DE2335947A1 - OIL MIST LUBRICATION MIX AND PROCESS FOR OIL MIST LUBRICATION - Google Patents

Description

k: Cr! TSAUWÄLTE -

CR. JUR. Dlrl-CHEM. WALTER BEIL ^Wi «Wed 1973

ALFRED Üücr »~ tfcER
- DR. JjUR. DiPL-CHSM. HJ. VVOLFP DR. JUR. HANS CHR. BEJL

FRANKFURTAM MAIN-HDCHST AOfIQNSTRASSiM

Our no. 18 765

Chevron Research Company San Francisco, CaI., V.St.A.

Oil mist lubrication mixture and process for oil mist lubrication

In the case of oil lubrication, fine droplets of an oil mixture are created pneumatically distributed on the surfaces to be lubricated of various machine elements. The invention relates focus on oil mist lubricants and their methods of application.

Oil mist systems have their reliability and usefulness proven in numerous areas. You will be on different

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Sectors used in industry and commerce, starting from Rented stress, e.g. in dental facilities, up to very difficult operating conditions, e.g. J3. in lubrication iron backup rolls in steel mills. Fog lubrication is a clean method of lubrication that has little external contamination and it works effectively and equally, ensures centralized distribution and is economical in terms of material consumption.

Mist lubrication creates an oil mist, a micro mist or aerosol, and pneumatically conveyed to the surface to be lubricated by compressed air or another gas. This is where it condenses Aerosol, the droplets flow together or as it is in the terminology the mist lubrication means, experience an "ite classification" by hitting a surface at high speed.

The oil mist can be generated in various ways. A device is preferably used which consists of a storage vessel which opens for a Venturi nozzle. Pressurized gas is blown through the Venturi nozzle, the lubricant is sucked out of the storage vessel and mechanically broken down into tiny droplets by the turbulence of the air flow. Downstream, the mixture collides with baffles, where the large drops, which are difficult to dispose of, converge and return to the storage vessel. The remaining oil particles form an aerosol with particle diameters in the range from 0.1 to 20 μm. Relatively large amounts of air or gas are used to transport the lubricant pneumatically. The Ülkonzentration in the feed mixture is in the order of magnitude won 4 g of oil to 1 "kg air.

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, (reclassification),, ^ ..,. χ ..- The reclassification 'is usually brought about by valves oxier openings (reclassers) that direct the aerosol in the desired' direction and accelerate so that it finally wets the surface to be lubricated, or the reclassifiers cause the aerosol to condense "so that the lubricant drips off. The surface to be lubricated is wetted on impact, as the particles in the mist or aerosol flow together when they hit a surface at high speed Just like when using a spray can! The high-speed aerosol that hits the surface condenses completely on a small area if the spray nozzle is close to the surface, but if the spray nozzle is further away, the frictional losses of the air reduce the speed of the aerosol, so that only a fraction of the liquid is collected on the surface and the rest is lost as "stray mist ^11. The choice of suitable opening and the optimal aerosol speed for lubrication depends on the type of element to be lubricated and a number of τοη factors that are related to the condition and composition of the mist lubricant, such as the viscosity of the oil, the particle size and concentration of the Aerosols, of existing additives, temperature, Mo molecular weight and chemical constitution.

In general, smaller particles are needed to reclassify the oil have a higher speed, while large aerosol particles, such as those in visible mist, lightly cover the surfaces at lower Wet speed. Particles with a diameter of 6 µm start at a speed of 7.6 meters per minute (0.8 km / h} flow together and show good wetting properties at 21 m per minute, while particles of 0.5 pn, diameter

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hit at a speed of 1.5 km per hour (90 km / h) need to be reclassified. Such high speeds are normally not achievable in practice, which has the consequence that the droplets with a smaller diameter become one Forming Stray Nebulae

At the points in the mist system where lubrication is to take place, the speed of the aerosol must be great enough to ensure wetting, but the aerosol must also be conveyed slowly enough onto the surface during pneumatic transport to prevent excessive wetting and to avoid lubricant losses in the oil lines. If there are large droplets of oil in the aerosol, they easily moisten and lubricate a bearing or other surface, but they also tend to condense inside the supply pipes xa. If the particle size is too small and the speed in the vicinity of the element to be lubricated xa is low the droplets do not converge, but scatter fog is formed, which is a serious problem. A very fine aerosol can only be brought with difficulty by reclassifying it into samia flow, and this leads to strong scattering mist and smog in the atmosphere. Of course, the N * b «l old of a certain particle size distribution is generated, so that the stray mist, which originates from the lower end of the drop size distribution, ie from droplets with a diameter of less than 0.5 μm, is a problem that is difficult to eliminate.

