NO792141L - COMPOSITIVE LUBRICANT. - Google Patents

Abstract

Compound lubricant.

Description

The present invention relates to lubricant compositions, methods for their production, additives to lubricants and methods for using such compounds

put lubricants.

Abrasive particles in a lubricant are usually considered undesirable, as the presence of such particles can cause damage to the surfaces to be lubricated. It is therefore common to insert an oil filter in the flow path of the circulating lubricant in an internal combustion engine to remove such particles.

However, it has now surprisingly been found that the addition of a

smaller amount of suitable finely divided particles of a selected abrasive for a lubricant, e.g. a lubricating oil or a lubricating grease, has a. beneficial effect on the surfaces that are lubricated by the lubricant, especially when the resulting lubricant composition is used for lubrication during the "run-in" of such surfaces, as it e.g. takes place at moving parts in a vehicle during its break-in period.

According to the present invention, a compound lubricant has been produced which comprises a main weight proportion of a lubricant component which is evenly mixed with a smaller weight proportion of added particles of an abrasive with a hardness value of at least 9 according to the Mohs scale, the size distribution of the abrasive particles being such that the average particle size is less than 2 µm and the largest particle size is less than 3 µm. In order to avoid misunderstandings, it must be stated in particular that the designation ^um used here has the same meaning as in the diamond subject, which means that l^um is equal to one thousandth of a millimetre.

The invention further specifies a method for production

of a compound lubricant, as this method involves adding a smaller weight proportion of abrasive particles with a hardness of at least 9 according to the Mohs scale to a main weight proportion of an abrasive component, these abrasive particles having such a size distribution that the average particle size is smaller than 2 µm and the largest particle size is less than 3 µm. Preferably, the average particle size of the added abrasive particles is about 1 µm and most preferably the added abrasive particles have a fairly narrow size distribution, which means that the maximum particle size is less than 2.5 µm. It is also preferable that the shape of the added abrasive particles is mostly regular or "block-forming", that is to say in the form of extremely small blocks or rather than in the form of spindles, irregular disks or plates. This preferred morphology can be expressed numerically by specifying that the ratio between the largest and smallest cross-sectional dimensions of the bulk of the particles should be. less than 3:1 and preferably less than 2:1.

As indicated, the added abrasive particles must have a hardness

of at least 3 on the Mohs scale. Suitable abrasives then include diamond, which has a hardness of 10 according to the Mohs scale, as well as the so-called cubic form of boron nitride, which is otherwise known as borazone, which is said to have a similar hardness to diamond, and boron carbide. One must distinguish between the cubic form of boron nitride and the so-called hexagonal form, which is soft and not abrasive. This hexagonal form of boron nitride is thus not suitable for the abrasive particles used in accordance with the invention, and the term "abrasive" as used here is not intended to include hexagonal boron nitride.

As the lubricant components that form the basis of the compound lubricants according to the invention are mainly of an oil-like nature, it is preferable that the abrasive particles used to form such compound lubricants have a high surface affinity towards oils, which means that they are relatively hydrophobic , as it has been found that such particles can be particularly effectively distributed evenly in ordinary oil-like lubricant components. In this regard, it has been found that diamond particles have a suitably high surface affinity for oil-like substances and in view of this property and also because of the beneficial properties which they impart to the lubricant compositions to which they are added, diamond particles are considered the preferred abrasive particles for use in according to the invention i.

A particularly suitable source for such diamond particles

• is diamond dust produced by grinding and crushing

of diamonds, whether natural or synthetic. Such dust also occurs during the production of synthetic diamonds.

It is of no importance for the purposes of the invention whether dust from a natural diamond or from one of synthetic origin is used. A mixture of natural and synthetic diamond particles can be used. Also mixtures of diamond particles (natural and/or synthetic) and other suitable abrasives, e.g. borazone, can be used. ' Diamond dust is usually graded, e.g. by sieve, in several size bands corresponding to the following sieve grades: coarse 16-72 stitches per linear empty medium 72-150 stitches - per linear empty fine 150-400 stitches per linear inch ' subview about 4 0^um and less.

