Carbonate-containing polyurea lubricating grease and its use

Abstract

The present invention relates to a polyurea lubricating grease composition comprising a polyurea thickener and at least one organic carbonate, lubricating points or parts comprising the polyurea lubricating grease composition, seals comprising sealing materials from fluorinated elastomers and uses of the lubricating grease.

Description

[Technical Field]

[0001] The object of the present invention is a polyurea lubricating grease composition comprising a polyurea thickener and at least one organic carbonate, a lubrication point or component each comprising a polyurea lubricating grease component and a seal comprising a fluorinated elastomer sealing material, and the use of the lubricating grease. [Background technology]

[0002] Tribosystems are used in many technical fields, where it is important to use lubricants to reduce friction and wear at the contact surfaces of moving parts. Depending on the application, lubricants of different viscosities can be used. Lubricating oils have a liquid, flowable viscosity, while lubricating greases have a semi-solid to solid, often gel-like, viscosity.

[0003] Lubricating greases are characterized by the fact that the liquid oil component is incorporated and held by the thickener component. The pasty nature and the tendency to stretch and plastically deform, together with the adhesive properties, of the lubricating grease ensure that the lubricating grease wets the lubrication points and that the lubricating effect occurs on surfaces subjected to tribological stress. In addition to additives, lubricating greases basically contain a thickener dispersed in a base oil.

[0004] The most important rheological properties of lubricating greases are viscosity or yield point, avoidance of post-hardening and excessive oil separation under thermal and mechanical stress, and stable viscosity-temperature and viscosity-shear behavior. High practicality is required to create a lubricating grease with high usability depending on the application.

[0005] Lubricating greases are often used in encapsulated or sealed environments to protect the lubrication points from water, minimize loss of lubricating grease, and prevent the ingress of particles such as sand and dust. Typical applications for lubricating greases are the lubrication of ball bearings, plain bearings, gearboxes, or constant velocity drive shafts.

[0006] Polyurea lubricating greases are often used for lubrication points exposed to high temperatures and / or harsh environments. When seals are used under these conditions, the seal selection often relies on fluorinated elastomers, which are particularly thermally and chemically resilient. The tendency of fluorinated elastomers to harden and become brittle in the presence of polyurea lubricants often limits the availability of such lubricant / seal combinations.

[0007] Various additives have already been proposed to improve compatibility with fluorinated elastomers, for example, in EP 0 562 062, WO 2012 / 082285, U.S. Pat. No. 10,106,759, U.S. Pat. No. 10,066,186, U.S. Pat. No. 10,106,759, U.S. Pat. App. No. 2015 / 0291906, U.S. Pat. No. 10,066,186, U.S. Pat. App. No. 2016 / 0002560, and EP 3,374,479.

[0008] Carbonates such as ethylene carbonate (CN107903987) or propylene carbonate (US4298481) are known as lubricating oil activators / dispersants for inorganic thickeners, but are not known as additives for polyurea thickeners. Summary of the Invention [Problem to be solved by the invention]

[0009] The object of the present invention is to improve the useful properties of polyurea lubricating greases, such as viscosity, shear stability and service life, which lubricating greases are in particular not post-cured or only post-cured as little as possible, respectively. Furthermore, for use as sealing materials, polyurea lubricating greases should be provided which have improved compatibility with fluorinated elastomers, and which lubricating greases whose useful properties are not adversely affected by possible additives for increasing compatibility with fluorinated elastomers. [Means for solving the problem]

[0010] This object is solved by the subject matter of the independent claims. Preferred embodiments are the subject matter of the dependent claims or are described below.

[0011] The polyurea grease composition according to the present invention has the following composition: a) a base oil (optionally including a base oil mixture) in an amount of 55 to 95% by weight, preferably 70 to 90% by weight; b) at least one polyurea thickener in an amount of 1 to 20% by weight, preferably 1.5 to 15% by weight; c) at least one inorganic carbonate, where the organic carbonate contains 4 to 8 carbon atoms in an amount of 0.1 to 10% by weight, preferably 0.2 to 5% by weight, particularly preferably 0.5 to 2% by weight.

[0012] Beyond c), further additives may be used, such as: d) at least one additive, preferably in an amount of 0.5 to 40% by weight, in particular 2 to 10% by weight.

[0013] The polyurea grease composition optionally further contains 1 to 20 wt. %, preferably 1 to 15 wt. %, of a thickener based on soap and / or complex soap thickener.

