Base oil and lubricating fluid composition containing said base oil

Abstract

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

Description

[0001] Base oil and lubricating fluid composition containing the base oil

[0002] The present invention relates to a base oil comprising polyalphaolefins, polymer esters, and polyalkylene glycols, and to 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, in particular 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 or may come into contact with food and / or animal feed.

[0003] Introduction and state of the art

[0004] Hydraulic and gear oils consist of a base oil and additives added to increase the service life and performance of the lubricating fluid. The base oil can consist of a blend of different oils.

[0005] To determine the performance of a lubricating fluid, various mechanical-dynamic tests are conducted. The Research Center for Gear and Transmission Engineering (FZG) at the Technical University of Munich has developed a test rig that can be used to test gear lubricants for their ability to prevent scuffing of gear surfaces and flanks. An important parameter for industrial gear oils is the failure load level in the FZG test A / 8.3 / 90 according to DIN ISO 14635-1. In this test, the scuffing load capacity of lubricants is determined on an FZG gear stress testing machine. For this purpose, a pair of test gears with a special tooth geometry runs in the lubricating fluid under test. The temperature and speed are specified. The load on the tooth flanks is gradually applied using a weighted lever that clamps one of the shafts against the other.Starting at force level 4, the pinion tooth flanks are inspected for any damage after each force level. When force level 12 is reached without any damage occurring, the measurement is complete. 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 either works or it doesn't. Another technically relevant requirement that goes beyond DIN 51517-3 is a high micropitting resistance. Micropitting resistance refers to the ability of a lubricating fluid to avoid micropitting damage.

[0006] Micropitting occurs on tooth flanks under high load in the area of ​​mixed friction. The primary influence on the development of micropitting is the thickness of the lubricant film at operating temperature. In addition, the use of chemically active additives can significantly promote the development of micropitting. The addition of friction-improving additives (friction modifiers) can help prevent micropitting. US 9347016 B2 describes the use of a dialkyl dithiophosphate as an effective component against micropitting. EP 0949320 A2 cites phosphonates and phosphites (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 to prevent micropitting.

[0007] To determine the micropitting resistance of a lubricating fluid, the FVA 54 micropitting test is used. It is carried out on an FZG standard torque testing machine. This test consists of two consecutive parts: a step test to determine the damage load level and an endurance test to assess the long-term tribological behavior. In the step test, the load is increased step by step from load level 5 to load level 10, with each load level lasting 16 hours. The endurance test initially runs for 80 hours at load level 8 and then 5 x 80 hours at load level 10. After each load level, the pinion is removed and the profile form deviation and the proportion of micropitting on the tooth flank are determined for three teeth. In addition, the weight loss of the pinion due to wear is determined. The profile form deviation is used to determine the damage load level in the step test. If a value of 7.5 pm is exceeded, the damage load level is reached.If the limit value is not exceeded after the first five force levels, failure load level 10 is reached. If all six force levels are completed without exceeding the limit value, the result is indicated as SKS greater than 10. In practice, elastomer compatibility is also important, since prolonged use of the oil can cause elastomers, such as radial shaft seals, to shrink and lead to leaks. Likewise, an oil can cause excessive swelling, which can also lead to leaks. Various NBR and FKM elastomer types are typically used in industrial gear units, with NBR types in particular being highly sensitive to the composition of the base oil mixture.

[0008] For the lubrication of industrial gears in the food processing industry, physiologically safe lubricating fluids must be used, as possible contact of the lubricating fluid with food cannot be completely ruled out. The selection of raw materials that can be used to produce food-grade (H1) lubricating fluids is severely limited compared to technical lubricating fluids. All of the above-mentioned friction modifiers are not permitted in the formulation of food-grade lubricating fluids.

[0009] The requirements for hydraulic oil for industrial use are described in DIN 51524-1, DIN 51524-2, and DIN 51524-3. Hydraulic oils offer protection against wear and corrosion. HLP-classified oils (DIN 51524-2) offer improved wear protection compared to HL-classified oils (DIN 51524-1). HVLP-classified oils (DIN 51524-3) offer, in addition to improved wear protection, a 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 the fluid's viscosity, and at high temperatures due to leakage caused by a decrease in the fluid's viscosity. High efficiency over a wide temperature range can therefore be achieved with oils with a high viscosity index.

