The invention concerns lubricating compositions having improved properties. Another aspect of the invention relates to additive compositions which impart antiwear and antiscuffing properties to lubricating compositions used for internal combustion engines such as gasoline engine and diesel engine.

Additives known as antiwear agents are employed to increase the load carrying capacity of lubricants. The antiwear agents promote the formation of a surface film and thereby prevent wear of the contacting surfaces. The mechanical efficiency enhanced by decreased friction loss further results in decreased fuel consumption and energy savings.

It is known that certain organic molybdenum complexes possess antiwear properties as well as other desirable lubricating characteristics as disclosed in U.S. Pat. No. 4,889,647. Surprisingly, it has been now discovered that the molybdenum complexes described therein produce a synergistic antiwear effect in combination with certain organic sulfur compounds.

According to the invention, there are provided synergistic antiwear compositions comprising:

• (1) an organomolybdenum complex prepared by reacting about 1 mole fatty oil, about 1.0 to 2.5 moles diethanolamine and a molybdenum source sufficient to yield about 0.1 to 12.0 percent of molybdenum based on the weight of the complex, and
• (2) an organic sulfur compound selected from the group consisting of
  • (i) 1,3,4-thiadiazole compounds of the formula: wherein R and R' are independently selected from C_1-22-alkyl groups, terpene residue and maleic acid residue of the formula and R² and R³ represent C_1-22-alkyl and C_5-7-cycloalkyl groups, either R² or R³ may be hydrogen and either R or R' may be hydrogen when R² or R³ are C_9-22-alkyl groups;
  • (ii) bisdithiocarbamate compounds of the formula wherein R⁴, R⁵, R⁶, and R⁷ are aliphatic hydrocarbyl groups having 1 to 13 carbon atoms and R⁸ is an alkylene group having 1 to 8 carbon atoms;
  • (iii) dithiocarbamates of the formula wherein R⁴ and R⁵ represent alkyl groups having 1 to 8 carbon atoms, M represents metals of the periodic groups IIA, IIIA, VA, VIA, IB, VIB, VIII and a salt moiety formed from an amine of the formula R¹¹, R¹² and R¹³ being independently selected from hydrogen and aliphatic groups having 1 to 18 carbon atoms and n is the valence of M;
  • (iv) phosphorodithioates of the formula wherein X and X' are independently selected from S and O, R⁹ and R¹⁰ represent hydrogen and alkyl groups having 1 to 22 carbon atoms, M represents metals of the periodic groups IIA, IIIA, VA, VIA, IB, VIB, VIII and a salt moiety formed from an amine of the formula R¹¹, R¹² and R¹³ being independently selected from hydrogen and aliphatic groups having 1 to 18 carbon atoms and n is the valence of M; and
  • (v) phosphorodithioate esters of the formula wherein R⁴ and R⁵ may be the same or different and are selected from alkyl groups having 1 to 8 carbon atoms; and the ratio of the molybdenum complex to the sulfur compound is about 1:5 to about 5:1.

Another aspect of the invention concerns lubricating compositions having improved lubricating properties and comprising a major portion of an oil of lubricating viscosity and about 0.1 to 10.0 percent by weight of a composition comprising (1) an organomolybdenum complex prepared by reacting about 1 mole fatty oil, about 1.0 to 2.5 moles diethanolamine and a molybdenum source sufficient to yield about 0.1 to 12.0 percent of molybdenum based on the weight of the complex and (2) a sulfur compound of the formula I, II, III, IV or V.

The organomolybdenum component of the invention is prepared by sequentially reacting fatty oil, diethanolamine and a molybdenum source by the condensation method described in U.S. Pat. No. 4,889,647, incorporated herein by reference. The reaction yields a reaction product mixture. The major components are believed to have the structural formulae wherein R represents a fatty oil residue. The preferred fatty oils are glyceryl esters of higher fatty acids containing at least 12 carbon atoms and may contain 22 carbon atoms and higher. Such esters are commonly known as vegetable and animal oils. Vegetable oils particularly useful are oils derived from coconut, corn, cottonseed, linseed, peanut, soybean and sunflower seed. Similarly, animal fatty oils such as tallow may be used.

The source of molybdenum is an oxygen-containing molybdenum compound capable of reacting with the intermediate reaction product of fatty oil and diethanolamine to form an ester-type molybdenum complex. The source of molybdenum includes, among others, ammonium molybdates, molybdenum oxides and mixtures thereof.

The 1,3,4-thiadiazoles of formula I may be prepared by the method disclosed in U.S. Pat. No. 4,761,842 and U.S. Pat. No. 4,880,437. Terpene residues are preferably derived from pinene and limonene having the structural formulae given hereinbelow.

