Base oil and lubricating fluid composition containing the base oil

Abstract

The invention relates to a base oil comprising polyalphaolefins, polymer esters, and polyalkylene glycols, and a lubricating fluid composition containing the base oil. The lubricating fluid composition can be used for the lubrication of gears and for use in hydraulic systems, particularly for lubrication in the food processing industry.

Description

[0001] The present invention relates to a base oil comprising polyalphaolefins, polymer esters, and polyalkylene glycols, and a lubricating fluid composition containing the base oil and additives. The lubricating fluid composition can be used for the lubrication of gears and for use in hydraulic systems, particularly for lubrication in the food processing industry. A particular area of ​​application for the base oils and lubricating fluid compositions according to the invention is lubrication points that come into contact with, or may come into contact with, food and / or animal feed. Introduction and state of the art

[0002] Hydraulic and gear oils consist of a base oil and additives that are added to increase the service life and performance of the lubricating fluid. The base oil can be a mixture of different oils.

[0003] To determine the performance of a lubricating fluid, various mechanical-dynamic tests are conducted. The Research Center for Gears and Transmissions at the Technical University of Munich (FZG) has developed a test rig that allows lubricants for transmissions to be tested for their suitability in preventing scuffing of the surfaces and flanks of gears. An important characteristic for industrial gear oils is the damage force level in the FZG test A / 8.3 / 90 according to DIN ISO 14635-1. In this test, the scuffing load-carrying capacity of lubricants is determined on an FZG gear clamping test machine. For this purpose, a test gear pair with a special tooth geometry runs in the lubricating fluid being tested. Temperature and speed are predetermined. The load on the tooth flanks is applied incrementally via a weighted lever that clamps one of the shafts against the other.From force level 4 onwards, the pinion tooth flanks are inspected for any damage after each force level has been completed. The measurement is completed when force level 12 is reached without any damage occurring. The standard for hydraulic oil (DIN 51524-2 HLP) requires at least force level 10, while the standard for circulating oils (DIN 51517-3 CLP) requires at least force level 12. The result is either "Pass" or "Fail" – it works or it doesn't.

[0004] Another technically relevant requirement, going beyond DIN 51517-3, is a high gray spot resistance. Gray spot resistance refers to the property of a lubricating fluid to prevent the damage pattern of gray spotting (also known as "micropitting").

[0005] Micropitting occurs on tooth flanks under high loads in the mixed friction regime. The primary influence on the formation of micropitting is the lubricating film thickness at operating temperature. Furthermore, the use of chemically active additives can significantly promote the formation of micropitting. The addition of friction modifiers can help prevent micropitting. US 9347016 B2 describes the use of a dialkyldithiophosphate as an effective component against micropitting. EP 0949320 A2 mentions phosphonates and phoshites (e.g., dioleyl phosphite), succinimides, pyrrolidinones, molybdenum carboxylates, and oleylamide as friction modifiers for preventing micropitting. US 6184186 B1 claims the use of molybdenum carboxylates and sulfurized isobutylenes for preventing micropitting.

[0006] To determine the micropitting load-bearing capacity of a lubricating fluid, the FVA 54 micropitting test is used, which is performed on a standard FZG clamping test machine. This test consists of two consecutive parts: a step test to determine the damage force level and an endurance test to assess the long-term tribological behavior. In the step test, the load is increased incrementally from force level 5 to force level 10, with each force level lasting 16 hours. The endurance test initially runs for 80 hours at force level 8 and then for 5 x 80 hours at force level 10. After each force level, the pinion is removed, and the profile shape deviation and the micropitting content of the tooth flank are determined on three teeth. The wear-induced weight loss of the pinion is also determined. The profile shape deviation is used to determine the damage force level in the step test. If a value exceeding 7.5 µm is reached, the damage force level has been reached.If the limit is not exceeded after the first five force levels, damage force level 10 is reached. If all six force levels are completed without exceeding the limit, the result is given as SKS greater than 10.

