GB714497A - Improvements in or relating to lubricating oils - Google Patents

Abstract

Polythio and poly seleno-acetic acid esters of the general formula R.OOC.CH2-(X)n-CH2.COO.R wherein R is an alkyl, aryl or cycloalkyl radical which may contain halogen substituents, X is sulphur or selenium and n is 2, 3 or 4 when X is sulphur and is 2 or 3 when X is selenium may be prepared by the following methods. In the case where X is sulphur, the corresponding a -chloro or bromo-acetic esters may be reacted with sodium di- or polysulphides in alcoholic solution, the corresponding a -mercapto esters may be oxidized to give the disulphides or the a -mercapto esters may be reacted with sulphur dichloride or monochloride to give the tri- and tetra-sulphides respectively. Thus, in example (1) n-butyl monochloracetate and alcoholic sodium disulphide yield di-n-butyl-dithiodiacetate; (2) sodium polysulphide used as in (1) yields di-n-butyl-trithiodiacetate; (3) n-butyl thioglycollate and sulphur monochloride in benzene yield di-n-butyl tetrathiodiacetate. In like manner, ethyl monochloracetate may be used to form a mixture of diethyl di- and tri-thiodiacetates, 2-ethyl-hexyl monochloracetate to form di (2-ethyl-hexyl) trithiodiacetate, cyclohexyl monochloracetate to form the dithiodiacetate and b -chloroethyl chloracetate to form di (b -chloroethyl) dithiodiacetate. The aryl dithio esters are preferably prepared via the Bunte salts; thus, phenyl monochloracetate may be reacted with sodium thiosuphate and the product converted into the disulphide by addition of iodine. The diseleno compounds such as di (n-butyl) diselenoacetate may be prepared by reacting the a -halo ester such as n-butyl chloracetate with aqueous alcoholic sodium or potassium seleno-sulphate. The triseleno esters may be prepared by treating the corresponding seleno mercaptans with selenium oxychloride in ice-cold carbon disulphide; the seleno mercaptans are obtained from the a -halo esters by reaction with sodium hydrogen selenide in alcoholic solution in an atmosphere of hydrogen. The acetate-esters are use in lubricating-oil compositions (see Group III). The Provisional Specification defines "n" in the above general formula as an integer not less than 2.ALSO:Extreme pressure additives have the general formula ROOC.CH2-(X)n-CH2-COOR where R is an alkyl, aryl or cycloalkyl radical which may contain halogen substituents, X is sulphur or silenium and n is 2 or 3 or, when X is sulphur, may also be 4. Thus, a lubricating composition comprises a mineral lubricating oil base, a minor proportion of an additive as defined above sufficient substantially to increase the load-carrying capacity of the oil and a minor proportion of a mercapto-arylene-thiazole, a derivative thereof or an alkyl thiuram disulphide to inhibit the staining of copper or cuprous metals, or of an organic halogenated compound further to increase the load-carrying capacity of the oil. Moreover, a turbine oil comprises a mineral lubricating oil base, a minor proportion of one of the above defined ester additives sufficient substantially to increase the load carrying capacity of the oil, the addition being halogen free, and agents controlling oxidation stability and corrosion of ferrous metals. In a modification, a lubricating composition comprises a mineral lubricating oil base and a minor proportion sufficient substantially to increase the load carrying capacity of the oil, of an additive ester of the above general formula, n being 3 or 4 when X is sulphur and 2 or 3 when X is selenium. Examples of the ester-additives are diethyl dithio diacetate, di-n-butyl trithio diacetate, diphenyl dithio diacetate, di-n-butyl diseleno diacetate, di-n-butyl tetrathio diacetate, di-(2-ethyl hexyl) trithiodiacetate, dicyclohexyl dithiodiacetate and di (b -chlorethyl) dithiodiacetate. The anti-oxidants specified for use include tert.-butyl cresol, 2:4-dimethyl-6-tert.-butyl phenol, 2.6-di-tert,-butyl-p-cresol, diphenolamine and phenyl-a or b -naphthylamine. The anti-corrosion compounds are preferably the acid esters of long chain mono-esters of polyhydric alcohols described in Specification 643,025. The copper-stain inhibitor may be mercapto-benzothiazole, benzothiazole disulphide, benzothiazole hydroxymethyl sulphide, tetramethyl or tetraethyl thiuram or any other described in Specification 561,941. Specified halogenated organic compounds are hexachlorethane and chlorinated paraffin wax. The polythio and sclero acetate esters are used in amounts of up to 10 per cent. Examples are given. The preparation of the esters is described (see Group IV (b)). The Provisional Specification defines "n" in the above general formula as an integer not less than 2.