Polymers such as polypropylene and polyester account for more than 50 per cent of global nonwovens production. Such PET and PP fibres are also used in carded nonwovens. Here it is mainly wiping cloths, but also hygiene products and industrial applications such as geo-, automotive and filter textiles that are used on a large scale.
In less than 20 per cent of these nonwovens, however, natural fibres or fibres from renewable resources such as viscose are the raw material of choice. And cotton also plays hardly any role except in the narrow range of cotton wool pads. Consumers have been worried not only recently by the idea that giant plastic islands the size of entire countries swim in the world’s oceans. And the idea that micro plastics can be found in many foods is not pleasant for anyone.
At first glance, cleaning cloths and plastic bags may not have much in common. But conventional, water jet-bonded disposable wipes contain polyester or polypropylene fibres. In the wild on land or at sea, they too slowly degrade into tiny particles, the infamous micro plastics. It is time for the industry to think about ecological alternatives, writes Bodo Heetderks of Trützschler Nonwovens GmbH in the trade journal ‘melliland Textilberichte’.
The special challenge in processing natural fibres is that consumers love wiping cloths and are formulating ever higher demands in terms of natural feel, softness and skin compatibility. The demand for “more natural” products is growing visibly.
Except for countries in Southeast Asia, however, cotton has hardly played a role in hydro entangled nonwovens to date, and its use is limited to admixtures of up to 15 per cent. The reasons for this are short fibre lengths as well as the tendency to fibre tears and the associated risks in the carding process.
Sustainability Through Novel Cotton Nonwovens
As early as the mid-1980s, the requirements for throughput and fibre orientation in web formation were growing. Here the demand in the early 21st century was already evident. Optimized nonwoven carding machines are the basis for the highly efficient use of cotton fibres even today. Asian producers also like to process raw cotton with a staple length of 17-24 mm and a correspondingly low short fibre content.
Apart from the fibre length, knot-like structures, the so-called neps, pose a further challenge. Even the classic cotton spinning mill distinguishes between fibre and shell neps. Mechanical stresses on the fibres increase the number of fibre neps, so the carding technology used is of great importance. Web formation with conventional roller carding machines generally increases the number of neps due to the high degree of mixing. This process is therefore not suitable for efficient cotton processing.
A technology with mechanical web take-off and aerodynamic airlay carding, on the other hand, is optimally designed for processing cotton. They are characterized by a high production output and only a slight increase in neps both with 100 per cent bleached cotton and blends with viscose fibres.
Downstream machines for hydro entanglement as well as dryers and winders operate independently of the lengths of the fibre types used. And the filtration system used is designed to also process cotton with a high proportion of short fibres. Only the number and type of filter stages have to be adapted when using natural fibres.