The Dyeing of Cellulose Acetate with Non‐ionic Dyes IIIndashDyeing from the Vapour Phase

Abstract

A study has been made of the absorption from the vapour phase, by secondary cellulose acetate, of five model dyes. These are p‐nitroaniline, NN‐dimethyl‐p‐nitroaniline, azobenzene, p‐aminoazobenzene, and NN′‐dimethyl‐p‐aminoazobenzene. The amounts absorbed at equilibrium have been measured, and their dependence on the vapour pressure of the dyes and the temperature of the substrate has been established.The vapour pressures of the dyes have been measured over a range of temperatures, those of azobenzene by manometry and the remainder by Knudsen's effusion method. The results together with the absorption data yield absorption isotherms from which are derived the isosteric heats of absorption of the dyes on cellulose acetate. The values, in the above order, are as followsndash21.2,–21.4,–17.8,–22.0, a22.7 kcal. /mole.The vapour pressure data are also used to evaluate the heats of vaporisation or sublimation of the dyes. These heats are applied to aqueous dyeing data already published to derive the absolute heats of association of the dyes on cellulose acetate. The results are in substantial agreement with the heats of absorption of the vaporised dyes.A brief study has been made of the absorption by, nylon and Terylene of vaporised azobenzene. The results for nylon yield a value for the heat of absorption of–18.0 kcal./mole. The results for Terylene are insufficiently complete for quantitative treatment.