The Wonderful World of Nonwovens

Colin F.White,Consultant MCW Technologies.

One of the first problems one encounters when speaking about nonwovens is that almost no one outside of the nonwovens business itself, knows what nonwovens are. A visit to the local supermarket and then asking the shoppers 'what is a nonwoven?' is unlikely to produce any positive response, and yet all of these everyday shoppers probably use nonwovens regularly in their daily life and possibly have products made from nonwovens in their shopping trolley.

Even official bodies have difficulty in describing exactly what is a nonwoven and at times, equally importantly, what it is not.

EDANA, the European Disposables and Nonwovens Association, based in Brussels, has a rather neat if somewhat imprecise definition:

Nonwovens are unique engineered fabrics offering cost-effective solutions for an increasingly wide range of applications.

When you look at this, it unfortunately does not tell you very much except that they are fabrics of some sort, unique, man-made and useful!

There is a much more official definition which comes into play in legal and custom and excise matters and this is contained within the European Committee for Normalisation definition EN29092, but this, like many a legal definition before it, tends to confuse rather than to clarify. So, where did these somewhat mysterious fabric-Like materials come from?

BACKGROUND AND ORIGINS. With the advantage of hindsight, we can find structures that we would classify today as nonwovens, dating way back in history. For example, although today we would not class all felt materials as nonwovens, they are close relatives and there are references to felts as early as the eighth century BC. The Mongolian tribes of Asia also had felt materials and references are present in the writings of ancient Greece and Rome.

In Japan, the production of a type of 'paper' known as Choya Gunsai using long (15-17mm) fibres was used to make clothes between 983BC and 4AD and is still used today to form a traditional kamiko, or 'paper' robe. In China, it was observed that when silk worms are ready to spin their cocoons and fall from the spinning trellis onto a flat surface, they secrete filaments in the form of a 'flat cocoon'. Records from the Song Dynasty (960-1279) describe fabrics made directly from these filaments. Some of the most modern forms of nonwovens are produced by a similar route directly from the spun polymer.

More recent history dates from the 1930's when Johnson & Johnson in the USA were trying to find a better way to make surgical gauzes. They came up with the idea of taking fibres, spreading them into a sheet and rather than condensing that sheet of fibres into a thread as in the textile process, adding a treatment which would bond the fibre web together and so form a 'non-woven' fabric.

Today, using the basic web forming step but with high-energy water jets entangling the fibres together into the web, a modern day version of surgical gauze is produced.

In Europe, Freudenberg (still the world's largest producers of nonwovens) back in the 1930's were trying to find a substitute for leather, which was their original business, and produced the first nonwovens based on leather fibres.

Other companies such as Kimberly-Clark and Kendall were all trying to produce nonwoven structures for use as textile replacement materials using parts of the already existing textile technologies.

In other technologies such as papermaking, companies were also looking at the possibilities offered by using long natural and man-made fibres to produce 'speciality papers'.

CH Dexter in the USA produced in 1934 the first commercial long fibred 'speciality papers' using a modified papermaking technique.

By 1940 Dexter had produced a range of what we now know as wetlaid nonwoven structures from a range of natural and man-made fibres including glass and other organic and inorganic fibres.

The fibres, although long in papermaking terms, were generally shorter than the fibres that could be used in the textile based processes.

A similar logical extension step occurred in the exploration of the making of fabrics directly from the polymeric materials being used to produce the man-made fibres, cutting out the fibre production step. The knowledge gained from producing man-made fibres led to the development of processes for making fabric directly from the polymer and the technologies now known as spunlaid, melt blown, and film based nonwovens were born.

As a result of this development activity, we can now identify a number of preexisting technologies from which were borrowed techniques that formed the basis of the nonwovens industry as we know it today, namely, leather processing, textiles, papermaking and the petrochemical business.

THE EXCITING ENTREPRENEURIAL STAGE. Nonwoven development through the 1980s and through into the 1990s expanded on the general ideas of trying to find ways of producing better fabrics, more efficiently and increasingly using technology hybridisation.

The early, relatively simple structures had done an excellent job of introducing the concept of nonwoven structures into many different applicational areas, but the market requirements were now becoming more sophisticated. Using methods developed from the basic borrowed technologies, producers started to realise the potential of totally new fabric structures that could be produced by combining these base line technologies together.

Most of the web forming techniques required additional processes of bonding and finishing to make the basic web into a form suitable for the selected end use.

These webs of fibres and/or filaments could be bonded together by chemical, thermal or mechanical means, and the bonded webs could then be further treated to provide water repellency, flame retardancy, increased stiffness or enhanced softness.

