Producing polyurea-thickened lubricating greases having improved lubrication properties and aging stability

Abstract

The invention relates to a method for producing a polyurea-thickened lubricating-grease intermediate product, consisting of or comprising the following steps: a) providing at least one first thickener precursor; b) providing at least one second thickener precursor; c) metering the provided thickener precursors from steps a) and b) into a mixing chamber, optionally additionally adding at least one additive; d) mixing the at least two thickener precursors and the optional at least one further additive in the mixing chamber, and reacting the two thickener precursors; e) obtaining at least one polyurea-thickened lubricating-grease intermediate product, wherein, in order to achieve cooling during the reaction in step d), at least one of the thickener precursors provided in steps a) and b) and / or the at least one additive from step c) has a temperature in a range of 0°C to less than 40°C, preferably in a range of 10°C to less than 40°C.

Description

[0001] Production of polyurea-thickened lubricating greases with improved lubrication properties and aging stability

[0002] The present invention relates to the field of lubricating grease production, in particular the production of polyurea-thickened lubricating greases. The invention provides a process for producing lubricating grease precursors and for producing the final lubricating grease. Furthermore, the use of an apparatus for producing a lubricating grease according to the invention and a lubricating grease according to the invention are provided.

[0003] For tribosystems, such as those used in 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.

[0004] The hallmark of a lubricating grease is that a liquid oil component is absorbed and held in place by a thickener component. The gel-like nature of a lubricating grease and its ability to be spreadable and easily deformed, together with its adhesive properties, ensures that the lubricating grease wets the lubrication point and develops its lubricating effect on the tribologically stressed surfaces. In addition to additives, lubricating greases essentially consist of a thickener dispersed in a base oil. The most important rheological properties of a lubricating grease include its consistency or yield point, the prevention of post-curing and excessive oil separation under thermal and mechanical stress, and stable viscosity-temperature behavior and viscosity-shear behavior.In order to create a lubricating grease with high utility value depending on the application requirements, a high degree of practical experience is required.

[0005] In the field of lubricating greases, it is important that the thickener is distributed in small and uniform particle sizes, while simultaneously producing the thickener molecules with high selectivity and significantly reduced chemical side reactions in order to produce aging-resistant and material-compatible lubricating greases. Lubricating greases produced in this way lead to extended rolling bearing service life, greater bearing stability, excellent noise performance, improved compatibility with sealing materials, reduced health risks for users, and better environmental compatibility.

[0006] The production of polyurea-thickened lubricating greases is a central research topic. GB 776548A discloses a process for producing metal soap-thickened lubricating greases, the principle of which can also be applied to polyurea greases. The reaction mixture is subjected to high shear in a reaction zone. Alternatively, a fully or partially reacted reaction mixture can be circulated between a sheared and a non-sheared zone with the addition of new reactants.

[0007] EP 1062307B1 discloses a discontinuous manufacturing process for producing not only soap-thickened greases but also polyurea lubricating greases. During production, a polyurea lubricating grease is circulated through a homogenizer and sheared. This is intended to achieve good noise performance as tested using the SKF BeQuiet method.

[0008] EP 1322732B1 discloses the discontinuous production of a low-noise lubricating grease with a defined thickener particle size of 95% less than 100 μm. First, the thickener is prepared by reacting diisocyanates and amines. Subsequently, a mixture of a thickener and a base oil is sheared for some time at a temperature of 35°C to 55°C to the desired particle size, then heated to a temperature of 150°C to 175°C, and finally cooled to a temperature of 25°C to 105°C. The grease is then ground to obtain a homogeneous lubricating grease. US 2010 / 0029526A1 discloses the production of low-noise polyurea lubricating greases by the sequential addition of two or more amines pre-dissolved in oil to an isocyanate pre-dissolved in oil present in the reactor.

[0009] EP1322732B1 discloses the continuous production of polyurea lubricating greases by reactive injection molding. The reactants, amine and isocyanate, are diluted / dissolved separately in a solvent and then simultaneously injected into a high-pressure injection unit under high pressure, producing the polyurea thickener.

[0010] US8703671 B2 discloses the continuous production of polyurea lubricating greases using a reactive (twin-screw) extruder. A feature of this process is that reaction components, such as isocyanates and amines, are added at various points in the extruder, while base oil can be added at other points. The addition of reaction components pre-dissolved in oil is also described. Furthermore, the temperatures in the individual reaction zones (mixing-cooling zone) are described.

[0011] EP3031888B1 describes the production of polyurea lubricating greases by simultaneously introducing amines pre-dissolved in oil and isocyanates dissolved in oil into a shear cell with a defined shear rate of greater than 10 2 1 / s. The shear rate is defined as the quotient of the relative velocity between a rotating inner component and the inner wall of the shear cell and the smallest distance between these two components. Shearing of the reaction components, pre-dissolved in oil, occurs within 15 minutes of their contact. The reaction of isocyanate and amine takes place at 60–120 °C.

[0012] EP3255130A1 describes the production of a low-noise lubricating grease based on at least one aromatic amine and other amines according to the process of EP3031888, in which the process is applied in such a way that the average thickener particle size of the resulting lubricating grease has an arithmetic mean of <1.6 pm. The average particle size is determined using the static light scattering method.

