EP0951527B1 - Operating fluid for lifetime lubricated internal combustion engines - Google Patents

Abstract

The invention relates to an operating fluid which can be efficiently used for lifetime lubrication and cooling of an internal combustion engine. As basic liquid, said fluid contains a polyalkylene glycol obtained from ethylen oxide and propylen oxide and an additive compound, consisting of a) 0.012 -1.0 wt.% of a reaction product from diphenylamine and 2.4.4.-trymethylpentene; b) 0.01-1.0 wt.% of a pentaerythrite partially or totally esterified with an alkyl-substituting p-hydroxy propionic acid; c) 0.01-1.0 wt.% of a mono- or di-(C4-C8)alkyl phosphoric acid-(C10-C15) alkylamide; d) 0.01-1.0 wt.% of the triphenylthiophosphate; e) 0.01-0.1 wt.% of a tolutriazole aminoethylized with a straight chain or branched alkyl group with 2-10 carbon atoms and/or f) 0.01-0.1 wt.% of the 1H-benzotriazole.

Description

The invention relates to a functional fluid for Lifetime lubricated internal combustion engines, which the Properties of a lubricant and a coolant united in itself and due to their novel composition has significant advantages over known motor oils. It finds its application in internal combustion engines that are made from conventional metallic materials are made but also in engines made of ceramic parts consist.

The classic internal combustion engines consist of one Variety of main components such as pistons, piston rings, Piston pins, connecting rods, connecting rod bearings, liners, crankshafts, Crankshaft bearings, camshafts, valves, valve guides and valve train elements that deal with relatively high Moving speed against each other while doing significant Cover wear paths. Typically, these are Components made of metallic materials such as cast iron, steel, Made of aluminum, brass and bronze alloys and are therefore subject to typical system wear.

To keep the friction between the components as low as possible and thus keep the wear at a low level, the friction points of these combustion engines with Lubricants, which are usually made of hydrocarbons, Mineral oils or synthetic oils consists. The tribologically strong, of temperature and Impurities but rather slightly loaded valve train is supplied from the same oil supply as the thermally highly stressed, with combustion residues loaded crank mechanism. Oil life and change intervals are determined by the latter.

To fulfill the diverse lubrication tasks Motor oils additives are added which cover the performance range of engine oil and which ones - each for yourself or in combination - to perform very specific tasks to have. A significant proportion of these additives are used the metallic materials sliding on each other To protect wear, corrosion or welding (seizure).

Have up to 35% of the particle emissions of a diesel engine their origin in motor oil. The same applies to the Hydrocarbons in the exhaust gas from gasoline engines. A considerable one Part of the particle emissions consists of non-co-burning Additives such as phosphorus, sulfur, zinc, barium compounds and many others, which are not only those Promote soot particle emissions, but also the catalytic converter contaminate, consume and therefore replaced must be as soon as the effective minimum concentration in the Base oil is below.

Newer materials such as hard metals, monolithic and layered ceramics, Sintered ceramics, carbon and tribological Coatings enable today in connection with constructive Measures new solutions for lubricating the Internal combustion engine with far lower lubricant consumption, than conventional conventional internal combustion engines metallic materials occurs.

Since the component surfaces sliding on each other from internal combustion engines manufactured in newer materials, which in hereinafter simply referred to as "ceramic motors" are no longer just of a metallic nature, they can there is no need for any additives that protect them from corrosion today or contact with materials of the surfaces sliding on each other under all circumstances should prevent. The much better wear resistance of the newer materials mentioned (tend to eat some not at all) allows a much larger one Share of mixed friction than this with conventional ones Motors made of metallic materials is possible.

Under these mixed friction conditions - or even in Dry run - but are then due to the partial elimination of wear-reducing liquid lubrication material substitute functions enables: The one with conventional engines required wear reserve and the low shear The lubricants get into the surface of each other sliding materials shifted.

Ceramic materials are characterized by high degrees of hardness, high melting points, low density, low thermal expansion, reduced corrosion and high resistance to thermal and chemical stresses. For this reason, molded parts made of ceramic materials are increasingly being used where metallic materials no longer meet the mechanical, thermal or chemical stresses. Especially aluminum oxide (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), silicon nitride (Si ₃ N ₄ ), silicon carbide (SiC), cubic boron nitride (BN), aluminum nitride (AlN) and boron carbide (B ₄ C) are considered as materials , which will be suitable materials and coatings for the production of components for internal combustion engines in the future.

