Preparation method of an insulated wire

A preparation method of an insulated wire, comprising:

• preparing a core material that includes forming a bonding layer on a conductor, wherein a process of forming the bonding layer comprises:
• mixing polyamide-imide, polyimide, and organic solvent to obtain a bonding-layer mixed liquid, and performing coating and curing multiple times on the conductor by using the bonding-layer mixed liquid, wherein in mass percentage, the bonding-layer mixed liquid comprises:
• the polyamide-imide 20%-30%, the polyimide 1%-3%, and the organic solvent 67%-79%;
• and
• preparing an insulating layer that includes adding thermoplastic polyimide particles to an extruder after the extruder is vacuumed first;
• melting and extruding at an outer side of the core material after preheating;
• holding at 260° C.-280° C. for 10 s-30 s after the extruding;
• and then cooling, so as to form a thermoplastic polyimide insulating layer, wherein the extruding is carried out under a negative pressure condition;
• a vacuum suction for applying the negative pressure is controlled to be larger than or equal to 0.3 MPa;
• a preheating temperature during the preheating is controlled to be 200° C.-320° C.;
• and an extruding temperature during the extruding is 370° C.-410° C.