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Mastering “Materials Science”

Paper, a flexible, versatile, variable composite material, is an ideal fit for nano advances. Oddly enough, within the paper industry, there's little discussion, on a management and marketing level, o...


June 1, 2008
By Pulp & Paper Canada

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Paper, a flexible, versatile, variable composite material, is an ideal fit for nano advances. Oddly enough, within the paper industry, there’s little discussion, on a management and marketing level, of the ways that paper, board and specialties fit into the nano equation.

A tennis buff can listen to her iPod Nano, while employing a nano strength-flexible racket to hit a ball with a nanocore. Nano sunscreen will help protect her skin, while a nano fabric dome will allow sun to enter, but keep out the rain and wind. She could take a lunch break to flip through a fashion magazine, containing a silica nanoparticle system for better printability, and enjoy a sandwich kept fresh with a wrap or box employing a WBBC (water based barrier coating) with nano minerals to eliminate fluorocarbons and minimize petroleum based polymers. While she might have chosen the new tennis racket based upon a nano message in the ad campaign, or chosen the balls for the same reason, most likely, the roof over her head and the performance-enhanced paper never entered her mind, much less the role of nanotechnology in these materials.

Even without fanfare, nano progress and opportunities in paper and board continue to add up:

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• Coatings that are thinner, smoother, tougher, water-based and non toxic

• Surfaces that are smoother; have better printability; sometimes topped with nano inks

• Whiteness and brightness fine-tuned within the sheet and on the surface

• Base sheets that are mineral-rich, adding property enhancements, and with less fibre–silica nanoparticle advances are key

• Grades that are stronger and lighter

• New hybrids with polymeric films, metals, and alternative fibres

• Intelligent RFID and other brains embedded into a nano-based sheet

• Less raw material, with increased sustainability, biodegradability, and easier recycling

• Closed-loop water cleanliness with nano-filtration

• Fragrance enhancement, and hygiene boost

Why Go Nano?

The main reason for applying nanotechnology solutions is added value. In fact, nanotechnology for papermakers is all about mastering materials science, because paper is a composite material, and a mix of organic and inorganic materials “extraordinaire.” Nano is the road to greater potential profits for papermakers and their customers. Even so, nano tends to be invisible to the end-user, and even to papermakers, who sometimes view it as just the latest material advance, or even the latest sales pitch.

Calculate Your Nano Value

On a machine-by-machine basis, nanoparticle- based filler for fibre substitution, combined with lower basis weights because of greater strength, are saving the industry huge sums of money, and/or gaining higher performance and enhanced sheet properties. Market pressures faced by printers and converters have masked the benefits achieved through paper producer cost savings, and even new benefits delivered for the same or a lower price. Producers, who have “evolved” grades to higher levels have probably gained the most.

Next Steps

Papermaking wet end retention aids have long been “nano.” So what’s next? Look for further advances in retention/dewatering chemistry and strides in coating, as coating chemists and engineers have been on the frontier of nanoscience for some time now. Changes in pore structure are now possible on a nanoscale, and can result in major changes in optics and printability. Pigments designed on a nanoscale will one day result in improvements in paper strength.

According to Tony Lyons, director of applications technology for Imerys Pigments for Paper, “We have discovered that kaolin pigments under 100 nanometres in thickness will have improved stiffness over conventional kaolin pigments in many coating and surface pigmentation applications. Our recently patented Barrisurf mineral approach to barrier coating is one of those practical nanotechnologies being offered for paper. We have also developed nano dimensional clays, like Contour Xtreme for paper coating that not only is nano in dimension, but can also be used to fine-tune coating structures on a nanoscale when used with conventional pigments.”

Stora Enso’s Kaj Backfolk affirms that, “the addition of nanoparticles in polymers to change optical, mechanical and barrier properties is at hand.”

Also look for the continued progress with nano-engineering of coating components, facilitated by latex binders. Nanostructure- based adhesives can deliver producers higher strength paper coating surface to improve printability, especially when higher tack inks are used. Latex nano structures are now commonly designed to enhance various paper properties, such as stiffness and opacity, for a range of increasingly lighter-weight grades.

There is academic research going on in the Nordic institutions looking at dry spray coating. This can help reduce water usage, which would help with sustainability and can theoretically have some pretty spectacular results. However, it does translate to capital investment and the development of new coating formulation technology.

