| 摘要 |
PROBLEM TO BE SOLVED: To provide an extrusion die which enables attainment of polytetrafluoroethylene fibers being uniform and stable in the lengthwise direction even when a reduction ratio is increased, in extrusion of paste of the fibers. SOLUTION: A compound prepared by adding an appropriate organic solvent to polytetrafluoroethylene powder is preformed and pressed to be supplied for extrusion. A land of a die for paste extrusion is formed to have a stepped structure of a straight part 1b and a tapered part 1a, and radius parts 3 are provided for stepped parts, so that polytetrafluoroethylene fibers being uniform and stable in the lengthwise direction can be extruded even when a reduction ratio is so high as 500-1500. A taper angle of the tapered part 1a is set desirably at 5-10 deg. in order to perform stable paste extrusion at the high reduction ratio. The extrusion die having the aforesaid structure can be used for extrusion of ceramic slurry. |
