Base oil and lubricating oil composition containing said base oil

Abstract

The present invention relates to a base oil comprising a polyalphaolefin, a polymeric ester and a polyalkylene glycol, and to a lubricating oil composition containing the base oil, which can be used for the lubrication of transmissions and hydraulic systems, particularly in the food processing industry.

Description

[Technical field]

[0001] The present invention relates to a base oil comprising polyalphaolefins, polymeric esters and polyalkylene glycols, and to a lubricating oil composition comprising said base oil and additives. This lubricating oil composition can be used for lubricating gears (transmissions) and hydraulic systems, particularly in the food processing industry. A particular application field of the base oil and lubricating oil composition according to the present invention is lubricating points that come into contact or may come into contact with food and / or animal feed. [Background technology]

[0002] Hydraulic and gear oils are composed of a base oil and additives that are added to improve the life and performance of the lubricant. The base oil may be composed of a mixture of different oils.

[0003] Various mechanical dynamic tests are carried out to determine the performance of lubricants. The Research Center for Gear and Transmission Engineering (FZG) at the Technical University of Munich has developed a test device that can be used to test the suitability of gear lubricants to prevent seizure on the gear surfaces and flanks. An important parameter for industrial gear oils is the load stage in the FZG test A / 8.3 / 90 according to DIN ISO 14635-1. In this test, the scuffing load capacity of the lubricant is measured using an FZG gear load tester. For this purpose, a test gear pair with a special tooth profile is run in the lubricant to be tested. The temperature and speed are specified. The tooth flank is gradually loaded via a lever carrying a weight, and one shaft is fixed relative to the other. From load stage 4, the pinion tooth flank is inspected for damage after the end of each load stage. If load stage 12 is reached without damage occurring, the measurement is completed. The hydraulic oil requirement standard (DIN 51524-2 HLP) requires at least load stage 10, and the circulating oil requirement standard (DIN 51517-3 CLP) requires at least load stage 12. The result is either "pass" or "fail", i.e. it either works or it doesn't.

[0004] Another technically important requirement beyond DIN 51517-3 is high resistance to grey staining. "Grey staining resistance" refers to the ability of a lubricant to prevent damage caused by grey staining (also known as "micropitting").

[0005] Gray staining occurs on the tooth surface under high loads in mixed friction areas. The lubricant film thickness at the operating temperature has a major influence on the occurrence of gray staining. Furthermore, the use of chemically active additives can significantly promote the occurrence of gray staining. The addition of friction-improving additives (friction modifiers) can help prevent gray staining. US Patent No. 9,347,016 (B2) describes the use of dialkyldithiophosphates as effective components against micropitting. European Patent Application Publication No. 0,949,320 (A2) describes phosphonates and phosphites (e.g., dioleyl phosphite), succinimides, pyrrolidinones, molybdenum carboxylates and oleylamides as friction modifiers to prevent micropitting. US Patent No. 6,184,186 (B1) proposes the use of molybdenum carboxylates and sulfurized isobutylene to prevent micropitting.

[0006] The FVA54 micropitting test is carried out on an FZG standard load testing machine and is used to determine the micropitting resistance of lubricants. The test consists of two consecutive parts: a step test to determine the load stage and a durability test to evaluate the long-term tribological behavior. In the step test, the load is gradually increased from load stage 5 to load stage 10, and the test time for each load stage is 16 hours. The durability test is carried out first at load stage 8 for 80 hours and then at load stage 10 for 5 x 80 hours. After the end of each load stage, the pinion is removed and the tooth profile deviation and the percentage of gray spots on the tooth flank are determined for three teeth. In addition, the weight loss of the pinion due to wear is determined. The tooth profile deviation is used to determine the load stage in the step test. A load stage is reached when a value of 7.5 μm is exceeded. Load stage 10 is reached if the limit value is not exceeded after the first five load stages. If all six load stages are passed without exceeding the limit, then an SKS of greater than 10 results.