[0014] In this case, the mixed grease containing the polyurea thickener and the soap and / or complex soap thickener is also referred to as a polyurea grease composition.

[0015] The terms polyurea grease composition and polyurea grease are used synonymously below.

[0016] The base oil is a general lubricating oil that is liquid at room temperature. In any case, the base oil preferably has a viscosity of 20 to 2500 mm at 40°C. 2 / s, especially 40-500mm 2 / s kinematic viscosity.

[0017] Base oils can be classified as mineral or synthetic. For example, naphthenic and paraffinic mineral oils are considered mineral oils when classified according to API Group I. Chemically modified low-aromatic and low-sulfur mineral oils, which have a low proportion of saturates and improved viscosity / temperature behavior compared to Group I oils classified according to API Groups II and III, are also suitable.

[0018] Particularly, synthetic oils include polyethers, esters, polyalphaolefins, polyglycols, alkylaromatics and mixtures thereof, and silicone oils. Polyether compounds may have free hydroxyl groups, but may also be fully etherified or end-etherified, and / or may be prepared from starting compounds having one or more hydroxyl and / or carboxyl (—COOH) groups. Optionally, alkylated polyphenyl ethers are also possible, either as a single component or, more preferably, as a mixed component. Esters of aromatic di-, tri-, or tetracarboxylic acids with one or more C2-C22 alcohols; esters of adipic acid, sebacic acid, trimethylolpropane, neopentyl glycol, pentaerythritol, or dipentaerythritol with aliphatic branched or unbranched, saturated or unsaturated C2-C22 carbonic acids; C18 dimer acid esters with C2-C22 alcohols; and complex esters, either individually or in any mixture, may be suitably used.

[0019] Polyurea thickeners are organic thickening systems, which may be obtained by converting one or more amine components with one or more isocyanate components.

[0020] The extractives for producing polyurea thickeners / thickeners are primary amines and isocyanates.

[0021] The amines are monoamine hydrocarbyl, diamine, or polyamine hydrocarbylene compounds. The hydrocarbyl or hydrocarbylene groups each preferably have 6 to 20 carbon atoms, particularly preferably 6 to 15 carbon atoms. The hydrocarbylene groups preferably have aliphatic groups, in particular alkyl or alkylene groups. Suitable amines or suitable polyureas are described, respectively, in EP 0 508 115 A1, from line 51 on page 1 to the bottom of page 16.

[0022] The isocyanate component is preferably a mono- and / or polyisocyanate, and the polyisocyanate is preferably a hydrocarbon having two isocyanate groups. The isocyanate has 5 to 20, preferably 6 to 15, carbon atoms and preferably contains an aromatic group.

[0023] The amine component may be monofunctional, difunctional, or polyfunctional, and the isocyanate component may be monofunctional, difunctional, or polyfunctional, or both.

[0024] According to one embodiment, polyurea thickeners are available as reaction products of diisocyanates and C6-C20 hydrocarbyl monoamines. However, reaction products of monoisocyanates, optionally with additional diisocyanates, can be present along with the diamine. Polyurea thickeners typically do not have polymeric properties and are, for example, dimers, trimers, or tetramers. Thus, in addition to polyisocyanates, isocyanates of the R-NCO (monoisocyanate) type can also be used, where R preferably represents a hydrocarbon group having 5 to 20 carbon atoms.

[0025] Preferred are diureas obtainable from diisocyanates and monoamines, or tetraureas obtainable from diisocyanates, monoamines and diamines, in each case as defined above. Particularly preferred are - 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 mono- and diamines.

[0026] The polyurea thickener is preferably prepared by reacting in situ an amine component and an isocyanate component in the base oil.

[0027] Bentonites such as montmorillonite (wherein the sodium ions are optionally substituted or partially substituted, respectively, by organically modified ammonium ions), aluminosilicates, aluminum oxide, hydrophobic and hydrophilic silicic acids may additionally be used as optional inorganic thickeners, optionally together with oil-soluble polymers (e.g. polyolefins, poly(meth)acrylates, polyisobutylene, polybutene or polystyrene copolymers) as co-thickeners.

[0028] Bentonite, aluminosilicates, aluminum oxide, silicic acid, amorphous silicon dioxide and / or oil-soluble polymers can be added for the preparation of the base grease or can be added later as additives in a second step. Inorganic thickeners, in particular bentonite, aluminosilicates, aluminum oxide, silicic acid and amorphous silicon dioxide, are preferably not used individually in any case.

