A combined future: tracking the trends in machine clothing: machine clothing innovations will come party by combining sometimes disparate technologies to meet the needs of papermakers better.

From plastic wires to multi-layer fabrics and high-tech materials, innovation--sometimes incremental, sometimes dramatic--has always driven the market for machine clothing.

For this feature, Solutions! asked machine clothing manufacturers to identify what they felt were the most promising innovations in machine clothing and describe bow they are coming (or have come) to market. One common theme was that machine clothing innovation arises partly from the ability to pair sometimes disparate technologies. In this case, one and one may equal well more than two.

IT JUST SEAMED RIGHT

Seamed multiaxial press fabrics were high on the list of machine clothing innovations for Mike Royo, director R&D, U.S. press fabrics, for Albany International, Albany, New York, LISA. "These fabrics have the potential to combine the benefits of two major clothing innovations. Seamed fabrics offered safety, ran cleanly, and reduced downtime. Multiaxial fabrics featured steady state performance, better pressure uniformity, and better CD profiles." Seamed multiaxial press fabrics combine the best of both of these worlds said Royo.

John Hawes, vice president technical/R&D, U.S. press fabrics, for Albany International pointed to engineered coatings as another major innovation. He said such coatings offer optimized sheet contact, adhesion/release, and anti-rewet properties. "These coatings allow an additional 'degree of freedom' in designing a press fabric where previously mutually exclusive goals--fast startup and long life can now be met."

SUPPORT IS CRITICAL

Steve Cole, director of marketing for Weavexx, Wake Forest, North Carolina, USA, agreed that combining technology has encouraged machine clothing innovation. In the forming area, he pointed to fabrics with a plain-weave top surface with support shute binding technology that eliminates interlayer wear Cole said that this design can provide very high fiber support, a wide range of permeabilities, and very thin caliper.

"This design provides a higher fiber support index (FSI)--up to 195--compared with other fabric designs. Higher FSI produces improved mechanical retention. This means chemical usage can decrease and sheet quality can improve."

The combination of high FSI and high CFM--up to 500--gives this design very high drainage capacity according to Cole. "Low caliper yarns in both machine direction (MD) and cross machine direction (CMD) mean that caliper and void volume are minimal. Caliper and void volume are comparable to that of finemesh, double layer fabric, thereby eliminating water carry."

In press felts, Cole cited diagonal-elliptical needling as a major innovation. The technology of diagonal-elliptical needling makes felts using a curved needle board that enables the needles to penetrate the fabric diagonally at variable angles. "By combining elliptical needle movement with diagonal penetration vectors, press felt surface quality and uniformity dramatically improve," said Cole. He noted that diagonal needling can produce the following:

* Increased sheet dryness through improved pressure transfer

* Fewer sheet breaks through higher dryness

* Improved runnability through less needle damage

* Improved surface smoothness and two-sidedness.

RETHINKING THE FUTURE

Bill Jeffrey, communications manager at Voith Fabrics, Raleigh, North Carolina, USA, sees a multifaceted future for making clothing that includes composite materials and stronger partnerships between machine clothing and paper machinery.

"Composite materials are the future of clothing because we can design fabrics that translate into desired sheet properties and make papermaking more efficient," he said. "Perhaps the most important breakthroughs are coming from total rethinking of clothing and machinery to meet a particular need such as the co-development of the shoe press and innovative belts and clothing. Fewer breaks, a stronger sheet, and energy reduction are all possible at higher production rates."

In the press section, Jeffrey noted that tri-axially oriented fibers are a critical element in multi-layer, nonwoven technology. "These fibers deliver sheet smoothness while simultaneously allowing furnish fiber reduction and lower energy consumption. The primary process solution provided by the tri-axial layer results from its uniform, open structure that significantly improves dewatering over extended periods."

In addition to MD and CMD open water removal channels, the tri-axial system provides superior z-direction flow properties in demanding press nips noted Jeffrey. "With the open channels, the tri-axial system otters z-direction resilience to yield higher permeability control over the life of the fabric. Composites like these achieve the duality of market value and process value to make them a new standard."

TWO NAMES, ONE IDEA

Roger Danby, vice president, forming development, for AstenJohnson, Charleston, South Carolina, USA, focused on an innovation known under different names in different regions. "Europeans refer to this as the surface support binder (SSB)," he said. "In North America, it is intrinsic weft--a name coined by the AstenJohnson research group." Danby said that the intrinsic weft concept now finds use across all paper grades, from linerboard to tissue.

Intrinsic weft products incorporate a plain weave or a 2x1 weave on the paper side. The base is a 6-shed base or an alternate standard 4-shed. "The combination using the intrinsic weft technique allows the papermaker to have the best of both worlds--a fine top surface for papermaking on a coarse base structure that provides life and stability without the delamination that was a major problem with standard triple layer structures," Danby said.

Papermakers using fabrics with intrinsic weft report improved formation and fines retention on the surface and increases in first pass retention. This provides cost savings on retention aids according to Danby. "These improvements come from the very fine top papermaking surface," he said. "Improved 2 sigma CMD basis weight profiles are due to the increased CMD stiffness and stability. Increased life comes from the much greater wear volume of the 6-shed base. The uniform papermaking surface gives improved print quality."

BLUE SKY IDEAS

Although these innovations are already available, Solutions! asked the panel to identify the best "blue sky" ideas in machine clothing that the industry may follow in coming years. John Hawes of Albany International focused on adaptive dewatering media that can, in one rotating belt, provide adequate fiber support for sheet formation, good contact area and compressive properties for wet pressing, and excellent resistance to high temperature for drying.

"The adaptive permeability nature of the structure would ideally be controlled by a sensing mechanism (smart material) to determine the dewatering needs of the paper web. This could allow major reductions in the size of machines needed and economical production of niche grades. The economics of this technology would not be based on speed and tonnage but on low capital outlays and production flexibility. This technology might also receive hearty support from the global environmental community."

Hawes noted that this concept depends considerably on further development of high-consistency forming, impulse pressing, and impingement drying. "In the current economic environment, a relatively small chance exists that an established paper or clothing producer would invest in this concept. It might interest an entrepreneurial core of investors," Hawes concluded.

Bill Jeffrey of Voith Fabrics noted that "blue sky" paper technology will require making a sheet on a more uniform clothing surface and adapting paper machines to dewater and smooth the sheet even more precisely throughout forming, pressing, and drying. "'Extreme performance' clothing has been developed for firefighting and space travel. Similarly, new material blends will take papermaking to higher quality, consistency, and performance."

IN THIS ARTICLE YOU WILL LEARN:

* Hew seamed multiaxial press fabrics can combine the benefits of two major clothing innovations

* The benefits of fabrics with a plain-weave top surface with support shute binding technology

* Why tri-axially oriented fibers are a critical element in mufti layer, nonwoven technology

ADDITIONAL RESOURCES:

* Albany International: www.albint.com, click an "paper machine clothing."

* Weavexx: www.weavexx.com click on "technology."

* Voith Fabrics: www.papermachineclothing.com/ index.htm, click on "technical reports."

* AstenJohnson: www.astenjohnson.com, click on "paper machine clothing."