GB666738A - Extreme pressure lubricants and additives therefor - Google Patents

Abstract

Polyvalent metal soaps of mercapto acids R1SR2COOH, where R1 is an alkyl group, R2 is an alkylene group and where the total number of carbon atoms in R1 and R2 is between 9 and 25, are made by preparing an alkali metal salt of such an acid and forming the soap by double decomposition. R1 has preferably 8-20 C atoms and R2 is a short-chain, preferably of 1-5 C atoms. The mercapto acids may be made by reacting the corresponding mercaptans such as those obtained from petroleum oils, e.g. by the H2S treatment of olefines, with a carboxylic acid or a substance readily converted thereto, containing a double bond, e.g. acrylonitrile and a base, e.g. NaOH, may be present to hydrolyse the mercapto-nitrile as soon as it is formed. The acids may also be made by reacting, e.g. beta-propiolactone with the mercaptan, c.f. Specification 648,672, optionally in the presence of a base such as NaOH or KOH, by reacting the corresponding metal mercaptide, e.g. the sodium salt of a C8-C20 aliphatic mercaptan with a chloro- or other halo-aliphatic acid of up to 10 or more carbon atoms, e.g. beta-chloropropionic or chloracetic acid, or by reacting a C8-C20 aliphatic mercaptan with an unsaturated acid such as undecylenic acid. Branched-chain mercaptans are preferred, especially C8-12 mercaptans. For salt formation sodium hydroxide is preferred and the addition of a water-soluble salt of the polyvalent metal is preferably effected along with a hydrocarbon, e.g. light naphtha or heavier fraction, in which the soap may be soluble. Lead salts are preferred, other salts specified being those of Zn, Mn, Cu, Co, Ca, Ba or Sr. In examples: (1) a C12, and (2) a C8 branched-chain aliphatic mercaptan is reacted with acrylonitrile, the product hydrolysed with NaOH and treated with lead acetate in aqueous solution in the presence of pet. naphtha from which the lead soap is recovered after separation.ALSO:A lubricating oil composition comprises a major proportion of a mineral oil base lubricant and a minor proportion of a polyvalent metal soap of a mercapto acid of formula R1SR2COOH where R1 is an alkyl group and R2 is an alkylene group, and where the total carbon atoms in R1 and R2 is 9-25 R1 preferably has 8-20 C atoms and R2 is a short chain preferably of 1-5 C atoms. Specified metals are Zn, Mn, Cu, Co, Ca, Ba, Sr or Pb, which is preferred. Branched chain C 8-12 mercaptans are preferred. Oil and grease mixtures may be made and the additives used preferably in a concentration of 1-20 per cent. Conventional additives may also be present. A table illustrates the superiority in load characteristics of a lead soap derived from a C12 mercaptan over lead oleate in calcium base greases.