How is melt blown cloth formed?

　　The melt blowing method is also one of the direct polymer web forming methods. It is to extrude the polymer melt extruded by the screw extruder by blowing with high-speed and high-temperature airflow or other means to cause the melt stream to be extremely stretched. The very fine fibers are formed, and then gathered on a web forming drum or a web forming curtain to form a web, which is finally strengthened by self-adhesive action to make a meltblown fiber nonwoven fabric.

　　1. Similarities and differences with spunbond

　　Also known as the direct spinning method, it uses melt spinning and other methods to spread the continuous filaments formed by melt spinning and stretching of polymer chips, and then make products through processes such as bonding and finishing.

　　a Same point

　　① The polymer must be extruded from the spinneret in the molten state

　　② The fiber web can be strengthened into a non-woven fabric through thermal bonding (surface bonding or point bonding) or self-bonding

　　b Difference

　　①In the spunbonding method: cooling by quenching air and stretching at the same time to form continuous filaments, which are laid on the net curtain

　　In the melt-blown method: high-speed hot air blowing and extreme stretching to form ultra-fine short fibers, which fly to the netting curtain or condensing drum at a very high speed to form a web

　　② Spunbond method: There are many ways to strengthen the web. In addition to thermal bonding, needle punching, spunlacing, chemical bonding and other methods can also be adopted.

　　Melt-blown method: mainly rely on thermal bonding or self-bonding

　　2. Traditional process

　　Polymer feeding→melt extrusion→fiber formation→fiber cooling→web forming→bonding (fixed web)→trimming and winding→after finishing or special finishing

　　Feeding —— The polymer is generally made into small spherical or granular slices, poured into a bucket or hopper, and fed into the screw extruder

　　Melt extrusion—— At the feeding end of the screw extruder, the polymer chips should be mixed with stabilizers, brighteners and other additives and masterbatch and other necessary raw materials, after being fully stirred and mixed, they will enter the screw extruder and be heated. The melt is finally sent to the spinneret by the metering pump through the filter. In the melt blown process, the general extruder also uses its shearing and thermal degradation effects to reduce the molecular weight of the polymer.

　　Fiber formation —— The filtered clean melt passes through the distribution system, and then is evenly sent to each group of spinnerets to make the extrusion volume of each spinneret uniform. The spinneret of meltblown fiber is different from other spinning methods. The spinneret holes must be arranged in a straight line, and the upper and lower sides have high-speed air jet holes.

　　Fiber cooling-a large amount of room temperature air is sucked in at the same time on both sides of the spinneret, mixed with the hot air stream containing ultra-fine fibers to cool it down, and the molten ultra-fine fibers are cooled and solidified.

　　Netting——In the production of meltblown fiber nonwoven fabric, the spinneret can be placed horizontally or vertically. If placed horizontally, the superfine fibers are sprayed on a circular collecting drum to form a web; if placed vertically, the fibers fall onto a horizontally moving web forming curtain to condense into a web.

　　Adhesion (fixed net)-the self-adhesive reinforcement mentioned above is sufficient for some applications of melt blown cloth, such as: the fiber net is required to have a relatively fluffy structure, good air retention rate or porosity Wait. For many other applications, self-adhesive reinforcement alone is not enough. Hot-rolling bonding, ultrasonic bonding, or other reinforcement methods are also required. Hot roll bonding

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