Introduction to the characteristics of the docan method spunbond production process-detailed introduction of professional technology

This method adopts the patent of German Lurg Company and is widely used in the production of spunbonded non-woven fabrics. The Dokan method uses rectangular spinnerets, each spinneret is 45cm long, and the top is divided into seven spinneret areas. When polypropylene is used as the raw material, when the linear density of the production is 0.17tex (1.5 denier), each spinneret hole area is 150 holes: the linear density is 0.33~0.56tex (3~5 denier), 100 holes: thread The density is 0.56~1.71ex (5~15 and), 35 holes. The slicing bin enters the screw extruder, and through the metering pump and the spinneret, a thin stream of melt is discharged. Under the blowing of the cooling air, the filament is cooled, and then the filament enters the air drafting device. The high-pressure air accelerates the thread, thereby realizing the drafting orientation. The pressure of high-pressure air is as high as 20-22 atmospheres, the drawing speed is 3500-4000mmin, or even higher, and the draw ratio is more than 1:200. After such drawing, the strength of the filament meets the requirements. The nozzle of the drafting device is easily damaged due to the action of high-pressure air and friction with the filament, so wear-resistant materials must be used. After the filament is drawn, it reaches the end of the drafting pipe. This section of the pipe is horn-shaped. The high-pressure airflow suddenly diffuses and decelerates here, producing aerodynamic coanda effect, thereby separating the fibers from each other. The filament output from the bell mouth of the drawing pipe is very fluffy, close to a single state, and its moving speed is also reduced to 20200m/min. Due to the air suction effect of the suction device under the condensation net curtain, the filament is in the condensation net curtain The upper bunk is placed into a net. Condensed mesh curtains generally use metal wire mesh or polyester filament woven mesh. The bell mouth of the stretched pipe can be arranged at a certain angle or parallel to the direction of movement of the condensation curtain. Through proper arrangement, there can be no obvious joints between the webs formed by each spinneret, so as to improve the uniformity of the webs. The Dokan method can produce fiber webs with a basis weight of 20～2000g/m2, and by controlling the movement speed of the condensed mesh curtain, fiber webs with different weights can be obtained. The minimum web width obtained by the Docan method is 900mm (a spinneret), and the maximum can reach more than 5m. Pre-reinforcement should be carried out immediately after forming the net. Low-weight fiber webs are generally heat-reinforced, and high-weight fiber webs are pre-reinforced by needle punching and the main reinforcement method is selected according to product requirements. The production speed of the Docan method is high. When the web basis weight is 80g/m2, the output speed is 30-50m/min. The aspect and strength ratio of the fiber web produced by Dokan method can reach 1.5:1.