Wet-laid forming in nonwovens: Where do we go from here?

Wet-Laid Forming in Nonwovens: Where Do We Go From Here?

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by Alexander A. Koukoulas, Ph.D.

At the Research, Innovation & Science for Engineered Fabrics (RISE® 2016) Meeting sponsored by INDA, I had the pleasure of speaking about the the production of nonwoven composites using wet-laid forming technologies, and providing thoughts about its future growth. For industry outsiders, most nonwovens are manufactured using either one of two main process technologies: dry-forming and wet-laid forming. The latter is a smaller subset of the two and is based on conventional papermaking process technologies. At its most fundamental level, wet-laid forming can be viewed as dewatering process wherein a dilute mix of fibers in suspension is transformed into a paper-like web. Products made using wet-laid forming include industrial papers, such as Nomex® paper and glass mats, and consumer products, such as disposable wipes. Highlights from this invited talk are presented below. 

Wet-laid forming provides a high degree on freedom for fiber selection, additives and functional chemicals that can be used to create an array of engineered nonwoven composites to meet the demands of range of downstream applications.

Wet-laid forming provides a high degree on freedom for fiber selection, additives and functional chemicals that can be used to create an array of engineered nonwoven composites to meet the demands of range of downstream applications.

Nonwovens Market. The world of nonwovens represents a rapidly-growing $37 billion industry, delivering a range of product solutions that can meet the strictest of industrial and consumer demands. Nonwovens are ubiquitous—from personal hygiene products to automotive fabrics and filtration media—they are found in almost any product and market segment. And, the industry is growing, both organically and through the introduction of novel products that can meet the consumer demands of tomorrow.

Multiple Degrees of Freedom in Material Selection. From a new product development standpoint, the multiple degrees of freedom in wet-laid nonwovens design and engineering opens the door to product innovation and the development of unique differentiated products to meet consumer needs. Nonwoven products leverage a rich palate of materials options, including fibers, pigments and specialty chemicals, as well as a range of process delivery options, including former design and the addition of specialized unit operations such as hydroentangling systems, in-line coaters and calendering. From a materials selection perspective, nonwovens can be engineered from a range of material types including: natural and synthetic fibers, binder systems, inorganic fillers and catalysts. And, unlike dry-laid forming, wet-laid forming can use a range of high-performance staple fibers, such as aramid and carbon fiber, to develop unique products with exceptional utility. Lastly, wet-laid forming can leverage the hydrogen bonding potential of natural fibers to create lightweight materials of exceptional dry strength, while maintaining their ability to disperse upon rewetting. This explains the increasing use of wet-laid manufacturing platforms to produce consumer products, such as disposable wipes.

Improved Process Technologies. From an engineering standpoint, improvements in wet-laid forming technologies have been substantive enabling the deployment of machines with unprecedented scale. The largest papermachine in the world is 428 meters long, 11 meters wide, with operating speeds of 2000 meters per minute. Clearly, scale and the technologies that support scale, such as pressurized head box design, polymer-based machine clothing, extended-nip forming technologies, synchronous drives and machine control systems have contributed to impressive advances in productivity. This, combined with advanced water saving technologies, give wet-laid forming processing significant economic advantages over competitive forming types in certain product applications.

Demand for “Green” Products. Consumer expectations are shifting towards products that can mitigate environmental impact and those derived from sustainable, renewable resources. For example, at least 15 states and the District of Columbia have placed severe restrictions and in some cases outright bans of the sale of plastic bags. In this regard, expanded use of short natural fibers in the production of both consumer and industrial products alike will continue to drive the expanded use of wet-laid forming.

Expanding Population Growth. The world’s population is expected to increase from its current 7.4 billion to over 9.0 billion in 2050. While the percentage of younger individuals (age 19 or less) will decrease, the population of those over 65 years of age will significantly increase. An aging population will bring about demands for new products and specialized services. In addition, a rising middle class will present opportunities for product growth across all segments, especially in food packaging and consumer products. Moreover, secular trends that place increasing importance on sustainability and wealth creation, including a rising consumer class in developing countries, will be strong catalysts to a growing demand for nonwovens products. As a result, market opportunities for nonwoven products are expected to remain strong.

On the Horizon. There are many exciting new technologies under development that have the potential for redefining wet-laid forming, improving efficiency and performance, and making it more cost competitive. For example, foam forming technology, which can displace up to 80% of water used in the manufacturing process, is seen as a real opportunity for both transforming the cost of production and imparting novel product properties, such as higher bulk. Wet-laid forming is ideally suited to incorporate nanocellulose, a new class of renewable materials with exceptional strength. Wet-laid forming combined with the in situ production of nanocellulose opens up tremendous opportunities for the development of novel composite structures and coatings.

In summary, wet-laid forming is a well-established technology. As such, it presents little technical risk to project developers looking to expand their product lines, especially in growing market segments such as consumer products and disposable wipes. Technology barriers, such as high water intensity, have been largely eliminated and machine configurations benefit from large economies of scale. Wet-laid forming provides new product developers with exceptional degrees of freedom that can enable the design and production of composites using a range of high performance fibers. It provides a platform for expanding utilization of natural fibers including nanocellulose in novel product applications, such as battery separators and bio-based composites. As such, wet-laid forming is expected to see expanded growth as a manufacturing platform in both industrial and consumer segments.

Postscript. Since presenting this invited talk, my long-time collaborator, Dr. Martin Hubbe of NC State University, and I published a comprehensive review of wet-end chemical approaches to wet-laid nonwovens manufacturing. In this review, we discuss scientific advances in the field and discuss the many strategies for optimizing wet-end chemistry and the various process technologies used to produce nonwovens. Although both synthetic and natural fibers are considered, emphasis is placed on applications where cellulosic fibers are a significant component of the nonwoven product, such as dispersable wipes. Topics covered include: fiber properties and surface chemistry; fiber dispersion; hydroentangling (spunlacing); and foam forming. This article appears in the May 2016 issue of BioResources. To obtain a full PDF copy of the article, click here.

© A2K Consultants LLC 2016