Method for recycling lubricating grease

Abstract

The invention relates to a method for recycling used lubricating grease containing polymeric hydrocarbons or polymeric esters as a thickener. In said method, the base oil is recovered along with the thickener as a component of a recycled lubricating grease obtainable in this way.

Description

[0001] Process for recycling lubricating greases

[0002] The present invention relates to a process for recycling used lubricating greases containing polymeric hydrocarbons or polymeric esters as thickeners, with recovery of the base oil together with the thickener as a component of a recycled lubricating grease thus obtainable.

[0003] State of the art

[0004] For many technical applications, it is important to use lubricants to reduce friction and wear on the contact surfaces of moving parts. Depending on the application, lubricants of different consistencies can be used. Lubricating oils have a liquid and flowable consistency, while lubricating greases have a semi-solid to solid—often gel-like—consistency.

[0005] The characteristic of a lubricating grease is that a liquid oil component is absorbed and held in place by a thickener component. The nature of a lubricating grease and its ability to be spreadable and easily deformed, together with its adhesive properties, ensures that the grease wets the lubrication point and develops its lubricating effect on the tribologically stressed surfaces. They are used in particular for the lubrication of less well-sealed machine elements, such as rolling or plain bearings, open gears, and guides.

[0006] Lubricating greases contain a thickener that is homogeneously dispersed in a base oil, as well as solid or liquid additives. Additional additives, such as emulsifiers, are often used to ensure the thickener is stably dispersed in the base oil. A wide variety of liquids are known as base oils. Organic and inorganic compounds are used as thickeners.

[0007] In the Federal Republic of Germany, over 34,000 tons of used lubricating greases are generated every year, particularly in the lubrication of tribological systems such as rolling bearings, where lubricating greases account for a share of around 80%. In many cases, lubricating greases are used in what is known as loss lubrication, which generates large amounts of contaminated grease that must be disposed of in an environmentally friendly manner. Examples of corresponding applications can be found in rolling and plain bearings in energy plants (e.g. wind and hydropower), agriculture, the steel and cement industries, mining, and the food processing industry. In contrast to lifetime-lubricated machine elements or tribological systems, the lubricating greases used in the lubrication of loss-lubricated applications often undergo slight thermo-oxidative or mechanical aging, but are frequently contaminated with wear particles, dust, and moisture.This is because the corresponding lubrication points are only inadequately protected against environmental influences or the aforementioned contaminants are to be flushed out by relubricating grease.

[0008] Even though lubricating greases have a comparatively small market share compared to lubricating oils, their recycling is worthwhile because lubricating greases are manufactured with a high expenditure of thermal and mechanical energy.

[0009] Various processes are known for thermally recycling used lubricating grease that is no longer suitable for its original purpose, with the goal of utilizing its energy content. However, such processes do not allow for material recycling, i.e., the reuse of the product as a lubricant.

[0010] In the rolling bearing industry, the first technical solutions now exist for the separate collection of used or old lubricating grease resulting from loss lubrication. For example, EP2447485 B1 describes a reusable used lubricating grease cartridge that allows the separate removal of used lubricating grease from a rolling bearing and subsequent emptying into a waste collection container. Used lubricating grease is therefore used lubricating grease, such as that found at the lubrication point or in the vicinity of the lubrication point, or in a reservoir associated with one or more lubrication points, without having been collected and consolidated. Through this collection and consolidation, the used lubricating grease becomes used lubricating grease, which is then subjected to a recycling process.To date, reuse has typically involved purifying lubricating greases, separating the thickener from the base oil and resulting in the loss of the thickener structure. With approximately 4 to 20% thickener and approximately 75 to 95% base oil by mass, thickener and base oil are the main components of most lubricating greases. If both can be purified in one and the same recycling process, the amount of waste and the energy and time required for recycling lubricating greases can be minimized.

[0011] According to a recent survey by the National Lubricating Grease Institute (NLGI), the group of metal standard and complex soap greases represents the largest contingent of lubricating greases at approximately 90% (NLGI Grease Production Survey Report 2020).

[0012] According to DE19739659 A1, the oil-containing components, along with impurities such as dirt and metal debris, are first removed from the used lubricating grease, which is preferably collected separately, in a multi-stage oil recovery process. The base oil is extracted from the used lubricating grease in an extractor in a multi-stage extraction process by adding an extraction agent. The resulting oil-extraction agent mixture (extract) is then separated from the raffinate with thickener and impurities in a downstream separator. The raffinate with thickener is in a semi-solid to solid state and is further dried to evaporate solvent residues. The multi-stage thickener recovery process consists of an extraction stage and crystallization. The thickener is separated from the drying residue using a suitable solvent, such as methanol or a methanol-chloroform mixture.In the extraction stage, the thickeners are dissolved by the added extractant, while the impurities remain undissolved.

[0013] Object of the invention

[0014] When loss lubrication occurs in rolling or plain bearings or gears operating at low rotational or sliding speeds, a large portion of the grease volume introduced into these applications for loss lubrication often does not directly engage in shear contact, but rather serves as a reservoir to seal the tribological contact pairs. In these cases, a comparatively large volume of the grease is often subjected to little mechanical and / or oxidative stress, and the thickener structure of the grease is largely preserved. In this case, it is advisable to choose a recycling process that causes no or only comparatively little damage to the thickener structure of the grease.

[0015] When reprocessing lubricating greases, it is desirable not to separate the thickener and base oil and to purify them in separate steps. Furthermore, reprocessing should not result in any irreversible change in the thickener structure and the associated loss of thickening effect. The object of the invention is therefore to avoid the above-described disadvantages of the prior art and to provide a process with which lubricating greases can be recycled as cost-effectively and energy-efficiently as possible, and in as few steps as possible. The process should also be applicable to lubricating greases whose components, in particular the thickener, were produced from renewable raw materials. This would make it possible to feed materials produced with natural CO2 consumption into a recurring product life cycle, thus avoiding climate-damaging emissions.

[0016] Summary of the invention

[0017] The invention is defined by the independent claims. Preferred embodiments are the subject of the subclaims or described below.

[0018] The invention relates to a method for reprocessing used lubricating greases (old lubricating grease), which become a used lubricating grease through use and collection, comprising the following steps: a) collecting used, uniform lubricating greases from lubrication points to obtain a used lubricating grease, wherein the used lubricating grease contains at least one thickener, additives, a base oil and optionallycomprises solid impurities and the thickener comprises polymeric hydrocarbons or polymeric esters, b) providing a solvent having a boiling point or an upper boiling point in the case of a boiling range of 40 to 140°C at standard pressure, c) suspending the used lubricating grease in the solvent to obtain a suspension comprising a liquid phase comprising at least the base oil and the solvent and a solid phase in the liquid phase comprising at least the thickener in suspended form, wherein at least the base oil and the solvent are mixed in the form of a uniform liquid phase, d) separating any solid impurities from the suspension, e.g. by sedimentation, e) removing the solvent (e.g. more than 75% by weight or more than 90% by weight of the solvent used) from the suspension by distillation or by extraction with supercritical CO2, to obtain a recycled lubricating grease.

