EP2027234B1 - Lubricant compositions containing complex esters - Google Patents

Description

Field of the invention

The invention is in the field of lubricants. It relates to lubricant compositions according to claim 1 containing complex esters of increased viscosity and the use of these lubricant compositions as, for example, gear, industrial or engine oil.

State of the art

The commercially available lubricant compositions or lubricants are made from a variety of different natural or synthetic components. To improve the required properties depending on the field of application additives and / or other additives are added. The base oils often consist of mineral oils, highly refined mineral oils, alkylated mineral oils, poly-α-olefins (PAO), polyalkylene glycols, phosphate esters, silicone oils, diesters and esters of polyhydric alcohols. In particular, mineral oils of classes Solvent Neutral and mineral oils of classes XHVI, VHVI, Group II and Group III. come used.

The different lubricants such as engine oil, turbine oil; Hydraulic fluid, gear oil, compressor oil and the like must meet extremely high criteria such as high viscosity index, good lubricity, high sensitivity to oxidation, good thermal stability or the like.

High performance lubricating oil formulations used as gear, industrial or engine oils are especially oils with high performance profile in terms of shear stability, low temperature viscosity, longevity, evaporation loss, energy efficiency (fuel efficiency), seal compatibility and wear protection. Such oils are currently preferred with PAO (especially PAO 6) or Gr. II or Gr. III mineral oils as carrier liquids and with specific polymers (polyisobutylene = PIB, olefin copolymers = ethylene / propylene copolymers = OCP, polyalkyl methacrylates = PMA) formulated as thickener or viscosity index improver in addition to the usual additive components. Along with PAOs, low viscosity esters such as e.g. DIDA (diisodecyl adipate), DITA (diisotridecyl adipate) or TMTC (trimethylolpropanol caprylate), used in particular as solubilizers for polar additive types and for the optimization of sealing compatibilities.

Disadvantages of the use of the PAOs or of the polymers are generally the high costs and the low shear stability as well as the low-temperature viscosity of the lubricants in the case of the use of polymers.

Ester-based lubricating oils are known per se and have been used for some time (see Ullmanns Enzyklopadie der technischen Chemie, 3rd edition, 15th volume, 1964, pp. 285-294 ). Common esters are reaction products of dicarboxylic acids with moderate alcohols, such as 2-ethylhexanol, or reaction products of polyols, such as trimethylolpropane, and fatty acids, such as oleic acid or a mixture of n-octane and n-decanoic acid. If, for example, dicarboxylic acids are used in addition to monocarboxylic acids and polyols in ester production, the dicarboxylic acid acts crosslinking, which leads to an increase in the molecular weight of the ester and ultimately to higher viscosities or improved thickening effects in lubricant formulations. Such esters are commonly referred to as complex esters. Lower low-temperature viscosities of the formulations prepared with esters, and thus improved handling at lower temperatures, have been described in particular for esters with branched alkyl chains.

The requirements of the art for lubricating oils are reflected in common specifications by class, e.g. Multi-grade oils, which correspond to the viscosity classes SAE 75-W90 for gear oils, or 0-W20 or 0-W30 for engine oils, can be used practically in all seasons.

There is still a particular need for additives of a polymeric or oligomeric nature, which are used as additives to meet the requirements of very shear-stable lubricant compositions that can be used in a wide range. Furthermore, these additives should at least not degrade the viscosity index. There are some viscosity index improvers known, but do not show good shear stability such as in US 4,156,673 shown. From the EP 488432 (= US5070131 ) are known polymers with good shear stability, which are made of poly (polyalkenyl) couplings. In the DE3544061 (= US4822508 ) high-shear-grade transmission oils are described which contain viscosity index-improving additives based on esters of acrylic or methacrylic acid.

In the US 5,451,630 Olefin copolymers (OCP) are described which have good shear stability. It is further described that the good shear stability decreases with the size of the molecule and thus with an increased viscosity. This disintegration of the polymers by increased shear forces leads to a reduction in the viscosity in the lubricant.