The ability of the oil to atomize and condense becomes great Attention paid, but still needs a mist lubricant have other properties, such as suitable viscosity, lubricity, Abrasion resistance, high pressure resistance, oxidation

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resistance, no formation of deposits or corrosion and rust protection.

The stray mist is the most annoying problem of mist lubrication systems. The "lubricated machine element is generally exposed to the air and the mist which escapes reclassification escapes." into the atmosphere, where it is a potential health and safety hazard as it is in the vicinity and precipitates on the respiratory organs «Bs were already mechanical Separation methods developed to collect the stray mist, e.g. with Using centrifugal separators. · These devices remove particles up to. 0.2 µm down, but they require an additional one Lead and are still rarely used · They are often unaffordable too expensive·

By adding additives to the oil mist, the necessary reduction in the formation of scattered mist could not yet be achieved by a long way without adversely affecting the other important properties of the lubricants Polymers, such as those usually used as pour point depressants (polyester) or as viscosity index improvers in sufficient quantities for these purposes "be erwendet, increase" the viscosity of the oil too strong, reduce its shear stability or make it pneumatically untransportierbar or, bend ultimately exclusion ^6, they do not reduce the stray mist share to under a few percent, when taken in reasonable jaengen apply * The growing attention paid to the stray mist with regard to air pollution, the cleanliness of the plant and the potential health and fire hazard, has drawn our interest to this problem

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drastically reduce, the other functional characteristics of the mist lubricant do not worsen.

Polymers are usually used in significant amounts (3-40% by weight) in lubricating oils as pour point depressants, viscosity index improvers and dispersant additives. Polyesters (e.g. polyalkyl methacrylates) are used in accordance with American patent 3,510 h25 to prevent the formation of scattered mist, but are not as effective as polyolefins for this purpose. British Patent 1,099,550 proposes certain polyesters and polyisobutene polymers which are used as viscosity index improvers and which have a low shear resistance for the prevention of stray mist. Additives of the type known up to now should achieve a reduction in the stray mist content to around 2-IO percent. A mist lubrication process can be regarded as technically satisfactory if it works with less than about 10 percent scatter mist.

It has now been found that the undesired scatter mist in mist lubrication can be reduced to surprisingly low levels (less than 1 $) with the aid of a lubrication method in which the mist is pneumatically conveyed to the surface to be lubricated and there without significant scatter mist formation and without loss the properties required of a mist lubricant is reclassified if the lubricant contains 0.001 to 2 wt. The polyolefins are preferably C ₂ C 'copolymers whose basic structure consists of non-voluminous chains and which have a minimum number of side

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Have chains with a minimum length, as it is necessary to maintain the oil solubility. χ is equal to 3 to about 12 ", with the proviso that the olefin be a copolymer of ethylene must" are preferred in particular (ethylene-propylene) C ^ C - copolymers having 40-80 mole percent ethylene and a ^ average molecular weight of about 20,000 or above · As a direct result of the use of the mist preventers according to the invention, a reduction in the scatter mist was achieved to values that were far lower than previously achieved. In addition, the reduction in the scatter mist is achieved with a percentage lower polymer content. The polymers according to the invention worsen the other puncture characteristics of the mist lubricant not.