[0029] Soap or complex soap thickeners based on calcium, lithium, or aluminum salts are particularly suitable as organic thickeners. Soaps are available, for example, as conversion products of calcium hydroxide, lithium hydroxide, or aluminum alcoholates with saturated or unsaturated monocarboxylic acids, for example, having 10 to 32 carbon atoms, especially 16 to 20 carbon atoms, optionally substituted, for example, as hydroxyl groups, esters, or anhydrides. Esterified dicarboxylic acid semiamides (C12-C24) based on terephthalic acid can also be used. In this case, the corresponding greases are also called soap thickeners. The presence of a complexing agent converts the soap into a complex soap. Suitable complexing agents are: (a) saturated or unsaturated monocarboxylic acids, hydroxycarboxylic acids having 2 to 8, especially 2 to 4, carbon atoms or dicarboxylic acids having 2 to 16, especially 2 to 12, carbon atoms, in each case substituted with alkali salts (preferably lithium salts), alkaline earth salts (preferably calcium salts) or aluminum salts, and / or (b) alkali or alkaline earth salts of boronic acids and / or phosphorous acids, in particular their conversion products with LiOH and / or Ca(OH)2.

[0030] Simple, mixed or complex soaps based on Li, Na, Mg, Ca, Al, Ti salts and carboxylic or sulfonic acids can be added as additives during or after the preparation of the base grease, or these soaps can be formed in situ during the preparation of the grease.

[0031] Aluminum hydroxybenzoate stearate can be used, for example, to prepare aluminum complex soap-thickened lubricating greases. Lithium 12-hydroxystearate thickeners are typical representatives of lithium soap greases, while calcium 12-hydroxystearate is typical of calcium soap greases.

[0032] According to a preferred alternative, polyurea thickeners and soap or complex soap thickeners are used together, with Ca soap or Ca complex soap, respectively, being particularly preferred in a mixing ratio of, for example, 10:1 to 1:10, in particular 5:1 to 1:5 (in each case by weight:weight).The soap or complex soap thickener and polyurea thickener are then preferably used in combination in an amount of 5 to 25% by weight, with respect to the polyurea grease composition according to claim 1, with at least 1% by weight, preferably at least 1.5% by weight, of polyurea thickener being used in each case, based on the polyurea grease composition.

[0033] Examples of solid lubricants that can be used include polymer powders such as polyamide, polyimide, or PTFE, melamine cyanurate, graphite, metal oxides, boron nitride, silicates such as magnesium silicate hydrate (talc), metal sulfides such as sodium tetraborate, potassium tetraborate, molybdenum sulfide, tungsten sulfide, or mixed sulfides based on tungsten, molybdenum, bismuth, tin, and zinc, and inorganic salts of alkali metals and alkaline earth metals such as calcium carbonate, sodium, and calcium phosphate.Other carbon-based solid lubricants such as carbon black or nanotubes can also be used.

[0034] Similarly, lignin derivatives such as alkali or alkaline earth lignin sulfonates, especially calcium lignin sulfonate, can be used to achieve specific properties, for example 2-15 wt. % (according to WO 2011 / 095155 or US Pat. No. 8,507,421).

[0035] In the context of the present invention, it has surprisingly been found that the addition of the claimed organic carbonates improves the useful properties of the polyurea lubricating greases according to the invention, and that the use of organic carbonates improves the compatibility of the polyurea lubricating greases with fluorinated elastomers.

[0036] The organic carbonate has 4 to 8 carbon atoms. The radical or component of the organic carbonate (apart from the carbonate group itself) is hydrocarbon, i.e., the organic carbonate is not substituted with heteroatoms.

[0037] Cyclic carbonates having 4 to 8 carbon atoms, especially 4 or 5 carbon atoms, are preferred. Examples include diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, diisopropyl carbonate, dibutyl carbonate, and diisobutyl carbonate. Examples of cyclic organic carbonates that can be used include propylene carbonate (4-methyl-1,3-dioxolan-2-one), 2,3-butylene carbonate (4,5-dimethyl-1,3-dioxolan-2-one), 1,2-butylene carbonate (4-ethyl-1,3-dioxolan-2-one), hexahydro-1,3-benzodioxol-2-one, and 1,3-benzodioxol-2-one, with propylene carbonate being preferred.

[0038] The organic cyclic carbonate may be added as an additive during the manufacture of the polyurea grease, but preferably after the thickener system has been fully formed during the cooling stage.

