EP0141758B1 - Lubricant compositions containing solid additives - Google Patents

Description

The present invention relates to lubricant compositions containing dispersed particles of lithium fluoride, calcium and / or barium.

It is known to disperse in oils solid lubricants such as molybdenum disulphide, graphite or its derivatives or even polytetrafluoroethylene. These additives have the drawback of not having very high thermal and chemical stability.

The dispersion in the form of sub-micron particles of lithium fluoride, calcium flora and / or barium fluoride in mineral or synthetic base lubricating oils considerably increases the carrying capacity of these base oils.

These particles are introduced by any known means into base oils. A particularly recommended means consists in preparing a concentrated dispersion by mixing, for example in a ball mill, fluorides with lubricating oils.

One can thus obtain stable concentrated dispersions containing up to 50% by weight of fluoride in oils, such as for example oils refined with solvents "1 00 Neutral" to "500 Neutral". Although they can be used as such, these concentrates can be diluted in oils preferably belonging to the same chemical family as that of the oil of the concentrate. These dilutions are a function of the subsequent use of the lubricant composition. Concentrated or diluted dispersions can easily contain only fluoride particles of size less than 0.5 micron.

In order to stabilize the dispersion, it is recommended to add a dispersant to the medium, the definition and quantity of which are chosen, in a known manner, as a function of the oil. These dispersants are usually chosen from calcium or barium alkylaryl sulphonates, calcium or barium alkylphenates and polysuccinimides. For example, for oils refined with solvents, it is preferred to use an ashless additive of the polysuccinimide type as dispersant.

The effect of the lubricant compositions is highlighted, in particular when the loads applied to the parts in contact or to the friction surfaces are medium or strong: in these cases, one can note a limitation of wear compared to the lubricant compositions classics. The properties of compositions based on synthetic oils such as lubricating esters, esters of dicarboxylic acids and monoalcohols, esters of neopentyl polyols and mono carboxylic acids, polyethers obtained by fixing alkylene oxides on compounds with atom atoms mobile hydrogen and fluorides according to the invention are particularly interesting.

Although the properties of lithium, calcium and barium fluorides are similar, the dispersions in oils of mixtures of calcium and barium fluorides in the respective proportions by weight from 60 to 35 for 40 to 65 and particularly in the proportions of 1 eutectic, that is to say 38% by weight of calcium fluoride and 62% by weight of barium fluoride, lead to more advantageous results than by using calcium and barium fluorides alone and characterized by their presence of the lubricant compositions of the present invention.

ou

dans laquelle:

• R_z est l'hydrogène ou un radical alkyle inférieur comportant de 1 à 3 atomes de carbone,
• a possède la valeur de 2 ou 4.
• R₁ et Z répondent aux définitions suivantes:

The properties of such dispersions can be advantageously supplemented by combining, with calcium and barium fluorides, an organic additive which is soluble in oils of formula:

or

in which:

• R _z is hydrogen or a lower alkyl radical containing from 1 to 3 carbon atoms,
• a has the value of 2 or 4.
• R ₁ and Z meet the following definitions:

tandis que R, est l'hydrogène, ou un radical alkyle contenant de 1 à 6 atomes de carbone ou le groupement

R et R' étant soit un atome d'hydrogène, soit le groupement méthyle CH₃, ou R₁ et Z forment ensemble un radical alkylène linéaire de 3 à 10 atomes de carbone.Z is constituted by a hydrogen atom and R ₁ is a hydrogen atom or an alkyl radical containing from 1 to 6 carbon atoms, an aryl radical or a cyclanic radical from 3 to 10 carbon atoms, or R and Z are identical or different alkyl radicals containing from 1 to 6 carbon atoms, or Z is the group

while R, is hydrogen, or an alkyl radical containing from 1 to 6 carbon atoms or the group

R and R 'being either a hydrogen atom or the methyl group CH ₃ , or R ₁ and Z together form a linear alkylene radical of 3 to 10 carbon atoms.

These organic fluorinated additives, described in French application 82.00964, can be introduced into the dispersion in the reports

The compositions containing the two types of fluorides have friction and wear reduction properties over a wide range of loads and temperatures and lead to results superior to those obtained with traditional additives such as zinc alkyldithiophosphates.

The compositions of the invention find application in ⁷ engines, transmissions hy hydraulics, deformation without metal chips, etc.

The following nonlimiting examples serve to illustrate the invention. Those which do not incorporate the characteristic of the invention are obviously cited for comparison.

Examples 1 to 8

The anti-wear power and the load capacity of compositions containing as base oil the mineral oil “200 Neutral Solvent” and as additives LiF, CaF ₂ , BaF ₂ , the eutectic CaF ₂ - BaF _z containing 38% by weight of CaF ₂ and 62% by weight of BaF ₂ are determined using the EP Shell 4-ball machine, the description of which is given in "Annual Book of ASTM Standards", Part 24 (1979), pages 680 to 688.

The anti-wear test consists in applying a constant load of 70 daN for 1 hour then in measuring the diameters of the wear marks on the three fixed balls.

The load capacity test consists of measuring the diameters of the wear marks as a function of the load applied. The results are expressed in Wear Charge Index (I.C.U.). The operating conditions and the calculation method of the I.C.U. are described in ASTM method 2783-71 T.

The results are shown in Table 1.

The metal fluoride dispersions are stabilized by the ashless dispersant polysuccinimide (OLOA 1200).