[0007] Compatibility with elastomers is also important in practice, as elastomers such as radial shaft seals can shrink over time, leading to leakage. Similarly, oil can cause excessive swelling, leading to leakage. In industrial gearboxes, various types of NBR and FKM elastomers are commonly used, and the NBR types in particular react strongly to the composition of the base oil mixture.

[0008] For the lubrication of industrial gearboxes in the food processing industry, physiologically harmless lubricants must be used, since the possibility of the lubricant coming into contact with food cannot be completely excluded. The selection of raw materials available for the production of lubricants suitable for food (food grade (H1)) is very limited compared to industrial lubricants. None of the friction modifiers mentioned above are permitted in the formulation of "food grade" lubricants.

[0009] The requirements for industrial hydraulic oils are set out in DIN 51524-1, DIN 51524-2 and DIN 51524-3. Hydraulic oils provide protection against wear and corrosion, with HLP-classified oils (DIN 51524-2) offering improved wear protection compared to HL oils (DIN 51524-1), and HVLP-classified oils (DIN 51524-3) having, in addition to improved wear protection, a more stable temperature-viscosity behavior (viscosity index) and therefore usable over a wider temperature range.

[0010] A high viscosity index is also desirable. Pressure losses in hydraulic systems reduce efficiency. Pressure losses can occur at low temperatures due to the increase in oil viscosity, and at high temperatures due to leakage caused by the decrease in oil viscosity. Thus, by using oils with a high viscosity index, high efficiency can be achieved over a wide temperature range.

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

[0012] US Patent Publication No. 2021 / 0348079 (A) discloses lubricating oils based on terpolymers of diesters, olefins and acrylates. The terpolymers are polymerized diesters selected from di(C4-C22 alkyl)esters of maleic acid, fumaric acid, 2-methylmaleic acid, 2,3-dimethylmaleic acid, 2-methylfumaric acid, 2,3-dimethylfumaric acid, or mixtures thereof as polymerization products with C6-C40 α-olefins and C4-C40 alkyl (meth)acrylates. As optional base oils for the lubricating oils, polyα-olefins or alkylene oxides, etc. are proposed.

[0013] JP 2007-268697 A discloses an oil composition based on Fischer-Tropsch hydrocarbons and n-paraffins, and optionally aromatic and naphthalene hydrocarbon oils. The oil composition may optionally further contain synthetic oils such as poly-α-olefins or polyalkylene glycols, or polymers such as polymerization products of unsaturated carboxylic acid residues, such as maleic or fumaric acid ester polymers polymerized with olefin monomers.

[0014] The object of the present invention is to provide a base oil and a lubricant containing said base oil, in particular a lubricant usable as a gear oil and / or hydraulic oil. The base oil must be such that the lubricant can incorporate the necessary additives and that the additives in the base oil have the desired effect. According to one embodiment, the raw materials should be selected so that the lubricant can also be used in the food processing industry. The choice of raw materials is regulated in the United States, for example, by the standards of the Food and Drug Administration (FDA). As a gear oil, the lubricant must according to one design meet DIN 51517-3 of the CLP regulation and, in addition, must have a "high" level of gray staining resistance in the micropitting test according to FVA54, especially from viscosity grade 220 (ISO VG220). For use as a hydraulic oil, the lubricant of the low viscosity class must also meet DIN 51524-3 (HVLP). All viscosity classes require good compatibility with common NBR elastomers (NBR is the abbreviation for "nitrile butadiene rubber") and fluororubber elastomers (FKM elastomers). Summary of the Invention

