EP0815187B1

EP0815187B1 - Lubricant and fuel compositions containing an organo-substituted diphenyl sulfide

Info

Publication number: EP0815187B1
Application number: EP96905480A
Authority: EP
Inventors: Andrew Gene Horodysky; Ross Allan Kremer
Original assignee: ExxonMobil Oil Corp
Current assignee: ExxonMobil Oil Corp
Priority date: 1995-03-20
Filing date: 1996-02-14
Publication date: 2002-05-29
Anticipated expiration: 2016-02-14
Also published as: AU690829B2; DE69621434D1; EP0815187A1; JP3184226B2; EP0815187A4; DE69621434T2; JPH10510319A; AU4922596A; WO1996029381A1

Description

This invention relates to fuel and lubricant compositions which are based on specific substituted diphenyl sulfides in combination with succinimide and dithiophosphate additives. The lubricant compositions use substantially monoalkyl ring-substituted diphenyl sulfides as basestocks which achieve particularly good performance, especially improved antiwear and extreme pressure properties, when combined with the specified additives.
Alkyldiarylsulfide high temperature lubricants, dithiophosphate (or phosphorodithioate) antiwear agents, and polymer-substituted succinic acid derivative ashless detergents are each known in the art individually as components of lubricant compositions.
U.S. Patent Nos. 3,172,892 and 3,272,746 disclose polymer-substituted succinamides and succinimides which are useful in lubricant compositions and are prepared by reacting a polymer-substituted succinic acid or succinic anhydride with an alkylene polyamine.
U.S. Patent No. 3,194,812 teaches the use of high molecular alkenyl-n-para-aminophenyl succinimide as a dispersing agent in lubricants.
U.S. Patent No. 3,216,936 discloses lubricant additives which are predominantly amides and imides prepared by reacting an alkylene amine with a polymer-substituted succinic acid or anhydride and an aliphatic hydrocarbon monocarboxylic acid. The compounds are adapted for use with metal phosphorodithioates.
U.S. Patent No. 3,691,220 describes diorganophosphoro- dithioates prepared from the corresponding acid and a basic zinc compound in the presence of isopropyl alcohol, which are used as additives for lubricating oils.
U.S. Patent No. 3,804,763 discloses dispersant compositions useful as additives for lubricating oils, prepared by reacting a carboxylic acylating agent having at least 30 carbon atoms, e.g., a polymer-substituted succinic acid, anhydride or ester, with a hydroxy compound, a polyoxyalkylene polyamine, and an alkylene amine.
U.S. Patent No. 4,153,564 teaches compounds that act as emulsifiers, detergents, and antioxidants for lubricating compositions, prepared by reacting an alkenylsuccinic anhydride acid with an aromatic amine-aldehyde resin.
U.S. Patent No. 4,234,435 describes lubricant additives which are prepared by reacting an acylating agent derived from a polyalkene and a dibasic carboxylic such as maleic acid or derivative, with a polyethylene polyamine, and in which the polyalkene has a number average molecular weight (M_n) of 1300 to 5000 and a ratio of weight average to number average molecular weight (M_w/M_n) of 1.5 to 4.
U.S. Patent No. 4,255,271 shows phosphorodithioate additives for reducing friction and wear when added to a lubricant, prepared by reacting a phosphosulfurized hydrocarbyl oxazoline with a nitrogen containing compound and an olefin.
U.S. Patent No. 4,522,736 discloses products having utility as a dispersant and/or anticorrosion agent when used in a lubricant, which are prepared by reacting a polyalkenylsuccinic compound with an aromatic secondary amine or hindered phenol containing a hydroxyalkyl group, followed by reaction with an alkanolamine or an aminomethane.
U.S. Patent No. 4,652,387 teaches borated reaction products of an alkenyl succinic compound, an aryl amine and an aminoalcohol which are described as highly effective dispersant and antioxidant/anticorrosion additives for lubricant compositions.
U.S. Patent No. 4,840,744 describes polyamino alkenyl or alkyl succinimides containing carbamate functionalities, which are useful as dispersants in lubricating oils.
U.S. Patent No. 4,895,579 discloses products providing dispersant and antioxidant activity to lubricant compositions, which are prepared by reacting an alkenylsuccinic compound with an arylamine and a hindered alcohol.
U.S. Patent No. 5,171,915 teaches the alkylation of any of a wide variety of aromatic compounds, including diphenylsulfide, using as an alkylating agent a monoolefinic dimer of an olefin obtained as a by-product in the production of high viscosity index polyalphaolefins (HVI-PAO). The alkylation reaction is carried out in the presence of a Friedel-Crafts compound or zeolite as an alkylation catalyst. The alkylated aromatic compounds are stated to be useful as lubricant additives imparting antioxidant and antiwear properties.
British Patent No. 1,093,945 discloses alkyldiarylsulfides useful as high temperature functional fluids such as lubricants.
US 5,344,578 discloses alkyl ethers of sulfur-containing hydroxyl-derived aromatics for use as high-performance synthetic lubricant base stocks with superior catalytic thermal/oxidative stabilities, anti-wear and load-carrying properties.
US 4,161,451 discloses a lubricating oil additive composition having improved oxidation properties. The composition comprises antioxidents including aromatic sulfides.