The coarse, medium and fine size class is used for polishing and grinding several types of materials, including diamond itself, as the relevant material and treatment type determine the most suitable size class.

As the name suggests, it is usually not possible to classify

finer sub-screen sizes of diamond dust by sieving methods.

Instead, this dust can be further graded by air screening, centrifugation, slurping (that is, grading the particles by means of an upward flow in a liquid), or by settling in a liquid, e.g. an oil (sedimentation). Typical size classes (in ^um) for sub-sieve size diamond dust include 0/2, 0.5/3, 2/6, 4/8, 6/12, 8/12

and 20/40. In practicing the present invention, diamond dust of size class 0/2 µm is preferred as a source for the particles added to the lubricant component. Diamond dust of size class 0/2^um is available on the market,

but has so far not been commercially exploited to a significant extent. A further advantage of the present invention is consequently that it enables a new use for a substance that has not been of much use until now.

The preferred compound lubricants according to the invention thus comprise a main weight proportion of a lubricant component which is evenly mixed with a smaller weight proportion of diamond dust whose particle size does not exceed approx. 2^um.

When designing compound lubricants according to the invention, it is important that the mixed abrasive particles are evenly dispersed throughout the lubricant. Microscopic examination of typical compositions has shown that practically all the mixed particles are mutually separated by the lubricant component. It is preferable that compound lubricants according to the invention exhibit such properties. It has been found that diamond particles can be easily distributed in oil-like lubricants in the above-mentioned degree of dispersion by first suspending the particles in the lubricant component using conventional mechanical means and then exposing the suspension thus formed for a longer time to ultrasonic vibrations. An ultrasonic transducer can e.g. immersed in the lubricant suspension or a container containing the suspension can be placed in an ultrasonic bath.

The extent of the required ultrasonic treatment will naturally depend on the added ultrasonic power to the suspension and also on the frequency of the ultrasonic vibrations. However, it will always be possible in a simple way to determine whether a satisfactory degree of dispersion has been achieved by means of microscopic examination as described above. The amount of abrasive particles distributed in the lubricant component can vary within wide limits, although usually only a very small proportion is required, e.g. less than 0.1%.

Preferably, the abrasive particles are present in the compound lubricant at a concentration of 4.0 to 800 mg/liter,

and preferably from 20 to 400 mg/litre. Most preferably, they should

set abrasive particles present in a concentration from 25 to 100 mg/litre.

The invention also includes concentrated mixtures for addition to a lubricant component to form compound lubricants of the kind discussed above. Such concentrates can e.g. comprise a dispersion medium which can be mixed with and adapted to the base component as well as at least 20 mg/litre, in particular from 20 to 4000 mg/litre and preferably from 100 to 2000 mg/litre of said abrasive particles. Ideally, the concentrate should contain from 125 to 500 mg/litre of said abrasive particles. Expressed in carats per 150 ml contains the concentrates preferably (rounded) 0.1 to 20 carats/150 ml, especially 0.5 to 10 carats/

150 ml and preferably around 1 carat/150 ml.

The dispersion medium used for the production of these concentrates is preferably an oil, but other liquids which are miscible with lubricants can also be used, e.g. isopropyl alcohol.

It must also be stated that the compound lubricants in accordance

to the invention can be produced by adding to a lubricant component a solid material composition comprising the abrasive particles as well as a dispersant which is miscible with lubricant and/or a binder. Such material compositions in solid form constitute a further embodiment

variant of the present invention. The fixed material composition can e.g. present in the form of tablets or other shaped bodies containing the abrasive particles and a binder which is miscible with the lubricant, e.g.

a wax.

The lubricant component used in the formation of compound lubricants according to the invention can be an oil with a lubricating viscosity or a lubricating grease.

