Method for regenerating lubricating grease by heating

Abstract

The subject of this invention is a method for regenerating used grease, the method comprising liquefying residual grease containing base oil and thickener by heating, and obtaining regenerated grease containing at least a portion of base oil and thickener.

Description

Technical Field

[0001] The present invention relates to a method for regenerating used grease, the method comprising liquefying residual grease comprising a base oil and a thickener by heating, and obtaining a regenerated grease comprising at least a portion of the base oil and a thickener, the thickener comprising a polymeric hydrocarbon or a polymeric ester as a thickener. Background Technology

[0002] 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 to flowable consistency, while greases have a semi-solid to solid (typically gel-like) consistency.

[0003] Lubricating greases are characterized by the incorporation and retention of liquid oil components by thickener components. The texture of the grease, its spreadability and deformability, combined with its adhesive properties, ensures that the grease wets the lubrication points and that the lubricating effect is achieved on surfaces subjected to frictional stress. They are particularly used for lubricating poorly sealed machine parts, such as rolling or sliding bearings, open gearboxes, and guideways.

[0004] Lubricating greases contain thickeners evenly distributed in a base oil, as well as solid or liquid additives. Additional auxiliary substances, such as emulsifiers, are often used to ensure the thickeners are stably dispersed in the base oil. A wide variety of substances are referred to as base oils. Organic and inorganic compounds are used as thickeners.

[0005] In the Federal Republic of Germany, over 34,000 tons of used lubricating grease are generated annually, particularly in the lubrication of friction systems such as rolling bearings, where grease accounts for approximately 80% of the total. In many cases, grease is used in so-called wear lubrication, which generates significant amounts of contaminated grease that must be disposed of in an environmentally friendly manner. Such applications can be found, for example, in rolling and sliding bearings in power plants (e.g., wind and hydropower), agriculture, the steel and cement industries, mining, and food processing industries. In wear lubrication applications, grease typically undergoes minimal thermal oxidative or mechanical aging compared to machine parts or friction systems that require lifetime lubrication, but is frequently contaminated by wear particles, dust, and moisture. This is because the associated lubrication points are not adequately sealed against environmental influences, or because the aforementioned contaminants are intended to be flushed away from the lubrication points by replenishing grease.

[0006] Although greases have a relatively small market share compared to lubricating oils, their regeneration is worthwhile because they are produced at the cost of high thermal and mechanical energy.

[0007] Various methods are known to process used grease that is no longer suitable for its original purpose through heat recovery, aiming to utilize the energy value of the waste grease. However, such methods do not allow for material regeneration, i.e., the reuse of the product as a lubricant.

[0008] In the rolling bearing industry, there are currently initial technical solutions for collecting used or waste grease generated from wear lubrication in a classified manner. For example, EP2447485 B1 describes a reusable used grease box that allows used grease to be removed from rolling bearings by type and subsequently discharged into a waste collection container. Through collection and consolidation, waste grease and used grease become residual grease, which is then fed into a regeneration process.

[0009] To date, the reuse process has typically involved purifying the grease by separating the thickener from the base oil, resulting in the loss of the thickener structure. Thickener and base oil constitute the majority of most greases, with approximately 4 to 20% by mass of thickener and approximately 75 to 95% by mass of base oil. If both could be purified in a single regeneration process, the material losses, energy, and time required for grease regeneration could be minimized.

[0010] According to a recent survey by the National Lubricating Grease Institute (NLGI), standard metallic and complex soap-based greases account for approximately 90% of all greases (NLGI Grease Production Survey Report 2020).

[0011] According to DE19739659 A1, in a multi-stage oil recovery process, oily components and contaminants (such as dirt and metal shavings) are first removed from residual grease (preferably collected by type). The base oil is extracted from the residual grease via a multi-stage extraction process using an extractant added in an extractor. The resulting oil-extractant mixture (extract) is then separated from the raffinate containing thickeners and impurities in a downstream separator. The raffinate containing thickeners is in a semi-solid to solid state and is further dried to evaporate any residual solvent. The multi-stage thickener recovery process consists of an extraction stage and a crystallization stage. The thickener is separated from the dried residue using a suitable solvent (such as methanol or a methanol-chloroform mixture). In the extraction stage, the thickener is dissolved by the added extractant, while impurities remain undissolved.

[0012] Patent application DE 102023121428, which was not published at the time of filing, describes a method for regenerating residual grease that has been thickened by a polymer, wherein the residual grease is initially suspended in an organic and nonpolar solvent, such as boiling point gasoline conforming to DIN 51632-1 and DIN 51632-2.

