Mineral-oil free lubricant

Abstract

The invention relates to a lubricant comprising at least one ester composition, calcium carbonate, and at least one overbased alkylbenzenesulfonate. The lubricant according to the invention is mineral oil-free and contains exclusively esters as the oil component, making it readily biodegradable according to the requirements of the OECD 301 test method.

Description

Background of the invention

[0001] The invention relates to a lubricant comprising at least one ester composition, calcium carbonate and at least one overbased alkylbenzenesulfonate. 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. Description of the invention

[0006] The object of the invention is to create a lubricant that is completely biodegradable.

[0007] This object is achieved by a lubricant comprising at least one ester composition comprising at least one ester, calcium carbonate, and at least one overbased mono-, di-, or tri-alkylbenzenesulfonate, wherein at least one alkyl group of the mono-, di-, or tri-alkylbenzenesulfonate is a (C3-C30) alkyl group. The lubricant according to the invention is mineral oil-free and contains exclusively esters as the oil component, making it readily biodegradable according to the requirements of the OECD 301 test method. Since it contains exclusively esters as the oil component instead of mineral oil, the lubricant according to the invention is still fluid even at very low temperatures (-10°C to -20°C) and also has a very high pressure absorption capacity.

[0008] 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.

[0009] 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.

[0010] In an advantageous embodiment of the invention, it is provided that the mineral oil-free lubricant comprises 30 wt.% to 80 wt.% of the ester composition, 5 wt.% to 20 wt.% calcium carbonate and 5 wt.% to 25 wt.% of the overbased mono-, di- or tri-alkylbenzenesulfonate.

[0011] In a particularly advantageous embodiment of the invention, it is provided that the mineral oil-free lubricant comprises 50 wt.% to 65 wt.% of the ester composition, 10 wt.% to 15 wt.% calcium carbonate and 12 wt.% to 20 wt.% of the overbased mono-, di- or tri-alkylbenzenesulfonate.

[0012] 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)).

[0013] An exemplary composition of an advantageous embodiment of the lubricant according to the invention is given in Table 1.

[0014] The lubricant according to the invention can be produced by a process comprising 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.

[0015] The process is particularly distinguished 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 manufacturing process. Furthermore, the process 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.

[0016] The conditions for producing the lubricant are chosen such that the ester composition is not decomposed under these conditions. For this purpose, the base number (TBN = "Total Base Number") is determined during the production process. This 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). The basicity of the mixture in step a) is limited to a TBN of a maximum of 550 mg KOH / g and in step b) to a TBN of a maximum of 450 mg KOH / g. Controlling and adjusting or limiting the basicity of the mixture advantageously ensures that the esters in the mixture do not saponify, especially 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 wt.A concentration of 0.5 to 20 wt.% in step b) significantly reduces the possibility of ester hydrolysis. Choosing 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.

[0017] 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.

[0018] 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.

[0019] The mixture can be adjusted in step a) 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.

[0020] The mixture can also be adjusted in step b) to a base number (TBN) in the range of 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 of 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.

[0021] The mixture can be further heated in step a) to a temperature in the range of 35°C to 85°C or 45°C to 60°C, in particular 40°C to 82°C. Alternatively, the mixture can also be heated in step a) to a temperature in the range of 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.

[0022] The mixture can be heated in step b) 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 can also be heated in step b) 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.

[0023] The mixture can be heated in step c) to a temperature in the range of 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.

[0024] The water content of the mixture in step b) can be 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.%.

[0025] 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.

[0026] 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.

[0027] 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

[0028] Figure 1 shows 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 3shows 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

[0029] The following examples represent exemplary embodiments of the process for producing the lubricant 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:

[0030] 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:

[0031] 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:

[0032] 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:

[0033] 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:

[0034] 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:

[0035] 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:

[0036] 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. A lubricant comprising at least one ester composition comprising at least one ester, calcium carbonate and at least one overbased mono-, di- or tri-alkylbenzenesulfonate, wherein at least one alkyl group of the mono-, di- or tri-alkylbenzenesulfonate is a (C3-C30) alkyl group, and which is mineral oil-free and contains exclusively ester as the oil component.

2. Lubricant according to claim 1, characterized in that it comprises 30 wt% to 80 wt% of the ester composition, 5 wt% to 20 wt% calcium carbonate and 5 wt% to 25 wt% of the overbased mono-, di- or tri-alkylbenzenesulfonate.

3. Lubricant according to claim 1 or 2, characterized in that 50 wt% to 65 wt% of the ester composition, 10 wt% to 15 wt% calcium carbonate and 12 wt% to 20 wt% of the overbased mono-, di- or tri-alkylbenzenesulfonate.

4. Lubricant according to one of claims 1 to 3, characterized in thatat least one alkyl group of the mono-, di- or tri-alkylbenzenesulfonate is a (C10-C18) alkyl group.

5. Lubricant according to one of claims 1 to 4, characterized in that it is readily biodegradable according to the requirements of the OECD 301 test method.

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