[0013] EP 3150688 B1 describes the production of a lubricating grease based on isocyanate and a mixture of alicyclic and aliphatic amines according to the process of EP3031888. The noise requirements for the correspondingly produced grease are "peak high 32-64s of < 1.5 and a level high 32-64s of < 10" and are defined using the FAG method (also known as ISO 21250-3 "Method MQ"). JP 2017115109A describes a special design of the rotor / stator shear cell mentioned in EP 3031888, in which the shear rate of amines pre-dissolved in oil and isocyanates pre-dissolved in oil can be adjusted independently of the speed of the rotating component by varying the shear gap width.

[0014] The state of the art does not indicate that the reaction temperature plays a significant role in the quality of the resulting lubricating grease. Previously known production processes for polyurea lubricating greases either describe continuous production processes that cannot be used in the stirred reactors widely used in the lubricant industry for batch production of lubricating greases, or discontinuous processes in which no solution has been found for the problem of shear heating occurring at high shear rates and the exothermic reaction of amines, alcohols, and isocyanates. This leads to the formation of undesirable chemical by-products or degradation products during thickener synthesis and thus to adverse lubricating grease properties.

[0015] For example, temperature-induced dissociation of the urea group can lead to re-formed free amines that can increase plastics intolerance and skin intolerance. Free amines can also cause an increased odor nuisance. Free amines also pose a toxicological health risk for users. Furthermore, an increased reaction temperature could lead to evaporation of any volatile amines or alcohols (such as cyclohexylamine / cyclohexanol) that have not yet reacted with the isocyanate, thus preventing the desired polyurea thickener and its properties (e.g. thickening performance). Another effect that could occur is that isocyanates that have not yet reacted with amines and alcohols are no longer soluble due to excessively high temperatures and possiblyResidual moisture present in the oils also decomposes via intermediate formation of carbamic acid and subsequent decarboxylation to form free aromatic amines, which, as already described, pose a number of disadvantages. Free isocyanates also pose a toxicological health risk to users. Furthermore, possible oligomerization of isocyanates (uretdione formation, isocyanurate formation) or the formation of biuret oligomers or allophanate oligomers could lead to reduced thickening performance and increased thermal and oxidative aging of lubricating greases. Experience has shown that free amines, alcohols, or isocyanates often lead to unintentional post-solidification of polyurea lubricating greases during storage or use.

[0016] The object of the present invention was therefore to provide a process for producing a polyurea-thickened lubricating grease which has high quality and aging stability, as well as to limit the formation of undesirable by-products in the thickener production step. This object was achieved according to the invention in a first aspect by providing a process for producing at least one polyurea-thickened lubricating grease intermediate, consisting of or comprising the following steps: a) providing at least one first thickener precursor; b) providing at least one second thickener precursor; c) dosing the thickener precursors provided from steps a) and b) into a mixing chamber, optionally additionally adding at least one additive; d) mixing the at least two thickener precursors and optionally at least one further additive in the mixing chamber and reacting the two thickener precursors;e) Obtaining at least one polyurea-thickened lubricating grease intermediate; wherein, to achieve cooling during the reaction in step d), at least one of the thickener precursors provided in steps a) and b) and / or the at least one additive from step c) has a temperature in a range from 0°C to below 40°C, preferably in a range from 10°C to below 40°C.

[0017] The present invention generally relates to the production of lubricating greases based on various base oils and thickeners based on organically substituted urea and / or urethane molecules with aliphatic, cycloaliphatic, and aromatic hydrocarbon groups. Due to the simultaneous presence of multiple urea or urethane groups, corresponding lubricating greases are called polyurea or polyurethane lubricating greases, or, as a hybrid form, polyurea / polyurethane lubricating greases. The umbrella term used is generally polyurea lubricating grease or polyurea-thickened lubricating grease.

[0018] A "grease intermediate" within the scope of the present invention is a product that forms the basis for a lubricating grease, but is further processed so that it can be used in grease-lubricated tribosystems. The lubricating grease intermediate is typically a thickener, which may already be present together with at least one base oil and / or at least one additive and is converted into a final product through further process steps such as heating and / or grinding. Furthermore, the lubricating grease intermediate or thickener can preferably be a polyurea thickener, which is then converted into a polyurea-thickened lubricating grease final product with the addition of further base oils and further additives in further process steps.

[0019] The thickener precursors provided in steps a) and b) are reactants that react in the mixing and reaction step d) to form the thickener or the lubricating grease intermediate. These are preferably amines and / or alcohols and isocyanates as described below.

[0020] The additive added in step c) is an optional component in the production of lubricating grease and can be added to improve or achieve certain properties of the lubricating grease.

[0021] In one embodiment, the lubricating grease intermediate is a polyurea thickener made from reaction products of amines and isocyanates. According to one embodiment, the polyurea thickener is available as a reaction product of diisocyanates with C6 to C20 hydrocarbyl monoamines. However, the reaction products of monoisocyanates, optionally plus additional diisocyanates, with diamines can also be present. The polyurea thickeners preferably do not have a polymeric character, but are, for example, dimers, trimers, tetramers, or other oligomers. In addition to the polyisocyanates, isocyanates of the R-NCO type (monoisocyanates) can also be used, where R represents a hydrocarbon radical with preferably 5 to 20 carbon atoms.