[0019] - Reclaimed base oil comprising base oil from the used lubricating grease and

[0020] - recovered thickener from the used lubricating grease and

[0021] - Recovered additives comprising additives from the used lubricating grease, wherein the used lubricating grease, the suspension and the recycled lubricating grease are not exposed at any time during the process to a temperature higher than the dropping point of the used lubricating grease minus 52°C, preferably than the dropping point of the used lubricating grease minus 60°C or minus 75°C, particularly preferably minus 90°C, wherein the thickener is or comprises either a polymeric hydrocarbon or a polymeric ester, wherein the solvent

[0022] - in the case of polymeric hydrocarbons as thickener is a hydrocarbon (as hydrocarbon solvent) and

[0023] - in the case of polymeric esters, the thickener is a hydrocarbon, a C3 to C5 ketone, in particular a C3 and / or C4 ketone, or mixtures thereof, whereby if only hydrocarbons are used as solvents, these are also referred to below as hydrocarbon solvents.

[0024] In addition to the base oil, the used lubricating grease contains polymeric hydrocarbons or polymeric esters as thickeners, with the thickener being suspended in the solvent-base oil mixture as solid particles or in the form of solid particles. Uniform lubricating greases are those that contain at least the same thickener and the same base oil types (cumulatively in each case), i.e., in this case, each containing a polymeric hydrocarbon or a polymeric ester as a thickener and the same base oil type, in particular at least the same base oil. The fact that a suspension is obtained does not mean that other substances cannot also be present in emulsified form.

[0025] Base oil types of a uniform lubricating grease are those of a uniform compound type, e.g., identical or different hydrocarbons or identical or different esters as the base oil. For example, if a used lubricating grease contains esters and hydrocarbons as its base oil, then the second lubricating grease combined with it will also contain a mixture of identical or different esters and identical or different hydrocarbons; in particular, the base oils are identical.

[0026] In the case of thickeners based on polymeric hydrocarbons, various non-polar base oils soluble in the solvents described can be used, which are liquid at room temperature and in particular have a kinematic viscosity of 20 to 2500 mm 2 / s, especially from 40 to 500 mm 2 / s, each at 40°C. Hydrocarbons such as polyalphaolefins (PAO), mineral oils and / or esters are particularly suitable as base oils.

[0027] In the case of thickeners based on polymeric esters, in addition to non-polar base oils, more polar base oils such as esters or polyglycols can be used.

[0028] The hydrocarbon solvent may be an aliphatic and / or cycloaliphatic hydrocarbon, preferred are n-alkanes or branched alkanes, in particular mixtures thereof.

[0029] The boiling point or boiling range of the solvent is between 40 and 140°C at atmospheric pressure (1023 mbar). If necessary, distillation is carried out under vacuum so that the solvent reaches a boiling point no higher than 52°C, preferably 60°C or 75°C, and even better 90°C, below the dropping point of the used lubricant. When a polymeric ester is used as a thickener, C3 to C5 ketones or a mixture of the previously described hydrocarbons and C3 to C5 ketones can also be used, along with mixtures of the ketones.

[0030] In one embodiment, any solid impurities are removed from the suspension by filtration, with particles larger than 200 pm or larger than 30 pm, in particular larger than 15 pm, remaining in the filter residue. The filter cake can be washed with the solvent, and the eluate can be added to the suspension before or during step e). The suspension can be treated with a filter drying agent.

[0031] Detailed description of the invention

[0032] Suitable lubricating greases for reprocessing are polyolefin-thickened lubricating greases, such as those known from US3850828, US2917458, US3290244, US3392119, US5874391, EP0942063A or EP0795597B1.

[0033] The used grease contains polymeric hydrocarbons as thickeners. Suitable greases include:

[0034] - Polyethylene, possibly mixed with atactic polypropylene,

[0035] - Polypropylene, possibly mixed with atactic polypropylene or polyethylene,

[0036] - Ethylene and polypropylene copolymer, possibly in a mixture with polypropylene and / or polyethylene,

[0037] - a polyolefin with a rubber component or mixtures of different rubber components,

[0038] - Methylenepentene polymer, optionally in a mixture with polypropylene, with polyethylene and / or with ethylene and polypropylene copolymer.

[0039] Suitable thickeners are polyethylenes with a molecular weight of 20,000-500,000 g / mol, more preferably 50,000 to 250,000 g / mol (each Mw) and preferably a density above 0.94 g / cm 3, in particular in a mixture with an atactic polypropylene having a molecular weight preferably below 100,000 g / mol (Mw) and preferably a melt index above 20, in particular above 50. The ratio of the atactic polypropylene to the polyethylene is preferably 1:1 to 1:10, more preferably 2:1 to 5:1. Particularly suitable are thickeners based on oil-soluble amorphous polypropylenes having a molecular weight in the range from 300 to 10,000 g / mol and an intrinsic viscosity of up to 0.4, which in particular contain 2 to 5 wt.%, based on the lubricating grease, of an isotactic polypropylene having a molecular weight in the range from 100,000 to 1,000,000 g / mol (Mw) and a melting point in the range from 121°C to 210°C.Preferably co- or homo-polymers of propylene with a weight average molecular weight greater than or equal to 200,000 g / mol and a low molecular weight (co- or homo-)polymer of propylene with a weight average molecular weight of less than or equal to 100,000 g / mol.

[0040] Particularly suitable are thickener compositions based on polymethylpentene (4-methylpentene-1-based polymer) with a melting point of more than 200°C, especially more than 225°C in combination with the low molecular weight (weight average of 50,000 to 100,000 g / mol) propylene copolymers or homopolymers described in the previous section. A commercially available product, for example, is TPX DX 820 from Mitsui Chemicals Europe GmbH. This is a 4-methylpentene-1 polyolefin.

[0041] The polymeric esters are, in particular, polyhydroxyalkanoates (PHAs), e.g., polyhydroxy(C4- to C12-)alkanoates, preferably poly-3-hydroxyalkanoates, most preferably poly-3-hydroxybutyric acid. The thickening performance of the above polyhydroxyalkanoates can be further enhanced by further chemical modifications with one or more crosslinkers.

