The reason why the mask can not be made with a mask machine is because the core material of the gap mask: melt-blown cloth.
The "heart" meltblown of the mask is really sprayed out. . .
At the end of January, citing a report from China Daily, the person in charge of the mask factory in Xinxiang, Henan said that the current price of one ton of melt-blown cloth has increased by nearly ten thousand yuan.
On February 23, according to surging news reports, Ms. He, the head of a clothing factory in Quzhou, Zhejiang Province, said: meltblown cloth is the core of masks. There is no stock at all. The price is one price a day, and the unit price per ton has been from the original 20,000 yuan. It has risen to more than 200,000 yuan.
In just one month, many companies have switched to masks. Although the price of melt-blown fabrics has risen greatly, the shortage of melt-blown fabrics in the country is scarce, and there are not so many melt-blown fabric supply markets. Now they are stuck in melt-blown fabrics. Cloth link.
01
What is meltblown
Cut a used medical mask, you will find: the mask has three layers, (inner layer) moisture absorption layer, (middle layer) core filter layer, and (outer layer) water blocking layer.
The "heart" meltblown of the mask is really sprayed out. . .
Because according to the national production regulations, medical masks contain at least 3 layers of non-woven fabrics (N95 grade masks, the structure is optimized: (middle layer) the core filter layer is more, and the thickness is thicker).
The "heart" meltblown of the mask is really sprayed out. . .
S layer: Polypropylene special resin (Sinopec)-Nonwoven Fabric Factory-Mask FactoryLayer M: Special resin for polypropylene with high melt index (Sinopec)-Modified plastics factory (During epidemic prevention, Sinopec researched and produced special materials for meltblown fabrics)-Meltblown nonwoven fabric factory-Mask factory.
Meltblown cloth, commonly known as the "heart" of the mask, is the filter layer in the middle of the mask, which can filter bacteria and prevent the spread of germs. Meltblown cloth is a film made of polypropylene with a high melt index. It is a film composed of many criss-cross fibers stacked in random directions. The fiber diameter ranges from 0.5 to 10 microns, and the fiber diameter is about 30 cents of the hair. one.
The "heart" meltblown of the mask is really sprayed out. . .
The following picture is a photograph of the structure of the meltblown cloth:
The "heart" meltblown of the mask is really sprayed out. . .
(Photographed by Fina Desktop Scanning Electron Microscope)When you see the picture, do you worry that the gap in the meltblown cloth is so large, how do you filter viruses in the environment? Although the size of the new coronavirus is very small, about 100 nanometers (0.1 micrometers), the virus cannot exist independently. The main transmission routes are secretions and droplets when sneezing. The size of the droplets is about 5 micrometers. One, second, the meltblown fabric is essentially a fiber filter. When the droplets containing the virus are close to the meltblown fabric, they will also be electrostatically adsorbed on the surface and cannot penetrate.
The "heart" meltblown of the mask is really sprayed out. . .
Schematic diagram of fiber filtration mechanismAlthough the raw materials of the S layer and M layer of the mask are all polypropylene special resins, the special materials for meltblown fabrics and other nonwoven fabric raw materials are very different in production process and performance.
The "heart" meltblown of the mask is really sprayed out. . .
Meltblown ▲
02
Where did the meltblown cloth come from?
The special material for meltblown cloth is polypropylene with high melt index. The higher the polypropylene melt index, the finer the melt-blown fibers, and the better the filterability of the melt-blown cloth.
The "heart" meltblown of the mask is really sprayed out. . .
Special material for meltblown cloth photo by Li Yinghao ▲Let's see how the meltblown fabric is produced:
Don't underestimate this video. On February 23, Shanghai Petrochemical urgently researched and developed the meltblown non-woven special material for trial production successfully. It can produce 6 tons per day, which will help add nearly 6 million pieces of disposable medical masks per day.
The "heart" meltblown of the mask is really sprayed out. . .
Since the raw material polypropylene for melt-blown cloth is derived from petroleum, petrochemical companies have an advantage in producing melt-blown cloth. In order to solve the problem of high melt index, Shanghai Petrochemical has set up a research and development team to carry out formulation research, test analysis and scale-up tests, and strives to overcome the difficulties of equipment and technology before finally successfully overcoming the problem of high melt index polypropylene modification production.
The "heart" meltblown of the mask is really sprayed out. . .
Employees are analyzing the melt index of the samples. Photo by Xu Ruosun▲It is reported that through process optimization, Shanghai Petrochemical is expected to increase production by about 2 tons per day in the short term, reaching a daily production of 8 tons of special materials for meltblown cloth. It should be known that domestic melt-blown non-woven fabrics were relatively niche, with an annual production capacity of 53,500 tons, accounting for 1% of the non-woven fabric production capacity. They are mainly used to produce masks, environmentally friendly materials, clothing, battery separators and other products.
The "heart" meltblown of the mask is really sprayed out. . .
Photo by Li Yinghao ▲
It is said that the melting index of Shanghai Petrochemical's previous products is only one-thirtieth of the special material for mask melt-blown cloth. Facing the challenges of insufficient hardware such as slow pelletizing speed of the extruder, short cooling distance, and insufficient screw length, the company tried to find ways to make use of the existing equipment by transforming the electronic control system and transmission system, calling other production line sinks, and optimizing the die head. Carry out emergency transformation and adjustment to meet production needs.
03
Content extension
Comparing the cross-sectional views of N95 masks and medical surgical masks, the scanning electron microscope pictures can clearly see that the thickness of the melt-blown cloth of the surgical mask is 156 microns, and the thickness of the melt-blown cloth layer of the N95 grade mask is 521 microns, which is 3 Times.
The "heart" meltblown of the mask is really sprayed out. . .
Cross-sectional view of a medical surgical mask, taken by a Feina desktop scanning electron microscopeThe "heart" meltblown of the mask is really sprayed out. . .
Cross-sectional view of N95 mask, taken by FINA desktop scanning electron microscopeAccording to the analysis of professional analysts, due to the relatively strong demand for domestic masks, especially medical masks, there is a short-term supply gap in melt-blown non-woven fabrics. However, due to the gradually controlled epidemic situation in Hubei Province, the demand for masks is expected to gradually decline, so the price in the short term It will maintain a high level, but the probability of a sharp increase is relatively small. With the epidemic prevention and control in place in the future, the price of melt-blown non-woven fabrics is expected to fall back to normal levels.