[0007] For practical purposes, elastomer compatibility is also important, as prolonged use of the oil can cause elastomers, such as radial shaft seals, to shrink and leak. Similarly, an oil can cause excessive swelling, which can also lead to leaks. Industrial gearboxes typically use various NBR and FKM elastomer types, with the NBR types being particularly sensitive to the composition of the base oil mixture.

[0008] For the lubrication of industrial gearboxes in the food processing industry, since potential contact of the lubricating fluid with the food cannot be completely ruled out, lubricating fluids that are physiologically safe must be used. The selection of raw materials that can be used to produce food-grade (H1) lubricating fluids is significantly more limited compared to technical lubricating fluids. All of the aforementioned friction modifiers are prohibited in the formulation of food-grade lubricating fluid.

[0009] The requirements for hydraulic oils for industrial use are described in DIN 51524-1, DIN 51524-2, and DIN 51524-3. Hydraulic oils offer protection against wear and corrosion, with HLP-classified oils (DIN 51524-2) providing improved wear protection compared to HL oils (DIN 51524-1). HVLP-classified oils (DIN 51524-3), in addition to improved wear protection, exhibit more stable temperature-viscosity behavior (viscosity index) and can therefore be used in a wider temperature range.

[0010] Furthermore, a high viscosity index is desirable. Pressure losses in hydraulic systems reduce efficiency. These can occur at low temperatures due to an increase in fluid viscosity and at high temperatures due to leakage caused by a decrease in fluid viscosity. High efficiency over a wide temperature range can therefore be achieved with oils that have a high viscosity index.

[0011] In the past, highly refined white oils, gas-to-liquid (GTL) oils, polyalphaolefins, polyisobutylenes, polyalkylene glycols, alkylated naphthalenes, native and synthetic esters, and mixtures of these components have been discussed as base oils for "food-grade" hydraulic and gear oils.

[0012] US 2021 / 0348079 A1 discloses a lubricant based on a terpolymer of diester, olefin, and acrylate. The terpolymer is a polymerized diester selected from a di(C4-C22-alkyl) ester of maleic acid, fumaric acid, 2-methylmaleic acid, 2,3-dimethylmaleic acid, 2-methylfumaric acid, 2,3-dimethylfumaric acid, or mixtures thereof, as a polymerization product with a C6-C40 alpha-olefin and a C4-C40 alkyl(meth)acrylate. Optional base oils for the lubricant include, among others, polyalphaolefins or alkylene oxides.

[0013] JP 2007-268697 A discloses oil compositions based on Fischer-Tropsch hydrocarbons and n-paraffins, as well as optionally aromatic and naphthalenic hydrocarbon oils. The oil compositions may optionally further contain synthetic oils such as poly-alpha-olefins or polyalkylene glycols, or polymers such as polymerization products of unsaturated carboxylic acid esters like maleic acid ester or fumaric acid ester polymers polymerized with an olefinic monomer. Object of the invention

[0014] The object of the invention is to provide a base oil and a lubricating fluid containing the base oil, wherein the lubricating fluid is intended to be usable, among other things, as gear oil and / or hydraulic oil. The base oil is to be such that it can absorb the additives necessary for the lubricating fluid and that the additives in the base oil exert the desired effect. According to one embodiment, the raw materials are to be selected so that the lubricating fluids can also be used in the food processing industry. The selection of raw materials is regulated in the USA, for example, by the requirements of the US Food and Drug Administration (FDA). As a gear oil, the lubricating fluid, according to one embodiment, is to comply with the CLP standard DIN 51517-3 and, in addition, particularly from viscosity grade 220 (ISO VG 220) upwards, exhibit a gray spot resistance rating of "high" in the micropitting test according to FVA 54.To be used as hydraulic oil, even low viscosity grades of the lubricating fluid must meet DIN 51524-3 (HVLP). Good compatibility with common NBR elastomers (NBR stands for "Nitrile Butadiene Rubber") and fluorocarbon elastomers (FKM elastomers) is desired in all viscosity grades. Summary of the invention

[0015] The problem is solved by the subject matter of the independent claims. Advantageous embodiments are the subject matter of the dependent claims or described below.