In accordance with the present invention, compositions suitable for use in lubricants and fuels are provided comprising 1) a substantially moalkyl ring-substituted diphenyl sulfide; 2) a succinic dispersant component; and 3) a dithiophosphate, also known as a phosphorodithioate. The succinic dispersant is a polymer-substituted succinic acid derivative, that is, a polymer-substituted succinimide, succinamide, or succinic acid ester in which the alcohol or phenol moiety of the ester group may optionally contain amide, imide or amine nitrogen functionality, or mixtures of the amide, imide and/or ester.
Lubricant compositions comprising the foregoing three components, preferably using the alkylated diphenyl sufides as the lubricant basestock, have unexpectedly good antiwear and extreme pressure properties as well as other desirable properties such as those of corrosion resistance and high temperature cleanliness.
The substantially monoalkyl groups in the ring substituted diphenyl sulfide are substituted for the hydrogen atoms bonded to ring carbon atoms. Such alkyl groups may be cyclic, linear or branched. Moreover, one or more hydrogen and/or carbon atoms in such groups may be substituted with S, N, O, P and/or F. The monoalkyl-substituted diphenyl sulfide may contain, for example, 1 to 8, preferably 1 to 2 ring-substituted organo groups, with each substituent organo group containing in the range, for example, of 1 to 500, preferably 5 to 50, and most preferably 10 to 30 carbon atoms. The preferred diphenyl sulfides are the monoalkylated diphenyl sulfides in which the alkyl group is linear and contains from 5 to 40 carbon atoms. For certain lubricant and/or fuel uses, the substituted diphenyl sulfide is preferably a monoalkyldiphenyl sulfide in which the alkyl group contains from 10 to 20 carbon atoms.
The substantially monoalkyl ring-substituted diphenyl sulfide is generally prepared by reacting diphenyl sulfide in the presence of an alkylation catalyst with an organic substitution reactant having the same structure as the organo group to be substituted except that it contains a preferably terminal double-bonded carbon atom which becomes bonded to a ring carbon atom of the diphenyl sulfide. Thus, to obtain an n-alkyldiphenyl sulfide, the diphenyl sulfide is reacted with an alpha-olefin containing the same number of carbon atoms as the n-alkyl substituent. Mixtures of different organic substitution reactants containing terminal double-bonded carbon atoms as well as mixtures of such reactants containing terminal double-bonded carbon atoms and those containing internal double-bonded carbon atoms may also be used. Generally speaking, the molar ratio of organic substitution reactant to diphenyl sulfide varies from 0.5:1.0 to 10.0:1.0 and preferably from 1.0:1.0 to 4.0:1.0.
The alkylation catalyst used to prepared the organo-substituted diphenyl sulfide may be, for example, a Friedel-Crafts catalyst such as aluminum trichloride or boron trifluoride. Preferably, however, the reaction is carried out in the presence of a zeolite catalyst, to obtain a substantially mono-substituted diphenyl sulfide. Such zeolite catalyst should be at least partly in the acidic (H) form to confer the acidity for the reaction but may contain other cations also such as ammonium (NH₄+), and is preferably a large pore zeolite such as a faujasite, e.g., zeolite X, Y, USY, UHP-Y, ZSM-20 or zeolite beta. Another zeolite which may be used is zeolite MCM-22 (U.S. Patent Nos. 4,954,325; 5,100,534 and 5,103,066). The reaction is normally effected at temperatures ranging from ambient to 350°C, preferably from 100-250°C and most preferably from 180-240°C. The reaction can be performed, for example, in a batch or semi-batch mode by continuous or partial addition of catalyst or organic substitution reactant to the diphenyl sulfide. Catalyst can be used at levels ranging from 1 gram/mole of aromatic to 100 grams/mole of aromatic, preferably from 5 gram/mole of aromatic to 50 grams/mole of aromatic, and most preferably from 10-30 grams catalyst/mole of aromatic. The catalyst may be steamed, calcined or fresh.
The monoalkyldiphenyl sulfides, obtained with the zeolite catalysts, exhibit superior properties in comparison to the organo-substituted diphenyl sulfides prepared by reaction of the organic substitution reactant, e.g. alpha-olefin, with the diphenyl sulfide in the presence of AlCl₃ and other proton, and Lewis acids.
The monoalkyl-substituted diphenyl sulfides obtained with zeolite alkylation catalysts are substantially, i.e., up to 100% and at least 95-98% mono-substituted, e.g., monoalkylated, which can be demonstrated by gas chromatographic methods.
The monoalkyl-substituted diphenyl sulfide may be used as the main base stock oil in lubricant or as the main component of a fuel composition or in combination with other synthetic and/or mineral oil fluids. In either case, it will generally have a viscosity in the range, for example, of 2 to 1000 cSt (2 - 1000 x 10^-5 m²/s), preferably 3 to 100 cSt (3 - 100 x 10^-5 m²/s), and more preferably 3 to 30 cSt (3 - 30 x 10^-5 m²/s), at 100°C, and be present in the composition in the range, for example, of 0.5 to 95 wt.% or more, preferably 2 to 90 wt.%, with concentrations of 2 to 20 wt.% being preferred in some applications, particularly when another base stock oil is used with the substituted diphenyl sulfide, and 25 to 90 wt.% in the other applications.
The compounds making up the dispersant component, singly or in combination, viz., a polymer substituted succinic acid derivative which is the 1) succinimide; 2) succinamide; or 3) succinic acid ester in which the alcohol or phenol moiety of the ester group may optionally contain amide, imide or amine nitrogen functionality, are very complex mixtures of condensation reaction products of the respective reactant. Some of the components of the mixture may, for example, have any of the following structures

