SMOKE REDUCING ADDITIVES FOR TWO-CYCLE ENGINE LUBRICANT-FUEL MIXTURE

Abstract: A lubricant-fuel mixture containing an amine salt and/or amide of a benzoic acid or thiobenzoic acid derivative, an amine salt of a phosphoric acid derivative, or certain quaternary ammonium hydroxides is effective in reducing the smoke emitted during operation of a two-cycle internal combustion engine.

Description: SMOKE REDUCING ADDITIVES FOR TWO-CYCLE ENGINE LUBRICANT-FUEL MIXTURE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a lubricant-fuel mixture for two-cycle internal combustion engines in which the mixture has reduced smoke emission due to the presence of an amine salt and/or amide of a derivative of benzoic acid or thiobenzoic acid, a hydrocarbyl substi¬ tuted amine salt of a derivative of phosphoric acid, or certain quaternary ammonium hydroxides. 2. Description of Related Art In the last several years, the use of spark-ignited two- cycle internal combustion engines has increased significantly. This is due to their use in a variety of garden and recreational equipment such as motorcycles, marine outboard engines, snowmobiles, power mowers, snow blowers, chain saws, and the like. As such, the amount of smoke released from two-cycle engines has become a major environ¬ mental concern to engine manufacturers and fuel suppliers. However, few smoke reducing additives are commercially available, and the few that are contain metals, which are environmentally undesirable. Amine salts of certain benzoic acid derivatives have been used as extreme pressure (EP) agents for water-based metal cutting fluids (see for example, Japanese Patent No. 55023132). Substituted benzoic acids have also been used as EP agents in water-based fluids (see for example, U.S. Patent 4,569,776). U.S. Patent No. 4,434,066 discloses a water based hydraulic fluid containing a combination of a hydroxyl-substituted aromatic acid component and a nitroaromatic compound component. U.S. Patent No. 4,012,331 discloses a lubricating oil composition comprising a sulfur compound prepared by reacting a trithiolan compound with a thiol compound in the presence of a base. Similarly, U.S. Patents 4,787,916 and 4,902,437, together with the patents disclosed therein, describe the use of quaternary ammonium hydroxides in fuels and in lubricating oils, respectively. More recently, the use of a hydrocarbyl substituted amine salt and/or amide of benzoic acid as an antioxidant in lubricating oils and as a flow improver in middle distillates has been disclosed in copending- applications U.S. Serial Nos. 582,316 and 545,002, respectively. However, none of these publications suggest the particular ashless two-cycle engine lubricant-fuel mixture disclosed herein or its effectiveness in reducing the smoke formed during combustion of the mixture. SUMMARY OF THE INVENTION In one embodiment, this invention concerns a two-cycle engine lubricant-fuel mixture that comprises (a) a lubricating oil basestock, (b) a distillate fuel, and (c) one of the following oil-soluble additives: (i) a hydrocarbyl substituted amine salt and/or amide of a compound having the formula H I x I c = x R5 wherein X is oxygen or sulfur, and Ri, R2, R3, R4 and R5 are selected from hydrogen; a hydro¬ carbyl group containing from 1 to 24 carbon atoms; a hydroxy group; and an oxygen-containing hydrocarbyl group containing from 1 to 24 carbon atoms and at least one of the radicals Ri, R2, R3, R4 or R5 is a hydrocarbyl group containing from 1 to 24 carbon atoms; (ii) a hydrocarbyl substituted amine salt of a compound having the formula wherein X is oxygen or sulfur and R6 and R7 are selected from hydrogen and a hydrocarbyl group containing from 1 to 28 carbon atoms; or (iii) a quaternary ammonium hydroxide having the -p1 Λυvi»minιuιl1 un wherein Rs is a hydrocarbon radical or a hydroxy terminated radical having from 1 to 24 carbon atoms, Rg is a hydrocarbon radical having from 1 to 24 carbon atoms, and Rio and RJJ are hydro¬ carbon radicals having from 4 to 24 carbon atoms. In another embodiment, this invention concerns a method for reducing smoke emission from a two-cycle