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The Nanoval process - Best for finefiber spunbonds

February 10, 2006

Main features are the use of cold air at moderate pressure with robust equipment to produce fine filaments. The process is based on a different mechanism producing fine and finest filaments: one melt monofil splits up into a number (normally around 50, but up to several hundreds) of finer ones. If the equipment obeys the desired aero- and hydrodynamics there is a set of operating variables where splitting is observed. This is a strong hydrodynamic effect which cannot be observed in other fiber spinning processes with filament drawing.   

Filaments produced with this process are very fine and they are continuous, practically no shots. The following data for the Nanoval process always refer to the mean filament diameter d50 as statements like  down to m ,  1 μm to 10 μm  or the like can not be seen as well defined, although being widely found. With standard Nanoval process a mean filament diameter below μm down to 2 μm can be reached. With  Nanovlies  a new product going into the nano region has been introduced recently. Filament mean diameters here go down to and below 1 μm, e.g. in a PP spunbond of d50 = 1.2 μm about 2/3 are below 1 μm and go down to 0.4 μm = 400 nm. Although focus of the Nanoval process is finest filaments, coarse ones up to a mean diameter of 15 μm and more can be produced, too. At present this however is not the main target.

A comparison of Nanoval with other meltblown processes shows that throughput per hole is distinctly higher for the Nanoval process, whereas throughput per meter is for all processes in a  similar range with slight advantages for Nanoval and Biax coarse fibers compared with conventional meltblown.

Also, the air consumption per kilogram of melt sees the three compared processes in a similar range. But, if in conventional meltblown finest filaments are the target, throughput must be reduced, an impact not existing for the Nanoval process or at least being much weaker. Anyway, Nanoval needs no quenching air at high throughputs and coarse fibers due to spinning with cold air.

All three factors—air quality as well as heating and compressing the air—can be combined in the energy consumption per kilogram of spunmelt. Nanoval uses cold air  for spinning, needs no heating of the air.

Energy consumption of the Nanoval process for every filament diameter is much smaller than in other processes and energy has to be aid. The difference becomes bigger, the finer the filaments are. The reason is that compressing the air needs less energy than heating it. To compress a stream of 1000 kg/hour of ambient air to one bar of power of 17.7 KW is needed at adiabatic compression and it is heated to 64°C. Whereas one bar is sufficient for most melt blowing processes, heating up to 64°C for meltblown processes by far does not  give the needed temperatures between 260°C and 300°C, or in the cases of finer fibers up to 400°C. Therefore, heating determines energy consumption—and the Nanoval process uses cold air or, to be precise, can use any temperature caused by compression and above.
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