The oil can be made up of any of the usual oil-

types used for lubricant compositions or a mixture of two or more such oils. The oil used can thus be chosen from among mineral oils, vegetable oils,

such as castor oil, and mixtures of these oils. Typical mineral oils include paraffinic, naphthenic and aromatic mineral oils as well as mixtures of two or more such oils. Alternatively, the oil in question may be a synthetic oil, a mixture of synthetic oils or a mixture of one or more synthetic oils with a mineral oil, with a vegetable oil or with mixtures of such oils. Typical synthetic oils include the following types: silicone, organic ester, poly-glycol, phosphate, polyisobutylene, polyphenyl ether, silicate, chlorinated aromatic and fluorochemical. The oil can be, for example, a car oil ( e.g. SAE 10W, 20W, 30, 40, 50, 10W-30 or 20W-50) a gear oil (e.g. SAE 75, 80, 90, 140 or 250) an automatic transmission oil, a hydraulic oil of light, medium or heavy type or for extra low temperature, a machine oil, an oil for use in aircraft (eg an oil of air speed rating 80 or 100) or an oil for refrigeration systems. Detér gen oils can also are used.

The oil used may contain normal proportions of any of the usual additives or mixtures thereof. Such additives may include dispersing agents, detergents, anti-wear additives, anti-corrosion agents, anti-oxidizing agents, viscosity-improving agents, anti-varnish agents, high-pressure additives, pour-point suppressors, anti-foam additives and the like. The choice of type and amount of such additives will naturally depend on the intended use of the compound lubricant in question. The concentrate mixtures according to the invention can be formed by using similar oils.

As indicated above, the lubricant component may alternatively be a lubricating grease. Any lubricating grease of a type that is usually used as a lubricant can also be used in the present context. The lubricating grease can thus e.g. consists of a petroleum oil thickened with a metallic soap. The lubricating grease can e.g. also be an axle grease. The choice of lubricant will depend on the intended application of the resulting lubricant composition. Silicone grease can also be used.

Compositions according to the present invention have been found to be particularly useful when treating mechanical parts with the aim of reducing the frictional resistance to movement between such parts. In particular, they can be used to treat such parts in the mechanisms in which they are mounted, by simply using existing compound lubricants instead of the lubricants that are usually used within an extended period of time (which may nevertheless be short compared to the mechanism's total effective lifetime), while the mechanism is kept in normal operation.

The invention thus also applies to a method for reducing frictional resistance for relative movement between mechanical parts, said mechanical parts being moved in relation to each other continuously or intermittently for a certain extended period of time, while the parts are lubricated with a compound lubricant according to the invention.

The required operating period in this connection will naturally depend on a number of variable sizes, such as e.g. the nature of the relative movement, the material of the mechanical parts, the concentration of the abrasive and the quantity supplied per time unit of the compound lubricant. In practice, it has been found that a 'significant' reduction in frictional resistance to movement can be achieved if the treatment is carried out for 100,000 to 5,000,000, preferably from 1,000,000 to 2,500,000 duty cycles for the parts. simple reciprocating movement of parts that move back and forth in relation to each other or a single revolution of parts that rotate in relation to each other. It will be understood that by carrying out the method of the invention, complementary low-friction surfaces will be obtained on pairs of said mechanical parts.

Compound lubricants according to the invention have been found

to be of particular use when treating internal combustion engines in the manner described above, namely by replacing the usual motor oil with a compound lubricant according to the invention, and a significant reduction in fuel consumption has been observed after such treatment. Gearboxes can advantageously be treated in a similar way, and in this case it has been found that the treatment has led to increased efficiency for the gearbox. It will thus be understood that a significant reduction in fuel consumption can be achieved by treating the engine and/or gearbox of a vehicle in accordance with the method of the invention.

This treatment is preferably carried out during the initial break-in period for the vehicle's engine, during which the engine's bearings are adapted. However, the treatment can also be carried out with favorable results on vehicles that have already been driven in.