internal combustion engine by operating the engine with the lubricant-fuel mixture described above. DETAILED DESCRIPTION OF THE INVENTION In general, the two-cycle engine lubricant-fuel mixture of this invention requires a lubricating oil basestock, a distillate fuel, and one of the following: an amine salt and/or amide of a derivative of benzoic acid or dithiobenzoic acid, an amine salt of a phosphoric acid derivative, or a particular class of quaternary ammonium hydroxides. However, if desired, other lubricant and distil¬ late fuel additives may be present in the mixture as well. The lubricating oil basestock can be derived from natural lubricating oils, synthetic lubricating oils, or mixtures thereof. In general. the lubricating oil basestock will have a kinematic viscosity ranging from about 5 to about 10,000 cSt at 40 β C, although typical applications will require an oil having a viscosity ranging from about 10 to about 1,000 cSt at 40 β C. Natural lubricating oils include animal oils, vegetable oils (e.g., castor oil and lard oil), petroleum oils, mineral oils, and oils derived from coal or shale. Synthetic oils include hydrocarbon oils and halo-substituted hydrocarbon oils such as polymerized and interpolymerized olefins (e.g.. polybutylenes, polypropylenes, propylene-isobutylene copolymers, chlorinated polybutylenes, poly(l-hexenes), poly(l-octenes), poly(l- decenes), etc., and mixtures thereof); alkylbenzenes (e.g.. dodecyl- benzenes, tetradecylbenzenes, dinonylbenzenes, di(2-ethylhexyl)ben¬ zene, etc.); polyphenyls (e.g.. biphenyls, terphenyls, alkylated polyphenyls, etc.); alkylated diphenyl ethers, alkylated diphenyl sulfides, as well as their derivatives, analogs, and homologs thereof; and the like. Synthetic lubricating oils also include alkylene oxide polymers, interpolymers, copolymers and derivatives thereof wherein the terminal hydroxyl groups have been modified by esterification, etherification, etc. This class of synthetic oils is exemplified by polyoxyalkylene polymers prepared by polymerization of ethylene oxide or propylene oxide; the alky! and aryl ethers of these polyoxyalkylene polymers (e.g., methyl-polyisopropylene glycol ether having an average molecular weight of 1000, diphenyl ether of polyethylene glycol having a molecular weight of 500-1000, diethyl ether of polypropylene glycol having a molecular weight of 1000-1500); and mono- and polycarboxylic esters thereof (e.g., the acetic acid esters, mixed C3-C8 fatty acid esters, and C13 oxo acid diester of tetraethylene glycol). Another suitable class of synthetic lubricating oils com¬ prises the esters of dicarboxylic acids (e.g.., phthalic acid, succinic acid, alky! succinic acids and alkenyl succinic acids, maleic acid, azelaic acid, suberic acid, sebasic acid, fumaric acid, adipic acid, linoleic acid di er, malonic acid, alkylmalonic acids, alkenyl malonic acids, etc.) with a variety of alcohols (e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol, di¬ ethylene glycol monoether, propylene glycol, etc.). Specific examples of these esters include dibutyl adipate, di (2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyl diester of linoleic acid dimer, and the complex ester formed by reacting one mole of sebacic acid with two moles of tetra- ethylene glycol and two moles of 2-ethylhexanoic acid, and the like, Esters useful as synthetic oils also include those made from C5 to C12 onocarboxylic acids and polyols and polyol ethers such as neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaeryl- thritol, tripentaerythr tol, and the like. Sil con-based oils (such as the polyalkyl-, polyaryl-, polyalkoxy-, or polyaryloxy-siloxane oils and silicate oils) comprise another useful class of synthetic lubricating oils. These oils include tetraethyl silicate, tetraisopropyl silicate, tetra-(2-ethyl- hexyl) silicate, tetra-(4-methyl-2-ethylhexyl) silicate, tetra(p-tert- butylphenyl) silicate, hexa-(4-methyl-2-pentoxy)-disiloxane, poly(methyl)-siloxanes and poly(methylphenyl) siloxanes, and the like- Other synthetic lubricating oils include liquid esters of phosphorus- containing acids (e.g., tricresyl