[0042] The thickener may contain other thickener components such as metal and metal complex soaps or polyureas.

[0043] The hydrocarbon or hydrocarbon solvent can be an aliphatic and / or cycloaliphatic hydrocarbon; preference is given to n-alkanes or branched alkanes, especially mixtures thereof. Typical examples are special-boiling-point spirits according to DIN 51632-1 and -2 with grades 80 / 120, 100 / 125, (DIN Type I) 60 / 95, (DIN Type II) 80 / 110, and (DIN Type III) 100 / 140, particularly preferred are dearomatized grades, and particularly preferred are special-boiling-point spirit 60 / 95. When reference is made to "hydrocarbon" in this context, this naturally also includes multiple hydrocarbons or hydrocarbon mixtures. In the case of polymeric esters as thickeners, polar solvents such as C3 to C5 ketones, in particular a C3 and / or C4 ketone, can also be used, either in pure form, as a mixture of the ketones with each other, or in a mixture of one or more of the ketones with the previously described hydrocarbons. Ketones can be used, for example:Acetone, methyl ethyl ketone (butan-2-one), pentan-2-one, pentan-3-one or mixtures thereof can be used.

[0044] Various non-polar base oils soluble in the described solvents can be used, whereby the base oils are liquid at room temperature with a kinematic viscosity of 20 to 2500 mm 2 / s, especially from 40 to 500 mm 2 / s, each at 40°C.

[0045] Such a base oil can be classified as a mineral oil or a synthetic oil. Mineral oils include naphthenic mineral oils and paraffin-based mineral oils, as classified according to API Group I. Chemically modified aromatic and low-sulfur mineral oils with a low saturates content and improved viscosity-temperature behavior compared to API Group I oils, classified according to API Groups II and III, are also suitable. Synthetic oils include, in particular, polyalphaolefins, alkylaromatics, alkylnaphthalenes, and their mixtures.Esters can also be used, particularly those that are soluble in the solvents mentioned, such as esters of aromatic di-, tri-, or tetracarboxylic acids with one or more C2 to C22 alcohols present in the solvent or in a mixture, esters of adipic acid, sebacic acid, trimethylolpropane, neopentyl glycol, pentaerythritol, or dipentaerythritol with aliphatic branched or unbranched, saturated or unsaturated C2 to C22 carboxylic acids, C18 dimer acid esters with C2 to C22 alcohols, complex esters, as individual components or in a mixture. Esters based on rapeseed oil, sunflower oil, and other oilseeds are also suitable, optionally in a mixture with the aforementioned base oils, provided the base oil is soluble in the solvent or miscible with it without phase separation.

[0046] Polyglycols are suitable as base oils for polymeric ester thickeners. Polyglycols as base oils can contain free hydroxyl groups, but can also be fully etherified or end-esterified and / or made from a starting compound with one or more hydroxyl and / or carboxyl groups (-COO(H)). According to a particular embodiment, the polyglycols contain (-O-(CH2)4-)n units that have the following structural unit in terms of linkage: -O-(CH2)4-O-, and optionally also contain other alkylene oxide units, such as ethylene oxide (-O-(CH2CH2)-) and / or propylene oxide units (-O-(CH2 CH(CH3)-) distributed in blocks or randomly. Polyglycols as base oils are less suitable for hydrocarbon thickeners.

[0047] Diphenyl ethers or polyphenyl ethers, possibly alkylated, are also possible as sole components or as mixed components.

[0048] Suitable base oils may also be or contain polyalphaolefins, e.g. those obtainable from the polymerization, optionally using metallocene catalysts, of C4 and C14 LAO (LAO = linear alpha olefin), C6 and C16 LAO; C8, C10 and C12 LAO; C8 and C14 LAO; C6, C10 and C14 LAO; C4 and C12 LAO as copolymers or as mixtures of the respective homopolymers.

[0049] Suitable additives include antioxidants, wear inhibitors, corrosion inhibitors, detergents, dyes, lubricity improvers, adhesion improvers, viscosity additives, friction reducers, and extreme pressure additives, metal deactivators, as well as solid lubricants, preferably in concentrations < 5%. Suitable additives are polyisobutene succinic acid and / or polyisobutene succinic acid polyacrylamide. Additives remaining in the filter residue can be subsequently added back to the recycled lubricating grease.

[0050] According to one embodiment, the suspension is filtered using suitable filtration processes in which particles larger than 200 pm or larger than 30 pm, particularly larger than 15 pm, remain in the filter residue. The filter can have a pore size or mesh size of 200 pm or smaller, preferably 30 pm or smaller, and particularly preferably 15 pm or smaller. The filter can have paper, textile fabric, or metal as the filter material, or a packed bed as the filter mass. Filtration processes that can be used include suction filtration, pressure filtration, edge-gap filters, filter presses, preferably chamber filter presses, and hot filtration processes in which the maximum filtration temperature is preferably at least 52°C, at least 60°C, or at least 75°C, preferably at least 90°C below the dropping point temperature of the used lubricating grease. Depth filtration processes using glass fiber or synthetic fiber fabrics are also suitable.During or after filtration, the suspension can be rinsed with the solvent previously used to suspend the thickener. The filterability of the suspension can be improved by ultrasonic treatment or treatment in a disperser.

[0051] Particles smaller than 15 pm, such as wear particles, can be removed from the suspension using magnetic separators to separate magnetic iron and steel particles, such as those that can occur during wear of lubricated machine components. Electrostatic precipitators can be used to separate ionizable wear particles, and fractional centrifugation or hydrocyclones can be used to separate abrasion and dirt particles that have a greater density than the grease thickener particles, such as sand or metal particles.

[0052] Furthermore, methods for removing polar degradation products from the suspension can be carried out, such as fractional solid / liquid and liquid / liquid extraction with solvents of different polarity (e.g. water / alcohol mixtures), chromatographic methods or electrophoretic methods.

[0053] The filterability of the suspension can be improved by ultrasonic treatment or treatment in a disperser.

[0054] A simple method for introducing additives is to add them to the suspension, especially after filtration, and independently of solvent removal. This allows the additives to be distributed more homogeneously in the grease because the improved solvency of the solvent-base oil mixture, or its lower viscosity, can be utilized before the solvent is removed. Examples of such additives include aminic and phenolic antioxidants, alkylated or aromatic phosphoric acid esters, zinc dithiophosphates, and sulfurized esters. These are soluble or suspendable additives.