After the treatment according to the invention, the lubrication is finished with a lubricant containing abrasive particles, and then a normal lubricant is used. In practice, it has been found that a significant improvement in fuel economy and operating efficiency can be achieved if the treatment according to the invention takes place while driving approx. 800 km with the vehicle in question.

The following test results will further illustrate the present invention: Tests were carried out with different amounts of diamond dust of different sub-sieve sizes, several different commercially available oils of lubricating viscosity were added. The diamond dust was distributed in the oil using a rotating mechanical mixer. The dispersion thus obtained was then exposed to ultrasonic energy in a commercially available ultrasonic bath for cleaning purposes during half an hour. At the end of this time, microscopic examinations showed that the diamond particles had been completely distributed in the oil, which means that all particles were completely mutually separated and completely surrounded by oil. A commercial car oil with the addition of 0/2 µm diamond dust in an amount of 125 mg/litre of oil was used for lubrication of a car engine during the break-in period. According to this, a car manufactured in normal continuous production and with a nominal engine capacity of 2000 cc<3> was driven in accordance with the manufacturers' regulations, except that the recommended engine oil had been added with 0/2 µm diamond dust in a proportion of 125 mg/litre of oil. Petrol consumption was measured at around 12.3 km per litres, and this must then be compared with the manufacturer's specified values of 8.4 - 9.5 km per litres. The engine ran extremely quietly and smoothly after this break-in period.

Tests have also shown that the oils to which diamond dust had been added could be used for the treatment of white metal bearings in aluminum engines as well as in cast iron engines, and these compound lubricants were also effective in the treatment of plastic bearings. When such oils containing diamond dust were used during the break-in of the bearings, the bearings would then run extremely smoothly.

On inspection of bearings driven in using lubricating oil containing diamond dust of the order of 0/2 µm, these bearings showed a glass-like polish. Based on these samples, it would seem that diamond dust of a size of 0/2 µm had a leveling effect on the bearing surfaces that the relevant lubricating oil comes into contact with during run-in.

Preliminary experiments have also shown that similarly good results can be obtained by adding 0/2 µm diamond dust to a commercial lubricating grease.

Results obtained with diamond dust with a particle size greater than 0/2 µm have proven to be mainly unsatisfactory, as the bearings in particular showed poor surface polishing and wear that could not be accepted. Several lowers had "sat down". Although compound lubricants according to the invention are usually intended for use during the initial operating period of the relevant mechanism to be lubricated, e.g. during the entry of a vehicle,

can they also be used e.g. for treating engines, gearboxes and differentials for vehicles that have been in use for some time.

A Ford Corsair that had been driven for 123,000 km was e.g. treated in accordance with the present invention in the following manner. A dispersion of 200 mg of 0/2 µm diamond dust in 0.568 liters of engine oil was added to the vehicle's oil tank. The vehicle was then driven 800 km, after which the engine oil was changed.

The fuel consumption before and after treatment was as follows:

Before the treatment: After the treatment:

9.9 km/litre 12 km/litre

This represents a reduction in fuel consumption of 21%. Similar tests were carried out on a Citroen GS (vehicle A), an Audi that had been driven 32,000 km (vehicle B) as well as three new Audis that had already been driven in (vehicles C, D and E).

The results were as follows:

For vehicles C, D and E, 200 mg of diamond dust in 0.284 liters of oil was added to the existing oil in the engine, while 100 mg of diamond dust in 0.142 liters of oil was added to the existing oil in the gearbox.

