Base oil and lubricating liquid composition containing base oil

Abstract

The present invention relates to a base oil comprising a polyalphaolefin, a polyester, and a polyalkylene glycol, and a lubricating liquid composition comprising the same. The lubricating liquid composition can be used for lubrication of transmissions and hydraulic systems, in particular for lubrication in the food preparation industry.

Description

Technical Field

[0001] The present invention relates to a base oil comprising polyalphaolefin, polyester and polyalkylene glycol and a lubricating fluid composition comprising the base oil and additives. The lubricating fluid composition can be used for lubrication of gears (transmissions) and in hydraulic systems, in particular for lubrication in the food processing industry. The specific application areas of the base oil and lubricating fluid composition according to the present invention are lubrication points that are in contact or may be in contact with food and / or animal feed. Background Art

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

[0003] Various mechanical dynamic tests were performed to determine the properties of the lubricant. und Getriebebau) has developed a test rig that can be used to test the suitability of gear lubricants for preventing seizure on the gear surfaces and flanks. An important parameter for industrial gear oils is the damage force level in FZG test A / 8.3 / 90 according to DIN ISO 14635-1. In this test, the scuffing load capacity of a lubricant is determined using an FZG gear tension tester. For this purpose, a pair of test gears with a special tooth shape are run in the lubricating fluid to be tested. The temperature and speed are specified. The load on the tooth flanks is applied in stages by means of a lever equipped with a weight, which supports one shaft on the other. Starting with force level 4, the pinion tooth flanks are checked for any damage after each force level. If force level 12 is reached without damage, the measurement is complete. The requirement standard for hydraulic oils (DIN 51524-2HLP) requires at least force level 10, while the requirement standard for circulating oils (DIN 51517-3CLP) requires at least force level 12. The result is either "pass" or "fail" - valid or invalid.

[0004] Another technology-related requirement that goes beyond DIN 51517-3 is high grey staining resistance. The term "grey staining resistance" refers to the ability of a lubricating fluid to prevent damage caused by grey staining (also called "micropitting").

[0005] Under high loads in the mixed friction area, gray staining will occur on the tooth side. The thickness of the lubricating film at operating temperature has a major influence on the occurrence of gray staining. In addition, the use of chemically active additives can significantly promote the occurrence of gray staining. The addition of friction improving additives (friction modifiers) helps to prevent gray staining. US 9347016B2 describes the use of dialkyl dithiophosphates as an active ingredient for preventing micropitting. EP 0949320 A2 mentions phosphates and phosphites (such as dienyl phosphites), succinimides, pyrrolidones, molybdenum carboxylates and oleamides as friction modifiers for preventing micropitting. US 6184186B1 requires the use of molybdenum carboxylates and sulfided isobutylene to prevent micropitting.

[0006] The FVA 54 micropitting test is carried out on an FZG standard tension testing machine and is used to determine the micropitting resistance of lubricating fluids. The test consists of two consecutive parts: a step test to determine the damage force level and a durability test to evaluate the tribological long-term behavior. In the step test, the load is gradually increased from force level 5 to force level 10, with a test duration of 16 hours per force level. The durability test is initially run for 80 hours at force level 8 and then 5x 80 hours at force level 10. After each force level, the pinion is removed and the tooth profile shape deviation and the proportion of gray staining on the tooth flank are determined on three teeth. In addition, the weight loss due to pinion wear is determined. The profile shape deviation is used to determine the damage force level in the profile shape deviation. If a value of 7.5 μm is exceeded, the damage force level is reached. If the limit value is not exceeded after the first five force levels, the damage force level 10 is reached. If all six force levels are passed without exceeding the limit value, the result is an SKS greater than 10.

[0007] Elastomer compatibility is also important in practice, since elastomers (such as radial shaft seals) can shrink and cause leakage if oil is used for a long time. Likewise, oil can cause excessive swelling, which can also cause leakage. Various types of NBR and FKM elastomers are often used in industrial gearboxes, with the NBR types reacting particularly 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 contact between the lubricant and food cannot be completely excluded. The choice of raw materials that can be used to produce lubricants suitable for use with food (food grade (H1)) is very limited for technical lubricants. None of the friction modifiers mentioned above are permitted for the formulation of "food grade" lubricants.