phosphate, trioctyl phosphate, diethyl ester of decylphosphonic acid), polymeric tetrahydrofurans, polyalphaolefins, 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 tar sands bitumen) without further purification or treatment. Examples of unrefined oils include a shale oil obtained directly from a retorting operation, a petroleum oil obtained directly from distil¬ lation, or an ester oil obtained directly from an esterification process, each of which is then used without further treatment. Refined oils are similar to the unrefined oils except that refined oils have been treated in one or more purification steps 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. Rerefined oils are obtained by treating refined 3 in processes similar to those used to obtain the refined oils. 1 -e rerefined oils are also known as reclaimed or reprocessed oils and often are additionally processed by techniques for removal of spent additives and oil breakdown products. If desired, other additives known in the art may be added to the lubricating base oil. Such additives include dispersants, anti- wear agents, antioxidants, corrosion inhibitors, detergents, pour point depressants, extreme pressure additives, viscosity index improvers, friction modifiers, and the like. These additives are typically disclosed, for example, in "Lubricant Additives" by C. V. Smalhear and R. Kennedy Smith, 1967, pp. 1-11 and in U.S. Patent 4,105,571, the disclosures of which are incorporated herein by refer¬ ence. The distillate fuels used in two-cycle engines are well known to those skilled in the art and usually contain a major portion of a normally liquid fuel such as hydrocarbonaceous petroleum distil¬ late fuel (e.g., motor gasoline as defined by ASTM Specification D-439-73). Such fuels can also contain non-hydrocarbonaceous mate¬ rials such as alcohols, ethers, organo-nitro compounds and the like (e.g. ethanol, ethanol , diethyl ether, methyl ethyl ether, nitro- ethane), are also within the scope of this invention as are liquid fuels derived from vegetable or mineral sources such as corn, alfalfa, shale, and coal. Examples of such fuel mixtures are combinations of gasoline and ethanol, diesel fuel and ether, gasoline and nitro- methane, etc. Particularly preferred is gasoline, that is, a mixture of hydrocarbons having an ASTM boiling point of 60 β C at the 10% distillation point to about 205'C at the 90% distillation point. Two-cycle fuels may also contain other additives which are well known to those skilled in the art. These can include anti-knock agents such as tetra-alkyl lead compounds, lead scavengers such as halo-alkanes (e.g., eihylene dichloride and ethylene dibro ide), dyes, cetane improvers, anti-oxidants such as 2,6-di-tertiary-butyl-4- methylphenol, rust inhibitors such as alkylated succinic acids and anhydrides, bacteriostatic agents, gum inhibitors, metal deactivators, demulsifiers, upper cylinder lubricants, anti-icing agents, and the like. This invention is useful with lead-free as well as lead con¬ taining fuels. The lubricant-fuel mixture of this invention will also contain a hydrocarbyl substituted amine salt and/or amide of an oil- soluble benzoic acid or thiobenzoic acid derivative, an amine salt of a phosphoric acid derivative, or a particular class of quaternary ammonium hydroxides. The hydrocarbyl substituted amine salt and/or amide (prefer¬ ably an amine salt) of an oil-soluble benzoic acid or thiobenzoic acid derivative has the formula R5 wherein X is oxygen or sulfur, preferably sulfur, and Ri, R2, R3, R4 and R5 are selected from hydrogen; a hydrocarbyl group containing from 1 to 24 carbon atoms, preferably an alkyl group containing from 1 to 18 carbon atoms; a hydroxy group, i.e., -OH; and an oxygen-containing hydrocarbyl group containing from 1 to 24 carbon atoms and at least one of the radicals Ri, R2, R3, R4 or R5 is a hydrocarbyl, preferably an alkyl group, containing from 1 to 24, preferably from 1 to 18 carbon atoms, most preferably from 1 to 6 carbon atoms. Specific exam p les of the benzoic or dit iobenzoic acid derivatives include 4-hydroxy 3,5 ditertiary butyl