METHOD FOR THE PRODUCTION OF LITHIUM COMPLEX SOAPS AND LITHIUM CALCIUM COMPLEX SOAP LUBRICANTS

Description

[0001] The invention relates to a process for producing lithium complex soap lubricating greases or lithium-calcium complex soap lubricating greases and corresponding lubricating greases produced by this process and their use. Introduction and state of the art

[0002] Lithium soaps have long been known as thickeners in lubricating greases. An organic acid, usually a fatty acid, saponified with lithium hydroxide is used as a thickener in a base oil. A common thickener is 12-hydroxystearic acid, for example, with lithium 12-hydroxystearate. Greases based on lithium soaps are referred to as (simple) lithium soap lubricating greases.

[0003] In contrast, the production of lithium complex soap greases is based on a thickener produced by reacting lithium hydroxide with a fatty acid and a complexing agent. Here, too, a long-chain hydroxy fatty acid is often the fatty acid of choice, while the complexing agent is a shorter-chain dicarboxylic acid. Greases based on lithium complex soaps as thickeners are characterized by high dropping points, good water resistance, and wide operating temperature ranges.

[0004] The idea here is that the mutual, interacting combination of both soaps—the lithium salt of the hydroxy fatty acid and the dicarboxylic acid—creates a soap compound stabilized by hydrogen bonds. The often shorter-chain dicarboxylic acids or dicarboxylic acid salts can act as "bridge builders" to create bonding forces between the mostly long-chain fatty acid soap molecules. This leads to an increase in the dropping point beyond the usual level of a "simple" lithium soap (e.g., a maximum of 190°C - 210°C), because additional bonding forces must be overcome during melting. Lithium complex soap greases can exhibit dropping points significantly higher than 250°C. Raw materials often used are 12-hydroxystearic acid, lithium hydroxide or a solution / slurry of lithium hydroxide and aliphatic dicarboxylic acids such as adipic acid (C6), azelaic acid (C8), sebacic acid (C10) or boric acid.

[0005] Lithium complex soap greases are typically produced by the combined saponification of at least one long-chain hydroxy fatty acid and at least one dicarboxylic acid under heat in the presence of a base oil or base oil mixture. Suitable base oils include paraffinic or naphthenic mineral oils or their mixtures (Group 1 oils), synthetic oils such as polyalphaolefins, polyalkylene glycols, or Group II oils, including mixtures thereof. Silicone oils can also be used as base oils.

[0006] The direct production of lithium complex soaps in ester-based base oils is not possible because the formation of undesirable reaction products competes with the saponification reaction. The lithium soap can also be formed indirectly through saponification of a dicarboxylic acid ester, which in turn can be formed as an intermediate between dicarboxylic acid and alcohol (including polyhydric alcohols). The use of ready-made soaps to circumvent (partial) hydrolysis of the esters used is difficult for the formation of the complex soap structure.

[0007] In prior art manufacturing processes, saponification typically occurs in the base oil. US Patent No. 2,898,296 discloses the production of a lithium complex soap lubricating grease starting from a fatty acid and a dicarboxylic acid soap, which are boiled together in a base oil with LiOH*H2O (monohydrate).

[0008] US 2940930 A describes the production of a lithium complex soap lubricating grease in a batch process, wherein in a first step a polyhydric alcohol such as ethylene glycol is added to a mixture of mono- and dicarboxylic acid in a base oil and this mixture is saponified together with lithium hydroxide in a subsequent step.

[0009] US 4444669 A makes it clear that the manufacturing process can have a significant influence on the achievable dropping point. The lithium complex soap grease is produced by adding a carboxylic acid, a dicarboxylic acid, and an aqueous LiOH solution to the base oil in a continuously operating reactor. For saponification, the temperature is gradually increased to 176°C. The water formed during the saponification reaction is kept in the system by pressurizing it and subsequently removed in a controlled manner. A small amount of water can be introduced into the reaction zone.

[0010] US 3791973 A describes the production of a lithium complex soap lubricating grease with dropping points above 260°C from the sequential reaction of first a hydroxy fatty acid in the base oil with a concentrated aqueous lithium hydroxide solution under hot conditions. Subsequently, after cooling and addition of the aliphatic dicarboxylic acid, this reaction is followed by a concentrated aqueous lithium hydroxide solution and reheating. The temperature regime and the reaction rate of the aliphatic dicarboxylic acid with the base are important here. This results in a mixed soap in which lithium monocarboxylate is linked by the dilithium dicarboxylates.

[0011] EP 2361296 B1 describes the production of a mixed complex grease based on a lithium soap based on a hydroxy fatty acid with the complexing calcium or magnesium soaps based on a dicarboxylic acid via an autoclaving process. The thickener-forming raw materials are combined in a base oil with a small amount of water to initiate the reaction. It is worth noting that the dropping point of mineral oil-based greases is around 220°C, and higher dropping points of up to 260°C can be achieved using polyalkylene glycol base oils.

[0012] If very non-polar base oils such as polyalphaolefins are used, high dropping points above 250°C are difficult to achieve for lithium complex soap greases. This can be explained by the fact that there is no true complex soap in the form of a soap thickener compound formed from the two carboxylic acids. Rather, there is a separate mixture of the two lithium soaps, fatty acids and dicarboxylic acids, which do not interact and are not combined to form a mixed soap compound. The additional interactions between the two lithium soap types that occur in true lithium complex soaps, such as hydrogen bonds, are absent or present only to a small extent. As a result, the dropping point is comparatively lower. To increase the dropping point, dropping point improvers must be used.Dropping point depressants suitable for lithium complex soap greases are often based on alkyl borate esters, the use of which is described, for example, in WO 2016 / 123067 A1.