[0009] The requirements for hydraulic oils for industrial use are described in DIN 51524-1, DIN 51524-2 and DIN 51524-3. Hydraulic oils provide protection against wear and corrosion, so that HLP oils (DIN 515 24-2) have improved wear protection compared to HL oils (DIN 51524-1). HVLP oils (DIN 51524-3) have, in addition to improved wear protection, a more stable temperature-viscosity behavior (viscosity index) and can therefore be used over a wider temperature range.

[0010] A high viscosity index is also desirable. Pressure losses in a hydraulic system can reduce efficiency. These can occur at low temperatures due to an increase in fluid viscosity, while leaks due to a decrease in fluid viscosity can also occur at high temperatures. Therefore, using an oil with a high viscosity index can achieve high efficiency over a wide temperature range.

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

[0012] US2021 / 0348079 A discloses a lubricant based on a terpolymer of diester, olefin and acrylate. The terpolymer is selected from di(C4-C22-alkyl) esters of maleic acid, fumaric acid, 2-methylmaleic acid, 2,3-dimethylmaleic acid, 2-methylfumaric acid, 2,3-trimethylfumaric acid, or a mixture of a polymerization product with C6-C40-α-olefin and (meth) acrylic acid C4-C40 alkyl ester. Polyalphaolefin or alkylene oxide is suggested as an optional base oil for the lubricant.

[0013] JP 2007-268697 A discloses an oil composition based on Fischer-Tropsch hydrocarbons and normal paraffins and optionally aromatic and naphthenic oils. The oil composition may optionally further comprise a synthetic oil, such as poly-alpha-olefins or polyalkylene glycols or polymers, such as polymerisation products of unsaturated carboxylic acid residues, such as maleate or fumarate polymers polymerised with olefin monomers. Summary of the invention

[0014] The object of the present invention is to provide a base oil and a lubricating fluid containing the base oil, wherein the lubricating fluid can be used as a gear oil and / or a hydraulic oil in particular. The base oil should be able to adopt the additives required for the lubricating fluid, and the additives in the base oil have the desired effect. According to one embodiment, the selection of raw materials should make the lubricating fluid also usable in the food processing industry. The selection of raw materials is regulated in the United States, such as the specifications of the U.S. Food and Drug Administration (FDA). As a gear oil, the lubricating oil should comply with the CLP standard DIN 51517-3, and in addition, it should also be tested for micropitting according to FVA 54, with a "high" level of anti-gray staining, in particular viscosity grade 220 (ISO VG 220). In order to be used as a hydraulic oil, the lubricating fluid of the low viscosity grade should also comply with DIN51524-3 (HVLP). In all viscosity grades, it is necessary to have good compatibility with common NBR elastomers (NBR is the abbreviation of "nitrile rubber") and fluorinated rubber elastomers (FKM elastomers).

[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.

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

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

[0018] 1-25 wt. %, preferably 2-15 wt. %, of the polyester can be obtained as a polymerization product of:

[0019] One or more α / β-unsaturated dicarboxylic acid diesters, the alcohol group having 3 to 10 carbon atoms, in particular 4 to 8 carbon atoms; and one or more C4 to C18 α-olefins, in particular C10 to C16 α-olefins or C12 to C16 α-olefins;

[0020] 1-25% by weight, preferably 2 to 4% by weight, of polyalkylene glycols obtainable from alkylene oxides, wherein the alkylene oxides include:

[0021] Butylene oxide, or

[0022] Propylene oxide and at least one C4 to C8 alkylene oxide.

[0023] According to another embodiment, a base oil comprises:

[0024] 81-96 wt% of the above poly-α-olefin;

[0025] 2-15% by weight of the above polyester;

[0026] 2-4% by weight of the above-mentioned polyalkylene glycols.

