Patent GB-678118-A (GB)
Title: Improvements in or relating to the prevention of oxidation of organic compounds
IPC: C07C69/52
Filed: 1950-08-15
Abstract: As antioxidants in synthetic rubber are employed gem-bis-(2-hydroxy-5-alkoxyphenyl)-alkanes, particularly those of the general formula <FORM:0678118/IV (a)/1> (wherein R represents an alkyl group and R1, R11 and R111 represent hydrogen atoms or alkyl groups), alone or in conjunction with other antioxidants (e.g. phenyl-b -naphthylamine, naphthols, substituted naphthols, substituted phenols, substituted catechols, substituted hydroquinones, alkyl phenol sulphides or ketone-amine condensation products).  In an example, 0.25 per cent of 2 : 2-bis-(21-hydroxy - 31 - tert. - butyl - 51 - methoxyphenyl)-propane is added to a low unsaturation isobutylene-isoprene copolymer.  Other synthetic rubbers specified are polymers of conjugated diolefines having 4-6 carbon atoms in the molecule (e.g. 1 : 3-butadiene, isoprene, 2 : 3-dimethylbutadiene - 1 : 3, 2 - chlorobutadiene, piperylene or 2-methylpentadiene-1 : 3) or copolymers thereof with mono-ethylenically unsaturated compounds (e.g. acrylonitrile, methyl methacrylate, styrene, a -methylstyrene, vinylnaphthalenes, vinyl ketones, vinylidene chloride or diethyl fumarate.  Specification 513,521 is referred to.ALSO:The invention comprises gem-bis-(2-hydroxy-5-alkoxyphenyl)-alkanes, particularly those of the general formula <FORM:0678118/IV (b)/1> (wherein R represents an alkyl group and R1, R11 and R111 represent hydrogen atoms or alkyl groups) and use thereof as antioxidants for hydrocarbons and natural or synthetic rubber (alone or with other antioxidants, of which a list is given).  The antioxidants may be prepared by condensing an aldehyde or ketone with two molecular proportions of the appropriate alkoxyphenol in the presence of approximately one molecular proportion of sulphuric or hydrochloric acid, preferably with the addition of a trace of a mercapto-acid when using a ketone, and advantageously in a solvent at a temperature not above about 50 DEG C.  In examples: (1) 2-tert.-butyl-4-methoxyphenol is agitated with acetone in heptane in the presence of concentrated hydrochloric acid and thioglycollic acid; (2) 4-methoxyphenol is allowed to stand with acetone and hydrochloric acid; (3) 2-tert.-butyl-4-methoxyphenol is warmed and agitated with aqueous formaldehyde and hydrochloric acid. A list of additional products is given, and also examples of synthetic rubber and hydrocarbon oil compositions containing the products as antioxidants (see Groups III and IV (a)).  Specification 513,521 is referred to.ALSO:As antioxidants in hydrocarbon oils (e.g. lubricating oils or motor fuels) are employed gem-bis-(2-hydroxy-5-alkoxyphenyl)-alkanes, particularly those of the general formula: <FORM:0678118/III/1> (wherein R represents an alkyl group and R1, R11 and R111 represent hydrogen atoms or alkyl groups), alone or in conjunction with other antioxidants (e.g. phenyl-b -naphthylamine, naphthols, substituted naphthols, substituted phenols, substituted catechols, substituted hydroquinones, alkyl phenol sulphides or ketone-amine condensation products).  Suitable proportions of antioxidant are 0.0003-0.015 per cent by weight in gasoline and 0.02-10 (preferably 1-2) per cent by weight in lubricating oils. Examples describe the addition of 2 : 2-bis-(21 - hydroxy - 31 - tert. - butyl - 51 - methoxyphenyl)-propane to the following materials: a cracked leaded commercial premium gasoline; a grease comprising a metal stearate thickened mineral oil; a highly refined mineral oil.  It is also stated that the antioxidants are particularly useful in turbine oils (highly refined lubricating oils containing rust preventives, pour depressants, V.I. improvers, metallic soaps and other additives). Specification 513,521 is referred to.