[0013] US 2010 / 0197535 A1 discloses a process for producing a soap concentrate such as a lithium soap, lithium complex soap, lithium-calcium soap, or calcium complex soap in a reactive extruder, wherein an oil, such as hydrogenated castor oil, and the metal hydroxide or 12-hydroxystearic acid, optionally as a component of the oil, and the metal hydroxide are fed into a first zone, and a complexing agent is fed into a further zone. The first zone is optionally followed by a water injection zone, then the reaction zone, a deaeration zone, and a cooling zone.

[0014] JP H11-302682 A discloses a process for producing a lubricating grease. The process involves reacting an aqueous solution of lithium hydroxide monohydrate and an aliphatic dicarboxylic acid with a homogeneous mixture of base oil and fatty acid or hydroxy fatty acid, and optionally with an additional amount of aliphatic dicarboxylic acid, when heated. The reaction with the dissolved monocarboxylic acid only begins in the presence of the base oil and the dispersing aid. Lithium hydroxide and dicarboxylic acid exist in parallel in water, but a saponification reaction is not induced. The hydroxy fatty acid is not added to the already formed dicarboxylic acid soap.

[0015] US4582619 and US2019 / 300813 describe the production of lithium complex soap lubricating greases from the components LiOH, dicarboxylic acid, and hydroxy fatty acid. For this purpose, both acids are added together to the base oil and then reacted with an aqueous lithium hydroxide solution.

[0016] What all the manufacturing processes described above have in common is that the saponification is carried out in the base oil, which is usually olephilic.

[0017] Manufacturing methods were also described to achieve the formation of a soap compound in the case of mixed soaps, which contains not only lithium soaps but also alkaline earth soaps as complex soaps. Object of the invention

[0018] The object of the invention is to provide a process for the production of lithium complex soap lubricating greases or lithium-calcium complex soap lubricating greases that allows for the simplest and most energy-efficient process possible, as well as safe handling of the raw materials used. High dropping points should also be achieved and additional raw materials should be usable compared to conventional processes, especially with regard to the dicarboxylic acids that can be used. Summary of the invention

[0019] The present invention relates to a process for producing lithium complex soap lubricating greases or lithium-calcium complex soap lubricating greases according to claim 1. It differs from known processes in that the dicarboxylic acid is first saponified with lithium hydroxide and / or calcium hydroxide in bulk as a solid in aqueous solution. After saponification with the hydroxy fatty acid, complex soap lubricating greases are obtained.

[0020] Preferred embodiments are the subject of the subclaims or are shown below.

[0021] The process for producing lithium complex soap greases or lithium-calcium complex soap greases comprises at least the following steps: Saponification of one or more dicarboxylic acids with one or two metal hydroxides as a solid, preferably in powder form, according to one of the following three alternatives: (A1) Saponification with lithium hydroxide, preferably in powder form, and one or more dicarboxylic acids or (A2) Saponification with lithium hydroxide and calcium hydroxide, preferably in powder form, and one or more dicarboxylic acids, or (A3) Saponification with calcium hydroxide, preferably in powder form, and one or more dicarboxylic acids, each in an aqueous environment comprising more than 80 wt.% water with respect to all liquid feedstocks (ieFeed materials which are liquid at 25°C) to obtain one or more metal salts of the dicarboxylic acids, wherein both dicarboxyl groups of the dicarboxylic acids are essentially completely saponified; bringing into contact with one or more liquid or liquefied by heating hydroxy fatty acids and dissolving the metal salt(s) in the liquid hydroxy fatty acid; bringing into contact with base oil; adding further metal hydroxides, wherein according to alternative: (A1) lithium hydroxide or calcium hydroxide; (A2) lithium hydroxide and calcium hydroxide or only lithium hydroxide or only calcium hydroxide; or (A3) lithium hydroxide is added; for saponification with the at least one hydroxy fatty acid; driving off water with heating; heating to a final temperature; and cooling and adding further base oil.

[0022] Preferably, the procedure is carried out in the order described above.

[0023] Preferred embodiments are the subject of the subclaims or described below.

[0024] The aqueous environment is characterized by a liquid phase that, with respect to the substances used that are liquid at 25°C (= 100 wt.%), comprises more than 80 wt.%, in particular more than 90 wt.% water, and preferably consists of 100 wt.% water. If the dicarboxylic acid used is liquid at 25°C, it is not considered a liquid substance within the meaning of this definition.

[0025] According to one embodiment of the invention, a dicarboxylic acid is placed in water or in the aqueous environment, heated (e.g. to 60°C) and then mixed with metal hydroxide (e.g. lithium hydroxide), preferably in powder form, to saponify the dicarboxylic acid as completely as possible, if necessary also slightly overstoichiometrically.

[0026] However, the stoichiometric excess should be limited and in particular the excess should be small, e.g. a) be chosen so that the excess is less than 10 mol%, preferably less than 5 mol% with respect to the subsequently used hydroxy fatty acid or b) alternatively the excess should be less than 10 mol% with respect to the reaction of dicarboxylic acid with the metal hydroxide (e.g. lithium hydroxide).