dithiobenzoic acid; 4-hydroxy 3,5 ditertiary butyl benzoic acid; 3,5 dimethyl dithioben¬ zoic acid; 4-hydroxy 3,5 dimethyl dithiobenzoic acid and the like. The oil soluble additive is formed in a conventional manner by mixing substantially equi olar amounts of the benzoic acid deriva¬ tive and a hydrocarbyl substituted amine at temperatures generally in the range of 20 β C - lOO'C. The hydrocarbyl groups of the amine include groups which may be straight or branched chain, saturated or unsaturated, aliphatic, cycloaliphatic, aryl, alkaryl, etc. Said hydrocarbyl groups may contain other groups, or atoms, e.g. hydroxy groups, carbonyl groups, ester groups, or oxygen, or sulfur, or chlorine atoms, etc. These hydrocarbyl groups will usually be long chain, e.g. * C12 to C40, e.g. C14 to C24. However, some short chains, e.g. Ci to Cn may be in¬ cluded as long as the total numbers of carbons is sufficient for solubility. Thus, the resulting compound should contain a sufficient hydrocarbon content so as to be oil-soluble. The number of carbon atoms necessary to confer oil solubility will vary with the degree of polarity of the compound. The compound will preferably also have at least one straight chain alkyl segment extending from the compound containing 8 to 40, e.g. 12 to 30 carbon atoms. The amines may be primary, secondary, tertiary or quater¬ nary, but preferably are secondary. If amides are to be made, then primary or secondary amines will be used. Examples of primary amines include n-dodecyl amine, n- tridecyl amine, C13 Oxo amine, coco amine, tallow amine, behenyl amine, etc. Examples of secondary amines include methyl-lauryl amine, dodecyl-octyl amine, coco-methyl amine, tallow-methylamine, methyl- n-octyl amine, methyl-n-dodecyl amine, methyl-behenyl amine, ditallow amine etc. Examples of tertiary amines include coco-diethyl amine, cyclohexyl-diethyl amine, coco-dimethyl amine, tri-n-octyl amine, di-methyl-dodecyl amine, methyl-ethyl-coco amine, methyl-cetyl stearyl amine, etc. Amine mixtures may also be used and many amines derived from natural materials are mixtures. The preferred amines include the long straight chain alkyl amines containing from 8 to 40, preferably from 12 to 24, carbon atoms. Naturally occurring amines, which are gener¬ ally mixtures, are preferred. Examples include coco amines derived from coconut oil which is a mixture of primary amines with straight chain alkyl groups ranging from Cβ to Cis- Another example is di tallow amine, derived from hydrogenated tallow acids, which amine is a mixture of C14 to Ci8 straight chain alkyl groups. Ditallow amine is particularly preferred. The hydrocarbyl substituted amine salt of an oil-soluble phosphoric acid derivative has the formula X I R6θ - p - XH 0R7 wherein X is oxygen or sulfur, preferably sulfur, and R5 and R7 are selected from hydrogen and a hydrocarbyl group containing from 1 to 28 carbon atoms, preferably an alkyl group containing from 4 to 12 carbon atoms. Preferably, at least one of the radicals R_ or R7 is a hydro¬ carbyl group, preferably an alkyl group, containing from 3 to 18 carbon atoms. Specific examples of the phosphoric acid derivative include dioctyldithiophosphoric acid; dihexyldithiophosphoric acid; dibutyl- dithiophosphoric acid; didodecylphenyldithiophosphoric acid; dioctyl- phosphoric acid; butylhexyldithiophosphoric acid; butyloctyldithi0- phosphoric acid; and the like. The phosphoric acid derivative may be formed in a conven¬ tional manner by mixing substantially equimolar amounts of the phos¬ p oric acid derivative and a hydrocarbyl substituted amine at tempera¬ tures generally in the range of 15 to 100°C. The hydrocarbyl substi¬ tuted amines include those described with respect to the preparation of the aforedescribed second component. The preferred amines include - li ¬ the long straight chain al amines containing from 8 to 40, prefer¬ ably from 12 to 18, carbon atoms. Naturally occurring amines, which are generally mixtures, are preferred. Examples include coco amines derived from coconut oil which is a mixture of primary amines with straight chain alkyl groups ranging from Cs