EP2311926A1 - Additive for lubricant for improving the tribologic properties, a method for its production and application - Google Patents

Abstract

Lubricant comprises ceramic nanoparticles as additives comprising aluminum oxide, aluminum nitride, silicon dioxide, titanium dioxide, zirconium oxide, yttrium oxide, tungsten oxide, tantalum pentoxide, vanadium pentoxide, niobium pentoxide, cerium dioxide, boron carbide, aluminum titanate, boron nitride, molybdenum disilicide, silicon carbide, silicon nitride, titanium carbide, titanium nitride, zirconium diboride and/or clay minerals, and thermally stable carbonates and/or sulfates. The nanoparticles represent an ellipsoid with three semi-axes a, b and c. Lubricant comprises ceramic nanoparticles as additives comprising aluminum oxide, aluminum nitride, silicon dioxide, titanium dioxide, zirconium oxide, yttrium oxide, tungsten oxide, tantalum pentoxide, vanadium pentoxide, niobium pentoxide, cerium dioxide, boron carbide, aluminum titanate, boron nitride, molybdenum disilicide, silicon carbide, silicon nitride, titanium carbide, titanium nitride, zirconium diboride and/or clay minerals, and thermally stable carbonates and/or sulfates. The nanoparticles represent an ellipsoid with three semi-axes a, b and c, which are not equal to each other, or equal to each other. The ratio of a and b is 1-100, a and c is 1-1000, and b and c is 1:100. An independent claim is also included for preparing the lubricant, comprising mixing the nanoparticles in a base fluid with optionally further additives, dispersing the resulting mixture by mechanical action, and optionally adding further additives.

Description

The present invention relates to new additives for lubricants for improving the tribological properties, a process for their preparation and their use.

Lubricants are native oils, such as castor oil or rapeseed oil, mineral oils, e.g. naphthenic mineral oils, and / or synthetic oils, e.g. Polyalphaolefins or ester oils. These serve to reduce friction, which causes noise and especially material wear. In addition, the use of lubricants also allows the heat dissipation. Depending on the intended use, the lubricants are subjected to a wide variety of additives.

In the case of lubricants, in addition to the corrosion protection, the thermal stability, the viscosity index, the pour point, also the tribological properties are of crucial importance. In the first place, the reduction of friction, wear, an improvement of the lubricating effect, including a heat dissipating function and the load carrying capacity. The load carrying capacity is a measure of the ability to prevent the welding of materials.

Zinc dithiophosphate (ZnDTP), zinc 4-methylpentyl-2-dithiophosphate and zinc dialkyl dithiophosphate are used as synthetic lubricant additives for wear protection. Their tribological effect comes about through intensive chemical reaction with metals on the sliding surface. This forms reaction layers that protect the surface from wear and welding under extreme pressure. A disadvantage of these lubricant compositions is that they can only be effective at temperatures higher than room temperature. Furthermore, the lubricant compositions known in the art do not have sufficient high temperature stability and the "depot effect" is very rapidly consumed due to the high rate of decomposition at higher temperatures. In addition, these additives are not sufficiently effective at too low temperatures due to the low decomposition rates.

Furthermore, it is off Teng, Jin-li et al in "Characterization and tribological properties of surface modified SiO 2 nanoparticles", Gongcheng Xuebao (2006), 24 (6), 874-876 ; the use of surface-modified nanoparticles known. This modification is costly and expensive.

Tao, Xu et al. describe in Journal of Physics D: Applied Physics (1996), 29 (11), 2932-2937 "The ball-bearing effect of diamond nanoparticles as an oil additive However, nanoparticles that are significantly smaller than 100 nm are too small to effectively exert this effect on standard steel surfaces, ie on polished and lapped steel surfaces, and indeed these particles disappear in the valleys of the Thus, this effect must be seriously challenged, and it must rather be assumed that these nanoparticles polish the surface and thereby level it, thereby minimizing the friction A true and lasting AW effect ("anti-rock"). Wear "=" wear protection ") can not be guaranteed here.

Starting from this prior art, the object of the present invention to find additives for lubricants to improve the tribological properties, which have a tribological operation over a wide temperature range, especially at low temperatures, and can be provided inexpensively. In doing so, a composition should be found which is particularly useful for very low temperatures, e.g. prevail in starting processes in the automobile, but also at high temperatures, where standard additives are thermally completely decomposed and thus ineffective, an effect.

