To introduce the fine fiber spinning technology Polyester fine fiber has the advantages of soft feel, full fabric and so on, and has excellent drape and crisp, and the clothes made with it are loved by people. Fine fibers can be produced by conventional spinning, high-speed spinning, FDY and drawing warping equipment. Due to the small density of monofilament and the low strength of monofilament, it is easy to produce hair and break in production and use. The diameter strain of spinneret used for spinning is small and the rheological property of melt is better, so the requirements for raw materials and spinning process are higher. 1. Slice ingredients Due to the low strength of the fine fiber, the requirement of polyester chip for spinning raw material is high. First of all, it is required that the impurity content in the slice is small, if the impurity content is high, it is easy to produce hair and break the head when spinning. Secondly, the indicators of the slice are uniform and stable, otherwise it will make the production and product quality unstable. In addition, the heat resistance of the slice is better, because the rheological property of the melt is better when spinning fine fibers, so the spinning temperature is high, and the heat resistance of the slice is less thermal degradation. 2. Dry the slices When spinning fine fiber, the degradation is great because of the high spinning temperature. In order to reduce degradation, the water content of the slices must be strictly controlled. The water content of the slices should be below 25ppm. In addition, it is required that the drying quality is uniform, the dry slice powder is small, and the viscosity is small during the drying process, otherwise it is easy to produce floating silk, hair silk and broken silk. 3. Spinning temperature Higher spinning temperature can improve the rheological properties of melt through the spinneret hole, delay the cooling time of melt trickle and maintain a higher surface temperature. The general temperature is controlled between 290 and 300℃. The smaller the density of monofilament, the higher the temperature should be used. With the increase of spinning temperature, the viscosity drop of oil-free silk will be larger. If the viscosity drops too much, the fine fiber is more prone to hair and breakage. In general, the viscosity reduction of conventional spinning should be less than 0.03, but it should be less than 0.015.M when spinning fine fibers, the total linear density is low, the screw spit out less, in order to solve the viscosity reduction is too large, can use low temperature screw, high temperature box. Generally, the screw temperature is 284 ~ 286 art, and the box temperature is 295 ~ 298℃. In this way, a fine flow of melt with good fluidity can be obtained, and it can be smoothly stretched through high speed. 4. Spinning components (1) Component pressure spinning fine fiber POY, to have a higher component pressure, improve the filtration effect and shear stress, so that the melt extrusion temperature, improve the rheological properties of the melt, improve spinnability. However, too high initial pressure of the component will make the component boost too fast and shorten the service cycle. General component pressure use 12 ~ 18MPa. (2) Component filter material Component filter material changed from sea sand to metal sand. The special amorphous structure of metal sand makes its filtering capacity much higher than that of sea sand, and its filtering capacity of melt impurities is much greater than that of sea sand, and its warming effect on melt is also better than that of sea sand. Taking the production of 166dtex/192F specification of POY as an example, the best metal sand ratio is coarse-grained medium particle l fine-grained 121, the filtration effect is better, POY spinning smoothly. 5. Cooling conditions If the wind speed is too large or too small, the unevenness of the strip will increase and the tensile property will be affected, which is caused by the periodic displacement of the freezing point. Therefore, good blowing conditions should be appropriate wind speed and good laminar flow of air flow. When high-speed spinning is used, the cooling process is less affected by the uneven wind speed, and the performance change of FDY is not as obvious as that of conventional spinning when the wind speed is changed, so increasing the speed of GR1 in an appropriate range can improve the strip uniformity and dyeing uniformity of the silk. In order to reduce the orientation and crystallinity of fine fibers, the cooling conditions should be moderate. If the orientation and crystallinity of the fine fiber are high, it will make the fine fiber stretch processing more difficult. Therefore, set up insulation areas, raise the wind temperature or reduce the wind speed to moderate cooling. The wind speed of conventional spinning is 0.1-0.2m /S, the wind speed of high-speed spinning is 0.25-0.35m /s, and the relative humidity is 75%±5%. 6. Cluster location The spinning tension has a great influence on the winding. The spinning tension is subject to rheological resistance, inertial force and air friction. For fine fibers, the specific surface area is large, and the air friction is large, so it is necessary to raise the location of the bunching point or shorten the tunnel to reduce the air friction. In high-speed spinning, due to the high spinning speed and large tension on the spinning process, the importance of the binding point position is more prominent, otherwise it can not spin and wind. Some equipment will oil bunching position from the original 1.4m to 0.7m, the effect is better. If the cross-section is irregular, the location of the bunching point should be raised. Because the specific surface area of the special-shaped cross section fiber is larger, the primary fiber is easy to dissipate heat, the cooling speed is fast, and the freezing point is obviously shifted upward. Generally, the bunching position is between 0.7 and 1.0m from the spinneret to the top oil nozzle. Shortening the bunching distance can reduce the tow tension, the birefringence of the primary fiber and the increase of the binding position can also reduce the sway of the fine fiber. 7. Apply oil The specific surface area of fine fibers is large, and the oil content is higher than that of ordinary silk, generally 0.7% to 1%. The oil used should have good permeability and smoothness. Double nozzles are used for oiling. 8. Spinneret aperture Selecting the aperture of spinneret reasonably and designing spinneret scientifically is one of the keys to spinning fine fiber. The size of the aperture not only conforms to the shear rate law of melt flow in micropores, but also keeps the stretch ratio of the nozzle in a small range. The shear rate of conventional spinning can be (0.7 ~ 1.0)×10000 s-1, and that of high-speed spinning can be (1.8 ~ 2.2)×10000 s-1. 9. Stretch factor and temperature As a fine fiber used for imitation silk, in order to highlight its simulation effect, it is generally processed into stretched silk. In order to adapt to the high orientation and high crystallization of fine fiber winding, the tensile multiple must be reduced, and the smaller the density of monofilament, the greater the degree of reduction. However, the strength of the finished silk does not decrease due to the reduction of the tensile multiple, and the elongation remains unchanged. Under ordinary tensile temperature, the tensile stress of fine fiber is large, the smaller the linear density of monofilament, the more likely to appear hair, broken, boiling water shrinkage is also larger. The experiment shows that it is better to increase the tensile temperature by 5 ~ 8℃. If the drawing temperature is too high, the finished silk will produce color streaks. In addition, the drawing speed should be chosen to be low to avoid producing a large number of hairs and broken heads. 10. Network processing The friction coefficient of fine fiber is large and unwinding is difficult. For example, 83dtex/ 72F specifications of silk, if directly in the double twisting machine to strengthen twisting, will cause a large number of hair due to unwinding tension. The higher the unwinding speed, the more serious the hair condition. For this reason, fine fibers must be mesh processed. The smaller the monofilament density of the fine fiber, the easier the network processing due to its small flexural stiffness, and the satisfactory network degree (20 ~ 30 /m) can be obtained under lower air pressure.