[0016] The base oil according to the invention comprises: 81 to 96 wt.% polyalphaolefins as oligomers of C6- to C14- alpha-olefins, especially C8- to C12- alpha-olefins; 2 to 15 wt.% polymer esters available as a polymerization product of one or more alpha / beta-unsaturated dicarboxylic acid diesters, wherein the alcohol groups have 3 to 10 carbon atoms, in particular 4 to 8 carbon atoms, with one or more C4 to C18 alpha-olefins, in particular C12 to C16 alpha-olefins; 2 to 4 wt.% polyalkylene glycols obtainable from alkylene oxides, wherein the alkylene oxides comprise butylene oxide or propylene oxide and at least one C4 to C8 alkylene oxide.

[0017] In another embodiment, the above-mentioned polyalphaolefins, polymer esters, and polyalkylene glycols together constitute more than 90 wt.%, and in particular more than 95 wt.%, of the base oil. Preferably, the above-mentioned polyalphaolefins, polymer esters, and polyalkylene glycols add up to 100 wt.% in the base oil. Thus, the base oil consists of the above-mentioned components.

[0018] According to one embodiment, the polyalphaolefin is an oligomer of 1-octene, 1-decene, and / or 1-dodecene, and in particular an oligomer of 1-octene or 1-decene or 1-octene and 1-decene. The degree of polymerization of the polyalphaolefins can range from 3 to 25. Also independent of this, the viscosity of the polyalphaolefins is preferably from 4 to 300 mmHg. 2 / s at 100°C (kinematic viscosity determined according to DIN EN ISO 3104). The polyalphaolefins can also be used as hydrogenated products.

[0019] The polymer esters are preferably copolymers of maleic and / or fumaric acid (full) esters and one or more C4 to C18 alpha-olefins. The alcohol groups of the dicarboxylic acid diesters are, in particular, linear and / or branched monoalcohols with 3 to 10 carbon atoms, especially 4 to 8 carbon atoms. The dicarboxylic acids of the dicarboxylic acid diester preferably have 4 to 12 carbon atoms, especially 4 to 6 carbon atoms. Chain lengths of 10 to 16 carbon atoms, especially 14 to 16 carbon atoms, are preferred for the alpha-olefins of the polymer esters. These can be linear and / or branched, preferably linear. The molar ratio of the alpha-olefins to the dicarboxylic acid diesters can be 1.5 to 1 to 1 to 1.5, especially 1 to 0.9 to 0.9 to 1. The polymer esters have, in particular, an average molecular weight of 1000 to 5000 g / mol and, in particular, 1500 to 2500 g / mol (in each case as number averages).

[0020] According to one embodiment, the polyalkylene glycols comprise 30-70 mol% propylene oxide and 70-30 mol% butylene oxide, or consist primarily of these. The polyalkylene glycols are preferably soluble at room temperature in the polyalphaolefins or polyalphaolefin mixtures with which they are used.

[0021] The lubricity fluid composition includes or consists of at least: - 90 to 98 wt.% of the base oil; - 0.01 to 2 wt.%, preferably 0.1 to 0.3 wt.%, of the friction modifier mentioned below, and / or 0.01 to 2 wt.%, preferably 0.05 to 0.6 wt.%, of the following anti-wear additive, based on the base oil; and - other additives, in particular 0.1 to 2 wt.% of the other additives.

[0022] According to one design, the lubricant fluid composition comprises or consists of: - 94 to 98 wt.% of the base oil; - 0.01 to 2 wt.%, preferably 0.1 to 0.3 wt.%, of the friction modifier mentioned below, and / or 0.01 to 2 wt.%, preferably 0.05 to 0.6 wt.%, of the following anti-wear additive, based on the base oil; - other additives, in particular 0.1 to 2 wt.% of the other additives.

[0023] The lubricating fluid composition includes the base oil and at least one of the following additives: - an amine-reacted alkyl phosphate, in particular mono- or di- C1- to C12-alkyl phosphate, as a wear protection additive, in particular 0.01 to 2 wt.%, preferably 0.1 to 0.6 wt.% and / or - a polyol monoester, in particular a C12 to C24 fatty acid ester of possibly ethoxylated polyols, in particular possibly ethoxylated sorbitan monooleate, as a friction modifier in particular 0.01 to 2 wt.% each, preferably 0.05 to 0.3 wt.%.