[0022] Preference is given to diureas obtainable from diisocyanates and monoamines, or tetraureas obtainable from diisocyanates, monoamine, and diamine, each as defined above. Particular preference is given to diureas based on 4,4'-diphenylmethane diisocyanate (MDI) or toluene-2,4-diisocyanate (TDI) and aliphatic, aromatic, and / or cyclic primary monoamines, or tetraureas based on MDI or TDI and aliphatic, aromatic, and / or cyclic monoamines and diamines.

[0023] Step d), in which the two thickener precursors prepared in steps a) and b) are mixed together, is responsible for producing the lubricating grease intermediate, preferably the polyurea thickener. For this purpose, a preferably prepared amine and / or an alcohol react exothermically with an isocyanate to form urea or urethane, respectively.

[0024] The concentrations of desired urea / urethane molecules and undesired by-products resulting from the reaction of polyurea thickeners depend significantly on their reaction rates and equilibrium positions. Due to the exothermic nature of the reactions, the equilibrium position is shifted significantly toward the products. The reaction rate depends on the reaction kinetics and mass transfer. The reaction kinetics increase with increasing temperature. Mass transfer depends significantly on the concentration of the reactants and the flow behavior (e.g., mixing / viscosity) and is thus also indirectly linked to the temperature. Reactions with high reaction kinetics are generally limited by mass transfer, whereas mass transfer is often of lesser importance in kinetically limited reactions. The kinetics of urea / urethane formation through the reaction of amines / alcohols with isocyanates are very high.It is therefore more mass-transfer-limited, which is why shearing is often used during the reaction in the state of the art. The kinetics of the undesired side reactions are slow compared to the urea formation reaction and are therefore predominantly kinetically limited. Increasing the reaction temperature increases the kinetics of the side reactions, whereas the urea / urethane formation reaction is not significantly altered by the mass-transfer limitation. Thus, increasing the reaction temperature leads to increased by-product formation.

[0025] It has surprisingly been found according to the invention that the formation of by-products can be limited by adding at least one of the thickener precursors and / or at least one additive at a temperature between 0°C and below 40°C, preferably in a range from 10°C to below 40°C, particularly preferably in a range from 10°C to below 35°C. This is particularly surprising since, in the prior art, the reactor jacket is cooled to control the temperature, particularly in a stirred reactor. However, this cooling via the reactor jacket is not sufficient to adjust the temperature in the reactor such that the formation of by-products is minimized. Inadequate cooling via the reactor jacket can be observed in particular when the thickening effect of the produced lubricating grease intermediate sets in and the convective heat transfer is greatly reduced.In contrast to the above-mentioned prior art, which largely does not contain any information on the influence of temperature or cooling, the invention defines a particularly advantageous method by the specified temperature range.

[0026] Preferably, in step c), a cooled additive having a temperature of 0 to 40°C, preferably having a temperature of 10°C to below 40°C, particularly preferably having a temperature of 10°C to below 35°C, is added. It is particularly preferred if the additive is a cooled base oil.

[0027] Preferably, the at least one additive can be added at a temperature below 0°C in step d) to achieve cooling. When added at a temperature below 0°C, the formation of condensation is preferably avoided by measures known to those skilled in the art, for example, by using a dry atmosphere or inert gas.

[0028] The present invention preferably relates to a process according to the invention, wherein the first thickener precursor provided in step a) is selected from the group consisting of primary amines, preferably monoaminohydrocarbyl, di- or polyaminohydrocarbylene compounds having 6 to 20 carbon atoms or alcohols having hydrocarbyl or hydrocarbylene groups having 6 to 20 carbon atoms, or mixtures of the above, wherein the first thickener precursor is present as a pure substance or as a mixture with at least one base oil.

[0029] Suitable amines as the first thickener precursor are listed, for example, in EP 0508115 A1 from page 1, line 51 to page 16 below. Suitable alcohols may also contain hydrocarbyl or hydrocarbylene groups, preferably each having 6 to 20 carbon atoms, particularly preferably 6 to 18 carbon atoms. The hydrocarbylene group preferably contains aliphatic groups, in particular alkyl or alkylene groups. Aromatic groups may also be used. They may be monoalcohols, diols, or polyols. Preference is given to monoalcohols and D-alcohols, particularly preferred are monoalcohols with a chain length of 6 to 18 carbon atoms.

[0030] The base oil can be classified as mineral oil or synthetic oil. Examples of 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.

[0031] Synthetic oils include, in particular, polyethers, esters, polyalphaolefins, polyglycols, and alkylaromatics, as well as mixtures thereof, as well as silicone oils. The polyether compound can contain free hydroxyl groups, but can also be fully etherified or end-esterified, and / or be made from a starting compound with one or more hydroxyl and / or carboxyl groups (-COOH). Polyphenyl ethers, optionally alkylated, are also possible as sole components or, even better, as blends. Suitable for use are esters of an aromatic di-, tri- or tetracarboxylic acid with one or a mixture of C2 to C22 alcohols, 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 mixtures.Furthermore, the process according to the invention preferably relates to one in which the at least second thickener precursor provided in step b) is selected from the group consisting of: isocyanates, preferably mono- and / or polyisocyanates having 5 to 20, particularly preferably 6 to 15 carbon atoms, or mixtures of those mentioned above, wherein the second thickener precursor is present as a pure substance or as a mixture with at least one base oil.