[0011] 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 in the past as base oils for food-grade hydraulic and gear oils. US 2021 / 0348079 A discloses lubricants 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 as a polymerization product with a C6-C40-alpha-olefin and a C4-C40-alkyl (meth)acrylate. Polyalphaolefins or alkylene oxides are suggested as optional base oils for the lubricant.

[0012] JP 2007-268697 A discloses oil compositions based on Fischer-Tropsch hydrocarbons and n-paraffins, as well as optionally aromatic and naphthalene 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, such as maleic acid ester or fumaric acid ester polymers, polymerized with an olefinic monomer.

[0013] 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 can be used, among other things, as a gear oil and / or as a hydraulic oil. The base oil should be such that it can absorb the additives required for the lubricating fluid and the additives in the base oil have the desired effect. According to one embodiment, the raw materials should be selected so that the lubricating fluids can also be used in the food processing industry. In the USA, the selection of raw materials is regulated, for example, by the specifications of the US Food and Drug Administration (FDA). As a gear oil, the lubricating fluid should, according to one embodiment, comply with the CLP standard DIN 51517-3 and, in addition, particularly from viscosity class 220 (ISO VG 220), exhibit a micropitting resistance of the rating level "high" in the micropitting test according to FVA 54.To be used as a hydraulic oil, even low viscosity classes of the lubricating fluid must meet DIN 51524-3 (HVLP) standards. Good compatibility with common NBR elastomers (NBR is the abbreviation for "Nitrile Butadiene Rubber") and fluorocarbon rubber elastomers (FKM elastomers) is desired in all viscosity classes. 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 subclaims or are described below.

[0016] The base oil according to the invention comprises:

[0017] 50-98% by weight, preferably 81 to 96% by weight, polyalphaolefins as oligomers of C6 to C14 alpha-olefins, in particular C8 to C12 alpha-olefins;

[0018] 1-25% by weight, preferably 2 to 15% by weight, of polymer esters obtainable 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 C10 to C16 alpha-olefins or C12 to C16 alpha-olefins;

[0019] 1 -25 wt.%, preferably 2 to 4 wt.%, polyalkylene glycols obtainable from alkylene oxides, wherein the alkylene oxides

[0020] Butylene oxide or

[0021] Propylene oxide and at least one C4 to C8 alkylene oxide.

[0022] According to another embodiment, the base oil comprises

[0023] 81 - 96 wt.% of the above polyalphaolefins;

[0024] 2 - 15 wt.% of the above polymer esters;

[0025] 2 - 4 wt.% of the above polyalkylene glycols.

[0026] According to another embodiment, the above polyalphaolefins, polymer esters, and polyalkylene glycols together constitute more than 90 wt.%, in particular more than 95 wt.%, of the base oil. Preferably, the above polyalphaolefins, polymer esters, and polyalkylene glycols add up to 100 wt.% in the base oil. Thus, the base oil consists of the above components.

[0027] According to one embodiment, the polyalphaolefin is an oligomer of a 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 be from 3 to 25. Also independently of this, the viscosity of the polyalphaolefins is preferably from 4 to 300 mm 2 / s at 100°C (kinematic viscosity determined according to DIN EN ISO 3104). The polyalphaolefins can also be used as hydrogenated products.

[0028] 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 having 3 to 10 carbon atoms, in particular 4 to 8 carbon atoms. The dicarboxylic acids of the dicarboxylic acid diester preferably have 4 to 12 carbon atoms, in particular 4 to 6 carbon atoms. For the alpha-olefins of the polymer esters, chain lengths of 10 to 16 carbon atoms, in particular 14 to 16 carbon atoms, are preferred. These can be linear and / or branched, preferably linear. The molar ratio of the alpha-olefins to the dicarboxylic acid diesters can be 1.5:1 to 1:1.5, in particular 1:0.9 to 0.9:1. The polymer esters in particular have an average molecular weight of 1000 to 5000 g / mol and in particular 500 to 2500 g / mol (each as number average).

[0029] The molar ratio of the alpha-olefins to the dicarboxylic acid diesters can be 1.5 to 1 to 1 to 1.5, in particular 1 to 0.9 to 0.9 to 1.

