GB586333A - Anti-oxidants for mineral lubricating oils - Google Patents

Abstract

Oxidation of mineral lubricating oils is inhibited by incorporating therein 0.02 to 5 per cent. of a substance of the general formula:- <FORM:0586333/III/1> where R and R1 are the same or different aliphatic, aromatic or alkyl-substituted aromatic groups, X is oxygen or sulphur, a, b and n are each 0 or 1 and x is 2, 3 or 4. Particularly suitable is a substance of the general <FORM:0586333/III/2> formula:- (RX)2P-(S) x-P(RX)2 where R, X, n and x have the significance given above. The R groups may contain substituent groups or atoms such as alkyl, aryl, alkoxy, carboxyl, hydroxyl, sulphhydryl, nitro, amino, aldehyde, esterified carboxyl or halogen - substituted hydrocarbon groups or halogen atoms. Specific substances mentioned are bis [di(octylphenoxy) phosphorus] disulphide, bis [di(octylphenoxy) thiophosphorus] trisulphide, bis [di(2-ethylhexoxy) phosphorus] tetrasulphide, bis [di-(4-methyl-cyclohexoxy) thiophosphorus] trisulphide and bis (dicresyl thiophosphorus) disulphide. The mineral lubricating oil employed may be a hydrogenated oil or a white oil and, if desired, may be blended with animal, vegetable or fish oils or their hydrogenated or voltolized products. The lubricating oil compositions may also contain detergents such as metal soaps, metal petroleum sulphonates, metal phenates, metal alcoholates, metal alkyl phenol sulphides, metal organo phosphates, thiophosphates, phosphites and thiophosphites, metal salicylates, metal xanthates and thioxanthates, metal thiocarbamates, reaction products of metal phenates and sulphur, reaction products of metal phenates and phosphorus sulphides and metal phenol sulphonates. Specific detergents mentioned are barium tert. octyl phenol sulphide, calcium tert, amyl phenol sulphide, nickel oleate, barium octadecylate, calcium phenyl stearate, zinc diisopropyl salicylate, aluminium naphthenate, calcium cetyl phosphate, barium di-tert. amyl phenol sulphide, calcium petroleum sulphonate, zinc methyl cyclohexyl thiophosphate and calcium dichlorostearate. Other addition agents which may be present in the lubricating oil compositions are dyes, pour depressors, heat-thickened fatty oils, sulphurized fatty oils, organo-metallic compounds, metallic or other soaps, sludge dispersers, antioxidants, thickeners, viscosity index improvers, oiliness agents, resins, rubber, olefin polymers, voltolized fats, voltolized mineral oils, voltolized waxes, colloidal solids such as graphite or zinc oxide and solvents and assisting agents such as esters, ketones, alcohols, aldehydes, and halogenated or nitrated compounds. Alcohols specifically mentioned are octyl, lauryl, cetyl, stearyl, heptadecyl, oleyl, phenyl octyl and octadecyl benzyl alcohols, naphthenic alcohols, alcohols found in woolfat and sperm oil and alcohols prepared by the oxidation of petroleum hydrocarbons such as paraffin wax or petrolatum. Instead of the pure alcohols, natural products, such as woolfat or sperm oil, containing the alcohols may be employed. The lubricating oil compositions may be crankcase lubricants, extreme pressure lubricants, engine flushing oils, general machinery oils, rust preventive compositions or greases. In examples, mineral lubricating oil compositions are described which contain (1) bis [di(tert.-octylphenoxy) thiophosphorus] trisulphide with or without iron naphthenate, (2) bis [di(4-methyl-cyclohexoxy) thiophosphorus] trisulphide and iron naphthenate, (3) bis [di(tert.