[0027] Preferably, the reaction is carried out with approximately the same molar amount of metal hydroxide (e.g., lithium hydroxide) relative to the dicarboxylic acid. The metal hydroxides are used to saponify one or more dicarboxylic acids in bulk, as solids, preferably in powder form. This means that they are not dissolved beforehand in another solvent, but rather in the "aqueous environment." Adding the base in powder form offers occupational safety advantages: It avoids the use of hot metal hydroxide solution. The saponification is completed in a very short time.

[0028] The di-lithium dicarboxylate or di-metal dicarboxylate formed may be poorly soluble in water, depending on the dicarboxylic acid used, and in such a case may precipitate as a finely divided salt.

[0029] In the next step, the monohydroxycarboxylic acid is added in its pure form, preferably as a solid, in dry form, and the mixture is heated to, for example, 85°C. The dicarboxylic acid soap dissolves in the molten hydroxycarboxylic acid. At this point, the mixture required to form the complex soap between hydroxycarboxylic acid and dicarboxylic acid or the respective reaction products is already formed. The mixture is then admixed with the required amount of base oil (e.g., 45% by weight of the base oil in the finished lubricating grease), heated to, for example, 90°C, and then mixed with the additional metal hydroxide, such as lithium hydroxide, particularly in powder form, to saponify the hydroxycarboxylic acid. After a certain reaction time, the mixture is initially heated to, for example, 100°C to begin dewatering the mixture, which is then completed at, for example, 105°C after additional base oil has been added (e.g., 30% of the base oil in the finished lubricating grease).

[0030] This reaction initiated the formation of complex soaps in an aqueous medium. Once the complex soap structure was reliably formed, it was converted into an oleophilic base oil. After dehydration, the remaining amount of base oil can be added. The reaction mixture is heated to a final temperature of greater than 120°C or greater than 160°C, preferably greater than 180°C, e.g., to 190 to 210°C. It is then cooled and, during the cooling phase, suitable additives are added to complete the lubricating grease.

[0031] A mixed calcium-lithium complex soap grease can also be produced using the described method. The complexing dicarboxylic acid can be reacted with either lithium hydroxide or calcium hydroxide. The hydroxycarboxylic acid is reacted with the other hydroxide accordingly. A key advantage of mixed lithium-calcium complex soap greases is the lower raw material and process costs. Calcium-lithium complex soap greases are preferably obtained using a lithium hydroxide to calcium hydroxide ratio of 1:9 to 9:1 (by weight).

[0032] A further advantage of the lithium complex soap lubricating greases or calcium-lithium complex soap lubricating greases produced in this way is the preferred option of molar reaction of the metal hydroxides with the dicarboxylic and monohydroxycarboxylic acids. This allows the production of lubricating greases without any unreacted lithium hydroxide components. Since June 2020, an investigation has been underway to determine whether lithium hydroxide should be classified as reprotoxic category 1A - H360 FD (CoRAP list). According to the state of the art, lubricating greases with lithium soap thickeners are often produced with an excess of lithium hydroxide. Due to the poor water solubility of lithium hydroxide, an excess is used to ensure complete conversion of the carboxylic acids used. Detailed description of the invention

[0033] Conventional lubricating oils that are liquid at room temperature are suitable as base oils. The base oil preferably has a kinematic viscosity of 20 to 2500 mm² / s, in particular 40 to 500 mm² / s, in each case at 40 °C. The term "base oil" also includes a mixture of different base oils.

[0034] The base oils can be classified as mineral oils or synthetic oils. Examples of mineral oils considered include naphthenic mineral oils and paraffin-based mineral oils, as classified according to API Group I. Chemically modified mineral oils with low aromatic and sulfur content, low in saturates, and improved viscosity / temperature behavior compared to Group I oils, classified according to API Groups II and III, are also suitable.

[0035] Synthetic oils include 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 made from a starting compound with one or more hydroxyl and / or carboxyl groups (-COOH). Polyphenyl ethers, possibly 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 any mixture.

[0036] Lithium complex soaps are thickeners based on metal soaps, which are obtained by reacting a dicarboxylic acid with lithium hydroxide and a hydroxycarboxylic acid with lithium hydroxide. If, as an alternative to pure lithium complex soap, one wishes to produce a mixed thickener from lithium and calcium complex soap, one reacts a) the dicarboxylic acid with lithium hydroxide and a hydroxycarboxylic acid with calcium hydroxide, or b) the dicarboxylic acid with calcium hydroxide and the hydroxycarboxylic acid with lithium hydroxide.

[0037] Aliphatic dicarboxylic acids with chain lengths from C6 to C12, such as adipic acid (C6), azelaic acid (C8), and sebacic acid (C10), can be used as dicarboxylic acids. Aromatic dicarboxylic acids such as terephthalic acid can also be used. The latter, a rather unusual combination for lithium complex greases, were previously only possible through the detour of separate saponification of corresponding terephthalic acid esters, whereby the alcohol is preferentially removed from the equilibrium.

[0038] Such a thickener system is more easily accessible via the reaction according to the invention in an aqueous medium.

[0039] C12 to C30 hydroxycarboxylic acids or mixtures thereof can be used as hydroxycarboxylic acids, with hydroxycarboxylic acids with 16 to 20 carbon atoms generally being preferred. In particular, hydroxystearic acid is used, for example, as 9-hydroxy, 10-hydroxy, or 12-hydroxystearic acid. Ricinoleic acid, an unsaturated, linear omega-9 fatty acid, can also be used. 12-hydroxybehenic acid (C22) or 10-hydroxypalmitic acid can also be used as hydroxy fatty acids. Dihydroxystearic acids such as 9,10-dihydroxystearic acid can also be used as hydroxy fatty acids. Hydroxycarboxylic acids are monocarboxylic acids.

