New Lubricating Compositions

Abstract

A lubricating composition comprising a lubricating oil and at least one thioorganometallic complex of the general formula : ##SPC1## In which M is selected from the transition metals and zinc, cadmium, tin, lead, antimony and bismuth; n is the oxidation degree of M, R.sub.1 and R.sub.2 are each a monovalent hydrocarbon radical having one to 20 carbon atoms and 0 to 3 heteroatoms selected from the group consisting of halogen, oxygen, sulfur and nitrogen; Y is selected from the hydrogen atom and the radicals R', R'O, R'S and R'CO in which R' is a hydrocarbon radical of one to 20 carbon atoms; Y and R.sub.1 or R.sub.2 may form a divalent hydrocarbon radical containing one to 20 carbon atoms and 0-3 heteroatoms selected from oxygen, sulfur and nitrogen; and each atom Z is oxygen or sulfur, at least one of the 2n atoms Z being sulfur.

Description

This invention relates to the use of thioorganometallic complexes as additives, for example in lubricating compositions, transmission fluids, transformer oils, greases and elastomers.

It relates particularly to lubricating compositions comprising at least one lubricating oil and at least one of said thioorganometallic complexes, said compositions having an unexpectedly increased stability to oxidation.

A known technique for improving the stability of lubricants and particularly motor oils to oxidation consists of adding antioxidants thereto, said antioxidants being usually zinc dithiophosphates, dithiocarbamates, phenols or amines.

These products have one or more of the following disadvantages:

-- their antioxidant activity is rather low, particularly in the presence of such metals as iron and copper,

-- they are affected by temperature increases,

-- they produce sludge,

-- they are corrosive with respect to certain engine parts, for example the silver bearings.

It has now unexpectedly been found that the thioorganometallic complexes hereafter defined have a high antioxidant activity, even at high temperature and in the presence of metals at high concentrations. These compounds may be used as well with base oils of petroleum origin as with synthetic base oils. They give good anti-wear and extreme pressure properties to the lubricating oils to which they are added. The lubricating compositions of this invention contain at least one thioorganic complex of the formula: ##SPC2##

These thioorganometallic complexes are based on the element M which may be tin, antimony, lead, bismuth, zinc, cadmium or a transition metal element, for example chromium, manganese, iron, cobalt, nickel or copper, said element M, at the oxidation degree n, being linked with n coordinates, either identical or different, as hereinafter defined:

R.sub.1 and R.sub.2 are each a monovalent radical which may be a hydrocarbon radical, for example an aliphatic, alicyclic or aromatic radical, or a halo- or nitro-derivative thereof. They may contain 1 to 3 heteroatoms such as oxygen, sulfur or nitrogen. They usually contain one to 20 carbon atoms.

Y is a hydrogen atom or a radical R', R'-O-, R'-S- or R'-CO- in which R' is a monovalent hydrocarbon radical of, for example, 1 to 20 carbon atoms.

Y and R.sub.1 or R.sub.2 may form a divalent hydrocarbon radical of one to 20 carbon atoms with 0 to 3 oxygen, sulfur or nitrogen atoms.

Each atom Z may be oxygen or sulfur, provided that at least one Z is sulfur in at least one of the coordinates.

Each coordinate may have two mesomeric forms each having a negative charge: ##SPC3##

It may be represented by only one formula: ##SPC4##

The following monovalent radicals are illustrative of R.sub.1 and R.sub.2 : methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec. butyl, tert. butyl, pentyl, isopentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, heptadecyl, methoxy, ethoxy, propoxy, butoxy, cyclopentyl, cyclohexyl, cycloheptyl, phenyl, benzyl, phenethyl, cumyl, para-iodophenyl, para-nitrobenzyl, methoxyphenyl, vinylpropenyl, 2-butenyl-3-pentenyl, ethynyl, propynyl, 2-furyl,2-thienyl and trifluoromethyl.

The following monovalent radicals are illustrative of Y:

Methyl, ethyl, isopropyl, sec. butyl, octyl, decyl, dodecyl, phenyl, benzyl, methoxy, ethoxy, propoxy, methylthio, ethylthio, acetyl, propionyl, phenethyl, cyclopentyl, cyclohexyl and cycloheptyl.

The following compounds are illustrative of the compounds which may be used in this invention: ##SPC5## ##SPC6## ##SPC7##

The thioorganic complexes may be manufactured according to known methods, e.g., U. S. patent 3,184,410, especially at Column 2, lines 6-7 and 51-53 pertaining to molybdenum complexes, as well as the Bulletin of the Chemical Society of Japan, Volume 40, 2819-2822 (1967).

