| 摘要 |
The invention concerns a method which consists in: a) forming by extrusion an extruded thermoplastic tube (20) having, when coming out of the extruder, a diameter D1; b) then subjecting said extruded tube of diameter D1 to a radiation treatment, so as to produced a cross-linked tube (21); c) after bringing said cross-linked tube (21) to a temperature not less than a temperature substantially equal to the melting point of its crystalline phase, subjecting it, in displacement, to a radial monoaxial expansion for form an expanded tube (22) of diameter D2, then cooling it down to a temperature, typically room temperature, at which it can be cut into tube portions (23) with length substantially equal to the height of said caps (1); and e) assembling or forming a head (10, 100, 101, 102, 103) on said tube portion (23), so as to obtain a cap or top (1), with heat-shrinkable skirt, economical and having a homogeneous skirt (11, 12) free of axial connection line.
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