Removing paraffin‐based wax coatings from old corrugated containers using supercritical carbon dioxide

Supercritical carbon dioxide (SC‐CO 2 ) extractions of paraffin‐based wax coatings from saturated and curtain‐coated old corrugated containers (OCC) are reported. Extractions were performed in a 500‐mL reactor (300 bar, 100°C, 50 g CO 2 /min and 1 h). Wax removal efficiencies of 98 and 70% for saturated and curtain‐coated OCC, respectively, were obtained. Under similar conditions, extractions in the presence of water resulted in an extraction efficiency of 99% for saturated OCC. Decreasing the operating pressure to 200 bar decreased the extraction efficiency to approximately 50%. Gas chromatography (GC) of the wax coatings on OCC, before and after extraction with SC‐CO 2 , showed a slight shift in the molecular weight distribution of the paraffin wax (after SC‐CO 2 extraction) toward higher molecular weights for both saturating wax and curtain‐coating wax. There was no evidence of chemical degradation or modification of the paraffin wax coatings by SC‐CO 2 . The packing density, packing arrangement, and dimensions of the curtain‐coated OCC in the extraction apparatus affected the extraction efficiency. Loose packing compared to tight packing, 1 × 1 cm squares versus 1 × 20 cm strips, had higher extraction efficiencies; a random packing arrangement was better than packing with the fluting material in the direction of SC‐CO 2 flow. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2699–2704, 2002