[0013] Subsequently, mechanical impurities such as metal shavings and dirt particles can be separated first by filtration or other suitable methods, followed by distillation (to recover the solvent used) and further processing steps to recover the thickener and grease. This process uses flammable hydrocarbon solvents, although it may be desirable to largely avoid their use.

[0014] The purpose of this invention

[0015] When lossy lubrication occurs in applications, particularly those operating at high rotational or sliding speeds, a significant portion of the grease introduced for lossy lubrication can directly enter the shear zone, rather than serving as a reservoir for sealing frictional contact mating. In these cases, a relatively large volume fraction of the grease typically experiences high mechanical stress, and the grease's thickener structure is largely shear-degraded during use. This invention is also applicable to greases whose thickener structure is mechanically damaged or severely compromised during use; in contrast, the method according to DE 102023121428 aims to largely preserve the thickener structure of the residual grease during repair.

[0016] When reprocessing grease, it is desirable to avoid separating the thickener from the base oil and to clean them in a separate step. During reprocessing, the mechanically damaged thickener structure should be rebuilt along with the base oil so that its thickening effect is the same as, or at least nearly the same as, that of new, unused grease. Therefore, there should be no or only minimal loss of thickening effect. Thus, the object of this invention is to avoid the disadvantages of the prior art described above and to provide a method for regenerating grease as economically and efficiently as possible, avoiding the addition of solvents and achieving this in an energy-efficient manner with as few steps as possible. Summary of the Invention

[0017] This invention is defined by the independent claims. Preferred embodiments are the subject of the dependent claims, or are described below.

[0018] This invention relates to a method for processing used grease to obtain regenerated grease, wherein the used grease becomes residual grease through use and collection, and the method includes at least the following steps:

[0019] a) Collect used grease from lubrication points to obtain residual grease, preferably from homogeneous grease, wherein the residual grease contains at least a thickener, additives, base oil, and solid impurities if present, and the thickener contains polymeric hydrocarbons or polymeric esters.

[0020] b) Heating at least the residual grease to a temperature of 100°C to 300°C, preferably 160°C to 260°C, to liquefy the residual grease, thereby obtaining liquefied grease, wherein the heating is preferably carried out in an inert gas atmosphere and / or under reduced pressure.

[0021] c) Separating solid components from liquefied grease.

[0022] d) To rebuild the grease with a thickener structure by solidifying the liquefied grease, preferably by cooling it at least 40°C, preferably at least 60°C, on a cooling plate, cooling conveyor, or rotating cooling drum, particularly in the absence of mechanical shear, to form a polymeric hydrocarbon thickener structure.

[0023] e) Optionally, the grease may be homogenized by mixing, with other additives and / or additional base oils added as necessary to adjust the desired consistency.

[0024] f) Optionally, further homogenization may be performed in a three-roll mill, gear colloid mill, high-pressure homogenizer, rotor-stator, or rotor-rotor disperser.

[0025] g) Optionally filter the grease again.

[0026] h) Optionally, degas the grease.

[0027] Among other factors, residual grease liquefies upon heating due to the melting and / or dissolution of the thickener in the base oil.

[0028] The separation in step c) can be carried out by sedimentation, by centrifugation, by magnetic separators for magnetic particles and / or by electrostatic separators for ionizable particles, particularly by filtration using filters with pore sizes or mesh sizes of 15 µm or smaller.

[0029] Liquefied grease can be treated with a desiccant to remove water, particularly in the form of a filtered desiccant. Furthermore, any water can evaporate during heating, optionally by applying reduced pressure. Similarly, regenerated grease can be dried, for example, by freeze-drying.

[0030] In addition to base oil, residual grease also contains polymeric hydrocarbons or polymeric esters as thickeners.

[0031] Polymeric hydrocarbons preferably have a melting point below 260°C, particularly below 240°C. Disregarding this, the melting point is preferably above 100°C. The melting point or melting point in each case refers to the raw material used.

[0032] The dropping point of residual grease containing polymeric hydrocarbon-based thickeners is preferably between 100°C and 240°C.

[0033] In the case of polymeric esters, these polymeric esters preferably have a melting range of 100°C to about 170°C. The melting point or melting point associated with the melting range refers to the raw material used in each case.

[0034] The dropping point of the residual grease having a thickener based on a polymeric ester is preferably between 100°C and 150°C.

