DE69404447T2 - LUBRICANT COMPOSITION CONTAINING COMPLEXES OF ALKOXYLATED AMINE, ACID AND ADENINE - Google Patents

Description

This invention relates to a composition containing a complex which is the reaction product of alkoxylated amine, acid and adenine and an improved lubricating oil composition containing the reaction product and the use of such complexes to reduce friction and/or improve fuel economy and/or inhibit copper corrosion in an internal combustion engine.

There are many cases, as is well known, particularly under "boundary lubrication" conditions, where two rubbing surfaces must be lubricated or otherwise protected to prevent wear and ensure continued motion. Moreover, when, as in most cases, the friction between the two surfaces increases the force required for motion, and when motion is an integral part of an energy conversion system, it is highly desirable to effect lubrication in a manner which minimizes that friction. As is also well known, both wear and friction can be reduced with varying degrees of success by adding a suitable additive or combination thereof to a natural or synthetic lubricant. Similarly, again with varying degrees of success, continued motion can be ensured by adding one or more suitable additives.

To protect internal combustion engines from wear, engine lubricating oils have been provided with antiwear and antioxidant additives. The main oil additive for the last 40 years to provide antiwear and antioxidant properties has been zinc dialkyldithiophosphate (ZDDP). For example, US-A-4 575 431 discloses a lubricating oil additive composition containing dihydrocarbyl hydrogendithiophosphates and sulfur-free hydrocarbyl dihydrogenphosphates and dihydrocarbyl hydrogenphosphates, the composition being at least 50% neutralized with a hydrocarbylamine having 10 to 30 carbon atoms in the hydrocarbyl group. US-A-4 089 790 discloses an extreme pressure lubricating oil comprising (1) hydrated potassium borate, (2) an antiwear agent selected from (a) ZDDP, (b) an ester, an amide, or an amine salt of a dihydrocarbyl dithiophosphoric acid, or (c) a zinc alkylaryl sulfonate, and (3) an oil-soluble organic sulfur compound. However, oil formulations containing ZDDP require friction modifiers to reduce energy losses in overcoming friction. Such energy losses result in reduced fuel efficiency. In addition, oil additive packages containing ZDDP are environmentally detrimental. ZDDP contributes to under-engine deposits that lead to increased oil consumption and emissions. In addition, ZDDP is not ashless. Various ashless oil additive packages have recently been developed based on these environmental considerations. However, many ashless additive packages tend to be corrosive to copper, resulting in additional components in the additive package to provide corrosion protection. Most of the engine oils currently available on the market contain a lower phosphorus content due to the poisoning of the exhaust gas detoxification catalysts by phosphorus.

US-A-5 076 945 discloses a lubricating oil composition containing an amine salt of a dithiobenzoic acid. The amines used to prepare the salts are long-chain hydrocarbon amines.

US-A-3,849,319 and US-A-3,951,973 describe lubricant compositions containing di- and tri(hydrocarbylammonium)trithiocyanurates. The hydrocarbyl radicals include alkyl, aralkyl, aryl, alkaryl and cycloalkyl and the examples relate to alkylamines. These lubricant compositions were found to have improved load-bearing properties.

It would be desirable to have a lubricating oil additive that offers excellent anti-wear, antioxidant, friction reducing, fuel economy properties and environmental benefits (less fuel, less phosphorus, i.e. less exhaust emissions). It would also be desirable to find additives that inhibit copper corrosion. It would be a further advantage if these additives do not add phosphorus to the lubricating oil composition.

This invention relates to a novel composition containing alkoxylated amine, acid and adenine. It also relates to an improved lubricating oil composition that reduces friction and/or improves fuel economy in an internal combustion engine and, in some cases, exhibits improved inhibition of copper corrosion and/or antiwear and antioxidant properties.

The present invention provides a composition comprising the reaction product of alkoxylated amine, acid and adenine, wherein the reaction product is a complex having the following formula

wherein Z is derived from either a hydrocarbyl salicylic acid, trithiocyanuric acid, a hydrocarbyl sulfonic acid, a dihydrocarbyl dithiophosphoric acid or a dihydrocarbyl dithiobenzoic acid, wherein R is a hydrocarbyl group having 2 to 22 carbon atoms, R¹ is hydrogen or a hydrocarbyl group having 1 to 20 carbon atoms, x and y are each independently integers from 1 to 15, provided that the sum of x + y is 2 to 20, and a, b and c are independent numbers from 1.0 to 3.0, wherein the ratios of a:b, a:c and b:c are in the range of 1.0:3.0 to 3.0:1.0.

