GB918801A - Antioxidant compositions - Google Patents

Abstract

Fats, vegetable oils, mineral oils, and waxes are stabilized by incorporating in them as antioxidant a complex mixture of phenolic substances which is obtained by reacting a phenol of formula <FORM:0918801/III/1> where R1 and R2 are hydrogen, methyl, or ethyl radical, the total number of carbon atoms in R1 and R2 together being not greater than 3, with an alkylating agent having 3-12 carbon atoms, to provide a crude alkylate containing a mixture of alkylated and unalkylated phenols, and then reacting the crude mixture with an aldehyde containing at least 2 carbon atoms. The product so obtained contains a mixture of alkylated mono-nuclear phenols, alkylated polynuclear phenols, predominantly of the bisphenol type, and unalkylated polynuclear phenols. The alkyl groups in the substituted phenols may be straight-chain alkyl groups, cycloalkyl groups, aralkyl groups, or halogen substituted aralkyl groups. Aldehydes which may be used for the reaction include glyoxal, propionaldehyde, benzaldehyde, glutaraldehyde, chloral, and aldol.ALSO:Natural and synthetic rubber compositions contain as antioxidant a complex mixture of phenols obtained by reacting a phenol of the formula <FORM:0918801/IV(a)/1> where R1 and R2 are hydrogen, methyl, or ethyl radicals and may be the same or different, the total number of carbon atoms in R1 and R2 together being not greater than 3, with an alkylating agent having 3-12 carbon atoms to provide a crude alkylate containing a mixture of alkylated and unalkylated phenols, and then reacting the crude mixture with an aldehyde containing at least 2 carbon atoms. The mixture so obtained contains alkylated mononuclear phenols, alkylated polynuclear phenols predominantly of the bis-phenol type, and unalkylated polynuclear phenols. The alkyl groups in the alkylated phenols may be straight chain alkyl groups, cycloalkyl groups, aralkyl groups, or halogen substituted aralkyl groups. The mixture of phenols may be incorporated in vulcanized or unvulcanized natural or synthetic rubbers. It is usually added during the compounding of the rubber batch but in some cases it may be applied from a solution to a rubber article by dipping. Specified synthetic rubbers include polymers of 1.3-butadienes and copolymers of these with styrene vinyl naphthalene, acrylic acid, methyl acrylate, acrylonitrile, isobutylene, methyl vinyl ether, and methyl vinyl ketone. In an example, a phenolic mixture, obtained by reacting a mixture of isomeric xylenols with di-isobutylene and reacting the intermediate product with glutaraldehyde, is incorporated in a rubber stock comprising smoked sheet blend, "Calcene T" (Registered Trade Mark), zinc oxide, stearic acid, sulphur, and diphenylguanidine, and in a rubber stock comprising pale crepe rubber, whiting, titanium dioxide, zinc oxide, stearic acid, sulphur, and mercaptobenzothiazole disulphide.ALSO:A phenol of the general formula <FORM:0918801/IV (b)/1> where R1 and R2 are hydrogen, methyl, or ethyl radicals and may be the same or different, the total number of carbon atoms in R1 and R2 combined being not greater than 3, is reacted with an alkylating agent having from 3 to 12 carbon atoms to provide a crude alkylate containing a mixture of alkylated and unalkylated phenols (this latter expression meaning that the phenols contain no alkyl substituents other than methyl or ethyl), and the crude mixture is then reacted with an aldehyde containing at least two carbon atoms so as to convert the unalkylated phenols and at least some of the alkylated phenols to polynuclear phenols predominantly of the bisphenol type i.e. containing two phenol nuclei per aldehyde group of the reactant aldehyde. A mixture is thus obtained which contains alkylated mono-nuclear phenols, alkylated polynuclear (mostly bis) and unalkylated polynuclear phenols. The alkylating agent may be one which introduces into the aromatic nucleus an unsubstituted alkyl group, or an aralkyl, cycloalkyl, or halogen substituted aralkyl group. Phenols, cresols, and xylenols may be used as starting material. The alkylating agent may be an olefin, an organic halide, or an alcohol having 3-12, preferably 4-9 carbon atoms. A large number of suitable alkylating agents is given, and among those specified are butenes, amylenes, hexenes, octenes, nonenes, cyclohexene, cyclopentene, styrene, 3-chlorostyrene, t-butyl chloride, mixed amyl chlorides, mixed amyl bromides, cyclohexyl chloride, cyclopentyl chloride, p-(a -chloroethyl)toluene, benzyl chloride, p-chlorobenzyl chloride, t-butyl alcohol, hexanol-3, nonalon-4, 1.1.3.3-tetramethyl butanol, cyclohexanol, and b -phenylethyl alcohol. When an olefin is used, the alkylation may be carried out in presence of a Friedel-Craft type catalyst at 20-120 DEG C. and pressures up to 1,000 lb./in2. Similar conditions are used when the alkylating agent is an organic halide. Somewhat more vigorous conditions are used when alcohols are employed. Specified aldehydes include glyoxal, acetaldehyde, iso-valeraldehyde, p-chlorobenzaldehyde, salicylaldehyde, chloroacetaldehyde, chloral, and aldol. The condensation with the aldehyde is carried out in presence of a catalyst e.g. sulphuric acid at 20-100 DEG C. Examples are given. The products obtained may be used as antioxidants for natural and synthetic rubber, waxes, fats, vegetable and mineral oils, and thermoplastic resins.