[0032] Mono- and / or polyisocyanates are suitable as the isocyanate component (second thickener precursor), with the polyisocyanates preferably being hydrocarbons with two isocyanate groups. The isocyanates have 5 to 20, preferably 6 to 15, carbon atoms and preferably contain aromatic groups.

[0033] Preferred within the scope of the present invention is a process according to the invention, wherein the at least one additive is selected from the group consisting of base oils, volatile hydrocarbons, cooled or liquefied gases, amines, alcohols, isocyanates, antioxidants, wear inhibitors, corrosion inhibitors, detergents, dyes, lubricity improvers, adhesion improvers, viscosity additives, friction reducers, high-pressure additives or metal deactivators, simple and / or complex soaps, preferably in the form of lithium, sodium, magnesium, calcium, aluminum or titanium soaps, water or mixtures thereof.

[0034] These soaps can either be added as an additive or, alternatively, formed in situ during grease production. Preferably, the polyurea-thickened lubricating grease intermediate or polyurea thickener and the soap or complex soap thickener are used together and further processed into a final product. Lithium soaps, aluminum or aluminum complex soaps, calcium sulfonate or calcium sulfonate complex soaps, calcium soaps or calcium complex soaps are particularly preferred, preferably in a mixing ratio of 10:1 to 1:10, in particular 5:1 to 1:5 (mass:mass). Soap or complex soap thickeners and polyurea thickeners are then preferably used together in an amount of 5 to 25 wt.% with respect to the polyurea-thickened lubricating grease (end product), wherein the polyurea-thickened lubricating grease intermediate product or the polyurea thickener is used in an amount of at least 1 wt.% is used, preferably at least 1.5 wt.%, in each case with respect to the polyurea-thickened lubricating grease (end product).

[0035] Preferably, solid lubricants such as polymer powders, preferably polyamides, polyimides or PTFE, melamine cyanurate, graphite, metal oxides, boron nitride, silicates, e.g., magnesium silicate hydrate (talc), sodium tetraborate, potassium tetraborate, metal sulfides such as molybdenum disulfide, tungsten disulfide or mixed sulfides based on tungsten, molybdenum, bismuth, tin, and zinc, inorganic salts, for example of alkali and alkaline earth metals, such as calcium carbonate, sodium and calcium phosphates, can be used as additives. Carbon black or other carbon-based solid lubricants such as nanotubes can also be added as additives. Likewise, lignin derivatives such as alkali or alkaline earth ligninsulfonates, in particular calcium ligninsulfonates, can be used to achieve specific properties, e.g. 2 to 15 wt.% (according to WO2011095155A1 or US 8507421 B2).

[0036] Furthermore, organic carbonates can be added as additives, which improve the performance properties of the polyurea-thickened lubricating greases according to the invention, and the compatibility of polyurea-thickened lubricating greases with fluorinated elastomers is improved through the use of organic carbonates. The organic carbonates preferably have 4 to 8 carbon atoms. The radicals or constituents of the organic carbonates are hydrocarbons (apart from the carbonate group itself), i.e. the organic carbonate is not heteroatom-substituted. Cyclic carbonates are preferred, in particular those with 4 to 8, in particular 4 or 5, carbon atoms. The organic cyclic carbonate can be added as an additive to the polyurea-thickened lubricating grease according to the invention during production, but preferably after production of the polyurea-thickened lubricating grease intermediate in the cooling phase.

[0037] Further additives which can preferably be added within the scope of the present invention are preferably selected from:

[0038] • primary antioxidants such as amine compounds (e.g. alkylamines or 1-phenylaminonaphthalene), aromatic amines such as phenylnaphthylamines or diphenylamines or polymeric hydroxyquinolines (e.g. TMQ), phenol compounds (e.g. 2,6-di-tert-butyl-4-methylphenol), zinc dithiocarbamate or zinc dithiophosphate;

[0039] • secondary antioxidants such as phosphites, e.g. tris(2,4-ditert-butylphenyl phosphite) or bis(2,4-ditert-butylphenyl)-pentaerythritol diphosphite or thioethers (e.g. cresol thioether);

[0040] • High pressure additives and / or anti-wear additives such as sulfur or organic sulfur compounds such as polysulfides or sulfurized olefins, overbased calcium sulfonates, thiophosphates, phosphorus compounds such as amine-neutralized alkyl phosphates; • Inorganic or organic boron compounds, zinc dialkyldithiophosphate, organic bismuth compounds; thiophosphonates such as triphenylthiophosphate, phosphonates (phosphites) such as dioctylphosphonate, alkylsulfonates, thiocarbamates such as methylenebis(dibutyldithiocarbamates and dithiocarbamates.