In addition, it is preferred that the additives for lubricants exhibit a pronounced mechanical and thermal resistance and thus can be used at high temperatures of preferably up to 1000 ° C, where conventional previously known lubricant additives usually fail.

Furthermore, the tribological action of the additives should preferably be carried out in a purely mechanical manner and without chemical reactions.

Further, there is a need for a lubricant having tribological properties which is chemically inert and does not react with other components commonly contained in additive packages for improving lubricating performance. This prevents a detrimental effect on the performance of other additives.

Furthermore, these alternatives to compositions of conventional zinc dithiophosphate based lubricant additives and of ashless lubricant additives should at least be equal in performance and performance gaps not covered by conventional AW additives and / or extreme pressure (EP) additives , shut down.

Finally, it is preferred if the lubricant additives have a relatively high thermal conductivity and thus can very well dissipate heat from the lubrication gap in which they are used. In addition, the lubricants produced therefrom should have an improved load carrying capacity.

This object is achieved by the new additives for lubricants containing nanoparticles, which are substantially spherical.

The lubricants are native oils, e.g. Castor oil or rapeseed oil, mineral, e.g. naphthenic mineral oils, and / or synthetic oils, e.g. Polyalphaolefin or ester oils. In this case, the term lubricant includes all common and commercially available lubricating oils.

These are, for example, soybean oil, palm oil, palm kernel oil, sunflower oil, corn oil, linseed oil, rapeseed oil, thistle oil, wheat germ oil, rice oil, coconut oil, almond oil, apricot kernel oil, avocado oil, jojoba oil, hazelnut oil, walnut oil, peanut oil, pistachio oil, triglycerides of medium-chain vegetable fatty acids (so-called MCT oils) and PUFA oils (PUFA = polyunsaturated fatty acids such as eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and α-linolenic acid; semisynthetic triglycerides such as caprylic acid / capric acid tricycerides such as Miglyol types; oleostearin, paraffin oil, glyceryl stearate, isopropyl myristate, diisopropyl adipate, 2-ethylhexanoic acid ethylstearyl ester, liquid hydrogenated polyisobutenes, squalane, squalene; animal oils and fats such as fish oils such as mackerel, sprat, tuna, halibut, cod and cod Salmon oil, lanolin poppy seed oil, Tung oil, tall oil, wood oil, resins and waxes, liquid terpenes and terpene oils, blown native oils from natural oils, complex esters, alkoxylated products, lard oil, whipped cream, sheep fat, vegetable and animal waxes, spermacet, silicone oils and / or carnauba.

The present invention therefore relates to additives for lubricants containing nanoparticles, which are substantially spherical.

The additives according to the invention for lubricants have a tribological effect at temperatures of from 20 to 1000 ° C., preferably from room temperature to 400 ° C., more preferably up to 250 ° C.

Nanoparticles within the meaning of the invention are preferably ceramic nanoparticles. These are particularly preferably selected from the group Al ₂ O ₃ , AlN, SiO ₂ , TiO ₂ , ZrO ₂ , Y ₂ O ₃ , WO ₃ , Ta ₂ O ₅ , V ₂ O ₅ , Nb ₂ O ₅ , CeO ₂ , Boron carbide, aluminum titanate, BN, MoSi ₂ , SiC, Si ₃ N ₄ , TiC, TiN, ZrB ₂ , clay minerals (eg montmorillonite) and / or mixtures thereof and thermally stable carbonates and / or sulfates such as zinc carbonate and / or zinc sulfate.

Substantially spherical in the sense of the invention means that the particles represent an ellipspoid with three semiaxes a, b and c, for which a ≠ b ≠ c or a = b = c. The ratios of the semiaxes are preferably a: b = 1-100, a: c = 1-1000, b: c = 1: 100 (see Fig. 1 ).

The spherical nanoparticles according to the invention preferably have a particle size of 1 to 5000 nm, preferably 10 to 500 nm, very particularly preferably 50 to 300 nm, measured as primary particles.

In a preferred embodiment of the invention, the nanoparticles have no surface modification, e.g. by chemically bound siloxanes and / or silanes.

Furthermore, it is preferred that the nanoparticles have a thermal conductivity of 1 to 100 W / mK, more preferably 20 to 80 W / mK, particularly preferably 40 to 60 W / mK.

