From the perspective of mask composition, medical surgical masks generally have three layers: the inner and outer layers are non-woven fabrics, and the middle filter layer is melt blown cloth. “Meltblown cloth” is commonly known as the “heart” of masks. It has good filtering, shielding, heat insulation and oil absorption properties, and is an important raw material for the production of medical surgical masks and N95 masks.
The main raw material of meltblown cloth is polypropylene, which is a superfine electrostatic fiber cloth with a fiber diameter of about 2 microns. Its diameter is only one-tenth of the diameter of the outer fiber of the mask, which can effectively capture dust. When droplets containing viruses come close to the meltblown cloth, they will also be electrostatically adsorbed on the surface and cannot penetrate. Therefore, it is a necessary raw material for the production of filter masks.
Melt blown cloth is a kind of non-woven fabric. Non-woven fabric, also known as non-woven fabric, is composed of oriented or random fibers without warp and weft threads. It is named because the appearance and some properties are similar to woven fabric. At present, there are many processing techniques for non-woven fabrics, such as spunbonding, meltblown, hot rolling, spunlace and so on. Among them, the non-woven fabric made by melt-blown method is called melt-blown non-woven fabric. Melt-blowing method refers to a spinning method in which the newly extruded polymer melt is stretched and solidified rapidly by high-speed hot airflow.
The non-woven fabric produced by the melt-blown method has finer fibers, a larger surface area, and has better filtering, shielding, heat insulation and oil absorption properties, which are unmatched by non-woven fabrics produced by other processes. The following figure shows the principle diagram of melt-blown fabric production by melt-blown process.
The melt blown cloth is produced by the melt blown process, and its equipment mainly includes: screw extruder, melt blown cloth metering pump, melt blown screen changer, melt blown device, winding device, air system (hot air blower and heater )Wait. The function of the screw extruder is to melt the sliced material; the function of the melt blown cloth metering pump is to accurately measure, control the output and the fineness of the fiber, and deliver the melt to the spinneret continuously and evenly. The function of the melt blown screen changer is to filter out the impurities in the melt, so as not to block the spinneret holes. The function of the winding device is to pack the melt blown cloth into rolls. The function of the air system (hot air blower and heater) is to provide the temperature and pressure of the hot air used for spinning air stretching.