One society-driven shift concerns the elimination of fluorocarbons in coatings, as well as the focus on minimizing petroleum-based extruded polymeric films. Food applications of paper and board are proving successful with new water-based barrier coatings (WBBC), which achieve barrier targets for grease, oils and vapor by employing a patented mineral formulation, functioning on the nano level.

Nano, Asian Style

For papermakers comfortable with current approaches to papermaking, it’s time to look out for the new fast lane of machines in China, setting new speed records at high filler loadings. Says Dave Lovell, Eka Chemicals marketing director, Asia Pacific, “Our latest nanoparticle retention chemistry proved itself first in China. We developed Compozil Fx for several fast machines, and helped them increase productivity. It’s not just about speed, however, because the filler level is up, fibre costs are down, and they have breaks under control.”

Back in the early 80s’, some of the earliest converters to the original silica nanoparticle systems were in Canada. High filler content was achieved by all of the major producers, helping them with runnability, formation, quality and even cost reduction. Art Ragauskas, professor at Georgia Tech’s Institute of Paper Science and Technology, suggests that at least 1,000 machines now employ nanoparticle retention systems for better formation, and that many bag producers have employed the benefits of an open sheet structure beyond the paper mill, and in converting operations. Ragauskas adds, “Nano sizing to improve surface sizing and nanoparticles to improve coating hold-out have raised the bar in printing on a wide range of paper grades.”

In certain grades, such as white top, producers now routinely employ silica nanoparticle systems. KemiArt of Finland and North America’s Simpson Tacoma Kraft have led the way in packaging print quality, and are a model for others to do so. Eurocan has employed a silica nanoparticle system to achieve an open sheet, which is attractive to packagers of cement, and others who need their bags to breathe during filling operations and afterwards.

Industry visionaries see a rising tide for forest-based products, as producers seek bio-solutions in their products, and better recyclablity. In short, the future rests with nano-composites with an advantage going to natural materials with the potential for super functionality and proven sustainability.

Concludes the Swedish Royal Institute of Technology’s Professor Tom Lindstrom, “Nanotechnology presents enormous opportunities, making even more environmentally-friendly products from cellulose possible. The forest has a head start in bio-nano development. We humans simply have to catch up to what nature
is doing on its own, and develop new products in a sustainable way.”

Martin Koepenick, Innova has written about the paper industry and innovations in technology for over 25 years. He can be reached at mkoepen@earthlink.net.

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Nanocrystalline Cellulose

A New Material with Unimaginable Properties

FPInnovations, founded one year ago as a result of the merger of Feric, Forintek, and Paprican, has launched a research program based on transformative technologies. These technologies could significantly modify the vocation of mills and the entire industry in the near future. The program was made possible by the substantial support of the Federal government.

One of the program’s areas of research is nanotechnology. The program’s mandate consists in developing nanotechnology research, as well as an application network, for the benefit of the forestry sector.

To be considered a nanomaterial, three conditions are essential. First, the particle dimension must be between 1 and 200 nm. This range corresponds to the midway point between classical physics and quantum physics, and brings us to the second condition -nanomaterials must possess unique properties that are different from the raw material (ex. electrical, physical, chemical, optical properties). Finally, the process used to obtain these properties must be both reproducible and controllable.

In the FPInnovations nanotechnology program, one of the stated objectives is to identify and transfer to our industry nanotechnology-derived applications. However, a second objective is the development of a product derived from Canadian fibre: nanocrystalline cellulose (NCC). A basic structural unit of cellulose microfibrils, NCC was isolated and identified in the 1990s and was the subject of many doctoral theses, especially in the laboratory of Professor Derek Gray of McGill University. Along with his colleague, the late Dr. Jean-Franois Revol, he, among others, demonstrated the optical properties of nanocrystalline cellulose.

NCC is needle-shaped (10×200 nm) and features many remarkable properties. NCC crystals possess a large specific surface and are as strong as steel. Furthermore, they are able to self-assemble in solution and, once dry, can form translucent and iridescent films.

FPInnovations-Paprican researchers achieved a technological breakthrough when they developed a pilot-scale process by which kilograms of NCC can be produced from chemical pulp. This achievement paves the way for the development of new products and the exploration of practical applications. FPInnovations-Paprican has been working on some potential applications: oxygen permeability control for boxboard packaging materials; use as a reinforcing agent for biodegradable polymers and nanocomposites; development of iridescent films with reflected light control; use as an additive in varnishes and paints and use as a barrier limiting the emission of volatile organic compounds.