[0041] • active ingredients that improve oiliness, such as C2 to C6 polyols, fatty acids, fatty acid esters or animal or vegetable oils;

[0042] • Anti-corrosive agents such as sulfonates such as petroleum sulfonate, dinonyl naphthalene sulfonate or sorbitan esters; neutral or overbased calcium sulfonates, magnesium sulfonates, sodium sulfonates, calcium and sodium naphthalene sulfonates, sulfonic acid esters, disodium sebacate, calcium salicylates, amine phosphates, succinates;

[0043] • Metal deactivators such as benzotriazoles, e.g. methylbenzotriazole dialkylamine, sterically hindered phenols, sodium nitrite;

[0044] • Viscosity improvers such as polymethacrylate, polyisobutylene, oligo Dec-1-ene, polystyrene;

[0045] Friction reducers, some with wear protection properties, such as organomolybdenum complexes (OMC), molybdenum dialkyl dithiophosphates, molybdenum dialkyl dithiocarbamates, especially molybdenum di-n-butyldithiocarbamate and molybdenum dialkyldithiocarbamate (Mo2mS n(dialkylcarbanate)2 with m = 0 to 3 and n = 4 to 1), zinc dithiocarbamate or zinc dithiophosphate; or a trinuclear molybdenum compound corresponding to the formula

[0046] MOsSkLnQz, in which L are independently selected ligands having organogroups with carbon atoms as disclosed in US 6172013 B1 to make the compound soluble or dispersible in the oil, wherein n ranges from 1 to 4, k ranges from 4 to 7, Q is selected from the group of neutral electron donor compounds consisting of amines, alcohols, phosphines and ethers, and z is in the range from 0 to 5 and includes non-stoichiometric values ​​(cf. DE 102007048091); • organic acids such as isostearic acid, functional polymers such as

[0047] Oleylamides, organic compounds based on polyether and amide, e.g.

[0048] Alkyl polyethylene glycol tetradecylene glycol ether, PIBSI

[0049] (Polyisobutylenesuccinimide) or PIBSA

[0050] (polyisobutylene succinic anhydride), partial glycerides,

[0051] Dialkyl hydrogen phosphonates, alkyl succinates.

[0052] Further preferred is a process according to the invention, wherein cooling of the reaction in step d) is further achieved by adding evaporating components as additives in step c).

[0053] When using evaporating components, cooling is achieved by utilizing their evaporation enthalpy. The boiling point of this component is preferably below the reaction temperature of the two thickener precursors.

[0054] Further preferred within the scope of the present invention is a process according to the invention, wherein cooling of the reaction in step d) is further achieved by adding subliming components as additives in step c).

[0055] Preferably, the process according to the invention relates to one in which the base oil has a kinematic viscosity of 12 to 2500 mm 2 / s, preferably from 30 to 500 mm 2 / s at a temperature of 40 °C.

[0056] It is also preferred within the scope of the present invention that the mixing in step d) takes place in the mixing chamber under shear.

[0057] Preferably, reactants that are poorly or insoluble in base oil can be converted into a lubricating grease intermediate by shearing in the mixing chamber. Also, reactants that are poorly or insoluble in base oil at temperatures below 20°C can preferably be converted by shearing as described herein.

[0058] During the formation reaction of the polyurea-thickened lubricating grease intermediate (thickener) from amines (or alcohol) and isocyanate, di- or tetraurea, for example, can be formed, depending on the selected raw materials and their stoichiometry. These molecules can aggregate and, through the heating process, form a three-dimensional thickener structure, which can also be referred to as thickener particles. The kinetics, including temperature control and mechanical shear in the mixing and / or shear chamber, can influence the three-dimensional formation of the thickener and thus its properties. Shearing is particularly preferably carried out at a shear rate of at least 10 2 1 / s , preferably with a maximum shear rate of 10 7 1 / s , particularly preferably in a range of at least 10 2 1 / s up to a maximum of 10 6 1 / s .

[0059] Preferably, the shear rate is determined from a ratio between the speed difference of the adjacent rotating or non-rotating components (e.g. rotor and stator) and their distance. -

[0060] It is also preferred within the scope of the present invention if the shearing is carried out by means of at least one of the following:

[0061] Rotor-rotor shearing device, ie, for example, and preferably a homogenizing device with two rotatable shearing elements arranged within a housing or container which can be driven in opposite or the same direction, as stated, for example, in a European patent with the number EP 1125625 or EP 1825 907.

[0062] Rotor-stator shearing device, ie, for example, and preferably a homogenizing device with a rotatable shearing element arranged within a housing or container, which is movable relative to a stationary stator, as stated, for example, in European patent EP3031888B1 or EP3255130A1,

[0063] Rotor-stator-rotor shearing device, ie, for example, and preferably a homogenizing device with two rotatable shearing elements arranged within a housing or container, which can be driven in opposite or the same direction, and an additional stationary stator, as specified, for example, in the said European patent with the number EP 1125625 or EP 1825 907.

[0064] high-pressure injection chamber,

[0065] Static mixer,

[0066] Extruders, especially screw extruders.

[0067] Pump unit / pump.

