Method for separating the layers of multilayer plastics that comprise at least a first layer and a second layer made of different plastics, which uses a system for separating the layers of multilayer plastics, the system comprising: - an input hopper for introducing the multilayer plastic fragments, - a vessel placed after the input hopper, - a discharge tank placed after the vessel, - a mechanical recompression machine connected to the discharge tank, - a pump connected to the discharge tank, - a boiler connected to the vessel and to the mechanical recompression machine, - a mechanical separation unit placed after the discharge tank, - a mechanical sorting unit placed after the mechanical separation unit, - a valve between the input hopper and the vessel, a discharge valve between the vessel and the discharge tank, a recovery valve between the discharge tank and the mechanical recompression machine, a valve between the discharge tank and the pump, and an inlet control valve between the boiler and the vessel, the method comprising the following stages: - pressurising the vessel with preheated vapour generated in a boiler and introduced into the vessel until the interior of the vessel reaches a pressure of between 1 bar and 12 bar, and a temperature between 100oC and 191.12oC, - taking the interior of the discharge tank placed after the vessel to a relative pressure of between -0.7 bar and 0.1 bar, and a temperature between 15oC and 25oC, - shredding the multilayer plastics into multilayer plastic fragments, - introducing the multilayer plastic fragments in the vessel and keeping them in it for a time between 10 seconds and 60 seconds, thereby weakening the union between the layers of the multilayer plastic fragments, - transferring the multilayer plastic fragments from the vessel to the discharge tank, where they are kept for a time between 1 minute and 5 minutes, - transferring the multilayer plastic fragments from the discharge tank to the mechanical separation unit, where the multilayer plastic fragments are separated into single-layer plastic fragments, and - transferring the single-layer plastic fragments from the mechanical separation unit to the mechanical sorting unit, where the single-layer plastic fragments are sorted by material, wherein the multilayer plastic fragments of the vessel placed in the discharge tank return to the vessel to be again subjected to the stage consisting in keeping them for a time between 10 seconds and 60 seconds, weakening the union between the layers of the multilayer plastic fragments. - an input hopper for introducing the multilayer plastic fragments, - a vessel placed after the input hopper, - a discharge tank placed after the vessel, - a mechanical recompression machine connected to the discharge tank, - a pump connected to the discharge tank, - a boiler connected to the vessel and to the mechanical recompression machine, - a mechanical separation unit placed after the discharge tank, - a mechanical sorting unit placed after the mechanical separation unit, - a valve between the input hopper and the vessel, a discharge valve between the vessel and the discharge tank, a recovery valve between the discharge tank and the mechanical recompression machine, a valve between the discharge tank and the pump, and an inlet control valve between the boiler and the vessel, - pressurising the vessel with preheated vapour generated in a boiler and introduced into the vessel until the interior of the vessel reaches a pressure of between 1 bar and 12 bar, and a temperature between 100oC and 191.12oC, - taking the interior of the discharge tank placed after the vessel to a relative pressure of between -0.7 bar and 0.1 bar, and a temperature between 15oC and 25oC, - shredding the multilayer plastics into multilayer plastic fragments, - introducing the multilayer plastic fragments in the vessel and keeping them in it for a time between 10 seconds and 60 seconds, thereby weakening the union between the layers of the multilayer plastic fragments, - transferring the multilayer plastic fragments from the vessel to the discharge tank, where they are kept for a time between 1 minute and 5 minutes, - transferring the multilayer plastic fragments from the discharge tank to the mechanical separation unit, where the multilayer plastic fragments are separated into single-layer plastic fragments, and - transferring the single-layer plastic fragments from the mechanical separation unit to the mechanical sorting unit, where the single-layer plastic fragments are sorted by material,