According to a further aspect of the present invention there is provided a lubricant composition comprising a major amount of a lubricating oil base stock and a minor amount of a complex having formula (I).

According to a further aspect, the present invention provides the use of a complex having the above-described Formula (I) for inhibiting copper corrosion associated with the use of lubricating oil compositions in an internal combustion engine.

According to a further aspect, the present invention provides the use of a complex having the formula (I) described above for reducing friction and/or improving fuel efficiency in an internal combustion engine.

The present invention also provides the use of a complex having the formula (I) described above for reducing wear in an internal combustion engine.

In the lubricating oil composition of the present invention, the lubricating oil contains a major amount of a lubricating oil base stock. The lubricating oil base stocks are well known in the art and can be derived from natural lubricating oils, synthetic lubricating oils, or mixtures thereof. In general, the lubricating oil base stock has a kinematic viscosity in the range of about 5 to about 10,000 cSt at 40°C.

Natural lubricating oils include animal oils, vegetable oils (e.g. castor oil and lard oil), petroleum-based oils, mineral oils and oils derived from coal and shale.

Synthetic oils include hydrocarbon oils and halogen-substituted hydrocarbon oils such as polymerized and interpolymerized olefins, alkylbenzenes, polyphenyls, alkylated diphenyl ethers, alkylated diphenyl sulfides, and their derivatives, analogs and homologs, and the like. Synthetic lubricating oils also include alkylene oxide polymers, interpolymers, copolymers and derivatives thereof in which the terminal hydroxyl groups have been modified by esterification, etherification, etc. Another class of synthetic lubricating oils comprises the esters of dicarboxylic acids with a variety of alcohols. Esters useful as synthetic oils also include those made from C5 to C12 monocarboxylic acids and polyols and polyol ethers.

Silicon-based oils (such as the polyalkyl, polyaryl, polyalkoxy or polyaryloxy siloxane oils and silicate oils) comprise another useful class of synthetic lubricating oils. Other Synthetic lubricating oils include liquid esters of phosphorus-containing acids, polymeric tetrahydrofurans, poly-α-olefins, and the like.

The lubricating oil may be derived from unrefined, refined, rerefined oils or mixtures thereof. Unrefined oils are obtained directly from a natural source or synthetic source (e.g., coal, shale or bitumen from tar sands) without further purification or treatment. Examples of unrefined oils include a shale oil obtained directly from a carbonization process, a petroleum oil obtained directly from distillation or an ester oil obtained directly from an esterification process, each of which is used without further purification. Refined oils are similar to unrefined oils except that refined oils have been treated in one or more purification stages to improve one or more properties. Suitable purification techniques include distillation, hydrotreating, dewaxing, solvent extraction, acid or base extraction, filtration and percolation, all of which are known to those skilled in the art. Re-refined oils are obtained by treating refined oils in processes similar to those used to obtain the refined oils. These re-refined oils are also known as reused or reclaimed oils and have often been additionally treated with techniques to remove spent additives and oil degradation products.

In the oil-soluble complexes of the present invention having the formula (I), R is preferably a hydrocarbon group having 2 to 18 carbon atoms, especially 6 to 18 carbon atoms, and R¹ is preferably hydrogen or a hydrocarbon group having 1 to 16 carbon atoms, most preferably hydrogen. Such hydrocarbon groups include aliphatic (alkyl or alkenyl) and alicyclic groups. The aliphatic or alicyclic groups may be substituted with amino, hydroxy, mercapto and the like, and may be interrupted by O, S and N. The sum of x+y is preferably 2 to 15.

The complexes of the invention are prepared by reacting alkoxylated, preferably propoxylated or ethoxylated, especially ethoxylated amines with acid and adenine. Adenines are commercially available or can be prepared by methods known in the art. Adenine can be purchased from Aldrich Chemical Company. Ethoxylated and/or propoxylated amines are commercially available from Sherex Chemicals under the trade name Varonic and from Akzo Corporation under the trade names Ethomeen, Ethoduomeen and Propomeen. Examples of preferred amines include ethoxylated (5) coco-alkylamine, ethoxylated (2) tallow-alkylamine, ethoxylated (15) coco-alkylamine and ethoxylated (5) soy-alkylamine and ethoxylated (10) stearylamine. Propoxylated amines can replace ethoxylated amines.