[0039] Furthermore, the lubricating grease composition according to the invention comprises conventional additives for protection against the effects of metals, acting as anticorrosion, antioxidants and chelating compounds, free radical scavengers, reaction layer formers, etc. Additives such as carbodiimides or epoxides which improve the resistance of the ester base oil to hydrolysis may also be added.

[0040] Typical additives within the scope of the present invention are antioxidants, wear protectants, anticorrosive agents, detergents, dyes, lubrication promoters, adhesion promoters, viscosity additives, friction reducers, high pressure additives and metal deactivators. Mention may be made by way of example of the following: primary antioxidants, such as amine compounds (e.g., alkylamines or 1-phenylaminonaphthalene), aromatic amines such as phenylnaphthylamine or diphenylamine, or polymeric hydroxyquinolines (e.g., TMQ), phenolic compounds (e.g., 2,6-di-tert-butyl-4-methylphenol), zinc dithiocarbamate, or zinc dithiophosphate; secondary antioxidants, such as phosphites, for example tris(2,4-di-tert-butylphenyl phosphite) or bis(2,4-di-tert-butylphenyl)-pentaerythritol diphosphite or thioethers (for example cresol thioether); High pressure and / or wear protection additives, for example sulfur or organic sulfur compounds, such as polysulfides or sulfurized olefins, overbased calcium sulfonates, thiophosphates, phosphorus compounds, such as amine-neutralized alkyl phosphates, etc.; Inorganic or organic boron compounds, zinc dialkyldithiophosphates, organic bismuth compounds; thiophosphonates such as triphenylthiophosphate, phosphonates (phosphites) such as dioctylphosphonate, alkylsulfonates, thiocarbamates such as methylene-bis(dibutylthiocarbamate), dithiocarbamates; Active ingredients that improve "oiliness," such as C2-C6 polyols, fatty acids, fatty acid esters, or animal or vegetable oils; Corrosion inhibitors, such as petroleum sulfonates, dinonylnaphthalene sulfonates or sorbitan esters; neutral or overbased calcium sulfonates, magnesium sulfonates, sodium sulfonates, calcium and sodium naphthalene sulfonates, sulfonic acid esters, disodium sebacate, calcium salicylate, amine phosphates, succinates, etc.; Metal deactivators, such as benzotriazoles such as methylbenzotriazodialkylamines, sterically hindered phenols, sodium nitrite, etc.; Viscosity enhancers, such as polymethacrylates, polyisobutylenes, oligo-dec-1-enes, polystyrenes, etc.; Friction reducers with partial antiwear properties, such as organomolybdenum complexes (OMC), molybdenum-di-alkyl-dithiophosphates, molybdenum-di-alkyl-dithiocarbamates, in particular molybdenum-di-n-butyl-dithiocarbamate and molybdenum-di-alkyl-dithiocarbamates (Mo 2m S n (dialkyldithiocarbamate)2 (m=0-3 and n=4-1), zinc dithiocarbamate or zinc dithiophosphate, etc.; or trinuclear molybdenum compounds corresponding to the following formula: Mo3S k L n Q z where L represents an independently selected ligand, the ligand comprising an organic group having carbon atoms to render the compound soluble or dispersible in oil, as disclosed in U.S. Pat. No. 6,172,013; n is 1 to 4; k is 4 to 7; Q is selected from the group of neutral electron donor compounds consisting of amines, alcohols, phosphines, and ethers; and z is 0 to 5, including non-stoichiometric values (see German Patent Application Publication No. DE 102007048091); organic acids such as isostearic acid; functional polymers such as oleylamide; organic compounds based on polyethers and amides, such as alkyl polyethylene glycol tetradecylene glycol ether, PIBSI (polyisobutylene succinimide) or PIBSA (polyisobutylene anhydride); partial glycerides; dialkyl hydrogen phosphonates; alkyl succinic acids; and the like.

[0041] The polyurea grease compositions of the present invention have, in particular, the following structure: a) 55 to 95% by weight, in particular 70 to 90% by weight, of a base oil; b) 1 to 20% by weight, in particular 1.5 to 15% by weight, of a polyurea thickener; c) 0.1 to 10% by weight, in particular 0.2 to 5% by weight, particularly preferably 0.5 to 2% by weight, of an organic carbonate; and the following optional ingredients: d) 0.5 to 40% by weight, in particular 2 to 10% by weight, of additives; e) 0 to 20% by weight, in particular 0 to 5% by weight, of an inorganic thickener such as amorphous SiO2 or silicic acid; and f) 0 to 20% by weight, in particular 0.1 to 15% by weight, of a solid lubricant; g) 0 to 20% by weight, in particular 1 to 15% by weight, of a further organic thickener based on calcium, lithium or aluminum soap, in particular a soap or complex soap thickener; Additionally, possible further components such as lignin derivatives.