[0015] This problem is solved by the subject matter of the independent claims. Advantageous embodiments are the subject matter of the dependent claims or are described below. The base oil according to the present invention comprises: 50 to 98% by weight, preferably 81 to 96% by weight, of polyα-olefins as oligomers of C6 to C14 α-olefins, in particular C8 to C12 α-olefins; a polymeric ester obtained as a polymerization product of 1 to 25% by weight, preferably 2 to 15% by weight, of one or more α / β-unsaturated dicarboxylic acid diesters, the alcohol group of which has 3 to 10 carbon atoms, in particular 4 to 8 carbon atoms, with one or more C4 to C18 α-olefins, in particular C10 to C16 α-olefins or C12 to C16 α-olefins; and A polyalkylene glycol obtained from 1 to 25% by weight, preferably 2 to 4% by weight, of an alkylene oxide, the alkylene oxide being Butylene oxide, or Contains propylene oxide and at least one C4-C8 alkylene oxide.

[0016] According to another embodiment, the base oil comprises: 81 to 96 weight percent of said polyα-olefin; 2 to 15 weight percent of said polymer ester; and 2 to 4% by weight of said polyalkylene glycol Includes.

[0017] According to another embodiment, the polyα-olefin, the polymer ester and the polyalkylene glycol together account for more than 90% by weight of the base oil, in particular more than 95% by weight of the base oil.Preferably, the polyα-olefin, the polymer ester and the polyalkylene glycol together account for 100% by weight of the base oil.The base oil is therefore composed of the above components.

[0018] According to one embodiment, the polyα-olefin is an oligomer of 1-octene, 1-decene and / or 1-dodecene, in particular an oligomer of 1-octene or 1-decene or 1-octene and 1-decene. The degree of polymerization of the polyα-olefin may be between 3 and 25.

[0019] Regardless of this, the viscosity of the poly-α-olefin (kinetic viscosity measured in accordance with DIN EN ISO 3104) is preferably 4 to 300 mm at 100° C. 2 The poly-α-olefins can also be used as hydrogenated products.

[0020] The polymeric esters are preferably copolymers of maleic and / or fumaric acid (fully / fully esterified) esters with one or more C4-C18 α-olefins. The alcohol groups of the dicarboxylic acid diesters are in particular linear and / or branched monoalcohols having 3-10 carbon atoms, in particular 4-8 carbon atoms. The dicarboxylic acids of the dicarboxylic acid diesters preferably have 4-12 carbon atoms, in particular 4-6 carbon atoms. The α-olefins of the polymeric esters preferably have chain lengths of 10-16 carbon atoms, in particular 14-16 carbon atoms. They may be linear and / or branched, but are preferably linear. The molar ratio of the α-olefins to the dicarboxylic acid diesters may be 1.5:1 to 1:1.5, in particular 1:0.9 to 0.9:1. The polymeric esters have an average molecular weight in particular of 1000 to 5000 g / mol, in particular 1500 to 2500 g / mol (respectively as number average).

[0021] The molar ratio of the α-olefin to the dicarboxylic acid diester may be from 1.5:1 to 1:1.5, in particular from 1:0.9 to 0.9:1.

[0022] According to one embodiment, the polyalkylene glycol comprises or in particular consists of 30-70 mol % propylene oxide and 70-30 mol % C4-C8 alkylene oxide, in particular butylene oxide. The polyalkylene glycol is preferably soluble at room temperature in the polyα-olefin or polyα-olefin mixture with which it is used.

[0023] The lubricating oil composition comprises a base oil according to at least one of the preceding claims and at least one of the following additives: - Amine reacted alkyl phosphates and / or - Polyol monoester.

[0024] The lubricating oil composition preferably comprises or consists of at least: - 90 to 98 wt.-% of said base oil; - 0.01 to 2% by weight, preferably 0.1 to 0.3% by weight, based on the base oil, of one of the following friction modifiers, and / or 0.01 to 2% by weight, preferably 0.05 to 0.6% by weight, of the following antiwear additives: - other additives, in particular 0.1-2% by weight of other additives.