[0030] According to one embodiment, the polyalkylene glycols comprise, or consist in particular of, 30-70 mol% propylene oxide and 70-30 mol% C4 to C8 alkylene oxides, in particular butylene oxide. The polyalkylene glycols are preferably soluble at room temperature in the polyalphaolefins or polyalphaolefin mixtures with which they are used.

[0031] The lubricating fluid composition comprises the base oil according to at least one of the preceding claims, and at least one of the following additives

[0032] - amine-converted alkyl phosphate and / or

[0033] - Polyol monoesters. The lubricating fluid composition preferably comprises or consists of at least:

[0034] - 90 to 98 wt% of the base oil;

[0035] - 0.01 to 2% by weight, preferably 0.1 to 0.3% by weight, of the friction modifier mentioned below, and / or

[0036] 0.01 to 2% by weight, preferably 0.05 to 0.6% by weight, of the wear protection additive mentioned below, based on the base oil; and

[0037] - other additives, in particular 0.1 to 2 wt.% of the other additives.

[0038] According to one embodiment, the lubricating fluid composition comprises or consists of:

[0039] - 94 to 98 wt% of the base oil;

[0040] - 0.01 to 2% by weight, preferably 0.1 to 0.3% by weight, of the friction modifier mentioned below, and / or

[0041] 0.01 to 2% by weight, preferably 0.05 to 0.6% by weight, of the wear protection additive mentioned below, based on the base oil;

[0042] - other additives, in particular 0.1 to 2 wt.% of the other additives.

[0043] The lubricating fluid composition comprises the base oil and at least one of the following additives:

[0044] - an amine-converted alkyl phosphate, in particular mono- or di- C1- to C12- alkyl phosphate, as wear protection additive, in particular 0.01 to 2 wt.%, preferably 0.1 to 0.6 wt.% and / or

[0045] - a polyol monoester, in particular a C12 to C24 fatty acid ester of optionally ethoxylated polyols, in particular optionally ethoxylated sorbitan mono-oleate, as friction modifier, in particular in each case 0.01 to 2 wt.%, preferably 0.05 to 0.3 wt.%.

[0046] The amine-converted alkyl phosphate is preferably a mono- or di-C1 to C12 alkyl phosphate reacted with at least C10 to C18 alkylamines. The reaction is preferably carried out in such a way 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 tetra-methylnonylamine and C11 to C14 alkylamines. Commercial products include Irgalube® 349 from BASF SE or Additin® RC 3760 from LANXESS (CAS Reg. No. 80939-62-4). The amine-converted alkyl phosphate is an antiwear additive.

[0047] The polyol monoester is preferably a C12 to C24 fatty acid ester of polyols such as glycerin, polyglycerin, or sorbitan. The polyol can also be fully 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.

[0048] The C12 to C24 mono-fatty acid esters of possibly partially ethoxylated polyols act as friction modifiers.

[0049] The base oil in a lubricating fluid composition or the lubricating fluid composition can be used as hydraulic and gear oil, in particular in the food processing industry and / or the feed processing industry.

[0050] The weight percentages refer to the total composition (unless expressly stated otherwise) and are valid independently of each other.

[0051] The above polyalphaolefins, polymer esters and polyalkylene glycols are not chemically pure products and when they are mentioned in the singular, this also means a mixture of different molecules, each of which individually corresponds to the given specification.

[0052] Detailed description of the invention

[0053] 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. The polyalphaolefins are oligomers of, in particular, linear 1-alkenes, in particular 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 mm 2 / s The polyalphaolefin can be, for example, an oligomer of 50 to 80 wt.% 1-decene and 50 to 20 wt.% 1-dodecene.

[0054] 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.

[0055] 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 produced by metallocene catalysis.

[0056] 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.

[0057] Polymer esters are polymers resulting from C,C bond formation that contain side chains with ester groups. These include, in particular, copolymers of alpha, beta-unsaturated dicarboxylic acid esters, such as maleic or fumaric acid esters, with unbranched alpha-olefins in particular. Polymer esters and their preparation are described, for example, in DE 3223694 C2 and US Pat. No. 5,435,928 A.

[0058] 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 are present, for example, as homopolymers of butylene oxide or as copolymers of propylene oxide and butylene oxide. Copolymers consisting of 30-70% propylene oxide and 70-30% butylene oxide are preferably used here. The polyalkylene glycols, in particular, have one or two terminal hydroxy groups.