In a further preferred embodiment of the invention, the nanoparticles have a thermal stability of from room temperature to 1000 ° C., more preferably from RT to 400, particularly preferably from RT to 250.

The content of nanoparticles in the lubricant is preferably 0.05 to 95% by weight, more preferably 0.1 to 50% by weight, particularly preferably 0.5 to 5% by weight, based on the lubricant.

In a further embodiment of the invention, the nanoparticles are dispersed in a base fluid. In a further preferred embodiment of the invention, the base fluid may correspond to the later intended lubricant (oils). However, it is also possible to use water for dispersion.

The base fluid is preferably selected from the group consisting of soybean oil, palm oil, palm kernel oil, sunflower oil, corn oil, linseed oil, rapeseed oil, thistle oil, wheat germ oil, rice oil, coconut oil, almond oil, apricot kernel oil, avocado oil, jojoba oil, hazelnut oil, walnut oil, peanut oil, Pistachio nut oil, triglycerides of medium-chain vegetable fatty acids (so-called MCT oils) and PUFA oils (PUFA = polyunsaturated fatty acids such as eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and α-linolenic acid, semisynthetic triglycerides such as caprylic acid) Capric acid tricycerides such as the miglyol types; oleostearin, paraffin oil, glyceryl stearate, isopropyl myristate, diisopropyl adipate, 2-ethylhexanoic acid ethylstearyl esters, liquid hydrogenated polyisobutenes, squalane, squalene, animal oils and fats such as fish oils such as mackerel, sprat, tuna, Halibut, cod and salmon oil, lanolin poppy seed oil, tung oil, tall oil, wood oil, resins and waxes, liquid terpenes and terpene oils, blown native oils from native oils, complex esters, alkoxylated products. Lard oil, Unschlitt, sheep fat, vegetable and animal waxes, spermacet, silicone oils, carnauba and / or water.

It has also proven to be advantageous that the nanoparticles are chemically inert, not microbiologically degradable and non-oxidizable.

In addition to the additives according to the invention, it is additionally possible to use further constituents selected from the group consisting of viscosity index improvers, detergents, dispersants, defoamers, EP additives, pour point depressants, corrosion protection additives, non-ferrous metal inhibitors, Friction modifiers, lubrication improvers, antioxidants, tackiness agents, demulsifiers, emulsifiers, deaerators, wetting agents, water in the form of emulsions, solid lubricants, thickeners, such as soap thickeners; Polyureas, bentonites, polymorphic silicas, solubilizers, flame retardants, thixotropic agents, dilating agents, anti-wear additives (AW) additives, dyes, pigments, tracers and / or fragrances, are used in the lubricant.

The content of further constituents in the lubricant is preferably 0.001 to 50.00 wt .-%, more preferably 0.50 to 20 wt .-%, particularly preferably 1.00 to 5.00 wt .-%, each based on the Lubricant.

1. (a) Mischen der im wesentlichen sphärischen Nanoteilchen in einem Basisfluid mit gegebenenfalls weiteren Additiven; und
2. (b) Dispergieren durch mechanische Einwirkung auf die aus Verfahrensschritt (a) resultierende Mischung und gegebenenfalls
3. (c) die Zudosierung weiterer Additive.

The subject of the present invention is also a process for the preparation of the additives for a lubricant characterized by the following process steps:

1. (a) mixing the substantially spherical nanoparticles in a base fluid with optionally further additives; and
2. (B) dispersing by mechanical action on the mixture resulting from process step (a) and optionally
3. (c) the addition of further additives.

It is preferred that the mechanical action mentioned under (b) is carried out by means of rolling, ultraturrax, ultrasound, spray drying, electrostatic methods, pH change, use of dispersing aids, stirrers and mills, in particular ball mills, for (wet) grinding.

These are commercially available devices and commercially available starting materials

Another object of the present invention are the additives obtainable by this process mentioned above for lubricants.

Another object of the invention are lubricants containing nanoparticles which are substantially spherical. It applies to the nanoparticles, the above definitions and embodiments and the Fig.1 ,

In a further embodiment of the invention, the lubricants additionally comprise further constituents selected from the group consisting of viscosity index improvers, detergents, dispersants, defoamers, E P additives, pour point depressants, corrosion protection additives, non-ferrous metal inhibitors, friction additives. modifiers, lubricating improvers, antioxidants, tackiness agents, demulsifiers, emulsifiers, deaerators, wetting agents, water in the form of emulsions, solid lubricants, thickeners, such as soap thickeners; Polyureas, bentonites, polymorphic silicas, solubilizers, flame retardants, thixotropic agents, dilating agents, anti-wear additives, dyes, pigments, tracers and / or fragrances.