[0025] According to one embodiment, the lubricating oil composition comprises or consists of: - 94 to 98 wt.-% of said base oil; - 0.01 to 2% by weight, preferably 0.1 to 0.3% by weight, based on the base oil, of one of the following friction modifiers, and / or 0.01 to 2% by weight, preferably 0.05 to 0.6% by weight, of the following antiwear additives: - other additives, in particular 0.1-2% by weight of other additives.

[0026] The lubricating oil composition comprises the base oil and at least one of the following additives: - in particular 0.01 to 2% by weight, preferably 0.1 to 0.6% by weight, of amine-reacted alkyl phosphates, in particular mono- or di-C1 to C12 alkyl phosphates, as anti-wear additives, and / or - in particular 0.01 to 2% by weight, preferably 0.05 to 0.3% by weight, of polyol monoesters, in particular C12 to C24 fatty acid esters of optionally ethoxylated polyols, in particular optionally ethoxylated sorbitan monooleate, as friction modifiers.

[0027] The amine-reacted alkyl phosphate is preferably a mono- or di-C1-C12 alkyl phosphate reacted with at least a C10-C18 alkyl amine. Preferably, the reaction is carried out such that the alkyl phosphate is neutralized or partially neutralized. Suitable examples include mono- and diisooctyl esters of phosphoric acid reacted with tert-alkylamines and C12-C14 primary amines (CAS Registry Number 68187-67-7), or mono- and dihexyl esters of phosphoric acid reacted with tetra-methylnonylamine and C11-C14 alkyl amines.

[0028] Commercially available products include, for example, Irgalube® 349 from BASF SE or Additin® RC 3760 (CAS Registry Number 80939-62-4) from LANXESS. The amine-reacted alkyl phosphates are anti-wear additives.

[0029] The polyol monoester is preferably a C12-C24 fatty acid ester of a polyol such as glycerol, polyglycerol or sorbitan. The polyol may 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.

[0030] The C12 to C24 mono-fatty acid esters of optionally partially ethoxylated polyols act as friction modifiers.

[0031] Said base oil in a lubricating oil composition or said lubricating oil composition can be used as hydraulic oil and gear oil, especially in the food processing industry and / or the feed processing industry.

[0032] Weight percentages are based on the composition as a whole (unless expressly stated otherwise) and are applied independently of one another.

[0033] The above poly-alpha-olefins, polymeric esters and polyalkylene glycols are not chemically pure products, but when they are listed in the singular, they also refer to mixtures of different molecules which each individually correspond to the listed specifications. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] Hydraulic and gear oils are composed of a base oil and additives that are added to improve the life and performance of the lubricant. The base oil used in the present invention is a mixture of the polyalphaolefins, polymeric esters and polyalkylene glycols described above.

[0035] Polyα-olefins are in particular oligomers of linear 1-alkenes, in particular 1-octene, 1-decene and / or 1-dodecene, which are produced, for example, using Lewis acid catalysts (for example, U.S. Pat. No. 6,824,671 (B2)) or metallocene catalysts (mPAOs, U.S. Pat. No. 9,365,663 (B2), U.S. Pat. No. 9,701,595 (B2)) and have a kinematic viscosity at 100° C. (kV100) of 2 to 300 mm 2 The polyα-olefin may be, for example, an oligomer of 50 to 80% by weight of 1-decene and 50 to 20% by weight of 1-dodecene.

[0036] According to one embodiment, the polyα-olefins are mixtures of a1) oligomers of 1-decene and b1) oligomers of 1-octene, or a2) oligomers of 1-dodecene and b2) oligomers of 1-octene and / or 1-decene. These mixtures can be characterized in more detail as follows: 5-95% by weight of oligomers a1) or a2) and 5-95% by weight of oligomers b1) or b2). The polyα-olefins may be produced by metallocene catalysis.

[0037] In many cases, polyα-olefins with different viscosities, e.g. 4 to 100 mm at 100°C, 2 / sec. and 50-300 mm at 100°C. 2 It is advantageous to mix the oligomer with a viscosity of about 1000 .mu.m / sec.

