GB790568A - Aryl polysulphides and their production and cutting oils containing the same - Google Patents

Abstract

Aryl polysulphides are prepared by adding a mixture of alkyl substituted benzyl monochlorides and alkyl substituted xylylene dichlorides in which the molar ratio of monochlorides to dichlorides is at least 2 : 1 and preferably 3 : 1, to a stoichiometric excess of an alkali-metal polysulphide at a temperature of at least 160 DEG F., the rate of addition not exceeding substantially the rate of reaction of the mixture of aryl chlorides with alkali metal polysulphide. The aryl polysulphides are used in cutting-oil compositions (see Group III). The polysulphides obtained, which contain an average of 3-4 sulphur atoms in each sulphur bridge, may be reacted further with elemental sulphur to give products containing an average of nearly 5 sulphur atoms per sulphur bridge. Alternatively the mixture of aryl chlorides may be reacted simultaneously with alkali metal polysulphide and sulphur. The reactions are preferably carried out in a hydrocarbon diluent such as a gas oil or fuel oil. The product is a mixture of compounds of formula R-Sx-R1-Sx-R and R-Sx-R wherein R is an alkyl-substituted benzyl radical, R1 is an alkyl-substituted xylylene radical and x is at least 3. Polysulphides of formula R-Sx-R1-Sx-R may be prepared individually or in selected combination by appropriate selection of starting materials or by separation from a mixture of polysulphides using selective solvents such as 2-methyl-2 : 4-pentanediol, pentane, isopropanol and amyl alcohol. The mixture of mono- and di-chlorides used as starting material may be prepared by reacting alkyl-substituted benzenes with formaldehyde and hydrogen chloride. In an example a catalytic reformate, comprising approximately equal parts of trimethyl- and ethylmethyl-benzenes together with minor amounts of other alkylbenzenes, was reacted with hydrochloric acid and paraldehyde to give a product containing trimethyl- and methyl-ethyl-benzyl monochlorides and the corresponding xylylene dichlorides, in a ratio of approximately 3 : 1, together with unreacted material. This mixture was slowly added to a mixture of aqueous sodium tetrasulphide and gas oil and the whole refluxed to give a concentrate containing a mixture of the corresponding benzyl tetrasulphides and xylylene ditetrasulphides having sulphur bridges containing about 4 sulphur atoms. The concentrate was treated further with sulphur to give approximately 5 sulphur atoms in the sulphur bridges.ALSO:Aryl polysulphides containing alkyl benzyl and alkyl xylylene radicals (see Group IV (b) are used as additives in cutting oil compositions. The polysulphides may be used as concentrates in hydrocarbon diluents such as gas or fuel oils. The concentrates may be blended with mineral cutting oil bases and free sulphur may be present in the composition. Other specified additives are lard oil, graphite, chlorinated wax, chlorinated biphenyl and antioxidants. In an example aryl polysulphide concentrates in gas oil are blended with a mineral lubricating oil containing dissolved sulphur, and such a blend also containing lard oil and a chlorinated biphenyl is tested in metal working operations.