It is preferred that the content of further constituents from 0.001 to 50.00 wt .-%, more preferably 0.50 to 20 wt .-%, particularly preferably 1.00 to 5.00 wt .-%, each based on the Lubricant is.

The invention also relates to the use of the additives according to the invention for lubricants for improving the tribological properties and the load carrying capacity. It primarily includes the reduction of friction, wear, an improvement of the lubricating effect, including a heat-dissipating function. The load carrying capacity is a measure of the ability to prevent the welding of materials.

The lubricants according to the invention can be used in a variety of ways by the additives according to the invention. Particular applications to be mentioned are high temperature applications in lubricating pastes, e.g. for pressing in plain bearing bushings and roller bearing rings, for pressing on toothed and sprocket wheels, for lubricating guides, joints and threads and as an assembly aid; for use in engine oils and in gear oils, in fats and release agents and in heat transfer fluids as well as in hydraulic fluids (power transmission fluids) for flame retardancy.

In addition, these can be used as metal-working fluids to reduce the high forces that can occur in metalworking and metal forming and as a cooling lubricant.

Furthermore, these can be used for FDA applications, ie food-safe applications, since it can be assumed for a large proportion of nanoparticles according to the invention that These are harmless to health and therefore may be used as ingredients for food.

Lubricants which contain the additives according to the invention can also obtain the eco-label, since the additives have neither an aquatoxicity nor a warm-blooded toxicity.

• Ausführungsbeispiele:
  • Es werden 90 % sphärische Nanopartikel aus SiO₂, mit einem Teilchendurchmesser von 100 nm, mit 10% DITA (Di-Isotridecyladipat ) pur bzw. 10 % Rapsöl pur als Grundöle zu einer Paste angerührt. In dieser Paste sind die Nanopartikel noch nicht vereinzelt, was daran zu erkennen ist, dass die Paste undurchsichtig ist. Nachdem die Paste einmal über einen Walzenstuhl mit der engsten Spaltweite gefahren wurden, erhält man ein transparentes oder zumindest transluzentes Gel, was ein deutlicher Hinweis darauf ist, dass die Nanopartikel vollständig dispergiert sind.

The present invention will be explained in more detail with reference to the following example, without limiting it:

• EXAMPLES
  • There are 90% spherical nanoparticles of SiO ₂ , with a particle diameter of 100 nm, with 10% pure DITA (di-Isotridecyladipat) or 10% pure rapeseed oil as base oils mixed into a paste. In this paste, the nanoparticles are still not isolated, as indicated by the fact that the paste is opaque. Once the paste has been driven over a roller mill with the narrowest gap width, a transparent or at least translucent gel is obtained, which is a clear indication that the nanoparticles are completely dispersed.

These concentrates with DITA or pure Rabsöl are then used to make a lubricating oil or grease.

As shown in Table 1, 1% nanoparticle concentrations in the respective base oils are realized. The wear protection (AW) properties were compared with the lubricating oils not added with additives by means of test runs on the Vierkugel apparatus according to DIN 51350 and on a vibration-friction-wear (SRV) test rig. These results are listed below. TABLE 1 template VKA-dome according to DIN 51350-3 (1hx300N) DITA pure 0.92 mm DITA with 1% nanoparticles 0.50 mm Pure rapeseed oil 0.75 mm Rapeseed oil with 1% nanoparticles 0.45 mm

In the case of the lubricants according to the invention, a clear AW effect can be seen, since the value for the wear cup is almost halved. <b> TABLE 2 Vibratory Abrasive Wear (SRV) Step Test in Rapeseed Oil </ b> Concentration of nanoparticles from SiO ₂ in rapeseed oil [%] Results [Good Load / Failure Load] At room temperature Results [Good Load / Failure Load] At 80 ° C 0 600/700 N 600/700 N 0.1 600/600 N 700/900 N 1 800/900 N 1100 / 1200N 3 1200 N 1100 / 1200N

In rapeseed oil (see Table 2), a significant effect can be observed for the Vibration Rubbing (SRV) test as the SRV Good Load (a measure of load bearing capacity and oil wear) can be nearly doubled.