An optimum viscosity index improver shows only a minor contribution to the viscosity of the lubricant at low temperatures and a large contribution at operating temperatures. In addition, a high stability should be present even at elevated shear forces.

The task was thus to increase the shear stability of the lubricant composition and to achieve a good low-temperature viscosity. Both are usually worsened by polymeric or oligomeric additives such as thickeners, viscosity index improvers or polymeric dispersants.

From the EP 1281701 are known synthetic lubricants prepared from polyneopentyl polyol and a mixture of linear and branched acids, wherein the ester has a viscosity of 68 to 400 mm ² / s at 40 ° C. These have been developed for use in refrigerated compressor fluids.

From the EP 938536 For example, lubricants containing synthetic esters obtained by reacting polyols with mixtures of monocarboxylic acids and optionally polybasic acids and having increased thermal and oxidative stability are known. The viscosity of the ester is at 100 ° C maximum about 80 mm ² / s. No information was given on shear stability.

From the WO99 / 16849 are known gear oil formulations with highly viscous Komplexestem, PAO, low viscosity polyol esters and additives. On the one hand, it was the object to provide high-shear-stable lubricant compositions with new thickener systems which at least do not worsen the viscosity index and can be used in a wide range of applications. Cryogenic viscosities and / or shear stabilities should be improved as compared to conventional prior art thickener or VI improvers and compatibility of the thickener system with the remaining components of the lubricant formulations, especially at lower temperatures, to be ensured. Another object was to either reduce or eliminate the content of common polymeric and / or oligomeric thickeners or VI improvers (eg OCP's, PIB's, polyalkyl methacrylates) in the lubricant compositions, as well as expensive carrier components such as PAO by Gr. To replace II or III oils. For lubricating oils, which already have Gr. II or Gr. III oils were formulated, however, was an exchange of these Gr. II and III oils by cheaper Gr. I oils desirable. Technically, the reduction or elimination of common polymers should provide shear stability and low temperature viscosity benefits.

A particular problem is when the lubricants, in addition to increased oxidation stability and low cryogenic viscosity, must have improved compatibility with sealing materials. The known lubricants based on linear esters with good oxidation stability are saturated, but cause softening of the usual sealing materials. Conversely, unsaturated ester types, derived for example from oleic acid, behave better than sealants, but have greatly reduced oxidation stabilities. Particular problems arise compared to sealing materials such as NBR (nitrile-butyl rubber) and their hydrogenated variants (HNBR).

There is still a need for improved lubricants with high biodegradability. Another object of the present invention has been to provide lubricants to make available, in addition to the properties mentioned have a good compatibility with sealing materials.

The other properties, in particular the lubricity and rheological properties of the lubricant must not be adversely affected.

It has been found that certain high-viscosity esters perform the above-described tasks in an excellent manner.

Description of the invention

1. a) Polyolen und Monocarbonsäuren und Dicarbonsäuren oder von
2. b) Polyolen und Monoalkoholen und Dicarbonsäuren oder von
3. c) Polyolen und Monoalkoholen und Monocarbonsäuren und Dicarbonsäuren erhalten wird,

dadurch gekennzeichnet, dass als weitere Komponente der Schmierstoffzusammensetzung ein polares Polymer ausgewählt aus der Gruppe, die gebildet wird von Alkylfumarat-alpha-olefin-Copolymer, Alkylmaleat-alpha-olefin-Copolymer und Alkyl-methacrylat-alpha-olefin-Copolymer in einer Konzentration von 0,5 bis 30 Gew.-% bezogen auf die Gesamtmenge der Schmierstoffzusammensetzung enthalten ist. Es konnte für die genannten Komplexester gezeigt werden, dass die Scherstabilität der Schmierstoffzusammensetzung enthaltend diese Ester sehr gute Ergebnisse erzielt und die Viskosität nur geringfügig abnimmt. Des Weiteren konnte der Gehalt an Polymeren reduziert werden. Der Verlust der kinematischen Viskosität wurde bestimmt bei 100 °C