The complexes according to the invention are the reaction product of

(a) an alkoxylated, preferably a propoxylated or ethoxylated, in particular an ethoxylated amine having the formula

where R, x and y are as defined previously,

(b) an acid which is either a hydrocarbyl salicylic acid, trithiocyanuric acid, a hydrocarbyl sulfonic acid, a dihydrocarbyl dithiophosphoric acid or a dihydrocarbyl dithiobenzoic acid, and

(c) an adenine with the formula

where R¹ is as defined above.

Preferred hydrocarbon salicylic acids used to react with the alkoxylated amines and adenines to form the complexes of the invention have the following formula:

wherein R¹ is a hydrocarbon group having 2 to 30 carbon atoms, preferably a hydrocarbon group having 2 to 26 carbon atoms. Such hydrocarbon groups include aliphatic (alkyl or alkenyl) and alicyclic groups. The aliphatic and alicyclic groups may be substituted with hydroxy, alkoxy, cyano, nitro and the like, and the alicyclic groups may contain O, N and S as heteroatoms. These substituted salicylic acids are commercially available or may be prepared by methods known in the art, e.g., US-A-5,023,366.

Trithiocyanuric acid can exist in different tautomeric forms, which are represented by the formulas II, III or mixtures thereof:

Trithiocyanuric acid is prepared by methods well known in the art. These methods involve the treatment of cyanuric chloride with sulfur nucleophiles according to the following reaction scheme:

Other sulfur nucleophiles that can be used in the above reaction scheme include sodium sulfide, thiourea, and thioacetic acid.

Preferred hydrocarbon sulfonic acids used for reaction with alkoxylated amines and adenines to form the complexes of the invention have the following formula

wherein R¹ is a hydrocarbon group having 2 to 30 carbon atoms, preferably a hydrocarbon group having 2 to 26 carbon atoms. Such hydrocarbon groups include aliphatic (alkyl or alkenyl) and alicyclic groups. The aliphatic and alicyclic groups may be substituted by hydroxy, alkoxy, cyano, nitro and the like and the alicyclic groups may contain O, S and N as heteroatoms. These sulfonic acids are commercially available or can be prepared by methods well known in the art.

Preferred dihydrocarbon dithiophosphoric acids which react with alkoxylated amines and adenines to form of the complexes according to the invention have the following formula:

wherein R² and R³ are each independently hydrocarbon groups having 3 to 30 carbon atoms, preferably 3 to 20 carbon atoms. Those hydrocarbon groups include aliphatic (alkyl and alkenyl) and alicyclic groups. The aliphatic and alicyclic groups may be substituted with hydroxy, alkoxy, cyano, nitro and the like and the alicyclic groups may contain O, S or N as heteroatoms. Especially preferred dialkyldithiophosphoric acids are prepared from mixed (85%) 2-butyl alcohol and (15%) isooctyl alcohol (mixed primary and secondary alcohols). Dihydrocarbyldithiophosphoric acids can be purchased from Exxon Chemical Company.

Preferred dihydrocarbyldithiobenzoic acids used to react with the alkoxylated amines and adenines to form the complexes of the invention have the following formula:

in which R² to R⁶ are each preferably hydrogen, a hydrocarbon group having 1 to 18 carbon atoms or a hydroxy group, with the proviso that at least one of R² to R⁵ is a hydrocarbon group, preferably an alkyl group having 1 to 18 carbon atoms, especially 1 to 6 carbon atoms. R³ and R⁵ are most preferably tert-butyl groups and R⁴ is preferably hydroxy. The sum of x + y is preferably 2 to 15. The hydrocarbon groups include aliphatic (alkyl or alkenyl) and alicyclic groups which may be substituted by hydroxy, amino, cyano and the like and may be interrupted by O, S or N.

Dithiobenzoic acids can be prepared from a phenol according to the following procedure. A phenol of the formula

is dissolved in a solvent such as dimethyl sulfoxide and treated under nitrogen with potassium hydroxide dissolved in a minimal amount of water. Under nitrogen, carbon disulfide is then added to this mixture, which is maintained at about room temperature. The resulting reaction mixture is heated to between 25 and 100ºC for 1 to 3 hours and then added to an acidified water solution. The resulting dithiobenzoic acid can be extracted by solvent extraction using, for example, ether and evaporating the solvent.