[0038] Polymeric esters are polymers resulting from C=C bonds containing side chains with ester groups. They include in particular copolymers of α,β-unsaturated dicarboxylic esters, such as maleic or fumaric acid esters, with, in particular, unbranched α-olefins. Polymeric esters and their preparation are described, for example, in German Patent No. 3223694 (C2) and US Pat. No. 5435928 (A).

[0039] Polyalkylene glycols are the polymerization reaction products of water and / or monohydric or dihydric starting alcohols with 1,2-epoxides such as ethylene oxide, propylene oxide and / or butylene oxide, and contain at least propylene oxide and at least one C4-C8 alkylene oxide. Polyalkylene glycols exist, for example, as homopolymers of butylene oxide or as copolymers of propylene oxide and butylene oxide. Here, copolymers consisting of 30-70% propylene oxide and 70-30% butylene oxide are preferably used. Polyalkylene glycols have in particular one or two terminal hydroxy groups.

[0040] For compatibility with elastomers, it is desirable to add a swelling agent, typically an ester, to the lubricating oil composition. Similarly, too high a swelling agent content can lead to excessive swelling and even leakage.

[0041] Various NBR and FKM elastomer types are used in industrial gearboxes, with the NBR types in particular reacting strongly to the composition, i.e. the polarity of the base oil mixture.

[0042] Examples of swelling agents include monoesters, diesters, polyol esters, and complex esters of, for example, C1-C18 alcohols with C2-C18 carboxylic acids. Monoesters and diesters of interest here 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 selected so that the elastomer does not swell by more than 10% by volume. As a rule, this means that the swelling agent is present in the lubricating oil composition in a proportion of 0.5 to 6% by weight, in particular 1 to 4% by weight. An example is di(2-ethylhexyl) sebacate. However, it has been found that the polyalkylene glycols used also act as swelling agents.

[0043] Other additives that may be used in the lubricating oil composition include antioxidants, antiwear agents, corrosion inhibitors, detergents, colorants, friction reducers, viscosity improvers, high pressure additives, metal deactivators, and nanoscale solids. Examples include: As primary antioxidants, amine compounds (e.g. alkylamines or 1-phenylaminonaphthalene), aromatic amines such as phenylnaphthylamine or diphenylamine or polymeric hydroxyquinolines (e.g. TMQ), phenolic compounds (e.g. 2,6-ditert-butyl-4-methylphenol), organic dithiocarbamates or dithiophosphates, etc.; As secondary antioxidants, phosphites, such as tris(2,4-ditert-butylphenyl phosphite) or bis(2,4-ditert-butylphenyl)-pentaerythritol diphosphite or thioethers, such as cresol thioethers; As high pressure and / or antiwear additives, organic sulfur compounds such as polysulfides or sulfurized olefins, thiophosphates (e.g. triphenylthiophosphate) and dithiophosphates, phosphites and phosphonates (e.g. di-n-octylphosphonate), phosphates (e.g. substituted triphenylphosphates or amine-neutralized alkyl phosphates), inorganic or organic boron compounds, thiocarbamates and dithiocarbamates (e.g. methylenebis(dibutyldithiocarbamate)), etc.; As corrosion inhibitors, sulfonates, e.g. petroleum sulfonates, dinonylnaphthalene sulfonates; 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, etc.; Metal deactivators, such as benzotriazoles, e.g., methylbenzotriazole dialkylamines, sterically hindered phenols, sodium nitrite, etc.; Viscosity improvers, such as polymethacrylates, polyisobutylenes, polystyrenes, etc.; As friction reducers, organic acids (e.g. isostearic acid), fatty acid esters of polyols, which may be partially ethoxylated, such as glycerol or sorbitan, partial glycerides, animal or vegetable oils, dialkyl hydrogen phosphonates, carboxylic acid amides, such as oleylamide, organic compounds based on polyethers and amides, e.g. alkyl polyethylene glycol tetradecylene glycol esters, alkyl succinates, PIBSI (polyisobutylene succinimide) or PIBSA (polyisobutylene succinic anhydride), some of which also have antiwear properties. As solids: To obtain certain properties, particles can be used in gear oils (boron nitride, silicon dioxide, layered silicates such as bentonite, carbon nanotubes). To avoid negative effects on the tribological performance, very small particles are used (so-called nanoparticles with a particle size smaller than 500 nm, preferably smaller than 100 nm, particularly preferably smaller than 50 nm).

