Methods for Improving the Quality of Meltblown Nonwovens
Melt-blown non-woven fabric is a kind of non-woven fabric made by melt-blown non-woven fabric machine by spraying polymer melt through high temperature and high-speed airflow so that it can be rapidly stretched.
After the polymer chips are heated and pressurized into a molten state by a screw extruder, they reach the spinneret hole at the front end of the nozzle through the melt distribution channel, and then pass through two convergent high-speed, high-temperature airflows of the melt-blown nonwoven machine after extrusion. stretch to refine it. The attenuated fibers are cooled and solidified on the screen curtain device to form a meltblown nonwoven fabric.
Continuous meltblown nonwoven production technology has experienced more than 20 years of development in my country, and its application fields have expanded from battery separators, filter materials, oil-absorbing materials, and thermal insulation materials to medical, sanitation, health care, protection, and other fields.
Its production technology has also developed from a single meltblown production to a composite direction. Among them, the melt-blown composite material treated with electrostatic electret can be widely used in electronic manufacturing, food, beverage, chemical industry, airports, hotels, and other places due to its low initial resistance, and large dust holding capacity and high filtration efficiency. Purification treatment and medical high-performance masks, industrial and civil dust collector filter bags.
Meltblown nonwoven fabric of polypropylene material (it is an ultra-fine electrostatic fiber cloth that can capture dust), the pore size and thickness of the fibers affect the filtering effect. Particles of different diameters are filtered by different principles, such as particle volume, impact, and diffusion principles that lead to being blocked by fibers, and some particles are filtered by electrostatic fibers through electrostatic attraction principles.
The test of filtration efficiency is carried out under the particle size specified in the standard, and different standards will use particles of different sizes for testing. BFE usually uses bacterial aerosol particles with an average particle diameter of 3µm, while PFE generally uses sodium chloride particles with a diameter of 0.075µm. Purely from the filtering effect, the effect of PFE is higher than that of BFE.
In the standard test of KN95 masks, particles with an aerodynamic diameter of 0.3µm are used as the test objects, because particles larger or smaller than this diameter are easier to be intercepted by filter fibers, while particles with an intermediate size of 0.3µm are more difficult to filter. Although the virus is small in size, it cannot spread in the air alone. It needs droplets and droplet nuclei as carriers to scatter in the air, so it can be easily filtered out.
The core of meltblown cloth technology is: on the premise of reducing breathing resistance at a minimum, it can also achieve a high-efficiency filtration effect, especially meltblown cloth above N95, VFE grade meltblown cloth to electret masterbatch formulation, meltblown material performance, The spinning effect of the meltblown line, especially the addition of electret masterbatch, will affect the thickness and uniformity of the spun fiber, and achieving low resistance and high efficiency is the core technology.
Factors affecting the quality of meltblown cloth
MFI of polymer raw materials
As the best barrier layer for masks, meltblown cloth is an extremely fine material, and the interior is made up of many criss-cross microfibers stacked in random directions. Taking PP as an example, the higher the MFI, the finer the filaments drawn during melt-blown processing, and the better the filtration performance.
Thermal jet angle
The hot air injection angle mainly affects the stretching effect and fiber morphology. Smaller angles encourage the thin streams to form parallel fiber bundles, resulting in poor nonwoven uniformity. If the angle tends to 90°, a highly dispersed and turbulent airflow will be generated, which is conducive to the random distribution of fibers on the condensed mesh curtain, and the final meltblown cloth has good anisotropic performance.
Screw extrusion speed
Under the condition of constant temperature, the screw extrusion rate should be kept within a certain range: before a certain critical point, the faster the extrusion speed of the melt-blown non-woven fabric machine, the higher the weight of the melt-blown non-woven fabric, and the greater the strength;
At the critical value, the strength of the melt-blown fabric decreases, especially when the MFI>1000, which may be because the extrusion rate of the melt-blown non-woven fabric machine is too high, resulting in insufficient drafting of the filaments and serious filaments, so the fabric surface The bonding fibers are reduced, and the strength of the meltblown cloth is reduced.
Thermal velocity and temperature
Under the same conditions of temperature, screw speed, and receiving distance (DCD), the faster the hot airspeed, the smaller the fiber diameter, the softer the non-woven fabric feels, and the more the fibers are entangled, resulting in a denser and smoother fiber web. Strength increases.
Receive distance (DCD)
An excessively long receiving distance in the melt-blown non-woven production line will lead to a decrease in vertical and horizontal strength and bending strength, and the non-woven fabric will feel fluffy, which will lead to a decrease in filtration efficiency and filtration resistance in the melt-blown process.
Meltblown die head (hard index)
The mold material and process temperature setting in the meltblown nonwoven machine. Use some low-end die steel instead, there will be some invisible cracks in the process of use, the aperture processing is rough, and the precision is poor. The result is uneven spinneret, poor toughness, different spinneret thickness, and easy-to-produce crystallization.
Net bottom suction
Process parameters such as air volume and air pressure for suction at the bottom of the net.
The speed of the net curtain is slow, the weight of the meltblown cloth is high, and the filtration efficiency is higher. On the contrary, also established.
Electret voltage, electret time, electret molybdenum wire distance, electret ambient humidity, etc. will affect parameters such as filtration quality.
The methods for improving the quality of melt-blown non-woven fabrics are introduced above. The parameter settings of the melt-blown non-woven fabric machine and the quality of raw materials will affect the melt-blown non-woven fabrics. If you plan to buy high quality meltblown nonwoven machine, welcome to contact us.
AZX is a professional China custom non-woven machine manufacturer, specializing in the production of S (spunbond), M (meltblown), SS, SXS, SSS, SMS, SMMS, SSMMS, and other types of PP (polypropylene) spunbond and meltblown without Textile production line. Founded in 2009, our group has been involved in non-woven machinery, non-woven fabrics, medical supplies, and other fields, providing high-quality products and services to global users.