The alkyl groups represented by R and R' contain preferably 1 to 22 carbon atoms and may be branched or straight chain. Particularly preferred are compounds wherein both alkyl groups together contain a total of at least 22 carbon atoms. Groups R² and R³ in the formula I represent branched or straight chain alkyl groups containing 1 to 22 carbon atoms and cyclic aliphatic groups such as cyclohexyl, cyclopentyl and cycloheptyl.

The bisdithiocarbamates of formula II are known compounds described in U.S. Pat. No. 4,648,985, incorporated herein by reference. The compounds are characterized by groups R⁴ to R⁷ which are the same or different and are hydrocarbyl groups having 1 to 13 carbon atoms. The group R⁸ is an aliphatic group such as straight and branched alkylene groups containing 1 to 8 carbons. Particularly preferred is methylenebis (dibutyldithiocarbamate) available commercially under the tradename VANLUBE® 7723 from R.T. Vanderbilt Company, Inc.

The dithiocarbamates of the formula III are known compounds. One of the processes of preparation is disclosed in U.S. Pat. No. 2,492,314. Groups R⁴ and R⁵ in the formula III represent branched and straight chain alkyl groups having 1 to 8 carbon atoms. Particularly preferred are antimony dithiocarbamates.

The phosphorodithioates of the formula IV are known, commercially available materials. One of the processes of preparation is taught by U.S. Pat. No. 4,215,067. Groups R⁹ and R¹⁰ represent branched and straight chain alkyl groups having 1-22 groups and may be derived from fatty acids. The metal ion in formula III and IV may be selected from the following groups of the Periodic Table: IIA, IIIA, VA, VIA, IB, VIB and VIII. Amine salts of the compounds are also useful synergists of the invention. Exemplary, salts include, among others, those prepared from alkyl amines and mixed alkyl amines. Particularly useful are fatty acid amines.

The phosphorodithioate esters of the formula V are known compounds. One of the processes of manufacture is disclosed in U.S. Pat. No. 3,567,638. Groups R⁴ and R⁵ in the formula V may be the same or different and may be selected from branched and straight chain alkyl groups. Preferred are groups containing 1 to 8 carbon atoms.

The sulfur compounds are known to possess certain lubricating properties such as oxidation, wear and corrosion inhibition in various lubricating media. Sometimes, however, the sulfur compounds alone do not provide adequate antiwear protection for the varied heavy duty applications of many industrial and automotive lubricants.

Moreover, under certain conditions, the high concentrations of sulfur compounds may produce an adverse effect on the overall performance of the lubricant.

Unexpectedly, the above sulfur compounds produce synergistic antiwear effect when combined with organomolybdenum compounds in certain ratios. Synergism is displayed by compositions containing about 1 to 5 parts by weight of the sulfur compound to about 5 to 1 part by weight of the molybdenum compound.

Another advantage of the synergistic combination is that the compositions possess good antioxidant properties. Even in instances where the sulfur compounds do not possess an antioxidant activity, the combination with the molybdenum complexes provides a composition with good overall antioxidant properties.

The synergistic compositions may be incorporated in any lubricating media by known methods. The compositions impart antiwear as well as oxidation inhibiting and extreme pressure properties to natural and synthetic lubricants formulated as oils or greases.

The base oils employed as lubricant vehicles are typical natural and synthetic oils used in automotive and industrial applications such as, among others, turbine oils, hydraulic oils, gear oils, crankcase oils and diesel oils. Natural base oils include mineral oils, petroleum oil, paraffinic oils and the ecologically desirable vegetable oils. Typical synthetic oils include pentaerythritol esters, poly-alpha-olefins, hydrogenated mineral oils, silicones and silanes.

The compositions of the invention may be incorporated in the lubricant in an amount effective to produce the desired antiwear characteristics. An amount from about 0.1 to 10.0 percent will be sufficient for most applications. A preferred range is from about 0.5 to about 3.0 percent by weight of the total lubricant composition.

The lubricating compositions may contain other conventional additives depending on the intended use of the lubricant. For example, formulations may contain rust inhibitors such as metal salts of alkylnaphthalenesulfonic acids, demulsifiers, dispersants, detergents and supplemental antioxidants, particularly alkylated diphenylamines.

The grease formulations may contain various thickening agents such as, among others, silicate minerals, metal soaps and organic polymers.

The following examples are given for the purpose of illustrating the invention and are not intended in any way to limit the invention. All percentages and parts are based on weight unless otherwise indicated.

