Multilayer thermoplastic structure

A multilayer structure comprising:

• at least three layers comprising thermoplastic polymers and having no greater than 0.1% by weight of the total weight of the three layers, of vinyl chloride polymers and of plasticizers of a molecular mass less than 1000, forming a structure having a total thickness of between 100 and 400 μm, said structure simultaneously exhibiting:
• a modulus of elasticity of less than 350 MPa,
• an amount of compounds which can be extracted with boiling hexane of less than 5%, and
• a haze/thickness ratio of less than 6%/200 μm.

A method of manufacturing a multilayer structure based on thermoplastic polymers and not exceeding 0.1%, by weight of the weight of the total multilayer structure, of vinyl chloride polymers and of plasticizers of a molecular mass less than 1000 and comprising at least 3 layers, said method comprising:

• providing a first layer comprising at least 60%, by weight of the total weight of said first layer, of at least one polyolefin of controllable crystallinity defined as comprising at least 90%, by weight of the total weight of the at least one polyolefin, of a compound selected from the group consisting of ethylene, propylene and butene and as having a softening temperature of less than 121° C., thickness of the first layer being at least 20% of a total thickness of the structure and the first layer having a modulus of elasticity of less than 350 MPa;
• providing a second layer, positioned between the first layer and a third layer, comprising at least 40%, by weight of the total weight of said second layer, of at least one polyolefin of controllable crystallinity, the second layer having an overall softening temperature of less than 121° C.;
• providing the third layer comprising at least 50%, by weight of the weight of said third layer, of at least one polyolefin of controllable crystallinity, the thickness of the third layer being from 5 to 30% of the total thickness of the structure and the third layer having a modulus of elasticity less than the modulus of elasticity of the first layer;
• co-extruding the three layers;
• and
• subjecting the co-extruding layers to at least one stage of drawing by at least 100% at a temperature between the maximum crystallization temperature of the polyolefins of controllable crystallinity (Tc) and Tm+15° C., wherein Tm denotes minimum melting temperature of the polyolefins, to at least one stage of relaxation at constant dimensions lasting at least 10 s in the same temperature range, and then to a stage of sudden cooling to a temperature of less than the maximum crystallization temperature Tc.