DEINKING CONDITIONS FOR YELLOW DIRECTORY USING FORMAMIDINE SULFINIC ACID AS A REPULPING CHEMICAL

A study was performed to assess the quality of recycled pulp obtained after repulping and flotation of yellow directory. The colour-strippin g efficiency of the printed ink was evaluated by treating yellow pages with formamidine sulfinic acid in an alkaline medium. The effect of a lkalinity and formamidine sulfinic acid concentration on the optical a nd mechanical properties of deinked pulp was measured. The Yellow dye used in a local telephone directory can be significantly decolourized by formamidine sulfinic acid in an alkaline condition. The selective a ddition of a nonionic surfactant could further improve the brightness of the repulped fibre after flotation. The effect of formamidine sulfi nic acid concentration, alkalinity, repulping temperature and buffer s olution was determined on coloured pulps.