However, ceramic parts are subject like parts from others Materials the abrasion. With suitable lubricants therefore also to ensure here that the friction is as low as possible. It already has different approaches Given the solution to the problem, such as arising from friction Material losses of molded ceramic parts are adequately prevented can be. The following proposed solutions are worth mentioning:

According to a proposal, various materials such as oils, Additives, polymers, solid lubricants and soaps in ceramic, composite materials before the completion of the ceramic molding are incorporated, which makes the finished molding receives self-lubricating properties. However, the mechanical Properties of the ceramic material adversely changed.

According to another process, the surfaces should be more ceramic Molded parts with different materials such as Metal films, solid lubricants or polymer films coated to increase the sliding properties of the surfaces. Such surface coatings are used in mechanical, thermal or chemical stress on the ceramic parts but rubbed off after a short time, as their wear reserve is low, so that they are only temporarily effective.

Another possibility is to use known ones soluble anti-friction additives to a liquid lubricant, e.g. a mineral oil that was previously used for Reduction of the friction between metal surfaces was used. However, these funds are based on one specific reaction with the metal surface, its atoms are bound ionically or covalently, and can therefore at ceramic materials not used promisingly as the additives are not from the ceramic surface be adsorbed or react chemically with it.

It has also been proposed to use solid lubricants such as Graphite or molybdenum disulfide, dispersed in oils and then apply them to ceramic surfaces. Such Solids, however, lead to clogging of filters and Also need to be applied in large amounts to be effective to be. Solid lubricants can also be present in the presence of a Liquid does not form a solid film on a surface, so this proposal also satisfies the problem Reduction of the friction loss of ceramic motors too achieve, not solve.

In WO-A-92/07923 it has already been proposed to Reduction of frictional losses on ceramic surfaces to use a liquid containing a monomer. In the Liquid does not polymerize the monomer initially, however is the polymerization by the flash temperature between the surfaces slid past each other, causing a polymer film directly on the stressed surfaces trains. As a result, the monomers are used up proportionately quickly and the lubricant needs to be changed frequently become.

All previously known solutions have not yet been able to solve the problem of reducing the friction loss of mechanically, thermally or chemically stressed ceramic surfaces satisfactorily, which is the prerequisite for practical and durable internal combustion engines. However, since even a tribologically and material-optimized motor does not allow any concessions in terms of service life and mechanical efficiency, there are certain minimum requirements for wear resistance and coefficient of friction µ . The coefficient of friction µ ranges from 0.001 to 0.01 in the case of liquid friction, which - with a low mixed friction component - prevails in the conventional engine. Completely dry friction pairings with these limit values are, however, neither known from the literature nor from the relevant tribo databases, so that at least the piston / sleeve system must continue to be lubricated. But then, instead of a mineral oil, an easily degradable medium should be used in such a minimal amount that it does not have to be changed or supplemented during vehicle life. Then it will no longer be noticed by the vehicle user, just as he no longer takes notice of the filling media for the transmission and air conditioning.

The liquid medium, according to the invention, both the tasks a lubricant as well as a coolant, is referred to below as "functional fluid". Crucial for the functional fluid suitable for life according to the invention it is that these are not tribological contains relevant and effective additives, which change intervals participate. Rather, it exists tribologically relevant mode of action in that the base oil of the invention Functional fluid with e.g. ceramic Material surface a tribologically chemical Response. Because the base oil compared to the Additives in any amount are consumed not yourself.

a) 0,01 bis 1,0 Gew.-% eines Reaktionsproduktes aus Diphenylamin und 2.4.4-Trimethylpenten;

b) 0,01 bis 1,0 Gew.-% eines teilweise oder vollständig mit einer alkylsubstituierten p-Hydroxypropionsäure veresterten Pentaerythrits;

c) 0,01 bis 1,0 Gew.-% eines Mono- oder Di-(C₄-C₈)alkylphosphorsäure-(C₁₀-C₁₅)alkylamids;

d) 0,01 bis 1,0 Gew.-% des Triphenylthiophosphats;

e) 0,01 bis 0,1 Gew.-% eines mit einer geradkettigen oder verzweigten Alkylgruppe mit 2 bis 10 Kohlenstoffatomen aminomethylierten Tolutriazols und/oder

f) 0,01 bis 0,1 Gew.-% des 1H-Benzotriazols.