to Cjs- Another example is tallow amine, derived from hydrogenated tallow acids, which amine is a mixture of C14 to Ci8 straight chain alkyl groups. Tallow amine is particularly preferred. The oil-soluble quaternary ammonium hydroxide has the formula wherein Rs is a hydrocarbon radical (or group) or a hydroxy terminated radical (or group) having from 1 to 24 carbon atoms, Rg is a hydrocar¬ bon radical having from 1 to 24 (preferably from 4 to 24) carbon atoms, and Rio and RJJ are hydrocarbon radicals having from 4 to 24 carbon atoms. The hydrocarbon radicals (Rβ, Rg, Rio, and Rπ) can be alkyl groups, unsaturated paraffin groups, cyclic hydrocarbon groups, aryl groups, arylalkyl groups or mixtures thereof. In addition, said groups can be normal, branched, substituted groups or mixtures there¬ of. The hydrocarbon radicals may also contain other atoms such as nitrogen, oxygen, or sulfur; e.g., in the form of an alcohol, an amine, a ketone, a sulfide, a thiosulfide, and other functionalities. Quaternary ammonium hydroxides in which the hydrocarbon radical is octyl, dodecyl, decyl, octadecyl, capryl radicals, or their mixtures are preferred. Preferred quaternary ammonium hydroxides are dimethyl dioctadecyl ammonium hydroxide, tetraoctyl ammonium hydroxide, tricaprylmethyl ammonium hydroxide, or mixtures thereof. Tetraoctyl ammonium hydroxide, tricapryl ethyl ammonium hydroxide, or mixtures thereof are especially preferred, with tricaprylmethyl ammonium hydroxide being most preferred. The quaternary ammonium hydroxides described hereinabove can be readily prepared from their corresponding commercially available quaternary ammonium salt, such as a halide. For example, a quaternary ammonium chloride may be contacted with an anion exchange resin such that the chloride is exchanged to produce the corresponding quaternary ammonium hydroxide. Oil-soluble, as used herein, means that the additive is soluble in the mixture at ambient temperatures, e.g., at least to the extent of about 5 wt.% additive in the mixture at 25 β C. As is well known to those skilled in the art, two-cycle engine lubricating oils are often added directly to the fuel to form a mixture of oil and fuel which is then introduced into the engine cylinder. Such lubricant-fuel blends generally contain per 1 part of oil about 20-250 parts fuel, typically they contain 1 part oil to about 30-100 parts fuel. The amount of additive in the mixture can vary broadly depending on the lubricant-fuel mixture ratio. Accordingly, only an amount effective in reducing the smoke of the mixture need be added. In practice, however, the amount of additive added will range from about 0.1 to about 5 wt.%, preferably from about 0.5 to about 1 wt.%, based on weight of lubricant in the lubricant-fuel mixture. The invention will be further understood by reference to the following Example, which include preferred embodiments of this inven¬ tion. Exampl e Three samples of the same lubricant-fuel mixture were tested in a single cylinder Yamaha snowmobile engine to determine the maximum smoke produced by each sample. The mixture comprised a commercially available two-cycle engine lubricating oil and a commercially avail¬ able unleaded gasoline having an RON of 91 and an oil to fuel ratio of 1 to 33. The samples tested were the lubricant-fuel mixture without additives, the mixture with a conventional smoke reducing additive (barium sulfonate), and the mixture with dihydrogenated tallow amine:4-hydroxy-3,5-ditert-butyldithiobenzoate (DTA.-DTB). The maximum smoke produced wher operating the engine at 4500 rpm and applying a 10 N (Newton meter) _oad was measured by inserting an optical opacity smokemeter into the exhaust system. The same procedure was repeated using dihydrogenated tallow amine: dioctyldithiophosphate (DTA:DDP) and tricapryl methyl ammonium hydroxide (TCMAH) instead of DTA:DTB. The results of these tests are shown in Table 1 below. Table 1 The data in Table 1 show that the additives of this inven¬ tion provide a reduction in smoke comparable with that of barium sulfonate (a commercially available additive) without the formation of ash.