[0024] The amine-reacted alkyl phosphate is preferably a mono- or di-C1- to C12-alkyl phosphate reacted with at least C10- to C18-alkylamines. Preferably, the reaction is carried out such that the alkyl phosphate is neutralized or partially neutralized. Suitable examples are mono- and diisooctyl esters of phosphoric acid reacted with tert-alkylamines and C12- to C14-primary amines (CAS Reg. No. 68187-67-7) or phosphoric acid mono- and dihexyl esters reacted with tetramethylnylamine and C11- to C14-alkylamines.

[0025] Commercial products include, for example, Irgalube® 349 from BASF SE or Additin® RC 3760 from LANXESS (CAS Reg. No. 80939-62-4). The amine-reacted alkyl phosphate is a wear protection additive.

[0026] The polyol monoester is preferably a C12 to C24 fatty acid ester of polyols such as glycerol, polyglycerol, or sorbitan. The polyol may also be wholly or partially ethoxylated. Suitable examples are polysorbate 20, polysorbate 40, polysorbate 60, polysorbate 120, glyceryl monostearate, glyceryl monooleate, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, or polyglyceryl-4-isostearate.

[0027] The C12 to C24 mono-fatty acid esters of possibly partially ethoxylated polyols act as friction modifiers.

[0028] The above percentage weights refer to the overall composition (unless explicitly stated otherwise) and apply independently of each other.

[0029] The above polyalphaolefins, polymer esters and polyalkylene glycols are not chemically pure products and when they are mentioned in the singular, this also refers to a mixture of different molecules, each of which individually meets the specified specification. Detailed description of the invention

[0030] Hydraulic and gear oils consist of a base oil and additives that are added to increase the service life and performance of the lubricating fluid. In the present invention, a mixture of the above-mentioned polyalphaolefins, polymer esters, and polyalkylene glycols is used as the base oil.

[0031] Polyalphaolefins are oligomers of, in particular, linear 1-alkenes, especially 1-octene, 1-decene and / or 1-dodecene, which are produced, for example, using Lewis acid catalysts (e.g., US 6824671 B2) or metallocene catalysts (mPAOs, US 9365663 B2, US 9701595 B2) and whose kinematic viscosity at 100°C (kV 100) is between 2 and 300 mm². 2 / s may lie.

[0032] According to one embodiment, the polyalphaolefins are a mixture of a1) oligomers of 1-decene and b1) oligomers of 1-octene, or a mixture of a2) oligomers of 1-dodecene and b2) oligomers of 1-octene and / or 1-decene. These mixtures can be further characterized as follows: 5–95 wt.% of oligomers a1) or a2) and 5–95 wt.% of oligomers b1) or b2). The polyalphaolefins can be prepared by metallocene catalysis.

[0033] It is often advantageous to mix polyalphaolefins of different viscosities, e.g., oligomers with a viscosity of 4 to 100 mm. 2 / s at 100°C and oligomers with a viscosity of 50 to 300 mm 2 / s at 100°C.

[0034] Polymer esters are defined as polymers resulting from C,C linkages that contain side chains with ester groups. According to the present invention, this includes copolymers of alpha, beta unsaturated dicarboxylic acid esters, such as maleic or fumaric acid esters, with particularly unbranched alpha-olefins. Polymer esters and their preparation are described, for example, in DE 3223694 C2 and US 5435928 A.

[0035] Polyalkylene glycols are the polymeric reaction products of water and / or a mono- or dihydric starting alcohol with 1,2-epoxides such as ethylene oxide, propylene oxide, and / or butylene oxide, comprising at least propylene oxide and at least one C4 to C8 alkylene oxide. The polyalkylene glycols exist, for example, as homopolymers of butylene oxide or as copolymers of propylene oxide and butylene oxide. Copolymers consisting of 30–70% propylene oxide and 30–70% butylene oxide are preferably used in this context. The polyalkylene glycols particularly feature one or two terminal hydroxyl groups.