[0044] To prepare the lubricating oil composition according to the invention, for example, a portion of the base oil (e.g., 5-25% by weight) is introduced together with additives that are particularly oil-soluble but generally exist as solids under normal conditions, and heated to 90-110°C with continuous stirring to ensure that these additives are dissolved in the base oil. The temperature is reduced to below 60°C by adding a further portion of the base oil. The liquid and optionally oil-insoluble additives, solids, and the remaining amount of base oil are then added and mixed with further stirring until the mixture is completely homogeneous.

[0045] The lubricating oil compositions according to the invention are particularly suitable for use in industrial gearboxes (spur, helical, bevel, hypoid and planetary gearboxes) and hydraulic systems, especially those used in the food or animal feed industries.

[0046] A gearbox is a machine element capable of changing a motion variable (e.g. change of force, torque). Depending on the gearbox design, the gearbox is enclosed in a housing and lubricated with a lubricant. Seals are used to prevent the lubricant from leaking out. In addition to special design characteristics, the seal material must be chemically stable with respect to the lubricant used.

[0047] Therefore, compatibility with elastomers plays an important role in the development of lubricants. The same applies to the resistance of hydraulic seals used to seal hydraulic systems filled with hydraulic oil.

[0048] As part of the present invention, lubricants have been developed for use as gear oils and hydraulic oils which meet the requirements of DIN 51517-3 (more precisely: tests for relative volume change, change in Shore A hardness, tensile strength, elongation at break as described in DIN ISO 1817) and the Dynamic Elastomer Compatibility Test (Freudenberg test standard FS PLM 111 0008).

[0049] <Experimental Example> Manufacturing: A portion of the base oil (5-25%), in this case the polar oil components, i.e. esters and polyalkylene glycols, is introduced together with the additives that are solid at room temperature and heated to 90-110°C with continuous stirring until a clear solution is obtained. The temperature is reduced to below 60°C by adding the remaining (unheated) base oil. The liquid additives are then added and mixed by further stirring for about 15 minutes until the mixture is completely homogeneous. After further cooling to below 40°C, the oil can be filled.

[0050] In addition to the base oil components listed, the formulations each contain an additive package.

[0051] The following substances were used: PAO6 poly-α-olefin: Spectrasyn 6 from ExxonMobil Chemical; Synfluid PAO6 cSt from Chevron Phillips Chemical; Durasyn 166 from Ineos Oligmers mPAO150 Metallocene-catalyzed poly-α-olefins: Spectrasyn Elite 150 from ExxonMobil Chemical; Synfluid mPAO150 cSt from Chevron Phillips Chemical Di(2-ethylhexyl) sebacate Croda Priolube 1856; Nyco Nycobase 20307 FG; Zschimmer & Schwarz Lubricit DOS Polymer ester Italmatch Ketjenlube 240 Polyalkylene glycol DOW UCON OSP-32 Anti-Wear Additives - Additives (AW Additives) Amine neutralized alkyl phosphate, Irgalube 349 from BASF SE Additive package Triphenyl phosphorothionate, phenolic antioxidants, amine antioxidants, sorbitan monooleate, N-methyl-N-(1-oxo-9-octadecenyl)glycine, polydimethylsiloxane and benzotriazole derivatives, sorbitan monooleate are used as friction modifiers.