[0055] The solvent can be removed from the suspension by distillation, extraction with supercritical carbon dioxide, or drying. The solvent is preferably removed under reduced pressure, e.g., at < 850 mbar to 2 mbar. The reduced pressure is adjusted so that the boiling point, or the upper boiling point in the case of a boiling range of the solvent, does not exceed a temperature calculated from the dropping point of the used lubricating grease of minus 52°C, preferably minus 60°C, and particularly preferably minus 90°C. Removing the solvent does not mean that it has to be removed completely. The solvent can be recovered and recycled by condensing the solvent. During recovery, it can be subjected to fractional distillation for purification.Water can be removed by phase separation, desiccants, hygroscopic filter absorbers or as part of vacuum distillation.

[0056] The process according to the invention may further comprise, inter alia, the following optional steps: Liquid or solid additives, additional base oil and / or additional thickeners, each as described above, may be added to the recycled lubricating grease, in particular to achieve the desired consistency.

[0057] The recycled grease can be homogenized, for example, using a rotor / stator homogenizer, a high-pressure homogenizer, and / or a toothed colloid mill, especially after adding additional additives, additional base oil, and / or additional thickener. Furthermore, the recycled grease can be deaerated using a perforated disc or vacuum deaerator.

[0058] The process may further comprise drying the recycled lubricating grease, in particular freeze-drying.

[0059] A particular aspect of the invention is the recycling of lubricating greases used in loss-lubricated rolling bearings, plain bearings, or gears, for example in wind turbines, hydropower plants, rolling mills, machine tools, paper machines, ore processing plants, cement mills, and plants in food production and agriculture, where either large amounts of grease waste are generated or the exposure of used lubricating grease to the environment is to be avoided. Another particular aspect of the invention is the recycling of lubricating greases used in lifetime-lubricated applications in which they have undergone only minimal oxidative aging and can be reprocessed using the process according to the invention. Such applications include, for example, the lubrication of wheel bearings in vehicles, rolling and plain bearings in stationary machines and assemblies, as well as encapsulated constant velocity joints and dual-mass flywheels.With the lubricating grease recycling process according to the invention, the following results can typically be obtained after recycling, each comparing used lubricating grease with recycled lubricating grease and in particular (unused) lubricating grease (equal to fresh lubricating grease) with recycled lubricating grease:.

[0060] Consistency decrease determined with the cone penetration according to DIN ISO 2137 (worked penetration) by a maximum of plus 40 units (0.1 mm), preferably a maximum of plus 30 units (0.1 mm),

[0061] Drop in drop ...

[0062] Recycling yield >60 wt.% based on the amount of grease used, especially >80% wt., based on the amount of grease used (used grease).

[0063] The invention is explained by the figures:

[0064] Fig. 1 illustrates the general procedure with possible execution variants

[0065] Fig. 2 shows an SEM image of the used grease 1

[0066] Fig.3 shows a SEM image of the recycled grease according to Example 1 (invention) for comparison with Fig. 2

[0067] Fig. 4 shows an SEM image of a recycled grease according to Example 2 (reference with no longer fibril-like thickener structure).

[0068] Experimental part

[0069] To illustrate the invention and reference examples for the recycling process, used greases with simulated, i.e. simulated, mechanical impurities were produced

[0070] Used lubricating greases 1 and 4

[0071] The working greases were prepared according to US 5874391 Example 1 with the following compositions, which differed in the base oil and the additives as well as the subsequent stirring in of mechanical impurities: Table 1 The SEM image of the grease used in used grease 1 , before its contamination, is shown in Fig. 2 and shows a net-like thickener structure.

[0072] Table 2 Table 2 (continued) Used greases 2 and 3

[0073] Production according to EP0795597B1 and its embodiment using the polymer thickener with the following compositions, which differ in the base oil and additives, an additional polypropylene polymer and the subsequent stirring in of simulated mechanical impurities:

[0074] Table 3 Table 3 (continued)

[0075] Table 4 Used grease 5

[0076] To simulate mechanical contamination, 0.15 wt.% metallic impurities (100Cr6 metal chips) and 0.45 wt.% inorganic impurities (quartz sand) were added to a 99.4 wt.% commercially available lithium soap-thickened mineral oil grease (RENOLIT UNIRAIL 2 from Fuchs Lubricants Germany). Before and after the addition of the mechanical impurities, the grease had a dropping point of 194°C, both as fresh and as used.

[0077] Used grease 6

[0078] To simulate mechanical contamination, 0.15 wt.% metallic impurities (100Cr6 metal chips) and 0.45 wt.% inorganic impurities (quartz sand) were added to a 99.4 wt.% commercially available polyurea-thickened PAO grease (RENOLIT PU PEM 2 from Fuchs Lubricants Germany). Before the addition of the mechanical impurities, the resulting grease had a dropping point of 268°C as a lubricating grease and a dropping point of 256°C as a used grease.

[0079] Used grease 7

[0080] According to Table 5, 83.97% of a commercially available sunflower oil with an oleic acid content of over 90 wt.% ("High Oleic Sunflower Ester Oil Dakolub MB 9300 from DAKO AG) was heated to 150°C in a stirred tank until it was completely melted in the base oil. The mixture was then cooled to 60°C, 1.03 wt.% of additives were added, and the mixture was then homogenized using a 3-roll mill. The resulting lubricating grease was modified by adding 0.7 wt.% iron abrasion and 0.63 wt.% quartz sand as technical impurities to the used lubricating grease. Before the addition of the mechanical impurities, the lubricating grease produced in this way had a dropping point of 120°C, and as used grease, it also had a dropping point of 120°C. Table 5

[0081] Example 1 (Invention)

[0082] Used grease 1 was recycled as follows:

[0083] - 50g used lubricating grease 1 ,

[0084] - Determination of the dropping point of the used lubricating grease: 151 °C,

[0085] - Addition of 100g of special boiling point spirit 60 / 95,

[0086] - Suspending the used lubricating grease in a stirred tank at room temperature,

[0087] - Separation of the metal particles in the suspension by a permanent magnet,

[0088] - Filtration of the suspension through a paper filter with 12 to 15 pm pore size,

[0089] - Wash the filter residue with another 50g of special boiling point petrol 60 / 95,

[0090] - Filling a rotary evaporator with the filtrate,

[0091] - Heating the filtrate to 60°C (=89°C below the determined dropping point),

[0092] - Step-by-step installation from vacuum to 14mbar,

[0093] - Distillation and condensation of the special boiling point spirit 60 / 95 and

[0094] - Dry for 45 hours at room temperature to obtain the recycled grease. Compared to the original grease, the recycled grease has the following characteristics:

[0095] Grease recycled grease Delta

[0096] Worked penetration [0.1 mm] 289 310 +21 NLGI class 2 1 -1 Dropping point [°C] 152 151 - 1

[0097] The following quantity balance was achieved in recycling:

[0098] 50.3g weighed used grease 1

[0099] 150g gasoline (for suspending and rinsing)

[0100] 4.5g filter residue for disposal

[0101] 42g recycled grease

[0102] The SEM image of the recycled grease is shown in Fig. 3 and shows a net-like thickener structure, which is largely similar to that of the grease (see Fig. 2).