Xn the accompanying drawings, Figure 1 shows the prevention of Stray fog through different polymers. The open circles show the rapid reduction of the stray fog to very low values (less than 0.3 percent stray fog) due to very small amounts of the preferred C C ^ copolymers with a molecular weight of 100,000. The triangle points show the effectiveness of a polybutenene (PB) with a molecular weight of 50,000. The two scatter points (PAMA) correspond to polyalkyl methacrylates with a molecular weight of 30,000 or 500,000, the more effective methacrylate (taking into account the lower concentration) being the one with the higher molecular weight. FIG. 2 shows the amount of mist in mg per .mu.m drop diameter that is generated per minute by the nozzle of a nebulization device according to the test method described here will. With this method, the drop size distribution of the Oil mist recorded in order to reduce the

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in addition to the amount of oil found (droplet diameter below 0.5 pn) to be highlighted. It can be seen that the amount of oil in the drop size range of the scattering mist is drastically reduced by adding polymers. «The bold circles refer to the base oil, a neutral oil with a viscosity of 108 cSt at 37» 8 ° C, without added polymers. The triangle points refer to a blend of the same base oil containing 0.06% by weight of a polymethacrylate polymer with a molecular weight of 30,000. The open circles refer to the same base oil with an addition of 0.05% by weight of a C ₉ C copolymer with a molecular weight of 150,000. FIG. 2 shows in a graphic representation the effectiveness of the copolymers according to the invention in reducing the scattering mist. Only a negligible amount of scatter mist is formed if the base oil contains the very small amount of 0.05% by weight of the CC copolymer, while the base oil alone generates considerable amounts of scatter mist and the mixture containing polymethacrylate still shows the sharp initial increase in the amount of scatter mist shows when the drop size is small. ,

Surprisingly, low scatter mist values are obtained (less than with oil mist lubrication in which oil mixtures are used which have very low percentages (θ, 001-2% by weight ) of certain polyolefins. These polymers have (l) a non-voluminous structure, have (2) a minimum number of side chains and side chains of minimum length to maintain oil solubility, (3) have an average molecular weight greater than 5,000 and preferably greater than about 20,000 and are obtained either by polymerization of monomers or by degradation of polymers with higher

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Maintain molecular weight and shift (4) the particle size distribution in the oil mist towards larger droplets.

These properties are found in oil-soluble CC copolymers of ethylene with an average molecular weight of more than 5,000 and preferably about 20,000 or more (the molecular weights are generally determined from the viscosity), which contain 40-80 mol percent ethylene and in which G is a 0 o "" ° \ ö ^{M <mo} ~ olefin and preferably a CC, monoolefin, with the proviso that the polymers are oil-soluble. The term "copolymers" includes polymers derived from two or more different monomers. Preferred among these are C ₂ ⁰ *? °° Ρ ° 1Υ ^ιηθΓΘ

The success of the oil mist system depends on the change in the "physical" bhan Condition of the lubricant from a coherent Liquid into an aerosol and back into a cohesive one Liquid is transformed. These two mechanisms Fog formation and reclassification are influenced by a multitude of oil properties. Some oils are very easy to remove into mist, which is especially true for the lighter, low viscosity oils. From the point of view of maximum yield in the case of nebulization, transport and as little as possible Return, lubricants are particularly desirable that have more part «· Produce a size of about 1-10 yuui.

The reclassification, on the other hand, depends on the size of the particles and their speed. Insufficient reclassification leads to stray mist which cannot be used as a lubricant.

The inventive polymers act in such a way that they the

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Reduce stray fog to lower levels by reducing the smallest droplets in the aerosol »which are a diameter below 0.5 fim owning, diminishing or eliminating · The details the mechanism by which the addition of polymers affects an oil's ability to aerosolize and reclassify, have not yet been fully clarified. Viscoelastic properties, density of the electrostatic charge, size of iropfea and Aerosol concentrations are important factors The preferred polymers (C C copolymers) have a fairly good shear stability, however, this property is not a critical factor in the choice of polymers for their ability to prevent of stray fog. In particular, a CC copolymer with a Molecular weight of 100,000, which is a neutral oil with a viscosity of 108 cSt at 3718 C was added showed only 0.3 percent Stray mist if it is present in the oil in an amount of 0.05% by weight was. The same copolymer showed only a ll reduction in the viscosity index in a shear stability test.