To achieve the object, the invention provides a functional fluid for a lifetime-lubricated motor, which contains as base fluid a polyalkylene glycol made of ethylene oxide and propylene oxide, to which an additive mixture consisting of is added

a) 0.01 to 1.0 wt .-% of a reaction product of diphenylamine and 2,4,4-trimethylpentene;

b) 0.01 to 1.0% by weight of a pentaerythritol partially or completely esterified with an alkyl-substituted p-hydroxypropionic acid;

c) 0.01 to 1.0% by weight of a mono- or di- (C ₄ -C ₈ ) alkylphosphoric acid (C ₁₀ -C ₁₅ ) alkylamide;

d) 0.01 to 1.0% by weight of the triphenylthiophosphate;

e) 0.01 to 0.1% by weight of a tolutriazole and / or aminomethylated with a straight-chain or branched alkyl group having 2 to 10 carbon atoms

f) 0.01 to 0.1% by weight of the 1H-benzotriazole.

Such a functional fluid combines several advantages in itself. The strong friction and wear reducing Effect of polyalkylene glycols makes them an ideal one Engine lubricant. This is surprising because Polyalkylene glycols so far in the field of engine lubrication have practically not been used. Motor oils for Internal combustion engines are predominant today Part made of mineral oil and mixtures of synthetic mineral oils and esters. In addition, polyalkylene glycols are better have thermal properties as mineral oils and therefore also the task of a coolant to absorb the process heat and for component cooling of an internal combustion engine can take over.

Of particular note, however, is that polyalkylene glycols are physiologically harmless and have a high biological Show degradability when it comes to using polyalkylene glycols low molecular weights. Products with molecular weights from 4,000 g / mol are broken down up to 80% in 28 days. Each the lower the molar masses, the higher the biological Degradability. The disposal of the invention Functional fluid is also facilitated in that they are free from the wear protection and heavy metals added to high pressure additives and can be burned without smoke and soot in the internal combustion engine.

In the composition of the functional fluid according to the invention great value was placed on long-term stability. Tests have shown that they work under practical conditions up to 2,000 operating hours and more for a sufficient tribological effect and cooling of the engine ensures that a single filling for the entire life of the engine is sufficient.

Excellent engine lubrication and cooling can be achieved with an optimal biodegradability of the invention Connect functional fluid when through Polyaddition made from ethylene oxide and propylene oxide Polyalkylene glycol a molecular weight between 300 and 700 g / mol, preferably between 400 and 600 g / mol. This polyalkylene glycol is said to consist of ethylene oxide and propylene oxide in a weight ratio of 30:70 to 70:30.

The excellent properties of the invention Functional liquid put the addition of a balanced Additive mixture ahead.

One of the indispensable components of the additive mixture a reaction product of diphenylamine and 2.4.4-trimethylpentene, where the molar ratio of diphenylamine to 2,4.4-trimethylpentene is preferably between 1: 1.1 and 1: 2.5. Such reaction products are part of liquid Stabilizer mixtures for polyols already in EP-A-574 651 described.

It has an antioxidant effect in the additive mixture Containing pentaerythritol esters proven especially when all four hydroxyl groups of pentaerythritol with one alkyl-substituted p-hydroxyphenylpropionic acid esterified are. The phenyl residue of p-hydroxyphenylpropionic acid should preferably in the 3- and / or 5-position an alkyl group wear. Connections with a are particularly advantageous branched alkyl group of 3 to 5 carbon atoms in 3- and 5-position, the tertiary-butyl group being a preferred position Has.

Another component of the additive mixture is a phosphoric acid amide, which is characterized by particularly valuable properties distinguished if it is from mono- or dihexylphosphoric acid derives. Manufactured from this are preferred Phosphoric acid alkylamides in which the alkyl group 10 to 15 Includes carbon atoms.

Furthermore, in the additive mixture used according to the invention also contain one or more triazoles. Either in a mixture with the 1H-benzotriazole or alone the aminomethylated tolutriazole stabilizes the invention Functional fluid is particularly good when it comes with a or two branched hydrocarbon groups each with 5 to 10 carbon atoms on the pendant nitrogen is alkylated.

The good biodegradability for the invention Functional fluid used is by the following examples are shown.

example 1 Growth test on land plants

The basic liquid with a molecular weight of 460 mg / mol was on its possible inhibitory effect on the growth of Land plants tested according to OECD Guideline 208.

