PROCESS FOR PURIFYING A PVC CONTAINING HEAVY METALS

• Main Authors: MOREL, Patrick, DEYRIS, Pierre-Alexandre, LAURENT, Mickaël, GRISON, Claude
• Format: Patent
• Language: English; French; German
• Published: 21.08.2024
• Subjects: AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F,C08G; CHEMISTRY; COMPOSITIONS BASED THEREON; GENERAL PROCESSES OF COMPOUNDING; INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS; MAKING GRANULES OR PREFORMS; METALLURGY; ORGANIC MACROMOLECULAR COMPOUNDS; PERFORMING OPERATIONS; PREPARATION OR PRETREATMENT OF THE MATERIAL TO BESHAPED; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIALCONTAINING PLASTICS; THEIR PREPARATION OR CHEMICAL WORKING-UP; TRANSPORTING; WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL; WORKING-UP

The invention relates to a method for purifying a polyvinyl chloride (PVC) polymer comprising at least one heavy metal compound. The method aims to extract heavy metals from PVC formulations and to recover PVC or PVC compounds free of heavy metal compounds. The method consists in dissolving (a) the PVC using a green solvent, 2-methyltetrahydrofuran (2-MeTHF). The heavy metals are subsequently separated (b) from the organic PVC solution, either by centrifugation or by solubilisation, and transferred to an aqueous phase. The PVC is subsequently precipitated (c) under specific conditions related to the nature of the solvent. The recovered PVC (d, e) is in powder form comprising the PVC additives free of the extracted heavy metals. The method operates in a closed loop, wherein the solvents are recycled (f) in order to limit the environmental impact of the method.