Patent ID: 6521168
Filing Date: 2003-02-18
Classification: B29C,B29L

Abstract:
A process for orienting and drawing a multiple-layer tubular of thermoplastic materials, comprising:a) bringing a tubular exiting from a preheating tunnel, to an orienting temperature of a first material layer of the tubular having a highest orienting temperature, while material of remaining layers of the tubular are still in a plastic state; b) performing a first partial drawing of said first material layer while the remaining layers are plastically deforming to follow an expansion of the first material layer; c) during the partial drawing of said first material layer, a drawing value is reached which equals a difference between a maximum obtainable drawing value of said first material layer and a maximum drawing value of the remaining layers; d) dropping the temperature of the tubular down to the orienting temperature of a second material layer of the tubular; e) drawing said second material layer while continuing to draw the first material layer; and f) repeating steps d) and e) for each remaining material layer until a maximum allowable degree of drawing is achieved for each layer.