in which R is the residue of a homopolymer or copolymer of ethylenically unsaturated monomers, e.g., an alkyl or alkenyl group which is the residue of a polyalkene in which the alkene contains, for example, 2 to 20 carbon atoms and R has at least 20, preferably at least 50, and up to 300 or more carbon atoms, and has a number average molecular weight (M_n) of, for example, 300 to 10,000, preferably 500 to 2,000; Z is (separately in formula 2) hydrogen or an aliphatic or aromatic organic radical containing carbon, hydrogen and optionally nitrogen and/or oxygen and/or is the residue of an amino compound which is reacted with a polymer-substituted succinic acid derivative acylating agent, and Y is an aliphatic or aromatic radical containing carbon, hydrogen, nitrogen and optionally oxygen and/or is the residue of an alcohol containing amide, imide or amine nitrogen functionality, which is reacted with a polymer substituted succinic acid derivative acylating agent.
The dispersant is prepared, for example, by reacting maleic anhydride or acid with a suitable polymer, e.g., of an alkene containing, for example 2 to 20 carbon atoms, which contains a double bond or a halogen atom, e.g., chlorine, to obtain a polymer substituted succinic acid or anhydride acylating agent. The latter is then reacted with an appropriate hydrocarbyl substituted amine, or an alcohol or phenol which may optionally contain amide, imide or amine nitrogen functionality, to obtain the desired dispersant. Some suitable dispersants are polymer-substituted succinamides and succinimides and disclosed in US Patents Nos. 3,172,892 in which Z is the residue attached to a reactive nitrogen atom of an ethylene polyamine having the formula
where x is an integer, e.g., of 1 to 5, and R is hydrogen or lower alkyl;a polyisobutenyl substituted succinimide as disclosed in US Patent No. 3,194,812 in which Z is para-aminophenyl; the polymer-substituted succinamides disclosed in US Patent No. 3,272,746 in which Z is any of a wide variety of nitrogen-containing and non-nitrogen containing groups and preferably the residue attached to a reactive nitrogen atom of an alkylene polyamine having the formula
where n is an integer preferably less than 10, A is a hydrogen or hydrocarbon radical, and the alkylene group has less than 8 carbon atoms; polymer-substituted succinamides and succinimides disclosed in US Patent No. 3,216,936 in which Z in the imides and at least one Z in the amides is the residue attached to a reactive nitrogen atom of an alkylene polyamine or mixture of alkylene polyamines having the formula H₂N - (alkylene NH)_xH in which x is an integer preferably less than 6 and the alkylene is a lower alkylene, e.g., containing up to 4 carbon atoms, and cyclic homologs of such amines, e.g., piperazine; mixtures of polymer substituted succinamides, succinimides and succinic acid esters as disclosed in US Patent No. 3,804,763 in which Z in the imides and at least one Z in the amides may be the residue attached to a reactive nitrogen atom of any of a wide variety of polyoxyalkylene polyamines and alkylene polyamines, and Y in the ester may be the residue attached to a hydroxy group of any of a wide variety of nitrogen-containing and non-nitrogen containing hydroxy compounds, e.g., monohydric and polyhydric alcohols and phenols, polyalkylene glycols, monoesters of polyhydric compounds, aminoalcohols, aminophenols, etc.; polymer substituted succinimides as disclosed in US Patent No. 4,153,564 in which Z is the residue attached to a reactive nitrogen atom of an aromatic amine-aldehyde resin or the latter product reacted with an aromatic triazole and an aldehyde; polymer substituted succinamides and succinimides as disclosed in US Patent No. 4,234,435 in which the polymer substituent R is derived from any of a large group of homopolymers and copolymers of a wide variety ethylenically unsaturated monomers, preferably hydrocarbon monomers, which have a number average molecular weight (M_n) of 1300 to 5000 and a ratio of weight average molecular weight (M_w) to M_n of from 1.5 to 4, and Z in the imides and at least one Z in the amides is the residue attached to a reactive nitrogen atom of an alkylene polyamine such as those disclosed in several of the other patents cited in this