[0059] For elastomer compatibility, the addition of a swelling agent, typically an ester, to the lubricating fluid composition is desirable. Likewise, too high a swelling agent content leads to excessive swelling, which can also cause leaks. Various NBR and FKM elastomer types are used in industrial gears, with NBR types in particular being highly sensitive to the composition, i.e., the polarity, of the base oil mixture.

[0060] Examples of swelling agents include monoesters, diesters, polyol esters, and complex esters, e.g., of C1 to C18 alcohols with a C2 to C18 carboxylic acid. Suitable monoesters 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 glycerin, neopentyl glycol, trimethylolpropane, pentaerythritol, or dipentaerythritol. The swelling agent content is selected to ensure a volume expansion of the elastomer of no more than 10%.Typically, this means that the swelling agent is present in the lubricating fluid composition in a proportion of 0.5 to 6 wt.%, especially 1 to 4 wt.%. One example is di(2-ethylhexyl) sebacate. However, it has been found that the polyalkylene glycol used also acts as a swelling agent.

[0061] Other possible additives for the lubricating fluid composition include antioxidants, wear inhibitors, corrosion inhibitors, detergents, dyes, friction reducers, viscosity improvers, high-pressure additives, metal deactivators, and nanoscale solids. Examples include:

[0062] • 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), organic dithiocarbamates or dithiophosphates;

[0063] • 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);

[0064] • High-pressure additives and / or anti-wear additives such as organic sulfur compounds such as polysulfides or sulfurized 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(dibutyldithiocarbamate));

[0065] • Corrosion inhibitors such as sulfonates, such as petroleum sulfonate, dinonyl naphthalene sulfonate; neutral or overbased calcium sulfonates, magnesium sulfonates, sodium sulfonates, calcium and sodium naphthalene sulfonates, sulfonic acid esters, amine phosphates; N-methyl-N-(1-oxo-9-octadecenyl)glycine;

[0066] • Metal deactivators such as benzotriazoles, such as methylbenzotriazole dialkylamine, sterically hindered phenols, sodium nitrite;

[0067] • Viscosity improvers such as polymethacrylate, polyisobutylene, polystyrene;

[0068] • Friction reducers, some with anti-wear 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 oleyl amides, organic compounds based on polyethers and amides, e.g. alkyl polyethylene glycol tetradecylene glycol ethers, alkyl succinates, PIBSI (polyisobutylene succinic acid imide) or PIBSA (polyisobutylene succinic anhydride).

[0069] • 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 especially preferably smaller than 50 nm) are used.

[0070] To prepare the lubricating fluid composition according to the invention, a portion of the base oil (e.g., 5 to 25 wt.%) is initially introduced together with the additives, which are particularly oil-soluble but generally present as solids under normal conditions, and heated to 90 to 110°C with continuous stirring to ensure dissolution of these additives in the base oil. By adding a further portion of the base oil, the temperature is reduced to below 60°C. Liquid and optionally oil-insoluble additives and solids, as well as the remaining amount of base oil, are then added and mixed by further stirring until complete homogeneity of the mixture is achieved.

[0071] The lubricating fluid composition according to the invention is particularly suitable for use in industrial gears (spur, helical, bevel, hypoid, and planetary gears) and hydraulic systems, especially those used in the food or feed industry. A gear is a machine element with which motion variables (e.g., changes in force or torque) can be changed. Depending on the design of the gear, these are enclosed in a housing and lubricated with a lubricating fluid. Seals are used to prevent the lubricating fluid from leaking out. In addition to special design properties, the sealing materials must also be chemically stable to the lubricating fluids used.

[0072] Elastomer compatibility therefore plays an important role in lubricant development. The same applies to the durability of hydraulic seals used to seal hydraulic systems filled with hydraulic oils.

[0073] 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).

[0074] Test examples:

[0075] Production:

[0076] A portion of the base oil (5-25%), in this case the polar oil components, namely esters and polyalkylene glycol, is added together with the additives, which are solid at room temperature, and heated to 90 to 110°C with continuous stirring until a clear solution is obtained. By adding the remaining (unheated) base oil, the temperature is reduced to below 60°C. The liquid additives are then added and mixed with further stirring for approximately 15 minutes until the mixture is completely homogeneous. Upon further cooling to temperatures below 40°C, the oil is ready for bottling.

