Monitoring and characterization of ink vehicle autoxidation by inverse gas chromatography

It is now well-established that increased usage of vegetable oils in offset ink formulas aggravates the deinking problems in recycling plants during summer months. The seasonal loss of brightness of recycled paper has been ascribed to increased bonding of oxidatively aged prints to the paper surface. The progress of the oxidative aging of soya bean and linseed oils was followed by inverse gas chromatography. We first report here the rate and extent of vegetable oil oxidation, by measuring the changes in Kovats retention index as a function of the oxidation time. We then characterized the physicochemical changes accompanying the oxidation of vegetable oils from measurements of the partial heat of mixing in the infinite dilution regime.