paragraph; polymer-substituted succinamides, succinimides, or succinic acid esters as disclosed in US Patent No. 4,522,736 in which in the case of succinamides and succinimides, at least one Z is the residue attached to a reactive nitrogen atom of an aromatic secondary amine subsequently reacted with an alkanolamine or aminomethane, or in the case of succinic acid esters, Y is the residue attached to a hydroxy group of a hindered phenol containing a hydroxy group subsequently reacted an alkanolamine or aminomethane; borated mixtures of polymer-substituted succinamides, succinimides and succinic acid esters as disclosed in US Patent No. 4,652,387 in which in the case of the succinamides and succinimides, Z in the imide and at least one Z in the amide is the residue attached to a reactive nitrogen atom of a diarylamine and/or an aminoalcohol and in the case of the succinic acid esters, Y is the residue attached to a hydroxy group of an aminoalcohol; polymer-substituted succinimides as disclosed in US Patent No. 4,840,744 in which Z contains carbamate functionalities; and polymer-substituted succinamides and succinimides as disclosed in US Patent No. 4,895,579 in which Z in the imides and at least one Z in the amides is the residue attached to a reactive nitrogen atom of an aromatic amine, further reacted with a hindered alcohol.
The polymer substituted succinic acid derived dispersant may be present in the composition in an amount, for example, of 0.1 to 25 wt.%, preferably 0.15 to 10 wt.%, and most preferably 1 to 7 wt.% based on the weight of the composition.
The dithiophosphate component of the compositions of this invention is in most cases derived from an organodithiophosphoric acid having the formula
in which R₁ and R₂ are separate hydrocarbyl radicals or together form with the phosphorus and oxygen atoms monomeric ring structures or polymeric chain structures. Preferably, the dithiophosphate is a metal salt of a dihydrocarbyl dithiophosphoric acid where the metal is a member of Group II of the Periodic table, particularly zinc and barium and preferably zinc. Ashless dithiophosphates may also be used, e.g., reaction products of an alkylene oxide, an amine or an olefin with an organodithiophosphoric acid as is well-known in the art. In defining the acid with reference to the foregoing formula, the R₁ and R₂ groups may be the same or different and are selected from the group consisting of alkyl, cycloalkyl, aryl, alkaryl and aralkyl radicals, the radicals having from 3 to 30 carbon atoms. Such R₁ and R₂ groups may be exemplified by n-propyl, iso-propyl, n-butyl, iso-butyl, amyl, hexyl, decyl, dodecyl, octadecyl, eicosyl, pentacosyl, benzyl, phenethyl, cyclohexyl, phenyl, naphthyl, tolyl, t-amylphenyl, didodecylphenyl, wax phenyl, where the wax portion contains 24 carbon atoms, and the like. It is also contemplated that neoalkyl radicals, such as 2,2-dimethyl-1-propyl, 2,2,4-trimethyl-1-butyl, 2,2-dimethyl-1-decyl and 2,2,4-trimethyl-1-hexadecyl, may be used.
Illustrative of the acids which can be used and in which R₁ and R₂ are the same are the dipropyl, dibutyl, dihexyl, didodecyl, dioctadecyl, dicyclohexyl, dibenzyl, diphenethyl, diphenyl, ditolyl, didodecylphenyl, diwaxphenyl, di(2,2-dimethyl-1-propyl), di(2,2,4-trimethyl-1-butyl), di(2,2-dimethyl-1-decyl) and di(2,2-4-trimethyl-1-hexadecyl) dithiophosphoric acid.
Useful acids in which R₁ and R₂ are different are illustrated by the following: n-propyl amyl, amyl decyl, hexyl dodecyl, decyl cyclohexyl, benzyl phenyl and the like dithiophosphoric acids.
Preferably R₁ and R₂ are alkyl groups containing 1 to 50 carbon atoms, more preferably 3 to 20 carbon atoms.
These metal dithiophosphates are known, as shown, for example in US Patents Nos. 3,216,936 and 3,691,220. Examples of dithiophosphoric acids in which R₁ and R₂ together define a monomeric ring structure or a polymeric chain structure are those containing one or more oxazoline groups as shown in U.S. Patent No. 4,255,271.
The dithiophosphate component may be present in the composition in an amount, for example, 0.05 to 10 wt.%, preferably 0.1 to 5 wt.%, and most preferably 0.2 to 3 wt.% based on the weight of the composition.