[0103] Example 2 (Reference)

[0104] The recycling of used grease 1 was produced as follows:

[0105] - 51g used lubricating grease 1 ,

[0106] - Determination of the dropping point of the used lubricating grease: 151 °C,

[0107] - Addition of 110g of special boiling point spirit 60 / 95,

[0108] - Suspending the used lubricating grease in a stirred tank at room temperature,

[0109] - Separation of the metal particles in the suspension by a permanent magnet,

[0110] - Filtration of the suspension through a paper filter with a pore size of 12 to 15 pm,

[0111] - Rinse the filter residue with another 56g of special boiling point petrol,

[0112] - Filling a rotary evaporator with the filtrate,

[0113] - Heating the filtrate to 60°C (=89°C below the determined dropping point),

[0114] - Step-by-step installation from vacuum to 16mbar,

[0115] - Distillation and condensation of the 60 / 95 special boiling point spirit and - Subsequent drying of the recovered lubricating grease for 4 hours at 100°C in a drying cabinet. The drying temperature is thus only 51°C below the dropping point and was already too high because the recycled lubricating grease had softened.

[0116] The recycled grease has the following characteristics compared to the lubricating grease:

[0117] Grease recycled grease Delta

[0118] Work penetration [0.1 mm] 289 340 +53

[0119] NLGI class 2 1 -1

[0120] Dropping point [°C] 152 150 - 2

[0121] The following quantity balance was achieved in recycling:

[0122] 51 g of used grease 1 166 g of petrol (for suspension and rinsing) 3.2 g of filter residue for disposal 41 g of recycled grease

[0123] The following scanning electron microscope images show that at excessively high process temperatures, the recycled lubricating grease contains a thickener which, in comparison to the lubricating grease, is destroyed in its original fibril-like structure and therefore no longer thickens well.

[0124] The SEM image of the recycled grease is shown in Fig. 4 and shows a no longer fibril-like thickener structure.

[0125] Example 3 (Invention)

[0126] Recycling of used lubricating grease 2 a) 25g used lubricating grease 2, b) Determination of the dropping point of the used lubricating grease: 191 °C, c) Addition of 75g special boiling point spirit 60 / 95, d) Suspension of the lubricating grease in a stirred vessel at room temperature, e) Separation of the metal particles in the suspension using a permanent magnet, f) Filtration of the suspension through a paper filter with a pore size of 12 to 15 pm, g) Washing of the filter residue with a further 53g special boiling point spirit h) Filling a rotary evaporator with the filtrate, i) Heating of the filtrate to 60°C, j) Gradual application of vacuum to 14mbar, k) Distillation and condensation of the special boiling point spirit 60 / 95 and l) Drying of the regenerated lubricating grease for 18h at room temperature in the vacuum chamber at 200mbar to obtain the recycled lubricating grease.

[0127] The recycled grease has the following characteristics compared to the lubricating grease:

[0128] Grease recycled grease Delta

[0129] Work penetration [0.1 mm] 295 324 +29

[0130] NLGI class 2 1 -1

[0131] Dropping point [°C] 202 196 -6

[0132] The following quantity balance was achieved in recycling:

[0133] 25g weighed used grease 2

[0134] 128g special boiling point spirit 60 / 95 (for suspending and rinsing)

[0135] 0.94g filter residue for disposal

[0136] 22.1 g recycled grease.

[0137] Example 4 (Invention)

[0138] Recycling of used lubricating grease 3 a) 25.3g used lubricating grease 3, b) Determination of the dropping point of the used lubricating grease: 211 °C, c) Addition of 75g of special boiling point spirit 60 / 95, d) Suspension of the used lubricating grease in a stirred vessel at room temperature, e) Separation of the metal particles in the suspension using a permanent magnet, f) Filtration of the suspension through a paper filter with a pore size of 12 to 15 pm, g) Washing of the filter residue with a further 25g of special boiling point spirit 60 / 95, h) Filling a rotary evaporator with the filtrate, i) Heating of the filtrate to 60°C, j) Gradual application of vacuum to 16mbar, k) Distillation and condensation of the special boiling point spirit 60 / 95, l) Drying of the regenerated lubricating grease for 18h at room temperature in the vacuum chamber at 200mbar to preserve the recycled grease.

[0139] The recycled grease has the following characteristics compared to the lubricating grease:

[0140] Grease recycled grease Delta

[0141] Work penetration [0.1 mm] 238 275 +37

[0142] NLGI class 3 2 -1

[0143] Dropping point [°C] 222 218 - 4

[0144] The following quantity balance was achieved in recycling:

[0145] 25.3g weighed used grease 3

[0146] 101 g of special boiling point spirit 60 / 95 (for suspending and rinsing)

[0147] 1.6g filter residue for disposal

[0148] 20.0g recycled grease

[0149] Example 5 (Invention)

[0150] Recycling of used lubricating grease 1 with an alternative solvent to example 1. a) 25.5 used lubricating grease 1 , b) Determination of the dropping point of the used lubricating grease: 151 °C, c) Addition of 80g cyclohexane, d) Suspension of the lubricating grease in a stirred vessel at room temperature, e) Separation of the metal particles in the suspension using a permanent magnet, f) Filtration of the suspension through a paper filter with a pore size of 12 to 15 pm, g) Washing of the filter residue with a further 25g cyclohexane, h) Filling a rotary evaporator with the filtrate, i) Heating of the filtrate to 60°C, j) Stepwise application of vacuum to 30mbar, k) Distillation and condensation of the cyclohexane, l) Subsequent drying of the regenerated lubricating grease for 18h at room temperature in the vacuum chamber at 200mbar to obtain the recycled lubricating grease.

