DE102006027602A1 - Lubricant compositions containing complex esters - Google Patents

Abstract

Proposed are lubricant compositions with good shear stability, determined by the loss of kinematic viscosity at 100 ° C, containing base oil and a synthetic complex ester, the complex ester having a kinematic viscosity at 40 ° C greater than 400 and up to 50,000 mm <SUP> 2 </ SUP> / s and obtained by reacting 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. Furthermore, the use of said lubricant compositions containing the complex esters as vehicle transmission, axle, industrial gear, compressor, turbine or engine oil is proposed.

Description

Field of the invention

The Invention is in the field of lubricants. It concerns Lubricating compositions 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 even lubricants are made a variety of different natural or synthetic Components made. To improve the required properties Depending on the field of application, additives and / or other additives 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 the classes Solvent neutral and mineral oils Classes XHVI, VHVI, Group II and Group III. come used.

The different lubricants such as engine oil, turbine oil; Hydraulic fluid, Transmission oil, compressor oil and similar have to meet extremely high criteria such as high viscosity index, good lubrication, high sensitivity to oxidation, good thermal stability or comparable.

High-performance lubricating oil formulations, which are used as gear, industrial or engine oils are especially oils with a high performance profile Shear stability, Low temperature viscosity, longevity, Evaporation loss, energy efficiency (fuel efficiency), seal compatibility as well as wear protection. Such oils are currently preferred with PAO (especially PAO 6) or Gr. II or Gr. III mineral oils as carrier liquids as well as with special polymers (Polyisobutylene = PIB, Olefincopolymere = Ethylene / propylene copolymers = OCP, polyalkylmethacrylates = PMA) as thickener or viscosity index improver in addition to the usual Formulated additive components. Together with PAOs are usually also low viscosity esters such as e.g. DIDA (diisodecyl adipate), DITA (diisotridecyl adipate) or TMTC (trimethylolpropanol caprylate), especially as a solubilizer for polar Additive types as well as for the optimization of sealing compatibilities used.

adversely When using the PAOs or the polymers are usually the high cost and low shear stability as well as the low temperature viscosity of the lubricants in the case of using polymers.

Esterbasierte lubricating oils are known per se and have been used for some time (see Ullmanns encyclopedia the technical chemistry, 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 e.g. Trimethylolpropane, and fatty acids, e.g. Oleic acid or a mixture of n-octane and n-decanoic acid. For example dicarboxylic acids in addition to monocarboxylic acids and polyols used in the ester production, the dicarboxylic acid acts crosslinking, what to increase of molecular weights of the ester and ultimately to higher viscosities or improved thickening effects in lubricant formulations leads. Such esters usually become referred to as complex esters. Lower Cryogenic Viscosities prepared with esters and thus an improved Handleability at lower temperatures were especially for esters described with branched alkyl chains.

The Requirements of the technology at lubricating oils are reflected in the usual Specifications by class, e.g. Multi-grade oils which the viscosity classes SAE 75-W90 for Gear oils, or 0-W20 or 0-W30 for engine oils can correspond 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.

One optimum viscosity index improver shows only minor Contribution to the viscosity the lubricant at low temperatures and a big contribution at operating temperatures. Furthermore should be high stability even at elevated shear available.

The Task was therefore the shear stability of the lubricant composition to increase and a good low temperature viscosity to reach. Both are due to polymeric or oligomeric additives such as Thickener, viscosity index improver or polymeric dispersants usually deteriorates.

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.

It On the one hand, the task was high shear stable lubricant compositions with new thickener systems that provide the viscosity index at least not worsen and can be used in a wide range are. Low-temperature viscosities and / or shear stabilities should be compared to usual, the prior art thickener or VI improvers be improved as well as the compatibility of the thickener system with the remaining components of the lubricant formulations, in particular at lower temperatures, guaranteed stay. Another task was the content of common polymers and / or oligomeric thickeners or VI improvers (e.g., OCP's, PIB's, polyalkylmethacrylates) either in the lubricant compositions or to reduce to eliminate as well as expensive carrier components like PAO by Gr. II or III oils to replace. For Lubricating oils, which already with Gr. II or Gr. III oils were formulated however, an exchange of these Gr. II and III oils by cheaper Gr. I oils desirable. Technically, the reduction or elimination should be the usual Polymer advantages regarding shear stability and low temperature viscosity result.

One special problem is when the lubricants in addition to increased oxidation stability and lower Low temperature viscosity an improved compatibility across from Must have sealing materials. The well-known lubricants based on linear esters with good oxidation stability are more saturated Nature, lead however, to soften the usual Sealing materials. Conversely, unsaturated ester types behave which are derived, for example, from oleic acid, while better against Sealing materials, however, have greatly reduced oxidation stabilities. Special problem occurs over sealing materials such as NBR (Nitrile-butyl-rubber) and their hydrogenated variants (HNBR) on.

It There is still a need for improved high-lubricity lubricants biodegradability. Another task of the present Invention has been to provide lubricant available provide, in addition to the properties mentioned a good compatibility across from Have sealing materials.

there allowed to the other properties, in particular the lubricity and rheological properties of the lubricant is not detrimental to be influenced.

