Process for recycling used plastics based on polyethylene using a light hydrocarbon solvent

Device for purifying plastic feedstock, which comprises polyethylene, said device including:

• a) a section for dissolving the plastic feedstock in a dissolution solvent, operated at a dissolution temperature of between 150 and 250° C. and at a dissolution pressure of between 1.0 and 18.0 MPa absolute, to obtain at least one crude polymer solution;
• and then
• b) a section for purifying the polymer solution, including:
• b1) an insoluble matter separation sub-section;
• and/or
• b2) a washing sub-section, by contact with a dense solution;
• and/or
• b3) an extraction sub-section, by contact with an extraction solvent;
• and/or
• b4) an impurity adsorption sub-section by contact with an adsorbent;
• and then
• c) a solvent-polymer separation section including at least one supercritical separation section operated at a temperature of between 160 and 300° C. and a pressure Psupercritical of between 2.7 and 10.0 MPa absolute, followed by at least one solvent recovery section, operated at a temperature of between 160 and 300° C. and a pressure between the pressure of the supercritical separation section Psupercritical and 0.000005 MPa (i.e. 5 Pa), to obtain at least one purified polyethylene fraction.