Claims: CLAIMS: 1. A lubricating oil-fuel mixture comprising (a) a lubricating oil basestock, (b) a distillate fuel, and (c) one of the following oil-soluble additives; (i) a hydrocarbyl substituted amine salt and/or amide of a compound having the formula R5 wherein X is oxygen or sulfur, and Rj, R2, R3, R4 and R5 are selected from hydrogen; a hydro¬ carbyl group containing from 1 to 24 carbon atoms; a hydroxy group; and an oxygen-containing hydrocarbyl group containing from 1 to 24 carbon atoms and at least one of the radicals Ri, R , R3, R4 or R5 is a hydrocarbyl group containing from 1 to 24 carbon atoms; (ii) a hydrocarbyl substituted amine salt of a CCϋipQUnu iiαVi ng tnc l OFiliU i α R6θ - P - XH OR7 wherein X is oxygen or sulfur and RQ and R7 are selected from hydrogen and a hydrocarbyl group containing from 1 to 28 carbon atoms; or (iii) a quaternary ammonium hydroxide having the formula wherein Rs is a hydrocarbon radical or a hydroxy terminated radical having from 1 to 24 carbon atoms, Rg is a hydrocarbon radical having from 1 to 24 carbon atoms, and Rio and R \ are hydro¬ carbon radicals having from 4 to 24 carbon atoms. 2. The mixture of claim 1 wherein the oil-soluble additive in (c)(i) is an amine salt. 3. The mixture of claim 2 wherein X in (c)(i) and (c)(ii) is sulfur. 4. The mixture of claim 3 wherein the hydrocarbyl substi¬ tuted amine in (c)(i) and (c)(ii) is a tallow amine. 5. The mixture of claim 4 wherein the tallow amine in (c)(i) is a ditallow amine salt of 4-hydroxy-3, 5-di-tert-butyldithio¬ benzoic acid. 6. The mixture of claim 4 wherein the tallow amine in (c)(ii) is a tallow amine salt of an alkyl substituted dithiophos- phoric acid. 7. The mixture of claim 1 wherein the quaternary ammonium hydroxide in (c)(iii) is selected from the group consisting of dimethyl dioctadecyl ammonium hydroxide, tetraoctyl ammonium hydro¬ xide, tricaprylmethyl ammonium hydroxide, and mixtures thereof. 8. The mixture of claim 1 wherein from about 0.1 to about 5 wt.% of the oil-soluble additive is present therein and the volume ratio of lubricant to fuel ranges from about 1:20 to about 1:250. 9. The mixture of claim 8 wherein fuel is gasoline. 10. A method for reducing the smoke emitted from a two- cycle internal combustion engine by operating the engine with the mixture of claim 1.

Inventors: HABEEB JACOB JOSEPH, MAY CHRISTOPHER JOHN, HABEEB, JACOB, JOSEPH, MAY, CHRISTOPHER, JOHN
Applicants: EXXON RESEARCH ENGINEERING CO, EXXON RESEARCH AND ENGINEERING COMPANY
Application year: 1991
Main classification: C10M133
IPC codes: C10L1, C10L10, C10M133, C10M135, C10M169, C10N30, C10N40, F02B75