Today, I will introduce you to the high-speed spinning process

 The principle of high-speed spinning is the same as that of conventional spinning, but because the spinning speed increases, the tension on the spinning process increases, and the requirements for melt are higher. Therefore, the process flow of POY is different from UDY. It is the primary silk made by melting extrusion, spinning and high-speed winding of the dried slices. The production process of POY is dry slicing → melt extrusion → pre-filtration → mixing → metering → filtration → spinning → cooling forming → oiling → winding →POY bobbin. 1. Melt extrusion The pre-crystallized, dried polyester slices are fed into the screw extruder. The screw extruder has the functions of slice feeding, melting extrusion, mixing and metering extrusion. The polyester slice is fed into the screw groove of the screw extruder from the feeding port. Due to the rotation of the screw, the slice is carried forward, and the slice constantly absorbs the heat supplied by the heating device. On the other hand, due to the friction between the slice and the slice, the friction between the slice and the screw and the sleeve, and the shear action between the liquid layer, a part of the mechanical energy is converted into heat energy, and the temperature of the slice increases during the advance process and gradually melts into melt. During the melting process, the polyester polymer changes in temperature, pressure and morphology, from solid (glassy state) into a highly elastic state, and with the further increase of temperature, plastic flow occurs and becomes a viscous fluid (viscous flow state). The viscous polyester macromolecules are mixed uniformly under the push of the screw and the resistance of the screw outlet, and the pressure is increased, and the melt is extruded. This process is called melt extrusion. Screw extruder has two types of horizontal and vertical, screw in the space is horizontally installed for horizontal, vertical installation for vertical. The horizontal screw extruder is easy to install, disassemble and maintain, but the screw is an overhanging beam, and the measuring section is easy to wear. The screw of vertical screw extruder is not easy to bend, and the head wear is less, but the plant height is increased, and the installation and disassembly and maintenance are more troublesome. At present, screw extruders are generally horizontal. Screw extruder can be divided into single thread, double thread, single screw and double screw extruder according to the number of thread heads and screw roots. According to the screw speed can be divided into ordinary type (speed less than 100r/min) and high-speed extruder. In recent years, the development speed of screw extruders is fast, and it is developing in the direction of large-scale, large length-diameter ratio and high-speed. 2. Pre-filter Because the melt contains certain mechanical impurities and unmelted gel particles, spinning directly will not only affect its spinnability, but also affect the quality of the product. Therefore, in order to ensure the purity of the melt and stabilize the fiber quality, in addition to setting the filter assembly in the spinning assembly, it is generally necessary to set the filter in the melt conveying pipe or the melt distribution pipe of the spinning machine, usually called the pre-filter. Before spinning, the melt goes through a filter to remove mechanical impurities and unmelted gel particles to improve spinning performance and extend the service life of spinning components. The pre-filter is generally two-chamber filtration, using one chamber first, when the pressure drop exceeds 5 ~ 10MPa, the filter is switched. Usually, the switching cycle is 10 to 20 days, and the switching time is 2 to 3 minutes. Commonly used filter media are woven metal mesh, sintered metal fiber felt, shape, pleated or flat mesh shape. In order to improve the filtration performance, more than two filter media are often used to compose the filter element. After pre-filtration, the residence time of melt is increased, and the viscosity of melt is increased. Therefore, if the slice quality is good and no mechanical impurities are brought into the feeding system, no pre-filter can be used. 

 3. Melt distribution pipeline A pipe through which polyester melt is transported and distributed to each spinning box. The pipe is required to be as short as possible, the time to be sent to each box is uniform, the melt heat dissipation in the pipe is less, and there is no melt dead Angle. 

 4. Static mixing Static mixing is achieved by means of a mixer installed in the melt conveying pipe. The high viscosity polymer melt flows in the pipe in a laminar state, thus forming radial gradient differences in temperature, residence time and viscosity. A static mixer is installed in the pipe to reduce the adverse effect of this difference on spinning. When spinning, it is sometimes necessary to add different compositions of polymers or some stabilizers, antistatic agents and other additives, in order to mix evenly, a special static mixer can be assembled in the head of the screw extruder. A screw extruder with a static mixer can be used to make colored polyester by mixing ordinary polyester slices with dyed masterbatch. The static mixer has two basic functions: one is the mixing effect on the material, that is, the material is divided into a trickle and then mixed; The second is the mixing effect on the material, that is, the flow state of the material liquid is constantly changed, so as to produce a certain shear plasticizing effect on the material liquid. Therefore, the static mixer installed in the melt pipe can reduce the stratified flow caused by the high viscosity in the melt and make the physical properties of the melt uniform. If the melt is fully mixed in the screw extruder, the melt distribution tube has few dead angles and the static mixer can be eliminated.

 5. Metering pump Metering pump is a high precision standard component used in melt spinning, and is one of the key components in the spinning process. The melt is precisely measured by the metering pump and sent to the spinneret assembly, and then extruded from the spinneret hole to form a fiber, thus ensuring a uniform thickness of the filament. At the same time, the metering pump can pressurize the melt to meet the needs of spinning.

 6. Spinning components The spinning assembly is composed of spinneret plate, distribution plate, melt filter material, etc. The melt sent by the metering pump is finally filtered, and the mechanical impurities and gel particles in the melt are further filtered by the filter material to prevent the blockage of the spinneret hole. Make the melt fully mixed to prevent the viscosity difference between the melt; The melt is evenly distributed to each small hole of the spinneret to form a uniform trickle. The requirements of the component are: the melt should be evenly distributed to the small holes of the spinneret, the channel resistance is the same, and there should be no dead Angle in the component, so as to avoid the melt residence time is too long and the cracking or formation of gel; Good sealing and filtering effect, long service cycle, easy assembly and disassembly of components, reliable sealing; All parts in direct contact with the melt should be resistant to high temperature and corrosion. Because of the large extrusion capacity and flow resistance of high-speed spinning, the particle size of the filter material is required to be slightly larger than that of conventional spinning.

 At the same time, because of the high spinning speed and high shearing stress, the length-diameter ratio of spinneret holes is higher than that of conventional spinning. 

 7. Cool forming The thin flow of melt expelled from the spinneret hole solidified into filament strips under the action of side blowing wind, and stretched by 100 ~ 250 times, which was about 2 ~ 4 times larger than conventional spinning. As the melt solidifies and the filament cools, a large amount of heat is released to the surrounding air. This heat is carried away mainly by convective heat transfer with moving air (side-blowing wind). The cooling speed of the wire is required to be uniform, the freezing point position is fixed, and it is not affected by the surrounding air flow and produces violent shaking. Due to the large amount of high-speed spinning and the amount of heat released, the wind speed and humidity of the cooling blower are high, and the wind temperature is low. 

 8. Cluster oiling After the fibers are cooled and formed, they are bunched and oiled before entering the spinning channel to reduce the winding tension. There are two ways of oiling the oil pan and the oil nozzle. Because of the high running speed of the filament and the large amount of oil, the metering pump is generally used to supply the oil nozzle. 

 9.POY winding The key to high-speed spinning is high-speed winding: under high-speed conditions, the smooth running of equipment, the quality of the formation of the yarn bobbin, the convenience of operation and other problems are more prominent than that of conventional spinning. It is required that the winding tension, winding speed, and the reciprocating speed of the wire guide, friction roller, and the linear speed of the transverse wire guide are kept stable during the running process to ensure the uniform structure and linear density of the primary fiber.