[0042] The weight percentages refer to the total composition and are applied independently in each case. A component assigned to group a), b), c), or d) cannot simultaneously be a component of another group a) to d). The weight percentages of each component, including any optional components not listed above, add up to 100%.

[0043] The thickener is used in particular so that the composition contains so much thickener that a cone penetration value (worked penetration) of 220 to 430 mm / 10 (25°C), preferably 265 to 385 mm / 10 (determined according to DIN ISO 2137) is obtained.

[0044] The polyurea in the polyurea grease composition is generally produced by reacting the above-mentioned amines with isocyanates, preferably in situ in the base oil.

[0045] According to the method for producing a polyurea grease composition on which the present invention is based, First, a precursor (base grease) is formed by combining at least a base oil, an amine component, and an isocyanate component; - Heating at a temperature above 120°C, particularly above 150°C to produce a base grease; - Cool the base grease, preferably below 100°C, even below 80°C, and add the additives.

[0046] If further thickening components are added to the polyurea base grease, such as soap or complex soap thickeners, this can be done, for example, after preparation of the base grease, during the cooling curve at an appropriate temperature (e.g. adding the soap or complex soap thickener, in particular Ca soap or Ca complex soap, respectively, at 140-115°C).

[0047] To produce the base grease, it is heated to a temperature above 120° C., preferably above 150° C. The conversion to the base grease is carried out in a heated reactor, which may also be configured as an autoclave or a vacuum reactor.

[0048] The formation of the thickener structure is then completed in a second step by cooling, and further components such as additives and / or base oils are optionally added to set the desired viscosity or desired property profile. The second step can be carried out in the reactor of the first step, but the base grease is preferably transferred from the reactor to a separate stirred tank for cooling and mixing of any further components.

[0049] The application of the present invention to pure polyurea greases can also be extended to mixed thickener systems containing polyurea thickener moieties. The preparation of polyurea greases containing lime soap moieties (simple and complex soaps of hydroxymonocarboxylic acids, e.g., 12-hydroxystearic acid) is disclosed, for example, in U.S. Pat. No. 5,084,193. The method of U.S. Pat. No. 5,084,193 can also be used to prepare the polyurea greases of the present invention.

[0050] The lubricating greases according to the invention are particularly suitable for use in or for plain bearings, ball bearings, gearboxes or also constant velocity drive shafts. Lubricating greases according to the invention which comprise primarily polyurea thickeners as thickeners are particularly suitable as high temperature greases.

[0051] A particular aspect of the present invention is to provide a lubricating grease that is compatible with seals made from fluorinated elastomers, which, due to their exceptional resistance to heat, weather conditions, and many chemicals, are often the seals of choice for a wide variety of constructions, depending on the conditions of use, such as high temperatures and / or chemically aggressive media.

[0052] Fluororubber (often abbreviated as FKM or FPM) belongs to a type of fluorinated elastomer. Crosslinking, such as diamine crosslinking, bisphenol crosslinking, or peroxide crosslinking, is used as a function of the desired fluoroelastomer properties. Rubbers that share vinylidene (di)fluoride (VDF) as one of the monomers are called fluororubbers. The two most important types of fluororubbers are copolymers of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) and copolymers of VDF, HFP, and tetrafluoroethylene (TFE). Representative commercial products of fluororubbers are sold under the trademarks Viton®, Tecnoflon®, Dyneon®, or Dai-El®.

[0053] Furthermore, there are polymers of VDF, HFP, TFE and perfluoromethylvinylether (PMVE), polymers of VDF, TFE and propylene and polymers of VDF, HFP, TFE, PMVE and ethers.

[0054] In addition to fluororubbers there is also the group of fluorinated elastomers, such as perfluororubbers (FFKM), tetrafluoroethylene / propylene rubbers (FEPM) and fluorinated silicone rubbers (FVMQ).

[0055] The seals are used in the form of or as part of seals at lubrication points where polyurea grease is used. Seals are a distinct class of important structural elements.

[0056] In principle, there is a distinction between static and dynamic sealing points. In particular, in the case of moving parts, seals are often called dynamic sealing points, since they require lubrication. However, examples of static seals also include static housing seals, for example to prevent leakage in gearboxes.