From the work of J. W. Gibbs et al on surface free energy or surface tension is known that the -chermodyuaiaischeu Properties of the coherent fluid itself differ considerably from those of the surface or phase interface. Similar differences were found with the viscoelastic Properties to be expected and found »For drops of medium size is the ratio of liquid in mass to liquid on the surface quite large, and the properties of the coherent fluid predominate. Aoer for the smaller droplets that make up the mist lubricants, is applicable; this no longer. Thermodynamic and viscoelastic upper

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surface properties gain more in levers. Significance compared to those of the liquid, which is reflected on the particle size, solubility, adsorption, etc. _o. That makes it difficult if not; impossible to draw conclusions about those of the mist from knowledge of the properties of the liquid.

As shown above, polymers have an influence on the particle size of the aerosol and - most importantly - on the size distribution of the droplets. With a suitable choice of the polymers, an aerosol is obtained whose particle size distribution is shifted towards larger droplets. By varying the type and concentration of the Polymex ^% en, the difficulty in re-melting the particles can be minimized.

# ^
LUBRICANT

When using lubricants with a higher viscosity, such as they are needed in steel mills, for example, seemed at first there is little need for means to reduce the stray fog. It was believed that the high viscosity of the lubricant would not allow the formation of small droplets (less than 0.5 μm), which are responsible for the stray mist. This premise now turned out to be wrong.

A mineral oil or a synthetic hydrocarbon with a suitable one can be used as the base oil for the lubricants according to the invention viscosity, d. H. a viscosity in the range from 2.7 to 10,825 cSt can be used at 37.8 C · The oil can be a paraffin or eim iaphthene, a corresponding mixture can also be used

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werden- but paraffins because of their oxidation resistance best suited · The characterization of an oil as "paraffinic finish", "naphthenic" or "gemischtbasisch ¹ · based on a series -from factors in Nelson" Petroleum Refining Engineering "(4th Ed., McGraw-Hill Book Co., Inc., 1958 ) The oil can be a single refining cut, or a mixture of two or more oils in appropriate proportions can be used to make the mixture A suitable mixture is, for example, a mixture that has a ratio of about 40-60 atkT neutral oil with a viscosity of about 108 cSt at 37.8 ° C and a bright stock with a viscosity of about 865 cSt at 37.8 ° C , 8 ° C. The shading oil forms the main part of the mixture according to the invention and makes up about 90-98% by weight of the mixture and preferably about 93-96% by weight. The viscosity is usually determined by the requirements of the machine element to be lubricated nte determined. The fogging ability is adapted to requirements by regulating the viscosity of the oil fog system by heating the oil or the air in the fog generator. Devices without heating can generally only be operated with old oils whose viscosity at the lowest operating temperature is below 215 cSt. From the point of view of the mist system, the oil is with; the lowest: viscosity that fulfills its function as a lubricant, most suitable. Oils with a very high wax content can clog the very small openings of the reclaimer, this applies, for example, to oils whose cloud points are at or above room temperature. Oils with these properties are of course not usable.

Synthetic lubricants such as alkyl, aryl and alkaryl phosphate esters, alkylbenzenes, polyoxyalkylene esters or glycols, orthosilicates

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etc. are also useful base oils for the present invention Oil mist mixtures when separated or in mixable combinations applied by lubricating viscosity

In the case of oil and / or air heaters, the stability properties are the lubricant is of crucial importance. Since the oil is often continuously in the. Cycle is used, it must be thermally stable and resistant to oxidation. For this reason, oxidation inhibitors are added to the mixture. Even "Various other additives are commonly used in operating oils to improve their functions. These additives act as ! Anti-rust agents, lubricity agents, extreme pressure additives, yer-. Wear protection agents, detergents, foam inhibitors, metal deactivators en, metal wetting agents, etc. These additives are dem Known to those skilled in the art, a typical oxidation inhibitor is, for example, zinc dialkyldithiophosphate · Also polymers that act as pour point have a lowering effect, such as polyalkyl methacrylates, may be present. These additives make up a total of about 1 to about 10% by weight of the mixture.

Mixing can be achieved by simply combining the various components getting produced. In general, all components provided in smaller quantities are added to the base oil; you can be added in pure form or as concentrates in oil solutions, if the oil used as a solvent can be atomized and is compatible with the Grundö1 »The components can all work at the same time be mixed with each other, or turn it two or more the components are mixed with each other separately and the remaining components are mixed are then used to produce the finished mixture added.