Different amounts of basic fluid were made with semi-natural Soil mixed, with test concentration of 0, 1.0, 3.2, 10, 32, 100, 320 and 1,000 mg / kg dry soil were checked. 10 seeds from two types of plants, namely Oats (Avena sativa) and lettuce (Lactuca sativa) were divided into four seeded parallel containers, the soil samples with the above mentioned concentrations of the base liquid contained. The containers became 16 at 20 to 24.5 ° C per day Hours of exposure (6,500 to 6,600 lux) and then 8 hours in Kept dark. The containers were made with glass plates covered. After the seedlings were grown, per Container five plants away to make room for that to get the remaining five plants. The test was then for continued for a period of 18 days. The following Observations were recorded: seedling germination, visual appearance of the young plants (including the record of the dead plants), wet weight of the individual plants.

None of the doses used could be clearly identified Delay in germination of Avena seedlings sative and Lactuca sativa can be observed. In addition, also no other adverse effects like death or leaf damage in both plant varieties between 1 and 1,000 mg / kg of the tested basic fluid. Only the average moisture weight (growth) was slight for both plant varieties at 1,000 mg / kg decreased, which, however, is not statistically significant was viewed. It can therefore be concluded that the Effective concentrations for the germination of the seedlings and that Survival of Avena sativa and Lactuca sativa seedlings of the basic fluid examined is equal to or greater than 1,000 mg / kg are. The active concentration was used for growth both plant varieties are considered to be 1,000 mg / kg.

Example 2 Assessment of biodegradability (Manometric Respirometry Test)

The biodegradability of the basic fluid with a Molecular weight of 460 g / mol was aerated aqueous medium using the Manometric Respirometry Test checked. The study complied with the OECD Guidelines for Testing of Chemicals Number 301 F and Method C.4-D in Commission Directive 92/69 / EEC.

1.) Zwei parallel geimpfte Kontrollen, die aus dem aktivierten Schlamm und dem Impfgut bestanden, denen kein Testmaterial zugegeben wurde (Blindprobe),

2.) eine Probe zur Kontrolle, wobei Anilin in einer Nährlösung mit einer Konzentration von 100 mg/l und Impfgut zusammengegeben wurden und

3.) eine Probe zur Kontrolle der Toxizität, die 100 mg/l sowohl der zu prüfenden Grundflüssigkeit als auch des aktivierten Schlammes und des Impfgutes enthielten.

Two parallel aqueous solutions of the test material with concentrations of 100 mg / l were prepared; the test solutions were inoculated with activated sludge obtained from the municipal sewage works (final concentration corresponds to 30 mg / l suspended solids). The following control solutions were prepared for the study:

1.) Two controls vaccinated in parallel, which consisted of the activated sludge and the inoculum, to which no test material was added (blank sample),

2.) a sample for control purposes, aniline being combined in a nutrient solution with a concentration of 100 mg / l and inoculum and

3.) a sample to control the toxicity, which contained 100 mg / l of the basic liquid to be tested as well as the activated sludge and the inoculum.

The samples were sealed at 21 ° C in the dark Incubated tubes, taking the test solutions with a magnetic stirrer were stirred. Biodegradation was achieved by the measured daily biological oxygen consumption. Moreover were the concentrations of dissolved organic carbon and the pH at the beginning and end of the test measured.

The basic liquid examined was 89% organic degraded, measured based on oxygen consumption. The dissolved organic carbon was 100% after 28 days consumed. The extent of biodegradation after 10 Days 64%. Accordingly, the base liquid can be as biodegradable. The toxicity control showed no significant toxic effects on the im Microorganisms contained in sludge. The one for positive control approach used with aniline reached after 28 days among the same test conditions a biodegradation of 87%. This shows that the inoculum and the test conditions are suitable were.

Example 3 Inhibition of algae growth Scenedesmus subspicatus

The acute toxicity of the base fluid with the molecular weight 460 g / mol in water was affected by the Algae strain Scenedesmus subspicatus determined. The study corresponded to the OECD Guideline for Testing of Chemicals Number 201 and to Method C.3 of Commission Directive 92/69 / EEC and was carried out under GLP conditions.

