EXPERIMENTAL EVALUATION OF REGENERATED XYLENE SOLVENT FOR PRIMER PRODUCTION USING THE ECO PLUS 122 SYSTEM

Industrial xylene used in alkyd-primer production undergoes progressive degradation during repeated manufacturing cycles, leading to the accumulation of oxidized aromatic fragments, polymerized species, and moisture-related impurities. These changes adversely affect volatility, density, residue content, and, ultimately, coating-film performance. This study investigates the effectiveness of thermal regeneration using the ECO PLUS 122 system as a method to restore degraded xylene to a quality suitable for reuse in alkyd formulations. The feedstock was first classified into five contamination levels (CXL0 - CXL4), and representative high-severity fractions were regenerated and evaluated across seven physicochemical indicators and three coating-performance metrics. A stable vapour-temperature plateau near 120°C was observed during regeneration, indicating selective evaporation of volatile components while retaining high-molecular-weight residues. Regeneration yield decreased predictably with increasing contamination severity, ranging from 78 % for Low-contamination feedstock to 58 % for Very High-contamination levels. Physicochemical analysis showed substantial restoration of solvent properties: density stabilized at 0.865 - 0.867 g cm⁻³, colour index was reduced to 14 - 19 Pt-Co, residue content returned to 0.08 - 0.12 %, moisture levels remained within 40 - 70 ppm, and volatility deviation was limited to 3 - 6 %. Non-volatile residue values (8 - 16 mg 100 mL⁻¹) confirmed the removal of resinous and polymerized contaminants. Performance testing of alkyd-primer films validated the functional suitability of regenerated xylene. Hardness decreased only slightly from 78 HB (standard) to 73 HB (RXL4), while corrosion loss increased moderately from 12 to 18 mg cm⁻². The drying time remained within 31 - 36 min, compared to 35 min for standard xylene, indicating preserved curing kinetics and evaporation behaviour. Overall, the results demonstrate that thermal regeneration is a reliable, scalable, and environmentally beneficial approach for restoring industrial xylene, reducing solvent waste, and maintaining coating-film performance in alkyd-primer production.