[0040] The ratio of hydroxycarboxylic acid to dicarboxylic acid is usually adjusted in molar ratios of 1:1 to 10:1. This depends on the desired properties of the fat.

[0041] In addition, the lubricating grease compositions according to the invention contain conventional additives to protect against corrosion, oxidation, and metal influences, which act as chelating agents, radical scavengers, reaction layer formers, and the like. Additives that improve the hydrolysis resistance of ester base oils, such as carbodiimides or epoxides, can also be added.

[0042] Common additives within the meaning of the invention include antioxidants, wear inhibitors, corrosion inhibitors, detergents, dyes, lubricity improvers, adhesion promoters, viscosity additives, friction reducers, high-pressure additives, and metal deactivators. Examples include: 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; 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); Extreme pressure additives and / or anti-wear additives such as sulphur or organic sulphur compounds such as polysulphides or sulphurised olefins, overbased calcium sulphonates, thiophosphates, phosphorus compounds such as amine-neutralised alkyl phosphates, inorganic or organic boron compounds, zinc dialkyldithiophosphate, organic bismuth compounds; thiophosphonates such as triphenylthiophosphate, phosphonates (phosphites) such asDioctyl phosphonate, alkyl sulfonates, thiocarbamates such as methylene-bis(dibutyldithiocarbamates and dithiocarbamates; oiliness-improving agents such as C2 to C6 polyols, fatty acids, fatty acid esters or animal or vegetable oils; anti-corrosion 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; metal deactivators such as benzotriazoles such as methylbenzotriazole dialkylamine, sterically hindered phenols, sodium nitrite; viscosity improvers such asPolymethacrylate, polyisobutylene, oligo-Dec-1-ene, polystyrenes; friction reducers, some with wear protection properties, such as organomolybdenum complexes (OMC), molybdenum dialkyl dithiophosphates, molybdenum dialkyl dithiocarbamates, in particular molybdenum di-n-butyldithiocarbamate and molybdenum dialkyldithiocarbamate (Mo2mSn(dialkylcarbamate)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 Mo 3 S k L n Q z, 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 e.g.is in the range from 0 to 5 and includes non-stoichiometric values ​​(cf. DE 102007048091 A1); organic acids such as isostearic acid, functional polymers such as oleylamides, organic compounds based on polyethers and amides, e.g. alkyl polyethylene glycol tetradecylene glycol ethers, PIBSI or PIBSA, partial glycerides, dialkyl hydrogen phosphonates, alkyl succinates.

[0043] Solid lubricants that can be used include, for example, polymer powders such as 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 of, for example, alkali and alkaline earth metals, such as calcium carbonate, sodium and calcium phosphates, as well as carbon black or other carbon-based solid lubricants such as nanotubes.

[0044] Lignin derivatives, such as alkali or alkaline earth ligninsulfonates, especially calcium ligninsulfonates, can also be used to achieve specific properties (according to WO 2011095155 A1 or US 8507421 B2). Lignin derivatives and solid lubricants are not considered additives.

[0045] The lithium complex soap greases preferably comprise: a) 55 to 95 wt.%, in particular 70 to 90 wt.%, of the base oil; b) 5 to 25 wt.%, in particular 5 to 20 wt.%, of the lithium complex soap as thickener and optionally the following optional components: c) 0 to 40 wt.%, in particular 0.5 to 10 wt.%, of additives; d) 0 to 20 wt.%, in particular 0 to 5 wt.%, of inorganic thickeners, such as bentonite or amorphous SiO 2 or silicic acid; and e) 0 to 20 wt.%, in particular 0.1 to 15 wt.%, of solid lubricants; f) 0 to 5 wt.%, in particular 0.1 to 5 wt.%, of lignin derivatives.

[0046] As an alternative to pure lithium complex soap grease, lithium-calcium complex soap greases contain: a) 55 to 95 wt.%, in particular 70 to 90 wt.%, of the base oil; b) 5 to 25 wt.%, in particular 5 to 20 wt.%, of the lithium-calcium complex soap as thickener, wherein the ratio of lithium and calcium content is freely selectable within a ratio of 90:10 to 10:90, preferably 80:20 to 20:80, based on the metal hydroxides (LiOH and Ca(OH) 2 ), and, where applicable, the following optional components: c) 0 to 40 wt.%, in particular 0.5 to 10 wt.%, additives; d) 0 to 20 wt.%, in particular 0 to 5 wt.%, inorganic thickeners, such as bentonite or amorphous SiO 2 or silica; and e) 0 to 20 wt.%, in particular 0.1 to 15 wt.%, solid lubricants; f) 0 to 5 wt.%, in particular 0.1 to 5 wt.%, lignin derivatives.

[0047] Preferably, no inorganic thickeners are used.

[0048] The wt% values ​​refer to the total composition and apply independently of each other. The wt% values ​​add up to 100 wt% for each selection of components, including any optional components not listed above.

[0049] In particular, the thickener or the soap is used as a thickener in such a way that the composition contains enough thickener to obtain a cone penetration value (worked penetration) of 220 to 430 mm / 10 (at 25°C), preferably 265 to 385 mm / 10 (at 25°C) (determined according to DIN ISO 2137).