[0068] The shearing particularly preferably takes place in a rotor-rotor-stator system as described in EP 1125625 or EP 1825 907. In a preferred embodiment, the process according to the invention can be one for producing a polyurea-thickened lubricating grease, consisting of or comprising the steps as described above and additionally comprising the steps: f) heating the intermediate product obtained in step e) to a temperature of above 100°C with stirring; g) cooling the heated intermediate product from step f) to a temperature of below 100°C, preferably below 80°C; h) obtaining a polyurea-thickened lubricating grease.

[0069] The polyurea-thickened grease obtained in step h) is preferably considered as a final product for use in tribosystems.

[0070] A further aspect of the present invention is a process for producing at least one polyurea-thickened lubricating grease intermediate, consisting of or comprising the following steps: a) providing at least one first thickener precursor; b) providing at least one second thickener precursor; c) dosing the thickener precursors provided from steps a) and b) into a mixing chamber, optionally additionally adding at least one additive; d) mixing the at least two thickener precursors and the optionally at least one further additive in the mixing chamber and reacting the two thickener precursors; e) obtaining a polyurea-thickened lubricating grease intermediate, wherein pure amine or a mixture of pure amines and / or alcohol is provided as the first thickener precursor.

[0071] Pure amine and / or thickener precursor is understood to be completely or substantially free of base oils and / or additives as described herein.

[0072] Preferably, and as already described, in step a) at least one amine is selected as the first thickener precursor provided, preferably selected from the group consisting of primary amines, preferably monoaminohydrocarbyl, di- or polyaminohydrocarbylene compounds having 6 to 20 carbon atoms, or mixtures of those mentioned above, and / or in step a) at least one alcohol is selected as the first thickener precursor provided, preferably selected from the group consisting of alcohols with hydrocarbyl or hydrocarbylene groups having 6 to 20 carbon atoms, or mixtures of those mentioned above, and, the second thickener precursor provided in step (b) is selected from the group consisting of isocyanates, preferably mono- and / or polyisocyanates having 5 to 20, particularly preferably 6 to 15 carbon atoms, or mixtures of those mentioned above,wherein the first and / or the second thickener precursor is present as a pure substance or as a mixture with at least one base oil.,

[0073] Preferably, the process according to the invention, as described above, additionally comprises the steps: f) heating the intermediate product obtained in step e) to a temperature above 100°C with stirring; g) cooling the heated intermediate product from step f) to a temperature below 100°C, preferably below 80°C; h) obtaining a polyurea-thickened lubricating grease.

[0074] As already explained, a polyurea-thickened lubricating grease obtained within the scope of the present invention is the process product from the in-situ reaction of the amines and isocyanates described herein, preferably in the base oil, which is heated following the intermediate product preparation and then cooled again to obtain the polyurea-thickened lubricating grease as the final product.

[0075] The invention has been described above with reference to a method. In a further aspect, the invention relates to a device or the use of a device. The invention achieves the object described above with regard to the device or the use in that the device comprises a mixing chamber for mixing the thickener precursors and a stirred reactor. The mixing chamber preferably has a shearing element and at least two metering inlets for metering the thickener precursors. The mixing chamber is preferably connected to the stirred reactor via a line. The stirred reactor preferably has a stirrer. Furthermore, the stirred reactor preferably has a cooling jacket which is designed to cool the stirred reactor. According to one embodiment, the stirred reactor is connected to the mixing chamber via a connection.

[0076] The device and its use utilize the same advantages and preferred embodiments as the method according to the invention, and vice versa. In this regard, reference is made to the above statements, and their content is incorporated herein.

[0077] A further aspect of the present invention is the provision of a polyurea-thickened lubricating grease, preferably obtained or obtainable by a process according to one of the preceding embodiments, comprising a) 55 to 95% by weight, preferably 70 to 90% by weight, of base oil; b) 1 to 20% by weight, preferably 1.5 to 15% by weight, of polyurea thickener; and optionally at least one further component c) 0.5% by weight to 40% by weight, preferably 2 to 10% by weight, of additives; d) 0 to 20% by weight, preferably 0 to 5% by weight, of inorganic thickeners, preferably silicon oxide; f) 0 to 20% by weight, preferably 0.1 to 15% by weight, of solid lubricants; g) 0 to 20% by weight, in particular 1 to 15% by weight, of further organic thickeners, preferably soap or complex soap thickeners based on calcium, lithium or aluminum soaps. h) 1 to 15 wt.% lignin derivatives, wherein the polyurea-thickened lubricating grease is substantially free of biuret. Biuret forms as an undesirable by-product, e.g.as biuret oligomers in the reaction of free and / or partially reacted isocyanates with amines. This is undesirable because it can lead to reduced thickening performance and increased thermal and oxidative aging of lubricating greases. Furthermore, biuret can dissociate during the process, resulting in a free amine group. As already described above, free amines formed during temperature-induced dissociation of the urea group can lead to increased plastic and / or elastomer intolerance and skin intolerance. Free amines can also cause an increased odor nuisance. Free amines also pose a toxicological health risk to users.

[0078] “Substantially free from” in the context of the present invention means values ​​for certain substances which are present below the detection limit or in an amount of not more than 2000 ppm, preferably 1000 ppm, particularly preferably 500 ppm.

