Method for producing profiled fibers having low broken filament rate by polyester FDY process

A method for preparing profiled fibers with a low lousiness rate by a polyester fully drawn yarn (FDY) process, comprising that:

• when preparing the profiled fibers by the FDY process, horizontal and longitudinal positions of wire guide ceramic pieces on a pre-entangling wire guide frame are adjusted to maintain a vertical alignment of a filament bundle in a pre-entangling device having a pre-entangling yarn path and achieve an optimal jitter effect of the filament bundle in the pre-entangling yarn path, so as to prepare the profiled fibers with the low lousiness rate;
• wherein the profiled fibers comprise triangular profiled fibers, trilobal profiled fibers or flat profiled fibers;
• when the profiled fibers are the triangular profiled fibers, a lousiness rate is 0.35-0.65%;
• when the profiled fibers are the trilobal profiled fibers, the lousiness rate is 0.85-1.25%;
• when the profiled fibers are the flat profiled fibers, the lousiness rate is 0.5-0.85%;
• wherein a jitter condition of the filament bundle in the pre-entangling device is detected by fiber optic sensors;
• wherein optical fibers of the fiber optic sensors are divided into two groups, located directly in front of and behind the pre-entangling yarn path respectively, both arranged in horizontal arrays along a horizontal symmetry axis of the pre-entangling device;
• wherein a diameter of the optical fibers is smaller than a diameter of each monofilament in the filament bundle;
• wherein the fiber optic sensors detect left and right deviation distances of all monofilaments passing vertically from top to bottom through the horizontal symmetry axis relative to a longitudinal central axis of the pre-entangling yarn path;
• a distance value corresponding to the longitudinal central axis of the pre-entangling yarn path is set to 0, with leftward distances as positive values and rightward distances as negative values;
• a computer central processing unit (CPU) collects distance data, then counts and calculates a discrete distribution coefficient of variation (CV) value of the deviation distances, and generates a time-distance curve based on the distance data, at a maximum left jitter distance and a maximum right jitter distance of the monofilaments, a horizontal upper jitter limit line and a lower jitter limit line are drawn respectively, with a center line drawn exactly midway between the upper and lower jitter limit lines;
• using the center line as a reference, the upper jitter limit line is shifted downward by 20% of a distance between the upper jitter limit line and the lower jitter limit line and the lower jitter limit line is shifted upward by 20% of the distance between the upper jitter limit line and the lower jitter limit line to define an upper boundary line and a lower boundary line of a normal jitter range;
• then using the center line as the reference, the upper boundary line is shifted downward by 30% of the distance between the upper jitter limit line and the lower jitter limit line and the lower boundary line is shifted upward by 30% of the distance between the upper jitter limit line and the lower jitter limit line to define an upper offset line and a lower offset line;
• when the time-distance curve appears in an area above the upper boundary line or below the lower boundary line continuously for 2 ms, the entire area where the curve appears during this period is defined as a “long segment”;
• when the curve appears only in an area between the upper offset line and the lower offset line continuously for 2 ms, the entire area where the curve appears during this period is defined as a “short segment”;
• when the discrete distribution coefficient of variation (CV) value of the deviation distances is <3.5%, the center line coincides with the longitudinal central axis of the pre-entangling yarn path, and no “long segments” or “short segments” appear in the time-distance curve, so that the filament bundle maintains the vertical alignment and achieves the optimal jitter effect in the pre-entangling device, the optimal jitter effect being defined by the discrete distribution coefficient of variation (CV) value being <3.5%, the center line coinciding with the longitudinal central axis of the pre-entangling yarn path, and the absence of “long segments” and “short segments”.