[0050] The process is carried out in such a way that the thickener in the lithium complex soap lubricating grease or in the lithium-calcium complex soap lubricating grease is produced by in-situ reaction of the above-mentioned hydroxycarboxylic acids and dicarboxylic acids with lithium hydroxide or lithium and calcium hydroxide, wherein the saponification reaction of the dicarboxylic acid is carried out in an aqueous medium. The salt thus formed is then absorbed by a molten hydroxy fatty acid or a hydroxy fatty acid in its liquid state, followed by conversion into an oily phase. Subsequently, saponification of the hydroxy fatty acid is carried out by adding dry lithium hydroxide or calcium hydroxide in the stoichiometrically required amount. The water is then driven off during the further temperature progression and the reaction mixture is heated to a defined final temperature. After a defined cooling phase, at temperatures of e.g.60° to 80°C usual additives, solids or other base oil components can be added.

[0051] According to the process underlying the present invention for producing lithium complex fatty soap lubricating greases or lithium-calcium complex soap lubricating greases, a precursor (base grease) is first prepared by combining at least the dicarboxylic acid and water with lithium hydroxide or calcium hydroxide at preferably 20° to 85°C, in particular 40° to 70°C, adding the hydroxycarboxylic acid at preferably above 60°C or above 75°C, in particular between greater than 80 and 90°C, a first portion of the base oil and lithium hydroxide or calcium hydroxide at preferably greater than 70°C or greater than 80°C, in particular at 90 to 100°C, boiling out the water at preferably at least 100°C, in particular greater than 100°C or greater than 105°C (expulsion temperature), adding a further portion of base oil and heating to a defined final temperature greater than 120°C, preferably at least 130°C or preferably at least 150°C, e.g. 190 to 210°C, cooling the base grease and adding further oils, additives, solid lubricants or another thickener component.

[0052] To produce the lithium complex base grease, it is preferably heated to temperatures above 180°C, in particular at least 190°C. The conversion to the base grease takes place in a heated reactor, which can also be designed as an autoclave or vacuum reactor.

[0053] 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.

[0054] According to one embodiment, for example, lithium-calcium complex soap lubricating greases are produced by using calcium 12-hydroxystearate as the base thickener, which is complexed with lithium sebacate. The production of these base greases requires temperatures between 130°C and 160°C, preferably 150°C as the final temperature.

[0055] The lubricating greases according to the invention are particularly suitable for use in or for plain bearings and rolling bearings in a wide range of industrial applications. Lithium complex greases are all-purpose greases with an extended temperature range. The use of calcium-lithium complex soap can positively influence raw material costs, as a lower amount of lithium can be used.

[0056] The lithium complex soap lubricating greases or lithium-calcium complex soap lubricating greases produced by the process according to the invention preferably have a high dropping point of over 260°C for the lithium complex soap lubricating greases and over 190°C for the lithium-calcium complex soap lubricating greases.

[0057] In the following examples, the characteristics of the lithium complex greases according to the invention are compared with those produced by a conventional route. The conventional production method is described here for Example 4 and can be applied to the other examples by analogy. Comparison example:

[0058] 718.1 g of polyalphaolefin PAO 40 were placed in a heatable reaction vessel equipped with a stirrer, and 186 g of 12-hydroxystearic acid and 49.4 g of sebacic acid were added while stirring. This mixture was heated to 85°C in the reaction vessel with stirring and held at this temperature for 30 minutes. A mixture of 46.5 grams of lithium hydroxide monohydrate, suspended in 150 grams of hot water, was then added. The mixture was held at 85°C in the reaction vessel with stirring for 30 minutes. The temperature was then increased to 100°C. The reaction mixture was then heated to 105°C to expel the water. After this step, 500 g of polyalphaolefin PAO 40, which had previously been heated to 100°C in a separate vessel, were added, followed by boiling the mixture to a final temperature of 205°C. The fat was then cooled to 60°C and homogenized using a colloid mill. Example 1: Production of a lithium complex soap grease with azelaic acid

[0059] 39.0 g of azelaic acid and 160 g of water were placed in a heatable reaction vessel equipped with a stirrer. The mixture was heated to 60°C and 18.2 g of lithium hydroxide powder was added.

[0060] After a reaction time of 30 minutes, 186.0 g of 12-hydroxystearic acid were added and the mixture was heated to 85°C. This was followed by the addition of 550 g of polyalphaolefin PAO 40. The mixture was stirred until homogeneous, and 26.9 g of lithium hydroxide powder was added, followed by a reaction time of 30 minutes.

[0061] The mixture was then heated to 100°C, and another 380 g of polyalphaolefin PAO 40 was added. The reaction mixture was then heated to 105°C to expel any remaining water. Following this step, 300 g of polyalphaolefin PAO 40 was added, followed by boiling the mixture to a final temperature of 205°C. The fat was then cooled to 60°C and homogenized using a colloid mill.