[0035] The regenerated grease preferably has a cone penetration value (working cone penetration) of 200 to 430 mm / 10 (at 25°C), preferably 220 to 385 mm / 10, as determined according to ISO 2137.

[0036] A homogeneous grease is one that contains at least the same thickener (i.e., a compound of the type "polymeric hydrocarbon" or "polymeric ester") and the same type of base oil (e.g., a compound of the same class), particularly the same polymeric hydrocarbon or polymeric ester as the thickener and the same base oil. At a minimum, the additional base oil must be miscible with the (first) base oil.

[0037] Different base oils can be used, which are liquid at room temperature and, in particular, have a viscosity of 12 to 2500 mm at 40°C. 2 / s, preferably 20 to 2500 mm 2 / s, and most preferably 40 to 500 mm 2 Kinematic viscosity / s. Suitable base oils particularly include hydrocarbons, such as polyalphaolefins (PAO), mineral oils, and / or esters. The base oils preferably have a boiling point above 260°C, and especially above 300°C.

[0038] In the case of thickeners based on polymeric esters, in addition to non-polar base oils, more polar base oils, such as esters, can also be used.

[0039] According to one embodiment, any solid impurities are separated from molten grease by filtration, wherein particles larger than 15 µm, preferably larger than 5 µm, and most preferably larger than 2 µm are retained in the filtrate residue. For this purpose, the filtration device can be heated, and it can further have an pore size or filter screen size of less than 15 µm, preferably less than 5 µm, and most preferably less than 2 µm. Multiple filtrations can also be performed continuously with gradually decreasing filter screen sizes / pore diameters. Detailed Implementation

[0040] Greases suitable for reprocessing or residual greases include polyolefin-thickened greases, such as those described in US3850828A, US 2917458A, US 3290244A, US 3392119A, US 5874391A, EP 0942063A1 or EP0795597B1.

[0041] Residual grease contains polymeric hydrocarbons as thickeners. Suitable examples include, for instance:

[0042] -Polyethylene, optionally a mixture with atactic polypropylene,

[0043] - Polypropylene, optionally a mixture with atactic polypropylene or polyethylene,

[0044] - An ethylene and polypropylene copolymer, optionally a mixture with polypropylene and / or polyethylene,

[0045] - Polyolefins containing rubber components or mixtures of various rubber components,

[0046] - Methylene pentene polymer, optionally a mixture with polypropylene, polyethylene and / or ethylene-polypropylene copolymer.

[0047] Polymeric hydrocarbons are long-chain compounds in which more than 99% of all atoms, especially 99.9%, are composed of carbon and hydrogen.

[0048] Suitable thickeners have a molecular weight of 20,000 to 500,000 g / mol, more preferably 50,000 to 250,000 g / mol (Mw, in each case), and preferably a density greater than 0.94 g / cm³. 3 The polyethylene, particularly in the form of a mixture with atactic polypropylene, preferably with a molecular weight of less than 100,000 g / mol (Mw) and preferably with a melt flow index of more than 20, particularly more than 50. The ratio of atactic polypropylene to polyethylene is preferably 1:1 to 1:10, more preferably 2:1 to 5:1.

[0049] The thickener is based on oil-soluble amorphous polypropylene with a molecular weight in the range of 300 to 10,000 g / mol (Mw) and an intrinsic viscosity of at most 0.4, particularly in an amount of 2% to 5% by weight, and isotactic polypropylene with a molecular weight in the range of 100,000 to 1,000,000 g / mol (Mw) and a melting point in the range of 121°C to 210°C. Preferably, it is a copolymer or homopolymer of propylene having a weight-average molecular weight greater than or equal to 200,000 g / mol and a low molecular weight (copolymer or homopolymer) of propylene having a weight-average molecular weight less than or equal to 100,000 g / mol.

[0050] Thickener compositions are based on a combination of polymethylpentene (a polymer based on 4-methylpentene-1) with a melting point above 200°C or above 225°C and a low molecular weight (weight average 50,000 to 100,000 g / mol) copolymer or homopolymer of propylene as described in the preceding section. Suitable commercial products are, for example, TPX DX 820 from Mitsui Chemicals Europe GmbH. It is a 4-methylpentene-1 polyolefin. All polymers that can be completely liquefied and / or dissolved at the high temperatures used in this process are suitable.

[0051] Polymer esters, particularly polyhydroxyalkanoates (PHAs), such as polyhydroxy (C4 to C12) alkanoates, preferably poly-3-hydroxyalkanoates, and most preferably poly-3-hydroxybutyric acid. The thickening properties of the aforementioned polyhydroxyalkanoates can be further enhanced by additional chemical modification with one or more crosslinking agents.