1. i) für Getriebeöle, Achsenöle sowie Kupplungsöle für Automatik- und Schaltgetriebe nach CEC L-45-T-93 (20 Stunden) und liegt bei weniger als 8 %, bevorzugt bei weniger als 5 % und insbesondere bevorzugt bei weniger als 4 %;
2. ii) für Hydraulikflüssigkeiten, für stationär eingesetzte Industriegetriebeöle, für Öle zur Schmierung von Windturbinen, für Gasturbinenöle, für Kompressorenöle und Stossdämpferflüssigkeiten bestimmt nach CEC L-45-T-93 (20 Stunden) und liegt bei weniger als 15 % und bevorzugt bei weniger als 8 %;
3. iii) für Zweitakt- und Viertaktmotorenöle sowie für Diesel- und Ottomotorenöle bestimmt nach Scherung nach ASTM D 3945 (30 Zyklen) und liegt bei weniger als 15 %, bevorzugt bei weniger als 10 % und insbesondere bevorzugt bei weniger als 7 %.

The invention relates to a lubricant composition with a good shear stability determined by the loss of kinematic viscosity at 100 ° C, containing base oil and a synthetic complex ester, wherein the complex ester has a kinematic viscosity at 40 ° C of greater than 400 and up to 50,000 mm 2 / s and by implementing

1. a) polyols and monocarboxylic acids and dicarboxylic acids or of
2. b) polyols and monoalcohols and dicarboxylic acids or of
3. c) obtaining polyols and monoalcohols and monocarboxylic acids and dicarboxylic acids,

characterized in that as further component of the lubricant composition is a polar polymer selected from the group consisting of alkylfumarate-alpha-olefin copolymer, alkylmaleate-alpha-olefin copolymer and alkyl-methacrylate-alpha-olefin copolymer in a concentration of 0.5 to 30 wt .-% based on the total amount of the lubricant composition. It could be shown for the mentioned complex esters that the shear stability of the lubricant composition containing these esters gives very good results and the viscosity only slightly decreases. Furthermore, the content of polymers could be reduced. The loss of kinematic viscosity was determined at 100 ° C

1. i) for gear oils, axle oils and clutch oils for automatic and manual transmission according to CEC L-45-T-93 (20 hours) and is less than 8%, preferably less than 5% and most preferably less than 4%;
2. (ii) for hydraulic fluids, stationary industrial gear oils, wind turbine lubrication oils, gas turbine oils, compressor oils and shock absorber fluids to CEC L-45-T-93 (20 hours), less than 15% and preferably less than 8th %;
3. (iii) for two-stroke and four-stroke engine oils and diesel and gasoline oils, determined by shearing according to ASTM D 3945 (30 cycles) and less than 15%, preferably less than 10% and most preferably less than 7%.

The shear applies in the context of the invention as a permanent shear. Since the viscosity of the base oil by the shear does not decrease or only very slightly, the determination is the loss of viscosity after shear as a parameter for the complex esters meaningful.

In addition, it has surprisingly been found that oil temperatures in transmission or axle applications are lower when formulating lubricants with the high viscosity complex ester. This was demonstrated using the industry-standard ARKL test (VW PV 1454).
Furthermore, it has been shown that the further use of low concentrations of a polar polymer such as, for example, an alkylfumarate-alpha-olefin, a polyalkylmethacrylate or an alkylmethacrylate-alpha-olefin system in a lubricant composition containing the higher viscosity ester often acts as a solubilizer for the ester and lower the viscosity of the lubricant composition in a synergistic manner.
It could further be shown that expensive, higher-viscosity PAO types, for example PAO 60 or PAO 100 or conventional thickeners such as OCP or PIB, which were added to lubricants as thickeners, can alternatively be formulated with the complex esters to be obtained according to the invention and give comparably good results lead to improved properties. Preference is given to the simultaneous admixture of polar polymers as a further component, for example those mentioned above.