This program has enabled us to establish links with Nano-Qubec, CIPP in Trois-Rivires, QC, the INRS nergie, Matriaux et Tlcommunications research centre in Varennes, QC and the Institut des Communications Graphiques du Qubec, as well as the University of Ottawa, the University of British Columbia, and McGill University.

Now that the barrier of grams to kilograms in the production of NCC has been broken, the next challenge on our drawing board consists in progressing from kilograms to tonnes!

FPInnovations is now rapidly progressing in the development of an ecological, redispersible, renewable, recyclable, and carbon-neutral nanomaterial that will be used in numerous applications in the near future.

Prepared by Jean Bouchard, Ph. D., a Principal Scientist with FPInnovations -Paprican.

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Canada’s Promise in Nano

McGill University claims to have the leading position in nanoscience in the country. Chemistry professors Theo van deVen and Derek Gray, former Paprican scientists and both holders of NSERC-Paprican Industrial Research Chairs utilize tools like an atomic force microscope to study the surface properties of nanoscale cellulose fibres to improve bonding capacity in paper sheets. Recently, Gray has focused on self-assembling cellulose nanocrystals in suspension. “The nanocrystals form a chiral, twisted structure, which diffracts light and gives colours we can see in suspension,”says Gray.

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Seeing The Big Picture

Mikhail Roco, senior advisor to the National Science Foundation, stresses the importance of business experts to drive governmental and university projects beyond the lab. “Scientists don’t always understand the business of manufacturing. To increase innovation, we need business models, and business agility.”

Kaj Backfolk, manager, coating and functional printing with Stora Enso says, “Nanoparticles were initially special niche products and now they are used, in some cases, as bulk products. Recent product launches using nanoparticles in coating or surface formulations add to the practical role of nano in papermaking.”

Comments Lennart Nilsson, Eka Chemicals director of global marketing, “As paper evolves, we now have the understanding of nanoparticle systems to keep pace, and sometimes open up new possibilities. Going back several decades, we focused on increasing filler loads, and better formation. While we still help to reduce fibre content, increasingly, we are part of new composite sheets, which print better, break less often on printing presses, and recycle more easily.”

Says Phil Jones, director of technical marketing & new ventures for Imerys, “The forest is perhaps the world’s largest nano machine, and paper machines the ultimate nano processes. While carbon nanofibres cost millions per ton, tree By Martin Koepenick

fibre costs only hundreds of dollars per ton. In many cases tree fibre is better than sophisticated man-made fibres. When you mix cellulose with minerals, another gift from nature, and you apply paper and materials science to the two, you have the potential for a diverse, economical 21st century marvel in industry. The more we recognize this potential, the greater the potential for higher prices for paper and board.”

Tom Lindstrom, professor at Sweden’s Royal Institute of Technology says, “Multi-layer technology is a hot area in paper science today, improving pulp’s properties through nanotechnology. This involves building up a material that consists of different layers, each differently charged (positively or negatively) than the surrounding layers. The issue so far is to find efficient production methods. The technology as such is ready for reaping. With such means, very strong paper materials can be produced.”

Art Ragauskas, Professor at Georgia Tech’s Institute of Paper Science & Technology emphasizes the fact that the behaviour of materials at the nanoscale is nothing like that of the large scale. “The advances in nano science and engineering provide practical solutions for many of today’s needs in packaging, especially high-barrier properties, super-hydrophobic self-cleaning surfaces, novel security features, functional barriers and antibacterial/antifungal properties. Finally, as our ability to template and replicate biological features on a nanoscale develops, new printing and imaging technologies will be developed.”

As Theodore H. Wegner of the U. S. Forest Service puts it, “Our understanding of how molecular and nanoscale cell wall components (i. e. cellulose, hemicellulose, lignin) are assembled is growing rapidly. By understanding the functional genomics of how trees produce and assemble these molecular components and nanodimensional architectures into the cell wall, we should be able to manipulate and create new, novel nanoscale structures with unique physical properties and multifunctional surfaces. This enabling science along with technological advances in the manufacturing of nano-enabled macroscale materials will allow u
s to create new generations of high performance, value-added products.”