Application case of nanofiber filter membrane with high efficiency and low resistance filter material

1. Product application background

Affected by the new crown pneumonia, the domestic demand for masks has greatly increased, and the market supply of melt blown cloth as the core effective filter material for masks is huge. Electrospinning is a nano-fiber membrane production process. The use of electrospinning nano-fiber membranes for air filtration has great advantages. On the one hand, nano-fibers have a higher porosity and at the same time have smaller nanopores. The electrospinning process itself will be a process of electret treatment, reducing the production process steps and shortening the production time.

2. Product advantages

Electrospun continuous nanofibers are a new type of fiber material. On the one hand, electrospun nanofibers can not only intercept large particles through mechanical screening, but also have more significant direct interception effects and inertial impact effects on particle filtration. It is beneficial to improve the filtration efficiency of the fiber membrane; on the other hand, the nanofiber has a large specific surface area and good surface adsorption, which can increase the probability that the suspended micro particles in the air diffuse to the surface and deposit, and part of the small particles that enter the membrane can be adsorbed The retention improves the filtration efficiency of fine particles; at the same time, the high porosity, the uniform pore size distribution, and the interpenetrating porous structure between the fibers ensure that the nanofiber membrane has a relatively low pressure drop.

3. Product application

(1) Nanofiber filter membrane replaces melt blown cloth

General medical masks are composed of 3 layers, the inner and outer layers are spunbonded non-woven fabrics, with a layer of meltblown non-woven fabric in between. The outer layer of non-woven fabric can prevent droplets, the inner layer of non-woven fabric can absorb moisture, and the middle layer is a melt blown cloth, and the filtering and anti-bacterial effect can reach more than 95%.

The production of melt blown cloth is to melt the high-melt fiber material through the high-speed and high-pressure hot air stream, and then spray it from the spinning micro-holes, and draw it into ultra-fine fibers with a diameter of 0.3~7μm, like a marshmallow, under the guidance of airflow Spread it evenly on the collection device and use its own waste heat to glue the net. At this time, the melt-blown cloth only has a filtration efficiency of about 30%, and the melt-blown cloth needs to be charged with a certain amount of electric charge by means of high-voltage electrode discharge, which is called electret treatment, so that the electrostatic effect is used to absorb particles and filter efficiency. Can be increased to more than 80%.

The filtering effect is mainly divided into electrostatic effect, interception effect, collision effect, screen effect and Brown effect. Larger particles can be intercepted and filtered out by the filter material. When a part of it passes through the mesh channel of the filter material, the particles hit the fiber and are adsorbed by molecular gravity. In addition, some small-scale and low-speed particles are adsorbed by fibers during Brownian diffusion. In addition, the meltblown fabric fibers processed by electret are electrostatically charged, and very fine particles will be attracted by the electrostatic effect.

Electrospinning (Electrospinning) refers to the polymer fluid under the action of a high-voltage electrostatic field of thousands of volts to tens of thousands of volts, so that the polymer droplets overcome the surface tension to produce jetting trickles, which stretch and solidify during the jetting process. On the receiving screen, the technology of finally forming a non-woven, continuous mesh fiber mat is the current method that can directly and continuously prepare polymer nanofibers. Electrospinning has the advantages of stable performance, superior quality, wide variety of spinnable materials and controllable process. It has a wide range of application prospects in the development of engineering materials for physical interception of pollution. It is a safe, environmentally friendly and efficient air filter material.

At present, the large-scale electrospinning equipment owned by the team’s laboratory uses electrospinning to spin nanofiber filaments to the base spunbond non-woven fabric to form nanofiber filter membranes and base spunbond non-woven fabrics to form high-efficiency and low-resistance filtration Floor.

The upper layer of the electrospun nanofiber filter layer is nanofibers, and the lower layer is a micron-level non-woven filter material, which improves the filtration efficiency and can effectively filter particles or bacteria and viruses above 0.1 micron. The high porosity and fine pores of nanofibers have high efficiency and low resistance filtering effect. It can meet the KN95 protection standard specified in GB2626-2006 "Self-priming filter anti-particulate respirator for respiratory protective equipment".