The kinematic viscosity of the complex ester to be used is preferably from 800 to 25,000 mm ² / s, in particular from 1,200 to 10,000 mm ² / s, more preferably from 1,300 to 5,000 mm ² / s and most preferably from 1,500 to 3,000 mm ² / s. It has surprisingly been found that the use of these esters leads to very low losses of the kinematic viscosity of the lubricant composition after permanent shear. This feature makes it possible to use in lubricants exposed to high shear stress.

Lubricant compositions containing the complex ester in a concentration of from 3 to 90% by weight, based on the total amount of lubricant composition, are preferred according to the invention. Particular preference is given to a concentration of 7-50% by weight and more preferably of 10-34% by weight.

In further preferred embodiments, the lubricant compositions are characterized in that in the reaction according to a) monocarboxylic acids as branched monocarboxylic acids or mixtures of linear and branched monocarboxylic acids are used, each having a carbon number of 5 to 40 carbon atoms, wherein preferably the content of branched Mono acid greater than 90 mol% based on the total content the acid mixture is. The monocarboxylic acids preferably have 8 to 30 C atoms and in particular 10 to 18 C atoms. In particular, the monocarboxylic acids are selected from the group formed by the following branched acids: 2,2-dimethylpropanoic acid, neoheptanoic acid, neo-octanoic acid, neononanoic acid, isohexanoic acid, neodecanoic acid, 2-ethylhexanoic acid, 3-propylhexylic acid, 3,5,5-trimethylhexanoic acid, isoheptanoic acid, Isooctanoic acid, isononanoic acid, isostearic acid, isopalmitic acid, Guerbetsäure C32, Guerbetsäure C34 or Guerbetsäure C36 and Isodekansäure. The linear acids are preferably selected from the group formed by valeric acid, caproic acid, heptanoic acid, caprylic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, palmitic acid, margaric acid, stearic acid, nonadecanoic acid, arachic acid, behenic acid, lignoceric acid, myristic acid , Cerotic acid, melissic acid, tricosanoic acid, and pentacosanoic acid 2-ethylhexanoic acid, isotridecanoic acid, myristic acid, palm oleic acid, oleic acid, elaidic acid, petroselinic acid, linoleic acid, linolenic acid, elaeostearic acid, gadoleic acid, and erucic acid and their technical mixtures. Preferred branched monocarboxylic acids are isononanoic acid, isostearic acid and 2-ethylhexanoic acid.

Preference is given to lubricant compositions which contain complex esters which are obtained by reacting polyols with dicarboxylic acids and branched monocarboxylic acids. These stated preferred esters of polyols, dicarboxylic acids and branched monocarboxylic acids preferably have a viscosity of from 1,300 to 5,000 mm ² / s and very particularly preferably from 1,500 to 3,000 mm ² / s.

For the purposes of the invention, the base oil contained in the lubricant composition is understood as meaning an oil selected from the group consisting of mineral oils, highly refined mineral oils, alkylated mineral oils, poly-α-olefins, polyalkylene glycols, phosphate esters, silicone oils, diesters and Esters of polyhydric alcohols and mineral oils of classes Solvent Neutral and mineral oils of classes XHVI, VHVI, Group II and Group III and GTL basestock (gas-to-liquid base oil). The poly-α-olefins can preferably be composed of C6- to C18-α-olefins and mixtures thereof. Especially preferred are poly-α-decenes.

