Mineral oil-free lubricant and method for producing a mineral oil-free lubricant

Description

Background of the invention

[0001] The invention relates to a process for producing a lubricant, in which an overbased calcium sulfonate is first produced or prepared, which is then converted from the vaterite form to the calcite form, and finally a calcium sulfonate grease is produced by heating the mixture. The invention further relates to a lubricant produced by this process. State of the art

[0002] Lubricants are used to reduce friction and wear, to dampen vibrations, for sealing, and as corrosion protection for tools, machines, engines, as well as motor vehicles, aircraft, ships, and their parts. A distinction is made between liquid (lubricating oils), pasty (lubricating greases), and solid (solid lubricants such as graphite) lubricants. Lubricating greases typically consist of a lubricating oil, a thickener, and auxiliary materials and additives. Lubricating greases generally contain approximately 80% lubricating oil, 5-10% thickener, and 10-15% additives. Examples of lubricating oils that can be used are mineral oils, natural or synthetic ester oils, polyalphaolefins, or silicone oils. Synthetic ester oils include, for example, monocarboxylic acid esters, dicarboxylic acid esters, polyol esters, and complex esters. In addition to various soaps or inorganic substances (e.g.,Bentonite) often uses calcium sulfonates, which, in addition to their thickening effect in the grease, also have a corrosion-inhibiting effect due to their basic properties.

[0003] Calcium sulfonate greases currently available on the market are based exclusively on mineral oils or synthetic base oils such as polyalphaolefins (PAO). Mineral oils and PAO make up up to 80% of the grease. The core components for producing calcium sulfonate grease are so-called overbased calcium sulfonates, which are produced by reacting alkylbenzenesulfonic acids with calcium hydroxide and calcium oxide by introducing carbon dioxide into a mineral carrier oil. Commercially available overbased calcium sulfonates generally contain more than 50% mineral oil. These components do not allow the production of rapidly biodegradable calcium sulfonate greases. Since complete dispersion of calcium sulfonates in mineral oils or PAO is generally not possible, solubilizers such as water, organic solvents, and acids must also be added, which must then be removed after production.Filtration is often necessary to remove non-dispersed solid particles.

[0004] "Biodegradability" refers to the decomposition of a lubricant into inorganic substances such as water, salts, carbon dioxide, and biomass with the help of microorganisms. According to the current state of the art, the complete biodegradability of lubricants is determined exclusively by the OECD 301 test methods, which are based on the production of CO2. Biodegradability is determined at the end of a "10-day test window" and after 28 days of testing. If the lubricant has achieved the required degree of degradation of at least 60% both at the end of the 10-day window and after 28 days of incubation, it is classified as "readily biodegradable" and can be awarded, for example, the EU Ecolabel (EEL).

[0005] WO 2004 / 106474 A1 describes lubricants with improved biodegradability based on a biodegradable oil, such as a polyol ester (C5-C8) or a polyalkylene glycol, a calcium sulfonate-based thickener, and a naturally occurring phospholipid. However, the thickener used is a mixture of overbased magnesium and calcium sulfonates based on mineral oil. Due to the significant mineral oil content, complete biodegradability according to OECD 301 cannot be achieved with the lubricant described in WO 2004 / 106474 A1.

[0006] DE 22 25 714 A1 discloses a process for producing overbased lubricant additives by preparing a reaction mixture of an oil-soluble detergent or dispersant, a basic magnesium compound, an organic compound containing hydroxyl groups, a promoter, and optionally water in an inert solvent. This reaction mixture is reacted with an acidic gas and heated to remove volatile components. In preparing the reaction mixture, at least one salt of an aliphatic monoamine, diamine, or polyamine, each containing a maximum of 10 carbon atoms, or of an aromatic amine with an inorganic acid, an aliphatic monocarboxylic acid containing 1 to 20 carbon atoms (including the carbon atom in the carboxyl group), an aliphatic di- or polycarboxylic acid containing 2 to 10 carbon atoms, or an aromatic carboxylic acid is used as the promoter. Description of the invention

[0007] The object of the invention is to provide a process for producing a lubricant that does not require the use or addition of mineral oil, as well as to create a lubricant that is completely biodegradable.