Claims (14)

Additives for lubricants containing nanoparticles that are substantially spherical. Additives for lubricants according to claim 1, characterized in that they have a tribological effect and an improved load carrying capacity at temperatures of 20 to 1000 ° C. Lubricant additives according to claim 1 or 2, characterized in that the nanoparticle is a ceramic nanoparticle. Additives for lubricants according to claim 3, characterized in that ceramic nanoparticles are selected from the group Al ₂ O ₃ , AlN, SiO ₂ , TiO ₂ , ZrO ₂ , Y ₂ O ₃ , WO ₃ , Ta ₂ O ₅ , V ₂ O. ₅ , Nb ₂ O ₅ , CeO ₂ , boron carbide, aluminum titanate, BN, MoSi ₂ , SiC, Si ₃ N ₄ , TiC, TiN, ZrB ₂ , clay minerals (eg montmorillonite) and / or mixtures thereof and thermally stable carbonates and / or sulfates. Additives for lubricants according to one of claims 1 to 4, characterized in that the nanoparticles have a particle size of 1 to 5000 nm. Additives for lubricants according to one of claims 1 to 5, characterized in that the nanoparticles represent an ellipsoid with three half-axes a, b and c, for which applies a ≠ b ≠ c or a = b = c, wherein the ratios of the semi-axes a: b = 1-100, a: c = 1-1000, b: c = 1: 100. Additives for lubricants according to one of claims 1 to 6, characterized in that the nanoparticles have a thermal conductivity of 1 to 100 W / mK. Lubricant additives according to any one of claims 1 to 7, characterized in that the nanoparticles are dispersed in a base fluid. Lubricant additives according to claim 8, characterized in that the base fluid is water and / or at least one oil selected from the group consisting of soybean oil, palm oil, palm kernel oil, sunflower oil, corn oil, linseed oil, rapeseed oil , Thistle oil, wheat germ oil, rice oil, coconut oil, almond oil, apricot kernel oil, avocado oil, jojoba oil, hazelnut oil, walnut oil, peanut oil, pistachio oil, triglycerides of medium-chain fatty acids and PUFA oils (PUFA = polyunsaturated fatty acids), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and α-linolenic acid; semisynthetic triglycerides, such as caprylic acid / capric acid tricycerides, miglyol types; Oleostearin, paraffin oil, glyceryl stearate, isopropyl myristate, diisopropyl adipate, 2-ethylhexanoic acid ethylstearyl ester, liquid hydrogenated polyisobutenes, squalane, squalene; animal oils and fats such as fish oils such as mackerel, sprat, tuna, halibut, cod and salmon oil, lanolin poppy oil, tung oil, tall oil, wood oil, resins and waxes, liquid terpenes and terpene oils, blown native oils from native oils , Complex esters, alkoxylated products, Lard oil, Unschlitt, sheep fat, vegetable and animal waxes, spermacet, silicone oils and / or carnauba. Additives for lubricants according to one or more of claims 1 to 9, characterized in that the content of nanoparticles 0.05 to 95 wt .-%, based on the lubricant is. Process for the preparation of the additives for a lubricant according to one of Claims 1 to 12, characterized by the following process steps: (a) mixing the nanoparticles in a base fluid with optionally further additives; and (B) dispersing by mechanical action on the mixture resulting from process step (a) and optionally (c) the addition of further additives. Lubricants, characterized in that they contain nanoparticles which are substantially spherical. Lubricant according to claim 12, characterized in that it additionally contains further constituents selected from the group consisting of viscosity index improvers, Detergents, dispersants, defoamers, EP additives, pour-point depressants, anti-corrosion additives, non-ferrous metal inhibitors, friction modifiers, lubricity improvers, antioxidants, tackiness agents, demulsifiers, Emulsifiers, deaerators, wetting agents, water in the form of emulsions, solid lubricants, thickeners, soap thickeners; Polyureas, bentonites, polymorphic silicas, solubilizers, flame retardants, thixotropic agents, dilating agents, anti-wear additive (AW), dyes, pigments, tracers and / or fragrances. Use of the additives for lubricants according to one or more of claims 1 to 10 for improving the tribological properties and the load carrying capacity.

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