[0151] The recycled grease has the following characteristics compared to the lubricating grease:

[0152] Grease recycled grease Delta

[0153] Work penetration [0.1 mm] 289 328 +39

[0154] NLGI class 2 1 1

[0155] Dropping point [°C] 152 150 -2

[0156] The following quantity balance was achieved in recycling:

[0157] 25.5g weighed used grease 1

[0158] 105g cyclohexane (for suspending and rinsing)

[0159] 1.1 g filter residue for disposal

[0160] 19.9 recycled grease

[0161] Example 6 (Invention)

[0162] Recycling of used lubricating grease 1 with an alternative solvent to example 1. a) 25.7g of used lubricating grease 1, b) Determination of the dropping point of the used lubricating grease: 151°C, c) Addition of 50.2g of special boiling point spirit 40 / 60, d) Suspension of the lubricating grease in a stirred vessel at room temperature, e) Separation of the metal particles in the suspension using a permanent magnet, f) Filtration of the suspension through a paper filter with a pore size of 12 to 15pm, g) Washing of the filter residue with a further 41g of special boiling point spirit 40 / 60, h) Filling a rotary evaporator with the filtrate, i) Heating of the filtrate to 60°C, j) Gradual application of vacuum to 27mbar, k) Distillation and condensation of the special boiling point spirit 40 / 60, l) Drying of the regenerated lubricating grease for 18h at room temperature in the vacuum chamber at 200mbar to obtain of the recycled lubricating grease.

[0163] The recycled grease has the following characteristics compared to the lubricating grease:

[0164] Grease recycled grease Delta

[0165] Work penetration [0.1 mm] 289 302 +13

[0166] NLGI class 2 1.5 -0.5

[0167] Dropping point [°C] 152 150 -2

[0168] The following quantity balance was achieved in recycling:

[0169] 25.7g weighed used grease 1

[0170] 91.2g special boiling point spirit 40 / 60 (for suspending and rinsing)

[0171] 1.3g filter residue for disposal

[0172] 20.1 g recycled grease

[0173] Example 7 (Invention)

[0174] The recycling of used grease 4 was carried out as follows:

[0175] 25.8g used grease 4,

[0176] Determination of the dropping point of the used lubricating grease: 148°C,

[0177] Addition of 50.2g of special boiling point spirit 60 / 95,

[0178] Suspending the lubricating grease in a stirred tank at room temperature, separating the metal particles in the suspension using a permanent magnet, filtering the suspension through a paper filter with a pore size of 12 to 15 pm, washing the filter residue with another 32.7 g of special boiling point spirit 60 / 95,

[0179] Filling a rotary evaporator with the filtrate,

[0180] Heating the filtrate to 60°C,

[0181] Step-by-step installation from vacuum to 44 mbar,

[0182] Distillation and condensation of the special boiling point spirit 60 / 95, subsequent drying of the regenerated lubricating grease for 18 hours at room temperature in the vacuum chamber at 200 mbar to obtain the recycled lubricating grease.

[0183] The recycled grease has the following characteristics compared to the lubricating grease:

[0184] Grease recycled grease Delta

[0185] Work penetration [0.1 mm] 320 342 +22

[0186] NLGI class 1 1 0

[0187] Dropping point [°C] 150 149 -1

[0188] The following quantity balance was achieved in recycling:

[0189] 25.8g weighed used grease 4

[0190] 82.9g special boiling point spirit 60 / 95 (for suspending and rinsing)

[0191] 0.5g filter residue for disposal

[0192] 21.1 g recycled grease

[0193] Example 8 (Invention)

[0194] Recycling of used lubricating grease 2 with an alternative solvent to Example 3 a) 25.7g of used lubricating grease 2, b) Determination of the dropping point of the used lubricating grease: 191 °C, c) Addition of 56.4g of special-boiling point spirit 40 / 60, d) Suspension of the lubricating grease in a stirred vessel at room temperature, e) Separation of the metal particles in the suspension using a permanent magnet, f) Filtration of the suspension through a paper filter with a pore size of 12 to 15 pm, g) Washing of the filter residue with a further 100.5g of special-boiling point spirit 40 / 60, h) Filling a rotary evaporator with the filtrate, i) Heating of the filtrate to 59°C, j) Gradual application of vacuum to 45 mbar, k) Distillation and condensation of the special-boiling point spirit 40 / 60, l) Drying of the regenerated lubricating grease 18h at room temperature in the vacuum chamber at 200mbar to obtain the recycled lubricating grease.

[0195] The recycled grease has the following characteristics compared to the lubricating grease:

[0196] Grease recycled grease Delta

[0197] Work penetration [0.1 mm] 299 317 +18

[0198] NLGI grade 1 .5 1 -0.5

[0199] Dropping point [°C] 202 194 - 8

[0200] The following quantity balance was achieved in recycling:

[0201] 25.7g weighed used grease 2

[0202] 156.9g special boiling point spirit 40 / 60 (for suspending and rinsing)

[0203] 3.2g filter residue for disposal

[0204] 16.8g recycled grease

[0205] Example 9 (Invention)

[0206] Recycling of used lubricating grease 3 with an alternative solvent to Example 4 a) 26.0g used grease 3, b) Determination of the dropping point of used lubricating grease 3: 211 °C, c) Addition of 84g of special boiling point spirit 40 / 60, d) Suspension of the lubricating grease in a stirred vessel at room temperature, e) Separation of the metal particles in the suspension using a permanent magnet, f) Filtration of the suspension through a paper filter with a pore size of 12 to 15pm, g) Washing of the filter residue with a further 122g of special boiling point spirit 40 / 60, h) Filling a rotary evaporator with the filtrate, i) Heating of the filtrate to 60°C, j) Stepwise application of vacuum to 51 mbar, k) Distillation and condensation of the special boiling point spirit 40 / 60, l) Drying of the regenerated lubricating grease for 18h at room temperature in the vacuum chamber at 200mbar to obtain the recycled lubricating grease.

[0207] The recycled grease has the following characteristics compared to the lubricating grease:

[0208] Grease recycled grease Delta

[0209] Work penetration [0.1 mm] 238 249 +11

[0210] NLGI class 3 3 0

[0211] Dropping point [°C] 222 220 - 2

[0212] The following quantity balance was achieved in recycling:

[0213] 26.0g weighed used grease 3

[0214] 206g special boiling point spirit 40 / 60 (for suspending and rinsing)

[0215] 1.2g filter residue for disposal

[0216] 23.2g recycled grease

[0217] Example 10 (Reference)

[0218] Recycling of used grease 1 with fluorinated and chlorinated solvent a) 25.5g used grease 1, b) Determination of the dropping point of the used lubricating grease 1: 151 °C, c) Addition of 89.3g 1,2,2-trifluoro-1,2,2-trichloroethane, d) Suspension of the lubricating grease in a stirred vessel at room temperature, e) Separation of the metal particles in the suspension by a permanent magnet, f) Filtration of the suspension through a paper filter with 12 to 15 pm pore size, g) Washing of the filter residue with a further 72.3g 1,2,2-trifluoro-1,2,2-trichloroethane, h) Filling a rotary evaporator with the filtrate, i) Heating of the filtrate to 63°C, j) Stepwise application of vacuum to 53 mbar, k) Distillation and condensation of the 1,2,2-trifluoro-1,2,2-trichloroethane, l) Drying of the recovered grease for 36h at room temperature in a vacuum chamber at 200mbar to obtain the recycled grease.