[0027] According to another embodiment, the above poly-α-olefin, polyester and polyalkylene glycol together constitute more than 90% by weight of the base oil, in particular more than 95% by weight. Preferably, the sum of the above poly-α-olefin, polyester and polyalkylene glycol in the base oil is 100% by weight. The base oil is composed of the above ingredients.

[0028] According to one embodiment, the polyalphaolefin is an oligomer of 1-octene, 1-decene and / or 1-dodecene, in particular 1-octyne or 1-decene or an oligomer of 1-octene and 1-decene. The degree of polymerization of the polyalphaolefin may be 3 to 25.

[0029] Likewise, however, the viscosity of the polyα-olefin at 100° C. is preferably in the range of 4 to 300 mm 2 / s (kinematic viscosity determined in accordance with DIN EN ISO 3104). Poly-α-olefins can also be used as hydrogenation products.

[0030] The polyester is preferably a copolymer of maleic acid and / or fumaric acid (completely / completely esterified) esters and one or more C4 to C18 alpha-olefins. The alcohol group of the dicarboxylic acid diester is in particular a linear and / or branched monohydric alcohol having 3 to 10 carbon atoms, in particular 4 to 8 carbon atoms. The dicarboxylic acid of the dicarboxylic acid diester preferably has 4 to 12 carbon atoms, in particular 4 to 6 carbon atoms. For the alpha-olefins of the polyester, chain lengths of 10 to 16 carbon atoms, in particular 14 to 16 atoms, are preferred. These can be linear and / or branched, preferably linear. The molar ratio of alpha-olefins to dicarboxylic acid diesters can be from 1.5:1 to 1:1.5, in particular from 1:0.9 to 0.9:1. The average molecular weight of the polyester is in particular from 1000 to 5000 g / mol, in particular from 1500 to 2500 g / mol (in each case number average).

[0031] The molar ratio of the α-olefin to the dicarboxylic acid diester may be 1.5:1 to 1:1.5, specifically 1:0.9 to 0.9:1.

[0032] According to one embodiment, the polyalkylene glycol comprises or consists in particular of 30-70 mol % of propylene oxide and 70-30 mol % of C4 to C8 alkylene oxide, in particular butylene oxide. The polyalkylene glycols are preferably soluble at room temperature in the polyalphaolefin or polyalphaolefin mixture in which they are used.

[0033] The lubricating fluid composition comprises a base oil according to at least one of the preceding claims and at least one of the following additives:

[0034] - amine-reactive alkyl phosphates,

[0035] and / or

[0036] -Polyol monoesters.

[0037] The lubricating fluid composition preferably comprises or consists at least of the following ingredients:

[0038] - 90 to 98% by weight of base oil;

[0039] - 0.01 to 2% by weight, preferably 0.1 to 0.3% by weight, of the following friction modifiers, and / or

[0040] 0.01 to 2 wt %, preferably 0.05 to 0.6 wt %, based on the base oil, of the following antiwear additives; and

[0041] - Other additives, in particular 0.1 to 2% by weight of other additives.

[0042] According to one embodiment, the lubricating fluid composition comprises or consists of:

[0043] - 94 to 98% by weight of base oil;

[0044] - 0.01 to 2% by weight, preferably 0.1 to 0.3% by weight, of the following friction modifiers, and / or

[0045] 0.01 to 2% by weight, preferably 0.05 to 0.6% by weight, of the above antiwear additives, based on the base oil;

[0046] - Other additives, in particular 0.1 to 2% by weight of other additives.

[0047] The lubricating fluid composition comprises a base oil and at least one of the following additives:

[0048] - amine-reactive alkyl phosphates, in particular mono- or di-C1 to C12 alkyl phosphates, as antiwear additives, in particular 0.01 to 2% by weight, preferably 0.1 to 0.6% by weight,

[0049] and / or

[0050] - as friction modifier, polyol monoesters, in particular C12 to C24 fatty acid esters of optionally ethoxylated polyols, in particular optionally ethoxylated sorbitan monooleate, in particular 0.01 to 2% by weight, preferably 0.05 to 0.3% by weight.