[0079] The polyurea-thickened lubricating grease according to the invention preferably has a cone penetration value of 200 to 400 mm / 10, preferably of 265 to 385 mm / 10, determined according to DIN ISO 2137.

[0080] The penetration of a lubricating grease is the penetration depth - measured in 0.1 mm - of a standard cone under defined conditions.

[0081] It is preferred if a soap or complex soap thickener is present as component g) in the polyurea-thickened lubricating grease. If this is the case, the soap or complex soap thickener is added, for example, after preparation of the base grease during the cooling curve at a suitable temperature (e.g., at 140 to 115°C, the soap or complex soap thickener, in particular calcium soap or calcium complex soap, is added).

[0082] To produce the base grease, heating is preferably carried out at temperatures above 100°C, or more preferably above 130°C. The heating takes place after the thickener precursors have reacted to form the lubricating grease intermediate. The conversion to the base grease takes place in a heated reactor, which can also be designed as an autoclave or vacuum reactor.

[0083] Subsequently, in a second step, the formation of the thickener structure is completed by cooling, and if necessary, additional components such as additives and / or base oil are added to adjust the desired consistency or property profile. The second step can be carried out in the reactor used for the first step, but preferably the base oil is transferred from the reactor to a separate stirred tank for cooling and mixing in any additional components.

[0084] The invention is described in more detail below using a preferred embodiment with reference to the attached figure.

[0085] Fig. 1 shows an exemplary embodiment of a plant 2 for the process according to the invention and the use according to the invention. The plant 2 has a mixing chamber 16 for mixing the thickener precursors and a stirred reactor 11. The mixing chamber 16 has a shearing element 17 and metering inlets 18 for metering the thickener precursors. The figure shows four separate metering inlets AD by way of example, although three inlets are sufficient for the process proposed here. The mixing chamber 16 is connected to the stirred reactor 11 via a line 13. The stirred reactor 11 has a stirrer 12 and a cooling jacket 14. The stirred reactor 11 is connected to the mixing chamber 16 via a connection 15.

[0086] The mixing chamber 16 has the shearing element 17, wherein the shearing element 17 - as shown - can be designed as a rotating shearing element 17 or as a rotor-rotor shearing device, rotor-stator shearing device, rotor-stator-rotor shearing device, high-pressure injection chamber, static mixer, extruder, in particular screw extruder or as a pump unit / pump.

[0087] With reference to Fig. 1, the process according to the invention can be described as follows: The first thickener precursor and the second thickener precursor are metered into the mixing chamber 16 via metering inlets 18, for example, metering inlets A and B. The thickener precursors are mixed in the mixing chamber 16 while reacting the thickener precursors and are sheared by means of the shearing element 17. Optionally, an additive can be metered into the mixing chamber 16, for example, via the metering inlet C. At least one of the thickener precursors and / or the additive are added according to the invention at a temperature in a range from 0 °C to below 40 °C. The mixture can be transferred via line 13 into the stirred reactor 13 and stirred there by means of the stirrer 12. Furthermore, the fluid contained in the stirred reactor 11 can be cooled by means of the cooling jacket 14. The fluid can be transferred from the stirred reactor 11 into the mixing zone 16 via the connection 15.In order to obtain the polyurea-thickened lubricating grease from the polyurea-thickened lubricating grease intermediate, the intermediate is preferably heated in the stirred reactor 11 to a temperature of above 100 °C with stirring, then cooled and finally the polyurea-thickened lubricating grease is obtained.

Claims

Claims 1. A process for producing a polyurea-thickened lubricating grease intermediate, consisting of or comprising the following steps: a) providing at least one first thickener precursor; b) providing at least one second thickener precursor; c) dosing the thickener precursors provided from steps a) and b) into a mixing chamber, optionally adding at least one additive; d) mixing the at least two thickener precursors and the optionally at least one further additive in the mixing chamber and reacting the two thickener precursors; e) obtaining at least one polyurea-thickened lubricating grease intermediate; wherein, to achieve cooling during the reaction in step d), at least one of the thickener precursors provided in steps a) and b) and / or the at least one additive from step c) has a temperature in a range from 0°C to below 40°C, preferably in a range from 10°C to below 40°C.

2. The process according to claim 1, wherein the first thickener precursor provided in step a) is selected from the group consisting of primary amines, preferably monoaminohydrocarbyl, di- or polyaminohydrocarbylene compounds having 6 to 20 carbon atoms or alcohols having hydrocarbyl or hydrocarbylene groups having 6 to 20 carbon atoms, or mixtures of the above, wherein the first thickener precursor is present as a pure substance or as a mixture with at least one base oil.

3. The process according to claim 1 or 2, wherein the at least second thickener precursor provided in step b) is selected from the group consisting of: isocyanates, preferably mono- and / or polyisocyanates having 5 to 20, particularly preferably 6 to 15 carbon atoms, or mixtures of the above, wherein the second thickener precursor is present as a pure substance or as a mixture with at least one base oil.