[0052] Thickeners may contain other thickeners, such as metal and metal complex soaps or polyureas, provided that these thickeners can be completely liquefied and / or dissolved in the base oil at elevated temperatures.

[0053] Various polar and non-polar base oils can be used in residual greases; they are liquids at room temperature and have kinematic viscosities ranging from 12 to 2500 mmHg at 40°C. 2 / s, especially 40 to 500 mm 2 Base oils can be classified as mineral oils or synthetic oils. Mineral oils include, for example, naphthenic and paraffinic mineral oils, as classified under API Group I. Chemically modified aromatic and low-sulfur mineral oils classified under API Groups II and III, which have a lower proportion of saturated compounds and improved viscosity-temperature behavior compared to API Group I oils, are also suitable. Base oils should be understood to specifically include polyalphaolefins, alkyl aromatics, alkyl diphenyl ethers, alkyl naphthalenes, and mixtures thereof.

[0054] Esters can also be used, such as esters of aromatic di, tri, or tetracarboxylic acids with C2 to C22 alcohols (alone or in mixtures), 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, esters of C18 dimer acids with C2 to C22 alcohols, and complex esters (as a single component or in mixtures). Esters of unsaturated fatty acids, such as oleic acid with polyols, are also applicable.

[0055] As base oils for polymeric hydrocarbons, polyalphaolefins (PAOs), such as C8 to C14, especially C10, alpha-olefin oligomers, alkyl aromatics, alkyl diphenyl ethers, alkyl naphthalenes and mixtures thereof, as well as hydrocarbon oils such as mineral oils can be used.

[0056] Ester compounds can be used as base oils for polymeric esters, such as esters of aromatic di, tri, or tetracarboxylic acids with C2 to C22 alcohols (alone or in mixtures), 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, esters of C18 dimer acids with C2 to C22 alcohols, and complex esters (as a single component or in mixtures). Esters of unsaturated fatty acids, such as oleic acid with polyols, are also suitable.

[0057] Suitable additives include antioxidants, anti-wear agents, corrosion inhibitors, detergents, colorants, lubrication improvers, adhesion promoters, viscosity additives, friction reducers and high-pressure additives, metal passivators, and solid lubricants, preferably at a concentration of less than 5%. Suitable additives include polyisobutylene succinic acid and / or polyisobutylene succinic acid-polyacrylamide. Additives remaining in the filter residue can then be re-added to the regenerated grease.

[0058] Thermal filtration is performed using a filtration process, in which particles larger than 15 µm or larger than 5 µm, particularly larger than 2 µm, are retained in the filter cake. The filter may include paper, textiles, or metal as the filter material, or a bed of filter media.

[0059] In this process, filtration can also be carried out under an inert gas atmosphere to prevent oxidation of the grease or filter material. Deep filtration using glass fiber or synthetic fiber fabrics is also suitable. If, in addition to foreign contaminants or metal shavings, undissolved or molten solid grease additives remain in the filter residue, such as oil-insoluble solid lubricants, these additives can subsequently be reintroduced as new material in further stages of the reprocessing.

[0060] Solids can be removed from liquefied residual grease, for example, magnetic separators can be used to remove magnetic iron and steel particles, such as those that may appear due to wear on lubricated machine parts. Electrostatic separators can be used to remove ionizable wear particles.

[0061] The method according to the invention may further include the optional step of adding liquid or solid additives, additional base oils and / or additional thickeners (each as described above) to the liquefied grease, preferably during or after heating, particularly to achieve the desired consistency.

[0062] Regenerated grease can be homogenized, for example, using a gear colloid mill, a high-pressure homogenizer, or a roller mill, especially after the addition of additional additives, additional base oils, and / or additional thickeners. Furthermore, regenerated grease can be degassed using a perforated disc degasser or a vacuum degasser.

[0063] A particular aspect of the invention is the regeneration of grease used in worn-out rolling bearings, sliding bearings, or gearboxes in facilities such as wind turbines, hydroelectric power plants, rolling mills, machine tools, paper machines, ore processing plants, cement plants, and food production and agriculture, where large amounts of grease waste are generated or where it is necessary to prevent the release of used grease into the environment.

