GB820170A - Improvements in rubber compositions and in antioxidants therefor - Google Patents

Abstract

A composition of natural or synthetic rubber has incorporated therein as a non-staining antioxidant a bis-(3-methyl-4-hydroxy-5-hydrocarbon phenyl)-cycloalkane: <FORM:0820170/IV (a)/1> wherein n is an integer from 1 to 10 and R is a monovalent tertiary alkyl radical or an aralkyl radical of from 4 to 10 carbon atoms. Specified alkylating agents for producing the R radicals are isobutylene, isoamylene, 2-methyl pentene-1, 2-ethyl pentene-1, 2-methyl propene-1, 2-ethyl propene-1, 2-methyl hexene-1, di-isobutylene, styrene, a -methyl styrene, p-methyl styrene, p-methyl a -methyl styrene, and the corresponding ethyl and propyl styrenes, allyl benzene, limonene, and camphene. Particularly effective antioxidants are 1,1-bis-(3-methyl-4-hydroxy-5-t-butyl phenyl)-cyclohexane and 1,1-bis-(3-methyl - 4 - hydroxy - 5 - alpha - phenylethyl phenyl)-cyclohexane. The natural or synthetic rubber composition preferably contains 0.1 to 5 parts by weight of antioxidant per 100 parts rubber. Specified synthetic rubbers are polymers of conjugated dienes, such as butadiene-1,3, piperylene, isoprene, 2,3-dimethylbutadiene-1,3, chloroprene, cyano-butadiene-1,3, and copolymers thereof with styrene, chlorostyrene, isobutylene, acrylonitrile, methacrylonitrile, acrylic and methacrylic acids, alkyl acrylates and methacrylates, vinylidene chloride, vinyl pyridine, or other unsaturated compound copolymerizable therewith. In an example is described the preparation of 1,1-bis-(3-methyl-4-hydroxy - 5 - t - butylphenyl) - cyclohexane (see Group IV (b)), and tests of the oxygen resistance and flexing resistance after ageing of a natural rubber composition containing this antioxidant.ALSO:An antioxidant for natural or synthetic rubber consists of a bis (3-methyl-4-hydroxy-5 hydrocarbon phenyl) cycloalkane of the formula <FORM:0820170/IV (a)/1> wherein n is an integer from 1 to 10 and R is a monovalent tertiary alkyl radical or an aralkyl radical of from 4 to 10 carbon atoms. The compound is prepared by alkylating a bis (3-methyl-4-hydroxy phenyl cycloalkane. Specified alkylating agents for producing the R radicals are isobutylene, isoamylene, 2-methyl pentene1,2 - ethyl pentene - 1,2 - methyl propene - 1,2-ethyl propene - 1,2 - methyl hexene - 1, di - isobutylene, styrene, a - methyl styrene, p-methyl styrene, p-methyl a -methyl styrene, and the corresponding ethyl and propyl styrenes, allyl benzene, limonene, and camphene. The alkylating reaction is preferably effected at above 50 DEG C. in the presence of a solvent such as hexane, heptane, benzene, toluene, or hydrochloric or acetic acid, and of an acidic condensation catalyst, e.g. sulphuric or para-toluene sulphonic acid, boron trifluoride, boron trifluoride etherate, zinc chloride, ferric chloride, aluminium chloride, hydrogen chloride, phosphoric acid, or an acid-activated clay. At least 2 mols. of the alkylating agent are reacted with 1 mol. of the cycloalkane. In an example there is described the preparation of 1,1 bis-(3-methyl-4 - hydroxy 5 - t - butyl - phenyl) cyclohexane by the reaction of 1-1 bis-(3-methyl-4-hydroxyphenyl) cyclohexane and isobutylene in the presence of benzene and concentrated sulphuric acid.