[0057] The seals are formed, for example, as O-rings or profile rings, radial shaft seals, sliding ring seals, gland seals, flat seals, lip seals, wipers, sealing cords, etc. Examples of applications include radial shaft seals for generator shafts, gland seals for pumps, sliding ring seals for chemical reactors and bead mills (stirrer shaft seals), shaft seals for dryers, screw conveyors and conveyor belts, sealing elements for hydraulic and pneumatic systems (presses, construction vehicles, etc.), and seals for ball bearings and plain bearings. [Example]

[0058] The present invention is described below by way of examples, but is not limited thereto. Details of the examples and properties of the lubricating greases are set out in Tables 1 to 5 below.

[0059] Example 1: Production of greases B1-A to B1-C A heatable reactor containing a stirrer was charged with 630 g of Group II oil (hard, hydrogenated, paraffinic; 105-110 cSt at 40°C). To this was added 113.4 g of 4,4-methylene-bis-diphenyl diisocyanate, and the contents of the reactor were heated to 60°C with stirring. A heatable reactor containing a stirrer was charged with 630 g of PAO 8, and 87.6 g of p-toluidine and 9.0 g of cyclohexylamine were added. The contents of the reactor were heated to 60°C. The contents of this reactor were transferred to the reactor where the isocyanate was dissolved. The thickener was formed in an exothermic reaction. The thickener-oil mixture was then heated over a period of 2 hours to a final temperature of 160°C. After the reaction mixture was cooled to a temperature of 100°C, 15.0 g of Irganox L101 and 15.0 g of Irganox L115 were added. The mixture was cooled to 60°C and mixed with the desired amount of propylene carbonate (0-1 wt%). Finally, the lubricating grease was homogenized using a colloid mill.

[0060] [Table 1]

[0061] Example 2: Production of greases B2-A to B2-C A heatable reaction vessel containing a stirrer was charged with 1305.0 g of Group I oil (mineral oil, paraffinic; 110 cSt at 40°C) and 88.5 g of 4,4-methylene-bis-diphenyl diisocyanate. The contents of the reaction vessel were heated to 60°C with stirring. 91.5 g of n-octylamine was then added to the contents of the reaction vessel. An exothermic reaction occurred, accompanied by the formation of a thickener. The reaction mixture was heated with stirring to a final temperature of 160°C within 2 hours and then cooled to 60°C. The desired amount of propylene carbonate (0-1 wt%) was then added, and the grease was finally homogenized using a colloid mill. The properties of the resulting polyurea grease are summarized in Table 2.

[0062] [Table 2]

[0063] Example 3: Production of greases B3-A to B3-C A heatable reaction vessel containing a stirrer was charged with 369.7 g of Group I oil (paraffinic; 480 cSt at 40°C) and 567.2 g of Group II oil (hard, hydrogenated, paraffinic; 105-110 cSt at 40°C).

[0064] To this mixture, 94.2 g of 4,4-methylene-bis-diphenyl diisocyanate was added, and the reaction vessel was heated to 60°C with stirring. Next, a mixture of 37.3 g of cyclohexylamine and 47.8 g of n-octylamine was added, corresponding to the exothermic formation of the thickener. The reaction mixture was heated with stirring to a final temperature of 160°C within 2 hours. Upon reaching a final temperature of 160°C, 300.0 g of Group II oil (hard, hydrogenated, paraffinic; 105-110 cSt at 40°C) was added. The reaction mixture was then cooled to 130°C and 44.8 g of calcium 12-hydroxystearate was added. The temperature of 130°C was maintained for 30 minutes. The reaction mixture was then cooled to 110°C and 7.5 g of a phenolic antioxidant (Irganox L115) and 31.5 g of an inorganic filler were added. After cooling to 60°C, the desired amount of propylene carbonate (0-1 wt%) was added, followed by an additive package consisting of an amine antioxidant, a high-pressure additive, an AW additive, a non-ferrous metal passivator, and a corrosion inhibitor. Finally, the grease was homogenized on a three-roll mill.

[0065] The physical properties of the resulting calcium soap-containing polyurea grease are summarized in Table 3. The dropping point was measured in accordance with DIN ISO 2176.

