| 摘要 |
This process is of the type consisting in forming (tubular) tubing 5 made from synthetic material by means of an annular die 4 and in passing this tubing 5, without external cooling and with a zero or negative internal blowing rate, over a cooling mandrel 14 arranged downstream of and beneath the die 4. According to the invention, it consists in adjusting the output from the die and the drawing (stretching) rate of the tubing so that the latter, without radial clamping, comes into contact with the generatrices of the mandrel 14 which, being at least partially conical, is convergent towards the downstream, sizes this tubing and has a larger internal diameter than the exit diameter of the die 4. In one application, the tubing leaving the die 4 is composed of at least one internal layer 11a made from a slippery synthetic material having a low coefficient of friction and of an external layer 11b made from a synthetic material having, on the surface, adherency. <IMAGE>
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