[0051] The amine-reactive alkyl phosphate is preferably a mono- or di-C1 to C12 alkyl phosphate reacted with at least a C10 to C18 alkylamine. Preferably, the reaction is carried out in a manner where the alkyl phosphate is neutralized or partially neutralized. Suitable examples are monooctyl and diisooctyl phosphates (CAS Reg. No. 68187-67-7) reacted with tertiary alkylamines and C12 to C14 primary amines or monohexyl and dihexyl phosphates reacted with tetra-methylnonylamine and C11 to C14 alkylamines.

[0052] Commercial products such as BASF AG 349 or Lanxess RC 3760 (CAS Reg. No. 80939-62-4). Amine-reacted alkyl phosphate ester is an anti-wear additive.

[0053] The polyol monoester is preferably a C12 to C24 fatty acid ester of a polyol such as glycerol, polyglycerol or sorbitan. The polyol may also be ethoxylated in whole or in part. 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.

[0054] C12 to C24 mono fatty acid esters of optionally partially ethoxylated polyols are used as friction modifiers.

[0055] The base oil in the lubricating fluid composition or the lubricating fluid composition can be used as hydraulic oil and gear oil, in particular in the food processing industry and / or feed processing industry.

[0056] The percentages by weight refer to the total composition (unless expressly stated otherwise) and apply independently of one another. DETAILED DESCRIPTION

[0057] Hydraulic oil and gear oil are composed of base oil and additives, and the addition of these additives can extend the service life and performance of the lubricating fluid. The base oil used in the present invention is a mixture of the above-mentioned polyalphaolefin, polyester and polyalkylene glycol.

[0058] Polyalphaolefins are oligomers of linear 1-olefins, in particular 1-octene, 1-decene and / or 1-dodecene, produced, for example, using Lewis acid catalysts (e.g., US 6824671 B2) or metallocene catalysts (mPAO, US 9365663 B2, US 9701595 B2), and whose kinematic viscosity at 100° C. (kV 100) can be between 2 and 300 mm 2 The polyalphaolefin may be, for example, an oligomer of 50 to 80 wt% 1-decene and 50 to 20 wt% 1-dodecene.

[0059] According to one embodiment, the polyalphaolefin is a1) a mixture of 1-decene oligomers and b1) a mixture of 1-octene oligomers, or a2) a mixture of 1-dodecene oligomers and b2) a mixture of 1-octene oligomers and / or 1-decene oligomers. 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 polyalphaolefin can be prepared by metallocene catalysis.

[0060] It is often advantageous to mix polyalphaolefins of different viscosities, for example polyolefins having a viscosity of 4 to 100 mm at 100°C. 2 / s oligomer and a viscosity of 50 to 300 mm at 100°C 2 / s of oligomers.

[0061] Polyesters are polymers formed by C, C bonds with ester side chains. These include in particular copolymers of α, β unsaturated dicarboxylic acid esters, such as maleates or fumarates, in particular with unbranched α olefins. For example, the polyesters described in DE 3223694 C2 and US 5435928 A and their preparation.

[0062] Polyalkylene glycols are polymerization products of water and / or monohydric or dihydric starter 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 to C8 alkylene oxide. For example, polyalkylene glycols are present in the form of homopolymers of butylene oxide or copolymers of propylene oxide and butylene oxide. In this case, preference is given to using copolymers consisting of 30-70% propylene oxide and 70-30% butylene oxide. Polyalkylene glycols have in particular one or two terminal hydroxyl groups.

[0063] For elastomer compatibility, it is desirable to add a swelling agent (usually an ester) to the lubricating fluid composition. Likewise, too high a swelling agent level can result in excessive swelling, which can also lead to leakage.

[0064] 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.