[0008] The object is achieved according to the invention by a process for producing a lubricant, which comprises the following steps: a) Preparation of an overbased calcium sulfonate, comprising the following steps: dissolving at least one mono-, di- or tri-alkylbenzenesulfonic acid, wherein at least one alkyl group is a (C3-C30) alkyl group, in at least one ester composition, wherein the ester composition comprises at least one ester; admixing calcium hydroxide and calcium oxide; heating the mixture to a temperature in the range from 30°C to 90°C and introducing carbon dioxide into the mixture, wherein the mixture is adjusted to a base number (TBN) of at most 550 mg KOH / g; b) conversion of the overbased calcium sulfonate from the vaterite form to the calcite form, comprising the following steps: adjusting the mixture to a water content in the range from 2 wt.% to wt.-20%; heating the mixture to a temperature in the range of 80°C to 105°C, wherein the mixture is adjusted to a base number of not more than 450 mg KOH / g; and c) producing a calcium sulfonate grease by heating the mixture to a temperature in the range of 90°C to 200°C.

[0009] The process according to the invention is particularly characterized by the fact that both the calcium sulfonate and the grease containing it are produced exclusively on an ester basis, so that the end product contains no mineral oil and is therefore easily and completely biodegradable. The lubricant according to the invention achieves the required degree of degradation of at least 60% at the end of the so-called 10-day window and after 28 days, thus meeting the requirements of the OECD 301 test method. Furthermore, replacing mineral oil with organic or synthetic esters eliminates the need for solubilizers, eliminating the need for laborious removal at the end of the production process. Furthermore, the process according to the invention ensures that the overbased calcium sulfonates are completely dispersed in the reaction mixture, thus eliminating the need for filtration at the end of the process.

[0010] According to the invention, the conditions for producing the lubricant are selected such that the ester composition is not decomposed under these conditions. For this purpose, the total base number (TBN) is determined during the production process. This total base number is a measure of the basicity of the reaction mixture, i.e., the ability of the substances contained in the mixture to neutralize acid. The unit [mg KOH / g] refers to the basicity of potassium hydroxide (KOH). According to the invention, the basicity of the mixture is limited to a maximum TBN of 550 mg KOH / g in step a) and to a maximum TBN of 450 mg KOH / g in step b). Controlling, adjusting, or limiting the basicity of the mixture advantageously prevents the esters in the mixture from saponifying, particularly under the influence of the high temperatures in steps b) and c). The moderate addition of water also contributes to this.Adjusting the mixture to a water content in the range of 2% to 20% by weight in step b) significantly reduces the possibility of ester hydrolysis. Selecting the lowest possible temperatures, especially in steps a) and b), also advantageously ensures that the esters remain stable in the mixture. This method is particularly advantageous for producing a mineral oil-free, biodegradable calcium sulfonate grease.

[0011] The at least one alkyl group of the mono-, di-, or tri-alkylbenzenesulfonic acid can be linear, branched, and / or cyclic alkyl groups. In an advantageous embodiment of the invention, at least one alkyl group of the mono-, di-, or tri-alkylbenzenesulfonic acid is a (C10-C18) alkyl group.

[0012] Examples of suitable esters include mono- and dicarboxylic acid esters, polyol esters, and complex esters, as well as native ester oils such as rapeseed oil. The ester composition can consist of a single ester or a mixture of two or more different esters.

[0013] In an advantageous embodiment of the invention, it is further provided that the mixture in step a) is adjusted to a base number (TBN) in the range of 150 to 550 mg KOH / g, preferably 210 to 450 mg KOH / g or 320 to 420 mg KOH / g, in particular 211 to 399 mg KOH / g. Alternatively, the base number of the mixture in step a) can also be adjusted to a TBN in the range of 200 to 500 mg KOH / g or 300 to 500 mg KOH / g or 400 to 500 mg KOH / g or 150 to 450 mg KOH / g or 250 to 450 mg KOH / g or 350 to 450 mg KOH / g or 200 to 400 mg KOH / g or 300 to 400 mg KOH / g.

[0014] In a further advantageous embodiment of the invention, it is provided that the mixture in step b) is adjusted to a base number (TBN) in the range from 50 to 450 mg KOH / g, preferably 70 to 350 mg KOH / g or 100 to 250 mg KOH / g, in particular 80 to 220 mg KOH / g. Alternatively, the base number of the mixture in step b) can also be adjusted to a TBN in the range from 100 to 450 mg KOH / g or 200 to 450 mg KOH / g or 300 to 450 mg KOH / g or 350 to 450 mg KOH / g or 50 to 300 mg KOH / g or 100 to 300 mg KOH / g or 200 to 300 mg KOH / g or 150 to 250 mg KOH / g.