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test method

The percentage of stray mist was measured directly, using an "Alemite weaver generator, which operated with a water pressure in the intake port of 50-75 cm and an air and oil temperature of 15-95 C. The aerosol was about 3» 3 m to a junction with 18-23 reclassifiers (Aleraite nozzles No. 5, Alemite Division, Stewart- ¥ arner Corporation, Chicago, Illinois) The condensed mist that dripped from the reclassers was soaked in a flat beaker and weighed The non-condensed fog (stray fog) was collected in a vacuum by a Papiex'filtex, which was weighed before and after the test. Fog is the percentage of scattered fog. The method is sensitive and allows measurements up to hundredths of a percent. The droplet size distribution ± n normal web and scattered fog was quantitatively determined with the aid of an Anderson air sampler, a commercially available device (2000, Inc., Salt Lake City, Utah) which was developed for measuring the distribution of aerosol particles. The specimens were at a distance of only 60 Ciu from the drip size. Fog ore euger taken lest glngen the drops lost _t köüdensierten in Verbinduugsrohr to Reklassierdüsen.

BEWERCTMO

Table I shows the influence of the polymer type on the maturity of the polymer odex * Copolyiueren for Herabietzuiig vou stray mist,

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Very high molecular weight polymethacrylate in an amount of 0.2% by weight in a neutral mineral oil gives 1.05 percent stray mist. But a polypropylene with a much lower molecular weight is much more effective than the ester in preventing stray mist. Finally, the low molecular weight CC copolymer is considerably more effective than polypropylene at the same percentage by weight · Structural analysis of polymers! shows that · to prevent stray fog polyolefins with a non-bulky backbone, a minimum number of side chains and a minimum length of these side chains to maintain oil solubility are preferred. So there is polyethylene in itself a very advantageous structure for the reduction of stray fog, but it is not oil soluble enough. The according to the invention CC copolymers (40-80 mol percent ethylene), on the other hand, have the Property of the oil solubility and are effective additives for the prevention of stray mist. In Figure 1 are these observations graphically represented.

TABLE I. Effectiveness of different types of Polna

MG ¹ ■ _ 2 υ stray fog ³

————— ■ - Koni. '

1. Polyalkyl methacrylate 500,000 0.20 1.05

2. CgC copolymers 300,000 0.20 0.25

3. Polypropylene 50,000 O, 20 0.42

Molecular weight

Concentration iu percent by weight in a neutral oil with a Viscosity of 108 cSt at 37.8 ° C

■ ^ Percentage of scattered fog, measured as described on other Sxelle

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As can be seen from Table II, the polymers are at the same concentration in general, the higher the molecular weight, the more effective in preventing stray fog, as is the case with polyisobutylene, for example is applicable. However, this is not necessarily valid for the preferred C C "copolymers. These copolymers reach you most effective Mol ekul ax 'weight for the prevention of stray fog about 20,000 odex above and experienced as the molecular weight is increased no more noticeable improvement,

TABLE II

Influence of Mo1ekular ^ ewi cht s of the polymer ί stray fog MG ¹ Conc. ² 9 o, 5o 1. Polyisobutylene 50,000 0.20 0.35 2. Polyisobutylene 800,000 0.20 0.15 3. CC copolymer 100,000 0.20 0.25 k. CC copolymer 300,000 0.20

Molecular weight

^ Concentration in percent by weight in an IV neutral oil with a viscosity of 108 cSt at 37.8 ° C

Percentage of scattered fog, measured as described elsewhere

Table III shows the remarkable influence of the concentration, which can be seen in the decrease in the scattering mist with increasing concentration of the polymer at constant molecular weight and type. Abez * again, the influence is _{not so pronounced in the case of the preferred CC q} copolymers, which are just as effective (very effective) in reducing the amount of build-up mist at 0.2% by weight as at noticeably higher percentages by weight.

