Processes and Machines for Nonwovens Production

According to DIN 61210, nonwovens are defined as fabrics that consist entirety or to an essentiai part of fibers. Fibers that define the character of nonwovens are randomized or orientated in a certain direction. The connection between the fibers is affected by positive (interiacing) or nonpositive (congiutination) means. 

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Chapter 6 Processes and Machines for Nonwovens Production Adolf Graber... 

One effective way to lower the cost of making nonwovens of high mass per unit areas is seen in the elimination of some of the process steps and the combination of others for the production of reclaimed fibres and for web formation. This combination of processes makes use of a special breaking-down machine. It is designed to make a novel mat-like structure based on textile waste, eliminating some of the cost-intensive working steps. 

Nonwovens The textile and paper industries are based on the two oldest (wet and dry) processes. Manufacturers of nonwovens for plastics draw on both. With the wet, there are basically two types namely the Fourdrinier and cylinder machine types that have been modified. In addition, two basic types exist for the process formation of the web and application of the bonding agent or system where mechanical carding of fibers is used. The particular equipment and method of operation to be used, with their many modifications, is influenced by desired requirements such as mechanical properties, softness, surface condition, tenacity, etc. There are certain t) es of so-called nonwoven fabric that are directly formed from short or chopped fiber as well as continuous filaments. They are produced by loosely compressing together fibers, yarns, rovings, etc. with or without a scrim cloth carrier assembled by mechanical, chemical, thermal, or solvent methods. Products of this type include melted and spun-bonded fabrics. 

Needle-punched warp-knitted nonwoven material serves us as a further example of how important the quality of reclaimed fibres is. This material is used to substitute for the components of polyurethane foam in laminated composites. The purely textile composite resulting allows one to recycle both the production waste generated and the composite structure itself at the end of its life (see Chapter 3). To make sure a nonwoven containing 40% of reclaimed fibres can be well processed on a warp-knitting machine and shows full functionality when used as a laminated composite for a motor vehicle seat, the reclaimed fibre used needs to meet the following requirements ... 

The melt blowing process responds to process variables more readily than most of the other nonwoven processes to produce a wide variety of end products. The actual process parameters that determine final web properties involve the selection of polymer or resin, conditions in the extruder or melt tank, geometry and condition at the die tip and fiber distribution and separation at laydown. Modem melt-blown lines are designed with highly automated machine and process control equipment, which allow for quick selection of particular parameters and easy machine adjustments. 

Meltblown technology is similar to spunbond technology whereby the production of ultra-fine filament nonwovens takes place under very economical process conditions. Within this process, a thermoplastic polymer is extruded through a linear-length die which contains several hundred small ports or orifices. Streams of hot air exit the die nose to rapidly attenuate the extrudate to form very fine filaments. These filaments are then air-blown at high velocity onto a collector screen. This forms a filtered and bonded nonwoven web which is subsequently wound for further processing. Similar to spunbonded roll materials, meltblowns will exhibit good machine direction and cross direction stability and wear resistance. 

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