Claims (28)

1. Compound lubricant, characterized in that it comprises a main weight proportion of a lubricant component which is evenly mixed with a smaller weight proportion of added particles of an abrasive with a hardness value of at least 9 according to the Mohs scale, the size distribution of the abrasive particles being such that the average particle size is less than 2^ um and the largest particle size is less than 3 µm. 2. Lubricant as stated in claim 1, characterized in that the average particle size for the added abrasive particles is approx. lyU m. 3. Lubricant as stated in claim 1 or 2, characterized in that the largest particle size for the added abrasive particles is less than 2.5 µm. 4. Lubricant as specified in claims 1-3, characterized in that the shape of the added abrasive particles is such that the ratio between their largest and smallest transverse dimension is less than 3:1. 5. Lubricant as specified in claims 1-4, characterized in that the added abrasive particles have a high surface affinity to oil-like materials. 6. Lubricant as specified in claims 1-5, characterized in that the added abrasive particles consist of natural or synthetic diamond dust. 7. Lubricant as specified in claims 1-6, characterized in that the dispersion of the abrasive particles is such that practically all particles are mutually separated by lubricant and each particle is completely surrounded by a layer of lubricant. 8. Lubricant as specified in claims 1-7, characterized in that the concentration of the added abrasive particles is from 4.0 to 800 mg/litre. 9. Lubricant as stated in claim 8, characterized in that the concentration of the added abrasive particles is from 20 to 400 mg/litre. 10. Lubricant as stated in claim 9, characterized in that the concentration of the added abrasive particles is from 25 to 100 mg/litre. 11. Concentrate for addition to a lubricant component to form a compound lubricant in accordance with claims 1 - 10, characterized in that the concentrate comprises a dispersion medium which is miscible with said lubricant component and contains evenly distributed at least 20 mg/litre of said abrasive particles . 12. Concentrate as stated in claim 11, characterized in that it contains 20 to 4000 mg/litre of said abrasive particles. 13. Concentrate as stated in claim 12, characterized in that it comprises 100 to 2000 mg/litre of said abrasive particles. 14. Concentrate as stated in claim 13, characterized in that it contains 125 to 500 mg/litre of said abrasive particles. 15. Solid material composition for addition to a lubricant component to form a compound lubricant as indicated 1 - 10, characterized in that the material composition comprises said abrasive particles as well as a dispersant which is miscible in the lubricant component, and/or a binder. 16. Material composition as stated in claim 15, characterized in that it is in the form of a tablet or other shaped body. 17. Method for reducing the frictional resistance by relative movement between lubricated mechanical parts, characterized in that said mechanical parts are operated continuously or intermittently for an extended period of time, while the parts are lubricated with a "compound lubricant according to claims 1 - 10. 18. Method as stated in claim 17, characterized in that said mechanical parts are operated for 100,000 to 5,000,000 duty cycles (as defined in the description). 19. Method as stated in claim 18, characterized in that the mechanical parts are operated for 1,000,000 to 2,500,000 duty cycles (as defined in the description). 20. Method as stated in claims 17 - 19, characterized in that the compound lubricant is removed at the end of said operating period, after which the mechanical parts are lubricated with a lubricant that does not contain added abrasive particles. 21. Method as stated in claims 17 - 20, characterized in that complementary low-friction surfaces are produced on at least a pair of said mechanical parts. 22. Method as stated in claims 17 - 21, characterized in that the mechanical parts are made up of components in an internal combustion engine. 23. Method as stated in claims 17 - 22, characterized in that said mechanical parts are made up of components in a gearbox or differential. 24. Procedure for operating an internal combustion engine in such a way that its fuel consumption is reduced, characterized by the relevant engine being operated for an extended period of time continuously or intermittently, while the engine is lubricated with a lubricant according to: claims 1 - 10. 25. Method as stated in claim 24, characterized in that the engine is operated for 100,000 to 5,000,000 duty cycles (as defined in the description). 26. Method as stated in claim 25, characterized in that the engine is operated for 1,000,000 to 2,500,000 duty cycles (as defined in the description). 27. Method as stated in claims 24 - 26, characterized in that the engine is operated in the manner determined for its initial run-in. 28. Method for producing a compound lubricant in accordance with claims 1-10, characterized in that the abrasive particles are mixed with said lubricant component to form a dispersion, which is then exposed to ultrasonic vibrations.