[0077] In addition to the listed base oil components, the formulations each contain an additive package.

[0078] The following materials 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, Chevron Phillips Chemical

[0079] Di(2-Ethylhexyl)-se-Priolube 1856, Croda; Nycobase 20307 FG, Nyco; Lubricit bacat DOS, Zschimmer&Schwarz

[0080] Polymer ester Ketjenlube 240, Italmatch

[0081] Polyalkylene glycol UCON OSP-32, DOW

[0082] Wear protection additive amine-neutralized alkyl phosphate, Irgalube 349, BASF SE

[0083] -Additive (AW additive)

[0084] Additive package triphenylphosphorothionate, phenolic antioxidant, aminic antioxidant, sorbitan monooleate, N-methyl-N-(1-oxo-9-octadecenyl)glycine, polydimethylsiloxane and benzotriazole derivative, whereby sorbitan monooleate is the friction modifier used.

[0085] Table 1 The following methods were used in Tables 1 and 2: kV 40 [mm 2 / s] Kinematic viscosity at 40°C determined according to DIN

[0086] EN ISO 3104

[0087] VI viscosity index according to DIN ISO 2909

[0088] LAV air release capacity at 75°C determined according to DIN

[0089] ISO 9120

[0090] Elastomer compatibility according to DIN ISO 1817, 168h at 100°C for 72 NBR 902 Corrosion protection against steel finger test according to DIN ISO 7120-B Steel, synthetic seawater FZG A / 8.3 / 90, SKS achieved failure load level in the FZG test A / 8.3 / 90 according to DIN ISO 14635-1

[0091] 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

[0092] Micropitting, profile deviation [pm] FVA 54, profile deviation after LS 9 micropitting, achieved SchaFVA 54, achieved damage load level (SKS), damage load level, assessment GFT = micropitting resistance high = high

[0093] The polymer esters and polyalkylene glycol used are highly suitable additives to the PAO oil because they are able to maintain a high viscosity index. A higher viscosity index means a higher lubricating film thickness at operating temperature, which contributes to better wear protection.

[0094] A purely PAO-based formulation (Test 1) does not provide sufficient elastomer compatibility. NBR elastomers shrink and can lead to leaks. Formulations containing either polyalkylene glycol (Test 2) or ester (Test 3) show only slight volume losses. The best result is achieved with a formulation containing both ester and polyalkylene glycol (PAG) in addition to POA (Test 4). Furthermore, corrosion protection against salt water cannot be guaranteed with the purely PAO-based formulation, despite the same additives.

[0095] Compared to the ester-containing but polyalkylene glycol-free version (Test 3), the air separation performance in Test 4 is not improved. Table 2

[0096] Test series 2 shows that, among additives, the content of amine-neutralized alkyl phosphates plays a decisive role in passing or failing the important mechanical-dynamic tests. At a low content (Test 5), high micropitting resistance can be achieved even without the addition of polyalkylene glycol. However, only damage load 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 load level greater than 12 is achieved in the FZG test, but the micropitting resistance is insufficient. The reduced amine phosphate content in Test 4 can be compensated for by the oil-soluble polyalkylene glycol without exhibiting negative effects in the micropitting test.

[0097] The base oil mixture described here supports the corrosion protection properties and elastomer compatibility of the lubricant and allows for a balanced additive mix suitable for food grade lubricants, which meets the sometimes conflicting requirements.

Claims

Patent claims 1. Base oil comprising 50 - 98 wt.% polyalphaolefins as oligomers of C6- to C14-alpha-olefins; 1–25 wt% polymer esters as polymerization products of one or more alpha / beta-unsaturated dicarboxylic acid diesters, wherein the alcohol groups have 3 to 10 carbon atoms; and C4 to C18 alpha olefins; 1 - 25 wt.% polyalkylene glycols obtainable from alkylene oxides, wherein the alkylene oxides are butylene oxide or comprise propylene oxide and at least one C4 to C8 alkylene oxide.

2. The base oil according to claim 1 comprising 81 - 96 wt.% of polyalphaolefins; 2 - 15 wt.% of the polymer esters; 2 - 4 wt.% of polyalkylene glycols.

