GB891234A - New aromatic diamines - Google Patents

Abstract

Mineral oils, such as lubricating oils and motor fuels, are stabilized against oxidation and ozonation by incorporating therein a diamine of the formula <FORM:0891234/III/1> wherein R is a secondary alkyl or cycloalkyl group, and R1 is an alkyl group. The preferred proportions of diamine are from 0,001% to 2,0% of the weight of oil.ALSO:Natural and synthetic rubbers and other synthetic polymers are stabilized against oxidation and ozonization by incorporating therein a diamine of the formula <FORM:0891234/IV (a)/1> wherein R is a secondary alkyl or cycloalkyl group, and R1 is an alkyl group. The diamines are preferably used in proportions of from 0,5 to 5,0% of the weight of rubber or polymer. In Example 5, four mixes are prepared, each containing butadiene styrene copolymer, zinc oxide, stearic acid, high abrasion furnace black, softening agent, processing oil, sulphur, and benzthiazyl sulphencyclohexylamide. N-methyl-N-isopropyl-p-phenylene diamine is added to mix B, N-methyl-N-sec.-butyl-p-phenylene diamine is added to mix C, and 2,2,4-trimethyl-6-ethoxy-1,2-dihydroquinoline is added to mix D. No anti-ozonant is added to mix A. The mixes are cured for 35 minutes at 153 DEG C. Strips of the vulcanized rubbers are exposed in a stretched state to air containing 10 parts of ozone per 108 parts of air, and the degree of surface-cracking is observed periodically. The rubbers prepared from mixes B and C are superior to the other two. Example 1 gives the results of tests on the resistance to ozonized oxygen of solutions of natural rubber in chloroform containing (A) no anti-ozonant, (B) N,N1-di-sec.-butyl-p-phenylene diamine, (C) N-methyl-N-isopropyl-p-phenylene diamine, (D) N-methyl-N-cyclohexyl-p-phenylene diamine, (E) N-methyl-N-sec.-butyl-p-phenylene diamine, and (F) N-ethyl-N-isopropyl-p-phenylene diamine. Solutions (C), (D), (E) and (F) are markedly superior to solution (B) in resistance to ozonation. The anti-ozonant effect of the N,N-disubstituted p-phenylene diamines is enhanced by the incorporation of paraffin or microcrystalline wax in the rubber. Other synthetic rubbers referred to are polymers of butadiene, isobutene, methylbutadiene, and chlorobutadiene, and copolymers of these compounds with each other or with acrylonitrile, styrene, and methyl methacrylate. Other polymers which may be treated are polythene, polypropylene, polyvinyl chloride and polystyrene.ALSO:Disubstituted p-phenylene diamines of the formula <FORM:0891234/IV (b)/1> wherein R is a secondary alkyl or cycloalkyl group and R1 is an alkyl group, are produced by reduction of a disubstituted aniline <FORM:0891234/IV (b)/2> wherein X is a nitroso, nitro or azo group. The reduction may be carried out (i) with hydrogen in the presence of nickel, palladium, or platinum, (ii) with zinc, iron or tin in the presence of aqueous acids, or (iii) by sodium sulphide or sodium hydrosulphite in the presence of alkali. R may be isopropyl, secondary butyl, secondary amyl, hex-2-yl, oct-2-yl, cyclohexyl, 2-methylcyclohexyl, or 4-methylcyclohexyl. R1 may be any C1-C4 alkyl group. In Example 1, sodium nitrite is added slowly to an ice-cold solution of N-methyl-N-isopropyl aniline dissolved in dilute hydrochloric acid. After stirring for 2 hours, any excess nitrous acid is removed by addition of urea or sulphamic acid. Zinc dust and hydrochloric acid are then added, and the mixture is stirred until a colourless solution is obtained. The solution is made alkaline with sodium carbonate, benzene is added, and the mixture is filtered. The benzene layer is separated from the filtrate, dried with sodium sulphate, and distilled under reduced pressure to yield N-methyl-N-isopropyl-p-phenylene diamine. Examples 2 and 3 describe the preparation of N-methyl-N-cyclohexyl- and N-ethyl-N-isopropyl-p-phenylene diamine, respectively. In Example 6, sulphanilic acid is diazotised, and the diazonium compound is coupled with N-methyl-N-isopropylaniline. The azo compound is then reduced with sodium hydrosulphite, in the presence of sodium hydroxide, to give N-methyl-N-isopropyl-p-phenylene-diamine. Example 7 describes the preparation of N-methyl-N-sec.-butyl-p-phenylene diamine by reduction of N-methyl-N-sec.-butyl-4-nitroaniline with iron filings and formic acid. The disubstituted p-phenylene diamines have use in the preservation of natural and synthetic rubbers (see Group IV(a)) and also in the stabilization of mineral oils (see Group III).