[0066] [Table 3]

[0067] Measurement of compatibility with fluorinated elastomers The compatibility of polyurea grease with fluorinated elastomers was measured using vinylidene fluoride hexafluoropropylene copolymer (type: SRE-FKM / 2X according to DIN ISO 13226). For this purpose, test specimens with a diameter of 30 mm and a thickness of 2 mm were punched out of elastomer sheets of SRE-FKM / 2X. The test specimens were immersed in the polyurea greases mentioned above at 180 °C or 160 °C for 7 days and then evaluated.

[0068] The fluorinated elastomers were evaluated in the following manner after wiping off the grease with a clean cloth: a) Measurement of indentation hardness (Shore A) according to DIN EN ISO 7619-1, where the test specimens had an indentation hardness (Shore A) of 78 before treatment, and b) Manual bending test. The bending test was carried out by bending the elastomer on pipes with diameters of 3 cm and 1 cm to evaluate the elasticity of the elastomer.

[0069] The stabilizing effect of propylene carbonate was demonstrated in soaking tests: despite high soaking temperatures of 180°C, increasing propylene carbonate content showed no or very little signs of embrittlement.

[0070] When polypropylene carbonate is used in polyurea greases, the fluorinated elastomers tend to cure slowly or not at all. According to the elastomer manufacturers' recommendations, greases that cause a hardness change of significantly more than 10 points in terms of indentation hardness (Shore A) according to DIN EN ISO 7619-1 are considered incompatible with the respective elastomer.

[0071] The results are summarized in Table 4.

[0072] [Table 4]

[0073] Adding 0.5% propylene carbonate to grease B2-B halved the increase in hardness of the FKM elastomer. Adding 1% propylene carbonate (B2-C) reduced the increase to a harmless 3 points in terms of indentation hardness (Shore A) according to DIN EN ISO 7619-1.

[0074] Considering the maximum permissible hardness change of 10 points (Shore A indentation hardness according to DIN EN ISO 7619-1), the comparative grease B3-A shows a slight result (+8). The addition of 0.3% propylene carbonate (B3-B) already pushed the hardness change back into the harmless range. The addition of 1% propylene carbonate (B3-C) barely affected the hardness change of the elastomer.

[0075] Examples 4A and 4B In addition to improving the compatibility of the polyurea grease composition with the fluorinated elastomer, the addition of carbonate may improve useful properties related to shelf life and post-cure behavior.

[0076] A heatable agitator was charged with 875.0 g of Group I oil (paraffinic; 105-110 cSt at 40°C) and 875.0 g of Group II oil (hard, hydrogenated, paraffinic; 105-110 cSt at 40°C). To this oil mixture was added 31.5 g of 4,4-methylene-bis-diphenyl diisocyanate (MDI). The reactor contents were heated with stirring to 55°C. At 55°C, a mixture of 12.5 g of cyclohexylamine and 16.0 g of N-octylamine was slowly metered in. The exothermic reaction of the isocyanate and amine mixture raised the temperature to 72°C. This temperature was held for 30 minutes to complete thickener formation. With constant stirring, the reaction mixture was heated to a final temperature of 160°C within 3 hours. The reactor contents were then cooled to 135°C, and 180.0 g of calcium 12-hydroxystearate was then added. This mixture was stirred at constant temperature for 30 minutes. The batch was cooled to 60°C with further stirring, and 10.0 g of an amine-based antioxidant (Irganox L57) was then added. The base grease batch was then split into Parts A and B. Part B was transferred to a planetary mixer, and 0.5% propylene carbonate was added at 25°C and mixed for 15 minutes.

[0077] Both sub-batches A and B were subsequently homogenized by colloid mill: Example 4A: without propylene carbonate / Example 4B: with 0.5 wt. % propylene carbonate.

[0078] Example 4C A heatable agitator was charged with 875.0 g of Group I oil (paraffinic; 105-110 cSt at 40°C) and 875.0 g of Group II oil (hard, hydrogenated, paraffinic; 105-110 cSt at 40°C). To this oil mixture was added 31.5 g of 4,4-methylenebisdiphenyl diisocyanate (MDI). The reactor contents were heated with stirring to 55°C. At 55°C, a mixture of 12.5 g of cyclohexylamine and 16.0 g of N-octylamine was slowly metered in. The exothermic reaction of the isocyanate and amine mixture caused the temperature to rise to 72°C. This temperature was held for 30 minutes to complete thickener formation. The reaction mixture was heated with constant stirring to a final temperature of 160°C within 3 hours.

