At present, the world is actively preventing and controlling the epidemic. The most basic protective equipment for residents is masks. Because viruses require high standards for masks, manufacturers must use melt blown cloth in anti-virus masks. Now, what kind of filter material is melt blown cloth? Let's understand it together! Can the meltblown cloth filter layer be washed with water?
About melt blown cloth
Melt blown cloth is the core material of the mask. The melt blown cloth is mainly made of polypropylene, and the fiber diameter can reach 1 to 5 microns. There are many voids, fluffy structure and good anti-wrinkle ability. The ultra-fine fibers with unique capillary structure increase the number and surface area of fibers per unit area, so that the meltblown cloth has good filterability, shielding, heat insulation and oil absorption. It can be used in air, liquid filter materials, isolation materials, absorbing materials, mask materials, thermal insulation materials, oil absorbing materials and wiping cloths.
On March 8, 2020, the State-owned Assets Supervision and Administration Commission of the State Council introduced that in the face of the blowout demand for the core material of masks, the State-owned Assets Supervision and Administration Commission of the State Council has guided and promoted relevant central enterprises to accelerate the construction of production lines, put into production as soon as possible, and expand the supply of melt blown cloth market for the epidemic Prevention and control provide protection. According to the news from the State-owned Assets Supervision and Administration Commission of the State-owned Assets Supervision and Administration Commission of the Medical Supplies Special Working Group, as of 24:00 on March 6, the output of meltblown cloth by the central enterprises on that day reached approximately 26 tons. As the new production line is completed and put into production, the output of melt blown cloth is expected to increase significantly in the next week. The State-owned Assets Supervision and Administration Commission and central enterprises will continue to increase efforts to ensure the supply of medical materials such as raw materials for the production of medical masks.
What is meltblown cloth?
The main structure of medical mask is three-layer non-woven fabric, namely SMS structure.
The inner S layer is ordinary non-woven fabric, which is mainly hygroscopic;
The outer S layer is a non-woven fabric with waterproof treatment, which is mainly used to insulate the liquid sprayed by the patient and have the effect of preventing droplets;
The middle M layer uses an electret-treated meltblown non-woven fabric, which can filter suspended bacterial particles and is the most important core layer.
Melt blown cloth, commonly known as the "heart" of masks. Its main raw material is polypropylene, a film made of many crisscross fibers stacked in random directions. The fiber diameter ranges from 0.5 to 10 microns, and the fiber diameter is about one-thirtieth of the hair.
The picture below is a photo of the structure of melt blown cloth:
Seeing this, are you a little confused? How does the meltblown cloth filter out viruses in the environment?
Take the new type of coronavirus as an example. Although the size of the new type of coronavirus is very small, about 100 nanometers (0.1 microns), the virus cannot exist independently. Its transmission routes are mainly secretions and droplets when sneezing. Around 5 microns, this is one;
Second, the meltblown cloth is essentially a fiber filter. When the virus-containing droplets are close to the meltblown cloth, they will be electrostatically adsorbed on the surface and cannot penetrate.
Water washing damages its own structure, which is easy to cause cracking, and electrostatic adsorption is gone, and it cannot block the virus and affect the filtration efficiency. Without static electricity, melt blown cloth is not as good as cloth, and the filtration efficiency is only 35%.
Although the S layer and M layer of the mask are made of special polypropylene resin, there are some differences in the production process between the special material for meltblown cloth and other non-woven materials. For example, the M layer has one more modified plastic Link.
Petroleum → Atmospheric and Vacuum Unit / Secondary Coking Hydrogenated Naphtha / Hydrocracked Light Naphtha → Ethylene Cracking Unit → Ethylene/Propylene → Ethylene Oxide/Polypropylene (Special Resin)
S layer (spunbond layer): polypropylene special resin → sent to non-woven fabric factory to produce S layer → sent to mask factory
M layer (melt blown layer): polypropylene special resin → sent to modified plastics factory to produce special material for melt blown cloth → sent to melt blown non-woven fabric factory to make M layer → sent to mask factory
How did the melt blown cloth come from?
The special material for melt blown cloth is polypropylene with high melt index. The higher the melt index of polypropylene, the finer the melt-blown fiber and the better the filterability of the melt-blown cloth.
