| 摘要 |
PROBLEM TO BE SOLVED: To enable excellent flexibility or bending resistance by producing a specific polytetrafluoroethylene tube. SOLUTION: Solvent naphtha or other petroleum low boiling point lubricant is uniformly mixed with a polytetrafluoroethylene powder obtained by an emulsion polymn. method as an extrusion aid to form a preformed product which is, in turn, charged in the cylinder of an extruder to be extruded from a die and the extrudate is introduced into an oven body consisting of a drying zone and a baking zone. This polyteytrafluoroethylene unbaked tube is heated in the drying zone to evaporate the extrusion aid contained in the unbaked tube. Subsequently, this unbaked tube is heated in the baking zone to form a molded tube which is, in turn, further quenched immediately after baking. By this constitution, a polytetrafluoroethylene tube with a degree of crystallization of 30-50% and a ratio of strengths in the longitudinal and diameter directions thereof of 2.5:1-1:1 and excellent in flexibility and bending resistance can be realized. |