The compositions of this invention may be combined or blended with other synthetic oils and/or mineral oils and particularly with synthetic polyalphaolefins (PAO). Any suitable blending ratio of substituted diphenylsulfide to other synthetic oil and/or mineral oil may be used; for example, a base stock blend of 20 wt.% of substituted diphenylsulfide and 80 wt.% PAO has been found to be very advantageous. However, the monoalkyl ring-substituted diphenylsulfide may constitute a major proportion of the base stock oil up to 100%.
In general, mineral oils, both paraffinic, naphthenic and mixtures thereof, employed as part of base stock oil in the lubricant, or grease vehicle, may be of any suitable lubricating viscosity range, as for example, from 1.0 cSt (1 x 10^-5 m²/s) at 100°C to 1000 cSt (1 x 10^-2 m²/s) at 100°C and preferably, from 2.0 to 60 cSt (2 - 60 x 10^-5 m²/s at 100°C. The preferred oils may have viscosity indexes ranging to 150. The average molecular weights of these oils may range from 250 to 800.
Suitable synthetic oils include polyalphaolefins, e.g., polyisobutylene, polybutenes, or hydrogenated polydecenes, polypropylene glycol, polyethylene glycol, trimethylpropane esters, neopentyl e.g. pentaerythritol, esters, di(2-ethylhexyl) sebacate, di(2-ethylhexyl) adipate, dibutyl phthalate, fluorocarbons, silicate esters and esters of phosphorus-containing acids and alkylsubstituted diphenyl ethers.
The compositions of the invention may also be used in greases or in any of the foregoing synthetic and/or mineral base stock oils thickened with an appropriate thickener or gelling agents. These may include any of the conventional metal salts or soaps, which are dispersed in the lubricating vehicle in grease-forming quantities in an amount to impart to the resulting grease composition the desired consistency. Other thickening agents that may be employed in the grease formulation may comprise the non-soap thickeners, such as surface-modified clays and silicas, aryl ureas, calcium complexes and similar materials. In general, grease thickeners may be employed which do not melt and dissolve when used at the required temperature within a particular environment; however, in all other aspects, any material which is normally employed for thickening or gelling hydrocarbon fluids for forming greases can be used in preparing greases in accordance with the present invention.
If a mineral oil or synthetic oil base stock oil of lubricating viscosity, in addition to the substituted diphenyl sulfide is utilized in the composition, it may be present in an amount, for example of 2 to 98 wt.%, preferably 5 to 90 wt.%, based on the total composition.
In addition to the three essential components of the compositions of this invention and an additional synthetic or mineral base stock oil, if used, various combinations of other components commonly used in lubricants and other functional fluids may also be included, e.g., additional dispersants, metallic detergents (phenates, sulfonates, and/or salicylates), antioxidants (as exemplified by hindered phenols, arylamines, dithiocarbamates, etc.), polymeric viscosity index improvers (polyisobutylene, styrene-diene copolymers, polymethacrylates, etc.), auxiliary antiwear or extreme pressure additives (heterocyclic triazoles, dimercaptothiadiazoles, dithiocarbamates, phosphites, phosphonates, acid phosphates, thiophosphates, phosphonothionates, borates, etc.), corrosion inhibitors, emulsifiers, demulsifiers, seal swell agents, antistain additives, and the like.
When formulated as a lubricant, the composition of this invention can be used in demanding applications such as diesel engine oils which generate large quantities of performance-property robbing particulate soot, or in somewhat less demanding applications such as turbine, circulating, or hydraulic oils, or in thickened lubricants such as greases.
Although the preferred use of the composition of this invention may reside in lubricant applications, use in fuels would also provide many of the same performance advantages. Concentrations of 1 to 1,000 pounds of components per thousand barrels of fuel are preferred. Fuel compositions include hydrocarbon fuels, oxygenated fuels, and mixtures of hydrocarbon and oxygenated fuels. Use of a mixture of aromatic fluid and dispersant would be especially advantageous in fuels.
The following examples further illustrate the invention.