[0065] Examples of swelling agents are monoesters, diesters, polyol esters and complex esters, for example esters of C1 to C18 alcohols with C2 to C18 carboxylic acids. The monoesters and diesters discussed 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 polyols such as glycerol, neopentyl glycol, trimethylolpropane, pentaerythritol or dipentaerythritol. The proportion of swelling agent is selected so that the volume expansion of the elastomer does not exceed 10%. Typically, this means that the proportion of swelling agent in the lubricating fluid composition is 0.5 to 6% by weight, in particular 1 to 4% by weight. One example is di(2-ethylhexyl) sebacate. However, it was found that the polyalkylene glycols used also act as swelling agents.

[0066] Other possible additives to the lubricating fluid composition are antioxidants, anti-wear agents, preservatives, detergents, colorants, friction reducers, viscosity improvers, high pressure additives, metal passivators and nano-scale solids. Examples include:

[0067] Primary antioxidants, such as amine compounds (e.g., alkylamines or 1-phenylaminonaphthalene), aromatic amines (e.g., phenylnaphthylamine or diphenylamine or polymeric hydroxyquinoline (e.g., TMQ)), phenolic compounds (e.g., 2,6-di-tert-butyl-4-methylphenol), organic dithiocarbamates or dithiophosphates;

[0068] Secondary antioxidants, such as phosphites (e.g. tris(2,4-di-tert-butylphenyl phosphite) or bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphate or thioethers (e.g. cresol thioether));

[0069] high-pressure additives and / or antiwear agents, such as organic sulfur compounds (e.g. polysulfides or sulfurized olefins), thiophosphates (e.g. triphenylthiophosphate) and dithiophosphates, phosphites and phosphates (e.g. di-n-octyl phosphate), phosphates (e.g. substituted triphenylphosphates or amine-neutralized alkyl phosphates), inorganic or organic boron compounds, thiocarbamates and dithiocarbamates (e.g. methylene bis(dibutyldithiocarbamate));

[0070] preservatives, such as sulfonates (e.g., petroleum sulfonates, dinonylnaphthalene sulfonate, neutral or overbased calcium sulfonates, magnesium sulfonates, sodium sulfonates, calcium naphthalene sulfonate, and sodium naphthalene sulfonate), sulfonate esters, amine phosphates, N-methyl-N-(1-oxo-9-octadecenyl)glycine;

[0071] Metal deactivators, such as benzotriazole (such as methylbenzotriazole dialkylamine), sterically hindered phenols, and sodium nitrite;

[0072] Viscosity improvers, such as polymethacrylate, polyisobutylene, polystyrene;

[0073] Friction reducers, some with antiwear properties (such as organic acids (such as isostearic acid), fatty acid esters of polyols (such as glycerol or sorbitan), which may be partially ethoxylated, partial glycerides, animal or vegetable oils, dialkyl hydrogen phosphates, carboxylic acid amides (such as oleylamide), organic compounds based on polyethers and amides (such as alkyl polyethylene glycol tetradecanediol ethers), alkyl succinates, PIBSI (polyisobutylene succinimide) or PIBSA (polyisobutylene succinic anhydride)).

[0074] Solids: Particles (boron nitride, silicon dioxide, sheet silicates such as bentonite, carbon nanotubes) can be used in gear oils to achieve certain properties. Very small particles (so-called nanoparticles with a particle size of less than 500 nm, preferably less than 100 nm, particularly preferably less than 50 nm) are used to avoid negative effects on the friction properties.

[0075] To prepare the lubricating fluid composition of the invention, for example, a portion of the base oil (e.g. 5 to 25% by weight) is introduced together with additives, in particular oil-soluble, but usually present in solid form under normal conditions, and heated to 90 to 110° C. with continuous stirring to ensure that these additives are dissolved in the base oil. By adding another portion of the base oil, the temperature is reduced to below 60° C. The liquid and optionally oil-insoluble additives and solids and the remaining amount of base oil are then added and mixed with further stirring until the mixture is completely homogeneous.

[0076] The lubricating fluid composition according to the invention is particularly suitable for use in industrial gearboxes (spur gearboxes, helical gearboxes, bevel gearboxes, spiral bevel gearboxes and epicyclic gearboxes) and hydraulic systems, in particular those used in the food or animal feed industry.