When the complexes of the invention are derived from a hydrocarbon salicylic acid, they are prepared by adding the salicylic acid to a mixture of adenine and alkoxylated amine. Because of the exothermic nature of the reaction, the reaction mixture should be stirred during the addition of the salicylic acid.

When the complexes of the invention are derived from trithiocyanuric acid, they are prepared by adding trithiocyanuric acid to a mixture of adenine and alkoxylated amine. Because of the exothermic nature of the reaction, the reaction mixture should be stirred during the addition of the trithiocyanuric acid. The amounts of reactants are approximately stoichiometric, although a slight excess of trithiocyanuric acid, which has three reactive hydrogen atoms, may be used.

When the complexes of the invention are derived from a dihydrocarbyl dithiobenzoic acid, they are prepared as described below. This preparation is based on a molar ratio of approximately 1:1:1, although this ratio may vary. About 10 to 20% of the required amount of alkoxylated amine (based on the thiobenzoic acid) is added to the dithiobenzoic acid with heating and stirring. Temperatures may range from about 25 to about 180°C. About 10 to 20% of the required amount of adenine is then added. This sequential addition process is repeated until the required amount (based on the above ratio of approximately 1:1:1 of amine:acid:adenine) is reached. A precipitate (polymeric and unidentified material) will form if this alternative addition method is not used.

When the complexes of the invention are derived from a hydrocarbon sulfonic acid, they are prepared by adding the sulfonic acid to a mixture of adenine and alkoxylated amine. Because of the exothermic nature of this reaction, the reaction mixture should be stirred during the addition of the sulfonic acid.

When the complexes of the invention are derived from a dihydrocarbyl dithiophosphoric acid, they are prepared as described below. This preparation is based on a molar ratio of approximately 1:1:1, although this ratio may vary. About 10 to 20% of the required amount of alkoxylated amine (based on the phosphoric acid) is added to the dihydrocarbyl dithiophosphoric acid with heating and stirring. Temperatures may range from about 25 to about 180°C. About 10 to 20% of the required amount of adenine is then added. This sequential addition process is repeated until the required amount (based on the above ratio of approximately 1:1:1 of amine:acid:adenine) is reached. A precipitate (polymeric and unidentified material) will form if this alternative addition method is not used.

The exact stoichiometry of the bonds in the complexes of formula (I) is not known since each molecule in the complex may have several sites that can participate in the hydrogen bonding process either as an acceptor or as a donor. Because of the variety of bonding possibilities, the molar ratios a:b:c can be varied over a wide range, based on the donor/acceptor sites on each of the three molecules, and therefore a, b and c in formula (I) are numbers that are not necessarily integers. When the acid is trithiocyanuric acid, there are a total of forty-five (45) combinations of interacting sites between the three molecules that make up the complex of formula (I). When the acid is hydrocarbylsulfonic acid or hydrocarbylsalicylic acid, there are a total of thirty (30) possibilities of interacting sites between the three molecules that make up the complex of formula (I). When the acid is dihydrocarbyldithiobenzoic acid or dihydrocarbyldithiophosphoric acid, there are a total of fifteen (15) possible sites of interaction between the three molecules making up the complex of formula (I). For example, a:b:c can be 1:2:1 or 1:1:3.

The lubricating oil composition of the present invention comprises a major amount of lubricating oil basestock and a minor amount of the alkoxylated amine:acid:adenine complex. When the acid is either trithiocyanuric acid, hydrocarbylsulfonic acid or hydrocarbylsalicylic acid, the amount of complex is typically from about 0.001% to about 5% by weight based on the oil basestock. Preferably, the amount of amine salt is from about 0.05% to about 1.0% by weight. When the acid is either dihydrocarbyldithiobenzoic acid or dihydrocarbyldithiophosphoric acid, the concentration of the complex having the general formula (I) may typically range from 0.1 to 5% by weight, and preferably from 0.5 to 1.5% by weight, based on the oil. The amount of complex is such that it is an effective amount to provide one or more of improved fuel efficiency, reduced friction, inhibition of copper corrosion, anti-wear properties and antioxidant properties when the lubricating oil composition is used in an internal combustion engine.