[0062] Table 1 compares the characteristics of the grease according to the invention with a grease produced by a conventional route, namely according to the comparative example above (comparison). Table 1 Measured value method Comparison invention RP-instant [0.1mm] DIN ISO 2137 232 213 RP-24h [0.1mm] DIN ISO 2137 209 200 Δ(RP-immediate - RP-24h) 23 13 WP60 [0.1mm] DIN ISO 2137 250 220 WP60000 [0.1mm] DIN ISO 2137 280 268 Δ(WP60-WP60,000) 30 48 Dropping point [°C] DIN ISO 2176 291°C 297°C ÖA 100°C / 18h [wt.%] DIN 51817 0,9% 1,0% RP = Rest Penetration, ÖA = Oil Separation

[0063] The advantage of the lithium complex soap lubricating grease produced by the process according to the invention lies, among other things, in the improved thickener yield: the worked penetration WP60 shows a significantly firmer grease. Example 2: Production of a lithium complex soap grease with terephthalic acid

[0064] 35.0 g of terephthalic acid and 150 g of water were placed in a heatable reaction vessel equipped with a stirrer. The mixture was heated to 60°C, and 17.7 g of lithium hydroxide powder were added. After a reaction time of 30 minutes, 190.1 g of 12-hydroxystearic acid were added, and the mixture was heated to 85°C. This was followed by the addition of 550 g of polyalphaolefin PAO 40.

[0065] The mixture was stirred until homogeneous, and 26.6 g of lithium hydroxide powder was added, followed by a 30-minute reaction time. The mixture was then heated to 100°C, and another 380 g of polyalphaolefin PAO 40 was added. The reaction mixture was then heated to 105°C to expel any remaining water.

[0066] After this step, 300.8 g of polyalphaolefin PAO 40 were added, followed by boiling the mixture to a final temperature of 205°C. The fat was then cooled to 60°C and homogenized using a colloid mill.

[0067] The following table summarizes the grease's characteristics. Since conversion with terephthalic acid is not possible using the conventional boiling process, no comparative data can be provided here. Table 2 Measured value method invention RP-instant [0.1mm] DIN ISO 2137 243 RP-24h [0.1mm] DIN ISO 2137 233 Δ(RP-immediate - RP-24h) 10 WP60 [0.1mm] DIN ISO 2137 271 WP60000 [0.1mm] DIN ISO 2137 261 Δ(WP60-WP60,000) 10 Dropping point [°C] DIN ISO 2176 >300 ÖA 100°C / 18h [wt.%] DIN 51817 4,3 Example 3: Production of a lithium complex soap grease with sebacic acid and ester oil

[0068] 26.5 g of sebacic acid and 160 g of water were placed in a heatable reaction vessel equipped with a stirrer. The mixture was heated to 60°C, and 11.5 g of lithium hydroxide powder were added. After a reaction time of 30 minutes, 123.5 g of 12-hydroxystearic acid were added, and the mixture was heated to 85°C. This was followed by the addition of 594.4 g of a polyol ester (viscosity 320 mm² / s at 40°C). The mixture was stirred until homogeneous, and 17.8 g of lithium hydroxide powder were added, followed by a reaction time of 30 minutes.

[0069] The mixture was then heated to 100°C, and another 396.2 g of polyol ester was added. The reaction mixture was then heated to 105°C to expel any remaining water. Following this step, 330.2 g of polyol ester was added, followed by boiling the mixture to a final temperature of 205°C. The fat was then cooled to 60°C and homogenized using a colloid mill.

[0070] Table 3 compares the characteristics of this grease with a grease produced via a conventional route according to the comparative example above. Table 3 Measured value method Comparison invention RP-instant [0.1mm] DIN ISO 2137 278 273 RP-24h [0.1mm] DIN ISO 2137 251 238 Δ(RP-immediate - RP-24h) 27 35 WP60 [0.1mm] DIN ISO 2137 297 277 WP60000 [0.1mm] DIN ISO 2137 321 304 Δ(WP60-WP60,000) 24 27 Dropping point [°C] DIN ISO 2176 290°C 280°C ÖA 100°C / 18h [wt.%] DIN 51817 5,2% 4,0% Odor After fatty alcohol clearly unobtrusive

[0071] The advantage of the lithium complex grease with the new process is that the ester used is not (partially) hydrolyzed. In the conventional process, the formation of fatty alcohols can be detected by their odor. Furthermore, the new process route leads to an improved thickener yield. Example 4: Production of a lithium complex soap grease with sebacic acid in polyalphaolefin

[0072] 49.4 g of sebacic acid and 150 g of water were placed in a heatable reaction vessel equipped with a stirrer. The mixture was heated to 60°C while stirring.

[0073] 20.5 grams of dry lithium hydroxide powder were added to the mixture and stirred for 30 minutes at constant temperature. Then, 186.0 g of 12-hydroxystearic acid were added, and the mixture was heated to 85°C with stirring. This was followed by the addition of 550 g of polyalphaolefin 40, which had previously been preheated to 100°C. After mixing, 26.0 g of dry lithium hydroxide powder were added. The reaction mixture was then allowed to react with stirring for 30 minutes. The reaction mixture was heated to 100°C, followed by the addition of 365 g of polyalphaolefin 40 (preheated to 100°C). The mixture was then heated to 105°C for dehydration. After reaching 105°C, 303.1 g of polyalphaolefin 40 were added, and the mixture was heated to a final temperature of 205°C over a period of 2.5 hours. The fat was then cooled to 60°C and homogenized using a colloid mill.Table 4 compares the characteristics of this grease with those of a grease produced via a conventional route according to the comparative example above. Table 4 Measured value method Comparison invention RP-instant [0.1mm] DIN ISO 2137 226 221 RP-24h [0.1mm] DIN ISO 2137 197 207 Δ(RP-immediate - RP-24h) 29 14 WP60 [0.1mm] DIN ISO 2137 241 233 WP60000 [0.1mm] DIN ISO 2137 305 258 Δ(WP60-WP60,000) 64 25 Dropping point [°C] DIN ISO 2176 291°C 290°C ÖA 100°C / 18h [wt.%] DIN 51817 0,6% 1,4%

[0074] The advantage of the lithium complex grease over the new process lies on the one hand in the significantly higher mechanical stability (lower ΔWP60 / WP60,000) and on the other hand in the lower post-curing at rest.

