Method for recycling a plastic material
AssigneeSolvay (Societe Anonyme)
InventorsBernard Vandenhende, Jean-Philippe Dumont
Life of this patent
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Abstract
Process for recycling a plastic, according to which the plastic is brought into contact with a solvent capable of dissolving the same and the plastic dissolved in the solvent is precipitated using a non-solvent in the presence of a phase-separating agent, in which the phase-separating agent is compatible with the solvent and incompatible with the non-solvent, and is also present when the plastic is brought into contact with the solvent, and improves the dissolution of the plastic by the solvent.
Claims12
Process for recycling a plastic, according to which the plastic is brought into contact with a solvent capable of dissolving the same and the plastic dissolved in the solvent is precipitated using a non-solvent in the presence of a phase-separating agent, in which the phase-separating agent is compatible with the solvent and incompatible with the non-solvent, and is also present when the plastic is brought into contact with the solvent, and improves the dissolution of the plastic by the solvent.
Process according to any one of the preceding claims, in which the non-solvent is added gradually to the solvent comprising the dissolved plastic and in which the pressure is reduced below atmospheric pressure during the gradual addition of non-solvent.
Process according to any one of the preceding claims, in which the solubility parameter of the solvent is close to that of the plastic, and that of the phase-separating agent is:
- lower than the solubility parameter of the plastic if the solubility parameter of the non-solvent is higher than that of the plastic
- higher than the solubility parameter of the plastic if the solubility parameter of the non-solvent is lower than that of the plastic.
Process according to any one of the preceding claims, in which the non-solvent is water and the phase-separating agent is a non-polar organic compound.
Process according to any one of the preceding claims, in which the solvent and the phase-separating agent are substantially removed from the precipitation medium by evaporation at a temperature lower than the boiling point of the non-solvent.
Process according to any one of the preceding claims, where the plastic is PVC, the solvent is MEK, the non-solvent is water and the phase-separating agent is an aliphatic hydrocarbon having from 5 to 7 carbon atoms.
Process according to any one of the preceding claims, in which the plastic is PVC and according to which:
- (a) the PVC is brought into contact with the solvent and the phase-separating agent and is dissolved;
- (b) the precipitation of the PVC dissolved in the solvent is brought about by injecting steam into the resultant solution, which permits removal of the solvent and the phase-separating agent by evaporation and thus gives a remaining mixture essentially consisting of water and of solid particles of PVC;
- (c) the particles of PVC are recovered.
Dependencies are inferred from the claim text.