The polyols according to the invention are branched or linear alcohols of the general formula (I) R ¹ (OH) _n in which R ^{1 is} an aliphatic or cycloaliphatic group having 2 to 20 carbon atoms and n is at least 2. Preferably, the polyols are selected from the group consisting of neopentyl glycol, 2,2-dimethylolbutane, trimethylolethane, trimethylolpropane, trimethylolbutane, mono-pentaerythritol, di-pentaerythritol, tri-pentaerythritol, ethylene glycol, propylene glycol, polyalkylene glycol, 1,4-butanediol, 1,3-propanediol and glycerin. Particularly preferred are trimethylolpropane, mono-pentaerythritol and di-pentaerythritol.
In further preferred embodiments, the lubricant compositions are characterized in that branched or linear alcohols of the general formula (II) (R ² OH) are used as monoalcohols in the reaction according to b), in which R ^{2 is} an aliphatic or cycloaliphatic group having 2 to 24 Carbon atoms and 0 and / or 1, 2 or 3 carries double bonds. Preferably, the monoalcohols are selected from the group consisting of caproic alcohol, caprylic alcohol, 2-ethylhexyl alcohol, capric alcohol, lauryl alcohol, isotridecyl alcohol, myristyl alcohol, cetyl alcohol, palmoleyl alcohol, stearyl alcohol, isostearyl alcohol, oleyl alcohol, elaidyl alcohol, petroselinyl alcohol, linolyl alcohol , Linolenyl alcohol, elaeostearyl alcohol, arachyl alcohol, gadoleyl alcohol, behenyl alcohol, erucyl alcohol and brassidyl alcohol and their technical mixtures.
The dicarboxylic acids to be used according to the invention for preparing the complex esters are preferably oxalic, malonic, succinic, glutaric, adipic, pimelic, cork, azelaic, sebacic, brassylic, thapsic and phellogenic acids. The anhydrides of the dicarboxylic acids are also suitable for the reaction according to the invention. Especially preferred are azelaic acid or sebacic acid and their anhydrides.
The reaction to form the reaction products of the complex esters proceeds in known syntheses for the preparation of esters. The preparation of the esters can also be carried out by known methods according to the invention so that there are selectively free carboxyl and / or free hydroxyl groups and that these products are used with free carboxyl and / or free hydroxyl groups in the lubricant composition. According to the invention, the free carboxyl groups present can furthermore be reacted with amines to give amides and the resulting compounds can be present as complex esters in the lubricant composition in the meaning of the invention. The lubricant compositions according to the invention contain as further component a polar polymer in a concentration of 0.5 to 30 wt .-% based on the total amount of lubricant composition. Preferred is a concentration of 1 to 18 wt .-% and particularly preferably from 2 to 12 wt .-%.
The polar polymers to be used in the present invention are selected from the group consisting of alkyl fumarate-α-olefin copolymer, alkyl maleate-α-olefin copolymer, and alkyl methacrylate-α-olefin copolymer.

In addition to good shear stability, the complex esters to be used according to the invention show a high compatibility with sealing materials which are commonly used. The test for compatibility with sealing materials can be carried out, for example, according to the standard test ASTM D 471, for example for 168 h at 100 ° C. According to this test, the complex esters to be used according to the invention show an increase in volume of not more than 20%, preferably not more than 10%, a hardness loss of less than 15%, preferably less than 10% and a decrease in elongation at break of less than 50%, preferably less than 30%.
Stability issues of sealants over ester-based lubricant compositions are particularly evident when using nitrile or acrylonitrile-butadiene rubber or its hydrogenated variants. Typically, these sealing materials are softened by esters as a lubricant, which is manifested by an increase in volume. This softening leads to a reduced hardness and reduced tear strength or elongation at break.
In a preferred embodiment of the invention, the compatibility of the complex esters to be used with sealing materials selected from the group consisting of NR (natural rubber), NBR (nitrile-butadiene rubber), HNBR (hydrogenated-nitrile-butyl-rubber ), FPM (fluororubber), ACM (acrylate rubber), PTFE (Teflon), PU (polyurethane), silicone, polyacrylate and neoprene, especially preferred over NBR, HNBR and ACM.
In a preferred embodiment of the use according to the invention, the stability of the sealing materials to esters with branched alkyl groups is determined by the abovementioned test ASTM D 471 and the stated criteria are met.