[0064] Another specific aspect of the invention is the regeneration of greases used in lifetime lubrication applications, wherein these greases undergo only minimal oxidative aging and can be reprocessed using the methods of the invention. Such applications include, for example, the lubrication of wheel bearings in vehicles, the lubrication of rolling and sliding bearings in stationary machinery and units, and the lubrication of sealed constant velocity drive shafts and dual-mass flywheels.

[0065] Using the grease regeneration method of the present invention, the following results are typically obtained after regeneration, in each case comparing the residual grease with the regenerated grease, and in particular comparing the (unused) grease (equivalent to fresh grease) with the regenerated grease:

[0066] - The consistency variation measured by cone penetration (working cone penetration) according to DIN ISO 2137, ranging from -50 to +40 units (0.1 mm) of the maximum value, preferably from -30 to +30 units (0.1 mm).

[0067] -The dropping point, according to DIN ISO 22285, varies from -15°C to +30°C, preferably from -10°C to +25°C.

[0068] - The regeneration yield is greater than 70% by weight, depending on the amount of grease used, and in particular, the regeneration yield is greater than 90% by weight, depending on the amount of grease used (residual grease).

[0069] exist Figure 1 The diagram illustrates a general process flow with possible implementation variations.

[0070] Experimental Section

[0071] To illustrate the embodiments and reference embodiments of the present invention of the regeneration method, residual grease containing simulated, i.e., artificially added mechanical impurities was produced.

[0072] Residual grease 1

[0073] According to EP0795597B1 and its embodiments, residual grease 1 is produced using a polymer thickener having the following composition, the difference being the addition of a base oil and additives, an additional polypropylene polymer, and subsequently simulated mechanical impurities:

[0074] Table 1

[0075]

[0076] Residual grease 2

[0077] According to Table 2, in a stirred tank according to Table 2, a mixture of commercially available sunflower oil (“High Oleic Sunflower Ester Oil Dakolub MB 9300” from DAKO AG) with 83.97% oleic acid content exceeding 90% by weight and 15% by weight of crosslinked poly-3-hydroxybutyric acid was heated to 150°C to allow the additive to completely melt in the base oil. The mixture was then cooled to 60°C, 1.03% by weight of the additive was added, and the mixture was homogenized using a three-roll mill. The resulting grease was modified to simulate residual grease by adding 0.7% by weight of iron filings and 0.63% by weight of silica sand as technical contaminants. The grease produced in this manner before the addition of mechanical impurities had a dropping point of 120°C, and as a residual grease, it also had a dropping point of 120°C.

[0078] Table 2

[0079]

[0080] Example 1 (Invention)

[0081] Regenerate the residual grease 1 as follows:

[0082] -500 g residual grease 1,

[0083] - Determination of the dropping point of residual grease: 221℃,

[0084] - Fill the residual grease into a heatable, pressure-resistant, sealed, and breathable stirred reactor.

[0085] - Applications of inert gas atmospheres (nitrogen),

[0086] Heat the grease to 190°C to completely liquefy it.

[0087] - Use permanent magnets to separate metal particles.

[0088] - Perform multi-stage filtration of hot liquid grease in the following order.

[0089] 1) Coarse-grained metal filter with a 220 µm mesh size

[0090] 2) It is then passed through a metal filter with a 40 µm mesh size.

[0091] 3) Then pass it through a paper filter with a pore size of 5 µm.

[0092] - By pouring liquefied grease onto a metal plate pre-cooled to 15°C without mechanical shearing, the temperature is cooled from 190°C to 120°C within 4 minutes.

[0093] - Scrape the cooled grease off the cooling plate and transfer it to another mixing container;

[0094] - Stir to homogenize the grease.

[0095] - Stir in 3.75 g of additive (as before, in 4 g of base oil according to Table 1),

[0096] - The grease is homogenized on a three-roll mill and degassed under reduced pressure.

[0097] Compared to lubricating grease, regenerated lubricating grease exhibits the following characteristics:

[0098]

[0099] Example 2 (Invention)

[0100] Regenerate the residual grease 2 as follows:

[0101] -500 g residual grease 2,

[0102] - Determination of the dropping point of residual grease: 221℃,

[0103] - Fill the residual grease into a heatable, pressure-resistant, sealed, and breathable stirred reactor.

[0104] - Generates an inert gas atmosphere (nitrogen).

[0105] Heat the grease to 190°C to completely liquefy it.

[0106] - Use permanent magnets to separate metal particles.

[0107] - Perform multi-stage filtration of hot liquid grease in the following order.