[0219] The recycled grease has the following characteristics compared to the lubricating grease:

[0220] Grease recycled grease Delta

[0221] Work penetration [0.1 mm] 289 377 +88

[0222] NLGI class 2 0 -2

[0223] Dropping point [°C] 152 134 - 18

[0224] The following quantity balance was achieved in recycling:

[0225] 25.5g weighed used grease 1

[0226] 161.6g trifluorotrichloroethane (for suspending and rinsing)

[0227] 1.7g filter residue for disposal

[0228] 24.6g recycled grease

[0229] Compared to the invention examples, the recycled grease softened significantly more than one NLGI grade (-2). It is assumed that some of the polymer thickener dissolved and then no longer crystallized in its original, well-thickening form.

[0230] Example 11 (Reference)

[0231] Recycling of used grease 1 with chlorinated solvent a) 25.7g used grease 1, b) Determination of the dropping point of the used grease: 151 °C, c) Addition of 92g dichloromethane, d) Suspension of the used grease in a stirred vessel at room temperature, e) Separation of the metal particles in the suspension using a permanent magnet, f) Filtration of the suspension through a paper filter with a pore size of 12 to 15 pm, g) Washing of the filter residue with a further 60.3g dichloromethane, h) Filling a rotary evaporator with the filtrate, i) Heating of the filtrate to 61 °C, j) Stepwise application of vacuum to 63 mbar, k) Distillation and condensation of the dichloromethane, l) Drying of the regenerated lubricating grease for 36h at room temperature in the vacuum chamber at 200mbar to obtain the recycled lubricating grease.

[0232] The recycled grease has the following characteristics compared to the lubricating grease:

[0233] Grease recycled grease Delta

[0234] Work penetration [0.1 mm] 289 410 +121

[0235] NLGI class 2 00 -3

[0236] Dropping point [°C] 152 101 - 51

[0237] The following quantity balance was achieved in recycling:

[0238] 25.7g weighed used grease 1

[0239] 152.3 g dichloromethane (for suspending and rinsing)

[0240] 6.8 g filter residue for disposal

[0241] 16.7g recycled grease

[0242] Compared to the invention examples, the recycled grease softened significantly more than three NLGI grades (-3) and exhibited a significantly greater drop point depression. It was observed that the thickener could not be evenly suspended in fine particles, resulting in a large amount of residue remaining in the filter, and predominantly only base oil was filtered out. Example 12 (Reference)

[0243] Recycling of used grease 5, as an example of a lithium soap-thickened lubricating grease, and solvent according to examples 6, 8 and 9 a) 25.3 g of used grease 5, b) Determination of the dropping point of used grease 5: 194°C, c) Addition of 151.3 g of special-boiling point spirit 40 / 60, d) Suspension of the used grease in a stirred vessel at room temperature, e) Separation of the metal particles in the suspension using a permanent magnet, f) Filtration of the suspension through a paper filter with a pore size of 12 to 15 pm, g) Washing of the filter residue with a further 99.3 g of special-boiling point spirit 40 / 60, h) Filling a rotary evaporator with the filtrate, i) Heating of the filtrate to 62°C, j) Stepwise application of vacuum to 66 mbar, k) Distillation and condensation of the special-boiling point spirit 40 / 60, l) Drying of the recovered grease for 36h at room temperature in a vacuum chamber at 200mbar to obtain the recycled grease.

[0244] The recycled grease has the following characteristics compared to the lubricating grease:

[0245] Grease recycled grease

[0246] Worked penetration [0.1 mm] 276 no grease

[0247] NLGI Class 2

[0248] Dropping point [°C] 194

[0249] The following quantity balance was achieved in recycling:

[0250] 25.3g weighed used grease 5

[0251] 250.6g of special boiling point spirit 40 / 60 (for suspending and rinsing)

[0252] 16.1 g filter residue for disposal

[0253] 7.8g of recovered oily substance, which is not a lubricating grease. This test example demonstrates that soap-thickened lubricating greases cannot be suspended sufficiently to allow easy filtering using a low-temperature process with aliphatic or cycloaliphatic solvents, even when using a comparatively high solvent quantity. This is indicated by the comparatively high filter residue, in which a large portion of the thickener remains.

[0254] Example 13 (Reference)

[0255] Recycling of used grease 6, as an example of a polyurea-thickened lubricating grease, and solvent according to examples 6, 8 and 9 a) 25.5 g of used grease 6, b) Determination of the dropping point of the used grease: 256°C, c) Addition of 105.9 g of special-boiling point spirit 40 / 60, d) Suspension of the used grease in a stirred vessel at room temperature, e) Separation of the metal particles in the suspension using a permanent magnet, f) Filtration of the suspension through a paper filter with a pore size of 12 to 15 pm, g) Washing of the filter residue with a further 109.5 g of special-boiling point spirit 40 / 60, h) Filling a rotary evaporator with the filtrate, i) Heating of the filtrate to 61 °C, j) Stepwise application of vacuum to 70 mbar, k) Distillation and condensation of the special-boiling point spirit 40 / 60, l) Drying of the recovered grease for 36h at room temperature in a vacuum chamber at 200mbar to obtain the recycled grease.

[0256] The recycled grease has the following characteristics compared to the lubricating grease:

[0257] Grease recycled grease

[0258] Worked penetration [0.1 mm] 255 no grease

[0259] NLGI class 2 to 3

[0260] Dropping point [°C] 268 The following mass balance was achieved in recycling:

[0261] 25.5g weighed used grease 6

[0262] 215.4g special boiling point spirit 40 / 60 (for suspending and rinsing)

[0263] 16.3g filter residue for disposal

[0264] 10.6g of recovered oily substance, which is not grease.

[0265] The test example demonstrates that even polyurea-thickened lubricating greases cannot be suspended sufficiently to allow easy filtering, even at high solvent concentrations, using a low-temperature process with aliphatic or cycloaliphatic solvents. This is indicated by the comparatively high filter residue, in which a large portion of the thickener remains.