[0015] In a further advantageous embodiment of the invention, it is provided that the mixture in step a) is heated to a temperature in the range from 35°C to 85°C or 45°C to 60°C, in particular 40°C to 82°C. Alternatively, the mixture in step a) can also be heated to a temperature in the range from 45°C to 85°C or 55°C to 85°C or 65°C to 85°C or 75°C to 85°C or 40°C to 70°C or 50°C to 70°C or 60°C to 70°C or 50°C to 80°C or 55°C to 75°C.

[0016] In a further advantageous embodiment of the invention, the mixture in step b) is heated to a temperature in the range of 87°C to 102°C or 85°C to 100°C, in particular 88°C to 99°C. Alternatively, the mixture in step b) can also be heated to a temperature in the range of 90°C to 102°C or 95°C to 102°C or 87°C to 100°C or 90°C to 100°C.

[0017] In a further advantageous embodiment of the invention, it is provided that the mixture in step c) is heated to a temperature in the range from 100°C to 180°C or 110°C to 170°C, in particular 125°C to 160°C. Alternatively, the mixture in step c) can also be heated to a temperature in the range of 120°C to 180°C or 130°C to 180°C or 140°C to 180°C or 150°C to 180°C or 160°C to 180°C or 150°C to 170°C or 100°C to 160°C or 110°C to 160°C or 120°C to 160°C or 130°C to 160°C or 140°C to 160°C or 170°C to 180°C.

[0018] In an advantageous embodiment of the invention, it is further provided that the water content of the mixture in step b) is adjusted to a proportion in the range of 5 wt.% to 18 wt.%, in particular 7 wt.% to 15 wt.%. Alternatively, the water content of the mixture in step b) can also be adjusted to a proportion in the range of 5 to 15 wt.%, or 10 to 15 wt.%, or 7 to 18 wt.%, or 10 to 18 wt.%, or 9 to 13 wt.%.

[0019] To adjust the basicity of the reaction mixture in step b) to a desired TBN, calcium hydroxide and / or at least one mono-, di-, or tri-alkylbenzenesulfonic acid, wherein at least one alkyl group is a (C3-C30) alkyl group, and / or at least one ester composition, wherein the ester composition comprises at least one ester, can be added to the mixture. Furthermore, the addition of one or more of the above-mentioned substances can positively influence the conversion from the vaterite form to the calcite form with regard to the completeness of the conversion.

[0020] To further improve the properties of the lubricant according to the invention, additional auxiliaries and / or additives can be added to the reaction mixture. For example, acetic acid can be added, preferably in step b), to optionally adjust the desired basicity and to increase the dropping point through the resulting calcium acetate. Furthermore, 12-hydroxystearic acid can be added, preferably after conversion to the calcite form, to optimize the lubricant with regard to its hydrophobic properties, i.e., to increase its resistance to water. To further improve the corrosion protection of the lubricant, phenolic antioxidants (e.g., Irganox®< L 107, BASF), aminic antioxidants (e.g., Irganox®< L 57, BASF), and / or dimercaptothiadiazole derivatives (ADDITIN®< RC 8213 (Lanxess)), for example, can also be added.In principle, all common additives that improve the consistency and properties of the lubricant according to the invention can be added.

[0021] The invention further relates to a lubricant produced by the inventive process described above. The inventive lubricant contains no mineral oil and is therefore readily biodegradable according to the requirements of the OECD 301 test method. Furthermore, unlike mineral oil-containing greases, it remains fluid even at very low temperatures (-10°C to -20°C) and also has a higher pressure absorption capacity.

[0022] The at least one alkyl group of the mono-, di-, or tri-alkylbenzenesulfonate can be linear, branched, and / or cyclic alkyl groups. In an advantageous embodiment of the invention, at least one alkyl group of the mono-, di-, or tri-alkylbenzenesulfonate is a (C10-C18) alkyl group.

[0023] The ester composition can comprise, for example, a synthetic ester and / or a native (organic) ester. Examples of suitable esters include mono- and dicarboxylic acid esters, polyol esters, and complex esters, as well as native ester oils such as rapeseed oil. The ester composition can consist of a single ester or a mixture of two or more different esters. The ester composition should preferably have a viscosity in the range of 2 mm² / s to 1,200 mm² / s, preferably 10 mm² / s to 500 mm² / s.