A laboratory test was conducted by using the original Falex machine to simulate the valve train wear of an automobile engine. The V-blocks and pin were washed in mineral spirits with an ultrasonic cleaner, rinsed with acetone, air dried and weighed. The test sample (60 g) was placed into the oil cup. The motor was switched on and the loading arm was placed on the ratchet wheel. Upon reaching the reference load of 227 kg, the ratchet wheel was disengaged and the load was maintained constant for 3.5 hours. Thereafter, the motor was switched off. The V-blocks and pin were washed, dried and weighed. The weight loss, a measure of wear, was recorded and compiled in Table I.

The test was performed with a molybdenum complex in conjunction with the following ashless sulfur compound synergists of the invention: S-dicarbobutoxyethyl 0,0-dipropylphosphorodithioate (hereinafter phosphorodithioate ester) and methylenebis(dibutyldithiocarbamate). The molybdenum complex was a reaction product of coconut oil, 2,2'-iminobisethanol and hexammonium salt of molybdic acid. The base oil was a hydrofinished naphthenic oil (ISO VG 22 manufactured by Sun Refining and Marketing Co.).

The results compiled in Table I indicate that the molybdenum complex and the above sulfur compounds act as synergists towards inhibition of wear. Modified Falex Wear Test
Component, Mass Percent Sample 1 2 3 4 5 6 Molybdenum complex 1.0 1.5 -- 0.5 -- 0.5 Phosphorodithioate ester -- -- 1.0 0.5 -- -- Methylenebis(dibutyldithiocarbamate) -- -- -- -- 1.5 1.0 Test Parameters Test Time, min. 40* 75* 20* 210 210 210 Total Weight Loss, mg. 433 542.8 -- 14.6 86.4 3.4 *Test terminated due to excessive wear

The modified Falex Wear Test described in Example 1 was performed with the same molybdenum complex in conjunction with the following metal salts of the sulfur compound synergists: nickel dilauryldithiocarbamate, calcium di-2-ethylhexyldithiophosphate, aluminum di-2-ethylhexyldithiophosphate, tellurium di-2-ethylhexyldithiophosphate, and C_12-14-alkylamine salt of tert-octyl phosphates (hereinafter dithiophosphate amine salt). The base oil was a hydrofinished naphthenic oil (ISO VG 22).

The results compiled in Table II herein indicate that the molybdenum complex and the above salts of the sulfur compounds act as synergists towards inhibition of wear. Modified Falex Wear Test
Component, Mass Percent Sample 7 8 9 10 11 12 13 14 15 16 17 Molybdenum complex 1.5 -- 0.5 -- 0.5 -- 0.5 -- 0.5 -- 0.5 Nickel dithiocarbamate -- 1.5 1.0 -- -- -- -- -- -- -- -- Calcium dithiophosphate -- -- -- 1.5 1.0 -- -- -- -- -- -- Aluminum dithiophosphate -- -- -- -- -- 1.5 1.0 -- -- -- -- Tellurium dithiophosphate -- -- -- -- -- -- -- 1.5 1.0 -- -- Dithiophosphate amine salts -- -- -- -- -- -- -- -- -- 1.5 1.0 Test Parameters Test Time, min. 75* 5* 210 5* 210 210 210 120* 210 2* 210 Total Weight Loss, mg. 542.8 366.8 14.9 366.6 90.1 33.5 18.4 84.8 17.7 5.6** 41.9 * Test terminated due to excessive wear **High galling fail

A thin film oxygen uptake test was conducted essentially according to the method described by Chia-Soon Ju et al, J. Am. Soc. Lubricating Eng., 40, 2, 75-83, 1984. The oxidation induction time of the lubricant was measured under conditions which simulate the high temperature oxidation processes in automotive engines by modified rotary bomb oxidation test method ASTM D-2272. The test was conducted with 1.5 gram samples of hydrofinished naphthenic oil, ISO VG 22. The composition of the invention described in Example 1 and, for comparison, the individual components, were added to the oil in the amount indicated in Table III. The test was conducted at 160°C and initial oxygen pressure of 620.6 kPa (90 psi). A "pass" oil has a high induction time, while a "fail" oil has a low induction time. The compositions of the invention display good antioxidative effect as demonstrated by the data compiled in Table III. Thin Film Oxygen Uptake Test
Component, Mass Percent Sample 18 19 20 21 Molybdenum complex 1.0 1.5 -- 0.5 Methylenebis (dibutyldithiocarbamate) -- 1.5 1.0 Test Parameter Average Induction Time, min. 10 10 75 93

The above embodiments have shown various aspects of the present invention. Other variations will be evident to those skilled in the art and such modifications are intended to be within the scope of the invention as defined by the appended claims.