3. The base oil according to claim 1 or 2, wherein the polyalphaolefins, polymer esters and polyalkylene glycols together constitute more than 90 wt.%, in particular more than 95 wt.%, of the base oil and preferably the polyalphaolefins, the polymer esters and the polyalkylene glycols add up to 100 wt.% in the base oil.

4. The base oil according to at least one of the preceding claims, wherein the alcohol groups of the dicarboxylic acid diesters are linear and / or branched monoalcohols with 3 to 10 carbon atoms, in particular 4 to 8 carbon atoms.

5. The base oil according to at least one of the preceding claims, wherein the dicarboxylic acid of the dicarboxylic acid diester has 4 to 12 carbon atoms, in particular 4 to 6 carbon atoms.

6. The base oil according to at least one of the preceding claims, wherein the alpha-olefins of the polymer esters have 10 to 16 carbon atoms, in particular 14 to 16 carbon atoms.

7. The base oil according to at least one of the preceding claims, wherein the dicarboxylic acid diester is a maleic acid diester and / or a fumaric acid diester.

8. The base oil according to at least one of the preceding claims, wherein the molar ratio of the alpha-olefins to the dicarboxylic acid diesters is 1.5 to 1 to 1.5, in particular 1 to 0.9 to 0.9 to 1.

9. The base oil according to at least one of the preceding claims, wherein the polymer ester has a mean molecular weight of 1000 to 5000 g / mol, in particular 1500 to 2500 g / mol, as the number average.

10. The base oil according to at least one of the preceding claims, wherein the polyalphaolefin(s) are characterized by one or more of the following properties: a) the polyalphaolefins are oligomers of 1-octene, 1-decene and / or 1-dodecene; b) the degree of polymerization of the polyalphaolefins is 3 to 25; c) the polyalphaolefins have a viscosity of 4 to 300 mmHg. 2 / s at 100°C; d) the polyalphaolefin is a hydrogenated oligomer; e) the polyalphaolefin is an oligomer of 50 to 80 wt.% 1-decene and 50 to 20 wt.% 1-dodecene; f) the polyalphaolefin is a mixture of oligomers, wherein at least one oligomer is produced by metallocene catalysis; and g) the polyalphaolefin is a mixture of 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.

11. The base oil according to at least one of the preceding claims, wherein the polyalphaolefin contains a mixture of a1) oligomers of 1-decene and b1) oligomers of 1-octene; or wherein the polyalphaolefin is or contains a mixture of a2) oligomers of 1-dodecene and b2) oligomers of 1-octene and / or 1-decene.

12. The base oil according to claim 11, wherein the polyalphaolefin is a mixture of oligomers a) and b) with 5 - 95 wt.% of oligomers a1 ) or a2) and 5 - 95 wt.% of oligomers b1 ) or b2).

13. The base oil according to at least one of the preceding claims, wherein the polyalkylene glycol is obtainable from alkylene oxides, wherein the alkylene oxides are 30-70 mol% propylene oxide and comprise 70-30 mol% C4- to C8- alkylene oxides, especially butylene oxide.

14. Lubricating fluid composition comprising the base oil according to at least one of the preceding claims, and at least one of the following additives - amine-reacted alkyl phosphate and / or - Polyol monoester.

15. The lubricating fluid composition according to claim 14 comprising - 0.01 to 2 wt.%, preferably 0.1 to 0.6 wt.% of the amine-reacted alkyl phosphate(s), and / or - 0.01 to 2 wt.%, preferably 0.05 to 0.3 wt.% of the polyol monoester(s).

16. The lubricating fluid composition according to claim 14 or 15, wherein - - the ester group of the polyol monoester is a C12 to C24 fatty acid and the polyol of the polyol monoester may be ethoxylated, and / or - the amine-reacted alkyl phosphates are reacted with at least C10 to C18 alkylamines and the alkyl phosphate is preferably a mono- or di- C1 to C12 alkyl phosphate.

17. Use of the base oil according to at least one of claims 1 to 13 in a lubricating fluid composition or the lubricating fluid composition according to at least one of claims 14 to 16 as hydraulic and gear oil, in particular in the food processing industry and / or the feed processing industry.