[0079] The reactor contents were then cooled to 135°C, after which 180.0 g of calcium 12-hydroxystearate was added. The mixture was stirred at a constant temperature for 30 minutes. At 135°C, 20.0 g (1.0%) of propylene carbonate was added with stirring. The batch was then cooled to 80°C, and 10.0 g of an amine-based antioxidant (Irganox L57) was added. The batch was then ground in a colloid mill. The resulting properties are summarized in Table 5 below.

[0080] [Table 5]

[0081] By adding organic carbonate, a slight viscosity softening is achieved with a worked penetration of WP 60. By adding propylene carbonate, the dropping point of the grease is slightly lowered, but oil separation remains the same.

[0082] At elevated temperatures (100°C) compared to 25°C, significant differences in post-cure behavior can be seen: the static penetration of grease samples stored at 100°C for 24 hours (RP-24h) is significantly reduced compared to those stored for 24 hours at 25°C, and the grease is post-cured (see ΔRP-24h). Adding 1% propylene carbonate reduced this post-cure effect by approximately 30%.

[0083] A similar picture can be observed during post-cure at the worked penetration temperature of WP60 (100°C). It can be seen that by adding 1% propylene carbonate, grease samples stored at 100°C for 24 hours and then cooled to 25°C can completely avoid post-cure during worked penetration of WP60 compared to grease samples stored at 25°C (see WP60-24h value), while greases without propylene carbonate show significant post-cure.

[0084] FE9 testing of the greases revealed further benefits of the organic carbonate: for example greases 4B and 4C, downtime F10 and F50 improved by more than 50% with the addition of propylene carbonate.

Claims

1. a) at least one base oil; b) at least one polyurea thickener; and c) at least one organic carbonate containing from 4 to 8 carbon atoms, a) 55 to 95 wt. % of said base oil; b) 1 to 20% by weight of said polyurea thickener; c) 0.1 to 10% by weight of said organic carbonate.

2. a) 70 to 90 wt. % of said base oil; b) 1.5 to 15 wt. % of said polyurea thickener; c) 0.2 to 5% by weight, particularly preferably 0.5 to 2% by weight, of said organic carbonate.

3. d) 0.5 to 40% by weight, in particular 2 to 10% by weight, of additives; e) 0 to 20% by weight, in particular 0 to 5% by weight, of an inorganic thickener; 3. A polyurea grease composition according to claim 1, further comprising: f) 0 to 20% by weight, in particular 0.1 to 15% by weight, of a solid lubricant.

4. g) 0 to 20% by weight, in particular 1 to 15% by weight, of an organic thickener, in particular a soap or complex soap thickener based on calcium, lithium or aluminum soap, in particular lithium soap.

5. 5. The polyurea grease composition according to any one of claims 1 to 4, which is free of bentonite, aluminosilicates, aluminium oxide, silicic acid and amorphous silicon dioxide, in particular free of inorganic thickeners.

6. A polyurea grease composition according to any one of claims 1 to 5, wherein the organic carbonate is a cyclic carbonate, in particular propylene carbonate.

7. 7. A polyurea grease composition according to any one of claims 1 to 6, characterized in that it comprises a worked penetration cone penetration value, measured according to ISO 2137, of 220 to 430 mm / 10 at 25°C, preferably 265 to 385 mm / 10 at 25°C.

8. The base oil has a kinematic viscosity at 40°C of 20 to 2500 mm ２ / s, preferably 40 to 500 mm ２ The polyurea grease composition according to any one of claims 1 to 7, wherein

9. The polyurea grease composition according to any one of claims 1 to 8, a seal including a sealing material; The sealing material is made of elastic fluororesin, lubrication point.

10. a) at least one lubrication point; b) a seal including a sealing material, the sealing material being made of an elastic fluororesin; and c) the polyurea grease composition of any one of claims 1 to 7 in contact with the lubrication point and the seal.

11. The lubrication point according to claim 9 or the part according to claim 10, wherein the elastic fluororesin is a fluororubber elastomer.

12. Lubrication point according to claim 9 or part according to claim 10, wherein the seal is an O-ring or profile ring, a radial shaft seal, a slide ring seal, a gland seal, a flat seal, a lip seal, a wiper or a sealing cord.

13. The part according to claim 10, wherein the part is a shaft, a gearbox, a piston, a joint, a ball bearing or a plain bearing.

14. Use of a polyurea grease composition according to any one of claims 1 to 7 on a lubrication point or part according to claims 9 to 13.

15. heating at least a portion of the base oil to produce a polyurea; and adding the organic carbonate after the preparation of the polyurea in the base oil during cooling to a temperature of from 100°C to 135°C.

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