Non woven fabrics include polyester, polypropylene, nylon, spandex, acrylic, etc. based on their composition; Different ingredients will have completely different styles of non-woven fabrics. There are many production processes for the manufacturing of non-woven fabrics, and melt blown non-woven fabric is a process of melt blown method. It is one of the non-woven fabric production processes and also one of the direct polymer mesh forming methods. It is the process of extruding polymer melt from screw extruders through high-speed and high-temperature airflow blowing or other means to cause extreme stretching of the melt flow and form extremely fine fibers, which then gather on the mesh forming drum or mesh curtain to form a fiber mesh, Finally, the melt blown fiber nonwoven fabric is reinforced by self bonding.
Melt blown fabric is mainly made of polypropylene as the main raw material, and the fiber diameter can reach 1-5 microns. The ultra-fine fibers with unique capillary structures, such as multiple voids, fluffy structure, and good wrinkle resistance, increase the number and surface area of fibers per unit area, thus making the melt blown fabric have good filtration, shielding, insulation, and oil absorption properties. Can be used in fields such as air and liquid filtration materials, isolation materials, absorbent materials, mask materials, insulation materials, oil absorbing materials, and wiping cloths.
The fiber diameter of the melt blown layer is extremely fine, basically around 2 microns (um), so it is only one tenth of the diameter of the spunbond layer. The finer the melt blown layer, the more it can block the entry of small particles. For example, the KN95 mask refers to a flow rate of 85L that can block 95% of small particles (0.3um) under normal circumstances. This plays a crucial role in filtering bacteria and preventing blood infiltration, which is why it is called the heart of a mask.
Traditional process flow
Polymer feeding → Melting extrusion → Fiber formation → Fiber cooling → Mesh formation → Bonding (fixed mesh) → Edge cutting and winding → Post finishing or special finishing
Polymer feeding – PP polymer raw materials are generally made into small spherical or granular slices, poured into buckets or hoppers, and fed into screw extruders.
Melt extrusion – At the feed end of the screw extruder, polymer chips are mixed with necessary raw materials such as stabilizers, whitening agents, and color masterbatch. After thorough stirring and mixing, they enter the screw extruder and are heated at high temperature to form a melt. Finally, the melt is fed into the spinneret through a filter by a metering pump. In melt blown processes, extruders generally reduce the molecular weight of polymers through their shear and thermal degradation effects.
Fiber formation – The filtered clean melt needs to go through a distribution system and then be evenly fed into each group of spinnerets, so that the extrusion amount of each spinneret hole is consistent. The spinneret plate for melt blown fibers is different from other spinning methods in that the spinneret holes must be arranged in a straight line, with high-speed airflow spout holes on both sides.
Fiber cooling – A large amount of room temperature air is simultaneously sucked in on both sides of the spinneret, mixed with the hot air flow containing ultrafine fibers to cool them down, and the melted ultrafine fibers are cooled and solidified.
Web formation – In the production of melt blown fiber nonwoven fabrics, the spinneret can be placed horizontally or vertically. If placed horizontally, then ultrafine fibers are sprayed onto a circular collection drum to form a mesh; If placed vertically, the fibers will fall onto a horizontally moving mesh curtain and condense into a mesh.
Adhesive (fixed mesh) – The self adhesive reinforcement mentioned above is sufficient for certain purposes of melt blown fabrics, such as requiring the fiber mesh to have a fluffy structure, good air retention or porosity, etc. For many other purposes, self adhesive reinforcement alone is not enough, and hot rolling bonding, ultrasonic bonding, or other reinforcement methods are also needed.
Post time: Dec-15-2023