Comparative Examples A to G

The examples illustrate the effect on lubrication properties of mixing a typical lubricating mineral oil with varying amounts of a substantially monoalkyl ring-substituted diphenyl sulfide.
To a vigorously stirred mixture of diphenyl sulfide (186.2 g, 1.0 mile) and 1-hexadecene (224.4 g, 1.0 mole) in a flask fitted with thermocouple and reflux condenser was added 19.1 g of FCC Octacat® USY catalyst. The mixture was heated to 200°C with stirring for six hours. After cooling to room temperature, the mixture was filtered to remove catalyst and vacuum distilled at 170°C at 0.5-1.5 mmHg (67 - 200 Pa) to remove unreacted starting materials.
The foregoing substantially monoalkylated diphenyl sulfide (ADPS) was blended in varying amounts with a paraffinic neutral lubricating base stock mineral oil having a viscosity of 100 Saybolt seconds at 40°C and the blends, together with the pure ADPS and mineral oil were tested for their lubrication properties, using the Four Ball Wear Test described in test method ASTM D2266 and/or U.S. Patent No. 4,761,482.
Results are shown in Table I in terms of wear scar diameter and "K" factor which is a function of wear volumes and is a dimensionless number defined as the product of the wear volume times the metal hardness divided by the product of the distance travelled and the load. The "K" factor is relatively independent of test conditions, provided effective lubrication is maintained. The "K" factor allows for Hertzian diameter and permits calculations of wear rates that can be related to machine life under various operating conditions and metallurgy.

