Detailed introduction of the separation technology of spunbond nonwoven fiber

When spinning in a spunbond system, after the traction and ventilation air comes out of the drafting device, the gathered yarn bundles should be dispersed into evenly distributed monofilaments, that is, spliced, and evenly spread on the web forming machine to form uniform fibers Mesh, thereby producing a uniformly distributed non-woven fabric. However, due to various reasons, such as improper cooling or unstable airflow, some filaments are difficult to separate, and several filaments are tangled together and fall on the cloth surface in the form of'parallel filaments'. The existence of'parallel filaments' not only affects the appearance and feel of the product, but also affects the uniformity of the product, which is a quality defect of non-woven fabrics. Therefore, according to the technological characteristics, various production lines will adopt corresponding technical means to eliminate the phenomenon of 'parallel filaments' and improve product quality. There are three separation methods: flow separation, mechanical separation and electrostatic separation. Airflow filament separation is achieved by using the principles of fluid mechanics and aerodynamics of airflow. When the traction and ventilation air comes out of the drafting device, the high-speed airflow is not easy to disperse the crowded tow, and will blow up the fiber web laying on the web surface and interfere with the web laying process. Therefore, after realizing the drafting of the melt flow, it is necessary to reduce the drafting flow rate and spread it to make the laying process go smoothly. In the production of non-woven fabrics, the common methods for air flow deceleration and diffusion are as follows: First, increase the flow section of the air channel. According to the basic laws of fluid mechanics, the airflow will slow down. The second is to introduce'supplemental air', use the negative pressure generated by the high-speed airflow to inhale the static airflow, and use the acceleration process of the ambient air to weaken the ventilation energy, thereby achieving the purpose of deceleration. The diffusion channel is a large horn-shaped component with a small horizontal cross-section, and the upper part of the small end is connected with the draft channel at the bottom. The bottom of the largest horn is the mesh belt. When the traction and drafting air flows out of the drafting device, the airflow speed is very fast, but after spreading to the channel, due to the gradual expansion of the cross section, the air flow rate begins to decrease, and turbulent diffusion is formed in all directions, and the airflow speed drops to The speed of the strips is the same. The strips are gathered together from the original state and spread out evenly on the net machine to become a uniformly distributed non-woven product. The air flow distribution line product has the advantages of uniform distribution of mesh and less silk, but the lateral strength is lower, and the MD/CD strength is relatively large. This phenomenon is more prominent in the production of a small number of products. The mechanical point of silk There are two main forms of mechanical yarn separation, one is the swing roller type yarn separation device, and the other is the swing type yarn separation device, both of which come from a non-woven production line made in Italy. 01Swing roller The swing roller divider is used in the multi-slit positive drafting production line produced by NWT. This shunt technology was also used in the spststicking production line produced in China before 2000. During the operation of the production line, the air flow and the tow from the drafting device pass through two swing rollers. Under the clamping of the oscillating roller, the wall effect of the airflow makes the airflow with traction swing back and forth with the oscillating roller, and the traction part swings in the swinging direction, thereby realizing wire separation. Because the non-woven fabric produced by this machine has many filaments, poor uniformity, and thick fibers, this production line has been phased out. 02 Pendulum splitter The pendulum splitter is used in the production line of STP Company and is also the splitter solution for the widely used tubular draft spinning system. Since the drawing process shrinks the filaments evenly distributed on the plane to the drainage tube with a small cross-section, it is difficult for the airflow and fibers to be uniformly distributed from the'point' to the plane through air diffusion after the airflow and fibers exit the drainage tube. The working part of the pendulum separator is a fixed reflector and a reciprocating pendulum installed at the outlet of the drafting device. The swing plate is driven by a motor and swings back and forth at a certain angle and frequency. After the traction air collides with the tractor, it ejects to the swing plate in the swing state and separates from each other under the action of mechanical force, so as to achieve the purpose of wire separation. Although the non-woven fabric produced by this machine still has the phenomenon of silk mixing'cloudiness', its uniformity is better than NWT, and the drafting speed is faster. Therefore, this production line is still being improved and developed. Electrostatic dot wire Electrostatic separation is a new technology to solve the problem of 'parallel lines'. The electrostatic wire point refers to the outlet drafting device installed with a pair of high-voltage plates, and an electrostatic field of up to tens of KV (KV) can be formed between the plate electrodes. When the two ends of the high-voltage electric field are made at the same time, all ribbons have the same pole. Sexual charges repel each other in polarity under the action of electric field force, and the strips will be separated to achieve the purpose of silk. The product uniformity produced by the electrostatic separation method is better, but because the filaments are repelled and separated by electrostatic force, the movement in the MD direction is less restricted, so the adjacent filaments in the MD and CD directions are more diffused. Will influence each other, it is difficult to diffuse, so the power of CD direction will be lower.