[0036] For elastomer compatibility, the addition of a swelling agent, typically an ester, to the lubricating fluid composition is desirable. Conversely, an excessively high concentration of swelling agent leads to excessive swelling, which can also cause leakage. Various NBR and FKM elastomer types are used in industrial gearboxes, with the NBR types being particularly sensitive to the composition, i.e., the polarity, of the base oil mixture.

[0037] Examples of swelling agents include monoesters, diesters, polyol esters, and complex esters, such as those of C1 to C18 alcohols with a C2 to C18 carboxylic acid. Suitable mono- and diesters include esters of linear or branched monohydric alcohols such as methanol, ethanol, isopropanol, isobutanol, 2-ethylhexanol, 3,5,5-trimethylhexanol, or 7-methyloctanol with typical fatty acids or dicarboxylic acids, such as caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, isostearic acid, oleic acid, linoleic acid, linolenic acid, adipic acid, suberic acid, sebacic acid, or phthalic acid. Polyol esters include the formal reaction products of linear or branched carboxylic acids with polyhydric alcohols such as glycerol, neopentyl glycol, trimethylolpropane, pentaerythritol, or dipentaerythritol. The proportion of swelling agent is chosen so that the resulting volume expansion of the elastomer does not exceed 10%.This generally means that the swelling agent is present in the lubricating fluid composition at a proportion of 0.5 to 6 wt%, particularly 1 to 4 wt%. An example is di(2-ethylhexyl) sebacate. However, it has been found that the polyalkylene glycol used also acts as a swelling agent.

[0038] Other possible additives for the lubricating fluid composition include antioxidants, anti-wear agents, corrosion inhibitors, detergents, dyes, friction modifiers, viscosity improvers, high-pressure additives, metal deactivators, and nanoscale solids. Examples include: • Primary antioxidants such as amine compounds (e.g., alkylamines or 1-phenyllaminonaphthalene), aromatic amines such as phenylnaphtylamines or diphenylamines or polymeric hydroxyquinolines (e.g., TMQ), phenol compounds (e.g., 2,6-di-tert-butyl-4-methylphenol), organic dithiocarbamates or dithiophosphates; • secondary antioxidants such as phosphites, e.g. tris(2,4-ditert-butylphenyl p-hosphite) or bis(2,4-ditert-butylphenyl)-pentaerythritol diphosphite or thioethers (e.g. cresol thioethers); • High-pressure additives and / or anti-wear additives such as organic sulfur compounds like polysulfides or sulphured olefins, thiophosphates (e.g. triphenyl thiophosphate) and dithiophosphates, phosphites and phosphonates (e.g. di-n-octylphosphonate), phosphates (e.g. substituted triphenyl phosphates or amine-neutralized alkyl phosphates), inorganic or organic boron compounds, thiocarbamates and dithiocarbamates (e.g. methylene bis(dibutyl dithiocarbamate)); • Corrosion inhibitors such as sulfonates, e.g., petroleum sulfonate, dinonylnaphthalenesulfonate; neutral or hyperbasic calcium sulfonates, magnesium sulfonates, sodium sulfonates, calcium and sodium naphthalenesulfonates, sulfonic acid esters, amine phosphates; N-methyl-N-(1-oxo-9-octadecenyl)glycine; • Metal deactivators such as benzotriazoles, e.g., methylbenzotriazole dialkylamine, sterically hindered phenols, sodium nitrite; • Viscosity improvers such as polymethacrylate, polyisobutylene, polystyrene; • Friction reducers, some with wear-protection properties, such as organic acids (e.g., isostearic acid), fatty acid esters of possibly partially ethoxylated polyols such as glycerol or sorbitan, partial glycerides, animal or vegetable oils, dialkyl hydrogen phosphonates, carboxylic acid amides such as oleylamides, organic compounds based on polyethers and amides, e.g., alkyl polyethylene glycol tetradecylene glycol ethers, alkyl succinates, PIBSI (polyisobutylene succinic imide) or PIBSA (polyisobutylene succinic anhydride). • Solids: In gear oils, the use of particles (boron nitride, silicon dioxide, layered silicates such as bentonite, carbon nanotubes) is possible to achieve specific properties. To avoid negative effects on tribological performance, very small particles (so-called nanoparticles with particle sizes smaller than 500 nm, preferably smaller than 100 nm, and particularly preferably smaller than 50 nm) are used.

