This will be clearly evident from the sophisticated products on show at INDEX 11 – the leading nonwovens exhibition which takes place at Palexpo in Geneva, Switzerland, from April 12-15 2011.
The actual term ‘nonwovens’ dates back to more than half a century ago, when the materials were often regarded as low-price substitutes for traditional textiles and generally made from carded, staple fibres on converted textile processing machinery.
The yarn spinning stage is omitted in the nonwoven processing of staple fibres, with bonding of the web by various methods – chemical, mechanical or thermal – replacing the weaving or knitting together of the yarns in traditional textiles.
Dividing today’s nonwoven products into three major areas – drylaid, wet-laid or spunlaid – it can be said that drylaid materials have their origins in textiles, wet-laid materials in papermaking, and spunlaid products in polymer extrusion and plastics.
In nonwoven manufacturing systems, the fibre material or extruded thermoplastic is deposited or laid on a forming or conveying surface, and the physical environment at this phase can be dry (quenched in air), wet or molten – drylaid, wetlaid or spun.
The web formation phase of nonwoven manufacturing processes transforms previously prepared/formed fibres, filaments or thermoplastic resins or films, into layers of loosely-arranged networks – webs, batts, mats or sheets.
Mechanical and fluid means are employed to achieve the preferred orientation in the web, through the use of machinery initially adapted from the textile, paper or extrusion industries, but which today are achieved with specifically designed equipment. Other critical fabric parameters established at the web formation stage are the unfinished product weight and the manufactured width.
Each web-forming system is used for specific fibres or products, although the exception here is with highloft nonwoven production, which employs cards and crosslappers as well as air-forming systems.
Spunlaid shift
A key trend observed over the past 20 years has been a tremendous shift – especially for the hygiene and medical markets – away from drylaid techniques to spunlaid products, to the extent that the latter now account for well over 40% of nonwovens manufactured worldwide.
Spunlaid nonwovens – spunbond, meltblown, apertured films and the many layered combinations of these products – are manufactured with machinery developed from polymer extrusion, with the fibre structures simultaneously formed from molten filaments and manipulated.
In a basic spunbonding system, sheets of synthetic filaments are extruded from polymer onto a conveyor as a randomly-oriented web in the closest approximation to a continuous polymer-to-fabric operation.
Most of the first proprietary spunbonding systems were developed by synthetic fibre producers such as DuPont in the USA and Rhône-Poulenc in France.
DuPont is regarded as the first to successfully commercialise spunbonding with its Typar product, launched as a tufted carpet backing system in the mid-1960s.
The first commercial spunbonding system to be offered was the Docan system developed by the Lurgi engineering group in the 1960s and the next major step towards the global commercialisation of the spunbond process was with the introduction of Reifenhäuser’s Reicofil system in 1984.
The first Reifenhäuser Reicofil spunbonding line was installed in China in 1986. Today, the latest Reocofil technology is capable of producing twenty times what was possible on that first line.
The technology has also allowed the consumer products companies to demonstrate a considerable reduction in the weights of items such as diapers – with like-for-like performance – over the past 20 years.
The concept of the meltblowing of thermoplastics to form microfibres of less than 10 microns, meanwhile, was first demonstrated back in the early 1950s by the US Naval Research Laboratories, which was interested in developing such fibres to collect radioactive particles in the upper atmosphere to monitor the worldwide testing of nuclear weapons.
In the late 60s and early 70s, Exxon Research, in looking for uses for its newly commercialised polyolefin – polypropylene – tried to use a polypropylene reactor slurry to produce synthetic paper. Its researchers became aware of the Naval Research Laboratories publications and these served as a starting point for a multi-year, multi-million dollar project.
Exxon opted to license the resulting meltblowing technology, rather than commercialise it, with considerable success.
The most commonly accepted and current definition for the meltblowing process is “a one‑step process in which high‑velocity fluid – normally air – blows molten thermoplastic resin from an extruder die tip onto a conveyor, take‑up screen, or substrate, to form a fine fibred self‑bonded web”.
The extremely fine fibres of the conventional meltblowing process result in a soft, self‑bonded fabric with excellent covering power and opacity. Because of the fineness and tremendous number of fibres, meltblown webs can develop significant bonding strength through fibre entanglement.
The many small pores and oleophilic and hydrophobic nature of PP webs made it a natural candidate for oil sorbents and wipes. Hydrophilic additives and/or topical treatments provided hydrophilicity, which enabled a number of companies to produce and market meltblown webs starting in the early 1970s. This market is continuing to grow at a 7‑8% rate.
Kimberly‑Clark, the most prominent practitioner of the meltblowing process, has made many valuable innovations. Its SMS patents opened the medical fabric and surgical wrap applications, and the company’s patented ‘CoForm’ technology has been widely used in wipes.
Today, meltblown layers are critical in composite spunmelt fabrics for personal hygiene products and vital to a large number of filtration processes.
The next step?
The latest trend to have a significant impact is the incorporation of nanofibre nonwoven layers into products – most notably, to date, in the area of filtration fabrics.
The next major change is likely to be a shift away from petrochemical-based polymers and fibres towards biobased alternatives such as polylactic acid (PLA), for some, if not all technologies.
How significant this will be is dependent on a number of factors beyond the control of the industry. It could even be driven by legislation, as the push towards reducing the reliance on petrochemicals is an issue of increasing importance to legislators, businesses and the general public.. The industry is focused on this trend, which is the subject of extensive R&D efforts on the part of both technology suppliers and nonwovens manufacturers.
