Prepn. of 2,2,4-tri-methyl-1, 2-di-hydro-quinoline polymer - contg. dimer, by polymerisation in dil. hydrochloric acid, as rubber antioxidant

A polymer contg. at least 25 wt.% of dimerised 2,2,4-trimethyl-1,2-dihydroquinoline (I) is prepd. by polymerising crude monomeric (I) in presence of 15-25 wt.% of HCl; the amt. of HCl is 0.2-0.5 mols./mol. of (I) + amines present in (I) as impurities. The monomeric (I) may be obtd. by reacting aniline with acetone, diacetone alcohol, or mesityl oxide, at not above 120 deg.C, with p-toluene sulphonic acid as catalyst. The reaction mixt., contg. aniline and high-boiling amines as impurities, may be used without purification, or (I) may be purified. Polymerisation is at 80-100 (90-100) deg.C under atmos. pressure. The polymer may be isolated by dissolving the reaction mixt. in an organic solvent, e.g. benzene, followed by neutralisation and evapn. of the solvent, or the reaction mixt. may be dispersed in water and then granulated. The polymer contg. the dimer is an antioxidant for rubber.