For example they can be manufactured from the corresponding .beta. - diketones. In some cases, when the desired .beta. - diketones is not available, they may be manufactured by any convenient method, for example by reacting an ester with a monoketone. When the Y group is not hydrogen, it may be directly linked to the .beta. - diketone or after that a thiorganic complex has been formed with it or one of its sulfur derivatives. For example a sodium salt of a .beta. - diketone may be reacted with an alkyl halide to obtain an alkyl group representative of Y.

The synthesis of the thioorganic complexes which are used in this invention comprises the step of sulfurizing the available or manufactured .beta. - diketone. This sulfurization is carried out according to any known method. Hydrogen sulfide may be used, for example, as the sulfurizing agent, either in acidic medium or not, optionally in a solvent. This sulfurization may be carried out in the presence of a salt of the desired metal. In that case there is obtained the desired thioorganic complex or a mixture of complexes of the given formula. When the sulfurization is carried out without a metal salt, there is obtained, in some cases, a mono-thioketone or a dithioketone, or a mixture of both, or a mixture of one or two of them with the starting .beta. - diketone. It is sufficient as a rule, to contact the desired salt of metal with the ketones or their mixtures to obtain a thioorganic complex or a mixture of thioorganic complexes of the given formula.

The present invention applies to all types of base oils, for example those obtained by extracting petroleum fractions with solvents or by any other refining or synthesis process.

The thioorganic complexes are added to the base oils in low proportions, for example from 0.05 to 5 percent by weight and preferably from 0.2 to 2 percent by weight.

The outstanding antioxidant properties that the thioorganic complexes confer to the lubricating oils appear to result from the hydroperoxides destruction power and the reactivity with free radicals of these complexes.

The anti-wear and extreme-pressure properties are related to the power of these complexes to adhere on the metal surfaces, which results in a protection of the latter.

The following examples are given for illustration purposes.

EXAMPLES 1 TO 5

The thioorganometallic complexes of table I have been admixed with the base oils in the given amounts. The resulting mixtures have been subjected to a particularly severe oxidation test: the sample is vigorously stirred with iron naphthenate (6 ppm) and lead oxide (6 grams per liter) at 160.degree.C in oxygen: the amount of oxygen absorbed in 7 hours is noted. The lower this amount, the better the resistance to oxidation of the mixture.

By way of comparison a pure base oil of the solvent type, a base oil of the solvent type containing a conventional antioxidant and a pure synthetic oil of the ester type have been subjected to the same test. The results are given in table I ##SPC8##

EXAMPLES 6 TO 8

The thioorganic complexes of table II have been admixed with base oils in the amounts given in table II.

The resulting mixtures have been subjected to tests according to the "Federal Test Method Standard" 791 a No 6 503 of Dec. 30, 1961. There was used a "Precision Shell Four Ball E.P. Tester" machine working at 1,500 rpm.

By way of comparison, the same tests have been carried out with a pure base oil and a base oil containing a conventional extreme-pressure additive. The results, expressed as the charge before soldering, are given in table II. ##SPC9##

EXAMPLES 9 TO 12

The thioorganometallic complexes of table I have been admixed with a base oil in the specified amounts. The resulting mixtures have been subjected to a severe oxidation test: a sample is vigorously stirred with iron naphthenate (6ppm) and lead oxide (6 grams per liter) at 160.degree.C in oxygen: the oxygen amount absorbed in 7 hours is noted. The lower this amount the higher the resistance to oxidation of the mixture.

The results are given in table III ##SPC10##

Claims

What we claim as this invention is:

1. A lubricating composition comprising a lubricating oil and from 0.05 to 5 percent by weight with respect to the oil of at least one thioorganometallic complex of the general formula: ##SPC11##

in which M is a metal in the divalent state selected from the group consisting of the transition metals, zinc, cadmium, tin and lead; n is 2; R.sub.1 and R.sub.2 when taken individually are each selected from the group consisting of a monovalent hydrocarbon radical of one to 20 carbon atoms, a halohydrocarbon radical of one to 20 carbon atoms and a methoxy phenyl radical; Y when taken individually is selected from the group consisting of the hydrogen atom and the radicals R', R'O, R'S and R'CO in which R' is a hydrocarbon radical of one to 20 carbon atoms; Y and R.sub.1, when taken together, form a divalent hydrocarbon radical of one to 20 carbon atoms; and each atom Z is oxygen or sulfur, providing that at least one of the Z atoms of the complex is sulfur.

2. A lubricating composition according to claim 1, wherein the lubricating oil is selected from base oils of petroleum origin and synthetic lubricants.

3. A lubricating composition according to claim 1, wherein the content of the thioorganometallic complex is 0.2 - 2 percent by weight.

4. A lubricating composition according to claim 1 wherein all Z are sulfur and M is selected from the group consisting of nickel, cobalt and zinc.

5. A lubricating composition according to claim 4 wherein M is nickel.

6. A lubricating composition according to claim 4 wherein M is zinc.