It It has been found that certain high-viscosity esters have the abovementioned Perform tasks in an excellent way.

Description of the invention

• a) Polyolen und Monocarbonsäuren und Dicarbonsäuren oder von
• b) Polyolen und Monoalkoholen und Dicarbonsäuren oder von
• c) Polyolen und Monoalkoholen und Monocarbonsäuren und Dicarbonsäuren erhalten wird.

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 implementation 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 is obtained.

• 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 %;
• 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 %;
• 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 %.

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

• 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%;
• (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 %;
• (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 sense of the invention as permanent shear. There the viscosity of the base oil the shear does not decrease or only insignificantly decreases the determination of the loss of viscosity after shear as a parameter for the complex esters meaningful.

In addition, surprisingly be found that oil temperatures in gearbox or axle applications lower if lubricants with the highly viscous complex ester be formulated. This could be done by means of the industry standard ARKL tests (VW PV 1454) are shown.

Of further it could be shown that further use is less Concentrations of a polar polymer such as, an alkyl fumarate alpha-olefin, a polyalkyl methacrylate or an alkyl methacrylate-alpha-olefin system in one of the higher viscosity Ester containing lubricant composition often as a solubilizer for the Ester acts as well as low temperature viscosities of the lubricant composition can lower in a synergistic way.

It could be further shown that expensive, more viscous PAO types, for example PAO 60 or PAO 100 or conventional thickeners as OCP or PIB added to lubricants as thickeners, alternatively with the invention to be included Complex esters can be formulated and to comparably good or improved properties (their. Preference is given to the simultaneous admixture of polar polymers as another component, for example the one 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.

According to the invention preferred are lubricant compositions containing the complex ester in one Concentration of 3 to 90 wt .-% based on the total amount of Lubricant composition. Particularly preferred is a concentration from 7-50 % By weight, and more preferably from 10 to 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 Monoacid is greater than 90 mol% based on the total content of the acid mixture. 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 consisting of the following branched acids: 2,2-dimethylpropanoic, neoheptanoic, neo-octanoic, neononanoic, isohexanoic, neodecanoic, 2-ethylhexanoic, 3-propylhexylic, 3,5,5-trimethylhexanoic, isoheptanoic, 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, heptane acid, caprylic, pelargonic, capric, undecanoic, lauric, tridecanoic, tetradecanoic, pentadecanoic, palmitic, margaric, stearic, nonadecanoic, arachidic, behenic, lignoceric, myristic, cerotic, melissic, tricanoic, and pentacosanoic Palm-oleic, oleic, elaidic, petroselic, linoleic, linolenic, elaeostearic, gadoleic, and erucic acids 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.

in the The meaning of the invention is that in the lubricant composition containing base oil an oil understood that selected is high from the group formed by mineral oils refined mineral oils, alkylated mineral oils, Poly-α-olefins, polyalkylene glycols; Phosphate esters, silicone oils, diesters and esters of polyvalent ones Alcohols and mineral oils Classes Solvent Neutral and Mineral Oils Class XHVI, VHVI, Group II and Group III and GTL basestock (gas-to-liquid base oil). The Poly-α-olefins can do it 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 used according to the invention dicarboxylic acids for the preparation of the complex esters are preferably oxalic, malonic, amber, Glutaric, adipic, pimelic, cork, azelaic, sebacic, brassyl, Thapsis, and phellogenic acid. Also the arhydrides of dicarboxylic acids are suitable for implementation according to the invention. Particularly preferred are azelaic or sebacic acid and their anhydrides.

The Reaction to the reaction products of the complex esters begins in known syntheses for the preparation of esters. The production The ester can according to the invention by known methods also so carried out be that specifically free carboxyl and / or free hydroxyl groups and that these products with free carboxyl and / or free Hydroxyl groups are used in the lubricant composition. The available free carboxyl groups can continue according to the invention be converted with amines to amides and the resulting compounds as a complex ester according to the invention in the lubricant composition be included.

In further preferred embodiments contain the lubricant compositions according to the invention as a further component, a polar polymer in a concentration from 0.5 to 30% by weight based on the total amount of lubricant composition. Preferred is a concentration of 1 to 18 wt .-% and especially preferably from 2 to 12% by weight.

The used according to the invention Polar polymers are preferably selected from the group formed is derived from alkyl fumarate-α-olefin copolymer, Alkyl maleate-α-olefin copolymer, polyalkyl methacrylate, propylene oxide polymer, Ethylene oxide-propylene oxide copolymer and alkyl methacrylate-α-olefin copolymer.

Next good shear stability show the invention to be used Complex ester a high compatibility across from Sealing materials, commonly Find use. The test for compatibility with sealing materials For example, according to the standard test ASTM D 471 performed be, for example, over 168 h at 100 ° C. After this test, the complex esters to be used according to the invention show in the case of sealing materials a volume increase of max. 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 problems of sealing materials opposite Ester-based lubricant compositions are particularly prominent when using nitrile or acrylonitrile-butadiene rubber or their hydrogenated variants. Typically, these sealing materials softened by ester as a lubricant, resulting in an increase in volume appears in appearance. This softening leads to a reduced hardness and decreased tear strength or elongation at break.

