In just one month, many companies switched to producing masks, but they still couldn’t meet the market and got stuck in the meltblown cloth link.
What is meltblown cloth
Cut out a used medical mask, you will find: the mask has three layers, (inner layer) absorbent layer, (middle layer) core filter layer, and (outer layer) water blocking layer.
Because according to national production regulations, medical masks contain at least 3 layers of non-woven fabrics (N95-level masks, structurally optimized: (medium layer) core filter layers have more layers and thicker thickness).
S layer: Resin for polypropylene (Sinopec) -Non-woven fabric factory-Mask factory
Layer M: High-melt-index polypropylene special resin (Sinopec)-Modified Plastic Factory (During Epidemic Prevention, Sinopec has developed special materials for meltblown cloth)-Meltblown non-woven fabric factory-Mask factory.
Meltblown cloth, commonly known as the “heart” of a 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 kind of film made of polypropylene with a high melt index. It is a film composed of many criss-cross fibers in a random direction. The fiber diameter ranges from 0.5 to 10 microns, and the fiber diameter is about 30% of the hair diameter. one.
The following picture is a photo of the meltblown cloth structure:
(Photographed by Feina Desktop Scanning Electron Microscope)
When you see the picture, are you worried? The gap between 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 microns), the virus cannot exist on its own. The main transmission channels are secretions and droplets when sneezing. The size of the droplets is about 5 microns. First, second, the meltblown cloth is essentially a fiber filter. After the virus-containing droplets approach the meltblown cloth, they will also be electrostatically adsorbed on the surface and impermeable.
Schematic diagram of fiber filtration mechanism
Meltblown cloth ▲
Where did the meltblown cloth come from?
The special material for meltblown cloth is polypropylene with high melt index. The higher the melt index of polypropylene, the finer the fibers are meltblown, and the better the filterability of the meltblown fabrics made.
Special material for meltblown cloth
Let’s see how meltblown cloth is produced:
Don’t underestimate this video. On February 23, Shanghai Petrochemical’s emergency R & D and production of meltblown non-woven fabrics was successfully trial-produced. It can produce 6 tons per day, which will help increase the number of disposable medical masks by nearly 6 million pieces per day.
Because polypropylene, the raw material of meltblown cloth, is derived from petroleum, petrochemical companies have an advantage in producing meltblown cloth. In order to solve the problem of high melt index, Shanghai Petrochemical Co., Ltd. set up a research and development team to carry out formulation research, test analysis and scale-up experiment, and worked hard to overcome various difficulties in equipment and technology.
Employees are analyzing the melt index of the samples
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 output of 8 tons of meltblown cloth. It should be known that the domestic meltblown non-woven fabrics were relatively small, with an annual production capacity of 53,500 tons , accounting for 1% of the non-woven fabric production capacity. It is mainly used for the production of masks, environmental protection materials, clothing, battery separators and other products.
It is said that the melting index of Shanghai Petrochemical’s previous products is only one-third of the special material for mask meltblown cloth. Facing the challenges of insufficient hardware such as slow pelletizing speed of the extruder, short cooling distance, insufficient screw length, etc., the company tried to find ways to adapt to existing equipment conditions by transforming the electronic control system and transmission system, calling other production line sinks, and optimizing the die head. Make emergency reconstruction and adjustments to meet production needs.