If desired, other additives known in the art may be added to the lubricating oil base stock. Such additives include dispersants, antiwear agents, antioxidants, rust inhibitors, other corrosion inhibitors, detergents, pour point depressants, extreme pressure additives, viscosity index improvers, other friction modifiers, hydrolysis stabilizers and the like. These additives are typically disclosed, for example, in "Lubricant Additives" by C. V. Smalhear and R. Kennedy Smith, 1967, pages 1 to 11, and in US-A-4,105,571.

The lubricating oil composition of the present invention can be used in the lubrication system of essentially any internal combustion engine, including automobile and truck engines, two-stroke engines, aircraft piston engines, marine and railroad engines, and the like. Also suitable are lubricating oils for gas-fired engines, alcohol-fired (e.g., methanol-fired) engines, stationary power machines, turbines, and the like.

This invention will be further explained with reference to the following example, which includes a preferred embodiment of the invention.

example 1

This example illustrates the preparation of a complex of the invention containing ethoxylated amine, trithiocyanuric acid and adenine. 68 g of ethoxylated (5) coco-alkylamine and 13 g of adenine were heated to 70°C with stirring in a three-necked round-bottom flask equipped with a thermometer and condenser with water cooling. 14 g of trithiocyanuric acid was gradually added to the stirred amine solution. During the addition, the temperature rose to 105°C due to an exothermic reaction between acid and amine-adenine components. The reaction mixture was used without further purification.

Example 2

This complex containing ethoxylated amine, trithiocyanuric acid and adenine is an effective friction reducing agent as shown in this example. Ball-On-Cylinder (BOC) friction tests were carried out using the experimental procedure described by S. Jahanmir and M. Beltzer in ASLE Transaction, Volume 29, Number 3, Page 425 (1985) using a force of 0.8 N (1 kg) applied to a 12.5 mm diameter steel ball in contact with a rotating 43.9 mm diameter steel cylinder. The cylinder rotated in a bowl containing sufficient lubricating oil to cover 2 mm of the bottom of the cylinder. The cylinder was rotated at 0.25 rpm. The friction force was continuously monitored by means of a load transducer. In the tests carried out, the friction coefficients reached equilibrium values after 7 to 10 revolutions of the cylinder. The friction experiments were carried out with an oil temperature of 100ºC. Various amounts of the complex prepared in Example 1 were added to Solvent 150 N. The results of the BOC friction test are shown in Table 1. Table 1

* S150N is a solvent extracted, dewaxed, hydrogen finished neutral lubricating oil base stock obtained from approved paraffinic raw materials (viscosity 32 cSt at 40ºC, 150 Saybolt seconds).

As can be seen from the results in Table 1, as little as 0.05 wt.% of the complex shows a 79% reduction in the coefficient of friction. These results demonstrate that the present complexes are capable of significant reductions in the coefficient of friction of a lubricant base stock, resulting in lower friction and thus better fuel efficiency when the lubricating oil is used in an internal combustion engine.

Example 3

This example illustrates the preparation of a complex according to the invention containing an ethoxylated amine, alkylsalicylic acid and adenine. 101 g of ethoxylated (5) coco-alkylamine and 4 g of adenine were heated to 80°C with stirring in a three-necked round-bottom flask equipped with a thermometer and a water-cooled condenser. 100 g of salicylic acid having the formula

were gradually added to the stirred amine/adenine solution. During the addition, the temperature rose to 104ºC due to the exothermic reaction between acid and amine. The reaction was maintained at 104ºC for 1.5 hours and then cooled to room temperature. The reaction mixture was a complex of the invention and was used without further purification.

Example 4

The ethoxylated amine, alkyl salicylic acid, adenine-containing complex is an effective friction modifier as demonstrated in this example. The ball-on-cylinder friction tests (BOC tests) were conducted using the experimental procedure described in Example 2. Various Amounts of complex prepared in Example 3 were added to Solvent 150 N. The results of the BOC friction tests are presented in Table 2. Table 2

As can be seen from the results in Table 2, as little as 0.1 wt.% of complex showed a 78% reduction in the friction coefficient. These results demonstrate that the present complexes are capable of significant reductions in the friction coefficient of a lubricant base stock, resulting in less friction and thus higher fuel efficiency when the lubricating oil is used in an internal combustion engine.

