The Future with Cellulose Nonwovens

 

At the end of this past month the Sustainnovation Renewables Journal, Istanbul, Turkey, published a piece detailing the next century’s use of cellulose based nonwovens. The article was written by Lüder Gerking, CEO, Nanoval GmbH & Co. KG

Gerking explains that a person in our industry might say that the industrial raw-material was coal in the 19th century, oil in the 20th  century, and will be cellulose in the 21st century.

Cellulose, he writes, is of natural origin from wood or other plants. It may serve for eating, clothing, and heating. The first manmade fiber of economical importance was viscose or rayon on this basis, which nearly was replaced by synthetic fibers beginning in the 1930s. It recovered recently, though from a low level. The reason is not only that they are from renewable resources, but in contrast with the oil-based fibers like PP, PE, PET, PA, and others, they are biological degradable and compostable. In the modern term: sustainable.

In times of increasing oil prices, cellulose fiber products for textiles, hygiene, medical, and other end uses have a high advantage on synthetics as they absorb and retain moisture, are comfortable to wear, and pleasant fort human skin, according to Gerking. He says the feedstock pulp for cellulose fibers is available in abundance, but it takes some efforts and costs to make a spinning dope in solving the cellulose, e.g. to an aqueous Lyocell solution. The solvent reported by Gerking is NMMO and has to be recovered by water evaporation and redressed for new use. Investment and energy consumption to this process section take a high amount of the manufacturing costs. This seems to be the main reason that nonwovens for wipes, hygiene, and medical products from cellulose only beginning to come up.

Nanoval has developed a spinning process in which continuous filaments are spun from orifices, normally holes, and split-up from the exiting liquid monofilaments into a multitude of finer filaments. This effect occurs less by drawing than by shear forces of an accompanying air flow, inducing a pressure into the monofilaments until they burst, breaking up the outer skin--the sheath. From one spin-hole several, up to more than 100, single finer filaments are generated. This effect still is surprising to the fraternity of fiber-makers, as spinning always is done by attenuating, whether by the spinning wheel or from melts or solutions.

The Nanoval process can handle both of them, always at the tendency to finer fibers due to the splitting effect. A first Nanoval plant for spunlaid cellulose nonwovens according to this split-fiber technology is operated in the institute TITK in Rudolstadt at Schwarza, a place also called the cradle of German synthetic fiber industry. They perform the spindope at a LIST reactor and recover the solvent NMMO. The cellulose coagulates in the split filaments, and the solvent has to be washed out with water.

As a special feature, the process can start from paper/kraft pulp, cheaper than dissolving pulp, which normally is used for viscose and Lyocell making, and can even start from wastepaper. To increase the moisture absorbency SAP particles can be added to the spinning dope and the spun webs can absorb 25 times of its fiber weight.

To go into the production of cellulose nonwovens a high entry-step has to be made. This is the generation of its own fiber feedstock, rather complex compared with taking PP chips, simply feeding it to an extruder – recovery is not necessary. But in the long run, Nanoval expects a high market share for spunlaid cellulose nonwovens.