[0039] To produce the lubricating fluid composition according to the invention, a portion of the base oil (e.g., 5 to 25 wt.%) is placed together with the additives, which are particularly oil-soluble but generally exist as solids under normal conditions, and heated to 90 to 110°C with continuous stirring to ensure that these additives dissolve in the base oil. The temperature is then lowered to below 60°C by adding another portion of the base oil. Liquid and optionally oil-insoluble additives and solids, as well as the remaining base oil, are then added and mixed by further stirring until complete homogeneity of the mixture is achieved.

[0040] The lubricating fluid composition according to the invention is particularly suitable for use in industrial gearboxes (spur gear, helical gear, bevel gear, hypoid and planetary gears) and hydraulic systems, especially those used in the food or feed industry.

[0041] A gearbox is a machine element used to change motion parameters (e.g., force or torque). Depending on the gearbox design, it is enclosed in a housing and lubricated with a fluid. Seals are used to prevent the fluid from leaking out. In addition to specific design properties, the sealing materials must also be chemically resistant to the lubricating fluids used.

[0042] Elastomer compatibility therefore plays an important role in lubricant development. The same applies to the durability of hydraulic seals, which are used to seal hydraulic systems filled with hydraulic oils.

[0043] Within the scope of the present invention, a lubricating fluid for use as a gear and hydraulic oil was developed which meets the requirements of DIN 51517-3 (more precisely: the tests described in DIN ISO 1817 for relative volume change, change in Shore A hardness, tensile strength and elongation at break) as well as the dynamic elastomer compatibility test (Freudenberg test specification FS PLM 111 0008). Experimental examples: Production:

[0044] A portion of the base oil (5-25%), specifically the polar oil components esters and polyalkylene glycol, is placed together with the additives, which are solid at room temperature, and heated to 90-110°C with continuous stirring until a clear solution is obtained. The temperature is then lowered to below 60°C by adding the remaining (unheated) base oil. The liquid additives are then added and mixed for approximately 15 minutes with further stirring until complete homogeneity is achieved. The oil can then be bottled after further cooling to below 40°C.

[0045] In addition to the listed base oil components, each formulation contains an additive package.

[0046] The following substances were used: PAO 6 Polyalphaolefin: Spectrasyn 6, ExxonMobil Chemical; Synfluid PAO 6 cSt, Chevron Phillips Chemical; Durasyn 166, Ineos Oligomers mPAO 150 Polyalphaolefin, metallocene catalyzed: Spectrasyn Elite 150, ExxonMobil Chemical; Synfluid mPAO 150 cSt, ChevronPhillips Chemical Di(2-ethylhexyl)-se-bacate polymer ester polyalkylene glycol Priolube 1856, Croda; Nycobase 20307 FG, Nyco; LubricitDOS, Zschimmer&SchwarzKetjenlube 240, ItalmatchUCON OSP-32, DOW Anti-wear additive (AW additive) amine-neutralized alkyl phosphate, Irgalube 349, BASF SE Additive package Triphenylphosphorothionate, phenolic antioxidant, amine antioxidant, sorbitan monooleate, N-methyl-N-(1-oxo-9-octadecenyl)glycine, polydimethylsiloxane and benzotriazole derivative, wherein the sorbitan monooleate is the friction modifier used. Table 1 1 2 3 4 Comparison Comparison Comparison According to the invention PAO 6 [wt.%] 43,99 40,99 39,79 36,79 mPAO 150 [wt.%] 54,60 54,60 49,60 49,60 Di(2-ethylhexyl) sebacate[wt.%] - - 2,00 2,00 Polymer esters [wt.%] - - 7,20 7,20 Polyalkylene glycol [wt.%] - 3,0 - 3,0 AW additive [wt.%] 0,33 0,33 0,33 0,33 Additive package [wt.%] 1,08 1,08 1,08 1,08 kV [mm 2 / s] 220 220 220 220 VI 178 179 178 179 LAV [min] 6,2 4,0 4,5 5,7 Elastomer compatibility [ΔV %] -5,7 -0,5 -0,7 -0,3 Corrosion protection against steel and synthetic seawater. fail passport passport passport FZG A / 8,3 / 90, SKS larger larger greater than 12 FE8, mw50 / mk50 [mg] 1,0 / 168