Example 5

A solution of 3 g of ethoxylated (5) coco-alkylamine was heated to 50-110°C with stirring. 0.5 g of 4-hydroxy-3,5-di- tert-butyldithiobenzoic acid was then added to the heated and stirred solution, followed by 125 mg of adenine. This procedure of sequential addition of dithiobenzoic acid and adenine was repeated until 2 g of acid and 500 mg of adenine had been added to the solution. The sequential (consecutive) procedure was used to prevent precipitation of polymeric materials as a by-product.

Example 6

Ball-on-cylinder friction (BOC) tests were conducted using the ethoxylated (5) coco-alkylamine:dithiobenzoate:adenine complex of Example 5 in Solvent 150N base oil using several concentrations of the additive. The BOC tests were conducted using the experimental procedure described in Example 2. The data are shown in Table 3. Table 3

** Primen JMT is predominantly a primary C₁₈-tert-alkylamine manufactured by Rohm & Haas.

As can be seen from the data in Table 3, the adenine-containing complex achieves a lower friction coefficient than can be achieved with the comparable complex without adenine or a primed JMT:DTB complex.

Example 7

This example illustrates the preparation of a complex according to the invention containing ethoxylated amine, alkylsulfonic acid and adenine. 41 g of ethoxylated (2) tallow amine and 1 g of adenine were heated to 60°C with stirring in a three-necked round bottom flask equipped with a thermometer and a water-cooled condenser. 58 g of alkylsulfonic acid having the formula

were gradually added to the stirred amine/adenine solution. During the addition, the temperature rose to 105°C due to the exothermic reaction between acid and amine. The reaction mixture was kept at 105°C for 1.5 h and then cooled to room temperature. The reaction mixture was a complex according to the invention and was used without further purification.

Example 8

The complex containing ethoxylated amine, alkyl sulfonic acid and adenine is an effective friction modifier as demonstrated in this example. Ball-on-cylinder friction (BOC) tests were conducted using the experimental procedure described in Example 2. Various amounts of the complex prepared in Example 7 were added to Solvent 150 N. The results of the BOC friction tests are shown in Table 4. Table 4

As can be seen from the results in Table 4, as little as 1.0 wt.% of the complex exhibits a reduction in the coefficient of friction of 81%. These results demonstrate that the present complexes are capable of significant reductions in the coefficient of friction of a lubricant base stock, resulting in lower friction and thus better fuel efficiency when the lubricating oil is used in an internal combustion engine.

Example 9

This example illustrates the preparation of the new complexes of the invention. A solution of 80 g of diisooctyldithiophosphoric acid was heated to 50-100°C with stirring. 10 g of ethoxylated (5) coco-alkylamine was then added to the heated and stirred solution, followed by 1 g of adenine. This process of sequential addition of ethoxylated amine and adenine was repeated until 75 g of ethoxylated (5) coco-alkylamine and 7 g of adenine had been added to the solution. The sequential addition process was used to prevent precipitation of by-product. The complex was then collected upon cooling and used without further purification.

Example 10

This example illustrates the excellent copper corrosion protection provided by the inventive complex as prepared in Example 9. The copper corrosion test was conducted as follows. Copper corrosion tests were based on ASTM D-2440. 25 g of the oil sample was placed in a 0.5" test tube with 30 cm of copper wire wound to 0.5" and stretched to a final length of 2". The test tube was then heated to 110°C for 120 hours. During the test period, nitrogen was bubbled through the oil at 17 cc/min. At the end of the test, a 5 g sample of oil was removed and analyzed for copper content. The copper corrosion results are shown in Table 5. Table 5

* DDP (secondary) contains a mixture of isobutyl (85%) and isooctyl (15%) as the alkyl component.

Example 11

This example illustrates the excellent anti-wear properties of the inventive complex. Anti-wear properties are measured by the four-ball wear test as follows. The four-ball test used is described in detail in ASTM Method D-2266. In this test, three balls are mounted in a lubricating cup and an upper rotating ball is pressed against the lower three balls. The test balls used were made of AISI 52100 steel with a hardness of 65 Rockwell C (840 Vickers) and a centerline roughness of 25 mm. Prior to testing, the steel balls and all retainers were washed with 1,1,1-trichloroethane. The steel balls were subsequently washed with a laboratory detergent to remove all solvent residues, rinsed with water and dried under nitrogen.

