GB723133A - Oxidation-inhibited, silver non-corrosive lubricants - Google Patents

Abstract

Zinc salts of esters of dithiophosphoric acid for use in lubricants are prepared by reacting P2S5 with an alcohol at about 120-200 DEG F. and treating the esters obtained with zinc oxide at 70-170 DEG F. Mixed esters may be obtained using different alcohols, e.g. 3 mols. of methyl and 1 of hexyl alcohol to 1 mol. of P2S5. In examples, isopropyl or sec. butyl alcohol and methylisobutylcarbinol are reacted with P2S5, and the product treated with zinc oxide, in one case in the presence of a petroleum oil as diluent. Water of neutralization is removed with calcium sulphate or by blowing with air.ALSO:A lubricant comprises a major proportion of a lubricating oil, a zinc salt of an ester of dithiophosphoric acid in amount sufficient to inhibit oxidation, and calcium oxide or hydroxide dispersed in said oil in sufficient amount to inhibit the silver corrosivity, the dispersion being stabilized with a polyvalent metal sulphonate. The oil may be mineral or synthetic, e.g. alkylene or alkylene oxide type polymers, dicarboxylic acid esters and liquid esters of phosphorus acids, examples being given. The zinc salts are represented <FORM:0723133/III/1> p where R, R1 are alkyl, aryl, alkaryl aralkyl or other cyclic hydrocarbon radicals, which may contain substituents such as Cl, Br, O and N in proportions such as not to alter substantially their hydrocarbon nature, and containing together 7-50 carbon atoms, R preferably having 1-25 and R1 6-25. Mixed esters wherein R is derived from an alcohol of not more than 4 and R1 from an alcohol of 6-18 carbon atoms are preferred. Many esters are specified. The amount of zinc salt used is preferably .05-2 per cent by weight of the total but concentrates containing 50 per cent or more may be prepared. The polyvalent metal sulphonates include calcium and borium salts of sulphonic acids from petroleum, polyolefins or alkyl aromatic hydrocarbons of molecular weight about 350-900. The amount used is .1-10 per cent, and the amount of lime dispersed .02-7 per cent of the total. The initial dispersion is effected by adding a dihydric alcohol such as ethylene glycol with the calcium oxide or hydroxide to the oil. The sulphonate is then added and the mixture heated to remove the alcohol as described in Specification 718,714. Oiliness, blooming, peptizing and thickening agents, V.I. improvers, and pour point depressants may be incorporated. Examples describe the preparation of zinc salts of mixed esters of diothiophosphoric acid with isopropyl or sec butyl alcohol and methylisobutylcarbinol, and with methyl and hexyl alcohols (see Group IV (b)). The inhibiting effect of varying amounts of a dispersion in oil of calcium oxide stabilized with calcium petroleum sulphonate on the silver corrosion of a solvent-refined oil containing the zinc salt of a mixed ester of dithiophosphoric acid with sec butyl alcohol and methylisopropylcarbinol is illustrated.