In addition to the properties already mentioned, the complex esters to be used according to the invention also exhibit good oxidation and thermal stability. This could be determined according to DIN EN ISO 4263-3.

For the purposes of the invention, the terms lubricant composition, lubricant, lubricating oil and formulation are used interchangeably.

In addition to the other components mentioned, the lubricant composition according to the invention may contain further additives which are selected from the group formed by polymer thickeners, viscosity index improvers, antioxidants, corrosion inhibitors, detergents, dispersants, demulsifiers, defoamers, dyes, wear protection additives, EP (Extreme Pressure) and AW (Antiwear) Additives and Friction Modifiers.

Another object of the invention is the use of the lubricant composition according to the invention, in particular in the preferred embodiments, as Fahrzeuggetriebe-, axle, industrial gear, compressor, turbine or engine oil. Particularly preferred is the use as Fahrzeuggetriebe-, axle, clutch or industrial gear oil.

Examples

Example 1-10 (B1-B10): Comparison of Different Lubricant Compositions Table 1 shows a summary of example and comparative example formulations. Formulations VB1, B2, B4, B5, B6, B8 and B9 are comparative example formulations. It is clear that, based on the high-viscosity esters HVE I or HVE II, SAE grade 75W-90 gear oils with good low temperature properties had to be formulated (low dynamic viscosities, all <300,000 mPa.s, measured at -40 ° C). Striking is the improved shear stability of the example formulations (except B5 and B6, which are aimed exclusively at the one inventive effect of improving low temperature properties and the ability to use Gr III mineral oils rather than PAO 6) compared to Comparative Example (VB1). The effect is all the more clear when one considers that VB1 was formulated with PIB and OCP systems, which are considered to be particularly shear stable. It can be seen that the use of high-viscosity esters also opens formulations with good low-temperature viscosities by means of PAO 8 or a group III mineral oil instead of PAO 6 (see B4, B5, B6). It has been shown that the use of certain polymers at lower concentrations has synergistic effects on improving low temperature viscosities (see B2 compared to B3, B2 compared to B7, B2 compared to B10 and B5 compared to B6). This could be achieved both by means of alkyl methacrylate polymers (see B5 and B6), alkyl methacrylate-α-olefin copolymers (see B3), alkylmaleate-α-olefin copolymers (see B7) and by means of alkylfumarate-α-olefin copolymers. Copolymers (see B10) show. In the case of the use of alkyl methacrylate polymers, the shear stability of the formulations was worse (see B5 and B6), which was due to the shear of the alkyl methacrylate polymer. It can also be seen that formulations based on HVE II bring advantages in the mean steady state temperature in the ARKL test (VW PV 1454) (see VB1 compared to B8 and B9). This test reflects operating oil temperatures in transmission and axle applications and is all the more positive the lower the observed temperatures are. It was also noticeable that coefficients of friction could be reduced and wear by use of the oils according to the invention decreased. This was demonstrated by the industry standard SRV test (see VB1 compared to B2).