[0077] A gearbox is a machine element by which a motion variable (e.g. change of force, torque) can be changed. Depending on the design of the gearbox, it is surrounded by a housing and lubricated with a lubricating fluid. Seals are used to prevent the lubricating fluid from escaping. In addition to special design properties, the sealing material must also be chemically stable to the lubricating fluid used.

[0078] Elastomer compatibility therefore plays an important role in the development of lubricants. The same applies to the resistance of hydraulic seals, which are used to seal hydraulic systems filled with hydraulic oil.

[0079] As part 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 for relative volume change, Shore A hardness change, tensile strength and elongation at break described in DIN ISO 1817) and the dynamic elastomer compatibility test (Freudenberg test specification FS PLM 1110008).

[0080] Experimental example:

[0081] Manufacturer:

[0082] In this case, part of the base oil amount (5-25%), i.e. the polar oil components, i.e. the esters and polyalkylene glycols, is provided 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 additive is then added and mixing is carried out by further stirring for about 15 minutes until the mixture is completely homogeneous. After further cooling to below 40°C, oiling can be done.

[0083] In addition to the listed base oil ingredients, each formulation also contains an additive package.

[0084] The following substances were used:

[0085] PAO 6 polyalphaolefin: Spectrasyn 6, ExxonMobil Chemical; SynfluidPAO 6 cSt, Chevron Phillips Chemical; Durasyn 166, INEOS Oligomers

[0086] mPAO 150 polyalphaolefin, metallocene catalyzed: Spectrasyn Elite 150, ExxonMobil Chemical; Synfluid mPAO 150 cSt, Chevron Phillips Chemical

[0087] Di(2-ethylhexyl) sebacate Priolube 1856, Kruda; Nycobase 20307 FG, New York; Lubricit DOS, Zschimmer & Schwarz

[0088] Polyester Ketjenlube 240, Italmacher

[0089] Polyalkylene glycol UCON OSP-32,DOW

[0090] Antiwear agent-additive (AW additive) Amine neutralized alkyl phosphate ester, Irgalube 349, BASF SE

[0092] The additive package includes triphenyl thiophosphate, phenolic antioxidant, amine antioxidant, sorbitan monooleate, N-methyl-N-(1-oxo-9-octadecene)glycine, polydimethylsiloxane and benzotriazole derivatives, wherein sorbitan monooleate is the friction modifier used.

[0093] Table 1

[0094] 1 2 3 4 Comparative Example Comparative Example Comparative Example According to the present 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 Polyester [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 <![CDATA[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 of steel and synthetic seawater fail pass pass pass FZG A / 8.3 / 90,SKS More than 12 More than 12 More than 12 FE8,mw50 / mk50[mg] 1.0 / 168

[0095] The following methods were used in Tables 1 and 2:

[0096]

[0097] The polyesters and polyalkylene glycols used are very suitable additives for PAO oils because they are able to maintain a high viscosity index. A higher viscosity index means a greater lubricating film thickness at operating temperature, which contributes to better wear protection.

[0098] Purely PAO-based formulations (test 1) do not provide adequate elastomer compatibility. The NBR elastomer shrinks and causes leakage. Formulations containing polyalkylene glycols (test 2) or esters (test 3) show only a slight volume loss. The best results are obtained with formulations containing esters and polyalkylene glycols (PAGs) in addition to POA (test 4). In addition, the purely PAO-based formulations do not guarantee corrosion protection against salt water, despite the same additives.

[0099] There was no improvement in air separation capacity in Test 4 compared to the version containing ester but no polyalkylene glycol (Test 3).