Application range of melt blown cloth
(1) Medical and health cloths: surgical gowns, protective clothing, disinfection wraps, masks, diapers, sanitary napkins, etc.;
(2) Home decoration cloth: wall cloth, table cloth, bed sheet, bedspread, etc.;
(3) Garment cloth: lining, adhesive interlining, wadding, shaped cotton, various synthetic leather base cloth, etc.;
(4) Industrial cloth: filter material, insulating material, cement packaging bag, geotextile, covering cloth, etc.;
(5) Agricultural cloth: crop protection cloth, seedling raising cloth, irrigation cloth, thermal insulation curtain, etc.;
(6) Others: space cotton, thermal insulation materials, linoleum, cigarette filters, tea bags, itd.
The meltblown cloth filter material is randomly distributed and bonded together by polypropylene superfine fibers. The appearance is white, flat and soft. The material fiber fineness is 0.5-1.0μm. The random distribution of fibers provides more thermal bonding between fibers. Opportunities, so that the melt blown gas filter material has a larger specific surface area, a higher porosity (≥75%). After high-pressure electret filtration efficiency, the product has the characteristics of low resistance, high efficiency and high dust holding capacity.
Melt blown cloth use
Melt blown cloth uses polypropylene as the main raw material, and the fiber diameter can reach 0.5-10 microns. These ultra-fine fibers with unique capillary structure increase the number and surface area of fibers per unit area, so that the melt blown cloth has good air filtration properties. , Is a relatively good mask material. In large, medium and small medical institutions, in earthquake- and flood-affected areas, and in the high incidence of SARS, avian influenza and H1N1 virus, melt blown filter paper plays an irreplaceable role with its strong filtering performance. effect.
The melt blown cloth is mainly used for:
1. Filter material
2. Medical and health materials
3. Environmental protection materials
4. Clothing materials
5. Battery separator material
6. Wipe materials
How to distinguish the authenticity of meltblown cloth
The inferior products of the two layers are easy to identify. A useful medical mask must have three layers, with spunbonded non-woven fabric on both sides, and a meltblown fabric of sufficient weight in the middle. The picture shows the melt blown cloth, and the filtering effect is related to its weight (grams per square meter). This range is 18-500g, and the filtering effect is good for 40-50g or more. Do not buy masks without meltblown cloth! Identify true and false meltblown cloth masks. "A good meltblown cloth looks white rather than transparent because it weighs enough. It looks obviously different from the spunbond non-woven fabrics on both sides</h2>, straightforward. In other words, it looks like paper. If it looks different but obviously thin, it is a meltblown cloth with a small weight. The thinner the meltblown cloth, the worse the effect.
Simple identification method:
First, as the name suggests, the melt blown layer will melt when encountering fire, but will not burn. Paper will burn in fire.
Second, the melt-blown layer has static electricity. If you tear the melt-blown layer into strips, you will obviously feel the electrostatic adsorption effect, and you can also adsorb strips of the melt-blown layer on the stainless steel. You can remove the used mask and check it to avoid wearing a fake mask~
How many masks can 1 ton of meltblown cloth produce
One ton of meltblown cloth can make masks at a one-time loss of about 1.05 million, KN95 600,000, medical N95 400,000, according to the actual production rate can be appropriately increased.
Is the meltblown cloth electrostatically charged?
In order to make breathing as smooth as possible while meeting protection requirements, qualified meltblown masks will undergo an electret process. The surface of the fiber after the electret has a large amount of electric charge, and the fine particles are intercepted by the electrostatic adsorption effect. We can also use the classic physical feature of electrostatic adsorption to verify whether the meltblown cloth is charged. The electret non-woven fabric will have obvious attraction to hair, iron filings, itd. Although the amount of meltblown cloth in a single mask is small, the effect of adsorbing hair may not be obvious, but the existence of electric charge can also make it adsorb on the wall. Although some of the fake and inferior masks have meltblown cloth, they have not been electret, or because the electret technology is not enough, the storage time is too long, etc., which causes a large amount of electric charge to dissipate, and its protective performance will naturally not meet the standard.