Example ADPS, Wt. % Wear Scar Diameter, mm Wear, K Factor

A 0 1.62 372

B 1 1.87 662

C 2 1.53 300

D 5 1.57 327

E 25 1.29 149

F 50 1.38 195

G 100 0.7 13
As shown by the results of Table 1, little improvement in wear response was exhibited using 1, 2, and 5% alkylated diphenyl sulfide blended into a typical paraffinic neutral lubricating mineral oil in the absence of any other added components.

Examples 1 and 2 and Comparative Examples H to L

These examples illustrate the effect on lubrication properties of the mineral oil described in Comparative Examples A to G blended with additive amounts of the ADPS described in the comparative examples, a polyisobutylene succinimide dispersant, and/or a mixed alcohol derived zinc dithiophosphate (ZnDTP). The polyisobutylene succinimide dispersant was prepared as described in previously cited US Patent No. 4,234,435 and in which the radical "R" in previously given formula 1) for the component is the residue of a polyisobutylene having a molecular weight as defined in the latter patent and the radical "Z" in such formula is the residue of a polyethylene polyamine as defined in the patent, and the zinc dithiophosphate is the zinc salt of a dithiophosphoric acid where R₁ and R₂ in previously given formula 4) for these compounds is a mixture of C₃-C₈ alkyl groups. The compositions were subjected to the Four Ball Wear Test as described in Comparative Examples A to G and the makeup of the compositions and the results of the tests are shown in Table II.

Example	ADPS, 0Wt.%	ZnDTP, Wt.%	Dispersant Wt. %	Wear Scar Diameter, mm	Average (3 Runs) Wear Scar Diameter, mm	Wear, K Factor x 10E-8	Average (3 Runs) Wear, K Factor X 10E-8
H	0	0	9	1.57	1.61	332	363
				1.67		420
				1.58		337
I	0	0.05	0	1.63	1.61	382	367
				1.54		305
				1.66		414
J	0	0.05	9	0.56	1.2	323	201
				0.55		4
				1.5		275
1	10	0.05	9	0.57	0.79	5	45
				1.23		125
				0.57		5
2	25	0.05	9	0.55	0.78	4	41
				0.58		5
				1.21		116
K	10	0.05	0	0.93	1.33	39	218
				1.52		292
				1.56		323
L	25	0.05	0	0.71	1.11	13	114
				1.29		149
				1.35		180

The results of Table II indicate that the addition of substantially monoalkyl ring-substituted diphenylsulfide in concentrations of 10 and 25% to mineral oil in the presence of dispersant and dithiophosphate (Examples 1 and 2) improves the wear characteristics. In contrast, significantly less improvement was obtained by the use of 10 and 25% substituted diphenyl sulfide in the presence of 0.05% dithiophosphate but in the absence of any polymeric dispersant (Examples K and L).

Examples 3 and 4 and Comparative Examples M and N

These examples illustrate the effect on lubricating properties of adding a substantially monoalkyl ring-substituted diphenyl sulfide to partially spent mineral oil-based lubricants containing a polymer-substituted succinimide ashless dispersant and a dithio-phosphate.
A fully formulated commercially obtained diesel engine oil derived from mineral oil base stocks and containing both polymer-substituted succinimide ashless dispersant and zinc dithiophosphate was run in a GM 6.2 liter diesel engine for 50 hours at 1,000 rpm with coolant and oil gallery temperatures of 120°C, a fuel flow of 9 kg/hr, and fuel and inlet air temperatures of 35°C and 32°C, respectively. The absolute intake air and exhaust back pressures were 97 kPa and 10-3 kPa, respectively. During this time period, the wear properties of the oil significantly diminished, due in part to the combustion byproducts (soot) and aging of the lubricant. This oil containing (partially) depleted dispersant and zinc dithiophosphate, was evaluated for wear protection, using the procedure of the preceding examples, in two separate determinations (Examples Ma and Mb). The ADPS utilized in the preceding examples in an amount of 5 wt.% was then added to the depleted oil and two separate wear evaluations were again performed (Examples 3a and 3b). The results are shown in Table III which, in addition to Wear Scar Diameter and K Factor, includes values for Wear Ratio, defined as the Wear Scar Diameter/Hertz Diameter. For a 40 kg load, the estimated mean Hertz diameter = 0.30 (mm).