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- TABLE III Influence of the concentration of the »Polyanran

MG

Kong *

Stray fog

0.01 1.70 0.02 0.70 0.20 0.25 0.50 0.20 0.02 1.20 0.05 0.90 0.10 0.65 0.20 0.50 1.00 0.35 o, o6 3.00 0.60 0.85

1. C C copolymer 300,000

2. CJQ-- Copolymer 300,000

3. C C “copolymer 300,000

4. C C copolymer 300,000

5. Polyisobutylene 50,000

6. Polyisobutylene 50,000

7. Polyisobutylene 50,000

8. Polyisobutylene 50,000 9, · Polyisobutylene 50,000

10. Polyalkyl methacrylate 30,000

11 x polyalkyl methacrylate 30,000

Gross weight

Concentration in percent by weight in a neutral oil with a viscosity of 108 cSt at 37.8 ° C

^ Percentage of scattered fog, measured as described elsewhere

It has been shown that by adding polymers to an oil mist the droplet size distribution in the direction of larger droplets is moved. This effect increases with increasing concentration of the polymer and increasing size of the polymer molecules. the However, polymer size can be changed in at least two ways werdenι on the one hand by changing the molecular weight and on the other hand by changing; the weight of the one thing or of the monomers. So both have polymers with the same molecular weight, one of which consists of polyester units with a

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Side chain, and the other one consists of propylene units, extraordinarily -different molecular sizes. The polypropylene molecule is much larger than the polyester molecule because most of its atoms are in the backbone and contribute to its length, while most of the atoms of the polyester molecule are in the side groups can be found and contribute more to its volume Dei * Bs was found to be polymers with a thin skeleton and the smallest Side chain! *, Which still guarantee oil solubility, e.g. C C copolymers, shift the size distribution in oil mists to larger droplets in a much more effective way than polyalkyl methacrylates and long-chain polyolefins with voluminous backbones and long ones Side chains.

When using the thin polymers according to the invention it was found the influence of the concentration as large up to about 0.1 percent by weight and then relatively small and always less higher concentrations. In contrast, in the case of voluminous polymers, the concentration dependence is initially not so great, but it increases at higher concentrations before it reaches a certain level.

The suitable choice of the chemical structure, the molecular weight and the concentration permits an optimal reduction in the proportion of the smallest droplets and a relatively small reduction in the proportion of the larger ones. This leads directly to a reduction in the stray fog without impairing the desired fog. Direct comparisons with polyesters show that with these the scattering mist can be reduced to about 1 percent when the concentrations of the polyester reach about 1 percent, but that much lower concentrations de? before eyeing C ₂ ^{C #} f copolymers j

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i.e. concentrations of 0.1 percent, the stray fog to about 0.2 Reduce percent and, as a result, much more wanker additives for Reduction of stray fog are.

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Claims (6)

- 2ο - claims 1.) Oil mist lubrication mixture for mist lubrication with low Percentage of stray mist containing a major amount of an oil of lubricating viscosity and an additive to reduce it of the scatter mist, characterized in that the additive jsur reduction of the scatter mist from ο, οοΐ to 2 percent by weight consists of an oil-soluble copolymer of ethylene with other monomeric olefins, the 'copolymer being a result of the viscosity has a determined average molecular weight of at least 5,000. 2.) oil mist lubrication mixture according to claim 1, characterized in that that the additive to reduce the scattering mist is a copolymer of ethylene and a monomeric C - C, monoolefin and that the copolymer consists of 4o-8o mol percent ethylene. 3.) oil mist lubrication mixture according to claim 1, characterized in that that the additive to reduce the scattering mist, is a copolymer of ethylene and propylene and from 4o-8o Mole percent ethylene. h.) Oil mist lubrication mixture according to one of claims 1, 2 or 3, characterized in that the copolymer lowers the amount of thunder mist to below 0.5 percent in order to reduce the scatter mist. 5.) Method for mist lubrication with a low percentage of scatter mist, characterized in that one is a mixture according to one of the preceding claims in a fog 30988B / 1324 leads the mist pneumatically to a surface to be lubricated conveyed and reclassified the fog on this area. 6.) The method according to claim 5, characterized in that the percentage of stray fog is less than 0.5 percent For: Chevron Research Company (Dr. H. at. Wolff) Lawyer Blank page