As the core component of the mask, how to choose a good meltblown cloth

　　The core component of masks has become the most popular material in the current mask production chain.

　　Medical surgical masks are usually made of three layers of non-woven fabrics, and the middle layer is the most important filter layer and barrier. The material used is melt blown non-woven fabric.

　　Melt blown cloth seems to have nothing special, but its production process is very complicated, and its production process can be summarized into three steps: first refining S petroleum NAO from petroleum, then chemically processing it into polypropylene, and then melt blown Craft made into cloth.

　　Raw material selection

　　Polypropylene (PP) easy filament is a very thin fiber (2～3) μ with high melt index (MFI≥1500g/10min). As shown in Figure 3, the resulting meltblown cloth gap is much larger than the size of the new coronavirus (about 0.1μm), but it still has a strong ability to filter viruses in the environment.

　　Viruses cannot exist on their own. The main routes of transmission are secretions and sneeze droplets, about 5μm in size. Secondly, melt blown cloth is essentially a fiber filter. When virus-containing droplets approach the meltblown cloth, they will also be electrostatically attracted to the surface and cannot pass through.

　　Reasons for unqualified meltblown cloth

　　1. Spinneret and melt blown equipment

　　2. Electrostatic electret equipment

　　3. Base material of long-lasting electrostatic electret

　　4. Melt spraying materials or high-melt finger-like fiber materials

　　5. Experienced machine regulator

　　6. Meltblown production site management

　　Fourth, the choice of meltblown materials

　　1. Melting: polypropylene can be melted to a suitable high level by adding thermally degraded hydrogen peroxide or metallocene hydrogen adjustment method to produce nanofibers.

　　2.The melting point of the particles should be reduced to between 150-170 °C.

　　3. After the main electret particles are added, the welded cloth produces electrostatic adsorption performance through the electret device, thereby blocking the virus.

　　4. After the polypropylene particles are modified, the fibers sprayed by the melt blowing machine under high temperature and high pressure are thin and long.

　　5. The fluid fiber sprayed from the raw material melt nozzle is soft, tough and firm.

　　6. High temperature sterilization.

　　Five, electret masterbatch selection

　　1. Static load time, regardless of the long-term charging time, it can be up to 1 year or more.

　　2. The main batch of electret does not block the melt hole, and the fusible cloth is equipped with electric charge. How to make the positive charge on the fusible cloth stay on the fusible cloth for a long period of time can go through half a year or a year without losing power. This has become a key indicator for testing the electret master batch and electret process.

　　3. Long blocking period, long-acting electret, PFE95.

　　6. Electret process treatment

　　1. Corona charging is a common method for melt-blown electret treatment. Factors such as charging voltage, charging time, charging distance, and environmental humidity will affect the electret treatment effect. The charging voltage has the most obvious influence on the electret effect, the charging distance has the largest influence on the dielectric effect, and the charging time has the smallest influence. Pay attention when adjusting the machine.

　　2. The environmental humidity has an effect on the generation and loss of static electricity. Fusing enterprises should monitor the temperature and humidity of the workshop at any time. Add equipment to keep the temperature and humidity of the workshop within the proper range.

　　7. Melt blown materials

　　1. Molten polypropylene stays for a long time under high temperature and high pressure, it is easy to sinter and carbonize.

　　2. When adjusting the machine temperature, first determine whether the actual temperature of the cylinder and mold on the melt blower is consistent with the set temperature. Generally speaking, the temperature displayed by the small melt blown equipment will be very different from the actual temperature.

　　3. Melting refers to 1500 polypropylene, if the temperature is set above 270℃, it is a bit high.

　　8. Melt blowing equipment selection

　　1. The configuration should be complete: extruder → screen changer (filter) → metering pump → die head → switchboard (auxiliary hot air) → spinneret → mesh to form a melt blown cloth.

　　2. The speed of the extruder, the parameters of the metering pump, the advantages and disadvantages of the die head, the flow temperature and speed parameters of the hot air, the angle of the die head, the angle of the fan blades, the receiving distance of the meltblown material, etc., the adsorption parameters under the mesh forming device determine the melting The quality of the spray cloth.

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