[0052] [Table 1]

[0053] In Tables 1 and 2, the following methods were applied: kV 40 [mm 2 / s] kinematic viscosity at 40 °C measured according to DIN EN ISO 3104 VI Viscosity index according to DIN ISO 2909 Air release capacity at 75°C measured according to LAV DIN ISO 9120 Compatibility with elastomers According to DIN ISO 1817, 72 NBR 902, 168 hours at 100°C Steel corrosion protection, artificial seawater Steel finger test according to DIN ISO7120-B FZG A / 8.3 / 90, Load stage reached in FZG test A / 8.3 / 90 according to SKS DIN ISO14635-1 FE8, mw50 / mk50 [mg] Wear value of rolling elements / cage calculated in FE8 test (D-7.5 / 80-80) according to DIN 51819-3 (50% probability of wear) Micropitting, profile deviation [μm] Profile deviation according to FVA54, LS9 High resistance to micropitting, load stage reached, rating FVA54, load stage reached (SKS), rating GFT = gray spots = high.

[0054] The polymer esters and polyalkylene glycols used are highly suitable additives for PAO oils because they maintain a high viscosity index, which means a thicker lubricant film thickness at operating temperatures, contributing to improved wear protection.

[0055] The purely PAO-based formulation (Example 1) did not provide sufficient elastomer compatibility; the NBR elastomer could shrink, leading to leakage. Formulations containing polyalkylene glycol (Example 2) or ester (Example 3) showed only slight volume loss. The best results were obtained with the formulation containing both ester and polyalkylene glycol (PAG) in addition to POA (Example 4). Furthermore, corrosion protection against salt water could not be guaranteed with the purely PAO-based formulation, despite the same additives.

[0056] Compared to the version containing the ester but no polyalkylene glycol (Example 3), Example 4 did not improve air release capabilities.

[0057] [Table 2]

[0058] Test series 2 shows that, among the additives, the content of amine neutralized alkyl phosphate plays a decisive role in passing the important mechanical dynamics tests. At low contents (example 5), high gray spot resistance could be obtained without the addition of polyalkylene glycol. However, only load stage 11 could be reached in the FZG test. At high contents of amine phosphate and the presence of polyalkylene glycol (example 6), load stages greater than 12 were reached in the FZG test, but the gray spot load-bearing capacity was insufficient. The reduction in the amine phosphate content in example 4 could be compensated for by the oil-soluble polyalkylene glycol without any adverse effects in the micropitting test.

[0059] The base oil blends described herein support the corrosion inhibition properties and elastomer compatibility of the lubricant, allowing for a balanced additive formulation suitable for "food grade" lubricants, fulfilling sometimes conflicting requirements.

Claims

1. A base oil comprising: 50 to 98% by weight of a polyalphaolefin as an oligomer of C6 - C14 α - olefins; 1 to 25% by weight of a polyester as a polymerization product of one or more α / β - unsaturated dicarboxylic acid diesters having an alcohol group with 3 to 10 carbon atoms and a C4 - C18 α - olefin; and 1 to 25% by weight of a polyalkylene glycol obtained from an alkylene oxide, where the alkylene oxide is butylene oxide, or comprises propylene oxide and at least one C4 - C8 alkylene oxide.

2. In the base oil according to Claim 1, 81 to 96% by weight of the polyalphaolefin; 2 to 15% by weight of the polyester; and 2 to 4% by weight of the polyalkylene glycol are included, the base oil.

3. In the base oil according to Claim 1, the polyalphaolefin, the polyester and the polyalkylene glycol together occupy more than 90% by weight of the base oil, the base oil.

4. In the base oil according to Claim 1, the alcohol group of the dicarboxylic acid diester is a linear and / or branched mono - alcohol having 3 to 10 carbon atoms, the base oil.

