Almost 500,000 tons of nonwovens are currently used annually in the production of filters, which corresponds to approx. 10% of current worldwide industrial nonwovens manufactured. Here, the filter market is split into 2 areas: airand liquid filtration. While in excess of 170,000 tons of nonwovens were manufactured for gas/air filters in 2015, the volume for liquid filters was almost double at around 295,000 tons.
Melt blowing is a conventional fabrication method of micro- and nanofibers where a polymer melt is extruded through small nozzles surrounded by high speed blowing gas. The randomly deposited fibers form a nonwoven sheet product applicable for filtration, sorbents, apparels and drug delivery systems. The substantial benefits of melt blowing are simplicity, high specific productivity and solvent-free operation. Choosing an appropriate combination of polymers with optimized rheological and surface properties, scientists have been able to produce melt-blown fibers with an average diameter of down to 36 nm.
During volcanic activity a fibrous material may be drawn by vigorous wind from molten basaltic magma called Pele’s hair. The same phenomenon applies for melt blowing of polymers. The first research on melt blowing was a naval attempt in the USA to produce fine filtration materials for radiation measurements on drone aircraft in the 1950s. Later on, Exxon Corporation developed the first industrial process based on the melt blowing principle with high throughput levels.China produces 40% of the non-woven fabric in the world with the majority produced in Hebei , Shandong and Jiangxi province.
The main uses of melt-blown nonwovens and other innovative approaches are as follows.
Nonwoven melt-blown fabrics are porous. As a result, they can filter liquids and gases. Their applications include water treatment, masks, and air-conditioning filters.
The high absorption of melt-blown fabrics is exploited in disposable diapers and feminine hygiene products.