Patent ID: 8158042

Claim:
A method for manufacturing a polytetrafluoroethylene (PTFE) fiber, wherein the method involves slitting an oriented PTFE film in a lengthwise direction of the film so as to manufacture a PTFE filament, comprising: subjecting a PTFE film that has been oriented to emboss processing, the emboss processing being applied linearly along the lengthwise direction of the PTFE film and applied in a zigzag shape or a convexo-concave shape in a width direction of the PTFE film; and then, slit processing the PTFE film in the lengthwise direction, whereby a PTFE filament comprising a plurality of network structures is obtained, wherein each of the network structures comprises single fibrils that are distributed so as to form a first pair of opposing sides that are parallel to one another and a second pair of opposing sides that are parallel to one another, the first pair of opposing sides that are parallel to one another being different from the second pair of opposing sides that are parallel to one another, wherein each of the network structures is bounded by a closed path that is formed by the single fibrils, wherein each of the network structures is arranged adjacent to one another, wherein the slit processing comprises feeding the film to a revolving pin roll with needles so as to open the film to form the plurality of network structures, wherein an average fineness of the single fibrils constituting the PTFE fiber is 4.5 dtex or less, and wherein a distribution of fineness of the single fibrils constituting the PTFE fiber is a single-peak distribution with the peak at a center.