Method for the extraction and transformation, by alcoholysis and hydrolysis, of phthalates contained in pvc plastics

A process for recovering phthalic acid and a reusable target PVC plastic from a PVC feedstock containing at least one phthalate, comprising:

• a) a solid-liquid extraction of said PVC feedstock in the form of particles (1) by placing said particles of the PVC feedstock in contact with a solvent (9) including at least one alcohol of formula CnH2n+1OH, n being a positive integer less than 4 or greater than 8, to produce a liquid phase enriched in said phthalate and a solid phase including PVC plastic depleted in said phthalate;
• b) chemical transformation of said phthalate of said liquid phase into dialkyl phthalate of formula C6H4(COOCnH2n+1)2 by transesterification using said alcohol to enrich said liquid phase in said dialkyl phthalate;
• c) a solid-liquid separation between said solid phase and said liquid phase to produce at least one solid stream including the PVC plastic depleted in said phthalate (6) so as to recover said target PVC plastic;
• d) a separation of said liquid phase, to produce at least a first liquid effluent including said dialkyl phthalate (5, 14) and a second liquid effluent comprising at least said solvent (7, 12);
• e) an optional purification of said first liquid effluent (14) obtained in step d) comprising said dialkyl phthalate, from the phthalate partially converted and/or not converted in step b) and optionally from the soluble impurities, to produce a liquid product (16) consisting essentially of said dialkyl phthalate, and a liquid residue (17) comprising said phthalate partially converted and/or not converted in step b) and optionally said soluble impurities;
• f) an optional additional step f1) and/or optional additional step f2) of chemical transformation, by transesterification, of said phthalate not converted and/or partially converted in step b), to dialkyl phthalate of formula C6H4(COOCnH2n+1)2 using said alcohol, said step f1) being carried out between steps c) and d) by sending said liquid phase obtained on conclusion of all of steps a), b) and c) to a first additional transesterification reactor to produce a second liquid stream (13) enriched in said dialkyl phthalate of formula C6H4(COOCnH2n+1)2, said second liquid stream (13) being sent to step d), and said step f2) being carried out after step e) by sending said liquid residue (17) to a second additional transesterification reactor to produce a third liquid stream (15) enriched in said dialkyl phthalate of formula C6H4(COOCnH2n+1)2, said third liquid stream (15) being sent back to step d);
• g) a chemical transformation of said phthalate obtained in step d) or in the optional step e) to phthalic acid of formula C6H4(COOH)2 by hydrolysis using water to produce an effluent (19) including an aqueous phase comprising said phthalic acid;
• and
• h) a separation of said phthalic acid from step g) and converted to a solid form in order to produce at least one solid stream of phthalic acid (20).