[0100] Table 2

[0101]

[0102]

[0103] Test series 2 shows that the content of amine-neutralized alkyl phosphates in the additive plays a decisive role in whether important mechanical dynamic tests are passed or not. Due to the low content (test 5), high resistance to gray staining can be achieved even without the addition of polyalkylene glycol. However, only force level 11 damage can be achieved in the FZG test. In the case of higher amine phosphate contents and the presence of polyalkylene glycol (test 6), the damage force level in the FZG test is greater than 12, but the gray staining load-bearing capacity is insufficient. The reduced amine phosphate content in test 4 can be compensated by the oil-soluble polyalkylene glycol without any negative effect in the micropitting test.

[0104] The base oil blends described herein support the corrosion protection properties and elastomer compatibility of the lubricant and allow for a balanced additive package suitable for "food grade" lubricants, meeting sometimes conflicting requirements.

Claims

1. Base oil, including: 50-98 wt% polyalphaolefin as oligomers of C6 to C14 alpha-olefins; 1-25% by weight of polyester as the polymerization product of: one or more α / β unsaturated dicarboxylic acid diesters, wherein the alcohol group has 3 to 10 carbon atoms; and C4 to C18 alpha-olefins; 1-25% by weight of polyalkylene glycols obtainable from alkylene oxides, wherein the alkylene oxides include: Butylene oxide, or Propylene oxide and at least one C4 to C8 alkylene oxide.

2. The base oil according to claim 1, comprising: 81-96 wt% of said poly-alpha-olefin; 2-15 wt% of said polyester; 2-4 wt% of the polyalkylene glycol.

3. The base oil according to claim 1 or 2, wherein the polyalphaolefin, the polyester and the polyalkylene glycol together constitute more than 90% by weight of the base oil, in particular more than 95% by weight, preferably the polyalphaolefin, the polyester and the polyalkylene glycol account for 100% by weight of the base oil.

4. The base oil according to claim 1, wherein the alcohol radical of the dicarboxylic acid diester is a linear and / or branched monoalcohol having 3 to 10 carbon atoms, in particular 4 to 8 carbon atoms.

5. The base oil according to claim 1, wherein the dicarboxylic acid of the dicarboxylic diester has 4 to 12 carbon atoms, in particular 4 to 6 carbon atoms.

6. Base oil according to at least one of the preceding claims, wherein the α-olefin of the polyester has 10 to 16 carbon atoms, in particular 14 to 16.

7. 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 claim 1, wherein the molar ratio of the alpha-olefin to the dicarboxylic acid diester is from 1.5:1 to 1:1.5, in particular from 1:0.9 to 0.9:

1.

9. The base oil according to claim 1, wherein the polyester has a number average molecular weight of 1000 to 5000 g / mol, in particular 1500 to 2500 g / mol.

10. The base oil according to at least one of the preceding claims, wherein 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 3 to 25; c) the poly-α-olefin has a viscosity of 4 to 300 mm at 100°C 2 / s; 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, at least one of which is produced by a metallocene catalyst; and g) the polyalphaolefin is a mixture of: Viscosity 4 to 100 mm at 100°C 2 / s oligomers, and Viscosity 50 to 300 mm at 100°C 2 / s of oligomers.

11. The base oil according to claim 1, wherein the polyalphaolefin is a mixture of or comprises: a1) 1-decene oligomers, and b1) 1-octene oligomers; or Wherein the polyalphaolefin is a mixture of or comprising the following substances: a2) 1-dodecene oligomers, 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 to 95% by weight of oligomer a1) or a2), and 5 to 95% by weight of oligomer b1) or b2).

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

14. A lubricating fluid composition comprising a base oil according to at least one of the preceding claims and at least one of the following additives: - amine-reactive alkyl phosphates, and / or -Polyol monoesters.

15. The lubricating fluid composition according to claim 14, comprising: - 0.01 to 2% by weight, preferably 0.1 to 0.6% by weight, of an amine-reactive alkyl phosphate, and / or - 0.01 to 2% by weight, preferably 0.05 to 0.3% by weight, of polyol monoesters.

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 is optionally ethoxylated, and / or - The amine-reactive alkyl phosphate is reacted with at least a C10 to C18 alkyl amine, and the alkyl phosphate is preferably a mono- or di-C1 to C12 alkyl phosphate.

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

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