The four-ball tests were carried out at 100ºC, 60 kg load and 1200 rpm for a period of 45 minutes. After each test, the balls were washed and the wear scar diameter (WSD) was measured on the lower balls was measured using a light microscope. Using the WSD values, the wear volume (WV) was calculated from standard equations (See Wear Control Handbook, edited by MB Peterson and WO Winer, page 451, American Society of Mechanical Engineers [1980]). The percentage of wear reduction (%WR) for each oil tested was then calculated using the following formula:

% WR = (1- WV with additive/WV without additive) 100

The results of the four-ball test are described in Table 6. Table 6

S150N is a solvent extracted, dewaxed, hydrogen finished neutral lubricating oil base stock obtained from approved paraffinic raw materials (viscosity 32 cSt at 40ºC, 150 Saybolt seconds).

The values in Table 6 show that even at low concentration (< 0.2%) the present adenine complex has excellent antiwear properties compared to the corresponding amine salt without adenine.

Claims (19)

1. A composition comprising a complex which is the reaction product of alkoxylated amine, acid and adenine, said complex having the formula wherein Z is derived from either a hydrocarbyl salicylic acid, trithiocyanuric acid, a hydrocarbyl sulfonic acid, a dihydrocarbyl dithiophosphoric acid or a dihydrocarbyl dithiobenzoic acid, wherein R is a hydrocarbyl group having 2 to 22 carbon atoms, R¹ is hydrogen or a hydrocarbyl group having 1 to 20 carbon atoms, x and y are each independently integers from 1 to 15, provided that the sum of x + y is 2 to 20, and a, b and c are independent numbers from 1.0 to 3.0, wherein the ratios of a:b, a:c and b:c are in the range of 1.0:3.0 to 3.0:1.0. 2. A composition according to claim 1, wherein Z is a hydrocarbon sulfonic acid having the following formula where R¹ is a hydrocarbon group having 2 to 30 carbon atoms. 3. Composition according to claim 1, wherein Z is a hydrocarbon salicylic acid having the following formula: 3. A composition according to claim 1, wherein Z is a hydrocarbon salicylic acid having the following formula: where R¹ is a hydrocarbon group having 2 to 30 carbon atoms. 4. A composition according to claim 2 or claim 3, wherein R¹ is a hydrocarbon group having 2 to 26 carbon atoms. 5. A composition according to claim 1, wherein Z is derived from a dihydrocarbyldithiobenzoic acid having the following formula wherein R², R³, R⁴, R⁵ and R⁶ are independently hydrogen or a hydrocarbon group having 1 to 24 carbon atoms or a hydroxy group, with the proviso that at least one of R² to R⁵ is a hydrocarbon group. 6. A composition according to claim 5 wherein R⁴ is hydroxy. 7. A composition according to claim 5 or claim 6, wherein at least one of R² to R⁵ is alkyl having 1 to 18 carbon atoms. 8. A composition according to any one of claims 5 to 7, wherein R³ and R⁵ are tert-butyl. 9. A composition according to claim 1, wherein Z is derived from a dihydrocarbyldithiophosphoric acid having the following general structure where R² and R³ are each independently hydrocarbon groups having 3 to 30 carbon atoms. 10. A composition according to claim 9, wherein R² and R³ are alkyl or alkenyl groups having 3 to 20 carbon atoms. 11. A composition according to any one of claims 1 to 10, wherein R is alkyl or alkenyl having 6 to 18 carbon atoms. 12. Composition according to one of claims 1 to 11, in which the sum of x + y is 2 to 15. 13. A composition according to any one of claims 1 to 12, wherein in the adenine R¹ is hydrogen. 14. Lubricating oil composition for internal combustion engines, (a) a larger quantity of lubricating oil base material and (b) a minor amount of a complex according to any one of claims 1 to 13 includes. 15. The composition of claim 14, wherein the complex is as claimed in any one of claims 5 to 11 and the amount of complex is about 0.1 to about 5.0 weight percent based on the oil base stock. 16. A composition according to claim 14, wherein the complex is according to any one of claims 1 to 4 and the amount of complex about 0.001 to about 5.0 wt.% based on the oil base material. 17. Use of a complex according to one of claims 1 to 13 in a lubricating oil composition for improving fuel economy in an internal combustion engine. 18. Use of a composition according to any one of claims 1 to 13 in a lubricating oil composition for reducing wear and/or inhibiting corrosion of copper. 19. Use of a composition according to any one of claims 1 to 13 as a friction modifier in a lubricating oil composition for internal combustion engines.