In a preferred embodiment the invention is the compatibility the complex ester to be used over sealing materials, the selected are from the group formed by NR (natural rubber), NBR (Nitrile Butadiene Rubber), HNBR (Hydrogenated Nitrile Butyl Rubber), FPM (fluoro rubber), ACM (acrylate rubber), PTFE (Teflon), PU (Polyurethane), silicone, polyacrylate and neoprene, particularly preferred across from NBR, HNBR and ACM.

In a preferred embodiment the use according to the invention will the stability the sealing materials opposite Branched-chain alkyl esters according to the above test ASTM D 471 determined and it meets the criteria mentioned.

The to be used according to the invention Complex esters also show one besides the already mentioned properties good oxidation and thermal stability. This could be determined according to DIN EN ISO 4263-3.

in the For purposes of the invention, the terms lubricant composition, Lubricant, lubricating oil and Formulation used synonymously.

Next The said further components can be used in the lubricant composition according to the invention still contain other additives that are selected from the group that is formed by polymer thickeners, viscosity index improvers, antioxidants, Corrosion inhibitors, detergents, dispersants, demulsifiers, defoamers, Dyes, anti-wear additives, EP (extreme pressure) and AW (antiwear) additives and friction enhancers (Friction Modifier).

One Another object of the invention is the use of the lubricant composition according to the invention especially in the preferred embodiments, as Fahrzeuggetriebe-, Axle, industrial gear, compressor, turbine or engine oil. Especially it is preferred to use it as a vehicle transmission, 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. 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), alkyl maleate-α-olefin copolymers (cf. B7) as well as by means of alkyl fumarate-α-olefin copolymers (see B10). 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 used methods and the exact names of the used Starting materials are explained in Table 1.

Claims (11)

A lubricant composition having a good shear stability determined by the loss of kinematic viscosity at 100 ° C containing base oil and a synthetic complex ester, the complex ester having a kinematic viscosity at 40 ° C of greater than 400 and up to 50,000 mm ² / s and 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. Lubricant composition according to claim 1, characterized characterized in that the loss of kinematic viscosity at 100 ° C i) for gear oils, axle oils as well clutch oils for automatic and manual transmission, designed according to CEC L-45-T-93 (20 hours) less than 8%, ii) for hydraulic fluids, for stationary use Industrial gear oils, for oils for lubrication of wind turbines, for Gas turbine oils, for compressor oils and shock absorber fluids, determined to CEC L-45-T-93 (20 hours), less than 15%, ii) for two-stroke and four-stroke engine oils also for Diesel and gasoline engine oils, determined to ASTM D 3945 (30 cycles), less than 15%. A lubricant composition according to claim 1 or 2, characterized in that the complex ester in a concentration from 3 to 90% by weight based on the total amount of lubricant composition is present. Lubricant composition according to one of claims 1 to 3, characterized in that in the reaction according to a) in Claim 1 as monocarboxylic acids branched monocarboxylic acids or mixtures of linear and branched monocarboxylic acids each will have a carbon number of 5 to 40 carbon atoms exhibit. Lubricant composition according to one of claims 1 to 4, characterized in that the polyols 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 at least 2 is. A lubricant composition according to any one of claims 1 to 5, characterized in that the monoalcohols are branched or linear alcohols of general formula (II) (R ² OH) in which R ^{2 is} an aliphatic or cycloaliphatic group having 2 to 20 carbon atoms. Lubricant composition according to claims 1 to 6, characterized in that dicarboxylic acids are selected from the group is formed by oxalic, malonic, succinic, glutaric, adipic, pimelic, Cork, azealine, sebacine, brassyl, thapsis, and phellogenic acid. Lubricant composition according to one of claims 1 to 7, characterized in that as a further component a polar Containing polymer is in a concentration of 0.5 to 30 wt .-% (especially 1-18 and more preferably 2 to 12) based on the total amount Lubricant composition. Lubricant composition according to one of claims 1 to 8, characterized in that the polar polymer is selected from the group formed by polyalkyl methacrylate, alkyl fumarate-alpha-olefin copolymer, Alkyl maleate-alpha-olefin copolymer, Propylene oxide polymer, ethylene oxide-propylene oxide copolymer and alkyl methacrylate-alpha-olefin copolymer. Lubricant composition according to one of claims 1 to 9, characterized in that further additives may be included can the selected are from the group formed by polymer thickener, viscosity index improver, Antioxidants, corrosion inhibitors, detergents, dispersants, Demulsifiers, defoamers, Dyes, anti-wear additives, EP (extreme pressure) and AW (antiwear) additives and friction enhancers (Friction Modifier). Use of lubricant compositions according to claims 1 to 10 as vehicle transmission, axle, industrial gear, compressor, Turbine or engine oil.