[0266] Example 14 (Invention with cross-linked 3-PHA derivative and biodegradable ester)

[0267] Used grease 7 was recycled as follows:

[0268] - 12g used grease 7,

[0269] - Determination of the dropping point of the used lubricating grease: 120°C,

[0270] - Addition of 31 g of special boiling point spirit 60 / 95,

[0271] - Suspending the used lubricating grease in a stirred tank at room temperature,

[0272] - Separation of the metal particles in the suspension by a permanent magnet,

[0273] - Filtration of the suspension through a paper filter with 12 to 15 pm pore size,

[0274] - Wash the filter residue with another 10g of special boiling point petrol 60 / 95,

[0275] - Filling a rotary evaporator with the filtrate,

[0276] - Heating the filtrate to 60°C (=60°C below the determined dropping point),

[0277] - Step-by-step installation from vacuum to 14mbar,

[0278] - Distillation and condensation of the special boiling point spirit 60 / 95 and

[0279] - Dry for 36h at room temperature to obtain the recycled grease.

[0280] The recycled grease has the following characteristics compared to the grease: Grease recycled grease Delta

[0281] Worked penetration [0.1 mm] 301 279 -22 NLGI class I to 2 2 -1 ,5 Dropping point [°C] 120 120 0

[0282] The following quantity balance was achieved in recycling: 12g weighed used lubricating grease 1 41g gasoline (for suspending and rinsing)

[0283] 1.4g filter residue for disposal

[0284] 9.8g recycled grease

Claims

Patent claims 1. A method for reprocessing used lubricating greases which become a used lubricating grease through use and collection, comprising the following steps: a) collecting used, uniform lubricating greases from lubrication points to obtain a used lubricating grease, wherein the used lubricating grease contains at least one thickener, additives, a base oil and, if applicable,comprises solid impurities and the thickener comprises polymeric hydrocarbons or polymeric esters, b) providing a solvent having a boiling point or an upper boiling point in the case of a boiling range of 40 to 140°C at standard pressure, c) suspending the used lubricating grease in the solvent to obtain a suspension comprising a liquid phase comprising at least the base oil and the solvent, and a solid phase in the liquid phase comprising at least the thickener in suspended form, wherein at least the base oil and the solvent are mixed in the form of a uniform liquid phase, d) separating any solid impurities from the suspension, e) removing the solvent from the suspension by distillation or by extraction with supercritical CO2, to obtain a recycled lubricating grease. - Reclaimed base oil comprising base oil from the used lubricating grease and - recovered thickeners from used lubricating grease and - Recovered additives comprising additives from the used lubricating grease, wherein the used lubricating grease, the suspension and the recycled lubricating grease are not exposed at any time during the process to a temperature higher than the dropping point of the used lubricating grease minus 52°C, preferably minus 60°C, particularly preferably minus 90°C; wherein the thickener is or comprises either a polymeric hydrocarbon or a polymeric ester, wherein the solvent - in the case of polymeric hydrocarbons as thickener, a hydrocarbon is used as hydrocarbon solvent and - in the case of polymeric esters as thickener, it is a hydrocarbon, a C3, C4 or C5 ketone or mixtures thereof.

2. The method according to claim 1, wherein the recycled lubricating grease has an increase in worked penetration by a maximum of plus 40 0.1 mm, preferably by a maximum of plus 30 0.1 mm compared to the used lubricating grease, in particular compared to the lubricating grease.

3. The method according to claim 1 or 2, wherein the recycled lubricating grease has a reduction in the dropping point by a maximum of 15°C, preferably by a maximum of 10°C, and particularly preferably by a maximum of 5°C compared to the used lubricating grease, in particular compared to the lubricating grease.

4. The method according to at least one of the preceding claims, wherein the method further comprises homogenizing the recycled lubricating grease in a three-roll mill, a rotor / stator homogenizer, a high-pressure homogenizer and / or a toothed colloid mill, optionally with the addition of lubricant additives, further base oil and / or thickener to the recycled lubricating grease before or during the homogenization.

5. The process according to at least one of the preceding claims, wherein the separation in step d) is carried out by filtration to obtain a filter cake, in particular with a filter having a pore size or mesh size of 200 pm and smaller, preferably 30 pm and smaller, and particularly preferably 15 pm and smaller.

6. The process according to claim 5, wherein the filter cake is washed with the solvent and the eluate is added to the suspension before or during step e).

7. The method according to at least one of the preceding claims, wherein the separation in step d) is carried out by sedimentation.

8. The method according to at least one of the preceding claims, wherein the separation in step d) is carried out by centrifugation or hydrocyclones.

9. Method according to at least one of the preceding claims, wherein magnetic particles are removed from the suspension by means of a magnetic separator and / or ionizable particles are removed from the suspension by means of an electrostatic precipitator.

10. The method according to at least one of the preceding claims, wherein the removal of the solvent is carried out by distillation, preferably under reduced pressure, wherein the reduced pressure is adjusted so that the boiling point or the upper boiling point in the case of a boiling range of the solvent does not exceed a temperature calculated from the dropping point of the used lubricating grease minus 90°C.

11. The process according to at least one of the preceding claims, wherein the process further comprises treating the suspension with a liquid extractant which forms a decantable 2-phase system with the liquid phase.

12. The method according to at least one of the preceding claims, wherein the method further comprises adding lubricant additives and / or further base oil to the suspension before step e).

13. The method according to at least one of the preceding claims, wherein the method comprises treating the suspension with a drying agent, in particular in the form of a filter drying agent.

14. The method according to at least one of the preceding claims, wherein the thickener in the form of a polymeric hydrocarbon is a polyolefin, in particular - a mixture of a polyethylene and an atactic polypropylene, - an ethylene / propylene copolymer, - a mixture of a polyolefin and a rubber polymer, in particular based on natural rubber, polyisobutadiene, styrene-butadiene rubber, ethylene-propylene-diene rubber, ethylene-propylene rubber and / or polyisobutylene; or - a polymethylenepentene with a melting point of more than 200°C, in particular more than 225°C 15. The process according to at least one of the preceding claims, wherein the polymeric hydrocarbon has an average molecular weight of greater than 20,000 g / mol (Mw).

16. Process according to at least one of the preceding claims, wherein the polymeric hydrocarbon has a melting point of greater than 100°C, in particular greater than 120°C.

17. The process according to at least one of the preceding claims, wherein the hydrocarbon, in particular the hydrocarbon solvent, comprises aliphatic and / or cycloaliphatic hydrocarbons and preferably alkanes, and particularly preferably is special-boiling point gasoline 40 / 60 or 60 / 95.

18. The method according to at least one of the preceding claims, wherein the method comprises drying the recycled lubricating grease, in particular freeze-drying.

19. The process according to at least one of the preceding claims, wherein the base oil is liquid at 25°C, is soluble in the solvent, in particular the hydrocarbon solvent, and the base oil has a kinematic viscosity of 20 to 2500 mm 2 / s, especially from 40 to 500 mm 2 / s, each at 40°C.

Images