[0108] 1) Coarse-grained metal filter with a 220 µm mesh size

[0109] 2) It is then passed through a metal filter with a 40 µm mesh size.

[0110] 3) Then pass it through a paper filter with a pore size of 5 µm.

[0111] - By pouring liquefied grease onto a metal plate pre-cooled to 15°C without mechanical shearing, the temperature is cooled from 190°C to 120°C within 4 minutes.

[0112] - Scrape the cooled grease off the cooling plate and transfer it to another mixing container;

[0113] - Stir to homogenize the grease.

[0114] - Stir in 3.75 g of additive (as before, in 4 g of base oil according to Table 1),

[0115] - The grease is homogenized on a three-roll mill and degassed under reduced vacuum.

[0116] Compared to lubricating grease, regenerated lubricating grease exhibits the following characteristics:

[0117]

Claims

1. A method for reprocessing used grease to obtain regenerated grease, wherein the used grease is converted into residual grease through use and collection, the method comprising at least the following steps: a) Collect used grease from lubrication points to obtain residual grease, wherein the residual grease contains at least a thickener, additives, base oil, and optional solid impurities, and the thickener contains polymeric hydrocarbons or polymeric esters. b) Heating at least the residual grease to a temperature of 100°C to 300°C, preferably 120°C to 260°C, to liquefy the residual grease, thereby obtaining liquefied grease. c) Separating the solid components from the liquefied grease. d) Reconstructing a grease having a thickener structure by solidifying the liquefied grease and cooling it to at least 40°C to form a thickener structure of the polymeric hydrocarbon or the polymeric ester.

2. The method according to claim 1, wherein the grease having a thickener structure is reconstructed by solidifying the liquefied grease and forming the thickener structure of the polymeric hydrocarbon or the polymeric ester by cooling at least 60°C.

3. The method according to claim 1 or 2, wherein the base oil - It is a liquid at 25°C, and / or - the base oil has a kinematic viscosity at 40°C of 12 to 2500 mm 2 / s, preferably 20 to 2500 mm 2 / s, more preferably 40 to 500 mm 2 / s.

4. The method according to at least one of the prior claims, wherein the thickener in the form of a polymeric hydrocarbon is a polyolefin, particularly - A mixture of polyethylene and atactic polypropylene. - Ethylene / propylene copolymer, - Blends of polyolefins and rubber polymers, particularly rubber polymers based on natural rubber, polyisobutylene, styrene-butadiene rubber, ethylene-propylene-diene rubber, ethylene-propylene rubber, and / or polyisobutylene; or - Polymethylene pentene with a melting point above 200°C, especially above 225°C.

5. The method according to at least one of the prior claims, wherein the polymeric hydrocarbon has an average molecular weight (Mw) greater than 20,000 g / mol.

6. The method according to at least one of the prior claims, wherein the polymeric hydrocarbon has a melting point above 100°C, particularly above 120°C, and also independently below 300°C, particularly below 260°C.

7. The method according to any one of claims 1, 2 and / or 3, wherein the thickener comprises a polyhydroxyalkanoate-based polymeric ester, preferably poly-3-hydroxybutyric acid, wherein, preferably, in each case, further chemical modification with one or more crosslinking agents is carried out.

8. The method according to at least one of the prior claims, wherein the method further comprises adding a lubricant additive and / or an additional base oil and / or an additional thickener to the liquefied grease.

9. The method according to at least one of the prior claims, wherein the method comprises treating the liquefied grease with a desiccant, particularly a desiccant in the form of a filter desiccant, to separate water, and / or to evaporate any water during heating.

10. The method according to at least one of the prior claims, wherein the separation in step c) is performed by filtration, particularly using a filter with an pore size or mesh size of 15 µm or smaller.

11. The method according to at least one of the prior claims, wherein the separation in step c) is - Through settlement - By centrifugation, - By using a magnetic separator for magnetic particles, and / or - Through an electrostatic separator for ionizable particles.

12. The method according to at least one of the prior claims, wherein the method further comprises homogenizing the regenerated grease in a three-roll mill, a rotor / stator homogenizer, a high-pressure homogenizer and / or a gear colloid mill, optionally adding lubricant additives and / or additional base oils and / or thickeners to the regenerated grease before or during homogenization.

13. The method according to at least one of the prior claims, wherein the method comprises drying the regenerated grease, particularly freeze-drying.

14. The method according to at least one of the prior claims, wherein the cooling is carried out within at most 5 minutes, preferably without shearing, while forming the thickener structure of the polymeric hydrocarbon.

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