S. subspicatus cells were grown over a period of 72 Hours in six parallel samples of an aqueous nutrient solution (100 ml), each 100 mg / l of the base liquid contained. Another three parallel samples were in the tests included as blank samples and contained no base liquid. The incubation was done in a laboratory shaker 24 ± 1 ° C with constant exposure (7,000 lux). Samples of the algal suspensions were made after 0, 24, 48 and 72 Taken hours and the number of cells using one Spectrophotometer determined at 665 nm. As a growth parameter the area under the growth curve was determined.

It was recognized by this experiment that the basic fluid no inhibitory effect at the concentrations used on the algae strain Scenedesmus subspicatus.

Example 4 Determination of the acute toxicity of the Basic liquid on rainbow trout

The acute toxicity of the base fluid with the molecular weight 460 g / mol on rainbow trout (Oncorhynchus mykiss) was based on the method of the OECD Guidelines for Testing of Chemicals (1992) number No. 203 referred to as method C.1 Commission Directive 92/69 / EEC carried out under GLP conditions.

Two groups of ten fish each were in one aqueous dispersion of the base liquid at a concentration of 100 mg / l for a period of 96 hours below semi-static test conditions (daily renewal of the Test medium) exposed.

Another group of ten fish was under control same conditions, but without adding the base liquid, tested. The fish were in aquariums, the 20 liters of the test medium contained. The temperature, pH and the oxygen concentration of the test solutions were during of the study recorded daily. Fish mortality and other effects were seen after 3, 6, 24, 48, 72 and 96 hours observed.

There were no signs of death or toxicity in the test group or in the control group.

This shows that the basic fluid is none Toxicity on rainbow trout in the used Has concentrations.

Claims (10)

1. Functional fluid for a lifetime-lubricated engine, characterized in that it contains as a basic fluid a polyalkylene glycol produced from ethylene oxide and propylene oxide to which an additive mixture is added, consisting of

   a) 0.01 - 1.0 wt.% of a reaction product from diphenylamine and 2,4,4-trimethylpentene;

   b) 0.01 - 1.0 wt.% of a pentaerythritol partially or completely esterified with an alkyl-substituted p-hydroxyphenylpropionic acid;

   c) 0.01-1.0 wt.% of a mono- or di-(C₄-C₈) alkylphosphoric acid-(C₁₀-C₁₅) alkylamide;

   d) 0.01-1.0 wt.% of the triphenylthiophosphate;

   e) 0.01-0.1 wt.% of a amino-methylated tolutriazole, which is alkylated with a straight-chain or branched alkyl group with 2 - 10 carbon atoms, and/or

   f) 0.01-0.1 of the 1H-benzotriazole.
2. Functional fluid according to claim 1, characterized in that the polyalkylene glycol used as the basic fluid has a molecular weight of 300 - 700 g/mole and consists of ethylene oxide and propylene oxide at a ratio of weights of 30:70 to 70:30.
3. Functional fluid according to claim 2, characterized in that the polyalkylene glycol used as the basic fluid has a molecular weight of 400 - 600 g/mole.
4. Functional fluid according to claim 1, characterized in that in the reaction product, contained in the additive mixture, of diphenylamine and 2,4,4-trimethylpentene the molar ratio of diphenylamine and 2,4,4-trimethylpentene is between 1:1.1 and 1:2.5.
5. Functional fluid according to claim 1, characterized in that the pentaerythritol ester, contained in the additive mixture, is esterified at all four hydroxyl groups with a (C₂-C₁₀) alkyl-substiated p-hydroxyphenylpropionic acid.
6. Functional fluid according to claim 5, characterized in that the p-hydroxyphenylpropionic acid used for the esterification of the pentaerythritol is substituted in the 3 and/or 5 position with a branched alkyl group of 3 - 5 carbon atoms.
7. Functional fluid according to claim 1, characterized in that the phosphoric acid amide, contained in the additive mixture, is a mono- or dihexylphosphoric acid alkylamide, wherein the alkylamide group comprises 10-15 carbon atoms.
8. Functional fluid according to claim 1, characterized in that the amino-methylated tolutriazole, contained in the additive mixture, is alkylated with one or two branched hydrocarbon groups each with 5 - 10 carbon atoms at the lateral nitrogen.
9. Use of the functional fluid according to the claims 1 to 8, characterized in that it is used in the lubricant circulation as well as in the cooling agent circulation of the engine.
10. Use of the functional fluid according to the claims 1 to 8, characterized in that it is used in an engine, which has ceramized or ceramic surfaces in the friction loaded regions.