Also shown in Table 1 are the values of the binding load and the welding load which show that the metallic fluorides have a more marked effect at high loads than at low loads.

Examples 9 to 11

A dispersion of barium fluoride and calcium barium eutectic is prepared in a polyether (Emkarox FC 31-140), obtained by fixing a mixture of 75 parts by weight of ethylene oxide and 25 parts by weight of propylene oxide on trimethylolpropane and having an average molecular weight of 1500. The compositions and the results according to standard ASTM 2783-71 T, are given in table 2.

Examples 12 to 17

This series of examples demonstrates the formation of reaction films with fluoride dispersions and their good thermal resistance under the following tribological conditions:

The tests are carried out on a sphere-plane tribometer with the metallic couple Steel 100 C6 (Sphere), Cast iron G (Plan). The principle diagram of the sphere-plane contact geometry tribometer appears in the review WEAR, 53 (1979), p. 10. The load is 1 daN, the sliding speed of 1 mm s ^―1 , the sliding length of 1 cm: 0.1 ml of lubricant deposited in the contact is used and the temperature is raised by 20 ° C min ^―1 .

For the compositions used, at 275 ° C., the oil disappeared by evaporation and thermo-oxidative decomposition, but the friction is continued to dryness while continuing to raise the temperature.

Table 3 gives the results obtained with the compositions tested, that is to say the film breaking temperature and the value of the coefficient of friction before breaking.

Compared with Example 16 according to the invention, Example 12 shows that no friction reducing film is formed, the value of the coefficient of friction indicated is that obtained before the disappearance of the lubricant, in dry friction. , it reaches the value of 0.37 corresponding to the non-lubricated friction between steel and cast iron GL.

Examples 18 and 19

The following examples show the advantages which one derives from the association of calcium or calcium-barium fluorides with fluorinated organic anti-wear additives soluble in lubricating bases. Amines and amino alcohols with fluorinated chains, which are remarkable anti-wear additives in the field of low loads and medium loads, provide a complementary anti-wear effect, which makes it possible to obtain effective compositions in a wide range of temperatures and loads.

The tests were carried out under the conditions described above for examples 1 to 8.

The compositions and the results obtained (according to standard ASTM 2783-71 T) are given in Table 4.

Examples 20 to 22

The results of these examples show that the fluoride dispersions remain effective when they are combined with the traditional additives used in the composition of oils for internal combustion engines, such as freezing inhibitors, additives improving the viscosity index, anti-oxidant, and anti-corrosive additives. The tests, wear and load capacity were carried out with the EP Shell 4-ball machine under conditions identical to those of the tests in Examples 1 to 8.

Table 5 shows the results obtained by dispersing in three oils containing all the conventional additives, except the anti-wear zinc dialkyldithiophosphates, 1% by weight of BaF _z or of CaF _{2 /} BaF ₂ mixture in the proportions of 1 eutectic containing 38% by weight of CaF ₂ and 62% by weight of BaF ₂ .

• - une huile SAE 15 W 40 classique pour moteurs à essence;
• - une huile SAE 10 W 30 à base semi-synthétique (mélange d'ester de triméthylolpropane et de polyoléfines) pour moteurs à essence;
• - une huile SAE 15 W 30 pour moteurs Diesel.

These three compositions, without zinc dialkyldithiophosphates, correspond respectively to:

• - a conventional SAE 15 W 40 oil for petrol engines;
• - an SAE 10 W 30 oil with a semi-synthetic base (mixture of trimethylolpropane ester and polyolefins) for petrol engines;
• - SAE 15 W 30 oil for Diesel engines.

The main additives of these oils are polymethacrylates as freezing inhibitors and improving the viscosity index, polysuccinimides as dispersants, calcium alkylarylsulfonates as detergents.

Diesel oil has the particularity of containing both as dispersant-detergents, a calcium phenate, a calcium sulfonate and a polysuccinimide.

Claims (5)

1. Lubricant composition based on mineral or synthetic oil containing solid lubricant additives in the form of a dispersion of submicron particles, characterized in that it contains, as such additives, a mixture of calcium fluoride and of barium fluoride consisting of 60 to 35 parts of calcium fluoride and of 40 to 65 parts of barium fluoride, by weight, per 100 parts of mixture.

2. Composition according to Claim 1, characterized in that the calcium fluoride and the barium fluoride in the mixture are in the proportions by weight of the eutectic: CaF_2/BaF₂ = 38/62.

3. Composition according to either of Claims 1 and 2, characterized in that it contains up to 50% by weight of the mixture of calcium fluoride and barium fluoride.

4. Composition according to one of Claims 1 to 3, characterized in that it contains an oil-soluble organic fluoro additive, of formula:

in which

R₂ is hydrogen or a lower alkyl radical containing from 1 to 3 carbon atoms,

a has the value 2 or 4,

R₁ and Z meet the following definitions:

Z consists of a hydrogen atom and R₁ is a hydrogen atom or an alkyl radical containing from 1 to 6 carbon atoms, an aryl radical or an alicyclic radical containing from 3 to 10 carbon atoms, or

R₁ and Z are identical or different alkyl radicals containing from 1 to 6 carbon atoms, or Z is the group―CH_Z-

while R₁ is hydrogen or an alkyl radical containing 1 to 6 carbon atoms or the group

R and R' being either a hydrogen atom or the methyl group CH₃,

or R₁ and Z together form a linear alkylene radical containing from 3 to 10 carbon atoms.

5. Composition according to Claim 4, characterized in that the weight ratio