Patent GB-806014-A (GB)
Title: Phenolic antioxidants
IPC: C08K5/13
Filed: 1956-06-04
Abstract: Fats and gasolines contain as antioxidants substituted xylenes having two phenolic substituents linked one to each methyl group thereof, the phenolic substituents having from 0 to 2 ring positions substituted with at least one radical selected from alkyl radicals having 1 to 5 carbon atoms, tertiary alkyl radicals having from 4 to 9 carbon atoms and aralkyl radicals.  Such compounds are obtainable by reacting an a ,a 1-dihalogenated xylene with phenol or a substituted phenol (see Group IV (b)).ALSO:Natural and synthetic rubber compositions comprise as anti-oxidant a substituted xylene having two phenolic substituents linked one to each methyl group, the phenolic substituents having 0 to 2 ring positions substituted with at least one radical selected from alkyl radicals having from 1 to 5 carbon atoms, tertiary alkyl radicals having 4 to 9 carbon atoms and aralkyl radicals (see Group IV (b)).  The rubber-compositions described contain crepe rubber, zinc oxide, sulphur, hexamethylene tetramine, stearic acid and, as antioxidants products obtained by condensing a ,a 1-p-xylene and p-cresol, a ,a 1 - dichloro - o - and p - xylenes and p - cresol, a ,a 1 - dichloro - o - and p - xylenes and o - cresol, a ,a 1 - dichloro - o - and p - xylenes and o - a  - phenylethyl phenol, a ,a 1-dichloro - xylene and 3,4 - xylenol, a ,a 1 - dichloro - xylene and 2,4 - xylenol, a ,a 1 - dichloro - xylene and mixed cresols and a ,a 1-dichloro - xylene and 2,5 - xylenol. The term "rubber" is intended to include natural and synthetic rubbers, e.g. polychloroprene, polymerization products of a major proportion of a mono-olefin, e.g. isobutylene and a minor proportion of a poly-olefin, e.g. butadiene or isoprene, e.g. butyl rubber, the rubbery copolymers of butadiene and styrene and of butadiene and acrylonitrile.ALSO:The invention comprises a substituted xylene having two phenolic substituents linked one to each methyl group, the phenolic substituents having from 0 to 2 ring positions substituted with at least one radical selected from alkyl radicals having from 1 to 5 carbon atoms, tertiary alkyl radicals having from 4 to 9 carbon atoms and aralkyl radicals, and a process of preparing a substituted xylene which includes the step of reacting at 90-200 DEG  C. in the presence of 0.5 to 5 per cent w./w. of a condensation catalyst, a ,a 1-dichloroxylenes with phenol and/or a substituted phenol having up to two ring positions substituted with at least one radical selected from alkyl radicals having from 1 to 5 carbon atoms, tertiary alkyl radicals having from 4 to 9 carbon atoms and aralkyl radicals.  In general the products of the invention can be prepared by reacting a ,a 1-dihalo (i.e. chloro, bromo or iodo) xylenes with phenol or substituted phenols.  Representative phenolic starting materials mentioned include phenols, cresols, xylenols, ethyl and propyl phenols, thymols, carvacrol, mono- and di-a -phenyl ethyl phenols, tertiary-butyl phenol, multiple ring compounds such as naphthols and diphenyl phenols, dihydric phenols such as catechol, resorcinol and hydroquinone, polyhydric phenols such as phloroglucinol and pyrogallol.  The a ,a 1-dihaloxylenes may be reacted with simple phenolic compositions and the products alkylated with isobutylene, tertiary pentenes, octenes or nonenes or with styrene, vinyl toluene or a -methyl styrene. Alternatively the phenolic starting material may be alkylated or aralkylated before reaction with the a ,a 1-dihaloxylenes. Condensation catalysts mentioned include alkane sulphonic acid, sulphuric acid, benzene and toluene sulphonic acids, activated clay, stannic chloride, ferrous and ferric halides, stannous and stannic halides, boron trifluoride, zinc chloride aluminium halides and oxide and metallic iron.  In examples: products in accordance with the invention are produced by condensing p-cresol with a ,a 1-dichloro-p-xylene in the presence of iron filings (1); o-cresol with a ,a 1-dichloro-o- and p-xylenes (2); 3,4-xylenol with a ,a 1-dichloro-p-xylenes (3); 2,4-xylenol with a ,a 1-dichloro-p-xylene (4); mono-tert.-butyl-p-cresol with a ,a 1-dichloro - p - xylene (5); o - a  - phenylethyl phenol with a ,a 1-dichloro-o- and p-xylenes; (6) and mixed xylenes (7), all in the presence of zinc chloride and of benzene also in examples (3), (4) and (7). Volatile constituents are removed from the reaction products by heating in vacuo.  The products are antioxidants for natural and synthetic rubber (see Group IV (a)), oils, gasolines, fats and other unsaturated organic compounds.