Spunbond process system

The spunbond process is a nonwoven manufacmring system involving direct conversion of a polymer into continuous filaments, integrated with the conversion of the filaments into a random laid nonwoven fabric. Examples for the used technologies are shown in the Figs 5.1—5.4. 

Besides these general procedures, applied to the production of PO fibers before 1965, other modem ways have been developed and used for melt spinning. They include high and ultrahigh speed spinning, the split-film method, the spunbond process, and the melt-blown system. 

Compared with the spunbond process, the melt-blown system (spray method) produces microdenier (sprayed) fibers. Molten or dissolved fiber-forming PO polymers are forced with a spray gun or through a multiple-hole extruder to disrupt the filament into a high velocity hot air jet, to form superfine fibers less... 

The conventional fiber producing route (long system) is essential for the production of certain types of continuous filament and for the equipment used in association with the spunbonding process. 

In the spunbonded process, filament formation can be accomplished with one large spinneret having several thousands holes or with banks of smaller spinnerets containing at least 40 holes. After exiting the spinneret, the molten filaments are quenehed by a cross-flow air system, then pulled away from the spinneret and attenuated (drawn) by high pressure air. 

Asahi Chemical Industries (ACl, Japan) are now the leading producers of cuprammonium rayon. In 1990 they made 28,000 t/yr of filament and spunbond nonwoven from cotton ceUulose (65). Their continuing success with a process which has suffered intense competition from the cheaper viscose and synthetic fibers owes much to their developments of high speed spinning technology and of efficient copper recovery systems. Bemberg SpA in Italy, the only other producer of cuprammonium textile fibers, was making about 2000 t of filament yam in 1990. 

After the development of spunbonded and meltblown processes, combined systems such as SMS (spunbonded/meltblown/spunbonded) were developed to combine the benefits of each fabric type. In the late 1990s bicomponent spun-bonded technology was introduced. 

However, modern melt spinning distribution system technology has clearly demonstrated the capability to produce fibers with smaller size and better consistency than either of the two aforementioned techniques. Multicomponent fiber sizes as low as -0.04 pm (-40 nm) have now been demonstrated commercially at attractive production rates [22]. In addition, micro-sized (1-10 pm) and nano-sized (<1 pm) multicomponent fibers can be produced with improved production rates, economics and physical properties over the other systems, and with an even broader choice of polymers [22]. Multicomponent fiber production can be used to create fibers in staple or continuous filament form using the spunbond and melt blowing processes. 

All the known methods for spunbond fabrication with spin extruders process the chips into a melt, which is then guided by means of spinning heads with internal melt piping systems and spinning pumps and extruded through the spinnerets (with different round, rectangular cross sections) to the filaments. Following the filament path, the main takeup ways to obtain the filament bundle are [163, 164] ... 

There are many compact spunbond systems with considerable flexibility in the basic process (e.g., the Reifenhauser or the Lurgi Docan process). 

Recently, tricomponent spinning systems have been developed to coextrude three different polymers into each fibre. Interestingly, some bi-component cross-sections have been utilised in spunbond fabrics, in which filaments are extruded directly into a non-woven web without forming fibres as an intermediate product. The precision of polymer control to form the cross-section wiU continue to advance. After persistent research. Hills has been able to produce spin packs capable of stuffing hundreds of islands into each fibre cross-section, which enables the production of submicron microfibres. The future thus lies in further reduction of the ultimate denier of the fibres, improved spinning processes with more control, and exploration of more interesting applications for bi-component fibres with varying polymers and processes. 

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