4. A process according to any one of the preceding claims, wherein the at least one additive is selected from the group consisting of base oils, volatile hydrocarbons, refrigerated or liquefied gases, amines, alcohols, isocyanates, antioxidants, wear inhibitors, corrosion inhibitors, detergents, dyes, lubricity improvers, adhesion improvers, viscosity additives, friction reducers, extreme pressure additives and metal deactivators, simple and / or complex soaps, preferably present as lithium, sodium, magnesium, calcium, aluminum or titanium soaps, water or mixtures thereof.

5. A process according to any one of the preceding claims, wherein cooling of the reaction in step d) is further achieved by adding evaporating or sublimating components as additives in step c).

6. Process according to one of the preceding claims, wherein the base oil has a kinematic viscosity of 12 to 2500 mm2 / s, preferably 30 to 500 mm2 / s at a temperature of 40 °C.

7. A process according to any one of the preceding claims, wherein the mixing in step d) takes place in the mixing chamber under shear.

8. The method according to claim 7, wherein the shearing is carried out at a shear rate of at least 10 2 1 / s, preferably with a maximum shear rate of 10 7 1 / s , particularly preferably in a range of at least 10 2 1 / s up to a maximum of 10 6 1 / s.

9. A method according to claim 7 or 8, wherein the shearing is carried out by means of at least one of the following: Rotor-rotor shearing device, Rotor-stator shearing device, Rotor-stator-rotor shearing device, high-pressure injection chamber, Static mixer, Extruder, especially screw extruder, pump unit / pump.

10. A process for producing a polyurea-thickened lubricating grease, consisting of or comprising the steps according to any one of the preceding claims and additionally the steps: f) heating the intermediate product obtained in step e) to a temperature above 100°C with stirring; g) cooling the heated intermediate product from step f) to a temperature below 100°C, preferably below 80°C; h) obtaining a polyurea-thickened lubricating grease.

11. A process for producing at least one polyurea-thickened lubricating grease intermediate, consisting of or comprising the following steps: a) providing at least one first thickener precursor; b) providing at least one second thickener precursor; c) dosing the thickener precursors provided from steps a) and b) into a mixing chamber, optionally adding at least one additive; d) mixing the at least two thickener precursors and the optionally at least one further additive in the mixing chamber and reacting the two thickener precursors; e) obtaining a polyurea-thickened lubricating grease intermediate, wherein pure amine or a mixture of pure amines and / or alcohol is provided as the first thickener precursor.

12. The process according to claim 11, wherein in step a) at least one amine is selected as the first thickener precursor, preferably selected from the group consisting of primary amines, preferably monoaminohydrocarbyl, di- or polyaminohydrocarbylene compounds having 6 to 20 carbon atoms, or mixtures of those mentioned above, and / or wherein in step a) at least one alcohol is selected as the first thickener precursor, preferably selected from the group consisting of alcohols with hydrocarbyl or hydrocarbylene groups having 6 to 20 carbon atoms, or mixtures of those mentioned above, and wherein the second thickener precursor provided in step (b) is selected from the group consisting of isocyanates, preferably mono- and / or polyisocyanates having 5 to 20, particularly preferably 6 to 15 carbon atoms, or mixtures of those mentioned above,wherein the first and / or the second thickener precursor is present as a pure substance or as a mixture with at least one base oil., 13. A process for producing a polyurea-thickened lubricating grease, consisting of or comprising the steps according to any one of claims 11 or 12 and additionally the steps: f) heating the intermediate product obtained in step e) to a temperature above 100°C with stirring; g) cooling the heated intermediate product from step f) to a temperature below 100°C, preferably below 80°C; h) obtaining a polyurea-thickened lubricating grease.

14. Use of a device comprising a mixing chamber (16) for mixing the thickener precursors, a stirred reactor (11), wherein the mixing chamber (16) has a shearing element (17) and at least two metering inlets (18) for metering the thickener precursors and is connected to the stirred reactor via a line (13), in particular wherein the stirred reactor (11) has a stirrer (12) and a cooling jacket (14) and is optionally connected to the mixing zone (16) via a connection (15), for producing a polyurea-thickened lubricating grease (10) or a polyurea-thickened lubricating grease intermediate using a process according to one of the preceding claims.

15. Polyurea-thickened lubricating grease, preferably obtained or obtainable by a process according to one of the preceding claims, comprising a) 55 to 95% by weight, preferably 70 to 90% by weight, base oil; b) 1 to 20% by weight, preferably 1.5 to 15% by weight, polyurea thickener; and optionally at least one further component c) 0.5% by weight to 40% by weight, preferably 2 to 10% by weight, additives; d) 0 to 20% by weight, preferably 0 to 5% by weight, inorganic thickeners, preferably silicon oxide; f) 0 to 20% by weight, preferably 0.1 to 15% by weight, solid lubricants; g) 0 to 20% by weight, in particular 1 to 15% by weight, of further organic thickeners, preferably soap or complex soap thickeners based on calcium, lithium or aluminum soaps, h) 1 to 15% by weight of lignin derivatives, wherein the polyurea-thickened lubricating grease is substantially free of biuret.

16. Polyurea-thickened lubricating grease according to claim 15, wherein the polyurea-thickened lubricating grease has a cone penetration value of 200 to 400 mm / 10, preferably in the range of 265 to 385 mm / 10, determined according to DIN ISO 2137.

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