INK REMOVAL FROM POLYPROPYLENE SHEETS BY ALKYLTRIMETHYLAMMONIUMBROMIDES: THE EFFECT OF CONCENTRATION, ALKYL CHAIN LENGTH OF CNTAB AND TEMPERATURE ON THE SOLUBILIZATION OF INK

摘要

The removal of printed solvent-based ink from polypropylene (PP) sheets was investigated by using cationic surfactants having different carbon atoms of the alkyl chain length, 12, 14 and 16 for dodecyl-, tetradecyl-and cetyl-trimethylammonium bromides (i.e., DTAB, TTAB, and CTAB, respectively). The amount of ink removed by CnTAB (alkyltrimethylammonium bromide) improved as the CnTAB concentration or the number of carbon atoms of the alkyl chain length of CnTAB increased at 30 °C. Complete deinking at this condition occurs at 7xCMC, 14xCMC and 18xCMC for CTAB, TTAB and DTAB, respectively, where CMC is the critical micelle concentration. Increasing the temperature from 35 ° to 50 °C either improved or decreased deinking depending on the surfactant concentration. Solubilization, which plays an important role in the deinking process when concentration exceeds CMC, gives a good explanation for the effect of surfactant concentration and the alkyl chain length of surfactant at 30 °C. The ability of ink particle to be solubilized in CnTAB solutions increases with increasing CnTAB concentration and the number of carbon atoms of the alkyl chain length of CnTAB which agree well with deinking performance at the same temperature. In contrast, the solubilization of ink particles decreases systematically with increasing temperatures in the range 35 ° -50 °C and can not explain the non-sequence of deinking levels at the same temperature range. This may be explained by the characteristic of ink removed from the PP surface which was tiny and of uniform size and suspended in blue solution at 30 °C, but were larger with irregular shape and non uniform size in clear solution when the temperature was higher than 30 °C.