Verfahren zur Herstellung von als Haerter fuer Epoxydharze dienenden Dianhydriden aromatisch substituierter Tetracarbonsaeuren

摘要

The invention comprises aralkyl dianhydrides of the general formula wherein R, R1, R11 and R111 may be the same or different and represent hydrogen atoms or alkyl groups such that and each contain 2 to 6 carbon atoms and Ph. is a phenylene group which may be substituted with alkyl radicals containing 1 to 6 carbon atoms. They may be prepared by condensing polyalkylbenzenes of the formula conveniently technical mixtures of isomers, with maleic anhydride at at least 135 DEG C. in the presence of a free radical catalyst, e.g. inorganic and organic peroxides, peroxy acids and various nitrogen-containing compounds and organometallic compounds. Alternatively the dianhydrides may be obtained by the above process employing monoanhydrides of the general formula as starting materials. The dianhydrides, may be used as curing agents for epoxy resins (see Division C3). U.S.A. Specification 2,949,441 is referred to.ALSO:The invention comprises curable compositions comprising an epoxy resin and one or more dianhydrides of the general formula wherein R, R1, R1 1 and R1 1 1 may be the same or different and represent hydrogen atoms or alkyl groups such that and each contain 2 to 6 carbon atoms and Ph is a phenylene group which may be substituted with alkyl radicals containing 1 to 6 carbon atoms, in such amounts that the ratio of anhydride equivalents to epoxy equivalents is at least 0.6:1. It is preferred that the ratio be 0.85:1 to 1.5:1 and particularly effective dianhydrides are phenylene-bis-(3-butane-1, 2-dicarboxylic acid anhydride) and phenylene-bis-(3-methyl-3-butane-1, 2-dicarboxylic acid anhydride). The duration and temperature of the curing reaction can be varied considerably but the compositions are suitably cured by heating first to 75 DEG to 85 DEG C. for 2 to 3 hours and then at 150 DEG to 250 DEG C. for 10 to 24 hours to obtain cured resins having maximum heat distortion temperatures. Reinforcing materials, inert powders, fillers, pigments and auxiliary catalyst extenders may also be present in the curable compositions. Specified epoxy resins are epichlorohydrin-bis-phenol-A liquid resins; epoxidized esters of polyethylenically unsaturated monocarboxylic acids, unsaturated alcohols and unsaturated carboxylic acids; epoxidized derivatives of polyethylenically unsaturated polycarboxylic acids; epoxidized polyesters obtained by reacting an unsaturated polyhydric alcohol and/or unsaturated polycarboxylic acid or anhydride and epoxidized polymers; and polymers of diolefins. Specified auxiliary materials that may be present are benzyldimethylamine and pyromellitic dianhydride. U.S.A. Specification 2,949,441 is referred to.