All methods used and the exact names of the starting materials used are explained in Table 1. Table 1: Comparative Example (VB1) and Example (B1-B10) Formulations (SAE 75W-90 Gear Oils) composition VB1 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 PAO 6 52.00% 27.00% 54.20% 54.60% 54.60% 45.00% 45.10% 54.60% PAO 8 47.90% PDO I 37.00% DIDA 10.00% 10.00% 10.00% 10.00% 10.00% PDB II 33.80% 29.10% 30.10% 24.30% 31.30% 29.10% 33.00% 24.30% 29.10% PIB I 13.00% OCP I 13.00% Gr. III mineral oil 53.90% 50.70% Alkyl methacrylate-α-olefin copolymer I 14.00% 4.30% Alkyl methacrylate I 9.80% 5.00% 8.60% Alkylmaleate-α-olefin copolymer I 4.30% Alkyl fumarate-α-olefin copolymer I 4.30% Additive package I 12.00% 12.00% 12.00% 12.00% 12.00% 12.00% 12.00% 12.00% 12.00% 12.00% 12.00% Results Kinem. Visc. 100 ° C (DIN 51562) 16.64 mm ² / s 17.27 mm ² / s 16.56 mm ² / s 16.42 mm ² / s 16.36 mm ² / s 16.55 mm ² / s 17.21 mm ² / s 15.25 mm ² / s 16.63 mm ² / s 16.53 mm ² / s 15.41 mm ² / s Kinem. Visc. 40 ° C (DIN 51562) 114.93 mm ² / s 127.46 mm ² / s 108.65 mm ² / s 107.91 mm ² / s 106.85 mm ² / s 104.70 mm ² / s 106.03 mm ² / s 97.52 mm ² / s 105.47 mm ² / s 99.25 mm ² / s 98.47 mm ² / s dyn. Visc. - 40 ° C (DIN 51398) 115000 mPa s 279000 mPa s 118000 mPa s 98000 mPa s 122000 mPa s 67200 mPa s 153000 mPa s 78800 mPa s 98400 mPa s 96000 mPa s 94200 mPa s Pour point (ASTM D 97) -50 ° C -53 ° C -49 ° C -53 ° C -51 ° C -48 ° C -45 ° C -49 ° C -50 ° C viscosity Index 157 149 165 164 165 171 178 165 171 181 166 Shear stability: loss kinemat. Visc. 100 ° C (DIN 51562, CEC L-45-T-93) 8.1% 4.70% 3.70% 3.90% 4.20% 12.50% 10.00% 03.05% 3.60% Medium steady-state temperature ARKL test (VW PV 1454) 133 ° C 129.1 ° C 130.4 ° C SRV: maximum / minimum coefficient of friction * 0.145 / 0.095 0.136 / 0.073 SRV: maximum roughness depth * 2.00 μm 0.86 μm Tread depth * 2.23 μm 1.48 μm Shaft depth * 0.61 μm 0.48 μm PAO 4: Nexbase 2004 from Neste Oil Corp.
PAO 6: Nexbase 2006 from Neste Oil Corp.
PAO 8. Nexbase 2008 from Neste Oil Corp.
HVE I: Commercially available high-viscosity ester with kinematics measured at 40 ° C. Visc. of 445 mm ² / s (eg Synative ES 3237 from Cognis)
HVE II: High-viscosity ester with kinematics measured at 40 ° C. Visc. of 2000 mm ² / s; obtained according to known methods by reaction of pentaerythritol, isostearic acid and sebacic acid
DIDA: Diisodecyladipate, eg Synative ES DIDA from Cognis Deutschland GmbH & Co. KG Gr. III mineral oil: Nexbase 3043 from Neste Oil Corp. Alkyl methacrylate-α-olefin copolymer I: Viscobase 11-574 from RohMax Alkyl methacrylate I: Viscoplex 0-101 from RohMax Alkylmaleate-α-olefin copolymer I: Gear-Lube 7930 Alkylfumarate-α-olefin copolymer I: Gear Lube 7960 additive package I: Anglamol 6004 J from Lubrizol
PEB I: Lubrizol 8406 from Lubrizol
OCP I: Lubrizol 8407 from Lubrizol
* SRV test conditions: device SRV 1 from Optimol Instruments Prüftechnik GmbH load increased within 22 minutes to 200 N, further 5 minutes at 300 N, remaining 43 minutes at 600 N; Test duration: 70 Mi-Temperature: 100 ° C -Gleitweg of the ball: 1.00 mm -Frequenz: 50 Hz -Material combination: ball 10 mm diameter on cylinder with lapped surface