[0024] The lubricant according to the invention may additionally comprise at least one additive. Examples of additives that may be present are phenolic antioxidants (e.g., Irganox®< L 107, BASF), amine antioxidants (e.g., Irganox®< L 57, BASF), and / or dimercaptothiadiazole derivatives (ADDITIN®< RC 8213 (Lanxess)).

[0025] An exemplary composition of an advantageous embodiment of the lubricant according to the invention is given in Table 1. Table 1: Components: Typical percentage: Synthetic ester 60 Alkyl(C10 - C18)benzenesulfonate, calcium salt 16 Calcium 12-hydroxystearate 9 Calcium acetate 1 Calcium carbonate 12 Irganox ®< L 57 0,5 Irganox ®< L 107 0,5 ADDITIN ®< RC 8213 1

[0026] Further advantages and features of the invention will become apparent from the figures and the following examples, which show exemplary and preferred embodiments of the invention. Short description of the figures

[0027] Figure 1shows the formation of overbased calcium sulfonate, whereby calcium carbonate micelles are initially formed from calcium hydroxide, calcium oxide, and CO 2 , to which alkylbenzenesulfonates then attach with their polar groups. The nonpolar (lipophilic) alkyl residues are directed outwards and thus surround the CaCO 3 micelles, allowing them to be completely dispersed in a base oil (ester composition). Figure 2 shows the structure of overbased calcium sulfonate after addition of Ca(OH) 2 . Figure 3 shows the structure of a mixture of overbased calcium sulfonate, Ca(OH) 2 , benzoic sulfonic acid (di- or mono-alkyl, C10 - C18) and acetic acid. Description of exemplary and preferred embodiments of the invention

[0028] The following examples represent exemplary embodiments of the method according to the invention, wherein features described or shown here may constitute an object of the invention individually or in any combination with one another, unless the context of the above description clearly indicates otherwise. Example 1:

[0029] 284 g of benzoic acid C10-18-alkyl derivative are dissolved in 500 g of bis(2-ethylhexyl) sebacate (V40: 10 mm2 / s). 10 g of calcium hydroxide are then added and the mixture is stirred for 30 min at 50 °C. 133 g of calcium oxide and 115 g of Ca(OH)2 are then added, and the mixture is homogenized by further stirring. The temperature is then increased to 60 °C. 110 ml of water is then added, and carbon dioxide is passed through the mixture. The mixture now has a TBN of 367 mg KOH / g. 300 g of bis(2-ethylhexyl) sebacate, 200 g of benzoic acid C10-18-alkyl derivative, and 120 g of water are then added to the mixture. The mixture is heated to 99 °C. After the calcium carbonate has been converted from vaterite to calcite, the mixture is dehydrated at 110 °C. The TBN is now 162 mg KOH / g. The mixture is then heated to 160 °C and held at this temperature for one hour.After cooling, the grease has a consistency (according to ASTM D217) of 331 mm / 10 after 60 double strokes. Further technical data can be found in Table 2. Example 2:

[0030] 280 g of benzoic acid C10-14-alkyl derivative are dissolved in 700 g of a complex ester (fatty acids, C18-unsaturated, dimerized, polymer with 2-ethylhexanol and neopentyl glycol) (V40: 110.5 mm2 / s). Then, 11 g of calcium hydroxide are added and stirred for 45 minutes at 50 °C. Then, 151 g of calcium oxide and 151 g of Ca(OH)2 are added, and the mixture is homogenized by further stirring. The temperature is then increased to 82 °C. 130 g of water is added, and carbon dioxide is passed through the mixture. The mixture now has a TBN of 399 mg KOH / g. Next, 300 g of complex ester (fatty acids, C18-unsaturated, dimerized, polymer with 2-ethylhexanol and neopentyl glycol), 220 g of C10-14-alkyl benzosulfonic acid, 21 g of acetic acid, 72 g of Ca(OH) 2 , and 180 g of water are added to the mixture. The mixture is heated to 92 °C. After the calcium carbonate has been converted from the vaterite to the calcite form, the mixture is dehydrated at 110 °C.The TBN is now 220 mg KOH / g. The mixture is then heated to 160 °C and held at this temperature for one hour. After cooling, the grease has a consistency (according to ASTM D217) of 292 mm / 10 after 60 double strokes. Further technical data can be found in Table 2. Example 3:

[0031] 280 g of benzoic acid C10-14-alkyl derivative are dissolved in 500 g of neopentyl glycol diisostearate (saturated ester) (V40: 48 mm 2 / s). 11 g of calcium hydroxide are added and the mixture is stirred for 45 minutes at 50 °C. 151 g of calcium oxide and 131 g of Ca(OH) 2 are then added, and the mixture is homogenized by further stirring. The temperature is then increased to 62 °C. 130 ml of water is added, and carbon dioxide is passed through the mixture. The mixture now has a TBN of 369 mg KOH / g. Then, 300 g of neopentyl glycol diisostearate (saturated ester), 243 g of C10-14 alkyl benzoic acid, 21 g of acetic acid, 72 g of Ca(OH)2, and 65 g of water are added to the mixture. The mixture is heated to 92 °C. After the calcium carbonate has been converted from the vaterite to the calcite form, the mixture is dehydrated at 110 °C. The TBN is now 188 mg KOH / g. The mixture is then heated to 160 °C and kept at this temperature for one hour.After cooling, the grease has a consistency (according to ASTM D217) of 272 mm / 10 after 60 double strokes. Further technical data can be found in Table 2. Example 4:

[0032] 260 g of C10-18-alkyl benzosulfonic acid are dissolved in 1000 g of complex ester (pentaerythritol-sebacic acid-isostearic acid copolymer) (V40: 1200 mm 2 / s). 9 g of calcium hydroxide are added and stirred for 30 min at 50 °C. Then, 101 g of calcium oxide and 104 g of Ca(OH) 2 are added, and the mixture is homogenized by further stirring. The temperature is then increased to 60 °C. 130 ml of water is added, and carbon dioxide is passed through the mixture. The mixture has a TBN of 335 mg KOH / g. Then, 400 g of bis(2-ethylhexyl) sebacate (V40: 12.5 mm2 / s), 270 g of C10-14-alkyl benzoic acid, 75 g of Ca(OH)2, and 195 g of water are added to the mixture. The mixture is heated to 92 °C. After the calcium carbonate has been converted from the vaterite to the calcite form, 150 g of 12-hydroxystearic acid are added, and the mixture is dehydrated at 110 °C. The TBN is now 159 mg KOH / g.The mixture is then heated to 160 °C and held at this temperature for one hour. After cooling, the grease has a consistency (according to ASTM D217) of 261 mm / 10 after 60 double strokes. Further technical data can be found in Table 2. Example 5:

[0033] 300 g of C10-18-alkyl benzoic acid are dissolved in 550 g of trimethylolpropane trioleate (V40: 46 mm 2 / s). Then, 120 g of calcium oxide and 100 g of Ca(OH) 2 are added, and the mixture is homogenized by further stirring. The temperature is then increased to 60 °C. 80 ml of water is added, and carbon dioxide is passed through the mixture. The mixture now has a TBN of 297 mg KOH / g. 280 g of trimethylolpropane trioleate, 280 g of C10-14-alkyl benzoic acid, 72 g of Ca(OH) 2, and 75 g of water are then added to the mixture. The mixture is heated to 92 °C. After the calcium carbonate has been converted from the vaterite to the calcite form, the mixture is dehydrated at 110 °C. The TBN is now 180 mg KOH / g. The mixture is then heated to 150 °C and held at this temperature for half an hour. After cooling, the grease has a consistency (according to ASTM D217) of 299 mm / 10 after 60 double strokes.Further technical data can be found in Table 2. Example 6:

[0034] 310 g of C8-C22-alkyl benzoic acid are dissolved in 550 g of trimethylolpropane trioleate (V40: 46 mm 2 / s). Then, 120 g of calcium oxide and 100 g of Ca(OH) 2 are added, and the mixture is homogenized by further stirring. The temperature is then increased to 60 °C. 80 ml of water is added, and carbon dioxide is passed through the mixture. The mixture now has a TBN of 297 mg KOH / g. 280 g of trimethylolpropane trioleate, 254 g of C8-C22-alkyl benzoic acid, 75 g of Ca(OH) 2 , 25 g of acetic acid, and 70 g of water are then added to the mixture. The mixture is heated to 92 °C. After the calcium carbonate has been converted from vaterite to calcite, the mixture is dehydrated at 110 °C and 100 g of caproic acid is added. The TBN is now 161 mg KOH / g. The mixture is then heated to 150 °C and held at this temperature for half an hour. After cooling, the grease has a consistency (according to ASTM D217) of 287 mm / 10 after 60 double strokes.Further technical data can be found in Table 2. Example 7:

[0035] 322 g of C10-18-alkyl benzoic acid are dissolved in 600 g of rapeseed oil (V40: 35 mm2 / s). Then, 140 g of calcium oxide and 80 g of Ca(OH)2 are added, and the mixture is homogenized by further stirring. The temperature is then increased to 40 °C. 62 ml of water is added, and carbon dioxide is passed through the mixture. The mixture now has a TBN of 211 mg KOH / g. 240 g of rapeseed oil (V40: 35 mm2 / s), 288 g of C10-14-alkyl benzoic acid, 24 g of acetic acid, 70 g of Ca(OH)2, and 49 g of water are then added to the mixture. The mixture is heated to 88 °C. After the calcium carbonate has been converted from vaterite to calcite, 167 g of 12-hydroxystearic acid is added and the mixture is dehydrated at 110 °C. The TBN is now 80 mg KOH / g. The mixture is then heated to 125 °C and held at this temperature for 15 minutes. After cooling, the grease has a consistency (according to ASTM D217) of 299 mm / 10 after 60 double strokes.Further technical data can be found in Table 2. Table 2: Penetration depth (ASTM D217) [mm / 10] Dropping point (IP 396) [°C] Resistance to water spray (ASTM D 4049) [%] Example 1 331 222 97 Example 2 292 299 81 Example 3 272 280 87 Example 4 261 244 52 Example 5 299 224 93 Example 6 287 287 81 Example 7 299 288 78

Claims

1. Method for producing a lubricant comprising the following steps: a) Preparing an overbased calcium sulphonate, comprising the following steps: - Dissolving at least one mono-, di- or tri-alkylbenzenesulfonic acid, wherein at least one alkyl group is a (C3-C30) alkyl group, in at least one ester composition, wherein the ester composition comprises at least one ester; - Admixing calcium hydroxide and calcium oxide; - Heating the mixture to a temperature in the range from 30°C to 90°C and introducing carbon dioxide into the mixture, wherein the mixture is adjusted to a base number (TBN) of at most 550 mg KOH / g; b) Conversion of the overbased calcium sulphonate from the vaterite form to the calcite form, which comprises the following steps: - Adjusting the mixture to a water content in the range from 2 wt.-% to wt.-20%; - Heating the mixture to a temperature in the range from 80°C to 105°C, wherein the mixture is adjusted to a base number of at most 450 mg KOH / g; and c) Preparing a calcium sulphonate fat by heating the mixture to a temperature in the range from 90°C to 200°C.

2. Method according to claim 1, characterised in that at least one alkyl group of the mono-, di- or tri-alkylbenzenesulphonic acid is a (C10-C18)-alkyl group.

3. Method according to claim 1 or 2, characterised in that the mixture is adjusted in step a) to a base number in the range from 150 to 550 mg KOH / g, preferably 210 to 450 mg KOH / g or 320 to 420 mg KOH / g, in particular 211 to 399 mg KOH / g.

4. Method according to any one of claims 1 to 3, characterised in that the mixture is adjusted in step b) to a base number in the range from 50 to 450 mg KOH / g, preferably 70 to 350 mg KOH / g or 100 to 250 mg KOH / g, in particular 80 to 220 mg KOH / g.

5. Method according to any one of claims 1 to 4, characterised in that the mixture is heated in step a) to a temperature in the range from 35°C to 85°C or 45°C to 60°C, in particular 40°C to 82°C.

6. Method according to any one of claims 1 to 5, characterised in that the mixture is heated in step b) to a temperature in the range from 87°C to 102°C or 85°C to 100°C, in particular 88°C to 99°C.

7. Method according to any one of claims 1 to 6, characterised in that the mixture is heated in step c) to a temperature in the range from 100°C to 180°C or 110°C to 170°C, in particular 125°C to 160°C.

8. Method according to any one of claims 1 to 7, characterised in that the water content of the mixture is adjusted in step b) to a proportion in the range from 5% by weight to 18% by weight, in particular 7% by weight to 15% by weight.

9. Method according to any one of claims 1 to 8, characterised in that calcium hydroxide and / or at least one mono-, di- or tri-alkylbenzenesulfonic acid, wherein at least one alkyl group is a (C3-C30)-alkyl group, and / or at least one ester composition, wherein the ester composition comprises at least one ester, is / are admixed to the mixture in step b).

10. Lubricant produced in the method according to any one of claims 1 to 9.