[0047] The following methods were applied in Tables 1 and 2: kV 40 [mm 2 / s] Kinematic viscosity at 40°C determined according to DIN EN ISO 3104 VI Viscosity index according to DIN ISO 2909 LAV Air separation efficiency at 75°C determined according to DIN ISO 9120 Elastomer compatibility according to DIN ISO 1817, 168h at 100°C for 72 NBR 902 Corrosion protection against steel, synthetic seawater Steel finger test according to DIN ISO 7120-B FZG A / 8,3 / 90, SKS Damage force level achieved in the vehicle test A / 8.3 / 90 according to DIN ISO 14635-1 FE8, mw50 / mk50 [mg] Calculated wear values ​​of the rolling elements / cage (50% wear probability) in the FE8 test (D-7.5 / 80-80) according to DIN 51819-3 Micropitting, profile deviation [µm] Micropitting, achieved damage level, rating FVA 54, profile deviation according to LS 9FVA 54, achieved damage force level (SKS), rating GFT = grey spot bearing capacity high = high

[0048] The polymer esters and polyalkylene glycol used are very suitable additives to the PAO oil, as they are able to maintain the high viscosity index. A higher viscosity index means a greater lubricating film thickness at operating temperature, which contributes to better wear protection.

[0049] A purely PAO-based formulation (Test 1) does not offer sufficient elastomer compatibility. NBR elastomers shrink and can lead to leaks. Formulations containing either polyalkylene glycol (Test 2) or esters (Test 3) show only slight volume losses. The best result is achieved with a formulation containing both POA, esters, and polyalkylene glycol (PAG) (Test 4). Furthermore, despite the same additives, corrosion protection against salt water cannot be guaranteed with the purely PAO-based formulation.

[0050] Compared to the ester-containing but polyalkylene glycol-free version (test 3), the air separation capacity is not improved in test 4. Table 2 5 6 4 PAO 6 [wt.%] 37,72 36,77 36,79 mPAO 150 [wt.%] 47,00 49,50 49,60 Di(2-ethylhexyl) sebacate[wt.%] 2,00 2,00 2,00 Polymer esters [wt.%] 12,00 7,20 7,20 Polyalkylene glycol [wt.%] - 3,0 3,0 AW additive [wt.%] 0,20 0,45 0,33 Remaining additive package [wt.%] 1,08 1,08 1,08 kV 40 [mm 2 / s] 220 220 220 VI 178 179 179 LAV 75°C [min] 5,5 5,7 72 NBR 902: ΔV [%] -0,4 -0,3 Steel finger test passport passport passport FZG A / 8,3 / 90, SKS 11 greater than 12 greater than 12 FE8, mw50 / mk50 0 / 227 2,0 / 71,4 1,0 / 168 Micropitting [µm] 6,2 7,7 6,8 Micropitting, achieved damage level, rating SKS 10 GFThigh SKS 9 GFT medium SKS 10GFT high

[0051] Test series 2 shows that the content of amine-neutralized alkyl phosphates among the additives plays a crucial role in passing or failing the important mechanical-dynamic tests. At a low content (test 5), a high gray stain resistance can be achieved even without the addition of polyalkylene glycol. However, only damage level 11 can be achieved in the FZG test. With a higher content of amine phosphates and in the presence of polyalkylene glycol (test 6), damage level greater than 12 is achieved in the FZG test, but the gray stain resistance is insufficient. The reduced amine phosphate content in test 4 can be compensated for by the oil-soluble polyalkylene glycol without any negative effects in the micropitting test.

[0052] The base oil mixture described here supports the corrosion protection properties and elastomer compatibility of the lubricant and allows for a suitable and balanced additive package for "food grade" lubricants, which meets the partly conflicting requirements.