This was the phase of a production/development led industry which was very exciting and in which many developments took place that were based on no more than the plant owners whim or an over enthusiastic development team, but it showed just what potential (if not always commercial potential) the nonwovens business had.

However, globalisation and the introduction of marketing as an essential management discipline changed and set the scene for the next phase of development.

THE CURRENT SCENE. The rapid and sustained growth of the nonwovens business (from 40,000 tonnes in Western European countries in 1981 to over 1 million tonnes in 2000) has stimulated continuing development and innovation.

Market place acceptance has moved product requirements from the early substitute category, to quite sophisticated end use specifications dictated by the ultimate consumers asking for higher performance characteristics.

Consequently, the basic manufacturing technologies have had to be developed and extended to make them capable of producing webs to these higher specifications.

In the textile based technologies, used to produce carded nonwoven webs of various types, we now have the capability to handle a whole range of fibre diameters from below 1 decitex to 20 decitex and more and from 25-80mm in fibre length, to produce both directional and truly randomised structures.

These web forming techniques, combined with different types of bonding, have maintained the position of fibre based nonwovens and over 50% of the world production of nonwovens is produced by this textile based web forming technology.

Wetlaid nonwovens, based on the papermaking technologies, have secured a special almost niche market of their own. Despite the fact that for the most part this technology is limited to using short fibres (6mm being a typical fibre length), the wetlay route has achieved a whole range of remarkably uniform wetlaid nonwovens that are based on almost any of the currently available natural and man-made fibres. Recent developments in this area of simultaneous forming of three layer webs could result in a considerable expansion of this sector and work to combine wet laid webs with spunlaid filaments to produce composites will also create growth in the sector.

A 'sister' technology, short fibre airlaid nonwovens, was actually developed with the objective of producing paper grades including soft tissue without the use of water. Kimberly-Clark built an early machine to evaluate this but found that whilst technically it was possible to make good product, it was not commercially viable with low production speeds. However, the technology used has given rise to a whole family of absorbent cellulose structures that have found widespread acceptance in the absorbent hygiene products sector. At this time the main applicational areas are in feminine hygiene products, adult incontinence products and probably in the near future, in disposable baby diapers. These nonwovens are also finding applications in tabletop materials, food packaging, filtration etc.

The potential for this technology is very large, as fibres other than cellulose can be combined into multilayer structures with truly unique characteristics.

In the 'polymer to web' technologies, the early entrants during the 160's such as DuPont, Monsanto, Freudenberg, have been joined by many others attracted into this area by the availability of 'turnkey' equipment from companies such as Reifenhauser GmbH in Germany who have sold such machines all over the world.

Much of the material that is based on polypropylene goes to supply the constantly growing needs of the absorbent products sector, particularly disposable baby diapers. In Europe, this sector consumes 341,000 tonnes of nonwovens per year, of which 143,000 tonnes (42%) is produced by the spunlaid/meltblown technologies.

In this technology recent interest has been in the ability of some of the new systems to produce very fine decitex filaments, bicomponent webs, different polymers, i.e., polypropylene and polyester and composites based on the various combinations of spunlaid and meltblown that are now feasible.

A longside the lightweight polypropylene webs are a range of heavyweight polypropylene webs that find application as geotextiles for road construction and drainage.

There is also a considerable amount of heavyweight polyester based material that goes into roofing substrates and geotextiles of various types.

New suppliers of equipment that has been modified in the light of past operational experience can now offer the capability to produce the more sophisticated webs that are now being necessary to meet the end use performance specifications now required by the ultimate end users.

THE FUTURE SCENE. The combination of the growth and the resilience of the nonwovens industry to cyclic changes have encouraged raw material suppliers (fibres, polymers and additives) to produce materials specifically for the nonwovens sector.

This has brought about significant improvements in product quality and reproducibility and widened the scope for the application on nonwovens in many new markets.

Combined with this, the improvements in web forming systems and the development of novel bonding technologies have also had a marked effect on the acceptance of nonwovens as materials in their own right in many new applications.

Geographically, the production and use of nonwovens is now a truly international business and all of these factors taken together would indicate that this relatively new industry is assured of a prosperous and exciting future.

PRODUCTS THAT USE NONWOVENS. At the beginning I commented that most people would not know what a nonwoven was or where it is used.

I have tried to address the question as to what is a nonwoven, but to illustrate some of the ever expanding products and applications, the above table listings are but a few of the many diverse uses to which nonwovens are put. One might reasonably conclude that it is truly a wonderful world of nonwovens in every phase of our everyday lives.