Example Alkylated Diphenyl Sulfide, Wt.% Wear Scar Diameter, mm Wear K Factor Wear Ratio

Ma 0 1.36 182 4.53

Mb 0 1.42 218 4.73

3a 5 0.90 34.6 3.00

3b 5 0.89 33.7 2.96
The procedure of Example 3 and Comparative Example M was repeated on a different commercially obtained mineral oil based diesel engine oil also containing a polymer-substituted succinimide dispersant and zinc dithiophosphate, except that only a single wear evaluation was obtained for the partially depleted oil containing no ADPS (Comparative Example N) and that containing 5 wt. ADPS (Example 4). The results are shown in Table IV.

Example Alkylated Diphenyl Sulfide, Wt.% Wear Scar Diameter, mm Wear K Factor Wear Ratio

N 0 1.31 160 4.37

4 5 0.84 26 2.80
As can be clearly observed from the data in Tables III and IV, the presence of substantially monoalkyl substituted diphenyl sulfide in the oil containing both ashless dispersant and dithiophosphate significantly reduced the wear damage in 4-Ball Wear testing, as measured by the Wear Scar diameters, or resulting "K" Factors and Wear Ratios. The Wear Volumes ("K" Factors) were found to be reduced to 1/6 of their corresponding value when compared to the identical oils without the monoalkyl ring-substituted diphenyl sulfide.

Claims

A lubricant or fuel composition comprising 1) an organo, substantially monoalkyl, ring-substituted diphenyl sulfide; 2) a dispersant component comprising a polymer-substituted succinimide, component comprising a polymer-substituted succinimide, succinamide and/or succinic acid ester, and 3) a dithiophosphate.
The composition of claim 1 in which the monoalkyldiphenyl sulfide contains an alkyl group having 10 to 20 carbon atoms.
The composition of claim 1 in which the alcohol or phenol moiety of the ester group of the succinic acid ester contains amide, amide or amine nitrogen functionality.
The composition of claim 1 or 2 in which the dispersant is a succinimide comprising at least one compound having the formula
and/or a succinamide comprising at least one compound having the formula
in which R is an alkyl or alkenyl group which is the residue of a polyalkene in which the alkene contains 2 to 20 carbon atoms and R has at least 20 carbon atoms and Z is hydrogen or an aliphatic or aromatic organic radical containing carbon, hydrogen and optionally nitrogen and/or oxygen, and/or is the residue attached to a reactive nitrogen atom of an amino compound which is reacted with a polymer-substituted succinic acid acylating agent.
The composition of claim 4 in which Z in formula 1) and/or at least one Z in formula 2) is the residue attached to an active nitrogen atom of an alkylene polyamine having the formula
in which n is an integer less than 10, A is a hydrogen or hydrocarbon radical, and the alkylene group has less than 8 carbon atoms.
The composition of claim 5 in which the amino compound is an alkylene polyamine having the formula
in which n is an integer less than 10, A is a hydrogen or hydrocarbon radical, and the alkylene group has less than 8 carbon atoms.
The composition of any of claims 1 to 6 in which the dithiophosphate is a zinc salt of dithiophosphoric acid havinq the formula
in which R₁ and R₂ are separately alkyl groups containing 3 to 30 carbon atoms.
The composition of claim 1 comprising 0.5 to 95 wt.% of the organo, substantially monoalkyl ring-substituted diphenyl sulfide, 0.1 to 25 wt.% of the dispersant component, and 0.05 to 10 wt.% of the dithiophosphate.
The composition of claim 8 comprising 2 to 90 wt.% of the organo, substantially monoalkyl ring-substituted diphenyl sulfide, 0.15 to 10 wt.% of the dispersant component, and 0.1 to 5 wt.% of the dithiophosphate.
The composition of claim 9 comprising 1 to 7 wt.% of the dispersant component, and 0.2 to 3 wt.% of the dithiophosphate.
The composition of claim 1 also comprising a mineral oil, synthetic oil, or a mixture of mineral and synthetic oil, of lubricating viscosity.
The composition of claim 11 which the mineral oil, synthetic oil or the mixture is present in an amount of from 2 to 98 wt.%.
The composition of claim 12 in which the mineral oil, synthetic oil, or the mixture is present in an amount of 5 to 90 wt.%.