The origins of airlaid products began as an attempt to replace corrugated fluting media with a more cost efficient method for providing strong, bulky, protective packaging. The initial technology available and the cost structure involved ended up diverting airlaid materials into industrial wipes, baby wipes, feminine hygiene items and tabletop products. And for the best part of two decades, this is mainly where airlaid materials were found. Recent advances in commercial technology and capacity expansions, however, have altered the picture and airlaid technology is now entering a new phase of growth and product diversification.
In the early days of airlaid there were primarily three properties that airlaid products brought—absorbency, wet strength and softness. Today the picture has changed. The ability of modern airlaid systems to incorporate a broad range of synthetic fibers and diverse bonding technology has yielded a whole new range of properties, namely:
• controlled absorption & liquid Delivery
• wet dimensional stability
• thermal embossability
• dry bulk & wet bulk
• gradient & controlled porosity
• hydrophobic zones and surfaces
• abrasion resistance
• chemical resistance
• absorbency under load and retention
• specific fluid absorption
• additive compatability
• multiple ply structures
In addition to the expanded matrix of properties, there is now the potential to produce a wide range of composite structures online, incorporating: spunbonded and thermal bonded coverstocks, carded, high bulk acquisition layers, apertured films and thin and thick barrier films.
Utilization of these new functional properties and the use of multilayer composite technology has opened up new markets and product opportunities, a few of these have been highlighted here.
Traditional food packaging products have been made for many years utilizing multiple plies of absorbent tissue products, which are typically stitch laminated to a barrier film material. While these products have served as effective, low cost absorbent pads for poultry and red meat packaging, there are some significant drawbacks. The film tends to delaminate from the pad when it is wet and the lack of wet strength in the tissue results in an unattractive pulp mass at the bottom of the tray when the meat is removed. Most significantly, the tissue product will absorb fluid but has poor retention properties so fluid can re-emerge into the pack.
Food and Drug Administration’s (FDA) approval of certain superabsorbents (SAPs) in both granular and fibrous form for indirect food contact provided an excellent opportunity for airlaid manufacturers. Airlaid technology represents an ideal vehicle for efficient use of superabsorbents and a number of different new product formats have been designed. An example of the differences between the traditional technology and an airlaid product is shown in Figure 1.
Airlaid products can provide cost effective absorbency, wet strength, and can combine the permeable or impermeable barrier layers on line for maximum efficiency. The final product is an attractive looking pad that retains its integrity when wet and has better fluid retention properties providing an attractive case-ready package.
The ability to produce a web with multiple layers in the Z-direction and the fact that these layers can be made of diverse materials and have different characteristics makes airlaid fabrics ideal materials for filtration applications.
An airlaid material can be produced with a gradient pore structure with coarse synthetic fibers on the top surface through to fine, tightly packed cellulosic fibers on the bottom surface. This structure allows for large particle capture, high filtration efficiency and reduced pressure drop.
Modern airlaid fabrics now have the potential to be made of 100% synthetic fibers. This opens up a whole new market for long life durable filter grades. The excellent uniformity and outstanding bulk that the airlaid process provides allow for improved air filtration performance in these grades.
Combining airlaid structures with fast acting superabsorbent powders or fibers and/or specific liquid scavengers has enabled the production of filters that can remove water and other impurities from fuel for liquid filter systems.
The capability of airlaid materials to act as a liquid delivery medium combined with the property of reabsorbing liquids has made the product an ideal material for a wide range of homecare cleaning applications. Airlaid materials are now being used as a strong absorbent wipe product carrying: disinfectant cleaning solutions, furniture polish, leather and vinyl cleaning agents and fabric stain removers.
Composite airlaid products incorporating additional nonwovens on one or two surfaces are being used as disposable mops for floor and surface cleaning. Airlaid offers the absorbency to carry the high liquid volumes that are required to provide satisfactory floor coverage and can provide the necessary wet surface abrasion for cleaning without fiber linting.
Airlaid materials can be made with widely different surfaces—absorbent on one side, water repellent on the other; abrasive on one side, smooth and absorbent on the other—that enable a range of new product types to be envisioned.
Ideas from the past often end up repeating themselves and, sure enough, some of the newer applications for airlaid materials return to the material’s origins in the packaging business. Airlaid materials are beginning to be used in a broad range of the packaging applications, including:
• Re-pulpable box liners for shipping delicate finished parts (e.g. chrome, furnishings) These products utilize a specialty binding system which allows the airlaid product to be repulped along with the corrugated container while providing a soft, non-scuff surface.
• Re-pulpable, recyclable high bulk products which provide outstanding cushioning and protection for delicate materials while being environmentally friendly.
• Absorbent materials for the handling of liquid packages and hazardous liquid packages. These products can even be designed with additives, which, in the event of a liquid spill, would absorb a hazardous chemical and neutralize it.
It would be inappropriate to end any discussion of new airlaid markets without referencing two of largest developments that have been ongoing for some time but may now be approaching their realization.
Airlaid products are being used in the production of a new category of the baby diaper product—the swim diaper. While this category is a very small niche of the diaper business, many of these products are made on machines that also manufacture training pants. The use of airlaid in the swim diaper has opened the avenue toward training pants. From there, the next step for airlaid is into small size diapers and beyond.
There has been much publicity over the last few months regarding the introduction of moist toilet tissue rolls into the U.S. market. Two of the industry leaders have now introduced products in this format and another has the product available in a tub format. All of these products use the softness and wet strength characteristics of airlaid as the substrate of choice.
The investment in technology and capacity that the airlaid industry has undergone during the last two years is unprecedented, the range of opportunities and capabilities that airlaid products now represent fully support the initiatives.
Richard Knowlson has been involved in the nonwovens & paper business since 1983, working specifically in the area of airlaid nonwovens since 1987. Within the Concert group he manages the company’s business development activities and works with the management group in setting new strategic directions for the company