5. In the base oil according to Claim 1, the one or more α / β - unsaturated dicarboxylic acid diesters contain a dicarboxylic acid group having 4 to 12 carbon atoms, the base oil.

6. In the base oil according to Claim 1, the α - olefin of the polyester has 10 to 16 carbon atoms, the base oil.

7. In the base oil according to Claim 1, the one or more α / β - unsaturated dicarboxylic acid diesters are maleic acid diester and / or fumaric acid diester, the base oil.

8. In the base oil according to Claim 1, the molar ratio of the α - olefin to the one or more α / β - unsaturated dicarboxylic acid diesters is 1.5:1 to 1:1.5, the base oil.

9. In the base oil according to Claim 1, the polyester has an average molecular weight of 1000 to 5000 g / mol as a number average, the base oil.

10. In the base oil according to Claim 1, the polyalphaolefin is characterized by one or more of the following properties: a) the polyalphaolefin is an oligomer of 1 - octene, 1 - decene and / or 1 - dodecene; b) The degree of polymerization of the poly-α-olefin is from 3 to 25; c) The poly-α-olefin has a viscosity of 4 to 300 mm ２ / second at 100 °C; d) The poly-α-olefin is a hydrogenated oligomer; e) The poly-α-olefin is an oligomer of 50 to 80% by weight of 1-decene and 50 to 20% by weight of 1-dodecene; f) The poly-α-olefin is a mixture of oligomers in which at least one oligomer is produced by metallocene catalysis; and g) The poly-α-olefin is a mixture of an oligomer having a viscosity of 4 to 100 mm ２ / sec at 100°C and an oligomer having a viscosity of 50 to 300 mm ２ / sec at 100°C Base oil.

11. In the base oil according to Claim 1, the poly-α-olefin is a1) an oligomer of 1-decene and b1) an oligomer of 1-octene, or a mixture containing the mixture; or the poly-α-olefin is a2) an oligomer of 1-dodecene and b2) an oligomer of 1-octene and / or 1-decene, or a base oil containing the mixture.

12. In the base oil according to Claim 11, the poly-α-olefin is 5 to 95% by weight of the oligomer of a1) or a2) above, and 5 to 95% by weight of the oligomer of b1) or b2) above A base oil which is a mixture of oligomers a) and b) containing.

13. In the base oil according to Claim 1, the polyalkylene glycol is obtained from an alkylene oxide, and the alkylene oxide is 30 to 70 mol% of propylene oxide and 70 to 30 mol% of C4 - C8 alkylene oxide A base oil containing.

14. A lubricating oil composition comprising the base oil according to any one of Claims 1 to 13 and at least one of the following additives: - amine-reacted alkyl phosphate and / or - polyol monoester.

15. In the lubricating oil composition according to Claim 14, - 0.01 to 2% by weight of the amine-reacted alkyl phosphate and / or - A lubricating oil composition containing 0.01 to 2% by weight of the polyol monoester.

16. In the lubricating oil composition according to Claim 14, - the polyol monoester has an ester group consisting of C12 - C24 fatty acids, or - the polyol monoester has an ester group consisting of C12 - C24 fatty acids, and the polyol monoester has a polyol group ethoxylated with a polyol group, and / or - the amine-reacted alkyl phosphate is reacted with at least C10 - C18 alkylamine, or - The alkyl phosphate reacted with the amine is a reaction product with at least a C10-C18 alkylamine, and the alkyl phosphate is a mono- or di-C1-C12 alkyl phosphate, a lubricating oil composition.

17. Use of the base oil according to any one of claims 1 to 13 in a lubricating oil composition, wherein the lubricating oil composition is used as a hydraulic oil or a gear oil in the food processing industry or the feed processing industry.

18. Use of the lubricating oil composition according to claim 14 as a hydraulic oil or a gear oil.

19. Use according to claim 18 in the food processing industry and / or the feed processing industry.