, characterized in that, The highly alkaline calcium sulfonate thickener comprises calcium dodecyl sulfonate in combination with calcium octadecyl sulfonate.

14. The lubricating grease according to one or more of the preceding claims, characterized in that, The grease contains, by weight of the total grease, 1% to 20% by weight, preferably 3% to 15% by weight, and more preferably 4% to 11% by weight of bentonite and / or pyrolytic silica as co-thickeners.

15. Use of a grease according to one or more of the preceding claims for lubricating joints and actuators in an automobile.

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