[0075] In summary, with regard to the properties of the lithium complex greases produced according to the invention, it can be said that the new production process: leads to an improved thickener yield, whereby lubricating greases of the same consistency can be produced more cheaply, depending on the base oil used, the thickener has an improved work stability, for the first time lithium complex greases with terephthalate thickener content can be produced, lithium complex greases with ester oils that are less stable to hydrolysis can be produced, in addition the process according to the invention can be carried out more quickly and offers increased work safety, since the lye does not have to be produced and added separately.

[0076] The following two examples describe the production of mixed lithium-calcium complex soap lubricating greases and calcium-lithium complex soap lubricating greases. Example 5: Production of a lithium-calcium complex soap grease with sebacic acid

[0077] 38.6 g of sebacic acid, 14.1 g of calcium hydroxide, and 150 g of water were placed in a heatable reaction vessel equipped with a stirrer. The mixture was heated to 90°C with stirring. 180.0 g of 12-hydroxystearic acid were then added and mixed for 30 minutes until a dough-like mass was formed. 500 g of polyalphaolefin 8 (preheated to 100°C) were added to the reaction mixture with stirring and mixed for 30 minutes. 25.2 g of dry lithium hydroxide powder were then added to this mixture, and the reaction mixture was stirred for 30 minutes at the same temperature. The reaction mixture was then heated to 100°C, followed by the addition of 300 g of preheated polyalphaolefin 8. The mixture was then heated to 105°C, during which the mixture was dehydrated. After reaching 105°C, 442.2 g of polyalphaolefin 8 were added and the mixture was heated to a final temperature of 205°C over a period of 2.5 hours.The fat was then cooled to 60°C and homogenized using a colloid mill.

[0078] The following table shows the characteristics of the lithium-calcium complex grease. Table 5 Measured value method Conventional process New process RP-instant [0.1mm] DIN ISO 2137 289 295 RP-24h [0.1mm] DIN ISO 2137 249 276 Δ(RP-immediate - RP-24h) 40 19 WP60 [0.1mm] DIN ISO 2137 307 306 WP60000 [0.1mm] DIN ISO 2137 349 344 Δ(WP60-WP60,000) 42 38 Dropping point [°C] DIN ISO 2176 257 263 ÖA 100°C / 18h [wt.%] DIN 51817 10 6,8 Water resistance DIN 51807-1 40°C [BWST] 0 0 90°C [BWST] 0 0

[0079] The formation of the lithium-calcium complex soap grease results in a high dropping point. Compared to the conventional process (started in base oil), the process according to the invention delivers a grease with increased consistency stability and reduced oil separation. Water resistance is also at a high level, even in 90°C hot water with resistance level 0 (BWST 0). The calcium soap content has a positive effect here.

[0080] Compared to a pure lithium complex grease, 30-40% lithium hydroxide can be saved, which has a positive effect on the purchase costs. Example 6: Production of a calcium-lithium complex soap grease with sebacic acid

[0081] In a heatable reaction vessel equipped with a stirrer, 26.0 g of sebacic acid were placed in 150 g of water and heated to 60°C. While stirring, 11.3 g of lithium hydroxide powder were added, and the mixture was stirred for 30 minutes to ensure complete reaction. The mixture was heated to 85°C while stirring, 121.5 g of 12-hydroxystearic acid was added, and stirring was continued until a homogeneous mixture was formed.

[0082] To this, 600 g of a 1:1 mixture consisting of a Group I oil (SN600) and a naphthenic base oil (T110) were added and homogenized with stirring. Subsequently, 15.0 g of calcium hydroxide powder were added, and the mixture was stirred for 30 minutes at 85°C to ensure complete saponification. The reaction mixture was then heated to 100°C, followed by the addition of 400 g of the base oil described above, which had been preheated to 100°C. The brew was then heated to 105°C, during which the mixture was dehydrated. A further 326.2 grams of the preheated base oil were then added. After the mixture was dehydrated, the final temperature was increased from 150°C. After cooling to 60°C, the mixture was homogenized using a colloid mill. Table 6 Measured value method Conventional process New process RP-instant [0.1mm] DIN ISO 2137 308 294 RP-24h [0.1mm] DIN ISO 2137 291 289 Δ(RP-immediate - RP-24h) 17 5 WP60 [0.1mm] DIN ISO 2137 311 304 WP60000 [0.1mm] DIN ISO 2137 348 328 Δ(WP60-WP60,000) 37 24 Dropping point [°C] DIN ISO 2176 200 196 ÖA 40°C / 18h [wt.%] DIN 51817 1,2 2,0 ÖA 100°C / 18h [wt.%] DIN 51817 7,0 7,9 Water resistance 40°C [BWST] DIN 51807-1 0 0 90°C [BWST] DIN 51807-1 1 1

[0083] Due to the formation of the calcium-lithium complex soap, the dropping point is below that of the lithium-calcium complex grease from Example 5. Compared to the conventional process, the new process route produces greases with better mechanical stability and slightly improved thickener yield. The calcium-lithium complex soap grease is economically very attractive: The base grease described in Example 6 can be considered a cost-effective alternative to lithium 12-hydroxystearate greases. Furthermore, the manufacturing process is more energy-efficient, as it operates at a comparatively low process temperature of 150°C compared to the usual >200°C.