Several engine oils were prepared with esters (comparative example formulations) (B13 - B15) and their properties were tested. For comparison, the measurement results for comparable engine oils of the prior art are also listed (B11 and B12). The results are given in the following Table 2: composition B 11 B12 B13 B14 B15 PAO 4 20 47 20 41.5 47 PAO 6 44.2 11.1 44.5 9.8 26 PDB II 3.5 19 15 Gr. III mineral oil 20 20 20 17.7 Alkyl methacrylate-α-olefin copolymer I 3.5 9.9 Alkyl methacrylate I 0.3 Additive package I 12 12 12 12 12 Results Kinem. Visc. 100 ° C (DIN 51562) 7.18 10.77 / 10.61 6.93 10.59 / 10.48 9.50 Kinem. Visc. 40 ° C (DIN 51562) 38.82 61.79 38.71 62.40 59.40 dyn. Visc. - 35 ° C (DIN 51398) 5800 26100 8500 viscosity Index 150 166 140 160 142 Shear stability: loss kinemat. Visc. 100 ° C (DIN 51562, CEC L-45-T-93) 36.8% 3.0%

Claims (10)

1. A lubricant composition having a good shear stability determined by the loss of kinematic viscosity at 100°C, comprising base oil and a synthetic complex ester, said complex ester having a kinematic viscosity at 40°C of greater than 400 and up to 50 000 mm²/s and being obtained by reaction of:

   a) polyols and monocarboxylic acids and dicarboxylic acids or of

   b) polyols and monoalcohols and dicarboxylic acids or of

   c) polyols and monoalcohols and monocarboxylic acids and dicarboxylic acids, characterized in that, as a further component of the lubricant composition, a polar polymer selected from the group formed by alkyl fumarate-alpha-olefin copolymer, alkyl maleate-alpha-olefin copolymer and alkyl methacrylate-alpha-olefin copolymer is present in a concentration of from 0.5 to 30% by weight based on the total amount of the lubricant composition.
2. The lubricant composition according to claim 1, characterized in that the complex ester is present in a concentration of from 3 to 90% by weight based on the total amount of lubricant composition.
3. The lubricant composition according to either of claims 1 and 2, characterized in that the monocarboxylic acids used in the reaction according to a) in claim 1 are branched monocarboxylic acids or mixtures of linear and branched monocarboxylic acids, each of which has a carbon number of from 5 to 40 carbon atoms.
4. The lubricant composition according to any one of claims 1 to 3, characterized in that the polyols are branched or linear alcohols of the general formula (I) R1(OH)n in which R1 is an aliphatic or cycloaliphatic group having from 2 to 20 carbon atoms and n is at least 2.
5. The lubricant composition according to any one of claims 1 to 4, characterized in that the monoalcohols are branched or linear alcohols of the general formula (II) (R2OH) in which R2 is an aliphatic or cycloaliphatic group having from 2 to 20 carbon atoms.
6. The lubricant composition according to claims 1 to 5, characterized in that dicarboxylic acids are selected from the group formed by oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, brassylic acid, thapsic acid and phellogenic acid.
7. The lubricant composition according to any one of claims 1 to 16, characterized in that the polar polymer is present in a concentration of 1-18% by weight and particularly preferably from 2 to 12% by weight based on the total amount of lubricant composition.
8. The lubricant composition according to any one of claims 1 to 7, characterized in that further additives may be present, said additives being selected from the group formed by polymer thickeners, viscosity index improvers, antioxidants, corrosion inhibitors, detergents, dispersants, demulsifiers, defoamers, dyes, wear protection additives, EP (extreme pressure) and AW (antiwear) additives and friction modifiers.
9. The lubricant composition according to any one of claims 1 to 8, characterized in that the synthetic complex ester is a highly viscous ester obtained by reaction of pentaerythritol, isostearic acid and sebacic acid, having a kinematic viscosity, measured at 40°C, of 2000 mm²/s.
10. The use of lubricant compositions according to any one of claims 1 to 9 as vehicle transmission oil, axle oil, industrial transmission oil, compressor oil, turbine oil or motor oil.