-octylphenoxy) thiophosphorus] trisulphide and the calcium salt of a petroleum sulphonic acid, (4) bis [di-(4-methyl-cyclohexoxy) phosphorus] disulphide, barium para-octyl phenol sulphide and sodium-calcium petroleum sulphonates and (5) bis (dicresyl thiophosphorus) disulphide and barium 2, 4-diamyl phenol sulphide. Specification 559,685 is referred to.ALSO:Substances of the general formula <FORM:0586333/IV/1> where R and R1 are the same or different aliphatic, aromatic or alkyl-substituted aromatic groups, X is oxygen or sulphur, a, b and n are each 0 or 1 and x is 2, 3 or 4, are employed as anti-oxidants for mineral lubricating oils. Particularly suitable are those substances of the general formula <FORM:0586333/IV/2> where R, X, n and x have the significance given above. The R groups may contain substituent groups or atoms such as alkyl, aryl, alkoxy, carboxyl, hydroxyl, sulphhydryl, nitro, amino, aldehyde, esterified carboxyl or halogen-substituted hydrocarbon groups or halogen atoms. Specific substances mentioned are bis-[di-(octylphenoxy) phosphorus] disulphide, bis-[di-(octylphenoxy) thiophosphorus] trisulphide, bis-[di-(2-ethyl-hexoxy) phosphorus] tetrasulphide, bis-[di - (4 - methyl - cyclohexoxy) thiophosphorus] trisulphide, bis-(dicresyl thiophosphorus) disulphide and bis-[di-(4-methylcyclohexoxy) phosphorus] disulphide. The substances are prepared by first reacting an alcohol, phenol or aliphatic or aromatic mercaptan with a sulphide of phosphorus, such as P2S3, P2S5, P4S3 or P4S7, to form a partially esterified thiophosphorus or thiophosphoric acid, and then further reacting this product as such or in the form of a metal salt with an oxidising agent, such as iodine, potassium tri-iodide, ferric chloride, sodium hypochlorite or oxygen itself, or with a sulphur halide such as sulphur dichloride or sulphur monochloride. Suitable alcohols which may be employed include octyl alcohol, cetyl alcohol, stearyl alcohol, methyl cyclohexanol, oleyl alcohol, wax alcohols, phenyl ethyl alcohol and phenyl octyl alcohol. Sulphurized alcohol such as sulphurized oleyl alcohol may also be used. Included with the phenols are their alkylated derivatives and the naphthols as well as derivatives of these containing substituents such as halogen, nitro groups, amino groups, carboxyl groups and esterified carboxyl groups. Typical preferred phenolic materials are the cresols, xylenols, mesitol, butyl phenol, amyl phenol, diamyl phenol, tertiary octyl phenol, cetyl phenol, octadecyl phenol, cashew nut shell phenol, phenyl phenol, petroleum phenols and wax alkylated phenols. Instead of the phenols themselves there may be employed phenol sulphides, such as those obtained by reacting phenols with sulphur halides. Among these phenol sulphides are included tertiary octyl phenol sulphide, di-tertiary amyl phenol sulphide, cetyl phenol sulphide and wax alkylated phenol sulphides. Suitable products may also be prepared from mixed organosubstituted thio acids of phosphorus, for example those prepared by reaction of a sulphide of phosphorus with a mixture of a phenol and an alcohol, a phenol and a mercaptan, a phenol sulphide and an alcohol, a phenol and a phenol sulphide, an alcohol and a mercaptan or a cyclic alcohol and a straight chain alcohol. Thus, for example, a mixture of tertiary octyl phenol sulphide and decanol may be treated with P2S5 and the resulting mixed thiophosphoric acid converted to the desired di-, tri-or tetra-sulphide. In examples: (1) 2-ethyl hexanol is reacted with P2S3 and the product neutralized with alcoholic sodium hydroxide; the neutralized product is then reacted with sulphur monochloride to give bis-[di-(2-ethylhexoxy) phosphorus] tetrasulphide; (2) tert.-octyl phenol is reacted with P2S5 and then with sulphur dichloride to give bis-[di-(tert.-octyl-phenoxy) thiophosphorus] trisulphide; (3) 4-methyl-cyclohexanol is reacted with P2S5 and then with sulphur dichloride to give bis-[di - (4 - methyl - cyclohexoxy) thiophosphorus] trisulphide; and (4) m-cresol is reacted with P2S5 in presence of pyridine; the pyridine salt of di-m-cresyl-dithiophosphoric acid thus obtained is oxidised with potassium tri-iodide to give bis-(dicresylthiophosphorus) disulphide. Specification 559,685 is referred to.