[0084] In summary, it can be said that the manufacturing process according to the invention can also be used to produce lithium-calcium complex soap lubricating greases which are particularly economically very attractive, have excellent water resistance and have good consistency stability.

Claims

1. Method for the producing of lithium complex soap lubricating greases or lithium-calcium complex soap lubricating greases comprising at least the following steps: - saponification of one or more dicarboxylic acids with one or two metal hydroxides as a solid according to one of the following three alternatives: (A1) saponification with lithium hydroxide and one or more dicarboxylic acids, or (A2) saponification with lithium hydroxide and calcium hydroxide and one or more dicarboxylic acids, or (A3) saponification with calcium hydroxide and one or more dicarboxylic acids, each in an aqueous environment comprising, with respect to the liquid phase, more than 80 wt.% of water with respect to all liquid feedstocks, to obtain one or more metal salts of the dicarboxylic acids, wherein both dicarboxyl groups of the dicarboxylic acids are substantially completely saponified; - bringing into contact with one or more liquid hydroxy fatty acids or hydroxy fatty acids liquefied by heating and dissolving the metal salt(s) in the liquid hydroxy fatty acid; - bringing into contact with base oil; - addition of further metal hydroxides, wherein according to alternative: (A1) lithium hydroxide or calcium hydroxide; (A2) lithium hydroxide and calcium hydroxide or lithium hydroxide only or calcium hydroxide only; or (A3) lithium hydroxide is added; for saponification with the at least one hydroxy fatty acid; - expulsion of water under heating; - heating to a final temperature; and - cooling down and addition of more base oil.

2. Method according to claim 1, wherein the saponification of the one or more dicarboxylic acids in the aqueous environment takes place at 20° to 85°C, preferably 40 to 70°C.

3. Method according to claim 1 or 2, wherein the hydroxycarboxylic acid is liquefied by heating and is preferably heated to above 60°C before being brought into contact.

4. Method according to at least one of the preceding claims, wherein the saponification of the one or more hydroxycarboxylic acids takes place at a temperature above 80°C.

5. Method according to at least one of the preceding claims, wherein the expulsion temperature for the expulsion of water is at least 100°C, preferably greater than 105°C.

6. Method according to at least one of the preceding claims, wherein the final temperature is greater than 120°C, in particular 190 to 210°C.

7. Method according to at least one of the preceding claims, wherein, after reaching the final temperature, cooling is carried out and further base oil, additives, solid lubricants and / or a further thickener component are added below 120°C or preferably below 80°C.

8. Method according to at least one of the preceding claims, wherein the base oil has a kinematic viscosity of from 20 to 2500 mm2 / s, in particular from 40 to 500 mm2 / s, in each case at 40 °C.

9. Method according to at least one of the preceding claims, wherein the one or more dicarboxylic acids are aliphatic dicarboxylic acids having 6 to 12 carbon atoms or cyclo-aliphatic or aromatic dicarboxylic acids having 8 to 12 carbon atoms.

10. Method according to at least one of the preceding claims, wherein the one or more hydroxycarboxylic acids comprise 12 to 30 carbon atoms, preferably 16 to 20 carbon atoms.

11. Method according to at least one of the preceding claims, wherein hydroxycarboxylic acid and dicarboxylic acid are used in a molar ratio of 1:1 to 10:1.

12. Method according to at least one of the preceding claims, wherein the metal hydroxides are used in bulk, preferably in powder form.

13. Method according to at least one of the preceding claims, wherein the lithium complex soap lubricating greases comprise: a) 55 to 95 wt.%, in particular 70 to 90 wt.%, of the base oil; b) 5 to 25 wt.%, in particular 5 to 20 wt.%, of the lithium complex soap; and, and optionally the following optional components: c) 0 to 40 wt. %, in particular 0.5 to 10 wt.%, of additives; d) 0 to 20 wt.%, in particular 0 to 5 wt.%, of inorganic thickeners; and e) 0 to 20 wt.%, in particular 0.1 to 15 wt.%, of solid lubricants.

14. Method according to at least one of the preceding claims 1 to 12, wherein the lithium-calcium complex soap lubricating greases comprise: a) 55 to 95 wt.%, in particular 70 to 90 wt.%, of the base oil; b) 5 to 25 wt.%, in particular 5 to 20 wt.%, of the lithium-calcium complex soap, wherein the weight ratio in relation to the lithium hydroxide to calcium hydroxide used is 1:9 to 9:1, and optionally the following optional components: c) 0 to 40 wt.%, in particular 0.5 to 10 wt.%, of additives; d) 0 to 20 wt.%, in particular 0 to 5 wt.%, of inorganic thickeners; and e) 0 to 20 wt.%, in particular 0.1 to 15 wt.%, of solid lubricants.

15. Lithium complex soap lubricating greases or lithium-calcium complex soap lubricating grease produced by the method according to at least one of the preceding claims, preferably with a dropping point of above 260°C for the lithium complex soap lubricating greases and preferably with a dropping point of above 190°C for the lithium-calcium complex soap lubricating greases.

16. Use of the lithium complex soap lubricating greases or lithium-calcium complex soap lubricating greases according to claim 15 for slide bearings and rolling bearings.